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Ghilardi SJ, O'Reilly BM, Sgro AE. Intracellular signaling dynamics and their role in coordinating tissue repair. WILEY INTERDISCIPLINARY REVIEWS. SYSTEMS BIOLOGY AND MEDICINE 2020; 12:e1479. [PMID: 32035001 PMCID: PMC7187325 DOI: 10.1002/wsbm.1479] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/16/2019] [Revised: 12/20/2019] [Accepted: 12/31/2019] [Indexed: 12/11/2022]
Abstract
Tissue repair is a complex process that requires effective communication and coordination between cells across multiple tissues and organ systems. Two of the initial intracellular signals that encode injury signals and initiate tissue repair responses are calcium and extracellular signal-regulated kinase (ERK). However, calcium and ERK signaling control a variety of cellular behaviors important for injury repair including cellular motility, contractility, and proliferation, as well as the activity of several different transcription factors, making it challenging to relate specific injury signals to their respective repair programs. This knowledge gap ultimately hinders the development of new wound healing therapies that could take advantage of native cellular signaling programs to more effectively repair tissue damage. The objective of this review is to highlight the roles of calcium and ERK signaling dynamics as mechanisms that link specific injury signals to specific cellular repair programs during epithelial and stromal injury repair. We detail how the signaling networks controlling calcium and ERK can now also be dissected using classical signal processing techniques with the advent of new biosensors and optogenetic signal controllers. Finally, we advocate the importance of recognizing calcium and ERK dynamics as key links between injury detection and injury repair programs that both organize and execute a coordinated tissue repair response between cells across different tissues and organs. This article is categorized under: Models of Systems Properties and Processes > Mechanistic Models Biological Mechanisms > Cell Signaling Laboratory Methods and Technologies > Imaging Models of Systems Properties and Processes > Organ, Tissue, and Physiological Models.
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Affiliation(s)
- Samuel J. Ghilardi
- Department of Biomedical Engineering and the Biological Design CenterBoston UniversityBostonMassachusetts
| | - Breanna M. O'Reilly
- Department of Biomedical Engineering and the Biological Design CenterBoston UniversityBostonMassachusetts
| | - Allyson E. Sgro
- Department of Biomedical Engineering and the Biological Design CenterBoston UniversityBostonMassachusetts
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Levin M, Martyniuk CJ. The bioelectric code: An ancient computational medium for dynamic control of growth and form. Biosystems 2018; 164:76-93. [PMID: 28855098 PMCID: PMC10464596 DOI: 10.1016/j.biosystems.2017.08.009] [Citation(s) in RCA: 112] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2017] [Revised: 08/20/2017] [Accepted: 08/22/2017] [Indexed: 12/19/2022]
Abstract
What determines large-scale anatomy? DNA does not directly specify geometrical arrangements of tissues and organs, and a process of encoding and decoding for morphogenesis is required. Moreover, many species can regenerate and remodel their structure despite drastic injury. The ability to obtain the correct target morphology from a diversity of initial conditions reveals that the morphogenetic code implements a rich system of pattern-homeostatic processes. Here, we describe an important mechanism by which cellular networks implement pattern regulation and plasticity: bioelectricity. All cells, not only nerves and muscles, produce and sense electrical signals; in vivo, these processes form bioelectric circuits that harness individual cell behaviors toward specific anatomical endpoints. We review emerging progress in reading and re-writing anatomical information encoded in bioelectrical states, and discuss the approaches to this problem from the perspectives of information theory, dynamical systems, and computational neuroscience. Cracking the bioelectric code will enable much-improved control over biological patterning, advancing basic evolutionary developmental biology as well as enabling numerous applications in regenerative medicine and synthetic bioengineering.
