Astrocyte dysfunction in epileptogenesis: the role of adenosine

项目摘要/摘要：该资助申请研究了星形胶质细胞增生及其导致的基于腺苷的神经调节功能障碍是癫痫（即癫痫发生）发展的机制原因的假设。这一点很重要，因为迄今为止还没有有效的癫痫预防方法。本研究旨在探索小鼠癫痫持续状态（SE）触发的癫痫发生和内源性腺苷癫痫控制系统的功能障碍，以寻找基于星形胶质细胞的癫痫发生机制，从而为开发新的抗癫痫治疗方法提供基础。该建议基于以下发现：(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）星形胶质增生是癫痫发生的标志；（iv） ADK在癫痫星形胶质性海马中过表达；(v)通过植入释放腺苷的细胞来增加腺苷，防止点燃性癫痫发作。（vi）转基因过表达ADK增加癫痫易感性；（vii）转基因小鼠局部减少ADK可防止癫痫发生。我们的中心假设是，癫痫发生触发事件（例如SE）诱导星形胶质细胞形成，导致ADK的区域上调，这是癫痫发生的必要组成部分，通过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。解决这一假设的模型系统包括在杏仁核内应用kainic酸（KA）在小鼠海马形成的CA3区选择性地启动癫痫发生，并将释放adk缺陷腺苷的胚胎干（ES）细胞移植到癫痫发生区。在Aim 1中，我们将在ca3选择性癫痫发生的小鼠模型中研究星形胶质细胞形成、ADK上调和癫痫发作的因果关系、时间和空间关系。在Aim 2中，我们将使用一组不同的ADK转基因小鼠，在这些小鼠中，我们可以从分子上分离ADK表达与星形胶质细胞形成的细胞类型特异性功能，以独立研究这两种机制。在Aim 3中，我们将使用缺乏adk的ES细胞衍生的海马内植入物作为预防癫痫发生的治疗方法。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新的基于干细胞的治疗方法。公共卫生相关性：目前，没有可用的治疗方法来预防癫痫的发展。本研究研究了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.