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Arici M, Hsu SC, Ferrandi M, Barassi P, Ronchi C, Torre E, Luraghi A, Chang GJ, Ferrari P, Bianchi G, Peri F, Zaza A, Rocchetti M. Selective SERCA2a activator as a candidate for chronic heart failure therapy. J Transl Med 2024; 22:77. [PMID: 38243248 PMCID: PMC10797746 DOI: 10.1186/s12967-024-04874-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2023] [Accepted: 01/08/2024] [Indexed: 01/21/2024] Open
Abstract
BACKGROUND The sarcoplasmic reticulum (SR) Ca2+ ATPase (SERCA2a) depression substantially contributes to diastolic dysfunction in heart failure (HF), suggesting that SERCA2a stimulation may be a mechanism-based HF therapy. Istaroxime is a drug endowed with both a SERCA2a stimulatory activity and a Na+/K+ pump inhibitory activity for acute HF treatment. Its main metabolite PST3093 shows a more favorable therapeutic profile as compared to the parent drug, but it is still unsuitable for chronic usage. Novel PST3093 derivatives have been recently developed for oral (chronic) HF treatment; compound 8 was selected among them and here characterized. METHODS Effects of compound 8 were evaluated in a context of SERCA2a depression, by using streptozotocin-treated rats, a well-known model of diastolic dysfunction. The impact of SERCA2a stimulation by compound 8 was assessed at the cellular level ad in vivo, following i.v. infusion (acute effects) or oral administration (chronic effects). RESULTS As expected from SERCA2a stimulation, compound 8 induced SR Ca2+ compartmentalization in STZ myocytes. In-vivo echocardiographic analysis during i.v. infusion and after repeated oral administration of compound 8, detected a significant improvement of diastolic function. Moreover, compound 8 did not affect electrical activity of healthy guinea-pig myocytes, in line with the absence of off-target effects. Finally, compound 8 was well tolerated in mice with no evidence of acute toxicity. CONCLUSIONS The pharmacological evaluation of compound 8 indicates that it may be a safe and selective drug for a mechanism-based treatment of chronic HF by restoring SERCA2a activity.
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Affiliation(s)
- Martina Arici
- Department of Biotechnology and Biosciences, Università Degli Studi di Milano-Bicocca, P.Za Della Scienza 2, 20126, Milan, Italy
| | - Shih-Che Hsu
- CVie Therapeutics Limited, Taipei, 11047, Taiwan
| | - Mara Ferrandi
- Windtree Therapeutics Inc, Warrington, PA, 18976, USA
| | - Paolo Barassi
- Windtree Therapeutics Inc, Warrington, PA, 18976, USA
| | - Carlotta Ronchi
- Department of Biotechnology and Biosciences, Università Degli Studi di Milano-Bicocca, P.Za Della Scienza 2, 20126, Milan, Italy
| | - Eleonora Torre
- Department of Biotechnology and Biosciences, Università Degli Studi di Milano-Bicocca, P.Za Della Scienza 2, 20126, Milan, Italy
| | - Andrea Luraghi
- Department of Biotechnology and Biosciences, Università Degli Studi di Milano-Bicocca, P.Za Della Scienza 2, 20126, Milan, Italy
| | | | | | - Giuseppe Bianchi
- Windtree Therapeutics Inc, Warrington, PA, 18976, USA
- Università Vita-Salute San Raffaele, 20132, Milan, Italy
| | - Francesco Peri
- Department of Biotechnology and Biosciences, Università Degli Studi di Milano-Bicocca, P.Za Della Scienza 2, 20126, Milan, Italy
| | - Antonio Zaza
- Department of Biotechnology and Biosciences, Università Degli Studi di Milano-Bicocca, P.Za Della Scienza 2, 20126, Milan, Italy.
| | - Marcella Rocchetti
- Department of Biotechnology and Biosciences, Università Degli Studi di Milano-Bicocca, P.Za Della Scienza 2, 20126, Milan, Italy.
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2
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Arici M, Ferrandi M, Barassi P, Hsu SC, Torre E, Luraghi A, Ronchi C, Chang GJ, Peri F, Ferrari P, Bianchi G, Rocchetti M, Zaza A. Istaroxime Metabolite PST3093 Selectively Stimulates SERCA2a and Reverses Disease-Induced Changes in Cardiac Function. J Pharmacol Exp Ther 2023; 384:231-244. [PMID: 36153005 DOI: 10.1124/jpet.122.001335] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2022] [Revised: 07/11/2022] [Accepted: 08/01/2022] [Indexed: 01/03/2023] Open
Abstract
Heart failure (HF) therapeutic toolkit would strongly benefit from the availability of ino-lusitropic agents with a favorable pharmacodynamics and safety profile. Istaroxime is a promising agent, which combines Na+/K+ pump inhibition with sarcoplasmic reticulum Ca2+ ATPase (SERCA2a) stimulation; however, it has a very short half-life and extensive metabolism to a molecule named PST3093. The present work aims to investigate whether PST3093 still retains the pharmacodynamic and pharmacokinetic properties of its parent compound. We studied PST3093 for its effects on SERCA2a and Na+/K+ ATPase activities, Ca2+ dynamics in isolated myocytes, and hemodynamic effects in an in vivo rat model of diabetic [streptozotocin (STZ)-induced] cardiomyopathy. Istaroxime infusion in HF patients led to accumulation of PST3093 in the plasma; clearance was substantially slower for PST3093 than for istaroxime. In cardiac rat preparations, PST3093 did not inhibit the Na+/K+ ATPase activity but retained SERCA2a stimulatory activity. In in vivo echocardiographic assessment, PST3093 improved overall cardiac performance and reversed most STZ-induced abnormalities. PST3093 intravenous toxicity was considerably lower than that of istaroxime, and it failed to significantly interact with 50 off-targets. Overall, PST3093 is a "selective" SERCA2a activator, the prototype of a novel pharmacodynamic category with a potential in the ino-lusitropic approach to HF with prevailing diastolic dysfunction. Its pharmacodynamics are peculiar, and its pharmacokinetics are suitable to prolong the cardiac beneficial effect of istaroxime infusion. SIGNIFICANCE STATEMENT: Heart failure (HF) treatment would benefit from the availability of ino-lusitropic agents with favourable profiles. PST3093 is the main metabolite of istaroxime, a promising agent combining Na+/K+ pump inhibition and sarcoplasmic reticulum Ca2+ ATPase2a (SERCA2a) stimulation. PST3093 shows a longer half-life in human circulation compared to istaroxime, selectively activates SERCA2a, and improves cardiac performance in a model of diabetic cardiomyopathy. Overall, PST3093 as a selective SERCA2a activator can be considered the prototype of a novel pharmacodynamic category for HF treatment.
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Affiliation(s)
- Martina Arici
- Department of Biotechnology and Biosciences, Università degli Studi di Milano-Bicocca, Milan, Italy (M.A., E.T., A.L., C.R., F.P., M.R., A.Z.); Windtree Therapeutics Inc., Warrington, Pennsylvania (M.F., P.B., P.F., G.B.); CVie Therapeutics Limited, Taipei, Taiwan (S.-C.H.); Graduate Institute of Clinical Medicinal Sciences, College of Medicine, Chang Gung University, Tao-Yuan, Taiwan (G.-J.C.); and Università Vita-Salute San Raffaele, Milan, Italy (G.B.)
| | - Mara Ferrandi
- Department of Biotechnology and Biosciences, Università degli Studi di Milano-Bicocca, Milan, Italy (M.A., E.T., A.L., C.R., F.P., M.R., A.Z.); Windtree Therapeutics Inc., Warrington, Pennsylvania (M.F., P.B., P.F., G.B.); CVie Therapeutics Limited, Taipei, Taiwan (S.-C.H.); Graduate Institute of Clinical Medicinal Sciences, College of Medicine, Chang Gung University, Tao-Yuan, Taiwan (G.-J.C.); and Università Vita-Salute San Raffaele, Milan, Italy (G.B.)
| | - Paolo Barassi
- Department of Biotechnology and Biosciences, Università degli Studi di Milano-Bicocca, Milan, Italy (M.A., E.T., A.L., C.R., F.P., M.R., A.Z.); Windtree Therapeutics Inc., Warrington, Pennsylvania (M.F., P.B., P.F., G.B.); CVie Therapeutics Limited, Taipei, Taiwan (S.-C.H.); Graduate Institute of Clinical Medicinal Sciences, College of Medicine, Chang Gung University, Tao-Yuan, Taiwan (G.-J.C.); and Università Vita-Salute San Raffaele, Milan, Italy (G.B.)
| | - Shih-Che Hsu
- Department of Biotechnology and Biosciences, Università degli Studi di Milano-Bicocca, Milan, Italy (M.A., E.T., A.L., C.R., F.P., M.R., A.Z.); Windtree Therapeutics Inc., Warrington, Pennsylvania (M.F., P.B., P.F., G.B.); CVie Therapeutics Limited, Taipei, Taiwan (S.-C.H.); Graduate Institute of Clinical Medicinal Sciences, College of Medicine, Chang Gung University, Tao-Yuan, Taiwan (G.-J.C.); and Università Vita-Salute San Raffaele, Milan, Italy (G.B.)
| | - Eleonora Torre
- Department of Biotechnology and Biosciences, Università degli Studi di Milano-Bicocca, Milan, Italy (M.A., E.T., A.L., C.R., F.P., M.R., A.Z.); Windtree Therapeutics Inc., Warrington, Pennsylvania (M.F., P.B., P.F., G.B.); CVie Therapeutics Limited, Taipei, Taiwan (S.-C.H.); Graduate Institute of Clinical Medicinal Sciences, College of Medicine, Chang Gung University, Tao-Yuan, Taiwan (G.-J.C.); and Università Vita-Salute San Raffaele, Milan, Italy (G.B.)
| | - Andrea Luraghi
- Department of Biotechnology and Biosciences, Università degli Studi di Milano-Bicocca, Milan, Italy (M.A., E.T., A.L., C.R., F.P., M.R., A.Z.); Windtree Therapeutics Inc., Warrington, Pennsylvania (M.F., P.B., P.F., G.B.); CVie Therapeutics Limited, Taipei, Taiwan (S.-C.H.); Graduate Institute of Clinical Medicinal Sciences, College of Medicine, Chang Gung University, Tao-Yuan, Taiwan (G.-J.C.); and Università Vita-Salute San Raffaele, Milan, Italy (G.B.)
| | - Carlotta Ronchi
- Department of Biotechnology and Biosciences, Università degli Studi di Milano-Bicocca, Milan, Italy (M.A., E.T., A.L., C.R., F.P., M.R., A.Z.); Windtree Therapeutics Inc., Warrington, Pennsylvania (M.F., P.B., P.F., G.B.); CVie Therapeutics Limited, Taipei, Taiwan (S.-C.H.); Graduate Institute of Clinical Medicinal Sciences, College of Medicine, Chang Gung University, Tao-Yuan, Taiwan (G.-J.C.); and Università Vita-Salute San Raffaele, Milan, Italy (G.B.)
| | - Gwo-Jyh Chang
- Department of Biotechnology and Biosciences, Università degli Studi di Milano-Bicocca, Milan, Italy (M.A., E.T., A.L., C.R., F.P., M.R., A.Z.); Windtree Therapeutics Inc., Warrington, Pennsylvania (M.F., P.B., P.F., G.B.); CVie Therapeutics Limited, Taipei, Taiwan (S.-C.H.); Graduate Institute of Clinical Medicinal Sciences, College of Medicine, Chang Gung University, Tao-Yuan, Taiwan (G.-J.C.); and Università Vita-Salute San Raffaele, Milan, Italy (G.B.)
