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El Msehli S, Lambert A, Baldacci-Cresp F, Hopkins J, Boncompagni E, Smiti SA, Hérouart D, Frendo P. Crucial role of (homo)glutathione in nitrogen fixation in Medicago truncatula nodules. New Phytol 2011; 192:496-506. [PMID: 21726232 DOI: 10.1111/j.1469-8137.2011.03810.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Legumes form a symbiotic interaction with bacteria of the Rhizobiaceae family to produce nitrogen-fixing root nodules under nitrogen-limiting conditions. We examined the importance of glutathione (GSH) and homoglutathione (hGSH) during the nitrogen fixation process. Spatial patterns of the expression of the genes involved in the biosynthesis of both thiols were studied using promoter-GUS fusion analysis. Genetic approaches using the nodule nitrogen-fixing zone-specific nodule cysteine rich (NCR001) promoter were employed to determine the importance of (h)GSH in biological nitrogen fixation (BNF). The (h)GSH synthesis genes showed a tissue-specific expression pattern in the nodule. Down-regulation of the γ-glutamylcysteine synthetase (γECS) gene by RNA interference resulted in significantly lower BNF associated with a significant reduction in the expression of the leghemoglobin and thioredoxin S1 genes. Moreover, this lower (h)GSH content was correlated with a reduction in the nodule size. Conversely, γECS overexpression resulted in an elevated GSH content which was correlated with increased BNF and significantly higher expression of the sucrose synthase-1 and leghemoglobin genes. Taken together, these data show that the plant (h)GSH content of the nodule nitrogen-fixing zone modulates the efficiency of the BNF process, demonstrating their important role in the regulation of this process.
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Affiliation(s)
- Sarra El Msehli
- UMR Interactions Biotiques et Santé Végétale, Université de Nice-Sophia Antipolis, Sophia-Antipolis cedex, France
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2
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Iyamu EW, Perdew HA, Woods GM. Oxidant-mediated modification of the cellular thiols is sufficient for arginase activation in cultured cells. Mol Cell Biochem 2011; 360:159-68. [PMID: 21918827 DOI: 10.1007/s11010-011-1053-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2011] [Accepted: 09/02/2011] [Indexed: 11/25/2022]
Abstract
Increased arginase activity in the vasculature has been implicated in the regulation of nitric oxide (NO) homeostasis, leading to the development of vascular disease and the promotion of tumor cell growth. Recently, we showed that cysteine, in the presence of iron, promotes arginase activity by driving the Fenton reaction. In the present report, we showed that induction of oxidative stress in erythroleukemic cells with the thiol-specific oxidant, diamide, led to an increase in arginase activity by 42% (P = 0.02; vs. control). By using specific antibodies, it was demonstrated that this increase correlated with an increase in arginase-1 levels in the cells and with corresponding decreases in glutathione and protein thiol levels. Treatment of cells with aurothiomalate (ATM), a protein thiol-complexing agent, diminished the activity of arginase and arginase-1 levels by 19.5 and 35.2%, respectively (vs. control) and significantly decreased both glutathione and protein thiol levels, further implicating the thiol redox system in the cellular activation of arginase. Furthermore, diamide significantly altered the kinetics of arginase, resulting in the doubling of its V(max) (vs. control). Our presented data demonstrate, for the first time that the intracellular arginase activation is may be enhanced in part, via a cellular thiol-mediated mechanism.
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Affiliation(s)
- Efemwonkiekie W Iyamu
- Division of Hematology and Oncology, Children's Mercy Hospital, Kansas City, MO 64108, USA.
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3
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Yang L, Wu D, Wang X, Cederbaum AI. Depletion of cytosolic or mitochondrial thioredoxin increases CYP2E1-induced oxidative stress via an ASK-1-JNK1 pathway in HepG2 cells. Free Radic Biol Med 2011; 51:185-96. [PMID: 21557999 PMCID: PMC3109094 DOI: 10.1016/j.freeradbiomed.2011.04.030] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/23/2010] [Revised: 03/30/2011] [Accepted: 04/15/2011] [Indexed: 12/30/2022]
Abstract
Thioredoxin is an important reducing molecule in biological systems. Increasing CYP2E1 activity induces oxidative stress and cell toxicity. However, whether thioredoxin protects cells against CYP2E1-induced oxidative stress and toxicity is unknown. SiRNA were used to knockdown either cytosolic (TRX-1) or mitochondrial thioredoxin (TRX-2) in HepG2 cells expressing CYP2E1 (E47 cells) or without expressing CYP2E1 (C34 cells). Cell viability decreased 40-60% in E47 but not C34 cells with 80-90% knockdown of either TRX-1 or TRX-2. Depletion of either thioredoxin also potentiated the toxicity produced either by a glutathione synthesis inhibitor or by TNFα in E47 cells. Generation of reactive oxygen species and 4-HNE protein adducts increased in E47 but not C34 cells with either thioredoxin knockdown. GSH was decreased and adding GSH completely blocked E47 cell death induced by either thioredoxin knockdown. Lowering TRX-1 or TRX-2 in E47 cells caused an early activation of ASK-1, followed by phosphorylation of JNK1 after 48 h of siRNA treatment. A JNK inhibitor caused a partial recovery of E47 cell viability after thioredoxin knockdown. In conclusion, knockdown of TRX-1 or TRX-2 sensitizes cells to CYP2E1-induced oxidant stress partially via ASK-1 and JNK1 signaling pathways. Both TRX-1 and TRX-2 are important for defense against CYP2E1-induced oxidative stress.
