DNA Methylation of PTGIS Enhances Hepatic Stellate Cells Activation and Liver Fibrogenesis.

Xue-Yin Pan,Hai-Di Li,Hui-Min Huang,Hai-Xia Yu,Xiao-Ming Meng,Cheng Huang,Fang-Tian Bu,Xin Chen,Yang Yang,Jun Li,Qin Wang,Hong-Wu Meng

doi:10.3389/fphar.2018.00553

Abstract

The activation of hepatic stellate cells (HSCs) is a central event in the progression of liver fibrosis. Multiple studies proved that DNA methylation might accelerate HSCs activation. However, the specific pathogenesis of liver fibrosis remains not fully addressed. Our laboratory performed Genome methylation screening to find out the methylated gene in mice with liver fibrosis. The pilot experiments showed that the promoter of prostacyclin synthase (PTGIS) gene was hypermethylated in CCl4-induced liver fibrosis mouse model. Moreover, the down-regulated PTGIS expression can be restored by DNMTs-RNAi and 5-aza-2-deoxycytidine (5-azadC), an inhibitor of DNA methyltransferase (DNMTs). Methylation-specific PCR (MSP) showed that the methylation status of PTGIS in HSC-T6 cells cultures with TGF-β1 (10 ng/mL) was elevated compared with control group. Chromatin immunoprecipitation (ChIP) assay indicated that PTGIS methylation was mainly induced by DNMT1 and DNMT3b. We further investigated the function of PTGIS in liver fibrosis by Recombinant Hepatic-adeno-associated virus (rAAV8)-PTGIS overexpression. The data indicated that overexpression of PTGIS in mouse liver accompanied by elevated apoptosis-related proteins expression in primary HSCs. Conversely, PTGIS silencing mediated by RNAi enhanced the expression of α-SMA and COL1a1 in vitro. Those results illustrated that adding PTGIS expression inhibits the activation of HSCs and alleviates liver fibrosis. Therefore, our study unveils the role of PTGIS in HSCs activation, which may provide a possible explanation for CCl4-mediated liver fibrosis.

Highlights

Liver fibrosis, characterized with the progressively increased accumulation of extracellular matrix (ECM) compounds in liver, is a wound-healing response to various chronic hepatic injuries including virus infection, alcohol abuse and high-fat diet (Bataller and Brenner, 2005; Hernandez-Gea and Friedman, 2011; Trautwein et al, 2015)
These data indicated that liver fibrosis mice model were well established and prostacyclin synthase (PTGIS) expression was decreased in CCl4-induced mice model
Our experiment results suggested that DNA methylation of PTGIS plays a pivotal role in the progression of liver fibrosis and hepatic stellate cells (HSCs) activation

Summary

Introduction

Liver fibrosis, characterized with the progressively increased accumulation of ECM compounds in liver, is a wound-healing response to various chronic hepatic injuries including virus infection, alcohol abuse and high-fat diet (Bataller and Brenner, 2005; Hernandez-Gea and Friedman, 2011; Trautwein et al, 2015). PTGIS Alleviates Liver Fibrosis muscle actin (α-SMA)-positive myofibroblast-like cells (Rippe and Brenner, 2004; Mallat and Lotersztajn, 2013). The hepatic architecture will be disturbed by the prolonged and repeated accumulation of ECM proteins by which can form fibrotic scars and nodules, leading to hepatic dysfunction (Hernandez-Gea and Friedman, 2011; Trautwein et al, 2015). The mechanisms governing the role of the HSCs in fibrosis are still not fully defined

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