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Veltman K, Harris C, Ahmad Y, Jolliet O. A mechanistic model for thiol redox dynamics in the organogenesis stage rat conceptus. Reprod Toxicol 2018; 82:38-49. [PMID: 30292673 PMCID: PMC9999374 DOI: 10.1016/j.reprotox.2018.09.005] [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: 04/27/2018] [Revised: 08/07/2018] [Accepted: 09/19/2018] [Indexed: 11/17/2022]
Abstract
Precise control of the glutathione/glutathione disulfide (GSH/GSSG) redox balance is vital for the developing embryo, but regulatory mechanisms are poorly understood. We developed a novel, mechanistic mass-balance model for GSH metabolism in the organogenesis stage (gestational day 10.0-11.13) rat conceptus predicting the dynamics of 8 unique metabolites in 3 conceptal compartments: the visceral yolk sac (VYS), the extra-embryonic fluid (EEF) and the embryo proper (EMB). Our results show that thiol concentrations in all compartments are well predicted by the model. Protein synthesis is predicted to be a major efflux pathway for all amino acid precursors of GSH synthesis and an essential model element. Our model provides quantitative insights in the transport fluxes and enzymatic fluxes needed to maintain thiol redox balances under normal physiological conditions. This is crucial to further elucidate the mechanisms through which chemical exposure can perturb redox homeostasis, causing oxidative stress, and potentially birth defects.
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Affiliation(s)
- K Veltman
- Department of Environmental Health Sciences, University of Michigan, 1420 Washington Heights, Ann Arbor, MI 48109-2029, USA.
| | - C Harris
- Department of Environmental Health Sciences, University of Michigan, 1420 Washington Heights, Ann Arbor, MI 48109-2029, USA
| | - Y Ahmad
- Department of Environmental Health Sciences, University of Michigan, 1420 Washington Heights, Ann Arbor, MI 48109-2029, USA
| | - O Jolliet
- Department of Environmental Health Sciences, University of Michigan, 1420 Washington Heights, Ann Arbor, MI 48109-2029, USA
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Salmina AB, Komleva YK, Szijártó IA, Gorina YV, Lopatina OL, Gertsog GE, Filipovic MR, Gollasch M. H2S- and NO-Signaling Pathways in Alzheimer's Amyloid Vasculopathy: Synergism or Antagonism? Front Physiol 2015; 6:361. [PMID: 26696896 PMCID: PMC4675996 DOI: 10.3389/fphys.2015.00361] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2015] [Accepted: 11/16/2015] [Indexed: 12/02/2022] Open
Abstract
Alzheimer's type of neurodegeneration dramatically affects H2S and NO synthesis and interactions in the brain, which results in dysregulated vasomotor function, brain tissue hypoperfusion and hypoxia, development of perivascular inflammation, promotion of Aβ deposition, and impairment of neurogenesis/angiogenesis. H2S- and NO-signaling pathways have been described to offer protection against Alzheimer's amyloid vasculopathy and neurodegeneration. This review describes recent developments of the increasing relevance of H2S and NO in Alzheimer's disease (AD). More studies are however needed to fully determine their potential use as therapeutic targets in Alzheimer's and other forms of vascular dementia.
