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Inhibition of thioredoxin reductase (TrxR) is a crucial strategy for the discovery of antineoplastic drugs. 6-Shogaol (6-S), a primary bioactive compound in ginger, has high anticancer activity. However, its potential mechanism of action has not been thoroughly investigated. In this study, we demonstrated for the first time that 6-S, a novel TrxR inhibitor, promoted oxidative-stress-mediated apoptosis in HeLa cells. The other two constituents of ginger, 6-gingerol (6-G) and 6-dehydrogingerduone (6-DG), have a similar structure to 6-S but fail to kill HeLa cells at low concentrations. 6-Shogaol specifically inhibits purified TrxR1 activity by targeting selenocysteine residues. It also induced apoptosis and was more cytotoxic to HeLa cells than normal cells. The molecular mechanism of 6-S-mediated apoptosis involves TrxR inhibition, followed by an outburst of reactive oxygen species (ROS) production. Furthermore, TrxR knockdown enhanced the cytotoxic sensitivity of 6-S cells, highlighting the physiological significance of targeting TrxR by 6-S. Our findings show that targeting TrxR by 6-S reveals a new mechanism underlying the biological activity of 6-S and provides meaningful insights into its action in cancer therapeutics.

Diffuse large B-cell lymphoma (DLBCL) is a haematological malignancy representing the most diagnosed non-Hodgkin’s lymphoma (NHL) subtype. Despite the approved chemotherapies available in clinics, some patients still suffer from side effects and relapsed disease. Recently, studies have reported the role of the Trx system and the BCR signalling pathway in cancer development and drug resistance. In this regard, we assessed a potential link between the two systems and evaluated the effects of [Au(d2pype)2]Cl (TrxR inhibitor) and ibrutinib (BTK inhibitor) alone and in combination on the cell growth of two DLBCL lymphoma cell lines, SUDHL2 and SUDHL4. In this study, we show higher expression levels of the Trx system and BCR signalling pathway in the DLBCL patient samples compared to the healthy samples. The knockdown of TrxR using siRNA reduced BTK mRNA and protein expression. A combination treatment with [Au(d2pype)2]Cl and ibrutinib had a synergistic effect on the inhibition of lymphoma cell proliferation, the activation of apoptosis, and, depending on lymphoma cell subtype, ferroptosis. Decreased BTK expression and the cytoplasmic accumulation of p65 were observed after the combination treatment in the DLBCL cells, indicating the inhibition of the NF-κB pathway. Thus, the co-targeting of BTK and TrxR may be an effective therapeutic strategy to consider for DLBCL treatment.

Among the plethora of nanosystems used in the field of theranostics, iron oxide nanoparticles (IONPs) occupy a central place because of their biocompatibility and magnetic properties. In this study, we highlight the radiosensitizing effect of two IONPs formulations (namely 7 nm carboxylated IONPs and PEG5000-IONPs) on A549 lung carcinoma cells when exposed to 225 kV X-rays after 6 h, 24 h and 48 h incubation. The hypothesis that nanoparticles exhibit their radiosensitizing effect by weakening cells through the inhibition of detoxification enzymes was evidenced by thioredoxin reductase activity monitoring. In particular, a good correlation between the amplification effect at 2 Gy and the residual activity of thioredoxin reductase was observed, which is consistent with previous observations made for gold nanoparticles (NPs). This emphasizes that NP-induced radiosensitization does not result solely from physical phenomena but also results from biological events.

Recent achievements in the area of studying biological activity of new natural compounds toward thioredoxin reductase 1 (TrxR1) are considered. The most important chemotypes of the compounds exhibiting activity toward TrxR1 were revealed. The pharmacophoric environment of the electron-deficient olefin group that possesses a chemical potential for covalent inhibiting to TrxR1 was examined. [ABSTRACT FROM AUTHOR]

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β-Lapachone as a natural novel anticancer candidate is under clinical trials. Previous studies suggested that β-lapachone works by redox activation to ablate cancer cells. However, it is still unclear whether thioredoxin reductase (TrxR), one of the key redox catalytic enzymes in cells, plays a role in the pharmacological effects of β-lapachone. Herein, we present that β-lapachone kills human promyelocytic leukemia HL-60 cells with preference over other cancer cells and normal cells. The follow-up studies demonstrate that β-lapachone induces the HL-60 cell apoptosis through inhibition of TrxR and further elevation of oxidative stress. Overexpression of the TrxR alleviates the efficiency of β-lapachone while knockdown of the enzyme increases the β-lapachone cytotoxicity, scientifically underpinning the correlation of the observed biological behaviors of β-lapachone to TrxR inhibition. The disclosure of the novel action mechanism of β-lapachone sheds light on understanding its capacity in interfering with cellular redox signaling and supports β-lapachone as an anticancer drug candidate. [Display omitted] • β-Lapachone is an excellent natural candidate drug that exerts antitumor activity through regulating the redox system. • Inhibition of thioredoxin reductase (TrxR) by β-lapachone accounts for triggering redox activation-mediated HL-60 cell apoptosis. • β-Lapachone kills human promyelocytic leukemia HL-60 cells with preference over other cancer cells and normal cells. • β-Lapachone enables targeting TrxR to enlarge the understanding of its mechanism for regulating the redox system and unleash its therapeutic potential. [ABSTRACT FROM AUTHOR]

Shikonin, a naturally occurring naphthoquinone with potent anti-tumor activity, has been reported to induce cancer cell death via targeting selenoenzyme thioredoxin reductase 1 (TrxR1; TXNRD1). However, the interaction between shikonin and TrxR1 remains unclear, and the roles of the cellular antioxidant system in shikonin induced cell death are obscure. Here, we found that shikonin modified the Sec498 residue of TrxR1 to fully inhibit its antioxidant activity, however, the shikonin-modified TrxR1 still remained intrinsic NADPH oxidase activity, which promotes superoxide anions production. Besides, TrxR1 efficiently reduced shikonin in both selenocysteine dependent and selenocysteine independent manners, and the oxygen-coupled redox cycling of shikonin also generates excessive superoxide anions. The inhibitory effects and the redox cycling of shikonin towards TrxR1 caused cancer cell ROS-dependent necroptosis. Interestingly, as we evaluated, some cancer cell lines were insensitive to shikonin, especially kelch-like ECH associated protein 1 (KEAP1)-mutant non-small cell lung cancer (NSCLC) cells, which harbor constitutive activation of the nuclear factor-erythroid 2-related factor 2 (NRF2). NADPH bankruptcy caused by glucose starvation or glucose limitation (inhibiting glucose transporter 1 by BAY-876) could efficiently overcome the resistance of KEAP1-mutant NSCLC cells to shikonin. Glucose-6-phosphate dehydrogenase (G6PD), was known as a rate-limiting enzyme in the pentose phosphate pathway, however, the pharmacological inhibition of G6PD by 6-aminonicotinamide (6-AN), enhanced the shikonin-induced cytotoxicity but has no selectivity on KEAP1-mutant NSCLC cells. This study will be helpful in applying shikonin for potential chemotherapy, and in combinational treatment of KEAP1-mutant NSCLC. [Display omitted] • Shikonin is a poor substrate of selenoprotein TrxR1 but promotes tumor cell necroptosis. • Shikonin arylates the Sec498 residue of TrxR1 thereby triggering the SecTRAPs generation. • Sec-to-Cys mutation of TrxR1 supports the high-efficiency oxygen-coupled shikonin redox recycling. • Inhibition of G6PD activity by 6-AN promotes shikonin-induced cell death. • Glucose limitation by BAY-876 sensitives of KEAP1-mutant NSCLC cells to shikonin. [ABSTRACT FROM AUTHOR]

