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Qi C, Lavriha P, Bayraktar E, Vaithia A, Schuster D, Pannella M, Sala V, Picotti P, Bortolozzi M, Korkhov VM. Structures of wild-type and selected CMT1X mutant connexin 32 gap junction channels and hemichannels. SCIENCE ADVANCES 2023; 9:eadh4890. [PMID: 37647412 PMCID: PMC10468125 DOI: 10.1126/sciadv.adh4890] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2023] [Accepted: 07/27/2023] [Indexed: 09/01/2023]
Abstract
In myelinating Schwann cells, connection between myelin layers is mediated by gap junction channels (GJCs) formed by docked connexin 32 (Cx32) hemichannels (HCs). Mutations in Cx32 cause the X-linked Charcot-Marie-Tooth disease (CMT1X), a degenerative neuropathy without a cure. A molecular link between Cx32 dysfunction and CMT1X pathogenesis is still missing. Here, we describe the high-resolution cryo-electron cryo-myography (cryo-EM) structures of the Cx32 GJC and HC, along with two CMT1X-linked mutants, W3S and R22G. While the structures of wild-type and mutant GJCs are virtually identical, the HCs show a major difference: In the W3S and R22G mutant HCs, the amino-terminal gating helix partially occludes the pore, consistent with a diminished HC activity. Our results suggest that HC dysfunction may be involved in the pathogenesis of CMT1X.
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Affiliation(s)
- Chao Qi
- Institute of Molecular Biology and Biophysics, ETH Zurich, Zurich, Switzerland
- Laboratory of Biomolecular Research, Paul Scherrer Institute, Villigen, Switzerland
| | - Pia Lavriha
- Institute of Molecular Biology and Biophysics, ETH Zurich, Zurich, Switzerland
- Laboratory of Biomolecular Research, Paul Scherrer Institute, Villigen, Switzerland
| | - Erva Bayraktar
- Veneto Institute of Molecular Medicine (VIMM), Padua, Italy
- Department of Physics and Astronomy “G. Galilei”, University of Padua, Padua, Italy
| | - Anand Vaithia
- Institute of Molecular Biology and Biophysics, ETH Zurich, Zurich, Switzerland
- Laboratory of Biomolecular Research, Paul Scherrer Institute, Villigen, Switzerland
| | - Dina Schuster
- Institute of Molecular Biology and Biophysics, ETH Zurich, Zurich, Switzerland
- Laboratory of Biomolecular Research, Paul Scherrer Institute, Villigen, Switzerland
- Institute of Molecular Systems Biology, ETH Zurich, Zurich, Switzerland
| | - Micaela Pannella
- Veneto Institute of Molecular Medicine (VIMM), Padua, Italy
- Department of Physics and Astronomy “G. Galilei”, University of Padua, Padua, Italy
| | - Valentina Sala
- Veneto Institute of Molecular Medicine (VIMM), Padua, Italy
| | - Paola Picotti
- Institute of Molecular Systems Biology, ETH Zurich, Zurich, Switzerland
| | - Mario Bortolozzi
- Veneto Institute of Molecular Medicine (VIMM), Padua, Italy
- Department of Physics and Astronomy “G. Galilei”, University of Padua, Padua, Italy
| | - Volodymyr M. Korkhov
- Institute of Molecular Biology and Biophysics, ETH Zurich, Zurich, Switzerland
- Laboratory of Biomolecular Research, Paul Scherrer Institute, Villigen, Switzerland
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2
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Ping F, Zhang C, Wang X, Wang Y, Zhou D, Hu J, Chen Y, Ling J, Zhou J. Cx32 inhibits the autophagic effect of Nur77 in SH-SY5Y cells and rat brain with ischemic stroke. Aging (Albany NY) 2021; 13:22188-22207. [PMID: 34551394 PMCID: PMC8507301 DOI: 10.18632/aging.203526] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Accepted: 09/02/2021] [Indexed: 12/15/2022]
Abstract
The pathogenesis of cerebral ischemia-reperfusion (I/R) is complex. Cx32 expression has been reported to be up-regulated in ischemic lesions of aged human brain. Nevertheless, the function of Cx32 during cerebral I/R is poorly understood. Autophagy is of vital importance in the pathogenesis of cerebral I/R. In the current study, we found that oxygen-glucose deprivation/reoxygenation (OGD/R) or I/R insult significantly induced the up-regulation of Cx32 and activation of autophagy. Inhibition of Cx32 alleviated OGD/R or I/R injury, and further activated autophagy. In addition, Nur77 expression was found to be up-regulated after OGD/R or I/R. After inhibiting Cx32, the expression of Nur77 was further increased and Nur77 was translocated from nucleus to mitochondrial. Inhibition of Cx32 also activated mitophagy by promoting autophagosome formation and up-regulating the expression of mitochondrial autophagy marker molecules. Of note, in the siNur77-transfected cells, the number of dysfunctional mitochondrial was increased, and mitophagy was suppressed, which aggravated OGD/R-induced neuronal injury. In conclusion, Cx32 might act as a regulatory factor of Nur77 controlling neuronal autophagy in the brains. Understanding the mechanism of this regulatory pathway will provide new insight into the role Cx32 and Nur77 in cerebral ischemia, offering new opportunities for therapeutics.
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Affiliation(s)
- Fengfeng Ping
- Department of Reproductive Medicine, Wuxi People's Hospital Affiliated to Nanjing Medical University, Wuxi 214023, China
| | - Chao Zhang
- Department of Reproductive Medicine, Wuxi People's Hospital Affiliated to Nanjing Medical University, Wuxi 214023, China
| | - Xue Wang
- Wuxi School of Medicine, Jiangnan University, Wuxi 214122, China
| | - Yan Wang
- Department of Good Clinical Practice, The Affiliated Wuxi Children's Hospital of Nanjing Medical University, Wuxi 214023, China
| | - Danli Zhou
- Department of Good Clinical Practice, The Affiliated Wuxi Children's Hospital of Nanjing Medical University, Wuxi 214023, China
| | - Jing Hu
- Department of Good Clinical Practice, The Affiliated Wuxi Children's Hospital of Nanjing Medical University, Wuxi 214023, China
| | - Yanhua Chen
- Department of Good Clinical Practice, The Affiliated Wuxi Children's Hospital of Nanjing Medical University, Wuxi 214023, China
| | - Jingjing Ling
- Department of Good Clinical Practice, The Affiliated Wuxi Children's Hospital of Nanjing Medical University, Wuxi 214023, China
| | - Jia Zhou
- State Key Laboratory of Natural Medicines, China Pharmaceutical University, Nanjing 211198, China
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3
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Khan AK, Jagielnicki M, Bennett BC, Purdy MD, Yeager M. Cryo-EM structure of an open conformation of a gap junction hemichannel in lipid bilayer nanodiscs. Structure 2021; 29:1040-1047.e3. [PMID: 34129834 PMCID: PMC9616683 DOI: 10.1016/j.str.2021.05.010] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2020] [Revised: 02/26/2021] [Accepted: 05/14/2021] [Indexed: 12/30/2022]
Abstract
To mediate cell-to-cell communication via gap junction channels (GJCs), connexins (Cx) traffic as hexameric hemichannels to the plasma membrane, which dock end-to-end between adjacent cell membranes, thereby forming a dodecameric intercellular conduit. Hemichannels also function independently to mediate the passage of contents between the cytoplasm and extracellular space. To generate hemichannels, the mutation N176Y was introduced into the second extracellular loop of Cx26. The electron cryomicroscopy structure of the hexameric hemichannel in lipid bilayer nanodiscs displays an open pore and a 4-helix bundle transmembrane design that is nearly identical to dodecameric GJCs. In contrast to the high resolution of the transmembrane α-helices, the extracellular loops are less well resolved. The conformational flexibility of the extracellular loops may be essential to facilitate surveillance of hemichannels in apposed cells to identify compatible Cx isoforms that enable intercellular docking. Our results also provide a structural foundation for previous electrophysiologic and permeation studies of Cx hemichannels.
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Affiliation(s)
- Ali K Khan
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Sheridan G. Snyder Translational Research Building, Rm 320, 480 Ray C. Hunt Drive, Charlottesville, VA 22908, USA
| | - Maciej Jagielnicki
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Sheridan G. Snyder Translational Research Building, Rm 320, 480 Ray C. Hunt Drive, Charlottesville, VA 22908, USA
| | - Brad C Bennett
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Sheridan G. Snyder Translational Research Building, Rm 320, 480 Ray C. Hunt Drive, Charlottesville, VA 22908, USA
| | - Michael D Purdy
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Sheridan G. Snyder Translational Research Building, Rm 320, 480 Ray C. Hunt Drive, Charlottesville, VA 22908, USA
| | - Mark Yeager
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Sheridan G. Snyder Translational Research Building, Rm 320, 480 Ray C. Hunt Drive, Charlottesville, VA 22908, USA; Center for Membrane Biology, University of Virginia School of Medicine, Charlottesville, VA 22908, USA; Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA 22908, USA; Department of Medicine, Division of Cardiovascular Medicine, University of Virginia School of Medicine, Charlottesville, VA 22908, USA.
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4
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Retamal MA, Fernandez-Olivares A, Stehberg J. Over-activated hemichannels: A possible therapeutic target for human diseases. Biochim Biophys Acta Mol Basis Dis 2021; 1867:166232. [PMID: 34363932 DOI: 10.1016/j.bbadis.2021.166232] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Revised: 07/21/2021] [Accepted: 07/26/2021] [Indexed: 12/14/2022]
Abstract
In our body, all the cells are constantly sharing chemical and electrical information with other cells. This intercellular communication allows them to respond in a concerted way to changes in the extracellular milieu. Connexins are transmembrane proteins that have the particularity of forming two types of channels; hemichannels and gap junction channels. Under normal conditions, hemichannels allow the controlled release of signaling molecules to the extracellular milieu. However, under certain pathological conditions, over-activated hemichannels can induce and/or exacerbate symptoms. In the last decade, great efforts have been put into developing new tools that can modulate these over-activated hemichannels. Small molecules, antibodies and mimetic peptides have shown a potential for the treatment of human diseases. In this review, we summarize recent findings in the field of hemichannel modulation via specific tools, and how these tools could improve patient outcome in certain pathological conditions.
