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Dotti P, Fernandez-Tenorio M, Janicek R, Márquez-Neila P, Wullschleger M, Sznitman R, Egger M. A deep learning-based approach for efficient detection and classification of local Ca²⁺ release events in Full-Frame confocal imaging. Cell Calcium 2024; 121:102893. [PMID: 38701707 DOI: 10.1016/j.ceca.2024.102893] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2023] [Revised: 03/24/2024] [Accepted: 04/23/2024] [Indexed: 05/05/2024]
Abstract
The release of Ca2+ ions from intracellular stores plays a crucial role in many cellular processes, acting as a secondary messenger in various cell types, including cardiomyocytes, smooth muscle cells, hepatocytes, and many others. Detecting and classifying associated local Ca2+ release events is particularly important, as these events provide insight into the mechanisms, interplay, and interdependencies of local Ca2+release events underlying global intracellular Ca2+signaling. However, time-consuming and labor-intensive procedures often complicate analysis, especially with low signal-to-noise ratio imaging data. Here, we present an innovative deep learning-based approach for automatically detecting and classifying local Ca2+ release events. This approach is exemplified with rapid full-frame confocal imaging data recorded in isolated cardiomyocytes. To demonstrate the robustness and accuracy of our method, we first use conventional evaluation methods by comparing the intersection between manual annotations and the segmentation of Ca2+ release events provided by the deep learning method, as well as the annotated and recognized instances of individual events. In addition to these methods, we compare the performance of the proposed model with the annotation of six experts in the field. Our model can recognize more than 75 % of the annotated Ca2+ release events and correctly classify more than 75 %. A key result was that there were no significant differences between the annotations produced by human experts and the result of the proposed deep learning model. We conclude that the proposed approach is a robust and time-saving alternative to conventional full-frame confocal imaging analysis of local intracellular Ca2+ events.
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Affiliation(s)
- Prisca Dotti
- Department of Physiology, Universität Bern, Bern, Switzerland; ARTORG Center, Universität Bern, Bern, Switzerland
| | | | | | | | | | | | - Marcel Egger
- Department of Physiology, Universität Bern, Bern, Switzerland.
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2
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Egger C, Fernandez-Tenorio M, Blanch J, Janicek R, Egger M. Dual mode of action of IP 3-dependent SR-Ca 2+ release on local and global SR-Ca 2+ release in ventricular cardiomyocytes. J Mol Cell Cardiol 2024; 186:107-110. [PMID: 37993093 DOI: 10.1016/j.yjmcc.2023.11.009] [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: 08/31/2023] [Revised: 10/23/2023] [Accepted: 11/17/2023] [Indexed: 11/24/2023]
Abstract
In heart muscle, the physiological function of IP3-induced Ca2+ release (IP3ICR) from the sarcoplasmic reticulum (SR) is still the subject of intense study. A role of IP3ICR may reside in modulating Ca2+-dependent cardiac arrhythmogenicity. Here we observe the propensity of spontaneous intracellular Ca2+ waves (SCaW) driven by Ca2+-induced Ca2+ release (CICR) in ventricular myocytes as a correlate of arrhythmogenicity on the organ level. We observe a dual mode of action of IP3ICR on SCaW generation in an IP3R overexpression model. This model shows a mild cardiac phenotype and mimics pathophysiological conditions of increased IP3R activity. In this model, IP3ICR was able to increase or decrease the occurrence of SCaW depending on global Ca2+ activity. This IP3ICR-based regulatory mechanism can operate in two "modes" depending on the intracellular CICR activity and efficiency (e.g. SCaW and/or local Ryanodine Receptor (RyR) Ca2+ release events, respectively): a) in a mode that augments the CICR mechanism at the cellular level, resulting in improved excitation-contraction coupling (ECC) and ultimately better contraction of the myocardium, and b) in a protective mode in which the CICR activity is curtailed to prevent the occurrence of Ca2+ waves at the cellular level and thus reduce the probability of arrhythmogenicity at the organ level.
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Affiliation(s)
- Caroline Egger
- Department of Physiology, University of Bern, Buehlplatz 5, CH 3012 Bern, Switzerland; Department of Emergency Medicine (Notfallzentrum) Inselspital - University of Bern, Freiburgstrasse 10, CH 3010 Bern, Switzerland
| | | | - Joaquim Blanch
- Department of Physiology, University of Bern, Buehlplatz 5, CH 3012 Bern, Switzerland
| | - Radoslav Janicek
- Department of Physiology, University of Bern, Buehlplatz 5, CH 3012 Bern, Switzerland
| | - Marcel Egger
- Department of Physiology, University of Bern, Buehlplatz 5, CH 3012 Bern, Switzerland.
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3
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Jin X, Meletiou A, Chung J, Tilunaite A, Demydenko K, Dries E, Puertas RD, Amoni M, Tomar A, Claus P, Soeller C, Rajagopal V, Sipido K, Roderick HL. InsP 3R-RyR channel crosstalk augments sarcoplasmic reticulum Ca 2+ release and arrhythmogenic activity in post-MI pig cardiomyocytes. J Mol Cell Cardiol 2023; 179:47-59. [PMID: 37003353 DOI: 10.1016/j.yjmcc.2023.03.015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/17/2022] [Revised: 03/08/2023] [Accepted: 03/28/2023] [Indexed: 04/03/2023]
Abstract
Ca2+ transients (CaT) underlying cardiomyocyte (CM) contraction require efficient Ca2+ coupling between sarcolemmal Ca2+ channels and sarcoplasmic reticulum (SR) ryanodine receptor Ca2+ channels (RyR) for their generation; reduced coupling in disease contributes to diminished CaT and arrhythmogenic Ca2+ events. SR Ca2+ release also occurs via inositol 1,4,5-trisphosphate receptors (InsP3R) in CM. While this pathway contributes negligeably to Ca2+ handling in healthy CM, rodent studies support a role in altered Ca2+ dynamics and arrhythmogenic Ca2+ release involving InsP3R crosstalk with RyRs in disease. Whether this mechanism persists in larger mammals with lower T-tubular density and coupling of RyRs is not fully resolved. We have recently shown an arrhythmogenic action of InsP3-induced Ca2+ release (IICR) in end stage human heart failure, often associated with underlying ischemic heart disease (IHD). How IICR contributes to early stages of disease is however not determined but highly relevant. To access this stage, we chose a porcine model of IHD, which shows substantial remodelling of the area adjacent to the infarct. In cells from this region, IICR preferentially augmented Ca2+ release from non-coupled RyR clusters that otherwise showed delayed activation during the CaT. IICR in turn synchronised Ca2+ release during the CaT but also induced arrhythmogenic delayed afterdepolarizations and action potentials. Nanoscale imaging identified co-clustering of InsP3Rs and RyRs, thereby allowing Ca2+-mediated channel crosstalk. Mathematical modelling supported and further delineated this mechanism of enhanced InsP3R-RyRs coupling in MI. Our findings highlight the role of InsP3R-RyR channel crosstalk in Ca2+ release and arrhythmia during post-MI remodelling.