| | - Francesco Peri
- Department of Biotechnology and Biosciences, Università degli Studi di Milano-Bicocca, Milan, Italy (M.A., E.T., A.L., C.R., F.P., M.R., A.Z.); Windtree Therapeutics Inc., Warrington, Pennsylvania (M.F., P.B., P.F., G.B.); CVie Therapeutics Limited, Taipei, Taiwan (S.-C.H.); Graduate Institute of Clinical Medicinal Sciences, College of Medicine, Chang Gung University, Tao-Yuan, Taiwan (G.-J.C.); and Università Vita-Salute San Raffaele, Milan, Italy (G.B.)
| | - Patrizia Ferrari
- Department of Biotechnology and Biosciences, Università degli Studi di Milano-Bicocca, Milan, Italy (M.A., E.T., A.L., C.R., F.P., M.R., A.Z.); Windtree Therapeutics Inc., Warrington, Pennsylvania (M.F., P.B., P.F., G.B.); CVie Therapeutics Limited, Taipei, Taiwan (S.-C.H.); Graduate Institute of Clinical Medicinal Sciences, College of Medicine, Chang Gung University, Tao-Yuan, Taiwan (G.-J.C.); and Università Vita-Salute San Raffaele, Milan, Italy (G.B.)
| | - Giuseppe Bianchi
- Department of Biotechnology and Biosciences, Università degli Studi di Milano-Bicocca, Milan, Italy (M.A., E.T., A.L., C.R., F.P., M.R., A.Z.); Windtree Therapeutics Inc., Warrington, Pennsylvania (M.F., P.B., P.F., G.B.); CVie Therapeutics Limited, Taipei, Taiwan (S.-C.H.); Graduate Institute of Clinical Medicinal Sciences, College of Medicine, Chang Gung University, Tao-Yuan, Taiwan (G.-J.C.); and Università Vita-Salute San Raffaele, Milan, Italy (G.B.)
| | - Marcella Rocchetti
- Department of Biotechnology and Biosciences, Università degli Studi di Milano-Bicocca, Milan, Italy (M.A., E.T., A.L., C.R., F.P., M.R., A.Z.); Windtree Therapeutics Inc., Warrington, Pennsylvania (M.F., P.B., P.F., G.B.); CVie Therapeutics Limited, Taipei, Taiwan (S.-C.H.); Graduate Institute of Clinical Medicinal Sciences, College of Medicine, Chang Gung University, Tao-Yuan, Taiwan (G.-J.C.); and Università Vita-Salute San Raffaele, Milan, Italy (G.B.)
| | - Antonio Zaza
- Department of Biotechnology and Biosciences, Università degli Studi di Milano-Bicocca, Milan, Italy (M.A., E.T., A.L., C.R., F.P., M.R., A.Z.); Windtree Therapeutics Inc., Warrington, Pennsylvania (M.F., P.B., P.F., G.B.); CVie Therapeutics Limited, Taipei, Taiwan (S.-C.H.); Graduate Institute of Clinical Medicinal Sciences, College of Medicine, Chang Gung University, Tao-Yuan, Taiwan (G.-J.C.); and Università Vita-Salute San Raffaele, Milan, Italy (G.B.)
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3
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Avvisato R, Jankauskas SS, Santulli G. Istaroxime and Beyond: New Therapeutic Strategies to Specifically Activate SERCA and Treat Heart Failure. J Pharmacol Exp Ther 2023; 384:227-230. [PMID: 36581352 DOI: 10.1124/jpet.122.001446] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2022] [Accepted: 10/17/2022] [Indexed: 12/31/2022] Open
Affiliation(s)
- Roberta Avvisato
- Department of Medicine, Division of Cardiology, Wilf Family Cardiovascular Research Institute, Einstein-Mount Sinai Diabetes Research Center (ES-DRC), Einstein Institute for Aging Research (R.A., S.S.J., G.S.) and Department of Molecular Pharmacology, Institute for Neuroimmunology and Inflammation, Fleischer Institute for Diabetes and Metabolism (FIDAM) (G.S.), Albert Einstein College of Medicine, New York, New York
| | - Stanislovas S Jankauskas
- Department of Medicine, Division of Cardiology, Wilf Family Cardiovascular Research Institute, Einstein-Mount Sinai Diabetes Research Center (ES-DRC), Einstein Institute for Aging Research (R.A., S.S.J., G.S.) and Department of Molecular Pharmacology, Institute for Neuroimmunology and Inflammation, Fleischer Institute for Diabetes and Metabolism (FIDAM) (G.S.), Albert Einstein College of Medicine, New York, New York
| | - Gaetano Santulli
- Department of Medicine, Division of Cardiology, Wilf Family Cardiovascular Research Institute, Einstein-Mount Sinai Diabetes Research Center (ES-DRC), Einstein Institute for Aging Research (R.A., S.S.J., G.S.) and Department of Molecular Pharmacology, Institute for Neuroimmunology and Inflammation, Fleischer Institute for Diabetes and Metabolism (FIDAM) (G.S.), Albert Einstein College of Medicine, New York, New York
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4
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Forzano I, Mone P, Mottola G, Kansakar U, Salemme L, De Luca A, Tesorio T, Varzideh F, Santulli G. Efficacy of the New Inotropic Agent Istaroxime in Acute Heart Failure. J Clin Med 2022; 11:7503. [PMID: 36556120 PMCID: PMC9786901 DOI: 10.3390/jcm11247503] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2022] [Revised: 12/14/2022] [Accepted: 12/15/2022] [Indexed: 12/24/2022] Open
Abstract
Current therapeutic strategies for acute heart failure (AHF) are based on traditional inotropic agents that are often associated with untoward effects; therefore, finding new effective approaches with a safer profile is dramatically needed. Istaroxime is a novel compound, chemically unrelated to cardiac glycosides, that is currently being studied for the treatment of AHF. Its effects are essentially related to its inotropic and lusitropic positive properties exerted through a dual mechanism of action: activation of the sarcoplasmic reticulum Ca2+ ATPase isoform 2a (SERCA2a) and inhibition of the Na+/K+-ATPase (NKA) activity. The advantages of istaroxime over the available inotropic agents include its lower arrhythmogenic action combined with its capability of increasing systolic blood pressure without augmenting heart rate. However, it has a limited half-life (1 hour) and is associated with adverse effects including pain at the injection site and gastrointestinal issues. Herein, we describe the main mechanism of action of istaroxime and we present a systematic overview of both clinical and preclinical trials testing this drug, underlining the latest insights regarding its adoption in clinical practice for AHF.
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Affiliation(s)
- Imma Forzano
- Division of Cardiology, Department of Advanced Biomedical Sciences, “Federico II” University, 80131 Naples, Italy
| | - Pasquale Mone
- Division of Cardiology, Department of Medicine, Wilf Family Cardiovascular Research Institute, Einstein Institute for Aging Research, Albert Einstein College of Medicine, New York, NY 10461, USA
| | - Gaetano Mottola
- Casa di Cura “Montevergine”, Mercogliano, 83013 Avellino, Italy
| | - Urna Kansakar
- Division of Cardiology, Department of Advanced Biomedical Sciences, “Federico II” University, 80131 Naples, Italy
| | - Luigi Salemme
- Casa di Cura “Montevergine”, Mercogliano, 83013 Avellino, Italy
| | - Antonio De Luca
- Department of Mental and Physical Health and Preventive Medicine, University of Campania “Vanvitelli”, 81100 Caserta, Italy
| | - Tullio Tesorio
- Casa di Cura “Montevergine”, Mercogliano, 83013 Avellino, Italy
| | - Fahimeh Varzideh
- Division of Cardiology, Department of Advanced Biomedical Sciences, “Federico II” University, 80131 Naples, Italy
| | - Gaetano Santulli
- Division of Cardiology, Department of Advanced Biomedical Sciences, “Federico II” University, 80131 Naples, Italy
- Division of Cardiology, Department of Medicine, Wilf Family Cardiovascular Research Institute, Einstein Institute for Aging Research, Albert Einstein College of Medicine, New York, NY 10461, USA
- Department of Molecular Pharmacology, Einstein-Mount Sinai Diabetes Research Center (ES-DRC), Einstein Institute for Neuroimmunology and Inflammation (INI), Fleischer Institute for Diabetes and Metabolism (FIDAM), Albert Einstein College of Medicine, New York, NY 10461, USA
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5
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Luraghi A, Ferrandi M, Barassi P, Arici M, Hsu SC, Torre E, Ronchi C, Romerio A, Chang GJ, Ferrari P, Bianchi G, Zaza A, Rocchetti M, Peri F. Highly Selective SERCA2a Activators: Preclinical Development of a Congeneric Group of First-in-Class Drug Leads against Heart Failure. J Med Chem 2022; 65:7324-7333. [PMID: 35580334 PMCID: PMC9150102 DOI: 10.1021/acs.jmedchem.2c00347] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
![]()
The stimulation of
sarcoplasmic reticulum calcium ATPase SERCA2a
emerged as a novel therapeutic strategy to efficiently improve overall
cardiac function in heart failure (HF) with reduced arrhythmogenic
risk. Istaroxime is a clinical-phase IIb compound with a double mechanism
of action, Na+/K+ ATPase inhibition and SERCA2a
stimulation. Starting from the observation that istaroxime metabolite
PST3093 does not inhibit Na+/K+ ATPase while
stimulates SERCA2a, we synthesized a series of bioisosteric PST3093
analogues devoid of Na+/K+ ATPase inhibitory
activity. Most of them retained SERCA2a stimulatory action with nanomolar
potency in cardiac preparations from healthy guinea pigs and streptozotocin
(STZ)-treated rats. One compound was further characterized in isolated
cardiomyocytes, confirming SERCA2a stimulation and in vivo showing
a safety profile and improvement of cardiac performance following
acute infusion in STZ rats. We identified a new class of selective
SERCA2a activators as first-in-class drug candidates for HF treatment.
