Cytokine degradation by biofilms of Porphyromonas gingivalis

The aim of this study was to determine whether biofilms of Porphyromonas gingivalis could proteolytically degrade the cytokines interleukin (IL)-1beta, IL-6, or IL-1 receptor antagonist (IL-1ra). Biofilms were grown on membrane filters on the surface of Wilkins-Chalgren blood agar. The biofilms were removed from the plates, and solutions containing 2.5 microg/ml of each cytokine were added. Following incubation for up to 4.0 h, supernatants from the biofilms were subjected to SDS-PAGE. The separated proteins were transferred by Western blotting to PVDF membranes and probed with peroxidase-conjugated antibodies recognizing both the intact cytokines and their degradation products. After 2 h, no intact IL-1beta, IL-6, or IL-1ra were detectable. Cytokine proteolysis also occurred in the presence of horse serum. These results demonstrate that biofilm-grown P. gingivalis can degrade both pro- and anti-inflammatory cytokines and so may be able to perturb cytokine networks in vivo by eliminating cytokines from the local environment.