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Van Campenhout R, Leroy K, Cooreman A, Tabernilla A, Cogliati B, Kadam P, Vinken M. Connexin-Based Channels in the Liver. Compr Physiol 2022; 12:4147-4163. [PMID: 35950654 DOI: 10.1002/cphy.c220007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Connexin proteins oligomerize in hexameric structures called connexin hemichannels, which then dock to form gap junctions. Gap junctions direct cell-cell communication by allowing the exchange of small molecules and ions between neighboring cells. In this way, hepatic gap junctions support liver homeostasis. Besides serving as building blocks for gap junctions, connexin hemichannels provide a pathway between the intracellular and the extracellular environment. The activation of connexin hemichannels is associated with acute and chronic liver pathologies. This article discusses the role of gap junctions and connexin hemichannels in the liver. © 2022 American Physiological Society. Compr Physiol 12:1-17, 2022.
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Affiliation(s)
- Raf Van Campenhout
- Entity of In Vitro Toxicology and Dermato-Cosmetology, Department of Pharmaceutical and Pharmacological Sciences, Vrije Universiteit Brussel, Brussels, Belgium
| | - Kaat Leroy
- Entity of In Vitro Toxicology and Dermato-Cosmetology, Department of Pharmaceutical and Pharmacological Sciences, Vrije Universiteit Brussel, Brussels, Belgium
| | - Axelle Cooreman
- Entity of In Vitro Toxicology and Dermato-Cosmetology, Department of Pharmaceutical and Pharmacological Sciences, Vrije Universiteit Brussel, Brussels, Belgium
| | - Andrés Tabernilla
- Entity of In Vitro Toxicology and Dermato-Cosmetology, Department of Pharmaceutical and Pharmacological Sciences, Vrije Universiteit Brussel, Brussels, Belgium
| | - Bruno Cogliati
- School of Veterinary Medicine and Animal Science, Department of Pathology, University of São Paulo, São Paulo, Brazil
| | - Prashant Kadam
- Entity of In Vitro Toxicology and Dermato-Cosmetology, Department of Pharmaceutical and Pharmacological Sciences, Vrije Universiteit Brussel, Brussels, Belgium
| | - Mathieu Vinken
- Entity of In Vitro Toxicology and Dermato-Cosmetology, Department of Pharmaceutical and Pharmacological Sciences, Vrije Universiteit Brussel, Brussels, Belgium
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Applicability of Scrape Loading-Dye Transfer Assay for Non-Genotoxic Carcinogen Testing. Int J Mol Sci 2021; 22:ijms22168977. [PMID: 34445682 PMCID: PMC8396440 DOI: 10.3390/ijms22168977] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Revised: 07/30/2021] [Accepted: 07/31/2021] [Indexed: 12/27/2022] Open
Abstract
Dysregulation of gap junction intercellular communication (GJIC) is recognized as one of the key hallmarks for identifying non-genotoxic carcinogens (NGTxC). Currently, there is a demand for in vitro assays addressing the gap junction hallmark, which would have the potential to eventually become an integral part of an integrated approach to the testing and assessment (IATA) of NGTxC. The scrape loading-dye transfer (SL-DT) technique is a simple assay for the functional evaluation of GJIC in various in vitro cultured mammalian cells and represents an interesting candidate assay. Out of the various techniques for evaluating GJIC, the SL-DT assay has been used frequently to assess the effects of various chemicals on GJIC in toxicological and tumor promotion research. In this review, we systematically searched the existing literature to gather papers assessing GJIC using the SL-DT assay in a rat liver epithelial cell line, WB-F344, after treating with chemicals, especially environmental and food toxicants, drugs, reproductive-, cardio- and neuro-toxicants and chemical tumor promoters. We discuss findings derived from the SL-DT assay with the known knowledge about the tumor-promoting activity and carcinogenicity of the assessed chemicals to evaluate the predictive capacity of the SL-DT assay in terms of its sensitivity, specificity and accuracy for identifying carcinogens. These data represent important information with respect to the applicability of the SL-DT assay for the testing of NGTxC within the IATA framework.
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Dydowiczová A, Brózman O, Babica P, Sovadinová I. Improved multiparametric scrape loading-dye transfer assay for a simultaneous high-throughput analysis of gap junctional intercellular communication, cell density and viability. Sci Rep 2020; 10:730. [PMID: 31959888 PMCID: PMC6971000 DOI: 10.1038/s41598-020-57536-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2019] [Accepted: 12/31/2019] [Indexed: 12/28/2022] Open
Abstract
Gap junctional intercellular communication (GJIC) is a vital cellular process required for maintenance of tissue homeostasis. In vitro assessment of GJIC represents valuable phenotypic endpoint that could be effectively utilized as an integral component in modern toxicity testing, drug screening or biomedical in vitro research. However, currently available methods for quantifying GJIC with higher-throughputs typically require specialized equipment, proprietary software and/or genetically engineered cell models. To overcome these limitations, we present here an innovative adaptation of traditional, fluorescence microscopy-based scrape loading-dye transfer (SL-DT) assay, which has been optimized to simultaneously evaluate GJIC, cell density and viability. This multiparametric method was demonstrated to be suitable for various multiwell microplate formats, which facilitates an automatized image acquisition. The assay workflow is further assisted by an open source-based software tools for batch image processing, analysis and evaluation of GJIC, cell density and viability. Our results suggest that this approach provides a simple, fast, versatile and cost effective way for in vitro high-throughput assessment of GJIC and other related phenotypic cellular events, which could be included into in vitro screening and assessment of pharmacologically and toxicologically relevant compounds.
