Phimister Andrew J, Williams Kurt J, Van Winkle Laura S, Plopper Charles G
Department of Molecular Biosciences, University of California, Davis, CA 95616, USA.
J Pharmacol Exp Ther. 2005 Aug;314(2):506-13. doi: 10.1124/jpet.105.084533. Epub 2005 Apr 21.
Glutathione plays many critical roles within the cell, including offering protection from reactive chemicals. The bioactivated toxicant naphthalene forms chemically reactive intermediates that can deplete glutathione and covalently bind to cellular proteins. Naphthalene selectively injures the nonciliated epithelial cells of the intrapulmonary airways (i.e., Clara cells). This study attempted to define what role glutathione loss plays in naphthalene cytotoxicity by comparing Swiss-Webster mice treated with naphthalene with those treated with the glutathione depletor diethylmaleate. High-resolution imaging techniques were used to evaluate acute changes in Clara cell ultrastructure, membrane permeability, and cytoskeleton structure. A single dose of either diethylmaleate (1000 mg/kg) or naphthalene (200 mg/kg) caused similar glutathione losses in intrapulmonary airways (< 20% of control). Diethylmaleate did not increase membrane permeability, disrupt mitochondria, or lead to cell death--hallmark features of naphthalene cytotoxicity. However, diethylmaleate treatment did cause Clara cell swelling, plasma membrane blebs, and actin cytoskeleton disruptions similar to naphthalene treatment. Structural changes in mitochondria and Golgi bodies also were noted. Changes in ATP levels were measured as an indication of overall cell function, in isolated airway explants incubated with diethylmaleate, naphthalene, or naphthalene metabolites in vitro. Only the reactive metabolites of naphthalene caused significant ATP losses. Unlike the lethal injury caused by naphthalene, the disruptive cellular changes associated with glutathione loss from diethylmaleate seemed to be reversible after recovery of glutathione levels. This suggests that glutathione depletion may be responsible for some aspects of naphthalene cytotoxicity, but it is not sufficient to cause cell death without further stresses.
谷胱甘肽在细胞内发挥着许多关键作用，包括保护细胞免受活性化学物质的侵害。生物活化的有毒物质萘会形成化学反应性中间体，这些中间体能够消耗谷胱甘肽并与细胞蛋白质共价结合。萘会选择性地损伤肺内气道的无纤毛上皮细胞（即克拉拉细胞）。本研究试图通过比较用萘处理的瑞士-韦伯斯特小鼠和用谷胱甘肽消耗剂马来酸二乙酯处理的小鼠，来确定谷胱甘肽损失在萘细胞毒性中所起的作用。采用高分辨率成像技术来评估克拉拉细胞超微结构、膜通透性和细胞骨架结构的急性变化。单次给予马来酸二乙酯（1000毫克/千克）或萘（200毫克/千克）会导致肺内气道中谷胱甘肽有相似程度的损失（<对照组的20%）。马来酸二乙酯不会增加膜通透性、破坏线粒体或导致细胞死亡——这些都是萘细胞毒性的标志性特征。然而，马来酸二乙酯处理确实会导致克拉拉细胞肿胀、质膜泡形成以及肌动蛋白细胞骨架破坏，这与萘处理相似。还观察到线粒体和高尔基体的结构变化。在体外将分离的气道外植体与马来酸二乙酯、萘或萘代谢物一起孵育时，测量ATP水平的变化以作为整体细胞功能的指标。只有萘的反应性代谢物会导致显著的ATP损失。与萘造成的致命损伤不同，与马来酸二乙酯导致的谷胱甘肽损失相关的细胞破坏性变化在谷胱甘肽水平恢复后似乎是可逆的。这表明谷胱甘肽耗竭可能是萘细胞毒性某些方面的原因，但在没有进一步应激的情况下，它不足以导致细胞死亡。
