title: Cyclosporin-A induced toxicity in rat renal collecting duct cells: interference with enhanced hypertonicity induced apoptosis.
abstract: OBJECTIVE
  Rat renal inner medullary collecting duct (IMCD) cells are physiologically exposed to a wide range of ambient tonicity. To maintain their function upon changes in osmolality, IMCD cells induce expression of osmoprotective and antiapoptotic genes, mainly mediated by the transcription factor Tonicity Enhancer Binding Protein (TonEBP). Some drugs like Cyclosporin-A (CsA) are discussed to interfere with the activity of TonEBP and thereby mediate their nephrotoxic effects. The aim of our study was to further understand CsA toxicity during elevation of ambient osmolality.
  
  
  METHODS
  First we examined cytotoxicity of CsA in IMCD exposed to elevated tonicity. Employing microarray analysis of gene expression, real-time PCR and immunoassays, we scrutinized pathways contributing to this effect.
  
  
  RESULTS
  We show that in IMCD cells CsA but not FK506 increases apoptosis upon an increase in tonicity. This effect is independent of cellular TonEBP localization or activity and reactive oxygen species. Microarray studies revealed marked quantitative differences in gene expression. Functional analysis showed overrepresentation of genes associated with cell death in presence of CsA. This correlated with increased mRNA expression of genes associated with the death receptor pathway and detection of TNFα in culture medium of cells treated with CsA.
  
  
  CONCLUSIONS
  Our results show that CsA cytotoxicity is induced under elevated ambient osmolality and that death receptor signaling probably contributes to CsA cytotoxicity.
authors.affiliation: Department of Internal Medicine D, Experimental Nephrology, University of Muenster, Muenster, Germany.
authors.forename: Laura K
authors.initials: LK
authors.lastname: Schenk
authors.forename: Markus M
authors.initials: MM
authors.lastname: Rinschen
authors.forename: Jens
authors.initials: J
authors.lastname: Klokkers
authors.forename: Sunil M
authors.initials: SM
authors.lastname: Kurian
authors.forename: Ute
authors.initials: U
authors.lastname: Neugebauer
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Salomon
authors.forename: Hermann
authors.initials: H
authors.lastname: Pavenstaedt
authors.forename: Eberhard
authors.initials: E
authors.lastname: Schlatter
authors.forename: Bayram
authors.initials: B
authors.lastname: Edemir
mesh_terms: D000818:Animals; D017209:Apoptosis; D002478:Cells, Cultured; D016572:Cyclosporine / Q000633:toxicity*; D005260:Female; D005786:Gene Expression Regulation; D007166:Immunosuppressive Agents / Q000633:toxicity*; D007685:Kidney Tubules, Collecting / Q000166:cytology* / Q000187:drug effects; D050778:NFATC Transcription Factors / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D009994:Osmolar Concentration; D051381:Rats; D017208:Rats, Wistar; D017382:Reactive Oxygen Species / Q000378:metabolism; D053218:Receptors, Death Domain / Q000378:metabolism; D016559:Tacrolimus / Q000633:toxicity; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D007166:Immunosuppressive Agents; D050778:NFATC Transcription Factors; D017382:Reactive Oxygen Species; D053218:Receptors, Death Domain; D014409:Tumor Necrosis Factor-alpha; D016572:Cyclosporine; D016559:Tacrolimus