A Multi-Scale Approach to Cardiac Arrhythmia: from the Molecule to the Organ

描述(由申请人提供)：这项建议的总体目标是通过应用创新技术、计算机建模和使用长QT综合征1型和2型(LQT1和LQT2)的新遗传模型来研究SCD的新机制。这种多管齐下的方法包括切除的雄性LQT2兔和接受房室结消融(LQT1-AVB)的LQT1兔。这些兔的心肌细胞在细胞水平上的研究将被用来研究性激素在调节心肌细胞钙动态的关键蛋白功能中的作用。由于钙瞬变和动作电位动力学是通过钙诱导的钙释放和钙瞬变对钙敏感膜电流(ICa、L、INCx和Iks)的反馈而双向耦合的，因此评估不稳定的钙循环和改变的复极对触发活动的相对贡献通常是困难的。本文建议首先研究无Vm影响的亚细胞钙循环动力学以表征RyR的敏感性，然后用钳制动作电位波形研究Vm对钙循环动力学的单向效应(即没有Cai对Vm的反馈)，从而确定导致心律失常的全细胞Cai振荡的条件，研究无CAT影响的Vm动力学以研究ICa重开促进的EADS，L在改变复极的情况下研究EADS，最后用双向耦合的游离CaI和自由Vm动力学来研究CaI振荡和ICa重开的协同效应。迭代将由泛函 对特定电流及其生物物理性质的电生理测量，以及生化和电生理研究(以及测量的亚细胞钙动力学特性-火花频率和钙波阈值)，以校准用于探索致心律失常状态(不安全区域)和安全区域(无自发性心律失常或SCD)的计算模型参数的相关范围。组织和器官水平的研究将检验触发活动与双稳态波传导(双兴奋性)和组织异质性相结合的作用同步性调节R-on-T现象，并测试短-长-短序列是否增加EAD的形成和组织的异质性，从而自我推进直到TDP的开始，以及TDP和PVT是否由Ica介导的波前和混沌同步来维持。

DESCRIPTION (provided by applicant): The overall goal of this proposal is to investigate new mechanisms that underlie SCD through the application of innovative technology, computer modeling and the use of new genetic models of long QT syndrome type 1and type 2 (LQT1 and LQT2). This multi-pronged approach includes the investigation of orchiectomized male LQT2 rabbits and LQT1 rabbits that underwent ablation of the AV node (LQT1-AVB). Studies at the cellular levels with myocytes derived from these rabbits will be used to investigate the role of sex hormones in modulation of the function of key proteins that regulate calcium dynamics in cardiomyocytes. Since the calcium (Ca) transients and action potential dynamics are bi-directionally coupled through Ca-induced-Ca-release and the feedback of the Ca transient on Ca-sensitive membrane current (ICa,L, INCX, and IKs), assessing the relative contributions of unstable Ca cycling and altered repolarization to triggered activity is in general difficult. Here e propose to investigate the subcellular Ca cycling dynamics first without Vm influence to characterize RyR sensitivity, and then with a clamped action potential waveform to investigate the uni-directional effect of Vm on Ca cycling dynamics (i.e. without feedback of Cai on Vm), thereby identify conditions leading to arrhythmogenic whole cell Cai oscillations, Vm dynamics without CaT influence to study EADs facilitated by reopening of ICa,L in the presence of altered repolarization, and finally bi-directionally coupled free Cai and free Vm dynamics to investigate synergistic effects of Cai oscillations and reopening of ICa,. Iteration will consist of functional electrophysiological measurements of the specific currents and their biophysical properties, and biochemical and electrophysiological studies (as well as measured subcellular Ca dynamical properties-spark frequency and Ca wave threshold), to calibrate relevant ranges of computational model parameters to be used in the exploration of arrhythmogenic state (unsafe zone) and safe zone (no spontaneous arrhythmias or SCD). Studies at the tissue and organ levels will examine the role synchronization of the triggered activity combined with bi-stable wave conduction (bi- excitability) and tissue heterogeneities mediate the R-on-T phenomenon as well as test whether short-long-short sequence increases EAD formations and tissue heterogeneities, thus self propels until the onset of TdP and weather TdP and PVT are maintained by Ica-mediated wavefronts and chaos synchronization.