Cholesterol is necessary both for the toxic effect of Aβ peptides on vascular smooth muscle cells and for Aβ binding to vascular smooth muscle cell membranes

Accumulation of beta amyloid (Aâ) in the brain is central to the pathogenesis of Alzheimer's disease. Aâ can bind to membrane lipids and this binding may have detrimental effects on cell function. In this study, surface plasmon resonance technology was used to study Aâ binding to membranes. Aâ peptides bound to synthetic lipid mixtures and to an intact plasma membrane preparation isolated from vascular smooth muscle cells. Aâ peptides were also toxic to vascular smooth muscle cells. There was a good correlation between the toxic effect of Aâ peptides and their membrane binding. 'Ageing' the Aâ peptides by incubation for 5 days increased the proportion of oligomeric species, and also increased toxicity and the amount of binding to lipids. The toxicities of various Aâ analogs correlated with their lipid binding. Significantly, binding was influenced by the concentration of cholesterol in the lipid mixture. Reduction of cholesterol in vascular smooth muscle cells not only reduced the binding of Aâ to purified plasma membrane preparations but also reduced Aâ toxicity. The results support the view that Aâ toxicity is a direct consequence of binding to lipids in the membrane. Reduction of membrane cholesterol using cholesterol-lowering drugs may be of therapeutic benefit because it reduces Aâ-membrane binding.