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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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Knighten JM, Aziz T, Pleshinger DJ, Annamdevula N, Rich TC, Taylor MS, Andrews JF, Macarilla CT, Francis CM. Algorithm for biological second messenger analysis with dynamic regions of interest. PLoS One 2023; 18:e0284394. [PMID: 37167308 PMCID: PMC10174521 DOI: 10.1371/journal.pone.0284394] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2022] [Accepted: 03/29/2023] [Indexed: 05/13/2023] Open
Abstract
Physiological function is regulated through cellular communication that is facilitated by multiple signaling molecules such as second messengers. Analysis of signal dynamics obtained from cell and tissue imaging is difficult because of intricate spatially and temporally distinct signals. Signal analysis tools based on static region of interest analysis may under- or overestimate signals in relation to region of interest size and location. Therefore, we developed an algorithm for biological signal detection and analysis based on dynamic regions of interest, where time-dependent polygonal regions of interest are automatically assigned to the changing perimeter of detected and segmented signals. This approach allows signal profiles to be rigorously and precisely tracked over time, eliminating the signal distortion observed with static methods. Integration of our approach with state-of-the-art image processing and particle tracking pipelines enabled the isolation of dynamic cellular signaling events and characterization of biological signaling patterns with distinct combinations of parameters including amplitude, duration, and spatial spread. Our algorithm was validated using synthetically generated datasets and compared with other available methods. Application of the algorithm to volumetric time-lapse hyperspectral images of cyclic adenosine monophosphate measurements in rat microvascular endothelial cells revealed distinct signal heterogeneity with respect to cell depth, confirming the utility of our approach for analysis of 5-dimensional data. In human tibial arteries, our approach allowed the identification of distinct calcium signal patterns associated with atherosclerosis. Our algorithm for automated detection and analysis of second messenger signals enables the decoding of signaling patterns in diverse tissues and identification of pathologic cellular responses.
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Affiliation(s)
- Jennifer M Knighten
- Department of Physiology and Cell Biology, University of South Alabama College of Medicine, Mobile, Alabama, United States of America
| | - Takreem Aziz
- Department of Physiology and Cell Biology, University of South Alabama College of Medicine, Mobile, Alabama, United States of America
| | - Donald J Pleshinger
- Department of Pharmacology, University of South Alabama College of Medicine, Mobile, Alabama, United States of America
| | - Naga Annamdevula
- Department of Pharmacology, University of South Alabama College of Medicine, Mobile, Alabama, United States of America
| | - Thomas C Rich
- Department of Pharmacology, University of South Alabama College of Medicine, Mobile, Alabama, United States of America
- Center for Lung Biology, University of South Alabama College of Medicine, Mobile, Alabama, United States of America
| | - Mark S Taylor
- Department of Physiology and Cell Biology, University of South Alabama College of Medicine, Mobile, Alabama, United States of America
| | - Joel F Andrews
- Bioimaging Core Facility, University of South Alabama College of Medicine, Mobile, Alabama, United States of America
| | - Christian T Macarilla
- Department of Physiology and Cell Biology, University of South Alabama College of Medicine, Mobile, Alabama, United States of America
| | - C Michael Francis
- Department of Physiology and Cell Biology, University of South Alabama College of Medicine, Mobile, Alabama, United States of America
- Center for Lung Biology, University of South Alabama College of Medicine, Mobile, Alabama, United States of America
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3
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Glucose and NAADP trigger elementary intracellular β-cell Ca 2+ signals. Sci Rep 2021; 11:10714. [PMID: 34021189 PMCID: PMC8140081 DOI: 10.1038/s41598-021-88906-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2020] [Accepted: 04/15/2021] [Indexed: 11/12/2022] Open
Abstract
Pancreatic β-cells release insulin upon a rise in blood glucose. The precise mechanisms of stimulus-secretion coupling, and its failure in Diabetes Mellitus Type 2, remain to be elucidated. The consensus model, as well as a class of currently prescribed anti-diabetic drugs, are based around the observation that glucose-evoked ATP production in β-cells leads to closure of cell membrane ATP-gated potassium (KATP) channels, plasma membrane depolarisation, Ca2+ influx, and finally the exocytosis of insulin granules. However, it has been demonstrated by the inactivation of this pathway using genetic and pharmacological means that closure of the KATP channel alone may not be sufficient to explain all β-cell responses to glucose elevation. We have previously proposed that NAADP-evoked Ca2+ release is an important step in stimulus-secretion coupling in pancreatic β-cells. Here we show using total internal reflection fluorescence (TIRF) microscopy that glucose as well as the Ca2+ mobilising messenger nicotinic acid adenine dinucleotide phosphate (NAADP), known to operate in β-cells, lead to highly localised elementary intracellular Ca2+ signals. These were found to be obscured by measurements of global Ca2+ signals and the action of powerful SERCA-based sequestration mechanisms at the endoplasmic reticulum (ER). Building on our previous work demonstrating that NAADP-evoked Ca2+ release is an important step in stimulus-secretion coupling in pancreatic β-cells, we provide here the first demonstration of elementary Ca2+ signals in response to NAADP, whose occurrence was previously suspected. Optical quantal analysis of these events reveals a unitary event amplitude equivalent to that of known elementary Ca2+ signalling events, inositol trisphosphate (IP3) receptor mediated blips, and ryanodine receptor mediated quarks. We propose that a mechanism based on these highly localised intracellular Ca2+ signalling events mediated by NAADP may initially operate in β-cells when they respond to elevations in blood glucose.
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4
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Cserne Szappanos H, Vincze J, Bodnár D, Dienes B, Schneider MF, Csernoch L, Szentesi P. High Time Resolution Analysis of Voltage-Dependent and Voltage-Independent Calcium Sparks in Frog Skeletal Muscle Fibers. Front Physiol 2020; 11:599822. [PMID: 33384612 PMCID: PMC7769825 DOI: 10.3389/fphys.2020.599822] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Accepted: 11/25/2020] [Indexed: 11/29/2022] Open
Abstract
In amphibian skeletal muscle calcium (Ca2+) sparks occur both as voltage-dependent and voltage-independent ligand-activated release events. However, whether their properties and their origin show similarities are still in debate. Elevated K+, constant Cl- content solutions were used to initiate small depolarizations of the resting membrane potential to activate dihydropyridine receptors (DHPR) and caffeine to open ryanodine receptors (RyR) on intact fibers. The properties of Ca2+ sparks observed under control conditions were compared to those measured on depolarized cells and those after caffeine treatment. Calcium sparks were recorded on intact frog skeletal muscle fibers using high time resolution confocal microscopy (x-y scan: 30 Hz). Sparks were elicited by 1 mmol/l caffeine or subthreshold depolarization to different membrane potentials. Both treatments increased the frequency of sparks and altered their morphology. Images were analyzed by custom-made computer programs. Both the amplitude (in ΔF/F0; 0.259 ± 0.001 vs. 0.164 ± 0.001; n = 24942 and 43326, respectively; mean ± SE, p < 0.001) and the full width at half maximum (FWHM, in μm; parallel with fiber axis: 2.34 ± 0.01 vs. 1.92 ± 0.01, p < 0.001; perpendicular to fiber axis: 2.08 ± 0.01 vs. 1.68 ± 0.01, p < 0.001) of sparks was significantly greater after caffeine treatment than on depolarized cells. 9.8% of the sparks detected on depolarized fibers and about one third of the caffeine activated sparks (29.7%) overlapped with another one on the previous frame on x-y scans. Centre of overlapping sparks travelled significantly longer distances between consecutive frames after caffeine treatment then after depolarization (in μm; 1.66 ± 0.01 vs. 0.95 ± 0.01, p < 0.001). Our results suggest that the two types of ryanodine receptors, the junctional RyRs controlled by DHPRs and the parajunctional RyRs are activated independently, using alternate ways, with the possibility of cooperation between neighboring release channels.
