背景:慢性原发性疼痛(CPP)是一种原因不明的顽固性疼痛,具有明显的情绪困扰和/或功能障碍,是全球残疾的主要因素。缺乏在人类中模拟CPP的合适动物模型使抑制疾病进展的努力受挫。2R,6R-羟基去甲氯胺酮(2R,6R-HNK)是氯胺酮的主要抗抑郁代谢产物,也具有抗伤害作用。然而,镇痛机制及其对CPP是否有效尚不清楚。
方法:基于长期增强(LTP)诱导的高频或低频电刺激(HFS/LFS)诱发的伤害性疼痛,我们希望通过无创低频经皮神经电刺激(LF-PENS)开发一种新型CPP小鼠模型,该模型具有情绪和认知合并症.单/重复2R,将6R-HNK或其他药物腹膜内(i.p.)或鞘内(i.t.)注射到未治疗或CPP小鼠中以研究其在CPP模型中的镇痛作用。各种行为测试被用来检测疼痛的变化,心情和记忆。免疫荧光染色,westernblot,通过Fluo-8-AM对培养的背根神经节(DRG)神经元进行逆转录-定量实时聚合酶链反应(RT-qPCR)和钙成像来阐明2R的作用和机制,体内或体外6R-HNK。
结果:鞘内注射2R,6R-HNK,而不是腹膜内2R,6R-HNK或鞘内注射S-氯胺酮,成功缓解HFS引起的疼痛。重要的是,鞘内2R,在LF-PENS诱导的CPP模型中,6R-HNK以剂量依赖性方式显示双侧疼痛敏感性和抑郁及认知合并症的有效缓解。机械上,2R,6R-HNK显着减弱神经元兴奋过度和降钙素基因相关肽(CGRP)的上调,瞬时受体电位锚蛋白1(TRPA1)或香草素1(TRPV1),和外周伤害性途径中的囊泡谷氨酸转运蛋白2(VGLUT2)。此外,2R,6R-HNK抑制了TRPA1或/和TRPV1的激动剂引起的培养的DRG神经元中的钙反应和CGRP过表达。引人注目的是,2R的抑制作用,这些疼痛相关分子和机械性异常性疼痛上的6R-HNK基本上被TRPA1拮抗剂薄荷醇闭塞。
结论:在新设计的CPP模型中,我们的发现强调了鞘内2R的潜在效用,6R-HNK用于预防和治疗CPP。TRPA1介导的CGRP上调和神经元在伤害性途径中的过度兴奋可能同时具有CPP的独特特征和解决过程。
BACKGROUND: Chronic primary pain (CPP) is an intractable pain of unknown cause with significant emotional distress and/or dysfunction that is a leading factor of disability globally. The lack of a suitable animal model that mimic CPP in humans has frustrated efforts to curb disease progression. 2R, 6R-hydroxynorketamine (2R, 6R-HNK) is the major antidepressant metabolite of ketamine and also exerts antinociceptive action. However, the analgesic mechanism and whether it is effective for CPP are still unknown.
METHODS: Based on nociplastic pain is evoked by long-term potentiation (LTP)-inducible high- or low-frequency electrical stimulation (HFS/LFS), we wanted to develop a novel CPP mouse model with mood and cognitive comorbidities by noninvasive low-frequency percutaneous electrical nerve stimulation (LF-PENS). Single/repeated 2R, 6R-HNK or other drug was intraperitoneally (i.p.) or intrathecally (i.t.) injected into naïve or CPP mice to investigate their analgesic effect in CPP model. A variety of behavioral tests were used to detect the changes in pain, mood and memory. Immunofluorescent staining, western blot, reverse transcription-quantitative real-time polymerase chain reaction (RT-qPCR) and calcium imaging of in cultured dorsal root ganglia (DRG) neurons by Fluo-8-AM were used to elucidate the role and mechanisms of 2R, 6R-HNK in vivo or in vitro.
RESULTS: Intrathecal 2R, 6R-HNK, rather than intraperitoneal 2R, 6R-HNK or intrathecal S-Ketamine, successfully mitigated HFS-induced pain. Importantly, intrathecal 2R, 6R-HNK displayed effective relief of bilateral pain hypersensitivity and depressive and cognitive comorbidities in a dose-dependent manner in LF-PENS-induced CPP model. Mechanically, 2R, 6R-HNK markedly attenuated neuronal hyperexcitability and the upregulation of calcitonin gene-related peptide (CGRP), transient receptor potential ankyrin 1 (TRPA1) or vanilloid-1 (TRPV1), and vesicular glutamate transporter-2 (VGLUT2) in peripheral nociceptive pathway. In addition, 2R, 6R-HNK suppressed calcium responses and CGRP overexpression in cultured DRG neurons elicited by the agonists of TRPA1 or/and TRPV1. Strikingly, the inhibitory effects of 2R, 6R-HNK on these pain-related molecules and mechanical allodynia were substantially occluded by TRPA1 antagonist menthol.
CONCLUSIONS: In the newly designed CPP model, our findings highlighted the potential utility of intrathecal 2R, 6R-HNK for preventing and therapeutic modality of CPP. TRPA1-mediated uprgulation of CGRP and neuronal hyperexcitability in nociceptive pathways may undertake both unique characteristics and solving process of CPP.