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Affiliation(s)
- Xin Jin
- KU Leuven, Department of Cardiovascular Sciences, Laboratory of Experimental Cardiology, B-3000 Leuven, Belgium
| | - Anna Meletiou
- Department of Physiology, University of Bern, Bern, Switzerland
| | - Joshua Chung
- KU Leuven, Department of Cardiovascular Sciences, Laboratory of Experimental Cardiology, B-3000 Leuven, Belgium; Cell Structure and Mechanobiology Group, Department of Biomedical Engineering, Melbourne School of Engineering, University of Melbourne, Australia
| | - Agne Tilunaite
- Cell Structure and Mechanobiology Group, Department of Biomedical Engineering, Melbourne School of Engineering, University of Melbourne, Australia; Systems Biology Laboratory, School of Mathematics and Statistics, and Department of Biomedical Engineering, University of Melbourne, Australia
| | - Kateryna Demydenko
- KU Leuven, Department of Cardiovascular Sciences, Laboratory of Experimental Cardiology, B-3000 Leuven, Belgium
| | - Eef Dries
- KU Leuven, Department of Cardiovascular Sciences, Laboratory of Experimental Cardiology, B-3000 Leuven, Belgium
| | - Rosa Doñate Puertas
- KU Leuven, Department of Cardiovascular Sciences, Laboratory of Experimental Cardiology, B-3000 Leuven, Belgium
| | - Matthew Amoni
- KU Leuven, Department of Cardiovascular Sciences, Laboratory of Experimental Cardiology, B-3000 Leuven, Belgium
| | - Ashutosh Tomar
- KU Leuven, Department of Cardiovascular Sciences, Laboratory of Experimental Cardiology, B-3000 Leuven, Belgium
| | - Piet Claus
- KU Leuven, Department of Cardiovascular Sciences, Laboratory of Experimental Cardiology, B-3000 Leuven, Belgium
| | | | - Vijay Rajagopal
- Cell Structure and Mechanobiology Group, Department of Biomedical Engineering, Melbourne School of Engineering, University of Melbourne, Australia
| | - Karin Sipido
- KU Leuven, Department of Cardiovascular Sciences, Laboratory of Experimental Cardiology, B-3000 Leuven, Belgium
| | - H Llewelyn Roderick
- KU Leuven, Department of Cardiovascular Sciences, Laboratory of Experimental Cardiology, B-3000 Leuven, Belgium.
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4
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Deb A, Tow BD, Qing Y, Walker M, Hodges ER, Stewart JA, Knollmann BC, Zheng Y, Wang Y, Liu B. Genetic Inhibition of Mitochondrial Permeability Transition Pore Exacerbates Ryanodine Receptor 2 Dysfunction in Arrhythmic Disease. Cells 2023; 12:204. [PMID: 36672139 PMCID: PMC9856515 DOI: 10.3390/cells12020204] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2022] [Revised: 12/12/2022] [Accepted: 12/21/2022] [Indexed: 01/06/2023] Open
Abstract
The brief opening mode of the mitochondrial permeability transition pore (mPTP) serves as a calcium (Ca2+) release valve to prevent mitochondrial Ca2+ (mCa2+) overload. Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a stress-induced arrhythmic syndrome due to mutations in the Ca2+ release channel complex of ryanodine receptor 2 (RyR2). We hypothesize that inhibiting the mPTP opening in CPVT exacerbates the disease phenotype. By crossbreeding a CPVT model of CASQ2 knockout (KO) with a mouse missing CypD, an activator of mPTP, a double KO model (DKO) was generated. Echocardiography, cardiac histology, and live-cell imaging were employed to assess the severity of cardiac pathology. Western blot and RNAseq were performed to evaluate the contribution of various signaling pathways. Although exacerbated arrhythmias were reported, the DKO model did not exhibit pathological remodeling. Myocyte Ca2+ handling was similar to that of the CASQ2 KO mouse at a low pacing frequency. However, increased ROS production, activation of the CaMKII pathway, and hyperphosphorylation of RyR2 were detected in DKO. Transcriptome analysis identified altered gene expression profiles associated with electrical instability in DKO. Our study provides evidence that genetic inhibition of mPTP exacerbates RyR2 dysfunction in CPVT by increasing activation of the CaMKII pathway and subsequent hyperphosphorylation of RyR2.
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Affiliation(s)
- Arpita Deb
- Department of Biological Sciences, Mississippi State University, Starkville, MS 39762, USA
| | - Brian D. Tow
- Department of Biological Sciences, Mississippi State University, Starkville, MS 39762, USA
| | - You Qing
- Beijing Key Laboratory for Agricultural Application and New Technique, College of Plant Science and Technology, Bioinformatics Center, Beijing University of Agriculture, Beijing 102206, China
| | - Madelyn Walker
- Department of Biological Sciences, Mississippi State University, Starkville, MS 39762, USA
| | - Emmanuel R. Hodges
- School of Pharmacy, Division of BioMolecular Sciences, University of Mississippi, Oxford, MS 38677, USA
| | - James A. Stewart
- School of Pharmacy, Division of BioMolecular Sciences, University of Mississippi, Oxford, MS 38677, USA
| | - Björn C. Knollmann
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Yi Zheng
- Beijing Key Laboratory for Agricultural Application and New Technique, College of Plant Science and Technology, Bioinformatics Center, Beijing University of Agriculture, Beijing 102206, China
| | - Ying Wang
- Department of Biological Sciences, Mississippi State University, Starkville, MS 39762, USA
| | - Bin Liu
- Department of Biological Sciences, Mississippi State University, Starkville, MS 39762, USA
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5
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Chung J, Tilūnaitė A, Ladd D, Hunt H, Soeller C, Crampin EJ, Johnston ST, Roderick HL, Rajagopal V. IP 3R activity increases propensity of RyR-mediated sparks by elevating dyadic [Ca 2+]. Math Biosci 2023; 355:108923. [PMID: 36395827 DOI: 10.1016/j.mbs.2022.108923] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Revised: 10/15/2022] [Accepted: 10/15/2022] [Indexed: 11/16/2022]
Abstract
Calcium (Ca2+) plays a critical role in the excitation contraction coupling (ECC) process that mediates the contraction of cardiomyocytes during each heartbeat. While ryanodine receptors (RyRs) are the primary Ca2+ channels responsible for generating the cell-wide Ca2+ transients during ECC, Ca2+ release, via inositol 1,4,5-trisphosphate (IP3) receptors (IP3Rs) are also reported in cardiomyocytes to elicit ECC-modulating effects. Recent studies suggest that the localization of IP3Rs at dyads grant their ability to modify the occurrence of Ca2+ sparks (elementary Ca2+ release events that constitute cell wide Ca2+ releases associated with ECC) which may underlie their modulatory influence on ECC. Here, we aim to uncover the mechanism by which dyad-localized IP3Rs influence Ca2+ spark dynamics. To this end, we developed a mathematical model of the dyad that incorporates the behaviour of IP3Rs, in addition to RyRs, to reveal the impact of their activity on local Ca2+ handling and consequent Ca2+ spark occurrence and its properties. Consistent with published experimental data, our model predicts that the propensity for Ca2+ spark formation increases in the presence of IP3R activity. Our simulations support the hypothesis that IP3Rs elevate Ca2+ in the dyad, sensitizing proximal RyRs towards activation and hence Ca2+ spark formation. The stochasticity of IP3R gating is an important aspect of this mechanism. However, dyadic IP3R activity lowers the Ca2+ available in the junctional sarcoplasmic reticulum (JSR) for release, thus resulting in Ca2+ sparks with similar durations but lower amplitudes.
