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Masjoan Juncos JX, Nadeem F, Shakil S, El-Husari M, Zafar I, Louch WE, Halade GV, Zaky A, Ahmad A, Ahmad S. Myocardial SERCA2 Protects Against Cardiac Damage and Dysfunction Caused by Inhaled Bromine. J Pharmacol Exp Ther 2024; 390:146-158. [PMID: 38772719 PMCID: PMC11192580 DOI: 10.1124/jpet.123.002084] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2023] [Revised: 05/03/2024] [Accepted: 05/08/2024] [Indexed: 05/23/2024] Open
Abstract
Myocardial sarcoendoplasmic reticulum calcium ATPase 2 (SERCA2) activity is critical for heart function. We have demonstrated that inhaled halogen (chlorine or bromine) gases inactivate SERCA2, impair calcium homeostasis, increase proteolysis, and damage the myocardium ultimately leading to cardiac dysfunction. To further elucidate the mechanistic role of SERCA2 in halogen-induced myocardial damage, we used bromine-exposed cardiac-specific SERCA2 knockout (KO) mice [tamoxifen-administered SERCA2 (flox/flox) Tg (αMHC-MerCreMer) mice] and compared them to the oil-administered controls. We performed echocardiography and hemodynamic analysis to investigate cardiac function 24 hours after bromine (600 ppm for 30 minutes) exposure and measured cardiac injury markers in plasma and proteolytic activity in cardiac tissue and performed electron microscopy of the left ventricle (LV). Cardiac-specific SERCA2 knockout mice demonstrated enhanced toxicity to bromine. Bromine exposure increased ultrastructural damage, perturbed LV shape geometry, and demonstrated acutely increased phosphorylation of phospholamban in the KO mice. Bromine-exposed KO mice revealed significantly enhanced mean arterial pressure and sphericity index and decreased LV end diastolic diameter and LV end systolic pressure when compared with the bromine-exposed control FF mice. Strain analysis showed loss of synchronicity, evidenced by an irregular endocardial shape in systole and irregular vector orientation of contractile motion across different segments of the LV in KO mice, both at baseline and after bromine exposure. These studies underscore the critical role of myocardial SERCA2 in preserving cardiac ultrastructure and function during toxic halogen gas exposures. SIGNIFICANCE STATEMENT: Due to their increased industrial production and transportation, halogens such as chlorine and bromine pose an enhanced risk of exposure to the public. Our studies have demonstrated that inhalation of these halogens leads to the inactivation of cardiopulmonary SERCA2 and results in calcium overload. Using cardiac-specific SERCA2 KO mice, these studies further validated the role of SERCA2 in bromine-induced myocardial injury. These studies highlight the increased susceptibility of individuals with pathological loss of cardiac SERCA2 to the effects of bromine.
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Affiliation(s)
- Juan Xavier Masjoan Juncos
- Department of Anesthesiology and Perioperative Medicine, University of Alabama at Birmingham, Birmingham, Alabama (J.X.M.J., F.N., S.S., M.E.-H., I.Z, A.Z., A.A., S.A.); Institute for Experimental Medical Research, Oslo University Hospital and KG Jebsen Cardiac Research Center and Center for Heart Failure Research, University of Oslo, Oslo, Norway (W.E.L.); and Division of Cardiovascular Sciences, University of South Florida, Tampa, Florida (G.V.H.)
| | - Fahad Nadeem
- Department of Anesthesiology and Perioperative Medicine, University of Alabama at Birmingham, Birmingham, Alabama (J.X.M.J., F.N., S.S., M.E.-H., I.Z, A.Z., A.A., S.A.); Institute for Experimental Medical Research, Oslo University Hospital and KG Jebsen Cardiac Research Center and Center for Heart Failure Research, University of Oslo, Oslo, Norway (W.E.L.); and Division of Cardiovascular Sciences, University of South Florida, Tampa, Florida (G.V.H.)
| | - Shazia Shakil
- Department of Anesthesiology and Perioperative Medicine, University of Alabama at Birmingham, Birmingham, Alabama (J.X.M.J., F.N., S.S., M.E.-H., I.Z, A.Z., A.A., S.A.); Institute for Experimental Medical Research, Oslo University Hospital and KG Jebsen Cardiac Research Center and Center for Heart Failure Research, University of Oslo, Oslo, Norway (W.E.L.); and Division of Cardiovascular Sciences, University of South Florida, Tampa, Florida (G.V.H.)
| | - Malik El-Husari
- Department of Anesthesiology and Perioperative Medicine, University of Alabama at Birmingham, Birmingham, Alabama (J.X.M.J., F.N., S.S., M.E.-H., I.Z, A.Z., A.A., S.A.); Institute for Experimental Medical Research, Oslo University Hospital and KG Jebsen Cardiac Research Center and Center for Heart Failure Research, University of Oslo, Oslo, Norway (W.E.L.); and Division of Cardiovascular Sciences, University of South Florida, Tampa, Florida (G.V.H.)
| | - Iram Zafar
- Department of Anesthesiology and Perioperative Medicine, University of Alabama at Birmingham, Birmingham, Alabama (J.X.M.J., F.N., S.S., M.E.-H., I.Z, A.Z., A.A., S.A.); Institute for Experimental Medical Research, Oslo University Hospital and KG Jebsen Cardiac Research Center and Center for Heart Failure Research, University of Oslo, Oslo, Norway (W.E.L.); and Division of Cardiovascular Sciences, University of South Florida, Tampa, Florida (G.V.H.)
| | - William E Louch
- Department of Anesthesiology and Perioperative Medicine, University of Alabama at Birmingham, Birmingham, Alabama (J.X.M.J., F.N., S.S., M.E.-H., I.Z, A.Z., A.A., S.A.); Institute for Experimental Medical Research, Oslo University Hospital and KG Jebsen Cardiac Research Center and Center for Heart Failure Research, University of Oslo, Oslo, Norway (W.E.L.); and Division of Cardiovascular Sciences, University of South Florida, Tampa, Florida (G.V.H.)
| | - Ganesh V Halade
- Department of Anesthesiology and Perioperative Medicine, University of Alabama at Birmingham, Birmingham, Alabama (J.X.M.J., F.N., S.S., M.E.-H., I.Z, A.Z., A.A., S.A.); Institute for Experimental Medical Research, Oslo University Hospital and KG Jebsen Cardiac Research Center and Center for Heart Failure Research, University of Oslo, Oslo, Norway (W.E.L.); and Division of Cardiovascular Sciences, University of South Florida, Tampa, Florida (G.V.H.)
| | - Ahmed Zaky
- Department of Anesthesiology and Perioperative Medicine, University of Alabama at Birmingham, Birmingham, Alabama (J.X.M.J., F.N., S.S., M.E.-H., I.Z, A.Z., A.A., S.A.); Institute for Experimental Medical Research, Oslo University Hospital and KG Jebsen Cardiac Research Center and Center for Heart Failure Research, University of Oslo, Oslo, Norway (W.E.L.); and Division of Cardiovascular Sciences, University of South Florida, Tampa, Florida (G.V.H.)
| | - Aftab Ahmad
- Department of Anesthesiology and Perioperative Medicine, University of Alabama at Birmingham, Birmingham, Alabama (J.X.M.J., F.N., S.S., M.E.-H., I.Z, A.Z., A.A., S.A.); Institute for Experimental Medical Research, Oslo University Hospital and KG Jebsen Cardiac Research Center and Center for Heart Failure Research, University of Oslo, Oslo, Norway (W.E.L.); and Division of Cardiovascular Sciences, University of South Florida, Tampa, Florida (G.V.H.)
| | - Shama Ahmad
- Department of Anesthesiology and Perioperative Medicine, University of Alabama at Birmingham, Birmingham, Alabama (J.X.M.J., F.N., S.S., M.E.-H., I.Z, A.Z., A.A., S.A.); Institute for Experimental Medical Research, Oslo University Hospital and KG Jebsen Cardiac Research Center and Center for Heart Failure Research, University of Oslo, Oslo, Norway (W.E.L.); and Division of Cardiovascular Sciences, University of South Florida, Tampa, Florida (G.V.H.)
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2
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Wegener JW, Mitronova GY, ElShareif L, Quentin C, Belov V, Pochechueva T, Hasenfuss G, Ackermann L, Lehnart SE. A dual-targeted drug inhibits cardiac ryanodine receptor Ca 2+ leak but activates SERCA2a Ca 2+ uptake. Life Sci Alliance 2024; 7:e202302278. [PMID: 38012000 PMCID: PMC10681910 DOI: 10.26508/lsa.202302278] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2023] [Revised: 11/16/2023] [Accepted: 11/17/2023] [Indexed: 11/29/2023] Open
Abstract
In the heart, genetic or acquired mishandling of diastolic [Ca2+] by ryanodine receptor type 2 (RyR2) overactivity correlates with risks of arrhythmia and sudden cardiac death. Strategies to avoid these risks include decrease of Ca2+ release by drugs modulating RyR2 activity or increase in Ca2+ uptake by drugs modulating SR Ca2+ ATPase (SERCA2a) activity. Here, we combine these strategies by developing experimental compounds that act simultaneously on both processes. Our screening efforts identified the new 1,4-benzothiazepine derivative GM1869 as a promising compound. Consequently, we comparatively studied the effects of the known RyR2 modulators Dantrolene and S36 together with GM1869 on RyR2 and SERCA2a activity in cardiomyocytes from wild type and arrhythmia-susceptible RyR2R2474S/+ mice by confocal live-cell imaging. All drugs reduced RyR2-mediated Ca2+ spark frequency but only GM1869 accelerated SERCA2a-mediated decay of Ca2+ transients in murine and human cardiomyocytes. Our data indicate that S36 and GM1869 are more suitable than dantrolene to directly modulate RyR2 activity, especially in RyR2R2474S/+ mice. Remarkably, GM1869 may represent a new dual-acting lead compound for maintenance of diastolic [Ca2+].
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Affiliation(s)
- Jörg W Wegener
- Department of Cardiology and Pulmonology, Heart Research Center Göttingen, University Medical Center of Göttingen (UMG), Göttingen, Germany
- DZHK (German Centre for Cardiovascular Research), Partner Site Göttingen, Göttingen, Germany
| | - Gyuzel Y Mitronova
- Department of NanoBiophotonics, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
- DZHK (German Centre for Cardiovascular Research), Partner Site Göttingen, Göttingen, Germany
| | - Lina ElShareif
- Department of Cardiology and Pulmonology, Heart Research Center Göttingen, University Medical Center of Göttingen (UMG), Göttingen, Germany
| | - Christine Quentin
- Department of NanoBiophotonics, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Vladimir Belov
- Department of NanoBiophotonics, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Tatiana Pochechueva
- Department of Cardiology and Pulmonology, Heart Research Center Göttingen, University Medical Center of Göttingen (UMG), Göttingen, Germany
- DZHK (German Centre for Cardiovascular Research), Partner Site Göttingen, Göttingen, Germany
| | - Gerd Hasenfuss
- Department of Cardiology and Pulmonology, Heart Research Center Göttingen, University Medical Center of Göttingen (UMG), Göttingen, Germany
- DZHK (German Centre for Cardiovascular Research), Partner Site Göttingen, Göttingen, Germany
| | - Lutz Ackermann
- Georg-August University of Göttingen, Institute of Organic and Biomolecular Chemistry, Göttingen, Germany
- DZHK (German Centre for Cardiovascular Research), Partner Site Göttingen, Göttingen, Germany
| | - Stephan E Lehnart
- Department of Cardiology and Pulmonology, Heart Research Center Göttingen, University Medical Center of Göttingen (UMG), Göttingen, Germany
- DZHK (German Centre for Cardiovascular Research), Partner Site Göttingen, Göttingen, Germany
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3
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Shao X, Tian Y, Liu J, Yan Z, Ding Y, Hao X, Wang D, Shen L, Luo E, Guo XE, Luo P, Luo W, Cai J, Jing D. Rescuing SERCA2 pump deficiency improves bone mechano-responsiveness in type 2 diabetes by shaping osteocyte calcium dynamics. Nat Commun 2024; 15:890. [PMID: 38291059 PMCID: PMC10828510 DOI: 10.1038/s41467-024-45023-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2022] [Accepted: 01/12/2024] [Indexed: 02/01/2024] Open
Abstract
Type 2 diabetes (T2D)-related fragility fractures represent an increasingly tough medical challenge, and the current treatment options are limited. Mechanical loading is essential for maintaining bone integrity, although bone mechano-responsiveness in T2D remains poorly characterized. Herein, we report that exogenous cyclic loading-induced improvements in bone architecture and strength are compromised in both genetically spontaneous and experimentally-induced T2D mice. T2D-induced reduction in bone mechano-responsiveness is directly associated with the weakened Ca2+ oscillatory dynamics of osteocytes, although not those of osteoblasts, which is dependent on PPARα-mediated specific reduction in osteocytic SERCA2 pump expression. Treatment with the SERCA2 agonist istaroxime was demonstrated to improve T2D bone mechano-responsiveness by rescuing osteocyte Ca2+ dynamics and the associated regulation of osteoblasts and osteoclasts. Moreover, T2D-induced deterioration of bone mechano-responsiveness is blunted in mice with osteocytic SERCA2 overexpression. Collectively, our study provides mechanistic insights into T2D-mediated deterioration of bone mechano-responsiveness and identifies a promising countermeasure against T2D-associated fragility fractures.
