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Deng K, Thorn P. Presynaptic-like mechanisms and the control of insulin secretion in pancreatic β-cells. Cell Calcium 2022; 104:102585. [DOI: 10.1016/j.ceca.2022.102585] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2022] [Revised: 03/24/2022] [Accepted: 03/26/2022] [Indexed: 12/18/2022]
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2
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Lammert E, Thorn P. The Role of the Islet Niche on Beta Cell Structure and Function. J Mol Biol 2019; 432:1407-1418. [PMID: 31711959 DOI: 10.1016/j.jmb.2019.10.032] [Citation(s) in RCA: 46] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2019] [Revised: 10/25/2019] [Accepted: 10/29/2019] [Indexed: 01/15/2023]
Abstract
The islets of Langerhans or pancreatic islets are pivotal in the control of blood glucose and are complex microorgans embedded within the larger volume of the exocrine pancreas. Humans can have ~3.2 million islets [1] which, to our current knowledge, function in a similar manner to sense circulating blood glucose levels and respond with the secretion of a mix of different hormones that act to maintain glucose concentrations around a specific set point [2]. At a cellular level, the control of hormone secretion by glucose and other secretagogues is well-understood [3]. The key signal cascades have been identified and many details of the secretory process are known. However, if we shift focus from single cells and consider cells within intact islets, we do not have a comprehensive model as to how the islet environment influences cell function and how the islets work as a whole. This is important because there is overwhelming evidence that the structure and function of the individual endocrine cells are dramatically affected by the islet environment [4,5]. Uncovering the influence of this islet niche might drive future progress in treatments for Type 2 diabetes [6] and cell replacement therapies for Type 1 diabetes [7]. In this review, we focus on the insulin secreting beta cells and their interactions with the immediate environment that surrounds them including endocrine-endocrine interactions and contacts with capillaries.
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Affiliation(s)
- Eckhard Lammert
- Institute of Metabolic Physiology, Heinrich Heine University, Düsseldorf, Germany; Institute for Vascular and Islet Cell Biology, German Diabetes Center, Leibniz Center for Diabetes Research, Heinrich Heine University, Düsseldorf, Germany; German Center for Diabetes Research (DZD e.V.), Neuherberg, Germany
| | - Peter Thorn
- Charles Perkins Centre, School of Medical Sciences, University of Sydney, Camperdown, NSW 2006, Australia.
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3
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Félix-Martínez GJ, Godínez-Fernández JR. Modeling the spatiotemporal distribution of Ca
2+
during action potential firing in human pancreatic
β
-cells. Biomed Phys Eng Express 2017. [DOI: 10.1088/2057-1976/aa669f] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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4
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Gan WJ, Zavortink M, Ludick C, Templin R, Webb R, Webb R, Ma W, Poronnik P, Parton RG, Gaisano HY, Shewan AM, Thorn P. Cell polarity defines three distinct domains in pancreatic β-cells. J Cell Sci 2016; 130:143-151. [PMID: 26919978 PMCID: PMC5394774 DOI: 10.1242/jcs.185116] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2015] [Accepted: 02/08/2016] [Indexed: 12/15/2022] Open
Abstract
The structural organisation of pancreatic β-cells in the islets of Langerhans is relatively unknown. Here, using three-dimensional (3D) two-photon, 3D confocal and 3D block-face serial electron microscopy, we demonstrate a consistent in situ polarisation of β-cells and define three distinct cell surface domains. An apical domain located at the vascular apogee of β-cells, defined by the location of PAR-3 (also known as PARD3) and ZO-1 (also known as TJP1), delineates an extracellular space into which adjacent β-cells project their primary cilia. A separate lateral domain, is enriched in scribble and Dlg, and colocalises with E-cadherin and GLUT2 (also known as SLC2A2). Finally, a distinct basal domain, where the β-cells contact the islet vasculature, is enriched in synaptic scaffold proteins such as liprin. This 3D analysis of β-cells within intact islets, and the definition of distinct domains, provides new insights into understanding β-cell structure and function. Summary: 3D imaging methods identify three structural and functional domains within β-cells in islets: apical, lateral and basal.