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Affiliation(s)
- Andrea Luraghi
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, Milano 20126, Italy
| | - Mara Ferrandi
- Windtree Therapeutics Inc., Warrington, Pennsylvania 18976, United States
| | - Paolo Barassi
- Windtree Therapeutics Inc., Warrington, Pennsylvania 18976, United States
| | - Martina Arici
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, Milano 20126, Italy
| | | | - Eleonora Torre
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, Milano 20126, Italy
| | - Carlotta Ronchi
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, Milano 20126, Italy
| | - Alessio Romerio
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, Milano 20126, Italy
| | - Gwo-Jyh Chang
- Cardiovascular Medicine, Chang Gung University, Tao-Yuan 333323 Taiwan
| | - Patrizia Ferrari
- Windtree Therapeutics Inc., Warrington, Pennsylvania 18976, United States
| | - Giuseppe Bianchi
- Windtree Therapeutics Inc., Warrington, Pennsylvania 18976, United States.,Università Vita-Salute San Raffaele, Milano 20132, Italy
| | - Antonio Zaza
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, Milano 20126, Italy
| | - Marcella Rocchetti
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, Milano 20126, Italy
| | - Francesco Peri
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, Milano 20126, Italy
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6
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Torre E, Arici M, Lodrini AM, Ferrandi M, Barassi P, Hsu SC, Chang GJ, Boz E, Sala E, Vagni S, Altomare C, Mostacciuolo G, Bussadori C, Ferrari P, Bianchi G, Rocchetti M. SERCA2a stimulation by istaroxime improves intracellular Ca2+ handling and diastolic dysfunction in a model of diabetic cardiomyopathy. Cardiovasc Res 2021; 118:1020-1032. [PMID: 33792692 PMCID: PMC8930067 DOI: 10.1093/cvr/cvab123] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/12/2020] [Revised: 01/20/2021] [Accepted: 03/31/2021] [Indexed: 12/17/2022] Open
Abstract
Aims Diabetic cardiomyopathy is a multifactorial disease characterized by an early onset of diastolic dysfunction (DD) that precedes the development of systolic impairment. Mechanisms that can restore cardiac relaxation improving intracellular Ca2+ dynamics represent a promising therapeutic approach for cardiovascular diseases associated to DD. Istaroxime has the dual properties to accelerate Ca2+ uptake into sarcoplasmic reticulum (SR) through the SR Ca2+ pump (SERCA2a) stimulation and to inhibit Na+/K+ ATPase (NKA). This project aims to characterize istaroxime effects at a concentration (100 nmol/L) marginally affecting NKA, in order to highlight its effects dependent on the stimulation of SERCA2a in an animal model of mild diabetes. Methods and results Streptozotocin (STZ) treated diabetic rats were studied at 9 weeks after STZ injection in comparison to controls (CTR). Istaroxime effects were evaluated in vivo and in left ventricular (LV) preparations. STZ animals showed (i) marked DD not associated to cardiac fibrosis, (ii) LV mass reduction associated to reduced LV cell dimension and T-tubules loss, (iii) reduced LV SERCA2 protein level and activity and (iv) slower SR Ca2+ uptake rate, (v) LV action potential (AP) prolongation and increased short-term variability (STV) of AP duration, (vi) increased diastolic Ca2+, and (vii) unaltered SR Ca2+ content and stability in intact cells. Acute istaroxime infusion (0.11 mg/kg/min for 15 min) reduced DD in STZ rats. Accordingly, in STZ myocytes istaroxime (100 nmol/L) stimulated SERCA2a activity and blunted STZ-induced abnormalities in LV Ca2+ dynamics. In CTR myocytes, istaroxime increased diastolic Ca2+ level due to NKA blockade albeit minimal, while its effects on SERCA2a were almost absent. Conclusions SERCA2a stimulation by istaroxime improved STZ-induced DD and intracellular Ca2+ handling anomalies. Thus, SERCA2a stimulation can be considered a promising therapeutic approach for DD treatment.
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Affiliation(s)
- Eleonora Torre
- Department of Biotechnology and Biosciences, Università degli Studi di Milano-Bicocca, Milan, Italy
| | - Martina Arici
- Department of Biotechnology and Biosciences, Università degli Studi di Milano-Bicocca, Milan, Italy
| | - Alessandra Maria Lodrini
- Department of Biotechnology and Biosciences, Università degli Studi di Milano-Bicocca, Milan, Italy
| | - Mara Ferrandi
- Windtree Therapeutics Inc., Warrington, Pennsylvania, USA
| | - Paolo Barassi
- Windtree Therapeutics Inc., Warrington, Pennsylvania, USA
| | | | | | | | - Emanuela Sala
- Department of Biotechnology and Biosciences, Università degli Studi di Milano-Bicocca, Milan, Italy
| | - Sara Vagni
- Department of Biotechnology and Biosciences, Università degli Studi di Milano-Bicocca, Milan, Italy
| | | | - Gaspare Mostacciuolo
- Department of Biotechnology and Biosciences, Università degli Studi di Milano-Bicocca, Milan, Italy
| | | | | | | | - Marcella Rocchetti
- Department of Biotechnology and Biosciences, Università degli Studi di Milano-Bicocca, Milan, Italy
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7
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Hortigon-Vinagre MP, Zamora V, Burton FL, Smith GL. The Use of Voltage Sensitive Dye di-4-ANEPPS and Video-Based Contractility Measurements to Assess Drug Effects on Excitation-Contraction Coupling in Human-Induced Pluripotent Stem Cell-Derived Cardiomyocytes. J Cardiovasc Pharmacol 2021; 77:280-290. [PMID: 33109927 DOI: 10.1097/fjc.0000000000000937] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Accepted: 10/09/2020] [Indexed: 12/21/2022]
Abstract
ABSTRACT Because cardiotoxicity is one of the leading causes of drug failure and attrition, the design of new protocols and technologies to assess proarrhythmic risks on cardiac cells is in continuous development by different laboratories. Current methodologies use electrical, intracellular Ca2+, or contractility assays to evaluate cardiotoxicity. Increasingly, the human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) are the in vitro tissue model used in commercial assays because it is believed to recapitulate many aspects of human cardiac physiology. In this work, we demonstrate that the combination of a contractility and voltage measurements, using video-based imaging and fluorescence microscopy, on hiPSC-CMs allows the investigation of mechanistic links between electrical and mechanical effects in an assay design that can address medium throughput scales necessary for drug screening, offering a view of the mechanisms underlying drug toxicity. To assess the accuracy of this novel technique, 10 commercially available inotropic drugs were tested (5 positive and 5 negative). Included were drugs with simple and specific mechanisms, such as nifedipine, Bay K8644, and blebbistatin, and others with a more complex action such as isoproterenol, pimobendan, digoxin, and amrinone, among others. In addition, the results provide a mechanism for the toxicity of itraconazole in a human model, a drug with reported side effects on the heart. The data demonstrate a strong negative inotropic effect because of the blockade of L-type Ca2+ channels and additional action on the cardiac myofilaments. We can conclude that the combination of contractility and action potential measurements can provide wider mechanistic knowledge of drug cardiotoxicity for preclinical assays.
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MESH Headings
- Action Potentials/drug effects
- Arrhythmias, Cardiac/chemically induced
- Arrhythmias, Cardiac/metabolism
- Arrhythmias, Cardiac/physiopathology
- Calcium Channels, L-Type/drug effects
- Calcium Channels, L-Type/metabolism
- Cardiotoxicity
- Cell Differentiation
- Cells, Cultured
- Excitation Contraction Coupling/drug effects
- Fluorescent Dyes/chemistry
- Humans
- Induced Pluripotent Stem Cells/drug effects
- Induced Pluripotent Stem Cells/metabolism
- Induced Pluripotent Stem Cells/pathology
- Microscopy, Fluorescence
- Microscopy, Video
- Myocardial Contraction/drug effects
- Myocytes, Cardiac/drug effects
- Myocytes, Cardiac/metabolism
- Myocytes, Cardiac/pathology
- Myofibrils/drug effects
- Myofibrils/metabolism
- Myofibrils/pathology
- Pyridinium Compounds/chemistry
- Risk Assessment
- Time Factors
- Toxicity Tests
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Affiliation(s)
- Maria Pura Hortigon-Vinagre
- Departamento de Bioquímica y Biología Molecular y Genética, Facultad de Ciencias, Universdad de Extremadura, Badajoz, Spain
| | - Victor Zamora
- Departamento de Ingeniería Mecánica, Energética y de los Materiales, Escuela de Ingerierias Industriales, Universidad de Extremadura, Badajoz, Spain
| | - Francis L Burton
- Institute of Cardiovascular and Medical Sciences, College of Medical, Veterinary and Life Science, University of Glasgow, Glasgow, United Kingdom ; and
- Clyde Biosciences Ltd, BioCity Scotland, Newhouse, United Kingdom
| | - Godfrey L Smith
- Institute of Cardiovascular and Medical Sciences, College of Medical, Veterinary and Life Science, University of Glasgow, Glasgow, United Kingdom ; and
- Clyde Biosciences Ltd, BioCity Scotland, Newhouse, United Kingdom
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8
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Olgar Y, Tuncay E, Degirmenci S, Billur D, Dhingra R, Kirshenbaum L, Turan B. Ageing-associated increase in SGLT2 disrupts mitochondrial/sarcoplasmic reticulum Ca 2+ homeostasis and promotes cardiac dysfunction. J Cell Mol Med 2020; 24:8567-8578. [PMID: 32652890 PMCID: PMC7412693 DOI: 10.1111/jcmm.15483] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Revised: 04/30/2020] [Accepted: 05/24/2020] [Indexed: 12/12/2022] Open
Abstract
The prevalence of death from cardiovascular disease is significantly higher in elderly populations; the underlying factors that contribute to the age‐associated decline in cardiac performance are poorly understood. Herein, we identify the involvement of sodium/glucose co‐transporter gene (SGLT2) in disrupted cellular Ca2+‐homeostasis, and mitochondrial dysfunction in age‐associated cardiac dysfunction. In contrast to younger rats (6‐month of age), older rats (24‐month of age) exhibited severe cardiac ultrastructural defects, including deformed, fragmented mitochondria with high electron densities. Cardiomyocytes isolated from aged rats demonstrated increased reactive oxygen species (ROS), loss of mitochondrial membrane potential and altered mitochondrial dynamics, compared with younger controls. Moreover, mitochondrial defects were accompanied by mitochondrial and cytosolic Ca2+ ([Ca2+]i) overload, indicative of disrupted cellular Ca2+‐homeostasis. Interestingly, increased [Ca2+]i coincided with decreased phosphorylation of phospholamban (PLB) and contractility. Aged‐cardiomyocytes also displayed high Na+/Ca2+‐exchanger (NCX) activity and blood glucose levels compared with young‐controls. Interestingly, the protein level of SGLT2 was dramatically increased in the aged cardiomyocytes. Moreover, SGLT2 inhibition was sufficient to restore age‐associated defects in [Ca2+]i‐homeostasis, PLB phosphorylation, NCX activity and mitochondrial Ca2+‐loading. Hence, the present data suggest that deregulated SGLT2 during ageing disrupts mitochondrial function and cardiac contractility through a mechanism that impinges upon [Ca2+]i‐homeostasis. Our studies support the notion that interventions that modulate SGLT2‐activity can provide benefits in maintaining [Ca2+]i and cardiac function with advanced age.
