EFFECT OF PORPHYROMONAS-GINGIVALIS ON EPITHELIAL-CELL MMP-9 TYPE-IV COLLAGENASE PRODUCTION

Porphyromonas gingivalis is reportedly capable of stimulating the expr ession of host cell matrix metalloproteinases (MMP), contributing to t issue destruction However, the impact of this bacterium on specific mo lecules remains to be determined. In this study, we evaluate the effec t of P. gingivalis on regulation of MMP-9 expression in human gingival epithelial cells (HGEC). Various inocula of P. gingivalis were added to cultures of HGEC. The effects of live bacteria, heat-killed bacteri a, and outer membrane extract were analyzed. MMP-9 secretion by HGEC w as evaluated by enzyme-linked immunosorbent assay. For inocula smaller than one bacterium per cell, the quantity of MMP-9 secreted by HGEC w as increased in comparison to control conditions. For inocula from 2.5 to 250 bacteria per cell, an inhibition of MMP-9 secretion in a dose- response fashion was observed, with a maximum reduction (ranging from 80 to 95% in five experiments) at 50 bacteria per cell, Gelatin zymogr ams confirmed the decrease in MMP-9 secretion. A band of 83 kDa, corre sponding to activated enzyme, mas present for inocula of 0.5 to 50 bac teria. Inhibition took place without any alteration of epithelial cell viability. Heat-killed bacteria and outer membrane extract also provo ked proenzyme activation but did not inhibit MMP-9 secretion. These re sults demonstrate a direct effect of P. gingivalis on HGEC, suggesting a specific action on the collagen renewal process at the interface be tween the epithelium and connective tissue.