Protective effect of autophagy on endoplasmic reticulum stress induced apoptosis of alveolar epithelial cells in rat models of COPD

Abstract

During the present study, we explored the protective effects of autophagy on endoplasmic reticulum (ER) stress (ERS) induced apoptosis belonging to alveolar epithelial cells (AECs) in rat models with chronic obstructive pulmonary disease (COPD). Fifty-six 12-week-old male Sprague–Dawley (SD) rats were randomly assigned into the COPD group (rats exposed to cigarette smoke (CS)), the 3-methyladenine (3-MA) intervention group (COPD rats were administrated with 10 mg/kg autophagy inhibitors), the chloroquine (CQ)-intervention group (COPD rats were administrated 40 mg/kg CQ), and the control group (rats breathed in normal saline). The forced expiratory volume in 0.3 s/forced vital capacity (FEV_0.3/FVC%), inspiratory resistance (RI), and dynamic lung compliance (Cdyn) were measured and recorded. The expressions of PKR-like ER kinase (PERK) and CCAAT/enhancer-binding protein-homologous protein (CHOP) were detected by immunohistochemistry. The cell apoptotic rates of AECs were analyzed by terminal deoxynucleotidyl transferase (TdT) mediated dUTP-biotin nick end-labeling (TUNEL) staining. The expression levels of light chain 3 (LC3-II), p62, Beclin-1, ATG5, ATG7, Caspase-12, and Caspase-3 were detected by Western blotting. Results showed that the COPD group exhibited a lower FEV_0.3/FVC% and Cdyn, and a higher RI than the control group. Compared with the control group, the integrated optical density (IOD) values of PERK and CHOP, the apoptotic rate of AECs, and expressions of LC3-II, Beclin-1, ATG5, ATG7, Caspase-3, and Caspase-12 expressions were significantly higher, whereas p62 expression was significantly lower in the COPD group. Based on the results obtained during the present study, it became clear that the inhibition of autophagy could attenuate the ERS-induced apoptosis of AECs in rats with COPD.