Elevated levels of nitrate in rheumatoid arthritis

Nitric oxide (NO) is a free radical that plays important roles in many physiological and pathological processes. Evidence suggests that NO participates in the pathogenesis of inflammatory reactions in many autoimmune and inflammatory diseases such as rheumatoid arthritis (RA). The purpose of this study was to evaluate serum concentrations of NO in patients with RA and to determine whether they correlate with clinical and laboratory parameters of RA disease activity. Twenty-seven RA patients were recruited for the study and compared with 20 healthy subjects. Serum NO concentrations were measured indirectly in terms of nitrate using colorimetric assay. Disease activity was determined by laboratory and clinical findings. Mean serum concentrations of nitrate were significantly higher than those of healthy controls (P < 0.05). Among the disease activity parameters, C-reactive protein, number of swollen and tender joints, Ritchie articular index, and disease activity scores correlated significantly with serum NO levels. Our results suggest that these levels can serve as a reliable parameter of disease activity in patients with RA. Further knowledge about the precise role of NO may lead to better understanding of the pathogenesis of RA. Furthermore, modulation of NO synthesis may represent a new approach to the treatment of inflammatory and autoimmune conditions.