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Affiliation(s)
- Michael Levin
- Allen Discovery Center at Tufts University, Biology Department, Tufts University, 200 Boston Avenue, Suite 4600 Medford, MA 02155, USA.
| | - Christopher J Martyniuk
- Department of Physiological Sciences and Center for Environmental and Human Toxicology, University of Florida Genetics Institute, Interdisciplinary Program in Biomedical Sciences Neuroscience, College of Veterinary Medicine, University of Florida, Gainesville, FL, 32611, USA
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3
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Willebrords J, Maes M, Crespo Yanguas S, Vinken M. Inhibitors of connexin and pannexin channels as potential therapeutics. Pharmacol Ther 2017; 180:144-160. [PMID: 28720428 PMCID: PMC5802387 DOI: 10.1016/j.pharmthera.2017.07.001] [Citation(s) in RCA: 106] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
While gap junctions support the exchange of a number of molecules between neighboring cells, connexin hemichannels provide communication between the cytosol and the extracellular environment of an individual cell. The latter equally holds true for channels composed of pannexin proteins, which display an architecture reminiscent of connexin hemichannels. In physiological conditions, gap junctions are usually open, while connexin hemichannels and, to a lesser extent, pannexin channels are typically closed, yet they can be activated by a number of pathological triggers. Several agents are available to inhibit channels built up by connexin and pannexin proteins, including alcoholic substances, glycyrrhetinic acid, anesthetics and fatty acids. These compounds not always strictly distinguish between gap junctions, connexin hemichannels and pannexin channels, and may have effects on other targets as well. An exception lies with mimetic peptides, which reproduce specific amino acid sequences in connexin or pannexin primary protein structure. In this paper, a state-of-the-art overview is provided on inhibitors of cellular channels consisting of connexins and pannexins with specific focus on their mode-of-action and therapeutic potential.
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Affiliation(s)
- Joost Willebrords
- Department of In Vitro Toxicology and Dermato-cosmetology, Faculty of Medicine and Pharmacy, Vrije Universiteit Brussel, Laarbeeklaan 103, Brussels, Belgium
| | - Michaël Maes
- Department of In Vitro Toxicology and Dermato-cosmetology, Faculty of Medicine and Pharmacy, Vrije Universiteit Brussel, Laarbeeklaan 103, Brussels, Belgium
| | - Sara Crespo Yanguas
- Department of In Vitro Toxicology and Dermato-cosmetology, Faculty of Medicine and Pharmacy, Vrije Universiteit Brussel, Laarbeeklaan 103, Brussels, Belgium
| | - Mathieu Vinken
- Department of In Vitro Toxicology and Dermato-cosmetology, Faculty of Medicine and Pharmacy, Vrije Universiteit Brussel, Laarbeeklaan 103, Brussels, Belgium.
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Kotwani M. Modeling and Simulation of Calcium Dynamics in Fibroblast Cell Involving Excess Buffer Approximation (EBA), ER Flux and SERCA Pump. ACTA ACUST UNITED AC 2015. [DOI: 10.1016/j.procs.2015.04.263] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Bathany C, Beahm D, Felske JD, Sachs F, Hua SZ. High throughput assay of diffusion through Cx43 gap junction channels with a microfluidic chip. Anal Chem 2010; 83:933-9. [PMID: 21182279 DOI: 10.1021/ac102658h] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
This paper describes a microfluidic-based assay capable of measuring gap-junction mediated dye diffusion in cultured cells. The technique exploits multistream laminar flow to selectively expose cells to different environments, enabling continuous loading of cells in one compartment while monitoring, in real time, dye diffusion into cells of a neighboring compartment. A simple one-dimensional diffusion model fit to the data extracted the diffusion coefficient of four different dyes, 5-(6)-carboxyfluorescein, 5-chloromethylfluorescein, Oregon green 488 carboxylic acid, and calcein. Different inhibitors were assayed for their ability to reduce dye coupling. The chip can screen multiple inhibitors in parallel in the same cell preparation, demonstrating its potential for high throughput. The technique provides a convenient method to measure gap junction mediated diffusion and a screen for drugs that affect gap junction communication.
