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Martinez-Lozada Z, Todd FW, Schober AL, Krizman E, Robinson MB, Murai KK. Cooperative and competitive regulation of the astrocytic transcriptome by neurons and endothelial cells: Impact on astrocyte maturation. J Neurochem 2023; 167:52-75. [PMID: 37525469 PMCID: PMC10543513 DOI: 10.1111/jnc.15908] [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: 03/01/2023] [Revised: 06/19/2023] [Accepted: 06/20/2023] [Indexed: 08/02/2023]
Abstract
Astrocytes have essential roles in central nervous system (CNS) health and disease. During development, immature astrocytes show complex interactions with neurons, endothelial cells, and other glial cell types. Our work and that of others have shown that these interactions are important for astrocytic maturation. However, whether and how these cells work together to control this process remains poorly understood. Here, we test the hypothesis that cooperative interactions of astrocytes with neurons and endothelial cells promote astrocytic maturation. Astrocytes were cultured alone, with neurons, endothelial cells, or a combination of both. This was followed by astrocyte sorting, RNA sequencing, and bioinformatic analysis to detect transcriptional changes. Across culture configurations, 7302 genes were differentially expressed by 4 or more fold and organized into 8 groups that demonstrate cooperative and antagonist effects of neurons and endothelia on astrocytes. We also discovered that neurons and endothelial cells caused splicing of 200 and 781 mRNAs, respectively. Changes in gene expression were validated using quantitative PCR, western blot (WB), and immunofluorescence analysis. We found that the transcriptomic data from the three-culture configurations correlated with protein expression of three representative targets (FAM107A, GAT3, and GLT1) in vivo. Alternative splicing results also correlated with cortical tissue isoform representation of a target (Fibronectin 1) at different developmental stages. By comparing our results to published transcriptomes of immature and mature astrocytes, we found that neurons or endothelia shift the astrocytic transcriptome toward a mature state and that the presence of both cell types has a greater effect on maturation than either cell alone. These results increase our understanding of cellular interactions/pathways that contribute to astrocytic maturation. They also provide insight into how alterations to neurons and/or endothelial cells may alter astrocytes with implications for astrocytic changes in CNS disorders and diseases.
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Affiliation(s)
- Zila Martinez-Lozada
- Departments of Pediatrics and Systems Pharmacology & Translational Therapeutics, The Children’s Hospital of Philadelphia, University of Pennsylvania, Philadelphia, PA, USA, 19104-4318
| | - Farmer W. Todd
- Centre for Research in Neuroscience, Department of Neurology & Neurosurgery, Brain Repair and Integrative Neuroscience Program, The Research Institute of the McGill University Health Centre, Montreal General Hospital, Montreal, Quebec, Canada H3G 1A4
| | - Alexandra L. Schober
- Centre for Research in Neuroscience, Department of Neurology & Neurosurgery, Brain Repair and Integrative Neuroscience Program, The Research Institute of the McGill University Health Centre, Montreal General Hospital, Montreal, Quebec, Canada H3G 1A4
| | - Elizabeth Krizman
- Departments of Pediatrics and Systems Pharmacology & Translational Therapeutics, The Children’s Hospital of Philadelphia, University of Pennsylvania, Philadelphia, PA, USA, 19104-4318
| | - Michael B. Robinson
- Departments of Pediatrics and Systems Pharmacology & Translational Therapeutics, The Children’s Hospital of Philadelphia, University of Pennsylvania, Philadelphia, PA, USA, 19104-4318
| | - Keith K. Murai
- Centre for Research in Neuroscience, Department of Neurology & Neurosurgery, Brain Repair and Integrative Neuroscience Program, The Research Institute of the McGill University Health Centre, Montreal General Hospital, Montreal, Quebec, Canada H3G 1A4
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Martinez-Lozada Z, Hewett SJ, Zafra F, Ortega A. Editorial: The known, the unknown, and the future of glutamate transporters. Front Cell Neurosci 2022; 16:1005834. [PMID: 36060278 PMCID: PMC9433117 DOI: 10.3389/fncel.2022.1005834] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2022] [Accepted: 08/04/2022] [Indexed: 11/29/2022] Open
Affiliation(s)
- Zila Martinez-Lozada
- Department of Pediatrics, The Children's Hospital of Philadelphia, Philadelphia, PA, United States
- *Correspondence: Zila Martinez-Lozada
| | - Sandra J. Hewett
- Program in Neuroscience, Department of Biology, Syracuse University, Syracuse, NY, United States
| | - Francisco Zafra
- Center of Molecular Biology Severo Ochoa, School of Science, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, Madrid, Spain
- Instituto de Investigación Sanitaria del Hospital Universitario La Paz — IdiPAZ, Madrid, Spain
| | - Arturo Ortega
- Department of Toxicology, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Ciudad de México, Mexico
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Sears SMS, Roberts SH, Hewett SJ. Hyperexcitability and brain morphological differences in mice lacking the cystine/glutamate antiporter, system x c. J Neurosci Res 2021; 99:3339-3353. [PMID: 34747522 DOI: 10.1002/jnr.24971] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2020] [Revised: 09/11/2021] [Accepted: 09/16/2021] [Indexed: 01/17/2023]
Abstract
System xc - (Sxc - ) is a heteromeric antiporter (L-cystine/L-glutamate exchanger) expressed predominately on astrocytes in the central nervous system. Its activity contributes importantly to the maintenance of the ambient extracellular glutamate levels, as well as, to cellular redox homeostasis. Since alterations in glutamate levels and redox modifications could cause structural changes, we analyzed gross regional morphology of thionin-stained brain sections and cellular and subcellular morphology of Golgi-Cox stained layer V pyramidal neurons in the primary motor cortex (PM1) of mice naturally null for SLC7A11 (SLC7A11sut/sut )-the gene that encodes the substrate specific light chain (xCT) for Sxc - . Intriguingly, in comparison to age- and sex-matched wild-type (SLC7A11+/+ ) littermate controls, we found morphologic changes-including increased dendritic complexity and mushroom spine area in males and reduced corpus callosum and soma size in females-that have previously been described, in each case, as morphological correlates of excitability. Consistent with this, we found that both male and female SLC7A11sut/sut mice had lower convulsive seizure thresholds and greater seizure severity than their sex-matched wild-type (SLC7A11+/+ ) littermates after acute challenge with two pharmacologically distinct chemoconvulsants: the Glu receptor agonist, kainic acid (KA), or the GABAA receptor antagonist, pentylenetetrazole (PTZ). These results suggest that the loss of Sxc - signaling in males and females perturbs excitatory/inhibitory (E/I) balance in vivo, potentially through its regulation of cellular and subcellular morphology.
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Affiliation(s)
- Sheila M S Sears
- Department of Biology, Program in Neuroscience, Syracuse University, Syracuse, New York, USA
| | - Sarah H Roberts
- Department of Biology, Program in Neuroscience, Syracuse University, Syracuse, New York, USA
| | - Sandra J Hewett
- Department of Biology, Program in Neuroscience, Syracuse University, Syracuse, New York, USA
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4
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Daher B, Vučetić M, Pouysségur J. Cysteine Depletion, a Key Action to Challenge Cancer Cells to Ferroptotic Cell Death. Front Oncol 2020; 10:723. [PMID: 32457843 PMCID: PMC7221143 DOI: 10.3389/fonc.2020.00723] [Citation(s) in RCA: 58] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2020] [Accepted: 04/16/2020] [Indexed: 12/11/2022] Open
Abstract
Cancer cells are characterized as highly proliferative at the expense of enhancement of metabolic rate. Consequently, cancer cells rely on antioxidant defenses to overcome the associated increased production of reactive oxygen species (ROS). The reliance of tumor metabolism on amino acids, especially amino acid transport systems, has been extensively studied over the past decade. Although cysteine is the least abundant amino acid in the cell, evidences described it as one of the most important amino acid for cell survival and growth. Regarding its multi-functionality as a nutrient, protein folding, and major component for redox balance due to its involvement in glutathione synthesis, disruption of cysteine homeostasis appears to be promising strategy for induction of cancer cell death. Ten years ago, ferroptosis, a new form of non-apoptotic cell death, has been described as a result of cysteine insufficiency leading to a collapse of intracellular glutathione level. In the present review, we summarized the metabolic networks involving the amino acid cysteine in cancer and ferroptosis and we focused on describing the recently discovered glutathione-independent pathway, a potential player in cancer ferroptosis resistance. Then, we discuss the implication of cysteine as key player in ferroptosis as a precursor for glutathione first, but also as metabolic precursor in glutathione-independent ferroptosis axis.
