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Chen YL, Baker TM, Lee F, Shui B, Lee JC, Tvrdik P, Kotlikoff MI, Sonkusare SK. Calcium Signal Profiles in Vascular Endothelium from Cdh5-GCaMP8 and Cx40-GCaMP2 Mice. J Vasc Res 2021; 58:159-171. [PMID: 33706307 PMCID: PMC8102377 DOI: 10.1159/000514210] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2020] [Accepted: 12/23/2020] [Indexed: 01/04/2023] Open
Abstract
INTRODUCTION Studies in Cx40-GCaMP2 mice, which express calcium biosensor GCaMP2 in the endothelium under connexin 40 promoter, have identified the unique properties of endothelial calcium signals. However, Cx40-GCaMP2 mouse is associated with a narrow dynamic range and lack of signal in the venous endothelium. Recent studies have proposed many GCaMPs (GCaMP5/6/7/8) with improved properties although their performance in endothelium-specific calcium studies is not known. METHODS We characterized a newly developed mouse line that constitutively expresses GCaMP8 in the endothelium under the VE-cadherin (Cdh5-GCaMP8) promoter. Calcium signals through endothelial IP3 receptors and TRP vanilloid 4 (TRPV4) ion channels were recorded in mesenteric arteries (MAs) and veins from Cdh5-GCaMP8 and Cx40-GCaMP2 mice. RESULTS Cdh5-GCaMP8 mice showed lower baseline fluorescence intensity, higher dynamic range, and higher amplitudes of individual calcium signals than Cx40-GCaMP2 mice. Importantly, Cdh5-GCaMP8 mice enabled the first recordings of discrete calcium signals in the intact venous endothelium and revealed striking differences in IP3 receptor and TRPV4 channel calcium signals between MAs and mesenteric veins. CONCLUSION Our findings suggest that Cdh5-GCaMP8 mice represent significant improvements in dynamic range, sensitivity for low-intensity signals, and the ability to record calcium signals in venous endothelium.
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Affiliation(s)
- Yen Lin Chen
- Robert M. Berne Cardiovascular Research Center, University of Virginia, Charlottesville, Virginia, USA
| | - Thomas M Baker
- Robert M. Berne Cardiovascular Research Center, University of Virginia, Charlottesville, Virginia, USA
| | - Frank Lee
- Department of Biomedical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, New York, USA
| | - Bo Shui
- Department of Biomedical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, New York, USA
| | - Jane C Lee
- Department of Biomedical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, New York, USA
| | - Petr Tvrdik
- Departments of Neurosurgery and Neuroscience and Bioengineering, University of Virginia, Charlottesville, Virginia, USA
| | - Michael I Kotlikoff
- Department of Biomedical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, New York, USA
| | - Swapnil K Sonkusare
- Robert M. Berne Cardiovascular Research Center, University of Virginia, Charlottesville, Virginia, USA,
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, Virginia, USA,
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Taylor MS, Francis M. Decoding dynamic Ca(2+) signaling in the vascular endothelium. Front Physiol 2014; 5:447. [PMID: 25452732 PMCID: PMC4233915 DOI: 10.3389/fphys.2014.00447] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2014] [Accepted: 10/31/2014] [Indexed: 12/15/2022] Open
Abstract
Although acute and chronic vasoregulation is inherently driven by endothelial Ca(2+), control and targeting of Ca(2+)-dependent signals are poorly understood. Recent studies have revealed localized and dynamic endothelial Ca(2+) events comprising an intricate signaling network along the vascular intima. Discrete Ca(2+) transients emerging from both internal stores and plasmalemmal cation channels couple to specific membrane K(+) channels, promoting endothelial hyperpolarization and vasodilation. The spatiotemporal tuning of these signals, rather than global Ca(2+) elevation, appear to direct endothelial functions under physiologic conditions. In fact, altered patterns of dynamic Ca(2+) signaling may underlie essential endothelial dysfunction in a variety of cardiovascular diseases. Advances in imaging approaches and analyses in recent years have allowed for detailed detection, quantification, and evaluation of Ca(2+) dynamics in intact endothelium. Here, we discuss recent insights into these signals, including their sources of origination and their functional encoding. We also address key aspects of data acquisition and interpretation, including broad applications of automated high-content analysis.
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Affiliation(s)
- Mark S Taylor
- Department of Physiology, University of South Alabama College of Medicine Mobile, AL, USA
| | - Michael Francis
- Department of Pharmacology, University of South Alabama College of Medicine Mobile, AL, USA
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Taylor MS, Francis M, Qian X, Solodushko V. Dynamic Ca(2+) signal modalities in the vascular endothelium. Microcirculation 2012; 19:423-9. [PMID: 22443172 DOI: 10.1111/j.1549-8719.2012.00180.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The endothelium is vital to normal vasoregulation. Although acute vasodilation associated with broad endothelial Ca(2+) elevation is well known, the control and targeting of Ca(2+) -dependent signals in the endothelium are poorly understood. Recent studies have revealed localized IP(3) -motivated Ca(2+) events occurring basally along the intima that may provide the fundamental basis for various endothelial influences. Here, we provide an overview of dynamic endothelial Ca(2+) signals and discuss the potential role of these signals in constant endothelial control of arterial tone and the titration of functional responses in vivo. In particular, we focus on the functional architecture contributing to the properties and ultimate impact of these signals, and explore new avenues in evaluating their prevalence and specific modalities in intact tissue. Finally, we discuss spatial and temporal effector recruitment through modification of these inherent signals. It is suggested that endothelial Ca(2+) signaling is a continuum in which the specific framework of store-release components and cellular targets along the endothelium allows for differential modes of Ca(2+) signal expansion and distinctive profiles of effector recruitment. The precise composition and distribution of these inherent components may underlie dynamic endothelial control and specialized functions of different vascular beds.
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Affiliation(s)
- Mark S Taylor
- Department of Physiology, University of South Alabama College of Medicine, Mobile, Alabama 36688, USA.
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Yuen WW, Du NR, Shvartsman D, Arany PR, Lam H, Mooney DJ. Statistical platform to discern spatial and temporal coordination of endothelial sprouting. Integr Biol (Camb) 2012; 4:292-300. [PMID: 22318325 PMCID: PMC3654550 DOI: 10.1039/c2ib00057a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Many biological processes, including angiogenesis, involve intercellular feedback and temporal coordination, but inference of these relations is often drowned in low sample sizes or noisy population data. To address this issue, a methodology was developed to statistically study spatial lateral inhibition and temporal synchronization in one specific biological process, endothelial sprouting mediated by Notch signaling. Notch plays an essential role in the development of organized vasculature, but the effects of Notch on the temporal characteristics of angiogenesis are not well understood. Results from this study showed that Notch lateral inhibition operates at distances less than 31 μm. Furthermore, combining time lapse microscopy with an intraclass correlation model typically used to analyze family data showed intrinsic temporal synchronization among endothelial sprouts originating from the same microcarrier. Such synchronization was reduced with Notch inhibitors, but was enhanced with the addition of Notch ligands. These results indicate that Notch plays a critical role in the temporal regulation of angiogenesis, as well as spatial control, and this method of analysis will be of significant utility in studies of a variety of other biological processes.