Mycobacterium tuberculosis (Mtb) produces an unconventional flavohemoglobin (Mtb FHb) that carries a FAD-binding site similar to D-lactate dehydrogenases (D-LDH) and oxidizes D-lactate into pyruvate. The molecular mechanism by which Mtb FHb functions in Mtb remains unknown. We discovered that the D-LDH-type FAD-binding site in Mtb FHb overlaps with another FAD-binding motif similar to thioredoxin reductases and reduces DTNB in the presence of NADPH similar to trxB of Mtb. These results suggested that Mtb FHb is functioning as a disulfide oxidoreductase. Interestingly, D-lactate created a conformational change in Mtb FHb and attenuated its ability to oxidize NADPH. Mass spectroscopy demonstrated that Mtb FHb reduces des- myo- inositol mycothiol in the presence of D-lactate unlike NADPH, indicating that D-lactate changes the specificity of Mtb FHb from di-thiol to di-mycothiol. When M. smegmatis carrying deletion in the fhb II gene (encoding a homolog of Mtb FHb) was complemented with the fhb gene of Mtb , it exhibited four- to fivefold reductions in lipid peroxidation and significant enhancement in the cell survival under oxidative stress. These results were corroborated by reduced lipid peroxidation and enhanced cell survival of wild-type M. smegmatis after overexpression of the fhb gene of Mtb. Since D-lactate is a by-product of lipid peroxidation and Mtb FHb is a membrane-associated protein, D-lactate-mediated reduction of mycothiol disulfide by Mtb FHb may uniquely equip Mtb to relieve the toxicity of D-lactate accumulation and protect the cell from oxidative damage, simultaneously balancing the redox environment under oxidative stress that may be vital for the pathogenesis of Mtb. [ABSTRACT FROM AUTHOR]

The cytosolic selenoprotein thioredoxin reductase 1 (TrxR1, TXNRD1), and to some extent mitochondrial TrxR2 (TXNRD2), can be inhibited by a wide range of electrophilic compounds. Many such compounds also yield cytotoxicity toward cancer cells in culture or in mouse models, and most compounds are likely to irreversibly modify the easily accessible selenocysteine residue in TrxR1, thereby inhibiting its normal activity to reduce cytosolic thioredoxin (Trx1, TXN) and other substrates of the enzyme. This leads to an oxidative challenge. In some cases, the inhibited forms of TrxR1 are not catalytically inert and are instead converted to prooxidant NADPH oxidases, named SecTRAPs, thus further aggravating the oxidative stress, particularly in cells expressing higher levels of the enzyme. In this review, the possible molecular and cellular consequences of these effects are discussed in relation to cancer therapy, with a focus on outstanding questions that should be addressed if targeted TrxR1 inhibition is to be further developed for therapeutic use. [ABSTRACT FROM AUTHOR]

Novel agents are required to increase the radiosensitivity of cancer and improve the outcome of radiotherapy. Thioredoxin (Trx) and thioredoxin reductase (TrxR) reduce the oxidized cysteine thiols in several proteins, which regulate cellular redox, survival, proliferation, DNA synthesis, transcription factor activity and apoptosis. TrxR is essential for maintaining a conducive redox state for tumor growth, survival and resistance to therapy. Therefore, it is an appealing pharmacological target for the radiosensitization of tumors. Ionizing radiation (IR) is known to cause cytotoxicity through ROS, oxidative stress and DNA damage. Inhibition of thioredoxin system augments IR induced oxidative stress and potentiates cytotoxic effects. However, TrxR also regulates several critical cellular processes in normal cells. Here, we highlight the pre-clinical research and pharmacological studies to surmise possible utility of different TrxR inhibitors for radiosensitization. This review provides a succinct perspective on the role of TrxR inhibitors during the radiotherapy of cancer.

Mycobacterium tuberculosis (Mtb) produces an unconventional flavohemoglobin (MtbFHb) that carries a FAD-binding site similar to D-lactate dehydrogenases (D-LDH) and oxidizes D-lactate into pyruvate. The molecular mechanism by which MtbFHb functions in Mtb remains unknown. We discovered that the D-LDH-type FAD-binding site in MtbFHb overlaps with another FAD-binding motif similar to thioredoxin reductases and reduces DTNB in the presence of NADPH similar to trxB of Mtb. These results suggested that MtbFHb is functioning as a disulfide oxidoreductase. Interestingly, D-lactate created a conformational change in MtbFHb and attenuated its ability to oxidize NADPH. Mass spectroscopy demonstrated that MtbFHb reduces des-myo-inositol mycothiol in the presence of D-lactate unlike NADPH, indicating that D-lactate changes the specificity of MtbFHb from di-thiol to di-mycothiol. When M. smegmatis carrying deletion in the fhbII gene (encoding a homolog of MtbFHb) was complemented with the fhb gene of Mtb, it exhibited four- to fivefold reductions in lipid peroxidation and significant enhancement in the cell survival under oxidative stress. These results were corroborated by reduced lipid peroxidation and enhanced cell survival of wild-type M. smegmatis after overexpression of the fhb gene of Mtb. Since D-lactate is a by-product of lipid peroxidation and MtbFHb is a membrane-associated protein, D-lactate-mediated reduction of mycothiol disulfide by MtbFHb may uniquely equip Mtb to relieve the toxicity of D-lactate accumulation and protect the cell from oxidative damage, simultaneously balancing the redox environment under oxidative stress that may be vital for the pathogenesis of Mtb.

Thioredoxin Reductase (TrxR) functions to recycle thioredoxin (Trx) during hydroperoxide metabolism mediated by peroxiredoxins and is currently being targeted using the FDA-approved anti-rheumatic drug, auranofin (AF), to selectively sensitize cancer cells to therapy. AF treatment decreased TrxR activity and clonogenic survival in small cell lung cancer (SCLC) cell lines (DMS273 and DMS53) as well as the H727 atypical lung carcinoid cell line. AF treatment also significantly sensitized DMS273 and H727 cell lines in vitro to sorafenib, an FDA-approved multi-kinase inhibitor that depleted intracellular glutathione (GSH). The pharmacokinetic, pharmacodynamic, and safety profile of AF was examined in nude mice with DMS273 xenografts administered AF intraperitoneally at 2 mg/kg or 4 mg/kg (IP) once (QD) or twice daily (BID) for 1-5 d. Plasma levels of AF were 10-20 μM (determined by mass spectrometry of gold), and the optimal inhibition of TrxR activity was obtained at 4 mg/kg once daily, with no effect on glutathione peroxidase 1 activity. This AF treatment extended for 14 d, inhibited TrxR (>75%), and resulted in a significant prolongation of median overall survival from 19 to 23 d ( p  = .04, N  = 30 controls, 28 AF). In this experiment, there were no observed changes in animal bodyweight, complete blood counts (CBCs), bone marrow toxicity, blood urea nitrogen, or creatinine. These results support the hypothesis that AF effectively inhibits TrxR both in vitro and in vivo in SCLC, sensitizes NETs and SCLC to sorafenib, and could be repurposed as an adjuvant therapy with targeted agents that induce disruptions in thiol metabolism.

Lymphatic filariasis and its associated health hazards have taken enormous tolls especially in the tropical and sub-tropical countries round the globe. Our present work contemplates the immunomodulatory role of filarial Thioredoxin reductase (TrxR) for the survival of the parasite inside the human host. For this, the protein TrxR was purified from the filarial parasite Setaria cervi and further substantiated through specific anti-TrxR antibody raised in mice. Both commercially available anti-TrxR antibody and laboratory raised antibody produced a single band with a molecular mass of ~80 kDa on western blot. The protein is optimally active at pH 7.0 and at temperature 37 °C. This protein contains both alpha helix and beta pleated sheet with selenocysteine at its active site. The Km was found to be 2.75 ± 0.49 mM. TrxR was found to downregulate lipopolysaccharide (LPS)-induced inflammation in macrophages due to inhibition of TLR4-NF-κB pathway. The result was further supported by the downregulation of inflammasome pathway and activation of alternatively activated macrophages upon TrxR treatment. Hence this study projects insights into the importance of filarial TrxR in host-parasite interface as well as it illustrates novel therapeutic strategy towards anti-filarial drug development. • Purification and characterization of filarial Thioredoxin reductase (TrxR) • TrxR exhibits anti-inflammatory action on LPS induced inflamed macrophages. • Filarial TrxR downregulates the TLR4-NF-κB axis and prevents NLRP3 inflammasome activation. • Immunomodulatory action of TrxR supports parasite survival within the host. [ABSTRACT FROM AUTHOR]

