Concurrent upregulation of endogenous proapoptotic and antiapoptotic factors in failing human hearts.
BACKGROUND
Despite widespread activation of proapoptotic stimuli and mediators, the degree of apoptosis in failing hearts is not very high. Endogenous antiapoptotic mechanisms are thought to be triggered by the heart-failure process. We investigated whether activation of endogenous apoptosis inhibitors plays a part when death receptor and mitochondrial apoptotic pathways have been triggered.


METHODS
We evaluated various proapoptotic and antiapoptotic factors in myocardial tissue specimens obtained from normal and explanted end-stage ischemic and dilated cardiomyopathic hearts. Caspases (CASPs) 3, 8 and 9, total and activated Bcl-2 homology domain 3-interacting domain death agonist, the X-linked inhibitor of apoptosis (XIAP), and DNA fragmentation factor (DFF) proteins were analyzed by western blotting. Expression of messenger RNA was measured by reverse-transcription polymerase chain reaction for the XIAP, DIABLO, CFLAR and DFF genes. We also assessed CASP3, CASP8 and CASP9 and DFF activity. Cytochrome c1 localization in myocytes was analyzed by immunohistochemistry and immunoelectron microscopy.


RESULTS
We collected myocardial tissue from eight cardiomyopathic hearts and five normal hearts. Cytochrome c1 was released from mitochondria into the cytosol in the cardiomyopathic hearts but CASP9 was not activated. CASP8 activity was increased compared with that in normal myocardium. Although CASP3 was cleaved, activity was not greatly increased because of an increase in XIAP and decrease in DIABLO expression. DFF proteins were conspicuously absent.


CONCLUSIONS
Concurrent upregulation of endogenous antiapoptotic mechanisms can interrupt the apoptotic cascade and prevents cell loss despite the presence of multiple proapoptotic factors. This period might offer a therapeutic window for restoration of myocardial function in heart failure.
Haider
Nezam
N
University of California Irvine School of Medicine, Irvine, CA, USA.
Arbustini
Eloisa
E
Gupta
Sudhir
S
Liu
Han
H
Narula
Navneet
N
Hajjar
Roger
R
Moorjani
Narain
N
Westaby
Stephen
S
Semigran
Marc J
MJ
Dec
G William
GW
Chandrashekhar
Y
Y
Narula
Jagat
J
D017209:Apoptosis; D009202:Cardiomyopathies / Q000378:metabolism*; D053148:Caspase 3 / Q000378:metabolism; D053181:Caspase 8 / Q000378:metabolism; D053453:Caspase 9 / Q000378:metabolism; D005260:Female; D019254:Genes, bcl-2; D006801:Humans; D008297:Male; D017202:Myocardial Ischemia / Q000378:metabolism*; D015854:Up-Regulation
C505407:CASP3 protein, human; C505530:CASP8 protein, human; C506433:CASP9 protein, human; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9