Publications by authors named "Samuel Sossalla"

129 Publications

Generation and cardiac differentiation of an induced pluripotent stem cell line from a patient with arrhythmia-induced cardiomyopathy.

Stem Cell Res 2021 Feb 20;53:102263. Epub 2021 Feb 20.

Clinic for Cardiology & Pneumology, University Medical Center Goettingen, and DZHK (German Centre for Cardiovascular Research), partner site Goettingen, Germany. Electronic address:

Arrhythmia-induced cardiomyopathy (AIC) is characterized by left-ventricular systolic dysfunction caused by persistent arrhythmia. To date, genetic or pathological drivers causing AIC remain unknown. Here, we generated induced pluripotent stem cells (iPSCs) from an AIC patient. The AIC-iPSCs exhibited full pluripotency and differentiation characteristics and maintained a normal karyotype after reprogramming. The AIC-iPSCs differentiated into functional beating AIC-iPSC-cardiomyocytes (CMs), which represents the cell-type of interest to study molecular, genetic and functional aspects of AIC.
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http://dx.doi.org/10.1016/j.scr.2021.102263DOI Listing
February 2021

Loss of CASK Accelerates Heart Failure Development.

Circ Res 2021 Feb 17. Epub 2021 Feb 17.

Internal Medicine II, University Hospital Regensburg, GERMANY.

Increased myocardial activity of Ca/calmodulin-dependent kinase II (CaMKII) leads to heart failure (HF) and arrhythmias. In Drosophila neurons, interaction of CaMKII with Ca/CaM-dependent serine protein kinase (CASK) has been shown to inhibit CaMKII activity, but the consequences of this regulation for HF and ventricular arrhythmias are unknown. We hypothesize that CASK associates with CaMKII in human and mouse hearts thereby limiting CaMKII activity, and that altering CASK expression in mice changes CaMKII activity accordingly, with functional consequences for contractile function and arrhythmias. Immunoprecipitation revealed that CASK associates with CaMKII in human hearts. CASK expression is unaltered in HF but increased in patients with aortic stenosis. In mice, cardiomyocyte-specific knockout of CASK (CASK-KO) increased CaMKII auto-phosphorylation at the stimulatory T287 site, but reduced phosphorylation at the inhibitory T305/306 site. CASK-KO mice showed increased CaMKII-dependent sarcoplasmic reticulum (SR) Ca leak, reduced SR Ca-content, increased susceptibility to ventricular arrhythmias, greater loss of ejection fraction, and increased mortality after transverse aortic constriction. Intriguingly, stimulation of the cardiac glucagon-like peptide 1-receptor with exenatide increased CASK expression resulting in increased inhibitory CaMKII T305 phosphorylation, reduced CaMKII activity, and reduced SR Ca leak in WT but not CASK KO. CASK associates with CaMKII in the human heart. CASK-KO in mice increases CaMKII activity, leading to contractile dysfunction and arrhythmias. Increasing CASK expression reduces CaMKII activity, improves Ca handling and contractile function.
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http://dx.doi.org/10.1161/CIRCRESAHA.120.318170DOI Listing
February 2021

25 Years' Experience with Redo Operations in Cardiac Surgery-Third-Time Sternotomy Procedures.

Thorac Cardiovasc Surg 2020 Dec 24. Epub 2020 Dec 24.

Department of Cardiothoracic Surgery, University Medical Center, Regensburg, Germany.

Background:  Over the years, open heart surgery has become more complex, and especially reoperative surgery, more demanding. The risk of third-time or more sternotomy procedures is unclear.

Methods:  We reviewed our institutional experience of 25 years based on two generations of cardiac surgeons in a German university medical center to document frequency, outcome, and complications of the various types of open heart procedures.

Results:  Overall, we included 104 patients with a mean age of 64 ± 13 years. The EuroSCORE II (European System for Cardiac Operative Risk Evaluation) calculated an average mortality risk of 15.7 ± 15.4%. Subgroup comparison of isolated coronary artery bypass grafting (CABG), aortic valve replacement, and mitral valve replacement procedures did not delineate significantly different risk profiles except for the incidence of acute myocardial infarction, which was present in every second patient (53.3%) scheduled for CABG surgery. The time interval to previous surgery was 4.7 ± 6.3 years on average. Most frequent surgical procedures were valve operations, which were accomplished in 72 patients (69.2%), whereas coronary bypass surgery was performed in 23 patients (22.1%) only. Combined procedures were performed in 27 patients. Complex aortic arch replacement with a frozen elephant trunk procedure was necessary in six patients. Overall, 30-day survival was 81.7%.

Conclusion:  In conclusion, third-time and more sternotomy procedures offer acceptable outcome and should therefore be considered in appropriate patients.
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http://dx.doi.org/10.1055/s-0040-1719157DOI Listing
December 2020

Catheter ablation for atrial fibrillation in patients with end-stage heart failure and eligibility for heart transplantation.

ESC Heart Fail 2020 Dec 13. Epub 2020 Dec 13.

Clinic for Thoracic and Cardiovascular Surgery, Herz- und Diabeteszentrum NRW, Ruhr-Universität Bochum, Bad Oeynhausen, Germany.

Aims: Timely referrals for transplantation and left ventricular assist device (LVAD) play a key role in favourable outcomes in patients with advanced heart failure (HF). The purpose of the Catheter Ablation for atrial fibrillation in patientS with end-sTage heart faiLure and Eligibility for Heart Transplantation (CASTLE-HTx) trial is to test the hypothesis that atrial fibrillation (AF) ablation has beneficial effects on mortality and morbidity during 'waiting time' for heart transplantation (HTx) or to prolong the time span until LVAD implantation.

Methods And Results: CASTLE-HTx is a randomized evaluation of ablative treatment of AF in patients with severe left ventricular dysfunction who are candidates and eligible for HTx. The primary endpoint is the composite of all-cause mortality, worsening of HF requiring a high urgent transplantation, or LVAD implantation. The secondary study endpoints are all-cause mortality, cardiovascular mortality, cerebrovascular accidents, worsening of HF requiring unplanned hospitalization, AF burden reduction, unplanned hospitalization due to cardiovascular reason, all-cause hospitalization, quality of life, number of delivered implantable cardioverter defibrillator therapies, time to first implantable cardioverter defibrillator therapy, number of device-detected ventricular tachycardia/ventricular fibrillation episodes, left ventricular function, exercise tolerance, and percentage of right ventricular pacing. Ventricular myocardial tissue will be obtained from patients who will undergo LVAD implantation or HTx to assess the effect of catheter ablation on human HF myocardium. CASTLE-HTx will randomize 194 patients over a minimum time period of 2 years.

Conclusions: CASTLE-HTx will determine if AF ablation has beneficial effects on mortality in patients with end-stage HF who are eligible for HTx.
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http://dx.doi.org/10.1002/ehf2.13150DOI Listing
December 2020

"Predictors of pacemaker implantation after TAVI according to kind of prosthesis and risk profile: a systematic review and contemporary meta-analysis".

Eur Heart J Qual Care Clin Outcomes 2020 Dec 8. Epub 2020 Dec 8.

Division of Cardiology, Cardiovascular and Thoracic Department, Città della Salute e della Scienza Hospital and University of Turin, Italy.

