title: Reconciling depressed Ca2+ sparks occurrence with enhanced RyR2 activity in failing mice cardiomyocytes.
abstract: Abnormalities in cardiomyocyte Ca2+ handling contribute to impaired contractile function in heart failure (HF). Experiments on single ryanodine receptors (RyRs) incorporated into lipid bilayers have indicated that RyRs from failing hearts are more active than those from healthy hearts. Here, we analyzed spontaneous Ca2+ sparks (brief, localized increased in [Ca2+]i) to evaluate RyR cluster activity in situ in a mouse post-myocardial infarction (PMI) model of HF. The cardiac ejection fraction of PMI mice was reduced to ∼30% of that of sham-operated (sham) mice, and their cardiomyocytes were hypertrophied. The [Ca2+]i transient amplitude and sarcoplasmic reticulum (SR) Ca2+ load were decreased in intact PMI cardiomyocytes compared with those from sham mice, and spontaneous Ca2+ sparks were less frequent, whereas the fractional release and the frequency of Ca2+ waves were both increased, suggesting higher RyR activity. In permeabilized cardiomyocytes, in which the internal solution can be controlled, Ca2+ sparks were more frequent in PMI cells (under conditions of similar SR Ca2+ load), confirming the enhanced RyR activity. However, in intact cells from PMI mice, the Ca2+ sparks frequency normalized by the SR Ca2+ load in that cell were reduced compared with those in sham mice, indicating that the cytosolic environment in intact cells contributes to the decrease in Ca2+ spark frequency. Indeed, using an internal "failing solution" with less ATP (as found in HF), we observed a dramatic decrease in Ca2+ spark frequency in permeabilized PMI and sham myocytes. In conclusion, our data show that, even if isolated RyR channels show more activity in HF, concomitant alterations in intracellular media composition and SR Ca2+ load may mask these effects at the Ca2+ spark level in intact cells. Nonetheless, in this scenario, the probability of arrhythmogenic Ca2+ waves is enhanced, and they play a potential role in the increase in arrhythmia events in HF patients.
authors.affiliation: Institut National de la Santé et de la Recherche Médicale (INSERM), UMR-S 1180, LabEx LERMIT, DHU TORINO, and Faculté de Pharmacie, Université Paris Sud, Université Paris-Saclay, 92296 Châtenay-Malabry, France Institut National de la Santé et de la Recherche Médicale (INSERM), UMR-S 1180, LabEx LERMIT, DHU TORINO, and Faculté de Pharmacie, Université Paris Sud, Université Paris-Saclay, 92296 Châtenay-Malabry, France Instituto de Investigación, Hospital 12 de Octubre, 28041 Madrid, Spain ana-maria.gomez@inserm.fr gemaruiz@h12o.es.
authors.forename: Gema
authors.initials: G
authors.lastname: Ruiz-Hurtado
authors.affiliation: Institut National de la Santé et de la Recherche Médicale (INSERM), UMR-S 1180, LabEx LERMIT, DHU TORINO, and Faculté de Pharmacie, Université Paris Sud, Université Paris-Saclay, 92296 Châtenay-Malabry, France Institut National de la Santé et de la Recherche Médicale (INSERM), UMR-S 1180, LabEx LERMIT, DHU TORINO, and Faculté de Pharmacie, Université Paris Sud, Université Paris-Saclay, 92296 Châtenay-Malabry, France.
authors.forename: Linwei
authors.initials: L
authors.lastname: Li
authors.affiliation: Instituto de Investigación Hospital Universitario La Paz, 28046 Madrid, Spain.
authors.forename: María
authors.initials: M
authors.lastname: Fernández-Velasco
authors.affiliation: Departamento de Bioquímica, Centro de Investigación y de Estudios Avanzados del IPN, 07360 México City, D.F., México.
