Histatin 5 inhibits apoptosis in human gingival fibroblasts induced by Porphyromonas gingivalis cell-surface polyssacharide

The cell-surface components of Porpbyromonas gingivalis have various biological activities. In the present study, we investigated the virulence of several cell-surface components prepared from P. gingivalis in human gingival fibroblasts (HGF). Furthermore the preventive effect of salivary protein histatin 5 was invesitgated. P. gingivalis polysaccharide (PS) significantly inhibited HGF proliferation, but lipopolysaccharide and outer-membrane protein did not. By using ELISA analysis, DNA fragmentation in HGFs was observed intracellularly when treated with the PS. These results suggest that the PS of P. gingivalis can induce apoptosis in HGF. Pretreatment of PS with histatin 5 restrained the inhibitory effect of PS on HGF proliferation. Histatin 5 also suppressed the apoptotic cell death in HGF induced by PS stimulation. The present study suggests that the PS of P. gingivalis can modulate the cell population in periodontal tissue, causing periodontitis by inducing HGF cell death through apoptosis. Also histatin 5 can inhibit the PS activity and may play an important part in the regulation of inflammatory periodontal diseases.