Peripheral neuropathic pain arises as a consequence of injury to sensory neurons; the development of ectopic activity in these neurons is thought to be critical for the induction and maintenance of such pain. Local anaesthetics and anti-epileptic drugs can suppress hyperexcitability; however, these drugs are complicated by unwanted effects on motor, central nervous system and cardiac function, and alternative more selective treatments to suppress hyperexcitability are therefore required. Here we show that a glutamate-gated chloride channel modified to be activated by low doses of ivermectin (but not glutamate) is highly effective in silencing sensory neurons and reversing neuropathic pain-related hypersensitivity. Activation of the glutamate-gated chloride channel expressed in either rodent or human induced pluripotent stem cell-derived sensory neurons in vitro potently inhibited their response to both electrical and algogenic stimuli. We have shown that silencing is achieved both at nerve terminals and the soma and is independent of membrane hyperpolarization and instead likely mediated by lowering of the membrane resistance. Using intrathecal adeno-associated virus serotype 9-based delivery, the glutamate-gated chloride channel was successfully targeted to mouse sensory neurons in vivo, resulting in high level and long-lasting expression of the channel selectively in sensory neurons. This enabled reproducible and reversible modulation of thermal and mechanical pain thresholds in vivo; analgesia was observed for 3 days after a single systemic dose of ivermectin. We did not observe any motor or proprioceptive deficits and noted no reduction in cutaneous afferent innervation or upregulation of the injury marker ATF3 following prolonged glutamate-gated chloride channel expression. Established mechanical and cold pain-related hypersensitivity generated by the spared nerve injury model of neuropathic pain was reversed by ivermectin treatment. The efficacy of ivermectin in ameliorating behavioural hypersensitivity was mirrored at the cellular level by a cessation of ectopic activity in sensory neurons. These findings demonstrate the importance of aberrant afferent input in the maintenance of neuropathic pain and the potential for targeted chemogenetic silencing as a new treatment modality in neuropathic pain.

中文翻译：

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使用工程谷氨酸门控氯离子通道沉默感觉神经元并从源头治疗神经性疼痛


周围神经性疼痛是由于感觉神经元损伤而引起的；这些神经元异位活动的发展被认为对于诱发和维持此类疼痛至关重要。局部麻醉药和抗癫痫药可以抑制过度兴奋；然而，这些药物由于对运动、中枢神经系统和心脏功能产生不良影响而变得复杂，因此需要替代性更具选择性的治疗来抑制过度兴奋。在这里，我们表明，经过修饰以由低剂量伊维菌素（但不是谷氨酸）激活的谷氨酸门控氯离子通道在沉默感觉神经元和逆转神经性疼痛相关的超敏反应方面非常有效。体外啮齿动物或人类诱导的多能干细胞来源的感觉神经元中表达的谷氨酸门控氯离子通道的激活可有效抑制它们对电刺激和致痛刺激的反应。我们已经证明，沉默是在神经末梢和体细胞上实现的，并且与膜超极化无关，而可能是通过降低膜电阻介导的。使用基于鞘内腺相关病毒血清型9的递送，谷氨酸门控氯离子通道成功地靶向小鼠体内感觉神经元，从而导致该通道在感觉神经元中选择性地高水平和持久表达。这使得体内热和机械疼痛阈值的可重复和可逆调节成为可能；单次全身剂量伊维菌素后观察镇痛效果 3 天。 我们没有观察到任何运动或本体感觉缺陷，并且注意到在延长谷氨酸门控氯离子通道表达后，皮肤传入神经支配没有减少或损伤标记物 ATF3 上调。伊维菌素治疗逆转了由神经性疼痛的幸存神经损伤模型产生的机械性和冷痛相关的超敏反应。伊维菌素改善行为超敏反应的功效在细胞水平上反映在感觉神经元异位活动的停止上。这些发现证明了异常传入输入在维持神经性疼痛中的重要性以及靶向化学遗传学沉默作为神经性疼痛新治疗方式的潜力。