Oral antimicrobial peptides and biological control of caries

Abstract

The presence of antimicrobial peptides (AMPs) in saliva may be a biological factor that contributes to susceptibility or resistance to caries. This manuscript will review AMPs in saliva, consider their antimicrobial and immunomodulatory functions, and evaluate their potential role in the oral cavity for protection of the tooth surface as well as the oral mucosa. These AMPs are made in salivary gland and duct cells and have broad antimicrobial activity. Alpha-defensins and LL37 are also released by neutrophils into the gingival crevicular fluid. Both sources may account for their presence in saliva. A recent study in middle school children aimed to determine a possible correlation between caries prevalence in children and salivary concentrations of the antimicrobial peptides human beta-defensin-3 (hBD-3), the cathelicidin, LL37, and the alpha-defensins. The levels of these AMPs were highly variable in the population. While levels of LL37 and hBD-3 did not correlate with caries experience, the mean alpha-defensin level was significantly higher in children with no caries than in children with caries (p < 0.005). We conclude that several types of AMPs that may have a role in oral health are present in unstimulated saliva. Low salivary levels of alpha-defensin may represent a biological factor that contributes to caries susceptibility. Our observation could lead to new ways to prevent caries and to a new tool for caries risk assessment.

Figure 1

Diagram indicating the presence of antimicrobial peptides in saliva (blue), in gingival epithelium (pink), and in neutrophils (PMNs) migrating into the oral cavity via the gingival crevicular fluid. All of these sources of antimicrobial peptides may aid protection of the mucosa from bacterial infection and the tooth surface from caries.

Figure 2

HNP 1–3 concentration in saliva as a function of caries score. The HNP1–3 peptides are closely related and are all detected by the immunoassay used. Note statistically significant difference between the caries groups and the 0 Caries group; * p < 0.05; *** p < 0.005.