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Affiliation(s)
- Henrietta Cserne Szappanos
- Department of Biochemistry and Molecular Biology, School of Medicine, University of Maryland, Baltimore, Baltimore, MD, United States
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - János Vincze
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Dóra Bodnár
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Beatrix Dienes
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Martin F. Schneider
- Department of Biochemistry and Molecular Biology, School of Medicine, University of Maryland, Baltimore, Baltimore, MD, United States
| | - László Csernoch
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Péter Szentesi
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
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5
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Shah SI, Ong HL, Demuro A, Ullah G. PunctaSpecks: A tool for automated detection, tracking, and analysis of multiple types of fluorescently labeled biomolecules. Cell Calcium 2020; 89:102224. [PMID: 32502904 PMCID: PMC7343294 DOI: 10.1016/j.ceca.2020.102224] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Revised: 05/12/2020] [Accepted: 05/21/2020] [Indexed: 01/21/2023]
Abstract
Recent advances in imaging technology and fluorescent probes have made it possible to gain information about the dynamics of subcellular processes at unprecedented spatiotemporal scales. Unfortunately, a lack of automated tools to efficiently process the resulting imaging data encoding fine details of the biological processes remains a major bottleneck in utilizing the full potential of these powerful experimental techniques. Here we present a computational tool, called PunctaSpecks, that can characterize fluorescence signals arising from a wide range of biological molecules under normal and pathological conditions. Among other things, the program can calculate the number, areas, life-times, and amplitudes of fluorescence signals arising from multiple sources, track diffusing fluorescence sources like moving mitochondria, and determine the overlap probability of two processes or organelles imaged using indicator dyes of different colors. We have tested PunctaSpecks on synthetic time-lapse movies containing mobile fluorescence objects of various sizes, mimicking the activity of biomolecules. The robustness of the software is tested by varying the level of noise along with random but known pattern of appearing, disappearing, and movement of these objects. Next, we use PunctaSpecks to characterize protein-protein interaction involved in store-operated Ca2+ entry through the formation and activation of plasma membrane-bound ORAI1 channel and endoplasmic reticulum membrane-bound stromal interaction molecule (STIM), the evolution of inositol 1,4,5-trisphosphate (IP3)-induced Ca2+ signals from sub-micrometer size local events into global waves in human cortical neurons, and the activity of Alzheimer's disease-associated β amyloid pores in the plasma membrane. The tool can also be used to study other dynamical processes imaged through fluorescence molecules. The open source algorithm allows for extending the program to analyze more than two types of biomolecules visualized using markers of different colors.
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Affiliation(s)
| | - Hwei Ling Ong
- Secretory Physiology Section, NIDCR, NIH, Bethesda, MD, 20892,USA
| | - Angelo Demuro
- Department of Neurobiology and Behavior, University of California, Irvine, CA 92697, USA
| | - Ghanim Ullah
- Department of Physics, University of South Florida, Tampa, FL 33647, USA.
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6
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Tian Q, Schröder L, Schwarz Y, Flockerzi A, Kaestner L, Zeug A, Bruns D, Lipp P. Large scale, unbiased analysis of elementary calcium signaling events in cardiac myocytes. J Mol Cell Cardiol 2019; 135:79-89. [DOI: 10.1016/j.yjmcc.2019.08.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/16/2019] [Revised: 07/26/2019] [Accepted: 08/12/2019] [Indexed: 12/12/2022]
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7
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Shah SI, Smith M, Swaminathan D, Parker I, Ullah G, Demuro A. CellSpecks: A Software for Automated Detection and Analysis of Calcium Channels in Live Cells. Biophys J 2018; 115:2141-2151. [PMID: 30447989 DOI: 10.1016/j.bpj.2018.10.015] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2018] [Revised: 09/27/2018] [Accepted: 10/22/2018] [Indexed: 02/01/2023] Open
Abstract
To couple the fidelity of patch-clamp recording with a more high-throughput screening capability, we pioneered a, to our knowledge, novel approach to single-channel recording that we named "optical patch clamp." By using highly sensitive fluorescent Ca2+ indicator dyes in conjunction with total internal fluorescence microscopy techniques, we monitor Ca2+ flux through individual Ca2+-permeable channels. This approach provides information about channel gating analogous to patch-clamp recording at a time resolution of ∼2 ms with the additional advantage of being massively parallel, providing simultaneous and independent recording from thousands of channels in the native environment. However, manual analysis of the data generated by this technique presents severe challenges because a video recording can include many thousands of frames. To overcome this bottleneck, we developed an image processing and analysis framework called CellSpecks capable of detecting and fully analyzing the kinetics of ion channels within a video sequence. By using randomly generated synthetic data, we tested the ability of CellSpecks to rapidly and efficiently detect and analyze the activity of thousands of ion channels, including openings for a few milliseconds. Here, we report the use of CellSpecks for the analysis of experimental data acquired by imaging muscle nicotinic acetylcholine receptors and the Alzheimer's disease-associated amyloid β pores with multiconductance levels in the plasma membrane of Xenopus laevis oocytes. We show that CellSpecks can accurately and efficiently generate location maps and create raw and processed fluorescence time traces; histograms of mean open times, mean close times, open probabilities, durations, and maximal amplitudes; and a "channel chip" showing the activity of all channels as a function of time. Although we specifically illustrate the application of CellSpecks for analyzing data from Ca2+ channels, it can be easily customized to analyze other spatially and temporally localized signals.
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Affiliation(s)
| | | | - Divya Swaminathan
- Department of Neurobiology and Behavior,University of California Irvine, Irvine, California
| | - Ian Parker
- Department of Neurobiology and Behavior,University of California Irvine, Irvine, California; Department of Physiology and Biophysics, University of California Irvine, Irvine, California
| | - Ghanim Ullah
- Department of Physics, University of South Florida, Tampa, Florida.
| | - Angelo Demuro
- Department of Neurobiology and Behavior,University of California Irvine, Irvine, California.
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8
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Fowler ED, Drinkhill MJ, Norman R, Pervolaraki E, Stones R, Steer E, Benoist D, Steele DS, Calaghan SC, White E. Beta1-adrenoceptor antagonist, metoprolol attenuates cardiac myocyte Ca 2+ handling dysfunction in rats with pulmonary artery hypertension. J Mol Cell Cardiol 2018; 120:74-83. [PMID: 29807024 PMCID: PMC6013283 DOI: 10.1016/j.yjmcc.2018.05.015] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/04/2018] [Accepted: 05/22/2018] [Indexed: 01/13/2023]
Abstract
Right heart failure is the major cause of death in Pulmonary Artery Hypertension (PAH) patients but is not a current, specific therapeutic target. Pre-clinical studies have shown that adrenoceptor blockade can improve cardiac function but the mechanisms of action within right ventricular (RV) myocytes are unknown. We tested whether the β1-adrenoceptor blocker metoprolol could improve RV myocyte function in an animal model of PAH, by attenuating adverse excitation-contraction coupling remodeling. PAH with RV failure was induced in rats by monocrotaline injection. When PAH was established, animals were given 10 mg/kg/day metoprolol (MCT + BB) or vehicle (MCT). The median time to the onset of heart failure signs was delayed from 23 days (MCT), to 31 days (MCT + BB). At 23 ± 1 days post-injection, MCT + BB showed improved in vivo cardiac function, measured by echocardiography. RV hypertrophy was reduced despite persistent elevated afterload. RV myocyte contractility during field stimulation was improved at higher pacing frequencies in MCT + BB. Preserved t-tubule structure, more uniform evoked Ca2+ release, increased SERCA2a expression and faster ventricular repolarization (measured in vivo by telemetry) may account for the improved contractile function. Sarcoplasmic reticulum Ca2+ overload was prevented in MCT + BB myocytes resulting in fewer spontaneous Ca2+ waves, with a lower pro-arrhythmic potential. Our novel finding of attenuation of defects in excitation contraction coupling by β1-adrenoceptor blockade with delays in the onset of HF, identifies the RV as a promising therapeutic target in PAH. Moreover, our data suggest existing therapies for left ventricular failure may also be beneficial in PAH induced RV failure.