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Affiliation(s)
- William W Yuen
- School of Engineering and Applied Sciences, Harvard University, Wyss Institute for Biologically Inspired Engineering, USA
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Thul R, Bellamy TC, Roderick HL, Bootman MD, Coombes S. Calcium oscillations. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2008; 641:1-27. [PMID: 18783168 DOI: 10.1007/978-0-387-09794-7_1] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Changes in cellular Ca2+ concentration control a wide range of physiological processes, from the subsecond release of synaptic neurotransmitters, to the regulation of gene expression over months or years. Ca2+ can also trigger cell death through both apoptosis and necrosis, and so the regulation of cellular Ca2+ concentration must be tightly controlled through the concerted action of pumps, channels and buffers that transport Ca2+ into and out of the cell cytoplasm. A hallmark of cellular Ca2+ signalling is its spatiotemporal complexity: stimulation of cells by a hormone or neurotransmitter leads to oscillations in cytoplasmic Ca2+ concentration that can vary markedly in time course, amplitude, frequency, and spatial range. In this chapter we review some of the biological roles of Ca2+, the experimental characterisation of complex dynamic changes in Ca2+ concentration, and attempts to explain this complexity using computational models. We consider the 'toolkit' of cellular proteins which influence Ca2+ concentrarion, describe mechanistic models of key elements of the toolkit, and fit these into the framework of whole cell models of Ca2+ oscillations and waves. Finally, we will touch on recent efforts to use stochastic modelling to elucidate elementary Ca2+ signal events, and how these may evolve into global signals.
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Affiliation(s)
- Ruediger Thul
- School of Mathematical Sciences, University of Nottingham, Nottingham, UK
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8
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Yamashita M. ‘Quantal’ Ca2+release reassessed - a clue to oscillation and synchronization. FEBS Lett 2006; 580:4979-83. [PMID: 16938295 DOI: 10.1016/j.febslet.2006.08.023] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2006] [Accepted: 08/14/2006] [Indexed: 11/26/2022]
Abstract
Ca(2+) release from intracellular Ca(2+) stores, a pivotal event in Ca(2+) signaling, is a 'quantal' process; it terminates after a rapid release of a fraction of stored Ca(2+). To explain the 'quantal' nature, 'all-or-none' model and 'steady-state' model were proposed. This article shortly reviews these hypotheses and considers a recently proposed mechanism, 'luminal potential' model, in which the membrane potential of Ca(2+) store regulates Ca(2+) efflux. By reassessing the 'quantal' nature, other important features of Ca(2+) signaling, oscillation and synchronization, are highlighted. The mechanism for 'quantal' Ca(2+) release may underlie the temporal and spatial control of Ca(2+) signaling.
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Affiliation(s)
- Masayuki Yamashita
- Department of Physiology I, Nara Medical University, Shijo-cho 840, Kashihara 634-8521, Japan.
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Stamatakis M, Mantzaris NV. Modeling of ATP-mediated signal transduction and wave propagation in astrocytic cellular networks. J Theor Biol 2006; 241:649-68. [PMID: 16460762 DOI: 10.1016/j.jtbi.2006.01.002] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2005] [Revised: 11/12/2005] [Accepted: 01/03/2006] [Indexed: 11/17/2022]
Abstract
Astrocytes, a special type of glial cells, were considered to have supporting role in information processing in the brain. However, several recent studies have shown that they can be chemically stimulated by neurotransmitters and use a form of signaling, in which ATP acts as an extracellular messenger. Pathological conditions, such as spreading depression, have been linked to abnormal range of wave propagation in astrocytic cellular networks. Nevertheless, the underlying intra- and inter-cellular signaling mechanisms remain unclear. Motivated by the above, we constructed a model to understand the relationship between single-cell signal transduction mechanisms and wave propagation and blocking in astrocytic networks. The model incorporates ATP-mediated IP3 production, the subsequent Ca2+ release from the ER through IP3R channels and ATP release into the extracellular space. For the latter, two hypotheses were tested: Ca2+- or IP3-dependent ATP release. In the first case, single astrocytes can exhibit excitable behavior and frequency-encoded oscillations. Homogeneous, one-dimensional astrocytic networks can propagate waves with infinite range, while in two dimensions, spiral waves can be generated. However, in the IP3-dependent ATP release case, the specific coupling of the driver ATP-IP3 system with the driven Ca2+ subsystem leads to one- and two-dimensional wave patterns with finite range of propagation.
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Affiliation(s)
- Michail Stamatakis
- Department of Chemical and Biomolecular Engineering, Rice University, Houston, TX 77005, USA
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Mauban JRH, Wilkinson K, Schach C, Yuan JXJ. Histamine-mediated increases in cytosolic [Ca2+] involve different mechanisms in human pulmonary artery smooth muscle and endothelial cells. Am J Physiol Cell Physiol 2005; 290:C325-36. [PMID: 16162658 PMCID: PMC1351365 DOI: 10.1152/ajpcell.00236.2005] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Agonist stimulation of human pulmonary artery smooth muscle cells (PASMC) and endothelial cells (PAEC) with histamine showed similar spatiotemporal patterns of Ca(2+) release. Both sustained elevation and oscillatory patterns of changes in cytosolic Ca(2+) concentration ([Ca(2+)](cyt)) were observed in the absence of extracellular Ca(2+). Capacitative Ca(2+) entry (CCE) was induced in PASMC and PAEC by passive depletion of intracellular Ca(2+) stores with 10 microM cyclopiazonic acid (CPA; 15-30 min). The pyrazole derivative BTP2 inhibited CPA-activated Ca(2+) influx, suggesting that depletion of CPA-sensitive internal stores is sufficient to induce CCE in both PASMC and PAEC. The recourse of histamine-mediated Ca(2+) release was examined after exposure of cells to CPA, thapsigargin, caffeine, ryanodine, FCCP, or bafilomycin. In PASMC bathed in Ca(2+)-free solution, treatment with CPA almost abolished histamine-induced rises in [Ca(2+)](cyt). In PAEC bathed in Ca(2+)-free solution, however, treatment with CPA eliminated histamine-induced sustained and oscillatory rises in [Ca(2+)](cyt) but did not affect initial transient increase in [Ca(2+)](cyt). Furthermore, treatment of PAEC with a combination of CPA (or thapsigargin) and caffeine (and ryanodine), FCCP, or bafilomycin did not abolish histamine-induced transient [Ca(2+)](cyt) increases. These observations indicate that 1) depletion of CPA-sensitive stores is sufficient to cause CCE in both PASMC and PAEC; 2) induction of CCE in PAEC does not require depletion of all internal Ca(2+) stores; 3) the histamine-releasable internal stores in PASMC are mainly CPA-sensitive stores; 4) PAEC, in addition to a CPA-sensitive functional pool, contain other stores insensitive to CPA, thapsigargin, caffeine, ryanodine, FCCP, and bafilomycin; and 5) although the CPA-insensitive stores in PAEC may not contribute to CCE, they contribute to histamine-mediated Ca(2+) release.