Background: Permanent pacemaker implantation (PPI) may be required after transcatheter aortic valve implantation (TAVI). Evidence on PPI prediction has largely been gathered from high risk patients receiving first generation valve implants.

Objectives: We undertook a meta-analysis of the existing literature to examine the incidence and predictors of PPI after TAVI according to generation of valve, valve type and surgical risk.

Methods: We made a systematic literature search for studies with ≥100 patients reporting the incidence and adjusted predictors of PPI after TAVI. Subgroup analyses examined these features according to generation of valve, specific valve type and surgical risk.

Results: We obtained data from 43 studies, encompassing 29,113 patients. PPI rates ranged from 6.7% - 39.2% in individual studies with a pooled incidence of 19% (95% CI 16-21). Independent predictors for PPI were age (OR 1.05; 95% CI: 1.01-1.09), left bundle branch block (LBBB) (OR: 1.45; 95% CI: 1.12 to 1.77), right bundle branch block (RBBB) (OR: 4.15; 95% CI: 3.23 to 4.88), implantation depth (OR: 1.18; 95% CI: 1.11 to 1.26) and self-expanding valve prosthesis (OR 2.99; 95% CI: 1.39-4.59). Among subgroups analyzed according to valve type, valve generation and surgical risk, independent predictors were RBBB, self-expanding valve type, first degree atrioventricular block and implantation depth.

Conclusions: The principle independent predictors for PPI following TAVI are age, RBBB, LBBB, self-expanding valve type and valve implantation depth. These characteristics should be taken into account in pre-procedural assessment to reduce PPI rates. PROSPERO ID CRD42020164043.
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http://dx.doi.org/10.1093/ehjqcco/qcaa089DOI Listing
December 2020

Decreased GLUT1/NHE1 RNA expression in whole blood predicts disease severity in patients with COVID-19.

ESC Heart Fail 2021 02 20;8(1):309-316. Epub 2020 Nov 20.

Department of Internal Medicine II (Cardiology), University Hospital Regensburg, Franz-Josef-Strauß-Allee 11, Regensburg, 93053, Germany.

Aims: We aimed to assess whether expression of whole-blood RNA of sodium proton exchanger 1 (NHE1) and glucose transporter 1 (GLUT1) is associated with COVID-19 infection and outcome in patients presenting to the emergency department with respiratory infections. Furthermore, we investigated NHE1 and GLUT1 expression in the myocardium of deceased COVID-19 patients.

Methods And Results: Whole-blood quantitative assessment of NHE1 and GLUT1 RNA was performed using quantitative PCR in patients with respiratory infection upon first contact in the emergency department and subsequently stratified by SARS-CoV-2 infection status. Assessment of NHE1 and GLUT1 RNA using PCR was also performed in left ventricular myocardium of deceased COVID-19 patients. NHE1 expression is up-regulated in whole blood of patients with COVID-19 compared with other respiratory infections at first medical contact in the emergency department (control: 0.0021 ± 0.0002, COVID-19: 0.0031 ± 0.0003, P = 0.01). The ratio of GLUT1 to NHE1 is significantly decreased in the blood of COVID-19 patients who are subsequently intubated and/or die (severe disease) compared with patients with moderate disease (moderate disease: 0.497 ± 0.083 vs. severe disease: 0.294 ± 0.0336, P = 0.036). This ratio is even further decreased in the myocardium of patients who deceased from COVID-19 in comparison with the myocardium of non-infected donors.

Conclusions: NHE1 and GLUT1 may be critically involved in the disease progression of SARS-CoV-2 infection. We show here that SARS-CoV-2 infection critically disturbs ion channel expression in the heart. A decreased ratio of GLUT1/NHE1 could potentially serve as a biomarker for disease severity in patients with COVID-19.
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http://dx.doi.org/10.1002/ehf2.13063DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7835506PMC
February 2021

The E3 ubiquitin ligase HectD3 attenuates cardiac hypertrophy and inflammation in mice.

Commun Biol 2020 Oct 9;3(1):562. Epub 2020 Oct 9.

Department of Internal Medicine III (Cardiology, Angiology, Intensive Care), University Medical Center Kiel, Kiel, Germany.

Myocardial inflammation has recently been recognized as a distinct feature of cardiac hypertrophy and heart failure. HectD3, a HECT domain containing E3 ubiquitin ligase has previously been investigated in the host defense against infections as well as neuroinflammation; its cardiac function however is still unknown. Here we show that HectD3 simultaneously attenuates Calcineurin-NFAT driven cardiomyocyte hypertrophy and the pro-inflammatory actions of LPS/interferon-γ via its cardiac substrates SUMO2 and Stat1, respectively. AAV9-mediated overexpression of HectD3 in mice in vivo not only reduced cardiac SUMO2/Stat1 levels and pathological hypertrophy but also largely abolished macrophage infiltration and fibrosis induced by pressure overload. Taken together, we describe a novel cardioprotective mechanism involving the ubiquitin ligase HectD3, which links anti-hypertrophic and anti-inflammatory effects via dual regulation of SUMO2 and Stat1. In a broader perspective, these findings support the notion that cardiomyocyte growth and inflammation are more intertwined than previously anticipated.
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http://dx.doi.org/10.1038/s42003-020-01289-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7547098PMC
October 2020

Long-term effects of empagliflozin on excitation-contraction-coupling in human induced pluripotent stem cell cardiomyocytes.

J Mol Med (Berl) 2020 12 9;98(12):1689-1700. Epub 2020 Oct 9.

Department of Internal Medicine II, University Medical Center Regensburg, Franz-Josef-Strauß-Allee 11, 93053, Regensburg, Germany.

The SGLT2 inhibitor empagliflozin improved cardiovascular outcomes in patients with diabetes. As the cardiac mechanisms remain elusive, we investigated the long-term effects (up to 2 months) of empagliflozin on excitation-contraction (EC)-coupling in human cardiomyocytes derived from induced pluripotent stem cells (iPSC-CM) in a blinded manner. IPSC from 3 donors, differentiated into pure iPSC-CM (4 differentiations), were treated with a clinically relevant concentration of empagliflozin (0.5 μmol/l) or vehicle control. Treatment, data acquisition, and analysis were conducted externally blinded. Epifluorescence microscopy measurements in iPSC-CM showed that empagliflozin has neutral effects on Ca transient amplitude, diastolic Ca levels, Ca transient kinetics, or sarcoplasmic Ca load after 2 weeks or 8 weeks of treatment. Confocal microscopy determining possible effects on proarrhythmogenic diastolic Ca release events showed that in iPSC-CM, Ca spark frequency and leak was not altered after chronic treatment with empagliflozin. Finally, in patch-clamp experiments, empagliflozin did not change action potential duration, amplitude, or resting membrane potential compared with vehicle control after long-term treatment. Next-generation RNA sequencing (NGS) and mapped transcriptome profiles of iPSC-CMs untreated and treated with empagliflozin for 8 weeks showed no differentially expressed EC-coupling genes. In line with NGS data, Western blots indicate that empagliflozin has negligible effects on key EC-coupling proteins. In this blinded study, direct treatment of iPSC-CM with empagliflozin for a clinically relevant duration of 2 months did not influence cardiomyocyte EC-coupling and electrophysiology. Therefore, it is likely that other mechanisms independent of cardiomyocyte EC-coupling are responsible for the beneficial treatment effect of empagliflozin. KEY MESSAGES: This blinded study investigated the clinically relevant long-term effects (up to 2 months) of empagliflozin on cardiomyocyte excitation-contraction (EC)-coupling. Human cardiomyocytes derived from induced pluripotent stem cells (iPSC-CM) were used to study a human model including a high repetition number of experiments. Empagliflozin has neutral effects on cardiomyocyte Ca transients, sarcoplasmic Ca load, and diastolic sarcoplasmic Ca leak. In patch-clamp experiments, empagliflozin did not change the action potential. Next-generation RNA sequencing, mapped transcriptome profiles, and Western blots of iPSC-CM untreated and treated with empagliflozin showed no differentially expressed EC-coupling candidates.
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http://dx.doi.org/10.1007/s00109-020-01989-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7679329PMC
December 2020

