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Li J, Sundnes J, Hou Y, Laasmaa M, Ruud M, Unger A, Kolstad TR, Frisk M, Norseng PA, Yang L, Setterberg IE, Alves ES, Kalakoutis M, Sejersted OM, Lanner JT, Linke WA, Lunde IG, de Tombe PP, Louch WE. Stretch Harmonizes Sarcomere Strain Across the Cardiomyocyte. Circ Res 2023; 133:255-270. [PMID: 37401464 PMCID: PMC10355805 DOI: 10.1161/circresaha.123.322588] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/27/2023] [Revised: 06/07/2023] [Accepted: 06/22/2023] [Indexed: 07/05/2023]
Abstract
BACKGROUND Increasing cardiomyocyte contraction during myocardial stretch serves as the basis for the Frank-Starling mechanism in the heart. However, it remains unclear how this phenomenon occurs regionally within cardiomyocytes, at the level of individual sarcomeres. We investigated sarcomere contractile synchrony and how intersarcomere dynamics contribute to increasing contractility during cell lengthening. METHODS Sarcomere strain and Ca2+ were simultaneously recorded in isolated left ventricular cardiomyocytes during 1 Hz field stimulation at 37 °C, at resting length and following stepwise stretch. RESULTS We observed that in unstretched rat cardiomyocytes, differential sarcomere deformation occurred during each beat. Specifically, while most sarcomeres shortened during the stimulus, ≈10% to 20% of sarcomeres were stretched or remained stationary. This nonuniform strain was not traced to regional Ca2+ disparities but rather shorter resting lengths and lower force production in systolically stretched sarcomeres. Lengthening of the cell recruited additional shortening sarcomeres, which increased contractile efficiency as less negative, wasted work was performed by stretched sarcomeres. Given the known role of titin in setting sarcomere dimensions, we next hypothesized that modulating titin expression would alter intersarcomere dynamics. Indeed, in cardiomyocytes from mice with titin haploinsufficiency, we observed greater variability in resting sarcomere length, lower recruitment of shortening sarcomeres, and impaired work performance during cell lengthening. CONCLUSIONS Graded sarcomere recruitment directs cardiomyocyte work performance, and harmonization of sarcomere strain increases contractility during cell stretch. By setting sarcomere dimensions, titin controls sarcomere recruitment, and its lowered expression in haploinsufficiency mutations impairs cardiomyocyte contractility.
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Affiliation(s)
- Jia Li
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Norway (J.L., Y.H., M.L., M.R., T.R.K., M.F., P.A.N., I.E.S., O.M.S., I.G.L., W.E.L.)
- KG Jebsen Center for Cardiac Research, University of Oslo, Norway (J.L., Y.H., M.L., M.R., T.R.K., M.F., I.E.S., O.M.S., I.G.L., W.E.L.)
| | | | - Yufeng Hou
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Norway (J.L., Y.H., M.L., M.R., T.R.K., M.F., P.A.N., I.E.S., O.M.S., I.G.L., W.E.L.)
- KG Jebsen Center for Cardiac Research, University of Oslo, Norway (J.L., Y.H., M.L., M.R., T.R.K., M.F., I.E.S., O.M.S., I.G.L., W.E.L.)
| | - Martin Laasmaa
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Norway (J.L., Y.H., M.L., M.R., T.R.K., M.F., P.A.N., I.E.S., O.M.S., I.G.L., W.E.L.)
- KG Jebsen Center for Cardiac Research, University of Oslo, Norway (J.L., Y.H., M.L., M.R., T.R.K., M.F., I.E.S., O.M.S., I.G.L., W.E.L.)
| | - Marianne Ruud
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Norway (J.L., Y.H., M.L., M.R., T.R.K., M.F., P.A.N., I.E.S., O.M.S., I.G.L., W.E.L.)
- KG Jebsen Center for Cardiac Research, University of Oslo, Norway (J.L., Y.H., M.L., M.R., T.R.K., M.F., I.E.S., O.M.S., I.G.L., W.E.L.)
| | - Andreas Unger
- Institute of Physiology II, University of Münster, Germany (A.U., W.A.L.)
| | - Terje R. Kolstad
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Norway (J.L., Y.H., M.L., M.R., T.R.K., M.F., P.A.N., I.E.S., O.M.S., I.G.L., W.E.L.)
- KG Jebsen Center for Cardiac Research, University of Oslo, Norway (J.L., Y.H., M.L., M.R., T.R.K., M.F., I.E.S., O.M.S., I.G.L., W.E.L.)
| | - Michael Frisk
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Norway (J.L., Y.H., M.L., M.R., T.R.K., M.F., P.A.N., I.E.S., O.M.S., I.G.L., W.E.L.)
- KG Jebsen Center for Cardiac Research, University of Oslo, Norway (J.L., Y.H., M.L., M.R., T.R.K., M.F., I.E.S., O.M.S., I.G.L., W.E.L.)
| | - Per Andreas Norseng
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Norway (J.L., Y.H., M.L., M.R., T.R.K., M.F., P.A.N., I.E.S., O.M.S., I.G.L., W.E.L.)
| | | | - Ingunn E. Setterberg
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Norway (J.L., Y.H., M.L., M.R., T.R.K., M.F., P.A.N., I.E.S., O.M.S., I.G.L., W.E.L.)
- KG Jebsen Center for Cardiac Research, University of Oslo, Norway (J.L., Y.H., M.L., M.R., T.R.K., M.F., I.E.S., O.M.S., I.G.L., W.E.L.)
| | - Estela S. Alves
- Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden (E.S.A., M.K., J.T.L.)
| | - Michaeljohn Kalakoutis
- Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden (E.S.A., M.K., J.T.L.)
| | - Ole M. Sejersted
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Norway (J.L., Y.H., M.L., M.R., T.R.K., M.F., P.A.N., I.E.S., O.M.S., I.G.L., W.E.L.)
- KG Jebsen Center for Cardiac Research, University of Oslo, Norway (J.L., Y.H., M.L., M.R., T.R.K., M.F., I.E.S., O.M.S., I.G.L., W.E.L.)
| | - Johanna T. Lanner
- Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden (E.S.A., M.K., J.T.L.)
| | - Wolfgang A. Linke
- Institute of Physiology II, University of Münster, Germany (A.U., W.A.L.)
| | - Ida G. Lunde
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Norway (J.L., Y.H., M.L., M.R., T.R.K., M.F., P.A.N., I.E.S., O.M.S., I.G.L., W.E.L.)
- KG Jebsen Center for Cardiac Research, University of Oslo, Norway (J.L., Y.H., M.L., M.R., T.R.K., M.F., I.E.S., O.M.S., I.G.L., W.E.L.)
| | - Pieter P. de Tombe
- Department of Physiology and Biophysics, University of Illinois at Chicago (P.P.d.T.)
- Phymedexp, Université de Montpellier, INSERM, CNRS, France (P.P.d.T.)
| | - William E. Louch
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Norway (J.L., Y.H., M.L., M.R., T.R.K., M.F., P.A.N., I.E.S., O.M.S., I.G.L., W.E.L.)
- KG Jebsen Center for Cardiac Research, University of Oslo, Norway (J.L., Y.H., M.L., M.R., T.R.K., M.F., I.E.S., O.M.S., I.G.L., W.E.L.)
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2
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Katti P, Hall AS, Parry HA, Ajayi PT, Kim Y, Willingham TB, Bleck CKE, Wen H, Glancy B. Mitochondrial network configuration influences sarcomere and myosin filament structure in striated muscles. Nat Commun 2022; 13:6058. [PMID: 36229433 PMCID: PMC9561657 DOI: 10.1038/s41467-022-33678-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2022] [Accepted: 09/28/2022] [Indexed: 12/24/2022] Open
Abstract
Sustained muscle contraction occurs through interactions between actin and myosin filaments within sarcomeres and requires a constant supply of adenosine triphosphate (ATP) from nearby mitochondria. However, it remains unclear how different physical configurations between sarcomeres and mitochondria alter the energetic support for contractile function. Here, we show that sarcomere cross-sectional area (CSA) varies along its length in a cell type-dependent manner where the reduction in Z-disk CSA relative to the sarcomere center is closely coordinated with mitochondrial network configuration in flies, mice, and humans. Further, we find myosin filaments near the sarcomere periphery are curved relative to interior filaments with greater curvature for filaments near mitochondria compared to sarcoplasmic reticulum. Finally, we demonstrate variable myosin filament lattice spacing between filament ends and filament centers in a cell type-dependent manner. These data suggest both sarcomere structure and myofilament interactions are influenced by the location and orientation of mitochondria within muscle cells.