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Affiliation(s)
- Ewan D Fowler
- Multidisciplinary Cardiovascular Research Centre, University of Leeds, Leeds, UK; School of Physiology, Pharmacology and Neuroscience, Faculty of Biomedical Sciences, University of Bristol, Bristol, UK
| | - Mark J Drinkhill
- Multidisciplinary Cardiovascular Research Centre, University of Leeds, Leeds, UK
| | - Ruth Norman
- Multidisciplinary Cardiovascular Research Centre, University of Leeds, Leeds, UK
| | | | - Rachel Stones
- Multidisciplinary Cardiovascular Research Centre, University of Leeds, Leeds, UK
| | - Emma Steer
- Multidisciplinary Cardiovascular Research Centre, University of Leeds, Leeds, UK
| | - David Benoist
- Multidisciplinary Cardiovascular Research Centre, University of Leeds, Leeds, UK; L'institut de rythmologie et modélisation cardiaque, Inserm U-1045, Université de Bordeaux, Bordeaux, France
| | - Derek S Steele
- Multidisciplinary Cardiovascular Research Centre, University of Leeds, Leeds, UK
| | - Sarah C Calaghan
- Multidisciplinary Cardiovascular Research Centre, University of Leeds, Leeds, UK
| | - Ed White
- Multidisciplinary Cardiovascular Research Centre, University of Leeds, Leeds, UK.
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9
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Galice S, Xie Y, Yang Y, Sato D, Bers DM. Size Matters: Ryanodine Receptor Cluster Size Affects Arrhythmogenic Sarcoplasmic Reticulum Calcium Release. J Am Heart Assoc 2018; 7:e008724. [PMID: 29929992 PMCID: PMC6064922 DOI: 10.1161/jaha.118.008724] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/15/2018] [Accepted: 05/16/2018] [Indexed: 11/19/2022]
Abstract
BACKGROUND Ryanodine receptors (RyR) mediate sarcoplasmic reticulum calcium (Ca2+) release and influence myocyte Ca2+ homeostasis and arrhythmias. In cardiac myocytes, RyRs are found in clusters of various sizes and shapes, and RyR cluster size may critically influence normal and arrhythmogenic Ca2+ spark and wave formation. However, the actual RyR cluster sizes at specific Ca2+ spark sites have never been measured in the physiological setting. METHODS AND RESULTS Here we measured RyR cluster size and Ca2+ sparks simultaneously to assess how RyR cluster size influences Ca2+ sparks and sarcoplasmic reticulum Ca2+ leak. For small RyR cluster sizes (<50), Ca2+ spark frequency is very low but then increases dramatically at larger cluster sizes. In contrast, Ca2+ spark amplitude is nearly maximal even at relatively small RyR cluster size (≈10) and changes little at larger cluster size. These properties agreed with computational simulations of RyR gating within clusters. CONCLUSIONS Our study explains how this combination of properties may limit arrhythmogenic Ca2+ sparks and wave propagation (at many junctions) while preserving the efficacy and spatial synchronization of Ca2+-induced Ca2+-release during normal excitation-contraction coupling. However, variations in RyR cluster size among individual junctions and RyR sensitivity could exacerbate heterogeneity of local sarcoplasmic reticulum Ca2+ release and arrhythmogenesis under pathological conditions.
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Affiliation(s)
- Samuel Galice
- Department of Pharmacology, University of California Davis, Davis, CA
| | - Yuanfang Xie
- Department of Pharmacology, University of California Davis, Davis, CA
| | - Yi Yang
- Department of Pharmacology, University of California Davis, Davis, CA
| | - Daisuke Sato
- Department of Pharmacology, University of California Davis, Davis, CA
| | - Donald M Bers
- Department of Pharmacology, University of California Davis, Davis, CA
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10
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Nieves-Cintrón M, Syed AU, Buonarati OR, Rigor RR, Nystoriak MA, Ghosh D, Sasse KC, Ward SM, Santana LF, Hell JW, Navedo MF. Impaired BK Ca channel function in native vascular smooth muscle from humans with type 2 diabetes. Sci Rep 2017; 7:14058. [PMID: 29070899 PMCID: PMC5656614 DOI: 10.1038/s41598-017-14565-9] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2017] [Accepted: 10/11/2017] [Indexed: 01/04/2023] Open
Abstract
Large-conductance Ca2+-activated potassium (BKCa) channels are key determinants of vascular smooth muscle excitability. Impaired BKCa channel function through remodeling of BKCa β1 expression and function contributes to vascular complications in animal models of diabetes. Yet, whether similar alterations occur in native vascular smooth muscle from humans with type 2 diabetes is unclear. In this study, we evaluated BKCa function in vascular smooth muscle from small resistance adipose arteries of non-diabetic and clinically diagnosed type 2 diabetic patients. We found that BKCa channel activity opposes pressure-induced constriction in human small resistance adipose arteries, and this is compromised in arteries from diabetic patients. Consistent with impairment of BKCa channel function, the amplitude and frequency of spontaneous BKCa currents, but not Ca2+ sparks were lower in cells from diabetic patients. BKCa channels in diabetic cells exhibited reduced Ca2+ sensitivity, single-channel open probability and tamoxifen sensitivity. These effects were associated with decreased functional coupling between BKCa α and β1 subunits, but no change in total protein abundance. Overall, results suggest impairment in BKCa channel function in vascular smooth muscle from diabetic patients through unique mechanisms, which may contribute to vascular complications in humans with type 2 diabetes.
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Affiliation(s)
| | - Arsalan U Syed
- Department of Pharmacology, University of California, Davis, CA, 95616, USA
| | - Olivia R Buonarati
- Department of Pharmacology, University of California, Davis, CA, 95616, USA
| | - Robert R Rigor
- Department of Pharmacology, University of California, Davis, CA, 95616, USA
| | - Matthew A Nystoriak
- Diabetes and Obesity Center, Department of Medicine, University of Louisville, Louisville, KY, 40202, USA
| | - Debapriya Ghosh
- Department of Pharmacology, University of California, Davis, CA, 95616, USA
| | | | - Sean M Ward
- Department of Physiology and Cell Biology, University of Nevada, Reno School of Medicine, Reno, NV, 89557, USA
| | - Luis F Santana
- Department of Physiology & Membrane Biology, University of California, Davis, CA, 95616, USA
| | - Johannes W Hell
- Department of Pharmacology, University of California, Davis, CA, 95616, USA
| | - Manuel F Navedo
- Department of Pharmacology, University of California, Davis, CA, 95616, USA.
