Sequential opening of mitochondrial ion channels as a function of glutathione redox thiol status
Sequential opening of mitochondrial ion channels as a function of glutathione redox thiol status
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DOI：
10.1074/jbc.m702841200
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发表时间：
2007-07-27
影响因子：
4.8
通讯作者：
O'Rourke, Brian
中科院分区：
文献类型：
--
作者：
Aon, Miguel A.;Cortassa, Sonia;O'Rourke, Brian
线粒体膜电位（ΔΨm）去极化导致缺血后心脏中的细胞死亡以及电和收缩功能障碍。线粒体活性氧产生和清除之间的失衡先前被认为与内膜阴离子通道（IMAC）的激活有关，该通道不同于通透性转换孔（PTP），是心肌细胞对代谢应激的第一反应。谷胱甘肽氧化还原对GSH/GSSG与ΔΨm以及NADH/NAD⁺氧化还原状态平行波动。在此我们表明，还原型谷胱甘肽的耗竭是心肌细胞中线粒体同步振荡的另一个触发因素，并且中等的GSH/GSSG比值导致可逆的ΔΨm去极化，尽管广泛的巯基氧化会诱导不可逆的PTP激活。响应二酰胺的线粒体功能障碍分阶段发生，从ΔΨm的振荡发展到持续去极化，同时伴有GSH的耗竭。线粒体振荡可被IMAC抑制剂4'-氯地西泮消除，而环孢菌素A无效。在皂素透化的心肌细胞中，巯基氧化还原状态被系统地固定在GSH/GSSG比值从300:1到20:1的范围内。在150:1 - 100:1的比值下，ΔΨm可逆地去极化，并且一种基质定位的荧光标记物得以保留；然而，将GSH/GSSG降低到50:1会不可逆地使ΔΨm去极化，并诱导活性氧产生、NAD(P)H氧化以及基质成分丢失的最大速率。通过抑制GSH摄取、NADPH依赖的谷胱甘肽还原酶或NADH/NADPH转氢酶改变了线粒体对GSH的敏感性，这表明基质GSH的再生或补充是至关重要的。结果表明，GSH/GSSG氧化还原状态控制着心肌细胞中由巯基氧化触发的线粒体离子通道（IMAC先于PTP）的顺序开放。
Mitochondrial membrane potential (Delta Psi(m)) depolarization contributes to cell death and electrical and contractile dysfunction in the post-ischemic heart. An imbalance between mitochondrial reactive oxygen species production and scavenging was previously implicated in the activation of an inner membrane anion channel (IMAC), distinct from the permeability transition pore (PTP), as the first response to metabolic stress in cardiomyocytes. The glutathione redox couple, GSH/GSSG, oscillated in parallel with Delta Psi(m) and the NADH/NAD(+) redox state. Here we show that depletion of reduced glutathione is an alternative trigger of synchronized mitochondrial oscillation in cardiomyocytes and that intermediate GSH/GSSG ratios cause reversible Delta Psi(m) depolarization, although irreversible PTP activation is induced by extensive thiol oxidation. Mitochondrial dysfunction in response to diamide occurred in stages, progressing from oscillations in Delta Psi(m) to sustained depolarization, in association with depletion of GSH. Mitochondrial oscillations were abrogated by 4'-chlorodiazepam, an IMAC inhibitor, whereas cyclosporin A was ineffective. In saponin-permeabilized cardiomyocytes, the thiol redox status was systematically clamped at GSH/GSSG ratios ranging from 300:1 to 20:1. At ratios of 150:1-100:1, Delta Psi(m) depolarized reversibly, and a matrix-localized fluorescent marker was retained; however, decreasing the GSH/GSSG to 50:1 irreversibly depolarized Delta Psi(m) and induced maximal rates of reactive oxygen species production, NAD(P)H oxidation, and loss of matrix constituents. Mitochondrial GSH sensitivity was altered by inhibiting either GSH uptake, the NADPH-dependent glutathione reductase, or the NADH/NADPH transhydrogenase, indicating that matrix GSH regeneration or replenishment was crucial. The results indicate that GSH/GSSG redox status governs the sequential opening of mitochondrial ion channels (IMAC before PTP) triggered by thiol oxidation in cardiomyocytes.