platelets in inflammation306632/... · 2010. 3. 30. · platelets express receptors involved in...
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Linköping University Medical Dissertations No. 1176
Platelets in inflammation
Role of complement protein C1q, Creactive protein and tolllike receptors
Caroline Skoglund
Division of Drug Research Department of Medical and Health Sciences
Faculty of Health Sciences Linköping University, SWEDEN
Linköping 2010
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© Caroline Skoglund 2010 ISBN 9789173934183 ISSN 03450082 over: Adhering platelets stained for F‐actin and visualized Cwith fluorescence microscopy During the course of research underlying this thesis, Caroline Skoglund was enrolled in Forum Scientium. A multidisciplinary doctoral program at Linköping University, Sweden Printed by LiUtryck, Linköping, Sweden, 2010
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“I find that a great part of the information I have wfas acquired by looking up something and inding something else on the way” (Franklin P. Adams 1881‐1960)
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ABSTRACT Platelets are proven essential in haemostasis, however, they are now also increasingly recognized as cells with important immunomodulatory properties, e.g. through interaction with leukocytes and several species of bacteria and by release inflammatory mediators upon activation. Moreover, platelets express receptors involved in immunity and inflammation such as Fcγ‐receptor IIa, complement protein C1q‐receptors (gC1qR, cC1qR, CD93 and α2β1) and toll‐like receptors (TLR‐1, ‐2, ‐4, ‐6 and ‐9). C1q, C‐reactive protein (CRP) and TLRs are all pattern recognition molecules able to recognize non‐self structures and initiate an immune response. Uncontrolled or misdirected activation of platelets and the immune response is involved in the onset and progress of several conditions with an inflammatory component, such as coronary artery disease and autoimmune diseases. Hence, the aims of the present thesis were to investigate the effects and
q mechanisms of C1 and CRP on platelet activation, and to clarify the intracellular signaling events provoked by TLR‐2 stimulation of platelets. Platelet interaction with immune complexes is poorly understood, however by utilizing well‐characterized model surfaces with adsorbed IgG and microscopy, we show that both C1q and CRP are able to inhibit FcγR‐mediated platelet adhesion and spreading. Using isolated platelets in suspension and flow cytometry, we also found that C1q triggers a rapid, moderate and transient up‐regulation of P‐selectin that is sensitive to blockade of gC1qR and protein kinase C (PKC), but not blockade of α2β1. Additionally, subsequent platelet activation by collagen or collagen‐related peptide (GPVI specific) is inhibited by C1q, suggesting a role for GPVI in C1q‐mediated regulation of collagen‐induced platelet activation. Whole blood studies revealed that C1q inhibits total cell aggregation, formation of platelet‐leukocyte aggregates, and potentiates the production of reactive oxygen species (ROS), all in a platelet‐dependent manner. Furthermore, using the TLR‐2/1 agonist Pam3CSK4 we found that TLR‐2/1‐activation of platelets is mediated via a P2X1‐dependent increase in intracellular free Ca2+, P2Y1 and P2Y12 –receptor ligation, and activation of cyclooxygenase. We also found that platelets express IRAK‐1, however, without being rapidly phosphorylated upon Pam3CSK4 stimulation and thus probably not involved in the early aggregation/secretion response. Furthermore, TLR‐2/6 stimulation does not lead to platelet activation but instead inhibits TLR‐2/1‐provoked activation.
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Taken together, these findings further strengthen the role of platelets as key layers in inflammatory processes. p
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POPULÄRVETENSKAPLIG SAMMANFATTNING Blodplättarna (trombocyterna) har en viktig roll i hemostasen, d.v.s. den process som hjälper till att stoppa en blödning som uppstått då ett blodkärl skadats. När blodplättarna aktiveras blir de större, ändrar form och klumpar ihop sig (aggregerar), allt för att täppa till och förhindra blodförlust. Förutom denna uppgift, så har det på senare år även visat sig att blodplättarna har andra viktiga egenskaper, till exempel så medverkar de i den inflammatoriska processen. Inflammation är en viktig del i kroppens försvar mot framför allt bakterieinfektioner, då immunförsvaret jobbar hårt för att bekämpa de skadliga inkräktarna. Blodplättarna kan bland annat samverka med vita blodkroppar och frisätter ämnen som påverkar såväl dom själva som andra typer av celler. På sin yta uttrycker blodplättarna olika igenkänningsmolekyler, så kallade receptorer, som binder in och reagerar på specifika ämnen, vilket ofta leder till aktivering. Under den tidiga fasen av inflammationen ökar blodets nivåer av C‐reaktivt protein (CRP) snabbt och komplementsystemet, som är en viktig del av vårt medfödda immunförsvar, aktiveras. C1q är ett av proteinerna som ingår i komplementsystemet. Det har också visat sig att blodplättar kan aktiveras av vissa bakterier, t.ex. via receptorer på blodplättarna som kallas toll‐lika receptorer (TLR:er), och som reagerar på olika bakteriestrukturer. Idag vet vi att en okontrollerad eller felriktad aktivering av blodplättar och ett immunförsvar i obalans kan bidra till inflammatoriska sjukdomar som hjärt‐kärlsjukdom och autoimmuna sjukdomar. Det är därför viktigt att förstå de bakomliggande mekanismerna. Syftet med studierna som ingår i den här avhandlingen var således att studera hur C1q och CRP påverkar aktivering av blodplättar samt att klargöra hur aktivering via TLR‐2/1 går till, genom att undersöka vilka signaler som skickas inuti cellen. Resultaten visar att CRP och C1q minskar blodplättarnas förmåga att binda in till och sprida ut sig på en IgG‐yta, som normalt är en kraftigt blodplättsaktiverande yta. Vidare fann vi att C1q som ges till blodplättar i lösning, ökar uttrycket av P‐selektin på ytan av blodplättarna, och att detta beror på aktivering av receptorn gC1qR och enzymet proteinkinas C. Dessutom så såg vi att C1q hämmar den fortsatta aktiveringen av blodplättarna som uppkommer om man tillsätter kollagen. Kollagen är ett protein som finns rikligt i kärlväggen och som vid en kärlskada exponeras och har aktiverande verkan på blodplättar. Därför är det mycket intressant
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om C1q kan fungera som en naturlig regulator för denna process. I helblod fann vi också att C1q hämmar aggregatbildningen mellan blodplättar och vita blodkroppar, och samtidigt ökar produktionen av reaktiva syremetaboliter. Reaktiva syremetaboliter är viktiga för att bekämpa bakterier vid en infektion. Genom att använda Pam3CSK4, en molekyl som specifikt aktiverar blodplättarna via TLR‐2/1‐receptorn, såg vi att aktiveringen är beroende av en ATP‐receptorförmedlad frisättning av kalcium inuti cellen. Dessutom är aktivering av enzymet cyklooxygenas och de båda receptorerna för ADP (P2Y1 and P2Y12) inblandade. Sammantaget så visar resultaten att C1q, CRP och TLR:er, som alla medverkar i vårt immunförsvar, också har förmåga att reglera blodplättarnas aktivitet. Dessa rön bidrar till en bättre förståelse av blodplättarnas roll och beteende id inflammation och kan i framtiden leda till utveckling av nya läkemedel för tt reglera blodplättarnas aktivitet vid kroniska inflammatoriska sjukdomar. va
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TABLE OF CONTENTS ABSTRACT............................................................................................................................i POPULÄRVETENSKAPLIG SAMMANFATTNING.................................................... iii TABLE OF CONTENTS.................................................................................................... vi ABBREVIATIONS...............................................................................................................8 LIST OF PAPERS ................................................................................................................9
....on ............................................................................ 11
INTRODUCTION .......................spects of inflammatiecognition receptors ................................................................................ 11
..................................................................................11 General aPattern rPlatelets .................................................................................................................... 12
Biology, structure and function ......................................................................... 12 Platelet granules..............
................................................................................ 16
................................................................................... 13 Platelet receptors ...............
...ction ................................................................................ 17
................................................................................ 14 Platelet‐bacteria interaction
........................................................................................ 17 Platelet‐leukocyte intera
........................................................................................ 18 Neutrophils ......................The complement‐system.Complement protein C1q ........................................................................................ 20
Structure and synthesis ...................................................................................... 20 C1q receptors ..Cellular effects
C‐reactive protein .................................................................................................... 22
.................................................................................................... 21
.................................................................................................... 21
Historical background........................................................................................ 22 Structure, synthesis and ligands ........................................................................ 22 Complement acCellular effects and
Toll‐like receptors ................................................................................................... 25
tivation and regulation by CRP ................................................ 23 role in inflammation .......................................................... 24
Structure, ligands and function ......................................................................... 25 TLR signaling ...................................................................................................... 25 TLR2 .......TLR expres
Fcγ receptors............................................................................................................ 27
............................................................................................................ 26 sion and function in platelets .......................................................... 27
AIMS...................................................................................................................................29 COMMENTS ON METHIsolation of blood cells ............................................................................................ 31
ODS..........................................................................................31
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Platelets (Paper I, II and IV)............................................................................... 31 Neutrophils (Paper II) ................................
ear cells (PaperIV) .....................sorption ........................................................ 32
........................................................ 31 Mononucl
......................................................................... 33
........................................................ 32 Surface methylation and protein adEllipsometry ....................................Platelet adhesion and morphology ........................................................................ 33
Platelet adhesion to coverslips with adsorbed IgG and HSA ............................ 34 Fluorescence microscopy an
te................................................ 35
d image analysis................................................... 34 Enzymatic detection of pla
................................................ 35
let adhesion to collagencoated microplates ..... 35 Phosphatidylserine expression ..............................
roduction ..................................selectin expression................................................ 35
Thromboxane B2 pt
......................... 36 Flow cytome ry analysis of P‐
......................... 36 Soluble P‐selectin............................................................................
.................. secretion ........................ 37
Cytosolic Ca2+ measurements ......................................gometry and dense granule
whole blood .......................................... 38 Light‐transmission aggre
................................................................. 38 Luminol‐dependent ROS‐production in
.....................te formation ................................................................ 38
Whole blood aggregation ..eukocyte aggregablot experiments ...................................................................................... 39
Platelet‐lWestern Statistics ................................................................................................................... 39 SUMMARY OF PAPERS .................................................................................................41 RESULTS & DISCUSSION..............................................................................................43
a‐mediated platelet adhesion 3
Inhibitory effects of C1q and CRP in FcγRII
6 and activation........................................................................................................... 4Adhesion of platelets to ligand‐bound CRP ........................................................... 4
gulates collagen and . 48
C1q induces P‐selectin expression and re
. 51 collagen‐related peptide activation in washed platelets in suspension ............Regulatory effects of C1q in whole blood .............................................................TLR‐2/1‐activation of platelets is mediated by ATP‐dependent Ca2+ increases, ADP receptors and activation of cyclooxygenase ....................... 54 CONCLUSIONS.................................................................................................................57 ACKNOWLEDGEMENTS ...............................................................................................59 REFERENCES ...................................................................................................................63
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ABBREVIATIONS ACD acid‐citrate dextrose solution ADP adenosine diphosphate
sphate n 1q
ATP adenosine triphoC1q complement proteiCOX cyclooxygenase
CRP C‐reactive protein HSA human serum albumin
1 ciated kinase‐1 IgG immunoglobulin G IRAK‐ interleukin‐1 receptor assoKRG Krebs‐Ringers glucose
ex 2 crophage‐activating lipopeptide‐2
MAC membrane attack complived maMALP‐ mycoplasma‐der
MBL mannose binding lectin mCRP monomeric CRP
SK
MyD88 myeloid differentiation factor 88 Pam3C 4 s)triacylated lipopeptide Pam3Cys‐Ser‐(Ly
rn 4
PAMP pathogen associated molecular patter
C lear cells PAR protease activated recepto
nonuc saline
PBM peripheral blood moPBS phosphate bufferedPCh phosphorylcholine
e ‐3‐kinase
PFA paraformaldehydPI3‐K phosphoinositidePKC protein kinase C
PLC phospholipase C PRM pattern recognition molecule
PRP platelet rich plasma PRR pattern recognition receptor
‐1 igand‐1 PS phosphatidylserine
otein lPSGL P‐selectin glycoprROS reactive oxygen species
r r activating peptide
TLR toll‐like receptoP toTRA thrombin recep
e ATXA2 thromboxanXB
2 e BT
2 thromboxan
2
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LIST OF PAPERS This thesis is based on the following Papers, which will be referred to by their roman numerals: I Caroline Skoglund, Jonas Wetterö, Thomas Skogh, Christopher
Sjöwall, Pentti Tengvall and Torbjörn Bengtsson. C‐reactive protein and C1q regulate platelet adhesion and activation on adsorbed immunoglobulin G and albumin. Immunology and Cell Biology 2008; 86: 466474
II Caroline Skoglund, Jonas Wetterö, Pentti Tengvall and Torbjörn Bengtsson. C1q induces a rapid up‐regulation of P‐selectin and modulates collagen‐ and collagen‐related peptide‐triggered activation in human platelets. Immunobiology In Press 2010; doi:10.1016/j.imbio.
2009.11.004
III Caroline Skoglund, Jonas Wetterö and Torbjörn Bengtsson. C1q regulates collagen‐dependent production of reactive oxygen species, formation of platelet‐leukocyte aggregates and levels of
n whole blood. 201
soluble P‐selectin i 0; Manuscript
IV Hanna Kälvegren, Caroline Skoglund, Christian Helldahl, Maria Lerm, Magnus Grenegård and Torbjörn Bengtsson. Toll‐like receptor 2 stimulation of platelets is mediated by purinergic P2X
1‐dependent Ca2+ mobilisation, cyclooxygenase and purinergic P2Y1 and P2Y12 receptor activation. Thrombosis and Haemostasis 2010; 103: 398407
Papers are reprinted with permission from Nature Publishing Group (Paper I), Elsevier (Paper II) and Schattauer (Paper IV)
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INTRODUCTION
General aspects of inflammation The skin and epithelial mucosa constitute a first line of defence in order to protect our bodies from injury and infection. However, if a foreign particle/organism e.g. a bacteria, fungus or virus in some way pass these barriers the inflammatory reaction is crucial in order to uphold our defence against infection and tissue injury [1]. The inflammatory response, described already 5000 years ago by Celcus and Galen, is characterized by the five classical cardinal signs: robur (redness), calor (heat), tumor (swelling), dolor (pain) and finally functio laesa (loss of function) [1, 2]. In the acute inflammatory state, e.g. upon intrusion of a pathogen cells present at the site of infection such as macrophages, and neutrophils recruited from the blood stream, quickly react and try to fight off the infection with the help of the complement system. This process is a part of our innate (unspecific/natural) immunity. Later on, the acquired (specific/adaptive) immunity, mainly involving dendritic cells, T‐cells and antibodies produced from B‐cells responds to the ongoing inflammation. During the whole process, inflammatory mediators such as prostaglandins, leukotriens and cytokines are released. Moreover a systemic acute‐phase response which alters the synthesis of certain proteins, e.g. C‐reactive protein (CRP) and serum‐amyloid A is initiated [1, 3, 4]. Today it is known that an inappropriate or misdirected inflammatory reaction is involved in the onset and progression of many different disorders, such as coronary artery disease and autoimmune diseases.
Pattern recognition receptors Pattern‐recognition molecules (PRMs) or pattern‐recognition receptors (PRRs) as they are denoted when performing as receptors, are molecules involved in innate immunity that recognize foreign structures and initiate an immune‐response. PRMs/PRRs can be cell‐associated, as well as found in the fluid phase, and recognize specific molecular structures known as pathogen associated molecular patterns (PAMPs). Toll‐like receptors (TLRs), CRP and complement protein C1q, are all PRMs/PRRs able to bind to foreign structures. Other PRMs/PRRs include mannose‐binding lectin (MBL), surfactant‐protein A and D (SP‐A and SP‐D), L‐ficolin/P35 (Ficolin‐2) and H‐ficolin (Ficolin‐3). Apart from TLRs, nod‐like receptors (NODs) and retinoic
acid‐inducible gene‐I like receptors (RLRs) and scavenger receptors are cell‐associated PRRs. Several recent reviews describing PRMs/PRRs and their role in innate immunity as well as regulators of adaptive immunity are available [4‐7]. Apart from the traditional inflammatory cells, e.g. neutrophils and macrophages, platelets have emerged as potent actors in inflammation. In the present thesis we have examined the effects and mechanisms of platelet interaction with C1q and CRP and clarified some intracellular events upon TLR‐2/1 activation.
Platelets
Biology, structure and function
Small undefined particles in blood were first observed and described already 1780 by Hewson and later in the middle of the 19in
byMplde
th century also reported several other researches, e.g. Donné, Beale and Zimmermann, [8]. In 1865, ax Schultze was the first to publish a convincing report on the presence of atelets in blood and in 1882 Giulio Bizzozero described platelets in more tail and also started to elucidate their role in hemostasis [9, 10].
B A
Figure 1. A) Differential interference contrast (DIC) microscopy image showing unstimulated isolated blood platelets in suspension. B) Fluorescence microscopy mage showing activated platelets adhered to a protein (fibrinogen) coated
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surface. Scale bars: 10 µm. Platelets are non‐nucleated cell fragments derived from megakaryocytes, most often present in the bone marrow. Since megakaryocytes are able to migrate to other tissues, formation of platelets may also occur in the blood stream and in the lungs [11‐13]. However, the exact mechanism by which platelets are formed is still incompletely understood [11]. Interestingly, it
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was recently shown that exposure of megakaryocytes to high shear rates lead to increased formation of platelets, possibly indicating that platelets produced from megakaryocytes present in the microvasculature is governed by circulatory forces [14]. The resting platelet (Figure 1A) has a discoid shape, an average size of 2 to 5 µm in diameter and a thickness of about 0.5 µm [15]. Non‐activated platelets circulate for 7 to 10 days at a concentration of 150‐400 x 109 cells/L blood before being degraded in the liver or spleen [16]. The main known function of platelets is to participate in haemostasis. If exposed to subendothelial structures (e.g. collagen) in an injured vessel, circulating platelets respond quickly (within seconds), become activated, adhere and start to form a hemostatic plug, with the purpose to form a temporary shield to stop an ongoing bleeding (reviewed in [17, 18]). In order to get a more permanent repair of the injured vessel, the coagulation‐cascade is activated e.g. by negatively charged phosphatidylserine (PS) expressed on the activated platelet and tissue factor present on damaged cells in the vessel wall.
c iActivation of the oagualat on cascade leads to formation of a fibrin network and a more stabile plug [19]. Upon activation platelets change shape, going from discoid to a spread morphology, and increase their size considerably (Figure 1B). Their ability to do so is dependent upon rapid reorganization of the actin‐cytoskeleton [20, 21].
Platelet granules
Apart from their important role in haemostasis, it has become evident that platelets also are active players involved in inflammation and immunity. Platelets contain granules of at least three different types, α‐granules, dense granules and lysosomes. The granules store a variety of substances that are secreted when platelets are activated. Released granule components regulate further platelet activation and recruitment of inflammatory cells. The α‐granules are the most abundant ranging from 40‐100 per platelet [15]. They contain proteins that upon secretion are expressed on the platelet surface e.g. adhesion molecules such as P‐selectin (CD62P) as well as soluble factors that are released into the extracellular space, for example the chemokines CCL5 (RANTES) and CXCL8 (IL‐8). Moreover, they also hold substances involved in growth, angiogenesis and coagulation [22]. It has recently been reported that α‐granules contain 284 different proteins [23] and that the α‐granules are not
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as homogenous as was previously considered. The release of granule contents may be differently regulated depending on the stimulus [24]. Platelets contain almost a 10‐fold fewer dense granules than α‐granules, and these contain e.g. adenine nucleotides (ATP, GTP, ADP and GDP), serotonin, divalent cations (Ca2+, Mg2+) and lysosomal membrane proteins (LAMPs). Lysosomes in platelets contain similar substances as lysosomes in other types of cells e.g. LAMPs, hydrolases and cathepsins [22]. Furthermore, despite not having a nucleus, platelets are indeed capable of synthesizing proteins [25]. The ability of platelets to not only release immunomodulatory mediators such as IL‐1β from pre‐loaded granules but also to synthesize this cytokine further support the importance of platelets in inflammation [26].
