Astrocyte dysfunction in epileptogenesis: the role of adenosine

描述(申请人提供)：星形胶质细胞功能障碍在癫痫发生中的作用：腺苷项目的作用概述/摘要本拨款提案研究星形胶质细胞增生症和由此导致的腺苷神经调节功能障碍是癫痫发展(即癫痫发生)的机制原因这一假说。这一点很重要，因为到目前为止还没有有效的癫痫预防方法。本研究将探讨癫痫持续状态(SE)引发的癫痫发生和内源性腺苷癫痫控制系统的功能障碍，以寻求基于星形胶质细胞的癫痫发生机制，从而为新的抗癫痫药物的开发提供基础。该建议基于下列发现：(I)腺苷激酶(ADK)是调节腺苷的关键酶；(Ii)在成人大脑中，ADK在星形胶质细胞中表达；(Iii)星形胶质细胞增生症是癫痫发生的标志；(Iv)ADK在癫痫的星形胶质细胞海马区过度表达；(V)通过植入腺苷释放细胞来增强腺苷可以防止点燃的癫痫发作。(Vi)ADK转基因过表达增加癫痫易感性；(Vii)在转基因小鼠中局部减少ADK可防止癫痫的发生。我们的中心假设是，癫痫发生的触发事件(例如SE)诱导星形胶质细胞增生，从而导致ADK作为癫痫发生的必要组成部分的区域上调，而干细胞来源的脑植入物重建脑腺苷可以防止这种癫痫发生。解决这一假说的模型系统包括杏仁核内应用红藻氨酸(KA)选择性地在小鼠海马结构的CA3区启动癫痫发生，以及将ADK缺陷的腺苷释放胚胎干细胞(ES)移植到致痫区域。具体目标：在目标1中，我们将研究CA3选择性癫痫小鼠模型中星形胶质细胞增生症、ADK上调和癫痫发作的因果、时间和空间关系。在目标2中，我们将使用一组不同的ADK转基因小鼠，在其中我们可以从分子上分离ADK表达的细胞类型的特定功能与星形胶质细胞增生症，以独立地研究这两种机制。在目标3中，我们将使用ADK缺乏的ES细胞来源的海马区植入治疗方法来预防癫痫的发生。这些研究的预期结果是将星形细胞ADK定义为预防癫痫发作的靶点，并将这些发现转化为一种基于干细胞的新治疗方法。公共卫生相关性：目前，还没有预防癫痫发展的治疗方法。这项建议研究大脑自身基于腺苷的癫痫控制系统的功能缺陷，作为癫痫的机制原因，并将这些发现转化为一种通过植入腺苷释放干细胞来预防癫痫的新方法。

DESCRIPTION (provided by applicant): Astrocyte dysfunction in epileptogenesis: the role of adenosine Project Summary/Abstract This grant proposal studies the hypothesis that astrogliosis and resulting dysfunction of adenosine-based neuromodulation is a mechanistic cause for the development of epilepsy (i.e. epileptogenesis). This is of importance, since to date no effective prophylaxis for epilepsy is available. This proposal will explore status epilepticus (SE)- triggered epileptogenesis and dysfunction of the endogenous adenosine-based seizure control system in mice in search for an astrocyte-based mechanism of epileptogenesis and thus may provide a foundation for the development of novel antiepileptogenic therapies. The proposal is based on the following findings: (i) Adenosine kinase (ADK) is the key enzyme for the regulation of adenosine; (ii) In adult brain, ADK is expressed in astrocytes; (iii) Astrogliosis is a hallmark of epileptogenesis; (iv) ADK is over-expressed within epileptic astrogliotic hippocampus; (v) Augmentation of adenosine by implants of adenosine releasing cells prevents kindled seizures. (vi) Transgenic overexpression of ADK increases seizure susceptibility; (vii) Local reduction of ADK in transgenic mice prevents epileptogenesis. Our CENTRAL HYPOTHESIS is that an epileptogenesis triggering event (e.g. SE) induces astrogliosis with resultant regional upregulation of ADK as a necessary component of epileptogenesis and that reconstitution of brain adenosine by stem cell derived brain implants can prevent such epileptogenesis. The model system to address this hypothesis consists of intraamygdaloid application of kainic acid (KA) to initiate epileptogenesis selectively in the CA3 area of the hippocampal formation of mice and to transplant ADK-deficient adenosine releasing embryonic stem (ES) cells into the epileptogenic region. SPECIFIC AIMS: In Aim 1 we will study the causal, temporal, and spatial relations of astrogliosis, upregulation of ADK and seizures in a mouse model of CA3-selective epileptogenesis. In Aim 2 we will use a panel of different Adk-transgenic mice, in which we can molecularly separate cell-type specific functions of ADK expression from astrogliosis, to study both mechanisms independently. In Aim 3 we will use ADK-deficient ES cell-derived intrahippocampal implants in a therapeutic approach to prevent epileptogenesis. The expected outcome of these studies is to define astrocytic ADK as a target for the prevention of epileptic seizures and to translate these findings into a novel stem cell based treatment approach. PUBLIC HEALTH RELEVANCE: Currently, no therapy is available to prevent the development of epilepsy. This proposal studies a defective function of the brain's own adenosine-based seizure control system as a mechanistic cause for epilepsy and translates these findings into a novel approach to prevent epilepsy by implanting adenosine releasing stem cells.