Search

Abstract Over the past seven decades, research on autotrophic and heterotrophic model organisms has defined how the flow of electrons ("reducing power") from high-energy inorganic sources, through biological systems, to low-energy inorganic products like water, powers all of Life's processes. Universally, an initial major biological recipient of these electrons is nicotinamide adenine dinucleotide-phosphate, which thereby transits from an oxidized state (NADP+) to a reduced state (NADPH). A portion of this reducing power is then distributed via the cellular NADPH-dependent disulfide reductase systems as sequential reductions of disulfide bonds. Along the disulfide reduction pathways, some enzymes have active sites that use the selenium-containing amino acid, selenocysteine, in place of the common but less reactive sulfur-containing cysteine. In particular, the mammalian/metazoan thioredoxin systems are usually selenium-dependent as, across metazoan phyla, most thioredoxin reductases are selenoproteins. Among the roles of the NADPH-dependent disulfide reductase systems, the most universal is that they provide the reducing power for the production of DNA precursors by ribonucleotide reductase (RNR). Some studies, however, have uncovered examples of NADPH-independent disulfide reductase systems that can also support RNR. These systems are summarized here and their implications are discussed. Graphical abstract fx1 Highlights • All species generate NADPH intracellularly, which fuels disulfide reductase systems. • Mammals have an NADPH-independent disulfide reductase system fueled by methionine. • Transsulfuration reversal allows Met-fueled reductase system yet makes Met essential. • Transsulfuration reversal and a Se- dependent TrxR family co-evolved with metazoans. • Metazoan selenoprotein TrxR1 and transsulfuration each support redox signaling. [ABSTRACT FROM AUTHOR]

Abstract This review highlights the contributions of Jean Chaudière to the field of selenium biochemistry. Chaudière was the first to recognize that one of the main reasons that selenium in the form of selenocysteine is used in proteins is due to the fact that it strongly resists permanent oxidation. The foundations for this important concept was laid down by Al Tappel in the 1960's and even before by others. The concept of oxygen tolerance first recognized in the study of glutathione peroxidase was further advanced and refined by those studying [NiFeSe]-hydrogenases, selenosubtilisin, and thioredoxin reductase. After 200 years of selenium research, work by Marcus Conrad and coworkers studying glutathione peroxidase-4 has provided definitive evidence for Chaudière's original hypothesis (Ingold et al., 2018) [36]. While the reaction of selenium with oxygen is readily reversible, there are many other examples of this phenomenon of reversibility. Many reactions of selenium can be described as "easy in – easy out". This is due to the strong nucleophilic character of selenium to attack electrophiles, but then this reaction can be reversed due to the strong electrophilic character of selenium and the weakness of the selenium-carbon bond. Several examples of this are described. Graphical abstract fx1 Highlights • Reactions of selenium are readily reversible in comparison to sulfur. • Contribution of Jean Chaudière to selenium biochemistry is highlighted. • Contribution of Al Tappel to selenium biochemistry is highlighted. • Selenium protects certain cell types. • Potential role of thioredoxin reductase in cystic fibrosis. [ABSTRACT FROM AUTHOR]

Abstract Mammalian cells employ elaborate antioxidant systems to effectively handle reactive oxygen and nitrogen species (ROS and RNS). At the heart of these systems operate two selenoprotein families consisting of glutathione peroxidase (GPx) and thioredoxin reductase (TrxR) enzymes. Although mostly studied in the context of oxidative stress, considerable evidence has amassed to indicate that these selenoenzymes also play important roles in nitrosative stress responses. GPx and TrxR, together with their redox partners, metabolize nitrosothiols and peroxynitrite, two major RNS. As such, these enzymes play active roles in the cellular defense against nitrosative stress. However, under certain conditions, these enzymes are inactivated by nitrosothiols or peroxynitrite, which may exacerbate oxidative and nitrosative stress in cells. The selenol groups in the active sites of GPx and TrxR enzymes are critically involved in these beneficial and detrimental processes. Further elucidation of the biochemical interactions between distinct RNS and GPx/TrxR will lead to a better understanding of the roles of these selenoenzymes in cellular homeostasis and disease. Graphical abstract fx1 Highlights • Nitrosothiols and peroxynitrite mediate diverse phatho-physiological responses. • GPx and TrxR selenoenzymes contribute to metabolism of nitrosothiols and peroxynitrite. • Selenoenzymes contribute to cellular defense against nitrosative stress. • Selenoenzymes are susceptible to inactivation by nitrosothiols and peroxynitrite. [ABSTRACT FROM AUTHOR]

Background Toxoflavin (1,6-dimethylpyrimido[5,4-e][1,2,4]triazine-5,7-dione; xanthothricin) is a well-known natural toxin of the pyrimidinetriazinedione type that redox cycles with oxygen under reducing conditions. In mammalian systems, toxoflavin is an inhibitor of Wnt signaling as well as of SIRT1 and SIRT2 activities, but other molecular targets in mammalian cells have been scarcely studied. Interestingly, in a library of nearly 400,000 compounds (PubChem assay ID 588456), toxoflavin was identified as one out of only 56 potential substrates of the mammalian selenoprotein thioredoxin reductase 1 (TrxR1, TXNRD1). This activity was here examined in further detail. Methods Kinetic parameters in interactions of toxoflavin with rat or human TrxR isoenzymes were determined and compared with those of juglone (5-Hydroxy-1,4-naphthoquinone; walnut toxin) and 9,10-phenanthrene quinone. Selenocysteine dependence was examined using Sec-to-Cys and Sec-to-Ser substituted variants of recombinant rat TrxR1. Results Toxoflavin was confirmed as an efficient substrate for TrxR. Rat and human cytosolic TrxR1 supported NADPH-dependent redox cycling coupled to toxoflavin reduction, accompanied by H 2 O 2 production under aerobic conditions. Apparent kinetic parameters for the initial rates of reduction showed that rat TrxR1 displayed higher apparent turnover ( k cat  = 1700 ± 330 min −1 ) than human TrxR1 ( k cat  = 1100  ±  82 min −1 ) but also a higher Km ( K m  = 24 ± 4.3 μM for human TrxR1 versus K m  = 54  ±  18 μM for rat TrxR1). Human TrxR2 (TXNRD2) was less efficient in reduction of toxoflavin ( K m  = 280 ± 110 μM and k cat  = 740 ± 240 min −1 ). The activity was absolutely dependent upon selenocysteine (Sec). Toxoflavin was also a subversive substrate indirectly inhibiting reduction of other substrates of TrxR1. Conclusions Our results identify toxoflavin as an efficient redox cycling substrate of mammalian TrxR enzymes, in a strict Sec-dependent manner. General significance Тhe interactions of toxoflavin with mammalian TrxR isoenzymes can help to explain parts of the molecular mechanisms giving rise to the well-known toxicity as well as pro-oxidant properties of this toxin. [ABSTRACT FROM AUTHOR]

