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Mammano F, Paller AS, White TW. Connexin Hemichannel Inhibition and Human Genodermatoses. J Invest Dermatol 2024:S0022-202X(24)02053-0. [PMID: 39269388 DOI: 10.1016/j.jid.2024.08.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2024] [Revised: 07/29/2024] [Accepted: 08/07/2024] [Indexed: 09/15/2024]
Abstract
Pathogenic variants in genes encoding connexins that cause skin diseases, such as keratitis-ichthyosis-deafness (KID) syndrome and hidrotic ectodermal dysplasia (HED) or Clouston syndrome, display increased hemichannel activity. Mechanistic insights derived from biophysical studies of the variant connexins support the hypothesis that inhibition of the acquired hemichannel activity could alleviate epidermal pathology. Use of pharmacological blockers and engineered mAbs in mouse models of HED and KID confirm that hemichannel inhibition is a promising target for new therapeutic approaches to KID and HED. Insights from this work could apply to other connexin-based genetic skin diseases in which hemichannel activity is elevated.
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Affiliation(s)
- Fabio Mammano
- Institute of Biochemistry and Cell Biology, Italian National Research Council, Rome, Italy; Department of Physics and Astronomy "G. Galilei", University of Padova, Padova, Italy
| | - Amy S Paller
- Department of Dermatology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA
| | - Thomas W White
- Department of Physiology and Biophysics, Stony Brook University School of Medicine, Stony Brook, New York, USA.
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2
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Li J, Wang X, Zhang H, Hu X, Peng X, Jiang W, Zhuo L, Peng Y, Zeng G, Wang Z. Fenamates: Forgotten treasure for cancer treatment and prevention: Mechanisms of action, structural modification, and bright future. Med Res Rev 2024. [PMID: 39171404 DOI: 10.1002/med.22079] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2022] [Revised: 08/03/2024] [Accepted: 08/08/2024] [Indexed: 08/23/2024]
Abstract
Fenamates as classical nonsteroidal anti-inflammatory agents are widely used for relieving pain. Preclinical studies and epidemiological data highlight their chemo-preventive and chemotherapeutic potential for cancer. However, comprehensive reviews of fenamates in cancer are limited. To accelerate the repurposing of fenamates, this review summarizes the results of fenamates alone or in combination with existing chemotherapeutic agents. This paper also explores targets of fenamates in cancer therapy, including COX, AKR family, AR, gap junction, FTO, TEAD, DHODH, TAS2R14, ion channels, and DNA. Besides, this paper discusses other mechanisms, such as regulating Wnt/β-catenin, TGF-β, p38 MAPK, and NF-κB pathway, and the regulation of the expressions of Sp, EGR-1, NAG-1, ATF-3, ErbB2, AR, as well as the modulation of the tumor immune microenvironment. Furthermore, this paper outlined the structural modifications of fenamates, highlighting their potential as promising leads for anticancer drugs.
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Affiliation(s)
- Junfang Li
- School of Pharmacy, Lanzhou University, Lanzhou, Gansu, China
| | - Xiaodong Wang
- School of Pharmacy, Lanzhou University, Lanzhou, Gansu, China
| | - Honghua Zhang
- School of Pharmacy, Lanzhou University, Lanzhou, Gansu, China
| | - Xiaoling Hu
- School of Pharmacy, Lanzhou University, Lanzhou, Gansu, China
| | - Xue Peng
- School of Pharmaceutical Science, Hengyang Medical School, University of South China, Hengyang, Hunan, China
| | - Weifan Jiang
- Postdoctoral Station for Basic Medicine, School of Basic Medicine, Hengyang Medical School, University of South China, Hengyang, Hunan, China
- The Affiliated Nanhua Hospital, Hengyang Medical School, University of South China, Hengyang, Hunan, China
| | - Linsheng Zhuo
- School of Pharmaceutical Science, Hengyang Medical School, University of South China, Hengyang, Hunan, China
- Postdoctoral Station for Basic Medicine, School of Basic Medicine, Hengyang Medical School, University of South China, Hengyang, Hunan, China
| | - Yan Peng
- School of Pharmaceutical Science, Hengyang Medical School, University of South China, Hengyang, Hunan, China
| | - Guo Zeng
- Postdoctoral Station for Basic Medicine, School of Basic Medicine, Hengyang Medical School, University of South China, Hengyang, Hunan, China
| | - Zhen Wang
- School of Pharmaceutical Science, Hengyang Medical School, University of South China, Hengyang, Hunan, China
- Postdoctoral Station for Basic Medicine, School of Basic Medicine, Hengyang Medical School, University of South China, Hengyang, Hunan, China
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3
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Szarka G, Ganczer A, Balogh M, Tengölics ÁJ, Futácsi A, Kenyon G, Pan F, Kovács-Öller T, Völgyi B. Gap junctions fine-tune ganglion cell signals to equalize response kinetics within a given electrically coupled array. iScience 2024; 27:110099. [PMID: 38947503 PMCID: PMC11214328 DOI: 10.1016/j.isci.2024.110099] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2024] [Revised: 03/06/2024] [Accepted: 05/22/2024] [Indexed: 07/02/2024] Open
Abstract
Retinal ganglion cells (RGCs) summate inputs and forward a spike train code to the brain in the form of either maintained spiking (sustained) or a quickly decaying brief spike burst (transient). We report diverse response transience values across the RGC population and, contrary to the conventional transient/sustained scheme, responses with intermediary characteristics are the most abundant. Pharmacological tests showed that besides GABAergic inhibition, gap junction (GJ)-mediated excitation also plays a pivotal role in shaping response transience and thus visual coding. More precisely GJs connecting RGCs to nearby amacrine and RGCs play a defining role in the process. These GJs equalize kinetic features, including the response transience of transient OFF alpha (tOFFα) RGCs across a coupled array. We propose that GJs in other coupled neuron ensembles in the brain are also critical in the harmonization of response kinetics to enhance the population code and suit a corresponding task.
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Affiliation(s)
- Gergely Szarka
- University of Pécs, Szentágothai Research Centre, Pécs, Hungary
- University of Pécs, Department of Neurobiology, Pécs, Hungary
- MTA-PTE NAP 2 Retinal Electrical Synapses Research Group, Pécs, Hungary
- Center for Neuroscience, University of Pécs, Pécs, Hungary
- SzKK Imaging Core Facility, Szentágothai Research Centre, University of Pécs, Pécs, Hungary
| | - Alma Ganczer
- University of Pécs, Szentágothai Research Centre, Pécs, Hungary
- University of Pécs, Department of Neurobiology, Pécs, Hungary
- MTA-PTE NAP 2 Retinal Electrical Synapses Research Group, Pécs, Hungary
- Center for Neuroscience, University of Pécs, Pécs, Hungary
| | - Márton Balogh
- University of Pécs, Szentágothai Research Centre, Pécs, Hungary
- University of Pécs, Department of Neurobiology, Pécs, Hungary
- MTA-PTE NAP 2 Retinal Electrical Synapses Research Group, Pécs, Hungary
- Center for Neuroscience, University of Pécs, Pécs, Hungary
| | - Ádám Jonatán Tengölics
- University of Pécs, Szentágothai Research Centre, Pécs, Hungary
- University of Pécs, Department of Neurobiology, Pécs, Hungary
- MTA-PTE NAP 2 Retinal Electrical Synapses Research Group, Pécs, Hungary
- Center for Neuroscience, University of Pécs, Pécs, Hungary
| | - Anett Futácsi
- University of Pécs, Szentágothai Research Centre, Pécs, Hungary
- MTA-PTE NAP 2 Retinal Electrical Synapses Research Group, Pécs, Hungary
- Center for Neuroscience, University of Pécs, Pécs, Hungary
- SzKK Imaging Core Facility, Szentágothai Research Centre, University of Pécs, Pécs, Hungary
| | | | - Feng Pan
- The Hong Kong Polytechnic University, Hong Kong, China
| | - Tamás Kovács-Öller
- University of Pécs, Szentágothai Research Centre, Pécs, Hungary
- University of Pécs, Department of Neurobiology, Pécs, Hungary
- MTA-PTE NAP 2 Retinal Electrical Synapses Research Group, Pécs, Hungary
- Center for Neuroscience, University of Pécs, Pécs, Hungary
- SzKK Imaging Core Facility, Szentágothai Research Centre, University of Pécs, Pécs, Hungary
| | - Béla Völgyi
- University of Pécs, Szentágothai Research Centre, Pécs, Hungary
- University of Pécs, Department of Neurobiology, Pécs, Hungary
- MTA-PTE NAP 2 Retinal Electrical Synapses Research Group, Pécs, Hungary
- Center for Neuroscience, University of Pécs, Pécs, Hungary
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4
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Lee HC, Oliveira NMM, Hastings C, Baillie-Benson P, Moverley AA, Lu HC, Zheng Y, Wilby EL, Weil TT, Page KM, Fu J, Moris N, Stern CD. Regulation of long-range BMP gradients and embryonic polarity by propagation of local calcium-firing activity. Nat Commun 2024; 15:1463. [PMID: 38368410 PMCID: PMC10874436 DOI: 10.1038/s41467-024-45772-4] [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: 06/01/2023] [Accepted: 02/02/2024] [Indexed: 02/19/2024] Open
Abstract
Many amniote vertebrate species including humans can form identical twins from a single embryo, but this only occurs rarely. It has been suggested that the primitive-streak-forming embryonic region emits signals that inhibit streak formation elsewhere but the signals involved, how they are transmitted and how they act has not been elucidated. Here we show that short tracks of calcium firing activity propagate through extraembryonic tissue via gap junctions and prevent ectopic primitive streak formation in chick embryos. Cross-regulation of calcium activity and an inhibitor of primitive streak formation (Bone Morphogenetic Protein, BMP) via NF-κB and NFAT establishes a long-range BMP gradient spanning the embryo. This mechanism explains how embryos of widely different sizes can maintain positional information that determines embryo polarity. We provide evidence for similar mechanisms in two different human embryo models and in Drosophila, suggesting an ancient evolutionary origin.
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Affiliation(s)
- Hyung Chul Lee
- Department of Cell and Developmental Biology, University College London, Gower Street, London, WC1E 6BT, UK.
- School of Biological Sciences and Technology, College of Natural Sciences, Chonnam National University, 77 Yongbong-ro, Gwangju, 61186, Korea.
| | - Nidia M M Oliveira
- Department of Cell and Developmental Biology, University College London, Gower Street, London, WC1E 6BT, UK
- College of Professional Services, Murdoch University, 90 South St, Murdoch, WA, 6150, Australia
| | - Cato Hastings
- Department of Cell and Developmental Biology, University College London, Gower Street, London, WC1E 6BT, UK
| | | | - Adam A Moverley
- Department of Cell and Developmental Biology, University College London, Gower Street, London, WC1E 6BT, UK
- Department of Cell and Developmental Biology, Institute for Regenerative Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Hui-Chun Lu
- Department of Cell and Developmental Biology, University College London, Gower Street, London, WC1E 6BT, UK
- Centre for Craniofacial & Regenerative Biology, Faculty of Dentistry, Oral and Craniofacial Sciences, King's College London, Guy's Tower, London, SE1 9RT, UK
| | - Yi Zheng
- Departments of Mechanical Engineering, Biomedical Engineering, and Cell & Developmental Biology, University of Michigan, Ann Arbor, MI, USA
- Department of Biomedical and Chemical Engineering, Syracuse University, Syracuse, NY, USA
- BioInspired Syracuse Institute for Materials and Living Systems, Syracuse University, Syracuse, NY, USA
| | - Elise L Wilby
- Department of Zoology, University of Cambridge, Downing Street, Cambridge, CB2 3EJ, UK
| | - Timothy T Weil
- Department of Zoology, University of Cambridge, Downing Street, Cambridge, CB2 3EJ, UK
| | - Karen M Page
- Department of Mathematics, University College London, Gower Street, London, WC1E 6BT, UK
| | - Jianping Fu
- Departments of Mechanical Engineering, Biomedical Engineering, and Cell & Developmental Biology, University of Michigan, Ann Arbor, MI, USA
| | - Naomi Moris
- The Francis Crick Institute, 1 Midland Road, London, NW1 1AT, UK
| | - Claudio D Stern
- Department of Cell and Developmental Biology, University College London, Gower Street, London, WC1E 6BT, UK.