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Affiliation(s)
- Prasanna Katti
- National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD, USA
| | | | - Hailey A Parry
- National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD, USA
| | - Peter T Ajayi
- National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD, USA
| | - Yuho Kim
- National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD, USA
| | - T Bradley Willingham
- National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD, USA
| | - Christopher K E Bleck
- National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD, USA
| | - Han Wen
- National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD, USA
| | - Brian Glancy
- National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD, USA.
- National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health Bethesda, Bethesda, MD, USA.
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3
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Zechini L, Camilleri-Brennan J, Walsh J, Beaven R, Moran O, Hartley PS, Diaz M, Denholm B. Piezo buffers mechanical stress via modulation of intracellular Ca 2+ handling in the Drosophila heart. Front Physiol 2022; 13:1003999. [PMID: 36187790 PMCID: PMC9515499 DOI: 10.3389/fphys.2022.1003999] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2022] [Accepted: 08/26/2022] [Indexed: 11/13/2022] Open
Abstract
Throughout its lifetime the heart is buffeted continuously by dynamic mechanical forces resulting from contraction of the heart muscle itself and fluctuations in haemodynamic load and pressure. These forces are in flux on a beat-by-beat basis, resulting from changes in posture, physical activity or emotional state, and over longer timescales due to altered physiology (e.g. pregnancy) or as a consequence of ageing or disease (e.g. hypertension). It has been known for over a century of the heart's ability to sense differences in haemodynamic load and adjust contractile force accordingly (Frank, Z. biology, 1895, 32, 370-447; Anrep, J. Physiol., 1912, 45 (5), 307-317; Patterson and Starling, J. Physiol., 1914, 48 (5), 357-79; Starling, The law of the heart (Linacre Lecture, given at Cambridge, 1915), 1918). These adaptive behaviours are important for cardiovascular homeostasis, but the mechanism(s) underpinning them are incompletely understood. Here we present evidence that the mechanically-activated ion channel, Piezo, is an important component of the Drosophila heart's ability to adapt to mechanical force. We find Piezo is a sarcoplasmic reticulum (SR)-resident channel and is part of a mechanism that regulates Ca2+ handling in cardiomyocytes in response to mechanical stress. Our data support a simple model in which Drosophila Piezo transduces mechanical force such as stretch into a Ca2+ signal, originating from the SR, that modulates cardiomyocyte contraction. We show that Piezo mutant hearts fail to buffer mechanical stress, have altered Ca2+ handling, become prone to arrhythmias and undergo pathological remodelling.
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Affiliation(s)
- Luigi Zechini
- Deanery of Biomedical Sciences, Edinburgh Medical School, Edinburgh University, Edinburgh, United Kingtom
- Centre for Inflammation Research, Deanery of Clinical Sciences, Edinburgh Medical School, Edinburgh, United Kingtom
| | - Julian Camilleri-Brennan
- Deanery of Biomedical Sciences, Edinburgh Medical School, Edinburgh University, Edinburgh, United Kingtom
| | - Jonathan Walsh
- Deanery of Biomedical Sciences, Edinburgh Medical School, Edinburgh University, Edinburgh, United Kingtom
| | - Robin Beaven
- Deanery of Biomedical Sciences, Edinburgh Medical School, Edinburgh University, Edinburgh, United Kingtom
| | - Oscar Moran
- Istituto di Biofisica, Consiglio Nazionale delle Ricerche- CNR, Genoa, Italy
| | - Paul S. Hartley
- Department of Life and Environmental Science, Faculty of Science and Technology, Bournemouth University, Poole, United Kingtom
| | - Mary Diaz
- Deanery of Biomedical Sciences, Edinburgh Medical School, Edinburgh University, Edinburgh, United Kingtom
| | - Barry Denholm
- Deanery of Biomedical Sciences, Edinburgh Medical School, Edinburgh University, Edinburgh, United Kingtom
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4
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Song Y, Huang P, Liu X, Zhao Z, Wang Y, Cui B, Duan L. Light-inducible deformation of mitochondria in live cells. Cell Chem Biol 2021; 29:109-119.e3. [PMID: 34157274 DOI: 10.1016/j.chembiol.2021.05.015] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2020] [Revised: 03/30/2021] [Accepted: 05/26/2021] [Indexed: 12/22/2022]
Abstract
Mitochondria, the powerhouse of the cell, are dynamic organelles that undergo constant morphological changes. Increasing evidence indicates that mitochondria morphologies and functions can be modulated by mechanical cues. However, the mechano-sensing and -responding properties of mitochondria and the relation between mitochondrial morphologies and functions are unclear due to the lack of methods to precisely exert mechano-stimulation on and deform mitochondria inside live cells. Here, we present an optogenetic approach that uses light to induce deformation of mitochondria by recruiting molecular motors to the outer mitochondrial membrane via light-activated protein-protein hetero-dimerization. Mechanical forces generated by motor proteins distort the outer membrane, during which the inner mitochondrial membrane can also be deformed. Moreover, this optical method can achieve subcellular spatial precision and be combined with different optical dimerizers and molecular motors. This method presents a mitochondria-specific mechano-stimulator for studying mitochondria mechanobiology and the interplay between mitochondria shapes and functions.
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Affiliation(s)
- Yutong Song
- Department of Biomedical Engineering, The Chinese University of Hong Kong, Sha Tin, Hong Kong SAR, China
| | - Peiyuan Huang
- Department of Biomedical Engineering, The Chinese University of Hong Kong, Sha Tin, Hong Kong SAR, China
| | - Xiaoying Liu
- Department of Biomedical Engineering, The Chinese University of Hong Kong, Sha Tin, Hong Kong SAR, China
| | - Zhihao Zhao
- Department of Biomedical Engineering, The Chinese University of Hong Kong, Sha Tin, Hong Kong SAR, China
| | - Yijin Wang
- Department of Biomedical Engineering, The Chinese University of Hong Kong, Sha Tin, Hong Kong SAR, China
| | - Bianxiao Cui
- Department of Chemistry, Stanford University, Stanford, CA 94305, USA.
| | - Liting Duan
- Department of Biomedical Engineering, The Chinese University of Hong Kong, Sha Tin, Hong Kong SAR, China; Shun Hing Institute of Advanced Engineering (SHIAE), The Chinese University of Hong Kong, Sha Tin, Hong Kong SAR, China.
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5
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Caffarra Malvezzi C, Cabassi A, Miragoli M. Mitochondrial mechanosensor in cardiovascular diseases. VASCULAR BIOLOGY 2020; 2:R85-R92. [PMID: 32923977 PMCID: PMC7439846 DOI: 10.1530/vb-20-0002] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Accepted: 06/22/2020] [Indexed: 12/26/2022]
Abstract
The role of mitochondria in cardiac tissue is of utmost importance due to the dynamic nature of the heart and its energetic demands, necessary to assure its proper beating function. Recently, other important mitochondrial roles have been discovered, namely its contribution to intracellular calcium handling in normal and pathological myocardium. Novel investigations support the fact that during the progression toward heart failure, mitochondrial calcium machinery is compromised due to its morphological, structural and biochemical modifications resulting in facilitated arrhythmogenesis and heart failure development. The interaction between mitochondria and sarcomere directly affect cardiomyocyte excitation-contraction and is also involved in mechano-transduction through the cytoskeletal proteins that tether together the mitochondria and the sarcoplasmic reticulum. The focus of this review is to briefly elucidate the role of mitochondria as (mechano) sensors in the heart.
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Affiliation(s)
| | - Aderville Cabassi
- Department of Medicine and Surgery, University of Parma, Parma, Italy
| | - Michele Miragoli
- Department of Medicine and Surgery, University of Parma, Parma, Italy.,Center of Excellence for Toxicological Research, Department of Medicine and Surgery, University of Parma, Parma, Italy.,Department of Cardiovascular Medicine, Humanitas Clinical and Research Center - IRCCS, 20090 Rozzano, Milan, Italy
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6
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Eldarov CM, Vangely IM, Vays VB, Sheval EV, Holtze S, Hildebrandt TB, Kolosova NG, Popkov VA, Plotnikov EY, Zorov DB, Bakeeva LE, Skulachev VP. Mitochondria in the Nuclei of Rat Myocardial Cells. Cells 2020; 9:E712. [PMID: 32183238 PMCID: PMC7140638 DOI: 10.3390/cells9030712] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2019] [Revised: 03/03/2020] [Accepted: 03/05/2020] [Indexed: 01/01/2023] Open
Abstract
Electron microscopic study of cardiomyocytes taken from healthy Wistar and OXYS rats and naked mole rats (Heterocephalus glaber) revealed mitochondria in nuclei that lacked part of the nuclear envelope. The direct interaction of mitochondria with nucleoplasm is shown. The statistical analysis of the occurrence of mitochondria in cardiomyocyte nuclei showed that the percentage of nuclei with mitochondria was roughly around 1%, and did not show age and species dependency. Confocal microscopy of normal rat cardiac myocytes revealed a branched mitochondrial network in the vicinity of nuclei with an organization different than that of interfibrillar mitochondria. This mitochondrial network was energetically functional because it carried the membrane potential that responded by oscillatory mode after photodynamic challenge. We suggest that the presence of functional mitochondria in the nucleus is not only a consequence of certain pathologies but rather represents a normal biological phenomenon involved in mitochondrial/nuclear interactions.
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Affiliation(s)
- Chupalav M Eldarov
- A.N. Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991 Moscow, Russia
| | - Irina M Vangely
- A.N. Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991 Moscow, Russia
| | - Valeriya B Vays
- A.N. Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991 Moscow, Russia
| | - Eugene V Sheval
- A.N. Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991 Moscow, Russia
| | - Susanne Holtze
- Department of Reproduction Management, Leibniz-Institute for Zoo and Wildlife Research, Alfred-Kowalke-Str. 17, 10315 Berlin, Germany
| | - Thomas B Hildebrandt
- Department of Reproduction Management, Leibniz-Institute for Zoo and Wildlife Research, Alfred-Kowalke-Str. 17, 10315 Berlin, Germany
| | - Natalia G Kolosova
- Institute of Cytology and Genetics, Siberian Branch of Russian Academy of Sciences, Novosibirsk 630090, Russia
| | - Vasily A Popkov
- A.N. Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991 Moscow, Russia
| | - Egor Y Plotnikov
- A.N. Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991 Moscow, Russia
| | - Dmitry B Zorov
- A.N. Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991 Moscow, Russia
| | - Lora E Bakeeva
- A.N. Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991 Moscow, Russia
| | - Vladimir P Skulachev
- A.N. Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991 Moscow, Russia
- Faculty of Bioengineering and Bioinformatics, Lomonosov Moscow State University, 119992 Moscow, Russia
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7
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Tuning mitochondrial structure and function to criticality by fluctuation-driven mechanotransduction. Sci Rep 2020; 10:407. [PMID: 31941960 PMCID: PMC6962425 DOI: 10.1038/s41598-019-57301-1] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2018] [Accepted: 12/28/2019] [Indexed: 01/11/2023] Open
Abstract
Cells in vascular walls are exposed to blood pressure variability (BPV)-induced cycle-by-cycle fluctuations in mechanical forces which vary considerably with pathology. For example, BPV is elevated in hypertension but reduced under anesthesia. We hypothesized that the extent of mechanical fluctuations applied to vascular smooth muscle cells (VSMCs) regulates mitochondrial network structure near the percolation transition, which also influences ATP and reactive oxygen species (ROS) production. We stretched VSMCs in culture with cycle-by-cycle variability in area strain ranging from no variability (0%), as in standard laboratory conditions, through abnormally small (6%) and physiological (25%) to pathologically high (50%) variability mimicking hypertension, superimposed on 0.1 mean area strain. To explore how oxidative stress and ATP-dependent metabolism affect mitochondria, experiments were repeated in the presence of hydrogen peroxide and AMP-PNP, an ATP analog and competitive inhibitor of ATPases. Physiological 25% variability maintained activated mitochondrial cluster structure at percolation with a power law distribution and exponent matching the theoretical value in 2 dimensions. The 25% variability also maximized ATP and minimized cellular and mitochondrial ROS production via selective control of fission and fusion proteins (mitofusins, OPA1 and DRP1) as well as through stretch-sensitive regulation of the ATP synthase and VDAC1, the channel that releases ATP into the cytosol. Furthermore, pathologically low or high variability moved mitochondria away from percolation which reduced the effectiveness of the electron transport chain by lowering ATP and increasing ROS productions. We conclude that normal BPV is required for maintaining optimal mitochondrial structure and function in VSMCs.
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Leichner JM, Konyukhov E, Kamoun D, Yaniv Y. Real time mitochondrial dimension measurements. J Biol Methods 2019; 6:e111. [PMID: 31453260 PMCID: PMC6706126 DOI: 10.14440/jbm.2019.262] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2018] [Revised: 07/31/2018] [Accepted: 08/08/2018] [Indexed: 11/23/2022] Open
Abstract
Mitochondrial volume is correlated with cell function and internal cell processes. Changes in mitochondrial volume were associated with advanced states of cardiac disease. Thus, measurements of mitochondrial dimension deformations are important to the understanding of cell function and its deterioration. Existing methods either allow measurements of the volume of isolated mitochondria, which are an inferior model to that of isolated cells, or they allow short time measurements that are toxic to the cells. Recent studies have discovered that mitochondrial deformation along a given cell axis can be measured by using the Fourier transformation on the variation in transmitted light intensity induced by the periodic lattice of myofilaments alternating with mitochondrial rows. However, this method was used only offline and in a line scan mode, making it impossible to measure both axes. We designed an open source program in LabVIEW to take advantage of the transmitted light diffraction technique and quantify mitochondrial two dimension (2D) deformation in cardiomyocytes, in situ in real time for long periods (more than several seconds). We validated the program on synthetic and on experimental images from rabbit and rat ventricular myocytes. The program can analyze offline and real time simultaneous 2D mitochondrial deformation dynamics as well as also sarcomere length dynamics. Moreover, the program can accurately analyze images acquired from different cameras. Quantification of mitochondrial 2D deformations is a powerful tool for exploring cell biophysics and bioenergetics mechanisms and will lay the foundation for a future clinical tool for quantifying mitochondrial volume changes associated with different cardiac diseases.
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Affiliation(s)
| | - Evgene Konyukhov
- Biomedical Engineering Faculty, Technion-IIT, Haifa 32000, Israel
| | - David Kamoun
- Biomedical Engineering Faculty, Technion-IIT, Haifa 32000, Israel
| | - Yael Yaniv
- Biomedical Engineering Faculty, Technion-IIT, Haifa 32000, Israel
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9
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Zorov DB, Vorobjev IA, Popkov VA, Babenko VA, Zorova LD, Pevzner IB, Silachev DN, Zorov SD, Andrianova NV, Plotnikov EY. Lessons from the Discovery of Mitochondrial Fragmentation (Fission): A Review and Update. Cells 2019; 8:E175. [PMID: 30791381 PMCID: PMC6406845 DOI: 10.3390/cells8020175] [Citation(s) in RCA: 64] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2019] [Revised: 02/14/2019] [Accepted: 02/15/2019] [Indexed: 01/12/2023] Open
Abstract
Thirty-five years ago, we described fragmentation of the mitochondrial population in a living cell into small vesicles (mitochondrial fission). Subsequently, this phenomenon has become an object of general interest due to its involvement in the process of oxidative stress-related cell death and having high relevance to the incidence of a pathological phenotype. Tentatively, the key component of mitochondrial fission process is segregation and further asymmetric separation of a mitochondrial body yielding healthy (normally functioning) and impaired (incapable to function in a normal way) organelles with subsequent decomposition and removal of impaired elements through autophagy (mitophagy). We speculate that mitochondria contain cytoskeletal elements, which maintain the mitochondrial shape, and also are involved in the process of intramitochondrial segregation of waste products. We suggest that perturbation of the mitochondrial fission/fusion machinery and slowdown of the removal process of nonfunctional mitochondrial structures led to the increase of the proportion of impaired mitochondrial elements. When the concentration of malfunctioning mitochondria reaches a certain threshold, this can lead to various pathologies, including aging. Overall, we suggest a process of mitochondrial fission to be an essential component of a complex system controlling a healthy cell phenotype. The role of reactive oxygen species in mitochondrial fission is discussed.