Platelet receptors
Platelet adhesion to structures revealed in the subendothelial matix upon vessel injury is crucial in order to prevent blood loss [17]. However, uncontrolled platelet activation may cause fatal complications, such as thrombosis. Thrombus formation in coronary arteries due to rupture of an atherosclerotic plaque may lead to myocardial infarction, which is a major cause of death in the western world [27]. The activity of platelets is mediated and regulated via receptors present on the platelet surface. Platelets express many types of receptors, those that are essential for haemostasis as well as receptors implicated in other activities, e.g. inflammation and antimicrobial defence, reviewed in [17, 28, 29]. The following section highlights some selected platelet receptors, including a few that are highly relevant for the present thesis (ADP‐, ATP‐ and collagen‐receptors). Platelet toll‐like
receptors, C1q receptors and Fcγ‐receptors are further discussed in specific sections below. The vonWillebrand receptor complex (GPIb‐IX‐V) is involved in the initial adhesion of platelets to the injured vessel and belongs to the leucine‐rich repeat family of receptors. GPIb‐IX‐V binds to vonWillebrand factor (vWF) adsorbed from plasma to exposed collagen or endogenous vWF from the endothelium at high shear stress [17, 28, 30]. Firm adhesion of platelets is then initiated due to interaction between platelet integrin α2β1 (GPIa/IIa, originally described as very‐late‐activation antigen VLA‐2) and collagen in the vessel wall. There are around 2000‐4000 α2β1 per platelet [29]. However, there are still some controversies in the current model of α2β1 dependent platelet activation. Initially, it was considered that α2β1 was constitutively expressed on the platelet surface in a high‐affinity state and upon collagen
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ligation interaction with some other receptor resulted in platelet activation [17]. However, Jung and Moroi have shown that the ability of α2β1 to bind soluble collagen increases if platelets are first pre‐stimulated with another agonist [31, 32]. As for many integrins, α2β1 is thus also thought to require a conformational change in order to transform to a high‐affinity state and efficiently bind collagen. However, the complete signaling events (“inside‐out signaling”) leading to this conformational change are insufficiently understood [17]. It has also been suggested that there exist an intermediate form of the α2β1, where collagen may bind without the receptor being in a high‐affinity state [33]. The other collagen receptor on platelets is the immunoglobulin superfamily receptor GPVI. GPVI is non‐covalently associated to the FcR‐γ chain of the FcγRIIa (CD32) receptor and thus coupled to the associated ITAM‐signaling [34, 35]. GPVI‐mediated activation leads to an abundant secretion of granule contents and induces integrin activation [17]. Other receptors involved in platelet adhesion are the
ptor) integrins αvβ3 (vitronectin receptor), α5β1 (fibronectin rece and α6β1(laminin receptor)[29]. Platelet aggregation is dependent upon fibrinogen binding to the αIIbβ3‐integrin (GPIIb/IIIa). This fibrinogen receptor is abundantly expressed with approximately 50000‐80000 receptors per platelet. The main ligand is fibrinogen, however, the receptor also recognizes several other ligands containing an RGD sequence (arginine‐glycine‐aspartic acid), e.g. fibronectin, vWf and thrombospondin. Before ligand‐binding the αIIbβ3‐integrin also requires “inside‐out” signaling leading to a conformational switch exposing the RGD‐binding sequence [17, 27]. Platelets express several receptors belonging to the G‐protein coupled family of receptors (7‐transmembrane receptors) e.g. thrombin receptors (protease‐activated receptors PAR‐1, PAR‐4), thromboxane A2 receptor (TX) and ADP receptors (P2Y1 and P2Y12). Thrombin is formed during the coagulation cascade and binds to PAR‐1 and PAR‐4 leading to a massive platelet activation [36]. PAR activation is unique in that thrombin cleaves the receptor, thus exposing a new N‐terminal that serves as the receptor ligand [37]. Interestingly, other proteases are also able to cleave PARs, inducing activation. For example, proteases from the periodontal pathogen
e 3Porphyromonas gingivalis are shown to activate plat lets in this way [ 8]. Both PARs couple to Gαq and Gα12/13 [29]. ATP is not only released from dense granules upon platelet activation but also from erythrocytes [39]. Platelets express two types of ADP receptors
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P2Y1 and P2Y12 [40, 41]. P2Y1 induces activation via Gαq and P2Y12 is linked to Gαi [27]. By analyzing mRNA levels Wang et al. confirmed the two ADP receptors to be present on platelets, and also found that P2Y12 mRNA levels were higher than levels for P2Y1 [42]. However, P2Y1 is shown to display higher affinity for ADP compared to P2Y12 [43]. The receptor for adenosine triphosphate (ATP) is denoted P2X1 and is also a ligand‐gated calcium channel [44]. Interestingly, when examining mRNA levels at different time points, Wang et al. found markedly reduced levels of P2X1 mRNA over time, whereas the mRNA levels for the ADP receptors remained unchanged or only slightly reduced, indicating that the ATP‐receptor has a much shorter halflife [42]. Both ADP and ATP receptors are important amplifiers of responses provoked by other receptor agonists [45, 46]. They are also easily esensitized, however the mechanism of desensitation is incompletely nderstood [47]. du
Plateletbacteria interaction Direct interaction between platelets and bacteria leading to platelet activation has been reported in several studies in vitro and in vivo, recently reviewed by Fitzgerald et al. [48]. Bacteria‐induced platelet activation may cause serious conditions such as endocarditis [49] and immune thrombocytopenic purpura [50]. In the case of Staphylococcus aureus induced
interest g b et a e tendocarditis, in reports y Nguyen al. [51] nd P erschke e al. [52] show involvement of gC1qR (C1q‐receptor) on the platelet surface. Among the bacterial species known to interact with platelets are Staphylococccus aureus [53], Staphylococccus epidermis [54], Enterococcus spp. [55], Helicobacter pylori [56] and Porphyromonas gingivalis [38]. Moreover, our group have previously shown that Chlamydia pneumoniae, a common respiratory pathogen, binds to platelets and triggers aggregation, P‐selectin expression and lipoxygenase‐dependent production of reactive oxygen species (ROS) [57, 58]. In addition, several species of bacteria are found in atherosclerotic plaques and it is plausible that they are released into the bloodstream during plaque rupture or during angioplasty, thereby activating circulating platelets [59‐61]. However, platelets also possess anti‐bacterial properties as they hold platelet microbicidal proteins (PMPs) including chemokines, platelet factor 4 and fibrinopeptide B, which are released upon platelet activation [48].
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Plateletleukocyte interaction Interaction between platelets and leukocytes and subsequent formation of aggregates is considered to be clinically relevant [62‐64]. The initial interaction involves P‐selectin, that is abundantly expressed on the surface of activated platelets, and its ligand on leukocytes, P‐selectin glycoprotein ligand 1 (PGSL‐1). Blockade of P‐selectin‐PSGL‐1 interaction inhibits IgG mediated platelet‐neutrophil binding and associated ROS‐production [65]. However, several other adhesion mechanisms are also described including firm adhesion accomplished via fibrinogen binding to GPIIb/IIIa on platelets and Mac‐1 (CD11b/CD18) on leukocytes [66] as well as interaction between platelet intracellular adhesion molecule‐2 (ICAM‐2) and CD11a/CD18 (LFA‐1) on neutrophils [67]. Our group and others have reported several cellular consequences upon platelet‐leukocyte interaction e.g. tyrosine phosphorylation and modified production of ROS, chemotaxis and phagocytosis [65, 68‐72].
Neutrophils Neutrophils, discovered by Schultze in the 1860s [73], belong to the polymorphonuclear granulocytes together with basophils and eosinophils. Mature neutrophils are around 10 µm in diameter and are produced daily in a number of 1.6 x 109/ kg bodyweight from stem cells in the red bone marrow. In healthy individuals, neutrophils have a lifespan in circulation of 10 hours before they migrate into surrounding tissues where they survive for 1 to 2 days [74‐76]. The main function of neutrophils is to participate in our defence against invading microbes. Very simplified, neutrophils in the blood stream are captured and activated by molecules and receptors up‐regulated on the endothelium upon tissue injury and infection. Neutrophils then migrate towards the site of inflammation in response to increased concentrations of released pro‐inflammatory molecules (chemotaxis), whereafter they phagocytose and kill intruding microbes. An important part of the microbicidal mechanism in neutrophils is the oxidative burst, leading to formation of ROS. The production of ROS is accomplished via a multicomponent nicotinamide‐adenine‐dinucleotide‐phosphate (NADPH) oxidase enzyme system. Since the NADPH‐oxidase may be located both in the plasma membrane and in membranes of granules/phagosomes ROS‐production may be extracellular as well as intracellular (reviewed in [75, 77]). Recently described, neutrophils may also form microbe‐capturing
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neutrophil extracellular traps (NETs), i.e. extracellular fibers of chromatin and granule proteins [78].
The complementsystem The complement‐system, outlined in Figure 2, is an important defence and clearance system and a major part of our innate immunity. It is comprised of approximately 30 soluble or membrane‐bound proteins and activation of the complement‐cascade is today known to occur via at least three different pathways, the classical pathway, mannose‐binding lectin pathway and alternative pathway [79, 80]. Most proteins in the cascade are named with a “C” followed by a number (the number in the order in which the respective proteins were discovered) and a letter indicating the fragment. Classical pathway activation is initiated upon binding of C1q to antibody (IgG or IgM)‐antigen complexes. Or, alternatively by gram‐negative bacterial walls, viral envelopes, cytoskeletal filaments, myelin or CRP [80]. Together with serine proteases C1r and C1s, C1q forms the C1‐complex that cleaves C4 and C2, leading to generation of the classical C3‐convertase. The mannose‐binding lectin pathway is activated as mannan‐binding protein (MBP) recognizes and binds to carbohydrate structures found on a variety of microorganisms. MBP‐associated serine proteases (MASPs) then form a complex with MBP and cleave C4. The alternative pathway is an important amplification loop that is activated by C3b deposited on surfaces on e.g. pathogens, cells or biomaterials/adsorbed proteins upon activation of classical and MBL‐pathways. Furthermore, there is a constant ongoing hydrolysis (“tickover”) of native C3 in plasma leading to formation of C3b that will react and bind to amino‐ or hydroxyl‐groups on surfaces, if present close enough. Together with factor B and the help of factor D, surface bound C3b forms the alternative‐C3 convertase [79, 80]. Even though the three pathways are initiated differently they all lead to cleavage of C3 and C5 followed by formation of a membrane‐attack‐complex (MAC) responsible for making pores in the membrane of an intruding pathogen, often resulting in lysis. However, classical pathway activation by phosphorylcholine‐bound CRP is an exception, where the cascade is halted at the C3 level (further discussed below) [81]. Moreover, all pathways are tightly regulated by several proteins (e.g properdin, C1‐inhibitor, factor I, factor H and DAF (decay accelerating factor)), especially the more “unspecific” alternative pathway where C3b bound to host cells is quickly inhibited by regulatory proteins [79, 82].
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Figure 2. Schematic illustration of the three different activation pathways of complement. The classical pathway is initiated upon binding of C1q to immunoglobulin G or M, or by phosphorylcholinebound Creactive protein (CRP). Mannosebinding lectin (MBL) recognizes sugar residues (mannose) on intruding pathogens, leading to activation of the cascade. The alternative pathway is initiated by surface binding of C3b. Indifferent of which pathway that serves as initiator, the cascade leads to cleavage of C3, C5, formation of membrane attackcomplex (MAC) and formation of inflammatory mediators. All pathways are tightly regulated by several proteins (in italic) of which properdin is the only known positive regulator.
Classical pathway
Antibody-antigen complexesC-reactive protein
Mannose-binding lectinpathway
Sugar residues
Alternative pathway
Surface of e.g. a bacteriaor a biomaterial
C3-convertasesC3-convertases
MBLMASPsC4C2
C3C3b
C3a
C5-convertasesC5-convertases
C5C5bC6C7C8C9
C5a
C1q C1r C1s
C4
C2
C3b
Factor B
Factor D
Properdin
C5b-9 (MAC)C5b-9 (MAC)
Lysis
Regulators:
C1-INHfactor Ifactor HCR1MCPC4bpDAF
Classical pathway
Antibody-antigen complexesC-reactive protein
Classical pathway
Antibody-antigen complexesC-reactive protein
Mannose-binding lectinpathway
Sugar residues
Mannose-binding lectinpathway
Sugar residues
Alternative pathway
Surface of e.g. a bacteriaor a biomaterial
Alternative pathway
Surface of e.g. a bacteriaor a biomaterial
C3-convertasesC3-convertases
MBLMASPsC4C2
C3C3b
C3aC3C3b
C3a
C5-convertasesC5-convertases
C5C5bC6C7C8C9
C5aC5C5bC6C7C8C9
C5a
C1q C1r C1s
C4
C2
C3b
Factor B
Factor D
Properdin
C5b-9 (MAC)C5b-9 (MAC)
Lysis
Regulators:
C1-INHfactor Ifactor HCR1MCPC4bpDAF
Regulators:
C1-INHfactor Ifactor HCR1MCPC4bpDAF
Several protein fragments formed during cleavage of proteins throughout the cascade do not participate in the subsequent steps of the cascade. These fragments are instead involved in other parts of the inflammatory process, for example C3a and C5a which are called anaphylatoxins and are potent chemotactic substances, and iC3b that is an important opsonin. Many celltypes also express receptors for complement proteins and cleavage products, e.g. complement receptor 1 (CR1, CD35) which binds C3b. Complement is also considered to bridge the innate and the adaptive immune
systems. For example, C3 degradation products (C3d and C3dg) enhances antigen presentation by dendritic cells and the production of antibodies from B‐cells [80].
Complement protein C1q
Structure and synthesis
C1q is the target recognition molecule of the classical pathway, as described above. C1q has a hexameric structure and consists of 18 polypeptide chains (called A, B and C‐chains) with an amino‐terminal collagen‐like region and a carboxyl‐rich terminal globular region [83, 84]. The protein structure has been described as a “bundle of tulips”, schematically shown in Figure 3. The collagenous part of the C1q molecule resembles collagen molecules which are haracterized by repeating sequences with Glycine‐X‐Y, where X and Y often re proline, hydroxyproline or hydroxyllysine residues [84, 85]. ca
20
Structurally, C1q is also closely related to the proteins in a family called collectins (collagen‐like lectins), to which MBP, conglutinin, collectin‐43 and SP‐A, and SP‐D belong. However, in contrast to the collectins, C1q does not have a carbohydrate recognition domain [79]. Whereas most complement proteins are produced in the liver, C1q is continuously synthesized by macrophages and dendritic cells [79, 86, 87] and the production is regulated by e.g. lipopolysaccharide (LPS), interleukin‐6 (IL‐6), interferon‐γ (IFN‐γ) and anti‐inflammatory steroids (dexamethasone and prednisone) [85, 88, 89]. C1q circulates in plasma at concentrations of 80‐180 µg/mL but is also present in tissues [79, 85].
Collagenlike part
Globular
heads
Figure 3. Schematic structure of C1q with the globular heads and the collagenlike stalk.
21
C1q receptors
Many cell types are reported to bind C1q, including endothelial cells [90], monocytes and granulocytes [91], fibroblasts [92], epithelial and smooth muscle cells [93], platelets [94], dendritic cells [95] and lymphocytes [96]. However, the literature regarding receptors responsible for C1q binding is still somewhat inconclusive. For example Steinberger et al. [97] recognized CD93 to be identical to the previously described C1qRp, shown to enhance phagocytosis in monocytes. In contradiction, McGreal et al. [98] have demonstrated that CD93 is indeed equal to C1qRp, however they found that it does not bind C1q. There are also conflicting results regarding the described receptor for the globular heads of the C1q molecule, gC1qR/p33. As reviewed by Ghebrehiwet et al. [99], gC1qR/p33 is expressed on the cell surface leading to cellular responses upon C1q binding. On the other hand, van den Berg et al. [100] did not detect any gC1qR/p33 on the surface of monocytes, neutrophils or Raji cells unless cells were first treated with saponin indicating that gC1qR/p33 is an intracellular protein, and apparently not expressed on the extracellular surface of cells. One receptor that several authors agree on as capable of binding C1q as well as to be present on cell surfaces is the cC1qR (also denoted calreticulin in the literature). cC1qR binds the collagenous part of C1q [94, 101]. Interestingly, Edelson et al. [102] reported that the α2β1‐integrin is a C1q binding receptor on mast cells and ligation with C1q induced mast cell activation and cytokine secretion. Other receptors suggested to bind C1q are CD91 (low‐density lipoprotein receptor‐
related protein 1 or alfa‐2‐macroglobulin receptor) [103] and CD35 (CR1) [104]. Platelets express both gC1qR and cC1qR [94, 105, 106]. In agreement with the findings by van den Berg et al., where gC1qR is found as an intracellular protein, gC1qR‐expression on platelets is shown to be activation dependent [107]. The somewhat controversial CD93 is also present on platelets [108]. Moreover, the α2β1‐integrin is one of the collagen binding receptors on platelets [29]. Receptor‐independent binding of C1q to the platelet surface (via chondroitin sulphate) has also been reported recently [109].
Cellular effects
The most apparent function of C1q is to recognize and mediate clearance of potential harmful pathogens by initiation of the classical complement cascade via binding to antigen‐bound IgG or PCh‐bound CRP. However, several direct cellular effects are also attributed to C1q. For example C1q induces cytokine
22
release from mast cells [102], increases chemotaxis of dendritic cells [95] stimulates IgG production from Staphylococcus aureus activated B‐cells [96] and enhances Fcγ‐receptor mediated phagocytosis in macrophages and monocytes [110]. Direct effects of C1q on platelets include massive P‐selectin expression accompanied with increase in cytosolic inositol‐1,4,5‐triphosphate (IP3) [111], enhancement of aggregation in response to sub‐optimal concentrations of IgG‐aggregates [112], and inhibition of mmunecomplex‐induced aggregation [113, 114]. Moreover, platelet ggregation induced by collagen is inhibited by C1q [115, 116]. ia
Creactive protein
Historical background
C‐reactive protein (CRP) was discovered in 1930 by Tillet and Francis as they studied sera from patients suffering from pneumonia. They found a non‐antibody serum component in sera from acute ill patients that precipitated with a “fraction C” derived from pneumococcus bacteria. When patients recovered, the “C‐reaction” was diminished [117, 118]. Bacterial C‐polysaccharide was later shown to be responsible for the C‐reaction, hence the name C‐reactive protein [118, 119].
Structure, synthesis and ligands
CRP is a part of the evolutionary conserved family of proteins called pentraxins and is together with serum amyloid P (SAP) denoted a short pentraxin, whereas pentraxin 3 is regarded as a long pentraxin. CRP is an acute phase protein, meaning that the plasma concentration increases rapidly (within 48 hours) and potently (up to a 1000 times in the case of CRP) in response to infection and inflammation, and is normalized again as the infection is cleared [4, 120]. The CRP molecule is made up of 5 identical non‐covalently associated 23 kDa subunits that are symmetrically arranged around a central pore [121]. CRP has affinity for phosphorylcholine (PCh), present on microorgansims, damaged cells and oxidized low‐density lipoproteins to which it binds in a Ca2+ dependent manner [122‐124]. On the opposite side of the molecule, CRP displays binding sites for C1q [125] and Fcγ‐receptors [126]. Moreover, CRP is described to bind nuclear antigens [127]. The pentameric CRP molecule may irreversibly dissociate into monomers called mCRP (sometimes also denoted modified CRP or neo‐CRP). Dissociation occurs when CRP encounters an acidic environment and in
23
absence of Ca2+ and also if exposed to high urea concentrations [128, 129]. However, other alternative mechanisms for mCRP generation may certainly be involved in vivo e.g. in the inflammatory environment of an atherosclerotic plaque. Most CRP‐production takes place in the liver in response to IL‐6 [130], but extrahepatic production is also described [3, 131, 132]. Furthermore, regarding the regulation of CRP‐production, Enocsson et al. recently showed that CRP synthesis induced by IL‐6 is inhibited by IFN‐α. Possibly, this is an important clue to why the concentration of CRP is not raised during viral infections or in systemus lupus erythrematosus (SLE) patients, where IFN‐α levels are increased [133]. Indeed, the fact that the plasma level of CRP is not elevated upon a viral infection is used clinically to distinguish between bacterial and viral infections.
Complement activation and regulation by CRP
CRP bound to PCh on microorgansims or damaged cells activates the classical complement cascade via binding to C1q. However, the cascade does not yield much complement activity past the C3 level, indicating that activation is mainly restricted to the first part of the cascade and does not give rise to an abundant MAC formation [81, 134]. The restricted complement activation by CRP is suggested to be due to interaction between CRP and factor H, of which the latter is an important regulator of the alternative pathway. Thus, interaction between factor H and CRP inhibits the amplification loop of the alternative pathway leading to less activation past the C3 level [134‐136]. A binding motif for native CRP on complement factor H‐related protein 4 has also been reported [137]. Recently mCRP was also shown to bind factor H in the fluid‐phase, leading to increased inactivation of C3b [138]. Furthermore, interaction between C4‐binding protein, which is another complement regulatory protein, and CRP has also been described [139]. In addition, our group has previously shown that complement activation at PCh model surfaces is down‐regulated by fluid‐phase interaction between CRP and C1q at high CRP‐levels (>150 mg/mL) [140]. The CRP mediated complement activation leads to sufficient opsonization, but yields no complement induced lysis, suggesting that CRP has both host defence and anti‐inflammatory roles [134].
