title: Pretreatment with hyperoxia reduces in vivo infarct size and cell death by apoptosis with an early and delayed phase of protection.
abstract: OBJECTIVE
  Exposure to normobaric hyperoxia protects the heart against ischemia-reperfusion injury ex vivo. In the present study, we investigated the effect of the early and late phase of hyperoxia on in vivo myocardial infarction and apoptosis.
  
  
  METHODS
  Rats were exposed to room air preoxygenation (O(2)≥ 95%) followed by regional ischemia (30 min) and 0, 90, 180, and 360 min of reperfusion. Hyperoxic exposure was performed for 120 min either immediately or 24h before coronary occlusion followed by 360-min reperfusion. Infarct size was evaluated by Evans blue/triphenyltetrazolium chloride staining. Apoptosis in the infarcted area was evaluated by terminal deoxy-nucleotidyl transferase-mediated deoxy uridine triphosphate (dUTP) nick end-labeling (TUNEL). Caspase 3 activity was measured by fluorometric enzyme assay, Bcl-2 and Bax protein expression assessed by western blotting and DNA laddering assessed with DNA gel electrophoresis.
  
  
  RESULTS
  The infarct size did not increase with increasing duration of reperfusion. However, apoptosis as evaluated by Bcl-2/Bax ratio, caspase 3 activity, and TUNEL-positive cells increased with increasing time of reperfusion. Both early and delayed pretreatment with hyperoxia reduced infarct size (p = 0.0013, p = 0.046), ameliorated ischemic arrhythmias and increased Bcl-2/Bax ratio (p = 0.015, p = 0.0159). Only hyperoxia immediately before coronary occlusion decreased caspase 3 activity (p = 0.026) and decreased TUNEL-positive staining (p = 0.046) with no visible DNA laddering.
  
  
  CONCLUSIONS
  Detection of myocardial apoptosis increased with prolongation of reperfusion time, as opposed to infarct detection where reperfusion was essential to detect infarction, but the infarct size did not increase with time. Pretreatment with hyperoxia significantly decreased infarct size and apoptotic cell death. Pretreatment, immediately before coronary occlusion, was most cardioprotective.
authors.affiliation: Department of Physiology and Pharmacology, Birjand University of Medical Sciences, Birjand, Iran. alaabasiouni@hotmail.com
authors.forename: Mohsen
authors.initials: M
authors.lastname: Foadoddini
authors.forename: Mansour
authors.initials: M
authors.lastname: Esmailidehaj
authors.forename: Hosein
authors.initials: H
authors.lastname: Mehrani
authors.forename: Seid Homayoon
authors.initials: SH
authors.lastname: Sadraei
authors.forename: Leila
authors.initials: L
authors.lastname: Golmanesh
authors.forename: Hannaneh
authors.initials: H
authors.lastname: Wahhabaghai
authors.forename: Guro
authors.initials: G
authors.lastname: Valen
authors.forename: Ali
authors.initials: A
authors.lastname: Khoshbaten
mesh_terms: D000818:Animals; D017209:Apoptosis; D001145:Arrhythmias, Cardiac / Q000209:etiology; D001794:Blood Pressure / Q000502:physiology; D053148:Caspase 3 / Q000378:metabolism; D053938:DNA Fragmentation; D006339:Heart Rate / Q000502:physiology; D019157:Ischemic Preconditioning, Myocardial / Q000379:methods*; D008297:Male; D009203:Myocardial Infarction / Q000473:pathology / Q000503:physiopathology / Q000517:prevention & control*; D015428:Myocardial Reperfusion Injury / Q000473:pathology / Q000503:physiopathology / Q000517:prevention & control; D010100:Oxygen / Q000097:blood; D010102:Oxygen Inhalation Therapy / Q000379:methods*; D010313:Partial Pressure; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors; D051028:bcl-2-Associated X Protein / Q000378:metabolism
chemical_list: C494828:Bax protein, rat; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein; C505410:Casp3 protein, rat; D053148:Caspase 3; D010100:Oxygen