review article parkinson s disease: the mitochondria-iron...

Review ArticleParkinsonrsquos Disease The Mitochondria-Iron Link

Yorka Muntildeoz Carlos M Carrasco Joaquiacuten D Campos Pabla Aguirre and Marco T Nuacutentildeez

Iron and Biology of Aging Laboratory Department of Biology Faculty of Sciences Universidad de Chile Santiago Chile

Correspondence should be addressed to Marco T Nunez mnunezuchilecl

Received 21 January 2016 Revised 12 April 2016 Accepted 13 April 2016

Academic Editor Ruben Gomez-Sanchez

Copyright copy 2016 Yorka Munoz et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

Mitochondrial dysfunction iron accumulation and oxidative damage are conditions often found in damaged brain areas ofParkinsonrsquos disease We propose that a causal link exists between these three events Mitochondrial dysfunction results not onlyin increased reactive oxygen species production but also in decreased iron-sulfur cluster synthesis and unorthodox activation ofIron Regulatory Protein 1 (IRP1) a key regulator of cell iron homeostasis In turn IRP1 activation results in iron accumulationand hydroxyl radical-mediated damage These three occurrencesmdashmitochondrial dysfunction iron accumulation and oxidativedamagemdashgenerate a positive feedback loop of increased iron accumulation and oxidative stress Here we review the evidence thatpoints to a link between mitochondrial dysfunction and iron accumulation as early events in the development of sporadic andgenetic cases of Parkinsonrsquos disease Finally an attempt is done to contextualize the possible relationship between mitochondriadysfunction and iron dyshomeostasis Based on published evidence we propose that iron chelationmdashby decreasing iron-associatedoxidative damage and by inducing cell survival and cell-rescue pathwaysmdashis a viable therapy for retarding this cycle

1 Introduction

Parkinsonrsquos disease (PD) is the most frequent neurode-generative movement disorder worldwide Despite substan-tial amount of research its founding causes remain elu-sive Hence while the initial causes of PD are not clearlydetermined factors like aging mitochondrial dysfunctionoxidative stress and inflammation are thought to have apathogenic role in the disease [1ndash8] PD is characterized bydegeneration of dopaminergic neurons of the substantia nigrapars compacta (SNpc) and the presence of proteinaceouscytoplasmic inclusions called Lewy bodies [9 10] Loss ofdopaminergic neurons in the SNpc produces a decrease indopamine levels in the corpus striatum generating a deregula-tion of basal ganglia circuitries that leads to the appearance ofmotor symptoms including resting tremor rigidity bradyki-nesia and postural instability In addition nonmotor symp-toms such as depression cognitive deficits gastrointestinalproblems sleep disturbances and smell loss have beenidentified Sporadic cases represent more than 90 of totalPD patients but there are several inherited forms caused bymutations in single genes Although sporadic and familial PD

cases have similar outcomes inherited forms of the diseaseusually begin at earlier ages and are associated with atypicalclinical features [11]

Mitochondrial dysfunction is a plausible cause of PDneu-rodegeneration Endogenous and exogenous mitochondrialtoxins like nitric oxide 4-hydroxynonenal aminochromeparaquat rotenone and others have been linked to spo-radic forms of the disease [7 12ndash16] and mitochondrialdefects have been described in SNpc mitochondria of PDpatients [17 18] Additionally as discussed below several PD-associated proteins including 120572-synuclein (120572-syn) ParkinPTEN-induced putative kinase 1 (PINK1) protein deglycaseDJ-1 leucine-rich repeat kinase 2 (LRRK2) and P-typeATPase A2 (ATP13A2) point to a role for mitochondria inthe development of the disease

In another aspect of PD neurodegeneration a large bodyof literature strongly indicates that excess redox-active ironis involved in the pathogenesis of PD [19ndash34] Iron in itsferrous (Fe2+) and ferric (Fe3+) states is present in Lewybodies as well as in many other amyloid structures [35ndash37]Iron content in the SNpc is higher than in other areas of thebrain [38] and is even higher in PD patients [39] Here we

Hindawi Publishing CorporationParkinsonrsquos DiseaseVolume 2016 Article ID 7049108 21 pageshttpdxdoiorg10115520167049108

2 Parkinsonrsquos Disease

review the evidence that points tomitochondrial dysfunctionand the subsequent iron accumulation as early events in thedevelopment of PD

2 Cell Iron

Iron has been described as an important cofactor in manyproteins involved in crucial biological processes includingcellular respiration nitrogen fixation photosynthesis DNAsynthesis and repair oxygen transport metabolism of xeno-biotics and neurotransmitter synthesis [40ndash49] In mostproteins iron is present in iron-sulfur clusters (ISCs) either as[2Fe-2S] [4Fe-4S] or [3Fe-4S] clusters [50 51]Themain fea-ture of iron as prosthetic group resides in its high redox flex-ibility Thus iron has the capacity to exchange one electroneither by oxidation (Fe2+ rarr Fe3+) or by reduction (Fe3+ rarrFe2+)This flexibility is very important in biological processessuch as cellular respiration where the transport of electronsdepends on 12 ISCs present in complex I to complex III andon5 heme-containing proteins transporting electrons throughcomplexes III and I [52]

Increases in redox-active iron directly associate withincreased reactive oxygen species (ROS) generation andwith changes in the intracellular reduction potential due toglutathione oxidation [53 54] Within the cell most iron isassociated with proteins as either iron oxy-hydroxy crystalsin ferritin or forming part of ISCs and heme prostetic groupsAround 1 of cell iron is in a redox-active form called thelabile iron pool or labile cell iron [55ndash58] The predominantcomponent of this pool is Fe2+-glutathione but iron is alsobound weakly to phosphate citrate carboxylates carbohy-drates nucleotides polypeptides and other molecules [5960] Through the Fenton reaction reactive iron catalyzesthe production of hydroxyl radical (∙OH) in the presenceof H2O2 in a self-renewed cycle caused by the presence of

oxygen as an electron acceptor and intracellular reductantssuch as glutathione (GSH) and ascorbate as electron donors[28] These characteristics of the intracellular environmentdemand a tight regulation of the reactive iron pool to decreasehydroxyl radical production

Redox-active ironmediatesGSH consumption [54] Afterexposure to increasing concentrations of iron SH-SY5Ydopaminergic cells undergo sustained iron accumulationand produce a biphasic change in intracellular GSH levelsincreasingGSH levels at low iron concentrations and decreas-ing them thereafter Indeed cell exposure to high iron con-centrations markedly decreases the GSHGSSG molar ratioand theGSHhalf-cell reduction potential with the associatedloss in cell viability [54]

Iron levels in the SNpc increase significantly with age andPD patients present an even greater increase that correlateswith clinical PD status [64ndash69] Experimental evidence showsthat iron is crucial to the degeneration of SNpc dopaminergicneurons in the model of PD caused by 1-methyl-4-phenyl-1236-tetrahydropyridine (MPTP)Mice fed for 6weekswitha low iron diet before the administration of MPTP presentneuronal protection normal striatal dopamine levels andno changes in motor behavior when compared with controlanimals fed a normal iron content diet [70] Furthermore

increased iron levels in the brain aggravate dopaminergic celldeath and motor impairment after MPTP treatment and thiscondition is attenuated by treatment with the iron chelatordesferrioxamine (DFO) [71]

Clinical studies have not provided an evident correlationbetween dietary iron intake and risk of Parkinsonrsquos diseasein humans [72ndash75] Nevertheless some reports point toa higher incidence of PD in hereditary hemochromatosispatients [76ndash79] although other reports found no correlationbetween these two diseases [80ndash82] It is possible that undernormal conditions the iron homeostasis system protects thebrain from iron accumulation due to dietary variations Thishomeostasis is most likely lost in iron-overload disease statesyet

Overall these antecedents suggest that increased redox-active iron in the SNpc is part of the neurodegenerativeprocess in PD possibly due to increased oxidative stress andoxidative damage

3 Iron Homeostasis in Mitochondria

Mitochondria consume about 90 of cellular oxygen andtransform 1ndash5 of this oxygen into superoxide anion (O

2

∙minus)due to the leaking of electrons that takes place in their passagethrough complexes III and I [83ndash86] During aging the activ-ity of these complexes decreases leading to higher oxidantproduction of O

2

∙minus and H2O2[86 87] The superoxide anion

generated in this process dismutates into hydrogen peroxideeither spontaneously or following catalysis by superoxidedismutase (SOD) [88 89] Proteins containing ISCs inmitochondria are significantly vulnerable to oxidative stressparticipating in redox sensing and signaling reactions [9091]

The mitochondrion has an active exchange of iron withthe cytoplasm as required for the mitochondrial synthesisof heme and ISCs (Figure 1(a)) [92ndash94] Kinetic experimentsshow that extracellular iron is readily incorporated intomitochondria Indeed iron incorporation into mitochondriaapparently has a kinetic preference over incorporation intothe cytoplasm (Figure 1(b)) (also see [94 95]) Possiblemech-anisms for this preferential delivery include siderophore-mediated iron transport from the plasma membrane to themitochondrion [96 97] the entrance of iron into the cell byfluid-phase endocytosis with subsequent delivery to mito-chondria without passing through the cytoplasmic labile ironpool (cLIP) [98] and iron delivery to mitochondrion bydirect interaction with transferrin-containing endosomes[99]

Mitoferrin-2 a protein located in the innermitochondrialmembrane represents the main pathway of mitochondrialiron uptake whereas the ABCB7 andABCB8 transporters areinvolved in ISC export [100ndash103] (Figure 1) Inward transportof iron by mitoferrin-2 apparently is regulated Studies withthe mitoferrin Mrs3p and Mrs4p yeast homologs revealedthat inner mitochondrial membrane vesicles show rapiduptake of Fe2+ in response to iron starvation [104]There is noreported evidence as to how cell or mitochondrial iron levelscould regulate mitoferrin-2 levels Additionally mitoferrin

Parkinsonrsquos Disease 3

mLIP

cLIP

FLVCR1b

ABCB10ABCB7ABCB8

ISC

Apo-IRP1DMT1TfR1 (inactive)

Holo-IRP1(active)

MtFt(storage)

Heme

DMT1

Mtfn2

(a)

0 100 200 300 400

08

09

10

11

No FAS

RPA (mLIP)

FAS

Calcein (cLIP)

Time (s)

Calc

ein

or R

PA fl

uore

scen

ce (F

F0)

(b)

Figure 1 (a) Mitochondrial iron traffic Iron enters mitochondria from the cLIP in a process mediated by the inner mitochondrial irontransporter Mtfn2 and probably by DMT1 located in the outer membrane Upon entering iron incorporates into the mLIP from where itdistributes for heme and ISC synthesis or for storage in mFt Heme leaves the mitochondrion through ABCB10 and the mitochondrial hemeexporter FLVCR1b located in the inner and outer mitochondrial membranes respectively ISCs are transported out of the mitochondrionby the ABCB7 transporter and probably by the ABCB8 transporter as well In the cytoplasm ISCs bind to the corresponding apoproteinsIRP1 binds a 4Fe-4S cluster the holoprotein is inactive to induce the transcriptional regulation of cell iron-import proteins like DMT1 andTfR1 In contrast apo-IRP1 normally abundant under low cell iron conditions upregulates the expression of iron-import proteins like DMT1and TfR1 ABC ATP-binding cassette transporter cLIP cytoplasmic labile iron pool DMT1 divalent metal transporter 1 FLVCR1b felineleukemia virus subgroup C receptor 1B transporter ISC iron-sulfur cluster mFt mitochondrial ferritin mLIP mitochondrial iron poolMtfn2 mitoferrin-2 TfR1 transferrin receptor 1 (b) Kinetic determination of iron entrance into the cLIP andmLIP SH-SY5Y cells preloadedwith the mitochondrial iron sensor rhodamine B-[(110-phenanthroline-5-yl)aminocarbonyl]benzyl ester (RPA) and the cytoplasmic ironsensor calcein were challenged with 40 120583M ferrous ammonium sulfate (Fe) and changes in RPA and calcein fluorescence were followed in amultiplate fluorescence reader [61 62] Iron binding quenches RPA and calcein fluorescence thus a decrease in RPA or calcein fluorescenceis directly proportional to iron entrance into the mLIP or cLIP respectively Note that the initial rate of iron entrance into the mLIP (119870 =00536 plusmn 00021Δ(119865119865

0)sec) is larger than the rate of iron entrance into the cytoplasmic LIP (119870 = 00206 plusmn 00070Δ(119865119865

0)sec) Values

represent mean plusmn SD of quadruplicates 119875 = 0004


Control M30 Rotenone

3

0M30Rotenone

(a)

0

1

2

3BO

DIP

Y ox

idat

ion

M30RotenoneM30RotenoneControl

lowastlowastlowast

lowastlowastlowast

lowastlowastlowast

(b)

Figure 2 The iron Chelator M30 protect SH-SY5Y cells from rotenone-induce lipid peroxidation (a) Mitochondrial lipid peroxidation wasevaluated by greenred fluorescence changes of C11-BODIPY581591 (ThermoFisher Scientific-Molecular Probes) as described [63] Oxidationof C11-BODIPY581591 results in a shift of the fluorescence emission peak from 590 nm (red nonoxidized) to 510 nm (green oxidized) SH-SY5Y cells were preincubated or not for 24 hours with 500 nM of M30 in DMEM-10 FCS medium and then loaded for 15 minutes at 37∘Cwith 1 120583M C11-BODIPY581591 Confocal images were obtained 15 minutes both before (Control M30) and after (Rotenone M30Rotenone)applying 80120583M rotenone to the cells Representative images are shown where the ratio of green over (green + red) fluorescence wasconverted into a pseudothermal scale using the ImageJ program (b) Changes in C11-BODIPY581591 oxidation quantified by the thermalscale Values represent the mean plusmn SD of 40ndash52 individual cell measures per experimental condition Significance between mean differenceswas determined by one-way ANOVA and Tukey post hoc test lowastlowastlowast119875 lt 0001

dysregulation under pathological conditions promotes mito-chondrial iron accumulation [100 104]

A recent report described a role for mitoferrin-2 in thedevelopment of Friedreichrsquos ataxia by showing that mito-ferrin-2 downregulation improved many of the conditionsof frataxin deficiency whereas its overexpression exacer-bated them [105] Similarly loss-of-function mutations inABCB7 produce a sideroblastic anemia condition called X-chromosome-linked sideroblastic anemia in which patientsshow iron accumulation in mitochondria [101 102]

A fraction of the intramitochondrial iron is redox-activePetrat et al demonstrated presence of a chelatable ironpool which renders mitochondria sensitive to iron-mediatedoxidative damage [106] Evidence from our laboratory showsthat complex I inhibition generates mitochondrial lipidperoxidation as determined by C11-BODIPY581591 oxidation[63] which is probably caused by redox-active iron since

it is inhibited by coincubation with the iron chelator M30(Figure 2)

4 Mitochondrial Dysfunction in PD

Mitochondrial dysfunction and oxidative stress have longbeen implied as pathophysiological mechanisms underlyingPD [17 107] Mitochondria not only have a key role inelectron transport and oxidative phosphorylation but also arethe main cellular source of ROS and they are involved incalcium homeostasis and in the regulation and initiation ofcell death pathways [1] Mitochondria isolated from humanbrain tissues and peripheral cells of sporadic PD patientsexhibit reduced mitochondrial complex I activity [108] andpostmortemSNpc tissues from idiopathic PDpatients displaydecreased number of complex I subunits [107 109 110]Mitochondrial complex I activity is reduced in the SNpc [111]


and the frontal cortex [112] in patients with PD Howevertotal protein and mitochondrial mass from SNpc of patientswith PD are similar to controls [111] The main consequencesof mitochondrial complex I inhibition in humans and exper-imental models are decreased ATP levels [113 114] decreasedglutathione levels and increased oxidative damage [115ndash118]Other reported effects are reduction in the concentrations ofDA accompanied with decreased density of DA receptors anddiminished activity of TH (reviewed in [119]) increased totalSNpc iron content [120] increased redox-active iron [121122] decreased Fe-S cluster synthesis [61 123] and calciumdysregulation [124ndash126] Any one of these events may resultin cell death once the homeostaticmechanisms are surpassed

The first evidence of mitochondrial dysfunction as acausal source of PD was obtained in the 1980s when fourstudents developed marked Parkinsonism after intravenousinjection of an illicit drug contaminated with MPTP Becauseof the striking Parkinson-like features and additional patho-logical data it was proposed that MPTP selectively damageddopaminergic neurons in the SNpc causing the Parkinsonsyndromes [127] Later studies showed that MPTP causesan irreversible destruction of the dopaminergic nigrostriatalpathway that results in symptoms of Parkinsonism in pri-mates and mice [128ndash130]

In animalmodels of PD inhibition of complex I byMPTPor 6-hydroxydopamine (6-OHDA) results in iron accumula-tion in the SNpc [131 132] Importantly iron chelators effec-tively abrogate this neurodegenerative process (see below)Thus with all probability redox-active iron mediates thedegenerative process of SNpc neurons induced by inhibitionof complex I

5 IRP1 The Link between MitochondrialDysfunction and Iron Dyshomeostasis

Iron Regulatory Proteins 1 and 2 (IRP1 and IRP2) are largelyresponsible for maintaining cytoplasmic iron levels throughthe translational regulation of iron homeostasis proteinsIRPs bind to RNA stem loops called iron responsive elements(IREs) which are found in untranslated regions of targetmRNAs that encode proteins involved in iron metabolismBinding of IRPs to IREs in the 51015840-untranslated region inhibitsthe translation of mRNA as is the case for the iron-storageprotein ferritin Binding of IRPs to IREs present in the31015840-untranslated region increases the stability of mRNAsthus increasing the translation of DMT1 and the transferrinreceptor [133 134]

