title: Neuronal death induced by nanomolar amyloid β is mediated by primary phagocytosis of neurons by microglia.
abstract: Alzheimer disease is characterized by neuronal loss and brain plaques of extracellular amyloid β (Aβ), but the means by which Aβ may induce neuronal loss is not entirely clear. Although high concentrations of Aβ (μM) can induce direct toxicity to neurons, we find that low concentration (nM) induce neuronal loss through a microglia-mediated mechanism. In mixed neuronal-glial cultures from rat cerebellum, 250 nM Aβ1-42 (added as monomers, oligomers or fibers) induced about 30% loss of neurons between 2 and 3 days. This neuronal loss occurred without any increase in neuronal apoptosis or necrosis, and no neuronal loss occurred with Aβ42-1. Aβ greatly increased the phagocytic capacity of microglia and induced phosphatidylserine exposure (an "eat-me" signal) on neuronal processes. Blocking exposed phosphatidylserine by adding annexin V or an antibody to phosphatidylserine or inhibiting microglial phagocytosis by adding either cytochalasin D (to block actin polymerization) or cyclo(RGDfV) (to block vitronectin receptors) significantly prevented neuronal loss. Loss of neuronal synapses occurred in parallel with loss of cell bodies and was also prevented by blocking phagocytosis. Inhibition of phagocytosis prevented neuronal loss with no increase in neuronal death, even after 7 days, suggesting that microglial phagocytosis was the primary cause of neuronal death induced by nanomolar Aβ.
authors: Department of Biochemistry, University of Cambridge, Cambridge CB2 1QW, United Kingdom. us230@cam.ac.uk
authors: Urte
authors: U
authors: Neniskyte
authors: Jonas J
authors: JJ
authors: Neher
authors: Guy C
authors: GC
authors: Brown
mesh_terms: D000544:Alzheimer Disease / Q000378:metabolism* / Q000473:pathology; D016229:Amyloid beta-Peptides / Q000378:metabolism* / Q000494:pharmacology; D000818:Animals; D017304:Annexin A5 / Q000378:metabolism; D002478:Cells, Cultured; D018920:Coculture Techniques; D015638:Cytochalasin D / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D006801:Humans; D039302:Integrin alphaVbeta3 / Q000037:antagonists & inhibitors / Q000378:metabolism; D017628:Microglia / Q000378:metabolism* / Q000473:pathology; D009474:Neurons / Q000378:metabolism* / Q000473:pathology; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology; D010446:Peptide Fragments / Q000378:metabolism* / Q000494:pharmacology; D010456:Peptides, Cyclic / Q000494:pharmacology; D010587:Phagocytosis; D010718:Phosphatidylserines / Q000378:metabolism; D051381:Rats; D013997:Time Factors
chemical_list: D016229:Amyloid beta-Peptides; D017304:Annexin A5; D039302:Integrin alphaVbeta3; D019384:Nucleic Acid Synthesis Inhibitors; D010446:Peptide Fragments; D010456:Peptides, Cyclic; D010718:Phosphatidylserines; C075222:amyloid beta-protein (1-42); D015638:Cytochalasin D