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Affiliation(s)
- Joshua Chung
- Department of Biomedical Engineering, The University of Melbourne, Melbourne, VIC 3010, Australia; Laboratory of Experimental Cardiology, Department of Cardiovascular Sciences, KU Leuven, 3000, Leuven, Belgium
| | - Agnė Tilūnaitė
- Department of Biomedical Engineering, The University of Melbourne, Melbourne, VIC 3010, Australia; School of Mathematics and Statistics, The University of Melbourne, Melbourne, VIC 3010, Australia
| | - David Ladd
- Department of Biomedical Engineering, The University of Melbourne, Melbourne, VIC 3010, Australia; School of Mathematics and Statistics, The University of Melbourne, Melbourne, VIC 3010, Australia; ARC Centre of Excellence in Convergent Bio-Nano Science and Technology, School of Chemical and Biomedical Engineering, The University of Melbourne, Melbourne, VIC 3010, Australia
| | - Hilary Hunt
- School of Mathematics and Statistics, The University of Melbourne, Melbourne, VIC 3010, Australia
| | | | - Edmund J Crampin
- Department of Biomedical Engineering, The University of Melbourne, Melbourne, VIC 3010, Australia; School of Mathematics and Statistics, The University of Melbourne, Melbourne, VIC 3010, Australia; ARC Centre of Excellence in Convergent Bio-Nano Science and Technology, School of Chemical and Biomedical Engineering, The University of Melbourne, Melbourne, VIC 3010, Australia
| | - Stuart T Johnston
- School of Mathematics and Statistics, The University of Melbourne, Melbourne, VIC 3010, Australia; ARC Centre of Excellence in Convergent Bio-Nano Science and Technology, School of Chemical and Biomedical Engineering, The University of Melbourne, Melbourne, VIC 3010, Australia
| | - H Llewelyn Roderick
- Laboratory of Experimental Cardiology, Department of Cardiovascular Sciences, KU Leuven, 3000, Leuven, Belgium.
| | - Vijay Rajagopal
- Department of Biomedical Engineering, The University of Melbourne, Melbourne, VIC 3010, Australia; Baker Department of Cardiometabolic Health, The University of Melbourne, Melbourne, VIC 3010, Australia.
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6
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Demydenko K, Ekhteraei-Tousi S, Roderick HL. Inositol 1,4,5-trisphosphate receptors in cardiomyocyte physiology and disease. Philos Trans R Soc Lond B Biol Sci 2022; 377:20210319. [PMID: 36189803 PMCID: PMC9527928 DOI: 10.1098/rstb.2021.0319] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The contraction of cardiac muscle underlying the pumping action of the heart is mediated by the process of excitation-contraction coupling (ECC). While triggered by Ca2+ entry across the sarcolemma during the action potential, it is the release of Ca2+ from the sarcoplasmic reticulum (SR) intracellular Ca2+ store via ryanodine receptors (RyRs) that plays the major role in induction of contraction. Ca2+ also acts as a key intracellular messenger regulating transcription underlying hypertrophic growth. Although Ca2+ release via RyRs is by far the greatest contributor to the generation of Ca2+ transients in the cardiomyocyte, Ca2+ is also released from the SR via inositol 1,4,5-trisphosphate (InsP3) receptors (InsP3Rs). This InsP3-induced Ca2+ release modifies Ca2+ transients during ECC, participates in directing Ca2+ to the mitochondria, and stimulates the transcription of genes underlying hypertrophic growth. Central to these specific actions of InsP3Rs is their localization to responsible signalling microdomains, the dyad, the SR-mitochondrial interface and the nucleus. In this review, the various roles of InsP3R in cardiac (patho)physiology and the mechanisms by which InsP3 signalling selectively influences the different cardiomyocyte cell processes in which it is involved will be presented. This article is part of the theme issue ‘The cardiomyocyte: new revelations on the interplay between architecture and function in growth, health, and disease’.
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Affiliation(s)
- Kateryna Demydenko
- Laboratory of Experimental Cardiology, Department of Cardiovascular Sciences, KU Leuven, Leuven, Belgium
| | - Samaneh Ekhteraei-Tousi
- Laboratory of Experimental Cardiology, Department of Cardiovascular Sciences, KU Leuven, Leuven, Belgium
| | - H Llewelyn Roderick
- Laboratory of Experimental Cardiology, Department of Cardiovascular Sciences, KU Leuven, Leuven, Belgium
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7
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Jin X, Amoni M, Gilbert G, Dries E, Doñate Puertas R, Tomar A, Nagaraju CK, Pradhan A, Yule DI, Martens T, Menten R, Vanden Berghe P, Rega F, Sipido K, Roderick HL. InsP 3R-RyR Ca 2+ channel crosstalk facilitates arrhythmias in the failing human ventricle. Basic Res Cardiol 2022; 117:60. [PMID: 36378362 DOI: 10.1007/s00395-022-00967-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/27/2022] [Revised: 10/13/2022] [Accepted: 10/31/2022] [Indexed: 11/16/2022]
Abstract
Dysregulated intracellular Ca2+ handling involving altered Ca2+ release from intracellular stores via RyR channels underlies both arrhythmias and reduced function in heart failure (HF). Mechanisms linking RyR dysregulation and disease are not fully established. Studies in animals support a role for InsP3 receptor Ca2+ channels (InsP3R) in pathological alterations in cardiomyocyte Ca2+ handling but whether these findings translate to the divergent physiology of human cardiomyocytes during heart failure is not determined. Using electrophysiological and Ca2+ recordings in human ventricular cardiomyocytes, we uncovered that Ca2+ release via InsP3Rs facilitated Ca2+ release from RyR and induced arrhythmogenic delayed after depolarisations and action potentials. InsP3R-RyR crosstalk was particularly increased in HF at RyR clusters isolated from the T-tubular network. Reduced SERCA activity in HF further facilitated the action of InsP3. Nanoscale imaging revealed co-localisation of InsP3Rs with RyRs in the dyad, which was increased in HF, providing a mechanism for augmented Ca2+ channel crosstalk. Notably, arrhythmogenic activity dependent on InsP3Rs was increased in tissue wedges from failing hearts perfused with AngII to promote InsP3 generation. These data indicate a central role for InsP3R-RyR Ca2+ signalling crosstalk in the pro-arrhythmic action of GPCR agonists elevated in HF and the potential for their therapeutic targeting.