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Affiliation(s)
- Xi Shao
- Department of Biomedical Engineering, Fourth Military Medical University, Xi'an, China
| | - Yulan Tian
- Department of Biomedical Engineering, Fourth Military Medical University, Xi'an, China
| | - Juan Liu
- Department of Biomedical Engineering, Fourth Military Medical University, Xi'an, China
| | - Zedong Yan
- Department of Biomedical Engineering, Fourth Military Medical University, Xi'an, China
| | - Yuanjun Ding
- Department of Biomedical Engineering, Fourth Military Medical University, Xi'an, China
| | - Xiaoxia Hao
- Department of Biomedical Engineering, Fourth Military Medical University, Xi'an, China
| | - Dan Wang
- Department of Biomedical Engineering, Fourth Military Medical University, Xi'an, China
| | - Liangliang Shen
- The State Key Laboratory of Cancer Biology, Department of Biochemistry and Molecular Biology, Fourth Military Medical University, Xi'an, China
| | - Erping Luo
- Department of Biomedical Engineering, Fourth Military Medical University, Xi'an, China
| | - X Edward Guo
- Bone Bioengineering Laboratory, Department of Biomedical Engineering, Columbia University, New York, NY, USA
| | - Peng Luo
- Department of Neurosurgery, Xijing Hospital, Fourth Military Medical University, Xi'an, China.
| | - Wenjing Luo
- The Ministry of Education Key Lab of Hazard Assessment and Control in Special Operational Environment, Fourth Military Medical University, Xi'an, China.
| | - Jing Cai
- College of Basic Medicine, Shaanxi University of Chinese Medicine, Xianyang, China.
| | - Da Jing
- Department of Biomedical Engineering, Fourth Military Medical University, Xi'an, China.
- The Ministry of Education Key Lab of Hazard Assessment and Control in Special Operational Environment, Fourth Military Medical University, Xi'an, China.
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4
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Morishita Y, Tamura S, Mochizuki K, Harada Y, Takamatsu T, Hosoi H, Tanaka H. Generation of myocyte agonal Ca 2+ waves and contraction bands in perfused rat hearts following irreversible membrane permeabilisation. Sci Rep 2023; 13:803. [PMID: 36646772 PMCID: PMC9842683 DOI: 10.1038/s41598-023-27807-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Accepted: 01/09/2023] [Indexed: 01/18/2023] Open
Abstract
Although irreversible cardiomyocyte injury provokes intracellular Ca2+ ([Ca2+]i) overload, the underlying dynamics of this response and its effects on cellular morphology remain unknown. We therefore visualised rapid-scanning confocal fluo4-[Ca2+]i dynamics and morphology of cardiomyocytes in Langendorff-perfused rat hearts following saponin-membrane permeabilisation. Our data demonstrate that 0.4% saponin-treated myocytes immediately exhibited high-frequency Ca2+ waves (131.3 waves/min/cell) with asynchronous, oscillatory contractions having a mean propagation velocity of 117.8 μm/s. These waves slowly decreased in frequency, developed a prolonged decay phase, and disappeared in 10 min resulting in high-static, fluo4-fluorescence intensity. The myocytes showing these waves displayed contraction bands, i.e., band-like actin-fibre aggregates with disruption of sarcomeric α-actinin. The contraction bands were not attenuated by the abolition of Ca2+ waves under pretreatment with ryanodine plus thapsigargin, but were partially attenuated by the calpain inhibitor MDL28170, while mechanical arrest of the myocytes by 2,3-butanedione monoxime completely attenuated contraction-band formation. The depletion of adenosine 5'-triphosphate by the mitochondrial electron uncoupler carbonyl cyanide 4-trifluoromethoxy phenylhydrazone also attenuated Ca2+ waves and contraction bands. Overall, saponin-induced myocyte [Ca2+]i overload provokes agonal Ca2+ waves and contraction bands. Contraction bands are not the direct consequence of the waves but are caused by cross-bridge interactions of the myocytes under calpain-mediated proteolysis.
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Affiliation(s)
- Yuma Morishita
- Department of Pathology and Cell Regulation, Kyoto Prefectural University of Medicine, Graduate School of Medical Science, Kyoto, 602-8566, Japan.,Department of Pediatrics, Kyoto Prefectural University of Medicine, Graduate School of Medical Science, Kyoto, 602-8566, Japan
| | - Shoko Tamura
- Department of Pathology and Cell Regulation, Kyoto Prefectural University of Medicine, Graduate School of Medical Science, Kyoto, 602-8566, Japan
| | - Kentaro Mochizuki
- Department of Pathology and Cell Regulation, Kyoto Prefectural University of Medicine, Graduate School of Medical Science, Kyoto, 602-8566, Japan
| | - Yoshinori Harada
- Department of Pathology and Cell Regulation, Kyoto Prefectural University of Medicine, Graduate School of Medical Science, Kyoto, 602-8566, Japan
| | - Tetsuro Takamatsu
- Department of Medical Photonics, Kyoto Prefectural University of Medicine, Kyoto, 602-8566, Japan
| | - Hajime Hosoi
- Department of Pediatrics, Kyoto Prefectural University of Medicine, Graduate School of Medical Science, Kyoto, 602-8566, Japan
| | - Hideo Tanaka
- Department of Pathology and Cell Regulation, Kyoto Prefectural University of Medicine, Graduate School of Medical Science, Kyoto, 602-8566, Japan.
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5
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Hutchings DC, Pearman CM, Madders GWP, Woods LS, Eisner DA, Dibb KM, Trafford AW. PDE5 Inhibition Suppresses Ventricular Arrhythmias by Reducing SR Ca 2+ Content. Circ Res 2021; 129:650-665. [PMID: 34247494 PMCID: PMC8409902 DOI: 10.1161/circresaha.121.318473] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
[Figure: see text].
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Affiliation(s)
- David C Hutchings
- Unit of Cardiac Physiology, Division of Cardiovascular Sciences, Faculty of Biology Medicine and Health, University of Manchester, Manchester Academic Health Sciences Centre, United Kingdom
| | - Charles M Pearman
- Unit of Cardiac Physiology, Division of Cardiovascular Sciences, Faculty of Biology Medicine and Health, University of Manchester, Manchester Academic Health Sciences Centre, United Kingdom
| | - George W P Madders
- Unit of Cardiac Physiology, Division of Cardiovascular Sciences, Faculty of Biology Medicine and Health, University of Manchester, Manchester Academic Health Sciences Centre, United Kingdom
| | - Lori S Woods
- Unit of Cardiac Physiology, Division of Cardiovascular Sciences, Faculty of Biology Medicine and Health, University of Manchester, Manchester Academic Health Sciences Centre, United Kingdom
| | - David A Eisner
- Unit of Cardiac Physiology, Division of Cardiovascular Sciences, Faculty of Biology Medicine and Health, University of Manchester, Manchester Academic Health Sciences Centre, United Kingdom
| | - Katharine M Dibb
- Unit of Cardiac Physiology, Division of Cardiovascular Sciences, Faculty of Biology Medicine and Health, University of Manchester, Manchester Academic Health Sciences Centre, United Kingdom
| | - Andrew W Trafford
- Unit of Cardiac Physiology, Division of Cardiovascular Sciences, Faculty of Biology Medicine and Health, University of Manchester, Manchester Academic Health Sciences Centre, United Kingdom
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Sato D, Uchinoumi H, Bers DM. Increasing SERCA function promotes initiation of calcium sparks and breakup of calcium waves. J Physiol 2021; 599:3267-3278. [PMID: 33963531 PMCID: PMC8249358 DOI: 10.1113/jp281579] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2021] [Accepted: 05/04/2021] [Indexed: 01/16/2023] Open
Abstract
KEY POINTS Increasing sarcoplasmic/endoplasmic reticulum calcium ATPase (SERCA) pump activity enhances sarcoplasmic reticulum calcium (Ca) load, which increases both ryanodine receptor opening and driving force of Ca release flux. Both of these effects promote Ca spark formation and wave propagation. However, increasing SERCA activity also accelerates local cytosolic Ca decay as the wave front travels to the next cluster, which limits wave propagation. As a result, increasing SERCA pump activity has a biphasic effect on the propensity of arrhythmogenic Ca waves, but a monotonic effect to increase Ca spark frequency and amplitude. ABSTRACT Waves of sarcoplasmic reticulum (SR) calcium (Ca) release can cause arrhythmogenic afterdepolarizations in cardiac myocytes. Ca waves propagate when Ca sparks at one Ca release unit (CRU) recruit new Ca sparks in neighbouring CRUs. Under normal conditions, Ca sparks are too small to recruit neighbouring Ca sparks where Ca sensitivity is also low. However, under pathological conditions such as a Ca overload or ryanodine receptor (RyR) sensitization, Ca sparks can be larger and propagate more readily as macro-sparks or full Ca waves. Increasing SERCA pump activity promotes SR Ca load, which promotes RyR opening and increases driving force of the Ca release flux from SR to cytosol, promoting Ca waves. However, high sarcoplasmic/endoplasmic reticulum calcium ATPase (SERCA) activity can also decrease local cytosolic [Ca] as it approaches the next CRU, thereby reducing wave appearance and propagation. In this study, we use a physiologically detailed model of subcellular Ca cycling and experiments in phospholamban-knockout mice, to show how Ca waves are initiated and propagate and how different conditions contribute to the generation and propagation of Ca waves. We show that reducing diffusive coupling between Ca sparks by increasing SERCA activity prevents Ca waves by reducing [Ca] at the next CRU, as do Ca buffers, low intra-SR Ca diffusion and distance between CRUs. Increasing SR Ca uptake rate has a biphasic effect on Ca wave propagation; initially it enhances Ca spark probability and amplitude and CRU coupling, thereby promoting arrhythmogenic Ca wave propagation, but at higher levels SR Ca uptake can abort those arrhythmogenic Ca waves.
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Affiliation(s)
- Daisuke Sato
- Department of Pharmacology, University of California, Davis School of Medicine, California, USA
| | - Hitoshi Uchinoumi
- Department of Pharmacology, University of California, Davis School of Medicine, California, USA.,Department of Cardiology, Yamaguchi University School of Medicine, Yamaguchi, Japan
| | - Donald M Bers
- Department of Pharmacology, University of California, Davis School of Medicine, California, USA
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7
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Association with SERCA2a directs phospholamban trafficking to sarcoplasmic reticulum from a nuclear envelope pool. J Mol Cell Cardiol 2020; 143:107-119. [DOI: 10.1016/j.yjmcc.2020.04.025] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/28/2020] [Revised: 04/08/2020] [Accepted: 04/23/2020] [Indexed: 11/22/2022]
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8
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Valverde CA, Mazzocchi G, Di Carlo MN, Ciocci Pardo A, Salas N, Ragone MI, Felice JI, Cely-Ortiz A, Consolini AE, Portiansky E, Mosca S, Kranias EG, Wehrens XHT, Mattiazzi A. Ablation of phospholamban rescues reperfusion arrhythmias but exacerbates myocardium infarction in hearts with Ca2+/calmodulin kinase II constitutive phosphorylation of ryanodine receptors. Cardiovasc Res 2020; 115:556-569. [PMID: 30169578 DOI: 10.1093/cvr/cvy213] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/24/2018] [Revised: 07/03/2018] [Accepted: 08/27/2018] [Indexed: 12/12/2022] Open
Abstract
AIMS Abnormal Ca2+ release from the sarcoplasmic reticulum (SR), associated with Ca2+-calmodulin kinase II (CaMKII)-dependent phosphorylation of RyR2 at Ser2814, has consistently been linked to arrhythmogenesis and ischaemia/reperfusion (I/R)-induced cell death. In contrast, the role played by SR Ca2+ uptake under these stress conditions remains controversial. We tested the hypothesis that an increase in SR Ca2+ uptake is able to attenuate reperfusion arrhythmias and cardiac injury elicited by increased RyR2-Ser2814 phosphorylation. METHODS AND RESULTS We used WT mice, which have been previously shown to exhibit a transient increase in RyR2-Ser2814 phosphorylation at the onset of reperfusion; mice with constitutive pseudo-phosphorylation of RyR2 at Ser2814 (S2814D) to exacerbate CaMKII-dependent reperfusion arrhythmias and cardiac damage, and phospholamban (PLN)-deficient-S2814D knock-in (SDKO) mice resulting from crossbreeding S2814D with phospholamban knockout deficient (PLNKO) mice. At baseline, S2814D and SDKO mice had structurally normal hearts. Moreover none of the strains were arrhythmic before ischaemia. Upon cardiac I/R, WT, and S2814D hearts exhibited abundant arrhythmias that were prevented by PLN ablation. In contrast, PLN ablation increased infarct size compared with WT and S2814D hearts. Mechanistically, the enhanced SR Ca2+ sequestration evoked by PLN ablation in SDKO hearts prevented arrhythmogenic events upon reperfusion by fragmenting SR Ca2+ waves into non-propagated and non-arrhythmogenic events (mini-waves). Conversely, the increase in SR Ca2+ sequestration did not reduce but rather exacerbated I/R-induced SR Ca2+ leak, as well as mitochondrial alterations, which were greatly avoided by inhibition of RyR2. These results indicate that the increase in SR Ca2+ uptake is ineffective in preventing the enhanced SR Ca2+ leak of PLN ablated myocytes from either entering into nearby mitochondria and/or activating additional CaMKII pathways, contributing to cardiac damage. CONCLUSION Our results demonstrate that increasing SR Ca2+ uptake by PLN ablation can prevent the arrhythmic events triggered by CaMKII-dependent phosphorylation of RyR2-induced SR Ca2+ leak. These findings underscore the benefits of increasing SERCA2a activity in the face of SR Ca2+ triggered arrhythmias. However, enhanced SERCA2a cannot prevent but rather exacerbates I/R cardiac injury.