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Affiliation(s)
- Wan J Gan
- School of Biomedical Sciences, University of Queensland, St Lucia, Queensland 4072, Australia.,Charles Perkins Centre, John Hopkins Drive, University of Sydney, Camperdown, New South Wales, 2050, Australia
| | - Michael Zavortink
- School of Biomedical Sciences, University of Queensland, St Lucia, Queensland 4072, Australia
| | - Christine Ludick
- School of Biomedical Sciences, University of Queensland, St Lucia, Queensland 4072, Australia
| | - Rachel Templin
- Centre for Microscopy and Microanalysis, University of Queensland, St Lucia, Queensland 4072, Australia
| | - Robyn Webb
- Centre for Microscopy and Microanalysis, University of Queensland, St Lucia, Queensland 4072, Australia
| | - Richard Webb
- Centre for Microscopy and Microanalysis, University of Queensland, St Lucia, Queensland 4072, Australia
| | - Wei Ma
- Charles Perkins Centre, John Hopkins Drive, University of Sydney, Camperdown, New South Wales, 2050, Australia
| | - Philip Poronnik
- Department of Physiology, School of Medical Sciences, The University of Sydney, Camperdown, New South Wales, 2006, Australia
| | - Robert G Parton
- Centre for Microscopy and Microanalysis, University of Queensland, St Lucia, Queensland 4072, Australia.,Institute for Molecular Bioscience, University of Queensland, St Lucia, Queensland 4072, Australia
| | - Herbert Y Gaisano
- Department of Medicine, University of Toronto, Toronto, Ontario, M5S1A8, Canada
| | - Annette M Shewan
- School of Chemistry and Molecular Biosciences, University of Queensland, St Lucia, Queensland 4072, Australia
| | - Peter Thorn
- School of Biomedical Sciences, University of Queensland, St Lucia, Queensland 4072, Australia .,Charles Perkins Centre, John Hopkins Drive, University of Sydney, Camperdown, New South Wales, 2050, Australia
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5
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Castiello FR, Heileman K, Tabrizian M. Microfluidic perfusion systems for secretion fingerprint analysis of pancreatic islets: applications, challenges and opportunities. LAB ON A CHIP 2016; 16:409-31. [PMID: 26732665 DOI: 10.1039/c5lc01046b] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
A secretome signature is a heterogeneous profile of secretions present in a single cell type. From the secretome signature a smaller panel of proteins, namely a secretion fingerprint, can be chosen to feasibly monitor specific cellular activity. Based on a thorough appraisal of the literature, this review explores the possibility of defining and using a secretion fingerprint to gauge the functionality of pancreatic islets of Langerhans. It covers the state of the art regarding microfluidic perfusion systems used in pancreatic islet research. Candidate analytical tools to be integrated within microfluidic perfusion systems for dynamic secretory fingerprint monitoring were identified. These analytical tools include patch clamp, amperometry/voltametry, impedance spectroscopy, field effect transistors and surface plasmon resonance. Coupled with these tools, microfluidic devices can ultimately find applications in determining islet quality for transplantation, islet regeneration and drug screening of therapeutic agents for the treatment of diabetes.
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Affiliation(s)
- F Rafael Castiello
- Biomedical Engineering Department, McGill University, Montreal, QC H3A 2B4, Canada.
| | - Khalil Heileman
- Biomedical Engineering Department, McGill University, Montreal, QC H3A 2B4, Canada.
| | - Maryam Tabrizian
- Biomedical Engineering Department, McGill University, Montreal, QC H3A 2B4, Canada.
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6
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Hoang Do O, Thorn P. Insulin secretion from beta cells within intact islets: location matters. Clin Exp Pharmacol Physiol 2015; 42:406-14. [PMID: 25676261 PMCID: PMC4418378 DOI: 10.1111/1440-1681.12368] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2014] [Revised: 12/21/2014] [Accepted: 01/06/2015] [Indexed: 12/17/2022]
Abstract
The control of hormone secretion is central to body homeostasis, and its dysfunction is important in many diseases. The key cellular steps that lead to hormone secretion have been identified, and the stimulus-secretion pathway is understood in outline for many endocrine cells. In the case of insulin secretion from pancreatic beta cells, this pathway involves the uptake of glucose, cell depolarization, calcium entry, and the triggering of the fusion of insulin-containing granules with the cell membrane. The wealth of information on the control of insulin secretion has largely been obtained from isolated single-cell studies. However, physiologically, beta cells exist within the islets of Langerhans, with structural and functional specializations that are not preserved in single-cell cultures. This review focuses on recent work that is revealing distinct aspects of insulin secretion from beta cells within the islet.
