title: Rapid, nongenomic stimulation of multidrug resistance protein 2 (Mrp2) activity by glucocorticoids in renal proximal tubule.
abstract: In renal proximal tubule, multidrug resistance protein 2 (Mrp2) actively transports many organic anions into urine, including drugs and metabolic wastes. Upon exposure to nephrotoxicants or during endotoxemia, both Mrp2 activity and expression are up-regulated. This may result from induced de novo synthesis of Mrp2 or post-transcriptional events involving specific signaling pathways. Here, we investigated glucocorticoid signaling to Mrp2 in killifish renal proximal tubules, a model system in which transport activity can be measured using a fluorescent substrate and confocal imaging. Exposure of tubules to dexamethasone rapidly increased Mrp2-mediated fluorescein methotrexate transport. Other glucocorticoid receptor (GR) ligands, cortisol and triamcinolone acetonide, also stimulated Mrp2-mediated transport. The GR antagonist, mifepristone 17β-hydroxy-11β-[4-dimethylamino phenyl]-17α-[1-propynyl]estra-4,9-dien-3-one (RU486), abolished stimulation by all three ligands, whereas the mineralocorticoid receptor antagonist, spironolactone, was ineffective. Consistent with action through a nongenomic mechanism, dexamethasone stimulation of Mrp2-mediated transport was insensitive to cycloheximide and actinomycin D, and immunohistochemistry revealed no alterations in Mrp2 expression at the luminal membrane. (9S-(9α,10β,12α))-2,3,9,10,11,12-hexahydro-10-hydroxy-10-(methoxycarbonyl)-9-methyl-9,12-epoxy-1H-diindolo[1,2,3-fg:3',2',1'-kl]pyrrolo[3,4-i][1,6]benzodiazocin-1-one (K252a), an inhibitor of the tyrosine receptor kinase subfamily, reduced the dexamethasone effect, as did the specific hepatocyte growth factor receptor (c-Met) tyrosine kinase inhibitor, (2R)-1-[[5-[(Z)-[5-[[(2,6-dichlorophenyl)methyl]sulfonyl]-1,2-dihydro-2-oxo-3H-indol-3-ylidene]methyl]-2,4-dimethyl-1H-pyrrol-3-yl]carbonyl]-2-(1-pyrrolidinylmethyl)pyrrolidine (PHA-665752). Hepatocyte growth factor (HGF), an endogenous ligand for c-Met, stimulated Mrp2-mediated transport. This effect was reversed by PHA-665752 but not by RU486. Inhibition of mitogen-activated protein kinase/extracellular signal-regulated kinase kinase (MEK 1/2) also abolished the effects of dexamethasone and HGF. Our results disclose a novel mechanism by which glucocorticoids acting through GR, c-Met, and MEK1/2 cause rapid, nongenomic stimulation of Mrp2-mediated transport in renal proximal tubules. This up-regulation may be nephroprotective, enhancing efflux of metabolic wastes and toxicants during cell and tissue stress.
authors.affiliation: Department of Pharmacology and Toxicology, Radboud University Nijmegen Medical Centre/Nijmegen Centre for Molecular Life Sciences, Nijmegen, The Netherlands.
authors.forename: Brigitte
authors.initials: B
authors.lastname: Prevoo
authors.forename: David S
authors.initials: DS
authors.lastname: Miller
authors.forename: Femke M
authors.initials: FM
authors.lastname: van de Water
authors.forename: Kimberley E
authors.initials: KE
authors.lastname: Wever
authors.forename: Frans G M
authors.initials: FG
authors.lastname: Russel
authors.forename: Gert
authors.initials: G
authors.lastname: Flik
authors.forename: Rosalinde
authors.initials: R
authors.lastname: Masereeuw
mesh_terms: D000818:Animals; D002460:Cell Line; D023781:Fundulidae; D005938:Glucocorticoids / Q000494:pharmacology*; D007687:Kidney Tubules, Proximal / Q000187:drug effects* / Q000378:metabolism*; D000089762:Multidrug Resistance-Associated Protein 2; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000819:agonists / Q000096:biosynthesis*; D013997:Time Factors
chemical_list: D005938:Glucocorticoids; D000089762:Multidrug Resistance-Associated Protein 2; D027425:ATP-Binding Cassette, Sub-Family C Proteins