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Affiliation(s)
- Carlos A Valverde
- Centro de Investigaciones Cardiovasculares 'Dr. Horacio E. Cingolani', CCT-La Plata-CONICET, Facultad de Cs. Médicas, UNLP, 60 y 120 s/n, La Plata CP, Argentina
| | - Gabriela Mazzocchi
- Centro de Investigaciones Cardiovasculares 'Dr. Horacio E. Cingolani', CCT-La Plata-CONICET, Facultad de Cs. Médicas, UNLP, 60 y 120 s/n, La Plata CP, Argentina
| | - Mariano N Di Carlo
- Centro de Investigaciones Cardiovasculares 'Dr. Horacio E. Cingolani', CCT-La Plata-CONICET, Facultad de Cs. Médicas, UNLP, 60 y 120 s/n, La Plata CP, Argentina
| | - Alejandro Ciocci Pardo
- Centro de Investigaciones Cardiovasculares 'Dr. Horacio E. Cingolani', CCT-La Plata-CONICET, Facultad de Cs. Médicas, UNLP, 60 y 120 s/n, La Plata CP, Argentina
| | - Nehuen Salas
- Centro de Investigaciones Cardiovasculares 'Dr. Horacio E. Cingolani', CCT-La Plata-CONICET, Facultad de Cs. Médicas, UNLP, 60 y 120 s/n, La Plata CP, Argentina
| | - María Ines Ragone
- Grupo de Farmacología Experimental, (GFEYEC), Departamento of Ciencias Biológicas, Facultad de Ciencias Exactas - CONICET., La Plata, Argentina
| | - Juan I Felice
- Centro de Investigaciones Cardiovasculares 'Dr. Horacio E. Cingolani', CCT-La Plata-CONICET, Facultad de Cs. Médicas, UNLP, 60 y 120 s/n, La Plata CP, Argentina
| | - Alejandra Cely-Ortiz
- Centro de Investigaciones Cardiovasculares 'Dr. Horacio E. Cingolani', CCT-La Plata-CONICET, Facultad de Cs. Médicas, UNLP, 60 y 120 s/n, La Plata CP, Argentina
| | - Alicia E Consolini
- Grupo de Farmacología Experimental, (GFEYEC), Departamento of Ciencias Biológicas, Facultad de Ciencias Exactas - CONICET., La Plata, Argentina
| | - Enrique Portiansky
- Laboratorio de Análisis de Imágenes, Facultad de Cs. Veterinarias, UNLP, La Plata, Argentina
| | - Susana Mosca
- Centro de Investigaciones Cardiovasculares 'Dr. Horacio E. Cingolani', CCT-La Plata-CONICET, Facultad de Cs. Médicas, UNLP, 60 y 120 s/n, La Plata CP, Argentina
| | - Evangelia G Kranias
- Department of Pharmacology and Cell Biophysics, University of Cincinnati College of Medicine, Cincinnati, OH 45267, USA
| | - Xander H T Wehrens
- Department of Molecular Physiology and Biophysics, Cardiovascular Research Institute, Center for Space Medicine, Baylor College of Medicine, Houston, TX, USA.,Department of Medicine (in Cardiology), Cardiovascular Research Institute, Center for Space Medicine, Baylor College of Medicine, Houston, TX, USA.,Department of Pediatrics, Cardiovascular Research Institute, Center for Space Medicine, Baylor College of Medicine, Houston, TX, USA
| | - Alicia Mattiazzi
- Centro de Investigaciones Cardiovasculares 'Dr. Horacio E. Cingolani', CCT-La Plata-CONICET, Facultad de Cs. Médicas, UNLP, 60 y 120 s/n, La Plata CP, Argentina
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9
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Henry AD, MacQuaide N, Burton FL, Rankin AC, Rowan EG, Drummond RM. Spontaneous Ca 2+ transients in rat pulmonary vein cardiomyocytes are increased in frequency and become more synchronous following electrical stimulation. Cell Calcium 2018; 76:36-47. [PMID: 30253263 DOI: 10.1016/j.ceca.2018.09.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2018] [Revised: 08/09/2018] [Accepted: 09/02/2018] [Indexed: 12/13/2022]
Abstract
The pulmonary veins have an external sleeve of cardiomyocytes that are a widely recognised source of ectopic electrical activity that can lead to atrial fibrillation. Although the mechanisms behind this activity are currently unknown, changes in intracellular calcium (Ca2+) signalling are purported to play a role. Therefore, the intracellular Ca2+ concentration was monitored in the pulmonary vein using fluo-4 and epifluorescence microscopy. Electrical field stimulation evoked a synchronous rise in Ca2+ in neighbouring cardiomyocytes; asynchronous spontaneous Ca2+ transients between electrical stimuli were also present. Immediately following termination of electrical field stimulation at 3 Hz or greater, the frequency of the spontaneous Ca2+ transients was increased from 0.45 ± 0.06 Hz under basal conditions to between 0.59 ± 0.05 and 0.65 ± 0.06 Hz (P < 0.001). Increasing the extracellular Ca2+ concentration enhanced this effect, with the frequency of spontaneous Ca2+ transients increasing from 0.45 ± 0.05 Hz to between 0.75 ± 0.06 and 0.94 ± 0.09 Hz after electrical stimulation at 3 to 9 Hz (P < 0.001), and this was accompanied by a significant increase in the velocity of Ca2+ transients that manifested as waves. Moreover, in the presence of high extracellular Ca2+, the spontaneous Ca2+ transients occurred more synchronously in the initial few seconds following electrical stimulation. The ryanodine receptors, which are the source of spontaneous Ca2+ transients in pulmonary vein cardiomyocytes, were found to be arranged in a striated pattern in the cell interior, as well as along the periphery of cell. Furthermore, labelling the sarcolemma with di-4-ANEPPS showed that over 90% of pulmonary vein cardiomyocytes possessed T-tubules. These findings demonstrate that the frequency of spontaneous Ca2+ transients in the rat pulmonary vein are increased following higher rates of electrical stimulation and increasing the extracellular Ca2+ concentration.
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Affiliation(s)
- Alasdair D Henry
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, UK
| | - N MacQuaide
- Institute of Cardiovascular and Medical Sciences, College of Medical, Veterinary and Life Sciences, University of Glasgow, UK
| | - F L Burton
- Institute of Cardiovascular and Medical Sciences, College of Medical, Veterinary and Life Sciences, University of Glasgow, UK
| | - A C Rankin
- Institute of Cardiovascular and Medical Sciences, College of Medical, Veterinary and Life Sciences, University of Glasgow, UK
| | - E G Rowan
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, UK
| | - R M Drummond
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, UK.
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10
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Abstract
Mitochondrial dysfunction underlines a multitude of pathologies; however, studies are scarce that rescue the mitochondria for cellular resuscitation. Exploration into the protective role of mitochondrial transcription factor A (TFAM) and its mitochondrial functions respective to cardiomyocyte death are in need of further investigation. TFAM is a gene regulator that acts to mitigate calcium mishandling and ROS production by wrapping around mitochondrial DNA (mtDNA) complexes. TFAM's regulatory functions over serca2a, NFAT, and Lon protease contribute to cardiomyocyte stability. Calcium- and ROS-dependent proteases, calpains, and matrix metalloproteinases (MMPs) are abundantly found upregulated in the failing heart. TFAM's regulatory role over ROS production and calcium mishandling leads to further investigation into the cardioprotective role of exogenous TFAM. In an effort to restabilize physiological and contractile activity of cardiomyocytes in HF models, we propose that TFAM-packed exosomes (TFAM-PE) will act therapeutically by mitigating mitochondrial dysfunction. Notably, this is the first mention of exosomal delivery of transcription factors in the literature. Here we elucidate the role of TFAM in mitochondrial rescue and focus on its therapeutic potential.
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Affiliation(s)
- George H Kunkel
- Department of Physiology and Biophysics, Health Sciences Centre, 1216, School of Medicine, University of Louisville, 500, South Preston Street, Louisville, KY, 40202, USA
| | - Pankaj Chaturvedi
- Department of Physiology and Biophysics, Health Sciences Centre, 1216, School of Medicine, University of Louisville, 500, South Preston Street, Louisville, KY, 40202, USA.
| | - Suresh C Tyagi
- Department of Physiology and Biophysics, Health Sciences Centre, 1216, School of Medicine, University of Louisville, 500, South Preston Street, Louisville, KY, 40202, USA
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11
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Hu LYR, Ackermann MA, Hecker PA, Prosser BL, King B, O’Connell KA, Grogan A, Meyer LC, Berndsen CE, Wright NT, Jonathan Lederer W, Kontrogianni-Konstantopoulos A. Deregulated Ca 2+ cycling underlies the development of arrhythmia and heart disease due to mutant obscurin. SCIENCE ADVANCES 2017; 3:e1603081. [PMID: 28630914 PMCID: PMC5462502 DOI: 10.1126/sciadv.1603081] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2016] [Accepted: 04/17/2017] [Indexed: 05/05/2023]
Abstract
Obscurins are cytoskeletal proteins with structural and regulatory roles encoded by OBSCN. Mutations in OBSCN are associated with the development of hypertrophic cardiomyopathy (HCM) and dilated cardiomyopathy (DCM). Specifically, the R4344Q mutation present in immunoglobulin domain 58 (Ig58) was the first to be linked with the development of HCM. To assess the effects of R4344Q in vivo, we generated the respective knock-in mouse model. Mutant obscurins are expressed and incorporated normally into sarcomeres. The expression patterns of sarcomeric and Ca2+-cycling proteins are unaltered in sedentary 1-year-old knock-in myocardia, with the exception of sarco/endoplasmic reticulum Ca2+ adenosine triphosphatase 2 (SERCA2) and pentameric phospholamban whose levels are significantly increased and decreased, respectively. Isolated cardiomyocytes from 1-year-old knock-in hearts exhibit increased Ca2+-transients and Ca2+-load in the sarcoplasmic reticulum and faster contractility kinetics. Moreover, sedentary 1-year-old knock-in animals develop tachycardia accompanied by premature ventricular contractions, whereas 2-month-old knock-in animals subjected to pressure overload develop a DCM-like phenotype. Structural analysis revealed that the R4344Q mutation alters the distribution of electrostatic charges over the Ig58 surface, thus interfering with its binding capabilities. Consistent with this, wild-type Ig58 interacts with phospholamban modestly, and this interaction is markedly enhanced in the presence of R4344Q. Together, our studies demonstrate that under sedentary conditions, the R4344Q mutation results in Ca2+ deregulation and spontaneous arrhythmia, whereas in the presence of chronic, pathological stress, it leads to cardiac remodeling and dilation. We postulate that enhanced binding between mutant obscurins and phospholamban leads to SERCA2 disinhibition, which may underlie the observed pathological alterations.
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Affiliation(s)
- Li-Yen R. Hu
- Department of Biochemistry and Molecular Biology, University of Maryland, Baltimore, Baltimore, MD 21201, USA
| | - Maegen A. Ackermann
- Department of Biochemistry and Molecular Biology, University of Maryland, Baltimore, Baltimore, MD 21201, USA
| | - Peter A. Hecker
- Division of Cardiovascular Medicine, Department of Medicine, University of Maryland, Baltimore, Baltimore, MD 21201, USA
| | - Benjamin L. Prosser
- Department of Physiology, Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
- Department of Physiology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Brendan King
- Department of Biochemistry and Molecular Biology, University of Maryland, Baltimore, Baltimore, MD 21201, USA
| | - Kelly A. O’Connell
- Division of Cardiovascular Medicine, Department of Medicine, University of Maryland, Baltimore, Baltimore, MD 21201, USA
| | - Alyssa Grogan
- Department of Biochemistry and Molecular Biology, University of Maryland, Baltimore, Baltimore, MD 21201, USA
| | - Logan C. Meyer
- Department of Chemistry and Biochemistry, James Madison University, Harrisonburg, VA 22807, USA
| | - Christopher E. Berndsen
- Department of Chemistry and Biochemistry, James Madison University, Harrisonburg, VA 22807, USA
| | - Nathan T. Wright
- Department of Chemistry and Biochemistry, James Madison University, Harrisonburg, VA 22807, USA
| | - W. Jonathan Lederer
- Department of Physiology, Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
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12
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Roselló-Lletí E, Tarazón E, Ortega A, Gil-Cayuela C, Carnicer R, Lago F, González-Juanatey JR, Portolés M, Rivera M. Protein Inhibitor of NOS1 Plays a Central Role in the Regulation of NOS1 Activity in Human Dilated Hearts. Sci Rep 2016; 6:30902. [PMID: 27481317 PMCID: PMC4969592 DOI: 10.1038/srep30902] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2016] [Accepted: 07/08/2016] [Indexed: 12/22/2022] Open
Abstract
An essential factor for the production of nitric oxide by nitric oxide synthase 1 (NOS1), major modulator of cardiac function, is the cofactor tetrahydrobiopterin (BH4). BH4 is regulated by GTP cyclohydrolase 1, the rate-limiting enzyme in BH4 biosynthesis which catalyses the formation of dihydroneopterin 3'triphosfate from GTP, producing BH4 after two further steps catalyzed by 6-pyruvoyltetrahydropterin synthase and sepiapterin reductase. However, there are other essential factors involved in the regulation of NOS1 activity, such as protein inhibitor of NOS1 (PIN), calmodulin, heat shock protein 90, and NOS interacting protein. All these molecules have never been analysed in human non-ischemic dilated hearts (DCM). In this study we demonstrated that the upregulation of cardiac NOS1 is not accompanied by increased NOS1 activity in DCM, partly due to the elevated PIN levels and not because of alterations in biopterin biosynthesis. Notably, the PIN concentration was significantly associated with impaired ventricular function, highlighting the importance of this NOS1 activity inhibitor in Ca(2+) homeostasis. These results take a central role in the current list of targets for future studies focused on the complex cardiac dysfunction processes through more efficient harnessing of NOS1 signalling.
