Mitochondrial glutathione depletion by glutamine in growing tumor cells
Mitochondrial glutathione depletion by glutamine in growing tumor cells
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DOI：
10.1016/s0891-5849(00)00392-0
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发表时间：
2000-11-01
影响因子：
7.4
通讯作者：
Estrela, JM
中科院分区：
文献类型：
--
作者：
Carretero, J;Obrador, E;Estrela, JM
在体内研究了L-谷氨酰胺（Gln）对荷埃利希瘤（EAT）小鼠肿瘤细胞线粒体谷胱甘肽（mtGSH）水平的影响。在喂食富含Gin的饮食（GED;其中30%的总饮食氮来自Gin）或营养完全元素饮食（SD）的小鼠中，肿瘤生长相似。与非荷瘤小鼠相比，肿瘤生长导致SD小鼠血液Gin水平下降，但GED小鼠血液Gin水平没有下降。喂食GED的小鼠中的肿瘤细胞显示出比从喂食SD的小鼠中分离的细胞更高的转氨酶和更低的Gin合成酶活性。在喂食GED的小鼠的肿瘤细胞中，胞浆谷氨酸浓度比喂食SD的小鼠高2倍。谷氨酸含量的这种增加抑制了肿瘤线粒体对GSH的摄取，并导致线粒体GSH（mtGSH）含量（在正常细胞（如淋巴细胞或肝细胞）的线粒体中未发现）的选择性耗竭，达到饲喂SD的小鼠肿瘤线粒体中发现的水平的57%。在喂食GED的小鼠的肿瘤细胞中，6-重氮-5-正亮氨酸-或L-谷氨酸-γ-肼诱导的转氨酶活性抑制降低了细胞溶质谷氨酸含量，并将线粒体对GSH的摄取恢复到喂食SD的小鼠的EAT细胞中发现的速率。由Gln引起的mtGSH的部分损失不影响活性氧中间体（ROI）的产生或线粒体功能（例如，细胞内过氧化氢水平、O-2（-.）发现从喂食SD或GED的小鼠分离的肿瘤细胞中的线粒体生成、线粒体膜电位、线粒体大小、三磷酸腺苷和二磷酸腺苷含量以及耗氧量相似;然而，TNF-α刺激后的线粒体生成ROI增加。我们的研究结果表明，谷氨酸衍生自谷氨酰胺促进谷胱甘肽转运到线粒体的抑制，这可能使肿瘤细胞更容易受到氧化应激诱导的介质。(C)2000 Elsevier Science Inc.
The effect of L-glutamine (Gln) on mitochondrial glutathione (mtGSH) levels in tumor cells was studied in vivo in Ehrlich ascites tumor (EAT)-bearing mice. Tumor growth was similar in mice fed a Gin-enriched diet (GED; where 30% of the total dietary nitrogen was from Gin) or a nutritionally complete elemental diet (SD). As compared with non-tumor-bearing mice, tumor growth caused a decrease of blood Gin levels in mice fed an SD but not in those fed a GED. Tumor cells in mice fed a GED showed higher glutaminase and lower Gin synthetase activities than did cells isolated from mice fed an SD. Cytosolic glutamate concentration was 2-fold higher in tumor cells from mice fed a GED (similar to4 mM) than in those fed an SD. This increase in glutamate content inhibited GSH uptake by tumor mitochondria and led to a selective depletion of mitochondrial GSH (mtGSH) content (not found in mitochondria of normal cells such as lymphocytes or hepatocytes) to similar to 57% of the level found in tumor mitochondria of mice fed an SD. In tumor cells of mice fed a GED, 6-diazo-5-norleucine- or L-glutamate-gamma -hydrazine-induced inhibition of glutaminase activity decreased cytosolic glutamate content and restored GSH uptake by mitochondria to the rate found in EAT cells of mice fed an SD. The partial loss of mtGSH elicited by Gin did not affect generation of reactive oxygen intermediates (ROIs) or mitochondrial functions (e.g., intracellular peroxide levels, O-2(-.) generation, mitochondrial membrane potential, mitochondrial size, adenosine triphosphate and adenosine diphosphate contents, and oxygen consumption were found similar in tumor cells isolated from mice fed an SD or a GED); however, mitochondrial production ROIs upon TNF-alpha stimulation was increased. Our results demonstrate that glutamate derived from glutamine promotes an inhibition of GSH transport into mitochondria, which may render tumor cells more susceptible to oxidative stress-induced mediators. (C) 2000 Elsevier Science inc.