ABCB1 and Alzheimer disease: The expression of ABCB1 on human brain endothelium has been reported to decrease, and to be inversely associated with cerebral Aβ levels, in the BBB during normal aging (Vogelgesang et al., 2002; Toornvliet et al., 2006; Bartels et al., 2009) and in AD (Wijesuriya et al., 2010; Deo et al., 2014; Chiu et al., 2015).