Descending Modulation of Nerve Injury and Injury-Evoked Pain

神经损伤和损伤引起的疼痛的降序调节

• 批准号: 7966916
• 负责人: Toni Shippenberg
• 金额: $ 70.74万
• 依托单位: NATIONAL INSTITUTE ON DRUG ABUSE
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/7966916
• 关键词: AMPA Receptors; Acquired Immunodeficiency Syndrome; Acute; Adverse effects; Affect; Agonist; Analgesics; Animal Model; Attenuated; Behavior; Brain; Brain region; Constipation; Data; Development; Diabetes Mellitus; Dose; Etiology; Exhibits; Family; Formalin; Formalin Tests; Fright; Gene Deletion; Genes; Hour; Hyperalgesia; Hypersensitivity; Immunohistochemistry; Indium; Inflammation; Inflammatory; Injection of therapeutic agent; Injury; Knockout Mice; Legal; Lentivirus Vector; Limb structure; Maintenance; Mechanics; Mediating; Modeling; Morphine; Mus; Neurons; Neuropathy; Neurosciences; Nociception; Nociceptors; Opiates; Output; Pain; Pain management; Peripheral; Persistent pain; Pharmaceutical Preparations; Phase; Physicians; Posterior Horn Cells; Primary Hyperalgesias; Process; Protein Family; Proteins; Rattus; Receptor Activation; Relative (related person); Role; Secondary Hyperalgesias; Sensory; Series; Spinal; Spinal Cord; Synapses; Synaptic Transmission; System; Techniques; Testing; Therapeutic; Therapeutic Effect; Thermal Hyperalgesias; Time; Tissues; Ventilatory Depression; Viral; allodynia; antiretroviral therapy; compliance behavior; dorsal horn; dysphoria; endogenous opioids; inflammatory pain; injured; kappa opioid receptors; member; mu opioid receptors; nerve injury; novel; novel therapeutics; pain behavior; painful neuropathy; receptor function; relating to nervous system; response; transmission process

The rostral ventromedial medulla (RVM), with its projections to the dorsal horn, constitutes the efferent component of a pain-control system that descends from the brain to the spinal cord. Considerable evidence has emerged regarding participation of this system in persistent pain conditions such as inflammation and neuropathy. The role of this brain region in mediating the analgesic effects of opiates such as morphine is well known. The RVM normally exerts an inhibitory influence on dorsal horn neurons However, persistent noxious stimulation triggers dynamic, time-related alterations in RVM synaptic activity. In inflammatory pain models, descending facilitation transiently increases reducing the net effect of inhibition. Over time, descending inhibition increases resulting in decreased nocifensive behavior. After nerve injury, RVM plasticity leads to facilitation of spinal cord nociceptive output, exacerbation of primary hyperalgesia and enhanced sensory input from adjacent regions (secondary hyperalgesia). AMPA receptor activation in the RVM has been shown to inhibit spinal nociceptive transmission and nocifensive behavior. Increased AMPA receptor function in the RVM is implicated in the activity-dependent plasticity that occurs in response to persistent pain produced by tissue inflammation. Targeting and synaptic clustering of AMPA receptors is essential for efficient excitatory transmission. NP1 is a member of the pentraxin family of proteins that is expressed exclusively in neurons and facilitates AMPA receptor clustering. Given the postulated role of NP1 in excitatory synaptic transmission and the role of AMPA receptor systems in pain processing, we have used gene deletion and viral-mediated transfer techniques to examine whether manipulations that target this protein can affect the expression of persistent pain. To investigate the role of NP1 in inflammatory pain, we quantified pain-related behavior in wildtype and NP1 knock out mice following intraplantar formalin injection; an animal model of tonic pain resulting from tissue injury. This test is characterized by two phases of pain behavior: an early phase caused by direct activation of peripheral nociceptors (05 min after injection) and a late phase (1540 min after injection) which reflects early central hypersensitivity. Mice lacking the gene encoding NP1 exhibited significantly greater nocifensive behavior in the late phase of the formalin test relative to wildtypes. However, neither early phase behavior nor basal nociceptive thresholds were altered suggesting that lack of NP1 specifically exacerbates inflammatory hypersensitivity induced by intraplantar formalin. Immunohistochemistry revealed a marked induction of NP1 in the RVM within 20 min after formalin injection. Significant induction was still apparent two hours after injection. To determine whether NP1 expression in the RVM is involved in the descending modulation of nociception, we generated a series of lentiviral vectors to enable region-specific silencing or over-expression of the NP1 protein. Silencing NP1 expression in the RVM of rats significantly potentiated formalin-evoked nocifensive behaviors, consistent with an obligatory role of NP1 in the RVM in the descending inhibition of tonic pain. Our studies also suggest that targeting this protein is effective in the treatment of neuropathic pain. Pain after nerve injury has long been explained by increased excitability of primary afferents and sensitization of dorsal horn nociceptive circuits. However, more recent studies have revealed that descending facilitatory influences from the RVM are critical for the maintenance of experimental neuropathic pain . To determine the contribution of NP1 to nerve-injury evoked pain, we assessed mechanical hypersensitivity in wild type and NP1 knock out mice following spared nerve injury. Nerve injury led to marked mechanical hypersensitivity of the injured limb. This enhanced nociception is significantly inhibited in NP1 knockout mice. In order to probe the specific involvement of RVM NP1 in mediating the attenuated response of NP1 knockout mice, we infused a lentiviral vector which drives expression of functional NP1 protein directly into the RVM. Selective rescue of RVM NP1 expression in knockout mice restores allodynia produced by nerve injury. Consistent with the data obtained in NP1 knockout mice, silencing NP1 expression in the RVM of rats prior to nerve injury inhibits allodynia. Furthermore, it decreases mechanical hyperalgesia. These findings are consistent with the observation that descending facilitatory systems arising in the RVM are necessary for the maintenance of neuropathic pain and identify NP1 in the RVM as a critical element in the descending facilitation of nerve-injury evoked pain. Together, these data suggest that targeting NP1 may be a novel therapeutic strategy for reversing persistent pain of diverse etiologies. On-going studies are examining the role of NP1 in other conditions of perisistent pain including those associated with diabetes and AIDS antiretroviral therapy. The role of other members of the pentraxin family in pain modulation is currently being assessed.

