Singh Ashok K, Jiang Yin, Gupta Shveta
Department of Veterinary Population Medicine, College of Veterinary Medicine, University of Minnesota, 1333 Gortner Avenue, St Paul, Minnesota 55108, USA.
Alcohol. 2007 Dec;41(8):591-606. doi: 10.1016/j.alcohol.2007.08.003. Epub 2007 Nov 5.
Although alcohol drinking increases susceptibility to human immunodeficiency virus (HIV) infection, possible mechanisms underlying the effects of alcohol are not yet known. Since the HIV envelope protein gp120 plays a key role in progression of HIV infection, the aim of the present study was to evaluate the toxicity and degradation of gp120 in hepatocytes isolated from liver of alcohol-preferring rats drinking either 15% ethanol in water or pure water for 70 days. The hypothesis was that alcohol drinking augmented the toxicity, but suppressed degradation of gp120. Hepatocytes from water-drinking rats (C-cells) or ethanol-drinking rats (Et-cells) were treated with laptacystin, anti-CD4 antibodies, CCR5 antagonist, or mannose, followed by [(125)I]gp120 or native gp120. At predetermined intervals, control (C) and ethanol exposed (Et) cells were analyzed for toxicity and degradation of gp120. In C-cells, [(125)I]gp120 binding and internalization peaked within 5-45 min and remained elevated for up to 10h and then decreased gradually. In Et-cells, [(125)I]gp120 binding peaked comparably to C-cells, but the binding remained to the peak level throughout the experimental period. C-cells exhibited the lysosomal/ubiquitin-mediated degradation of intracellular gp120, resulting in released gp120 fragments into the incubation medium that suppressed gp120-CD4 binding, improved cell viability, and inhibited gp120-induced apoptosis. Ethanol drinking suppressed gp120 degradation in and release of gp120 fragments from hepatocytes. The incubation medium of Et-cells did not suppress gp120-CD4 binding or the gp120-mediated apoptosis in hepatocytes. Thus, chronic alcohol drinking augmented the adverse effects of gp120 possibly by suppressing its degradation in hepatocytes. The present observation also suggests that a number of CCR5 or ubiquitin-based therapeutic drugs may not be effective in suppressing HIV infection in alcohol-drinking subjects.
尽管饮酒会增加人类免疫缺陷病毒（HIV）感染的易感性，但酒精作用的潜在机制尚不清楚。由于HIV包膜蛋白gp120在HIV感染进程中起关键作用，本研究旨在评估从饮用含15%乙醇的水或纯水70天的嗜酒大鼠肝脏中分离出的肝细胞中gp120的毒性和降解情况。假设是饮酒会增强gp120的毒性，但抑制其降解。用乳胞素、抗CD4抗体、CCR5拮抗剂或甘露糖处理饮水大鼠（C细胞）或饮酒大鼠（Et细胞）的肝细胞，然后加入[¹²⁵I]gp120或天然gp120。在预定的时间间隔，分析对照（C）和乙醇处理（Et）细胞中gp120的毒性和降解情况。在C细胞中，[¹²⁵I]gp120的结合和内化在5 - 45分钟内达到峰值，并在长达10小时内保持升高，然后逐渐下降。在Et细胞中，[¹²⁵I]gp120的结合峰值与C细胞相当，但在整个实验期间结合一直保持在峰值水平。C细胞表现出溶酶体/泛素介导的细胞内gp120降解，导致gp120片段释放到孵育培养基中，从而抑制gp120 - CD4结合、提高细胞活力并抑制gp120诱导的细胞凋亡。饮酒抑制了肝细胞中gp120的降解及其片段的释放。Et细胞的孵育培养基不能抑制肝细胞中gp120 - CD4结合或gp120介导的细胞凋亡。因此，长期饮酒可能通过抑制肝细胞中gp120的降解来增强其不良反应。本观察结果还表明，一些基于CCR5或泛素的治疗药物可能对抑制饮酒者的HIV感染无效。
