Abnormal intracellular calcium release in heart failure

描述（由申请人提供）：心力衰竭（HF）是一种日益普遍的疾病，当心肌无法维持足够的心输出量时发生。HF患者遭受并最终死于心脏机械功能的进行性衰竭（泵衰竭）或室性心律失常。与心肌细胞肥大和/或死亡相关的心脏病理结构重塑是HF的常见特征。由于心脏Ryanodine受体（RyR 2）功能失调（即“渗漏RyR 2”）引起的肌浆网（SR）的Ca释放改变已与HF中的收缩功能障碍和心律失常以及衰竭心脏的结构重塑有关。然而，缺乏将RyR 2功能异常与HF因果联系起来的直接证据。目前还不清楚RyR 2异常如何导致HF的不同表现，如收缩功能障碍和血管生成。类似地，RyR 2介导的信号传导在衰竭心脏中肥大途径和细胞死亡的激活中的具体作用和机制仍有待阐明。这些信息对于理解HF的病理生理学和开发新型的机械靶向HF疗法至关重要。因此，我们将使用SR Ca释放失调的新遗传模型直接检查异常RyR 2介导的Ca信号传导和心脏病理过程之间的因果关系。此外，我们的研究结果对“真实的”HF的适用性将在临床相关的 确认RyR 2功能障碍。具体目标是：1）确定钙依赖性心脏病遗传模型中异常SR Ca释放和收缩功能障碍之间的关系; 2）确定钙依赖性心脏病遗传模型中将失调的SR Ca释放与病理性重塑和肌细胞死亡联系起来的特定细胞内信号传导机制;和3）：为了检验SR Ca释放失调导致HF的假设，并探索Ca释放不应性的正常化作为临床治疗策略，HF的相关模型我们提出了一种系统的，综合的方法来测试这些假设，使用先进的和最先进的方法，包括单RyR 2通道记录，细胞多房室钙成像，多细胞钙成像和收缩测量，钙和膜电位映射在整个心脏，并在体内的电和机械功能的测量。我们的系统方法将使我们能够直接解决第一次的具体机制，因果关系异常SR钙释放收缩功能障碍和病理性重塑，并探索新的治疗策略，通过针对这些机制的HF。

DESCRIPTION (provided by applicant): Heart failure (HF) is an increasingly prevalent disease that occurs when the cardiac muscle is unable to maintain a sufficient cardiac output. HF patients suffer, and eventually die from either progressive failure of cardiac mechanical function (pump failure) or ventricular arrhythmias. Pathological structural remodeling of the heart associated with myocyte hypertrophy and/or death is a common feature of HF. Altered Ca release from the sarcoplasmic reticulum (SR) due to deregulated cardiac ryanodine receptor (RyR2) function (i.e. "leaky RyR2s") has been implicated in both contractile dysfunction and arrhythmias in HF as well as in the structural remodeling of the failing heart. However, direct evidence to causally link abnormal RyR2 function to HF is lacking. It also remains unclear how RyR2 abnormalities can lead to such differing manifestations of HF as contractile dysfunction and arrhythmogenesis. Similarly, the specific role and mechanisms of RyR2-mediated signaling in activation of hypertrophic pathways and cell death in the failing heart remains to be elucidated. This information is essential for understanding the pathophysiology of HF and for the development of novel, mechanistically-targeted HF therapies. Thus, we will directly examine the cause- effect relationships between abnormal RyR2-mediated Ca signaling and cardiac pathological processes using novel genetic models of dysregulated SR Ca release. Furthermore, the applicability of our findings to "real" HF will be tested in a clinically relevant model with confirmed RyR2 dysfunction. The specific aims are: 1) To determine the relationship between abnormal SR Ca release and contractile dysfunction in genetic models of Ca-dependent cardiac disease; 2) To define the specific intracellular signaling mechanisms that link dysregulated SR Ca release to pathological remodeling and myocyte death in genetic models of Ca-dependent cardiac disease; and 3):To test the hypothesis that dysregulated SR Ca release contributes to HF and probe normalization of Ca release refractoriness as a treatment strategy in a clinically relevant model of HF. We propose a systematic, integrated approach to test these hypotheses using advanced and state-of-the-art methods including single RyR2 channel recordings, cellular multi- compartmental Ca imaging, multicellular Ca imaging and contraction measurements, Ca- and membrane potential mapping in whole hearts, and measurements of in vivo electrical and mechanical function. Our systematic approach will allow us to directly address for the first time the specific mechanisms that causally link abnormal SR Ca release to contractile dysfunction and pathological remodeling and to explore new therapeutic strategies for HF by targeting these mechanisms.