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Zhang J, Wang S, Liu Z, Zhong C, Lei Y, Zheng Q, Xu Y, Shan S, He H, Ren T. Connexin 25 maintains self-renewal and functions of airway basal cells for airway regeneration. Stem Cell Res Ther 2024; 15:286. [PMID: 39256871 PMCID: PMC11389295 DOI: 10.1186/s13287-024-03908-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2024] [Accepted: 08/28/2024] [Indexed: 09/12/2024] Open
Abstract
BACKGROUND The formation of stem cell clones enables close contact of stem cells inside. The gap junctions in such clone spheres establish a microenvironment that allows frequent intercellular communication to maintain self-renewal and functions of stem cells. Nevertheless, the essential gap junction protein for molecular signaling in clones is poorly known. METHODS Primary human airway basal cells (hBCs) were isolated from brushing samples through bronchoscopy and then cultured. A tightly focused femtosecond laser was used to excite the local Ca2+ in an individual cell to initiate an internal Ca2+ wave in a clone to screen gap junction proteins. Immunoflourescence staining and clonogenicity assay were used to evaluate self-renewal and functions. RNA and protein levels were assessed by PCR and Western blot. Air-liquid interface assay was conducted to evaluate the differentiation potential. A Naphthalene injury mouse model was used to assess the regeneration potential. RESULTS Herein, we identify Connexin 25 (Cx25) dominates intercellular Ca2+ communications in clones of hBCs in vitro to maintain the self-renewal and pluripotency of them. The self-renewal and in vitro differentiation functions and in vivo regeneration potential of hBCs in an airway damage model are both regulated by Cx25. The abnormal expression of Cx25 is validated in several diseases including IPF, Covid-19 and bronchiectasis. CONCLUSION Cx25 is essential for hBC clones in maintaining self-renewal and functions of hBCs via gap junctions.
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Affiliation(s)
- Jingyuan Zhang
- Department of Respiratory Medicine, Shanghai Sixth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, 600 Yishan Road, Shanghai, 200233, China
- School of Biomedical Engineering, Shanghai Jiao Tong University, 1954 Huashan Road, Shanghai, 200030, China
| | - Shaoyang Wang
- Department of Respiratory Medicine, Shanghai Sixth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, 600 Yishan Road, Shanghai, 200233, China
- School of Biomedical Engineering, Shanghai Jiao Tong University, 1954 Huashan Road, Shanghai, 200030, China
| | - Zeyu Liu
- Department of Respiratory Medicine, Shanghai Sixth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, 600 Yishan Road, Shanghai, 200233, China
| | - Cheng Zhong
- Department of Respiratory Medicine, Shanghai Sixth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, 600 Yishan Road, Shanghai, 200233, China
| | - Yuqiong Lei
- Department of Respiratory Medicine, Shanghai Sixth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, 600 Yishan Road, Shanghai, 200233, China
| | - Qi Zheng
- Department of Respiratory Medicine, Shanghai Sixth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, 600 Yishan Road, Shanghai, 200233, China
| | - Yongle Xu
- Department of Respiratory Medicine, Shanghai Sixth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, 600 Yishan Road, Shanghai, 200233, China
| | - Shan Shan
- Department of Respiratory Medicine, Shanghai Sixth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, 600 Yishan Road, Shanghai, 200233, China
| | - Hao He
- School of Biomedical Engineering, Shanghai Jiao Tong University, 1954 Huashan Road, Shanghai, 200030, China.
| | - Tao Ren
- Department of Respiratory Medicine, Shanghai Sixth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, 600 Yishan Road, Shanghai, 200233, China.
- Shanghai Key Laboratory of Sleep Disordered Breathing, 600 Yishan Road, Shanghai, 200233, China.
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2
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Rivers RJ, Meininger CJ. The Tissue Response to Hypoxia: How Therapeutic Carbon Dioxide Moves the Response toward Homeostasis and Away from Instability. Int J Mol Sci 2023; 24:ijms24065181. [PMID: 36982254 PMCID: PMC10048965 DOI: 10.3390/ijms24065181] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2023] [Revised: 03/02/2023] [Accepted: 03/05/2023] [Indexed: 03/30/2023] Open
Abstract
Sustained tissue hypoxia is associated with many pathophysiological conditions, including chronic inflammation, chronic wounds, slow-healing fractures, microvascular complications of diabetes, and metastatic spread of tumors. This extended deficiency of oxygen (O2) in the tissue sets creates a microenvironment that supports inflammation and initiates cell survival paradigms. Elevating tissue carbon dioxide levels (CO2) pushes the tissue environment toward "thrive mode," bringing increased blood flow, added O2, reduced inflammation, and enhanced angiogenesis. This review presents the science supporting the clinical benefits observed with the administration of therapeutic CO2. It also presents the current knowledge regarding the cellular and molecular mechanisms responsible for the biological effects of CO2 therapy. The most notable findings of the review include (a) CO2 activates angiogenesis not mediated by hypoxia-inducible factor 1a, (b) CO2 is strongly anti-inflammatory, (c) CO2 inhibits tumor growth and metastasis, and (d) CO2 can stimulate the same pathways as exercise and thereby, acts as a critical mediator in the biological response of skeletal muscle to tissue hypoxia.
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Affiliation(s)
- Richard J Rivers
- Department of Anesthesia and Critical Care Medicine, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Cynthia J Meininger
- Department of Medical Physiology, Texas A&M University School of Medicine, Bryan, TX 77807, USA
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3
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Fabrication of Doxorubicin-Loaded Lipid-Based Nanocarriers by Microfluidic Rapid Mixing. Biomedicines 2022; 10:biomedicines10061259. [PMID: 35740280 PMCID: PMC9219747 DOI: 10.3390/biomedicines10061259] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2022] [Revised: 05/20/2022] [Accepted: 05/26/2022] [Indexed: 02/01/2023] Open
Abstract
Doxorubicin (Dox) is a widely known chemotherapeutic drug that has been encapsulated into liposomes for clinical use, such as Doxil® and Myocet®. Both of these are prepared via remote loading methods, which require multistep procedures. Additionally, their antitumor efficacy is hindered due to the poor drug release from PEGylated liposomes in the tumor microenvironment. In this study, we aimed to develop doxorubicin-loaded lipid-based nanocarriers (LNC-Dox) based on electrostatic interaction using microfluidic technology. The resulting LNC-Dox showed high loading capacity, with a drug-to-lipid ratio (D/L ratio) greater than 0.2, and high efficacy of drug release in an acidic environment. Different lipid compositions were selected based on critical packing parameters and further studied to outline their effects on the physicochemical characteristics of LNC-Dox. Design of experiments was implemented for formulation optimization. The optimized LNC-Dox showed preferred release in acidic environments and better therapeutic efficacy compared to PEGylated liposomal Dox in vivo. Thus, this study provides a feasible approach to efficiently encapsulate doxorubicin into lipid-based nanocarriers fabricated by microfluidic rapid mixing.
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4
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Sherwood MW, Oliet SHR, Panatier A. NMDARs, Coincidence Detectors of Astrocytic and Neuronal Activities. Int J Mol Sci 2021; 22:7258. [PMID: 34298875 PMCID: PMC8307462 DOI: 10.3390/ijms22147258] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Revised: 06/30/2021] [Accepted: 06/30/2021] [Indexed: 12/18/2022] Open
Abstract
Synaptic plasticity is an extensively studied cellular correlate of learning and memory in which NMDARs play a starring role. One of the most interesting features of NMDARs is their ability to act as a co-incident detector. It is unique amongst neurotransmitter receptors in this respect. Co-incident detection is possible because the opening of NMDARs requires membrane depolarisation and the binding of glutamate. Opening of NMDARs also requires a co-agonist. Although the dynamic regulation of glutamate and membrane depolarization have been well studied in coincident detection, the role of the co-agonist site is unexplored. It turns out that non-neuronal glial cells, astrocytes, regulate co-agonist availability, giving them the ability to influence synaptic plasticity. The unique morphology and spatial arrangement of astrocytes at the synaptic level affords them the capacity to sample and integrate information originating from unrelated synapses, regardless of any pre-synaptic and post-synaptic commonality. As astrocytes are classically considered slow responders, their influence at the synapse is widely recognized as modulatory. The aim herein is to reconsider the potential of astrocytes to participate directly in ongoing synaptic NMDAR activity and co-incident detection.
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Affiliation(s)
- Mark W. Sherwood
- University of Bordeaux, INSERM, Neurocentre Magendie, U1215, F-3300 Bordeaux, France;
| | | | - Aude Panatier
- University of Bordeaux, INSERM, Neurocentre Magendie, U1215, F-3300 Bordeaux, France;
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5
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Okamoto T, Park EJ, Kawamoto E, Usuda H, Wada K, Taguchi A, Shimaoka M. Endothelial connexin-integrin crosstalk in vascular inflammation. Biochim Biophys Acta Mol Basis Dis 2021; 1867:166168. [PMID: 33991620 DOI: 10.1016/j.bbadis.2021.166168] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2021] [Revised: 04/18/2021] [Accepted: 05/02/2021] [Indexed: 02/06/2023]
Abstract
Cardiovascular diseases including blood vessel disorders represent a major cause of death globally. The essential roles played by local and systemic vascular inflammation in the pathogenesis of cardiovascular diseases have been increasingly recognized. Vascular inflammation triggers the aberrant activation of endothelial cells, which leads to the functional and structural abnormalities in vascular vessels. In addition to humoral mediators such as pro-inflammatory cytokines and prostaglandins, the alteration of physical and mechanical microenvironment - including vascular stiffness and shear stress - modify the gene expression profiles and metabolic profiles of endothelial cells via mechano-transduction pathways, thereby contributing to the pathogenesis of vessel disorders. Notably, connexins and integrins crosstalk each other in response to the mechanical stress, and, thereby, play an important role in regulating the mechano-transduction of endothelial cells. Here, we provide an overview on how the inter-play between connexins and integrins in endothelial cells unfold during the mechano-transduction in vascular inflammation.
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Affiliation(s)
- Takayuki Okamoto
- Department of Pharmacology, Faculty of Medicine, Shimane University, 89-1 Enya-cho, Izumo-city, Shimane 693-8501, Japan.
| | - Eun Jeong Park
- Department of Molecular Pathobiology and Cell Adhesion Biology, Mie University Graduate School of Medicine, 2-174 Edobashi, Tsu-city, Mie 514-8507, Japan
| | - Eiji Kawamoto
- Department of Molecular Pathobiology and Cell Adhesion Biology, Mie University Graduate School of Medicine, 2-174 Edobashi, Tsu-city, Mie 514-8507, Japan; Department of Emergency and Disaster Medicine, Mie University Graduate School of Medicine, 2-174 Edobashi, Tsu-city, Mie 514-8507, Japan
| | - Haruki Usuda
- Department of Pharmacology, Faculty of Medicine, Shimane University, 89-1 Enya-cho, Izumo-city, Shimane 693-8501, Japan
| | - Koichiro Wada
- Department of Pharmacology, Faculty of Medicine, Shimane University, 89-1 Enya-cho, Izumo-city, Shimane 693-8501, Japan
| | - Akihiko Taguchi
- Department of Regenerative Medicine Research, Foundation for Biomedical Research and Innovation at Kobe, 2-2 Minatojima-Minamimachi, Chuo-ku, Kobe 650-0047, Japan
| | - Motomu Shimaoka
- Department of Molecular Pathobiology and Cell Adhesion Biology, Mie University Graduate School of Medicine, 2-174 Edobashi, Tsu-city, Mie 514-8507, Japan.
