title: Rapid modulation of P-glycoprotein-mediated transport at the blood-brain barrier by tumor necrosis factor-alpha and lipopolysaccharide.
abstract: At the blood-brain barrier, P-glycoprotein, an ATP-driven drug efflux pump, selectively limits drug access to the brain parenchyma, impeding pharmacotherapy of a number of central nervous system (CNS) disorders. We previously used confocal imaging to demonstrate in isolated rat brain capillaries that endothelin-1 (ET-1), acting through an ET(B) receptor, NO synthase, and protein kinase C, rapidly and reversibly reduces P-glycoprotein transport function. In this study, we define a link between the brain's innate immune response and functional regulation of P-glycoprotein. We show that exposing brain capillaries to the inflammatory cytokine tumor necrosis factor-alpha (TNF-alpha), activated a TNF-R1 receptor, released ET-1, activated ET(B) receptor signaling, and essentially abolished P-glycoprotein-mediated transport. Bacterial lipopolysaccharide, a potent activator of the brain's innate immune response, reduced P-glycoprotein activity through TNF-alpha release, ET-1 release, and ET(B) receptor signaling. TNF-alpha and LPS effects had a rapid onset (minutes), were reversible, and did not involve changes in tight junctional permeability. These findings define a signaling pathway through which P-glycoprotein activity is acutely modulated. They show that this key component of the selective/active blood-brain barrier is an early target of cytokine signaling during the innate immune response and suggest ways to manipulate the barrier for improved CNS pharmacotherapy.
authors.affiliation: Laboratory of Pharmacology and Chemistry, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA.
authors.forename: Anika M S
authors.initials: AM
authors.lastname: Hartz
authors.forename: Björn
authors.initials: B
authors.lastname: Bauer
authors.forename: Gert
authors.initials: G
authors.lastname: Fricker
authors.forename: David S
authors.initials: DS
authors.lastname: Miller
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B / Q000187:drug effects*; D000818:Animals; D001812:Blood-Brain Barrier / Q000187:drug effects* / Q000276:immunology; D007113:Immunity, Innate / Q000187:drug effects*; D008070:Lipopolysaccharides / Q000494:pharmacology; D021381:Protein Transport / Q000187:drug effects; D051381:Rats; D044023:Receptor, Endothelin B / Q000378:metabolism*; D047888:Receptors, Tumor Necrosis Factor, Type I / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
chemical_list: D018435:ATP Binding Cassette Transporter, Subfamily B; D008070:Lipopolysaccharides; D044023:Receptor, Endothelin B; D047888:Receptors, Tumor Necrosis Factor, Type I; D014409:Tumor Necrosis Factor-alpha