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.
Smith
Robert M
RM
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
Suleman
Naushaad
N
Lacerda
Lydia
L
Opie
Lionel H
LH
Akira
Shizuo
S
Chien
Kenneth R
KR
Sack
Michael N
MN
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