A novel target for the treatment of temporal lobe epilepsy

 描述（由申请人提供）：癫痫是一种常见的神经系统疾病，影响全球5000万人。大约30%的癫痫患者具有治疗抵抗性（难治性）癫痫发作，从而呈现出主要的临床挑战和负担。难治性癫痫最常见的形式是内侧颞叶癫痫（MTLE），其特征在于自发性癫痫发作、神经心理缺陷和海马硬化。目前，手术切除癫痫病灶是这种疾病的最佳治疗策略;然而，这种手术仅用于一部分病例。因此，迫切需要开发替代疗法。 电压门控钠通道（VGSC）SCN 1A、SCN 2A和SCN 3A的突变与几种癫痫亚型相关，包括Dravet综合征（DS）和遗传性癫痫伴热性惊厥+（GEFS+）。最近在癫痫性脑病患者中发现了VGSC SCN 8A的功能获得突变。然而，我们的实验室已经证明，与野生型同窝出生的小鼠相比，具有降低通道活性或表达的Scn 8a突变的小鼠对诱导的癫痫发作更具抵抗力。此外，我们能够显着改善癫痫发作的严重程度和恢复正常寿命的Scn 1a突变体模型DS和GEFS+通过共分离的Scn 8a突变或海马敲低Scn 8a表达。由于海马是癫痫发作的产生和形态学变化的MTLE的主要网站，我们假设，选择性减少海马中的SCN 8A表达将提供一个有效的策略，治疗MTLE。我们将以三个具体目标来检验这一假设。在目的1中，我们将在广泛使用的MTLE海马内海人酸小鼠模型中确定降低海马Scn 8a表达对自发性癫痫发作频率和严重程度的影响。通过海马体注射表达针对Scn 8a的短发夹RNA的腺相关病毒载体（AAV-3）来实现Scn 8a表达的降低。将使用连续视频/EEG分析在AAV-3处理的小鼠中监测癫痫发作活性，并将其与注射乱序构建体（AAV-GFP）的对照小鼠进行比较。在目的2中，我们将确定海马Scn 8a表达的减少是否也可以预防或改善行为和海马形态学的变化以及在该MTLE模型中观察到的变化。最后，在目的3中，我们比较了来自AAV-3和AAV-GFP处理的小鼠的海马切片的生物物理性质，以直接检查神经元兴奋性。我们还将测试使用新型化合物部分药理学阻断Nav1.6是否可以减少MTLE小鼠模型海马切片中的神经元样爆发活性，并且我们将探索不同VGSC对MTLE发展的贡献。这项临床相关的提议将为靶向SCN 8A作为MTLE治疗的可行性提供重要的见解，更广泛地说，用于其他形式的难治性癫痫。

 DESCRIPTION (provided by applicant): Epilepsy is a common neurological disorder that affects 50 million people worldwide. Approximately 30% of epileptic patients have treatment resistant (refractory) seizures, thereby presenting a major clinical challenge and burden. The most common form of refractory epilepsy is mesial temporal lobe epilepsy (MTLE), characterized by spontaneous seizures, neuropsychological deficits, and hippocampal sclerosis. At present, surgical resection of the epilepsy focus is the best treatment strategy for this disorder; however, this procedure is only used in a subset of cases. Consequently, there is an urgent need to develop alternative treatments. Mutations in the voltage-gated sodium channels (VGSCs) SCN1A, SCN2A, and SCN3A are associated with several epilepsy subtypes including Dravet syndrome (DS) and genetic epilepsy with febrile seizures plus (GEFS+). Gain of function mutations in the VGSC SCN8A have recently identified in individuals with epileptic encephalopathies. However, our laboratory has demonstrated that mice with Scn8a mutations that reduce channel activity or expression are more resistant to induced seizures when compared to their wild-type littermates. In addition, we were able to dramatically ameliorate seizure severity and restore normal lifespans to Scn1a mutants that model DS and GEFS+ by either co-segregation of an Scn8a mutation or hippocampal knockdown of Scn8a expression. Since the hippocampus is the major site of seizure generation and morphological changes in MTLE, we hypothesize that selective reduction of SCN8A expression in the hippocampus will provide an effective strategy for the treatment of MTLE. We will test this hypothesis with three specific aims. In Aim 1, we will establish the effect on spontaneous seizure frequency and severity of reducing hippocampal Scn8a expression in the widely used intra-hippocampal kainic acid mouse model of MTLE. Reduced Scn8a expression will be achieved by hippocampal injection of an adeno-associated viral vector expressing a short hairpin RNA against Scn8a (AAV-3). Seizure activity will be monitored in AAV-3 treated mice using continuous video/EEG analysis and will be compared to control mice injected with a scrambled construct (AAV-GFP). In Aim 2, we will determine if hippocampal reduction of Scn8a expression could also prevent or ameliorate the changes in behavior and hippocampal morphology and that are observed in this model of MTLE. Finally, in Aim 3, we compare the biophysical properties of hippocampal slices from the AAV-3 and AAV-GFP treated mice in order to directly examine neuronal excitability. We will also test if partial pharmacological block of Nav1.6, using novel compounds, can reduce seizure-like bursting activity in hippocampal slices from the MTLE mouse model, and we will explore the contribution of the different VGSCs to the development of MTLE. This clinically relevant proposal will provide important insight into the feasibility of targeting SCN8A as a treatment for MTLE, and more broadly, for other forms of refractory epilepsy.