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目的探讨沉默信号调控因子(SIRT1)在烟酰胺腺嘌呤二核苷酸(NAD)保护神经轴突中的作用。方法应用长春新碱毁损法制备背根神经节轴突变性细胞模型,应用透射电镜、RT-PCR、Western blot方法,观察正常背根神经节培养组、长春新碱毁损组、NAD保护组神经轴突的生长变化、超微结构变化和SIRT1 mRNA及SIRT1蛋白的表达变化。结果NAD保护组毁损8h后轴突远端始发生轻微肿胀,断离。透射电镜结果显示,长春新碱毁损组轴突肿胀,大量髓样小体出现,微丝微管排列紊乱,聚集,溶解,被絮状沉淀物和膜性结构所代替。NAD保护组可见较多平行排列的微丝微管,轴突肿胀较轻。RT-PCR结果显示,NAD保护组的SIRT1基因表达较毁损组上调。Western blot结果显示,损伤组可见其蛋白表达量明显降低,NAD保护组中SIRT1蛋白表达较毁损组上调。结论SIRT1参与NAD对轴突变性的保护作用。
Objective To investigate the role of SIRT1 in the protection of neuronal axons by nicotinamide adenine dinucleotide (NAD). Methods The model of axon degeneration of dorsal root ganglion was prepared by vincristine desquamation. Transmission electron microscopy, RT-PCR and Western blotting were used to observe the changes of axons in normal dorsal root ganglion, vincristine-lesioned group and NAD-protected group Sudden growth changes, ultrastructural changes and SIRT1 mRNA and SIRT1 protein expression changes. Results In the NAD protection group, a slight swelling and detachment occurred at the distal part of the axon after 8 hours of rupture. Transmission electron microscopy showed vincristine damaged axons swelling, a large number of medullary bodies appear, arranged in a disorder of microfilament microtubules, aggregation, dissolution, was flocculent sediment and membrane structure replaced. NAD protection group visible more parallel arrangement of microfilament microtubules, axonal swelling lighter. The results of RT-PCR showed that the SIRT1 gene expression in NAD-protected group was up-regulated compared with that in the damaged group. Western blot results showed that the protein expression of the lesion group was significantly decreased, and the expression of SIRT1 protein in the NAD group was higher than that in the lesion group. Conclusion SIRT1 is involved in the protective effect of NAD on axonal degeneration.