Background

Alpha-7 nicotinic acetylcholine receptor (α7 nAChR) was reported to have a critical role in the regulation of pain sensitivity and neuroinflammation. However, the expression level of α7 nAChR in dorsal root ganglion (DRG) and the underlying neuroinflammatory mechanisms associated with hyperalgesia are still unknown.

Methods

In the present study, the expression and mechanism of α7 nAChR in chronic inflammatory pain was investigated using a complete Freund’s adjuvant (CFA)-induced chronic inflammatory pain model. Subsequently, a series of assays including immunohistochemistry, western blotting, and quantitative real-time polymerase chain reaction (qRT-PCR) were performed.

Results

α7 nAChR was mostly colocalized with NeuN in DRG and upregulated after CFA injection. Microinjection of α7 nAChR siRNA into ipsilateral L4/5 DRGs aggravated the CFA-induced pain hypersensitivity. Intrathecal α7 nAChR agonist GTS-21 attenuated the development of CFA-induced mechanical and temperature-related pain hypersensitivities. In neuronal the SH-SY5Y cell line, the knockdown of α7 nAChRs triggered the upregulation of TRAF6 and NF-κB under CFA-induced inflammatory conditions, while agitation of α7 nAChR suppressed the TRAF6/NF-κB activation. α7 nAChR siRNA also exacerbated the secretion of pro-inflammatory mediators from LPS-induced SH-SY5Y cells. Conversely, α7 nAChR-specific agonist GTS-21 diminished the release of interleukin-1beta (IL-1β), IL-6, IL-8, and tumor necrosis factor-α (TNFα) in SH-SY5Y cells under inflammatory conditions. Mechanistically, the modulation of pain sensitivity and neuroinflammatory action of α7 nAChR may be mediated by the TRAF6/NF-κB signaling pathway.

Conclusions

The findings of this study suggest that α7 nAChR may be potentially utilized as a therapeutic target for therapeutics of chronic inflammatory pain.

中文翻译：

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背根神经节α7烟碱型乙酰胆碱受体在完全弗氏佐剂性慢性炎性疼痛中的作用

背景

据报道，α-7 烟碱型乙酰胆碱受体 (α7 nAChR) 在调节疼痛敏感性和神经炎症中起关键作用。然而，背根神经节（DRG）中α7 nAChR的表达水平以及与痛觉过敏相关的潜在神经炎症机制仍然未知。

方法

在本研究中，使用完全弗氏佐剂（CFA）诱导的慢性炎性疼痛模型研究了 α7 nAChR 在慢性炎性疼痛中的表达和机制。随后，进行了一系列检测，包括免疫组织化学、蛋白质印迹和定量实时聚合酶链反应 (qRT-PCR)。

结果

α7 nAChR 主要与 DRG 中的 NeuN 共定位，并在 CFA 注射后上调。将 α7 nAChR siRNA 显微注射到同侧 L4/5 DRG 中可加重 CFA 诱导的疼痛超敏反应。鞘内注射 α7 nAChR 激动剂 GTS-21 减弱了 CFA 诱导的机械和温度相关疼痛超敏反应的发展。在神经元 SH-SY5Y 细胞系中，α7 nAChR 的敲低在 CFA 诱导的炎症条件下触发了 TRAF6 和 NF-κB 的上调，而 α7 nAChR 的激动抑制了 TRAF6/NF-κB 的活化。α7 nAChR siRNA 也加剧了 LPS 诱导的 SH-SY5Y 细胞中促炎介质的分泌。相反，α7 nAChR 特异性激动剂 GTS-21 减少了炎症条件下 SH-SY5Y 细胞中白细胞介素 1β (IL-1β)、IL-6、IL-8 和肿瘤坏死因子-α (TNFα) 的释放。

结论

这项研究的结果表明，α7 nAChR 可能潜在地用作治疗慢性炎症性疼痛的治疗靶点。