2 Hz电针对SNI诱导神经病理性疼痛大鼠背根神经节IRF8的作用

ELECTROACUPUNCTURE AT 2 Hz RELIEVES MECHANICAL HYPERSENSITIVITY THROUGH REGULATION OF IRF8 IN DORSAL ROOT GANGLION OF RATS WITH SPARED NERVE INJURY-INDUCED NEUROPATHIC PAIN

目的:探讨2 Hz电针(electroacupuncture,EA)是否通过抑制坐骨神经分支选择性损伤(spared nerve injury,SNI)所致神经病理性疼痛大鼠背根神经节(dorsal root ganglion,DRG)的干扰素调节因子8(transcription factors interferon regulatory factor 8,IRF8)的mRNA和蛋白表达,从而缓解神经病理性疼痛的痛敏行为。方法:雄性SD大鼠30只,随机分为3组:假手术组(Sham)、模型组(SNI)和电针组(SNI+EA)。SNI+EA组于SNI术后第1天给予双侧的足三里和三阴交穴位进行电针治疗,隔日电针,持续21天;于术前1天、术后第3、5、7、10、14、21天分别测定机械缩足反射阈值(paw withdrawal threshold,PWT)。在电针的第3、7、14、21天,分别取大鼠L4-6的DRG,应用RT-PCR及Western blot检测IRF8的mRNA及蛋白表达水平,用免疫荧光技术检测IRF8的蛋白表达分布情况。结果:与SNI组相比,在电针干预后的第3、7、10、14和21天,机械缩足反射阈值显著上升(P<0.05);与SNI组相比,给予电针治疗后,SNI大鼠DRG的IRF8 mRNA和蛋白表达以及CD11b的mRNA的表达均显著下调(P<0.05,P<0.01,P<0.001);与SNI组相比,在电针干预后的第7天,免疫荧光结果显示大鼠DRG的IRF8和CD11b表达明显减少,IRF8与CD11b共定位减少。结论:2 Hz电针对SNI所致的神经病理性疼痛大鼠的机械痛敏具有缓解作用,可能镇痛机制是通过下调DRG的IRF8表达抑制DRG小胶质细胞的活化,进而抑制神经病理性疼痛的发生发展。

Objective： The study was designed to explore whether transcription factors interferon regula- tory factor 8 （IRF8） is involved in the analgesic effect of 2 Hz electroacupuncture （EA） at 2 Hz on neuro- pathic pain in rats with spared nerve injury （SNI）. Methods： Thirty male SD rats were randomly divided into Sham, SNI and SNI ＋ EA groups in this experiment. The rats with SNI were treated with 2 Hz EA in Zusanli and Sanyinjiao acupoints bilaterally once every two days. Paw withdrawal threshold （PWT） in response to mechanical stimulation was measured by yon Frey filaments one day before operation and on day 3, 5, 7, 10, 14, and 21 after injury. After continuously 2 Hz EA for 3, 7, 14, 21 days treatment, we examined the mRNA and protein levels of IRF8 in L4-6 dorsal root ganglion （DRG） of rats using RT-PCR. Western blot and immunofluorescence analysis was used to determine the distribution of IRF8. Results：Compared to the SNI group, 2 Hz EA not only significantly alleviated SNI-induced mechanical hypersen- sitivity, but also reduced the mRNA and protein level of IRF8, mRNA level of CDllb in DRG of SNI rats （P〈0.05 or P〈0.01）. Moreover, the results of immunofluorescence displayed significant down-regulation of DRG IRF8 and CDllb protein expression, as well as double staining of IRF8 and CDllb in SNI ＋ EA group compared with SNI group, Conclusion： Two Hz EA potentially reduces mechanical hypersensitivity induced by SNI and this may be attributed to down-regulation of IRF8 in DRG of rats and inhibition of the activation of microglia.