Importantly IRP1 activity depends on the protein havingor not a 4Fe-4S cluster Binding of the 4Fe-4S cluster to IRP1renders the protein inactive to bind to mRNA [135] Low celliron induces the dissociation of this 4Fe-4S cluster activatingIRP1 and inducing the expression of iron uptake proteins likethe transferrin receptor 1 (TfR1) and dimetal iron transporter1 (DMT1) [136] Furthermore IRP1 is sensitive to severaloxidative stress stimulus hydrogen peroxide nitric oxideand peroxynitrite all activate IRP1 by induction of ISC disas-sembly [137 138] while superoxide inhibits aconitase activity[139]

IRP1 is deregulated in PD tissue since postmortem braintissue from PD patients displays increased IRP1 activity whencompared to tissue from control individuals Increased IRP1activity was found also in the ipsilateral ventral mesen-cephalon of 6-OHDA-treated rats [140] Studies performedin our laboratory showed that in SH-SY5Y cells inhibition ofcomplex I by rotenone results in decreased Fe-S cluster syn-thesis and increased IRP1 mRNA binding activity accompa-nied by increased cLIP [61]Therefore inhibition of complex Iand the subsequent activation of IRP1 lead to increasedDMT1and TfR1 expression increased iron uptake and increasedROS generation

6 Environmental Toxicants MitochondrialDysfunction and Iron Dyshomeostasis

A considerable body of evidence epidemiologically linksexposure to environmental toxicants like paraquat androtenone to the generation of PD in rural workers [141ndash144] The herbicide paraquat is a free radical generator thatinhibits mitochondrial electron-transport activity [145ndash147]and causes dopaminergic neuron loss 120572-synuclein aggrega-tion and motor deficits in rodents with a dramatic increasein free radical formation [148ndash150] Moreover systemicapplication of paraquat reduces motor activity and inducesdose-dependent loss of striatal tyrosine hydroxylase positive(TH+) fibers and SNpc neurons in mice [151ndash154] Paraquathas been proposed to cause Parkinsonism in humans How-ever the clinical and epidemiological evidence in this regardis still inconclusive [1 144 155 156] In fact paraquatremains one of themost widely used herbicides in developingcountries [157 158]

Although its associationwith PD is not firmly establishedemerging evidence links paraquat exposure to brain ironaccumulation Patients from acute paraquat poisoning dis-played excessive brain iron deposition [159] Similarly incu-bation of rat primary mesencephalic cultures with paraquatresulted in increased production of H

2O2and Fe2+ at times

preceding cell death [160] Mechanistic studies identifiedm-aconitase from astrocytes as the main mediator in ROSproduction although neurons were identified as the primarydying cell type and death was attenuated by addition of cata-lase andor a cell permeable iron chelator [160] We proposethat these results are consistent with a mechanism wherebyparaquat affects mitochondrial activity resulting in increasedROS production and increased iron content a combinationthat induces neuronal death by hydroxyl radical-mediateddamage

Rotenone is a classic complex I inhibitor [161 162] Bothrotenone and MPP+ inhibit complex I NADH dehydro-genase shutting off mitochondrial respiration and causingselective injury of SNpcneurons [128 163ndash166] Rotenone andMPP+ also produce superoxide anion in submitochondrialparticles [167ndash169] Chronic rotenone administration tomicereproduces Parkinson-like syndromes that include death ofSNpc neurons complex I inhibition and Lewy bodies-likefibrillar cytoplasmic inclusions containing ubiquitin and 120572-synuclein [141 170]


Treatment with rotenone induces iron accumulation inanimal and cell models [61 171] Rats treated with rotenoneevidence iron accumulation in the SNpc the striatum theglobus pallidus and other brain areas and treatmentwith ironchelating agents significantly reduces iron deposition and theloss of dopaminergic neurons in these areas [171] Similarlytreatment of SH-SY5Y dopaminergic neuroblastoma cellswhit rotenone results in mitochondrial iron accumulationand oxidative damage [172] The mitochondria-tagged ironchelator Q1 abolishes both effects [94] Overall these data areconsistent with the notion that inhibition of complex I resultsin the dysregulation of iron homeostasis in dopaminergiccells

In summary although the epidemiological evidence thatlinks paraquat or rotenone exposure with PD still needs con-solidation increasing evidence shows that inhibition ofmito-chondrial activity by these compounds results in iron accu-mulation The mechanisms causing this accumulation areunknown Considering the previous in vitro evidences dis-cussed above iron accumulation may be mediated by activa-tion of IRP1 due to decreased ISC synthesis

7 PD Genes Associated with MitochondrialDysfunction and Iron Accumulation

As detailed below a wealth of reports indicate that theproduct of a number of PD-associated genes including120572-synParkin PINK1 DJ-1 LRRK2 and ATP13A2 disrupts mito-chondrial function Moreover this disruption is generallyassociated with increased iron load Here we will reviewthe evidence that links mitochondrial dysfunction and ironaccumulation in familial cases of PD

71 120572-Syn The function of wild type 120572-syn is still an openissue [173 174] There is consensus however that misfoldingand aggregation of 120572-syn underlie its toxicity in both PDand Lewy body-associated dementia [173] Accumulation ofcytosolic 120572-syn can render toxic endogenous dopamine [175]and acts as a seed promoting the formation of cytosolicinclusions [176] If degradation pathways do not clear theseaggregates promptly neurodegeneration can ensue

There is a reciprocal relationship between 120572-syn activityand mitochondrial function thus 120572-syn overexpression indopaminergic cell lines results in mitochondrial alterationsaccompanied by increased levels of ROS [177ndash180] The N-terminal sequence of 120572-syn contains a cryptic mitochondrialtargeting signal and 120572-syn has been localized intomitochon-dria after acidification of the cytosol or 120572-syn overexpression[181 182] Mitochondrial 120572-syn decreases the activity of com-plex I increases ROS production [183] causes cytochromec release increases mitochondrial calcium and nitric oxidelevels and induces oxidative modification of mitochondrialcomponents [184] Moreover mice that overexpress 120572-synA53T exhibit dysmorphic mitochondria with evidence ofDNA damage [185] while administration of MPTP to micethat overexpress 120572-syn leads to swollen and morphologicallyabnormal mitochondria [186] An open issue is whether120572-syn aggregation promotes mitochondrial dysfunction orvice versa Probably both phenomena are interrelated 120572-syn

induces mitochondrial dysfunction and mitochondrial dys-function induces 120572-syn aggregation [187]

Recent evidence suggests that 120572-syn aggregation inducesiron accumulation In PD patient brains neurons containing120572-syn deposits also display increased iron concentrationsand upregulated levels of Nedd4 Family Interacting Protein1 (Ndfip1) an adaptor for the neuronal precursor cell-expressed developmentally downregulated 4 (Nedd4) familyof E3 ligases [188] Similarly rat midbrain neurons and PC12cells overexpressing human 120572-syn accumulate increased lev-els of iron and show iron redistribution from the cytoplasmto the perinuclear region within 120572-synuclein-rich inclusions[189]

Interactions between iron and 120572-syn most probably con-tribute to the process of neurodegeneration [190] Furtherwork indicated that divalent metals including Fe2+ Mn2+Co2+ and Ni2+ bind to the C-terminal of 120572-syn and the N-terminus residues 119ndash124 were recognized as the main bind-ing site of divalent metal ions [191] Incubation of wild typeandmutant120572-synwith Fe3+ resulted in the formation of shortthick fibrils [192] In BE(2)-M17 cells overexpressing wildtype or mutant 120572-syn (A30P and A53T) treatment with Fe2+dopamine and hydrogen peroxide generated 120572-syn-positiveinclusions which also contained ubiquitin [193] SimilarlyFe2+-treated BE(2)-M17 cells were more susceptible to Fe2+-induced DNA damage when overexpressing mutant 120572-syn[194] In contrast Mg2+ inhibits both spontaneous and Fe2+-induced aggregation of wild type but not A53T 120572-syn [195]and dopamine suppresses the Fe3+-induced fibrillation of 120572-syn [196]

Interestingly 120572-syn aggregation in turn produces oxida-tive stress in a processmediated bymetal ions like Fe andMnthus generating a vicious cycle between oxidative stress and120572-syn aggregation [197ndash201] Moreover pesticides such asrotenone paraquat and dieldrin and metal ions (iron man-ganese copper lead mercury zinc and aluminum) inducea conformational change in 120572-syn and directly accelerate therate of formation of 120572-syn fibrils in vitro [202ndash204] In addi-tion the simultaneous presence of metal ions and pesticidesleads to synergistic effects on the rate of fibrillation [205]

In summary there seems to be a cyclic associationbetween 120572-syn and iron in which 120572-syn induces iron accu-mulation and iron induces 120572-syn aggregation This cycleis aggravated by 120572-syn-induced mitochondrial dysfunctionThese associations may originate a sequence of events inwhich 120572-syn aggregation inducesmitochondrial dysfunctionwhich in turn results in iron accumulation and further 120572-synaggregation and hydroxyl radical-mediated damage

72 Parkin Various mutations in Parkin an E3 ubiquitinligase of the ubiquitin-proteasome system lead to an auto-somal recessive PD form which also is seen in some young-onset sporadic PD cases [206 207] Abundant evidence linksParkin to mitochondrial function Cultured fibroblasts frompatients carrying Parkin mutations present longer and morebranched mitochondria than controls [208] and leukocytemitochondrial complex I and IV activities are reduced in PD


patients who are homozygous for Parkin mutations [209]Parkin-deficient mice have decreased levels of mitochondrialcomplexes I and IV in the striatum together with increasedprotein and lipid peroxidation [210] In addition Parkin-nullD melanogaster mutants develop muscle degeneration withmitochondrial pathology and display decreased resistance tooxidative stress [211 212]Moreover overexpression of Parkinattenuates the dopaminergic neurodegeneration induced byMPTP through protection of mitochondria and reductionof 120572-syn in the nigrostriatal pathway [213] After chronicMPTP administration Parkin overexpression preventsmotordeficits and dopaminergic cell loss in mice [214]

Published observations linking Parkin mutations andiron accumulation are scarce In an initial study PD patientscarrying Parkin mutations as well as mutation carriers with-out clinical manifestations of the disease showed increasedechogenicity of the SNpc which in asymptomatic Parkinmutation carriers was associated with abnormal nigrostriatalF-dopa positron emission tomography [215 216] Recently aR2lowast relaxometry study in the SNpc of genetic and idiopathicPD patients reported that R2lowast values indicative of irondeposition were increased in idiopathic PD patients and inpatients carrying Parkin and LRRK2 mutations when com-pared to control subjects [217]

Overall the bulk of the evidence points to a relationshipbetween Parkin and mitochondria structural functionalityFurther investigations are needed to assert if PD Parkinmutations also result in iron dyshomeostasis

73 PINK1 Mutations in PINK1 a serine-threonine proteinkinase localized to the mitochondrial membrane via an N-terminal mitochondrial targeting sequence [218] lead to arare autosomal form of PD It is generally accepted thatPINK1 has a physiological role in mitochondria mainte-nance suppressing mitochondrial oxidative stress fissionand autophagy [219] PINK1 KO mice exhibit age-dependentmoderate reduction in striatal dopamine levels accompaniedby low locomotor activity [220ndash222] These mice show noloss of dopaminergic neurons in the SNpc region but displaydecreased striatal innervations [223 224] together withdecreased mitochondrial respiration and mitochondrial aco-nitase activity in the striatum [220]

Fibroblasts from patients homozygous for the G309D-PINK1 mutation have reduced complex I activity and evi-dence oxidative damage compared with cells from controlindividuals [225] In flies PINK1 deficiency results in lossof dopaminergic cells enhanced susceptibility to oxidativestress reduced mitochondrial mass with disorganized mor-phology and decreased ATP levels [226] Parkin and PINK1work in a common pathway with Parkin acting downstreamof PINK1 [226ndash228] Under conditions of severe mitochon-drial damage PINK1 and Parkin act to induce mitophagyand mitochondrial membrane depolarization [229] PINK1also regulates mitochondrial dynamics through interactionwith the fissionfusion machinery [230] Further geneticstudies inDrosophila revealed that the PINK1Parkin pathwayregulates mitochondrial morphology by tipping the balanceof mitochondrial fissionfusion dynamics toward fission in

dopaminergic and hippocampal neurons [230 231] andmuscle cells [232ndash234]

In SNpc dopaminergic neurons PINK1 is required tomaintain normal mitochondrial morphology and membranepotential exerting this neuroprotective effects by inhibitingROS formation [235] In human dopaminergic neuronsPINK1 deficiency produces mitochondrial dysfunction andmarked oxidative stressThese defects result in reduced long-term cell viability with neurons dying via cytochrome c-mediated apoptosis [236] Additionally PINK1 knockdownSH-SY5Y cells show decreased resistance against thapsigar-gin-induced apoptosis while PINK1 overexpression restoresit [237]

Evidence linking PINK1 and iron is scarce Patientscarrying a PINK1 mutation display a significantly larger areaof SNpc echogenicity assessed with transcranial ultrasoundrelative to healthy controls [238] In a Drosophila modelPINK1 mutants present increased superoxide levels whichinduce 4Fe-4S cluster inactivation and increased iron levels inthe mitochondrion [239] As discussed above decreased ISCsynthesis can lead to iron accumulation through IRP1 activa-tion [61]

Overall published data indicates that under conditions ofPINK1 deficiency mitochondrial quality control mechanismsare compromised resulting in increased ROS production andapoptotic cell death Up to date evidence of a relationshipbetween PINK1 loss of function and iron dyshomeosta-sis is discrete but enticing The observation of decreasedmitochondrial aconitase activity indicative of a possibledecrease in ISC synthesis and the observed link betweenPINK1 mutations and superoxide-mediated iron accumu-lation in mitochondria are powerful incentives to studypossible changes in iron homeostasis under PINK1 deficiencyand to assess how these changes impact on cell death

74 DJ-1 DJ-1 is a multitask protein that participates in theprotection of cells from oxidative stress-related death [240ndash243] DJ-1 null mice show decreased locomotor activity areduction in the release of evoked dopamine in striatum butno loss of SNpc dopaminergic neurons [223 224] A relation-ship between DJ-1 and mitochondrial function has long beensuspected [244] however DJ-1-null mice show no apparentmitochondrial defects [223 224] In contrast ROS pro-duction mitochondrial structural damages and complex Ideficit are significantly higher inDJ-1-null cultured dopamin-ergic neurons [245]

To date the evidence linking DJ-1 and iron is scanty PDpatients carrying DJ-1 mutations have an area in the SNpcof significantly larger echogenicity than in healthy controls[238] As SNpc hyperechogenicity is related to increased ironcontent these findings suggest that DJ-1mutationsmay resultin iron accumulation

75 LRRK2 LRRK2 is a cytosolic serine-threonine-proteinkinase with a fraction of about 10 associated with theoutermitochondriamembrane Overall LRRK2micemodelsdisplay mild or no functional disruption of nigrostriataldopaminergic neurons of the SNpc [246] Recently a new


LRRK2 knock-in mice evidenced profound mitochondrialabnormalities in the striatum of older homozygous micewhich are consistent with mitochondrial fission arrestdescribed previously [247] In skin biopsies from humanLRRK2 G2019S carriers however mitochondrial functionand morphology are perturbed as demonstrated by reducedmitochondrial membrane potential reduced intracellularATP levels mitochondrial elongation and increased mito-chondrial interconnectivity [248] LRRK2 mutations reducethe activity of peroxiredoxin 3 an antioxidant enzyme locatedwithin mitochondria This effect appears to be phosphoryla-tion-dependent [249 250]

To date just a few studies have shown a relationshipbetween LRRK2 dysfunction and iron accumulation In arecent study determining R2lowast relaxometry rate high nigraliron deposition in LRRK2 mutation carriers was demon-strated [217] In a small cohort of patients it was found thatR2lowast values in the SNpc were increased in idiopathic PDpatients and LRRK2mutation-carrying patients as comparedwith controls with LRRK2 mutation patient having largerR2lowast values than idiopathic PD patients [217] Similarlystudies using transcranial sonography showed that LRRK2-associated PD patients had increased iron levels in the SNpc[238 251] These evidences support the notion that PDresulting from a variation in the LRRK2 allele has an ironaccumulation component that affects neurodegeneration viaincreased oxidative damage Further analysis will be requiredto evaluate this hypothesis

76 ATP13A2 ATP13A2 is a lysosomal P-type 5 ATPaseMutations in its gene are associated with a juvenile-onsetlevodopa-responsive PD type named familial Kufor-Rakebsyndrome [252 253] ATP13A2 null mice display late-onsetsensorimotor deficits and deposition of 120572-syn aggregateswithout changes in the number of dopaminergic neuronsin the SNpc or in striatal dopamine levels [254] ArguablyATP13A2 may help prevent neurodegeneration both byinhibiting 120572-syn aggregation and by supporting normallysosomal and mitochondrial function [253]

A relationship between ATP13A2 and mitochondrialfunction is emerging Reduced activity of ATP13A2 mutantsmay lead to mitochondrial defects [255] and higher ROSlevels [256] Fibroblasts from Kufor-Rakeb syndromepatients show lower mitochondrial membrane potential andlower ATP synthesis rates than fibroblast from controls [257]In addition overexpression of ATP13A2 inhibits cadmium-induced mitochondrial fragmentation while silencingATP13A2 expression induces mitochondrial fragmentation[258] It remains to be elucidated if ATP13A2-associatedmitochondrial dysfunction is due to a primary effect of onmitochondria integrity or is secondary to other event(s) likeincreased 120572-syn aggregation

