Abnormal intracellular calcium release in heart failure

描述(申请人提供)：心力衰竭(HF)是一种日益流行的疾病，当心肌无法维持足够的心输出量时发生。心衰患者遭受心脏机械功能进行性衰竭(泵衰竭)或室性心律失常的折磨，最终死亡。心脏病理结构重构与心肌细胞肥大和/或死亡相关，是心衰的共同特征。心脏兰尼定受体(RyR2)功能失调引起的肌浆网(SR)钙释放的改变(即RyR2的泄漏)与心衰时的收缩功能障碍和心律失常以及心功能衰竭的结构重构有关。然而，缺乏将RyR2功能异常与心衰联系起来的直接证据。目前还不清楚RyR2异常如何导致不同的心衰表现，如收缩功能障碍和心律失常。同样，RyR2介导的信号在衰竭心脏肥大通路激活和细胞死亡中的具体作用和机制仍有待阐明。这些信息对于了解心力衰竭的病理生理学和开发新的、机械靶向的心力衰竭疗法是必不可少的。因此，我们将利用SR钙释放异常的新遗传模型，直接研究RyR2介导的钙信号异常与心脏病理过程之间的因果关系。此外，我们的发现对“真正的”心衰的适用性将在一项临床相关的研究中进行测试。 已确认RyR2功能障碍的模型。其具体目的是：1)确定钙依赖型心脏病遗传模型中SR钙释放异常与收缩功能障碍之间的关系；2)确定钙依赖型心脏病遗传模型中SR钙释放异常与病理重构和心肌细胞死亡之间的特定细胞内信号机制；3)验证SR钙释放异常参与心衰的假说，并探讨钙释放难治性正常化作为心衰临床相关模型的治疗策略。我们提出了一种系统的、集成的方法来验证这些假设，方法包括单RyR2通道记录、细胞多室钙成像、多细胞钙成像和收缩测量、整个心脏的钙和膜电位标测以及体内电和机械功能的测量。我们的系统方法将使我们能够首次直接解决SR Ca释放异常与收缩功能障碍和病理重塑之间的具体机制，并通过靶向这些机制来探索新的治疗策略。

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.