ABCB6 and Parkinson disease: The decreased expression and/or functional activity of ABC-BBB transporters in Alzheimer’s disease (AD) and Parkinson’s disease (PD) patients (Zlokovic, 2011), and in the brain of AD animal models proved that the decreased expression and/or functional activity of ABC-BBB transporters led to the accumulation of amyloid beta peptide (Aβ) (Cirrito et al., 2005).