Objective: Cysteine proteinases Arg- and Lys-gingipains of Porphyromonas gingivalis are thought to be involved in tissue destruction and perturbation of host defense mechanisms. In the present study, we propose that gingipains can act on syndecan-1, a cell surface proteoglycan found on gingival epithelial cells and involved in cell-cell and cell-matrix adhesion as well as in growth factor binding. Method: Human gingival epithelial cells were incubated with culture supernatants of P. gingivalis ATCC 33277 and gingipain deficient mutants. Levels of syndecan-1 released in the culture medium were assessed by an ELISA assay. Results: The amount of syndecan-1 released in the culture medium increased following stimulation of epithelial cells with the culture supernatant of the wild type strain. On the other hand, heat-inactivated supernatant of strain ATCC 33277 or supernatant from the Arg- and Lys-gingipain deficient mutant (KDP128) had few effect. Gene inactivation of only Arg-gingipains A and B resulted in a decreased amount of released syndecan-1. Immunofluorescence analysis confirmed the high expression of syndecan-1 on gingival epithelial cells and the attenuation of the immunostaining when cells were exposed to the supernatant of the wild-type strain of P. gingivalis. Conclusion: These results suggest that gingipains of P. gingivalis may contribute directly or indirectly to the cleavage and/or shedding of syndecan-1 from the epithelium cell surface. This phenomenon may be important in invasion of periodontal connective tissues and in modulation of host defenses since syndecan-1 shedding was recently reported to enhance microbial virulence. This study was supported by the Canadian Institutes of Health Research.

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