Cardioplegic arrest induces apoptosis signal-pathway in myocardial endothelial cells and cardiac myocytes.
OBJECTIVE
Myocardial ischemia-reperfusion is associated with free radical-mediated injury and may be involved in cardiac apoptosis. The purpose of our study was to investigate (1) if cardioplegia-induced ischemia-reperfusion initiates cardiac apoptosis signal pathway, and (2) if this is mediated by free radicals.


METHODS
We subjected 13 pigs (56+/-10 kg) to 1 h of cold crystalloid cardioplegic arrest (CA) on cardiopulmonary bypass (CPB), and collected five transmural LV biopsies: prior to CPB (baseline), at 60 min CA, at 15 and 30 min reperfusion on CPB, and at 120 min post CPB. Two additional pigs were subjected to CPB but not CA and two further pigs were neither subjected to CPB nor CA and served as sham-operated time controls. LV specimens were cut at 7 microm and immunocytochemically stained against active caspase-3 and 85 kDa poly(ADP-ribose) polymerase (PARP) as apoptosis signal-pathway key enzymes, nitrotyrosine as indicator for peroxynitrite (ONOO(-))-mediated tissue injury, and 8-iso-prostaglandin-F(2)alpha as indicator for oxygen free radical-mediated lipid peroxidation. Specimen were assessed using a scale of 0 (negative) to 3 (highly positive), and cardiomyocytes were quantitatively investigated using TV densitometry.


RESULTS
At 60 min CA, caspase-3 was increased by 9.2+/-3.7 gray units and remained on this level until 2 h post CPB (P</=0.003 vs. baseline); nitrotyrosine increased over time to reach a maximum of +8.5+/-8.1 gray units at 120 min post CPB (P=0.016); and there was a trend for increased 8-iso-prostaglandin-F(2)alpha at 60 min CA (+3.6+/-4.7 gray units; P=0.089). At 60 min CA, 92% of the hearts showed active caspase-3, only 42% demonstrated nitrotyrosine formation, and 58% exhibited 8-iso-prostaglandin-F(2)alpha. At 120 min post CPB, most hearts positive for caspase-3 were also positive for nitrotyrosine (83%), and 8-iso-prostaglandin-F(2)alpha (75%), but no heart showed PARP cleavage. Hearts subjected to CPB but not CA as well as time controls remained negative for all variables.


CONCLUSIONS
Our data show that CA initiates apoptosis signal-pathway in myocardial endothelium and myocytes; however, this did not result in apoptotic cell death as we did not find PARP cleavage. Further, the data suggest that CA-induced apoptosis signal pathway activation is not mediated by free radicals as caspase-3 activation preceded both nitrotyrosine and 8-iso-prostaglandin-F(2)alpha formation.
Fischer
Uwe M
UM
Department of Cardiothoracic Surgery1, University of Cologne, Cologne, Germany.
Klass
Oliver
O
Stock
Ulrike
U
Easo
Jerry
J
Geissler
Hans J
HJ
Fischer
Juergen H
JH
Bloch
Wilhelm
W
Mehlhorn
Uwe
U
D000818:Animals; D017209:Apoptosis; D015415:Biomarkers / Q000032:analysis; D002315:Cardiopulmonary Bypass; D053148:Caspase 3; D020169:Caspases / Q000032:analysis; D015237:Dinoprost / Q000031:analogs & derivatives*; D004730:Endothelium, Vascular / Q000473:pathology*; D028441:F2-Isoprostanes / Q000032:analysis; D005260:Female; D006324:Heart Arrest, Induced / Q000009:adverse effects*; D007150:Immunohistochemistry / Q000379:methods; D008297:Male; D023421:Models, Animal; D015428:Myocardial Reperfusion Injury / Q000473:pathology*; D032383:Myocytes, Cardiac / Q000473:pathology*; D015398:Signal Transduction; D013552:Swine; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000032:analysis
D015415:Biomarkers; D028441:F2-Isoprostanes; C075750:8-epi-prostaglandin F2alpha; C002744:3-nitrotyrosine; D014443:Tyrosine; D015237:Dinoprost; D053148:Caspase 3; D020169:Caspases