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. Conclusion: 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.