Angiotensin-(1-7) Attenuated Cigarette Smoking-related Pulmonary Fibrosis via Improving the Impaired Autophagy Caused by Nicotinamide Adenine Dinucleotide Phosphate Reduced Oxidase 4-Dependent Reactive Oxygen Species

Cigarette smoking is acknowledged as the major risk factor of pulmonary fibrosis. Angiotensin (Ang) II has been reported to aggravate smoking-induced lung fibrosis, whereas the effect of Ang-(1-7) on smoking-related lung fibrosis remains unknown. The autophagy, being activated by reactive oxygen species (ROS), is identified as a novel mechanism of pulmonary fibrosis. However, whether autophagy is involved in regulation of smoking-induced lung fibrosis still needs investigation. Here, we aim to investigate the effect of Ang-(1-7) on smoking-related lung fibrosis by the regulation of autophagy and ROS. In vivo, Ang-(1-7) was constantly infused into passive smoking rats for 8 weeks. In vitro, primary lung fibroblasts were pretreated with antioxidant, nicotinamide adenine dinucleotide phosphate reduced oxidase (NOX) 4 siRNA, or light chain (LC) 3B siRNA before exposure to cigarette smoke extract (CSE). GFP-mCherry red fluorescent protein-LC3 advenovirus was introduced to evaluate the autophagic flux in cells. We found that Ang-(1-7) reduced hydrogen peroxide (H₂O₂) concentration, protein levels of NOX4, and autophagy impairment, as well as improving lung fibrosis induced by smoking stimulation in vivo. In vitro, CSE treatment elevated NOX4 protein expression and ROS production, resulting in the accumulation of impaired autophagosomes in fibroblasts. LC3B depletion enhanced CSE-induced collagen synthesis. Treatment with antioxidants or NOX4 siRNA inhibited CSE-induced insufficient autophagic flux and collagen production. In contrast, the action of Ang-(1-7) opposed the effects of CSE. In conclusion, Ang-(1-7) improves smoking-induced pulmonary fibrosis via attenuating the impaired autophagy caused by NOX4-dependent ROS in vivo and in vitro.