ATP-binding cassette transporter A1 (ABCA1) deficiency does not attenuate the brain-to-blood efflux transport of human amyloid-β peptide (1-40) at the blood-brain barrier

ATP-binding cassette transporter A1 (ABCA1) mediates apolipoprotein-dependent cholesterol release from cellular membranes. Recent studies using ABCA1 knockout mice have demonstrated that ABCA1 affects amyloid-β peptide (Aβ) levels in the brain and the production of senile plaque. Cerebral Aβ(1-40) was eliminated from the brain to the circulating blood via the blood-brain barrier (BBB), which expresses ABCA1. Therefore, in the present study, we examined whether ABCA1 affects the brain-to-blood efflux transport of human Aβ(1-40)(hAβ(1-40)) at the BBB. The apparent uptake of [¹²⁵I]hAβ(1-40) into ABCA1-expressing HEK293 cells was not significantly different from that into parental HEK293 cells. In addition, the apparent uptake was not significantly affected even in the presence of apolipoprotein A-I as a cholesterol release acceptor. Moreover, [¹²⁵I]hAβ(1-40) elimination from mouse brain across the BBB was not significantly different between ABCA1-deficient and wild-type mice 60 min after its administration into the cerebrum. These results suggest that ABCA1 does not directly transport hAβ(1-40) and a deficiency of ABCA1 does not attenuate the brain-to-blood efflux transport of hAβ(1-40) across the BBB.