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Affiliation(s)
- Mauricio A Retamal
- Universidad del Desarrollo, Programa de Comunicación Celular en Cáncer, Santiago, Chile; Universidad del Desarrollo, Centro de Fisiología Celular e Integrativa, Santiago, Chile.
| | | | - Jimmy Stehberg
- Laboratorio de Neurobiología, Instituto de Ciencias Biomédicas, Facultad de medicina y Facultad de Ciencias de la Vida, Universidad Andres Bello, Santiago, Chile
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Fan Y, Zhu S, Wang J, Zhao Y, Wang X. Propofol protects against oxygen/glucose deprivation‑induced cell injury via gap junction inhibition in astrocytes. Mol Med Rep 2020; 22:2896-2904. [PMID: 32945367 PMCID: PMC7453496 DOI: 10.3892/mmr.2020.11357] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2020] [Accepted: 06/22/2020] [Indexed: 11/29/2022] Open
Abstract
Stroke is one of the leading causes of mortality and disability worldwide with limited clinical therapies available. The present study isolated primary astrocytes from the brains of rats and treated them with oxygen-glucose deprivation and re-oxygenation (OGD/R) to mimic hypoxia/reperfusion (H/R) injury in vitro to investigate stroke. It was revealed that propofol (2,6-diisopropylphenol), an intravenous sedative and anesthetic agent, protected against oxygen/glucose-deprivation (OGD) and induced cell injury. Furthermore, propofol exerted a protective effect by inhibiting gap junction function, which was also revealed to promote cell death in astrocytes. The present study further identified that propofol suppressed gap junction function by downregulating the protein expression levels of connexin43 (Cx43), which is one of the most essential components of gap junctions in astrocytes. In addition, when the expression levels of Cx43 were downregulated using small interfering RNA, OGD/R-induced cell death was decreased. Conversely, cell death was enhanced when Cx43 was overexpressed, which was reversed following propofol treatment. In summary, propofol protects against OGD-induced injury in astrocytes by decreasing the protein expression levels of Cx43 and suppressing gap junction function. The present study improved our understanding of how propofol protects astrocytes from OGD/R-induced injury.
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Affiliation(s)
- Yanting Fan
- Department of Anesthesiology, Guangzhou Women and Children's Medical Center, Guangzhou Medical University, Guangzhou, Guangdong 510623, P.R. China
| | - Siyu Zhu
- Department of Medical Imaging, Collaborative Innovation Center for Cancer Medicine, State Key Laboratory of Oncology in South China, Sun Yat‑sen University Cancer Center, Guangzhou, Guangdong 510060, P.R. China
| | - Jing Wang
- Department of Anesthesiology, State Key Laboratory of Oncology in South China, Sun Yat‑sen University Cancer Center, Guangzhou, Guangdong 510060, P.R. China
| | - Yuping Zhao
- Department of Anesthesiology, Guangzhou Women and Children's Medical Center, Guangzhou Medical University, Guangzhou, Guangdong 510623, P.R. China
| | - Xudong Wang
- Department of Anesthesiology, State Key Laboratory of Oncology in South China, Sun Yat‑sen University Cancer Center, Guangzhou, Guangdong 510060, P.R. China
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Tajada S, Villalobos C. Calcium Permeable Channels in Cancer Hallmarks. Front Pharmacol 2020; 11:968. [PMID: 32733237 PMCID: PMC7358640 DOI: 10.3389/fphar.2020.00968] [Citation(s) in RCA: 50] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2020] [Accepted: 06/15/2020] [Indexed: 12/17/2022] Open
Abstract
Cancer, the second cause of death worldwide, is characterized by several common criteria, known as the “cancer hallmarks” such as unrestrained cell proliferation, cell death resistance, angiogenesis, invasion and metastasis. Calcium permeable channels are proteins present in external and internal biological membranes, diffusing Ca2+ ions down their electrochemical gradient. Numerous physiological functions are mediated by calcium channels, ranging from intracellular calcium homeostasis to sensory transduction. Consequently, calcium channels play important roles in human physiology and it is not a surprise the increasing number of evidences connecting calcium channels disorders with tumor cells growth, survival and migration. Multiple studies suggest that calcium signals are augmented in various cancer cell types, contributing to cancer hallmarks. This review focuses in the role of calcium permeable channels signaling in cancer with special attention to the mechanisms behind the remodeling of the calcium signals. Transient Receptor Potential (TRP) channels and Store Operated Channels (SOC) are the main extracellular Ca2+ source in the plasma membrane of non-excitable cells, while inositol trisphosphate receptors (IP3R) are the main channels releasing Ca2+ from the endoplasmic reticulum (ER). Alterations in the function and/or expression of these calcium channels, as wells as, the calcium buffering by mitochondria affect intracellular calcium homeostasis and signaling, contributing to the transformation of normal cells into their tumor counterparts. Several compounds reported to counteract several cancer hallmarks also modulate the activity and/or the expression of these channels including non-steroidal anti-inflammatory drugs (NSAIDs) like sulindac and aspirin, and inhibitors of polyamine biosynthesis, like difluoromethylornithine (DFMO). The possible role of the calcium permeable channels targeted by these compounds in cancer and their action mechanism will be discussed also in the review.
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Affiliation(s)
- Sendoa Tajada
- Instituto de Biología y Genética Molecular (IBGM), Universidad de Valladolid and Consejo Superior de Investigaciones Científicas (CSIC), Valladolid, Spain
| | - Carlos Villalobos
- Instituto de Biología y Genética Molecular (IBGM), Universidad de Valladolid and Consejo Superior de Investigaciones Científicas (CSIC), Valladolid, Spain
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Reyes JF, Sackmann C, Hoffmann A, Svenningsson P, Winkler J, Ingelsson M, Hallbeck M. Binding of α-synuclein oligomers to Cx32 facilitates protein uptake and transfer in neurons and oligodendrocytes. Acta Neuropathol 2019; 138:23-47. [PMID: 30976973 PMCID: PMC6570706 DOI: 10.1007/s00401-019-02007-x] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2018] [Revised: 04/03/2019] [Accepted: 04/03/2019] [Indexed: 12/11/2022]
Abstract
The intercellular transfer of alpha-synuclein (α-syn) has been implicated in the progression of Parkinson's disease (PD) and multiple system atrophy (MSA). The cellular mechanisms underlying this process are now beginning to be elucidated. In this study, we demonstrate that the gap junction protein connexin-32 (Cx32) is centrally involved in the preferential uptake of α-syn oligomeric assemblies (oα-syn) in neurons and oligodendrocytes. In vitro, we demonstrate a clear correlation between Cx32 expression and oα-syn uptake. Pharmacological and genetic strategies targeting Cx32 successfully blocked oα-syn uptake. In cellular and transgenic mice modeling PD and MSA, we observed significant upregulation of Cx32 which correlates with α-syn accumulation. Notably, we could also demonstrate a direct interaction between α-syn and Cx32 in two out of four human PD cases that was absent in all four age-matched controls. These data are suggestive of a link between Cx32 and PD pathophysiology. Collectively, our results provide compelling evidence for Cx32 as a novel target for therapeutic intervention in PD and related α-synucleinopathies.
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Affiliation(s)
- Juan F Reyes
- Department of Clinical Pathology and Department of Clinical and Experimental Medicine, Linköping University, Linköping, Sweden.
| | - Christopher Sackmann
- Department of Clinical Pathology and Department of Clinical and Experimental Medicine, Linköping University, Linköping, Sweden
| | - Alana Hoffmann
- Department of Molecular Neurology, University Hospital Erlangen, Erlangen, Germany
| | - Per Svenningsson
- Department of Clinical Neuroscience, Karolinska Institute, Stockholm, Sweden
| | - Jürgen Winkler
- Department of Molecular Neurology, University Hospital Erlangen, Erlangen, Germany
| | - Martin Ingelsson
- Section of Geriatrics, Department of Public Health and Caring Sciences, Uppsala University, Uppsala, Sweden
| | - Martin Hallbeck
- Department of Clinical Pathology and Department of Clinical and Experimental Medicine, Linköping University, Linköping, Sweden.
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Xiang Y, Wang Q, Guo Y, Ge H, Fu Y, Wang X, Tao L. Cx32 exerts anti-apoptotic and pro-tumor effects via the epidermal growth factor receptor pathway in hepatocellular carcinoma. J Exp Clin Cancer Res 2019; 38:145. [PMID: 30947731 PMCID: PMC6449973 DOI: 10.1186/s13046-019-1142-y] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Accepted: 03/18/2019] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND Abnormal expression or distribution of connexin 32 (Cx32) is associated with hepatocarcinogenesis, but the role of Cx32 and the underlying mechanisms are still unclear. METHODS The expression level of Cx32 in 96 hepatocellular carcinoma (HCC) specimens was determined using western blotting and immunohistochemistry. The correlation between Cx32 expression and clinicopathological parameters was analyzed. The cell apoptosis rate was examined using flow cytometry and western blotting. The role of Cx32 in the Src kinase and epidermal growth factor receptor (EGFR) signaling pathways was measured by quantitative real-time PCR, western blotting and coimmunoprecipitation (CO-IP). The effect of Cx32 overexpression on the streptonigrin (SN)-induced tumor growth suppression and apoptosis was assessed in nude mice. RESULTS Our study showed that overexpressed Cx32 accumulated in the cytoplasm and that Cx32-containing gap junctions (GJs) were nearly absent in HCC specimens. Upregulated Cx32 expression was highly correlated with advanced tumor-node-metastasis (TNM) stage and poor tumor differentiation and was an independent predictive marker for poor prognosis in HCC. Overexpression of Cx32 significantly inhibited SN-induced apoptosis by activating the EGFR signaling pathway in vitro and in vivo. Moreover, the expression levels of Cx32 and EGFR were positively correlated in HCC specimens. The CO-IP experiments demonstrated that Cx32 could bind to Src kinase, and the western blotting results revealed that Cx32 increased the levels of EGFR and p-EGFR by upregulating Src expression. CONCLUSION The present study demonstrated that overexpressed and internalized Cx32 was associated with advanced TNM stage and poor tumor differentiation and predicted poor prognosis in HCC. Cx32 facilitated HCC progression by blocking chemotherapy-induced apoptosis in vitro and in vivo via interacting with Src and thus promoting the phosphorylation of EGFR, subsequently activating the EGFR signaling pathway. Cx32 may be a potential biomarker and a new therapeutic target for HCC.
