Balanced expression of mitochondrial apoptosis regulatory proteins correlates with long-term survival of cardiac allografts.
Abnormal regulation of apoptosis is observed in ischemic injury and may contribute to the pathogenesis of atherosclerosis. However, its role in cardiac allograft vasculopathy (CAV), the fundamental lesion of chronic rejection (CR) in heart transplantation, remains uncertain. To clarify this issue, apoptosis was quantitated in myocardium and coronary arteries from 5 cardiac allograft donors (NL) and explanted hearts of 24 patients with ischemic cardiomyopathy (IsCM) and 15 patients with CR. Tissue samples were analyzed via end-labeling fragmented DNA [via deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL)] and immunoblotting for activated caspase-3 and -9. Myocyte apoptosis assessed by TUNEL was similarly increased over NL (0.21%) in both the CR (0.88%; P < 0.01) and IsCM (0.88%; P < 0.01) groups. Activated caspase-9 levels were significantly higher in CR (14.7%) compared with IsCM (6.9%; P < 0.01) and NL (0%) groups, whereas activated caspase-3 levels were similarly elevated in both CR and IsCM (7.8 and 6.5% vs. 0% in NL; P < 0.01 and P < 0.05) groups. Expression of myocardial Bcl-2 and Bax was increased in CR compared with both NL (Bax, 4.3-fold; P < 0.01; Bcl-2, 5.9-fold; P < 0.01) and IsCM (IsCM: Bax, 2.2-fold; P < 0.05; Bcl-2, 3.2-fold; P < 0.01) groups. The rate of apoptosis and the Bcl-2/Bax ratio independently correlated to graft survival in CR (activation of caspase-9: r = 0.87; P < 0.01; Bcl-2/Bax: r = 0.57; P = 0.05). Compared with native atherosclerosis, coronary arteries with CAV showed more medial apoptosis (7.8-fold; P < 0.01) and higher Bcl-2 levels (5.1-fold; P < 0.01) with lower Bax levels (threefold; P < 0.05) in the intima. These results indicate that abnormal Bcl-2 and Bax expression in myocardium and coronary arteries of cardiac allografts with CR is distinct from that in IsCM and suggest that balancing Bcl-2 to Bax in transplanted hearts promotes long-term graft survival.
Tung
Thomas C
TC
Division of Cardiothoracic Surgery, Department of Surgery, University of California at Los Angeles Medical Center, David Geffen School of Medicine, Los Angeles, CA 90095, USA.
Cui
Guanggen
G
Oshima
Kiyohiro
K
Laks
Hillel
H
Sen
Luyi
L
D000293:Adolescent; D000328:Adult; D000368:Aged; D009202:Cardiomyopathies / Q000378:metabolism* / Q000473:pathology / Q000601:surgery; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002648:Child; D003324:Coronary Artery Disease / Q000378:metabolism / Q000473:pathology / Q000601:surgery; D053938:DNA Fragmentation / Q000502:physiology*; D005260:Female; D006085:Graft Survival / Q000502:physiology*; D016027:Heart Transplantation; D006801:Humans; D015151:Immunoblotting; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D008928:Mitochondria / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D014184:Transplantation, Homologous; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein
C494826:BAX protein, human; C494811:BCL2L1 protein, human; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases