title: The Isoquinolone Derived Prolyl Hydroxylase Inhibitor ICA Is a Potent Substrate of the Organic Anion Transporters 1 and 3.
abstract: OBJECTIVE
  Many cellular responses to hypoxia are mediated by the transcription factor complex hypoxia-inducible factor (HIF). HIF stability is governed by a family of dioxygenases called HIF prolyl hydroxylases (PHDs). Isoquinolone-derived PHD inhibitors, like 2-(1-chloro-4-hydroxyisoquinoline-3-carboxamido) acetate (ICA), which stabilize the intracellular HIF-α have been suggested as a potentially beneficial therapeutic strategy for the treatment of disorders associated with ischemia. To stabilize HIF-α, ICA has to be taken up into proximal tubule cells (PCTs) across the basolateral membrane by one of the organic anion transporters 1, 2 or 3 (OAT1, OAT2 or OAT3). The release into the urine across the luminal membrane may be mediated by OAT4.
  
  
  METHODS
  To demonstrate interaction of ICA with human OAT1, OAT2, OAT3 and OAT4, ICA was tested on these transporters stably transfected in HEK293 cells by using p-aminohippurate (PAH), cGMP and estrone-3-sulfate (ES) as reference substrates, respectively.
  
  
  RESULTS
  Uptakes of PAH and ES in OAT1- and OAT3-transfected HEK293 cells were inhibited by ICA with half-maximal inhibition values of 0.29 ± 0.05 and 2.58 ± 0.16 µM, respectively. OAT2 was less sensitive to ICA. Efflux experiments identified ICA as an OAT1 and OAT3 substrate. Preloading OAT4-transfected HEK293 cells with ICA stimulated ES uptake by 18.3 ± 3.8%.
  
  
  CONCLUSIONS
  The uptake of ICA across the basolateral membrane of PCTs occurs mainly by OAT1 and the efflux into the tubular lumen by OAT4.
authors.forename: Kei
authors.initials: K
authors.lastname: Schulz
authors.forename: Yohannes
authors.initials: Y
authors.lastname: Hagos
authors.forename: Gerhard
authors.initials: G
authors.lastname: Burckhardt
authors.forename: Gunnar
authors.initials: G
authors.lastname: Schley
authors.forename: Nikolai
authors.initials: N
authors.lastname: Burzlaff
authors.forename: Carsten
authors.initials: C
authors.lastname: Willam
authors.forename: Birgitta C
authors.initials: BC
authors.lastname: Burckhardt
mesh_terms: D004970:Estrone / Q000031:analogs & derivatives* / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D007546:Isoquinolines / Q000493:pharmacokinetics* / Q000494:pharmacology; D027362:Organic Anion Transport Protein 1 / Q000378:metabolism*; D029362:Organic Anion Transporters, Sodium-Independent / Q000378:metabolism*; D064800:Prolyl-Hydroxylase Inhibitors / Q000493:pharmacokinetics* / Q000494:pharmacology; D010130:p-Aminohippuric Acid / Q000378:metabolism
chemical_list: D007546:Isoquinolines; D027362:Organic Anion Transport Protein 1; D029362:Organic Anion Transporters, Sodium-Independent; D064800:Prolyl-Hydroxylase Inhibitors; C114338:organic anion transport protein 3; D004970:Estrone; C017296:estrone sulfate; D010130:p-Aminohippuric Acid