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Affiliation(s)
- Lili Yang
- Department of Pharmacology and Systems Therapeutics, Mount Sinai School of Medicine, New York, NY 10029, USA
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4
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Sharma SK, Banyal HS. Characterization of Plasmodium berghei glutathione synthetase. Parasitol Int 2011; 60:321-3. [PMID: 21377539 DOI: 10.1016/j.parint.2011.02.006] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2010] [Revised: 02/18/2011] [Accepted: 02/28/2011] [Indexed: 11/16/2022]
Abstract
Plasmodium berghei contained 0.454±0.031 U/mg of glutathione synthetyase (GS). GS was purified using solid ammonium sulfate and Sephadex G-200 from P. berghei infected mouse erythrocytes. SDS-PAGE showed purified GS as a single band protein of 70 kDa and its Km for γ-glutamylcysteine, glycine and ATP being 0.33 mM, 8.3 mM and 0.43 mM respectively with noncompetitive inhibition by GSH. The malaria parasite enzyme was optimally active at 37°C and pH 8.0-8.5. Heavy metals significantly inhibited parasite GS activity.
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Affiliation(s)
- S K Sharma
- Department of Biosciences, Himachal Pradesh University, Shimla, India.
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5
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Abstract
The activity of glutathione synthetase from bovine lens was examined as a functions of the concentration of L-gamma-glutamyl-L-alpha-aminobutyrate, the dipeptide substrate required in the formation of ophthalmic acid. Several significant anomalies of the glutathione synthetase-catalyzed formation of ophthalmic acid were found. Curvilinearity of double reciprocal plots occurred with this substrate; this curvilinearity shows substrate activation of the reaction which is likely a result of negative cooperativity. Both ATP4- and, to a lesser extent Mg2+ inhibited the reaction, whereas MgATP2- is the substrate; maximum activity occurred with 2 mM Mg2+ in excess of the concentration of added ATP. This investigation shows that it is necessary to establish a defined set of conditions for reporting enzyme activity and that the usual practice of using very large concentrations of Mg2+ relative to ATP, and 5- to 20-fold excess of the dipeptide will give less than optimum activity. The unit of enzyme activity is suggested to be that activity in ml using 2 mM ATP, 4 mM Mg2+, 30 mM glycine and 15 mM L-gamma-glutamyl-alpha-aminobutyrate, which results in the formation of 1 nmole/minute of ADP or P(i). In this study, 5'-AMP was for the first time, shown to be an inhibitor of the reaction with a K(i) of 0.9 mM.
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Du T, Ciccotosto GD, Cranston GA, Kocak G, Masters CL, Crouch PJ, Cappai R, White AR. Neurotoxicity from glutathione depletion is mediated by Cu-dependent p53 activation. Free Radic Biol Med 2008; 44:44-55. [PMID: 18045546 DOI: 10.1016/j.freeradbiomed.2007.09.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/22/2007] [Revised: 09/05/2007] [Accepted: 09/05/2007] [Indexed: 01/21/2023]
Abstract
Loss of intracellular neuronal glutathione (GSH) is an important feature of neurodegenerative disorders including Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis. The consequences of GSH depletion include increased oxidative damage to proteins, lipids, and DNA and subsequent cytotoxic effects. GSH is also an important modulator of cellular copper (Cu) homeostasis and altered Cu metabolism is central to the pathology of several neurodegenerative diseases. The cytotoxic effects of Cu in cells depleted of GSH are not well understood. We have previously reported that depletion of neuronal GSH levels results in cell death from trace levels of extracellular Cu due to elevated Cu(I)-mediated free radical production. In this study we further examined the molecular pathway of trace Cu toxicity in neurons and fibroblasts depleted of GSH. Treatment of primary cortical neurons or 3T3 fibroblasts with the glutathione synthetase inhibitor buthionine sulfoximine resulted in substantial loss of intracellular GSH and increased cytotoxicity. We found that both neurons and fibroblasts revealed increased expression and activation of p53 after depletion of GSH. The increased p53 activity was induced by extracellular trace Cu. Furthermore, we showed that in GSH-depleted cells, Cu induced an increase in oxidative stress resulting in DNA damage and activation of p53-dependent cell death. These findings may have important implications for neurodegenerative disorders that involve GSH depletion and aberrant Cu metabolism.
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Affiliation(s)
- Tai Du
- Department of Pathology, The University of Melbourne, Melbourne, VIC 3010, Australia
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7
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Iwata C, Wang X, Uchida K, Nakanishi N, Hattori Y. Buthionine sulfoximine causes endothelium dependent hyper-relaxation and hypoadiponectinemia. Life Sci 2007; 80:873-8. [PMID: 17137603 DOI: 10.1016/j.lfs.2006.11.012] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2006] [Revised: 10/27/2006] [Accepted: 11/07/2006] [Indexed: 11/27/2022]
Abstract
A close relationship between oxidative stress, endothelial dysfunction, and hypoadiponectinemia has been observed. The present study was performed to investigate how glutathione depletion via buthionine sulfoximine (BSO) administration affects endothelial function and adiponectin levels in rats. Acetylcholine (Ach)-induced vasodilation was significantly enhanced in BSO-treated rats, compared with control rats. This was completely abolished by L-NAME, and Ach-induced vasodilation was not observed in the aorta without endothelium. These results suggest that Ach-induced hyper-relaxation of the aorta in BSO-treated rats is completely dependent on the presence of endothelium and mediated by changes in eNOS activity. Catalase significantly inhibited this relaxation to Ach and no effect of catalase on sodium nitroprusside-induced relaxation of the aorta without endothelium was observed in BSO-treated rats. Thus, hyper-relaxation of the aorta in BSO-treated rats is likely caused by H2O2 in addition to NO produced by the endothelium via an eNOS-dependent mechanism. Hypoadiponectinemia and decreased levels of adiponectin mRNA in adipose tissue were observed in BSO-treated rats. Protein expression of eNOS and SODs (SOD-1 and SOD-2) in the aorta was increased and plasma NOx levels were decreased in BSO-treated rats. Our results suggest that oxidative stress induced by BSO causes eNOS uncoupling and hyper-relaxation by producing H2O2, and that BSO-induced oxidative stress causes hypoadiponectinemia, probably by increasing H2O2 production in adipose tissue.
