The tachykinin hemokinin-1 (HK-1) is involved in immunological processes, inflammation, and pain. Although the neurokinin 1 receptor (NK1R) is described as its main target, several effects are mediated by currently unidentified receptor(s). The role of HK-1 in pain is controversial, depending on the involvement of peripheral and central sensitization mechanisms in different models. We earlier showed the ability of HK-1 to activate the trigeminovascular system, but the mechanisms need to be clarified. Therefore, in this study, we investigated HK-1-induced transcriptomic alterations in cultured rat trigeminal ganglion (TRG) primary sensory neurons. HK-1 was applied for 6 or 24 h in 1 μM causing calcium-influx in these neurons, 500 nM not inducing calcium-entry was used for comparison. Next-generation sequencing was performed on the isolated RNA, and transcriptomic changes were analyzed to identify differentially expressed (DE) genes. Functional analysis was performed for gene annotation using the Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and Reactome databases. NK1R and Neurokinin receptor 2 (NK2R) were not detected. Neurokinin receptor 3 (NK3R) was around the detection limit, which suggests the involvement of other NKR isoforms or other receptors in HK-1-induced sensory neuronal activation. We found protease-activated receptor 1 (PAR1) and epidermal growth factor receptor (EGFR) as DE genes in calcium signaling. The transmembrane protein anthrax toxin receptor 2 (ANTXR2), a potential novel pain-related target, was upregulated. Acid-sensing ion channel 1; 3 (Asic1,3), N-methyl-D-aspartate (NMDA) and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) glutamate receptors decreased, myelin production and maintenance related genes (Mbp, Pmp2, Myef2, Mpz) and GNDF changed by HK-1 treatment. Our data showed time and dose-dependent effects of HK-1 in TRG cell culture. Result showed calcium signaling as altered event, however, we did not detect any of NK receptors. Presumably, the activation of TRG neurons is independent of NK receptors. ANTXR2 is a potential new target, PAR-1 has also important role in pain, however their connection to HK-1 is unknown. These findings might highlight new targets or key mediators to solve how HK-1 acts on TRG.

中文翻译：

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Hemokinin-1 诱导大鼠初级感觉神经元疼痛相关信号传导过程的转录组改变，与 NK1 速激肽受体激活无关

速激肽血激肽-1 (HK-1)​​ 参与免疫过程、炎症和疼痛。尽管神经激肽 1 受体 (NK1R) 被描述为其主要靶标，但目前尚未识别的受体介导了多种效应。HK-1 在疼痛中的作用存在争议，具体取决于不同模型中外周和中枢敏化机制的参与情况。我们之前展示了 HK-1 激活三叉血管系统的能力，但其机制需要阐明。因此，在本研究中，我们研究了 HK-1 在培养的大鼠三叉神经节 (TRG) 初级感觉神经元中诱导的转录组改变。HK-1 以 1 μM 的浓度应用 6 或 24 小时，导致这些神经元中钙内流，使用 500 nM 不诱导钙内流进行比较。对分离的 RNA 进行新一代测序，并分析转录组变化以鉴定差异表达 (DE) 基因。使用基因本体论 (GO)、京都基因和基因组百科全书 (KEGG) 和 Reactome 数据库对基因注释进行功能分析。未检测到 NK1R 和神经激肽受体 2 (NK2R)。神经激肽受体 3 (NK3R) 接近检测限，这表明其他 NKR 亚型或其他受体参与了 HK-1 诱导的感觉神经元激活。我们发现蛋白酶激活受体 1 (PAR1) 和表皮生长因子受体 (EGFR) 作为钙信号转导中的 DE 基因。跨膜蛋白炭疽毒素受体 2 (ANTXR2) 是一种潜在的新型疼痛相关靶标，其表达上调。酸敏感离子通道1；3（Asic1,3）、N-甲基-D-天冬氨酸（NMDA）和α-氨基-3-羟基-5-甲基-4-异恶唑丙酸（AMPA）谷氨酸受体减少，髓磷脂生成和维持相关基因（Mbp， HK-1 处理改变了 Pmp2、Myef2、Mpz) 和 GNDF。我们的数据显示 HK-1 在 TRG 细胞培养中的时间和剂量依赖性效应。结果显示钙信号传导发生改变，但是我们没有检测到任何 NK 受体。据推测，TRG 神经元的激活不依赖于 NK 受体。ANTXR2是一个潜在的新靶点，PAR-1在疼痛中也发挥着重要作用，但它们与HK-1的联系尚不清楚。这些发现可能会突出新的目标或关键调解者，以解决 HK-1 如何作用于 TRG。