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Affiliation(s)
- Dmitry B Zorov
- A.N.Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow 119991, Russia.
- V.I. Kulakov National Medical Research Center of Obstetrics, Gynecology and Perinatology, Moscow 117997, Russia.
| | - Ivan A Vorobjev
- A.N.Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow 119991, Russia.
- Department of Biology, School of Science and Technology, Nazarbayev University, Astana 010000, Kazakhstan.
| | - Vasily A Popkov
- A.N.Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow 119991, Russia.
- V.I. Kulakov National Medical Research Center of Obstetrics, Gynecology and Perinatology, Moscow 117997, Russia.
| | - Valentina A Babenko
- A.N.Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow 119991, Russia.
- V.I. Kulakov National Medical Research Center of Obstetrics, Gynecology and Perinatology, Moscow 117997, Russia.
| | - Ljubava D Zorova
- A.N.Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow 119991, Russia.
- V.I. Kulakov National Medical Research Center of Obstetrics, Gynecology and Perinatology, Moscow 117997, Russia.
| | - Irina B Pevzner
- A.N.Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow 119991, Russia.
- V.I. Kulakov National Medical Research Center of Obstetrics, Gynecology and Perinatology, Moscow 117997, Russia.
| | - Denis N Silachev
- A.N.Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow 119991, Russia.
- V.I. Kulakov National Medical Research Center of Obstetrics, Gynecology and Perinatology, Moscow 117997, Russia.
| | - Savva D Zorov
- Faculty of Bioengineering and Bioinformatics, Lomonosov Moscow State University, Moscow 119992, Russia.
| | - Nadezda V Andrianova
- Faculty of Bioengineering and Bioinformatics, Lomonosov Moscow State University, Moscow 119992, Russia.
| | - Egor Y Plotnikov
- A.N.Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow 119991, Russia.
- V.I. Kulakov National Medical Research Center of Obstetrics, Gynecology and Perinatology, Moscow 117997, Russia.
- Institute of Molecular Medicine, Sechenov First Moscow State Medical University, Moscow 119146, Russia.
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10
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Rog-Zielinska EA, O'Toole ET, Hoenger A, Kohl P. Mitochondrial Deformation During the Cardiac Mechanical Cycle. Anat Rec (Hoboken) 2018; 302:146-152. [PMID: 30302911 PMCID: PMC6312496 DOI: 10.1002/ar.23917] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2018] [Revised: 04/22/2018] [Accepted: 05/11/2018] [Indexed: 12/17/2022]
Abstract
Cardiomyocytes both cause and experience continual cyclic deformation. The exact effects of this deformation on the properties of intracellular organelles are not well characterized, although they are likely to be relevant for cardiomyocyte responses to active and passive changes in their mechanical environment. In the present study we provide three‐dimensional ultrastructural evidence for mechanically induced mitochondrial deformation in rabbit ventricular cardiomyocytes over a range of sarcomere lengths representing myocardial tissue stretch, an unloaded “slack” state, and contracture. We also show structural indications for interaction of mitochondria with one another, as well as with other intracellular elements such as microtubules, sarcoplasmic reticulum and T‐tubules. The data presented here help to contextualize recent reports on the mechanosensitivity and cell‐wide connectivity of the mitochondrial network and provide a structural framework that may aide interpretation of mechanically‐regulated molecular signaling in cardiac cells. Anat Rec, 302:146–152, 2019. © 2018 The Authors. The Anatomical Record published by Wiley Periodicals, Inc. on behalf of American Association of Anatomists.
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Affiliation(s)
- E A Rog-Zielinska
- Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg, Bad Krozingen, and Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - E T O'Toole
- Department of Molecular, Cellular and Developmental Biology, University of Colorado at Boulder, Boulder, Colorado, USA
| | - A Hoenger
- Department of Molecular, Cellular and Developmental Biology, University of Colorado at Boulder, Boulder, Colorado, USA
| | - P Kohl
- Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg, Bad Krozingen, and Faculty of Medicine, University of Freiburg, Freiburg, Germany
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11
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Bioenergetic Feedback between Heart Cell Contractile Machinery and Mitochondrial 3D Deformations. Biophys J 2018; 115:1603-1613. [PMID: 30274832 DOI: 10.1016/j.bpj.2018.08.039] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2017] [Revised: 08/12/2018] [Accepted: 08/29/2018] [Indexed: 12/21/2022] Open
Abstract
In the heart, mitochondria are arranged in pairs sandwiched between the contractile machinery, which is the major ATP consumer. Thus, in response to the contraction-relaxation cycle of the cell, the mitochondrial membrane should deform accordingly. Membrane deformations in isolated ATP synthesis or in isolated mitochondria affect ATP production. However, it is unknown whether physiological deformation of the mitochondrial membrane in response to the contraction-relaxation cycle can act as a bioenergetic signaling mechanism between ATP demand to supply. We used both experimental and computational tools to reveal whether bioenergetic feedback exists between heart cell contractile machinery and mitochondrial three-dimensional (3D) deformations. We measured the mitochondrial 3D deformation in contracting rabbit cardiac myocytes and used published data on rat cardiac myocytes. These measurements were an input to a novel biophysics model that includes a description of ionic molecules on the mitochondrial membrane, Ca2+ cycling, and mitochondrial membrane stress. As is the case for rat cardiomyocytes, in rabbit cardiomyocytes, the mitochondrial length contracted and expanded with a similar dynamic as the sarcomere length. In contrast, the mitochondrial width expanded and then contracted with a similar dynamic as the mitochondrial length. Differences in the extent of deformation and fractional deformation between the width- and thick-axes were quantified and interpreted as the degree anisotropy between those respective axes. Finally, the model predicts that significant bioenergetic feedback between heart cell contractile machinery and mitochondrial 3D deformations does exist in unloaded rabbit and rat cells. However, this feedback is not a dominant mechanism in ATP supply to demand matching.
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12
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Walewska A, Kulawiak B, Szewczyk A, Koprowski P. Mechanosensitivity of mitochondrial large-conductance calcium-activated potassium channels. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2018; 1859:797-805. [PMID: 29775559 DOI: 10.1016/j.bbabio.2018.05.006] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2018] [Revised: 04/29/2018] [Accepted: 05/10/2018] [Indexed: 12/01/2022]
Abstract
Potassium channels have been discovered in the inner mitochondrial membrane of various cells. These channels can regulate the mitochondrial membrane potential, the matrix volume, respiration and reactive species generation. Therefore, it is believed that their activation is cytoprotective in various tissues. In our study, the single-channel activity of a large-conductance calcium-activated potassium channel (mitoBKCa) was measured by the patch-clamp technique on mitoplasts derived from mitochondria isolated from human glioma U-87 MG cells. Here, we show for the first time that mechanical stimulation of mitoBKCa channels results in an increased probability of channel opening. However, the mechanosensitivity of mitoBKCa channels was variable with some channels exhibiting no mechanosensitivity. We detected the expression of mechanosensitive BKCa-STREX exon in U-87 MG cells and hypotesize, based on previous studies demonstrating the presence of multiple BKCa splice variants that variable mechanosensitivity of mitoBKCa could be the result of the presence of diverse BKCa isoforms in mitochondria of U-87 MG cells. Our findings indicate the possible involvement of the mitoBKCa channel in mitochondria activities in which changes in membrane tension and shape play a crucial role, such as fusion/fission and cristae remodeling.