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Affiliation(s)
- Esther Roselló-Lletí
- Cardiocirculatory Unit, Health Research Institute Hospital La Fe (IIS La Fe), Valencia, Spain
| | - Estefanía Tarazón
- Cardiocirculatory Unit, Health Research Institute Hospital La Fe (IIS La Fe), Valencia, Spain
| | - Ana Ortega
- Cardiocirculatory Unit, Health Research Institute Hospital La Fe (IIS La Fe), Valencia, Spain
| | - Carolina Gil-Cayuela
- Cardiocirculatory Unit, Health Research Institute Hospital La Fe (IIS La Fe), Valencia, Spain
| | - Ricardo Carnicer
- Department of Cardiovascular Medicine, University of Oxford, United Kingdom
| | - Francisca Lago
- Cellular and Molecular Cardiology Research Unit, Department of Cardiology and Institute of Biomedical Research, University Clinical Hospital, Santiago de Compostela, Spain
| | - Jose Ramón González-Juanatey
- Cellular and Molecular Cardiology Research Unit, Department of Cardiology and Institute of Biomedical Research, University Clinical Hospital, Santiago de Compostela, Spain
| | - Manuel Portolés
- Cardiocirculatory Unit, Health Research Institute Hospital La Fe (IIS La Fe), Valencia, Spain
| | - Miguel Rivera
- Cardiocirculatory Unit, Health Research Institute Hospital La Fe (IIS La Fe), Valencia, Spain
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13
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Salazar-Cantú A, Pérez-Treviño P, Montalvo-Parra D, Balderas-Villalobos J, Gómez-Víquez NL, García N, Altamirano J. Role of SERCA and the sarcoplasmic reticulum calcium content on calcium waves propagation in rat ventricular myocytes. Arch Biochem Biophys 2016; 604:11-9. [DOI: 10.1016/j.abb.2016.05.018] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2016] [Revised: 05/14/2016] [Accepted: 05/26/2016] [Indexed: 11/25/2022]
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14
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Logantha SJRJ, Stokke MK, Atkinson AJ, Kharche SR, Parveen S, Saeed Y, Sjaastad I, Sejersted OM, Dobrzynski H. Ca(2+)-Clock-Dependent Pacemaking in the Sinus Node Is Impaired in Mice with a Cardiac Specific Reduction in SERCA2 Abundance. Front Physiol 2016; 7:197. [PMID: 27313537 PMCID: PMC4889599 DOI: 10.3389/fphys.2016.00197] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2016] [Accepted: 05/17/2016] [Indexed: 12/23/2022] Open
Abstract
Background: The sarcoplasmic reticulum Ca2+-ATPase (SERCA2) pump is an important component of the Ca2+-clock pacemaker mechanism that provides robustness and flexibility to sinus node pacemaking. We have developed transgenic mice with reduced cardiac SERCA2 abundance (Serca2 KO) as a model for investigating SERCA2's role in sinus node pacemaking. Methods and Results: In Serca2 KO mice, ventricular SERCA2a protein content measured by Western blotting was 75% (P < 0.05) lower than that in control mice (Serca2 FF) tissue. Immunofluorescent labeling of SERCA2a in ventricular, atrial, sinus node periphery and center tissue sections revealed 46, 45, 55, and 34% (all P < 0.05 vs. Serca2 FF) lower labeling, respectively and a mosaic pattern of expression. With telemetric ECG surveillance, we observed no difference in basal heart rate, but the PR-interval was prolonged in Serca2 KO mice: 49 ± 1 vs. 40 ± 1 ms (P < 0.001) in Serca2 FF. During exercise, heart rate in Serca2 KO mice was elevated to 667 ± 22 bpm, considerably less than 780 ± 17 bpm (P < 0.01) in Serca2 FF. In isolated sinus node preparations, 2 mM Cs+ caused bradycardia that was equally pronounced in Serca2 KO and Serca2 FF (32 ± 4% vs. 29 ± 5%), indicating no change in the pacemaker current, If. Disabling the Ca2+-clock with 2 μM ryanodine induced bradycardia that was less pronounced in Serca2 KO preparations (9 ± 1% vs. 20 ± 3% in Serca2 FF; P < 0.05), suggesting a disrupted Ca2+-clock. Mathematical modeling was used to dissect the effects of membrane- and Ca2+-clock components on Serca2 KO mouse heart rate and sinus node action potential. Computer modeling predicted a slowing of heart rate with SERCA2 downregulation and the heart rate slowing was pronounced at >70% reduction in SERCA2 activity. Conclusions:Serca2 KO mice show a disrupted Ca2+-clock-dependent pacemaker mechanism contributing to impaired sinus node and atrioventricular node function.
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Affiliation(s)
| | - Mathis K Stokke
- Institute for Experimental Medical Research, Oslo University Hospital and University of OsloOslo, Norway; Center for Heart Failure Research, University of OsloOslo, Norway; Clinic for Internal Medicine, Lovisenberg Deaconess Hospital ASOslo, Norway
| | - Andrew J Atkinson
- Institute of Cardiovascular Sciences, University of Manchester Manchester, UK
| | - Sanjay R Kharche
- Institute of Cardiovascular Sciences, University of Manchester Manchester, UK
| | - Sajida Parveen
- Institute of Cardiovascular Sciences, University of Manchester Manchester, UK
| | - Yawer Saeed
- Institute of Cardiovascular Sciences, University of Manchester Manchester, UK
| | - Ivar Sjaastad
- Institute for Experimental Medical Research, Oslo University Hospital and University of OsloOslo, Norway; Center for Heart Failure Research, University of OsloOslo, Norway
| | - Ole M Sejersted
- Institute for Experimental Medical Research, Oslo University Hospital and University of OsloOslo, Norway; Center for Heart Failure Research, University of OsloOslo, Norway
| | - Halina Dobrzynski
- Institute of Cardiovascular Sciences, University of Manchester Manchester, UK
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15
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Manotheepan R, Danielsen TK, Sadredini M, Anderson ME, Carlson CR, Lehnart SE, Sjaastad I, Stokke MK. Exercise training prevents ventricular tachycardia in CPVT1 due to reduced CaMKII-dependent arrhythmogenic Ca2+ release. Cardiovasc Res 2016; 111:295-306. [PMID: 27161030 DOI: 10.1093/cvr/cvw095] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/10/2015] [Accepted: 05/01/2016] [Indexed: 01/05/2023] Open
Abstract
AIMS Catecholaminergic polymorphic ventricular tachycardia type 1 (CPVT1) is caused by mutations in the cardiac ryanodine receptor (RyR2) that lead to disrupted Ca(2+) handling in cardiomyocytes and ventricular tachycardia. The aim of this study was to test whether exercise training could reduce the propensity for arrhythmias in mice with the CPVT1-causative missense mutation Ryr2-R2474S by restoring normal Ca(2+) handling. METHODS AND RESULTS Ryr2-R2474S mice (RyR-RS) performed a 2 week interval treadmill exercise training protocol. Each exercise session comprised five 8 min intervals at 80-90% of the running speed at maximal oxygen uptake (VO2max) and 2 min active rest periods at 60%. VO2max increased by 10 ± 2% in exercise trained RyR-RS (ET), while no changes were found in sedentary controls (SED). RyR-RS ET showed fewer episodes of ventricular tachycardia compared with RyR-RS SED, coinciding with fewer Ca(2+) sparks and waves, less diastolic Ca(2+) leak from the sarcoplasmic reticulum, and lower phosphorylation levels at RyR2 sites associated with Ca(2) (+)-calmodulin-dependent kinase type II (CaMKII) compared with RyR-RS SED. The CaMKII inhibitor autocamtide-2-related inhibitory peptide and also the antioxidant N-acetyl-l-cysteine reduced Ca(2+) wave frequency in RyR-RS equally to exercise training. Protein analysis as well as functional data indicated a mechanism depending on reduced levels of oxidized CaMKII after exercise training. Two weeks of detraining reversed the beneficial effects of the interval treadmill exercise training protocol in RyR-RS ET. CONCLUSION Long-term effects of interval treadmill exercise training reduce ventricular tachycardia episodes in mice with a CPVT1-causative Ryr2 mutation through lower CaMKII-dependent phosphorylation of RyR2.
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Affiliation(s)
- Ravinea Manotheepan
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway Center for Heart Failure Research, University of Oslo, Oslo, Norway
| | - Tore K Danielsen
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway Center for Heart Failure Research, University of Oslo, Oslo, Norway
| | - Mani Sadredini
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway Center for Heart Failure Research, University of Oslo, Oslo, Norway
| | - Mark E Anderson
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Cathrine R Carlson
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway Center for Heart Failure Research, University of Oslo, Oslo, Norway
| | - Stephan E Lehnart
- Clinic of Cardiology and Pulmonology, Heart Research Center Göttingen, Göttingen, Germany
| | - Ivar Sjaastad
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway Center for Heart Failure Research, University of Oslo, Oslo, Norway
| | - Mathis K Stokke
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway Center for Heart Failure Research, University of Oslo, Oslo, Norway Clinic for Internal Medicine, Lovisenberg Diakonale Hospital, Oslo, Norway
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16
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Abstract
In the heart, Ca(2+) signals regulate a variety of biological functions ranging from contractility to gene expression, cellular hypertrophy and death. In this review, we summarize the role of local Ca(2+) homeostasis in these processes in healthy cardiac muscle cells, and highlight how mismanaged Ca(2+) handling contributes to the pathophysiology of conditions such as cardiac arrhythmia, ischemic heart disease, cardiac hypertrophy and heart failure. Aiming to provide an introduction to the field with a clinical perspective, we also indicate how current and future therapies may modulate cardiomyocytes Ca(2+) handling for the treatment of patients.
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Affiliation(s)
| | - William E Louch
- b Institute for Experimental Medical Research, Oslo University Hospital Ullevål and University of Oslo , Oslo , Norway
| | - Ivar Sjaastad
- b Institute for Experimental Medical Research, Oslo University Hospital Ullevål and University of Oslo , Oslo , Norway
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17
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Mazzocchi G, Sommese L, Palomeque J, Felice JI, Di Carlo MN, Fainstein D, Gonzalez P, Contreras P, Skapura D, McCauley MD, Lascano EC, Negroni JA, Kranias EG, Wehrens XHT, Valverde CA, Mattiazzi A. Phospholamban ablation rescues the enhanced propensity to arrhythmias of mice with CaMKII-constitutive phosphorylation of RyR2 at site S2814. J Physiol 2016; 594:3005-30. [PMID: 26695843 DOI: 10.1113/jp271622] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2015] [Accepted: 12/14/2015] [Indexed: 01/27/2023] Open
Abstract
KEY POINTS Mice with Ca(2+) -calmodulin-dependent protein kinase (CaMKII) constitutive pseudo-phosphorylation of the ryanodine receptor RyR2 at Ser2814 (S2814D(+/+) mice) exhibit a higher open probability of RyR2, higher sarcoplasmic reticulum (SR) Ca(2+) leak in diastole and increased propensity to arrhythmias under stress conditions. We generated phospholamban (PLN)-deficient S2814D(+/+) knock-in mice by crossing two colonies, S2814D(+/+) and PLNKO mice, to test the hypothesis that PLN ablation can prevent the propensity to arrhythmias of S2814D(+/+) mice. PLN ablation partially rescues the altered intracellular Ca(2+) dynamics of S2814D(+/+) hearts and myocytes, but enhances SR Ca(2+) sparks and leak on confocal microscopy. PLN ablation diminishes ventricular arrhythmias promoted by CaMKII phosphorylation of S2814 on RyR2. PLN ablation aborts the arrhythmogenic SR Ca(2+) waves of S2814D(+/+) and transforms them into non-propagating events. A mathematical human myocyte model replicates these results and predicts the increase in SR Ca(2+) uptake required to prevent the arrhythmias induced by a CaMKII-dependent leaky RyR2. ABSTRACT Mice with constitutive pseudo-phosphorylation at Ser2814-RyR2 (S2814D(+/+) ) have increased propensity to arrhythmias under β-adrenergic stress conditions. Although abnormal Ca(2+) release from the sarcoplasmic reticulum (SR) has been linked to arrhythmogenesis, the role played by SR Ca(2+) uptake remains controversial. We tested the hypothesis that an increase in SR Ca(2+) uptake is able to rescue the increased arrhythmia propensity of S2814D(+/+) mice. We generated phospholamban (PLN)-deficient/S2814D(+/+) knock-in mice by crossing two colonies, S2814D(+/+) and PLNKO mice (SD(+/+) /KO). SD(+/+) /KO myocytes exhibited both increased SR Ca(2+) uptake seen in PLN knock-out (PLNKO) myocytes and diminished SR Ca(2+) load (relative to PLNKO), a characteristic of S2814D(+/+) myocytes. Ventricular arrhythmias evoked by catecholaminergic challenge (caffeine/adrenaline) in S2814D(+/+) mice in vivo or programmed electric stimulation and high extracellular Ca(2+) in S2814D(+) /(-) hearts ex vivo were significantly diminished by PLN ablation. At the myocyte level, PLN ablation converted the arrhythmogenic Ca(2+) waves evoked by high extracellular Ca(2+) provocation in S2814D(+/+) mice into non-propagated Ca(2+) mini-waves on confocal microscopy. Myocyte Ca(2+) waves, typical of S2814D(+/+) mice, could be evoked in SD(+/+) /KO cells by partially inhibiting SERCA2a. A mathematical human myocyte model replicated these results and allowed for predicting the increase in SR Ca(2+) uptake required to prevent the arrhythmias induced by a Ca(2+) -calmodulin-dependent protein kinase (CaMKII)-dependent leaky RyR2. Our results demonstrate that increasing SR Ca(2+) uptake by PLN ablation can prevent the arrhythmic events triggered by SR Ca(2+) leak due to CaMKII-dependent phosphorylation of the RyR2-S2814 site and underscore the benefits of increasing SERCA2a activity on SR Ca(2+) -triggered arrhythmias.