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Affiliation(s)
- Chigusa Iwata
- Department of Endocrinology and Metabolism, Dokkyo University School of Medicine, Mibu, Tochigi, Japan
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Faucet-Marquis V, Pont F, Størmer FC, Rizk T, Castegnaro M, Pfohl-Leszkowicz A. Evidence of a new dechlorinated ochratoxin A derivative formed in opossum kidney cell cultures after pretreatment by modulators of glutathione pathways: correlation with DNA-adduct formation. Mol Nutr Food Res 2006; 50:530-42. [PMID: 16671059 DOI: 10.1002/mnfr.200500219] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Ochratoxin A (OTA), a nephrotoxic mycotoxin probably implicated in human Balkan endemic nephropathy and associated urothelial tumors, induces renal carcinomas in rodents and nephrotoxicity in pigs. OTA induces DNA-adduct formation, but the structure of the adducts and their role in nephrotoxicity and carcinogenicity have only partly been elucidated. In vivo, 2-mercaptoethane sulfonate (MESNA) protects rats against OTA-induced nephrotoxicity but not against carcinogenicity, indicating two different mechanisms leading to nephrotoxicity or carcinogenicity. To better understand how DNA-adduct could be generated, opossum kidney cells (OK) have been treated by OTA alone or in presence of several compounds such as MESNA or N-acetylcysteine (another agent that, like MESNA, reduces oxidative stress by increasing of free thiols in kidney), buthionine sulfoximine (BSO) (an inhibitor of glutathione-synthase), and alpha amino-3-chloro-4,5-dihydro-5-isoxazole acetic acid (ACIVICIN) (an inhibitor of gamma glutamyl transpeptidase). Cytotoxicity of OTA on OK cells was evaluated by applying the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. None of the listed agents diminished OTA cytotoxicity significantly; ACIVICIN even increases OTA cytotoxicity. In contrast, analysis of the HPLC profiles of OTA metabolites produced during these incubations indicated that the pattern, the quantity of metabolites, and the nature of the derivatives were modulated by these agents. Ochratoxin B (OTB), open-ring ochratoxin A (OP-OA), 4 hydroxylated OTA, 10 hydroxylated OTA, OTA without phenylalanine, OTB without phenylalanine, and a dechlorinated OTA metabolite could be identified by nano-ESI-IT-MS.
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Affiliation(s)
- Virginie Faucet-Marquis
- Department BioSyM, Laboratoire de Génie Chimique, UMR CNRS/INPT/UPS5503, Auzeville-Tolosane, France
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9
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Vergauwen B, De Vos D, Van Beeumen JJ. Characterization of the Bifunctional γ-Glutamate-cysteine Ligase/Glutathione Synthetase (GshF) of Pasteurella multocida. J Biol Chem 2006; 281:4380-94. [PMID: 16339152 DOI: 10.1074/jbc.m509517200] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Glutamate-cysteine ligase (gamma-ECL) and glutathione synthetase (GS) are the two unrelated ligases that constitute the glutathione biosynthesis pathway in most eukaryotes, purple bacteria, and cyanobacteria. gamma-ECL is a member of the glutamine synthetase family, whereas GS enzymes group together with highly diverse carboxyl-to-amine/thiol ligases, all characterized by the so-called two-domain ATP-grasp fold. This generalized scheme toward the formation of glutathione, however, is incomplete, as functional steady-state levels of intracellular glutathione may also accumulate solely by import, as has been reported for the Pasteurellaceae member Haemophilus influenzae, as well as for certain Gram-positive enterococci and streptococci, or by the action of a bifunctional fusion protein (termed GshF), as has been reported recently for the Gram-positive firmicutes Streptococcus agalactiae and Listeria monocytogenes. Here, we show that yet another member of the Pasteurellaceae family, Pasteurella multocida, acquires glutathione both by import and GshF-driven biosynthesis. Domain architecture analysis shows that this P. multocida GshF bifunctional ligase contains an N-terminal gamma-proteobacterial gamma-ECL-like domain followed by a typical ATP-grasp domain, which most closely resembles that of cyanophycin synthetases, although it has no significant homology with known GS ligases. Recombinant P. multocida GshF overexpresses as an approximately 85-kDa protein, which, on the basis of gel-sizing chromatography, forms dimers in solution. The gamma-ECL activity of GshF is regulated by an allosteric type of glutathione feedback inhibition (K(i) = 13.6 mM). Furthermore, steady-state kinetics, on the basis of which we present a novel variant of half-of-the-sites reactivity, indicate intimate domain-domain interactions, which may explain the bifunctionality of GshF proteins.
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Affiliation(s)
- Bjorn Vergauwen
- Laboratory of Protein Biochemistry and Protein Engineering, Ghent University, Belgium
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10
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Gupta S, Srivastava AK, Banu N. Setaria cervi: kinetic studies of filarial glutathione synthetase by high performance liquid chromatography. Exp Parasitol 2005; 111:137-41. [PMID: 16087176 DOI: 10.1016/j.exppara.2005.06.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2005] [Revised: 06/23/2005] [Accepted: 06/26/2005] [Indexed: 11/25/2022]
Abstract
The bovine filarial worm Setaria cervi was found to have abundance of glutathione synthetase (GS; EC 6.3.2.3) activity, the enzyme being involved in catalysing the final step of glutathione (GSH) biosynthesis. A RP-HPLC method involving precolumn derivatization with o-phthalaldehyde has been followed for the estimation of GS activity in crude filarial preparations. Subcellular fractionation of the enzyme was undertaken and it was confirmed to be a soluble protein residing mainly in cytosolic fraction. Attempts to determine the Km value for L-gamma-glutamyl-L-cysteine gave a distinctly nonlinear double-reciprocal plot in which data obtained at relatively high dipeptide concentrations (>1 mM) extrapolate to a Km value of about 400 microM whereas data obtained at lower concentrations (<0.1 mM) extrapolate to a value of about 33 microM. Km was determined to be around 950 and 410 microM for ATP and glycine, respectively. The effect of various amino acids was studied on enzyme activity at 1mM concentration. L-cystine caused a significant enzyme inhibition of 11%. Preincubation with N-ethylmaleimide also resulted in significant inhibition of GS activity.
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Affiliation(s)
- Sapna Gupta
- Division of Biochemistry, Central Drug Research Institute, Lucknow 226 001, India.
