Neuropathic pain is a debilitating chronic condition that remains difficult to treat. More efficacious and safer therapeutics are needed. A potential target for therapeutic intervention recently identified by our group is the G-protein coupled receptor 160 (GPR160) and the cocaine- and amphetamine-regulated transcript peptide (CARTp) as a ligand for GPR160. Intrathecal administration of CARTp in rodents causes GPR160-dependent behavioral hypersensitivities. However, the molecular and biochemical mechanisms underpinning GPR160/CARTp-induced behavioral hypersensitivities in the spinal cord remain poorly understood. Therefore, we performed an unbiased RNA transcriptomics screen of dorsal horn spinal cord (DH-SC) tissues harvested at the time of peak CARTp-induced hypersensitivities and identified nucleotide-binding oligomerization domain-containing protein 2 (Nod2) as a gene that is significantly upregulated. Nucleotide-binding oligomerization domain-containing protein 2 is a cytosolic pattern-recognition receptor involved in activating the immune system in response to bacterial pathogens. While NOD2 is well studied under pathogenic conditions, the role of NOD2-mediated responses in nonpathogenic settings is still not well characterized. Genetic and pharmacological approaches reveal that CARTp-induced behavioral hypersensitivities are driven by NOD2, with co-immunoprecipitation studies indicating an interaction between GPR160 and NOD2. Cocaine- and amphetamine-regulated transcript peptide-induced behavioral hypersensitivities are independent of receptor-interacting protein kinase 2 (RIPK2), a common adaptor protein to NOD2. Immunofluorescence studies found NOD2 co-expressed with endothelial cells rather than glial cells, implicating potential roles for CARTp/NOD2 signaling in these cells. While these findings are based only on studies with male mice, our results identify a novel pathway by which CARTp causes behavioral hypersensitivities in the DH-SC through NOD2 and highlights the importance of NOD2-mediated responses in nonpathogenic settings.

中文翻译：

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CARTp/GPR160 通过 NOD2 介导小鼠的行为超敏反应。


神经性疼痛是一种使人衰弱的慢性疾病，仍然难以治疗。需要更有效、更安全的治疗方法。我们小组最近确定的治疗干预的潜在靶点是 G 蛋白偶联受体 160 （GPR160） 和可卡因和苯丙胺调节的转录肽 （CARTp） 作为 GPR160 的配体。在啮齿动物中鞘内施用 CARTp 会导致 GPR160 依赖性行为超敏反应。然而，支撑 GPR160/CARTp 诱导脊髓行为超敏反应的分子和生化机制仍然知之甚少。因此，我们对在 CARTp 诱导的超敏反应高峰时收获的背角脊髓 （DH-SC） 组织进行了无偏倚的 RNA 转录组学筛选，并将核苷酸结合寡聚化结构域包含的蛋白 2 （Nod2） 鉴定为显着上调的基因。包含核苷酸结合寡聚结构域的蛋白 2 是一种胞质模式识别受体，参与激活免疫系统以响应细菌病原体。虽然 NOD2 在致病条件下得到了很好的研究，但 NOD2 介导的反应在非致病性环境中的作用仍未得到很好的表征。遗传学和药理学方法显示，CARTp 诱导的行为超敏反应是由 NOD2 驱动的，免疫共沉淀研究表明 GPR160 和 NOD2 之间存在相互作用。可卡因和苯丙胺调节的转录肽诱导的行为超敏反应与受体相互作用蛋白激酶 2 （RIPK2） 无关，RIPK2 是 NOD2 的常见衔接蛋白。 免疫荧光研究发现 NOD2 与内皮细胞而不是神经胶质细胞共表达，这表明 CARTp/NOD2 信号在这些细胞中的潜在作用。虽然这些发现仅基于对雄性小鼠的研究，但我们的结果确定了 CARTp 通过 NOD2 在 DH-SC 中引起行为超敏反应的新途径，并强调了 NOD2 介导的反应在非致病性环境中的重要性。