Amyloid β peptide 25-35 increases albumin permeability and induces apoptosis in an endothelial cell monolayer

The presence of insoluble deposits of amyloid β peptide (Aβ) on vascular walls is one of the hallmark features of Alzheimer disease. Moreover, blood brain barrier impairment has also been observed in this disease. In this report, we demonstrate the direct toxicity of Aβ to cultured endothelial cells (EC). Aβ-induced EC death is blocked by antioxidants and agents that decrease intracellular Ca²⁺. Furthermore, Aβ application to EC increases intracellular Ca²⁺ concentration. These points indicate that free radical generation and loss of Ca²⁺ homeostasis are pivotal to Aβ-induced degeneration. The EC death induced by Aβ is also blocked by endonucleases and protein synthesis inhibitors, indicating that Aβ initiates an apoptotic pathway in EC. Lastly, subtoxic levels of Aβ increase albumin transfer through EC monolayers. These results provide evidence for the hypothesis that Aβ adversely affects the physiology and survival of vascular endothelial cells, leading to breaches in blood brain barrier integrity, and thus contributing to the neuropathological cascade observed in Alzheimer disease.