Early-immediate gene Egr1 is associated with TGFβ1 regulation of epigenetic reader Bromodomain-containing protein 4 via the canonical Smad3 signaling in hepatic stellate cells in vitro and in vivo
Early-immediate gene Egr1 is associated with TGFβ1 regulation of epigenetic reader Bromodomain-containing protein 4 via the canonical Smad3 signaling in hepatic stellate cells in vitro and in vivo
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早期直接基因 Egr1 通过体外和体内肝星状细胞中的规范 Smad3 信号传导与表观遗传阅读器含 Bromodomain 蛋白 4 的 TGFβ1 调节相关
DOI：
10.1096/fj.202201263r
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发表时间：
2022
期刊：
影响因子：
4.8
通讯作者：
Yajun Zhou
中科院分区：
文献类型：
--
作者：
Haimeng Tian;Feifan Xu;Feifei Zhao;Nachuan Pan;Sidan Lu;Xin Jia;Yajun Zhou
当肝脏慢性损伤时，多种细胞因子刺激肝星状细胞(HSCs)，导致基因表达谱改变，从而导致HSC激活，这是肝纤维化形成的关键步骤。活化的HSCs是导致肝纤维化的主要因素。溴结构域包含蛋白4(BRD4)是一种重要的表观遗传学读物，它集中在数百个与多种促纤维化途径相关的基因的增强子上，从而指导HSC的激活和纤维化反应。本研究旨在检测转化生长因子-β1(TGFBRD1)对肝干细胞β4表达的影响，并探讨其在体内和体外的作用机制。实验采用异源转化生长因子β1基因敲除小鼠(转化生长因子β1+/−)、体内基因敲除和硫代乙酰胺诱导的肝损伤模型。结果表明，转化生长因子β1可促进HSC中BRD4的表达，这一作用至少是通过Smad3信号通路和早期生长反应基因Egr1来实现的。转化生长因子β-1诱导的Smad3信号转导途径增加了Egr1的表达，并促进了Egr1与BRD4启动子在-111bp附近的结合，促进了BRD4的表达。在TAA诱导的小鼠肝损伤模型中，Egr1基因敲除降低了HSC中BRD4的表达，减轻了肝纤维化。双重荧光染色显示在人肝纤维化区域活化的HSC中BRD4的表达显著增加，与p-Smad3和Egr1的上调平行。这项研究提示了主要的促纤维化细胞因子转化生长因子β1在肝星状细胞激活和肝纤维化形成中的作用的新的分子事件。
Upon chronic damage of the liver, multiple cytokines stimulate hepatic stellate cells (HSCs), causing the alterations of gene expression profiles and thus leading to HSC activation, a key step in liver fibrogenesis. Activated HSCs is the dominant contributors to liver fibrosis. Bromodomain containing protein 4 (BrD4), an important epigenetic reader, was demonstrated to concentrate at hundreds of enhancers associated with genes involved in multiple profibrotic pathways, thereby directing HSC activation and the fibrotic responses. The present studies were designed to examin the effect of transforming growth factor beta-1 (TGFβ1), the most potent pro-fibrotic cytokine, on BrD4 expression in HSCs and, if so, elucidated the underlying mechanisms in vitro and in vivo. The experiments employed the heterogeneous TGFβ1 knockout (TGFβ1+/−) mice, gene knockdown in vivo, and a model of thioacetamide (TAA)-induced liver injury. The results revealed that TGFβ1 enhanced BrD4 expression in HSCs, which was mediated, at least, by Smad3 signaling and early-immediate gene Egr1 (early growth response-1). TGFβ1-induced Smad3 signaling increased Egr1 expression and promoted Egr1 binding to BrD4 promoter at a site around –111 bp, promoting BrD4 expression. Egr1 knockdown reduced BrD4 expression in HSCs in mouse model of TAA-induced liver injury and lessened liver fibrosis. Double fluorescence staining demonstrated a strong increase in BrD4 expression in activated HSCs in fibrotic areas of human livers, paralleling the up-regulation of p-Smad3 and Egr1. This research suggested novel molecular events underlying the roles of the master pro-fibrotic cytokine TGFβ1 in HSC activation and liver fibrogenesis.