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Affiliation(s)
- Cédric Bathany
- Department of Mechanical and Aerospace Engineering, SUNY-Buffalo, Buffalo, New York 14260, USA
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Animal cells connected by nanotubes can be electrically coupled through interposed gap-junction channels. Proc Natl Acad Sci U S A 2010; 107:17194-9. [PMID: 20855598 DOI: 10.1073/pnas.1006785107] [Citation(s) in RCA: 241] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Tunneling nanotubes (TNTs) are recently discovered conduits for a previously unrecognized form of cell-to-cell communication. These nanoscale, F-actin-containing membrane tubes connect cells over long distances and facilitate the intercellular exchange of small molecules and organelles. Using optical membrane-potential measurements combined with mechanical stimulation and whole-cell patch-clamp recording, we demonstrate that TNTs mediate the bidirectional spread of electrical signals between TNT-connected normal rat kidney cells over distances of 10 to 70 μm. Similar results were obtained for other cell types, suggesting that electrical coupling via TNTs may be a widespread characteristic of animal cells. Strength of electrical coupling depended on the length and number of TNT connections. Several lines of evidence implicate a role for gap junctions in this long-distance electrical coupling: punctate connexin 43 immunoreactivity was frequently detected at one end of TNTs, and electrical coupling was voltage-sensitive and inhibited by meclofenamic acid, a gap-junction blocker. Cell types lacking gap junctions did not show TNT-dependent electrical coupling, which suggests that TNT-mediated electrical signals are transmitted through gap junctions at a membrane interface between the TNT and one cell of the connected pair. Measurements of the fluorescent calcium indicator X-rhod-1 revealed that TNT-mediated depolarization elicited threshold-dependent, transient calcium signals in HEK293 cells. These signals were inhibited by the voltage-gated Ca(2+) channel blocker mibefradil, suggesting they were generated via influx of calcium through low voltage-gated Ca(2+) channels. Taken together, our data suggest a unique role for TNTs, whereby electrical synchronization between distant cells leads to activation of downstream target signaling.
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Elson EC. Complex life forms may arise from electrical processes. Theor Biol Med Model 2010; 7:26. [PMID: 20576122 PMCID: PMC2908058 DOI: 10.1186/1742-4682-7-26] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2010] [Accepted: 06/24/2010] [Indexed: 11/21/2022] Open
Abstract
There is still not an appealing and testable model to explain how single-celled organisms, usually following fusion of male and female gametes, proceed to grow and evolve into multi-cellular, complexly differentiated systems, a particular species following virtually an invariant and unique growth pattern. An intrinsic electrical oscillator, resembling the cardiac pacemaker, may explain the process. Highly auto-correlated, it could live independently of ordinary thermodynamic processes which mandate increasing disorder, and could coordinate growth and differentiation of organ anlage.
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Affiliation(s)
- Edward C Elson
- Department of Electrical and Computer Engineering, University of Maryland, College Park, College Park, Maryland 20742, USA.
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Almirza W, Peters P, van Meerwijk W, van Zoelen E, Theuvenet A. Different roles of inositol 1,4,5-trisphosphate receptor subtypes in prostaglandin F2α-induced calcium oscillations and pacemaking activity of NRK fibroblasts. Cell Calcium 2010; 47:544-53. [DOI: 10.1016/j.ceca.2010.05.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2010] [Revised: 05/10/2010] [Accepted: 05/11/2010] [Indexed: 11/25/2022]
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9
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Dernison M, Kusters J, Peters P, van Meerwijk W, Ypey D, Gielen C, van Zoelen E, Theuvenet A. Local induction of pacemaking activity in a monolayer of electrically coupled quiescent NRK fibroblasts. Cell Calcium 2008; 44:429-40. [DOI: 10.1016/j.ceca.2008.02.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2007] [Revised: 12/22/2007] [Accepted: 02/11/2008] [Indexed: 11/30/2022]
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10
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Almirza WH, Dernison MM, Peters PHJ, van Zoelen EJJ, Theuvenet APR. Role of the prostanoid FP receptor in action potential generation and phenotypic transformation of NRK fibroblasts. Cell Signal 2008; 20:2022-9. [PMID: 18703136 DOI: 10.1016/j.cellsig.2008.07.013] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2008] [Revised: 07/11/2008] [Accepted: 07/17/2008] [Indexed: 11/30/2022]
Abstract
By using an shRNA approach to knockdown the expression of the prostaglandin (PG)-F(2alpha) receptor (FP-R), the role of PGF(2alpha) in the process of phenotypic transformation of normal rat kidney (NRK) fibroblasts has been studied. Our data show that PGF(2alpha) up-regulates Cox-2 expression both at the mRNA and protein level, indicating that activation of FP-R in NRK fibroblasts induces a positive feedback loop in the production PGF(2alpha). Knockdown of FP-R expression fully impaired the ability of PGF(2alpha) to induce a calcium response and subsequent depolarization in NRK cells. However, these cells could still undergo phenotypic transformation when treated with a combination of EGF and retinoic acid, but in contrast to the wild-type cells, this process was not accompanied by a membrane depolarization to -20 mV. Knockdown of FP-R expression also impaired the spontaneous firing of calcium action potentials by density-arrested NRK cells. These data show that a membrane depolarization is not a prerequisite for the acquisition of a transformed phenotype. Furthermore, our data provide the first direct evidence that activity of PGF(2alpha) by putative pacemaker cells underlies the generation of calcium action potentials in NRK monolayers.