Effects of visualization of successful revascularization on chest pain and quality of life in chronic coronary syndrome: study protocol for the multi-center, randomized, controlled PLA-pCi-EBO-pilot-trial.

Trials 2020 Oct 8;21(1):838. Epub 2020 Oct 8.

University Heart Centre Regensburg, Department of Internal Medicine II, University Hospital Regensburg, Regensburg, Germany.

Background: Stable coronary artery disease (CAD), recently termed chronic coronary syndrome (CCS), is a highly prevalent disease. Current treatment strategies often include a relevant placebo effect. The hypothesis is that visual angiographic demonstration of the coronary arteries before and after successful percutaneous coronary intervention (PCI) by itself reduces the symptom burden of stable CAD/CCS.

Design And Methods: The PLA-pCi-EBO-pilot-trial is a prospective, multi-center, randomized, controlled investigator-initiated pilot trial to study the effect of visual demonstration of successful PCI on quality of life (QoL) and angina pectoris (AP) in patients with symptomatic stable CAD/CCS. All patients with stable CAD/CCS and successful PCI will be screened. One hundred forty four patients with a frequency of AP ≥ 2/week will be randomized 1:1 stratified for AP frequency > 1/day. The control group will receive the common written procedural report on the procedure. Patients in the intervention group will additionally be given a printout picture of their coronary angiogram both before and after PCI. Primary endpoints are change in the Seattle Angina Questionnaire (SAQ)-derived QoL score 1 and 6 months after PCI. Secondary endpoints are changes in other SAQ-derived scores and dyspnea (NYHA score) 1 and 6 months after PCI.

Discussion: The PLA-pCi-EBO-pilot-trial evaluates the effect of visual angiographic result demonstration on disease symptoms and QoL in patients with stable CAD/CCS on top of PCI. A positive outcome of our study would encourage the routine use of angiographic picture demonstration and has thus the potential to change daily routine in the catheterization laboratory.

Trial Registration: German Clinical Trials Register DRKS00017524 . Registered on 5 July 2019.
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http://dx.doi.org/10.1186/s13063-020-04710-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7542727PMC
October 2020

Protected complex percutaneous coronary intervention and transcatheter aortic valve replacement using extracorporeal membrane oxygenation in a high-risk frail patient: a case report.

J Med Case Rep 2020 Sep 23;14(1):163. Epub 2020 Sep 23.

Department of Internal Medicine II, University Medical Center Regensburg, Franz-Josef-Strauß-Allee 11, 93053, Regensburg, Germany.

Background: Transcatheter aortic valve replacement has become a routine procedure for patients with severe symptomatic aortic stenosis at increased surgical risk. Not much is known about using prophylactic support with venoarterial extracorporeal membrane oxygenation in patients undergoing transcatheter aortic valve replacement and eventually concomitant complex percutaneous coronary intervention.

Case Presentation: We present a successful procedure of transcatheter aortic valve replacement and high-risk percutaneous coronary intervention utilizing venoarterial extracorporeal membrane oxygenation for hemodynamic support in a very frail 88-year-old Caucasian woman with severe symptomatic aortic stenosis and coronary bypass grafting in the past. Echocardiography revealed a "low-flow low-gradient" aortic stenosis (mean transvalvular gradient 30 mmHg, aortic valve area 0.4 cm, significant calcification), a left ventricular ejection fraction of 35%, severe mitral regurgitation with moderate stenosis (mean transvalvular gradient 7 mmHg), with a systolic pulmonary artery pressure of 80 mmHg. Moreover, pre-interventional coronary angiography exposed a severe left main ostial stenosis and sequential subtotal heavily calcified stenosis of the left anterior descending artery . Computed tomographic angiography showed no heavy tortuosity but moderate calcification of the iliofemoral arteries. The procedure was performed under general anesthesia in our hybrid operating room. Extracorporeal membrane oxygenation was established by left femoral percutaneous cannulation using a 21-Fr venous and 15-Fr arterial cannula. Subsequently, complex percutaneous coronary intervention with implantation of two drug-eluting stents from the left main into the left anterior descending artery was performed via a right femoral arterial 7F sheath. Thereafter, a 23-mm Sapien 3 aortic valve prosthesis (Edwards, Irvine, CA, USA) was implanted via right femoral artery in the usual manner, whereby the arterial pigtail catheter for marking the aortic annulus during transcatheter aortic valve replacement was inserted over a Check-Flo® Hemostasis Assembly (Cook Medical, Bloomington, IN, USA) on a Y-adapter via the arterial extracorporeal membrane oxygenation cannula. After extracorporeal membrane oxygenation decannulation, vascular closure was easily performed using the MANTA vascular closure device in order to reduce procedural time and risk of access site complications.

Conclusions: In summary, we demonstrate the feasibility of elective prophylactic extracorporeal membrane oxygenation implementation in selected very high-risk and frail patients undergoing transcatheter aortic valve replacement and percutaneous coronary intervention in order to avoid intraprocedural complications.
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http://dx.doi.org/10.1186/s13256-020-02474-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7510274PMC
September 2020

Empagliflozin inhibits Na /H exchanger activity in human atrial cardiomyocytes.

ESC Heart Fail 2020 Sep 18. Epub 2020 Sep 18.

Department of Internal Medicine II, University Hospital Regensburg, Regensburg, Germany.

Aims: Recent clinical trials have proven gliflozins to be cardioprotective in diabetic and non-diabetic patients. However, the underlying mechanisms are incompletely understood. A potential inhibition of cardiac Na /H exchanger 1 (NHE1) has been suggested in animal models. We investigated the effect of empagliflozin on NHE1 activity in human atrial cardiomyocytes.

Methods And Results: Expression of NHE1 was assessed in human atrial and ventricular tissue via western blotting. NHE activity was measured as the maximal slope of pH recovery after NH pulse in isolated carboxy-seminaphtarhodafluor 1 (SNARF1)-acetoxymethylester-loaded murine ventricular and human atrial cardiomyocytes. NHE1 is abundantly expressed in human atrial and ventricular tissue. Interestingly, compared with patients without heart failure (HF), atrial NHE1 expression was significantly increased in patients with HF with preserved ejection fraction and atrial fibrillation. The largest increase in atrial and ventricular NHE1 expression, however, was observed in patients with end-stage HF undergoing heart transplantation. Importantly, acute exposure to empagliflozin (1 μmol/L, 10 min) significantly inhibited NHE activity to a similar extent in human atrial myocytes and mouse ventricular myocytes. This inhibition was also achieved by incubation with the well-described selective NHE inhibitor cariporide (10 μmol/L, 10 min).