Activating mutations in the KEAP1/NRF2 pathway characterize a subset of non-small cell lung cancer (NSCLC) associated with chemoresistance and poor prognosis. We herein evaluated the relationship between 64 oxidative stress-related genes and overall survival data from 35 lung cancer datasets. Thioredoxin reductase-1 (TXNRD1) stood out as the most significant predictor of poor outcome. In a cohort of NSCLC patients, high TXNRD1 protein levels correlated with shorter disease-free survival and distal metastasis-free survival post-surgery, including a subset of individuals treated with platinum-based adjuvant chemotherapy. Bioinformatics analysis revealed that NSCLC tumors harboring genetic alterations in the NRF2 pathway (KEAP1, NFE2L2 and CUL3 mutations, and NFE2L2 amplification) overexpress TXNRD1 , while no association with EGFR, KRAS, TP53 and PIK3CA mutations was found. In addition, nuclear accumulation of NRF2 overlapped with upregulated TXNRD1 protein in NSCLC tumors. Functional cell assays and gene dependency analysis revealed that NRF2, but not TXNRD1, has a pivotal role in KEAP1 mutant cells' survival. KEAP1 mutants overexpress TXNRD1 and are less susceptible to the cytotoxic effects of the TXNRD1 inhibitor auranofin when compared to wild-type cell lines. Inhibition of NRF2 with siRNA or ML-385, and glutathione depletion with buthionine-sulfoximine, sensitized KEAP1 mutant A549 cells to auranofin. NRF2 knockdown and GSH depletion also augmented cisplatin cytotoxicity in A549 cells, whereas auranofin had no effect. In summary, these findings suggest that TXNRD1 is not a key determinant of malignant phenotypes in KEAP1 mutant cells, although this protein can be a surrogate marker of NRF2 pathway activation, predicting tumor recurrence and possibly other aggressive phenotypes associated with NRF2 hyperactivation in NSCLC. [Display omitted] • Amid 64 redox genes, TXNRD1 shows association with poor survival in NSCLC. • High TXNRD1 levels predict poor DFS and DMFS in a cohort of NSCLC patients. • TXNRD1 expression correlates with NRF2 target gene signature in NSCLC. • High TXNRD1 overlaps with altered NRF2/KEAP1 axis, but not other NSCLC mutations. • NRF2, but not TXNRD1, is key for survival/platinum resistance of KEAP1 mutant cells. [ABSTRACT FROM AUTHOR]

Increasing evidence suggests the significant contribution of high levels of thioredoxin reductase (TrxR) in various stages of tumorigenesis and resistance to tumor chemotherapy. Thus, inhibition of TrxR with small molecules is an attractive strategy for cancer therapy. Eriocalyxin B (EriB), a naturally occurring diterpenoid extracted from Isodon eriocalyx, has reflected potential anticancer activities through numerous pathways. Here, we describe that EriB covalently modifies GSH and selectively inhibits TrxR activity by targeting the Sec residue of the enzyme. Pharmacological inhibition of TrxR by EriB results in elevated ROS levels, reduced total GSH and thiols content, which ultimately induced potent RKO cell apoptosis mediated by oxidative stress. Importantly, EriB indicates potent synthetic lethality with GSH inhibitors, BSO, in RKO cells. In summary, our results highlight that targeting TrxR by EriB explores a novel mechanism for the biological action of EriB. This opened up a new therapeutic indication for using EriB to combat cancers. [Display omitted] • Eriocalyxin B (EriB) selectively inhibits thioredoxin reductase with an IC 50 value of approximately 0.42 μM. • At nanomolar concentration, EriB shows potent synthetic lethality with GSH inhibitor, BSO, in colorectal cancer RKO cells. • EriB induces robust oxidative stress-mediated apoptosis in RKO cells. [ABSTRACT FROM AUTHOR]

The slowing-down de novo drug-discovery emphasized the importance of repurposing old drugs. This is particularly true when combating infections caused by therapy-refractory microorganisms, such as Scedosporium species and Lomentospora prolificans. Recent studies on Scedosporium responses to oxidative stress underscored the importance of targeting the underlying mechanisms. Auranofin, ebselen, PX-12, honokiol, and to a lesser extent, conoidin A are known to disturb redox-homeostasis systems in many organisms. Their antifungal activity was assessed against 27 isolates belonging to the major Scedosporium species: S. apiospermum, S. aurantiacum, S. boydii, S. dehoogii, S. minutisporum, and Lomentospora prolificans. Auranofin and honokiol were the most active against all Scedosporium species (mean MIC50 values of 2.875 and 6.143 μg/ml, respectively) and against L. prolificans isolates (mean MIC50 values of 4.0 and 3.563 μg/ml respectively). Combinations of auranofin with voriconazole or honokiol revealed additive effects against 9/27 and 18/27 isolates, respectively. Synergistic interaction between auranofin and honokiol was only found against one isolate of L. prolificans. The effects of auranofin upon exposure to oxidative stress were also investigated. For all species except S. dehoogii, the maximal growth in the presence of auranofin significantly decreased when adding a sublethal dose of menadione. The analysis of the expression of genes encoding oxidoreductase enzymes upon exposure of S. apiospermum to honokiol unveiled the upregulation of many genes, especially those coding peroxiredoxins, thioredoxin reductases, and glutaredoxins. Altogether, these data suggest that auranofin and honokiol act via dampening the redox balance and support their repurposing as antifungals against Scedosporium species and L. prolificans. [ABSTRACT FROM AUTHOR]

Copper (Cu) is one of the toxic elements that cause environmental pollution. As a result of excessive accumulation of copper in the organism, it causes damage in various organs and tissues and hemolysis in erythrocytes. Astaxanthin (ATX) is a pigment belonging to the xanthophyll family, which is an oxygenated derivative of carotenoids. Thanks to its powerful antioxidant properties, ATX has an extraordinary potential to protect the organism against various diseases, especially cancer. The main objective of this study was to investigate the toxic effect of copper ions on the glucose 6-phosphate dehydrogenase (G6PD), 6-phospho-gluconate dehydrogenase (6PGD), glutathione reductase (GR), glutathione S-transferase (GST), and thioredoxin reductase (TrxR) enzymes and the role of astaxanthin in reducing this effect. In in vivo study, Wistar Albino male rats (n=28) were randomly divided into 4 groups: the control group, copper (Cu2+) group, astaxanthin (ATX) group, and copper + astaxanthin (Cu2++ATX) group. The results show that G6PD enzyme activity in Cu2+ group was strongly inhibited (p ˂ 0.05), while in other groups, there were no significant effects compared to the control group (p ⩾ 0.05). 6PGD enzyme activity was significantly reduced in Cu2+ group compared to that in the control group (p ˂ 0.05), and GR enzyme activity was lower in Cu2+ group compared to that in the control group (p ˂ 0.05). Similarly, when GST enzyme activity was evaluated, a strong decrease was observed in the Cu2+ group compared to that in the control group (p ˂ 0.05), while the enzyme activity in the Cu2++ATX group approached the control group (p ⩾ 0.05). When TrxR enzyme activity level was examined, a statistically significant decrease was observed in the Cu2+ and Cu2++ATX groups (p ˂ 0.05), and the enzyme activity in the ATX group was found to be close to that in the control group. When in vitro results were evaluated, it was observed that copper ions inhibited G6PD enzyme purified from rat erythrocyte tissues with IC50=1.90 μM value and Ki = 0.97 μM ± 0.082 value and the inhibition was non-competitive. From the results, it can be concluded that Cu2+ ions have an inhibitory effect on rat erythrocyte pentose phosphate pathway and antioxidant system enzymes both in vivo and in vitro, and astaxanthin reduces this effect. [ABSTRACT FROM AUTHOR]

Low‐molecular‐weight (low Mr) thioredoxin reductases (TrxRs) are homodimeric NADPH‐dependent dithiol flavoenzymes that reduce thioredoxins (Trxs) or Trx‐like proteins involved in the activation networks of enzymes, such as the bacterial class Ib ribonucleotide reductase (RNR). During the last few decades, TrxR‐like ferredoxin/flavodoxin NADP+ oxidoreductases (FNRs) have been discovered and characterized in several types of bacteria, including those not encoding the canonical plant‐type FNR. In Bacillus cereus, a TrxR‐like FNR has been shown to reduce the flavodoxin‐like protein NrdI in the activation of class Ib RNR. However, some species only encode TrxR and lack the homologous TrxR‐like FNR. Due to the structural similarity between TrxRs and TrxR‐like FNRs, as well as variations in their occurrence in different microorganisms, we hypothesized that low Mr TrxR may be able to replace TrxR‐like FNR in, for example, the reduction of NrdI. In this study, characterization of TrxR from B. cereus has revealed a weak FNR activity toward NrdI reduction. Additionally, the crystal structure shows that only one out of two binding sites of the B. cereus TrxR homodimer is occupied with NADPH, indicating a possible asymmetric co‐substrate binding in TrxR. [ABSTRACT FROM AUTHOR]

