title: In vivo activation of human pregnane X receptor tightens the blood-brain barrier to methadone through P-glycoprotein up-regulation.
abstract: The ATP-driven drug export pump, P-glycoprotein, is a primary gatekeeper of the blood-brain barrier and a major impediment to central nervous system (CNS) pharmacotherapy. Reducing P-glycoprotein activity dramatically increases penetration of many therapeutic drugs into the CNS. Previous studies in rat showed that brain capillary P-glycoprotein was transcriptionally up-regulated by the pregnane X receptor (PXR), a xenobiotic-activated nuclear receptor. Here we used a transgenic mouse expressing human PXR (hPXR) to determine the consequences of increased blood-brain barrier P-glycoprotein activity. P-glycoprotein expression and transport activity in brain capillaries from transgenic mice was significantly increased when capillaries were exposed to the hPXR ligands, rifampin and hyperforin, in vitro and when the mice were dosed with rifampin in vivo. Plasma rifampin levels in induced mice were comparable with literature values for patients. We also administered methadone, a CNS-acting, P-glycoprotein substrate, to control and rifampin-induced transgenic mice and measured the drug's antinociceptive effect. In rifampin-induced mice, the methadone effect was reduced by approximately 70%, even though plasma methadone levels were similar to those found in transgenic controls not exposed to rifampin. Thus, hPXR activation in vivo increased P-glycoprotein activity and tightened the blood-brain barrier to methadone, reducing the drug's CNS efficacy. This is the first demonstration of the ability of blood-brain barrier PXR to alter the efficacy of a CNS-acting drug.
authors.affiliation: Laboratory of Pharmacology and Chemistry, National Institute of Environmental Health Sciences, National Institutes of Health, 111 TW Alexander Drive, Research Triangle Park, NC 27709, USA.
authors.forename: Björn
authors.initials: B
authors.lastname: Bauer
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Yang
authors.forename: Anika M S
authors.initials: AM
authors.lastname: Hartz
authors.forename: Emily R
authors.initials: ER
authors.lastname: Olson
authors.forename: Rong
authors.initials: R
authors.lastname: Zhao
authors.forename: J Cory
authors.initials: JC
authors.lastname: Kalvass
authors.forename: Gary M
authors.initials: GM
authors.lastname: Pollack
authors.forename: David S
authors.initials: DS
authors.lastname: Miller
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B / Q000235:genetics; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism*; D018528:ATP-Binding Cassette Transporters / Q000235:genetics; D000700:Analgesics / Q000494:pharmacology; D000818:Animals; D001812:Blood-Brain Barrier; D001921:Brain / Q000098:blood supply / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D008691:Methadone / Q000378:metabolism / Q000493:pharmacokinetics* / Q000494:pharmacology; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D000077297:Pregnane X Receptor; D011987:Receptors, Steroid / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D012293:Rifampin / Q000493:pharmacokinetics / Q000494:pharmacology; D015854:Up-Regulation
chemical_list: D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D018528:ATP-Binding Cassette Transporters; D000700:Analgesics; D000077297:Pregnane X Receptor; D011987:Receptors, Steroid; C095122:multidrug resistance protein 3; D008691:Methadone; D012293:Rifampin