Background Selenoproteins (25 genes in human) co-translationally incorporate selenocysteine using a UGA codon, normally used as a stop signal. The human selenoproteome is primarily regulated by selenium bioavailability with a tissue-specific hierarchy. Methods We investigated the hierarchy of selenoprotein expression in response to selenium concentration variation in four cell lines originating from kidney (HEK293, immortalized), prostate (LNCaP, cancer), skin (HaCaT, immortalized) and liver (HepG2, cancer), using complementary analytical methods. We performed (i) enzymatic activity, (ii) RT-qPCR, (iii) immuno-detection, (iv) selenium-specific mass spectrometric detection after non-radioactive 76 Se labeling of selenoproteins, and (v) luciferase-based reporter constructs in various cell extracts. Results We characterized cell-line specific alterations of the selenoproteome in response to selenium variation that, in most of the cases, resulted from a translational control of gene expression. We established that UGA-selenocysteine recoding efficiency, which depends on the nature of the SECIS element, dictates the response to selenium variation. Conclusions We characterized that selenoprotein hierarchy is cell-line specific with conserved features. This analysis should be done prior to any experiments in a novel cell line. General significance We reported a strategy based on complementary methods to evaluate selenoproteome regulation in human cells in culture. [ABSTRACT FROM AUTHOR]

Glutathione peroxidase (Gpx1) is the major selenoprotein in most tissues in animals. Knockout (KO) of Gpx1 decreases Gpx1 activity to near zero and substantially reduces liver selenium (Se) levels, but has no overt effects in otherwise healthy mice. To investigate the impact of deletion of Gpx1 on Se metabolism, Se flux, and apparent Se requirements, KO, Gpx1 heterozygous (Het), and Gpx1 wild-type (WT) mice were fed Se-deficient diet for 17 weeks, then repleted with graded levels of Se (0-0.3 μg Se/g as Na2SeO3) for 7 days, and selenoprotein activities and transcripts were determined in blood, liver, and kidney. Se deficiency decreased the activities of plasma Gpx3, liver Gpx1, liver Txnrd, and liver Gpx4 to 3, 0.3, 11, and 50% of WT Se-adequate levels, respectively, but the Gpx1 genotype had no effect on growth or changes in activity or expression of selenoproteins other than Gpx1. Se repletion increased selenoprotein transcripts to Se-adequate levels after 7 days; Se response curves and apparent Se requirements for selenoprotein transcripts were similar to those observed in studies starting with Se-adequate mice. With short-term Se repletion, selenoenzyme activities resulted in three Se response curve patterns: (1) liver and kidney Gpx1, Gpx4, and Txnrd activities were sigmoidal or hyperbolic with breakpoints (0.08-0.19 μg Se/g) that were double those observed in studies starting with Se-adequate mice; (2) red blood cell Gpx1 activity was not significantly changed; and (3) plasma Gpx3 activity only increased substantially with 0.3 μg Se/g. Plasma Gpx3 is secreted from kidney. In this short-term study, kidney Gpx3 mRNA reached plateau levels at 0.1 μg Se/g, and other kidney selenoenzyme activities reached plateau levels at ≤ 0.2 μg Se/g, so sufficient Se should have been present in kidney. Thus, the delayed increase in plasma Gpx3 activity suggests that newly synthesized and secreted kidney Gpx3 is preferentially retained in kidney or rapidly cleared by binding to basement membranes in kidney or in other tissues. This repletion study shows that loss of capacity to incorporate Se into Gpx1 in Gpx1 KO mice does not dramatically alter expression of other Se biomarkers, nor the short-term flux of Se from intestine to liver to kidney. [ABSTRACT FROM AUTHOR]

Abstract Thioredoxin glutathione reductase (TGRsec) is a multi-domain flavoprotein that plays a principal role in redox homeostasis maintenance. We have previously demonstrated the role of selenocysteine in maintaining TGRsec structure-function, but the role of the glutaredoxin (Grx) domain and FAD is still unclear. In the present study, the urea-induced unfolding of recombinant Fasciola gigantica TGRsec (FgTGRsec) and its N-terminal truncated variant (ΔNTD-FgTGRsec) were examined to understand the role of the Grx domain and FAD in the stabilization of FgTGRsec and ΔNTD-FgTGRsec. Our results showed that both proteins underwent unfolding in a three state manner. First, the protein undergoes a conformational transition rendering a near-native state with no FAD bound, and then full unfolding of the apo-dimer occurs without dissociation. The Grx domain stabilized the global FgTGRsec structure and positively regulated FgTGRsec activity, and alteration in the FAD microenvironment was directly proportional to the loss of thioredoxin reductase (TrxR) and glutathione reductase activities. Based on these results, we concluded that the Grx domain stabilizes the full-length FgTGRsec protein for efficient catalysis. Thus, we suggest that in platyhelminth parasites, during evolution, the Grx domain merged with the TrxR domain to confer higher catalytic activity and provide additional structural stability to the full-length TGR. Highlights • The selenoenzyme TGR is a multi-functional flavoenzyme that plays a principal role in redox homeostasis maintenance. • The role of the glutaredoxin (Grx) domain and FAD in any TGR is still unclear. • In the present study, we examined the role of the Grx domain and FAD in the stabilization of FgTGRsec and ΔNTD-FgTGRsec. • Our results showed that the Grx domain stabilized the overall FgTGRsec structure and positively regulated FgTGRsec activity. • We suggest that in platyhelminth parasites, during evolution, the Grx domain merged with the TrxR domain to confer higher catalytic activity and provide additional structural stability to the full-length TGR. [ABSTRACT FROM AUTHOR]

Purpose: Accumulating data demonstrate that oxidative stress may play a crucial role in obsessive-compulsive disorder (OCD). This study aimed to investigate the role of 8-F2-isoprostane, thioredoxin (Trx), and thioredoxin reductase (TrxR) in children with OCD. Materials and methods: Thirty-three drug-free children with OCD and 35 healthy controls were included in this study. The severity of OCD symptoms was assessed via the Children's Yale Brown Obsessive-Compulsive Scale. The severity of anxiety levels was determined through the Screen for Child Anxiety-Related Emotional Disorders. Plasma levels of 8-F2-isoprostane, Trx, and TrxR were measured using commercial enzyme-linked immunosorbent assay kits. Results: Plasma 8-F2-isoprostane, Trx, and TrxR levels did not show any significant differences between patient and control groups. There were no significant correlations between plasma levels of these antioxidants and severity of OCD. Conclusions: Findings of this study did not support the involvement of oxidative stress in the etiology of childhood OCD. [ABSTRACT FROM AUTHOR]

Thioredoxin reductase-1 (TXNRD1) inhibition effectively activates nuclear factor (erythroid-derived 2)-like 2 (Nrf2) responses and attenuates lung injury in acute respiratory distress syndrome (ARDS) and bronchopulmonary dysplasia (BPD) models. Upon TXNRD1 inhibition, heme oxygenase-1 (HO-1) is disproportionally increased compared with Nrf2 target NADPH quinone oxidoreductase-1 (Nqo1). HO-1 has been investigated as a potential therapeutic target in both ARDS and BPD. TXNRD1 is predominantly expressed in airway epithelial cells; however, the mechanism of HO-1 induction by TXNRD1 inhibitors is unknown. We tested the hypothesis that TXNRD1 inhibition induces HO-1 via Nrf2-dependent mechanisms. Wild-type (WT), Nrf2KO1.3, and Nrf2KO2.2 cells were morphologically indistinguishable, indicating that Nrf2 can be deleted from murine-transformed club cells (mtCCs) using CRISPR/Cas9 gene editing. Hemin, a Nrf2-independent HO-1-inducing agent, significantly increased HO-1 expression in WT, Nrf2KO1.3, and Nrf2KO2.2. Auranofin (AFN) (0.5 µM) inhibited TXNRD1 activity by 50% and increased Nqo1 and Hmox1 mRNA levels by 6- and 24-fold, respectively, in WT cells. Despite similar levels of TXNRD1 inhibition, Nqo1 mRNA levels were not different between control and AFN-treated Nrf2KO1.3 and Nrf2KO2.2. AFN slightly increased Hmox1 mRNA levels in Nrf2KO1.3 and Nrf2KO2.2 cells compared with controls. AFN failed to increase HO-1 protein in Nrf2KO1.3 and Nrf2KO2.2 compared with a 36-fold increase in WT mtCCs. Our data indicate that Nrf2 is the primary mechanism by which TXNRD1 inhibitors increase HO-1 in lung epithelia. Future studies will use ARDS and BPD models to define the role of HO-1 in attenuation of lung injury by TXNRD1 inhibitors. [ABSTRACT FROM AUTHOR]

Abstract A series of four new mononuclear cationic gold(I) complexes containing nitrogen functionalized N -heterocyclic carbenes (NHCs) was synthesized and fully characterized by spectroscopic methods. The X-ray structures of three complexes are presented. These lipophilic gold(I) complexes originate from a pharmacomodulation of previously described gold(I)-NHC complexes, by replacing an aliphatic spacer with an aromatic one. The Log P values of the resulting complexes increased by 0.7–1.5, depending on the substituents in comparison to the aliphatic-linker systems. The new series of complexes has been investigated in vitro for their anti-cancer activities in PC-3 (prostate cancer) and T24 (bladder cancer) cell lines and in the non-cancerous MC3T3 (osteoblast) cell line. All tested complexes show high activities against the cancer cell lines with GI 50 values lower than 500 nM. One complex (11) has been selected for further investigations. It has been tested in vitro in six cancer cell lines from different origins (prostate, bladder, lung, bone, liver and breast) and two non-cancerous cell lines (osteoblasts, fibroblasts). Moreover, cellular uptake measurements were indicative of a good bioavailability. By various biochemical assays, this complex was found to effectively inhibit the thioredoxin reductase (TrxR) and its cytotoxicity towards prostate PC-3, bladder T24 and liver HepG2 cells was found to be ROS-dependent. Graphical abstract Image 1 Highlights • Mononuclear cationic gold(I)-NHCs complexes containing nitrogen substituents linked to the carbenes as anti-cancer agents. • High antiproliferative activity in vitro against prostate PC-3 and bladder T24 cancer cells. • Replacing aliphatic linkers by aromatic one increases drastically lipophilicity. • Higher lipophilicity leads to higher cytotoxicity. • Higher cytotoxicity affects also selectivity. [ABSTRACT FROM AUTHOR]

Highlights • C. elegans without cytoplasmic thioredoxin system were more susceptible to MeHg. • TRX-2, TRXR-2, TRX-3, TRX-4, TRX-5 did not afford protection against MeHg. • Age-specific sensitivity corresponded partially to GSH levels and TRXR-1 expression. • Age-specific response corresponded to the pattern of Hg accumulation. Abstract Methylmercury (MeHg) is an environmental pollutant linked to many neurological defects, especially in developing individuals. The thioredoxin (TRX) system is a key redox regulator affected by MeHg toxicity, however the mechanisms and consequences of MeHg-induced dysfunction are not completely understood. This study evaluated the role of the TRX system in C. elegans susceptibility to MeHg during development. Worms lacking or overexpressing proteins from the TRX family were exposed to MeHg for 1 h at different developmental stage: L1, L4 and adult. Worms without cytoplasmic thioredoxin system exhibited age-specific susceptibility to MeHg when compared to wild-type (wt). This susceptibility corresponded partially to decreased total glutathione (GSH) levels and enhanced degeneration of dopaminergic neurons. In contrast, the overexpression of the cytoplasmic system TRX-1/TRXR-1 did not provide substantial protection against MeHg. Moreover, transgenic worms exhibited decreased protein expression for cytoplasmic thioredoxin reductase (TRXR-1). Both mitochondrial thioredoxin system TRX-2/TRXR-2, as well as other thioredoxin-like proteins: TRX-3, TRX-4, TRX-5 did not show significant role in C. elegans resistance to MeHg. Based on the current findings, the cytoplasmic thioredoxin system TRX-1/TRXR-1 emerges as an important age-sensitive protectant against MeHg toxicity in C. elegans. [ABSTRACT FROM AUTHOR]

The thioredoxin system plays a role in a variety of physiological functions, including cell growth, differentiation, apoptosis, tumorigenesis, and immunity. We previously confirmed that butaselen (BS), a novel thioredoxin reductase inhibitor, can inhibit the growth of various human cancer cell lines, yet the underlying mechanism remains elusive. In this study, we investigated the anti-tumor effect of BS in vivo through regulating the immune system of KM mice. We found that BS inhibits tumor proliferation by promoting the activation of splenic lymphocytes in mice. BS can elevate the percentage of CD4−CD8+ T lymphocytes and the secretion of downstream cytokines in mice via downregulating the expression of programmed death-ligand 1 (PD-L1) on the tumor cells’ surface in vivo. Further study in HepG2 and BEL-7402 cells showed that decrease of PD-L1 level after BS treatment was achieved by inhibiting signal transducer and activator of transcription 3 (STAT3) phosphorylation. Taken together, our results suggest that BS has a role in promoting the immune response by reducing PD-L1 expression via the STAT3 pathway, and subsequently suppresses tumorigenesis. [ABSTRACT FROM AUTHOR]

