New Molecular Target for Cardiac Aging

 描述(由申请人提供)：本申请涉及衰老对心血管功能、心脏老化(CA)和充血性心力衰竭(CHF)影响的最基本方面之一。心肌老化会导致心功能和β-肾上腺素能储备的进行性下降，从而增加CHF和心脏发病率的风险。然而，确切的机制尚不清楚。本研究旨在探讨3-肾上腺素能受体(ARs)介导的信号通路在CA中的作用和机制。这一途径对心功能有负面影响，但在与年龄相关的心功能障碍方面受到的关注有限。我们最近的观察表明，随着年龄的增长，心功能的负性调节、[Ca~(2+)]_i调节和肌细胞内肾上腺素能信号的有效性增强，从而上调了心肌的β_3-AR。慢性β3-AR刺激可引起心肌诱导型一氧化氮合酶(INOS)表达上调及其解偶联。INOS去偶联引起的氧化应激进一步加重心功能不全。这些由衰老引起的改变在3-AR基因敲除的老年小鼠中被阻止，而在野生型(WT)老年小鼠中被3-受体拮抗剂(ANT)逆转，提示心脏的3-AR的改变可能是CA发生发展的关键因素。我们将检验Central假说，即作为衰老诱导的交感神经过度驱动(伴随着儿茶酚胺水平升高)的结果，心脏ç3-AR信号的上调不仅有助于CA，而且是CA的重要原因。因此，用选择性的？3-ANT拮抗？3-AR在预防和治疗CA方面是有效的，导致？3-AR的表达和心肌细胞的钙循环/处理正常化，同时有助于保护？1-和？2-AR，并有助于老年人的心室动脉去僵硬。研究将在年龄匹配和性别匹配的SPF幼鼠和老年小鼠中进行，其中对照野生型(WT)、？3Tg/？3KO和老年WT使用和不使用慢性？3-ANT治疗。提出了三个具体目标来研究完整的动物、分离的心肌细胞和分子机制。采用综合和多学科的方法，对这些动物的左室结构改变、左室和心肌细胞以及血管功能、心脏钙处理、基因表达、氧化还原状态、一氧化氮合酶偶联状态和神经激素激活的连续和同步测量将表征？3-AR介导的与CA相关的分子和细胞信号转导的功能反应的变化，并确定？3-ANT治疗在CA中的作用和机制。这项工作将从多个层面(心脏、细胞、亚细胞和分子)揭示衰老引起的改变。 并收集关于3-、1-和2-ARs的平衡以及3-AR介导的一氧化氮信号如何影响衰老时心血管功能的重要见解。这是一项极具创新性的建议，其结果将产生重大影响，加深我们对CA和CHF关键机制的理解，并可能为这一重要问题带来新的治疗靶点。这些研究也为研究人类CA中的3-受体阻滞剂提供了理论基础。

 DESCRIPTION (provided by applicant): This application addresses one of the most fundamental aspects of the effect of aging on cardiovascular function, cardiac aging (CA), and congestive heart failure (CHF). Myocardial aging leads to a progressive decline in cardiac function and ß-adrenergic reserve, which increases the risk of CHF and cardiac morbidity. However, the precise mechanism is unclear. This grant investigates the role and mechanism of the signaling pathway mediated by ß3-adrenergic receptors (ARs) in CA. This pathway has negative effects on cardiac function, but has received limited attention in age-associated cardiac dysfunction. Our recent observations have shown that aging up-regulates cardiac ß3-ARs with enhanced ß3-AR-mediated negative modulations on cardiac function, [Ca2+]i regulation and the effectiveness of ß-adrenergic signaling. Chronic ß3-AR stimulation triggers up-regulation of cardiac inducible nitric oxide synthase (iNOS) and its uncoupling. Oxidant stress from iNOS uncoupling further aggravates cardiac dysfunction. These aging-induced alterations were prevented in ß3-AR knockout (ß3KO) aged mice and were reversed through treatment with a ß3-antagonist (ANT) in wild- type (WT) aged mice, suggesting that alteration of cardiac ß3-AR may be a critical element in the development of CA. We will test the Central Hypothesis that up-regulation of cardiac ß3-AR signaling, as a consequence of aging-induced sympathetic overdrive (with elevated catecholamine levels), not only contributes to, but is an important cause of CA. Thus, antagonizing ß3-AR with a selective ß3-ANT would be effective on the prevention and treatment of CA, leading to a normalization of ß3-AR expression and Ca2+ cycling/handling of cardiomyocytes, while contributing to the preservation of ß1-and ß2-ARs and ventricular arterial de-stiffening in the elderly. Studies will be conducted in age-matched and sex-matched SPF young and aged mice of control wild-type (WT), ß3KO, ß3TG/ß3KO and aged WT with and without chronic ß3-ANT treatment. Three specific aims are proposed to study intact animals, isolated cardiomyocytes, and molecular mechanisms. Using an integrative and multidisciplinary approach, serial and simultaneous measurements of LV structure alterations, LV and myocyte as well as vascular functional performance, cardiac calcium handling, gene expression, redox state, NOS coupling status, and neurohormonal activation in these animals will characterize the alterations of ß3-AR-mediated functional responses with related molecular and cellular signal transductions of CA and define the role and mechanism of ß3-ANT therapy in CA. This work will unravel aging-induced alterations at multiple levels (heart, cellular, sub-cellular, and molecular) and glean crucial insights concerning how the balance of ß3- , ß1-, and ß2-ARs and the altered ß3-AR-mediated nitric oxide signaling affects cardiovascular performance in aging. This is a highly innovative proposal, and the outcomes will have a high impact, enhancing our understanding of the pivotal mechanisms of CA and CHF and may lead to new therapeutic targets for this important problem. These studies may also provide the rationale for the study of ß3-blockers in human CA.