Two recent studies report neurodegeneration with brainiron accumulation in one Pakistani [259] and one Chilean[257] Kufor-Rakeb syndrome patients Both patients showedabnormal bilateral hypo intensity in the putamen and cau-date nuclei on T2lowast diffuse MRI images In the Pakistanipatient case the clinicians attributed the abnormalMRI hypointensity to iron deposition [259] In the Chilean patient

the clinicians attributed the hypo intensity to ferritin depositsthough they did not perform tests to exclude the possibility ofdeposition of other metal ions [257] However another studyreported opposite results in an adolescent Brazilian patientwith homozygous ATP13A2mutation [260] It is possible thatbrain metal ion accumulation only occurs very late in thecourse of the disease or in cases in which ATP13A2mutationslead to a total loss of protein function such as the Pakistanipatient described by Schneider et al [259] Additional studiesin patientswith pathogenicATP13A2mutations are needed toclarify this point

In summary the activities of several PD genes namely120572-syn Parkin PINK1 DJ-1 LRRK2 and ATP13A2 areinvolved in the maintenance of mitochondrial function andintegrity Mutations in these genes that result in familialPD are accompanied by decreased mitochondrial activityand increased oxidative stress Emerging evidence points toiron dyshomeostasis as a direct or indirect consequence ofdecreased mitochondrial activity There is much to learnregarding the mechanisms linking particular mitochondria-associated PD proteins with iron dyshomeostasis

The question arises on the reasons why dopaminergicneurons from SNpc are more sensitive to neurodegen-eration than similar neurons in the midbrain Neuronsfrom SNpc have increased IRP1 activity [61 123 261] andincreased DMT1 expression [262ndash264] coupled to decreasedferritin expression [265ndash267] which most probably results inincreased redox-active iron and oxidative damage Similarlyintrinsic L-type calciumchannel pace-marker activity and theassociated tendency to elevated calcium levels [268 269] puta metabolic burden in these neurons Both aspects iron andcalcium burden are particular factors in SNpc neurons thatcould be augmented by mitochondrial dysfunction

8 Iron Mitochondrial Dynamicsand Mitophagy

Mitochondria are highly dynamic organelles that continu-ously fuse and divide through the processes of fusion andfission respectively Increases in the fission events generatefragmented mitochondria whereas fusion events produceelongated mitochondria A balance between mitochondrialfusion and fission is important in cellular function [270] andan imbalance can promote neuronal dysfunction and celldeath [269 271] In neurons mitochondrial fission is crucialfor axonal transport of the organelles into areas of highmetabolic demand whereas mitochondrial fusion supportssubstitution and regeneration of mitochondrial proteinsmitochondrial DNA repair and functional recovery Indeedenhanced mitochondrial fragmentation was associated withinduction of neuronal death triggered by oxidative stress[272]

Dynamin-related protein 1 (Drp1) is a key regulatorof mitochondrial fission and it has been associated withneuronal cell death induced by glutamate toxicity or oxygen-glucose deprivation in vitro and after ischemic brain damagein vivo [273] Many studies have demonstrated that post-translational modification of Drp1 (phosphorylation ubiq-uitination S-nitrosylation and others) affects Drp1 activity


and contributes to altered mitochondria dynamics and neu-rodegeneration in cell culture systems [274ndash278] Recentlyit was shown that ferric ammonium citrate (FAC) decreasedcell viability and promoted cell death of HT-22 cells [279]The FAC-induced iron overload triggered mitochondrialfragmentation and Drp1(Ser637) dephosphorylation by cal-cineurin Iron chelation and pharmacological inhibitionof calcineurin prevented mitochondrial fragmentation andapoptotic death These findings suggest that under iron-induced toxicity calcineurin-mediated dephosphorylation ofDrp1(Ser637) mediates neuronal cell loss by modulatingmitochondrial dynamics [279]

As mentioned above several groups observed that a defi-ciency in Parkin and PINK1 leads tomitochondrial pathology[211 234 280 281] PINK1 overexpression suppressed thetranslocation of Drp1 from the cytosol to the mitochondriamaintaining mitochondrial function [282] In Drp1-deficientcells the ParkinPINK1 knockdown phenotype did not occurindicating that mitochondrial alterations observed in Parkin-or PINK1-deficient cells are associated with an increase inmitochondrial fission [281] Moreover Drp1 seems to activateautophagymitophagy pathways for morphologic remodel-ing of mitochondria in PINK1-deficient neuroblastoma cells[283] Currently the inhibition of Drp1 has been proposed asa strategy of neuroprotection inmany neurodegenerative dis-eases because the altered Drp1 activity promotes exacerbatedmitochondrial fragmentation

Iron induces calcium release from intracellular storesincrease that is mediated by the ryanodine receptor (RyR)calcium channel [284] A recent study showed that in hip-pocampal neurons iron induced a RyR-dependent increase inmitochondria-associated Drp1 together with increased mito-chondrial fragmentation [285]These results suggest that ironaccumulation contributes to mitochondrial fission and pre-sumably to the impairment of neuronal function by a mech-anism that involves RyR activation calcium release andDrp1activation

9 Iron Chelation as a TherapeuticApproach for the Treatment of PD

Iron chelators are molecules from different origins with theability to coordinate iron ions In general three distinctgroups are identified siderophores isolated from lithotrophicbacteria phytochemicals and synthetic molecules Histori-cally the clinical use of these chelators has been focused onthe treatment of iron-overload syndromes such as hemochro-matosis120573-thalassemiamyelodysplastic syndrome and otherblood transfusion-requiring diseases [286 287] As discussedabove however during the last years a growing set of evi-dences has demonstrated thatmany neurodegenerative disor-ders prominently PD present an iron accumulation compo-nent in the affected brain areas [7 288ndash292] Desferrioxamine(DFO) in 6-OHDA intoxicated rats provided the first evi-dence of neuroprotection by iron chelation Injection of DFOin one cerebral ventricle of rats previously intoxicated showedpartial protection from depletion of DA in the striatumand improvement in behavioral tests with respect to theintoxicated rats without DFO administration [293] Recently

intranasal administration of DFO to the 120572-syn rat model ofPD decreased Fe+3 content and the number of 120572-syn inclu-sions but did not protect dopaminergic neurons from death[294] Administration of DFO to endotoxin-shocked miceattenuates the inflammatory response by suppressing theactivation of mitogen-activated protein kinase (MAPKs) andNF-120581B [295] suggesting an anti-inflammatory effect of DFOThis is a potentially important observation given that inflam-mation is associatedwith the dysregulation of iron homeosta-sis [296ndash298]

Given the positive effects of DFO and other chelators likeclioquinol and deferiprone (DFP) in PD and other modelsof neurodegeneration [290 299ndash301] a series of new 8-OH-quinoline-based chelators was developed which include VK-28 HLA-20 M30 and VAR VK-28 [302] HLA-20 [299]M30 [303] and VAR [304] were shown to protect TH+cells in murine MPTP and 6-OHDA intoxicated modelsand increase DA content in the striatum In addition to the8-hydroxyquinoline chelatormoiety HLA-20M30 andVARalso have the monoamine oxidase (MAO) inhibitor grouppropargyl conforming bifunctional iron chelatorMAOinhibitor drugs These molecules were demonstrated tochelate iron decreaseDAbreakdown and induce prosurvivalfactors through putative interactions with signaling compo-nents Indeed M30 was shown to upregulate protein levels ofhypoxia inducible factor 1120572 (HIF-1120572) through decreasing theactivity ofHIF-degrading enzymeHIF prolyl hydrolase [305ndash307] As a consequencemany prosurvival genes controlled byHIF-1120572were upregulated afterM30 administration includingvascular endothelial growth factor erythropoietin enolase-1 transferrin receptor 1 heme oxygenase-1 inducible nitricoxide synthase and glucose transporter 1 [307] In additionmRNAs for brain-derived neurotrophic factor glial cell-derived neurotrophic factor and three antioxidant enzymes(catalase superoxide dismutase-1 and glutathione peroxi-dase) were also upregulated by M30 administration [307308] Possibly these later genes are activated through thepropargyl moiety via induction of increased phosphoryla-tion of protein kinase C mitogen-activated protein kinase(MAPKERK) protein kinase B and glycogen synthasekinase-3120573s [304] In addition Naoi andMaruyama suggestedthat the propargyl moiety might stabilize the mitochon-drial membrane through direct interaction with proteincomponents of the mitochondrial permeability transitionpore leading to increasing levels of antiapoptotic Bcl-2 andBcl-xL proteins [309] Supporting the prosurvival effectsof iron chelators a recent study showed that M30 andother hydroxyquinoline-based iron chelators regenerate theneuritic tree in cultured DA neurons treated with sublethalconcentrations of MPP+ in addition M30 given orallyregenerated nigrostriatal fibers mouse model after MPTPintoxication [310] Following themultifunctional approach iniron chelation others studies tested iron chelators with D2D3 dopamine receptor agonists to attack themotor symptomsand the oxidative stress simultaneously in the MPTP andlactacystin PD models Interestingly the authors found thatactivation of D3 dopamine receptors was important for theprotective effect of these molecules [311 312]


Environmental

endogenous toxins

Mitochondriadysfunction

Iron chelation

DecreasedISC

synthesis

DecreasedATP

synthesis

IncreasedIRP1 activity

DecreasedGSHGSSG

ratio

Increasedoxidative loadand damage

With time protein aggregation

proteasome dysfunction decreased mitophagy

microgliosisinflammation cytochrome c leak activation of death

pathways

Apoptosis

Survivalgenes

Mitochondrion-associated PD genes

Increasedredox-active Fe

OH∙

and

darr FPN1uarr DMT1

Figure 3 Mitochondrial dysfunction leads to iron accumulation and cell death Mitochondrial dysfunction in PD caused either byenvironmental or endogenous toxins or by genetic dysfunctions results in decreased ATP and ISC synthesis The lack of ISCs results ina false low iron signal and the spurious activation of IRP1 Activation of IRP1 results in increased redox-active iron levels mediated byincreased expression of DMT1 and TfR1 and decreased expression of FPN1 Because of hydroxyl radical generation through the Fentonreaction increased redox-active iron results in a decreased GSHGSSG ratio and an increased oxidative load The decrease in GSH furtheraffectsmitochondrial activityWith time the increased oxidative load induces protein aggregation and saturation of the ubiquitin-proteasomesystem further mitochondrial dysfunction an inflammatory microenvironment increased cytochrome c leak and activation of deathpathways Iron chelation has been demonstrated to slow this cycle by decreasing iron-associated oxidative damage and by induction ofcell survival and cell-rescue pathways Environmental and endogenous toxins paraquat rotenone MPTP nitric oxide 4-hydroxynonenaladvanced glycation end products and aminochromeMitochondria-associated PD genes withmitochondrial dysfunction component 120572-SynParkin PINK1 DJ-1 LRRK2 and ATP13A2

Other studies reported that some phytochemicals eval-uated in their capacity to confer neuroprotection in PDmodels acted through iron chelation [313] Curcumin alyphenolic compound fromCurcuma longadecreases the ironcontent in the SNpc of 6-OHDA lesioned rats and partiallyprotects them from the decrease in the number of TH+ cells[314] Moreover ginkgetin a biflavonoid from Ginkgo bilobashowed neuroprotection and attenuated the decrease inmito-chondrial membrane potential in dopaminergic cell cultures[295] In addition ginkgetin enhanced the performance inthe rotarod test and attenuated SNpc neuron lost in theMPTPmouse model [295]

Despite the promising character of the field only the rel-atively old iron chelator deferiprone (DFP) has been tested inclinical trials for the treatment of PDDFP is a small lipophilicmolecule that is orally active since it crosses the intestinal andblood-brain barriers DFP also permeates the cell and mito-chondrial membranes interchanging iron between mito-chondria cytoplasm and extracellular apotransferrin that isnot only chelating iron but also redistributing it [315] Theability to ldquomoverdquo iron out ofmitochondria is a very importantproperty because as discussed earlier the mitochondrionhas a prominent reactive iron pool and is the major ROSproducer in the cell [28 94 316]

A pilot clinical trial of DFP in PD patients tested witha design comparing the progression in iron content troughMRI and behavior alterations by the Unified ParkinsonrsquosDisease Rating Scale was successful Comparison betweengroups that began the treatment with a six-month difference(ldquoearly startrdquo and ldquodelay startrdquo groups) showed significantimprovement in the parameters in the ldquoearly startrdquo groupcompared with the ldquodelay startrdquo group [317]

A possible drawback of putative iron chelating therapy isthat chelators may facilitate the depletion of systemic ironwith severe consequences for other organs like the heart theliver and the hematopoietic system [286 287] The detectedundesirable effects of iron chelation include neutropenia in asmall percent of DFP-treated patients [317] and the possibilityof high blood pressure resulting from the selective inhibitionof peripheral MAO-A by the propargyl moiety of M30 andVAR [304] Maneuvers designed to counteract these undesir-able effects of iron chelation should be sought-after in futuresstudies

Clioquinol recently evaluated in clinical trials [318 319]presented apparently neurotoxic properties at high dosesIndeed clioquinol was indicated like the causative agentof subacute myelo-optic neuropathy (SMON) [320] DNA


double-strands breaks induction [321] superoxide dismutase1 inhibition [322] and nerve growth factor-induced Trkreceptor autophosphorylation inhibition [323] In additionthe clioquinol derivative PBT2 showed low effectiveness andin some cases adverse effects in a recently phase-2 trial forHuntingtonrsquos disease [324]

Overall the above evidence shows that iron chelationis a promising therapeutic approach to slow or rescue theneurodegenerative process of PD The development of newchelators should consider characteristics to make them spe-cific for cell type and effective at lower concentration thanthose actually in use A high affinity for iron seems not to berelevant for neuroprotection [325] but as Mena et al showed[172]mitochondrial targeting should enhancemitochondrialprotection and neuroprotective capacity In summary theneuroprotective effects of iron chelation reported up to dateare a stimuli for the development of newmultifunctional ironchelators with blood-brain barrier permeability and mito-chondrial targeting with significant activity at pharmacolog-ical concentrations and devoid of noxious side effects

10 Concluding Remarks

Themitochondrion is themain intrinsic ROS producer in thecell and has an intensive traffic of iron due to the synthesis ofISCs and heme prosthetic groups Because of the Fenton reac-tion mitochondrial levels of ROS and iron need to be tightlyregulated to avoid generation of the damaging hydroxyl radi-cal In both idiopathic and familial cases of PDmitochondrialdysfunction iron accumulation and oxidative damage arecommonly found in defective neurons We propose thatthese three occurrences are causally linked (Figure 3) Mito-chondrial dysfunction product of endogenous or exogenoustoxins or genetic predisposition results not only in increasedROS production but also in decreased ISC synthesis and IRP1activation In turn IRP1 activation results in iron accumu-lation and hydroxyl radical-mediated damage These threeeventsmdashmitochondrial dysfunction iron accumulation andoxidative damagemdashgenerate a positive feedback loop ofincreased iron accumulation and oxidative stress Interven-tion at someof these three levelsmay retard the progression ofthe disease Pharmacologically this effect could be achievedwith the use of multifunctional molecules with iron chelationcapacity since iron chelation has been linked to the protec-tion against oxidative damage and the activation of prosur-vival pathways

Disclosure

FONDECYT had no role in study design data collection andanalysis decision to publish or preparation of the paper

Competing Interests

The authors have declared that no competing interests existregarding the publication of this paper

Acknowledgments

This work was funded by the National Council for Scientificand Technological Research of Chile FONDECYT Grant1030068

References

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[2] P Jenner D T Dexter J Sian A H V Schapira and C DMarsden ldquoOxidative stress as a cause of nigral cell death inParkinsonrsquos disease and incidental Lewy body diseaserdquo Annalsof Neurology vol 32 supplement 1 pp S82ndashS87 1992

[3] S Mullin and A H V Schapira ldquoPathogenic mechanisms ofneurodegeneration in parkinson diseaserdquo Neurologic Clinicsvol 33 no 1 pp 1ndash17 2015

[4] A H Schapira ldquoMitochondria in the aetiology and pathogene-sis of Parkinsonrsquos diseaserdquoThe Lancet Neurology vol 7 no 1 pp97ndash109 2008

[5] Z I AlamA Jenner S E Daniel et al ldquoOxidativeDNAdamagein the Parkinsonian brain an apparent selective increase in 8-hydroxyguanine levels in substantia nigrardquo Journal of Neuro-chemistry vol 69 no 3 pp 1196ndash1203 1997

[6] E C Hirsch S Vyas and S Hunot ldquoNeuroinflammation inParkinsonrsquos diseaserdquo Parkinsonism and Related Disorders vol18 no 1 pp S210ndashS212 2012

[7] F A Zucca J Segura-Aguilar E Ferrari et al ldquoInteractions ofiron dopamine and neuromelanin pathways in brain aging andParkinsonrsquos diseaserdquo Progress in Neurobiology 2015

[8] M Rodriguez C Rodriguez-Sabate IMorales A Sanchez andM Sabate ldquoParkinsonrsquos disease as a result of agingrdquo Aging Cellvol 14 no 3 pp 293ndash308 2015

[9] L S Forno ldquoNeuropathology of Parkinsonrsquos diseaserdquo Journal ofNeuropathology and Experimental Neurology vol 55 no 3 pp259ndash272 1996

[10] KC Luk andVM-Y Lee ldquoModeling Lewypathology propaga-tion in Parkinsonrsquos diseaserdquoParkinsonismandRelatedDisordersvol 20 no 1 pp S85ndashS87 2014

[11] M Vila and S Przedborski ldquoGenetic clues to the pathogenesisof Parkinsonrsquos diseaserdquoNatureMedicine vol 10 supplement ppS58ndashS62 2004

[12] A J Duncan and S J R Heales ldquoNitric oxide and neurologicaldisordersrdquo Molecular Aspects of Medicine vol 26 no 1-2 pp67ndash96 2005

[13] P Jenner ldquoOxidative stress in Parkinsonrsquos diseaserdquo Annals ofNeurology vol 53 supplement 3 pp S26ndashS38 2003

