The Experts below are selected from a list of 10407 Experts worldwide ranked by ideXlab platform
Elias S J Arner - One of the best experts on this subject based on the ideXlab platform.
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inhibition and crosslinking of the selenoprotein Thioredoxin Reductase 1 by p benzoquinone
Redox biology, 2020Co-Authors: Nan Shu, Qing Cheng, Elias S J Arner, Michael J DaviesAbstract:Abstract Quinones are common in nature, and often cytotoxic. Their proposed toxicity mechanisms involve redox cycling with radical generation, and/or reactions with nucleophiles, such as protein cysteine (Cys) residues, forming adducts via Michael addition reactions. The selenenyl anion of selenocysteine (Sec) is a stronger nucleophile, more prevalent at physiological pH, and more reactive than the corresponding thiolate anion of Cys. We therefore hypothesized that Sec residues should be readily modified by quinones and with potential consequences for the structure and function of selenoproteins. Here, we report data on the interaction of p-benzoquinone (BQ) with the selenoprotein Thioredoxin Reductase-1 (TrxR1), which exposes an accessible Sec residue upon physiological reduction by NADPH. Our results reveal that BQ targets NADPH-reduced TrxR1 and inhibits its activity using 5,5′-dithiobis(2-nitrobenzoic acid) or juglone as model substrates, consistent with the targeting of both the Cys and Sec residues of TrxR1. In the absence of NADPH, BQ modified the non-catalytic Cys residues, leading to subunit crosslinking, mainly through disulfides, which also resulted in some loss of activity. This crosslinking was time-dependent and independent of the Sec residue. Addition of NADPH after BQ pre-treatment could resolve the disulfide-linked crosslinking. TrxR activity loss was also observed upon incubation of J774A.1 cells or cell lysates with BQ. These data suggest that BQ readily targets TrxR1, albeit in a rather complex manner, which results in structural changes and loss of enzyme activity. We suggest that TrxR1 targeting can explain some of the cytotoxicity of BQ, and potentially also that of other quinone compounds.
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specific irreversible targeting of the selenoprotein Thioredoxin Reductase 1 in cancer therapy
Free Radical Biology and Medicine, 2018Co-Authors: Elias S J ArnerAbstract:The cytosolic selenoprotein Thioredoxin Reductase 1 (TrxR1, TXNRD1) is a key enzyme for redox control of cell function and antioxidant capacity. Many cancer cells have high levels of TrxR1 as a means of surviving their increased endogenous oxidative stress. This in turn has led to the hypothesis that TrxR1 may be an anticancer drug target, especially as the enzyme is dispensable for normal adult cells. Interestingly TrxR1 is also inhibited by several anticancer drugs in clinical use, including cisplatin, chlorambucil, nitrosoureas and melphalan. It is also a well-known target of gold compounds such as auranofin, currently in clinical trials for anticancer treatment. It has not been known, however, whether inhibition of TrxR1 is a mechanism leading to some of the anticancer effects seen upon use of some of these compounds, or whether this enzyme inhibition is merely a correlative event due to a high inherent reactivity of TrxR1. Novel findings with more specific inhibitors however suggest that TrxR1 can indeed be an authentic anticancer drug target, the inhibition of which yields anticancer efficacy in mouse models without overt toxicity to normal cells and tissues.
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Thioredoxin Reductase 1 and nadph directly protect protein tyrosine phosphatase 1b from inactivation during h2o2 exposure
Journal of Biological Chemistry, 2017Co-Authors: Qing Cheng, Elias S J Arner, Markus Dagnell, Paul E Pace, Jeroen Frijhoff, Arne Ostman, Mark B Hampton, Christine C WinterbournAbstract:Regulation of growth factor signaling involves reversible inactivation of protein tyrosine phosphatases (PTPs) through the oxidation and reduction of their active site cysteine. However, there is limited mechanistic understanding of these redox events and their co-ordination in the presence of cellular antioxidant networks. Here we investigated interactions between PTP1B and the peroxiredoxin 2 (Prx2)/Thioredoxin 1 (Trx1)/Thioredoxin Reductase 1 (TrxR1) network. We found that Prx2 becomes oxidized in PDGF-treated fibroblasts, but only when TrxR1 has first been inhibited. Using purified proteins, we also found that PTP1B is relatively insensitive to inactivation by H2O2 but found no evidence for a relay mechanism in which Prx2 or Trx1 facilitates PTP1B oxidation. Instead, these proteins prevented PTP1B inactivation by H2O2 Intriguingly, we discovered that TrxR1/NADPH directly protects PTP1B from inactivation when present during the H2O2 exposure. This protection was dependent on the concentration of TrxR1 and independent of Trx1 and Prx2. The protection was blocked by auranofin and required an intact selenocysteine residue in TrxR1. This activity likely involves reduction of the sulfenic acid intermediate form of PTP1B by TrxR1 and is therefore distinct from the previously described reactivation of end-point oxidized PTP1B, which requires both Trx1 and TrxR1. The ability of TrxR1 to directly reduce an oxidized phosphatase is a novel activity that can help explain previously observed increases in PTP1B oxidation and PDGF receptor phosphorylation in TrxR1 knockout cells. The activity of TrxR1 is therefore of potential relevance for understanding the mechanisms of redox regulation of growth factor signaling pathways.