Conclusions: This is the first study systematically analysing NHE1 expression in human atrial and ventricular myocardium of HF patients. We show that empagliflozin inhibits NHE in human cardiomyocytes. The extent of NHE inhibition was comparable with cariporide and may potentially contribute to the improved outcome of patients in clinical trials.
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http://dx.doi.org/10.1002/ehf2.13024DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7755005PMC
September 2020

CaMKIIδC Drives Early Adaptive Ca Change and Late Eccentric Cardiac Hypertrophy.

Circ Res 2020 Oct 21;127(9):1159-1178. Epub 2020 Aug 21.

Department of Pharmacology, University of California, Davis, CA (S.L.-H., A.W.H., S.M., B.M.W., J.B., D.M.B.).

Rationale: CaMKII (Ca-Calmodulin dependent protein kinase) δC activation is implicated in pathological progression of heart failure (HF) and CaMKIIδC transgenic mice rapidly develop HF and arrhythmias. However, little is known about early spatio-temporal Ca handling and CaMKII activation in hypertrophy and HF.

Objective: To measure time- and location-dependent activation of CaMKIIδC signaling in adult ventricular cardiomyocytes, during transaortic constriction (TAC) and in CaMKIIδC transgenic mice.

Methods And Results: We used human tissue from nonfailing and HF hearts, 4 mouse lines: wild-type, KO (CaMKIIδ-knockout), CaMKIIδC transgenic in wild-type (TG), or KO background, and wild-type mice exposed to TAC. Confocal imaging and biochemistry revealed disproportional CaMKIIδC activation and accumulation in nuclear and perinuclear versus cytosolic regions at 5 days post-TAC. This CaMKIIδ activation caused a compensatory increase in sarcoplasmic reticulum Ca content, Ca transient amplitude, and [Ca] decline rates, with reduced phospholamban expression, all of which were most prominent near and in the nucleus. These early adaptive effects in TAC were entirely mimicked in young CaMKIIδ TG mice (6-8 weeks) where no overt cardiac dysfunction was present. The (peri)nuclear CaMKII accumulation also correlated with enhanced HDAC4 (histone deacetylase) nuclear export, creating a microdomain for transcriptional regulation. At longer times both TAC and TG mice progressed to overt HF (at 45 days and 11-13 weeks, respectively), during which time the compensatory Ca transient effects reversed, but further increases in nuclear and time-averaged [Ca] and CaMKII activation occurred. CaMKIIδ TG mice lacking δB exhibited more severe HF, eccentric myocyte growth, and nuclear changes. Patient HF samples also showed greatly increased CaMKIIδ expression, especially for CaMKIIδC in nuclear fractions.

Conclusions: We conclude that in early TAC perinuclear CaMKIIδC activation promotes adaptive increases in myocyte Ca transients and nuclear transcriptional responses but that chronic progression of this nuclear Ca-CaMKIIδC axis contributes to eccentric hypertrophy and HF.
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http://dx.doi.org/10.1161/CIRCRESAHA.120.316947DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7547876PMC
October 2020

Sacubitrilat reduces pro-arrhythmogenic sarcoplasmic reticulum Ca leak in human ventricular cardiomyocytes of patients with end-stage heart failure.

ESC Heart Fail 2020 10 25;7(5):2992-3002. Epub 2020 Jul 25.

Abt. Kardiologie und Pneumologie/Herzzentrum, Georg-August-Universität Göttingen, Göttingen, Germany.

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 cycling remain elusive.

Methods And Results: Confocal microscopy (Fluo-4 AM) was used to investigate pro-arrhythmogenic sarcoplasmic reticulum (SR) Ca 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 release, SR Ca load, and Ca -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 -spark frequency (CaSpF) nor pro-arrhythmogenic SR Ca 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 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 Ca leak by 76 ± 5%; n = 101/4 vs. 108/4, P < 0.01 each), whereas sole Val treatment did not. Systolic Ca release, SR Ca load, and Ca -transient kinetics including SERCA activity (k ) 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 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 homeostasis in human end-stage HF by reducing pro-arrhythmogenic SR Ca leak without acutely affecting systolic Ca release and inotropy. These effects might contribute to the mortality benefits observed in the PARADIGM-HF trial.
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http://dx.doi.org/10.1002/ehf2.12918DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7586991PMC
October 2020

The molecular mechanisms associated with the physiological responses to inflammation and oxidative stress in cardiovascular diseases.

Biophys Rev 2020 Aug 21;12(4):947-968. Epub 2020 Jul 21.

Department of Molecular and Experimental Cardiology, Ruhr University Bochum, MABF 01/597, 44780, Bochum, Germany.

The complex physiological signal transduction networks that respond to the dual challenges of inflammatory and oxidative stress are major factors that promote the development of cardiovascular pathologies. These signaling networks contribute to the development of age-related diseases, suggesting crosstalk between the development of aging and cardiovascular disease. Inhibition and/or attenuation of these signaling networks also delays the onset of disease. Therefore, a concept of targeting the signaling networks that are involved in inflammation and oxidative stress may represent a novel treatment paradigm for many types of heart disease. In this review, we discuss the molecular mechanisms associated with the physiological responses to inflammation and oxidative stress especially in heart failure with preserved ejection fraction and emphasize the nature of the crosstalk of these signaling processes as well as possible therapeutic implications for cardiovascular medicine.
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http://dx.doi.org/10.1007/s12551-020-00742-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7429613PMC
August 2020

Contribution of the neuronal sodium channel Na1.8 to sodium- and calcium-dependent cellular proarrhythmia.

J Mol Cell Cardiol 2020 07 11;144:35-46. Epub 2020 May 11.

Department of Cardiology and Pneumology, University Hospital, Georg-August University Göttingen, and DZHK (German Center for Cardiovascular Research), partner site Göttingen, Germany; Department of Internal Medicine II, University Medical Center Regensburg, Regensburg, Germany. Electronic address:

Objective: In myocardial pathology such as heart failure a late sodium current (I) augmentation is known to be involved in conditions of arrhythmogenesis. However, the underlying mechanisms of the I generation are not entirely understood. By now evidence is growing that non-cardiac sodium channel isoforms could also be involved in the I generation. The present study investigates the contribution of the neuronal sodium channel isoform Na1.8 to arrhythmogenesis in a clearly-defined setting of enhanced I by using anemone toxin II (ATX-II) in the absence of structural heart disease.

Methods: Electrophysiological experiments were performed in order to measure I, action potential duration (APD), SR-Ca-leak and cellular proarrhythmic triggers in ATX-II exposed wild-type (WT) and SCN10A mice cardiomyocytes. In addition, WT cardiomyocytes were stimulated with ATX-II in the presence or absence of Na1.8 inhibitors. I was measured by using the whole cell patch clamp method.

