Acid-Sensing Ion Channels in Cardiac Ischemia

描述(申请人提供)：在美国大约有600万人患有慢性心绞痛，这是一种由冠状动脉疾病背景下的心肌缺血引起的疼痛感觉。缺血是由感觉(传入)神经元感知的，这些心脏传入神经的激活不仅会导致心绞痛，还会产生交感神经兴奋，这在心肌缺血和梗死的情况下是有害的。尽管如此，导致心脏感觉神经元激活的潜在机制仍然知之甚少。我们的目标是验证酸敏离子通道(ASIC)是心肌缺血传感器的假设。这一假说是基于以前的工作，即在心肌缺血的情况下，心脏的pH降低，我们的初步数据表明，ASICs有助于心脏传入神经元的酸诱发电流。我们将在三个具体目标上检验这一假设。具体目标1将确定三种ASIC蛋白中的哪一种对来自背根节和结状神经节的心脏感觉神经元的酸门离子通道起作用。我们已经开发出一种方法，专门标记体内的心脏感觉神经元，以便以后可以在分离培养中鉴定它们。这将使我们能够鉴定心脏传入中表达的ASIC，并利用ASIC基因敲除小鼠和异源表达来检验它们的功能作用。特定目的2将研究质子和ASICs在活体心肌缺血感觉中的作用。我们将在小鼠模型中测试ASICs的药物和遗传(敲除)中断是否会改变对心酸和缺血的反应。特指目标3将验证这一假说，即酸与其他化学介质一起工作，以兴奋心脏传入，它们可能激活汇聚的细胞内信号机制。这项工作将为对心肌缺血作出反应的信号和传感器提供新的见解，并确定新的治疗靶点和新的治疗方法。

DESCRIPTION (provided by applicant): Approximately 6 million people in the United States suffer from chronic angina, a painful sensation resulting from myocardial ischemia in the setting of coronary artery disease. Ischemia is sensed by sensory (afferent) neurons, and activation of these cardiac afferents leads not only to angina, but also produces sympathoexcitation, which is detrimental in the settings of myocardial ischemia and infarction. Still, the underlying mechanisms that cause activation of cardiac sensory neurons are poorly understood. Our goal is to test the hypothesis that acid-sensing ion channels (ASICs) are sensors of cardiac ischemia. This hypothesis is based on previous work that indicates that pH is reduced in the heart in the setting of myocardial ischemia, and our preliminary data that ASICs contribute to acid-evoked currents in cardiac afferent neurons. We will test this hypothesis in three specific aims. Specific Aim 1 will determine which of the three ASIC proteins contribute to acid-gated ion channels in cardiac sensory neurons from the DRG and nodose ganglia. We have developed a means to specifically label cardiac sensory neurons in vivo so that they can later be identified in isolated culture. This will allow us to identify the ASICs expressed in cardiac afferents, and examine their functional roles using ASIC knockout mice and heterologous expression. Specific Aim 2 will investigate the contribution of protons and ASICs to sensation of cardiac ischemia in vivo. We will test whether pharmacological and genetic (knockouts) disruption of ASICs alters the response to cardiac acidosis and ischemia in a mouse model. Specific Aim 3 will test the hypothesis that acid is working in conjunction with other chemical mediators to excite cardiac afferents, and they may activate convergent intracellular signaling mechanisms. This work will provide new insights into the signals and sensors that respond to cardiac ischemia, and define new therapeutic targets and novel approaches for its treatment.