Molecular Determinants of Mitochondrial Instability and Arrhythmias

线粒体不稳定和心律失常的分子决定因素

• 批准号: 9326466
• 负责人: FADI GABRIEL AKAR
• 金额: $ 51.15万
• 依托单位: JOHNS HOPKINS UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-04-01 至 2021-02-28
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9326466
• 关键词: Acids; Action Potentials; Acute; Adult; Arrhythmia; Behavior; Benzodiazepine Receptor; Blood flow; Cardiac Myocytes; Cells; Cessation of life; Cicatrix; Complex; Coronary; Cyclosporine; Data; Electrophysiology (science); Functional disorder; Gap Junctions; Genetic Models; Goals; Heart; Heart Abnormalities; Heart Arrest; Heterogeneity; Human; Image; Imaging Techniques; Impairment; In Vitro; Incidence; Infarction; Injury; Inner mitochondrial membrane; Ischemia; Knock-out; Ligands; Mediating; Membrane Potentials; Metabolic; Methods; Mitochondria; Modeling; Molecular; Mus; Muscle Cells; Myocardial Infarction; Myocardium; Neonatal; Optics; Organelles; Oxidative Stress; Pharmacology; Phase; Property; Proteins; Reactive Oxygen Species; Recovery; Refractory; Reperfusion Injury; Reperfusion Therapy; Rest; Risk; Role; Secondary to; Tissues; Ventricular; Ventricular Fibrillation; Ventricular Tachycardia; Work; base; blood pump; catalase; cyclophilin D; experience; extracellular; heart rhythm; hemodynamics; induced pluripotent stem cell; innovation; insight; knockout animal; loss of function; mitochondrial permeability transition pore; monolayer; mortality; novel; overexpression; prevent; restoration; spatiotemporal; sudden cardiac death; therapeutic target

Sudden Cardiac Death (SCD) occurs in more than half a million people every year and arrhythmias, resulting in hemodynamic insufficiency followed by death, account for the majority of SCD cases. Arrhythmias secondary to scar formation are well understood, but mechanisms by which acute ischemia/reperfusion (I/R) injury promotes ventricular tachycardia and fibrillation (VT/VF) are more complex. I/R-related arrhythmias depend on dynamic properties of the tissue, including Ca2+-mediated triggers, functional conduction block, decreased gap junctional conductance, heterogeneous shortening of the action potential (AP) and dispersion of refractoriness. These complex electrophysiological (EP) changes are caused by limitations in ATP supply, changes in reactive oxygen species (ROS), accumulation of detrimental intracellular (Ca2+, Na+, acid) and extracellular (K+, lactate) constituents, all of which can be traced to a common origin, namely impaired mitochondrial function. Our group was the first to recognize the importance of heterogeneous mitochondrial instability, including sustained depolarization or oscillation of the mitochondrial inner membrane potential (∆Ψm), across clusters of myocytes or regions within the heart, in setting the stage for VT/VF. However, the mechanisms behind mitochondrial instability during reperfusion are unclear and how they contribute to arrhythmias is not well understood. While inhibition of the mitochondrial permeability transition pore (mPTP) decreases infarct size, cyclosporine A-mediated inhibition of mPTP has little or no effect on arrhythmia incidence after ischemia, suggesting that the early dysfunction and late injury mechanisms may be distinct. In contrast, we found that mitochondrial benzodiazepine receptor (mBzR) ligands are very effective at restoring the action potential and suppressing arrhythmias induced by I/R, in parallel with their ability to prevent or reverse mitochondrial depolarization. Indeed, our exciting preliminary data suggests that mBzR, rather than mPTP, is more important in terms of ∆Ψm and electrical stability during the early reperfusion phase. Here, we will use innovative approaches to image the dynamics of ∆Ψm, Vm, matrix Ca and ROS during I/R at the cellular and whole 2+ heart scales, combined with powerful genetic models to selectively knockout the key proteins involved in modulating mPTP (cyclophilin D; PPIF), mitochondrial Ca2+ (the mitochondrial Ca2+uniporter; MCU), and the mBzR (translocator protein; TSPO), to define the causal mechanisms underlying mitochondrial instability and arrhythmias on reperfusion. This project will move the field from conclusions based on pharmacological inference to molecular understanding, allowing us to focus our efforts on the correct mitochondrial targets to pursue to prevent I/R-induced arrhythmias with the goal of decreasing the burden of SCD.

心脏性猝死（SCD）每年发生在50多万人中，心律失常导致 血流动力学功能不全，随后死亡，占SCD病例的大多数。心律失常继发于 瘢痕形成是众所周知的，但急性缺血/再灌注（I/R）损伤促进瘢痕形成的机制是， 室性心动过速和纤维性颤动（VT/VF）更为复杂。I/R相关心律失常取决于动态 组织特性，包括Ca 2+介导的触发、功能性传导阻滞、间隙连接减少 电导，动作电位（AP）的不均匀缩短和不应期的分散。这些 复杂的电生理学（EP）变化是由ATP供应的限制、活性氧的变化、 有害的细胞内（Ca 2+，Na+，酸）和细胞外（K+，乳酸）的积累 所有这些都可以追溯到一个共同的起源，即受损的线粒体功能。我们集团 是第一个认识到异质性线粒体不稳定性的重要性，包括持续的 线粒体内膜电位（线粒体膜电位）的去极化或振荡，跨簇 心肌细胞或心脏内的区域，在设置VT/VF的阶段。然而，背后的机制 再灌注期间线粒体的不稳定性尚不清楚，它们如何导致心律失常也不清楚 明白虽然线粒体通透性转换孔（mPTP）的抑制降低了梗死面积， 环孢霉素A介导的mPTP抑制对缺血后心律失常的发生率几乎没有影响或没有影响， 提示早期功能障碍和晚期损伤机制可能不同。相反，我们发现， 线粒体苯二氮受体（mBzR）配体在恢复动作电位方面非常有效， 抑制I/R诱导的心律失常，同时具有预防或逆转线粒体 去极化事实上，我们令人兴奋的初步数据表明，mBzR，而不是mPTP， 在早期再灌注阶段的心率和电稳定性方面。在这里，我们将使用创新的 方法成像的动态钙，Vm，矩阵钙和活性氧在I/R在细胞和整体 2个以上 心脏量表，结合强大的遗传模型，选择性地敲除相关的关键蛋白质 在调节mPTP（亲环素D; PPIF），线粒体Ca 2+（线粒体Ca 2+单向转运体; MCU）， 和mBzR（转运蛋白; TSPO），以确定线粒体的因果机制 不稳定和心律失常。这个项目将把这个领域从基于 药理学推断分子的理解，使我们能够集中精力在正确的 线粒体靶点，以预防I/R诱导的心律失常，目的是减少 SCD。