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11
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Abstract
Gamma-glutamylcysteine synthetase (gamma-GCS) and glutathione synthetase (GS), distinct enzymes that together account for glutathione (GSH) synthesis, have been isolated and characterized from several Gram-negative prokaryotes and from numerous eukaryotes including mammals, amphibians, plants, yeast, and protozoa. Glutathione synthesis is relatively uncommon among the Gram-positive bacteria, and, to date, neither the genes nor the proteins involved have been identified. In the present report, we show that crude extracts of Streptococcus agalactiae catalyze the gamma-GCS and GS reactions and can synthesize GSH from its constituent amino acids. The putative gene for S. agalactiae gamma-GCS was identified and cloned, and the corresponding protein was expressed and purified. Surprisingly, it was found that the isolated enzyme catalyzes both the ATP-dependent synthesis of L-gamma-glutamyl-L-cysteine from L-glutamate and L-cysteine and the ATP-dependent synthesis of GSH from L-gamma-glutamyl-L-cysteine and glycine. This novel bifunctional enzyme, referred to as gamma-GCS-GS, has been characterized in terms of catalytic activity, substrate specificity, and inhibition by GSH, cystamine, and transition state analog sulfoximines. The N-terminal 518 amino acids of gamma-GCS-GS (total M(r) 85,000) show 32% identity and 43% similarity with E. coli gamma-GCS (M(r) 58,000), but the C-terminal putative GS domain (remaining 202 amino acids) of gamma-GCS-GS shows no significant homology with known GS sequences. The C terminus (360 amino acids) is, however, homologous to D-Ala, D-Ala ligase (24% identity; 38% similarity), an enzyme having the same protein fold as known GS proteins. These results are discussed in terms of the evolution of GSH synthesis and the possible occurrence of a similar bifunctional GSH synthesis enzyme in other bacterial species.
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Affiliation(s)
- Blythe E Janowiak
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA
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Frendo P, Harrison J, Norman C, Hernández Jiménez MJ, Van de Sype G, Gilabert A, Puppo A. Glutathione and homoglutathione play a critical role in the nodulation process of Medicago truncatula. Mol Plant Microbe Interact 2005; 18:254-9. [PMID: 15782639 DOI: 10.1094/mpmi-18-0254] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Legumes form a symbiotic interaction with bacteria of the Rhizobiaceae family to produce nitrogen-fixing root nodules under nitrogen-limiting conditions. This process involves the recognition of the bacterial Nod factors by the plant which mediates the entry of the bacteria into the root and nodule organogenesis. We have examined the importance of the low molecular weight thiols, glutathione (GSH) and homoglutathione (hGSH), during the nodulation process in the model legume Medicago truncatula. Using both buthionine sulfoximine, a specific inhibitor of GSH and hGSH synthesis, and transgenic roots expressing GSH synthetase and hGSH synthetase in an antisense orientation, we showed that deficiency in GSH and hGSH synthesis inhibited the formation of the root nodules. This inhibition was not correlated to a modification in the number of infection events or to a change in the expression of the Rhizobium sp.-induced peroxidase rip1, indicating that the low level of GSH or hGSH did not alter the first steps of the infection process. In contrast, a strong diminution in the number of nascent nodules and in the expression of the early nodulin genes, Mtenod12 and Mtenod40, were observed in GSH and hGSH-depleted plants. In conclusion, GSH and hGSH appear to be essential for proper development of the root nodules during the symbiotic interaction.
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Affiliation(s)
- Pierre Frendo
- Interactions Plantes-Microorganismes et Santé Végétale, UMR CNRS-INRA-Université de Nice-Sophia Antipolis, 400, Route des Chappes, BP167, 06903 Sophia-Antipolis Cedex, France
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13
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Abstract
Intestinal epithelial tight junction (TJ) barrier dysfunction may lead to inflammation and mucosal injury. Glutamine (GLN) plays a role in maintenance of intestinal barrier function in various animal models and critically ill humans. Recent evidence from intestinal cell monolayers indicates that GLN maintains transepithelial resistance and decreases permeability. The mechanisms of these effects remain undefined. We hypothesized that GLN affects proteins involved in the intercellular junctional complex. GLN availability was controlled in Caco-2 monolayers by addition to the medium and treatment with methionine sulfoximine (MSO) to inhibit glutamine synthetase (GS). Expression of TJ proteins, claudin-1, occludin, and zonula occluden (ZO)-1 was measured by immunoblotting. Localization of TJ proteins was evaluated by immunofluorescence light microscopy. Structure of TJ was determined by transmission electron microscopy (TEM). Deprivation of GLN decreased claudin-1, occludin, and ZO-1 protein expression and caused a disappearance of perijunctional claudin-1 and a reduction of occludin but had no effect on ZO-1. TEM revealed that MSO-treated cells in the absence of GLN formed irregular junctional complexes between the apical lateral margins of adjoining cells. These findings indicate that TJ protein expression and cellular localization in Caco-2 cell monolayers rely on GLN. This mechanism may similarly relate to GLN-mediated modulation of intestinal barrier function in stressed animals and humans.
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Affiliation(s)
- Nan Li
- Division of Neonatology, Department of Pediatrics, University of Florida College of Medicine, Gainesville, Florida 32610, USA
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14
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Abstract
It is well known that intracellular antioxidant glutathione (GSH) plays major roles in the maintenance of redox status and defense of oxidative stress. Ras, a small GTP-binding protein, may send growth-stimulating message to the nucleus through downstream Rac oncoprotein and superoxide (O(2*-)). These findings led us to investigate the effects of GSH and melatonin, a free-radical scavenger, on Ras-Rac-O(2*-)-related growth signal transduction. Our results demonstrate that overexpression of the inducible Ha-ras oncogene by isopropyl-beta-D-thiogalactoside (IPTG) increases the levels of reactive oxygen species (ROS, including O(2*-) and hydrogen peroxide (H(2)O(2))) and GSH in an Ha-ras-transformed NIH/3T3 fibroblast cell line. On the contrary, melatonin significantly suppresses ras-triggered cell growth by inhibiting the increase of ROS and GSH. Moreover, severe apoptosis of this transformed cell line occurred when the cell redox balance between ROS and GSH was dramatically changed in the presence of IPTG and L-buthionine-[S,R]-sulfoximine (BSO, a specific inhibitor of GSH synthetase). That BSO-induced cell apoptosis needs Ras to increase the ROS level was demonstrated by the free-radical scavenger melatonin. It effectively blocked cell apoptosis, but cell growth was also slowed without affecting Ras expression. Based on our studies, two approaches can be applied to treating ras-related cancers. One is utilizing melatonin to suppress cancer cell proliferation, and the other is utilizing BSO to induce cancer-cell apoptosis. Cotreatment of ras-related cancer cells with melatonin and BSO stops cell growth as well as apoptosis. Whether these cancer cells will undergo further regression or become recurrent merits investigation.