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Affiliation(s)
- Joseph R H Mauban
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, and Biomedical Sciences Graduate Program, University of California, San Diego, La Jolla 92093-0725, USA
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11
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Liang W, Buluc M, van Breemen C, Wang X. Vectorial Ca2+ release via ryanodine receptors contributes to Ca2+ extrusion from freshly isolated rabbit aortic endothelial cells. Cell Calcium 2005; 36:431-43. [PMID: 15451626 DOI: 10.1016/j.ceca.2004.04.003] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2004] [Revised: 04/06/2004] [Accepted: 04/07/2004] [Indexed: 11/19/2022]
Abstract
In this study, we identified ryanodine receptors (RyRs) as a component of a cytosolic Ca(2+) removal pathway in freshly isolated rabbit aortic endothelial cells. In an earlier article, we reported that the sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA) and Na(+)/Ca(2+) exchanger (NCX) function in series to extrude cytosolic Ca(2+) to the extracellular space. Here we employed caffeine and ryanodine as modulators of RyR and showed that they act as the linkage between SERCA and NCX in removing Ca(2+) from the cytoplasm. Our data indicate that both 15 mM caffeine and 1 microM ryanodine facilitated Ca(2+) extrusion by activating RyRs while 100 microM ryanodine had the opposite effect by blocking RyRs. A further attempt to investigate RyR pharmacology revealed that in the absence of extracellular Ca(2+), ryanodine at 1 microM, but not 100 microM, stimulated Ca(2+) loss from the endoplasmic reticulum (ER). Blockade of RyR had no effect on the Ca(2+) removal rate when NCX had been previously blocked. In addition, the localization of RyR was determined using confocal microscopy of BODIPY TR-X fluorescent staining. Taken together, our findings suggest that in freshly isolated endothelial cells Ca(2+) is removed in part by transport through SERCA, RyR, and eventually NCX, and that RyR and NCX are in close functional proximity near the plasma membrane. After blockade of this component, Ca(2+) extrusion could be further inhibited by carboxyeosin, indicating a parallel contribution by the plasmalemmal Ca(2+)-ATPase (PMCA).
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Affiliation(s)
- Willmann Liang
- Department of Pharmacology and Therapeutics, The James Hogg iCAPTURE Centre for Cardiovascular and Pulmonary Research, St. Paul's Hospital, University of British Columbia, Vancouver, BC V6Z 1Y6, Canada
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12
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Abstract
Endothelial cells (EC) form a unique signal-transducing surface in the vascular system. The abundance of ion channels in the plasma membrane of these nonexcitable cells has raised questions about their functional role. This review presents evidence for the involvement of ion channels in endothelial cell functions controlled by intracellular Ca(2+) signals, such as the production and release of many vasoactive factors, e.g., nitric oxide and PGI(2). In addition, ion channels may be involved in the regulation of the traffic of macromolecules by endocytosis, transcytosis, the biosynthetic-secretory pathway, and exocytosis, e.g., tissue factor pathway inhibitor, von Willebrand factor, and tissue plasminogen activator. Ion channels are also involved in controlling intercellular permeability, EC proliferation, and angiogenesis. These functions are supported or triggered via ion channels, which either provide Ca(2+)-entry pathways or stabilize the driving force for Ca(2+) influx through these pathways. These Ca(2+)-entry pathways comprise agonist-activated nonselective Ca(2+)-permeable cation channels, cyclic nucleotide-activated nonselective cation channels, and store-operated Ca(2+) channels or capacitative Ca(2+) entry. At least some of these channels appear to be expressed by genes of the trp family. The driving force for Ca(2+) entry is mainly controlled by large-conductance Ca(2+)-dependent BK(Ca) channels (slo), inwardly rectifying K(+) channels (Kir2.1), and at least two types of Cl( -) channels, i.e., the Ca(2+)-activated Cl(-) channel and the housekeeping, volume-regulated anion channel (VRAC). In addition to their essential function in Ca(2+) signaling, VRAC channels are multifunctional, operate as a transport pathway for amino acids and organic osmolytes, and are possibly involved in endothelial cell proliferation and angiogenesis. Finally, we have also highlighted the role of ion channels as mechanosensors in EC. Plasmalemmal ion channels may signal rapid changes in hemodynamic forces, such as shear stress and biaxial tensile stress, but also changes in cell shape and cell volume to the cytoskeleton and the intracellular machinery for metabolite traffic and gene expression.
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Affiliation(s)
- B Nilius
- Department of Physiology, KU Leuven, Campus Gasthuisberg, Leuven, Belgium.
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Avdonin P, Ryan US, Hayes B. Receptor-dependent regulation of [Ca2+]i and phospholipase C in vascular endothelial cells. J Recept Signal Transduct Res 2000; 20:235-54. [PMID: 11192020 DOI: 10.3109/10799890009150646] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Affiliation(s)
- P Avdonin
- Institute of Experimental Cardiology, Cardiology Research Center, Moscow, Russia
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Røttingen J, Iversen JG. Ruled by waves? Intracellular and intercellular calcium signalling. ACTA PHYSIOLOGICA SCANDINAVICA 2000; 169:203-19. [PMID: 10886035 DOI: 10.1046/j.1365-201x.2000.00732.x] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The field of calcium signalling has evolved rapidly the last 20 years. Physiologists had worked with cytosolic Ca2+ as the coupler of excitation and contraction of muscles and as a secretory signal in exocrine glands and in the synapses of the brain for several decades before the discovery of cellular calcium as a second messenger. Development of powerful techniques for measuring the concentration of cytosolic free calcium ions in cell suspensions and later in single cells and even in different cellular compartments, has resulted in an upsurge in the knowledge of the cellular machinery involved in intracellular calcium signalling. However, the focus on intracellular mechanisms might have led this field of study away from physiology. During the last few years there is an increasing evidence for an important role of calcium also as an intercellular signal. Via gap junctions calcium is able to co-ordinate cell populations and even organs like the liver. Here we will give an overview of the general mechanisms of intracellular calcium signalling, and then review the recent data on intercellular calcium signals. A functional coupling of cells in different tissues and organs by the way of calcium might be an important mechanism for controlling and synchronizing physiological responses
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Affiliation(s)
- J Røttingen
- Laboratory of Intracellular Signalling, Department of Physiology, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
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Shimamura K, Sekiguchi F, Sunano S. Tension oscillation in arteries and its abnormality in hypertensive animals. Clin Exp Pharmacol Physiol 1999; 26:275-84. [PMID: 10225137 DOI: 10.1046/j.1440-1681.1999.03030.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
1. The mechanisms of oscillatory contraction of arterial smooth muscle in vitro are discussed. 2. The membrane potential and cytoplasmic free Ca2+ concentration in smooth muscle cells oscillate in the presence of agonists. 3. The oscillatory change in the membrane potential of smooth muscle cells is related to Ca2+ release from intracellular stores. 4. Gap junctions between smooth muscle cells play important roles in the synchronized oscillation of the cytoplasmic free Ca2+ concentration in this population of cells. 5. Endothelial cells may increase or decrease the tension oscillation of smooth muscle cells. 6. In arteries from hypertensive rats, an increase in membrane excitability and the number of gap junctions between smooth muscle cells and impaired endothelial function are the main factors responsible for the modulation of tension oscillation.
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Affiliation(s)
- K Shimamura
- Research Institute of Hypertension, Kinki University, Osaka, Japan.