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Affiliation(s)
- Xin Jin
- Department of Cardiovascular Sciences, Laboratory of Experimental Cardiology, KU Leuven, 3000, Leuven, Belgium.,Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA, USA
| | - Matthew Amoni
- Department of Cardiovascular Sciences, Laboratory of Experimental Cardiology, KU Leuven, 3000, Leuven, Belgium
| | - Guillaume Gilbert
- Department of Cardiovascular Sciences, Laboratory of Experimental Cardiology, KU Leuven, 3000, Leuven, Belgium
| | - Eef Dries
- Department of Cardiovascular Sciences, Laboratory of Experimental Cardiology, KU Leuven, 3000, Leuven, Belgium
| | - Rosa Doñate Puertas
- Department of Cardiovascular Sciences, Laboratory of Experimental Cardiology, KU Leuven, 3000, Leuven, Belgium
| | - Ashutosh Tomar
- Department of Cardiovascular Sciences, Laboratory of Experimental Cardiology, KU Leuven, 3000, Leuven, Belgium
| | - Chandan K Nagaraju
- Department of Cardiovascular Sciences, Laboratory of Experimental Cardiology, KU Leuven, 3000, Leuven, Belgium
| | - Ankit Pradhan
- Department of Cardiovascular Sciences, Laboratory of Experimental Cardiology, KU Leuven, 3000, Leuven, Belgium
| | - David I Yule
- Department of Pharmacology and Physiology, Medical Center School of Medicine and Dentistry, University of Rochester, 601 Elmwood Avenue, Box 711, Rochester, NY, 14642, USA
| | - Tobie Martens
- Laboratory for Enteric NeuroScience (LENS), Translational Research Center for Gastrointestinal Disorders (TARGID), KU Leuven, 3000, Leuven, Belgium.,Cell and Tissue Imaging Cluster (CIC), KU Leuven, 3000, Leuven, Belgium
| | - Roxane Menten
- Department of Cardiovascular Sciences, Laboratory of Experimental Cardiology, KU Leuven, 3000, Leuven, Belgium
| | - Pieter Vanden Berghe
- Laboratory for Enteric NeuroScience (LENS), Translational Research Center for Gastrointestinal Disorders (TARGID), KU Leuven, 3000, Leuven, Belgium.,Cell and Tissue Imaging Cluster (CIC), KU Leuven, 3000, Leuven, Belgium
| | - Filip Rega
- Department of Cardiovascular Sciences, Laboratory of Experimental Cardiology, KU Leuven, 3000, Leuven, Belgium.,Department of Cardiology and Department of Cardiac Surgery, University Hospitals Leuven, Leuven, Belgium
| | - Karin Sipido
- Department of Cardiovascular Sciences, Laboratory of Experimental Cardiology, KU Leuven, 3000, Leuven, Belgium
| | - H Llewelyn Roderick
- Department of Cardiovascular Sciences, Laboratory of Experimental Cardiology, KU Leuven, 3000, Leuven, Belgium.
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8
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Varma D, Almeida JFQ, DeSantiago J, Blatter LA, Banach K. Inositol 1,4,5-trisphosphate receptor - reactive oxygen signaling domain regulates excitation-contraction coupling in atrial myocytes. J Mol Cell Cardiol 2022; 163:147-155. [PMID: 34755642 PMCID: PMC8826595 DOI: 10.1016/j.yjmcc.2021.10.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/19/2020] [Revised: 09/03/2021] [Accepted: 10/13/2021] [Indexed: 02/03/2023]
Abstract
The inositol 1,4,5-trisphosphate receptor (InsP3R) is up-regulated in patients with atrial fibrillation (AF) and InsP3-induced Ca2+ release (IICR) is linked to pro-arrhythmic spontaneous Ca2+ release events. Nevertheless, knowledge of the physiological relevance and regulation of InsP3Rs in atrial muscle is still limited. We hypothesize that InsP3R and NADPH oxidase 2 (NOX2) form a functional signaling domain where NOX2 derived reactive oxygen species (ROS) regulate InsP3R agonist affinity and thereby Ca2+ release. To quantitate the contribution of IICR to atrial excitation-contraction coupling (ECC) atrial myocytes (AMs) were isolated from wild type and NOX2 deficient (Nox2-/-) mice and changes in the cytoplasmic Ca2+ concentration ([Ca2+]i; fluo-4/AM, indo-1) or ROS (2',7'-dichlorofluorescein, DCF) were monitored by fluorescence microscopy. Superfusion of AMs with Angiotensin II (AngII: 1 μmol/L) significantly increased diastolic [Ca2+]i (F/F0, Ctrl: 1.00 ± 0.01, AngII: 1.20 ± 0.03; n = 7; p < 0.05), the field stimulation induced Ca2+ transient (CaT) amplitude (ΔF/F0, Ctrl: 2.00 ± 0.17, AngII: 2.39 ± 0.22, n = 7; p < 0.05), and let to the occurrence of spontaneous increases in [Ca2+]i. These changes in [Ca2+]i were suppressed by the InsP3R blocker 2-aminoethoxydiphenyl-borate (2-APB; 1 μmol/L). Concomitantly, AngII induced an increase in ROS production that was sensitive to the NOX2 specific inhibitor gp91ds-tat (1 μmol/L). In NOX2-/- AMs, AngII failed to increase diastolic [Ca2+]i, CaT amplitude, and the frequency of spontaneous Ca2+ increases. Furthermore, the enhancement of CaTs by exposure to membrane permeant InsP3 was abolished by NOX inhibition with apocynin (1 μM). AngII induced IICR in Nox2-/- AMs could be restored by addition of exogenous ROS (tert-butyl hydroperoxide, tBHP: 5 μmol/L). In saponin permeabilized AMs InsP3 (5 μmol/L) induced Ca2+ sparks that increased in frequency in the presence of ROS (InsP3: 9.65 ± 1.44 sparks*s-1*(100μm)-1; InsP3 + tBHP: 10.77 ± 1.5 sparks*s-1*(100μm)-1; n = 5; p < 0.05). The combined effect of InsP3 + tBHP was entirely suppressed by 2-APB and Xestospongine C (XeC). Changes in IICR due to InsP3R glutathionylation induced by diamide could be reversed by the reducing agent dithiothreitol (DTT: 1 mmol/L) and prevented by pretreatment with 2-APB, supporting that the ROS-dependent post-translational modification of the InsP3R plays a role in the regulation of ECC. Our data demonstrate that in AMs the InsP3R is under dual control of agonist induced InsP3 and ROS formation and suggest that InsP3 and NOX2-derived ROS co-regulate atrial IICR and ECC in a defined InsP3R/NOX2 signaling domain.
