SIRT1在NAD保护神经轴突作用中的表达变化

 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8?h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。

Expression of SIRT1 during axonal degeneration by NAD

Objective To explore expression of SIRT1 in delaying axonal degeneration by NAD. Methods After establishing an axonal degeneration model of DRG neurons induced by vincristine, transmission electron microscopy, RT-PCR, and Western blotting analysis were used to observe expressions of mRNA and protein of SIRT1 in the normal group, injury group and protection group. Results The axons were swollen and disrupted in the distal end of axon at 4 h in vitro culture of the injury group. Obvious protective effects were detected in the experimental groups containing NAD, and the end of axon showed light degeneration at 12 h in culture. Transmission electron microscopy showed that the smooth endoplasmic reticulum of the axons dilated and formed vacuoles in the injury group. Also, the normal neurofilament axonal metastructure decreased and turned to granular fragments. RT-PCR examination showed that mRNA 'expression of S1RT1 in the vincristine injury group obviously decreased. However, expression of SIRT1 was up-regulated after adding NAD. The result of Western blot showed that protein expression of SIRT1 was significantly down-regulated in the injury group, while in the NAD protection groups, expression of SIRT1 was heightened. Con-clusion NAD plays an important role in preventing axonal degeneration, and SIRT1 probably participates in preventing axonal degeneration of NAD.