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Shi B, Isseroff RR. Intracellular calcium oscillations in cell populations of ras-transfected I-7 subline of human HaCaT keratinocytes. J Invest Dermatol 1997; 109:765-9. [PMID: 9406818 DOI: 10.1111/1523-1747.ep12340777] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
We have observed oscillations of intracellular Ca2+ (Ca[i]) concentration in populations of ras-transfected HaCaT keratinocytes of I-7 subline. In postconfluent monolayers of I-7 keratinocytes, an increase in extracellular Ca2+ (Ca[o]) concentration to 0.25-0.5 mM induced sinusoidal Ca(i) oscillations, which persisted longer than 1 h with amplitudes of 50-150 nM and periods of 5-10 min. Thapsigargin, which depletes internal Ca2+ stores, did not prevent Ca(o)-induced Ca(i) oscillations, and it also induced Ca(i) oscillations in the ras-transfected I-7 line. Removal of extracellular Ca2+ or addition of Ca2+-entry blocker La3+ or SK&F 96365 inhibited Ca(i) oscillations, suggesting that Ca(i) oscillations in ras-transfected HaCaT keratinocytes were dependent on Ca2+ influx across the plasma membrane. Because the Ca(o)-induced Ca(i) oscillations have been observed only in ras-transfected I-7 subline and not in its nontransfected parental HaCaT line, this may provide a partial explanation for the divergent responses of ras-transfected and nontransfected keratinocytes to Ca(o) signal for control of growth and differentiation.
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Affiliation(s)
- B Shi
- Department of Dermatology, University of California Davis School of Medicine, 95616, USA
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de Roos AD, Willems PH, Peters PH, van Zoelen EJ, Theuvenet AP. Synchronized calcium spiking resulting from spontaneous calcium action potentials in monolayers of NRK fibroblasts. Cell Calcium 1997; 22:195-207. [PMID: 9330790 DOI: 10.1016/s0143-4160(97)90013-0] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The correlation between the intracellular Ca2+ concentration ([Ca2+]i) and membrane potential in monolayers of density-arrested normal rat kidney (NRK) fibroblasts was investigated. Using the fluorescent probe Fura-2, spontaneous repetitive spike-like increases in [Ca2+]i (Ca2+ spikes) were observed that were synchronised throughout the entire monolayer. Ca2+ spikes disappeared in Ca(2+)-free solutions and could be blocked by the L-type Ca2+ channel antagonist felodipine. Simultaneous measurements of [Ca2+]i and membrane potential showed that these Ca2+ spikes were paralleled by depolarisations of the plasma membrane. Using patch clamp measurements, action potential-like depolarisations consisting of a fast spike depolarisation followed by a plateau phase were seen with similar kinetics as the Ca2+ spikes. The action potentials could be blocked by L-type Ca2+ channel blockers and were dependent on extracellular Ca2+. The plateau phase was predominantly determined by a Cl- conductance and was dependent on intracellular Ca2+. The presence of voltage-dependent L-type Ca2+ channels in NRK cells was confirmed by patch clamp measurements in single cells. It is concluded that monolayers of density-arrested NRK fibroblasts exhibit spontaneous Ca2+ action potentials leading to synchronised Ca2+ spiking. This excitability of monolayers of fibroblasts may represent a novel Ca2+ signaling pathway in electrically coupled fibroblasts, cells that were hitherto considered to be inexcitable.
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Affiliation(s)
- A D de Roos
- Department of Cell Biology, University of Nijmegen, The Netherlands
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Røttingen JA, Camerer E, Mathiesen I, Prydz H, Iversen JG. Synchronized Ca2+ oscillations induced in Madin Darby canine kidney cells by bradykinin and thrombin but not by ATP. Cell Calcium 1997; 21:195-211. [PMID: 9105729 DOI: 10.1016/s0143-4160(97)90044-0] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
In an earlier report, we described synchronous Ca2+ oscillations in globally stimulated, subconfluent MDCK cells [Røttingen J-A, Enden T., Camerer E., Iversen J-G., Prydz H. Binding of human factor VIIa to tissue factor induces cytosolic Ca2+ signals in J82 cells, transfected COS-1 cells, Madin-Darby canine kidney cells and in human endothelial cells induced to synthesize tissue factor. J Biol Chem 1995; 270: 4650-4660]. In order to elucidate the mechanisms behind these oscillations, we have analyzed the fluctuations in cytosolic Ca2+ in single, Fura-2 loaded, MDCK cells grown to subconfluence, after stimulation with bradykinin, thrombin and ATP. All three agonists gave rise to an initial Ca2+ spike followed by oscillations or transients. Both the initial and subsequent spikes appeared to be due mainly to release of Ca2+ from internal stores, since they remained after Ca2+ influx was impeded by either La3+ or by chelation of extracellular Ca2+ with EGTA. The secondary spikes were apparently synchronized when the cells were (permanently and globally) stimulated with bradykinin or thrombin, but each cell seemed to oscillate independently when stimulated in the same way with ATP. Synchronized secondary spikes arose with a constant frequency and amplitude, independent of agonist concentration in contrast to most Ca2+ oscillations observed. Pretreatment of the cells with octanol to block gap junctions, or with EGTA or La3+ to inhibit Ca2+ influx, abolished the synchronization induced by bradykinin or thrombin. We observed that in the MDCK cell layer there are some "pacemaker' cells and hypothesize that these have a higher sensitivity for the agonists than their neighboring cells. From these pacemakers, an intercellular Ca2+ wave can be seen to spread to adjacent cells in the presence of intact gap junctions, thereby initiating concurrent transients in all cells. The Ca2+ wave is amplified by release from internal stores, probably owing to the bell-shaped Ca2+ activation curve of the IP3 receptor and by subsequent Ca2+ influx through Ca2+ release activated channels.
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Affiliation(s)
- J A Røttingen
- Department of Physiology, University of Oslo, Norway
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Morgan AJ, Jacob R. Ca2+ influx does more than provide releasable Ca2+ to maintain repetitive spiking in human umbilical vein endothelial cells. Biochem J 1996; 320 ( Pt 2):505-17. [PMID: 8973560 PMCID: PMC1217959 DOI: 10.1042/bj3200505] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
We investigated why oscillations of intracellular Ca2+ concentrations ([Ca2+]i) in endothelial cells challenged by sub-maximal histamine run down in Ca(2+)-free medium despite stores retaining most of their Ca2+. One explantation is that only a small subpopulation of the Ca2+ stores oscillate and are completely emptied of Ca2+. To investigate if influx refills an empty store subpopulation, we differentiated between cations entering the cell and those released from internal stores by using extracellular Sr2+ as a Ca2+ surrogate; we distinguished between [Sr2+]i and [Ca2+]i by using the larger effect of Sr2+ on fura 2 fluorescence at 360 nm (F360). Ca2+ was still available for release when oscillations had run down since oscillations promptly reappeared on addition of Sr2+o and these were predominantly of Ca2+ (indicated by F360 changes). Also, totally depleting Ca2+ stores inhibited Sr(2+)-induced oscillations, suggesting that Sr2+ entry leads to Ca2+ release. In contrast, Ba2+o was unable to stimulate oscillations. Finally, oscillations generated by photolytic release of inositol trisphosphate (IP3) analogues were similarly sensitive to extracellular Ca2+ and Sr2+. We conclude that stores (or a sub-population) are not completely depleted of Ca2+ when oscillations run down in Ca(2+)-free medium. Bivalent cation entry therefore maintains sensitivity to IP3, possibly by maintaining luminal bivalent cation levels.
