Myocardial apoptosis and infarction after ischemia/reperfusion are attenuated by kappa-opioid receptor agonist.
OBJECTIVE
It remains unclear whether U50488H (a selective kappa-opioid receptor agonist) produces anti-apoptotic effect during ischemia and reperfusion (I/R). Therefore, the effect of U50488H on myocardial apoptosis was investigated in the present study.


METHODS
Rats were subjected to 45min coronary artery occlusion and 180min of reperfusion. U50488H (1.5mg/kg IV) was given prior to occlusion. Nor-Binaltorphimine (nor-BNI) (2mg/kg IV), a selective kappa-opioid receptor antagonist, was given 10min prior to U50488H. Cardiac apoptosis was evaluated by terminal deoxynucleotidyl transferase mediated dUTP-biotin nick end labeling (TUNEL) assay and in situ identification of nuclear DNA fragmentation.


RESULTS
The ultrastructure injury of myocardium, myocardial infarct size, and plasma CK and LDH were reduced significantly with administration of U50488H before I/R, whereas the effects of U50488H were abolished by nor-BNI. DNA fragments were visualized by agarose electrophoresis, and clear DNA ladder formation was observed in myocardial tissue from hearts subjected to I/R. Administration of U50488H before ischemia exerted a significant anti-apoptotic effect as evidenced by markedly weaker DNA ladder formation. TUNEL staining showed U50488H treatment before I/R significantly reduced the percentage of apoptotic cells, which was blocked by 5-HD, a mitochondrial k(ATP) channel blocker. In accordance, U50488H treatment significantly inhibited I/R-induced elevated activities of caspase-3 and caspase-9. U50488H also produced an increase in Bcl-2 and a decrease in Bax protein expression in the I/R heart, and the anti-apoptotic effects of U50488H were all blocked by nor-BNI.


CONCLUSIONS
U50488H reduces myocardial necrosis and apoptosis after I/R and activation of kappa-opioid receptor may mediate a role in U50488H-induced myocardial protection.
Rong
Fan
F
Department of Physiology, National Key Discipline of Cell Biology, Xijing Hospital, Fourth Military Medical University, Shaanxi Province, PR China.
Peng
Zhang
Z
Ye
Ming-Xiang
MX
Zhang
Quan-Yu
QY
Zhao
Yin
Y
Zhang
Shu-Miao
SM
Guo
Hai-Tao
HT
Hui
Bi
B
Wang
Yue-Min
YM
Liang
Cheng
C
Gu
Chun-Hu
CH
Tao
Chen
C
Cui
Qin
Q
Yu
Shi-Qiang
SQ
Yi
Ding-Hua
DH
Pei
Jian-Ming
JM
D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer / Q000627:therapeutic use*; D000818:Animals; D000959:Antihypertensive Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D053148:Caspase 3 / Q000187:drug effects / Q000378:metabolism; D053453:Caspase 9 / Q000187:drug effects / Q000378:metabolism; D053938:DNA Fragmentation / Q000187:drug effects; D008297:Male; D046529:Microscopy, Electron, Transmission; D009203:Myocardial Infarction / Q000209:etiology / Q000473:pathology / Q000517:prevention & control*; D009206:Myocardium / Q000473:pathology; D009271:Naltrexone / Q000031:analogs & derivatives / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D017473:Receptors, Opioid, kappa / Q000819:agonists*; D015427:Reperfusion Injury / Q000150:complications / Q000188:drug therapy* / Q000473:pathology; D051028:bcl-2-Associated X Protein / Q000187:drug effects / Q000378:metabolism
D000959:Antihypertensive Agents; D009292:Narcotic Antagonists; D019253:Proto-Oncogene Proteins c-bcl-2; D017473:Receptors, Opioid, kappa; D051028:bcl-2-Associated X Protein; C051844:norbinaltorphimine; D009271:Naltrexone; D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; D053148:Caspase 3; D053453:Caspase 9