Epilepsy is one of the furthermost common neurodegenerative diseases affecting above 50 million individuals worldwide. The pathogenesis of epileptic seizures is not satisfactorily explored, and hence more effective anti-convulsive therapies are indispensable. Current study aimed to investigate the mechanisms of the potential neuroprotective effects of sildenafil/selenium on chemically-induced convulsions in mice. Kindling model was induced using pentylenetetrazol (PTZ; 35 mg/Kg, 11 doses, intraperitoneally, every other day). PTZ-insulted groups were treated intraperitoneally with sildenafil (20 mg/Kg), selenium (0.2 mg/Kg) or their combination; 30 min before PTZ administration. PTZ-kindled model showed a significant loss of neuronal cells concurrently with nitrative/oxidative stress and lipid peroxidation. This was associated with enhanced expression of inducible nitric oxide synthase (iNOS), hemeoxygenase-1 (HO-1) and vascular endothelial growth factor (VEGF) along with increased activity of thioredoxin reductase (TrxR) in hippocampal tissue. Individual treatment with sildenafil or selenium showed partial neuroprotection, simultaneously with lower hippocampal expression of 4-hydroneonenal (4-HNE), nitrotyrosine, iNOS and HO-1, yet without reaching normal levels. Sildenafil, but not selenium, enhanced the expression of VEGF and the endothelial cell marker CD34. The joint treatment with sildenafil and selenium preserved hippocampal neuronal count, improved kindling score, blunted lipid peroxides and nitrotyrosine levels, concomitantly with iNOS inhibition, normalization of TrxR activity and HO-1 expression, and evident neo-angiogenesis. Current study demonstrated the roles of several central signalling cascades in the sildenafil/selenium-evoked neuroprotection represented in, at least in part, amelioration of nitrative/oxidative stress alongside modulation of angiogenesis. Thus, sildenafil combined with selenium could be repurposed as a potential therapeutic regimen for delaying epilepsy progression. [ABSTRACT FROM AUTHOR]

Gold(I) complexes containing stabilising ligands such as phosphines or N -heterocyclic carbenes (NHCs) are known to be inhibitors of the enzyme thioredoxin reductase (TrxR) and therefore act as potential apoptosis-inducing anticancer drug candidates. The conjugation of biomolecules overexpressed in cancer cells to the gold complexes makes them semi-targeted metabolites. Auranofin, an anti-arthritis agent, encompasses this property and exhibits anti-tumour activities. The synthesis, characterization and biological evaluation of four novel N -heterocyclic carbene-gold(I)-thiosugar complexes derived from glucose, lactose and galactose is reported. The reactions of 1,3-dibenzyl-4,5-diphenyl-imidazol-2-ylidene gold(I) chloride (NHC∗-Au-Cl) with pre-synthesized glycosyl thiols under mildly basic conditions gave the desired NHC-Au-thiosugar complexes in high to excellent yields (79–91%). The complexes retain the strong and redox-active Au-S bond contained in Auranofin. All complexes showed good solubility in biological media and were tested against the NCI 60 cancer cell panel for cytotoxicity. The synthesized NHC∗-Au derivatives showed good activity in the medium to low micromolar region, while complex 2 showed activity in the low micromolar to nanomolar region against the tested cell lines. To provide a theoretical structure of 4 , computational calculations were carried out based on the crystal structures of NHC-Au-SCN and NHC-Au-S-C 6 H 4 OMe. [ABSTRACT FROM AUTHOR]

To elucidate the effect of selenium (Se) on antioxidant function of mammary glands in dairy cows and the underlying mechanism, an experiment was conducted using a single-factor completely randomized design study. Bovine mammary epithelial cells (BMECs) were randomly divided into four groups: control, Se treatment, 2,4-dinitrochlorobenzene (DNCB) inhibition, and Se prevention. Treatment of BMECs with Se was found to significantly reverse decreased cell proliferation and the expression of thioredoxin reductase (TrxR) after DNCB exposure. DNCB-induced activation of apoptosis signaling kinase-1 (ASK-1), which activates the mitogen-activated protein kinase (MAPK) pathway, was reduced in BMECs treated with Se. Additionally, our results indicated that Se treatment resulted in lower intracellular accumulation of arachidonic acid (ARA) and 15-hydroperoxyeicosatetraenoic acid (15-HPETE) due to suppressed expression of cytosolic phospholipase A2 (cPLA2) regulated by p38MAPK and c-Jun N-terminal kinase (JNK) in DNCB-stimulated BMECs. Taken together, these findings suggest that Se treatment improved the antioxidant function of dairy cow mammary glands and protected cells from oxidative damage primarily by increasing the activity of TrxR, inhibiting the activation of the MAPK signaling pathway, and thus decreasing the content of ARA and its related metabolites. [ABSTRACT FROM AUTHOR]

Chalcones present in edible plants possess anti-cancer and anti-inflammatory properties, with the Michael acceptor moiety reported to be responsible for their biological activities. In this study, two novel dihydrotriazine-chalcone compounds previously identified to exert anti-proliferative effects through dual-targeting of dihydrofolate reductase (DHFR) and thioredoxin reductase (TrxR), were evaluated for their anti-invasive and anti-inflammatory abilities. At non-lethal concentrations, the compounds suppressed in vitro migration of MDA-MB-231 breast carcinoma cells, which was correlated with a dose-dependent downregulation of phorbol 12-myristate 13-acetate (PMA)-induced matrix metalloproteinase-9 (MMP-9) expression and secretion. At similar concentrations, these chalcone-based compounds suppressed expression of inflammatory mediators inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) in lipopolysaccharides (LPS)-stimulated murine macrophage-like RAW 264.7 cells, as well as tumor necrosis factor alpha (TNF-α) in LPS-stimulated human monocytes isolated from healthy donors. Mechanistically, inhibition of cancer cell invasion and inflammation by the compounds were mediated through suppression of the nuclear factor-kappaB (NF-κB) signaling pathway, which corroborated with the reported mechanism of action of chalcones. Their abilities to target multiple biological mediators relevant to multi-step carcinogenesis and with bioactivities stronger than those of the parent chalcone scaffold have warranted dihydrotriazine-chalcone compounds as promising candidates for use in pharmacological intervention of aggressive cancers. [ABSTRACT FROM AUTHOR]