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Affiliation(s)
- Oanh Hoang Do
- School of Biomedical Sciences, University of Queensland, St Lucia, Brisbane, Qld, Australia
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7
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Félix-Martínez GJ, Godínez-Fernández JR. Modeling Ca(2+) currents and buffered diffusion of Ca(2+) in human β-cells during voltage clamp experiments. Math Biosci 2015; 270:66-80. [PMID: 26476144 DOI: 10.1016/j.mbs.2015.09.009] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2014] [Revised: 09/03/2015] [Accepted: 09/28/2015] [Indexed: 11/27/2022]
Abstract
Macroscopic Ca(2+) currents of the human β-cells were characterized using the Hodgkin-Huxley formalism. Expressions describing the Ca(2+)-dependent inactivation process of the L-type Ca(2+) channels in terms of the concentration of Ca(2+) were obtained. By coupling the modeled Ca(2+) currents to a three-dimensional model of buffered diffusion of Ca(2+), we simulated the Ca(2+) transients formed in the immediate vicinity of the cell membrane during voltage clamp experiments performed in high buffering conditions. Our modeling approach allowed us to consider the distribution of the Ca(2+) sources over the cell membrane. The effect of exogenous (EGTA) and endogenous Ca(2+) buffers on the temporal course of the Ca(2+) transients was evaluated. We show that despite the high Ca(2+) buffering capacity, nanodomains are formed in the submembrane space, where a peak Ca(2+) concentration between ∼76 and 143 µM was estimated from our simulations. In addition, the contribution of each Ca(2+) current to the formation of the Ca(2+) nanodomains was also addressed. Here we provide a general framework to incorporate the spatial aspects to the models of the pancreatic β-cell, such as a more detailed and realistic description of Ca(2+) dynamics in response to electrical activity in physiological conditions can be provided by future models.
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Affiliation(s)
- Gerardo J Félix-Martínez
- Department of Electrical Engineering, Universidad Autónoma Metropolitana Iztapalapa, México, D.F., Mexico .
| | - J Rafael Godínez-Fernández
- Department of Electrical Engineering, Universidad Autónoma Metropolitana Iztapalapa, México, D.F., Mexico
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8
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Wang J, Ewing AG. Simultaneous study of subcellular exocytosis with individually addressable multiple microelectrodes. Analyst 2015; 139:3290-5. [PMID: 24740449 DOI: 10.1039/c4an00058g] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We report the application of individually addressable microelectrode arrays (MEAs) to study the heterogeneity of cell exocytosis at the subcellular level. Multiple subcellular-size electrodes are covered by a single PC12 cell for the investigation of subcellular exocytosis. PC12 cells have been seeded and cultured on top of three kinds of MEAs containing 16, 25, or 36 square microelectrodes (4 μm width in a 4 by 4 MEA, 3 μm width in a 5 by 5 MEA, 2 μm width in a 6 by 6 MEA). After collagen coating, single cells were found to cover several electrodes and these were selected for the study of subcellular exocytosis. Amperometric results show that single cell and subcellular heterogeneity in single cell exocytosis can be electrochemically detected with these MEAs. The results also show that these MEAs are suitable for detecting fast chemical events at single cells, as well as for developing multifunctional electrochemical sensors.
