ATP-binding cassette transporter G1 and apolipoprotein M are ‘Novel players’ in cholesterol transport at the blood-brain barrier

Abstract

Aim: Impaired cholesterol/lipoprotein metabolism is linked to neurodegenerative diseases. Cerebral cholesterol homeostasis is maintained by the highly efficient blood-brain barrier (BBB) and flux of the oxysterols 24(S)- and 27-hydroxycholesterol, potent liver-X-receptor (LXR) activators. HDL/apolipoproteins support cerebral lipid transfer and loss of ATP-binding cassette transporters (ABC)G1 and G4 results in toxic accumulation of oxysterols in the brain. The HDL-associated apolipoprotein (apo)M is positively correlated with pre-ß HDL formation in plasma; its presence and function in the brain was thus far unknown. Using an in vitro model of the BBB we examined expression, regulation and functions of ABCG1, ABCG4, and apoM in primary cerebrovascular endothelial cells.