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Affiliation(s)
- Jih I Chuang
- Department of Physiology, College of Medicine, National Cheng Kung University, Tainan, Taiwan
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de Matos DG, Gasparrini B, Pasqualini SR, Thompson JG. Effect of glutathione synthesis stimulation during in vitro maturation of ovine oocytes on embryo development and intracellular peroxide content. Theriogenology 2002; 57:1443-51. [PMID: 12054203 DOI: 10.1016/s0093-691x(02)00643-x] [Citation(s) in RCA: 116] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Cysteamine and beta-mercaptoethanol supplementation of in vitro maturation (IVM) medium has been found to increase intracellular glutathione (GSH) content in oocytes and to improve embryo development and quality in several species. The objective of this experiment was to study the effect of cysteamine and beta-mercaptoethanol added during IVM of sheep oocytes on GSH synthesis and embryo development. Furthermore, we examined if cysteamine addition (hence GSH production) had an effect on the reduction of the intracellular peroxide content. We matured oocytes obtained from ovaries collected at a slaughterhouse in vitro in the presence of 0, 50, 100, and 200 microM cysteamine (Experiment 1) or with 0, 50, 100, and 200 microM beta-mercaptoethanol (Experiment 2). Following fertilization and embryo development, there was a increasing level of morula and blastocyst development in the presence of cysteamine, reaching significance in the presence of 200 microM (P < 0.05). However, beta-mercaptoethanol did not influence on the rate of embryo development. GSH levels were measured in oocytes matured in the presence or absence of 200 microM cysteamine (Experiment 3) or 50 microM beta-mercaptoethanol (Experiment 4), with or without buthionine sulfoximide (BSO), an inhibitor of GSH synthesis. Results demonstrated that for both cysteamine and beta-mercaptoethanol, intracellular GSH levels increased against control values (P < 0.01), which was abolished in the presence of BSO. Finally, we reduced intracellular peroxide levels, as measured by the relative fluorescence of the intracellular peroxide probe, carboxy-H2DCFDA, in the presence of either 200 microM cysteamine or 50 microM beta-mercaptoethanol (Experiment 5). These results demonstrate that cysteamine, but not beta-mercaptoethanol, when present during IVM, stimulates sheep embryo development; both cysteamine and beta-mercaptoethanol stimulate GSH synthesis; the increase in intracellular GSH is associated with a decrease in peroxide levels within oocytes.
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Zhou XJ, Vaziri ND, Wang XQ, Silva FG, Laszik Z. Nitric oxide synthase expression in hypertension induced by inhibition of glutathione synthase. J Pharmacol Exp Ther 2002; 300:762-7. [PMID: 11861779 DOI: 10.1124/jpet.300.3.762] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Induction of chronic oxidative stress by glutathione (GSH) depletion has been shown to cause hypertension in normal rats. This was accompanied by and perhaps in part due to inactivation and sequestration of NO by reactive oxygen species (ROS), leading to diminished NO bioavailability. This study was designed to examine renal histology, nitric oxide synthase (NOS) isotype expression, and nitrotyrosine distribution in this model. Sprague-Dawley rats were subjected to oxidative stress by administration of the GSH synthase inhibitor buthionine sulfoximine (BSO; 30 mM/l in drinking water) for 2 weeks. The controls were given tap water. Blood pressure, renal histology, tissue expression of endothelial and inducible NOS (eNOS and iNOS) and nitrotyrosine, tissue GSH content, and urinary excretion of NO metabolites (NOx) were examined. The BSO-treated group showed a 3-fold decrease in tissue GSH content, a marked elevation in blood pressure, and a significant reduction in the urinary excretion of NOx. Histological examination of kidneys revealed no significant abnormalities in either group. In addition, no significant differences were observed in either intensities or localizations of eNOS and iNOS in the kidney. However, the BSO-treated group exhibited intense accumulation in the renal tissue of nitrotyrosine, which is the footprint of NO oxidation by ROS. These observations suggest that oxidative stress-induced hypertension is not caused by either structural abnormality of or depressed NOS expression by the kidney in this model. Instead, it is associated with and perhaps partially related to enhanced renal NO inactivation by ROS and diminished NO bioavailability.
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Affiliation(s)
- Xin J Zhou
- Department of Pathology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9073, USA.
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Canals S, Casarejos MJ, de Bernardo S, Rodríguez-Martín E, Mena MA. Glutathione depletion switches nitric oxide neurotrophic effects to cell death in midbrain cultures: implications for Parkinson's disease. J Neurochem 2001; 79:1183-95. [PMID: 11752059 DOI: 10.1046/j.1471-4159.2001.00635.x] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Nitric oxide (NO) exerts neurotrophic and neurotoxic effects on dopamine (DA) function in primary midbrain cultures. We investigate herein the role of glutathione (GSH) homeostasis in the neurotrophic effects of NO. Fetal midbrain cultures were pretreated with GSH synthesis inhibitor, L-buthionine-(S,R)-sulfoximine (BSO), 24 h before the addition of NO donors (diethylamine/nitric oxide-complexed sodium and S-nitroso-N-acetylpenicillamine) at doses tested previously as neurotrophic. Under these conditions, the neurotrophic effects of NO disappeared and turned on highly toxic. Reduction of GSH levels to 50% of baseline induced cell death in response to neurotrophic doses of NO. Soluble guanylate cyclase (sGC) and cyclic GMP-dependent protein kinase (PKG) inhibitors protected from cell death for up to 10 h after NO addition; the antioxidant ascorbic acid also protected from cell death but its efficacy decreased when it was added after NO treatment (40% protection 2 h after NO addition). The pattern of cell death was characterized by an increase in chromatin condensed cells with no DNA fragmentation and with breakdown of plasmatic membrane. The inhibition of RNA and protein synthesis and of caspase activity also protected from cell death. This study shows that alterations in GSH levels change the neurotrophic effects of NO in midbrain cultures into neurotoxic. Under these conditions, NO triggers a programmed cell death with markers of both apoptosis and necrosis characterized by an early step of free radicals production followed by a late requirement for signalling on the sGC/cGMP/PKG pathway.
