Saliva components theory

Important Components of Saliva

Important components of saliva with some examples within each component group :

Electrolyte : Bicarbonate ,calcium ,fluoride , phosphate ,Sodium , Potassium

Enzymes: α-amylase , Invertase , protease , lipase
Mucins : MUC5B(MG1) , MUC7(MG2)
Immunoglobulins IgA ,IgG , IgM , IgAs
Lipids : Neutral lipids, glycolipids , phospholipids
Non-immunoglobulin : Histidin-rich proteins, lactoferrin , lysozyme,
Proteins: Peroxidase, proline-rich proteins, salivary agglutinins, statherin

Function of The Important Components of Saliva

Lubrication : Mucins , proline-rich glycoproteins , water
Antimicrobial : Amylase, complement, defensins, lysozyme, lactoferrin, lactoperoxidase, mucins, cystatins, proline-rich glycoproteins, secretory IgA, secretory Leukocyte protease inhibitor , statherin , thrombospondin , sialoperoxidase
Growth factor :Epidermal growth factor(EGF), transforming growth factor- alpha(TGF-α) , transforming growth factor-beta(TGF-β) , fibroblast growth factor(FGF) ,
insulin-like growth factor(IGF-I & IGF-II), nerve growth factor(NGF).
Mucosal integrity : Mucins , electrolytes , water
Lavage/cleansing: Water
Buffering : Bicarbonate , phosphate ione , proteins
Remineralization : Calcium , phosphate , statherin , anioic proline-rich proteins


Inorganic Components of Saliva

Calcium and phosphate

Help to prevent dissolution of dental enamel
Calcium
1,4 mmol/l (1,7 mmol/l in stimulated saliva)
sublingual > submandibular > parotis
Phosphate
6 mmol/l (4 mmol/l in stimulated saliva)
90% in ionic form
pH around 6 – hydroxyapatite(Ca10(PO4)6(OH)2) is unlikely to dissolve
Increase of pH - precipitation of calcium salts => dental calculus

Hydrogen carbonate

Buffer
Low in unstimulated saliva, increases with flow rate
Pushes pH of stimulated saliva up to 8
pH 5,6 critical for dissolution of enamel
Defence against acids produced by cariogenic bacteria
Derived actively from CO2 by carbonic anhydrase


Fluoride
The mineral fluoride is very important for healthy teeth
Low concentration, similar to plasma
Thiocyanate (also known as rhodanide) is the anion [SCN]−
Antibacterial (oxidated to hypothiocyanite OSCN- by active oxygen produced from bacterial peroxides by lactoperoxidase)
Higher conc. => lower incidence of caries
Sodium, potassium, chloride
Lead, cadmium, copper
May reflect systemic concentrations - diagnostics

Organic components

Organic components of saliva
Mucins
Proline-rich proteins
Amylase
Lipase
Peroxidase
Lysozyme
Lactoferrin
sIgA
Histatins
Statherin
Blood group substances, sugars, steroid hormones, amino acids, ammonia, urea


Multifunctionality

Salivary

Functions
Anti-
Bacterial
Buffering
Digestion
Mineral-
ization
Lubricat-
ion &Visco-
elasticity
Tissue
Coating
Anti-
Fungal
Anti-
Viral
Carbonic anhydrases,
Histatins
Amylases,
Mucins, Lipase
Cystatins,
Histatins, Proline-
rich proteins,
Statherins
Mucins, Statherins
Amylases,
Cystatins, Mucins,
Proline-rich proteins, Statherins
Histatins
Cystatins,
Mucins
Amylases, Cystatins,
Histatins, Mucins,
Peroxidases


Mucins :
are high molecular weight glycosylated proteins that form a major part of a protective biofilm on the surface of epithelial cells, where they can provide a barrier to particulate matter and bind microorganisms

Mucins

Lubrication
Glycoproteins - protein core with many oligosaccharide side chains attached by O-glycosidic bond
More than 40% of carbohydrates
Hydrophillic, entraining water (resists dehydration)
Unique rheological properties (e.g., high elasticity, adhesiveness, and low solubility)
Two major mucins (MG1 and MG2)

Amylases

Calcium metalloenzyme
Hydrolyzes (1-4) bonds of starches such as amylose and amylopectin
Several salivary isoenzymes
Maltose is the major end-product (20% is glucose)
Parotis; 30% of total protein in parotid saliva
“Appears” to have digestive function - inactivated in stomach, provides disaccharides for acid-producing bacteria
it also present in tears, serum, bronchial, and male and female urogenital secretions.
A role in modulating bacterial adherence?


Proline-rich Proteins (PRPs)
Proline-rich proteins (PRPs) is a class of intrinsically unstructured proteins
15-20% of parotid saliva
Containing several repeats of a short proline-rich sequence
Inhibitors of calcium phosphate crystal growth
Subdivided into three groups
Acidic 45%
Basic 30%
Glycosylated 25%
Interacts specifically with Fusobacterium nucleatum and may interfere with plaque formation

Proline-rich proteins and Statherins

• Inhibit the spontaneous
precipitation of calcium phosphate
salts and the growth of
hydroxyapatite crystals on the
tooth surface,
preventing the formation of salivary and dental calculus

Lactoferrin

Iron-binding protein
„Nutritional“ immunity (iron starvation)
Binds free iron in the saliva causing bactericidal or bacteriostatic effects on various microorganisms requiring iron for their survival such as Streptococcus mutans group
• Provides fungicidal, antiviral, anti-inflammatory, and immunomodulatory functions
But unfortunatly Some microorganisms (e.g., E. coli) have adapted to this mechanism by producing enterochelins.
bind iron more effectively than lactoferrin
iron-rich enterochelins are then reabsorbed by bacteria
Lactoferrin, with or without iron, can be degraded by some bacterial proteases.

Lysozyme

Present in numerous organs and most body fluids
Also called muramidase
hydrolysis of (1-4) bond between N-acetylmuramic acid and N-acetylglucosamine in the peptidoglycan layer of bacteria.
Gram negative bacteria generally more resistant than gram positive because of outer LPS layer

Histatins

A group of small histidine-rich proteins
A family of related cationic proteins rich in histidine
• Broad antimicrobial activity against bacteria and yeasts
Potent inhibitors of Candida albicans growth

Cystatins

Are inhibitors of cysteine-proteases
Are ubiquitous in many body fluids
Considered to be protective against unwanted proteolysis
bacterial proteases
lysed leukocytes
May play inhibit proteases in periodontal tissues
Also have an effect on calcium phosphate precipitation


Salivary peroxidase systems
Sialoperoxidase (SP, salivary peroxidase)
Produced in acinar cells of parotid glands
Also present in submandibular saliva
Readily adsorbed to various surfaces of mouth
enamel, salivary sediment, bacteria, dental plaque
Serves as a catalyst for the oxidation of the salivary thiocyanate ion by hydrogen peroxide into hypothiocyanate - a potent antibacterial substance

Myeloperoxidase (MP)

From leukocytes entering via gingival crevice
15-20% of total peroxidase in whole saliva