坐骨神经结扎大鼠脊髓组织Toll样受体4及下游细胞因子表达的变化

Changes of Toll-like receptor 4 and its downstream cytokines in spinal cord of rat model of neuropathic pain

目的：观察大鼠坐骨神经结扎（CCI）后脊髓背角Toll样受体4（TLR4）及脊髓内IL-1β、TNF-α表达的变化，探讨神经病理性疼痛可能的治疗靶点。方法：结扎大鼠右侧坐骨神经，术后1、3、7、10、14d观察大鼠热痛阈及机械性痛阈的变化，采用实时定量RT-PCR、免疫荧光及Western印迹观察L1～L6段脊髓组织TLR4基因及蛋白表达的变化，ELISA法测量脊髓组织IL-1β、TNF-α表达的变化；以假手组大鼠作为对照。结果：坐骨神经结扎后，大鼠右足热痛阈及机械性痛阈明显降低，脊髓背角TLR4基因及蛋白表达明显增加，明显高于假手术组（P〈0．05）；脊髓组织IL-1β、TNF-α的含量也明显升高，明显高于假手术组（P〈0．05）。结论：坐骨神经结扎可能通过诱导TLR4表达，促进下游细胞因子释放，导致痛阈降低；TLR4有望成为治疗病理性疼痛的新靶点。

Objective：To investigate the changes of toll like receptor 4 expression and its downstream cytokines TNF-α, IL- 1β in the spinal cord in rat chronic constriction injury （CCI） models, and to discuss the potential target for treatment of neuropathic pain. Methods： Neuropathic pain was produced by CCI of right sciatic nerve as described previously. On the 1^st , 3^rd , 7^th and 14^th day after surgery, the expression of TLR4 mRNA and protein in L1-L6 was assessed by RT-PCR and Western blotting, respectively; the distribution of TLR4 in the spinal cord was detected by immunofluorescence. The levels of TNF-α, IL-1β in the spinal cord were detected by ELISA. Thermal and mechanical nociceptive thresholds were assessed with paw withdrawal latency to radiant heat and von Frey filaments. Rats receive sham operation served as controls. Results： The mechanical allodynia and thermal hyperalgesia were induced in animals after CCI. The paw withdrawal latency （PWL） and paw withdrawal threshold （PWT） of right paw were decreased after CCI （P〈0. 05）, and the expression of TLR4 mRNA and protein was significantly increased （P〈0.05）; the levels of TNF-α and IL-1β in SF were also significantly increased after CCI compared with that in the sham control （P〈0.05）. Conclusion： CCI -induced toll-like receptor 4 activation may increase the expression of cytokines and subsequently decrease pain threshold, indicating that TLR4 might be a potential target for the treatment of neuropathic pain.