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Lunde IG, Aronsen JM, Melleby AO, Strand ME, Skogestad J, Bendiksen BA, Ahmed MS, Sjaastad I, Attramadal H, Carlson CR, Christensen G. Cardiomyocyte-specific overexpression of syndecan-4 in mice results in activation of calcineurin-NFAT signalling and exacerbated cardiac hypertrophy. Mol Biol Rep 2022; 49:11795-11809. [PMID: 36205855 PMCID: PMC9712407 DOI: 10.1007/s11033-022-07985-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2022] [Accepted: 09/24/2022] [Indexed: 02/01/2023]
Abstract
BACKGROUND Cardiomyocyte hypertrophy is a hallmark of cardiac dysfunction in patients with aortic stenosis (AS), and can be triggered by left ventricular (LV) pressure overload in mice by aortic banding (AB). Syndecan-4 is a transmembrane heparan sulphate proteoglycan which is found increased in the myocardium of AS patients and AB mice. The role of syndecan-4 in cardiomyocyte hypertrophy is not well understood. PURPOSE OF THE STUDY We developed mice with cardiomyocyte-specific overexpression of syndecan-4 (Sdc4-Tg) and subjected these to AB to examine the role of syndecan-4 in hypertrophy and activation of the pro-hypertrophic calcineurin-NFAT signalling pathway. METHODS AND RESULTS Sdc4-Tg mice showed exacerbated cardiac remodelling upon AB compared to wild type (WT). At 2-6 weeks post-AB, Sdc4-Tg and WT mice showed similar hypertrophic growth, while at 20 weeks post-AB, exacerbated hypertrophy and dysfunction were evident in Sdc4-Tg mice. After cross-breeding of Sdc4-Tg mice with NFAT-luciferase reporter mice, we found increased NFAT activation in Sdc4-Tg hearts after AB. Immunoprecipitation showed that calcineurin bound to syndecan-4 in Sdc4-Tg hearts. Isolated cardiomyocytes from Sdc4-Tg mice showed alterations in Ca2+ fluxes, suggesting that syndecan-4 regulated Ca2+ levels, and thereby, activating the syndecan-4-calcineurin complex resulting in NFAT activation and hypertrophic growth. Similarly, primary cardiomyocyte cultures from neonatal rats showed increased calcineurin-NFAT-dependent hypertrophic growth upon viral Sdc4 overexpression. CONCLUSION Our study of mice with cardiomyocyte-specific overexpression of Sdc4 have revealed that syndecan-4 is important for activation of the Ca2+-dependent calcineurin-NFAT signalling pathway, hypertrophic remodelling and dysfunction in cardiomyocytes in response to pressure overload.
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Affiliation(s)
- Ida G Lunde
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway.
- KG Jebsen Center for Cardiac Research, University of Oslo, Oslo, Norway.
- Division of Diagnostics and Technology, Akershus University Hospital, Lørenskog, Norway.
- Institute for Experimental Medical Research (IEMR), Oslo University Hospital Ullevaal, Building 7, 4th floor, Kirkeveien 166, 0407, Oslo, Norway.
| | - J Magnus Aronsen
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway
- Institute for Medical Biosciences, University of Oslo, Oslo, Norway
| | - A Olav Melleby
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway
- Institute for Medical Biosciences, University of Oslo, Oslo, Norway
| | - Mari E Strand
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway
- KG Jebsen Center for Cardiac Research, University of Oslo, Oslo, Norway
| | - Jonas Skogestad
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway
- Institute for Medical Biosciences, University of Oslo, Oslo, Norway
| | - Bård A Bendiksen
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway
- KG Jebsen Center for Cardiac Research, University of Oslo, Oslo, Norway
| | - M Shakil Ahmed
- Institute for Surgical Research, Oslo University Hospital and University of Oslo, Oslo, Norway
| | - Ivar Sjaastad
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway
- KG Jebsen Center for Cardiac Research, University of Oslo, Oslo, Norway
| | - Håvard Attramadal
- Institute for Surgical Research, Oslo University Hospital and University of Oslo, Oslo, Norway
| | - Cathrine R Carlson
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway
- KG Jebsen Center for Cardiac Research, University of Oslo, Oslo, Norway
| | - Geir Christensen
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway
- KG Jebsen Center for Cardiac Research, University of Oslo, Oslo, Norway
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Ottesen AH, Raiborg C, Melleby AO, Hansen MSH, Hafver TL, Sandbu RA, Aronsen JM, Etholm L, Stokke MK, Sjaastad I, Louch WE, Carlson CR, Christensen G, Rosjo H. Synapsin 2 regulates NCX1 trafficking and is down-regulated in the failing myocardium, which increases the risk of ventricular arrhythmia and heart failure mortality. Eur Heart J 2022. [DOI: 10.1093/eurheartj/ehac544.2974] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Abstract
Background
Synapsin 2 (Syn2) modulates vesicle transport in the post-synaptic terminal in the brain, and has been linked to sudden unexplained death in epilepsy, but has never previously been studied in the myocardium.
Purpose
Given the association of vesicle transport in the brain and the heart, and the similarity of sudden death in epilepsy and cardiac arrhythmias, we have studied the role of Syn2 in the heart.
Methods
We explored left ventricular (LV) Syn2 levels in various experimental heart failure (HF) models and assessed mortality in Syn2 knock out (KO) mice vs. wild type (WT) littermates after pressure-overload induced by aortic banding. We used confocal imaging and virus transduction to characterize Syn2 localization and co-localization with NCX and Rab proteins. We verified Syn2-NCX interaction by immunoprecipitation, mass spectrometry, and surface resonance experiments. We investigated calcium handling in isolated cardiomyocytes. Susceptibility for ventricular arrhythmias was also tested in Langendorff-perfused hearts.