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11
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Wullschleger M, Blanch J, Egger M. Functional local crosstalk of inositol 1,4,5-trisphosphate receptor- and ryanodine receptor-dependent Ca2+ release in atrial cardiomyocytes. Cardiovasc Res 2017; 113:542-552. [PMID: 28158491 DOI: 10.1093/cvr/cvx020] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/01/2016] [Accepted: 01/31/2017] [Indexed: 11/12/2022] Open
Abstract
Aims Enhanced inositol 1,4,5-trisphosphate receptor (InsP3R2) expression has been associated with a variety of proarrhythmogenic cardiac disorders. The functional interaction between the two major Ca2+ release mechanisms in cardiomyocytes, Ca2+ release mediated by ryanodine receptors (RyR2s) and InsP3-induced intracellular Ca2+ release (IP3ICR) remains enigmatic. We aimed at identifying characterizing local IP3ICR events, and elucidating functional local crosstalk mechanisms between cardiac InsP3R2s and RyR2s under conditions of enhanced cardiac specific InsP3R2 activity. Methods and results Using confocal imaging and two-dimensional spark analysis, we demonstrate in atrial myocytes (mouse model cardiac specific overexpressing InsP3R2s) that local Ca2+ release through InsP3Rs (Ca2+ puff) directly activates RyRs and triggers elementary Ca2+ release events (Ca2+ sparks). In the presence of increased intracellular InsP3 concentrations IP3ICR can modulate RyRs openings and Ca2+ spark probability. We show as well that IP3ICR remains under local control of Ca2+ release through RyRs. Conclusions Our results support the concept of bidirectional interaction between RyRs and InsP3Rs (i.e. Ca2+ sparks and Ca2+ puffs) in atrial myocytes. We conclude that highly efficient InsP3 dependent SR-Ca2+ flux constitute the main mechanism of functional crosstalk between InsP3Rs and RyRs resulting in more Ca2+ sensitized RyRs to trigger subsequent Ca2+-induced Ca2+ release activation. In this way, bidirectional local interaction of both SR-Ca2+ release channels may contribute to the shaping of global Ca2+ transients and thereby to contractility in cardiac myocytes.
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MESH Headings
- Animals
- Calcium Signaling/drug effects
- Electric Stimulation
- Endothelin-1/pharmacology
- Heart Atria/metabolism
- Image Processing, Computer-Assisted
- Inositol 1,4,5-Trisphosphate/metabolism
- Inositol 1,4,5-Trisphosphate Receptors/drug effects
- Inositol 1,4,5-Trisphosphate Receptors/genetics
- Inositol 1,4,5-Trisphosphate Receptors/metabolism
- Mice, Inbred C57BL
- Mice, Transgenic
- Microscopy, Confocal
- Myocardial Contraction
- Myocytes, Cardiac/drug effects
- Myocytes, Cardiac/metabolism
- Phenotype
- Receptor Cross-Talk/drug effects
- Ryanodine Receptor Calcium Release Channel/drug effects
- Ryanodine Receptor Calcium Release Channel/metabolism
- Sarcoplasmic Reticulum/metabolism
- Time Factors
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12
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Maltsev AV, Maltsev VA, Stern MD. Stabilization of diastolic calcium signal via calcium pump regulation of complex local calcium releases and transient decay in a computational model of cardiac pacemaker cell with individual release channels. PLoS Comput Biol 2017; 13:e1005675. [PMID: 28792496 PMCID: PMC5562330 DOI: 10.1371/journal.pcbi.1005675] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Revised: 08/18/2017] [Accepted: 07/06/2017] [Indexed: 11/18/2022] Open
Abstract
Intracellular Local Ca releases (LCRs) from sarcoplasmic reticulum (SR) regulate cardiac pacemaker cell function by activation of electrogenic Na/Ca exchanger (NCX) during diastole. Prior studies demonstrated the existence of powerful compensatory mechanisms of LCR regulation via a complex local cross-talk of Ca pump, release and NCX. One major obstacle to study these mechanisms is that LCR exhibit complex Ca release propagation patterns (including merges and separations) that have not been characterized. Here we developed new terminology, classification, and computer algorithms for automatic detection of numerically simulated LCRs and examined LCR regulation by SR Ca pumping rate (Pup) that provides a major contribution to fight-or-flight response. In our simulations the faster SR Ca pumping accelerates action potential-induced Ca transient decay and quickly clears Ca under the cell membrane in diastole, preventing premature releases. Then the SR generates an earlier, more synchronized, and stronger diastolic LCR signal activating an earlier and larger inward NCX current. LCRs at higher Pup exhibit larger amplitudes and faster propagation with more collisions to each other. The LCRs overlap with Ca transient decay, causing an elevation of the average diastolic [Ca] nadir to ~200 nM (at Pup = 24 mM/s). Background Ca (in locations lacking LCRs) quickly decays to resting Ca levels (<100 nM) at high Pup, but remained elevated during slower decay at low Pup. Release propagation is facilitated at higher Pup by a larger LCR amplitude, whereas at low Pup by higher background Ca. While at low Pup LCRs show smaller amplitudes, their larger durations and sizes combined with longer transient decay stabilize integrals of diastolic Ca and NCX current signals. Thus, the local interplay of SR Ca pump and release channels regulates LCRs and Ca transient decay to insure fail-safe pacemaker cell operation within a wide range of rates.
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Affiliation(s)
- Alexander V. Maltsev
- Laboratory of Cardiovascular Science, Intramural Research Program, National Institute on Aging, NIH, 251 Bayview Blvd., Baltimore, MD, United States of America
| | - Victor A. Maltsev
- Laboratory of Cardiovascular Science, Intramural Research Program, National Institute on Aging, NIH, 251 Bayview Blvd., Baltimore, MD, United States of America
| | - Michael D. Stern
- Laboratory of Cardiovascular Science, Intramural Research Program, National Institute on Aging, NIH, 251 Bayview Blvd., Baltimore, MD, United States of America
- * E-mail:
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13
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Davoodi M, Segal S, Kirschner Peretz N, Kamoun D, Yaniv Y. Semi-automated program for analysis of local Ca 2+ spark release with application for classification of heart cell type. Cell Calcium 2017; 64:83-90. [PMID: 28216082 DOI: 10.1016/j.ceca.2017.02.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2017] [Revised: 02/07/2017] [Accepted: 02/07/2017] [Indexed: 01/30/2023]
Abstract
Local Ca2+ spark releases are essential to the Ca2+ cycling process. Thus, they play an important role in ventricular and atrial cell contraction, as well as in sinoatrial cell automaticity. Characterizing their properties in healthy cells from different regions in the heart can reveal the basic biophysical differences among these regions. We designed a semi-automatic Matlab Graphical User Interface (called Sparkalyzer) to characterize parameters of Ca2+ spark release from any major cardiac tissue, as recorded in line-scan mode with a confocal laser-scanning microscope. We validated the algorithm on experimental images from rabbit sinoatrial, atrial, and ventricular cells loaded with Fluo-4 AM. The program characterizes general image parameters of Ca2+ transients and sparks: spark duration, which indicates for how long the spark provides Ca2+ to the closed intracellular mechanisms (typical value: 25±1, 23±1, 26±1ms for sinoatrial, atrial, and ventricular cells, respectively); spark amplitude, which indicates the amount of Ca2+ released by a single spark (1.6±0.1, 1.6±0.2, 1.4±0.1F/F0 for sinoatrial, atrial, and ventricular cells, respectively); spark length, which is the length of the Ca2+ wavelets fired out of a row of ryanodine receptors (5±0.1, 5±0.2, 3.4±0.3μm for sinoatrial, atrial, or ventricular cells, respectively) and number of sparks (0.14±0.02, 0.025±0.01, 0.02±0.01 for 1μm in 1s for sinoatrial, atrial, and ventricular cells, respectively). This method is reliable for Ca2+ spark analysis of sinoatrial, atrial, or ventricular cells. Moreover, by examining the average value of Ca2+ spark characteristics and their scattering around the mean, atrial, ventricular and sinoatrial cells can be differentiated.