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6
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Connexins in the Heart: Regulation, Function and Involvement in Cardiac Disease. Int J Mol Sci 2021; 22:ijms22094413. [PMID: 33922534 PMCID: PMC8122935 DOI: 10.3390/ijms22094413] [Citation(s) in RCA: 57] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2021] [Revised: 04/12/2021] [Accepted: 04/20/2021] [Indexed: 12/20/2022] Open
Abstract
Connexins are a family of transmembrane proteins that play a key role in cardiac physiology. Gap junctional channels put into contact the cytoplasms of connected cardiomyocytes, allowing the existence of electrical coupling. However, in addition to this fundamental role, connexins are also involved in cardiomyocyte death and survival. Thus, chemical coupling through gap junctions plays a key role in the spreading of injury between connected cells. Moreover, in addition to their involvement in cell-to-cell communication, mounting evidence indicates that connexins have additional gap junction-independent functions. Opening of unopposed hemichannels, located at the lateral surface of cardiomyocytes, may compromise cell homeostasis and may be involved in ischemia/reperfusion injury. In addition, connexins located at non-canonical cell structures, including mitochondria and the nucleus, have been demonstrated to be involved in cardioprotection and in regulation of cell growth and differentiation. In this review, we will provide, first, an overview on connexin biology, including their synthesis and degradation, their regulation and their interactions. Then, we will conduct an in-depth examination of the role of connexins in cardiac pathophysiology, including new findings regarding their involvement in myocardial ischemia/reperfusion injury, cardiac fibrosis, gene transcription or signaling regulation.
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7
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Charvériat M, Mouthon F, Rein W, Verkhratsky A. Connexins as therapeutic targets in neurological and neuropsychiatric disorders. Biochim Biophys Acta Mol Basis Dis 2021; 1867:166098. [PMID: 33545299 DOI: 10.1016/j.bbadis.2021.166098] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2020] [Revised: 01/06/2021] [Accepted: 01/19/2021] [Indexed: 12/16/2022]
Abstract
Astrocytes represent the reticular part of the central nervous system; gap junctions formed by connexins Cx43, Cx30- and Cx26 provide for homocellular astrocyte-astrocyte coupling, whereas connexins Cx30, Cx32, Cx43, and Cx47 connect astrocytes and oligodendrocytes. Astroglial networks are anatomically and functionally segregated being homologous to neuronal ensembles. Connexons, gap junctions and hemichannels (unpaired connexons) are affected in various neuropathologies from neuropsychiatric to neurodegenerative diseases. Manipulation of astrocytic connexins modulates the size and outreach of astroglial syncytia thus affecting astroglial homeostatic support. Modulation of astrocytic connexin significantly modifies pharmacological profile of many CNS drugs, which represents an innovative therapeutic approach for CNS disorders; this approach is now actively tested in pre-clinical and clinical studies. Wide combination of connexin modulators with CNS drugs open new promising perspectives for fundamental studies and therapeutic strategies.
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Affiliation(s)
| | | | | | - A Verkhratsky
- Faculty of Biology, Medicine and Health, The University of Manchester, Manchester M13 9PT, UK; Achucarro Centre for Neuroscience, IKERBASQUE, Basque Foundation for Science, 48011 Bilbao, Spain
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8
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Nielsen BS, Zonta F, Farkas T, Litman T, Nielsen MS, MacAulay N. Structural determinants underlying permeant discrimination of the Cx43 hemichannel. J Biol Chem 2019; 294:16789-16803. [PMID: 31554662 DOI: 10.1074/jbc.ra119.007732] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2019] [Revised: 09/24/2019] [Indexed: 02/03/2023] Open
Abstract
Connexin (Cx) gap junction channels comprise two hemichannels in neighboring cells, and their permeability is well-described, but permeabilities of the single Cx hemichannel remain largely unresolved. Moreover, determination of isoform-specific Cx hemichannel permeability is challenging because of concurrent expression of other channels with similar permeability profiles and inhibitor sensitivities. The mammalian Cx hemichannels Cx30 and Cx43 are gated by extracellular divalent cations, removal of which promotes fluorescent dye uptake in both channels but atomic ion conductance only through Cx30. To determine the molecular determinants of this difference, here we employed chimeras and mutagenesis of predicted pore-lining residues in Cx43. We expressed the mutated channels in Xenopus laevis oocytes to avoid background activity of alternative channels. Oocytes expressing a Cx43 hemichannel chimera containing the N terminus or the first extracellular loop from Cx30 displayed ethidium uptake and, unlike WT Cx43, ion conduction, an observation further supported by molecular dynamics simulations. Additional C-terminal truncation of the chimeric Cx43 hemichannel elicited an even greater ion conductance with a magnitude closer to that of Cx30. The inhibitory profile for the connexin hemichannels depended on the permeant, with conventional connexin hemichannel inhibitors having a higher potency toward the ion conductance pathway than toward fluorescent dye uptake. Our results demonstrate a permeant-dependent, isoform-specific inhibition of connexin hemichannels. They further reveal that the outer segments of the pore-lining region, including the N terminus and the first extracellular loop, together with the C terminus preclude ion conductance of the open Cx43 hemichannel.
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Affiliation(s)
- Brian Skriver Nielsen
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Francesco Zonta
- Shanghai Institute for Advanced Immunochemical Studies, ShanghaiTech University, Shanghai 201210, China
| | - Thomas Farkas
- Department of Immunology and Microbiology, Faculty of Health and Medical Sciences, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Thomas Litman
- Department of Immunology and Microbiology, Faculty of Health and Medical Sciences, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Morten Schak Nielsen
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Nanna MacAulay
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, 2200 Copenhagen, Denmark
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9
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Vincze R, Péter M, Szabó Z, Kardos J, Héja L, Kovács Z. Connexin 43 Differentially Regulates Epileptiform Activity in Models of Convulsive and Non-convulsive Epilepsies. Front Cell Neurosci 2019; 13:173. [PMID: 31133805 PMCID: PMC6523398 DOI: 10.3389/fncel.2019.00173] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2018] [Accepted: 04/11/2019] [Indexed: 11/13/2022] Open
Abstract
The influence of astrocytic cell networks on neuronal network activity is an emerging issue in epilepsy. Among the various mechanisms by which astrocytes modulate neuronal function, synchronization of astrocytes via gap junction channels is widely considered to be a crucial mechanism in epileptic conditions, contributing to the synchronization of the neuronal cell networks, possibly inducing recurrent epileptiform activity. Here, we explored whether modulation of astrocytic gap junctions could alter epileptic seizures in different types of epilepsy. Opening of gap junctions by trimethylamine intensifies seizure-like events (SLEs) in the low-[Mg2+] in vitro model of temporal lobe epilepsy, while alleviates seizures in the in vivo WAG/Rij rat model of absence epilepsy. In contrast, application of the gap junction blocker carbenoxolone prevents the appearance of SLEs in the low-[Mg2+] epilepsy model, but aggravates seizures in non-convulsive absence epilepsy, in vivo. Pharmacological dissection of neuronal vs. astrocytic connexins shows that astrocytic Cx43 contribute to seizure formation to a significantly higher extent than neuronal Cx36. We conclude that astrocytic gap junctions are key players in the formation of epileptiform activity and we provide a scheme for the different mode of action in the convulsive and non-convulsive epilepsy types.
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Affiliation(s)
- Renáta Vincze
- Functional Pharmacology Research Group, Institute of Organic Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Budapest, Hungary
| | - Márton Péter
- Functional Pharmacology Research Group, Institute of Organic Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Budapest, Hungary
| | - Zsolt Szabó
- Functional Pharmacology Research Group, Institute of Organic Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Budapest, Hungary
| | - Julianna Kardos
- Functional Pharmacology Research Group, Institute of Organic Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Budapest, Hungary
| | - László Héja
- Functional Pharmacology Research Group, Institute of Organic Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Budapest, Hungary
| | - Zsolt Kovács
- Department of Biology, Eötvös Loránd University, Savaria University Centre, Szombathely, Hungary
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10
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Therapeutic Targeting of Connexin Channels: New Views and Challenges. Trends Mol Med 2018; 24:1036-1053. [PMID: 30424929 DOI: 10.1016/j.molmed.2018.10.005] [Citation(s) in RCA: 60] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2018] [Revised: 10/09/2018] [Accepted: 10/11/2018] [Indexed: 12/22/2022]
Abstract
Connexins, in particular connexin 43 (Cx43), function as gap junction channels (GJCs) and hemichannels (HCs). Only recently, specific tools have been developed to study their pleiotropic functions. Based on various protein interaction sites, distinct connexin-mimetic peptides have been established that enable discrimination between the function of HCs and GJCs. Although the precise mechanism of action of most of these peptides is still a matter of debate, an increasing number of studies report on important effects of those compounds in disease models. In this review, we summarize the structure, life cycle, and the most important physiological and pathological functions of both connexin GJCs and HCs. We provide a critical overview on the use of connexin-targeting peptides, in particular targeting Cx43, with a special focus on the remaining questions and hurdles to be taken in the research field of connexin channels.
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11
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Function of Connexins in the Interaction between Glial and Vascular Cells in the Central Nervous System and Related Neurological Diseases. Neural Plast 2018; 2018:6323901. [PMID: 29983707 PMCID: PMC6015683 DOI: 10.1155/2018/6323901] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2018] [Revised: 05/06/2018] [Accepted: 05/14/2018] [Indexed: 02/05/2023] Open
Abstract
Neuronal signaling together with synapse activity in the central nervous system requires a precisely regulated microenvironment. Recently, the blood-brain barrier is considered as a “neuro-glia-vascular unit,” a structural and functional compound composed of capillary endothelial cells, glial cells, pericytes, and neurons, which plays a pivotal role in maintaining the balance of the microenvironment in and out of the brain. Tight junctions and adherens junctions, which function as barriers of the blood-brain barrier, are two well-known kinds in the endothelial cell junctions. In this review, we focus on the less-concerned contribution of gap junction proteins, connexins in blood-brain barrier integrity under physio-/pathology conditions. In the neuro-glia-vascular unit, connexins are expressed in the capillary endothelial cells and prominent in astrocyte endfeet around and associated with maturation and function of the blood-brain barrier through a unique signaling pathway and an interaction with tight junction proteins. Connexin hemichannels and connexin gap junction channels contribute to the physiological or pathological progress of the blood-brain barrier; in addition, the interaction with other cell-cell-adhesive proteins is also associated with the maintenance of the blood-brain barrier. Lastly, we explore the connexins and connexin channels involved in the blood-brain barrier in neurological diseases and any programme for drug discovery or delivery to target or avoid the blood-brain barrier.
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12
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Cotter ML, Boitano S, Vagner J, Burt JM. Lipidated connexin mimetic peptides potently inhibit gap junction-mediated Ca 2+-wave propagation. Am J Physiol Cell Physiol 2018; 315:C141-C154. [PMID: 29631365 DOI: 10.1152/ajpcell.00156.2017] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Connexin (Cx) mimetic peptides (e.g., Gap27: SRPTEKTIFII; Peptide5: VDCFLSRPTEKT) reversibly inhibit hemichannel (HCh) and gap junction channel (GJCh) function in a concentration- and time-dependent manner (HCh: ~5 µM, <1 h; GJCh: ~100 µM, > 1 h). We hypothesized that addition of a hexadecyl tail to SRPTEKT (SRPTEKT- Hdc) would improve its ability to concentrate in the plasma membrane and consequently increase its inhibitory efficacy. We show that SRPTEKT- Hdc inhibited intercellular Ca2+-wave propagation in Cx43-expressing MDCK and rabbit tracheal epithelial cells in a time (61-75 min)- and concentration (IC50: 66 pM)-dependent manner, a concentration efficacy five orders of magnitude lower than observed for the nonlipidated Gap27. HCh-mediated dye uptake was inhibited by SRPTEKT- Hdc with similar efficacy. Following peptide washout, HCh-mediated dye uptake was restored to control levels, whereas Ca2+-wave propagation was only partially restored. Scrambled and reverse sequence lipidated peptides had no detectable inhibitory effect on Ca2+-wave propagation or dye uptake. Cx43 expression was unchanged by SRPTEKT- Hdc incubation; however, Triton-insoluble Cx43 was reduced by SRPTEKT- Hdc exposure and reversed following washout. In summary, our results show that SRPTEKT- Hdc blocked HCh function and intercellular Ca2+ signaling at concentrations that minimally affected dye coupling. Selective inhibition of intercellular Ca2+ signaling, likely indicative of channel conformation-specific SRPTEKT- Hdc binding, could contribute significantly to the protective effects of these mimetic peptides in settings of injury. Our data also demonstrate that lipidation represents a paradigm for development of highly potent, efficacious, and selective mimetic peptide inhibitors of hemichannel and gap junction channel-mediated signaling.
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Affiliation(s)
- Maura L Cotter
- Department of Physiology, University of Arizona , Tucson, Arizona
| | - Scott Boitano
- Department of Physiology, University of Arizona , Tucson, Arizona.,Asthma and Airway Disease Research Center, University of Arizona , Tucson, Arizona.,Bio5 Collaborative Research Institute, University of Arizona , Tucson, Arizona
| | - Josef Vagner
- Bio5 Collaborative Research Institute, University of Arizona , Tucson, Arizona.,Department of Pharmacology, University of Arizona , Tucson, Arizona
| | - Janis M Burt
- Department of Physiology, University of Arizona , Tucson, Arizona
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Verónica Donoso M, Hernández F, Villalón T, Acuña-Castillo C, Pablo Huidobro-Toro J. Pharmacological dissection of the cellular mechanisms associated to the spontaneous and the mechanically stimulated ATP release by mesentery endothelial cells: roles of thrombin and TRPV. Purinergic Signal 2018; 14:121-139. [PMID: 29349673 DOI: 10.1007/s11302-017-9599-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2017] [Accepted: 12/19/2017] [Indexed: 02/06/2023] Open
Abstract
Endothelial cells participate in extracellular ATP release elicited by mechanosensors. To characterize the dynamic interactions between mechanical and chemical factors that modulate ATP secretion by the endothelium, we assessed and compared the mechanisms participating in the spontaneous (basal) and mechanically stimulated secretion using primary cultures of rat mesentery endothelial cells. ATP/metabolites were determined in the cell media prior to (basal) and after cell media displacement or a picospritzer buffer puff used as mechanical stimuli. Mechanical stimulation increased extracellular ATP that peaked within 1 min, and decayed to basal values in 10 min. Interruption of the vesicular transport route consistently blocked the spontaneous ATP secretion. Cells maintained in media lacking external Ca2+ elicited a spontaneous rise of extracellular ATP and adenosine, but failed to elicit a further extracellular ATP secretion following mechanical stimulation. 2-APB, a TRPV agonist, increased the spontaneous ATP secretion, but reduced the mechanical stimulation-induced nucleotide release. Pannexin1 or connexin blockers and gadolinium, a Piezo1 blocker, reduced the mechanically induced ATP release without altering spontaneous nucleotide levels. Moreover, thrombin or related agonists increased extracellular ATP secretion elicited by mechanical stimulation, without modifying spontaneous release. In sum, present results allow inferring that the spontaneous, extracellular nucleotide secretion is essentially mediated by ATP containing vesicles, while the mechanically induced secretion occurs essentially by connexin or pannexin1 hemichannel ATP transport, a finding fully supported by results from Panx1-/- rodents. Only the latter component is modulated by thrombin and related receptor agonists, highlighting a novel endothelium-smooth muscle signaling role of this anticoagulant.
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Affiliation(s)
- M Verónica Donoso
- Centro Desarrollo de NanoCiencia y Nanotecnología, CEDENNA y Laboratorio de Farmacología, Departamento de Biología, Facultad de Química y Biología, Universidad de Santiago, Alameda Lib. B. O'Higgins 3363, Estación Central, Santiago, Chile
| | - Felipe Hernández
- Centro Desarrollo de NanoCiencia y Nanotecnología, CEDENNA y Laboratorio de Farmacología, Departamento de Biología, Facultad de Química y Biología, Universidad de Santiago, Alameda Lib. B. O'Higgins 3363, Estación Central, Santiago, Chile
| | - Tania Villalón
- Centro Desarrollo de NanoCiencia y Nanotecnología, CEDENNA y Laboratorio de Farmacología, Departamento de Biología, Facultad de Química y Biología, Universidad de Santiago, Alameda Lib. B. O'Higgins 3363, Estación Central, Santiago, Chile
| | - Claudio Acuña-Castillo
- Centro Desarrollo de NanoCiencia y Nanotecnología, CEDENNA y Laboratorio de Farmacología, Departamento de Biología, Facultad de Química y Biología, Universidad de Santiago, Alameda Lib. B. O'Higgins 3363, Estación Central, Santiago, Chile
| | - J Pablo Huidobro-Toro
- Centro Desarrollo de NanoCiencia y Nanotecnología, CEDENNA y Laboratorio de Farmacología, Departamento de Biología, Facultad de Química y Biología, Universidad de Santiago, Alameda Lib. B. O'Higgins 3363, Estación Central, Santiago, Chile.
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14
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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: 15.1] [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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15
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Kim Y, Griffin JM, Nor MNM, Zhang J, Freestone PS, Danesh-Meyer HV, Rupenthal ID, Acosta M, Nicholson LFB, O'Carroll SJ, Green CR. Tonabersat Prevents Inflammatory Damage in the Central Nervous System by Blocking Connexin43 Hemichannels. Neurotherapeutics 2017; 14:1148-1165. [PMID: 28560708 PMCID: PMC5722754 DOI: 10.1007/s13311-017-0536-9] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The cis benzopyran compound tonabersat (SB-220453) has previously been reported to inhibit connexin26 expression in the brain by attenuating the p38-mitogen-activated protein kinase pathway. We show here that tonabersat directly inhibits connexin43 hemichannel opening. Connexin43 hemichannels have been called "pathological pores" based upon their role in secondary lesion spread, edema, inflammation, and neuronal loss following central nervous system injuries, as well as in chronic inflammatory disease. Both connexin43 hemichannels and pannexin channels released adenosine triphosphate (ATP) during ischemia in an in vitro ischemia model, but only connexin43 hemichannels contributed to ATP release during reperfusion. Tonabersat inhibited connexin43 hemichannel-mediated ATP release during both ischemia and reperfusion phases, with direct channel block confirmed using electrophysiology. Tonabersat also reduced connexin43 gap junction coupling in vitro, but only at higher concentrations, with junctional plaques internalized and degraded via the lysosomal pathway. Systemic delivery of tonabersat in a rat bright-light retinal damage model (a model for dry age-related macular degeneration) resulted in significantly improved functional outcomes assessed using electroretinography. Tonabersat also prevented thinning of the retina, especially the outer nuclear layer and choroid, assessed using optical coherence tomography. We conclude that tonabersat, already given orally to over 1000 humans in clinical trials (as a potential treatment for, and prophylactic treatment of, migraine because it was thought to inhibit cortical spreading depression), is a connexin hemichannel inhibitor and may have the potential to be a novel treatment of central nervous system injury and chronic neuroinflammatory disease.
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Affiliation(s)
- Yeri Kim
- Department of Ophthalmology, Faculty of Medical and Health Sciences, University of Auckland, Auckland, 1142, New Zealand
- New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, 1142, New Zealand
| | - Jarred M Griffin
- Centre for Brain Research, Faculty of Medical and Health Sciences, University of Auckland, Auckland, 1142, New Zealand
| | - Mohd N Mat Nor
- New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, 1142, New Zealand
- School of Optometry and Vision Science, Faculty of Medical and Health Sciences, University of Auckland, Auckland, 1142, New Zealand
- Faculty of Medicine, University Sultan Zainal Abidin, Kuala Terengganu, Malaysia
| | - Jie Zhang
- Department of Ophthalmology, Faculty of Medical and Health Sciences, University of Auckland, Auckland, 1142, New Zealand
- New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, 1142, New Zealand
| | - Peter S Freestone
- Department of Physiology, Faculty of Medical and Health Sciences, University of Auckland, Auckland, 1142, New Zealand
| | - Helen V Danesh-Meyer
- Department of Ophthalmology, Faculty of Medical and Health Sciences, University of Auckland, Auckland, 1142, New Zealand
- New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, 1142, New Zealand
| | - Ilva D Rupenthal
- Department of Ophthalmology, Faculty of Medical and Health Sciences, University of Auckland, Auckland, 1142, New Zealand
- New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, 1142, New Zealand
- Buchanan Ocular Therapeutics Unit, Faculty of Medical and Health Sciences, University of Auckland, Auckland, 1142, New Zealand
| | - Monica Acosta
- New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, 1142, New Zealand
- School of Optometry and Vision Science, Faculty of Medical and Health Sciences, University of Auckland, Auckland, 1142, New Zealand
| | - Louise F B Nicholson
- Centre for Brain Research, Faculty of Medical and Health Sciences, University of Auckland, Auckland, 1142, New Zealand
| | - Simon J O'Carroll
- Centre for Brain Research, Faculty of Medical and Health Sciences, University of Auckland, Auckland, 1142, New Zealand
| | - Colin R Green
- Department of Ophthalmology, Faculty of Medical and Health Sciences, University of Auckland, Auckland, 1142, New Zealand.
- New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, 1142, New Zealand.
