Astrocyte- and neuron-derived extracellular vesicles from Alzheimer's disease patients effect complement-mediated neurotoxicity

We have previously shown that blood astrocytic-origin extracellular vesicles (AEVs) from Alzheimers disease (AD) patients contain high complement levels. To test the hypothesis that circulating EVs from AD patients can induce complement-mediated neurodegeneration, we assessed the neurotoxicity of immunocaptured AEVs (with anti-GLAST antibody), neuronal-origin NEVs (with anti-L1CAM antibody), and multicellular-origin (with anti-CD81 antibody) EVs from the plasma of AD, frontotemporal lobar degeneration (FTLD) and control participants. AEVs (and, less effectively, NEVs) of AD participants induced Membrane Attack Complex (MAC) expression on recipient neurons, membrane disruption, reduced neurite density, and decreased cell viability in rat cortical neurons and human IPSC-derived neurons. Neurodegenerative effects were not produced by multicellular-origin EVs from AD participants or AEVs/NEVs from FTLD or control participants, and were suppressed by the MAC inhibitor CD59 and other complement inhibitors. Our results support the stated hypothesis and suggest that neuronal MAC deposition is necessary for AEV/NEV-mediated neurodegeneration in AD.