Effects of dipeptide bestatin on Porphyromonas gingivalis and epithelial cells

Background: Dipeptide bestatin has been previously reported to selectively inhibit the growth of Porphyromonas gingivalis. The aims of this study were to investigate the mechanism of action of bestatin and to evaluate its eff ect on epithelial cells. Methods: The inhibitory effect of bestatin on P. g ingivalis was tested in vitro (culture medium) and in vivo (guinea pig mode l). Radiolabeled compounds were used to investigate the effect of bestatin on the uptake of amino acids and peptides. The cytotoxic effect of bestatin was evaluated using a keratinocyte cell line. Results: The growth inhibition of P. gingivalis by bestatin was concentrati on-dependent. Even at high concentrations, compounds possessing a chemical structure or an aminopeptidase inhibitor activity related to bestatin had n o effect on growth of P. gingivalis. When injected in the presence of P. gi ngivalis, bestatin was able to prevent the development of a necrotic absces s in a guinea pig model. Data were obtained suggesting that bestatin does n ot act on proteinases of P. gingivalis. Rather, bestatin was found to inhib it the intracellular uptake of radioactivity from C-14-labeled amino acids or heat-denatured type I collagen. This was not observed with a spontaneous mutant of P. gingivalis, whose growth was not affected by bestatin. In the second part of the study, bestatin was found to have no effect on epitheli al cell viability in culture at concentrations effective on P. gingivalis. In addition, bestatin did not show effects on epithelial cell migration or production of gelatinases. Conclusions: This study suggests that bestatin selectively inhibits growth of P. gingivalis by affecting the intracellular uptake of amino acids and p eptides, which serve as energy and nitrogen sources for this bacterial spec ies. Bestatin has no cytotoxicity and may represent a therapeutic molecule for local treatment of P. gingivalis-associated periodontitis.