Elevated Urinary 8-hydroxydeoxyguanosine, a Biomarker of Oxidative Stress, and Lack of Association with Antioxidant Vitamins in Chronic Obstructive Pulmonary Disease

Objective: The purpose of this study was to investigate whether patients with COPD are under oxidative stress and to elucidate the relationship between the level of oxidative stress and antioxidant vitamins.

Methodology: Nineteen male patients with COPD and 13 age- matched male control subjects were studied. Urinary 8-hydroxydeoxyguanosine (8-OHdG) concentrations were determined using an enzyme-linked immunosorbent assay kit and corrected for creatinine concentrations. Serum levels of vitamin C, alpha-tocopherol, and beta-carotene were determined by high performance liquid chromatography.

Results: The median (interquartile range) 8-OHdG excretion was 8.1 ng/mg (5.3-10.9 ng/mg) in control subjects and 12.2 ng/mg (9.8-15.5 ng/mg) in COPD patients (P < 0.01). Urinary 8-OHdG levels were significantly elevated in ex-smokers in the COPD group compared with ex-smokers in the control group. Urinary 8-OHdG level was negatively correlated with FVC (r = -0.42, P = 0.016), FEV1 (r = -0.49, P = 0.0048), and oxygen tension in arterial blood (r = -0.41, P = 0.0005). No significant differences in antioxidant levels were demonstrated between the two groups. There were no significant correlations between urinary 8-OHdG excretion and the serum concentrations of antioxidant vitamins.

Conclusion: The burden of oxidative stress was observed to increase in COPD patients as judged by urinary 8-OHdG. A depletion of antioxidant vitamins in serum was not essential for this phenomenon. Elevated urinary 8-OHdG level may not be attributable to smoking status or to antioxidant vitamins in COPD.