24
Cellular effects role in inflammation
Elevated levels of CRP have been implicated in conditions with a chronic inflammatory component, such as coronary artery disease. A minor, but still elevated level of CRP is shown to predict cardiovascular and thrombotic events, initially described by Ridker et al. [141] and then confirmed in
tu h d
and
numerous s dies [142, 143]. This as lead to the evelopment of high sensitive‐assays to accurately detect moderate increases in CRP. Apart from mediating complement activation, CRP also affects various cellular responses in many different cell types. Recent reviews summarizing these effects and role the of CRP in inflammation are available [122, 134, 144‐147]. Both pro‐ and anti‐inflammatory effects are described, for example, CRP promotes proliferation of smooth muscle and endothelial cells [148], formation of monocyte‐platelet aggregates [149] as well as inhibits neutrophil ROS‐production and chemotactic response [150, 151]. To further complicate the scenario, native and mCRP elicit different and sometimes opposite responses [152‐154]. Only a few studies have investigated the effect of CRP on platelets. Monomeric CRP is shown to induce an aggregatory response whereas the native CRP molecule does not [155]. On the contrary, enzymatically digested CRP inhibits platelet aggregation [156]. Pentameric CRP binds to immunoglobulin G receptors FcγRIIa (CD32) [157] and FcγRI (CD64) [158] and monomeric but not native CRP is capable of binding to FcγRIII (CD16) [153]. CRP ligation of FcγRs is presumed to have the same effects as the binding of IgG, thus leading to activation upon ligation to the stimulatory FcγRI and FcγRIIa‐receptors and inhibition when binding to FcγRIIIa [122]. CRP interaction with FcγRs is thus considered to contribute to the opsonizing effects of CRP. Indeed, binding of CRP to FcγRIIa results in increased phagocytosis [159]. Despite numerous studies during the past decades, the question is still if CRP is an innocent bystander, a protective olecule, a risk marker and/or an active contributor to the inflammatory rocess. mp
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Tolllike receptors
Structure, ligands and function
Initially, toll‐protein was discovered in the Drosophila fly (fruit fly) where it participates in the protection against fungal infection [160]. Later, a whole family of receptors that resembled the toll‐protein were found in mammals, hence the name toll‐like receptors (TLRs) [6, 161]. In 1998, the findings by Poltorak et al. [162] lead to the conclusion that TLRs serve as recognition molecules and inducers of intracellular signaling. These authors showed that signal transduction was inhibited in mice with a mutation in the TLR‐4 gene, making them resistant to LPS but still sensitive to infection by gram‐negative bacteria. TLRs are expressed in cells participating in the immune response as well as in cells considered as non‐immune, e.g. B‐cells, natural killer (NK) cells, macrophages, dendritic cells, platelets, fibroblasts, endothelial cells and epithelial cells [6]. So far 12 TLRs have been discovered [163]. They are found both on the cell surface (TLR‐1, 2, 4, 5, 6, 11) and as intracellular receptors (TLR‐3, 7, 8, 9) and are responsible for recognizing a diverse range of PAMPs, (Figure 4) thus triggering an inflammatory response. Recognized PAMPs include bacterial cell wall components, LPS, single and double stranded‐RNA and DNA, viral envelope proteins and flagellin [163]. During the past years, TLRs have attracted a lot of interest and several extensive reviews are available [6, 163‐166].
TLR signaling
Upon binding of PAMPs to TLRs, various TIR‐domain containing adaptor‐proteins are recruited i.e. MyD88 (myeloid differentiation factor 88), TIRAP (TIR‐containing adaptor protein), TRIF (TIR‐containing adaptor including IFN‐β) and TRAM (TRIF‐related adaptor protein). Different TLRs recruit one or a combination of adaptors, and the signaling can be divided into MyD88‐dependent and TRIF‐dependent pathways [6, 163]. In the MyD88‐dependent pathway IRAKs (interleukin‐1 receptor‐associated kinases) 1, 2 and 4 are recruited leading to a signal‐cascade including IRAK‐phosphorylation and MAP kinases (mitogen‐activated protein kinase). Finally, transcription factors NFκB (nuclear factor kappa‐light‐chain‐enhancer of activated B cells) and IRFs (interferon regulatory factors) are activated leading to production of inflammatory cytokines, chemokines and interferons [6, 163, 164]. Relevant to the present thesis, C1q (possibly via both gC1qR and cC1qR) was recently shown to down‐regulate TLR‐4 induced production of IL‐12, but not IL‐6 or
TNF [167, 168]. Furthermore, in a study by Fraser et al. [169] C1q and MBL inhibited IL‐1α and IL‐1β, and enhanced IL‐10, IL‐1 receptor antagonist, monocyte chemoattractant protein‐1, and IL‐6 secretion. Additionally, in a recent study by Lood et al. [170], C1q inhibited IFN‐α secretion from immune‐complex, herpes simplex virus and CpG‐DNA stimulated PBMC peripheral blood mononuclear cells) and immune‐complex, CpG‐DNA timulated plasmacytoid dendritic cells. (s
26
TLR-2
TLR-4TLR-2/1 TLR-2/6 TLR-5
TLR-11
HemaglutininPeptidoglycan
LAMospholipomannan
poarabinomannanPorins
Glycosylphosphophatidyl-Inositol Mucin
LPSMannan
GlycoinositolphospholipidsVirial envelope proteins
Triacyl lipopeptides
ZymosanLipoteichoic acid
Diacyl Lipopeptides
Figure 4. Tolllike receptors (TLRs) are expressed on the membrane and intracellularly on a wide range of cells where they recognize conserved microbial molecules, collectively named pathogenassociated molecular patterns (PAMPs). Recognition of PAMPs by TLRs is an important part of the innate immune system. In the present thesis we have investigated the intracellular signaling upon TLR2/1 stimulation of platelets, using a triacylated lipopeptide as ligand.
TLR2
Of all TLRs, TLR‐2 is able to recognize the highest number of PAMPs, e.g. bacterial lipoproteins [171, 172], peptidoglycans [173] whole Chlamydia pneumoniae bacteria [174], and LPS from certain bacteria such as Porphyromonas gingivalis [175]. TLR‐2 forms heterodimers with TLR‐1 or TLR‐6 and the dimerization is crucial for ligand‐binding and further
PhLi
CD36
Flagellin
CD14MD2LBP
Uropathogenic bacteriaProfillin like molecule
TLR-3TLR-9TRL-7 TLR-8
EndosomedsRNAssRNA
CpG-DNAHemozonin
ds-DNA virusesssRNA virus ssRNA virus
TLR-2
TLR-4TLR-2/1 TLR-2/6 TLR-5
TLR-11
HemaglutininPeptidoglycan
LAMospholipomannan
poarabinomannanPorins
Glycosylphosphophatidyl-Inositol Mucin
LPSMannan
GlycoinositolphospholipidsVirial envelope proteins
Triacyl lipopeptides
ZymosanLipoteichoic acid
Diacyl LipopeptidesPhLi
CD36
Flagellin
CD14MD2LBP
Uropathogenic bacteriaProfillin like molecule
TLR-3TLR-9TRL-7 TLR-8
EndosomedsRNAssRNA
CpG-DNAHemozonin
ds-DNA virusesssRNA virus ssRNA virus
TLR-3TLR-9TRL-7 TLR-8
EndosomedsRNAssRNA
CpG-DNAHemozonin
ds-DNA virusesssRNA virus ssRNA virus
27
intracellular signaling [163, 176, 177]. TLR‐2/TLR‐1 recognizes triacylated lipopeptides (e.g. Pam3Cys‐Ser‐(Lys)4, Pam3CSK4), whereas TLR‐2/TLR‐6 binds diacylated lipopeptides (e.g. Mycoplasma‐derived macrophage‐activating lipopeptide 2, MALP‐2) [178]. Furthermore, CD36 is found to be a co‐receptor for TLR‐2/TLR‐6 [179, 180]. CD36 is a scavenger receptor present on platelets, monocytes, adipocytes, hepatocytes and epithelial cells that for example oxidized low density lipoproteins and thrombospondin‐1 [181].
TLR expression and function in platelets
Using flow cytometry, Cognasse et al [182] identified TLR‐2, 4 and 9 on platelets and megakaryocytes and by analysis of mRNA and protein levels, Shiraki et al. [183] also demonstrated TLR‐1 and 6 in platelets. The functional consequences of TLR activation in platelets are at the moment under intense investigation. It has previously been shown that stimulation of TLR‐4 increases platelet adhesion to fibrinogen under flow and that it causes thrombocytopenia in TLR‐4 deficient mice, whereas wild type mice remain unaffected [184]. Activation of TLR‐2/TLR‐6 with the synthetic lipopeptide Pam3CSK4 induces platelet aggregation, secretion and mobilization of Ca2+ in washed platelets [185, 186], however, has no detectable stimulatory effects on platelets in plasma [187].
Fcγ receptors Fcγ receptors recognize the constant part of the immunoglobulin molecule, mediating cellular effects such as immune complex elimination, cytokine production and phagocytosis. At present four types of FcγRs are described, FcγRI (CD64), FcγRII (CD32), FcγRIII (CD16) and FcγRIV. FcγRII and FcγRIII are also further divided into subclasses denoted a and b. All receptors, except for FcγRIIb mediate a cellular activating signal, reviewed in [188‐190]. Platelets express FcγRIIa and ligation induces platelet activation mediated via phospholipase C and increased levels of intracellular free Ca2+ [191].
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29
AIMS The role of platelets in inflammation and immunity is an expanding field of research. The overall aim of this thesis was to investigate the effects of the attern‐recognition molecules/receptors C1q, CRP and TLR‐2/1 on platelet pactivation.
he sp T
ecific aims of the enclosed studies were to:
• elucidate the effects of C1q and C‐reactive protein on platelet adhesion and activation utilizing well‐characterized model surfaces with adsorbed human immunoglobulin G and human serum albumin (Paper I).
• clarify the role of C1q in platelet activation including the involvement
of receptors and intracellular signaling events (Paper II).
• investigate the regulatory role of C1q on collagen‐induced platelet activation on isolated platelets and in whole blood, respectively
(Papers II‐III).
• study the effects of C1q on production of reactive‐oxygen species and
formation of platelet‐leukocyte aggregates in whole blood. (Paper III).
• reveal the intracellular signaling events provoked by toll‐like receptor‐2 stimulation of platelets (Paper VI).
30
31
COMMENTS ON METHODS Fm
or further experimental details and source of chemicals and buffers, see aterials and methods sections of Paper I‐IV, respectively.
Isolation of blood cells The blood used in the present thesis was heparinized whole blood collected from apparently healthy, non‐medicating consenting donors at the blood bank, University Hospital, Linköping, Sweden.
Platelets (P per I, II and IV)
There are several methods available for isolating platelets involving centrifugation [192] and gel filtration [193]. In the present studies platelets were isolated by centrifugation and several washing steps according to the protocol by Bengtsson and Grenegård [194]. To avoid activation during the isolation procedure all buffers were prepared without Ca
a
2+ and only plastic utensils were used. Briefly, 5 parts of whole blood was mixed with 1 part of an acid‐dextrose solution (ACD) pH 4.6 and centrifuged at 220 x g for 20 minutes. Platelet rich plasma (PRP) was collected and centrifuged at 480 x g for 20 minutes. In order to investigate changes in cytosolic Ca2+ (Paper II and IV) platelets in PRP were loaded with 4 µM Fura‐2‐acetoxymethylester (FURA‐2‐AM) during 45 minutes of incubation before centrifugation. Furthermore, in Paper VI, some platelets were isolated in the presence of platelet inhibitors apyrase (0.5 U/ml) and aspirin (100 µM). The platelet pellet was washed three times by careful replacement of the buffer in direct contact with the pellet using Krebs Ringers Phosphate buffer (KRG, pH 7.4). Platelets were then carefully re‐suspended in KRG and the cell count determined using a Bürker chamber. Morphological examination by light microscopy showed that the isolated platelets were solitary and appeared non‐activated. Platelets were diluted in KRG and kept at room temperature for up to 2 hours until experiments. Immediately before each experiment, the extracellular concentration of Ca2+ was restored to 1 mM.
Neutrophils (Paper II)
Neutrophils were isolated according to Böyum and others [195, 196]. In short, whole blood was layered onto Lymphoprep and Polymorphprep and centrifuged at 480 x g for 40 minutes at room temperature. The fraction
32
containing neutrophils was collected and washed in PBS (pH 7.4) at 480 x g for 10 minutes. Any remaining red blood cells were removed by brief hypotonic lysis at 4° C followed by washing in calcium free KRG at 200 x g at 4° C. Isolated neutrophils were counted and kept on ice until experiments.
Mononuclear cells (Paper IV)
Peripheral blood mononuclear cells (PBMCs) were isolated according to Welin et al. [197]. Briefly, whole blood was layered onto Lymphoprep and centrifuged at 480 x g for 40 minutes before washing in calcium free KRG. Prior to Western Blot experiments, isolated PBMCs were lysed in RIPA buffer and any remaining cellular debris was removed by centrifugation at 17500 x g for 10 minutes at 4 °C.
Surface thylation and protein on In Paper I cell‐adhesion experiments were performed on custom made hydrophobic, highly protein adsorptive, glass cover slips. Similarly treated silicon wafers were produced for protein adsorption studies by ellipsometry, a method that require a suitable reflective substratum. Any potential organic and inorganic contaminations were first removed by sequential incubations of wafers and cover slips in a mixture of distilled water and hydrogen peroxide combined with NH
me adsorpti
4OH followed by hydrogen peroxide together with hydrochloric acid, respectively, for 5 minutes at 80°C. After extensive rinsing in distilled water, ethanol and finally xylene, surfaces were methylated (made hydrophobic) by wet silanization (1% (v/v) dichlorodimethylsilane (Cl2(CH3)2Si) in xylene for 5 minutes). Excessive
w r y o ethylasilane as emoved b rinsing in xylene and ethan l and the m ted surfaces were kept in ethanol until experiments within 2 weeks. Prior to adhesion experiments, monolayers of normal human immunoglobulin G (IgG) or human serum albumin (HSA) were spontaneously adsorbed onto the surfaces by incubation with 1 mg/mL protein in PBS, at room temperature for one hour. Previous studies have shown that proteins adsorbed to methylated surfaces are retained at the surfaces upon incubation with blood plasma and cells, with neglible non‐specific bias from cell‐material interactions. Thus, these surfaces are very suitable when studying protein‐protein and protein‐cell interactions [198].
33
Ellipsometry In the 1960s Leo Vroman performed the first ellipsometry studies on plasma protein adsorption onto model surfaces [199]. The use of ellipsometry to detect protein adsorption in biomaterial research is extensively reviewed in [200, 201]. This optical technique is based on changes in polarization‐state and intensity of monochromatic light upon reflection on a surface. When proteins adsorb onto the surface and form an organic film, the ellipsometric angels (∆ and Ψ) become changed. The thickness (d) and refractive index (N) of the protein film can be iterated from these changes (d is often expressed in Ångström) [200]. Compared to more conventional methods used to quantify and identify adsorbed proteins, such as ELISA and RIA, ellipsometry does not require any labelling of proteins or detection antibodies. Ellipsometry is a very convenient and rapid technique that also allows for evaluation of adsorption kinetics. Furthermore, polyclonal antibodies may be used to identify adsorbed proteins [200‐202]. It was also shown in a previous study, that ellipsometric quantification agree well with quantitative RIA [203]. However, the main disadvantages of the method are that monoclonal antibodies are not well suited for ellipsometric measurements and the surfaces need to be flat and optically reflecting without too much light scattering [200]. In Paper I, ellipsometry was used to characterize the adsorption of IgG and HSA onto hydrophobic silicon, and to investigate the monolayer interactions with CRP and C1q. IgG and HSA surfaces were prepared as described above and incubated with C1q and CRP (alone or in combination) in KRG for 3 minutes before rinsing. Total protein deposition was determined and after incubation in antibody solutions (polyclonal anti‐C1q or anti‐CRP for 30 minutes) the absolute amounts of C1q and CRP on the surfaces were determined.
Platelet adhesion and morphology Platelet adhesion, spreading and overall ability to increase the available surface area are crucial events in haemostasis. Several different approaches to study platelet adhesion and the mechanisms involved have been employed over the years, for example microscopic analysis [204, 205], radioisotope‐labelling of adhering platelets [206], measurement of total P‐selectin in lyzed platelets [207] and enzymatic detection [208]. In this thesis, two different setups were used; i) Adhesion to protein coated coverslips combined with
fluorescence‐microscopy and image analysis, and ii) enzymatic detection (acid‐phosphatase) of platelet adhesion to collagen in microtiter wells.
Platelet adhesion to coverslips with adsorbed IgG and HSA
In Paper I, the methylated cover slips with adsorbed IgG or HSA (described above) were deployed in 24‐well plates. Physiological concentrations (80 mg/mL) of isolated C1q and CRP were co‐incubated for 3 minutes before addition to the wells and subjected to another 3‐minute incubation. Isolated platelets (1 x 108 /mL) were added and allowed to adhere for 30 minutes. Supernatants were collected for TXB2 analysis, and adhered platelets were fixed in 4 % paraformaldehyde (PFA) in PBS. In order to visualize adhering platelets and their morphology, cells were permeabilized and stained for F‐actin using lysophosphatidylcholine (100 µg/mL) and bodipy‐phallacidin (0.6 µg/mL).
Fluorescence microscopy and image analysis
The number of platelets adhering to IgG and HSA coated cover slips and their morphology after exposure to C1q and CRP were evaluated using fluorescence microscopy. Platelets on a total of 10 images per treatment were counted and morphologically evaluated using four morphological categories adapted from Allan et al. and Frank et al. [209, 210]. The categories were: A) round or discoid, B) dendritic or early pseudopodial, C) intermediate or late pseudopodial and D) fully spread. Representative images of the different categories are shown in Figure 5. To enable subsequent image analysis, acquisitions were carried out at identical settings. Image analysis was performed with the open source freeware Image J. Color images were converted to black and white images (8‐bit) and by applying a threshold platelet adhesion was then quantified by means of average cellular area of adhering platelets and total area covered by platelets.
34
Figure 5. Morphological cathegories: A) round or discoid,
D C B A
B) dendritic or early pseudopodial, C) intermediate or late pseudopodial, D) fully spread
35
Enzymatic detection of platelet adhesion to collagencoated microplates
In Paper II, the impact of C1q on platelet adhesion to collagen was evaluated using a method previously described by Eriksson and Whiss [211]. In short, wells in a 96‐well plate were coated with collagen by incubation with 0.1 mg/mL bovine collagen over night. Excess protein was removed by washing in physiological saline, before addition of PRP in absence or presence of C1q (80 µg/mL). After 1 hour, non‐adhering cells were removed by washing in saline followed by enzymatic detection of acid‐phosphatase in adherent platelets using p‐nitrophenyl‐phosphate in a citrate buffer. The reaction was topped after 1 hour by addition of NaOH and absorbance was read at 405 m. sn
Phosphatidylserine expression Upon activation and adhesion, platelets express negatively charged phosphatidylserine (PS) on their membrane which may serve as an enhancer of coagulation [212]. In Paper I, expression of PS on the surface of platelets adhering to protein coated cover slips was evaluated. Platelet adhesion experiments were carried out as described above. A commercially available kit comprising annexin‐V‐FITC was used and samples were analysed for PS expression by fluorescence microscopy.
Thromboxane B2 producti nThromboxane B
o 2 (TXB2) is a more stable metabolite of TXA2, a
cyclooxygenase product and a potent potentiator of platelet activation. Using a commercially available ELISA kit, levels of TXB2 were evaluated in supernatants from the adhesion experiments in Paper I, and in Paper IV from latelets in suspension stimulated with a TLR‐2 receptor agonist in presence r absence of several inhibitors. po
Flow cytometry analysis of Pselectin expression P‐selectin is a widely used marker of activated platelets since it is released from α‐granules upon activation [22]. In Paper II, up‐regulation of P‐selectin on the platelet surface was measured with flow cytometry. Isolated platelets were pre‐incubated in a 24‐well plate at 37°C for 5 minutes, in absence or presence of gC1qR and α2β1‐integrin blocking antibodies or a PKC‐inhibitor (GF109203X), before addition of C1q or TRAP. Samples were collected after
36
15‐120 seconds of stimulation. To evaluate the effect of C1q on collagen and collagen‐related peptide induced up‐regulation of P‐selectin, platelets were pre‐incubated with C1q for 5 minutes prior to addition of collagen, collagen‐related peptide or TRAP and samples were taken after 15‐120 seconds. Immunofluorescense staining was performed using an anti‐P‐selectin FITC‐conjugated antibody. Before flow cytometry analysis samples were fixed in 1 % PFA and diluted in PBS. A total of 10000 events were collected in the platelet gate for each sample and data was analysed using the CellQuestPro software.
