Author:
Zhang Yue,Li Ting,Pan Miaoxia,Wang Wei,Huang Wenhui,Yuan Yafei,Xie Zhanzhan,Chen Yixin,Peng Jun,Li Xu,Meng Ying
Abstract
Abstract
Background
Cigarette smoking (CS) is a strong risk factor for idiopathic pulmonary fibrosis (IPF). It can activate lung fibroblasts (LF) by inducing redox imbalance. We previously showed that clearing mitochondrial reactive oxygen species (mtROS) protects against CS-induced pulmonary fibrosis. However, the precise mechanisms of mtROS in LF need further investigation. Here we focused on mtROS to elucidate how it was regulated by CS in LF and how it contributed to LF activation.
Methods
We treated cells with 1% cigarette smoking extract (CSE) and examined mtROS level by MitoSOX™ indicator. And the effect of CSE on expression of SIRT1, SOD2, mitochondrial NOX4 (mtNOX4), fatty acid oxidation (FAO)-related protein PPARα and CPT1a and LF activation marker Collagen I and α-SMA were detected. Nile Red staining was performed to show cellular lipid content. Then, lipid droplets, autophagosome and lysosome were marked by Bodipy 493/503, LC3 and LAMP1, respectively. And lipophagy was evaluated by the colocalization of lipid droplets with LC3 and LAMP1. The role of autophagy on lipid metabolism and LF activation were explored. Additionally, the effect of mitochondria-targeted ROS scavenger mitoquinone and SIRT1 activator SRT1720 on mitochondrial oxidative stress, autophagy flux, lipid metabolism and LF activation were investigated in vitro and in vivo.
Results
We found that CS promoted mtROS production by increasing mtNOX4 and decreasing SOD2. Next, we proved mtROS inhibited the expression of PPARα and CPT1a. It also reduced lipophagy and upregulated cellular lipid content, suggesting lipid metabolism was disturbed by CS. In addition, we showed both insufficient FAO and lipophagy resulted from blocked autophagy flux caused by mtROS. Moreover, we uncovered decreased SIRT1 was responsible for mitochondrial redox imbalance. Furthermore, we proved that both SRT1720 and mitoquinone counteracted the effect of CS on NOX4, SOD2, PPARα and CPT1a in vivo.
Conclusions
We demonstrated that CS decreased SIRT1 to activate LF through dysregulating lipid metabolism, which was due to increased mtROS and impaired autophagy flux. These events may serve as therapeutic targets for IPF patients.
Funder
Key Laboratory of Emergency and Trauma (Hainan Medical University), Ministry of Education
National Natural Science Foundation of China
Natural Science Foundation of Guangdong Province
Youth Project of Dean's Fund of Nanfang Hospital of Southern Medical University
Publisher
Springer Science and Business Media LLC
Subject
General Biochemistry, Genetics and Molecular Biology,General Medicine
Cited by
17 articles.
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