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Affiliation(s)
- S Canals
- Departamento de Investigación, Servicio de Neurobiología, Hospital Ramón y Cajal, Madrid, Spain
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18
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Abstract
Recent studies have shown that aflatoxin B1 enhances reactive oxygen species formation and causes oxidative damage, which may ultimately contribute to the cytotoxicity and carcinogenic effect of aflatoxin B1. Ebselen, 2-phenyl-1,2-benzoisoseleazol-3(H)-one, a synthetic seleno-organic compound has been shown to possess glutathione peroxidase-like activity and free radical scavenging ability. Thus present study was designed to investigate the protective effect of ebselen on aflatoxin B1-induced cytotoxicity in primary rat hepatocytes. Aflatoxin B1-induced cytotoxicity and lipid peroxidation were determined by lactate dehydrogenase leakage and malondialdehyde generation, respectively. Intracellular reactive oxygen species level was measured using the fluorescent probe 2',7'-dichlorofluorescin diacetate, and the intracellular reduced glutathione concentration was determined with a fluorometric method. Ebselen was found to display a dose-dependent protective effect on lactate dehydrogenase leakage and malondialdehyde generation caused by aflatoxin B1 exposure. The results also demonstrate that ebselen efficiently inhibits the intracellular reactive oxygen species formation in aflatoxin B1-treated hepatocytes in a dose and time-dependent manner. It was also noted that ebselen was able to increase the intracellular reduced glutathione concentration, both in the control and in aflatoxin B1-treated hepatocytes. The protection of ebselen against aflatoxin B1 cytotoxicity, however, was not affected by lowering the concentration of intracellular reduced glutathione. The overall data indicate that ebselen possesses a potent protective effect against aflatoxin B1-induced cytotoxicity, and the main mechanism involved in the protection may be its strong capability in inhibiting intracellular reactive oxygen species formation and preventing oxidative damage.
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Affiliation(s)
- C F Yang
- Department of Community, Occupational and Family Medicine, Faculty of Medicine, National University of Singapore, Republic of Singapore
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Benderra Z, Trussardi A, Morjani H, Villa AM, Doglia SM, Manfait M. Regulation of cellular glutathione modulates nuclear accumulation of daunorubicin in human MCF7 cells overexpressing multidrug resistance associated protein. Eur J Cancer 2000; 36:428-34. [PMID: 10708946 DOI: 10.1016/s0959-8049(99)00288-9] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Multidrug resistance (MDR) is frequently associated with the overexpression of P-glycoprotein (Pgp) and/or multidrug resistance associated protein (MRP1), both members of the ABC superfamily of transporters. Pgp and MRP1 function as ATP-dependent efflux pumps that extrude cytotoxic drugs from tumour cells. Glutathione (GSH) has been considered to play an important role in the MRP1-mediated MDR. In our study, we examined the effects of buthionine sulphoximine (BSO), an inhibitor of GSH biosynthesis, on the nuclear accumulation of daunorubicin (DNR), in etoposide (VP16) and doxorubicin (ADR) resistant MCF7 cell lines, overexpressing respectively MRP1 (MCF7/VP) and Pgp (MCF7/ADR). The study of DNR transport was carried out using scanning confocal microspectrofluorometry. This technique allows the determination of the nuclear accumulation of anthracyclines in single living tumour cells. Treatment of MCF7/VP cells with BSO increased the sensitivity of these cells to DNR whilst the cytotoxicity of the drug in MCF7/ADR cells remained unchanged. In MCF7 resistant cells treated with BSO, their GSH level decreased as observed by confocal microscopy. DNR nuclear accumulation in MCF7/VP cells was increased by BSO whereas in MCF7/ADR cells BSO was unable to significantly increase the DNR nuclear accumulation. These data suggest a requirement for GSH in MRP1-mediated resistance whilst the nuclear efflux of GSH conjugates is probably not the primary mechanism of Pgp-mediated MDR. Finally, BSO might be a useful agent in clinical assays for facilitating detection of MRP1 expression.
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Affiliation(s)
- Z Benderra
- Unité MéDIAN, UFR de Pharmacie, IFR53, EA2063 51 rue Cognacq Jay, 51096, Reims, France
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Tsuboi S, Kiyono K, Ono B, Sakaue T, Ogata K. S-(1,2-Dicarboxyethyl)glutathione in yeast: partial purification of its synthesizing enzyme. Biol Pharm Bull 1999; 22:21-5. [PMID: 9989656 DOI: 10.1248/bpb.22.21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
S-(1,2-Dicarboxyethyl)glutathione (DCE-GS) was found in Saccharomyces cerevisiae, but not in bacterial species nor in a unicellular alga (Acetabularia acetabulum). The enzyme that catalyzes condensation of L-malate and glutathione (GSH) to form DCE-GS was partially purified from baker's yeast. It had a molecular mass of 49 kDa and was monomeric and the Km values were 2.2 and 1.4 mM for L-malate and GSH, respectively. The enzyme had a pH optimum of 7.5. DCE-GS levels in yeast cells were significantly higher in aerobic cultures than in anaerobic ones. DCE-GS was synthesized in cells cultured between 20 and 35 degrees C.