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Affiliation(s)
- Aneta Dydowiczová
- Masaryk University, Faculty of Science, RECETOX, Kamenice 5, CZ-62500, Brno, Czech Republic
| | - Ondřej Brózman
- Masaryk University, Faculty of Science, RECETOX, Kamenice 5, CZ-62500, Brno, Czech Republic
| | - Pavel Babica
- Masaryk University, Faculty of Science, RECETOX, Kamenice 5, CZ-62500, Brno, Czech Republic
| | - Iva Sovadinová
- Masaryk University, Faculty of Science, RECETOX, Kamenice 5, CZ-62500, Brno, Czech Republic.
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Pei H, Zhai C, Li H, Yan F, Qin J, Yuan H, Zhang R, Wang S, Zhang W, Chang M, Wang Y, Pei X. Connexin 32 and connexin 43 are involved in lineage restriction of hepatic progenitor cells to hepatocytes. Stem Cell Res Ther 2017; 8:252. [PMID: 29116012 PMCID: PMC5678556 DOI: 10.1186/s13287-017-0703-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2017] [Revised: 09/06/2017] [Accepted: 10/19/2017] [Indexed: 12/16/2022] Open
Abstract
BACKGROUND Bi-potential hepatic progenitor cells can give rise to both hepatocytes and cholangiocytes, which is the last phase and critical juncture in terms of sequentially hepatic lineage restriction from any kind of stem cells. If their differentiation can be controlled, it might access to functional hepatocytes to develop pharmaceutical and biotechnology industries as well as cell therapies for end-stage liver diseases. METHODS In this study, we investigated the influence of Cx32 and Cx43 on hepatocyte differentiation of WB-F344 cells by in vitro gain and loss of function analyses. An inhibitor of Cx32 was also used to make further clarification. To reveal p38 MAPK pathway is closely related to Cxs, rats with 70% partial hepatectomy were injected intraperitoneally with a p38 inhibitor, SB203580. Besides, the effects of p38 MAPK pathway on differentiation of hepatoblasts isolated from fetal rat livers were evaluated by addition of SB203580 in culture medium. RESULTS In vitro gain and loss of function analyses showed overexpression of Connexin 32 and knockdown of Connexin 43 promoted hepatocytes differentiation from hepatic progenitor cells. In addition, in vitro and ex vivo research revealed inhibition of p38 mitogen-activated protein kinase pathway can improve hepatocytes differentiation correlating with upregulation of Connexin 32 expression and downregulation of Connexin 43 expression. CONCLUSIONS Here we demonstrate that Connexins play crucial roles in facilitating differentiation of hepatic progenitors. Our work further implicates that regulators of Connexins and their related pathways might provide new insights to improve lineage restriction of stem cells to mature hepatocytes.
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Affiliation(s)
- Haiyun Pei
- Stem Cell and Regenerative Medicine Lab, Beijing Institute of Transfusion Medicine, Beijing, 100850 China
- South China Institute of Biomedicine, Guangzhou, 510005 China
| | - Chao Zhai
- Stem Cell and Regenerative Medicine Lab, Beijing Institute of Transfusion Medicine, Beijing, 100850 China
| | - Huilin Li
- Stem Cell and Regenerative Medicine Lab, Beijing Institute of Transfusion Medicine, Beijing, 100850 China
| | - Fang Yan
- Tissue Engineering Lab, Beijing Institute of Transfusion Medicine, Beijing, 100850 China
| | - Jinhua Qin
- Stem Cell and Regenerative Medicine Lab, Beijing Institute of Transfusion Medicine, Beijing, 100850 China
- Tissue Engineering Lab, Beijing Institute of Transfusion Medicine, Beijing, 100850 China
- South China Institute of Biomedicine, Guangzhou, 510005 China
| | - Hongfeng Yuan
- Stem Cell and Regenerative Medicine Lab, Beijing Institute of Transfusion Medicine, Beijing, 100850 China
| | - Rui Zhang
- Stem Cell and Regenerative Medicine Lab, Beijing Institute of Transfusion Medicine, Beijing, 100850 China
| | - Shuyong Wang
- Stem Cell and Regenerative Medicine Lab, Beijing Institute of Transfusion Medicine, Beijing, 100850 China
- Tissue Engineering Lab, Beijing Institute of Transfusion Medicine, Beijing, 100850 China
- South China Institute of Biomedicine, Guangzhou, 510005 China
| | - Wencheng Zhang
- Stem Cell and Regenerative Medicine Lab, Beijing Institute of Transfusion Medicine, Beijing, 100850 China
| | - Mingyang Chang
- Tissue Engineering Lab, Beijing Institute of Transfusion Medicine, Beijing, 100850 China
| | - Yunfang Wang
- Tissue Engineering Lab, Beijing Institute of Transfusion Medicine, Beijing, 100850 China
| | - Xuetao Pei
- Stem Cell and Regenerative Medicine Lab, Beijing Institute of Transfusion Medicine, Beijing, 100850 China
- South China Institute of Biomedicine, Guangzhou, 510005 China
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Qin J, Chang M, Wang S, Liu Z, Zhu W, Wang Y, Yan F, Li J, Zhang B, Dou G, Liu J, Pei X, Wang Y. Connexin 32-mediated cell-cell communication is essential for hepatic differentiation from human embryonic stem cells. Sci Rep 2016; 6:37388. [PMID: 27874032 PMCID: PMC5118817 DOI: 10.1038/srep37388] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2016] [Accepted: 10/28/2016] [Indexed: 12/13/2022] Open
Abstract
Gap junction-mediated cell-cell interactions are highly conserved and play essential roles in cell survival, proliferation, differentiation and patterning. We report that Connexin 32 (Cx32)-mediated gap junctional intercellular communication (GJIC) is necessary for human embryonic stem cell-derived hepatocytes (hESC-Heps) during step-wise hepatic lineage restriction and maturation. Vitamin K2, previously shown to promote Cx32 expression in mature hepatocytes, up-regulated Cx32 expression and GJIC activation during hepatic differentiation and maturation, resulting in significant increases of hepatic markers expression and hepatocyte functions. In contrast, negative Cx32 regulator 2-aminoethoxydiphenyl borate blocked hESC-to-hepatocyte maturation and muted hepatocyte functions through disruption of GJIC activities. Dynamic gap junction organization and internalization are phosphorylation-dependent and the p38 mitogen-activated protein kinases pathway (MAPK) can negatively regulate Cxs through phosphorylation-dependent degradation of Cxs. We found that p38 MAPK inhibitor SB203580 improved maturation of hESC-Heps correlating with up-regulation of Cx32; by contrast, the p38 MAPK activator, anisomycin, blocked hESC-Heps maturation correlating with down-regulation of Cx32. These results suggested that Cx32 is essential for cell-cell interactions that facilitate driving hESCs through hepatic-lineage maturation. Regulators of both Cx32 and other members of its pathways maybe used as a promising approach on regulating hepatic lineage restriction of pluripotent stem cells and optimizing their functional maturation.
