Abstract
Expression of breast cancer resistance protein (Bcrp) at the blood-brain barrier (BBB) has been revealed recently. To investigate comprehensively the potential role of Bcrp at the murine BBB, a chemically diverse set of model compounds (cimetidine, alfuzosin, dipyridamole, and LY2228820) was evaluated using a multiexperimental design. Bcrp1 stably transfected MDCKII cell monolayer transport studies demonstrated that each compound had affinity for Bcrp and that polarized transport by Bcrp was abolished completely by the Bcrp inhibitor chrysin. However, none of the compounds differed in brain uptake between Bcrp wild-type and knockout mice under either an in situ brain perfusion or a 24-h subcutaneous osmotic minipump continuous infusion experimental paradigm. In addition, alfuzosin and dipyridamole were shown to undergo transport by P-glycoprotein (P-gp) in an MDCKII-MDR1 cell monolayer model. Alfuzosin brain uptake was 4-fold higher in mdr1a(–/–) mice than in mdr1a(+/+) mice in in situ and in vivo studies, demonstrating for the first time that it undergoes P-gp-mediated efflux at the BBB. In contrast, P-gp had no effect on dipyridamole brain penetration in situ or in vivo. In fact, in situ BBB permeability of these solutes appeared to be primarily dependent on their lipophilicity in the absence of efflux transport, and in situ brain uptake clearance correlated with the intrinsic transcellular passive permeability from in vitro transport and cellular accumulation studies. In summary, Bcrp mediates in vitro transport of various compounds, but seems to play a minimal role at the BBB in vivo.
Footnotes
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This study was supported in part by the National Institutes of Health National Institute of General Medical Sciences [Grant GM61191]; and Eli Lilly and Company.
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Article, publication date, and citation information can be found at http://dmd.aspetjournals.org.
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doi:10.1124/dmd.108.025064.
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ABBREVIATIONS: BBB, blood-brain barrier; CNS, central nervous system; P-gp, P-glycoprotein; ABC, ATP-binding cassette; MRP/Mrp, multidrug resistance-associated protein; BCRP/Bcrp, breast cancer resistance protein; GF120918, N-(4-[2-(1,2,3,4-tetrahydro-6,7-dimethoxy-2-isoquinolinyl)ethyl]-phenyl)-9,10-dihydro-5-methoxy-9-oxo-4-acridine carboxamide; MDR/mdr, multidrug resistance; LY2228820, 5-[2-tert-butyl-4-(4-fluorophenyl)-1H-imidazol-5-yl]-3-(2,2-dimethylpropyl)-3H-imidazo[4,5-b]pyridin-2-amine; MDCK, Madin-Darby canine kidney; LSN335984, (R)-4-[(1a,6,10b)-1,1-dichloro-1,1a,6,10b-tetrahydrodibenzo[a,e]cyclopropa[c]cyclohepten-6-yl]-[(5-quinolinyloxy)methyl]-1-piperazineethanol; LY335979, zosuquidar; PBS, phosphate-buffered saline; DMSO, dimethyl sulfoxide; A, apical; B, basolateral; HPLC, high-performance liquid chromatography; MS/MS, tandem mass spectrometry; BSA, bovine serum albumin; PBST, PBS containing 0.1% Tween 20; ANOVA, analysis of variance; OATP/oatp, organic anion-transporting protein; PSC833, valspodar.
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↵1 Current affiliation: Roche R&D Center (China) Ltd., Shanghai, China.
- Received October 9, 2008.
- Accepted March 6, 2009.
- The American Society for Pharmacology and Experimental Therapeutics
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