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cytosolic Thioredoxin Reductase 1 is required for correct disulfide formation in the er
The EMBO Journal, 2017Co-Authors: Greg J Poet, Elias S J Arner, Philip Robinson, Ojore B V Oka, Marcel Van Lith, Zhenbo Cao, Marie Anne Pringle, Neil J. BulleidAbstract:Folding of proteins entering the secretory pathway in mammalian cells frequently requires the insertion of disulfide bonds. Disulfide insertion can result in covalent linkages found in the native structure as well as those that are not, so‐called non‐native disulfides. The pathways for disulfide formation are well characterized, but our understanding of how non‐native disulfides are reduced so that the correct or native disulfides can form is poor. Here, we use a novel assay to demonstrate that the reduction in non‐native disulfides requires NADPH as the ultimate electron donor, and a robust cytosolic Thioredoxin system, driven by Thioredoxin Reductase 1 (TrxR1 or TXNRD1). Inhibition of this reductive pathway prevents the correct folding and secretion of proteins that are known to form non‐native disulfides during their folding. Hence, we have shown for the first time that mammalian cells have a pathway for transferring reducing equivalents from the cytosol to the ER, which is required to ensure correct disulfide formation in proteins entering the secretory pathway. ![][1] Correcting non‐native disulfides in secreted proteins, an unexpected role for the cytosol. [1]: /embed/graphic-1.gif
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cytosolic Thioredoxin Reductase 1 is required for correct disulfide formation in the er
The EMBO Journal, 2017Co-Authors: Greg J Poet, Elias S J Arner, Philip Robinson, Ojore B V Oka, Marcel Van Lith, Zhenbo Cao, Marie Anne Pringle, Neil J. BulleidAbstract:Folding of proteins entering the secretory pathway in mammalian cells frequently requires the insertion of disulfide bonds. Disulfide insertion can result in covalent linkages found in the native structure as well as those that are not, so-called non-native disulfides. The pathways for disulfide formation are well characterized, but our understanding of how non-native disulfides are reduced so that the correct or native disulfides can form is poor. Here, we use a novel assay to demonstrate that the reduction in non-native disulfides requires NADPH as the ultimate electron donor, and a robust cytosolic Thioredoxin system, driven by Thioredoxin Reductase 1 (TrxR1 or TXNRD1). Inhibition of this reductive pathway prevents the correct folding and secretion of proteins that are known to form non-native disulfides during their folding. Hence, we have shown for the first time that mammalian cells have a pathway for transferring reducing equivalents from the cytosol to the ER, which is required to ensure correct disulfide formation in proteins entering the secretory pathway.
Dolph L Hatfield - One of the best experts on this subject based on the ideXlab platform.
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the 15kda selenoprotein and Thioredoxin Reductase 1 promote colon cancer by different pathways
PLOS ONE, 2015Co-Authors: Petra A Tsuji, Bradley A Carlson, Minhyuk Yoo, Salvador Naranjosuarez, Vadim N Gladyshev, Esther Asaki, Harold E Seifried, William C Reinhold, Cindy D Davis, Dolph L HatfieldAbstract:Selenoproteins mediate much of the cancer-preventive properties of the essential nutrient selenium, but some of these proteins have been shown to also have cancer-promoting effects. We examined the contributions of the 15kDa selenoprotein (Sep15) and Thioredoxin Reductase 1 (TR1) to cancer development. Targeted down-regulation of either gene inhibited anchorage-dependent and anchorage-independent growth and formation of experimental metastases of mouse colon carcinoma CT26 cells. Surprisingly, combined deficiency of Sep15 and TR1 reversed the anti-cancer effects observed with down-regulation of each single gene. We found that inflammation-related genes regulated by Stat-1, especially interferon-γ-regulated guanylate-binding proteins, were highly elevated in Sep15-deficient, but not in TR1-deficient cells. Interestingly, components of the Wnt/β-catenin signaling pathway were up-regulated in cells lacking both TR1 and Sep15. These results suggest that Sep15 and TR1 participate in interfering regulatory pathways in colon cancer cells. Considering the variable expression levels of Sep15 and TR1 found within the human population, our results provide insights into new roles of selenoproteins in cancer.
