Alzheimer's beta-amyloid peptide 1-42 induces a phagocytic response in murine microglia

Beta-amyloid (A beta) peptides are a key component of the senile plaques that characterize Alzheimer's disease. Cytokine-producing microglia have been shown to be intimately associated with amyloid deposits and have also been implicated as scavengers responsible for clearing A beta deposits. However, little is known about the initial activation of these microglia or the effect of A beta on phagocytosis. Murine BV-2 microglia were used to assess the effect of synthetic A beta 1-42 on phagocytosis by quantifying uptake of fluorescent microspheres, acetylated low-density lipoproteins, and zymosan particles by flow cytometry. A beta 1-42 stimulated microglial phagocytosis in a time- and dose-dependent manner. A beta fibrils produced the greatest potentiation, and once activated, phagocytosis remained elevated after removal of A beta from the cultures. A beta-stimulated phagocytosis could be blocked if proteoglycans were first complexed to A beta fibrils. These data suggest that A beta fibrils act as an immune signal to stimulate microglial phagocytosis and that extracellular matrix molecules may modify A beta function.