Thioredoxin Reductase Activity Research Articles

NRF2 and Thioredoxin Reductase 1 as Modulators of Interactions between Zinc and Selenium.

Selenium and zinc are essential trace elements known to regulate cellular processes including redox homeostasis. During inflammation, circulating selenium and zinc concentrations are reduced in parallel, but underlying mechanisms are unknown. Accordingly, we modulated the zinc and selenium supply of HepG2 cells to study their relationship. HepG2 cells were supplied with selenite in combination with a short- or long-term zinc treatment to investigate intracellular concentrations of selenium and zinc together with biomarkers describing their status. In addition, the activation of the redox-sensitive transcription factor NRF2 was analyzed. Zinc not only increased the nuclear translocation of NRF2 after 2 to 6 h but also enhanced the intracellular selenium content after 72 h, when the cells were exposed to both trace elements. In parallel, the activity and expression of the selenoprotein thioredoxin reductase 1 (TXNRD1) increased, while the gene expression of other selenoproteins remained unaffected or was even downregulated. The zinc effects on the selenium concentration and TXNRD activity were reduced in cells with stable NRF2 knockdown in comparison to control cells. This indicates a functional role of NRF2 in mediating the zinc/selenium crosstalk and provides an explanation for the observed unidirectional behavior of selenium and zinc.

Sensitization of Multidrug Resistant Cancer Cells to Doxorubicin Using Ebselen by Disturbing Cellular Redox Status.

Multidrug resistance (MDR) poses a significant problem in cancer treatment, often causing adverse effects during chemotherapy. Ebselen (Ebs), a synthetic organoselenium compound, affects cellular redox status in cancer cells. In the study, we observed that Ebs disrupted cellular redox balance and sensitized drug-resistant cells to doxorubicin (DOX) treatment. The combination of Ebs and DOX led to increased intracellular reactive oxygen species (ROS) levels and lipid peroxidation while decreasing the activity of thioredoxin reductase (TrxR) and cellular antioxidants in drug-resistant cells. Furthermore, this combination treatment demonstrated notable chemosensitizing effects by reducing cell viability and proliferation in MDR cells compared to DOX treatment alone. Additionally, the combination of Ebs and DOX induced DNA fragmentation and exhibited G2/M phase cell cycle arrest. Immunofluorescent analysis revealed that the Ebs and DOX combination upregulated the expression of p53 and p21, which activated the mitochondrial-dependent apoptotic pathway. The combination treatment also enhanced the upregulation of proapoptotic markers such as Bax, Caspase-3, -9, and cytochrome C, while downregulating the expression of the antiapoptotic marker Bcl-2. Therefore, the current discoveries suggest that Ebs could be employed as a drug candidate for reversing MDR in cancer cells by regulating cellular redox homeostasis.

Alleviation of Copper-Induced Hepatotoxicity by Bergenin: Diminution of Oxidative Stress, Inflammation, and Apoptosis via Targeting SIRT1/FOXO3a/NF-κB Axes and p38 MAPK Signaling.

Despite its biological importance, excess copper induces organ damage, especially to the liver. Disruption of critical signaling cascades that control redox status, inflammatory responses, and cellular apoptosis significantly contributes to the copper-induced hepatotoxicity. The present work explored the hepatoprotective ability of bergenin against the copper-induced hepatotoxicity using male Wistar rats as a mammalian model. The results revealed that bergenin suppressed the copper-evoked histopathological changes and hepatocellular necrosis as indicated by decreased activity of the liver enzymes ALT and AST in the sera of the copper-intoxicated rats. It decreased hepatic copper content and the copper-induced oxidative stress as revealed by reduced lipid peroxidation and improved activity of the antioxidant enzymes thioredoxin reductase, glutathione peroxidase, catalase, and superoxide dismutase. Bergenin downregulated the inflammatory cytokines TNF-α and IL-6, and the inflammatory cell infiltration to the liver tissues. Additionally, it inhibited the copper-induced apoptosis as indicated by significant reduction in caspase-3 activity. At the molecular level, bergenin activated the antioxidant transcription factor FOXO3a, inhibited the nuclear translocation of the inflammatory transcription factor NF-κB, and suppressed the inflammatory signaling molecules p38 MAPK and c-Fos. Interestingly, bergenin improved the expression of the anti-apoptotic protein Bcl2 and reduced the pro-apoptotic protein BAX. Bergenin markedly enhanced the expression of the histone deacetylase protein SIRT1 that regulates activity of NF-κB and FOXO3a. Collectively, these findings highlight the alleviating activity of bergenin against the copper-induced hepatotoxicity via controlling oxidative stress, inflammation, and apoptosis potentially through upregulation of SIRT1, activation of FOXO3a along with suppression of NF-κB and p38 MAPK signaling.