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Affiliation(s)
- Yusuf Olgar
- Departments of Biophysics, Ankara University Faculty of Medicine, Ankara, Turkey
| | - Erkan Tuncay
- Departments of Biophysics, Ankara University Faculty of Medicine, Ankara, Turkey
| | - Sinan Degirmenci
- Departments of Biophysics, Ankara University Faculty of Medicine, Ankara, Turkey
| | - Deniz Billur
- Departments of Histology-Embriyology, Ankara University Faculty of Medicine, Ankara, Turkey
| | - Rimpy Dhingra
- St. Boniface Hospital Albrechtsen Research Centre, Institute of Cardiovascular Sciences, University of Manitoba, Winnipeg, MB, Canada
| | - Lorrie Kirshenbaum
- St. Boniface Hospital Albrechtsen Research Centre, Institute of Cardiovascular Sciences, University of Manitoba, Winnipeg, MB, Canada
| | - Belma Turan
- Departments of Biophysics, Ankara University Faculty of Medicine, Ankara, Turkey
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9
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Bossu A, Kostense A, Beekman HDM, Houtman MJC, van der Heyden MAG, Vos MA. Istaroxime, a positive inotropic agent devoid of proarrhythmic properties in sensitive chronic atrioventricular block dogs. Pharmacol Res 2018; 133:132-140. [PMID: 29753687 DOI: 10.1016/j.phrs.2018.05.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/18/2018] [Revised: 04/25/2018] [Accepted: 05/01/2018] [Indexed: 02/07/2023]
Abstract
Current inotropic agents in heart failure therapy associate with low benefit and significant adverse effects, including ventricular arrhythmias. Istaroxime, a novel Na+/K+-transporting ATPase inhibitor, also stimulates SERCA2a activity, which would confer improved inotropic and lusitropic properties with less proarrhythmic effects. We investigated hemodynamic, electrophysiological and potential proarrhythmic and antiarrhythmic effects of istaroxime in control and chronic atrioventricular block (CAVB) dogs sensitive to drug-induced Torsades de Pointes arrhythmias (TdP). In isolated normal canine ventricular cardiomyocytes, istaroxime (0.3-10 μM) evoked no afterdepolarizations and significantly shortened action potential duration (APD) at 3 and 10 μM. Istaroxime at 3 μg/kg/min significantly increased left ventricular (LV) contractility (dP/dt+) and relaxation (dP/dt-) respectively by 81 and 94% in anesthetized control dogs (n = 6) and by 61 and 49% in anesthetized CAVB dogs (n = 7) sensitive to dofetilide-induced TdP. While istaroxime induced no ventricular arrhythmias in control conditions, only single ectopic beats occurred in 2/7 CAVB dogs, which were preceded by increase of short-term variability of repolarization (STV) and T wave alternans in LV unipolar electrograms. Istaroxime pre-treatment (3 μg/kg/min for 60 min) did not alleviate dofetilide-induced increase in repolarization and STV, and mildly reduced incidence of TdP from 6/6 to 4/6 CAVB dogs. In six CAVB dogs with dofetilide-induced TdP, administration of istaroxime (90 μg/kg/5 min) suppressed arrhythmic episodes in two animals. Taken together, inotropic and lusitropic properties of istaroxime in CAVB dogs were devoid of significant proarrhythmic effects in sensitive CAVB dogs, and istaroxime provides a moderate antiarrhythmic efficacy in prevention and suppression of dofetilide-induced TdP.
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Affiliation(s)
- Alexandre Bossu
- Department of Medical Physiology, Division Heart & Lungs, University Medical Center Utrecht, Utrecht, The Netherlands.
| | - Amée Kostense
- Department of Medical Physiology, Division Heart & Lungs, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Henriette D M Beekman
- Department of Medical Physiology, Division Heart & Lungs, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Marien J C Houtman
- Department of Medical Physiology, Division Heart & Lungs, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Marcel A G van der Heyden
- Department of Medical Physiology, Division Heart & Lungs, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Marc A Vos
- Department of Medical Physiology, Division Heart & Lungs, University Medical Center Utrecht, Utrecht, The Netherlands
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10
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Identification of Na+/K+-ATPase inhibition-independent proarrhythmic ionic mechanisms of cardiac glycosides. Sci Rep 2017; 7:2465. [PMID: 28550304 PMCID: PMC5446409 DOI: 10.1038/s41598-017-02496-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2016] [Accepted: 04/13/2017] [Indexed: 12/17/2022] Open
Abstract
The current study explored the Na+/K+-ATPase (NKA) inhibition-independent proarrhythmic mechanisms of cardiac glycosides (CGs) which are well-known NKA inhibitors. With the cytosolic Ca2+ chelated by EGTA and BAPTA or extracellular Ca2+ replaced by Ba2+, effects of bufadienolides (bufalin (BF) and cinobufagin (CBG)) and cardenolides (ouabain (Oua) and pecilocerin A (PEA)) on the L-type calcium current (ICa,L) were recorded in heterologous expression Cav1.2-CHO cells and human embryonic stem cell-derived cardiomyocytes (hESC-CMs). BF and CBG demonstrated a concentration-dependent (0.1 to 100 µM) ICa,L inhibition (maximal ≥50%) without and with the NKA activity blocked by 10 µM Oua. BF significantly shortened the action potential duration at 1.0 µM and shortened the extracellular field potential duration at 0.01~1.0 µM. On the other hand, BF and CBG at 100 µM demonstrated a strong inhibition (≥40%) of the rapidly activating component of the delayed rectifier K+ current (IKr) in heterologous expression HEK293 cells and prolonged the APD of the heart of day-3 Zebrafish larva with disrupted rhythmic contractions. Moreover, hESC-CMs treated with BF (10 nM) for 24 hours showed moderate yet significant prolongation in APD90. In conclusion, our data indicate that CGs particularly bufadienolides possess cytosolic [Ca2+]i- and NKA inhibition- independent proarrhythmic potential through ICa,L and IKr inhibitions.
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11
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Zeng M, Jiang W, Tian Y, Hao J, Cao Z, Liu Z, Fu C, Zhang P, Ma J. Andrographolide inhibits arrhythmias and is cardioprotective in rabbits. Oncotarget 2017; 8:61226-61238. [PMID: 28977859 PMCID: PMC5617419 DOI: 10.18632/oncotarget.18051] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2017] [Accepted: 04/21/2017] [Indexed: 01/01/2023] Open
Abstract
Andrographolide has a protective effect on the cardiovascular system. To study its cardic-electrophysiological effects, action potentials and voltage-gated Na+ (INa), Ca2+ (ICaL), and K+ (IK1, IKr, Ito and IKur) currents were recorded using whole-cell patch clamp and current clamp techniques. Additionally, the effects of andrographolide on aconitine-induced arrhythmias were assessed on electrocardiograms in vivo. We found that andrographolide shortened action potential duration and reduced maximum upstroke velocity in rabbit left ventricular and left atrial myocytes. Andrographolide attenuated rate-dependence of action potential duration, and reduced or abolished delayed afterdepolarizations and triggered activities induced by isoproterenol (1 μM) and high calcium ([Ca2+]o=3.6 mM) in left ventricular myocytes. Andrographolide also concentration-dependently inhibited INa and ICaL, but had no effect on Ito, IKur, IK1, or IKr in rabbit left ventricular and left atrial myocytes. Andrographolide treatment increased the time and dosage thresholds of aconitine-induced arrhythmias, and reduced arrhythmia incidence and mortality in rabbits. Our results indicate that andrographolide inhibits cellular arrhythmias (delayed afterdepolarizations and triggered activities) and aconitine-induced arrhythmias in vivo, and these effects result from INa and ICaL inhibition. Andrographolide may be useful as a class I and IV antiarrhythmic therapeutic.
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Affiliation(s)
- Mengliu Zeng
- Cardio-Electrophysiological Research Laboratory, Medical College of Wuhan University of Science and Technology, Wuhan, Hubei, China
| | - Wanzhen Jiang
- Cardio-Electrophysiological Research Laboratory, Medical College of Wuhan University of Science and Technology, Wuhan, Hubei, China
| | - Youjia Tian
- Cardio-Electrophysiological Research Laboratory, Medical College of Wuhan University of Science and Technology, Wuhan, Hubei, China
| | - Jie Hao
- Cardio-Electrophysiological Research Laboratory, Medical College of Wuhan University of Science and Technology, Wuhan, Hubei, China
| | - Zhenzhen Cao
- Cardio-Electrophysiological Research Laboratory, Medical College of Wuhan University of Science and Technology, Wuhan, Hubei, China
| | - Zhipei Liu
- Cardio-Electrophysiological Research Laboratory, Medical College of Wuhan University of Science and Technology, Wuhan, Hubei, China
| | - Chen Fu
- Cardio-Electrophysiological Research Laboratory, Medical College of Wuhan University of Science and Technology, Wuhan, Hubei, China
| | - Peihua Zhang
- Cardio-Electrophysiological Research Laboratory, Medical College of Wuhan University of Science and Technology, Wuhan, Hubei, China
| | - Jihua Ma
- Cardio-Electrophysiological Research Laboratory, Medical College of Wuhan University of Science and Technology, Wuhan, Hubei, China
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12
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Wu Y, Wang L, Ma J, Song Y, Zhang P, Luo A, Fu C, Cao Z, Wang X, Shryock JC, Belardinelli L. Protein kinase C and Ca(2+) -calmodulin-dependent protein kinase II mediate the enlarged reverse INCX induced by ouabain-increased late sodium current in rabbit ventricular myocytes. Exp Physiol 2015; 100:399-409. [PMID: 25641541 DOI: 10.1113/expphysiol.2014.083972] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2014] [Accepted: 01/23/2015] [Indexed: 11/08/2022]
Abstract
NEW FINDINGS What is the central question of this study? What are the effects of protein kinase C (PKC) and Ca(2+) -calmodulin-dependent protein kinase II (CaMKII) on late sodium current (INaL ), reverse Na(+) -Ca(2+) exchange current (reverse INCX ) or intracellular Ca(2+) levels changed by ouabain? What is the main finding and its importance? Ouabain, even at low concentrations (0.5-8.0 μm), can increase INaL and reverse INCX , and these effects may contribute to the effect of the glycoside to increase Ca(2+) transients and contractility. Both PKC and CaMKII activities may mediate or modulate these processes. It has been reported that the cardiac glycoside ouabain can increase the late sodium current (INaL ), as well as the diastolic intracellular calcium concentration and contractile shortening. Whether an increase of INaL participates in a pathway that can mediate the positive inotropic response to ouabain is unknown. We therefore determined the effects of ouabain on INaL , reverse Na(+) -Ca(2+) exchange current (reverse INCX ), intracellular Ca(2+) ([Ca(2+) ]i ) levels and contractile shortening in rabbit isolated ventricular myocytes. Ouabain (0.1-8 μm) markedly increased INaL and reverse INCX in a concentration-dependent manner, with significant effects at concentrations as low as 0.5 and 1 μm. These effects of ouabain were suppressed by the INaL inhibitors TTX and ranolazine, the protein kinase C inhibitor bisindolylmaleimide and the Ca(2+) -calmodulin-dependent protein kinase II inhibitor KN-93. The enhancement by 0.5 μm ouabain of ventricular myocyte contractility and intracellular Ca(2+) transients was suppressed by 2.0 μm TTX. We conclude that ouabain, even at low concentrations (0.5-8.0 μm), can increase INaL and reverse INCX , and these effects may contribute to the effect of the glycoside to increase Ca(2+) transients and contractility. Both protein kinase C and Ca(2+) -calmodulin-dependent protein kinase II activities may mediate or modulate these processes.
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Affiliation(s)
- Ying Wu
- Cardio-Electrophysiological Research Laboratory, Medical College of Wuhan University of Science and Technology, Wuhan, China
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13
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Huang CLH. SERCA2a stimulation by istaroxime: a novel mechanism of action with translational implications. Br J Pharmacol 2014; 170:486-8. [PMID: 23822610 DOI: 10.1111/bph.12288] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2013] [Accepted: 05/23/2013] [Indexed: 12/16/2022] Open
Abstract
UNLABELLED Sarcoplasmic reticular (SR) Ca(2+) -ATPase (SERCA2a) is central to cardiac electrophysiological and mechanical function. It ensures full diastolic relaxation minimizing delayed after-potentials that would otherwise compromise membrane electrophysiological stability, and optimizes SR Ca(2+) refilling and systolic contraction. Previous studies demonstrated that the small molecule agent istaroxime stimulates SERCA2a-ATPase activity, restoring its function in failing hearts, and enhancing indices of mechanical, and SR Ca(2+) release and re-uptake, activity. Ferrandi et al (2013) now elegantly demonstrate its ability to dissociate the phospholamdan (PB) bound to cardiac SERCA2a, thereby removing the inhibitory effect of PB on SERCA2a. This effect was independent of the cAMP/PKA system and modified a specific SERCA2a reaction step. They used SERCA-enriched SR preparations from a rigorously validated and realistic physiological, canine model of cardiac failure with established Na(+) -K(+) -ATPase sensitivity to cardiac glycosides and SR Ca(2+) handling features. These findings potentially translate into a novel management of the major and increasingly important public health challenge of chronic cardiac failure. LINKED ARTICLE This article is a commentary on Ferrandi et al., pp. 1849-1861 of volume 169 issue 8. To view this paper visit http://dx.doi.org/10.1111/bph.12278.