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Affiliation(s)
- Jinhua Qin
- Stem Cell and Regenerative Medicine Lab, Beijing Institute of Transfusion Medicine, Beijing 100850, China
- Tissue Engineering Lab, Beijing Institute of Transfusion Medicine, Beijing 100850, China
- South China Research Center for Stem Cell and Regenerative Medicine, South China Institute of Biomedicine, Guangzhou 510005, China
| | - Mingyang Chang
- Tissue Engineering Lab, Beijing Institute of Transfusion Medicine, Beijing 100850, China
| | - Shuyong Wang
- Stem Cell and Regenerative Medicine Lab, Beijing Institute of Transfusion Medicine, Beijing 100850, China
- Tissue Engineering Lab, Beijing Institute of Transfusion Medicine, Beijing 100850, China
- South China Research Center for Stem Cell and Regenerative Medicine, South China Institute of Biomedicine, Guangzhou 510005, China
| | - Zhenbo Liu
- CAS Key Laboratory of Genome Sciences and Information, Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing 100101, China
| | - Wei Zhu
- CAS Key Laboratory of Genome Sciences and Information, Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing 100101, China
| | - Yi Wang
- Tissue Engineering Lab, Beijing Institute of Transfusion Medicine, Beijing 100850, China
| | - Fang Yan
- Tissue Engineering Lab, Beijing Institute of Transfusion Medicine, Beijing 100850, China
| | - Jian Li
- Laboratory of Hematological Pharmacology, Beijing Institute of Transfusion Medicine, Beijing 100850, China
| | - Bowen Zhang
- Stem Cell and Regenerative Medicine Lab, Beijing Institute of Transfusion Medicine, Beijing 100850, China
- South China Research Center for Stem Cell and Regenerative Medicine, South China Institute of Biomedicine, Guangzhou 510005, China
| | - Guifang Dou
- Laboratory of Hematological Pharmacology, Beijing Institute of Transfusion Medicine, Beijing 100850, China
| | - Jiang Liu
- CAS Key Laboratory of Genome Sciences and Information, Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing 100101, China
| | - Xuetao Pei
- Stem Cell and Regenerative Medicine Lab, Beijing Institute of Transfusion Medicine, Beijing 100850, China
- South China Research Center for Stem Cell and Regenerative Medicine, South China Institute of Biomedicine, Guangzhou 510005, China
| | - Yunfang Wang
- Tissue Engineering Lab, Beijing Institute of Transfusion Medicine, Beijing 100850, China
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Willebrords J, Crespo Yanguas S, Maes M, Decrock E, Wang N, Leybaert L, da Silva TC, Veloso Alves Pereira I, Jaeschke H, Cogliati B, Vinken M. Structure, Regulation and Function of Gap Junctions in Liver. ACTA ACUST UNITED AC 2016; 22:29-37. [PMID: 27001459 DOI: 10.3109/15419061.2016.1151875] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Gap junctions are a specialized group of cell-to-cell junctions that mediate direct intercellular communication between cells. They arise from the interaction of two hemichannels of adjacent cells, which in turn are composed of six connexin proteins. In liver, gap junctions are predominantly found in hepatocytes and play critical roles in virtually all phases of the hepatic life cycle, including cell growth, differentiation, liver-specific functionality and cell death. Liver gap junctions are directed through a broad variety of mechanisms ranging from epigenetic control of connexin expression to post-translational regulation of gap junction activity. This paper reviews established and novel aspects regarding the architecture, control and functional relevance of liver gap junctions.