Naringenin and caffeic acid increase ethanol production in yeast cells by reducing very high gravity fermentation-related oxidative stress.

Very high gravity (VHG) fermentation is an industrial-scale process utilizing a sugar concentration above 250g/L to attain a significant ethanol concentration, with the advantages of decreased labor, production costs, water usage, bacterial contamination, and energy consumption. Saccharomyces cerevisiae is one of the most extensively employed organisms in ethanol fermentation through VHG technology. Conversely, high glucose exposure leads to numerous stress factors that negatively impact the ethanol production efficiency of this organism. Here, the impact of various phytochemicals added to the VHG medium on viability, glucose consumption, ethanol production efficiency, total antioxidant-oxidant status (TAS and TOS), and the response of the enzymatic antioxidant system of yeast were investigated. 2.0 mM naringenin and caffeic acid increased ethanol production by 2.453 ± 0.198 and 1.261 ± 0.138-fold, respectively. The glucose consumption rate exhibited a direct relationship with ethanol production in the naringenin-supplemented group. The highest TAS was determined as 0.734 ± 0.044 mmol Trolox Eq./L in the same group. Furthermore, both phytochemical compounds exhibited robust positive correlations with TAS (rnaringenin = 0.9986; rcaffeic acid = 0.9553) and TOS levels (rnaringenin = -0.9824; rcaffeic acid = -0.9791). While naringenin caused statistically significant increases in glutathione reductase (GR) and thioredoxin reductase (TrxR) activities, caffeic acid significantly increased TrxR and superoxide dismutase (SOD). Both phytochemicals seem to impact the ethanol production ability by regulating the redox status of the cells. We believe that the incorporation of particularly cost-effective antioxidants into the fermentation medium may serve as an alternative way to enhance the efficiency of bioethanol production using VHG technology.

Identification and characterization of archaeal-type FAD synthase as a novel tractable drug target from the parasitic protozoa Entamoeba histolytica.

Flavin adenine dinucleotide (FAD) is an essential cofactor for numerous flavoenzymes present in all living organisms. The biosynthesis of FAD from riboflavin involves two sequential reactions catalyzed by riboflavin kinase and flavin adenine dinucleotide synthase (FADS). Entamoeba histolytica, the protozoan parasite responsible for amebiasis, apparently lacks a gene encoding FADS that share similarity with bacterial and eukaryotic canonical FADS, yet it can synthesize FAD. In this study, we have identified the gene responsible for FADS and thoroughly characterized physiological and biochemical properties of FADS from E. histolytica. Phylogenetic analysis revealed that the gene was likely laterally transferred from archaea. The kinetic properties of recombinant EhFADS were consistent with the notion that EhFADS is of archaeal origin, exhibiting KM and kcat values similar to those of the arachaeal enzyme while significantly differing from the human counterpart. Repression of gene expression of EhFADS by epigenetic gene silencing caused substantial reduction in FAD levels and parasite growth, underscoring the importance of EhFADS for the parasite. Furthermore, we demonstrated that EhFADS gene silencing reduced thioredoxin reductase activity, which requires FAD as a cofactor and makes the ameba more susceptible to metronidazole. In summary, this study unveils unique evolutionary and biochemical features of EhFADS and underscores its significance as a promising drug target in combating human amebiasis.IMPORTANCEFAD is important for all forms of life, yet its role and metabolism are still poorly studied in E. histolytica, the protozoan parasite causing human amebiasis. Our study uncovers the evolutionary unique key enzyme, archaeal-type FADS for FAD biosynthesis from E. histolytica for the first time. Additionally, we showed the essentiality of this enzyme for parasite survival, highlighting its potential as target for drug development against E. histolytica infections.

