The Role of Oxidative Stress in Hyperuricemia and Xanthine Oxidoreductase (XOR) Inhibitors

Figure 3

Uric acid and oxidative stress. XOR, which is a critical enzyme in the production of uric acid, can produce O₂^– and H₂O₂. Then, the reaction between O₂^– and NO reduces NO bioavailability, which is a main cause of endothelial dysfunction. Moreover, O₂^– can undergo the disproportionation reaction into H₂O₂ by superoxide dismutase (SOD), and O₂^– and H₂O₂ can also be converted to the more cytotoxic oxidants peroxynitrate (ONOO^–), hydroxyl anion (OH^–), and hypochlorous acid (HOCl), which are more harmful to cells. These high levels of ROS result in oxidative stress. On the other hand, several experimental and clinical studies support a role for uric acid as a contributory causal factor in multiple conditions, including oxidation and antioxidant effects. The critical point is that UA becomes a strong prooxidant in the intracellular environment and is associated with various factors, such as inflammation and endothelial dysfunction.