Differential roles of Porphyromonas gingivalis lipopolysaccharide and Escherichia coli lipopolysaccharide in maturation and antigen-presenting functions of dentritic cells.

OBJECTIVE The aim of this research is to study the roles of Porphyromonas gingivalis-lipopolysaccharide (P. gingivalis-LPS) and Escherichia coli-lipopolysaccharide (E. coli-LPS) on maturation and antigen-presenting functions of dendritic cells (DCs), and to provide experimental evidences to explore the possible mechanism of DCs in periodontitis. MATERIALS AND METHODS Flow cytometry was used to detect CD11c, MHC-II, CD80, CD86 and CD40 expression on DCs which were stimulated by P. gingivalis-LPS or E. coli-LPS and ELISA was used to detect IL-12, IFN-γ, IL-10 and IL-13 secreted by DCs. CCK8 was used to assay CD4+T cells proliferation after co-cultured with DCs stimulated by P. gingivalis-LPS or E. coli-LPS and ELISA was used to detect IL-2, IFN-γ, IL-10 and IL-13 secreted by T cells. TLR4 inhibitor (polymyxin B) or TLR2 and TLR4 inhibitor (OxPAPC) was added to P. gingivalis-LPS group and E. coli-LPS group to observe the effects of these two TLR inhibitors on the maturation and antigen-presenting functions of DCs. RESULTS The capacity of P. gingivalis-LPS to stimulate DCs maturation was similar to that of E. coli-LPS. The amount of IL-12 and IFN-γ secreted by DCs in P. gingivalis-LPS group was significantly lower than that of E. coli-LPS group (p < 0.05), meanwhile, IL-10 and IL-13 secreted by DCs in P. gingivalis-LPS group was significantly higher than that of E. coli-LPS group (p < 0.05). DCs stimulated by both P. gingivalis-LPS and E. coli-LPS could promote the proliferation of CD4+T cells. The amount of IL-2 and IFN-γ secreted by T cells stimulated by DCs in P. gingivalis-LPS group was significantly lower than that of E. coli-LPS group (p < 0.05), meanwhile, IL-10 secreted by T cells stimulated by DCs in P. gingivalis-LPS group was significantly higher than that of E. coli-LPS group (p < 0.05). When TLR4 inhibitor was added to E. coli-LPS group, maturation and antigen-presenting functions of DCs were significantly inhibited. When TLR4 inhibitor was added to P. gingivalis-LPS group, maturation and antigen-presenting functions of DCs were not significantly inhibited. When TLR2 and TLR4 inhibitor was added to P. gingivalis-LPS group, maturation and antigen-presenting functions of DCs were significantly inhibited. CONCLUSIONS P. gingivalis-LPS could prime DCs maturation and antigen-presenting functions. DCs stimulated by P. gingivalis-LPS are prone to induce a stronger Th2 cell responses while DCs stimulated by E. coli-LPS are prone to induce a stronger Th1 cell responses. P. gingivalis-LPS triggers DCs through TLR2 pathway while E. coli-LPS triggers DCs through TLR4 pathway.