Dioscin, a Steroidal Saponin Isolated from Dioscorea nipponica, Attenuates Collagen-Induced Arthritis by Inhibiting Th17 Cell Response.

Dioscin, a steroidal saponin isolated from Dioscorea nipponica Makino, has previously been shown to possess antiarthritic effects. However, the underlying mechanism is still elusive. Herein, we investigated the therapeutic effects of dioscin on collagen-induced arthritis (CIA) in DBA/1 mice and related mechanism. Cytokine production in CII-specific immune responses were measured by enzyme-linked immunosorbent assay (ELISA); Th17 cell-related gene expression, including IL-17A, ROR γτ and IL-23p19, were detected by qPCR analysis; Surface marker, T regulatory (Treg) cells and intracellular cytokines (IL-17A and IFN- γ ) were evaluated by flow cytometry. We performed Th17 cell differentiation assay in vitro. Results showed that, in vivo, dioscin treatment significantly reduced the severity of CIA, which was accompanied by decreased Th17 response, but not Th1 and Treg response; dioscin-treated mice also showed lower percentage of CD11b + Gr-1 + neutrophils; In vitro, dioscin treatment suppressed the differentiation of naive CD4 + T cells into Th17 cell and decreased IL-17A production. Collectively, our results indicate that dioscin exerts antiarthritic effects by inhibiting Th17 cell immune response.