Suppression of Early and Late Afterdepolarizations by Heterozygous Knockout of the Na+/Ca2+ Exchanger in a Murine Model
Nils Bögeholz,Paul Pauls,B. Klemens Bauer,Jan S. Schulte,Dirk G. Dechering,Gerrit Frommeyer,Uwe Kirchhefer,Joshua I. Goldhaber,Frank Müller,Lars Eckardt,Christian Pott +10 more
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TLDR
This is the first study to demonstrate that genetic inhibition of NCX protects against afterdepolarizations and to investigate the underlying mechanisms.Abstract:
Background— The Na+/Ca2+ exchanger (NCX) has been implied to cause arrhythmias. To date, information on the role of NCX in arrhythmogenesis derived from models with increased NCX expression, hypertrophy, and heart failure. Furthermore, the exact mechanism by which NCX exerts its potentially proarrhythmic effect, ie, by promoting early afterdepolarization (EAD) or delayed afterdepolarization (DAD) or both, is unknown.
Methods and Results— We investigated isolated cardiomyocytes from a murine model with heterozygous knockout of NCX (hetKO) using the patch clamp and Ca2+ imaging techniques. Action potential duration was shorter in hetKO with IKtot not being increased. The rate of spontaneous Ca2+ release events and the rate of DADs were unaltered; however, DADs had lower amplitude in hetKO. A DAD triggered a spontaneous action potential significantly less often in hetKO when compared with wild-type. The occurrence of EADs was also drastically reduced in hetKO. ICa activity was reduced in hetKO, an effect that was abolished in the presence of the Ca2+ buffer BAPTA.
Conclusions— Genetic suppression of NCX reduces both EADs and DADs. The following molecular mechanisms apply: (1) Although the absolute number of DADs is unaffected, an impaired translation of DADs into spontaneous action potentials results from a reduced DAD amplitude. (2) EADs are reduced in absolute number of occurrence, which is presumably a consequence of shortened action potential duration because of reduced NCX activity but also reduced ICa the latter possibly being caused by a direct modulation of Ca2+-dependent ICa inhibition by reduced NCX activity. This is the first study to demonstrate that genetic inhibition of NCX protects against afterdepolarizations and to investigate the underlying mechanisms.read more
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TECRL, a new life-threatening inherited arrhythmia gene associated with overlapping clinical features of both LQTS and CPVT.
Harsha D. Devalla,Roselle Gélinas,Roselle Gélinas,Elhadi H. Aburawi,Abdelaziz Beqqali,Philippe Goyette,Christian Freund,Marie A. Chaix,Marie A. Chaix,Rafik Tadros,Rafik Tadros,Rafik Tadros,Hui Jiang,Antony Le Béchec,Jantine Monshouwer-Kloots,Tom Zwetsloot,Georgios Kosmidis,Frédéric Latour,Azadeh Alikashani,Maaike Hoekstra,Jurg Schlaepfer,Christine L. Mummery,Brian Stevenson,Zoltán Kutalik,Zoltán Kutalik,Antoine A.F. de Vries,Lena Rivard,Lena Rivard,Arthur A.M. Wilde,Mario Talajic,Mario Talajic,Arie O. Verkerk,Lihadh Al-Gazali,John D. Rioux,John D. Rioux,Zahurul A. Bhuiyan,Robert Passier,Robert Passier +37 more
TL;DR: It is reported that mutations in TECRL are associated with inherited arrhythmias characterized by clinical features of both LQTS and CPVT and treatment with flecainide, a class Ic antiarrhythmic drug, significantly reduced the triggered activity in these cells.
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Hypertrophic cardiomyopathy-linked mutation in troponin T causes myofibrillar disarray and pro-arrhythmic action potential changes in human iPSC cardiomyocytes.
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TL;DR: Opa1 deficiency was associated with increased sensitivity to I/R, imbalance in dynamic mitochondrial Ca2+ uptake, and subsequent increase in NCX activity, and no difference was observed in the expression of other main fission/fusion protein, oxidative phosphorylation, apoptotic markers, or mitochondrial permeability transition pore function.
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Proarrhythmic Remodeling of Calcium Homeostasis in Cardiac Disease; Implications for Diabetes and Obesity.
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Cardiac expression of the CREM repressor isoform CREM-IbΔC-X in mice leads to arrhythmogenic alterations in ventricular cardiomyocytes
Jan S. Schulte,Edda Fehrmann,M. A. Tekook,D. Kranick,Benedikt Fels,Na Li,Xander H.T. Wehrens,Alexander Heinick,Matthias D. Seidl,Wilhelm Schmitz,Frank U. Müller +10 more
TL;DR: The results suggest that the inhibition of CRE-dependent transcription contributes to the formation of an arrhythmogenic substrate in chronic heart disease.
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