title: Both PKA and Epac pathways mediate N-acetylcysteine-induced Connexin43 preservation in rats with myocardial infarction.
abstract: Cardiac remodeling was shown to be associated with reduced gap junction expression after myocardial infarction. A reduction in gap junctional proteins between myocytes may trigger ventricular arrhythmia. Therefore, we investigated whether N-acetylcysteine exerted antiarrhythmic effect by preserving connexin43 expression in postinfarcted rats, focusing on cAMP downstream molecules such as protein kinase A (PKA) and exchange protein directly activated by cAMP (Epac). Male Wistar rats after ligating coronary artery were randomized to either vehicle, or N-acetylcysteine for 4 weeks starting 24 hours after operation. Infarct size was similar between two groups. Compared with vehicle, cAMP levels were increased by N-acetylcysteine treatment after infarction. Myocardial connexin43 expression was significantly decreased in vehicle-treated infarcted rats compared with sham operated rats. Attenuated connexin43 expression and function were blunted after administering N-acetylcysteine, assessed by immunofluorescent analysis, dye coupling, Western blotting, and real-time quantitative RT-PCR of connexin43. Arrhythmic scores during programmed stimulation in the N-acetylcysteine-treated rats were significantly lower than those treated with vehicle. In an ex vivo study, enhanced connexin43 levels afforded by N-acetylcysteine were partially blocked by either H-89 (a PKA inhibitor) or brefeldin A (an Epac-signaling inhibitor) and completely blocked when H-89 and brefeldin A were given in combination. Addition of either the PKA specific activator N6Bz or Epac specific activator 8-CPT did not have additional increased connexin43 levels compared with rats treated with lithium chloride alone. These findings suggest that N-acetylcysteine protects ventricular arrhythmias by attenuating reduced connexin43 expression and function via both PKA- and Epac-dependent pathways, which converge through the inactivation of glycogen synthase kinase-3β.
authors.affiliation: Department of Medicine, Cardiology Section, Tainan Municipal An-Nan Hospital-China Medical University, Tainan, Taiwan ; Department of Medicine, China Medical University, Taichung, Taiwan ; Department of Internal Medicine, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan.
authors.forename: Tsung-Ming
authors.initials: TM
authors.lastname: Lee
authors.forename: Shinn-Zong
authors.initials: SZ
authors.lastname: Lin
authors.forename: Nen-Chung
authors.initials: NC
authors.lastname: Chang
mesh_terms: D000111:Acetylcysteine / Q000494:pharmacology* / Q000627:therapeutic use; D000818:Animals; D001145:Arrhythmias, Cardiac / Q000188:drug therapy / Q000378:metabolism; D020126:Brefeldin A / Q000494:pharmacology; D002316:Cardiotonic Agents / Q000494:pharmacology* / Q000627:therapeutic use; D018031:Connexin 43 / Q000235:genetics / Q000378:metabolism*; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D004353:Drug Evaluation, Preclinical; D016166:Free Radical Scavengers / Q000494:pharmacology; D017629:Gap Junctions / Q000378:metabolism; D015870:Gene Expression / Q000187:drug effects; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism; D007546:Isoquinolines / Q000494:pharmacology; D008297:Male; D009203:Myocardial Infarction / Q000188:drug therapy / Q000378:metabolism*; D010539:Permeability / Q000187:drug effects; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D013449:Sulfonamides / Q000494:pharmacology; D020257:Ventricular Remodeling / Q000187:drug effects
chemical_list: D002316:Cardiotonic Agents; D018031:Connexin 43; D016166:Free Radical Scavengers; C580592:Gja1 protein, rat; D020662:Guanine Nucleotide Exchange Factors; D007546:Isoquinolines; D047428:Protein Kinase Inhibitors; D011500:Protein Synthesis Inhibitors; C526973:Rapgef3 protein, rat; D013449:Sulfonamides; D020126:Brefeldin A; D000242:Cyclic AMP; D000071679:Glycogen Synthase Kinase 3 beta; C000605508:Gsk3b protein, rat; D017868:Cyclic AMP-Dependent Protein Kinases; D038362:Glycogen Synthase Kinase 3; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide; D000111:Acetylcysteine