Results
We found Syn2, but not synapsin 1, to be expressed in the myocardium. LV Syn2 levels were markedly downregulated in the failing myocardium after experimental myocardial infarction or aortic banding. Syn2 KO mice had increased mortality compared to WT littermates following aortic banding, but demonstrated no clear clinical or echocardiographic phenotype, except reduced fractional shortening. Given no clear etiology for increased mortality, we next explored the association between Syn2 and ion-channel vesicle transport, calcium handling and ventricular arrhythmias. By confocal imaging and viral transduction, we found Syn2 to localize in vesicles in HL-1 cells, where Syn2 co-localized with Rab2, Rab3, Rab7 and NCX1. Syn2 was also found to interact with NCX1 as tested by immunoprecipitation, mass spectrometry, and surface resonance experiments. NCX1 levels were downregulated in the membrane fraction in the left ventricle of Syn2 KO mice compared to WT littermates following aortic banding. We observed increased frequency of calcium sparks and waves in isolated Syn2 KO cardiomyocytes compared to controls. We found enhanced susceptibility of Syn2 KO mice for ventricular arrhythmias compared to WT littermates mice during ISO stress testing in explanted hearts. Hearts from Syn2 KO mice also demonstrated more severe ventricular arrhythmias compared to hearts from WT littermates controls.
Conclusions
We report for the first time that Syn2 is expressed in the myocardium and that Syn2 seems to regulate NCX1 transport and localization. We also found markedly reduced LV Syn2 levels in HF individuals and mice that lacked Syn2 more frequent displayed severe ventricular arrhythmias and had increased mortality. Hence, our data suggest that reduced Syn2 in the failing myocardium may lead to increased mortality, possibly linked to altered NCX trafficking and subsequent ventricular arrhythmias.
Funding Acknowledgement
Type of funding sources: None.
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Affiliation(s)
- A H Ottesen
- Akershus University Hospital , Lørenskog , Norway
| | - C Raiborg
- Oslo University Hospital , Oslo , Norway
| | | | | | - T L Hafver
- Oslo University Hospital , Oslo , Norway
| | - R A Sandbu
- Oslo University Hospital , Oslo , Norway
| | | | - L Etholm
- Oslo University Hospital , Oslo , Norway
| | - M K Stokke
- Oslo University Hospital , Oslo , Norway
| | - I Sjaastad
- Oslo University Hospital , Oslo , Norway
| | - W E Louch
- Oslo University Hospital , Oslo , Norway
| | | | | | - H Rosjo
- Akershus University Hospital , Lørenskog , Norway
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3
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Silva GJJ, Parvan R, Shen X, Frisk M, Altara R, Strand ME, Rypdal KB, Lunde IG, Louch WE, Aronsen JM, Stenslokken KO, Stokke MK, Cataliotti A. ProANP31-67 ameliorates adverse cardiac remodeling and improves systolic and diastolic functions in a preclinical model of cardiorenal syndrome. Cardiovasc Res 2022. [DOI: 10.1093/cvr/cvac066.080] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Abstract
Funding Acknowledgements
Type of funding sources: Public grant(s) – National budget only. Main funding source(s): South-Eastern Norway Regional Health Authority (HSØ-RHF, Project No. 25674)
Background
The cardiac hormone proANP31-67, a linear fragment of the N-terminal Atrial Natriuretic Peptide, has known enhancing renal effects. More recently, we described the cardio protective effects of this hormone in a model of chronic hypertension. More specifically, independently of the blood pressure level, proANP31-67 improved diastolic function, attenuated cardiac fibrosis, and reduced hypertrophy.
Purpose
The current study was designed to assess the cardiorenal effects of proANP31-67 in a rodent model of hampered renal function, followed by cardiac injury produced by ischemia/reperfusion (I/R).
Methods
Right uninephrectomy (UNX) was performed in Wistar rats (n=28). Sixteen weeks after UNX, rats underwent cardiac I/R injury and randomly assigned to proANP31-67 (50 ng/kg/day s.c., n=15) or Vehicle (n=13) for four weeks post I/R. Echocardiographic examinations were performed at baseline (before UNX), 16 weeks after UNX, and four weeks after I/R. At the end of the study, cardiomyocytes were isolated and tissue samples were collected.
Results
Chronic UNX resulted in diastolic impairment (E/A: 1.47±0.08 at baseline vs 0.98±0.14 at 16 wks post UNX, p=0.0010). I/R further accentuated the development of the cardiorenal syndrome, and induced a mild systolic dysfunction in the placebo treated animals. However, four weeks of treatment with proANP31-67 preserved systolic function (EF: 62±3% placebo vs 74±2% proANP31-67, p<0.0001), and reverted the diastolic dysfunction (E/A: 0.72±0.15 placebo vs 1.24±0.11 proANP31-67, p=0.0134). ProANP31-67 ameliorated the adverse cardiac remodeling (i.e., reduction in the cardiomyocyte cross-sectional area and interstitial fibrosis), enhanced Ca2+ handling, and improved cardiomyocyte t-tubules´ structural changes compared to vehicle. At the cellular level, in vitro experiments demonstrated the direct effect of proANP31-67 on cardiomyocyte hypertrophy (assessed by [3H]-leucine incorporation) induced by endothelin 1 and angiotensin II.
Conclusion
ProANP31-67 has a direct cardiomyocyte protective effect, leading to an improvement in Ca2+ homeostasis and t-tubules´ structures and, prevents the development of systolic and diastolic dysfunction in a pre-clinical model of cardiorenal syndrome.