Novel gold-based complex GC7 suppresses cancer cell proliferation via impacting energy metabolism mediated by mitochondria

Due to their pivotal roles in regulating energy metabolism and apoptosis, mitochondria in cancer cells have been considered a vulnerable and feasible target. Many anticancer agents, e.g., metal-based compounds, are found to target and disturb mitochondria primarily, which may lead to the disturbance of energy metabolism and, more importantly, the initiation of apoptosis. In this work, a gold-based complex 7 (GC7) was synthesized and evaluated in a series of different cancer cell lines. The anticancer efficacies of GC7 on cell viability, apoptosis, and colony formation were determined. Cellular thioredoxin reductase (TrxR) activity, oxygen consumption rate (OCR), glucose uptake, and lactate production following GC7 treatment were evaluated and analyzed. The Jeko-1 and A549 xenograft models were used to assess GC7’s tumor-suppressing effects. The results showed that GC7 possessed a broad-spectrum anticancer effect, with IC50 values ranging from 0.43 to 1.2 μM in multiple cancer cell lines, which was more potent than gold-based auranofin (∼2–6 folds). GC7 (0.3 and 1 μM) efficiently induced apoptosis of Jeko-1, A549, and HCT116 cells, and it suppressed the sphere formation of cancer stem cells GSC11 and GSC23 cells at 0.1 μM, and it completely eliminated colony at 0.3 μM. The preliminary mechanistic study showed that GC7 inhibited cellular TrxR activity, suppressed mitochondrial OCR, reduced mitochondrial membrane potential (MMP), decreased glucose uptake, and possibly suppressed glycolysis to reduce lactate production. GC7 was predicted to have a similar yet slightly different pharmacokinetic profile as auranofin. Finally, GC7 (20 mg/kg, oral, 5/week, or 3 mg/kg, IP, 3/week) significantly inhibited tumor growth. In conclusion, GC7 showed great potential in suppressing cancer cell proliferation, probably via inhibiting TrxR and impacting mitochondria-mediated energy metabolism.

Heteronuclear Complexes with Promising Anticancer Activity against Colon Cancer.

This study investigates the activity of novel gold(I) and copper(I)/zinc(II) heteronuclear complexes against colon cancer. The synthesised heteronuclear Au(I)-Cu(I) and Au(I)-Zn(II) complexes were characterised and evaluated for their anticancer activity using human colon cancer cell lines (Caco-2). The complexes exhibited potent cytotoxicity, with IC50 values in the low micromolar range, and effectively induced apoptosis in cancer cells. In the case of complex [Cu{Au(Spy)(PTA)}2]PF6 (2), its cytotoxicity is ×10 higher than its mononuclear precursor, while showing low cytotoxicity towards differentiated healthy cells. Mechanistic studies revealed that complex 2 inhibits the activity of thioredoxin reductase, a key enzyme involved in redox regulation, leading to an increase in reactive oxygen species (ROS) levels and oxidative stress, in addition to an alteration in DNA's tertiary structure. Furthermore, the complexes demonstrated a strong binding affinity to bovine serum albumin (BSA), suggesting the potential for effective drug delivery and bioavailability. Collectively, these findings highlight the potential of the investigated heteronuclear Au(I)-Cu(I) and Au(I)-Zn(II) complexes as promising anticancer agents, particularly against colon cancer, through their ability to disrupt redox homeostasis and induce oxidative stress-mediated cell death.

