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

描述（由申请人提供）：本提案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（LQT 1和LQT 2）的新遗传模型，研究SCD的新机制。这种多管齐下的方法包括研究接受房室结消融术（LQT 1-AVB）的睾丸切除雄性LQT 2家兔和LQT 1家兔。来自这些兔子的肌细胞在细胞水平上的研究将用于研究性激素在调节心肌细胞中钙动力学的关键蛋白质的功能调节中的作用。由于钙（Ca）瞬变和动作电位动力学通过Ca诱导的Ca释放和Ca瞬变对Ca敏感性膜电流（伊卡、L、INCX和IKs）的反馈双向耦合，因此通常难以评估不稳定Ca循环和复极改变对触发活动的相对贡献。本文拟先研究不受Vm影响的亚细胞Ca循环动力学，以表征RyR敏感性，然后用钳位动作电位波形研究Vm对Ca循环动力学的单向影响（即，没有Cai对Vm的反馈），从而鉴定导致致炎性全细胞Cai振荡的条件，没有CaT影响的Vm动力学，以研究通过伊卡的重新开放促进的埃兹，L的存在下改变复极，最后双向耦合自由Cai和自由Vm动态研究协同效应的Cai振荡和重新开放的伊卡。迭代将由功能性组成 特定电流及其生物物理特性的电生理学测量，以及生物化学和电生理学研究（以及测量的亚细胞Ca动力学特性-火花频率和Ca波阈值），以校准用于探索致心律失常状态（不安全区）和安全区（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查触发活动与双稳态波传导（双兴奋性）和组织异质性相结合介导的R-on-T现象的作用同步，以及测试短-长-短序列是否增加EAD形成和组织异质性，从而自我推进直到TdP开始，以及TdP和PVT是否由Ica介导的波前和混沌同步维持。

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.