Antiarrhythmic effect mediated by κ-opioid receptor is associated with Cx43 stabilization.
OBJECTIVE
Acute myocardial ischemia induces electrical and chemical uncoupling of gap junctions, which contributes to conduction abnormalities and re-entrant arrhythmias. We tested the hypothesis that structure and function of Connexin43 may vibrate during acute myocardial ischemia and reperfusion and κ-opioid receptor stimulation may stabilize the alteration of Connexin43.


METHODS
An animal intervention study was conducted with comparison to a control group.


METHODS
University preclinical research laboratory.


METHODS
Age-, weight-, and sex-matched Sprague-Dawley rats.


METHODS
Adult rat hearts were subjected to ischemia or ischemia/reperfusion, which was induced by temporary occlusion of the left main coronary artery. U50488H was given 10 mins before tissue specimens were taken or before ischemia (1.5 mg/kg, intravenous) and nor-BNI was given 15 mins before tissue specimens were taken or before ischemia (2 mg/kg, intravenous). Tissue samples came from left ventricular myocardium of the rat hearts.


RESULTS
Electrocardiogram, immunohistochemistry, immunoblotting, and reverse transcription-polymerase chain reaction were used to measure changes of arrhythmias, protein, and gene expression of Connexin43, respectively. κ-opioid receptor activation with U50 decreased arrhythmia in a model of myocardial ischemia and reperfusion. In normal hearts, immunohistochemical data showed reduced amount and lateralization of Connexin43 induced by κ-opioid receptor activation, whereas immunoblotting data demonstrated no significant changes between control and U50 group. During ischemia, however, Connexin43 protein underwent dephosphorylation and degradation, and Connexin43 mRNA was upregulated. These alterations were significantly attenuated on κ-opioid receptor stimulation. During ischemia and reperfusion, Connexin43 protein underwent dephosphorylation and degradation and recovered slowly during reperfusion. Activation of κ-opioid receptor accelerated recovery of phosphorylated and total Connexin43.


CONCLUSIONS
In normal rat hearts, Connexin43 translocates from intercellular junctions to intracellular locations on κ-opioid receptor activation. In rat hearts experiencing acute myocardial ischemia and reperfusion, protein and gene expression of Connexin43 undergo vibration. This phenomenon is stabilized when κ-opioid receptor is activated and by the fact that κ-opioid receptor produces antiarrhythmic effects.
Zhang
Quan-Yu
QY
Department of Physiology, National Key Discipline of Cell Biology, Fourth Military Medical University, and the Department of Emergency, Xijing Hospital, Fourth Military Medical University, Xi'an, Shaanxi Province, People's Republic of China.
Wang
Wei
W
Shi
Quan-Xing
QX
Li
Yu-Long
YL
Huang
Jing-Hui
JH
Yao
Yuan
Y
Li
Juan
J
Zhang
Shu-Miao
SM
Fan
Rong
R
Zhou
Jing-Jun
JJ
Guo
Hai-Tao
HT
Wang
Yue-Min
YM
Yin
Wen
W
Pei
Jian-Ming
JM
D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer / Q000378:metabolism / Q000494:pharmacology*; D000818:Animals; D001145:Arrhythmias, Cardiac / Q000188:drug therapy* / Q000503:physiopathology; D015153:Blotting, Western; D018031:Connexin 43 / Q000187:drug effects / Q000378:metabolism*; D004195:Disease Models, Animal; D005260:Female; D017629:Gap Junctions / Q000187:drug effects; D007150:Immunohistochemistry; D008297:Male; D017202:Myocardial Ischemia / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D015428:Myocardial Reperfusion Injury / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D017473:Receptors, Opioid, kappa / Q000378:metabolism*; D012016:Reference Values; D020133:Reverse Transcriptase Polymerase Chain Reaction
D018031:Connexin 43; D017473:Receptors, Opioid, kappa; D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer