Effects of glutamate uptake on the neuropathophysiology of Huntintgton's disease

描述(申请人提供)：亨廷顿病(HD)是一种主要遗传的、不可治愈的神经退行性疾病，主要影响纹状体和皮质纹状体通路。虽然HD的最终命运是纹状体和皮质的选择性神经变性，但越来越多的证据表明，皮质纹状体回路中的信息处理失调，而不仅仅是死亡，是HD神经病理生理学的基础。例如，在纹状体，调节失调的皮质纹状体依赖的谷氨酸能信号和神经化学环境的变化导致一系列异常的纹状体放电模式，早在细胞丢失之前。与这一观点一致的事实是，负责调节谷氨酸(GLU)突触水平的主要谷氨酸转运体GLT1在HD小鼠模型的纹状体中功能失调。结果，在这些模型中，纹状体抗坏血酸(维生素C；AA)的水平显著降低，这是一种直接与GLU摄取程度和皮质纹状体兴奋性有关的抗氧化维生素。此外，GLU的摄取和AA的释放还通过塑造纹状体神经元的放电模式来调节纹状体的兴奋性。由于纹状体中适当水平的GLU摄取和AA是行为输出所必需的，这些机制可能在HD神经病理中发挥关键作用。有趣的是，β-内酰胺类抗生素头孢曲松上调了GLT1的功能表达，并减弱了R6/2小鼠HD行为表型的多种迹象，这是最具特征的HD模型。因此，拟议研究的总体目标是表征头孢曲松通过GLT1介导的GLU摄取增加对HD神经生理学的影响。我们推测，头孢曲松将使R6/2小鼠纹状体神经元活动模式的改变正常化，并逆转纹状体AA缺陷。我们将用两种平行的方法来检验我们的假设。在一个实验中，我们将使用电生理学来记录自由行为的R6/2小鼠和使用头孢曲松或赋形剂治疗的野生型小鼠的纹状体神经元的活动。我们将记录神经元整体的单个单位的尖峰活动和局部场电位，以研究GLU摄取在行为相关纹状体活动中的作用。在单独但相似处理的动物中，我们将使用伏安法结合皮质刺激来监测谷氨酸摄取对R6/2小鼠纹状体依赖的AA释放的影响。这些研究将为评价头孢曲松作为HD的潜在治疗方法提供依据。不幸的是，目前还没有有效的治疗方法或治疗方法。由于HD在美国影响着约30,000人，还有约150,000人面临遗传该基因的风险，因此对HD的进一步研究具有重大的公共卫生意义。

DESCRIPTION (provided by applicant): Huntington's disease (HD) is a dominantly inherited, incurable neurodegenerative disease affecting primarily the striatum and corticostriatal pathway. Although the ultimate fate of HD is selective neurodegeneration in striatum and cortex, emerging evidence suggests that dysregulated information processing in the corticostriatal circuit, rather than death alone, underlies HD neuropathophysiology. In striatum, for example, dysregulated corticostriatal-dependent glutamatergic signaling and alterations in the neurochemical milieu result in a host of abnormal striatal firing patterns long before cell loss. Consistent with this view is the fact that GLT1, which is the primary glutamate (GLU) transporter responsible for regulating synaptic levels of GLU, is dysfunctional in striatum of HD mouse models. As a result, the level of striatal ascorbate (vitamin C; AA), which is an antioxidant vitamin directly linked to the degree of GLU uptake and corticostriatal excitability, is markedly decreased in these models. Uptake of GLU and AA release, moreover, modulate excitability of striatum by shaping the firing patterns of striatal neurons. Because proper levels of both GLU uptake and AA in striatum are necessary for behavioral output, these mechanisms likely play key roles in HD neuropathology. Interestingly, the ?-lactam antibiotic ceftriaxone upregulates the functional expression of GLT1 and attenuates multiple signs of the HD behavioral phenotype in the R6/2 mouse, which is the most characterized HD model. Therefore, the overall goal of the proposed research is to characterize the effects of a ceftriaxone-mediated increase in GLU uptake via GLT1 on the neurophysiology of HD. We hypothesize that ceftriaxone will normalize the altered activity patterns of striatal neurons and reverse deficient striatal AA in the R6/2 mouse. We will test our hypothesis with two parallel approaches. In one we will use electrophysiology to record activity of striatal neurons in freely behaving R6/2 mice and wild-type littermate controls treated with either ceftriaxone or vehicle. We will record spike activity of single-units and local field potentials of neuronal ensembles to investigate the role of GLU uptake on behaviorally relevant striatal activity. In separate, but similarly treated animals, we will use voltammetry coupled with cortical stimulation to monitor the effects of glutamate uptake on corticostriatal-dependent release of AA in striatum of R6/2 mice. These studies will provide the basis for evaluating ceftriaxone as a potential therapy for HD. Unfortunately, there are currently no effective cures or treatments for HD. Because HD affects ~30,000 people in the United States and ~150,000 more are at risk for inheriting the gene, further research on HD has significant public health implications.