Role of nitric oxide in the activation of NF-κB, AP-1 and NOSII expression in articular chondrocytes

Objective and design: Determine the sources of nitric oxide (NO) and evaluate its role in the activation of nuclear Factor-kappaB (NF-kappaB) and activator protein-1 (AP-1) and in the expression of NO synthase II (NOS II), induced by interleukin-1beta (IL-1). Material or subjects: Primary cultures of bovine articular chondrocytes. Treatment: The cells were treated with IL-1, 5 ng/ml with or without the NO donor S-nitroso-N-acetylpenicillamine (SNAP), in concentrations ranging from 10 to 3 00 muM. Methods: NF-kappaB and AP-1 activation were evaluated by electrophoretic mobility shift assay. Northern blot was used to detect NOS II mRNA levels and western blot to evaluate IkappaB-alpha, NOS I and NOS II protein levels. Results: Under basal conditions, chondrocytes expressed NOS 1, which was lost upon IL-1 treatment. SNAP inhibited IL-1-induced NF-kappaB activation and NOS II expression. When added alone, SNAP induced AP-1 activation to approximately the same extent as IL-1. Conclusions: These results suggest that, in chondrocytes, NO is a key regulator of the signaling pathways leading from IL-1 to NF-kappaB and AP-1 activation and to the expression of genes that are involved in the pathophysiology of arthritic diseases.