Increasing levels of serum antioxidant status, total antioxidant power, in systemic sclerosis

Oxidative stress is one of the important factors that contribute to tissue damage in systemic sclerosis (SSc). Since the physiological response to oxidative stress is regulated by multiple antioxidant systems, it is important to measure quantitatively the total antioxidant capacity in the biological specimens. To determine the clinical significance of total antioxidant power (TAP) in SSc, we investigated the prevalence and clinical correlation of serum TAP levels in SSc patients. Serum TAP levels were examined in 49 patients with SSc by colorimetric microplate assay. The assay measures the total abilities for reducing Cu++ into Cu+. Clinical evaluation including medical history, physical examination, and laboratory tests were conducted for all SSc patients. Serum TAP levels were significantly elevated in SSc patients compared to normal controls (p < 0.01). When values higher than the mean + 2SD of the control serum samples were considered to be elevated, TAP levels were elevated in 24% of total SSc patients, with 26% of diffuse cutaneous SSc patients and 23% of limited cutaneous SSc patients. Serum TAP levels were correlated positively with C-reacting protein (r = 0.35, p ≤ 0.05). However, no other significant correlation was observed between serum TAP levels and clinical features in SSc patients. These results suggested that oxidative stress is enhanced in SSc patients, and serum TAP levels increase as an indicator of the global response to oxidative stress.