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Affiliation(s)
- GJJ Silva
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway , Oslo , Norway
| | - R Parvan
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway , Oslo , Norway
| | - X Shen
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway , Oslo , Norway
| | - M Frisk
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway , Oslo , Norway
| | - R Altara
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway , Oslo , Norway
| | - ME Strand
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway , Oslo , Norway
| | - KB Rypdal
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway , Oslo , Norway
| | - IG Lunde
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway , Oslo , Norway
| | - WE Louch
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway , Oslo , Norway
| | - JM Aronsen
- Institute of Basic Medical Sciences, Faculty of Medicine, University of Oslo , Oslo , Norway
| | - K-O Stenslokken
- Institute of Basic Medical Sciences, Faculty of Medicine, University of Oslo , Oslo , Norway
| | - MK Stokke
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway , Oslo , Norway
| | - A Cataliotti
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway , Oslo , Norway
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4
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Frisk M, Le C, Shen X, Røe ÅT, Hou Y, Manfra O, Silva GJJ, van Hout I, Norden ES, Aronsen JM, Laasmaa M, Espe EKS, Zouein FA, Lambert RR, Dahl CP, Sjaastad I, Lunde IG, Coffey S, Cataliotti A, Gullestad L, Tønnessen T, Jones PP, Altara R, Louch WE. Etiology-Dependent Impairment of Diastolic Cardiomyocyte Calcium Homeostasis in Heart Failure With Preserved Ejection Fraction. J Am Coll Cardiol 2021; 77:405-419. [PMID: 33509397 PMCID: PMC7840890 DOI: 10.1016/j.jacc.2020.11.044] [Citation(s) in RCA: 49] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/25/2020] [Revised: 10/26/2020] [Accepted: 11/16/2020] [Indexed: 12/11/2022]
Abstract
BACKGROUND Whereas heart failure with reduced ejection fraction (HFrEF) is associated with ventricular dilation and markedly reduced systolic function, heart failure with preserved ejection fraction (HFpEF) patients exhibit concentric hypertrophy and diastolic dysfunction. Impaired cardiomyocyte Ca2+ homeostasis in HFrEF has been linked to disruption of membrane invaginations called t-tubules, but it is unknown if such changes occur in HFpEF. OBJECTIVES This study examined whether distinct cardiomyocyte phenotypes underlie the heart failure entities of HFrEF and HFpEF. METHODS T-tubule structure was investigated in left ventricular biopsies obtained from HFrEF and HFpEF patients, whereas cardiomyocyte Ca2+ homeostasis was studied in rat models of these conditions. RESULTS HFpEF patients exhibited increased t-tubule density in comparison with control subjects. Super-resolution imaging revealed that higher t-tubule density resulted from both tubule dilation and proliferation. In contrast, t-tubule density was reduced in patients with HFrEF. Augmented collagen deposition within t-tubules was observed in HFrEF but not HFpEF hearts. A causative link between mechanical stress and t-tubule disruption was supported by markedly elevated ventricular wall stress in HFrEF patients. In HFrEF rats, t-tubule loss was linked to impaired systolic Ca2+ homeostasis, although diastolic Ca2+ removal was also reduced. In contrast, Ca2+ transient magnitude and release kinetics were largely maintained in HFpEF rats. However, diastolic Ca2+ impairments, including reduced sarco/endoplasmic reticulum Ca2+-ATPase activity, were specifically observed in diabetic HFpEF but not in ischemic or hypertensive models. CONCLUSIONS Although t-tubule disruption and impaired cardiomyocyte Ca2+ release are hallmarks of HFrEF, such changes are not prominent in HFpEF. Impaired diastolic Ca2+ homeostasis occurs in both conditions, but in HFpEF, this mechanism for diastolic dysfunction is etiology-dependent.
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Affiliation(s)
- Michael Frisk
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway; K.G. Jebsen Center for Cardiac Research, University of Oslo, Oslo, Norway. https://twitter.com/IEMRLouch
| | - Christopher Le
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway; K.G. Jebsen Center for Cardiac Research, University of Oslo, Oslo, Norway
| | - Xin Shen
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway; K.G. Jebsen Center for Cardiac Research, University of Oslo, Oslo, Norway
| | - Åsmund T Røe
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway; K.G. Jebsen Center for Cardiac Research, University of Oslo, Oslo, Norway
| | - Yufeng Hou
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway; K.G. Jebsen Center for Cardiac Research, University of Oslo, Oslo, Norway
| | - Ornella Manfra
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway; K.G. Jebsen Center for Cardiac Research, University of Oslo, Oslo, Norway
| | - Gustavo J J Silva
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway; K.G. Jebsen Center for Cardiac Research, University of Oslo, Oslo, Norway
| | - Isabelle van Hout
- Department of Physiology, HeartOtago, University of Otago, Otago, New Zealand
| | - Einar S Norden
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway; K.G. Jebsen Center for Cardiac Research, University of Oslo, Oslo, Norway; Bjørknes College, Oslo, Norway
| | - J Magnus Aronsen
- Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
| | - Martin Laasmaa
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway; K.G. Jebsen Center for Cardiac Research, University of Oslo, Oslo, Norway
| | - Emil K S Espe
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway; K.G. Jebsen Center for Cardiac Research, University of Oslo, Oslo, Norway
| | - Fouad A Zouein
- Department of Pharmacology and Toxicology, American University of Beirut Medical Center, Faculty of Medicine, Riad El-Solh, Beirut, Lebanon
| | - Regis R Lambert
