NAD+ Improved Experimental Autoimmune Encephalomyelitis by Regulating SIRT1 to Inhibit PI3K/ Akt /mTOR Signaling Pathway
Authors: Wang Jinli , Song Xueqin , Tan Guojun , Sun Pengtao , Guo Li , Zhang Ning , Jueqiong Wang , Li Bin 
Published: September 2021

Abstract
Objective: To investigate the effect of NAD+ on thymus autophagy in experimental autoimmune encephalomyelitis (EAE) mice through SIRT1. Methods: Data sets GSE135511 and GSE131279 related to fatty liver in multiple sclerosis were downloaded from GEO database to search for differentially expressed genes. KEGG and GO pathway enrichment analysis was performed to construct PPI network, identify important modules and hub genes, and analyze the expression of hub genes. Animal experiments: Forty female C57BL/6 mice were randomly divided into 4 groups: control group, EAE group, NAD+ group and SIRT1 inhibitor group. The EAE model was prepared by MOG35-55 polypeptide immunoassay. The NAD+ group and SIRT1 inhibitor group were treated with NAD+ drug and fed for 4 weeks. The neurological function scores of the mice in each group were evaluated weekly. Cell experiment: The thymus tissues of wild-type mice were removed, ground and filtered into single-cell suspension, and then cultured. The thymus tissues were divided into four groups: control group, EAE group, NAD+ group and SIRT1 inhibitor group. MOG 35-55 (1μg/ mL) was given to induce EAE model in vitro. Both the NAD+ group and the SIRT1 inhibitor group were treated with NAD+. The expression of LC-3B was observed by immunofluorescence. The expressions of p-PI3K, p-AKT, p-mTOR, P62, Beclin1, LC-3B and SIRT1 were detected by WB. Results: Data sets GSE135511 and GSE131279 contained 95 up-regulated DEGs and 89 down-regulated DEGs. Enrichment analysis showed that it was mainly concentrated in PI3K-Akt-mTOR and autophagy pathway. SIRT1 was low expressed in the disease group. The EAE group, the NAD+ group and the SIRT1 inhibitor group all showed different degrees of morbidity. At week 2, there was no significant difference between the EAE group and the NAD+ group and the SIRT1 inhibitor group, but the neurological function score of the SIRT1 inhibitor group was significantly higher than that of the NAD+ group. The neurological function score of SIRT1 inhibitor group was the highest at 3 and 4 weeks. WB test showed that the expressions of P62, Beclin1, LC-3B and SIRT1 were the highest in the NAD+ group, while the expressions of p-PI3K, p-Akt and p-mTOR were the highest in the EAE group, followed by the SIRT1 inhibitor group, the NAD+ group and the control group. Cell experiment: Immunofluorescence showed that the fluorescence intensity of LC-3B in NAD+ group was the highest, followed by SIRT1 inhibitor group, EAE group, and control group. WB test showed that the expressions of P62, Beclin1, LC-3B and SIRT1 were the highest in the NAD+ group, followed by SIRT1 inhibitor group, EAE group and control group. The expressions of p-PI3K, p-AKT and p-mTOR were the highest in EAE group, followed by SIRT1 inhibitor group, NAD+ group and control group. Conclusion: NAD+ exerted a protective effect on EAE mice by inhibiting PI3K/ Akt /mTOR signaling pathway through SIRT1, and prevented EAE mice from sustained damage.