The Experts below are selected from a list of 264 Experts worldwide ranked by ideXlab platform
Garth Powis - One of the best experts on this subject based on the ideXlab platform.
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Molecular pharmacology and antitumor activity of palmarumycin-based inhibitors of Thioredoxin Reductase
Molecular cancer therapeutics, 2006Co-Authors: Garth Powis, Peter Wipf, Stephen M. Lynch, Anne Birmingham, D. Lynn KirkpatrickAbstract:The cytosolic Thioredoxin redox system composed of Thioredoxin-1 and the NADPH-dependent Thioredoxin Reductase-1 Reductase is an important regulator of cell growth and survival. Thioredoxin-1 is overexpressed in many human tumors where it is associated with increased cell proliferation, decreased apoptosis, and decreased patient survival. We hypothesized that Thioredoxin Reductase-1 provides a target to inhibit the activity of overexpressed Thioredoxin-1 for the development of novel anticancer agents. We found that the naphthoquinone spiroketal fungal metabolite palmarumycin CP1 is a potent inhibitor of Thioredoxin Reductase-1, but attempts to exploit the activity of palmarumycin CP1 analogues as antitumor agents in vivo were hampered by their insolubility. We have therefore developed PX-916, a water-soluble prodrug of a palmarumycin CP1 analogue. PX-916 rapidly releases the parent compound at physiologic pH and in plasma but is stable at acid pH, allowing its i.v. administration. PX-916 is a potent inhibitor of purified human Thioredoxin Reductase-1 and of Thioredoxin Reductase-1 activity in cells and tumor xenografts when given to mice and inhibits the downstream targets of Thioredoxin-1 signaling, hypoxia-inducible factor-1alpha, and vascular endothelial growth factor in tumors. PX-916 showed excellent antitumor activity against several animal tumor models with some cures. Thus, the study shows that water-soluble inhibitors of Thioredoxin Reductase-1, such as PX-916, can block Thioredoxin-1 signaling in tumors producing marked inhibition of tumor growth.
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Water-soluble organotellurium compounds inhibit Thioredoxin Reductase and the growth of human cancer cells.
Anti-cancer drug design, 2000Co-Authors: Lars Engman, Alfred Gallegos, Takahiro Kanda, Ryan Williams, Garth PowisAbstract:The Thioredoxin system (NADPH, Thioredoxin Reductase/ Thioredoxin) is important for cancer cell growth and inhibition of apoptosis and presents an attractive target for anticancer drug development. Thioredoxin Reductase is a selenocysteine-containing flavoenzyme that catalyzes the reduction of oxidized Thioredoxin. This enzyme could therefore be used for regulating the activity of the Thioredoxin system. Water-soluble organotellurium compounds of the diaryl telluride, alkyl aryl telluride and dialkyl telluride type, carrying sulfopropyl groups, were found to be the most efficient tellurium-based inhibitors of Thioredoxin Reductase ever tested. Some of the compounds inhibited the enzyme at submicromolar levels. The compounds also inhibited the growth of MCF-7 and HT-29 human cancer cells in culture at the 5-10 microM level but their hydrophilicity seemed to restrict cellular uptake.
