Superoxide Flashes Reveal Novel Properties of Mitochondrial Reactive Oxygen Species Excitability in Cardiomyocytes
Superoxide Flashes Reveal Novel Properties of Mitochondrial Reactive Oxygen Species Excitability in Cardiomyocytes
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超氧化物闪光揭示了心肌细胞线粒体活性氧兴奋性的新特性。
DOI：
10.1016/j.bpj.2012.01.044
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发表时间：
2012-03-07
影响因子：
3.4
通讯作者：
Cheng, Heping
中科院分区：
文献类型：
--
作者：
Li, Kaitao;Zhang, Wanrui;Cheng, Heping
超氧化物闪光代表由线粒体通透性转换孔 (mPTP) 瞬时打开引起的线粒体活性氧 (ROS) 的量子和爆发性产生。鉴于它们在代谢、缺血再灌注损伤和细胞凋亡中的关键作用，闪现特性的表征对于进一步研究这种新发现的线粒体现象的机制和生理学将很有价值。在这里，我们基于从延时共焦图像堆栈中提取的二维特征图的分割以及校正闪光幅度直方图的光学畸变的理论，开发了闪光探测器FlashSniper。通过对心肌细胞中超氧化物闪光的大规模分析，我们证明了肌膜下和肌原纤维间线粒体之间均匀的线粒体 ROS 兴奋性，以及连续闪光事件之间的间隔呈指数分布。闪光点火表现出三种不同的模式：从静止突然上升（44％），以指数足上升（27％），或在基座前体之后发生上升（29％），与可兴奋细胞中的动作电位启动非常相似。然而，超氧化物闪光的光学模糊校正幅度及其持续时间变化很大，表明单线粒体 ROS 激发的随机自动性。线粒体膜电位的同时测量表明，分级去极化，而不是全或无，反映了闪光的前体和主峰。我们认为，超氧化物闪速产生是一个再生过程，其主导因素是单个线粒体中有限数量的单位（例如 mPTP）的随机、自主募集。
Superoxide flash represents quantal and bursting production of mitochondrial reactive oxygen species (ROS) instigated by transient opening of the mitochondrial permeability transition pore (mPTP). Given their critical role in metabolism, ischemia-reperfusion injury, and apoptosis, characterization of flash properties would be valuable to further mechanistic and physiological studies of this newly discovered mitochondrial phenomenon. Here we developed the flash detector FlashSniper based on segmentation of two-dimensional feature maps extracted from time-lapse confocal image stacks, and on the theory for correcting optical distortion of flash-amplitude histograms. Through large-scale analysis of superoxide flashes in cardiomyocytes, we demonstrated uniform mitochondrial ROS excitability among subsarcolemmal and intermyofibrillar mitochondria, and exponential distribution of intervals between consecutive flash events. Flash ignition displayed three different patterns: an abrupt rise from quiescence (44%), a rise with an exponential foot (27%), or a rise occurring after a pedestal precursor (29%), closely resembling action-potential initiation in excitable cells. However, the optical blurring-corrected amplitudes of superoxide flashes were highly variable, as were their durations, indicating stochastic automaticity of single-mitochondrion ROS excitation. Simultaneous measurement of mitochondrial membrane potential revealed that graded, rather than all-or-none, depolarization mirrored the precursor and the primary peak of the flash. We propose that superoxide flash production is a regenerative process dominated by stochastic, autonomous recruitment of a limited number of units (e.g., mPTPs) in single mitochondria.