- Department of Physiology, HeartOtago, University of Otago, Otago, New Zealand
| | - Christen P Dahl
- Department of Cardiology, Oslo University Hospital, Rikshospitalet, Oslo, Norway; Research Institute for Internal Medicine, Oslo University Hospital, Rikshospitalet, Oslo, Norway
| | - Ivar Sjaastad
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway; K.G. Jebsen Center for Cardiac Research, University of Oslo, Oslo, Norway; Department of Cardiology, Oslo University Hospital, Ullevål, Oslo, Norway
| | - Ida G Lunde
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway; K.G. Jebsen Center for Cardiac Research, University of Oslo, Oslo, Norway
| | - Sean Coffey
- Department of Medicine and HeartOtago, Dunedin School of Medicine, University of Otago, Dunedin, New Zealand
| | - Alessandro Cataliotti
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway; K.G. Jebsen Center for Cardiac Research, University of Oslo, Oslo, Norway
| | - Lars Gullestad
- Department of Cardiology, Oslo University Hospital, Rikshospitalet, Oslo, Norway; Research Institute for Internal Medicine, Oslo University Hospital, Rikshospitalet, Oslo, Norway
| | - Theis Tønnessen
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway; K.G. Jebsen Center for Cardiac Research, University of Oslo, Oslo, Norway; Department of Cardiothoracic Surgery, Oslo University Hospital Ullevål, Oslo, Norway
| | - Peter P Jones
- Department of Physiology, HeartOtago, University of Otago, Otago, New Zealand
| | - Raffaele Altara
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway; K.G. Jebsen Center for Cardiac Research, University of Oslo, Oslo, Norway. https://twitter.com/IEMRLouch
| | - William E Louch
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway; K.G. Jebsen Center for Cardiac Research, University of Oslo, Oslo, Norway
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5
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Lipsett DB, Frisk M, Aronsen JM, Nordén ES, Buonarati OR, Cataliotti A, Hell JW, Sjaastad I, Christensen G, Louch WE. Cardiomyocyte substructure reverts to an immature phenotype during heart failure. J Physiol 2019; 597:1833-1853. [PMID: 30707448 PMCID: PMC6441900 DOI: 10.1113/jp277273] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2018] [Accepted: 01/28/2019] [Indexed: 12/16/2022] Open
Abstract
Key points As reactivation of the fetal gene program has been implicated in pathological remodelling during heart failure (HF), we examined whether cardiomyocyte subcellular structure and function revert to an immature phenotype during this disease. Surface and internal membrane structures appeared gradually during development, and returned to a juvenile state during HF. Similarly, dyadic junctions between the cell membrane and sarcoplasmic reticulum were progressively ‘packed’ with L‐type Ca2+ channels and ryanodine receptors during development, and ‘unpacked’ during HF. Despite similarities in subcellular structure, dyads were observed to be functional from early developmental stages, but exhibited an impaired ability to release Ca2+ in failing cardiomyocytes. Thus, while immature and failing cardiomyocytes share similarities in subcellular structure, these do not fully account for the marked impairment of Ca2+ homeostasis observed in HF.
Abstract Reactivation of the fetal gene programme has been implicated as a driver of pathological cardiac remodelling. Here we examined whether pathological remodelling of cardiomyocyte substructure and function during heart failure (HF) reflects a reversion to an immature phenotype. Using scanning electron microscopy, we observed that Z‐grooves and t‐tubule openings at the cell surface appeared gradually during cardiac development, and disappeared during HF. Confocal and super‐resolution imaging within the cell interior revealed similar structural parallels; disorganization of t‐tubules in failing cells was strikingly reminiscent of the late stages of postnatal development, with fewer transverse elements and a high proportion of longitudinal tubules. Ryanodine receptors (RyRs) were observed to be laid down in advance of developing t‐tubules and similarly ‘orphaned’ in HF, although RyR distribution along Z‐lines was relatively sparse. Indeed, nanoscale imaging revealed coordinated packing of L‐type Ca2+ channels and RyRs into dyadic junctions during development, and orderly unpacking during HF. These findings support a ‘last in, first out’ paradigm, as the latest stages of dyadic structural development are reversed during disease. Paired imaging of t‐tubules and Ca2+ showed that the disorganized arrangement of dyads in immature and failing cells promoted desynchronized and slowed Ca2+ release in these two states. However, while developing cells exhibited efficient triggering of Ca2+ release at newly formed dyads, dyadic function was impaired in failing cells despite similar organization of Ca2+ handling proteins. Thus, pathologically deficient Ca2+ homeostasis during HF is only partly linked to the re‐emergence of immature subcellular structure, and additionally reflects lost dyadic functionality. As reactivation of the fetal gene program has been implicated in pathological remodelling during heart failure (HF), we examined whether cardiomyocyte subcellular structure and function revert to an immature phenotype during this disease. Surface and internal membrane structures appeared gradually during development, and returned to a juvenile state during HF. Similarly, dyadic junctions between the cell membrane and sarcoplasmic reticulum were progressively ‘packed’ with L‐type Ca2+ channels and ryanodine receptors during development, and ‘unpacked’ during HF. Despite similarities in subcellular structure, dyads were observed to be functional from early developmental stages, but exhibited an impaired ability to release Ca2+ in failing cardiomyocytes. Thus, while immature and failing cardiomyocytes share similarities in subcellular structure, these do not fully account for the marked impairment of Ca2+ homeostasis observed in HF.
