Tokyo Metropolitan Institute of Public Health, Hyakunin-cho, Shinjuku-ku, Tokyo 169-0073, Japan.
Chem Biol Interact. 2010 Dec 5;188(3):393-403. doi: 10.1016/j.cbi.2010.09.004. Epub 2010 Sep 15.
The cytotoxic effects and biotransformation of harmine and harmaline, which are known β-carboline alkaloids and potent hallucinogens, were studied in freshly isolated rat hepatocytes. The exposure of hepatocytes to harmine caused not only concentration (0-0.50mM)- and time (0-3h)-dependent cell death accompanied by the formation of cell blebs and the loss of cellular ATP, reduced glutathione, and protein thiols but also the accumulation of glutathione disulfide. Of the other analogues examined, the cytotoxic effects of harmaline and harmol (a metabolite of harmine) at a concentration of 0.5mM were less than those of harmine. The loss of mitochondrial membrane potential and generation of oxygen radical species in hepatocytes treated with harmine were greater than those with harmaline and harmol. In the oxygen consumption of mitochondria isolated from rat liver, the ratios of state-3/state-4 respiration of these β-carbolines were decreased in a concentration-dependent manner. In addition, harmine resulted in the induction of the mitochondrial permeability transition (MPT), and the effects of harmol and harmaline were less than those of harmine. At a weakly toxic level of harmine (0.25mM), it was metabolized to harmol and its monoglucuronide and monosulfate conjugates, and the amounts of sulfate rather than glucuronide predominantly increased with time. In the presence of 2,5-dichloro-4-nitrophenol (50μM; an inhibitor of sulfotransferase), harmine-induced cytotoxicity was enhanced, accompanied by decrease in the amount of harmol-sulfate conjugate, due to an increase in the amount of unconjugated harmol and the inhibition of harmine loss. Taken collectively, these results indicate that (a) mitochondria are target organelles for harmine, which elicits cytotoxicity through mitochondrial failure related to the induction of the MPT, mitochondrial depolarization, and inhibition of ATP synthesis; and (b) the toxic effects of harmine are greater than those of either its metabolite harmol or its analogue harmaline, suggesting that the onset of harmine-induced cytotoxicity may depend on the initial and/or residual concentrations of harmine rather than on those of its metabolites.
已知色胺和色林碱是β-咔啉生物碱和强效致幻剂，本研究旨在探讨其在新鲜分离的大鼠肝细胞中的细胞毒性作用和生物转化。暴露于色胺的肝细胞不仅会导致细胞死亡，而且还会导致细胞起泡和细胞内 ATP、还原型谷胱甘肽和蛋白巯基减少，同时还会导致谷胱甘肽二硫化物的积累。在所研究的其他类似物中，在 0.5mM 的浓度下，色林碱和 harmol（色胺的代谢物）的细胞毒性作用小于色胺。与色林碱和 harmol 相比，用色胺处理的肝细胞中线粒体膜电位丧失和氧自由基生成更大。在从大鼠肝中分离的线粒体的耗氧量中，这些β-咔啉类化合物的状态 3/状态 4 呼吸的比值呈浓度依赖性降低。此外，色胺导致线粒体通透性转换（MPT）的诱导，并且 harmol 和色林碱的作用小于色胺。在弱毒性水平的色胺（0.25mM）下，它被代谢为 harmol 及其单葡萄糖醛酸和单硫酸盐缀合物，并且硫酸盐的量而不是葡萄糖醛酸的量随时间主要增加。在 2,5-二氯-4-硝基苯酚（50μM；磺基转移酶抑制剂）存在下，色胺诱导的细胞毒性增强，同时 harmol-硫酸盐缀合物的量减少，这是由于未缀合的 harmol 量增加和色胺损失的抑制所致。总的来说，这些结果表明：（a）线粒体是色胺的靶细胞器，它通过与 MPT、线粒体去极化和 ATP 合成抑制相关的线粒体衰竭引起细胞毒性；（b）色胺的毒性作用大于其代谢物 harmol 或其类似物色林碱，这表明色胺诱导的细胞毒性的发生可能取决于色胺的初始和/或残留浓度，而不是其代谢物的浓度。