Soluble Pselectin Previous studies have shown that P‐selectin may be cleaved off from the platelet surface and circulate as soluble P‐selectin in plasma [213]. In Paper III, the levels of soluble P‐selectin were investigated using an ELISA, according to the manufacturer’s instructions. Whole blood was incubated with C1q, Reopro and/or collagen, under stirring conditions at 37°C. Samples were removed after 15 and 45 minutes of incubation and plasma was collected by centrifugation at 1000 x g for 10 minutes.
Cytosolic Ca2+ measurements Ca2+ ions are involved in numerous signal transduction pathways and regulate many cellular processes (for example comprehensively reviewed in [214]). In Paper II and IV, changes in cytosolic Ca2+ concentration in platelets upon C1q or toll‐like receptor stimulation were monitored using the fluorescent ratiometric probe FURA‐2. During the isolation procedure, platelets were loaded with an acetoxymethylester‐derivate of the FURA‐2 molecule (FURA‐2‐AM). FURA‐2‐AM is lipophilic and thus able to pass through the membrane into the cytosol, where the AM‐part is cleaved off by esterases, trapping the rest of the polar and calcium‐sensitive FURA‐2 inside the cell. The use of FURA‐2 and other calcium indicators is reviewed by Paredes et al. [215]. An advantage of the FURA‐2 dye is that it is exited at different wavelengths, depending on if it has Ca2+ bound or not. Thus, the fluorescence emission was registered at 510 nm upon continuous excitation at 340 and 380 nm, respectively. Experiments were carried out in 1.5 mL aliquots of FURA‐2 loaded platelets under constant stirring and at 37°C. Addition of Triton‐X‐100 (0.1%) followed by EGTA (25 mM) revealed the minimal and maximal ratios necessary for calculation of the relative changes
37
and absolute concentrations in free cytosolic Ca2+ with the formula by Grynkiewicz et al. [216]. In Paper IV the release of Ca2+ from intracellular stores was separated from the store‐operated influx of Ca2+ via addition of 0.5 M EGTA prior to stimulation with TLR‐2/‐1 agonist Pam3CSK4.
Lighttransmission aggregometry and dense granule secretion In 1962, G.V. Born was the first to report that aggregation of platelets could be monitored using light‐transmission [217]. Today, this methodology is still one of the most frequently used to study platelet aggregation. Over the years, instruments have been further developed e.g. making it possible to also measure aggregation in whole blood and to combine the aggregation measurements with bioluminescence detection of platelet dense‐granule secretion, measured as ATP release (reviewed in [218]). Furthermore, production of ROS may also be quantified in the very same setup, through luminol‐dependent chemiluminescence [219]. The light‐transmission technique also to some extent allows detection of changes in platelet shape‐change [220]. The method is based on the transmittance of light (infrared), passing through a sample in a cuvette, to a detector. When platelets in PRP or in buffer suspension start to aggregate, e.g. upon stimulation with a receptor agonist, the amount of light that pass the cuvette to the detector is increased. Via calibrating towards plasma without platelets or buffer, the extent of aggregation is quantified, and most often expressed as % aggregation. In order to simultaneously measure dense‐granule secretion a mixture of luciferine/luciferase is added to the sample. Dense granule ATP that is released from platelets upon activation is hydrolyzed as the luciferase enzyme oxidizes the luciferine molecule and light (luminescence) is emitted. By registering the luminescence signal provoked from addition of a fixed dose of external ATP, the absolute concentration of ATP is easily calculated. Detection of aggregation and ATP‐secretion was performed in Paper VI, using a lumi‐aggregometer. Briefly, isolated platelets in KRG supplemented with a luciferin‐luciferase mixture were pre‐incubated at 37 °C at stirring conditions (800rpm), for 5 minutes in presence or absence of antagonist prior to addition of agonist.
38
Platelet leukocyte aggregate formation In Paper II platelet‐neutrophil aggregate formation was investigated using isolated platelets and neutrophils from the same donor. Both cell types were pre‐warmed for 5 minutes in absence or presence of C1q (80 mg/mL) prior to mixing and subsequent stimulation with collagen. Samples were collected after 30‐150 seconds of stimulation and fixed in PFA before analys. The interaction between platelets and leukocytes in whole blood was evaluated in Paper III, where samples from the aggregation (impedance) experiments described above were fixed in PFA, stained for F‐actin using bodipy‐
Luminoldependent ROSproduction in whole blood In Paper III, production of ROS in whole blood was studied using luminol‐dependent chemiluminescence. The technique was described by Allen and Loos in the 70´s [221] and detection of ROS during the respiratory burst from neutrophils using luminol is reviewed in [219]. When luminol comes in contact with ROS it is exited and as the molecule returns to its non‐exited state light (chemiluminescense) is emitted which can be recorded in a luminometer. Luminol is a very sensitive indicator of ROS and also allows for detection of the kinetics of ROS production. However, the chemiluminescense reaction is dependent upon peroxidase [219], and in order to avoid that the amount of peroxidase is a limiting factor, experiments are usually performed in presence of extra horseradish peroxidase. Briefly, ROS‐production was analyzed in the lumi‐aggregometer, combined with the impedance measurements described above. Whole blood was diluted in physiological saline containing luminol (100 mM) and horseradish peroxidase (4 U/mL). Some samples were pre‐incubated with C1q and Reopro before addition of collagen and ROS‐production was monitored for 45 minutes.
Whole blood aggregation In Paper III we used the lumi‐aggregometer to measure aggregation in whole blood induced by collagen in absence or presence of C1q. This was done by inserting platinum‐electrodes into the cuvette with diluted (1:1) whole blood. As the electrodes become coated with aggregating cells (most presumably both platelets and leukocytes), the impedance increases [218]. Thus, calibaration was performed so that a 40 mm change in the original trace, orresponded to a 20 ohm increase in impedance between the two lectrodes. ce
39
phallacidin and for platelet CD42b using an anti‐CD42b RPE‐conjugated antibody. Aggregates in a total of 100 fields of vision were examined and aggregates were classified as small size aggregates (one to three leukocytes with a few bound platelets), medium size aggregates (4‐10 leukocytes with bound platelets) and large size aggregates (more than 10 leukocytes with ound platelets). Furthermore, solitary platelets and leukocytes were ounted. bc
Western blot experiments To investigate the intracellular signaling system associated with TLR‐2 activation of platelets we used western blot to elucidate the role of MyD88 and IRAK‐1. Briefly, isolated platelets were stimulated with Pam3CSK4 (10‐100 µg/mL) for 10 to 600 seconds before lysis upon addition of Laemmli buffer and incubation at 98°C for 5 minutes. Isolated PBMC served as positive contol. Proteins were separated on a SDS‐PAGE (sodium dodecylsulphate‐polyacrylamide) gel and transfered to PVDF membranes using a Mini Trans‐Blot Electrophoresis Transfer Cell. After blocking with dry milk or bovine serum albumin and several washing steps, membranes were incubated with anti‐MyD88 antibody for 1 hour or anti‐IRAK‐1 or anti‐phospho‐IRAK‐1 antibodies over night followed by incubation with a secondary goat anti‐rabbit HRP conjugated antibody for 1 hour. To control for protein loading, an anti‐β‐tubulin antibody was used. Proteins on membranes were visualized sing an acridan‐based chemiluminescence reaction (ECL‐plus) and images ere taken using a CCD‐camera.
uw
Statistics Results are presented as arithmetic averages ± standard error of the means (SEM). The number of individual experiments (individual blood donors) is indicated by n. Statistical significance was evaluated using or one‐way analysis of variance (ANOVA) or Student´s t‐test and paired measurements were used when applicable. All statistical analyses were performed with GraphPad Prism 4.
40
SUMMARY OF PAPERS Paper I Pre‐incubation of C1q and CRP in the fluid phase leads to deposition of both proteins on adsorbed IgG. Surface bound C1q, alone or in combination with CRP, and fluid‐phase CRP inhibits platelet adhesion and activation. The results suggest that C1q and CRP both have the ability to inhibit FcγRIIa‐ mediated platelet activation, especially if combined together.
IgG IgG IgG IgG IgG IgG IgG IgG
Fluid-phase
Reduced platelet adhesion, shape change, PS expression and TXA2 production
Reduced platelet adhesion, shape change andPS expression
IgG IgG IgG IgG IgG IgG IgG IgGIgG IgG IgG IgG IgG IgG IgG IgG
Fluid-phase
Reduced platelet adhesion, shape change, PS expression and TXA2 production
Reduced platelet adhesion, shape change andPS expression
41
Paper II C1q induces a rapid but moderate and transient up‐regulation of P‐selectin mediated via gC1qR and protein kinase C. Further platelet activation induced by collagen and collagen‐related peptideand formation of platelet‐neutrophil aggregates is diminished by C1q.
α2β1
GPVIgC1qR
P-selectin
PKC
Platelet
Neutrophil
Collagen
P-selectin
α
PSGL-1
α
Collagen-relatedpeptide
α2β1
GPVIgC1qR
P-selectin
PKC
Platelet
Neutrophil
Collagen
P-selectin
α
PSGL-1
α
Collagen-relatedpeptide
Platelets
Leukocytes
Collagen
ROS
ROS
Platelets
Leukocytes
Platelets
Leukocytes
Collagen
ROS
ROS
Paper III Incubation of C1q with whole blood inhibits collagen‐induced aggregation, release of soluble P‐selectin and formation of large size platelet‐leukocyte aggregates, whereas the production of ROS is potentiated. Inhibition of the platelet fibrinogen receptor suggests that the effects are platelet‐dependent.
Paper IV TLR‐2/1 stimulation of platelets with Pam3CSK4 induces aggregation and granule secretion via P2X1‐mediated Ca2+ mobilization, production of thromboxane metabolites and ADP receptor activation. TLR‐2/6 agonist MALP‐2 inhibits Pam3CSK4‐induced activation. Moreover, platelets also express MyD88 and IRAK‐1, however, they appear not to be involved in the early signaling events provoked by Pam3CSK4.
42
[Ca2+]i
ATP
P2X1
ADP
P2Y12 P2Y1
TXA2
TLR-2/1
TLR-2/6
Pam3CSK4
MALP-2
-
PI3-
kina
se, P
LC
AggregationSecretion
IRAK-1MyD88
P2X1
COX
Late response?
granule
PLC
ATP
TX
Ca2+
[Ca2+]i
ATP
P2X1
ADP
P2Y12 P2Y1
TXA2
TLR-2/1
TLR-2/6
Pam3CSK4
MALP-2
-
PI3-
kina
se, P
LC
AggregationSecretion
IRAK-1MyD88
P2X1
COX
Late response?
granule
PLC
ATP
TX[Ca2+]i
ATP
P2X1
ADP
P2Y12 P2Y1
TXA2
TLR-2/1
TLR-2/6
Pam3CSK4
MALP-2
-
PI3-
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se, P
LC
AggregationSecretion
IRAK-1MyD88
P2X1
COX
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granule
PLC
ATP
TX
Ca2+
43
RESULTS & DISCUSSION Platelets are well known for their important role in haemostasis, where they are activated, adhere and form aggregates in order to keep up the integrity of an injured vessel. However, we also appreciate that platelet activation is not always entirely beneficial. Thrombotic complications, initiated for example by the rupture of an atherosclerotic plaque, may lead to complications such as myocardial infarction and stroke, resulting in significant suffering, and in the worst case death. Besides the crucial role of platelets in haemostasis and thrombosis, they are also shown to play an active part in immunity. For example, they interact with certain bacteria such as P. gingivalis and C. pneumoniae, express toll‐like receptors (TLRs) and receptors for complement (C1q‐receptors) and immunoglobulin G (FcγRIIa). Furthermore, platelet granules contain numerous inflammatory mediators which are released upon platelet activation. Clearly, platelets are potent cells active in various inflammatory processes and an increased depth in knowledge regarding the mechanisms involved is needed. Thus, the studies included in the present hesis aim to elucidate the effects and mechanisms of C1q and CRP on latelets, and the intracellular signaling induced by TLR‐2/1 activation. tp
Inhibitory effects of C1q and CRP in FcγRIIamediated platelet adhesion and activation Platelet activation may be evaluated by measuring aggregation with a light‐transmission technique or surface expression of activation markers (e.g. P‐selectin) with flow cytometry. These techniques are utilized in Paper II‐IV. In Paper I, we instead set out to use a well characterized model system with adsorbed plasma proteins (IgG and HSA) to study the adhesion and activation of isolated platelets in presence of C1q and/or CRP. Adsorbed IgG is indeed relevant in this case as it may be considered as a large immune complex, previously shown to activate complement, platelets and neutrophils [65, 222‐225]. Adsorbed plasma proteins are also involved in the recognition of non‐self materials and the associated inflammatory reaction, reviewed in [226, 227]. Moreover, immune complexes also play an active part in several clinical disorders with an inflammatory component such as autoimmune diseases, recently reviewed in [228]. Several bacterial species induce platelet aggregation via FcγRIIa, the IgG receptor present on platelets. The aggregation is dependent on co‐stimulation via another receptor, such as
44
GPIIb/IIIa or GP1b [229, 230]. Activation via FcγRIIa induces intracellular signaling mediated via phospholipase C leading to increased levels of Ca2+ [191]. In many experimental setups, the presence of FcγRIIa on the platelet surface therefore makes it difficult to utilize antibodies as blocking tools, as the Fc‐part of the so called “blocking antibody” may instead initiate activation. This is actually the case in Paper II, where the antibodies described to block the gC1qR also initiates a potent Ca2+ response, even when used at relatively low concentrations (>3µg/mL). Despite all the effects described above, the mechanisms and role of FcγRIIa ligataion on platelets are still insufficiently understood. In the adhesion experiments performed in Paper I, C1q and CRP were pre‐incubated for 3 minutes prior to addition to the IgG or HSA coated cover glasses. Protein adsorption was evaluated with ellipsometry and the results showed that C1q binds to the IgG surface, as might be expected, and only a minimal deposition of CRP was detected. However, when C1q and CRP were pre‐incubated both proteins could be detected at the surfaces. Thus, it seems as though C1q facilitates the binding of CRP to adsorbed IgG. Interestingly, C1q and CRP are shown to interact in the fluid‐phase [140, 231]. In a previous study by our group fluid‐phase interaction between C1q and CRP was responsible for down‐regulation of complement activation at high CRP concentrations (above 150 mg/L) [140]. As the concentration used in Paper I
p e (80µg/mL) is physiologically relevant, a fluid‐ has interaction is plausible also in this setup. Platelets were allowed to adhere to the IgG and HSA coated surfaces, in absence or presence of C1q and/or CRP. When analyzing the number of adhering platelets, an inhibitiory effect was seen both by C1q and CRP. The combination of both proteins seemed most effective, inhibiting adhesion by 25% compared to IgG control, although not statistically significant, Table 1. However, since adsorbed IgG is a very potent activation ligand for platelets as ell as other cells [65, 222], even seemingly moderate effects may be of mportance. wi
45
Previous studies have shown that genetic polymorphisms influence the function of FcγRs, leading to differences in for example the amount of IgG that is bound [232, 233]. Such polymorphisms could to some extent explain the quite broad variation among donors in the platelet response to IgG‐coated surfaces. This is in line with the findings by Peerschke and Ghebrehiwet, reporting that the regulatory effects of C1q on immune complex‐induced aggregation are donor dependent [112]. As another activation parameter we classified the adhesion behaviour of platelets according to four different morphological categories, described in detail in the comments on methods section. On an IgG reference surface, most platelets were extensively spread, and exposed numerous pseudopodia. Upon ddition of C1q cells instead showed a much smaller and discoid shape. CRP lone also shifted the morphology towards less spreading, (Figure 6). aa
control C1q CRP C1q + CRP
IgG 4144 ± 826 3641 ± 899 3403 ± 533 3100 ± 445
HSA 3309 ± 823 1847 ± 466 2464 ± 657 1912 ± 522
Hydrophobic 8066 ± 937 4538 ± 1075 6937 ± 781 6552 ± 1351
Table 1. Number of adhering platelets. Number of platelets adhering to IgG or HSA spontaneously adsorbed to a hydrophobic glass surface. Expressed as number of platelets/ mm2 ± SEM.
Morphological distribution of platelets adhering to adsorbed IgG. Platelets were classified into four different categories where I is the least and IV the most spread morphology. The different morphological types are expressed as % of the total number of cells on a total of 10 images per treatment ± SEM.
Figure 6.
pes
I II III IV I II III IV I II III IV I II III IV0
10
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70
control C1q CRP C1qCRP
IgG
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Adhesion of platelets to ligandbound CRP In a previous report from our group, a model surface expressing PCh was developed and used to capture CRP from serum and to characterize the role of CRP in classical complement activation [140]. Briefly, this model surface is comprised of 3 layers of cross linked fibrinogen coupled to PCh bound to keyhole limpet hemocyanin (PCh‐KLH). In addition to the results in Paper I showing inhibitory effects of CRP on platelet adhesion to IgG, we also have unpublished results on the effects on platelet adhesion to ligand‐bound CRP, using the PCh‐KLH surface described above. With ellipsometry we found that
The inhibitory effects were also reflected in the expression of PS, where C1q and CRP, alone or in combination, reduced the PS expression compared to the IgG control. On the other hand, CRP per se did not affect platelet production of TXA2 whereas C1q alone or in combination with CRP reduced the production ith 60% and 84%, respectively, compared to IgG control after 15 minutes of w
incubation. Interaction between platelets and immune complexes and the role of C1q has previously been evaluated in a few studies, although with contradictory results. In a study by Peerschke and Ghebrehiwet [112], C1q enhanced platelet aggregation in response to a dose of aggregated IgG that did not induce a response on its own. The same group have also reported that C1q amplifys the binding of immune complexes to platelets in whole blood [234]. On the other hand, using C1q concentrations similar to those used in Paper I, Sloand et al. [113] and Vollertsen et al. [114] found that C1q inhibits platelet aggregation induced by IgG immune complexes. The effects of CRP on platelets are poorly studied and as far as we know, prior to this study, CRP interaction with C1q has not been evaluated in an experimental model that specifically targets IgG‐mediated stimulation of platelets. However, some studies are published regarding the effects of CRP on platelet aggregation. Enzymatically modified CRP is reported to inhibit platelet aggregation [156]. Since CRP showed inhibitory effects in our study (Paper I), this may suggest that a significant portion of the CRP present in our experimental system is monomeric. Indeed, dissociation of the pentameric CRP molecule is shown to occur at cell membranes [235]. Possibly, dissociation of CRP may also occur upon encountering adsorbed plasma roteins. Yet, in a study by Potempa et al. [155] monomeric CRP instead nduced platelet activation whereas the pentameric CRP had no effects. pi
incubation of a PCh‐expressing surface with pentameric CRP for 2 hours yields an approximately 28 ± 9 Å thick CRP layer on top of the PCh. Addition of platelets to immobilized CRP revealed that ligand‐bound CRP only moderately induces platelet adhesion, as compared to fibrinogen which is a otent adhesive agent. The adhesion pattern was more similar to that on the SA surface. Representative images are shown in Figure 7.
pH
FIB
RIN
OG
ENPC
-KLH
CR
PH
SA
5 min 10 min 30 min
FIB
RIN
OG
ENPC
-KLH
CR
PH
SA
5 min 10 min 30 min
Figure 7. Platelets adhere only moderatly to ligandbound CRP. PChKLH surfaces were prepared as described in Sjöwall et al. [140]. Essentially, 3 layers of cross linked fibrinogen were coupled to phosphorylcholine attached to keyhole limpet hemocyanin (denoted PChKLH). After two hours of incubation with CRP (0.1 mg/mL), surfaces were rinsed and platelets were added and left to adhere for 530 minutes. Nonadhering platelets were then washed off, whereas attached cells were stained for Factin using bodipyhallacidin and visualized using fluorescence microscopy. Representative mages from one of three individual experiments. Scale bars indicate 10 µm. pi
47
48
Albumin is often regarded as biologically “inert” when it comes to platelet adhesion and activation, relative to other surfaces. Yet, on the contrary, platelet adhesion to albumin in vitro may involve RGD‐binding receptors on the platelet, depending on the conformational state of adsorbed albumin [236]. CRP ligation to FcγRs is presumed to account for the opsonizing properties of CRP [122, 145]. The adhesion results presented here are in agreement as they show that ligand bound CRP does not lead to a direct and specific platelet activation via FcγRIIa. Combined with the observations in Paper I, we draw the conclusion that CRP does not induce massive activation of platelets, despite the expression of FcγRIIa on the platelet surface, but instead blocks further FcγRIIa‐mediated platelet activation.