Enhance the Antimycobacterial Activity of Streptomycin with Ebselen as an Antibiotic Adjuvant Through Disrupting Redox Homeostasis.

Tuberculosis (TB) remains a major health threat worldwide, and the spread of drug-resistant (DR) TB impedes the reduction of the global disease burden. Ebselen (EbSe) targets bacterial thioredoxin reductase (bTrxR) and causes an imbalance in the redox status of bacteria. Previous work has shown that the synergistic action of bTrxR and sensitization to common antibiotics by EbSe is a promising strategy for the treatment of DR pathogens. Thus, we aimed to evaluate whether EbSe could enhance anti-TB drugs against Mycobacterium marinum (M. marinum) which is genetically related to Mycobacterium tuberculosis (Mtb) and resistant to many antituberculosis drugs. Minimum inhibitory concentrations (MIC) of isoniazid (INH), rifampicin (RFP), and streptomycin (SM) against M. marinum were determined by microdilution. The Bliss Independence Model was used to determine the adjuvant effects of EbSe over the anti-TB drugs. Thioredoxin reductase activity was measured using the DTNB assay, and its effects on bacterial redox homeostasis were verified by the elevation of intracellular ROS levels and intracellular GSH levels. The adjuvant efficacy of EbSe as an anti-TB drug was further evaluated in a mouse model of M. marinum infection. Cytotoxicity was observed in the macrophage cells Raw264.7 and mice model. The results reveal that EbSe acts as an antibiotic adjuvant over SM on M. marinum. EbSe + SM disrupted the intracellular redox microenvironment of M. marinum by inhibiting bTrxR activity, which could rescue mice from the high bacterial load, and accelerated recovery from tail injury with low mammalian toxicity. The above studies suggest that EbSe significantly enhanced the anti-Mtb effect of SM, and its synergistic combination showed low mammalian toxicity in vitro and in vivo. Further efforts are required to study the underlying mechanisms of EbSe as an antibiotic adjuvant in combination with anti-TB drug MS.

Biological Properties of Boletus edulis Extract on Caco-2 Cells: Antioxidant, Anticancer, and Anti-Inflammatory Effects.

Boletus edulis (BE) is a mushroom well known for its taste, nutritional value, and medicinal properties. The objective of this work was to study the biological effects of BE extracts on human colon carcinoma cells (Caco-2), evaluating parameters related to oxidative stress and inflammation. In this study, a hydroethanolic extract of BE was obtained by ohmic heating green technology. The obtained BE extracts are mainly composed of sugars (mainly trehalose), phenolic compounds (taxifolin, rutin, and ellagic acid), and minerals (K, P, Mg, Na, Ca, Zn, Se, etc.). The results showed that BE extracts were able to reduce cancer cell proliferation by the induction of cell cycle arrest at the G0/G1 stage, as well as cell death by autophagy and apoptosis, the alteration of mitochondrial membrane potential, and caspase-3 activation. The extracts modified the redox balance of the cell by increasing the ROS levels associated with a decrease in the thioredoxin reductase activity. Similarly, BE extracts attenuated Caco-2 inflammation by reducing both iNOS and COX-2 mRNA expression and COX-2 protein expression. In addition, BE extracts protected the intestine from the oxidative stress induced by H2O2. Therefore, this study provides information on the potential use of BE bioactive compounds as anticancer therapeutic agents and as functional ingredients to prevent oxidative stress in the intestinal barrier.

Coenzyme A protects against ferroptosis via CoAlation of thioredoxin reductase 2.