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14
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Ferrandi M, Barassi P, Tadini-Buoninsegni F, Bartolommei G, Molinari I, Tripodi MG, Reina C, Moncelli MR, Bianchi G, Ferrari P. Istaroxime stimulates SERCA2a and accelerates calcium cycling in heart failure by relieving phospholamban inhibition. Br J Pharmacol 2014; 169:1849-61. [PMID: 23763364 DOI: 10.1111/bph.12278] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2013] [Revised: 05/10/2013] [Accepted: 05/15/2013] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND AND PURPOSE Calcium handling is known to be deranged in heart failure. Interventions aimed at improving cell Ca(2) (+) cycling may represent a promising approach to heart failure therapy. Istaroxime is a new luso-inotropic compound that stimulates cardiac contractility and relaxation in healthy and failing animal models and in patients with acute heart failure (AHF) syndrome. Istaroxime is a Na-K ATPase inhibitor with the unique property of increasing sarcoplasmic reticulum (SR) SERCA2a activity as shown in heart microsomes from humans and guinea pigs. The present study addressed the molecular mechanism by which istaroxime increases SERCA2a activity. EXPERIMENTAL APPROACH To study the effect of istaroxime on SERCA2a-phospholamban (PLB) complex, we applied different methodologies in native dog healthy and failing heart preparations and heterologous canine SERCA2a/PLB co-expressed in Spodoptera frugiperda (Sf21) insect cells. KEY RESULTS We showed that istaroxime enhances SERCA2a activity, Ca(2) (+) uptake and the Ca(2) (+) -dependent charge movements into dog healthy and failing cardiac SR vesicles. Although not directly demonstrated, the most probable explanation of these activities is the displacement of PLB from SERCA2a.E2 conformation, independently from cAMP/PKA. We propose that this displacement may favour the SERCA2a conformational transition from E2 to E1, thus resulting in the acceleration of Ca(2) (+) cycling. CONCLUSIONS AND IMPLICATIONS Istaroxime represents the first example of a small molecule that exerts a luso-inotropic effect in the failing human heart through the stimulation of SERCA2a ATPase activity and the enhancement of Ca(2) (+) uptake into the SR by relieving the PLB inhibitory effect on SERCA2a in a cAMP/PKA independent way.
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Affiliation(s)
- Mara Ferrandi
- Prassis Sigma-Tau Research Institute, Settimo Milanese, Milan, Italy
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15
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You J, Moon H, Lee BY, Jin JY, Chang ZE, Kim SY, Park J, Hwang YS, Kim J. Cardiomyocyte sensor responsive to changes in physical and chemical environments. J Biomech 2014; 47:400-9. [DOI: 10.1016/j.jbiomech.2013.11.013] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2013] [Revised: 11/05/2013] [Accepted: 11/06/2013] [Indexed: 10/26/2022]
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16
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Sikkel MB, Hayward C, MacLeod KT, Harding SE, Lyon AR. SERCA2a gene therapy in heart failure: an anti-arrhythmic positive inotrope. Br J Pharmacol 2014; 171:38-54. [PMID: 24138023 PMCID: PMC3874695 DOI: 10.1111/bph.12472] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2013] [Revised: 09/16/2013] [Accepted: 09/24/2013] [Indexed: 01/14/2023] Open
Abstract
Therapeutic options that directly enhance cardiomyocyte contractility in chronic heart failure (HF) therapy are currently limited and do not improve prognosis. In fact, most positive inotropic agents, such as β-adrenoreceptor agonists and PDE inhibitors, which have been assessed in HF patients, cause increased mortality as a result of arrhythmia and sudden cardiac death. Cardiac sarcoplasmic reticulum Ca(2)(+) -ATPase2a (SERCA2a) is a key protein involved in sequestration of Ca(2)(+) into the sarcoplasmic reticulum (SR) during diastole. There is a reduction of SERCA2a protein level and function in HF, which has been successfully targeted via viral transfection of the SERCA2a gene into cardiac tissue in vivo. This has enhanced cardiac contractility and reduced mortality in several preclinical models of HF. Theoretical concerns have been raised regarding the possibility of arrhythmogenic adverse effects of SERCA2a gene therapy due to enhanced SR Ca(2)(+) load and induction of SR Ca(2)(+) leak as a result. Contrary to these concerns, SERCA2a gene therapy in a wide variety of preclinical models, including acute ischaemia/reperfusion, chronic pressure overload and chronic myocardial infarction, has resulted in a reduction in ventricular arrhythmias. The potential mechanisms for this unexpected beneficial effect, as well as mechanisms of enhancement of cardiac contractile function, are reviewed in this article.
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Affiliation(s)
- Markus B Sikkel
- Myocardial Function Section, National Heart and Lung Institute, Imperial CollegeLondon, UK
| | - Carl Hayward
- Myocardial Function Section, National Heart and Lung Institute, Imperial CollegeLondon, UK
- NIHR Cardiovascular Biomedical Research Unit, Royal Brompton HospitalLondon, UK
| | - Kenneth T MacLeod
- Myocardial Function Section, National Heart and Lung Institute, Imperial CollegeLondon, UK
| | - Sian E Harding
- Myocardial Function Section, National Heart and Lung Institute, Imperial CollegeLondon, UK
| | - Alexander R Lyon
- Myocardial Function Section, National Heart and Lung Institute, Imperial CollegeLondon, UK
- NIHR Cardiovascular Biomedical Research Unit, Royal Brompton HospitalLondon, UK
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17
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Pressor mechanism evaluation for phytochemical compounds using in silico compound–protein interaction prediction. Regul Toxicol Pharmacol 2013; 67:115-24. [DOI: 10.1016/j.yrtph.2013.07.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2012] [Revised: 07/20/2013] [Accepted: 07/22/2013] [Indexed: 01/30/2023]
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18
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Bueno-Orovio A, Sánchez C, Pueyo E, Rodriguez B. Na/K pump regulation of cardiac repolarization: insights from a systems biology approach. Pflugers Arch 2013; 466:183-93. [PMID: 23674099 DOI: 10.1007/s00424-013-1293-1] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2013] [Revised: 05/02/2013] [Accepted: 05/03/2013] [Indexed: 11/26/2022]
Abstract
The sodium-potassium pump is widely recognized as the principal mechanism for active ion transport across the cellular membrane of cardiac tissue, being responsible for the creation and maintenance of the transarcolemmal sodium and potassium gradients, crucial for cardiac cell electrophysiology. Importantly, sodium-potassium pump activity is impaired in a number of major diseased conditions, including ischemia and heart failure. However, its subtle ways of action on cardiac electrophysiology, both directly through its electrogenic nature and indirectly via the regulation of cell homeostasis, make it hard to predict the electrophysiological consequences of reduced sodium-potassium pump activity in cardiac repolarization. In this review, we discuss how recent studies adopting the systems biology approach, through the integration of experimental and modeling methodologies, have identified the sodium-potassium pump as one of the most important ionic mechanisms in regulating key properties of cardiac repolarization and its rate dependence, from subcellular to whole organ levels. These include the role of the pump in the biphasic modulation of cellular repolarization and refractoriness, the rate control of intracellular sodium and calcium dynamics and therefore of the adaptation of repolarization to changes in heart rate, as well as its importance in regulating pro-arrhythmic substrates through modulation of dispersion of repolarization and restitution. Theoretical findings are consistent across a variety of cell types and species including human, and widely in agreement with experimental findings. The novel insights and hypotheses on the role of the pump in cardiac electrophysiology obtained through this integrative approach could eventually lead to novel therapeutic and diagnostic strategies.
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Affiliation(s)
- Alfonso Bueno-Orovio
- Department of Computer Science, University of Oxford, Wolfson Building, Parks Road, Oxford, OX1 3QD, UK,
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19
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Oubaassine R, Weckering M, Kessler L, Breidert M, Roegel J, Eftekhari P. Insulin interacts directly with Na+/K+ATPase and protects from digoxin toxicity. Toxicology 2012; 299:1-9. [DOI: 10.1016/j.tox.2012.04.013] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2012] [Revised: 04/16/2012] [Accepted: 04/21/2012] [Indexed: 01/09/2023]
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20
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Soliman D, Wang L, Hamming KSC, Yang W, Fatehi M, Carter CC, Clanachan AS, Light PE. Late Sodium Current Inhibition Alone with Ranolazine Is Sufficient to Reduce Ischemia- and Cardiac Glycoside-Induced Calcium Overload and Contractile Dysfunction Mediated by Reverse-Mode Sodium/Calcium Exchange. J Pharmacol Exp Ther 2012; 343:325-32. [DOI: 10.1124/jpet.112.196949] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
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21
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Grandi E, Pandit SV, Voigt N, Workman AJ, Dobrev D, Jalife J, Bers DM. Human atrial action potential and Ca2+ model: sinus rhythm and chronic atrial fibrillation. Circ Res 2011; 109:1055-66. [PMID: 21921263 DOI: 10.1161/circresaha.111.253955] [Citation(s) in RCA: 252] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
RATIONALE Understanding atrial fibrillation (AF) requires integrated understanding of ionic currents and Ca2+ transport in remodeled human atrium, but appropriate models are limited. OBJECTIVE To study AF, we developed a new human atrial action potential (AP) model, derived from atrial experimental results and our human ventricular myocyte model. METHODS AND RESULTS Atria versus ventricles have lower I(K1), resulting in more depolarized resting membrane potential (≈7 mV). We used higher I(to,fast) density in atrium, removed I(to,slow), and included an atrial-specific I(Kur). I(NCX) and I(NaK) densities were reduced in atrial versus ventricular myocytes according to experimental results. SERCA function was altered to reproduce human atrial myocyte Ca2+ transients. To simulate chronic AF, we reduced I(CaL), I(to), I(Kur) and SERCA, and increased I(K1),I(Ks) and I(NCX). We also investigated the link between Kv1.5 channelopathy, [Ca2+]i, and AF. The sinus rhythm model showed a typical human atrial AP morphology. Consistent with experiments, the model showed shorter APs and reduced AP duration shortening at increasing pacing frequencies in AF or when I(CaL) was partially blocked, suggesting a crucial role of Ca2+ and Na+ in this effect. This also explained blunted Ca2+ transient and rate-adaptation of [Ca2+]i and [Na+]i in chronic AF. Moreover, increasing [Na+]i and altered I(NaK) and I(NCX) causes rate-dependent atrial AP shortening. Blocking I(Kur) to mimic Kv1.5 loss-of-function increased [Ca2+]i and caused early afterdepolarizations under adrenergic stress, as observed experimentally. CONCLUSIONS Our study provides a novel tool and insights into ionic bases of atrioventricular AP differences, and shows how Na+ and Ca2+ homeostases critically mediate abnormal repolarization in AF.