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Affiliation(s)
- W H Almirza
- Department of Cell Biology, Faculty of Science, Radboud University Nijmegen, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
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Kusters JMAM, van Meerwijk WPM, Ypey DL, Theuvenet APR, Gielen CCAM. Fast calcium wave propagation mediated by electrically conducted excitation and boosted by CICR. Am J Physiol Cell Physiol 2008; 294:C917-30. [DOI: 10.1152/ajpcell.00181.2007] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We have investigated synchronization and propagation of calcium oscillations, mediated by gap junctional excitation transmission. For that purpose we used an experimentally based model of normal rat kidney (NRK) cells, electrically coupled in a one-dimensional configuration (linear strand). Fibroblasts such as NRK cells can form an excitable syncytium and generate spontaneous inositol 1,4,5-trisphosphate (IP3)-mediated intracellular calcium waves, which may spread over a monolayer culture in a coordinated fashion. An intracellular calcium oscillation in a pacemaker cell causes a membrane depolarization from within that cell via calcium-activated chloride channels, leading to an L-type calcium channel-based action potential (AP) in that cell. This AP is then transmitted to the electrically connected neighbor cell, and the calcium inflow during that transmitted AP triggers a calcium wave in that neighbor cell by opening of IP3receptor channels, causing calcium-induced calcium release (CICR). In this way the calcium wave of the pacemaker cell is rapidly propagated by the electrically transmitted AP. Propagation of APs in a strand of cells depends on the number of terminal pacemaker cells, the L-type calcium conductance of the cells, and the electrical coupling between the cells. Our results show that the coupling between IP3-mediated calcium oscillations and AP firing provides a robust mechanism for fast propagation of activity across a network of cells, which is representative for many other cell types such as gastrointestinal cells, urethral cells, and pacemaker cells in the heart.
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12
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Kusters JMAM, Dernison MM, van Meerwijk WPM, Ypey DL, Theuvenet APR, Gielen CCAM. Stabilizing role of calcium store-dependent plasma membrane calcium channels in action-potential firing and intracellular calcium oscillations. Biophys J 2005; 89:3741-56. [PMID: 16169971 PMCID: PMC1366943 DOI: 10.1529/biophysj.105.062984] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In many biological systems, cells display spontaneous calcium oscillations (CaOs) and repetitive action-potential firing. These phenomena have been described separately by models for intracellular inositol trisphosphate (IP3)-mediated CaOs and for plasma membrane excitability. In this study, we present an integrated model that combines an excitable membrane with an IP3-mediated intracellular calcium oscillator. The IP3 receptor is described as an endoplasmic reticulum (ER) calcium channel with open and close probabilities that depend on the cytoplasmic concentration of IP3 and Ca2+. We show that simply combining this ER model for intracellular CaOs with a model for membrane excitability of normal rat kidney (NRK) fibroblasts leads to instability of intracellular calcium dynamics. To ensure stable long-term periodic firing of action potentials and CaOs, it is essential to incorporate calcium transporters controlled by feedback of the ER store filling, for example, store-operated calcium channels in the plasma membrane. For low IP3 concentrations, our integrated NRK cell model is at rest at -70 mV. For higher IP3 concentrations, the CaOs become activated and trigger repetitive firing of action potentials. At high IP3 concentrations, the basal intracellular calcium concentration becomes elevated and the cell is depolarized near -20 mV. These predictions are in agreement with the different proliferative states of cultures of NRK fibroblasts. We postulate that the stabilizing role of calcium channels and/or other calcium transporters controlled by feedback from the ER store is essential for any cell in which calcium signaling by intracellular CaOs involves both ER and plasma membrane calcium fluxes.
