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García-Rodríguez C, Duarte Y, Ardiles ÁO, Sáez JC. The antiseizure medication valproate increases hemichannel activity found in brain cells, which could worsen disease outcomes. J Neurochem 2024; 168:1045-1059. [PMID: 38291613 DOI: 10.1111/jnc.16062] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2023] [Revised: 01/12/2024] [Accepted: 01/16/2024] [Indexed: 02/01/2024]
Abstract
Glial cells play relevant roles in neuroinflammation caused by epilepsy. Elevated hemichannel (HC) activity formed by connexins (Cxs) or pannexin1 (Panx1) largely explains brain dysfunctions commonly caused by neuroinflammation. Glia express HCs formed by Cxs 43, 30, or 26, while glia and neurons both express HCs formed by Panx1. Cx43 HCs allow for the influx of Ca2+, which promotes glial reactivity, enabling the release of the gliotransmitters that contribute to neuronal over-stimulation. Valproate (VPA), an antiseizure medication, has pleiotropic actions on neuronal molecular targets, and their action on glial cell HCs remains elusive. We used HeLa cells transfected with Cx43, Cx30, Cx26, or Panx1 to determine the effect of VPA on HC activity in the brain. VPA slightly increased HC activity under basal conditions, but significantly enhanced it in cells pre-exposed to conditions that promoted HC activity. Furthermore, VPA increased ATP release through Cx43 HCs. The increased HC activity caused by VPA was resistant to washout, being consistent with in silico studies, which predicted the binding site for VPA and Cx43, as well as for Panx1 HCs on the intracellular side, suggesting that VPA first enters through HCs, after which their activity increases.
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Affiliation(s)
- Claudia García-Rodríguez
- Centro Interdisciplinario de Neurociencias de Valparaíso, Instituto de Neurociencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Yorley Duarte
- Facultad de Ciencias de la Vida, Center for Bioinformatics and Integrative Biology, Universidad Andrés Bello, Santiago, Chile
| | - Álvaro O Ardiles
- Centro Interdisciplinario de Neurociencias de Valparaíso, Instituto de Neurociencias, Universidad de Valparaíso, Valparaíso, Chile
- Facultad de Medicina, Escuela de Medicina, Universidad de Valparaíso, Valparaíso, Chile
| | - Juan C Sáez
- Centro Interdisciplinario de Neurociencias de Valparaíso, Instituto de Neurociencias, Universidad de Valparaíso, Valparaíso, Chile
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2
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Yang D, Chen M, Yang S, Deng F, Guo X. Connexin hemichannels and pannexin channels in toxicity: Recent advances and mechanistic insights. Toxicology 2023; 488:153488. [PMID: 36918108 DOI: 10.1016/j.tox.2023.153488] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2023] [Revised: 03/10/2023] [Accepted: 03/11/2023] [Indexed: 03/14/2023]
Abstract
Connexin hemichannels and pannexin channels are two types of transmembrane channels that allow autocrine/paracrine signalling through the exchange of ions and molecules between the intra- and extracellular compartments. However, owing to the poor selectivity of permeable ions and metabolites, the massive opening of these plasma membrane channels can lead to an excessive influx of toxic substances and an outflux of essential metabolites, such as adenosine triphosphate, glutathione, glutamate and ions, resulting in unbalanced cell homeostasis and impaired cell function. It is becoming increasingly clear that these channels can be activated in response to external stimuli and are involved in toxicity, yet their concrete mechanistic roles in the toxic effects induced by stress and various environmental changes remain poorly defined. This review provides an updated understanding of connexin hemichannels and pannexin channels in response to multiple extrinsic stressors and how these activated channels and their permeable messengers participate in toxicological pathways and processes, including inflammation, oxidative damage, intracellular calcium imbalance, bystander DNA damage and excitotoxicity.
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Affiliation(s)
- Di Yang
- Department of Occupational and Environmental Health Sciences, School of Public Health, Peking University, No. 38 Xueyuan Road, Beijing, China
| | - Mengyuan Chen
- Department of Occupational and Environmental Health Sciences, School of Public Health, Peking University, No. 38 Xueyuan Road, Beijing, China
| | - Sijia Yang
- Department of Occupational and Environmental Health Sciences, School of Public Health, Peking University, No. 38 Xueyuan Road, Beijing, China
| | - Furong Deng
- Department of Occupational and Environmental Health Sciences, School of Public Health, Peking University, No. 38 Xueyuan Road, Beijing, China
| | - Xinbiao Guo
- Department of Occupational and Environmental Health Sciences, School of Public Health, Peking University, No. 38 Xueyuan Road, Beijing, China.
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3
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Patel KHK, Hwang T, Se Liebers C, Ng FS. Epicardial adipose tissue as a mediator of cardiac arrhythmias. Am J Physiol Heart Circ Physiol 2022; 322:H129-H144. [PMID: 34890279 PMCID: PMC8742735 DOI: 10.1152/ajpheart.00565.2021] [Citation(s) in RCA: 22] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Obesity is associated with higher risks of cardiac arrhythmias. Although this may be partly explained by concurrent cardiometabolic ill-health, growing evidence suggests that increasing adiposity independently confers risk for arrhythmias. Among fat depots, epicardial adipose tissue (EAT) exhibits a proinflammatory secretome and, given the lack of fascial separation, has been implicated as a transducer of inflammation to the underlying myocardium. The present review explores the mechanisms underpinning adverse electrophysiological remodeling as a consequence of EAT accumulation and the consequent inflammation. We first describe the physiological and pathophysiological function of EAT and its unique secretome and subsequently discuss the evidence for ionic channel and connexin expression modulation as well as fibrotic remodeling induced by cytokines and free fatty acids that are secreted by EAT. Finally, we highlight how weight reduction and regression of EAT volume may cause reverse remodeling to ameliorate arrhythmic risk.
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Affiliation(s)
| | - Taesoon Hwang
- National Heart and Lung Institute, Imperial College London, London, United Kingdom
| | - Curtis Se Liebers
- National Heart and Lung Institute, Imperial College London, London, United Kingdom
| | - Fu Siong Ng
- National Heart and Lung Institute, Imperial College London, London, United Kingdom
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4
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Orellana VP, Tittarelli A, Retamal MA. Connexins in melanoma: Potential role of Cx46 in its aggressiveness. Pigment Cell Melanoma Res 2021; 34:853-868. [PMID: 33140904 DOI: 10.1111/pcmr.12945] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2020] [Revised: 10/20/2020] [Accepted: 10/27/2020] [Indexed: 12/19/2022]
Abstract
Melanoma is the most aggressive skin cancer, and in metastatic advanced states, it is completely refractory to chemotherapy. Therefore, it is relevant to understand the molecular bases that rule their aggressiveness. Connexins (Cxs) are proteins that under normal physiological conditions participate in intercellular communication, via the exchange of signaling molecules between the cytoplasm and extracellular milieu and the exchange of ions/second messengers between the cytoplasm of contacting cells. These proteins have shown important roles in cancer progression, chemo- and radiotherapy resistance, and metastasis. Accordingly, Cx26 and Cx43 seem to play important roles in melanoma progression and metastasis. On the other hand, Cx46 is typically expressed in the eye lens, where it seems to be associated with oxidative stress protection in fiber lens cells. However, in the last decade, Cx46 expression has been associated with breast and brain cancers, due to its role in potentiation of both extracellular vesicle release and cancer stem cell-like properties. In this review, we analyzed a potential role of Cx46 as a new biomarker and therapeutic target in melanoma.