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Affiliation(s)
- G Mazzocchi
- Centro de Investigaciones Cardiovasculares, CCT-La Plata-CONICET, Facultad de Cs Médicas, UNLP, La Plata, Argentina
| | - L Sommese
- Centro de Investigaciones Cardiovasculares, CCT-La Plata-CONICET, Facultad de Cs Médicas, UNLP, La Plata, Argentina
| | - J Palomeque
- Centro de Investigaciones Cardiovasculares, CCT-La Plata-CONICET, Facultad de Cs Médicas, UNLP, La Plata, Argentina
| | - J I Felice
- Centro de Investigaciones Cardiovasculares, CCT-La Plata-CONICET, Facultad de Cs Médicas, UNLP, La Plata, Argentina
| | - M N Di Carlo
- Centro de Investigaciones Cardiovasculares, CCT-La Plata-CONICET, Facultad de Cs Médicas, UNLP, La Plata, Argentina
| | - D Fainstein
- Centro de Investigaciones Cardiovasculares, CCT-La Plata-CONICET, Facultad de Cs Médicas, UNLP, La Plata, Argentina
| | - P Gonzalez
- Cátedra de Patología, Facultad de Cs Médicas, UNLP, La Plata, Argentina
| | - P Contreras
- Departamento de Fisiología, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay
| | - D Skapura
- Departments of Molecular Physiology and Biophysics, Medicine (in Cardiology), and Pediatrics, Baylor College of Medicine, Cardiovascular Research Institute, Houston, TX, 77030, USA
| | - M D McCauley
- Departments of Molecular Physiology and Biophysics, Medicine (in Cardiology), and Pediatrics, Baylor College of Medicine, Cardiovascular Research Institute, Houston, TX, 77030, USA
| | - E C Lascano
- Departamento de Biología Comparada, Celular y Molecular, Universidad Favaloro, Ciudad Autónoma de Buenos Aires, Argentina
| | - J A Negroni
- Departamento de Biología Comparada, Celular y Molecular, Universidad Favaloro, Ciudad Autónoma de Buenos Aires, Argentina
| | - E G Kranias
- Department of Pharmacology, University of Cincinnati College of Medicine, Cincinnati, OH, 45267
| | - X H T Wehrens
- Departments of Molecular Physiology and Biophysics, Medicine (in Cardiology), and Pediatrics, Baylor College of Medicine, Cardiovascular Research Institute, Houston, TX, 77030, USA
| | - C A Valverde
- Centro de Investigaciones Cardiovasculares, CCT-La Plata-CONICET, Facultad de Cs Médicas, UNLP, La Plata, Argentina
| | - A Mattiazzi
- Centro de Investigaciones Cardiovasculares, CCT-La Plata-CONICET, Facultad de Cs Médicas, UNLP, La Plata, Argentina
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18
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Roe AT, Frisk M, Louch WE. Targeting cardiomyocyte Ca2+ homeostasis in heart failure. Curr Pharm Des 2015; 21:431-48. [PMID: 25483944 PMCID: PMC4475738 DOI: 10.2174/138161282104141204124129] [Citation(s) in RCA: 74] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2014] [Accepted: 08/06/2014] [Indexed: 12/19/2022]
Abstract
Improved treatments for heart failure patients will require the development of novel therapeutic strategies that target basal disease
mechanisms. Disrupted cardiomyocyte Ca2+ homeostasis is recognized as a major contributor to the heart failure phenotype, as it
plays a key role in systolic and diastolic dysfunction, arrhythmogenesis, and hypertrophy and apoptosis signaling. In this review, we outline
existing knowledge of the involvement of Ca2+ homeostasis in these deficits, and identify four promising targets for therapeutic intervention:
the sarcoplasmic reticulum Ca2+ ATPase, the Na+-Ca2+ exchanger, the ryanodine receptor, and t-tubule structure. We discuss
experimental data indicating the applicability of these targets that has led to recent and ongoing clinical trials, and suggest future therapeutic
approaches.
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Affiliation(s)
| | | | - William E Louch
- Institute for Experimental Medical Research, Kirkeveien 166, 4.etg. Bygg 7, Oslo University Hospital Ullevål, 0407 Oslo, Norway.
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19
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Cab45S promotes cell proliferation through SERCA2b inhibition and Ca2+ signaling. Oncogene 2015; 35:35-46. [PMID: 25772237 DOI: 10.1038/onc.2015.56] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2014] [Revised: 12/07/2014] [Accepted: 12/19/2014] [Indexed: 12/14/2022]
Abstract
Cytosolic Ca(2+), closely related to endoplasmic reticulum (ER) Ca(2+), plays a critical role in regulating cell proliferation and tumorigenesis. However, the role of ER lumen proteins in regulating cytosolic Ca(2+) level remains poorly understood. Here, we find that the Cab45S, localizes in the ER lumen, inhibits sarco/ER Ca(2+)-ATPase 2b (SERCA2b) activity through its first EF-hand domain directly binding to the intra-lumenal loop 4 of SERCA2b, and reduces ER Ca(2+). STIM1 activation, induced by the Cab45S-dependent drop in ER Ca(2+), together with the upregulation of the plasma membrane Ca(2+) channel TRPC1 ultimately increases extracellular Ca(2+) influx. Furthermore, increased cytosolic Ca(2+) level elicits Ca(2+)-NFAT signaling and promotes cell proliferation. Consistently, in cervical carcinoma patients, Cab45S is upregulated. Thus, our data reveal that the ability of Cab45S to inhibit SERCA2b activity is crucial for its role as a modulator of cell proliferation and tumor growth.
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20
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Clarke JD, Caldwell JL, Horn MA, Bode EF, Richards MA, Hall MCS, Graham HK, Briston SJ, Greensmith DJ, Eisner DA, Dibb KM, Trafford AW. Perturbed atrial calcium handling in an ovine model of heart failure: potential roles for reductions in the L-type calcium current. J Mol Cell Cardiol 2015; 79:169-79. [PMID: 25463272 PMCID: PMC4312356 DOI: 10.1016/j.yjmcc.2014.11.017] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/19/2013] [Revised: 11/10/2014] [Accepted: 11/11/2014] [Indexed: 12/19/2022]
Abstract
Heart failure (HF) is commonly associated with reduced cardiac output and an increased risk of atrial arrhythmias particularly during β-adrenergic stimulation. The aim of the present study was to determine how HF alters systolic Ca(2+) and the response to β-adrenergic (β-AR) stimulation in atrial myocytes. HF was induced in sheep by ventricular tachypacing and changes in intracellular Ca(2+) concentration studied in single left atrial myocytes under voltage and current clamp conditions. The following were all reduced in HF atrial myocytes; Ca(2+) transient amplitude (by 46% in current clamped and 28% in voltage clamped cells), SR dependent rate of Ca(2+) removal (kSR, by 32%), L-type Ca(2+) current density (by 36%) and action potential duration (APD90 by 22%). However, in HF SR Ca(2+) content was increased (by 19%) when measured under voltage-clamp stimulation. Inhibiting the L-type Ca(2+) current (ICa-L) in control cells reproduced both the decrease in Ca(2+) transient amplitude and increase of SR Ca(2+) content observed in voltage-clamped HF cells. During β-AR stimulation Ca(2+) transient amplitude was the same in control and HF cells. However, ICa-L remained less in HF than control cells whilst SR Ca(2+) content was highest in HF cells during β-AR stimulation. The decrease in ICa-L that occurs in HF atrial myocytes appears to underpin the decreased Ca(2+) transient amplitude and increased SR Ca(2+) content observed in voltage-clamped cells.
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Affiliation(s)
- Jessica D Clarke
- Institute of Cardiovascular Science, Manchester Academic Health Science Centre, 3.24 Core Technology Facility, 46 Grafton St, Manchester M13 9PT, UK
| | - Jessica L Caldwell
- Institute of Cardiovascular Science, Manchester Academic Health Science Centre, 3.24 Core Technology Facility, 46 Grafton St, Manchester M13 9PT, UK
| | - Margaux A Horn
- Institute of Cardiovascular Science, Manchester Academic Health Science Centre, 3.24 Core Technology Facility, 46 Grafton St, Manchester M13 9PT, UK
| | - Elizabeth F Bode
- Institute of Cardiovascular Science, Manchester Academic Health Science Centre, 3.24 Core Technology Facility, 46 Grafton St, Manchester M13 9PT, UK
| | - Mark A Richards
- Institute of Cardiovascular Science, Manchester Academic Health Science Centre, 3.24 Core Technology Facility, 46 Grafton St, Manchester M13 9PT, UK
| | - Mark C S Hall
- Liverpool Heart and Chest Hospital, Thomas Drive, Liverpool L14 3PE, UK
| | - Helen K Graham
- Institute of Cardiovascular Science, Manchester Academic Health Science Centre, 3.24 Core Technology Facility, 46 Grafton St, Manchester M13 9PT, UK
| | - Sarah J Briston
- Institute of Cardiovascular Science, Manchester Academic Health Science Centre, 3.24 Core Technology Facility, 46 Grafton St, Manchester M13 9PT, UK
| | - David J Greensmith
- Institute of Cardiovascular Science, Manchester Academic Health Science Centre, 3.24 Core Technology Facility, 46 Grafton St, Manchester M13 9PT, UK
| | - David A Eisner
- Institute of Cardiovascular Science, Manchester Academic Health Science Centre, 3.24 Core Technology Facility, 46 Grafton St, Manchester M13 9PT, UK
| | - Katharine M Dibb
- Institute of Cardiovascular Science, Manchester Academic Health Science Centre, 3.24 Core Technology Facility, 46 Grafton St, Manchester M13 9PT, UK
| | - Andrew W Trafford
- Institute of Cardiovascular Science, Manchester Academic Health Science Centre, 3.24 Core Technology Facility, 46 Grafton St, Manchester M13 9PT, UK.
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21
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Shiels HA, Galli GL. The Sarcoplasmic Reticulum and the Evolution of the Vertebrate Heart. Physiology (Bethesda) 2014; 29:456-69. [DOI: 10.1152/physiol.00015.2014] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The sarcoplasmic reticulum (SR) is crucial for contraction and relaxation of the mammalian cardiomyocyte, but its role in other vertebrate classes is equivocal. Recent evidence suggests differences in SR function across species may have an underlying structural basis. Here, we discuss how SR recruitment relates to the structural organization of the cardiomyocyte to provide new insight into the evolution of cardiac design and function in vertebrates.
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Affiliation(s)
- Holly A. Shiels
- Faculty of Life Sciences, University of Manchester, Manchester, United Kingdom; and
| | - Gina L.J. Galli
- Faculty of Medical and Human Sciences, University of Manchester, Manchester, United Kingdom
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22
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Fioresi M, Simões MR, Furieri LB, Broseghini-Filho GB, Vescovi MVA, Stefanon I, Vassallo DV. Chronic lead exposure increases blood pressure and myocardial contractility in rats. PLoS One 2014; 9:e96900. [PMID: 24841481 PMCID: PMC4026242 DOI: 10.1371/journal.pone.0096900] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2013] [Accepted: 04/13/2014] [Indexed: 11/18/2022] Open
Abstract
We investigated the cardiovascular effects of lead exposure, emphasising its direct action on myocardial contractility. Male Wistar rats were sorted randomly into two groups: control (Ct) and treatment with 100 ppm of lead (Pb) in the drinking water. Blood pressure (BP) was measured weekly. At the end of the treatment period, the animals were anaesthetised and haemodynamic parameters and contractility of the left ventricular papillary muscles were recorded. Blood and tissue samples were properly stored for further biochemical investigations. Statistical analyses were considered to be significant at p<0.05. The lead concentrations in the blood reached approximately 13 µg/dL, while the bone was the site of the highest deposition of this metal. BP in the Pb-treated group was higher from the first week of lead exposure and remained at the same level over the next four weeks. Haemodynamic evaluations revealed increases in systolic (Ct: 96±3.79 vs. Pb: 116±1.37 mmHg) and diastolic blood pressure (Ct: 60±2.93 vs. Pb: 70±3.38 mmHg), left ventricular systolic pressure (Ct: 104±5.85 vs. Pb: 120±2.51 mmHg) and heart rate (Ct: 307±10 vs. Pb: 348±16 bpm). Lead treatment did not alter the force and time derivatives of the force of left ventricular papillary muscles that were contracting isometrically. However, our results are suggestive of changes in the kinetics of calcium (Ca++) in cardiomyocytes increased transarcolemmal Ca++ influx, low Ca++ uptake by the sarcoplasmic reticulum and high extrusion by the sarcolemma. Altogether, these results show that despite the increased Ca++ influx that was induced by lead exposure, the myocytes had regulatory mechanisms that prevented increases in force, as evidenced in vivo by the increased systolic ventricular pressure.
