Sex Differences in Molecular Heterogeneity of Cardiac Repolarization

描述(由申请人提供)：本提案是对RFA的修订申请，以促进妇女健康研究中的新科学。尽管心脏病是美国男性和女性的头号杀手，但在心脏临床试验中，只有27%的参与者是女性。在基础研究中，大多数实验只在雄性动物身上进行。因此，人们对基本的分子机制知之甚少也就不足为奇了，即使是对于如此重要的临床基本因素，例如为什么女性的心脏动作电位比男性的动作电位长。更少人知道为什么70%的先天性长QT综合征患者是女性，以及为什么女性特别容易患药物引起的心律失常。这项申请建议通过确定心脏中两个主要的再极化电流--IKR和IKS的性依赖和激素调节的分子基础，来推动女性健康研究中的科学。这项研究是强烈的假说驱动的，总体的指导性假说是IKR和IKS电生理和药理学特征的差异导致心脏复极的性别差异。这与目前的概念背道而驰，即纯粹的动作电位时程是心律失常易感性的关键决定因素。我们认为，重要的因素不是动作电位的绝对长度，而是IKR和IKS的相对贡献，以及它们的药理敏感性，这是心律失常发生的关键因素。IkR和IKs的α亚基分别为HERG和KCNQ1。然而，它们的相对表达、电生理和药理学特征是由KCNE辅助亚基的存在决定的。我们的假设是，这些亚基的激素调节是决定男性和女性肌细胞差异的主要因素。我们将通过测定男性和女性皮肤细胞诱导的多能干细胞(IPSCs)来源的人心肌细胞以及雄性、雌性和去卵巢(OVX)豚鼠的心室肌细胞的IKR和IKS电生理图谱来验证这一假设。我们还将把心肌细胞暴露在雌二醇和睾酮中，以测试激素对电流的直接影响，并使用分子干预来确定亚单位的特异性。我们将利用实验数据建立人和豚鼠动作电位的数学模型，其中包含IKR和IKS的激素调节。我们将使用这些模型来预测复极的动态行为(例如，恢复、QT延长和药物敏感性)，这些行为可以在我们的实验人和豚鼠模型中进行测试。这些创新的模拟研究将提供可检验的假说，这些假说很容易适用于人类的电生理研究。 公共卫生相关性：这项建议试图了解心脏电活动和药理敏感性的性别差异的基础。性别是一个经常被忽视的基本临床变量，它可能对健康结果产生重大影响。了解心脏性别差异的基础提供了在确定治疗目标方面取得翻译进展的机会，有可能改善患者的预后并改善男性和女性的医疗保健。

DESCRIPTION (provided by applicant): This proposal is a revised application in response to an RFA for R21 applications to advance Novel Science in Women's Health Research. Although heart disease is the #1 killer of both Men and Women in the US, only 27% of participants in cardiac clinical trials are women. In basic research, most experiments are performed on male animals only. It is therefore not surprising that little is known about the basic molecular mechanisms even for such clinically important fundamental factors such as why female cardiac action potentials are longer than male action potentials. Even less is known about why 70% of congenital Long QT syndrome patients are women, and why women are at particular risk for drug induced arrhythmias. This application proposes to advance science in women's health research by determining the molecular basis for sex dependence and hormonal regulation of IKr and IKs, the two major repolarizing currents in heart. This research is strongly hypothesis driven, and the overall guiding hypothesis is that differences in the electrophysiological and pharmacological profile of IKr and IKs are responsible for sex differences in cardiac repolarization. This is a departure from the current concept that it is purely the action potential duration that is the key determinant of arrhythmia susceptibility. We are proposing that the important factor is not the absolute action potential length, but the relative contribution of IKr and IKs, combined with their pharmacological sensitivities that are a critical factor in arrhythmogenesis. The alpha subunits of IKr and IKs are HERG and KCNQ1 respectively. However, their relative expression, electrophysiological and pharmacological profiles are determined by the presence of KCNE ancillary subunits. Our hypothesis is that hormonal regulation of these subunits is the major factor in determining differences between male and female myocytes. We will test this hypothesis by determining IKr and IKs electrophysiological profile in human cardiomyocytes derived from male and female induced Pluripotent Stem Cells (iPSCs) from skin cells, as well as ventricular myocytes from male, female and ovariectomized (OVX) guinea pigs. We will also expose myocytes to estradiol and testosterone to test the direct effects of hormones on currents and use molecular interventions to determine subunit specificity. We will use the experimental data to develop mathematical models of human and guinea-pig action potentials which contain hormonal regulation of IKr and IKs. We will use these models to make predictions about the dynamic behavior of repolarization (e.g., restitution, QT prolongation and pharmacological sensitivity) which can be tested in our experimental human and guinea pig models. These innovative simulation studies will provide testable hypotheses which are readily applicable to electrophysiological studies in humans. PUBLIC HEALTH RELEVANCE: This proposal seeks to understand the basis of sex-differences in the electrical activity and pharmacological sensitivity of the heart. Sex is an often overlooked fundamental clinical variable, which can have a significant impact on health outcome. Understanding the basis of cardiac sex differences offers the opportunity for translational advances in the identification of therapeutic targets with the potential to improve patient outcomes and improve healthcare for both men and women.