PGP and Alzheimer disease: Consistent with previous studies (Wijesuriya et al., 2010; Jeynes and Provias, 2011; Carrano et al., 2014; Chiu et al., 2015), we found that P-gp protein levels in brain capillary samples from AD patients were significantly lower compared to brain capillaries from cognitive normal individuals (CNI; Figure 1C); β-actin served as loading control.