Rheumatoid arthritis (RA) is a systemic autoimmune disorder characterized by chronic and progressive inflammation and destruction of joint. Fibroblast-like synoviocytes (FLS) in the synovium exhibit a critical role in the initiation and progression of joint inflammation and damage in RA. Stable-activated RA FLS exert an anomalous ability for proliferation, migration, and invasion [1]. Increasing evidence indicates that directly targeting FLS might be a novel promising strategy for RA [2].

Conventional, biological and targeted synthetic disease-modifying antirheumatic drugs (DMARDs) have resulted in fine effect for patients with RA, however, these anti-rheumatic drugs are not effective in all patients, and may have potentially serious toxicity and high cost [3]. Therefore, it is necessary to seek the novel alternative therapeutic drugs for RA. The natural compounds purified from medicinal herbs have been considered the merits of wide sources, low toxicity, and reasonable prices [4]. Thus, exploiting novel herbal medicine-based antirheumatic agents may provide potential drugs for treatment of RA.

Coptisine is a natural bioactive small‐molecular compound purified from Coptis chinensis (CC), a well-known traditional Chinese herbal medicine which is usually used to treat some inflammatory disorders, such as acute enteritis and diarrhea [5]. Previous studies indicate that coptisine has therapeutic potential for cancer, inflammatory disorders, bacterial infection and cardiovascular diseases [6]. For instance, coptisine suppressed osteosarcoma cell proliferation, migration, invasion, and angiogenesis, and reduced in vivo tumor growth [7]. It has been reported that coptisine reduced productions of histamine, IL‐4 and TNF‐α in (DNP‐IgE/HSA) ‐stimulated rat RBL‐2H3 cells [8]. Coptisine also exerts the cardiovascular protection in NaS2O4‐induced H9C2 cardiomyocyte by suppressing autophagy and apoptosis markers [9]. Additionally, some studies reported that coptisine might be an appropriate candidate as a new anti‐infective agent [10], [11]. However, it is still unknown whether coptisine has a potential for treatment of RA.

In the present study, we evaluated the effect of coptisine on RA FLS functions and explored its underlying molecular mechanisms. Moreover, we evaluated in vivo effect of coptisine on improvement of the severity of arthritis in mice with collagen-induced arthritis (CIA).