Hypoxic postconditioning reduces cardiomyocyte loss by inhibiting ROS generation and intracellular Ca2+ overload

Cardiothoracic Research Laboratory, Carlyle Fraser Heart Center, Crawford Long Hospital, Emory University School of Medicine, Atlanta, Georgia Submitted 31 December 2003 ; accepted in final form 21 November 2004 We have shown that intermittent interruption of immediate reflow at reperfusion (i.e., p...

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Published in:American journal of physiology. Heart and circulatory physiology 2005-04, Vol.288 (4), p.H1900-H1908
Main Authors: Sun, He-Ying, Wang, Ning-Ping, Kerendi, Faraz, Halkos, Michael, Kin, Hajime, Guyton, Robert A, Vinten-Johansen, Jakob, Zhao, Zhi-Qing
Format: Article
Language:English
Subjects:
Animals
Calcium - metabolism
Cell Communication - physiology
Cell Survival - physiology
Cells, Cultured
Cytochromes c - metabolism
Hydrogen Peroxide - metabolism
Hypoxia - metabolism
Hypoxia - pathology
In Vitro Techniques
Ischemic Preconditioning, Myocardial
L-Lactate Dehydrogenase - metabolism
Luminescent Measurements
Malondialdehyde - metabolism
Myocardial Reperfusion Injury - metabolism
Myocardial Reperfusion Injury - pathology
Myocytes, Cardiac - cytology
Myocytes, Cardiac - metabolism
Rats
Rats, Wistar
Reactive Oxygen Species - metabolism
Superoxide Dismutase - metabolism
Superoxides - metabolism
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Summary:Cardiothoracic Research Laboratory, Carlyle Fraser Heart Center, Crawford Long Hospital, Emory University School of Medicine, Atlanta, Georgia Submitted 31 December 2003 ; accepted in final form 21 November 2004 We have shown that intermittent interruption of immediate reflow at reperfusion (i.e., postconditioning) reduces infarct size in in vivo models after ischemia. Cardioprotection of postconditioning has been associated with attenuation of neutrophil-related events. However, it is unknown whether postconditioning before reoxygenation after hypoxia in cultured cardiomyocytes in the absence of neutrophils confers protection. This study tested the hypothesis that prevention of cardiomyocyte damage by hypoxic postconditioning (Postcon) is associated with a reduction in the generation of reactive oxygen species (ROS) and intracellular Ca 2+ overload. Primary cultured neonatal rat cardiomyocytes were exposed to 3 h of hypoxia followed by 6 h of reoxygenation. Cardiomyocytes were postconditioned after the 3-h index hypoxia by three cycles of 5 min of reoxygenation and 5 min of rehypoxia applied before 6 h of reoxygenation. Relative to sham control and hypoxia alone, the generation of ROS (increased lucigenin-enhanced chemiluminescence, SOD-inhibitable cytochrome c reduction, and generation of hydrogen peroxide) was significantly augmented after immediate reoxygenation as was the production of malondialdehyde, a product of lipid peroxidation. Concomitant with these changes, intracellular and mitochondrial Ca 2+ concentrations, which were detected by fluorescent fluo-4 AM and X-rhod-1 AM staining, respectively, were elevated. Cell viability assessed by propidium iodide staining was decreased consistent with increased levels of lactate dehydrogenase after reoxygenation. Postcon treatment at the onset of reoxygenation reduced ROS generation and malondialdehyde concentration in media and attenuated cardiomyocyte death assessed by propidium iodide and lactate dehydrogenase. Postcon treatment was associated with a decrease in intracellular and mitochondrial Ca 2+ concentrations. These data suggest that Postcon treatment reduces reoxygenation-induced injury in cardiomyocytes and is potentially mediated by attenuation of ROS generation, lipid peroxidation, and intracellular and mitochondrial Ca 2+ overload. reactive oxygen species; hypoxia; reoxygenation; superoxide; ischemia; reperfusion Address for reprint requests and other correspondence: Z.-Q. Zhao, Cardiothorac
ISSN:0363-6135
1522-1539
DOI:10.1152/ajpheart.01244.2003