Study Of Age Dependent Changes Concerning The Aβ Oligomers And Tau Proteins In APP/PS1/Tau Triple Transgenic Mice

Objective: Alzheimer’s Disease(AD)is the most common type of disease that causes dementia.Its clinical manifestations are mainly related to mental symptoms such as progressive memory loss,cognitive dysfunction,and agitation.Family members and society have huge spiritual and economic burdens related to AD.The main pathological manifestations of AD are senile plaques(SP)formed by the deposition of pathological amyloid beta(Aβ),and neurofibrillary tangles(NFTs)caused by excessive phosphorylation of microtubule-associated Tau protein,and is accompanied by changes in synaptic function and neuroinflammatory response.At present,the pathogenesis of AD is unclear.The main hypotheses include the Aβ cascade hypothesis,Tau protein hypothesis,oxidative stress hypothesis,and neuroinflammation hypothesis.Among them,the Aβcascade hypothesis is the most widely recognized one.In the past ten years,research on Aβ oligomers is the major topic and gained more and more evidence that Aβ oligomers are the real pathogens of AD.At the same time,there are various animal models for AD research,including the most commonly used APP and Tau single transgenic mice,APP /PS1 double transgenic mice,APP / PS1 / Tau triple transgenic mice,and 5x FAD transgenic mice.They simulated the production process of Aβ or Tau.Among them,APP / PS1 / Tau was established by Oddo et al.in 2003.It is a mature transgenic mouse models to study AD.At the same time,there is the interaction between Aβ and Tau,and the Tau gene transferred in this strain of mice also participate in the disease process.Therefore,the mouse of this strain is considered to be the best tool to simulate AD process at present.The pathogenesis of AD is extremely complicated.Aβ oligomers can be subdivided into dimers,tetramers,hexamers,Aβ*56,protofibrils and fibrils,etc.according to the degree of aggregation.Tau protein has up to 30 phosphorylation sites.At present,there are various studies on the pathogenesis of AD.Most of the researches on the pathogenesis of AD are very detailed,but most studies only involve one aspect of Aβ or Tau.In addition,since the APP protein that produces Aβ is a transmembrane protein,Aβ produced by hydrolysis may exist intracellularly or extracellularly,and may play in different roles in the course of the disease.Therefore,we plan to use APP / PS1 / Tau as the blueprint,based on the continuous changes of Aβ and Tau proteins in the disease process,to reveal the disease process from a macro perspective,and look for the possible correlation between Aβ and Tau protein,in order to provide theoretical basis for further reveal of the pathological process in AD.Research method: We selected APP / PS1 / Tau triple transgenic mice,2-15 months old,4 mice per month,a total of 56 mice.At the same time,the corresponding control group(non-transgenic)was selected as same pattern,all female.According to the age of the month,8 mice were collected for each month,and then the relevant biomarkers were tested.Including the brain was homogenization after cardiac perfusion,and Western Blot and Dot Blot methods were used to determine intracellular and extracellular levels of biomarkers in brain tissue,the concentration of soluble and insoluble Aβ,and the concentration of Tau protein phosphorylated at different sites,as well as changes in biomarkers of nerve damage and inflammation.All the biomarkers were compared with background mice of the same month age.Results: In this study,we used APP / PS1 / Tau triple transgenic mice to collect brain tissue at 1-month-old intervals,and performed age dependent changes concerning Aβoligomers,several phosphorylated Tau proteins related to AD,and related synaptic proteins.At the same time,the possible relationship between Aβ,Tau and other biomarkers was studied,and more rigorous information about the above indexes is given.Among complex Aβ oligomers and Tau proteins with different phosphorylation sites,(1)extracellular oligomers are predominantly dimers,tetramers,hexamers,and Aβ56,while intracellular are predominantly the hexamers and Aβ56.(2)extracellular hexamer and pTau S404 show high in early and late stage,lower in middle stage,extracellular hexamer may be an oligomer that promotes S404 site to be phosphorylated.(3)extracellular and intracellular Aβ56,intracellular hexamer,p-Tau T181 dimer first increased and then decreased,and then increased again in the late stage of disease,these three oligomers may be related to T181 site.(5)p-Tau S396 exists as a dimer,and the concentration gradually increases,and p-Tau T231 also gradually increases;(6)p-Tau S199 is gradually dephosphorylated as the disease progresses.Conclusion: For the disease process of AD,many Aβ oligomers and phosphorylated Tau proteins had significant changes before memory and learning function changed.The time point of this change was 5-month-old in triple transgenic mice.After the age of 5 months,they then decrease again,and then enters the stage of dementia after this "honeymoon period".Oligomers with different degrees of aggregation and different positions also act on different Tau proteins.