C1q induces Pselectin expression and regulates collagen and collagenrelated peptide activation in washed platelets in s osu pensi n
In Paper I, C1q had even more pronounced inhibitory effects when spontaneously adsorbed to a hydrophobic surface compared to when bound to IgG. Speculatively, the orientation of the C1q molecule is displayed differently, as C1q is known to bind IgG with its globular heads [231], the collagenous part will be more readily available for interactions with other molecules and cells. On a C1q‐coated hydrophobic it is instead likely that both the collagen‐like part and globular heads are exposed for further interaction with platelets. This would enable interaction with any of the C1q receptors previously described on platelets. At present, we do not know the contribution, if any, of the C1q receptors in the inhibitory effects seen in Paper I. To date, several receptors for C1q are reported on platelets e.g. gC1qR, cC1qR and CD93 [106, 108]. Furthermore, the α2β1‐integrin on mast cells binds C1q [102] and α2β1 is one of the collagen binding rece torsexpressed in platelets [29]. In Paper II we investigated the effects of C1q on platelet expression of P‐selectin using flow cytometry. We also evaluated the role of gC1qR, α
p
2β1, intracellular Ca changes and protein kinase C. Furthermore, we studied the regulatory role of C1q in collagen receptor‐mediated activation of platelets and formation of platelet‐neutrophil aggregates. As shown in Figure 8, addition of C1q at a physiological concentration (80 µg/mL) induced a rapid but moderate and transient up‐regulation of P‐selectin. The up‐regulation was dose‐dependent up to 80 µg/mL and seen already 5 seconds after
2+
addition of C1q. A higher concentration of C1q did not yield any additional effects and the increased P‐selectin level was normalized again within 3 to 5 minutes. We speculate that this may be due to shedding of the P‐selectin olecule. Indeed, increased circulating levels of soluble P‐selectin are found n several conditions, such as cardiovascular disease and stroke [213, 237]. mi
contr
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Figure 8. C1q induces a moderate but rapid (A) and dosedependent (B) upregulation of Pselectin on the surface of washed platelets. Platelets were prewarmed for 5 minutes before addition of C1q (80 µg/mL). Samples were taken in duplicates after 5 (insert) to 45 seconds and Pselectin expression as evaluated with flow cytometry. TRAP, known to induce an abundant
a w
49
expression of Pselectin, served s positive control. Peerschke et al. [111] have reported increased P‐selectin expression on platelets stimulated with multimeric/aggregated C1q using fluorescence microscopy. In contradiction to our results, the C1q‐provoked up‐regulation of P‐selectin in their experiments was of a magnitude equal to that induced by thrombin and furthermore, the aggregated C1q used in their study also induced platelet aggregation. This group also found that the expression of P‐selectin was accompanied by a raise in IP3, which releases Ca2+ from intracellular stores via binding to specific receptors [238]. Addition of the C1q used in Paper II to isolated platelets in suspension does not induce an aggregatory response (unpublished results), nor any changes in the level of
50
cytosolic intracellular Ca2+, measured with FURA‐2. However, we found that an inhibitor for protein kinase C (PKC) diminished the C1q‐induced up‐egulation of P‐selectin. PKC is an important mediator participating in the rintracellular response triggered by various agonsists [239]. Next, using antibodies directed towards two different epitopes of the gC1qR (clones 60.11 and 74.5.2) and an anti‐α2β1 antibody (AK7), we confirmed that the up‐regulation of P‐selectin was dependent upon gC1qR whereas the anti‐α2β1 antibody showed no effect. C1q binding to gC1qR has been reported to induce various cellular responses e.g. regulation of monocyte‐derived dendritic cell differentiation and chemotaxis [95, 240] and activation of complement on the platelet membrane [241]. Several bacteria also utilize the C1qR in order to bind to cells and regulate cellular responses e.g. S. aureus gwhich bind to platelets via gC1qR [51, 52]. As one part of the C1q molecule is structurally similar to collagen, we proceeded by evaluating the effects of C1q on collagen‐induced platelet activation. Figure 9 shows that pre‐incubation of platelets with C1q for 5 minutes inhibited a subsequent collagen‐ as well as collagen‐related peptide‐ induced up‐regulation of P‐selectin. This is in agreement with other authors that have reported that C1q may blunt a collagen‐provoked aggregatory response [115, 116]. A novel finding in Paper II is that C1q also modulates the collagen related‐peptide‐induced response, which is GPVI specific [242]. The α2β1‐integrin is considered to be the collagen receptor responsible for platelet adhesion to collagen, whereas GPVI is regarded to mediate activation [29, 243]. Our finding that C1q also regulates GPVI‐triggered activation may shed some light on the effects of C1q on adhesion to collagen in Paper II and in a previous study where C1q does show inhibitory effects on platelet adhesion to collagen [244]. Our study, as well as previous results by Eriksson and Whiss [211, 245] show clearly that platelet adhesion to collagen in the adhesion assay used in Paper II is mediated via α2β1. Thus, the inhibitory effects of C1q on platelet aggregation in suspension previously described [115, 116] may entirely or in part be due to C1q interaction with GPVI and not α2β1. Regardless, the regulatory effects of C1q on collagen‐induced platelet activation are highly interesting since collagen is exposed in the injured vessel wall, recruiting and activating platelets. Our results indicate that C1q is a potent endogenous regulator of this process.
0102030405060708090
100110
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Collagen-related peptideC1q + Collagen-related peptide
15 sec 45 sec 90 sec
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CD
62P
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essi
on (%
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olla
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ptid
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Figure 9. C1q inhibits collagen and collagenrelated peptideinduced platelet activation. Platelets were incubated with C1q (80 µg/mL) for 5 minutes prior to addition of collagen or collagenrelated peptide. Samples were ollected after 15 to 90 seconds and Pselectin expression was analysed with low cytometry. cf The physiological relevance of C1q mediated inhibition was further explored by analysis of platelet‐neutrophil aggregates. Formation of such aggregates is observed in several inflammatory disorders [63]. Moreover, we and others have previously shown the importance of P‐selectin interaction with its ligand PSGL‐1 in the formation of aggregates [63, 65]. In Paper II, platelets incubated with C1q for 5 minutes showed reduced collagen activation ependent binding to neutrophils (isolated from the same donor). This urther strengthens the anti‐inflammatory capacity of C1q. df
51
Regulatory effects of C1q in whole blood In Paper III we continued to study the effects of C1q on collagen‐induced activation in a whole blood experimental setup. In agreement with previous findings by others using washed cells or platelets in PRP [115, 116], C1q dose‐dependently inhibited collagen‐induced aggregation also in whole blood. Blockade of the GPIIb/IIIa receptor with Reopro showed that the whole blood aggregation response was mainly platelet dependent. Furthermore, microscopic analysis showed that collagen‐induced formation
of large‐ and medium‐sized platelet‐leukocyte aggregates was inhibited if the blood was first treated with C1q, Figure 10. This finding is in good agreement with the results in Paper II, indicating that the C1q‐mediated effects are thus ikely physiologically relevant since they are also detectable in a more omplex system such as whole blood. lc
Unstim
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gate
s
Figure 10. C1q regulates the formation of plateletleukocyte aggregates in whole blood upon collagen stimulation. Whole blood incubated with 80 µg/mL C1q for 5 minutes before addition of 2 µg/mL collagen. Cells were stained for Factin and CD42b and plateletleukocyte aggregate formation was evaluated in a fluorescence microscope. A small size aggregate was defined as one to three leukocytes with a few bound platelets, medium size aggregates as 10 leukocytes with bound platelets and large aggregates as more then 10 eukocytes (often indistinguishable from each other) with bound platelets. 4l
52
An interesting finding is that C1q potentiated the production of ROS, measured with luminol‐dependent chemiluminescense (Figure 11), whereas the aggregation was inhibited as described above. Platelet‐neutrophil crosstalk has been shown to increase ROS‐production in several studies, dependent upon both soluble factors and membrane receptors [65, 69, 70]. Furthermore, platelet aggregation is inhibited by scavengers such as catalase
[65]. Thus, in Paper III we speculate that the formation of small aggregates instead of large ones upon pre‐incubation with C1q may lead to facilitated nd more effective cross‐talk between platelets and leukocytes and therefore n increased formation of ROS. aa
53
Figure 11. C1q potentiates ROSproduction in whole blood. The production of ROS was measured for 45 minutes upon collagen stimulation of whole blood, in absence or presence of 80 µg/µL C1q and/or Reopro. A) Time traces of the chemiluminescence response, black trace is collagen control and red trace is C1q + collagen. B) Total ROSproduction during the first 15 minutes of incubation In previous studies, immobilized C1q induces ROS‐production from neutrophils [246, 247]. On the other hand, monomeric C1q does not trigger a respiratory burst on its own, but it increases the ROS‐production from neutrophils in response to aggregated IgG [246]. Since C1q receptors are present on many different celltypes, including leukocytes, the potentiated ROS‐production seen in Paper III may also be due to C1q stimulation of receptors on other cells. However, addition of Reopro showed that the roduction of ROS was platelet dependent, indicating that platelet‐leukocyte nteraction has a crucial role. pi
Control
C1q
Reopro
+ C1q
Reopro
0250050007500
1000012500150001750020000 **
**
Che
mim
ulin
esce
nce
(Tot
al R
OS
prod
uctio
n)
A B
0 10 20 30 400
500
1000
1500
2000
Collagen controlC1q 80 µg/ml
Time (min)
Che
milu
min
esce
nce
(CPM
)
Collagen
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TLR2/1activation of platelets is mediated by ATPdependent Ca2+ increases, ADP receptors and activation of cyclooxygenase Previous investigations from our group have shown that platelets bind and become activated by the respiratory pathogen C. pneumoniae and periodontal bacteria P. gingivalis [58, 248]. Platelet interaction with various species of bacteria has been shown to be of importance in numerous studies, reviewed in [48, 249]. Platelets express several TLRs, which recognize conserved molecular patterns present on pathogens [182, 183]). In Paper VI we have investigated the mechanisms of platelet activation upon TLR‐2‐stimulation.
T in TLR‐2 forms heterodimers with TLR‐1 or LR‐6, and are the present study activated by the lipopeptide Pam3CSK4 and MALP‐2, respectively. By measuring aggregation and secretion we found that ligation of TLR‐2/1 leads to a dose‐dependent platelet aggregation accompanied by dense granule secretion. This is in agreement with previous findings by Berg et al. [186] and Blair et al. [250]. However, in a study by Ward et al. Pam3CSK4 failed to induce aggregation in PRP [187], possibly indicating the presence of inhibitory factor(s) in plasma. Utilizing several inhibitors of platelet receptors and proteins involved in intracellular signaling, we found that the aggregation was dependent upon both ADP receptors P2Y1 and P2Y12 as well as the ATP receptor P2X1. Moreover, the Pam3CSK4 induced aggregation was inhibited by aspirin, U73122 and BAPT‐AM indicating important roles for cyclooxygenase (COX) metabolites (e.g TXA2), phospholipase C (PLC) and cytosolic free Ca2+, respectively. Since the calcium chelator BAPT‐AM showed significant inhibitory effects, we next evaluated changes in intracellular free Ca2+ after Pam3CSK4‐stimulation of FURA‐2 loaded platelets. TLR‐2/1‐stimulation gave rise to a massive increase in the level of intracellular free Ca2+. However, as for many of the receptors and mediators discussed in previous sections, there are conflicting results also in the published reports on the ability of Pam3CSK4 to induce changes in intracellular Ca2+ [186, 187]. In harmony with aggregation experiments, we found that the Ca2+ increase was sensitive to blockade of COX, PLC and P2X1, however inhibitors towards P2Y1 and P2Y12 were without effect. Moreover, the Pam3CSK4‐induced Ca2+ increase was PI3‐kinase dependent. In correlation, Blair et al [250] have reported that Pam3 SKC ‐4induced activation is associated with increased PI3‐kinase activity. In accordance with the inhibitory effects by aspirin, we found that Pam
3CSK4 induces formation of TXA2. This response was also sensitive to the ATP‐
receptor antagonist, whereas the ADP receptor antagonists were without effects. Table 2 summarizes the effects of the signal transduction inhibitors on the different parameters assayed in Paper VI. Table 2. The effect of receptor antagonists and signal transduction inhibitors on Pam3CSK4 induced platelet activation.
Aggregation Secr ion et Intracellular Ca2+ TXA2 production Aspirin (COX‐inhibitor) X X X X Cangrelor (P2Y12‐antagonist) X X O O MRS2179 (P2Y1‐antagonist) X X O O MRS215 t) 9 (P2X is1‐antagon X X X X U73122 (PLC‐inhibitor) X n.d X n.d BAPTAM (Ca chelator) 2+ X n .d n .d X LY2940 itor) 2 (PI3‐kinase inhib n .d n .d X n .dMALP2 (TLR2/6 agonist) X X X X
55
The TLR‐2/6 agonist MALP‐2 did not stimulate platelet activation. However, an interesting finding is that pre‐incubation of platelets with MALP‐2 dose‐dependently diminished the Pam3CSK4‐induced response. We propose that ALP‐2 competes with Pam
X indicates inhibition O indicates no inhibition n.d denotes not determined
3CSK4 in the binding to TLR‐2, thus impeding the Mformation of TLR‐2/1 dimers As described in the introduction, TLR‐stimulation often leads to cytokine release via activation of the adaptor protein MyD88 and IRAKs. In TLR‐2‐ mediated signaling, MyD88 recruits IRAK‐4 which leads to phosphorylation of IRAK‐1 [163, 164]. During our studies in identifying MyD88 in platelets, the article by Zang et al. [251] was published, showing platelet expression of MyD88. In Paper IV, we demonstrate using Western blot that platelets in addition express IRAK‐1. However, IRAK‐1 was not phosphorylated upon Pam3CSK4‐stimulation indicating that the early signaling response from TLR‐2/1 in platelets is MyD88‐independent. We speculate that TLR‐2/1‐ activation in later phases of the signaling transduction machinery engages the MyD88 pathway leading to protein translation, cytokine release and an inflammatory response in platelets.
56
57
CONCLUSIONS The general conclusion from the present thesis is that C1q and CRP are able o regulate platelet activation. Furthermore, TLR‐2/1‐activation of platelets is ependent upon purinergic receptor activation and cyclooxygenase activity. td
ore s M pecifically we have found that:
•
C1q facilitates the binding of CRP to adsorbed IgG.
• Physiological concentrations of C1q and CRP, in combination or alone, inhibit FcγRIIa‐mediated platelet adhesion and spreading. C1q in absence or presence of CRP also inhibits the formation of TXA2.
• C1q induces a rapid and dose‐dependent but moderate and transient Ca
2+‐independent up‐regulation of P‐selectin that is sensitive to blockade of gC1qR and PKC, but not to blockade of α2β1.
• C1q inhibits collagen‐ and collagen‐related peptide‐induced P‐selectin expression, as well as collagen‐provoked formation of platelet‐
neutrophil aggregates.
• C1q inhibits aggregation in whole blood and formation of platelet‐leukocyte aggregates, and potentiates the production of ROS, all in a
platelet‐dependent manner.
• TLR‐2/1‐activation of platelets is mediated via P2X
1‐dependent increase in intracellular free Ca2+, P2Y1 and P2Y12‐receptors and
genase activation of cyclooxy .
• TLR‐2/6‐stimulation per se does not yield platelet activation but it
inhibits subsequent TLR‐2/1‐induced platelet activation.
• Platelets express IRAK‐1, however TLR‐2/1 ligation does not lead to a rapid phosphorylation of IRAK‐1.
58
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ACKNOWLEDGEMENTS Jag har många att tack för att avhandlingen na u är tryckt. Ett STORT tack till: Torbjörn Bengtsson, min huvudhandledare, för att du gav mig chansen att börja forska, för ditt stöd och engagemang under doktorandtiden och för allt du lärt mig om forskning och undervisning. Din goda egenskap, att lyfta fram det positiva, kan verkligen vända en vid första anblicken usel dag på labbet till något bra, vilket ger ny energi att kämpa vidare! Tack också för alla ikastunder där vi avhandlat allt från försöksplanering till bilproblem och enaste OS‐result ten. fs a Jonas Wetterö, min biträdande handledare, för att du är den mest omtänksamma och hjälpsamma handledare man som doktorand kan ha. Inget r för stort eller för smått, du är verkligen en god förebild och mentor. oreover, tack fö att du lärt mig hitta i kulve
äM r rten, det är balett! Pentti Tengvall, min biträdande handledare, för att du entusiastiskt tagit dig id för mina frågor och kommit med goda synpunkter som hjälpt mig framåt. ack också för ditt arbete med strategiområdet Material i Medicin. tT essutom vill jag tacka de som på ett eller annat sätt varit inblandade i mitt rojekt och som med under min tid soDp funnits m doktorand, TACK: homas Skogh och Christopher Sjöwall för alla CRP‐möten, givande amarbete, god hjälp aTs och gl da hejarop! agnus Grenegård, som lärt mig mycket om undervisning och forskning ch om hur man b
M(o äst och snabbast denaturerar protein). gneta Askendal för ovärderling hjälp i labbet på IFM, för alla trevliga A
samtal och ”tjänstekakor”. mina nuvarande som ”gamla” doktorandkollegor som delat dalar och toppar med mig, AnnCharlotte Svensson Holm, Therese Eriksson, Anna Asplund Persson, Peter Garvin, Louise Levander, Ida Bergström, Simon Jönsson,
60
JMohanna Lönn, Sofia Pettersson, Helena Enocsson, Paula Linderbäck, artina Nylander.
anna Kälvegren, handledare, arbetskamrat, samarbetspartner och god vän. ack för att du drar med mig på upptåg på östgötska landsbHT ygden! Peter Gunnarsson och Andreas ”the mentor” Eriksson för att ni lärt mig allt jag kan om ultimate fighting….. Tack Peter för trevliga fikastunder och diskussioner kring trombocyter, filmer och allt möjligt annat. Tack Andreas för kloka råd om em mina skor. statistik och för att du fraktar h Liza Ljungberg, en mästare i tapetsering och Hanna Björck, festfixare och rt director, för att ni tog med mig på storstadsäventyr när jag som mest ehövde en paus! ab lla medarbetare vid avdelningen, speciellt tack till Anita Thunberg, du är
lippa! aen k alla studenter, examensarbetare och stipendiater som funnits på labbet ör en kortare eller längre tid. Speciellt tack till Christian Helldahl för din
‐arbetet. fgedigna insats med TLR ina kontorskamrater Iréne Rydberg och Ingrid Hurtig för att vi har så revligt på vå ntor! mt
rt ko
Kajsa Uvda Natalia Abrikossoval och för vårt goda samarbete.
blodgivare och personal på blodtappen som alla bidragit till min forskning.
Forskarskolan Forum Scientium med Stefan Klintstöm i spetsen. Tack också till mina vänner utanför labbet, Veronica, Peter & Nils som bjuder på goda middagar, många skratt och trevligt sällskap. Cicci & Lotta, mycket goda vänner, även om vi ses allt för llan! Sarah, trots att vi inte träffas lika ofta numera så känns det ändå som m det var igår, när vi väl ses! sä
o
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Sist men igen in verkl te minst, ett STORT tack till min familj: Mamma och Pappa som givit mig de allra bästa av förutsättningar och som lltid ser till att jag har det bra. Mina syskon Peter och Josefine, tack för att i är doman ni är.
ormo du är b M r, eundransvärd. När jag blir stor vill jag bli som du! isbeth, Anders och Hans för att ni får mig att känna att jag är en del av er amilj!Lf
allt. eter, för att du finns vid min sida, det betyder mest av en här boken är både ”en slutarbit” och ”en börjarbit”.
PD Finansiärerna av denna avhandling är:
Materials in Medicine (MiM) och flammation Centre (CIRC)
StrategiområdenaCardiovascular Research InVetenskapsrådet Landstinget i Östergötland Hjärt‐Lungfonden Fonden för forskning utan djurförsök Trygg Hansas forskningsfond Svenska sällskapet för Medicinsk forskning tiftelserna Goljes minne, Lars Hiertas minne, anna Svartz, Magnus Bergvall and Eleonora Demoroutis
SN
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REFERENCES
1. Janeway, C.A., Jr., Travers, P., Walport, M., and Shlomchik, M., J., ogy. The immune system in health and disease. 6th ed. 2005, arland Science Publishing.
ImmunobiolNew York: G
2. Rather, L.J., Disturbance of function (functio laesa): the legendary fifth alen to the four cardinal signs of . 303‐22.
cardinal sign of inflammation, added by GCelsus. Bull N Y Acad Med, 1971. 47(3): p
3. Calabro, P., Willerson, J.T., and Yeh, E.T., Inflammatory cytokines stimulated ry smooth muscle cells. Creactive protein production by human coronary arte
Circulation, 2003. 108(16): p. 1930‐2. 4. Bottazzi, B., Doni, A., Garlanda, C., and Mantovani, A., An Integrated View of
traxins as a Paradigm. Annu Rev Immunol, Humoral Innate Immunity: Pen2009. 28: p. 157‐83.
rn recognition receptors and control of 21‐33.
