Atrial Excitation-Contraction Coupling, Calcium Signaling and Electro-Mechanical Alternans

项目摘要/摘要 心房肌细胞兴奋收缩偶联(ECC)与肌浆网(SR)钙释放 具有独特的特征，这是由于缺乏或不规则的横管膜组织所致 系统。心房肌细胞有交界性(j-SR)和非交界性(Nj-SR)两种类型。CA从j-释放- 钙是由电压门控的L型钙通道(ICa，L)控制的，而NJ-SR则释放钙 通过随后传播的波状钙诱导钙释放(CICR)而发生，由新发现的火- 弥散-摄取-火(FDUF)机制。IP3受体诱导的钙释放(IICR)通过以下途径参与ECC 增强正性肌力，也会导致致心律失常的钙释放和交替。心脏交替变种一直是 与心律失常有关，包括房颤。Alternans被定义为节拍到节拍的交替 动作电位时程(动作电位时程、电交替)、收缩强度和钙瞬变(CAT) 幅度，从而产生动态心律失常底物。双向耦合的干扰 [Ca]i和膜电压(Vm)的调节([Ca]i↔Vm偶联)是交链霉菌发生的主要原因。 心脏结构和电特性的性别差异与心律失常的差异有关 敏感度和测定交替物的诱导性。将重点放在FDUF机制上，总体目标是 建立心房ECC、钙释放和心房交替的机制模型及其性别特异性 细胞、细胞对和器官水平。 具体目的1.确定心房交替的FDUF依赖机制。我们将确定关键的 新的FDUF范式在心房交替中的作用，检验了1)j-SR和Nj-SR解偶联的假设 SR钙释放促进反向FDUF并触发交替；2)FDUF触发信号(ICA，L，交界处) 3)SERCA依赖钙摄取；4)线粒体钙缓冲，能量学 氧化还原信号和IICR调制FDUF和Alternans。 具体目标2.确定细胞对中的FDUF交替机制。Alternans要么由Vm驱动，要么由Ca驱动。 VM驱动的Alternans在空间上是同质的，而Ca驱动的Alternans在空间上可能是不协调的 在较短的距离上，区域交替为异相。细胞对定义了基本的结构和功能 信元间通信的单元。我们将测试1)猫和apd交替的时空组织 细胞对，2)在钙驱动的交替中，FDUF机制，SERCA，线粒体信号和IICR 确定细胞对交替；以及3)VM驱动的交替如何在相邻细胞中沉淀CAT交替。 具体目标3.确定钙驱动和虚拟驱动的时空组织和机制 组织交替物。我们将在器官层面(灌流的心脏、活的动物)确定机制， 1)钙驱动和2)电压驱动交替的表现和时空组织，以及测试 降低易导致心律失常的交替发作风险的药物干预。

PROJECT SUMMARY/ABSTRACT In atrial myocytes excitation-contraction coupling (ECC) and Ca release from the sarcoplasmic reticulum (SR) have unique features that result from the lack or the irregular organization of the transverse tubule membrane system. Atrial myocytes have two types of SR, junctional (j-SR) and non-junctional (nj-SR). Ca release from j- SR is controlled by Ca entry through voltage-gated L-type Ca channels (ICa,L) whereas release from nj-SR occurs by subsequent propagating wave-like Ca-induced Ca release (CICR) driven by the newly identified 'fire- diffuse-uptake-fire' (FDUF) mechanism. IP3 receptor-induced Ca release (IICR) contributes to ECC by enhancing inotropy, but also leads to arrhythmogenic Ca release and alternans. Cardiac alternans has been linked to cardiac arrhythmia, including atrial fibrillation. Alternans is defined as beat-to-beat alternations in action potential (AP) duration (APD, electrical alternans), contraction strength and Ca transient (CaT) amplitude, and thereby generates a dynamic arrhythmia substrate. Disturbances of the bi-directional coupling of [Ca]i and membrane voltage (Vm) regulation ([Ca]i↔Vm coupling) are responsible for alternans occurrence. Sex differences in cardiac structural and electrical properties have been linked to differences in arrhythmia susceptibility and determine alternans inducibility. Focusing on the FDUF mechanism, the overall goals are to establish a mechanistic model of atrial ECC, Ca release and atrial alternans and its sex-specific attributes at cellular, cell pair and organ level. Specific aim 1. Determine FDUF-dependent mechanisms of atrial alternans. We will determine the critical role of the novel FDUF paradigm in atrial alternans, testing the hypotheses that 1) uncoupling of j-SR and nj- SR Ca release promotes 'reverse' FDUF and triggers alternans; 2) the FDUF trigger signal (ICa,L, junctional CaT) has Vm dependence, and that 3) SERCA dependent Ca uptake; 4) mitochondrial Ca buffering, energetics and redox signaling and 5) IICR modulate FDUF and alternans. Specific aim 2. Determine FDUF alternans mechanisms in cell pairs. Alternans is either Vm- or Ca-driven. Vm-driven alternans is spatially homogeneous, while Ca-driven alternans can be spatially discordant where over short distances regions alternate out-of-phase. Cell pairs define the elementary structural and functional unit of cell-cell communication. We will test 1) the spatio-temporal organization of CaT and APD alternans in cell pairs, 2) how during Ca-driven alternans the FDUF mechanism, SERCA, mitochondrial signaling and IICR determine cell pair alternans; and 3) how Vm-driven alternans precipitates CaT alternans in adjacent cells. Specific aim 3. Determine the spatio-temporal organization and mechanisms of Ca- and Vm-driven tissue alternans. We will determine at organ level (perfused hearts, live animals) the mechanisms, manifestations and spatio-temporal organization of 1) Ca-driven and 2) voltage-driven alternans, and test pharmacological interventions to reduce pro-arrhythmic alternans risk.