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Okada Y. Physiology of the volume-sensitive/regulatory anion channel VSOR/VRAC: part 2: its activation mechanisms and essential roles in organic signal release. J Physiol Sci 2024; 74:34. [PMID: 38877402 PMCID: PMC11177392 DOI: 10.1186/s12576-024-00926-3] [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: 05/05/2024] [Accepted: 06/01/2024] [Indexed: 06/16/2024]
Abstract
The volume-sensitive outwardly rectifying or volume-regulated anion channel, VSOR/VRAC, which was discovered in 1988, is expressed in most vertebrate cell types, and is essentially involved in cell volume regulation after swelling and in the induction of cell death. This series of review articles describes what is already known and what remains to be uncovered about the functional and molecular properties as well as the physiological and pathophysiological roles of VSOR/VRAC. This Part 2 review article describes, from the physiological and pathophysiological standpoints, first the pivotal roles of VSOR/VRAC in the release of autocrine/paracrine organic signal molecules, such as glutamate, ATP, glutathione, cGAMP, and itaconate, as well as second the swelling-independent and -dependent activation mechanisms of VSOR/VRAC. Since the pore size of VSOR/VRAC has now well been evaluated by electrophysiological and 3D-structural methods, the signal-releasing activity of VSOR/VRAC is here discussed by comparing the molecular sizes of these organic signals to the channel pore size. Swelling-independent activation mechanisms include a physicochemical one caused by the reduction of intracellular ionic strength and a biochemical one caused by oxidation due to stimulation by receptor agonists or apoptosis inducers. Because some organic substances released via VSOR/VRAC upon cell swelling can trigger or augment VSOR/VRAC activation in an autocrine fashion, swelling-dependent activation mechanisms are to be divided into two phases: the first phase induced by cell swelling per se and the second phase caused by receptor stimulation by released organic signals.
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Affiliation(s)
- Yasunobu Okada
- National Institute for Physiological Sciences (NIPS), 5-1 Higashiyama, Myodaiji, Okazaki, Aichi, 444-8787, Japan.
- Department of Integrative Physiology, Graduate School of Medicine, Akita University, Akita, Japan.
- Department of Physiology, School of Medicine, Aichi Medical University, Nagakute, Japan.
- Graduate University for Advanced Studies (SOKENDAI), Hayama, Kanagawa, Japan.
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2
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El-Kenawi A, Berglund A, Estrella V, Zhang Y, Liu M, Putney RM, Yoder SJ, Johnson J, Brown J, Gatenby R. Elevated Methionine Flux Drives Pyroptosis Evasion in Persister Cancer Cells. Cancer Res 2023; 83:720-734. [PMID: 36480167 PMCID: PMC9978888 DOI: 10.1158/0008-5472.can-22-1002] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Revised: 09/29/2022] [Accepted: 12/02/2022] [Indexed: 12/13/2022]
Abstract
Induction of cell death represents a primary goal of most anticancer treatments. Despite the efficacy of such approaches, a small population of "persisters" develop evasion strategies to therapy-induced cell death. While previous studies have identified mechanisms of resistance to apoptosis, the mechanisms by which persisters dampen other forms of cell death, such as pyroptosis, remain to be elucidated. Pyroptosis is a form of inflammatory cell death that involves formation of membrane pores, ion gradient imbalance, water inflow, and membrane rupture. Herein, we investigate mechanisms by which cancer persisters resist pyroptosis, survive, then proliferate in the presence of tyrosine kinase inhibitors (TKI). Lung, prostate, and esophageal cancer persister cells remaining after treatments exhibited several hallmarks indicative of pyroptosis resistance. The inflammatory attributes of persisters included chronic activation of inflammasome, STING, and type I interferons. Comprehensive metabolomic characterization uncovered that TKI-induced pyroptotic persisters display high methionine consumption and excessive taurine production. Elevated methionine flux or exogenous taurine preserved plasma membrane integrity via osmolyte-mediated effects. Increased dependency on methionine flux decreased the level of one carbon metabolism intermediate S-(5'-adenosyl)-L-homocysteine, a determinant of cell methylation capacity. The consequent increase in methylation potential induced DNA hypermethylation of genes regulating metal ion balance and intrinsic immune response. This enabled thwarting TKI resistance by using the hypomethylating agent decitabine. In summary, the evolution of resistance to pyroptosis can occur via a stepwise process of physical acclimation and epigenetic changes without existing or recurrent mutations. SIGNIFICANCE Methionine enables cancer cells to persist by evading pyroptotic osmotic lysis, which leads to genome-wide hypermethylation that allows persisters to gain proliferative advantages.
