表观遗传学调控脊髓和杏仁中央核神经元组蛋白乙酰化对应激诱发内脏痛的抑制作用

Visceral pain is one of main symptoms of irritable bowel syndrome (IBS). The mechanisms of IBS occurrence are still unclear and an effective therapeutic treatment for IBS is lacking. The incidence and exacerbation of IBS are associated with stress. Our preliminary studies showed that the stress of three day repeated forced swim developed visceral hypersensitivity, a visceral pain model of IBS. Spinal intrathecal injection of histone deacetylase (HDAC) inhibitors and infusion of HDAC inhibitors into the central nucleus of the amygdala (CeA) attenuated stress-induced visceral pain. In this study, changes in the histone acetylation, electrophysiological properties, expression of certain of inhibitory neurotransmitters such as γ-aminobutyric acid (GABA) and type II metabotropic glutamate receptor mGluR2/3 in the CeA and the dorsal horn of spinal cord related to visceral pain in stress-induced visceral pain model and intervention with HDAC inhibitors will be examined. Whether GABAA receptor and mGluR2/3 in the spinal cord and the CeA are involved in the inhibitory role of HDAC inhibitor on stress-induced visceral pain will be clarified. The role of the CeA and the spinal cord in the development of stress-induced visceral pain will be further investigated. All data from this study will provide a theoretical basis for the development of new analgesic drugs on visceral pain based on the target of epigenetic mechanisms.

内脏痛是肠易激综合征的主要症状之一，其发病机理尚不明确且缺乏有效治疗药物。肠易激综合征的发病和症状加重与应激密切相关。我们预实验发现三天强迫游泳应激诱发大鼠内脏痛敏化，能模拟肠易激综合征症状；脊髓和杏仁中央核应用组蛋白去乙酰化酶（HDAC）抑制剂能阻断应激诱发的内脏痛，提示表观遗传学调控参与内脏痛发生发展过程，但其机制尚不清楚。本课题采用电生理和分子生物学等技术，观察强迫游泳应激刺激以及HDAC抑制剂干预对内脏相关脊髓节段和杏仁中央核的组蛋白乙酰化水平、神经元电生理特性和相关抑制性递质γ-氨基丁酸（GABA）和代谢性II型谷氨酸受体mGluR2/3表达的影响，明确GABAA受体和mGluR2/3受体是否介导HDAC抑制剂对强迫游泳应激诱发内脏痛的调制作用，阐明杏仁中央核和脊髓在应激诱发产生内脏痛的神经机制，为研制以表观遗传学调控为作用靶点，治疗肠易激综合征及伴发内脏痛的药物提供理论依据。

研究背景：.肠易激综合征（irritable bowel syndrome, IBS）等功能性疼痛综合征的发病率呈逐年增加的趋势，IBS的发病和症状加重与精神因素有关，但是其机制还不清楚，表观遗传学机制和痛觉下行调控是否参与更是知之甚少。..研究内容：.本研究应用记录内脏运动反应、脊髓背角内脏相关神经元电生理学记录、蛋白印迹技术等方法观察组蛋白乙酰化水平变化及痛觉下行调控是否参与重复强迫游泳（forced swim, FS）应激及颌面部炎症合并复合应激诱发的内脏痛敏化和躯体痛敏化。组蛋白乙酰化酶抑制剂辛二酰苯胺异羟肟酸（suberoylanilide hydroamic acid，SAHA）、5-HT3受体和胆囊收缩素（cholecystokinin, CCK）2受体参与的痛觉下行易化系统激活和5-HT2C受体参与的下行抑制系统功能减弱是否导致颌面部炎症合并应激引起的内脏痛敏化和躯体痛敏化。..研究结果：.1. 表观遗传学调控参与应激诱发的内脏痛敏化：脊髓鞘内注射SAHA可以翻转连续3天FS引起的内脏痛敏化。.2. 组蛋白去乙酰化酶抑制剂丙戊酸钠调控应激诱发的内脏痛敏化和躯体痛敏化：连续腹腔注射丙戊酸钠可以翻转3天FS应激引起的内脏痛觉敏化，鞘内注射选择性5-HT2C受体拮抗剂能翻转脊髓中5-HT2C受体表达的下调，以及丙戊酸钠的镇痛作用。 .3. 颌面部炎症合并应激对脊髓背角内脏相关神经元的影响：束缚应激引起脊髓背角快速反应型内脏相关神经元放电在第4、7周明显增高，颌面部炎症合并束缚应激引起快速反应型内脏痛相关神经元放电在应激后第4周明显增高，但是持续反应型内脏相关神经元放电在应激后第7周明显增高。.4.颌面部炎症合并复合应激刺激诱发大鼠躯体痛敏化和焦虑抑郁样表现：脊髓5-HT3受体参与应激引起的躯体痛敏化。CCK2受体可能通过激活脊髓细胞外信号调节激酶1/2（ERK1/2）参与颌面部炎症合并应激诱导内脏痛敏化和躯体痛敏化。..结论： .重复FS应激及颌面部炎症合并复合应激可诱发内脏痛敏化和躯体痛敏化，表观遗传学机制和痛觉下行调控在痛敏化的发生中有重要作用。本课题揭示了组蛋白乙酰化、5-HT受体和CCK2受体介导应激诱发内脏痛和躯体痛的机制，为研制新型镇痛药提供了理论依据。