TY - JOUR A1 - Wagner, Michael A1 - Sadek, Mirna S. A1 - Dybkova, Nataliya A1 - Mason, Fleur E. A1 - Klehr, Johann A1 - Firneburg, Rebecca A1 - Cachorro, Eleder A1 - Richter, Kurt A1 - Klapproth, Erik A1 - Kuenzel, Stephan R. A1 - Lorenz, Kristina A1 - Heijman, Jordi A1 - Dobrev, Dobromir A1 - El-Armouche, Ali A1 - Sossalla, Samuel A1 - Kämmerer, Susanne T1 - Cellular mechanisms of the anti-arrhythmic effect of cardiac PDE2 overexpression JF - International Journal of Molecular Sciences N2 - Background: Phosphodiesterases (PDE) critically regulate myocardial cAMP and cGMP levels. PDE2 is stimulated by cGMP to hydrolyze cAMP, mediating a negative crosstalk between both pathways. PDE2 upregulation in heart failure contributes to desensitization to β-adrenergic overstimulation. After isoprenaline (ISO) injections, PDE2 overexpressing mice (PDE2 OE) were protected against ventricular arrhythmia. Here, we investigate the mechanisms underlying the effects of PDE2 OE on susceptibility to arrhythmias. Methods: Cellular arrhythmia, ion currents, and Ca\(^{2+}\)-sparks were assessed in ventricular cardiomyocytes from PDE2 OE and WT littermates. Results: Under basal conditions, action potential (AP) morphology were similar in PDE2 OE and WT. ISO stimulation significantly increased the incidence of afterdepolarizations and spontaneous APs in WT, which was markedly reduced in PDE2 OE. The ISO-induced increase in I\(_{CaL}\) seen in WT was prevented in PDE2 OE. Moreover, the ISO-induced, Epac- and CaMKII-dependent increase in I\(_{NaL}\) and Ca\(^{2+}\)-spark frequency was blunted in PDE2 OE, while the effect of direct Epac activation was similar in both groups. Finally, PDE2 inhibition facilitated arrhythmic events in ex vivo perfused WT hearts after reperfusion injury. Conclusion: Higher PDE2 abundance protects against ISO-induced cardiac arrhythmia by preventing the Epac- and CaMKII-mediated increases of cellular triggers. Thus, activating myocardial PDE2 may represent a novel intracellular anti-arrhythmic therapeutic strategy in HF. KW - PDE2 KW - arrhythmia KW - CaMKII KW - heart failure Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-285888 SN - 1422-0067 VL - 22 IS - 9 ER - TY - JOUR A1 - Maurer, Wiebke A1 - Hartmann, Nico A1 - Argyriou, Loukas A1 - Sossalla, Samuel A1 - Streckfuss-Bömeke, Katrin T1 - Generation of homozygous Na\(_{v}\)1.8 knock-out iPSC lines by CRISPR Cas9 genome editing to investigate a potential new antiarrhythmic strategy JF - Stem Cell Research N2 - The sodium channel Na\(_{v}\)1.8, encoded by SCN10A, is reported to contribute to arrhythmogenesis by inducing the late I\(_{Na}\) and thereby enhanced persistent Na\(^{+}\) current. However, its exact electrophysiological role in cardiomyocytes remains unclear. Here, we generated induced pluripotent stem cells (iPSCs) with a homozygous SCN10A knock-out from a healthy iPSC line by CRISPR Cas9 genome editing. The edited iPSCs maintained full pluripotency, genomic integrity, and spontaneous in vitro differentiation capacity. The iPSCs are able to differentiate into iPSC-cardiomyocytes, hence making it possible to investigate the role of Na\(_{v}\)1.8 in the heart. KW - arrhythmogenesis KW - cardiomyocytes KW - induced pluripotent stem cells Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-300936 VL - 60 ER - TY - JOUR A1 - Eiringhaus, Jörg A1 - Wünsche, Christoph M. A1 - Tirilomis, Petros A1 - Herting, Jonas A1 - Bork, Nadja A1 - Nikolaev, Viacheslav O. A1 - Hasenfuss, Gerd A1 - Sossalla, Samuel A1 - Fischer, Thomas H. T1 - Sacubitrilat reduces pro‐arrhythmogenic sarcoplasmic reticulum Ca\(^{2+}\) leak in human ventricular cardiomyocytes of patients with end‐stage heart failure JF - ESC Heart Failure N2 - Aims Inhibition of neprilysin and angiotensin II receptor by sacubitril/valsartan (Val) (LCZ696) reduces mortality in heart failure (HF) patients compared with sole inhibition of renin–angiotensin system. Beneficial effects of increased natriuretic peptide levels upon neprilysin inhibition have been proposed, whereas direct effects of sacubitrilat (Sac) (LBQ657) on myocardial Ca\(^{2+}\) cycling remain elusive. Methods and results Confocal microscopy (Fluo‐4 AM) was used to investigate pro‐arrhythmogenic sarcoplasmic reticulum (SR) Ca\(^{2+}\) leak in freshly isolated murine and human ventricular cardiomyocytes (CMs) upon Sac (40 μmol/L)/Val (13 μmol/L) treatment. The concentrations of Sac and Val equalled plasma concentrations of LCZ696 treatment used in PARADIGM‐HF trial. Epifluorescence microscopy measurements (Fura‐2 AM) were performed to investigate effects on systolic Ca\(^{2+}\) release, SR Ca\(^{2+}\) load, and Ca\(^{2+}\)‐transient