Selma A. Serra, Julio Martí-Almor, Kathryn W. Aguilar-Agon, Josep Comín-Colet, Anna Garcia-Elias, Begoña Benito, Cristina Enjuanes, Laia Yañez-Bisbe, Svetlana Reilly, José M. Fernández-Fernández, Marta Tajes, Institut Català de la Salut, [Garcia-Elias A, Yañez-Bisbe L] Programa de Biologia Vascular i Metabolisme, Vall d’Hebron Institut de Recerca (VHIR), Barcelona, Spain. Group of Biomedical Research in Heart Diseases, Hospital del Mar Medical Research Institute (IMIM), Barcelona, Spain. [Tajes M] Group of Biomedical Research in Heart Diseases, Hospital del Mar Medical Research Institute (IMIM), Barcelona, Spain. Research Group in Cardiovascular Disorders (BIOHEART), Bellvitge Biomedical Research Institute (IDIBELL), L′Hospitalet de Llobregat, Spain. [Enjuanes C] Research Group in Cardiovascular Disorders (BIOHEART), Bellvitge Biomedical Research Institute (IDIBELL), L′Hospitalet de Llobregat, Spain. Cardiology Department, Hospital de Bellvitge, L’Hospitalet de Llobregat, Spain. [Comín-Colet J] Research Group in Cardiovascular Disorders (BIOHEART), Bellvitge Biomedical Research Institute (IDIBELL), L′Hospitalet de Llobregat, Spain. Cardiology Department, Hospital de Bellvitge, L’Hospitalet de Llobregat, Spain. Department of Clinical Sciences, University of Barcelona School of Medicine, Barcelona, Spain. [Serra SA] Laboratory of Molecular Physiology, Department of Experimental and Health Sciences, Universitat Pompeu Fabra, Barcelona, Spain. [Benito B] Programa de Biologia Vascular i Metabolisme, Vall d’Hebron Institut de Recerca (VHIR), Barcelona, Spain. Group of Biomedical Research in Heart Diseases, Hospital del Mar Medical Research Institute (IMIM), Barcelona, Spain. Departament de Medicina, Universitat Autònoma de Barcelona, Bellaterra, Spain. Servei de Cardiologia, Vall d’Hebron Hospital Universitari, Barcelona, Spain. Universitat Autònoma Barcelona, Bellaterra, Spain. Centro de Investigación Biomédica en Red de Enfermedades Cardiovasculares (CIBER-CV), Instituto de Salud Carlos III, Madrid, Spain, and Vall d'Hebron Barcelona Hospital Campus
HL-1 cells; L-type calcium channels; Calcium regulation Células HL-1; Canales de calcio tipo L; Regulación del calcio Cel·lules HL-1; Canals de calci tipus L; Regulació del calci MicroRNAs (miRNAs) participate in atrial remodeling and atrial fibrillation (AF) promotion. We determined the circulating miRNA profile in patients with AF and heart failure with reduced ejection fraction (HFrEF), and its potential role in promoting the arrhythmia. In plasma of 98 patients with HFrEF (49 with AF and 49 in sinus rhythm, SR), differential miRNA expression was determined by high-throughput microarray analysis followed by replication of selected candidates. Validated miRNAs were determined in human atrial samples, and potential arrhythmogenic mechanisms studied in HL-1 cells. Circulating miR-199a-5p and miR-22-5p were significantly increased in HFrEF patients with AF versus those with HFrEF in SR. Both miRNAs, but particularly miR-199a-5p, were increased in atrial samples of patients with AF. Overexpression of both miRNAs in HL-1 cells resulted in decreased protein levels of L-type Ca2+ channel, NCX and connexin-40, leading to lower basal intracellular Ca2+ levels, fewer inward currents, a moderate reduction in Ca2+ buffering post-caffeine exposure, and a deficient cell-to-cell communication. In conclusion, circulating miR-199a-5p and miR-22-5p are higher in HFrEF patients with AF, with similar findings in human atrial samples of AF patients. Cells exposed to both miRNAs exhibited altered Ca2+ handling and defective cell-to-cell communication, both findings being potential arrhythmogenic mechanisms. This work was funded by the following grants, awarded to B.B.: Sociedad Española de Cardiología, Sección de Arritmias y Electrofisiología 2012; Sociedad Española de Cardiología, Sección de Insuficiencia Cardíaca 2013; Fondo Investigación Sanitaria (FIS)—Instituto Carlos III 2013 (PI13/01830); and Societat Catalana de Cardiologia 2016. Awarded to K.W.A-A. and S.R.: British Heart Foundation (BHF) Intermediate Research Fellowship. Awarded to J.M.F.F.: grant from the Spanish Ministry of Science and Innovation (RTI2018-094809-B-I00). “María de Maeztu” Programme for Units of Excellence in R&D to the Departament de Ciències Experimentals i de la Salut (MDM-2014-0370) and FEDER (Fondo Europeo de Desarrollo Regional) also contributed to this work.