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disruption of Thioredoxin Reductase 1 protects mice from acute acetaminophen induced hepatotoxicity through enhanced nrf2 activity
Chemical Research in Toxicology, 2013Co-Authors: Andrew D Patterson, Marcus Conrad, Bradley A Carlson, Minhyuk Yoo, Jessica A Bonzo, Kristopher W Krausz, Chi Chen, Frank J Gonzalez, Dolph L HatfieldAbstract:The critical importance of glutathione in mitigating the deleterious effects of electrophile generating drugs such as acetaminophen (APAP) is well established. However, the role of other antioxidant systems, such as that provided by Thioredoxin, has not been extensively studied. Selenoprotein Thioredoxin Reductase 1 (Txnrd1) is important for attenuating activation of the apoptosis signaling-regulating kinase 1 (ASK1) and the c-Jun N-terminal kinase (JNK) pathway caused by high doses of APAP. Therefore, a detailed investigation of the role of Txnrd1 in APAP-induced hepatotoxicity was conducted. Liver-specific Txnrd1 knockout mice (Txnrd1(ΔLiv)) were generated and treated with a hepatotoxic dose (400 mg/kg) of APAP for 1 or 6 h. Liver toxicity was assessed by measuring the activities of liver enzymes aspartate aminotransferase and alanine aminotransferase in serum, in addition to histopathological analysis of liver sections and analysis of glutathione levels. At 1 h post-APAP treatment, total and mitochondrial glutathione levels in control and Txnrd1(ΔLiv) mice were similarly depleted. However, at 6 h post-APAP treatment, Txnrd1(ΔLiv) mice were resistant to APAP toxicity as liver enzymes and histology were not significantly different from the corresponding untreated mice. Analyses revealed the compensatory up-regulation of many of the nuclear factor erythroid 2-related factor 2 (NRF2) target genes and proteins in Txnrd1(ΔLiv) mice with and without APAP treatment. Yet, JNK was phosphorylated to a similar extent in APAP-treated control mice. The results suggest that Txnrd1(ΔLiv) mice are primed for xenobiotic detoxication primarily through NRF2 activation.
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Thioredoxin Reductase 1 protects against chemically induced hepatocarcinogenesis via control of cellular redox homeostasis
Carcinogenesis, 2012Co-Authors: Bradley A Carlson, Minhyuk Yoo, Ryuta Tobe, Charles Mueller, Salvador Naranjosuarez, Victoria Hoffmann, Vadim N Gladyshev, Dolph L HatfieldAbstract:Thioredoxin Reductase 1 (TR1) controls the redox state of protein thiols in mammalian cells and has been shown to have roles in both preventing and promoting cancer. To define the role of this selenoenzyme in hepatocellular carcinoma development, we examined tumor incidence in the liver of mice with tissue-specific knockout of mouse TR1 subjected to the liver carcinogen, diethylnitrosamine (DEN). TR1-deficient livers manifested ~90% tumor incidence compared with ~16% in control livers. The TR1-dependent effect was observed independent of sex, and, in control mice, tumorigenesis did not affect the expression of TR1. On the other hand, we observed upregulation of another selenoenzyme, glutathione peroxidase 2 (GPx2), and components of the glutathione (GSH) system, including those that generate reduced GSH. Overall, this study shows that TR1 protects against chemically induced hepatocarcinogenesis via the control of the cellular redox state, whereas its role in promoting this type of cancer is minimal.
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Thioredoxin Reductase 1 deficiency enhances selenite toxicity in cancer cells via a Thioredoxin independent mechanism
Biochemical Journal, 2012Co-Authors: Ryuta Tobe, Bradley A Carlson, Minhyuk Yoo, Vadim N Gladyshev, Noelia Fradejas, Soledad Calvo, Dolph L HatfieldAbstract:Selenium is an essential trace element in mammals, but is toxic at high levels. It is best known for its cancer prevention activity, but cancer cells are more sensitive to selenite toxicity than normal cells. Since selenite treatment leads to oxidative stress, and the Trx (Thioredoxin) system is a major antioxidative system, we examined the interplay between TR1 (Trx Reductase 1) and Trx1 deficiencies and selenite toxicity in DT cells, a malignant mouse cell line, and the corresponding parental NIH 3T3 cells. TR1-deficient cells were far more sensitive to selenite toxicity than Trx1-deficient or control cells. In contrast, this effect was not seen in cells treated with hydrogen peroxide, suggesting that the increased sensitivity of TR1 deficiency to selenite was not due to oxidative stress caused by this compound. Further analyses revealed that only TR1-deficient cells manifested strongly enhanced production and secretion of glutathione, which was associated with increased sensitivity of the cells to selenite. The results suggest a new role for TR1 in cancer that is independent of Trx reduction and compensated for by the glutathione system. The results also suggest that the enhanced selenite toxicity of cancer cells and simultaneous inhibition of TR1 can provide a new avenue for cancer therapy.
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hif independent regulation of Thioredoxin Reductase 1 contributes to the high levels of reactive oxygen species induced by hypoxia
PLOS ONE, 2012Co-Authors: Salvador Naranjosuarez, Bradley A Carlson, Minhyuk Yoo, Vadim N Gladyshev, Petra A Tsuji, Dolph L HatfieldAbstract:Cellular adaptation to hypoxic conditions mainly involves transcriptional changes in which hypoxia inducible factors (HIFs) play a critical role. Under hypoxic conditions, HIF protein is stabilized due to inhibition of the activity of prolyl hydroxylases (EGLNs). Because the reaction carried out by these enzymes uses oxygen as a co-substrate it is generally accepted that the hypoxic inhibition of EGLNs is due to the reduction in oxygen levels. However, several studies have reported that hypoxic generation of mitochondrial reactive oxygen species (ROS) is required for HIF stabilization. Here, we show that hypoxia downregulates Thioredoxin Reductase 1 (TR1) mRNA and protein levels. This hypoxic TR1 regulation is HIF independent, as HIF stabilization by EGLNs inhibitors does not affect TR1 expression and HIF deficiency does not block TR1 hypoxic-regulation, and it has an effect on TR1 function, as hypoxic conditions also reduce TR1 activity. We found that, when cultured under hypoxic conditions, TR1 deficient cells showed a larger accumulation of ROS compared to control cells, whereas TR1 over-expression was able to block the hypoxic generation of ROS. Furthermore, the changes in ROS levels observed in TR1 deficient or TR1 over-expressing cells did not affect HIF stabilization or function. These results indicate that hypoxic TR1 down-regulation is important in maintaining high levels of ROS under hypoxic conditions and that HIF stabilization and activity do not require hypoxic generation of ROS.