kinetics in freshly isolated murine ventricular CMs. The impact of Sac on myocardial contractility was evaluated using in toto‐isolated, isometrically twitching ventricular trabeculae from human hearts with end‐stage HF. Under basal conditions, the combination of Sac/Val did not influence diastolic Ca\(^{2+}\)‐spark frequency (CaSpF) nor pro‐arrhythmogenic SR Ca\(^{2}\) leak in isolated murine ventricular CMs (n CMs/hearts = 80/7 vs. 100/7, P = 0.91/0.99). In contrast, Sac/Val treatment reduced CaSpF by 35 ± 9% and SR Ca\(^{2+}\) leak by 45 ± 9% in CMs put under catecholaminergic stress (isoproterenol 30 nmol/L, n = 81/7 vs. 62/7, P < 0.001 each). This could be attributed to Sac, as sole Sac treatment also reduced both parameters by similar degrees (reduction of CaSpF by 57 ± 7% and SR Ca2+ leak by 76 ± 5%; n = 101/4 vs. 108/4, P < 0.01 each), whereas sole Val treatment did not. Systolic Ca2+ release, SR Ca\(^{2+}\) load, and Ca\(^{2+}\)‐transient kinetics including SERCA activity (k\(_{SERCA}\)) were not compromised by Sac in isolated murine CMs (n = 41/6 vs. 39/6). Importantly, the combination of Sac/Val and Sac alone also reduced diastolic CaSpF and SR Ca\(^{2+}\) leak (reduction by 74 ± 7%) in human left ventricular CMs from patients with end‐stage HF (n = 71/8 vs. 78/8, P < 0.05 each). Myocardial contractility of human ventricular trabeculae was not acutely affected by Sac treatment as the developed force remained unchanged over a time course of 30 min (n trabeculae/hearts = 3/3 vs. 4/3). Conclusion This study demonstrates that neprilysin inhibitor Sac directly improves Ca\(^{2+}\) homeostasis in human end‐stage HF by reducing pro‐arrhythmogenic SR Ca\(^{2+}\) leak without acutely affecting systolic Ca\(^{2+}\) release and inotropy. These effects might contribute to the mortality benefits observed in the PARADIGM‐HF trial. KW - heart failure KW - entresto KW - Neprilysin inhibition KW - Ca cycling KW - SR Ca leak KW - arrhythmia Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-218479 VL - 7 IS - 5 SP - 2992 EP - 3002 ER - TY - JOUR A1 - Budde, Heidi A1 - Hassoun, Roua A1 - Tangos, Melina A1 - Zhazykbayeva, Saltanat A1 - Herwig, Melissa A1 - Varatnitskaya, Marharyta A1 - Sieme, Marcel A1 - Delalat, Simin A1 - Sultana, Innas A1 - Kolijn, Detmar A1 - Gömöri, Kamilla A1 - Jarkas, Muhammad A1 - Lódi, Mária A1 - Jaquet, Kornelia A1 - Kovács, Árpád A1 - Mannherz, Hans Georg A1 - Sequeira, Vasco A1 - Mügge, Andreas A1 - Leichert, Lars I. A1 - Sossalla, Samuel A1 - Hamdani, Nazha T1 - The interplay between S-glutathionylation and phosphorylation of cardiac troponin I and myosin binding protein C in end-stage human failing hearts JF - Antioxidants N2 - Oxidative stress is defined as an imbalance between the antioxidant defense system and the production of reactive oxygen species (ROS). At low levels, ROS are involved in the regulation of redox signaling for cell protection. However, upon chronical increase in oxidative stress, cell damage occurs, due to protein, DNA and lipid oxidation. Here, we investigated the oxidative modifications of myofilament proteins, and their role in modulating cardiomyocyte function in end-stage human failing hearts. We found altered maximum Ca\(^{2+}\)-activated tension and Ca\(^{2+}\) sensitivity of force production of skinned single cardiomyocytes in end-stage human failing hearts compared to non-failing hearts, which was corrected upon treatment with reduced glutathione enzyme. This was accompanied by the increased oxidation of troponin I and myosin binding protein C, and decreased levels of protein kinases A (PKA)- and C (PKC)-mediated phosphorylation of both proteins. The Ca\(^{2+}\) sensitivity and maximal tension correlated strongly with the myofilament oxidation levels, hypo-phosphorylation, and oxidative stress parameters that were measured in all the samples. Furthermore, we detected elevated titin-based myocardial stiffness in HF myocytes, which was reversed by PKA and reduced glutathione enzyme treatment. Finally, many oxidative stress and inflammation parameters were significantly elevated in failing hearts compared to non-failing hearts, and corrected upon treatment with the anti-oxidant GSH enzyme. Here, we provide evidence that the altered mechanical properties of failing human cardiomyocytes are partially due to phosphorylation, S-glutathionylation, and the interplay between the two post-translational modifications, which contribute to the development of heart failure. KW - myofilament proteins KW - oxidative stress KW - inflammation KW - phosphorylation KW - S-glutathionylation Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-242701 SN - 2076-3921 VL - 10 IS - 7 ER -