组胺H3受体拮抗剂对II型复杂性区域疼痛综合征的镇痛作用及机制

Complex regional pain syndrome II (CRPS-2) is an neuropathic pain associated with autonomic nervous system disorders. Because it is not sensitive to conventional analgesics, more efficacious drugs and targets are urgently required. Our previous studies have found that central histamine can inhibit the CRPS-2's neuralgia. However, histamine does not cross the blood brain barrier. Histamine H3 receptors (H3R) are predominantly expressed in the central nervous system, where they negatively regulate histamine release. Our preliminary experiments found that administration of thioperamide significantly attenuated the allodynia and hyperalgesia induced by partial sciatic nerve ligation (PSL) in a dose-dependent manner. However, to our surprise, the hypersensitivity of HDC-/- mice induced by PSL was also attenuated by thioperamide administration, suggesting that the analgesic effect may be histamine-independent. We also found that intervention of locus coeruleus - noradrenergic (LC-NA) system with electrical damage or drugs blocked the analgesic effect of thioperamide in CRPS-2. Thioperamide also enhanced the locus coeruleus neuronal excitability, suggesting that the H3R antagonists may have an analgesic effect in CRPS-2 by intervention of descending noradrenergic pathways. So, in this project, we intends to clarify the role of H3R antagonists on CRPS-2 neuralgia and its underling mechanism by using a variety of transgenic mice, viral transfection, combined with patch clamp and microelectrode recording technologies, and provide a new theoretical basis for clinical strategies.

II型复杂性区域疼痛综合征(CRPS-2)是一种与自主神经系统障碍相关的神经痛，因其对常规镇痛药不敏感，迫切需要寻找新的药物与靶点。课题组前期研究发现中枢组胺可以抑制CRPS-2的神经痛，但因组胺不能通过血脑屏障而无法成药。组胺H3受体(H3R)主要分布在中枢神经系统，负反馈调节组胺的合成与释放。预实验发现，H3R拮抗剂噻普酰胺(Thio)可以有效干预CRPS-2神经痛的发生与维持。然而，预实验意外地发现阻断组胺功能并不能阻断其作用，提示其作用可能是组胺非依赖的。预实验还发现电毁损或药物阻断蓝斑-去甲肾上腺素(LC-NA)系统可以阻断Thio的作用，Thio还可以增强蓝斑神经元的兴奋性，提示H3R拮抗剂的镇痛作用可能是通过LC-NA来发挥的。本课题拟利用多种转基因小鼠、病毒转染，结合膜片钳、在体微电极记录等技术，阐明H3R拮抗剂对CRPS-2神经痛的作用和机制，为临床提供新策略和理论依据。

复杂性区域疼痛综合征(Complex regional pain syndrome, CRPS)是一种与自主神经系统障碍相关的慢性疼痛综合征。CRPS-2 患者除了具有肢体水肿、肌营养不良伴萎缩等自主神经系统障碍之外，还伴有受累肢体的持续性烧灼痛，对外界非伤害性刺激的痛觉超敏(allodynia)和对伤害性刺激的痛觉过敏(hyperalgesia)等典型的神经病理性疼痛症状，严重影响患者的生存质量。临床针对CRPS-2的治疗尚无较好的方法，使用药物控制疼痛是主要的治疗手段。但是患者对经典的镇痛药物(如阿片类)反应差，抗癫痫药或抗抑郁药只部分缓解少数病人的疼痛，且伴随较多副作用。因此，迫切需要深入研究CRPS-2神经病理性疼痛的病理过程及特征，寻找新的有效药物治疗的靶点。本项目实施3年以来，我们观察发现：（1）PSL术后1天，3天，7天H3R mRNA水平和蛋白表达水平均显著提高。而Thioperamide给药可以抑制H3R表达。（2）给予0-7天三种不同结构类型的H3R拮抗剂thioperamide、clobenpropit和A331440以及与H3R选择性激动剂immepip合用可以显著抑制小鼠后爪诱发性机械痛觉超敏和热痛过敏的作用。（3）PSL术后第7天单次给予或者术后8-14天连续7天给予thioperamide，对诱发性疼痛有抑制作用。（4）在H3R敲除小鼠PSL术后1-7天给予thioperamide，没有镇痛作用。（5）在野生型小鼠PSL术后使用H1、H2受体拮抗剂，给予HDC酶的抑制剂α-FMH阻断组胺的作用，不能抑制thioperamide镇痛作用。（6）在HDC-/-小鼠上造模后，thioperamide镇痛作用也依然存在。（7）电刺激毁损蓝斑核，可以阻断thioperamide镇痛作用；（8）PSL手术后第7天组动物脑片蓝斑神经元sEPSC，mEPSC等各项突触传递功能指标均下降。（9）术后7天组动物脑片蓝斑神经元自发动作电位频率也下降。（10）thioperamide可以抑制术后7天组动物脑片蓝斑神经元突触功能的变化。在此基础上，我们整理发现H3R拮抗剂对CRPS-2的神经病理性疼痛有非常好的抑制作用，这种作用的确与本项目提出假说时一致，不是通过组胺系统来发挥的，而是通过干预下行抑制系统蓝斑-去甲肾上腺素系统来发挥的。