ROS are known as important mediators of ARDS (41–44), and enzymes related to the production of ROS (xanthine oxidase (XOR) (45), endothelial nitric oxide synthase (eNOS) (46), cytochrome P450 (CYP) (7), and NADPH oxidase (NOX) (47)) have been reported to be involved in ARDS. This evidence concerns the gene XDH and acute respiratory distress syndrome.