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Affiliation(s)
- D B Lipsett
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway
| | - M Frisk
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway.,KG Jebsen Center for Cardiac Research, University of Oslo, Oslo, Norway
| | - J M Aronsen
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway.,Bjørknes College, Oslo, Norway
| | - E S Nordén
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway.,KG Jebsen Center for Cardiac Research, University of Oslo, Oslo, Norway
| | - O R Buonarati
- Department of Pharmacology, University of California Davis, Davis, CA, USA
| | - A Cataliotti
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway.,KG Jebsen Center for Cardiac Research, University of Oslo, Oslo, Norway
| | - J W Hell
- Department of Pharmacology, University of California Davis, Davis, CA, USA
| | - I Sjaastad
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway.,KG Jebsen Center for Cardiac Research, University of Oslo, Oslo, Norway
| | - G Christensen
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway.,KG Jebsen Center for Cardiac Research, University of Oslo, Oslo, Norway
| | - W E Louch
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway.,KG Jebsen Center for Cardiac Research, University of Oslo, Oslo, Norway
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Skogestad J, Lines GT, Louch WE, Sejersted OM, Sjaastad I, Aronsen JM. Evidence for heterogeneous subsarcolemmal Na + levels in rat ventricular myocytes. Am J Physiol Heart Circ Physiol 2019; 316:H941-H957. [PMID: 30657726 DOI: 10.1152/ajpheart.00637.2018] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The intracellular Na+ concentration ([Na+]) regulates cardiac contractility. Previous studies have suggested that subsarcolemmal [Na+] is higher than cytosolic [Na+] in cardiac myocytes, but this concept remains controversial. Here, we used electrophysiological experiments and mathematical modeling to test whether there are subsarcolemmal pools with different [Na+] and dynamics compared with the bulk cytosol in rat ventricular myocytes. A Na+ dependency curve for Na+-K+-ATPase (NKA) current was recorded with symmetrical Na+ solutions, i.e., the same [Na+] in the superfusate and internal solution. This curve was used to estimate [Na+] sensed by NKA in other experiments. Three experimental observations suggested that [Na+] is higher near NKA than in the bulk cytosol: 1) when extracellular [Na+] was high, [Na+] sensed by NKA was ~6 mM higher than the internal solution in quiescent cells; 2) long trains of Na+ channel activation almost doubled this gradient; compared with an even intracellular distribution of Na+, the increase of [Na+] sensed by NKA was 10 times higher than expected, suggesting a local Na+ domain; and 3) accumulation of Na+ near NKA after trains of Na+ channel activation dissipated very slowly. Finally, mathematical models assuming heterogeneity of [Na+] between NKA and the Na+ channel better reproduced experimental data than the homogeneous model. In conclusion, our data suggest that NKA-sensed [Na+] is higher than [Na+] in the bulk cytosol and that there are differential Na+ pools in the subsarcolemmal space, which could be important for cardiac contractility and arrhythmogenesis. NEW & NOTEWORTHY Our data suggest that the Na+-K+-ATPase-sensed Na+ concentration is higher than the Na+ concentration in the bulk cytosol and that there are differential Na+ pools in the subsarcolemmal space, which could be important for cardiac contractility and arrhythmogenesis. Listen to this article's corresponding podcast at https://ajpheart.podbean.com/e/heterogeneous-sodium-in-ventricular-myocytes/ .
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Affiliation(s)
- J Skogestad
- Institute for Experimental Medical Research, Oslo University Hospital Ullevål and University of Oslo , Oslo , Norway
| | - G T Lines
- Simula Research Laboratory, Center for Cardiological Innovation , Oslo , Norway
| | - W E Louch
- Institute for Experimental Medical Research, Oslo University Hospital Ullevål and University of Oslo , Oslo , Norway.,K. G. Jebsen Center for Cardiac Research, University of Oslo , Oslo , Norway
| | - O M Sejersted
- Institute for Experimental Medical Research, Oslo University Hospital Ullevål and University of Oslo , Oslo , Norway
| | - I Sjaastad
- Institute for Experimental Medical Research, Oslo University Hospital Ullevål and University of Oslo , Oslo , Norway.,K. G. Jebsen Center for Cardiac Research, University of Oslo , Oslo , Norway
| | - J M Aronsen
- Institute for Experimental Medical Research, Oslo University Hospital Ullevål and University of Oslo , Oslo , Norway.,Bjørknes College , Oslo , Norway
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7
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Frisk M, Espe EK, Røe ÅT, Aronsen JM, Zhang L, Enger UH, Sejersted OM, Sjaastad I, Sjaastad I, Louch WE. Ventricular Wall Stress Predicts Disruption of Cardiomyocyte T-Tubule Structure and Ca2+ Homeostasis across the Infarcted Heart. Biophys J 2015. [DOI: 10.1016/j.bpj.2014.11.602] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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Aronsen JM, Skogestad J, Lewalle A, Louch WE, Hougen K, Stokke MK, Swift F, Niederer S, Smith NP, Sejersted OM, Sjaastad I. Hypokalaemia induces Ca²⁺ overload and Ca²⁺ waves in ventricular myocytes by reducing Na⁺,K⁺-ATPase α₂ activity. J Physiol 2014; 593:1509-21. [PMID: 25772299 DOI: 10.1113/jphysiol.2014.279893] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2014] [Accepted: 10/02/2014] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Hypokalaemia is a risk factor for development of ventricular arrhythmias. In rat ventricular myocytes, low extracellular K(+) (corresponding to clinical moderate hypokalaemia) increased Ca(2+) wave probability, Ca(2+) transient amplitude, sarcoplasmic reticulum (SR) Ca(2+) load and induced SR Ca(2+) leak. Low extracellular K(+) reduced Na(+),K(+)-ATPase (NKA) activity and hyperpolarized the resting membrane potential in ventricular myocytes. Both experimental data and modelling indicate that reduced NKA activity and subsequent Na(+) accumulation sensed by the Na(+), Ca(2+) exchanger (NCX) lead to increased Ca(2+) transient amplitude despite concomitant hyperpolarization of the resting membrane potential. Low extracellular K(+) induced Ca(2+) overload by lowering NKA α2 activity. Triggered ventricular arrhythmias in patients with hypokalaemia may therefore be attributed to reduced NCX forward mode activity linked to an effect on the NKA α2 isoform. ABSTRACT Hypokalaemia is a risk factor for development of ventricular arrhythmias. The aim of this study was to determine the cellular mechanisms leading to triggering of arrhythmias in ventricular myocytes exposed to low Ko. Low Ko, corresponding to moderate hypokalaemia, increased Ca(2+) transient amplitude, sarcoplasmic reticulum (SR) Ca(2+) load, SR Ca(2+) leak and Ca(2+) wave probability in field stimulated rat ventricular myocytes. The mechanisms leading to Ca(2+) overload were examined. Low Ko reduced Na(+),K(+)-ATPase (NKA) currents, increased cytosolic Na(+) concentration and increased the Na(+) level sensed by the Na(+), Ca(2+) exchanger (NCX). Low Ko also hyperpolarized the resting membrane potential (RMP) without significant alterations in action potential duration. Experiments in voltage clamped and field stimulated ventricular myocytes, along with mathematical modelling, suggested that low Ko increases the Ca(2+) transient amplitude by reducing NKA activity despite hyperpolarization of the RMP. Selective inhibition of the NKA α2 isoform by low dose ouabain abolished the ability of low Ko to reduce NKA currents, to increase Na(+) levels sensed by NCX and to increase the Ca(2+) transient amplitude. We conclude that low Ko, within the range of moderate hypokalaemia, increases Ca(2+) levels in ventricular myocytes by reducing the pumping rate of the NKA α2 isoform with subsequent Na(+) accumulation sensed by the NCX. These data highlight reduced NKA α2 -mediated control of NCX activity as a possible mechanism underlying triggered ventricular arrhythmias in patients with hypokalaemia.
