composition and function of saliva

Dennis E. Lopatin, Ph.D.Dennis E. Lopatin, Ph.D.Slide no. Slide no. 11

Composition and function of salivaComposition and function of saliva


Major salivary componentsMajor salivary components

Mucin 1 (MG1)Mucin 1 (MG1)sIgAsIgA

Mucin 2 (MG2)Mucin 2 (MG2)LactoferrinLactoferrin

PeroxidasesPeroxidasesAmylasesAmylases

Carbonic anhydrasesCarbonic anhydrasesProline-rich proteinsProline-rich proteins

LysozymeLysozymeStatherinsStatherins

HistatinsHistatins

11 1010 100100 10001000 1000010000

Size (kDa)Size (kDa)


MultifunctionalityMultifunctionality

SalivarySalivaryFamiliesFamilies

Anti-Anti-BacterialBacterial

BufferingBuffering

DigestionDigestion

Mineral-Mineral-izationization

Lubricat-Lubricat-ion &Visco-ion &Visco-elasticityelasticity

TissueTissueCoatingCoating

Anti-Anti-FungalFungal

Anti-Anti-ViralViral

Carbonic anhydrases,Carbonic anhydrases,HistatinsHistatins

Amylases,Amylases,Mucins, LipaseMucins, Lipase

Cystatins,Cystatins,Histatins, Proline-Histatins, Proline-rich proteins,rich proteins,StatherinsStatherins

Mucins, StatherinsMucins, Statherins

Amylases,Amylases,Cystatins, Mucins, Cystatins, Mucins, Proline-rich proteins, StatherinsProline-rich proteins, Statherins

HistatinsHistatins

Cystatins,Cystatins,MucinsMucins

Amylases, Cystatins,Amylases, Cystatins,Histatins, Mucins,Histatins, Mucins,PeroxidasesPeroxidases

adapted from M.J. Levine, 1993adapted from M.J. Levine, 1993


Mucin FunctionsMucin Functions Tissue CoatingTissue Coating

– Protective coating about hard and soft tissuesProtective coating about hard and soft tissues– Primary role in formation of acquired pelliclePrimary role in formation of acquired pellicle– Concentrates anti-microbial molecules at mucosal interfaceConcentrates anti-microbial molecules at mucosal interface

LubricationLubrication– Align themselves with direction of flow (characteristic of Align themselves with direction of flow (characteristic of

asymmetric molecules)asymmetric molecules)– Increases lubricating qualities (film strength)Increases lubricating qualities (film strength)– Film strength determines how effectively opposed moving Film strength determines how effectively opposed moving

surfaces are kept apartsurfaces are kept apart


Mucin Functions (cont’d)Mucin Functions (cont’d)

Aggregation of bacterial cellsAggregation of bacterial cells– Bacterial adhere to mucins may result in surface Bacterial adhere to mucins may result in surface

attachment, orattachment, or– Mucin-coated bacteria may be unable to attach to surfaceMucin-coated bacteria may be unable to attach to surface

Bacterial adhesionBacterial adhesion– Mucin oligosaccharides mimic those on mucosal cell Mucin oligosaccharides mimic those on mucosal cell

surfacesurface– React with bacterial adhesins, thereby blocking themReact with bacterial adhesins, thereby blocking them


AmylasesAmylases

• Hydrolyzes Hydrolyzes (1-4) bonds of starches such as (1-4) bonds of starches such as amylose and amylopectinamylose and amylopectin

• Maltose is the major end-product (20% is glucose)Maltose is the major end-product (20% is glucose)• Why is it also present in tears, serum, bronchial, and Why is it also present in tears, serum, bronchial, and

male and female urogenital secretions?male and female urogenital secretions?• A role in modulating bacterial adherence?A role in modulating bacterial adherence?


Lingual LipaseLingual Lipase

Secreted by von Ebner’s glands of tongueSecreted by von Ebner’s glands of tongue Involved in first phase of fat digestionInvolved in first phase of fat digestion Hydrolyzes medium- to long-chain triglyceridesHydrolyzes medium- to long-chain triglycerides Important in digestion of milk fat in new-bornImportant in digestion of milk fat in new-born Unlike other mammalian lipases, it is highly Unlike other mammalian lipases, it is highly

hydrophobic and readily enters fat globuleshydrophobic and readily enters fat globules


StatherinsStatherins Calcium phosphate salts of dental enamel are solubleCalcium phosphate salts of dental enamel are soluble Supersaturation of calcium phosphates maintain Supersaturation of calcium phosphates maintain

enamel integrityenamel integrity Statherins prevent precipitation or crystallization of Statherins prevent precipitation or crystallization of

supersaturated calcium phosphate in ductal saliva and supersaturated calcium phosphate in ductal saliva and oral fluidoral fluid


