Expression, Up-Regulation, and Transport Activity of the Multidrug-Resistance Protein Abcg2 at the Mouse Blood-Brain Barrier
- 1 May 2004
- journal article
- Published by American Association for Cancer Research (AACR) in Cancer Research
- Vol. 64 (9) , 3296-3301
- https://doi.org/10.1158/0008-5472.can-03-2033
Abstract
The breast cancer resistance protein (BCRP/ABCG2) is, like P-glycoprotein (P-gp), a member of the ABC family of drug transporters. These proteins actively transport various anticancer drugs from cells, causing multidrug resistance. The physiological expression of P-gp/ABCB1 at the blood-brain barrier (BBB) effectively restricts the brain uptake of many antitumor drugs by mediating their active efflux from the brain to the blood vessel lumen. However, little is known about the function of Abcg2 at the BBB in vivo. We used in situ brain perfusion to measure the uptake of two known Abcg2 substrates, prazosin and mitoxantrone, and the nonsubstrate vinblastine by the brains of wild-type and P-gp-deficient mutant mdr1a(−/−) mice with or without the P-gp/Abcg2 inhibitor GF120918 or the P-gp inhibitor PSC833. P-gp had no effect on the brain transport of prazosin and mitoxantrone at the mouse BBB, but wild-type and P-gp-deficient mouse brains perfused with GF120918 or a high concentration of prazosin showed carrier-mediated effluxes of prazosin and mitoxantrone from the brain that did not involve P-gp. In contrast, the brain uptake of vinblastine was restricted only by P-gp and not by Abcg2 at the BBB. The amounts of abcg2 mRNA in cortex homogenates and capillary-enriched fractions of wild-type and mdr1a(−/−) mouse brains were measured by real-time quantitative reverse transcription-PCR. There was ∼700-times more abcg2 mRNA in brain microvessels than in the cortex of the wild-type mice, confirming that Abcg2 plays an important role at the BBB. There was also ∼3 times more abcg2 mRNA in the microvessels from P-gp-deficient mutant mouse brains than in the microvessels of wild-type mouse brains. These findings confirm that Abcg2 is a physiological transporter at the BBB that restricts the permeability of the brain to its substrates in vivo. Lastly, the defective P-gp in the mutant mdr1a(−/−) mice was associated with increased abcg2 mRNA at the BBB and a greater export of prazosin and mitoxantrone from the brain, as measured in the P-gp-deficient mice versus the wild-type mice.Keywords
This publication has 26 references indexed in Scilit:
- Expression and functional characterization of ABCG2 in brain endothelial cells and vesselsThe FASEB Journal, 2003
- Characterization of Drug Transport, ATP Hydrolysis, and Nucleotide Trapping by the Human ABCG2 Multidrug TransporterPublished by Elsevier ,2002
- A new multidrug resistance protein at the blood–brain barrierBiochemical and Biophysical Research Communications, 2002
- From MDR to MXR: new understanding of multidrug resistance systems, their properties and clinical significanceCellular and Molecular Life Sciences, 2001
- Development of an In Situ Mouse Brain Perfusion Model and its Application to mdr1a P-Glycoprotein-Deficient MiceJournal of Cerebral Blood Flow & Metabolism, 2000
- Stimulation of P‐glycoprotein‐mediated drug transport by prazosin and progesteroneEuropean Journal of Biochemistry, 1999
- Isolated brain capillaries: an in vitro model of blood–brain barrier researchPublished by Cambridge University Press (CUP) ,1998
- Identification of a P-Glycoprotein-Deficient Subpopulation in the CF-1 Mouse Strain Using a Restriction Fragment Length PolymorphismToxicology and Applied Pharmacology, 1997
- Brain Perfusion Systems for Studies of Drug Uptake and Metabolism in the Central Nervous SystemPublished by Springer Nature ,1996
- Disruption of the mouse mdr1a P-glycoprotein gene leads to a deficiency in the blood-brain barrier and to increased sensitivity to drugsPublished by Elsevier ,1994