How Neurons Internalize Alzheimer's Disease Amyloid β Protein

Abstract

ObjectiveThe objective is to investigate cellular mechanisms mediating the internalization of beta‐amyloid 40 (Aβ40) in part of the neurovascular unit, neurons, and blood‐brain barrier (BBB) endothelial cells.MethodsLocalization of fluorescein labeled Aβ40 (F‐Aβ40) and other endocytotic markers in wild type (WT) mouse brain slices, PC12 cells, rat primary hippocampal (RPH) neurons, and bovine brain microvascular endothelial (BBME) cells was investigated using laser confocal or fluorescence microscopy. The uptake of fluorophores in these cells was quantified by flow cytometry.ResultsLaser confocal micrographs of WT mouse brain slices treated with F‐Aβ40 demonstrated selective accumulation of the protein in cortical and hippocampal neurons via non‐saturable, energy independent, and non‐endocytotic pathways. A significant portion of internalized Aβ40 is located outside of the endosomal or lysosomal compartments, which may accumulate without degradation. In contrast, BBME cells exhibit energy dependent uptake of Aβ40, and accumulate the protein in acidic cell organelles, indicative of endocytotic uptake.ConclusionThe difference in internalization of Aβ40 between neurons and BBB endothelial cells may provide clues to understanding how various cells can regulate Alzheimer's disease (AD) proteins and help explain the vulnerability of cortical and hippocampal neurons to AD toxicity.