Rudney JD (2000). Saliva and Dental Plaque.
Adv Dent Res 14:29-39.
Lamkin MS, Oppenheim FG (1993). Structural features of salivary function. Crit Rev Oral Biol
Med 4:251-259.

 Demographic change - the number of elderly will increase
 Implications:
 Increases in diseases affecting salivary glands
 Sjogren's syndrome, other autoimmune diseases,
 Head and neck cancer (radiation therapy)
 Increased use of medications with effects on saliva
 Anticholinergic (antihistamines, antidepressants)
• Reduced flow - indirect/direct effects on proteins
 Beta adrenergic agonists and antagonists
• Direct effects on protein synthesis/secretion
• (asthma, hypertension, cardiovascular disease)

 Current artificial salivas replace mainly fluids, ions
 Genetically-engineered human salivary proteins soon
 Raised from seed
 Which ones go in artificial saliva? How much to add?
 Already toothpastes/rinses containing saliva proteins
 Biotène™ (peroxidase, lysozyme lactoferrin)
 Histatin rinses/gels in trials
 Clinicians will need to be able to evaluate new products

 Different secretory cells in different glands
 Serous acinar - water, ions, proteins
 Most in parotid, less in SM/SL
 Mucus acinar - complex glycoproteins
 Only SM/SL and minor glands
 Different proteins emphasized in different glands
 Duct cells also secrete proteins - differs among glands
 Immune system cells contribute proteins
 B cell product (S-IgA) translocated into ducts
 Neutrophils - indirect leakage into gingival crevice
 Leakage from gingival fluid contributes serum proteins (WS only)
 Oral epithelial cells release surface proteins (whole saliva only)

 Protect oral surfaces by forming pellicle
 Statherin , acidic proline-rich proteins , amylase , histatins , cystatins , MUC7 mucin , lysozyme , albumin, carbonic anhydrase
 Lubrication - oral surfaces must slide freely
 Statherin , MUC5B mucin (also reflux protection)
 Maintain saliva calcium in equilibrium with enamel
 Saliva supersaturated with calcium and phosphate
 Precipitation must be prevented
 Statherin , aPRP , histatins , cystatins

 Initial breakdown of starches Amylase
 Binding/detoxification of dietary tannins
 aPRP , basic PRP , histatins
 Protein processing Kallikrein and other proteases
 Swallowing MUC5B

 Antimicrobial functions (bacteria, fungi, viruses)
 Direct - cell killing Histatins , lysozyme , amylase , MUC7 , lactoferrin , defensins , peroxidase
 Indirect - Inhibition of infectivity, microbial metabolism, bacterial/viral proteases Lactoferrin , cystatins , histatins , basic
PRP , SLIPI , peroxidase , S-IgA
 "Aggregation" - bind to microbes, clear by swallowing MUC7 , lysozyme , lactoferrin , glcosylated PRP , parotid agglutinin , extraparotid glycoprotein , S-IgA

 Microbial use of saliva proteins (coevolution)
 Microbial adherence to pellicle proteins Statherin , aPRP , amylase , MUC5B , MUC7 , lysozyme , lactoferrin , glcosylated
PRP , parotid agglutinin , extra-parotid glycoprotein , S-IgA , peroxidase
 Microbial metabolism of salivary proteins MUC5B
 Microbial use to metabolize host diet Amylase

 Most saliva proteins have more than one function
 Different domains on the same protein for different functions
 Most saliva proteins cans be "amphifunctional”
 Some actions help host, others seem to help microbes
 Also can be mediated by different domains
 Many proteins share similar functions - redundancy
 Multiple gene families
 2-4 closely linked genes coding very similar proteins
• aPRP , bPRP , gPRP , cystatins , histatins , amylase , MU Cs
• Multiple alleles for each gene
 Unrelated proteins with the same function - backup systems?

 Many salivary proteins are cleaved by proteases
 During secretion or in the mouth
 aPRP , bPRP , gPRP , histatins , S-IgA
 Fragments may function differently than intact proteins
 Proteins function differently together than they do alone
 Lysozyme , lactoferrin , peroxidase
 Salivary proteins bind in large heterotypic complexes
 MUC5B , amylase , aPRP , S-IgA , peroxidase , lysozyme , lactoferrin , statherin
 Complexes function differently than component proteins

aPRP statherin histatins
Schupbach et. al. 2001, Eur J Oral Sci 109:60

statherin histatins
Schupbach et. al. 2001, Eur J Oral Sci 109:60

 Multiple gene family
 Small tyrosine-rich phosphoproteins
 Negatively charged Ca 2+ binding N-terminal
 Two phosphoserines - additional negative charges
 Maintains Ca 2+ balance, strongly prevents precipitation
 Binds tooth surfaces and changes conformation
 C-terminal rich in "bulky" tyrosines
 Lubrication of tooth surfaces (pellicle)
 Adherence of Actinomyces species (pellicle)

 Multiple gene family
 Proline-rich phosphoproteins
 Negatively charged Ca 2+ binding N-terminal
 Two phosphoserines - additional negative charges
 Ca 2+ balance, strongly prevents precipitation
 Binds tooth surfaces and changes conformation
 C-terminal rich in "bulky" prolines
 Adherence of Streptococcus species (pellicle)
 Proteases cleave N-terminal from C-terminal
 Free C-terminal binds tannins; blocks bacterial adhesion

 Multigene family - largest is phosphoprotein, others not
 Small peptides after proteolysis
 Positive charge - histidine-rich
 Microbial cell damage - antibacterial and anti-fungal
 Also Ca 2+ balance, tannin binding, protease inhibitor
 Clinical interest - very safe - easy to make
 Early trials with histatin rinses and gels
 Some benefit in experimental gingivitis model
• No oral hygiene for a month
 No trials with caries, periodontitis, or candidiasis patients yet

 Products with added lysozyme , lactoferrin , peroxidase
 All influence aggregation/adherence, plus unique effects
 Px enzyme - bacterial H
2
O
2
+ saliva SCN -
 OSCN inhibits/kills bacteria
> OSCN -
 Removing H
2
O
2 may protect soft tissues
 Lz enzyme cleaves bacterial cell walls > lysis
 Also positive charge effects similar to histatins
 Lf sequesters iron from some microbes, but not all
 Unsaturated Lf is independently bactericidal
 Clinical interest - can be purified from cow's milk
 Biotène™ toothpaste, rinses, gum, dry mouth gels
 Minor to minimal benefit in published clinical trials

 Ideas about salivary protein function come from lab
 Experimental models are greatly simplified
 Change only one factor at a time
 The mouth is an extremely complex environment
 Difficult to isolate effects of single proteins
 Redundancy may “dilute” the effects of supplements
 We need to understand how different proteins work together
 Supplements may need to be in the form of protein complexes