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Affiliation(s)
- Asmaa El-Kenawi
- Department of Radiation Oncology, H. Lee Moffitt Cancer Center, Tampa, Florida.,Cancer Biology and Evolution Program, H. Lee Moffitt Cancer Center, Tampa, Florida
| | - Anders Berglund
- Department of Biostatistics and Bioinformatics, H. Lee Moffitt Cancer Center, Tampa, Florida
| | - Veronica Estrella
- Cancer Biology and Evolution Program, H. Lee Moffitt Cancer Center, Tampa, Florida.,Department of Cancer Physiology, H. Lee Moffitt Cancer Center, Tampa, Florida
| | - Yonghong Zhang
- Biostatistics and Bioinformatics Shared Resource, H. Lee Moffitt Cancer Center, Tampa, Florida
| | - Min Liu
- Proteomics and Metabolomics Core Facility, H. Lee Moffitt Cancer Center, Tampa, Florida
| | - Ryan M Putney
- Department of Biostatistics and Bioinformatics, H. Lee Moffitt Cancer Center, Tampa, Florida
| | - Sean J Yoder
- Molecular Genomics Core Facility, H. Lee Moffitt Cancer Center, Tampa, Florida
| | - Joseph Johnson
- Analytic Microscopy Core Facility, H. Lee Moffitt Cancer Center, Tampa, Florida
| | - Joel Brown
- Cancer Biology and Evolution Program, H. Lee Moffitt Cancer Center, Tampa, Florida.,Department of Integrated Mathematical Oncology, H. Lee Moffitt Cancer Center, Tampa, Florida
| | - Robert Gatenby
- Cancer Biology and Evolution Program, H. Lee Moffitt Cancer Center, Tampa, Florida.,Department of Integrated Mathematical Oncology, H. Lee Moffitt Cancer Center, Tampa, Florida.,Department of Radiology, H. Lee Moffitt Cancer Center, Tampa, Florida
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Taurine Supplementation as a Neuroprotective Strategy upon Brain Dysfunction in Metabolic Syndrome and Diabetes. Nutrients 2022; 14:nu14061292. [PMID: 35334949 PMCID: PMC8952284 DOI: 10.3390/nu14061292] [Citation(s) in RCA: 31] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2022] [Revised: 03/14/2022] [Accepted: 03/15/2022] [Indexed: 02/07/2023] Open
Abstract
Obesity, type 2 diabetes, and their associated comorbidities impact brain metabolism and function and constitute risk factors for cognitive impairment. Alterations to taurine homeostasis can impact a number of biological processes, such as osmolarity control, calcium homeostasis, and inhibitory neurotransmission, and have been reported in both metabolic and neurodegenerative disorders. Models of neurodegenerative disorders show reduced brain taurine concentrations. On the other hand, models of insulin-dependent diabetes, insulin resistance, and diet-induced obesity display taurine accumulation in the hippocampus. Given the possible cytoprotective actions of taurine, such cerebral accumulation of taurine might constitute a compensatory mechanism that attempts to prevent neurodegeneration. The present article provides an overview of brain taurine homeostasis and reviews the mechanisms by which taurine can afford neuroprotection in individuals with obesity and diabetes. We conclude that further research is needed for understanding taurine homeostasis in metabolic disorders with an impact on brain function.
