神经元限制性沉默因子调控μ型阿片受体表达参与髓核免疫炎性反应致神经根性痛的机制研究

Radicular pain is a pain syndrome of the innervated area coursed by the nerve noot impairment. With a high prevalence, a long disease course and a high rate of disability, radicular pain places an enormous economic burden on society. As underlying mechanisms are not clear, current treatments for radicular pain have poor efficacy. With a lumber disc herniation rat model in a pioneer study, we found that expressions of μ-opioid receptor (MOR) in spinal dorsal horn as well as in dorsal root ganglions (DRG) were significantly down-regulated. At the same time, mechanical allodynia and thermal hyperalgesia of the hind paw were observed. Evaluation of expressions of neuron restrictive silencing factor (NRSF) showed that it was greatly up-regulated in the DRG. We speculate that inflammatory mediators, which are released from autoimmune response of nucleus pulposus, would induce up-regulation of NRSF, followed by expression changes of MOR via NRSF mediated epigenetic mechanisms and finally the development of radicular pain. We plan first to observe the relationship between abnormal nociceptive behaviors and the expression change of MOR, as well as its potential regulators. Subsequently efforts will be made to explore the signal transduction pathways by which inflammatory mediators induce expression changes of NRSF. Finally, the method of chromatin immunoprecipitation (ChIP) will be used to elucidate the exact mechanisms underlying NRSF induced modulation of MOR expression. This study is of important significance for investigating the pathogenesis of chronic radicular pain, clarifying mechanisms underlying modulation of MOR expression, and screening of drug targets. Furthermore, it will provide new strategies for the prevention and treatment of chronic radicular pain.

神经根性痛是由于神经根异常导致的神经支配区域的疼痛综合征。神经根性痛发病广泛，病程迁延，致残率高，给社会经济带来沉重负担。因发病机制不清，治疗效果欠佳。采用椎间盘突出模型大鼠，我们观察到脊髓背角及背根神经节(DRG)中μ型阿片受体（MOR）表达下调，大鼠后肢出现痛敏状态；同时发现DRG中神经元限制性沉默因子（NRSF）表达显著增加。我们推测髓核自体免疫反应释放的炎性因子诱导NRSF表达上调，继而经表观遗传学机制调控MOR表达改变，导致了慢性神经根性痛的发生。本课题拟首先观察MOR及其潜在调控因素改变与痛行为异常的关系，随后探寻炎症因子导致NRSF表达变化的信号转导通路，最后通过染色体免疫共沉淀的研究方法，阐明NRSF调控MOR表达的确切机制。本研究对于明确慢性神经根性痛的发病机理，揭示MOR的表达调控机制，筛选慢性神经根性痛的镇痛靶点，为神经根性痛的预防和治疗提供新策略具有重要的意义。

神经根性痛是由于神经根异常导致的神经支配区域的疼痛综合征。神经根性痛发病广泛，病程迁延，致残率高，给社会经济带来沉重负担。因发病机制不清，治疗效果欠佳。采用椎间盘突出模型（LDH）大鼠，我们观察到脊髓背角及背根神经节(DRG)中μ型阿片受体（MOR）表达下调，大鼠后肢出现痛敏状态；同时发现DRG 中神经元限制性沉默因子（NRSF）表达显著增加。我们对NRSF在DRG中的分布情况进行了观察，进一步对不同时间点MOR及NRSF的表达进行定量观察研究发现，LDH大鼠DRG中MOR表达与NRSF表达呈显著负相关关系（r=0.901, P<0.001）。进一步采用反义寡核苷酸（AS-ODN）鞘内注射的方法，基因敲减NRSF在DRG中的表达，伴随着NRSF表达的下调，LDH模型大鼠DRG中MOR表达上调，伴随着吗啡镇痛效能的改善；我们进一步对NRSF表达改变的机制进行研究，发现LDH术后14天，DRG中ERK，P-ERK、AP-1、Sp-1等显著上调（P<0.05, n=8），同时采用免疫共沉淀（ChIP）的方法发现，NRSF启动子区域组蛋白乙酰化增加，转录活化；采用酶联免疫吸附试验（ELISA）分析显示，DRG中多种神经炎症因子表达增加，鞘内给予TNF-a的特异性抑制剂，可抑制NRSF的表达上调；进一步采用神经元原代培养的方法证实，TNF-a特异性抑制剂可以阻断TNF-a诱导的NRSF表达上调，提示神经炎症因子介导了LDH模型大鼠NRSF表达上调的过程。这些研究结果提示，腰椎间盘突出模型大鼠DRG中神经炎症反应，导致NRSF表达上调，继而抑制MOR表达，参与了椎间盘突出导致慢性神经根性痛的过程。本研究对于明确慢性神经根性痛的发病机理，揭示MOR 的表达调控机制，筛选慢性神经根性痛的镇痛靶点，为神经根性痛的预防和治疗提供新策略具有重要的意义。