MiR-204-3p Improves The Cognitive Function Of APP/PS1 Mice

Objectives:Alzheimer's disease(AD),as a major type of dementia,is a progressive and irreversible neurodegenerative disease characterized with cognitive impairment.The main pathological features of AD are senile plaques of amyloid-beta(A?)and neurofibrillary tangle(NFT)composed of phosphorylation of tau protein in the brain.The A?cascade hypothesis suggests that A?plaques induce excessive phosphorylation of tau protein,oxidative stress,neuroinflammatory responses,and neuronal death,ultimately accelerating the progression of AD.Micro RNAs(miRNAs)have been shown to contribute to the memory deficits in AD.In this study,we found that miR-204-3p was downregulated in the hippocampus and plasma of 6-month-old APPswe/PS1d E9(APP/PS1)mice.The aims of this study were:1)To clarify the effect of miR-204-3p on cognitive dysfunction in APP/PS1 mice;2)To explore the mechanism of miR-204-3p on cognitive impairment.3)To find possible compounds for treating cognitive impairment in APP/PS1 mice.Methods:MiRNA microarray was performed using the hippocampus of 6-month-old APPswe/PS1d E9(APP/PS1)mice.The miR-204-3p overexpression lentivirus(Lv-miR-204)was injected into bilateral hippocampus of APP/PS1 mice.The memory function was examined by Open filed,New-object reorganization,Fear condition and Morris water maze tests.Long-term potentiation(LTP)was recorded to evaluate the synaptic functions and the synapse morphology was examined by Golgi staining.The protein levels of synaptic proteins were determined by western blotting.The potential targets of miR-204-3p were predicted by Targetscan,and confirmed by luciferease assay and western blotting.The A?levels were determined by immuofluorescence and ELISA.The levels of 4-hydroxynonenal,3-nitrotyrosine,and 8-hydroxy-2'-deoxyguanosine were detected by ELISA and the level of H₂O₂ was examined by spectrophotometry.The level of Reactive oxygen species(ROS)was determined by fluorescence assay.Results:MiR-204-3p was down-regulated in the hippocampus and plasma of 6-month-old APP/PS1 mice as demonstrated by miRNA assay and RT-PCR,which indicated that miR-204 might play an important role in AD.MiR-204-3p overexpression attenuated memory and synaptic deficits in APP/PS1 mice.The amyloid levels and oxidative stress including 4-HNE,3-NT,8-OHDG were decreased in the hippocampus of APP/PS1mice after miR-204-3p overexpression.The luciferase assay and western blotting results showed that Nox4 was a target of miR-204-3p,and Nox4 inhibition by GLX351322 protected neuronal cells against A?induced neurotoxicity.Furthermore,GLX351322 treatment rescued synaptic and memory deficits,and decreased oxidative stress and amyloid levels in the hippocampus of APP/PS1 mice.Conclusions:Our study indicated that miR-204-3p over-expression attenuated synaptic and memory deficits and inhibit oxidative stress in APP/PS1 mice by targeting Nox4,and miR-204-3p overexpression and/or Nox4 inhibition might be a potential therapeutic strategy for AD treatment.