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Tureckova J, Kamenicka M, Kolenicova D, Filipi T, Hermanova Z, Kriska J, Meszarosova L, Pukajova B, Valihrach L, Androvic P, Zucha D, Chmelova M, Vargova L, Anderova M. Compromised Astrocyte Swelling/Volume Regulation in the Hippocampus of the Triple Transgenic Mouse Model of Alzheimer’s Disease. Front Aging Neurosci 2022; 13:783120. [PMID: 35153718 PMCID: PMC8829436 DOI: 10.3389/fnagi.2021.783120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2021] [Accepted: 12/27/2021] [Indexed: 11/13/2022] Open
Abstract
In this study, we aimed to disclose the impact of amyloid-β toxicity and tau pathology on astrocyte swelling, their volume recovery and extracellular space (ECS) diffusion parameters, namely volume fraction (α) and tortuosity (λ), in a triple transgenic mouse model of Alzheimer’s disease (3xTg-AD). Astrocyte volume changes, which reflect astrocyte ability to take up ions/neurotransmitters, were quantified during and after exposure to hypo-osmotic stress, or hyperkalemia in acute hippocampal slices, and were correlated with alterations in ECS diffusion parameters. Astrocyte volume and ECS diffusion parameters were monitored during physiological aging (controls) and during AD progression in 3-, 9-, 12- and 18-month-old mice. In the hippocampus of controls α gradually declined with age, while it remained unaffected in 3xTg-AD mice during the entire time course. Moreover, age-related increases in λ occurred much earlier in 3xTg-AD animals than in controls. In 3xTg-AD mice changes in α induced by hypo-osmotic stress or hyperkalemia were comparable to those observed in controls, however, AD progression affected α recovery following exposure to both. Compared to controls, a smaller astrocyte swelling was detected in 3xTg-AD mice only during hyperkalemia. Since we observed a large variance in astrocyte swelling/volume regulation, we divided them into high- (HRA) and low-responding astrocytes (LRA). In response to hyperkalemia, the incidence of LRA was higher in 3xTg-AD mice than in controls, which may also reflect compromised K+ and neurotransmitter uptake. Furthermore, we performed single-cell RT-qPCR to identify possible age-related alterations in astrocytic gene expression profiles. Already in 3-month-old 3xTg-AD mice, we detected a downregulation of genes affecting the ion/neurotransmitter uptake and cell volume regulation, namely genes of glutamate transporters, α2β2 subunit of Na+/K+-ATPase, connexin 30 or Kir4.1 channel. In conclusion, the aged hippocampus of 3xTg-AD mice displays an enlarged ECS volume fraction and an increased number of obstacles, which emerge earlier than in physiological aging. Both these changes may strongly affect intercellular communication and influence astrocyte ionic/neurotransmitter uptake, which becomes impaired during aging and this phenomenon is manifested earlier in 3xTg-AD mice. The increased incidence of astrocytes with limited ability to take up ions/neurotransmitters may further add to a cytotoxic environment.
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Affiliation(s)
- Jana Tureckova
- Department of Cellular Neurophysiology, Institute of Experimental Medicine, Czech Academy of Sciences, Prague, Czechia
- *Correspondence: Jana Tureckova,
| | - Monika Kamenicka
- Department of Cellular Neurophysiology, Institute of Experimental Medicine, Czech Academy of Sciences, Prague, Czechia
- Second Faculty of Medicine, Charles University, Prague, Czechia
| | - Denisa Kolenicova
- Department of Cellular Neurophysiology, Institute of Experimental Medicine, Czech Academy of Sciences, Prague, Czechia
- Second Faculty of Medicine, Charles University, Prague, Czechia
| | - Tereza Filipi
- Department of Cellular Neurophysiology, Institute of Experimental Medicine, Czech Academy of Sciences, Prague, Czechia
- Second Faculty of Medicine, Charles University, Prague, Czechia
| | - Zuzana Hermanova
- Department of Cellular Neurophysiology, Institute of Experimental Medicine, Czech Academy of Sciences, Prague, Czechia
- Second Faculty of Medicine, Charles University, Prague, Czechia
| | - Jan Kriska
- Department of Cellular Neurophysiology, Institute of Experimental Medicine, Czech Academy of Sciences, Prague, Czechia
| | - Lenka Meszarosova
- Department of Cellular Neurophysiology, Institute of Experimental Medicine, Czech Academy of Sciences, Prague, Czechia
| | - Barbora Pukajova
- Department of Cellular Neurophysiology, Institute of Experimental Medicine, Czech Academy of Sciences, Prague, Czechia
| | - Lukas Valihrach
- Laboratory of Gene Expression, Institute of Biotechnology, Czech Academy of Sciences, Vestec, Czechia
| | - Peter Androvic
- Laboratory of Gene Expression, Institute of Biotechnology, Czech Academy of Sciences, Vestec, Czechia
| | - Daniel Zucha
- Laboratory of Gene Expression, Institute of Biotechnology, Czech Academy of Sciences, Vestec, Czechia
- Faculty of Chemical Technology, University of Chemistry and Technology, Prague, Czechia
| | - Martina Chmelova
- Department of Cellular Neurophysiology, Institute of Experimental Medicine, Czech Academy of Sciences, Prague, Czechia
- Second Faculty of Medicine, Charles University, Prague, Czechia
| | - Lydia Vargova
- Department of Cellular Neurophysiology, Institute of Experimental Medicine, Czech Academy of Sciences, Prague, Czechia
- Second Faculty of Medicine, Charles University, Prague, Czechia