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Affiliation(s)
- Mirian Fioresi
- Department of Physiological Sciences, Federal University of Espírito Santo, Vitoria, Espírito Santo, Brazil
- Department of Nursing, Federal University of Espírito Santo, Vitoria, Espírito Santo, Brazil
- * E-mail:
| | - Maylla Ronacher Simões
- Department of Physiological Sciences, Federal University of Espírito Santo, Vitoria, Espírito Santo, Brazil
| | - Lorena Barros Furieri
- Department of Physiological Sciences, Federal University of Espírito Santo, Vitoria, Espírito Santo, Brazil
- Department of Nursing, Federal University of Espírito Santo, Vitoria, Espírito Santo, Brazil
| | | | | | - Ivanita Stefanon
- Department of Physiological Sciences, Federal University of Espírito Santo, Vitoria, Espírito Santo, Brazil
| | - Dalton Valentim Vassallo
- Department of Physiological Sciences, Federal University of Espírito Santo, Vitoria, Espírito Santo, Brazil
- Health Science Centre of Vitória-EMESCAM, Vitória, Espírito Santo, Brazil
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23
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Trantidou T, Rao C, Barrett H, Camelliti P, Pinto K, Yacoub MH, Athanasiou T, Toumazou C, Terracciano CM, Prodromakis T. Selective hydrophilic modification of Parylene C films: a new approach to cell micro-patterning for synthetic biology applications. Biofabrication 2014; 6:025004. [PMID: 24658120 DOI: 10.1088/1758-5082/6/2/025004] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
We demonstrate a simple, accurate and versatile method to manipulate Parylene C, a material widely known for its high biocompatibility, and transform it to a substrate that can effectively control the cellular microenvironment and consequently affect the morphology and function of the cells in vitro. The Parylene C scaffolds are fabricated by selectively increasing the material's surface water affinity through lithography and oxygen plasma treatment, providing free bonds for attachment of hydrophilic biomolecules. The micro-engineered constructs were tested as culture scaffolds for rat ventricular fibroblasts and neonatal myocytes (NRVM), toward modeling the unique anisotropic architecture of native cardiac tissue. The scaffolds induced the patterning of extracellular matrix compounds and therefore of the cells, which demonstrated substantial alignment compared to typical unstructured cultures. Ca(2+) cycling properties of the NRVM measured at rates of stimulation 0.5-2 Hz were significantly modified with a shorter time to peak and time to 90% decay, and a larger fluorescence amplitude (p < 0.001). The proposed technique is compatible with standard cell culturing protocols and exhibits long-term pattern durability. Moreover, it allows the integration of monitoring modalities into the micro-engineered substrates for a comprehensive interrogation of physiological parameters.
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Affiliation(s)
- T Trantidou
- Centre for Bio-Inspired Technology, Institute of Biomedical Engineering, Imperial College London, SW7 2BT, UK
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24
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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] [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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25
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Heinis FI, Andersson KB, Christensen G, Metzger JM. Prominent heart organ-level performance deficits in a genetic model of targeted severe and progressive SERCA2 deficiency. PLoS One 2013; 8:e79609. [PMID: 24223976 PMCID: PMC3817129 DOI: 10.1371/journal.pone.0079609] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2013] [Accepted: 09/24/2013] [Indexed: 11/28/2022] Open
Abstract
The cardiac SERCA2 Ca2+ pump is critical for maintaining normal Ca2+ handling in the heart. Reduced SERCA2a content and blunted Ca2+ reuptake are frequently observed in failing hearts and evidence implicates poor cardiac Ca2+ handling in the progression of heart failure. To gain insight into mechanism we investigated a novel genetic mouse model of inducible severe and progressive SERCA2 deficiency (inducible Serca2 knockout, SERCA2 KO). These mice eventually die from overt heart failure 7-10 weeks after knockout but as yet there have been no reports on intrinsic mechanical performance at the isolated whole heart organ level. Thus we studied whole-organ ex vivo function of hearts isolated from SERCA2 KO mice at one and four weeks post-knockout in adult animals. We found that isolated KO heart function was only modestly impaired one week post-knockout, when SERCA2a protein was 32% of normal. At four weeks post-knockout, function was severely impaired with near non-detectable levels of SERCA2. During perfusion with 10 mM caffeine, LV developed pressures were similar between 4-week KO and control hearts, and end-diastolic pressures were lower in KO. When hearts were subjected to ischemia-reperfusion injury, recovery was not different between control and KO hearts at either one or four weeks post-knockout. Our findings indicate that ex vivo function of isolated SERCA2 KO hearts is severely impaired long before symptoms appear in vivo, suggesting that physiologically relevant heart function in vivo can be sustained for weeks in the absence of robust SR Ca2+ flux.
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Affiliation(s)
- Frazer I. Heinis
- Department of Integrative Biology and Physiology, University of Minnesota Medical School, Minneapolis, Minnesota, United States of America
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, Minnesota, United States of America
| | - Kristin B. Andersson
- Institute for Experimental Medical Research, Oslo University Hospital Ullevaal and University of Oslo, Oslo, Norway
- Center for Heart Failure Research, University of Oslo, Oslo, Norway
| | - Geir Christensen
- Institute for Experimental Medical Research, Oslo University Hospital Ullevaal and University of Oslo, Oslo, Norway
- Center for Heart Failure Research, University of Oslo, Oslo, Norway
| | - Joseph M. Metzger
- Department of Integrative Biology and Physiology, University of Minnesota Medical School, Minneapolis, Minnesota, United States of America
- * E-mail:
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26
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Synchrony of cardiomyocyte Ca(2+) release is controlled by T-tubule organization, SR Ca(2+) content, and ryanodine receptor Ca(2+) sensitivity. Biophys J 2013; 104:1685-97. [PMID: 23601316 DOI: 10.1016/j.bpj.2013.03.022] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2012] [Revised: 02/27/2013] [Accepted: 03/13/2013] [Indexed: 02/06/2023] Open
Abstract
Recent work has demonstrated that cardiomyocyte Ca(2+)release is desynchronized in several pathological conditions. Loss of Ca(2+) release synchrony has been attributed to t-tubule disruption, but it is unknown if other factors also contribute. We investigated this issue in normal and failing myocytes by integrating experimental data with a mathematical model describing spatiotemporal dynamics of Ca(2+) in the cytosol and sarcoplasmic reticulum (SR). Heart failure development in postinfarction mice was associated with progressive t-tubule disorganization, as quantified by fast-Fourier transforms. Data from fast-Fourier transforms were then incorporated in the model as a dyadic organization index, reflecting the proportion of ryanodine receptors located in dyads. With decreasing dyadic-organization index, the model predicted greater dyssynchrony of Ca(2+) release, which exceeded that observed in experimental line-scan images. Model and experiment were reconciled by reducing the threshold for Ca(2+) release in the model, suggesting that increased RyR sensitivity partially offsets the desynchronizing effects of t-tubule disruption in heart failure. Reducing the magnitude of SR Ca(2+) content and release, whether experimentally by thapsigargin treatment, or in the model, desynchronized the Ca(2+) transient. However, in cardiomyocytes isolated from SERCA2 knockout mice, RyR sensitization offset such effects. A similar interplay between RyR sensitivity and SR content was observed during treatment of myocytes with low-dose caffeine. Initial synchronization of Ca(2+) release during caffeine was reversed as SR content declined due to enhanced RyR leak. Thus, synchrony of cardiomyocyte Ca(2+) release is not only determined by t-tubule organization but also by the interplay between RyR sensitivity and SR Ca(2+) content.
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27
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Hillestad V, Kramer F, Golz S, Knorr A, Andersson KB, Christensen G. Long-term levosimendan treatment improves systolic function and myocardial relaxation in mice with cardiomyocyte-specific disruption of the Serca2 gene. J Appl Physiol (1985) 2013; 115:1572-80. [PMID: 24072410 DOI: 10.1152/japplphysiol.01044.2012] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In human heart failure (HF), reduced cardiac function has, at least partly, been ascribed to altered calcium homeostasis in cardiomyocytes. The effects of the calcium sensitizer levosimendan on diastolic dysfunction caused by reduced removal of calcium from cytosol in early diastole are not well known. In this study, we investigated the effect of long-term levosimendan treatment in a murine model of HF where the sarco(endo)plasmatic reticulum ATPase (Serca) gene is specifically disrupted in the cardiomyocytes, leading to reduced removal of cytosolic calcium. After induction of Serca2 gene disruption, these mice develop marked diastolic dysfunction as well as impaired contractility. SERCA2 knockout (SERCA2KO) mice were treated with levosimendan or vehicle from the time of KO induction. At the 7-wk end point, cardiac function was assessed by echocardiography and pressure measurements. Vehicle-treated SERCA2KO mice showed significantly diminished left-ventricular (LV) contractility, as shown by decreased ejection fraction, stroke volume, and cardiac output. LV pressure measurements revealed a marked increase in the time constant (τ) of isovolumetric pressure decay, showing impaired relaxation. Levosimendan treatment significantly improved all three systolic parameters. Moreover, a significant reduction in τ toward normalization indicated improved relaxation. Gene-expression analysis, however, revealed an increase in genes related to production of the ECM in animals treated with levosimendan. In conclusion, long-term levosimendan treatment improves both contractility and relaxation in a heart-failure model with marked diastolic dysfunction due to reduced calcium transients. However, altered gene expression related to fibrosis was observed.
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Affiliation(s)
- Vigdis Hillestad
- Institute for Experimental Medical Research, Oslo University Hospital Ullevål and University of Oslo, Oslo, Norway
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28
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Lexow J, Poggioli T, Sarathchandra P, Santini MP, Rosenthal N. Cardiac fibrosis in mice expressing an inducible myocardial-specific Cre driver. Dis Model Mech 2013; 6:1470-6. [PMID: 23929940 PMCID: PMC3820269 DOI: 10.1242/dmm.010470] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Tamoxifen-inducible Cre-mediated manipulation of animal genomes has achieved wide acceptance over the last decade, with numerous important studies heavily relying on this technique. Recently, a number of groups have reported transient complications of using this protocol in the heart. In the present study we observed a previously unreported focal fibrosis and depressed left-ventricular function in tamoxifen-treated αMHC-MerCreMer-positive animals in a Tβ4shRNAflox × αMHC-MerCreMer cross at 6-7 weeks following standard tamoxifen treatment, regardless of the presence of the floxed transgene. The phenotype was reproduced by treating mice from the original αMHC-MerCreMer strain with tamoxifen. In the acute phase after tamoxifen treatment, cell infiltration into the myocardium was accompanied by increased expression of pro-inflammatory cytokines (IL-1β, IL-6, TNFα, IFNγ, Ccl2) and markers of hypertrophy (ANF, BNP, Col3a1). These observations highlight the requirement for including tamoxifen-treated MerCreMer littermate controls to avert misinterpretation of conditional mutant phenotypes. A survey of the field as well as the protocols presented here suggests that controlling the parameters of tamoxifen delivery is important in avoiding the chronic MerCreMer-mediated cardiac phenotype reported here.
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Affiliation(s)
- Jonas Lexow
- National Heart and Lung Institute, Heart Science Centre and Hammersmith Hospital Campus, Imperial College London, London, W12 0NN, UK
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29
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Louch WE, Stokke MK, Sjaastad I, Christensen G, Sejersted OM. No rest for the weary: diastolic calcium homeostasis in the normal and failing myocardium. Physiology (Bethesda) 2013; 27:308-23. [PMID: 23026754 DOI: 10.1152/physiol.00021.2012] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Following contraction of the heart, efficient relaxation (diastole) is essential for refilling the ventricles with blood. This review describes how ventricular relaxation is controlled by Ca(2+) homeostasis in cardiac muscle cells and how alterations in Ca(2+) cycling affect diastolic function in the normal and failing heart. These discussions illustrate that the diastolic phase is not simply a period of rest but rather involves highly regulated and dynamic Ca(2+) fluxes.
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Affiliation(s)
- William E Louch
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway.
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30
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Stokke MK, Tovsrud N, Louch WE, Øyehaug L, Hougen K, Sejersted OM, Swift F, Sjaastad I. I(CaL) inhibition prevents arrhythmogenic Ca(2+) waves caused by abnormal Ca(2+) sensitivity of RyR or SR Ca(2+) accumulation. Cardiovasc Res 2013; 98:315-25. [PMID: 23417043 DOI: 10.1093/cvr/cvt037] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
AIMS Arrhythmogenic Ca(2+) waves result from uncontrolled Ca(2+) release from the sarcoplasmic reticulum (SR) that occurs with increased Ca(2+) sensitivity of the ryanodine receptor (RyR) or excessive Ca(2+) accumulation during β-adrenergic stimulation. We hypothesized that inhibition of the L-type Ca(2+) current (I(CaL)) could prevent such Ca(2+) waves in both situations. METHODS AND RESULTS Ca(2+) waves were induced in mouse left ventricular cardiomyocytes by isoproterenol combined with caffeine to increase RyR Ca(2+) sensitivity. I(CaL) inhibition by verapamil (0.5 µM) reduced Ca(2+) wave probability in cardiomyocytes during electrostimulation, and during a 10 s rest period after ceasing stimulation. A separate type of Ca(2+) release events occurred during the decay phase of the Ca(2+) transient and was not prevented by verapamil. Verapamil decreased Ca(2+) spark frequency, but not in permeabilized cells, indicating that this was not due to direct effects on RyR. The antiarrhythmic effect of verapamil was due to reduced SR Ca(2+) content following I(CaL) inhibition. Computational modelling supported that the level of I(CaL) inhibition obtained experimentally was sufficient to reduce the SR Ca(2+) content. Ca(2+) wave prevention through reduced SR Ca(2+) content was also effective in heterozygous ankyrin B knockout mice with excessive SR Ca(2+) accumulation during β-adrenergic stimulation. CONCLUSION I(CaL) inhibition prevents diastolic Ca(2+) waves caused by increased Ca(2+) sensitivity of RyR or excessive SR Ca(2+) accumulation during β-adrenergic stimulation. In contrast, unstimulated early Ca(2+) release during the decay of the Ca(2+) transient is not prevented, and merits further study to understand the full antiarrhythmic potential of I(CaL) inhibition.