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16
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Nielsen BS, Hansen DB, Ransom BR, Nielsen MS, MacAulay N. Connexin Hemichannels in Astrocytes: An Assessment of Controversies Regarding Their Functional Characteristics. Neurochem Res 2017; 42:2537-2550. [DOI: 10.1007/s11064-017-2243-7] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2016] [Revised: 03/17/2017] [Accepted: 03/17/2017] [Indexed: 12/19/2022]
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17
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Begandt D, Good ME, Keller AS, DeLalio LJ, Rowley C, Isakson BE, Figueroa XF. Pannexin channel and connexin hemichannel expression in vascular function and inflammation. BMC Cell Biol 2017; 18:2. [PMID: 28124621 PMCID: PMC5267334 DOI: 10.1186/s12860-016-0119-3] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Control of blood flow distribution and tissue homeostasis depend on the tight regulation of and coordination between the microvascular network and circulating blood cells. Channels formed by connexins or pannexins that connect the intra- and extracellular compartments allow the release of paracrine signals, such as ATP and prostaglandins, and thus play a central role in achieving fine regulation and coordination of vascular function. This review focuses on vascular connexin hemichannels and pannexin channels. We review their expression pattern within the arterial and venous system with a special emphasis on how post-translational modifications by phosphorylation and S-nitrosylation of these channels modulate their function and contribute to vascular homeostasis. Furthermore, we highlight the contribution of these channels in smooth muscle cells and endothelial cells in the regulation of vasomotor tone as well as how these channels in endothelial cells regulate inflammatory responses such as during ischemic and hypoxic conditions. In addition, this review will touch on recent evidence implicating a role for these proteins in regulating red blood cell and platelet function.
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Affiliation(s)
- Daniela Begandt
- Robert M Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA, 22908, USA
| | - Miranda E Good
- Robert M Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA, 22908, USA
| | - Alex S Keller
- Robert M Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA, 22908, USA
| | - Leon J DeLalio
- Robert M Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA, 22908, USA
| | - Carol Rowley
- Robert M Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA, 22908, USA
| | - Brant E Isakson
- Robert M Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA, 22908, USA.,Department of Molecular Physiology and Biophysics, University of Virginia School of Medicine, Charlottesville, VA, USA
| | - Xavier F Figueroa
- Departamento de Fisiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile.
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18
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Bioglass promotes wound healing by affecting gap junction connexin 43 mediated endothelial cell behavior. Biomaterials 2016; 84:64-75. [DOI: 10.1016/j.biomaterials.2016.01.033] [Citation(s) in RCA: 86] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2015] [Revised: 01/12/2016] [Accepted: 01/15/2016] [Indexed: 02/08/2023]
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19
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Electroporation Loading and Dye Transfer: A Safe and Robust Method to Probe Gap Junctional Coupling. Methods Mol Biol 2016; 1437:155-69. [PMID: 27207293 DOI: 10.1007/978-1-4939-3664-9_11] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Intercellular communication occurring via gap junction channels is considered a key mechanism for synchronizing physiological functions of cells and for the maintenance of tissue homeostasis. Gap junction channels are protein channels that are situated between neighboring cells and that provide a direct, yet selective route for the passage of small hydrophilic biomolecules and ions. Here, an electroporation method is described to load a localized area within an adherent cell monolayer with a gap junction-permeable fluorescent reporter dye. The technique results in a rapid and efficient labeling of a small patch of cells within the cell culture, without affecting cellular viability. Dynamic and quantitative information on gap junctional communication can subsequently be extracted by tracing the intercellular movement of the dye via time-lapse microscopy.
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20
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Li X, Zhao H, Tan X, Kostrzewa RM, Du G, Chen Y, Zhu J, Miao Z, Yu H, Kong J, Xu X. Inhibition of connexin43 improves functional recovery after ischemic brain injury in neonatal rats. Glia 2015; 63:1553-67. [PMID: 25988944 DOI: 10.1002/glia.22826] [Citation(s) in RCA: 67] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2014] [Revised: 03/06/2015] [Accepted: 03/06/2015] [Indexed: 12/26/2022]
Affiliation(s)
- Xiaojing Li
- Department of Neurology; The Second Affiliated Hospital of Soochow University; Suzhou City China
- The Institute of Neuroscience, Soochow University; Suzhou City China
| | - Heqing Zhao
- Department of Neurology; The Second Affiliated Hospital of Soochow University; Suzhou City China
| | - Xianxing Tan
- Department of Neurology; The Second Affiliated Hospital of Soochow University; Suzhou City China
- The Institute of Neuroscience, Soochow University; Suzhou City China
| | - Richard M. Kostrzewa
- Department of Pharmacology; Quillen College of Medicine, East Tennessee State University; Johnson City Tennessee
| | - Gang Du
- Department of Neurology; The Second Affiliated Hospital of Soochow University; Suzhou City China
- The Institute of Neuroscience, Soochow University; Suzhou City China
| | - Yuanyuan Chen
- Department of Neurology; The Second Affiliated Hospital of Soochow University; Suzhou City China
- The Institute of Neuroscience, Soochow University; Suzhou City China
| | - Jiangtao Zhu
- Department of Neurology; The Second Affiliated Hospital of Soochow University; Suzhou City China
| | - Zhigang Miao
- The Institute of Neuroscience, Soochow University; Suzhou City China
| | - Hailong Yu
- Department of Neurology; Subei People's Hospital; Yangzhou City China
| | - Jiming Kong
- Department of Human Anatomy and Cell Science; Faculty of Medicine, University of Manitoba; Winnipeg Manitoba Canada
| | - Xingshun Xu
- Department of Neurology; The Second Affiliated Hospital of Soochow University; Suzhou City China
- The Institute of Neuroscience, Soochow University; Suzhou City China
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21
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Decrock E, De Bock M, Wang N, Bol M, Gadicherla AK, Leybaert L. Electroporation loading and flash photolysis to investigate intra- and intercellular Ca2+ signaling. Cold Spring Harb Protoc 2015; 2015:239-49. [PMID: 25734071 DOI: 10.1101/pdb.top066068] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Many cellular functions are driven by variations in the intracellular Ca(2+) concentration ([Ca(2+)]i), which may appear as a single-event transient [Ca(2+)]i elevation, repetitive [Ca(2+)]i increases known as Ca(2+) oscillations, or [Ca(2+)]i increases propagating in the cytoplasm as Ca(2+) waves. Additionally, [Ca(2+)]i changes can be communicated between cells as intercellular Ca(2+) waves (ICWs). ICWs are mediated by two possible mechanisms acting in parallel: one involving gap junctions that form channels directly linking the cytoplasm of adjacent cells and one involving a paracrine messenger, in most cases ATP, that is released into the extracellular space, leading to [Ca(2+)]i changes in neighboring cells. The intracellular messenger inositol 1,4,5-trisphosphate (IP3) that triggers Ca(2+) release from Ca(2+) stores is crucial in these two ICW propagation scenarios, and is also a potent trigger to initiate ICWs. Loading inactive, "caged" IP3 into cells followed by photolytic "uncaging" with UV light, thereby liberating IP3, is a well-established method to trigger [Ca(2+)]i changes in single cells that is also effective in initiating ICWs. We here describe a method to load cells with caged IP3 by local electroporation of monolayer cell cultures and to apply flash photolysis to increase intracellular IP3 and induce [Ca(2+)]i changes, or initiate ICWs. Moreover, the electroporation method allows loading of membrane-impermeable agents that interfere with IP3 and Ca(2+) signaling.
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Affiliation(s)
- Elke Decrock
- Department of Basic Medical Sciences, Physiology Group, Ghent University, 9000 Ghent, Belgium
| | - Marijke De Bock
- Department of Basic Medical Sciences, Physiology Group, Ghent University, 9000 Ghent, Belgium
| | - Nan Wang
- Department of Basic Medical Sciences, Physiology Group, Ghent University, 9000 Ghent, Belgium
| | - Mélissa Bol
- Department of Basic Medical Sciences, Physiology Group, Ghent University, 9000 Ghent, Belgium
| | - Ashish K Gadicherla
- Department of Basic Medical Sciences, Physiology Group, Ghent University, 9000 Ghent, Belgium
| | - Luc Leybaert
- Department of Basic Medical Sciences, Physiology Group, Ghent University, 9000 Ghent, Belgium
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22
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Chen YS, Green CR, Danesh-Meyer HV, Rupenthal ID. Neuroprotection in the treatment of glaucoma--A focus on connexin43 gap junction channel blockers. Eur J Pharm Biopharm 2015; 95:182-93. [PMID: 25676338 DOI: 10.1016/j.ejpb.2015.01.031] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2014] [Revised: 12/23/2014] [Accepted: 01/07/2015] [Indexed: 01/01/2023]
Abstract
Glaucoma is a form of optic neuropathy and a common cause of blindness, affecting over 60 million people worldwide with an expected rise to 80 million by 2020. Successful treatment is challenging due to the various causes of glaucoma, undetectable symptoms at an early stage and inefficient delivery of drugs to the back of the eye. Conventional glaucoma treatments focus on the reduction of elevated intraocular pressure (IOP) using topical eye drops. However, their efficacy is limited to patients who suffer from high IOP glaucoma and do not address the underlying susceptibility of retinal ganglion cells (RGC) to degeneration. Glaucoma is known as a neurodegenerative disease which starts with RGC death and eventually results in damage of the optic nerve. Neuroprotective strategies therefore offer a novel treatment option for glaucoma by not only preventing neuronal loss but also disease progression. This review firstly gives an overview of the pathophysiology of glaucoma as well as current treatment options including conventional and novel delivery strategies. It then summarizes the rational for neuroprotection as a novel therapy for glaucomatous neuropathies and reviews current potential neuroprotective strategies to preserve RGC, with a focus on connexin43 (Cx43) gap junction channel blockers.
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Affiliation(s)
- Ying-Shan Chen
- Buchanan Ocular Therapeutics Unit, Department of Ophthalmology, New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
| | - Colin R Green
- Buchanan Ocular Therapeutics Unit, Department of Ophthalmology, New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
| | - Helen V Danesh-Meyer
- Buchanan Ocular Therapeutics Unit, Department of Ophthalmology, New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
| | - Ilva D Rupenthal
- Buchanan Ocular Therapeutics Unit, Department of Ophthalmology, New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand.
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23
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Schalper KA, Carvajal-Hausdorf D, Oyarzo MP. Possible role of hemichannels in cancer. Front Physiol 2014; 5:237. [PMID: 25018732 PMCID: PMC4073485 DOI: 10.3389/fphys.2014.00237] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2014] [Accepted: 06/09/2014] [Indexed: 12/12/2022] Open
Abstract
In humans, connexins (Cxs) and pannexins (Panxs) are the building blocks of hemichannels. These proteins are frequently altered in neoplastic cells and have traditionally been considered as tumor suppressors. Alteration of Cxs and Panxs in cancer cells can be due to genetic, epigenetic and post-transcriptional/post-translational events. Activated hemichannels mediate the diffusional membrane transport of ions and small signaling molecules. In the last decade hemichannels have been shown to participate in diverse cell processes including the modulation of cell proliferation and survival. However, their possible role in tumor growth and expansion remains largely unexplored. Herein, we hypothesize about the possible role of hemichannels in carcinogenesis and tumor progression. To support this theory, we summarize the evidence regarding the involvement of hemichannels in cell proliferation and migration, as well as their possible role in the anti-tumor immune responses. In addition, we discuss the evidence linking hemichannels with cancer in diverse models and comment on the current technical limitations for their study.
