TLQP-21 and C3aR, a Novel Receptor/Ligand Interaction in Neuropathic Pain

描述(申请人提供)：周围神经病理性疼痛是由受损感觉神经元的异常活动引起的中枢神经系统的不适应变化引起的。越来越多的证据表明，脊髓的神经可塑性有助于神经病理性疼痛的发展和维持。我们已发表的初步数据表明，来源于神经分泌蛋白VGF(非缩写)的多肽可能作为感觉神经元信号，在神经损伤后启动和维持脊髓神经元的敏化[3]。拟议的研究将集中在VGF衍生多肽TLQP-21的脊髓信号机制上，并将在今年确定C3aR1(补体3a受体)为TLQP-21的受体的基础上进行。我们的初步数据表明，内源性TLQP-21参与了神经损伤诱导的超敏反应，TLQP-21诱导的痛觉过敏可被C3aR1抑制所阻断。这些发现表明C3aR1是一种新的抑制脊髓神经病理性疼痛传递的治疗靶点。本应用的目的是建立TLQP21/C3aR1系统作为神经病理性疼痛的基本功能成分。该方案的中心假设是TLQP-21激活脊髓背角的C3aR1，建立并维持神经病理性疼痛。具体目标1将检验TLQP-21的脊髓效应是由C3aR1介导的假设，以及C3aR1参与神经病理性疼痛的建立。这些研究将(1)确定TLQP-21和C3aR1在脊髓中的配体-受体关系；(2)确定TLQP-21的脊髓效应是否依赖于C3aR1的激活；以及(3)确定C3aR1是否参与神经病理性疼痛的行为体征。特定目标2将测试神经损伤增加神经元、小胶质细胞和/或星形胶质细胞中C3aR1表达的假设。这些研究将通过(1)表达分析和(2)TLQP-21/C3aR1在背角结合的抗体非依赖性可视化来研究神经损伤对脊髓C3aR1的影响。具体目标3将解决这一假设，即神经损伤后背角对TLQP-21/C3aR1激活的神经生理学反应增强。这些研究将考察神经损伤对(1)TLQP-21对背角神经元活动的调节作用，以及(2)TLQP-21在脊髓切片上引起的钙瞬变的影响。在这些研究完成后，我们将确定TLQP-21与C3aR1的关系以及它们在神经病理性疼痛的发生和维持中的作用。这些信息将产生重大影响，因为它将TLQP-21/C3aR1定义为治疗神经病理性疼痛的潜在药物治疗靶点。从这项研究中获得的知识将极大地推动慢性疼痛领域的发展，并可能延伸到与神经可塑性相关的其他治疗领域。

DESCRIPTION (provided by applicant): Peripheral neuropathic pain results from maladaptive changes in the central nervous system that are initiated by abnormal activity of injured sensory neurons. Increasing evidence indicates that neuroplasticity in the spinal cord contributes to the development and maintenance of neuropathic pain. Our published and preliminary data indicate that peptides derived from the neurosecretory protein VGF (non-acronymic) may function as sensory neuron signals that initiate and maintain sensitization of spinal neurons after nerve injury [3]. The proposed studies will focus on the spinal signaling mechanisms of the VGF-derived peptide TLQP-21 and will build upon the identification this year of C3aR1 (complement 3a receptor) as a receptor for TLQP-21. Our preliminary data show that endogenous TLQP-21 contributes to nerve injury-induced hypersensitivity and that TLQP-21 induced hyperalgesia is blocked by C3aR1 inhibition. These findings implicate C3aR1 as a novel therapeutic target for the inhibition of spinal neuropathic pain transmission. The objective of this application is to establish the TLQP21/C3aR1 system as an essential functional component of neuropathic pain. The central hypothesis of this proposal is that TLQP-21 activation of C3aR1 in dorsal horn of spinal cord establishes and maintains neuropathic pain. Specific aim 1 will test the hypothesis that the spinal effects of TLQP-21 are mediated by C3aR1 and that C3aR1 is involved in the establishment of neuropathic pain. The proposed studies will (1) characterize pharmacologically the ligand-receptor relationship of TLQP-21 and C3aR1 in spinal cord, (2) determine whether the spinal effects of TLQP-21 are dependent on C3aR1 activation, and (3) determine whether C3aR1 contributes to behavioral signs of neuropathic pain. Specific aim 2 will test the hypothesis that nerve injury increases expression of C3aR1 in neurons, microglia, and/or astrocytes. These studies will examine the effects of nerve injury on spinal C3aR1 using (1) expression analysis, and (2) antibody- independent visualization of TLQP-21/C3aR1 binding in dorsal horn. Specific aim 3 will address the hypothesis that neurophysiological responses to TLQP-21/C3aR1 activation in dorsal horn are enhanced after nerve injury. These studies will examine the effects of nerve injury on (1) TLQP-21 modulation of neuronal activity in dorsal horn using in vivo extracellular recording, and (2) TLQP-21 evoked Ca2+ transients in spinal cord slices. At the completion of these studies we will have determined the relationship of TLQP-21 to C3aR1 and their role in the development and maintenance of neuropathic pain. Such information will have a significant impact because it will define the TLQP-21/C3aR1 as a potential pharmacotherapeutic target for neuropathic pain. The knowledge acquired from this research will greatly advance the field of chronic pain and may extend to other therapeutic areas related to neuroplasticity.