PDE1 Inhibition Modulates Ca
            v
            1.2 Channel to Stimulate Cardiomyocyte Contraction

Rationale: cAMP activation of PKA (protein kinase A) stimulates excitation-contraction (EC) coupling, increasing cardiac contractility. This is clinically achieved by β-ARs (β-adrenergic receptor) stimulation or PDE3i (inhibition of phosphodiesterase type-3), although both approaches are limited by arrhythmia and chronic myocardial toxicity. PDE1i (Phosphodiesterase type-1 inhibition) also augments cAMP and enhances contractility in intact dogs and rabbits. Unlike β-ARs or PDE3i, PDE1i-stimulated inotropy is unaltered by β-AR blockade and induces little whole-cell Ca 2+ (intracellular Ca 2+ concentration; [Ca 2+ ] i ) increase. Positive inotropy from PDE1i was recently reported in human heart failure. However, mechanisms for this effect remain unknown. Objective: Define the mechanism(s) whereby PDE1i increases myocyte contractility. Methods and Results: We studied primary guinea pig myocytes that express the PDE1C isoform found in larger mammals and humans. In quiescent cells, the potent, selective PDE1i (ITI-214) did not alter cell shortening or [Ca 2+ ] i , whereas β-ARs or PDE3i increased both. When combined with low-dose adenylate cyclase stimulation, PDE1i enhanced shortening in a PKA-dependent manner but unlike PDE3i, induced little [Ca 2+ ] i rise nor augmented β-ARs. β-ARs or PDE3i reduced myofilament Ca 2+ sensitivity and increased sarcoplasmic reticulum Ca 2+ content and phosphorylation of PKA-targeted serines on TnI (troponin I), MYBP-C (myosin binding protein C), and PLN (phospholamban). PDE1i did not significantly alter any of these. However, PDE1i increased Ca v 1.2 channel conductance similarly as PDE3i (both PKA dependent), without altering Na + -Ca 2+ exchanger current density. Cell shortening and [Ca 2+ ] i augmented by PDE1i were more sensitive to Ca v 1.2 blockade and to premature or irregular cell contractions and [Ca 2+ ] i transients compared to PDE3i. Conclusions: PDE1i enhances contractility by a PKA-dependent increase in Ca v 1.2 conductance with less total [Ca 2+ ] i increase, and no significant changes in sarcoplasmic reticulum [Ca 2+ ], myofilament Ca 2+ -sensitivity, or phosphorylation of critical EC-coupling proteins as observed with β-ARs and PDE3i. PDE1i could provide a novel positive inotropic therapy for heart failure without the toxicities of β-ARs and PDE3i.

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Sarcoplasmic reticulum Ca 2+ load in human heart failure

Basic Research in Cardiology ◽

10.1007/s003950200032 ◽

2002 ◽

Vol 97 (7) ◽

pp. 1-1 ◽

Cited By ~ 12

Author(s):

Burkert Pieske ◽

Lars S. Maier ◽

Stephan Schmidt-Schweda

Keyword(s):

Heart Failure ◽

Sarcoplasmic Reticulum ◽

Human Heart ◽

Human Heart Failure

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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

Cardiovascular Research ◽

10.1093/cvr/cvaa123 ◽

2020 ◽

Cited By ~ 10

Author(s):

Detmar Kolijn ◽

Steffen Pabel ◽

Yanna Tian ◽

Mária Lódi ◽

Melissa Herwig ◽

...

Keyword(s):

Oxidative Stress ◽

Heart Failure ◽

Ejection Fraction ◽

Linear Regression Analysis ◽

Lipid Peroxide ◽

Dependent Manner ◽

Preserved Ejection Fraction ◽

Human Heart Failure ◽

Stress Dependent

Abstract 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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Ultrastructural uncoupling between T-tubules and sarcoplasmic reticulum in human heart failure

Cardiovascular Research ◽

10.1093/cvr/cvt030 ◽

2013 ◽

Vol 98 (2) ◽

pp. 269-276 ◽

Cited By ~ 52

Author(s):

H.-B. Zhang ◽

R.-C. Li ◽

M. Xu ◽

S.-M. Xu ◽

Y.-S. Lai ◽

...

Keyword(s):

Heart Failure ◽

Sarcoplasmic Reticulum ◽

Human Heart ◽

Human Heart Failure ◽

T Tubules

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Abnormal sarcoplasmic reticulum Ca2+activity and uptake in human heart failure

Journal of the American College of Cardiology ◽

10.1016/s0735-1097(96)80419-0 ◽

1996 ◽

Vol 27 (2) ◽

pp. 56-57 ◽

Cited By ~ 1

Author(s):

Ulrich Schmidt ◽

Maria Carles ◽

Roger J. Hajjar ◽

Thomas G. DiSalvo ◽

Marc J. Semigran ◽

...

Keyword(s):

Heart Failure ◽

Sarcoplasmic Reticulum ◽

Human Heart ◽

Human Heart Failure

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Alterations in sarcoplasmic reticulum gene expression in human heart failure. A possible mechanism for alterations in systolic and diastolic properties of the failing myocardium.