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Sellitto C, Li L, White TW. Connexin hemichannel inhibition ameliorates epidermal pathology in a mouse model of keratitis ichthyosis deafness syndrome. Sci Rep 2021; 11:24118. [PMID: 34916582 PMCID: PMC8677806 DOI: 10.1038/s41598-021-03627-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2021] [Accepted: 12/07/2021] [Indexed: 02/05/2023] Open
Abstract
AbstractMutations in five different genes encoding connexin channels cause eleven clinically defined human skin diseases. Keratitis ichthyosis deafness (KID) syndrome is caused by point mutations in the GJB2 gene encoding Connexin 26 (Cx26) which result in aberrant activation of connexin hemichannels. KID syndrome has no cure and is associated with bilateral hearing loss, blinding keratitis, palmoplantar keratoderma, ichthyosiform erythroderma and a high incidence of childhood mortality. Here, we have tested whether a topically applied hemichhanel inhibitor (flufenamic acid, FFA) could ameliorate the skin pathology associated with KID syndrome in a transgenic mouse model expressing the lethal Cx26-G45E mutation. We found that FFA blocked the hemichannel activity of Cx26-G45E in vitro, and substantially reduced epidermal pathology in vivo, compared to untreated, or vehicle treated control animals. FFA did not reduce the expression of mutant connexin hemichannel protein, and cessation of FFA treatment allowed disease progression to continue. These results suggested that aberrant hemichannel activity is a major driver of skin disease in KID syndrome, and that the inhibition of mutant hemichannel activity could provide an attractive target to develop novel therapeutic interventions to treat this incurable disease.
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Giaume C, Naus CC, Sáez JC, Leybaert L. Glial Connexins and Pannexins in the Healthy and Diseased Brain. Physiol Rev 2020; 101:93-145. [PMID: 32326824 DOI: 10.1152/physrev.00043.2018] [Citation(s) in RCA: 82] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Over the past several decades a large amount of data have established that glial cells, the main cell population in the brain, dynamically interact with neurons and thus impact their activity and survival. One typical feature of glia is their marked expression of several connexins, the membrane proteins forming intercellular gap junction channels and hemichannels. Pannexins, which have a tetraspan membrane topology as connexins, are also detected in glial cells. Here, we review the evidence that connexin and pannexin channels are actively involved in dynamic and metabolic neuroglial interactions in physiological as well as in pathological situations. These features of neuroglial interactions open the way to identify novel non-neuronal aspects that allow for a better understanding of behavior and information processing performed by neurons. This will also complement the "neurocentric" view by facilitating the development of glia-targeted therapeutic strategies in brain disease.
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Affiliation(s)
- Christian Giaume
- Collège de France, Center for Interdisciplinary Research in Biology (CIRB)/Centre National de la Recherche Scientifique, Unité Mixte de Recherche 7241/Institut National de la Santé et de la Recherche Médicale U1050, Paris, France; University Pierre et Marie Curie, Paris, France; MEMOLIFE Laboratory of Excellence and Paris Science Lettre Research University, Paris, France; Department of Cellular & Physiological Sciences, Life Sciences Institute, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada; Departamento de Fisiología, Pontificia Universidad Católica de Chile, Santiago, Chile; Instituo de Neurociencias, Centro Interdisciplinario de Neurociencias, Universidad de Valparaíso, Valparaíso, Chile; Physiology Group, Department of Basic and Applied Medical Sciences, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium
| | - Christian C Naus
- Collège de France, Center for Interdisciplinary Research in Biology (CIRB)/Centre National de la Recherche Scientifique, Unité Mixte de Recherche 7241/Institut National de la Santé et de la Recherche Médicale U1050, Paris, France; University Pierre et Marie Curie, Paris, France; MEMOLIFE Laboratory of Excellence and Paris Science Lettre Research University, Paris, France; Department of Cellular & Physiological Sciences, Life Sciences Institute, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada; Departamento de Fisiología, Pontificia Universidad Católica de Chile, Santiago, Chile; Instituo de Neurociencias, Centro Interdisciplinario de Neurociencias, Universidad de Valparaíso, Valparaíso, Chile; Physiology Group, Department of Basic and Applied Medical Sciences, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium
| | - Juan C Sáez
- Collège de France, Center for Interdisciplinary Research in Biology (CIRB)/Centre National de la Recherche Scientifique, Unité Mixte de Recherche 7241/Institut National de la Santé et de la Recherche Médicale U1050, Paris, France; University Pierre et Marie Curie, Paris, France; MEMOLIFE Laboratory of Excellence and Paris Science Lettre Research University, Paris, France; Department of Cellular & Physiological Sciences, Life Sciences Institute, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada; Departamento de Fisiología, Pontificia Universidad Católica de Chile, Santiago, Chile; Instituo de Neurociencias, Centro Interdisciplinario de Neurociencias, Universidad de Valparaíso, Valparaíso, Chile; Physiology Group, Department of Basic and Applied Medical Sciences, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium
| | - Luc Leybaert
- Collège de France, Center for Interdisciplinary Research in Biology (CIRB)/Centre National de la Recherche Scientifique, Unité Mixte de Recherche 7241/Institut National de la Santé et de la Recherche Médicale U1050, Paris, France; University Pierre et Marie Curie, Paris, France; MEMOLIFE Laboratory of Excellence and Paris Science Lettre Research University, Paris, France; Department of Cellular & Physiological Sciences, Life Sciences Institute, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada; Departamento de Fisiología, Pontificia Universidad Católica de Chile, Santiago, Chile; Instituo de Neurociencias, Centro Interdisciplinario de Neurociencias, Universidad de Valparaíso, Valparaíso, Chile; Physiology Group, Department of Basic and Applied Medical Sciences, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium
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7
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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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8
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Vanden Daele L, Boydens C, Van de Voorde J. Characterization of the retina-induced relaxation in mice. Graefes Arch Clin Exp Ophthalmol 2018; 256:1905-1912. [PMID: 30105641 DOI: 10.1007/s00417-018-4096-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2018] [Revised: 06/27/2018] [Accepted: 07/30/2018] [Indexed: 01/24/2023] Open
Abstract
PURPOSE The retinal relaxing factor (RRF) is a continuously released factor from the retina that causes vasorelaxation, the identity and potential role in physiology of which remain largely unknown. Experiments were performed to find out whether the RRF-induced relaxation is influenced by serotonin, glutamate, L-cysteine, the cytochrome P450 pathway, the cyclooxygenase pathway, or oxidative stress. In addition, the sensitivity of retinal and non-retinal arteries towards the RRF was compared. METHODS In vitro tension measurements were performed on isolated mouse femoral or bovine retinal arteries to study the vasorelaxing effect of the RRF, induced by mouse or bovine retinas. RESULTS The presence of serotonin, glutamate, or L-cysteine did not alter the RRF-induced relaxation. Increasing oxidative stress by hydroquinone and diethyldithiocarbamic acid sodium salt enhanced the RRF response. Inhibition of the cytochrome P450 or the cyclooxygenase pathway did not cause any alteration. Surprisingly, the RRF-induced relaxation was enhanced by the presence of flufenamic acid or carbenoxolone. Furthermore, bringing retinal tissue in close contact with retinal or non-retinal arteries induced comparable relaxations. CONCLUSIONS Serotonin, glutamate, L-cysteine, the cytochrome P450, and the cyclooxygenase pathway do not influence the RRF-induced relaxation and the RRF-induced relaxation seems to be resistant to oxidative stress. The mechanism responsible for the enhanced RRF-induced relaxation in the presence of flufenamic acid or carbenoxolone remains elusive and the RRF does not show more effectivity on retinal arteries.
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Affiliation(s)
- Laura Vanden Daele
- Department of Pharmacology - Vascular Research Unit, Ghent University, Corneel Heymanslaan 10, 9000, Ghent, Belgium
| | - Charlotte Boydens
- Department of Pharmacology - Vascular Research Unit, Ghent University, Corneel Heymanslaan 10, 9000, Ghent, Belgium
| | - Johan Van de Voorde
- Department of Pharmacology - Vascular Research Unit, Ghent University, Corneel Heymanslaan 10, 9000, Ghent, Belgium.
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Lara GG, Andrade GF, Cipreste MF, da Silva WM, Gastelois PL, Gomes DA, de Miranda MC, de Almeida Macedo WA, Neves MJ, de Sousa EMB. Protection of normal cells from irradiation bystander effects by silica-flufenamic acid nanoparticles. JOURNAL OF MATERIALS SCIENCE. MATERIALS IN MEDICINE 2018; 29:130. [PMID: 30074096 DOI: 10.1007/s10856-018-6134-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2018] [Accepted: 07/17/2018] [Indexed: 06/08/2023]
Abstract
The development of a myriad of nanoparticles types has opened new possibilities for the diagnostics and treatment of many diseases, especially for cancer. However, most of the researches done so far do not focus on the protection of normal cells surrounding a tumor from irradiation bystander effects that might lead to cancer recurrence. Gap-junctions are known to be involved in this process, which leads to genomic instability of neighboring normal cells, and flufenamic acid (FFA) is included in a new group of gap-junction blockers recently discovered. The present work explores the use of mesoporous silica nanoparticles MCM-41 functionalized with 3-Aminopropyltriethoxysilane (APTES) for anchoring the flufenamic acid for its prolonged and controlled release and protection from radiation bystander effects. MCM-41 and functionalized samples were structurally and chemically characterized with multiple techniques. The biocompatibility of all samples was tested in a live/dead assay performed in cultured MRC-5 and HeLa cells. HeLa cells cultured were exposed to 50 Gy of gamma-rays and the media transferred to fibroblast cells cultured separately. Our results show that MCM-41 and functionalized samples have high biocompatibility with MCR-5 and HeLa cells, and most importantly, the FFA delivered by these NPs was able to halt apoptosis, one of main bystander effects.
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Affiliation(s)
- Giovanna Gomes Lara
- Centro de Desenvolvimento da Tecnologia Nuclear, CDTN, Belo Horizonte, 31270-901, MG, Brazil
| | | | | | | | - Pedro Lana Gastelois
- Centro de Desenvolvimento da Tecnologia Nuclear, CDTN, Belo Horizonte, 31270-901, MG, Brazil
| | - Dawidson Assis Gomes
- Departamento de Bioquímica e Imunologia, Instituto de Ciências Biológicas, UFMG, Belo Horizonte, Brazil
| | | | | | - Maria Jose Neves
- Centro de Desenvolvimento da Tecnologia Nuclear, CDTN, Belo Horizonte, 31270-901, MG, Brazil
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Ouachikh O, Hafidi A, Boucher Y, Dieb W. Electrical Synapses are Involved in Orofacial Neuropathic Pain. Neuroscience 2018; 382:69-79. [PMID: 29746991 DOI: 10.1016/j.neuroscience.2018.04.041] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2018] [Revised: 04/24/2018] [Accepted: 04/26/2018] [Indexed: 12/28/2022]
Abstract
Accumulated evidences suggest important roles of glial GAP-junctions in pain. However, only a few studies have explored the role of neuronal GAP-junctions or electrical synapses in neuropathic pain (NP). Therefore, the present study explores the role of connexin 36 (Cx36) in NP using the chronic constriction injury of the infraorbital nerve (CCI-IoN) model in rat. A significant increase in Cx36 labeling was observed in the medullary dorsal horn (MDH) of CCI-IoN-lesioned compared to sham rats. The expression of Cx36 in CCI-IoN-lesioned rats revealed a rostroventral gradient of punctuate labeling within lamina IIo of the MDH. Cx36-positive somata and processes were also observed in MDH laminae IIi and III-V. These somata were mostly of the Gamma aminobutyric acid (GABA) and occasionally Glycine transporter 2 (GlyT2) cell subtypes. Moreover the GABA cell subtypes are highly coupled in lamina IIo as revealed by the intense Cx36 staining in this lamina. Pharmacological Cx36 blockade by intracisternal administration of mefloquine decreased significantly the mechanical allodynia observed in CCI-IoN-lesioned rats. Altogether, our findings demonstrated that Cx36 play an important role in mechanical allodynia by coupling GABA cells. Increasing cell coupling by enhancing Cx36 expression favors neuropathic pain while disrupting this coupling alleviates it. This mechanism may constitute a novel target for the treatment of orofacial mechanical allodynia.
