SK Current, beta-3 adrenoceptor activation and Sex Differences in Ventricular Arrhythmogenesis

项目摘要 这项研究项目的广泛和长期目标是检验以下假设：(1)阿帕明的反应- 对交感神经刺激敏感的小电导钙激活钾电流(IKAS)起重要作用 性别差异在心律失常发生机制中的作用及(2)β-3肾上腺素能受体 激活是抗心律失常的，并消除交感神经刺激时IKAS激活的性别差异。 在当前的资助期间，我们发现SK蛋白和IKAS在 在异丙肾上腺素或乙酰胆碱期间，性别差异的大小被放大 输液。阿帕明能更有效地减少室颤(VF)的相位奇异性(PSS)。 女性多于男性脑室。目前还不清楚哪种AR对异丙肾上腺素诱导的IKAS负责 激活。异丙肾上腺素在比β-3受体浓度低的情况下激活β-1和β2受体。 与β-1和β-2受体激活的作用相反，β-3受体激活发挥负性肌力作用 对心肌的影响。β-3受体可能是过量儿茶酚胺的缓冲器或救援者。我们 在犬室性心动过速的模型中显示，BRL-37344(一种β-3激动剂)具有抗心律失常的作用。我们 假设β-3受体的激活是抗心律失常的，并消除了IKAS激活的性别差异 在兔模型的交感神经刺激过程中。具体目标1：SK电流，β-3肾上腺素能受体激活， 室性心律失常的性别差异。我们将进行光学标测和膜片钳 在异丙肾上腺素存在的情况下对特定的β-1和β-2拮抗剂的研究。我们还将表演 光学标测研究，以确定米雷贝格隆对VF期间位相奇点(PSS)的影响 不含异丙肾上腺素。在其他实验中，我们将使用BRL-37344代替Mirabegron来测试 假设这种抗心律失常机制是其他β-3激动剂共有的一类效应。这个 然后将在兔心肌梗死模型上测试米拉贝格隆的抗心律失常作用。这些 研究结果将被用来检验这一假说，即β-3受体激活挽救了β-3受体促心律失常的作用。 刺激1和β2，间接减少IKAS，消除室颤患者PSS的性别差异。具体目标2： β3刺激下Na+-K+-ATPase(NKA)的激活与抗心律失常药物的性别差异 行动。β-3受体可激活NKA，从而减轻钙超载所致的心律失常。我们 假设NKA激活在β-3受体激活的抗心律失常作用中起重要作用。我们会 首先进行研究以确定兔的β-3AR、NKA蛋白和mRNA是否存在性别差异 脑室。光学映射研究将在哇巴因存在的情况下进行，哇巴因是一种特定的NKA阻滞剂，以 确定是否需要NKA公司来发挥β-3激活的抗心律失常作用。兔子 将使用心室动作电位模型进行计算机模拟研究，以评估 Nka激活在β-3受体激活抗心律失常机制中的作用

Project Summary The broad and long-term goal of this research project is to test the hypothesis that (1) the response of apamin- sensitive small conductance Ca2+-activated K+ (SK) current (IKAS) to sympathetic stimulation plays an important role in the mechanisms of sex differences in cardiac arrhythmogenesis and that (2) beta-3 adrenoceptor (AR) activation is antiarrhythmic and eliminates the sex difference of IKAS activation during sympathetic stimulation. In the current funding period, we discovered a significant sex difference of both the SK protein and IKAS at baseline and that the magnitudes of sex differences are amplified during isoproterenol or acetylcholine infusion. Apamin reduces the phase singularities (PSs) in ventricular fibrillation (VF) more effectively in the female than in the male ventricles. It is unclear which AR is responsible for the isoproterenol-induced IKAS activation. Isoproterenol activates the beta-1 and beta-2 ARs at lower concentrations than the beta-3 AR. Contrary to the effects of beta-1 and beta-2 AR activation, beta-3 AR activation exerts negative inotropic effects in the myocardium. Beta-3 ARs likely served as a buffer or rescuer of the excess catecholamines. We showed in a canine model of ventricular tachycardia that BRL-37344 (a beta-3 agonist) is antiarrhythmic. We hypothesize that beta-3 AR activation is antiarrhythmic and eliminates the sex difference of IKAS activation during sympathetic stimulation in the rabbit model. Specific Aim 1: SK current, beta-3 adrenoceptor activation, and Sex Differences in Ventricular Arrhythmogenesis. We will perform optical mapping and patch clamp studies with specific beta-1 and beta-2 antagonists in the presence of isoproterenol. We also will perform optical mapping studies to determine the effects of mirabegron on phase singularities (PSs) during VF with and without isoproterenol. In additional experiments, we will use BRL-37344 instead of mirabegron to test the hypothesis that this antiarrhythmic mechanism is a class effect shared by other beta-3 agonists. The antiarrhythmic action of mirabegron will then be tested in a rabbit model of myocardial infarction. These findings will be used to test the hypothesis that beta-3 AR activation rescues the proarrhythmic effects of beta- 1 and beta-2 stimulation, indirectly reduce IKAS, and eliminates the sex differences of PSs in VF. Specific Aim 2: Na+-K+ ATPase (NKA) activation during beta3 stimulation contributes to the sex differences of antiarrhythmic action. Beta-3 AR activates NKA, which may reduce Ca2+ overload-induced cardiac arrhythmias. We hypothesize that NKA activation plays a vital role in the antiarrhythmic effects of beta-3 AR activation. We will first perform studies to determine if there is a sex difference in beta-3 AR, NKA protein, and mRNA in rabbit ventricles. Optical mapping studies will be done in the presence of ouabain, a specific NKA blocker, to determine if the company of NKA is required for the antiarrhythmic effects of beta-3 activation. Rabbit ventricular action potential models will be used for computer simulation studies to assess the importance of NKA activation in the antiarrhythmic mechanisms of beta-3 AR activation.