CP-25, a novel compound, protects against autoimmune arthritis by modulating immune mediators of inflammation and bone damage.

Paeoniflorin-6'-O-benzene sulfonate (code: CP-25), a novel ester derivative of paeoniflorin (Pae), was evaluated in rats with adjuvant-induced arthritis (AA) to study its potential anti-arthritic activity. AA rats were treated with CP-25 (25, 50, or 100 mg/kg) from days 17 to 29 after immunization. CP-25 effectively reduced clinical and histopathological scores compared with the AA groups. CP-25-treated rats exhibited decreases in pro-inflammatory cytokines (IL-1β, IL-6, IL-17 and TNF-α) coupled with an increase in the anti-inflammatory cytokine TGF-β1 in the serum. CP-25 treatment inhibited M1 macrophage activation and enhanced M2 macrophage activation by influencing cytokine production. Decreases in Th17-IL-17 and the Th17-associated transcription factor RAR-related orphan receptor gamma (ROR-γt) dramatically demonstrated the immunomodulatory effects of CP-25 on abnormal immune dysfunction. In addition, CP-25 suppressed the production of receptor activator of nuclear factor kappa B ligand (RANKL) and matrix metalloproteinase (MMP) 9, which supported its anti-osteoclastic effects. The data presented here demonstrated that CP-25 significantly inhibited the progression of rat AA by reducing inflammation, immunity and bone damage. The protective effects of CP-25 in AA highlight its potential as an ideal new anti-arthritic agent for human RA.