Direct evidence of abca1-mediated efflux of cholesterol at the mouse blood–brain barrier Tuan Minh Do • Me ´lissa Ouellet • Fre ´de ´ric Calon • Giovanna Chimini • He ´le `ne Chacun • Robert Farinotti • Fanchon Bourasset Received: 9 March 2011 / Accepted: 28 May 2011 / Published online: 10 June 2011 Ó Springer Science+Business Media, LLC. 2011 Abstract We investigated the expression and function of Abca1 in wild-type C57BL/6, abca1(?/?), and abca1(-/-) mice brain capillaries forming the blood–brain barrier (BBB). We first demonstrated by quantitative RT- PCR and Western immunoblot that Abca1 was expressed and enriched in the wild-type mouse brain capillaries. In abca1(-/-) mice, we reported that the lack of Abca1 resulted in an 1.6-fold increase of the Abcg4 expression level compared to abca1(?/?) mice. Next, using the in situ brain perfusion technique, we showed that the [ 3 H]cho- lesterol brain uptake clearance (Cl up , ll/s/g brain), was significantly increased (107%) in abca1(-/-) mice com- pared to abca1(?/?) mice, meaning that the deficiency of Abca1 conducted to a significant decrease of the choles- terol efflux at the BBB level. In addition, the co-perfusion of probucol (Abca1 inhibitor) with [ 3 H]cholesterol resulted in an increase of [ 3 H]cholesterol Cl up (115%) in abca1 (?/?) but not in abca1(-/-) mice, meaning that probucol inhibited selectively the efflux function of Abca1. In conclusion, our results demonstrated that Abca1 was expressed in the mouse brain capillaries and that Abca1 functions as an efflux transporter through the mouse BBB. Keywords Blood–brain barrier  Cholesterol  Abca1  Abcg4  Abcb1  Abcg2  Mouse  In situ brain perfusion Abbreviations ABC ATP-binding cassette AD Alzheimer’s disease BBB Blood–brain barrier BCECs Brain capillary endothelial cells Cl up Brain uptake clearance PBS Phosphate-buffered saline Introduction ABCA1, which belongs to the superfamily of the ATP- binding cassette (ABC) proteins, is known for its efflux function of cholesterol from intracellular compartment to systemic and brain apolipoproteins [1]. ABCA1 is expressed in several tissues, including brain, placenta, and liver [2]. In the brain, ABCA1 is particularly expressed in neurons and glial cells [3, 4]. ABCA1 mRNA has also been detected in cultured human and rat brain capillaries endo- thelial cells (BCECs) [5]. In addition, the Abca1 protein has been identified in the brain capillaries of transgenic mice lacking Abca1 selectively in neurons and glial cells [4]. Associated with the basement membrane, pericytes and astrocytes end-foot, the brain capillary endothelial cells (BCECs) constitute the blood–brain barrier (BBB), which represents the main interface separating the blood circu- lation from the brain. The barrier effect is due to tight T. M. Do  R. Farinotti  F. Bourasset (&) Laboratory of Clinical Pharmacy, EA4123, Faculty of Pharmacy, University of Paris Sud 11, 5 rue Jean-Baptiste Cle ´ment, 92296 Cha ˆtenay-Malabry, France e-mail: fanchon.bourasset@wanadoo.fr M. Ouellet  F. Calon Faculty of Pharmacy, Laval University, Quebec, QC, Canada G. Chimini Centre d’Immunologie de Marseille-Luminy, INSERM-CNRS- Universite ´ de La Me ´diterrane ´e, Marseille, France H. Chacun Laboratory of Biopharmacy and Pharmaceutical Technology, CNRS UMR 8612, Faculty of Pharmacy, University of Paris Sud 11, Cha ˆtenay-Malabry, France 123 Mol Cell Biochem (2011) 357:397–404 DOI 10.1007/s11010-011-0910-6