authors.forename: Angélica
authors.initials: A
authors.lastname: Rueda
authors.affiliation: Institut National de la Santé et de la Recherche Médicale (INSERM), UMR-S 1180, LabEx LERMIT, DHU TORINO, and Faculté de Pharmacie, Université Paris Sud, Université Paris-Saclay, 92296 Châtenay-Malabry, France Institut National de la Santé et de la Recherche Médicale (INSERM), UMR-S 1180, LabEx LERMIT, DHU TORINO, and Faculté de Pharmacie, Université Paris Sud, Université Paris-Saclay, 92296 Châtenay-Malabry, France.
authors.forename: Florence
authors.initials: F
authors.lastname: Lefebvre
authors.affiliation: Institut National de la Santé et de la Recherche Médicale (INSERM), UMR-S 1180, LabEx LERMIT, DHU TORINO, and Faculté de Pharmacie, Université Paris Sud, Université Paris-Saclay, 92296 Châtenay-Malabry, France Institut National de la Santé et de la Recherche Médicale (INSERM), UMR-S 1180, LabEx LERMIT, DHU TORINO, and Faculté de Pharmacie, Université Paris Sud, Université Paris-Saclay, 92296 Châtenay-Malabry, France.
authors.forename: Yueyi
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Institut National de la Santé et de la Recherche Médicale (INSERM), UMR-S 1180, LabEx LERMIT, DHU TORINO, and Faculté de Pharmacie, Université Paris Sud, Université Paris-Saclay, 92296 Châtenay-Malabry, France Institut National de la Santé et de la Recherche Médicale (INSERM), UMR-S 1180, LabEx LERMIT, DHU TORINO, and Faculté de Pharmacie, Université Paris Sud, Université Paris-Saclay, 92296 Châtenay-Malabry, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Mateo
authors.affiliation: Maladies infectieuses et vecteurs: écologie, génétique, évolution et contrôle, Institut de recherche pour le développement, 34394 Montpellier, France.
authors.forename: Cécile
authors.initials: C
authors.lastname: Cassan
authors.affiliation: INSERM U955 and Department of Cardiology, AP-HP, Henri Mondor Hospital, Université Paris-Est Créteil, 94010 Créteil, France INSERM U955 and Department of Cardiology, AP-HP, Henri Mondor Hospital, Université Paris-Est Créteil, 94010 Créteil, France.
authors.forename: Barnabas
authors.initials: B
authors.lastname: Gellen
authors.affiliation: Institut National de la Santé et de la Recherche Médicale (INSERM), UMR-S 1180, LabEx LERMIT, DHU TORINO, and Faculté de Pharmacie, Université Paris Sud, Université Paris-Saclay, 92296 Châtenay-Malabry, France Institut National de la Santé et de la Recherche Médicale (INSERM), UMR-S 1180, LabEx LERMIT, DHU TORINO, and Faculté de Pharmacie, Université Paris Sud, Université Paris-Saclay, 92296 Châtenay-Malabry, France.
authors.forename: Jean Pierre
authors.initials: JP
authors.lastname: Benitah
authors.affiliation: Institut National de la Santé et de la Recherche Médicale (INSERM), UMR-S 1180, LabEx LERMIT, DHU TORINO, and Faculté de Pharmacie, Université Paris Sud, Université Paris-Saclay, 92296 Châtenay-Malabry, France Institut National de la Santé et de la Recherche Médicale (INSERM), UMR-S 1180, LabEx LERMIT, DHU TORINO, and Faculté de Pharmacie, Université Paris Sud, Université Paris-Saclay, 92296 Châtenay-Malabry, France ana-maria.gomez@inserm.fr gemaruiz@h12o.es.
authors.forename: Ana María
authors.initials: AM
authors.lastname: Gómez
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D020013:Calcium Signaling; D002478:Cells, Cultured; D006333:Heart Failure / Q000378:metabolism*; D006352:Heart Ventricles / Q000166:cytology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009203:Myocardial Infarction / Q000378:metabolism*; D032383:Myocytes, Cardiac / Q000378:metabolism*; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism*
chemical_list: D019837:Ryanodine Receptor Calcium Release Channel; D000255:Adenosine Triphosphate