Bratton S B, Lau S S, Monks T J
Center for Molecular and Cellular Toxicology, Division of Pharmacology and Toxicology, College of Pharmacy, University of Texas at Austin, 78712, USA.
Chem Res Toxicol. 2000 Jul;13(7):550-6. doi: 10.1021/tx0000015.
In this study, we show that 2,3,5-tris(glutathion-S-yl)hydroquinone (TGHQ), a putative metabolite of benzene, induces apoptosis in human promyelocytic leukemia (HL-60) cells. Prior to the onset of apoptosis, TGHQ depletes intracellular glutathione (GSH) in a reactive oxygen species (ROS)-independent manner. Neutral, Mg(2+)-dependent sphingomyelinases, which are normally inhibited by GSH, are subsequently activated, as evidenced by increases in intracellular ceramide and depletion of sphingomyelin. As ceramide levels rise, effector caspase (DEVDase) activity steadily increases. Interestingly, while catalase has no effect on TGHQ-mediated depletion of GSH, this hydrogen peroxide (H(2)O(2)) scavenger does inhibit DEVDase activity and apoptosis, provided the enzyme is added to HL-60 cells before an increase in ceramide can be observed. Since ceramide analogues inhibit the mitochondrial respiratory chain, these data imply that ceramide-mediated generation of H(2)O(2) is necessary for the activation of effector caspases-3 and/or -7, and apoptosis. In summary, these studies indicate that TGHQ, and perhaps many quinol-based toxicants and chemotherapeutics, may induce apoptosis in hematopoietic cells by depleting GSH and inducing the proapoptotic ceramide-signaling pathway.
在本研究中，我们发现苯的一种假定代谢产物2,3,5-三（谷胱甘肽-S-基）对苯二酚（TGHQ）可诱导人早幼粒细胞白血病（HL-60）细胞凋亡。在凋亡发生之前，TGHQ以不依赖活性氧（ROS）的方式消耗细胞内谷胱甘肽（GSH）。中性的、Mg(2+)依赖性鞘磷脂酶通常受GSH抑制，随后被激活，细胞内神经酰胺增加和鞘磷脂消耗可证明这一点。随着神经酰胺水平升高，效应半胱天冬酶（DEVDase）活性稳步增加。有趣的是，虽然过氧化氢酶对TGHQ介导的GSH消耗没有影响，但这种过氧化氢（H(2)O(2)）清除剂确实能抑制DEVDase活性和凋亡，前提是在观察到神经酰胺增加之前将该酶添加到HL-60细胞中。由于神经酰胺类似物抑制线粒体呼吸链，这些数据表明神经酰胺介导的H(2)O(2)生成对于效应半胱天冬酶-3和/或-7的激活以及凋亡是必要的。总之，这些研究表明TGHQ，可能还有许多基于喹啉的毒物和化疗药物，可能通过消耗GSH和诱导促凋亡神经酰胺信号通路来诱导造血细胞凋亡。
