title: Delayed adenosine A1 receptor preconditioning in rat myocardium is MAPK dependent but iNOS independent.
abstract: Adenosine A1 receptor delayed preconditioning (PC) against myocardial infarction has been well described; however, there have been limited investigations of the signaling mechanisms that mediate this phenomenon. In addition, there are multiple conflicting reports on the role of inducible nitric oxide synthase (iNOS) in mediating A1 late-phase PC. The purpose of this study was to determine the roles of the p38 and extracellular signal-regulated kinase (ERK) mitogen-activated protein kinases (MAPKs) in in vivo delayed A1 receptor PC and whether this protection at the myocyte level is due to upregulation of iNOS. Myocardial infarct size was measured in open-chest anesthetized rats 24 h after treatment with vehicle or the adenosine A1 agonist 2-chloro-N6-cyclopentyladenosine (CCPA; 100 microg/kg ip). Additional rats receiving CCPA were pretreated with the p38 inhibitor SB-203580 (1 mg/kg ip) or the MAPK/ERK kinase (MEK) inhibitor PD-098059 (0.5 mg/kg ip). At 24 h after CCPA administration, a group of animals was given the iNOS inhibitor 1400 W 10 min before ischemia. Treatment with CCPA reduced infarct size from 48 +/- 2 to 28 +/- 2% of the area at risk, an effect that was blocked by both SB-203580 and PD-098059 but not 1400 W. Ventricular myocytes isolated 24 h after CCPA injection exhibited significantly reduced oxidative stress during H2O2 exposure compared with myocytes from vehicle-injected animals, and this effect was not blocked by the iNOS inhibitor 1400 W. Western blot analysis of whole heart and cardiac myocyte protein samples revealed no expression of iNOS 6 or 24 h after CCPA treatment. These results indicate that adenosine A1 receptor delayed PC in rats is mediated by MAPK-dependent mechanisms, but this phenomenon is not associated with the early or late expression of iNOS.
authors.affiliation: Department of Surgery, Univ. of Kentucky College of Medicine, MN276, Chandler Medical Center, 800 Rose St., Lexington, KY 40536-0298, USA. rlasley@uky.edu
authors.forename: Robert D
authors.initials: RD
authors.lastname: Lasley
authors.forename: Byron J
authors.initials: BJ
authors.lastname: Keith
authors.forename: Gentian
authors.initials: G
authors.lastname: Kristo
authors.forename: Yukihiro
authors.initials: Y
authors.lastname: Yoshimura
authors.forename: Robert M
authors.initials: RM
authors.lastname: Mentzer
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives / Q000494:pharmacology; D058916:Adenosine A1 Receptor Antagonists; D000818:Animals; D004791:Enzyme Inhibitors / Q000494:pharmacology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D006352:Heart Ventricles; D006861:Hydrogen Peroxide / Q000494:pharmacology; D019157:Ischemic Preconditioning, Myocardial; D008297:Male; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009203:Myocardial Infarction / Q000473:pathology; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II; D016877:Oxidants / Q000494:pharmacology; D018384:Oxidative Stress / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D043682:Receptor, Adenosine A1 / Q000378:metabolism*; D013997:Time Factors; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D058916:Adenosine A1 Receptor Antagonists; D004791:Enzyme Inhibitors; D016877:Oxidants; D043682:Receptor, Adenosine A1; C058394:2-chloro-N(6)cyclopentyladenosine; D006861:Hydrogen Peroxide; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496318:Nos2 protein, rat; D048049:Extracellular Signal-Regulated MAP Kinases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D000241:Adenosine