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effect of selenium on rat Thioredoxin Reductase activity increase by supranutritional selenium and decrease by selenium deficiency
Biochemical Pharmacology, 1999Co-Authors: Margareta M Berggren, John R. Gasdaska, Jose F Mangin, Garth PowisAbstract:Thioredoxin Reductase is a newly identified selenocysteine-containing enzyme that catalyzes the NADPH-dependent reduction of the redox protein Thioredoxin. Thioredoxin stimulates cell growth, is found in dividing normal cells, and is over-expressed in a number of human cancers. Redox activity is essential for the growth effects of Thioredoxin; thus, Thioredoxin Reductase could be involved in regulating cell growth through its reduction of Thioredoxin. In rats fed a selenium-deficient diet (<0.01 ppm) for up to 98 days, Thioredoxin Reductase activity was decreased, compared with that of rats fed a normal selenium diet (0.1 ppm), in lung, liver, and kidney, while Thioredoxin Reductase activity in the spleen and prostate was unaltered. Rats fed a high selenium diet (1.0 ppm) exhibited a 1.5-fold increase in kidney and a 2.0-fold increase in lung Thioredoxin Reductase activity that began to return to control values after 20 and 69 days, respectively. Liver showed a 2.1-fold increase in Thioredoxin Reductase activity at 20 days only. Thioredoxin Reductase protein levels measured by western blotting using an antibody to human Thioredoxin Reductase were decreased in rats fed the selenium-deficient diet and did not increase in rats fed the high selenium diet. Rat Thioredoxin Reductase was shown to incorporate 75Selenium. Thus, in some tissues at least, the increase in Thioredoxin Reductase activity of rats fed a high selenium diet appears to be due to an increase in the specific activity of the enzyme, possibly caused by increased selenocysteine incorporation without an increase in Thioredoxin Reductase protein synthesis.
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Cloning, sequencing and functional expression of a novel human Thioredoxin Reductase
FEBS Letters, 1999Co-Authors: Pamela Y Gasdaska, Margareta M Berggren, Marla J Berry, Garth PowisAbstract:The DNA sequence encoding a novel human Thioredoxin Reductase has been determined. The protein is predicted to have 524 amino acids including a conserved -Cys-Val-Asn-Val-Gly-Cys catalytic site and a selenocysteine containing C-terminal -Gly-Cys-SeCys-Gly. The predicted molecular mass is 56.5. The newly identified TR sequence exhibits 54% identity to a previously reported human Thioredoxin Reductase and 37% identity to human glutathione Reductase. Transient transfection of human embryonal kidney cells results in a 5-fold increase in Thioredoxin Reductase activity but no increase in glutathione Reductase activity.
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Diaryl chalcogenides as selective inhibitors of Thioredoxin Reductase and potential antitumor agents.
Anticancer research, 1997Co-Authors: Lars Engman, Ian A. Cotgreave, Miguel Angulo, Charles W. Taylor, Gillian Paine-murrieta, Garth PowisAbstract:Thioredoxin Reductase is a selenocysteine containing flavoenzyme that catalyzes the NADPH dependent reduction of the redox protein Thioredoxin. Thioredoxin is over-expressed by a number of human tumors. Experimental studies have shown that Thioredoxin is responsible for the growth and transformed phenotype of some human cancer cells. Thus, Thioredoxin Reductase presents an attractive target for anticancer drug development to regulate the activity of the Thioredoxin system. We have examined a series of 12 organoselenium compounds and 16 organotellurium compounds, mostly of the diaryl chalcogenide type, as inhibitors of human Thioredoxin Reductase and have investigated the cytotoxicity and antitumor activity of some of the compounds. The organoselenium compound Ebselen was found to be a competitive inhibitor of human Thioredoxin Reductase (Ki 2.8 microM), while a number of organotellurium compounds were found to be noncompetitive inhibitors (Kis 2.3 to 35.2 microM). Human glutathione Reductase was not appreciably inhibited by any of the compounds, except for one dinitro organotellurium compound that caused inhibition with an IC50 of 0.5 microM and an over 20-fold selectivity compared to Thioredoxin Reductase. The compounds inhibited the growth of human cancer cells in culture with IC50s as low as 2 microM Some organotellurium compounds when administered daily by intraperitoneal injection to mice caused up to 50% inhibition of the growth of MCF-7 human breast cancer xenografts but the relative insolubility of the compounds was a limiting factor in their use.
Arne Holmgren - One of the best experts on this subject based on the ideXlab platform.
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Chaperone properties of Escherichia coli Thioredoxin and Thioredoxin Reductase.
