[Deposition and clearance of β-amyloid in the brain].

Amyloid β-protein (Aβ) is deposited as senile plaques and vascular amyloid in the brain of patients with Alzheimer's disease as well as in a significant proportion of non-demented elderly individuals. Microglia play critical roles in the uptake and proteolytic clearance of both the soluble and fibrillary forms of Aβ. Astrocytes separate fibrillary Aβ from neurons by extending hypertrophic processes and internalizing the Aβ into endosomes/lysosomes, suggesting their role in the degradation of Aβ. Recent studies have shown that perivascular clearance of Aβ is a two-step process, involving (i) the uptake of Aβ by glia limitans astrocytes and (ii) perivascular or transendothelial clearance after their secretion into the perivascular space.