Programmed cell death in idiopathic dilated cardiomyopathy is mediated by suppression of the apoptosis inhibitor Apollon.
BACKGROUND
Idiopathic dilated cardiomyopathy (DCM) is characterized by ventricular wall remodeling and an increased frequency of cardiac cell apoptosis. Apollon is a 528kD cell membrane-anchored protein that inhibits apoptosis by ubiquitinylation facilitating the degradation of Smac/Diablo and caspase-9. The present study tested the hypothesis that the Apollon/Smac system may mediate programmed cell death in DCM.


METHODS
Apollon and caspase-9 protein expression was assessed in left ventricular biopsies of explanted failing hearts using Western blotting in 36 DCM patients undergoing cardiac transplantation and in 10 controls. Human cardiac cells were transfected with a plasmid containing the human Apollon complementary DNA or control vector and were subsequently stressed by hypoxia. Apollon, Smac/Diablo, and caspase-9 expression were then examined in cell lysates by real-time polymerase chain reaction and a transferase-mediated dUTP nick-end labeling assay was used to determine the apoptotic index.


RESULTS
In DCM myocardial tissue, Apollon messenger (m)RNA and protein expression was down-regulated compared with control hearts (p < 0.001 and p < 0.005, respectively) concomitant with an increase in activated caspase-9 protein levels (p < 0.001). Cell stress resulted in increased apoptosis in cardiac cells in vitro and down-regulation of Apollon mRNA expression compared with control cells (p < 0.001). Transfection increased Apollon mRNA expression in cell lysates (p < 0.001) and completely prevented hypoxia-induced apoptosis associated with reduced expression of Smac/Diablo and activated caspase-9.


CONCLUSIONS
These results suggest that Apollon down-regulation plays a role in programmed cell death associated with DCM. Up-regulation of Apollon might therefore represent a novel therapeutic strategy in the treatment of DCM.
Department of Cardiothoracic Surgery, Center of Anatomy and Cell Biology, Medical University of Vienna, Vienna, Austria. seyedhossein.aharinejad@meduniwien.ac.at
Seyedhossein
S
Aharinejad
Olena
O
Andrukhova
Trevor
T
Lucas
Andreas
A
Zuckermann
Georg
G
Wieselthaler
Ernst
E
Wolner
Michael
M
Grimm
D000328:Adult; D001707:Biopsy, Needle; D015153:Blotting, Western; D002311:Cardiomyopathy, Dilated / Q000401:mortality / Q000473:pathology* / Q000601:surgery; D016022:Case-Control Studies; D053181:Caspase 8 / Q000378:metabolism*; D016923:Cell Death / Q000187:drug effects / Q000502:physiology*; D002478:Cells, Cultured; D018076:DNA, Complementary / Q000032:analysis; D015536:Down-Regulation; D005260:Female; D016027:Heart Transplantation; D006801:Humans; D020287:In Situ Nick-End Labeling; D051034:Inhibitor of Apoptosis Proteins / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D032383:Myocytes, Cardiac / Q000166:cytology / Q000187:drug effects*; D011336:Probability; D011446:Prospective Studies; D012016:Reference Values; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012680:Sensitivity and Specificity; D014162:Transfection; D051636:X-Linked Inhibitor of Apoptosis Protein / Q000494:pharmacology*
C401541:BIRC6 protein, human; D018076:DNA, Complementary; D051034:Inhibitor of Apoptosis Proteins; D051636:X-Linked Inhibitor of Apoptosis Protein; D053181:Caspase 8