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Affiliation(s)
- Kurt A Schalper
- Servicio Anatomía Patológica, Clínica Alemana de Santiago, Facultad de Medicina Clinica Alemana Universidad del Desarrollo Santiago, Chile ; Department of Pathology, Yale School of Medicine New Haven, CT, USA
| | | | - Mauricio P Oyarzo
- Servicio Anatomía Patológica, Clínica Alemana de Santiago, Facultad de Medicina Clinica Alemana Universidad del Desarrollo Santiago, Chile
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24
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Functional Role of Connexins and Pannexins in the Interaction Between Vascular and Nervous System. J Cell Physiol 2014; 229:1336-45. [DOI: 10.1002/jcp.24563] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2013] [Accepted: 01/16/2014] [Indexed: 01/22/2023]
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25
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Sondersorg AC, Busse D, Kyereme J, Rothermel M, Neufang G, Gisselmann G, Hatt H, Conrad H. Chemosensory information processing between keratinocytes and trigeminal neurons. J Biol Chem 2014; 289:17529-40. [PMID: 24790106 DOI: 10.1074/jbc.m113.499699] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Trigeminal fibers terminate within the facial mucosa and skin and transmit tactile, proprioceptive, chemical, and nociceptive sensations. Trigeminal sensations can arise from the direct stimulation of intraepithelial free nerve endings or indirectly through information transmission from adjacent cells at the peripheral innervation area. For mechanical and thermal cues, communication processes between skin cells and somatosensory neurons have already been suggested. High concentrations of most odors typically provoke trigeminal sensations in vivo but surprisingly fail to activate trigeminal neuron monocultures. This fact favors the hypothesis that epithelial cells may participate in chemodetection and subsequently transmit signals to neighboring trigeminal fibers. Keratinocytes, the major cell type of the epidermis, express various receptors that enable reactions to multiple environmental stimuli. Here, using a co-culture approach, we show for the first time that exposure to the odorant chemicals induces a chemical communication between human HaCaT keratinocytes and mouse trigeminal neurons. Moreover, a supernatant analysis of stimulated keratinocytes and subsequent blocking experiments with pyrodoxalphosphate-6-azophenyl-2',4'-disulfonate revealed that ATP serves as the mediating transmitter molecule released from skin cells after odor stimulation. We show that the ATP release resulting from Javanol® stimulation of keratinocytes was mediated by pannexins. Consequently, keratinocytes act as chemosensors linking the environment and the trigeminal system via ATP signaling.
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Affiliation(s)
- Anna Christina Sondersorg
- From the Department of Cell Physiology, Ruhr-University Bochum, Universitätsstrasse 150, Gebäude ND4, D-44780 Bochum, Germany and
| | - Daniela Busse
- From the Department of Cell Physiology, Ruhr-University Bochum, Universitätsstrasse 150, Gebäude ND4, D-44780 Bochum, Germany and
| | - Jessica Kyereme
- From the Department of Cell Physiology, Ruhr-University Bochum, Universitätsstrasse 150, Gebäude ND4, D-44780 Bochum, Germany and
| | - Markus Rothermel
- From the Department of Cell Physiology, Ruhr-University Bochum, Universitätsstrasse 150, Gebäude ND4, D-44780 Bochum, Germany and
| | - Gitta Neufang
- Dermatological Skin Care, Beiersdorf AG, D-20245 Hamburg, Germany
| | - Günter Gisselmann
- From the Department of Cell Physiology, Ruhr-University Bochum, Universitätsstrasse 150, Gebäude ND4, D-44780 Bochum, Germany and
| | - Hanns Hatt
- From the Department of Cell Physiology, Ruhr-University Bochum, Universitätsstrasse 150, Gebäude ND4, D-44780 Bochum, Germany and
| | - Heike Conrad
- From the Department of Cell Physiology, Ruhr-University Bochum, Universitätsstrasse 150, Gebäude ND4, D-44780 Bochum, Germany and
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26
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Nielsen MS, Axelsen LN, Sorgen PL, Verma V, Delmar M, Holstein-Rathlou NH. Gap junctions. Compr Physiol 2013; 2:1981-2035. [PMID: 23723031 DOI: 10.1002/cphy.c110051] [Citation(s) in RCA: 298] [Impact Index Per Article: 27.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Gap junctions are essential to the function of multicellular animals, which require a high degree of coordination between cells. In vertebrates, gap junctions comprise connexins and currently 21 connexins are known in humans. The functions of gap junctions are highly diverse and include exchange of metabolites and electrical signals between cells, as well as functions, which are apparently unrelated to intercellular communication. Given the diversity of gap junction physiology, regulation of gap junction activity is complex. The structure of the various connexins is known to some extent; and structural rearrangements and intramolecular interactions are important for regulation of channel function. Intercellular coupling is further regulated by the number and activity of channels present in gap junctional plaques. The number of connexins in cell-cell channels is regulated by controlling transcription, translation, trafficking, and degradation; and all of these processes are under strict control. Once in the membrane, channel activity is determined by the conductive properties of the connexin involved, which can be regulated by voltage and chemical gating, as well as a large number of posttranslational modifications. The aim of the present article is to review our current knowledge on the structure, regulation, function, and pharmacology of gap junctions. This will be supported by examples of how different connexins and their regulation act in concert to achieve appropriate physiological control, and how disturbances of connexin function can lead to disease.
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Affiliation(s)
- Morten Schak Nielsen
- Department of Biomedical Sciences and The Danish National Research Foundation Centre for Cardiac Arrhythmia, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
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27
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Burnstock G, Ralevic V. Purinergic signaling and blood vessels in health and disease. Pharmacol Rev 2013; 66:102-92. [PMID: 24335194 DOI: 10.1124/pr.113.008029] [Citation(s) in RCA: 227] [Impact Index Per Article: 20.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Purinergic signaling plays important roles in control of vascular tone and remodeling. There is dual control of vascular tone by ATP released as a cotransmitter with noradrenaline from perivascular sympathetic nerves to cause vasoconstriction via P2X1 receptors, whereas ATP released from endothelial cells in response to changes in blood flow (producing shear stress) or hypoxia acts on P2X and P2Y receptors on endothelial cells to produce nitric oxide and endothelium-derived hyperpolarizing factor, which dilates vessels. ATP is also released from sensory-motor nerves during antidromic reflex activity to produce relaxation of some blood vessels. In this review, we stress the differences in neural and endothelial factors in purinergic control of different blood vessels. The long-term (trophic) actions of purine and pyrimidine nucleosides and nucleotides in promoting migration and proliferation of both vascular smooth muscle and endothelial cells via P1 and P2Y receptors during angiogenesis and vessel remodeling during restenosis after angioplasty are described. The pathophysiology of blood vessels and therapeutic potential of purinergic agents in diseases, including hypertension, atherosclerosis, ischemia, thrombosis and stroke, diabetes, and migraine, is discussed.
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Affiliation(s)
- Geoffrey Burnstock
- Autonomic Neuroscience Centre, University College Medical School, Rowland Hill Street, London NW3 2PF, UK; and Department of Pharmacology, The University of Melbourne, Australia.
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28
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Wang N, De Bock M, Decrock E, Bol M, Gadicherla A, Bultynck G, Leybaert L. Connexin targeting peptides as inhibitors of voltage- and intracellular Ca2+-triggered Cx43 hemichannel opening. Neuropharmacology 2013; 75:506-16. [DOI: 10.1016/j.neuropharm.2013.08.021] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2013] [Revised: 08/19/2013] [Accepted: 08/20/2013] [Indexed: 12/21/2022]
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29
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Chen YS, Toth I, Danesh-Meyer HV, Green CR, Rupenthal ID. Cytotoxicity and vitreous stability of chemically modified connexin43 mimetic peptides for the treatment of optic neuropathy. J Pharm Sci 2013; 102:2322-31. [PMID: 23696181 DOI: 10.1002/jps.23617] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2013] [Revised: 04/09/2013] [Accepted: 04/29/2013] [Indexed: 11/07/2022]
Abstract
Optic neuropathy is associated with retinal ganglion cell (RGC) loss leading to optic nerve damage and visual impairment. Unregulated connexin (Cx) hemichannel opening plays a role in RGC loss. Thus, inhibition via Cx43-specific mimetic peptides (MP) may prevent further cell death. However, the highly hydrophilic character and poor stability of native peptides prevent their efficient delivery across biological membranes. The present study aimed to improve the stability of Cx43 MP by conjugation to C12-lipoamino acid (C12-Laa) or sugar groups. Unmodified and modified Cx43 MP were synthesized using solid-phase peptide synthesis. Their functionality was assessed by propidium iodide (PI) uptake into NT2 cells, a human testicular carcinoma progenitor cell line able to differentiate into astrocytes, whereas the stability in ocular vitreous was measured by reversed-phase high-performance liquid chromatography. PI uptake studies showed inhibition of hemichannel opening for unmodified and modified Cx43 MP. Stability measurements revealed improved stability of modified Cx43 MP, with two Laa groups increasing the peptide half-life in bovine vitreous more than twofold. Conjugation to C12 -Laa or sugar did not affect the functionality of Cx43 MP, but addition of two C12-Laa groups significantly improved peptide stability. Laa-modifications may therefore offer improved stability and retinal delivery of peptides in vivo.
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Affiliation(s)
- Ying-Shan Chen
- Department of Ophthalmology, New Zealand National Eye Centre, Faculty of Medical and Health Sciences, The University of Auckland, Auckland 1142, New Zealand
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Verselis VK, Srinivas M. Connexin channel modulators and their mechanisms of action. Neuropharmacology 2013; 75:517-24. [PMID: 23597508 DOI: 10.1016/j.neuropharm.2013.03.020] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2013] [Revised: 03/11/2013] [Accepted: 03/15/2013] [Indexed: 10/27/2022]
Abstract
Gap junction channels and hemichannels formed by the connexin family of proteins play important roles in many aspects of tissue homeostasis in the brain and in other organs. In addition, connexin channels have been proposed as pharmacological targets in the treatment of a number of human disorders. In this review, we describe the connexin-subtype selectivity and specificity of pharmacological agents that are commonly used to modulate connexin channels. We also highlight recent progress made toward identifying new agents for connexin channels that act in a selective and specific manner. Finally, we discuss developing insights into possible mechanisms by which these agents modulate connexin channel function. This article is part of the Special Issue Section entitled 'Current Pharmacology of Gap Junction Channels and Hemichannels'.
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Affiliation(s)
- Vytas K Verselis
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Miduturu Srinivas
- Department of Biological and Vision Sciences, SUNY College of Optometry, 33 West 42nd Street, New York, NY 10036, USA.