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Affiliation(s)
- Boutaina Daher
- Medical Biology Department, Centre Scientifique de Monaco (CSM), Monaco, Monaco
| | - Milica Vučetić
- Medical Biology Department, Centre Scientifique de Monaco (CSM), Monaco, Monaco
| | - Jacques Pouysségur
- Medical Biology Department, Centre Scientifique de Monaco (CSM), Monaco, Monaco
- Institute for Research on Cancer and Aging (IRCAN), CNRS, INSERM, Centre A. Lacassagne, Université Côte d'Azur, Nice, France
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Chase LA, VerHeulen Kleyn M, Schiller N, King AG, Flores G, Engelsman SB, Bowles C, Smith SL, Robinson AE, Rothstein J. Hydrogen peroxide triggers an increase in cell surface expression of system x c- in cultured human glioma cells. Neurochem Int 2019; 134:104648. [PMID: 31874187 DOI: 10.1016/j.neuint.2019.104648] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Revised: 12/15/2019] [Accepted: 12/18/2019] [Indexed: 12/14/2022]
Abstract
System xc- exchanges extracellular cystine for intracellular glutamate across the plasma membrane of many cell types. One of the physiological roles of System xc- is to provide cystine for synthesis of the antioxidant glutathione. Here we report that hydrogen peroxide (H2O2) triggers the translocation of System xc- to the plasma membrane within 10 min of the initial exposure. Specifically, we observed a three-fold increase in 35S-l-cystine uptake following a 10 min exposure to 0.3 mM H2O2. This effect was dose-dependent with an EC50 for H2O2 of 65 μM. We then used cell surface biotinylation analysis to test the hypothesis that the increase in activity is due to an increased number of transporters on the plasma membrane. We demonstrated that the amount of transporter protein, xCT, localized to the plasma membrane doubles within 10 min of H2O2 exposure as a result of an increase in its delivery rate and a reduction in its internalization rate. In addition, we demonstrated that H2O2 triggered a rapid decrease in total cellular glutathione which recovered within 2 h of the oxidative insult. The kinetics of glutathione recovery matched the time course for the recovery of xCT cell surface expression and System xc- activity following removal of the oxidative insult. Collectively, these results suggest that oxidants acutely modulate the activity of System xc- by increasing its cell surface expression, and that this process may serve as an important mechanism to increase de novo glutathione synthesis during periods of oxidative stress.
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Affiliation(s)
- Leah A Chase
- Department of Chemistry, Hope College, Holland, MI, 49423, USA; Department of Biology, Hope College, Holland, MI, 49423, USA.
| | | | - NaTasha Schiller
- Department of Chemistry, Hope College, Holland, MI, 49423, USA; Department of Biology, Hope College, Holland, MI, 49423, USA
| | - Abby Goltz King
- Department of Chemistry, Hope College, Holland, MI, 49423, USA
| | - Guillermo Flores
- Department of Chemistry, Hope College, Holland, MI, 49423, USA; Department of Biology, Hope College, Holland, MI, 49423, USA
| | | | | | - Sara Lang Smith
- Department of Biology, Hope College, Holland, MI, 49423, USA
| | - Anne E Robinson
- Department of Chemistry, Hope College, Holland, MI, 49423, USA; Department of Biology, Hope College, Holland, MI, 49423, USA
| | - Jeffrey Rothstein
- Department of Neurology, Department of Neuroscience, Johns Hopkins University, Baltimore, MD, 21287, USA
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Watson WH, Ritzenthaler JD, Peyrani P, Wiemken TL, Furmanek S, Reyes Vega AM, Burke TJ, Zheng Y, Ramirez JA, Roman J. Plasma cysteine/cystine and glutathione/glutathione disulfide redox potentials in HIV and COPD patients. Free Radic Biol Med 2019; 143:55-61. [PMID: 31369840 PMCID: PMC6848776 DOI: 10.1016/j.freeradbiomed.2019.07.031] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/16/2019] [Revised: 06/10/2019] [Accepted: 07/28/2019] [Indexed: 12/16/2022]
Abstract
Chronic obstructive pulmonary disease (COPD) is prevalent in patients infected with HIV. The purpose of this study was to test the hypothesis that systemic oxidation correlates with loss of lung function in subjects with COPD, and that HIV infection can contribute to creating such an environment. Subjects were recruited at the University of Louisville in the following groups: HIV-infected (n = 36), COPD (n = 32), HIV and COPD (n = 28), and uninfected controls with normal lung function (n = 34). HIV infection was assessed by viral load and CD4 cell counts. Pulmonary function was determined by spirometry, and plasma was collected for measurement of cysteine (Cys), cystine (CySS), glutathione (GSH) and GSH disulfide (GSSG) by HPLC followed by estimation of redox potentials (Eh) using the Nernst equation. Results showed that patients with COPD had more oxidized plasma Eh Cys/CySS than patients with normal lung function, but plasma Eh GSH/GSSG was unaltered. In addition, there was a correlation between the extent of plasma Eh Cys/CySS oxidation and loss of lung function, and this correlation remained even after correcting for age, sex, race and body mass index. HIV infection per se was not associated with increased oxidation of plasma Eh Cys/CySS, but plasma Eh Cys/CySS was more oxidized in patients with lower CD4-positve T cell counts. In patients with both HIV infection and COPD, there was a significant correlation between CD4 cell counts and lung function. Thus, systemic oxidation correlated with decreased lung function in subjects with COPD and decreased CD4 counts in subjects infected with HIV. Thus, factors contributing to plasma Eh Cys/CySS may represent novel mechanisms underlying the increased prevalence of COPD in people living with HIV.
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Affiliation(s)
- Walter H Watson
- Department of Medicine, Division of Gastroenterology, Hepatology and Nutrition, University of Louisville School of Medicine, USA; Department of Pharmacology & Toxicology, University of Louisville School of Medicine, USA.
