Targeting Cell Death to Prevent Ventricular Remodeling and Heart Failure

描述（由申请人提供）： 定义心肌梗死和从代偿性心脏肥大到失代偿性心力衰竭的进展的常见细胞事件是心肌细胞死亡。在急性梗死中，由于氧/营养缺乏，心肌细胞坏死是不可避免的，但随后是梗死周围区域的细胞自主死亡或凋亡波。同样，血流动力学应激的心脏首先经历肥大，但最终部分由于心肌细胞的凋亡损失而失败。重要的是，在急性梗死后存活心肌中发生肥大以平衡增加的血液动力学负荷;并且在压力超负荷肥大的失代偿中观察到由于缺乏血管生成引起的缺血，因此使心脏经受缺血和肥大应激作为最终共同途径。因此，在这两种情况下，有效靶向细胞凋亡具有保留功能性心肌的潜力。本提案将检验心肌细胞凋亡是由Bcl 2蛋白的BH 3亚家族的特异性应激反应性促凋亡因子诱导的假设，并且组合靶向心脏疾病中的相关因子可以是挽救心肌和预防不良心室重构的有效手段。在已发表的和初步的实验中，我们已经鉴定了两种密切相关的仅含BH 3的蛋白，Bnip 3（Bcl-2/腺病毒E1 B 19 kDa相互作用蛋白）和Bnip 3样蛋白X（Nix），它们在心肌中表达，可引起细胞凋亡，最重要的是，它们在心肌缺血（Bnip 3）和心肌肥大（Nix）中特异性上调。我们已经建立了可行的小鼠模型，其中每个因子的表达可以通过强制条件转基因和生殖系或心脏特异性基因消融进行实验调节。在具体目标#1中，我们将检验Bnip 3和Nix诱导的心肌细胞凋亡有助于心肌梗死和心肌缺血-再灌注损伤后的不利心室重构的假设。我们已经开发了显微外科手术程序，以产生心肌梗死和缺血再灌注损伤的小鼠与联合强制心脏表达和心脏特异性缺失的Nix和Bnip 3，随后通过磁共振成像为基础的一系列评估梗死面积和心肌结构和功能，以及心肌细胞凋亡的免疫组化检测，从而使我们能够分析的结果作为一个功能的Nix和Bnip 3的表达。在具体目标#2中，我们将检验Nix和Bnip 3诱导的心肌细胞凋亡有助于压力超负荷肥大的心肌病性代偿失调的假设。我们已经开发并验证了横向主动脉缩窄技术。因此，在这些研究中，将对具有Nix和Bnip 3的组合强制心脏表达和心脏特异性缺失的小鼠进行压力超负荷建模，并通过非侵入性超声心动图进行连续评价。这些研究将确定潜在的治疗靶点，以改善由心肌梗死和压力超负荷肥大引起的心力衰竭的结局。如果所述假设被证明是正确的，它将导致我们对心肌病的研究方法发生范式转变，从以压力为中心的方法转变为基于针对包括缺血性和肥大性压力在内的常见病理生理事件的方法。 公共卫生相关性： 心力衰竭是老龄化人群中非常常见的疾病，65岁以上年龄组的发病率和患病率最高，这也是最大的退伍军人人群群体（超过40%）。近三分之一的退伍军人患有缺血性心脏病，另外三分之一患有高血压和/或主动脉瓣狭窄，导致心力衰竭。该提案严格审查了两种心脏表达蛋白Bnip 3和Nix在这些条件下导致心肌细胞死亡的作用，具有开发临床治疗以挽救心肌和预防/治疗心力衰竭流行病的潜力。

DESCRIPTION (provided by applicant): The common cellular event that defines both myocardial infarction and the progression from compensated cardiac hypertrophy to decompensated heart failure is death of cardiomyocytes. In acute infarction, cardiomyocyte necrosis is inevitable due to oxygen/nutrient deprivation, but is followed by a wave of cell-autonomous death, or apoptosis, in the peri-infarct region. Likewise, hemodynamically stressed hearts first undergo hypertrophy, but ultimately fail in part due to apoptotic loss of cardiac myocytes. Importantly, hypertrophy develops in the surviving myocardium after an acute infarct to counterbalance increased hemodynamic load; and ischemia due to lack of angiogenesis is observed in decompensation of pressure overload hypertrophy, thus subjecting hearts to both ischemic and hypertrophic stress as a final common pathway. Therefore in both cases, effective targeting of apoptosis has the potential to retain functional myocardium. This proposal will examine the Hypothesis that cardiomyocyte apoptosis is induced by specific stress-reactive pro-apoptotic factors of the BH3 subfamily of Bcl2 proteins, and that combinatorially targeting the relevant factors in cardiac disease can be an effective means of salvaging myocardium and preventing adverse ventricular remodeling. In published and preliminary experiments we have identified two closely related BH3-only proteins, Bnip3 (Bcl-2/adenovirus E1B 19 kDa interacting protein) and Bnip3-like protein X (Nix), which are expressed in the myocardium, which can cause cellular apoptosis, and most importantly, which are specifically upregulated in myocardial ischemia (Bnip3) and cardiac hypertrophy (Nix). We have created viable mouse models in which the expression of each factor can be experimentally regulated through forced conditional transgenesis and germ-line or cardiac-specific gene ablation. In Specific Aim #1, we will test the hypothesis that Bnip3- and Nix-induced cardiomyocyte apoptosis contributes to adverse ventricular remodeling after myocardial infarction and myocardial ischemia-reperfusion injury. We have developed microsurgical procedures to generate myocardial infarction and ischemia-reperfusion injury in mice with combined forced cardiac expression and cardiac specific deletion of Nix and Bnip3, followed by magentic resonance imaging based serial assessment of infarct size and myocardial sturcture and function, and immunohistochemical detection of cardiomyocyte apoptosis, thus permitting us to analyze the outcomes as a function of Nix and Bnip3 expression. In Specific Aim #2, we will test the hypothesis that Nix- and Bnip3-induced cardiomyocyte apoptosis contributes to cardiomyopathic decompensation of pressure overload hypertrophy. We have developed and validated the technique of transverse aortic constriction. Thus, in these studies, mice with combined forced cardiac expression and cardiac specific deletion of Nix and Bnip3 will be subjected to pressure overload modeling and serially evaluated by noninvasive echocardiography. These studies will identify potential therapeutic targets to improve outcomes in heart failure, stemming from borh myocardial infarction and pressure overload hypertrophy. If the stated hypothesis is proved to be true, it will engender a paradigm shift change our approach to cardiomyopathies from stress-centricism, to one based on a targeting common pathophysiological events encompassing both ischemic and hypertrophic stresses. PUBLIC HEALTH RELEVANCE: Project Narrative Heart failure is a very common disease of the aging population, with the highest incidence and prevalence in the age group above 65, which is also the largest Veteran population group (more than 40%). Nearly one third of the Veterans have ischemic heart disease and another third have hypertension and/or aortic valve stenosis, which cause heart failure. This proposal critically examines the role of two cardiac expressed proteins, Bnip3 and Nix, in causing cardiac muscle cell death in these conditions, with the potential for development of clinical therapies to salvage cardiac muscle and prevent/treat the heart failure epidemic.