Astrocytic Glutamate Transporter 1 (GLT-1) enhancement for the treatment of seizures in Dravet Syndrome

项目摘要： 癫痫是一种常见的多因素神经系统疾病，影响约1%的人口。 电压门控钠离子通道的突变是几种单基因癫痫综合征的原因， SCN 1A基因中的杂合性功能丧失突变导致Dravet综合征（DS），一种严重的婴儿- 以难治性癫痫发作、发育迟缓和死亡率增加为特征的起病性疾病。而 与所有单基因癫痫一样，DS表型在具有相同突变的个体中表达突变。 （表明遗传或环境修饰剂可能影响临床严重程度），由此产生的癫痫发作是 通常对传统的抗癫痫药物（AED）有抗药性，其中一些实际上会加剧癫痫发作， disorder.因此，DS中的新型治疗性AED靶点是高度期望的。 我们和其他人已经确定了从突触中去除兴奋性神经递质谷氨酸的次优方法 由于星形胶质细胞谷氨酸转运蛋白（GLT-1）的表达减少， 先天性癫痫，在啮齿动物和人类。值得注意的是，GLT-1（称为兴奋性氨基酸转运蛋白2， EAAT 2）表达，当抑制时，可以通过常见的β内酰胺抗生素增强 （与这些化合物的抗菌特性无关），我们发现， 具有良好血脑屏障通透性的β-内酰胺类成员，抑制大鼠获得性癫痫发作 癫痫模型与DS相关，我们记录了一项临床观察， 当暴露于β-内酰胺类抗生素时癫痫发作抑制。同时，在DS SCN 1A单倍不足中， （Scn 1a +/-）小鼠模型中，我们发现GLT-1蛋白在皮质和海马中被抑制， 提出了GLT-1缺陷作为DS的一个合理的新的治疗靶点的前景。 因此，我们提出了一组探索性实验，旨在（1）测试GLT-1的临床效用 通过头孢曲松（或类似化合物）在DS治疗中的增强。(2)测试GLT-1减少是否是 Scn 1a +/-内表型，或复发性癫痫发作的产物，和（3）表征发育的 Scn 1a +/-小鼠中GLT-1表达的调节。 鉴于DS患者的癫痫发作对常规AED没有反应，我们提出的实验将是第一步 针对这种毁灭性综合征的新型连续抗癫痫治疗。除此之外，建议 这些实验将提供对星形胶质细胞谷氨酸转运在较温和的SCN 1A变异中的作用的深入了解 单倍不足和其他癫痫。由于GLT-1上调可以通过安全和有效的方法来实现， 便宜的药物，我们预计，从拟议的研究的有利结果将迅速转化为 DS或相关疾病的人体试验。

Project Summary: Epilepsy is a common, multifactorial neurological disorder affecting approximately 1% of the population. Mutations in voltage-gated sodium channels are responsible for several monogenic epilepsy syndromes, and heterozygous loss-of-function mutations in the SCN1A gene result in Dravet syndrome (DS), a severe infant- onset disease characterized by intractable seizures, developmental delays and increased mortality. While the DS phenotype, as in all monogenic epilepsies, expresses variably among individuals with the same mutation (suggesting that genetic or environmental modifiers may influence clinical severity), the resultant seizures are often resistant to conventional antiepileptic drugs (AEDs), some of which in fact exacerbate seizures in this disorder. Thus, a novel therapeutic AED target in DS is highly desirable. We and others have identified suboptimal removal of the excitatory neurotransmitter glutamate from synapses due to reduced expression of astrocytic glutamate transporter (GLT-1) as a contributor to acquired and congenital epilepsy, both in rodents and humans. Notably, GLT-1 (termed excitatory amino acid transporter 2, EAAT2 in humans) expression, when depressed, can be enhanced by common beta lactam antibiotics (unrelated to these compounds' antimicrobial properties), and we identified that treatment with ceftriaxone, a member of the β-lactam class with good blood-brain barrier penetrance, suppresses seizures in a rat acquired epilepsy model. Relevant to DS, we documented a clinical observation where children with DS experience seizure suppression when exposed to beta lactam antibiotics. In parallel, in a DS SCN1A haploinsufficiency (Scn1a+/-) mouse model, we identified that GLT-1 protein is depressed in cortex and hippocampus, which raises prospects for GLT-1 deficiency as a plausible novel therapeutic target in DS. Accordingly, we propose a set of exploratory experiments aimed to (1) test the clinical utility of GLT-1 enhancement by ceftriaxone (or analogous compound) in DS treatment. (2) test whether GLT-1 reduction is an Scn1a+/- endophenotype, or the product of recurrent seizures, and (3) characterize the developmental regulation of GLT-1 expression in the Scn1a+/- mouse. Given that seizures in DS do not respond to conventional AEDs, our proposed experiments will be the first step toward a novel adjunctive antiepileptic treatment in this devasting syndrome. Beyond DS, the proposed experiments will provide insight into the role of astrocytic glutamate transport in milder variants of SCN1A haploinsufficiency, and in other epilepsies. As GLT-1 upregulation may be accomplished by safe and inexpensive drugs, we anticipate that favorable results from the proposed studies will translate rapidly to human trials in DS or in related disorders.