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31
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Specificity in the participation of connexin proteins in flow-induced endothelial gap junction communication. Pflugers Arch 2013; 465:1293-302. [DOI: 10.1007/s00424-013-1245-9] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2012] [Revised: 02/05/2013] [Accepted: 02/06/2013] [Indexed: 01/07/2023]
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32
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Connexin43 mimetic peptide is neuroprotective and improves function following spinal cord injury. Neurosci Res 2013; 75:256-67. [PMID: 23403365 DOI: 10.1016/j.neures.2013.01.004] [Citation(s) in RCA: 81] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2012] [Revised: 12/07/2012] [Accepted: 01/13/2013] [Indexed: 12/29/2022]
Abstract
Connexin43 (Cx43) is a gap junction protein up-regulated after spinal cord injury and is involved in the on-going spread of secondary tissue damage. To test whether a connexin43 mimetic peptide (Peptide5) reduces inflammation and tissue damage and improves function in an in vivo model of spinal cord injury, rats were subjected to a 10g, 12.5mm weight drop injury at the vertebral level T10 using a MASCIS impactor. Vehicle or connexin43 mimetic peptide was delivered directly to the lesion via intrathecal catheter and osmotic mini-pump for up to 24h after injury. Treatment with Peptide5 led to significant improvements in hindlimb function as assessed using the Basso-Beattie-Bresnahan scale. Peptide5 caused a reduction in Cx43 protein, increased Cx43 phosphorylation and decreased levels of TNF-α and IL-1β as assessed by Western blotting. Immunohistochemistry of tissue sections 5 weeks after injury showed reductions in astrocytosis and activated microglia as well as an increase in motor neuron survival. These results show that administration of a connexin mimetic peptide reduces secondary tissue damage after spinal cord injury by reducing gliosis and cytokine release and indicate the clinical potential for mimetic peptides in the treatment of spinal cord patients.
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Abstract
Intercellular calcium (Ca(2+)) waves (ICWs) represent the propagation of increases in intracellular Ca(2+) through a syncytium of cells and appear to be a fundamental mechanism for coordinating multicellular responses. ICWs occur in a wide diversity of cells and have been extensively studied in vitro. More recent studies focus on ICWs in vivo. ICWs are triggered by a variety of stimuli and involve the release of Ca(2+) from internal stores. The propagation of ICWs predominately involves cell communication with internal messengers moving via gap junctions or extracellular messengers mediating paracrine signaling. ICWs appear to be important in both normal physiology as well as pathophysiological processes in a variety of organs and tissues including brain, liver, retina, cochlea, and vascular tissue. We review here the mechanisms of initiation and propagation of ICWs, the key intra- and extracellular messengers (inositol 1,4,5-trisphosphate and ATP) mediating ICWs, and the proposed physiological functions of ICWs.
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Affiliation(s)
- Luc Leybaert
- Department of Basic Medical Sciences, Physiology Group, Faculty of Medicine & Health Sciences, Ghent University, Ghent, Belgium.
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Low extracellular Ca2+ conditions induce an increase in brain endothelial permeability that involves intercellular Ca2+ waves. Brain Res 2012; 1487:78-87. [PMID: 22789903 DOI: 10.1016/j.brainres.2012.06.046] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2012] [Revised: 06/19/2012] [Accepted: 06/23/2012] [Indexed: 01/11/2023]
Abstract
The intracellular calcium concentration ([Ca(2+)](i)) is an important factor determining the permeability of endothelial barriers including the blood-brain barrier (BBB). However, nothing is known concerning the effect of spatially propagated intercellular Ca(2+) waves (ICWs). The propagation of ICWs relies in large part on channels formed by connexins that are present in endothelia. We hypothesized that ICWs may result in a strong disturbance of endothelial function, because the [Ca(2+)](i) changes are coordinated and involve multiple cells. Thus, we aimed to investigate the effect of ICWs on endothelial permeability. ICW activity was triggered in immortalized and primary brain endothelial cells by lowering the extracellular Ca(2+) concentration. Low extracellular Ca(2+) increased the endothelial permeability and this was significantly suppressed by buffering [Ca(2+)](i) with BAPTA-AM, indicating a central role of [Ca(2+)](i) changes. The endothelial permeability increase was furthermore inhibited by the connexin channel blocking peptide Gap27, which also blocked the ICWs, and by inhibiting protein kinase C (PKC), Ca(2+)/calmodulin-dependent kinase II (CaMKII) and actomyosin contraction. We compared these observations with the [Ca(2+)](i) changes and permeability alterations provoked by the inflammatory agent bradykinin (BK), which triggers oscillatory [Ca(2+)](i) changes without wave activity. BK-associated [Ca(2+)](i) changes and the endothelial permeability increase were significantly smaller than those associated with ICWs, and the permeability increase was not influenced by inhibition of PKC, CaMKII or actomyosin contraction. We conclude that ICWs significantly increase endothelial permeability and therefore, the connexins that underlie wave propagation form an interesting target to limit BBB alterations. This article is part of a Special Issue entitled Electrical Synapses.
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Large Pore Ion and Metabolite-Permeable Channel Regulation of Postnatal Ventricular Zone Neural Stem and Progenitor Cells: Interplay between Aquaporins, Connexins, and Pannexins? Stem Cells Int 2012; 2012:454180. [PMID: 22754577 PMCID: PMC3382389 DOI: 10.1155/2012/454180] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2012] [Accepted: 04/27/2012] [Indexed: 12/17/2022] Open
Abstract
The birth of new neurons from unspecialized neural stem and progenitor cells surrounding the lateral ventricles occurs throughout postnatal life. This process, termed neurogenesis, is complex and multistepped, encompassing several types of cellular behaviours, such as proliferation, differentiation, and migration. These behaviours are influenced by numerous factors present in the unique, permissive microenvironment. A major cellular mechanism for sensing the plethora of environmental cues directing this process is the presence of different channel forming proteins spanning the plasma membrane. So-called large pore membrane channels, which are selective for the passage of specific types of small molecules and ions, are emerging as an important subgroup of channel proteins. Here, we focus on the roles of three such large pore channels, aquaporin 4, connexin 43, and pannexin 1. We highlight both their independent functions as well as the accumulating evidence for crosstalk between them.
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De Bock M, Wang N, Bol M, Decrock E, Ponsaerts R, Bultynck G, Dupont G, Leybaert L. Connexin 43 hemichannels contribute to cytoplasmic Ca2+ oscillations by providing a bimodal Ca2+-dependent Ca2+ entry pathway. J Biol Chem 2012; 287:12250-66. [PMID: 22351781 PMCID: PMC3320976 DOI: 10.1074/jbc.m111.299610] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2011] [Revised: 02/16/2012] [Indexed: 11/06/2022] Open
Abstract
Many cellular functions are driven by changes in the intracellular Ca(2+) concentration ([Ca(2+)](i)) that are highly organized in time and space. Ca(2+) oscillations are particularly important in this respect and are based on positive and negative [Ca(2+)](i) feedback on inositol 1,4,5-trisphosphate receptors (InsP(3)Rs). Connexin hemichannels are Ca(2+)-permeable plasma membrane channels that are also controlled by [Ca(2+)](i). We aimed to investigate how hemichannels may contribute to Ca(2+) oscillations. Madin-Darby canine kidney cells expressing connexin-32 (Cx32) and Cx43 were exposed to bradykinin (BK) or ATP to induce Ca(2+) oscillations. BK-induced oscillations were rapidly (minutes) and reversibly inhibited by the connexin-mimetic peptides (32)Gap27/(43)Gap26, whereas ATP-induced oscillations were unaffected. Furthermore, these peptides inhibited the BK-triggered release of calcein, a hemichannel-permeable dye. BK-induced oscillations, but not those induced by ATP, were dependent on extracellular Ca(2+). Alleviating the negative feedback of [Ca(2+)](i) on InsP(3)Rs using cytochrome c inhibited BK- and ATP-induced oscillations. Cx32 and Cx43 hemichannels are activated by <500 nm [Ca(2+)](i) but inhibited by higher concentrations and CT9 peptide (last 9 amino acids of the Cx43 C terminus) removes this high [Ca(2+)](i) inhibition. Unlike interfering with the bell-shaped dependence of InsP(3)Rs to [Ca(2+)](i), CT9 peptide prevented BK-induced oscillations but not those triggered by ATP. Collectively, these data indicate that connexin hemichannels contribute to BK-induced oscillations by allowing Ca(2+) entry during the rising phase of the Ca(2+) spikes and by providing an OFF mechanism during the falling phase of the spikes. Hemichannels were not sufficient to ignite oscillations by themselves; however, their contribution was crucial as hemichannel inhibition stopped the oscillations.
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Affiliation(s)
- Marijke De Bock
- From the Department of Basic Medical Sciences, Physiology Group, Ghent University 9000 Ghent, Belgium
| | - Nan Wang
- From the Department of Basic Medical Sciences, Physiology Group, Ghent University 9000 Ghent, Belgium
| | - Melissa Bol
- From the Department of Basic Medical Sciences, Physiology Group, Ghent University 9000 Ghent, Belgium
| | - Elke Decrock
- From the Department of Basic Medical Sciences, Physiology Group, Ghent University 9000 Ghent, Belgium
| | - Raf Ponsaerts
- Department of Molecular Cell Biology, Laboratory of Molecular and Cellular Signaling, KULeuven, 3000 Leuven, Belgium, and
| | - Geert Bultynck
- Department of Molecular Cell Biology, Laboratory of Molecular and Cellular Signaling, KULeuven, 3000 Leuven, Belgium, and
| | - Geneviève Dupont
- Theoretical Chronobiology Unit, Université Libre de Bruxelles, 1050 Brussels, Belgium
| | - Luc Leybaert
- From the Department of Basic Medical Sciences, Physiology Group, Ghent University 9000 Ghent, Belgium
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Danesh-Meyer HV, Kerr NM, Zhang J, Eady EK, O'Carroll SJ, Nicholson LF, Johnson CS, Green CR. Connexin43 mimetic peptide reduces vascular leak and retinal ganglion cell death following retinal ischaemia. Brain 2012; 135:506-20. [DOI: 10.1093/brain/awr338] [Citation(s) in RCA: 151] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
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38
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Nualart-Marti A, Solsona C, Fields RD. Gap junction communication in myelinating glia. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1828:69-78. [PMID: 22326946 DOI: 10.1016/j.bbamem.2012.01.024] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2011] [Revised: 01/17/2012] [Accepted: 01/26/2012] [Indexed: 10/14/2022]
Abstract
Gap junction communication is crucial for myelination and axonal survival in both the peripheral nervous system (PNS) and central nervous system (CNS). This review examines the different types of gap junctions in myelinating glia of the PNS and CNS (Schwann cells and oligodendrocytes respectively), including their functions and involvement in neurological disorders. Gap junctions mediate intercellular communication among Schwann cells in the PNS, and among oligodendrocytes and between oligodendrocytes and astrocytes in the CNS. Reflexive gap junctions mediating transfer between different regions of the same cell promote communication between cellular compartments of myelinating glia that are separated by layers of compact myelin. Gap junctions in myelinating glia regulate physiological processes such as cell growth, proliferation, calcium signaling, and participate in extracellular signaling via release of neurotransmitters from hemijunctions. In the CNS, gap junctions form a glial network between oligodendrocytes and astrocytes. This transcellular communication is hypothesized to maintain homeostasis by facilitating restoration of membrane potential after axonal activity via electrical coupling and the re-distribution of potassium ions released from axons. The generation of transgenic mice for different subsets of connexins has revealed the contribution of different connexins in gap junction formation and illuminated new subcellular mechanisms underlying demyelination and cognitive defects. Alterations in metabolic coupling have been reported in animal models of X-linked Charcot-Marie-Tooth disease (CMTX) and Pelizaeus-Merzbarcher-like disease (PMLD), which are caused by mutations in the genes encoding for connexin 32 and connexin 47 respectively. Future research identifying the expression and regulation of gap junctions in myelinating glia is likely to provide a better understanding of myelinating glia in nervous system function, plasticity, and disease. This article is part of a Special Issue entitled: The Communicating junctions, roles and dysfunctions.
