NEUROMOLECULAR BASIS FOR PAIN IN SCI AND BURN INJURY

描述（由申请人提供）： 烧伤和脊髓损伤（SCI）后经常发生慢性疼痛。目前可用的治疗方法通常无效或仅部分有效。尽管慢性疼痛是烧伤和SCI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。我们最近的进展包括在大鼠中开发烧伤模型，该模型产生与脊髓背角（DH）神经元的过度兴奋相关的持久的机械异常性疼痛，并证明疼痛和DH过度兴奋伴随着DH小胶质细胞的激活而发生，在该模型中，疼痛的扩散通过扩散小胶质细胞激活而抑制。此外，我们已经表明，急性早期抑制小胶质细胞活化减弱烧伤引起的机械异常性疼痛和DH神经元过度兴奋。我们还证明了SCI后维持低于水平的疼痛与小胶质细胞的激活有关，并且一些小胶质细胞的功能受Na通道调节，并且可以通过Na通道阻断来减弱。最近，我们还发现活化的多形核中性粒细胞显著增加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，巨噬细胞浸润DRG烧伤和SCI后，在疼痛行为是明显的时候。我们还显示了在体内DH神经元的超兴奋性与烧伤和SCI后DH小胶质细胞的激活有关。我们现在计划通过以下具体目标，在取得进展的基础上再接再厉。1.阐明烧伤后DRG和DH神经元和胶质细胞的分子变化，并检查烧伤后疼痛的新药物治疗方法。2.研究钠通道阻断对SCI后小胶质细胞活性的影响，并确定通道阻断是否可以减少小胶质细胞活化和减轻疼痛行为。3.检查巨噬细胞浸润到水平和/或水平以下的DRG是否与SCI后神经性疼痛的发展和/或持续有关。4.确定Na通道阻断是否减弱SCI后巨噬细胞浸润到DRG中，以及中和TNF-α是否减少SCI后巨噬细胞浸润到DRG中。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防止这些细胞活化后的DRG神经元过度兴奋。 公共卫生相关性： 在退伍军人事务部和一般的美国人口中，对于与烧伤和脊髓损伤相关的疼痛的更有效的治疗存在非常大的需求。尽管慢性疼痛是烧伤患者最常见的主诉，但对烧伤后疼痛的发生和持续的机制知之甚少。烧伤、神经和脊髓损伤后产生的慢性疼痛和感觉迟钝通常对常规治疗方法有抵抗力。这些形式的疼痛代表了重大的治疗挑战，通常对现有疗法无反应或仅部分反应。我们的目标是识别和表征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。

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. PUBLIC HEALTH RELEVANCE: There is a very substantial need, within the VA and within the U.S. population in general, for more effective treatments for pain associated with burn injury and spinal cord injuries. Relatively little is known of the mechanisms responsible for the onset and persistence of pain following burn injury despite chronic pain being the most frequent complaint of burn-injured patients. Chronic pain and dysethesiae that develop following burn injury, nerve and spinal cord injuries are often resistant to conventional therapeutic approaches. These forms of pain represent significant therapeutic challenges, often being unresponsive or only partially responsive, to existing therapies. 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.