Metabolic mechanisms of cardioprotection through alpha-1A adrenergic receptor activation

项目总结/摘要 心力衰竭（HF）的特征是与肾上腺素能受体结合的儿茶酚胺水平显著升高。 受体（AR）在心脏。过度β-AR刺激的毒性作用已得到充分描述， 阻断β-AR的药物是当代HF治疗的基础。心脏α（α）1-AR已收到 然而，来自细胞和动物研究的数据表明，它们可以防止 HF。心脏中有两种α1-AR亚型：α1A和α1B。α1B介导心肌肥厚 由非选择性α1-AR激动剂如苯乙哌啶诱导。激活α1A可以防止 心肌细胞死亡，并增加收缩力在衰竭的心脏，虽然这些机制的基础 人们对适应性效应知之甚少。我们最近发现，口服选择性α1A激动剂药物， dabuzalgron在小鼠HF模型中保留ATP含量和线粒体功能。这些保护作用 被曲美替尼（一种用于治疗黑色素瘤的MEK-ERK 1/2抑制剂）消除。我们最近的初步数据 通过表明α1A激活可能通过以下途径改善心脏能量学， 增加葡萄糖利用率，通过增强的氧化作用将增强的糖酵解与葡萄糖氧化偶联 磷酸化这项提议的首要假设是，α 1A-AR通过以下途径保护衰竭的心脏： ERK 1/2介导的葡萄糖代谢增加，其抵消了 HF中的慢性β1过度刺激。在目标1中，我们将使用心肌细胞特异性α1A-AR敲除小鼠， 两种病理性肥大和HF小鼠模型，以证实心肌细胞α1As的需求， 达布扎隆的心脏保护作用在目的2中，我们将发现α1A-AR激活是否增强葡萄糖 利用体内横向主动脉缩窄结合体外 使用选择性药理学和基因沉默来确定关键代谢过程和信号传导的研究 受α1A激活影响的通路。目的3将明确ERK 1/2激活在α 1A介导的细胞凋亡中的作用。 代谢性心脏保护，使用曲美替尼和MEK-ERK轴的基因修饰来提供新的 ERK 1/2信号在葡萄糖代谢和线粒体功能调节中的作用。 总的来说，拟议的实验将扩大我们对心脏α 1A-AR的理解，并挑战 流行的范式，慢性儿茶酚胺激增发挥统一的有害影响，在衰竭的心脏。

PROJECT SUMMARY/ABSTRACT Heart failure (HF) is characterized by markedly elevated levels of catecholamines that bind to adrenergic receptors (ARs) in the heart. The toxic effects of excessive beta (β)-AR stimulation are well described, and drugs that block β-ARs are cornerstones of contemporary HF therapy. Cardiac alpha (α)1-ARs have received less attention, however data from cell and animal studies indicate that they protect against the development of HF. There are two α1-AR subtypes in the heart: α1A, and α1B. The α1B mediates cardiac hypertrophy induced by non-selective α1-AR agonists like phenylephrine. Activation of the α1A protects against cardiomyocyte death and increases contractility in the failing heart, though the mechanisms underlying these adaptive effects are poorly understood. We recently showed that an oral selective α1A agonist drug, dabuzalgron, preserves ATP content and mitochondrial function in mouse HF models. These protective effects were abrogated by trametinib, a MEK-ERK1/2 inhibitor used to treat melanoma. Our recent preliminary data expand upon these novel findings by suggesting that α1A activation may improve cardiac energetics through increased glucose utilization, coupling augmented glycolysis to glucose oxidation through enhanced oxidative phosphorylation. The overarching hypothesis of this proposal is that α1A-ARs protect the failing heart through an ERK1/2-mediated increase in glucose metabolism that counteracts the deleterious metabolic effects of chronic β1 hyperstimulation in HF. In Aim 1, we will use a cardiomyocyte-specific α1A-AR knockout mouse in two mouse models of pathological hypertrophy and HF to confirm the requirement of cardiomyocyte α1As for the cardioprotective effects of dabuzalgron. In Aim 2, we will find if α1A-AR activation enhances glucose utilization to provide energy for the failing heart using transverse aortic constriction in vivo coupled with in vitro studies using selective pharmacology and gene silencing to identify key metabolic processes and signaling pathways affected by α1A activation. Aim 3 will define the role of ERK1/2 activation in α1A-mediated metabolic cardioprotection, using both trametinib and genetic modification of MEK-ERK axis to provide new insights on the role of ERK1/2 signaling in the regulation of glucose metabolism and mitochondrial function. Collectively the proposed experiments will expand our understanding of cardiac α1A-ARs and challenge the prevailing paradigm that chronic catecholamine surge exerts uniformly deleterious effects in the failing heart.