Abstract
The purpose of this study was to examine whether in vivo drug distribution to the brain can be reconstructed by integrating P-glycoprotein (P-gp)/mdr1a expression levels, P-gp in vitro activity, and drug unbound fractions in mouse plasma and brain. For 11 P-gp substrates, in vitro P-gp transport activities were determined by measuring transcellular transport across monolayers of mouse P-gp-transfected LLC-PK1 (L-mdr1a) and parental cells. P-gp expression amounts were determined by quantitative targeted absolute proteomics. Unbound drug fractions in plasma and brain were obtained from the literature and by measuring brain slice uptake, respectively. Brain-to-plasma concentration ratios (Kp brain) and its ratios between wild-type and mdr1a/1b(−/−) mice (Kp brain ratio) were obtained from the literature or determined by intravenous constant infusion. Unbound brain-to-plasma concentration ratios (Kp,uu,brain) were estimated from Kp brain and unbound fractions. Based on pharmacokinetic theory, Kp brain ratios were reconstructed from in vitro P-gp transport activities and P-gp expression amounts in L-mdr1a cells and mouse brain capillaries. All reconstructed Kp brain ratios were within a 1.6-fold range of observed values. Kp brain then was reconstructed from the reconstructed Kp brain ratios and unbound fractions. Kp,uu,brain was reconstructed as the reciprocal of the reconstructed Kp brain ratios. For quinidine, loperamide, risperidone, indinavir, dexamethasone, paclitaxel, verapamil, loratadine, and diazepam, the reconstructed Kp brain and Kp,uu,brain agreed with observed and estimated in vivo values within a 3-fold range, respectively. Thus, brain distributions of P-gp substrates can be reconstructed from P-gp expression levels, in vitro activity, and drug unbound fractions.
Footnotes
This study was supported in part by Grants-in-Aid for Scientific Research (S) [KAKENHI: 18109002]; the Japan Society for the Promotion of Science (JSPS) Fellows [KAKENHI: 207291] from the JSPS; a Grant-in-Aid for Scientific Research on Priority Area [KAKENHI: 17081002] from The Ministry of Education, Culture, Sports, Science and Technology; and a Grant for Development of Creative Technology Seeds Supporting Program for Creating University Ventures from Japan Science and Technology Agency. This study was also supported in part by the Industrial Technology Research Grant Program from New Energy and the Industrial Technology Development Organization of Japan.
T.T. is a full professor and S.O. is an associate professor of Tohoku University, respectively, and are also directors of Proteomedix Frontiers. This research was not supported by Proteomedix Frontiers and their position at Proteomedix Frontiers does not present any financial conflicts.
Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
doi:10.1124/jpet.111.184200.
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The online version of this article (available at http://jpet.aspetjournals.org) contains supplemental material.-
ABBREVIATIONS:
- CNS
- central nervous system
- BBB
- blood-brain barrier
- bcrp
- breast cancer resistance protein
- ECF
- extracellular fluid
- fu,brain
- unbound fraction in brain
- fu,plasma
- unbound fraction in plasma
- HPLC
- high-performance liquid chromatography
- Kp brain
- brain-to-plasma concentration ratio
- Kp,uu,brain
- unbound brain-to-plasma concentration ratio
- LC-MS/MS
- liquid chromatography-tandem mass spectrometry
- MDR1
- multidrug resistance protein 1
- mdr1a
- multidrug resistance protein 1a
- MRM
- multiple reaction monitoring
- P-gp
- P-glycoprotein
- PPx
- pharmacoproteomics
- QTAP
- quantitative targeted absolute proteomics
- Papp
- apparent permeability
- oatp2
- organic anion-transporting polypeptide 2
- KO
- knockout
- WT
- wild type
- MDCK
- Madin-Darby canine kidney
- GR205171
- (S)-(2-methoxy-5-(5-trifluoromethyltetrazol-1-yl)-phenylmethylamino)-2(S)-phenylpiperidine.
- Received May 23, 2011.
- Accepted August 8, 2011.
- Copyright © 2011 by The American Society for Pharmacology and Experimental Therapeutics
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