However, decreased levels of Nrf2 and its stabilizer DJ1 (PARK7) in lung tissues of COPD patients have been observed, and multiple human studies have demonstrated that the NRF2–KEAP1–BACH1 equilibrium in lung and alveolar macrophages is lowered in the population of aged smokers and COPD patients. This evidence concerns the gene KEAP1 and chronic obstructive pulmonary disease.