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Affiliation(s)
- Viviana P Orellana
- Universidad del Desarrollo. Centro de Fisiología Celular e Integrativa, Clinica Alemana Facultad de Medicina, Santiago, Chile
- Universidad del Desarrollo. Programa de Comunicación Celular en Cáncer, Clínica Alemana Facultad de Medicina, Santiago, Chile
| | - Andrés Tittarelli
- Programa Institucional de Fomento a la Investigación, Desarrollo e Innovación (PIDi), Universidad Tecnológica Metropolitana (UTEM), Santiago, Chile
| | - Mauricio A Retamal
- Universidad del Desarrollo. Centro de Fisiología Celular e Integrativa, Clinica Alemana Facultad de Medicina, Santiago, Chile
- Universidad del Desarrollo. Programa de Comunicación Celular en Cáncer, Clínica Alemana Facultad de Medicina, Santiago, Chile
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5
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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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Francis M, Li C, Sun Y, Zhou J, Li X, Brenna JT, Ye K. Genome-wide association study of fish oil supplementation on lipid traits in 81,246 individuals reveals new gene-diet interaction loci. PLoS Genet 2021; 17:e1009431. [PMID: 33760818 PMCID: PMC8021161 DOI: 10.1371/journal.pgen.1009431] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2020] [Revised: 04/05/2021] [Accepted: 02/16/2021] [Indexed: 01/23/2023] Open
Abstract
Fish oil supplementation is widely used for reducing serum triglycerides (TAGs) but has mixed effects on other circulating cardiovascular biomarkers. Many genetic polymorphisms have been associated with blood lipids, including high- and low-density-lipoprotein cholesterol (HDL-C, LDL-C), total cholesterol, and TAGs. Here, the gene-diet interaction effects of fish oil supplementation on these lipids were analyzed in a discovery cohort of up to 73,962 UK Biobank participants, using a 1-degree-of-freedom (1df) test for interaction effects and a 2-degrees-of-freedom (2df) test to jointly analyze interaction and main effects. Associations with P < 1×10-6 in either test (26,157; 18,300 unique variants) were advanced to replication in up to 7,284 participants from the Atherosclerosis Risk in Communities (ARIC) Study. Replicated associations reaching 1df P < 0.05 (2,175; 1,763 unique variants) were used in meta-analyses. We found 13 replicated and 159 non-replicated (UK Biobank only) loci with significant 2df joint tests that were predominantly driven by main effects and have been previously reported. Four novel interaction loci were identified with 1df P < 5×10-8 in meta-analysis. The lead variant in the GJB6-GJB2-GJA3 gene cluster, rs112803755 (A>G; minor allele frequency = 0.041), shows exclusively interaction effects. The minor allele is significantly associated with decreased TAGs in individuals with fish oil supplementation, but with increased TAGs in those without supplementation. This locus is significantly associated with higher GJB2 expression of connexin 26 in adipose tissue; connexin activity is known to change upon exposure to omega-3 fatty acids. Significant interaction effects were also found in three other loci in the genes SLC12A3 (HDL-C), ABCA6 (LDL-C), and MLXIPL (LDL-C), but highly significant main effects are also present. Our study identifies novel gene-diet interaction effects for four genetic loci, whose effects on blood lipids are modified by fish oil supplementation. These findings highlight the need and possibility for personalized nutrition.
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Affiliation(s)
- Michael Francis
- Institute of Bioinformatics, University of Georgia, Athens, Georgia, United States of America
| | - Changwei Li
- Department of Epidemiology, Tulane University School of Public Health and Tropical Medicine, New Orleans, Louisiana, United States of America
| | - Yitang Sun
- Department of Genetics, University of Georgia, Athens, Georgia, United States of America
| | - Jingqi Zhou
- Department of Genetics, University of Georgia, Athens, Georgia, United States of America
| | - Xiang Li
- Department of Epidemiology, Tulane University School of Public Health and Tropical Medicine, New Orleans, Louisiana, United States of America
| | - J. Thomas Brenna
- Division of Nutritional Sciences, Cornell University, Ithaca, New York, United States of America
- Department of Pediatrics, Dell Pediatric Research Institute, University of Texas at Austin, Austin, Texas, United States of America
- Departments of Nutrition and Chemistry, University of Texas at Austin, Austin, Texas, United States of America
| | - Kaixiong Ye
- Institute of Bioinformatics, University of Georgia, Athens, Georgia, United States of America
- Department of Genetics, University of Georgia, Athens, Georgia, United States of America
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7
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Harnessing the therapeutic potential of antibodies targeting connexin hemichannels. Biochim Biophys Acta Mol Basis Dis 2021; 1867:166047. [PMID: 33418036 DOI: 10.1016/j.bbadis.2020.166047] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2020] [Revised: 11/17/2020] [Accepted: 12/03/2020] [Indexed: 12/20/2022]
Abstract
BACKGROUND Connexin hemichannels have been implicated in pathology-promoting conditions, including inflammation, numerous widespread human diseases, including cancer and diabetes, and several rare diseases linked to pathological point mutations. METHODS We analysed the literature focusing on antibodies capable of modulating hemichannel function, highlighting generation methods, applications to basic biomedical research and translational potential. RESULTS Anti-hemichannel antibodies generated over the past 3 decades targeted mostly connexin 43, with a focus on cancer treatment. A slow transition from relatively unselective polyclonal antibodies to more selective monoclonal antibodies resulted in few products with interesting characteristics that are under evaluation for clinical trials. Selection of antibodies from combinatorial phage-display libraries, has permitted to engineer a monoclonal antibody that binds to and blocks pathological hemichannels formed by connexin 26, 30 and 32. CONCLUSIONS All known antibodies that modulate connexin hemichannels target the two small extracellular loops of the connexin proteins. The extracellular region of different connexins is highly conserved, and few residues of each connexins are exposed. The search for new antibodies may develop an unprecedented potential for therapeutic applications, as it may benefit tremendously from novel whole-cell screening platforms that permit in situ selection of antibodies against membrane proteins in native state. The demonstrated efficacy of mAbs in reaching and modulating hemichannels in vivo, together with their relative specificity for connexins overlapping epitopes, should hopefully stimulate an interest for widening the scope of anti-hemichannel antibodies. There is no shortage of currently incurable diseases for which therapeutic intervention may benefit from anti-hemichannel antibodies capable of modulating hemichannel function selectively and specifically.
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8
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Feng Y, Yu P, Li J, Cao Y, Zhang J. Phosphatidylinositol 4-kinase β is required for the ciliogenesis of zebrafish otic vesicle. J Genet Genomics 2020; 47:627-636. [PMID: 33358778 DOI: 10.1016/j.jgg.2020.07.007] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Revised: 07/15/2020] [Accepted: 07/16/2020] [Indexed: 11/26/2022]
Abstract
The primary cilium, an important microtubule-based organelle, protrudes from nearly all the vertebrate cells. The motility of cilia is necessary for various developmental and physiological processes. Phosphoinositides (PIs) and its metabolite, PtdIns(4,5)P2, have been revealed to contribute to cilia assembly and disassembly. As an important kinase of the PI pathway and signaling, phosphatidylinositol 4-kinase β (PI4KB) is the one of the most extensively studied phosphatidylinositol 4-kinase isoform. However, its potential roles in organ development remain to be characterized. To investigate the developmental role of Pi4kb, especially its function on zebrafish ciliogenesis, we generated pi4kb deletion mutants using clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 technique. The homozygous pi4kb mutants exhibit an absence of primary cilia in the inner ear, neuromasts, and pronephric ducts accompanied by severe edema in the eyes and other organs. Moreover, smaller otic vesicle, malformed semicircular canals, and the insensitivity on sound stimulation were characteristics of pi4kb mutants. At the protein level, both in vivo and in vitro analyses revealed that synthesis of Pi4p was greatly reduced owing to the loss of Pi4kb. In addition, the expression of the Pi4kb-binding partner of neuronal calcium sensor-1, as well as the phosphorylation of phosphatidylinositol-4-phosphate downstream effecter of Akt, was significantly inhibited in pi4kb mutants. Taken together, our work uncovers a novel role of Pi4kb in zebrafish inner ear development and the functional formation of hearing ability by determining hair cell ciliogenesis.
