Acid-Sensing Ion Channels in Cardiac Ischemia

描述（由申请人提供）：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。然而，引起心脏感觉神经元激活的潜在机制尚不清楚。我们的目标是验证酸敏感离子通道（asic）是心脏缺血传感器的假设。这一假设是基于先前的研究表明，在心肌缺血的情况下，心脏的pH值降低，我们的初步数据表明，asic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中检验这一假设。特异性Aim 1将确定三种ASIC蛋白中的哪一种对来自DRG和结节神经节的心脏感觉神经元中的酸门控离子通道有贡献。我们已经开发了一种方法，可以在体内特异性标记心脏感觉神经元，以便以后在分离培养中识别它们。这将使我们能够识别在心脏事件中表达的ASIC，并使用ASIC敲除小鼠和异源表达来检查它们的功能作用。特异性目的2将研究质子和asic对体内心脏缺血感觉的贡献。我们将在小鼠模型中测试asic的药理学和遗传（敲除）破坏是否会改变对心脏酸中毒和缺血的反应。特异性Aim 3将验证酸与其他化学介质一起激发心脏传入的假设，并且它们可能激活趋同的细胞内信号传导机制。这项工作将为心脏缺血的信号和传感器提供新的见解，并为其治疗提供新的治疗靶点和新方法。

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.