Duplicated or Hybridized Peptide Functional Domains Promote Oral Homeostasis.

Proteins that have existed for millions of years frequently contain repeats of functional domains within their primary structure, thereby improving their functional capacity. In the evolutionary young statherin protein contained within the in vivo-acquired enamel pellicle (AEP), we identified a single functional domain (DR9) located within the protein N-terminal portion that exhibits a higher affinity for hydroxyapatite and more efficient protection against enamel demineralization compared to other native statherin peptides. Thus, we tested the hypothesis that multiplication of functional domains of naturally occurring pellicle peptides amplifies protection against enamel demineralization. In addition, a specific amino acid sequence from histatin 3 (RR-14) was introduced to the hybrid peptides for further testing. Enamel specimens were sectioned to 150-µm thickness and randomly grouped as follows: DR9, DR9-DR9, DR9-RR14, statherin, histatin 1, or distilled water (control). After submersion for 2 h at 37°C, the specimens were placed in 2 mL demineralization solution for 12 d at 37°C. Upon sample removal, the remaining solution was subjected to colorimetric assays to determine the amount of calcium and phosphate released from each specimen. DR9-DR9 amplified protection against enamel demineralization when compared to single DR9 or statherin. Notably, the hybrid peptide DR9-RR14 demonstrated relatively strong protection when the antimicrobial property of these peptides was tested against Candida albicans and Streptococcus mutans. DR9-RR14 was able to maintain 50% of the antifungal activity compared with RR14 for C. albicans and similar values of S. mutans killing activity. This study has pioneered the functional exploration of the natural peptide constituents of the AEP and their evolution-inspired engineered peptides. The knowledge obtained here may provide a basis for the development of stable (proteinase-resistant) synthetic peptides for therapeutic use against dental caries, dental erosion, and/or oral candidiasis.

The impact of stannous, fluoride ions and its combination on enamel pellicle proteome and dental erosion prevention.

OBJECTIVES: To compare the effects of stannous (Sn) and fluoride (F) ions and their combination on acquired enamel pellicle (AEP) protein composition (proteome experiment), and protection against dental erosion (functional experiment). METHODS: In the proteome experiment, bovine enamel specimens were incubated in whole saliva supernatant for 24h for AEP formation. They were randomly assigned to 4 groups (n=10), according to the rinse treatment: Sn (800ppm/6.7mM, SnCl2), F (225ppm/13mM, NaF), Sn and F combination (Sn+F) and deionized water (DIW, negative control). The specimens were immersed 3× in the test rinses for 2min, 2h apart. Pellicles were collected, digested, and analyzed for protein content using liquid chromatography electrospray ionization tandem mass spectrometry. In the functional experiment, bovine enamel specimens (n=10) were similarly treated for pellicle formation. Then, they were subjected to a five-day erosion cycling model, consisting of 5min erosive challenges (15.6 mM citric acid, pH 2.6, 6×/d) and 2min treatment with the rinses containing Sn, F or Sn+F (3×/d). Between the treatments, all specimens were incubated in whole saliva supernatant. Surface loss was determined by profilometry. RESULTS: Our proteome approach on bovine enamel identified 72 proteins that were common to all groups. AEP of enamel treated with Sn+F demonstrated higher abundance for most of the identified proteins than the other groups. The functional experiment showed reduction of enamel surface loss for Sn+F (89%), Sn (67%) and F (42%) compared to DIW (all significantly different, p<0.05). CONCLUSION: This study highlighted that anti-erosion rinses (e.g. Sn+F) can modify quantitatively and qualitatively the AEP formed on bovine enamel. Moreover, our study demonstrated a combinatory effect that amplified the anti-erosive protection on tooth surface.