Biochemical Journal, 2003Co-Authors: Renée Kern, Arne Holmgren, Abderrahim Malki, Gilbert RicharmeAbstract:Thioredoxin, Thioredoxin Reductase and NADPH form the Thioredoxin system and are the major cellular protein disulphide Reductase. We report here that Escherichia coli Thioredoxin and Thioredoxin Reductase interact with unfolded and denatured proteins, in a manner similar to that of molecular chaperones that are involved in protein folding and protein renaturation after stress. Thioredoxin and/or Thioredoxin Reductase promote the functional folding of citrate synthase and alpha-glucosidase after urea denaturation. They also promote the functional folding of the bacterial galactose receptor, a protein without any cysteines. Furthermore, redox cycling of Thioredoxin/Thioredoxin Reductase in the presence of NADPH and cystine stimulates the renaturation of the galactose receptor, suggesting that the Thioredoxin system functions like a redox-powered chaperone machine. Thioredoxin Reductase prevents the aggregation of citrate synthase under heat-shock conditions. It forms complexes that are more stable than those formed by Thioredoxin with several unfolded proteins such as reduced carboxymethyl alpha-lactalbumin and unfolded bovine pancreatic trypsin inhibitor. These results suggest that the Thioredoxin system, in addition to its protein disulphide isomerase activity possesses chaperone-like properties, and that its Thioredoxin Reductase component plays a major role in this function.
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Physiological functions of Thioredoxin and Thioredoxin Reductase.
European journal of biochemistry, 2000Co-Authors: Elias S.j. Arnér, Arne HolmgrenAbstract:Thioredoxin, Thioredoxin Reductase and NADPH, the Thioredoxin system, is ubiquitous from Archea to man. Thioredoxins, with a dithiol/disulfide active site (CGPC) are the major cellular protein disulfide Reductases; they therefore also serve as electron donors for enzymes such as ribonucleotide Reductases, Thioredoxin peroxidases (peroxiredoxins) and methionine sulfoxide Reductases. Glutaredoxins catalyze glutathione-disulfide oxidoreductions overlapping the functions of Thioredoxins and using electrons from NADPH via glutathione Reductase. Thioredoxin isoforms are present in most organisms and mitochondria have a separate Thioredoxin system. Plants have chloroplast Thioredoxins, which via ferredoxin-Thioredoxin Reductase regulates photosynthetic enzymes by light. Thioredoxins are critical for redox regulation of protein function and signaling via thiol redox control. A growing number of transcription factors including NF-kappaB or the Ref-1-dependent AP1 require Thioredoxin reduction for DNA binding. The cytosolic mammalian Thioredoxin, lack of which is embryonically lethal, has numerous functions in defense against oxidative stress, control of growth and apoptosis, but is also secreted and has co-cytokine and chemokine activities. Thioredoxin Reductase is a specific dimeric 70-kDa flavoprotein in bacteria, fungi and plants with a redox active site disulfide/dithiol. In contrast, Thioredoxin Reductases of higher eukaryotes are larger (112-130 kDa), selenium-dependent dimeric flavoproteins with a broad substrate specificity that also reduce nondisulfide substrates such as hydroperoxides, vitamin C or selenite. All mammalian Thioredoxin Reductase isozymes are homologous to glutathione Reductase and contain a conserved C-terminal elongation with a cysteine-selenocysteine sequence forming a redox-active selenenylsulfide/selenolthiol active site and are inhibited by goldthioglucose (aurothioglucose) and other clinically used drugs.
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Preparation and assay of mammalian Thioredoxin and Thioredoxin Reductase.
