Alzheimer's β-amyloid peptides induce inflammatory cascade in human vascular cells: the roles of cytokines and CD40

Accumulating evidence suggests that β-amyloid (Aβ)-induced inflammatory reactions may partially drive the pathogenesis of Alzheimer's disease (AD). Recent data also implicate similar inflammatory processes in cerebral amyloid angiopathy (CAA). To evaluate the roles of Aβ in the inflammatory processes in vascular tissues, we have tested the ability of Aβ to trigger inflammatory responses in cultured human vascular cells. We found that stimulation with Aβ dose-dependently increased the expression of CD40, and secretion of interferon-γ (IFN-γ) and interleukin-1β (IL-1β) in endothelial cells. Aβ also induced expression of IFN-γ receptor (IFN-γR) both in endothelial and smooth muscle cells. Characterization of the Aβ-induced inflammatory responses in the vascular cells showed that the ligation of CD40 further increased cytokine production and/or the expression of IFN-γR. Moreover, IL-1β and IFN-γ synergistically increased the Aβ-induced expression of CD40 and IFN-γR. We have recently found that Aβ induces expression of adhesion molecules, and that cytokine production and interaction of CD40–CD40 ligand (CD40L) further increase the Aβ-induced expression of adhesion molecules in these same cells. These results suggest that Aβ can function as an inflammatory stimulator to activate vascular cells and induces an auto-amplified inflammatory molecular cascade, through interactions among adhesion molecules, CD40–CD40L and cytokines. Additionally, Aβ_1–42, the more pathologic form of Aβ, induces much stronger effects in endothelial cells than in smooth muscle cells, while the reverse is true for Aβ_1–40. Collectively, these findings support the hypothesis that the Aβ-induced inflammatory responses in vascular cells may play a significant role in the pathogenesis of CAA and AD.