title: Albumin upregulates eNOS mRNA through ETRA/B in human proximal tubular epithelial cells.
abstract: BACKGROUND
  Proximal tubular cells respond to proteinuria by expressing several cytokines and inflammatory molecules that induce interstitial fibrosis. Increased attention has been drawn toward the systems of endothelin (ET) and nitric oxide (NO). This work contributes to the elucidation of the interplay between these two systems in proximal tubular epithelial cells (PTECs) after exposure in proteinuric conditions.
  
  
  METHODS
  HK-2 cells, a human PTEC line, were incubated with albumin, simulating proteinuric conditions. Cells were then lysed and either total RNA was isolated or whole cell extracts were prepared. PreproET-1, ET receptors (ETRA and ETRB) and NO synthases (eNOS, iNOS) mRNA accumulation was estimated by RT-PCR, and proteins by Western blot analysis. NO production was assessed using Griess reaction. Furthermore, we treated HK-2 cells with NO donor sodium nitroprusside, NO inhibitor L-NAME, ETRA inhibitor BQ123, ETRB inhibitor BQ788 and purified ET-1, and investigated the potential interplay between albumin-induced stimulation of NO or ET-1 systems.
  
  
  RESULTS
  We found that albumin upregulates preproET-1, ETRA, ETRB, eNOS and iNOS mRNA as well as protein and stimulates NO production. Additionally, we recorded an ETRA/B dependent regulation of albumin-induced eNOS expression.
  
  
  CONCLUSIONS
  For the first time an in vitro albumin-induced ET-1 and NO interplay was revealed.
authors.affiliation: Department of Biology, University of Patras, Patras, Greece. katsopan@upatras.gr
authors.forename: Panagiotis
authors.initials: P
authors.lastname: Kotsantis
authors.forename: Athanasios
authors.initials: A
authors.lastname: Papadimitropoulos
authors.forename: Anastasios
authors.initials: A
authors.lastname: Drakopoulos
authors.forename: John G
authors.initials: JG
authors.lastname: Vlachojannis
authors.forename: Panagiotis
authors.initials: P
authors.lastname: Katsoris
mesh_terms: D000418:Albumins / Q000502:physiology*; D002478:Cells, Cultured; D004847:Epithelial Cells / Q000502:physiology*; D006801:Humans; D007687:Kidney Tubules, Proximal / Q000166:cytology*; D052250:Nitric Oxide Synthase Type III / Q000235:genetics*; D012333:RNA, Messenger / Q000502:physiology*; D044022:Receptor, Endothelin A / Q000502:physiology*; D044023:Receptor, Endothelin B / Q000502:physiology*; D015854:Up-Regulation
chemical_list: D000418:Albumins; D012333:RNA, Messenger; D044022:Receptor, Endothelin A; D044023:Receptor, Endothelin B; C496314:NOS3 protein, human; D052250:Nitric Oxide Synthase Type III