Methods in enzymology, 1999Co-Authors: Elias S.j. Arnér, Liangwei Zhong, Arne HolmgrenAbstract:Publisher Summary This chapter describes the preparation and assay of mammalian Thioredoxin and Thioredoxin Reductase (TrxR). The amino acid sequences of mammalian TrxR revealed a strikingly high homology to glutathione Reductase. 14,19 The conserved features of all the structural components of glutathione Reductase are preserved in mammalian TrxR, including a redox active disulfide motif in the N-terminal FAD region, the NADPH binding region, and the carboxyterminal interface region that governs the association of the two subunits in the homodimeric holoenzyme. Mammalian Thioredoxin Reductase has gained increased interest due to its wide reductive capacity, the discovery of selenium in the enzyme, and its lipid hydroperoxide Reductase activity. As Thioredoxin shows a growing number of new roles in redox regulation of cellular processes and as an extracellular cytokine, the interest in TrxR in these contexts naturally follows. Future studies of mammalian Thioredoxin systems should be an exciting area of research, yielding results required for a deeper understanding of thiol redox control and mechanisms protecting against oxidative stress.
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[21] Thioredoxin and Thioredoxin Reductase
Methods in Enzymology, 1995Co-Authors: Arne Holmgren, Mikael BjornstedtAbstract:Publisher Summary This chapter summarizes current methods to determine Trx and Thioredoxin Reductase (TR). Thioredoxin (Trx) is a small (Mr 12,000) multifunctional and ubiquitous protein characterized by having a redox-active disulfide/dithiol within the conserved active site sequence: -Trp-Cys-Gly-Pro-Cys-. Oxidized Thioredoxin (Trx-S 2 ) has a disulfide, and reduced Thioredoxin [Trx-(SH) 2 ] has a dithiol. Thioredoxin Reductase specifically reduces Trx-S 2 to Trx-(SH) 2 using NADPH. The Trx-(SH) 2 form is a powerful protein disulfide Reductase. Thus, Trx, TR, and NADPH, collectively called the Thioredoxin system, operate as a powerful NADPH-dependent protein disulfide Reductase system. Thioredoxin has been isolated and characterized from a wide variety of prokaryotic and eukaryotic species. Mammalian Thioredoxins show about 25% sequence identity to the well-characterized E. coli protein with 108 residues. One classic function of the Thioredoxin system is to act as a hydrogen donor for ribonucleotide Reductase, which is essential for DNA synthesis. Redox control processes involve changes in the activity of an enzyme, a receptor, or a transcription factor via dithiol/disulfide interchange reactions. Mammalian Thioredoxin Reductase, with its broader substrate specificity, is likely to be involved in multiple signaling systems for redox control of cellular processes.
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Thioredoxin and Thioredoxin Reductase.
Methods in enzymology, 1995Co-Authors: Arne Holmgren, Mikael BjornstedtAbstract:Publisher Summary This chapter summarizes current methods to determine Trx and Thioredoxin Reductase (TR). Thioredoxin (Trx) is a small (Mr 12,000) multifunctional and ubiquitous protein characterized by having a redox-active disulfide/dithiol within the conserved active site sequence: -Trp-Cys-Gly-Pro-Cys-. Oxidized Thioredoxin (Trx-S 2 ) has a disulfide, and reduced Thioredoxin [Trx-(SH) 2 ] has a dithiol. Thioredoxin Reductase specifically reduces Trx-S 2 to Trx-(SH) 2 using NADPH. The Trx-(SH) 2 form is a powerful protein disulfide Reductase. Thus, Trx, TR, and NADPH, collectively called the Thioredoxin system, operate as a powerful NADPH-dependent protein disulfide Reductase system. Thioredoxin has been isolated and characterized from a wide variety of prokaryotic and eukaryotic species. Mammalian Thioredoxins show about 25% sequence identity to the well-characterized E. coli protein with 108 residues. One classic function of the Thioredoxin system is to act as a hydrogen donor for ribonucleotide Reductase, which is essential for DNA synthesis. Redox control processes involve changes in the activity of an enzyme, a receptor, or a transcription factor via dithiol/disulfide interchange reactions. Mammalian Thioredoxin Reductase, with its broader substrate specificity, is likely to be involved in multiple signaling systems for redox control of cellular processes.
