McVicker Benita L, Tuma Dean J, Kubik Jacy L, Tuma Pamela L, Casey Carol A
The Liver Study Unit, Department of Veterans Affairs Medical Center, 4101 Woolworth Avenue, Omaha, NE 68105, USA.
Alcohol Clin Exp Res. 2006 Nov;30(11):1906-15. doi: 10.1111/j.1530-0277.2006.00235.x.
It has been noted that alcohol-related liver diseases can be associated with an increase in apoptotic hepatocellular death. Moreover, the promotion of hepatocyte apoptosis may be linked to signals emanating from death receptors, particularly Fas [CD95/apoptosis-inducing protein 1 (APO-1)]. In the present study, we utilized an in vitro hepatic culture model [hybrid of human fibroblast (WI 38) and rat hepatoma (Fao) cells, WIF-B cells] to study potential contributing mechanisms involved in hepatocellular apoptosis following ethanol administration.
WIF-B cultures (differentiated hepatic cells that efficiently metabolize alcohol) were treated with or without ethanol and specific inhibitors of alcohol metabolism and cysteine protease activity, followed by morphological and biochemical examination of proapoptotic parameters.
The results of this work demonstrated that ethanol administration leads to an increase (45%-60%) in caspase-3 activity and that the induction of apoptosis was found to be linked to the metabolism of alcohol. Additionally, increases were observed in the activity of upstream initiator caspases (caspase-2 and caspase-8) that are directly related to membrane signaling events of death receptors such as Fas. Moreover, it was determined that the activation of caspase-3 could be blocked by the presence of a specific caspase-8 inhibitor, again linking death receptor-associated proteases to downstream effector caspase activity in alcohol-related death. Finally, ethanol administration was found to result in an increase in the amount of Fas protein present in the membrane fraction of the cell. The increase in membrane Fas protein indicates ligand-independent membrane targeting of Fas in the alcohol-treated cells that could potentially be a key signaling event in the induction of the proapoptotic caspase cascade.
The data presented here indicate that alcohol metabolism induces apoptosis in WIF-B cells that occurs, in part, by mechanisms involving signals emanating from death receptors.
已有研究指出，酒精性肝病可能与肝细胞凋亡增加有关。此外，肝细胞凋亡的促进可能与死亡受体发出的信号有关，尤其是Fas[CD95/凋亡诱导蛋白1(APO-1)]。在本研究中，我们利用体外肝脏培养模型[人成纤维细胞(WI 38)和大鼠肝癌(Fao)细胞的杂交体，WIF-B细胞]来研究乙醇给药后肝细胞凋亡的潜在促成机制。
用或不用乙醇以及酒精代谢和半胱氨酸蛋白酶活性的特异性抑制剂处理WIF-B培养物(能有效代谢酒精的分化肝细胞)，然后对促凋亡参数进行形态学和生化检查。
本研究结果表明，乙醇给药导致caspase-3活性增加(45%-60%)，且发现细胞凋亡的诱导与酒精代谢有关。此外，还观察到上游起始caspase( caspase-2和caspase-8)的活性增加，这些caspase与Fas等死亡受体的膜信号事件直接相关。此外，还确定caspase-3的激活可被特异性caspase-8抑制剂阻断，这再次将死亡受体相关蛋白酶与酒精相关死亡中的下游效应caspase活性联系起来。最后，发现乙醇给药导致细胞的膜部分中Fas蛋白的量增加。膜Fas蛋白的增加表明在酒精处理的细胞中Fas存在不依赖配体的膜靶向，这可能是诱导促凋亡caspase级联反应的关键信号事件。
此处呈现的数据表明，酒精代谢诱导WIF-B细胞凋亡，部分是通过涉及死亡受体发出信号的机制实现的。
