Immobilized amyloid precursor protein constructs: a tool for the in vitro screening of glial cell reactivity.
Astrocytes and microglia are closely associated with amyloid plaques in Alzheimer's disease (AD). Microglia constitute the first barrier surrounding plaques, although they seem to be unable to remove them efficiently. We evaluated the reaction of microglial cells from neonatal rats and mice to plaque mimetics. The C-terminal part of the amyloid precursor protein (APP) or amyloid peptide (A beta) was immobilized to either 60-microm or 2.8-microm beads and incubated with microglial cells. Beads of 60 microm, having approximately the size of senile plaques, were not phagocytosed, in contrast to 2.8-microm beads, which were phagocytosed by microglia but not by astrocytes. Once taken up by the cells, proteins immobilized to the beads were degraded rapidly, as confirmed by mass spectrometry and immunofluorescence with an antibody against beta-amyloid. On the other hand, no protein degradation was observed with 60-microm beads. Also, probably as a reaction to its incapability to phagocytose the beads, glia organized around the beads and started to proliferate. Cell proliferation was more pronounced when the beads contained the A beta epitope compared with the beads with an inert surface. This in vitro effect could be exploited to set up a screening assay for compounds that ameliorate the adverse reaction of microglia supposed to contribute to the pathogenesis of AD.
von Bernhardi
R
R
Faculty of Medicine, Universidad de los Andes, San Carlos de Apoquindo 2200, Las Condes, Santiago, Chile. rvonb@uandes.cl
Ramírez
G
G
Matile
H
H
Döbeli
H
H
D016229:Amyloid beta-Peptides / Q000494:pharmacology; D016564:Amyloid beta-Protein Precursor; D002478:Cells, Cultured; D003001:Cloning, Molecular; D004705:Endocytosis / Q000187:drug effects / Q000502:physiology; D010450:Endopeptidases / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D006801:Humans; D007202:Indicators and Reagents; D013058:Mass Spectrometry; D008863:Microspheres; D009457:Neuroglia / Q000187:drug effects*; D009573:Nitrites / Q000378:metabolism
D016229:Amyloid beta-Peptides; D016564:Amyloid beta-Protein Precursor; D007202:Indicators and Reagents; D009573:Nitrites; D010450:Endopeptidases