[14] M A Acuna R Perez-Nunez J Noriega et al ldquoAltered voltagedependent calcium currents in a neuronal cell line derived fromthe cerebral cortex of a trisomy 16 fetal mouse an animal modelof down syndromerdquo Neurotoxicity Research vol 22 no 1 pp59ndash68 2012

[15] M T Baltazar R J Dinis-Oliveira M de Lourdes Bastos A MTsatsakis J A Duarte and F Carvalho ldquoPesticides exposure asetiological factors of Parkinsonrsquos disease and other neurodegen-erative diseasesmdasha mechanistic approachrdquo Toxicology Lettersvol 230 no 2 pp 85ndash103 2014

[16] A Ayala J L Venero J Cano and AMachado ldquoMitochondrialtoxins and neurodegenerative diseasesrdquo Frontiers in Biosciencevol 12 no 3 pp 986ndash1007 2007


[17] A H V Schapira J M Cooper D Dexter P Jenner J B Clarkand C D Marsden ldquoMitochondrial complex I deficiency inParkinsonrsquos diseaserdquoThe Lancet vol 333 no 8649 p 1269 1989

[18] A Camilleri and N Vassallo ldquoThe Centrality of mitochondriain the pathogenesis and treatment of Parkinsonrsquos diseaserdquo CNSNeuroscience andTherapeutics vol 20 no 7 pp 591ndash602 2014

[19] K J Barnham and A I Bush ldquoMetals in Alzheimerrsquos andParkinsonrsquos diseasesrdquo Current Opinion in Chemical Biology vol12 no 2 pp 222ndash228 2008

[20] K Boelmans B Holst M Hackius et al ldquoBrain iron depositionfingerprints in Parkinsonrsquos disease and progressive supranuclearpalsyrdquoMovement Disorders vol 27 no 3 pp 421ndash427 2012

[21] S Bolognin L Messori and P Zatta ldquoMetal ion physiopathol-ogy in neurodegenerative disordersrdquoNeuroMolecular Medicinevol 11 no 4 pp 223ndash238 2009

[22] R R Crichton D T Dexter and R J Ward ldquoBrain iron metab-olism and its perturbation in neurological diseasesrdquo Journal ofNeural Transmission vol 118 no 3 pp 301ndash314 2011

[23] D T Dexter A Carayon F Javoy-Agid et al ldquoAlterations inthe levels of iron ferritin and other trace metals in Parkinsonrsquosdisease and other neurodegenerative diseases affecting the basalgangliardquo Brain vol 114 part 4 pp 1953ndash1975 1991

[24] J Galazka-Friedman E R Bauminger K Szlachta and AFriedman ldquoThe role of iron in neurodegenerationmdashmossbauerspectroscopy electron microscopy enzyme-linked immunos-orbent assay and neuroimaging studiesrdquo Journal of PhysicsCondensed Matter vol 24 Article ID 244106 2012

[25] D B Kell ldquoTowards a unifying systems biology understandingof large-scale cellular death and destruction caused by poorlyliganded iron Parkinsonrsquos Huntingtonrsquos Alzheimerrsquos prionsbactericides chemical toxicology and others as examplesrdquoArchives of Toxicology vol 84 no 11 pp 825ndash889 2010

[26] K Jomova D Vondrakova M Lawson and M Valko ldquoMetalsoxidative stress and neurodegenerative disordersrdquo Molecularand Cellular Biochemistry vol 345 no 1-2 pp 91ndash104 2010

[27] HMochizuki and T Yasuda ldquoIron accumulation in Parkinsonrsquosdiseaserdquo Journal of Neural Transmission vol 119 no 12 pp 1511ndash1514 2012

[28] M T Nunez P Urrutia N Mena P Aguirre V Tapia and JSalazar ldquoIron toxicity in neurodegenerationrdquo BioMetals vol 25no 4 pp 761ndash776 2012

[29] S L Rhodes and B Ritz ldquoGenetics of iron regulation and thepossible role of iron in Parkinsonrsquos diseaserdquo Neurobiology ofDisease vol 32 no 2 pp 183ndash195 2008

[30] S A Schneider and K P Bhatia ldquoExcess iron harms the brainthe syndromes of neurodegeneration with brain iron accumu-lation (NBIA)rdquo Journal of Neural Transmission vol 120 no 4pp 695ndash703 2013

[31] A M Snyder and J R Connor ldquoIron the substantia nigra andrelated neurological disordersrdquo Biochimica et Biophysica Acta(BBA)mdashGeneral Subjects vol 1790 no 7 pp 606ndash614 2009

[32] K J Thompson S Shoham and J R Connor ldquoIron and neu-rodegenerative disordersrdquo Brain Research Bulletin vol 55 no 2pp 155ndash164 2001

[33] L Zecca M B H Youdim P Riederer J R Connor and R RCrichton ldquoIron brain ageing and neurodegenerative disordersrdquoNature Reviews Neuroscience vol 5 no 11 pp 863ndash873 2004

[34] R JWard F A Zucca J H Duyn R R Crichton and L ZeccaldquoThe role of iron in brain ageing and neurodegenerative disor-dersrdquoThe Lancet Neurology vol 13 no 10 pp 1045ndash1060 2014

[35] D Das X Luo A Singh et al ldquoParadoxical role of prion proteinaggregates in redox-iron induced toxicityrdquo PLoSONE vol 5 no7 Article ID e11420 2010

[36] N Singh ldquoThe role of iron in prion disease and other neurode-generative diseasesrdquo PLoS Pathogens vol 10 no 9 2014

[37] D Berg M Gerlach M B H Youdim et al ldquoBrain ironpathways and their relevance to Parkinsonrsquos diseaserdquo Journal ofNeurochemistry vol 79 no 2 pp 225ndash236 2001

[38] B Hallgren and P Sourander ldquoThe effect of age on the non-haemin iron in the human brainrdquo Journal of Neurochemistryvol 3 no 1 pp 41ndash51 1958

[39] D Berg C Siefker and G Becker ldquoEchogenicity of thesubstantia nigra in Parkinsonrsquos disease and its relation to clinicalfindingsrdquo Journal of Neurology vol 248 no 8 pp 684ndash6892001

[40] S J Dixon and B R Stockwell ldquoThe role of iron and reactiveoxygen species in cell deathrdquo Nature Chemical Biology vol 10no 1 pp 9ndash17 2014

[41] J R Doom and M K Georgieff ldquoStriking while the iron is hotunderstanding the biological and neurodevelopmental effectsof iron deficiency to optimize intervention in early childhoodrdquoCurrent Pediatrics Reports vol 2 no 4 pp 291ndash298 2014

[42] M Gonzalez-Guerrero A Matthiadis A Saez and T A LongldquoFixating on metals new insights into the role of metals innodulation and symbiotic nitrogen fixationrdquo Frontiers in PlantScience vol 5 article 45 2014

[43] C Hidalgo and M T Nunez ldquoCalcium iron and neuronalfunctionrdquo IUBMB Life vol 59 no 4-5 pp 280ndash285 2007

[44] M Ilbert andV Bonnefoy ldquoInsight into the evolution of the ironoxidation pathwaysrdquo Biochimica et Biophysica Acta (BBA)mdashBioenergetics vol 1827 no 2 pp 161ndash175 2013

[45] C Munoz E Rios J Olivos O Brunser andM Olivares ldquoIroncopper and immunocompetencerdquo The British Journal of Nutri-tion vol 98 supplement 1 pp S24ndashS28 2007

[46] P Munoz A Humeres C Elgueta A Kirkwood C Hidalgoand M T Nunez ldquoIron mediates N-Methyl-D-aspartate recep-tor-dependent stimulation of calcium-induced pathways andhippocampal synaptic plasticityrdquo Journal of Biological Chem-istry vol 286 no 15 pp 13382ndash13392 2011

[47] J L Pierre M Fontecave and R R Crichton ldquoChemistry foran essential biological process the reduction of ferric ironrdquoBioMetals vol 15 no 4 pp 341ndash346 2002

[48] F W Outten and E C Theil ldquoIron-based redox switches inbiologyrdquo Antioxidants and Redox Signaling vol 11 no 5 pp1029ndash1046 2009

[49] L G Valerio Jr ldquoMammalian iron metabolismrdquo ToxicologyMechanisms and Methods vol 17 no 9 pp 497ndash517 2007

[50] R Lill ldquoFunction and biogenesis of iron-sulphur proteinsrdquoNature vol 460 no 7257 pp 831ndash838 2009

[51] N Maio and T A Rouault ldquoIron-sulfur cluster biogenesis inmammalian cells new insights into the molecular mechanismsof cluster deliveryrdquo Biochimica et Biophysica Acta (BBA)mdashMolecular Cell Research vol 1853 no 6 pp 1493ndash1512 2015

[52] T A Rouault and W H Tong ldquoIron-sulfur cluster biogenesisand human diseaserdquo Trends in Genetics vol 24 no 8 pp 398ndash407 2008

[53] S J Chinta M J Kumar M Hsu et al ldquoInducible alterationsof glutathione levels in adult dopaminergic midbrain neuronsresult in nigrostriatal degenerationrdquo The Journal of Neuro-science vol 27 no 51 pp 13997ndash14006 2007


[54] M T Nunez V Gallardo P Munoz et al ldquoProgressive ironaccumulation induces a biphasic change in the glutathione con-tent of neuroblastoma cellsrdquo Free Radical Biology and Medicinevol 37 no 7 pp 953ndash960 2004

[55] S Epsztejn O Kakhlon H Glickstein W Breuer and Z ICabantchik ldquoFluorescence analysis of the labile iron pool ofmammalian cellsrdquo Analytical Biochemistry vol 248 no 1 pp31ndash40 1997

[56] O Kakhlon and Z I Cabantchik ldquoThe labile iron poolcharacterization measurement and participation in cellularprocessesrdquo Free Radical Biology and Medicine vol 33 no 8 pp1037ndash1046 2002

[57] M Kruszewski ldquoLabile iron pool The main determinant ofcellular response to oxidative stressrdquo Mutation ResearchmdashFundamental and Molecular Mechanisms of Mutagenesis vol531 no 1-2 pp 81ndash92 2003

[58] C C Philpott andM-S Ryu ldquoSpecial delivery distributing ironin the cytosol of mammalian cellsrdquo Frontiers in Pharmacologyvol 5 article 173 2014

[59] R C Hider and X Kong ldquoIron speciation in the cytosol anoverviewrdquo Dalton Transactions vol 42 no 9 pp 3220ndash32292013

[60] R C Hider and X L Kong ldquoGlutathione a key component ofthe cytoplasmic labile iron poolrdquo BioMetals vol 24 no 6 pp1179ndash1187 2011

[61] N P Mena A L Bulteau J Salazar E C Hirsch and M TNunez ldquoEffect of mitochondrial complex I inhibition on Fe-Scluster protein activityrdquo Biochemical and Biophysical ResearchCommunications vol 409 no 2 pp 241ndash246 2011

[62] F Petrat DWeisheitM LensenH deGroot R Sustmann andU Rauen ldquoSelective determination of mitochondrial chelatableiron in viable cells with a new fluorescent sensorrdquo BiochemicalJournal vol 362 no 1 pp 137ndash147 2002

[63] G P C Drummen L C M Van Liebergen J A F Opden Kamp and J A Post ldquoC11-BODIPY581591 an oxidation-sensitive fluorescent lipid peroxidation probe (micro)spectro-scopic characterization and validation of methodologyrdquo FreeRadical Biology and Medicine vol 33 no 4 pp 473ndash490 2002

[64] P Riederer E Sofic W-D Rausch et al ldquoTransition metalsferritin glutathione and ascorbic acid in parkinsonian brainsrdquoJournal of Neurochemistry vol 52 no 2 pp 515ndash520 1989

[65] L Zecca M Gallorini V Schunemann et al ldquoIron neurome-lanin and ferritin content in the substantia nigra of normal sub-jects at different ages consequences for iron storage and neu-rodegenerative processesrdquo Journal of Neurochemistry vol 76no 6 pp 1766ndash1773 2001

[66] D T Dexter F R Wells F Agid et al ldquoIncreased nigral ironcontent in postmortem parkinsonian brainrdquo The Lancet vol330 no 8569 pp 1219ndash1220 1987

[67] S-F Wu Z-F Zhu Y Kong et al ldquoAssessment of cerebral ironcontent in patients with Parkinsonrsquos disease by the susceptibil-ity-weighted MRIrdquo European Review for Medical and Pharma-cological Sciences vol 18 no 18 pp 2605ndash2608 2014

[68] M Wieler M Gee and W R W Martin ldquoLongitudinalmidbrain changes in early Parkinsonrsquos disease iron content esti-mated fromR2lowastMRIrdquo Parkinsonism and RelatedDisorders vol21 no 3 pp 179ndash183 2015

[69] G Du T Liu M M Lewis et al ldquoQuantitative susceptibilitymapping of the midbrain in Parkinsonrsquos diseaserdquo MovementDisorders vol 31 no 3 pp 317ndash324 2016

[70] CW Levenson R G Cutler B Ladenheim J L Cadet J Hareand M P Mattson ldquoRole of dietary iron restriction in a mousemodel of Parkinsonrsquos diseaserdquo Experimental Neurology vol 190no 2 pp 506ndash514 2004

[71] L-H You F Li L Wang et al ldquoBrain iron accumulationexacerbates the pathogenesis of MPTP-induced Parkinsonrsquosdiseaserdquo Neuroscience vol 284 pp 234ndash246 2015

[72] C Anderson H Checkoway G M Franklin S Beresford TSmith-Weller and PD Swanson ldquoDietary factors in Parkinsonrsquosdisease the role of food groups and specific foodsrdquo MovementDisorders vol 14 no 1 pp 21ndash27 1999

[73] G Logroscino X Gao H Chen A Wing and A AscherioldquoDietary iron intake and risk of Parkinsonrsquos diseaserdquo AmericanJournal of Epidemiology vol 168 no 12 pp 1381ndash1388 2008

[74] Y Miyake K Tanaka W Fukushima et al ldquoDietary intake ofmetals and risk of Parkinsonrsquos disease a case-control study inJapanrdquo Journal of the Neurological Sciences vol 306 no 1-2 pp98ndash102 2011

[75] I Pichler M F Del Greco M Gogele et al ldquoSerum iron levelsand the risk of Parkinson disease a Mendelian randomizationstudyrdquo PLoS Medicine vol 10 no 6 Article ID e1001462 2013

[76] J E Nielsen L N Jensen and K Krabbe ldquoHereditary haemo-chromatosis a case of iron accumulation in the basal gangliaassociatedwith a parkinsonian syndromerdquo Journal of NeurologyNeurosurgery and Psychiatry vol 59 no 3 pp 318ndash321 1995

[77] M C J Dekker P C Giesbergen O T Njajou et al ldquoMutationsin the hemochromatosis gene (HFE) Parkinsonrsquos disease andparkinsonismrdquo Neuroscience Letters vol 348 no 2 pp 117ndash1192003

[78] R J Guerreiro J M Bras I Santana et al ldquoAssociation ofHFE common mutations with Parkinsonrsquos disease Alzheimerrsquosdisease andmild cognitive impairment in a Portuguese cohortrdquoBMC Neurology vol 6 article 24 2006

[79] W Nandar and J R Connor ldquoHFE gene variants affect iron inthe brainrdquo Journal of Nutrition vol 141 no 4 pp 729Sndash739S2011

[80] G Biasiotto S Goldwurm D Finazzi et al ldquoHFE gene muta-tions in a population of Italian Parkinsonrsquos disease patientsrdquoParkinsonism and Related Disorders vol 14 no 5 pp 426ndash4302008

[81] A H Aamodt L J Stovner K Thorstensen S Lydersen L RWhite and J O Aasly ldquoPrevalence of haemochromatosis genemutations in Parkinsonrsquos diseaserdquo Journal of Neurology Neuro-surgery and Psychiatry vol 78 no 3 pp 315ndash317 2007

[82] N Akbas H Hochstrasser J Deplazes et al ldquoScreening formutations of the HFE gene in Parkinsonrsquos disease patients withhyperechogenicity of the substantia nigrardquoNeuroscience Lettersvol 407 no 1 pp 16ndash19 2006

[83] A Boveris and E Cadenas ldquoMitochondrial production ofsuperoxide anions and its relationship to the antimycin insen-sitive respirationrdquo FEBS Letters vol 54 no 3 pp 311ndash314 1975

[84] E Cadenas and K J A Davies ldquoMitochondrial free radicalgeneration oxidative stress and agingrdquoFree Radical Biology andMedicine vol 29 no 3-4 pp 222ndash230 2000

[85] D Han E Williams and E Cadenas ldquoMitochondrial respira-tory chain-dependent generation of superoxide anion and itsrelease into the intermembrane spacerdquo Biochemical Journal vol353 no 2 pp 411ndash416 2001

[86] A D Romano E Greco G Vendemiale and G ServiddioldquoBioenergetics and mitochondrial dysfunction in aging recentinsights for a therapeutical approachrdquo Current PharmaceuticalDesign vol 20 no 18 pp 2978ndash2992 2014


[87] F Yin A Boveris and E Cadenas ldquoMitochondrial energymetabolism and redox signaling in brain aging and neurode-generationrdquoAntioxidants and Redox Signaling vol 20 no 2 pp353ndash371 2014

[88] J HirstM S King andK R Pryde ldquoThe production of reactiveoxygen species by complex Irdquo Biochemical Society Transactionsvol 36 no 5 pp 976ndash980 2008

[89] A J Kowaltowski N C de Souza-Pinto R F Castilho andA EVercesi ldquoMitochondria and reactive oxygen speciesrdquo Free Rad-ical Biology and Medicine vol 47 no 4 pp 333ndash343 2009

[90] J R Veatch M A McMurray Z W Nelson and D EGottschling ldquoMitochondrial dysfunction leads to nucleargenome instability via an iron-sulfur cluster defectrdquo Cell vol137 no 7 pp 1247ndash1258 2009

