1. Academic Validation
  2. SIRT1 prevents cigarette smoking-induced lung fibroblasts activation by regulating mitochondrial oxidative stress and lipid metabolism

SIRT1 prevents cigarette smoking-induced lung fibroblasts activation by regulating mitochondrial oxidative stress and lipid metabolism

  • J Transl Med. 2022 May 14;20(1):222. doi: 10.1186/s12967-022-03408-5.
Yue Zhang  # 1 Ting Li  # 1 Miaoxia Pan  # 1 Wei Wang 1 Wenhui Huang 1 Yafei Yuan 1 Zhanzhan Xie 1 Yixin Chen 1 Jun Peng 1 Xu Li 2 3 Ying Meng 4
Affiliations

Affiliations

  • 1 Department of Respiratory and Critical Care Medicine, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong, China.
  • 2 Department of Emergency Medicine, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong, China. [email protected].
  • 3 Ministry of Education, Key Laboratory of Hainan Trauma and Disaster Rescue, College of Emergency and Trauma, Hainan Medical University, Haikou, China. [email protected].
  • 4 Department of Respiratory and Critical Care Medicine, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong, China. [email protected].
  • # Contributed equally.
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.

Keywords

Autophagy; Cigarette smoking; Lipid metabolism; Mitochondrial oxidative stress; SIRT1.

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