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Affiliation(s)
- Moran Davoodi
- Biomedical Engineering Faculty, Technion-IIT, Haifa, Israel
| | - Sofia Segal
- Biomedical Engineering Faculty, Technion-IIT, Haifa, Israel
| | | | - David Kamoun
- Biomedical Engineering Faculty, Technion-IIT, Haifa, Israel
| | - Yael Yaniv
- Biomedical Engineering Faculty, Technion-IIT, Haifa, Israel.
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14
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Szymanska AF, Heylman C, Datta R, Gratton E, Nenadic Z. Automated detection and analysis of depolarization events in human cardiomyocytes using MaDEC. Comput Biol Med 2016; 75:109-17. [PMID: 27281718 DOI: 10.1016/j.compbiomed.2016.05.011] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2016] [Revised: 05/17/2016] [Accepted: 05/20/2016] [Indexed: 11/16/2022]
Abstract
Optical imaging-based methods for assessing the membrane electrophysiology of in vitro human cardiac cells allow for non-invasive temporal assessment of the effect of drugs and other stimuli. Automated methods for detecting and analyzing the depolarization events (DEs) in image-based data allow quantitative assessment of these different treatments. In this study, we use 2-photon microscopy of fluorescent voltage-sensitive dyes (VSDs) to capture the membrane voltage of actively beating human induced pluripotent stem cell-derived cardiomyocytes (hiPS-CMs). We built a custom and freely available Matlab software, called MaDEC, to detect, quantify, and compare DEs of hiPS-CMs treated with the β-adrenergic drugs, propranolol and isoproterenol. The efficacy of our software is quantified by comparing detection results against manual DE detection by expert analysts, and comparing DE analysis results to known drug-induced electrophysiological effects. The software accurately detected DEs with true positive rates of 98-100% and false positive rates of 1-2%, at signal-to-noise ratios (SNRs) of 5 and above. The MaDEC software was also able to distinguish control DEs from drug-treated DEs both immediately as well as 10min after drug administration.
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Affiliation(s)
- Agnieszka F Szymanska
- Department of Biomedical Engineering, University of California Irvine, Irvine, CA 92697, USA.
| | - Christopher Heylman
- Laboratory for Fluorescence Dynamics, Department of Biomedical Engineering, University of California Irvine, Irvine, CA 92697, USA
| | - Rupsa Datta
- Laboratory for Fluorescence Dynamics, Department of Biomedical Engineering, University of California Irvine, Irvine, CA 92697, USA
| | - Enrico Gratton
- Laboratory for Fluorescence Dynamics, Department of Biomedical Engineering, University of California Irvine, Irvine, CA 92697, USA
| | - Zoran Nenadic
- Department of Biomedical Engineering, University of California Irvine, Irvine, CA 92697, USA
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15
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Tang S, Reddish F, Zhuo Y, Yang JJ. Fast kinetics of calcium signaling and sensor design. Curr Opin Chem Biol 2015; 27:90-7. [PMID: 26151819 DOI: 10.1016/j.cbpa.2015.06.014] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2015] [Revised: 06/11/2015] [Accepted: 06/11/2015] [Indexed: 12/25/2022]
Abstract
Fast calcium signaling is regulated by numerous calcium channels exhibiting high spatiotemporal profiles which are currently measured by fluorescent calcium sensors. There is still a strong need to improve the kinetics of genetically encoded calcium indicators (sensors) to capture calcium dynamics in the millisecond time frame. In this review, we summarize several major fast calcium signaling pathways and discuss the recent developments and application of genetically encoded calcium indicators to detect these pathways. A new class of genetically encoded calcium indicators designed with site-directed mutagenesis on the surface of beta-barrel fluorescent proteins to form a pentagonal bipyramidal-like calcium binding domain dramatically accelerates calcium binding kinetics. Furthermore, novel genetically encoded calcium indicators with significantly increased fluorescent lifetime change are advantageous in deep-field imaging with high light-scattering and notable morphology change.
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Affiliation(s)
- Shen Tang
- Department of Chemistry, Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, GA 30303, United States
| | - Florence Reddish
- Department of Chemistry, Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, GA 30303, United States
| | - You Zhuo
- Department of Chemistry, Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, GA 30303, United States
| | - Jenny J Yang
- Department of Chemistry, Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, GA 30303, United States.
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16
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Ellefsen KL, Settle B, Parker I, Smith IF. An algorithm for automated detection, localization and measurement of local calcium signals from camera-based imaging. Cell Calcium 2014; 56:147-56. [PMID: 25047761 DOI: 10.1016/j.ceca.2014.06.003] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2014] [Revised: 06/10/2014] [Accepted: 06/15/2014] [Indexed: 10/25/2022]
Abstract
Local Ca(2+) transients such as puffs and sparks form the building blocks of cellular Ca(2+) signaling in numerous cell types. They have traditionally been studied by linescan confocal microscopy, but advances in TIRF microscopy together with improved electron-multiplied CCD (EMCCD) cameras now enable rapid (>500 frames s(-1)) imaging of subcellular Ca(2+) signals with high spatial resolution in two dimensions. This approach yields vastly more information (ca. 1 Gb min(-1)) than linescan imaging, rendering visual identification and analysis of local events imaged both laborious and subject to user bias. Here we describe a routine to rapidly automate identification and analysis of local Ca(2+) events. This features an intuitive graphical user-interfaces and runs under Matlab and the open-source Python software. The underlying algorithm features spatial and temporal noise filtering to reliably detect even small events in the presence of noisy and fluctuating baselines; localizes sites of Ca(2+) release with sub-pixel resolution; facilitates user review and editing of data; and outputs time-sequences of fluorescence ratio signals for identified event sites along with Excel-compatible tables listing amplitudes and kinetics of events.
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Affiliation(s)
- Kyle L Ellefsen
- Department of Neurobiology & Behavior, University of California, Irvine, CA 92697, USA
| | - Brett Settle
- Department of Neurobiology & Behavior, University of California, Irvine, CA 92697, USA
| | - Ian Parker
- Department of Neurobiology & Behavior, University of California, Irvine, CA 92697, USA; Department of Physiology & Biophysics, University of California, Irvine, CA 92697, USA
| | - Ian F Smith
- Department of Neurobiology & Behavior, University of California, Irvine, CA 92697, USA.
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17
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Jian Z, Han H, Zhang T, Puglisi J, Izu LT, Shaw JA, Onofiok E, Erickson JR, Chen YJ, Horvath B, Shimkunas R, Xiao W, Li Y, Pan T, Chan J, Banyasz T, Tardiff JC, Chiamvimonvat N, Bers DM, Lam KS, Chen-Izu Y. Mechanochemotransduction during cardiomyocyte contraction is mediated by localized nitric oxide signaling. Sci Signal 2014; 7:ra27. [PMID: 24643800 DOI: 10.1126/scisignal.2005046] [Citation(s) in RCA: 103] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Cardiomyocytes contract against a mechanical load during each heartbeat, and excessive mechanical stress leads to heart diseases. Using a cell-in-gel system that imposes an afterload during cardiomyocyte contraction, we found that nitric oxide synthase (NOS) was involved in transducing mechanical load to alter Ca(2+) dynamics. In mouse ventricular myocytes, afterload increased the systolic Ca(2+) transient, which enhanced contractility to counter mechanical load but also caused spontaneous Ca(2+) sparks during diastole that could be arrhythmogenic. The increases in the Ca(2+) transient and sparks were attributable to increased ryanodine receptor (RyR) sensitivity because the amount of Ca2(+) in the sarcoplasmic reticulum load was unchanged. Either pharmacological inhibition or genetic deletion of nNOS (or NOS1), but not of eNOS (or NOS3), prevented afterload-induced Ca2(+) sparks. This differential effect may arise from localized NO signaling, arising from the proximity of nNOS to RyR, as determined by super-resolution imaging. Ca(2+)-calmodulin-dependent protein kinase II (CaMKII) and nicotinamide adenine dinucleotide phosphate oxidase 2 (NOX2) also contributed to afterload-induced Ca(2+) sparks. Cardiomyocytes from a mouse model of familial hypertrophic cardiomyopathy exhibited enhanced mechanotransduction and frequent arrhythmogenic Ca(2+) sparks. Inhibiting nNOS and CaMKII, but not NOX2, in cardiomyocytes from this model eliminated the Ca2(+) sparks, suggesting mechanotransduction activated nNOS and CaMKII independently from NOX2. Thus, our data identify nNOS, CaMKII, and NOX2 as key mediators in mechanochemotransduction during cardiac contraction, which provides new therapeutic targets for treating mechanical stress-induced Ca(2+) dysregulation, arrhythmias, and cardiomyopathy.
