A20 suppresses inflammatory responses and bone destruction in human fibroblast‐like synoviocytes and in mice with collagen‐induced arthritis

Objective Nuclear factor‐κB (NF‐κB) has been implicated as a therapeutic target for the treatment of rheumatoid arthritis (RA). The purpose of this study was to determine whether A20, a universal inhibitor of NF‐κB, might have antiarthritic effects. Methods An adenovirus containing A20 complementary DNA (AdA20) was used to deliver A20 to human rheumatoid fibroblast‐like synoviocytes (FLS) in vitro as well as to mice with collagen‐induced arthritis (CIA) in vivo via intraarticular injection into the ankle joints bilaterally. Results In vitro experiments demonstrated that AdA20 suppressed NF‐κB activation, chemokine production, and matrix metalloproteinase secretion induced by tumor necrosis factor α in FLS. Mice with CIA that were treated with AdA20 had a lower cumulative disease incidence and severity of arthritis, based on hind paw thickness, radiologic and histopathologic findings, and inflammatory cytokine levels, than did control virus–injected mice. The protective effects of AdA20 were mediated by the inhibition of the NF‐κB signaling pathway. The severity of arthritis was also significantly decreased in the untreated front paws, indicating a beneficial systemic effect of local suppression of NF‐κB. Surprisingly, mice treated with AdA20 after the onset of CIA had significantly decreased arthritis severity from the onset of clinical signs to the end of the study. Conclusion These results suggest that using A20 to block the NF‐κB pathway in rheumatoid joints reduces both the inflammatory response and the tissue destruction. The development of an immunoregulatory strategy based on A20 may therefore have therapeutic potential in the treatment of RA.