Department of Pharmacology, School of Pharmacy, Fourth Military Medical University, Xi'an, China; State Key Laboratory of Toxicology and Medical Countermeasures, Beijing Key Laboratory of Neuropsychopharmacology, Beijing Institute of Pharmacology and Toxicology, 27th Taiping Road, Beijing, 100850, China.
Department of Pharmacology, School of Pharmacy, Fourth Military Medical University, Xi'an, China.
Brain Res Bull. 2019 Jul;149:75-85. doi: 10.1016/j.brainresbull.2019.04.016. Epub 2019 Apr 18.
Mammalian target of rapamycin complex 1 (mTORC1) inhibitors increase the incidence of pain in patients, and this finding has been replicated in animal models. However, reports on possible analgesics for this condition are scant. Accumulating evidence finds that nicotinic acetylcholine receptors (nAChRs) are involved in mediating pain. However, whether nicotine, a full agonist of nAChRs, alleviates mTORC1 inhibition-induced pain and its underlying mechanisms remain unknown. In this study, pain was induced in naïve male C57BL/6J mice by intraperitoneally injecting rapamycin acutely or repeatedly. Subsequently, pain thresholds, including mechanical and thermal pain, were measured. The involving signaling pathway was tested using western blot analysis and immunofluorescent assay. Changes in neuronal excitability caused by different treatments were also analyzed using whole-cell recording. Microinjection into the anterior cingulate cortex (ACC) was used to test the role of nAChRs containing the α4β2 or α7 subtype in this brain region in pain modulation. Our results showed that nicotine significantly reduced hyperalgesia in mice that received acute or repeated rapamycin injections, and reversed the effects of rapamycin on the phosphorylation of S6K, 4E-BP1, insulin receptor substrate-1 (IRS-1) at Ser636/639, AKT at Ser473, and ERK at Thr202/Tyr204. Whole-cell recording results showed that nicotine reduced the firing rates of pyramidal neurons in the ACC, and a pharmacological blockade of nAChRs containing the α4β2 or α7 subtype in ACC inhibited the antinociceptive effects of nicotine in mice with rapamycin-induced pain. Our findings indicate that analgesics targeting nAChRs can be developed to help patients with rapamycin-induced pain.
雷帕霉素靶蛋白复合物 1（mTORC1）抑制剂会增加患者疼痛的发生率，这一发现已在动物模型中得到证实。然而，关于这种情况的潜在镇痛药的报告却很少。越来越多的证据表明烟碱型乙酰胆碱受体（nAChRs）参与介导疼痛。然而，烟碱作为 nAChRs 的完全激动剂，是否能缓解 mTORC1 抑制诱导的疼痛及其潜在机制尚不清楚。在这项研究中，通过腹腔注射雷帕霉素急性或反复诱导 naive 雄性 C57BL/6J 小鼠产生疼痛，随后测量机械和热痛等疼痛阈值。使用 Western blot 分析和免疫荧光测定来测试涉及的信号通路。使用全细胞膜片钳记录分析不同处理引起的神经元兴奋性变化。通过向扣带前皮质（ACC）内微注射来测试该脑区含有α4β2 或α7 亚基的 nAChRs 在疼痛调节中的作用。我们的结果表明，尼古丁显著减轻了接受急性或重复雷帕霉素注射的小鼠的痛觉过敏，并逆转了雷帕霉素对 S6K、4E-BP1、胰岛素受体底物-1（IRS-1）在 Ser636/639 处的磷酸化、AKT 在 Ser473 处和 ERK 在 Thr202/Tyr204 处的磷酸化的影响。全细胞膜片钳记录结果表明，尼古丁降低了 ACC 中锥体神经元的放电率，而 ACC 中含有α4β2 或α7 亚基的 nAChRs 的药理学阻断抑制了尼古丁在雷帕霉素诱导疼痛的小鼠中的抗伤害作用。我们的研究结果表明，针对 nAChRs 的镇痛药可以被开发出来，以帮助患有雷帕霉素诱导疼痛的患者。
