Serum nitric oxide metabolites and disease activity in patients with systemic sclerosis

There is no surrogate marker in serum for defining disease activity in scleroderma (SSc). Nitric oxide (NO), which regulates vasodilation and possesses pro-inflammatory actions, has been implicated in the pathogenesis of SSc. We compared serum NO _x (total nitrate and nitrite) level in SSc patients to healthy controls and evaluated its correlation with detailed symptomatology and scoring systems for various organ involvement. Symptoms and physical findings that suggested disease activity in regard to various organs were documented. Lung function test, high-resolution computed tomographic (HRCT) scan of thorax and echocardiography were performed. Serum NO _x was measured by chemiluminescence. Serum NO _x levels in SSc (n = 43) were significantly higher (72.4 ± 47.8 μM) than age- and sex-matched controls (n = 41; 37.1 ± 13.5 μM; p < 0.001). Serum NO _x were not found to be associated with lung fibrosis defined by lung function parameters or inflammation and fibrosis scores on HRCT. Twenty-two patients were found to have elevated serum NO _x level defined as mean ± 2 SD of normal controls. Logistic regression analysis revealed that age (OR 1.12, p = 0.02) and elevated pulmonary arterial pressure (PAP) (n = 9; OR 145.3, p = 0.01) were predictive factors for elevated serum NO _x . Prednisolone use was associated with lower serum NO _x level (OR 0.06, p = 0.04). Elevated PAP of increasing severity was found to be associated with higher level of serum NO _x (p = 0.004 by trend). Serum NO _x in SSc patients were elevated compared to healthy controls. Serum NO _x level was determined by multiple factors including age, prednisolone use, and elevated PAP.