Rap1a高表达对SNL大鼠神经病理性疼痛及星形胶质细胞自噬的影响

Effect of highly expressed Rap1a on autophagy in astrocytes and neuropathic pain in rats after spinal nerve ligation

目的分析L5脊神经结扎(SNL)大鼠脊髓组织中Rap1a的表达及其对神经病理性疼痛的影响,探讨其作用机制。方法采用L5脊神经结扎法制备SNL大鼠模型,分为假手术(n=6)、SNL模型组(n=30)、生理盐水组(n=6)、Cont-shR组(n=6)、Rap1a-shR组(n=6)、雷帕霉素组(n=6),经由鞘内注射法处理后,采用Von-Frey纤维丝法检测大鼠机械痛阈值,采用RT-PCR和Western blot法检测大鼠脊髓组织和星形胶质细胞中Rap1a的表达、mTOR活性及自噬水平。结果 SNL大鼠脊髓组织中Rap1a的表达水平较生理盐水组显著上升,机械痛阈明显降低(P<0.05)。Rap1a shRNA腺病毒感染后,SNL大鼠机械痛阈明显升高(P<0.05),大鼠脊髓组织及分离培养的星形胶质细胞中细胞自噬标志分子LC3-Ⅱ/LC3-Ⅰ值升高,p62表达水平下降,细胞自噬水平增加,且mTOR活化水平降低(P<0.05)。细胞自噬诱导剂雷帕霉素作用后,星形胶质细胞及SNL大鼠脊髓组织细胞自噬水平均明显增加,SNL大鼠的机械痛阈显著升高(P<0.05)。结论神经损伤引起的Rap1a高表达对神经病理性疼痛的发展有促进作用,这一过程可能与Rap1a对mTOR信号通路及星形胶质细胞自噬水平的调节有关。

Objective To detect the expression of Rap1 a in the spinal cord tissue of rats after spinal nerve ligation（ SNL）,determine its effect on neuropathic pain,and investigate the underlying potential mechanism. Methods Rat model of SNL were produced by ligating lumbar nerve L5. Then the 60 rats were divided into shamoperation group（ n = 6）,SNL group（ n = 30）,model ＋ normal saline group（ n = 6）,model ＋ Cont-shR group（ n = 6）,model ＋ Rap1a-shR group（ n = 6）,and model ＋ rapamycin（ n = 6）.Rap1 a expression was then detected. Corresponding agents,such as normal saline,adenovirus Rap1 a shRNA and others were introduced into the spinal cord tissue of SNL rats by intrathecal injection. The mechanical withdrawal threshold（ MWT） of rats was measured by Von-Frey assay. RT-PCR and Western blotting were employed to detect the expression of Rap1 a,mTOR activity,as well as autophagy in SNL rats and cultured astrocyte. Results Compared to the shamoperation group,Rap1 a expression was significantly up-regulated in the spinal cord tissue of SNL rats,whereas the MWT of the rats was remarkably decreased（ P〈0. 05）.However,adenovirus Rap1 a shRNA infection significantly increased the MWT of SNL rats（ P〈0. 05）,and also enhanced the ratio of autophagy maker LC3-Ⅱ / LC3-Ⅰ and reduced the level of p62 in the spinal cord tissue of SNL rats and cultured astrocytes,indicating the increase of autophagy. Besides,the mTOR activity was also decreased by Rap1 a shRNA（ P〈0. 05）. Furthermore, rapamycin dramatically induced the autophagy in the astrocyte and spinal cord tissue as well as the MWT of SNL rats（ P〈0. 05）. Conclusion SNL-induced high expression of Rap1 a contributes to the development of neuropathic pain in SNL rats,which might be through activating the mTOR signal pathway and inhibiting the autophagy of astrocyte.