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Affiliation(s)
- Yufei Feng
- Affiliated Hospital of Guangdong Medical University & Key Laboratory of Zebrafish Model for Development and Disease of Guangdong Medical University, Zhanjiang 524001, China
| | - Ping Yu
- Affiliated Hospital of Guangdong Medical University & Key Laboratory of Zebrafish Model for Development and Disease of Guangdong Medical University, Zhanjiang 524001, China
| | - Jingyu Li
- Clinical and Translational Research Center, Shanghai First Maternity and Infant Hospital, School of Life Sciences and Technology, Tongji University, Shanghai 200092, China
| | - Ying Cao
- Clinical and Translational Research Center, Shanghai First Maternity and Infant Hospital, School of Life Sciences and Technology, Tongji University, Shanghai 200092, China
| | - Jingjing Zhang
- Affiliated Hospital of Guangdong Medical University & Key Laboratory of Zebrafish Model for Development and Disease of Guangdong Medical University, Zhanjiang 524001, China.
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9
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Godoy-Parejo C, Deng C, Zhang Y, Liu W, Chen G. Roles of vitamins in stem cells. Cell Mol Life Sci 2020; 77:1771-1791. [PMID: 31676963 PMCID: PMC11104807 DOI: 10.1007/s00018-019-03352-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2019] [Revised: 10/12/2019] [Accepted: 10/21/2019] [Indexed: 12/13/2022]
Abstract
Stem cells can differentiate to diverse cell types in our body, and they hold great promises in both basic research and clinical therapies. For specific stem cell types, distinctive nutritional and signaling components are required to maintain the proliferation capacity and differentiation potential in cell culture. Various vitamins play essential roles in stem cell culture to modulate cell survival, proliferation and differentiation. Besides their common nutritional functions, specific vitamins are recently shown to modulate signal transduction and epigenetics. In this article, we will first review classical vitamin functions in both somatic and stem cell cultures. We will then focus on how stem cells could be modulated by vitamins beyond their nutritional roles. We believe that a better understanding of vitamin functions will significantly benefit stem cell research, and help realize their potentials in regenerative medicine.
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Affiliation(s)
- Carlos Godoy-Parejo
- Centre of Reproduction, Development and Aging, Faculty of Health Sciences, University of Macau, Taipa, Macau SAR, China
| | - Chunhao Deng
- Centre of Reproduction, Development and Aging, Faculty of Health Sciences, University of Macau, Taipa, Macau SAR, China
| | - Yumeng Zhang
- Centre of Reproduction, Development and Aging, Faculty of Health Sciences, University of Macau, Taipa, Macau SAR, China
| | - Weiwei Liu
- Centre of Reproduction, Development and Aging, Faculty of Health Sciences, University of Macau, Taipa, Macau SAR, China
- Bioimaging and Stem Cell Core Facility, Faculty of Health Sciences, University of Macau, Taipa, Macau SAR, China
| | - Guokai Chen
- Centre of Reproduction, Development and Aging, Faculty of Health Sciences, University of Macau, Taipa, Macau SAR, China.
- Bioimaging and Stem Cell Core Facility, Faculty of Health Sciences, University of Macau, Taipa, Macau SAR, China.
- Institute of Translational Medicine, Faculty of Health Sciences, University of Macau, Taipa, Macau SAR, China.
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10
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Taha A, Sharifpanah F, Wartenberg M, Sauer H. Omega-3 and Omega-6 polyunsaturated fatty acids stimulate vascular differentiation of mouse embryonic stem cells. J Cell Physiol 2020; 235:7094-7106. [PMID: 32020589 DOI: 10.1002/jcp.29606] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2019] [Accepted: 01/13/2020] [Indexed: 12/14/2022]
Abstract
Polyunsaturated fatty acids (PUFAs) and their metabolites may influence cell fate regulation. Herein, we investigated the effects of linoleic acid (LA) as ω-6 PUFA, eicosapentaenoic acid (EPA) as ω-3 PUFA and palmitic acid (PA) on vasculogenesis of embryonic stem (ES) cells. LA and EPA increased vascular structure formation and protein expression of the endothelial-specific markers fetal liver kinase-1, CD31 as well as VE-cadherin, whereas PA was without effect. LA and EPA increased reactive oxygen species (ROS) and nitric oxide (NO), activated endothelial NO synthase (eNOS) and raised intracellular calcium. The calcium response was inhibited by the intracellular calcium chelator BAPTA, sulfo-N-succinimidyl oleate which is an antagonist of CD36, the scavenger receptor for fatty acid uptake as well as by a CD36 blocking antibody. Prevention of ROS generation by radical scavengers or the NADPH oxidase inhibitor VAS2870 and inhibition of eNOS by L-NAME blunted vasculogenesis. PUFAs stimulated AMP activated protein kinase-α (AMPK-α) as well as peroxisome proliferator-activated receptor-α (PPAR-α). AMPK activation was abolished by calcium chelation as well as inhibition of ROS and NO generation. Moreover, PUFA-induced vasculogenesis was blunted by the PPAR-α inhibitor GW6471. In conclusion, ω-3 and ω-6 PUFAs stimulate vascular differentiation of ES cells via mechanisms involving calcium, ROS and NO, which regulate function of the energy sensors AMPK and PPAR-α and determine the metabolic signature of vascular cell differentiation.
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Affiliation(s)
- Amer Taha
- Department of Physiology, Justus Liebig University Giessen, Giessen, Germany
| | - Fatemeh Sharifpanah
- Department of Physiology, Justus Liebig University Giessen, Giessen, Germany
| | - Maria Wartenberg
- Department of Cardiology, Clinic of Internal Medicine I, University Heart Center, Jena University Hospital, Jena, Germany
| | - Heinrich Sauer
- Department of Physiology, Justus Liebig University Giessen, Giessen, Germany
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Figueroa VA, Jara O, Oliva CA, Ezquer M, Ezquer F, Retamal MA, Martínez AD, Altenberg GA, Vargas AA. Contribution of Connexin Hemichannels to the Decreases in Cell Viability Induced by Linoleic Acid in the Human Lens Epithelial Cells (HLE-B3). Front Physiol 2020; 10:1574. [PMID: 32038277 PMCID: PMC6984129 DOI: 10.3389/fphys.2019.01574] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2019] [Accepted: 12/16/2019] [Indexed: 01/16/2023] Open
Abstract
Connexin (Cx) proteins form gap junction channels (GJC) and hemichannels that a allow bidirectional flow of ions and metabolites between the cytoplasm and extracellular space, respectively. Under physiological conditions, hemichannels have a very low probability of opening, but in certain pathologies, hemichannels activity can increase and induce and/or accelerate cell death. Several mechanisms control hemichannels activity, including phosphorylation and oxidation (i.e., S-nitrosylation). Recently, the effect of polyunsaturated fatty acids (PUFAs) such as linoleic acid (LA), were found to modulate Cxs. It has been seen that LA increase cell death in bovine and human lens cells. The lens is a structure allocated in the eye that highly depends on Cx for the metabolic coupling between its cells, a condition necessary for its transparency. Therefore, we hypothesized that LA induces lens cells death by modulating hemichannel activity. In this work, we characterized the effect of LA on hemichannel activity and survival of HLE-B3 cells (a human lens epithelial cell line). We found that HLE-B3 cells expresses Cx43, Cx46, and Cx50 and can form functional hemichannels in their plasma membrane. The extracellular exposure to 10–50 μM of LA increases hemichannels activity (dye uptake) in a concentration-dependent manner, which was reduced by Cx-channel blockers, such as the Cx-mimetic peptide Gap27 and TATGap19, La3+, carbenoxolone (CBX) and the Akt kinase inhibitor. Additionally, LA increases intracellular calcium, which is attenuated in the presence of TATGap19, a specific Cx43-hemichannel inhibitor. Finally, the long exposure of HLE-B3 cells to LA 20 and 50 μM, reduced cell viability, which was prevented by CBX. Moreover, LA increased the proportion of apoptotic HLE-B3 cells, effect that was prevented by the Cx-mimetic peptide TAT-Gap19 but not by Akt inhibitor. Altogether, these findings strongly suggest a contribution of hemichannels opening in the cell death induced by LA in HLE-B3 cells. These cells can be an excellent tool to develop pharmacological studies in vitro.