5. Palm, N.W. and Medzhitov, R., Patteadaptive immunity. Immunol Rev, 2009. 227(1): p. 2
Pathogen recognition in the innate 0(1): p. 1‐16.
6. Kumar, H., Kawai, T., and Akira, S., immune response. Biochem J, 2009. 42
n, G.K., Innate immune signals in atherosclerosis. 5‐24.
7. Lundberg, A.M. and HanssoClin Immunol, 2010. 134(1): p.
he discovery of platelets and their function. 8. Gazzaniga, V. and Ottini, L., TVesalius VII, 2001. 1: p. 22‐26.
Crivellato, E., Giulio Bizzozero and the discovery of platelets. 9. Ribatti, D. andLeuk Res, 2007. 31(10): p. 1339‐41.
65), G. Bizzozero (1882) and the discovery of 10. Brewer, D.B., Max Schultze (18the platelet. Br J Haematol, 2006. 133(3): p. 251‐8.
11. Italiano, J.E. and Hartwig, J.H., Megacaryocyte Development and Platelet sevier Science. p. 23‐Function, in Platelets, A.D. Michelson, Editor. 2007, El
44. 12. Kaufman, R.M., Airo, R., Pollack, S., and Crosby, W.H., Circulating
let release in the lung. Blood, 1965. 26(6): p. 720‐megakaryocytes and plate31.
13. Behnke, O. and Forer, A., From megakaryocytes to platelets: platelet morphogenesis takes place in the bloodstream. Eur J Haematol Suppl, 1998. 61: p. 3‐23.
14. Dunois‐Larde, C., Capron, C., Fichelson, S., Bauer, T., Cramer‐Borde, E., and Exposure of humaBaruch, D., n megakaryocytes to high shear rates
accelerates platelet production. Blood, 2009. 114(9): p. 1875‐83. t Structure, in Platelet .D. Michelson, Editor. 2007, 15. White, J.G., Platele s, A
Elsevier Science. p. 45‐74. 16. Cramer, A.D.A.E., Production of platelets, in Platelets in thrombotic and non
thrombotic disorders, C.P.P. Cresele, V. Fuster, and J. Vermylen, Editors. 2002, Cambridge University Press: Cambridge. p. 25.
64
17. Varga‐Szabo, echanisms inplatelets. Arterioscler ‐12.
lexity of platelet aggregation. Blood, 2007
D., Pleines, I., and Nieswandt, B., Cell adhesion m Thromb Vasc Biol, 2008. 28(3): p. 403
18. Jackson, S.P., The growing comp .109(12): p. 5087‐95.
take to make the perfect clot? : p. 41‐8.
19. Monroe, D.M. and Hoffman, M., What does itArterioscler Thromb Vasc Biol, 2006. 26(1)
20. Escolar, G., Krumwiede, M., and White, J.G., Organization of the actin esting and activated platelets in suspension. Am J Pathol, cytoskeleton of r
1986. 123(1): p. 86‐94. V.T., Cytoskeleton uman p ing. J
2. 21. Nachmias, of h latelets at rest and after spread
Cell Biol, 1980. 86(3): p. 795‐80, 22. Reed, G.L., Platelet Secretion, in Platelets, A.D. Michelson, Editor. 2007
Elsevier Science. p. 309‐318. 23. Maynard, D.M., Heijnen, H.F., Horne, M.K., White, J.G., and Gahl, W.A.,
Proteomic analysis of platelet alphagranules using mass spectrometry. J Thromb Haemost, 2007. 5(9): p. 1945‐55.
24. Italiano, J.E., Jr., Richardson, J.L., Patel‐Hett, S., Battinelli, E., Zaslavsky, A., Short, S., Ryeom, S., Folkman, J., and Klement, G.L., Angiogenesis is regulated by a novel mechanism: pro and antiangiogenic proteins are organized into
ially released. Blood, 2008. separate platelet alpha granules and different111(3): p. 1227‐33.
n 25. Warshaw, A.L., Laster, L., and Shulman, N.R., Protein synthesis by humaplatelets. J Biol Chem, 1967. 242(9): p. 2094‐7.
26. Lindemann, S., Tolley, N.D., Dixon, D.A., McIntyre, T.M., Prescott, S.M., Zimmerman, G.A., and Weyrich, A.S., Activated platelets mediate
ignaling by regulated interleukin 1be ol, inflammatory s ta synthesis. J Cell Bi2001. 154(3): p. 485‐90.
rothrombosis. Am J Cardiol, 2009. 27. Jennings, L.K., Role of platelets in athe103(3 Suppl): p. 4A‐10A.
esion mechanism platelet 28. Ruggeri, Z.M. and Mendolicchio, G.L., Adh s in function. Circ Res, 2007. 100(12): p. 1673‐85.
t receptors, in Platelets, A.D. 7‐144.
29. Clementson, K., J. and Clementson, J., M., PlateleMichelson, Editor. 2007, Elsevier Science. p. 11
30. Savage, B., Almus‐Jacobs, F., and Ruggeri, Z.M., Specific synergy of multiple ctions in platelet thrombus formation under flow. 66.
substratereceptor interaCell, 1998. 94(5): p. 657‐
31. Jung, S.M. and Moroi, M., Signaltransducing mechanisms involved in receptor integrin alpha(2)beta(1). J Biol
8016‐26. activation of the platelet collagenChem, 2000. 275(11): p.
32. Jung, S.M. and Moroi, M., Platelet collagen receptor integrin alpha2beta1 activation involves differential participation of ADPreceptor subtypes P2Y1 and P2Y12 but not intracellular calcium change. Eur J Biochem, 2001. 268(12): p. 3513‐22.
33. Van de Walle, G.R., Vanhoorelbeke, K., Majer, Z., Illyes, E., Baert, J., Pareyn, I., and Deckmyn, H., Two functional active conformations of the integrin
65
{alpha}2{beta}1, depending Chem, 2005. 280(44): p. 36873‐82.
gnalling in platelets: 1998. 19(6): p. 260‐4.
on activation condition and cell type. J Biol
34. Watson, S.P. and Gibbins, J., Collagen receptor siextending the role of the ITAM. Immunol Today,
35. Tsuji, M., Ezumi, Y., Arai, M., and Takayama, H., A novel association of Fc receptor gammachain with glycoprotein VI and their coexpression as a
‐collagen receptor in human platelets. J Biol Chem, 1997. 272(38): p. 2352831.
36. Kahn, M.L., Nakanishi‐Matsui, M., Shapiro, M.J., Ishihara, H., and Coughlin, vation of human 9‐87.
S.R., Proteaseactivated receptors 1 and 4 mediate actiplatelets by thrombin. J Clin Invest, 1999. 103(6): p. 87
37. Vu, T.K., Hung, D.T., Wheaton, V.I., and Coughlin, S.R., Molecular cloning of a functional thrombin receptor reveals a novel proteolytic mechanism of receptor activation. Cell, 1991. 64(6): p. 1057‐68.
38. Lourbakos, A., Yuan, Y.P., Jenkins, A.L., Travis, J., Andrade‐Gordon, P., Santulli, R., Potempa, J., and Pike, R.N., Activation of proteaseactivated receptors by gingipains from Porphyromonas gingivalis leads to platelet
icity. Blood, 2001. 97(12): p. aggregation: a new trait in microbial pathogen3790‐7.
39. Gonzalez‐Alonso, J., Olsen, D.B., and Saltin, B., Erythrocyte and the regulation of human skeletal muscle blood flow and oxygen delivery: role of circulating ATP. Circ Res, 2002. 91(11): p. 1046‐55.
40. Daniel, J.L., Dangelmaier, C., Jin, J., Ashby, B., Smith, J.B., and Kunapuli, S.P., Molecular basis for ADPinduced platelet activation. I. Evidence for three
ceptors on human platelets. J Biol Chem, 1998. 273(4): p. distinct ADP re2024‐9.
41. Kunapuli, S.P., Multiple P2 receptor subtypes on platelets: a new 1‐interpretation of their function. Trends Pharmacol Sci, 1998. 19(10): p. 39
4. 42. Wang, L., Östberg, O., Wihlborg, A.K., Brogren, H., Jern, S., and Erlinge, D.,
Quantification of ADP and ATP receptor expression in human platelets. J Thromb Haemost, 2003. 1(2): p. 330‐6.
43. Takasaki, J., Kamohara, M., Saito, T., Matsumoto, M., Matsumoto, S., Ohishi, T., Soga, T., Matsushime, H., and Furuichi, K., Molecular cloning of the
n with another (3): p. 432‐9.
platelet P2T(AC) ADP receptor: pharmacological comparisoADP receptor, the P2Y(1) receptor. Mol Pharmacol, 2001. 60
44. Mahaut‐Smith, M.P., Ennion, S.J., Rolf, M.G., and Evans, R.J., ADP is not an agonist at P2X(1) receptors: evidence for separate receptors stimulated by ATP and ADP on human platelets. Br J Pharmacol, 2000. 131(1): p. 108‐14.
45. Grenegård, M., Vretenbrant‐Öberg, K., Nylander, M., Desilets, S., Lindström, E.G., Larsson, A., Ramström, I., Ramström, S., and Lindahl, T.L., The ATPgated P2X1 receptor plays a pivotal role in activation of aspirintreated platelets by thrombin and epinephrine. J Biol Chem, 2008. 283(27): p. 18493‐504.
66
46. Storey, R.F., Newby, L.J., and Heptinstall, S., Effects of P2Y(1) and P2Y(12) gonists on platelet aggregation induce receptor anta d by different agonists in
human whole blood. Platelets, 2001. 12(7): p. 443‐7. in Platelets, A.D. Michelson, Editor. 47. Cattaneo, M., The Platelet P2 Receptors,
2007, Elsevier Science. p. 201‐220. 48. Fitzgerald, J.R., Foster, T.J., and Cox, D., The interaction of bacterial
pathogens with platelets. Nat Rev Microbiol, 2006. 4(6): p. 445‐57. 49. Fowler, V.G., Jr., Sanders, L.L., Kong, L.K., McClelland, R.S., Gottlieb, G.S., Li, J.,
Ryan, T., Sexton, D.J., Roussakis, G., Harrell, L.J., and Corey, G.R., Infective occus aureus: 59 prospectively identified cases endocarditis due to Staphyloc
with followup. Clin Infect Dis, 1999. 28(1): p. 106‐14. nfection and immune ter, 2004. 9(4): p. 342‐6.
50. Franchini, M. and Veneri, D., Helicobacter pylori ithrombocytopenic purpura: an update. Helicobac
51. Nguyen, T., Ghebrehiwet, B., and Peerschke, E.I., Staphylococcus aureus protein A recognizes platelet gC1qR/p33: a novel mechanism for
0. 68(4): p. staphylococcal interactions with platelets. Infect Immun, 2002061‐8.
52. Peerschke, E.I., Bayer, A.S., Ghebrehiwet, B., and Xiong, Y.Q., gC1qR/p33 blockade reduces Staphylococcus aureus colonization of target tissues in an
‐animal model of infective endocarditis. Infect Immun, 2006. 74(8): p. 441823.
53. Hawiger, J., Steckley, S., Hammond, D., Cheng, C., Timmons, S., Glick, A.D., and Des Prez, R.M., Staphylococciinduced human platelet injury mediated by protein A and immunoglobulin G Fc fragment receptor. J Clin Invest, 1979. 64(4): p. 931‐7.
54. Usui, Y., Ohshima, Y., Ichiman, Y., Ohtomo, T., Suganuma, M., and Yoshida, species of coagulaseK., Platelet aggregation induced by strains of various
negative staphylococci. Microbiol Immunol, 1991. 35(1): p. 15‐26. n by 55. Usui, Y., Ichiman, Y., Suganuma, M., and Yoshida, K., Platelet aggregatio
strains of enterococci. Microbiol Immunol, 1991. 35(11): p. 933‐42. 56. Byrne, M.F., Kerrigan, S.W., Corcoran, P.A., Atherton, J.C., Murray, F.E.,
Fitzgerald, D.J., and Cox, D.M., Helicobacter pylori binds von Willebrand factor and interacts with GPIb to induce platelet aggregation. Gastroenterology, 2003. 124(7): p. 1846‐54.
57. Kälvegren, H., Bylin, H., Leanderson, P., Richter, A., Grenegård, M., and Bengtsson, T., Chlamydia pneumoniae induces nitric oxide synthase and lipoxygenasedependent production of reactive oxygen species in platelets.
s. Thromb Haemost, 2005. Effects on oxidation of low density lipoprotein94(2): p. 327‐35.
58. Kälvegren, H., Majeed, M., and Bengtsson, T., Chlamydia pneumoniae binds to platelets and triggers Pselectin expression and aggregation: a causal role in cardiovascular disease? Arterioscler Thromb Vasc Biol, 2003. 23(9): p. 1677‐83.
59. Kälvegren, H., Fridfeldt, J., Garvin, P., Wind, L., Leanderson, P., Kristenson, M., Kihlstrom, E., Bengtsson, T., and Richter, A., Correlation between rises in
67
Chlamydia pneumoniaespecific antibodies, platelet activation and lipid onary intervention. Eur J Clin Microbiol peroxidation after percutaneous cor
Infect Dis, 2008. 27(7): p. 503‐11. 60. Shor, A., Kuo, C.C., and Patton, D.L., Detection of Chlamydia pneumoniae in
2. coronary arterial fatty streaks and atheromatous plaques. S Afr Med J, 19982(3): p. 158‐61.
61. Gaetti‐Jardim, E., Jr., Marcelino, S.L., Feitosa, A.C., Romito, G.A., and Avila‐Campos, M.J., Quantitative detection of periodontopathic bacteria in
2009. 58(Pt atherosclerotic plaques from coronary arteries. J Med Microbiol, 12): p. 1568‐75.
62. Ståhl, A.L., Sartz, L., Nelsson, A., Bekassy, Z.D., and Karpman, D., Shiga toxin and lipopolysaccharide induce plateletleukocyte aggregates and tissue
S factor release, a thrombotic mechanism in hemolytic uremic syndrome. PLoOne, 2009. 4(9): p. e6990.
63. May, A.E., Langer, H., Seizer, P., Bigalke, B., Lindemann, S., and Gawaz, M., Plateletleukocyte interactions in inflammation and atherothrombosis. Semin Thromb Hemost, 2007. 33(2): p. 123‐7.
64. Irving, P.M., Macey, M.G., Shah, U., Webb, L., Langmead, L., and Rampton, ates in inflammatory bowel . 361‐72.
D.S., Formation of plateletleukocyte aggregdisease. Inflamm Bowel Dis, 2004. 10(4): p
65. Wetterö, J., Tengvall, P., and Bengtsson, T., Platelets stimulated by IgGate neutrophils through a selectindependent 24(9): p. 1559‐73.
coated surfaces bind and activpathway. Biomaterials, 2003.
66. Weber, C. and Springer, T.A., Neutrophil accumulation on activated, surfaceadherent platelets in flow is mediated by interaction of Mac1 with
ting fibrinogen bound to alphaIIbbeta3 and stimulated by plateletactivafactor. J Clin Invest, 1997. 100(8): p. 2085‐93.
67. Diacovo, T.G., deFougerolles, A.R., Bainton, D.F., and Springer, T.A., A functional integrin ligand on the surface of platelets: intercellular adhesion
molecule2. J Clin Invest, 1994. 94(3): p. 1243‐51. 68. Evangelista, V., Manarini, S., Sideri, R., Rotondo, S., Martelli, N., Piccoli, A.,
Totani, L., Piccardoni, P., Vestweber, D., de Gaetano, G., and Cerletti, C., Platelet/polymorphonuclear leukocyte interaction: Pselectin triggers
dependent CD11b/CD18 adhesion: role of proteintyrosine phosphorylationPSGL1 as a signaling molecule. Blood, 1999. 93(3): p. 876‐85.
69. Bengtsson, T. and Grenegård, M., Leucocyte activation by collagen(6): p. stimulated platelets in whole blood. Scand J Clin Lab Invest, 2002. 62
451‐61. 70. Li, N., Hu, H., Lindqvist, M., Wikstrom‐Jonsson, E., Goodall, A.H., and
terioscler Hjemdahl, P., Plateletleukocyte cross talk in whole blood. ArThromb Vasc Biol, 2000. 20(12): p. 2702‐8.
71. Bengtsson, T., Zalavary, S., Stendahl, O., and Grenegård, M., Release of oxygen metabolites from chemoattractantstimulated neutrophils is inhibited by resting platelets: role of extracellular adenosine and actin polymerization. Blood, 1996. 87(10): p. 4411‐23.
68
72. Zalavary, S., Grenegård, M., Stendahl, O., and Bengtsson, T., Platelets enhance Fc(gamma) receptormediated phagocytosis and respiratory burst
: the role of purinergic modulation and actin polymerization. J in neutrophilsLeukoc Biol, 1996. 60(1): p. 58‐68.
hagocytosing leucocytes: 73. Brewer, D.B., Max Schultze and the living, moving, p1865. Med Hist, 1994. 38(1): p. 91‐101.
introbe, M.M., The Kinetics of 24: p. 780‐803.
74. Cartwright, G.E., Athens, J.W., and WGranulopoiesis in Normal Man. Blood, 1964.
ocytes: neutrophils and 75. Dale, D.C., Boxer, L., and Liles, W.C., The phagmonocytes. Blood, 2008. 112(4): p. 935‐45.
76. Bainton, D.F., Ullyot, J.L., and Farquhar, M.G., The development of ymorphonuclear leukocytes in human bone marrow. J Exp neutrophilic pol
Med, 1971. 134(4): p. 907‐34. 77. Nauseef, W.M., How human neutrophils kill and degrade microbes: an
integrated view. Immunol Rev, 2007. 219: p. 88‐102. 78. Brinkmann, V., Reichard, U., Goosmann, C., Fauler, B., Uhlemann, Y., Weiss,
linsky, A., Ne5663): p. 15
D.S., Weinrauch, Y., and Zych utrophil extracellular traps kill bacteria. Science, 2004. 303( 32‐5.
ent. 2 ed. 1995: Oxford University 79. Law, S.K.A. and Ried, K.B.M., ComplemPress.
The role of the complement system in . 33(2): p. 103‐12.
80. Rus, H., Cudrici, C., and Niculescu, F., innate immunity. Immunol Res, 2005
81. Berman, S., Gewurz, H., and Mold, C., Binding of Creactive protein to is. J Immunol, nucleated cells leads to complement activation without cytolys
1986. 136(4): p. 1354‐9. 82. Kang, Y.H., Tan, L.A., Carroll, M.V., Gentle, M.E., and Sim, R.B., Target pattern
classical and alternative recognition by complement proteins of thepathways. Adv Exp Med Biol, 2009. 653: p. 117‐28.
lickstein, L.B., C1qbinding proteins and C1q nol, 1999. 11(1): p. 42‐6.
83. Nicholson‐Weller, A. and Kreceptors. Curr Opin Immu
84. Reid, K.B. and Porter, R.R., Subunit composition and structure of J, subcomponent C1q of the first component of human complement. Biochem
1976. 155(1): p. 19‐23. 85. Lu, J.H., Teh, B.K., Wang, L., Wang, Y.N., Tan, Y.S., Lai, M.C., and Reid, K.B.,
ity. The classical and regulatory functions of C1q in immunity and autoimmunCell Mol Immunol, 2008. 5(1): p. 9‐21.
86. Schwaeble, W., Schafer, M.K., Petry, F., Fink, T., Knebel, D., Weihe, E., and Loos, M., Follicular dendritic cells, interdigitating cells, and cells of the monocytemacrophage lineage are the C1qproducing sources in the spleen.
ybridization and 95. 155(10): p. 4971‐8.
Identification of specific cell types by in situ himmunohistochemical analysis. J Immunol, 19
87. Muller, W., Hanauske‐Abel, H., and Loos, M., Biosynthesis of the first component of complement by human and guinea pig peritoneal macrophages: evidence for an independent production of the C1 subunits. J Immunol, 1978. 121(4): p. 1578‐84.
69
88. Armbrust, T., Nordmann, B., Kreissig, M., and Ramadori, G., C1Q synthesis by tissue mononuclear phagocytes from normal and from damaged rat liver: up
dexamethasone, downregulation by interferon gamma, and aride. Hep
regulation by lipopolysacch atology, 1997. 26(1): p. 98‐106.
THP: p. 197‐21
89. Walker, D.G., Expression and regulation of complement C1q by human1derived macrophages. Mol Chem Neuropathol, 1998. 34(2‐3) 8.
