Mitochondrial reactive oxygen species contribute to high NaCl-induced activation of the transcription factor TonEBP/OREBP.
Mitochondrial reactive oxygen species contribute to high NaCl-induced activation of the transcription factor TonEBP/OREBP.
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DOI：
10.1152/ajprenal.00378.2005
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发表时间：
2006-05
期刊：
影响因子：
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通讯作者：
Xiaoming Zhou;J. Ferraris;M. Burg
中科院分区：
文献类型：
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作者：
Xiaoming Zhou;J. Ferraris;M. Burg
高渗激活转录因子张力响应增强子/渗透压响应元件结合蛋白（TonEBP/OREBP），导致参与有机渗透调节剂（包括甘氨酸甜菜碱）的抗氧化保护性积累的基因表达增加，以及抗氧化保护性热休克蛋白表达增加。我们以前的研究表明，高NaCl增加活性氧（ROS），这有助于激活TonEBP/OREBP。线粒体是ROS的主要来源。本研究的目的是检查线粒体是否产生有助于TonEBP/OREBP激活的ROS。我们用鱼藤酮和myxothiazol抑制HEK 293细胞中线粒体ROS的产生，鱼藤酮和myxothiazol分别抑制线粒体复合物I和III。鱼藤酮（250 nM）和myxothiazol（12 nM）降低高NaCl诱导的ROS超过40%，而apocynin（100 μ M），NADPH氧化酶的抑制剂，和别嘌呤醇（100 μ M），黄嘌呤氧化酶的抑制剂，没有显着的效果。鱼藤酮和myxothiazol降低高NaCl诱导的TonEBP/OREBP转录活性（ORE/TonE报告基因测定）和BGT 1（甜菜碱转运蛋白）mRNA丰度的增加，范围为53%至69%。它们抑制高NaCl诱导的TonEBP/OREBP反式激活活性，但不抑制其核转位。在高渗应激时，ATP释放到培养基中被认为是触发细胞渗透反应的信号。然而，我们没有检测到ATP释放到培养基中或ATP酶，腺苷三磷酸双磷酸酶（20 U/ml）抑制高NaCl诱导的ORE/TonE报告活性，表明高NaCl诱导的TonEBP/OREBP激活不是由ATP释放介导的。我们的结论是，高NaCl增加线粒体ROS的产生，这有助于激活TonEBP/OREBP通过增加其反式激活活性。
Hypertonicity activates the transcription factor tonicity-responsive enhancer/osmotic response element binding protein (TonEBP/OREBP), resulting in increased expression of genes involved in osmoprotective accumulation of organic osmolytes, including glycine betaine, and in increased expression of osmoprotective heat shock proteins. Our previous studies showed that high NaCl increases reactive oxygen species (ROS), which contribute to activation of TonEBP/OREBP. Mitochondria are a major source of ROS. The purpose of the present study was to examine whether mitochondria produce the ROS that contribute to activation of TonEBP/OREBP. We inhibited mitochondrial ROS production in HEK293 cells with rotenone and myxothiazol, which inhibit mitochondrial complexes I and III, respectively. Rotenone (250 nM) and myxothiazol (12 nM) reduce high NaCl-induced ROS over 40%, whereas apocynin (100 microM), an inhibitor of NADPH oxidase, and allopurinol (100 microM), an inhibitor of xanthine oxidase, have no significant effect. Rotenone and myxothiazol reduce high NaCl-induced increases in TonEBP/OREBP transcriptional activity (ORE/TonE reporter assay) and BGT1 (betaine transporter) mRNA abundance ranging from 53 to 69%. They inhibit high NaCl-induced TonEBP/OREBP transactivating activity, but not its nuclear translocation. Release of ATP into the medium on hypertonic stress has been proposed to be a signal that triggers cellular osmotic responses. However, we do not detect release of ATP into the medium or inhibition of high NaCl-induced ORE/TonE reporter activity by an ATPase, apyrase (20 U/ml), indicating that high NaCl-induced activation of TonEBP/OREBP is not mediated by release of ATP. We conclude that high NaCl increases mitochondrial ROS production, which contributes to the activation of TonEBP/OREBP by increasing its transactivating activity.