Results: In WT cardiomyocytes exposure to ATX-II augmented I prolonged APD, increased SR-Ca-leak and induced proarrhythmic triggers such as early afterdepolarizations (EADs) and Ca-waves. All of them could be significantly reduced by applying Na1.8 blockers PF-01247324 and A-803467. Both blockers had no relevant effects on cellular electrophysiology of SCN10A cardiomyocytes. Moreover, in SCN10A-cardiomyocytes, the ATX-II-dependent increase in I, SR-Ca-leak and APD prolongation was less than in WT and comparable to the results which were obtained with WT cardiomyocytes being exposed to ATX-II and Na1.8 inhibitors in parallel. Moreover, we found a decrease in reverse mode NCX current and reduced CaMKII-dependent RyR2-phosphorylation after application of PF-01247324 as an underlying explanation for the Na-mediated Ca-dependent proarrhythmic triggers.

Conclusion: The current findings demonstrate that Na1.8 is a significant contributor for I-induced arrhythmic triggers. Therefore, Na1.8 inhibition under conditions of an enhanced I constitutes a promising antiarrhythmic strategy which merits further investigation.
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http://dx.doi.org/10.1016/j.yjmcc.2020.05.002DOI Listing
July 2020

Dantrolene reduces CaMKIIδC-mediated atrial arrhythmias.

Europace 2020 07;22(7):1111-1118

Department of Internal Medicine II, University Medical Center Regensburg, Franz-Josef-Strauß-Allee 11, 93053 Regensburg, Germany.

Aims: In atrial fibrillation (AF), an increased diastolic Ca2+ leak from the sarcoplasmic reticulum (SR) mediated by calcium/calmodulin-dependent-protein-kinaseIIδC (CaMKII) can serve as a substrate for arrhythmia induction and persistence. Dantrolene has been shown to stabilize the cardiac ryanodine-receptor. This study investigated the effects of dantrolene on arrhythmogenesis in human and mouse atria with enhanced CaMKII activity.

Methods And Results: Human atrial cardiomyocytes (CMs) were isolated from patients with AF. To investigate CaMKII-mediated arrhythmogenesis, atrial CMs from mice overexpressing CaMKIIδC (TG) and the respective wildtype (WT) were studied using confocal microscopy (Fluo-4), patch-clamp technique, and in vivo atrial catheter-based burst stimulations. Dantrolene potently reduced Ca2+ spark frequency (CaSpF) and diastolic SR Ca2+ leak in AF CMs. Additional CaMKII inhibition did not further reduce CaSpF or leak compared to dantrolene alone. While the increased SR CaSpF and leak in TG mice were reduced by dantrolene, no effects could be detected in WT. Dantrolene also potently reduced the pathologically enhanced frequency of diastolic SR Ca2+ waves in TG without having effects in WT. As an increased diastolic SR Ca2+ release can induce a depolarizing transient inward current, we could demonstrate that the incidence of afterdepolarizations in TG, but not in WT, mice was significantly diminished in the presence of dantrolene. To translate these findings into an in vivo situation we could show that dantrolene strongly suppressed the inducibility of AF in vivo in TG mice.

Conclusion: Dantrolene reduces CaMKII-mediated atrial arrhythmogenesis and may therefore constitute an interesting antiarrhythmic drug for treating patients with atrial arrhythmias driven by an enhanced CaMKII activity, such as AF.
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http://dx.doi.org/10.1093/europace/euaa079DOI Listing
July 2020

Empagliflozin improves endothelial and cardiomyocyte function in human heart failure with preserved ejection fraction via reduced pro-inflammatory-oxidative pathways and protein kinase Gα oxidation.

Cardiovasc Res 2021 Jan;117(2):495-507

Department of Molecular and Experimental Cardiology, Ruhr University Bochum, Bochum, Germany.

Aims: Sodium-glucose-cotransporter-2 inhibitors showed favourable cardiovascular outcomes, but the underlying mechanisms are still elusive. This study investigated the mechanisms of empagliflozin in human and murine heart failure with preserved ejection fraction (HFpEF).

Methods And Results: The acute mechanisms of empagliflozin were investigated in human myocardium from patients with HFpEF and murine ZDF obese rats, which were treated in vivo. As shown with immunoblots and ELISA, empagliflozin significantly suppressed increased levels of ICAM-1, VCAM-1, TNF-α, and IL-6 in human and murine HFpEF myocardium and attenuated pathological oxidative parameters (H2O2, 3-nitrotyrosine, GSH, lipid peroxide) in both cardiomyocyte cytosol and mitochondria in addition to improved endothelial vasorelaxation. In HFpEF, we found higher oxidative stress-dependent activation of eNOS leading to PKGIα oxidation. Interestingly, immunofluorescence imaging and electron microscopy revealed that oxidized PKG1α in HFpEF appeared as dimers/polymers localized to the outer-membrane of the cardiomyocyte. Empagliflozin reduced oxidative stress/eNOS-dependent PKGIα oxidation and polymerization resulting in a higher fraction of PKGIα monomers, which translocated back to the cytosol. Consequently, diminished NO levels, sGC activity, cGMP concentration, and PKGIα activity in HFpEF increased upon empagliflozin leading to improved phosphorylation of myofilament proteins. In skinned HFpEF cardiomyocytes, empagliflozin improved cardiomyocyte stiffness in an anti-oxidative/PKGIα-dependent manner. Monovariate linear regression analysis confirmed the correlation of oxidative stress and PKGIα polymerization with increased cardiomyocyte stiffness and diastolic dysfunction of the HFpEF patients.

Conclusion: Empagliflozin reduces inflammatory and oxidative stress in HFpEF and thereby improves the NO-sGC-cGMP-cascade and PKGIα activity via reduced PKGIα oxidation and polymerization leading to less pathological cardiomyocyte stiffness.
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http://dx.doi.org/10.1093/cvr/cvaa123DOI Listing
January 2021

Serelaxin alleviates cardiac fibrosis through inhibiting endothelial-to-mesenchymal transition via RXFP1.

Theranostics 2020 4;10(9):3905-3924. Epub 2020 Mar 4.

Department of Cardiology and Pneumology, University Medical Center of Göttingen, Georg-August University, Göttingen, Germany.

: Cardiac fibrosis is an integral constituent of every form of chronic heart disease, and persistence of fibrosis reduces tissue compliance and accelerates the progression to heart failure. Relaxin-2 is a human hormone, which has various physiological functions such as mediating renal vasodilation in pregnancy. Its recombinant form Serelaxin has recently been tested in clinical trials as a therapy for acute heart failure but did not meet its primary endpoints. The aim of this study is to examine whether Serelaxin has an anti-fibrotic effect in the heart and therefore could be beneficial in chronic heart failure. : We utilized two different cardiac fibrosis mouse models (ascending aortic constriction (AAC) and Angiotensin II (ATII) administration via osmotic minipumps) to assess the anti-fibrotic potential of Serelaxin. Histological analysis, immunofluorescence staining and molecular analysis were performed to assess the fibrosis level and indicate endothelial cells which are undergoing EndMT. TGFβ1-induced endothelial-to-mesenchymal transition (EndMT) assays were performed in human coronary artery endothelial cells and mouse cardiac endothelial cells (MCECs) and were examined using molecular methods. Chromatin immunoprecipitation-qPCR assay was utilized to identify the Serelaxin effect on chromatin remodeling in the promoter region in MCECs. : Our results demonstrate a significant and dose-dependent anti-fibrotic effect of Serelaxin in the heart in both models. We further show that Serelaxin mediates this effect, at least in part, through inhibition of EndMT through the endothelial Relaxin family peptide receptor 1 (RXFP1). We further demonstrate that Serelaxin administration is able to increase its own receptor expression (RXFP1) through epigenetic regulation in form of histone modifications by attenuating TGFβ-pSMAD2/3 signaling in endothelial cells. : This study is the first to identify that Serelaxin increases the expression of its own receptor RXFP1 and that this mediates the inhibition of EndMT and cardiac fibrosis, suggesting that Serelaxin may have a beneficial effect as anti-fibrotic therapy in chronic heart failure.
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http://dx.doi.org/10.7150/thno.38640DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7086357PMC
March 2020

Novel re-expression of L-type calcium channel Ca1.3 in left ventricles of failing human heart.