The Cystine-xCT transporter-Glutathione (GSH)-GPX4 axis is the canonical pathway to protect against ferroptosis. While not required for ferroptosis-inducing compounds (FINs) targeting GPX4, FINs targeting the xCT transporter require mitochondria and its lipid peroxidation to trigger ferroptosis. However, the mechanism underlying the difference between these FINs is still unknown. Given that cysteine is also required for coenzyme A (CoA) biosynthesis, here we show that CoA supplementation specifically prevents ferroptosis induced by xCT inhibitors but not GPX4 inhibitors. We find that, auranofin, a thioredoxin reductase inhibitor, abolishes the protective effect of CoA. We also find that CoA availability determines the enzymatic activity of thioredoxin reductase, but not thioredoxin. Importantly, the mitochondrial thioredoxin system, but not the cytosolic thioredoxin system, determines CoA-mediated ferroptosis inhibition. Our data show that the CoA regulates the in vitro enzymatic activity of mitochondrial thioredoxin reductase (TXNRD2) by covalently modifying the thiol group of cysteine (CoAlation) on Cys-483. Replacing Cys-483 with alanine on TXNRD2 abolishes its in vitro enzymatic activity and ability to protect cells from ferroptosis. Targeting xCT to limit cysteine import and, therefore, CoA biosynthesis reduced CoAlation on TXNRD2, an effect that was rescued by CoA supplementation. Furthermore, the fibroblasts from patients with disrupted CoA metabolism demonstrate increased mitochondrial lipid peroxidation. In organotypic brain slice cultures, inhibition of CoA biosynthesis leads to an oxidized thioredoxin system, mitochondrial lipid peroxidation, and loss in cell viability, which were all rescued by ferrostatin-1. These findings identify CoA-mediated post-translation modification to regulate the thioredoxin system as an alternative ferroptosis protection pathway with potential clinical relevance for patients with disrupted CoA metabolism.

Interactions of binary mixtures of metals on rainbow trout (Oncorhynchus mykiss) heart mitochondrial H2O2 homeodynamics

For continuous pumping of blood, the heart needs a constant supply of energy (ATP) that is primarily met via oxidative phosphorylation in the mitochondria of cardiomyocytes. However, sustained high rates of electron transport for energy conversion redox reactions predisposes the heart to the production of reactive oxygen species (ROS) and oxidative stress. Mitochondrial ROS are fundamental drivers of responses to environmental stressors including metals but knowledge of how combinations of metals alter mitochondrial ROS homeodynamics remains sparse. We explored the effects and interactions of binary mixtures of copper (Cu), cadmium (Cd), and zinc (Zn), metals that are common contaminants of aquatic systems, on ROS (hydrogen peroxide, H2O2) homeodynamics in rainbow trout (Oncorhynchus mykiss) heart mitochondria. Isolated mitochondria were energized with glutamate-malate or succinate and exposed to a range of concentrations of the metals singly and in equimolar binary concentrations. Speciation analysis revealed that Cu was highly complexed by glutamate or Tris resulting in Cu2+ concentrations in the picomolar to nanomolar range. The concentration of Cd2+ was 7.2–7.5 % of the total while Zn2+ was 15 % and 21 % of the total during glutamate-malate and succinate oxidation, respectively. The concentration-effect relationships for Cu and Cd on mitochondrial H2O2 emission depended on the substrate while those for Zn were similar during glutamate-malate and succinate oxidation. Cu + Zn and Cu + Cd mixtures exhibited antagonistic interactions wherein Cu reduced the effects of both Cd and Zn, suggesting that Cu can mitigate oxidative distress caused by Cd or Zn. Binary combinations of the metals acted additively to reduce the rate constant and increase the half-life of H2O2 consumption while concomitantly suppressing thioredoxin reductase and stimulating glutathione peroxidase activities. Collectively, our study indicates that binary mixtures of Cu, Zn, and Cd act additively or antagonistically to modulate H2O2 homeodynamics in heart mitochondria.