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Affiliation(s)
- Disha Varma
- Dept. of Internal Medicine/Cardiology, Rush University Medical Center, 1750 W. Harrison St, Chicago, IL 60612, USA.
| | - Jonathas F Q Almeida
- Dept. of Internal Medicine/Cardiology, Rush University Medical Center, 1750 W. Harrison St, Chicago, IL 60612, USA.
| | - Jaime DeSantiago
- Dept. of Physiology & Biophysics, Rush University Medical Center, 1750 W. Harrison St, Chicago, IL 60612, USA.
| | - Lothar A Blatter
- Dept. of Physiology & Biophysics, Rush University Medical Center, 1750 W. Harrison St, Chicago, IL 60612, USA.
| | - Kathrin Banach
- Dept. of Internal Medicine/Cardiology, Rush University Medical Center, 1750 W. Harrison St, Chicago, IL 60612, USA.
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9
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Zhang DG, Zhao T, Xu XJ, Lv WH, Luo Z. Dietary Marginal and Excess Selenium Increased Triglycerides Deposition, Induced Endoplasmic Reticulum Stress and Differentially Influenced Selenoproteins Expression in the Anterior and Middle Intestines of Yellow Catfish Pelteobagrus fulvidraco. Antioxidants (Basel) 2021; 10:antiox10040535. [PMID: 33805536 PMCID: PMC8067157 DOI: 10.3390/antiox10040535] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2021] [Revised: 03/21/2021] [Accepted: 03/25/2021] [Indexed: 11/16/2022] Open
Abstract
Selenium (Se) is an essential micro-mineral and plays important roles in antioxidant responses, and also influences lipid metabolism and selenoprotein expression in vertebrates, but the effects and mechanism remain unknown. The study was undertaken to decipher the insights into dietary Se influencing lipid metabolism and selenoprotein expression in the anterior and middle intestine (AI and MI) of yellow catfish Pelteobagrus fulvidraco. Yellow catfish (weight: 8.27 ± 0.03 g) were fed a 0.03- (M-Se), 0.25- (A-Se), or 6.39- (E-Se) mg Se/kg diet for 12 wk. AI and MI were analyzed for triglycerides (TGs) and Se concentrations, histochemistry and immunofluorescence, enzyme activities, and gene and protein levelsassociated with antioxidant responses, lipid metabolism, endoplasmic reticulum (ER) stress, and selenoproteome. Compared to the A-Se group, M-Se and E-Se diets significantly decreased weight gain (WG) and increased TGs concentration in the AI and MI. In the AI, compared with A-Se group, M-Se and E-Se diets significantly increased activities of fatty acid synthase, expression of lipogenic genes, and suppressed lipolysis. In the MI, compared to the A-Se group, M-Se and E-Se diets significantly increased activities of lipogenesis and expression of lipogenic genes. Compared with A-Se group, E-Se diet significantly increased glutathione peroxidase (GPX) activities in the AI and MI, and M-Se diet did not significantly reduce GPX activities in the AI and MI. Compared with the A- Se group, E-Se diet significantly increased glutathione peroxidase (GPX) activities in the plasma and liver, and M-Se diet significantly reduced GPX activities in the plasma and liver. Compared with the A-Se group, M-Se and E-Se groups also increased glucose-regulated protein 78 (GRP78, ER stress marker) protein expression of the intestine. Dietary Se supplementation also differentially influenced the expression of the 28 selenoproteins in the AI and MI, many of which possessed antioxidant characteristics. Compared with the A-Se group, the M-Se group significantly decreased mRNA levels of txnrd2 and txnrd3, but made no difference on mRNA levels of these seven GPX proteins in the MI. Moreover, we characterized sterol regulatory element binding protein 1c (SREBP1c) binding sites of three ER-resident proteins (selenom, selenon, and selenos) promoters, and found that Se positively controlled selenom, selenon, and selenos expression via SREBP1c binding to the selenom, selenon, and selenos promoter. Thus, dietary marginal and excess Se increased TGs deposition of yellow catfish P. fulvidraco, which might be mediated by ER-resident selenoproteins expression and ER stress.
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Affiliation(s)
- Dian-Guang Zhang
- Key Laboratory of Freshwater Animal Breeding, Fishery College, Huazhong Agricultural University, Ministry of Agriculture, Wuhan 430070, China; (D.-G.Z.); (T.Z.); (X.-J.X.); (W.-H.L.)
| | - Tao Zhao
- Key Laboratory of Freshwater Animal Breeding, Fishery College, Huazhong Agricultural University, Ministry of Agriculture, Wuhan 430070, China; (D.-G.Z.); (T.Z.); (X.-J.X.); (W.-H.L.)
| | - Xiao-Jian Xu
- Key Laboratory of Freshwater Animal Breeding, Fishery College, Huazhong Agricultural University, Ministry of Agriculture, Wuhan 430070, China; (D.-G.Z.); (T.Z.); (X.-J.X.); (W.-H.L.)
| | - Wu-Hong Lv
- Key Laboratory of Freshwater Animal Breeding, Fishery College, Huazhong Agricultural University, Ministry of Agriculture, Wuhan 430070, China; (D.-G.Z.); (T.Z.); (X.-J.X.); (W.-H.L.)
| | - Zhi Luo
- Key Laboratory of Freshwater Animal Breeding, Fishery College, Huazhong Agricultural University, Ministry of Agriculture, Wuhan 430070, China; (D.-G.Z.); (T.Z.); (X.-J.X.); (W.-H.L.)
- Laboratory for Marine Fisheries Science and Food Production Processes, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266237, China
- Correspondence: or ; Tel.: +86-27-8728-2113; Fax: +86-27-8728-2114
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10
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Capel RA, Bose SJ, Collins TP, Rajasundaram S, Ayagama T, Zaccolo M, Burton RAB, Terrar DA. IP 3-mediated Ca 2+ release regulates atrial Ca 2+ transients and pacemaker function by stimulation of adenylyl cyclases. Am J Physiol Heart Circ Physiol 2020; 320:H95-H107. [PMID: 33064562 PMCID: PMC7864251 DOI: 10.1152/ajpheart.00380.2020] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Inositol trisphosphate (IP3) is a Ca2+-mobilizing second messenger shown to modulate atrial muscle contraction and is thought to contribute to atrial fibrillation. Cellular pathways underlying IP3 actions in cardiac tissue remain poorly understood, and the work presented here addresses the question whether IP3-mediated Ca2+ release from the sarcoplasmic reticulum is linked to adenylyl cyclase activity including Ca2+-stimulated adenylyl cyclases (AC1 and AC8) that are selectively expressed in atria and sinoatrial node (SAN). Immunocytochemistry in guinea pig atrial myocytes identified colocalization of type 2 IP3 receptors with AC8, while AC1 was located in close vicinity. Intracellular photorelease of IP3 by UV light significantly enhanced the amplitude of the Ca2+ transient (CaT) evoked by electrical stimulation of atrial myocytes (31 ± 6% increase 60 s after photorelease, n = 16). The increase in CaT amplitude was abolished by inhibitors of adenylyl cyclases (MDL-12,330) or protein kinase A (H89), showing that cAMP signaling is required for this effect of photoreleased IP3. In mouse, spontaneously beating right atrial preparations, phenylephrine, an α-adrenoceptor agonist with effects that depend on IP3-mediated Ca2+ release, increased the maximum beating rate by 14.7 ± 0.5%, n = 10. This effect was substantially reduced by 2.5 µmol/L 2-aminoethyl diphenylborinate and abolished by a low dose of MDL-12,330, observations which are again consistent with a functional interaction between IP3 and cAMP signaling involving Ca2+ stimulation of adenylyl cyclases in the SAN pacemaker. Understanding the interaction between IP3 receptor pathways and Ca2+-stimulated adenylyl cyclases provides important insights concerning acute mechanisms for initiation of atrial arrhythmias. NEW & NOTEWORTHY This study provides evidence supporting the proposal that IP3 signaling in cardiac atria and sinoatrial node involves stimulation of Ca2+-activated adenylyl cyclases (AC1 and AC8) by IP3-evoked Ca2+ release from junctional sarcoplasmic reticulum. AC8 and IP3 receptors are shown to be located close together, while AC1 is nearby. Greater understanding of these novel aspects of the IP3 signal transduction mechanism is important for future study in atrial physiology and pathophysiology, particularly atrial fibrillation.
