In Vivo Imaging of Human MDR1 Transcription in the Brain and Spine of MDR1-Luciferase Reporter Mice.
P-glycoprotein (Pgp) [the product of the MDR1 (ABCB1) gene] at the blood-brain barrier (BBB) limits central nervous system (CNS) entry of many prescribed drugs, contributing to the poor success rate of CNS drug candidates. Modulating Pgp expression could improve drug delivery into the brain; however, assays to predict regulation of human BBB Pgp are lacking. We developed a transgenic mouse model to monitor human MDR1 transcription in the brain and spinal cord in vivo. A reporter construct consisting of ∼10 kb of the human MDR1 promoter controlling the firefly luciferase gene was used to generate a transgenic mouse line (MDR1-luc). Fluorescence in situ hybridization localized the MDR1-luciferase transgene on chromosome 3. Reporter gene expression was monitored with an in vivo imaging system following D-luciferin injection. Basal expression was detectable in the brain, and treatment with activators of the constitutive androstane, pregnane X, and glucocorticoid receptors induced brain and spinal MDR1-luc transcription. Since D-luciferin is a substrate of ABCG2, the feasibility of improving D-luciferin brain accumulation (and luciferase signal) was tested by coadministering the dual ABCB1/ABCG2 inhibitor elacridar. The brain and spine MDR1-luc signal intensity was increased by elacridar treatment, suggesting enhanced D-luciferin brain bioavailability. There was regional heterogeneity in MDR1 transcription (cortex > cerebellum) that coincided with higher mouse Pgp protein expression. We confirmed luciferase expression in brain vessel endothelial cells by ex vivo analysis of tissue luciferase protein expression. We conclude that the MDR1-luc mouse provides a unique in vivo system to visualize MDR1 CNS expression and regulation.
Department of Pharmaceutical Sciences, St. Jude Children's Research Hospital, Memphis, Tennessee (K.Y., C.C., R.S., S.G., R.K.T., A.C., E.G.S.); Department of Medicine, Division of Clinical Pharmacology, University of Western Ontario, London, Ontario, Canada (R.B.K.); and Department of Pharmaceutics, The University of Washington, Seattle, Washington (Y.S.L.).
Kazuto
K
Yasuda
Department of Pharmaceutical Sciences, St. Jude Children's Research Hospital, Memphis, Tennessee (K.Y., C.C., R.S., S.G., R.K.T., A.C., E.G.S.); Department of Medicine, Division of Clinical Pharmacology, University of Western Ontario, London, Ontario, Canada (R.B.K.); and Department of Pharmaceutics, The University of Washington, Seattle, Washington (Y.S.L.).
Cynthia
C
Cline
Department of Pharmaceutical Sciences, St. Jude Children's Research Hospital, Memphis, Tennessee (K.Y., C.C., R.S., S.G., R.K.T., A.C., E.G.S.); Department of Medicine, Division of Clinical Pharmacology, University of Western Ontario, London, Ontario, Canada (R.B.K.); and Department of Pharmaceutics, The University of Washington, Seattle, Washington (Y.S.L.).
Yvonne S
YS
Lin
Department of Pharmaceutical Sciences, St. Jude Children's Research Hospital, Memphis, Tennessee (K.Y., C.C., R.S., S.G., R.K.T., A.C., E.G.S.); Department of Medicine, Division of Clinical Pharmacology, University of Western Ontario, London, Ontario, Canada (R.B.K.); and Department of Pharmaceutics, The University of Washington, Seattle, Washington (Y.S.L.).
Rachel
R
Scheib
Department of Pharmaceutical Sciences, St. Jude Children's Research Hospital, Memphis, Tennessee (K.Y., C.C., R.S., S.G., R.K.T., A.C., E.G.S.); Department of Medicine, Division of Clinical Pharmacology, University of Western Ontario, London, Ontario, Canada (R.B.K.); and Department of Pharmaceutics, The University of Washington, Seattle, Washington (Y.S.L.).
Samit
S
Ganguly
Department of Pharmaceutical Sciences, St. Jude Children's Research Hospital, Memphis, Tennessee (K.Y., C.C., R.S., S.G., R.K.T., A.C., E.G.S.); Department of Medicine, Division of Clinical Pharmacology, University of Western Ontario, London, Ontario, Canada (R.B.K.); and Department of Pharmaceutics, The University of Washington, Seattle, Washington (Y.S.L.).
Ranjit K
RK
Thirumaran
Department of Pharmaceutical Sciences, St. Jude Children's Research Hospital, Memphis, Tennessee (K.Y., C.C., R.S., S.G., R.K.T., A.C., E.G.S.); Department of Medicine, Division of Clinical Pharmacology, University of Western Ontario, London, Ontario, Canada (R.B.K.); and Department of Pharmaceutics, The University of Washington, Seattle, Washington (Y.S.L.).
Amarjit
A
Chaudhry
Department of Pharmaceutical Sciences, St. Jude Children's Research Hospital, Memphis, Tennessee (K.Y., C.C., R.S., S.G., R.K.T., A.C., E.G.S.); Department of Medicine, Division of Clinical Pharmacology, University of Western Ontario, London, Ontario, Canada (R.B.K.); and Department of Pharmaceutics, The University of Washington, Seattle, Washington (Y.S.L.).
Richard B
RB
Kim
Department of Pharmaceutical Sciences, St. Jude Children's Research Hospital, Memphis, Tennessee (K.Y., C.C., R.S., S.G., R.K.T., A.C., E.G.S.); Department of Medicine, Division of Clinical Pharmacology, University of Western Ontario, London, Ontario, Canada (R.B.K.); and Department of Pharmaceutics, The University of Washington, Seattle, Washington (Y.S.L.) erin.schuetz@stjude.org.
Erin G
EG
Schuetz
D018435:ATP Binding Cassette Transporter, Subfamily B / Q000096:biosynthesis / Q000235:genetics; D000818:Animals; D001921:Brain / Q000378:metabolism*; D003952:Diagnostic Imaging; D005260:Female; D017930:Genes, Reporter / Q000502:physiology*; D006801:Humans; D049409:Luciferases, Firefly / Q000096:biosynthesis* / Q000235:genetics; D051379:Mice; D008822:Mice, Transgenic; D013131:Spine / Q000378:metabolism*; D014158:Transcription, Genetic / Q000502:physiology*
C513055:ABCB1 protein, human; D018435:ATP Binding Cassette Transporter, Subfamily B; D049409:Luciferases, Firefly