Disruption of Autonomic Pathways in Left Atrium by Inhibition of G Proteins

描述（由申请人提供）：房颤（AF）是最常见的心脏节律紊乱，是导致严重疾病（如充血性心力衰竭和脑血管栓塞（“卒中”））的主要原因。最近发现，与正常窦性心律患者相比，AF与死亡率显著增加相关。重要的是，这种心律失常的发生率随着年龄的增长而增加，结果是AF正在迅速成为老龄化人群中的最新“流行病”。因此，房颤的诊断和管理已成为心血管医学的一个重要和具有挑战性的方面。然而，有效治疗房颤的进展缓慢，很大程度上是由于对这种心律失常的潜在机制了解不足。在这方面，最近的研究表明，肺静脉和左心房后壁（PLA）在这种心律失常的发生中起着重要作用。因此，在PLA中进行了一些开创性的消融手术，尽管成功率参差不齐。在心脏中，G蛋白偶联受体（GPCR）及其同源信号伴侣，异源三聚体G蛋白，调节大多数机械和电功能。自主神经系统调节关键的心脏参数，如兴奋性、心率、收缩力、传导速度和不应性。与Gs偶联的β 2-肾上腺素能受体的激活导致心脏中传导速度和几种其他兴奋性反应的增加。与Gi偶联的毒蕈碱M2受体的激活导致心房中不应期的显著缩短。在组合中，这两个分支的自主神经系统已被证明创建AF的基板。因此，肾上腺素能和毒蕈碱受体或其合作伙伴Gi和Gs可能是可行的替代目标的治疗策略，旨在调节心脏中的致炎性影响。PLA可能是这些策略的一个特别有吸引力的目标，考虑到一个非常强大的和独特的自主的配置文件，被认为是有益的AF。肽模拟的C-末端的各种G1蛋白已被证明在许多系统中选择性地抑制受体信号转导作为竞争性抑制剂和阻断的能力，受体耦合到适当的G蛋白。在尝试修改AF的底物。我们建议使用针对GPCR/G蛋白界面的肽来选择性地抑制PLA中的副交感神经或交感神经通路。我们将使用单独的肽（即细胞穿透肽）或可以表达肽的小基因（质粒）。我们将在a）分离的犬心肌细胞中进行这些研究，以研究肽对介导自主神经效应的离子通道的影响，并在B）完整的狗中进行这些研究，将肽局部注射到PLA中，以抑制迷走神经或肾上腺素介导的AF。拟议的研究是朝着确定最终可能应用于治疗危及生命的心律失常的新型疗法迈出的重要一步。心房颤动（AF）是最常见的心脏节律紊乱，是导致严重疾病如充血性心力衰竭和中风的主要原因。然而，目前可用的AF治疗方案不是很有效。我们建议使用一种新的方法来治疗AF，通过抑制对这种心律失常的发生至关重要的神经的功能。通过使用一种新的抑制蛋白，我们将选择性地阻断左心房的这些神经。

DESCRIPTION (provided by applicant): Atrial fibrillation (AF) is the commonest rhythm disturbance of the heart, and is a major cause of serious morbidity such as congestive heart failure and cerebrovascular embolism (`stroke'). More recently, AF has been found to be associated with significantly increased mortality, compared to patients in normal sinus rhythm. Importantly, the incidence of this arrhythmia increases with age, with the result that AF is fast becoming the latest `epidemic' in an aging population. The diagnosis and management of AF have therefore become an important and challenging aspect of cardiovascular medicine. However, progress in effectively treating AF has been slow, in large part due to a poor understanding of the underlying mechanisms of this arrhythmia. In this regard, recent studies indicate an important role for the pulmonary veins and the posterior left atrium (PLA) in the genesis of this arrhythmia. Several pioneering ablative procedures have therefore been performed in the PLA, albeit with mixed success. In the heart, G protein coupled receptors (GPCRs) and their cognate signaling partners, the heterotrimeric G-proteins, regulate most mechanical and electrical functions. The autonomic nervous system regulates critical cardiac parameters such as excitability, heart rate, force of contraction, conduction velocity and refractoriness. Activation of 2-adrenergic receptors, which are coupled to Gs, leads to an increase in conduction velocity and several other excitatory responses in the heart. Activation of muscarinic M2 receptors, which are coupled to Gi, leads to a marked shortening of refractoriness in the atria. In combination, these two limbs of the autonomic nervous system have been demonstrated to create substrate for AF. Thus, the adrenergic and muscarinic receptors or their partners Gi and Gs may be viable alternative targets for therapeutic strategies designed to modulate arrhythmogenic influences in the heart. The PLA may be an especially attractive target for these strategies, on account of a very robust and unique autonomic profile that is thought to be conducive to AF. Peptides which mimic the C-terminus of the various G1 proteins have been shown in a number of systems to selectively inhibit receptor signaling by serving as competitive inhibitors and blocking the ability of the receptor to couple to the appropriate G protein. In an attempt to modify substrate for AF. We propose to use peptides directed at the GPCR/G protein interface to selectively inhibit parasympathetic or sympathetic pathways in the PLA. We will use either the peptide alone (i.e. cell-penetrating peptides) or a minigene (plasmid) that can express the peptide. We will perform these studies in a) isolated canine cardiomyocytes, to study the effects of the peptide(s) on ion-channels that mediate autonomic effects, and in b) intact dogs, with localized injection into the PLA in order to inhibit vagally or adrenergically-mediated AF. The proposed studies are an important stride towards identifying novel therapeutics that may eventually be applied to the treatment of life threatening arrhythmias. Atrial fibrillation (AF) is the commonest rhythm disturbance of the heart, and is a major cause of serious morbidity such as congestive heart failure and stroke. However, currently available treatment options for AF are not very effective. We propose to use a new method to treat AF, by inhibiting the function of the nerves that are critical to the genesis of this arrhythmia. By using a new inhibitory protein, we will selectively block these nerves in the left atrium.