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Affiliation(s)
- A J Morgan
- Vascular Biology Research Centre, King's College London, U.K
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21
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Corda S, Spurgeon HA, Lakatta EG, Capogrossi MC, Ziegelstein RC. Endoplasmic reticulum Ca2+ depletion unmasks a caffeine-induced Ca2+ influx in human aortic endothelial cells. Circ Res 1995; 77:927-35. [PMID: 7554146 DOI: 10.1161/01.res.77.5.927] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Intracellular Ca2+ pools contribute to changes in cytosolic [Ca2+] ([Ca2+]i), which play an important role in endothelial cell signaling. Recently, endothelial ryanodine-sensitive Ca2+ stores were shown to regulate agonist-sensitive intracellular Ca2+ pools. Since caffeine binds the ryanodine Ca2+ release channel on the endoplasmic reticulum in a variety of cell types, we examined the effect of caffeine on [Ca2+]i in human aortic endothelial cell monolayers loaded with the fluorescent probe indo 1. Under baseline conditions, 10 mmol/L caffeine induced a small increase in [Ca2+]i from 86 +/- 10 to 115 +/- 17 nmol/L (mean +/- SEM); this effect was similar to that of 5 mumol/L ryanodine and was unaffected by buffer Ca2+ removal. After depletion of an intracellular Ca2+ store by the irreversible endoplasmic reticulum Ca(2+)-ATPase inhibitor thapsigargin (1 mumol/L), ryanodine did not affect [Ca2+]i. In contrast, caffeine induced a large rapid increase in [Ca2+]i (176 +/- 19 to 338 +/- 35 nmol/L, P < .001) after thapsigargin exposure; this effect of caffeine was only observed when extracellular Ca2+ was present. A similar increase in [Ca2+]i was induced by caffeine after depletion of ryanodine- and histamine-sensitive Ca2+ stores or after pretreatment with the endoplasmic reticulum Ca(2+)-ATPase inhibitor cyclopiazonic acid (10 mumol/L). Thus, under baseline conditions the effect of caffeine on [Ca2+]i is similar to that of ryanodine and appears to be due to the release of an intracellular store. However, after depletion of an endoplasmic reticulum Ca2+ store, caffeine, but not ryanodine, stimulates Ca2+ influx, resulting in a large increase in [Ca2+]i.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- S Corda
- Laboratory of Cardiovascular Science, National Institute on Aging, National Institutes of Health, Baltimore, Md., USA
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22
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Wiley JS, Chen JR, Jamieson GP, Thurlow PJ. Agonists for endothelial P2 purinoceptors trigger a signalling pathway producing Ca2+ responses in lymphocytes adherent to endothelial cells. Biochem J 1995; 311 ( Pt 2):589-94. [PMID: 7487900 PMCID: PMC1136040 DOI: 10.1042/bj3110589] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Recirculation of lymphocytes through the body involves their frequent adhesion to endothelial cells but little is known of the signalling pathways between these two cell types. Lymphocytes from patients with chronic lymphocytic leukaemia were loaded with the Ca(2+)-sensitive indicator, fura 2, and allowed to adhere to either glass or monolayers of human umbilical-vein endothelial cells. Addition of ATP or UTP (1-10 microM) to the superfusate produced a transient rise in cytosolic Ca2+ concentration in the lymphocytes adherent to endothelium (24 of 35 cells). In contrast, ATP or UTP (1-10 microM) had no effect on the cytosolic Ca2+ of lymphocytes attached to glass. As the only lymphocyte receptor for ATP (P2Z class) requires higher ATP concentrations ( > 50 microM) for Ca2+ influx and is unresponsive to UTP, the involvement of a lymphocyte P2Z purinoceptor is unlikely. Various agonists including ATP, UTP, 2-methylthioATP, ADP and histamine all stimulated increases in endothelial cytosolic Ca2+ but only ATP and UTP (both agonists for endothelial P2U purinoceptors) triggered Ca2+ transients in adherent lymphocytes. Removal of extracellular Ca2+ did not abolish the ATP-induced rise in cytosolic Ca2+ concentration in lymphocytes adherent to endothelial cells. These findings show that stimulation of endothelial P2U purinoceptors triggers an endothelial-lymphocyte signalling pathway which releases internal Ca2+ in adherent lymphocytes.
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Affiliation(s)
- J S Wiley
- Department of Haematology, Austin and Repatriation Medical Centre, Heidelberg, Victoria, Australia
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23
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Wang X, Lau F, Li L, Yoshikawa A, van Breemen C. Acetylcholine-sensitive intracellular Ca2+ store in fresh endothelial cells and evidence for ryanodine receptors. Circ Res 1995; 77:37-42. [PMID: 7788880 DOI: 10.1161/01.res.77.1.37] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
In a freshly isolated endothelial cell preparation from rabbit aorta, the regulation of the acetylcholine (ACh)-sensitive intracellular Ca2+ store and the effects of the Ca(2+)-induced Ca2+ release agonists ryanodine and caffeine were studied using fura 2 imaging fluorescence microscopy. ACh (10 mumol/L) caused a transient release of Ca2+ from an intracellular store, presumably via an inositol tris-phosphate-sensitive mechanism. This ACh response could be repeated in the presence of extracellular Ca2+ but was obtained only once in Ca(2+)-free bathing solution, which shows that a depleted intracellular Ca2+ store can be rapidly refilled from the extracellular space. Refilling can be prevented by the endoplasmic reticulum Ca(2+)-ATPase inhibitor cyclopiazonic acid (10 mumol/L), implying that Ca2+ enters the cytoplasm before accumulation in the endoplasmic reticulum. Ionomycin (10 mumol/L) caused a large Ca2+ release even after the ACh-releasable store had been emptied, indicating the existence of other ACh-insensitive stores, perhaps including the mitochondria. In one third of the cells studied, ACh induced oscillations in [Ca2+]i that were dependent on extracellular Ca2+. Also investigated were the effects of caffeine and ryanodine. In this cell preparation neither caffeine nor ryanodine induced a Ca2+ transient but instead slowly increased [Ca2+]i. It was observed that both caffeine and ryanodine were able to slowly deplete the ACh-sensitive store. These results indicate the presence of functional ryanodine receptors in native endothelial cells and demonstrate overlap between the caffeine and agonist-sensitive Ca2+ stores. We also found that caffeine was able to directly inhibit the process of ACh-induced Ca2+ release.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- X Wang
- Department of Pharmacology and Therapeutics, Faculty of Medicine, University of British Columbia, Canada
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24
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Birch KA, Ewenstein BM, Golan DE, Pober JS. Prolonged peak elevations in cytoplasmic free calcium ions, derived from intracellular stores, correlate with the extent of thrombin-stimulated exocytosis in single human umbilical vein endothelial cells. J Cell Physiol 1994; 160:545-54. [PMID: 7521337 DOI: 10.1002/jcp.1041600318] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
We have used indo-1-loaded human endothelial cells (EC) in monolayer culture and quantitative laser scanning fluorescence microscopy techniques to investigate the magnitude and duration of the change in cytoplasmic free calcium ([Ca2+]i) required for thrombin-stimulated von Willebrand factor (vWF) secretion in individual EC. Both alpha-thrombin and a 14 amino acid thrombin receptor activating peptide stimulate an increase in EC [Ca2+]i that is agonist dose dependent. Low-dose agonist treatment generates asynchronous oscillations (i.e., repetitive spikes < 80 sec duration) in [Ca2+]i. Stimulation with higher agonist concentrations generates a prolonged single peak elevation in [Ca2+]i. Both the number of cells displaying prolonged [Ca2+]i peaks and the mean amplitude of the peaks increase as a function of agonist concentration. Higher doses of agonist also cause sustained elevations in [Ca2+]i that depend upon extracellular Ca2+. Oscillations in [Ca2+]i are not sufficient to stimulate significant vWF secretion, and sustained elevations in [Ca2+]i are not required for maximal secretion. Both the number of cells displaying prolonged peaks and the mean peak amplitude correlate with increasing levels of vWF secretion from the culture. We have used the expression of P-selectin, a secretory granule membrane protein, as a marker for measuring thrombin-induced exocytosis in individual EC. Both the number of secreting cells and the amount of secretion per cell increase as a function of thrombin concentration. The graded responses in [Ca2+]i amplitudes and the graded exocytotic response may be causally related.
