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

基本信息

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
项目类别：
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

项目摘要

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.

每年有超过 50 万人发生心脏性猝死 (SCD) 和心律失常，导致继发于死亡的血流动力学不足是大多数继发于心律失常的 SCD 病例。疤痕形成已广为人知，但急性缺血/再灌注 (I/R) 损伤促进的机制室性心动过速和心室颤动 (VT/VF) 更为复杂，与 I/R 相关的心律失常取决于动态。组织的特性，包括 Ca2+ 介导的触发因素、功能性传导阻滞、间隙连接减少电导、动作电位 (AP) 的异质缩短和不应期的分散。复杂的电生理 (EP) 变化是由 ATP 供应限制、活性氧变化引起的物种（ROS），细胞内（Ca2+、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根源，即线粒体功能受损。第一个认识到异质线粒体不稳定性的重要性，包括持续的线粒体不稳定性线粒体内膜电位 (ΔΨm) 的去极化或振荡，跨簇心肌细胞或心脏内的区域，为 VT/VF 奠定基础，但其背后的机制。再灌注期间线粒体的不稳定性尚不清楚，而且它们如何导致心律失常尚不清楚虽然抑制线粒体通透性转换孔 (mPTP) 可减少梗塞面积，环孢菌素 A 介导的 mPTP 抑制对缺血后心律失常的发生率影响很小或没有影响，表明早期功能障碍和晚期损伤机制可能不同，相反，我们发现。线粒体苯二氮卓受体 (mBzR) 配体对于恢复动作电位和抑制 I/R 引起的心律失常，同时具有预防或逆转线粒体功能的能力事实上，我们令人兴奋的初步数据表明 mBzR 比 mPTP 更重要。就早期再灌注阶段的 ΔΨm 和电稳定性而言，我们将使用创新的方法。在细胞和整个 I/R 过程中对 ΔΨm、Vm、基质 Ca 和 ROS 的动态进行成像的方法 2+ 心脏鳞片，结合强大的遗传模型，选择性地敲除相关的关键蛋白质调节 mPTP（亲环蛋白 D；PPIF）、线粒体 Ca2+（线粒体 Ca2+ 单向转运蛋白；MCU）、和 mBzR（易位蛋白；TSPO），以定义线粒体的因果机制该项目将推动该领域基于再灌注的不稳定和心律失常的结论。药理学推论到分子理解，使我们能够将精力集中在正确的方向上线粒体目标旨在预防缺血再灌注引起的心律失常，目标是减轻心脏负担 SCD。