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Affiliation(s)
- Agnieszka Walewska
- Laboratory of Intracellular Ion Channels, Nencki Institute of Experimental Biology, 3 Pasteur St., 02-093 Warsaw, Poland
| | - Bogusz Kulawiak
- Laboratory of Intracellular Ion Channels, Nencki Institute of Experimental Biology, 3 Pasteur St., 02-093 Warsaw, Poland
| | - Adam Szewczyk
- Laboratory of Intracellular Ion Channels, Nencki Institute of Experimental Biology, 3 Pasteur St., 02-093 Warsaw, Poland
| | - Piotr Koprowski
- Laboratory of Intracellular Ion Channels, Nencki Institute of Experimental Biology, 3 Pasteur St., 02-093 Warsaw, Poland.
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13
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Burton RAB, Rog-Zielinska EA, Corbett AD, Peyronnet R, Bodi I, Fink M, Sheldon J, Hoenger A, Calaghan SC, Bub G, Kohl P. Caveolae in Rabbit Ventricular Myocytes: Distribution and Dynamic Diminution after Cell Isolation. Biophys J 2017; 113:1047-1059. [PMID: 28877488 PMCID: PMC5653872 DOI: 10.1016/j.bpj.2017.07.026] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2016] [Revised: 05/16/2017] [Accepted: 07/06/2017] [Indexed: 12/12/2022] Open
Abstract
Caveolae are signal transduction centers, yet their subcellular distribution and preservation in cardiac myocytes after cell isolation are not well documented. Here, we quantify caveolae located within 100 nm of the outer cell surface membrane in rabbit single-ventricular cardiomyocytes over 8 h post-isolation and relate this to the presence of caveolae in intact tissue. Hearts from New Zealand white rabbits were either chemically fixed by coronary perfusion or enzymatically digested to isolate ventricular myocytes, which were subsequently fixed at 0, 3, and 8 h post-isolation. In live cells, the patch-clamp technique was used to measure whole-cell plasma membrane capacitance, and in fixed cells, caveolae were quantified by transmission electron microscopy. Changes in cell-surface topology were assessed using scanning electron microscopy. In fixed ventricular myocardium, dual-axis electron tomography was used for three-dimensional reconstruction and analysis of caveolae in situ. The presence and distribution of surface-sarcolemmal caveolae in freshly isolated cells matches that of intact myocardium. With time, the number of surface-sarcolemmal caveolae decreases in isolated cardiomyocytes. This is associated with a gradual increase in whole-cell membrane capacitance. Concurrently, there is a significant increase in area, diameter, and circularity of sub-sarcolemmal mitochondria, indicative of swelling. In addition, electron tomography data from intact heart illustrate the regular presence of caveolae not only at the surface sarcolemma, but also on transverse-tubular membranes in ventricular myocardium. Thus, caveolae are dynamic structures, present both at surface-sarcolemmal and transverse-tubular membranes. After cell isolation, the number of surface-sarcolemmal caveolae decreases significantly within a time frame relevant for single-cell research. The concurrent increase in cell capacitance suggests that membrane incorporation of surface-sarcolemmal caveolae underlies this, but internalization and/or micro-vesicle loss to the extracellular space may also contribute. Given that much of the research into cardiac caveolae-dependent signaling utilizes isolated cells, and since caveolae-dependent pathways matter for a wide range of other study targets, analysis of isolated cell data should take the time post-isolation into account.
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Affiliation(s)
- Rebecca A B Burton
- Department of Pharmacology, University of Oxford, Oxford, United Kingdom
| | - Eva A Rog-Zielinska
- National Heart and Lung Institute, Imperial College London, London, United Kingdom; Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg-Bad Krozingen, Faculty of Medicine, University of Freiburg, Freiburg, Germany.
| | | | - Rémi Peyronnet
- Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg-Bad Krozingen, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Ilona Bodi
- Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg-Bad Krozingen, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Martin Fink
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Judith Sheldon
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Andreas Hoenger
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, Colorado
| | - Sarah C Calaghan
- School of Biomedical Sciences, University of Leeds, Leeds, United Kingdom
| | - Gil Bub
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Peter Kohl
- Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg-Bad Krozingen, Faculty of Medicine, University of Freiburg, Freiburg, Germany
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Timmermann V, Dejgaard LA, Haugaa KH, Edwards AG, Sundnes J, McCulloch AD, Wall ST. An integrative appraisal of mechano-electric feedback mechanisms in the heart. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2017; 130:404-417. [PMID: 28851517 DOI: 10.1016/j.pbiomolbio.2017.08.008] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/22/2017] [Revised: 08/12/2017] [Accepted: 08/18/2017] [Indexed: 12/20/2022]
Abstract
Mechanically-induced alterations in cardiac electrophysiology are referred to as mechano-electric feedback (MEF), and play an important role in electrical regulation of cardiac performance. The influence of mechanical stress and strain on electrophysiology has been investigated at all levels, however the role of MEF in arrhythmia remains poorly understood. During the normal contraction of the heart, mechano-sensitive processes are an implicit component of cardiac activity. Under abnormal mechanical events, stretch-activated mechanisms may contribute to local or global changes in electrophysiology (EP). While such mechanisms have been hypothesised to be involved in mechanically-initiated arrhythmias, the details of these mechanisms and their importance remain elusive. We assess the theoretical role of stretch mechanisms using coupled models of cellular electrophysiology and sarcomere contraction dynamics. Using models of single ventricular myocytes, we first investigated the potential MEF contributions of stretch-activated currents (SAC), and stretch-induced myofilament calcium release, to test how strain and fibrosis may alter cellular electrophysiology. For all models investigated, SACs were alone not sufficient to create a pro-arrhythmic perturbation of the action potential with stretch. However, when combined with stretch-induced myofilament calcium release, the action potential could be shortened depending on the timing of the strain. This effect was highly model dependent, with a canine epicardial EP model being the most sensitive. These model results suggest that known mechanisms of mechano-electric coupling in cardiac myocyte may be sufficient to be pro-arrhythmic, but only in combination and under specific strain patterns.
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Affiliation(s)
- Viviane Timmermann
- Simula Research Laboratory, Martin Linges vei 25, Fornebu, 1364, Norway; Center for Cardiological Innovation, Songsvannsveien 9, Oslo, 0372, Norway; University California San Diego, 9500 Gilman Drive, La Jolla, CA, United States; University of Oslo, Gaustadallen 23 B, Oslo, 0373, Norway.
| | - Lars A Dejgaard
- Center for Cardiological Innovation, Songsvannsveien 9, Oslo, 0372, Norway; Department of Cardiology, Oslo University Hospital, Norway
| | - Kristina H Haugaa
- Center for Cardiological Innovation, Songsvannsveien 9, Oslo, 0372, Norway; Department of Cardiology, Oslo University Hospital, Norway
| | - Andrew G Edwards
- Simula Research Laboratory, Martin Linges vei 25, Fornebu, 1364, Norway; Center for Cardiological Innovation, Songsvannsveien 9, Oslo, 0372, Norway; University of Oslo, Gaustadallen 23 B, Oslo, 0373, Norway
| | - Joakim Sundnes
- Simula Research Laboratory, Martin Linges vei 25, Fornebu, 1364, Norway; Center for Cardiological Innovation, Songsvannsveien 9, Oslo, 0372, Norway; University of Oslo, Gaustadallen 23 B, Oslo, 0373, Norway
| | - Andrew D McCulloch
- University California San Diego, 9500 Gilman Drive, La Jolla, CA, United States
| | - Samuel T Wall
- Simula Research Laboratory, Martin Linges vei 25, Fornebu, 1364, Norway; Center for Cardiological Innovation, Songsvannsveien 9, Oslo, 0372, Norway.
