Serum copper/zinc superoxide dismutase levels in patients with rheumatoid arthritis

Rheumatoid arthritis is characterized by a chronic hypertrophic synovitis leading to destruction of connective tissue and functional damage of cartilage and bone structures. Reactive oxygen species play an important role in tissue injury in this disease. To clarify the role of the cellular antioxidant system in the protection against oxygen free radicals, we examined the levels of copper/zinc superoxide dismutase in the sera of patients with rheumatoid arthritis. We used an enzyme-linked immunosorbent assay which determines the concentration of copper/zinc superoxide dismutase independently from its enzymatic activity. We found that patients with rheumatoid arthritis have higher serum copper/zinc superoxide dismutase levels than control subjects. Copper/zinc superoxide dismutase also correlated positively with serum levels of both neopterin and rheumatoid factor, sensitive markers for disease activity in rheumatoid arthritis. These results support the hypothesis that the increased amount of copper/zinc superoxide dismutase is probably inadequate to exert an effective antioxidant protection but can result in a pro-inflammatory, pathogenic effect enhancing tissue damage. Furthermore, copper/zinc superoxide dismutase might be used as a marker of inflammatory activity in rheumatoid arthritis.