Qing Cheng - One of the best experts on this subject based on the ideXlab platform.
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inhibition and crosslinking of the selenoprotein Thioredoxin Reductase 1 by p benzoquinone
Redox biology, 2020Co-Authors: Nan Shu, Qing Cheng, Elias S J Arner, Michael J DaviesAbstract:Abstract Quinones are common in nature, and often cytotoxic. Their proposed toxicity mechanisms involve redox cycling with radical generation, and/or reactions with nucleophiles, such as protein cysteine (Cys) residues, forming adducts via Michael addition reactions. The selenenyl anion of selenocysteine (Sec) is a stronger nucleophile, more prevalent at physiological pH, and more reactive than the corresponding thiolate anion of Cys. We therefore hypothesized that Sec residues should be readily modified by quinones and with potential consequences for the structure and function of selenoproteins. Here, we report data on the interaction of p-benzoquinone (BQ) with the selenoprotein Thioredoxin Reductase-1 (TrxR1), which exposes an accessible Sec residue upon physiological reduction by NADPH. Our results reveal that BQ targets NADPH-reduced TrxR1 and inhibits its activity using 5,5′-dithiobis(2-nitrobenzoic acid) or juglone as model substrates, consistent with the targeting of both the Cys and Sec residues of TrxR1. In the absence of NADPH, BQ modified the non-catalytic Cys residues, leading to subunit crosslinking, mainly through disulfides, which also resulted in some loss of activity. This crosslinking was time-dependent and independent of the Sec residue. Addition of NADPH after BQ pre-treatment could resolve the disulfide-linked crosslinking. TrxR activity loss was also observed upon incubation of J774A.1 cells or cell lysates with BQ. These data suggest that BQ readily targets TrxR1, albeit in a rather complex manner, which results in structural changes and loss of enzyme activity. We suggest that TrxR1 targeting can explain some of the cytotoxicity of BQ, and potentially also that of other quinone compounds.
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Irreversible inhibition of cytosolic Thioredoxin Reductase 1 as a mechanistic basis for anticancer therapy.
Science Translational Medicine, 2018Co-Authors: William C. Stafford, Xiaoxiao Peng, Maria Hägg Olofsson, Xiaonan Zhang, Diane K. Luci, Qing Cheng, Lionel Trésaugues, Thomas S. Dexheimer, Nathan P. CoussensAbstract:Cancer cells adapt to their inherently increased oxidative stress through activation of the glutathione (GSH) and Thioredoxin (TXN) systems. Inhibition of both of these systems effectively kills cancer cells, but such broad inhibition of antioxidant activity also kills normal cells, which is highly unwanted in a clinical setting. We therefore evaluated targeting of the TXN pathway alone and, more specifically, selective inhibition of the cytosolic selenocysteine-containing enzyme TXN Reductase 1 (TXNRD1). TXNRD1 inhibitors were discovered in a large screening effort and displayed increased specificity compared to pan-TXNRD inhibitors, such as auranofin, that also inhibit the mitochondrial enzyme TXNRD2 and additional targets. For our lead compounds, TXNRD1 inhibition correlated with cancer cell cytotoxicity, and inhibitor-triggered conversion of TXNRD1 from an antioxidant to a pro-oxidant enzyme correlated with corresponding increases in cellular production of H2O2 In mice, the most specific TXNRD1 inhibitor, here described as TXNRD1 inhibitor 1 (TRi-1), impaired growth and viability of human tumor xenografts and syngeneic mouse tumors while having little mitochondrial toxicity and being better tolerated than auranofin. These results display the therapeutic anticancer potential of irreversibly targeting cytosolic TXNRD1 using small molecules and present potent and selective TXNRD1 inhibitors. Given the pronounced up-regulation of TXNRD1 in several metastatic malignancies, it seems worthwhile to further explore the potential benefit of specific irreversible TXNRD1 inhibitors for anticancer therapy.