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Affiliation(s)
- Yuke Xiang
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, 510080 People’s Republic of China
| | - Qin Wang
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, 510080 People’s Republic of China
| | - Yunquan Guo
- Tumor Research Institute, Xinjiang Medical University Affiliated Tumor Hospital and State Key Laboratory, Urumqi, 830000 People’s Republic of China
| | - Hui Ge
- Tumor Research Institute, Xinjiang Medical University Affiliated Tumor Hospital and State Key Laboratory, Urumqi, 830000 People’s Republic of China
| | - Yile Fu
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, 510080 People’s Republic of China
| | - Xiyan Wang
- Tumor Research Institute, Xinjiang Medical University Affiliated Tumor Hospital and State Key Laboratory, Urumqi, 830000 People’s Republic of China
| | - Liang Tao
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, 510080 People’s Republic of China
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Hernández-Guerra M, Hadjihambi A, Jalan R. Gap junctions in liver disease: Implications for pathogenesis and therapy. J Hepatol 2019; 70:759-772. [PMID: 30599172 DOI: 10.1016/j.jhep.2018.12.023] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/19/2018] [Revised: 12/03/2018] [Accepted: 12/12/2018] [Indexed: 02/07/2023]
Abstract
In the normal liver, cells interact closely through gap junctions. By providing a pathway for the trafficking of low molecular mass molecules, these channels contribute to tissue homeostasis and maintenance of hepatic function. Thus, dysfunction of gap junctions affects a wide variety of liver processes, such as differentiation, cell death, inflammation and fibrosis. In fact, dysfunctional gap junctions have been implicated, for more than a decade, in cholestatic disease, hepatic cancer and cirrhosis. Additionally, in recent years there is an increasing body of evidence that these channels are also involved in other relevant and prevalent liver pathological processes, such as non-alcoholic fatty liver disease, acute liver injury and portal hypertension. In parallel to these new clinical implications the available data include controversial observations. Thus, a comprehensive overview is required to better understand the functional complexity of these pores. This paper will review the most recent knowledge concerning gap junction dysfunction, with a special focus on the role of these channels in the pathogenesis of relevant clinical entities and on potential therapeutic targets that are amenable to modification by drugs.
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Affiliation(s)
| | | | - Rajiv Jalan
- UCL Institute for Liver and Digestive Health, Royal Free Medical School, London, UK
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10
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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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11
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Zhu Q, Lu Y, He X, Liu T, Chen H, Wang F, Zheng D, Dong H, Ma J. Entropy and Polarity Control the Partition and Transportation of Drug-like Molecules in Biological Membrane. Sci Rep 2017; 7:17749. [PMID: 29255188 PMCID: PMC5735159 DOI: 10.1038/s41598-017-18012-7] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2017] [Accepted: 12/05/2017] [Indexed: 11/09/2022] Open
Abstract
Partition and transportation of drug in the plasma membrane of a mammalian cell are the prerequisite for its function on target protein. Therefore, comprehensive understanding of the physicochemical properties and mechanism behind these complex phenomena is crucial in pharmaceutical research. By using the state-of-art molecular simulations with polarization effect implicitly or explicitly included, we studied the permeation behavior of 2-aminoethoxydiphenyl borate (2-APB), a broad-spectrum modulator for a number of membrane proteins. We showed that the protonation state and therefore the polarity of the drug is critical for its partition, and that the drug is likely to switch between different protonation states along its permeation pathway. By changing the degrees of freedom, protonation further affects the thermodynamic of the permeation pathway of 2-APB, leading to different entropic contributions. A survey on 54 analog structures with similar backbone to 2-APB showed that delicate balance between entropy and polarity plays an important role in drugs’ potency.
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Affiliation(s)
- Qiang Zhu
- Kuang Yaming Honors School, Nanjing University, Nanjing, 210023, P. R. China.,Institute of Theoretical and Computational Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210023, P. R. China
| | - Yilin Lu
- Kuang Yaming Honors School, Nanjing University, Nanjing, 210023, P. R. China
| | - Xibing He
- School of Pharmacy, University of Pittsburgh, 3501 Terrace Street, Pittsburgh, PA, 15213, USA
| | - Tao Liu
- Kuang Yaming Honors School, Nanjing University, Nanjing, 210023, P. R. China
| | - Hongwei Chen
- Kuang Yaming Honors School, Nanjing University, Nanjing, 210023, P. R. China
| | - Fang Wang
- Kuang Yaming Honors School, Nanjing University, Nanjing, 210023, P. R. China.,College of electronic information engineering, Sanjiang University, Nanjing, 210012, P. R. China
| | - Dong Zheng
- Institute of Theoretical and Computational Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210023, P. R. China
| | - Hao Dong
- Kuang Yaming Honors School, Nanjing University, Nanjing, 210023, P. R. China.
| | - Jing Ma
- Institute of Theoretical and Computational Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210023, P. R. China.
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12
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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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13
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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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14
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Transient receptor potential canonical type 3 channels: Interactions, role and relevance - A vascular focus. Pharmacol Ther 2017; 174:79-96. [DOI: 10.1016/j.pharmthera.2017.02.022] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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15
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Tang N, Liu J, Chen B, Zhang Y, Yu M, Cai Z, Chen H. Effects of gap junction intercellular communication on the docetaxel-induced cytotoxicity in rat hepatocytes. Mol Med Rep 2017; 15:2689-2694. [PMID: 28447724 DOI: 10.3892/mmr.2017.6295] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Accepted: 01/24/2017] [Indexed: 11/06/2022] Open
Abstract
The effect of gap junction intercellular communication (GJIC) on docetaxel-induced hepatotoxicity and its underlying mechanisms are largely unknown. The present study involved investigating the effect of downregulating GJs derived from connexin (Cx) 32 in BRL-3A cells by three different mechanisms: Using a low-density culture; suppression of Cx32 using small interfering RNA; and use of the chemical inhibitor 2‑aminoethoxydiphenyl borate (2‑APB), all of which led to attenuated docetaxel hepatotoxicity. In order to investigate the relevant mechanisms involved, apoptosis and caspase activities of BRL‑3A cells were determined. The increase of apoptosis and the activation of caspase‑3 and caspase‑9, but not caspase-8, were detected following cell exposure with docetaxel, demonstrating that the mitochondrial‑mediated apoptosis pathway is largely responsible for docetaxel hepatotoxicity. However, reduced apoptosis and caspase‑3, and ‑9 activities were observed following docetaxel application when BRL‑3A GJIC was deficient from the knockdown of Cx32 expression or pretreatment with 2‑APB. These observations illustrate that GJs are important in docetaxel-induced hepatotoxicity. Furthermore, inhibition of GJIC could prevent amplification of toxicity to docetaxel. Due to GJIC blockage, this hepatoprotection was associated, in part, with decreasing apoptosis of BRL‑3A cells through the mitochondrial pathway. The present study provides evidence for potential therapeutic targets for the treatment of docetaxel-induced liver injury.
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Affiliation(s)
- Nan Tang
- School of Pharmacy, Guangdong Medical University, Dongguan, Guangdong 523808, P.R. China
| | - Jinghua Liu
- School of Pharmacy, Guangdong Medical University, Dongguan, Guangdong 523808, P.R. China
| | - Bo Chen
- School of Pharmacy, Guangdong Medical University, Dongguan, Guangdong 523808, P.R. China
| | - Yuan Zhang
- The First Affiliated Hospital of Jinan University, Guangzhou, Guangdong 510632, P.R. China
| | - Meiling Yu
- Department of Pharmacy, The First Affiliated Hospital of Bengbu Medical College, Bengbu, Anhui 233004, P.R. China
| | - Ziqing Cai
- School of Pharmacy, Guangdong Medical University, Dongguan, Guangdong 523808, P.R. China
| | - Hongpeng Chen
- School of Information Engineering, Guangdong Medical University, Dongguan, Guangdong 523808, P.R. China
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16
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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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17
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Castillo-Galán S, Quezada S, Moraga FA, Ebensperger G, Herrera EA, Beñaldo F, Hernandez I, Ebensperger R, Ramirez S, Llanos AJ, Reyes RV. 2-AMINOETHYLDIPHENYLBORINATE MODIFIES THE PULMONARY CIRCULATION IN PULMONARY HYPERTENSIVE NEWBORN LAMBS WITH PARTIAL GESTATION AT HIGH ALTITUDE. Am J Physiol Lung Cell Mol Physiol 2016; 311:L788-L799. [PMID: 27542806 DOI: 10.1152/ajplung.00230.2016] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2016] [Accepted: 08/14/2016] [Indexed: 12/22/2022] Open
Abstract
Calcium signaling through store operated channels (SOC) is involved in hypoxic pulmonary hypertension. We determined whether a treatment with 2-aminoethyldiphenylborinate (2-APB), a compound with SOC blocker activity, reduces pulmonary hypertension and vascular remodeling. Twelve newborn lambs exposed to perinatal chronic hypoxia were studied, 6 of them received a 2-APB treatment and the other 6 received vehicle treatment, for 10 days in both cases. Throughout this period, we recorded cardiopulmonary variables and on day 11 we evaluated the response to an acute hypoxic challenge. Additionally, we assessed the vasoconstrictor and vasodilator function in isolated pulmonary arteries as well as their remodeling in lung slices. 2-APB reduced pulmonary arterial pressure at the third and tenth days, cardiac output between the fourth and eighth days, and pulmonary vascular resistance at the tenth day of treatment. The pulmonary vasoconstrictor response to acute hypoxia was reduced by the end of treatment. 2-APB also decreased maximal vasoconstrictor response to the thromboxane mimetic U46619 and endothelin-1 and increased maximal relaxation to 8-Br-cGMP. The maximal relaxation and potency to phosphodiesterase-5 and Rho-kinase inhibition with sildenafil and fasudil respectively, were also increased. Finally, 2-APB reduced the medial and adventitial layers' thickness, the expression of α-actin and the percentage of Ki67+ nuclei of small pulmonary arteries. Taken together, our results indicate that 2-APB reduces pulmonary hypertension, vasoconstrictor responses and pathological remodeling in pulmonary hypertensive lambs. We conclude that SOC targeting may be a useful strategy for the treatment of neonatal pulmonary hypertension, however, further testing of specific blockers is needed.
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Affiliation(s)
| | - Sebastián Quezada
- Universidad de Chile, Facultad de Medicina, Instituto de Ciencias Biomédicas (ICBM)
| | | | - Germán Ebensperger
- Facultad de Medicina, Universidad de Chile, Instituto de Ciencias Biomédicas (ICBM), Santiago, Chile
| | | | | | - Ismael Hernandez
- Facultad de Medicina, Universidad de Chile, Instituto de Ciencias Biomédicas (ICBM), Santiago, Chile
| | - Renato Ebensperger
- Facultad de Medicina, Universidad de Chile, Instituto de Ciencias Biomédicas (ICBM), Santiago, Chile
| | - Santiago Ramirez
- Facultad de Medicina, Universidad de Chile, Instituto de Ciencias Biomédicas (ICBM), Santiago, Chile
| | | | - Roberto V Reyes
- Universidad de Chile, Facultad de Medicina, Instituto de Ciencias Biomédicas (ICBM)
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18
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Sato T, Kaneko YK, Sawatani T, Noguchi A, Ishikawa T. Obligatory Role of Early Ca(2+) Responses in H2O2-Induced β-Cell Apoptosis. Biol Pharm Bull 2016; 38:1599-605. [PMID: 26424020 DOI: 10.1248/bpb.b15-00396] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Our previous study using apoptosis analysis suggested that Ca(2+) release through inositol 1,4,5-trisphosphate (IP3) receptors and the subsequent Ca(2+) influx through store-operated channels (SOCs) constitute a triggering signal for H2O2-induced β-cell apoptosis. In the present study, we further examined the obligatory role of early Ca(2+) responses in β-cell apoptosis induction. H2O2 induced elevation of the cytosolic Ca(2+) concentration ([Ca(2+)]c) consisting of two phases: an initial transient [Ca(2+)]c elevation within 30 min and a slowly developing one thereafter. The first phase was almost abolished by 2-aminoethoxydiphenylborate (2-APB), which blocks IP3 receptors and cation channels including SOCs, while the second phase was only partially inhibited by 2-APB. The inhibition by 2-APB of the second phase was not observed when 2-APB was added 30 min after the treatment with H2O2. 2-APB also largely inhibited elevation of the mitochondrial Ca(2+) concentration ([Ca(2+)]m) induced by H2O2 when 2-APB was applied simultaneously with H2O2, but not when applied 30 min after H2O2 application. In addition, 2-APB inhibited the release of mitochondrial cytochrome c to the cytosol induced by H2O2 when 2-APB was applied simultaneously with H2O2 but not 30 min post-treatment. H2O2-induced [Ca(2+)]m elevation and cell death were not inhibited by Ru360, an inhibitor of the mitochondrial calcium uniporter (MCU). These results suggest that the H2O2-induced initial [Ca(2+)]c elevation, occurring within 30 min and mediated by Ca(2+) release through IP3 receptors and subsequent Ca(2+) influx through SOCs, leads to [Ca(2+)]m elevation, possibly through a mechanism independent of MCU, thereby inducing cytochrome c release and consequent apoptosis.
