Increased xanthine oxidase activity in idiopathic pulmonary arterial hypertension.

To the Editors: Oxidative stress may play a role in the pathogenesis of idiopathic pulmonary arterial hypertension (IPAH) 1–4. A major contributor to oxidative stress is the endothelium-bound enzyme xanthine oxidase (XO), which is involved in the generation of superoxide anions and peroxynitrite 5. These reactive oxygen species have been implicated in endothelial dysfunction and vascular damage 5. In vivo , XO is bound to the surface of endothelial cells by glycosaminoglycans and can be released into plasma …