Summary: Radiotherapy is an effective treatment modality for breast cancer but, unfortunately, not all patients respond fully with a significant number experiencing local recurrences. Overexpression of thioredoxin and thioredoxin reductase has been reported to cause multidrug and radiation resistance - their inhibition may therefore improve therapeutic efficacy. Novel indolequinone compounds have been shown, in pancreatic cancer models, to inhibit thioredoxin reductase activity and exhibit potent anticancer activity. The present study evaluates, using in vitro breast cancer models, the efficacy of a novel indolequinone compound (IQ9) as a single agent and in combination with ionising radiation using a variety of endpoint assays including cell proliferation, clonogenic survival, enzyme activity, and western blotting. Three triple-negative breast cancer (MDA-MB-231, MDA-MB-468, and MDA-MB-436) and two luminal (MCF-7 and T47D) breast cancer cell lines were used. Results show that treatment with IQ9 significantly inhibited thioredoxin reductase activity, and inhibited cell growth and colony formation of breast cancer cells with IC50 values in the low micromolar ranges. Enhanced radiosensitivity of triple-negative breast cancer cells was observed, with sensitiser enhancement ratios of 1.20–1.43, but with no evident radiosensitisation of luminal breast cancer cell lines. IQ9 upregulated protein expression of thioredoxin reductase in luminal but not in triple-negative breast cancer cells which may explain the observed differential radiosensitisation. This study provides important evidence of the roles of the thioredoxin system as an exploitable radiobiological target in breast cancer cells and highlights the potential therapeutic value of indolequinones as radiosensitisers. ***This study was not part of a clinical trial. Clinical trial registration number: N/A [ABSTRACT FROM AUTHOR]

The emerging and spreading of multi-drug resistant (MDR) bacteria have been becoming one of the most severe threats to human health. Enhancing oxidative stress as mimicking immune system was considered as a potential strategy to fight against infection of MDR bacteria. In this study, we investigated the antibacterial efficiency of such a strategy which combines silver nanoparticles (AgNPs) with ebselen. The results showed that AgNPs and ebselen combination had significant synergistic killing effects both on Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) in vitro, including model strains of China Veterinary Culture Collection and MDR clinical isolates, which is similar as the combination of silver ion and ebselen. AgNPs exhibited to be a strong inhibitor of bacterial thioredoxin reductase, same as a free silver ion. Ebselen mitigated the cytotoxicity of AgNPs to HeLa cells. However, in a bacteria-cell coexistence condition, the synergistic bactericidal effect was only observed on S. aureus (p

Anticancer drugs that target cellular antioxidant systems have recently attracted much attention. Auranofin (AF) is currently evaluated in several clinical trials as an anticancer agent that targets the cytosolic and mitochondrial forms of the selenoprotein thioredoxin reductase, TXNRD1 and TXNRD2. Recently, two novel TXNRD1 inhibitors (TRi-1 and TRi-2) have been developed that showed anticancer efficacy comparable to AF, but with lower mitochondrial toxicity. However, the cellular action mechanisms of these drugs have not yet been thoroughly studied. Here we used several proteomics approaches to determine the effects of AF, TRi-1 and TRi-2 when used at IC50 concentrations with the mouse B16 melanoma and LLC lung adenocarcinoma cells, as these are often used for preclinical mouse models in evaluation of anticancer drugs. The results demonstrate that TRi-1 and TRi-2 are more specific TXNRD1 inhibitors than AF and reveal additional AF-specific effects on the cellular proteome. Interestingly, AF triggered stronger Nrf2-driven antioxidant responses than the other two compounds. Furthermore, AF affected several additional proteins, including GSK3A, GSK3B, MCMBP and EEFSEC, implicating additional effects on glycogen metabolism, cellular differentiation, inflammatory pathways, DNA replication and selenoprotein synthesis processes. Our proteomics data provide a resource for researchers interested in the multidimensional analysis of proteome changes associated with oxidative stress in general, and the effects of TXNRD1 inhibitors and AF protein targets in particular.

Background: Interstitial lung disease (ILD) treatment is a critical unmet need. Selenium is an essential trace element for human life and an antioxidant that activates glutathione, but the gap between its necessity and its toxicity is small and requires special attention. Whether selenium can be used in the treatment of ILD remains unclear., Methods: We investigated the prophylactic and therapeutic effects of selenite, a selenium derivative, in ILD using a murine model of bleomycin-induced idiopathic pulmonary fibrosis (IPF). We further elucidated the underlying mechanism using in vitro cell models and examined their relevance in human tissue specimens. The therapeutic effect of selenite in bleomycin-administered mice was assessed by respiratory function and histochemical changes. Selenite-induced apoptosis and reactive oxygen species (ROS) production in murine lung fibroblasts were measured., Results: Selenite, administered 1 day (inflammation phase) or 8 days (fibrotic phase) after bleomycin, prevented and treated deterioration of lung function and pulmonary fibrosis in mice. Mechanistically, selenite inhibited the proliferation and induced apoptosis of murine lung fibroblasts after bleomycin treatment both in vitro and in vivo. In addition, selenite upregulated glutathione reductase (GR) and thioredoxin reductase (TrxR) in murine lung fibroblasts, but not in lung epithelial cells, upon bleomycin treatment. GR and TrxR inhibition eliminates the therapeutic effects of selenite. Furthermore, we found that GR and TrxR were upregulated in the human lung fibroblasts of IPF patient samples., Conclusions: Selenite induces ROS production and apoptosis in murine lung fibroblasts through GR and TrxR upregulation, thereby providing a therapeutic effect in bleomycin-induced IPF., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Background/aim: Synovial sarcoma (SS) is a rare malignant tumor with a poor survival rate. We previously reported that a combination of auranofin (AUR), a thioredoxin reductase inhibitor, and celecoxib (CE), an anti-inflammatory drug, significantly impedes the local progression of osteosarcoma (OS). However, the role of redox regulation in SS remains to be elucidated. This study aimed to investigate the efficacy of combined treatment of AUR and CE on the local progression of SS in vivo., Materials and Methods: Nu/nu mice were implanted with the human SS cell line, Aska-SS, and treated with vehicle control, AUR, or a combination of AUR and CE (AUR-CE). Primary tumor size and weight were evaluated for the study duration and upon resection, respectively. Hematoxylin and eosin (H&E) and Ki-67 staining were performed to assess the local progression of SS., Results: A statistically significant reduction in tumor size and weight was observed in the AUR- and AUR-CE-treated groups upon excision compared to that in the vehicle-treated group. The AUR-CE-treated group showed synergistic inhibition of local tumor growth. H&E staining of local SS tumors revealed decreased cell density and nuclear deformation in the AUR- and AUR-CE-treated groups compared to those in the vehicle-treated group. Immunohistochemical staining revealed a statistically significant decrease in Ki-67-positive cells in the AUR-CE-treated group compared to the vehicle-treated group., Conclusion: The combination of AUR and CE showed significant potential for delaying the local progression of SS. These findings support the repurposing of AUR and CE as early treatment options for SS., (Copyright © 2024 International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)

Selenium (Se) is a micronutrient with essential physiological functions achieved through the production of selenoproteins. Adequate Se intake has health benefits and reduces mercury (Hg) toxicity, which is important due to its neurotoxicity. This study determined the Se status and redox enzyme, including selenoproteins’, activity in pregnant women highly exposed to Hg (between 1 to 54 µg Hg/L blood) via fish consumption. A cross-sectional study enrolling 513 women between the first and third trimester of pregnancy from Madeira, Portugal was conducted, encompassing collection of blood and plasma samples. Samples were analyzed for total Se and Hg levels in whole blood and plasma, and plasma activity of redox-active proteins, such as glutathione peroxidase (GPx), thioredoxin reductase (TrxR) and thioredoxin (Trx). Enzyme activities were related to Se and Hg levels in blood. Se levels in whole blood (65.0 ± 13.1 µg/L) indicated this population had a sub-optimal Se status, which translated to low plasma GPx activity (69.7 ± 28.4 U/L). The activity of TrxR (12.3 ± 5.60 ng/mL) was not affected by the low Se levels. On the other hand, the decrease in Trx activity with an increase in Hg might be a good indicator to prevent fetal susceptibility.