Raymond F. Burk - One of the best experts on this subject based on the ideXlab platform.
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Thioredoxin Reductase Reduces Lipid Hydroperoxides and Spares α-Tocopherol
Biochemical and biophysical research communications, 2002Co-Authors: James M. May, Jason D. Morrow, Raymond F. BurkAbstract:Abstract We investigated whether and how rat liver Thioredoxin Reductase spares α-tocopherol in biomembranes. Purified hydroperoxides of β-linoleoyl-γ-palmitoylphosphatidylcholine were decreased 35% by treatment with Thioredoxin Reductase and 54% by Thioredoxin Reductase plus E. coli Thioredoxin. Thioredoxin Reductase also halved the amount of hydroperoxides that had been formed during photoperoxidation of liposomes composed of β-linoleoyl-γ-palmitoylphosphatidylcholine, and of emulsions of both cholesterol and cholesteryl linolenate. In erythrocyte ghosts, Thioredoxin Reductase spared α-tocopherol from oxidation by both soybean lipoxygenase and ferricyanide. Thioredoxin Reductase also decreased F2-isoprostanes in ghosts oxidized by ferricyanide, suggesting that its ability to spare α-tocopherol relates to reduction of lipid hydroperoxides.
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Reduction of the ascorbyl free radical to ascorbate by Thioredoxin Reductase.
The Journal of biological chemistry, 1998Co-Authors: James M. May, Kristina E. Hill, Charles E. Cobb, Shalu Mendiratta, Raymond F. BurkAbstract:Recycling of ascorbic acid from its oxidized forms is required to maintain intracellular stores of the vitamin in most cells. Since the ubiquitous selenoenzyme Thioredoxin Reductase can recycle dehydroascorbic acid to ascorbate, we investigated the possibility that the enzyme can also reduce the one-electron-oxidized ascorbyl free radical to ascorbate. Purified rat liver Thioredoxin Reductase catalyzed the disappearance of NADPH in the presence of low micromolar concentrations of the ascorbyl free radical that were generated from ascorbate by ascorbate oxidase, and this effect was markedly stimulated by selenocystine. Dehydroascorbic acid is generated by dismutation of the ascorbyl free radical, and Thioredoxin Reductase can reduce dehydroascorbic acid to ascorbate. However, control studies showed that the amounts of dehydroascorbic acid generated under the assay conditions used were too low to account for the observed loss of NADPH. Electron paramagnetic resonance spectroscopy directly confirmed that the Reductase decreased steady-state ascorbyl free radical concentrations, as expected if Thioredoxin Reductase reduces the ascorbyl free radical. Dialyzed cytosol from rat liver homogenates also catalyzed NADPH-dependent reduction of the ascorbyl free radical. Specificity for Thioredoxin Reductase was indicated by loss of activity in dialyzed cytosol prepared from livers of selenium-deficient rats, by inhibition with aurothioglucose at concentrations selective for Thioredoxin Reductase, and by stimulation with selenocystine. Microsomal fractions prepared from rat liver showed substantial NADH-dependent ascorbyl free radical reduction that was not sensitive to selenium depletion. These results suggest that Thioredoxin Reductase can function as a cytosolic ascorbyl free radical Reductase that may complement cellular ascorbate recycling by membrane-bound NADH-dependent Reductases.