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Affiliation(s)
- Jun Wang
- Department of Chemistry and Molecular Biology, University of Gothenburg, Sweden
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9
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Low JT, Zavortink M, Mitchell JM, Gan WJ, Do OH, Schwiening CJ, Gaisano HY, Thorn P. Insulin secretion from beta cells in intact mouse islets is targeted towards the vasculature. Diabetologia 2014; 57:1655-63. [PMID: 24795086 PMCID: PMC4079948 DOI: 10.1007/s00125-014-3252-6] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/11/2013] [Accepted: 04/03/2014] [Indexed: 12/28/2022]
Abstract
AIMS/HYPOTHESIS We set out to test the hypothesis that insulin secretion from beta cells is targeted towards the vasculature. METHODS The spatial location of granule fusion was identified by live-cell two-photon imaging of mouse pancreatic beta cells within intact islets, using sulforhodamine B labelling. Three-dimensional (3D) immunofluorescence of pancreatic slices was used to identify the location of proteins associated with neuronal synapses. RESULTS We demonstrated an asymmetric, non-random, distribution of sites of insulin granule fusion in response to glucose and focal targeting of insulin granule secretion to the beta cell membrane facing the vasculature. 3D immunofluorescence of islets showed that structural proteins, such as liprin, piccolo and Rab2-interacting molecule, normally associated with neuronal presynaptic targeting, were present in beta cells and enriched at the vascular face. In contrast, we found that syntaxin 1A and synaptosomal-associated protein 25 kDa (SNAP25) were relatively evenly distributed across the beta cells. CONCLUSIONS/INTERPRETATION Our results show that beta cells in situ, within intact islets, are polarised and target insulin secretion. This evidence for an 'endocrine synapse' has wide implications for our understanding of stimulus-secretion coupling in healthy islets and in disease.
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Affiliation(s)
- Jiun T Low
- School of Biomedical Sciences, University of Queensland, St Lucia, QLD, 4072, Australia
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10
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Fan Y, Rubakhin SS, Sweedler JV. Collection of peptides released from single neurons with particle-embedded monolithic capillaries followed by detection with matrix-assisted laser desorption/ionization mass spectrometry. Anal Chem 2011; 83:9557-63. [PMID: 22053721 DOI: 10.1021/ac202338e] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Characterization of the stimulated release of neuropeptides from brain slices and individual cultured neurons requires efficient collection of the releasate from relatively large volumes of physiological saline. Here, several collection approaches are optimized using particle-embedded monolithic capillaries (PEMCs) with poly(stearyl methacrylate-co-ethylene glycol dimethacrylate) monolith acting as a "glue". Two distinct extraction particles, with either pyrrolidone (PY) or ethylenediamine (EDA) as the functional group on polystyrene backbone, have been embedded into capillaries having an inner diameter of 250 μm. The capillaries act as collection devices for sampling neuropeptide release; the collection protocols are described, and the extraction efficiency of the probes are characterized. Specifically, the binding of angiotensin II from a peptide mixture onto the PY and EDA columns was 16 and 28 pmol, respectively, in a volume of 20 μL of saline. The peptides released from these columns have been characterized via matrix-assisted laser desorption/ionization time-of-flight mass spectrometry with low femtomole detection limits. When the PEMC columns were positioned in close proximity to individual neurons and 50 mM KCl was used as the secretagogue, peptides released from individual identified cultured neurons isolated from Aplysia californica were collected and characterized.
