In vitro characterization of cardiac alternans mechanism

描述（由申请人提供）：交替是一种正常心律失常，是临床上重要的心源性猝死预测因子。虽然它在机制上与潜在致命性心律失常的发生有关，但其潜在的细胞机制尚不清楚。动作电位（AP）夹紧研究表明，膜电压或钙循环动力学的不稳定性可导致突变的发生，但由于这两个系统之间复杂的相互作用，它们的个体动力学很难通过实验来评估。相反，大多数研究集中在膜电压或（特别是）钙循环作为交替的“原因”，否定了两者对真正的肌细胞动力学的可能贡献。由于这两个系统代表不同的分子靶点，临床有效的治疗将需要了解它们在交替性心律失常发生中的作用。这些实验旨在克服将AP钳研究结果外推到正常、无阻尼细胞的固有困难，从而首次解决了电压和钙动力学对体外交替细胞的相对贡献。为了实现这一目标，提出了一种混合计算-实验方法，以解决以下具体目标：细胞交替体对动作电位形态敏感性的定量分析体外测定膜电压和钙循环对细胞交替的贡献。初步研究证实了所提出的实验的可行性，并表明膜电压和钙循环动力学对交替的贡献是不相等的。通过确定心脏交替的真正细胞机制，这些目标与NHLBI战略计划的目标直接相关，即“描述与健康和疾病相关的分子事件的机制”。概要：心脏性猝死（SCD）发生在心脏正常节律紊乱的时候，仅在美国，每年就有30多万人死于这种疾病。对SCD病因的研究已经确定了一种名为“交替”的疾病，它可能是SCD的前兆，但交替本身的病因尚不清楚。建议的实验将使用真正的心脏细胞来确定替代的机制，以便我们可以更好地尝试和预防它和/或其发展为SCD。

DESCRIPTION (provided by applicant): Alternans is a disturbance in normal cardiac rhythm that serves as a clinically important predictor of sudden cardiac death. Although it has been mechanistically linked to the initiation of potentially fatal arrhythmias, the underlying cellular mechanism of alternans itself remains unclear. Action potential (AP) clamping studies have shown that instabilities in either membrane voltage or calcium cycling dynamics can lead to the onset of altemans, but because of the complex interplay between these two systems their individual dynamics are difficult to experimentally assess. Instead, most research focuses on either membrane voltage or (especially) calcium cycling as "the" cause of alternans, negating the probable contribution of both to real myocyte dynamics. Because these two systems represent distinct molecular targets, clinically effective therapy will require an understanding of the role each plays in alternans arrhythmogenesis. The experiments outlined are designed to overcome the inherent difficulties in extrapolating AP clamp study results to normal, undamped cells, and thereby address the relative contributions of voltage and calcium dynamics to alternans in vitro for the first time. To accomplish this, a hybrid computational- experimental approach is proposed, to address the following Specific Aims: 1. Quantification of the sensitivity of cellular alternans to action potential morphology 2. In vitro determination of the contribution of membrane voltage and calcium cycling to cellular alternans. Preliminary studies have confirmed the feasibility of the proposed experiments and show an unequal contribution of both membrane voltage and calcium cycling dynamics to alternans. By determining the true cellular mechanism of cardiac alternans, these aims are directly relevant to the goal of the NHLBI's strategic plan to "delineate mechanisms that relate molecular events to health and disease." Lay summary: Sudden cardiac death (SCD) occurs when the normal rhythm of the heart becomes disordered and is responsible for more than 300,000 deaths each year, in the U.S. alone. Research into the causes of SCD has identified a disorder called "alternans" as a possible precursor to SCD but the cause of alternans itself remains unclear. The experiments proposed will use real heart cells to identify the mechanism(s) of alternans so that we may better try and prevent it and/or its progression to SCD.