Roles of microglia and prostaglandin receptors in neuroprotection

描述(由申请人提供)： 在退伍军人管理局的医疗保健系统中，迫切需要神经保护疗法，以促进创伤性脑损伤、中风和神经退行性疾病后神经元的存活。减轻神经元丢失的一个潜在领域集中在与神经元损伤相关的神经炎性过程的调节因素上。一个有希望的靶点是环氧合酶2(COX-2)，它催化合成前列腺素的限速步骤，在神经炎症和神经元丢失中发挥重要作用。在中风的动物模型中，当这种酶的活性被药物或遗传操作降低时，神经元存活率会增加。然而，使用COX-2抑制剂的神经保护疗法是有问题的，因为这些药物的使用与心血管并发症有关。因此，最近的努力已经开始识别COX-2下游的靶点，如前列腺素受体。最好的例子是前列腺素E2的EP1受体(PGE2)，它已被证明有助于兴奋性毒性后的神经元损伤。EP1的拮抗剂在中风模型和兴奋性毒性攻击后的体外培养模型中增加神经元的存活。其他炎症过程也会影响神经元的活性。中枢神经系统(CNS)损伤后，小胶质细胞等炎性细胞迁移到损伤区域，使神经元对兴奋性毒性损伤具有更强的抵抗力。然而，关于小胶质细胞如何通过EP1前列腺素受体与神经元相互作用来调节神经元的活性，人们知之甚少。我们最近发现，当小胶质细胞存在时，EP1拮抗剂的神经保护作用就会消失。这一发现表明，神经元EP1对神经元活性的贡献可以由小胶质细胞调节，在小胶质细胞与神经元损伤相关的活体实验中具有重要意义。根据我们的发现，我们假设小胶质细胞的神经保护特性是通过改变神经元中的EP1和EP4受体实现的。我们已经开发了一个强大的体外系统，使我们能够测试小胶质细胞与参与神经元存活的重要信号通路之间的这种新的相互作用。这项提议将检验这一假说，并可能确定以小胶质反应和EP受体调节为中心的新的神经保护策略。特定目标：特定目标#1：确定小胶质细胞是否通过减弱神经元EP1来调节神经保护。具体目标#2：确定小胶质细胞的可溶信号改变神经元的EP1反应并增加神经元对NMDA的抵抗力。具体目标#3：确定小胶质细胞诱导的神经元核EP1受体表达缺失是否有助于增加神经元存活率。具体目标#4：确定小胶质细胞的激活程度如何通过调节神经元EP1来促进神经元的存活。 公共卫生相关性： 创伤性脑损伤、脊髓损伤、中风和神经退行性疾病后，VA医疗保健系统迫切需要促进神经元存活的治疗方法。潜在新疗法的一个有希望的领域可能是调节大脑中导致神经元损伤的炎症成分。我们已经发现，大脑中一种名为小胶质细胞的炎性细胞可能通过改变神经元对其他称为前列腺素的炎性分子的反应来保护神经元。前列腺素是由环氧合酶2(COX-2)产生的，COX-2的抑制剂可以保护神经元。然而，使用COX-2抑制剂的治疗是有问题的，因为与使用它们相关的心血管并发症。因此，最近的努力已经开始识别COX-2下游的靶点，如前列腺素受体。我们已经开发了一种强大的神经元培养系统，使我们能够测试小胶质细胞如何改变调节神经元活性的EP1前列腺素受体。这项工作可能会发现以小胶质细胞反应和EP受体调节为中心的新的神经保护策略。

DESCRIPTION (provided by applicant): There is an urgent need in the VA health care system for neuroprotective therapies that can be applied to promote neuronal survival following traumatic brain injury, stroke and neurodegenerative disease. A potential area for mitigating neuronal loss centers on regulating elements of neuroinflammatory processes associated with neuronal injury. A promising target that has been shown to play a major role in neuroinflammation and neuronal loss is the enzyme cyclooxygenase 2 (COX-2) which catalyzes the rate- limiting step in the synthesis of prostanoids. In animal models of stroke, increased neuronal survival is seen when the activity of this enzyme is diminished by either pharmacological or genetic manipulation. However, neuroprotective therapies utilizing COX-2 inhibitors are problematic because of cardiovascular complications associated with the use of these drugs. As such, recent efforts have begun to identify targets down stream of COX-2 such as the prostanoid receptors. The best example of this is seen with the EP1 receptor for prostaglandin E2 (PGE2) which has been shown to contribute to neuronal injury following excitotoxicity. Antagonists of EP1 increase neuronal survival in stroke models and in vitro in culture models following excitotoxic assault. Other inflammatory processes can also affect neuronal viability. Following injury in the central nervous system (CNS), inflammatory cells such as microglia migrate to the injured area and can render neurons more resistant to excitotoxic insults. However, little is known about how microglia interact with neurons to modulate neuronal viability through the EP1prostanoid receptor. We recently discovered that the neuroprotective effect of EP1 antagonists is lost when microglia are present. This finding indicates that the contribution to neuronal viability by neuronal EP1 can be regulated by microglia and has important implications in vivo where microglia are associated with neuronal injury. Based on our findings, we hypothesize that the neuroprotective properties conferred by microglia are achieved by altering EP1 and EP4 receptors in neurons. We have developed a powerful in vitro system which enables us to test this novel interaction between microglia and an important signaling pathway involved in neuronal viability. This proposal will test the hypothesis and may identify new neuroprotective strategies centered on microglial responses and modulation of EP receptors. SPECIFIC OBJECTIVES: Specific Aim #1: Determine if microglia mediate neuroprotection through attenuation of neuronal EP1. Specific Aim #2: Identify the soluble signals from microglia that alter EP1 response in neurons and increase neuronal resistance to NMDA. Specific Aim #3: Determine if microglial-induced loss of neuronal nuclear EP1 receptor expression contributes to increased neuronal survival. Specific Aim #4: Determine how the degree of microglial activation contributes to neuronal viability through modulation of neuronal EP1. PUBLIC HEALTH RELEVANCE: There is an urgent need in the VA health care system for therapies that promote neuronal survival following traumatic brain injury, spinal cord injury, stroke and neurodegenerative disease. A promising area for potential new therapies may be directed at modulating components of inflammation in the brain that contribute to the injury of neurons. We have discovered that an inflammatory cell in the brain called microglia, may protect neurons by changing how neurons respond to other inflammatory molecules called prostanoids. Prostanoids are made by the enzyme cyclooxygenase 2 (COX-2) and inhibitors of COX-2 can protect neurons. However, therapies utilizing COX-2 inhibitors are problematic because of cardiovascular complications associated with their use. As such, recent efforts have begun to identify targets down stream of COX-2 such as the prostanoid receptors. We have developed a powerful neuronal culture system which enables us to test how microglia can change the EP1 prostanoid receptors that modulate neuronal viability. This work may identify new neuroprotective strategies centered on microglial responses and modulation of EP receptors.