The thiol-disulfide redox metabolism in platyhelminth parasites depends entirely on a single selenocysteine (Sec) containing flavoenzyme, thioredoxin glutathione reductase (TGR) that links the classical thioredoxin (Trx) and glutathione (GSH) systems. In the present study, we investigated the catalytic and structural properties of different variants of Fasciola gigantica TGR to understand the role of Sec. The recombinant full-length Sec containing TGR (FgTGRsec), TGR without Sec (FgTGR) and TGRsec without the N-terminal glutaredoxin (Grx) domain (∆NTD-FgTGRsec) were purified to homogeneity. Biochemical studies revealed that Sec597 is responsible for higher thioredoxin reductase (TrxR) and glutathione reductase (GR) activity of FgTGRsec. The N-terminal Grx domain was found to positively regulate the DTNB-based TrxR activity of FgTGRsec. The FgTGRsec was highly sensitive to inhibition by auranofin (AF). The structure of FgTGR was modeled, and the inhibitor AF was docked, and binding sites were identified. Unfolding studies suggest that all three proteins are highly cooperative molecules since during GdnHCl-induced denaturation, a monophasic unfolding of the proteins without stabilization of any intermediate is observed. The C m for GdnHCl induced unfolding of FgTGR was higher than FgTGRsec and ∆NTD-FgTGRsec suggesting that FgTGR without Sec was more stable in solution than the other protein variants. The free energy of stabilization for the proteins was also determined. To our knowledge, this is also the first report on unfolding and stability analysis of any TGR. [ABSTRACT FROM AUTHOR]

Botulinum (BoNTs) and tetanus (TeNT) neurotoxins are the most toxic substances known and form the growing family of Clostridial neurotoxins (CNT), the etiologic agents of botulism and tetanus. CNT are composed of a metalloprotease light chain (L), linked via a disulfide bond to a heavy chain (H). H mediates the binding to nerve terminals and the membrane translocation of L into the cytosol, where its substrates, the three SNARE proteins, are localized. L translocation is accompanied by unfolding and, once delivered on the cytosolic side of the endosome membrane, it has to be reduced and reacquire the native fold to be active. The Thioredoxin-Thioredoxin Reductase system (Trx-TrxR) specifically reduces the interchain disulfide bond while the cytosolic chaperone protein Hsp90 mediates L refolding. Both steps are essential for CNT activity and their inhibition efficiently blocks the neurotoxicity in cultured neurons and mice. Trx and its reductase physically interact with Hsp90 and are loosely bound to the cytosolic side of synaptic vesicles, the organelle exploited by CNT to enter nerve terminals and wherefrom L is translocated into the cytosol. Therefore, Trx, TrxR and Hsp90 orchestrate a chaperone-redox molecular machinery that enables the catalytic activity of the L inside nerve terminals. Given the fundamental role of L reduction and refolding, this machinery represents a rational target for the development of mechanism-based antitoxins. [ABSTRACT FROM AUTHOR]

Abstract: Elevated reactive oxygen species and antioxidant defense systems have been recognized as one of the hallmarks of cancer cells. As a major regulator of the cellular redox homeostasis, the selenoprotein thioredoxin reductase (TrxR) is increasingly considered as a promising target for anticancer drug development. The current approach to inhibit TrxR predominantly relies on the modification of the selenocysteine residue in the C‐terminal active site of the enzyme, in which it is hard to avoid the off‐target effects. By conjugating the anticancer drug gemcitabine with a 1,2‐dithiolane scaffold, an unprecedented prodrug strategy is disclosed that achieves a specific release of gemcitabine by TrxR in cells. As overexpression of TrxR is frequently found in different types of tumors, the TrxR‐dependent prodrugs are promising for further development as cancer chemotherapeutic agents. [ABSTRACT FROM AUTHOR]

Protein kinase G (PKG) Iα mediates the cyclic guanosine monophosphate-mediated vasodilatory effects induced by NO. Endothelium-derived hyperpolarizing factors (EDHFs), like H 2 O 2 can activate PKGIα in a cyclic guanosine monophosphate-independent manner, but whether this is true for all EDHFs (e.g., S -nitrosothiols) is unknown. Here, we investigated the contribution of PKGIα to bradykinin-, H 2 O 2 -, L- S -nitrosocysteine-, and light-induced relaxation in porcine coronary arteries, making use of the fact that thioredoxin reductase inhibition with auranofin or 1-chloro-2,4-dinitrobenzene potentiates PKGIα. Thioredoxin reductase inhibition potentiated bradykinin and H 2 O 2 , but not L- S -nitrosocysteine or light. The relaxations by the latter 2 and bradykinin, but not those by H 2 O 2 , were prevented by the soluble guanylyl cyclase (sGC) inhibitor 1H-[1,2,4]oxadiazolo[4,3- a ]quinoxalin-1-one. Yet, after S -nitrosothiol depletion with ethacrynic acid, thioredoxin reductase inhibition also potentiated light-induced relaxation, and this was prevented by the Na + -K + ATPase inhibitor ouabain. This indicates that photorelaxation depends on sGC activation by S -nitrosothiols, while only after S -nitrosothiol depletion oxidized PKGIα comes into play, and acts via Na + -K + ATPase. In conclusion, both bradykinin- and light-induced relaxation of porcine coronary arteries depend, at least partially, on oxidized PKGIα, and this does not involve sGC. H 2 O 2 also acts via oxidized PKGIα in an sGC-independent manner. Yet, S -nitrosothiol-induced relaxation is PKGIα-independent. Clearly, PKG activation does not contribute universally to all EDHF responses, and targeting PKGIα may only mimick EDHF under certain conditions. It is therefore unlikely that PKGIα activators will be universal vasodilators. [ABSTRACT FROM AUTHOR]

Mammalian thioredoxin reductase (TrxR) is a selenoprotein with three existing isoenzymes (TrxR1, TrxR2, and TrxR3), which is found primarily intracellularly but also in extracellular fluids. The main substrate thioredoxin (Trx) is similarly found (as Trx1 and Trx2) in various intracellular compartments, in blood plasma, and is the cell’s major disulfide reductase. Thioredoxin reductase is necessary as a NADPH-dependent reducing agent in biochemical reactions involving Trx. Genetic and environmental factors like selenium status influence the activity of TrxR. Research shows that the Trx/TrxR system plays a significant role in the physiology of the adipose tissue, in carbohydrate metabolism, insulin production and sensitivity, blood pressure regulation, inflammation, chemotactic activity of macrophages, and atherogenesis. Based on recent research, it has been reported that the modulation of the Trx/TrxR system may be considered as a new target in the management of the metabolic syndrome, insulin resistance, and type 2 diabetes, as well as in the treatment of hypertension and atherosclerosis. In this review evidence about a possible role of this system as a marker of the metabolic syndrome is reported. [ABSTRACT FROM AUTHOR]