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Affiliation(s)
- Yi Fan
- Department of Chemistry, University of Illinois at Urbana-Champaign, Illinois 61801, United States
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11
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Huang Y, Cai D, Chen P. Micro- and Nanotechnologies for Study of Cell Secretion. Anal Chem 2011; 83:4393-406. [DOI: 10.1021/ac200358b] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Affiliation(s)
- Yinxi Huang
- Division of Bioengineering, School of Chemical and Biomedical Engineering, Nanyang Technological University, Singapore 637457
| | - Dong Cai
- Biology Department, Boston College, Boston, Massachusetts 02467, United States
| | - Peng Chen
- Division of Bioengineering, School of Chemical and Biomedical Engineering, Nanyang Technological University, Singapore 637457
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12
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Monitoring of Cellular Dynamics with Electrochemical Detection Techniques. MODERN ASPECTS OF ELECTROCHEMISTRY 2011. [DOI: 10.1007/978-1-4614-0347-0_1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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13
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Iannacone JM, Ren S, Hatcher NG, Sweedler JV. Collecting peptide release from the brain using porous polymer monolith-based solid phase extraction capillaries. Anal Chem 2009; 81:5433-8. [PMID: 19485405 PMCID: PMC2810310 DOI: 10.1021/ac9005843] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Porous polymer monolithic (PPM) columns are employed to collect and concentrate neuronal release from invertebrate and vertebrate model systems, prior to their characterization with mass spectrometry. The monoliths are fabricated in fused-silica capillaries from lauryl methacrylate (LMA) and ethylene glycol dimethacrylate (EDMA). The binding capacities for fluorescein and for fluorescently labeled peptides are on the order of nanomoles per millimeter of length of monolith material for a capillary with an inner diameter of 200 microm. To evaluate this strategy for collecting peptides from physiological solutions, angiotensin I and insulin in artificial seawater are loaded onto, and then released from, the monoliths after a desalination rinse, resulting in femtomole limits of detection via matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Positioned in the extracellular media near Aplysia californica bag cell neurons, upon electrical stimulation, these LMA-EDMA monoliths are also used to collect and concentrate peptide release, with egg-laying hormones and acidic peptide detected. In addition, the collection of several known peptides secreted from chemically stimulated mouse brain slices demonstrates their ability to collect releasates from a variety of neuronal tissues. When compared to collection approaches using individual beads placed on brain slices, the PPM capillaries offer greater binding capacity. Moreover, they maintain higher spatial resolution, compared to the larger-volume, solid-phase extraction collection strategies.
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Affiliation(s)
- Jamie M. Iannacone
- Department of Chemistry and the Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801
| | - Shifang Ren
- Department of Chemistry and the Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801
| | - Nathan G. Hatcher
- Department of Chemistry and the Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801
| | - Jonathan V. Sweedler
- Department of Chemistry and the Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801
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14
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Amatore C, Arbault S, Bouret Y, Guille M, Lemaître F, Verchier Y. Invariance of exocytotic events detected by amperometry as a function of the carbon fiber microelectrode diameter. Anal Chem 2009; 81:3087-93. [PMID: 19290664 DOI: 10.1021/ac900059s] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Etched carbon fiber microelectrodes of different radii have been used for amperometric measurements of single exocytotic events occurring at adrenal chromaffin cells. Frequency, kinetic, and quantitative information on exocytosis provided by amperometric spikes were analyzed as a function of the surface area of the microelectrodes. Interestingly, the percentage of spikes with foot (as well as their own characteristics), a category revealing the existence of sufficient long-lasting fusion pores, was found to be constant whatever the microelectrode diameter was, whereas the probability of overlapping spikes decreased with the electrode size. This confirmed that the prespike foot could not feature accidental superimposition of separated events occurring at different places. Moreover, the features of amperometric spikes investigated here (charge, intensity and kinetics) were found constant for all microelectrode diameters. This demonstrated that the electrochemical measurement does not introduce significant bias onto the kinetics and thermodynamics of release during individual exocytotic events. All in all, this work evidences that information on exocytosis amperometrically recorded with the usual 7 microm diameter carbon fiber electrodes is biologically relevant, although the frequent overlap between spikes requires a censorship of the data during the analytical treatment.
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Affiliation(s)
- Christian Amatore
- Laboratoire PASTEUR, Département de Chimie, Ecole Normale Supérieure, CNRS UPMC Univ Paris 06, 24 rue Lhomond, 75231 Paris Cedex 05, France.
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15
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Monitoring of vesicular exocytosis from single cells using micrometer and nanometer-sized electrochemical sensors. Anal Bioanal Chem 2009; 394:17-32. [PMID: 19274456 DOI: 10.1007/s00216-009-2703-2] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2008] [Revised: 02/07/2009] [Accepted: 02/10/2009] [Indexed: 02/05/2023]
Abstract
Communication between cells by release of specific chemical messengers via exocytosis plays crucial roles in biological process. Electrochemical detection based on ultramicroelectrodes (UMEs) has become one of the most powerful techniques in real-time monitoring of an extremely small number of released molecules during very short time scales, owing to its intrinsic advantages such as fast response, excellent sensitivity, and high spatiotemporal resolution. Great successes have been achieved in the use of UME methods to obtain quantitative and kinetic information about released chemical messengers and to reveal the molecular mechanism in vesicular exocytosis. In this paper, we review recent developments in monitoring exocytosis by use of UMEs-electrochemical-based techniques including electrochemical detection using micrometer and nanometer-sized sensors, scanning electrochemical microscopy (SECM), and UMEs implemented in lab-on-a-chip (LOC) microsystems. These advances are of great significance in obtaining a better understanding of vesicular exocytosis and chemical communications between cells, and will facilitate developments in many fields, including analytical chemistry, biological science, and medicine. Furthermore, future developments in electrochemical probing of exocytosis are also proposed.