| | - Jeffrey D Ritzenthaler
- Department of Medicine, Division of Pulmonary, Critical Care, and Sleep Medicine, University of Louisville School of Medicine, USA
| | - Paula Peyrani
- Department of Medicine, Division of Infectious Diseases, University of Louisville School of Medicine, USA
| | - Timothy L Wiemken
- Department of Medicine, Division of Infectious Diseases, University of Louisville School of Medicine, USA
| | - Stephen Furmanek
- Department of Medicine, Division of Infectious Diseases, University of Louisville School of Medicine, USA
| | - Andrea M Reyes Vega
- Department of Medicine, Division of Infectious Diseases, University of Louisville School of Medicine, USA
| | - Tom J Burke
- Department of Medicine, Division of Gastroenterology, Hepatology and Nutrition, University of Louisville School of Medicine, USA
| | - Yuxuan Zheng
- Department of Pharmacology & Toxicology, University of Louisville School of Medicine, USA
| | - Julio A Ramirez
- Department of Medicine, Division of Infectious Diseases, University of Louisville School of Medicine, USA; Robley Rex VA Medical Center, Louisville, KY, USA
| | - Jesse Roman
- Department of Medicine, Division of Pulmonary, Critical Care, and Sleep Medicine, University of Louisville School of Medicine, USA; Robley Rex VA Medical Center, Louisville, KY, USA
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7
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Sears SMS, Hewett JA, Hewett SJ. Decreased epileptogenesis in mice lacking the System x c - transporter occurs in association with a reduction in AMPA receptor subunit GluA1. Epilepsia Open 2019; 4:133-143. [PMID: 30868123 PMCID: PMC6398109 DOI: 10.1002/epi4.12307] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2018] [Accepted: 01/19/2019] [Indexed: 12/18/2022] Open
Abstract
OBJECTIVE Although the cystine/glutamate antiporter System xc - (Sxc -) plays a permissive role in glioma-associated seizures, its contribution to other acquired epilepsies has not been determined. As such, the present study investigates whether and how Sxc - contributes to the pentylenetetrazole (PTZ) chemical kindling model of epileptogenesis. METHODS Male Sxc - null (sut/sut) mice and their wild-type littermates were administered PTZ (i.p.) daily for up to 21 days (kindling paradigm). Seizure severity was scored on a 5-point behavioral scale. Mossy fiber sprouting, cellular degeneration, and Sxc - light chain (xCT) messenger RNA (mRNA) were explored using Timm staining, thionin staining, and real-time quantitative polymerase chain reaction (qPCR), respectively. Levels of reduced and oxidized glutathione and cysteine were determined via high-performance liquid chromatography (HPLC). Plasma membrane protein levels of glutamate and γ-aminobutyric acid (GABA) receptor subunits as well as the K+/Cl- co-transporter KCC2 were quantified via western blot analysis. RESULTS Repeated administration of PTZ produced chemical kindling in only 50% of Sxc - null mice as compared to 82% of wild-type littermate control mice. Kindling did not result in any changes in xCT mRNA levels assessed in wild-type mice. No cellular degeneration or mossy fiber sprouting was discernible in either genotype. Except for a small, but significant, decrease in oxidized cysteine in the hippocampus, no other change in measured redox couples was determined in Sxc - null mice. Cortical levels of the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor subunit GluA1 were decreased in Sxc - null mice as compared to wild-type littermates, whereas all other proteins tested showed no difference between genotypes. SIGNIFICANCE This study provides the first evidence that Sxc - signaling contributes to epileptogenesis in the PTZ kindling model of acquired epilepsy. Further data indicate that a reduction in AMPA receptor signaling could underlie the resistance to PTZ kindling uncovered in Sxc - null mice.
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Affiliation(s)
- Sheila M. S. Sears
- Department of BiologyProgram in NeuroscienceSyracuse UniversitySyracuseNew York
| | - James A. Hewett
- Department of BiologyProgram in NeuroscienceSyracuse UniversitySyracuseNew York
| | - Sandra J. Hewett
- Department of BiologyProgram in NeuroscienceSyracuse UniversitySyracuseNew York
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8
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Ortega-Ferrusola C, Martin Muñoz P, Ortiz-Rodriguez JM, Anel-López L, Balao da Silva C, Álvarez M, de Paz P, Tapia JA, Anel L, Silva- Rodríguez A, Aitken RJ, Gil MC, Gibb Z, Peña FJ. Depletion of thiols leads to redox deregulation, production of 4-hydroxinonenal and sperm senescence: a possible role for GSH regulation in spermatozoa†. Biol Reprod 2018; 100:1090-1107. [DOI: 10.1093/biolre/ioy241] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2018] [Revised: 07/06/2018] [Accepted: 11/07/2018] [Indexed: 12/20/2022] Open
Affiliation(s)
| | - Patricia Martin Muñoz
- Laboratory of Equine Reproduction and Equine Spermatology, Veterinary Teaching Hospital, University of Extremadura, Cáceres, Spain
| | - Jose Manuel Ortiz-Rodriguez
- Laboratory of Equine Reproduction and Equine Spermatology, Veterinary Teaching Hospital, University of Extremadura, Cáceres, Spain
| | - Luis Anel-López
- Reproduction and Obstetrics Department of Animal Medicine and Surgery, University of León, Spain
| | | | - Mercedes Álvarez
- Reproduction and Obstetrics Department of Animal Medicine and Surgery, University of León, Spain
| | - Paulino de Paz
- Reproduction and Obstetrics Department of Animal Medicine and Surgery, University of León, Spain
| | - Jose Antonio Tapia
- Laboratory of Equine Reproduction and Equine Spermatology, Veterinary Teaching Hospital, University of Extremadura, Cáceres, Spain
| | - Luis Anel
- Reproduction and Obstetrics Department of Animal Medicine and Surgery, University of León, Spain
| | - Antonio Silva- Rodríguez
- Facility of Innovation and Analysis in Animal Source Foodstuffs, University of Extremadura, Cáceres, Spain
| | - Robert J Aitken
- Facility of Innovation and Analysis in Animal Source Foodstuffs, University of Extremadura, Cáceres, Spain
| | - M Cruz Gil
- Laboratory of Equine Reproduction and Equine Spermatology, Veterinary Teaching Hospital, University of Extremadura, Cáceres, Spain
| | - Zamira Gibb
- Priority Research Center in Reproductive Science, School of Environmental and Life Sciences, University of Newcastle, Callaghan, New South Wales, Australia
| | - Fernando J Peña
- Laboratory of Equine Reproduction and Equine Spermatology, Veterinary Teaching Hospital, University of Extremadura, Cáceres, Spain
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Lo M, Ling V, Wang YZ, Gout PW. The xc- cystine/glutamate antiporter: a mediator of pancreatic cancer growth with a role in drug resistance. Br J Cancer 2008; 99:464-72. [PMID: 18648370 PMCID: PMC2527809 DOI: 10.1038/sj.bjc.6604485] [Citation(s) in RCA: 149] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The xc− cystine transporter enhances biosynthesis of glutathione, a tripeptide thiol important in drug resistance and cellular defense against oxidative stress, by enabling cellular uptake of cystine, a rate-limiting precursor. Because it is known to regulate glutathione levels and growth of various cancer cell types, and is expressed in the pancreas, we postulate that it is involved in growth and drug resistance of pancreatic cancer. To examine this, we characterised expression of the xc− transporter in pancreatic cancer cell lines, MIA PaCa-2, PANC-1 and BxPC-3, as subjected to cystine-depletion and oxidative stress. The results indicate that these cell lines depend on xc−-mediated cystine uptake for growth, as well as survival in oxidative stress conditions, and can modulate xc− expression to accommodate growth needs. Immunohistochemical analysis showed that the transporter was differentially expressed in normal pancreatic tissues and overexpressed in pancreatic cancer tissues from two patients. Furthermore, gemcitabine resistance of cells was associated with elevated xc− expression and specific xc− inhibition by monosodium glutamate led to growth arrest. The results suggest that the xc− transporter by enhancing glutathione biosynthesis plays a major role in pancreatic cancer growth, therapy resistance and represents a potential therapeutic target for the disease.
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Affiliation(s)
- M Lo
- Department of Experimental Medicine, University of British Columbia, Vancouver, BC, Canada
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Numazawa S, Sakaguchi H, Aoki R, Taira T, Yoshida T. Regulation of the susceptibility to oxidative stress by cysteine availability in pancreatic beta-cells. Am J Physiol Cell Physiol 2008; 295:C468-74. [PMID: 18524943 DOI: 10.1152/ajpcell.00203.2008] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Pancreatic beta-cells are susceptible to oxidative stress, which is related closely to the islet dysfunction. In the present study, using the pancreatic cell lines HIT-T15 and RINm5F as known in vitro models of impaired beta-cell function as well as primary rat islet beta-cells, we observed a relationship between intracellular glutathione levels and oxidative stress-mediated cell dysfunction. Hydrogen peroxide and 4-hydroxy-2-nonenal caused cell death in HIT-T15 and RINm5F cells at lower concentrations compared with non-beta-cells, such as HepG2 and NRK-49F cells. The extent of the cytotoxicity caused by the model oxidants was inversely correlated well with intracellular glutathione levels in the cell lines used. Treatment of HIT-T15 and RINm5F cells with l-cysteine or l-cystine significantly augmented the glutathione contents, surpassing the effect of N-acetylcysteine, and abrogated 4-hydroxy-2-nonenal-mediated cytotoxicity almost completely. l-Cysteine increased intracellular glutathione levels in primary beta-cells as well. Supplementation of l-cysteine to the RINm5F cell culture inhibited 4-hydroxy-2-nonenal-mediated cytosolic translocation of PDX-1, a key transcription factor for beta-cell function. Intrinsic transport activities (V(max)/K(m)) of the l-cystine/l-glutamate exchanger in HIT-T15 and RINm5F cells were considerably lower than that in NRK-49F cells, although gene expressions of the exchanger were similar in these cells. Results obtained from the present study suggest that the restricted activity of the l-cystine/l-glutamate exchanger controls the levels of intracellular glutathione, thereby making beta-cells become susceptible to oxidative stress.
