Effect of Actinobacillus actinomycetemcomitans protease on the proliferation of gingival epithelial cells

OBJECTIVE: Actinobacillus actinomycetemcomitans (A. actinomycetemcomitans) has been implicated as an important pathogen in periodontal disease. The ai m of this report is to examine the effect of in vitro application of A. act inomycetemcomitans protease on the cell growth, DNA synthesis, and fibronec tin level of human gingival epithelial cells. MATERIALS AND METHODS: A. actinomycetemcomitans protease was isolated from the culture supernatant of A. actinomycetemcomitans. Human gingival epithel ial cells were incubated in the presence or absence of A. actinomycetemcomi tans protease (0.01, 0.1, or I U) for 48 h. The proliferation of cells were tested with the MTT assay and the BrdU assay. The fibronectin level was ex amined by flow cytometric analysis. RESULTS: The cell growth rate, DNA synthesis rate, and fibronectin level of the gingival epithelial cells that had been incubated with protease, were lower than the respective values in the untreated gingival epithelial cells ; as the dose of A. actinomycetemcomitans protease increased, the cell grow th rate, DNA synthesis rate, and fibronectin level of the gingival epitheli al cells decreased. A. actinomycetemcomitans protease may inhibit the proli feration of human gingival epithelial cells. CONCLUSIONS: This protease may play a key role as a major virulence factor in the development of periodontal disease.