神经病理性疼痛大鼠脊髓背角NF—κB及其下游肿瘤坏死因子α表达的变化

Expression of NF-κB and TNF-α in spinal dorsal horn in a rat model of neuropathic pain

目的观察大鼠脊髓背角中NF—κB及其下游肿瘤坏死因子α（TNF—α）在慢性坐骨神经挤压性损伤（CCI）疼痛模型中表达的变化规律。方法雄性SD大鼠76只，随机分为手术组（CCI组）和假手术组（Sham组）（n=38），于CCI前1d、CCI后1、4、7、14、21、28d各时间点测定机械痛阂及热痛阈后立即处死大鼠，取腰髓，采用实时荧光定量PCR和免疫荧光双标的方法分别测定NF-κB和TNF—α的mRNA含量和蛋白表达变化。结果CCI组大鼠手术侧机械痛阈及热痛阈明显降低，脊髓背角中NF-κB水平和TNF—α的表达增加，明显高于对侧和假手术组；NF-κB和TNF-α的mRNA水平于CCI后4d开始增加，分别为术前的（1．20±0．16，2．32±0．27）倍，7d达到高峰，为术前的（1．75±0．20，3．38±0．41）倍，随后TNF—α迅速下降，而NF-κB于CCI后28d仍为术前的（1．15±0．24）倍，维持于较高水平（P〈0．05）。术后第7天的免疫荧光双标显示NF—κB和TNF—α在术侧脊髓后角存在共定位表达。结论CCI致大鼠脊髓背角NF-κB活化并上调TNF-α的表达，参与神经病理性疼痛的调控过程。

Objective To investigate the expressions of NF-kB and TNF-α in lumbar spinal cord in a rat model of chronic constrictive injury （CCI）. Methods Seventy-six male SD rats were randomly divided into 2 groups （ n = 38 each） ： CCI group receiving chronic constriction injury and sham group receiving sham operation as control. The mechanical and thermal noeiceptive thresholds were assessed with paw withdrawal latency （PWL） to yon Frey filaments and radiant heat at different time points. Five animals were sacrificed at each time point for real-time polymerase chain reaction （real-time PCR） and another three animals sacrificed at 7 d post-operation for double-immunofluoreseence histochemical staining. Lumbar segments of spinal cord were removed. The expressions of NF-KB and TNF-α in spinal cord were examined by real-time PCR and double-immunofluorescenee histochemical technique. Results The post-operative thresholds to mechanical and thermal stimuli decreased obviously. As compared with contralateral side and sham group, the expressions of NF-KB and TNF-α mRNA increased significantly in ipsilateral spinal dorsal horn. Their expressions began to increase at 4 d post-operation and peaked at 7 d. Then TNF-α began to decrease while NF-KB maintained at a high level throughout the experiment. Double-immunofluorescence histochemical staining revealed extensive co-localization of NF-kB with TNF-α on ipsilateral side of dorsal horn. Conclusion The activation of NF-kB and its downstram inflammatory mediators may be involved in the regulation of neuropathic pain.