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Reduction of Dehydroascorbate to Ascorbate by the Selenoenzyme Thioredoxin Reductase
The Journal of biological chemistry, 1997Co-Authors: James M. May, Kristina E. Hill, Shalu Mendiratta, Raymond F. BurkAbstract:Abstract Recycling of ascorbate from its oxidized forms is essential to maintain stores of the vitamin in human cells. Whereas reduction of dehydroascorbate to ascorbate is thought to be largely GSH-dependent, we reconsidered the possibility that the selenium-dependent Thioredoxin system might contribute to ascorbate regeneration. We found that purified rat liver Thioredoxin Reductase functions as an NADPH-dependent dehydroascorbate Reductase, with an apparent K m of 2.5 mm for dehydroascorbate, and a k catof 90 min−1. Addition of 2.8 μm purified rat liver Thioredoxin lowered the apparent K m to 0.7 mm, without affecting the turnover (k cat of 71 min−1). Since Thioredoxin Reductase requires selenium, we tested the physiologic importance of this enzyme for dehydroascorbate reduction in livers from control and selenium-deficient rats. Selenium deficiency lowered liver Thioredoxin Reductase activity by 88%, glutathione peroxidase activity by 99%, and ascorbate content by 33%, but did not affect GSH content. NADPH-dependent dehydroascorbate Reductase activity due to Thioredoxin Reductase, on the basis of inhibition by aurothioglucose, was decreased 88% in dialyzed liver cytosolic fractions from selenium-deficient rats. GSH-dependent dehydroascorbate Reductase activity in liver cytosol was variable, but typically 2–3-fold that of NADPH-dependent activity. These results show that the Thioredoxin system can reduce dehydroascorbate, and that this function is required for maintenance of liver ascorbate content.
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Thioredoxin Reductase Activity Is Decreased by Selenium Deficiency
Biochemical and biophysical research communications, 1997Co-Authors: Kristina E. Hill, Gary W. Mccollum, Martha E. Boeglin, Raymond F. BurkAbstract:Animal Thioredoxin Reductase is a selenoprotein. In this study, Thioredoxin Reductase activities in liver, kidney, and brain have been compared in rats fed selenium-deficient and control diets for 14 weeks following weaning. Selenium deficiency caused a decrease in Thioredoxin Reductase activity from control to 4.5% in liver and 11% in kidney. However, brain Thioredoxin Reductase activity was not affected by selenium deficiency of this severity. Gold inhibited Thioredoxin Reductase activity in the liver in a manner typical of its effect on selenoenzymes. Repletion of selenium-deficient rats with injections of selenium caused Thioredoxin Reductase activity to increase more rapidly in the liver than glutathione peroxidase activity but more slowly than selenoprotein P. These results indicate that Thioredoxin Reductase activity in liver and kidney is sensitive to selenium nutritional status but that brain Thioredoxin Reductase activity is less sensitive.
Elias S.j. Arnér - One of the best experts on this subject based on the ideXlab platform.
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Cell Death by SecTRAPs: Thioredoxin Reductase as a Prooxidant Killer of Cells
PloS one, 2008Co-Authors: Karin Anestål, Stefanie Prast-nielsen, Narimantas Cenas, Elias S.j. ArnérAbstract:BackgroundSecTRAPs (selenium compromised Thioredoxin Reductase-derived apoptotic proteins) can be formed from the selenoprotein Thioredoxin Reductase (TrxR) by targeting of its selenocysteine (Sec) residue with electrophiles, or by its removal through C-terminal truncation. SecTRAPs are devoid of Thioredoxin Reductase activity but can induce rapid cell death in cultured cancer cell lines by a gain of function.Principal FindingsBoth human and rat SecTRAPs killed human A549 and HeLa cells. The cell death displayed both apoptotic and necrotic features. It did not require novel protein synthesis nor did it show extensive nuclear fragmentation, but it was attenuated by use of caspase inhibitors. The redox active disulfide/dithiol motif in the N-terminal domain of TrxR had to be maintained for manifestation of SecTRAP cytotoxicity. Stopped-flow kinetics showed that NADPH can reduce the FAD moiety in SecTRAPs at similar rates as in native TrxR and purified SecTRAPs could maintain NADPH oxidase activity, which was accelerated by low molecular weight substrates such as juglone. In a cellular context, SecTRAPs triggered extensive formation of reactive oxygen species (ROS) and consequently antioxidants could protect against the cell killing by SecTRAPs.ConclusionsWe conclude that formation of SecTRAPs could contribute to the cytotoxicity seen upon exposure of cells to electrophilic agents targeting TrxR. SecTRAPs are prooxidant killers of cells, triggering mechanisms beyond those of a mere loss of Thioredoxin Reductase activity.
