14,15-Epoxyeicosatrienoic Acid Suppresses Cigarette Smoke Extract-Induced Apoptosis in Lung Epithelial Cells by Inhibiting Endoplasmic Reticulum Stress

Abstract

Background/Aims: Epoxyeicosatrienoic acids (EETs), a type of lipid mediators produced by cytochrome P450 epoxygenases, exert anti-inflammatory, angiogenic, anti-oxidative and anti-apoptotic effects. However, the role of EETs in cigarette smoke-induced lung injury and the underlying mechanisms are not fully known. The aim of this study was to explore the effects of CYP2J2-EETs on cigarette smoke extracts (CSE)-induced apoptosis in human bronchial epithelial cell line (Beas-2B) and the possible mechanisms involved. Methods: Cytochrome P450 epoxygenase 2J2 (CYP2J2) and its metabolites EETs were assessed by western blotting or LC-MS-MS. Cell viability and apoptosis were determined by MTT assay and AnnexinV-PI staining. Reactive oxygen species (ROS) were assessed by measuring H2DCFDA. Caspase-3, HO-1, MAPK and endoplasmic reticulum (ER) stress-related markers GRP78, p-elF2a, and CHOP were evaluated by western blotting. Results: CSE suppressed expression of both CYP2J2 and EET by Beas-2B cells. CSE also induced apoptosis, the generation of ROS and the ER stress in Beas-2B cells. These changes were abolished by pretreatment with exogenous 14,15-EET while pretreatment with 14,15-EEZE, a selective EET antagonist, abolished the protective effects of 14,15-EET. In addition, EETs increased the expression of antioxidant enzyme HO-1. Furthermore, 14,15-EET reduced CSE-induced activation of p38 and JNK. Conclusion: The data suggest that CYP2J2-derived EETs protect against CSE-induced lung injury possibly through attenuating ER stress.