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Affiliation(s)
- Vania A Figueroa
- Instituto de Ciencias Biomédicas, Facultad de Ciencias de la Salud, Universidad Autónoma de Chile, Santiago, Chile.,Instituto de Ciencias de la Salud, Universidad de O'Higgins, Rancagua, Chile
| | - Oscar Jara
- Department of Pediatrics, University of Chicago, Chicago, IL, United States
| | - Carolina A Oliva
- Centro de Envejecimiento y Regeneración (CARE-UC), Departamento Biología Celular y Molecular, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Marcelo Ezquer
- Centro de Medicina Regenerativa, Facultad de Medicina, Clínica Alemana Universidad del Desarrollo, Santiago, Chile
| | - Fernando Ezquer
- Centro de Medicina Regenerativa, Facultad de Medicina, Clínica Alemana Universidad del Desarrollo, Santiago, Chile
| | - Mauricio A Retamal
- Universidad del Desarrollo, Centro de Fisiología Celular e Integrativa, Facultad de Medicina Clínica Alemana, Santiago, Chile.,Department of Cell Physiology and Molecular Biophysics, Texas Tech University Health Sciences Center, Lubbock, TX, United States.,Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, TX, United States
| | - Agustín D Martínez
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Guillermo A Altenberg
- Department of Cell Physiology and Molecular Biophysics, Texas Tech University Health Sciences Center, Lubbock, TX, United States.,Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, TX, United States
| | - Aníbal A Vargas
- Instituto de Ciencias de la Salud, Universidad de O'Higgins, Rancagua, Chile.,Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
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12
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Hu Z, Riquelme MA, Wang B, Bugay V, Brenner R, Gu S, Jiang JX. Cataract-associated connexin 46 mutation alters its interaction with calmodulin and function of hemichannels. J Biol Chem 2018; 293:2573-2585. [PMID: 29298900 PMCID: PMC5818178 DOI: 10.1074/jbc.ra117.001348] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2017] [Revised: 12/29/2017] [Indexed: 11/06/2022] Open
Abstract
Connexin channels help maintain eye lens homeostasis and transparency. The G143R missense substitution in connexin (Cx) 46 is associated with congenital Coppock cataracts; however, the underlying molecular mechanism is largely unknown. Here, we report that compared with WT Cx46, the G143R substitution abolishes hemichannel conductance in Xenopus oocytes and in HeLa cells. Moreover, this substitution is dominant-negative and inhibits conductance of WT Cx46. CD analysis indicated that the substitution greatly reduces the α-helical structure of the intracellular Cx46 loop domain. Protein pulldown assays and isothermal titration calorimetry revealed that this Cx46 domain directly interacts with calmodulin (CaM) in a Ca2+-dependent fashion, an observation confirmed by immunofluorescent co-localization of Cx46 with CaM. Interestingly, the G143R substitution enhanced the Cx46-CaM interaction and attenuated its abolishment by Ca2+ depletion. Moreover, Cx46 increased dye influx, and the G143R substitution augmented this effect. Inhibition of Ca2+-mediated CaM activation blocked hemichannel permeability. The membrane potential plays a crucial role in Cx46 membrane permeability. We found that the activity of hemichannels is detectable under rest and hyperpolarization conditions but is eliminated with depolarization. These results suggested that the G143R substitution impairs voltage-dependent electrical conductance and alters membrane permeability mediated by Cx46 hemichannels. The latter likely is caused by the substitution-induced structural changes of the intracellular loop domain associated with the increased interaction with CaM and reduced Ca2+ sensitivity. The data suggest that the G143R-induced enhancement of the CaM-Cx46 interaction results in altered hemichannel activities and might be related to cataract formation.
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Affiliation(s)
- Zhengping Hu
- From the Departments of Biochemistry and Structural Biology and
- the Second Xiangya Hospital, Central South University, Changsha 410011, China
| | | | - Bin Wang
- Cellular and Integrative Physiology, University of Texas Health Science Center, San Antonio, Texas 78229 and
| | - Vladislav Bugay
- Cellular and Integrative Physiology, University of Texas Health Science Center, San Antonio, Texas 78229 and
| | - Robert Brenner
- Cellular and Integrative Physiology, University of Texas Health Science Center, San Antonio, Texas 78229 and
| | - Sumin Gu
- From the Departments of Biochemistry and Structural Biology and
| | - Jean X Jiang
- From the Departments of Biochemistry and Structural Biology and
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13
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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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14
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Sáez PJ, Vargas P, Shoji KF, Harcha PA, Lennon-Duménil AM, Sáez JC. ATP promotes the fast migration of dendritic cells through the activity of pannexin 1 channels and P2X 7 receptors. Sci Signal 2017; 10:10/506/eaah7107. [PMID: 29162744 DOI: 10.1126/scisignal.aah7107] [Citation(s) in RCA: 109] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Upon its release from injured cells, such as infected, transformed, inflamed, or necrotic cells, extracellular adenosine-5'-triphosphate (ATP) acts as a danger signal that recruits phagocytes, such as neutrophils, macrophages, and dendritic cells (DCs), to the site of injury. The sensing of extracellular ATP occurs through purinergic (P2) receptors. We investigated the cellular mechanisms linking purinergic signaling to DC motility. We found that ATP stimulated fast DC motility through an autocrine signaling loop, which was initiated by the activation of P2X7 receptors and further amplified by pannexin 1 (Panx1) channels. Upon stimulation of the P2X7 receptor by ATP, Panx1 contributed to fast DC motility by increasing the permeability of the plasma membrane, which resulted in supplementary ATP release. In the absence of Panx1, DCs failed to increase their speed of migration in response to ATP, despite exhibiting a normal P2X7 receptor-mediated Ca2+ response. In addition to DC migration, Panx1 channel- and P2X7 receptor-dependent signaling was further required to stimulate the reorganization of the actin cytoskeleton. In vivo, functional Panx1 channels were required for the homing of DCs to lymph nodes, although they were dispensable for DC maturation. These data suggest that P2X7 receptors and Panx1 channels are crucial players in the regulation of DC migration to endogenous danger signals.
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Affiliation(s)
- Pablo J Sáez
- Departamento de Fisiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago 6513677, Chile. .,INSERM U932 Immunité et Cancer, Institut Curie, Paris Sciences et Lettres (PSL) Research University, 12 Rue Lhomond, Paris 75005, France
| | - Pablo Vargas
- INSERM U932 Immunité et Cancer, Institut Curie, Paris Sciences et Lettres (PSL) Research University, 12 Rue Lhomond, Paris 75005, France.,CNRS UMR144, Institut Curie, PSL Research University, 12 Rue Lhomond, Paris 75005, France
| | - Kenji F Shoji
- Departamento de Fisiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago 6513677, Chile
| | - Paloma A Harcha
- Departamento de Fisiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago 6513677, Chile.,Instituto Milenio, Centro Interdisciplinario de Neurociencias de Valparaíso, Valparaíso 2360103, Chile
| | - Ana-María Lennon-Duménil
- INSERM U932 Immunité et Cancer, Institut Curie, Paris Sciences et Lettres (PSL) Research University, 12 Rue Lhomond, Paris 75005, France.