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Affiliation(s)
- Mathis K Stokke
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway.
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31
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Sirenko S, Yang D, Li Y, Lyashkov AE, Lukyanenko YO, Lakatta EG, Vinogradova TM. Ca²⁺-dependent phosphorylation of Ca²⁺ cycling proteins generates robust rhythmic local Ca²⁺ releases in cardiac pacemaker cells. Sci Signal 2013; 6:ra6. [PMID: 23362239 DOI: 10.1126/scisignal.2003391] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The spontaneous beating of the heart is governed by spontaneous firing of sinoatrial node cells, which generate action potentials due to spontaneous depolarization of the membrane potential, or diastolic depolarization. The spontaneous diastolic depolarization rate is determined by spontaneous local submembrane Ca²⁺ releases through ryanodine receptors (RyRs). We sought to identify specific mechanisms of intrinsic Ca²⁺ cycling by which sinoatrial node cells, but not ventricular myocytes, generate robust, rhythmic local Ca²⁺ releases. At similar physiological intracellular Ca²⁺ concentrations, local Ca²⁺ releases were large and rhythmic in permeabilized sinoatrial node cells but small and random in permeabilized ventricular myocytes. Furthermore, sinoatrial node cells spontaneously released more Ca²⁺ from the sarcoplasmic reticulum than did ventricular myocytes, despite comparable sarcoplasmic reticulum Ca²⁺ content in both cell types. This ability of sinoatrial node cells to generate larger and rhythmic local Ca²⁺ releases was associated with increased abundance of sarcoplasmic reticulum Ca²⁺-ATPase (SERCA), reduced abundance of the SERCA inhibitor phospholamban, and increased Ca²⁺-dependent phosphorylation of phospholamban and RyR. The increased phosphorylation of RyR in sinoatrial node cells may facilitate Ca²⁺ release from the sarcoplasmic reticulum, whereas Ca²⁺-dependent increase in phosphorylation of phospholamban relieves its inhibition of SERCA, augmenting the pumping rate of Ca²⁺ required to support robust, rhythmic local Ca²⁺ releases. The differences in Ca²⁺ cycling between sinoatrial node cells and ventricular myocytes provide insights into the regulation of intracellular Ca²⁺ cycling that drives the automaticity of sinoatrial node cells.
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Affiliation(s)
- Syevda Sirenko
- Laboratory of Cardiovascular Science, Gerontology Research Center, National Institute on Aging Intramural Research Program, National Institutes of Health, 5600 Nathan Shock Drive, Baltimore, MD 21224, USA
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32
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Calcium flux balance in the heart. J Mol Cell Cardiol 2012; 58:110-7. [PMID: 23220128 DOI: 10.1016/j.yjmcc.2012.11.017] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/09/2012] [Revised: 11/08/2012] [Accepted: 11/22/2012] [Indexed: 11/22/2022]
Abstract
This article reviews the consequences of the need for the cardiac cell to be in calcium flux balance in the steady state. We first discuss how this steady state condition affects the control of resting [Ca(2+)]i. The next section considers how sarcoplasmic reticulum (SR) Ca content is controlled by a feedback mechanism whereby changes of SR Ca affect the amplitude of the Ca transient and this, in turn, controls sarcolemmal Ca fluxes. Subsequent sections review the effects of altering the activity of individual Ca handling proteins. Increasing the activity of the SR Ca-ATPase (SERCA) increases both the amplitude and rate constant of decay of the systolic Ca transient. The Ca flux balance condition requires that this must be achieved with no change of Ca efflux placing constraints on the magnitude of change of amplitude and decay rate. We analyze the quantitative dependence of Ca transient amplitude and SR content on SERCA activity. Increasing the open probability of the RyR during systole is predicted to have no steady state effect on the amplitude of the systolic Ca transient. We discuss the effects of changing the amplitude of the L-type Ca current in the context of both triggering Ca release from the SR and loading the cell with calcium. These manoeuvres are considered in the context of the effects of β-adrenergic stimulation. Finally, we review calcium flux balance in the presence of Ca waves.
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33
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Maxwell JT, Blatter LA. Facilitation of cytosolic calcium wave propagation by local calcium uptake into the sarcoplasmic reticulum in cardiac myocytes. J Physiol 2012; 590:6037-45. [PMID: 22988145 PMCID: PMC3530115 DOI: 10.1113/jphysiol.2012.239434] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2012] [Accepted: 09/16/2012] [Indexed: 11/08/2022] Open
Abstract
The widely accepted paradigm for cytosolic Ca(2+) wave propagation postulates a 'fire-diffuse-fire' mechanism where local Ca(2+)-induced Ca(2+) release (CICR) from the sarcoplasmic reticulum (SR) via ryanodine receptor (RyR) Ca(2+) release channels diffuses towards and activates neighbouring release sites, resulting in a propagating Ca(2+) wave. A recent challenge to this paradigm proposed the requirement for an intra-SR 'sensitization' Ca(2+) wave that precedes the cytosolic Ca(2+) wave and primes RyRs from the luminal side to CICR. Here, we tested this hypothesis experimentally with direct simultaneous measurements of cytosolic ([Ca(2+)](i); rhod-2) and intra-SR ([Ca(2+)](SR); fluo-5N) calcium signals during wave propagation in rabbit ventricular myocytes, using high resolution fluorescence confocal imaging. The increase in [Ca(2+)](i) at the wave front preceded depletion of the SR at each point along the calcium wave front, while during this latency period a transient increase of [Ca(2+)](SR) was observed. This transient elevation of [Ca(2+)](SR) could be identified at individual release junctions and depended on the activity of the sarco-endoplasmic reticulum Ca(2+)-ATPase (SERCA). Increased SERCA activity (β-adrenergic stimulation with 1 μM isoproterenol (isoprenaline)) decreased the latency period and increased the amplitude of the transient elevation of [Ca(2+)](SR), whereas inhibition of SERCA (3 μM cyclopiazonic acid) had the opposite effect. In conclusion, the data provide experimental evidence that local Ca(2+) uptake by SERCA into the SR facilitates the propagation of cytosolic Ca(2+) waves via luminal sensitization of the RyR, and supports a novel paradigm of a 'fire-diffuse-uptake-fire' mechanism for Ca(2+) wave propagation in cardiac myocytes.
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Affiliation(s)
- Joshua T Maxwell
- Department of Molecular Biophysics and Physiology, Rush University Medical Center, 1750 W. Harrison Street, Chicago, IL 60612, USA
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Domeier TL, Maxwell JT, Blatter LA. β-Adrenergic stimulation increases the intra-sarcoplasmic reticulum Ca2+ threshold for Ca2+ wave generation. J Physiol 2012; 590:6093-108. [PMID: 22988136 DOI: 10.1113/jphysiol.2012.236117] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
β-Adrenergic signalling induces positive inotropic effects on the heart that associate with pro-arrhythmic spontaneous Ca(2+) waves. A threshold level of sarcoplasmic reticulum (SR) Ca(2+) ([Ca(2+)](SR)) is necessary to trigger Ca(2+) waves, and whether the increased incidence of Ca(2+) waves during β-adrenergic stimulation is due to an alteration in this threshold remains controversial. Using the low-affinity Ca(2+) indicator fluo-5N entrapped within the SR of rabbit ventricular myocytes, we addressed this controversy by directly monitoring [Ca(2+)](SR) and Ca(2+) waves during β-adrenergic stimulation. Electrical pacing in elevated extracellular Ca(2+) ([Ca(2+)](o) = 7 mM) was used to increase [Ca(2+)](SR) to the threshold where Ca(2+) waves were consistently observed. The β-adrenergic agonist isoproterenol (ISO; 1 μM) increased [Ca(2+)](SR) well above the control threshold and consistently triggered Ca(2+) waves. However, when [Ca(2+)](SR) was subsequently lowered in the presence of ISO (by lowering [Ca(2+)](o) to 1 mM and partially inhibiting sarcoplasmic/endoplasmic reticulum calcium ATPase with cyclopiazonic acid or thapsigargin), Ca(2+) waves ceased to occur at a [Ca(2+)](SR) that was higher than the control threshold. Furthermore, for a set [Ca(2+)](SR) level the refractoriness of wave occurrence (Ca(2+) wave latency) was prolonged during β-adrenergic stimulation, and was highly dependent on the extent that [Ca](SR) exceeded the wave threshold. These data show that acute β-adrenergic stimulation increases the [Ca(2+)](SR) threshold for Ca(2+) waves, and therefore the primary cause of Ca(2+) waves is the robust increase in [Ca(2+)](SR) above this higher threshold level. Elevation of the [Ca(2+)](SR) wave threshold and prolongation of wave latency represent potentially protective mechanisms against pro-arrhythmogenic Ca(2+) release during β-adrenergic stimulation.
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Affiliation(s)
- Timothy L Domeier
- Department of Molecular Biophysics and Physiology, Rush University Medical Center, 1750 W. Harrison Street, Chicago, IL 60612, USA
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35
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Tveito A, Lines GT, Edwards AG, Maleckar MM, Michailova A, Hake J, McCulloch A. Slow Calcium-Depolarization-Calcium waves may initiate fast local depolarization waves in ventricular tissue. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2012; 110:295-304. [PMID: 22841534 DOI: 10.1016/j.pbiomolbio.2012.07.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2012] [Accepted: 07/16/2012] [Indexed: 10/28/2022]
Abstract
Intercellular calcium waves in cardiac myocytes are a well-recognized, if incompletely understood, phenomenon. In a variety of preparations, investigators have reported multi-cellular calcium waves or triggered propagated contractions, but the mechanisms of propagation and pathological importance of these events remain unclear. Here, we review existing experimental data and present a computational approach to investigate the mechanisms of multi-cellular calcium wave propagation. Over the past 50 years, the standard modeling paradigm for excitable cardiac tissue has seen increasingly detailed models of the dynamics of individual cells coupled in tissue solely by intercellular and interstitial current flow. Although very successful, this modeling regime has been unable to capture two important phenomena: 1) the slow intercellular calcium waves observed experimentally, and 2) how intercellular calcium events resulting in delayed after depolarizations at the cellular level could overcome a source-sink mismatch to initiate depolarization waves in tissue. In this paper, we introduce a mathematical model with subcellular spatial resolution, in which we allow both inter- and intracellular current flow and calcium diffusion. In simulations of coupled cells employing this model, we observe: a) slow inter-cellular calcium waves propagating at about 0.1 mm/s, b) faster Calcium-Depolarization-Calcium (CDC) waves, traveling at about 1 mm/s, and c) CDC-waves that can set off fast depolarization-waves (50 cm/s) in tissue with varying gap-junction conductivity.
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Affiliation(s)
- Aslak Tveito
- Center for Biomedical Computing, Simula Research Laboratory, Norway
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36
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Nivala M, Qu Z. Calcium alternans in a couplon network model of ventricular myocytes: role of sarcoplasmic reticulum load. Am J Physiol Heart Circ Physiol 2012; 303:H341-52. [PMID: 22661509 DOI: 10.1152/ajpheart.00302.2012] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Intracellular calcium (Ca) alternans in cardiac myocytes have been shown in many experimental studies, and the mechanisms remain incompletely understood. We recently developed a "3R theory" that links Ca sparks to whole cell Ca alternans through three critical properties: randomness of Ca sparks; recruitment of a Ca spark by neighboring Ca sparks; and refractoriness of Ca release units. In this study, we used computer simulation of a physiologically detailed mathematical model of a ventricular myocyte couplon network to study how sarcoplasmic reticulum (SR) Ca load and other physiological parameters, such as ryanodine receptor sensitivity, SR uptake rate, Na-Ca exchange strength, and Ca buffer levels affect Ca alternans in the context of 3R theory. We developed a method to calculate the parameters used in the 3R theory (i.e., the primary spark rate and the recruitment rate) from the physiologically detailed Ca cycling model and paced the model periodically to elicit Ca alternans. We show that alternans only occurs for an intermediate range of the SR Ca load, and the underlying mechanism can be explained via its effects on the 3Rs. Furthermore, we show that altering the physiological parameters not only directly changes the 3Rs but also alters the SR Ca load, having an indirect effect on the 3Rs as well. Therefore, our present study links the SR Ca load and other physiological parameters to whole cell Ca alternans through the framework of the 3R theory, providing a general mechanistic understanding of Ca alternans in ventricular myocytes.