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Affiliation(s)
- Satoshi Numazawa
- Dept. of Biochemical Toxicology, School of Pharmaceutical Sciences, Showa Univ., 1-5-8 Hatanodai, Shinagawa, Tokyo 142-8555, Japan.
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11
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Lo M, Wang YZ, Gout PW. The x(c)- cystine/glutamate antiporter: a potential target for therapy of cancer and other diseases. J Cell Physiol 2008; 215:593-602. [PMID: 18181196 DOI: 10.1002/jcp.21366] [Citation(s) in RCA: 307] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The x(c) (-) cystine/glutamate antiporter is a major plasma membrane transporter for the cellular uptake of cystine in exchange for intracellular glutamate. Its main functions in the body are mediation of cellular cystine uptake for synthesis of glutathione essential for cellular protection from oxidative stress and maintenance of a cystine:cysteine redox balance in the extracellular compartment. In the past decade it has become evident that the x(c) (-) transporter plays an important role in various aspects of cancer, including: (i) growth and progression of cancers that have a critical growth requirement for extracellular cystine/cysteine, (ii) glutathione-based drug resistance, (iii) excitotoxicity due to excessive release of glutamate, and (iv) uptake of herpesvirus 8, a causative agent of Kaposi's sarcoma. The x(c) (-) transporter also plays a role in certain CNS and eye diseases. This review focuses on the expression and function of the x(c) (-) transporter in cells and tissues with particular emphasis on its role in disease pathogenesis. The potential use of x(c) (-) inhibitors (e.g., sulfasalazine) for arresting tumor growth and/or sensitizing cancers is discussed.
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Affiliation(s)
- Maisie Lo
- Department of Experimental Medicine, University of British Columbia, Vancouver, BC, Canada
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Lastro M, Kourtidis A, Farley K, Conklin DS. xCT expression reduces the early cell cycle requirement for calcium signaling. Cell Signal 2007; 20:390-9. [PMID: 18054200 DOI: 10.1016/j.cellsig.2007.10.030] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2007] [Accepted: 10/30/2007] [Indexed: 12/24/2022]
Abstract
Calcium has long been recognized as an important regulator of cell cycle transitions although the mechanisms are largely unknown. A functional genomic screen has identified genes involved in the regulation of early cell cycle progression by calcium. These genes when overexpressed confer the ability to bypass the G1/S arrest induced by Ca(2+)-channel antagonists in mouse fibroblasts. Overexpression of the cystine-glutamate exchanger, xCT, had the greatest ability to evade calcium antagonist-induced cell cycle arrest. xCT carries out the rate limiting step of glutathione synthesis in many cell types and is responsible for the uptake of cystine in most human cancer cell lines. Functional analysis indicates that the cystine uptake activity of xCT overcomes the G1/S arrest induced by Ca(2+)-channel antagonists by bypassing the requirement for calcium signaling. Since cells overexpressing xCT were found to have increased levels and activity of the AP-1 transcription factor in G1, redox stimulation of AP-1 activity accounts for the observed growth of these cells in the presence of calcium channel antagonists. These results suggest that reduced calcium signaling impairs AP-1 activation and that xCT expression may directly affect cell proliferation.
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Affiliation(s)
- Michele Lastro
- Department of Biomedical Sciences, Gen*NY*Sis Center for Excellence in Cancer Genomics, University at Albany, State University of New York, Room 210, One Discovery Drive, Rensselaer, NY 12144-3456, United States
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13
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Kitiphongspattana K, Khan TA, Ishii-Schrade K, Roe MW, Philipson LH, Gaskins HR. Protective role for nitric oxide during the endoplasmic reticulum stress response in pancreatic beta-cells. Am J Physiol Endocrinol Metab 2007; 292:E1543-54. [PMID: 17264231 DOI: 10.1152/ajpendo.00620.2006] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Higher requirements for disulfide bond formation in professional secretory cells may affect intracellular redox homeostasis, particularly during an endoplasmic reticulum (ER) stress response. To assess this hypothesis, we investigated the effects of the ER stress response on the major redox couple (GSH/GSSG), endogenous ROS production, expression of genes involved in ER oxidative protein folding, general antioxidant defense, and thiol metabolism by use of the well-validated MIN6 beta-cell as a model and mouse islets. The data revealed that glucose concentration-dependent decreases in the GSH/GSSG ratio were further decreased significantly by ER-derived oxidative stress induced by inhibiting ER-associated degradation with the specific proteasome inhibitor lactacystin (10 microM) in mouse islets. Notably, minimal cell death was observed during 12-h treatments. This was likely attributed to the upregulation of genes encoding the rate limiting enzyme for glutathione synthesis (gamma-glutamylcysteine ligase), as well as genes involved in antioxidant defense (glutathione peroxidase, peroxiredoxin-1) and ER protein folding (Grp78/BiP, PDI, Ero1). Gene expression and reporter assays with a NO synthase inhibitor (Nomega-nitro-L-arginine methyl ester, 1-10 mM) indicated that endogenous NO production was essential for the upregulation of several ER stress-responsive genes. Specifically, gel shift analyses demonstrate NO-independent binding of the transcription factor NF-E2-related factor to the antioxidant response element Gclc-ARE4 in MIN6 cells. However, endogenous NO production was necessary for activation of Gclc-ARE4-driven reporter gene expression. Together, these data reveal a distinct protective role for NO during the ER stress response, which helps to dissipate ROS and promote beta-cell survival.
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14
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Weber H, Hühns S, Jonas L, Sparmann G, Bastian M, Schuff-Werner P. Hydrogen peroxide-induced activation of defense mechanisms against oxidative stress in rat pancreatic acinar AR42J cells. Free Radic Biol Med 2007; 42:830-41. [PMID: 17320765 DOI: 10.1016/j.freeradbiomed.2006.12.019] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/05/2006] [Revised: 12/08/2006] [Accepted: 12/15/2006] [Indexed: 01/04/2023]
Abstract
Oxidative stress has been implicated in the pathogenesis of acute pancreatitis. Generally, cells respond to oxidative stress with adaptive changes in gene expression aimed at preventing cellular damage and increasing their survival. However, the overall extent of these genetic changes remains poorly defined. This issue was, therefore, examined in the current study. Following exposure of rat pancreatic AR42J cells to 0.08 mM hydrogen peroxide (H(2)O(2)), a concentration failing to induce necrotic cell death, the expression of 96 stress-related genes was monitored by cDNA microarray analysis. H(2)O(2) provoked a time-dependent reorientation of 54 genes. In particular, at 6 and 24 h, 27 and 11 genes were induced, whereas 10 and 6 genes were suppressed, respectively, showing that the degree of change was stronger at the early time point, and that the number of up-regulated genes was obviously larger than the number of down-regulated genes. Reverse transcription-PCR for selected genes confirmed the gene expression pattern. Many of the differentially up-regulated genes can be related to the antioxidant enzymatic defense system, to cell cycle arrest, to repair and/or replacement of damaged DNA, to repair of damaged protein, and to activation of the NF-kappaB pathway. The results suggest that AR42J cells respond to sublethal oxidative stress with transient transcriptional activation of multiple defense mechanisms that may be an indication for a complex adaptation process. An understanding of the cellular stress responses may lead to new insights into the pathogenesis of oxidative stress-related diseases including acute pancreatitis.