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Affiliation(s)
- Joost Willebrords
- Department of In Vitro Toxicology and Dermato-Cosmetology, Faculty of Medicine and Pharmacy, Vrije Universiteit Brussel, Brussels, Belgium
| | - Sara Crespo Yanguas
- Department of In Vitro Toxicology and Dermato-Cosmetology, Faculty of Medicine and Pharmacy, Vrije Universiteit Brussel, Brussels, Belgium
| | - Michaël Maes
- Department of In Vitro Toxicology and Dermato-Cosmetology, Faculty of Medicine and Pharmacy, Vrije Universiteit Brussel, Brussels, Belgium
| | - Elke Decrock
- Department of Basic Medical Sciences, Physiology Group, Ghent University, Ghent, Belgium
| | - Nan Wang
- Department of Basic Medical Sciences, Physiology Group, Ghent University, Ghent, Belgium
| | - Luc Leybaert
- Department of Basic Medical Sciences, Physiology Group, Ghent University, Ghent, Belgium
| | - Tereza Cristina da Silva
- Department of Pathology, School of Veterinary Medicine and Animal Science, University of São Paulo, São Paulo, Brazil
| | - Isabel Veloso Alves Pereira
- Department of Pathology, School of Veterinary Medicine and Animal Science, University of São Paulo, São Paulo, Brazil
| | - Hartmut Jaeschke
- Department of Pharmacology, Toxicology and Therapeutics, University of Kansas Medical Center, Kansas City, Kansas, United States of America
| | - Bruno Cogliati
- Department of Pathology, School of Veterinary Medicine and Animal Science, University of São Paulo, São Paulo, Brazil
| | - Mathieu Vinken
- Department of In Vitro Toxicology and Dermato-Cosmetology, Faculty of Medicine and Pharmacy, Vrije Universiteit Brussel, Brussels, Belgium
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Vinken M, de Kock J, Oliveira AG, Menezes GB, Cogliati B, Dagli MLZ, Vanhaecke T, Rogiers V. Modifications in Connexin Expression in Liver Development and Cancer. ACTA ACUST UNITED AC 2012; 19:55-62. [DOI: 10.3109/15419061.2012.712576] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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Yamaji S, Droggiti A, Lu SC, Martinez-Chantar ML, Warner A, Varela-Rey M. S-Adenosylmethionine regulates connexins sub-types expressed by hepatocytes. Eur J Cell Biol 2010; 90:312-22. [PMID: 21093098 DOI: 10.1016/j.ejcb.2010.09.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2009] [Revised: 09/20/2010] [Accepted: 09/20/2010] [Indexed: 01/01/2023] Open
Abstract
Intercellular communication via GAP Junctions plays an important role in tissue homeostasis, apoptosis, carcinogenesis, cell proliferation and differentiation. Hepatocyte connexins (Cx) 26 and 32 levels are decreased during the de-differentiation process of primary hepatocytes in culture, a situation that is also characterized by a decrease in S-Adenosylmethionine (SAMe) levels. In this current study, we show that SAMe supplementation in cultured hepatocytes every 12h, leads to an up-regulation of Cx26 and 32 mRNA and protein levels and blocks culture-induced Cx43 expression, although it failed to increase Cx26 and 32 membrane localization and GAP junction intracellular communication. SAMe reduced nuclear β-catenin accumulation, which is known to stimulate the TCF/LEF-dependent gene transcription of Cx43. Moreover SAMe-induced reduction in Cx43 and β-catenin was prevented by the proteasome inhibitor MG132, and was not mediated by GSK3 activity. SAMe, and its metabolite 5'-methylthioadenosine (MTA) increased Cx26 mRNA in a process partially mediated by Adenosine A(2A) receptors but independent of PKA. Finally livers from MAT1A knockout mice, characterized by low hepatic SAMe levels, express higher Cx43 and lower Cx26 and 32 protein levels than control mice. These results suggest that SAMe maintains a characteristic expression pattern of the different Cxs in hepatocytes by differentially regulating their levels.
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Affiliation(s)
- Sachie Yamaji
- Department of Cell and Developmental Biology (formerly Anatomy and Developmental Biology), University College London, London, UK
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9
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Ale-Agha N, Galban S, Sobieroy C, Abdelmohsen K, Gorospe M, Sies H, Klotz LO. HuR regulates gap junctional intercellular communication by controlling beta-catenin levels and adherens junction integrity. Hepatology 2009; 50:1567-76. [PMID: 19676129 PMCID: PMC2784158 DOI: 10.1002/hep.23146] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
UNLABELLED Gap junctional intercellular communication (GJIC) plays a critical role in the regulation of tissue homeostasis and carcinogenesis and is modulated by the levels, subcellular localization, and posttranslational modification of gap junction proteins, the connexins (Cx). Here, using oval cell-like rat liver epithelial cells, we demonstrate that the RNA-binding protein HuR promotes GJIC through two mechanisms. First, HuR silencing lowered the levels of Cx43 protein and Cx43 messenger RNA (mRNA), and decreased Cx43 mRNA half-life. This regulation was likely due to the direct stabilization of Cx43 mRNA by HuR, because HuR associated directly with Cx43 mRNA, a transcript that bears signature adenylate-uridylate-rich (AU-rich) and uridylate-rich (U-rich) sequences in its 3'-untranslated region. Second, HuR silencing reduced both half-life and the levels of beta-catenin mRNA, also a target of HuR; accordingly, HuR silencing lowered the levels of whole-cell and membrane-associated beta-catenin. Coimmunoprecipitation experiments showed a direct interaction between beta-catenin and Cx43. Small interfering RNA (siRNA)-mediated depletion of beta-catenin recapitulated the effects of decreasing HuR levels: it attenuated GJIC, decreased Cx43 levels, and redistributed Cx43 to the cytoplasm, suggesting that depletion of beta-catenin in HuR-silenced cells contributed to lowering Cx43 levels at the membrane. Finally, HuR was demonstrated to support GJIC after exposure to a genotoxic agent, doxorubicin, or an inducer of differentiation processes, retinoic acid, thus pointing to a crucial role of HuR in the cellular response to stress and in physiological processes modulated by GJIC. CONCLUSION HuR promotes gap junctional intercellular communication in rat liver epithelial cells through two related regulatory processes, by enhancing the expression of Cx43 and by increasing the expression of beta-catenin, which, in turn, interacts with Cx43 and is required for proper positioning of Cx43 at the plasma membrane.
