Estrogen inhibits β-amyloid-induced abnormal phosphorylation of tau in rat hippocampal neurons

Objective: To study the abnormal phosphorylation of tau induced by β-amyloid protein in hippocampal neurons and neuroprotection by estrogen.Methods: Twenty-four SD rats were randomly and equally divided into a normal control group,an AD(Alzheimer's disease) group and an AD+estrogen group.AD models were established by injecting Aβ25-35 into the hippocampus of 16 of the rats and 2 weeks later,half the model rats received estrogen injection.The cognition of the 3 groups of rats was tested by Morris watermaze,the pathological changes of the hippocampus observed by Bielschowski staining,the tau hyperphosphorylation detected by immunohistochemical staining and the results compared.Results: Compared with the AD group,the results of the Morris watermaze test were significantly better(P0.001) in the AD+estrogen group,P-tau positive cells remarkably fewer(26.2±3.5,49.2±3.1,61.5±4.5,42.1±2.7,61.2±2.3,24.0±1.6 vs 45.4±3.1,106.7±7.6,79.3±3.2,67.7±2.9,97.5±2.9 and 46.7±5.8)(P0.01),and the neurofibrils in the hippocampus more regular.Conclusion: Estrogen improves the cognition of AD rats and inhibits β-amyloid-induced abnormal phosphorylation of tau in the hippocampus.