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

项目摘要/摘要 心力衰竭(HF)的特征是与肾上腺素能结合的儿茶酚胺水平显著升高。 心脏的受体(AR)。过度的β(β)-AR刺激的毒性效应得到了很好的描述，并且 阻断β-ARs的药物是当代心力衰竭治疗的基石。心脏α(α)1-AR已收到 然而，较少的关注来自细胞和动物研究的数据表明，它们防止发生 高频。心脏有两种α1-AR亚型：α1A和α1B。α1B介导心肌肥厚 由非选择性α1-AR激动剂如苯肾上腺素诱导。α1A的激活可防止 心肌细胞死亡并增加衰竭心脏的收缩能力，尽管其背后的机制 人们对适应性效应知之甚少。我们最近发现了一种口服选择性α1A激动剂药物， Dabuzalgron，在小鼠心力衰竭模型中保护ATP含量和线粒体功能。这些保护作用 曲美替尼是一种用于治疗黑色素瘤的MEK-ERK1/2抑制剂。我们最近的初步数据 在这些新发现的基础上，提出α1A激活可能通过以下途径改善心脏能量学 提高葡萄糖利用率，通过增强氧化作用将糖酵解与葡萄糖氧化结合起来 磷酸化。这一建议的主要假设是，α1A-AR通过 ERK1/2介导的葡萄糖代谢增加，抵消了 心衰时慢性β-1过度刺激。在目标1中，我们将使用心肌细胞特异性α1A-AR基因敲除小鼠 两种小鼠病理性肥厚和心力衰竭模型对心肌细胞α1As的需求 达布扎隆的心脏保护作用。在目标2中，我们将发现α1A-AR激活是否会增强血糖 利用体内和体外联合应用横主动脉缩窄为衰竭心脏提供能量 使用选择性药理学和基因沉默来识别关键代谢过程和信号的研究 受α1A激活影响的通路。目标3将确定ERK1/2激活在α1A介导的过程中的作用 代谢性心脏保护，使用曲美替尼和MEK-ERK轴的遗传修饰来提供新的 ERK1/2信号在调节葡萄糖代谢和线粒体功能中的作用。 总的来说，拟议的实验将扩大我们对心脏α1A-ARs的理解，并挑战 普遍认为，慢性儿茶酚胺激增对衰竭的心脏产生一致的有害影响。

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.