Heart Rhythm 2020 Jul 27;17(7):1193-1197. Epub 2020 Feb 27.

Cardiovascular Research Program, VA New York Harbor Healthcare System, Brooklyn, New York; Departments of Medicine, Cell Biology and Pharmacology, State University of New York Downstate Medical Center, Brooklyn, New York; Cardiology Division, Department of Medicine, New York University School of Medicine, New York, New York. Electronic address:

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http://dx.doi.org/10.1016/j.hrthm.2020.02.025DOI Listing
July 2020

Inhibition of Na1.8 prevents atrial arrhythmogenesis in human and mice.

Basic Res Cardiol 2020 02 20;115(2):20. Epub 2020 Feb 20.

Department of Internal Medicine II, University Medical Center Regensburg, Franz-Josef-Strauß-Allee 11, 93053, Regensburg, Germany.

Pharmacologic approaches for the treatment of atrial arrhythmias are limited due to side effects and low efficacy. Thus, the identification of new antiarrhythmic targets is of clinical interest. Recent genome studies suggested an involvement of SCN10A sodium channels (Na1.8) in atrial electrophysiology. This study investigated the role and involvement of Na1.8 (SCN10A) in arrhythmia generation in the human atria and in mice lacking Na1.8. Na1.8 mRNA and protein were detected in human atrial myocardium at a significant higher level compared to ventricular myocardium. Expression of Na1.8 and Na1.5 did not differ between myocardium from patients with atrial fibrillation and sinus rhythm. To determine the electrophysiological role of Na1.8, we investigated isolated human atrial cardiomyocytes from patients with sinus rhythm stimulated with isoproterenol. Inhibition of Na1.8 by A-803467 or PF-01247324 showed no effects on the human atrial action potential. However, we found that Na1.8 significantly contributes to late Na current and consequently to an increased proarrhythmogenic diastolic sarcoplasmic reticulum Ca leak in human atrial cardiomyocytes. Selective pharmacological inhibition of Na1.8 potently reduced late Na current, proarrhythmic diastolic Ca release, delayed afterdepolarizations as well as spontaneous action potentials. These findings could be confirmed in murine atrial cardiomyocytes from wild-type mice and also compared to SCN10A mice (genetic ablation of Na1.8). Pharmacological Na1.8 inhibition showed no effects in SCN10A mice. Importantly, in vivo experiments in SCN10A mice showed that genetic ablation of Na1.8 protects against atrial fibrillation induction. This study demonstrates that Na1.8 is expressed in the murine and human atria and contributes to late Na current generation and cellular arrhythmogenesis. Blocking Na1.8 selectively counteracts this pathomechanism and protects against atrial arrhythmias. Thus, our translational study reveals a new selective therapeutic target for treating atrial arrhythmias.
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http://dx.doi.org/10.1007/s00395-020-0780-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7033079PMC
February 2020

Skeletal muscle alterations in tachycardia-induced heart failure are linked to deficient natriuretic peptide signalling and are attenuated by RAS-/NEP-inhibition.

PLoS One 2019 4;14(12):e0225937. Epub 2019 Dec 4.

Department of Internal Medicine II, University Hospital Regensburg, Regensburg, Germany.

Background: Heart failure induced cachexia is highly prevalent. Insights into disease progression are lacking.

Methods: Early state of left ventricular dysfunction (ELVD) and symptomatic systolic heart failure (HF) were both induced in rabbits by tachypacing. Tissue of limb muscle (LM) was subjected to histologic assessment. For unbiased characterisation of early and late myopathy, a proteomic approach followed by computational pathway-analyses was performed and combined with pathway-focused gene expression analyses. Specimen of thoracic diaphragm (TD) served as control for inactivity-induced skeletal muscle alterations. In a subsequent study, inhibition of the renin-angiotensin-system and neprilysin (RAS-/NEP) was compared to placebo.

Results: HF was accompanied by loss of protein content (8.7±0.4% vs. 7.0±0.5%, mean±SEM, control vs. HF, p<0.01) and a slow-to-fast fibre type switch, establishing hallmarks of cachexia. In ELVD, the enzymatic set-up of LM and TD shifted to a catabolic state. A disturbed malate-aspartate shuttle went well with increased enzymes of glycolysis, forming the enzymatic basis for enforced anoxic energy regeneration. The histological findings and the pathway analysis of metabolic results drew the picture of suppressed PGC-1α signalling, linked to the natriuretic peptide system. In HF, natriuretic peptide signalling was desensitised, as confirmed by an increase in the ratio of serum BNP to tissue cGMP (57.0±18.6pg/ml/nM/ml vs. 165.8±16.76pg/ml/nM/ml, p<0.05) and a reduced expression of natriuretic peptide receptor-A. In HF, combined RAS-/NEP-inhibition prevented from loss in protein content (8.7±0.3% vs. 6.0±0.6% vs. 8.3±0.9%, Baseline vs. HF-Placebo vs. HF-RAS/NEP, p<0.05 Baseline vs. HF-Placebo, p = 0.7 Baseline vs. HF-RAS/NEP).

Conclusions: Tachypacing-induced heart failure entails a generalised myopathy, preceding systolic dysfunction. The characterisation of "pre-cachectic" state and its progression is feasible. Early enzymatic alterations of LM depict a catabolic state, rendering LM prone to futile substrate metabolism. A combined RAS-/NEP-inhibition ameliorates cardiac-induced myopathy independent of systolic function, which could be linked to stabilised natriuretic peptide/cGMP/PGC-1α signalling.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0225937PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6892497PMC
March 2020

The lipid droplet-associated protein ABHD5 protects the heart through proteolysis of HDAC4.

Nat Metab 2019 11 15;1(11):1157-1167. Epub 2019 Nov 15.

Institute of Experimental Cardiology, University of Heidelberg, Heidelberg, Germany.