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Affiliation(s)
- Omar Ouachikh
- EA 7280 - Neuro-psycho-pharmacologie des systèmes dopaminergiques sous corticaux, Université Clermont Auvergne, Clermont-Ferrand 63000, France
| | - Aziz Hafidi
- EA 7280 - Neuro-psycho-pharmacologie des systèmes dopaminergiques sous corticaux, Université Clermont Auvergne, Clermont-Ferrand 63000, France.
| | - Yves Boucher
- Faculté d'odontologie (Garançière), Université Paris-Diderot, Paris, France; Hôpital Pitié-Salpétrière, AP-HP, Paris, France
| | - Wisam Dieb
- EA 7280 - Neuro-psycho-pharmacologie des systèmes dopaminergiques sous corticaux, Université Clermont Auvergne, Clermont-Ferrand 63000, France; Faculté d'odontologie (Garançière), Université Paris-Diderot, Paris, France; Hôpital Pitié-Salpétrière, AP-HP, Paris, France
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11
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Ma Y, Han X, de Castro RB, Zhang P, Zhang K, Hu Z, Qin L. Analysis of the bystander effect in cone photoreceptors via a guided neural network platform. SCIENCE ADVANCES 2018; 4:eaas9274. [PMID: 29750200 PMCID: PMC5942910 DOI: 10.1126/sciadv.aas9274] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/10/2018] [Accepted: 03/21/2018] [Indexed: 06/08/2023]
Abstract
The mammalian retina system consists of a complicated photoreceptor structure, which exhibits extensive random synaptic connections. To study retinal development and degeneration, various experimental models have been used previously, but these models are often uncontrollable, are difficult to manipulate, and do not provide sufficient similarity or precision. Therefore, the mechanisms in many retinal diseases remain unclear because of the limited capability in observing the progression and molecular driving forces. For example, photoreceptor degeneration can spread to surrounding healthy photoreceptors via a phenomenon known as the bystander effect; however, no in-depth observations can be made to decipher the molecular mechanisms or the pathways that contribute to the spreading. It is then necessary to build dissociated neural networks to investigate the communications with controllability of cells and their treatment. We developed a neural network chip (NN-Chip) to load single neurons into highly ordered microwells connected by microchannels for synapse formation to build the neural network. By observing the distribution of apoptosis spreading from light-induced apoptotic cones to the surrounding cones, we demonstrated convincing evidence of the existence of a cone-to-cone bystander killing effect. Combining the NN-Chip with microinjection technology, we also found that the gap junction protein connexin 36 (Cx36) is critical for apoptosis spreading and the bystander effect in cones. In addition, our unique NN-Chip platform provides a quantitative, high-throughput tool for investigating signaling mechanisms and behaviors in neurons and opens a new avenue for screening potential drug targets to cure retinal diseases.
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Affiliation(s)
- Yuan Ma
- Department of Nanomedicine, Houston Methodist Research Institute, Houston, TX 77030, USA
- College of Materials Sciences and Optoelectronics, University of Chinese Academy of Sciences, Beijing 100049, China
- Department of Cell and Developmental Biology, Weill Cornell Medical College, New York, NY 10065, USA
| | - Xin Han
- Department of Nanomedicine, Houston Methodist Research Institute, Houston, TX 77030, USA
- Department of Cell and Developmental Biology, Weill Cornell Medical College, New York, NY 10065, USA
| | - Ricardo Bessa de Castro
- Department of Nanomedicine, Houston Methodist Research Institute, Houston, TX 77030, USA
- Department of Cell and Developmental Biology, Weill Cornell Medical College, New York, NY 10065, USA
- College of Engineering, Swansea University, Singleton Park, Swansea SA2 8PP, UK
| | - Pengchao Zhang
- Department of Nanomedicine, Houston Methodist Research Institute, Houston, TX 77030, USA
- Department of Cell and Developmental Biology, Weill Cornell Medical College, New York, NY 10065, USA
| | - Kai Zhang
- Department of Nanomedicine, Houston Methodist Research Institute, Houston, TX 77030, USA
- Department of Cell and Developmental Biology, Weill Cornell Medical College, New York, NY 10065, USA
| | - Zhongbo Hu
- College of Materials Sciences and Optoelectronics, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Lidong Qin
- Department of Nanomedicine, Houston Methodist Research Institute, Houston, TX 77030, USA
- Department of Cell and Developmental Biology, Weill Cornell Medical College, New York, NY 10065, USA
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Protein Kinase C Enhances Electrical Synaptic Transmission by Acting on Junctional and Postsynaptic Ca 2+ Currents. J Neurosci 2018; 38:2796-2808. [PMID: 29440551 DOI: 10.1523/jneurosci.2619-17.2018] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2017] [Revised: 01/15/2018] [Accepted: 02/02/2018] [Indexed: 11/21/2022] Open
Abstract
By synchronizing neuronal activity, electrical transmission influences the coordination, pattern, and/or frequency of firing. In the hemaphroditic marine-snail, Aplysia calfornica, the neuroendocrine bag cell neurons use electrical synapses to synchronize a 30 min afterdischarge of action potentials for the release of reproductive hormone. During the afterdischarge, protein kinase C (PKC) is activated, although its impact on bag cell neuron electrical transmission is unknown. This was investigated here by monitoring electrical synapses between paired cultured bag cell neurons using dual whole-cell recording. Voltage clamp revealed a largely voltage-independent junctional current, which was enhanced by treating with a PKC activator, PMA, before recording. We also examined the transfer of presynaptic action potential-like waveforms (generated in voltage clamp) to the postsynaptic cell (measured in current clamp). For control pairs, the presynaptic spike-like waveforms mainly evoked electrotonic potentials; however, when PKC was triggered, these stimuli consistently produced postsynaptic action potentials. To assess whether this involved changes to postsynaptic responsiveness, single bag cell neurons were injected with junctional-like current mimicking that evoked by a presynaptic action potential. Unlike control neurons, which were less likely to spike, cells in PMA always fired action potentials to the junctional-like current. Furthermore, PKC activation increased a postsynaptic voltage-gated Ca2+ current, which was recruited even by modest depolarization associated with an electrotonic potential. Whereas PKC inhibits gap junctions in most systems, bag cell neurons are rather unique, as the kinase potentiates the electrical synapse; in turn, this synergizes with augmented postsynaptic Ca2+ current to promote synchronous firing.SIGNIFICANCE STATEMENT Electrical coupling is a fundamental form of communication. For the bag cell neurons of Aplysia, electrical synapses coordinate a prolonged burst of action potentials known as the afterdischarge. We looked at how protein kinase C, which is upregulated with the afterdischarge, influences information transfer across the synapse. The kinase activation increased junctional current, a remarkable finding given that this enzyme is largely considered inhibitory for gap junctions. There was also an augmentation in the ability of a presynaptic neuron to provoke postsynaptic action potentials. This increased excitability was, in part, due to enhanced postsynaptic voltage-dependent Ca2+ current. Thus, protein kinase C improves the fidelity of electrotonic transmission and promotes synchronous firing by modulating both junctional and membrane conductances.
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Lara GG, Cipreste MF, Andrade GF, Silva WMD, Sousa EMBD. Response of Fibroblasts MRC-5 to Flufenamic Acid-Grafted MCM-41 Nanoparticles. Bioengineering (Basel) 2018; 5:bioengineering5010004. [PMID: 29315235 PMCID: PMC5874870 DOI: 10.3390/bioengineering5010004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2017] [Revised: 12/26/2017] [Accepted: 01/05/2018] [Indexed: 12/22/2022] Open
Abstract
Recently, flufenamic acid (FFA) was discovered among fenamates as a free radical scavenger and gap junction blocker; however, its effects have only been studied in cancer cells. Normal cells in the surroundings of a tumor also respond to radiation, although they are not hit by it directly. This phenomenon is known as the bystander effect, where response molecules pass from tumor cells to normal ones, through communication channels called gap junctions. The use of the enhanced permeability and retention effect, through which drug-loaded nanoparticles smaller than 200 nm may accumulate around a tumor, can prevent the local side effect upon controlled release of the drug. The present work, aimed at functionalizing MCM-41 (Mobil Composition of Matter No. 41) silica nanoparticles with FFA and determining its biocompatibility with human fibroblasts MRC-5 (Medical Research Council cell strain 5). MCM-41, was synthesized and characterized structurally and chemically, with multiple techniques. The biocompatibility assay was performed by Live/Dead technique, with calcein and propidium–iodide. MRC-5 cells were treated with FFA-grafted MCM-41 for 48 h, and 98% of cells remained viable, without signs of necrosis or morphological changes. The results show the feasibility of MCM-41 functionalization with FFA, and its potential protection of normal cells, in comparison to the role of FFA in cancerous ones.
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Affiliation(s)
- Giovanna Gomes Lara
- Centro de Desenvolvimento da Tecnologia Nuclear-CDTN-Avenida Presidente Antônio Carlos, 6.627-Campus UFMG, Belo Horizonte CEP 31270-901, Minas Gerais, Brazil.
| | - Marcelo Fernandes Cipreste
- Centro de Desenvolvimento da Tecnologia Nuclear-CDTN-Avenida Presidente Antônio Carlos, 6.627-Campus UFMG, Belo Horizonte CEP 31270-901, Minas Gerais, Brazil.
| | - Gracielle Ferreira Andrade
- Centro de Desenvolvimento da Tecnologia Nuclear-CDTN-Avenida Presidente Antônio Carlos, 6.627-Campus UFMG, Belo Horizonte CEP 31270-901, Minas Gerais, Brazil.
| | - Wellington Marcos da Silva
- Centro de Desenvolvimento da Tecnologia Nuclear-CDTN-Avenida Presidente Antônio Carlos, 6.627-Campus UFMG, Belo Horizonte CEP 31270-901, Minas Gerais, Brazil.
| | - Edésia Martins Barros de Sousa
- Centro de Desenvolvimento da Tecnologia Nuclear-CDTN-Avenida Presidente Antônio Carlos, 6.627-Campus UFMG, Belo Horizonte CEP 31270-901, Minas Gerais, Brazil.
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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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Leybaert L, Lampe PD, Dhein S, Kwak BR, Ferdinandy P, Beyer EC, Laird DW, Naus CC, Green CR, Schulz R. Connexins in Cardiovascular and Neurovascular Health and Disease: Pharmacological Implications. Pharmacol Rev 2017; 69:396-478. [PMID: 28931622 PMCID: PMC5612248 DOI: 10.1124/pr.115.012062] [Citation(s) in RCA: 171] [Impact Index Per Article: 24.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Connexins are ubiquitous channel forming proteins that assemble as plasma membrane hemichannels and as intercellular gap junction channels that directly connect cells. In the heart, gap junction channels electrically connect myocytes and specialized conductive tissues to coordinate the atrial and ventricular contraction/relaxation cycles and pump function. In blood vessels, these channels facilitate long-distance endothelial cell communication, synchronize smooth muscle cell contraction, and support endothelial-smooth muscle cell communication. In the central nervous system they form cellular syncytia and coordinate neural function. Gap junction channels are normally open and hemichannels are normally closed, but pathologic conditions may restrict gap junction communication and promote hemichannel opening, thereby disturbing a delicate cellular communication balance. Until recently, most connexin-targeting agents exhibited little specificity and several off-target effects. Recent work with peptide-based approaches has demonstrated improved specificity and opened avenues for a more rational approach toward independently modulating the function of gap junctions and hemichannels. We here review the role of connexins and their channels in cardiovascular and neurovascular health and disease, focusing on crucial regulatory aspects and identification of potential targets to modify their function. We conclude that peptide-based investigations have raised several new opportunities for interfering with connexins and their channels that may soon allow preservation of gap junction communication, inhibition of hemichannel opening, and mitigation of inflammatory signaling.