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Affiliation(s)
- Alla B. Salmina
- Department of Biochemistry, Medical, Pharmaceutical and Toxicological Chemistry, Krasnoyarsk State Medical University named after Prof. V.F. Voino-YasenetskyKrasnoyarsk, Russia
| | - Yulia K. Komleva
- Department of Biochemistry, Medical, Pharmaceutical and Toxicological Chemistry, Krasnoyarsk State Medical University named after Prof. V.F. Voino-YasenetskyKrasnoyarsk, Russia
| | - István A. Szijártó
- Experimental and Clinical Research Center, Charité - University Medicine Berlin and the Max Delbrück Center for Molecular MedicineBerlin, Germany
| | - Yana V. Gorina
- Department of Biochemistry, Medical, Pharmaceutical and Toxicological Chemistry, Krasnoyarsk State Medical University named after Prof. V.F. Voino-YasenetskyKrasnoyarsk, Russia
| | - Olga L. Lopatina
- Department of Biochemistry, Medical, Pharmaceutical and Toxicological Chemistry, Krasnoyarsk State Medical University named after Prof. V.F. Voino-YasenetskyKrasnoyarsk, Russia
| | - Galina E. Gertsog
- Department of Biochemistry, Medical, Pharmaceutical and Toxicological Chemistry, Krasnoyarsk State Medical University named after Prof. V.F. Voino-YasenetskyKrasnoyarsk, Russia
| | - Milos R. Filipovic
- Department of Chemistry and Pharmacy, Friedrich-Alexander-University of Erlangen-NürnbergErlangen, Germany
| | - Maik Gollasch
- Experimental and Clinical Research Center, Charité - University Medicine Berlin and the Max Delbrück Center for Molecular MedicineBerlin, Germany
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Bridges RJ, Natale NR, Patel SA. System xc⁻ cystine/glutamate antiporter: an update on molecular pharmacology and roles within the CNS. Br J Pharmacol 2012; 165:20-34. [PMID: 21564084 DOI: 10.1111/j.1476-5381.2011.01480.x] [Citation(s) in RCA: 353] [Impact Index Per Article: 29.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
System x(c)(-) is an amino acid antiporter that typically mediates the exchange of extracellular l-cystine and intracellular L-glutamate across the cellular plasma membrane. Studied in a variety of cell types, the import of L-cystine through this transporter is critical to glutathione production and oxidative protection. The exchange-mediated export of L-glutamate takes on added significance within the CNS, as it represents a non-vesicular route of release through which this excitatory neurotransmitter can participate in either neuronal signalling or excitotoxic pathology. When both the import of L-cystine and the export of L-glutamate are taken into consideration, system x(c)(-) has now been linked to a wide range of CNS functions, including oxidative protection, the operation of the blood-brain barrier, neurotransmitter release, synaptic organization, viral pathology, drug addiction, chemosensitivity and chemoresistance, and brain tumour growth. The ability to selectively manipulate system x(c)(-), delineate its function, probe its structure and evaluate it as a therapeutic target is closely linked to understanding its pharmacology and the subsequent development of selective inhibitors and substrates. Towards that goal, this review will examine the current status of our understanding of system x(c)(-) pharmacology and the structure-activity relationships that have guided the development of an initial pharmacophore model, including the presence of lipophilic domains adjacent to the substrate binding site. A special emphasis is placed on the roles of system x(c)(-) within the CNS, as it is these actions that are among the most exciting as potential long-range therapeutic targets.
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Affiliation(s)
- Richard J Bridges
- Center for Structural and Functional Neuroscience, Department of Biomedical and Pharmaceutical Sciences, University of Montana, Missoula, Montana 59812, USA.
