Xiao-Yan Qi1, Hai Huang1, Balazs Ordog1, Xiaobin Luo1, Patrice Naud1, Yiguo Sun1, Chia-Tung Wu1, Kristin Dawson1, Artavazd Tadevosyan1, Yu Chen1, Masahide Harada1, Dobromir Dobrev1, Stanley Nattel2. 1. From the Research Center and Department of Medicine, Montreal Heart Institute, Université de Montréal, Montreal, Quebec, Canada (X.-Y.Q., H.H., B.O., X.L., P.N., Y.S., C.-T.W., K.D., A.T., Y.C., M.H., S.N.); Department of Pharmacology and Therapeutics, McGill University, Montreal, Quebec, Canada (K.D., Y.C.); Department of Cardiology, Chang-Gung Memorial Hospital and University, Taoyuan, Taiwan, Republic of China (C.T.W., S.N.); Department of Cardiology, Fujita Health University School of Medicine, Toyoake, Japan (M.H.); and Institute of Pharmacology, Faculty of Medicine, University Duisburg-Essen, Essen, Germany (D.D.). 2. From the Research Center and Department of Medicine, Montreal Heart Institute, Université de Montréal, Montreal, Quebec, Canada (X.-Y.Q., H.H., B.O., X.L., P.N., Y.S., C.-T.W., K.D., A.T., Y.C., M.H., S.N.); Department of Pharmacology and Therapeutics, McGill University, Montreal, Quebec, Canada (K.D., Y.C.); Department of Cardiology, Chang-Gung Memorial Hospital and University, Taoyuan, Taiwan, Republic of China (C.T.W., S.N.); Department of Cardiology, Fujita Health University School of Medicine, Toyoake, Japan (M.H.); and Institute of Pharmacology, Faculty of Medicine, University Duisburg-Essen, Essen, Germany (D.D.). stanley.nattel@icm-mhi.org.
Abstract
RATIONALE: Fibroblasts are involved in cardiac arrhythmogenesis and contribute to the atrial fibrillation substrate in congestive heart failure (CHF) by generating tissue fibrosis. Fibroblasts display robust ion currents, but their functional importance is poorly understood. OBJECTIVE: To characterize atrial fibroblast inward-rectifier K(+) current (IK1) remodeling in CHF and its effects on fibroblast properties. METHODS AND RESULTS: Freshly isolated left atrial fibroblasts were obtained from controls and dogs with CHF (ventricular tachypacing). Patch clamp was used to record resting membrane potential (RMP) and IK1. RMP was significantly increased by CHF (from -43.2±0.8 mV, control, to -55.5±0.9 mV). CHF upregulated IK1 (eg, at -90 mV from -1.1±0.2 to -2.7±0.5 pA/pF) and increased the expression of KCNJ2 mRNA (by 52%) and protein (by 80%). Ba(2+) (300 μmol/L) decreased the RMP and suppressed the RMP difference between controls and dogs with CHF. Store-operated Ca(2+) entry (Fura-2-acetoxymethyl ester) and fibroblast proliferation (flow cytometry) were enhanced by CHF. Lentivirus-mediated overexpression of KCNJ2 enhanced IK1 and hyperpolarized fibroblasts. Functional KCNJ2 suppression by lentivirus-mediated expression of a dominant negative KCNJ2 construct suppressed IK1 and depolarized RMP. Overexpression of KCNJ2 increased Ca(2+) entry and fibroblast proliferation, whereas the dominant negative KCNJ2 construct had opposite effects. Fibroblast hyperpolarization to mimic CHF effects on RMP enhanced the Ca(2+) entry. MicroRNA-26a, which targets KCNJ2, was downregulated in CHF fibroblasts. Knockdown of endogenous microRNA-26 to mimic CHF effects unregulated IK1. CONCLUSIONS: CHF upregulates fibroblast KCNJ2 expression and currents, thereby hyperpolarizing RMP, increasing Ca(2+) entry, and enhancing atrial fibroblast proliferation. These effects are likely mediated by microRNA-26a downregulation. Remodeling-induced fibroblast KCNJ2 expression changes may play a role in atrial fibrillation promoting fibroblast remodeling and structural/arrhythmic consequences.
RATIONALE: Fibroblasts are involved in cardiac arrhythmogenesis and contribute to the atrial fibrillation substrate in congestive heart failure (CHF) by generating tissue fibrosis. Fibroblasts display robust ion currents, but their functional importance is poorly understood. OBJECTIVE: To characterize atrial fibroblast inward-rectifier K(+) current (IK1) remodeling in CHF and its effects on fibroblast properties. METHODS AND RESULTS: Freshly isolated left atrial fibroblasts were obtained from controls and dogs with CHF (ventricular tachypacing). Patch clamp was used to record resting membrane potential (RMP) and IK1. RMP was significantly increased by CHF (from -43.2±0.8 mV, control, to -55.5±0.9 mV). CHF upregulated IK1 (eg, at -90 mV from -1.1±0.2 to -2.7±0.5 pA/pF) and increased the expression of KCNJ2 mRNA (by 52%) and protein (by 80%). Ba(2+) (300 μmol/L) decreased the RMP and suppressed the RMP difference between controls and dogs with CHF. Store-operated Ca(2+) entry (Fura-2-acetoxymethyl ester) and fibroblast proliferation (flow cytometry) were enhanced by CHF. Lentivirus-mediated overexpression of KCNJ2 enhanced IK1 and hyperpolarized fibroblasts. Functional KCNJ2 suppression by lentivirus-mediated expression of a dominant negative KCNJ2 construct suppressed IK1 and depolarized RMP. Overexpression of KCNJ2 increased Ca(2+) entry and fibroblast proliferation, whereas the dominant negative KCNJ2 construct had opposite effects. Fibroblast hyperpolarization to mimic CHF effects on RMP enhanced the Ca(2+) entry. MicroRNA-26a, which targets KCNJ2, was downregulated in CHF fibroblasts. Knockdown of endogenous microRNA-26 to mimic CHF effects unregulated IK1. CONCLUSIONS:CHF upregulates fibroblast KCNJ2 expression and currents, thereby hyperpolarizing RMP, increasing Ca(2+) entry, and enhancing atrial fibroblast proliferation. These effects are likely mediated by microRNA-26a downregulation. Remodeling-induced fibroblast KCNJ2 expression changes may play a role in atrial fibrillation promoting fibroblast remodeling and structural/arrhythmic consequences.
Authors: Jordi Heijman; Azinwi Phina Muna; Tina Veleva; Cristina E Molina; Henry Sutanto; Marcel Tekook; Qiongling Wang; Issam H Abu-Taha; Marcel Gorka; Stephan Künzel; Ali El-Armouche; Hermann Reichenspurner; Markus Kamler; Viacheslav Nikolaev; Ursula Ravens; Na Li; Stanley Nattel; Xander H T Wehrens; Dobromir Dobrev Journal: Circ Res Date: 2020-07-30 Impact factor: 17.367