EFFECT OF FREE AND VESICLE-BOUND CYSTEINE PROTEINASES OF PORPHYROMONAS-GINGIVALIS ON PLASMA CLOT FORMATION - IMPLICATIONS FOR BLEEDING TENDENCY AT PERIODONTITIS SITES

Infection by Porphyromonas gingivalis is strongly associated,vith adul t periodontitis, with proteinases from this bacterium now considered t o be important virulence factors. In order to investigate possible pat hological functions of these enzymes, we examined the effect of both f ree and vesicle-bound forms of the two major cysteine proteinases (gin gipains) of P. gingivalis on plasma clot formation by using thrombin t ime (TT) measurements. Both Lys-gingipain (gingipain-K) and Arg-gingip ain (gingipain-R) prolonged plasma TT in a dose- and time-dependent ma nner, and this was also found with vesicles which are the biological c arriers of P. gingivalis proteinases. The increase in plasma TT by ves icles could be completely reversed by treatment with nonspecific cyste ine proteinase inhibitors but only partially by compounds selective fo r either gingipain-K or gingipain-R, Preincubation of vesicles with a gingipain-K-specific inhibitor (z-FK-ck) reduced plasma TT more than a gingipain-R-specific inhibitor (leupeptin), suggesting that under phy siological conditions gingipain-K was more effective in fibrinogen des truction. Each purified enzyme also markedly increased fibrinogen TT, gingipain-R being fourfold more potent than gingipain-K. However, in p lasma, gingipain-R was ineffective because of the inhibitory effect of albumin. These results imply that cysteine proteinases, especially gi ngipain-K, abrogate the clotting potential of fibrinogen and, therefor e, may contribute to the bleeding tendency and to persistent inflammat ion in periodontitis sites infected with P. gingivalis.