Is uric acid itself a player or a bystander in the pathophysiology of chronic heart failure?

Uric acid (UA) is the end product of purine metabolism in humans. Hyperuricemia is often found in patients with chronic heart failure (CHF). The increase of serum UA level is inversely associated with disease severity, cardiac function and prognosis of CHF. Some researchers found that UA had detrimental impact on the cardiovascular system, including mediating immune response upon cell injury, increasing endotoxin-stimulated tumor necrosis factor-alpha production and hence proinflammatory immune activation, increasing blood pressure, and so on. Other researchers found that UA had important antioxidant properties by scavenging various reactive oxygen species. So far, there is no evidence suggest that UA has detrimental effect on the pathophysiology of CHF. Xanthine oxidase (XO) is an enzyme that produces uric acid during purine metabolism. XO activity is up-regulated in failing heart, and serum UA levels reflect the degree of XO activation in CHF. XO plays an important role in the pathophysiology process of CHF, including myocyte apoptosis, endothelial dysfunction and cardiac mechanoenergetic uncoupling. The therapeutic effect of long-term XO inhibition has been confirmed in animal models and partly in human bodies. We hypothesize that UA itself is not a player but a bystander associated with the activation of XO in the pathophysiology of CHF.