Total glucosides of paeony inhibits Th1/Th17 cells via decreasing dendritic cells activation in rheumatoid arthritis

Total glucoside of paeony (TGP), an active compound extracted from paeony root, has been used in therapy for rheumatoid arthritis (RA). Th1 and Th17 cells are now believed to play crucial roles in the lesions of RA. However, the molecular mechanism of TGP in inhibition of Th1 and Th17 cells remains unclear. In this study, we found that TGP treatment significantly decreased percentage and number of Th1 and Th17 cells in collagen induced arthritis (CIA) mice. Consistently, treatment with TGP decreased expression of T-bet and RORγt as well as phosphorylation of STAT1 and STAT3. In particular, TGP treatment inhibited dendritic cells (DCs) maturation and reduced production of IL-12 and IL-6. Moreover, TGP-treatment RA patients showed shank population of matured DCs and IFN-γ-, IL-17-producing cells. Taken together, our results demonstrated that TGP inhibited maturation and activation of DCs, which led to impaired Th1 and Th17 differentiation in vivo.