The role of cardiac mitochondrial energetics in cardiac arrhythmias and SUDEP

项目摘要 Dravet综合征（DS）是一种严重的儿童癫痫，主要由功能丧失引起 钠离子通道基因突变。突变体的重叠神经和心脏表达模式 钠通道被认为是许多遗传疾病的病理生理学基础， 表现出癫痫和心脏病的表型。癫痫患者猝死的风险为20 比一般人多四倍。尽管近年来在了解 癫痫猝死（Sudden Unexpected Death in Epilepsy，SUDEP）的发病机制至今仍不清楚。提出 SUDEP的机制涉及呼吸暂停、肺水肿、呼吸系统功能失调、 脑循环、自主神经功能障碍或心律失常。除了作为一个发电站， 线粒体负责细胞内的长期离子平衡， 线粒体功能可能先于心律失常和癫痫事件。本项目谋求 发现新的机制，心脏兴奋性改变，由于受损的线粒体 Dravet综合征（DS）模型中的能量学，这是一种具有高SUDEP发生率的癫痫形式。我 核心假设是受损的线粒体能量和离子稳态倾向于 DS患者心律失常、癫痫发作和SUDEP样事件。我打算验证这个假设 通过以下两个具体目标：1）我们将确定线粒体是否在离子通道中发挥作用。 在DS小鼠模型中的稳态。这一目的将检验DS小鼠具有受损的 在应激期间缓冲细胞溶质Na+和Ca2+变化的能力。使用多个模型，我们将 确定线粒体在长期细胞离子平衡中的作用。2)我们将确定 如果DS小鼠的线粒体能量学和ATP供需匹配能力受损。 这一目的将验证DS小鼠线粒体能量增加活性氧的假设 物种（ROS）的生产和能力下降，ATP供应与需求相匹配。实验将 研究我们的DS小鼠模型中线粒体在整个器官产生ATP的能力， 分离的细胞和细胞器水平。这个项目的重要性在于它填补了 了解DS中SUDEP的机制和拟议实验的结果， 可能导致DS的新治疗方法。虽然这项赠款的重点是DS的作用 突变，由于SUDEP的高发病率，我们希望这些结果可能适用于 其他遗传性和非遗传性癫痫将是未来项目的重点。拟议的研究 将为该领域提供有价值的见解，并可能导致发现几种潜在的治疗方法， DS的目标。线粒体代表了一个理想的研究目标，因为人们越来越感兴趣， 线粒体的促凋亡机制和新的药物可能很快就可以在 癫痫模型

Project Summary Dravet Syndrome (DS) is a catastrophic pediatric epilepsy that largely arises from loss-of-function mutations in sodium channel genes. Overlapping neuronal and cardiac expression patterns of mutant sodium channels are proposed to underlie the pathophysiology of a number of genetic diseases that exhibit both epileptic and cardiac phenotypes. The risk of sudden death in epilepsy patients is twenty four times greater than the general population. Despite advances in recent years to understand the mechanisms of Sudden Unexpected Death in Epilepsy (SUDEP), it has remained elusive. Proposed mechanisms of SUDEP have implicated seizure-induced apnea, pulmonary edema, dysregulation of cerebral circulation, autonomic dysfunction, or cardiac arrhythmias. Besides being the powerhouse of the cell, the mitochondria is responsible for long term ionic balance in the cell and compromised mitochondrial function may precede cardiac arrhythmias and epileptic events. This project seeks to uncover novel mechanisms by which cardiac excitability is altered due to compromised mitochondrial energetics in Dravet Syndrome (DS) models, a form of epilepsy with a high incidence of SUDEP. My central hypothesis is that compromised mitochondrial energetics and ionic homeostasis predisposes DS patients to cardiac arrhythmias, seizures, and SUDEP-like events. I plan to test this hypothesis through the following two specific aims: 1) we will determine if mitochondria play a role in ionic homeostasis in mouse models of DS. This aim will test the hypothesis that DS mice have an impaired ability to buffer changes in cytosolic Na+ and Ca2+ during times of stress. Using multiple models, we will determine the role that the mitochondria plays in long-term cellular ionic balance. 2) We will determine if mitochondrial energetics and the ability to match ATP supply with demand is compromised in DS mice. This aim will test the hypothesis that mitochondrial energetic of DS mice have increased reactive oxygen species (ROS) production and a decreased ability match ATP supply with demand. Experiments will investigate the ability of mitochondria in our DS mouse models to generate ATP at the whole organ, isolated cell, and organelle level. The significance of this project is that it fills a major void in understanding the mechanism of SUDEP in DS and results from the proposed experiments have the potential to lead to new therapeutic treatments in DS. While this grant focuses on the role of DS mutations, due to the high incidence of SUDEP, it is our hope that these results may be applicable to other genetic and non-genetic epilepsies that will be the focus of future projects. The proposed studies will provide valuable insight to the field and may lead to the discovery of several potential therapeutic targets for DS. The mitochondria represent an ideal target to investigate, as there is growing interest in the mitochondrial mechanisms of arrhythmogenesis and novel drugs may soon be available to test in epilepsy models.