Mitochondrial Ca2+-induced K+ influx increases respiration and enhances ROS production while maintaining membrane potential
Mitochondrial Ca2+-induced K+ influx increases respiration and enhances ROS production while maintaining membrane potential
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DOI：
10.1152/ajpcell.00215.2006
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发表时间：
2007-01-01
影响因子：
5.5
通讯作者：
Stowe, David F.
中科院分区：
文献类型：
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作者：
Heinen, Andre;Camara, Amadou K. S.;Stowe, David F.
我们最近证明了线粒体生物能学和活性氧 (ROS) 产生的改变在离体心脏中线粒体 Ca2+ 敏感 K+ (mtK(Ca)) 通道开放诱导的预处理中的作用。然而，mtKCa 通道开放导致 ROS 产生触发预处理的潜在线粒体机制尚不清楚。我们假设次最大线粒体 K+ 流入会导致 ROS 产生，这是由于在完全充电的膜电位 (Delta Psi(m)) 下电子流增强的结果。为了检验这一假设，我们测量了 NS-1619（一种假定的 mtK(Ca) 通道开放剂）和缬氨霉素（一种 K+ 离子载体）对豚鼠心脏线粒体中线粒体呼吸、Delta Psi(m) 和 ROS 生成的影响。 NS-1619 (30 mu M) 使状态 2 和状态 4 呼吸分别增加 5.2 +/- 0.9 和 7.3 +/- 0.9 nmol O-2 center dot min(-1)center dot mg 蛋白质(-1)，与 NADH 连接的底物丙酮酸相比，增加 7.5 +/- 1.4 和 11.6 +/- 2.9 nmol O-2 center dot min(-1)center点毫克蛋白质（-1），分别与FADH（2）连接的底物琥珀酸盐（+鱼藤酮）； mtK(Ca) 通道阻断剂 paxilline 消除了这些效应。使用任一底物时，10-30 μM NS-1619 的 Delta Psi(m) 均未降低，但使用琥珀酸盐 + 鱼藤酮时，H2O2 释放增加了 44.8%（30 μM NS-1619 为 65.9 +/- 2.7%，时间对照为 21.1 +/- 3.8%）。相比之下，NS-1619 不会增加丙酮酸的 H2O2 释放。对于较低浓度的缬氨霉素也发现了类似的结果。尽管呼吸作用增加（这种情况能够导致电子泄漏增加），但琥珀酸+鱼藤酮支持的线粒体中 ROS 产量的增加是由于完全维持了 Delta Psi(m)。我们建议在状态 2 和 4 期间温和的基质 K+ 流入会增加线粒体呼吸，同时维持 Delta Psi(m)；这允许 O-2 吸收单线态电子并产生 ROS。
We recently demonstrated a role for altered mitochondrial bioenergetics and reactive oxygen species (ROS) production in mitochondrial Ca2+-sensitive K+ (mtK(Ca)) channel opening-induced preconditioning in isolated hearts. However, the underlying mitochondrial mechanism by which mtKCa channel opening causes ROS production to trigger preconditioning is unknown. We hypothesized that submaximal mitochondrial K+ influx causes ROS production as a result of enhanced electron flow at a fully charged membrane potential (Delta Psi(m)). To test this hypothesis, we measured effects of NS-1619, a putative mtK(Ca) channel opener, and valinomycin, a K+ ionophore, on mitochondrial respiration, Delta Psi(m), and ROS generation in guinea pig heart mitochondria. NS-1619 (30 mu M) increased state 2 and 4 respiration by 5.2 +/- 0.9 and 7.3 +/- 0.9 nmol O-2 center dot min(-1)center dot mg protein(-1), respectively, with the NADH-linked substrate pyruvate and by 7.5 +/- 1.4 and 11.6 +/- 2.9 nmol O-2 center dot min(-1)center dot mg protein(-1), respectively, with the FADH(2)-linked substrate succinate (+ rotenone); these effects were abolished by the mtK(Ca) channel blocker paxilline. Delta Psi(m) was not decreased by 10-30 mu M NS-1619 with either substrate, but H2O2 release was increased by 44.8% (65.9 +/- 2.7% by 30 mu M NS-1619 vs. 21.1 +/- 3.8% for time controls) with succinate + rotenone. In contrast, NS-1619 did not increase H2O2 release with pyruvate. Similar results were found for lower concentrations of valinomycin. The increase in ROS production in succinate + rotenone-supported mitochondria resulted from a fully maintained Delta Psi(m), despite increased respiration, a condition that is capable of allowing increased electron leak. We propose that mild matrix K+ influx during states 2 and 4 increases mitochondrial respiration while maintaining Delta Psi(m); this allows singlet electron uptake by O-2 and ROS generation.