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Affiliation(s)
- J M A M Kusters
- Department of Medical Physics and Biophysics, Institute for Neuroscience, Radboud University Nijmegen, Nijmegen, The Netherlands
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13
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Harks EGA, Peters PHJ, van Dongen JLJ, van Zoelen EJJ, Theuvenet APR. Autocrine production of prostaglandin F2αenhances phenotypic transformation of normal rat kidney fibroblasts. Am J Physiol Cell Physiol 2005; 289:C130-7. [PMID: 15758043 DOI: 10.1152/ajpcell.00416.2004] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We have used normal rat kidney (NRK) fibroblasts as an in vitro model system to study cell transformation. These cells obtain a transformed phenotype upon stimulation with growth-modulating factors such as retinoic acid (RA) or transforming growth factor-β (TGF-β). Patch-clamp experiments showed that transformation is paralleled by a profound membrane depolarization from around −70 to −20 mV. This depolarization is caused by a compound in the medium conditioned by transformed NRK cells, which enhances intracellular Ca2+levels and thereby activates Ca2+-dependent Cl−channels. This compound was identified as prostaglandin F2α(PGF2α) using electrospray ionization mass spectrometry. The active concentration in the medium conditioned by transformed NRK cells as determined using an enzyme immunoassay was 19.7 ± 2.5 nM ( n = 6), compared with 1.5 ± 0.1 nM ( n = 3) conditioned by nontransformed NRK cells. Externally added PGF2αwas able to trigger NRK cells that had grown to density arrest to restart their proliferation. This proliferation was inhibited when the FP receptor (i.e., natural receptor for PGF2α) was blocked by AL-8810. RA-induced phenotypic transformation of NRK cells was partially (∼25%) suppressed by AL-8810. Our results demonstrate that PGF2αacts as an autocrine enhancer and paracrine inducer of cell transformation and suggest that it may play a crucial role in carcinogenesis in general.
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Affiliation(s)
- E G A Harks
- Department of Cell Biology, Radboud University Nijmegen, Toernooiveld 1, 6525 ED Nijmegen, The Netherlands
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Torres JJ, Cornelisse LN, Harks EGA, Van Meerwijk WPM, Theuvenet APR, Ypey DL. Modeling action potential generation and propagation in NRK fibroblasts. Am J Physiol Cell Physiol 2004; 287:C851-65. [PMID: 15140749 DOI: 10.1152/ajpcell.00220.2003] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Normal rat kidney (NRK) fibroblasts change their excitability properties through the various stages of cell proliferation. The present mathematical model has been developed to explain excitability of quiescent (serum deprived) NRK cells. It includes as cell membrane components, on the basis of patch-clamp experiments, an inwardly rectifying potassium conductance ( GKir), an L-type calcium conductance ( GCaL), a leak conductance ( Gleak), an intracellular calcium-activated chloride conductance [ GCl(Ca)], and a gap junctional conductance ( Ggj), coupling neighboring cells in a hexagonal pattern. This membrane model has been extended with simple intracellular calcium dynamics resulting from calcium entry via GCaLchannels, intracellular buffering, and calcium extrusion. It reproduces excitability of single NRK cells and cell clusters and intercellular action potential (AP) propagation in NRK cell monolayers. Excitation can be evoked by electrical stimulation, external potassium-induced depolarization, or hormone-induced intracellular calcium release. Analysis shows the roles of the various ion channels in the ultralong (∼30 s) NRK cell AP and reveals the particular role of intracellular calcium dynamics in this AP. We support our earlier conclusion (De Roos A, Willems PH, van Zoelen EJ, and Theuvenet AP. Am J Physiol Cell Physiol 273: C1900–C1907, 1997) that AP generation and propagation may act as a rapid mechanism for the propagation of intracellular calcium waves, thus contributing to fast intercellular calcium signaling. The present model serves as a starting point to further analyze excitability changes during contact inhibition and cell transformation.
