SOD2 and chronic obstructive pulmonary disease: For instance, Hwang et al. found that the levels of FoxO3, a member of the Forkhead box class O (FoxO) regulating the expression of MnSOD, Cat, and other antioxidants in response to oxidative stress, were significantly decreased in lungs of smokers and COPD patients, as well as in lungs of mice exposed to CS.