XDH and kidney failure: Interestingly, XO has been identified to never hide its identity involving in upregulating the oxidative stress in setting of heart failure, chronic kidney disease as well as in a variety of pathophysiological circumstances 8-12, 15-17, resulting in damage of myocardium, renal tubular cells/podocytes, kidney parenchyma, endothelial cells and mitochondria 13, ultimately causing renal failure and failing of myocardium through increased renal interstitial and myocardial fibrosis 9, 14, 15.