Acid-Sensing Ion Channels in Cardiac Ischemia

描述（由申请人提供）：美国约有600万人患有慢性心绞痛，这是一种在冠状动脉疾病背景下由心肌缺血引起的疼痛感。 缺血由感觉（传入）神经元感知，并且这些心脏传入的激活不仅导致心绞痛，而且产生交感神经兴奋，这在心肌缺血和梗塞的情况下是有害的。 尽管如此，引起心脏感觉神经元激活的潜在机制仍知之甚少。 我们的目标是验证酸敏感离子通道（ASIC）是心肌缺血传感器的假设。 这一假设是基于以前的工作，表明pH值降低，在心脏的心肌缺血的设置，和我们的初步数据，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。 具体目标1将确定这三个ASIC蛋白质有助于从DRG和结状神经节的心脏感觉神经元的酸门控离子通道。 我们已经开发出一种方法，专门标记心脏感觉神经元在体内，使他们以后可以在分离的培养物中被识别。 这将使我们能够识别在心脏传入神经中表达的ASIC，并使用ASIC敲除小鼠和异源表达来检查它们的功能作用。 具体目标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。 具体目标3将测试酸与其他化学介质一起工作以激发心脏传入的假设，并且它们可能激活会聚的细胞内信号传导机制。 这项工作将为响应心脏缺血的信号和传感器提供新的见解，并为其治疗定义新的治疗靶点和新的方法。

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.