Enhanced expression of cystine/glutamate transporter in the lung caused by the oxidative-stress-inducing agent paraquat
Enhanced expression of cystine/glutamate transporter in the lung caused by the oxidative-stress-inducing agent paraquat
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DOI：
10.1016/j.freeradbiomed.2012.09.040
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发表时间：
2012-12-15
影响因子：
7.4
通讯作者：
Sato, Hideyo
中科院分区：
文献类型：
--
作者：
Kobayashi, Sho;Kuwata, Kazuho;Sato, Hideyo
在哺乳动物培养细胞中，胱氨酸/谷氨酸转运蛋白（称为系统X）的活性已被证明对于维持细胞内谷胱甘肽水平和细胞外胱氨酸/半胱氨酸氧化还原平衡至关重要。该转运蛋白的底物特异性亚基xCT被各种刺激强烈诱导，包括氧化应激，这表明xCT是针对这些类型的应激的适应性细胞防御系统之一。来自xCT缺陷小鼠的胚胎成纤维细胞不能存活，除非存在半胱氨酸前体N-乙酰半胱氨酸。然而，目前还不清楚xCT是否在体内具有类似的功能，因为xCT缺陷小鼠显然是正常的。在这项研究中，我们研究了百草枯诱导的氧化应激下的xCT缺陷小鼠的表型。百草枯剂量为45毫克/千克时，xCT缺陷小鼠的存活率明显低于野生型小鼠。在这种情况下，xCT缺陷小鼠肺中的总谷胱甘肽（还原型谷胱甘肽（GSH）+氧化型GSH）水平低于野生型小鼠肺中的水平。组织学检查显示，与野生型小鼠相比，百草枯给药使xCT缺陷小鼠的肺泡结构恶化。百草枯处理后，在xCT缺陷小鼠的肺中检测到明显的8-羟基-2 '-脱氧鸟苷和4-羟基-2-壬烯醛反应性。尽管在正常野生型小鼠的肺中可轻微检测到xCT表达，但百草枯给药诱导了肺中xCT mRNA的表达。在从野生型小鼠肺灌洗液中分离的肺泡巨噬细胞中检测到xCT mRNA的组成型表达，百草枯给药强烈增强了这些细胞中xCT mRNA的表达。百草枯处理的野生型小鼠支气管肺泡灌洗液中的GSH水平显著高于百草枯处理的xCT缺陷小鼠。这些结果表明，xCT有助于维持谷胱甘肽水平在肺和谷胱甘肽的氧化还原状态作为一种保护系统对百草枯在体内的毒性。(C)2012 Elsevier Inc. All rights reserved.
In mammalian cultured cells, the activity of a cystine/glutamate transporter, designated System x, has been shown to be essential for maintaining intracellular glutathione levels and the extracellular cystine/cysteine redox balance. The substrate-specific subunit of this transporter, xCT, is strongly induced by various stimuli, including oxidative stress, which suggests that xCT is one of the adaptive cellular defense systems against these types of stress. Embryonic fibroblasts from xCT-deficient mice fail to survive unless a cysteine precursor, N-acetylcysteine, is present. However, it is unclear whether xCT has similar functions in vivo because xCT-deficient mice are apparently normal. In this study, we investigated the phenotype of the xCT-deficient mice under paraquat-induced oxidative stress. At a paraquat dose of 45 mg/kg, the survival rate of the xCT-deficient mice was significantly lower than that of the wild-type mice. Under this condition, total glutathione (the reduced form of glutathione (GSH)+ the oxidized form of GSH) levels in the lungs of the xCT-deficient mice were lower than those in the lungs of the wild-type mice. Histopathological examinations showed that paraquat administration worsened the alveolar structure of the xCT-deficient mice compared with the wild-type mice. After paraquat treatment, obvious 8-hydroxy-2'-deoxyguanosine and 4-hydroxy-2-nonenal reactivity was detected in the lungs of the xCT-deficient mice. Although xCT expression was slightly detectable in the lungs of the normal wild-type mice, paraquat administration induced xCT mRNA expression in the lung. Constitutive expression of xCT mRNA was detected in alveolar macrophages isolated from the pulmonary lavage fluid of the wild-type mice, and paraquat administration strongly enhanced xCT mRNA expression in these cells. GSH levels in bronchoalveolar lavage fluid were significantly higher in the paraquat-treated wild-type mice than in the paraquat-treated xCT-deficient mice. These results suggest that xCT contributes to the maintenance of glutathione levels in lungs and the glutathione redox state as a protective system against paraquat toxicity in vivo. (C) 2012 Elsevier Inc. All rights reserved.