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Affiliation(s)
- J M Aronsen
- Institute for Experimental Medical Research, Oslo University Hospital Ullevål and University of Oslo, Oslo, Norway; Bjørknes College, Oslo, Norway
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Moltzau LR, Aronsen JM, Meier S, Nguyen CHT, Hougen K, Ørstavik Ø, Sjaastad I, Christensen G, Skomedal T, Osnes JB, Levy FO, Qvigstad E. SERCA2 activity is involved in the CNP-mediated functional responses in failing rat myocardium. Br J Pharmacol 2014; 170:366-79. [PMID: 23808942 DOI: 10.1111/bph.12282] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2012] [Revised: 06/03/2013] [Accepted: 06/10/2013] [Indexed: 11/29/2022] Open
Abstract
BACKGROUND AND PURPOSES Myocardial C-type natriuretic peptide (CNP) levels are increased in heart failure. CNP can induce negative inotropic (NIR) and positive lusitropic responses (LR) in normal hearts, but its effects in failing hearts are not known. We studied the mechanism of CNP-induced NIR and LR in failing hearts and determined whether sarcoplasmatic reticulum Ca(2+) ATPase2 (SERCA2) activity is essential for these responses. EXPERIMENTAL APPROACH Contractility, cGMP levels, Ca(2+) transient amplitudes and protein phosphorylation were measured in left ventricular muscle strips or ventricular cardiomyocytes from failing hearts of Wistar rats 6 weeks after myocardial infarction. KEY RESULTS CNP increased cGMP levels, evoked a NIR and LR in muscle strips, and caused phospholamban (PLB) Ser(16) and troponin I (TnI) Ser(23/24) phosphorylation in cardiomyocytes. Both the NIR and LR induced by CNP were reduced in the presence of a PKG blocker/cGMP analogue (Rp-8-Br-Pet-cGMPS) and the SERCA inhibitor thapsigargin. CNP increased the amplitude of the Ca(2+) transient and increased SERCA2 activity in cardiomyocytes. The CNP-elicited NIR and LR were not affected by the L-type Ca(2+) channel activator BAY-K8644, but were abolished in the presence of isoprenaline (induces maximal activation of cAMP pathway). This suggests that phosphorylation of PLB and TnI by CNP causes both a NIR and LR. The NIR to CNP in mouse heart was abolished 8 weeks after cardiomyocyte-specific inactivation of the SERCA2 gene. CONCLUSIONS AND IMPLICATIONS We conclude that CNP-induced PLB and TnI phosphorylation by PKG in concert mediate both a predictable LR as well as the less expected NIR in failing hearts.
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Affiliation(s)
- L R Moltzau
- Department of Pharmacology, Faculty of Medicine, University of Oslo and Oslo University Hospital, Oslo, Norway; KG Jebsen Cardiac Research Centre and Center for Heart Failure Research, Faculty of Medicine, University of Oslo, Oslo, Norway
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Holmen YD, Sjaastad I, Yndestad A, Ranheim T, Alfsnes K, Aronsen JM, Gullestad L, Aukrust P, Christensen G, Vinge LE. P627Systemic toll-like receptor 9 activation increases mortality in SERCA2a KO mediated diastolic heart failure. Cardiovasc Res 2014. [DOI: 10.1093/cvr/cvu098.55] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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Dugstad KU, Ulsund AH, Aronsen JM, Sjaastad I, Zaccolo M, Levy FO, Andressen KW. P605Unraveling tight spatiotemporal regulation of 5-HT4 receptor-mediated inotropic effects using targeted FRET-based cAMP sensors. Cardiovasc Res 2014. [DOI: 10.1093/cvr/cvu098.34] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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Boardman NT, Aronsen JM, Louch WE, Sjaastad I, Willoch F, Christensen G, Sejersted O, Aasum E. Impaired left ventricular mechanical and energetic function in mice after cardiomyocyte-specific excision of Serca2. Am J Physiol Heart Circ Physiol 2014; 306:H1018-24. [PMID: 24486508 DOI: 10.1152/ajpheart.00741.2013] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Sarco(endo)plasmic reticulum Ca2+ -ATPase (SERCA)2 transports Ca2+ from the cytosol into the sarcoplasmic reticulum of cardiomyocytes and is essential for maintaining myocardial Ca2+ handling and thus the mechanical function of the heart. SERCA2 is a major ATP consumer in excitation-contraction coupling but is regarded to contribute to energetically efficient Ca2+ handling in the cardiomyocyte. Previous studies using cardiomyocyte-specific SERCA2 knockout (KO) mice have demonstrated that decreased SERCA2 activity reduces the Ca2+ transient amplitude and induces compensatory Ca2+ transport mechanisms that may lead to more inefficient Ca2+ transport. In this study, we examined the relationship between left ventricular (LV) function and myocardial O2 consumption (MVo2) in ex vivo hearts from SERCA2 KO mice to directly measure how SERCA2 elimination influences mechanical and energetic features of the heart. Ex vivo hearts from SERCA2 KO hearts developed mechanical dysfunction at 4 wk and demonstrated virtually no working capacity at 7 wk. In accordance with the reported reduction in Ca2+ transient amplitude in cardiomyocytes from SERCA2 KO mice, work-independent MVo2 was decreased due to a reduced energy cost of excitation-contraction coupling. As these hearts also showed a marked impairment in the efficiency of chemomechanical energy transduction (contractile efficiency, i.e, work-dependent MVo2), hearts from SERCA2 KO mice were found to be mechanically inefficient. This ex vivo evaluation of mechanical and energetic function in hearts from SERCA2 KO mice brings together findings from previous experimental and mathematical modeling-based studies and demonstrates that reduced SERCA2 activity not only leads to mechanical dysfunction but also to energetic dysfunction.