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Affiliation(s)
- K A Birch
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts
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25
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Lancaster JR. Simulation of the diffusion and reaction of endogenously produced nitric oxide. Proc Natl Acad Sci U S A 1994; 91:8137-41. [PMID: 8058769 PMCID: PMC44560 DOI: 10.1073/pnas.91.17.8137] [Citation(s) in RCA: 499] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
In spite of intense recent investigation of the physiological and pathophysiological roles of endogenously produced nitric oxide (.NO) in mammalian systems, little quantitative information exists concerning the diffusion of this small nonelectrolyte from its source (NO synthase) to its targets of action. I present here a conceptual framework for analyzing the intracellular and intercellular diffusion and reaction of free .NO, using kinetic modeling and calculations of the diffusibility of .NO and its reactions in aqueous solution based on published data. If the half-life of .NO is greater than approximately 25 msec and the rates of reaction of .NO with its targets are slower than its diffusion or reaction with O2 (for which there is experimental evidence in at least some systems), then (i) .NO acts in vivo in a mostly paracrine fashion for a collection of .NO-producing cells, (ii) .NO diffuses to significant concentrations at distances relatively far removed from a single .NO-producing cell, and (iii) localized sites of vascularization will scavenge .NO (and thus decrease its actions) at distances many cell diameters away from that site. These conclusions have important implications with regard to the mechanism of endothelium-dependent relaxation, the autocrine vs. paracrine actions of .NO, and the role of the spatial relationship between specific sites of .NO formation and neighboring blood vessels in .NO-effected and -affected neuronal signal transmission.
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Affiliation(s)
- J R Lancaster
- Department of Surgery, University of Pittsburgh School of Medicine, PA 15261
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26
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Stucki JW, Somogyi R. A dialogue on Ca2+ oscillations: an attempt to understand the essentials of mechanisms leading to hormone-induced intracellular Ca2+ oscillations in various kinds of cell on a theoretical level. BIOCHIMICA ET BIOPHYSICA ACTA 1994; 1183:453-72. [PMID: 8286396 DOI: 10.1016/0005-2728(94)90073-6] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- J W Stucki
- Pharmakologisches Institut, Universität Bern, Switzerland
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27
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Abstract
Intercellular Ca2+ waves initiated by mechanical or chemical stimuli propagate between cells via gap junctions. The ability of a wide diversity of cells to display intercellular Ca2+ waves suggests that these Ca2+ waves may represent a general mechanism by which cells communicate. Although Ca2+ may permeate gap junctions, the intercellular movement of Ca2+ is not essential for the propagation of Ca2+ waves. The messenger that moves from one cell to the next through gap junctions appears to be IP3 and a regenerative mechanism for IP3 may be required to effect multicellular communication. Extracellularly mediated Ca2+ signaling also exists and this could be employed to supplement or replace gap junctional communication. The function of intercellular Ca2+ waves may be the coordination of cooperative cellular responses to local stimuli.
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Affiliation(s)
- M J Sanderson
- Department of Anatomy and Cell Biology, University of California, Los Angeles 90024
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28
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Marchenko SM, Sage SO. Electrical properties of resting and acetylcholine-stimulated endothelium in intact rat aorta. J Physiol 1993; 462:735-51. [PMID: 8331598 PMCID: PMC1175325 DOI: 10.1113/jphysiol.1993.sp019579] [Citation(s) in RCA: 78] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
1. The passive electrical properties and the effects of acetylcholine on the membrane potential of the endothelium of intact rat aorta were investigated using the whole cell mode of the patch clamp technique. 2. Unstimulated endothelium had a membrane potential of -58 +/- 8 mV (S.E.M., n = 193; range -47 to -76 mV). The input resistance was 43 +/- 13 M omega (S.E.M., n = 8; range 26-64 M omega). KCl and BaCl2, but not tetraethylammonium (2 mM), 4-aminopyridine (5 mM) or 4,4'-diisothiocyanatostilbene-2,2'-disulphonic acid (DIDS; 100 microM) depolarized the endothelium. 3. Acetylcholine (0.2-4 microM) evoked in most preparations a biphasic response with a transient hyperpolarization to a value close to the K+ reversal potential, followed by depolarization beyond the resting potential. In 46% of recordings, the depolarization was followed by oscillations in membrane potential. The duration of the hyperpolarization and magnitude of the depolarization was similar in all recordings from a given aorta, but varied greatly between different preparations. 4. Hyperpolarization of the endothelium below the K+ reversal potential reversed the direction of the first phase of the acetylcholine-evoked response, which was unaffected by tetraethylammonium, 4-aminopyridine, or DIDS. 5. The removal of extracellular Ca2+ evoked a depolarization of the endothelium from -61 +/- 3 to -34 +/- 3 mV (S.E.M., n = 9) over 2-15 min. Restoration of external Ca2+ evoked a transient hyperpolarization. 6. ACh applied in nominally Ca(2+)-free medium shortly after Ca2+ removal evoked only a transient hyperpolarization. After the establishment of a stable membrane potential in Ca(2+)-free medium, acetylcholine was without effect. 7. NiCl2 (2 mM) evoked a small depolarization of the endothelium (6 +/- 2 mV; S.E.M., n = 7). The subsequent removal of Ni2+ evoked a transient hyperpolarization. 8. In the presence of Ni2+, acetylcholine evoked a short-lived hyperpolarization. Both the application of Ni2+ and the removal of extracellular Ca2+ immediately blocked oscillations in membrane potential evoked by acetylcholine. 9. The blockers of voltage-operated Ca2+ channels, nifedipine (1-10 microM) and verapamil (20 microM) were without effect on the biphasic acetylcholine-evoked responses. 10. In preparations in which acetylcholine evoked large (20-45 mV) oscillations in membrane potential, depolarization of the endothelium alone, by current injection or application of KCl, did not evoke oscillations. 11. The activator of protein kinase C, phorbol 12, 13-dibutyrate (200 nM) depolarized and greatly increased the input resistance of the endothelium, presumably due to an effect on gap junctions.(ABSTRACT TRUNCATED AT 400 WORDS)
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29
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Lesh RE, Marks AR, Somlyo AV, Fleischer S, Somlyo AP. Anti-ryanodine receptor antibody binding sites in vascular and endocardial endothelium. Circ Res 1993; 72:481-8. [PMID: 8380362 DOI: 10.1161/01.res.72.2.481] [Citation(s) in RCA: 59] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The ryanodine receptor (RyR) functions as the calcium release channel of the sarcoplasmic reticulum activated by electromechanical coupling in skeletal and cardiac muscles. In smooth muscle, inositol trisphosphate releases calcium from internal stores during pharmacomechanical coupling, but these cells also contain ryanodine-sensitive calcium stores. In this study, we establish the presence of anti-RyR antibody binding sites in vascular and endocardial endothelium. Both types of endothelia also contain messenger RNA, which hybridizes to a cardiac RyR isoform cDNA probe. Western blots of endothelial cell homogenates demonstrate the presence of a single, high molecular weight band of protein that corresponds to the cardiac RyR isoform. Confocal micrographs of endothelial cells labeled with a specific anti-RyR antibody reveal an intense fluorescent signal surrounding the nucleus and distributed in a nonhomogeneous pattern throughout the cytoplasm. This pattern of fluorescence is consistent with the electron microscopic distribution of the endoplasmic reticulum. The pattern of immunofluorescence seen with the anti-RyR antibody is distinctly different from that seen with the mitochondrial fluorophore rhodamine 123. Our findings suggest that the RyR plays a role in endothelial signaling.
