Transcript Anti-microbial activities of saliva

Anti-microbial activities of saliva
Page no. 1
Dennis E. Lopatin, Ph.D.
Time course of sIgA appearance
Gestation
8w
Birth
11w 19w 26w
SC
Bronchial
Epithelium
Peyer’s
Patches
SC
Salivary
Gland
2-4w
Saliva:
Adult SC
No IgA
IgA
Cells
Adapted from Taubman & Smith, 1993
Page no. 2
1m
3m
Salivary
Antibody to
Initial Oral
and Gut Flora
Saliva
sIgA
6m
Tooth
Eruption
Early IgA
Peak
2y
?
Adult
Concentrations
Many Salivary IgA
Concentrations
in Adult Range
Dennis E. Lopatin, Ph.D.
Non-immunoglobulin anti-microbial
agents in whole saliva
Page no. 3
Dennis E. Lopatin, Ph.D.
Lactoferrin
Binds ferric iron (Fe3+) and unavailable for microbes
 Nutritional immunity
 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.
 In unbound state, a direct bactericidal effect

Page no. 4
Dennis E. Lopatin, Ph.D.
Lysozyme
Present in numerous organs and most body fluids
 Oral LZ is derived from at least four sources

– major and minor salivary glands, phagocytic cells and gingival
crevicular fluid (GCF)

Biological function
– Classic concept of anti-microbial activity of LZ is based on its
muramidase activity (hydrolysis of (1-4) bond between Nacetylmuramic acid and N-acetylglucosamine in the
peptidoglycan layer.
– Gram negative bacteria generally more resistant than gram
positive because of outer LPS layer
Page no. 5
Dennis E. Lopatin, Ph.D.
Other anti-microbial activities of LZ
Muramidase activity (lysis of peptidoglycan layer)
 Cationic-dependent activation of bacterial autolysins

– strongly cationic protein (pI 10.5-11)
– disrupts membranes
Aggregation of bacteria
 Inhibition of bacterial adhesion to tooth surfaces
 Inhibition of glucose uptake and acid production
 De-chaining of streptococci

Page no. 6
Dennis E. Lopatin, Ph.D.
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

Myeloperoxidase (MP)
– From leukocytes entering via gingival crevice
– 15-20% of total peroxidase in whole saliva
Page no. 7
Dennis E. Lopatin, Ph.D.
Components of the peroxidase
anti-microbial system
Peroxidase enzymes (SP or MP)
 Hydrogen peroxide (H2O2)

– oral bacteria (facultative aerobes/catalase negative) produce
large amounts of peroxide
» S. sanguis, S. mitis, S. mutans

Thiocyanate ion (SCN-) which is converted to
hypothiocyanite ion (OSCN-) by peroxidase
– salivary concentration is related to diet and smoking habits
Page no. 8
Dennis E. Lopatin, Ph.D.
Thiocyanate reactions
H2O2 + SCN-
SP and/or MP
OSCN- +H2O
Acid/Base Equilib.
HOSCN
Hypothiocianous acid
OSCN- + H+
Hypothiocyanite ion
The pK for HOSCN/OSCN- is 5.3
 More acid favors HOSCN
 Due to uncharged nature, HOSCN
penetrates bacterial cell envelope better

Page no. 9
Dennis E. Lopatin, Ph.D.
HOSCN/OSCN -mediated
cell damage
can oxidize sulfhydryl groups of enzymes
 block glucose uptake
 inhibit amino acid transport
 damage inner membrane, leading to leakage of cell
 disrupt electrochemical gradients

Page no. 10
Dennis E. Lopatin, Ph.D.
Regulation of oral microorganisms by SP/MP
Recovery
Food Ingestion
Unstimulated
bacteria
carbohydrates
Stimulation
thiols
spontaneous
Inhibited
bacteria
Autoinhibition
OSCN-/HOSCN
Inhibition
Page no. 11
O2
Active
bacteria
H+
SCN- + H2O2
+SP
Salivary Glands
Metabolism
Dennis E. Lopatin, Ph.D.
Histatins
A group of small histidine-rich proteins
 Potent inhibitors of Candida albicans growth
 Histatin 1, which is phosphorylated modulates
precipitation of calcium phosphates

Page no. 12
Dennis E. Lopatin, Ph.D.
Amylases

Well-known function as a digestive enzyme
– Calcium metalloenzyme, which hydrolyses the (1-4)
bonds of starches, such as amylose and amylopectin.

Anti-microbial activity
– potent inhibitor and specific inhibitor of N. gonorrheoeae
and Legionella pneumonophila in vitro.
– modulates adhesion of certain oral species to teeth and
other body surfaces
Page no. 13
Dennis E. Lopatin, Ph.D.
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

Page no. 14
Dennis E. Lopatin, Ph.D.