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Affiliation(s)
- Rebecca A Capel
- Department of Pharmacology, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - Samuel J Bose
- Department of Pharmacology, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - Thomas P Collins
- Department of Pharmacology, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - Skanda Rajasundaram
- Department of Pharmacology, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - Thamali Ayagama
- Department of Pharmacology, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - Manuela Zaccolo
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Rebecca-Ann Beatrice Burton
- Department of Pharmacology, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - Derek A Terrar
- Department of Pharmacology, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
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11
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Gilbert G, Demydenko K, Dries E, Puertas RD, Jin X, Sipido K, Roderick HL. Calcium Signaling in Cardiomyocyte Function. Cold Spring Harb Perspect Biol 2020; 12:cshperspect.a035428. [PMID: 31308143 DOI: 10.1101/cshperspect.a035428] [Citation(s) in RCA: 52] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Rhythmic increases in intracellular Ca2+ concentration underlie the contractile function of the heart. These heart muscle-wide changes in intracellular Ca2+ are induced and coordinated by electrical depolarization of the cardiomyocyte sarcolemma by the action potential. Originating at the sinoatrial node, conduction of this electrical signal throughout the heart ensures synchronization of individual myocytes into an effective cardiac pump. Ca2+ signaling pathways also regulate gene expression and cardiomyocyte growth during development and in pathology. These fundamental roles of Ca2+ in the heart are illustrated by the prevalence of altered Ca2+ homeostasis in cardiovascular diseases. Indeed, heart failure (an inability of the heart to support hemodynamic needs), rhythmic disturbances, and inappropriate cardiac growth all share an involvement of altered Ca2+ handling. The prevalence of these pathologies, contributing to a third of all deaths in the developed world as well as to substantial morbidity makes understanding the mechanisms of Ca2+ handling and dysregulation in cardiomyocytes of great importance.
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Affiliation(s)
- Guillaume Gilbert
- Laboratory of Experimental Cardiology, Department of Cardiovascular Sciences, KU Leuven, BE3000 Leuven, Belgium
| | - Kateryna Demydenko
- Laboratory of Experimental Cardiology, Department of Cardiovascular Sciences, KU Leuven, BE3000 Leuven, Belgium
| | - Eef Dries
- Laboratory of Experimental Cardiology, Department of Cardiovascular Sciences, KU Leuven, BE3000 Leuven, Belgium
| | - Rosa Doñate Puertas
- Laboratory of Experimental Cardiology, Department of Cardiovascular Sciences, KU Leuven, BE3000 Leuven, Belgium
| | - Xin Jin
- Laboratory of Experimental Cardiology, Department of Cardiovascular Sciences, KU Leuven, BE3000 Leuven, Belgium
| | - Karin Sipido
- Laboratory of Experimental Cardiology, Department of Cardiovascular Sciences, KU Leuven, BE3000 Leuven, Belgium
| | - H Llewelyn Roderick
- Laboratory of Experimental Cardiology, Department of Cardiovascular Sciences, KU Leuven, BE3000 Leuven, Belgium
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12
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Ladd D, Tilūnaitė A, Roderick HL, Soeller C, Crampin EJ, Rajagopal V. Assessing Cardiomyocyte Excitation-Contraction Coupling Site Detection From Live Cell Imaging Using a Structurally-Realistic Computational Model of Calcium Release. Front Physiol 2019; 10:1263. [PMID: 31632297 PMCID: PMC6783691 DOI: 10.3389/fphys.2019.01263] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2019] [Accepted: 09/17/2019] [Indexed: 01/11/2023] Open
Abstract
Calcium signaling plays a pivotal role in cardiomyocytes, coupling electrical excitation to mechanical contraction of the heart. Determining locations of active calcium release sites, and how their recruitment changes in response to stimuli and in disease states is therefore of central interest in cardiac physiology. Current algorithms for detecting release sites from live cell imaging data are however not easily validated against a known “ground truth,” which makes interpretation of the output of such algorithms, in particular the degree of confidence in site detection, a challenging task. Computational models are capable of integrating findings from multiple sources into a consistent, predictive framework. In cellular physiology, such models have the potential to reveal structure and function beyond the temporal and spatial resolution limitations of individual experimental measurements. Here, we create a spatially detailed computational model of calcium release in an eight sarcomere section of a ventricular cardiomyocyte, using electron tomography reconstruction of cardiac ultrastructure and confocal imaging of protein localization. This provides a high-resolution model of calcium diffusion from intracellular stores, which can be used as a platform to simulate confocal fluorescence imaging in the context of known ground truth structures from the higher resolution model. We use this capability to evaluate the performance of a recently proposed method for detecting the functional response of calcium release sites in live cells. Model permutations reveal how calcium release site density and mitochondria acting as diffusion barriers impact the detection performance of the algorithm. We demonstrate that site density has the greatest impact on detection precision and recall, in particular affecting the effective detectable depth of sites in confocal data. Our findings provide guidance on how such detection algorithms may best be applied to experimental data and give insights into limitations when using two-dimensional microscopy images to analyse three-dimensional cellular structures.