Proline-rich Proteins (PRPs)Proline-rich Proteins (PRPs)

Inhibit calcium phosphate crystal growthInhibit calcium phosphate crystal growth Present in the initially formed enamel pellicle and in Present in the initially formed enamel pellicle and in

“mature” pellicles“mature” pellicles


Enamel pellicle formationEnamel pellicle formation

0.1-1.0 µm thick layer of macromolecular material on 0.1-1.0 µm thick layer of macromolecular material on the mineral surface of teeththe mineral surface of teeth

Selective adsorption of hydroxyapatite-reactive salivary Selective adsorption of hydroxyapatite-reactive salivary proteins, serum proteins and microbial productsproteins, serum proteins and microbial products

Diffusion barrierDiffusion barrier– Protects against bacterial acidsProtects against bacterial acids– Slows loss of dissolved calcium and phosphate ionsSlows loss of dissolved calcium and phosphate ions


Remineralization of enamelRemineralization of enamel

Early (incipient) caries are repaired despite presence of Early (incipient) caries are repaired despite presence of mineralization inhibitors in salivamineralization inhibitors in saliva

Sound surface layer of early carious lesion forms Sound surface layer of early carious lesion forms impermeable barrier to diffusion of high mol.wt. impermeable barrier to diffusion of high mol.wt. inhibitors.inhibitors.

Still permeable to calcium and phosphate ionsStill permeable to calcium and phosphate ions Inhibitors may encourage mineralization by preventing Inhibitors may encourage mineralization by preventing

crystal growth on the surface of lesion by keeping crystal growth on the surface of lesion by keeping pores openpores open


Calculus formationCalculus formation

Calculus forms in plaque despite inhibitory action of Calculus forms in plaque despite inhibitory action of statherin and PRPs in salivastatherin and PRPs in saliva

May be due to failure to diffuse into calcifying May be due to failure to diffuse into calcifying plaqueplaque

Proteolytic enzymes of oral bacteria or lysed Proteolytic enzymes of oral bacteria or lysed leukocytes may destroy inhibitory proteinsleukocytes may destroy inhibitory proteins

Plaque bacteria may produce their own inhibitorsPlaque bacteria may produce their own inhibitors


Anti-microbial activities of salivaAnti-microbial activities of saliva


LactoferrinLactoferrin

Nutritional immunity (iron starvation)Nutritional immunity (iron starvation) Some microorganisms (e.g., Some microorganisms (e.g., E. coliE. coli) have adapted to this ) have adapted to this

mechanism by producing mechanism by producing enterochelinsenterochelins..– bind iron more effectively than lactoferrinbind iron more effectively than lactoferrin– iron-rich enterochelins are then reabsorbed by bacteriairon-rich enterochelins are then reabsorbed by bacteria

Lactoferrin, with or without iron, can be degraded by Lactoferrin, with or without iron, can be degraded by some bacterial proteases.some bacterial proteases.

In unbound state, a direct bactericidal effectIn unbound state, a direct bactericidal effect


LysozymeLysozyme Present in numerous organs and most body fluidsPresent in numerous organs and most body fluids Oral LZ is derived from at least four sourcesOral LZ is derived from at least four sources

– major and minor salivary glands, phagocytic cells and gingival major and minor salivary glands, phagocytic cells and gingival crevicular fluid (GCF)crevicular fluid (GCF)

Biological functionBiological function– Classic conceptClassic concept of anti-microbial activity of LZ is based on its of anti-microbial activity of LZ is based on its

muramidasemuramidase activity (hydrolysis of activity (hydrolysis of (1-4) bond between N-(1-4) bond between N-acetylmuramic acid and N-acetylglucosamine in the peptidoglycan layer.acetylmuramic acid and N-acetylglucosamine in the peptidoglycan layer.