| | - Juan C Sáez
- Departamento de Fisiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago 6513677, Chile. .,Instituto Milenio, Centro Interdisciplinario de Neurociencias de Valparaíso, Valparaíso 2360103, Chile
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15
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Role of astrocyte connexin hemichannels in cortical spreading depression. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1860:216-223. [PMID: 28864364 DOI: 10.1016/j.bbamem.2017.08.014] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2017] [Revised: 08/08/2017] [Accepted: 08/23/2017] [Indexed: 11/21/2022]
Abstract
Cortical spreading depression (CSD) is an intriguing phenomenon consisting of massive slow brain depolarizations that affects neurons and glial cells. It has been recognized since 1944, but its pathogenesis has only been uncovered during the last decade. Acute brain injuries can be further complicated by CSD in >50% of severe cases. This phenomenon is repetitive and produces a metabolic overload that increments secondary damage. Propagation of CSD is known to be linked to excitotoxicity, but the mechanisms associated with its initiation remain less understood. It has been shown that CSD can be initiated by increases in extracellular [K+] ([K+]e), and animal models use high [K+]e to promote CSD. Connexin hemichannel activity increases due to high [K+]e and low extracellular [Ca2+], conditions that occur after brain injury. Moreover, glial cell gap junction channels are fundamental in controlling extracellular medium composition, particularly in maintaining normal extracellular glutamate and K+ concentrations through "spatial buffering". However, the role of astrocytic gap junctions under tissue stress can change to damage spread in the acute damage zone whereas the reduced communication in adjacent zone would reduce cell dead propagation. Here, we review the main findings associated with CSD, and discuss the possible involvement of astrocytic connexin-based channels in secondary damage propagation. This article is part of a Special Issue entitled: Gap Junction Proteins edited by Jean Claude Herve.
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16
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Simon F, Tapia P, Armisen R, Echeverria C, Gatica S, Vallejos A, Pacheco A, Sanhueza ME, Alvo M, Segovia E, Torres R. Human Peritoneal Mesothelial Cell Death Induced by High-Glucose Hypertonic Solution Involves Ca 2+ and Na + Ions and Oxidative Stress with the Participation of PKC/NOX2 and PI3K/Akt Pathways. Front Physiol 2017; 8:379. [PMID: 28659813 PMCID: PMC5468383 DOI: 10.3389/fphys.2017.00379] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2017] [Accepted: 05/22/2017] [Indexed: 01/07/2023] Open
Abstract
Chronic peritoneal dialysis (PD) therapy is equally efficient as hemodialysis while providing greater patient comfort and mobility. Therefore, PD is the treatment of choice for several types of renal patients. During PD, a high-glucose hyperosmotic (HGH) solution is administered into the peritoneal cavity to generate an osmotic gradient that promotes water and solutes transport from peritoneal blood to the dialysis solution. Unfortunately, PD has been associated with a loss of peritoneal viability and function through the generation of a severe inflammatory state that induces human peritoneal mesothelial cell (HPMC) death. Despite this deleterious effect, the precise molecular mechanism of HPMC death as induced by HGH solutions is far from being understood. Therefore, the aim of this study was to explore the pathways involved in HGH solution-induced HPMC death. HGH-induced HPMC death included influxes of intracellular Ca2+ and Na+. Furthermore, HGH-induced HPMC death was inhibited by antioxidant and reducing agents. In line with this, HPMC death was induced solely by increased oxidative stress. In addition to this, the cPKC/NOX2 and PI3K/Akt intracellular signaling pathways also participated in HGH-induced HPMC death. The participation of PI3K/Akt intracellular is in agreement with previously shown in rat PMC apoptosis. These findings contribute toward fully elucidating the underlying molecular mechanism mediating peritoneal mesothelial cell death induced by high-glucose solutions during peritoneal dialysis.
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Affiliation(s)
- Felipe Simon
- Departamento de Ciencias Biologicas, Facultad de Ciencias Biologicas and Facultad de Medicina, Universidad Andres BelloSantiago, Chile.,Millennium Institute on Immunology and ImmunotherapySantiago, Chile
| | - Pablo Tapia
- Unidad de Paciente Critico, Hospital Clínico Metropolitano de La FloridaSantiago, Chile
| | - Ricardo Armisen
- Centro de Investigación y Tratamiento del Cancer, Facultad de Medicina, Universidad de ChileSantiago, Chile.,Center for Excellence in Precision Medicine Pfizer, Pfizer ChileSantiago, Chile
| | - Cesar Echeverria
- Centro Integrativo de Biología y Química Aplicada, Universidad Bernardo OHigginsSantiago, Chile
| | - Sebastian Gatica
- Departamento de Ciencias Biologicas, Facultad de Ciencias Biologicas and Facultad de Medicina, Universidad Andres BelloSantiago, Chile
| | - Alejandro Vallejos
- Departamento de Ciencias Biologicas, Facultad de Ciencias Biologicas and Facultad de Medicina, Universidad Andres BelloSantiago, Chile
| | - Alejandro Pacheco
- Sección de Nefrología, Departamento de Medicina, Hospital Clínico Universidad de ChileSantiago, Chile
| | - Maria E Sanhueza
- Sección de Nefrología, Departamento de Medicina, Hospital Clínico Universidad de ChileSantiago, Chile
| | - Miriam Alvo
- Sección de Nefrología, Departamento de Medicina, Hospital Clínico Universidad de ChileSantiago, Chile
| | - Erico Segovia
- Centro Integrativo de Biología y Química Aplicada, Universidad Bernardo OHigginsSantiago, Chile
| | - Rubén Torres
- Sección de Nefrología, Departamento de Medicina, Hospital Clínico Universidad de ChileSantiago, Chile.,Facultad de Medicina, Instituto de Ciencias Biomédicas, Universidad de ChileSantiago, Chile
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17
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Puebla C, Retamal MA, Acuña R, Sáez JC. Regulation of Connexin-Based Channels by Fatty Acids. Front Physiol 2017; 8:11. [PMID: 28174541 PMCID: PMC5258758 DOI: 10.3389/fphys.2017.00011] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2016] [Accepted: 01/06/2017] [Indexed: 01/29/2023] Open
Abstract
In this mini-review, we briefly summarize the current knowledge about the effects of fatty acids (FAs) on connexin-based channels, as well as discuss the limited information about the impact FAs may have on pannexins (Panxs). FAs regulate diverse cellular functions, some of which are explained by changes in the activity of channels constituted by connexins (Cxs) or Panxs, which are known to play critical roles in maintaining the functional integrity of diverse organs and tissues. Cxs are transmembrane proteins that oligomerize into hexamers to form hemichannels (HCs), which in turn can assemble into dodecamers to form gap junction channels (GJCs). While GJCs communicate the cytoplasm of contacting cells, HCs serve as pathways for the exchange of ions and small molecules between the intra and extracellular milieu. Panxs, as well as Cx HCs, form channels at the plasma membrane that enable the interchange of molecules between the intra and extracellular spaces. Both Cx- and Panx-based channels are controlled by several post-translational modifications. However, the mechanism of action of FAs on these channels has not been described in detail. It has been shown however that FAs frequently decrease GJC-mediated cell-cell communication. The opposite effect also has been described for HC or Panx-dependent intercellular communication, where, the acute FA effect can be reversed upon washout. Additionally, changes in GJCs mediated by FAs have been associated with post-translational modifications (e.g., phosphorylation), and seem to be directly related to chemical properties of FAs (e.g., length of carbon chain and/or degree of saturation), but this possible link remains poorly understood.