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Measurement of Thioredoxin and Thioredoxin Reductase.
Current protocols in toxicology, 2001Co-Authors: Elias S.j. Arnér, A HolmgrenAbstract:The Thioredoxin system is ubiquitous, providing reducing equivalents to essential biosynthetic enzymes like ribonucleotide Reductase. It is essential for cellular redox regulation, control of oxidative stress, and protection against oxidative damage. This unit includes protocols for measuring Thioredoxin or Thioredoxin Reductase in biological preparations or as purified enzymes.
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Physiological functions of Thioredoxin and Thioredoxin Reductase.
European journal of biochemistry, 2000Co-Authors: Elias S.j. Arnér, Arne HolmgrenAbstract:Thioredoxin, Thioredoxin Reductase and NADPH, the Thioredoxin system, is ubiquitous from Archea to man. Thioredoxins, with a dithiol/disulfide active site (CGPC) are the major cellular protein disulfide Reductases; they therefore also serve as electron donors for enzymes such as ribonucleotide Reductases, Thioredoxin peroxidases (peroxiredoxins) and methionine sulfoxide Reductases. Glutaredoxins catalyze glutathione-disulfide oxidoreductions overlapping the functions of Thioredoxins and using electrons from NADPH via glutathione Reductase. Thioredoxin isoforms are present in most organisms and mitochondria have a separate Thioredoxin system. Plants have chloroplast Thioredoxins, which via ferredoxin-Thioredoxin Reductase regulates photosynthetic enzymes by light. Thioredoxins are critical for redox regulation of protein function and signaling via thiol redox control. A growing number of transcription factors including NF-kappaB or the Ref-1-dependent AP1 require Thioredoxin reduction for DNA binding. The cytosolic mammalian Thioredoxin, lack of which is embryonically lethal, has numerous functions in defense against oxidative stress, control of growth and apoptosis, but is also secreted and has co-cytokine and chemokine activities. Thioredoxin Reductase is a specific dimeric 70-kDa flavoprotein in bacteria, fungi and plants with a redox active site disulfide/dithiol. In contrast, Thioredoxin Reductases of higher eukaryotes are larger (112-130 kDa), selenium-dependent dimeric flavoproteins with a broad substrate specificity that also reduce nondisulfide substrates such as hydroperoxides, vitamin C or selenite. All mammalian Thioredoxin Reductase isozymes are homologous to glutathione Reductase and contain a conserved C-terminal elongation with a cysteine-selenocysteine sequence forming a redox-active selenenylsulfide/selenolthiol active site and are inhibited by goldthioglucose (aurothioglucose) and other clinically used drugs.
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Preparation and assay of mammalian Thioredoxin and Thioredoxin Reductase.
Methods in enzymology, 1999Co-Authors: Elias S.j. Arnér, Liangwei Zhong, Arne HolmgrenAbstract:Publisher Summary This chapter describes the preparation and assay of mammalian Thioredoxin and Thioredoxin Reductase (TrxR). The amino acid sequences of mammalian TrxR revealed a strikingly high homology to glutathione Reductase. 14,19 The conserved features of all the structural components of glutathione Reductase are preserved in mammalian TrxR, including a redox active disulfide motif in the N-terminal FAD region, the NADPH binding region, and the carboxyterminal interface region that governs the association of the two subunits in the homodimeric holoenzyme. Mammalian Thioredoxin Reductase has gained increased interest due to its wide reductive capacity, the discovery of selenium in the enzyme, and its lipid hydroperoxide Reductase activity. As Thioredoxin shows a growing number of new roles in redox regulation of cellular processes and as an extracellular cytokine, the interest in TrxR in these contexts naturally follows. Future studies of mammalian Thioredoxin systems should be an exciting area of research, yielding results required for a deeper understanding of thiol redox control and mechanisms protecting against oxidative stress.