Catecholamines stimulate the first step of lipolysis by PKA-dependent release of the lipid droplet-associated protein ABHD5 from perilipin to co-activate the lipase ATGL. Here, we unmask a yet unrecognized proteolytic and cardioprotective function of ABHD5. ABHD5 acts and as a serine protease cleaving HDAC4. Through the production of an N-terminal polypeptide of HDAC4 (HDAC4-NT), ABHD5 inhibits MEF2-dependent gene expression and thereby controls glucose handling. ABHD5-deficiency leads to neutral lipid storage disease in mice. Cardiac-specific gene therapy of HDAC4-NT does not protect from intra-cardiomyocyte lipid accumulation but strikingly from heart failure, thereby challenging the concept of lipotoxicity-induced heart failure. ABHD5 levels are reduced in failing human hearts and murine transgenic ABHD5 expression protects from pressure-overload induced heart failure. These findings represent a conceptual advance by connecting lipid with glucose metabolism through HDAC4 proteolysis and enable new translational approaches to treat cardiometabolic disease.
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http://dx.doi.org/10.1038/s42255-019-0138-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6861130PMC
November 2019

CaM kinase II regulates cardiac hemoglobin expression through histone phosphorylation upon sympathetic activation.

Proc Natl Acad Sci U S A 2019 10 16;116(44):22282-22287. Epub 2019 Oct 16.

Department of Pharmacology and Toxicology, Medical Faculty, Technische Universität Dresden, 01307 Dresden, Germany;

Sympathetic activation of β-adrenoreceptors (β-AR) represents a hallmark in the development of heart failure (HF). However, little is known about the underlying mechanisms of gene regulation. In human ventricular myocardium from patients with end-stage HF, we found high levels of phosphorylated histone 3 at serine-28 (H3S28p). H3S28p was increased by inhibition of the catecholamine-sensitive protein phosphatase 1 and decreased by β-blocker pretreatment. By a series of in vitro and in vivo experiments, we show that the β-AR downstream protein kinase CaM kinase II (CaMKII) directly binds and phosphorylates H3S28. Whereas, in CaMKII-deficient myocytes, acute catecholaminergic stimulation resulted in some degree of H3S28p, sustained catecholaminergic stimulation almost entirely failed to induce H3S28p. Genome-wide analysis of CaMKII-mediated H3S28p in response to chronic β-AR stress by chromatin immunoprecipitation followed by massive genomic sequencing led to the identification of CaMKII-dependent H3S28p target genes. Forty percent of differentially H3S28p-enriched genomic regions were associated with differential, mostly increased expression of the nearest genes, pointing to CaMKII-dependent H3S28p as an activating histone mark. Remarkably, the adult hemoglobin genes showed an H3S28p enrichment close to their transcriptional start or end sites, which was associated with increased messenger RNA and protein expression. In summary, we demonstrate that chronic β-AR activation leads to CaMKII-mediated H3S28p in cardiomyocytes. Thus, H3S28p-dependent changes may play an unexpected role for cardiac hemoglobin regulation in the context of sympathetic activation. These data also imply that CaMKII may be a yet unrecognized stress-responsive regulator of hematopoesis.
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http://dx.doi.org/10.1073/pnas.1816521116DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6825262PMC
October 2019

KLF15-Wnt-Dependent Cardiac Reprogramming Up-Regulates SHISA3 in the Mammalian Heart.

J Am Coll Cardiol 2019 10;74(14):1804-1819

Institute of Pharmacology and Toxicology, University Medical Center Goettingen, Georg-August University, Goettingen, Germany; DZHK (German Center for Cardiovascular Research), partner site Goettingen, Germany. Electronic address:

Background: The combination of cardiomyocyte (CM) and vascular cell (VC) fetal reprogramming upon stress culminates in end-stage heart failure (HF) by mechanisms that are not fully understood. Previous studies suggest KLF15 as a key regulator of CM hypertrophy.

Objectives: This study aimed to characterize the impact of KLF15-dependent cardiac transcriptional networks leading to HF progression, amenable to therapeutic intervention in the adult heart.

Methods: Transcriptomic bioinformatics, phenotyping of Klf15 knockout mice, Wnt-signaling-modulated hearts, and pressure overload and myocardial ischemia models were applied. Human KLF15 knockout embryonic stem cells and engineered human myocardium, and human samples were used to validate the relevance of the identified mechanisms.

Results: The authors identified a sequential, postnatal transcriptional repression mediated by KLF15 of pathways implicated in pathological tissue remodeling, including distinct Wnt-pathways that control CM fetal reprogramming and VC remodeling. The authors further uncovered a vascular program induced by a cellular crosstalk initiated by CM, characterized by a reduction of KLF15 and a concomitant activation of Wnt-dependent transcriptional signaling. Within this program, a so-far uncharacterized cardiac player, SHISA3, primarily expressed in VCs in fetal hearts and pathological remodeling was identified. Importantly, the KLF15 and Wnt codependent SHISA3 regulation was demonstrated to be conserved in mouse and human models.

Conclusions: The authors unraveled a network interplay defined by KLF15-Wnt dynamics controlling CM and VC homeostasis in the postnatal heart and demonstrated its potential as a cardiac-specific therapeutic target in HF. Within this network, they identified SHISA3 as a novel, evolutionarily conserved VC marker involved in pathological remodeling in HF.
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http://dx.doi.org/10.1016/j.jacc.2019.07.076DOI Listing
October 2019

A High-Throughput Method as a Diagnostic Tool for HIV Detection in Patient-Specific Induced Pluripotent Stem Cells Generated by Different Reprogramming Methods.

Stem Cells Int 2019 5;2019:2181437. Epub 2019 Aug 5.

Clinic for Cardiology and Pneumology, University Medical Center Goettingen, Goettingen, Germany.

Induced pluripotent stem cells (iPSCs) provide a unique opportunity for generation of patient-specific cells for use in translational purposes. We aimed to compare iPSCs generated by different reprogramming methods regarding their reprogramming efficiency, pluripotency capacity, and the possibility to use high-throughput PCR-based methods for detection of human pathogenic viruses. iPSCs from skin fibroblasts (FB), peripheral blood mononuclear cells (PBMCs), or mesenchymal stem cells (MSCs) were generated by using three different reprogramming systems including chromosomal integrating and nonintegrating methods. Reprogramming efficiencies were in accordance with the literature, indicating that the parental cell type and the reprogramming method play a major role for the reprogramming efficiencies (FB: STEMCCA: 1.30 ± 0.18, Sendai virus: 1.37 ± 0.01, and episomal plasmids: 0.04 ± 0.02; PBMCs: Sendai virus: 0.002 ± 0.001, episomal plasmids: 0) but result in the same characteristics of pluripotency. We found the highest reprogramming efficiencies for MSC with 3.32 ± 1.2 by using episomal plasmids. Since GMP standard working procedures and screening units need virus contamination-free cell lines, we studied HIV-1 contamination in the generated iPSCs. We used the high-throughput cobas® 6800/8800 system, which is normally used for detection of HIV-1 in plasma of patients, and found that footprint-free reprogramming methods as episomal plasmids and Sendai virus are useful for the described virus detection method. This fast, cost-effective, robust, and reliable assay demonstrates the feasibility to use high-throughput PCR-based methods for detection of human pathogenic viruses in ps-iPSC lines that were generated with nongenome integrating reprogramming methods.
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http://dx.doi.org/10.1155/2019/2181437DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6701349PMC
August 2019

Junctophilin-2 expression rescues atrial dysfunction through polyadic junctional membrane complex biogenesis.

JCI Insight 2019 06 20;4(12). Epub 2019 Jun 20.

Heart Research Center Göttingen, Department of Cardiology & Pneumology, University Medical Center Göttingen, Göttingen, Germany.

