Boll M, Weber L W, Becker E, Stampfl A
Institute of Toxicology, GSF-National Research Center for Environment and Health, München, Neuherberg, Germany.
Z Naturforsch C J Biosci. 2001 Jul-Aug;56(7-8):649-59. doi: 10.1515/znc-2001-7-826.
CCl4-induced liver damage was modeled in monolayer cultures of rat primary hepatocytes with a focus on involvement of covalent binding of CCl4 metabolites to cell components and/or peroxidative damage as the cause of injury. (1) Covalent binding of 14C-labeled metabolites was detected in hepatocytes immediately after exposure to CCl4. (2) Low oxygen partial pressure increased the reductive metabolism of CCl4 and thus covalent binding. (3) [14C]-CCl4 was bound to lipids and to proteins throughout subcellular fractions. Binding occurred preferentially to triacylglycerols and phospholipids, with phosphatidylcholine containing the highest amount of label. (4) The lipid peroxidation potency of CCl4 revealed subtle differences compared to other peroxidative substances, viz., ADP-Fe3+ and cumol hydroperoxide, respectively. (5) CCl4, but not the other peroxidative substances, decreased the rate of triacylglycerol secretion as very low density lipoproteins. (6) The anti-oxidant vitamin E (alpha-tocopherol) blocked lipid peroxidation, but not covalent binding, and secretion of lipoproteins remained inhibited. (7) The radical scavenger piperonyl butoxide prevented CCl4-induced lipid peroxidation as well as covalent binding of CCl4 metabolites to cell components, and also restored lipoprotein metabolism. The results confirm that covalent binding of the CCl3* radical to cell components initiates the inhibition of lipoprotein secretion and thus steatosis, whereas reaction with oxygen, to form CCl3-OO*, initiates lipid peroxidation. The two processes are independent of each other, and the extent to which either process occurs depends on partial oxygen pressure. The former process may result in adduct formation and, ultimately, cancer initiation, whereas the latter results in loss of calcium homeostasis and, ultimately, apoptosis and cell death.
在大鼠原代肝细胞单层培养物中建立了四氯化碳诱导的肝损伤模型，重点研究四氯化碳代谢产物与细胞成分的共价结合和/或过氧化损伤作为损伤原因的参与情况。（1）在暴露于四氯化碳后立即在肝细胞中检测到14C标记代谢产物的共价结合。（2）低氧分压增加了四氯化碳的还原代谢，从而增加了共价结合。（3）[14C] - 四氯化碳与整个亚细胞组分中的脂质和蛋白质结合。结合优先发生在三酰甘油和磷脂上，其中磷脂酰胆碱含有的标记量最高。（4）与其他过氧化物质（即分别为ADP-Fe3+和氢过氧化枯烯）相比，四氯化碳的脂质过氧化能力显示出细微差异。（5）四氯化碳而非其他过氧化物质降低了极低密度脂蛋白形式的三酰甘油分泌速率。（6）抗氧化维生素E（α-生育酚）阻断脂质过氧化，但不阻断共价结合，脂蛋白分泌仍受抑制。（7）自由基清除剂胡椒基丁醚可预防四氯化碳诱导的脂质过氧化以及四氯化碳代谢产物与细胞成分的共价结合，还可恢复脂蛋白代谢。结果证实，CCl3自由基与细胞成分的共价结合引发脂蛋白分泌的抑制，从而导致脂肪变性，而与氧反应形成CCl3-OO则引发脂质过氧化。这两个过程相互独立，每个过程发生的程度取决于氧分压。前一个过程可能导致加合物形成，并最终引发癌症，而后一个过程则导致钙稳态丧失，并最终导致细胞凋亡和细胞死亡。