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Affiliation(s)
- Niloofar Ale-Agha
- Institut für umweltmedizinische Forschung (IUF) an der Heinrich-Heine-Universität Düsseldorf, Düsseldorf, Germany
| | - Stefanie Galban
- Institut für Biochemie und Molekularbiologie I, Heinrich-Heine-Universität Düsseldorf, Düsseldorf, Germany, Laboratory of Cellular and Molecular Biology, National Institute on Aging – Intramural Research Program, National Institutes of Health, Baltimore, MD, USA
| | - Christiane Sobieroy
- Institut für Biochemie und Molekularbiologie I, Heinrich-Heine-Universität Düsseldorf, Düsseldorf, Germany
| | - Kotb Abdelmohsen
- Laboratory of Cellular and Molecular Biology, National Institute on Aging – Intramural Research Program, National Institutes of Health, Baltimore, MD, USA
| | - Myriam Gorospe
- Laboratory of Cellular and Molecular Biology, National Institute on Aging – Intramural Research Program, National Institutes of Health, Baltimore, MD, USA
| | - Helmut Sies
- Institut für umweltmedizinische Forschung (IUF) an der Heinrich-Heine-Universität Düsseldorf, Düsseldorf, Germany, Institut für Biochemie und Molekularbiologie I, Heinrich-Heine-Universität Düsseldorf, Düsseldorf, Germany
| | - Lars-Oliver Klotz
- Institut für umweltmedizinische Forschung (IUF) an der Heinrich-Heine-Universität Düsseldorf, Düsseldorf, Germany, Institut für Biochemie und Molekularbiologie I, Heinrich-Heine-Universität Düsseldorf, Düsseldorf, Germany,Correspondence should be addressed to
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Vinken M, Doktorova T, Decrock E, Leybaert L, Vanhaecke T, Rogiers V. Gap junctional intercellular communication as a target for liver toxicity and carcinogenicity. Crit Rev Biochem Mol Biol 2009; 44:201-22. [PMID: 19635038 DOI: 10.1080/10409230903061215] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Direct communication between hepatocytes, mediated by gap junctions, constitutes a major regulatory platform in the control of liver homeostasis, ranging from hepatocellular proliferation to hepatocyte cell death. Inherent to this pivotal task, gap junction functionality is frequently disrupted upon impairment of the homeostatic balance, as occurs during liver toxicity and carcinogenicity. In the present paper, the deleterious effects of a number of chemical and biological toxic compounds on hepatic gap junctions are discussed, including environmental pollutants, biological toxins, organic solvents, pesticides, pharmaceuticals, peroxides, metals and phthalates. Particular attention is paid to the molecular mechanisms that underlie the abrogation of gap junction functionality. Since hepatic gap junctions are specifically targeted by tumor promoters and epigenetic carcinogens, both in vivo and in vitro, inhibition of gap junction functionality is considered as a suitable indicator for the detection of nongenotoxic hepatocarcinogenicity.
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Affiliation(s)
- Mathieu Vinken
- Department of Toxicology, Faculty of Medicine and Pharmacy, Vrije Universiteit Brussel, Brussels, Belgium.
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11
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Vinken M, Henkens T, De Rop E, Fraczek J, Vanhaecke T, Rogiers V. Biology and pathobiology of gap junctional channels in hepatocytes. Hepatology 2008; 47:1077-88. [PMID: 18058951 DOI: 10.1002/hep.22049] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The present review provides the state of the art of the current knowledge concerning gap junctional channels and their roles in liver functioning. In the first part, we summarize some relevant biochemical properties of hepatic gap junctional channels, including their structure and regulation. In the second part, we discuss the involvement of gap junctional channels in the occurrence of liver cell growth, liver cell differentiation, and liver cell death. We further exemplify their relevance in hepatic pathophysiology. Finally, a number of directions for future liver gap junctional channel research are proposed, and the up-regulation of gap junctional channel activity as a novel strategy in (liver) cancer therapy is illustrated.
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Affiliation(s)
- Mathieu Vinken
- Department of Toxicology, Vrije Universiteit Brussel, Laarbeeklaan 103, B-1090 Brussels, Belgium.
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12
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Borowczyk E, Johnson ML, Bilski JJ, Bilska MA, Redmer DA, Reynolds LP, Grazul-Bilska AT. Role of gap junctions in regulation of progesterone secretion by ovine luteal cells in vitro. Reproduction 2007; 133:641-51. [PMID: 17379658 DOI: 10.1530/rep-06-0178] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
To evaluate the role of gap junctions in the regulation of progesterone secretion, two experiments were conducted. In Experiment 1, luteal cells obtained on days 5, 10, and 15 were cultured overnight at densities of 50 x 10(3), 100 x 10(3), 300 x 10(3), and 600 x 10(3) cells/dish in medium containing: (1) no treatment (control), (2) LH, or (3) dbcAMP. In Experiment 2, luteal cells from days 5 and 10 of the estrous cycle were transfected with siRNA, which targeted the connexin (Cx) 43 gene. In Experiment 1, progesterone secretion, Cx43 mRNA expression, and the rates of gap junctional intercellular communication (GJIC), were affected by the day of the estrous cycle, cell density, and treatments (LH or dbcAMP). The changes in progesterone secretion were positively correlated with the changes in Cx43 mRNA expression and the rates of GJIC. Cx43 was detected on the luteal cell borders in every culture, and luteal cells expressed 3beta-hydroxysteroid dehydrogenase. In Experiment 2, two Cx43 gene-targeted sequences decreased Cx43 mRNA expression and progesterone production by luteal cells. The changes in Cx43 mRNA expression were positively correlated with changes in progesterone concentration in media. Thus, our data demonstrate a relationship between gap junctions and progesterone secretion that was supported by (1) the positive correlations between progesterone secretion and Cx43 mRNA expression and GJIC of luteal cells and (2) the inhibition of Cx43 mRNA expression by siRNA that resulted in decreased production of progesterone by luteal cells. This suggests that gap junctions may be involved in the regulation of steroidogenesis in the ovine corpus luteum.
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Affiliation(s)
- Ewa Borowczyk
- Department of Animal and Range Sciences, North Dakota State University, Fargo, North Dakota 58105, USA
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13
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Heng BC, Yu H, Yin Y, Lim SG, Cao T. Factors influencing stem cell differentiation into the hepatic lineage in vitro. J Gastroenterol Hepatol 2005; 20:975-87. [PMID: 15955203 DOI: 10.1111/j.1440-1746.2005.03856.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
A major area of research in transplantation medicine is the potential application of stem cells in liver regeneration. This would require well-defined and efficient protocols for directing the differentiation of stem cells into the hepatic lineage, followed by their selective purification and proliferation in vitro. The development of such protocols would reduce the likelihood of spontaneous differentiation of stem cells into divergent lineages upon transplantation, as well as reduce the risk of teratoma formation in the case of embryonic stem cells. Additionally, such protocols could provide useful in vitro models for studying hepatogenesis and liver metabolism. The development of pharmokinetic and cytotoxicity/genotoxicity screening tests for newly developed biomaterials and drugs, could also utilize protocols developed for the hepatic differentiation of stem cells. Hence, this review critically examines the various strategies that could be employed to direct the differentiation of stem cells into the hepatic lineage in vitro.
