The CO-releasing molecule CORM-2 is a novel regulator of the inflammatory process in osteoarthritic chondrocytes

OBJECTIVES: Previous work has shown that the CO-releasing molecule CORM-2 protects against cartilage degradation. The aim of this study was to examine whether CORM-2 can control the production of inflammatory mediators in osteoarthritic chondrocytes and determine the mechanisms involved. METHODS: Primary cultures of chondrocytes from OA patients were stimulated with IL-1beta. The production of reactive oxygen species, nitrite, PGE(2), TNF-alpha and IL-1 receptor antagonist (IL-1Ra) were measured in the presence or absence of CORM-2. The expression of nitric oxide synthase-2 (NOS-2), cyclo-oxygenase-2 (COX-2) and microsomal PG E synthase-1 (mPGES-1) was followed by western blot and real-time PCR. Activation of nuclear factor-kappaB (NF-kappaB) and hypoxia inducible factor-1alpha (HIF-1alpha), and phosphorylation of NF-kappaB inhibitory protein alpha (IkappaBalpha) were determined by ELISA. RESULTS: CORM-2 decreased the production of oxidative stress, nitrite and PGE(2). In addition, CORM-2 inhibited IL-1beta-induced TNF-alpha but enhanced IL-1Ra production. Treatment of chondrocytes with CORM-2 strongly down-regulated NOS-2 and mPGES-1 protein expression, whereas COX-2 was reduced to a lesser extent. These changes were accompanied by a significant decrease in mRNA expression for NOS-2 and mPGES-1. CORM-2 showed a concentration-dependent inhibition of DNA-binding activity for p65 NF-kappaB and HIF-1alpha. IkappaBalpha phosphorylation was also reduced by CORM-2 treatment. CONCLUSIONS: These data have opened new mechanisms of action for CORM-2, raising the prospect that CO-releasing molecules are an interesting strategy for the development of new treatments in articular conditions.