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.

猝死（SCD）每年发生超过50万人和心律不齐，导致 血液动力学功能不全随后死亡，占大多数SCD病例。继发性心律失常 疤痕形成是充分了解的，但是急性缺血/再灌注（I/R）损伤促进的机制 心室心动过速和纤颤（VT/VF）更为复杂。 I/R相关心律不齐取决于动态 组织的特性，包括Ca2+介导的触发器，功能传导块，减少了间隙连接 电导率，动作电位（AP）的异质缩短和磨性分散。这些 复杂的电生理（EP）变化是由ATP供应限制，活性氧的变化引起的 物种（ROS），有害细胞内（Ca2+，Na+，酸）和细胞外（K+，乳酸）的积累 构成，所有这些都可以追溯到共同的起源，即线粒体功能受损。我们的小组 是第一个认识到异质线粒体不稳定性的重要性的人，包括持续 线粒体内膜电势（∆ψm）的去极或振荡，跨簇 为VT/VF设置阶段，心脏或心脏内部的心肌细胞或区域。但是，背后的机制 再灌注过程中的线粒体不稳定尚不清楚，它们如何对心律不齐不好 理解。抑制线粒体通透性过渡孔（MPTP）降低了梗塞大小，但 环孢菌素A介导的MPTP抑制对缺血后心律不齐的入射几乎没有影响， 表明早期功能障碍和晚期损伤机制可能是不同的。相反，我们发现 线粒体苯二氮卓受体（MBZR）配体在恢复动作电位和 抑制由I/R诱导的心律不齐，与预防或反向线粒体的能力并行 去极化。确实，我们令人兴奋的初步数据表明，MBZR而不是MPTP更重要 在早期再灌注阶段的∆ψm和电稳定性方面。在这里，我们将使用创新 在蜂窝和整体上I/R期间I/R期间I/R的动力学成像的方法 2+ 心脏秤，结合强大的遗传模型，有选择地敲除涉及的关键蛋白 在调节MPTP（环蛋白D; PPIF）时，线粒体Ca2+（线粒体Ca2+ Uniporter; MCU）， 和MBZR（转运蛋白； TSPO），以定义线粒体的因果机制 再灌注的不稳定性和心律不齐。该项目将从基于结论的结论中移动 对分子理解的药理推断，使我们能够将精力集中在正确的 线粒体靶标可追求以防止I/R引起的心律不齐，目的是减少燃烧 scd。