Nohl Hans, Gille Lars, Kozlov Andrey, Staniek Katrin
Fundamental Pharmacology and Toxicology, University of Veterinary Medicine Vienna, Vienna, Austria.
Redox Rep. 2003;8(3):135-41. doi: 10.1179/135100003225001502.
The bioenergetic properties of mitochondria in combination with the high turnover rate of dioxygen qualify these organelles for the formation of reactive oxygen species (ROS). The assumption that mitochondria are the major intracellular source of ROS was essentially based on in vitro experiments with isolated mitochondria. The transfer of these data to the living cell may, however, be incorrect. Artefacts due to the preparation procedure or inadequate detection methods of ROS may lead to false positive results. Inhomogeneous results were found to be due to an interaction of the detection system with components of the respiratory chain which could be avoided by a recently developed non-invasive method. One of the most critical electron transfer steps in the respiratory chain is the electron bifurcation from ubiquinol to the cytochrome bc(1) complex. This electron bifurcation requires the free mobility of the head domain of the Rieske iron-sulfur protein. Inhibition of electron bifurcation by antimycin A causes leakage of single electrons to oxygen which results in the release of ROS. Hindrance of electron bifurcation was also observed following alterations of the physical state of membrane phospholipids in which the cytochrome bc(1) complex is inserted. Irrespective of whether the fluidity of the membrane was elevated or decreased, electron flow rates to the Rieske iron-sulfur protein were drastically reduced. Concomitantly superoxide radicals were released from these mitochondria, strongly suggesting the involvement of the ubiquinol/cytochrome bc(1) redox couple in this process.
线粒体的生物能量特性与高周转率的双原子氧相结合，使这些细胞器成为活性氧（ROS）形成的场所。线粒体是细胞内ROS主要来源的假设主要基于对分离出线粒体的体外实验。然而，将这些数据应用于活细胞可能是不正确的。由于制备过程或ROS检测方法不当导致的假象可能会产生假阳性结果。结果不一致被发现是由于检测系统与呼吸链成分之间的相互作用所致，而最近开发的一种非侵入性方法可以避免这种情况。呼吸链中最关键的电子传递步骤之一是从泛醇到细胞色素bc(1)复合物的电子分叉。这种电子分叉需要Rieske铁硫蛋白头部结构域的自由移动性。抗霉素A对电子分叉的抑制会导致单个电子泄漏到氧中，从而导致ROS的释放。在插入细胞色素bc(1)复合物的膜磷脂物理状态发生改变后，也观察到了电子分叉的受阻。无论膜的流动性是升高还是降低，流向Rieske铁硫蛋白的电子流速都会急剧降低。与此同时，超氧自由基从这些线粒体中释放出来，这强烈表明泛醇/细胞色素bc(1)氧化还原对参与了这一过程。
