The role of nitric oxide in articular cartilage breakdown in osteoarthritis.

It is increasingly appreciated that mediators typically associated with inflammatory arthritis, such as catabolic cytokines and nitric oxide, are produced by synovium and cartilage in osteoarthritis. The role that such mediators play in the progression of cartilage degradation in osteoarthritis is under intensive investigation. Nitric oxide is a highly reactive, cytotoxic free radical that has been implicated in tissue injury in a variety of diseases. Cartilage obtained from patients with osteoarthritis produces significant amounts of nitric oxide ex vivo, even in the absence of added stimuli such as interleukin-1 or lipopolysaccharide. In vitro, nitric oxide exerts detrimental effects on chondrocyte functions, including the inhibition of collagen and proteoglycan synthesis, enhanced apoptosis, and an inhibition of B1 integrin-dependent adhesion to the extra-cellular matrix. This paper reviews recent observations regarding the role of nitric oxide in osteoarthritis and presents evidence suggesting that the inhibition of nitric oxide production could be a desirable future therapeutic strategy.