Genetic depletion of cardiac myocyte STAT-3 abolishes classical preconditioning.
OBJECTIVE
To evaluate the functional requirement of signal transducer and activator of transcription-3 (STAT-3) in cardiac myocyte tolerance to ischemia (I) and in classical preconditioning.


METHODS
Cardiac myocyte STAT-3 was depleted in mice using Cre-lox p technology. Isolated cardiomyocytes from wild-type (WT) and STAT-3-deficient mice were evaluated for viability following simulated ischemia (SI; 26 h). Cardiomyocytes were then preconditioned by exposure to transient simulated ischemia or via the administration of preconditioning mimetics (100 microM adenosine, 100 microM diazoxide and 0.5 ng ml(-1) TNFalpha, individually and in combination) prior to index ischemia. To evaluate the effect of cardiac myocyte depletion of STAT-3 in the context of the intact heart, these experiments were performed in isolated perfused Langendorff heart preparations which were exposed to an index insult of 30-min global ischemia and 45-min reperfusion. Ischemic preconditioning was achieved by subjecting the hearts to four cycles of 5-min ischemia followed by 5-min reperfusion prior to index ischemia. Infarct size was measured following reperfusion.


RESULTS
Cell viability was diminished equally in wild-type and STAT-3-depleted cardiomyocytes. In contrast, ischemic and pharmacological preconditioning protected wild-type cardiomyocytes but not STAT-3-deficient cardiomyocytes. These results were mirrored in the intact heart.


CONCLUSIONS
The depletion of functional STAT-3 does not modulate tolerance to ischemic injury in cardiomyocytes. This signaling molecule, however, is crucial for the ischemic and all the tested pharmacological preconditioning programs.
Hatter Institute for Cardiology Research, Faculty of Health Sciences, University of Cape Town Observatory, Cape Heart Centre, Chris Barnard Building, Cape Town 7925, South Africa. rsmith@sun.ac.za
Robert M
RM
Smith
Naushaad
N
Suleman
Lydia
L
Lacerda
Lionel H
LH
Opie
Shizuo
S
Akira
Kenneth R
KR
Chien
Michael N
MN
Sack
D000818:Animals; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D019157:Ischemic Preconditioning, Myocardial; D051379:Mice; D018345:Mice, Knockout; D017202:Myocardial Ischemia / Q000378:metabolism*; D032383:Myocytes, Cardiac / Q000378:metabolism*; D010477:Perfusion; D050796:STAT3 Transcription Factor; D015534:Trans-Activators / Q000235:genetics* / Q000378:metabolism
D004268:DNA-Binding Proteins; D050796:STAT3 Transcription Factor; C494087:Stat3 protein, mouse; D015534:Trans-Activators