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: Mohsen Foadoddini, Mansour Esmailidehaj, Hosein Mehrani, Seid Homayoon Sadraei, Leila Golmanesh, Hannaneh Wahhabaghai, Guro Valen, Ali Khoshbaten
• Journal: European journal of cardio-thoracic surgery : official journal of the European Association for Cardio-thoracic Surgery (Eur J Cardiothorac Surg) Vol. 39 Issue 2 Pg. 233-40 (Feb 2011) ISSN: 1873-734X [Electronic] Germany
• PMID: 20655755 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2010 European Association for Cardio-Thoracic Surgery. Published by Elsevier B.V. All rights reserved.

Chemical References

• Bax protein, rat
• Proto-Oncogene Proteins c-bcl-2
• bcl-2-Associated X Protein
• Casp3 protein, rat
• Caspase 3
• Oxygen

Topics

• Animals
• Apoptosis
• Arrhythmias, Cardiac (etiology)
• Blood Pressure (physiology)
• Caspase 3 (metabolism)
• DNA Fragmentation
• Heart Rate (physiology)
• Ischemic Preconditioning, Myocardial (methods)
• Male
• Myocardial Infarction (pathology, physiopathology, prevention & control)
• Myocardial Reperfusion Injury (pathology, physiopathology, prevention & control)
• Oxygen (blood)
• Oxygen Inhalation Therapy (methods)
• Partial Pressure
• Proto-Oncogene Proteins c-bcl-2 (metabolism)
• Rats
• Rats, Wistar
• Time Factors
• bcl-2-Associated X Protein (metabolism)