Ljubkovic Marko, Mio Yasushi, Marinovic Jasna, Stadnicka Anna, Warltier David C, Bosnjak Zeljko J, Bienengraeber Martin
Department of Anesthesiology, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA.
Am J Physiol Cell Physiol. 2007 May;292(5):C1583-90. doi: 10.1152/ajpcell.00221.2006. Epub 2007 Jan 10.
Ischemic cardiac injury can be substantially alleviated by exposing the heart to pharmacological agents such as volatile anesthetics before occurrence of ischemia-reperfusion. A hallmark of this preconditioning phenomenon is its memory, when cardioprotective effects persist even after removal of preconditioning stimulus. Since numerous studies pinpoint mitochondria as crucial players in protective pathways of preconditioning, the aim of this study was to investigate the effects of preconditioning agent isoflurane on the mitochondrial bioenergetic phenotype. Endogenous flavoprotein fluorescence, an indicator of mitochondrial redox state, was elevated to 195 +/- 16% of baseline upon isoflurane application in intact cardiomyocytes, indicating more oxidized state of mitochondria. Isoflurane treatment also elicited partial dissipation of mitochondrial transmembrane potential, which remained depolarized even after anesthetic withdrawal (tetramethylrhodamine fluorescence intensity declined to 83 +/- 3 and 81 +/- 7% of baseline during isoflurane exposure and washout, respectively). Mild uncoupling, with preserved ATP synthesis, was also detected in mitochondria that were isolated from animals that had been previously preconditioned by isoflurane in vivo, revealing its memory nature. These mitochondria, after exposure to hypoxia and reoxygenation, exhibited better preserved respiration and ATP synthesis compared with mitochondria from nonpreconditioned animals. Partial mitochondrial depolarization was paralleled by a diminished Ca(2+) uptake into isoflurane-treated mitochondria, as indicated by the reduced increment in rhod-2 fluorescence when mitochondria were challenged with increased Ca(2+) (180 +/- 24 vs. 258 +/- 14% for the control). In conclusion, isoflurane preconditioning elicits partial mitochondrial uncoupling and reduces mitochondrial Ca(2+) uptake. These effects are likely to reduce the extent of the mitochondrial damage after the hypoxic stress.
在缺血-再灌注发生之前，将心脏暴露于挥发性麻醉剂等药理剂下，可显著减轻缺血性心脏损伤。这种预处理现象的一个标志是其记忆性，即即使在去除预处理刺激后，心脏保护作用仍会持续存在。由于众多研究指出线粒体是预处理保护途径中的关键参与者，因此本研究的目的是探讨预处理剂异氟烷对线粒体生物能量表型的影响。内源性黄素蛋白荧光是线粒体氧化还原状态的指标，在完整心肌细胞中应用异氟烷后，其升高至基线的195±16%，表明线粒体处于更氧化的状态。异氟烷处理还引起线粒体跨膜电位的部分消散，即使在停用麻醉剂后仍保持去极化状态（在异氟烷暴露和冲洗过程中，四甲基罗丹明荧光强度分别降至基线的83±3%和81±7%）。在从先前在体内经异氟烷预处理的动物分离的线粒体中，也检测到轻度解偶联且ATP合成得以保留，揭示了其记忆特性。与未预处理动物的线粒体相比，这些线粒体在暴露于缺氧和复氧后，表现出更好的呼吸和ATP合成保留。线粒体部分去极化伴随着异氟烷处理的线粒体对Ca(2+)摄取的减少，当线粒体受到增加的Ca(2+)刺激时，rhod-2荧光的增加减少表明了这一点（对照组为258±14%，而异氟烷处理组为180±24%）。总之，异氟烷预处理引起线粒体部分解偶联并减少线粒体Ca(2+)摄取。这些作用可能会减轻缺氧应激后线粒体损伤的程度。
