GPR34 in spinal microglia exacerbates neuropathic pain in mice
GPR34 in spinal microglia exacerbates neuropathic pain in mice
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DOI：
10.1186/s12974-019-1458-8
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发表时间：
2019-04-11
影响因子：
9.3
通讯作者：
Kiyama, Hiroshi
中科院分区：
文献类型：
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作者：
Sayo, Akira;Konishi, Hiroyuki;Kiyama, Hiroshi
背景神经病理性疼痛是由感觉神经损伤引起的，目前缺乏有效的治疗方法。小胶质细胞在感觉神经损伤后在脊髓背角中被激活并促进神经病理性疼痛。因此，由这些细胞表达的分子被认为是治疗策略的潜在靶标。我们以前的基因筛选研究使用小鼠模型的运动神经损伤表明，G蛋白偶联受体34基因（GPR34）是由神经损伤诱导。由于GPR34现在被认为是一种富含小胶质细胞的基因，因此我们探索了它可能参与神经性疼痛小鼠模型背角小胶质细胞激活的可能性。方法通过定量实时PCR测定野生型和L4脊神经损伤的GPR34缺陷小鼠中GPR34和促炎分子的mRNA表达。原位杂交用于鉴定GPR34在小胶质细胞中的表达，并用小胶质细胞标记物Iba1进行免疫组化以检查小胶质细胞的数量和形态。通过von Frey毛发试验评价机械敏感性。LysoPS-GPR34抑制剂鞘内给药，检测LysoPS-GPR34信号通路对机械敏感性的影响。结果L4神经损伤后，GPR34主要由小胶质细胞表达。WT和GPR34缺陷小鼠之间的小胶质细胞数量或形态学没有组织学差异。然而，在GPR34缺陷小鼠中，神经损伤诱导的小胶质细胞中促炎细胞因子表达水平和疼痛行为显著减弱。此外，鞘内给药的GPR34拮抗剂减少neuropathic pain.ConclusionsInhibition GPR34介导的信号GPR34基因缺失通过抑制小胶质细胞的促炎反应，而不影响其形态减少神经损伤引起的神经病理性疼痛。因此，抑制GPR34活性可能具有缓解神经性疼痛的治疗潜力。
BackgroundNeuropathic pain is caused by sensory nerve injury, but effective treatments are currently lacking. Microglia are activated in the spinal dorsal horn after sensory nerve injury and contribute to neuropathic pain. Accordingly, molecules expressed by these cells are considered potential targets for therapeutic strategies. Our previous gene screening study using a mouse model of motor nerve injury showed that the G-protein-coupled receptor 34 gene (GPR34) is induced by nerve injury. Because GPR34 is now considered a microglia-enrichedgene, we explored the possibility that it might be involved in microglial activation in the dorsal horn in a mouse model of neuropathic pain.MethodsmRNA expression of GPR34 and pro-inflammatory molecules was determined by quantitative real-time PCR in wild-type and GPR34-deficient mice with L4 spinal nerve injury. In situ hybridization was used to identify GPR34 expression in microglia, and immunohistochemistry with the microglial marker Iba1 was performed to examine microglial numbers and morphology. Mechanical sensitivity was evaluated by the von Frey hair test. Liquid chromatography-tandem mass spectrometry quantified expression of the ligand for GPR34, lysophosphatidylserine (LysoPS), in the dorsal horn, and a GPR34 antagonist was intrathecally administrated to examine the effect of inhibiting LysoPS-GPR34 signaling on mechanical sensitivity.ResultsGPR34 was predominantly expressed by microglia in the dorsal horn after L4 nerve injury. There were no histological differences in microglial numbers or morphology between WT and GPR34-deficient mice. However, nerve injury-induced pro-inflammatory cytokine expression levels in microglia and pain behaviors were significantly attenuated in GPR34-deficient mice. Furthermore, the intrathecal administration of the GPR34 antagonist reduced neuropathic pain.ConclusionsInhibition of GPR34-mediated signal by GPR34 gene deletion reduced nerve injury-induced neuropathic pain by suppressing pro-inflammatory responses of microglia without affecting their morphology. Therefore, the suppression of GPR34 activity may have therapeutic potential for alleviating neuropathic pain.