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Affiliation(s)
- Boon Chin Heng
- Stem Cell Laboratory, Faculty of Dentistry, National University of Singapore, Singapore
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Talhouk RS, Elble RC, Bassam R, Daher M, Sfeir A, Mosleh LA, El-Khoury H, Hamoui S, Pauli BU, El-Sabban ME. Developmental expression patterns and regulation of connexins in the mouse mammary gland: expression of connexin30 in lactogenesis. Cell Tissue Res 2005; 319:49-59. [PMID: 15517403 DOI: 10.1007/s00441-004-0915-5] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2004] [Accepted: 05/07/2004] [Indexed: 11/24/2022]
Abstract
The mammary gland reaches a fully differentiated phenotype at lactation, a stage characterized by the abundant expression of beta-casein. We have investigated the expression and regulation of gap junction proteins (connexins, Cx) during the various developmental stages of mouse mammary gland. Immunohistochemical analysis, with specific antibodies, reveals that Cx26 and Cx32 are expressed and confined to the cell borders of luminal epithelial cells in all developmental stages of the gland. Cx26 and Cx32 expression, at the mRNA and protein levels, increases in pregnancy and peaks in lactation. Whereas Cx43 mRNA decreases in pregnancy and lactation, the functional activity of Cx43 protein, which has been localized to myoepithelial cells, is regulated (through phosphorylation) during pregnancy and peaks during lactation. Cx30 mRNA and proteins have, for the first time, been detected in mammary gland epithelia. Using reverse transcription/polymerase chain reaction and sequencing techniques, we show that Cx30 is abundant in pregnant and lactating mammary gland. Cx30 protein levels have not been detected in the mammary gland prior to day 15 of pregnancy, whereas maximum expression occurs at the onset of lactation. In mouse mammary cells in culture, Cx30 is epithelial-cell-specific and is induced by lactogenic hormones. These data identify a novel player in mammary differentiation and suggest a potential role for Cx30 in the fully differentiated gland.
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Affiliation(s)
- Rabih S Talhouk
- Department of Biology, Faculty of Arts and Sciences, American University of Beirut, PO Box 11-0236, Beirut, Lebanon.
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Qin AL, Zhou XQ, Zhang W, Yu H, Xie Q. Characterization and enrichment of hepatic progenitor cells in adult rat liver. World J Gastroenterol 2004; 10:1480-6. [PMID: 15133858 PMCID: PMC4656289 DOI: 10.3748/wjg.v10.i10.1480] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
AIM: To detect the markers of oval cells in adult rat liver and to enrich them for further analysis of characterization in vitro.
METHODS: Rat model for hepatic oval cell proliferation was established with 2-acetylaminofluorene and two third partial hepatectomy (2-AAF/PH). Paraffin embedded rat liver sections from model (11 d after hepatectomy) and control groups were stained with HE and OV6, cytokeratin19 (CK19), albumin, alpha fetoprotein (AFP), connexin43, and c-kit antibodies by immunohistochemistry. Oval cell proliferation was measured with BrdU incorporation test. C-kit positive oval cells were enriched by using magnetic activated cell sorting (MACS) .The sorted oval cells were cultured in a low density to observe colony formation and to examine their characterization in vitro by immunocytochemistry and RT-PCR.
RESULTS: A 2-AAF/PH model was successfully established to activate the oval cell compartment in rat liver. BrdU incorporation test of oval cell was positive. The hepatic oval cells coexpressed oval cell specific marker OV6, hepatocyte-marker albumin and cholangiocyte-marker CK19. They also expressed AFP and connexin 43. C-kit, one hematopoietic stem cell receptor, was expressed in hepatic oval cells at high levels. By using c-kit antibody in conjunction with MACS, we developed a rapid oval cell isolation protocol. The sorted cells formed colony when cultured in vitro. Cells in the colony expressed albumin or CK19 or coexpressed both and BrdU incorporation test was positive. RT-PCR on colony showed expression of albumin and CK19 gene.
CONCLUSION: Hepatic oval cells in the 2-AAF/PH model had the properties of hepatic stem/progenitor cells. Using MACS, we established a method to isolate oval cells. The sorted hepatic oval cells can form colony in vitro which expresses different combinations of phenotypic markers and genes from both hepatocytes and cholangiocyte lineage.
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Affiliation(s)
- Ai-Lan Qin
- Department of Infectious Diseases, Ruijin Hospital, Shanghai 200025, China.
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El-Sabban ME, Sfeir AJ, Daher MH, Kalaany NY, Bassam RA, Talhouk RS. ECM-induced gap junctional communication enhances mammary epithelial cell differentiation. J Cell Sci 2003; 116:3531-41. [PMID: 12893812 DOI: 10.1242/jcs.00656] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The relationship between gap junctional intercellular communication (GJIC) and mammary cell (CID-9) differentiation in vitro was explored. CID-9 cells differentiate and express beta-casein in an extracellular matrix (ECM)- and hormone-dependent manner. In response to interaction with the ECM, cells in culture modulated the expression of their gap junction proteins at the transcriptional and post-translational levels. In the presence of EHS-matrix, connexins (Cx)26, 32 and 43 localized predominantly to the plasma membrane, and enhanced GJIC [as measured by Lucifer Yellow (LY) dye transfer assays] was noted. Inhibition of GJIC of cells on EHS-matrix with 18 alpha glycyrrhetinic acid (GA) resulted in reversible downregulation of beta-casein expression. In the presence of cAMP, cells cultured on plastic expressed beta-casein, upregulated Cx43 and Cx26 protein levels and enhanced GJIC. This was reversed in the presence of 18 alpha GA. cAMP-treated cells plated either on a non-adhesive PolyHEMA substratum or on plastic supplemented with function-blocking anti-beta 1 integrin antibodies, maintained beta-casein expression. These studies suggest that cell-ECM interaction alone may induce differentiation through changes in cAMP levels and formation of functional gap junctions. That these events are downstream of ECM signalling was underscored by the fact that enhanced GJIC induced partial differentiation in mammary epithelial cells in the absence of an exogenously provided basement membrane and in a beta 1-integrin- and adhesion-independent manner.