| | - Miroslava Anderova
- Department of Cellular Neurophysiology, Institute of Experimental Medicine, Czech Academy of Sciences, Prague, Czechia
- Second Faculty of Medicine, Charles University, Prague, Czechia
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Prevarskaya N, Skryma R, Shuba Y. Ion Channels in Cancer: Are Cancer Hallmarks Oncochannelopathies? Physiol Rev 2018; 98:559-621. [PMID: 29412049 DOI: 10.1152/physrev.00044.2016] [Citation(s) in RCA: 272] [Impact Index Per Article: 45.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Genomic instability is a primary cause and fundamental feature of human cancer. However, all cancer cell genotypes generally translate into several common pathophysiological features, often referred to as cancer hallmarks. Although nowadays the catalog of cancer hallmarks is quite broad, the most common and obvious of them are 1) uncontrolled proliferation, 2) resistance to programmed cell death (apoptosis), 3) tissue invasion and metastasis, and 4) sustained angiogenesis. Among the genes affected by cancer, those encoding ion channels are present. Membrane proteins responsible for signaling within cell and among cells, for coupling of extracellular events with intracellular responses, and for maintaining intracellular ionic homeostasis ion channels contribute to various extents to pathophysiological features of each cancer hallmark. Moreover, tight association of these hallmarks with ion channel dysfunction gives a good reason to classify them as special type of channelopathies, namely oncochannelopathies. Although the relation of cancer hallmarks to ion channel dysfunction differs from classical definition of channelopathies, as disease states causally linked with inherited mutations of ion channel genes that alter channel's biophysical properties, in a broader context of the disease state, to which pathogenesis ion channels essentially contribute, such classification seems absolutely appropriate. In this review the authors provide arguments to substantiate such point of view.
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Affiliation(s)
- Natalia Prevarskaya
- INSERM U-1003, Equipe Labellisée par la Ligue Nationale contre le Cancer et LABEX, Université Lille1 , Villeneuve d'Ascq , France ; Bogomoletz Institute of Physiology and International Center of Molecular Physiology, NASU, Kyiv-24, Ukraine
| | - Roman Skryma
- INSERM U-1003, Equipe Labellisée par la Ligue Nationale contre le Cancer et LABEX, Université Lille1 , Villeneuve d'Ascq , France ; Bogomoletz Institute of Physiology and International Center of Molecular Physiology, NASU, Kyiv-24, Ukraine
| | - Yaroslav Shuba
- INSERM U-1003, Equipe Labellisée par la Ligue Nationale contre le Cancer et LABEX, Université Lille1 , Villeneuve d'Ascq , France ; Bogomoletz Institute of Physiology and International Center of Molecular Physiology, NASU, Kyiv-24, Ukraine
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Akita T, Okada Y. Characteristics and roles of the volume-sensitive outwardly rectifying (VSOR) anion channel in the central nervous system. Neuroscience 2014; 275:211-31. [DOI: 10.1016/j.neuroscience.2014.06.015] [Citation(s) in RCA: 72] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2014] [Revised: 06/06/2014] [Accepted: 06/07/2014] [Indexed: 01/05/2023]
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Fabbro A, Sucapane A, Toma FM, Calura E, Rizzetto L, Carrieri C, Roncaglia P, Martinelli V, Scaini D, Masten L, Turco A, Gustincich S, Prato M, Ballerini L. Adhesion to carbon nanotube conductive scaffolds forces action-potential appearance in immature rat spinal neurons. PLoS One 2013; 8:e73621. [PMID: 23951361 PMCID: PMC3741175 DOI: 10.1371/journal.pone.0073621] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2013] [Accepted: 07/29/2013] [Indexed: 12/19/2022] Open
Abstract
In the last decade, carbon nanotube growth substrates have been used to investigate neurons and neuronal networks formation in vitro when guided by artificial nano-scaled cues. Besides, nanotube-based interfaces are being developed, such as prosthesis for monitoring brain activity. We recently described how carbon nanotube substrates alter the electrophysiological and synaptic responses of hippocampal neurons in culture. This observation highlighted the exceptional ability of this material in interfering with nerve tissue growth. Here we test the hypothesis that carbon nanotube scaffolds promote the development of immature neurons isolated from the neonatal rat spinal cord, and maintained in vitro. To address this issue we performed electrophysiological studies associated to gene expression analysis. Our results indicate that spinal neurons plated on electro-conductive carbon nanotubes show a facilitated development. Spinal neurons anticipate the expression of functional markers of maturation, such as the generation of voltage dependent currents or action potentials. These changes are accompanied by a selective modulation of gene expression, involving neuronal and non-neuronal components. Our microarray experiments suggest that carbon nanotube platforms trigger reparative activities involving microglia, in the absence of reactive gliosis. Hence, future tissue scaffolds blended with conductive nanotubes may be exploited to promote cell differentiation and reparative pathways in neural regeneration strategies.
