Thomas C, Will Y, Schoenberg S L, Sanderlin D, Reed D J
Department of Chemistry, MS-7539, Central Washington University, Ellensburg, WA 98926, USA.
Biochem Pharmacol. 2001 Mar 1;61(5):595-603. doi: 10.1016/s0006-2952(00)00577-3.
1,2-Dibromoethane (DBE) is an environmental contaminant that is metabolized by glutathione S-transferases to a haloethane-glutathione conjugate. Since haloethane-glutathione conjugates are known to alkylate nuclear DNA and cytoplasmic proteins, these effects were investigated in isolated rat liver mitochondria exposed to DBE by measuring guanine adducts and several aspects of oxidative phosphorylation including respiratory control ratios, respiratory enzyme activity, and ATP levels. Mitochondrial large-amplitude swelling and glutathione status were assessed to evaluate mitochondrial membrane integrity and function. When exposed to DBE, mitochondria became uncoupled rapidly, yet no large-amplitude swelling or extramitochondrial glutathione was observed. Mitochondrial GSH was depleted to 2-53% of controls after a 60-min exposure to micromolar quantities of DBE; however, no extramitochondrial GSH or GSSG was detected. The depletion of mitochondrial glutathione corresponded to an increase of an intramitochondrial GSH-conjugate which, based on HPLC elution profiles and retention times, appeared to be S,S'-(1,2-ethanediyl)bis(glutathione). Activities of the NADH oxidase and succinate oxidase respiratory enzyme systems were inhibited 10-74% at micromolar levels of DBE, with succinate oxidase inactivation occurring at lower doses. ATP concentrations in DBE-exposed mitochondria in the presence of succinate were 5-90% lower than in the controls. The DNA adduct S-[2-(N(7)-guanyl)ethyl]glutathione was detected by HPLC in mtDNA isolated from DBE-exposed mitochondria. The results suggest that respiratory enzyme inhibition, glutathione depletion, decreased ATP levels, and DNA alkylation in DBE-exposed mitochondria occur via the formation of an S-(2-bromoethyl)glutathione conjugate, the precursor of the episulfonium ion alkylating species of DBE.
1,2 - 二溴乙烷（DBE）是一种环境污染物，可被谷胱甘肽S - 转移酶代谢为卤代乙烷 - 谷胱甘肽共轭物。由于已知卤代乙烷 - 谷胱甘肽共轭物会使核DNA和细胞质蛋白烷基化，因此通过测量鸟嘌呤加合物以及氧化磷酸化的几个方面，包括呼吸控制率、呼吸酶活性和ATP水平，在暴露于DBE的离体大鼠肝线粒体中研究了这些效应。评估线粒体大幅度肿胀和谷胱甘肽状态以评估线粒体膜的完整性和功能。当暴露于DBE时，线粒体迅速解偶联，但未观察到大幅度肿胀或线粒体外谷胱甘肽。在暴露于微摩尔量的DBE 60分钟后，线粒体谷胱甘肽（GSH）耗竭至对照的2 - 53%；然而，未检测到线粒体外GSH或氧化型谷胱甘肽（GSSG）。线粒体谷胱甘肽的耗竭对应于线粒体内GSH共轭物的增加，基于高效液相色谱（HPLC）洗脱图谱和保留时间，该共轭物似乎是S,S' -（1,2 - 乙二基）双（谷胱甘肽）。在微摩尔水平的DBE下，NADH氧化酶和琥珀酸氧化酶呼吸酶系统的活性受到10 - 74%的抑制，琥珀酸氧化酶失活发生在较低剂量下。在存在琥珀酸的情况下，暴露于DBE的线粒体中的ATP浓度比对照低5 - 90%。通过HPLC在从暴露于DBE的线粒体中分离的线粒体DNA（mtDNA）中检测到DNA加合物S - [2 -（N（7） - 鸟嘌呤基）乙基]谷胱甘肽。结果表明，暴露于DBE的线粒体中的呼吸酶抑制、谷胱甘肽耗竭、ATP水平降低和DNA烷基化是通过形成S -（2 - 溴乙基）谷胱甘肽共轭物发生的，该共轭物是DBE的环硫鎓离子烷基化物种的前体。