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Thioredoxin Reductase 1 and nadph directly protect protein tyrosine phosphatase 1b from inactivation during h2o2 exposure
Journal of Biological Chemistry, 2017Co-Authors: Qing Cheng, Elias S J Arner, Markus Dagnell, Paul E Pace, Jeroen Frijhoff, Arne Ostman, Mark B Hampton, Christine C WinterbournAbstract:Regulation of growth factor signaling involves reversible inactivation of protein tyrosine phosphatases (PTPs) through the oxidation and reduction of their active site cysteine. However, there is limited mechanistic understanding of these redox events and their co-ordination in the presence of cellular antioxidant networks. Here we investigated interactions between PTP1B and the peroxiredoxin 2 (Prx2)/Thioredoxin 1 (Trx1)/Thioredoxin Reductase 1 (TrxR1) network. We found that Prx2 becomes oxidized in PDGF-treated fibroblasts, but only when TrxR1 has first been inhibited. Using purified proteins, we also found that PTP1B is relatively insensitive to inactivation by H2O2 but found no evidence for a relay mechanism in which Prx2 or Trx1 facilitates PTP1B oxidation. Instead, these proteins prevented PTP1B inactivation by H2O2 Intriguingly, we discovered that TrxR1/NADPH directly protects PTP1B from inactivation when present during the H2O2 exposure. This protection was dependent on the concentration of TrxR1 and independent of Trx1 and Prx2. The protection was blocked by auranofin and required an intact selenocysteine residue in TrxR1. This activity likely involves reduction of the sulfenic acid intermediate form of PTP1B by TrxR1 and is therefore distinct from the previously described reactivation of end-point oxidized PTP1B, which requires both Trx1 and TrxR1. The ability of TrxR1 to directly reduce an oxidized phosphatase is a novel activity that can help explain previously observed increases in PTP1B oxidation and PDGF receptor phosphorylation in TrxR1 knockout cells. The activity of TrxR1 is therefore of potential relevance for understanding the mechanisms of redox regulation of growth factor signaling pathways.
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84 Thioredoxin Reductase 1 directly protects protein tyrosine phosphatase 1b from inactivation by h2o2
Free Radical Biology and Medicine, 2016Co-Authors: Markus Dagnell, Qing Cheng, Elias S J Arner, Paul E Pace, Jeroen Frijhoff, Arne Ostman, Mark B Hampton, Christine C WinterbournAbstract:Regulation of growth factor signaling can occur through oxidation and reduction of the active site cysteine of protein tyrosine phosphatases (PTPs). Growth factor stimulation leads to increased H 2 O 2 production and subsequent PTP inactivation. However, there is limited understanding of how these redox events inter-relate with cellular antioxidant systems. Here we have investigated the interaction between PTP1B and the peroxiredoxin 2 (Prx2) / Thioredoxin 1 (Trx1) / Thioredoxin Reductase 1 (TrxR1) network. We found that Prx2 became oxidized in fibroblasts treated with PDGF, but only when TrxR1 had first been inhibited. Using purified proteins we showed that PTP1B was relatively insensitive to inactivation by H 2 O 2 , but found no evidence for a relay mechanism in which Prx2 or Trx1 facilitated PTP1B oxidation. Instead, these proteins protected PTP1B against inactivation by H 2 O 2 . Intriguingly, we discovered that TrxR1 directly protects PTP1B from inactivation by H 2 O 2 , independently of Trx1 and Prx2. This protection was blocked by auranofin and required an intact selenocysteine residue of TrxR1. This activity likely involves reduction of the sulfenic acid intermediate form of PTP1B and is distinct from the previously described reactivation of end-point oxidized PTP1B, which requires Trx1 as well as TrxR1. The ability of TrxR1 to reduce an oxidized phosphatase directly is a novel activity of potential relevance for understanding mechanisms of redox modulation of growth factor signaling pathways.
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details in the catalytic mechanism of mammalian Thioredoxin Reductase 1 revealed using point mutations and juglone coupled enzyme activities
Free Radical Biology and Medicine, 2016Co-Authors: Qing Cheng, Elias S J ArnerAbstract:The mammalian selenoprotein Thioredoxin Reductase 1 (TrxR1) is a key enzyme in redox regulation, antioxidant defense, and cellular growth. TrxR1 can catalyze efficient reduction of juglone (5-hydroxy-1,4-naphthoquinone; walnut toxin) in a reaction which, in contrast to reduction of most other substrates of TrxR1, is not dependent upon an intact selenocysteine (Sec, U) residue of the enzyme. Using a number of TrxR1 mutant variants, we here found that a sole Cys residue at the C-terminal tail of TrxR1 is required for high-efficiency juglone-coupled NADPH oxidase activity of Sec-deficient enzyme, occurring with mixed one- and two-electron reactions producing superoxide. The activity also utilizes the FAD and the N-terminal redox active disulfide/dithiol motif of TrxR1. If a sole Cys residue at the C-terminal tail of TrxR1, in the absence of Sec, was moved further towards the C-terminal end of the protein compared to its natural position at residue 497, juglone reduction was, surprisingly, further increased. Ala substitutions of Trp407, Asn418 and Asn419 in a previously described "guiding bar", thought to mediate interactions of the C-terminal tail of TrxR1 with the FAD/dithiol site at the N-terminal domain of the other subunit in the dimeric enzyme, lowered turnover with juglone about 4.5-fold. Four residues of Sec-deficient TrxR1 were found to be easily arylated by juglone, including the Cys residue at position 497. Based upon our observations we suggest a model for involvement of the juglone-arylated C-terminal motif of TrxR1 to explain its high activity with juglone. This study thus provides novel insights into the catalytic mechanisms of TrxR1. One-electron juglone reduction by TrxR1 producing superoxide should furthermore contribute to the well-known prooxidant cytotoxicity of juglone.
Vadim N Gladyshev - One of the best experts on this subject based on the ideXlab platform.
