Correlation of serum measures of nitric oxide production with lupus disease activity

Objective, To determine whether serum measures of nitric oxide production c orrelate with disease activity in patients with systemic lupus erythematosu s (SLE). Methods. We assayed the levels of serum nitrate/nitrite from 26 patients wi th SLE followed for 1-3 years and nitrotyrosine levels in sera from 28 addi tional patients with SLE; sera from 19 controls were tested in both assays. Lupus disease activity was determined via the physician's global assessmen t, the Lupus activity Index, and the SLE Disease Activity Index (SLEDAI) at the time of serum collection for the initial set of 26 patients, Statistic al correlations were determined using the Wilcoxon rank sum method and one- way ANOVA testing. Results. Serum levels of nitrate/nitrite were significantly higher in 26 pa tients with SLE compared to 19 controls (SLE, mean 29.5 mu M/ml. range 1-43 8; controls, mean 9.6 mu M/ml. range 0-51; p = 0.0004). Overall, there was a significant correlation between serum nitrate/nitrite: levels and SLEDAI scores (p = 0.0065). Renal variables within the SLEDAI had the highest corr elation with serum nitrate/nitrite (p = 0.0028). Serum nitrotyrosine levels were also significantly higher in patients with SLE versus controls (p = 0 .007) and in active SLE versus those with inactive SLE (p = 0.008). Conclusion. Serum nitrate/nitrite levels correlated with SLE disease activi ty, especially nephritis, in the majority of patients studied. Serum nitrot yrosine levels also differentiated controls from patients with lupus and pa tients with active from those with inactive disease. Due to the ease and lo w cost of these assays, serum measures of nitric oxide production appear a potentially useful adjunctive laboratory measure of disease activity in SLE and further implicate nitric oxide as an important mediator of disease in SLE.