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Affiliation(s)
- R E Lesh
- Department of Anesthesiology, University of Virginia Health Sciences Center, Charlottesville 22908
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30
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Thuringer D, Sauvé R. A patch-clamp study of the Ca2+ mobilization from internal stores in bovine aortic endothelial cells. II. Effects of thapsigargin on the cellular Ca2+ homeostasis. J Membr Biol 1992; 130:139-48. [PMID: 1291682 DOI: 10.1007/bf00231892] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Evidence was provided, in the preceding paper (Thuringer & Sauvé, 1992), that the external Ca(2+)-dependent phase of the Ca2+ signals evoked by bradykinin (BK) or caffeine in bovine aortic endothelial cells (BAE), differ in their respective sensitivity to procaine. To examine whether the emptying of the InsP3-sensitive Ca2+ store is the signal for activating the agonist-evoked Ca2+ entry, we have investigated the effects of thapsigargin (TSG), a known inhibitor of the microsomal Ca(2+)-ATPase activity in a variety of cell types, via the activity of calcium-activated potassium channels [K(Ca2+) channels]. In cell-attached experiments, the external application of TSG caused a sustained or oscillatory activation of K(Ca2+) channels depending on both the cells and doses tested. The TSG-evoked channel activity could be reversibly blocked by removing extracellular Ca2+, and strongly decreased by adding 10 mM procaine to the bath medium. In Ca(2+)-free external conditions, TSG did not promote an apparent Ca2+ discharge from internal stores but prevented in a dose- and time-dependent manner the subsequent agonist-evoked channel activity related to the release of internally sequestered Ca2+. These results confirm that TSG and BK release Ca2+ from the same internal stores but with different kinetics. Because the channel response to caffeine was found to be poorly sensitive to procaine, in contrast to that evoked by BK and TSG, it may be concluded that both BK and TSG activate the same Ca2+ entry pathway. Therefore, the emptying of the InsP3-sensitive Ca2+ store is likely to be the main signal for activating the agonist-evoked Ca2+ entry in BAE cells.
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Affiliation(s)
- D Thuringer
- Département de Physiologie, Université de Montréal, Québec, Canada
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31
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Salamonsen LA, Butt AR, Macpherson AM, Rogers PA, Findlay JK. Immunolocalization of the vasoconstrictor endothelin in human endometrium during the menstrual cycle and in umbilical cord at birth. Am J Obstet Gynecol 1992; 167:163-7. [PMID: 1442920 DOI: 10.1016/s0002-9378(11)91652-4] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
OBJECTIVE Our objective was to determine the localization of immunoreactive endothelin in human cyclic endometrium and in umbilical cord during normal delivery and after cesarean section. STUDY DESIGN Fixed dated endometrial tissue (n = 41) and umbilical cord (n = 6) were subjected to immunohistochemistry with an antiserum cross reacting with endothelin-1, -2 and -3. RESULTS Low levels of stromal endometrial staining were seen throughout the cycle. The strongest staining was in luminal epithelium throughout the secretory phase and in glandular epithelium in the late-secretory phase. In umbilical cord the most intense immunoreactivity was present on the amnion cells on the outer cord, with some staining in intermittent cells in the Wharton's jelly and in umbilical vein cells. No differences were detected between cord from normal delivery or cesarean section. CONCLUSION A paracrine role is suggested for endothelin in regulation of endometrial function and a role in vasoconstriction in the umbilical cord at birth.
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Affiliation(s)
- L A Salamonsen
- Prince Henry's Institute of Medical Research, Monash University, Clayton, Australia
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32
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Lynch M, Gillespie JI, Greenwell JR, Johnson C. Intracellular calcium 'signatures' evoked by different agonists in isolated bovine aortic endothelial cells. Cell Calcium 1992; 13:227-33. [PMID: 1586940 DOI: 10.1016/0143-4160(92)90011-g] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Agonist induced increases in intracellular free calcium, [Ca2+]i, were measured in single Fura-2 loaded bovine aortic endothelial (BAE) cells by dual wavelength microspectrofluorimetry. Low doses of ATP (less than 10 microM) induced complex changes in [Ca2+]i. These changes usually consisted of a large initial transient peak with subsequent fluctuations superimposed upon a maintained rise in [Ca2+]i. Higher doses of ATP (greater than 50 microM) produced much simpler biphasic increases in [Ca2+]i in individual cells. Acetylcholine and bradykinin also elicited increases in [Ca2+]i in single cells in confluent monolayers of endothelial cells. However, only acetylcholine produced complex fluctuations. High doses of acetylcholine evoked simple rises in [Ca2+]i similar to those seen with high doses of ATP. In contrast, bradykinin evoked relatively simple rises in [Ca2+]i at all doses used. These results indicate that the mechanisms responsible for generating agonist induced increases in [Ca2+]i in BAE cells are not homogeneous. ATP and acetylcholine produced more complex Ca2+ changes or 'signatures' in single confluent bovine aortic endothelial cells than bradykinin. All three agonists appeared to release Ca2+ from intracellular stores as well as stimulating Ca2+ influx. The possible mechanisms underlying these phenomena are discussed.
