PMID- 24508724 OWN - NLM STAT- MEDLINE DCOM- 20140514 LR - 20161125 IS - 1524-4571 (Electronic) IS - 0009-7330 (Linking) VI - 114 IP - 6 DP - 2014 Mar 14 TI - Exchange protein directly activated by cAMP mediates slow delayed-rectifier current remodeling by sustained beta-adrenergic activation in guinea pig hearts. PG - 993-1003 LID - 10.1161/CIRCRESAHA.113.302982 [doi] AB - RATIONALE: beta-Adrenoceptor activation contributes to sudden death risk in heart failure. Chronic beta-adrenergic stimulation, as occurs in patients with heart failure, causes potentially arrhythmogenic reductions in slow delayed-rectifier K(+) current (IKs). OBJECTIVE: To assess the molecular mechanisms of IKs downregulation caused by chronic beta-adrenergic activation, particularly the role of exchange protein directly activated by cAMP (Epac). METHODS AND RESULTS: Isolated guinea pig left ventricular cardiomyocytes were incubated in primary culture and exposed to isoproterenol (1 mumol/L) or vehicle for 30 hours. Sustained isoproterenol exposure decreased IKs density (whole cell patch clamp) by 58% (P<0.0001), with corresponding decreases in potassium voltage-gated channel subfamily E member 1 (KCNE1) mRNA and membrane protein expression (by 45% and 51%, respectively). Potassium voltage-gated channel, KQT-like subfamily, member 1 (KCNQ1) mRNA expression was unchanged. The beta1-adrenoceptor antagonist 1-[2-((3-Carbamoyl-4-hydroxy)phenoxy)ethylamino]-3-[4-(1-methyl-4-trifluoromethyl-2-imidazolyl)phenoxy]-2-propanol dihydrochloride (CGP-20712A) prevented isoproterenol-induced IKs downregulation, whereas the beta2-antagonist ICI-118551 had no effect. The selective Epac activator 8-pCPT-2'-O-Me-cAMP decreased IKs density to an extent similar to isoproterenol exposure, and adenoviral-mediated knockdown of Epac1 prevented isoproterenol-induced IKs/KCNE1 downregulation. In contrast, protein kinase A inhibition with a cell-permeable highly selective peptide blocker did not affect IKs downregulation. 1,2-Bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetate-AM acetoxymethyl ester (BAPTA-AM), cyclosporine, and inhibitor of nuclear factor of activated T cell (NFAT)-calcineurin association-6 (INCA6) prevented IKs reduction by isoproterenol and INCA6 suppressed isoproterenol-induced KCNE1 downregulation, consistent with signal-transduction via the Ca(2+)/calcineurin/NFAT pathway. Isoproterenol induced nuclear NFATc3/c4 translocation (immunofluorescence), which was suppressed by Epac1 knockdown. Chronic in vivo administration of isoproterenol to guinea pigs reduced IKs density and KCNE1 mRNA and protein expression while inducing cardiac dysfunction and action potential prolongation. Selective in vivo activation of Epac via sp-8-pCPT-2'-O-Me-cAMP infusion decreased IKs density and KCNE1 mRNA/protein expression. CONCLUSIONS: Prolonged beta1-adrenoceptor stimulation suppresses IKs by downregulating KCNE1 mRNA and protein via Epac-mediated Ca(2+)/calcineurin/NFAT signaling. These results provide new insights into the molecular basis of K(+) channel remodeling under sustained adrenergic stimulation. FAU - Aflaki, Mona AU - Aflaki M AD - From the Department of Medicine, Research Center, Montreal Heart Institute, Universite de Montreal, Montreal, Quebec, Canada (M.A., X.-Y.Q., L.X., B.O., A.T., X.L., A.M., Y.S., J.-C.T., S.N.); and Department of Pharmacology and Therapeutics, McGill University, Montreal, Quebec, Canada (M.A., S.N.). FAU - Qi, Xiao-Yan AU - Qi XY FAU - Xiao, Ling AU - Xiao L FAU - Ordog, Balazs AU - Ordog B FAU - Tadevosyan, Artavazd AU - Tadevosyan A FAU - Luo, Xiaobin AU - Luo X FAU - Maguy, Ange AU - Maguy A FAU - Shi, Yanfen AU - Shi Y FAU - Tardif, Jean-Claude AU - Tardif JC FAU - Nattel, Stanley AU - Nattel S LA - eng GR - MOP68929/Canadian Institutes of Health Research/Canada PT - Journal Article PT - Research Support, Non-U.S. Gov't DEP - 20140207 PL - United States TA - Circ Res JT - Circulation research JID - 0047103 RN - 0 (8-(4-chloro-phenylthio)-2'-O-methyladenosine-3'-5'-cyclic monophosphate) RN - 0 (Adrenergic beta-Agonists) RN - 0 (Delayed Rectifier Potassium Channels) RN - 0 (Guanine Nucleotide Exchange Factors) RN - 0 (Imidazoles) RN - 0 (NFATC Transcription Factors) RN - 0 (Propanolamines) RN - 0 (RNA, Small Interfering) RN - 0 (Receptors, Adrenergic, beta-1) RN - 139890-68-9 (1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid acetoxymethyl ester) RN - 1F7A44V6OU (Colforsin) RN - 46OL1UC10R (ICI 118551) RN - 526U7A2651 (Egtazic Acid) RN - CNU8DA2K9J (CGP 20712A) RN - E0399OZS9N (Cyclic AMP) RN - EC 3.1.3.16 (Calcineurin) RN - L628TT009W (Isoproterenol) RN - RWP5GA015D (Potassium) RN - SY7Q814VUP (Calcium) SB - IM MH - Action Potentials/drug effects/physiology MH - Adrenergic beta-Agonists/*toxicity MH - Animals MH - Calcineurin/physiology MH - Calcium/pharmacology MH - Cells, Cultured MH - Colforsin/pharmacology MH - Cyclic AMP/analogs & derivatives/pharmacology MH - Delayed Rectifier Potassium Channels/*metabolism MH - Egtazic Acid/analogs & derivatives/pharmacology MH - Guanine Nucleotide Exchange Factors/antagonists & inhibitors/genetics/*physiology MH - Guinea Pigs MH - Hypertrophy, Left Ventricular/etiology MH - Imidazoles/pharmacology MH - Ion Channel Gating/*drug effects/physiology MH - Isoproterenol/pharmacology/*toxicity MH - Myocytes, Cardiac/drug effects/metabolism MH - NFATC Transcription Factors/metabolism MH - Patch-Clamp Techniques MH - Potassium/metabolism MH - Propanolamines/pharmacology MH - RNA Interference MH - RNA, Small Interfering/pharmacology MH - Receptors, Adrenergic, beta-1/drug effects/*physiology MH - Second Messenger Systems/drug effects/physiology OTO - NOTNLM OT - arrhythmias, cardiac OT - calcineurin OT - heart failure OT - ion channels OT - beta-adrenergic receptors EDAT- 2014/02/11 06:00 MHDA- 2014/05/16 06:00 CRDT- 2014/02/11 06:00 PHST- 2014/02/11 06:00 [entrez] PHST- 2014/02/11 06:00 [pubmed] PHST- 2014/05/16 06:00 [medline] AID - CIRCRESAHA.113.302982 [pii] AID - 10.1161/CIRCRESAHA.113.302982 [doi] PST - ppublish SO - Circ Res. 2014 Mar 14;114(6):993-1003. doi: 10.1161/CIRCRESAHA.113.302982. Epub 2014 Feb 7.