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P1‐496: Acidic pH effects on beta‐amyloid aggregation and cytotoxicity
Author(s) -
Wang Min S.,
Sierks Michael R.
Publication year - 2008
Publication title -
alzheimer's and dementia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.713
H-Index - 118
eISSN - 1552-5279
pISSN - 1552-5260
DOI - 10.1016/j.jalz.2008.05.1079
Subject(s) - endosome , microglia , p3 peptide , senile plaques , fibril , chemistry , endocytosis , endocytic cycle , microbiology and biotechnology , intracellular , amyloid precursor protein , biochemistry of alzheimer's disease , proteases , transmembrane protein , amyloid (mycology) , biochemistry , biology , alzheimer's disease , inflammation , cell , enzyme , pathology , immunology , medicine , inorganic chemistry , disease , receptor
loid -peptide (A ) is a key event in Alzheimer’s disease (AD) pathogenesis. Alpha1-antichymotrypsin (ACT) is suggested to influence A fibrillogenesis, biological effects and clearance and to enhance A deposition in the brain. The role of activated astrocytes, which are found surrounding amyloid plaques in AD brains, is still poorly understood. These reactive cells over-express ACT and recent evidence suggests that astrocytes may remove and degrade extracellular A . Methods: We evaluated the ability of human astrocytes to bind and internalize A 1-42 alone and in combination with ACT using FACS, epi-fluorescence and confocal laser scanning microscopy (CLSM). Results: Fluorescence labelled A 1-42 (10 M) alone and combined with ACT (1000:1, 100:1 and 10:1 molar ratio) displayed different aggregation profiles, as determined with electron microscopy. ACT dose dependently changed the A 1-42 aggregation profile in favour of a more soluble fraction. No fibrils were observed in the presence of ACT at a molar ratio 10:1 (A 1-42/ACT). Fetal human astrocytes and adult astrocytes derived from post-mortem brain tissue (3 AD and 4 control cases) were challenged with these A mixtures for 2h to o/n, and Fluo A uptake assessed by FACS analysis. Both fetal and adult astrocytes time and dose-dependently became Fluo A -positive and o/n exposure to A 1-42 (10 M) resulted in 87.8 % (fetal), 50.6% (adult non-AD) and 58.1 % (adult AD) of the cells becoming A 1-42 positive. The fractions of A -positive cells further increased by 10 %, 35 % and 23.8 %, respectively, in the presence of ACT (10:1 molar ratio A 1-42/ ACT). Also astrocytic MCP-1 release, used as marker of astrocyte activation, increased dependent on A 1-42 dose. However, no difference between A alone and A /ACT mixtures was seen. As determined with epi-fluorescence microscopy and CLSM, most of the A 1-42 or A 1-42/ACT was cell membrane bound and only a minor fraction internalized. Conclusions: Thus, primary human astrocytes derived from different sources bind and internalize A 1-42, and this process can be modulated by ACT in vitro. Support: Dioraphte and ISAO (grant 06-517; RV), Alzheimer‘s Foundation and Swedish Research Council (SJ), Demensfonden, postdoctoral stipends from the Tegger Foundation (HMN).