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Affiliation(s)
- J J Torres
- Institute "Carlos I" for Theoretical and Computational Physics, University of Granada, Spain
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15
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Harks EGA, Scheenen WJJM, Peters PHJ, van Zoelen EJJ, Theuvenet APR. Prostaglandin F2 alpha induces unsynchronized intracellular calcium oscillations in monolayers of gap junctionally coupled NRK fibroblasts. Pflugers Arch 2003; 447:78-86. [PMID: 12851822 DOI: 10.1007/s00424-003-1126-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2003] [Accepted: 05/28/2003] [Indexed: 11/26/2022]
Abstract
We investigated the intracellular calcium oscillations induced by prostaglandin F2alpha (PGF2alpha) in individual cells of confluent, gap junction-coupled monolayers of normal rat kidney (NRK) fibroblasts. PGF2alpha (1000 nM) induced oscillations in more than 90% of the cells in the monolayer, but the frequency of these oscillations was highly variable between individual cells (0.2-1.4 min(-1)). The initial calcium peak resulted from calcium release from IP3-sensitive stores, while subsequent calcium transients were mediated by interplay between both IP3-sensitive calcium stores and calcium influx. The oscillation frequency was increased by sensitizing the IP3 receptor with thimerosal (10 microM) and depended on the extracellular calcium concentration. Thapsigargin (5 nM), which inhibits reuptake of calcium into the stores, only seemed to reduce the amplitude of the oscillation. Patch-clamp experiments revealed that PGF2alpha did not inhibit electrical coupling of the NRK cells in the monolayer. Gap junctional permeability of NRK cells thus appears to be sufficient to allow electrical coupling, resulting in a uniform membrane potential throughout the entire monolayer, but insufficient to synchronize the intracellular calcium oscillations upon PGF2alpha stimulation.
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Affiliation(s)
- Erik G A Harks
- Department of Cell Biology, University of Nijmegen, Toernooiveld 1, 6525 ED Nijmegen, The Netherlands
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16
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Harks EGA, Torres JJ, Cornelisse LN, Ypey DL, Theuvenet APR. Ionic basis for excitability of normal rat kidney (NRK) fibroblasts. J Cell Physiol 2003; 196:493-503. [PMID: 12891706 DOI: 10.1002/jcp.10346] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Ionic membrane conductances of normal rat kidney (NRK) fibroblasts were characterized by whole-cell voltage-clamp experiments on single cells and small cell clusters and their role in action potential firing in these cells and in monolayers was studied in current-clamp experiments. Activation of an L-type calcium conductance (GCaL) is responsible for the initiation of an action potential, a calcium-activated chloride conductance (GCl(Ca)) determines the plateau phase of the action potential, and an inwardly rectifying potassium conductance (GKir) is important for the generation of a resting potential of approximately -70 mV and contributes to action potential depolarization and repolarization. The unique property of the excitability mechanism is that it not only includes voltage-activated conductances (GCaL, GKir) but that the intracellular calcium dynamics is also an essential part of it (via GCl(Ca)). Excitability was found to be an intrinsic property of a fraction (approximately 25%) of the individual cells, and not necessarily dependent on gap junctional coupling of the cells in a monolayer. Electrical coupling of a patched cell to neighbor cells in a small cluster improved the excitability because all small clusters were excitable. Furthermore, cells coupled in a confluent monolayer produced broader action potentials. Thus, electrical coupling in NRK cells does not merely serve passive conduction of stereotyped action potentials, but also seems to play a role in shaping the action potential.
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Affiliation(s)
- E G A Harks
- Department of Cell Biology, University of Nijmegen, Nijmegen, The Netherlands
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17
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Harks EGA, Camiña JP, Peters PHJ, Ypey DL, Scheenen WJJM, van Zoelen EJJ, Theuvenet APR. Besides affecting intracellular calcium signaling, 2-APB reversibly blocks gap junctional coupling in confluent monolayers, thereby allowing measurement of single-cell membrane currents in undissociated cells. FASEB J 2003; 17:941-3. [PMID: 12626431 DOI: 10.1096/fj.02-0786fje] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
2-aminoethoxydiphenyl borate (2-APB) has been widely used as a blocker of the IP3 receptor and TRP channels, including store-operated calcium channels. We now show in monolayers of normal rat kidney cells (NRK/49F) that 2-APB completely and reversibly blocks gap junctional intercellular communication at concentrations similar to that required for inhibition of PGF2alpha-induced increases in intracellular calcium. Gap junctional conductances between NRK cells were estimated with single-electrode patch-clamp measurements and were fully blocked by 2-APB (50 microM), when applied extracellularly but not via the patch pipette. Half maximal inhibition (IC50) of electrical coupling in NRK cells was achieved at 5.7 microM. Similar results were obtained for human embryonic kidney epithelial cells (HEK293/tsA201) with an IC50 of 10.3 microM. Using 2-APB as an electrical uncoupler of monolayer cells, we could thus measure inward rectifier potassium, L-type calcium, and calcium-dependent chloride membrane currents in confluent NRK monolayers, with properties similar to those in dissociated NRK cells in the absence of 2-APB. The electrical uncoupling action described here is a new 2-APB property that promises to provide a powerful pharmacological tool to study single-cell properties in cultured confluent monolayers and intact tissues by electrical and chemical uncoupling of the cells without the need of prior dissociation.
