Microglial Regulation in Opioid Tolerance, Hyperalgesia and Addiction

描述（由申请方提供）：本提案的主要目的是确定滥用药物（即阿片类药物）对神经胶质细胞机制的影响，该机制有助于药物诱导的痛觉过敏和耐受。这些研究也可能有助于阐明物质滥用诱导的可塑性，即与药物成瘾中的渴望和复发相关的生理学。神经胶质细胞（特别是小胶质细胞和星形胶质细胞）曾经被认为仅在CNS中起支持作用，现在正受到深入研究，作为许多疾病的病理学的主要贡献者，包括神经性疼痛、阿片类药物耐受和最近的药物成瘾。在对CNS的应激（例如损伤或外源性施用）之后，小胶质细胞变得具有反应性，如通过增强的表面或胞质蛋白表达、形态学变化、增殖和迁移所定义的。有人提出，一旦激活，特定的小胶质细胞保持激活后或启动，即它们保留记忆以改变对随后刺激的反应。这可能是长期给药后阿片类药物耐受以及药物成瘾的潜在机制。我们建议通过调查以下假设来研究小胶质细胞在阿片类药物耐受中的作用：慢性阿片类药物诱导持续的CNS小胶质细胞反应，导致小胶质细胞和伤害性神经元之间的直接信号传导，表现为痛觉过敏和/或耐受。此外，我们推测，这种选择性激活增强细胞外ATP/ADP激活P2 X4受体启动小胶质细胞迁移。这些迁移细胞产生局部升高的趋化因子（即单核细胞趋化蛋白-1/CCL2）和其他可扩散的促炎因子，诱导背角神经元致敏和耐受形成。将使用体外原代新生儿皮质和成年脊髓小胶质细胞、体内成年大鼠并通过完成以下特定目的来研究总体假设：1）建立初步数据以表征阿片类药物诱导的小胶质细胞体外反应性。2)探讨阿片类药物诱导迁移的体内外机制。3)确定后激活的小胶质细胞是否保留记忆和机制，以改变对随后暴露于阿片类药物或应激源的反应。阐明阿片类药物耐受性的机制有可能通过为药物发现提供新的靶点来帮助目前药物无法治疗的大量患者人群。总之，这些研究将提供一个全面的和多学科的方法来研究中枢神经系统神经免疫激活的影响，特别是小胶质细胞反应阿片类药物耐受性和阿片类药物诱导的痛觉过敏。来自这些拟议研究的数据将提供重要的新信息，并可能导致新的药典，以减少阿片类药物耐受性。此外，这些结果可能对理解阿片类药物成瘾期间发生的CNS可塑性产生更深远的影响。公共卫生相关性：本提案的主要目的是确定滥用药物（即阿片类药物）对神经胶质细胞机制的影响，这些机制有助于药物诱导的痛觉过敏和耐受。这些研究也可能有助于阐明物质滥用诱导的可塑性，即与药物成瘾中的渴望和复发相关的生理学。

DESCRIPTION (provided by applicant): The primary purpose of this proposal is to identify the effects of drugs of abuse (i.e. opioids) on glial cell mechanisms that contribute to drug-induced hyperalgesia and tolerance. These studies may also aid in elucidating substance abuse-induced plasticity, the physiological correlate to craving and relapse in drug addiction. Once thought to only serve a supportive role in the CNS, glial cells (specifically microglia and astrocytes) are now coming under intense investigation as major contributors to the pathology of many disorders including neuropathic pain, opioid tolerance and most recently, drug addiction. Following stress to the CNS (e.g. injury or xenobiotic administration) microglia become reactive as defined by enhanced surface or cytosolic protein expression, morphological changes, proliferation and migration. It has been proposed that once activated, specific microglia remain as postactivated or primed, i.e. they retain a memory to alter responses to subsequent stimulation. This could be an underlying mechanism for opioid tolerance following chronic administration, as well as drug addiction. We propose to study the role of microglia in opioid tolerance through investigation of the following hypothesis: Chronic opioids induce sustained CNS microglial reactivity leading to direct signaling between microglia and nociceptive neurons which manifests as hyperalgesia and/or tolerance. Further, we hypothesize that this selective activation potentiates extracellular ATP/ADP activation of P2X4 receptors initiating microglial migration. These migrating cells produce locally elevated chemokines (i.e. Monocyte Chemoattractant Protein-1/CCL2) and other diffusible proinflammatory factors, inducing dorsal horn neuron sensitization and tolerance formation. The overall hypothesis will be investigated using in vitro primary neonatal cortical and adult spinal microglia, in vivo adult rats and through the completion of the following Specific Aims: 1) Build on preliminary data to characterize opioid-induced microglial reactivity in vitro. 2) Investigate the mechanism of opioid-induced migration in vitro and in vivo. 3) Determine whether postactivated microglia retain memory and mechanisms to alter responses to subsequent exposure to opioids or stressors. Elucidating the mechanisms of opioid tolerance has the potential to aid a large patient population not served by current drugs by providing new targets for drug discovery. Taken together, these studies will provide a comprehensive and multidisciplinary approach to investigate the influence of CNS neuroimmune activation, specifically microglial reactivity on opioid tolerance and opioid-induced hyperalgesia. The data from these proposed studies will provide important new information and may culminate in novel pharmacopeia to reduce opioid tolerance. In addition, the results may have a more far-reaching impact on understanding CNS plasticity that occurs during opioid drug addiction. PUBLIC HEALTH RELEVANCE: The primary purpose of this proposal is to identify the effects of drugs of abuse (i.e. opioids) on glial cell mechanisms that contribute to drug-induced hyperalgesia and tolerance. These studies may also aid in elucidating substance abuse-induced plasticity, the physiological correlate to craving and relapse in drug addiction.