Inhibition of EZH2 prevents acute respiratory distress syndrome (ARDS)-associated pulmonary fibrosis by regulating the macrophage polarization phenotype

Xiaowei Bao,Jianwen Bai,Na Liu,Xiandong Liu,Shougang Zhuang,Xiaohui Zhou,Lunxian Tang,Huijuan Ren,Qian Yang,Dongyang Zhao

doi:10.1186/s12931-021-01785-x

Abstract

BackgroundWe recently reported histone methyltransferase enhancer of zeste homolog 2 (EZH2) as a key epigenetic regulator that contributes to the dysfunction of innate immune responses to sepsis and subsequent lung injury by mediating the imbalance of macrophage polarization. However, the role of EZH2 in acute respiratory distress syndrome (ARDS)-associated fibrosis remains poorly understood.MethodsIn this study, we investigated the role and mechanisms of EZH2 in pulmonary fibrosis in a murine model of LPS-induced ARDS and in ex-vivo cultured alveolar macrophages (MH-S) and mouse lung epithelial cell line (MLE-12) by using 3-deazaneplanocin A (3-DZNeP) and EZH2 the small interfering (si) RNA.ResultsWe found that treatment with 3-DZNeP significantly ameliorated the LPS-induced direct lung injury and fibroproliferation by blocking EMT through TGF-β1/Smad signaling pathway and regulating shift of macrophage phenotypes. In the ex-vivo polarized alveolar macrophages cells, treatment with EZH2 siRNA or 3-DZNeP suppressed the M1 while promoted the M2 macrophage differentiation through modulating the STAT/SOCS signaling pathway and activating PPAR-γ. Moreover, we identified that blockade of EZH2 with 3-DZNeP suppressed the epithelial to mesenchymal transition (EMT) in co-cultured bronchoalveolar lavage fluid (BALF) and mouse lung epithelial cell line through down-regulation of TGF-β1, TGF-βR1, Smad2 while up-regulation of Smad7 expression.ConclusionsThese results indicate that EZH2 is involved in the pathological process of ARDS-associated pulmonary fibrosis. Targeting EZH2 may be a potential therapeutic strategy to prevent and treat pulmonary fibrosis post ARDS.

Highlights

We recently reported histone methyltransferase enhancer of zeste homolog 2 (EZH2) as a key epigenetic regulator that contributes to the dysfunction of innate immune responses to sepsis and subsequent lung injury by mediating the imbalance of macrophage polarization
We identified that p-STAT1 and SOCS3 were significantly inhibited while p-STAT6, SOCS1 and PPAR-γ were activated in the macrophages from bronchoalveolar lavage fluid (BALF) of 3-deazaneplanocin A (3-DZNeP) treatment acute lung injury (ALI) mice comparing with vehicle treat ALI mice (Fig. 2B, D, E)
We had previously reported that transferring of M2 macrophages to the recipient’s lung could reduce the expression of Transforming growth factor-β1 (TGF-β1) in the recipient’s lung [5], in this current study, we identified EZH2 inhibitor could modulate M2-like macrophage polarization in the BALF of acute respiratory distress syndrome (ARDS) mice, and further interact with epithelial cells and inhibit the epithelial to mesenchymal transition (EMT) through the regulation of TGF-β1/Smad signaling pathway

Summary

Introduction

We recently reported histone methyltransferase enhancer of zeste homolog 2 (EZH2) as a key epigenetic regulator that contributes to the dysfunction of innate immune responses to sepsis and subsequent lung injury by mediating the imbalance of macrophage polarization. Acute respiratory distress syndrome (ARDS) remains a major clinical challenge in critically ill patients which represents a stereotypic response to lung injury with transition from exudative inflammatory responses to a fibroproliferative phase [1]. 3-deazaneplanocin A (3-DZNeP) is an inhibitor of S-adenosylhomocysteine (SAH) hydrolase, which can inhibit the methylation level of H3K27 and the activity of EZH2 [16] It has been reported 3-DZNeP can effectively prevent tumor progression and fibrosis [15, 16]. It remains unknown whether EZH2 is involved in ARDS-associated pulmonary fibrosis

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Discussion

Conclusion