Circulation Research ◽

10.1161/01.res.72.2.463 ◽

1993 ◽

Vol 72 (2) ◽

pp. 463-469 ◽

Cited By ~ 285

Author(s):

M Arai ◽

N R Alpert ◽

D H MacLennan ◽

P Barton ◽

M Periasamy

Keyword(s):

Gene Expression ◽

Heart Failure ◽

Sarcoplasmic Reticulum ◽

Human Heart ◽

Human Heart Failure ◽

Diastolic Properties

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Na+/Ca2+ exchanger overexpression impairs frequency- and ouabain-dependent cell shortening in adult rat cardiomyocytes

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00397.2003 ◽

2004 ◽

Vol 287 (4) ◽

pp. H1435-H1445 ◽

Cited By ~ 20

Author(s):

Birgit Bölck ◽

Götz Münch ◽

Peter Mackenstein ◽

Martin Hellmich ◽

Ingo Hirsch ◽

...

Keyword(s):

Heart Failure ◽

Gene Transfer ◽

Mode Of Action ◽

Positive Inotropic Effect ◽

Inotropic Effect ◽

Adrenergic Stimulation ◽

Human Heart Failure ◽

Rat Cardiomyocytes ◽

Cell Shortening ◽

Reverse Mode

The Na+/Ca2+ exchanger (NCX) may influence cardiac function depending on its predominant mode of action, forward mode or reverse mode, during the contraction-relaxation cycle. The intracellular Na+ concentration ([Na+]i) and the duration of the action potential as well as the level of NCX protein expression regulate the mode of action of NCX. [Na+]i and NCX expression have been reported to be increased in human heart failure. Nevertheless, the consequences of altered NCX expression in heart failure are still a matter of discussion. We aimed to characterize the influence of NCX expression on intracellular Ca2+ transport in rat cardiomyocytes by adenoviral-mediated gene transfer. A five- to ninefold (dose dependent) overexpression of NCX protein was achieved after 48 h by somatic gene transfer (Ad.NCX.GFP) versus control (Ad.GFP). NCX activity, determined by Na+ gradient-dependent 45Ca2+-uptake, was significantly increased. The protein expressions of sarco(endo)plasmic reticulum Ca2+-ATPase, phospholamban, and calsequestrin were unaffected by NCX overexpression. Fractional shortening (FS) of isolated cardiomyocytes was significantly increased at low stimulation rates in Ad.NCX.GFP. After a step-wise enhancing frequency of stimulation to 3.0 Hz, FS remained unaffected in Ad.GFP cells but declined in Ad.NCX.GFP cells. The positive inotropic effect of the cardiac glycoside ouabain was less effective in Ad.NCX.GFP cells, whereas the positive inotropic effect of β-adrenergic stimulation remained unchanged. In conclusion, NCX overexpression results in a reduced cell shortening at higher stimulation frequencies as well as after inhibition of sarcolemmal Na+-K+-ATPase, i.e., in conditions with enhanced [Na+]i. At low stimulation rates, increased NCX expression enhances both intracellular systolic Ca2+ and contraction amplitude.

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Protein Kinase C-Mediated Cardiac Troponin I S43/45 Phosphorylation Causes Contractile Dysfunction in Human Heart Failure and in Rodents

Biophysical Journal ◽

10.1016/j.bpj.2018.11.200 ◽

2019 ◽

Vol 116 (3) ◽

pp. 29a

Author(s):

Vani S. Ravichandran ◽

Tabea M. Schatz ◽

Margaret V. Westfall

Keyword(s):

Heart Failure ◽

Protein Kinase C ◽

Protein Kinase ◽

Cardiac Troponin ◽

Human Heart ◽

Troponin I ◽

Cardiac Troponin I ◽

Contractile Dysfunction ◽

Human Heart Failure ◽

Kinase C

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Accelerated onset of heart failure in mice during pressure overload with chronically decreased SERCA2 calcium pump activity

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00720.2003 ◽

2004 ◽

Vol 286 (3) ◽

pp. H1146-H1153 ◽

Cited By ~ 66

Author(s):

Jo El J. Schultz ◽

Betty J. Glascock ◽

Sandra A. Witt ◽

Michelle L. Nieman ◽

Kalpana J. Nattamai ◽

...

Keyword(s):

Heart Failure ◽

Cardiac Contractility ◽

Pressure Overload ◽

Left Ventricular ◽

Wild Type ◽

Human Heart Failure ◽

Protein Levels ◽

Plasmic Reticulum ◽

Lv Mass ◽

Pump Activity

We recently developed a mouse model with a single functional allele of Serca2 ( Serca2+/–) that shows impaired cardiac contractility and relaxation without overt heart disease. The goal of this study was to test the hypothesis that chronic reduction in sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA)2 levels in combination with an increased hemodynamic load will result in an accelerated pathway to heart failure. Age-matched wild-type and Serca2+/– mice were subjected to 10 wk of pressure overload via transverse aortic coarctation surgery. Cardiac hypertrophy and heart failure were assessed by echocardiography, gravimetry/histology, hemodynamics, and Western blotting analyses. Our results showed that ∼64% of coarcted Serca2+/– mice were in heart failure compared with 0% of coarcted wild-type mice ( P < 0.05). Overall, morbidity and mortality were greatly increased in Serca2+/– mice under pressure overload. Echocardiography assessment revealed a significant increase in left ventricular (LV) mass, and LV hypertrophy in coarcted Serca2+/– mice converted from a concentric to an eccentric pattern, similar to that seen in human heart failure. Coarcted Serca2+/– mice had decreased contractile/systolic and relaxation/diastolic performance and/or function compared with coarcted wild-type mice ( P < 0.05), despite a similar duration and degree of pressure overload. SERCA2a protein levels were significantly reduced (>50%) in coarcted Serca2+/– mice compared with noncoarcted and coarcted wild-type mice. Our findings suggest that reduction in SERCA2 levels in combination with an increased hemodynamic load results in an accelerated pathway to heart failure.

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