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Affiliation(s)
- Luc Leybaert
- Physiology Group, Department of Basic Medical Sciences, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium (L.L.); Translational Research Program, Fred Hutchinson Cancer Research Center, Seattle, Washington (P.D.L.); Institute for Pharmacology, University of Leipzig, Leipzig, Germany (S.D.); Department of Pathology and Immunology, Department of Medical Specialization-Cardiology, University of Geneva, Geneva, Switzerland (B.R.K.); Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary (P.F.); Pharmahungary Group, Szeged, Hungary (P.F.); Department of Pediatrics, University of Chicago, Chicago, Illinois (E.C.B.); Department of Anatomy and Cell Biology, University of Western Ontario, Dental Science Building, London, Ontario, Canada (D.W.L.); Cellular and Physiological Sciences, Faculty of Medicine, The University of British Columbia, Vancouver, British Columbia, Canada (C.C.N.); Department of Ophthalmology and The New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand (C.R.G.); and Physiologisches Institut, Justus-Liebig-Universität Giessen, Giessen, Germany (R.S.)
| | - Paul D Lampe
- Physiology Group, Department of Basic Medical Sciences, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium (L.L.); Translational Research Program, Fred Hutchinson Cancer Research Center, Seattle, Washington (P.D.L.); Institute for Pharmacology, University of Leipzig, Leipzig, Germany (S.D.); Department of Pathology and Immunology, Department of Medical Specialization-Cardiology, University of Geneva, Geneva, Switzerland (B.R.K.); Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary (P.F.); Pharmahungary Group, Szeged, Hungary (P.F.); Department of Pediatrics, University of Chicago, Chicago, Illinois (E.C.B.); Department of Anatomy and Cell Biology, University of Western Ontario, Dental Science Building, London, Ontario, Canada (D.W.L.); Cellular and Physiological Sciences, Faculty of Medicine, The University of British Columbia, Vancouver, British Columbia, Canada (C.C.N.); Department of Ophthalmology and The New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand (C.R.G.); and Physiologisches Institut, Justus-Liebig-Universität Giessen, Giessen, Germany (R.S.)
| | - Stefan Dhein
- Physiology Group, Department of Basic Medical Sciences, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium (L.L.); Translational Research Program, Fred Hutchinson Cancer Research Center, Seattle, Washington (P.D.L.); Institute for Pharmacology, University of Leipzig, Leipzig, Germany (S.D.); Department of Pathology and Immunology, Department of Medical Specialization-Cardiology, University of Geneva, Geneva, Switzerland (B.R.K.); Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary (P.F.); Pharmahungary Group, Szeged, Hungary (P.F.); Department of Pediatrics, University of Chicago, Chicago, Illinois (E.C.B.); Department of Anatomy and Cell Biology, University of Western Ontario, Dental Science Building, London, Ontario, Canada (D.W.L.); Cellular and Physiological Sciences, Faculty of Medicine, The University of British Columbia, Vancouver, British Columbia, Canada (C.C.N.); Department of Ophthalmology and The New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand (C.R.G.); and Physiologisches Institut, Justus-Liebig-Universität Giessen, Giessen, Germany (R.S.)
| | - Brenda R Kwak
- Physiology Group, Department of Basic Medical Sciences, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium (L.L.); Translational Research Program, Fred Hutchinson Cancer Research Center, Seattle, Washington (P.D.L.); Institute for Pharmacology, University of Leipzig, Leipzig, Germany (S.D.); Department of Pathology and Immunology, Department of Medical Specialization-Cardiology, University of Geneva, Geneva, Switzerland (B.R.K.); Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary (P.F.); Pharmahungary Group, Szeged, Hungary (P.F.); Department of Pediatrics, University of Chicago, Chicago, Illinois (E.C.B.); Department of Anatomy and Cell Biology, University of Western Ontario, Dental Science Building, London, Ontario, Canada (D.W.L.); Cellular and Physiological Sciences, Faculty of Medicine, The University of British Columbia, Vancouver, British Columbia, Canada (C.C.N.); Department of Ophthalmology and The New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand (C.R.G.); and Physiologisches Institut, Justus-Liebig-Universität Giessen, Giessen, Germany (R.S.)
| | - Peter Ferdinandy
- Physiology Group, Department of Basic Medical Sciences, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium (L.L.); Translational Research Program, Fred Hutchinson Cancer Research Center, Seattle, Washington (P.D.L.); Institute for Pharmacology, University of Leipzig, Leipzig, Germany (S.D.); Department of Pathology and Immunology, Department of Medical Specialization-Cardiology, University of Geneva, Geneva, Switzerland (B.R.K.); Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary (P.F.); Pharmahungary Group, Szeged, Hungary (P.F.); Department of Pediatrics, University of Chicago, Chicago, Illinois (E.C.B.); Department of Anatomy and Cell Biology, University of Western Ontario, Dental Science Building, London, Ontario, Canada (D.W.L.); Cellular and Physiological Sciences, Faculty of Medicine, The University of British Columbia, Vancouver, British Columbia, Canada (C.C.N.); Department of Ophthalmology and The New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand (C.R.G.); and Physiologisches Institut, Justus-Liebig-Universität Giessen, Giessen, Germany (R.S.)
| | - Eric C Beyer
- Physiology Group, Department of Basic Medical Sciences, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium (L.L.); Translational Research Program, Fred Hutchinson Cancer Research Center, Seattle, Washington (P.D.L.); Institute for Pharmacology, University of Leipzig, Leipzig, Germany (S.D.); Department of Pathology and Immunology, Department of Medical Specialization-Cardiology, University of Geneva, Geneva, Switzerland (B.R.K.); Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary (P.F.); Pharmahungary Group, Szeged, Hungary (P.F.); Department of Pediatrics, University of Chicago, Chicago, Illinois (E.C.B.); Department of Anatomy and Cell Biology, University of Western Ontario, Dental Science Building, London, Ontario, Canada (D.W.L.); Cellular and Physiological Sciences, Faculty of Medicine, The University of British Columbia, Vancouver, British Columbia, Canada (C.C.N.); Department of Ophthalmology and The New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand (C.R.G.); and Physiologisches Institut, Justus-Liebig-Universität Giessen, Giessen, Germany (R.S.)
| | - Dale W Laird
- Physiology Group, Department of Basic Medical Sciences, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium (L.L.); Translational Research Program, Fred Hutchinson Cancer Research Center, Seattle, Washington (P.D.L.); Institute for Pharmacology, University of Leipzig, Leipzig, Germany (S.D.); Department of Pathology and Immunology, Department of Medical Specialization-Cardiology, University of Geneva, Geneva, Switzerland (B.R.K.); Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary (P.F.); Pharmahungary Group, Szeged, Hungary (P.F.); Department of Pediatrics, University of Chicago, Chicago, Illinois (E.C.B.); Department of Anatomy and Cell Biology, University of Western Ontario, Dental Science Building, London, Ontario, Canada (D.W.L.); Cellular and Physiological Sciences, Faculty of Medicine, The University of British Columbia, Vancouver, British Columbia, Canada (C.C.N.); Department of Ophthalmology and The New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand (C.R.G.); and Physiologisches Institut, Justus-Liebig-Universität Giessen, Giessen, Germany (R.S.)
| | - Christian C Naus
- Physiology Group, Department of Basic Medical Sciences, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium (L.L.); Translational Research Program, Fred Hutchinson Cancer Research Center, Seattle, Washington (P.D.L.); Institute for Pharmacology, University of Leipzig, Leipzig, Germany (S.D.); Department of Pathology and Immunology, Department of Medical Specialization-Cardiology, University of Geneva, Geneva, Switzerland (B.R.K.); Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary (P.F.); Pharmahungary Group, Szeged, Hungary (P.F.); Department of Pediatrics, University of Chicago, Chicago, Illinois (E.C.B.); Department of Anatomy and Cell Biology, University of Western Ontario, Dental Science Building, London, Ontario, Canada (D.W.L.); Cellular and Physiological Sciences, Faculty of Medicine, The University of British Columbia, Vancouver, British Columbia, Canada (C.C.N.); Department of Ophthalmology and The New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand (C.R.G.); and Physiologisches Institut, Justus-Liebig-Universität Giessen, Giessen, Germany (R.S.)
| | - Colin R Green
- Physiology Group, Department of Basic Medical Sciences, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium (L.L.); Translational Research Program, Fred Hutchinson Cancer Research Center, Seattle, Washington (P.D.L.); Institute for Pharmacology, University of Leipzig, Leipzig, Germany (S.D.); Department of Pathology and Immunology, Department of Medical Specialization-Cardiology, University of Geneva, Geneva, Switzerland (B.R.K.); Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary (P.F.); Pharmahungary Group, Szeged, Hungary (P.F.); Department of Pediatrics, University of Chicago, Chicago, Illinois (E.C.B.); Department of Anatomy and Cell Biology, University of Western Ontario, Dental Science Building, London, Ontario, Canada (D.W.L.); Cellular and Physiological Sciences, Faculty of Medicine, The University of British Columbia, Vancouver, British Columbia, Canada (C.C.N.); Department of Ophthalmology and The New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand (C.R.G.); and Physiologisches Institut, Justus-Liebig-Universität Giessen, Giessen, Germany (R.S.)
| | - Rainer Schulz
- Physiology Group, Department of Basic Medical Sciences, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium (L.L.); Translational Research Program, Fred Hutchinson Cancer Research Center, Seattle, Washington (P.D.L.); Institute for Pharmacology, University of Leipzig, Leipzig, Germany (S.D.); Department of Pathology and Immunology, Department of Medical Specialization-Cardiology, University of Geneva, Geneva, Switzerland (B.R.K.); Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary (P.F.); Pharmahungary Group, Szeged, Hungary (P.F.); Department of Pediatrics, University of Chicago, Chicago, Illinois (E.C.B.); Department of Anatomy and Cell Biology, University of Western Ontario, Dental Science Building, London, Ontario, Canada (D.W.L.); Cellular and Physiological Sciences, Faculty of Medicine, The University of British Columbia, Vancouver, British Columbia, Canada (C.C.N.); Department of Ophthalmology and The New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand (C.R.G.); and Physiologisches Institut, Justus-Liebig-Universität Giessen, Giessen, Germany (R.S.)
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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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Mie M, Takahashi T. Current condition and issues of animal evaluation models for cancer immunotherapy. Nihon Yakurigaku Zasshi 2016; 148:144-8. [PMID: 27581962 DOI: 10.1254/fpj.148.144] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Molchanova SM, Huupponen J, Lauri SE, Taira T. Gap junctions between CA3 pyramidal cells contribute to network synchronization in neonatal hippocampus. Neuropharmacology 2016; 107:9-17. [DOI: 10.1016/j.neuropharm.2016.02.033] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2015] [Revised: 01/28/2016] [Accepted: 02/24/2016] [Indexed: 10/22/2022]
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Lavrov I, Fox L, Shen J, Han Y, Cheng J. Gap Junctions Contribute to the Regulation of Walking-Like Activity in the Adult Mudpuppy (Necturus Maculatus). PLoS One 2016; 11:e0152650. [PMID: 27023006 PMCID: PMC4811563 DOI: 10.1371/journal.pone.0152650] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2015] [Accepted: 03/17/2016] [Indexed: 12/03/2022] Open
Abstract
Although gap junctions are widely expressed in the developing central nervous system, the role of electrical coupling of neurons and glial cells via gap junctions in the spinal cord in adults is largely unknown. We investigated whether gap junctions are expressed in the mature spinal cord of the mudpuppy and tested the effects of applying gap junction blocker on the walking-like activity induced by NMDA or glutamate in an in vitro mudpuppy preparation. We found that glial and neural cells in the mudpuppy spinal cord expressed different types of connexins that include connexin 32 (Cx32), connexin 36 (Cx36), connexin 37 (Cx37), and connexin 43 (Cx43). Application of a battery of gap junction blockers from three different structural classes (carbenexolone, flufenamic acid, and long chain alcohols) substantially and consistently altered the locomotor-like activity in a dose-dependent manner. In contrast, these blockers did not significantly change the amplitude of the dorsal root reflex, indicating that gap junction blockers did not inhibit neuronal excitability nonselectively in the spinal cord. Taken together, these results suggest that gap junctions play a significant modulatory role in the spinal neural networks responsible for the generation of walking-like activity in the adult mudpuppy.
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Affiliation(s)
- Igor Lavrov
- Institute of Fundamental Medicine and Biology, Kazan Federal University, Kazan, Russia
| | - Lyle Fox
- Departments of Pain Management and Neurosciences, Anesthesiology Institute, Cleveland Clinic, Cleveland, Ohio, United States of America
| | - Jun Shen
- Departments of Pain Management and Neurosciences, Anesthesiology Institute, Cleveland Clinic, Cleveland, Ohio, United States of America
| | - Yingchun Han
- Department of Pathobiology, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, United States of America
| | - Jianguo Cheng
- Departments of Pain Management and Neurosciences, Anesthesiology Institute, Cleveland Clinic, Cleveland, Ohio, United States of America
- * E-mail:
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Calkins TL, Piermarini PM. Pharmacological and Genetic Evidence for Gap Junctions as Potential New Insecticide Targets in the Yellow Fever Mosquito, Aedes aegypti. PLoS One 2015; 10:e0137084. [PMID: 26325403 PMCID: PMC4556631 DOI: 10.1371/journal.pone.0137084] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2015] [Accepted: 08/13/2015] [Indexed: 12/02/2022] Open
Abstract
The yellow fever mosquito Aedes aegypti is an important vector of viral diseases that impact global health. Insecticides are typically used to manage mosquito populations, but the evolution of insecticide resistance is limiting their effectiveness. Thus, identifying new molecular and physiological targets in mosquitoes is needed to facilitate insecticide discovery and development. Here we test the hypothesis that gap junctions are valid molecular and physiological targets for new insecticides. Gap junctions are intercellular channels that mediate direct communication between neighboring cells and consist of evolutionarily distinct proteins in vertebrate (connexins) and invertebrate (innexins) animals. We show that the injection of pharmacological inhibitors of gap junctions (i.e., carbenoxolone, meclofenamic acid, or mefloquine) into the hemolymph of adult female mosquitoes elicits dose-dependent toxic effects, with mefloquine showing the greatest potency. In contrast, when applied topically to the cuticle, carbenoxolone was the only inhibitor to exhibit full efficacy. In vivo urine excretion assays demonstrate that both carbenoxolone and mefloquine inhibit the diuretic output of adult female mosquitoes, suggesting inhibition of excretory functions as part of their mechanism of action. When added to the rearing water of 1st instar larvae, carbenoxolone and meclofenamic acid both elicit dose-dependent toxic effects, with meclofenamic acid showing the greatest potency. Injecting a double-stranded RNA cocktail against innexins into the hemolymph of adult female mosquitoes knock down whole-animal innexin mRNA expression and decreases survival of the mosquitoes. Taken together these data indicate that gap junctions may provide novel molecular and physiological targets for the development of insecticides.
