Reactive oxygen species induce Cox‐2 expression via TAK1 activation in synovial fibroblast cells

Oxidative stress within the arthritis joint has been indicated to be involved in generating mediators for tissue degeneration and inflammation. COX‐2 is a mediator in inflammatory action, pain and some catabolic reactions in inflamed tissues. Here, we demonstrated a direct relationship between oxidative stress and Cox‐2 expression in the bovine synovial fibroblasts. Furthermore, we elucidated a novel mechanism, in which oxidative stress induced phosphorylation of MAPKs and NF‐κB through TAK1 activation and resulted in increased Cox‐2 and prostaglandin E2 expression. Finally, we demonstrated that ROS‐induced Cox‐2 expression was inhibited by supplementation of an antioxidant such as N‐acetyl cysteamine and hyaluronic acidin vitro andin vivo. From these results, we conclude that oxidative stress is an important factor for generation of Cox‐2 in synovial fibroblasts and thus its neutralization may be an effective strategy in palliative therapy for chronic joint diseases