90. Andrews, B.S., Shadforth, M., Cunningham, P., and Davis, J.S.t., face of human endothelial cells. J Demonstration of a C1q receptor on the sur
Immunol, 1981. 127(3): p. 1075‐80. 91. Bobak, D.A., Frank, M.M., and Tenner, A.J., Characterization of C1q receptor
: effects of PDBu and fMLP. J Immunol, expression on human phagocytic cells1986. 136(12): p. 4604‐10.
92. Bordin, S., Kolb, W.P., and Page, R.C., C1Q receptors on cultured human 1983. 130(4): gingival fibroblasts: analysis of binding properties. J Immunol,
p. 1871‐5. 93. Bordin, S., Smith, M., Ghebrehiwet, B., Oda, D., and Page, R.C., Smooth muscle
nding sites for the C1q component of 51‐7.
and epithelial cells express specific bicomplement. Clin Immunol Immunopathol, 1992. 63(1): p.
elets possess specific ‐41.
94. Peerschke, E.I. and Ghebrehiwet, B., Human blood platbinding sites for C1q. J Immunol, 1987. 138(5): p. 1537
95. Vegh, Z., Kew, R.R., Gruber, B.L., and Ghebrehiwet, B., Chemotaxis of human ed
monocytederived dendritic cells to complement component C1q is mediatby the receptors gC1qR and cC1qR. Mol Immunol, 2006. 43(9): p. 1402‐7.
96. Young, K.R., Jr., Ambrus, J.L., Jr., Malbran, A., Fauci, A.S., and Tenner, A.J., Complement subcomponent C1q stimulates Ig production by human B lymphocytes. J Immunol, 1991. 146(10): p. 3356‐64.
97. Steinberger, P., Szekeres, A., Wille, S., Stockl, J., Selenko, N., Prager, E., Staffler, G., Madic, O., Stockinger, H., and Knapp, W., Identification of human
J Leukoc CD93 as the phagocytic C1q receptor (C1qRp) by expression cloning.Biol, 2002. 71(1): p. 133‐40.
98. McGreal, E.P., Ikewaki, N., Akatsu, H., Morgan, B.P., and Gasque, P., Human ind C1q. J C1qRp is identical with CD93 and the mNI11 antigen but does not b
Immunol, 2002. 168(10): p. 5222‐32. 99. Ghebrehiwet, B., Lim, B.L., Kumar, R., Feng, X., and Peerschke, E.I., gC1q
R/p33, a member of a new class of multifunctional and multicompartmental cellular proteins, is involved in inflammation and infection. Immunol Rev, 2001. 180: p. 65‐77.
100. van den Berg, R.H., Prins, F., Faber‐Krol, M.C., Lynch, N.J., Schwaeble, W., ular localization of the human receptor unol, 1997. 158(8): p. 3909‐16.
van Es, L.A., and Daha, M.R., Intracellfor the globular domains of C1q. J Imm
101. Ghebrehiwet, B. and Peerschke, E.I., cC1qR (calreticulin) and gC1qR/p33: ubiquitously expressed multiligand binding cellular proteins involved in inflammation and infection. Mol Immunol, 2004. 41(2‐3): p. 173‐83.
70
102. Edelson, B.T., Stricker, T.P., Li, Z., Dickeson, S.K., Shepherd, V.L., Santoro, S.A., and Zutter, M.M., Novel collectin/C1q receptor mediates mast cell activation and innate immunity. Blood, 2006. 107(1): p. 143‐50.
103. Ogden, C.A., deCathelineau, A., Hoffmann, P.R., Bratton, D., Ghebrehiwet, B., Fadok, V.A., and Henson, P.M., C1q and mannose binding lectin engagement
of cell surface calreticulin and CD91 initiates macropinocytosis and uptake ofapoptotic cells. J Exp Med, 2001. 194(6): p. 781‐95.
104. Klickstein, L.B., Barbashov, S.F., Liu, T., Jack, R.M., and Nicholson‐Weller, A., 35) is a receptor for C1q. Immunity, Complement receptor type 1 (CR1, CD
1997. 7(3): p. 345‐55. Platelet membrane receptors for the ematol, 1994. 31(4): p. 320‐8.
105. Peerschke, E.I. and Ghebrehiwet, B., complement component C1q. Semin H
106. Peerschke, E.I. and Ghebrehiwet, B., Platelet receptors for the complement ombosis. component C1q: implications for hemostasis and thr
Immunobiology, 1998. 199(2): p. 239‐49. 107. Peerschke, E.I., Murphy, T.K., and Ghebrehiwet, B., Activationdependent
human blood platelets. Thromb surface expression of gC1qR/p33 on Haemost, 2003. 89(2): p. 331‐9.
108. Nepomuceno, R.R. and Tenner, A.J., C1qRP, the C1q receptor that enhances phagocytosis, is detected specifically in human cells of myeloid lineage, endothelial cells, and platelets. J Immunol, 1998. 160(4): p. 1929‐35.
109. Hamad, O.A., Ekdahl, K.N., Nilsson, P.H., Andersson, J., Magotti, P., Lambris, J.D., and Nilsson, B., Complement activation triggered by chondroitin sulfate
mb Haemost, 2008. released by thrombin receptoractivated platelets. J Thro6(8): p. 1413‐21.
110. Bobak, D.A., Gaither, T.A., Frank, M.M., and Tenner, A.J., Modulation of FcR function by complement: subcomponent C1q enhances the phagocytosis of
culturederived ‐6.
IgGopsonized targets by human monocytes and macrophages. J Immunol, 1987. 138(4): p. 1150
111. Peerschke, E.I., Reid, K.B., and Ghebrehiwet, B., Platelet activation by C1q results in the induction of alpha IIb/beta 3 integrins (GPIIbIIIa) and the
lant activity. J Exp Med, 1993. 178(2): expression of Pselectin and procoagup. 579‐87.
let activation in . 5594‐8.
112. Peerschke, E.I. and Ghebrehiwet, B., C1q augments plateresponse to aggregated Ig. J Immunol, 1997. 159(11): p
113. Sloand, J.A., Mehta, R.L., Schmer, G., and Rosenfeld, S.I., Influence of C1q on h human platelets. Clin 4.
the interaction of model immune complexes witImmunol Immunopathol, 1995. 76(2): p. 127‐3
114. Vollertsen, R.S., McDuffie, F.C., and Bowie, E.J., Interaction of human platelets with particleadherent aggregated IgG: description of the experimental system and role of C1q and monomeric IgG. Clin Exp Immunol, 1983. 52(2): p. 423‐9.
115. Cazenave, J.P., Assimeh, S.N., Painter, R.H., Pachham, M.A., and Mustard, J.F., Clq inhibition of the interaction of collagen with human platelets. J Immunol, 1976. 116(1): p. 162‐3.
71
116. Csako, G. and Suba, E.A., A phaggregation: inhibition by Cl emost, 1981. 45(2): p. 110‐5.
117. Tillet, W.S. and Francis, T.J., Serological reactions in pneumonia with nontic fraction of pneumococcus. J Exp Med, 19
ysiologic regulator of collageninduced platelet q. Thromb Ha
protein soma 30. 52(4): p. 561‐571.
Creactive protein. Ann N Y Acad Sci, 118. McCarty, M., Historical perspective on1982. 389: p. 1‐10.
ific and NonSpecific Polysaccharides 31. 53(5): p. 625‐639.
119. Heidelberger, M. and Kendall, F.E., Specof Type Iv Pneumococcus. J Exp Med, 19
120. Kushner, I., Broder, M.L., and Karp, D., Control of the acute phase response. J Clin Serum Creactive protein kinetics after acute myocardial infarction.
Invest, 1978. 61(2): p. 235‐42. 121. Shrive, A.K., Cheetham, G.M., Holden, D., Myles, D.A., Turnell, W.G.,
Volanakis, J.E., Pepys, M.B., Bloomer, A.C., and Greenhough, T.J., Three ive protein. Nat Struct Biol, 1996. dimensional structure of human Creact
3(4): p. 346‐54. , T.W., Creactive protein: ligands, receptors 122. Marnell, L., Mold, C., and Du Clos
and role in inflammation. Clin Immunol, 2005. 117(2): p. 104‐11. 123. Volanakis, J.E. and Kaplan, M.H., Specificity of Creactive protein for choline
c Soc Exp Biol phosphate residues of pneumococcal Cpolysaccharide. ProMed, 1971. 136(2): p. 612‐4.
124. Chang, M.K., Binder, C.J., Torzewski, M., and Witztum, J.L., Creactive protein binds to both oxidized LDL and apoptotic cells through recognition of a
e of oxidized phospholipids. Proc Natl Acad ‐8.
common ligand: PhosphorylcholinSci U S A, 2002. 99(20): p. 13043
125. Volanakis, J.E. and Kaplan, M.H., Interaction of Creactive protein complexes with the complement system. II. Consumption of guinea pig complement by
(1): p. 9‐CRP complexes: requirement for human C1q. J Immunol, 1974. 11317.
126. Crowell, R.E., Du Clos, T.W., Montoya, G., Heaphy, E., and Mold, C., Creactive e U937. Evidence for 91. 147(10): p. 3445‐51.
protein receptors on the human monocytic cell linadditional binding to Fc gamma RI. J Immunol, 19
127. Robey, F.A., Jones, K.D., Tanaka, T., and Liu, T.Y., Binding of Creactive gical protein to chromatin and nucleosome core particles. A possible physiolo
role of Creactive protein. J Biol Chem, 1984. 259(11): p. 7311‐6. 128. Potempa, L.A., Siegel, J.N., Fiedel, B.A., Potempa, R.T., and Gewurz, H.,
Expression, detection and assay of a neoantigen (NeoCRP) associated with a 4(5): p. 531‐free, human Creactive protein subunit. Mol Immunol, 1987. 2
41. 129. Rees, R.F., Gewurz, H., Siegel, J.N., Coon, J., and Potempa, L.A., Expression of a
rabbit liver and muscle. Creactive protein neoantigen (neoCRP) in inflamedClin Immunol Immunopathol, 1988. 48(1): p. 95‐107.
130. Hurlimann, J., Thorbecke, G.J., and Hochwald, G.M., The liver as the site of Creactive protein formation. J Exp Med, 1966. 123(2): p. 365‐78.
72
131. Wilson, A.M., Swan, J.D., Ding, H., Zhang, Y., Whitbourn, R.J., Gurry, J., Yii, M., Wilson, A.C., Hill, M., Triggle, C., Best, J.D., and Jenkins, A.J., Widespread vascular production of Creactive protein (CRP) and a relationship between
d intimal hypertrophy. Atherosclerosis, 2007. serum CRP, plaque CRP an191(1): p. 175‐81.
132. Kuta, A.E. and Baum, L.L., Creactive protein is produced by a small number (1): p. of normal human peripheral blood lymphocytes. J Exp Med, 1986. 164
321‐6. 133. Enocsson, H., Sjöwall, C., Skogh, T., Eloranta, M.L., Rönnblom, L., and
Wetterö, J., Interferonalpha mediates suppression of Creactive protein: response in lupus flares? Arthritis explanation for muted Creactive protein
Rheum, 2009. 60(12): p. 3755‐60. ation 134. Mold, C., Gewurz, H., and Du Clos, T.W., Regulation of complement activ
by Creactive protein. Immunopharmacology, 1999. 42(1‐3): p. 23‐30. 135. Giannakis, E., Jokiranta, T.S., Male, D.A., Ranganathan, S., Ormsby, R.J.,
Fischetti, V.A., Mold, C., and Gordon, D.L., A common site within factor H SCR tococcal M 7 responsible for binding heparin, Creactive protein and strep
protein. Eur J Immunol, 2003. 33(4): p. 962‐9. 136. Jarva, H., Jokiranta, T.S., Hellwage, J., Zipfel, P.F., and Meri, S., Regulation of
complement activation by Creactive protein: targeting the complement inhibitory activity of factor H by an interaction with short consensus repeat domains 7 and 811. J Immunol, 1999. 163(7): p. 3957‐62.
137. Mihlan, M., Hebecker, M., Dahse, H.M., Halbich, S., Huber‐Lang, M., Dahse, R., Zipfel, P.F., and Jozsi, M., Human complement factor Hrelated protein 4
protein to necrotic cells. Mol binds and recruits native pentameric CreactiveImmunol, 2009. 46(3): p. 335‐44.
138. Mihlan, M., Stippa, S., Jozsi, M., and Zipfel, P.F., Monomeric CRP contributes to complement control in fluid phase and on cellular surfaces and increases
p. 1630‐phagocytosis by recruiting factor H. Cell Death Differ, 2009. 16(12):40.
139. Sjöberg, A.P., Trouw, L.A., McGrath, F.D., Hack, C.E., and Blom, A.M., Regulation of complement activation by Creactive protein: targeting of the inhibitory activity of C4bbinding protein. J Immunol, 2006. 176(12): p. 7612‐20.
140. Sjöwall, C., Wetterö, J., Bengtsson, T., Askendal, A., Almroth, G., Skogh, T., and Tengvall, P., Solidphase classical complement activation by Creactive protein (CRP) is inhibited by fluidphase CRPC1q interaction. Biochem Biophys Res Commun, 2007. 352(1): p. 251‐8.
141. Ridker, P.M., Cushman, M., Stampfer, M.J., Tracy, R.P., and Hennekens, C.H., Inflammation, aspirin, and the risk of cardiovascular disease in apparently healthy men. N Engl J Med, 1997. 336(14): p. 973‐9.
142. Curb, J.D., Abbott, R.D., Rodriguez, B.L., Sakkinen, P., Popper, J.S., Yano, K., and Tracy, R.P., Creactive protein and the future risk of thromboembolic stroke in healthy men. Circulation, 2003. 107(15): p. 2016‐20.
73
143. Blake, G.J., Rifai, N., Buring, J.E., and Ridker, P.M., Blood pressure, Creactive ardiovascular events. Circulation, 2003. 108(24): protein, and risk of future c
p. 2993‐9. 144. Sjöwall, C. and Wetterö, J., Pathogenic implications for autoantibodies
ive protein and other acute phase proteins. Clin Chim Acta, against Creact2007. 378(1‐2): p. 13‐23.
ctive protein: expression, structure, and function. ): p. 189‐97.
145. Volanakis, J.E., Human CreaMol Immunol, 2001. 38(2‐3
146. Du Clos, T.W. and Mold, C., Creactive protein: an activator of innate d a modulator o 4. immunity an f adaptive immunity. Immunol Res, 200
30(3): p. 261‐77. 147. Agrawal, A., CRP after 2004. Mol Immunol, 2005. 42(8): p. 927‐30. 148. Cirillo, P., Golino, P., Calabro, P., Cali, G., Ragni, M., De Rosa, S., Cimmino, G.,
Pacileo, M., De Palma, R., Forte, L., Gargiulo, A., Corigliano, F.G., Angri, V., Spagnuolo, R., Nitsch, L., and Chiariello, M., Creactive protein induces tissue factor expression and promotes smooth muscle and endothelial cell proliferation. Cardiovasc Res, 2005. 68(1): p. 47‐55.
149. Danenberg, H.D., Kantak, N., Grad, E., Swaminathan, R.V., Lotan, C., and Edelman, E.R., Creactive protein promotes monocyteplatelet aggregation: an additional link to the inflammatorythrombotic intricacy. Eur J Haematol, 2007. 78(3): p. 246‐52.
150. Zhong, W., Zen, Q., Tebo, J., Schlottmann, K., Coggeshall, M., and Mortensen, R.F., Effect of human Creactive protein on chemokine and chemotactic
taxis and signaling. J Immunol, 1998. factorinduced neutrophil chemo161(5): p. 2533‐40.
ion of phagocytic leukocyte activities 0. 67(4): p. 495‐500.
151. Mortensen, R.F. and Zhong, W., Regulatby Creactive protein. J Leukoc Biol, 200
152. Devaraj, S., Venugopal, S., and Jialal, I., Native pentameric Creactive protein displays more potent proatherogenic activities in human aortic endothelial
(1): p. 48‐cells than modified Creactive protein. Atherosclerosis, 2006. 18452.
153. Heuertz, R.M., Schneider, G.P., Potempa, L.A., and Webster, R.O., Native and on human neutrophils. modified Creactive protein bind different receptors
Int J Biochem Cell Biol, 2005. 37(2): p. 320‐35. 154. Khreiss, T., Jozsef, L., Potempa, L.A., and Filep, J.G., Opposing effects of C
reactive protein isoforms on shearinduced neutrophilplatelet adhesion and 713‐neutrophil aggregation in whole blood. Circulation, 2004. 110(17): p. 2
20. 155. Potempa, L.A., Zeller, J.M., Fiedel, B.A., Kinoshita, C.M., and Gewurz, H.,
Stimulation of human neutrophils, monocytes, and platelets by modified Cssing a neoantigenic specificity. Inflammation, reactive protein (CRP) expre
1988. 12(4): p. 391‐405. 156. Fiedel, B.A. and Gewurz, H., Cleaved forms of Creactive protein are
associated with platelet inhibition. J Immunol, 1986. 136(7): p. 2551‐5.
74
157. Bharadwaj, D., Stein, M.P., Volzer, M., Mold, C., and Du Clos, T.W., The major receptor for Creactive protein on leukocytes is fcgamma receptor II. J Exp
Med, 1999. 190(4): p. 585‐90. 158. Marnell, L.L., Mold, C., Volzer, M.A., Burlingame, R.W., and Du Clos, T.W., C
unol, reactive protein binds to Fc gamma RI in transfected COS cells. J Imm1995. 155(4): p. 2185‐93.
159. Bodman‐Smith, K.B., Gregory, R.E., Harrison, P.T., and Raynes, J.G., and FcgammaRIIa expression with FcgammaRI results in Creactive protein
IgGmediated phagocytosis. J Leukoc Biol, 2004. 75(6): p. 1029‐35. 160. Lemaitre, B., Nicolas, E., Michaut, L., Reichhart, J.M., and Hoffmann, J.A., The
ontrols the 86(6): p. 973‐83.
dorsoventral regulatory gene cassette spatzle/Toll/cactus cpotent antifungal response in Drosophila adults. Cell, 1996.
161. Medzhitov, R., Preston‐Hurlburt, P., and Janeway, C.A., Jr., A human homologue of the Drosophila Toll protein signals activation of adaptive immunity. Nature, 1997. 388(6640): p. 394‐7.
162. Poltorak, A., He, X., Smirnova, I., Liu, M.Y., Van Huffel, C., Du, X., Birdwell, D., Alejos, E., Silva, M., Galanos, C., Freudenberg, M., Ricciardi‐Castagnoli, P., Layton, B., and Beutler, B., Defective LPS signaling in C3H/HeJ and
lr4 gene. Science, 1998. 282(5396): p. C57BL/10ScCr mice: mutations in T2085‐8.
ke receptors and innate immunity. 163. Kumar, H., Kawai, T., and Akira, S., TollliBiochem Biophys Res Commun, 2009. 388(4): p. 621‐5.
, K., Role of adapters in Toll164. Akira, S., Yamamoto, M., and Takeda like receptor signalling. Biochem Soc Trans, 2003. 31(Pt 3): p. 637‐42.
edzhitov, R., Innate immune recognition. Annu Rev 97‐216.
165. Janeway, C.A., Jr. and MImmunol, 2002. 20: p. 1
166. Lee, M.S. and Kim, Y.J., Signaling pathways downstream of patternrecognition receptors and their cross talk. Annu Rev Biochem, 2007. 76: p. 447‐80.
167. Waggoner, S.N., Cruise, M.W., Kassel, R., and Hahn, Y.S., gC1q receptor ligation selectively downregulates human IL12 production through activation of the phosphoinositide 3kinase pathway. J Immunol, 2005. 175(7): p. 4706‐14.
168. Yamada, M., Oritani, K., Kaisho, T., Ishikawa, J., Yoshida, H., Takahashi, I., Kawamoto, S., Ishida, N., Ujiie, H., Masaie, H., Botto, M., Tomiyama, Y., and Matsuzawa, Y., Complement C1q regulates LPSinduced cytokine production
‐in bone marrowderived dendritic cells. Eur J Immunol, 2004. 34(1): p. 22130.
169. Fraser, D.A., Bohlson, S.S., Jasinskiene, N., Rawal, N., Palmarini, G., Ruiz, S., Rochford, R., and Tenner, A.J., C1q and MBL, components of the innate
06. immune system, influence monocyte cytokine expression. J Leukoc Biol, 2080(1): p. 107‐16.
170. Lood, C., Gullstrand, B., Truedsson, L., Olin, A.I., Alm, G.V., Rönnblom, L., Sturfelt, G., Eloranta, M.L., and Bengtsson, A.A., C1q inhibits immune complexinduced interferonalpha production in plasmacytoid dendritic cells:
75
a novel link between C1q deficiency and systemic lupus erythematosus pathogenesis. Arthritis Rheum, 2009. 60(10): p. 3081‐90.