A series of 22 novel metronidazole-triazole-styryl hybrids were synthesized and evaluated for their in vitro antiamoebic activity against HM1: IMSS strain of Entamoeba histolytica . Some of the hybrids were found to be more active (IC 50  = 0.12–0.35 μM) than the reference drug metronidazole (IC 50  = 1.79 μM). The most active compounds were found to be non-toxic (up to 50 μM) against the Vero cells showing a good safety profile of these hybrids. The docking and ADMET studies were also conducted to investigate the probable mode of action. Docking studies showed significant binding affinity in the active site of E. histolytica thioredoxin reductase (EhTrR) protein. [ABSTRACT FROM AUTHOR]

The toxicity of nanoparticles in a biological system is an integration of effects arising from surface functionality, particle size, ionic dissolution, etc. This complexity suggests that generalization of a material’s toxicity may be inappropriate. Moreover, from a medicinal point of view, toxicity can be used for treatment of malignant cells, such as cancer. In this study, highly biocompatible carbon nanodots (gCDs) were synthesized by reacting citric acid and urea in glycerol, which resulted in abundant hydroxyl functional groups on the particle surface. gCDs show excitation-dependent photoluminescence but with bright green to yellow emission. Importantly, a series of toxicity assessments showed that as-synthesized gCDs possessed exceptional biocompatibilities to various biological entities including 18 bacteria species, Petunia axillaris seedlings, and Artemia franciscana nauplii. Furthermore, the particles were shown to have low to no toxic effects on human embryonic kidney (HEK-293), breast (MCF-7), and oral squamous (CAL-27) carcinoma cell lines. Of particular interest, the gCDs displayed antiproliferative activities against ovarian choriocarcinoma cells (JAr/Jeg-3 cell lines), which may be further explored for cancer drug discovery. [ABSTRACT FROM AUTHOR]

Gold(III) compounds have received increasing attention in cancer research. Three gold complexes of general formula [Au III L]Cl, where L is benzil bis(thiosemicarbazonate), compound 1 , benzil bis(4-methyl-3-thiosemicarbazonate), compound 2 , or benzil bis(4-cyclohexyl-3-thiosemicarbazonate), compound 3 , have been synthesized and fully characterized, including the X-ray crystal structure of compound 3 , confirming square-planar geometry around the gold(III) centre. Compound 1 showed moderate cytotoxicity and accumulation in MCF7 breast cancer cells but did not inhibit thioredoxin reductase (TrxR) activity and did not induce reactive oxygen species (ROS) production. Compound 2 , the least cytotoxic, was found to be capable of modestly inhibiting TrxR activity and produced low levels of ROS in the MCF7 cell line. The most cytotoxic compound, 3 , had the highest cellular accumulation and its distribution pattern showed a clear preference for the cytosol and mitochondria of MCF7 cells. It readily hampered intracellular TrxR activity leading to a dramatic alteration of the cellular redox state and to the induction of cell death. [ABSTRACT FROM AUTHOR]

Thioredoxin (Trx) system has a defensive role against the harmful effect of oxidative stress in sperm. p53 is an important regulator of apoptosis and normal process of spermatogenesis. Regulation of p53 by redox state of the cell and Thioredoxin system has been reported. The aim of this study was to evaluate the ROS level, Thioredoxin reductase (TrxR) activity and p53 protein levels in sperm of asthenozoospermic and normozoospermic males. Semen samples from 80 donors were divided into asthenozoospermic (n = 40) and normozoospermic (n = 40) groups using the WHO criteria. DNA fragmentation (TUNEL assay) of spermatozoa was identified·H 2 O 2 and O 2 •− were determined by flow cytometry. p53 protein levels and TrxR activity were measured in sperm cell lysate by appropriate kit. Total antioxidant capacity (TAC) and thiol groups in seminal plasma were measured spectrophotometery. MDA content in seminal plasma was determined fluorometrically. Results The percentage of cells with H 2 O 2 , O 2 •− and DNA fragmentation was higher in asthenozoospermic compared to normozoospermic groups (p < 0.05). The p53 protein level was significantly higher in asthenozoospermic group (P < 0.001). TrxR activity in normozoospermic was significantly higher than asthenozoospermic group (P < 0.001). Total thiol groups and TAC levels were significantly higher in normozoospermic samples (P < 0.05). A significantly high negative correlation was seen between p53 protein levels with TrxR activity (r = − 0.49, P < 0.001), total motility (r = − 0.65, P < 0.001). p53 and ROS levels were increased in asthenozoospermic males while the TrxR activity was decreased. These changes lead to an increase in apoptotic, immotile and immature spermatozoa in the ejaculatory semen. [ABSTRACT FROM AUTHOR]

Newly synthesised mononuclear gold complexes containing the 2-BrC 6 F 4 PPh 2 ligand have been fully characterised and their anticancer activity towards five human tumor [prostate (PC3), glioblastoma (U87MG), cervical (HeLa), fibrosarcoma (HT1080), ovarian (SKOV-3)] and normal human embryonic kidney (Hek-293T) cell lines investigated. Some of the synthesised gold complexes displayed higher cytotoxicity than cisplatin towards PC-3, HeLa and U87MG cells and inhibited the thioredoxin reductase (TrxR) enzyme, which is considered a potential target for new compounds in cancer treatment. The more physiologically relevant tumor spheroid assay demonstrated the superior potency of these gold phosphine complexes in inhibiting the growth of cervical carcinoma cell line HeLa (3D) spheroidal models. The mechanism of cell death was shown to be apoptotic cell death through cell cycle arrest, mitochondrial membrane depolarisation and increased ROS production. [ABSTRACT FROM AUTHOR]

Exploration of novel drug targets has been the major thrust area in filarial research. In this regard, identification and characterization of oxidative enzymes that play pivotal role in the survival of filarial parasite inside host are of immense importance. In this study, we are reporting the presence of an important redox regulatory enzyme, thioredoxin reductase (TrxR) in the bovine filarial parasite Setaria cervi . TrxR was found to be exists throughout the developmental stages viz . oocyte, microfilaria and adult of the parasite. Since further studies on this enzyme require adequate quantity, influential extraction parameters were optimized statistically using response surface methodology (RSM) employing a seven factors based Box-Behnken design matrix. ANOVA analysis revealed the relative importance of each parameter and a regression equation was eventually developed that could predict the specific activity (SA) of TrxR. Finally the optimized extraction conditions predicted by RSM was 6.1 ml of 61.86 mM buffer, pH 6.0, with extraction temperature 39.96 °C for 180 min in addition to 450 rpm agitation and 20 μl/ml of protease inhibitor. Therefore this study is going to be the maiden report depicting the identity of TrxR in filarial parasite and the optimized extraction conditions for its isolation with better kinetic efficiency. [ABSTRACT FROM AUTHOR]

