| Objective:Alzheimer’s disease is a neurodegenerative disease mainly characterized by memory decline,progressive cognitive impairment and personality change.After angiocardiopathy,cerebrovascular disease and tumor,Alzheimer’s disease(AD)is the fourth factor contributing to death of elderly.AD is the most common factor of cognitive disorder in old people,which seriously affects patients’ living quality.However,the pathogenesis of AD is still unclear and no drugs can cure it.Currently,it is considered that the pathogenesis of AD is probably associated with β-amyloid peptide(Aβ)deposition,tau protein over phosphorylation,oxidative stress and inflammatory reaction.Perhaps,the accumulation of Aβ deposition is the radical factor leading to AD.Current researches suggest that there are partial changes in AD patients’ miRNA,which play a significant role in relevant cognitive impairment in AD.The precursor of miR-142 can be processed into miR-142-5p and miR-142-3p,and miR-142 is highly conservative among the species and plays an important role in many tumors,immune-related diseases and embryonic stem cell(ESC).Recent study manifests that miR-142 is associated with senility and it is reported that the expressions of miRNA-142 is significantly high in the hippocampus of AD’s patients and 10 months old APP transgenic mice.Besides,the fragile X mental retardation protein(FMRP),which coded by the fragile X mental retardation gene 1(FMR1),can regulate and combine with the targeted transport and translation of various mRNAs in the cytoplasm of neurons.It is believed that the non or low expression of FMRP caused by FMR1 dynamic mutation can affect the development and synaptic plasticity of neurons.It is believed that the expressions of miR-142 and FMRP in AD models have an effect on the expression of synaptic proteins.Therefore,the research used western blot,immunofluorescence,real-time PCR,morris water maze behavior test and other experimental methods to explore whether miR-142 regulate the expression of FMRP by binding the FMR1 gene,so as to regulate the expression of synapse-related proteins and improve the ability of learning and memory,which supplied a new theoretical basis for the treatment of Alzheimer’s disease.Methods:Thirty-six ten months old APP/PS1 transgenic mice were randomly divided into three groups named AD group,sh-miR-NC group and sh-miR group and twelve ten months old C57BL/6 mice as the control group.The LV-sh-miR-NC and LV-shmiR-142-3p were injected into the left side lateral ventricle in the corresponding group with 2ul each mouse.And these mice were fed in a warm and proper retentive environment for a week.After seven days,all the mice were used to the morris maze test and then the mouse brain were taken.Western blot,real-time PCR,immunofluorescence and other method were used to detect expressions of FMRP and other synapse-related proteins.Results:1.Morris water maze test results: positioning cruise experiment demonstrated that the escape latency of control group and sh-miR group were significantly decreased compared with AD group(p<0.05).The probe-trial test indicated that the proportion of total time of APP/PS1 mice spent in the target quadrant was significantly shorter than control group and sh-mirR-142 group(p<0.05).And there was no significant difference between AD group and sh-miR-NC group.The above results proved that the sh-miR-142-3p silencing can improve the memory deficits of APP/PS1 mice.2.Western blot and immunofluorescence results: The expressions of FMRP,PSD95 and Synapsin Ⅰ in hippocampus of control group and sh-miR group were both significantly increased compared with AD group(p<0.05).There was no significant difference between AD group and sh-miR-NC group.Conclusion:1.The inhibition of the expression of miR-142 can improve the learning and memory deficits of APP/PS1 mice.2.MiR-142 can regulate the expression of FMRP by binding FMRP,so as to affect the expression of synapse-related proteins. |
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