Histone H3K9 demethylase JMJD1A modulates hepatic stellate cells activation and liver fibrosis by epigenetically regulating peroxisome proliferator-activated receptor gamma

摘要

As a central event in liver fibrogenesis, hepatic stellate cell (HSC) transdifferentiation involves loss of regulation by adipogenic transcription factors such as peroxisome proliferator-activated receptor gamma; (PPAR gamma), which is epigenetically silenced during HSC activation. We hypothesized that JMJD1A, an H3K9 demethylase involved in adipogenic metabolism, could regulate PPAR gamma. In human HSC cell line, rat primary HSCs, and carbontetrachloride-induced mouse liver fibrogenesis model, we down-regulated the expression of JMJD1A using small interfering or short hairpin RNAs, and overexpressed its wild-type and mutant. We analyzed the effects of JMJD1A manipulation on the histone di-methyl-H3K9 (H3k9me2) status of PPAR gamma gene and the expression of PPAR gamma and fibrosis markers using chromatin immunoprecipitation, real-time quantitative RT-PCR and Western blot, and also investigated the in vitro and in vivo consequences on liver fibrosis and necrosis by Masson or hematoxylin-eosin staining, respectively. JMJD1A knockdown in HSCs correlated with reinforced H3K9me2 in the PPAR gamma gene promoter, and its down-regulation in both mRNA and protein led to increased expression of fibrosis markers, which could be consistently rescued by JMJD1A overexpression. Jmjd1a knockdown in situ resulted in significantly increased expression of alpha-smooth muscle actin (P = 0.005) and Col1a (P = 0.036), strengthened production of collagens (P = 0.028), and remarkably enhanced necrosis (P = 0.007) 4 weeks after treatment. This study suggests JMJD1A as a novel epigenetic regulator that modulates HSC activation and liver fibrosis through targeting PPAR gamma gene expression.