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Affiliation(s)
- S Tsuboi
- Faculty of Pharmaceutical Sciences, Okayama University, Japan
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21
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Abstract
Intraperitoneal administration of urate crystals to mice reduced subsequent macrophage conversion of arachidonic acid (AA) to prostaglandins (PGs) and 12-hydroxyeicosatetraenoic acid for up to 6 h. In contrast, levels of 12-hydroxyheptadecatrienoic acid (12-HHT) were markedly elevated. This metabolic profile was previously observed in vitro when recombinant cyclooxygenase (COX) enzymes were incubated with reduced glutathione (GSH). Analysis of peritoneal GSH levels revealed a fivefold elevation after urate crystal administration. The GSH synthesis inhibitor L-buthionine-[S,R]-sulfoximine partially reversed the urate crystal effect on both GSH elevation and PG synthesis. Moreover, addition of exogenous GSH to isolated peritoneal macrophages shifted AA metabolism from PGs to 12-HHT. Urate crystal administration reduced COX-1, but induced COX-2 expression in peritoneal cells. The reduction of COX-1 may contribute to the attenuation of PG synthesis after 1 and 2 h, but PG synthesis remained inhibited up to 6 h, when COX-2 levels were high. Overall, our results indicate that elevated GSH levels inhibit PG production in this model and provide in vivo evidence for the role of GSH in the regulation of PG biosynthesis.
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Affiliation(s)
- A Margalit
- Department of Pharmacology, Searle Research and Development, St. Louis, Missouri 63198, USA
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Sadunishvili T, Gvarliani N, Nutsubidze N, Kvesitadze G. Effect of methionine sulfoximine on nitrogen metabolism and externally supplied ammonium assimilation in kidney bean. Ecotoxicol Environ Saf 1996; 34:70-75. [PMID: 8793322 DOI: 10.1006/eesa.1996.0046] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
L-Methionine sulfoximine (MSO) at concentration 1.25 mM in vivo causes the inhibition of glutamine synthetase (GS) in both roots and leaves of young seedlings of kidney bean following the accumulation of high levels of ammonia and decrease in amounts of free amino acids that is more pronounced in leaves. The inhibition of GS by MSO in leaves in the case of externally supplied 5 mM (15NH4)2SO4 assimilation leads to ammonia accumulation and the decrease in the amounts of glutamine and glutamic acid and the intensity of the incorporation of 15N into them. In roots the inhibition of GS is not followed by the decrease of 15N content into glutamate. It is concluded that the pathway of ammonia primary assimilation in leaves is via GS and glutamate synthase (GOGAT), while in roots glutamate dehydrogenase also plays an important role in this process.
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Affiliation(s)
- T Sadunishvili
- Institute of Plant Biochemistry, Academy of Sciences, Tbilisi 380059, Republic of Georgia
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Okada S, Minamiyama Y, Hamazaki S, Toyokuni S, Sotomatsu A. Glutathione cycle dependency of ferric nitrilotriacetate-induced lipid peroxidation in mouse proximal renal tubules. Arch Biochem Biophys 1993; 301:138-42. [PMID: 8095133 DOI: 10.1006/abbi.1993.1125] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Parenteral administration of ferric nitrilotriacetate (Fe-NTA), a known carcinogen in mouse and rat kidneys, enhances iron-dependent lipid peroxidation (LP) and causes acute renal tubular necrosis. We assume that filtered Fe-NTA in vivo is rapidly reduced by cysteine, a component of glutathione which is hydrolyzed by gamma-GTP and dipeptidase, and that this reduced iron initiates lipid peroxidation in the lumen. In addition, the fatty acid composition of phospholipids between the cortex and the medulla may differ, because only the proximal tubules (which are located mainly in the cortex) are known to be vulnerable to LP. We tested these assumptions in the present study. Gas chromatographic determination of fatty acid composition in five male and five female 6-week-old normal ddY mice showed the ratio of polyunsaturated fatty acids to saturated fatty acids plus C18: 1, a single double-bond fatty acid, to be 0.98 +/- 0.08 (av +/- SD) in the male cortex and 1.00 +/- 0.08 in the female cortex. In the male and female medulla, however, it was 0.78 +/- 0.09 (P < 0.05, vs cortex) and 0.68 +/- 0.04 (P < 0.01, vs cortex), respectively. Pretreatment of the animals with buthionine sulfoximine, a glutathione synthetase inhibitor, and a procedure that reduces total glutathione content in the kidneys, suppressed LP. Reduced thiobarbituric acid reactive substances were also observed in animals treated with AT-125, a gamma-GTP inhibitor, and in animals with immature gamma-GTP activity. These results are consistent with our assumptions.
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Affiliation(s)
- S Okada
- Department of Pathology, Okayama University Medical School, Japan
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Kumar S, Ganguly NK, Kohli KK. Inhibition of cellular glutathione biosynthesis by rifampicin in Mycobacterium smegmatis. Biochem Int 1992; 26:469-76. [PMID: 1352683] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 03/25/2023]
Abstract
This study was carried out to investigate the mechanism of Rifampicin (RIF) induced glutathione (GSH) depletion in M. smegmatis. RIF at various concentrations decreased the activities of gamma glutamyl cysteine synthetase (GGCS) and GSH synthetase. Maximum decrease in the activities of biosynthetic enzymes of GSH was observed when 15 micrograms RIF ml-1 medium was incorporated in the growth medium before performing inoculations. The activity of GGCS was also decreased when three day grown M. smegmatis was exposed to 60 micrograms RIF ml-1 medium for a period of 6 h and 9 h. RIF did not alter the activity of gamma glutamyl transferase. The results of the present study demonstrate that the depletion caused by RIF in cellular GSH is due to its decreased biosynthesis whereas its degradation is not affected in M. smegmatis.