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Affiliation(s)
| | | | - Francesca Maria Toma
- Department of Chemical and Pharmaceutical Sciences, University of Trieste, Trieste, Italy
| | - Enrica Calura
- Department of Biology, University of Padua, Padova, Italy
| | - Lisa Rizzetto
- Department of Neuroscience, Psychology, Drug Research and Child's Health, University of Florence, Florence, Italy
- Innovation and Research Center, Fondazione Edmund Mach, San Michele all’Adige, Trento, Italy
| | - Claudia Carrieri
- European Molecular Biology Laboratory, Mouse Biology Unit, Monterotondo (Rome), Italy
| | - Paola Roncaglia
- International School for Advanced Studies (SISSA), Trieste, Italy
- European Bioinformatics Institute (EMBL-EBI), Hinxton, United Kingdom
| | - Valentina Martinelli
- International Centre for Genetic Engineering and Biotechnology (ICGEB), Trieste, Italy
| | - Denis Scaini
- Life Science Department, University of Trieste, Trieste, Italy
- SENIL, ELETTRA Synchrotron Light Source, Trieste, Italy
| | - Lara Masten
- Life Science Department, University of Trieste, Trieste, Italy
| | - Antonio Turco
- Department of Chemical and Pharmaceutical Sciences, University of Trieste, Trieste, Italy
| | | | - Maurizio Prato
- Department of Chemical and Pharmaceutical Sciences, University of Trieste, Trieste, Italy
| | - Laura Ballerini
- Life Science Department, University of Trieste, Trieste, Italy
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Cubillán L, Obregón F, Lima L. Neurites outgrowth and amino acids levels in goldfish retina under hypo‐osmotic or hyper‐osmotic conditions. Int J Dev Neurosci 2011; 30:55-61. [DOI: 10.1016/j.ijdevneu.2011.08.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2011] [Revised: 08/26/2011] [Accepted: 08/30/2011] [Indexed: 12/13/2022] Open
Affiliation(s)
- Lisbeth Cubillán
- Laboratorio de NeuroquímicaCentro de Biofísica y BioquímicaInstituto Venezolano de Investigaciones (IVIC)Apdo. 21827Caracas1020‐AVenezuela
| | - Francisco Obregón
- Laboratorio de NeuroquímicaCentro de Biofísica y BioquímicaInstituto Venezolano de Investigaciones (IVIC)Apdo. 21827Caracas1020‐AVenezuela
| | - Lucimey Lima
- Laboratorio de NeuroquímicaCentro de Biofísica y BioquímicaInstituto Venezolano de Investigaciones (IVIC)Apdo. 21827Caracas1020‐AVenezuela
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Le-Corronc H, Rigo JM, Branchereau P, Legendre P. GABA(A) receptor and glycine receptor activation by paracrine/autocrine release of endogenous agonists: more than a simple communication pathway. Mol Neurobiol 2011; 44:28-52. [PMID: 21547557 DOI: 10.1007/s12035-011-8185-1] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2011] [Accepted: 04/14/2011] [Indexed: 02/04/2023]
Abstract
It is a common and widely accepted assumption that glycine and GABA are the main inhibitory transmitters in the central nervous system (CNS). But, in the past 20 years, several studies have clearly demonstrated that these amino acids can also be excitatory in the immature central nervous system. In addition, it is now established that both GABA receptors (GABARs) and glycine receptors (GlyRs) can be located extrasynaptically and can be activated by paracrine release of endogenous agonists, such as GABA, glycine, and taurine. Recently, non-synaptic release of GABA, glycine, and taurine gained further attention with increasing evidence suggesting a developmental role of these neurotransmitters in neuronal network formation before and during synaptogenesis. This review summarizes recent knowledge about the non-synaptic activation of GABA(A)Rs and GlyRs, both in developing and adult CNS. We first present studies that reveal the functional specialization of both non-synaptic GABA(A)Rs and GlyRs and we discuss the neuronal versus non-neuronal origin of the paracrine release of GABA(A)R and GlyR agonists. We then discuss the proposed non-synaptic release mechanisms and/or pathways for GABA, glycine, and taurine. Finally, we summarize recent data about the various roles of non-synaptic GABAergic and glycinergic systems during the development of neuronal networks and in the adult.
