Porphyromonas gingivalis lipopolysaccharide promotes T- helper 17 cell differentiation from human CD4+ naive T cells via toll-like receptor-2 in vitro

Objectives: The persistence of T-helper 17 (Th17) cells has been shown to support chronic inflammation and mediate tissue destruction in periodontitis. However, little is known regarding the underlying mechanisms that regulate Th17 cell differentiation in the periodontal inflammatory context. The objective of this study was to explore the possible effect and mechanism of lipopolysaccharide (LPS) from Porphyromonas gingivalis on Th17 cell differentiation. Methods: Activated human CD4(+) CD45RA(+) naive T cells were stimulated with different doses of LPS from virulent and avirulent P. gingivalis strains combined with Th17 driven cytokines in vitro. Flow cytometry was used to analyze the differentiation ratio of Th17 cells. IL-17A protein expression and IL-17, retinoid-related orphan receptor C (RORC) and toll-like receptor 2 (TLR2) mRNA transcription were analysed by ELISA and real-time qPCR, respectively. The role of TLR2 in Th17 cell differentiation was further confirmed by TLR2 blocking assay. Results: LPS from P. gingivalis (Pg-LPS) up-regulated Th17 cell differentiation ratios, expression of IL-17 and RORC mRNA, and IL-17 concentration in culture supernatant, with 0.1 mu g/mL LPS from the virulent P. gingivalis strain being the most effectively. Furthermore, Pg-LPS also up-regulated expression of TLR2 on T cells during Th17 differentiation, and the differentiation was attenuated by treatment with TLR2 antibody. Conclusions: These results suggest that Pg-LPS promotes Th17 cell differentiation in vitro, and TLR2 signalling may be involved in this process. LPS from the virulent P. gingivalis strain up-regulated Th17 cell differentiation more effectively, which may be associated with the pathogenicity of different P. gingivalis strains.