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Affiliation(s)
- Eleonora Grandi
- Department of Pharmacology, University of California, Davis, 451 Health Sciences Dr, GBSF Room 3513, Davis, CA 95616-8636, USA
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Fan X, Ma J, Wan W, Zhang P, Wang C, Wu L. Increased intracellular calcium concentration causes electrical turbulence in guinea pig ventricular myocytes. SCIENCE CHINA-LIFE SCIENCES 2011; 54:240-7. [PMID: 21416323 DOI: 10.1007/s11427-011-4146-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2010] [Accepted: 12/21/2010] [Indexed: 01/25/2023]
Abstract
Dysregulation of intracellular Ca(2+) homeostasis is associated with various pathological conditions and arrhythmogenesis of the heart. The objective of this study was to investigate the effects of an acute increase in intracellular Ca(2+) concentration ([Ca(2+)](i)) on the electrophysiology of ventricular myocytes by mimicking intracellular Ca(2+) overload. The [Ca(2+)](i) was clamped to either a controlled (65-100 nmol L(-1)) or increased (1 μmol L(-1)) level. The transmembrane action potentials and ionic currents were recorded using whole-cell patch clamp techniques. We found that the acute increase in [Ca(2+)](i) shortened the action potential duration, reduced the action potential amplitude, maximum depolarization velocity and resting membrane potential, caused delayed after-depolarizations (DADs), and triggered activity-compared with these parameters in the control. The increased [Ca(2+)](i) augmented late I (Na) in a time-dependent manner, reduced I (CaL) and I (K1), and increased I (Kr) but not I (Ks). The results of this study can be used to explain calcium overload-induced ventricular arrhythmias.
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Affiliation(s)
- Xinrong Fan
- Cardio-Electrophysiological Research Laboratory, Medical College of Wuhan University of Science and Technology, Wuhan 430081, China
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Role and mechanism of subcellular Ca2+ distribution in the action of two inotropic agents with different toxicity. J Mol Cell Cardiol 2011; 50:910-8. [PMID: 21354172 DOI: 10.1016/j.yjmcc.2011.02.008] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/19/2011] [Accepted: 02/14/2011] [Indexed: 01/23/2023]
Abstract
Pro-arrhythmic risk strongly limits the therapeutic value of current inotropic interventions. Istaroxime (previously PST2744) is a novel inotropic agent, significantly less pro-arrhythmic than digoxin that, in addition to block Na(+)/K(+) pump, stimulates sarcoplasmic reticulum (SR) Ca(2+) ATPase (SERCA2). Here we compare istaroxime and digoxin effects to further address the role of SR modulation in reducing the toxicity associated with Na(+)/K(+) pump blockade. In murine ventricular myocytes both compounds increased cell twitch (inotropy) in a concentration-dependent fashion. At high concentrations digoxin, but not istaroxime, induced unstimulated contractions, a sign of pro-arrhythmic toxicity. To evaluate the mechanism of this difference, we compared the two drugs at concentrations exerting equal inotropy but different toxicity. At these concentrations: (1) the two drugs equally inhibited the Na(+)/K(+) pump; (2) digoxin induced larger increases in resting Ca(2+) and in diastolic Ca(2+) during pacing; (3) neither drug affected the relationship between RyR-mediated SR Ca(2+) leak and Ca(2+) content; (4) istaroxime, but not digoxin, enhanced SR Ca(2+) reuptake rate. In conclusion, digoxin toxicity was associated to larger accumulation of cytosolic Ca(2+), which did not result from RyR facilitation, but which might ultimately induce it to promote unstimulated Ca(2+) release. The lower toxicity of Na(+)/K(+) pump blockade by istaroxime may thus reflect improved Ca(2+) confinement within the SR, likely to result from concomitant SERCA2 stimulation.
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Koivumäki JT, Korhonen T, Tavi P. Impact of sarcoplasmic reticulum calcium release on calcium dynamics and action potential morphology in human atrial myocytes: a computational study. PLoS Comput Biol 2011; 7:e1001067. [PMID: 21298076 PMCID: PMC3029229 DOI: 10.1371/journal.pcbi.1001067] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2010] [Accepted: 12/21/2010] [Indexed: 02/02/2023] Open
Abstract
Electrophysiological studies of the human heart face the fundamental challenge that experimental data can be acquired only from patients with underlying heart disease. Regarding human atria, there exist sizable gaps in the understanding of the functional role of cellular Ca²+ dynamics, which differ crucially from that of ventricular cells, in the modulation of excitation-contraction coupling. Accordingly, the objective of this study was to develop a mathematical model of the human atrial myocyte that, in addition to the sarcolemmal (SL) ion currents, accounts for the heterogeneity of intracellular Ca²+ dynamics emerging from a structurally detailed sarcoplasmic reticulum (SR). Based on the simulation results, our model convincingly reproduces the principal characteristics of Ca²+ dynamics: 1) the biphasic increment during the upstroke of the Ca²+ transient resulting from the delay between the peripheral and central SR Ca²+ release, and 2) the relative contribution of SL Ca²+ current and SR Ca²+ release to the Ca²+ transient. In line with experimental findings, the model also replicates the strong impact of intracellular Ca²+ dynamics on the shape of the action potential. The simulation results suggest that the peripheral SR Ca²+ release sites define the interface between Ca²+ and AP, whereas the central release sites are important for the fire-diffuse-fire propagation of Ca²+ diffusion. Furthermore, our analysis predicts that the modulation of the action potential duration due to increasing heart rate is largely mediated by changes in the intracellular Na+ concentration. Finally, the results indicate that the SR Ca²+ release is a strong modulator of AP duration and, consequently, myocyte refractoriness/excitability. We conclude that the developed model is robust and reproduces many fundamental aspects of the tight coupling between SL ion currents and intracellular Ca²+ signaling. Thus, the model provides a useful framework for future studies of excitation-contraction coupling in human atrial myocytes.
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Affiliation(s)
- Jussi T. Koivumäki
- Department of Biotechnology and Molecular Medicine, A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland
| | - Topi Korhonen
- Department of Biotechnology and Molecular Medicine, A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland
| | - Pasi Tavi
- Department of Biotechnology and Molecular Medicine, A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland
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Acute heart failure with low cardiac output: can we develop a short-term inotropic agent that does not increase adverse events? Curr Heart Fail Rep 2010; 7:100-9. [PMID: 20625945 DOI: 10.1007/s11897-010-0021-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Acute heart failure represents an increasingly common cause of hospitalization, and may require the use of inotropic drugs in patients with low cardiac output and evidence of organ hypoperfusion. However, currently available therapies may have deleterious effects and increase mortality. An ideal inotropic drug should restore effective tissue perfusion by enhancing myocardial contractility without causing adverse effects. Such a drug is not available yet. New agents with different biological targets are under clinical development. In particular, istaroxime seems to dissociate the inotropic effect exerted by digitalis (inhibition of the membrane sodium/potassium adenosine triphosphatase) from the arrhythmic effect and to ameliorate diastolic dysfunction (via sarcoendoplasmic reticulum calcium adenosine triphosphatase activation). Additionally, the myosin activator omecamtiv mecarbil appears to have promising characteristics, while genetic therapy has been explored in animal studies only. Further investigations are needed to confirm and expand the effectiveness and safety of these agents in patients with acute heart failure and low cardiac output.
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26
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Macías A, Moreno C, Moral-Sanz J, Cogolludo A, David M, Alemanni M, Pérez-Vizcaíno F, Zaza A, Valenzuela C, González T. Celecoxib blocks cardiac Kv1.5, Kv4.3 and Kv7.1 (KCNQ1) channels: effects on cardiac action potentials. J Mol Cell Cardiol 2010; 49:984-92. [PMID: 20858500 DOI: 10.1016/j.yjmcc.2010.09.012] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/18/2010] [Revised: 07/30/2010] [Accepted: 09/14/2010] [Indexed: 12/23/2022]
Abstract
Celecoxib is a COX-2 inhibitor that has been related to an increased cardiovascular risk and that exerts several actions on different targets. The aim of this study was to analyze the effects of this drug on human cardiac voltage-gated potassium channels (Kv) involved on cardiac repolarization Kv1.5 (I(Kur)), Kv4.3+KChIP2 (I(to1)) and Kv7.1+KCNE1 (I(Ks)) and to compare with another COX-2 inhibitor, rofecoxib. Currents were recorded in transfected mammalian cells by whole-cell patch-clamp. Celecoxib blocked all the Kv channels analyzed and rofecoxib was always less potent, except on Kv4.3+KChIP2 channels. Kv1.5 block increased in the voltage range of channel activation, decreasing at potentials positive to 0 mV. The drug modified the activation curve of the channels that became biphasic. Block was frequency-dependent, increasing at fastest frequencies. Celecoxib effects were not altered by TEA(out) in R487Y mutant Kv1.5 channels but the kinetics of block were slower and the degree of block was smaller with TEA(in), indicating that celecoxib acts from the cytosolic side. We confirmed the blocking properties of celecoxib on native Kv currents from rat vascular cells, where Kv1.5 are the main contributors (IC(50)≈ 7 μM). Finally, we demonstrate that celecoxib prolongs the action potential duration in mouse cardiac myocytes and shortens it in guinea pig cardiac myocytes, suggesting that Kv block induced by celecoxib may be of clinical relevance.
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Affiliation(s)
- Alvaro Macías
- Instituto de Investigaciones Biomédicas Alberto Sols CSIC/UAM, Madrid, Spain
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Grandi E, Pasqualini FS, Bers DM. A novel computational model of the human ventricular action potential and Ca transient. J Mol Cell Cardiol 2009; 48:112-21. [PMID: 19835882 DOI: 10.1016/j.yjmcc.2009.09.019] [Citation(s) in RCA: 296] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/27/2009] [Revised: 08/18/2009] [Accepted: 09/30/2009] [Indexed: 11/17/2022]
Abstract
We have developed a detailed mathematical model for Ca handling and ionic currents in the human ventricular myocyte. Our aims were to: (1) simulate basic excitation-contraction coupling phenomena; (2) use realistic repolarizing K current densities; (3) reach steady-state. The model relies on the framework of the rabbit myocyte model previously developed by our group, with subsarcolemmal and junctional compartments where ion channels sense higher [Ca] vs. bulk cytosol. Ion channels and transporters have been modeled on the basis of the most recent experimental data from human ventricular myocytes. Rapidly and slowly inactivating components of I(to) have been formulated to differentiate between endocardial and epicardial myocytes. Transmural gradients of Ca handling proteins and Na pump were also simulated. The model has been validated against a wide set of experimental data including action potential duration (APD) adaptation and restitution, frequency-dependent increase in Ca transient peak and [Na](i). Interestingly, Na accumulation at fast heart rate is a major determinant of APD shortening, via outward shifts in Na pump and Na-Ca exchange currents. We investigated the effects of blocking K currents on APD and repolarization reserve: I(Ks) block does not affect the former and slightly reduces the latter; I(K1) blockade modestly increases APD and more strongly reduces repolarization reserve; I(Kr) blockers significantly prolong APD, an effect exacerbated as pacing frequency is decreased, in good agreement with experimental results in human myocytes. We conclude that this model provides a useful framework to explore excitation-contraction coupling mechanisms and repolarization abnormalities at the single myocyte level.
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Affiliation(s)
- Eleonora Grandi
- Department of Pharmacology, University of California, 451 Health Sciences Drive, GBSF Room 3513, Davis, CA 95616-8636, USA
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28
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Abstract
Antiarrhythmic drug therapy, broadly defined, is the mainstay of treatment and prevention of ventricular tachycardia (VT)/ventricular fibrillation (VF), which can lead to sudden death. This article evaluates the evidence for and appropriate use of class I antiarrhythmic drugs, class III antiarrhythmic drugs, beta-blockers, nondihydropyridine calcium-channel blockers, statins, angiotensin enzyme inhibitors, angiotensin receptor blockers, aldosterone blockers, and digoxin for antiarrhythmic benefits in patients who have a propensity for VT/VF and therefore are at risk of sudden death.