171. Aliprantis, A.O., Yang, R.B., Mark, M.R., Suggett, S., Devaux, B., Radolf, J.D., Klimpel, G.R., Godowski, P., and Zychlinsky, A., Cell activation and apoptosis by bacterial lipoproteins through tolllike receptor2. Science, 1999. 285(5428): p. 736‐9.
172. Takeuchi, O., Kaufmann, A., Grote, K., Kawai, T., Hoshino, K., Morr, M., Muhlradt, P.F., and Akira, S., Cutting edge: preferentially the Rstereoisomer of the mycoplasmal lipopeptide macrophageactivating lipopeptide2
ent activates immune cells through a tolllike receptor 2 and MyD88dependsignaling pathway. J Immunol, 2000. 164(2): p. 554‐7.
173. Schwandner, R., Dziarski, R., Wesche, H., Rothe, M., and Kirschning, C.J., Peptidoglycan and lipoteichoic acidinduced cell activation is mediated by tolllike receptor 2. J Biol Chem, 1999. 274(25): p. 17406‐9.
174. Netea, M.G., Kullberg, B.J., Galama, J.M., Stalenhoef, A.F., Dinarello, C.A., and Van der Meer, J.W., NonLPS components of Chlamydia pneumoniae stimulate cytokine production through Tolllike receptor 2dependent pathways. Eur J Immunol, 2002. 32(4): p. 1188‐95.
175. Hirschfeld, M., Weis, J.J., Toshchakov, V., Salkowski, C.A., Cody, M.J., Ward, D.C., Qureshi, N., Michalek, S.M., and Vogel, S.N., Signaling by tolllike receptor 2 and 4 agonists results in differential gene expression in murine macrophages. Infect Immun, 2001. 69(3): p. 1477‐82.
176. Jin, M.S., Kim, S.E., Heo, J.Y., Lee, M.E., Kim, H.M., Paik, S.G., Lee, H., and Lee, J.O., Crystal structure of the TLR1TLR2 heterodimer induced by binding of a triacylated lipopeptide. Cell, 2007. 130(6): p. 1071‐82.
177. Takeuchi, O., Sato, S., Horiuchi, T., Hoshino, K., Takeda, K., Dong, Z., Modlin, R.L., and Akira, S., Cutting edge: role of Tolllike receptor 1 in mediating
eins. J Immunol, 2002. 169(1): p. 10‐immune response to microbial lipoprot4.
178. Takeda, K., Takeuchi, O., and Akira, S., Recognition of lipopeptides by Tolllike receptors. J Endotoxin Res, 2002. 8(6): p. 459‐63.
179. Hoebe, K., Georgel, P., Rutschmann, S., Du, X., Mudd, S., Crozat, K., Sovath, S., f Shamel, L., Hartung, T., Zahringer, U., and Beutler, B., CD36 is a sensor o
diacylglycerides. Nature, 2005. 433(7025): p. 523‐7. 180. Jimenez‐Dalmaroni, M.J., Xiao, N., Corper, A.L., Verdino, P., Ainge, G.D.,
Larsen, D.S., Painter, G.F., Rudd, P.M., Dwek, R.A., Hoebe, K., Beutler, B., and Wilson, I.A., Soluble CD36 ectodomain binds negatively charged
coreceptor for TLR2. PLoS One, 2009. diacylglycerol ligands and acts as a4(10): p. e7411.
181. Silverstein, R.L. and Febbraio, M., CD36, a scavenger receptor involved in immunity, metabolism, angiogenesis, and behavior. Sci Signal, 2009. 2(72):
p. re3. 182. Cognasse, F., Hamzeh, H., Chavarin, P., Acquart, S., Genin, C., and Garraud,
O., Evidence of Tolllike receptor molecules on human platelets. Immunol Cell Biol, 2005. 83(2): p. 196‐8.
76
183. Shiraki, R., Inoue, N., Kawasaki, S., Takei, A., Kadotani, M., Ohnishi, Y., Ejiri, J., Kobayashi, S., Hirata, K., Kawashima, S., and Yokoyama, M., Expression of
9‐Tolllike receptors on human platelets. Thromb Res, 2004. 113(6): p. 3785.
184. Andonegui, G., Kerfoot, S.M., McNagny, K., Ebbert, K.V., Patel, K.D., and Kubes, P., Platelets express functional Tolllike receptor4. Blood, 2005. 106(7): p. 2417‐23.
185. Rex, S., Beaulieu, L.M., Perlman, D.H., Vitseva, O., Blair, P.S., McComb, M.E., Costello, C.E., and Freedman, J.E., Immune versus thrombotic stimulation of platelets differentially regulates signalling pathways, intracellular protein
omb Haemost, 2009. protein interactions, and alphagranule release. Thr102(1): p. 97‐110.
186. Berg, M., Offermanns, S., Seifert, R., and Schultz, G., Synthetic lipopeptide iol, Pam3CysSer(Lys)4 is an effective activator of human platelets. Am J Phys
1994. 266(6 Pt 1): p. C1684‐91. 187. Ward, J.R., Bingle, L., Judge, H.M., Brown, S.B., Storey, R.F., Whyte, M.K.,
Dower, S.K., Buttle, D.J., and Sabroe, I., Agonists of tolllike receptor (TLR)2 and TLR4 are unable to modulate platelet activation by adenosine
4(4): diphosphate and platelet activating factor. Thromb Haemost, 2005. 9p. 831‐8.
Fridman, W.H., aett, 2004. 92(3)
188. Cohen‐Solal, J.F., Cassard, L., nd Sautes‐Fridman, C., Fc gamma receptors. Immunol L : p. 199‐205.
c receptors. Annu Rev Immunol, 2001. 19: 189. Ravetch, J.V. and Bolland, S., IgG Fp. 275‐90.
cgamma receptors as regulators of 8. 8(1): p. 34‐47.
190. Nimmerjahn, F. and Ravetch, J.V., Fimmune responses. Nat Rev Immunol, 200
e platelet Fc 191. Anderson, G.P. and Anderson, C.L., Signal transduction by threceptor. Blood, 1990. 76(6): p. 1165‐72.
192. Mustard, J.F., Kinlough‐Rathbone, R.L., and Packham, M.A., Isolation of by centrifugation and washing. Methods human platelets from plasma
Enzymol, 1989. 169: p. 3‐11. tion of human platelets by albumin s Enzymol, 1989. 169: p. 1
193. Timmons, S. and Hawiger, J., Isolagradient and gel filtration. Method 1‐21.
194. Bengtsson, T. and Grenegård, M., Platelets amplify chemotactic peptidenges in Factin and calcium in human neutrophils. Eur J Cell Biol, : p. 345‐9.
induced cha1994. 63(2)
195. Boyum, A., Isolation of mononuclear cells and granulocytes from human blood. Isolation of monuclear cells by one centrifugation, and of granulocytes
nd sedimentation at 1 g. Scand J Clin Lab 89.
by combining centrifugation aInvest Suppl, 1968. 97: p. 77‐
196. Ferrante, A. and Thong, Y.H., Optimal conditions for simultaneous purification of mononuclear and polymorphonuclear leucocytes from human blood by the HypaqueFicoll method. J Immunol Methods, 1980. 36(2): p. 109‐17.
77
197. Welin, A., Winberg, M.E., Abdalla, H., Särndahl, E., Rasmusson, B., Stendahl, O., and Lerm, M., Incorporation of Mycobacterium tuberculosis
prerequisite for lipoarabinomannan into macrophage membrane rafts is athe phagosomal maturation block. Infect Immun, 2008. 76(7): p. 2882‐7.
198. Wetterö, J., Askendal, A., Bengtsson, T., and Tengvall, P., On the binding of to solid artificial surfaces in vitro. Biomaterials, 2002. 23(4): p. complement
981‐91. 199. Vroman, L., blood coagulation studies with the recording ellipsometer.
iscellaneous Publication, Washington:National Bureau of Standards M1964. 256: p. 335‐348.
200. Tengvall, P., Lundström, I., and Liedberg, B., Protein adsorption studies on nic surfaces: an ellipsometric and infrared spectroscopic
407‐22. model orgaapproach. Biomaterials, 1998. 19(4‐5): p.
in biomaterial research. 201. Elwing, H., Protein absorption and ellipsometryBiomaterials, 1998. 19(4‐5): p. 397‐406.
202. Tengvall, P., Askendal, A., and Lundström, I.I., Ellipsometric in vitro studies on the activation of complement by human immunoglobulins M and G after
urf B Biointerfaces, 2001. 20(1): adsorption to methylated silicon. Colloids Sp. 51‐62.
203. Benesch, J., Askendal, A., and Tengvall, P., Quantification of adsorbed human serum albumin at solid interfaces: a comparison between radioimmunoassay (RIA) and simple null ellipsometry. Colloids Surf B Interfaces, 2000(18): p. 71‐81.
204. Calaminus, S.D., Thomas, S., McCarty, O.J., Machesky, L.M., and Watson, S.P., h structure, the actin nodule, in the early
944‐52. Identification of a novel, actinricstages of platelet spreading. J Thromb Haemost, 2008. 6(11): p. 1
haracterization of surface205. Park, K., Mao, F.W., and Park, H., Morphological cinduced platelet activation. Biomaterials, 1990. 11(1): p. 24‐31.
206. Cazenave, J.P., Packham, M.A., and Mustard, J.F., Adherence of platelets to a tative method. J Lab Clin collagencoated surface: development of a quanti
Med, 1973. 82(6): p. 978‐90. 207. Nadar, S.K., Caine, G.J., Blann, A.D., and Lip, G.Y., Platelet adhesion in
hypertension: application of a novel assay of platelet adhesion. Ann Med, 2005. 37(1): p. 55‐60.
208. Bellavite, P., Andrioli, G., Guzzo, P., Arigliano, P., Chirumbolo, S., Manzato, F., and Santonastaso, C., A colorimetric method for the measurement of platelet
adhesion in microtiter plates. Anal Biochem, 1994. 216(2): p. 444‐50. 209. Allen, R.D., Zacharski, L.R., Widirstky, S.T., Rosenstein, R., Zaitlin, L.M., and
Burgess, D.R., Transformation and motility of human platelets: details of the d electron shape change and release reaction observed by optical an
microscopy. J Cell Biol, 1979. 83(1): p. 126‐42. 210. Frank, R.D., Dresbach, H., Thelen, H., and Sieberth, H.G., Glutardialdehyde
induced fluorescence technique (GIFT): a new method for the imaging of platelet adhesion on biomaterials. J Biomed Mater Res, 2000. 52(2): p. 374‐81.
78
211. Eriksson, A.C. and Whiss, P.A., Measurement of adhesion of human platelets icol Methods, in plasma to protein surfaces in microplates. J Pharmacol Tox
2005. 52(3): p. 356‐65. 212. Briede, J.J., Heemskerk, J.W., Hemker, H.C., and Lindhout, T., Heterogeneity
in microparticle formation and exposure of anionic phospholipids at the . plasma membrane of single adherent platelets. Biochim Biophys Acta, 1999
1451(1): p. 163‐72. 213. Kappelmayer, J., Nagy, B., Jr., Miszti‐Blasius, K., Hevessy, Z., and Setiadi, H.,
alue of Pselectin a ab Med, The emerging v s a disease marker. Clin Chem L2004. 42(5): p. 475‐86.
214. Clapham, D.E., Calcium signaling. Cell, 2007. 131(6): p. 1047‐58. , W., and Lechleiter, J.D., 215. Paredes, R.M., Etzler, J.C., Watts, L.T., Zheng
Chemical calcium indicators. Methods, 2008. 46(3): p. 143‐51. 216. Grynkiewicz, G., Poenie, M., and Tsien, R.Y., A new generation of Ca2+
ith greatly improved fluorescence properties. J Biol Chem, 1985. indicators w260(6): p. 3440‐50.
telets by adenosine diphosphate and its 217. Born, G.V., Aggregation of blood plareversal. Nature, 1962. 194: p. 927‐929.
.A., Whole blood platelet aggregometry nd ost, 2009. 35(2): p. 168‐80.
218. McGlasson, D.L. and Fritsma, G aplatelet function testing. Semin Thromb Hem
rophils. J 219. Dahlgren, C. and Karlsson, A., Respiratory burst in human neutImmunol Methods, 1999. 232(1‐2): p. 3‐14.
220. Gunnarsson, P., Levander, L., Påhlsson, P., and Grenegård, M., alpha(1)acid platelet shape change involves the Rho/Rho Thromb Haemost, 2009. 102(4): p. 694
glycoprotein (AGP)inducedkinase signalling pathway. ‐703.
221. Allen, R.C. and Loose, L.D., Phagocytic activation of a luminoldependent it alveolar and peritoneal macrophages. Biochem chemiluminescence in rabb
Biophys Res Commun, 1976. 69(1): p. 245‐52. n by isolated and aggregated 222. Palosuo, T. and Leikola, J., Platelet aggregatio
human IgG. Clin Exp Immunol, 1975. 20(2): p. 371‐4. 223. Tengvall, P., Askendal, A., and Lundström, I., Complement activation by IgG
Mater Res, 1996. 31(3): p. 305‐immobilized on methylated silicon. J Biomed12.
224. Wetterö, J., Bengtsson, T., and Tengvall, P., Complement activation on immunoglobulin Gcoated hydrophobic surfaces enhances the release of
chanism. J oxygen radicals from neutrophils through an actindependent meBiomed Mater Res, 2000. 51(4): p. 742‐51.
225. Nimeri, G., Öhman, L., Elwing, H., Wetterö, J., and Bengtsson, T., The influence of plasma proteins and platelets on oxygen radical production and
utrophils adhering to polymer surfaces. 5‐95.
Factin distribution in neBiomaterials, 2002. 23(8): p. 178
226. Tang, L. and Eaton, J.W., Inflammatory responses to biomaterials. Am J Clin Pathol, 1995. 103(4): p. 466‐71.
79
227. Nilsson, B., Ekdahl, K.N., Mollnes, T.E., and Lambris, J.D., The role of inflammation. Mol Immunol, 2007. complement in biomaterialinduced
44(1‐3): p. 82‐94. 228. Jancar, S. and Sanchez Crespo, M., Immune complexmediated tissue injury: a
multistep paradigm. Trends Immunol, 2005. 26(1): p. 48‐55. 229. Kerrigan, S.W., Douglas, I., Wray, A., Heath, J., Byrne, M.F., Fitzgerald, D., and
Cox, D., A role for glycoprotein Ib in Streptococcus sanguisinduced platelet aggregation. Blood, 2002. 100(2): p. 509‐16.
230. Fitzgerald, J.R., Loughman, A., Keane, F., Brennan, M., Knobel, M., Higgins, J., Visai, L., Speziale, P., Cox, D., and Foster, T.J., Fibronectinbinding proteins of Staphylococcus aureus mediate activation of human platelets via fibrinogen and fibronectin bridges to integrin GPIIb/IIIa and IgG binding to the FcgammaRIIa receptor. Mol Microbiol, 2006. 59(1): p. 212‐30.
231. McGrath, F.D., Brouwer, M.C., Arlaud, G.J., Daha, M.R., Hack, C.E., and Roos, tein A., Evidence that complement protein C1q interacts with Creactive pro
through its globular head region. J Immunol, 2006. 176(5): p. 2950‐7. 232. Wu, J., Edberg, J.C., Redecha, P.B., Bansal, V., Guyre, P.M., Coleman, K.,
Salmon, J.E., and Kimberly, R.P., A novel polymorphism of FcgammaRIIIa ase. J (CD16) alters receptor function and predisposes to autoimmune dise
Clin Invest, 1997. 100(5): p. 1059‐70. 233. Carcao, M.D., Blanchette, V.S., Wakefield, C.D., Stephens, D., Ellis, J.,
Matheson, K., and Denomme, G.A., Fcgamma receptor IIa and IIIa thrombocytopenic purpura. Br J polymorphisms in childhood immune
Haematol, 2003. 120(1): p. 135‐41. 234. Peerschke, E.I. and Ghebrehiwet, B., Platelet interactions with C1q in whole
of immune complexes or aggregated IgG. Clin 1992. 63(1): p. 45‐
blood and in the presenceImmunol Immunopathol, 50.
235. Wang, H.W. and Sui, S.F., Dissociation and subunit rearrangement of tive proteins. Biochem Biophys Res .
membranebound human CreacCommun, 2001. 288(1): p. 75‐9
236. Sivaraman, B. and Latour, R.A., The adherence of platelets to adsorbed ition of binding sites exposed by
. albumin by receptormediated recognadsorptioninduced unfolding. Biomaterials. 31(6): p. 1036‐44
hesion molecule Pselectin and 4(24): p. 2166‐79.
237. Blann, A.D., Nadar, S.K., and Lip, G.Y., The adcardiovascular disease. Eur Heart J, 2003. 2
238. Brass, L.F., Shaller, C.C., and Belmonte, E.J., Inositol 1,4,5triphosphateinduced granule secretion in platelets. Evidence that the activation of phospholipase C mediated by platelet thromboxane receptors involves a guanine nucleotide binding proteindependent mechanism distinct from that of thrombin. J Clin Invest, 1987. 79(4): p. 1269‐75.
239. Cohen, S., Braiman, A., Shubinsky, G., Ohayon, A., Altman, A., and Isakov, N., PKCtheta is required for hemostasis and positive regulation of thrombininduced platelet aggregation and alphagranule secretion. Biochem Biophys Res Commun, 2009. 385(1): p. 22‐7.
80
240. Hosszu, K.K., Santiago‐Schwarz, F., Peerschke, E.I., and Ghebrehiwet, B., Evidence that a C1q/C1qR system regulates monocytederived dendritic cell
unity. Innate differentiation at the interface of innate and acquired immImmun, 2009.
241. Peerschke, E.I., Yin, W., Grigg, S.E., and Ghebrehiwet, B., Blood platelets activate the classical pathway of human complement. J Thromb Haemost, 2006. 4(9): p. 2035‐42.
242. Morton, L.F., Hargreaves, P.G., Farndale, R.W., Young, R.D., and Barnes, M.J., Integrin alpha 2 beta 1independent activation of platelets by simple collagenlike peptides: collagen tertiary (triplehelical) and quaternary
r alpha 2 beta 1independent 2): p. 337‐44.
(polymeric) structures are sufficient alone foplatelet reactivity. Biochem J, 1995. 306 ( Pt
243. Surin, W.R., Barthwal, M.K., and Dikshit, M., Platelet collagen receptors, approaches for the prevention of
03. signaling and antagonism: emerging intravascular thrombosis. Thromb Res, 2008. 122(6): p. 786‐8
et, B., Modulation of platelet responses to 244. Peerschke, E.I. and Ghebrehiwcollagen by Clq receptors. J Immunol, 1990. 144(1): p. 221‐5.
245. Eriksson, A.C. and Whiss, P.A., Characterization of static adhesion of human faces in microplates. Blood Coagul
97‐206. platelets in plasma to protein surFibrinolysis, 2009. 20(3): p. 1
246. Tenner, A.J. and Cooper, N.R., Stimulation of a human polymorphonuclear he C1q subunit of the first complement 8(6): p. 2547‐52.
leukocyte oxidative response by tcomponent. J Immunol, 1982. 12
247. Goodman, E.B. and Tenner, A.J., Signal transduction mechanisms of C1qmediated superoxide production. Evidence for the involvement of temporally
munol, 1992. distinct staurosporineinsensitive and sensitive pathways. J Im148(12): p. 3920‐8.
248. Nylander, M., Lindahl, T.L., Bengtsson, T., and Grenegård, M., The yromonas gingivalis sensitisestelets, 2008. 19(5): p. 352‐8.
periodontal pathogen Porph human blood platelets to epinephrine. Pla
ci, 249. Kerrigan, S.W. and Cox, D., Plateletbacterial interactions. Cell Mol Life S2010. 67(4): p. 513‐23.
250. Blair, P., Rex, S., Vitseva, O., Beaulieu, L., Tanriverdi, K., Chakrabarti, S., Hayashi, C., Genco, C.A., Iafrati, M., and Freedman, J.E., Stimulation of Tolllike receptor 2 in human platelets induces a thromboinflammatory response through activation of phosphoinositide 3kinase. Circ Res, 2009. 104(3): p. 346‐54.
251. Zhang, G., Han, J., Welch, E.J., Ye, R.D., Voyno‐Yasenetskaya, T.A., Malik, A.B., Du, X., and Li, Z., Lipopolysaccharide stimulates platelet secretion and potentiates platelet aggregation via TLR4/MyD88 and the cGMPdependent protein kinase pathway. J Immunol, 2009. 182(12): p. 7997‐8004.