Here we present the preparation of 14 pairs of cis - and trans -diammine monochlorido platinum(II) complexes, coordinated to heterocycles (i.e., imidazole, 2-methylimidazole and pyrazole) and linked to various acylhydrazones, which were designed as potential inhibitors of the selenium-dependent enzymes glutathione peroxidase 1 (GPx-1) and thioredoxin reductase 1 (TrxR-1). However, no inhibition of bovine GPx-1 and only weak inhibition of murine TrxR-1 was observed in in vitro assays. Nonetheless, the cis configured diammine monochlorido Pt(II) complexes exhibited cytotoxic and apoptotic properties on various human cancer cell lines, whereas the trans configured complexes generally showed weaker potency with a few exceptions. On the other hand, the trans complexes were generally more likely to lack cross-resistance to cisplatin than the cis analogues. Platinum was found bound to the nuclear DNA of cancer cells treated with representative Pt complexes, suggesting that DNA might be a possible target. Thus, detailed in vitro binding experiments with DNA were conducted. Interactions of the compounds with calf thymus DNA were investigated, including Pt binding kinetics, circular dichroism (CD) spectral changes, changes in DNA melting temperatures, unwinding of supercoiled plasmids and ethidium bromide displacement in DNA. The CD results indicate that the most active cis configured pyrazole-derived complex causes unique structural changes in the DNA compared to the other complexes as well as to those caused by cisplatin, suggesting a denaturation of the DNA structure. This may be important for the antiproliferative activity of this compound in the cancer cells. [ABSTRACT FROM AUTHOR]

Thioredoxin reductase (TrxR) is a conserved protein that is involved in protecting organisms against various oxidative stresses. In this study, a thioredoxin reductase gene was cloned from the mud crab Scylla paramamosain (SpTrxR). The full-length cDNA of SpTrxR is comprised of 2724 bp with a 1791 bp open reading frame that encodes a putative protein of 596 amino acids. The deduced amino acid sequence of SpTrxR contains the typical TrxR domain. Quantitative real-time PCR analysis revealed that the SpTrxR mRNA was distributed abundantly in mud crabs, while strong expression was observed mainly in the gills. The expression of antioxidant enzyme genes (SpTrxR, SpTrx, SpSOD, and SpCAT) was measured using quantitative real-time PCR after acute ammonia and nitrite exposure. The results show that antioxidant enzyme genes (SpTrxR, SpTrx, SpSOD, and SpCAT) were modulated by acute ammonia and nitrite exposure. These results suggest that antioxidant enzyme genes play an important role in protecting organisms against oxidative stress. [ABSTRACT FROM AUTHOR]

Auranofin is a thiol-reactive gold (I)-containing compound with potential as a chemotherapeutic. Auranofin has the capacity to selectively inhibit endogenous antioxidant enzymes thioredoxin reductase (TrxR) and glutathione peroxidase (GPx), resulting in oxidative stress and the initiation of a pro-apoptotic cascade. The effect of Auranofin exposure on TrxR and GPx, and the potential for cellular protection through selenium supplementation was examined in the non-cancerous human cell line Swan-71. Auranofin exposure resulted in a concentration dependent differential inhibition of selenoprotein antioxidants. Significant inhibition of TrxR was observed at 20 nM Auranofin with inhibition of GPx from 10 µM. Significant increases in reactive oxygen species (ROS) were associated with antioxidant inhibition at Auranofin concentrations of 100 nM (TrxR inhibition) and 10 µM (TrxR and GPx inhibition), respectively. Evaluation of mitochondrial respiration demonstrated significant reductions in routine and maximal respiration at both 100 nM and 10 μM Auranofin. Auranofin treatment at concentrations of 10 μM and higher concentrations resulted in a ∼68% decrease in cellular viability and was associated with elevations in pro-apoptotic markers cytochrome c flux control factor (FCFc) at concentration of 100 nM and mitochondrial Bax at 10 μM. The supplementation of selenium (100 nM) prior to treatment had a generalized protective affect through the restoration of antioxidant activity with a significant increase in TrxR and GPx activity, a significant reduction in ROS and associated improvement in mitochondrial respiration and cellular viability (10 µM ∼48% increase). Selenium supplementation reduced the FCFc at low doses of Auranofin (<10 μM) however no effect was noted on either FCFc or Bax at concentrations above 10 μM. The inhibition of antioxidant systems in non-cancerous cells by Auranofin is strongly dose dependent, and this inhibition can be altered by selenium exposure. Therefore, Auranofin dose and the selenium status of patients are important considerations in the therapeutic use of Auranofin as an agent of chemosensitization. [ABSTRACT FROM AUTHOR]

Circadian rhythms are observed in most organisms on earth and are known to play a major role in successful adaptation to the 24-h cycling environment. Circadian phenotypes are characterized by a free-running period that is observed in constant conditions and an entrained phase that is observed in cyclic conditions. Thus, the relationship between the free-running period and phase of entrainment is of interest. A popular simple rule has been that the entrained phase is the expression of the period in a cycling environment (i.e., that a short period causes an advanced phase and a long period causes a delayed phase). However, there are experimental data that are not explained by this simple relationship, and no systematic study has been done to explore all possible period-phase relationships. Here, we show the existence of stable period-phase relationships that are exceptions to this rule. First, we analyzed period-phase relationships using populations with different degrees of genome complexity. Second, we generated isogenic F1 populations by crossing 14 classical period mutants to the same female and analyzed 2 populations with a short period/delayed phase and a long period/advanced phase. Third, we generated a mathematical model to account for such variable relationships between period and phase. Our analyses support the view that the circadian period of an organism is not the only predictor of the entrained phase. [ABSTRACT FROM AUTHOR]

In this study, the potential effects of thalidomide (Thal) on bleomycin (BLM)-induced pulmonary fibrosis were investigated. BALB/C mice model of pulmonary fibrosis induced by an intratracheal instillation of BLM was adopted, and then was intraperitoneally injected with Thal (10, 20, 50 mg/kg) daily for 8 days, while the control and BLM-treated mouse groups were injected with a saline solution. The effects of Thal on pulmonary injury were evaluated by the lung wet/dry weight ratios and histopathological examination. Inflammation of lung tissues was assessed by measuring the levels of interleukin (IL)-6, IL-8, tumor necrosis factor (TNF)-α, and transforming growth factor (TGF)-β in bronchoalveolar lavage fluid. Oxidative stress was evaluated by detecting the levels of reactive oxygen species (ROS), superoxide dismutase (SOD), total antioxidant capacity (T-AOC), and malondialdehyde (MDA) in lung tissue. The results indicated that Thal treatment remarkably attenuated pulmonary fibrosis, oxidative stress, and inflammation in mouse lungs. The antiinflammatory and antioxidant effects of Thal were also found in human lung fibroblasts. Thal administration significantly enhanced the activity of thioredoxin reductase; however, the other enzymes or proteins involved in biologic oxidation-reduction equilibrium were not affected. Our findings indicate that Thal-mediated suppression of pulmonary fibrosis is related to the inhibition of oxidative stress and inflammatory response. In summary, these results may provide a rationale to explore clinical application of Thal for the prevention of pulmonary fibrosis. [ABSTRACT FROM AUTHOR]

