Hence, the observation by Akkaya et al. that exposure of isolated murine brain capillaries to Aβ40 peptides caused a 42 ± 5.7% increase in expression of Nedd4, and a concurrent 42 ± 0.5% reduction in expression of Abcb1, presents a potential mechanism by which Aβ clearance could be impaired in AD, a cyclical process that is aggravated by Aβ itself [32]. This evidence concerns the gene ABCB1 and Alzheimer disease.