Microvessels from Alzheimer's disease brains kill neurons in vitro

Understanding the pathogenesis of Alzheimer's disease is of widespread interest because it is an increasingly prevalent disorder that is progressive, fatal, and currently untreatable. The dementia of Alzheimer's disease is caused by neuronal cell death. We demonstrate for the first time that blood vessels isolated from the brains of Alzheimer's disease patients can directly kill neurons in vitro. Either direct co-culture of Alzheimer's disease microvessels with neurons or incubation of cultured neurons with conditioned medium from microvessels results in neuronal cell death. In contrast, vessels from elderly nondemented donors are significantly (P<0.001) less lethal and brain vessels from younger donors are not neurotoxic. Neuronal killing by either direct co-culture with Alzheimer's disease microvessels or conditioned medium is dose- and time-dependent. Neuronal death can occur by either apoptotic or necrotic mechanisms. The microvessel factor is neurospecific, killing primary cortical neurons, cerebellar granule neurons, and differentiated PC-12 cells, but not non-neuronal cell types or undifferentiated PC-12 cells. Appearance of the neurotoxic factor is decreased by blocking microvessel protein synthesis with cycloheximide. The neurotoxic factor is soluble and likely a protein, because its activity is heat labile and trypsin sensitive. These findings implicate a novel mechanism of vascular-mediated neuronal cell death in Alzheimer's disease.