G9a/Glp调控神经病理性疼痛表观遗传学机制

Gene methylation is an essential part of epigenetics, and G9a/Glp are histone methyltransferases. In our pre-study investigation we found that with the decrease in pain threshold in mice pain models the expression of G9a/Glp upregulated markedly in the spinal cord dorsal horn; moreover, intrathecal inhibitors of G9a/Glp reduced pain threshold more along with increased neuronal instantanenous activity in the spinal cord, which indicates that G9a/Glp play a role in counter-regulating pain threshold. We proposed that G9a/Glp counter-regulate pain through mathylating GRIN2B on the following bases: 1) G9a/Glp involve in neuronal activity regulation; 2) G9a/Glp methylate gene GRIN2B resulting in NR2B downregulation; 3) overexpression of G9a/Glp in spinal neurons produced identical effects on NR2B expression and neuronal electrophysiology as those from knockdown of gene GRIN2B in spinal neurons, and 4) NR2B is a well-known mediator of neuronal activity. This study proposal will investigate the relationship among G9a/Glp, GRIN2B methylation and neuronal electroactivities in neuropathic pain models, and further will analyze the effects of G9a/Glp overexpression and knockdown on neuronal electroactivities and association with GRIN2B methylation in spinal neuronal stem cells. Our proposal possesses strong originality and will provide evidence to the mechanisms of epigenetic suppression of neuropathic pain, and the more pivotal goal is that it will give us a promising therapeutic target for neuropathic pain.

基因甲基化是表观遗传学重要特征，G9a/Glp是组蛋白甲基转移酶。先前研究中：疼痛模型小鼠痛阈降低同时G9a/Glp高表达于脊髓背角；鞘内注射G9a/Glp抑制剂痛阈降低更明显，脊髓自发放电频率增加，提示G9a/Glp可能反向调节痛阈。基于1）G9a/Glp参与神经电活动调节；2）G9a/Glp致GRIN2B甲基化，NR2B表达下调；3）脊髓神经元G9a/Glp过表达对NR2B及电生理影响与GRIN2B沉默表达相似；4）NR2B参与调控神经电活动，推测G9a/Glp可能通过GRIN2B甲基化达到反向调控疼痛的目的。研究拟以神经病理性疼痛模型探讨其与G9a/Glp、GRIN2B甲基化、神经电活动的关系；进而以脊髓源神经干细胞分析G9a/Glp过表达与沉默表达对神经电活动影响及与GRIN2B甲基化关系。研究具有源头创新性，将为神经病理性疼痛表观遗传学表达抑制机制提供数据，为疼痛治疗提供新靶点。

神经病理性疼痛因机制复杂和临床治疗效果不佳成为疼痛领域最为棘手的难题之一。甲基转移酶异源复合体G9a/Glp是介导组蛋白和多个基因甲基化的重要分子之一。谷氨酸NMDA受体参与并介导神经病理性疼痛痛阈的调控。我们的研究通过建立坐骨神经保留性损伤疼痛小鼠模型，在体和离体探讨了不同神经位点G9a/Glp、GRIN2B甲基化、神经电生理、多巴胺酪氨酸羟化酶Th基因甲基化、ΔFosB、疼痛阈值等之间的相互关系，从而为G9a/Glp相关的神经病理性疼痛表观遗传学机制提供基础数据。研究发现：（1）G9a/Glp具有介导SNI神经损伤神经病理性疼痛发生的新功能；（2）G9a/Glp通过GRIN2B基因甲基化实现对疼痛阈值的调控；（3）G9a/Glp-GRIN2B-ΔFosB是脊髓背角神经元在外周损伤后发生痛觉敏化的重要机制；（4）G9a/Glp通过脊髓上机制参与痛阈调控，也即通过改变VTA区多巴胺神经元Th基因甲基化参与疼痛阈值调控。我们将在此研究发现的基础上，更深入探讨脊髓和脊髓上神经病理性疼痛发生发展的表观遗传学机制，从而切实为神经病理性疼痛的有效干预提供必要的基础数据。