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Affiliation(s)
- Zhong Jian
- 1Department of Pharmacology, University of California, Davis, Davis, CA 95616, USA
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18
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Steele EM, Steele DS. Automated detection and analysis of Ca(2+) sparks in x-y image stacks using a thresholding algorithm implemented within the open-source image analysis platform ImageJ. Biophys J 2014; 106:566-76. [PMID: 24507597 PMCID: PMC3944640 DOI: 10.1016/j.bpj.2013.12.040] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2013] [Revised: 11/28/2013] [Accepted: 12/23/2013] [Indexed: 11/25/2022] Open
Abstract
Previous studies have used analysis of Ca(2+) sparks extensively to investigate both normal and pathological Ca(2+) regulation in cardiac myocytes. The great majority of these studies used line-scan confocal imaging. In part, this is because the development of open-source software for automatic detection of Ca(2+) sparks in line-scan images has greatly simplified data analysis. A disadvantage of line-scan imaging is that data are collected from a single row of pixels, representing only a small fraction of the cell, and in many instances x-y confocal imaging is preferable. However, the limited availability of software for Ca(2+) spark analysis in two-dimensional x-y image stacks presents an obstacle to its wider application. This study describes the development and characterization of software to enable automatic detection and analysis of Ca(2+) sparks within x-y image stacks, implemented as a plugin within the open-source image analysis platform ImageJ. The program includes methods to enable precise identification of cells within confocal fluorescence images, compensation for changes in background fluorescence, and options that allow exclusion of events based on spatial characteristics.
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Affiliation(s)
- Elliot M Steele
- School of Biomedical Sciences, University of Leeds, Leeds, England
| | - Derek S Steele
- School of Biomedical Sciences, University of Leeds, Leeds, England.
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19
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Santiago DJ, Ríos E, Shannon TR. Isoproterenol increases the fraction of spark-dependent RyR-mediated leak in ventricular myocytes. Biophys J 2013; 104:976-85. [PMID: 23473480 DOI: 10.1016/j.bpj.2013.01.026] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2012] [Revised: 12/21/2012] [Accepted: 01/17/2013] [Indexed: 10/27/2022] Open
Abstract
Recent research suggests that the diastolic ryanodine-receptor-mediated release of Ca(2+) (J(leak)) from the sarcoplasmic reticulum of ventricular myocytes occurs in spark and nonspark forms. Further information about the role(s) of these release manifestations is scarce, however. This study addresses whether the fraction of spark-mediated J(leak) increases due to β-adrenergic stimulation. Confocal microscopy was used to simultaneously image Ca(2+) sparks and quantify J(leak) in intact rabbit myocytes, either in the absence or in the presence of 125 nM isoproterenol. It was found that isoproterenol treatment shifts the spark-frequency-J(leak) relationship toward an increased sensitivity to a [Ca(2+)] trigger. In agreement, a small but significant increase in spark width was found for cells with matched baseline [Ca(2+)] and total SR [Ca(2+)]. The reconstruction of release fluxes, when applied to the average sparks from those selected cells, yielded a wider release source in the isoproterenol event, indicating the recruitment of peripheral ryanodine receptors. Overall, the results presented here indicate that β-adrenergic stimulation increases the spark-dependent fraction of J(leak). Working together, the increased Ca(2+) sensitivity and the greater spark width found during isoproterenol treatment may increase the probability of Ca(2+) wave generation.
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Affiliation(s)
- Demetrio J Santiago
- Department of Molecular Biophysics & Physiology, Rush University, Chicago, Illinois, USA
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20
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Abstract
Ca(2+) waves were probably first observed in the early 1940s. Since then Ca(2+) waves have captured the attention of an eclectic mixture of mathematicians, neuroscientists, muscle physiologists, developmental biologists, and clinical cardiologists. This review discusses the current state of mathematical models of Ca(2+) waves, the normal physiological functions Ca(2+) waves might serve in cardiac cells, as well as how the spatial arrangement of Ca(2+) release channels shape Ca(2+) waves, and we introduce the idea of Ca(2+) phase waves that might provide a useful framework for understanding triggered arrhythmias.
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Affiliation(s)
- Leighton T Izu
- Department of Pharmacology, University of California, Davis, USA.
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21
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Yip KP, Sham JSK. Tracking stars: automated two-dimensional analysis of Ca²⁺ events. Focus on "Automated region of interest analysis of dynamic Ca²⁺ signals in image sequences". Am J Physiol Cell Physiol 2012; 303:C233-5. [PMID: 22648951 DOI: 10.1152/ajpcell.00178.2012] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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22
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Li K, Zhang W, Fang H, Xie W, Liu J, Zheng M, Wang X, Wang W, Tan W, Cheng H. Superoxide flashes reveal novel properties of mitochondrial reactive oxygen species excitability in cardiomyocytes. Biophys J 2012; 102:1011-21. [PMID: 22404923 DOI: 10.1016/j.bpj.2012.01.044] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2011] [Revised: 01/02/2012] [Accepted: 01/27/2012] [Indexed: 11/18/2022] Open
Abstract
Superoxide flash represents quantal and bursting production of mitochondrial reactive oxygen species (ROS) instigated by transient opening of the mitochondrial permeability transition pore (mPTP). Given their critical role in metabolism, ischemia-reperfusion injury, and apoptosis, characterization of flash properties would be valuable to further mechanistic and physiological studies of this newly discovered mitochondrial phenomenon. Here we developed the flash detector FlashSniper based on segmentation of two-dimensional feature maps extracted from time-lapse confocal image stacks, and on the theory for correcting optical distortion of flash-amplitude histograms. Through large-scale analysis of superoxide flashes in cardiomyocytes, we demonstrated uniform mitochondrial ROS excitability among subsarcolemmal and intermyofibrillar mitochondria, and exponential distribution of intervals between consecutive flash events. Flash ignition displayed three different patterns: an abrupt rise from quiescence (44%), a rise with an exponential foot (27%), or a rise occurring after a pedestal precursor (29%), closely resembling action-potential initiation in excitable cells. However, the optical blurring-corrected amplitudes of superoxide flashes were highly variable, as were their durations, indicating stochastic automaticity of single-mitochondrion ROS excitation. Simultaneous measurement of mitochondrial membrane potential revealed that graded, rather than all-or-none, depolarization mirrored the precursor and the primary peak of the flash. We propose that superoxide flash production is a regenerative process dominated by stochastic, autonomous recruitment of a limited number of units (e.g., mPTPs) in single mitochondria.
