Rebamipide attenuates autoimmune arthritis severity in SKG mice via regulation of B cell and antibody production

Oxidative stress is involved in the pathophysiology of rheumatoid arthritis (RA). We investigated the therapeutic potential of rebamipide, a gastroprotective agent with a property of reactive oxygen species scavenger, on the development of inflammatory polyarthritis and the pathophysiological mechanisms by which rebamipide might confer anti-arthritic effects in SKG mice, an animal model of RA. Intraperitoneal (i.p.) injection of rebamipide attenuated the severity of clinical and histological arthritis. Rebampide treatment reduced the number of T helper type 1 (Th1), Th2, Th17, inducible T cell co-stimulator (ICOS)⁺ follicular helper T (Tfh) transitional type (T2) and mature B cells in the spleen, but increased the number of regulatory T (T_reg), CD19⁺ CD1d^high CD5^high, CD19⁺ CD25^high forkhead box protein 3 (FoxP3)⁺ regulatory B (B_reg) cells, memory B cells, and transitional type 1 (T1) B cells. In addition, flow cytometric analysis revealed significantly decreased populations of FAS⁺GL-7⁺ germinal centre B cells and B220^- CD138⁺ plasma cells in the spleens of rebamipide-treated SKG mice compared to controls. Rebamipide decreased germinal centre B cells and reciprocally induced B_reg cells in a dose-dependent manner in vitro. Rebamipide-induced B_reg cells had more suppressive capacity in relation to T cell proliferation and also inhibited Th17 differentiation from murine CD4⁺ T cells. Together, these data show that i.p. administration of rebamipide suppresses arthritis severity by inducing B_reg and T_reg cells and suppressing Tfh and Th17 cells in a murine model of RA.