Xanthine oxidase is involved in exercise-induced oxidative stress in chronic obstructive pulmonary disease

In the present study, we hypothesized that exhaustive exercise in patients with chronic obstructive pulmonary disease (COPD) results in glutathione ox idation and lipid peroxidation and that xanthine oxidase (XO) contributes t o free radical generation during exercise. COPD patients performed incremen tal cycle ergometry until exhaustion with (n = 8) or without (n = 8) prior treatment with allopurinol, an XO inhibitor. Reduced (GSH) and oxidized glu tathione (GSSG)) and lipid peroxides [malondialdehyde (MDA)I were measured in arterial blood. In nontreated COPD patients, maximal exercise (similar t o 75 W) resulted in a significant increase in the GSSG-to-GSH ratio (4.6 +/ - 0.9% at rest vs. 9.3 +/- 1.7% after exercise). In nontreated patients, MD A increased from 0.68 +/- 0.08 nmol/ml at rest up to 1.32 +/- 0.13 nmol/ml 60 min after cessation of exercise. In contrast, in patients treated with a llopurinol, GSSG-to-GSH ratio did not increase in response to exercise (5.0 +/- 1.2% preexercise vs. 4.6 +/- 1.1% after exercise). Plasma lipid peroxi de formation was also inhibited by allopurinol pretreatment (0.72 +/- 0.15 nmol/ml preexercise vs. 0.64 +/- 0.09 nmol/ml 60 min after exercise). We co nclude that strenuous exercise in COPD patients results in blood glutathion e oxidation and lipid peroxidation. This can be inhibited by treatment with allopurinol, indicating that XO is an important source for free radical ge neration during exercise in COPD.