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Affiliation(s)
- Kaitao Li
- Institute of Molecular Medicine and State Key Laboratory of Biomembrane and Membrane Biotechnology, Center for Life Sciences, Peking University, Beijing, China
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23
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Porta M, Zima AV, Nani A, Diaz-Sylvester PL, Copello JA, Ramos-Franco J, Blatter LA, Fill M. Single ryanodine receptor channel basis of caffeine's action on Ca2+ sparks. Biophys J 2011; 100:931-8. [PMID: 21320437 DOI: 10.1016/j.bpj.2011.01.017] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2010] [Revised: 01/03/2011] [Accepted: 01/10/2011] [Indexed: 10/18/2022] Open
Abstract
Caffeine (1, 3, 7-trimethylxanthine) is a widely used pharmacological agonist of the cardiac ryanodine receptor (RyR2) Ca(2+) release channel. It is also a well-known stimulant that can produce adverse side effects, including arrhythmias. Here, the action of caffeine on single RyR2 channels in bilayers and Ca(2+) sparks in permeabilized ventricular cardiomyocytes is defined. Single RyR2 caffeine activation depended on the free Ca(2+) level on both sides of the channel. Cytosolic Ca(2+) enhanced RyR2 caffeine affinity, whereas luminal Ca(2+) essentially scaled maximal caffeine activation. Caffeine activated single RyR2 channels in diastolic quasi-cell-like solutions (cytosolic MgATP, pCa 7) with an EC(50) of 9.0 ± 0.4 mM. Low-dose caffeine (0.15 mM) increased Ca(2+) spark frequency ∼75% and single RyR2 opening frequency ∼150%. This implies that not all spontaneous RyR2 openings during diastole are associated with Ca(2+) sparks. Assuming that only the longest openings evoke sparks, our data suggest that a spark may result only when a spontaneous single RyR2 opening lasts >6 ms.
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Affiliation(s)
- Maura Porta
- Department of Physiology, Midwestern University, Downers Grove, Illinois, USA
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24
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Picht E, Zima AV, Shannon TR, Duncan AM, Blatter LA, Bers DM. Dynamic calcium movement inside cardiac sarcoplasmic reticulum during release. Circ Res 2011; 108:847-56. [PMID: 21311044 DOI: 10.1161/circresaha.111.240234] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
RATIONALE Intra-sarcoplasmic reticulum (SR) free [Ca] ([Ca](SR)) provides the driving force for SR Ca release and is a key regulator of SR Ca release channel gating during normal SR Ca release or arrhythmogenic spontaneous Ca release events. However, little is known about [Ca](SR) spatiotemporal dynamics. OBJECTIVE To directly measure local [Ca](SR) with subsarcomeric spatiotemporal resolution during both normal global SR Ca release and spontaneous Ca sparks and to evaluate the quantitative implications of spatial [Ca](SR) gradients. METHODS AND RESULTS Intact and permeabilized rabbit ventricular myocytes were subjected to direct simultaneous measurement of cytosolic [Ca] and [Ca](SR) and FRAP (fluorescence recovery after photobleach). We found no detectable [Ca](SR) gradients between SR release sites (junctional SR) and Ca uptake sites (free SR) during normal global Ca release, clear spatiotemporal [Ca](SR) gradients during isolated Ca blinks, faster intra-SR diffusion in the longitudinal versus transverse direction, 3- to 4-fold slower diffusion of fluorophores in the SR than in cytosol, and that intra-SR Ca diffusion varies locally, dependent on local SR connectivity. A computational model clarified why spatiotemporal gradients are more detectable in isolated local releases versus global releases and provides a quantitative framework for understanding intra-SR Ca diffusion. CONCLUSIONS Intra-SR Ca diffusion is rapid, limiting spatial [Ca](SR) gradients during excitation-contraction coupling. Spatiotemporal [Ca](SR) gradients are apparent during Ca sparks, and these observations constrain models of dynamic Ca movement inside the SR. This has important implications for myocyte SR Ca handling, synchrony, and potentially arrhythmogenic spontaneous contraction.
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Affiliation(s)
- Eckard Picht
- Department of Pharmacology, University of California-Davis, 451 Health Sciences Drive, Davis, CA 95616, USA
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25
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Hartman JM, Sobie EA, Smith GD. Spontaneous Ca2+ sparks and Ca2+ homeostasis in a minimal model of permeabilized ventricular myocytes. Am J Physiol Heart Circ Physiol 2010; 299:H1996-2008. [PMID: 20852058 DOI: 10.1152/ajpheart.00293.2010] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Many issues remain unresolved concerning how local, subcellular Ca(2+) signals interact with bulk cellular concentrations to maintain homeostasis in health and disease. To aid in the interpretation of data obtained in quiescent ventricular myocytes, we present here a minimal whole cell model that accounts for both localized (subcellular) and global (cellular) aspects of Ca(2+) signaling. Using a minimal formulation of the distribution of local [Ca(2+)] associated with a large number of Ca(2+)-release sites, the model simulates both random spontaneous Ca(2+) sparks and the changes in myoplasmic and sarcoplasmic reticulum (SR) [Ca(2+)] that result from the balance between stochastic release and reuptake into the SR. Ca(2+)-release sites are composed of clusters of two-state ryanodine receptors (RyRs) that exhibit activation by local cytosolic [Ca(2+)] but no inactivation or regulation by luminal Ca(2+). Decreasing RyR open probability in the model causes a decrease in aggregate release flux and an increase in SR [Ca(2+)], regardless of whether RyR inhibition is mediated by a decrease in RyR open dwell time or an increase in RyR closed dwell time. The same balance of stochastic release and reuptake can be achieved, however, by either high-frequency/short-duration or low-frequency/long-duration Ca(2+) sparks. The results are well correlated with recent experimental observations using pharmacological RyR inhibitors and clarify those aspects of the release-reuptake balance that are inherent to the coupling between local and global Ca(2+) signals and those aspects that depend on molecular-level details. The model of Ca(2+) sparks and homeostasis presented here can be a useful tool for understanding changes in cardiac Ca(2+ )release resulting from drugs, mutations, or acquired diseases.
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Affiliation(s)
- Jana M Hartman
- Department of Applied Science, The College of William and Mary, Williamsburg, Virginia 23187, USA
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26
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Jia Z, Bien H, Entcheva E. A sensitive algorithm for automatic detection of space-time alternating signals in cardiac tissue. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2009; 2008:153-6. [PMID: 19162616 DOI: 10.1109/iembs.2008.4649113] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Alternans, a beat-to-beat alternation in cardiac signals, may serve as a precursor to lethal cardiac arrhythmias, including ventricular tachycardia and ventricular fibrillation. Therefore, alternans is a desirable target of early arrhythmia prediction/detection. For long-term records and in the presence of noise, the definition of alternans is qualitative and ambiguous. This makes their automatic detection in large spatiotemporal data sets almost impossible. We present here a quantitative combinatorics-derived definition of alternans in the presence of random noise and a novel algorithm for automatic alternans detection using criteria like temporal persistence (TP), representative phase (RP) and alternans ratio (AR). This technique is validated by comparison to theoretically-derived probabilities and by test data sets with white noise. Finally, the algorithm is applied to ultra-high resolution optical mapping data from cultured cell monolayers, exhibiting calcium alternans. Early fine-scale alternans, close to the noise level, were revealed and linked to the later formation of larger regions and evolution of spatially discordant alternans (SDA). This robust new technique can be useful in quantification and better understanding of the onset of arrhythmias and in general analysis of space-time alternating signals.
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Affiliation(s)
- Zhiheng Jia
- Biomedical Engineering department, Stony Brook University, Stony Brook, NY 11794, USA.