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Affiliation(s)
- Taiji Sato
- Department of Pharmacology, Graduate School of Pharmaceutical Sciences, University of Shizuoka
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19
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Gao L, Yang P, Qin P, Lu Y, Li X, Tian Q, Li Y, Xie C, Tian JB, Zhang C, Tian C, Zhu MX, Yao J. Selective potentiation of 2-APB-induced activation of TRPV1-3 channels by acid. Sci Rep 2016; 6:20791. [PMID: 26876731 PMCID: PMC4753485 DOI: 10.1038/srep20791] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2015] [Accepted: 01/12/2016] [Indexed: 12/19/2022] Open
Abstract
Temperature-sensitive TRP channels are important for responses to pain and inflammation, to both of which tissue acidosis is a major contributing factor. However, except for TRPV1, acid-sensing by other ThermoTRP channels remains mysterious. We show here that unique among TRPV1–3 channels, TRPV3 is directly activated by protons from cytoplasmic side. This effect is very weak and involves key cytoplasmic residues L508, D512, S518, or A520. However, mutations of these residues did not affect a strong proton induced potentiation of TRPV3 currents elicited by the TRPV1–3 common agonist, 2-aminoethoxydiphenyl borate (2-APB), no matter if the ligand was applied from extracellular or cytoplasmic side. The acid potentiation was common among TRPV1–3 and only seen with 2-APB-related ligands. Using 1H-nuclear magnetic resonance to examine the solution structures of 2-APB and its analogs, we observed striking structural differences of the boron-containing compounds at neutral/basic as compared to acidic pH, suggesting that a pH-dependent configuration switch of 2-APB-based drugs may underlie their functionality. Supporting this notion, protons also enhanced the inhibitory action of 2-APB on TRPM8. Collectively, our findings reveal novel insights into 2-APB action on TRP channels, which should facilitate the design of new drugs for these channels.
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Affiliation(s)
- Luna Gao
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China.,College of Life Sciences, Wuhan University, Wuhan, Hubei 430072, China
| | - Pu Yang
- Department of Integrative Biology and Pharmacology, The University of Texas Health Science Center at Houston, Houston, TX 77030
| | - Peizhong Qin
- College of Life Sciences, Wuhan University, Wuhan, Hubei 430072, China
| | - Yungang Lu
- Department of Integrative Biology and Pharmacology, The University of Texas Health Science Center at Houston, Houston, TX 77030
| | - Xinxin Li
- College of Life Sciences, Wuhan University, Wuhan, Hubei 430072, China
| | - Quan Tian
- College of Life Sciences, Wuhan University, Wuhan, Hubei 430072, China
| | - Yang Li
- College of Life Sciences, Wuhan University, Wuhan, Hubei 430072, China
| | - Chang Xie
- College of Life Sciences, Wuhan University, Wuhan, Hubei 430072, China
| | - Jin-bin Tian
- Department of Integrative Biology and Pharmacology, The University of Texas Health Science Center at Houston, Houston, TX 77030
| | - Chengwei Zhang
- Hefei National Laboratory of Microscale Physical Sciences, School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Changlin Tian
- Hefei National Laboratory of Microscale Physical Sciences, School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Michael X Zhu
- Department of Integrative Biology and Pharmacology, The University of Texas Health Science Center at Houston, Houston, TX 77030
| | - Jing Yao
- College of Life Sciences, Wuhan University, Wuhan, Hubei 430072, China
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20
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Dong H, Li W, Sun J, Li S, Klein ML. Understanding the Boron–Nitrogen Interaction and Its Possible Implications in Drug Design. J Phys Chem B 2015; 119:14393-401. [DOI: 10.1021/acs.jpcb.5b07783] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Hao Dong
- Kuang
Yaming Honors School, Nanjing University, Nanjing, P.R. China
- Institute
for Computational Molecular Science, Temple University, 1900 North
12th Street, Philadelphia, Pennsylvania 19122-6078, United States
| | - Wei Li
- School
of Chemistry and Chemical Engineering, Key Laboratory of Mesoscopic
Chemistry of Ministry of Education, Institute of Theoretical and Computational
Chemistry, Nanjing University, Nanjing, P.R. China
| | - Jianwei Sun
- Department
of Physics, Temple University, 1900 North 12th Street, Philadelphia, Pennsylvania 19122-6078, United States
| | - Shuhua Li
- School
of Chemistry and Chemical Engineering, Key Laboratory of Mesoscopic
Chemistry of Ministry of Education, Institute of Theoretical and Computational
Chemistry, Nanjing University, Nanjing, P.R. China
| | - Michael L. Klein
- Institute
for Computational Molecular Science, Temple University, 1900 North
12th Street, Philadelphia, Pennsylvania 19122-6078, United States
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21
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Salinas DG. Flux theory for Poisson distributed pores with Gaussian permeability. Channels (Austin) 2015; 10:111-8. [PMID: 26488853 DOI: 10.1080/19336950.2015.1100778] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
Abstract
The mean of the solute flux through membrane pores depends on the random distribution and permeability of the pores. Mathematical models including such randomness factors make it possible to obtain statistical parameters for pore characterization. Here, assuming that pores follow a Poisson distribution in the lipid phase and that their permeabilities follow a Gaussian distribution, a mathematical model for solute dynamics is obtained by applying a general result from a previous work regarding any number of different kinds of randomly distributed pores. The new proposed theory is studied using experimental parameters obtained elsewhere, and a method for finding the mean single pore flux rate from liposome flux assays is suggested. This method is useful for pores without requiring studies by patch-clamp in single cells or single-channel recordings. However, it does not apply in the case of ion-selective channels, in which a more complex flux law combining the concentration and electrical gradient is required.
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Affiliation(s)
- Dino G Salinas
- a Centro de Investigación Biomédica, Facultad de Medicina , Universidad Diego Portales , Santiago , Chile
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22
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Different gap junction-propagated effects on cisplatin transfer result in opposite responses to cisplatin in normal cells versus tumor cells. Sci Rep 2015. [PMID: 26215139 PMCID: PMC4517168 DOI: 10.1038/srep12563] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Previous work has shown that gap junction intercellular communication (GJIC) enhances cisplatin (Pt) toxicity in testicular tumor cells but decreases it in non-tumor testicular cells. In this study, these different GJIC-propagated effects were demonstrated in tumor versus non-tumor cells from other organ tissues (liver and lung). The downregulation of GJIC by several different manipulations (no cell contact, pharmacological inhibition, and siRNA suppression) decreased Pt toxicity in tumor cells but enhanced it in non-tumor cells. The in vivo results using xenograft tumor models were consistent with those from the above-mentioned cells. To better understand the mechanism(s) involved, we studied the effects of GJIC on Pt accumulation in tumor and non-tumor cells from the liver and lung. The intracellular Pt and DNA-Pt adduct contents clearly increased in non-tumor cells but decreased in tumor cells when GJIC was downregulated. Further analysis indicated that the opposite effects of GJIC on Pt accumulation in normal versus tumor cells from the liver were due to its different effects on copper transporter1 and multidrug resistance-associated protein2, membrane transporters attributed to intracellular Pt transfer. Thus, GJIC protects normal organs from cisplatin toxicity while enhancing it in tumor cells via its different effects on intracellular Pt transfer.
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23
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Muñoz MF, Puebla M, Figueroa XF. Control of the neurovascular coupling by nitric oxide-dependent regulation of astrocytic Ca(2+) signaling. Front Cell Neurosci 2015; 9:59. [PMID: 25805969 PMCID: PMC4354411 DOI: 10.3389/fncel.2015.00059] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2014] [Accepted: 02/07/2015] [Indexed: 12/28/2022] Open
Abstract
Neuronal activity must be tightly coordinated with blood flow to keep proper brain function, which is achieved by a mechanism known as neurovascular coupling. Then, an increase in synaptic activity leads to a dilation of local parenchymal arterioles that matches the enhanced metabolic demand. Neurovascular coupling is orchestrated by astrocytes. These glial cells are located between neurons and the microvasculature, with the astrocytic endfeet ensheathing the vessels, which allows fine intercellular communication. The neurotransmitters released during neuronal activity reach astrocytic receptors and trigger a Ca2+ signaling that propagates to the endfeet, activating the release of vasoactive factors and arteriolar dilation. The astrocyte Ca2+ signaling is coordinated by gap junction channels and hemichannels formed by connexins (Cx43 and Cx30) and channels formed by pannexins (Panx-1). The neuronal activity-initiated Ca2+ waves are propagated among neighboring astrocytes directly via gap junctions or through ATP release via connexin hemichannels or pannexin channels. In addition, Ca2+ entry via connexin hemichannels or pannexin channels may participate in the regulation of the astrocyte signaling-mediated neurovascular coupling. Interestingly, nitric oxide (NO) can activate connexin hemichannel by S-nitrosylation and the Ca2+-dependent NO-synthesizing enzymes endothelial NO synthase (eNOS) and neuronal NOS (nNOS) are expressed in astrocytes. Therefore, the astrocytic Ca2+ signaling triggered in neurovascular coupling may activate NO production, which, in turn, may lead to Ca2+ influx through hemichannel activation. Furthermore, NO release from the hemichannels located at astrocytic endfeet may contribute to the vasodilation of parenchymal arterioles. In this review, we discuss the mechanisms involved in the regulation of the astrocytic Ca2+ signaling that mediates neurovascular coupling, with a special emphasis in the possible participation of NO in this process.
