Department of Medical Pharmacology and Physiology, University of Missouri School of Medicine, Columbia, 65212, USA.
Alcohol Clin Exp Res. 2011 Dec;35(12):2128-38. doi: 10.1111/j.1530-0277.2011.01577.x. Epub 2011 Jul 25.
Binge drinking after chronic ethanol consumption is one of the important factors contributing to the progression of steatosis to steatohepatitis. The molecular mechanisms of this effect remain poorly understood. We have therefore examined in rats the effect of single and repeat ethanol binge superimposed on chronic ethanol intake on liver injury, activation of mitogen-activated protein kinases (MAPKs), and gene expression.
Rats were chronically treated with ethanol in liquid diet for 4 weeks followed by single ethanol binge (5 gm/kg body weight) or 3 similar repeated doses of ethanol. Serum alcohol and alanine amino transferase (ALT) levels were determined by enzymatic methods. Steatosis was assessed by histology and hepatic triglycerides. Activation of MAPK, 90S ribosomal kinase (RSK), and caspase 3 were evaluated by Western blot. Levels of mRNA for tumor necrosis factor alpha (TNFα), early growth response-1 (egr-1), and plasminogen activator inhibitor-1 (PAI-1) were measured by real-time qRT-PCR.
Chronic ethanol treatment resulted in mild steatosis and necrosis, whereas chronic ethanol followed by binge group exhibited marked steatosis and significant increase in necrosis. Chronic binge group also showed significant increase (compared with chronic ethanol alone) in the phosphorylation of extracellular regulated kinase 1 (ERK1), ERK2, and RSK. Phosphorylation of c-Jun N-terminal kinase (JNK) and p38 MAPK did not increase by the binge. Ethanol binge, after chronic ethanol intake, caused increase in mRNA for egr-1 and PAI-1, but not TNFα.
Chronic ethanol exposure increases the susceptibility of rat liver to increased injury by 1 or 3 repeat binge. Among other alterations, the activated levels of ERK1, and more so ERK2, were remarkably amplified by binge suggesting a role of these isotypes in the binge amplification of the injury. In contrast, p38 MAPK and JNK1/2 activities were not amplified. These binge-induced changes were also reflected in the increases in the RNA levels for egr-1 and PAI-1. This study offers chronic followed by repeat binge as a model for the study of progression of liver injury by ethanol and highlights the involvement of ERK1 and ERK2 isotypes in the amplification of liver injury by binge ethanol.
慢性乙醇摄入后 binge 饮酒是导致脂肪变性发展为脂肪性肝炎的重要因素之一。这种效应的分子机制仍知之甚少。因此，我们在大鼠中研究了单次和重复乙醇 binge 叠加慢性乙醇摄入对肝损伤、丝裂原活化蛋白激酶 (MAPK) 激活和基因表达的影响。
大鼠用液体饮食连续 4 周给予乙醇处理，然后给予单次乙醇 binge（5 gm/kg 体重）或 3 次类似的乙醇重复剂量。通过酶学法测定血清酒精和丙氨酸氨基转移酶 (ALT) 水平。通过组织学和肝甘油三酯评估脂肪变性。通过 Western blot 评估 MAPK、90S 核糖体激酶 (RSK) 和 caspase 3 的激活。通过实时 qRT-PCR 测量肿瘤坏死因子 α (TNFα)、早期生长反应-1 (egr-1) 和纤溶酶原激活物抑制剂-1 (PAI-1) 的 mRNA 水平。
慢性乙醇处理导致轻度脂肪变性和坏死，而慢性乙醇加 binge 组则表现出明显的脂肪变性和显著增加的坏死。慢性 binge 组的细胞外调节激酶 1 (ERK1)、ERK2 和 RSK 的磷酸化也显著增加（与单独慢性乙醇相比）。c-Jun N-末端激酶 (JNK) 和 p38 MAPK 的磷酸化没有增加。慢性乙醇摄入后 binge 会导致 egr-1 和 PAI-1 的 mRNA 增加，但 TNFα 没有增加。
慢性乙醇暴露会增加大鼠肝脏对 1 次或 3 次重复 binge 增加的损伤的易感性。在其他改变中，binge 显著放大了 ERK1，更重要的是 ERK2 的激活水平，表明这些同工型在 binge 放大损伤中起作用。相比之下，p38 MAPK 和 JNK1/2 的活性没有放大。这些 binge 诱导的变化也反映在 egr-1 和 PAI-1 的 RNA 水平增加上。本研究提供了慢性加重复 binge 的模型，用于研究乙醇引起的肝损伤进展，并强调了 ERK1 和 ERK2 同工型在 binge 乙醇引起的肝损伤放大中的作用。
