Postconditioning attenuates cardiomyocyte apoptosis via inhibition of JNK and p38 mitogen-activated protein kinase signaling pathways.
A sequence of intermittent interruptions of oxygen supply (i.e., postconditioning, Postcon) at reoxygenation reduces oxidant-induced cardiomyocyte loss. This study tested the hypothesis that prevention of cardiomyocyte apoptosis by Postcon is mediated by mitogen-activated protein kinases pathways. Primary cultured neonatal rat cardiomyocytes were exposed to 3 h hypoxia followed by 6 h of reoxygenation. Cardiomyocytes were postconditioned by three cycles each of 5 min reoxygenation and 5 min hypoxia after prolonged hypoxia. Relative to hypoxia alone, reoxygenation stimulated expression of JNKs and p38 kinases, corresponding to increased activity of JNKs (phospho-c-Jun) and p38 (phospho-ATF2). The level of TNFalpha in cell lysates, activity of cytosolic caspases-8, -3, expression of Bax and the number of apoptotic cardiomyocytes were increased while expression of Bcl-2 was decreased with reoxygenation. Consistent with an attenuation in generation of superoxide anions detected by lucigenin-enhanced chemiluminescence at early period of reoxygenation, treatment of cardiomyocytes with Postcon further reduced expression and activity of JNKs and p38 kinases, level of TNFalpha, the frequency of apoptotic cells and expression of Bax. However, the inhibitory effects of Postcon on these changes were lost when its application was delayed by 5 min after the start of reoxygenation. Addition of a JNK/p38 stimulator, anisomycin into cardiomyocytes at the beginning of reoxygenation eliminated protection by Postcon. These data suggest that 1) hypoxia/reoxygenation elicits cardiomyocyte apoptosis in conjunction with expression and activation of JNK and p38 kinases, release of TNFalpha, activation of caspases, and an increase in imbalance of pro-/anti-apoptotic proteins; 2) Postcon attenuates cardiomyocyte apoptosis, potentially mediated by inhibiting JNKs/p-38 signaling pathways and reducing TNFalpha release and caspase expression.
Sun
He-Ying
HY
Cardiothoracic Research Laboratory, Carlyle Fraser Heart Center, Emory Crawford Long Hospital, Emory University, 550 Peachtree St., NE, Atlanta, Georgia 30308-2225, USA.
Wang
Ning-Ping
NP
Halkos
Michael
M
Kerendi
Faraz
F
Kin
Hajime
H
Guyton
Robert A
RA
Vinten-Johansen
Jakob
J
Zhao
Zhi-Qing
ZQ
D000818:Animals; D017209:Apoptosis; D020169:Caspases / Q000378:metabolism; D053938:DNA Fragmentation; D000860:Hypoxia / Q000628:therapy; D019157:Ischemic Preconditioning, Myocardial; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism*; D008954:Models, Biological; D032383:Myocytes, Cardiac / Q000378:metabolism* / Q000473:pathology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism; D015427:Reperfusion Injury / Q000628:therapy; D015398:Signal Transduction; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D051028:bcl-2-Associated X Protein / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
D019253:Proto-Oncogene Proteins c-bcl-2; D017382:Reactive Oxygen Species; D014409:Tumor Necrosis Factor-alpha; D051028:bcl-2-Associated X Protein; D048031:JNK Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D020169:Caspases