Highlights Basic and Translational Science

Transcription

1 Highlights Basic and Translational Science Excitation-Contraction Coupling Frank R. Heinzel Medical University of Graz, Austria

2 Acknowledgments Ole Kemi, University of Glasgow, UK Julia Sprenger, University of Göttingen, Germany Georgios Kararigas, Charite University Hospital, Berlin, Germany Constantijn Franssen, VUmc Amsterdam, The Netherlands Judit Kalász, University of Debrecen, Hungary Uwe Primessnig and Senka Ljubojevic, University of Graz, Austria László Nagy, University of Debrecen, Hungary

3 Overview Gender aspects in ECC PMCA1 and 4 in the heart Cardiomyocyte Ca 2+ changes in HFPEF Effect of exercise on Ca 2+ alternans post MI Local camp regulation in SERCA microdomain L-OR-2828, a new Ca 2+ sensitizer

4 Background: Gender Electrophysiology Women have a higher resting heart rate than men independent of differences in autonomous tone (Jose and Collison 1970, Burke et al. 1996). Women have a slightly longer QT interval (~20 ms longer than in men) (Bazett, 1920; Molnar et al. 1996). Women are more likely to develop TdP tachycardias (Lehmann et al. 1996, Makkar et al. 1993)

5 Sex-specific ventricular transcriptional profiles and calcium current densities in patients with dilated cardiomyopathy G Kararigas, C E Molina, H Summer, P E Molina, I Julia, I Baczko, S Golz, R Hetzer, V Regitz-Zagrosek Charite University Hospital - Berlin - Germany, 2ICCC-CSIC, Hospital Santa Creu i Sant Pau - Barcelona - Spain, 3Bayer HealthCare - Wuppertal - Germany, 4Hospital de la Santa Creu i Sant Pau, Department of Cardiac Surgery - Barcelona - Spain, 5University of Szeged - Szeged - Hungary, 6German Heart Institute Berlin - Berlin - Germany,

6 Gender-Specific Gene Regulation in Heart Failure Biopsies: DCM: N= 5 female ; N=5 male NF : N=8 female; N=10 male N regulated gene clusters vs. non-failing up down Single gene differential expression False discovery rate (FDR)-adjusted P < 0.01 LV samples of men (n = 5) and women (n = 5) with end-stage non-ischaemic DCM were compared with LV samples of men (n = 10) and women (n = 8) with no cardiovascular disorder G Kararigas

7 Gender-Specific Regulation of Ca 2+ Signalling Genes 5-HT 6 receptor Prostagl. 6 receptor Purinergic P2X ion channel PLC β2 T-type Ca channel Although Ca 2+ signalling was induced in both sexes, male tissues had a significantly higher induction with a ca. 30% of genes encoding ion channels, accessory beta subunits and regulatory proteins being more induced in male than in female tissues. G Kararigas

8 Higher L-type Ca 2+ Current Density in Males with HF No sex differences in SR Ca 2+ load. G Kararigas

9 Previous Study Verkerk et al. Int Heart J. 2005;46: Etiology : DCM G Kararigas

10 Summary Sex-specific ventricular transcriptional profiles and calcium current densities in patients with dilated cardiomyopathy The study offers a novel sex-specific aspect of gene regulation in the human failing heart. L-type Ca 2+ channel regulation in heart failure is complex and includes gender-specific differences in function. G Kararigas

11 Independent roles for PMCA1 and 4 in the development of left ventricular hypertrophy and failure N Stafford, M Zi, M Shaheen, TM Mohamed, S Cook, S Prehar, L Neyses, EJ Cartwright University of Manchester, UK

12 Background Both isoforms 1 and 4 of PMCA are downregulated in failing human and rodent hearts. PMCA4 modulates cardiac hypertrophy regulates β-adrenergic signalling Cartwright,, Neyses. Sci China Life Sci. 2011;54:691-8.

13 Aim Study the role of PMCA1 and PMCA4 in cardiac remodeling Methods Generated cardiomyocyte-specific knockout mice PMCA1 -/- PMCA4 -/- PMCA1+4 -/- TAC banding (2 weeks), echocard., morphometry, cardiac myocyte Ca2+ transients N Stafford

14 Results: Baseline Morphology TAC (2 wks) (vs. WT TAC) Function/ Histology PMCA1 -/- phenotype change rapidly decomp. hypertrophy congestion, apopt. extensive fibrosis slowed CaT decay PMCA4 -/- phenotype change strongly attenuated hypertrophy (-86% vs. WT TAC) preserved syst./diast. function PMCA1+4 -/- phenotype change slight hypertrophy preserved EF reduced firbrosis 2% of cytosolic Ca2+ extrusion (PMCA1) N Stafford

15 Summary Novel evidence of isoform-specific roles for PMCA1 and 4 in cardiac muscle, both capable of influencing the pathological progression of cardiac hypertrophy. PMCA1 may be critical in adapting to the increased demands placed on the heart during pressure overload, whilst the inhibition of PMCA4 may negate the need to adapt altogether and could be a potential target for future antihypertrophic therapies. N Stafford

16 Impaired cardiomyocyte relaxation in a rat model of compensated renal failure and diastolic heart failure U. Primessnig, S. Pfeiffer, P. Wakula, M.Stipacek, T. Rau, T. Stojakovic, B. Pieske, F.R. Heinzel Medical University of Graz, Austria