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29
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Rocchetti M, Alemanni M, Mostacciuolo G, Barassi P, Altomare C, Chisci R, Micheletti R, Ferrari P, Zaza A. Modulation of Sarcoplasmic Reticulum Function by PST2744 [Istaroxime; (E,Z)-3-((2-Aminoethoxy)imino) Androstane-6,17-dione Hydrochloride)] in a Pressure-Overload Heart Failure Model. J Pharmacol Exp Ther 2008; 326:957-65. [DOI: 10.1124/jpet.108.138701] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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30
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De Luca L, Mebazaa A, Filippatos G, Parissis JT, Böhm M, Voors AA, Nieminen M, Zannad F, Rhodes A, El-Banayosy A, Dickstein K, Gheorghiade M. Overview of emerging pharmacologic agents for acute heart failure syndromes. Eur J Heart Fail 2008; 10:201-13. [PMID: 18279775 DOI: 10.1016/j.ejheart.2008.01.002] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/04/2007] [Revised: 11/15/2007] [Accepted: 01/02/2008] [Indexed: 01/08/2023] Open
Abstract
BACKGROUND Several therapies commonly used for the treatment of acute heart failure syndromes (AHFS) present some well-known limitations and have been associated with an early increase in the risk of death. There is, therefore, an unmet need for new pharmacologic agents for the early management of AHFS that may improve both short- and long-term outcomes. AIM To review the recent evidence on emerging pharmacologic therapies in AHFS. METHODS A systematic search of peer-reviewed publications was performed on MEDLINE, EMBASE and Clinical Trials.gov from January 1990 to August 2007. The results of unpublished or ongoing trials were obtained from presentations at national and international meetings and pharmaceutical industry releases. Bibliographies from these references were also reviewed, as were additional articles identified by content experts. RESULTS Cumulative data from large studies and randomised trials suggest that therapies with innovative mechanisms of action may safely and effectively reduce pulmonary congestion or improve cardiac performance in AHFS patients. CONCLUSION Some investigational agents for the management of AHFS are able to improve haemodynamics and/or clinical status. In spite of these promising findings, no new agent has demonstrated a clear benefit in terms of long-term clinical outcomes compared to placebo or conventional therapies.
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Affiliation(s)
- Leonardo De Luca
- Department of Cardiovascular Sciences, European Hospital, Rome, Italy
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31
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Abstract
Given the limitations of high-dose diuretics and vasodilators and the increasing literature showing that inotropes, regardless of the dose used, have a detrimental effect on mortality, a variety of new agents are under investigation for the treatment of pulmonary and systemic congestion and restoration of cardiac output in the setting of acute heart failure syndromes. The new therapeutic approach is based on two goals: short-term improvement in symptoms together with long-term improvement of cardiac function. This review describes new agents that are in preclinical and in clinical phases with realistic prospects: anti-endothelin, natriuretic peptides, istaroxime, levosimendan, myosin activators, and vasopressin antagonists. Those new therapeutic strategies aim to act at the cellular level to improve vessel and heart functions, with minimal side effects, together with improved sodium and water balance.
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32
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Lee AS, Wu TS, Su MJ. Pharmacological profile of the new inotropic agent AT-11. Eur J Pharmacol 2007; 580:224-30. [PMID: 18031738 DOI: 10.1016/j.ejphar.2007.10.056] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2007] [Revised: 10/02/2007] [Accepted: 10/22/2007] [Indexed: 11/30/2022]
Abstract
Although there are many classes of drugs, including cardiac glycosides, sympathomimetic inotropes, beta-adrenergic antagonists, angiotensin-converting enzyme inhibitors (ACE inhibitors) and spironolactone etc. used for the treatment of heart failure, the morbidity and mortality rates of patients after these treatments are not ameliorated. Chronic administration of Sympathomimetic inotropes also increased the arrhythmogenic effects. Consequently, improvement of treatment for heart failure remains a major medical challenge for the coming years. In this present experiment, the novel Na(+)-K(+) ATPase inhibitor AT-11 was characterized for its inotropic and toxic properties. Comparing AT-11 with ouabain, we found that AT-11 concentration-dependently increased contractility in guinea pig heart preparations, and the safety index of AT-11 was better than ouabain in vitro. In the in vivo study, AT-11 was also safer than ouabain at the equieffective dose. Moreover, AT-11 slowed heart rate more than ouabain did. This may be due to a larger AT-11-induced increase in vagal reflex than with ouabain and an indirect decrease in sympathetic tone to prevent Ca(2+) overload.
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Affiliation(s)
- An-Sheng Lee
- Institute of Pharmacology, College of Medicine, National Taiwan University, Taipei, Taiwan, ROC
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33
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Schoner W, Scheiner-Bobis G. Endogenous and exogenous cardiac glycosides: their roles in hypertension, salt metabolism, and cell growth. Am J Physiol Cell Physiol 2007; 293:C509-36. [PMID: 17494630 DOI: 10.1152/ajpcell.00098.2007] [Citation(s) in RCA: 337] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Cardiotonic steroids (CTS), long used to treat heart failure, are endogenously produced in mammals. Among them are the hydrophilic cardenolide ouabain and the more hydrophobic cardenolide digoxin, as well as the bufadienolides marinobufagenin and telecinobufagin. The physiological effects of endogenous ouabain on blood pressure and cardiac activity are consistent with the "Na(+)-lag" hypothesis. This hypothesis assumes that, in cardiac and arterial myocytes, a CTS-induced local increase of Na(+) concentration due to inhibition of Na(+)/K(+)-ATPase leads to an increase of intracellular Ca(2+) concentration ([Ca(2+)](i)) via a backward-running Na(+)/Ca(2+) exchanger. The increase in [Ca(2+)](i) then activates muscle contraction. The Na(+)-lag hypothesis may best explain short-term and inotropic actions of CTS. Yet all data on the CTS-induced alteration of gene expression are consistent with another hypothesis, based on the Na(+)/K(+)-ATPase "signalosome," that describes the interaction of cardiac glycosides with the Na(+) pump as machinery activating various signaling pathways via intramembrane and cytosolic protein-protein interactions. These pathways, which may be activated simultaneously or selectively, elevate [Ca(2+)](i), activate Src and the ERK1/2 kinase pathways, and activate phosphoinositide 3-kinase and protein kinase B (Akt), NF-kappaB, and reactive oxygen species. A recent development indicates that new pharmaceuticals with antihypertensive and anticancer activities may be found among CTS and their derivatives: the antihypertensive rostafuroxin suppresses Na(+) resorption and the Src-epidermal growth factor receptor-ERK pathway in kidney tubule cells. It may be the parent compound of a new principle of antihypertensive therapy. Bufalin and oleandrin or the cardenolide analog UNBS-1450 block tumor cell proliferation and induce apoptosis at low concentrations in tumors with constitutive activation of NF-kappaB.
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Affiliation(s)
- Wilhelm Schoner
- Institut für Biochemie und Endokrinologie, Fachbereich Veterinärmedizin, Justus-Liebig-Universität Giessen, Frankfurter Str 100, Giessen, Germany.
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34
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&NA;. Understanding the mechanisms and manifestations of digoxin toxicity helps in its management and treatment. DRUGS & THERAPY PERSPECTIVES 2007. [DOI: 10.2165/00042310-200723020-00007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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35
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Shin DD, Brandimarte F, De Luca L, Sabbah HN, Fonarow GC, Filippatos G, Komajda M, Gheorghiade M. Review of current and investigational pharmacologic agents for acute heart failure syndromes. Am J Cardiol 2007; 99:4A-23A. [PMID: 17239703 DOI: 10.1016/j.amjcard.2006.11.025] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Acute heart failure syndromes (AHFS) are a major public health problem and present a therapeutic challenge to clinicians. Commonly used agents in the treatment of AHFS include diuretics, vasodilators (eg, nitroglycerin, nitroprusside, nesiritide), and inotropes (eg, dobutamine, dopamine, milrinone). Patients admitted to hospital with AHFS and low cardiac output state (AHFS/LO) represent a subgroup with very high inhospital and postdischarge mortality rates. Most of these patients require intravenous inotropic therapy. However, the use of current intravenous inotropes has been associated with risk for hypotension, atrial and ventricular arrhythmias, and possibly increased postdischarge mortality, particularly in those with coronary artery disease. Consequently, there is an unmet need for new agents to safely improve cardiac performance (contractility and/or active relaxation) in this patient population. This article reviews a selection of current and investigational agents for the treatment of AHFS, with a main focus on the high-risk patient population with AHFS/LO.
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Affiliation(s)
- David D Shin
- Northwestern University Feinberg School of Medicine, Chicago, Illinois 60611, USA, and Division of Cardiology, European Hospital, Rome, Italy
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36
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Ghali JK, Smith WB, Torre-Amione G, Haynos W, Rayburn BK, Amato A, Zhang D, Cowart D, Valentini G, Carminati P, Gheorghiade M. A phase 1-2 dose-escalating study evaluating the safety and tolerability of istaroxime and specific effects on electrocardiographic and hemodynamic parameters in patients with chronic heart failure with reduced systolic function. Am J Cardiol 2007; 99:47A-56A. [PMID: 17239705 DOI: 10.1016/j.amjcard.2006.09.006] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Istaroxime (PST2744) is a luso-inotrope that stimulates the sarcoplasmic reticulum calcium adenosine triphosphatase isoform 2a without chronotropic effects. Additionally, it has beneficial effects on myocardial energetics. This phase 1-2 clinical trial in patients with chronic stable heart failure (HF) is the first evaluation of istaroxime in humans. Three cohorts of 6 patients each were exposed to 4 sequentially increasing 1-hour infusions with a random placebo. Doses were 0.005-5.0 micro/kg per min. Safety and hemodynamics were evaluated by impedance cardiography, digital Holter recorder, and electrocardiography. Pharmacokinetic data were obtained for 1 hour during treatment and for 6 hours after dosing. The mean age was 53+/-7 years, and the mean left ventricular ejection fraction was 0.27+/-0.08. Impedance cardiography demonstrated enhanced contractility as measured by the acceleration index, left cardiac work index, cardiac index, and pulse pressure at doses>or=1 micro/kg per min, with evidence of activity at doses of 0.5 micro/kg per min. Istaroxime shortened QTc. After infusion, the hemodynamic effect rapidly dissipated over 1-2 hours. Istaroxime was pharmacologically active and well tolerated at doses up to 3.33 micro/kg per min. Side effects were related to gastrointestinal symptoms and injection site pain at higher doses, which dissipated within minutes after the infusion ended. Ventricular ectopy was not altered. This study suggests that istaroxime is potentially useful in the treatment of HF and may offer a unique treatment for systolic and/or diastolic dysfunction. Additional studies are under way to further define its utility in acute HF.