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Seib TM, Patel SA, Bridges RJ. Regulation of the system x(C)- cystine/glutamate exchanger by intracellular glutathione levels in rat astrocyte primary cultures. Glia 2011; 59:1387-401. [PMID: 21590811 DOI: 10.1002/glia.21176] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2010] [Accepted: 03/18/2011] [Indexed: 12/31/2022]
Abstract
The system x(C)- (Sx(C)-) transporter functions to mediate the exchange of extracellular cystine (L-Cys(2)) and intracellular glutamate (L-Glu). Internalized L-Cys(2) serves as a rate-limiting precursor for the biosynthesis of glutathione (GSH), while the externalized L-Glu can contribute to either excitatory signaling or excitotoxicity. In the present study the influence of culture conditions (with and without dibutyryl-cAMP) and GSH levels on the expression of Sx(C)- were investigated in primary rat astrocyte cultures. Sx(C)- activity in dbcAMP-treated cells was nearly sevenfold greater than in untreated astrocytes and increased further (∼threefold) following the depletion of intracellular GSH with buthionine sulfoximine. This increase in Sx(C)- triggered by GSH depletion was only observed in the dbcAMP-treated phenotype and was distinct from the Nrf2-mediated response initiated by exposure to electrophiles. Changes in Sx(C)- activity correlated with increases in both protein and mRNA levels of the xCT subunit of the Sx(C)- heterodimer, an increase in the V(max) for L-Glu uptake and was linked temporally to GSH levels. This induction of Sx(C)- was not mimicked by hydrogen peroxide nor attenuated by nonspecific antioxidants but was partially prevented by the co-administration of the cell-permeant thiols GSH-ethyl ester and N-acetylcysteine. These findings demonstrate that the expression of Sx(C)- on astrocytes is dynamically regulated by intracellular GSH levels in a cell- and phenotype-dependent manner. The presence of this pathway likely reflects the inherent vulnerability of the CNS to oxidative damage and raises interesting questions as to the functional consequences of changes in Sx(C)- activity in CNS injury and disease.
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Affiliation(s)
- Todd Michael Seib
- CSFN, Center for Structural and Functional Neuroscience, Department of Biomedical and Pharmaceutical Sciences, University of Montana, Missoula, Montana 59812, USA
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The dynamics of cysteine, glutathione and their disulphides in astrocyte culture medium. J Biochem 2011; 150:95-102. [DOI: 10.1093/jb/mvr038] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Potential therapeutic advantage of ribose-cysteine in the inhibition of astrocytoma cell proliferation. Amino Acids 2010; 41:131-9. [DOI: 10.1007/s00726-010-0593-4] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2009] [Accepted: 04/02/2010] [Indexed: 02/07/2023]
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Napier S, Bingham M. Pharmacology of Glutamate Transport in the CNS: Substrates and Inhibitors of Excitatory Amino Acid Transporters (EAATs) and the Glutamate/Cystine Exchanger System x c −. TOPICS IN MEDICINAL CHEMISTRY 2008. [PMCID: PMC7123079 DOI: 10.1007/7355_2008_026] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
As the primary excitatory neurotransmitter in the mammalian CNS, l-glutamateparticipates not only in standard fast synaptic communication, but also contributes to higher order signalprocessing, as well as neuropathology. Given this variety of functional roles, interest has been growingas to how the extracellular concentrations of l-glutamate surroundingneurons are regulated by cellular transporter proteins. This review focuses on two prominent systems, eachof which appears capable of influencing both the signaling and pathological actions of l-glutamatewithin the CNS: the sodium-dependent excitatory amino acid transporters (EAATs) and the glutamate/cystineexchanger, system xc−(Sxc−). Whilethe family of EAAT subtypes limit access to glutamate receptors by rapidly and efficiently sequesteringl-glutamate in neurons and glia, Sxc−provides a route for the export of glutamate from cells into the extracellular environment. The primaryintent of this work is to provide an overview of the inhibitors and substrates that have been developedto delineate the pharmacological specificity of these transport systems, as well as be exploited as probeswith which to selectively investigate function. Particular attention is paid to the development of smallmolecule templates that mimic the structural properties of the endogenous substrates, l-glutamate,l-aspartate and l-cystine andhow strategic control of functional group position and/or the introduction of lipophilic R-groups can impactmultiple aspects of the transport process, including: subtype selectivity, inhibitory potency, and substrateactivity.
