Suppression of gingival inflammation induced by Porphyromonas gingivalis in rats by leupeptin

In this study, we developed a procedure to produce gingivitis in rats by in oculation of Porphyromonas gingivalis and studied the contribution of the b acterial cysteine proteinases, Arg-gingipain (Rgp) and Lys-gingipain (Kgp), to the pathology in the gingiva. To adhere the bacterium to periodontal ti ssues, a cotton thread was inserted between the first and second molar of r ight maxillary sites of rats. Rats in group A were administered with vehicl e alone after bacterial (strain W83) inoculation. In group B, the bacteria were inoculated in combination with leupeptin, a potent inhibitor of Rgp an d Kgp, and then leupeptin alone was administered the week after. Rats in gr oup C were administered leupeptin for 6 weeks after bacteria inoculation. A ll left maxillary gingiva in three groups showed no inflammatory changes. R ight maxillary gingiva of group A showed most of the clinical landmarks of gingivitis. Leupeptin exhibited only a little inhibitory effect on this gin givitis in group B, whereas it had a strong inhibitory effect on the inflam mation in group C. These results suggest that P. gingivalis-induced gingivi tis is attributable to Rgp and Kgp and that leupeptin is more effective in the late phase than the early stage of gingivitis.