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Affiliation(s)
- Jalal K Ghali
- Louisiana State University Health Sciences Center, Shreveport, Louisiana, USA
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37
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Mattera GG, Lo Giudice P, Loi FMP, Vanoli E, Gagnol JP, Borsini F, Carminati P. Istaroxime: a new luso-inotropic agent for heart failure. Am J Cardiol 2007; 99:33A-40A. [PMID: 17239702 DOI: 10.1016/j.amjcard.2006.09.004] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Istaroxime is a new luso-inotropic compound selected for the treatment of acute heart failure syndromes, which reduces sodium-potassium adenosine triphosphatase (ATPase) activity and stimulates the sarcoplasmic calcium ATPase isoform 2 reuptake function. The aim of this study was to evaluate the safety profile of istaroxime. For this purpose, istaroxime was administered during a 24-hour infusion to conscious dogs with chronic heart failure and to genetically cardiomyopathic BIO TO.2 hamsters for 34 weeks orally. The parameters recorded were arrhythmic events and hemodynamic effects in dogs and mortality in hamsters. In dogs, istaroxime at 1, 3, and 4 microg/kg per min did not trigger arrhythmic events or magnify preexisting events. It increased left ventricular (LV) dP/dtmax (about 50% at 3 microg/kg per min) and LV-dP/dtmax (about 20% at 3 microg/kg per min) without changing heart rate, blood pressure, or double product. At 4 microg/kg per min, istaroxime increased dP/dtmax>100% but induced intense emesis in all animals. In cardiomyopathic hamsters, the dose of 30 mg/kg prolonged the survival rate to 32%. In conclusion, istaroxime seems to be a promising and safe new drug for improving cardiac performance in the failing heart.
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Affiliation(s)
- Giovan Giuseppe Mattera
- Research and Development Division, sigma-tau Industrie Farmaceutiche Riunite SpA, Pomezia, Italy.
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38
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deGoma EM, Vagelos RH, Fowler MB, Ashley EA. Emerging therapies for the management of decompensated heart failure: from bench to bedside. J Am Coll Cardiol 2006; 48:2397-409. [PMID: 17174176 DOI: 10.1016/j.jacc.2006.08.039] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/18/2006] [Revised: 07/06/2006] [Accepted: 07/31/2006] [Indexed: 11/27/2022]
Abstract
While pharmaceutical innovation has been highly successful in reducing mortality in chronic heart failure, this has not been matched by similar success in decompensated heart failure syndromes. Despite outstanding issues over definitions and end points, we argue in this paper that an unprecedented wealth of pharmacologic innovation may soon transform the management of these challenging patients. Agents that target contractility, such as cardiac myosin activators and novel adenosine triphosphate-dependent transmembrane sodium-potassium pump inhibitors, provide inotropic support without arrhythmogenic increases in cytosolic calcium or side effects of more traditional agents. Adenosine receptor blockade may improve glomerular filtration and diuresis by exerting a direct beneficial effect on glomerular blood flow while vasopressin antagonists promote free water excretion without compromising renal function and may simultaneously inhibit myocardial remodeling. Urodilatin, the renally synthesized isoform of atrial natriuretic peptide, may improve pulmonary congestion via vasodilation and enhanced diuresis. Finally, metabolic modulators such as perhexiline may optimize myocardial energy utilization by shifting adenosine triphosphate production from free fatty acids to glucose, a unique and conceptually appealing approach to the management of heart failure. These advances allow optimism not only for the advancement of our understanding and management of decompensated heart failure syndromes but for the translational research effort in heart failure biology in general.
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Affiliation(s)
- Emil M deGoma
- Stanford University, Stanford, California 94305, USA
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39
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Wang L, Wible BA, Wan X, Ficker E. Cardiac glycosides as novel inhibitors of human ether-a-go-go-related gene channel trafficking. J Pharmacol Exp Ther 2006; 320:525-34. [PMID: 17095614 DOI: 10.1124/jpet.106.113043] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Direct block of the cardiac potassium channel human ether-a-go-go-related gene (hERG) by a large, structurally diverse group of therapeutic compounds causes drug-induced QT prolongation and torsades de pointes arrhythmias. In addition, several therapeutic compounds have been identified more recently that prolong the QT interval by inhibition of hERG trafficking to the cell surface. We used a surface expression assay to identify novel compounds that interfere with hERG trafficking and found that cardiac glycosides are potent inhibitors of hERG expression at the cell surface. Further investigation of digitoxin, ouabain, and digoxin revealed that all three cardiac glycosides reduced expression of the fully glycosylated cell surface form of hERG on Western blots, indicating that channel exit from the endoplasmic reticulum is blocked. Likewise, hERG currents were reduced with nanomolar affinity on long-term exposure. hERG trafficking inhibition was initiated by cardiac glycosides through direct block of Na(+)/K(+) pumps and not via off-target interactions with hERG or another closely associated protein in its processing or export pathway. In isolated guinea pig myocytes, long-term exposure to 30 nM of the clinically used drugs digoxin or digitoxin reduced hERG/rapidly activating delayed rectifier K(+) current (I(Kr)) currents by approximately 50%, whereas three other cardiac membrane currents--inward rectifier current, slowly activating delayed rectifier K(+) current, and calcium current--were not affected. Importantly, 100 nM digitoxin prolonged action potential duration on long-term exposure consistent with a reduction in hERG/I(Kr) channel number. Thus, cardiac glycosides are able to delay cardiac repolarization at nanomolar concentrations via hERG trafficking inhibition, and this may contribute to the complex electrocardiographic changes seen with compounds such as digitoxin.
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Affiliation(s)
- Lu Wang
- Rammelkamp Center for Education and Research, Case Western Reserve University, Cleveland, OH 44109, USA
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Bauman JL, Didomenico RJ, Galanter WL. Mechanisms, manifestations, and management of digoxin toxicity in the modern era. Am J Cardiovasc Drugs 2006; 6:77-86. [PMID: 16555861 DOI: 10.2165/00129784-200606020-00002] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Because of the common use of digoxin and because of its narrow therapeutic index, digoxin toxicity has been prevalent historically and, therefore, most clinicians are well aware of the classical dose/concentration-related signs and symptoms of toxicity. Yet, in the modern era the incidence of digoxin toxicity has been declining for a variety of reasons, including a new (lower) therapeutic range, the development of more effective drug therapies for heart failure, and more accurate dosing methods. In addition, digoxin toxicity, once commonly fatal, can now be quickly and effectively treated by the emergency administration of antidigoxin Fab fragments. Indeed, it may be possible to expand the use of Fab fragments to select patients with non-life-threatening digoxin toxicity, in order to save costs and improve patient comfort. Most cases of digoxin toxicity are caused by inappropriately high dosages, which are usually prescribed in the setting of renal dysfunction, while other cases can be attributed to system errors such as multiple prescriptions, poor patient counseling, or errors in transcribing. With modern computerized prescribing systems, such as direct physician order entry and prompts that alert the clinician to the potential for error, it is possible to decrease the incidence of digoxin toxicity even further. A realistic goal is to nearly eradicate once commonplace digoxin toxicity or at least make its occurrence a rare event.
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Affiliation(s)
- Jerry L Bauman
- Department of Pharmacy Practice, University of Illinois at Chicago, Chicago, Illinois 60612, USA.
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Rocchetti M, Besana A, Mostacciuolo G, Micheletti R, Ferrari P, Sarkozi S, Szegedi C, Jona I, Zaza A. Modulation of Sarcoplasmic Reticulum Function by Na+/K+Pump Inhibitors with Different Toxicity: Digoxin and PST2744 [(E,Z)-3-((2-Aminoethoxy)imino)androstane-6,17-dione Hydrochloride]. J Pharmacol Exp Ther 2004; 313:207-15. [PMID: 15576469 DOI: 10.1124/jpet.104.077933] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
OBJECTIVE To gain some insight on the lesser arrhythmogenic properties of PST2744 [(E,Z)-3-((2-aminoethoxy)imino)androstane-6,17-dione hydrochloride] compared with digoxin, we compared modulation of intracellular Ca2+ dynamics by the two agents. METHODS SERCA (sarcoplasmic reticulum Ca2+-ATPase) activity and Ca2+ leak rate were measured in sarcoplasmic reticulum (SR) vesicles from guinea pig ventricles. Membrane current, intracellular Ca2+, and twitch amplitude were evaluated in guinea pig ventricular myocytes with or without blockade of the Na+/Ca2+ exchanger. RESULTS In SR vesicles, PST2744 (30-300 nM), but not digoxin, increased SERCA activity; digoxin only (> or =0.1 nM) increased SR Ca2+ leak. In myocytes with blocked Na+/Ca2+ exchanger, Ca2+ reloading of caffeine-depleted SR was enhanced by PST2744 and slightly inhibited by digoxin. In myocytes with functioning Na+/Ca2+ exchanger, both agents increased diastolic Ca2+, SR Ca2+ content, the gain of Ca2+-induced Ca2+ release, the rate of cytosolic Ca2+ decay, twitch amplitude, and relaxation rate. Consistent with the observations in SR vesicles, the effects on SR Ca2+ content and Ca2+ decay rate were significantly larger for PST2744 than for digoxin. CONCLUSIONS In isolated SR vesicles, PST2744 and digoxin directly affected SR function in opposite ways; this could be reproduced in myocytes during Na+/Ca2+ exchanger blockade. Under physiological conditions (functioning Na+/Ca2+ exchanger), the two agents affected Ca2+ dynamics in the same direction, as expected by their Na+/K+ pump inhibition; however, differential SR modulation was still expressed by quantitative differences. Thus, the more favorable inotropy-to-toxicity ratio previously described for PST2744 appears to be associated with direct SERCA stimulation and/or lack of enhancement of Ca2+ leak.
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Affiliation(s)
- Marcella Rocchetti
- Dipartimento di Biotecnologie e Bioscienze, Università degli Studi Milano-Bicocca, P.zza della Scienza 2, 20126 Milano, Italy
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Ruch SR, Nishio M, Wasserstrom JA. Effect of cardiac glycosides on action potential characteristics and contractility in cat ventricular myocytes: role of calcium overload. J Pharmacol Exp Ther 2003; 307:419-28. [PMID: 12954807 DOI: 10.1124/jpet.103.049189] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
There is increasing evidence that cardiac glycosides act through mechanisms distinct from inhibition of the sodium pump but which may contribute to their cardiac actions. To more fully define differences between agents indicative of multiple sites of action, we studied changes in contractility and action potential (AP) configuration in cat ventricular myocytes produced by six cardiac glycosides (ouabain, ouabagenin, dihydroouabain, actodigin, digoxin, and resibufogenin). AP shortening was observed only with ouabain and actodigin. There was extensive inotropic variability between agents, with some giving full inotropic effects before automaticity occurred whereas others produced minimal inotropy before toxicity. AP shortening was not a result of alterations in calcium current or the inward rectifier potassium current, but correlated with an increase in steady-state outward current (Iss), which was sensitive to KB-R7943, a Na+-Ca2+ exchange (NCX) inhibitor. Interestingly, Iss was observed following exposure to ouabain and dihydroouabain, suggesting that an additional mechanism is operative with dihydroouabain that prevents AP shortening. Further investigation into differences in inotropy between ouabagenin, dihydroouabain and ouabain revealed almost identical responses under AP voltage clamp. Thus all agents appear to act on the sodium pump and thereby secondarily increase the outward reverse mode NCX current, but the extent of AP duration shortening and positive inotropy elicited by each agent is limited by development of their toxic actions. The quantitative differences between cardiac glycosides suggest that mechanisms independent of sodium pump inhibition may result from an altered threshold for calcium overload possibly involving direct or indirect effects on calcium release from the sarcoplasmic reticulum.
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Affiliation(s)
- Stuart R Ruch
- Department of Medicine, Feinberg Cardiovascular Research Institute, Northwestern University Medical School, Chicago, IL 60611, USA
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