NEUROMOLECULAR BASIS FOR PAIN IN SCI AND BURN INJURY

描述(由申请人提供)： 项目摘要慢性疼痛常见于烧伤和脊髓损伤(SCI)后。目前可用的治疗方法往往无效或只有部分有效。尽管慢性疼痛是烧伤和脊髓损伤患者的常见主诉，但对烧伤后疼痛的发生和持续的机制知之甚少。我们的目标是识别和表征导致烧伤和脊髓损伤后疼痛的细胞和分子机制，目的是为更有效的疼痛管理描绘特定的目标。我们的最新进展包括建立了一种大鼠烧伤模型，该模型产生了与脊髓背角(DH)神经元的超兴奋性相关的长期机械性痛觉异常，并证明了在该模型中，疼痛和DH的超兴奋性伴随着DH小胶质细胞的激活而发生，疼痛的传播与小胶质细胞的激活平行。此外，我们还发现，急性早期抑制小胶质细胞的激活可以减轻烧伤所致的机械性痛觉异常和去甲肾上腺素神经元的过度兴奋性。我们还证明，脊髓损伤后持续的低水平疼痛与小胶质细胞的激活有关，一些小胶质细胞的功能受钠通道调节，并可被钠通道阻滞剂减弱。最近，我们还发现，激活的中性粒细胞显著增加了DRG神经元的兴奋性，表现为阈值降低和放电频率增加。我们的初步数据表明，在烧伤和脊髓损伤后，当疼痛行为明显时，巨噬细胞渗入背根节。我们还发现，在烧伤和脊髓损伤后，在活体中的双氢脱氢酶神经元的高兴奋性与脱氢酶小胶质细胞的激活有关。我们现在计划通过以下具体目标在我们的进展基础上再接再厉。1.阐明烧伤后背根神经节、背根神经节、背根神经节和神经胶质细胞的分子变化，探讨烧伤疼痛的药物治疗新途径。2.观察钠通道阻滞剂对脊髓损伤后小胶质细胞活性的影响，确定通道阻断剂是否能减少小胶质细胞的激活，减轻疼痛行为。3.研究巨噬细胞在水平和/或低于水平的背根节内的渗透是否与脊髓损伤后神经病理性疼痛的发展和/或持续有关。4.确定钠通道阻滞剂是否能减少脊髓损伤后巨噬细胞对DRG的侵袭，以及中和肿瘤坏死因子-α是否能减少巨噬细胞对脊髓损伤后DRG的侵袭。5.研究巨噬细胞和小胶质细胞对DRG和DH神经元兴奋性的影响，并确定是否可以通过中和免疫细胞表达的细胞因子来预防这些细胞激活后的DRG神经元的过度兴奋性。

DESCRIPTION (provided by applicant): PROJECT SUMMARY Chronic pain occurs frequently after burn injury and spinal cord injury (SCI). Currently available treatments are often ineffective or only partially effective. Relatively little is known about the mechanisms responsible for the onset and persistence of pain following burn injury, despite chronic pain being a frequent complaint of burn- injured and SCI patients. Our goal is to identify and characterize cellular and molecular mechanisms that contribute to pain following burn and spinal cord injuries, with the objective of delineating specific targets for more effective pain management. Our recent progress includes development of a burn injury model in rats that produces long-lasting mechanical allodynia associated with hyperexcitability of spinal cord dorsal horn (DH) neurons, and demonstration that pain and DH hyperexcitability occur concomitant with activation of DH microglia, with the spread of pain paralleled by spreading microglial activation in this model. In addition, we have shown that acute early inhibition of microglial activation attenuates burn-induced mechanical allodynia and DH neuronal hyperexcitability. We have also demonstrated that the maintenance of below-level pain following SCI is associated with activation of microglia, and that some microglial functions are regulated by Na channels and can be attenuated with Na channel blockade. Recently, we have also shown that activated polymorphonuclear neutrophils significantly increase excitability of DRG neurons, as manifested by lowered threshold and increased firing frequency. Our preliminary data indicate that macrophages infiltrate DRG following burn injury and SCI, at a time when pain behavior is evident. We have also shown hyperexcitability in DH neurons in vivo in conjunction with activation of DH microglia following burn injury and SCI. We now plan to build upon our progress, via the following specific aims. 1. Elucidate the molecular changes in DRG and DH neurons, and glia, following burn injury, and examine novel pharmacotherapeutic approaches to pain following burn injury. 2. Investigate the effect of Na channel blockade on the activity of microglia following SCI, and determine whether channel blockade can reduce microglial activation and attenuate pain behavior. 3. Examine if infiltration of macrophages into at- and/or below-level DRG is associated with the development and/or persistence of neuropathic pain following SCI. 4. Determine whether Na channel blockade attenuates macrophage infiltration into DRG following SCI and whether neutralizing TNF-a reduce macrophage infiltration into DRG following SCI. 5. Investigate the effects of macrophages and microglia on the excitability of DRG and DH neurons, and determine whether DRG neuron hyperexcitability following activation of these cells can be prevented via neutralization of cytokines which are expressed by immune cells.