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the 15kda selenoprotein and Thioredoxin Reductase 1 promote colon cancer by different pathways
PLOS ONE, 2015Co-Authors: Petra A Tsuji, Bradley A Carlson, Minhyuk Yoo, Salvador Naranjosuarez, Vadim N Gladyshev, Esther Asaki, Harold E Seifried, William C Reinhold, Cindy D Davis, Dolph L HatfieldAbstract:Selenoproteins mediate much of the cancer-preventive properties of the essential nutrient selenium, but some of these proteins have been shown to also have cancer-promoting effects. We examined the contributions of the 15kDa selenoprotein (Sep15) and Thioredoxin Reductase 1 (TR1) to cancer development. Targeted down-regulation of either gene inhibited anchorage-dependent and anchorage-independent growth and formation of experimental metastases of mouse colon carcinoma CT26 cells. Surprisingly, combined deficiency of Sep15 and TR1 reversed the anti-cancer effects observed with down-regulation of each single gene. We found that inflammation-related genes regulated by Stat-1, especially interferon-γ-regulated guanylate-binding proteins, were highly elevated in Sep15-deficient, but not in TR1-deficient cells. Interestingly, components of the Wnt/β-catenin signaling pathway were up-regulated in cells lacking both TR1 and Sep15. These results suggest that Sep15 and TR1 participate in interfering regulatory pathways in colon cancer cells. Considering the variable expression levels of Sep15 and TR1 found within the human population, our results provide insights into new roles of selenoproteins in cancer.
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Thioredoxin Reductase 1 protects against chemically induced hepatocarcinogenesis via control of cellular redox homeostasis
Carcinogenesis, 2012Co-Authors: Bradley A Carlson, Minhyuk Yoo, Ryuta Tobe, Charles Mueller, Salvador Naranjosuarez, Victoria Hoffmann, Vadim N Gladyshev, Dolph L HatfieldAbstract:Thioredoxin Reductase 1 (TR1) controls the redox state of protein thiols in mammalian cells and has been shown to have roles in both preventing and promoting cancer. To define the role of this selenoenzyme in hepatocellular carcinoma development, we examined tumor incidence in the liver of mice with tissue-specific knockout of mouse TR1 subjected to the liver carcinogen, diethylnitrosamine (DEN). TR1-deficient livers manifested ~90% tumor incidence compared with ~16% in control livers. The TR1-dependent effect was observed independent of sex, and, in control mice, tumorigenesis did not affect the expression of TR1. On the other hand, we observed upregulation of another selenoenzyme, glutathione peroxidase 2 (GPx2), and components of the glutathione (GSH) system, including those that generate reduced GSH. Overall, this study shows that TR1 protects against chemically induced hepatocarcinogenesis via the control of the cellular redox state, whereas its role in promoting this type of cancer is minimal.
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Thioredoxin Reductase 1 deficiency enhances selenite toxicity in cancer cells via a Thioredoxin independent mechanism
Biochemical Journal, 2012Co-Authors: Ryuta Tobe, Bradley A Carlson, Minhyuk Yoo, Vadim N Gladyshev, Noelia Fradejas, Soledad Calvo, Dolph L HatfieldAbstract:Selenium is an essential trace element in mammals, but is toxic at high levels. It is best known for its cancer prevention activity, but cancer cells are more sensitive to selenite toxicity than normal cells. Since selenite treatment leads to oxidative stress, and the Trx (Thioredoxin) system is a major antioxidative system, we examined the interplay between TR1 (Trx Reductase 1) and Trx1 deficiencies and selenite toxicity in DT cells, a malignant mouse cell line, and the corresponding parental NIH 3T3 cells. TR1-deficient cells were far more sensitive to selenite toxicity than Trx1-deficient or control cells. In contrast, this effect was not seen in cells treated with hydrogen peroxide, suggesting that the increased sensitivity of TR1 deficiency to selenite was not due to oxidative stress caused by this compound. Further analyses revealed that only TR1-deficient cells manifested strongly enhanced production and secretion of glutathione, which was associated with increased sensitivity of the cells to selenite. The results suggest a new role for TR1 in cancer that is independent of Trx reduction and compensated for by the glutathione system. The results also suggest that the enhanced selenite toxicity of cancer cells and simultaneous inhibition of TR1 can provide a new avenue for cancer therapy.
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hif independent regulation of Thioredoxin Reductase 1 contributes to the high levels of reactive oxygen species induced by hypoxia
PLOS ONE, 2012Co-Authors: Salvador Naranjosuarez, Bradley A Carlson, Minhyuk Yoo, Vadim N Gladyshev, Petra A Tsuji, Dolph L HatfieldAbstract:Cellular adaptation to hypoxic conditions mainly involves transcriptional changes in which hypoxia inducible factors (HIFs) play a critical role. Under hypoxic conditions, HIF protein is stabilized due to inhibition of the activity of prolyl hydroxylases (EGLNs). Because the reaction carried out by these enzymes uses oxygen as a co-substrate it is generally accepted that the hypoxic inhibition of EGLNs is due to the reduction in oxygen levels. However, several studies have reported that hypoxic generation of mitochondrial reactive oxygen species (ROS) is required for HIF stabilization. Here, we show that hypoxia downregulates Thioredoxin Reductase 1 (TR1) mRNA and protein levels. This hypoxic TR1 regulation is HIF independent, as HIF stabilization by EGLNs inhibitors does not affect TR1 expression and HIF deficiency does not block TR1 hypoxic-regulation, and it has an effect on TR1 function, as hypoxic conditions also reduce TR1 activity. We found that, when cultured under hypoxic conditions, TR1 deficient cells showed a larger accumulation of ROS compared to control cells, whereas TR1 over-expression was able to block the hypoxic generation of ROS. Furthermore, the changes in ROS levels observed in TR1 deficient or TR1 over-expressing cells did not affect HIF stabilization or function. These results indicate that hypoxic TR1 down-regulation is important in maintaining high levels of ROS under hypoxic conditions and that HIF stabilization and activity do not require hypoxic generation of ROS.