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Affiliation(s)
- Manuel F Muñoz
- Facultad de Ciencias Biológicas, Departamento de Fisiología, Pontificia Universidad Católica de Chile Santiago, Chile
| | - Mariela Puebla
- Facultad de Ciencias Biológicas, Departamento de Fisiología, Pontificia Universidad Católica de Chile Santiago, Chile
| | - Xavier F Figueroa
- Facultad de Ciencias Biológicas, Departamento de Fisiología, Pontificia Universidad Católica de Chile Santiago, Chile
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Liu Z, Wang Q, Fan L, Wu DP, Zhang Y, Liu L, Tao L. Gap junction enhances phototoxicity of photodynamic therapy agent 2-[1-hexyloxyethyl]-2-devinylpyropheophorbide-a (HPPH). Lasers Surg Med 2014; 47:68-76. [DOI: 10.1002/lsm.22311] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/22/2014] [Indexed: 01/23/2023]
Affiliation(s)
- Zhen Liu
- Department of Pharmacology; Zhongshan School of Medicine; Sun Yat-Sen University; 74 Zhongshan 2nd Road Guangzhou 510080 China
| | - Qin Wang
- Department of Pharmacology; Zhongshan School of Medicine; Sun Yat-Sen University; 74 Zhongshan 2nd Road Guangzhou 510080 China
| | - Lixia Fan
- Department of Pharmacology; Zhongshan School of Medicine; Sun Yat-Sen University; 74 Zhongshan 2nd Road Guangzhou 510080 China
| | - Deng Pan Wu
- Department of Pharmacology; Pharmacy School of Xuzhou Medical College; China
| | - Yuan Zhang
- Department of Pharmacology; Zhongshan School of Medicine; Sun Yat-Sen University; 74 Zhongshan 2nd Road Guangzhou 510080 China
| | - Lucy Liu
- Department of Cell & Systems Biology; University of Toronto; Ontario M5S 3G5 Canada
| | - Liang Tao
- Department of Pharmacology; Zhongshan School of Medicine; Sun Yat-Sen University; 74 Zhongshan 2nd Road Guangzhou 510080 China
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Tong X, Han X, Yu B, Yu M, Jiang G, Ji J, Dong S. Role of gap junction intercellular communication in testicular leydig cell apoptosis induced by oxaliplatin via the mitochondrial pathway. Oncol Rep 2014; 33:207-14. [PMID: 25355463 DOI: 10.3892/or.2014.3571] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2014] [Accepted: 10/17/2014] [Indexed: 11/05/2022] Open
Abstract
Platinum agents are widely used in the chemotherapy of testicular cancer. However, adverse reactions and resistance to such agents have limited their application in antineoplastic treatment. The aim of the present study was to determine the role of gap junction intercellular communication (GJIC) composed of Cx43 on oxaliplatin‑induced survival/apoptosis in mouse leydig normal and cancer cells using MTT, Annexin V/PI double staining assays and western blot analysis. The results showed that GJIC exerted opposite effects on the mouse leydig cancer (I-10) and normal (TM3) cell apoptosis induced by oxaliplatin. In leydig cancer cells, survival of cells exposed to oxaliplatin was substantially reduced when gap junctions formed as compared to no gap junctions. Pharmacological inhibition of gap junctions by oleamide and 18-α-glycyrrhetinic acid resulted in enhanced survival/decreased apoptosis while enhancement of gap junctions by retinoic acid led to decreased survival/increased apoptosis. These effects occurred only in high‑density cultures (gap junction formed), while the pharmacological modulations had no effects when there was no opportunity for gap junction formation. Notably, GJIC played an opposite (protective) role in normal leydig cells survival/apoptosis following exposure to oxaliplatin. Furthermore, this converse oxaliplatin‑inducing apoptosis exerted through the functional gap junction was correlated with the mitochondrial pathway‑related protein Bcl-2/Bax and caspase‑3/9. These results suggested that in testicular leydig normal/cancer cells, GJIC plays an opposite role in oxaliplatin‑induced apoptosis via the mitochondrial pathway.
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Affiliation(s)
- Xuhui Tong
- Faculty of Pharmacy, Bengbu Medical College, Bengbu, Anhui 233030, P.R. China
| | - Xi Han
- Faculty of Pharmacy, Bengbu Medical College, Bengbu, Anhui 233030, P.R. China
| | - Binbin Yu
- Faculty of Pharmacy, Bengbu Medical College, Bengbu, Anhui 233030, P.R. China
| | - Meiling Yu
- Faculty of Pharmacy, Bengbu Medical College, Bengbu, Anhui 233030, P.R. China
| | - Guojun Jiang
- Faculty of Pharmacy, Bengbu Medical College, Bengbu, Anhui 233030, P.R. China
| | - Jie Ji
- Faculty of Pharmacy, Bengbu Medical College, Bengbu, Anhui 233030, P.R. China
| | - Shuying Dong
- Faculty of Pharmacy, Bengbu Medical College, Bengbu, Anhui 233030, P.R. China
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26
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De Bock M, Decrock E, Wang N, Bol M, Vinken M, Bultynck G, Leybaert L. The dual face of connexin-based astroglial Ca(2+) communication: a key player in brain physiology and a prime target in pathology. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2014; 1843:2211-32. [PMID: 24768716 DOI: 10.1016/j.bbamcr.2014.04.016] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 01/31/2014] [Revised: 04/11/2014] [Accepted: 04/12/2014] [Indexed: 12/21/2022]
Abstract
For decades, studies have been focusing on the neuronal abnormalities that accompany neurodegenerative disorders. Yet, glial cells are emerging as important players in numerous neurological diseases. Astrocytes, the main type of glia in the central nervous system , form extensive networks that physically and functionally connect neuronal synapses with cerebral blood vessels. Normal brain functioning strictly depends on highly specialized cellular cross-talk between these different partners to which Ca(2+), as a signaling ion, largely contributes. Altered intracellular Ca(2+) levels are associated with neurodegenerative disorders and play a crucial role in the glial responses to injury. Intracellular Ca(2+) increases in single astrocytes can be propagated toward neighboring cells as intercellular Ca(2+) waves, thereby recruiting a larger group of cells. Intercellular Ca(2+) wave propagation depends on two, parallel, connexin (Cx) channel-based mechanisms: i) the diffusion of inositol 1,4,5-trisphosphate through gap junction channels that directly connect the cytoplasm of neighboring cells, and ii) the release of paracrine messengers such as glutamate and ATP through hemichannels ('half of a gap junction channel'). This review gives an overview of the current knowledge on Cx-mediated Ca(2+) communication among astrocytes as well as between astrocytes and other brain cell types in physiology and pathology, with a focus on the processes of neurodegeneration and reactive gliosis. Research on Cx-mediated astroglial Ca(2+) communication may ultimately shed light on the development of targeted therapies for neurodegenerative disorders in which astrocytes participate. This article is part of a Special Issue entitled: Calcium signaling in health and disease. Guest Editors: Geert Bultynck, Jacques Haiech, Claus W. Heizmann, Joachim Krebs, and Marc Moreau.
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Affiliation(s)
- Marijke De Bock
- Department of Basic Medical Sciences, Physiology group, Faculty of Medicine and Health Sciences, Ghent University, B-9000 Ghent, Belgium
| | - Elke Decrock
- Department of Basic Medical Sciences, Physiology group, Faculty of Medicine and Health Sciences, Ghent University, B-9000 Ghent, Belgium.
| | - Nan Wang
- Department of Basic Medical Sciences, Physiology group, Faculty of Medicine and Health Sciences, Ghent University, B-9000 Ghent, Belgium
| | - Mélissa Bol
- Department of Basic Medical Sciences, Physiology group, Faculty of Medicine and Health Sciences, Ghent University, B-9000 Ghent, Belgium
| | - Mathieu Vinken
- Department of Toxicology, Center for Pharmaceutical Research, Faculty of Medicine and Pharmacy, Vrije Universiteit Brussel, B-1090 Brussels, Belgium
| | - Geert Bultynck
- Department of Cellular and Molecular Medicine, Laboratory of Molecular and Cellular Signalling, KULeuven, Campus Gasthuisberg O/N-I bus 802, B-3000 Leuven, Belgium
| | - Luc Leybaert
- Department of Basic Medical Sciences, Physiology group, Faculty of Medicine and Health Sciences, Ghent University, B-9000 Ghent, Belgium
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27
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Salinas DG. Fluxes theory in experiments with random distributed channels on vesicles. Channels (Austin) 2014; 8:258-63. [PMID: 24643013 DOI: 10.4161/chan.28011] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
When channels are randomly distributed in a population of vesicles, disregarding the number of channels per vesicle, these channels follow a Poisson distribution. This has been verified in many cases, determining the average of channels per vesicle. However, to determine kinetic parameters in population studies, a mathematical expression for the mean flux of solute through channels per vesicle is necessary. Hence, here, this mean flux is calculated, assuming Poisson distributed channels in a population of vesicle. Moreover, this result has been generalized to any number of different kinds of channels (i.e., channels with different permeabilities). These results, useful for in vitro experiments with mixed both channels and vesicles, can be supplemented with those from other techniques, in order to understanding how the nature of the lipid membrane affects kinetic parameters of channel.
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de Zwart-Storm EA, Martin PE, van Steensel MAM. Gap junction diseases of the skin: novel insights from new mutations. ACTA ACUST UNITED AC 2014. [DOI: 10.1586/edm.09.47] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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Du K, Williams CD, McGill MR, Xie Y, Farhood A, Vinken M, Jaeschke H. The gap junction inhibitor 2-aminoethoxy-diphenyl-borate protects against acetaminophen hepatotoxicity by inhibiting cytochrome P450 enzymes and c-jun N-terminal kinase activation. Toxicol Appl Pharmacol 2013; 273:484-91. [PMID: 24070586 PMCID: PMC3858533 DOI: 10.1016/j.taap.2013.09.010] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2013] [Revised: 09/12/2013] [Accepted: 09/13/2013] [Indexed: 12/13/2022]
Abstract
Acetaminophen (APAP) hepatotoxicity is the leading cause of acute liver failure in the US. Although many aspects of the mechanism are known, recent publications suggest that gap junctions composed of connexin32 function as critical intercellular communication channels which transfer cytotoxic mediators into neighboring hepatocytes and aggravate liver injury. However, these studies did not consider off-target effects of reagents used in these experiments, especially the gap junction inhibitor 2-aminoethoxy-diphenyl-borate (2-APB). In order to assess the mechanisms of protection of 2-APB in vivo, male C56Bl/6 mice were treated with 400 mg/kg APAP to cause extensive liver injury. This injury was prevented when animals were co-treated with 20 mg/kg 2-APB and was attenuated when 2-APB was administered 1.5 h after APAP. However, the protection was completely lost when 2-APB was given 4-6 h after APAP. Measurement of protein adducts and c-jun-N-terminal kinase (JNK) activation indicated that 2-APB reduced both protein binding and JNK activation, which correlated with hepatoprotection. Although some of the protection was due to the solvent dimethyl sulfoxide (DMSO), in vitro experiments clearly demonstrated that 2-APB directly inhibits cytochrome P450 activities. In addition, JNK activation induced by phorone and tert-butylhydroperoxide in vivo was inhibited by 2-APB. The effects against APAP toxicity in vivo were reproduced in primary cultured hepatocytes without use of DMSO and in the absence of functional gap junctions. We conclude that the protective effect of 2-APB was caused by inhibition of metabolic activation of APAP and inhibition of the JNK signaling pathway and not by blocking connexin32-based gap junctions.
