Anti-alzheimer's Disease Effect Of Fructo-oligosaccharides On Up-regulating Neprilysin Expression By Altering The Level Of Histone Acetylation

Objective: Alzheimer's disease(AD)is an age-related degenerative disease of the nervous system.Its clinical features are insidious onset,memory loss,cognitive dysfunction,behavioral abnormalities and social disorders.The etiology of AD is complex and diverse,the main pathological features are the deposition of ?-amyloid protein(A?)in the brain to form senile plaques,neurofibrillary tangles,and neuronal damage.A? metabolic disorders is an important factor in the development of AD,and the imbalance between the production and clearance of A? leads to the deposition of A?.Therefore,reducing A? deposition may be an effective way to prevent AD.Studies have shown that soluble A? oligomers are a major source of neurotoxicity.Neprilysin(NEP)as a kind of endonuclease is one of the major A?-degrading enzymes,which mainly degrading soluble A? oligomers.The expression of NEP decreased significantly in AD brain.When the expression of NEP was increased,A? deposition and toxicity were decreased,and cognitive impairment was improved.Evidence suggests that histone acetylation modification plays an important role in regulating the expression of NEP.Histone deacetylases(HDACs)is the key enzyme of histone acetylation modification.It was found that HDAC2,HDAC3 were highly expressed in AD Brain and histone deacetylases level(Ace-H3K9,Ace-H4K12)were significantly decreased.When inhibiting the expression of HDAC3,the expression of NEP in the brain of patients with cognitive impairment can be up-regulated.HDAC2 is highly homologous to HDAC3,whether inhibition of HDAC2 can up-regulate the expression of NEP in AD is not clear.Prebiotic is a dietary supplement that improves the health of its host by stimulating the growth of beneficial bacteria,it has an antagonistic effect on AD.Fructo-oligosaccharide(FOS)as an important prebiotic,has been proved to be a natural inhibitor of HDACs.However,FOS may up-regulate the expression of NEP by inhibiting the expression of HDAC2,but its specific mechanism remains to be confirmed.In this study,the anti-AD effect of FOS and its possible mechanism were investigated in vitro and in vivo.The results of this study may provide a theoretical basis for further elucidating the pathogenesis of AD and exploring the effective prevention and treatment of AD.Methods:5-month-old APPswe/PS1dE9 double transgenic mice were divided into AD model group and AD intervention group,and wild type mice were divided into wild control group and wild intervention group.The mice in the intervention group were fed a diet containing 5% FOS,and the mice in the control group were fed a normal diet.Continuous treatment for 6 months.Neurobehavioral tests were proceed in the end.The deposition of A? in the brain of mice was detected by immunohistochemistry.NEP and HDAC2 expression levels in mice brain tissue were detected by qRT-PCR and Western Blot,respectively.Western Blot to measure H3K9 and H4K12 expression levels.The HDAC2 gene in SH-SY5 Y cells was silenced by siRNA interference technique,and the expression of NEP in cells was detected by qRT-PCR and Western Blot.A database was established using SPSS 20.0 for statistical analysis,the difference was statistically significant at p < 0.05.Results:1.The results of open field experiments showed that the movement distance,the times of standing up,the times of modification in the AD model group and the times of standing up,the times of modification in the AD intervention group were lower than those in the wild control group(p < 0.05,p < 0.01);The movement distance,the times of standing up,the times of modification in the AD intervention group were higher than those in the AD model group(p < 0.05,p < 0.01).The results of avoiding darkness test showed that the latency of the AD model group was lower than that of the wild control group,and the number of errors was higher than that of the wild control group,the difference was statistically significant(p < 0.01);The latency of the AD intervention group was higher than that of the AD model group,the number of errors was lower than that of the AD model group,the difference was statistically significant(p < 0.05).2.The numbers of A? plaques in the brain tissue of the AD model group and the AD intervention group was higher than that of the wild control group(p < 0.05,p < 0.01);The numbers of A? plaques in the brain tissue of the AD intervention group was lower than that of the AD model group(p < 0.05).3.The expression of NEP mRNA and protein in brain tissue of the AD model group was lower than that of the wild control group(p < 0.05,p < 0.01);The expression of NEP mRNA and protein in brain tissue of the AD intervention group was higher than that of the AD model group(p < 0.05,p < 0.01).4.The expression of HDAC2 mRNA and protein of the AD model group was higher than that of the wild control group(p < 0.01);The expression of HDAC2 mRNA and protein of the AD intervention group was lower than that of the AD model group(p < 0.05,p < 0.01).5.The expression levels of Ace-H3K9 and Ace-H4K12 in the brain tissue of the AD model group and the AD intervention group were lower than those of the wild control group(p < 0.01);The expression levels of Ace-H3K9 and Ace-H4K12 in the brain tissue of the AD intervention group were higher than that of the AD model group(p < 0.05).6.The relative expression levels of NEP mRNA and protein in SH-SY5 Y cells silenced by HDAC2 increased(p < 0.01).Conclusions: FOS may change the level of histone acetylation and up-regulate the expression of NEP by inhibiting HDAC2,and thus reduce the A? deposition in the brain of AD model mice and improve cognitive dysfunction.