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protein kinase regulated expression and immune function of Thioredoxin Reductase 1 in mouse macrophages
Molecular Immunology, 2011Co-Authors: Bradley A Carlson, Marcus Conrad, Minhyuk Yoo, Vadim N Gladyshev, Dolph L Hatfield, Jin Mo ParkAbstract:Macrophages exposed to lipopolysaccharide (LPS) exhibit radical changes in mRNA and protein profiles. This shift in gene expression is geared not only to activate immune effector and regulatory mechanisms, but also to adjust the immune cell's metabolism to new physiological demands. However, it remains largely unknown whether immune function and metabolic state are mutually regulatory and, if so, how they are mechanistically interrelated in macrophages. Selenium, a dietary trace element exerting pleiotropic effects on immune homeostasis, and selenium-containing proteins (selenoproteins) may play a role in such coordination. We examined the incorporation of radiolabeled selenium into protein during LPS stimulation, and identified Thioredoxin Reductase 1 (TR1) as the only LPS-inducible selenoprotein in macrophages. TR1 induction occurred at the transcriptional level and depended on the intracellular signaling pathways mediated by p38 MAP kinase and IκB kinase. Macrophage-specific ablation of TR1 in mice resulted in a drastic decrease in the expression of VSIG4, a B7 family protein known to suppress T cell activation. These results reveal TR1 as both a regulator and a regulated target in the macrophage gene expression network, and suggest a link between selenium metabolism and immune signaling.
Minhyuk Yoo - One of the best experts on this subject based on the ideXlab platform.
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the 15kda selenoprotein and Thioredoxin Reductase 1 promote colon cancer by different pathways
PLOS ONE, 2015Co-Authors: Petra A Tsuji, Bradley A Carlson, Minhyuk Yoo, Salvador Naranjosuarez, Vadim N Gladyshev, Esther Asaki, Harold E Seifried, William C Reinhold, Cindy D Davis, Dolph L HatfieldAbstract:Selenoproteins mediate much of the cancer-preventive properties of the essential nutrient selenium, but some of these proteins have been shown to also have cancer-promoting effects. We examined the contributions of the 15kDa selenoprotein (Sep15) and Thioredoxin Reductase 1 (TR1) to cancer development. Targeted down-regulation of either gene inhibited anchorage-dependent and anchorage-independent growth and formation of experimental metastases of mouse colon carcinoma CT26 cells. Surprisingly, combined deficiency of Sep15 and TR1 reversed the anti-cancer effects observed with down-regulation of each single gene. We found that inflammation-related genes regulated by Stat-1, especially interferon-γ-regulated guanylate-binding proteins, were highly elevated in Sep15-deficient, but not in TR1-deficient cells. Interestingly, components of the Wnt/β-catenin signaling pathway were up-regulated in cells lacking both TR1 and Sep15. These results suggest that Sep15 and TR1 participate in interfering regulatory pathways in colon cancer cells. Considering the variable expression levels of Sep15 and TR1 found within the human population, our results provide insights into new roles of selenoproteins in cancer.
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disruption of Thioredoxin Reductase 1 protects mice from acute acetaminophen induced hepatotoxicity through enhanced nrf2 activity
Chemical Research in Toxicology, 2013Co-Authors: Andrew D Patterson, Marcus Conrad, Bradley A Carlson, Minhyuk Yoo, Jessica A Bonzo, Kristopher W Krausz, Chi Chen, Frank J Gonzalez, Dolph L HatfieldAbstract:The critical importance of glutathione in mitigating the deleterious effects of electrophile generating drugs such as acetaminophen (APAP) is well established. However, the role of other antioxidant systems, such as that provided by Thioredoxin, has not been extensively studied. Selenoprotein Thioredoxin Reductase 1 (Txnrd1) is important for attenuating activation of the apoptosis signaling-regulating kinase 1 (ASK1) and the c-Jun N-terminal kinase (JNK) pathway caused by high doses of APAP. Therefore, a detailed investigation of the role of Txnrd1 in APAP-induced hepatotoxicity was conducted. Liver-specific Txnrd1 knockout mice (Txnrd1(ΔLiv)) were generated and treated with a hepatotoxic dose (400 mg/kg) of APAP for 1 or 6 h. Liver toxicity was assessed by measuring the activities of liver enzymes aspartate aminotransferase and alanine aminotransferase in serum, in addition to histopathological analysis of liver sections and analysis of glutathione levels. At 1 h post-APAP treatment, total and mitochondrial glutathione levels in control and Txnrd1(ΔLiv) mice were similarly depleted. However, at 6 h post-APAP treatment, Txnrd1(ΔLiv) mice were resistant to APAP toxicity as liver enzymes and histology were not significantly different from the corresponding untreated mice. Analyses revealed the compensatory up-regulation of many of the nuclear factor erythroid 2-related factor 2 (NRF2) target genes and proteins in Txnrd1(ΔLiv) mice with and without APAP treatment. Yet, JNK was phosphorylated to a similar extent in APAP-treated control mice. The results suggest that Txnrd1(ΔLiv) mice are primed for xenobiotic detoxication primarily through NRF2 activation.
