Hippocampal astrocytic Kir4.1 channel function in Type 2 diabetic mice: impact on neuronal hyperexcitability

癫痫是美国最常见的神经系统疾病之一。糖尿病患者是一个亚组的患者， 患有这种疾病的风险增加，增加了他们的发病率和死亡率。而9.3%的 美国人患有糖尿病。它已被证明，不受控制的高血糖症（糖尿病） 增加了大脑中癫痫样活动的易感性，但其机制仍不清楚。有 迫切需要确定可能有助于将糖尿病和癫痫发作联系起来的潜在机制。癫痫是 是由神经元通讯中断引起的可能导致癫痫样活动的因素之一 是细胞外钾[K+]o在活跃突触区的积累。星形胶质细胞提供支持， 营养素的神经回路和维持细胞外离子平衡。此外，他们是最 大脑中有丰富的细胞类型，它们在癫痫中被强调，主要是由于能力下降 钾的吸收。与癫痫相关的一个重要的充分表征的过程是[K+]o的调节。 Kir4.1内向整流钾通道（Kir4.1 inwardly rectifiedpotassium channel，Kir4.1）主要位于突触周围的星形胶质细胞 进行钾的吸收过程。拟议研究的基本原理是基于我们发表的 数据显示来自糖尿病雄性小鼠海马脑切片的星形胶质细胞显示Kir4.1通道 蛋白质下调和钾吸收能力显著降低。本项目的目标是 为了发现糖尿病男性脑中Kir4.1下调与糖尿病样事件之间的关系， 将性别视为生物学变量的雌性小鼠。因此，我们的中心假设是， 糖尿病患者中癫痫表型的原因是星形胶质细胞不能缓冲过量的[K+]o， Kir4.1通道蛋白的下调。我们将通过测量星形胶质细胞Kir4.1通道mRNA来解决这一问题。 和蛋白水平，测试海马星形胶质细胞中Kir4.1通道活性，并评估海马星形胶质细胞中癫痫样活性。 4-氨基吡啶对雌性大鼠海马锥体神经元电生理反应的影响 小鼠最后，我们将表征和确定是否恢复海马Kir4.1通道蛋白， 通过病毒递送的星形胶质细胞将恢复星形胶质细胞Kir通道表达、膜电位、钡敏感性 电流和K+，并进一步将其与糖尿病小鼠中的神经元癫痫样活性相关。这些结果 将有助于新的信息，特别是对糖尿病（高葡萄糖）的知识，在大脑中， 对神经问题如癫痫中所见的神经元过度兴奋性有负面影响。我们的主要 目的是了解高血糖如何影响星形胶质细胞的稳态功能，导致神经元 兴奋过度

Epilepsy is one of the most common neurological disorders in the US. Diabetics are a subgroup of patients that are at increased risk of suffering from this condition, increasing their morbidity and mortality. Whereas, 9.3% of the United States population has diabetes. It has been shown that uncontrolled hyperglycemia (diabetes) increases the susceptibility to epileptiform-like activity in the brain but the mechanism is still unknown. There is a critical need in the identification a potential mechanism that may help link diabetes and seizures. Epilepsy is caused by a disruption of neuronal communication. One of the factors that may contribute to epileptiform activity is the accumulation of extracellular potassium [K+]o in active synaptic areas. Astrocytes provide support, deliver nutrients to neuronal circuits and maintain extracellular ion balance. Furthermore, they are one of the most abundant cell types in the brain and they have been highlighted in epilepsy mostly due to decreased capabilities in potassium uptake. One important well-characterized process that relates to epilepsy is the regulation of [K+]o. The Kir4.1 inwardly rectifying potassium channel (Kir4.1) located in astrocytes surrounding synapses largely carries out the process of potassium uptake. The rationale for the proposed study is based on our published data which shows that astrocytes from hippocampal brain slice from diabetic male mice display Kir4.1 channel protein downregulation and significant decrease in potassium uptake capability. The objective of this project is to find a relationship between Kir4.1 downregulation and seizure-like events in the brain of diabetic male and female mice considering sex as a biological variable. Therefore, our Central Hypothesis is that one of the major causes of the epileptic phenotype in diabetic patients is the inability to buffer excess [K+]o by astrocytes due to downregulation of the Kir4.1 channel protein. We will address this by measure astrocytic Kir4.1 channel mRNA and protein levels, test Kir4.1 channel activity in hippocampal astrocytes and assess the epileptiform activity in hippocampal pyramidal neurons in response to 4-aminopyridine application using electrophysiology in female mice. Finally, we will characterize and determine if reinstatement of Kir4.1 channels protein in hippocampal astrocytes via viral delivery will restore astrocytic Kir channel expression, membrane potential, barium sensitive currents and K+ and further correlate this with neuronal epileptiform-like activity in diabetic mice. These results will contribute to new information specifically to the knowledge of diabetes (high glucose) in the brain which may negatively contribute to neurological problems such as the neuronal hyperexcitability seen in epilepsy. Our main goal is to understand how hyperglycemia affects astrocytic homeostatic functions leading to neuronal hyperexcitability.