In vitro characterization of cardiac alternans mechanism

描述(由申请人提供)：交替性心律失常是一种正常心律紊乱，在临床上是心脏性猝死的重要预测指标。尽管它在机制上与潜在致命性心律失常的发生有关，但交替的潜在细胞机制本身仍不清楚。动作电位(AP)钳制研究表明，膜电压或钙循环动力学的不稳定性都可以导致Altemans的发生，但由于这两个系统之间复杂的相互作用，它们的单独动力学很难通过实验评估。相反，大多数研究集中于膜电压或(特别是)钙循环作为交替的原因，否定了两者对真实心肌细胞动力学的可能贡献。由于这两个系统代表着不同的分子靶点，临床有效的治疗将需要了解每一个系统在交替心律失常发生中所起的作用。概述的实验旨在克服将AP钳研究结果外推到正常、未受抑制的细胞的固有困难，从而首次解决电压和钙动力学对体外交替细胞的相对贡献。为此，提出了一种计算-实验相结合的方法，以解决以下具体目标：1.量化细胞交替对动作电位形态的敏感性2.在体外确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菌的贡献不相等。通过确定心脏交替的真实细胞机制，这些目标与NHLBI的战略计划的目标直接相关，该战略计划的目标是“描绘与健康和疾病有关的分子事件的机制。”总结：心脏性猝死(SCD)发生在心脏的正常节律紊乱时，每年仅在美国就有30多万人死于猝死。对SCD病因的研究发现，一种名为“Alternans”的疾病可能是SCD的先兆，但Alternans本身的原因尚不清楚。建议的实验将使用真实的心脏细胞来识别交替交替的机制(S)，以便我们可以更好地尝试和防止它和/或其进展为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.