DJ-1 Modulates Nrf2-mediated Protection in Human Primary Alveolar Type II Cells in Smokers.

Abstract Cigarette smoke (CS) is a main source of oxidative stress and a key risk factor for emphysema, which consists of alveolar wall destruction. Alveolar type II (ATII) cells are in the gas exchange regions of the lung. We isolated primary ATII cells from de-identified organ donors whose lungs were not suitable for transplantation. We analyzed the cell injury obtained from non-smokers, moderate smokers and heavy smokers. DJ-1 protects cells from oxidative stress and induces Nrf2 expression, which activates the antioxidant defense system. In ATII cells isolated from moderate smokers, we found DJ-1 expression by RT-PCR, and nuclear Nrf2 and HO-1 translocation by western blotting and immunocytofluorescence. In ATII cells isolated from heavy smokers, we detected Nrf2 and HO-1 cytoplasmic localization. Moreover, we found high oxidative stress as detected by 4-HNE (immunoblotting), inflammation by IL-8 and IL-6 levels by ELISA and apoptosis by TUNEL assay in ATII cells obtained from heavy smokers. Furthermore, we detected early DJ-1 and late Nrf2 expression after ATII cell treatment with cigarette smoke extract. We also overexpressed DJ-1 by adenovirus construct and we found that this restored Nrf2 and HO-1 expression and induced nuclear translocation in heavy smokers. Moreover, DJ-1 overexpression also decreased ATII cell apoptosis caused by cigarette smoke extract in vitro. Our results indicate that DJ-1 activates the Nrf2-mediated antioxidant defense system. Furthermore, DJ-1 overexpression can restore the impaired Nrf2 pathway leading to ATII cell protection in heavy smokers. This suggests a potential therapeutic strategy for targeting DJ-1 in CS-related lung diseases.