[91] H Beinert and P J Kiley ldquoFe-S proteins in sensing and regu-latory functionsrdquo Current Opinion in Chemical Biology vol 3no 2 pp 152ndash157 1999

[92] H A Dailey and P N Meissner ldquoErythroid heme biosynthesisand its disordersrdquo Cold Spring Harbor Perspectives in Medicinevol 3 no 4 Article ID a011676 2013

[93] O Stehling and R Lill ldquoThe role of mitochondria in cellulariron-sulfur protein biogenesis mechanisms connected pro-cesses and diseasesrdquo Cold Spring Harbor Perspectives inMedicine vol 3 no 7 pp 1ndash17 2013

[94] N P Mena P J Urrutia F Lourido C M Carrasco and M TNunez ldquoMitochondrial iron homeostasis and its dysfunctionsin neurodegenerative disordersrdquoMitochondrion vol 21 pp 92ndash105 2015

[95] M Shvartsman and Z Ioav Cabantchik ldquoIntracellular irontrafficking role of cytosolic ligandsrdquoBioMetals vol 25 no 4 pp711ndash723 2012

[96] U Muhlenhoff S Molik J R Godoy et al ldquoCytosolic monoth-iol glutaredoxins function in intracellular iron sensing andtrafficking via their bound iron-sulfur clusterrdquo Cell Metabolismvol 12 no 4 pp 373ndash385 2010

[97] C C Philpott ldquoComing into view eukaryotic iron chaperonesand intracellular iron deliveryrdquoThe Journal of Biological Chem-istry vol 287 no 17 pp 13518ndash13523 2012

[98] M Shvartsman E Fibach and Z I Cabantchik ldquoTransferrin-iron routing to the cytosol and mitochondria as studied by liveand real-time fluorescencerdquo Biochemical Journal vol 429 no 1pp 185ndash193 2010

[99] A D Sheftel A-S Zhang C Brown O S Shirihai and PPonka ldquoDirect interorganellar transfer of iron from endosometo mitochondrionrdquo Blood vol 110 no 1 pp 125ndash132 2007

[100] S Bekri G Kispal H Lange et al ldquoHuman ABC7 transportergene structure and mutation causing X-linked sideroblasticanemia with ataxia with disruption of cytosolic iron-sulfurprotein maturationrdquo Blood vol 96 no 9 pp 3256ndash3264 2000

[101] C Pondarre D R Campagna B Antiochos L Sikorski HMulhern and M D Fleming ldquoAbcb7 the gene responsiblefor X-linked sideroblastic anemia with ataxia is essential forhematopoiesisrdquo Blood vol 109 no 8 pp 3567ndash3569 2007

[102] K Sato Y Torimoto T Hosoki et al ldquoLoss of ABCB7 genepathogenesis of mitochondrial iron accumulation in erythrob-lasts in refractory anemiawith ringed sideroblast with isodicen-tric (X)(q13)rdquo International Journal of Hematology vol 93 no3 pp 311ndash318 2011

[103] Y Ichikawa M Bayeva M Ghanefar et al ldquoDisruption of ATP-binding cassette B8 in mice leads to cardiomyopathy througha decrease in mitochondrial iron exportrdquo Proceedings of the

National Academy of Sciences of the United States of Americavol 109 no 11 pp 4152ndash4157 2012

[104] C Pondarre B B Antiochos D R Campagna et al ldquoThemito-chondrial ATP-binding cassette transporter Abcb7 is essentialinmice and participates in cytosolic iron-sulfur cluster biogene-sisrdquoHumanMolecularGenetics vol 15 no 6 pp 953ndash964 2006

[105] J A Navarro J A Botella C Metzendorf M I Lind and SSchneuwly ldquoMitoferrin modulates iron toxicity in a Drosophilamodel of Friedreichrsquos ataxiardquo Free Radical Biology andMedicinevol 85 pp 71ndash82 2015

[106] F Petrat H de Groot and U Rauen ldquoSubcellular distributionof chelatable iron a laser scanningmicroscopic study in isolatedhepatocytes and liver endothelial cellsrdquo Biochemical Journalvol 356 no 1 pp 61ndash69 2001

[107] Y Mizuno S Ohta M Tanaka et al ldquoDeficiencies in complexI subunits of the respiratory chain in Parkinsonrsquos diseaserdquoBiochemical and Biophysical Research Communications vol 163no 3 pp 1450ndash1455 1989

[108] YMizuno S-I Ikebe NHattori et al ldquoRole ofmitochondria inthe etiology and pathogenesis of Parkinsonrsquos diseaserdquo Biochim-ica et Biophysica Acta (BBA)mdashMolecular Basis of Disease vol1271 no 1 pp 265ndash274 1995

[109] W D Parker Jr S J Boyson and J K Parks ldquoAbnormalities ofthe electron transport chain in idiopathic Parkinsonrsquos diseaserdquoAnnals of Neurology vol 26 no 6 pp 719ndash723 1989

[110] L A Bindoff M Birch-Machin N E F Cartlidge W D ParkerJr and D M Turnbull ldquoMitochondrial function in ParkinsonrsquosdiseaserdquoThe Lancet vol 334 no 8653 p 49 1989

[111] A H V Schapira J M Cooper D Dexter J B Clark P Jennerand C D Marsden ldquoMitochondrial complex I deficiency inParkinsonrsquos diseaserdquo Journal of Neurochemistry vol 54 no 3pp 823ndash827 1990

[112] W D Parker Jr J K Parks and R H Swerdlow ldquoComplex Ideficiency in Parkinsonrsquos disease frontal cortexrdquo Brain Researchvol 1189 no 1 pp 215ndash218 2008

[113] G P Davey S Peuchen and J B Clark ldquoEnergy thresholds inbrain mitochondria Potential involvement in neurodegenera-tionrdquo The Journal of Biological Chemistry vol 273 no 21 pp12753ndash12757 1998

[114] D Di Monte S A Jewell G Ekstrom M S Sandy and M TSmith ldquo1-Methyl-4-phenyl-1236-tetrahydropyridine (MPTP)and 1-methyl-4-phenylpyridine (MPP+) cause rapid ATPdepletion in isolated hepatocytesrdquo Biochemical and BiophysicalResearch Communications vol 137 no 1 pp 310ndash315 1986

[115] T L Perry D V Godin and S Hansen ldquoParkinsonrsquos diseasea disorder due to nigral glutathione deficiencyrdquo NeuroscienceLetters vol 33 no 3 pp 305ndash310 1982

[116] J Sian D T Dexter A J Lees S Daniel P Jenner and C DMarsden ldquoGlutathione-related enzymes in brain in Parkinsonrsquosdiseaserdquo Annals of Neurology vol 36 no 3 pp 356ndash361 1994

[117] A D Owen A H V Schapira P Jenner and C D MarsdenldquoOxidative stress and Parkinsonrsquos diseaserdquo Annals of the NewYork Academy of Sciences vol 786 pp 217ndash223 1996

[118] D T Dexter C J Carter F R Wells et al ldquoBasal lipid perox-idation in substantia nigra is increased in Parkinsonrsquos diseaserdquoJournal of Neurochemistry vol 52 no 2 pp 381ndash389 1989

[119] M Gerlach P Riederer H Przuntek and M B H YoudimldquoMPTP mechanisms of neurotoxicity and their implicationsfor Parkinsonrsquos diseaserdquo European Journal of PharmacologyMolecular Pharmacology vol 208 no 4 pp 273ndash286 1991


[120] D T Dexter F R Wells A J Lees et al ldquoIncreased nigral ironcontent and alterations in other metal ions occurring in brainin Parkinsonrsquos diseaserdquo Journal of Neurochemistry vol 52 no 6pp 1830ndash1836 1989

[121] W S Enochs T Sarna L Zecca P A Riley and H M SwartzldquoThe roles of neuromelanin binding of metal ions and oxida-tive cytotoxicity in the pathogenesis of Parkinsonrsquos disease ahypothesisrdquo Journal of Neural Transmission Parkinsonrsquos Diseaseand Dementia Section vol 7 no 2 pp 83ndash100 1994

[122] B A FaucheuxM-EMartin C Beaumont J-J Hauw Y Agidand E C Hirsch ldquoNeuromelanin associated redox-active ironis increased in the substantia nigra of patients with Parkinsonrsquosdiseaserdquo Journal of Neurochemistry vol 86 no 5 pp 1142ndash11482003

[123] D W Lee D Kaur S J Chinta S Rajagopalan and J KAndersen ldquoA disruption in iron-sulfur center biogenesis viainhibition of mitochondrial dithiol glutaredoxin 2 may con-tribute to mitochondrial and cellular iron dysregulation inmammalian glutathione-depleted dopaminergic cells implica-tions for Parkinsonrsquos diseaserdquoAntioxidants and Redox Signalingvol 11 no 9 pp 2083ndash2094 2009

[124] A H V Schapira ldquoCalcium dysregulation in Parkinsonrsquos dis-easerdquo Brain vol 136 no 7 pp 2015ndash2016 2013

[125] N Nishino S A Noguchi-Kuno T Sugiyama and C Tanakaldquo[3H]Nitrendipine binding sites are decreased in the substantianigra and striatum of the brain from patients with Parkinsonrsquosdiseaserdquo Brain Research vol 377 no 1 pp 186ndash189 1986

[126] J P Sheehan R H Swerdlow W D Parker S W Miller RE Davis and J B Tuttle ldquoAltered calcium homeostasis in cellstransformedbymitochondria from individualswith Parkinsonrsquosdiseaserdquo Journal of Neurochemistry vol 68 no 3 pp 1221ndash12331997

[127] J W Langston P Ballard J W Tetrud and I Irwin ldquoChronicParkinsonism in humans due to a product of meperidine-analog synthesisrdquo Science vol 219 no 4587 pp 979ndash980 1983

[128] J W Langston I Irwin and E B Langston ldquoPargyline preventsMPTP-induced parkinsonism in primatesrdquo Science vol 225 no4669 pp 1480ndash1482 1984

[129] R S Burns C C Chiueh S P Markey M H Ebert D MJacobowitz and I J Kopin ldquoA primate model of parkinsonismselective destruction of dopaminergic neurons in the parscompacta of the substantia nigra byN-methyl-4-phenyl-1236-tetrahydropyridinerdquo Proceedings of the National Academy ofSciences of the United States of America vol 80 no 14 pp 4546ndash4550 1983

[130] R E Heikkila A Hess and R C Duvoisin ldquoDopaminergicneurotoxicity of 1-methyl-4-phenyl-1256-tetrahydropyridinein micerdquo Science vol 224 no 4656 pp 1451ndash1453 1984

[131] J A Temlett J P Landsberg F Watt and G W GrimeldquoIncreased iron in the substantia nigra compacta of the MPTP-lesioned hemiparkinsonian African Green monkey evidencefrom proton microprobe elemental microanalysisrdquo Journal ofNeurochemistry vol 62 no 1 pp 134ndash146 1994

[132] E Oestreicher G J Sengstock P Riederer C W OlanowA J Dunn and G W Arendash ldquoDegeneration of nigros-triatal dopaminergic neurons increases iron within the sub-stantia nigra a histochemical and neurochemical studyrdquo BrainResearch vol 660 no 1 pp 8ndash18 1994

[133] M C Ghosh D-L Zhang and T A Rouault ldquoIron misregula-tion and neurodegenerative disease in mouse models that lackiron regulatory proteinsrdquo Neurobiology of Disease vol 81 pp66ndash75 2015

[134] D-L ZhangMCGhosh andTA Rouault ldquoThephysiologicalfunctions of iron regulatory proteins in iron homeostasismdashanupdaterdquo Frontiers in Pharmacology vol 5 article 124 2014

[135] J Wang C Fillebeen G Chen A Biederbick R Lill and KPantopoulos ldquoIron-dependent degradation of apo-IRP1 by theubiquitin-proteasome pathwayrdquoMolecular and Cellular Biologyvol 27 no 7 pp 2423ndash2430 2007

[136] K L Schalinske S A Anderson P T Tuazon O S ChenM CKennedy and R S Eisenstein ldquoThe iron-sulfur cluster of ironregulatory protein 1 modulates the accessibility of RNA bindingand phosphorylation sitesrdquo Biochemistry vol 36 no 13 pp3950ndash3958 1997

[137] C Bouton H Hirling and J-C Drapier ldquoRedox modulationof iron regulatory proteins by peroxynitriterdquo The Journal ofBiological Chemistry vol 272 no 32 pp 19969ndash19975 1997

[138] A Stys B Galy R R Starzynski et al ldquoIron regulatory protein1 outcompetes iron regulatory protein 2 in regulating cellulariron homeostasis in response to nitric oxiderdquo The Journal ofBiological Chemistry vol 286 no 26 pp 22846ndash22854 2011

[139] P R Gardner I Raineri L B Epstein and CWWhite ldquoSuper-oxide radical and iron modulate aconitase activity in mam-malian cellsrdquo The Journal of Biological Chemistry vol 270 no22 pp 13399ndash13405 1995

[140] J Salazar N Mena and M T Nunez ldquoIron dyshomeosta-sis in Parkinsonrsquos diseaserdquo Journal of Neural Transmission-Supplement no 71 pp 205ndash213 2006

[141] R Betarbet T B Sherer G MacKenzie M Garcia-Osuna AV Panov and J T Greenamyre ldquoChronic systemic pesticideexposure reproduces features of Parkinsonrsquos diseaserdquo NatureNeuroscience vol 3 no 12 pp 1301ndash1306 2000

[142] C M Tanner F Kame G W Ross et al ldquoRotenone paraquatand Parkinsonrsquos diseaserdquoEnvironmental Health Perspectives vol119 no 6 pp 866ndash872 2011

[143] W M Caudle Occupational Exposures and Parkinsonism vol131 of Handbook of Clinical Neurology 2015

[144] C Freire and S Koifman ldquoPesticides depression and suicidea systematic review of the epidemiological evidencerdquo Interna-tional Journal of Hygiene and Environmental Health vol 216 no4 pp 445ndash460 2013

[145] T Fukushima K Yamada A Isobe K Shiwaku and Y YamaneldquoMechanism of cytotoxicity of paraquat I NADH oxidationand paraquat radical formation via complex Irdquo Experimentaland Toxicologic Pathology vol 45 no 5-6 pp 345ndash349 1993

[146] T Yamamoto M Anno and T Sato ldquoEffects of paraquat onmitochondria of rat skeletal musclerdquo Comparative Biochemistryand Physiology Part C Comparative Pharmacology vol 86 no2 pp 375ndash378 1987

[147] T Tawara T Fukushima N Hojo et al ldquoEffects of paraquaton mitochondrial electron transport system and catecholaminecontents in rat brainrdquo Archives of Toxicology vol 70 no 9 pp585ndash589 1996

[148] F Cicchetti N Lapointe A Roberge-Tremblay et al ldquoSystemicexposure to paraquat and maneb models early Parkinsonrsquosdisease in young adult ratsrdquoNeurobiology of Disease vol 20 no2 pp 360ndash371 2005

[149] R J Dinis-Oliveira F Remiao H Carmo et al ldquoParaquatexposure as an etiological factor of Parkinsonrsquos diseaserdquo Neu-roToxicology vol 27 no 6 pp 1110ndash1122 2006

[150] K Kuter P Nowak K Gołembiowska and K OssowskaldquoIncreased reactive oxygen species production in the brainafter repeated low-dose pesticide paraquat exposure in rats


A comparisonwith peripheral tissuesrdquoNeurochemical Researchvol 35 no 8 pp 1121ndash1130 2010

[151] B J Day M Patel L Calavetta L-Y Chang and J S StamlerldquoA mechanism of paraquat toxicity involving nitric oxidesynthaserdquo Proceedings of the National Academy of Sciences of theUnited States of America vol 96 no 22 pp 12760ndash12765 1999

[152] A I Brooks CA ChadwickHAGelbardDA Cory-SlechtaandH J Federoff ldquoParaquat elicited neurobehavioral syndromecaused by dopaminergic neuron lossrdquo Brain Research vol 823no 1-2 pp 1ndash10 1999

[153] A L McCormack MThiruchelvam A B Manning-Bog et alldquoEnvironmental risk factors and Parkinsonrsquos disease selectivedegeneration of nigral dopaminergic neurons caused by theherbicide paraquatrdquo Neurobiology of Disease vol 10 no 2 pp119ndash127 2002

[154] PM RappoldM Cui A S Chesser et al ldquoParaquat neurotoxi-city ismediated by the dopamine transporter and organic cationtransporter-3rdquo Proceedings of the National Academy of Sciencesof the United States of America vol 108 no 51 pp 20766ndash207712011

[155] C Berry C La Vecchia and P Nicotera ldquoParaquat andParkinsonrsquos diseaserdquo Cell Death and Differentiation vol 17 no7 pp 1115ndash1125 2010

[156] G W Miller ldquoParaquat the red herring of Parkinsonrsquos diseaseresearchrdquo Toxicological Sciences vol 100 no 1 pp 1ndash2 2007

[157] B C Jones X Huang R BMailman L Lu and RWWilliamsldquoThe perplexing paradox of paraquat the case for host-basedsusceptibility andpostulated neurodegenerative effectsrdquo Journalof Biochemical and Molecular Toxicology vol 28 no 5 pp 191ndash197 2014

[158] K J Barnham and A I Bush ldquoBiological metals and metal-targeting compounds in major neurodegenerative diseasesrdquoChemical Society Reviews vol 43 no 19 pp 6727ndash6749 2014

[159] B Wu B Song S Tian et al ldquoCentral nervous system damagedue to acute paraquat poisoning a neuroimaging study with30 T MRIrdquo NeuroToxicology vol 33 no 5 pp 1330ndash1337 2012

[160] D Cantu J Schaack and M Patel ldquoOxidative inactivation ofmitochondrial aconitase results in iron and H

2O2-mediated

neurotoxicity in rat primary mesencephalic culturesrdquo PLoSONE vol 4 no 9 Article ID e7095 2009

[161] J W Langston and P A Ballard Jr ldquoParkinsonrsquos disease in achemist working with 1-methyl-4-phenyl-1256-tetrahydropy-ridinerdquoThe New England Journal of Medicine vol 309 no 5 p310 1983

[162] T B Sherer J R Richardson C M Testa et al ldquoMechanism oftoxicity of pesticides acting at complex I relevance to environ-mental etiologies of Parkinsonrsquos diseaserdquo Journal of Neurochem-istry vol 100 no 6 pp 1469ndash1479 2007

[163] W J Nicklas I Vyas and R E Heikkila ldquoInhibition of NADH-linked oxidation in brain mitochondria by 1-methyl-4-phenyl-pyridine a metabolite of the neurotoxin 1-methyl-4-phenyl-1256-tetrahydropyridinerdquo Life Sciences vol 36 no 26 pp2503ndash2508 1985

[164] R R Ramsay J I Salach J Dadgar and T P Singer ldquoInhibitionof mitochondrial NADH dehydrogenase by pyridine deriva-tives and its possible relation to experimental and idiopathicparkinsonismrdquo Biochemical and Biophysical Research Commu-nications vol 135 no 1 pp 269ndash275 1986

[165] M J Krueger T P Singer J E Casida and R R RamsayldquoEvidence that the blockade of mitochondrial respiration bythe neurotoxin 1-methyl-4-phenylpyridinium (MPP+) involves

binding at the same site as the respiratory inhibitor rotenonerdquoBiochemical and Biophysical Research Communications vol 169no 1 pp 123ndash128 1990

[166] J T Greenamyre G MacKenzie T-I Peng and S E StephansldquoMitochondrial dysfunction in Parkinsonrsquos diseaserdquo Biochemi-cal Society Symposium vol 66 pp 85ndash97 1999

[167] M Gerlach P Riederer and M B Youdim ldquoMolecular mech-anisms for neurodegeneration Synergism between reactiveoxygen species calcium and excitotoxic amino acidsrdquoAdvancesin Neurology vol 69 pp 177ndash194 1996

[168] J F Turrens and A Boveris ldquoGeneration of superoxide anionby the NADH dehydrogenase of bovine heart mitochondriardquoBiochemical Journal vol 191 no 2 pp 421ndash427 1980

[169] E Hasegawa K Takeshige T Oishi YMurai and SMinakamildquo1-Methyl-4-phenylpyridinium (MPP+) induces NADH-dependent superoxide formation and enhances NADH-dependent lipid peroxidation in bovine heart submitochondrialparticlesrdquo Biochemical and Biophysical Research Communica-tions vol 170 no 3 pp 1049ndash1055 1990

[170] T B Sherer R Betarbet C M Testa et al ldquoMechanism oftoxicity in rotenone models of Parkinsonrsquos diseaserdquoThe Journalof Neuroscience vol 23 no 34 pp 10756ndash10764 2003

[171] P Xiong X Chen C Y Guo N Zhang and B C Ma ldquoBaicalinand deferoxamine alleviate iron accumulation in differentbrain regions of Parkinsonrsquos disease ratsrdquo Neural RegenerationResearch vol 7 no 27 pp 2092ndash2098 2012

[172] N PMenaOGarcıa-Beltran F Lourido et al ldquoThenovelmito-chondrial iron chelator 5-((methylamino)methyl)-8-hydrox-yquinoline protects against mitochondrial-induced oxidativedamage and neuronal deathrdquo Biochemical and BiophysicalResearch Communications vol 463 no 4 pp 787ndash792 2015

[173] U Dettmer D Selkoe and T Bartels ldquoNew insights into cellular120572-synuclein homeostasis in health and diseaserdquo Current Opin-ion in Neurobiology vol 36 pp 15ndash22 2016

[174] J Burre ldquoThe synaptic function of 120572-synucleinrdquo Journal ofParkinsonrsquos Disease vol 5 no 4 pp 699ndash713 2015

[175] J Xu S-Y Kao F J S LeeW Song L-W Jin and B A YanknerldquoDopamine-dependent neurotoxicity of 120572-synuclein a mech-anism for selective neurodegeneration in Parkinson diseaserdquoNature Medicine vol 8 no 6 pp 600ndash606 2002

[176] H-J Lee and S-J Lee ldquoCharacterization of cytoplasmic 120572-synuclein aggregates Fibril formation is tightly linked to theinclusion-forming process in cellsrdquo The Journal of BiologicalChemistry vol 277 no 50 pp 48976ndash48983 2002

[177] L J Hsu Y Sagara A Arroyo et al ldquo120572-synuclein promotesmitochondrial deficit and oxidative stressrdquo The American Jour-nal of Pathology vol 157 no 2 pp 401ndash410 2000

[178] Y Tanaka S Engelender S Igarashi et al ldquoInducible expres-sion of mutant 120572-synuclein decreases proteasome activity andincreases sensitivity to mitochondria-dependent apoptosisrdquoHuman Molecular Genetics vol 10 no 9 pp 919ndash926 2001

[179] C E-HMoussa CWersinger Y Tomita andA Sidhu ldquoDiffer-ential cytotoxicity of human wild type and mutant 120572-synucleinin human neuroblastoma SH-SY5Y cells in the presence ofdopaminerdquo Biochemistry vol 43 no 18 pp 5539ndash5550 2004

[180] A Bir O Sen S Anand et al ldquo120572-synuclein-induced mito-chondrial dysfunction in isolated preparation and intact cellsimplications in the pathogenesis of Parkinsonrsquos diseaserdquo Journalof Neurochemistry vol 131 no 6 pp 868ndash877 2014

[181] N B Cole D DiEuliis P Leo D C Mitchell and R L Nuss-baum ldquoMitochondrial translocation of120572-synuclein is promoted


by intracellular acidificationrdquo Experimental Cell Research vol314 no 10 pp 2076ndash2089 2008

[182] S Shavali H M Brown-Borg M Ebadi and J Porter ldquoMito-chondrial localization of alpha-synuclein protein in alpha-synuclein overexpressing cellsrdquo Neuroscience Letters vol 439no 2 pp 125ndash128 2008

[183] L Devi V Raghavendran B M Prabhu N G Avadhaniand H K Anandatheerthavarada ldquoMitochondrial import andaccumulation of 120572-synuclein impair complex I in humandopaminergic neuronal cultures and Parkinson disease brainrdquoThe Journal of Biological Chemistry vol 283 no 14 pp 9089ndash9100 2008

[184] M S Parihar A Parihar M Fujita M Hashimoto andP Ghafourifar ldquoMitochondrial association of alpha-synucleincauses oxidative stressrdquoCellular andMolecular Life Sciences vol65 no 7-8 pp 1272ndash1284 2008

[185] L J Martin Y Pan A C Price et al ldquoParkinsonrsquos disease120572-synuclein transgenic mice develop neuronal mitochondrialdegeneration and cell deathrdquo The Journal of Neuroscience vol26 no 1 pp 41ndash50 2006

[186] DD Song CW Shults A Sisk E Rockenstein andEMasliahldquoEnhanced substantia nigramitochondrial pathology in human120572-synuclein transgenicmice after treatmentwithMPTPrdquoExper-imental Neurology vol 186 no 2 pp 158ndash172 2004

[187] M Zaltieri F Longhena M Pizzi C Missale P Spano and ABellucci ldquoMitochondrial dysfunction and 120572-synuclein synapticpathology in Parkinsonrsquos disease whorsquos on firstrdquo ParkinsonrsquosDisease vol 2015 Article ID 108029 10 pages 2015

[188] J Howitt A M Gysbers S Ayton et al ldquoIncreased Ndfip1 inthe substantia nigra of parkinsonian brains is associated withelevated iron levelsrdquo PLoS ONE vol 9 no 1 article e87119 2014

[189] R Ortega A Carmona S Roudeau et al ldquo120572-Synuclein over-expression induces increased iron accumulation and redistri-bution in iron-exposed neuronsrdquo Molecular Neurobiology vol53 no 3 pp 1925ndash1934 2016

[190] Y Peng C Wang H H Xu Y-N Liu and F Zhou ldquoBindingof 120572-synuclein with Fe(III) and with Fe(II) and biologicalimplications of the resultant complexesrdquo Journal of InorganicBiochemistry vol 104 no 4 pp 365ndash370 2010

[191] A Binolfi RM Rasia CW Bertoncini et al ldquoInteraction of 120572-synuclein with divalent metal ions reveals key differences a linkbetween structure binding specificity and fibrillation enhance-mentrdquo Journal of the American Chemical Society vol 128 no30 pp 9893ndash9901 2006

[192] Bharathi S S Indi and K S J Rao ldquoCopper- and iron-induceddifferential fibril formation in 120572-synuclein TEM studyrdquo Neuro-science Letters vol 424 no 2 pp 78ndash82 2007

[193] N Ostrerova-Golts L Petrucelli J Hardy J M Lee M Farerand B Wolozin ldquoThe A53T 120572-synuclein mutation increasesiron-dependent aggregation and toxicityrdquo The Journal of Neu-roscience vol 20 no 16 pp 6048ndash6054 2000

[194] F L Martin S J MWilliamson K E Paleologou R Hewitt OM A El-Agnaf and D Allsop ldquoFe(II)-induced DNA damagein 120572-synuclein-transfected human dopaminergic BE(2)-M17neuroblastoma cells detection by the Comet assayrdquo Journal ofNeurochemistry vol 87 no 3 pp 620ndash630 2003

[195] N Golts H Snyder M Frasier C Theisler P Choi and BWolozin ldquoMagnesium inhibits spontaneous and iron-inducedaggregation of120572-synucleinrdquo Journal of Biological Chemistry vol277 no 18 pp 16116ndash16123 2002

[196] R Cappai S-L Leek D J Tew et al ldquoDopamine promotes 120572-synuclein aggregation into SDS-resistant soluble oligomers via

a distinct folding pathwayrdquo The FASEB Journal vol 19 no 10pp 1377ndash1379 2005

[197] E Deas N Cremades P R Angelova et al ldquoAlpha-synucleinoligomers interact withmetal ions to induce oxidative stress andneuronal death in parkinsonrsquos diseaserdquo Antioxidants amp RedoxSignaling vol 24 no 7 pp 376ndash391 2016

[198] Q He N Song F Jia et al ldquoRole of 120572-synuclein aggregationand the nuclear factor E2-related factor 2heme oxygenase-1 pathway in iron-induced neurotoxicityrdquo The InternationalJournal of Biochemistry and Cell Biology vol 45 no 6 pp 1019ndash1030 2013

[199] W Xiang J C M Schlachetzki S Helling et al ldquoOxida-tive stress-induced posttranslational modifications of alpha-synuclein specific modification of alpha-synuclein by 4-hydroxy-2-nonenal increases dopaminergic toxicityrdquoMolecularand Cellular Neuroscience vol 54 pp 71ndash83 2013

[200] C Wang L Liu L Zhang Y Peng and F Zhou ldquoRedox reac-tions of the120572-synucleinminusCu2+ complex and their effects on neu-ronal cell viabilityrdquo Biochemistry vol 49 no 37 pp 8134ndash81422010

[201] M S Parihar A Parihar M Fujita M Hashimoto and PGhafourifar ldquoAlpha-synuclein overexpression and aggregationexacerbates impairment of mitochondrial functions by aug-menting oxidative stress in human neuroblastoma cellsrdquo TheInternational Journal of Biochemistry amp Cell Biology vol 41 no10 pp 2015ndash2024 2009

[202] G Yamin C B Glaser V N Uversky and A L Fink ldquoCertainmetals trigger fibrillation of methionine-oxidized 120572-synucleinrdquoThe Journal of Biological Chemistry vol 278 no 30 pp 27630ndash27635 2003

[203] A Santner and V N Uversky ldquoMetalloproteomics and metaltoxicology of 120572-synucleinrdquo Metallomics vol 2 no 6 pp 378ndash392 2010

[204] L A Munishkina A L Fink and V N Uversky ldquoConcertedaction of metals and macromolecular crowding on the fibrilla-tion of 120572-synucleinrdquo Protein and Peptide Letters vol 15 no 10pp 1079ndash1085 2008

[205] V N Uversky J Li K Bower and A L Fink ldquoSynergistic effectsof pesticides andmetals on the fibrillation of120572-synuclein impli-cations for Parkinsonrsquos diseaserdquo NeuroToxicology vol 23 no4-5 pp 527ndash536 2002

[206] C B Lucking A Durr V Bonifati et al ldquoAssociation betweenearly-onset Parkinsonrsquos disease and mutations in the parkingenerdquoTheNew England Journal of Medicine vol 342 no 21 pp1560ndash1567 2000

[207] M Periquet M Latouche E Lohmann et al ldquoParkinmutationsare frequent in patients with isolated early-onset parkinsonismrdquoBrain vol 126 no 6 pp 1271ndash1278 2003

[208] HMortiboys K JThomasW JHKoopman et al ldquoMitochon-drial function and morphology are impaired in parkin-mutantfibroblastsrdquo Annals of Neurology vol 64 no 5 pp 555ndash5652008

[209] M Muftuoglu B Elibol O Dalmizrak et al ldquoMitochondrialcomplex I and IV activities in leukocytes from patients withparkin mutationsrdquoMovement Disorders vol 19 no 5 pp 544ndash548 2004

[210] J J Palacino D Sagi M S Goldberg et al ldquoMitochondrial dys-function and oxidative damage in parkin-deficient micerdquo TheJournal of Biological Chemistry vol 279 no 18 pp 18614ndash186222004


[211] J C Greene A J Whitworth I Kuo L A Andrews M BFeany and L J Pallanck ldquoMitochondrial pathology and apop-totic muscle degeneration in Drosophila parkin mutantsrdquo Pro-ceedings of the National Academy of Sciences of the United Statesof America vol 100 no 7 pp 4078ndash4083 2003

[212] Y Pesah T PhamH Burgess et al ldquoDrosophila parkinmutantshave decreased mass and cell size and increased sensitivity tooxygen radical stressrdquo Development vol 131 no 9 pp 2183ndash2194 2004

[213] M Bian J Liu X Hong et al ldquoOverexpression of parkin ame-liorates dopaminergic neurodegeneration induced by 1-methyl-4-phenyl-1236-tetrahydropyridine in micerdquo PLoS ONE vol 7no 6 Article ID e39953 2012

[214] T Yasuda H Hayakawa T Nihira et al ldquoParkin-mediated pro-tection of dopaminergic neurons in a chronicMPTP-minipumpmouse model of parkinson diseaserdquo Journal of Neuropathologyand Experimental Neurology vol 70 no 8 pp 686ndash697 2011

[215] U Walter C Klein R Hilker R Benecke P P Pramstaller andD Dressler ldquoBrain parenchyma sonography detects preclinicalparkinsonismrdquo Movement Disorders vol 19 no 12 pp 1445ndash1449 2004

[216] D Berg ldquoDisturbance of iron metabolism as a contributingfactor to SN hyperechogenicity in Parkinsonrsquos disease impli-cations for idiopathic and monogenetic formsrdquo NeurochemicalResearch vol 32 no 10 pp 1646ndash1654 2007

[217] N Pyatigorskaya M Sharman J-C Corvol et al ldquoHigh nigraliron deposition in LRRK2 and Parkin mutation carriers usingR2 relaxometryrdquo Movement Disorders vol 30 pp 1077ndash10842015

[218] L Silvestri V Caputo E Bellacchio et al ldquoMitochondrialimport and enzymatic activity of PINK1 mutants associated torecessive parkinsonismrdquoHumanMolecular Genetics vol 14 no22 pp 3477ndash3492 2005

[219] L Aerts B De Strooper and V A Morais ldquoPINK1 activationmdashTurning on a promiscuous kinaserdquo Biochemical Society Trans-actions vol 43 pp 280ndash286 2015

[220] C A Gautier T Kitada and J Shen ldquoLoss of PINK1 causesmitochondrial functional defects and increased sensitivity tooxidative stressrdquoProceedings of theNational Academy of Sciencesof the United States of America vol 105 no 32 pp 11364ndash113692008

[221] S Gispert F Ricciardi A Kurz et al ldquoParkinson phenotypein aged PINK1-deficient mice is accompanied by progressivemitochondrial dysfunction in absence of neurodegenerationrdquoPLoS ONE vol 4 no 6 Article ID e5777 2009

[222] R S Akundi ZHuang J Eason et al ldquoIncreasedmitochondrialcalcium sensitivity and abnormal expression of innate immu-nity genes precede dopaminergic defects in Pink1-deficientmicerdquo PLoS ONE vol 6 no 1 Article ID e16038 2011

[223] R H Kim P D Smith H Aleyasin et al ldquoHypersensitivityof DJ-1-deficient mice to 1-methyl-4-phenyl-1236-tetrahy-dropyrindine (MPTP) and oxidative stressrdquo Proceedings of theNational Academy of Sciences of the United States of Americavol 102 no 14 pp 5215ndash5220 2005

[224] M S Goldberg A Pisani M Haburcak et al ldquoNigrostriataldopaminergic deficits and hypokinesia caused by inactivationof the familial Parkinsonism-linked gene DJ-1rdquoNeuron vol 45no 4 pp 489ndash496 2005

[225] H-H Hoepken S Gispert M Azizov et al ldquoParkinson patientfibroblasts show increased alpha-synuclein expressionrdquo Experi-mental Neurology vol 212 no 2 pp 307ndash313 2008

[226] I E Clark M W Dodson C Jiang et al ldquoDrosophila pink1is required for mitochondrial function and interacts geneticallywith parkinrdquo Nature vol 441 no 7097 pp 1162ndash1166 2006

