Effects Of Folic Acid On Cell Model Of Alzheimer's Disease By DNA Methylation

ObjectiveThis research investigated the effect of folic acid(FA)on Alzheimer's Disease(AD)model cells.The mechanism related to DNA methylation was analyzed.The aim of this study is to provide a possible way for the prevention and treatment of AD.MethodsThe N2a cells were stably transfected by APP695,and the SH-SY5Y cells were induced by OA to establish AD cell model.All the cells were divided into five groups:?normal cells(Control);?AD cell model treated without folic acid(AD+FA-D);?AD cell model with 10 ?mol/l folic acid(AD+FA-N);?AD cell model with 20?mol/l folic acid(AD+FA-L);?AD cell model with 40 ?mol/1 folic acid(AD+FA-H).After being treated with different concentrations of folic acid for 96 h,all the cells were collected for further analysis.The activity of DNA methyltransferases(DNMTs)was measured by Active Motifs DNA Methyltransferase Activity/Inhibition Assay kit.The protein expression of DNMTs,APP,PS1 ptau,PP2A-C and demethylated PP2A-C was detected by Western Blot.The intracellular concentrations of s-adenosylmethionine(SAM)and s-adenosylhomocysteine(SAH)were examined by HPLC method.The extracellular A? was evaluated by immunofluorescent test.The methylation level of PS1 gene was detected by MeDIP-qPCR.The activity evaluation of the cells was carried out by MTT.ResultsThe immunofluorescent results for N2a cells detection showed that,compared with AD+FA-N group,the A? expressions of AD+FA-L and AD+FA-H groups decreased(P<0.05),but that of AD+FA-D group increased(P<0.05).The levels of intracellular SAM and SAH showed that,compared with AD+FA-N group,the level of SAH in AD+FA-H group decreased(P<0.05),compared with AD+FA-N and AD+FA-D groups,the SAM/SAH levels in AD+FA-L group and AD+FA-H group increased(P<0.05).The evaluation of DNMTs activity in AD+FA-L and AD+FA-H groups were higher than those in AD+FA-D and AD+FA-N groups(P<0.05).The detection of the DNMTs,APP and PS1 protein showed that,compared with AD+FA-N group,the expressions of DNMTs protein in AD+FA-H group increased,and the DNMT3b protein in AD+FA-L group was higher than AD+FA-N and AD+FA-D groups(P<0.05).Compared with AD+FA-N group,the PS1 protein in AD+FA-H group decreased,and compared with AD+FA-D group,the PS1 protein in AD+FA-L,AD+FA-H and Control groups decreased(P<0.05).The results of MeDIP-qPCR showed that,compared with the AD+FA-N,AD+FA-D and AD+FA-L groups,the methylation levels of PS1 gene in AD+FA-H and Control groups increased(P<0.05).The viability detection of SH-SY5Y cells showed that,compared with the Control group,the cell activity decreased in AD cells.However it was increased in AD+FA-L and AD+FA-H groups,compared with that in AD+FA-D group(P<0.05).The expression of pTau,PP2A-C and dePP2A-C protein showed that,compared with the AD+FA-N group,the pTau protein in AD+FA-D group increased and in Control group decresed,compared with AD+FA-D group,pTau protein in AD+FA-L and AD+FA-H groups decreased(P<0.05),compared with the AD+FA-N group,dePP2A-C protein in AD+FA-D group increased,the result in AD+FA-H group was lower than that in AD+FA-N group,compared with AD+FA-D group,dePP2A-C protein in AD+FA-L and AD+FA-H groups decreased(P<0.05).The evaluation of DNMTs activity showed that,compared with AD+FA-N and AD+FA-D groups,AD+FA-L and AD+FA-H group DNMTs activity increased(P<0.05).The results of intracellular SAM and SAH showed that,compared with the AD+FA-D group,level of SAH in AD+FA-L,AD+FA-H and Control groups decreased,the results of SAM/SAH in AD+FA-H and AD+FA-L groups were higher than those in Control,AD+FA-D and AD+FA-N groups(P<0.05).ConclusionsIt was found that FA could effectively decrease the production of extracellular A?and the expression of intracellular pTau,and therefore,FA can prevent from AD.