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Affiliation(s)
- Anna Nualart-Marti
- Department of Pathology and Experimental Therapeutics, University of Barcelona, Barcelona, Spain.
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39
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Chandrasekhar A, Bera AK. Hemichannels: permeants and their effect on development, physiology and death. Cell Biochem Funct 2012; 30:89-100. [PMID: 22392438 DOI: 10.1002/cbf.2794] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2011] [Revised: 12/05/2011] [Accepted: 12/05/2011] [Indexed: 12/12/2022]
Abstract
Hemichannels, which are one half of the gap junction channels, have independent physiological roles. Although hemichannels consisting of connexins are more widely documented, hemichannels of pannexins, proteins homologous to invertebrate gap junction proteins also have been studied. There are at least 21 different connexin and three pannexin isotypes. This variety in isotypes results in tissue-specific hemichannels, which have been implicated in varied events ranging from development, cell survival, to cell death. Hemichannel function varies with its spatio-temporal opening, thus demanding a refined degree of regulation. This review discusses the activity of hemichannels and the molecules released in different physiological states and their impact on tissue functioning.
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40
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De Bock M, Culot M, Wang N, Bol M, Decrock E, De Vuyst E, da Costa A, Dauwe I, Vinken M, Simon AM, Rogiers V, De Ley G, Evans WH, Bultynck G, Dupont G, Cecchelli R, Leybaert L. Connexin channels provide a target to manipulate brain endothelial calcium dynamics and blood-brain barrier permeability. J Cereb Blood Flow Metab 2011; 31:1942-57. [PMID: 21654699 PMCID: PMC3185887 DOI: 10.1038/jcbfm.2011.86] [Citation(s) in RCA: 128] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The cytoplasmic Ca(2+) concentration ([Ca(2+)](i)) is an important factor determining the functional state of blood-brain barrier (BBB) endothelial cells but little is known on the effect of dynamic [Ca(2+)](i) changes on BBB function. We applied different agonists that trigger [Ca(2+)](i) oscillations and determined the involvement of connexin channels and subsequent effects on endothelial permeability in immortalized and primary brain endothelial cells. The inflammatory peptide bradykinin (BK) triggered [Ca(2+)](i) oscillations and increased endothelial permeability. The latter was prevented by buffering [Ca(2+)](i) with BAPTA, indicating that [Ca(2+)](i) oscillations are crucial in the permeability changes. Bradykinin-triggered [Ca(2+)](i) oscillations were inhibited by interfering with connexin channels, making use of carbenoxolone, Gap27, a peptide blocker of connexin channels, and Cx37/43 knockdown. Gap27 inhibition of the oscillations was rapid (within minutes) and work with connexin hemichannel-permeable dyes indicated hemichannel opening and purinergic signaling in response to stimulation with BK. Moreover, Gap27 inhibited the BK-triggered endothelial permeability increase in in vitro and in vivo experiments. By contrast, [Ca(2+)](i) oscillations provoked by exposure to adenosine 5' triphosphate (ATP) were not affected by carbenoxolone or Gap27 and ATP did not disturb endothelial permeability. We conclude that interfering with endothelial connexin hemichannels is a novel approach to limiting BBB-permeability alterations.
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Affiliation(s)
- Marijke De Bock
- Department of Basic Medical Sciences, Physiology Group, Ghent University, Ghent, Belgium
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41
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Pollok S, Pfeiffer AC, Lobmann R, Wright CS, Moll I, Martin PEM, Brandner JM. Connexin 43 mimetic peptide Gap27 reveals potential differences in the role of Cx43 in wound repair between diabetic and non-diabetic cells. J Cell Mol Med 2011; 15:861-73. [PMID: 20345849 PMCID: PMC3922673 DOI: 10.1111/j.1582-4934.2010.01057.x] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
During early wound healing (WH) events Connexin 43 (Cx43) is down-regulated at wound margins. In chronic wound margins, including diabetic wounds, Cx43 expression is enhanced suggesting that down-regulation is important for WH. We previously reported that the Cx43 mimetic peptide Gap27 blocks Cx43 mediated intercellular communication and promotes skin cell migration of infant cells in vitro. In the present work we further investigated the molecular mechanism of Gap27 action and its therapeutic potential to improve WH in skin tissue and diabetic and non-diabetic cells. Ex vivo skin, organotypic models and human keratinocytes/fibroblasts of young and old donors and of diabetic and non-diabetic origin were used to assess the impact of Gap27 on cell migration, proliferation, Cx43 expression, localization, phosphorylation and hemichannel function. Exposure of ex vivo WH models to Gap27 decreased dye spread, accelerated WH and elevated cell proliferation. In non-diabetic cell cultures Gap27 decreased dye uptake through Cx hemichannels and after scratch wounding cells showed enhanced migration and proliferation. Cells of diabetic origin were less susceptible to Gap27 during early passages. In late passages these cells showed responses comparable to non-diabetic cells. The cause of the discrepancy between diabetic and non-diabetic cells correlated with decreased Cx hemichannel activity in diabetic cells but excluded differences in Cx43 expression, localization and Ser368-phosphorylation. These data emphasize the importance of Cx43 in WH and support the concept that Gap27 could be a beneficial therapeutic to accelerate normal WH. However, its use in diabetic WH may be restricted and our results highlight differences in the role of Cx43 in skin cells of different origin.
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Affiliation(s)
- Simone Pollok
- Department of Dermatology and Venerology, University Hospital Hamburg-Eppendorf, Hamburg, Germany
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Rodríguez-Sinovas A, Sánchez JA, Fernandez-Sanz C, Ruiz-Meana M, Garcia-Dorado D. Connexin and pannexin as modulators of myocardial injury. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1818:1962-70. [PMID: 21839721 DOI: 10.1016/j.bbamem.2011.07.041] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2011] [Revised: 07/20/2011] [Accepted: 07/28/2011] [Indexed: 01/02/2023]
Abstract
Multicellular organisms have developed a variety of mechanisms that allow communication between their cells. Whereas some of these systems, as neurotransmission or hormones, make possible communication between remote areas, direct cell-to-cell communication through specific membrane channels keep in contact neighboring cells. Direct communication between the cytoplasm of adjacent cells is achieved in vertebrates by membrane channels formed by connexins. However, in addition to allowing exchange of ions and small metabolites between the cytoplasms of adjacent cells, connexin channels also communicate the cytosol with the extracellular space, thus enabling a completely different communication system, involving activation of extracellular receptors. Recently, the demonstration of connexin at the inner mitochondrial membrane of cardiomyocytes, probably forming hemichannels, has enlarged the list of actions of connexins. Some of these mechanisms are also shared by a different family of proteins, termed pannexins. Importantly, these systems allow not only communication between healthy cells, but also play an important role during different types of injury. The aim of this review is to discuss the role played by both connexin hemichannels and pannexin channels in cell communication and injury. This article is part of a Special Issue entitled: The Communicating junctions, composition, structure and characteristics.
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43
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Parthasarathi K, Bhattacharya J. Localized acid instillation by a wedged-catheter method reveals a role for vascular gap junctions in spatial expansion of acid injury. Anat Rec (Hoboken) 2011; 294:1585-91. [PMID: 21809471 DOI: 10.1002/ar.21460] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2010] [Revised: 05/31/2011] [Accepted: 06/22/2011] [Indexed: 01/23/2023]
Abstract
Acid aspiration is a major cause of acute lung injury. However, the mechanisms that underlie this spatial expansion of the injury remain undefined. In current animal models of acid injury, intratracheal acid instillation replicates the lung injury. However intratracheal instillation causes a global effect, precluding studies of how the injury spreads. Here, we report an airway catheter-based method for localized acid delivery in the isolated blood-perfused rat lung. We co-instilled hydrochloric acid with evans blue through the catheter into one lung and determined blood-free extravascular lung water in tissue samples from regions that either received, or did not receive the instilled acid. Tissue samples from the noncatheterized contralateral lung were used as controls. Lung water increased both in the regions that received acid, as well as in adjacent regions that did not. Pretreating the lung with vascular infusions of the gap junctional blocker, glycerrhetinic acid, blunted the acid-induced lung water increase at the adjacent regions. These findings indicate that endothelial gap junction communication causes spread of lung injury from regions that were directly acid injured, to adjacent sites that did not directly receive acid. Our new method for establishing localized acid injury provides evidence for a novel role for vascular gap junctions in the spatial expansion of acid injury.
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Affiliation(s)
- Kaushik Parthasarathi
- Departments of Physiology and Biomedical Engineering, University of Tennessee Health Science Center, Memphis, TN 38163, USA
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44
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De Vuyst E, Boengler K, Antoons G, Sipido KR, Schulz R, Leybaert L. Pharmacological modulation of connexin-formed channels in cardiac pathophysiology. Br J Pharmacol 2011; 163:469-83. [PMID: 21265827 PMCID: PMC3101610 DOI: 10.1111/j.1476-5381.2011.01244.x] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2010] [Revised: 12/09/2010] [Accepted: 01/02/2011] [Indexed: 12/17/2022] Open
Abstract
Coordinated electrical activity in the heart is supported by gap junction channels located at the intercalated discs of cardiomyocytes. Impaired gap junctional communication between neighbouring cardiomyocytes contributes to the development of re-entry arrhythmias after myocardial ischaemia. Current antiarrhythmic therapy is hampered by a lack of efficiency and side effects, creating the need for a new generation of drugs. In this review, we focus on compounds that increase gap junctional communication, thereby increasing the conduction velocity and decreasing the risk of arrhythmias. Some of these compounds also inhibit connexin 43 (Cx43) hemichannels, thereby limiting adenosine triphosphate loss and volume overload following ischaemia/reperfusion, thus potentially increasing the survival of cardiomyocytes. The compounds discussed in this review are: (i) antiarrythmic peptide (AAP), AAP10, ZP123; (ii) GAP-134; (iii) RXP-E; and (vi) the Cx mimetic peptides Gap 26 and Gap 27. None of these compounds have effects on Na(+) , Ca(2+) and K(+) channels, and therefore have no proarrhythmic activity associated with currently available antiarrhythmic drugs. GAP-134, RXP-E, Gap 26 and Gap 27 are pharmalogical agents with a favorable clinical safety profile, as already confirmed in phase I clinical trials for GAP-134. These agents show an excellent promise for treatment of arrhythmias in patients with ischaemic cardiomyopathy.