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Affiliation(s)
- Carlos Puebla
- Instituto de Ciencias Biomédicas, Facultad de Ciencias de la Salud, Universidad Autónoma de ChileSantiago, Chile; Centro de Fisiología Celular e Integrativa, Facultad de Medicina, Clínica Alemana Universidad del DesarrolloSantiago, Chile
| | - Mauricio A Retamal
- Centro de Fisiología Celular e Integrativa, Facultad de Medicina, Clínica Alemana Universidad del Desarrollo Santiago, Chile
| | - Rodrigo Acuña
- Centro de Fisiología Celular e Integrativa, Facultad de Medicina, Clínica Alemana Universidad del Desarrollo Santiago, Chile
| | - Juan C Sáez
- Departamento de Fisiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de ChileSantiago, Chile; Centro Interdisciplinario de Neurociencias de Valparaíso, Intituto Milenio, Universidad de ValparaísoValparaíso, Chile
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18
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Pogoda K, Kameritsch P, Retamal MA, Vega JL. Regulation of gap junction channels and hemichannels by phosphorylation and redox changes: a revision. BMC Cell Biol 2016; 17 Suppl 1:11. [PMID: 27229925 PMCID: PMC4896245 DOI: 10.1186/s12860-016-0099-3] [Citation(s) in RCA: 108] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Post-translational modifications of connexins play an important role in the regulation of gap junction and hemichannel permeability. The prerequisite for the formation of functional gap junction channels is the assembly of connexin proteins into hemichannels and their insertion into the membrane. Hemichannels can affect cellular processes by enabling the passage of signaling molecules between the intracellular and extracellular space. For the intercellular communication hemichannels from one cell have to dock to its counterparts on the opposing membrane of an adjacent cell to allow the transmission of signals via gap junctions from one cell to the other. The controlled opening of hemichannels and gating properties of complete gap junctions can be regulated via post-translational modifications of connexins. Not only channel gating, but also connexin trafficking and assembly into hemichannels can be affected by post-translational changes. Recent investigations have shown that connexins can be modified by phosphorylation/dephosphorylation, redox-related changes including effects of nitric oxide (NO), hydrogen sulfide (H2S) or carbon monoxide (CO), acetylation, methylation or ubiquitination. Most of the connexin isoforms are known to be phosphorylated, e.g. Cx43, one of the most studied connexin at all, has 21 reported phosphorylation sites. In this review, we provide an overview about the current knowledge and relevant research of responsible kinases, connexin phosphorylation sites and reported effects on gap junction and hemichannel regulation. Regarding the effects of oxidants we discuss the role of NO in different cell types and tissues and recent studies about modifications of connexins by CO and H2S.
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Affiliation(s)
- Kristin Pogoda
- Walter Brendel Centre of Experimental Medicine, Ludwig-Maximilians-Universität München and Munich University Hospital, München, Germany. .,DZHK (German Centre for Cardiovascular Research), partner site Munich Heart Alliance, München, Germany.
| | - Petra Kameritsch
- Walter Brendel Centre of Experimental Medicine, Ludwig-Maximilians-Universität München and Munich University Hospital, München, Germany.,DZHK (German Centre for Cardiovascular Research), partner site Munich Heart Alliance, München, Germany
| | - Mauricio A Retamal
- Centro de Fisiología Celular e Integrativa, Facultad de Medicina, Clínica Alemana Universidad del Desarrollo, Santiago, Chile
| | - José L Vega
- Experimental Physiology Laboratory (EPhyL), Antofagasta Institute, Universidad de Antofagasta, Antofagasta, Chile
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19
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Puebla C, Cisterna BA, Salas DP, Delgado-López F, Lampe PD, Sáez JC. Linoleic acid permeabilizes gastric epithelial cells by increasing connexin 43 levels in the cell membrane via a GPR40- and Akt-dependent mechanism. Biochim Biophys Acta Mol Cell Biol Lipids 2016; 1861:439-48. [PMID: 26869446 DOI: 10.1016/j.bbalip.2016.02.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2015] [Revised: 01/25/2016] [Accepted: 02/06/2016] [Indexed: 02/08/2023]
Abstract
Linoleic acid (LA) is known to activate G-protein coupled receptors and connexin hemichannels (Cx HCs) but possible interlinks between these two responses remain unexplored. Here, we evaluated the mechanism of action of LA on the membrane permeability mediated by Cx HCs in MKN28 cells. These cells were found to express connexins, GPR40, GPR120, and CD36 receptors. The Cx HC activity of these cells increased after 5 min of treatment with LA or GW9508, an agonist of GPR40/GPR120; or exposure to extracellular divalent cation-free solution (DCFS), known to increase the open probability of Cx HCs, yields an immediate increase in Cx HC activity of similar intensity and additive with LA-induced change. Treatment with a CD36 blocker or transfection with siRNA-GPR120 maintains the LA-induced Cx HC activity. However, cells transfected with siRNA-GPR40 did not show LA-induced Cx HC activity but activity was increased upon exposure to DCFS, confirming the presence of activatable Cx HCs in the cell membrane. Treatment with AKTi (Akt inhibitor) abrogated the LA-induced Cx HC activity. In HeLa cells transfected with Cx43 (HeLa-Cx43), LA induced phosphorylation of surface Cx43 at serine 373 (S373), site for Akt phosphorylation. HeLa-Cx43 but not HeLa-Cx43 cells with a S373A mutation showed a LA-induced Cx HC activity directly related to an increase in cell surface Cx43 levels. Thus, the increase in membrane permeability induced by LA is mediated by an intracellular signaling pathway activated by GPR40 that leads to an increase in membrane levels of Cx43 phosphorylated at serine 373 via Akt.
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Affiliation(s)
- Carlos Puebla
- Departamento de Fisiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile.
| | - Bruno A Cisterna
- Departamento de Fisiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile; Instituto Milenio, Centro Interdisciplinario de Neurociencias de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile
| | - Daniela P Salas
- Departamento de Fisiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Fernando Delgado-López
- Laboratorios de Biomedicina, Departamento de Ciencias Preclínicas, Facultad de Medicina, Universidad Católica del Maule, Talca, Chile
| | - Paul D Lampe
- Translational Research Program, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, United States
| | - Juan C Sáez
- Departamento de Fisiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile; Instituto Milenio, Centro Interdisciplinario de Neurociencias de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile.
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20
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Del Rio R, Quintanilla RA, Orellana JA, Retamal MA. Neuron-Glia Crosstalk in the Autonomic Nervous System and Its Possible Role in the Progression of Metabolic Syndrome: A New Hypothesis. Front Physiol 2015; 6:350. [PMID: 26648871 PMCID: PMC4664731 DOI: 10.3389/fphys.2015.00350] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2015] [Accepted: 11/09/2015] [Indexed: 01/26/2023] Open
Abstract
Metabolic syndrome (MS) is characterized by the following physiological alterations: increase in abdominal fat, insulin resistance, high concentration of triglycerides, low levels of HDL, high blood pressure, and a generalized inflammatory state. One of the pathophysiological hallmarks of this syndrome is the presence of neurohumoral activation, which involve autonomic imbalance associated to hyperactivation of the sympathetic nervous system. Indeed, enhanced sympathetic drive has been linked to the development of endothelial dysfunction, hypertension, stroke, myocardial infarct, and obstructive sleep apnea. Glial cells, the most abundant cells in the central nervous system, control synaptic transmission, and regulate neuronal function by releasing bioactive molecules called gliotransmitters. Recently, a new family of plasma membrane channels called hemichannels has been described to allow the release of gliotransmitters and modulate neuronal firing rate. Moreover, a growing amount of evidence indicates that uncontrolled hemichannel opening could impair glial cell functions, affecting synaptic transmission and neuronal survival. Given that glial cell functions are disturbed in various metabolic diseases, we hypothesize that progression of MS may relies on hemichannel-dependent impairment of glial-to-neuron communication by a mechanism related to dysfunction of inflammatory response and mitochondrial metabolism of glial cells. In this manuscript, we discuss how glial cells may contribute to the enhanced sympathetic drive observed in MS, and shed light about the possible role of hemichannels in this process.