Background: Lung adenocarcinoma (LUAD) is the primary form of lung cancer, yet the reliable biomarkers for early diagnosis remain insufficient. Thioredoxin reductase (TrxR) is strongly linked to the occurrence, development, and drug resistance of lung cancer, making it a potential biomarker. However, further research is required to assess its diagnostic value in LUAD., Methods: A retrospective analysis was performed on patients who underwent pulmonary nodule resection at our center from 2018 to 2022. Clinical data, including preoperative TrxR levels, imaging, and laboratory characteristics, were identified as study variables. Two prediction models were constructed using multiple logistic regression, and their prediction performance was evaluated comprehensively. Besides, bioinformatics analyses of TrxR coding genes including differential expression, functional enrichment, immune infiltration, drug sensitivity, and single-cell landscape were performed based on TCGA database, which were subsequently validated by Human Protein Atlas., Results: A total of 506 eligible patients (72 benign lesions, 77 AISs, 185 MIAs and 172 IACs) were identified in the clinical cohort. Two TrxR-based models were developed, which were able to distinguish between benign and malignant pulmonary nodules, as well as pathological subtypes of LUAD, respectively. The models exhibited good predictive ability with all AUC values ranging from 0.7 to 0.9. Based on calibration curves and clinical decision analysis, the nomogram models showed high reliability. Functional analysis indicated that TXNRD1 primarily participated in cell cycle and lipid metabolism. Immune infiltration analysis showed that TXNRD1 has a strong association with immune cells and could impact immunotherapy. Then, we identified small molecular compounds that inhibit TXNRD1 and confirmed TXNRD1 expression by single-cell landscape and immunohistochemistry., Conclusion: This study validated the diagnostic value of TrxR and TXNRD1 in clinical cohorts and transcriptional data, respectively. TrxR and TXNRD1 could be used in the risk diagnosis of early LUAD and facilitate personalized treatment strategies., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Authors.)

Thioredoxin reductase (TXNRD) is a selenoprotein that plays a crucial role in cellular antioxidant defense. Previously, a distinctive guiding bar motif was identified in TXNRD1, which influences the transfer of electrons. In this study, utilizing single amino acid substitution and Excitation-Emission Matrix (EEM) fluorescence spectrum analysis, we discovered that the guiding bar communicates with the FAD and modulates the electron flow of the enzyme. Differential Scanning Fluorimetry (DSF) analysis demonstrated that the aromatic amino acid in guiding bar is a stabilizer for TXNRD1. Kinetic analysis revealed that the guiding bar is vital for the disulfide reductase activity but hinders the selenocysteine-independent reduction activity of TXNRD1. Meanwhile, the guiding bar shields the selenocysteine residue of TXNRD1 from the attack of electrophilic reagents. We also found that the inhibition of TXNRD1 by caveolin-1 scaffolding domain (CSD) peptides and compound LCS3 did not bind to the guiding bar motif. In summary, the obtained results highlight new aspects of the guiding bar that restrict the flexibility of the C-terminal redox motif and govern the transition from antioxidant to pro-oxidant., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier B.V.)

Oxidative stress is hypothesized to play a role in pancreatic β-cell damage, potentially contributing to β-cell dysfunction and death in both type 1 and type 2 diabetes. Oxidative stress arises when naturally occurring reactive oxygen species (ROS) are produced at levels that overwhelm the antioxidant capacity of the cell. ROS, including superoxide and hydrogen peroxide, are primarily produced by electron leak during mitochondrial oxidative metabolism. Additionally, peroxynitrite, an oxidant generated by the reaction of superoxide and nitric oxide, may also cause β-cell damage during autoimmune destruction of these cells. β-cells are thought to be susceptible to oxidative damage based on reports that they express low levels of antioxidant enzymes compared to other tissues. Furthermore, markers of oxidative damage are observed in islets from diabetic rodent models and human patients. However, recent studies have demonstrated high expression of various isoforms of peroxiredoxins, thioredoxin, and thioredoxin reductase in β-cells and have provided experimental evidence supporting a role for these enzymes in promoting β-cell function and survival in response to a variety of oxidative stressors. This mini-review will focus on the mechanism by which thioredoxins and peroxiredoxins detoxify ROS and on the protective roles of these enzymes in β-cells. Additionally, we speculate about the role of this antioxidant system in promoting insulin secretion. [ABSTRACT FROM AUTHOR]

Jatroidaine A (1), a new tetranortirucallane-type triterpene, and two known analogues (2-3) were isolated from the leaves and branches of Jatropha multifida. Their structures were fully elucidated by extensive spectroscopic methods and comparison to known compounds. The absolute configuration of 1 was assigned by single-crystal X-ray diffraction analysis. All compounds were evaluated for their anti-inflammatory and thioredoxin reductase (TrxR) inhibitory activities. Unfortunately, no significant activity was observed. [ABSTRACT FROM AUTHOR]

The selenoprotein thioredoxin reductase 1 (TrxR1; TXNRD1) participates in multiple cellular processes and is regarded as a cellular target in anti-tumor drug discovery and development. TrxR1 has been reported to reduce menadione to menadiol and to produce superoxide anion radicals. However, the details of TrxR1-mediated menadione reduction have rarely been studied. In this study, we found that wild-type TrxR1 could reduce menadione in a less efficient way, but the U498C mutant variant supported high-efficiency menadione reduction in a Sec-independent manner. Meanwhile, the site-directed mutagenesis results showed that Cys64 mutant increased the K m values and decreased the catalytic efficiency, which was associated with a charge-transfer complex between FAD-Cys64. Mass spectrometry (MS) revealed that in NADPH pre-reduced TrxR1 but not oxidized TrxR1, the highly active Sec498 of wild-type TrxR1 was arylated by menadione and strongly impaired the DTNB reducing activity in a dose-dependent manner. TrxR1 reduced menadione more efficiently than glutathione reductase (GR), and interestingly menadione did not inhibit the GSSG reducing activity of GR. In summary, our results demonstrate that TrxR1 catalyzes the reduction of menadione in a Sec-independent manner, which highly depend on Cys498 instead of N-terminal redox motif, and the Sec498 of TrxR1 is the primary target of menadione. The interaction between menadione and TrxR1 revealed in this study may provide a valuable reference for the development of anticancer drugs targeting selenoprotein TrxR1. [Display omitted] • Mutation of Sec498 to Cys498 enhances both NADPH oxidation and superoxide production in TrxR1 mediated menadione reduction. •Menadione modifies the highly reactive Sec498 of TrxR1, thereby inhibiting the reduction activity of TrxR1. •Sec-containing TrxR1 is more reactive than yeast glutathione reductase in menadione reduction and interaction. [ABSTRACT FROM AUTHOR]

Thioredoxin reductase (TrxR) is a central component in the thioredoxin system by involving in catalyzing the reduction of thioredoxin, which is critical for organism survival. Because this system is essential, it is a promising target for novel antimicrobial agents. Herein, we solved the 1.9 Å high‐resolution structure of TrxR from Acinetobacter baumannii Thioredoxin reductase (AbTrxR), which is a Gram‐negative, pathogenic bacterium and a drug‐resistant superbug. AbTrxR was cofactor‐free and formed a dimer in solution. AbTrxR contained a longer dimerization loop2 and a shorter β7‐β8 connecting loop than other TrxRs. AbTrxR cofactor‐free form exhibited a flavin‐oxidizing (FO) conformation, whose NADPH domain was located close to the dimeric interface. This structural information might be helpful for development of new antibiotic agents targeting superbugs. [ABSTRACT FROM AUTHOR]

Amebiasis causes approximately 70,000 deaths annually and is the third cause of death due to parasites worldwide. It is treated primarily with metronidazole, which has adverse side effects, is mutagenic and carcinogenic, and emergence of resistance is an increasing concern. Unfortunately, better therapeutic alternatives are lacking. Re-purposing of older FDA approved drugs is advantageous to drug discovery since safety and pharmacokinetic effects in humans are already known. In high throughput screening studies, we recently demonstrated that auranofin, a gold containing compound originally approved to treat rheumatoid arthritis, has activity against trophozoites of E. histolytica, the causative agent of amebiasis. Auranofin's anti-parasitic activity is attributed to its monovalent gold molecule that readily inhibits E. histolytica thioredoxin reductase. This anti-oxidant enzyme is the only thiol-dependent flavo-reductase present in E. histolytica. Auranofin has also shown promising activity against other protozoans of significant public health importance. Altogether, this evidence suggests that auranofin has the potential to become a broad spectrum alternative therapeutic agent for diseases with a large global burden.

