Activation of brain endothelium by soluble aggregates of the amyloid-β protein involves nuclear factor-κB

Cerebrovascular accumulation of amyloid-β protein (Aβ) aggregates in Alzheimer's disease (AD) is proposed to contribute to disease progression and brain inflammation as a result of Aβ-induced increases in endothelial monolayer permeability and stimulation of the endothelium for cellular adhesion and transmigration. These deficiencies facilitate the entry of serum proteins and monocyte-derived microglia into the brain. In the current study, a role for nuclear factor-κB (NF-κB) in the activation of cerebral microvascular endothelial cells by Aβ is explored.Quantitative immunocytochemistry is employed to demonstrate that Aβ(1-40) preparations containing isolated soluble aggregates elicit the most pronounced activation and nuclear translocation of NF-κB. This rapid and transient response is observed down to physiological Aβ concentrations and parallels phenotypic changes in endothelial monolayers that are selectively elicited by soluble Aβ(1-40) aggregates. While monomeric and fibrillar preparations of Aβ(1-40) also activated NF-κB, this response was less pronounced, limited to a small cell population, and not coupled with phenotypic changes. Soluble Aβ(1-40) aggregate stimulation of endothelial monolayers for adhesion and subsequent transmigration of monocytes as well as increases in permeability were abrogated by inhibition of NF-κB activation. Together, these results provide additional evidence indicating a role for soluble Aβ aggregates in the activation of the cerebral microvascular endothelium and implicate the involvement of NF-κB signaling pathways in Aβ stimulation of endothelial dysfunction associated with AD.