Our model of experimental COPD showed that lung fibrosis was closely associated with reduced levels of many Nrf2-inducible antioxidant proteins (i.e., SOD, catalase, and GSH) in the lungs of CSE-treated animals, and whether this was due to the action of growth factors remains an interesting hypothesis to be examined in future studies. Here, SOD1 is linked to chronic obstructive pulmonary disease.