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15
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Pasqualini FS, Nesmith AP, Horton RE, Sheehy SP, Parker KK. Mechanotransduction and Metabolism in Cardiomyocyte Microdomains. BIOMED RESEARCH INTERNATIONAL 2016; 2016:4081638. [PMID: 28044126 PMCID: PMC5164897 DOI: 10.1155/2016/4081638] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/17/2016] [Revised: 11/03/2016] [Accepted: 11/07/2016] [Indexed: 01/11/2023]
Abstract
Efficient contractions of the left ventricle are ensured by the continuous transfer of adenosine triphosphate (ATP) from energy production sites, the mitochondria, to energy utilization sites, such as ionic pumps and the force-generating sarcomeres. To minimize the impact of intracellular ATP trafficking, sarcomeres and mitochondria are closely packed together and in proximity with other ultrastructures involved in excitation-contraction coupling, such as t-tubules and sarcoplasmic reticulum junctions. This complex microdomain has been referred to as the intracellular energetic unit. Here, we review the literature in support of the notion that cardiac homeostasis and disease are emergent properties of the hierarchical organization of these units. Specifically, we will focus on pathological alterations of this microdomain that result in cardiac diseases through energy imbalance and posttranslational modifications of the cytoskeletal proteins involved in mechanosensing and transduction.
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Affiliation(s)
- Francesco S. Pasqualini
- Disease Biophysics Group, Wyss Institute for Biologically Inspired Engineering, School of Engineering and Applied Sciences, Harvard Stem Cell Institute, Harvard University, Cambridge, MA, USA
- Institute for Regenerative Medicine (IREM), Wyss Translational Center, University and ETH Zurich, Zurich, Switzerland
| | - Alexander P. Nesmith
- Disease Biophysics Group, Wyss Institute for Biologically Inspired Engineering, School of Engineering and Applied Sciences, Harvard Stem Cell Institute, Harvard University, Cambridge, MA, USA
| | - Renita E. Horton
- Disease Biophysics Group, Wyss Institute for Biologically Inspired Engineering, School of Engineering and Applied Sciences, Harvard Stem Cell Institute, Harvard University, Cambridge, MA, USA
- James Worth Bagley College of Engineering and College of Agriculture and Life Sciences, Mississippi State University, Starkville, MS, USA
| | - Sean P. Sheehy
- Disease Biophysics Group, Wyss Institute for Biologically Inspired Engineering, School of Engineering and Applied Sciences, Harvard Stem Cell Institute, Harvard University, Cambridge, MA, USA
| | - Kevin Kit Parker
- Disease Biophysics Group, Wyss Institute for Biologically Inspired Engineering, School of Engineering and Applied Sciences, Harvard Stem Cell Institute, Harvard University, Cambridge, MA, USA
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16
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Haddad SMH, Samani A. A novel micro-to-macro approach for cardiac tissue mechanics. Comput Methods Biomech Biomed Engin 2016; 20:215-229. [DOI: 10.1080/10255842.2016.1214270] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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17
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Power ASC, Pham T, Loiselle DS, Crossman DH, Ward ML, Hickey AJ. Impaired ADP channeling to mitochondria and elevated reactive oxygen species in hypertensive hearts. Am J Physiol Heart Circ Physiol 2016; 310:H1649-57. [DOI: 10.1152/ajpheart.00050.2016] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/18/2016] [Accepted: 04/12/2016] [Indexed: 01/20/2023]
Abstract
Systemic hypertension initially promotes a compensatory cardiac hypertrophy, yet it progresses to heart failure (HF), and energetic deficits appear to be central to this failure. However, the transfer of energy between the mitochondria and the myofibrils is not often considered as part of the energetic equation. We compared hearts from old spontaneously hypertensive rats (SHRs) and normotensive Wistar controls. SHR hearts showed a 35% depression in mitochondrial function, yet produced at least double the amount of reactive oxygen species (ROS) in all respiration states in left ventricular (LV) homogenates. To test the connectivity between mitochondria and myofibrils, respiration was further tested in situ with LV permeabilized fibers by addition of multiple substrates and ATP, which requires hydrolysis to mediate oxidative phosphorylation. By trapping ADP using a pyruvate kinase enzyme system, we tested ADP channeling towards mitochondria, and this suppressed respiration and elevated ROS production more in the SHR fibers. The ADP-trapped state was also less relieved on creatine addition, likely reflecting the 30% depression in total CK activity in the SHR heart fibers. Confocal imaging identified a 34% longer distance between the centers of myofibril to mitochondria in the SHR hearts, which increases transverse metabolite diffusion distances (e.g., for ATP, ADP, and creatine phosphate). We propose that impaired connectivity between mitochondria and myofibrils may contribute to elevated ROS production. Impaired energy exchange could be the result of ultrastructural changes that occur with hypertrophy in this model of hypertension.
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Affiliation(s)
- Amelia S. C. Power
- School of Biological Sciences, Faculty of Science, The University of Auckland, Auckland, New Zealand; and
- Department of Physiology, Faculty of Medical and Health Sciences, The University of Auckland, Auckland, New Zealand
| | - Toan Pham
- Department of Physiology, Faculty of Medical and Health Sciences, The University of Auckland, Auckland, New Zealand
| | - Denis S. Loiselle
- Department of Physiology, Faculty of Medical and Health Sciences, The University of Auckland, Auckland, New Zealand
- Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand; and
| | - David H. Crossman
- Department of Physiology, Faculty of Medical and Health Sciences, The University of Auckland, Auckland, New Zealand
| | - Marie-Louise Ward
- Department of Physiology, Faculty of Medical and Health Sciences, The University of Auckland, Auckland, New Zealand
| | - Anthony J. Hickey
- School of Biological Sciences, Faculty of Science, The University of Auckland, Auckland, New Zealand; and
- Maurice Wilkins Centre, The University of Auckland, Auckland, New Zealand
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18
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Trans-mitochondrial coordination of cristae at regulated membrane junctions. Nat Commun 2015; 6:6259. [PMID: 25687472 PMCID: PMC4332397 DOI: 10.1038/ncomms7259] [Citation(s) in RCA: 127] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2014] [Accepted: 01/09/2015] [Indexed: 01/22/2023] Open
Abstract
Reminiscent of bacterial quorum sensing, mammalian mitochondria participate in inter-organelle communication. However, physical structures that enhance or enable interactions between mitochondria have not been defined. Here we report that adjacent mitochondria exhibit coordination of inner mitochondrial membrane cristae at inter-mitochondrial junctions (IMJs). These electron-dense structures are conserved across species, resistant to genetic disruption of cristae organization, dynamically modulated by mitochondrial bioenergetics, independent of known inter-mitochondrial tethering proteins mitofusins and rapidly induced by the stable rapprochement of organelles via inducible synthetic linker technology. At the associated junctions, the cristae of adjacent mitochondria form parallel arrays perpendicular to the IMJ, consistent with a role in electrochemical coupling. These IMJs and associated cristae arrays may provide the structural basis to enhance the propagation of intracellular bioenergetic and apoptotic waves through mitochondrial networks within cells. Mammalian mitochondria are capable of inter-organelle communication, but connections between mitochondria have not been defined. Here, Picard et al. report the presence of inter-mitochondrial junctions, electron-dense regions with coordinated inner membrane cristae that do not depend on mitofusins for their formation.
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19
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Coelho‐Filho OR, Shah RV, Neilan TG, Mitchell R, Moreno H, Kwong R, Jerosch‐Herold M. Cardiac magnetic resonance assessment of interstitial myocardial fibrosis and cardiomyocyte hypertrophy in hypertensive mice treated with spironolactone. J Am Heart Assoc 2014; 3:e000790. [PMID: 24965024 PMCID: PMC4309062 DOI: 10.1161/jaha.114.000790] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Background Nearly 50% of patients with heart failure (HF) have preserved LV ejection fraction, with interstitial fibrosis and cardiomyocyte hypertrophy as early manifestations of pressure overload. However, methods to assess both tissue characteristics dynamically and noninvasively with therapy are lacking. We measured the effects of mineralocorticoid receptor blockade on tissue phenotypes in LV pressure overload using cardiac magnetic resonance (CMR). Methods and Results Mice were randomized to l‐nitro‐ω‐methyl ester (l‐NAME, 3 mg/mL in water; n=22), or l‐NAME with spironolactone (50 mg/kg/day in subcutaneous pellets; n=21). Myocardial extracellular volume (ECV; marker of diffuse interstitial fibrosis) and the intracellular lifetime of water (τic; marker of cardiomyocyte hypertrophy) were determined by CMR T1 imaging at baseline and after 7 weeks of therapy alongside histological assessments. Administration of l‐NAME induced hypertensive heart disease in mice, with increases in mean arterial pressure, LV mass, ECV, and τic compared with placebo‐treated controls, while LV ejection fraction was preserved (>50%). In comparison, animals receiving both spironolactone and l‐NAME (“l‐NAME+S”) showed less concentric remodeling, and a lower myocardial ECV and τic, indicating decreased interstitial fibrosis and cardiomyocyte hypertrophy (ECV: 0.43±0.09 for l‐NAME versus 0.25±0.03 for l‐NAME+S, P<0.001; τic: 0.42±0.11 for l‐NAME groups versus 0.12±0.05 for l‐NAME+S group). Mice treated with a combination of l‐NAME and spironolactone were similar to placebo‐treated controls at 7 weeks. Conclusions Spironolactone attenuates interstitial fibrosis and cardiomyocyte hypertrophy in hypertensive heart disease. CMR can phenotype myocardial tissue remodeling in pressure‐overload, furthering our understanding of HF progression.
