title: Hypoxia inducible factor-1 protects against nitrate tolerance and stunning in rabbit cardiac myocytes.
abstract: OBJECTIVE
  We tested whether upregulation of hypoxia inducible factor-1 (HIF-1) would restore the blunted effects of natriuretic peptides and nitric oxide caused by chronic nitrate exposure and stunning in cardiac myocytes.
  
  
  METHODS
  HIF-1alpha was increased with deferoxamine (150 mg/kg for 2 days). Nitrate tolerance was induced by a chronic nitroglycerin patch (0.3 mg/h for 5 days). We used freshly isolated rabbit ventricular myocytes. Half the myocytes were subjected to simulated ischemia [15 min 95% N(2)-5% CO(2)] and reperfusion [reoxygenation] to produce stunning. Cell function was measured utilizing a video-edge detector. Shortening was examined at baseline and after brain natriuretic peptide (BNP, 10(-8), 10(-7) M) or S-nitroso-N-acetyl-penicillamine (SNAP, 10(-6), 10(-5) M) followed by KT5823 (cyclic GMP protein kinase inhibitor, 10(-6) M). We also measured cyclic GMP protein kinase protein levels and kinase activity.
  
  
  RESULTS
  In control, BNP (-29%) reduced percent shortening, while KT5823 partially restored function. Deferoxamine treated control myocytes responded similarly. In patched nonstunned myocytes, BNP (-12%) reduced shortening less and KT5823 did not increase function. However, deferoxamine restored the blunted effects of BNP (-21%) and KT5823. In stunned myocytes, BNP (-11%) reduced shortening less and KT5823 did not affect function. Deferoxamine increased the effects of BNP (-27%) and KT5823 in stunning. Patch combined with stunning also similarly blunted the effects of BNP (-12%) and KT5823. Deferoxamine improved the effects of BNP (-22%) and KT5823. Similar results were observed after SNAP. Stunning reduced cyclic GMP protein kinase activity and deferoxamine restored activity. Deferoxamine had no effect on kinase activity in nitrate tolerance.
  
  
  CONCLUSIONS
  We found that upregulation of HIF-1 could protect isolated cardiac myocytes against nitrate tolerance through a cyclic GMP protein kinase-independent mechanism and through a kinase-dependent mechanism in stunning.
authors.affiliation: Heart and Brain Circulation Laboratory, Department of Physiology and Biophysics, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, 675 Hoes Lane West, Piscataway, NJ 08854, USA.
authors.forename: Tao
authors.initials: T
authors.lastname: Tan
authors.forename: Harvey R
authors.initials: HR
authors.lastname: Weiss
mesh_terms: D000818:Animals; D002135:Calcium-Binding Proteins / Q000378:metabolism; D002227:Carbazoles / Q000494:pharmacology; D048430:Cell Shape / Q000187:drug effects; D017869:Cyclic GMP-Dependent Protein Kinases / Q000378:metabolism; D003676:Deferoxamine / Q000494:pharmacology / Q000627:therapeutic use; D004361:Drug Tolerance / Q000502:physiology*; D005260:Female; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism*; D008297:Male; D008954:Models, Biological; D009200:Myocardial Contraction / Q000187:drug effects; D017682:Myocardial Stunning / Q000378:metabolism / Q000503:physiopathology / Q000517:prevention & control*; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000502:physiology*; D020097:Natriuretic Peptide, Brain / Q000494:pharmacology; D005996:Nitroglycerin / Q000494:pharmacology*; D010766:Phosphorylation / Q000187:drug effects; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011817:Rabbits; D026423:S-Nitroso-N-Acetylpenicillamine / Q000494:pharmacology; D015854:Up-Regulation / Q000187:drug effects; D000099211:Phospholamban
chemical_list: D002135:Calcium-Binding Proteins; D002227:Carbazoles; D017869:Cyclic GMP-Dependent Protein Kinases; D003676:Deferoxamine; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D020097:Natriuretic Peptide, Brain; D005996:Nitroglycerin; D047428:Protein Kinase Inhibitors; D026423:S-Nitroso-N-Acetylpenicillamine; D000099211:Phospholamban; C073601:KT 5823