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Affiliation(s)
- David Ladd
- Systems Biology Lab, Department of Biomedical Engineering, School of Mathematics and Statistics, University of Melbourne, Melbourne, VIC, Australia.,ARC Centre of Excellence in Convergent Bio-Nano Science and Technology, School of Chemical and Biomedical Engineering, University of Melbourne, Melbourne, VIC, Australia.,Cell Structure and Mechanobiology Group, Department of Biomedical Engineering, University of Melbourne, Melbourne, VIC, Australia
| | - Agnė Tilūnaitė
- Systems Biology Lab, Department of Biomedical Engineering, School of Mathematics and Statistics, University of Melbourne, Melbourne, VIC, Australia
| | - H Llewelyn Roderick
- Laboratory of Experimental Cardiology, Department of Cardiovascular Sciences, KU Leuven, Leuven, Belgium
| | - Christian Soeller
- Living Systems Institute, University of Exeter, Exeter, United Kingdom
| | - Edmund J Crampin
- Systems Biology Lab, Department of Biomedical Engineering, School of Mathematics and Statistics, University of Melbourne, Melbourne, VIC, Australia.,ARC Centre of Excellence in Convergent Bio-Nano Science and Technology, School of Chemical and Biomedical Engineering, University of Melbourne, Melbourne, VIC, Australia
| | - Vijay Rajagopal
- Cell Structure and Mechanobiology Group, Department of Biomedical Engineering, University of Melbourne, Melbourne, VIC, Australia
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13
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Ronchi C, Badone B, Bernardi J, Zaza A. Action Potential Prolongation, β-Adrenergic Stimulation, and Angiotensin II as Co-factors in Sarcoplasmic Reticulum Instability. Front Physiol 2019; 9:1893. [PMID: 30687114 PMCID: PMC6333690 DOI: 10.3389/fphys.2018.01893] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2018] [Accepted: 12/14/2018] [Indexed: 12/26/2022] Open
Abstract
Introduction: Increases in action potential duration (APD), genetic or acquired, and arrhythmias are often associated; nonetheless, the relationship between the two phenomena is inconstant, suggesting coexisting factors. β-adrenergic activation increases sarcoplasmic reticulum (SR) Ca2+-content; angiotensin II (ATII) may increase cytosolic Ca2+ and ROS production, all actions stimulating RyRs opening. Here we test how APD interacts with β-adrenergic and AT-receptor stimulation in facilitating spontaneous Ca2+ release events (SCR). Methods: Under “action potential (AP) clamp”, guinea-pig cardiomyocytes (CMs) were driven with long (200 ms), normal (150 ms), and short (100 ms) AP waveforms at a CL of 500 ms; in a subset of CMs, all the 3 waveforms could be tested within the same cell. SCR were detected as inward current transients (ITI) following repolarization; ITI incidence and repetition within the same cycle were measured under increasing isoprenaline concentration ([ISO]) alone, or plus 100 nM ATII (30 min incubation+superfusion). Results: ITI incidence and repetition increased with [ISO]; at longer APs the [ISO]-response curve was shifted upward and ITI coupling interval was reduced. ATII increased ITI incidence more at low [ISO] and under normal (as compared to long) APs. Efficacy of AP shortening in suppressing ITI decreased in ATII-treated myocytes and at higher [ISO]. Conclusions: AP prolongation sensitized the SR to the destabilizing actions of ISO and ATII. Summation of ISO, ATII and AP duration effects had a “saturating” effect on SCR incidence, thus suggesting convergence on a common factor (RyRs stability) “reset” by the occurrence of spontaneous Ca2+ release events.
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Affiliation(s)
- Carlotta Ronchi
- Laboratory of Cardiac Cellular Physiology, Department of Biotechnology and Bioscience, University of Milano-Bicocca, Milan, Italy
| | - Beatrice Badone
- Laboratory of Cardiac Cellular Physiology, Department of Biotechnology and Bioscience, University of Milano-Bicocca, Milan, Italy
| | - Joyce Bernardi
- Laboratory of Cardiac Cellular Physiology, Department of Biotechnology and Bioscience, University of Milano-Bicocca, Milan, Italy
| | - Antonio Zaza
- Laboratory of Cardiac Cellular Physiology, Department of Biotechnology and Bioscience, University of Milano-Bicocca, Milan, Italy
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14
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Illaste A, Wullschleger M, Fernandez-Tenorio M, Niggli E, Egger M. Automatic Detection and Classification of Ca 2+ Release Events in Line- and Frame-Scan Images. Biophys J 2018; 116:383-394. [PMID: 30638961 DOI: 10.1016/j.bpj.2018.12.013] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2018] [Revised: 11/27/2018] [Accepted: 12/12/2018] [Indexed: 10/27/2022] Open
Abstract
Analysis of Ca2+ signals obtained in various cell types (i.e., cardiomyocytes) is always a tradeoff between acquisition speed and signal/noise ratio of the fluorescence signal. This becomes especially apparent during fast two- or three-dimensional confocal imaging when local intracellular fluorescence signals originating from Ca2+ release from intracellular Ca2+ stores (e.g., sarcoplasmic reticulum) need to be examined. Mathematical methods have been developed to remedy a high noise level by fitting each pixel with a transient function to "denoise" the image. So far, current available analytical approaches have been impaired by a number of constraints (e.g., inability to fit local, concurrent, and consecutive events) and the limited ability to customize implementation. Here, we suggest a, to our knowledge, novel approach for detailed analysis of subcellular micro-Ca2+ events based on pixel-by-pixel denoising of confocal frame- and line-scan images. The algorithm enables spatiotemporally overlapping events (e.g., a Ca2+ spark occurring during the decaying phase of a Ca2+ wave) to be extracted so that various types of Ca2+ events can be detected at a pixel time level of precision. The method allows a nonconstant baseline to be estimated for each pixel, foregoing the need to subtract fluorescence background or apply self-ratio methods before image analysis. Furthermore, by using a clustering algorithm, identified single-pixel events are grouped into "physiologically relevant" Ca2+ signaling events spanning multiple pixels (sparks, waves, puffs, transients, etc.), from which spatiotemporal event parameters (e.g., full duration at half maximal amplitude, full width at half maximal amplitude, amplitude, wave speed, rise, and decay times) can be easily extracted. The method was implemented with cross-platform open source software, providing a comprehensive and easy-to-use graphical user interface enabling rapid line-scan images and rapid frame-scan image sequences (up to 150 frames/s) to be analyzed and repetitive Ca2+ events (Ca2+ sparks and Ca2+ puffs) originating from clusters of Ca2+ release channels located in the sarcoplasmic reticulum membrane (ryanodine receptors and inositol 1,4,5-trisphosphate receptors) of isolated cardiomyocytes to be examined with a high level of precision.
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Affiliation(s)
- Ardo Illaste
- Department of Physiology, University of Bern, Bern, Switzerland
| | | | | | - Ernst Niggli
- Department of Physiology, University of Bern, Bern, Switzerland.
| | - Marcel Egger
- Department of Physiology, University of Bern, Bern, Switzerland.