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Qu K, Lee SW, Bian JS, Low CM, Wong PTH. Hydrogen sulfide: neurochemistry and neurobiology. Neurochem Int 2007; 52:155-65. [PMID: 17629356 DOI: 10.1016/j.neuint.2007.05.016] [Citation(s) in RCA: 194] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2007] [Revised: 05/16/2007] [Accepted: 05/24/2007] [Indexed: 11/19/2022]
Abstract
Current evidence suggests that hydrogen sulfide (H2S) plays an important role in brain functions, probably acting as a neuromodulator as well as an intracellular messenger. In the mammalian CNS, H2S is formed from the amino acid cysteine by the action of cystathionine beta-synthase (CBS) with serine (Ser) as the by-product. As CBS is a calcium and calmodulin dependent enzyme, the biosynthesis of H2S should be acutely controlled by the intracellular concentration of calcium. In addition, it is also regulated by S-adenosylmethionine which acts as an allosteric activator of CBS. H2S, as a sulfhydryl compound, has similar reducing properties as glutathione. In neurons, H2S stimulates the production of cAMP probably by direct activation of adenylyl cyclase and thus activate cAMP-dependent processes. In astrocytes, H2S increases intracellular calcium to an extent capable of inducing and propagating a "calcium wave", which is a form of calcium signaling among these cells. Possible physiological functions of H2S include potentiating long-term potentials through activation of the NMDA receptors, regulating the redox status, maintaining the excitatory/inhibitory balance in neurotransmission, and inhibiting oxidative damage through scavenging free radicals and reactive species. H2S is also involved in CNS pathologies such as stroke and Alzheimer's disease. In stroke, H2S appears to act as a mediator of ischemic injuries and thus inhibition of its production has been suggested to be a potential treatment approach in stroke therapy.
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Affiliation(s)
- K Qu
- Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
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Guebel DV, Torres NV, Cánovas M. Modeling analysis of the l(−)-carnitine production process by Escherichia coli. Process Biochem 2006. [DOI: 10.1016/j.procbio.2005.08.013] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Hayes D, Wiessner M, Rauen T, McBean GJ. Transport of L-[14C]cystine and L-[14C]cysteine by subtypes of high affinity glutamate transporters over-expressed in HEK cells. Neurochem Int 2005; 46:585-94. [PMID: 15863236 DOI: 10.1016/j.neuint.2005.03.001] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2004] [Revised: 02/28/2005] [Accepted: 03/01/2005] [Indexed: 01/28/2023]
Abstract
Transport of L-cystine across the cell membrane is essential for synthesis of the major cellular antioxidant, glutathione (gamma-glutamylcysteinylglycine). In this study, uptake of L-[14C]cystine by three of the high affinity sodium-dependent mammalian glutamate transporters (GLT1, GLAST and EAAC1) individually expressed in HEK cells has been determined. All three transporters display saturable uptake of L-[14C]cystine with Michaelis affinity (K(m)) constants in the range of 20-110 microM. L-glutamate and L-homocysteate are potent inhibitors of sodium-dependent L-[14C]cystine uptake in HEK(GLAST), HEK(GLT1) and HEK(EAAC1) cells. Reduction of L-[14C]cystine to L-[14C]cysteine in the presence of 1mM cysteinylglycine increases the uptake rate in HEK(GLT1), HEK(GLAST) and HEK(EAAC1) cells, but only a small proportion (<10%) of L-[14C]cysteine uptake in HEK(GLT1) and HEK(GLAST) cells occurs by the high affinity glutamate transporters. The majority (>90%) of L-[14C]cysteine transport in these cells is mediated by the ASC transport system. In HEK(EAAC1) cells, on the other hand, L-[14C]cysteine is transported equally by the ASC and EAAC1 transporters. L-homocysteine inhibits L-[14C]cysteine transport in both HEK(GLAST) and HEK(GLT1) cells, but not in HEK(EAAC1) cells. It is concluded that the quantity of L-[14C]cyst(e)ine taken up by individual high affinity sodium-dependent glutamate transporters is determined both by the extracellular concentration of amino acids, such as glutamate and homocysteine, and by the extracellular redox potential, which will control the oxidation state of L-cystine.
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Affiliation(s)
- Derek Hayes
- Department of Biochemistry, Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Dublin 4, Ireland
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