Activation of cardiac muscarinic M3 receptors induces delayed cardioprotection by preserving phosphorylated connexin43 and up-regulating cyclooxygenase-2 expression.
OBJECTIVE
Activation of muscarinic M(3) mucarinic acetylcholine receptors (M(3)-mAChRs) has been previously shown to confer short-term cardioprotection against ischaemic injuries. However, it is not known whether activation of these receptors can provide delayed cardioprotection. Consequently, the present study was undertaken to investigate whether stimulation of M(3)-mAChRs can induce delayed preconditioning in rats, and to characterize the potential mechanism.


METHODS
Rats were pretreated (24 h), respectively, with M(3)-mAChRs agonist choline, M(3)-mAChRs antagonist 4-DAMP or M(2)-mAChRs antagonist methoctramine followed by the administration of choline. This was followed by 30 min of ischaemia and then 3 h of reperfusion. Ischaemia-induced arrhythmias and ischaemia-reperfusion (I/R)-induced infarction were determined. The phosphorylation status of connexin43 (Cx43) after 30 min ischaemia, and the expression level of Hsp70, cyclooxygenase-2 (COX-2) and iNOS effected by administration of choline were also measured.


RESULTS
Compared to the control group, pretreatment with choline significantly decreased ischaemia-induced arrhythmias, reduced the total number of ventricular premature beats, the duration of ventricular tachycardia episodes and markedly reduced I/R-induced infarct size. Furthermore, choline attenuated ischaemia-induced dephosphorylation of Cx43, and up-regulated the expression of Hsp70 and COX-2. Administration of 4-DAMP abolished these changes, while methoctramine had no effect.


CONCLUSIONS
Our results suggest that stimulation of M(3)-mAChRs with choline elicits delayed preconditioning, which we propose is the result of up-regulation of the expression of COX-2 and inhibition of the ischaemia-induced dephosphorylation of Cx43. Therefore, M(3)-mAChRs represent a promising target for rendering cardiomyocytes tolerant to ischaemic injury.
Institute of Clinical Pharmacy, Second Affiliated Hospital, Harbin Medical University, Harbin, Heilongjiang, China.
Jinlong
J
Zhao
Yue
Y
Su
Yong
Y
Zhang
Zhenwei
Z
Pan
Lili
L
Yang
Xichuang
X
Chen
Yan
Y
Liu
Yanjie
Y
Lu
Zhimin
Z
Du
Baofeng
B
Yang
D000818:Animals; D001145:Arrhythmias, Cardiac / Q000201:enzymology / Q000209:etiology / Q000378:metabolism / Q000503:physiopathology / Q000517:prevention & control; D002794:Choline / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use; D018031:Connexin 43 / Q000096:biosynthesis* / Q000378:metabolism; D051546:Cyclooxygenase 2 / Q000096:biosynthesis* / Q000378:metabolism; D004195:Disease Models, Animal; D006439:Hemodynamics / Q000187:drug effects; D008297:Male; D018721:Muscarinic Agonists / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use; D009203:Myocardial Infarction / Q000201:enzymology / Q000209:etiology / Q000378:metabolism / Q000503:physiopathology / Q000517:prevention & control; D015428:Myocardial Reperfusion Injury / Q000150:complications / Q000201:enzymology / Q000378:metabolism / Q000503:physiopathology / Q000517:prevention & control*; D009206:Myocardium / Q000201:enzymology / Q000378:metabolism; D010766:Phosphorylation; D051381:Rats; D017208:Rats, Wistar; D043587:Receptor, Muscarinic M3 / Q000819:agonists* / Q000037:antagonists & inhibitors; D013997:Time Factors; D015854:Up-Regulation
D018031:Connexin 43; D018721:Muscarinic Agonists; D043587:Receptor, Muscarinic M3; D051546:Cyclooxygenase 2; D002794:Choline