[227] J Park S B Lee S Lee et al ldquoMitochondrial dysfunction inDrosophila PINK1mutants is complemented by parkinrdquoNaturevol 441 no 7097 pp 1157ndash1161 2006

[228] A Pilsl andK FWinklhofer ldquoParkin PINK1 andmitochondrialintegrity emerging concepts of mitochondrial dysfunction inParkinsonrsquos diseaserdquo Acta Neuropathologica vol 123 no 2 pp173ndash188 2012

[229] D Narendra A Tanaka D-F Suen and R J Youle ldquoParkin isrecruited selectively to impaired mitochondria and promotestheir autophagyrdquoThe Journal of Cell Biology vol 183 no 5 pp795ndash803 2008

[230] Y Yang Y Ouyang L Yang et al ldquoPink1 regulates mito-chondrial dynamics through interaction with the fissionfusionmachineryrdquo Proceedings of the National Academy of Sciences ofthe United States of America vol 105 no 19 pp 7070ndash70752008

[231] W Yu Y Sun S Guo and B Lu ldquoThe PINK1Parkin pathwayregulates mitochondrial dynamics and function in mammalianhippocampal and dopaminergic neuronsrdquo Human MolecularGenetics vol 20 no 16 Article ID ddr235 pp 3227ndash3240 2011

[232] Y D Chen X L Feng L Deng et al ldquoRisk factors for mortalityin severemultiply injury patients with acute hypoxemic respira-tory failurerdquo European Review for Medical and PharmacologicalSciences vol 19 no 19 pp 3693ndash3700 2015

[233] J Park G Lee and J Chung ldquoThe PINK1-Parkin pathway isinvolved in the regulation of mitochondrial remodeling pro-cessrdquo Biochemical and Biophysical Research Communicationsvol 378 no 3 pp 518ndash523 2009

[234] A C Poole R E Thomas L A Andrews H M McBride A JWhitworth and L J Pallanck ldquoThe PINK1Parkin pathway reg-ulates mitochondrial morphologyrdquo Proceedings of the NationalAcademy of Sciences of the United States of America vol 105 no5 pp 1638ndash1643 2008

[235] H-L Wang A-H Chou A-S Wu et al ldquoPARK6 PINK1mutants are defective in maintaining mitochondrial mem-brane potential and inhibiting ROS formation of substantianigra dopaminergic neuronsrdquo Biochimica et Biophysica ActamdashMolecular Basis of Disease vol 1812 no 6 pp 674ndash684 2011

[236] AWood-Kaczmar S Gandhi Z Yao et al ldquoPINK1 is necessaryfor long term survival and mitochondrial function in humandopaminergic neuronsrdquo PLoS ONE vol 3 no 6 Article IDe2455 2008

[237] L Li and G-K Hu ldquoPink1 protects cortical neurons fromthapsigargin-induced oxidative stress and neuronal apoptosisrdquoBioscience Reports vol 35 Article ID e00174 2015

[238] K J Schweitzer T Brussel P Leitner et al ldquoTranscranialultrasound in different monogenetic subtypes of Parkinsonrsquosdiseaserdquo Journal of Neurology vol 254 no 5 pp 613ndash616 2007

[239] G Esposito M Vos S Vilain et al ldquoAconitase causes irontoxicity in Drosophila pink1mutantsrdquo PLoS Genetics vol 9 no4 Article ID e1003478 2013

[240] T Yokota K Sugawara K Ito R Takahashi H Ariga andH Mizusawa ldquoDown regulation of DJ-1 enhances cell deathby oxidative stress ER stress and proteasome inhibitionrdquo Bio-chemical and Biophysical Research Communications vol 312 no4 pp 1342ndash1348 2003

[241] V Bonifati P Rizzu M J Van Baren et al ldquoMutations inthe DJ-1 gene associated with autosomal recessive early-onsetparkinsonismrdquo Science vol 299 no 5604 pp 256ndash259 2003


[242] C van derMerwe Z Jalali SefidDashti A Christoffels B Loosand S Bardien ldquoEvidence for a common biological pathwaylinking three Parkinsonrsquos disease-causing genes parkin PINK1and DJ-1rdquo European Journal of Neuroscience vol 41 no 9 pp1113ndash1125 2015

[243] T Taira Y Saito T Niki S M M Iguchi-Ariga K Takahashiand H Ariga ldquoDJ-1 has a role in antioxidative stress to preventcell deathrdquo EMBO Reports vol 5 no 2 pp 213ndash218 2004

[244] R M Canet-Aviles M A Wilson D W Miller et al ldquoTheParkinsonrsquos disease DJ-1 is neuroprotective due to cysteine-sulfinic acid-driven mitochondrial localizationrdquo Proceedings ofthe National Academy of Sciences of the United States of Americavol 101 no 24 pp 9103ndash9108 2004

[245] M Kurosawa D Uno K Hanawa and S KobayashildquoPolyamines stimulate the phosphorylation of phosphatidyli-nositol in rat mast cell granulesrdquo Allergy vol 45 no 4 pp262ndash267 1990

[246] I N Rudenko and M R Cookson ldquoHeterogeneity of leucine-rich repeat kinase 2 mutations genetics mechanisms andtherapeutic implicationsrdquoNeurotherapeutics vol 11 no 4 2014

[247] M Yue K M Hinkle P Davies et al ldquoProgressive dopamin-ergic alterations and mitochondrial abnormalities in LRRK2G2019S knock-in micerdquo Neurobiology of Disease vol 78 pp172ndash195 2015

[248] H Mortiboys K K Johansen J O Aasly and O BandmannldquoMitochondrial impairment in patients with Parkinson diseasewith the G2019Smutation in LRRK2rdquoNeurology vol 75 no 22pp 2017ndash2020 2010

[249] D C Angeles B-H Gan L Onstead et al ldquoMutations inLRRK2 increase phosphorylation of peroxiredoxin 3 exacerbat-ing oxidative stress-induced neuronal deathrdquoHumanMutationvol 32 no 12 pp 1390ndash1397 2011

[250] A R Esteves R H Swerdlow and S M Cardoso ldquoLRRK2 apuzzling protein insights into Parkinsonrsquos disease pathogene-sisrdquo Experimental Neurology vol 261 pp 206ndash216 2014

[251] K Brockmann and J Hagenah ldquoTCS in monogenic forms ofParkinsonrsquos diseaserdquo International Review of Neurobiology vol90 pp 157ndash164 2010

[252] E L Heinzen A Arzimanoglou A Brashear et al ldquoDistinctneurological disorders with ATP1A3 mutationsrdquo The LancetNeurology vol 13 no 5 pp 503ndash514 2014

[253] X Yang andY Xu ldquoMutations in the ATP13A2 gene and Parkin-sonism a preliminary reviewrdquo BioMed Research Internationalvol 2014 Article ID 371256 9 pages 2014

[254] P J Schultheis S M Fleming A K Clippinger et al ldquoAtp13a2-deficient mice exhibit neuronal ceroid lipofuscinosis limited120572-synuclein accumulation and age-dependent sensorimotordeficitsrdquo Human Molecular Genetics vol 22 no 10 pp 2067ndash2082 2013

[255] J-S Park B Koentjoro D Veivers A Mackay-Sim and C MSue ldquoParkinsonrsquos disease-associated human ATP13A2 (PARK9)deficiency causes zinc dyshomeostasis and mitochondrial dys-functionrdquo Human Molecular Genetics vol 23 no 11 pp 2802ndash2815 2014

[256] A M Gusdon J Zhu B Van Houten and C T Chu ldquoATP13A2regulates mitochondrial bioenergetics through macroauto-phagyrdquoNeurobiology of Disease vol 45 no 3 pp 962ndash972 2012

[257] M I Behrens N Bruggemann P Chana et al ldquoClinical spec-trum of Kufor-Rakeb syndrome in the Chilean kindred withATP13A2 mutationsrdquo Movement Disorders vol 25 no 12 pp1929ndash1937 2010

[258] D Ramonet A Podhajska K Stafa et al ldquoPARK9-associatedATP13A2 localizes to intracellular acidic vesicles and regulatescation homeostasis and neuronal integrityrdquo Human MolecularGenetics vol 21 no 8 Article ID ddr606 pp 1725ndash1743 2012

[259] S A Schneider C Paisan-Ruiz N P Quinn et al ldquoATP13A2mutations (PARK9) cause neurodegeneration with brain ironaccumulationrdquoMovement Disorders vol 25 no 8 pp 979ndash9842010

[260] H F Chien V Bonifati and E R Barbosa ldquoATP13A2-relatedneurodegeneration (PARK9) without evidence of brain ironaccumulationrdquo Movement Disorders vol 26 no 7 pp 1364ndash1365 2011

[261] J Salazar N Mena and M T Nunez ldquoIron dyshomeostasisin Parkinsonrsquos diseaserdquo Journal of Neural Transmission Supple-menta no 71 pp 205ndash213 2006

[262] J Salazar N Mena S Hunot et al ldquoDivalent metal transporter1 (DMT1) contributes to neurodegeneration in animal modelsof Parkinsonrsquos diseaserdquo Proceedings of the National Academy ofSciences of the United States of America vol 105 no 47 pp18578ndash18583 2008

[263] S Zhang J Wang N Song J Xie and H Jiang ldquoUp-regulationof divalent metal transporter 1 is involved in 1-methyl-4-phenylpyridinium (MPP(+))-induced apoptosis in MES235cellsrdquo Neurobiology of Aging vol 30 no 9 pp 1466ndash1476 2009

[264] E C Hirsch ldquoIron transport in Parkinsonrsquos diseaserdquo Parkinson-ism and Related Disorders vol 15 supplement 3 pp S209ndashS2112009

[265] J R Connor P J Boyer S L Menzies et al ldquoNeuropathologicalexamination suggests impaired brain iron acquisition in restlesslegs syndromerdquo Neurology vol 61 no 3 pp 304ndash309 2003

[266] L Zecca A Stroppolo A Gatti et al ldquoThe role of iron andmolecules in the neuronal vulnerability of locus coeruleusand substantia nigra during agingrdquo Proceedings of the NationalAcademy of Sciences of the United States of America vol 101 no26 pp 9843ndash9848 2004

[267] F A Zucca C Bellei S Giannelli et al ldquoNeuromelanin and ironin human locus coeruleus and substantia nigra during agingconsequences for neuronal vulnerabilityrdquo Journal of NeuralTransmission vol 113 no 6 pp 757ndash767 2006

[268] D I Dryanovski J N Guzman Z Xie et al ldquoCalcium entry and120572-synuclein inclusions elevate dendritic mitochondrial oxidantstress in dopaminergic neuronsrdquo The Journal of Neurosciencevol 33 no 24 pp 10154ndash10164 2013

[269] C S Chan J N Guzman E Ilijic et al ldquolsquoRejuvenationrsquo protectsneurons in mouse models of Parkinsonrsquos diseaserdquo Nature vol447 no 7148 pp 1081ndash1086 2007

[270] B Westermann ldquoMitochondrial fusion and fission in cell lifeand deathrdquo Nature Reviews Molecular Cell Biology vol 11 no12 pp 872ndash884 2010

[271] D-H Cho T Nakamura and S A Lipton ldquoMitochondrialdynamics in cell death and neurodegenerationrdquo Cellular andMolecular Life Sciences vol 67 no 20 pp 3435ndash3447 2010

[272] J Grohm N Plesnila and C Culmsee ldquoBid mediates fissionmembrane permeabilization and peri-nuclear accumulationof mitochondria as a prerequisite for oxidative neuronal celldeathrdquo Brain Behavior and Immunity vol 24 no 5 pp 831ndash838 2010

[273] J Grohm S-W Kim U Mamrak et al ldquoInhibition of Drp1provides neuroprotection in vitro and in vivordquo Cell Death andDifferentiation vol 19 no 9 pp 1446ndash1458 2012


[274] S Wasiak R Zunino and H M McBride ldquoBaxBak promotesumoylation of DRP1 and its stable association with mitochon-dria during apoptotic cell deathrdquo Journal of Cell Biology vol 177no 3 pp 439ndash450 2007

[275] C-R Chang and C Blackstone ldquoCyclic AMP-dependent pro-tein kinase phosphorylation of Drp1 regulates its GTPase activ-ity and mitochondrial morphologyrdquo The Journal of BiologicalChemistry vol 282 no 30 pp 21583ndash21587 2007

[276] J T Cribbs and S Strack ldquoReversible phosphorylation ofDrp1 by cyclic AMP-dependent protein kinase and calcineurinregulates mitochondrial fission and cell deathrdquo EMBO Reportsvol 8 no 10 pp 939ndash944 2007

[277] N Taguchi N Ishihara A Jofuku T Oka and K MiharaldquoMitotic phosphorylation of dynamin-related GTPase Drp1participates in mitochondrial fissionrdquo The Journal of BiologicalChemistry vol 282 no 15 pp 11521ndash11529 2007

[278] D-H Cho T Nakamura J Fang et al ldquo120573-Amyloid-relatedmitochondrial fission and neuronal injuryrdquo Science vol 324 no5923 pp 102ndash105 2009

[279] J Park D G Lee B Kim et al ldquoIron overload triggers mito-chondrial fragmentation via calcineurin-sensitive signals inHT-22 hippocampal neuron cellsrdquo Toxicology vol 337 pp 39ndash46 2015

[280] N Exner B TreskeD Paquet et al ldquoLoss-of-function of humanPINK1 results in mitochondrial pathology and can be rescuedby parkinrdquoThe Journal of Neuroscience vol 27 no 45 pp 12413ndash12418 2007

[281] A K Lutz N Exner M E Fett et al ldquoLoss of parkin orPINK1 function increases Drp1-dependent mitochondrial frag-mentationrdquoThe Journal of Biological Chemistry vol 284 no 34pp 22938ndash22951 2009

[282] Y Zhao F Chen S Chen X Liu M Cui and Q Dong ldquoTheParkinsonrsquos disease-associated gene PINK1 protects neuronsfrom ischemic damage by decreasing mitochondrial transloca-tion of the fission promoter Drp1rdquo Journal of Neurochemistryvol 127 no 5 pp 711ndash722 2013

[283] R K Dagda S J Cherra III S M Kulich A Tandon D Parkand C T Chu ldquoLoss of PINK1 function promotes mitophagythrough effects on oxidative stress and mitochondrial fissionrdquoThe Journal of Biological Chemistry vol 284 no 20 pp 13843ndash13855 2009

[284] P Munoz A Humeres C Elgueta A Kirkwood C Hidalgoand M T Nunez ldquoIron mediates N-methyl-d-aspartate recep-tor-dependent stimulation of calcium-induced pathways andhippocampal synaptic plasticityrdquo The Journal of BiologicalChemistry vol 286 no 15 pp 13382ndash13392 2011

[285] C D SanMartın A C Paula-Lima A Garcıa et al ldquoRyanodinereceptor-mediated Ca2+ release underlies iron-induced mito-chondrial fission and stimulates mitochondrial Ca2+ uptake inprimary hippocampal neuronsrdquo Frontiers in Molecular Neuro-science vol 7 article 13 2014

[286] H CHatcher R N Singh FM Torti and S V Torti ldquoSyntheticand natural iron chelators therapeutic potential and clinicaluserdquo Future Medicinal Chemistry vol 1 no 9 pp 1643ndash16702009

[287] E Poggiali E Cassinerio L Zanaboni and M D CappellinildquoAn update on iron chelation therapyrdquo Blood Transfusion vol10 no 4 pp 411ndash422 2012

[288] M B H Youdim D Ben-Shachar and P Riederer ldquoIs Parkin-sonrsquos disease a progressive siderosis of substantia nigra resulting

in iron and melanin induced neurodegenerationrdquo Acta Neu-rologica Scandinavica Supplement vol 80 no 126 pp 47ndash541989

[289] E Meyer M A Kurian and S J Hayflick ldquoNeurodegenerationwith brain iron accumulation genetic diversity and pathophys-iological mechanismsrdquoAnnual Review of Genomics and HumanGenetics vol 16 pp 257ndash279 2015

[290] G Kamalinia F Khodagholi F Shaerzadeh et al ldquoCationicalbumin-conjugated chelating agent as a novel brain drugdelivery system in neurodegenerationrdquo Chemical Biology andDrug Design vol 86 no 5 pp 1203ndash1214 2015

[291] E Gumienna-Kontecka M Pyrkosz-Bulska A Szebesczykand M Ostrowska ldquoIron chelating strategies in systemic metaloverload neurodegeneration and cancerrdquo Current MedicinalChemistry vol 21 no 33 pp 3741ndash3767 2014

[292] G Zorzi and N Nardocci ldquoTherapeutic advances in neurode-generation with brain iron accumulationrdquo International Reviewof Neurobiology vol 110 pp 153ndash164 2013

[293] D Ben-Shachar G Eshel J P M Finberg and M B HYoudim ldquoThe iron chelator desferrioxamine (desferal) retards6-hydroxydopamine-induced degeneration of nigrostriataldopamine neuronsrdquo Journal of Neurochemistry vol 56 no 4pp 1441ndash1444 1991

[294] F Febbraro K J Andersen V Sanchez-Guajardo N Tentillierand M Romero-Ramos ldquoChronic intranasal deferoxamineameliorates motor defects and pathology in the 120572-synucleinrAAV Parkinsonrsquos modelrdquo Experimental Neurology vol 247 pp45ndash58 2013

[295] Y-Q Wang M-Y Wang X-R Fu et al ldquoNeuroprotectiveeffects of ginkgetin against neuroinjury in Parkinsonrsquos diseasemodel induced by MPTP via chelating ironrdquo Free RadicalResearch vol 49 no 9 pp 1069ndash1080 2015

[296] P J Urrutia N P Mena and M T Nunez ldquoThe interplaybetween iron accumulation mitochondrial dysfunction andinflammation during the execution step of neurodegenerativedisordersrdquo Frontiers in Pharmacology vol 5 article 38 2014

