title: Interaction of endothelin-1 and nitric oxide pathways in human tubular epithelial cells under the influence of cyclosporine-A.
abstract: BACKGROUND
  The exact mechanism of cyclosporine (CsA) nephrotoxicity has not been clarified. In this study, we investigated the effect of pharmacological doses of CsA on the production of nitric oxide synthases (NOSs) and endothelin (ET) receptors (ETR-A, ETR-B), in human tubular cells [human kidney (HK)-2], to identify any implication of these pathways in CsA nephrotoxicity.
  
  
  METHODS
  Human tubular epithelial cells (HK-2) were cultured in the presence of CsA at various concentrations (0-1000 ng/mL). Reverse transcriptase-polymerase chain reaction (RT-PCR) was used to determine mRNA synthesis of NOSs (eNOS, iNOS) and ET receptors (ETR-A, ETR-B) and western blot analysis for the subsequent proteins.
  
  
  RESULTS
  A dose-dependent induction of synthesis of NO synthases eNOS and iNOS and ET receptors ETR-A and ETR-B was observed, even at therapeutic doses of CsA. An interaction between NO and ET-1 systems under the influence of CsA was also observed. Blockage of NO production was followed by down-regulation of ETR-B whereas blockade of ET pathway with ET receptor antagonists was followed by down-regulation of eNOS expression.
  
  
  CONCLUSIONS
  CsA induces NOSs as well as ET receptor mRNA and protein synthesis in tubular epithelial cells. The up-regulation of NO and ET-1 pathways is probably implicated in the nephrotoxic action of CsA, whereas an interplay between ETR-B and eNOS seems to be involved.
authors.affiliation: Internal Medicine-Nephrology, University Hospital of Patras, Patras, Greece.
authors.forename: Evangelos
authors.initials: E
authors.lastname: Papachristou
authors.forename: Athanasios
authors.initials: A
authors.lastname: Papadimitropoulos
authors.forename: Panagiotis
authors.initials: P
authors.lastname: Kotsantis
authors.forename: Dimitrios S
authors.initials: DS
authors.lastname: Goumenos
authors.forename: Panagiotis G
authors.initials: PG
authors.lastname: Katsoris
authors.forename: John G
authors.initials: JG
authors.lastname: Vlachojannis
mesh_terms: D053898:Biosynthetic Pathways; D002478:Cells, Cultured; D016572:Cyclosporine / Q000009:adverse effects / Q000494:pharmacology*; D019332:Endothelin-1 / Q000502:physiology*; D004847:Epithelial Cells / Q000187:drug effects* / Q000201:enzymology*; D006801:Humans; D007166:Immunosuppressive Agents / Q000009:adverse effects / Q000494:pharmacology*; D007674:Kidney Diseases / Q000139:chemically induced; D007684:Kidney Tubules / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology*; D009569:Nitric Oxide / Q000502:physiology*; D019001:Nitric Oxide Synthase / Q000096:biosynthesis* / Q000187:drug effects*
chemical_list: D019332:Endothelin-1; D007166:Immunosuppressive Agents; D009569:Nitric Oxide; D016572:Cyclosporine; D019001:Nitric Oxide Synthase