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Affiliation(s)
- Erik G A Harks
- Department of Cell Biology, University of Nijmegen, The Netherlands
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18
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Buchli R, Ndoye A, Arredondo J, Webber RJ, Grando SA. Identification and characterization of muscarinic acetylcholine receptor subtypes expressed in human skin melanocytes. Mol Cell Biochem 2001; 228:57-72. [PMID: 11855742 DOI: 10.1023/a:1013368509855] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The present study was designed to identify and characterize muscarinic acetylcholine receptors in normal human melanocytes. We used subtype-specific oligonucleotide primers to localize the five genetically defined mAChR mRNAs (ml through m5) by reverse transcription-polymerase chain reaction. These experiments showed that all five mAChR subtype mRNAs are expressed in melanocytes. The PCR products were verified by restriction analysis and Southern blotting. Receptors were visualized in cultures of normal human melanocytes and specimens of normal human skin by subtype-specific rabbit anti-receptor polyclonal antibodies. Radioligand binding assays with the lipophilic drug [3H]quinuclidinyl benzilate demonstrated approximately 9,000 high affinity binding sites/cell. Micromolar concentrations of muscarine or carbachol transiently increased intracellular Ca2+, which could be attenuated by atropine, demonstrating coupling of the receptors to mobilization of intracellular free Ca2+. Lower concentrations of muscarine induced spontaneous repetitive spike-like increases of intracellular Ca2+ which is characteristic for the activation of muscarinic receptors. These results indicate that normal human skin melanocytes express the ml, m2, m3, m4, and m5 subtypes of classic muscarinic acetylcholine receptors on their cell membrane and that these receptors regulate the concentration of intracellular free Ca2+, which may play an important physiologic role in melanocyte behavior and skin pigmentation.
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Affiliation(s)
- R Buchli
- Department of Dermatology, University of California, Davis, Sacramento 95817, USA
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19
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Shivakumar K, Kumaran C. L-type calcium channel blockers and EGTA enhance superoxide production in cardiac fibroblasts. J Mol Cell Cardiol 2001; 33:373-7. [PMID: 11162140 DOI: 10.1006/jmcc.2000.1309] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Since the recognition of the importance of calcium ions to cardiac contractility, the effects of alterations in calcium homeostasis on cardiac myocyte function have attracted immense attention. However, the possibility that changes in extracellular calcium concentration or the administration of calcium channel blockers may exert significant effects on cardiac fibroblasts has not hitherto been explored. This communication presents evidence, for the first time, that EGTA, calcium-free incubation and L-type calcium channel blockers increase endogenous superoxide production in adult rat cardiac fibroblasts. A combination of ryanodine and EGTA was found to have an even greater effect. The observations indicate that extracellular calcium levels influence endogenous superoxide production in cardiac fibroblasts and support the postulation that myocardial fibroblasts may contribute to the cardiac effects of calcium channel blockers and alterations in extracellular calcium concentration.
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Affiliation(s)
- K Shivakumar
- Division of Cellular and Molecular Cardiology, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum, Kerala, 695 011, India.
