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

Abstract

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 (HO) 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.

Inhibition of NADPH Oxidase 4 (NOX4) Signaling Attenuates Tuberculous Pleural Fibrosis

“…Several previous studies have evaluated the clinical relevance of autophagy in TB infection and the protective role of autophagy in bleomycin and cigarette-related lung fibrosis [34,37,38,39]. The protective effects of Ang (1–7) against bleomycin and cigarette-related lung fibrosis through inhibition NOX4-derived ROS is consistent with our finding that losartan and TAK-242 improved autophagy caused by NOX-ROS signaling in TB [34,39]. However, exploring the possible mechanism of NOX4 in autophagy inhibition in tuberculous pleurisy is still needed to identify the potential therapeutic target.…”

Self-eating: friend or foe? The emerging role of autophagy in fibrotic diseases

“…In contrast to the promotive effects of Ang II on fibrosis, Ang-(1-7) attenuated smoking-induced lung fibrosis by activating autophagy flux and reducing NOX4-dependent ROS production in the passive smoking rat model and cigarette smoke extract-treated fibroblasts. These protective effects of Ang-(1-7) were abolished by autophagy inhibitors, 3-MA and bafilomycin A1 117 . Toll-like receptor 4 (TLR4) is a critical player in the regulation of innate immunity.…”

Activation of angiotensin II type-2 receptor protects against cigarette smoke-induced COPD

“…Recent study showed that Ang-(1–7) is a poor G protein activator but it may act via Mas receptors in a yet unknown effector pathway to mediate anti-inflammatory and anti-fibrotic actions [ 44 ]. Ang-(1–7) treatment has been shown to attenuate CS-induced lung inflammation, fibrosis and oxidative damage in COPD moues models [ 19 , 20 ]. In addition, Mas receptors can act by forming heterodimers with AT1R to disrupt AT1R signaling responses [ 45 , 46 ].…”

“…Population-based clinical studies have revealed that the use of AT1R blockers was associated with slower progression of percent emphysema in general population, especially in former smokers [ 15 ], and with lower risk of pneumonia and lower mortality in COPD patients [ 16 , 17 ]. On the other hand, Ang-(1–7), by activating Mas receptors, exhibited anti-inflammatory, anti-oxidative and anti-fibrotic actions, restored autophagic functions, and improved locomotor activity in mouse models of COPD [ [18] , [19] , [20] ]. The role of AT2R in COPD is unknown.…”