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Affiliation(s)
- Marwan E El-Sabban
- Department of Human Morphology, Faculty of Medicine, American University of Beirut, PO Box 11-0236, Beirut, Lebanon.
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Yang J, Ichikawa A, Tsuchiya T. A novel function of connexin 32: marked enhancement of liver function in a hepatoma cell line. Biochem Biophys Res Commun 2003; 307:80-5. [PMID: 12849984 DOI: 10.1016/s0006-291x(03)01117-3] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Connexin 32 (Cx32) is the main gap junction protein in hepatocytes and plays an important role in the regulation of signal transfer and growth control in the liver by constructing gap junction channels and gap junctional intercellular communication (GJIC). In this study, the human Cx32 gene was transfected into a hepatoma cell line (HepG2) that showed aberrant expression of Cx32 and was deficient in GJIC. Cx32-transfected HepG2 not only expressed a higher level of Cx32 mRNA, but also showed increased GJIC compared with HepG2 and vector-transfected HepG2. Furthermore, the liver functions of ammonia removal and albumin secretion of HepG2 were markedly enhanced with Cx32 gene transfection. It may be expected to improve the cellular functions of the hepatoma cell line by Cx32 gene transfection and serve to develop an efficacious bioartificial liver.
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Affiliation(s)
- Jun Yang
- Division of Medical Devices, National Institute of Health Sciences, 1-18-1 Kamiyoga, Setagaya-ku, Tokyo, 158-8501, Japan
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Morsi AS, Godfrey RE, Chipman JK, Minchin SD. Characterisation of the connexin32 promoter and changes in response element complexes in rat liver and hepatocytes during culture associated with oxidative stress. Toxicol In Vitro 2003; 17:191-9. [PMID: 12650673 DOI: 10.1016/s0887-2333(03)00003-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Hepatic gap junctional intercellular communication (GJIC), mediated principally by connexin 32, provides a mechanism for regulating multicellular activities between neighbouring cells. The control of Cx32 gene expression at the transcriptional level has been investigated in rat liver tissue and in primary rat hepatocytes during culture. Several response elements have been identified and characterised using the electrophoretic mobility shift assay. Nuclear protein extract prepared from rat primary hepatocytes cultured for 2 h gave a larger number of DNA-protein complexes than observed with extracts from liver in vivo, including complexes containing Sp1. In contrast, nuclear extracts prepared from primary rat hepatocytes cultured for 96 h, and subject to oxidative stress, gave altered DNA-protein complexes when compared to those from hepatocytes cultured for 2 h. These results indicate that culture conditions, known to cause a loss of connexin expression, can modulate the transcription of Cx32 in hepatocytes by affecting the regulatory trans/cis-interactions of redox-sensitive zinc finger proteins within the promoter.
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Affiliation(s)
- A S Morsi
- School of Biosciences, The University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
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Dufresne J, Finnson KW, Gregory M, Cyr DG. Expression of multiple connexins in the rat epididymis indicates a complex regulation of gap junctional communication. Am J Physiol Cell Physiol 2003; 284:C33-43. [PMID: 12388089 DOI: 10.1152/ajpcell.00111.2002] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In the epididymis, Cx43 forms gap junctions between principal and basal cells but not between adjacent principal cells. Cx30.3, 31.1, and 32 were identified in adult rat epididymis by RT-PCR, whereas Cx26 was present in young rats. Postnatal development studies indicate that Cx26 mRNA was detectable only in the caput-corpus region of the epididymis and that levels increased by fivefold during the first 4 wk postnatally, when epithelial cells differentiate, and decrease to nondetectable levels thereafter. Cx31.1 and Cx32 mRNA levels were low throughout the epididymis in young rats and began to increase in the second and third weeks postnatally, when Cx26 levels are decreasing. Both Cx26 and Cx32 were localized to the lateral plasma membranes between adjacent epithelial cells of the epididymis. Colocalization studies indicate that Cx26 and Cx32 exist either independently of one another or can colocalize along the lateral plasma membrane of epithelial cells in young rats or between principal cells in the adult rat epididymis. The presence of multiple connexins (Cxs) and their differential regulation suggest that these play different roles in epididymal development.
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Affiliation(s)
- Julie Dufresne
- Institut National de la Recherche Scientifique-Institut Armand Frappier, Université du Québec, 245 Hymus Boulevard, Pointe-Claire, Québec, Canada H9R 1G6
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Couchie D, Holic N, Chobert MN, Corlu A, Laperche Y. In vitro differentiation of WB-F344 rat liver epithelial cells into the biliary lineage. Differentiation 2002; 69:209-15. [PMID: 11841479 DOI: 10.1046/j.1432-0436.2002.690414.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Differentiation of hepatic precursor cells in the biliary lineage has rarely been investigated, owing to the lack of convenient in vitro models. In this study, we used sodium butyrate and culture on Matrigel to promote differentiation of WB-F344 rat liver epithelial cells along the biliary phenotype. This differentiation was assessed by following the expression of phenotypic markers at the protein or mRNA level. Sodium butyrate induced cytokeratin 19 expression and gamma-glutamyltranspeptidase activity, together with a large increase in gamma-glutamyltranspeptidase mRNA IV, a transcript expressed at high levels in biliary cells. We also observed an increase in aquaporin-1 and beta4 integrin mRNAs, encoding two proteins expressed in adult biliary cells. Culture on Matrigel increased cytokeratin 19, gamma-glutamyltranspeptidase, and BDS7 expression in WB-F344 cells which still expressed aquaporin-1 and beta4 integrin. These results show that WB-F344 cells are able to differentiate in vitro along the biliary pathway, making them a candidate model for analyzing the molecular events associated with the hepatoblast-biliary cell transition.
