Estrogen Receptors and Nociceptive Signaling in Primary Afferent Neurons

描述(申请人提供)：临床研究表明，功能性疼痛综合征，如肠易激综合征(IBS)、纤维肌痛、慢性盆腔疼痛和躯体形式障碍的共同发病率接近40%至60%。与这些“功能性”疾病相关的间歇性或持续性内脏疼痛在女性中的发生率是男性的两到三倍。对这一现象的可能解释之一是雌激素对疼痛传递的调节。虽然先前已经显示了这种调制的中心位置，但在这里我们建议研究一个外围位置，背根神经节(DRG)。在DRG神经元中，17°-雌二醇(E_2)可迅速抑制由伤害性信号--三磷酸腺苷(ATP)诱导的细胞内钙离子流动。相反，E2也减弱了细胞对阿片受体(MOP)激动剂的抗伤害反应，这意味着E2可能会增强细胞对伤害信号的反应。 雌激素受体介导雌性小鼠初级感觉神经元的伤害性信号传递，这将验证一个普遍的假设，即作用于初级传入伤害性感受器的E2既有伤害感受作用，也有抗伤害感受作用，这取决于哪些信号会聚到DRG上。首先，将在野生型、雌激素受体a和雌激素受体基因敲除小鼠中研究不同的雌激素受体(ER)在E2激活嘌呤能(P2X)和香草素(TRPV1)受体中的作用。其次，由于我们假设E2在内脏和皮肤伤害性感受器上的作用可能不同，我们将比较基因敲除小鼠和野生型小鼠内脏和皮肤DRG神经元中逆行标记的P2X和TRPV1受体激活对[Ca2+]i的反应。第三，E_2可能通过干扰MOP而负性调节阿片类药物的镇痛作用。药理学操作将被用来确定内质网激活如何调节钙通道和MOP功能。受体结合将决定E2是否改变DRG中MOP的数量和亲和力，以及MOP与G蛋白偶联的位置特异性调节。这些实验将定义一个新的伤害性信号的调控位点(S)和机制。此外，它们将提供有关E2对初级感觉神经元的作用的重要信息，以更好地了解在功能性疼痛相关综合征的临床表现中观察到的性别差异。 伤害性感觉系统与功能性疾病的病因学有关，这些疾病通常合并抑郁、恐慌和其他精神障碍，都会带来健康风险。设计针对性别的新疗法将对功能性疼痛障碍患者的健康相关生活质量产生重大影响，显著减少治疗干预。

DESCRIPTION (provided by applicant): Clinical studies suggest the co-morbidity of functional pain syndromes such as irritable bowel syndrome (IBS), fibromyalgia, chronic pelvic pain and somatoform disorders approaches 40% to 60%. The incidence of episodic or persistent visceral pain associated with these "functional" disorders is two to three times higher in women than in men. One of the possible explanations for this phenomenon is the estrogen modulation of pain transmission. While a central site of this modulation has been shown previously, here we propose to study a peripheral site, the dorsal root ganglion (DRG). In DRG neurons, 17¿-estradiol (E2) rapidly inhibits intracellular calcium [Ca2+] flux induced by ATP, a putative nociceptive signal. Conversely, E2 also attenuates anti-nociceptive cellular responses to a ¿-opioid receptor (MOP) agonist, implying that E2 may enhance cellular responses to nociceptive signals. This proposal, Estrogen Receptors Mediate Nociceptive Signaling in Primary Sensory Neurons in Female Mice, will test a general hypothesis that E2 acting on primary afferent nociceptors has both pro-nociceptive and anti-nociceptive effects depending on which signals converge upon DRG. First, the role of different estrogen receptors (ER) in E2 activation of purinergic (P2X) and vanilloid (TRPV1) receptors will be studied in wild type, estrogen receptor-a and estrogen receptor-¿ knock-out mice. Second, since we hypothesize that E2 may act differently on visceral then on cutaneous nociceptors, we will compare the [Ca2+]i response to activation of P2X and TRPV1 receptors in retrograde-labeled visceral and cutaneous DRG neurons from knock-out and wild type mice. Third, E2 may negatively modulate opioid analgesia by interfering with MOP. Pharmacological manipulations will be used to determine how ER activation modulates Ca2+ channel and MOP functions. Receptor binding will determine if E2 alters the number and affinity of MOP in the DRG and the site-specific regulation of MOP coupling to G-proteins. Together these experiments will define a new site(s) and mechanism of E2 modulation of nociceptive signaling. Furthermore, they will provide important information about the action of E2 on primary sensory neurons for a better understanding of gender differences observed in the clinical presentation of functional pain-associated syndromes. Nociceptive systems are implicated in the etiology of functional disorders, which often are complicated by co-morbid depression, panic and other psychiatric disorders, all pose health risks. Designing new gender-specific therapies will have a major impact on health-related quality of life in patients with functional pain disorders, significantly reducing therapeutic interventions.