Acceleration of amyloidogenesis and memory impairment by estrogen deficiency through NF-κB dependent beta-secretase activation in presenilin 2 mutant mice

Nearly 7-10 million people are living with Alzheimer's disease (AD) worldwide. Senile plaques composed of beta-amyloid (A beta) are a pathological hallmark of Alzheimer's disease. Presenilin 2 (PS2) mutations increase A beta generation in the brains of AD patients. The A beta is generated through the sequential cleavage of amyloid precursor protein by beta- and gamma-secretases. Additionally, increasing evidences suggest that estrogen can reduce the development of AD via regulation of beta-secretases activity and beta-site APP-cleaving enzyme (BACE1) expression. But the underlying correlation mechanism of A beta generation by PS2 mutations and estrogen remains to be clarified. To investigate the anti-amyloidogenesis effect of estrogen in a PS2 mutative condition, we examined memory impairment in ovariectomized PS2 mutation (N141I) mice in which cognitive function was assessed by the Morris water maze test and passive avoidance test. In addition, Western blot analysis, immunostaining, immunofluorescence staining, ELISA and enzyme activity assays were used to examine the degree of A beta deposition in the brains. In the present study, A beta accumulated more in the ovariectomized PS2 mutant mice brain, and greatly worsened memory impairment and glial activation as well as neurogenic inflammation. In parallel with increased memory impairment, activity of beta-secretase and expression of the BACE1 increased in ovariectomized PS2 mutant mice. Much higher activity of NF-kappa B was observed by EMSA in ovariectomized PS2 mutant mice. In addition, the A beta level was decreased by treatment of beta-estradiol through inhibiting BACE1 expression in PS2 transfacted PC12 cells. These results suggest that mutation of PS2 can lead to NF-kappa B mediate amyloidogensis, and this effect can be amplified by the absence of estrogen. (C) 2015 Elsevier Inc. All rights reserved.