17 Aim to study cellular mechanisms of contractile dysfunction in a model of diastolic heart failure U. Primessnig

18 Model subtotal (5/6) nephrectomy in rats U. Primessnig

19 Results renal impairment, hypertension, hypertrophy U. Primessnig

20 Results HFPEF U. Primessnig

21 Results LV cardiomyocyte : slowed relaxation NXT U. Primessnig

22 Results LV cardiomyocyte : slowed Ca decay U. Primessnig

23 TAU (sec.) Results LV cardiomyocyte : reduced NCX forward U. Primessnig

24 Results NCX1 protein expression U. Primessnig

25 Summary Subtotal nephrectomy (NXT) in rats induces stable compensated renal failure and heart failure with preserved ejection fraction (HFPEF). Ca2+- mediated relaxation is prolonged at the level of cardiomyocytes. NCX1 forward mode activity is reduced despite increased NCX protein expression suggesting increased reverse mode activity of the NCX. U. Primessnig

26 Cardiomyocyte Contractile and Ca 2+ Handling Breakdown at High Stimulation Frequencies in Post-Myocardial Infarction Heart failure is Reversed by Exercise Training Ole J Kemi, Alex S. Johnston, Michael Dunne, Godfrey Smith University of Glasgow, UK

27 Background Alternans indicates beat-to-beat oscillation in contraction amplitude, Ca 2+ transient amplitude and/or action potential duration Alternans occurs at increased (pacing) frequencies. Propensity for alternans has been associated with an increased risk of arrhythmias. Alternans is observed with myocardial ischemia.

28 Model LAD ligation in Wistar rats Exercise training (TRN): intensity-controlled aerobic treadmill running at 90% of maximal oxygen uptake initiated 1-month post-mi, for a period of 2-3 months. Sacrifice : 3-4 months post MI Isolation of LV cardiomyocytes, Ca2+ indicators Fura-2 or Fluo-4 O. Kemi

29 Results : intracellular Ca 2+ transients O. Kemi

30 Results : Ca 2+ sparks and waves WAVES SPARKS O. Kemi

31 Results : Ca 2+ alternans O. Kemi

32 Summary Exercise training partly, but not fully reversed cardiomyocyte Ca 2+ handling abnormalities observed during increasing twitch-stimulation frequencies in post-mi HF. This suggests a mechanism that contributes to the improved reserve capacity and reduced arrhythmia susceptibility in failing hearts following exercise training. Mechanism: Ca 2+ alternans depends on SR [Ca 2+ ] fluctuations. SERCA function? [Diaz et al. 2004; CircRes] O. Kemi

33 Local camp dynamics in the SERCA2 compartment Studied by a targeted FRET biosensor Julia U. Sprenger, Viacheslav O. Nikolaev University of Göttingen, Germany

34 Background: Localized camp-regulation by phosphodiesterases (PDEs) in the heart Fischmeister R (2006). Circ Res 99:

35 Aim To understand camp-regulation in the SERCA2 microdomain! Julia U. Sprenger, Viacheslav O. Nikolaev

36 Methods transgenic mouse expressing a newly camp FRET biosensor targeted to SERCA2 via phospholamban (Epac1-camps-PLN) isolated cardiomyocytes comparison of local camp dynamics with those in the bulk cytosol 8 weeks post TAC and Sham J. Sprenger

37 Results FRET-sensor expression In Epac1-PLN mice, Epac1-PLN co-localizes with SERCA J. Sprenger

38 Results Differential β-adrenergic stimulation Baseline β1-adrenergic receptor stimulation led to a stronger increase of local camp levels at SERCA2 microdomain β2-adrenergic receptor stimulation had almost no impact on camp levels in the SERCA2 microdomain J. Sprenger

39 Results PDE isoforms at SERCA microdomain At baseline, FRET measurements reveal the predominant role of PDE4 [and PDE3] in the SERCA2 compartment.

40 Results Saturation of SERCA microdomain With beta-adrenergic pre-stimulation, differences in PDE-mediated functional compartmentation are alleviated J. Sprenger

41 Results Changes with TAC hypertrophy In 8 weeks TAC vs. Sham, 1. local SERCA PDE4 activity is reduced 2. no difference in PDE4 activity between cytosol and SERCA 3. total PDE activity in the cytosol is unchanged SHAM TAC J. Sprenger

42 Summary FRET revealed a stronger increase of local camp levels in the SERCA compartment as compared to the bulk cytosol after beta adrenergic stimulation a predominant role of PDE4 in the SERCA2 compartment at the basal state a decreased PDE4 signal in the SERCA2 compartment during hypertrophy Conclusions: A transgenic Epac1-camps-PLN mouse was successfully generated FRET measurements revealed distinct camp dynamics in the SERCA2 microdomain compared to the bulk cytosol and their alterations in cardiac hypertrophy J. Sprenger

43 Ca 2+ -sensitizing effects of OR in permeabilized cardiomyocytes UD MHSC Institute of Cardiology Division of Clinical Physiology, Debrecen, HU László Nagy

44 Background Levosimedan increases cardiac inotropy by increasing myofilament Sensitivity. Levosimedan has PDE-inhibiting effects and may cause hypotension.

45 Aim To assess the effects of a new putative Ca2+ sensitizer on cardiomyocyte myofilament sensitivity L. Nagy

46 Methods left ventricular tissue samples obtained from guinea pigs of either sex ( g), as well as from failing human hearts with dilated cardiomyopathy L. Nagy

47 L-OR 2828 (but not R-OR 2828) increases myofilament sensitivity L. Nagy

48 L-OR 2828 (but not R-OR 2828) increases myofilament sensitivity Guinea pig VM Human VM EC50 = μm. L. Nagy

49 Summary L-OR-2828 is a positive inotropic agent and Ca2+-sensitizer. The magnitude of the Ca2+-sensitizing effect of L-OR appeared to be comparable to that of levosimendan as seen in previous studies. The EC 50 of L-OR-2828 (2.435 μm) was lower than the EC 50 reported for levosimedan (9.19±2.42 nm, Lancaster et al. Eur J Pharmacol 1997) L. Nagy