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16
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Amatore C, Arbault S, Guille M, Lemaître F. Electrochemical Monitoring of Single Cell Secretion: Vesicular Exocytosis and Oxidative Stress. Chem Rev 2008; 108:2585-621. [DOI: 10.1021/cr068062g] [Citation(s) in RCA: 316] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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17
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Abstract
The redox chemistry of insulin was investigated at glassy carbon (GC) electrodes that were coated with films of chitosan (CHIT) and multiwalled carbon nanotubes (CNT). While bare electrodes deactivated quickly during insulin oxidation, the GC electrodes coated with CHIT and CHIT-CNT films generated stable insulin currents. The GC/CHIT-CNT electrodes were used for investigating the electrooxidation process of insulin and amperometric determination of insulin. The mass spectrometric, electron paramagnetic resonance, and separation studies of electrolyzed insulin solutions suggested that the loss of 4 mass units upon insulin oxidation at CNT could be accounted for by the formation of two dityrosine cross-links intramolecularly. At a potential of 0.700 V and physiological pH 7.40, the GC/CHIT-CNT electrodes displayed a detection limit of approximately 30 nM insulin (S/N = 3), sensitivity of 135 mA M(-1) cm(-2), linear dynamic range from 0.10 to 3.0 microM (R2 = 0.995), and superior operational and long-term stability. The CNT-based electrodes are promising new insulin detectors for diabetes-related studies such as fast chromatographic analysis of therapeutic insulin formulations or evaluation of quality of pancreatic islets prior to their transplantation.
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Affiliation(s)
- Maogen Zhang
- Department of Chemistry, University of Texas at San Antonio, San Antonio, Texas 78249-0698, USA
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18
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Wilson GS, Gifford R. Biosensors for real-time in vivo measurements. Biosens Bioelectron 2005; 20:2388-403. [PMID: 15854814 DOI: 10.1016/j.bios.2004.12.003] [Citation(s) in RCA: 363] [Impact Index Per Article: 19.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2004] [Revised: 11/01/2004] [Accepted: 12/02/2004] [Indexed: 11/29/2022]
Abstract
The current status of sensors capable of continuous measurement of analytes in biological media is reviewed. This review containing 173 references deals with devices whose use in single cells, tissue slices, animal models and humans has been demonstrated. In addition to sensors specific for glucose, lactate, glutamate, pyruvate, choline and acetylcholine, insights obtained from monitoring nitric oxide, Na(+), K(+), Ca(2+), and dopamine are presented. Performance criteria for sensor performance are described as is the subject of biosensor calibration. Biocompatibility issues are dealt with in some detail as is the status of continuous blood glucose monitoring in humans.
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Affiliation(s)
- George S Wilson
- Department of Chemistry, University of Kansas, Malott Hall, Lawrence, KS 66045, USA.