Liver fibrosis is an important stage in the progression of liver injury into cirrhosis or even liver cancer. Hepatic stellate cells (HSCs) are induced by transforming growth factor-β1 (TGF-β1) to produce α-smooth muscle actin (α-SMA) and collagens in liver fibrosis. Butaselen (BS), which was previously synthesized by our group, is an organic selenium compound that exerts antioxidant and tumor cell apoptosis–promoting effects by inhibiting the thioredoxin (Trx)/thioredoxin reductase (TrxR) system. The aim of this study was to investigate the potential effects of BS on liver fibrosis and explore the underlying molecular mechanisms of its action. Liver fibrosis models were established using male BALB/c mice through intraperitoneal injection of CCl4. BS was administered orally once daily at a dose of 36, 90, or 180 mg/kg. Silymarin (Si), which is a drug used for patients with nonalcoholic fatty liver disease and nonalcoholic steatohepatitis, was administered at a dose of 30 mg/kg per day as a control. The action mechanisms of BS against liver fibrosis progression were examined in HSCs. The study revealed that the activity and expression levels of TrxR were elevated in the mouse liver and serum after CCl4-induced liver fibrosis. Oral administration of BS relieved the pathological state of mice with liver fibrosis, showing significant therapeutic effects against liver fibrosis. Moreover, BS not only induced HSC apoptosis but also inhibited the production of α-SMA and collagens by HSCs by downregulating the TGF-β1 expression and blocking the TGF-β1/Smads pathway. The results of the study indicated that BS inhibited liver fibrosis by regulating the TGF-β1/Smads pathway.

Oxidative stress is hypothesized to play a role in pancreatic β-cell damage, potentially contributing to β-cell dysfunction and death in both type 1 and type 2 diabetes. Oxidative stress arises when naturally occurring reactive oxygen species (ROS) are produced at levels that overwhelm the antioxidant capacity of the cell. ROS, including superoxide and hydrogen peroxide, are primarily produced by electron leak during mitochondrial oxidative metabolism. Additionally, peroxynitrite, an oxidant generated by the reaction of superoxide and nitric oxide, may also cause β-cell damage during autoimmune destruction of these cells. β-cells are thought to be susceptible to oxidative damage based on reports that they express low levels of antioxidant enzymes compared to other tissues. Furthermore, markers of oxidative damage are observed in islets from diabetic rodent models and human patients. However, recent studies have demonstrated high expression of various isoforms of peroxiredoxins, thioredoxin, and thioredoxin reductase in β-cells and have provided experimental evidence supporting a role for these enzymes in promoting β-cell function and survival in response to a variety of oxidative stressors. This mini-review will focus on the mechanism by which thioredoxins and peroxiredoxins detoxify ROS and on the protective roles of these enzymes in β-cells. Additionally, we speculate about the role of this antioxidant system in promoting insulin secretion.

Natural products frequently have unique physiological activities and new action mechanisms due to their structural diversity and novelty, and are an important source for innovative drugs and lead compounds. We present herein that natural product santamarine targeted thioredoxin reductase (TrxR) to weaken its antioxidative function in cells, accompanied by accumulation of high levels of reactive oxygen species (ROS), and finally induced a new mechanism of tumor cell oxidative stress-mediated apoptosis. TrxR knockdown or overexpression cell lines were employed to further evaluate the cytotoxicity of santamarine regulated by TrxR, demonstrated that TrxR played a key role in the physiological effect of santamarine on cells. Santamarine targeting TrxR reveals its previously unrecognized mechanism of antitumor and provides a basis for the further development of santamarine as a potential cancer therapeutic agent.

Auranofin, as a thioredoxin reductase (TrxR) inhibitor, has promising anti-cancer activity in several cancer types. However, little is known about the inhibitory effect of auranofin on lung cancer cell growth. We, therefore, investigated the antigrowth effects of auranofin in various lung cancer cells with respect to cell death, reactive oxygen species (ROS), and glutathione (GSH) levels. Treatment with 0~5 µM auranofin decreased cell proliferation and induced cell death in Calu-6, A549, SK-LU-1, NCI-H460, and NCI-H1299 lung cancer cells at 24 h. In addition, 0~5 µM auranofin increased ROS levels, including O2•−, and depleted GSH levels in these cells. N-acetyl cysteine (NAC) prevented growth inhibition and mitochondrial membrane potential (MMP, ∆Ψm) loss in 3 and 5 µM auranofin-treated Calu-6 and A549 cells at 24 h, respectively, and decreased ROS levels and GSH depletion in these cells. In contrast, L-buthionine sulfoximine (BSO) enhanced cell death, MMP (∆Ψm) loss, ROS levels, and GSH depletion in auranofin-treated Calu-6 and A549 cells. Treatment with 3 and 5 µM auranofin induced caspase-3 activation and poly (ADP ribose) polymerase (PARP) cleavage in Calu-6 and A549 cells, respectively. Both were prevented by NAC, but enhanced by BSO. Moreover, TrxR activity was reduced in auranofin-treated Calu-6 and A549 cells. That activity was decreased by BSO, but increased by NAC. In conclusion, these findings demonstrate that auranofin-induced cell death is closely related to oxidative stress resulted from increased ROS levels and GSH depletion in lung cancer cells.

Mercury (Hg) is known for its neurotoxicity and is reported to activate microglia cells at low exposure levels. Since mercury decreases the activity of the glutathione and thioredoxin systems, we hypothesize that Hg would, in turn, disrupt microglia homeostasis by interfering with redox regulation of signaling pathways. Thus, in this work, we analyzed the effect of exposure to Hg2+ on nuclear translocation and activation of NF-kB (p50) and p38 and pro-inflammatory gene transcription (IL-1ß; iNOS, TNF-alpha) considering the interaction of Hg with the glutathione system and thioredoxin systems in microglial cells. N9 (mouse) microglia cells were exposed to different concentrations of Hg2+ and the 24 h EC50 for a reduction in viability was 42.1 ± 3.7 μM. Subsequent experiments showed that at sub-cytotoxic levels of Hg2+, there was a general increase in ROS (≈40%) accompanied by a significant depletion (60–90%) of glutathione (GSH) and thioredoxin reductase (TrxR) activity. Upon 6 h of exposure to Hg2+, p38 (but not p50) accumulated in the nucleus (50% higher than in control), which was accompanied by an increase in its phosphorylation. Transcript levels of both IL1-ß and iNOS were increased over two-fold relative to the control. Furthermore, pre-exposure of cells to the p38 inhibitor SB 239063 hindered the activation of cytokine transcription by Hg2+. These results show that disruption of redox systems by Hg2+ prompts the activation of p38 leading to transcription of pro-inflammatory genes in microglia cells. Treatment of N9 cells with NAC or sodium selenite—which caused an increase in basal GSH and TrxR levels, respectively, prevented the activation of p38 and the transcription of pro-inflammatory cytokines. This result demonstrates the importance of an adequate nutritional status to minimize the toxicity resulting from Hg exposure in human populations at risk.