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Affiliation(s)
- Heike Weber
- Institute of Clinical Chemistry and Laboratory Medicine, University of Rostock, Ernst-Heydemann-Strasse 6, 18057 Rostock, Germany.
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15
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Narang VS, Pauletti GM, Gout PW, Buckley DJ, Buckley AR. Sulfasalazine-induced reduction of glutathione levels in breast cancer cells: enhancement of growth-inhibitory activity of Doxorubicin. Chemotherapy 2007; 53:210-7. [PMID: 17356269 DOI: 10.1159/000100812] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2005] [Accepted: 02/28/2006] [Indexed: 11/19/2022]
Abstract
BACKGROUND We previously showed that the anti-inflammatory drug, sulfasalazine (salicylazosulfapyridine, SASP), can arrest proliferation of MCF-7 and MDA-MB-231 mammary cancer cells by inhibiting uptake of cystine via the x(c-) cystine/glutamate antiporter. Here we examined SASP with regard to reduction of cellular glutathione (GSH) levels and drug efficacy-enhancing ability. METHODS GSH levels were measured spectrophotometrically. Cellular drug retention was determined with 3H-labeled methotrexate, and drug efficacy with a colony formation assay. RESULTS Incubation of the mammary cancer cells with SASP (0.3-0.5 mM) led to reduction of their GSH content in a time- and concentration-dependent manner. Similar to MK-571, a multidrug resistance-associated protein inhibitor, SASP increased intracellular accumulation of methotrexate. Preincubation of cells with SASP (0.3 mM) significantly enhanced the potency of the anticancer agent doxorubicin (2.5 nM). CONCLUSIONS SASP-induced reduction of cellular GSH levels can lead to growth arrest of mammary cancer cells and enhancement of anticancer drug efficacy.
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Affiliation(s)
- Vishal S Narang
- College of Pharmacy, University of Cincinnati, Cincinnati, Ohio, USA
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16
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Guérin PJ, Furtak T, Eng K, Gauthier ER. Oxidative stress is not required for the induction of apoptosis upon glutamine starvation of Sp2/0-Ag14 hybridoma cells. Eur J Cell Biol 2006; 85:355-65. [PMID: 16412532 DOI: 10.1016/j.ejcb.2005.11.004] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2005] [Revised: 11/17/2005] [Accepted: 11/20/2005] [Indexed: 11/24/2022] Open
Abstract
L-glutamine (Gln) withdrawal rapidly triggers apoptosis in the murine hybridoma cell line Sp2/0-Ag14 (Sp2/0). In this report, we examined the possibility that Gln deprivation of Sp2/0 cells triggers an oxidative stress which would contribute to the activation of apoptotic pathways. Gln withdrawal triggered an oxidative stress in Sp2/0 cells, as indicated by an increased accumulation of reactive oxygen species (ROS) and an increase in the intracellular content in protein carbonyl groups. Gln starvation also caused a decrease in the intracellular levels of glutathione (GSH). However, a decrease in GSH was not sufficient to induce Sp2/0 cell death since reducing GSH levels with DL-buthionine-[S,R]-sulfoximine did not affect cell viability. The antioxidant N-acetyl-L-cysteine (NAC), while effective in inhibiting ROS accumulation and oxidative stress, did not prevent the loss in cell viability or the processing and activation of caspase-3 triggered by Gln starvation. On the other hand, NAC did reduce the formation of apoptotic bodies in dying cells. Altogether these results indicate that in Sp2/0 cells, Gln deprivation leads to the induction of an oxidative stress which, while involved in the formation of apoptotic bodies, is not essential to the activation of the cell death program.
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Affiliation(s)
- Paul J Guérin
- Department of Chemistry and Biochemistry, Laurentian University, 935 Ramsey Lake Road, Sudbury, Ont., Canada P3E 2C6
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17
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Bridges CC, Zalups RK. Cystine and glutamate transport in renal epithelial cells transfected with human system x(-) (c). Kidney Int 2005; 68:653-64. [PMID: 16014042 PMCID: PMC2409290 DOI: 10.1111/j.1523-1755.2005.00443.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
BACKGROUND System x(-) (c) is a heterodimeric transporter, comprised of a light chain, xCT, and heavy chain, 4F2hc, which mediates the sodium-independent exchange of cystine and glutamate at the plasma membrane. In the current study we tested the hypothesis that stable transfection of Madin-Darby canine kidney (MDCK) cells with human xCT and 4F2hc results in the expression of functional system x(-) (c). METHODS MDCK cells were transfected stably with human clones for xCT and 4F2hc. Analyses of time- and temperature-dependence, saturation kinetics, and substrate specificity of l-cystine and l-glutamate transport were carried out in control and xCT-4F2hc-transfected MDCK cells. We also measured the uptake of l-cystine in Xenopus oocytes expressing human xCT and/or 4F2hc or xCT and/or rBAT (a heavy chain homologous to 4F2hc). RESULTS All of the different sets of data revealed that transport of l-cystine and l-glutamate increased significantly (twofold to threefold) in the MDCK cells subsequent to transfection with xCT-4F2hc. Moreover, uptake of l-cystine also increased (about tenfold) in Xenopus oocytes expressing hxCT and h4F2hc. Biochemical analyses of l-cystine uptake in oocytes verified our findings in the transfected MDCK cells. Interestingly, in oocytes injected with rBAT with or without xCT, uptake of l-cystine was significantly greater than that in water-injected oocytes. CONCLUSION Our findings indicate that stable transfection of MDCK cells with xCT and 4F2hc results in a cell-line expressing a functional system x(-) (c) transporter that can utilize l-cystine and l-glutamate as substrates. This study apparently represents the first stable transfection of a mammalian cell line with system x(-) (c).
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Affiliation(s)
- Christy C Bridges
- Division of Basic Medical Sciences, Mercer University School of Medicine, Macon, Georgia 31207, USA
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18
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Abstract
Vitamin E is essential for normal neurological function. It is the major lipid-soluble, chain-breaking antioxidant in the body, protecting the integrity of membranes by inhibiting lipid peroxidation. Mostly on the basis of symptoms of primary vitamin E deficiency, it has been demonstrated that vitamin E has a central role in maintaining neurological structure and function. Orally supplemented vitamin E reaches the cerebrospinal fluid and brain. Vitamin E is a generic term for all tocopherols and their derivatives having the biological activity of RRR-alpha-tocopherol, the naturally occurring stereoisomer compounds with vitamin E activity. In nature, eight substances have been found to have vitamin E activity: alpha-, beta-, gamma- and delta-tocopherol; and alpha-, beta-, gamma- and delta-tocotrienol. Often, the term vitamin E is synonymously used with alpha-tocopherol. Tocotrienols, formerly known as zeta, , or eta-tocopherols, are similar to tocopherols except that they have an isoprenoid tail with three unsaturation points instead of a saturated phytyl tail. Although tocopherols are predominantly found in corn, soybean, and olive oils, tocotrienols are particularly rich in palm, rice bran, and barley oils. Tocotrienols possess powerful antioxidant, anticancer, and cholesterol-lowering properties. Recently, we have observed that alpha-tocotrienol is multi-fold more potent than alpha-tocopherol in protecting HT4 and primary neuronal cells against toxicity induced by glutamate as well as by a number of other toxins. At nanomolar concentration, tocotrienol, but not tocopherol, completely protected neurons by an antioxidant-independent mechanism. Our current work identifies two major targets of tocotrienol in the neuron: c-Src kinase and 12-lipoxygenase. Dietary supplementation studies have established that tocotrienol, fed orally, does reach the brain. The current findings point towards tocotrienol as a potent neuroprotective form of natural vitamin E.
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Affiliation(s)
- Chandan K Sen
- Davis Heart & Lung Research Institute, 473 West 12th Avenue, The Ohio State University Medical Center, Columbus, Ohio 43210, USA.