Atrial dysfunction is highly prevalent and associated with increased severity of heart failure. While rapid excitation-contraction coupling depends on axial junctions in atrial myocytes, the molecular basis of atrial loss of function remains unclear. We identified approximately 5-fold lower junctophilin-2 levels in atrial compared with ventricular tissue in mouse and human hearts. In atrial myocytes, this resulted in subcellular expression of large junctophilin-2 clusters at axial junctions, together with highly phosphorylated ryanodine receptor (RyR2) channels. To investigate the contribution of junctophilin-2 to atrial pathology in adult hearts, we developed a cardiomyocyte-selective junctophilin-2-knockdown model with 0 mortality. Junctophilin-2 knockdown in mice disrupted atrial RyR2 clustering and contractility without hypertrophy or interstitial fibrosis. In contrast, aortic pressure overload resulted in left atrial hypertrophy with decreased junctophilin-2 and RyR2 expression, disrupted axial junctions, and atrial fibrosis. Whereas pressure overload accrued atrial dysfunction and heart failure with 40% mortality, additional junctophilin-2 knockdown greatly exacerbated atrial dysfunction with 100% mortality. Strikingly, transgenic junctophilin-2 overexpression restored atrial contractility and survival through de novo biogenesis of polyadic junctional membrane complexes maintained after pressure overload. Our data show a central role of junctophilin-2 cluster disruption in atrial hypertrophy and identify transgenic augmentation of junctophilin-2 as a disease-mitigating rationale to improve atrial dysfunction and prevent heart failure deterioration.
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http://dx.doi.org/10.1172/jci.insight.127116DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6629097PMC
June 2019

[Drug-drug interactions you should know!]

Fortschr Neurol Psychiatr 2019 May 24;87(5):320-332. Epub 2019 May 24.

Drug-drug interactions (DDI) represent a significant problem in modern medicine. The number of patients with multi-morbidity, who take multiple drugs, is constantly increasing (polypharmacy). The related exponential increase in potential DDI is almost incomprehensible. In this article, we review pharmacodynamic DDI and provide clinically relevant examples. In addition, we extensively review pharmakokinetic DDI (e. g. through the cytochrome P450-system or p-glycoproteins) that can modify the plasma concentration of many compounds, thereby also increasing the likelihood of unwanted side effects. Finally we provide tools, which may help clinicians in their daily practice to identify and avoid potential DDI. In the context of an ageing society receiving polypharmacy, a better awareness of DDI and of strategies to prevent them is expected to reduce mortality and morbidity.
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http://dx.doi.org/10.1055/a-0894-9924DOI Listing
May 2019

Inhibition of the Hypoxia-Inducible Factor 1α-Induced Cardiospecific HERNA1 Enhance-Templated RNA Protects From Heart Disease.

Circulation 2019 06 29;139(24):2778-2792. Epub 2019 Mar 29.

MRC Clinical Sciences Centre, Imperial College London, United Kingdom (C.B., S.K., J.K.).

Background: Enhancers are genomic regulatory elements conferring spatiotemporal and signal-dependent control of gene expression. Recent evidence suggests that enhancers can generate noncoding enhancer RNAs, but their (patho)biological functions remain largely elusive.

Methods: We performed chromatin immunoprecipitation-coupled sequencing of histone marks combined with RNA sequencing of left ventricular biopsies from experimental and genetic mouse models of human cardiac hypertrophy to identify transcripts revealing enhancer localization, conservation with the human genome, and hypoxia-inducible factor 1α dependence. The most promising candidate, hypoxia-inducible enhancer RNA ( HERNA)1, was further examined by investigating its capacity to modulate neighboring coding gene expression by binding to their gene promoters by using chromatin isolation by RNA purification and λN-BoxB tethering-based reporter assays. The role of HERNA1 and its neighboring genes for pathological stress-induced growth and contractile dysfunction, and the therapeutic potential of HERNA1 inhibition was studied in gapmer-mediated loss-of-function studies in vitro using human induced pluripotent stem cell-derived cardiomyocytes and various in vivo models of human pathological cardiac hypertrophy.

Results: HERNA1 is robustly induced on pathological stress. Production of HERNA1 is initiated by direct hypoxia-inducible factor 1α binding to a hypoxia-response element in the histoneH3-lysine27acetylation marks-enriched promoter of the enhancer and confers hypoxia responsiveness to nearby genes including synaptotagmin XVII, a member of the family of membrane-trafficking and Ca-sensing proteins and SMG1, encoding a phosphatidylinositol 3-kinase-related kinase. Consequently, a substrate of SMG1, ATP-dependent RNA helicase upframeshift 1, is hyperphoshorylated in a HERNA1- and SMG1-dependent manner. In vitro and in vivo inactivation of SMG1 and SYT17 revealed overlapping and distinct roles in modulating cardiac hypertrophy. Finally, in vivo administration of antisense oligonucleotides targeting HERNA1 protected mice from stress-induced pathological hypertrophy. The inhibition of HERNA1 postdisease development reversed left ventricular growth and dysfunction, resulting in increased overall survival.

Conclusions: HERNA1 is a novel heart-specific noncoding RNA with key regulatory functions in modulating the growth, metabolic, and contractile gene program in disease, and reveals a molecular target amenable to therapeutic exploitation.
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http://dx.doi.org/10.1161/CIRCULATIONAHA.118.036769DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6571183PMC
June 2019

Protein kinase/phosphatase balance mediates the effects of increased late sodium current on ventricular calcium cycling.

Basic Res Cardiol 2019 02 20;114(2):13. Epub 2019 Feb 20.

Abt. Kardiologie und Pneumologie/Herzzentrum, Georg-August-Universität Göttingen, Robert-Koch-Str. 40, 37075, Göttingen, Germany.

Increased late sodium current (late I) is an important arrhythmogenic trigger in cardiac disease. It prolongs cardiac action potential and leads to an increased SR Ca leak. This study investigates the contribution of Ca/Calmodulin-dependent kinase II (CaMKII), protein kinase A (PKA) and conversely acting protein phosphatases 1 and 2A (PP1, PP2A) to this subcellular crosstalk. Augmentation of late I (ATX-II) in murine cardiomyocytes led to an increase of diastolic Ca spark frequency and amplitudes of Ca transients but did not affect SR Ca load. Interestingly, inhibition of both, CaMKII and PKA, attenuated the late I-dependent induction of the SR Ca leak. PKA inhibition additionally reduced the amplitudes of systolic Ca transients. FRET-measurements revealed increased levels of cAMP upon late I augmentation, which could be prevented by simultaneous inhibition of Na/Ca-exchanger (NCX) suggesting that PKA is activated by Ca-dependent cAMP-production. Whereas inhibition of PP2A showed no effect on late I-dependent alterations of Ca cycling, additional inhibition of PP1 further increased the SR Ca leak. In line with this, selective activation of PP1 yielded a strong reduction of the late I-induced SR Ca leak and did not affect systolic Ca release. This study indicates that phosphatase/kinase-balance is perturbed upon increased Na influx leading to disruption of ventricular Ca cycling via CaMKII- and PKA-dependent pathways. Importantly, an activation of PP1 at RyR2 may represent a promising new toehold to counteract pathologically increased kinase activity.
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http://dx.doi.org/10.1007/s00395-019-0720-7DOI Listing
February 2019