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15
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Vagos M, van Herck IGM, Sundnes J, Arevalo HJ, Edwards AG, Koivumäki JT. Computational Modeling of Electrophysiology and Pharmacotherapy of Atrial Fibrillation: Recent Advances and Future Challenges. Front Physiol 2018; 9:1221. [PMID: 30233399 PMCID: PMC6131668 DOI: 10.3389/fphys.2018.01221] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2018] [Accepted: 08/13/2018] [Indexed: 12/19/2022] Open
Abstract
The pathophysiology of atrial fibrillation (AF) is broad, with components related to the unique and diverse cellular electrophysiology of atrial myocytes, structural complexity, and heterogeneity of atrial tissue, and pronounced disease-associated remodeling of both cells and tissue. A major challenge for rational design of AF therapy, particularly pharmacotherapy, is integrating these multiscale characteristics to identify approaches that are both efficacious and independent of ventricular contraindications. Computational modeling has long been touted as a basis for achieving such integration in a rapid, economical, and scalable manner. However, computational pipelines for AF-specific drug screening are in their infancy, and while the field is progressing quite rapidly, major challenges remain before computational approaches can fill the role of workhorse in rational design of AF pharmacotherapies. In this review, we briefly detail the unique aspects of AF pathophysiology that determine requirements for compounds targeting AF rhythm control, with emphasis on delimiting mechanisms that promote AF triggers from those providing substrate or supporting reentry. We then describe modeling approaches that have been used to assess the outcomes of drugs acting on established AF targets, as well as on novel promising targets including the ultra-rapidly activating delayed rectifier potassium current, the acetylcholine-activated potassium current and the small conductance calcium-activated potassium channel. Finally, we describe how heterogeneity and variability are being incorporated into AF-specific models, and how these approaches are yielding novel insights into the basic physiology of disease, as well as aiding identification of the important molecular players in the complex AF etiology.
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Affiliation(s)
- Márcia Vagos
- Computational Physiology Department, Simula Research Laboratory, Lysaker, Norway
- Department of Informatics, University of Oslo, Oslo, Norway
| | - Ilsbeth G. M. van Herck
- Computational Physiology Department, Simula Research Laboratory, Lysaker, Norway
- Department of Informatics, University of Oslo, Oslo, Norway
| | - Joakim Sundnes
- Computational Physiology Department, Simula Research Laboratory, Lysaker, Norway
- Center for Cardiological Innovation, Oslo, Norway
| | - Hermenegild J. Arevalo
- Computational Physiology Department, Simula Research Laboratory, Lysaker, Norway
- Center for Cardiological Innovation, Oslo, Norway
| | - Andrew G. Edwards
- Computational Physiology Department, Simula Research Laboratory, Lysaker, Norway
- Center for Cardiological Innovation, Oslo, Norway
| | - Jussi T. Koivumäki
- BioMediTech Institute and Faculty of Biomedical Sciences and Engineering, Tampere University of Technology, Tampere, Finland
- A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland
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16
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Blanch i Salvador J, Egger M. Obstruction of ventricular Ca 2+ -dependent arrhythmogenicity by inositol 1,4,5-trisphosphate-triggered sarcoplasmic reticulum Ca 2+ release. J Physiol 2018; 596:4323-4340. [PMID: 30004117 PMCID: PMC6138286 DOI: 10.1113/jp276319] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2018] [Accepted: 07/06/2018] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Augmented inositol 1,4,5-trisphosphate (IP3 ) receptor (IP3 R2) expression has been linked to a variety of cardiac pathologies. Although cardiac IP3 R2 function has been in the focus of research for some time, a detailed understanding of its potential role in ventricular myocyte excitation-contraction coupling under pathophysiological conditions remains elusive. The present study focuses on mechanisms of IP3 R2-mediated sarcoplasmic reticulum (SR)-Ca2+ release in ventricular excitation-contraction coupling under IP3 R2-overexpressing conditions by studying intracellular Ca2+ events. We report that, upon IP3 R2 overexpression in ventricular myocytes, IP3 -induced Ca2+ release (IP3 ICR) modulates the SR-Ca2+ content via "eventless" SR-Ca2+ release, affecting the global SR-Ca2+ leak. Thus, IP3 R2 activation could act as a SR-Ca2+ gateway mechanism to escape ominous SR-Ca2+ overload. Our approach unmasks a so far unrecognized mechanism by which "eventless" IP3 ICR plays a protective role against ventricular Ca2+ -dependent arrhythmogenicity. ABSTRACT Augmented inositol 1,4,5-trisphosphate (IP3 ) receptor (IP3 R2) function has been linked to a variety of cardiac pathologies including cardiac arrhythmias. The functional role of IP3 -induced Ca2+ release (IP3 ICR) within ventricular excitation-contraction coupling (ECC) remains elusive. As part of pathophysiological cellular remodelling, IP3 R2s are overexpressed and have been repeatedly linked to enhanced Ca2+ -dependent arrhythmogenicity. In this study we test the hypothesis that an opposite scenario might be plausible in which IP3 ICR is part of an ECC protecting mechanism, resulting in a Ca2+ -dependent anti-arrhythmogenic response on the cellular scale. IP3 R2 activation was triggered via endothelin-1 or IP3 -salt application in single ventricular myocytes from a cardiac-specific IP3 R type 2 overexpressing mouse model. Upon IP3 R2 overexpression, IP3 R activation reduced Ca2+ -wave occurrence (46 vs. 21.72%; P < 0.001) while its block increased SR-Ca2+ content (∼29.4% 2-aminoethoxydiphenyl borate, ∼16.4% xestospongin C; P < 0.001), suggesting an active role of IP3 ICR in SR-Ca2+ content regulation and anti-arrhythmogenic function. Pharmacological separation of ryanodine receptor RyR2 and IP3 R2 functions and two-dimensional Ca2+ event analysis failed to identify local IP3 ICR events (Ca2+ puffs). SR-Ca2+ leak measurements revealed that under pathophysiological conditions, "eventless" SR-Ca2+ efflux via enhanced IP3 ICR maintains the SR-Ca2+ content below Ca2+ spark threshold, preventing aberrant SR-Ca2+ release and resulting in a protective mechanism against SR-Ca2+ overload and arrhythmias. Our results support a so far unrecognized modulatory mechanism in ventricular myocytes working in an anti-arrhythmogenic fashion.
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Affiliation(s)
| | - Marcel Egger
- Department of PhysiologyUniversity of BernBuehlplatz 5CH‐3012BernSwitzerland
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17
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Dixon RE. The anti-arrhythmic drIP 3 from a leaky SR. J Physiol 2018; 596:4291-4293. [PMID: 30047612 DOI: 10.1113/jp276793] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Affiliation(s)
- Rose E Dixon
- Department of Physiology & Membrane Biology, University of California Davis, Davis, CA, 95616, USA
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18
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Smyrnias I, Goodwin N, Wachten D, Skogestad J, Aronsen JM, Robinson EL, Demydenko K, Segonds-Pichon A, Oxley D, Sadayappan S, Sipido K, Bootman MD, Roderick HL. Contractile responses to endothelin-1 are regulated by PKC phosphorylation of cardiac myosin binding protein-C in rat ventricular myocytes. J Mol Cell Cardiol 2018; 117:1-18. [DOI: 10.1016/j.yjmcc.2018.02.012] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/21/2014] [Revised: 02/02/2018] [Accepted: 02/16/2018] [Indexed: 01/07/2023]
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