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19
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Yoshida F, Matsumura A, Yamamoto T, Kumada H, Nakai K. Enhancement of sodium borocaptate (BSH) uptake by tumor cells induced by glutathione depletion and its radiobiological effect. Cancer Lett 2004; 215:61-7. [PMID: 15374633 DOI: 10.1016/j.canlet.2004.06.023] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2004] [Revised: 06/10/2004] [Accepted: 06/14/2004] [Indexed: 11/18/2022]
Abstract
Sodium borocaptate (BSH) is widely used for boron neutron capture therapy (BNCT) of brain tumors. However, the mechanism of uptake by the tumor remains unclear. We investigated the sulfhydryl moiety of this compound. Down regulation of glutathione (GSH) by buthionine sulfoximine in cultured cells resulted in increase of BSH uptake (7.9-36.5%) compared to the control group and consequently the cytocidal effect of neutron irradiation also increased. On the other hand, the radiation caused damage by gamma-ray irradiation was suppressed when BSH uptake increased. These findings suggested that modulation of GSH enhanced the effect of B (n, alpha) reaction and the protective effect of secondary gamma-ray in BNCT.
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Affiliation(s)
- Fumiyo Yoshida
- University of Tsukuba, Graduate School of Comprehensive Human Sciences, Functional and Regulatory Medical Sciences, Tennodai 1-1-1, Tsukuba, Ibaraki 305-8575, Japan.
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20
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Baker DA, McFarland K, Lake RW, Shen H, Tang XC, Toda S, Kalivas PW. Neuroadaptations in cystine-glutamate exchange underlie cocaine relapse. Nat Neurosci 2003; 6:743-9. [PMID: 12778052 DOI: 10.1038/nn1069] [Citation(s) in RCA: 543] [Impact Index Per Article: 25.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2003] [Accepted: 04/11/2003] [Indexed: 11/08/2022]
Abstract
Repeated cocaine treatment and withdrawal produces changes in brain function thought to be involved in relapse to drug use. Withdrawal from repeated cocaine reduced in vivo extracellular glutamate in the nucleus accumbens of rats by decreasing the exchange of extracellular cystine for intracellular glutamate. In vivo restoration of cystine/glutamate exchange by intracranial perfusion of cystine or systemically administered N-acetylcysteine normalized the levels of glutamate in cocaine-treated subjects. To determine if the reduction in nonvesicular glutamate release is a mediator of relapse, we examined cocaine-primed reinstatement of drug seeking after cocaine self-administration was stopped. Reinstatement was prevented by stimulating cystine/glutamate exchange with N-acetylcysteine and restoring extracellular glutamate. Thus, withdrawal from repeated cocaine increases susceptibility to relapse in part by reducing cystine/glutamate exchange, and restoring exchanger activity prevents cocaine-primed drug seeking.
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Affiliation(s)
- David A Baker
- Department of Physiology and Neuroscience, Medical University of South Carolina, Charleston, South Carolina 29425, USA
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21
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Ruiz E, Siow RCM, Bartlett SR, Jenner AM, Sato H, Bannai S, Mann GE. Vitamin C inhibits diethylmaleate-induced L-cystine transport in human vascular smooth muscle cells. Free Radic Biol Med 2003; 34:103-10. [PMID: 12498985 DOI: 10.1016/s0891-5849(02)01192-9] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Adaptive increases in intracellular glutathione (GSH) in response to oxidative stress are mediated by induction of L-cystine uptake via the anionic amino acid transport system x(c)(-). The recently cloned transporter xCT forms a heteromultimeric complex with the heavy chain of 4F2 cell surface antigen (4F2hc/CD98). Depletion of GSH by the electrophile diethylmaleate (DEM) induces the activity and expression of xCT in peritoneal macrophages. We here examine the effects of vitamin C on induction of xCT by DEM in human umbilical artery smooth muscle cells. DEM caused time- (3-24 h) and concentration- (25-100 microM) dependent increases in L-cystine transport, with GSH depleted by 50% after 6 h and restored to basal values after 24 h. xCT mRNA levels increased after 4 h DEM treatment with negligible changes detected for 4F2hc mRNA. DEM caused a rapid (5-30 min) phosphorylation of p38(MAPK). Inhibition of p38(MAPK) by SB203580 (10 microM) enhanced DEM-induced increases in L-cystine transport and GSH, whereas inhibition of p42/p44(MAPK) (PD98059, 10 microM) had no effect. Pretreatment of cells with vitamin C (100 microM, 24 h) attenuated DEM-induced adaptive increases in L-cystine transport and GSH levels. Inhibition of p38(MAPK), but not p42/p44(MAPK), reduced the cytoprotective action of vitamin C. Our findings suggest that DEM induces activation of xCT via intracellular signaling pathways involving p38(MAPK), and that vitamin C, in addition to its antioxidant properties, may modulate this signaling pathway to protect smooth muscle cells from injury.
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Affiliation(s)
- Emilio Ruiz
- Centre for Cardiovascular Biology and Medicine, GKT School of Biomedical Sciences, King's College, University of London, London, UK
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22
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Catherwood MA, Powell LA, Anderson P, McMaster D, Sharpe PC, Trimble ER. Glucose-induced oxidative stress in mesangial cells. Kidney Int 2002; 61:599-608. [PMID: 11849402 DOI: 10.1046/j.1523-1755.2002.00168.x] [Citation(s) in RCA: 134] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
BACKGROUND Hyperglycemia is a well-recognized pathogenic factor of long-term complications in diabetes mellitus. Hyperglycemia not only generates reactive oxygen species but also attenuates antioxidant mechanisms creating a state of oxidative stress. METHODS Porcine mesangial cells were cultured in high glucose (HG) for ten days to investigate the effects on the antioxidant defenses of the cell. RESULTS Mesangial cells cultured in HG conditions had significantly reduced levels of glutathione (GSH) compared with those grown in normal glucose (NG). The reduced GSH levels were accompanied by decreased gene expression of both subunits of gamma-glutamylcysteine synthetase (gamma-GCS), the rate-limiting enzyme in de novo synthesis of GSH. Elevated levels of intracellular malondialdehyde (MDA) were found in cells exposed to HG conditions. HG also caused elevated mRNA levels of the antioxidant enzymes CuZn superoxide dismutase (SOD) and MnSOD. These changes were accompanied by increased mRNA levels of extracellular matrix proteins (ECM), fibronectin (FN) and collagen IV (CIV). Addition of antioxidants to high glucose caused a significant reversal of FN and CIV gene expression; alpha-lipoic acid also up-regulated gamma-GCS gene expression and restored intracellular GSH and MDA levels. CONCLUSIONS The results demonstrate the existence of glucose-induced oxidative stress in mesangial cells as evidenced by elevated MDA and decreased GSH levels. The decreased levels of GSH are as a result of decreased mRNA expression of gamma-GCS within the cell. Antioxidants caused a significant reversal of FN and CIV gene expression, suggesting an etiological link between oxidative stress and increased ECM protein synthesis.
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Affiliation(s)
- Mark A Catherwood
- Department of Clinical Biochemistry, Queen's University of Belfast, Royal Group of Hospitals, Belfast, United Kingdom.
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Powell LA, Nally SM, McMaster D, Catherwood MA, Trimble ER. Restoration of glutathione levels in vascular smooth muscle cells exposed to high glucose conditions. Free Radic Biol Med 2001; 31:1149-55. [PMID: 11705692 DOI: 10.1016/s0891-5849(01)00648-7] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Hyperglycemia-induced oxidative stress may play a key role in the pathogenesis of diabetic vascular disease. The purpose of this study was to determine the effects of glucose on levels of glutathione (a major intracellular antioxidant), the expression of gamma-glutamylcysteine synthetase (the rate-limiting enzyme in glutathione de novo synthesis), and DNA damage in human vascular smooth muscle cells in vitro. High glucose conditions and buthionine sulphoximine, an inhibitor of gamma-glutamylcysteine synthetase, reduced intracellular glutathione levels in vascular smooth muscle cells. This reduction was accompanied by a decrease in the mRNA expression of both subunits of gamma-glutamylcysteine synthetase as well as an increase in DNA damage. In high glucose conditions, incubation of the vascular smooth muscle cells with alpha-lipoic acid and L-cystine restored glutathione levels. We suggest that the decrease in GSH levels seen in high glucose conditions is mediated by the availability of cysteine (rate-limiting substrate in de novo glutathione synthesis) and the gene expression of the gamma-glutamylcysteine synthetase enzyme. Glutathione depletion is associated with an increase in DNA damage, which can be reduced when glutathione levels are restored.
