title: Preconditioning effects of steroids and hyperoxia on cardiac ischemia-reperfusion injury and vascular reactivity.
abstract: OBJECTIVE
  Corticosteroids and hyperoxia protect the heart against ischemia-reperfusion injury and may attenuate vascular reactivity. We hypothesized that (1) combining these two pretreatments induces an additive cardioprotection, (2) protection depends on activation of survival kinases and/or heat shock proteins, and (3) these interventions would change vascular reactivity into a more relaxed state.
  
  
  METHODS
  Male rats were randomized (n=10 in each group): 1. control, 2. dexamethasone (3mg/kg) injected 24 and 12 h before harvesting the hearts, 3. 60 min of hyperoxia (90-95% O(2)) immediately before harvest, 4. combination of dexamethasone and hyperoxia as in groups 2 and 3. The hearts were Langendorff-perfused and exposed to 30 min of global ischemia and reperfused for 120 min. Cardiac function was monitored and infarct size determined. Isometric tension to vasoconstrictive and vasodilatory agents was measured in femoral artery rings. Phosphorylation of survival kinases (protein kinase B/AKT, extracellular signal-regulated kinases (ERK1/2), the stress-activated/c-Jun NH2 terminal kinases (SAPK/JNK) and p38 MAPK), adenosine monophosphate dependent kinase (AMPK) and expression of heat shock protein 72 (HSP72) in hearts was evaluated by immunoblotting.
  
  
  RESULTS
  Infarct size was attenuated in all pretreated groups versus controls: 29% reduction in the combined group (p<0.01), 23% in hyperoxia group (p<0.05) and 31% in dexamethasone group (p<0.01). There was no significant difference between the treated groups. Combined pretreatment improved postischemic left ventricular end diastolic pressure compared to all other groups (p<0.001 vs controls, p=0.002 vs dexamethasone, p=0.005 vs hyperoxia). Combined pretreatment improved left ventricular developed pressure and coronary flow compared to controls (p<0.001 for both) and hyperoxia (p=0.0047 and p=0.0024, respectively). Combined pretreatment enhanced endothelium-independent relaxation (p=0.0032) compared to controls. Excepting ERK1/2 phosphorylation in the combined group during early reperfusion, there was no increased phosphorylation of the survival kinases AKT, p38, JNK, or AMPK and no increase of HSP72 expression.
  
  
  CONCLUSIONS
  Combined pretreatment by hyperoxia and dexamethasone improved postischemic heart function, but did not reduce infarct size compared to single pretreatment groups. Except of a possible role of ERK1/2, protection depended neither on survival kinases nor heat shock protein 72.
authors.affiliation: Department of Cardiothoracic Surgery, Faculty Division Ullevål University Hospital, Oslo, Norway. m.l.kaljusto@medisin.uio.no
authors.forename: Mari-Liis
authors.initials: ML
authors.lastname: Kaljusto
authors.forename: Kåre-Olav
authors.initials: KO
authors.lastname: Stensløkken
authors.forename: Tomohisa
authors.initials: T
authors.lastname: Mori
authors.forename: Andrey
authors.initials: A
authors.lastname: Panchenko
authors.forename: Marthe-Lise
authors.initials: ML
authors.lastname: Frantzen
authors.forename: Guro
authors.initials: G
authors.lastname: Valen
authors.forename: Jarle
authors.initials: J
authors.lastname: Vaage
mesh_terms: D000091162:AMP-Activated Protein Kinase Kinases; D000305:Adrenal Cortex Hormones / Q000627:therapeutic use*; D000818:Animals; D001794:Blood Pressure / Q000502:physiology; D003907:Dexamethasone / Q000494:pharmacology / Q000627:therapeutic use*; D004789:Enzyme Activation; D050884:HSP72 Heat-Shock Proteins / Q000378:metabolism; D015151:Immunoblotting; D019157:Ischemic Preconditioning, Myocardial / Q000379:methods*; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D008297:Male; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D015428:Myocardial Reperfusion Injury / Q000378:metabolism / Q000503:physiopathology* / Q000517:prevention & control; D009206:Myocardium / Q000378:metabolism; D010100:Oxygen / Q000008:administration & dosage*; D010770:Phosphotransferases / Q000378:metabolism; D011300:Preoperative Care / Q000379:methods*; D011494:Protein Kinases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D011897:Random Allocation; D051381:Rats
chemical_list: D000305:Adrenal Cortex Hormones; D050884:HSP72 Heat-Shock Proteins; D003907:Dexamethasone; D010770:Phosphotransferases; D011494:Protein Kinases; D051057:Proto-Oncogene Proteins c-akt; D048031:JNK Mitogen-Activated Protein Kinases; D048052:Mitogen-Activated Protein Kinase 3; D000091162:AMP-Activated Protein Kinase Kinases; D010100:Oxygen