Right ventricular contractile dysfunction after pressure overload

描述（由申请人提供）： 急性肺动脉高压引起的右心室（RV）收缩功能衰竭是大面积肺栓塞、缺氧性肺血管收缩、体外循环和心脏移植后发病和死亡的重要原因，但目前尚无有效的治疗策略。在申请人的实验室中在大型动物模型中进行的研究已经证明，急性肺动脉高压引起的RV收缩衰竭与RV中半胱氨酸蛋白酶钙蛋白酶的激活相关，并且在这种情况下的右心衰竭可以通过钙蛋白酶抑制剂来减弱。 钙蛋白酶的激活在骨骼肌和心肌功能障碍的多种模型中均有发生，但对钙蛋白酶激活的上游机制和下游靶点仍存在争议：根据实验模型，收缩功能障碍被归因于结构蛋白如结蛋白、血影蛋白、1-辅肌动蛋白或肌联蛋白的破坏;调节蛋白如肌钙蛋白-I、肌钙蛋白-T的修饰;或细胞凋亡的启动。 本项目的总体目标是确定急性右心室压力超负荷引起钙蛋白酶激活和右心室收缩功能障碍的机制。我们已经表明，降解的粘着斑复合物蛋白塔林，一个已知的钙蛋白酶底物，是高度相关的RV功能障碍的严重程度，并已获得初步数据显示，钙蛋白酶重新分配到心肌细胞膜在急性肺动脉高压。其他研究者提出钙蛋白酶可能受非电压门控钙通道TRPM 7、细胞外反应激酶ERK直接磷酸化或酪氨酸激酶src磷酸化钙蛋白酶靶点的调节。因此，我们提出以下两个假设：假设#1：急性肺动脉高压诱导的钙蛋白酶激活依赖于钙通道TRPM 7，ERK和/或src。 假设#2：急性肺动脉高压时局部钙蛋白酶激活通过粘着斑复合物（costameric）蛋白（如talin）的降解导致RV功能障碍。 为了检验这些假设，我们提出了以下具体目标：具体目标1：采用啮齿动物RV乳头肌的急性RV压力超负荷的新离体模型，以确认我们建立的急性RV压力超负荷的体内猪模型的结果。 具体目标2：确定导致压力超负荷诱导RV功能障碍的信号通路和蛋白质修饰。 具体目标3：确定压力超负荷诱导的RV功能障碍是否取决于TRPM 7、ERK或src。具体目标4：确定目前临床试验中的蛋白酶或蛋白激酶抑制剂是否可以减轻急性RV压力超负荷时的右心衰竭。 我们将使用已建立的大型动物（猪）体内急性肺动脉高压模型，结合使用分离的大鼠RV乳头肌的急性RV压力超负荷的新离体模型。将评估大鼠RV乳头肌在收缩应力下的蛋白质再分布和修饰的生化和组织学证据，并确定钙蛋白酶和蛋白激酶抑制剂对这些改变的影响，以模拟急性RV压力超负荷。在猪模型中进行的体内平行实验将用于确定离体啮齿动物乳头肌模型结果的生理学意义。将使用分离的乳头肌模型鉴定具有潜在临床实用性的药物，并在猪模型中进行测试。

DESCRIPTION (provided by applicant): Right ventricular (RV) contractile failure from acute pulmonary hypertension is an important cause of morbidity and mortality in conditions such as massive pulmonary embolism, hypoxic pulmonary vasoconstriction, and following cardiopulmonary bypass and cardiac transplantation, but effective therapeutic strategies are not currently available. Studies in the applicant's laboratory performed in a large animal model have demonstrated that RV contractile failure from acute pulmonary hypertension is associated with activation of the cysteine protease calpain in the RV, and that right heart failure in this setting may be attenuated by a calpain inhibitor. Calpain activation has been shown to occur in numerous models of both skeletal and cardiac muscle dysfunction, but there is controversy over both the upstream mechanism of calpain activation and the downstream targets of activated calpain: depending on the experimental model, contractile dysfunction has been attributed to disruption of structural proteins such as desmin, spectrin, 1-actinin or titin; modification of regulatory proteins such as troponin-I, troponin-T; or initiation of apoptosis. The overall goal of this project is to identify the mechanism by which acute RV pressure overload causes calpain activation and right ventricular contractile dysfunction during and following acute RV pressure overload. We have shown that degradation of the focal adhesion complex protein talin, a known calpain substrate, is highly correlated with the severity of RV dysfunction, and have obtained preliminary data showing that calpain redistributes to the myocyte membrane during acute pulmonary hypertension. Other investigators have proposed that calpain may be regulated by the non-voltage gated calcium channel TRPM7, by direct phosphorylation by the extracellular response kinase ERK, or by phosphorylation of calpain targets by the tyrosine kinase src. Therefore, we propose the following two hypotheses: Hypothesis #1: Acute pulmonary hypertension induced activation of calpain is dependent on the calcium channel TRPM7, ERK, and/or src. Hypothesis #2: Localized calpain activation in acute pulmonary hypertension causes RV dysfunction through degradation of focal adhesion complex (costameric) proteins such as talin. To test these hypotheses, we propose the following Specific Aims: Specific Aim 1: Employ a new ex vivo model of acute RV pressure overload using rodent RV papillary muscle to confirm findings from our established in vivo porcine model of acute RV pressure overload. Specific Aim 2: Identify signaling pathways and protein modifications that contribute to pressure overload induced RV dysfunction. Specific Aim 3: Determine if pressure overload induced RV dysfunction depends on TRPM7, ERK or src. Specific Aim 4: Determine whether protease or protein kinase inhibitors currently in clinical trials can attenuate right heart failure in acute RV pressure overload. We will use an established large animal (pig) in vivo model of acute pulmonary hypertension in conjunction with a new ex vivo model of acute RV pressure overload employing isolated rat RV papillary muscles. Rat RV papillary muscles subjected to contractile stress, modeling acute RV pressure overload, will be assessed for biochemical and histological evidence of protein redistribution and modification, and the effects of calpain and protein kinase inhibitors on these alterations will be determined. Parallel experiments performed in vivo in the pig model will be used to establish the physiological significance of findings from the ex vivo rodent papillary muscle model. Agents with potential clinical utility will be identified using the isolated papillary muscle model and tested in the pig model.