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Affiliation(s)
- N T Boardman
- Cardiovascular Research Group, Department of Medical Biology, Faculty of Health Sciences, UiT The Artic University of Norway, Tromsø, Norway
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Aronsen JM, Swift F, Sejersted OM. Cardiac sodium transport and excitation-contraction coupling. J Mol Cell Cardiol 2013; 61:11-9. [PMID: 23774049 DOI: 10.1016/j.yjmcc.2013.06.003] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/17/2013] [Revised: 05/17/2013] [Accepted: 06/05/2013] [Indexed: 01/12/2023]
Abstract
The excitation-contraction coupling (EC-coupling) links membrane depolarization with contraction in cardiomyocytes. Ca(2+) induced opening of ryanodine receptors (RyRs) leads to Ca(2+) induced Ca(2+) release (CICR) from the sarcoplasmic reticulum (SR) into the dyadic cleft between the t-tubules and SR. Ca(2+) is removed from the cytosol by the SR Ca(2+) ATPase (SERCA2) and the Na,Ca-exchanger (NCX). The NCX connects cardiac Ca(2+) and Na(+)-transport, leading to Na(+)-dependent regulation of EC-coupling by several mechanisms of which some still lack firm experimental evidence. Firstly, NCX might contribute to CICR during an action potential (AP) as Na(+)-accumulation at the intracellular site together with depolarization will trigger reverse mode exchange bringing Ca(2+) into the dyadic cleft. The controversial issue is the nature of the compartment in which Na(+) accumulates. It seems not to be the bulk cytosol, but is it part of a widespread subsarcolemmal space, a localized microdomain ("fuzzy space"), or as we propose, a more localized "spot" to which only a few membrane proteins have shared access (nanodomains)? Also, there seems to be spots where the Na,K-pump (NKA) will cause local Na(+) depletion. Secondly, Na(+) determines the rate of cytosolic Ca(2+) removal and SR Ca(2+) load by regulating the SERCA2/NCX-balance during the decay of the Ca(2+) transient. The aim of this review is to describe available data and current concepts of Na(+)-mediated regulation of cardiac EC-coupling, with special focus on subcellular microdomains and the potential roles of Na(+) transport proteins in regulating CICR and Ca(2+) extrusion in cardiomyocytes. We propose that voltage gated Na(+) channels, NCX and the NKA α2-isoform all regulate cardiac EC-coupling through control of the "Na(+) concentration in specific subcellular nanodomains in cardiomyocytes. This article is part of a Special Issue entitled "Na(+) Regulation in Cardiac Myocytes."
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Affiliation(s)
- J M Aronsen
- Institute for Experimental Medical Research, Oslo University Hospital Ullevål and University of Oslo, Oslo, Norway
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Hussain RI, Aronsen JM, Afzal F, Sjaastad I, Osnes JB, Skomedal T, Levy FO, Krobert KA. The functional activity of inhibitory G protein (G(i)) is not increased in failing heart ventricle. J Mol Cell Cardiol 2012; 56:129-38. [PMID: 23220156 DOI: 10.1016/j.yjmcc.2012.11.015] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/21/2012] [Revised: 11/22/2012] [Accepted: 11/24/2012] [Indexed: 11/16/2022]
Abstract
Beta-adrenergic receptor (βAR) inotropic effects are attenuated and muscarinic receptor-mediated inhibition thereof is enhanced in heart failure. We investigated if increased G(i) activity contributes to attenuated βAR-inotropic effects and potentiates muscarinic accentuated antagonism in failing rat ventricle. Contractility was measured in ventricular strips and adenylyl cyclase (AC) activity in ventricular membranes from rats with post-infarction heart failure (HF) or Sham-operated controls (Sham). The maximal βAR-mediated inotropic effect of isoproterenol was reduced by ~70% and basal, βAR- & forskolin-stimulated AC activity was significantly lower in HF vs. Sham. Carbachol-evoked antagonism of the βAR-mediated inotropic response was complete only in HF despite a ~40% reduction in the ability of carbachol to inhibit βAR-stimulated AC. However, neither the relative efficacy (contractility decreased by ~46%) nor the potency of carbachol to inhibit the βAR inotropic response differed between Sham and HF ventricle. Pertussis toxin (PTX) inactivation of G(i) did not increase the maximal βAR inotropic effect or the attenuated basal, βAR- & forskolin-stimulated AC activity in HF, but increased the potency of isoproterenol only in Sham (~0.5 log unit). In HF ventricle pretreated with PTX, simultaneous inhibition of phosphodiesterases 3,4 (PDE3,4) alone produced a larger inotropic response than isoproterenol in ventricle untreated with PTX (84% and 48% above basal respectively). In the absence of PTX, PDE3,4 inhibition evoked negligible inotropic effects in HF. These data are not consistent with the hypothesis that increased G(i) activity contributes to the reduced βAR-mediated inotropic response and AC activity in failing ventricle. The data, however, support the hypothesis that G(i), through chronic receptor independent inhibition of AC, together with PDE3,4 activity, is necessary to maintain a low basal level of contractility.