[297] Y Hu S Y Yu L J Zuo et al ldquoInvestigation on abnormalironmetabolism and related inflammation in parkinson diseasepatients with probable RBDrdquo PLoS ONE vol 10 Article IDe0138997 2015

[298] Z Zhang L Hou J-L Song et al ldquoPro-inflammatory cytokine-mediated ferroportin down-regulation contributes to the nigraliron accumulation in lipopolysaccharide-induced Parkinsonianmodelsrdquo Neuroscience vol 257 pp 20ndash30 2014

[299] H Zheng L M Weiner O Bar-Am et al ldquoDesign synthesisand evaluation of novel bifunctional iron-chelators as potentialagents for neuroprotection in Alzheimerrsquos Parkinsonrsquos andother neurodegenerative diseasesrdquo Bioorganic and MedicinalChemistry vol 13 no 3 pp 773ndash783 2005

[300] N G Faux C W Ritchie A Gunn et al ldquoPBT2 rapidlyimproves cognition in Alzheimerrsquos Disease additional phase IIanalysesrdquo Journal of Alzheimerrsquos Disease vol 20 no 2 pp 509ndash516 2010

[301] P Lei S Ayton A T Appukuttan et al ldquoClioquinol rescuesParkinsonism and dementia phenotypes of the tau knockoutmouserdquo Neurobiology of Disease vol 81 pp 168ndash175 2015

[302] D B Shachar N Kahana V Kampel AWarshawsky andM BH Youdim ldquoNeuroprotection by a novel brain permeable ironchelator VK-28 against 6-hydroxydopamine lession in ratsrdquoNeuropharmacology vol 46 no 2 pp 254ndash263 2004

[303] S Gal M Fridkin T Amit H Zheng and M B H YoudimldquoM30 a novel multifunctional neuroprotective drug with


potent iron chelating and brain selective monoamine oxidase-ab inhibitory activity for Parkinsonrsquos diseaserdquo Journal of NeuralTransmission-Supplement no 70 pp 447ndash456 2006

[304] O Bar-Am T Amit L Kupershmidt et al ldquoNeuroprotec-tive and neurorestorative activities of a novel iron chelator-brain selective monoamine oxidase-Amonoamine oxidase-Binhibitor in animal models of Parkinsonrsquos disease andagingrdquoNeurobiology of Aging vol 36 no 3 pp 1529ndash1542 2015

[305] Y Avramovich-Tirosh O Bar-Am T Amit M B H Youdimand O Weinreb ldquoUp-regulation of hypoxia-inducible factor(hif)-1120572 and hif-target genes in cortical neurons by the novelmultifunctional iron chelator anti-Alzheimer drug M30rdquo Cur-rent Alzheimer Research vol 7 no 4 pp 300ndash306 2010

[306] D Mechlovich T Amit O Bar-Am S Mandel M B HYoudim and OWeinreb ldquoThe novel multi-target iron chelatorM30 modulates HIF-1120572-related glycolytic genes and insulinsignaling pathway in the frontal cortex of APPPS1 AlzheimerrsquosdiseasemicerdquoCurrent Alzheimer Research vol 11 no 2 pp 119ndash127 2014

[307] L Kupershmidt O Weinreb T Amit S Mandel O Bar-Amand M B H Youdim ldquoNovel molecular targets of the neuro-protectiveneurorescue multimodal iron chelating drugM30 inthe mouse brainrdquo Neuroscience vol 189 pp 345ndash358 2011

[308] L Kupershmidt T Amit O Bar-Am M B H Youdim andO Weinreb ldquoNeuroprotection by the multitarget iron chelatorM30 on age-related alterations in micerdquo Mechanisms of Ageingand Development vol 133 no 5 pp 267ndash274 2012

[309] M Naoi and W Maruyama ldquoMonoamine oxidase inhibitorsas neuroprotective agents in age-dependent neurodegenerativedisordersrdquo Current Pharmaceutical Design vol 16 no 25 pp2799ndash2817 2010

[310] P Aguirre N P Mena CM Carrasco et al ldquoIron chelators andantioxidants regenerate neuritic tree and nigrostriatal fibers ofMPP+MPTP-lesioned dopaminergic neuronsrdquoPLoSONE vol10 no 12 Article ID e0144848 2015

[311] B Ghosh T Antonio M E A Reith and A K Dutta ldquoDis-covery of 4-(4-(2-((5-Hydroxy-1234-tetrahydronaphthalen-2-yl)(propyl)amino)ethyl)piperazin-1-yl)quinolin-8-ol and itsanalogues as highly potent dopamine D2D3 agonists and asiron chelator in vivo activity indicates potential applicationin symptomatic and neuroprotective therapy for Parkinsonrsquosdiseaserdquo Journal of Medicinal Chemistry vol 53 no 5 pp 2114ndash2125 2010

[312] S Gogoi T Antonio S Rajagopalan M Reith J Andersenand A K Dutta ldquoDopamine D

2D3agonists with potent iron

chelation antioxidant and neuroprotective properties potentialimplication in symptomatic and neuroprotective treatment ofParkinsonrsquos diseaserdquo ChemMedChem vol 6 no 6 pp 991ndash9952011

[313] S S Kang J Y Lee Y K Choi et al ldquoNeuroprotective effects ofnaturally occurring biflavonoidsrdquo Bioorganic amp MedicinalChemistry Letters vol 15 no 15 pp 3588ndash3591 2005

[314] X-X Du H-M Xu H Jiang N Song J Wang and J-XXie ldquoCurcumin protects nigral dopaminergic neurons by iron-chelation in the 6-hydroxydopamine rat model of Parkinsonrsquosdiseaserdquo Neuroscience Bulletin vol 28 no 3 pp 253ndash258 2012

[315] Y-S Sohn W Breuer A Munnich and Z I CabantchikldquoRedistribution of accumulated cell iron a modality of chela-tion with therapeutic implicationsrdquo Blood vol 111 no 3 pp1690ndash1699 2008

[316] M L-H Huang D J R Lane and D R Richardson ldquoMito-chondrial mayhem the mitochondrion as a modulator of iron

metabolism and its role in diseaserdquo Antioxidants and RedoxSignaling vol 15 no 12 pp 3003ndash3019 2011

[317] DDevos CMoreau J CDevedjian et al ldquoTargeting chelatableiron as a therapeutic modality in Parkinsonrsquos diseaserdquo Antioxi-dants amp Redox Signaling vol 21 no 2 pp 195ndash210 2014

[318] R Huckle ldquoPBT-1 Prana biotechnologyrdquo Current Opinion inInvestigational Drugs (London England 2000) vol 6 no 1 pp99ndash107 2005

[319] C W Ritchie A I Bush A Mackinnon et al ldquoMetal-proteinattenuation with iodochlorhydroxyquin (clioquinol) targetingA120573Amyloid deposition and toxicity in alzheimer disease a pilotphase 2 clinical trialrdquo Archives of Neurology vol 60 no 12 pp1685ndash1691 2003

[320] J Tateishi ldquoSubacute myelo-optico-neuropathy clioquinolintoxication in humans and animalsrdquo Neuropathology vol 20supplement 1 pp 20ndash24 2000

[321] M Katsuyama K Iwata M Ibi K Matsuno M Matsumotoand C Yabe-Nishimura ldquoClioquinol induces DNA double-strand breaks activation of ATM and subsequent activation ofp53 signalingrdquo Toxicology vol 299 no 1 pp 55ndash59 2012

[322] K Kawamura Y Kuroda M Sogo M Fujimoto T Inui and TMitsui ldquoSuperoxide dismutase as a target of clioquinol-inducedneurotoxicityrdquo Biochemical and Biophysical Research Communi-cations vol 452 no 1 pp 181ndash185 2014

[323] K Asakura A Ueda N Kawamura M Ueda T Mihara and TMutoh ldquoClioquinol inhibits NGF-induced Trk autophosphory-lation and neurite outgrowth in PC12 cellsrdquo Brain Research vol1301 pp 110ndash115 2009

[324] Huntington Study Group Reach2HD Investigators ldquoSafetytolerability and efficacy of PBT2 in Huntingtonrsquos disease aphase 2 randomised double-blind placebo-controlled trialrdquoThe Lancet Neurology vol 14 no 1 pp 39ndash47 2015

[325] S Abdelsayed N T Ha Duong C Bureau et al ldquoPiperazinederivatives as iron chelators a potential application in neurobi-ologyrdquo BioMetals vol 28 no 6 pp 1043ndash1061 2015

Submit your manuscripts athttpwwwhindawicom

Stem CellsInternational

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014


MEDIATORSINFLAMMATION

of


Behavioural Neurology

EndocrinologyInternational Journal of



Disease Markers


BioMed Research International

OncologyJournal of



Oxidative Medicine and Cellular Longevity


PPAR Research

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Immunology ResearchHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

ObesityJournal of



Computational and Mathematical Methods in Medicine

OphthalmologyJournal of


Diabetes ResearchJournal of



Research and TreatmentAIDS


Gastroenterology Research and Practice


Parkinsonrsquos Disease

Evidence-Based Complementary and Alternative Medicine

Volume 2014Hindawi Publishing Corporationhttpwwwhindawicom


review the evidence that points tomitochondrial dysfunctionand the subsequent iron accumulation as early events in thedevelopment of PD

2 Cell Iron

Iron has been described as an important cofactor in manyproteins involved in crucial biological processes includingcellular respiration nitrogen fixation photosynthesis DNAsynthesis and repair oxygen transport metabolism of xeno-biotics and neurotransmitter synthesis [40ndash49] In mostproteins iron is present in iron-sulfur clusters (ISCs) either as[2Fe-2S] [4Fe-4S] or [3Fe-4S] clusters [50 51]Themain fea-ture of iron as prosthetic group resides in its high redox flex-ibility Thus iron has the capacity to exchange one electroneither by oxidation (Fe2+ rarr Fe3+) or by reduction (Fe3+ rarrFe2+)This flexibility is very important in biological processessuch as cellular respiration where the transport of electronsdepends on 12 ISCs present in complex I to complex III andon5 heme-containing proteins transporting electrons throughcomplexes III and I [52]

Increases in redox-active iron directly associate withincreased reactive oxygen species (ROS) generation andwith changes in the intracellular reduction potential due toglutathione oxidation [53 54] Within the cell most iron isassociated with proteins as either iron oxy-hydroxy crystalsin ferritin or forming part of ISCs and heme prostetic groupsAround 1 of cell iron is in a redox-active form called thelabile iron pool or labile cell iron [55ndash58] The predominantcomponent of this pool is Fe2+-glutathione but iron is alsobound weakly to phosphate citrate carboxylates carbohy-drates nucleotides polypeptides and other molecules [5960] Through the Fenton reaction reactive iron catalyzesthe production of hydroxyl radical (∙OH) in the presenceof H2O2 in a self-renewed cycle caused by the presence of

oxygen as an electron acceptor and intracellular reductantssuch as glutathione (GSH) and ascorbate as electron donors[28] These characteristics of the intracellular environmentdemand a tight regulation of the reactive iron pool to decreasehydroxyl radical production

Redox-active ironmediatesGSH consumption [54] Afterexposure to increasing concentrations of iron SH-SY5Ydopaminergic cells undergo sustained iron accumulationand produce a biphasic change in intracellular GSH levelsincreasingGSH levels at low iron concentrations and decreas-ing them thereafter Indeed cell exposure to high iron con-centrations markedly decreases the GSHGSSG molar ratioand theGSHhalf-cell reduction potential with the associatedloss in cell viability [54]

Iron levels in the SNpc increase significantly with age andPD patients present an even greater increase that correlateswith clinical PD status [64ndash69] Experimental evidence showsthat iron is crucial to the degeneration of SNpc dopaminergicneurons in the model of PD caused by 1-methyl-4-phenyl-1236-tetrahydropyridine (MPTP)Mice fed for 6weekswitha low iron diet before the administration of MPTP presentneuronal protection normal striatal dopamine levels andno changes in motor behavior when compared with controlanimals fed a normal iron content diet [70] Furthermore

increased iron levels in the brain aggravate dopaminergic celldeath and motor impairment after MPTP treatment and thiscondition is attenuated by treatment with the iron chelatordesferrioxamine (DFO) [71]

Clinical studies have not provided an evident correlationbetween dietary iron intake and risk of Parkinsonrsquos diseasein humans [72ndash75] Nevertheless some reports point toa higher incidence of PD in hereditary hemochromatosispatients [76ndash79] although other reports found no correlationbetween these two diseases [80ndash82] It is possible that undernormal conditions the iron homeostasis system protects thebrain from iron accumulation due to dietary variations Thishomeostasis is most likely lost in iron-overload disease statesyet

Overall these antecedents suggest that increased redox-active iron in the SNpc is part of the neurodegenerativeprocess in PD possibly due to increased oxidative stress andoxidative damage

3 Iron Homeostasis in Mitochondria

Mitochondria consume about 90 of cellular oxygen andtransform 1ndash5 of this oxygen into superoxide anion (O

2

∙minus)due to the leaking of electrons that takes place in their passagethrough complexes III and I [83ndash86] During aging the activ-ity of these complexes decreases leading to higher oxidantproduction of O

2

∙minus and H2O2[86 87] The superoxide anion

generated in this process dismutates into hydrogen peroxideeither spontaneously or following catalysis by superoxidedismutase (SOD) [88 89] Proteins containing ISCs inmitochondria are significantly vulnerable to oxidative stressparticipating in redox sensing and signaling reactions [9091]

The mitochondrion has an active exchange of iron withthe cytoplasm as required for the mitochondrial synthesisof heme and ISCs (Figure 1(a)) [92ndash94] Kinetic experimentsshow that extracellular iron is readily incorporated intomitochondria Indeed iron incorporation into mitochondriaapparently has a kinetic preference over incorporation intothe cytoplasm (Figure 1(b)) (also see [94 95]) Possiblemech-anisms for this preferential delivery include siderophore-mediated iron transport from the plasma membrane to themitochondrion [96 97] the entrance of iron into the cell byfluid-phase endocytosis with subsequent delivery to mito-chondria without passing through the cytoplasmic labile ironpool (cLIP) [98] and iron delivery to mitochondrion bydirect interaction with transferrin-containing endosomes[99]

Mitoferrin-2 a protein located in the innermitochondrialmembrane represents the main pathway of mitochondrialiron uptake whereas the ABCB7 andABCB8 transporters areinvolved in ISC export [100ndash103] (Figure 1) Inward transportof iron by mitoferrin-2 apparently is regulated Studies withthe mitoferrin Mrs3p and Mrs4p yeast homologs revealedthat inner mitochondrial membrane vesicles show rapiduptake of Fe2+ in response to iron starvation [104]There is noreported evidence as to how cell or mitochondrial iron levelscould regulate mitoferrin-2 levels Additionally mitoferrin


mLIP

cLIP

FLVCR1b

ABCB10ABCB7ABCB8

ISC


Holo-IRP1(active)

MtFt(storage)

Heme

DMT1

Mtfn2

(a)

0 100 200 300 400

08

09

10

11

No FAS

RPA (mLIP)

FAS

Calcein (cLIP)

Time (s)

Calc

ein

or R

PA fl

uore

scen

ce (F

F0)

(b)



0)sec) Values




3

0M30Rotenone

(a)

0

1

2

3BO

DIP

Y ox

idat

ion


lowastlowastlowast

lowastlowastlowast

lowastlowastlowast

(b)





































































Environmental

endogenous toxins


Iron chelation

DecreasedISC

synthesis

DecreasedATP

synthesis


DecreasedGSHGSSG

ratio





pathways

Apoptosis

Survivalgenes



OH∙

and

darr FPN1uarr DMT1












Disclosure


Competing Interests


Acknowledgments


References








































































































































































2O2-mediated

























































































































































































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of

















mLIP

cLIP

FLVCR1b

ABCB10ABCB7ABCB8

ISC


Holo-IRP1(active)

MtFt(storage)

Heme

DMT1

Mtfn2

(a)

0 100 200 300 400

08

09

10

11

No FAS

RPA (mLIP)

FAS

Calcein (cLIP)

Time (s)

Calc

ein

or R

PA fl

uore

scen

ce (F

F0)

(b)



0)sec) Values




3

0M30Rotenone

(a)

0

1

2

3BO

DIP

Y ox

idat

ion


lowastlowastlowast

lowastlowastlowast

lowastlowastlowast

(b)





































































Environmental

endogenous toxins


Iron chelation

DecreasedISC

synthesis

DecreasedATP

synthesis


DecreasedGSHGSSG

ratio





pathways

Apoptosis

Survivalgenes



OH∙

and

darr FPN1uarr DMT1












Disclosure


Competing Interests


Acknowledgments


References








































































































































































2O2-mediated

























































































































































































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of


















3

0M30Rotenone

(a)

0

1

2

3BO

DIP

Y ox

idat

ion


lowastlowastlowast

lowastlowastlowast

lowastlowastlowast

(b)





































































Environmental

endogenous toxins


Iron chelation

DecreasedISC

synthesis

DecreasedATP

synthesis


DecreasedGSHGSSG

ratio





pathways

Apoptosis

Survivalgenes



OH∙

and

darr FPN1uarr DMT1












Disclosure


Competing Interests


Acknowledgments


References








































































































































































2O2-mediated

























































































































































































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of













































































Environmental

endogenous toxins


Iron chelation

DecreasedISC

synthesis

DecreasedATP

synthesis


DecreasedGSHGSSG

ratio





pathways

Apoptosis

Survivalgenes



OH∙

and

darr FPN1uarr DMT1












Disclosure


Competing Interests


Acknowledgments


References








































































































































































2O2-mediated

























































































































































































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of





















Disclosure


Competing Interests


Acknowledgments


References








































































































































































2O2-mediated

























































































































































































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of







































































































































































2O2-mediated

























































































































































































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of

















































































































































































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of
















review article parkinson s disease: the mitochondria-iron...

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