Regulation effect of koumine on T-helper cell polarization in rheumatoid arthritis

Koumine, an alkaloid, exerts therapeutic effects against rheumatoid arthritis (RA), and thus may have a potential application in novel treatment strategies against this disease. Herein, we investigated the regulatory effect of koumine on Th cell polarization using a "pyramid" structure model to elucidate the mechanism underlying its therapeutic effect on RA. The third layer of the model comprises the cytokine secretion layer, in which the effects of koumine on the balance of Th-related cytokines were investigated in mice with collagen-induced arthritis (CIA). Koumine showed significant therapeutic effects and reversed the imbalance of Th1/Th2 and Th17/Treg cytokines. In the Th cell polarization layer, the effects of koumine on the relative numbers of Th cell subsets in splenocytes of rats with CIA were examined. Koumine attenuated both of the increased Th1/Th2 and Th17/Treg subset ratios accompanied with its therapeutic effects. Finally, the primary cultured splenocytes from BALB/c mice were used to further investigate the effect of koumine on Th cell activation by evaluating cell proliferation induced by concanavalin A (Con A), lipopolysaccharides (LPS) and phytohemagglutinin (PHA). Koumine inhibited the cell proliferation responses and its effects on proliferation induced by Con A and PHA were greater than those by LPS, showing the relatively selective inhibition on the proliferation of Th cells. Our results suggest that koumine might restore the homeostasis of the network system with Th subsets and cytokines by inhibiting the activation of T cells, subsequently regulating the polarization of Th subsets and the downstream imbalance of pro/anti-inflammatory cytokines in RA.