The Role of the Complement System in Spinal Mechanisms of Chronic Pain

项目摘要/摘要 持续的疼痛影响着1亿美国人和1500万乌克兰人。免疫系统至关重要 有助于炎症性和神经性疼痛的发病机制，以及对机制的准确理解 通过这些特定的免疫介质有助于伤害性神经通路的敏化 对于制定更有效的治疗策略至关重要。补语系统是主要的 先天免疫的组成部分，通过不同的机制帮助宿主防御。尽管不断增长 有证据表明补体系统与各种慢性疼痛状态有关，其潜在机制是 不是很清楚。我们为美国和乌克兰团体之间的这项合作提议的主要目标 是为了阐明补体依赖的脊髓机制，这些机制有助于神经病理性的发展 在更广泛的层面上，促进建设和加强乌克兰的可持续研究能力。 机械过敏和自发性疼痛是神经病理性疼痛的共同特征。主 从脊髓到大脑的伤害性输出通路在这种异常的疼痛处理过程中是板层。 背角I投射神经元(PNS)。我们的膜片钳记录从这些神经元使用 创新的完整脊髓准备显示出脊髓输出的异常调节 备用神经损伤(SNI)，一种神经病理性疼痛的常见模型，很好地再现了临床的许多特征 神经性疼痛。最近的研究表明，神经病理性疼痛与脑脊液中 脊髓中的补体效应器，最终导致产生高度活跃的补体 产品C5a。鞘内注射C5a会引起痛觉过敏，而C5基因敲除(KO)和C5a 受体(C5aR1)拮抗剂在神经病理性疼痛的动物模型中产生镇痛作用。我们的预赛 数据显示，C5aR1 KO可预防SNI后的机械超敏反应。在卫生组织中发现了C5aR1 主要是在SNI后被激活的小胶质细胞上。此外，C5aR1的表达是 SNI后增加。我们将使用一种多学科的方法，包括膜片钳记录，光遗传学 刺激和多光子钙成像在创新型完整脊髓准备结合行为学中的应用 用药理学来验证我们的中心假设，即C5a/C5aR1信号在神经病变中发挥重要作用 通过增强输出的小胶质细胞依赖信号影响中枢敏感化的痛觉处理 Dh的Ipn椎板至棘上结构。这项提议将提供对 补体系统在中枢神经系统疼痛处理中的作用，并可能导致新的 针对补体系统的止痛药。在其更广泛的影响中，该项目将促进建立 ，并帮助吸引年轻的乌克兰科学家来乌克兰 在这个领域，提供他们的培训，并推动这个国家的慢性疼痛研究。

PROJECT SUMMARY / ABSTRACT Persistent pain affects 100 million Americans and 15 million Ukrainians. The immune system critically contributes to pathogenesis of inflammatory and neuropathic pain, and precise understanding of mechanisms through which particular immune mediators contribute to sensitization of nociceptive neuronal pathways will be essential for developing more efficacious treatment strategies. The complement system is a principal component of innate immunity that contributes to host defenses via diverse mechanisms. In spite of growing evidence implicating the complement system in various chronic pain states, the underlying mechanisms are not well understood. Our main objectives for this collaborative proposal between the US and Ukrainian groups are to elucidate complement-dependent spinal mechanisms that contribute to the development of neuropathic pain, and at a broader level, to promote building and strengthening sustainable research capacity in Ukraine. Mechanical hypersensitivity and spontaneous pain are common features of neuropathic pain. The main nociceptive output pathway from the spinal cord to the brain underlying this abnormal pain processing is lamina I projection neurons (PNs) of dorsal horn (DH). Our patch-clamp recordings from these neurons using an innovative intact spinal cord preparation demonstrate abnormal regulation of spinal cord output following spared nerve injury (SNI), a common model of neuropathic pain that well reproduces many features of clinical neuropathic pain. Recent studies suggest that neuropathic pain is associated with a robust upregulation of complement effectors in the spinal cord, which ultimately leads to production of a highly active complement product, C5a. Intrathecal administration of C5a produces allodynia, whereas C5 knockout (KO) and C5a receptor (C5aR1) antagonists produce analgesic effects in animal models of neuropathic pain. Our preliminary data show that C5aR1 KO prevents mechanical hypersensitivity following SNI. C5aR1 in the DH is found primarily on microglia that is known to be activated in the DH after SNI. Moreover C5aR1 expression is increased after SNI. We will use a multidisciplinary approach including patch-clamp recordings, optogenetic stimulation and multi-photon Ca2+ imaging in innovative intact spinal cord preparation combined with behavioral pharmacology to test our central hypothesis that C5a/C5aR1 signaling plays important roles in neuropathic pain processing by impacting central sensitization via microglia-dependent signaling that enhances the output of lamina I PNs of the DH to the supraspinal structures. This proposal will provide mechanistic insight into the function of the complement system in the CNS pain processing, and may lead to the development of new analgesic drugs that target complement system. In its broader impact, this project will promote establishment of Center for Excellence in brain disorder research in Ukraine, and help attracting young Ukrainian scientists to this field, providing their training and advancing chronic pain research in this country.