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Affiliation(s)
- Michael Nivala
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, USA
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37
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Tveito A, Lines GT, Hake J, Edwards AG. Instabilities of the resting state in a mathematical model of calcium handling in cardiac myocytes. Math Biosci 2012; 236:97-107. [PMID: 22391458 DOI: 10.1016/j.mbs.2012.02.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2011] [Revised: 02/09/2012] [Accepted: 02/15/2012] [Indexed: 11/28/2022]
Abstract
We analyze a recently published model of calcium handling in cardiac myocytes in order to find conditions for the presence of instabilities in the resting state of the model. Such instabilities can create calcium waves which in turn may be able to initiate cardiac arrhythmias. The model was developed by Swietach, Spitzer and Vaughan-Jones in order to study the effect, on calcium waves, of varying ryanodine receptor (RyR)-permeability, sarco/endoplasmic reticulum calcium ATPase (SERCA) and calcium diffusion. We study the model using the extracellular calcium concentration c(e) and the maximal velocity of the SERCA-pump v(SERCA) as control parameters. In the (c(e),v(SERCA))-domain we derive an explicit function v∗=v∗(c(e)), and we claim that any resting state based on parameters that lie above the curve (i.e. any pair (c(e),v(SERCA)) such that with v(SERCA) > v∗(c(e))) is unstable in the sense that small perturbations will grow and can eventually turn into a calcium wave. And conversely; any pair (c(e),v(SERCA)) below the curve is stable in the sense that small perturbations to the resting state will decay to rest. This claim is supported by analyzing the stability of the system in terms of computing the eigenmodes of the linearized model. Furthermore, the claim is supported by direct simulations based on the non-linear model. Since the curve separating stable from unstable states is given as an explicit function, we can show how stability depends on other parameters of the model.
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Affiliation(s)
- Aslak Tveito
- Center for Biomedical Computing, Simula Research Laboratory, and Center for Cardiological Innovation, Oslo University Hospital, Norway
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38
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Bell JR, Mellor KM, Wollermann AC, Ip WTK, Reichelt ME, Meachem SJ, Simpson ER, Delbridge LMD. Aromatase deficiency confers paradoxical postischemic cardioprotection. Endocrinology 2011; 152:4937-47. [PMID: 22028441 DOI: 10.1210/en.2011-1212] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The conventional view is that estrogen confers female cardioprotection. Estrogen synthesis depends on androgen availability, with aromatase regulating conversion of testosterone to estradiol. Extragonadal aromatase expression mediates estrogen production in some tissues, but a role for local steroid conversion has not yet been demonstrated in the heart. This study's goal was to investigate how aromatase deficiency influences myocardial function and ischemic resilience. RT-PCR analysis of C57Bl/6 mouse hearts confirmed cardiac-specific aromatase expression in adult females. Functional performance of isolated hearts from female aromatase knockout (ArKO) and aromatase wild-type mice were compared. Left ventricular developed pressures were similar in aerobic perfusion, but the maximal rate of rise of ventricular pressure was modestly reduced in ArKO hearts (3725 ± 144 vs. 4272 ± 154 mm Hg/sec, P < 0.05). After 25 min of ischemia, the recovery of left ventricular developed pressure was substantially improved in ArKO (percentage of basal at 60 min of reperfusion, 62 ± 8 vs. 30 ± 6%; P < 0.05). Hypercontracture was attenuated (end diastolic pressure, 25 ± 5 vs. 51 ± 1 mm Hg; P < 0.05), and lactate dehydrogenase content of coronary effluent was reduced throughout reperfusion in ArKO hearts. This was associated with a hyperphosphorylation of phospholamban and a reduction in phosphorylated Akt. Immediately after reperfusion, ArKO hearts exhibited increased incidence of ventricular premature beats (194 ± 70 vs. 46 ± 6, P < 0.05). These observations indicate more robust functional recovery, reduced cellular injury, and modified cardiomyocyte Ca(2+) handling in aromatase-deficient hearts. Our findings indicate that androgen-to-estrogen conversion may be of pathophysiologic importance to the heart and challenge the notion that estrogen deficiency is deleterious. These studies suggest the possibility that aromatase suppression may offer inotropic benefit in the acute ischemia/reperfusion setting with appropriate arrhythmia management.
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Affiliation(s)
- James R Bell
- Cardiac Phenomics Laboratory, Department of Physiology, University of Melbourne, Victoria 3010, Australia
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39
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Rodriguez AG, Han SJ, Regnier M, Sniadecki NJ. Substrate stiffness increases twitch power of neonatal cardiomyocytes in correlation with changes in myofibril structure and intracellular calcium. Biophys J 2011; 101:2455-64. [PMID: 22098744 DOI: 10.1016/j.bpj.2011.09.057] [Citation(s) in RCA: 111] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2011] [Revised: 09/14/2011] [Accepted: 09/30/2011] [Indexed: 12/16/2022] Open
Abstract
During neonatal development, there is an increase in myocardial stiffness that coincides with an increase in the contractility of the heart. In vitro assays have shown that substrate stiffness plays a role in regulating the twitch forces produced by immature cardiomyocytes. However, its effect on twitch power is unclear due to difficulties in measuring the twitch velocity of cardiomyocytes. Here, we introduce what we consider a novel approach to quantify twitch power by combining the temporal resolution of optical line scanning with the subcellular force resolution of micropost arrays. Using this approach, twitch power was found to be greater for cells cultured on stiffer posts, despite having lower twitch velocities. The increased power was attributed in part to improved myofibril structure (increased sarcomere length and Z-band width) and intracellular calcium levels. Immunofluorescent staining of α-actin revealed that cardiomyocytes had greater sarcomere length and Z-band width when cultured on stiffer arrays. Moreover, the concentration of intracellular calcium at rest and its rise with each twitch contraction was greater for cells on the stiffer posts. Altogether, these findings indicate that cardiomyocytes respond to substrate stiffness with biomechanical and biochemical changes that lead to an increase in cardiac contractility.
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Affiliation(s)
- Anthony G Rodriguez
- Department of Bioengineering, University of Washington, Seattle, Washington, USA
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40
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41
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Sung RJ, Lo CP, Hsiao PY, Tien HC. Targeting intracellular calcium cycling in catecholaminergic polymorphic ventricular tachycardia: a theoretical investigation. Am J Physiol Heart Circ Physiol 2011; 301:H1625-38. [DOI: 10.1152/ajpheart.00696.2010] [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: 01/24/2023]
Abstract
Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a malignant arrhythmogenic disorder linked to mutations in the cardiac ryanodine receptor (RyR2) and calsequestrin, predisposing the young to syncope and cardiac arrest. To define the role of β-adrenergic stimulation (BAS) and to identify potential therapeutic targeted sites relating to intracellular calcium cycling, we used a Luo-Rudy dynamic ventricular myocyte model incorporated with interacting Markov models of the L-type Ca2+ channel ( ICa,L) and RyR2 to simulate the heterozygous state of mouse RyR2 R4496C mutation (RyR2R4496C+/−) comparable with CPVT patients with RyR2 R4497C mutation. Characteristically, in simulated cells, pacing at 4 Hz or faster or pacing at 2 Hz under BAS with effects equivalent to those of isoproterenol at ≥0.1 μM could readily induce delayed afterdepolarizations (DADs) and DAD-mediated triggered activity (TA) in RyR2R4496C+/− but not in the wild-type via enhancing both ICa,L and sarcoplasmic reticulum (SR) Ca2+ ATPase ( IUP). Moreover, with the use of steady state values of isolated endocardial (Endo), mid-myocardial (M), and epicardial (Epi) cells as initial data for conducting single cell and one-dimensional strand studies, the M cell was more vulnerable for developing DADs and DAD-mediated TA than Endo and Epi cells, and the gap junction coupling represented by diffusion coefficient ( D) of ≤0.000766*98 cm2/ms was required for generating DAD-mediated TA in RyR2R4496C+/−. Whereas individual reduction of Ca2+ release channel of SR and Na-Ca exchanger up to 50% was ineffective, 30% or more reduction of either ICa,L or IUP could totally suppress the inducibility of arrhythmia under BAS. Of note, 15% reduction of both ICa,L and IUP exerted a synergistic antiarrhythmic efficacy. Findings of this model study confirm that BAS facilitates induction of ventricular tachyarrhythmias via its action on intracellular Ca2+ cycling and a pharmacological regimen capable of reducing ICa,L could be an effective adjunctive to β-adrenergic blockers for suppressing ventricular tachyarrhythmias during CPVT.
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Affiliation(s)
- Ruey J. Sung
- Institute of Life Sciences, National Central University, Taoyuan
- Division of Cardiovascular Medicine, Stanford University School of Medicine, Stanford, California
| | - Chu-Pin Lo
- Department of Financial and Computational Mathematics, Providence University, Taichung, Taiwan; and
| | - Pi Yin Hsiao
- Institute of Life Sciences, National Central University, Taoyuan
| | - Hui-Chun Tien
- Department of Financial and Computational Mathematics, Providence University, Taichung, Taiwan; and
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Bode EF, Briston SJ, Overend CL, O'Neill SC, Trafford AW, Eisner DA. Changes of SERCA activity have only modest effects on sarcoplasmic reticulum Ca2+ content in rat ventricular myocytes. J Physiol 2011; 589:4723-9. [PMID: 21825024 DOI: 10.1113/jphysiol.2011.211052] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Changes of the activity of the sarco-endoplasmic reticulum Ca(2+)-ATPase (SERCA) affect the amplitude of the systolic Ca(2+) transient and thence cardiac contractility. This is thought to be due to alterations of SR Ca(2+) content. Recent work on mice in which the expression of SERCA is decreased found that a large reduction of SERCA expression resulted in a proportionately much smaller decrease of SR Ca(2+) content. The aim of the current work was to investigate the quantitative nature of the dependence of both the amplitude of the systolic Ca(2+) transient and SR Ca(2+) content on SERCA activity during acute partial inhibition of SERCA. Experiments were performed on rat ventricular myocytes. Brief application of thapsigargin (1 μm) resulted in a decrease of SERCA activity as measured from the rate of decay of the systolic Ca(2+) transient. This was accompanied by a decrease in the amplitude of the systolic Ca(2+) transient which was linearly related to that of SERCA activity. However, the fractional decrease in the SR Ca(2+) content was much less than that of SERCA activity. On average SR Ca(2+) content was proportional to SERCA activity raised to the 0.38 ± 0.07 power. This shallow dependence of SR content on SERCA activity arises because Ca(2+) release is a steep function of SR Ca(2+) content. In contrast SR Ca(2+) content was increased 4.59 ± 0.40 (n = 8)-fold by decreasing ryanodine receptor opening with tetracaine (1 mm). Therefore a modest decrease of SR Ca(2+) content results in a proportionately larger fall of Ca(2+) release from the SR which can balance a larger initiating decrease of SERCA. In conclusion, the shallow dependence of SR Ca(2+) content on SERCA activity is expected for a system in which small changes of SR Ca(2+) content produce larger effects on the amplitude of the systolic Ca(2+) transient.
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Affiliation(s)
- E F Bode
- Unit of Cardiac Physiology, University of Manchester, 46 Grafton Street, Manchester, UK.
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43
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Li L, Louch WE, Niederer SA, Andersson KB, Christensen G, Sejersted OM, Smith NP. Calcium dynamics in the ventricular myocytes of SERCA2 knockout mice: A modeling study. Biophys J 2011; 100:322-31. [PMID: 21244828 DOI: 10.1016/j.bpj.2010.11.048] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2010] [Revised: 11/09/2010] [Accepted: 11/24/2010] [Indexed: 10/18/2022] Open
Abstract
We describe a simulation study of Ca²(+) dynamics in mice with cardiomyocyte-specific conditional excision of the sarco(endo)plasmic reticulum calcium ATPase (SERCA) gene, using an experimental data-driven biophysically-based modeling framework. Previously, we reported a moderately impaired heart function measured in mice at 4 weeks after SERCA2 gene deletion (knockout (KO)), along with a >95% reduction in the level of SERCA2 protein. We also reported enhanced Ca²(+) flux through the L-type Ca²(+) channels and the Na(+)/Ca²(+) exchanger in ventricular myocytes isolated from these mice, compared to the control Serca2(flox/flox) mice (flox-flox (FF)). In the current study, a mathematical model-based analysis was applied to enable further quantitative investigation into changes in the Ca²(+) handling mechanisms in these KO cardiomyocytes. Model parameterization based on a wide range of experimental measurements showed a 67% reduction in SERCA activity and an over threefold increase in the activity of the Na(+)/Ca²(+) exchanger. The FF and KO models were then validated against experimentally measured [Ca²(+)](i) transients and experimentally estimated sarco(endo)plasmic reticulum (SR) function. Simulation results were in quantitative agreement with experimental measurements, confirming that sustained [Ca²(+)](i) transients could be maintained in the KO cardiomyocytes despite severely impaired SERCA function. In silico analysis shows that diastolic [Ca²(+)](i) rises sharply with progressive reductions in SERCA activity at physiologically relevant pacing frequencies. Furthermore, an analysis of the roles of the compensatory mechanisms revealed that the major combined effect of the compensatory mechanisms is to lower diastolic [Ca²(+)](i). Finally, by using a comprehensive sensitivity analysis of the role of all cellular calcium handling mechanisms, we show that the combination of upregulation of the Na(+)/Ca²(+) exchanger and increased L-type Ca²(+) current is the most effective means to maintain diastolic and systolic calcium levels after loss of SERCA function.
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Affiliation(s)
- L Li
- University of Oxford, United Kingdom
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44
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Stokke MK, Briston SJ, Jølle GF, Manzoor I, Louch WE, Øyehaug L, Christensen G, Eisner DA, Trafford AW, Sejersted OM, Sjaastad I. Ca2+ wave probability is determined by the balance between SERCA2-dependent Ca2+ reuptake and threshold SR Ca2+ content. Cardiovasc Res 2011; 90:503-12. [DOI: 10.1093/cvr/cvr013] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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