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Affiliation(s)
- Herve Le-Corronc
- Institut National de la Santé et de la Recherche Médicale, U952, Centre National de la Recherche Scientifique, UMR 7224, Université Pierre et Marie Curie, 9 quai Saint Bernard, Paris, Ile de France, France
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Tucker B, Olson JE. Glutamate receptor-mediated taurine release from the hippocampus during oxidative stress. J Biomed Sci 2010; 17 Suppl 1:S10. [PMID: 20804584 PMCID: PMC2994387 DOI: 10.1186/1423-0127-17-s1-s10] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Background Hippocampal slices swell and release taurine during oxidative stress. The influence of cellular signalling pathways on this process is unclear. Glutamate signalling can facilitate volume regulation in other CNS preparations. Therefore, we hypothesize activation of taurine release by oxidative stress results from tissue swelling and is coupled to activation of glutamate receptors. Methods Rat hippocampi were incubated at room temperature for 2 hr in artificial cerebrospinal fluid (aCSF) equilibrated with 95% O2 plus 5% CO2. For some slices, 1 mM taurine was added to the aCSF to maintain normal tissue taurine content. Slices then were perfused with aCSF at 35° C and baseline data recorded before 2 mM H2O2 was added. For some studies, mannitol or inhibitors of glutamate receptors or the volume-regulated anion channel (VRAC) were added before and during H2O2 treatment. The intensity of light transmitted through the slice (the intrinsic optical signal, IOS) was determined at 1-min intervals. Samples of perfusate were collected at 2-min intervals and amino acid contents determined by HPLC. Data were analyzed by repeated measures ANOVA and post hoc Dunnett’s test with significance indicated for p<0.05. Results IOS of slices prepared without taurine treatment increased significantly by 3.3±1.3% (mean±SEM) during oxidative stress. Little taurine was detected in the perfusate of these slices and the rate of taurine efflux did not change during H2O2 exposure. The α-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate antagonist, 25 µM CNQX, but not the N-methyl-D-aspartate (NMDA) receptor antagonist, 10 µM MK-801, inhibited the increase in IOS during H2O2 treatment. Taurine-treated slices exposed to H2O2 showed no change in IOS; however, taurine efflux increased by 335±178%. When these slices were perfused with hypertonic aCSF (350 mOsm) or exposed to the VRAC inhibitor, 20 µM DCPIB, no increase in the taurine efflux rate was observed during H2O2 exposure. Taurine-treated slices perfused with 10 µM MK-801 during H2O2 exposure showed a 4.6±1.9% increase in IOS but no increase in the taurine efflux rate. Conclusions Taurine efflux via VRAC is critical for volume regulation of hippocampal slices exposed to oxidative stress. This increased taurine efflux does not result from direct activation of the taurine release pathway by H2O2. NMDA receptor activation plays an important role in taurine release during oxidative stress.
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Affiliation(s)
- Brian Tucker
- Department of Neuroscience, Cell Biology, and Physiology, Boonshoft School of Medicine, Wright State University, Dayton, Ohio, USA.
