title: Multiple blood-brain barrier transport mechanisms limit bumetanide accumulation, and therapeutic potential, in the mammalian brain.
abstract: There is accumulating evidence that bumetanide, which has been used over decades as a potent loop diuretic, also exerts effects on brain disorders, including autism, neonatal seizures, and epilepsy, which are not related to its effects on the kidney but rather mediated by inhibition of the neuronal Na-K-Cl cotransporter isoform NKCC1. However, following systemic administration, brain levels of bumetanide are typically below those needed to inhibit NKCC1, which critically limits its clinical use for treating brain disorders. Recently, active efflux transport at the blood-brain barrier (BBB) has been suggested as a process involved in the low brain:plasma ratio of bumetanide, but it is presently not clear which transporters are involved. Understanding the processes explaining the poor brain penetration of bumetanide is needed for developing strategies to improve the brain delivery of this drug. In the present study, we administered probenecid and more selective inhibitors of active transport carriers at the BBB directly into the brain of mice to minimize the contribution of peripheral effects on the brain penetration of bumetanide. Furthermore, in vitro experiments with mouse organic anion transporter 3 (Oat3)-overexpressing Chinese hamster ovary cells were performed to study the interaction of bumetanide, bumetanide derivatives, and several known inhibitors of Oats on Oat3-mediated transport. The in vivo experiments demonstrated that the uptake and efflux of bumetanide at the BBB is much more complex than previously thought. It seems that both restricted passive diffusion and active efflux transport, mediated by Oat3 but also organic anion-transporting polypeptide (Oatp) Oatp1a4 and multidrug resistance protein 4 explain the extremely low brain concentrations that are achieved after systemic administration of bumetanide, limiting the use of this drug for targeting abnormal expression of neuronal NKCC1 in brain diseases.
authors.affiliation: Department of Pharmacology, Toxicology, and Pharmacy, University of Veterinary Medicine Hannover, Germany.
authors.forename: Kerstin
authors.initials: K
authors.lastname: Römermann
authors.affiliation: Department of Pharmacology, Toxicology, and Pharmacy, University of Veterinary Medicine Hannover, Germany.
authors.forename: Maren
authors.initials: M
authors.lastname: Fedrowitz
authors.affiliation: Department of Pharmacology, Toxicology, and Pharmacy, University of Veterinary Medicine Hannover, Germany; Center for Systems Neuroscience, Hannover, Germany.
authors.forename: Philip
authors.initials: P
authors.lastname: Hampel
authors.affiliation: Department of Pharmacology, Toxicology, and Pharmacy, University of Veterinary Medicine Hannover, Germany.
authors.forename: Edith
authors.initials: E
authors.lastname: Kaczmarek
authors.affiliation: Department of Pharmacology, Toxicology, and Pharmacy, University of Veterinary Medicine Hannover, Germany.
authors.forename: Kathrin
authors.initials: K
authors.lastname: Töllner
authors.affiliation: Department of Medicinal Chemistry, University of Vienna, Vienna, Austria.
authors.forename: Thomas
authors.initials: T
authors.lastname: Erker
authors.affiliation: Department of Pharmaceutics, Virginia Commonwealth University, Richmond, VA, USA.
authors.forename: Douglas H
authors.initials: DH
authors.lastname: Sweet
authors.affiliation: Department of Pharmacology, Toxicology, and Pharmacy, University of Veterinary Medicine Hannover, Germany; Center for Systems Neuroscience, Hannover, Germany. Electronic address: wolfgang.loescher@tiho-hannover.de.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Löscher
mesh_terms: D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D001812:Blood-Brain Barrier / Q000187:drug effects / Q000502:physiology*; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D002034:Bumetanide / Q000031:analogs & derivatives / Q000493:pharmacokinetics*; D016466:CHO Cells; D002478:Cells, Cultured; D006224:Cricetinae; D003412:Cricetulus; D004058:Diffusion; D005260:Female; D049990:Membrane Transport Modulators / Q000494:pharmacology; D051379:Mice; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000502:physiology*; D027361:Organic Anion Transporters / Q000037:antagonists & inhibitors / Q000235:genetics; D029362:Organic Anion Transporters, Sodium-Independent / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology*; D027701:Organic Cation Transport Proteins / Q000502:physiology*; D011339:Probenecid / Q000494:pharmacology
chemical_list: D002034:Bumetanide; D049990:Membrane Transport Modulators; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D027361:Organic Anion Transporters; D029362:Organic Anion Transporters, Sodium-Independent; D027701:Organic Cation Transport Proteins; D011339:Probenecid; C489540:Abcc4 protein, mouse; C464433:Oatp2 protein, mouse; C114338:organic anion transport protein 3
keywords: Bumetanide derivatives; NKCC1; Organic anion transporters; Probenecid