title: Targeting blood-brain barrier sphingolipid signaling reduces basal P-glycoprotein activity and improves drug delivery to the brain.
abstract: P-glycoprotein, an ATP-driven drug efflux pump, is a major obstacle to the delivery of small-molecule drugs across the blood-brain barrier and into the CNS. Here we test a unique signaling-based strategy to overcome this obstacle. We used a confocal microscopy-based assay with isolated rat brain capillaries to map a signaling pathway that within minutes abolishes P-glycoprotein transport activity without altering transporter protein expression or tight junction permeability. This pathway encompasses elements of proinflammatory- (TNF-α) and sphingolipid-based signaling. Critical to this pathway was signaling through sphingosine-1-phosphate receptor 1 (S1PR1). In brain capillaries, S1P acted through S1PR1 to rapidly and reversibly reduce P-glycoprotein transport activity. Sphingosine reduced transport by a sphingosine kinase-dependent mechanism. Importantly, fingolimod (FTY720), a S1P analog recently approved for treatment of multiple sclerosis, also rapidly reduced P-glycoprotein activity; similar effects were found with the active, phosphorylated metabolite (FTY720P). We validated these findings in vivo using in situ brain perfusion in rats. Administration of S1P, FTY720, or FTY729P increased brain uptake of three radiolabeled P-glycoprotein substrates, (3)H-verapamil (threefold increase), (3)H-loperamide (fivefold increase), and (3)H-paclitaxel (fivefold increase); blocking S1PR1 abolished this effect. Tight junctional permeability, measured as brain (14)C-sucrose accumulation, was not altered. Therefore, targeting signaling through S1PR1 at the blood-brain barrier with the sphingolipid-based drugs, FTY720 or FTY720P, can rapidly and reversibly reduce basal P-glycoprotein activity and thus improve delivery of small-molecule therapeutics to the brain.
authors.affiliation: Laboratory of Toxicology and Pharmacology, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA. cannon1@niehs.nih.gov
authors.forename: Ronald E
authors.initials: RE
authors.lastname: Cannon
authors.forename: John C
authors.initials: JC
authors.lastname: Peart
authors.forename: Brian T
authors.initials: BT
authors.lastname: Hawkins
authors.forename: Christopher R
authors.initials: CR
authors.lastname: Campos
authors.forename: David S
authors.initials: DS
authors.lastname: Miller
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism*; D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects / Q000502:physiology; D001812:Blood-Brain Barrier / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002196:Capillaries / Q000166:cytology / Q000378:metabolism; D016503:Drug Delivery Systems; D005260:Female; D000068876:Fingolimod Hydrochloride; D007166:Immunosuppressive Agents / Q000494:pharmacology; D008246:Lysophospholipids / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D010755:Organophosphates / Q000494:pharmacology; D011409:Propylene Glycols / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D049349:Receptors, Lysosphingolipid / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D013107:Sphingolipids / Q000378:metabolism*; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D019108:Tight Junctions / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D014700:Verapamil / Q000494:pharmacology
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D002121:Calcium Channel Blockers; C525008:FTY 720P; D007166:Immunosuppressive Agents; D008246:Lysophospholipids; D009419:Nerve Tissue Proteins; D010755:Organophosphates; D011409:Propylene Glycols; D049349:Receptors, Lysosphingolipid; D013107:Sphingolipids; D014409:Tumor Necrosis Factor-alpha; C060506:sphingosine 1-phosphate; D014700:Verapamil; D000068876:Fingolimod Hydrochloride; D013110:Sphingosine