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Affiliation(s)
- Rodrigo Del Rio
- Centro de Investigación Biomédica, Universidad Autónoma de Chile Santiago, Chile ; Dirección de Investigación, Universidad Científica del Sur Lima, Perú
| | | | - Juan A Orellana
- Departamento de Neurología, Escuela de Medicina, Pontificia Universidad Católica de Chile Santiago, Chile
| | - Mauricio A Retamal
- Centro de Fisiología Celular e Integrativa, Facultad de Medicina. Clínica Alemana Universidad del Desarrollo Santiago, Chile
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21
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Retamal MA, León-Paravic CG, Ezquer M, Ezquer F, Rio RD, Pupo A, Martínez AD, González C. Carbon monoxide: A new player in the redox regulation of connexin hemichannels. IUBMB Life 2015; 67:428-37. [DOI: 10.1002/iub.1388] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2015] [Accepted: 05/05/2015] [Indexed: 01/23/2023]
Affiliation(s)
- Mauricio A. Retamal
- Centro de Fisiología Celular e Integrativa, Facultad de Medicina; Clínica Alemana Universidad del Desarrollo; Santiago Chile
| | - Carmen G. León-Paravic
- Centro de Fisiología Celular e Integrativa, Facultad de Medicina; Clínica Alemana Universidad del Desarrollo; Santiago Chile
| | - Marcelo Ezquer
- Centro de Medicina Regenerativa, Facultad de Medicina; Clínica Alemana Universidad del Desarrollo; Santiago Chile
| | - Fernando Ezquer
- Centro de Medicina Regenerativa, Facultad de Medicina; Clínica Alemana Universidad del Desarrollo; Santiago Chile
| | - Rodrigo Del Rio
- Centro de Investigación Biomédica; Universidad Autónoma de Chile; Santiago Chile
| | - Amaury Pupo
- Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias; Instituto de Neurociencia; Universidad de Valparaíso; Valparaíso Chile
| | - Agustín D. Martínez
- Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias; Instituto de Neurociencia; Universidad de Valparaíso; Valparaíso Chile
| | - Carlos González
- Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias; Instituto de Neurociencia; Universidad de Valparaíso; Valparaíso Chile
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22
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Salas D, Puebla C, Lampe PD, Lavandero S, Sáez JC. Role of Akt and Ca2+ on cell permeabilization via connexin43 hemichannels induced by metabolic inhibition. Biochim Biophys Acta Mol Basis Dis 2015; 1852:1268-77. [PMID: 25779082 DOI: 10.1016/j.bbadis.2015.03.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2014] [Revised: 02/25/2015] [Accepted: 03/06/2015] [Indexed: 10/23/2022]
Abstract
Connexin hemichannels are regulated under physiological and pathological conditions. Metabolic inhibition, a model of ischemia, promotes surface hemichannel activation associated, in part, with increased surface hemichannel levels, but little is known about its underlying mechanism. Here, we investigated the role of Akt on the connexin43 hemichannel's response induced by metabolic inhibition. In HeLa cells stably transfected with rat connexin43 fused to EGFP (HeLa43 cells), metabolic inhibition induced a transient Akt activation necessary to increase the amount of surface connexin43. The increase in levels of surface connexin43 was also found to depend on an intracellular Ca2+ signal increase that was partially mediated by Akt activation. However, the metabolic inhibition-induced Akt activation was not significantly affected by intracellular Ca2+ chelation. The Akt-dependent increase in connexin43 hemichannel activity in HeLa43 cells also occurred after oxygen-glucose deprivation, another ischemia-like condition, and in cultured cortical astrocytes (endogenous connexin43 expression system) under metabolic inhibition. Since opening of hemichannels has been shown to accelerate cell death, inhibition of Akt-dependent phosphorylation of connexin43 hemichannels could reduce cell death induced by ischemia/reperfusion.
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Affiliation(s)
- Daniela Salas
- Advanced Center for Chronic Diseases (ACCDIS) & Centro Estudios Moleculares de la Célula (CMEC), Facultad Ciencias Químicas y Farmacéuticas & Facultad Medicina, Universidad de Chile, Santiago, Chile; Departamento de Fisiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile.
| | - Carlos Puebla
- Departamento de Fisiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Paul D Lampe
- Translational Research Program, Human Biology and Public Health Sciences Divisions, Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue North, Seattle, WA 98109, USA
| | - Sergio Lavandero
- Advanced Center for Chronic Diseases (ACCDIS) & Centro Estudios Moleculares de la Célula (CMEC), Facultad Ciencias Químicas y Farmacéuticas & Facultad Medicina, Universidad de Chile, Santiago, Chile
| | - Juan C Sáez
- Departamento de Fisiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile; Instituto Milenio, Centro Interdisciplinario de Neurociencias de Valparaíso, Valparaíso, Chile.
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23
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Sáez PJ, Shoji KF, Aguirre A, Sáez JC. Regulation of hemichannels and gap junction channels by cytokines in antigen-presenting cells. Mediators Inflamm 2014; 2014:742734. [PMID: 25301274 PMCID: PMC4180397 DOI: 10.1155/2014/742734] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2014] [Accepted: 06/19/2014] [Indexed: 12/13/2022] Open
Abstract
Autocrine and paracrine signals coordinate responses of several cell types of the immune system that provide efficient protection against different challenges. Antigen-presenting cells (APCs) coordinate activation of this system via homocellular and heterocellular interactions. Cytokines constitute chemical intercellular signals among immune cells and might promote pro- or anti-inflammatory effects. During the last two decades, two membrane pathways for intercellular communication have been demonstrated in cells of the immune system. They are called hemichannels (HCs) and gap junction channels (GJCs) and provide new insights into the mechanisms of the orchestrated response of immune cells. GJCs and HCs are permeable to ions and small molecules, including signaling molecules. The direct intercellular transfer between contacting cells can be mediated by GJCs, whereas the release to or uptake from the extracellular milieu can be mediated by HCs. GJCs and HCs can be constituted by two protein families: connexins (Cxs) or pannexins (Panxs), which are present in almost all APCs, being Cx43 and Panx1 the most ubiquitous members of each protein family. In this review, we focus on the effects of different cytokines on the intercellular communication mediated by HCs and GJCs in APCs and their impact on purinergic signaling.
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Affiliation(s)
- Pablo J. Sáez
- Departamento de Fisiología, Pontificia Universidad Católica de Chile, Alameda 340, 6513677 Santiago, Chile
| | - Kenji F. Shoji
- Departamento de Fisiología, Pontificia Universidad Católica de Chile, Alameda 340, 6513677 Santiago, Chile
| | - Adam Aguirre
- Departamento de Fisiología, Pontificia Universidad Católica de Chile, Alameda 340, 6513677 Santiago, Chile
| | - Juan C. Sáez
- Departamento de Fisiología, Pontificia Universidad Católica de Chile, Alameda 340, 6513677 Santiago, Chile
- Instituto Milenio, Centro Interdisciplinario de Neurociencias de Valparaíso, Pasaje Harrington 287, Playa Ancha, 2360103 Valparaíso, Chile
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24
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Figueroa VA, Retamal MA, Cea LA, Salas JD, Vargas AA, Verdugo CA, Jara O, Martínez AD, Sáez JC. Extracellular gentamicin reduces the activity of connexin hemichannels and interferes with purinergic Ca(2+) signaling in HeLa cells. Front Cell Neurosci 2014; 8:265. [PMID: 25237294 PMCID: PMC4154469 DOI: 10.3389/fncel.2014.00265] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2014] [Accepted: 08/18/2014] [Indexed: 01/15/2023] Open
Abstract
Gap junction channels (GJCs) and hemichannels (HCs) are composed of protein subunits termed connexins (Cxs) and are permeable to ions and small molecules. In most organs, GJCs communicate the cytoplasm of adjacent cells, while HCs communicate the intra and extracellular compartments. In this way, both channel types coordinate physiological responses of cell communities. Cx mutations explain several genetic diseases, including about 50% of autosomal recessive non-syndromic hearing loss. However, the possible involvement of Cxs in the etiology of acquired hearing loss remains virtually unknown. Factors that induce post-lingual hearing loss are diverse, exposure to gentamicin an aminoglycoside antibiotic, being the most common. Gentamicin has been proposed to block GJCs, but its effect on HCs remains unknown. In this work, the effect of gentamicin on the functional state of HCs was studied and its effect on GJCs was reevaluated in HeLa cells stably transfected with Cxs. We focused on Cx26 because it is the main Cx expressed in the cochlea of mammals where it participates in purinergic signaling pathways. We found that gentamicin applied extracellularly reduces the activity of HCs, while dye transfer across GJCs was not affected. HCs were also blocked by streptomycin, another aminoglycoside antibiotic. Gentamicin also reduced the adenosine triphosphate release and the HC-dependent oscillations of cytosolic free-Ca2+ signal. Moreover, gentamicin drastically reduced the Cx26 HC-mediated membrane currents in Xenopus laevis oocytes. Therefore, the extracellular gentamicin-induced inhibition of Cx HCs may adversely affect autocrine and paracrine signaling, including the purinergic one, which might partially explain its ototoxic effects.