– Gram negative bacteria generally more resistant than gram positive Gram negative bacteria generally more resistant than gram positive because of outer LPS layerbecause of outer LPS layer


Other anti-microbial activities of LZOther anti-microbial activities of LZ Muramidase activity (lysis of peptidoglycan layer)Muramidase activity (lysis of peptidoglycan layer) Cationic-dependent activation of bacterial autolysinsCationic-dependent activation of bacterial autolysins

– strongly cationic protein (pI 10.5-11)strongly cationic protein (pI 10.5-11)– disrupts membranesdisrupts membranes

Aggregation of bacteriaAggregation of bacteria Inhibition of bacterial adhesion to tooth surfacesInhibition of bacterial adhesion to tooth surfaces Inhibition of glucose uptake and acid productionInhibition of glucose uptake and acid production De-chaining of streptococciDe-chaining of streptococci


HistatinsHistatins

A group of small histidine-rich proteinsA group of small histidine-rich proteins Potent inhibitors of Potent inhibitors of Candida albicansCandida albicans growth growth


CystatinsCystatins Are Are inhibitorsinhibitors of cysteine-proteases of cysteine-proteases Are ubiquitous in many body fluidsAre ubiquitous in many body fluids Considered to be protective against unwanted Considered to be protective against unwanted proteolysisproteolysis

– bacterial proteasesbacterial proteases

– lysed leukocyteslysed leukocytes

May play inhibit proteases in periodontal tissuesMay play inhibit proteases in periodontal tissues Also have an effect on calcium phosphate precipitationAlso have an effect on calcium phosphate precipitation


Salivary peroxidase systemsSalivary peroxidase systems

Sialoperoxidase (SP, salivary peroxidase)Sialoperoxidase (SP, salivary peroxidase)– Produced in acinar cells of parotid glandsProduced in acinar cells of parotid glands– Also present in submandibular salivaAlso present in submandibular saliva– Readily adsorbed to various surfaces of mouthReadily adsorbed to various surfaces of mouth

» enamel, salivary sediment, bacteria, dental plaqueenamel, salivary sediment, bacteria, dental plaque

Myeloperoxidase (MP)Myeloperoxidase (MP)– From leukocytes entering via gingival creviceFrom leukocytes entering via gingival crevice– 15-20% of total peroxidase in whole saliva15-20% of total peroxidase in whole saliva


Components of the peroxidase Components of the peroxidase anti-microbial systemanti-microbial system

Peroxidase enzymes (SP or MP)Peroxidase enzymes (SP or MP) Hydrogen peroxide (HHydrogen peroxide (H22OO22))

– oral bacteria (facultative aerobes/catalase negative) produce oral bacteria (facultative aerobes/catalase negative) produce large amounts of peroxidelarge amounts of peroxide

» S. sanguis, S. mitis, S. mutansS. sanguis, S. mitis, S. mutans

Thiocyanate ion (SCNThiocyanate ion (SCN--) which is converted to ) which is converted to hypothiocyanite ion (OSCNhypothiocyanite ion (OSCN--) by peroxidase) by peroxidase– salivary concentration is related to diet and smoking habitssalivary concentration is related to diet and smoking habits


Thiocyanate reactionsThiocyanate reactions

The pK for HOSCN/OSCNThe pK for HOSCN/OSCN-- is 5.3 is 5.3 More acid favors HOSCNMore acid favors HOSCN Due to uncharged nature, HOSCN Due to uncharged nature, HOSCN

penetrates bacterial cell envelope betterpenetrates bacterial cell envelope better

HH22OO22 + SCN + SCN-- OSCNOSCN-- +H +H22OOSP and/or MPSP and/or MP

HOSCNHOSCN OSCNOSCN-- + H+ + H+Hypothiocianous acidHypothiocianous acid Hypothiocyanite ionHypothiocyanite ion

Acid/Base Equilib.Acid/Base Equilib.


HOSCN/OSCNHOSCN/OSCN---mediated cell damage-mediated cell damage

can oxidize sulfhydryl groups of enzymescan oxidize sulfhydryl groups of enzymes block glucose uptakeblock glucose uptake inhibit amino acid transportinhibit amino acid transport damage inner membrane, leading to leakage of celldamage inner membrane, leading to leakage of cell disrupt electrochemical gradientsdisrupt electrochemical gradients


Regulation of oral microorganisms by SP/MPRegulation of oral microorganisms by SP/MP

UnstimulatedUnstimulatedbacteriabacteria

InhibitedInhibitedbacteriabacteria

ActiveActivebacteriabacteria

Food IngestionFood Ingestioncarbohydratescarbohydrates

StimulationStimulationStimulationStimulation

MetabolismMetabolismMetabolismMetabolism

HH++

RecoveryRecoveryRecoveryRecovery

OO22

thiolsthiols

InhibitionInhibitionInhibitionInhibition

Salivary GlandsSalivary GlandsSalivary GlandsSalivary Glands

SCNSCN-- + H + H22OO22OSCNOSCN--/HOSCN/HOSCN

AutoinhibitionAutoinhibition

spontaneousspontaneous

+SP+SP

composition and function of saliva

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