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Harvey VL, Saul MW, Garner C, McDonald RL. A role for the volume regulated anion channel in volume regulation in the murine CNS cell line, CAD. Acta Physiol (Oxf) 2010; 198:159-68. [PMID: 19811460 DOI: 10.1111/j.1748-1716.2009.02050.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
AIM The role of the volume regulated anion channel (VRAC) in a model CNS neuronal cell line, CAD, was investigated. METHODS Changes in cell volume following hypotonic challenges were measured using a video-imaging technique. The effect of the Cl(-) channel antagonists tamoxifen (10 microm) and 4,4'-diisothiocyanatostilbene-2,2'-disulphonic acid (DIDS; 100 microm) on regulatory volume decrease (RVD) were measured. The whole-cell voltage-clamp technique was used to characterize ICl(swell), the current underlying the VRAC. RESULTS Using the video-imaging technique, CAD cells were found to swell and subsequently exhibit RVD when subjected to a sustained hypotonic challenge from 300 mOsmol kg(-1) H(2)O to 210 mOsmol kg(-1) H(2)O. In the presence of tamoxifen (10 microm) or DIDS (100 microm) RVD was abolished, suggesting a role for the VRAC. A hypotonic solution (230 mOsmol kg(-1) H(2)O) evoked ICl(swell), an outwardly rectifying current displaying time-independent activation, which reversed upon return to isotonic conditions. The reversal potential (E(rev)) for ICl(swell) was -14.7 + or - 1.4 mV, similar to the theoretical E(rev) for a selective Cl(-) conductance. ICl(swell) was inhibited in the presence of DIDS (100 microm) and tamoxifen (10 microm), the DIDS inhibition being voltage dependent. CONCLUSIONS Osmotic swelling elicits an outwardly rectifying Cl(-) conductance in CAD cells. The ICl(swell) observed in these cells is similar to that observed in other cells, and is likely to provide a pathway for the loss of Cl(-) which leads to water loss and RVD. As ischaemia, brain trauma, hypoxia and other brain pathologies can cause cell swelling, CAD cells represent a model cell line for the study of neuronal cell volume regulation.
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Affiliation(s)
- V L Harvey
- Neuroscience, Pharmacology & Physiology, University College London, Gower Street, London WC1E 6BT, UK.
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Blum AE, Walsh BC, Dubyak GR. Extracellular osmolarity modulates G protein-coupled receptor-dependent ATP release from 1321N1 astrocytoma cells. Am J Physiol Cell Physiol 2009; 298:C386-96. [PMID: 19907018 DOI: 10.1152/ajpcell.00430.2009] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
We previously reported that ATP release from 1321N1 human astrocytoma cells could be stimulated either by activation of G protein-coupled receptors (GPCR) or by hypotonic stress. Cheema et al. (Cheema TA, Ward CE, Fisher SK. J Pharmacol Exp Ther 315: 755-763, 2005) have demonstrated that thrombin activation of protease-activated receptor 1 (PAR1) in 1321N1 cells and primary astrocytes acts synergistically with hypotonic stress to gate the opening of volume-sensitive organic osmolyte and anion channels (VSOAC) and that hypertonic stress strongly inhibits PAR1 gating of VSOAC. We tested the hypothesis that a VSOAC-type permeability might comprise a GPCR-regulated pathway for ATP export by determining whether PAR1-sensitive ATP release from 1321N1 cells is similarly potentiated by hypotonicity but suppressed by hypertonic conditions. Strong hypotonic stress by itself elicited ATP release and positively modulated the response to thrombin. Thrombin-dependent ATP release was also potentiated by mild hypotonic stress that by itself did not stimulate ATP export. Notably, PAR1-sensitive ATP export was greatly inhibited in hypertonic medium. Neither the potency nor efficacy of thrombin as an activator of proximal PAR1 signaling was affected by hypotonicity or hypertonicity. 1,9-Dideoxyforskolin and carbenoxolone similarly attenuated PAR1-dependent ATP release and suppressed the PAR1-independent ATP elicited by strong hypotonic stress. Probenecid attenuated PAR1-stimulated ATP release under isotonic but not mild hypotonic conditions and had no effect on PAR1-independent release stimulated by strong hypotonicity. PAR1-dependent ATP export under all osmotic conditions required concurrent signaling by Ca(2+) mobilization and Rho-GTPase activation. In contrast, PAR1-independent ATP release triggered by strong hypotonicity required neither of these intracellular signals. Thus, we provide the new finding that GPCR-regulated ATP release from 1321N1 astrocytoma cells is remarkably sensitive to both positive and negative modulation by extracellular osmolarity. This supports a model wherein GPCR stimulation and osmotic stress converge on an ATP release pathway in astrocytes that exhibits several features of VSOAC-type channels.
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Affiliation(s)
- Andrew E Blum
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, OH 44120, USA
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