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19
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Smukler SR, Tang L, Wheeler MB, Salapatek AMF. Exogenous nitric oxide and endogenous glucose-stimulated beta-cell nitric oxide augment insulin release. Diabetes 2002; 51:3450-60. [PMID: 12453899 DOI: 10.2337/diabetes.51.12.3450] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The role nitric oxide (NO) plays in physiological insulin secretion has been controversial. Here we present evidence that exogenous NO stimulates insulin secretion, and that endogenous NO production occurs and is involved in the regulation of insulin release. Radioimmunoassay measurement of insulin release and a dynamic assay of exocytosis using the dye FM1-43 demonstrated that three different NO donors-hydroxylamine (HA), sodium nitroprusside, and 3-morpholinosydnonimine (SIN-1)-each stimulated a marked increase in insulin secretion from INS-1 cells. Pharmacological manipulation of the guanylate cyclase/guanosine 3',5'-cyclic monophosphate pathway indicated that this pathway was involved in mediating the effect of the intracellular NO donor, HA, which was used to simulate endogenous NO production. This effect was further characterized as involving membrane depolarization and intracellular Ca(2+) ([Ca(2+)](i)) elevation. SIN-1 application enhanced glucose-induced [Ca(2+)](i) responses in primary beta-cells and augmented insulin release from islets in a glucose-dependent manner. Real-time monitoring of NO using the NO-sensitive fluorescent dye, diaminofluorescein, was used to provide direct and dynamic imaging of NO generation within living beta-cells. This showed that endogenous NO production could be stimulated by elevation of [Ca(2+)](i) levels and by glucose in both INS-1 and primary rat beta-cells. Scavenging endogenously produced NO-attenuated glucose-stimulated insulin release from INS-1 cells and rat islets. Thus, the results indicated that applied NO is able to exert an insulinotropic effect, and implicated endogenously produced NO in the physiological regulation of insulin release.
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Affiliation(s)
- Simon R Smukler
- Department of Physiology, University of Toronto, 1 King's College Circle, Toronto, Ontario, Canada M5S 1A8
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20
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Leung YM, Sheu L, Kwan E, Wang G, Tsushima R, Gaisano H. Visualization of sequential exocytosis in rat pancreatic islet beta cells. Biochem Biophys Res Commun 2002; 292:980-6. [PMID: 11944911 DOI: 10.1006/bbrc.2002.6712] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The examination of insulin exocytosis at the single cell level by conventional electrophysiologic and amperometric methods possesses inherent limitations, and may not accurately reflect the morphologic events of exocytosis of the insulin granule. To overcome some of these limitations, we show by epifluorescent microscopy of a fluorescent dye, FM1-43, its incorporation into the plasma membrane and oncoming insulin granules undergoing exocytosis, and their core proteins. Using this method, we tracked exocytosis in real-time in insulinoma INS-1 and single rat islet beta cells in response to KCl and glucose. We observed both single transient and multi-stepwise increases in membrane FM1-43 fluorescence, suggesting single granule exocytosis as well as sequential and compound exocytosis, respectively. Confocal microscopy of nonpermeabilized cells shows that some of the exocytosed insulin granules labeled by the FM1-43 dye could also be labeled with insulin antibodies, suggesting prolonged openings of the fusion pores and slow dissolution of the granule core proteins on the membrane surface.
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Affiliation(s)
- Yuk Man Leung
- Department of Medicine, University of Toronto, Toronto, Ontario, M5S 1A8, Canada
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Qian WJ, Kennedy RT. Spatial organization of Ca(2+) entry and exocytosis in mouse pancreatic beta-cells. Biochem Biophys Res Commun 2001; 286:315-21. [PMID: 11500039 DOI: 10.1006/bbrc.2001.5379] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Secretion from single pancreatic beta-cells was imaged using a novel technique in which Zn(2+), costored in secretory granules with insulin, was detected by confocal fluorescence microscopy as it was released from the cells. Using this technique, it was observed that secretion from beta-cells was limited to an active region that comprised approximately 50% of the cell perimeter. Using ratiometric imaging with indo-1, localized increases in intracellular Ca(2+) concentration ([Ca(2+)](i)) evoked by membrane depolarization were also observed. Using sequential measurements of secretion and [Ca(2+)](i) at single cells, colocalization of exocytotic release sites and Ca(2+) entry was observed when cells were stimulated by glucose or K(+). Treatment of cells with the Ca(2+) ionophore 4-Br-A23187 induced large Ca(2+) influx around the entire cell circumference. Despite the nonlocalized increase in [Ca(2+)](i), secretion evoked by 4-Br-A23187 was still localized to the same region as that evoked by secretagogues such as glucose. It is concluded that Ca(2+) channels activated by depolarization are localized to specific membrane domains where exocytotic release also occurs; however, localized secretion is not exclusively regulated by localized increases in [Ca(2+)](i), but instead involves spatial localization of other components of the exocytotic machinery.
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Affiliation(s)
- W J Qian
- Department of Chemistry, University of Florida, Gainesville, Florida 32611-7200, USA
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