CAT and chronic obstructive pulmonary disease: Oxidative/nitrosative stress caused by an imbalance between cellular production of reactive oxygen species/reactive nitrogen species and endogenous antioxidants such as stress response protein including HO-1 and classic antioxidant enzymes including superoxide dismutases, catalase, and glutathione peroxidase might play a major role in the progression of various lung diseases such as IPF, chronic obstructive pulmonary disease, and DAD18–22.