Inhibition of seizures and neuron excitability by acid-sensing ion channels

描述（由申请人提供）：癫痫发作引起显著的发病率和死亡率，许多病例对当前的医疗管理是难治的。因此，需要改进治疗。从更好地理解脑酸中毒的抗癫痫机制中可能会发展出治疗进展。人们早就知道，低pH值可以有效地抑制癫痫发作并降低神经元兴奋性，但这些作用背后的分子机制却知之甚少。最近在脑中鉴定质子受体可能提供脑pH和癫痫发作之间的分子联系。最近发现，这些受体之一，酸敏感离子通道ASIC1a是中枢神经元酸诱发电流所必需的。与对癫痫发作的抑制作用一致，初步数据表明在小鼠中过表达ASIC1a会减弱癫痫发作。相反，破坏ASIC1a会使癫痫发作更严重。总之，这些观察结果表明ASIC1a介导中枢性酸中毒的抗癫痫作用并降低神经元兴奋性的假设。为了验证这一假设，计划了三个目标。第一个目标将测试ASIC1a是否介导的抗癫痫作用的CO2，迅速穿过血脑屏障，降低中央pH值。野生型小鼠，ASIC1a空小鼠，ASIC1a过表达的转基因小鼠将注射化学惊厥剂和抗癫痫作用的CO2相对于空气将基因型之间进行比较。这些结果将表明ASIC1a和CO2的抗癫痫特性是否相关。第二个目标将测试ASIC1a是否介导酸在脑切片中的抗癫痫作用，其中pH可以更好地控制。第三个目的将测试ASIC1a对培养的海马神经元中的动作电位的酸抑制的影响。初步数据表明ASIC1a可能抑制动作电位，这可能有助于解释ASIC1a如何抑制体内癫痫发作。总之，这些实验将提供重要的洞察历史上建立良好，但了解甚少的抗癫痫作用的酸。它们还将导致更多的机制研究，以更深入地阐明ASIC1a如何发挥其抗癫痫作用。重要的是，这些研究也可能表明ASIC1a是抑制患者癫痫发作的新治疗靶点。确定新的和广泛的抗癫痫机制可能对难治性疾病患者特别有益。癫痫发作障碍引起显著的发病率和死亡率，并且通常难以进行医疗管理。研究癫痫发作抑制的新特征可能会导致具有替代作用机制的治疗。在这个应用程序中，我们探讨了癫痫发作抑制作用的一个知之甚少的基因，酸敏感离子通道1a，我们测试是否ASIC1a有助于建立良好的，但知之甚少脑酸中毒的抗癫痫作用。这些研究有可能促进Asic1a拮抗剂作为癫痫发作的新治疗方法的发展。

DESCRIPTION (provided by applicant): Seizure disorders cause significant morbidity and mortality, and many cases are refractory to current medical management. Thus, improved treatments are needed. Therapeutic advances might be developed from a better understanding of the antiepileptic mechanisms of brain acidosis. It has long been known that low pH effectively inhibits seizures and reduces neuron excitability, but the molecular mechanisms underlying these effects are poorly understood. The recent identification of proton receptors in the brain may provide a molecular link between brain pH and seizures. It was recently found that one of these receptors, the acid sensing ion channel ASIC1a is required for acid-evoked currents in central neurons. And consistent with an inhibitory effect on seizures, preliminary data indicate overexpressing ASIC1a in mice attenuates seizures. In contrast, disrupting ASIC1a makes seizures worse. Together, these observations suggest the hypothesis that ASIC1a mediates the antiepileptic effects of central acidosis and reduces neuron excitability. To test this hypothesis three aims are planned. The first aim will test whether ASIC1a mediates antiepileptic effects of CO2, which rapidly crosses the blood-brain barrier and lowers central pH. Wild-type mice, ASIC1a null mice, and ASIC1a overexpressing transgenic mice will be injected with a chemoconvulsant and the anti-epileptic effects of CO2 relative to air will be compared between genotypes. The results will provide an indication of whether the anti-epileptic properties of ASIC1a and CO2 are related. The second aim will test whether ASIC1a mediates the antiepileptic effects of acid in brain slices where pH can be better controlled. The third aim will test the effects of ASIC1a on acid inhibition of action potentials in cultured hippocampal neurons. Preliminary data suggest ASIC1a may inhibit action potentials, which may help explain how ASIC1a inhibits seizures in vivo. Together these experiments will provide important insight into the historically well established but poorly understood antiepileptic effects of acid. They will also lead to additional mechanistic studies to clarify in more depth how ASIC1a exerts its antiepileptic effects. Importantly, these studies may also suggest ASIC1a as a novel therapeutic target for inhibiting seizures in patients. Identifying novel and broad antiepileptic mechanisms may be especially beneficial to patients with refractory disease. Seizures disorders cause significant morbidity and mortality and are often refractory to medical management. Studying novel features of seizure inhibition may lead to treatments with alternative mechanisms of action. In this application we explore the seizure inhibiting effects of a poorly understood gene, acid-sensing ion channel 1a, and we test whether ASIC1a contributes to the well-established but poorly understood antiepileptic effects of brain acidosis. These studies have the potential to foster the development of Asic1a antagonists as a novel therapeutic approach to seizures.