title: The organic anion transport inhibitor probenecid increases brain concentrations of the NKCC1 inhibitor bumetanide.
abstract: Bumetanide is increasingly being used for experimental treatment of brain disorders, including neonatal seizures, epilepsy, and autism, because the neuronal Na-K-Cl cotransporter NKCC1, which is inhibited by bumetanide, is implicated in the pathophysiology of such disorders. However, use of bumetanide for treatment of brain disorders is associated with problems, including poor brain penetration and systemic adverse effects such as diuresis, hypokalemic alkalosis, and hearing loss. The poor brain penetration is thought to be related to its high ionization rate and plasma protein binding, which restrict brain entry by passive diffusion, but more recently brain efflux transporters have been involved, too. Multidrug resistance protein 4 (MRP4), organic anion transporter 3 (OAT3) and organic anion transporting polypeptide 2 (OATP2) were suggested to mediate bumetanide brain efflux, but direct proof is lacking. Because MRP4, OAT3, and OATP2 can be inhibited by probenecid, we studied whether this drug alters brain levels of bumetanide in mice. Probenecid (50 mg/kg) significantly increased brain levels of bumetanide up to 3-fold; however, it also increased its plasma levels, so that the brain:plasma ratio (~0.015-0.02) was not altered. Probenecid markedly increased the plasma half-life of bumetanide, indicating reduced elimination of bumetanide most likely by inhibition of OAT-mediated transport of bumetanide in the kidney. However, the diuretic activity of bumetanide was not reduced by probenecid. In conclusion, our study demonstrates that the clinically available drug probenecid can be used to increase brain levels of bumetanide and decrease its elimination, which could have therapeutic potential in the treatment of brain disorders.
authors.affiliation: Department of Pharmacology, Toxicology, and Pharmacy, University of Veterinary Medicine Hannover, Germany; Center for Systems Neuroscience, Hannover, Germany.
authors.forename: Kathrin
authors.initials: K
authors.lastname: Töllner
authors.affiliation: Department of Pharmacology, Toxicology, and Pharmacy, University of Veterinary Medicine Hannover, Germany; Center for Systems Neuroscience, Hannover, Germany.
authors.forename: Claudia
authors.initials: C
authors.lastname: Brandt
authors.affiliation: Department of Pharmacology, Toxicology, and Pharmacy, University of Veterinary Medicine Hannover, Germany; Center for Systems Neuroscience, 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; 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; D021461:Animals, Outbred Strains; D000927:Anticonvulsants / Q000097:blood / Q000378:metabolism / Q000493:pharmacokinetics; D001692:Biological Transport / Q000187:drug effects; D001812:Blood-Brain Barrier / Q000187:drug effects* / Q000378:metabolism; D001921:Brain / Q000187:drug effects* / Q000378:metabolism; D002034:Bumetanide / Q000097:blood / Q000378:metabolism / Q000493:pharmacokinetics* / Q000494:pharmacology; D002460:Cell Line; D004232:Diuretics / Q000097:blood / Q000378:metabolism / Q000493:pharmacokinetics; D004285:Dogs; D004347:Drug Interactions; D005260:Female; D006207:Half-Life; D006801:Humans; D007668:Kidney / Q000187:drug effects / Q000378:metabolism; D049990:Membrane Transport Modulators / Q000494:pharmacology*; D051379:Mice; D009419:Nerve Tissue Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D027361:Organic Anion Transporters / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D011339:Probenecid / Q000494:pharmacology*; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D049994:Sodium Potassium Chloride Symporter Inhibitors / Q000097:blood / Q000378:metabolism / Q000493:pharmacokinetics* / Q000494:pharmacology
chemical_list: D000927:Anticonvulsants; D004232:Diuretics; D049990:Membrane Transport Modulators; D009419:Nerve Tissue Proteins; D027361:Organic Anion Transporters; D011994:Recombinant Proteins; D049994:Sodium Potassium Chloride Symporter Inhibitors; D002034:Bumetanide; D011339:Probenecid
keywords: Blood–brain barrier; Cation chloride cotransporters; Drug transport; Epilepsy; Neonatal seizures