Auranofin (AF) is an FDA-approved antirheumatic drug with anticancer properties that acts as a thioredoxin reductase 1 (TrxR) inhibitor. The exact mechanisms through which AF targets cancer cells remain elusive. To shed light on the mode of action, this study provides an in-depth analysis on the molecular mechanisms and immunogenicity of AF-mediated cytotoxicity in the non-small cell lung cancer (NSCLC) cell line NCI–H1299 (p53 Null) and its two isogenic derivates with mutant p53 R175H or R273H accumulation.TrxR is highly expressed in a panel of 72 NSCLC patients, making it a valid druggable target in NSCLC for AF. The presence of mutant p53 overexpression was identified as an important sensitizer for AF in (isogenic) NSCLC cells as it was correlated with reduced thioredoxin (Trx) levels in vitro. Transcriptome analysis revealed dysregulation of genes involved in oxidative stress response, DNA damage, granzyme A (GZMA) signaling and ferroptosis. Although functionally AF appeared a potent inhibitor of GPX4 in all NCI–H1299 cell lines, the induction of lipid peroxidation and consequently ferroptosis was limited to the p53 R273H expressing cells. In the p53 R175H cells, AF mainly induced large-scale DNA damage and replication stress, leading to the induction of apoptotic cell death rather than ferroptosis. Importantly, all cell death types were immunogenic since the release of danger signals (ecto-calreticulin, ATP and HMGB1) and dendritic cell maturation occurred irrespective of (mutant) p53 expression. Finally, we show that AF sensitized cancer cells to caspase-independent natural killer cell-mediated killing by downregulation of several key targets of GZMA.Our data provides novel insights on AF as a potent, clinically available, off-patent cancer drug by targeting mutant p53 cancer cells through distinct cell death mechanisms (apoptosis and ferroptosis). In addition, AF improves the innate immune response at both cytostatic (natural killer cell-mediated killing) and cytotoxic concentrations (dendritic cell maturation).

α‐Diazo homophotalimides were reacted with various propiolic acids on Rh2(esp)2 catalysis. The resulting propiolate esters were transformed into novel, heterocyclic Δα,β‐spirobutenolides in good to excellent product yields. The approach represents a fundamentally novel entry into natural‐like Δα,β‐spirobutenolides present in many biologically active natural products as well as fully synthetic compounds endowed with diverse biological activities. The Δα,β‐spirobutenolides thus obtained were shown to inhibit thioredoxin reductase, a selenocysteine enzyme target for cancer. Moreover, for the best compound in the series (TrxR IC50 1.49±0.08 μM), by using MALDI‐TOF mass‐spectrometry it was shown that it selectively binds selenocysteine in the presence of a 10‐fold excess of cysteine. This validates the new compound as a promising lead for anticancer therapy development. [ABSTRACT FROM AUTHOR]

Objective(s): This study was undertaken to investigate the efficacy of telomerase activator-65 (Ta-65) and pomegranate peel against aging-induced deteriorations in the liver. Materials and Methods: The rats were divided into four groups: control, aged, aged rats treated with Ta-65, and pomegranate orally for two months. Results: Aging significantly increased the serum levels of total protein, globulins, and protein carbonyl and reduced the insulin-like growth factor 1 (IGF-1). It also elevated the hepatic malondialdehyde and decreased the hepatic glutathione S-transferase (GST) activity. Aging elevated the expression of thioredoxin reductase1, telomerase reverse transcriptase, and cytochrome 3a1 in the liver; it increased the p53 protein level and elevated the activity of caspase-3 in the liver indicating the occurrence of apoptosis. The architecture of the liver deteriorated in the aged rats, as shown by both light and electron microscopy examinations. The liver of the aged rats had many apoptotic hepatocytes with shrunken nuclei. Many hepatocytes had dilated rough endoplasmic reticulum, many lysosomes, and many fat droplets. Administration of Ta-65 and pomegranate to the aged rats normalized most of the previous biochemical parameters and improved the liver architecture. Conclusion: Ta-65 and pomegranate have anti-aging activity through targeting multiple cellular pathways. It is also noteworthy that Ta-65 was superior to pomegranate in its alleviative effects. [ABSTRACT FROM AUTHOR]

A series of gold(I) complexes with the general formula [Au(L2)(L′)] (L2=4‐phenyl‐N‐(prop‐2‐yn‐1‐yl)quinazoline‐2‐carboxamide, L′=PPh3 (triphenylphosphine), 1; TPA (1,3,5‐triaza‐7‐phosphaadamantane), 2, and Me2‐imy (1,3‐dimethylimidazol‐2‐ylidene), 3) were synthesized and fully characterized by spectroscopic methods. The alkynyl ligand L2 belongs to the quinazoline carboxamide class of ligands that are known to bind to the translocator protein (TSPO) at the outer mitochondrial membrane. 1 and 2 exert cytotoxic effects in bladder cancer cells with IC50 values in the low micromolar range. Further mechanistic analysis indicated that the two complexes both act by inducing reactive oxygen species and caspase‐mediated apoptosis. The complexes inhibit thioredoxin reductase, an established target of anticancer gold(I) complexes. Docking studies confirmed that after ligand exchange the free ligand L2 can interact with the TSPO binding site. [ABSTRACT FROM AUTHOR]

There is a drought of new antibacterial compounds that exploit novel targets. Thioredoxin reductase (TrxR) from the Gram-positive bacterial antioxidant thioredoxin system has emerged from multiple screening efforts as a potential target for auranofin, ebselen, shikonin, and allicin. Auranofin serves as the most encouraging proof of concept drug, demonstrating TrxR inhibition can result in bactericidal effects and inhibit Gram-positive bacteria in both planktonic and biofilm states. Minimal inhibitory concentrations are on par or lower than gold standard medications, even among drug resistant isolates. Importantly, existing drug resistance mechanisms that challenge treatment of infections like Staphylococcus aureus do not confer resistance to TrxR targeting compounds. The observed inhibition by multiple compounds and inability to generate a bacterial genetic mutant demonstrate TrxR appears to play an essential role in Gram-positive bacteria. These findings suggest TrxR can be exploited further for drug development. Examining the interaction between TrxR and these proof of concept compounds illustrates that compounds representing a new antimicrobial class can be developed to directly interact and inhibit the validated target. [ABSTRACT FROM AUTHOR]

Eating fish is often recommended as part of a healthful diet. However, fish, particularly large predatory fish, can contain significant levels of the highly toxic methylmercury (MeHg). Ocean fish in general also contain high levels of selenium (Se), which is reported to confer protection against toxicity of various metals including mercury (Hg). Se and Hg have a high mutual binding affinity, and each can reduce the toxicity of the other. This is an evolving area of extensive research and controversy with variable results in the animal and epidemiologic literature. MeHg is toxic to many organ systems through high affinity for –SH (thiol) ligands on enzymes and microtubules. Hg toxicity also causes oxidative damage particularly to neurons in the brain. Hg is a potent and apparently irreversible inhibitor of the selenoenzymes, glutathione peroxidases (GPX), and thioredoxin reductases (TXNRD) that are important antioxidants, each with a selenocysteine (SeCys) at the active site. Hg binding to the SeCys inhibits these enzymes, accounting in part for the oxidative damage that is an important manifestation of Hg toxicity, particularly if there is not a pool of excess Se to synthesize new enzymes. A molar excess of Se reflected in an Se:Hg molar ratio > 1 is often invoked as evidence that the Hg content can be discounted. Some recent papers now suggest that if the Se:Hg molar ratio exceeds 1:1, the fish is safe and the mercury concentration can be ignored. Such papers suggested that the molar ratio rather than the Hg concentration should be emphasized in fish advisories. This paper examines some of the limitations of current understanding of the Se:Hg molar ratio in guiding fish consumption advice; Se is certainly an important part of the Hg toxicity story, but it is not the whole story. We examine how Hg toxicity relates also to thiol binding. We suggest that a 1:1 molar ratio cannot be relied on because not all of the Se in fish or in the fish eater is available to interact with Hg. Moreover, in some fish, Se levels are sufficiently high to warrant concern about Se toxicity. [ABSTRACT FROM AUTHOR]

The free-living amoeba Acanthamoeba castellanii occurs worldwide in soil and water and feeds on bacteria and other microorganisms. It is, however, also a facultative parasite and can cause serious infections in humans. The annotated genome of A. castellanii (strain Neff) suggests the presence of two different thioredoxin reductases (TrxR), of which one is of the small bacterial type and the other of the large vertebrate type. This combination is highly unusual. Similar to vertebrate TrxRases, the gene coding for the large TrxR in A. castellanii contains a UGA stop codon at the C-terminal active site, suggesting the presence of selenocysteine. We characterized the thioredoxin system in A. castellanii in conjunction with glutathione reductase (GR), to obtain a more complete understanding of the redox system in A. castellanii and the roles of its components in the response to oxidative stress. Both TrxRases localize to the cytoplasm, whereas GR localizes to the cytoplasm and the large organelle fraction. We could only identify one thioredoxin (Trx-1) to be indeed reduced by one of the TrxRases, i.e., by the small TrxR. This thioredoxin, in turn, could reduce one of the two peroxiredoxins tested and also methionine sulfoxide reductase A (MsrA). Upon exposure to hydrogen peroxide and diamide, only the small TrxR was upregulated in expression at the mRNA and protein levels, but not the large TrxR. Our results show that the small TrxR is involved in the A. castellanii's response to oxidative stress. The role of the large TrxR, however, remains elusive. [ABSTRACT FROM AUTHOR]

