Inhibitory effects of curcumin against cytotoxicity of Porphyromonas gingivalis outer membrane vesicles

Objective: The purpose of this study was to examine whether curcumin, a turmeric root extract, protects human gingival epithelial (HGE) cells from the cytotoxic effects of Porphyromonas gingivalis outer membrane vesicles (OMVs). Design: OMVs were prepared fromP. gingivalis OMZ314 and used to stimulate human gingival epithelial (HGE) cells. The effects of curcumin on cellular expression of inflammatory cytokines were evaluated using real-time reverse transcription-polymerase chain reaction assays, while those on cellular migration were examined with a scratch wound assay. Furthermore, HGE cells were incubated with OMVs in the presence or absence of curcumin, then intracellular invasion by OMVs was observed with confocal laser scanning microscopy. Also, the effects of curcumin on cellular apoptotic death was examined. Results: Gene expressions of IL-6, IL-1 beta, and TNF-alpha in HGE cells stimulated with OMVs were significantly suppressed by curcumin in a dose-dependent manner, with suppressed protein production also noted. Moreover, curcumin inhibited the cytotoxic effects of OMVs on cellular migration. Finally, curcumin inhibited OMV adherence to and entry of cells, as well as cellular apoptotic death in a dose-dependent manner. Conclusions: Curcumin showed marked inhibitory effects against the cytotoxic actions of P. gingivalis OMVs, indicating possible potency for preventing periodontal disease.