Vitamin D/VDR Up-Regulates PP2A Protein Methylation To Relieve Alzheimer’s Disease In Mice

Objective:Vitamin D(VD)is a fat-soluble vitamin,which is closely related to human health.Many researchers have confirmed that serum VD concentration is related to Alzheimer’s disease(AD)and cognitive impairment,but the effect of VD on Alzheimer’s disease and its mechanism is rarely reported.This study mainly explores the research on the relieving effect of VD on the course of AD and its mechanism and provides new insights for the prevention of AD.Methods: The object of the in vitro experiment is SH-SY5 Y human neuroblastoma cells.Real-time fluorescent quantitative PCR(RT-PCR)and western blotting are used to detect the effect of VD on the expression of AD-related indicators in SH-SY5 Y cells.The degree of protein phosphatase 2(PP2A)methylation was divided into CON group,VD group,OKA group,OKA+VD group.Using CRISPR-Cas9 technology to knock out the MTHFR gene in SH-SY5 Y cells,the experiment was divided into the Vector group and the Cas9 MTHFR group.Explore the effect of vitamin D on AD-related indicators after knocking out MTHFR.In vivo experiments selected 20 SPF male ICR mice weighing between 15-18 g and randomly divided them into 4 groups: CON group,VD group,OKA group,OKA+VD group,and evaluated by Morris water maze and open field test Recognize the cognitive function of AD mice,and test the effect of Choleveridine Milk(CCE)on AD through experiments.Immunofluorescence was used to detect the effect of CCE on the expression of T-TAU in the brain of AD mice.The protein synthase inhibitor cycloheximide(CHX)and the protein degradation inhibitor MG132 are used to speculate how VD acts on MTHFR.Results: 1.One month after CCE pretreatment,Morris water maze and open field test found that VD treatment can alleviate memory deficits in AD mice.2.After VD treatment,compared with the OKA group,the expression levels of T-TAU and p-TAU in the cells and brain tissues of the OKA+VD group decreased,and the expression levels of MTHFR,PP2A,and LCMT-1 increased.3.Vitamin D treatment can specifically increase PP2A protein levels by enhancing PP2Ac methylation.4.After MTHFR gene knockout,MTHFR knockdown cells with high VDR expression caused by VD treatment no longer respond to the increase of LCMT-1 and PP2A,which eventually leads to the increase of T-TAU and p-TAU.5.There was no difference in the rate of decrease of MTHFR level between the OKA + VD group and the OKA group after CHX treatment.After treatment with MG132,the protein level of MTHFR in the OKA + VD group decreased slightly after 12 hours,indicating that VD enhanced the synthesis of MTHFR.The m RNA level of MTHFR in the OKA + VD group increased significantly,indicating that VD increased the expression of MTHFR through a pre-transcriptional mechanism.Conclusion: 1.VD can improve the memory ability of AD mice,down-regulate the expression of T-TAU and p-TAU,and promote the expression of MTHFR,PP2A,and LCMT-1.2.VD can promote the methylation of PP2Ac.3.VD can affect AD through MTHFR.4.VD up-regulates MTHFR through a pre-transcriptional effect.