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Affiliation(s)
- L A Powell
- Department of Clinical Biochemistry, The Royal Group of Hospitals, Belfast, UK.
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24
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Wagner CA, Lang F, Bröer S. Function and structure of heterodimeric amino acid transporters. Am J Physiol Cell Physiol 2001; 281:C1077-93. [PMID: 11546643 DOI: 10.1152/ajpcell.2001.281.4.c1077] [Citation(s) in RCA: 255] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Heterodimeric amino acid transporters are comprised of two subunits, a polytopic membrane protein (light chain) and an associated type II membrane protein (heavy chain). The heavy chain rbAT (related to b(0,+) amino acid transporter) associates with the light chain b(0,+)AT (b(0,+) amino acid transporter) to form the amino acid transport system b(0,+), whereas the homologous heavy chain 4F2hc interacts with several light chains to form system L (with LAT1 and LAT2), system y(+)L (with y(+)LAT1 and y(+)LAT2), system x (with xAT), or system asc (with asc1). The association of light chains with the two heavy chains is not unambiguous. rbAT may interact with LAT2 and y(+)LAT1 and vice versa; 4F2hc may interact with b(0,+)AT when overexpressed. 4F2hc is necessary for trafficking of the light chain to the plasma membrane, whereas the light chains are thought to determine the transport characteristics of the respective heterodimer. In contrast to 4F2hc, mutations in rbAT suggest that rbAT itself takes part in the transport besides serving for the trafficking of the light chain to the cell surface. Heavy and light subunits are linked together by a disulfide bridge. The disulfide bridge, however, is not necessary for the trafficking of rbAT or 4F2 heterodimers to the membrane or for the functioning of the transporter. However, there is experimental evidence that the disulfide bridge in the 4F2hc/LAT1 heterodimer plays a role in the regulation of a cation channel. These results highlight complex interactions between the different subunits of heterodimeric amino acid transporters and suggest that despite high grades of homology, the interactions between rbAT and 4F2hc and their respective partners may be different.
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Affiliation(s)
- C A Wagner
- Department of Cellular and Molecular Physiology, School of Medicine, Yale University, New Haven, Connecticut 06520, USA.
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25
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Kimura M, Goto S, Ihara Y, Wada A, Yahiro K, Niidome T, Aoyagi H, Hirayama T, Kondo T. Impairment of glutathione metabolism in human gastric epithelial cells treated with vacuolating cytotoxin from Helicobacter pylori. Microb Pathog 2001; 31:29-36. [PMID: 11427034 DOI: 10.1006/mpat.2001.0446] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Helicobacter pylori vacuolating cytotoxin (VacA) is believed to be one of the factors that induces gastric disease. Our previous study indicated that VacA causes a decrease in the intracellular ATP level in human gastric epithelial cells, suggesting to impair mitochondrial membrane potential followed by a decrease in energy metabolism (Kimura et al., Microb. Pathog., 1999, 26: 45--52). In the present study, we investigated whether the decrease in ATP level affects glutathione metabolism, in which its synthesis and efflux are ATP-dependent. Treatment of AZ-521 human gastric epithelial cells with 120 nM VacA for 6 h suppressed the efflux of oxidized glutathione (GSSG) in a dose- and time-dependent manner. The efflux of GSSG from the cells and glutathione (GSH) synthesis of cells treated with VacA were approximately 50 and 70% of those of the control, respectively. The turnover rate of intracellular GSH was also suppressed by VacA. Viability of the cells pretreated with VacA, then further incubated with H(2)O(2), was decreased by 50% at 6 h and 70% at 12 h. These results suggested that VacA impairs GSH metabolism in the gastric epithelial cells, which weakens the resistance of the cells against oxidative stress or cellular redox regulation by GSH.
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Affiliation(s)
- M Kimura
- Department of Applied Chemistry, Faculty of Engineering, Nagasaki University, Nagasaki 852-8521, Japan
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26
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Gochenauer GE, Robinson MB. Dibutyryl-cAMP (dbcAMP) up-regulates astrocytic chloride-dependent L-[3H]glutamate transport and expression of both system xc(-) subunits. J Neurochem 2001; 78:276-86. [PMID: 11461963 DOI: 10.1046/j.1471-4159.2001.00385.x] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Recent studies have shown that N(6),2'-O-dibutyryladenosine 3':5' cyclic monophosphate (dbcAMP) increases the expression of specific subtypes of Na(+)-dependent glutamate transporters in cultured astrocytes. Our group also found that treatment of astrocytes with dbcAMP for several days increases the Na(+)-independent accumulation of L-[3H]glutamate. In this study, the properties of this Na(+)-independent accumulation were characterized, and the mechanism by which dbcAMP up-regulates this process was investigated. This accumulation was markedly reduced in the absence of Cl(-) and was also inhibited by several anion-exchange inhibitors, including 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid, 4,4'-dinitrostilbene-2,2'-disulfonic acid and 4-acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic acid, suggesting that this activity is mediated by a Cl(-)-dependent transporter. In addition, this activity was inhibited by micromolar concentrations of several inhibitors of another Cl(-)-dependent (Na(+)-independent) transport activity frequently referred to as system xc(-) (L-cystine, L-alpha-aminoadipate, L-homocysteate, quisqualate, beta-N-oxalyl-l-alpha,beta-diaminopropionate, ibotenate). This activity was competitively inhibited by several phenylglycine derivatives previously characterized as inhibitors of metabotropic glutamate receptor activation. The concentration-dependence for Na(+)-independent, Cl(-)-dependent L-[3H]glutamate uptake activity was compared for dbcAMP-treated and untreated astrocytes. Treatment with dbcAMP increased the V(max) of this Cl(-)-dependent transport activity by sixfold but had no effect on the K(m) value. System xc(-) requires two subunits, xCT and 4F2hc/CD98, to reconstitute functional activity. We found that dbcAMP caused a twofold increase in the levels of xCT mRNA and a sevenfold increase in the levels of 4F2hc/CD98 protein. This study indicates that dbcAMP up-regulates Cl(-)-dependent L-[3H]glutamate transport activity in astrocytes and suggests that this effect is related to increased expression of both subunits of system xc(-). Because this activity is thought to be important for the synthesis of glutathione and protection from oxidant injury, understanding the regulation of system xc(-) may provide alternate approaches to limit this form of injury.
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Affiliation(s)
- G E Gochenauer
- Departments of Pediatrics and Pharmacology, Children's Hospital of Philadelphia, University of Pennsylvania, Philadelphia, Pennsylvania, USA
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Shih AY, Murphy TH. xCt cystine transporter expression in HEK293 cells: pharmacology and localization. Biochem Biophys Res Commun 2001; 282:1132-7. [PMID: 11302733 DOI: 10.1006/bbrc.2001.4703] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
xCT, the core subunit of the system x(c)(-) high affinity cystine transporter, belongs to a superfamily of glycoprotein-associated amino acid transporters. Although xCT was shown to promote cystine transport in Xenopus oocytes, little work has been done with mammalian cells (Sato, H., Tamba, M., Ishii, T., and Bannai, S. J. Biol. Chem. 274, 11455-11458, 1999). Therefore, we have constructed mammalian expression vectors for murine xCT and its accessory subunit 4F2hc and transfected them into HEK293 cells. We report that this transporter binds cystine with high affinity (81 microM) and displays a pharmacological profile expected for system x(c)(-). Surprisingly, xCT transport activity in HEK293 cells is not dependent on the co-expression of the exogenous 4F2hc. Expression of GFP-tagged xCT indicated a highly clustered plasma membrane and intracellular distribution suggesting the presence of subcellular domains associated with combating oxidative stress. Our results indicate that HEK293 cells transfected with the xCT subunit would be a useful vehicle for future structure-function and pharmacology experiments involving system x(c)(-).
