Effects of cocaine on cardiac ion channels

可卡因对心脏离子通道的影响

• 批准号: 6623098
• 负责人: MICHAEL E O'LEARY
• 金额: $ 7.85万
• 依托单位: THOMAS JEFFERSON UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-03-05 至 2005-02-28
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6623098
• 关键词: Xenopus; Xenopus oocyte; action potentials; cardiotoxin; cocaine; drug abuse; drug receptors; heart electrical activity; ion channel blocker; potassium channel; receptor binding; site directed mutagenesis; sodium channel; tissue /cell culture; voltage /patch clamp

The experiments outlined in this proposal will examine the medical and health consequences of cocaine abuse, which has been identified as NIDA as a serious problem in this country. Since 1998 the use of cocaine in the US has risen, in part due to the low cost and ample supply. Paralleling this trend has been an increase in the rate of emergency room admissions related to cocaine use and cocaine-related deaths. The exact causes of the cocaine-related fatalities in most cases are not known but many are believed to result from cardiac arrhythmias, the leading cause of death associated with cocaine abuse. In humans, cocaine is known to increase heart rate and blood pressure, effects that are primarily attributable to the sympathomimetic actions of this drug. Cocaine also produces significant changes in cardiac electrophysiology, decreasing the conduction and slowing the repolarization following an action potential. These electrical disturbances are believed to result from a direct anesthetic effect of cocaine on cardiac ion channels. In this proposal, we will investigate the cocaine sensitivity of sodium and potassium channels important for initiating and terminating the cardiac action potential. Inhibiting these channels disrupts the coordinated electrical activity of the heart, a well-known risk factor for the generation of ventricular arrhythmias. A combination of electrophysiology and molecular biology will be used to investigate the mechanisms of inhibition of these channels and to identity sites important for cocaine binding. The human cardiac sodium channel (hH1) and the human ether-a-g-go delayed rectifier potassium channel (HERG) will be expressed in mammalian cells and the resulting currents recorded using patch clamp techniques. Our data indicate that cocaine binding to these channels is state-dependent, with cocaine preferentially binding to the open and inactivated channels. Inactivation-deficient mutants of hH1 and HERG will be constructed to investigate the contribution of inactivation gating to cocaine binding and to facilitate the measurement of open-channel block. Additional mutants with the sixth transmembrane spanning segments, the putative anesthetic binding sites of these channels, will also be investigated. The proposed studies ill provide insight into the mechanisms underlying the cocaine-induced changes in cardiac electrophysiology and the cardiotoxic effects of this drug.

该提案中概述的实验将检查可卡因滥用对医疗和健康的影响，可卡因滥用已被 NIDA 确定为该国的一个严重问题。自 1998 年以来，美国可卡因的使用量有所增加，部分原因是成本低廉且供应充足。与这一趋势相平行的是，与可卡因使用相关的急诊室入院率和与可卡因相关的死亡人数有所增加。 在大多数情况下，与可卡因相关的死亡的确切原因尚不清楚，但据信许多病例是由心律失常造成的，心律失常是与可卡因滥用相关的主要原因。众所周知，可卡因会增加人类的心率和血压，这种作用主要归因于该药物的拟交感神经作用。可卡因还会使心脏电生理学产生显着变化，减少动作电位后的传导并减缓复极化。这些电干扰被认为是由可卡因对心脏离子通道的直接麻醉作用引起的。在本提案中，我们将研究钠和钾通道的可卡因敏感性，这对于启动和终止心脏动作电位很重要。抑制这些通道会破坏心脏的协调电活动，这是产生室性心律失常的众所周知的危险因素。电生理学和分子生物学的结合将用于研究这些通道的抑制机制并识别对可卡因结合重要的位点。人类心脏钠通道 (hH1) 和人类 ether-a-g-go 延迟整流钾通道 (HERG) 将在哺乳动物细胞中表达，并使用膜片钳技术记录产生的电流。我们的数据表明，可卡因与这些通道的结合是状态依赖性的，可卡因优先与开放和失活的通道结合。 将构建 hH1 和 HERG 失活缺陷突变体，以研究失活门控对可卡因结合的贡献，并促进开放通道阻断的测量。还将研究具有第六跨膜跨越片段（这些通道的假定麻醉剂结合位点）的其他突变体。拟议的研究将深入了解可卡因引起的心脏电生理学变化的机制以及该药物的心脏毒性作用。