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

描述（由申请人提供）：外周神经性疼痛是由中枢神经系统的适应不良变化引起的，这些变化是由受损感觉神经元的异常活动引发的。越来越多的证据表明，脊髓中的神经可塑性有助于神经病理性疼痛的发展和维持。我们发表的和初步的数据表明，来自神经分泌蛋白VGF（非首字母缩写）的肽可能作为感觉神经元信号发挥作用，在神经损伤后启动和维持脊髓神经元的敏化[3]。拟议的研究将侧重于VEGF衍生肽TLQP-21的脊髓信号传导机制，并将建立在今年C3 aR 1（补体3a受体）作为TLQP-21受体的鉴定基础上。我们的初步数据表明，内源性TLQP-21有助于神经损伤诱导的超敏反应，TLQP-21诱导的痛觉过敏被C3 aR 1抑制所阻断。这些发现暗示C3 aR 1作为抑制脊髓神经病理性疼痛传递的新的治疗靶点。本申请的目的是建立TLQP 21/C3 aR 1系统作为神经性疼痛的基本功能组分。该提议的中心假设是脊髓背角中的C3 aR 1的TLQP-21激活建立并维持神经性疼痛。具体目标1将检验TLQP-21的脊髓效应由C3 aR 1介导且C3 aR 1参与神经性疼痛的建立的假设。拟开展的研究将（1）明确TLQP-21和C3 aR 1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C3 aR 1激活，（3）确定C3 aR 1是否有助于神经性疼痛的行为体征。具体目标2将检验神经损伤增加神经元、小胶质细胞和/或星形胶质细胞中C3 aR 1表达的假设。这些研究将使用（1）表达分析和（2）背角中TLQP-21/C3 aR 1结合的抗体非依赖性可视化来检查神经损伤对脊髓C3 aR 1的影响。具体目标3将阐明神经损伤后对背角中TLQP-21/C3 aR 1激活的神经生理反应增强的假设。这些研究将检查神经损伤对（1）使用体内细胞外记录的背角中神经元活动的TLQP-21调节和（2）脊髓切片中TLQP-21诱发的Ca 2+瞬变的影响。在这些研究完成时，我们将确定TLQP-21与C3 aR 1的关系及其在神经性疼痛的发展和维持中的作用。这些信息将产生重大影响，因为它将TLQP-21/C3 aR 1定义为神经性疼痛的潜在药物靶点。从这项研究中获得的知识将大大推进慢性疼痛领域，并可能扩展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.