Division of Gastroenterology, Hepatology, and Nutrition , Department of Medicine, University of Louisville School of Medicine, Louisville, Kentucky; University of Louisville Alcohol Research Center , Louisville, Kentucky.
Alcohol Clin Exp Res. 2013 Nov;37(11):1920-9. doi: 10.1111/acer.12172. Epub 2013 Jul 26.
Recently, we have demonstrated that acute alcohol exposure due to binge drinking leads to hepatic steatosis with the deregulation of hepatic histone deacetylase (HDAC) expression. Various class I, II, and IV HDACs were down-regulated, whereas expression of HDAC3 was solely up-regulated. Hence, in the present work, we specifically examined the mechanistic role of HDAC3 in the development of hepatic steatosis occurring in response to binge alcohol administration.
C57BL/6 mice were gavaged 3 times with ethanol (EtOH) at a dose of 4.5 g/kg. HDAC inhibitor, Trichostatin A (TSA) was simultaneously injected intraperitoneally at a dose of 1 mg/kg. Hepatic steatosis, injury, expression of HDAC3 and carnitine palmitoyltransferase 1α (CPT1α) were evaluated. HDAC3 and histone H3 acetylation levels at the Cpt1α promoter were analyzed by chromatin immunoprecipitation (ChIP).
The binge EtOH-mediated increase in HDAC3 was prevented by simultaneous administration of HDAC inhibitor, TSA, which markedly attenuated hepatic steatosis and injury. Importantly, HDAC3 inhibition was able to normalize the down-regulation of Cpt1α expression. Causal role of HDAC3 in the transcriptional repression of Cpt1α was demonstrated by increased HDAC3 binding at the thyroid receptor element site in the Cpt1α distal promoter region. Further, a resultant decrease in the transcriptionally permissive histone H3 lysine 9 acetylation in the proximal promoter region near the transcriptional start site was observed. Notably, TSA treatment reduced HDAC3 binding and increased H3K9 acetylation at Cpt1α promoter leading to increased Cpt1α expression. These molecular events resulted in attenuation of binge alcohol-induced hepatic steatosis.
These findings provide insights into potential epigenetic mechanisms underlying transcriptional regulation of Cpt1α in the hepatic steatosis occurring in response to binge EtOH administration.
最近，我们已经证明，由于 binge drinking 导致的急性酒精暴露会导致肝内 steatosis，同时还会导致肝组织中组蛋白去乙酰化酶（HDAC）表达失调。各种 I 类、II 类和 IV 类 HDAC 被下调，而 HDAC3 的表达则被单独上调。因此，在本工作中，我们特别研究了 HDAC3 在 binge 酒精给药后发生的肝 steatosis 发展中的机制作用。
C57BL/6 小鼠经口给予 4.5g/kg 的乙醇（EtOH）3 次。同时，腹腔内注射组蛋白去乙酰化酶抑制剂 Trichostatin A（TSA），剂量为 1mg/kg。评估肝 steatosis、损伤、HDAC3 和肉毒碱棕榈酰转移酶 1α（CPT1α）的表达。通过染色质免疫沉淀（ChIP）分析 Cpt1α 启动子处的 HDAC3 和组蛋白 H3 乙酰化水平。
同时给予 HDAC 抑制剂 TSA 可预防 binge EtOH 介导的 HDAC3 增加，从而显著减轻肝 steatosis 和损伤。重要的是，HDAC3 抑制能够使 Cpt1α 表达的下调正常化。通过增加 Cpt1α 远端启动子区域的甲状腺受体元件位点的 HDAC3 结合，证明了 HDAC3 在 Cpt1α 转录抑制中的因果作用。此外，在靠近转录起始位点的近端启动子区域观察到转录允许的组蛋白 H3 赖氨酸 9 乙酰化的减少。值得注意的是，TSA 处理减少了 Cpt1α 启动子处的 HDAC3 结合并增加了 H3K9 乙酰化，从而增加了 Cpt1α 的表达。这些分子事件导致 binge 酒精诱导的肝 steatosis 减弱。
这些发现为 binge EtOH 给药后发生的肝 steatosis 中 Cpt1α 的转录调控的潜在表观遗传机制提供了新的见解。