M. Ikeda - One of the best experts on this subject based on the ideXlab platform.
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Localization of Thioredoxin Reductase and Thioredoxin in Normal Human Placenta and Their Protective Effect Against Oxidative Stress
Placenta, 1999Co-Authors: K. Ejima, H. Nanri, N. Toki, M. Kashimura, M. IkedaAbstract:Abstract Recent studies have indicated that oxidative stress is involved in the pathogenesis of pre-eclampsia. Oxidative stress damages systemic tissues, and placental damage may result in intrauterine growth retardation and fetal distress. Thus, this study attempted to elucidate the placental localization of Thioredoxin and Thioredoxin Reductase, substances that may reduce oxidative stress. Furthermore, it studied the defence mechanism of the Thioredoxin–Thioredoxin Reductase system against oxidative stress in mitochondria of normal human placenta where reactive oxygen species are primarily produced. The examination of Thioredoxin Reductase activity in subcellular fractions of human placenta indicated that Thioredoxin Reductase was located not only in cytoplasm, but also in mitochondria. The existence of Thioredoxin and Thioredoxin Reductase in human placenta was confirmed immunologically using antibodies raised against Thioredoxin and Thioredoxin Reductase. Thioredoxin and Thioredoxin Reductase were localized histochemically in cytotrophoblasts, decidua, and stromal cells in the stem villi. The addition of exogenous Thioredoxin and Thioredoxin Reductase to fumarase in mitochondria of human placenta displayed a protective effect against oxidative stress. In conclusion, this study confirmed the intracellular localization and the tissue distribution of Thioredoxin and Thioredoxin Reductase in human placenta. Moreover, the complete Thioredoxin–Thioredoxin Reductase system in human placenta may protect the placenta from damage caused by oxidative stress.
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Expression of Thioredoxin and Thioredoxin Reductase in placentae of pregnant mice exposed to lipopolysaccharide.
Placenta, 1999Co-Authors: K. Ejima, H. Nanri, M. Kashimura, Takehiko Koji, M. IkedaAbstract:We have previously shown that Thioredoxin and Thioredoxin Reductase were immunohistochemically localized in cytotrophoblasts, decidua and stromal cells in the stem villi of human placenta and that the addition of exogenous Thioredoxin and Thioredoxin Reductase to mitochondrial fractions from human placenta displayed a protective effect on fumarase activity against oxidative stress. In this study, to investigate further the roles of Thioredoxin and Thioredoxin Reductase in protecting pregnancy against oxidative stress, we examined the effect of lipopolysaccharide (LPS), which induces a variety of cytokines and produces radical oxygen species, on the expression of Thioredoxin and Thioredoxin Reductase in mouse placenta. We focused on the placental protective effect in the second trimester, when the onset of placental dysfunction might occasionally lead to a critical state for the fetus. Thus we analysed placentae from mice on day 13 of pregnancy at various time points after they were injected with LPS (50 microg/kg i.p.) or saline as a control. The expressions of Thioredoxin and Thioredoxin Reductase were evaluated by Western blotting and immunohistochemistry. Western blot analysis revealed that LPS approximately quadrupled the expression of both Thioredoxin and Thioredoxin Reductase in the placentae of pregnant mice. When both proteins were localized immunohistochemically, it was found that the decidua and the diploid trophoblasts in the basal zone were intensively stained. Furthermore, the expression of 4-hydroxy-2-nonenal (HNE)-modified proteins, which are markers of oxidative stress, was enhanced in placenta by LPS. Our study suggests that the induced Thioredoxin and Thioredoxin Reductase might protect the placenta from the stress induced by LPS.