title: Different effects of CsA and FK506 on aquaporin-2 abundance in rat primary cultured collecting duct cells.
abstract: Calcineurin (Cn) inhibitors (CnI) such as cyclosporine A (CsA) and FK506 are nephrotoxic immunosuppressant drugs, which decrease tubular function. Here, we examined the direct effect of CnI on aquaporin-2 (AQP2) expression in rat primary cultured inner medullary collecting duct cells. CsA (0.5-5 μM) but not FK 506 (0.01-1 μM) decreased expression of AQP2 protein and messenger RNA (mRNA) in a concentration and time dependent manner, without affecting mRNA stability. This effect was observed despite similar inhibition of Cn activity by both CnI, thereby suggesting that the CsA-dependent decrease in AQP2 expression was Cn independent. Another inhibitor of cyclophilin A, the primary intracellular target of CsA, had no effect on AQP2 expression. In order to investigate the mechanism of decreased AQP2 transcription, we studied activation status of two suggested transcriptional regulators of AQP2, cAMP-responsive element binding protein (CREB), and tonicity enhancer binding protein (TonEBP). Localization of TonEBP, as well as TonEBP-mediated gene transcription, was not affected by CsA. Phosphorylation of CREB at an activating phosphorylation site (S133) was decreased by CsA, but not by FK506. However, both CnI did not affect cellular cAMP levels. We show that CsA decreases transcription of AQP2, a process that is in part independent of Cn or cyclophilin A and suggests dependence on decreased activity of CREB.
authors.affiliation: Medizinische Klinik und Poliklinik D, Experimentelle Nephrologie, Universität Münster, Domagkstraße 3a, 48149, Münster, Germany.
authors.forename: Markus M
authors.initials: MM
authors.lastname: Rinschen
authors.forename: Jens
authors.initials: J
authors.lastname: Klokkers
authors.forename: Hermann
authors.initials: H
authors.lastname: Pavenstädt
authors.forename: Ute
authors.initials: U
authors.lastname: Neugebauer
authors.forename: Eberhard
authors.initials: E
authors.lastname: Schlatter
authors.forename: Bayram
authors.initials: B
authors.lastname: Edemir
mesh_terms: D000818:Animals; D051399:Aquaporin 2 / Q000096:biosynthesis* / Q000378:metabolism; D065095:Calcineurin Inhibitors; D002478:Cells, Cultured; D017362:Cyclic AMP Response Element-Binding Protein / Q000502:physiology; D016572:Cyclosporine / Q000494:pharmacology*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005260:Female; D038362:Glycogen Synthase Kinase 3 / Q000187:drug effects; D000071679:Glycogen Synthase Kinase 3 beta; D007685:Kidney Tubules, Collecting / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D016559:Tacrolimus / Q000494:pharmacology*; D014157:Transcription Factors / Q000502:physiology; D051176:beta Catenin / Q000187:drug effects
chemical_list: D051399:Aquaporin 2; D065095:Calcineurin Inhibitors; C495268:Ctnnb1 protein, rat; D017362:Cyclic AMP Response Element-Binding Protein; C492199:Nfat5 protein, rat; D012333:RNA, Messenger; D014157:Transcription Factors; D051176:beta Catenin; D016572:Cyclosporine; D000071679:Glycogen Synthase Kinase 3 beta; D048049:Extracellular Signal-Regulated MAP Kinases; D038362:Glycogen Synthase Kinase 3; D016559:Tacrolimus