脊髓GRK2/Eapc1调控小胶质细胞活化在电针缓解顺铂化疗致感觉异常中的作用机制研究

Our previous work shown that cisplatin triggered persistent activation of spinal cord microglia through strengthening the triggering receptor expressed on myeloid cells 2 (TREM2)/DNAX-activating protein of 12 kDa (DAP12) signaling, which further resulted in chemotherapy induced peripheral neuropathy. It has been demonstrated that electroacupuncture (EA) analgesia by regulating spinal microglial functions; Chemotherapy increased neuronal apoptosis, and the injuried neuron increased TREM2-Ligands expression. Our previous work also shown that EA analgesia on inflammatory pain by increasing the spinal G Protein Coupled Receptor Kinase 2 (GRK2)/exchange protein activated by cAMP (Epac1) ratio, subsequently regulating the microglial phenotype M1/M2; in cisplatin treated mice, EA alleviated cisplatin induced peripheral neuropathy (pain and numbness), decreased spinal TREM2 and microglial marker-Iba1, and increased spinal GRK2 level. Hence, the present study was designed to investigate the role of spinal GRK2/Epac1 regulating microglial phenotype in cisplatin induced peripheral neuropathic pain and numbness, and the mechanisms underlie the protective effects of EA on cisplatin induced peripheral neuropathy. This study will help to further understand the mechanisms underlie peripheral neuropathic pain and numbness associated with chemotherapy and the neuroprotective effects by acupuncture.

我们前期研究显示，脊髓TREM2/DAP12介导小胶质细胞持续活化，参与顺铂化疗小鼠外周神经病变。文献表明，电针可以调节脊髓小胶质细胞功能发挥镇痛作用；化疗会引起神经元凋亡，而损伤的神经元TREM2-L表达增加。我们前期工作显示，电针通过上调脊髓GRK2/Epac1比值，调节脊髓小胶质细胞M1/M2型比值抗炎镇痛；在顺铂化疗小鼠模型上，电针可缓解外周神经病变，下调脊髓TREM2和小胶质细胞Iba1，且能上调脊髓GRK2。那么，脊髓GRK2/Eapc1是否参与顺铂化疗性外周神经病变呢？电针又是否通过脊髓GRK2/Eapc1来调节TREM2/DAP12小胶质细胞活化分型来缓解顺铂化疗性外周神经病变呢？本项目拟以TREM2/DAP12调节小胶质细胞活化分型为切入点，研究脊髓GRK2/Eapc1在顺铂化疗致外周神经病变以及电针缓解作用中的机制，来深入理解化疗致外周神经病变及针刺作用的内在机理。

我们以往的工作表明，针刺对不同的慢性痛的镇痛效果不同；针刺可以通过调节脊髓背角GRK2或者Epac1调节小胶质细胞活化，下调致炎因子的表达，发挥镇痛的作用。本研究结果显示：1）顺铂化疗小鼠脊髓GRK2降低，TREM2、DAP12表达增加，M1型小胶质细胞活化，致炎细胞因子表达增加，小鼠表现出机械性痛觉超敏、感觉迟钝行为以及脚掌皮肤内神经末梢数量减少；2）鞘内注射TREM2中和抗体或小胶质细胞抑制剂均可缓解顺铂化疗引起的机械性痛觉超敏和感觉迟钝行为以及IENFs的减少，并且升高脊髓背角神经元GRK2在缓解顺铂化疗引起的外周神经病变的同时，还能显著抑制脊髓背角TREM2、DAP12和炎症因子的升高以及小胶质细胞活化；3）电针可以显著升高顺铂化疗小鼠脊髓背角GRK2水平，抑制顺铂化疗引起的脊髓背角TREM2、DAP12、致炎细胞因子以及小胶质细胞活化，缓解顺铂化疗引起的机械性痛觉超敏、感觉迟钝行为以及脚掌皮肤神经末梢数量的减少；4）特异性下调脊髓背角神经元GRK2水平显著抑制电针对顺铂化疗引起的外周神经病变以及小胶质细胞活化和神经炎症。本研究结果提示针刺通过调节脊髓背角神经元GRK2，从而调节小胶质细胞活化和神经炎症，发挥防治顺铂化疗引起的外周神经病变的作用。本项目从脊髓神经元GRK2调控小胶质细胞活化的角度研究了针刺防治化疗引起外周神经病变的机制，将有助于深入理解针刺镇痛、针刺防治化疗行外周神经病变的内在机制，为临床防治化疗性外周神经病变提供实验依据。