NFAT1在脊髓背角小胶质细胞中调节神经病理性疼痛机制的研究

Currently, the drugs for neuropathic pain fail to achieve adequate pain relief for patients. Hence, alternative therapeutic targets should be explored. Neuropathic pain resulting from peripheral nerve injury is associated with dramatic microglial activation and proliferation in the spinal dorsal horn. However, how microglia transform into reactive phenotypes is poorly understood. We found that the transcription factor NFAT1 expression were markedly upregulated in spinal microglia after spinal nerve injury, and the CpG island in NFAT1 promoter region was demethylated. In this project, by using behavioral, genetic, morphological and pharmacological approaches, we will investigate the role and regulation mechanism of NFAT1 in neuropathic pain, including: (1) The expression and distribution of NFAT1 in spinal cord in neuropathic pain. (2) The role of NFAT1 in the development and maintenance of SNL-induced neuropathic pain. (3) The demethylation mechanism of NFAT1 mediating its de novo expression. (4) The upstream signaling transduction pathway of NFAT1 and its downstream target genes. Our findings will reveal a newly observed mechanism for microglial activation and provide new strategy for the development of novel drugs targeting pain in terms of epigenetic regulation and signal transduction of NFAT1.

神经病理性疼痛镇痛药疗效有限，需要寻找新治疗靶点。脊髓小胶质细胞激活与增生参与中枢敏化和慢性疼痛，而脊髓小胶质细胞激活和增生机制尚不明确。我们发现外周神经损伤后转录因子NFAT1在脊髓背角小胶质细胞中表达显著增加,其启动子区CpG岛发生了去甲基化修饰。本项目拟采用脊神经结扎(Spinal nerve ligation，SNL）诱导的神经病理性疼痛模型，采用行为学、分子遗传学、形态学和药理学等方法，研究（1）SNL后NFAT1在脊髓背角的表达时程和细胞定位；（2）脊髓背角小胶质细胞NFAT1在神经病理性疼痛中的作用；（3）脊髓背角NFAT1表达增加的去甲基化机制；（4）脊髓背角小胶质细胞中NFAT1上游信号激活途径和下游靶基因。本研究将阐明背角小胶质细胞中NFAT1对疼痛行为的作用和细胞分子机制，从表达调控和信号传导角度为以NFAT1为靶点研发镇痛药物提供依据和思路。

神经损伤引起的神经病理性疼痛与脊髓小胶质细胞的增殖密切相关，但关于脊髓小胶质细胞增殖的分子机制目前还不清楚。我们的研究发现活化T细胞核因子1（NFAT1）在神经损伤引起的脊髓小胶质细胞增殖和神经病理性疼痛的发生和维持过程中发挥关键作用。NFAT1在脊髓中主要定位于小胶质细胞，NFAT1的表达在脊神经结扎诱导（SNL）的神经病理性疼痛模型小鼠中持续表达上调。小胶质细胞特异敲除NFAT1减轻SNL诱导的神经病理性疼痛。我们的进一步研究表明，NFAT1能够通过其调控的下游基因c-Myc参与小胶质细胞增殖的调控。小胶质细胞特异性表达c-Myc能够诱导疼痛行为和小胶质细胞的激活。通过抑制剂或siRNA抑制NFAT1和cMyc能够减轻SNL诱导的神经病理性疼痛行为。因此本研究证实NFAT1/cMYC轴是神经病理性疼痛条件下促进小胶质细胞的增殖的关键机制，很有可能发展成新的有效镇痛靶点。