Thioredoxin reductase (TR) regulates the intracellular redox environment by reducing thioredoxin (Trx). In anaerobes, recent findings indicate that the Trx redox network is implicated in the global redox regulation of metabolism but also actively participates in protecting cells against O2. In the anaerobe Desulfovibrio vulgaris Hildenborough (DvH), there is an intriguing redundancy of the Trx system which includes a classical system using NADPH as electron source, a non-canonical system using NADH and an isolated TR (DvTRi). The functionality of DvTRi was questioned due to its lack of reactivity with DvTrxs. Structural analysis shows that DvTRi is a NAD(P)H-independent TR but its reducer needs still to be identified. Moreover, DvTRi reduced by an artificial electron source is able to reduce in turn DvTrx1 and complexation experiments demonstrate a direct interaction between DvTRi and DvTrx1. The deletion mutant tri exhibits a higher sensitivity to disulfide stress and the gene tri is upregulated by O2 exposure. Having DvTRi in addition to DvTR1 as electron source for reducing DvTrx1 must be an asset to combat oxidative stress. Large-scale phylogenomics analyses show that TRi homologs are confined within the anaerobes. All TRi proteins displayed a conserved TQ/NGK motif instead of the HRRD motif, which is selective for the binding of the 2′-phosphate group of NADPH. The evolutionary history of TRs indicates that tr1 is the common gene ancestor in prokaryotes, affected by both gene duplications and horizontal gene events, therefore leading to the appearance of TRi through subfunctionalization over the evolutionary time.

Thioredoxin system comprised of thiorexin and NADPH dependent thiorexin reductase, is responsible for redox regulation of cells by controlling the apoptosis, proliferation and other vital processes of cells. The efficacy of thioredoxin system has been represented in a wide range of physiological and biological reactions in bacteria, yeast, plants, mammals and etc. including DNA synthesis, regulation of transcription factors, protein repairing, regulating the photosynthesis and controlling the apoptosis and preventing oxidative stresses, filamentous phage assembly, immune-modulating, neuronal survival, pregnancy and birth and many other physiological and biological functions. The up-regulation of thioredoxin has been observed in various malignancies, which was associated with tumor angiogenesis and development. In this regard, the thiordoxin system has become a putative target in new chemotherapeutic methods. In this study, we mentioned various features of thioredoxin system in malignant cells and reviewed the articles which have evaluated the expression rate of thioredoxin system in malignancies.

Maintaining redox homeostasis in the cell is critical for different cellular metabolisms and signal transduction pathways. In plants different molecular mechanisms are involved in maintaining cellular redox homeostasis. NADP/thioredoxin system, consisting of NADPH, NADP-thioredoxin reductase (NTR) and thioredoxin plays important role as electron donor to disulfide bonds in many cellular proteins. In this study, the gene encoding one of NTR isoform from rice, namely OsNTRB was cloned in pET28a as fusion with His6-tag and transferred to Roseta (DE3), a strain of Escherichia coli. Considerable amount of His-OsNTRB was produced after induction of bacteria culture with IPTG and purified using affinity chromatography. Heterologous expression and purification of recombinant form of OsNTRB enabled us to study the interaction of this protein with thioredoxin from barley (HvTrxh1) and E. coli (Ec Trx). The results showed that recombinant form of OsNTRB is active and can reduce both HvTrxh1 and EcTrx in vitro. However the rates of reaction with these two Trx were significantly different.

High-fat diet (HFD) can induce oxidative stress. Thioredoxin (Trx) and thioredoxin reductase (TrxR) are critical antioxidant proteins but how they are affected by HFD remains unclear. Using HFD-induced insulin-resistant mouse model, we show here that liver Trx and TrxR are significantly decreased, but, remarkably, the degree of their S-acylation is increased after consuming HFD. These HFD-induced changes in Trx/TrxR may reflect abnormalities of lipid metabolism and insulin signaling transduction. HFD-driven accumulation of 4-hydroxynonenal is another potential mechanism behind inactivation and decreased expression of Trx/TrxR. Thus, we propose HFD-induced impairment of liver Trx/TrxR as major contributor to oxidative stress and as a novel feature of insulin resistance.

Mutations in the DJ-1 gene have been shown to cause a rare autosomal-recessive genetic form of Parkinson’s disease (PD). The function of DJ-1 and its role in PD development has been linked to multiple pathways, however its exact role in the development of PD has remained elusive. It is thought that DJ-1 may play a role in regulating reactive oxygen species (ROS) formation and overall oxidative stress in cells through directly scavenging ROS itself, or through the regulation of ROS scavenging systems such as glutathione (GSH) or thioredoxin (Trx) or ROS producing complexes such as complex I of the electron transport chain. Previous work in this laboratory has demonstrated that isolated brain mitochondria consume H2O2 predominantly by the Trx/Thioredoxin Reductase (TrxR)/Peroxiredoxin (Prx) system in a respiration dependent manner (Drechsel et al., Journal of Biological Chemistry, 2010). Therefore we wanted to determine if mitochondrial H2O2 consumption was altered in brains from DJ-1 deficient mice (DJ-1−/−). Surprisingly, DJ-1−/− mice showed an increase in mitochondrial respiration-dependent H2O2 consumption compared to controls. To determine the basis of the increased H2O2 consumption in DJ1−/− mice, the activities of Trx, Thioredoxin Reductase (TrxR), GSH, glutathione disulfide (GSSG) and glutathione reductase (GR) were measured. Compared to control mice, brains from DJ-1−/− mice showed an increase in (1) mitochondrial Trx activity, (2) GSH and GSSG levels and (3) mitochondrial glutaredoxin (GRX) activity. Brains from DJ-1−/− mice showed a decrease in mitochondrial GR activity compared to controls. The increase in the enzymatic activities of mitochondrial Trx and total GSH levels may account for the increased H2O2 consumption observed in the brain mitochondria in DJ-1−/− mice perhaps as an adaptive response to chronic DJ-1 deficiency.