The Effects Of BACE1-specific DNA Aptamer On Alzheimer's Disease Transgenic Mouse Model

Alzheimer's disease is a progressive neurodegenerative disorder manifested by cognitive and memory impairment.There are more than 35 million people who suffer from AD worldwide,which results in enormous emotional and financial burdens on patients and society.The accumulation of ?-amyloid peptide in the brain is strongly implicated as a main hallmark of both the sporadic and familial forms of Alzheimer's disease.APP-derived toxic peptides are found at autopsy in AD brains.A? is cleaved from amyloid precursor protein(APP)by ?-secretase(?-site amyloid precursor protein cleaving enzyme 1,BACE1)and subsequently by y-secretase.BACE1 is considered the rate-limiting enzyme in the production of A?.Accumulation of BACE1 is observed in normal and dystrophic presynaptic terminals surrounding the amyloid plaques in brains of AD mouse models and patients.The impact of the drugs that are currently approved by the FDA for the treatment of Alzheimer's disease manifestations is modest,transient,and for only symptomatic treatment.Aptamers are oligonucleotides(single-stranded DNA or RNA)capable of binding to target molecules with high affinity and good specificity due to their tertiary structures.Compared to conventional antibodies,there are many attractive features for aptamers:low molecular weight,quick and reproducible synthesis in vitro,easy modification,good stability easy to long-term storage,low toxicity,low immunogenicity,rapid and nice tissue penetration.These advantages have made aptamer an excellent alternative as molecular probe for fundamental research and clinical applications.Aptamers are selected by a technology called systematic evolution of ligands by exponential enrichment(SELEX).Purified proteins are the most common targets for SELEX selection.Aptamers selected directly against proteins are able to inhibit the activity of target proteins with high affinity and good specificity,and can be used for investigation of mechanisms of interaction between proteins and nucleic acids.The research work of this topic is mainly divided into two parts.The first part:identify the AD transgenic mouse model Tg6799,and explore the model's simulation of AD symptoms and pathological features,which is the basis of the experimental study.The results show that Tg6799 is an effective AD animal model.Genotyping results showed two bands in the transgenic mice.A? immunofluorescence results were consistent with the results of gene identification.The plaque deposition occurred in the brain of the transgenic mice,and the number of plaques was increased with age.Water maze test results showed that the learning and memory ability of the transgenic mice was lower than that of the wild type group.The second part:the effects of BACE1-specific DNA aptamer on Alzheimer's disease transgenic mouse model.The transgenic mice were randomly divided into two groups,and lateral ventricle buried tube.After the surgery,the mice were allowed to rest three days,dosing once every three days for a total of fifteen times.The mice in the experimental group were given the aptamer Al,and the mice in the control group were given the ineffective aptamer sequence Alscr.The open field experiment,Y-maze test and water maze test results showed that the treatment of A1 could improve the cognitive abilities of mice and the exercise ability was not affected.ELISA showed that aptamer A1 could reduce the content of A? in hippocampus of mice.The results of the blot showed that the expression levels of sAPP? and BACE1 protein in the aptamer A1 treatment group were significantly lower than those in the control group.The results of plaque staining of thioflavine S showed that the number and density of senile plaques in the brain of aptamer A1 treatment group were lower than those in the control group.Our study provides research foundation for the development of newly specific potent BACE1 inhibitor,and offers new way and ideas for the treatment of AD.