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Affiliation(s)
- Travis L. Calkins
- Department of Entomology, Ohio Agricultural Research and Development Center, The Ohio State University, Wooster, Ohio, United States of America
| | - Peter M. Piermarini
- Department of Entomology, Ohio Agricultural Research and Development Center, The Ohio State University, Wooster, Ohio, United States of America
- * E-mail:
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21
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Beekharry CC, Zhu GZ, Magoski NS. Role for electrical synapses in shaping the output of coupled peptidergic neurons from Lymnaea. Brain Res 2015; 1603:8-21. [PMID: 25641041 DOI: 10.1016/j.brainres.2015.01.039] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2014] [Revised: 01/16/2015] [Accepted: 01/20/2015] [Indexed: 12/23/2022]
Abstract
Electrically coupled neurons communicate through channel assemblies called gap junctions, which mediate the transfer of current from one cell to another. Electrical synapses ensure spike synchronization and reliable transmission, which influences bursting patterns and firing frequency. The present study concerns an electrically coupled two-neuron network in the gastropod mollusc, Lymnaea stagnalis. The neurons, designated Visceral Dorsal 1 (VD1) and Right Parietal Dorsal 2 (RPD2), are peptidergic, innervate aspects of the cardio-respiratory system, and show strong coupling, such that they fire synchronously. Using dual sharp-electrode current-clamp recording and morphological staining in isolated brain preparations, the hypothesis that the electrical synapse is necessary for accurate network output was tested. We found that both cells make extensive projections within and out of the brain, including across the visceral-parietal connective, which links VD1 and RPD2. Cutting this connective uncoupled the neurons and disrupted the firing rate and pattern of RPD2 more than VD1, consistent with VD1 being the master and RPD2 the follower. The electrical synapse was inhibited by select gap junction blockers, with niflumic acid and 5-nitro-2-(3-phenylpropylamino) benzoic acid decreasing the VD1→RPD2 and RPD2→VD1 coupling coefficients, whereas carbenoxolone, α-glycyrrhetinic acid, meclofenamic acid, and quinine were ineffective. There was little-to-no impact on VD1↔RPD2 firing synchrony or frequency when coupling was reduced pharmacologically. However, in the presence of gap junction blockers, suppressing the activity of VD1 by prolonged hyperpolarization revealed a distinct, low-frequency firing pattern in RPD2. This suggests that strong electrical coupling is key to maintaining a synchronous output and proper firing rate.
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Affiliation(s)
- Christopher C Beekharry
- Department of Biomedical and Molecular Sciences, Queen׳s University, Kingston, ON, Canada K7L 3N6
| | - Guan Z Zhu
- Department of Biomedical and Molecular Sciences, Queen׳s University, Kingston, ON, Canada K7L 3N6
| | - Neil S Magoski
- Department of Biomedical and Molecular Sciences, Queen׳s University, Kingston, ON, Canada K7L 3N6.
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22
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Connexins in migration during development and cancer. Dev Biol 2014; 401:143-51. [PMID: 25553982 DOI: 10.1016/j.ydbio.2014.12.023] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2014] [Revised: 12/17/2014] [Accepted: 12/18/2014] [Indexed: 12/12/2022]
Abstract
Connexins, the gap junction proteins, through their multitude of actions are implicated in a variety of cell processes during animal development and cancer. They allow direct or paracrine/autocrine cell communication through their channel and hemi-channel functions. They enable adhesion and interact with a plethora of signalling molecules. Here, we review the common themes in developmental and pathological processes and we focus in their involvement in cell migration in four different systems: neurons, astrocytes, neural crest and cancer.
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23
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Levit NA, Sellitto C, Wang HZ, Li L, Srinivas M, Brink PR, White TW. Aberrant connexin26 hemichannels underlying keratitis-ichthyosis-deafness syndrome are potently inhibited by mefloquine. J Invest Dermatol 2014; 135:1033-1042. [PMID: 25229253 PMCID: PMC4363291 DOI: 10.1038/jid.2014.408] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2014] [Revised: 08/02/2014] [Accepted: 09/04/2014] [Indexed: 11/27/2022]
Abstract
Keratitis-ichthyosis-deafness (KID) syndrome is an ectodermal dysplasia caused by dominant mutations of connexin26 (Cx26). Loss of Cx26 function causes non-syndromic sensorineural deafness, without consequence in the epidermis. Functional analyses have revealed that a majority of KID-causing mutations confer a novel expansion of hemichannel activity, mediated by connexin channels in a non-junctional configuration. Inappropriate Cx26 hemichannel opening is hypothesized to compromise keratinocyte integrity and epidermal homeostasis. Pharmacological modulators of Cx26 are needed to assess the pathomechanistic involvement of hemichannels in the development of hyperkeratosis in KID syndrome. We have used electrophysiological assays to evaluate small molecule analogs of quinine for suppressive effects on aberrant hemichannel currents elicited by KID mutations. Here, we show that mefloquine inhibits several mutant hemichannel forms implicated in KID syndrome when expressed in Xenopus laevis oocytes (IC50≈16µM), using an extracellular divalent cation, zinc (Zn++), as a non-specific positive control for comparison (IC50≈3µM). Furthermore, we used freshly isolated transgenic keratinocytes to show that micromolar concentrations of mefloquine attenuated increased macroscopic membrane currents in primary mouse keratinocytes expressing human Cx26-G45E, a mutation causing a lethal form of KID syndrome.
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Affiliation(s)
- Noah A Levit
- Department of Physiology and Biophysics, Stony Brook University, Stony Brook, New York, USA
| | - Caterina Sellitto
- Department of Physiology and Biophysics, Stony Brook University, Stony Brook, New York, USA
| | - Hong-Zhan Wang
- Department of Physiology and Biophysics, Stony Brook University, Stony Brook, New York, USA
| | - Leping Li
- Department of Physiology and Biophysics, Stony Brook University, Stony Brook, New York, USA
| | - Miduturu Srinivas
- Department of Biological and Vision Sciences, SUNY College of Optometry, New York, USA
| | - Peter R Brink
- Department of Physiology and Biophysics, Stony Brook University, Stony Brook, New York, USA
| | - Thomas W White
- Department of Physiology and Biophysics, Stony Brook University, Stony Brook, New York, USA.
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24
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Dargaei Z, Colmers PLW, Hodgson HM, Magoski NS. Electrical coupling between Aplysia bag cell neurons: characterization and role in synchronous firing. J Neurophysiol 2014; 112:2680-96. [PMID: 25185820 DOI: 10.1152/jn.00494.2014] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
In neuroendocrine cells, hormone release often requires a collective burst of action potentials synchronized by gap junctions. This is the case for the electrically coupled bag cell neurons in the reproductive system of the marine snail, Aplysia californica. These neuroendocrine cells are found in two clusters, and fire a synchronous burst, called the afterdischarge, resulting in neuropeptide secretion and the triggering of ovulation. However, the physiology and pharmacology of the bag cell neuron electrical synapse are not completely understood. As such, we made dual whole cell recordings from pairs of electrically coupled cultured bag cell neurons. The junctional current was nonrectifying and not influenced by postsynaptic voltage. Furthermore, junctional conductance was voltage independent and, not surprisingly, strongly correlated with coupling coefficient magnitude. The electrical synapse also acted as a low-pass filter, although under certain conditions, electrotonic potentials evoked by presynaptic action potentials could drive postsynaptic spikes. If coupled neurons were stimulated to spike simultaneously, they presented a high degree of action potential synchrony compared with not-coupled neurons. The electrical synapse failed to pass various intracellular dyes, but was permeable to Cs(+), and could be inhibited by niflumic acid, meclofenamic acid, or 5-nitro-2-(3-phenylpropylamino)benzoic acid. Finally, extracellular and sharp-electrode recording from the intact bag cell neuron cluster showed that these pharmacological uncouplers disrupted both electrical coupling and afterdischarge generation in situ. Thus electrical synapses promote bag cell neuron firing synchrony and may allow for electrotonic spread of the burst through the network, ultimately contributing to propagation of the species.
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Affiliation(s)
- Zahra Dargaei
- Department of Biomedical and Molecular Sciences, Physiology Graduate Program, Queen's University, Kingston, Ontario, Canada
| | - Phillip L W Colmers
- Department of Biomedical and Molecular Sciences, Physiology Graduate Program, Queen's University, Kingston, Ontario, Canada
| | - Heather M Hodgson
- Department of Biomedical and Molecular Sciences, Physiology Graduate Program, Queen's University, Kingston, Ontario, Canada
| | - Neil S Magoski
- Department of Biomedical and Molecular Sciences, Physiology Graduate Program, Queen's University, Kingston, Ontario, Canada
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25
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Mylvaganam S, Ramani M, Krawczyk M, Carlen PL. Roles of gap junctions, connexins, and pannexins in epilepsy. Front Physiol 2014; 5:172. [PMID: 24847276 PMCID: PMC4019879 DOI: 10.3389/fphys.2014.00172] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2013] [Accepted: 04/13/2014] [Indexed: 12/19/2022] Open
Abstract
Enhanced gap junctional communication (GJC) between neurons is considered a major factor underlying the neuronal synchrony driving seizure activity. In addition, the hippocampal sharp wave ripple complexes, associated with learning and seizures, are diminished by GJC blocking agents. Although gap junctional blocking drugs inhibit experimental seizures, they all have other non-specific actions. Besides interneuronal GJC between dendrites, inter-axonal and inter-glial GJC is also considered important for seizure generation. Interestingly, in most studies of cerebral tissue from animal seizure models and from human patients with epilepsy, there is up-regulation of glial, but not neuronal gap junctional mRNA and protein. Significant changes in the expression and post-translational modification of the astrocytic connexin Cx43, and Panx1 were observed in an in vitro Co++ seizure model, further supporting a role for glia in seizure-genesis, although the reasons for this remain unclear. Further suggesting an involvement of astrocytic GJC in epilepsy, is the fact that the expression of astrocytic Cx mRNAs (Cxs 30 and 43) is several fold higher than that of neuronal Cx mRNAs (Cxs 36 and 45), and the number of glial cells outnumber neuronal cells in mammalian hippocampal and cortical tissue. Pannexin expression is also increased in both animal and human epileptic tissues. Specific Cx43 mimetic peptides, Gap 27 and SLS, inhibit the docking of astrocytic connexin Cx43 proteins from forming intercellular gap junctions (GJs), diminishing spontaneous seizures. Besides GJs, Cx membrane hemichannels in glia and Panx membrane channels in neurons and glia are also inhibited by traditional gap junctional pharmacological blockers. Although there is no doubt that connexin-based GJs and hemichannels, and pannexin-based membrane channels are related to epilepsy, the specific details of how they are involved and how we can modulate their function for therapeutic purposes remain to be elucidated.