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Thioredoxin Reductase 1 protects against chemically induced hepatocarcinogenesis via control of cellular redox homeostasis
Carcinogenesis, 2012Co-Authors: Bradley A Carlson, Minhyuk Yoo, Ryuta Tobe, Charles Mueller, Salvador Naranjosuarez, Victoria Hoffmann, Vadim N Gladyshev, Dolph L HatfieldAbstract:Thioredoxin Reductase 1 (TR1) controls the redox state of protein thiols in mammalian cells and has been shown to have roles in both preventing and promoting cancer. To define the role of this selenoenzyme in hepatocellular carcinoma development, we examined tumor incidence in the liver of mice with tissue-specific knockout of mouse TR1 subjected to the liver carcinogen, diethylnitrosamine (DEN). TR1-deficient livers manifested ~90% tumor incidence compared with ~16% in control livers. The TR1-dependent effect was observed independent of sex, and, in control mice, tumorigenesis did not affect the expression of TR1. On the other hand, we observed upregulation of another selenoenzyme, glutathione peroxidase 2 (GPx2), and components of the glutathione (GSH) system, including those that generate reduced GSH. Overall, this study shows that TR1 protects against chemically induced hepatocarcinogenesis via the control of the cellular redox state, whereas its role in promoting this type of cancer is minimal.
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Thioredoxin Reductase 1 deficiency enhances selenite toxicity in cancer cells via a Thioredoxin independent mechanism
Biochemical Journal, 2012Co-Authors: Ryuta Tobe, Bradley A Carlson, Minhyuk Yoo, Vadim N Gladyshev, Noelia Fradejas, Soledad Calvo, Dolph L HatfieldAbstract:Selenium is an essential trace element in mammals, but is toxic at high levels. It is best known for its cancer prevention activity, but cancer cells are more sensitive to selenite toxicity than normal cells. Since selenite treatment leads to oxidative stress, and the Trx (Thioredoxin) system is a major antioxidative system, we examined the interplay between TR1 (Trx Reductase 1) and Trx1 deficiencies and selenite toxicity in DT cells, a malignant mouse cell line, and the corresponding parental NIH 3T3 cells. TR1-deficient cells were far more sensitive to selenite toxicity than Trx1-deficient or control cells. In contrast, this effect was not seen in cells treated with hydrogen peroxide, suggesting that the increased sensitivity of TR1 deficiency to selenite was not due to oxidative stress caused by this compound. Further analyses revealed that only TR1-deficient cells manifested strongly enhanced production and secretion of glutathione, which was associated with increased sensitivity of the cells to selenite. The results suggest a new role for TR1 in cancer that is independent of Trx reduction and compensated for by the glutathione system. The results also suggest that the enhanced selenite toxicity of cancer cells and simultaneous inhibition of TR1 can provide a new avenue for cancer therapy.
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hif independent regulation of Thioredoxin Reductase 1 contributes to the high levels of reactive oxygen species induced by hypoxia
PLOS ONE, 2012Co-Authors: Salvador Naranjosuarez, Bradley A Carlson, Minhyuk Yoo, Vadim N Gladyshev, Petra A Tsuji, Dolph L HatfieldAbstract:Cellular adaptation to hypoxic conditions mainly involves transcriptional changes in which hypoxia inducible factors (HIFs) play a critical role. Under hypoxic conditions, HIF protein is stabilized due to inhibition of the activity of prolyl hydroxylases (EGLNs). Because the reaction carried out by these enzymes uses oxygen as a co-substrate it is generally accepted that the hypoxic inhibition of EGLNs is due to the reduction in oxygen levels. However, several studies have reported that hypoxic generation of mitochondrial reactive oxygen species (ROS) is required for HIF stabilization. Here, we show that hypoxia downregulates Thioredoxin Reductase 1 (TR1) mRNA and protein levels. This hypoxic TR1 regulation is HIF independent, as HIF stabilization by EGLNs inhibitors does not affect TR1 expression and HIF deficiency does not block TR1 hypoxic-regulation, and it has an effect on TR1 function, as hypoxic conditions also reduce TR1 activity. We found that, when cultured under hypoxic conditions, TR1 deficient cells showed a larger accumulation of ROS compared to control cells, whereas TR1 over-expression was able to block the hypoxic generation of ROS. Furthermore, the changes in ROS levels observed in TR1 deficient or TR1 over-expressing cells did not affect HIF stabilization or function. These results indicate that hypoxic TR1 down-regulation is important in maintaining high levels of ROS under hypoxic conditions and that HIF stabilization and activity do not require hypoxic generation of ROS.