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Affiliation(s)
- R I Hussain
- Department of Pharmacology, Faculty of Medicine, University of Oslo, Oslo, Norway
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Hussain RI, Afzal F, Mørk HK, Aronsen JM, Sjaastad I, Osnes JB, Skomedal T, Levy FO, Krobert KA. Cyclic AMP-dependent inotropic effects are differentially regulated by muscarinic G(i)-dependent constitutive inhibition of adenylyl cyclase in failing rat ventricle. Br J Pharmacol 2011; 162:908-16. [PMID: 21039419 DOI: 10.1111/j.1476-5381.2010.01097.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
BACKGROUND AND PURPOSE β-Adrenoceptor (β-AR)-mediated inotropic effects are attenuated and G(i) proteins are up-regulated in heart failure (HF). Muscarinic receptors constitutively inhibit cAMP formation in normal rat cardiomyocytes. We determined whether constitutive activity of muscarinic receptors to inhibit adenylyl cyclase (AC) increases in HF and if so, whether it modifies the reduced β-AR- or emergent 5-HT₄-mediated cAMP-dependent inotropic effects. EXPERIMENTAL APPROACH Contractility and AC activity were measured and related to each other in rat ventricle with post-infarction HF and sham-operated (Sham) controls with or without blockade of muscarinic receptors by atropine and inactivation of G(i) protein by pertussis toxin (PTX). KEY RESULTS Isoprenaline-mediated inotropic effects were attenuated and basal, isoprenaline- and forskolin-stimulated AC activity was reduced in HF compared with Sham. Atropine or PTX pretreatment increased forskolin-stimulated AC activity in HF hearts. β-AR-stimulated AC and maximal inotropic response were unaffected by atropine in Sham and HF. In HF, the potency of serotonin (5-HT) to evoke an inotropic response was increased in the presence of atropine with no change in the maximal inotropic response. Interestingly, PTX pretreatment reduced the potency of 5-HT to evoke inotropic responses while increasing the maximal inotropic response. CONCLUSIONS AND IMPLICATIONS Although muscarinic constitutive inhibition of AC is increased in HF, it does not contribute to the reduced β-AR-mediated inotropic effects in rat ventricle in HF. The data support the hypothesis that there are differences in the functional compartmentation of 5-HT₄ and β-AR AC signalling in myocardium during HF.
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Affiliation(s)
- R I Hussain
- Department of Pharmacology, Faculty of Medicine, University of Oslo and Oslo University Hospital, Oslo, Norway
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Afzal F, Andressen KW, Mørk HK, Aronsen JM, Sjaastad I, Dahl CP, Skomedal T, Levy FO, Osnes JB, Qvigstad E. 5-HT4
-elicited positive inotropic response is mediated by cAMP and regulated by PDE3 in failing rat and human cardiac ventricles. Br J Pharmacol 2009. [DOI: 10.1038/bjp.2008.339 [pii]] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
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Afzal F, Andressen KW, Mørk HK, Aronsen JM, Sjaastad I, Dahl CP, Skomedal T, Levy FO, Osnes JB, Qvigstad E. 5-HT4-elicited positive inotropic response is mediated by cAMP and regulated by PDE3 in failing rat and human cardiac ventricles. Br J Pharmacol 2008; 155:1005-14. [PMID: 18846035 DOI: 10.1038/bjp.2008.339] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
BACKGROUND AND PURPOSE The left ventricle in failing hearts becomes sensitive to 5-HT parallelled by appearance of functional G(s)-coupled 5-HT(4) receptors. Here, we have explored the regulatory functions of phosphodiesterases in the 5-HT(4) receptor-mediated functional effects in ventricular muscle from failing rat and human heart. EXPERIMENTAL APPROACH Extensive myocardial infarctions were induced by coronary artery ligation in Wistar rats. Contractility was measured in left ventricular papillary muscles of rat, 6 weeks after surgery and in left ventricular trabeculae from explanted human hearts. cAMP was quantified by RIA. KEY RESULTS In papillary muscles from postinfarction rat hearts, 5-HT(4) stimulation exerted positive inotropic and lusitropic effects and increased cAMP. The inotropic effect was increased by non-selective PDE inhibition (IBMX, 10 microM) and selective inhibition of PDE3 (cilostamide, 1 microM), but not of PDE2 (EHNA, 10 microM) or PDE4 (rolipram, 10 microM). Combined PDE3 and PDE4 inhibition enhanced inotropic responses beyond the effect of PDE3 inhibition alone, increased the sensitivity to 5-HT, and also revealed an inotropic response in control (sham-operated) rat ventricle. Lusitropic effects were increased only during combined PDE inhibition. In failing human ventricle, the 5-HT(4) receptor-mediated positive inotropic response was regulated by PDEs in a manner similar to that in postinfarction rat hearts. CONCLUSIONS AND IMPLICATIONS 5-HT(4) receptor-mediated positive inotropic responses in failing rat ventricle were cAMP-dependent. PDE3 was the main PDE regulating this response and involvement of PDE4 was disclosed by concomitant inhibition of PDE3 in both postinfarction rat and failing human hearts. 5-HT, PDE3 and PDE4 may have pathophysiological functions in heart failure.
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Affiliation(s)
- F Afzal
- Department of Pharmacology, University of Oslo, Oslo, Norway
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