The β-amyloid peptide of Alzheimer's disease decreases adhesion of vascular smooth muscle cells to the basement membrane

Cerebral amyloid angiopathy (CAA) is a major feature of Alzheimer's disease pathology. In CAA, degeneration of vascular smooth muscle cells (VSMCs) occurs close to regions of the basement membrane where the amyloid protein (Aâ) builds up. In this study, the possibility that Aâ disrupts adhesive interactions between VSMCs and the basement membrane was examined. VSMCs were cultured on a commercial basement membrane substrate (Matrigel). The presence of Aâ in the Matrigel decreased cell-substrate adhesion and cell viability. Full-length oligomeric Aâ was required for the effect, as N- and C-terminally truncated peptide analogues did not inhibit adhesion. Aâ that was fluorescently labelled at the N-terminus (fluo-Aâ) bound to Matrigel as well as to the basement membrane heparan sulfate proteoglycan (HSPG) perlecan and laminin. Adhesion of VSMCs to perlecan or laminin was decreased by Aâ. As perlecan influences VSMC viability through the extracellular signal-regulated kinase (ERK)1/2 signalling pathway, the effect of Aâ1-40 on ERK1/2 phosphorylation was examined. The level of phospho-ERK1/2 was decreased in cells following Aâ treatment. An inhibitor of ERK1/2 phosphorylation enhanced the effect of Aâ on cell adhesion. The studies suggest that Aâ can decrease VSMC viability by disrupting VSMC-extracellular matrix (ECM) adhesion.