Role of saliva proteinase 3 in dental caries

Abstract

Salivary analysis can be used to assess the severity of caries. Of the known salivary proteins, a paucity of information exists concerning the role of proteinase 3 (PR3), a serine protease of the chymotrypsin family, in dental caries. Whole, unstimulated saliva was collected from children with varying degrees of active caries and tested using a Human Protease Array Kit and an enzyme-linked immunosorbent assay. A significantly decreased concentration of salivary PR3 was noted with increasing severity of dental caries (P<0.01); a positive correlation (r=0.87; P<0.01; Pearson’s correlation analysis) was also observed between salivary pH and PR3 concentration. In an antibacterial test, a PR3 concentration of 250 ng·mL−1 or higher significantly inhibited Streptococcus mutans UA159 growth after 12 h of incubation (P<0.05). These studies indicate that PR3 is a salivary factor associated with the severity of dental caries, as suggested by the negative relationship between salivary PR3 concentration and the severity of caries as well as the susceptibility of S. mutans to PR3. Higher levels of proteinase 3 (PR3) in saliva are associated with lower levels of dental caries. Other salivary proteins have previously been shown to influence dental health. Ping Zhang, Xue-Dong Zhou and co-workers at the State Key Laboratory of Oral Diseases, Sichuan University, China, analyzed salivary proteins and the pH of saliva collected from 128 healthy six-year-old children. Caries-free children showed significantly higher levels of PR3 than those with caries. Salivary pH was not significantly associated with caries, but a higher pH was significantly associated with higher PR3 levels. The researchers investigated whether PR3 showed activity against Streptococcus mutans, a bacterium commonly associated with cavities. High levels of PR3 inhibited the growth of S. mutans. Further studies will be required to determine whether PR3 can be used to help prevent cavities.