title: Expression of the multidrug transporter MRP2 in the blood-brain barrier after pilocarpine-induced seizures in rats.
abstract: Multidrug resistance proteins (MRPs; symbol ABCC) are membrane glycoproteins that mediate the ATP-dependent export of a wide range of substrates from cells and thereby affect the bioavailability and disposition of many drugs. MRP2 (ABCC2) is expressed on the apical domain of hepatocytes, enterocytes of the proximal small intestine, and proximal renal tubular cells, but its location in the brain is a matter of debate. Most previous studies failed to determine MRP2 mRNA or protein in the brain or cell preparations from the brain of different species including humans. Based on our previous experience with the drug efflux transporter P-glycoprotein, we evaluated whether the immunohistochemical determination of MRP2 expression is sensitive to fixation and staining variables. Furthermore, we examined whether the MRP2 protein is overexpressed after experimentally induced seizures in rats, using the pilocarpine model of temporal lobe epilepsy. The MRP2 expression in the liver was used as positive control. MRP2 deficient TR- rats were used as negative controls. Despite various modifications in tissue fixation and immunohistochemical staining as well as use of different commercially available MRP2 antibodies, we never observed any unequivocal MRP2 staining in the brain of normal rats. However, after a pilocarpine-induced convulsive status epilepticus, clear MRP2 staining became visible in brain capillary endothelial cells and, less frequently, perivascular astroglia and neurons in various brain regions. In view of our recent data on brain access of antiepileptic drugs in MRP2 deficient TR- rats, seizure-induced over-expression of MRP2 in the blood-brain barrier is likely to impair drug penetration into the brain, thereby contributing to drug resistance in epilepsy.
authors.affiliation: Department of Pharmacology, Toxicology, and Pharmacy, University of Veterinary Medicine, Bünteweg 17, D-30559 Hannover, Germany.
authors.forename: Katrin
authors.initials: K
authors.lastname: Hoffmann
authors.forename: Alexandra M
authors.initials: AM
authors.lastname: Gastens
authors.forename: Holger A
authors.initials: HA
authors.lastname: Volk
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Löscher
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism; D000818:Animals; D000911:Antibodies, Monoclonal; D001812:Blood-Brain Barrier / Q000378:metabolism*; D001921:Brain / Q000378:metabolism*; D018432:Drug Resistance, Multiple; D004833:Epilepsy, Temporal Lobe / Q000139:chemically induced / Q000378:metabolism*; D005260:Female; D007150:Immunohistochemistry; D008297:Male; D026901:Membrane Transport Proteins / Q000378:metabolism*; D051379:Mice; D000089762:Multidrug Resistance-Associated Protein 2; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000378:metabolism*; D010862:Pilocarpine; D012333:RNA, Messenger; D051381:Rats; D011919:Rats, Inbred Strains; D017208:Rats, Wistar; D012640:Seizures / Q000139:chemically induced / Q000378:metabolism*
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000911:Antibodies, Monoclonal; D026901:Membrane Transport Proteins; D000089762:Multidrug Resistance-Associated Protein 2; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D010862:Pilocarpine; D012333:RNA, Messenger; C000715087:ABCC2 protein, human