The study included investigation of effects of the thioredoxin reductase isolated from serum of human on oxidative stress induced in rats, through histopathological examination of the heart and liver, and the measurement of the biochemical parameters, which included: thioredoxin reductase, creatine kinase, alanine aminotransferase, aspartate aminotransferase, total bilirubin, albumin and uric acid. Treating experimental animals with 1% hydrogen peroxide led to a significant increase in thioredoxin reductase, creatine kinase, aspartate aminotransferase and total bilirubin compared to control group, while a significant decrease in: albumin and uric acid, but non-significant in alanine aminotransferase. As well as, a different dose 2 and 4mgl Kg of rat body weight of isolated TrxR with 1% hydrogen peroxide improved parameter levels through decrease oxidative stress that induced in rats. The results of the histopathological examination revealed slight to moderate changes in the heart, while no distinguishing changes were observed in the heart of the group treated with hydrogen peroxide and injected with enzyme in intraperitoneally with 4 mg/ kg of rat weight compared to control group. In the liver, there was observed vascular degeneration and thickening of hepatic capsule as a result of chronic congestion and degeneration in the blood vessels which after treatment with 1% hydrogen peroxide compared to control group, but there was noticeable improvement in the liver of group treated with hydrogen peroxide and injected with the enzyme in intraperitoneally with 4 mg/kg of rat weight, and these results confirm the role of the enzyme in the protection of the body from oxidative stress, the use of the enzyme can reduce the severity of different diseases.

Background: Thioredoxin, NADPH, and thioredoxin reductase form the thioredoxinsystem which exists in all living cells. Oxidants have a major role in cancer pathogenesis;therefore, it is necessary to study the role of redox-active compounds such as thioredoxinreductase to increase our knowledge about the molecular mechanisms involved in cancerpathogenesis and ultimately design more effective treatments. The research on the roleof the thioredoxin system in pancreatic cancer is limited; hence, we intend to comparethe tissue distribution and activity of thioredoxin reductase in pancreatic cancer withhealthy tissues located at the tumor margins.Methods: A total of 29 patients with pancreatic cancer participated in this study.The tissue distribution was determined by immunohistochemistry analysis. We useda commercial ELISA kit to determine enzyme activity.Results: There was no significant difference between the tumor tissue and itsnormal surrounding tissue in terms of thioredoxin reductase activity (P=0.56). However,there was a significant difference when we considered the different disease stages. Asignificant relationship also existed between the staining intensity of thioredoxinreductase and disease stage (P=0.022).Conclusion: There was no observed difference between the pancreatic cancertissue and its healthy margin in terms of thioredoxin reductase activity and tissuedistribution. This finding did not support its possible role in pancreatic cancerpathogenesis.

Two new families of dithiocarbamate gold(I) complexes derived from benzenesulfonamide with phosphine or carbene as ancillary ligands have been synthesized and characterized. In the screening of their in vitro activity on human colon carcinoma cells (Caco-2), we found that the more lipophilic complexes—those with the phosphine PPh3—exhibited the highest anticancer activity whilst also displaying significant cancer cell selectivity. [Au(S2CNHSO2C6H5)(PPh3)] (1) and [Au(S2CNHSO2-p-Me-C6H4)(IMePropargyl)] (8) produce cell death, probably by intrinsic apoptosis (mitochondrial membrane potential modification) and caspase 3 activation, causing cell cycle arrest in the G1 phase with p53 activation. Besides this, both complexes might act as multi-target anticancer drugs, as they inhibit the activity of the enzymes thioredoxin reductase (TrxR) and carbonic anhydrase (CA IX) with the alteration of the redox balance, and show a pro-oxidant effect.

Rhodopseudomonas palustris ferredoxin:NADP+ oxidoreductase (RpFNR) belongs to a novel group of thioredoxin reductase-type FNRs with partly characterized redox properties. Based on the reactions of RpFNR with the 3-acetylpyridine adenine dinucleotide phosphate redox couple, we estimated the two-electron reduction midpoint potential of the FAD cofactor to be −0.285 V. 5-Deaza-FMN-sensitized photoreduction revealed −0.017 V separation of the redox potentials between the first and second electron transfer events. We examined the mechanism of oxidation of RpFNR by several different groups of nonphysiological electron acceptors. The kcat/Km values of quinones and aromatic N-oxides toward RpFNR increase with their single-electron reduction midpoint potential. The lower reactivity, mirroring their lower electron self-exchange rate, is also seen to have a similar trend for nitroaromatic compounds. A mixed single- and two-electron reduction was characteristic of quinones, with single-electron reduction accounting for 54% of the electron flux, whereas nitroaromatics were reduced exclusively via single-electron reduction. It is highly possible that the FADH· to FAD oxidation reaction is the rate-limiting step during the reoxidation of reduced FAD. The calculated electron transfer distances in the reaction with quinones and nitroaromatics were close to those of Anabaena and Plasmodium falciparum FNRs, thus demonstrating their similar “intrinsic” reactivity.

Pancreatic cancer accounts for nearly one fourth of all new cancers worldwide. Little progress in the development of novel or adjuvant therapies has been made over the past few decades and new approaches to the treatment of pancreatic cancer are desperately needed. Pharmacologic ascorbate (P-AscH−, high-dose, intravenous vitamin C) is being investigated in clinical trials as an adjunct to standard-of-care chemoradiation treatments. In vitro, P-AscH− has been shown to sensitize cancer cells to ionizing radiation in a manner that is dependent on the generation of H2O2 while simultaneously protecting normal tissue from radiation damage. There is renewed interest in Auranofin (Au), an FDA-approved medication utilized in the treatment of rheumatoid arthritis, as an anti-cancer agent. Au inhibits the thioredoxin antioxidant system, thus increasing the overall peroxide burden on cancer cells. In support of current literature demonstrating Au’s effectiveness in breast, colon, lung, and ovarian cancer, we offer additional data that demonstrate the effectiveness of Au alone and in combination with P-AscH− and ionizing radiation in pancreatic cancer treatment. Combining P-AscH− and Au in the treatment of pancreatic cancer may confer multiple mechanisms to increase H2O2-dependent toxicity amongst cancer cells and provide a promising translatable avenue by which to enhance radiation effectiveness and improve patient outcomes.

Emerging research in mammalian cells suggests that ionic (AgNO3) and nano silver (AgNP) can disrupt the metabolism of selenium which plays a vital role in oxidative stress control. However, the effect of silver (Ag) on selenoprotein function in fish is poorly understood. Here we evaluate the effects of AgNO3 and citrate coated AgNP (cit-AgNP) on selenoprotein function and oxidative stress using a fish cell line derived from the rainbow trout (Oncorhynchus mykiss) intestine (RTgutGC). Cell viability was evaluated using a cytotoxicity assay which measures simultaneously metabolic activity, membrane integrity and lysosome integrity. Cells exposed to equimolar amounts of AgNO3 and cit-AgNP accumulated the same amount of silver intracellularly, however AgNO3 was more toxic than cit-AgNP. Selenoenzymes glutathione peroxidase (GPx) and thioredoxin reductase (TrxR) mRNA levels and enzyme activity were measured. While mRNA levels remained unaffected by AgNO3 or cit-AgNP, the enzyme activity of GPx was inhibited by AgNO3 (1 µM) and cit-AgNP (5 µM) and TrxR activity was inhibited by AgNO3 (0.4 µM) and cit-AgNP (1, 5 µM). Moreover, cells exposed to 1 µM of AgNO3 and cit-AgNP showed an increase in metallothionein b (MTb) mRNA levels at 24 h of exposure, confirming the uptake of silver, but returned to control levels at 72 h suggesting silver scavenging by MTb. Oxidative stress was not observed at any of the doses of AgNO3 or cit-AgNP tested. Overall, this study shows that AgNO3 or cit-AgNP can inhibit the activity of selenoenzymes but do not induce oxidative stress in RTgutGC cells.