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Affiliation(s)
- S Kumar
- Department of Biochemistry, Postgraduate Institute of Medical Education and Research, Chandigarh, India
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25
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Persaud C, Jackson AA. 5-L-oxoprolinuria and glycine sufficiency. Clin Chem 1991; 37:1660-1. [PMID: 1680036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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Siegers CP, Bartels L, Riemann D. Effects of fasting and glutathione depletors on the GSH-dependent enzyme system in the gastrointestinal mucosa of the rat. Pharmacology 1989; 38:121-8. [PMID: 2727048 DOI: 10.1159/000138529] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
In rats, the glutathione content of the gastrointestinal mucosa amounted to 50-60% of that of the liver. The GSH-S-transferase activity towards an aryl substrate (CDNB) was low in the stomach, colon and rectum, i.e. 5% of hepatic activity. In the small intestine there was a typical decline of activity from proximal to distal segments. GSH-Peroxidase was much lower in the intestinal mucosa as compared to the stomach and liver, whereas the GSSG-reductase was 2-3 times higher in the gastrointestinal tract in comparison to the liver. Fasting for 24 h significantly decreased the GSH content, GSH-aryltransferase and GSSG-reductase activities in the liver but not in the intestine, where even higher GSH concentrations were found in the proximal segments. L-Buthionine-sulfoximine, an inhibitor of the GSH-synthesis, caused a marked decrease of the GSH levels in the liver, stomach, proximal small intestine, colon and rectum and a concomitant decline in GSSG-reductase activity. Among the GSH-depleting agents, paracetamol exerted the strongest effect, whereas 1,1-dichloroethylene and phorone only decreased the GSH content in the liver and stomach.
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Affiliation(s)
- C P Siegers
- Institute of Toxicology, Medical University of Lübeck, FRG
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Kato H, Tanaka T, Nishioka T, Kimura A, Oda J. Role of cysteine residues in glutathione synthetase from Escherichia coli B. Chemical modification and oligonucleotide site-directed mutagenesis. J Biol Chem 1988; 263:11646-51. [PMID: 3042775] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Escherichia coli B glutathione synthetase is composed of four identical subunits; each subunit contains 4 cysteine residues (Cys-122, -195, -222, and -289). We constructed seven different mutant enzymes containing 3, 2, or no cysteine residues/subunit by replacement of cysteine codons with those of alanine in the gsh II gene using site-directed mutagenesis. Three mutant enzymes, Ala289, Ala222/289, Cys-free (Ala122/195/222/289), in which cysteine at residue 289 was replaced with alanine, were not inactivated by 5,5'-dithiobis(2-nitrobenzoate) (DTNB), while the other four mutants retaining Cys-289 were inactivated at the wild-type rate. From these selective inactivations of mutant enzymes by DTNB, the sulfhydryl group modified by DTNB was unambiguously identified as Cys-289. In this way, Cys-289 was found to be also a target of modification with 2-nitrothiocyanobenzoate and N-ethylmaleimide, while Cys-195 was of p-chloromercuribenzoate. These results suggest that both Cys-195 and Cys-289 were not essential for the activity of the glutathione synthetase, but chemical modification of either one of the two sulfhydryl groups resulted in complete loss of the activity. Replacement of Cys-122 to Ala-122 enhanced the reactivity of Cys-289 with sulfhydryl reagents.
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Affiliation(s)
- H Kato
- Institute for Chemical Research, Kyoto University, Japan
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Affiliation(s)
- F Frappier
- UA CNRS 484, Faculté de Pharmacie, Paris, France
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Kato H, Chihara M, Nishioka T, Murata K, Kimura A, Oda J. Homology of Escherichia coli B glutathione synthetase with dihydrofolate reductase in amino acid sequence and substrate binding site. J Biochem 1987; 101:207-15. [PMID: 3553173 DOI: 10.1093/oxfordjournals.jbchem.a121893] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Glutathione synthetase from Escherichia coli B showed amino acid sequence homology with mammalian and bacterial dihydrofolate reductases over 40 residues, although these two enzymes are different in their reaction mechanisms and ligand requirements. The effects of ligands of dihydrofolate reductase on the reaction of E. coli B glutathione synthetase were examined to find resemblances in catalytic function to dihydrofolate reductase. The E. coli B enzyme was potently inhibited by 7,8-dihydrofolate, methotrexate, and trimethoprim. Methotrexate was studied in detail and proved to bind to an ATP binding site of the E. coli B enzyme with K1 value of 0.1 mM. The homologous portion of the amino acid sequence in dihydrofolate reductases, which corresponds to the portion coded by exon 3 of mammalian dihydrofolate reductase genes, provided a binding site of the adenosine diphosphate moiety of NADPH in the crystal structure of dihydrofolate reductase. These analyses would indicate that the homologous portion of the amino acid sequence of the E. coli B enzyme provides the ATP binding site. This report gives experimental evidence that amino acid sequences related by sequence homology conserve functional similarity even in enzymes which differ in their catalytic mechanisms.
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Abstract
Six factors were analyzed which may be involved in the decline of glutathione synthesis in the aging lens and cataract, with special emphasis placed upon the human lens. The factors included: 1) lability of gamma-glutamylcysteine synthetase, 2) paucity of gamma-glutamylcysteine synthetase in primate lenses as compared to other mammalian lenses, 3) enzyme activity reduction with age in the human lens, 4) rate control by reactant scarcity, especially of cysteine and magnesium ion, 5) rate control by inhibition using 5'-AMP, 5'-ADP and glutathione, and 6) possible dissociation of the multi-enzyme complex. It was concluded that decline of the glutathione synthetic capacity in vivo would be most likely caused by reduction of gamma-glutamylcysteine synthetase activity rather than of glutathione synthetase activity.
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Abstract
Substrate analogs have been obtained that selectively inhibit the reactions of the gamma-glutamyl cycle or that are susceptible to only limited metabolism by the cycle. Thus, glutathione synthesis may be inhibited and analogs of glutathione may be synthesized that do not participate in transpeptidation. Specific inhibitors of gamma-glutamylcyclotransferase and 5-oxoprolinase have been obtained. The findings offer new approaches to the in vivo study of the cycle and also to the design of more specifically directed analogs of inhibitors such as methionine sulfoximine and 6-diazo-5-oxonorleucine.
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