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Affiliation(s)
- Vania A Figueroa
- Departamento de Fisiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile Santiago, Chile ; Centro de Fisiología Celular e Integrativa, Facultad de Medicina, Clínica Alemana Universidad del Desarrollo Santiago, Chile
| | - Mauricio A Retamal
- Centro de Fisiología Celular e Integrativa, Facultad de Medicina, Clínica Alemana Universidad del Desarrollo Santiago, Chile
| | - Luis A Cea
- Departamento de Fisiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile Santiago, Chile
| | - José D Salas
- Centro de Fisiología Celular e Integrativa, Facultad de Medicina, Clínica Alemana Universidad del Desarrollo Santiago, Chile
| | - Aníbal A Vargas
- Departamento de Fisiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile Santiago, Chile
| | - Christian A Verdugo
- Centro de Fisiología Celular e Integrativa, Facultad de Medicina, Clínica Alemana Universidad del Desarrollo Santiago, Chile
| | - Oscar Jara
- Instituto Milenio, Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso Valparaíso, Chile
| | - Agustín D Martínez
- Instituto Milenio, Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso Valparaíso, Chile
| | - Juan C Sáez
- Departamento de Fisiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile Santiago, Chile ; Instituto Milenio, Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso Valparaíso, Chile
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25
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Sáez JC, Leybaert L. Hunting for connexin hemichannels. FEBS Lett 2014; 588:1205-11. [PMID: 24631534 DOI: 10.1016/j.febslet.2014.03.004] [Citation(s) in RCA: 143] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2014] [Revised: 03/01/2014] [Accepted: 03/03/2014] [Indexed: 10/25/2022]
Abstract
Connexin hemichannels (connexons) are building blocks of gap junctions but also function as free unapposed channels, which has become an active field of research. Defining functions of hemichannels and their involvement in any biological event requires ruling out possible participation of other channels that share biophysical and regulatory properties, for example pannexins, CALHM1 and P2X receptors. The lack of specific inhibitors for these channels has become an obstacle in elucidating the role of connexin hemichannels. Several experimental approaches are now available to identify hemichannels at the cell surface and to characterize their electrophysiological, permeability and regulatory properties. The use of connexin knockout/knockdown, and the development of peptides that target intracellular connexin domains and specific antibodies directed to extracellular domains have helped to dissect the role of hemichannels in endogenously expressing systems. Moreover, studies of connexin mutants in exogenous expression systems have provided convincing evidence on hemichannels in the pathogenesis of several human genetic diseases. We here present a brief overview of connexin hemichannels as functional channels and itemize a list of aspects to consider when concluding on their involvement.
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Affiliation(s)
- Juan C Sáez
- Departamento de Fisiología, Pontificia Universidad Católica de Chile, Santiago and Instituto Milenio, Centro Interdisciplinario de Neurociencias de Valparaíso, Valparaíso, Chile.
| | - Luc Leybaert
- Physiology Group, Department of Basic Medical Sciences, Faculty of Medicine and Health Sciences, Ghent University, De Pintelaan 185 (Block B - Rm 031), 9000 Ghent, Belgium.
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26
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Lohman AW, Isakson BE. Differentiating connexin hemichannels and pannexin channels in cellular ATP release. FEBS Lett 2014; 588:1379-88. [PMID: 24548565 DOI: 10.1016/j.febslet.2014.02.004] [Citation(s) in RCA: 137] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2014] [Revised: 02/06/2014] [Accepted: 02/06/2014] [Indexed: 12/22/2022]
Abstract
Adenosine triphosphate (ATP) plays a fundamental role in cellular communication, with its extracellular accumulation triggering purinergic signaling cascades in a diversity of cell types. While the roles for purinergic signaling in health and disease have been well established, identification and differentiation of the specific mechanisms controlling cellular ATP release is less well understood. Multiple mechanisms have been proposed to regulate ATP release with connexin (Cx) hemichannels and pannexin (Panx) channels receiving major focus. However, segregating the specific roles of Panxs and Cxs in ATP release in a plethora of physiological and pathological contexts has remained enigmatic. This multifaceted problem has arisen from the selectivity of pharmacological inhibitors for Panxs and Cxs, methodological differences in assessing Panx and Cx function and the potential compensation by other isoforms in gene silencing and genetic knockout models. Consequently, there remains a void in the current understanding of specific contributions of Panxs and Cxs in releasing ATP during homeostasis and disease. Differentiating the distinct signaling pathways that regulate these two channels will advance our current knowledge of cellular communication and aid in the development of novel rationally-designed drugs for modulation of Panx and Cx activity, respectively.
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Affiliation(s)
- Alexander W Lohman
- Department of Molecular Physiology and Biophysics, University of Virginia, Charlottesville, VA 22098, United States; Robert M. Berne Cardiovascular Research Center, University of Virginia, Charlottesville, VA 22908, United States
| | - Brant E Isakson
- Department of Molecular Physiology and Biophysics, University of Virginia, Charlottesville, VA 22098, United States; Robert M. Berne Cardiovascular Research Center, University of Virginia, Charlottesville, VA 22908, United States.
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27
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Okada Y, Miyazaki T, Fujiyama R, Toda K. Wing (Ib) cells in frog taste discs detect dietary unsaturated fatty acids. Comp Biochem Physiol A Mol Integr Physiol 2013; 166:434-40. [PMID: 23872318 DOI: 10.1016/j.cbpa.2013.07.016] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2013] [Revised: 06/11/2013] [Accepted: 07/10/2013] [Indexed: 11/17/2022]
Abstract
The effects of unsaturated fatty acids on membrane properties were studied using conventional whole-cell patch-clamp recording of isolated wing (Ib) cells in bullfrog (Lithobates catesbeianus) taste discs. Applying arachidonic acid to the bath induced monophasic inward currents in 60% of wing cells and biphasic inward and outward currents in the other cells. The intracellular dialysis of arachidonic acid did not induce an inward current; however, it enhanced a slowly developing Ba(2+)-sensitive outward current. The effects of various unsaturated fatty acids were explored under the condition of Cs(+) internal solution. Linoleic and α-linolenic acids induced large inward currents. Oleic, eicosapentaenoic and docosahexaenoic acids elicited the same inward currents as those of arachidonic acid. Wing cells, under the basal condition with Cs(+) internal solution, displayed a small inward current of -1.1±0.1pA/pF at -50mV (n=40), in which the peak existed at a membrane potential of -49mV. Removing external Ca(2+) further increased the inward current by -2.9±0.3pA/pF at -50mV (n=4) from the basal current and the peak was located at -55mV. External linoleic acid (50μM) also induced a similar inward current of -5.6±0.6pA/pF at -50mV (n=19) from the basal current and the peak was located at -61mV. External Ca(2+)-free saline and linoleic acid induced similar current/voltage (I/V) relationships elicited by a ramp voltage as well as voltage steps. Linoleic acid-induced currents were not influenced by replacing internal EGTA with BAPTA, whereas inward currents disappeared under the elimination of external Na(+) and addition of flufenamic acid. These results suggest that dietary unsaturated fatty acids may depolarize wing (Ib) cells, which affects the excitability of these cells.
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Affiliation(s)
- Yukio Okada
- Integrative Sensory Physiology, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Nagasaki 852-8588, Japan.
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