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Soeller C, Jayasinghe ID, Li P, Holden AV, Cannell MB. Three-dimensional high-resolution imaging of cardiac proteins to construct models of intracellular Ca2+ signalling in rat ventricular myocytes. Exp Physiol 2009; 94:496-508. [PMID: 19139064 DOI: 10.1113/expphysiol.2008.043976] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Quantitative understanding of the Ca(2+) handling in cardiac ventricular myocytes requires accurate knowledge of cardiac ultrastructure and protein distribution. We have therefore developed high-resolution imaging and analysis approaches to measure the three-dimensional distribution of immunolabelled proteins with confocal microscopy. Labelling of single rat cardiac myocytes with an antibody to the Z-line marker alpha-actinin revealed a complex architecture of sarcomere misalignment across single cells. Double immunolabelling was used to relate the Z-line structure to the distribution of ryanodine receptors (RyRs, the intracellular Ca(2+) release channels) and the transverse tubular system. Both RyR and transverse tubular system distributions exhibited frequent dislocations from the simple planar geometry generally assumed in existing mathematical models. To investigate potential effects of these irregularities on Ca(2+) dynamics, we determined the three-dimensional distribution of RyR clusters within an extended section of a single rat ventricular myocyte to construct a model of stochastic Ca(2+) dynamics with a measured Ca(2+) release unit (CRU) distribution. Calculations with this model were compared with a second model in which all CRUs were placed on flat planes. The model with a realistic CRU distribution supported Ca(2+) waves that spread axially along the cell at velocities of approximately 50 mum s(-1). By contrast, in the model with planar CRU distribution the axial wave spread was slowed roughly twofold and wave propagation often nearly faltered. These results demonstrate that spatial features of the CRU distribution on multiple length scales may significantly affect intracellular Ca(2+) dynamics and must be captured in detailed mechanistic models to achieve quantitative as well as qualitative insight.
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Affiliation(s)
- Christian Soeller
- Department of Physiology, School of Medical Sciences, University of Auckland, Private Bag 92019, Auckland, New Zealand.
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Li P, Wei W, Cai X, Soeller C, Cannell MB, Holden AV. Evolution of Intracellular Ca2 + Waves from about 10,000 RyR Clusters: Towards Solving a Computationally Daunting Task. FUNCTIONAL IMAGING AND MODELING OF THE HEART 2009. [DOI: 10.1007/978-3-642-01932-6_2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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Abstract
The calcium ion (Ca(2+)) is the simplest and most versatile intracellular messenger known. The discovery of Ca(2+) sparks and a related family of elementary Ca(2+) signaling events has revealed fundamental principles of the Ca(2+) signaling system. A newly appreciated "digital" subsystem consisting of brief, high Ca(2+) concentration over short distances (nanometers to microns) comingles with an "analog" global Ca(2+) signaling subsystem. Over the past 15 years, much has been learned about the theoretical and practical aspects of spark formation and detection. The quest for the spark mechanisms [the activation, coordination, and termination of Ca(2+) release units (CRUs)] has met unexpected challenges, however, and raised vexing questions about CRU operation in situ. Ample evidence shows that Ca(2+) sparks catalyze many high-threshold Ca(2+) processes involved in cardiac and skeletal muscle excitation-contraction coupling, vascular tone regulation, membrane excitability, and neuronal secretion. Investigation of Ca(2+) sparks in diseases has also begun to provide novel insights into hypertension, cardiac arrhythmias, heart failure, and muscular dystrophy. An emerging view is that spatially and temporally patterned activation of the digital subsystem confers on intracellular Ca(2+) signaling an exquisite architecture in space, time, and intensity, which underpins signaling efficiency, stability, specificity, and diversity. These recent advances in "sparkology" thus promise to unify the simplicity and complexity of Ca(2+) signaling in biology.
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Affiliation(s)
- Heping Cheng
- Institute of Molecular Medicine, National Laboratory of Biomembrane and Membrane Biotechnology, Peking University, Beijing, China.
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Shirokova N, Niggli E. Studies of RyR function in situ. Methods 2008; 46:183-93. [PMID: 18848990 DOI: 10.1016/j.ymeth.2008.09.017] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2008] [Accepted: 09/12/2008] [Indexed: 10/21/2022] Open
Abstract
The ryanodine receptors (RyRs) are intracellular Ca2+ release channels of the sarcoplasmic reticulum (SR) involved in many cellular responses, including muscle excitation-contraction coupling. Multiple biochemical and biophysical methods are available to study RyR functions. However, most of them are somewhat limited because they can only be used to examine channels which are purified from the SR and no longer in their natural environment. In this review we discuss optical methods for studying RyR functions in situ. We describe several techniques for the investigation of local (microscopic) intracellular Ca2+ signals (a.k.a Ca2+ sparks) by means of confocal microscopy and flash photolysis of caged compounds. We discuss how these studies can and will continue to contribute to our understanding of RyR function in physiological and pathological conditions.
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Affiliation(s)
- Natalia Shirokova
- Department of Pharmacology & Physiology, UMDNJ-New Jersey Medical School, 185 South Orange Avenue, Newark, NJ 07103, USA.
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Increasing sensitivity of Ca2+ spark detection in noisy images by application of a matched-filter object detection algorithm. Biophys J 2008; 95:6016-24. [PMID: 18835890 DOI: 10.1529/biophysj.108.135251] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Microscopic calcium (Ca2+) events (such as Ca2+ sparks) are an important area for study, as they help clarify the mechanism(s) underlying intracellular signaling. In the heart, Ca2+ sparks occur as a result of Ca2+ release from the sarcoendoplasmic reticulum, via ryanodine receptor channels. Measurement of Ca2+ spark properties can provide valuable information about the control of ryanodine receptor channel gating in situ, but requires high spatiotemporal resolution imaging, which produces noisy datasets that are problematic for spark detection. Automated detection algorithms may overcome visual detection bias, but missed and false-positive events can distort the distribution of measured Ca2+ spark properties. We present a sensitive and reliable method for the automated detection of Ca2+ sparks in datasets obtained using confocal line-scanning or total internal reflection fluorescence microscopy. This matched-filter detection algorithm(MFDA) employs a user-defined object, chosen to mimic Ca2+ spark properties, and the experimental dataset is searched for instances of the object. Detection certainty is provided by nonparametric statistical testing. The supplied codes can also refine the search object on the basis of those detected to further increase detection sensitivity. In comparison to a commonly used, intensity-thresholding algorithm, the MFDA is more sensitive and reliable, particularly at low signal/noise ratios. The MFDA can also be easily adapted to other signal-detection problems in noisy datasets.
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Abstract
Ca(2+) sparks arise from the stochastic opening of spatially discrete clusters of ryanodine receptors called a Ca(2+) release unit (CRU). If the RyR clusters were not spatially separated, then Ca(2+) released from one RyR would immediately diffuse to its neighbor and lead to uncontrolled, runaway Ca(2+) release throughout the cell. While physical separation provides some isolation from neighbors, CRUs are not incommunicado. When inter-neighbor interactions become large enough, Ca(2+) waves spontaneously emerge. A more circumscribed interaction shows up in high-speed two-dimensional confocal images as jumping Ca(2+) sparks that seem to be sequentially activated along the Z-line and across Z-lines. However, since Ca(2+) sparks are stochastic events how can we tell whether two sparks occurring close together in space and time are causally related or appeared simply by coincidence? Here we develop a mathematical method to disentangle cause and coincidence in a statistical sense. From our analysis we derive three fundamental properties of Ca(2+) spark generation: 1), the "intrinsic" spark frequency, the spark frequency one would observe if the CRUs were incommunicado; 2), the coupling strength, which measures how strongly one CRU affects another; and 3), the range over which the communication occurs. These parameters allow us to measure the effect RyR regulators have on the intrinsic activity of CRUs and on the coupling between them.
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Affiliation(s)
- Leighton T Izu
- Department of Internal Medicine, University of Kentucky College of Medicine, Lexington, Kentucky, USA.
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