SOD1 and rheumatoid arthritis: Excessive oxidative stress has been reported in RA patients and animal models and is accompanied by the overproduction of ROS and MDA and the downregulation of GSH-Px, CAT, and SOD [25, 26], suggesting that MDA is likely to be a critical factor of oxidative damage, while GSH-Px, CAT, and SOD are described as antioxidants.