Molecular basis and proarrhythmic role of enhanced small conductance Ca2+ activated K+ channels in patients with atrial fibrillation

心房颤动患者增强小电导Ca2+激活K通道的分子基础及其促心律失常作用

• 批准号: 349202494
• 负责人: Professor Dr. Dobromir Dobrev
• 金额: --
• 依托单位: Institut für Pharmakologie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2017
• 资助国家: 德国
• 起止时间: 2016-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/349202494?language=en
• 关键词: Molecular; basis; proarrhythmic; role; enhanced

Atrial fibrillation (AF) is a frequent arrhythmia increasing morbidity and mortality. Current antiarrhythmic drugs have suboptimal efficacy and potentially severe adverse effects. There is a clear need for the identification of new atrial selective targets for AF therapy, since this produces less unwanted ventricular effects. Although atrial selective small conductance Ca2+ activated K+ channels (SK channels) have emerged as a potential target for anti AF therapy, their precise function and specific contribution to AF mechanisms in the human atrium is not established. The role of potentially increased SK channel current (ISK) in atrial arrhythmogenesis is complex. It might favour reentry by abbreviating action potential duration (APD), but can also be antiarrhythmic by reducing automaticity/triggered activity through membrane hyperpolarization/reduced excitability. Based on our previous work highlighting a central role for AF related Ca2+ handling abnormalities in atrial cardiomyocytes and our preliminary work on ISK dysregulation in AF patients, we hypothesize that enhanced ISK provides a link between Ca2+ dependent triggered activity (SR Ca2+ leak) and reentry (shorter APD), playing a critical role in the formation of the proarrhythmic substrate supporting AF maintenance. Therefore, the primary goal of this application is to discover and dissect the cellular and molecular mechanisms of enhanced ISK in AF and to delineate the precise contributions of ISK to APD shortening and arrhythmia mechanisms in AF patients. As an initial step we will exploit molecular biology techniques to validate the expression of SK channel isoforms and their regulatory proteins, identify the cellular and molecular determinants of SK channel trafficking and establish potential abnormalities in the complex organization and local regulation of SK channels that could alter Ca2+ dependent channel gating in AF patients. Then we will functionally assess the Ca2+ concentration response relationship of ISK including contribution of Ca2+ influx vs. internal Ca2+ release, explore the role of different actin based and microtubule driven trafficking pathways and test the effects of AF relevant atrial rates on the regulation of ISK in AF patients. Finally we will refine the contribution of ISK to human atrial AP and dissect the proarrhythmic (contribution to the reentrant substrate by causing APD shortening) and anti arrhythmic (protection against afterdepolarization mediated focal ectopic [triggered] activity) consequences of pharmacological ISK modulation in AF patients. Combined the proposed experiments will provide molecular and functional insights into the ISK determinants, their remodeling and regulation in AF. Ultimately, the insights from this work should facilitate the identification of novel therapeutic targets in AF patients.

心房颤动（房颤）是一种常见的心律失常，其发病率和死亡率不断增加.目前的抗疟疾药物疗效欠佳，并可能产生严重的副作用。明确需要识别用于AF治疗的新的心房选择性靶点，因为这产生较少的不期望的心室效应。尽管心房选择性小电导钙激活钾通道（SK通道）已成为抗房颤治疗的潜在靶点，但其在人心房房颤机制中的确切功能和特异性作用尚不明确。潜在增加的SK通道电流（ISK）在心房肌发生中的作用是复杂的。它可能通过延长动作电位时程（APD）有利于折返，但也可以通过减少自律性/通过膜超极化/降低兴奋性触发活动来抗心律失常。基于我们先前的工作强调了心房肌细胞中AF相关Ca 2+处理异常的核心作用，以及我们对AF患者ISK失调的初步研究，我们假设增强的ISK提供了Ca 2+依赖性触发活动（SR Ca 2+泄漏）和折返（较短APD）之间的联系，在支持AF维持的促心律失常底物的形成中发挥关键作用。因此，本申请的主要目标是发现和剖析AF中ISK增强的细胞和分子机制，并描述ISK对AF患者APD缩短和心律失常机制的精确贡献。作为第一步，我们将利用分子生物学技术来验证SK通道亚型及其调控蛋白的表达，确定SK通道运输的细胞和分子决定因素，并建立可能改变AF患者Ca 2+依赖性通道门控的SK通道复杂组织和局部调控的潜在异常。然后，我们将从功能上评估ISK的Ca 2+浓度反应关系，包括Ca 2+内流与内部Ca 2+释放的贡献，探索不同的肌动蛋白和微管驱动的运输途径的作用，并测试AF相关的心房率对AF患者ISK调节的影响。最后，我们将细化ISK对人类心房AP的贡献，并分析AF患者中药物ISK调节的预防（通过引起APD缩短对折返底物的贡献）和抗心律失常（保护免受后去极化介导的局灶性异位[触发]活动）后果。结合拟议的实验将提供分子和功能的ISK决定因素，他们的重塑和AF的监管。最终，从这项工作的见解应有助于识别新的治疗AF患者的目标。