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Affiliation(s)
- Kuo Du
- Department of Pharmacology, Toxicology & Therapeutics, University of Kansas Medical Center, Kansas City, Kansas, USA
| | - C. David Williams
- Department of Pharmacology, Toxicology & Therapeutics, University of Kansas Medical Center, Kansas City, Kansas, USA
| | - Mitchell R. McGill
- Department of Pharmacology, Toxicology & Therapeutics, University of Kansas Medical Center, Kansas City, Kansas, USA
| | - Yuchao Xie
- Department of Pharmacology, Toxicology & Therapeutics, University of Kansas Medical Center, Kansas City, Kansas, USA
| | - Anwar Farhood
- Department of Pathology, St. David’s North Austin Medical Center, Austin, TX 78756, USA
| | - Mathieu Vinken
- Department of Toxicology, Center for Pharmaceutical Sciences, Vrije Universiteit Brussels, 1090 Brussels, Belgium
| | - Hartmut Jaeschke
- Department of Pharmacology, Toxicology & Therapeutics, University of Kansas Medical Center, Kansas City, Kansas, USA
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30
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Zhang C, Tong X, Qi B, Yu X, Dong S, Zhang S, Li X, Yu M. Components of Panax notoginseng saponins enhance the cytotoxicity of cisplatin via their effects on gap junctions. Mol Med Rep 2013; 8:897-902. [PMID: 23900706 DOI: 10.3892/mmr.2013.1597] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2013] [Accepted: 07/12/2013] [Indexed: 11/05/2022] Open
Abstract
Previously, Panax notoginseng saponin (PNS)-induced enhancement of gap junction (GJ) formation or function was observed to be responsible for the increased cytotoxic action of cisplatin. PNS has three constituents, ginsenoside Rg1 and Rb1, and notoginsenoside R1. The active compounds in PNS responsible for enhancing the cytotoxicity of cisplatin remain unknown. Thus, the effects of the main components of PNS on the cytotoxicity of cisplatin were investigated, as well as the correlation with the modulation of GJ function in transfected HeLa cells. The cytotoxicity of cisplatin (0.25-1 µg/ml) was increased in the presence of GJs. By contrast, the cytotoxicity of cisplatin was decreased when GJs were inhibited by a GJ blocker or by the inhibition of connexin expression. Ginsenoside Rg1 (100 µM) and notoginsenoside R1 (100 µM) were observed to significantly enhance cisplatin cytotoxicity in cells with functional GJs. Ginsenoside Rb1 had no effect on the cytotoxicity of cisplatin in the presence or absence of functional GJs. Cell exposure to ginsenoside Rg1 and notoginsenoside R1 for 4 h led to significant enhancement of a dye-coupled GJ in a dose-dependent manner; however, no effect was observed in cells exposed to ginsenoside Rb1. The present results indicate that ginsenoside Rg1 and notoginsenoside R1 are the active compounds responsible for enhancing the cytotoxic action of cisplatin induced by PNS in the presence of functional GJs.
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Affiliation(s)
- Cuiling Zhang
- Department of Pharmacology, Bengbu Medical College, Bengbu, Anhui 233030, P.R. China
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31
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Tong X, Dong S, Yu M, Wang Q, Tao L. Role of heteromeric gap junctions in the cytotoxicity of cisplatin. Toxicology 2013; 310:53-60. [PMID: 23747833 DOI: 10.1016/j.tox.2013.05.010] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2013] [Revised: 05/17/2013] [Accepted: 05/23/2013] [Indexed: 02/05/2023]
Abstract
In several systems, the presence of gap junctions made of a single connexin has been shown to enhance the cytotoxicity of cisplatin. However, most gap junction channels in vivo appear to be heteromeric (composed of more than one connexin isoform). Here we explore in HeLa cells the cytotoxicity to cisplatin that is enhanced by heteromeric gap junctions composed of Cx26 and Cx32, which have been shown to be more selective among biological permeants than the corresponding homomeric channels. We found that survival and subsequent proliferation of cells exposed to cisplatin were substantially reduced when gap junctions were present than when there were no gap junctions. Functional inhibition of gap junctions by oleamide enhanced survival/proliferation, and enhancement of gap junctions by retinoic acid decreased survival/proliferation. These effects occurred only in high density cultures, and the treatments were without effect when there was no opportunity for gap junction formation. The presence of functional gap junctions enhanced apoptosis as reflected in markers of both early-stage and late-stage apoptosis. Furthermore, analysis of caspases 3, 8 and 9 showed that functional gap junctions specifically induced apoptosis by the mitochondrial pathway. These results demonstrate that heteromeric Cx26/Cx32 gap junctions increase the cytotoxicity of cisplatin by induction of apoptosis via the mitochondrial pathway.
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Affiliation(s)
- Xuhui Tong
- Department of Pharmacy, Bengbu Medical College, Bengbu 233000, PR China
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32
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Tang N, Wang Q, Wu D, Zhang S, Zhang Y, Tao L. Differential effects of paclitaxel and docetaxel on gap junctions affects their cytotoxicities in transfected HeLa cells. Mol Med Rep 2013; 8:638-44. [PMID: 23799576 DOI: 10.3892/mmr.2013.1546] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2013] [Accepted: 05/23/2013] [Indexed: 11/06/2022] Open
Abstract
Gap junctions (GJs) enhance the cytotoxicity of specific cancer chemotherapeutic drugs and therefore, the inhibition of functional GJs may represent a mechanism by which the toxicity of chemotherapeutics in cancer cells can be reduced. In the present study, the effects and mechanisms of paclitaxel and docetaxel on GJ intercellular communication (GJIC) and the modulation of drug cytotoxicity were investigated in HeLa cells that were stably transfected with the connexin (Cx) 32 expression plasmid. Paclitaxel, but not docetaxel, was observed to inhibit dye‑coupling through junctional channels. Gating closure rather than the alteration of Cx32 expression or its membrane localization was responsible for the inhibitory action of paclitaxel on GJ function following short‑term exposure. The results revealed that the cytotoxicity of paclitaxel or docetaxel increased in the presence of functional GJs compared with that observed when GJIC was suppressed. In addition, paclitaxel‑induced downregulation of GJIC decreased the cytotoxicity of paclitaxel in the presence of functional GJs compared with that of docetaxel, which did not affect Cx32 channels. These observations demonstrated that the differential effects of paclitaxel and docetaxel on GJIC may affect the cytotoxicity of chemotherapeutic drugs. The present study provides a promising new approach to select antineoplastics and improve drug efficacy in carcinoma cells that form GJs.
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Affiliation(s)
- Nan Tang
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, Guangdong 510080, P.R. China
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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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34
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Fromenty B. Bridging the gap between old and new concepts in drug-induced liver injury. Clin Res Hepatol Gastroenterol 2013; 37:6-9. [PMID: 23333233 DOI: 10.1016/j.clinre.2012.12.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/03/2012] [Accepted: 12/06/2012] [Indexed: 02/04/2023]
Abstract
Recent studies have provided important information in the field of drug-induced liver injury (DILI), in particular regarding the pathogenesis of acetaminophen hepatotoxicity. However, these studies have sometimes left aside some old (but seminal) findings. Efforts should be made to bridge the gap between old and new concepts in DILI.
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Affiliation(s)
- B Fromenty
- Inserm, U991, université de Rennes 1, 35000 Rennes, France.
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35
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Yu ML, Zhang CL, Yuan DD, Tong XH, Tao L. Panax notoginseng saponins enhances the cytotoxicity of cisplatin via increasing gap junction intercellular communication. Biol Pharm Bull 2012; 35:1230-7. [PMID: 22863918 DOI: 10.1248/bpb.b110535] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Panax Notoginseng Saponins (PNS) have been well known to have anti-tumor activity and enhance cytotoxicity of some cancer chemotherapy agents, but the mechanisms underlying these effects are still unknown. This study investigates the effect of PNS on cytotoxicity of cisplatin and the relationship between this effect and the modulation of gap junctions (GJ) function by PNS in a transfected cell line. The cytotoxicity of cisplatin (0.25-1 µg/mL) was increased in the presence of GJ. Inhibition of gap junction by either GJ blocker or interception of Connexin (Cx) expression decreased the cytotoxicity of cisplatin. Increasing GJ function enhanced cytotoxicity of cisplatin, only in the cells with functional GJ. PNS (50-200 µg/mL) significantly enhanced cisplatin cytotoxicity, but this effect required functional gap junctions between the cells. Exposure of the cells to PNS (50-200 µg/mL) for 4 h leads to a significant enhance in dye coupling of GJ in a dose-dependent manner. These results suggest that PNS increases the cytotoxicity of cisplatin through enhancement of GJ activity.
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Affiliation(s)
- Mei-ling Yu
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou 510080, P. R. China
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36
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Abstract
Intercellular calcium (Ca(2+)) waves (ICWs) represent the propagation of increases in intracellular Ca(2+) through a syncytium of cells and appear to be a fundamental mechanism for coordinating multicellular responses. ICWs occur in a wide diversity of cells and have been extensively studied in vitro. More recent studies focus on ICWs in vivo. ICWs are triggered by a variety of stimuli and involve the release of Ca(2+) from internal stores. The propagation of ICWs predominately involves cell communication with internal messengers moving via gap junctions or extracellular messengers mediating paracrine signaling. ICWs appear to be important in both normal physiology as well as pathophysiological processes in a variety of organs and tissues including brain, liver, retina, cochlea, and vascular tissue. We review here the mechanisms of initiation and propagation of ICWs, the key intra- and extracellular messengers (inositol 1,4,5-trisphosphate and ATP) mediating ICWs, and the proposed physiological functions of ICWs.
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Affiliation(s)
- Luc Leybaert
- Department of Basic Medical Sciences, Physiology Group, Faculty of Medicine & Health Sciences, Ghent University, Ghent, Belgium.
