Characteristics and mechanisms of pain in sickle cell disease

描述（由申请人提供）：镰状细胞病（SCD）伴随急性疼痛发作（“危象”）叠加在慢性疼痛上。阿片类药物是严重疼痛的唯一疗法，但需要高剂量的阿片类药物来治疗SCD疼痛。长期使用阿片类药物可能导致继发性不良反应和阿片类药物耐受。SCD中慢性疼痛的潜在机制仍不清楚。描述SCD中的疼痛并确定其潜在机制是开发新的镇痛疗法所必需的。因此，本建议的目标是使用SCD的小鼠模型来检查在这种情况下导致疼痛的外周和脊髓机制。建立的SCD小鼠模型提供了独特的优势，因为它们与人类遗传、血液学和病理学疾病相似。我们推测炎症、缺氧再灌注损伤和“危象”引起的伤害感受器持续激活导致中枢敏感化。我们的初步数据表明，SCD小鼠表现出皮肤（机械，热和冷）和深（握力下降）痛觉过敏与SCD患者中观察到的相似。我们将采用多学科的方法，结合相关的行为学、电生理学和神经化学研究来验证以下假设：（1）镰刀小鼠表现出皮肤和深部痛觉过敏，这可以通过外周大麻素来调节。我们将通过测量对机械、热和冷刺激的退缩反应以及使用握力测量的深部/肌肉骨骼疼痛来检查皮肤疼痛。我们假设足底注射大麻素受体激动剂可以减少皮肤痛觉过敏，这是通过激活CB 1和CB 2受体实现的。(2)SCD伴随着外周神经纤维的激活以及皮肤和脊髓中疼痛的炎性介质。我们将研究导致神经元激活和致敏的外周和脊髓中促炎细胞的激活。(3)SCD中的疼痛涉及伤害性脊髓神经元的敏化。我们将记录单个的，确定的宽动态范围和高阈值的背角神经元在控制和SCD小鼠与痛觉过敏的电生理反应。在拟定的研究中，我们将使用表达镰状血红蛋白的转基因杂合BERK（hBERK）小鼠和表达正常人血红蛋白（HbA-BERK）的年龄和性别匹配的对照小鼠。镰状hBERK小鼠具有混合的遗传背景，并携带人类1和2S球蛋白的连锁转基因的单拷贝。它们是敲除鼠1珠蛋白的纯合子和敲除鼠2珠蛋白的杂合子。HbA-BERK对照具有相同的遗传背景。我们预计，镰状小鼠将表现出类似于SCD疼痛的疼痛特征，大麻素激活CB 1和C2受体将减弱痛觉过敏，外周和中枢敏化有助于镰状小鼠的疼痛。这些研究结果将为SCD疼痛机制提供新的信息。了解SCD疼痛的基本机制将导致开发新的和更有效的方法来治疗SCD疼痛。

DESCRIPTION (provided by applicant): Sickle cell disease (SCD) is accompanied by acute painful episodes ("crises") superimposed on chronic pain. Opioids are the only therapy for severe pain, but high doses of opioids are required to treat pain in SCD. Chronic opioid use may lead to secondary adverse effects and opioid tolerance. The mechanisms underlying chronic pain in SCD remain unknown. Characterizing pain in SCD and defining the underlying mechanisms is required to develop novel analgesic therapies. Therefore, the goal of this proposal is to use a murine model of SCD to examine peripheral and spinal mechanisms that contribute to pain in this condition. Established mouse models of SCD offer a unique advantage because of their similarity to human genetic, hematologic and pathological disease. We hypothesize that persistent activation of nociceptors by inflammation, hypoxia- reperfusion injury and "crises" leads to central sensitization. Our preliminary data indicate that mice with SCD exhibit cutaneous (mechanical, heat and cold) and deep (decreased grip force) hyperalgesia similar to that observed in patients with SCD. We will employ a multidisciplinary approach with correlative behavioral, electrophysiological and neurochemical studies to examine the following hypotheses: (1) sickle mice exhibit cutaneous and deep hyperalgesia, which can be modulated by peripheral cannabinoids. We will examine cutaneous pain by measuring withdrawal responses to mechanical, heat and cold stimuli and deep/musculoskeletal pain using measurement of grip force. We hypothesize that intraplantar administration of cannabinoid receptor agonists reduce cutaneous hyperalgesia and this occurs through activation of CB1 and CB2 receptors. (2) SCD is accompanied by activation of peripheral nerve fibers and inflammatory mediators of pain in the skin and spinal cord. We will examine the activation of pro-inflammatory cells in the periphery and spinal cord that lead to neuronal activation and sensitization. (3) Pain in SCD involves sensitization of nociceptive spinal neurons. We will record electrophysiological responses of single, identified wide dynamic range and high threshold dorsal horn neurons in control and in SCD mice with hyperalgesia. In the proposed studies, we will use transgenic heterozygous BERK (hBERK) mice expressing sickle hemoglobin and age and sex matched control mice expressing normal human hemoglobin (HbA-BERK). Sickle hBERK mice have a mixed genetic background and carry a single copy of linked transgenes for human 1 and 2S globins. They are homozygous for knockout of murine 1 globin and heterozygous for knockout of murine 2 globin. HbA-BERK controls have an identical genetic background. We expect that sickle mice will show pain characteristics similar to pain in SCD, that activation of CB1 and C2 receptors by cannabinoids will attenuate hyperalgesia and that peripheral and central sensitization contributes to pain in sickle mice. Results of these studies will provide new information on the mechanisms underlying pain in SCD. Understanding the basic mechanisms of pain in SCD will lead to the development of novel and more effective approaches to treat pain in SCD.