延髓头端腹内侧（RVM）及其向背角的投射，构成了从大脑向下延伸到脊髓的疼痛控制系统的传出部分。大量证据表明该系统参与持续性疼痛病症，例如炎症和神经病变。该大脑区域在介导吗啡等阿片类药物的镇痛作用中的作用是众所周知的。 RVM 通常对背角神经元产生抑制作用，然而，持续的有害刺激会触发 RVM 突触活动的动态、与时间相关的变化。 在炎性疼痛模型中，下降促进短暂增加，减少了抑制的净效应。 随着时间的推移，下降抑制增加，导致伤害行为减少。神经损伤后，RVM 可塑性导致脊髓伤害性输出的促进、原发性痛觉过敏的加剧以及邻近区域的感觉输入的增强（继发性痛觉过敏）。 RVM 中的 AMPA 受体激活已被证明可以抑制脊髓伤害性传递和伤害行为。 RVM 中 AMPA 受体功能的增强与活动依赖性可塑性有关，这种可塑性是对组织炎症产生的持续疼痛做出反应而发生的。 AMPA 受体的靶向和突触聚集对于有效的兴奋性传递至关重要。 NP1 是五聚蛋白家族的成员，仅在神经元中表达并促进 AMPA 受体聚集。 鉴于 NP1 在兴奋性突触传递中的假定作用以及 AMPA 受体系统在疼痛处理中的作用，我们使用基因删除和病毒介导的转移技术来检查针对该蛋白的操作是否会影响持续性疼痛的表达。为了研究 NP1 在炎性疼痛中的作用，我们量化了足底注射福尔马林后野生型和 NP1 敲除小鼠的疼痛相关行为。组织损伤引起的强直性疼痛的动物模型。该测试的特点是疼痛行为的两个阶段：早期阶段由外周伤害感受器直接激活（注射后 05 分钟）引起，晚期阶段（注射后 1540 分钟）反映早期中枢超敏反应。与野生型相比，缺乏编码 NP1 基因的小鼠在福尔马林测试的后期表现出明显更强的伤害行为。然而，早期行为和基础伤害感受阈值均未改变，表明缺乏 NP1 会特别加剧足底内福尔马林诱导的炎症超敏反应。 免疫组织化学显示注射福尔马林后 20 分钟内 RVM 中 NP1 显着诱导。注射后两小时仍然有明显的诱导作用。为了确定 RVM 中的 NP1 表达是否参与伤害感受的下行调节，我们生成了一系列慢病毒载体，以实现 NP1 蛋白的区域特异性沉默或过度表达。沉默大鼠 RVM 中的 NP1 表达可显着增强福尔马林诱发的伤害行为，这与 RVM 中 NP1 在强直性疼痛下降抑制中的必然作用一致。我们的研究还表明，针对这种蛋白质可有效治疗神经性疼痛。 长期以来，神经损伤后的疼痛一直被解释为初级传入神经的兴奋性增加和背角伤害性回路的敏化。然而，最近的研究表明，RVM 的下降促进影响对于实验性神经病理性疼痛的维持至关重要。为了确定 NP1 对神经损伤引起的疼痛的影响，我们评估了野生型和 NP1 敲除小鼠在神经损伤后的机械超敏反应。神经损伤导致受伤肢体明显的机械过敏。这种增强的伤害感受在 NP1 敲除小鼠中被显着抑制。为了探究 RVM NP1 在介导 NP1 敲除小鼠的减毒反应中的具体参与，我们将驱动功能性 NP1 蛋白直接表达的慢病毒载体注入 RVM。选择性挽救基因敲除小鼠中的 RVM NP1 表达可恢复神经损伤产生的异常性疼痛。与在 NP1 敲除小鼠中获得的数据一致，在神经损伤之前沉默大鼠 RVM 中的 NP1 表达可抑制异常性疼痛。此外，它还能减少机械性痛觉过敏。这些发现与以下观察结果一致：RVM 中出现的下降易化系统对于维持神经性疼痛是必要的，并且将 RVM 中的 NP1 确定为神经损伤诱发疼痛的下降易化的关键元素。总之，这些数据表明，靶向 NP1 可能是逆转不同病因引起的持续性疼痛的一种新的治疗策略。正在进行的研究正在研究 NP1 在其他持续性疼痛病症中的作用，包括与糖尿病和艾滋病抗逆转录病毒治疗相关的病症。目前正在评估五聚蛋白家族其他成员在疼痛调节中的作用。