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Affiliation(s)
- Shanthini Mylvaganam
- Neurobiology, Toronto Western Research Institute, University Health Network and University of Toronto Toronto, ON, Canada
| | - Meera Ramani
- Neurobiology, Toronto Western Research Institute, University Health Network and University of Toronto Toronto, ON, Canada
| | - Michal Krawczyk
- Neurobiology, Toronto Western Research Institute, University Health Network and University of Toronto Toronto, ON, Canada
| | - Peter L Carlen
- Neurobiology, Toronto Western Research Institute, University Health Network and University of Toronto Toronto, ON, Canada
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26
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Lohman AW, Isakson BE. Differentiating connexin hemichannels and pannexin channels in cellular ATP release. FEBS Lett 2014; 588:1379-88. [PMID: 24548565 DOI: 10.1016/j.febslet.2014.02.004] [Citation(s) in RCA: 137] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2014] [Revised: 02/06/2014] [Accepted: 02/06/2014] [Indexed: 12/22/2022]
Abstract
Adenosine triphosphate (ATP) plays a fundamental role in cellular communication, with its extracellular accumulation triggering purinergic signaling cascades in a diversity of cell types. While the roles for purinergic signaling in health and disease have been well established, identification and differentiation of the specific mechanisms controlling cellular ATP release is less well understood. Multiple mechanisms have been proposed to regulate ATP release with connexin (Cx) hemichannels and pannexin (Panx) channels receiving major focus. However, segregating the specific roles of Panxs and Cxs in ATP release in a plethora of physiological and pathological contexts has remained enigmatic. This multifaceted problem has arisen from the selectivity of pharmacological inhibitors for Panxs and Cxs, methodological differences in assessing Panx and Cx function and the potential compensation by other isoforms in gene silencing and genetic knockout models. Consequently, there remains a void in the current understanding of specific contributions of Panxs and Cxs in releasing ATP during homeostasis and disease. Differentiating the distinct signaling pathways that regulate these two channels will advance our current knowledge of cellular communication and aid in the development of novel rationally-designed drugs for modulation of Panx and Cx activity, respectively.
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Affiliation(s)
- Alexander W Lohman
- Department of Molecular Physiology and Biophysics, University of Virginia, Charlottesville, VA 22098, United States; Robert M. Berne Cardiovascular Research Center, University of Virginia, Charlottesville, VA 22908, United States
| | - Brant E Isakson
- Department of Molecular Physiology and Biophysics, University of Virginia, Charlottesville, VA 22098, United States; Robert M. Berne Cardiovascular Research Center, University of Virginia, Charlottesville, VA 22908, United States.
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27
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Patel D, Zhang X, Veenstra RD. Connexin hemichannel and pannexin channel electrophysiology: how do they differ? FEBS Lett 2014; 588:1372-8. [PMID: 24434538 DOI: 10.1016/j.febslet.2013.12.023] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2013] [Revised: 12/20/2013] [Accepted: 12/30/2013] [Indexed: 12/21/2022]
Abstract
Connexin hemichannels are postulated to form a cell permeabilization pore for the uptake of fluorescent dyes and release of cellular ATP. Connexin hemichannel activity is enhanced by low external [Ca(2+)]o, membrane depolarization, metabolic inhibition, and some disease-causing gain-of-function connexin mutations. This paper briefly reviews the electrophysiological channel conductance, permeability, and pharmacology properties of connexin hemichannels, pannexin 1 channels, and purinergic P2X7 receptor channels as studied in exogenous expression systems including Xenopus oocytes and mammalian cell lines such as HEK293 cells. Overlapping pharmacological inhibitory and channel conductance and permeability profiles makes distinguishing between these channel types sometimes difficult. Selective pharmacology for Cx43 hemichannels (Gap19 peptide), probenecid or FD&C Blue #1 (Brilliant Blue FCF, BB FCF) for Panx1, and A740003, A438079, or oxidized ATP (oATP) for P2X7 channels may be the best way to distinguish between these three cell permeabilizing channel types. Endogenous connexin, pannexin, and P2X7 expression should be considered when performing exogenous cellular expression channel studies. Cell pair electrophysiological assays permit the relative assessment of the connexin hemichannel/gap junction channel ratio not often considered when performing isolated cell hemichannel studies.
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Affiliation(s)
- Dakshesh Patel
- Department of Pharmacology, SUNY Upstate Medical University, Syracuse, NY 13210, United States
| | - Xian Zhang
- Department of Pharmacology, SUNY Upstate Medical University, Syracuse, NY 13210, United States
| | - Richard D Veenstra
- Department of Pharmacology, SUNY Upstate Medical University, Syracuse, NY 13210, United States.
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28
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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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29
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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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30
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Li XZ, Ma KT, Guan BC, Li L, Zhao L, Zhang ZS, Si JQ, Jiang ZG. Fenamates block gap junction coupling and potentiate BKCa channels in guinea pig arteriolar cells. Eur J Pharmacol 2013; 703:74-82. [PMID: 23420003 PMCID: PMC3615131 DOI: 10.1016/j.ejphar.2013.02.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2012] [Revised: 02/01/2013] [Accepted: 02/06/2013] [Indexed: 10/27/2022]
Abstract
We determined the actions of the fenamates, flufenamic acid (FFA) and niflumic acid (NFA), on gap junction-mediated intercellular coupling between vascular smooth muscle cells (VSMC) in situ of acutely isolated arteriole segments from the three vascular beds: the spiral modiolar artery (SMA), anterior inferior cerebellar artery (AICA) and mesenteric artery (MA), and on non-junctional membrane channels in dispersed VSMCs. Conventional whole-cell recording methods were used. FFA reversibly suppressed the input conductance (Ginput) or increased the input resistance (Rinput) in a concentration dependent manner, with slightly different IC50s for the SMA, AICA and MA segments (26, 33 and 56 μM respectively, P>0.05). Complete electrical isolation of the recorded VSMC was normally reached at ≥ 300 μM. NFA had a similar effect on gap junction among VSMCs with an IC50 of 40, 48 and 62 μM in SMA, AICA and MA segments, respectively. In dispersed VSMCs, FFA and NFA increased outward rectifier K(+)-current mediated by the big conductance calcium-activated potassium channel (BKCa) in a concentration-dependent manner, with a similar EC50 of ∼300 μM for both FFA and NFA in the three vessels. Iberiotoxin, a selective blocker of the BKCa, suppressed the enhancement of the BKCa by FFA and NFA. The KV blocker 4-AP had no effect on the fenamates-induced K(+)-current enhancement. We conclude that FFA and NFA blocked the vascular gap junction mediated electrical couplings uniformly in arterioles of the three vascular beds, and complete electrical isolation of the recorded VSMC is obtained at ≧300μM; FFA and NFA also activate BKCa channels in the arteriolar smooth muscle cells in addition to their known inhibitory effects on chloride channels.
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Affiliation(s)
- Xin-Zhi Li
- Department of Physiology, Tongji Medical College of Huazhong University of Science and Technology, Wuhan 430030, P.R. China
- The Key Laboratory of Xinjiang Endemic and Ethnic Diseases, Medical College of Shihezi University, Shihezi, 832002, P.R. China
| | - Ke-Tao Ma
- The Key Laboratory of Xinjiang Endemic and Ethnic Diseases, Medical College of Shihezi University, Shihezi, 832002, P.R. China
| | - Bing-Cai Guan
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, 050017, P.R. China
| | - Li Li
- The Key Laboratory of Xinjiang Endemic and Ethnic Diseases, Medical College of Shihezi University, Shihezi, 832002, P.R. China
| | - Lei Zhao
- The Key Laboratory of Xinjiang Endemic and Ethnic Diseases, Medical College of Shihezi University, Shihezi, 832002, P.R. China
| | - Zhong-Shuang Zhang
- The Key Laboratory of Xinjiang Endemic and Ethnic Diseases, Medical College of Shihezi University, Shihezi, 832002, P.R. China
| | - Jun-Qiang Si
- Department of Physiology, Tongji Medical College of Huazhong University of Science and Technology, Wuhan 430030, P.R. China
- The Key Laboratory of Xinjiang Endemic and Ethnic Diseases, Medical College of Shihezi University, Shihezi, 832002, P.R. China
| | - Zhi-Gen Jiang
- Oregon Hearing Research Center, NRC04, Oregon Health and Science University, Portland, OR, 97239 USA
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31
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Guinamard R, Simard C, Del Negro C. Flufenamic acid as an ion channel modulator. Pharmacol Ther 2013; 138:272-84. [PMID: 23356979 DOI: 10.1016/j.pharmthera.2013.01.012] [Citation(s) in RCA: 98] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2012] [Accepted: 12/26/2012] [Indexed: 12/29/2022]
Abstract
Flufenamic acid has been known since the 1960s to have anti-inflammatory properties attributable to the reduction of prostaglandin synthesis. Thirty years later, flufenamic acid appeared to be an ion channel modulator. Thus, while its use in medicine diminished, its use in ionic channel research expanded. Flufenamic acid commonly not only affects non-selective cation channels and chloride channels, but also modulates potassium, calcium and sodium channels with effective concentrations ranging from 10(-6)M in TRPM4 channel inhibition to 10(-3)M in two-pore outwardly rectifying potassium channel activation. Because flufenamic acid effects develop and reverse rapidly, it is a convenient and widely used tool. However, given the broad spectrum of its targets, experimental results have to be interpreted cautiously. Here we provide an overview of ion channels targeted by flufenamic acid to aid in interpreting its effects at the molecular, cellular, and system levels. If it is used with good practices, flufenamic acid remains a useful tool for ion channel research. Understanding the targets of FFA may help reevaluate its physiological impacts and revive interest in its therapeutic potential.
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32
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Freitas AS, Xavier ALR, Furtado CM, Hedin-Pereira C, Fróes MM, Menezes JRL. Dye coupling and connexin expression by cortical radial glia in the early postnatal subventricular zone. Dev Neurobiol 2012; 72:1482-97. [PMID: 22234946 DOI: 10.1002/dneu.22005] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2011] [Revised: 12/21/2011] [Accepted: 12/29/2011] [Indexed: 11/08/2022]
Abstract
In this study, we have analyzed the specific contribution of the cortical radial glia (RG) for gap junctional communication (GJC) within the postnatal subventricular zone (SVZ). To specifically target RG as source of dye-coupling in situ, we have developed a new technique that involves direct cell loading through the processes that reach the pial surface, with a mix of gap junction permeant (Lucifer yellow, LY) and nonpermeant (rhodamine-conjugated dextran 3 KDa, RD) fluorochromes, the latter used as a marker for direct loaded cells. Tissue sections were analyzed for identification of directly loaded (LY+RD+) and coupled cells (LY+RD-) in the SVZ. Directly loaded cells were restricted to the region underlying the pial loading surface area. Coupled cells were distributed in a bistratified manner, along the outer dorsal surface of the SVZ and aligning the ventricle, leaving the SVZ core relatively free. Blocking GJC prior to pial loading greatly reduced dye coupling. Phenotypic analysis indicated that coupling by RG excludes neuroblasts and is mostly restricted to cells of glial lineage. Notwithstanding, no corresponding restriction to specific cell phenotype was found for two connexin isotypes, Cx43 and Cx45, in the postnatal SVZ. The extensive homocellular cell coupling by RG suggests an important role in the regulation of neurogenesis and functional compartmentalization of the postnatal SVZ.
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Affiliation(s)
- Andressa S Freitas
- Programa de Anatomia and Programa de Ciências Morfológicas, Lab. Neuroanatomia Celular, Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, Brazil
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33
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Bodendiek SB, Rubinos C, Trelles MP, Coleman N, Jenkins DP, Wulff H, Srinivas M. Triarylmethanes, a new class of cx50 inhibitors. Front Pharmacol 2012; 3:106. [PMID: 22685432 PMCID: PMC3368247 DOI: 10.3389/fphar.2012.00106] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2012] [Accepted: 05/18/2012] [Indexed: 11/30/2022] Open
Abstract
The paucity of specific pharmacological agents has been a major impediment for delineating the roles of gap junction (GJ) channels formed by connexin proteins in physiology and pathophysiology. Here, we used the selective optimization of side activities (SOSA) approach, which has led to the design of high affinity inhibitors of other ion channels, to identify a specific inhibitor for channels formed by Cx50, a connexin subtype that is primarily expressed in the lens. We initially screened a library of common ion channel modulating pharmacophores for their inhibitory effects on Cx50 GJ channels, and identified four new classes of compounds. The triarlymethane (TRAM) clotrimazole was the most potent Cx50 inhibitor and we therefore used it as a template to explore the structure activity relationship (SAR) of the TRAMs for Cx50 inhibition. We describe the design of T122 (N-[(2-methoxyphenyl)diphenylmethyl]-1,3-thiazol-2-amine) and T136 (N-[(2-iodophenyl)diphenylmethyl]-1,3-thiazol-2-amine), which inhibit Cx50 with IC50s of 1.2 and 2.4 μM. Both compounds exhibit at least 10-fold selectivity over other connexins as well as major neuronal and cardiac voltage-gated K+ and Na+ channels. The SAR studies also indicated that the TRAM pharmacophore required for connexin inhibition is significantly different from the pharmacophore required for blocking the calcium-activated KCa3.1 channel. Both T122 and T136 selectively inhibited Cx50 GJ channels in lens epithelial cells, suggesting that they could be used to further explore the role of Cx50 in the lens. In addition, our results indicate that a similar approach may be used to find specific inhibitors of other connexin subtypes.
