title: Transport of cyclosporin A across the brain capillary endothelial cell monolayer by P-glycoprotein.
abstract: P-glycoprotein, a multidrug transporter protein, exists in the brain capillary endothelium. To study the function of P-glycoprotein in brain capillary endothelium as a barrier against cyclosporin A, we examined the interaction of cyclosporin A with P-glycoprotein expressed in cultured brain capillary endothelial cells (MBEC4). P-glycoprotein of MBEC4 specifically bound [125I]iodoaryl azidoprazosin, and the binding was inhibited by cyclosporin A and vincristine. Intracellular accumulation of cyclosporin A in MBEC4 was about one-third the amount accumulated in mouse aortic endothelial cells (MAEC3), a cell line that did not express P-glycoprotein. The reduced accumulation of cyclosporin A in MBEC4 was increased by verapamil, a competitive inhibitor of transport function of P-glycoprotein. Cyclosporin A was preferentially transported from basal to apical side when the cell monolayer of MBEC4 was formed; however this transendothelial transport was not observed across cell monolayer of MAEC3. Verapamil inhibited the transendothelial transport of cyclosporin A across the MBEC4 monolayer. Thus P-glycoprotein in brain capillary endothelium could transport cyclosporin A across the endothelium from the basal to the apical side. These observations suggest that P-glycoprotein is involved in the complex function of the blood-brain barrier as a secretory detoxifying transporter of cyclosporin A.
authors.affiliation: Institute of Molecular and Cellular Biosciences, University of Tokyo, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Shirai
authors.forename: M
authors.initials: M
authors.lastname: Naito
authors.forename: T
authors.initials: T
authors.lastname: Tatsuta
authors.forename: J
authors.initials: J
authors.lastname: Dong
authors.forename: K
authors.initials: K
authors.lastname: Hanaoka
authors.forename: K
authors.initials: K
authors.lastname: Mikami
authors.forename: T
authors.initials: T
authors.lastname: Oh-hara
authors.forename: T
authors.initials: T
authors.lastname: Tsuruo
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000345:Affinity Labels; D000818:Animals; D001692:Biological Transport; D001812:Blood-Brain Barrier; D001921:Brain / Q000098:blood supply*; D002352:Carrier Proteins / Q000378:metabolism*; D002478:Cells, Cultured; D016572:Cyclosporine / Q000378:metabolism*; D004730:Endothelium, Vascular / Q000378:metabolism*; D015151:Immunoblotting; D008562:Membrane Glycoproteins / Q000378:metabolism*; D051379:Mice; D014700:Verapamil / Q000494:pharmacology
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000345:Affinity Labels; D002352:Carrier Proteins; D008562:Membrane Glycoproteins; D016572:Cyclosporine; D014700:Verapamil