Novel Treatment Strategies for Targeting Posttraumatic Epilepsy

描述(由申请人提供)： 创伤后癫痫(PTE)是创伤性脑损伤(TBI)在平民和军人人群中常见的后果。虽然已经进行了一些研究来评估这种临床综合征的病理生理学，但还没有在人类PTE人群中得到证实的治疗方法。我们最近的发现表明，中度液压冲击性脑损伤导致创伤后数周至数月的癫痫发作阈值降低。行为、电生理和组织病理学数据支持这种神经元和回路兴奋的改变。此外，在这项拨款提案中总结的初步研究结果表明，在脑损伤后30分钟进行适度的创伤后低温(33oC)可以提高癫痫阈值，降低神经元的脆弱性和海马区异常的轴突萌发。因此，本提案将以这些令人兴奋的发现为基础，通过研究受体依赖在脑外伤后癫痫易感性发展中的作用机制，首次采用包括亚低温和神经递质受体定向治疗在内的联合治疗方法来改善创伤结局，减少PTE的发生率。在具体目标1中，将使用包括电生理学和认知评估在内的临床相关结果指标来确定损伤严重程度对亚急性(1周和4周)和慢性(12周和1年)癫痫易感性的影响。创伤的严重程度与PTE的临床表现有关，但目前还没有直接解决这一问题的实验。在这一系列研究中，将在创伤后的几个时间点给予阈值以下剂量的癫痫诱导剂戊四唑(PTZ)，以确定癫痫阈值是否发生损伤严重程度相关的变化。在具体目标2中，将评估创伤后由于抑制性(GABAA)和兴奋性(NR2B)受体功能失衡而导致局部海马区回路活动改变的证据。这些研究将确定癫痫持续状态后受体定位的变化是否会影响脑外伤后癫痫易感性的发展。此外，还将进行海马区神经元脆弱性的模式以及苔藓纤维发芽的证据，以确定这些创伤后果是否与癫痫阈值的变化有关。定量免疫细胞化学、免疫印迹和原位杂交方法将用于区域和细胞蛋白质和mRNA的评估，以确定这些损伤严重程度相关的变化。最后，在具体目标3中，将测试一种新的联合治疗策略，包括适度创伤后低温联合NR2B受体阻滞剂(RO25,6981)。在中枢神经系统损伤后，适度低温的益处已经得到了很好的证明，但对于PTE来说，这一点尚不清楚。因此，这种联合方法可能是提供治疗PTE的临床前疗效数据的关键。单一治疗模式的优点和局限性也将直接与这种组合方法进行比较，以评估治疗窗口、剂量反应和治疗效果。根据初步发现，这种组合方法应该可以防止神经元丢失、受体易损性以及包括癫痫发作活动和认知功能在内的行为结果测量。建议的研究将由一组经验丰富的研究人员进行，他们在脑损伤的病理生理学和治疗方面有良好的记录。来自这些研究的数据可能被用来支持针对这一脆弱患者群体的PTE的临床试验。

DESCRIPTION (provided by applicant): Posttraumatic epilepsy (PTE) is a frequent consequence of traumatic brain injury (TBI) in both the civilian and military population. Although some investigations have been conducted to evaluate the pathophysiology of this clinical syndrome, no proven therapies have been validated in the human PTE population. Our recent findings demonstrate that moderate fluid percussion brain injury in rats leads to reduced seizure threshold weeks to months after trauma. This alteration in neuronal and circuit excitation is supported by behavioral, electrophysiological and histopathological data. In addition, preliminary findings summarized in this grant proposal demonstrate that modest posttraumatic hypothermia (33oC) induced 30 minutes after TBI increases seizure threshold, reduces neuronal vulnerability and aberrant axonal sprouting in the hippocampus. Therefore, the present proposal will build on these exciting findings by investigating receptor-dependent mechanisms of action on the development of seizure susceptibility after TBI and will for the first time utilize a combination therapeutic approach including modest hypothermia and neurotransmitter receptor directed therapy to improve traumatic outcome and reduce the incidence of PTE. In Specific Aim 1, the impact of injury severity on subacute (1 and 4 weeks) and chronic (12 wks and 1 yr) seizure susceptibility using clinically relevant outcome measures including electrophysiology and cognitive assessment will be determined. Injury severity has been associated with the clinical manifestation of PTE but there currently are no experiments directly addressing this issue. In this series of studies, a subthreshold dose of the seizure-inducing agent pentylenetetrazole (PTZ) will be given at several post-traumatic time points to determine if injury severity- dependent changes in seizure threshold occur. In Specific Aim 2, evidence for alterations in local hippocampal circuit activity after trauma due to an imbalance in inhibitory (GABAA) and excitatory (NR2B) receptor function will be assessed. These studies will determine if changes in receptor localization seen after status epilepticus influence the development of seizure susceptibility after TBI. In addition, patterns of neuronal vulnerability in hippocampal regions as well as evidence for mossy fiber sprouting will be conducted to determine if these traumatic consequences can be correlated with changes in seizure threshold. Quantitative immunocytochemical, western blotting and in situ hybridization approaches for regional and cellular protein and mRNA assessment will be performed to determine these injury severity-dependent changes. Finally, in Specific Aim 3, a novel combination treatment strategy including modest posttraumatic hypothermia combined with a NR2B receptor blocker (Ro 25,6981) will be tested. The benefits of modest hypothermia are well documented after CNS injury but are unknown for PTE. Therefore, this combination approach may be the key to providing pre-clinical efficacy data in treating PTE. The benefits and limitations of single treatment paradigms will also be directly compared to this combination approach to assess therapeutic window, dose response as well as therapeutic efficacy. Based on preliminary findings, this combination approach should provide protection against neuronal drop-out, receptor vulnerability as well as behavioral outcome measures including seizure activity and cognitive function. The proposed studies will be performed by a group of experienced investigators that have a proven track record in the pathophysiology and treatment of TBI. Data from these studies could potentially be used to support clinical trials targeting PTE in this vulnerable patient population.