FASN regulates CSE-induced apoptosis, oxidative stress and mitochondrial damage in type 2 alveolar epithelial cells by regulating NRF2 expression and nuclear translocation

Smoking is a major etiological factor in numerous chronic lung diseases. However, the precise underlying mechanisms remain incompletely elucidated. In this study, we investigated the effects of cigarette smoke extract (CSE) on mitochondrial oxidative phosphorylation (OXPHOS), mitochondrial structure, and the antioxidant regulator Nuclear factor erythroid 2-related factor 2 (NRF2) in a rat lung epithelial-T-antigen negative cell line (RLE-6TN), focusing on the associated molecular pathways. CSE exposure significantly reduced cell viability, induced oxidative-antioxidant imbalance, and disrupted OXPHOS complex subunit expression and mitochondrial ultrastructure. Furthermore, an increased BCL2-Associated X (BAX) / B-cell lymphoma/leukemia 2 (BCL2) ratio activated the intrinsic apoptosis pathway. NRF2 knockdown exacerbated CSE-induced mitochondrial damage and apoptosis. Co-immunoprecipitation (co-IP) analysis revealed a direct interaction between NRF2 and Fatty Acid Synthase (FASN). CSE treatment significantly reduced NRF2-FASN binding. Notably, FASN knockout amplified oxidative stress, exacerbated damage to OXPHOS and mitochondrial structure, and diminished NRF2 expression and nuclear translocation. Collectively, our findings demonstrate that CSE exposure impairs NRF2 expression and nuclear translocation by disrupting FASN expression and its interaction with FASN. This impairment leads to mitochondrial OXPHOS dysfunction, structural damage, and ultimately apoptosis. Our findings identify FASN as a potential therapeutic target for mitigating smoking-associated lung injury.