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Pocrnich CE, Shao Q, Liu H, Feng MM, Harasym S, Savage M, Khimdas S, Laird DW, Hutnik CML. The effect of connexin43 on the level of vascular endothelial growth factor in human retinal pigment epithelial cells. Graefes Arch Clin Exp Ophthalmol 2011; 250:515-22. [DOI: 10.1007/s00417-011-1871-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2011] [Revised: 10/29/2011] [Accepted: 11/15/2011] [Indexed: 10/15/2022] Open
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Pathological hemichannels associated with human Cx26 mutations causing Keratitis-Ichthyosis-Deafness syndrome. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1818:2014-9. [PMID: 21933663 DOI: 10.1016/j.bbamem.2011.09.003] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2011] [Revised: 08/30/2011] [Accepted: 09/06/2011] [Indexed: 12/25/2022]
Abstract
Connexin (Cx) proteins form intercellular gap junction channels by first assembling into single membrane hemichannels that then dock to connect the cytoplasm of two adjacent cells. Gap junctions are highly specialized structures that allow the direct passage of small molecules between cells to maintain tissue homeostasis. Functional activity of nonjunctional hemichannels has now been shown in several experimental systems. Hemichannels may constitute an important diffusional exchange pathway with the extracellular space, but the extent of their normal physiological role is currently unknown. Aberrant hemichannel activity has been linked to mutations of connexin proteins involved in genetic diseases. Here, we review a proposed role for hemichannels in the pathogenesis of Keratitis-Ichthyosis-Deafness (KID) syndrome associated with connexin26 (Cx26) mutations. Continued functional evaluation of mutated hemichannels linked to human hereditary disorders may provide additional insights into the mechanisms governing their regulation in normal physiology and dysregulation in disease. This article is part of a Special Issue entitled: The Communicating junctions, composition, structure and characteristics.
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Durnin L, Mutafova-Yambolieva VN. Cyclic ADP-ribose requires CD38 to regulate the release of ATP in visceral smooth muscle. FEBS J 2011; 278:3095-108. [PMID: 21740519 PMCID: PMC4838287 DOI: 10.1111/j.1742-4658.2011.08233.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
It is well established that the intracellular second messenger cADP-ribose (cADPR) activates Ca(2+) release from the sarcoplasmic reticulum through ryanodine receptors. CD38 is a multifunctional enzyme involved in the formation of cADPR in mammals. CD38 has also been reported to transport cADPR in several cell lines. Here, we demonstrate a role for extracellular cADPR and CD38 in modulating the spontaneous, but not the electrical field stimulation-evoked, release of ATP in visceral smooth muscle. Using a small-volume superfusion assay and an HPLC technique with fluorescence detection, we measured the spontaneous and evoked release of ATP in bladder detrusor smooth muscles isolated from CD38(+/+) and CD38(-/-) mice. cADPR (1 nM) enhanced the spontaneous overflow of ATP in bladders isolated from CD38(+/+) mice. This effect was abolished by the inhibitor of cADPR receptors on sarcoplasmic reticulum 8-bromo-cADPR (80 μM) and by ryanodine (50 μm), but not by the nonselective P2 purinergic receptor antagonist pyridoxal phosphate 6-azophenyl-2',4'-disulfonate (30 μM). cADPR failed to facilitate the spontaneous ATP overflow in bladders isolated from CD38(-/-) mice, indicating that CD38 is crucial for the enhancing effects of extracellular cADPR on spontaneous ATP release. Contractile responses to ATP were potentiated by cADPR, suggesting that the two adenine nucleotides may work in synergy to maintain the resting tone of the bladder. In conclusion, extracellular cADPR enhances the spontaneous release of ATP in the bladder by influx via CD38 and subsequent activation of intracellular cADPR receptors, probably causing an increase in intracellular Ca(2+) in neuronal cells.
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Affiliation(s)
- Leonie Durnin
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV 89557-0575, USA
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Skeberdis VA, Rimkute L, Skeberdyte A, Paulauskas N, Bukauskas FF. pH-dependent modulation of connexin-based gap junctional uncouplers. J Physiol 2011; 589:3495-506. [PMID: 21606109 DOI: 10.1113/jphysiol.2011.209072] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Gap junction (GJ) channels formed from connexin (Cx) proteins provide a direct pathway for electrical and metabolic cell–cell communication exhibiting high sensitivity to intracellular pH (pH(i)). We examined pH(i)-dependent modulation of junctional conductance (g(j)) of GJs formed of Cx26, mCx30.2, Cx36, Cx40, Cx43, Cx45, Cx46, Cx47 and Cx50 by reagents representing several distinct groups of uncouplers, such as long carbon chain alkanols (LCCAs), arachidonic acid, carbenoxolone, isoflurane, flufenamic acid and mefloquine. We demonstrate that alkalization by NH4Cl to pH ∼8 increased g(j) in cells expressing mCx30.2 and Cx45, yet did not affect g(j) of Cx26, Cx40, Cx46, Cx47 and Cx50 and decreased it in Cx43 and Cx36 GJs. Unexpectedly, cells expressing Cx45, but not other Cxs, exhibited full coupling recovery after alkalization with NH4Cl under the continuous presence of LCCAs, isoflurane and mefloquine. There was no coupling recovery by alkalization in the presence of arachidonic acid, carbenoxolone and flufenamic acid. In cells expressing Cx45, IC50 for octanol was 0.1, 0.25 and 2.68 mm at pH(i) values of 6.9, 7.2 and 8.1, respectively. Histidine modification of Cx45 protein by N-bromosuccinimide reduced the coupling-promoting effect of NH4Cl as well as the uncoupling effect of octanol. This suggests that LCCAs and some other uncouplers may act through the formation of hydrogen bonds with the as-of-yet unidentified histidine/s of the Cx45 GJ channel protein.
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Affiliation(s)
- Vytenis A Skeberdis
- Lithuanian University of Health Sciences, Institute of Cardiology, 17 Sukilėliųu Avenue, Kaunas 50009, Lithuania
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Bathany C, Beahm D, Felske JD, Sachs F, Hua SZ. High throughput assay of diffusion through Cx43 gap junction channels with a microfluidic chip. Anal Chem 2010; 83:933-9. [PMID: 21182279 DOI: 10.1021/ac102658h] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
This paper describes a microfluidic-based assay capable of measuring gap-junction mediated dye diffusion in cultured cells. The technique exploits multistream laminar flow to selectively expose cells to different environments, enabling continuous loading of cells in one compartment while monitoring, in real time, dye diffusion into cells of a neighboring compartment. A simple one-dimensional diffusion model fit to the data extracted the diffusion coefficient of four different dyes, 5-(6)-carboxyfluorescein, 5-chloromethylfluorescein, Oregon green 488 carboxylic acid, and calcein. Different inhibitors were assayed for their ability to reduce dye coupling. The chip can screen multiple inhibitors in parallel in the same cell preparation, demonstrating its potential for high throughput. The technique provides a convenient method to measure gap junction mediated diffusion and a screen for drugs that affect gap junction communication.
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Affiliation(s)
- Cédric Bathany
- Department of Mechanical and Aerospace Engineering, SUNY-Buffalo, Buffalo, New York 14260, USA
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Hill AA, Garcia AJ, Zanella S, Upadhyaya R, Ramirez JM. Graded reductions in oxygenation evoke graded reconfiguration of the isolated respiratory network. J Neurophysiol 2010; 105:625-39. [PMID: 21084689 DOI: 10.1152/jn.00237.2010] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Neurons depend on aerobic metabolism, yet are very sensitive to oxidative stress and, as a consequence, typically operate in a low O(2) environment. The balance between blood flow and metabolic activity, both of which can vary spatially and dynamically, suggests that local O(2) availability markedly influences network output. Yet the understanding of the underlying O(2)-sensing mechanisms is limited. Are network responses regulated by discrete O(2)-sensing mechanisms or, rather, are they the consequence of inherent O(2) sensitivities of mechanisms that generate the network activity? We hypothesized that a broad range of O(2) tensions progressively modulates network activity of the pre-Bötzinger complex (preBötC), a neuronal network critical to the central control of breathing. Rhythmogenesis was measured from the preBötC in transverse neonatal mouse brain stem slices that were exposed to graded reductions in O(2) between 0 and 95% O(2), producing tissue oxygenation values ranging from 20 ± 18 (mean ± SE) to 440 ± 56 Torr at the slice surface, respectively. The response of the preBötC to graded changes in O(2) is progressive for some metrics and abrupt for others, suggesting that different aspects of the respiratory network have different sensitivities to O(2).
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Affiliation(s)
- Andrew A Hill
- New Jersey Institute of Technology and Rutgers University, 195 University Drive, Boyden Hall, Newark, NJ 07102, USA.
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Yau HJ, Baranauskas G, Martina M. Flufenamic acid decreases neuronal excitability through modulation of voltage-gated sodium channel gating. J Physiol 2010; 588:3869-82. [PMID: 20724367 DOI: 10.1113/jphysiol.2010.193037] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The electrophysiological phenotype of individual neurons critically depends on the biophysical properties of the voltage-gated channels they express. Differences in sodium channel gating are instrumental in determining the different firing phenotypes of pyramidal cells and interneurons; moreover, sodium channel modulation represents an important mechanism of action for many widely used CNS drugs. Flufenamic acid (FFA) is a non-steroidal anti-inflammatory drug that has been long used as a blocker of calcium-dependent cationic conductances. Here we show that FFA inhibits voltage-gated sodium currents in hippocampal pyramidal neurons; this effect is dose-dependent with IC(50) = 189 μm. We used whole-cell and nucleated patch recordings to investigate the mechanisms of FFA modulation of TTX-sensitive voltage-gated sodium current. Our data show that flufenamic acid slows down the inactivation process of the sodium current, while shifting the inactivation curve ~10 mV toward more hyperpolarized potentials. The recovery from inactivation is also affected in a voltage-dependent way, resulting in slower recovery at hyperpolarized potentials. Recordings from acute slices demonstrate that FFA reduces repetitive- and abolishes burst-firing in CA1 pyramidal neurons. A computational model based on our data was employed to better understand the mechanisms of FFA action. Simulation data support the idea that FFA acts via a novel mechanism by reducing the voltage dependence of the sodium channel fast inactivation rates. These effects of FFA suggest that it may be an effective anti-epileptic drug.
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Affiliation(s)
- Hau-Jie Yau
- Department of Physiology, Northwestern University Feinberg School of Medicine, 303 E. Chicago Avenue, Chicago, IL 60611, USA
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Mutolo D, Bongianni F, Cinelli E, Pantaleo T. Role of neurokinin receptors and ionic mechanisms within the respiratory network of the lamprey. Neuroscience 2010; 169:1136-49. [PMID: 20540991 DOI: 10.1016/j.neuroscience.2010.06.004] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2010] [Revised: 05/04/2010] [Accepted: 06/03/2010] [Indexed: 11/27/2022]
Abstract
We have suggested that in the lamprey, a medullary region called the paratrigeminal respiratory group (pTRG), is essential for respiratory rhythm generation and could correspond to the pre-Bötzinger complex (pre-BötC), the hypothesized kernel of the inspiratory rhythm-generating network in mammals. The present study was performed on in vitro brainstem preparations of adult lampreys to investigate whether some functional characteristics of the respiratory network are retained throughout evolution and to get further insights into the recent debated hypotheses on respiratory rhythmogenesis in mammals, such as for instance the "group-pacemaker" hypothesis. Thus, we tried to ascertain the presence and role of neurokinins (NKs) and burst-generating ion currents, such as the persistent Na(+) current (I(NaP)) and the Ca(2+)-activated non-specific cation current (I(CAN)), described in the pre-Bötzinger complex. Respiratory activity was monitored as vagal motor output. Substance P (SP) as well as NK1, NK2 and NK3 receptor agonists (400-800 nM) applied to the bath induced marked increases in respiratory frequency. Microinjections (0.5-1 nl) of SP as well as the other NK receptor agonists (1 microM) into the pTRG increased the frequency and amplitude of vagal bursts. Riluzole (RIL) and flufenamic acid (FFA) were used to block I(NaP) and I(CAN), respectively. Bath application of either RIL or FFA (20-50 microM) depressed, but did not suppress respiratory activity. Coapplication of RIL and FFA at 50 microM abolished the respiratory rhythm that, however, was restarted by SP microinjected into the pTRG. The results show that NKs may have a modulatory role in the lamprey respiratory network through an action on the pTRG and that I(NaP) and I(CAN) may contribute to vagal burst generation. We suggest that the "group-pacemaker" hypothesis is tenable for the lamprey respiratory rhythm generation since respiratory activity is abolished by blocking both I(NaP) and I(CAN), but is restored by enhancing network excitability.