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Affiliation(s)
- Otavio R. Coelho‐Filho
- Cardiovascular Division, Department of Medicine, Harvard Medical School, Boston, MA (O.R.C.F., R.V.S., T.G.N., R.K.)
- Department of Internal Medicine, State University of Campinas (UNICAMP), São Paulo, Brazil (O.R.C.F., H.M.)
| | - Ravi V. Shah
- Cardiovascular Division, Department of Medicine, Harvard Medical School, Boston, MA (O.R.C.F., R.V.S., T.G.N., R.K.)
| | - Tomas G. Neilan
- Cardiovascular Division, Department of Medicine, Harvard Medical School, Boston, MA (O.R.C.F., R.V.S., T.G.N., R.K.)
- Division of Cardiology, Department of Medicine and the Cardiac MR PET CT Program, Massachusetts General Hospital, Harvard Medical School, Boston, MA (T.G.N.)
- Division of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA (T.G.N.)
| | - Richard Mitchell
- Department of Pathology, Harvard Medical School, Boston, MA (R.M.)
| | - Heitor Moreno
- Department of Internal Medicine, State University of Campinas (UNICAMP), São Paulo, Brazil (O.R.C.F., H.M.)
| | - Raymond Kwong
- Cardiovascular Division, Department of Medicine, Harvard Medical School, Boston, MA (O.R.C.F., R.V.S., T.G.N., R.K.)
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20
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Saks V, Schlattner U, Tokarska-Schlattner M, Wallimann T, Bagur R, Zorman S, Pelosse M, Santos PD, Boucher F, Kaambre T, Guzun R. Systems Level Regulation of Cardiac Energy Fluxes Via Metabolic Cycles: Role of Creatine, Phosphotransfer Pathways, and AMPK Signaling. SYSTEMS BIOLOGY OF METABOLIC AND SIGNALING NETWORKS 2014. [DOI: 10.1007/978-3-642-38505-6_11] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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21
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Yaniv Y, Juhaszova M, Sollott SJ. Age-related changes of myocardial ATP supply and demand mechanisms. Trends Endocrinol Metab 2013; 24:495-505. [PMID: 23845538 PMCID: PMC3783621 DOI: 10.1016/j.tem.2013.06.001] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/22/2013] [Revised: 05/30/2013] [Accepted: 06/03/2013] [Indexed: 01/03/2023]
Abstract
In advanced age, the resting myocardial oxygen consumption rate (MVO2) and cardiac work (CW) in the rat remain intact. However, MVO2, CW and cardiac efficiency achieved at high demand are decreased with age, compared to maximal values in the young. Whether this deterioration is due to decrease in myocardial ATP demand, ATP supply, or the control mechanisms that match them remains controversial. Here we discuss evolving perspectives of age-related changes of myocardial ATP supply and demand mechanisms, and critique experimental models used to investigate aging. Specifically, we evaluate experimental data collected at the level of isolated mitochondria, tissue, or organism, and discuss how mitochondrial energetic mechanisms change in advanced age, both at basal and high energy-demand levels.
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Affiliation(s)
- Yael Yaniv
- Laboratory of Cardiovascular Science, Biomedical Research Center, Intramural Research Program, National Institute on Aging, NIH, Baltimore, Maryland, USA
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22
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Coelho-Filho OR, Shah RV, Mitchell R, Neilan TG, Moreno H, Simonson B, Kwong R, Rosenzweig A, Das S, Jerosch-Herold M. Quantification of cardiomyocyte hypertrophy by cardiac magnetic resonance: implications for early cardiac remodeling. Circulation 2013; 128:1225-33. [PMID: 23912910 PMCID: PMC5308548 DOI: 10.1161/circulationaha.112.000438] [Citation(s) in RCA: 95] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/05/2012] [Accepted: 07/24/2013] [Indexed: 12/29/2022]
Abstract
BACKGROUND Cardiomyocyte hypertrophy is a critical precursor to the development of heart failure. Methods to phenotype cellular hypertrophy noninvasively are limited. The goal was to validate a cardiac magnetic resonance-based approach for the combined assessment of extracellular matrix expansion and cardiomyocyte hypertrophy. METHODS AND RESULTS Two murine models of hypertension (n=18, with n=15 controls) induced by l-N(G)-nitroarginine methyl ester (L-NAME) and pressure overload (n=11) from transaortic constriction (TAC) were imaged by cardiac magnetic resonance at baseline and 7 weeks after L-NAME treatment or up to 7 weeks after TAC. T1 relaxation times were measured before and after gadolinium contrast. The intracellular lifetime of water (τic), a cell size-dependent parameter, and extracellular volume fraction, a marker of interstitial fibrosis, were determined with a model for transcytolemmal water exchange. Cardiomyocyte diameter and length were measured on FITC-wheat germ agglutinin-stained sections. The τic correlated strongly with histological cardiomyocyte volume-to-surface ratio (r=0.78, P<0.001) and cell volume (r=0.75, P<0.001). Histological cardiomyocyte diameters and cell volumes were higher in mice treated with L-NAME compared with controls (P<0.001). In the TAC model, cardiac magnetic resonance and histology showed cell hypertrophy at 2 weeks after TAC without significant fibrosis at this early time point. Mice exposed to TAC demonstrated a significant, longitudinal, and parallel increase in histological cell volume, volume-to-surface ratio, and τic between 2 and 7 weeks after TAC. CONCLUSION The τic measured by contrast-enhanced cardiac magnetic resonance provides a noninvasive measure of cardiomyocyte hypertrophy. Extracellular volume fraction and τic can track myocardial tissue remodeling from pressure overload.