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37
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Affiliation(s)
- Marion Maurel
- INSERM U1053, Université Bordeaux Segalen, Bordeaux, France
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38
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De Bock M, Wang N, Bol M, Decrock E, Ponsaerts R, Bultynck G, Dupont G, Leybaert L. Connexin 43 hemichannels contribute to cytoplasmic Ca2+ oscillations by providing a bimodal Ca2+-dependent Ca2+ entry pathway. J Biol Chem 2012; 287:12250-66. [PMID: 22351781 PMCID: PMC3320976 DOI: 10.1074/jbc.m111.299610] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2011] [Revised: 02/16/2012] [Indexed: 11/06/2022] Open
Abstract
Many cellular functions are driven by changes in the intracellular Ca(2+) concentration ([Ca(2+)](i)) that are highly organized in time and space. Ca(2+) oscillations are particularly important in this respect and are based on positive and negative [Ca(2+)](i) feedback on inositol 1,4,5-trisphosphate receptors (InsP(3)Rs). Connexin hemichannels are Ca(2+)-permeable plasma membrane channels that are also controlled by [Ca(2+)](i). We aimed to investigate how hemichannels may contribute to Ca(2+) oscillations. Madin-Darby canine kidney cells expressing connexin-32 (Cx32) and Cx43 were exposed to bradykinin (BK) or ATP to induce Ca(2+) oscillations. BK-induced oscillations were rapidly (minutes) and reversibly inhibited by the connexin-mimetic peptides (32)Gap27/(43)Gap26, whereas ATP-induced oscillations were unaffected. Furthermore, these peptides inhibited the BK-triggered release of calcein, a hemichannel-permeable dye. BK-induced oscillations, but not those induced by ATP, were dependent on extracellular Ca(2+). Alleviating the negative feedback of [Ca(2+)](i) on InsP(3)Rs using cytochrome c inhibited BK- and ATP-induced oscillations. Cx32 and Cx43 hemichannels are activated by <500 nm [Ca(2+)](i) but inhibited by higher concentrations and CT9 peptide (last 9 amino acids of the Cx43 C terminus) removes this high [Ca(2+)](i) inhibition. Unlike interfering with the bell-shaped dependence of InsP(3)Rs to [Ca(2+)](i), CT9 peptide prevented BK-induced oscillations but not those triggered by ATP. Collectively, these data indicate that connexin hemichannels contribute to BK-induced oscillations by allowing Ca(2+) entry during the rising phase of the Ca(2+) spikes and by providing an OFF mechanism during the falling phase of the spikes. Hemichannels were not sufficient to ignite oscillations by themselves; however, their contribution was crucial as hemichannel inhibition stopped the oscillations.
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Affiliation(s)
- Marijke De Bock
- From the Department of Basic Medical Sciences, Physiology Group, Ghent University 9000 Ghent, Belgium
| | - Nan Wang
- From the Department of Basic Medical Sciences, Physiology Group, Ghent University 9000 Ghent, Belgium
| | - Melissa Bol
- From the Department of Basic Medical Sciences, Physiology Group, Ghent University 9000 Ghent, Belgium
| | - Elke Decrock
- From the Department of Basic Medical Sciences, Physiology Group, Ghent University 9000 Ghent, Belgium
| | - Raf Ponsaerts
- Department of Molecular Cell Biology, Laboratory of Molecular and Cellular Signaling, KULeuven, 3000 Leuven, Belgium, and
| | - Geert Bultynck
- Department of Molecular Cell Biology, Laboratory of Molecular and Cellular Signaling, KULeuven, 3000 Leuven, Belgium, and
| | - Geneviève Dupont
- Theoretical Chronobiology Unit, Université Libre de Bruxelles, 1050 Brussels, Belgium
| | - Luc Leybaert
- From the Department of Basic Medical Sciences, Physiology Group, Ghent University 9000 Ghent, Belgium
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39
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Patel SJ, Milwid JM, King KR, Bohr S, Iracheta A, Li M, Vitalo A, Parekkadan B, Jindal R, Yarmush ML. Gap junction inhibition prevents drug-induced liver toxicity and fulminant hepatic failure. Nat Biotechnol 2012; 30:179-83. [PMID: 22252509 PMCID: PMC3609650 DOI: 10.1038/nbt.2089] [Citation(s) in RCA: 89] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2011] [Accepted: 12/08/2011] [Indexed: 02/07/2023]
Abstract
Drug-induced liver injury (DILI) limits the development and application of many therapeutic compounds and presents major challenges to the pharmaceutical industry and clinical medicine. Acetaminophen-containing compounds are among the most frequently prescribed drugs and are also the most common cause of DILI. Here we describe a pharmacological strategy that targets gap junction communication to prevent amplification of fulminant hepatic failure and acetaminophen-induced hepatotoxicity. We demonstrate that connexin 32 (Cx32), a key hepatic gap junction protein, is an essential mediator of DILI by showing that mice deficient in Cx32 are protected against liver damage, acute inflammation and death caused by liver-toxic drugs. We identify a small-molecule inhibitor of Cx32 that protects against liver failure and death in wild-type mice when co-administered with known hepatotoxic drugs. These findings indicate that gap junction inhibition could provide a pharmaceutical strategy to limit DILI and improve drug safety.
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Affiliation(s)
- Suraj J Patel
- Center for Engineering in Medicine and the Department of Surgery, Massachusetts General Hospital, and the Shriners Burns Hospital, Boston, MA 02114, USA
- Harvard-MIT Division of Health Science and Technology, Harvard Medical School, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Jack M Milwid
- Center for Engineering in Medicine and the Department of Surgery, Massachusetts General Hospital, and the Shriners Burns Hospital, Boston, MA 02114, USA
- Harvard-MIT Division of Health Science and Technology, Harvard Medical School, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Kevin R King
- Center for Engineering in Medicine and the Department of Surgery, Massachusetts General Hospital, and the Shriners Burns Hospital, Boston, MA 02114, USA
| | - Stefan Bohr
- Center for Engineering in Medicine and the Department of Surgery, Massachusetts General Hospital, and the Shriners Burns Hospital, Boston, MA 02114, USA
| | - Arvin Iracheta
- Center for Engineering in Medicine and the Department of Surgery, Massachusetts General Hospital, and the Shriners Burns Hospital, Boston, MA 02114, USA
| | - Matthew Li
- Center for Engineering in Medicine and the Department of Surgery, Massachusetts General Hospital, and the Shriners Burns Hospital, Boston, MA 02114, USA
| | - Antonia Vitalo
- Center for Engineering in Medicine and the Department of Surgery, Massachusetts General Hospital, and the Shriners Burns Hospital, Boston, MA 02114, USA
| | - Biju Parekkadan
- Center for Engineering in Medicine and the Department of Surgery, Massachusetts General Hospital, and the Shriners Burns Hospital, Boston, MA 02114, USA
| | - Rohit Jindal
- Center for Engineering in Medicine and the Department of Surgery, Massachusetts General Hospital, and the Shriners Burns Hospital, Boston, MA 02114, USA
- Department of Biomedical Engineering, Rutgers University, Piscataway NJ 08854, USA
| | - Martin L Yarmush
- Center for Engineering in Medicine and the Department of Surgery, Massachusetts General Hospital, and the Shriners Burns Hospital, Boston, MA 02114, USA
- Harvard-MIT Division of Health Science and Technology, Harvard Medical School, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
- Department of Biomedical Engineering, Rutgers University, Piscataway NJ 08854, USA
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Yang Y, Cao MH, Wang Q, Yuan DD, Li L, Tao L. The effects of 2-aminoethoxydiphenyl borate and diphenylboronic anhydride on gap junctions composed of Connexin43 in TM₄ sertoli cells. Biol Pharm Bull 2011; 34:1390-7. [PMID: 21881223 DOI: 10.1248/bpb.34.1390] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
2-Aminoethoxydiphenyl borate (2-APB) has recently been demonstrated to inhibit gap junction (GJ) channels, whereas the underlying mechanisms are still unknown. Using mouse TM₄ Sertoli cell which expresses connexin43 (Cx43), we explored the effects of 2-APB and its analogues on dye-coupling through junctional channels formed by Cx43 and on expression of Cx43. Exposure of the cells to 2-APB (1-50 µM) and one of its analogues diphenylboronic anhydride (DPBA) (1-30 µM) for 4 h leads to a significant decrease in dye coupling of GJ in a concentration-dependent manner. The inhibitory effects of 2-APB and DPBA are reversible since decreased GJ coupling resumes after the two compounds are washed out. The disfunction of GJ induced by 2-APB and DPBA is associated with a decrease in total amount of Cx43 protein and number of GJs on the cell membrane. 2-APB and DPBA do not alter Cx43 phosphorylation state and the level of Cx43 mRNA expression. The loss of Cx43 protein is prevented by either lysosomal or proteasomal inhibitor, suggesting that the decrease in Cx43 results from a 2-APB or DPBA-enhanced degradation of Cx43. The present results indicate that 2-APB and DPBA inhibit GJ communication through decreasing Cx43 expression in TM₄ cells.
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Affiliation(s)
- Yan Yang
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-Sen University, China
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41
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Shigemasa Y, Kito Y, Hashitani H, Suzuki H. Factors which determine the duration of follower potentials in longitudinal smooth muscle isolated from the guinea-pig stomach antrum. J Smooth Muscle Res 2011; 47:89-110. [PMID: 21979408 DOI: 10.1540/jsmr.47.89] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
In isolated longitudinal muscle tissues of the guinea-pig stomach antrum, recording electrical responses from smooth muscle cells revealed a periodical generation of follower potentials with variable durations. The I-D relationship, made by plotting the duration as a function of the interval before generating follower potential, was linear. Experiments were carried out to investigate the effects of chemicals which had been known to modulate the release of Ca(2+) from the internal stores (2-aminoethoxy-diphenyl-borate, cyclopiazonic acid, caffeine), inhibit mitochondrial metabolic activity (m-chlorophenyl hydrazone, 2-deoxy-D-glucose, potassium cyanide, rotenone), inhibit ATP-sensitive K-channels distributed in mitochondria (glibenclamide, 5-hydroxydecanoic acid) and inhibit the activity of proteinkinase C (chelerythrine), on the I-D relationship of follower potentials. The effects of depolarization on follower potentials were assessed by stimulating tissues with high potassium solution. Experiments were carried out mainly in the presence of nifedipine which minimized the movements of muscles with no modulation of follower potentials. Cycropiazonic acid and caffeine reduced the slope of I-D relationship, with associated reduction of the duration and frequency of follower potentials. 2-Aminoethoxydiphenyl borate reduced the duration and amplitude and increased the frequency of follower potentials, with depolarization of the membrane, and the effects were simulated by high potassium solution. m-Chlorophenyl hydrazone, potassium cyanide, 2-deoxy-D-glucose, rotenone, 5-hydroxydecanoic acid and glibenclamide reduced the slope of I-D relationship, with associated reduction of the frequency of follower potentials. Chelerythrine did not modulate the slope of I-D relationship, with reduced frequency of follower potentials. It seemed likely that the amount of Ca(2+) released from the internal stores and also mitochondrial function had causal relationship to the duration of pacemaker potentials, suggesting that internal Ca-stores and mitochondria are taking the central role for determining the duration of the pacemaker activity. Proteinkinase C did not seem to participate to the function of mitochondria and internal Ca(2+) stores.