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Affiliation(s)
- M Lynch
- Department of Physiological Sciences, Medical School, The University, Newcastle upon Tyne, UK
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33
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Laskey RE, Adams DJ, Cannell M, van Breemen C. Calcium entry-dependent oscillations of cytoplasmic calcium concentration in cultured endothelial cell monolayers. Proc Natl Acad Sci U S A 1992; 89:1690-4. [PMID: 1542661 PMCID: PMC48518 DOI: 10.1073/pnas.89.5.1690] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Bovine endothelial cell monolayers grown to confluence and stimulated with bradykinin responded with periodic fluctuations in intracellular Ca2+ concentration ([Ca2+]i) when exposed to K(+)-free Hepes-buffered saline. The fluctuations in [Ca2+]i measured with fura-2 were synchronized among the population of cells observed and were sensitive to extracellular Ca2+ concentration ([Ca2+]o). Thapsigargin, which inhibits the endoplasmic reticular Ca2(+)-ATPase, did not inhibit the [Ca2+]i oscillations. Removal of extracellular Ca2+ or inhibition of Ca2+ entry by using La3+ or 1-(beta- [3-(4-methoxyphenyl)proproxy]-4-methoxyphenethyl)-1H-imidazole hydrochloride (SKF 96365) abolished the [Ca2+]i oscillations in endothelial cell monolayers. The fluctuations in [Ca2+]i were therefore dependent on Ca2+ influx rather than Ca2+ mobilization from intracellular stores. Simultaneous measurements of membrane potential (Em) using the potential-sensitive bisoxonol dye bis(1,3-dibutylbarbituric acid)trimethine oxonol [Di-BAC4(3)] and [Ca2+]i using fura-2 showed that Em oscillated at the same frequency as the fluctuations in [Ca2+]i. The peak depolarization signal coincided with the maximum rate of increase in the [Ca2+]i signal. Oscillations in the Em signal were inhibited by removal of Ca2+ or by addition of 1 mM Ni2+ to the external solution. Taken together, these observations suggest that the change in Em is the consequence of oscillatory changes in a membrane conductance that also allows Ca2+ to enter the cell. Oscillations in the DiBAC4(3) signal may reflect a rhythmic entry of Ca2+ through nonselective cation channels.
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Affiliation(s)
- R E Laskey
- Department of Molecular and Cellular Pharmacology, University of Miami School of Medicine, FL 33101
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34
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Carter TD, Bogle RG, Bjaaland T. Spiking of intracellular calcium ion concentration in single cultured pig aortic endothelial cells stimulated with ATP or bradykinin. Biochem J 1991; 278 ( Pt 3):697-704. [PMID: 1898358 PMCID: PMC1151402 DOI: 10.1042/bj2780697] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Single pig aortic endothelial cells in culture loaded with the Ca(2+)-sensitive fluorescent dye Indo-1 were stimulated with ATP (0.1-100 microM) or bradykinin (0.1-5.0 nM). Spiking or oscillations of [Ca2+]i were seen in approx. 50% of cells stimulated with either agonist. Non-spiking or transient responses in which [Ca2+]i returned to pre-stimulation levels rapidly 9120-250 s), or sustained responses in which [Ca2+]i remained elevated for many minutes, were seen in a further 20% of cells in each case, stimulated with either agonist. There was a marked variation between individual cells in the latency, magnitude, frequency and overall pattern of oscillations induced by ATP and bradykinin, although the patterns of response to bradykinin were less variable. In cells where repetitive spikes were seen, a relation between concentration of ATP and the latency of the response and the frequency of spiking was evident. Effects of removal of extracellular Ca2+, elevation of extracellular K+ concentration (35 or 70 mM) or exposure to phorbol 12,13-dibutyrate or 1,2-dioctanoyl-sn-glycerol were tested on the spiking Ca2+ responses. Each of these procedures reversibly slowed or prevented Ca2+ spiking evoked by ATP or bradykinin. In contrast, the inactive phorbol ester 4 alpha-phorbol didecanoate had no effect on Ca2+ spiking evoked by these hormones. Our results thus indicate that the responses of single cells to ATP or bradykinin exhibit marked heterogeneity, and suggest that secretory events driven by extracellular Ca2+ may be regulated by repetitive spikes or oscillations of Ca2+.
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Affiliation(s)
- T D Carter
- Division of Neurophysiology and Neuropharmacology, N.I.M.R., Mill Hill, London, U.K
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35
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Berridge MJ. Caffeine inhibits inositol-trisphosphate-induced membrane potential oscillations in Xenopus oocytes. Proc Biol Sci 1991; 244:57-62. [PMID: 1677197 DOI: 10.1098/rspb.1991.0051] [Citation(s) in RCA: 32] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Immature Xenopus oocytes injected with inositol 1,4,5-trisphosphate (Ins(1,4,5)P3) give a complex electrophysiological response comprising an a early depolarizing spike followed by a burst of oscillations. These two components have been interpreted on the basis of an interaction between two internal calcium stores: an Ins(1,4,5) P3-sensitive pool responsible for the early spike which then primes an Ins(1,4,5) P3-insensitive pool to begin to oscillate through a process of calcium-induced calcium release (Berridge, M. J., J. Physiol., Lond. 403, 589-599 (1988)). The role of the latter was investigated in Xenopus oocytes by using the drug caffeine which can trigger calcium-induced calcium release in muscle cells. Caffeine had no effect on the early Ins(1,4,5)P3-induced spike but it suppressed the subsequent oscillations. The spontaneous oscillations observed in some oocytes were also abolished by caffeine. Oscillation amplitude and duration was slightly reduced following incubation of oocytes with adenosine or isobutylmethylxanthine. Because these two agents gave large membrane hyperpolarizations indicative of an increase in cyclic AMP, it can be concluded that this second messenger is not responsible for the inhibitory action of caffeine. The ability of caffeine to abolish oscillations while not affecting the early Ins(1,4,5) P3 response is discussed with regard to the two-pool model for generating calcium oscillations.
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Affiliation(s)
- M J Berridge
- University of Cambridge, Department of Zoology, U.K
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36
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Abstract
The use of techniques to visualize the stimulus-induced changes in [Ca2+]i that occur at the single cell level has revealed that intracellular Ca2+ signals can be remarkably organized in space (waves), as well as in time (oscillations). New insights are beginning to emerge into how these complex Ca2+ signals may be generated, and into how Ca2+ signals may be transmitted from cell to cell.
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Affiliation(s)
- T R Cheek
- AFRC Laboratory of Molecular Signalling, Department of Zoology, University of Cambridge, UK
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37
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Neylon CB, Irvine RF. Thrombin attenuates the stimulatory effect of histamine on Ca2+ entry in confluent human umbilical vein endothelial cell cultures. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(20)64314-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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38
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Laskey RE, Adams DJ, Purkerson S, van Breemen C. Cytosolic calcium ion regulation in cultured endothelial cells. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1991; 304:257-71. [PMID: 1803902 DOI: 10.1007/978-1-4684-6003-2_21] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Mechanisms involved in Ca2+ homeostasis and stimulus-secretion coupling in cultured endothelial cells in response to humoral and physical stimuli include passive leak, activation of ion channels, and chemical second messengers. Calcium entry is controlled by receptor activation, passive leak, and mechanical stretch. The rate at which Ca2+ enters the cell through these pathways is dependent on the transmembrane potential which governs the electrochemical gradient for Ca2+ and which is set by participation of various K channels.
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Affiliation(s)
- R E Laskey
- Department of Molecular and Cellular Pharmacology, University of Miami School of Medicine, FL 33101
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