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Affiliation(s)
- Otavio R Coelho-Filho
- Cardiovascular Division, Department of Medicine, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA 02114
- Department of Internal Medicine, State University of Campinas (UNICAMP), Boston, MA
| | - Ravi V Shah
- Cardiovascular Division, Department of Medicine, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA 02114
| | - Richard Mitchell
- Department of Pathology, Brigham and Women’s Hospital, Boston, MA
| | - Tomas G Neilan
- Cardiovascular Division, Department of Medicine, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA 02114
| | - Heitor Moreno
- Department of Internal Medicine, State University of Campinas (UNICAMP), Boston, MA
| | - Bridget Simonson
- Cardiovascular Institute, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA
| | - Raymond Kwong
- Cardiovascular Division, Department of Medicine, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA 02114
| | - Anthony Rosenzweig
- Cardiovascular Institute, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA
| | - Saumya Das
- Cardiovascular Institute, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA
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Swart CW, Dithebe K, van Wyk PWJ, Pohl CH, Swart HC, Coetsee E, Lodolo E, Kock JLF. Intracellular gas bubbles deform organelles in fermenting brewing yeasts. JOURNAL OF THE INSTITUTE OF BREWING 2013. [DOI: 10.1002/jib.60] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- C. W. Swart
- Department of Microbial, Biochemical and Food Biotechnology; University of the Free State; Bloemfontein; 9300; South Africa
| | - K. Dithebe
- Department of Microbial, Biochemical and Food Biotechnology; University of the Free State; Bloemfontein; 9300; South Africa
| | - P. W. J. van Wyk
- Centre for Microscopy; University of the Free State; Bloemfontein; 9300; South Africa
| | - C. H. Pohl
- Department of Microbial, Biochemical and Food Biotechnology; University of the Free State; Bloemfontein; 9300; South Africa
| | - H. C. Swart
- Department of Physics; University of the Free State; Bloemfontein; 9300; South Africa
| | - E. Coetsee
- Department of Physics; University of the Free State; Bloemfontein; 9300; South Africa
| | - E. Lodolo
- SAB Ltd Brewing Centre of Excellence; PO Box 123902; Alrode; 1451; South Africa
| | - J. L. F. Kock
- Department of Microbial, Biochemical and Food Biotechnology; University of the Free State; Bloemfontein; 9300; South Africa
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24
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Matters of the heart in bioenergetics: mitochondrial fusion into continuous reticulum is not needed for maximal respiratory activity. J Bioenerg Biomembr 2012; 45:319-31. [DOI: 10.1007/s10863-012-9494-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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25
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Fujioka H, Tandler B, Haldar SM, Jain MK, Hoppel CL. String mitochondria in mouse soleus muscle. Microsc Res Tech 2012; 76:237-41. [PMID: 23174930 DOI: 10.1002/jemt.22158] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2012] [Accepted: 11/02/2012] [Indexed: 11/06/2022]
Abstract
Red myofibers in mouse soleus muscle have two spatially distinct populations of mitochondria: one where these organelles are disposed in large clusters just inside the sarcolemma and the other situated between the myofibrils. In most cases, the interfibrillar mitochondria (IFM), which are much smaller than the subsarcolemmal ones (SSM), are arranged as pairs, with each member on opposite sides of the Z-line. In some myofibers, the IFM have fused end-to-end to form greatly elongated organelles, which we call "string mitochondria." Although narrow, these can be many sarcomeres in length. The SSM do not form string mitochondria. Most of the string mitochondria exhibit many instances of "pinching," a process involved in mitochondrial division. Elements of sarcoplasmic reticulum are intimately involved with each mitochondrial membrane invagination. It appears as if the fusion:fission balance of IFM in the soleus muscle is slightly out of kilter, with end-to-end fusion predominating over fission.
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Affiliation(s)
- Hisashi Fujioka
- Electron Microscopy Facility, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106, USA.
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26
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Abstract
The permeabilized cells and muscle fibres technique allows one to study the functional properties of mitochondria without their isolation, thus preserving all of the contacts with cellular structures, mostly the cytoskeleton, to study the whole mitochondrial population in the cell in their natural surroundings and it is increasingly being used in both experimental and clinical studies. The functional parameters (affinity for ADP in regulation of respiration) of mitochondria in permeabilized myocytes or myocardial fibres are very different from those in isolated mitochondria in vitro. In the present study, we have analysed the data showing the dependence of this parameter upon the muscle contractile state. Most remarkable is the effect of recently described Ca(2+)-independent contraction of permeabilized muscle fibres induced by elevated temperatures (30-37°C). We show that very similar strong spontaneous Ca(2+)-independent contraction can be produced by proteolytic treatment of permeabilized muscle fibres that result in a disorganization of mitochondrial arrangement, leading to a significant increase in affinity for ADP. These data show that Ca(2+)-insensitive contraction may be related to the destruction of cytoskeleton structures by intracellular proteases. Therefore the use of their inhibitors is strongly advised at the permeabilization step with careful washing of fibres or cells afterwards. A possible physiologically relevant relationship between Ca(2+)-regulated ATP-dependent contraction and mitochondrial functional parameters is also discussed.
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27
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Abstract
Cardiac optical mapping has proven to be a powerful technology for studying cardiovascular function and disease. The development and scientific impact of this methodology are well-documented. Because of its relevance in cardiac research, this imaging technology advances at a rapid pace. Here, we review technological and scientific developments during the past several years and look toward the future. First, we explore key components of a modern optical mapping set-up, focusing on: (1) new camera technologies; (2) powerful light-emitting-diodes (from ultraviolet to red) for illumination; (3) improved optical filter technology; (4) new synthetic and optogenetic fluorescent probes; (5) optical mapping with motion and contraction; (6) new multiparametric optical mapping techniques; and (7) photon scattering effects in thick tissue preparations. We then look at recent optical mapping studies in single cells, cardiomyocyte monolayers, atria, and whole hearts. Finally, we briefly look into the possible future roles of optical mapping in the development of regenerative cardiac research, cardiac cell therapies, and molecular genetic advances.
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Affiliation(s)
- Todd J Herron
- Department of Internal Medicine, Cardiovascular Research Center, University of Michigan, 2800 Plymouth Road, Ann Arbor, MI 48109-2800, USA
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28
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Siebert T, Günther M, Blickhan R. A 3D-geometric model for the deformation of a transversally loaded muscle. J Theor Biol 2012; 298:116-21. [DOI: 10.1016/j.jtbi.2012.01.009] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2011] [Revised: 12/25/2011] [Accepted: 01/04/2012] [Indexed: 11/26/2022]
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29
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Lloyd D, Cortassa S, O'Rourke B, Aon MA. What yeast and cardiomyocytes share: ultradian oscillatory redox mechanisms of cellular coherence and survival. Integr Biol (Camb) 2012; 4:65-74. [PMID: 22143867 PMCID: PMC3348865 DOI: 10.1039/c1ib00124h] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The coherent and robust, yet sensitively adaptable, nature of organisms is an astonishing phenomenon that involves massive parallel processing and concerted network performance at the molecular level. Unravelling the dynamic complexities of the living state underlines the essential operation of ultradian oscillations, rhythms and clocks for the establishment and maintenance of functional order simultaneously on fast and slower timescales. Non-invasive monitoring of respiration, mitochondrial inner membrane potentials, and redox states (especially those of NAD(P)H, flavin, and the monochlorobimane complex of glutathione), even after more than 50 years research, continue to provide both new insights and biomedical applications. Experiments with yeast and in cardiac cells reveal astonishing parallels and similarities in their dynamic biochemical organization.
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Affiliation(s)
- David Lloyd
- School of Biosciences, Cardiff University, Museum Avenue, Cardiff CF10 3AT Wales, UK.
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30
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Azarias G, Chatton JY. Selective ion changes during spontaneous mitochondrial transients in intact astrocytes. PLoS One 2011; 6:e28505. [PMID: 22145050 PMCID: PMC3228761 DOI: 10.1371/journal.pone.0028505] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2011] [Accepted: 11/09/2011] [Indexed: 01/11/2023] Open
Abstract
The bioenergetic status of cells is tightly regulated by the activity of cytosolic enzymes and mitochondrial ATP production. To adapt their metabolism to cellular energy needs, mitochondria have been shown to exhibit changes in their ionic composition as the result of changes in cytosolic ion concentrations. Individual mitochondria also exhibit spontaneous changes in their electrical potential without altering those of neighboring mitochondria. We recently reported that individual mitochondria of intact astrocytes exhibit spontaneous transient increases in their Na+ concentration. Here, we investigated whether the concentration of other ionic species were involved during mitochondrial transients. By combining fluorescence imaging methods, we performed a multiparameter study of spontaneous mitochondrial transients in intact resting astrocytes. We show that mitochondria exhibit coincident changes in their Na+ concentration, electrical potential, matrix pH and mitochondrial reactive oxygen species production during a mitochondrial transient without involving detectable changes in their Ca2+ concentration. Using widefield and total internal reflection fluorescence imaging, we found evidence for localized transient decreases in the free Mg2+ concentration accompanying mitochondrial Na+ spikes that could indicate an associated local and transient enrichment in the ATP concentration. Therefore, we propose a sequential model for mitochondrial transients involving a localized ATP microdomain that triggers a Na+-mediated mitochondrial depolarization, transiently enhancing the activity of the mitochondrial respiratory chain. Our work provides a model describing ionic changes that could support a bidirectional cytosol-to-mitochondria ionic communication.
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Affiliation(s)
- Guillaume Azarias
- Department of Cell Biology and Morphology, University of Lausanne, Lausanne, Switzerland
| | - Jean-Yves Chatton
- Department of Cell Biology and Morphology, University of Lausanne, Lausanne, Switzerland
- Cellular Imaging Facility, University of Lausanne, Lausanne, Switzerland
- * E-mail:
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