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Affiliation(s)
- A Y Shih
- Department of Psychiatry, University of British Columbia, 4N1-2255 Wesbrook Mall, Vancouver, British Columbia, V6T 1Z3, Canada.
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Allen JW, Shanker G, Aschner M. Methylmercury inhibits the in vitro uptake of the glutathione precursor, cystine, in astrocytes, but not in neurons. Brain Res 2001; 894:131-40. [PMID: 11245823 DOI: 10.1016/s0006-8993(01)01988-6] [Citation(s) in RCA: 87] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Maintenance of adequate intracellular glutathione (GSH) levels is vital for intracellular defense against oxidative damage. The toxic effects of methylmercury (MeHg) are attributable, at least in part, to elevated levels of reactive oxygen species, and thus decreases in GSH synthesis may increase methylmercury toxicity. Astrocytes have recently been proposed to play an essential role in providing GSH precursors to neurons. Therefore, cystine transport, a prerequisite to GSH production, was characterized in cultured astrocytes and neurons, and the effects of methylmercury on this transport were assessed. Astrocytes and neurons both possessed temperature dependent transport systems for cystine. Astrocytes accumulated cystine by Na+-independent (X(C)-) and -dependent (X(AG)-) systems while neurons used exclusively Na+-independent systems. Inhibition of the X(AG)- transport system decreased cystine transport in astrocytes to levels equivalent to those in sodium-depleted conditions, suggesting that cystine is carried by a glutamate/aspartate transporter in astrocytes. Inhibition of the multifunction ectoenzyme/amino acid transporter gamma-glutamyltranspeptidase (GGT) decreased cystine transport in both neurons and astrocytes. Inhibition of System X(C)- with quisqualate also decreased cystine uptake in both astrocytes and neurons. These data demonstrate that cultured astrocytes accumulate cystine via three independent mechanisms, System X(AG)-, System X(C)-, and GGT, while cultured hippocampal neurons use System X(C)- and GGT exclusively. Inhibition of cystine uptake in astrocytes by methylmercury appears to be due to actions on the System X(AG)- transporter.
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Affiliation(s)
- J W Allen
- Department of Physiology and Pharmacology, Wake Forest University, School of Medicine Medical Center Blvd, Winston-Salem, NC 27157-1083, USA
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Seres T, Knickelbein RG, Warshaw JB, Johnston RB. The phagocytosis-associated respiratory burst in human monocytes is associated with increased uptake of glutathione. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2000; 165:3333-40. [PMID: 10975851 DOI: 10.4049/jimmunol.165.6.3333] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
During the phagocytic respiratory burst, oxygen is converted to potent cytotoxic oxidants. Monocytes and macrophages are potentially long-lived, and we have hypothesized that protective mechanisms against oxidant stress are varied and fully expressed in these cells. We report here that the respiratory burst in monocytes is accompanied by an increase in the uptake of [35S]glutathione ([35S]GSH) after 20-30 min to levels up to 10-fold greater than those at baseline. By 30 min, 49% of the cell-associated radioactivity was in the cytosol, 41% was in membrane, and 10% was associated with the nuclear fraction. GSH uptake was inhibited by catalase, which removes hydrogen peroxide (H2O2), and micromolar H2O2 stimulated GSH uptake effectively in monocytes and also lymphocytes. Oxidation of GSH to glutathione disulfide with H2O2 and glutathione peroxidase prevented uptake. Acivicin, which inhibits GSH breakdown by gamma-glutamyl transpeptidase (GGT), had no effect on the enhanced uptake seen during the respiratory burst. Uptake of cysteine or cystine, possible products of GGT activity, stayed the same or decreased during the respiratory burst. These results suggest that a GGT-independent mechanism is responsible for the enhanced GSH uptake seen during the respiratory burst. We describe here a sodium-independent, methionine-inhibitable transport system with a Km (8.5 microM) for GSH approximating the plasma GSH concentration. These results suggest that monocytes have a specific GSH transporter that is triggered by the release of H2O2 during the respiratory burst and that induces the uptake of GSH into the cell. Such a mechanism has the potential to protect the phagocyte against oxidant damage.
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Affiliation(s)
- T Seres
- Department of Pediatrics, Yale University School of Medicine, New Haven, CT 06520, USA
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Compromised glutamate transport in human glioma cells: reduction-mislocalization of sodium-dependent glutamate transporters and enhanced activity of cystine-glutamate exchange. J Neurosci 2000. [PMID: 10594060 DOI: 10.1523/jneurosci.19-24-10767.1999] [Citation(s) in RCA: 240] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Elevated levels of extracellular glutamate ([Glu](o)) can induce seizures and cause excitotoxic neuronal cell death. This is normally prevented by astrocytic glutamate uptake. Neoplastic transformation of human astrocytes causes malignant gliomas, which are often associated with seizures and neuronal necrosis. Here, we show that Na(+)-dependent glutamate uptake in glioma cell lines derived from human tumors (STTG-1, D-54MG, D-65MG, U-373MG, U-251MG, U-138MG, and CH-235MG) is up to 100-fold lower than in astrocytes. Immunohistochemistry and subcellular fractionation show very low expression levels of the astrocytic glutamate transporter GLT-1 but normal expression levels of another glial glutamate transporter, GLAST. However, in glioma cells, essentially all GLAST protein was found in cell nuclei rather than the plasma membrane. Similarly, brain tissues from glioblastoma patients also display reduction of GLT-1 and mislocalization of GLAST. In glioma cell lines, over 50% of glutamate transport was Na(+)-independent and mediated by a cystine-glutamate exchanger (system x(c)(-)). Extracellular L-cystine dose-dependently induced glutamate release from glioma cells. Glutamate release was enhanced by extracellular glutamine and inhibited by (S)-4-carboxyphenylglycine, which blocked cystine-glutamate exchange. These data suggest that the unusual release of glutamate from glioma cells is caused by reduction-mislocalization of Na(+)-dependent glutamate transporters in conjunction with upregulation of cystine-glutamate exchange. The resulting glutamate release from glioma cells may contribute to tumor-associated necrosis and possibly to seizures in peritumoral brain tissue.
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Sasada T, Nakamura H, Ueda S, Iwata S, Ueno M, Takabayashi A, Yodoi J. Secretion of thioredoxin enhances cellular resistance to cis-diamminedichloroplatinum (II). Antioxid Redox Signal 2000; 2:695-705. [PMID: 11213475 DOI: 10.1089/ars.2000.2.4-695] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Thioredoxin (TRX) is a redox-active protein induced by a variety of stress and secreted from cells. Collecting evidence revealed that extracellular TRX shows cytokine- and chemokine-like activities. In the present study, we studied the role of secreted TRX on cellular resistance to cis-diamminedichloroplatinum (II) (CDDP). The CDDP-resistant variants of HeLa cells not only have enhanced expression of intracellular TRX, but also show increased secretion of TRX into the culture medium, compared to the parental cells. The CDDP-resistant cells also exhibit an enhanced L-cystine uptake capability, which results in a significant increase in the intracellular sulfhydryl content, including glutathione (GSH). Exogenous administration of recombinant TRX (rTRX) increases cellular resistance to CDDP and augments the L-cystine uptake in the parental HeLa cells. Moreover, depletion of L-cystine from the culture medium or combined treatment with L-cystine uptake inhibitors increases cellular sensitivity to CDDP in the CDDP-resistant cells. These findings suggest that secreted TRX may play an important role in the acquisition of cellular CDDP resistance through enhancement of the L-cystine uptake activity, and that the L-cystine transport system, as well as the TRX system, may be a novel therapeutic target in CDDP-resistant cancer cells.
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Affiliation(s)
- T Sasada
- Department of Biological Responses, Institute for Virus Research, Kyoto University, Kyoto 606-8507, Japan
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