MMP-12 and S100s in saliva reflect different aspects of periodontal inflammation

Matrix metalloproteinase (MMP)-12, S100A8/A9, and S100Al2 are involved in innate immune responses. We addressed whether different aspects of oral health and non-disease-related covariates influence their levels in saliva. 436 participants were clinically examined, completed a health questionnaire, and provided stimulated saliva. Salivary levels of MMP-12, S100A8/A9, and S100Al2 were determined by enzyme-linked immunosorbent assays. Lower MMP-12 levels were observed in individuals 40-64 years old (yo) compared to < 40 yo, and higher S100A8/A9 levels were found in individuals > 64 yo compared to 40-64 yo. Smokers exhibited lower MMP-12 and S100Al2 levels compared to non-smokers. All three proteins were elevated in individuals with bleeding on probing (BOP) > 20% compared to those with BOP <= 20%, and the S100A8/A9 levels were higher in individuals having >= 10% gingival pocket depths (PPD) >= 4 mm compared to the ones with shallow pockets < 4 mm. The extent of alveolar bone loss or presence of manifest caries did not alter any of the markers. MMP-12, S100A8/A9, and S100A12 levels were higher in participants with high periodontal inflammatory burden. All three proteins correlated positively to BOP, PPD, and to several inflammatory mediators. The explanatory variables for MMP-12 in saliva were age, smoking, presence of any tumor, and percentage of PPD 4 mm. The determinant of salivary S100A8/A9 was percentage of BOP, while S100Al2 levels were associated with percentage of BOP and presence of any tumor. Taken together, MMP-12 and the S100/calgranulin levels in saliva reflect different aspects of periodontal inflammation. Smoking and age should be taken into account in further investigation of these proteins as biomarker candidates of periodontal disease.