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Affiliation(s)
- Elke De Vuyst
- Department of Basic Medical Sciences – Physiology group, Faculty of Medicine and Health Sciences, Ghent UniversityGhent, Belgium
| | - Kerstin Boengler
- Institut für Pathophysiologie, Zentrum für Innere Medizin, Universitätsklinikum EssenEssen, Germany
| | - Gudrun Antoons
- Department for Experimental Cardiology, O & N1, K.U.LeuvenLeuven, Belgium
| | - Karin R Sipido
- Department for Experimental Cardiology, O & N1, K.U.LeuvenLeuven, Belgium
| | - Rainer Schulz
- Institut für Physiologie, Justus-Liebig Universität GießenGießen, Germany
| | - Luc Leybaert
- Department of Basic Medical Sciences – Physiology group, Faculty of Medicine and Health Sciences, Ghent UniversityGhent, Belgium
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45
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Azorin N, Raoux M, Rodat-Despoix L, Merrot T, Delmas P, Crest M. ATP signalling is crucial for the response of human keratinocytes to mechanical stimulation by hypo-osmotic shock. Exp Dermatol 2011; 20:401-7. [PMID: 21355886 DOI: 10.1111/j.1600-0625.2010.01219.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Touch is detected through receptors located in the skin and the activation of channels in sensory nerve fibres. Epidermal keratinocytes themselves, however, may sense mechanical stimulus and contribute to skin sensation. Here, we showed that the mechanical stimulation of human keratinocytes by hypo-osmotic shock releases adenosine triphosphate (ATP) and increases intracellular calcium. We demonstrated that the release of ATP was found to be calcium independent because emptying the intracellular calcium stores did not cause ATP release; ATP release was still observed in the absence of external calcium and it persisted on chelating cytosolic calcium. On the other hand, the released ATP activated purinergic receptors and mobilized intracellular calcium stores. The resulting depletion of stored calcium led to the activation of capacitative calcium entry. Increase in cytosolic calcium concentration was blocked by the purinergic receptor blocker suramin, phospholipase C inhibitor and apyrase, which hydrolyses ATP. Collectively, our data demonstrate that human keratinocytes are mechanically activated by hypo-osmotic shock, leading first to the release of ATP, which in turn stimulates purinergic receptors, resulting in the mobilization of intracellular calcium and capacitative calcium entry. These results emphasize the crucial role of ATP signalling in the transduction of mechanical stimuli in human keratinocytes.
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Affiliation(s)
- Nathalie Azorin
- Université de la Méditerranée, Centre National de la Recherche Scientifique (CNRS) UMR6231, Marseille, France
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Sun J, Usune S, Zhao Y, Migita K, Katsuragi T. Multidrug resistance protein transporter and Ins(1,4,5)P₃-sensitive Ca²+-signaling involved in adenosine triphosphate export via Gq protein-coupled NK₂-receptor stimulation with neurokinin A. J Pharmacol Sci 2010; 114:92-8. [PMID: 20736509 DOI: 10.1254/jphs.10145fp] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022] Open
Abstract
The purpose of this study is to identify the membrane transport machinery and cell signaling involved in the neurokinin A-inducible release of adenosine triphosphate (ATP) as an autocrine/paracrine signal from cultured guinea-pig taenia coli (T. coli) smooth muscle cells (SMCs). ATP release evoked by neurokinin A was inhibited by L-659877, a NK(2)-receptor antagonist; by modulators for Ins(1,4,5)P(3)-sensitive Ca(2+)-signaling, U-73122, thapsigargin, and 2-APB; and by W-7, a calmodulin inhibitor, and staurosporine, a protein kinase C (PKC) inhibitor, but not by wortmannin, a phosphoinositide 3-kinase inhibitor. The evoked release was suppressed by a multidrug resistance protein (MRP)-transporter inhibitors, MK-571, indomethacin, and benzbromarone, but not by CFTR-inh 172, a CFTR-Cl(-) channel blocker, and α-glycyrrhetinic acid, a gap junction hemichannel blocker. Neurokinin A caused a marked accumulation of Ins(1,4,5)P(3) and an increase in [Ca(2+)](i) in the cultured cells. These findings suggest that stimulation of Gq/(11) protein-coupled NK(2) receptor with neurokinin A caused a substantial release of ATP from cultured T. coli SMCs and that the evoked release may be mediated by Ins(1,4,5)P(3)-sensitive Ca(2+)-signaling, further by PKC and Ca(2+)/calmodulin signals, and finally by an activation of MRP transporters as the membrane device.
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Affiliation(s)
- Jing Sun
- Department of Medical Research Center, School of Medicine, Fukuoka University, Japan
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Hawat G, Benderdour M, Rousseau G, Baroudi G. Connexin 43 mimetic peptide Gap26 confers protection to intact heart against myocardial ischemia injury. Pflugers Arch 2010; 460:583-92. [PMID: 20514543 DOI: 10.1007/s00424-010-0849-6] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2010] [Revised: 05/08/2010] [Accepted: 05/11/2010] [Indexed: 12/27/2022]
Abstract
Unapposed connexin 43 hemichannels (Cx43Hc) are present on sarcolemma of cardiomyocytes. Whereas Cx43Hc remain closed during physiological conditions, their opening under ischemic stress contributes to irreversible tissue injury and cell death. To date, conventional blockers of connexin channels act unselectively on both gap junction channels and unapposed hemichannels. Here, we test the hypothesis that Gap26, a synthetic structural mimetic peptide deriving from the first extracellular loop of Cx43 and a presumed selective blocker of Cx43Hc, confers resistance to intact rat heart against ischemia injury. Langendorff-perfused intact rat hearts were utilized. Regional ischemia was induced by 40-min occlusion of the left anterior descendent coronary and followed by 180 min of reperfusion. Gap26 was applied either 10 min before or 30 min after the initiation of ischemia. Interestingly, myocardial infarct size was reduced by 48% and 55% in hearts treated with Gap26 before or during ischemia, respectively, compared to untreated hearts. Additionally, myocardial perfusate flow was increased in both groups during reperfusion by 37% and 32%, respectively. Application of Gap26 increased survival of isolated cardiomyocytes after simulated ischemia-reperfusion by nearly twofold compared to untreated cells. On the other hand, superfusion of tsA201 cells transiently expressing Cx43 with Gap26 caused 61% inhibition of Cx43Hc-mediated currents recorded using the patch clamp technique. In summary, we demonstrate for the first time that Cx43 mimetic peptide Gap26 confers protection to intact heart against ischemia-reperfusion injury whether administered before or after the occurrence of ischemia. In addition, we provide unequivocal evidence for the inhibitory effect of Gap26 on genuine Cx43Hc.
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Affiliation(s)
- Ghayda Hawat
- Centre de Biomédecine, Hôpital du Sacré-Coeur de Montréal, 5400 Gouin Ouest Blvd., Montréal, H4J 1C5, QC, Canada
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MRP transporters as membrane machinery in the bradykinin-inducible export of ATP. Naunyn Schmiedebergs Arch Pharmacol 2010; 381:315-20. [PMID: 20135098 DOI: 10.1007/s00210-009-0490-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2009] [Accepted: 12/23/2009] [Indexed: 10/19/2022]
Abstract
Adenosine triphosphate (ATP) plays the role of an autocrine/paracrine signal molecule in a variety of cells. So far, however, the membrane machinery in the export of intracellular ATP remains poorly understood. Activation of B2-receptor with bradykinin-induced massive release of ATP from cultured taenia coli smooth muscle cells. The evoked release of ATP was unaffected by gap junction hemichannel blockers, such as 18alpha-glycyrrhetinic acid and Gap 26. Furthermore, the cystic fibrosis transmembrane regulator (CFTR) coupled Cl(-) channel blockers, CFTR(inh)172, 5-nitro-2-(3-phenylpropylamino)-benzoic acid, Gd3(+) and glibenclamide, failed to suppress the export of ATP by bradykinin. On the other, the evoked release of ATP was greatly reduced by multidrug resistance protein (MRP) transporter inhibitors, MK-571, indomethacin, and benzbromarone. From western blotting analysis, blots of MRP 1 protein only, but not MRP 2 and MRP 3 protein, appeared at 190 kD. However, the MRP 1 protein expression was not enhanced after loading with 1 muM bradykinin for 5 min. Likewise, niflumic acid and fulfenamic acid, Ca2(+)-activated Cl(-) channel blockers, largely abated the evoked release of ATP. The possibility that the MRP transporter system couples with Ca2(+)-activated Cl(-) channel activities is discussed here. These findings suggest that MRP transporters, probably MRP 1, unlike CFTR-Cl(-) channels and gap junction hemichannels, may contribute as membrane machinery to the export of ATP induced by G-protein-coupled receptor stimulation.
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Astrocyte-mediated distributed plasticity at hypothalamic glutamate synapses. Neuron 2009; 64:391-403. [PMID: 19914187 DOI: 10.1016/j.neuron.2009.10.021] [Citation(s) in RCA: 159] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/02/2009] [Indexed: 11/21/2022]
Abstract
Afferent activity can induce fast, feed-forward changes in synaptic efficacy that are synapse specific. Using combined electrophysiology, caged molecule photolysis, and Ca(2+) imaging, we describe a plasticity in which the recruitment of astrocytes in response to afferent activity causes a fast and feed-forward, yet distributed increase in the amplitude of quantal synaptic currents at multiple glutamate synapses on magnocellular neurosecretory cells in the hypothalamic paraventricular nucleus. The plasticity is largely multiplicative, consistent with a proportional increase or "scaling" in the strength of all synapses on the neuron. This effect requires a metabotropic glutamate receptor-mediated rise in Ca(2+) in the astrocyte processes surrounding the neuron and the release of the gliotransmitter ATP, which acts on postsynaptic purinergic receptors. These data provide evidence for a form of distributed synaptic plasticity that is feed-forward, expressed quickly, and mediated by the synaptic activation of neighboring astrocytes.
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D'hondt C, Ponsaerts R, De Smedt H, Bultynck G, Himpens B. Pannexins, distant relatives of the connexin family with specific cellular functions? Bioessays 2009; 31:953-74. [PMID: 19644918 DOI: 10.1002/bies.200800236] [Citation(s) in RCA: 135] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Intercellular communication (IC) is mediated by gap junctions (GJs) and hemichannels, which consist of proteins. This has been particularly well documented for the connexin (Cx) family. Initially, Cxs were thought to be the only proteins capable of GJ formation in vertebrates. About 10 years ago, however, a new GJ-forming protein family related to invertebrate innexins (Inxs) was discovered in vertebrates, and named the pannexin (Panx) family. Panxs, which are structurally similar to Cxs, but evolutionarily distinct, have been shown to be co-expressed with Cxs in vertebrates. Both protein families show distinct properties and have their own particular function. Identification of the mechanisms that control Panx channel gating is a major challenge for future work. In this review, we focus on the specific properties and role of Panxs in normal and pathological conditions.
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Affiliation(s)
- Catheleyne D'hondt
- Laboratory of Molecular and Cellular Signalling, KULeuven, Campus Gasthuisberg O/N, Leuven, Belgium
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