Zhang K, Chew M, Yang E B, Wong K P, Mack P
Department of Experimental Surgery, Singapore General Hospital, Singapore.
Mol Pharmacol. 2001 Apr;59(4):837-43. doi: 10.1124/mol.59.4.837.
Glutathione (GSH), glutathione S-transferase (GST), and glutathione conjugate export pump (GS-X pump) have been shown to participate collectively in the detoxification of many anticancer drugs, including cisplatin. Identification and regulation of the rate-limiting step in the overall system for cisplatin detoxification is of crucial importance for sensitization of human tumor cells to cisplatin. In this study, the GSH content, GST activity, and GS-X pump activity were regulated separately to examine effects of the regulation on cisplatin cytotoxicity and cisplatin-induced DNA interstrand cross-links (ICL) in HepG2 cells. Seventy-percent depletion of GSH by buthionine sulfoximine (BSO) and 50% increase of GSH by monoethyl GSH ester (GSHe) potentiated and decreased cisplatin cytotoxicity, respectively. This was reflected by a significant decrease and increase of their respective IC(50) values by 62 and 107%. Cisplatin-induced ICL was also potentiated by depletion of GSH by BSO and decreased by enrichment of GSH by GSHe, as shown by a 125% increase and a 34% decrease of cross-linked DNA compared with control samples exposed to cisplatin alone (p = 0.008 and 0.03, respectively). On the other hand, inhibition of GST and GS-X pump by ethacrynic acid, quercetin, tannic acid, and indomethacin at concentrations that inhibited activities of GST and GS-X pump by more than 50% had no significant effects on cisplatin cytotoxicity and cisplatin-induced DNA ICL in these cells. The results showed that of the parameters measured, intracellular GSH seems to be the rate-limiting factor, and its regulation would provide a more promising strategy for sensitization of human liver tumor cells to cisplatin.
谷胱甘肽（GSH）、谷胱甘肽S-转移酶（GST）和谷胱甘肽共轭物输出泵（GS-X泵）已被证明共同参与包括顺铂在内的多种抗癌药物的解毒过程。鉴定和调节顺铂解毒整个系统中的限速步骤对于人类肿瘤细胞对顺铂的致敏至关重要。在本研究中，分别调节GSH含量、GST活性和GS-X泵活性，以检查这种调节对HepG2细胞中顺铂细胞毒性和顺铂诱导的DNA链间交联（ICL）的影响。丁硫氨酸亚砜胺（BSO）使GSH耗竭70%，单乙基谷胱甘肽酯（GSHe）使GSH增加50%，分别增强和降低了顺铂的细胞毒性。这分别通过它们各自的IC50值显著降低和升高62%和107%得到反映。与仅暴露于顺铂的对照样品相比，BSO使GSH耗竭和顺铂诱导的ICL也增强，GSHe使GSH富集则使ICL降低，交联DNA分别增加125%和降低34%（p分别为0.008和0.03）。另一方面，依他尼酸、槲皮素、单宁酸和吲哚美辛在抑制GST和GS-X泵活性超过50%的浓度下对这些细胞中的顺铂细胞毒性和顺铂诱导的DNA ICL没有显著影响。结果表明，在所测量的参数中，细胞内GSH似乎是限速因素，对其进行调节将为人类肝癌细胞对顺铂的致敏提供更有前景的策略。
