Background. Neuropathic pain is a common chronic pain, which is related to hypersensitivity to stimulus and greatly affects the quality of life of patients. Maladaptive gene changes and molecular signaling underlie the sensitization of nociceptive pathways. We previously found that the activation of microglial glucagon-like peptide 1 receptor (GLP-1R) could potently relieve formalin-, bone cancer-, peripheral nerve injury-, and diabetes-induced pain hypersensitivity. So far, little is known about how the gene profile changes upon the activation of GLP-1R signaling in the pathophysiology of neuropathic pain. Methods. Spinal nerve ligation (SNL) was performed to induce neuropathic pain in rats. Mechanical allodynia was assessed using von Frey filaments. The expression of IL-10, β-endorphin, and μ-opioid receptor (MOR) was examined by real-time quantitative polymerase chain reaction (qPCR) and whole-cell recording. Measurements of cellular excitability of the substantia gelatinosa (SG) neurons by whole-cell recording were carried out. R packages of differential gene expression analysis based on the negative binomial distribution (DESeq2) and weighted correlation network analysis (WGCNA) were used to analyze differential gene expression and the correlated modules among GLP-1R clusters in neuropathic pain. Results. The GLP-1R agonist, exenatide, has an antiallodynic effect on neuropathic pain, which could be reversed by intrathecal injections of the microglial inhibitor minocycline. Furthermore, differential gene expression analysis (WGCNA) indicated that intrathecal injections of exenatide could reverse the abnormal expression of 591 genes in the spinal dorsal horn induced by nerve injury. WGCNA revealed 58 modules with a close relationship between the microglial GLP-1R pathway and features of nerve injuries, including pain, ligation, paw withdrawal latency (PWL), and anxiety. The brown module was identified as the highest correlated module, and the Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis indicated that inflammatory responses were most correlated with PWL. To further unravel the changes of hyperalgesia-related neuronal electrophysiological activity mediated by microglia GLP-1 receptors, whole-cell recording identified that MOR agonism stimulated a robust outward current in the sham groups compared with the spinal nerve ligation (SNL) groups. This inhibitory effect on the SNL group was more sensitive than that of the sham group after bath application of β-endorphin. Conclusions. Our results further confirmed that the GLP-1R pathway is involved in alleviating pain hypersensitivity mediated by spinal microglia activation, and inflammatory responses were the most correlated pathway associated with PWL changes in response to exenatide treatment. We found that the identification of gene regulation in response to GLP-1R activation is an effective strategy for identifying new therapeutic targets for neuropathic pain. Investigation for the activation of spinal microglial GLP-1R which might ameliorate inflammatory responses through gene expression and structural changes is providing a potential biomarker in pain management.

中文翻译：

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神经性疼痛中 GLP-1R 信号传导的小胶质细胞激活促进了炎症反应中的基因表达适应

背景。神经性疼痛是一种常见的慢性疼痛，与对刺激的超敏反应有关，严重影响患者的生活质量。适应不良的基因变化和分子信号传导是伤害感受通路敏感的基础。我们之前发现小胶质细胞胰高血糖素样肽 1 受体 (GLP-1R) 的激活可以有效缓解福尔马林、骨癌、周围神经损伤和糖尿病引起的疼痛超敏反应。到目前为止，对于神经性疼痛的病理生理学中 GLP-1R 信号激活后基因谱如何变化知之甚少。方法。进行脊髓神经结扎（SNL）以诱导大鼠的神经性疼痛。使用 von Frey 细丝评估机械异常性疼痛。IL-10、β的表达通过实时定量聚合酶链反应 (qPCR) 和全细胞记录检查 -内啡肽和μ - 阿片受体 (MOR)。进行了通过全细胞记录测量明胶质 (SG) 神经元的细胞兴奋性。基于负二项分布（DESeq2）和加权相关网络分析（WGCNA）的差异基因表达分析R包用于分析神经性疼痛中GLP-1R簇之间的差异基因表达和相关模块。结果. GLP-1R 激动剂艾塞那肽对神经性疼痛具有抗异常性疼痛作用，可以通过鞘内注射小胶质细胞抑制剂米诺环素来逆转。此外，差异基因表达分析（WGCNA）表明，鞘内注射艾塞那肽可以逆转神经损伤引起的脊髓背角591个基因的异常表达。WGCNA 揭示了 58 个模块，这些模块与小胶质细胞 GLP-1R 通路与神经损伤特征（包括疼痛、结扎、缩爪潜伏期 (PWL) 和焦虑）之间存在密切关系。棕色模块被确定为相关性最高的模块，京都基因和基因组百科全书（KEGG）分析表明炎症反应与 PWL 最相关。为了进一步揭示由小胶质细胞 GLP-1 受体介导的痛觉过敏相关神经元电生理活动的变化，全细胞记录发现，与脊髓神经结扎 (SNL) 组相比，MOR 激动在假手术组中刺激了强大的外向电流。这种对 SNL 组的抑制作用在沐浴后比假手术组更敏感。β-内啡肽。结论。我们的研究结果进一步证实，GLP-1R 通路参与减轻由脊髓小胶质细胞激活介导的疼痛超敏反应，而炎症反应是与艾塞那肽治疗后 PWL 变化相关的最相关通路。我们发现识别响应 GLP-1R 激活的基因调控是识别神经性疼痛新治疗靶点的有效策略。研究激活脊髓小胶质细胞 GLP-1R 可能通过基因表达和结构变化改善炎症反应，这为疼痛管理提供了潜在的生物标志物。