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Affiliation(s)
- Yuhsuke Shigemasa
- Department of Cell Physiology, Nagoya City University Medical School, Mizuho-ku, Nagoya, Japan
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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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Locke D, Kieken F, Tao L, Sorgen PL, Harris AL. Mechanism for modulation of gating of connexin26-containing channels by taurine. J Gen Physiol 2011; 138:321-39. [PMID: 21844220 PMCID: PMC3171079 DOI: 10.1085/jgp.201110634] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2011] [Accepted: 07/18/2011] [Indexed: 11/20/2022] Open
Abstract
The mechanisms of action of endogenous modulatory ligands of connexin channels are largely unknown. Previous work showed that protonated aminosulfonates (AS), notably taurine, directly and reversibly inhibit homomeric and heteromeric channels that contain Cx26, a widely distributed connexin, but not homomeric Cx32 channels. The present study investigated the molecular mechanisms of connexin channel modulation by taurine, using hemichannels and junctional channels composed of Cx26 (homomeric) and Cx26/Cx32 (heteromeric). The addition of a 28-amino acid "tag" to the carboxyl-terminal domain (CT) of Cx26 (Cx26(T)) eliminated taurine sensitivity of homomeric and heteromeric hemichannels in cells and liposomes. Cleavage of all but four residues of the tag (Cx26(Tc)) resulted in taurine-induced pore narrowing in homomeric hemichannels, and restored taurine inhibition of heteromeric hemichannels (Cx26(Tc)/Cx32). Taurine actions on junctional channels were fully consistent with those on hemichannels. Taurine-induced inhibition of Cx26/Cx32(T) and nontagged Cx26 junctional channels was blocked by extracellular HEPES, a blocker of the taurine transporter, confirming that the taurine-sensitive site of Cx26 is cytoplasmic. Nuclear magnetic resonance of peptides corresponding to Cx26 cytoplasmic domains showed that taurine binds to the cytoplasmic loop (CL) and not the CT, and that the CT and CL directly interact. ELISA showed that taurine disrupts a pH-dependent interaction between the CT and the CT-proximal half of the CL. These studies reveal that AS disrupt a pH-driven cytoplasmic interdomain interaction in Cx26-containing channels, causing closure, and that the Cx26CT has a modulatory role in Cx26 function.
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Affiliation(s)
- Darren Locke
- Department of Pharmacology and Physiology, New Jersey Medical School, University of Medicine and Dentistry of New Jersey, Newark, USA.
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Ye N, Bathany C, Hua SZ. Assay for molecular transport across gap junction channels in one-dimensional cell arrays. LAB ON A CHIP 2011; 11:1096-1101. [PMID: 21293824 DOI: 10.1039/c0lc00350f] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Transport across gap junction channels (GJCs) between neighboring cells is critical to synchronizing cell's electrical and metabolic activities and maintaining cell homeostasis. Here we present a non-invasive microfluidic method to measure molecular diffusion across GJCs in multiple 1D cell arrays in real time. Using the chip, selective loading of a membrane permeant fluorescence dye (carboxyfluorescein) in Normal Rat Kidney (NRK) cells shows that the dye was able to diffuse through three cells along single cell chains in ∼35 minutes. Application of 100 µM 2-aminoethoxydiphenyl borate (2-APB) reversibly inhibits connexin-43 gap junctions in NRK cells; 0.8 mM 1-heptanol inhibits the diffusion partially. The method offers rapid exchange of reagents, enabling sequential screening of multiple gap junction specific drugs with only one preparation of cells. It is capable of measuring gap junction mediated diffusion between single cells.
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Affiliation(s)
- Nannan Ye
- Department of Physiology and Biophysics, SUNY-Buffalo, Buffalo, NY 14260, USA
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Ma KT, Guan BC, Yang YQ, Nuttall AL, Jiang ZG. 2-Aminoethoxydiphenyl borate blocks electrical coupling and inhibits voltage-gated K+ channels in guinea pig arteriole cells. Am J Physiol Heart Circ Physiol 2010; 300:H335-46. [PMID: 21037232 DOI: 10.1152/ajpheart.00737.2010] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
2-Aminoethoxydiphenyl borate (2-APB) analogs are potentially better vascular gap junction blockers than others widely used, but they remain to be characterized. Using whole cell and intracellular recording techniques, we studied the actions of 2-APB and its potent analog diphenylborinic anhydride (DPBA) on vascular smooth muscle cells (VSMCs) and endothelial cells in situ of or dissociated from arteriolar segments of the cochlear spiral modiolar artery, brain artery, and mesenteric artery. We found that both 2-APB and DPBA reversibly suppressed the input conductance (G(input)) of in situ VSMCs (IC(50) ≈ 4-8 μM). Complete electrical isolation of the recorded VSMC was achieved at 100 μM. A similar gap junction blockade was observed in endothelial cell tubules of the spiral modiolar artery. Similar to the action of 18β-glycyrrhetinic acid (18β-GA), 2-APB and DPBA depolarized VSMCs. In dissociated VSMCs, 2-APB and DPBA inhibited the delayed rectifier K(+) current (I(K)) with an IC(50) of ∼120 μM in the three vessels but with no significant effect on G(input) or the current-voltage relation between -140 and -40 mV. 2-APB inhibition of I(K) was more pronounced at potentials of ≤20 mV than at +40 mV and more marked on the fast component than on the slow component, which was mimicked by 4-aminopyridine but not by tetraethylammonium, nitrendipine, or charybdotoxin. In contrast, 18β-GA caused a linear inhibition of I(K) between 0 to +40 mV, which was similar to the action of tetraethylammonium or charybdotoxin. Finally, the 2-APB-induced inhibition of electrical coupling and I(K) was not affected by the inositol 1,4,5-trisphosphate receptor antagonist xestospongin C. We conclude that 2-APB analogs are a class of potent and reversible vascular gap junction blockers with a weak side effect of voltage-gated K(+) channel inhibition. They could be gap junction blockers superior to 18β-GA only when Ca(2+)-actived K(+) channel inhibition by the latter is a concern but inositol 1,4,5-trisphosphate receptor and voltage-gated K(+) channel inhibitions are not.
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Affiliation(s)
- Ke-Tao Ma
- Oregon Hearing Research Center, Oregon Health and Science University, Portland, Oregon 97239, USA
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Abstract
The epithelial cells of Reissner's membrane (RM) are capable of transporting Na(+) out of endolymph via epithelial Na(+) channel (ENaC). However, much remains to be known as to mechanism of regulation of Na(+) absorption in RM. We investigated P2Y signaling as a possible regulatory mechanism of ENaC in gerbil RM using voltage-sensitive vibrating probe technique and immunohistochemistry. Results showed that UTP induced partial inhibition of the amiloride-sensitive short-circuit current but did not change short-circuit current when applied in the presence of amiloride. The inhibitory effect of UTP was not completely reversible in minutes. The response to UTP was inhibited by reactive blue-2 and 2',3'-O-(4-benzoylbenzoyl)adenosine 5'-triphosphate but not by suramin or pyridoxalphosphate-6-azophenyl-2', 4'-disulfonic acid, which indicates this P2Y receptor as the P2Y(4) subtype. The phospholipase C (PLC) inhibitors 1-[6[[(17beta)-3-methoxyestra-1,3,5(10)-trien-17-yl]amino]hexyl]-1H-pyrrole-2,5-dione and 1-O-octadecyl-2-O-methyl-rac-glycero-3-phosphocholine markedly inhibited the effect of UTP on ENaC. In contrast, neither modulation of protein kinase C nor application of 2-aminoehoxydiphenyl borate affected P2Y(4)-mediated inhibition of ENaC. Immunoreactive staining for P2Y(4) was observed in the RM, apical membrane of stria vascularis, spiral ligament, and organ of Corti, including outer hair cell, inner hair cell, outer pillar cell, Deiters' cell, and Hensen cell. These results suggest that the physiological role of P2Y(4) receptor in RM is likely to regulate Na(+) homeostasis in the endolymph. The acute inhibition of ENaC activity by activation of P2Y(4) receptor is possibly mediated by decrease of phosphatidylinositol 4,5-biphosphate in the plasma membrane through PLC activation.
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Wang Q, You T, Yuan D, Han X, Hong X, He B, Wang L, Tong X, Tao L, Harris AL. Cisplatin and oxaliplatin inhibit gap junctional communication by direct action and by reduction of connexin expression, thereby counteracting cytotoxic efficacy. J Pharmacol Exp Ther 2010; 333:903-11. [PMID: 20215407 DOI: 10.1124/jpet.109.165274] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Cisplatin [cis-diamminedichloroplatinum(II)]/oxaliplatin [1,2-diamminocyclohexane(trans-1)oxolatoplatinum(II)] toxicity is enhanced by functional gap junctions between treated cells, implying that inhibition of gap junctions may decrease cytotoxic activity of these platinum-based agents. This study investigates the effect of gap junction modulation by cisplatin/oxaliplatin on cytotoxicity in a transformed cell line. The effects were explored using junctional channels expressed in transfected HeLa cells and purified hemichannels. Junctional channels showed a rapid, dose-dependent decrease in dye coupling with exposure to cisplatin/oxaliplatin. With longer exposure, both compounds also decreased connexin expression. Both compounds inhibit the activity of purified connexin hemichannels, over the same concentration range that they inhibit junctional dye permeability, demonstrating that inhibition occurs by direct interaction of the drugs with connexin protein. Cisplatin/oxaliplatin reduced the clonogenic survival of HeLa cells at low density and high density in a dose-dependent manner, but to a greater degree at high density, consistent with a positive effect of gap junctional intercellular communication (GJIC) on cytotoxicity. Reduction of GJIC by genetic or pharmacological means decreased cisplatin/oxaliplatin toxicity. At low cisplatin/oxaliplatin concentrations, where effects on connexin channels are minimal, the toxicity increased with increased cell density. However, higher concentrations strongly inhibited GJIC, and this counteracted the enhancing effect of greater cell density on toxicity. The present results indicate that inhibition of GJIC by cisplatin/oxaliplatin decreases their cytotoxicity. Direct inhibition of GJIC and reduction of connexin expression by cisplatin/oxaliplatin may thereby compromise the effectiveness of these compounds and be a factor in the development of resistance to this class of chemotherapeutic agents.
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Affiliation(s)
- Qin Wang
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, People's Republic of China
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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: 131] [Impact Index Per Article: 8.7] [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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49
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Structure of the connexin 26 gap junction channel at 3.5 Å resolution. Nature 2009; 458:597-602. [DOI: 10.1038/nature07869] [Citation(s) in RCA: 559] [Impact Index Per Article: 37.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2008] [Accepted: 02/09/2009] [Indexed: 11/09/2022]
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50
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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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