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Dowling-Warriner CV, Trosko JE. Induction of gap junctional intercellular communication, connexin43 expression, and subsequent differentiation in human fetal neuronal cells by stimulation of the cyclic AMP pathway. Neuroscience 2000; 95:859-68. [PMID: 10670453 DOI: 10.1016/s0306-4522(99)00411-x] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Expression of gap junction proteins and cell-cell communication was studied in the human neural-glial cell line, SVG, as a first step in defining whether the SVG cells could be used as a model system to study the role of gap junctions in neuronal precursor cells. SVG cells were found to express connexin43 protein that co-migrated with WB-F344 rat liver connexin43 and that reacted with connexin43-specific antibodies on Western blots. However, fluorescence recovery after photobleaching analysis of 5,6-carboxyfluorescein-loaded cells failed to show significant dye coupling. Agents that stimulate the adenylyl cyclase/cAMP pathway were used to induce gap junctional intercellular communication in the SVG cultures. A 24-48 h treatment of SVG cells with 5 microM forskolin or 5 microM forskolin + 200 microM 3-isobutyl-1-methylxanthine increased the percentage of dye-coupled cells from 5-65%, using the fluorescent recovery after photobleaching method. The increase in dye coupling induced by forskolin or forskolin + 3-isobutyl-1-methylxanthine was inhibited by octanol, which is known to block gap junction-mediated cell communication. Western blot analysis of total protein extracts revealed the appearance of a higher molecular weight connexin43 protein band after treatment of SVG cells with forskolin or forskolin + 3-isobutyl-1-methylxanthine, that was not observed in vehicle-treated controls. Alkaline phosphatase treatment of total protein extracts from forskolin or forskolin + 3-isobutyl-1-methylxanthine-treated cells reduced the higher molecular weight band to approximately 41,000 the same as observed in the control extracts. The alkaline phosphatase treatment demonstrates that the higher molecular weight band was due to a phosphorylation event stimulated by forskolin or the forskolin + 3-isobutyl-1-methylxanthine combination. In addition, treatment of the SVG cells with the forskolin or forskolin + 3-isobutyl-l-methylxanthine stimulated outgrowth of neurite-like processes from the cell body which immunostained positive for the connexin43 protein as well as protein markers for neurons and oligodendrocytes. We hypothesize that the SVG cells may represent a neuronal progenitor cell population that has the ability to differentiate when exposed to the appropriate signals.
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Affiliation(s)
- C V Dowling-Warriner
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, USA
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Waldo KL, Lo CW, Kirby ML. Connexin 43 expression reflects neural crest patterns during cardiovascular development. Dev Biol 1999; 208:307-23. [PMID: 10191047 DOI: 10.1006/dbio.1999.9219] [Citation(s) in RCA: 149] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We used transgenic mice in which the promoter sequence for connexin 43 linked to a lacZ reporter was expressed in neural crest but not myocardial cells to document the pattern of cardiac neural crest cells in the caudal pharyngeal arches and cardiac outflow tract. Expression of lacZ was strikingly similar to that of cardiac neural crest cells in quail-chick chimeras. By using this transgenic mouse line to compare cardiac neural crest involvement in cardiac outflow septation and aortic arch artery development in mouse and chick, we were able to note differences and similarities in their cardiovascular development. Similar to neural crest cells in the chick, lacZ-positive cells formed a sheath around the persisting aortic arch arteries, comprised the aorticopulmonary septation complex, were located at the site of final fusion of the conal cushions, and populated the cardiac ganglia. In quail-chick chimeras generated for this study, neural crest cells entered the outflow tract by two pathways, submyocardially and subendocardially. In the mouse only the subendocardial population of lacZ-positive cells could be seen as the cells entered the outflow tract. In addition lacZ-positive cells completely surrounded the aortic sac prior to septation, while in the chick, neural crest cells were scattered around the aortic sac with the bulk of cells distributed in the bridging portion of the aorticopulmonary septation complex. In the chick, submyocardial populations of neural crest cells assembled on opposite sides of the aortic sac and entered the conotruncal ridges. Even though the aortic sac in the mouse was initially surrounded by lacZ-positive cells, the two outflow vessels that resulted from its septation showed differential lacZ expression. The ascending aorta was invested by lacZ-positive cells while the pulmonary trunk was devoid of lacZ staining. In the chick, both of these vessels were invested by neural crest cells, but the cells arrived secondarily by displacement from the aortic arch arteries during vessel elongation. This may indicate a difference in derivation of the pulmonary trunk in the mouse or a difference in distribution of cardiac neural crest cells. An independent mouse neural crest marker is needed to confirm whether the differences are indeed due to species differences in cardiovascular and/or neural crest development. Nevertheless, with the differences noted, we believe that this mouse model faithfully represents the location of cardiac neural crest cells. The similarities in location of lacZ-expressing cells in the mouse to that of cardiac neural crest cells in the chick suggest that this mouse is a good model for studying mammalian cardiac neural crest and that the mammalian cardiac neural crest performs functions similar to those shown for chick.
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Affiliation(s)
- K L Waldo
- Institute of Molecular Medicine and Genetics, Medical College of Georgia, Augusta, Georgia, 30912-2640, USA.
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