Leptin attenuates cardiac apoptosis after chronic ischaemic injury.
OBJECTIVE
We have previously shown that activation of leptin signalling in the heart reduces cardiac morbidity and mortality after myocardial infarction (MI). In the present study, we tested the hypothesis that leptin signalling limits cardiac apoptosis after MI through activation of signal transducer and activator of transcription (STAT)-3 responsive anti-apoptotic genes, including B-cell lymphoma (bcl)-2 and survivin, that serve to downregulate the activity of caspase-3.


RESULTS
Hearts from C57BL/6J and three groups of leptin-deficient Ob/Ob mice (food-restricted, ad libitum, and leptin-repleted) were examined 4 weeks after permanent left coronary artery ligation or sham operation. Inflammatory and apoptotic cell number was determined in cardiac sections by immunostaining. Expression of cardiac bcl-2, survivin, and pro and active caspase-3 was determined and correlated with in vitro caspase-3 activity. In the absence of MI, both lean and obese leptin-deficient mice exhibited increased cardiac apoptosis compared with wild-type mice. After MI, the highest rates of apoptosis were seen in the infarcted tissue of lean and obese Ob/Ob mice. Further, leptin-deficient hearts, as well as hearts from wild-type mice treated with the STAT-3 inhibitor WP1066, exhibited blunted anti-apoptotic bcl-2 and survivin gene expression, and increased caspase-3 protein expression and activity. The increased caspase-3 activity and apoptosis in hearts of leptin-deficient mice after MI was significantly attenuated in Ob/Ob mice replete with leptin, reducing apoptosis to levels comparable to that observed in wild-type mice after MI.


CONCLUSIONS
These results demonstrate that intact leptin signalling post-MI acts through STAT-3 to increase anti-apoptotic bcl-2 and survivin gene expression and reduces caspase-3 activity, consistent with a cardioprotective role of leptin in the setting of chronic ischaemic injury.
McGaffin
Kenneth R
KR
Cardiovascular Institute, University of Pittsburgh Medical Center, 1750 Bioscience Tower, 200 Lothrop Street, Pittsburgh, PA 15213, USA. mcgaffinkr@upmc.edu
Zou
Baobo
B
McTiernan
Charles F
CF
O'Donnell
Christopher P
CP
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D053148:Caspase 3 / Q000378:metabolism; D002908:Chronic Disease; D003331:Coronary Vessels / Q000601:surgery; D004195:Disease Models, Animal; D007249:Inflammation / Q000378:metabolism / Q000473:pathology; D051034:Inhibitor of Apoptosis Proteins; D020738:Leptin / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D008026:Ligation; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D009203:Myocardial Infarction / Q000378:metabolism* / Q000473:pathology; D009206:Myocardium / Q000378:metabolism* / Q000473:pathology; D010766:Phosphorylation; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D011725:Pyridines / Q000494:pharmacology; D012097:Repressor Proteins; D050796:STAT3 Transcription Factor / Q000037:antagonists & inhibitors / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D000077022:Survivin; D020032:Tyrphostins / Q000494:pharmacology; D051025:bcl-Associated Death Protein / Q000378:metabolism
C494820:Bad protein, mouse; C117749:Birc5 protein, mouse; D051034:Inhibitor of Apoptosis Proteins; D020738:Leptin; D008869:Microtubule-Associated Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D011725:Pyridines; D012097:Repressor Proteins; D050796:STAT3 Transcription Factor; C494087:Stat3 protein, mouse; D000077022:Survivin; D020032:Tyrphostins; C519885:WP1066; D051025:bcl-Associated Death Protein; C505409:Casp3 protein, mouse; D053148:Caspase 3