Molecular Hepatology-Alcohol Dependent Diseases, II. Medical Clinic, Faculty of Medicine at Mannheim, University of Heidelberg, Theodor-Kutzer-Ufer 1-3, Mannheim, Germany.
J Hepatol. 2010 Mar;52(3):407-16. doi: 10.1016/j.jhep.2009.12.003. Epub 2010 Jan 6.
BACKGROUND & AIMS: Adverse alcohol effects in the liver involve oxidative metabolism, fat deposition and release of fibrogenic mediators, including TGF-beta. The work presents an assessment of liver damaging cross-talk between ethanol and TGF-beta in hepatocytes.
To investigate TGF-beta effects on hepatocytes, microarray analyses were performed and validated by qRT-PCR, Western blot analysis and immunohistochemistry. The cellular state was determined by assessing lactate dehydrogenase, cellular glutathione, reactive oxygen species, lipid peroxidation and neutral lipid deposition. RNA interference was used for gene silencing in vitro.
TGF-beta is induced in mouse livers after chronic ethanol insult, enhances ethanol induced oxidative stress and toxicity towards cultured hepatocytes plus induces lipid-, oxidative stress metabolism- and fibrogenesis-gene expression signatures. Interestingly, TGF-beta down-regulates alcohol metabolizing enzyme Adh1 mRNA in cultured hepatocytes and liver tissue from TGF-beta transgenic mice via the ALK5/Smad2/3 signalling branch, with Smad7 as a potent negative regulator. ADH1 deficiency is a determining factor for the increased lipid accumulation and Cyp2E1 dependent toxicity in liver cells upon alcohol challenge. Further, ADH1 expression was decreased during liver damage in an intragastric ethanol infusion mouse model.
In the presence of ethanol, TGF-beta displays pro-steatotic action in hepatocytes via decreasing ADH1 expression. Low ADH1 levels are correlated with enhanced hepatocyte damage upon chronic alcohol consumption by favoring secondary metabolic pathways.
肝脏中不良的酒精作用涉及氧化代谢、脂肪沉积和纤维生成介质（包括 TGF-β）的释放。本研究评估了乙醇和 TGF-β在肝细胞中的肝损伤串扰。
为了研究 TGF-β对肝细胞的影响，进行了微阵列分析，并通过 qRT-PCR、Western blot 分析和免疫组织化学进行了验证。通过评估乳酸脱氢酶、细胞谷胱甘肽、活性氧、脂质过氧化和中性脂质沉积来确定细胞状态。体外使用 RNA 干扰进行基因沉默。
慢性乙醇刺激后，TGF-β在小鼠肝脏中被诱导，增强了乙醇诱导的氧化应激和对培养的肝细胞的毒性，并诱导了脂质、氧化应激代谢和纤维化基因表达特征。有趣的是，TGF-β通过 ALK5/Smad2/3 信号通路下调培养的肝细胞和 TGF-β转基因小鼠肝组织中的酒精代谢酶 Adh1 mRNA，Smad7 作为一种有效的负调节剂。ADH1 缺乏是酒精挑战时肝细胞中脂质积累增加和 Cyp2E1 依赖性毒性的决定因素。此外，在胃内乙醇输注小鼠模型中，ADH1 表达在肝损伤过程中降低。
在乙醇存在的情况下，TGF-β通过降低 ADH1 表达在肝细胞中表现出促脂肪生成作用。低 ADH1 水平与慢性酒精摄入后增强的肝细胞损伤相关，通过促进次级代谢途径。
