Sildenafil inhibits the ROS production by xanthine oxidase

Xanthine oxidase (XO) catalyzes the hydroxylation of a wide variety of substrates, including purines, pirimidines, pterins d aldehydes, to acids1. At relatively high oxygen pressure, it generates reactive oxygen species (ROS) as superoxides and hydroxyl radicals. The XO, detected in endothelial and epithelial cell outer surface, has been involved in ischemia/reperfusion injury1,2. Furthermore, XO-ROS production has been implicated in chronic hearth failure, inflammatory diseases, LDL oxidation, atherosclerosis, hypertension, cancer, aging1. Allopurinol, a hypoxanthine analogue developed as xanthine oxidase inhibitor 30 years ago, and oxypurinol, its oxidation product, have proved to be effe…

Low levels of xanthine dehydrogenase and cellular retinol binding protein in tumor mammary epithelial cells are responsible of the retinoic acid deficit

The tumor breast cells MCF-7 can synthesize retinoic acid startinf from retinaldehyde

Estrogen Inhibits Retinoic Acid Biosynthesis In Tumor Breast Epithelial Cell Lines

Low levels of both xanthine dehydrogenase and cellular retinol binding protein are responsible of the retinoic acid deficiency in malignant human mammary epithelial cells (abstract)