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20
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Masereeuw R, van Pelt AP, van Os SH, Willems PH, Smits P, Russel FG. Probenecid interferes with renal oxidative metabolism: a potential pitfall in its use as an inhibitor of drug transport. Br J Pharmacol 2000; 131:57-62. [PMID: 10960069 PMCID: PMC1572299 DOI: 10.1038/sj.bjp.0703541] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
The anionic drug probenecid has been traditionally used as an inhibitor of renal organic anion transport. More recently the drug was found to inhibit organic cation transport as well, and it is used to retain intracellularly loaded fluorophores. In these investigations it is implicitly assumed that probenecid performs its activity through competition for transport. Here we studied the possibility that probenecid provokes its effect through inhibition of cellular oxidative metabolism. Oxygen consumption was measured in isolated rat kidney cortex mitochondria. At concentrations of 1 mM or higher, probenecid increased the resting state (state 4) and decreased the ADP-stimulated respiration (state 3). A complete loss in respiratory control was observed at 10 mM probenecid. After incubating isolated rat kidney proximal tubular cells (PTC) for 30 min with probenecid a concentration-dependent reduction in ATP content was observed, which was significant at concentrations of 1 mM and higher. Using digital image fluorescence microscopy the membrane potential in PTC was measured with bisoxonol. The mitochondrial effects of probenecid were paralleled by a depolarization of the plasma membrane, immediately after drug addition. All events are likely to be a result of membrane disordering due to the lipophilic character of probenecid, and may explain, at least in part, the various inhibitory effects found for the drug. We recommend to be cautious with applying probenecid in cellular research.
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Affiliation(s)
- R Masereeuw
- Department of Pharmacology and Toxicology 233 University Medical Centre Nijmegen, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands.
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21
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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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22
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Parak WJ, Domke J, George M, Kardinal A, Radmacher M, Gaub HE, de Roos AD, Theuvenet AP, Wiegand G, Sackmann E, Behrends JC. Electrically excitable normal rat kidney fibroblasts: A new model system for cell-semiconductor hybrids. Biophys J 1999; 76:1659-67. [PMID: 10049346 PMCID: PMC1300142 DOI: 10.1016/s0006-3495(99)77325-x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
In testing various designs of cell-semiconductor hybrids, the choice of a suitable type of electrically excitable cell is crucial. Here normal rat kidney (NRK) fibroblasts are presented as a cell line, easily maintained in culture, that may substitute for heart or nerve cells in many experiments. Like heart muscle cells, NRK fibroblasts form electrically coupled confluent cell layers, in which propagating action potentials are spontaneously generated. These, however, are not associated with mechanical disturbances. Here we compare heart muscle cells and NRK fibroblasts with respect to action potential waveform, morphology, and substrate adhesion profile, using the whole-cell variant of the patch-clamp technique, atomic force microscopy (AFM), and reflection interference contrast microscopy (RICM), respectively. Our results clearly demonstrate that NRK fibroblasts should provide a highly suitable test system for investigating the signal transfer between electrically excitable cells and extracellular detectors, available at a minimum cost and effort for the experimenters.
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Affiliation(s)
- W J Parak
- Institut für Angewandte Physik, Ludwig-Maximilians Universität, Munich, Germany
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23
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De Roos A, Willems PH, van Zoelen EJ, Theuvenet AP. Synchronized Ca2+ signaling by intercellular propagation of Ca2+ action potentials in NRK fibroblasts. THE AMERICAN JOURNAL OF PHYSIOLOGY 1997; 273:C1900-7. [PMID: 9435495 DOI: 10.1152/ajpcell.1997.273.6.c1900] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The intercellular propagation of Ca2+ waves by diffusion of inositol trisphosphate has been shown to be a general mechanism by which nonexcitable cells communicate. Here, we show that monolayers of normal rat kidney (NRK) fibroblasts behave like a typical excitable tissue. In confluent monolayers of these cells, Ca2+ action potentials can be generated by local depolarization of the monolayer on treatment with either bradykinin or an elevation of the extracellular K+ concentration. These electronically propagating action potentials travel intercellularly over long distances in an all-or-none fashion at a speed of approximately 6.1 mm/s and can be blocked by L-type Ca2+ channel blockers. The action potentials are generated by depolarizations beyond the threshold value for L-type Ca2+ channels of about -15 mV. The result of these locally induced, propagating Ca2+ action potentials is an almost synchronous, transient increase in the intracellular Ca2+ concentration in large numbers of cells. These data show that electrically coupled fibroblasts can form an excitable syncytium, and they elucidate a novel mechanism of intercellular Ca2+ signaling in these cells that may coordinate synchronized multicellular responses to local stimuli.
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Affiliation(s)
- A De Roos
- Department of Cell Biology, University of Nijmegen, The Netherlands
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