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Affiliation(s)
- D Mutolo
- Dipartimento di Scienze Fisiologiche, Università degli Studi di Firenze, Viale GB Morgagni 63, 50134 Firenze, Italy.
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Gajda BM, Fong AY, Milsom WK. Species differences in respiratory rhythm generation in rodents. Am J Physiol Regul Integr Comp Physiol 2010; 298:R887-98. [DOI: 10.1152/ajpregu.00339.2009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We examined the role of riluzole (RIL)- and flufenamic acid (FFA)-sensitive mechanisms in respiratory rhythmogenesis in rats and hamsters using the in situ arterially perfused preparation. Based on the hypothesis that respiratory networks in animals capable of autoresuscitation would have a greater prevalence of membrane mechanisms that promote endogenous bursting, we predicted that older (weaned) hamsters (a hibernating species) would be more sensitive to the blockade of RIL- and FFA-sensitive mechanisms than age-matched rats and that younger (preweaned) rats would behave more like hamsters. Consistent with this, we found that respiratory motor output in weaned hamsters [>21 days postnatal (P21)] was highly sensitive to RIL (0.2–20 μM), while in young rats (P12–14) it was less so (only affected at higher concentrations of RIL), and weaned rats were not affected at all. On the other hand, respiratory motor output was equally reduced by FFA (0.25–25 μM) in both young and weaned rats but was unaffected in weaned hamsters. Coapplication of RIL and FFA (RIL + FFA) produced greater inhibition of respiration in both young and weaned rats compared with either drug alone. In contrast, in weaned hamsters, FFA coapplication offset the inhibitory effect of RIL alone. Increasing respiratory drive with hypercapnia/acidosis ameliorated the respiratory inhibition produced by RIL + FFA in weaned rats but had no effect in young rats. Data from the present study indicate that respiratory rhythmogenesis in young rats is more dependent on excitatory RIL-sensitive and FFA-sensitive mechanisms than older rats and that fundamental differences exist in the respiratory rhythmogenic mechanisms between rats and hamsters.
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Affiliation(s)
- B. M. Gajda
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada
| | - A. Y. Fong
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada
| | - W. K. Milsom
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada
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Hanstein R, Zhao JB, Basak R, Smith DN, Zuckerman YY, Hanani M, Spray DC, Gulinello M. Focal Inflammation Causes Carbenoxolone-Sensitive Tactile Hypersensitivity in Mice. ACTA ACUST UNITED AC 2010; 3:123-133. [PMID: 21151805 DOI: 10.2174/1876386301003010123] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
A focal and transitory inflammation induced by injection of complete Freund's adjuvant (CFA) in the submandibular skin of mice elicits pain behavior that persists for several weeks after the initial inflammation has resolved. Chronic pain, assessed as tactile hypersensitivity to stimulation with von Frey filaments, was evident from 1-7 weeks following CFA injection, although inflammation at the injection site was resolved by 3-4 weeks. In contrast, there were no changes in tactile sensitivity in the paw (un-injected site for comparison), no alterations in open field behavior and no differences in a functional observation battery evident in CFA-treated mice compared to controls (saline-injected) or to baseline (before CFA injection). Neither strain (Balb/c vs. C57BL/6) nor sex differences in baseline tactile threshold were significant in the submandibular skin. CFA-induced tactile hypersensitivity was also not a function of strain or sex. A single intraperitoneal injection of the gap junction blocker carbenoxolone (CBX) restored normal tactile thresholds in CFA-treated mice when administered at the peak of inflammation (1 week), after significant resolution of inflammation (3 weeks) or after total resolution of inflammation (4 and 5 weeks) without altering the tactile threshold of control subjects, tactile threshold in the paw or open field behavior. Thus, in this novel model of post-inflammatory pain, transitory inflammation induced persistent sex- and strain-independent behavioral hypersensitivity that was reversed by the gap junction blocker CBX, suggesting neuronal and/or glial plasticity as a major component of the chronic pain.
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Affiliation(s)
- Regina Hanstein
- Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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Giaume C, Theis M. Pharmacological and genetic approaches to study connexin-mediated channels in glial cells of the central nervous system. ACTA ACUST UNITED AC 2009; 63:160-76. [PMID: 19963007 DOI: 10.1016/j.brainresrev.2009.11.005] [Citation(s) in RCA: 105] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2009] [Revised: 11/18/2009] [Accepted: 11/19/2009] [Indexed: 11/18/2022]
Abstract
This review gives an overview of connexin expression in glial cells of the central nervous system, the different modes of connexin action, including gap junctional channels and hemichannels, as well as the available methodologies to measure their activity. We summarize the strengths and limitations of current pharmacological and genetic approaches to interfere with connexin channel functions. We outline new avenues not only to study specific mechanisms by which connexins exert these functions but also to selectively investigate well-defined coupling compartments among glial networks.
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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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46
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Marins M, Xavier AL, Viana NB, Fortes FS, Fróes MM, Menezes JR. Gap junctions are involved in cell migration in the early postnatal subventricular zone. Dev Neurobiol 2009; 69:715-30. [DOI: 10.1002/dneu.20737] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
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Fernández M, Lao-Peregrín C, Martín ED. Flufenamic acid suppresses epileptiform activity in hippocampus by reducing excitatory synaptic transmission and neuronal excitability. Epilepsia 2009; 51:384-90. [PMID: 19732136 DOI: 10.1111/j.1528-1167.2009.02279.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
PURPOSE In this study, we explore the antiepileptic effects of flufenamic acid (FFA) in order to identify the cellular mechanisms that underlie the potential anticonvulsant properties of this nonsteroidal antiinflammatory compound. METHODS The mechanisms of FFA action were analyzed using an in vitro model in which epileptiform activity was induced in hippocampal slices by perfusion with 100 microm 4-aminopyridine (4-AP) added to a modified Mg(2+)-free solution. The activity of CA1 pyramidal neurons as well as the synaptic connection between CA3 and CA1 was monitored using extracellular and patch-clamp recordings. RESULTS Epileptiform activity was suppressed in hippocampal neurons by FFA at concentrations between 50 and 200 microm. Glutamatergic excitatory synaptic transmission was diminished by FFA without modifying recurrent gamma-aminobutyric acid (GABA)ergic synaptic inhibition. Several lines of evidence indicated that FFA did not decrease neurotransmitter release probability, implicating a postsynaptic mechanism of action. FFA also potently reduced neuronal excitability, but did not alter the amplitude, duration, or undershoot of action potentials. CONCLUSIONS Our results suggest that FFA exerts an anticonvulsive effect on hippocampal pyramidal neurons by simultaneously decreasing glutamatergic excitatory synaptic activity and reducing neuronal excitability. Therefore, our study provides experimental evidence that FFA may represent an effective pharmacologic agent in the treatment of epilepsy in the mammalian central nervous system.
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Affiliation(s)
- Miriam Fernández
- Laboratory of Neurophysiology and Synaptic Plasticity, Regional Center for Biomedical Research (CRIB), University of Castilla-La Mancha, Albacete, Spain
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Ye ZC, Oberheim N, Kettenmann H, Ransom BR. Pharmacological "cross-inhibition" of connexin hemichannels and swelling activated anion channels. Glia 2009; 57:258-69. [PMID: 18837047 DOI: 10.1002/glia.20754] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The study of ion channels has relied heavily on the use of pharmacological blocking agents. However, many of these agents have multiple effects, which may compromise interpretation of results when the affected mechanisms/pathways mediate similar functions. Volume regulated anion channels (VRAC) and connexin hemichannels can both mediate the release of glutamate and taurine, although these channels have distinct activation stimuli and hemichannels, but not VRAC, are permeable to Lucifer Yellow (LY). It has been reported that some anion channel blockers may inhibit connexin hemichannels. We further examined the effects of classic gap junction/hemichannel blockers and anion channel blockers on these channels. The typical VRAC blockers, NPPB, IAA-94, and tamoxifen blocked low divalent cation-induced glutamate and taurine release and LY loading, presumed due to hemichannel opening. The blocking action of these compounds on hemichannels was concentration dependent and fell within the same range where the drugs classically block VRACs. Conversely, carbenoxolone (CBX), the most widely used gap junction/hemichannel blocker, was an effective blocker of VRAC-mediated glutamate and taurine release, and blocked these channels at similar concentrations at which it blocked hemichannels. The CBX effect on VRACs was verified using astrocytes from connexin 43 knock out (Cx43 KO) animals. In these cells, the hypotonic induced amino acid flux was retained whereas the low divalent cation solution-induced flux was lost. These results extend our knowledge about "cross-inhibition" of VRACs and gap junctions/hemichannels by certain pharmacological agents. Given the overlap in function of these two types of channels, great care must be exerted in using pharmacological blockers to identify one channel from the other.
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Affiliation(s)
- Zu-Cheng Ye
- Department of Neurology, University of Washington School of Medicine, Seattle, Washington 98104, USA.
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49
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Juszczak GR, Swiergiel AH. Properties of gap junction blockers and their behavioural, cognitive and electrophysiological effects: animal and human studies. Prog Neuropsychopharmacol Biol Psychiatry 2009; 33:181-98. [PMID: 19162118 DOI: 10.1016/j.pnpbp.2008.12.014] [Citation(s) in RCA: 172] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/30/2008] [Revised: 12/22/2008] [Accepted: 12/22/2008] [Indexed: 10/21/2022]
Abstract
Gap junctions play an important role in brain physiology. They synchronize neuronal activity and connect glial cells participating in the regulation of brain metabolism and homeostasis. Gap junction blockers (GJBs) include various chemicals that impair gap junction communication, disrupt oscillatory neuronal activity over a wide range of frequencies, and decrease epileptic discharges. The behavioural and clinical effects of GJBs suggest that gap junctions can be involved in the regulation of locomotor activity, arousal, memory, and breathing. Severe neuropsychiatric side effects suggest the involvement of gap junctions in mechanisms of consciousness. Unfortunately, the available GJBs are not selective and can bind to targets other than gap junctions. Other problems in behavioural studies include the possible adverse effects of GJBs, for example, retinal toxicity and hearing disturbances, changes in blood-brain transport, and the metabolism of other drugs. Therefore, it is necessary to design experiments properly to avoid false, misleading or uninterpretable results. We review the pharmacological properties and electrophysiological, behavioural and cognitive effects of the available gap junction blockers, such as carbenoxolone, glycyrrhetinic acid, quinine, quinidine, mefloquine, heptanol, octanol, anandamide, fenamates, 2-APB, several anaesthetics, retinoic acid, oleamide, spermine, aminosulfonates, and sodium propionate. It is concluded that despite a number of different problems, the currently used gap junction blockers could be useful tools in pharmacology and neuroscience.
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Affiliation(s)
- Grzegorz R Juszczak
- Department of Animal Behaviour, Institute of Genetics and Animal Breeding, Jastrzebiec, ul. Postepu 1, 05-552 Wolka Kosowska, Poland.
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Longitudinal neuronal organization and coordination in a simple vertebrate: a continuous, semi-quantitative computer model of the central pattern generator for swimming in young frog tadpoles. J Comput Neurosci 2009; 27:291-308. [PMID: 19288183 PMCID: PMC2731935 DOI: 10.1007/s10827-009-0143-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2008] [Revised: 10/14/2008] [Accepted: 02/10/2009] [Indexed: 12/21/2022]
Abstract
When frog tadpoles hatch their swimming requires co-ordinated contractions of trunk muscles, driven by motoneurons and controlled by a Central Pattern Generator (CPG). To study this co-ordination we used a 3.5 mm long population model of the young tadpole CPG with continuous distributions of neurons and axon lengths as estimated anatomically. We found that: (1) alternating swimming-type activity fails to self-sustain unless some excitatory interneurons have ascending axons, (2) a rostro-caudal (R-C) gradient in the distribution of excitatory premotor interneurons with short axons is required to obtain the R-C gradient in excitation and resulting progression of motoneuron firing necessary for forward swimming, (3) R-C delays in motoneuron firing decrease if excitatory motoneuron to premotor interneuron synapses are present, (4) these feedback connections and the electrical synapses between motoneurons synchronise motoneuron discharges locally, (5) the above findings are independent of the detailed membrane properties of neurons.
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