Lee Y S, Kang Y S, Lee S H, Kim J A
Department of Physiology, College of Medicine, Kwandong University, Kangnung 210-701, Korea.
Cell Death Differ. 2000 Oct;7(10):925-32. doi: 10.1038/sj.cdd.4400717.
Previously, tamoxifen (TAM) has been shown to induce apoptosis through elevation of intracellular Ca2+ in HepG2 human hepatoblastoma cells. In this study we investigated the role of reactive oxygen species (ROS) in the TAM-induced apoptosis, and interrelationship between intracellular Ca2+ and ROS. TAM induced a slow and sustained increase in intracellular ROS level. An antioxidant, N-acetylcysteine significantly inhibited both ROS production and apoptosis induced by TAM, suggesting that ROS may play an essential role in the TAM-induced apoptosis. In a time frame ROS generation followed intracellular Ca2+ increase, and the extracellular and intracellular Ca2+ chelation with EGTA and BAPTA/AM, respectively, completely inhibited the TAM-induced ROS production, indicating that intracellular Ca2+ may mediate the ROS generation. Inhibitors of NAD(P)H oxidase, diphenylene iodonium, phenylarsine oxide and neopterine, significantly blocked the TAM-induced ROS generation and apoptosis, implying that this oxidase may act as a source enzyme for the production of ROS. These results suggest that non-phagocytic NAD(P)H oxidase may play a novel role as a mediator of the apoptosis associated with intracellular Ca2+ in HepG2 cells.
此前已表明，他莫昔芬（TAM）可通过提高人肝癌HepG2细胞内的Ca2+水平来诱导细胞凋亡。在本研究中，我们调查了活性氧（ROS）在TAM诱导的细胞凋亡中的作用，以及细胞内Ca2+与ROS之间的相互关系。TAM诱导细胞内ROS水平缓慢且持续升高。抗氧化剂N-乙酰半胱氨酸显著抑制了TAM诱导的ROS生成和细胞凋亡，这表明ROS可能在TAM诱导的细胞凋亡中起重要作用。在一个时间范围内，ROS的生成跟随细胞内Ca2+的增加，分别用乙二醇双四乙酸（EGTA）和1,2-双（2-氨基苯氧基）乙烷-N,N,N',N'-四乙酸四乙酰甲酯（BAPTA/AM）进行细胞外和细胞内Ca2+螯合，完全抑制了TAM诱导的ROS生成，表明细胞内Ca2+可能介导ROS的生成。烟酰胺腺嘌呤二核苷酸磷酸（NAD(P)H）氧化酶抑制剂二亚苯基碘鎓、苯砷氧化物和新蝶呤显著阻断了TAM诱导的ROS生成和细胞凋亡，这意味着该氧化酶可能作为ROS产生的源酶。这些结果表明，非吞噬性NAD(P)H氧化酶可能作为HepG2细胞中与细胞内Ca2+相关的细胞凋亡的介质发挥新的作用。