Oral administration of glutathione modulates exercise-related metabolic and oxidative factors in skeletal muscles of mice

Exercise activates the metabolic system in skeletal muscles, which is modulated by antioxidant supplementation. Some antioxidants such as glutathione accelerate metabolic adaptation induced by exercise training, whereas other antioxidants such as vitamin C suppress it. Thus, the present study aimed to elucidate the effects of oral administration of glutathione and vitamin C on metabolic and redox responses after acute exercise in mice. ICR mice were randomly divided into sedentary, exercise, exercise with glutathione, and exercise with vitamin C groups. In the exercise groups, mice were subjected to treadmill running at 30 m/min for 30 min. Immediately after exercise, glutathione (2% w/v, 5uL/g body weight) or vitamin C (10% w/v, 5uL/g body weight) were administered. Gastrocnemius muscle and plasma samples were collected at 3 h post-exercise. We found that plasma creatine kinase levels were only elevated in the exercise group. Malondialdehyde levels in skeletal muscle were elevated after exercise, but this elevation was suppressed by glutathione administration. PGC-1α expression was increased in both the exercise and glutathione groups compared with the sedentary group; however, the expressions of its downstream proteins were only increased in the glutathione group. Reduced glutathione form was notably increased in the mitochondria, whereas oxidized glutathione was significantly increased in the cytosol of the glutathione administration group compared with the exercise group. Thioredoxin reductase activity was also higher in the glutathione group than in the sedentary and exercise groups. Thus, this study demonstrates that post-exercise glutathione administration accelerates the exercise-induced responses of mitochondrial factors in skeletal muscle, which may be mediated by the modulation of the redox system.

Modulation of the Nrf-2 and HO-1 signalling axis is associated with Betaine's abatement of fluoride-induced hepatorenal toxicities in rats.

Sodium fluoride (NaF) ingestion has several detrimental effects in humans and rodents. NaF mechanisms of toxicity include perturbation of intracellular redox homeostasis and apoptosis. Betaine (BET) is a modified amino acid with anti-inflammatory, antioxidant, and anti-apoptotic properties. This study investigates BET's effect on NaF-induced hepatorenal toxicities in rats. Experimental rats (n=30) were randomly assigned to groups (n=6) and treated by gavage for 28 days. Group I (2 mL of distilled water), Group II (NaF: 9 mg/kg) alone, Group III: (BET: 100 mg/kg), Group IV: (NaF: 9 mg/kg and BET 1: 50 mg/kg), and Group V: (NaF: 9 mg/kg and BET 2: 100 mg/kg). Our findings revealed significantly (p<0.05) increased hepatic transaminase activities alongside creatinine and urea levels following NaF-alone treatment in addition to increased oxidative status, lipid peroxidation, reactive oxygen and nitrogen species, decreased superoxide dismutase, catalase, glutathione-s-transferase, glutathione peroxidase, glutathione, and total sulfhydryl groups. The reduced levels of nuclear factor erythroid 2-related factor-2 and the activities of heme oxygenase-1, thioredoxin, and thioredoxin reductase in NaF-alone treated rats equally compromised cellular molecular responses to oxidative stress. Also, NaF increased (p<0.05) hepatorenal inflammatory biomarkers-nitric oxide, interleukin-10, myeloperoxidase, and xanthine oxidase. Furthermore, caspase-3 and caspase-9 were increased (p<0.05) in rats treated with NaF alone. Contrastingly, BET was observed to alleviate the harmful effects of NaF. Treatment with BET mitigated NaF-induced oxido-inflammatory responses and apoptosis in the experimental rat's hepatorenal system. The study demonstrates the potential of BET to abate NaF-induced hepatorenal toxicity.

Synthesis, characterization and anti-ovarian cancer activities of novel biphenyl-NHC-gold(I) complexes

Fifteen novel biphenyl-N-heterocyclic carbene (NHC)-gold(I) complexes were designed and synthesized to treat ovarian cancer (OC). Among these, complex Au-1 showed significant antiproliferative activity against A2780 cells and A2780/CDDP cells. Notably, Au-1 exhibited low toxicity to normal ovarian epithelial IOSE-80 cells. Further studies revealed that Au-1 strongly inhibited thioredoxin reductase (TrxR) activity. Collectively, our results demonstrated that Au-1 could be a promising candidate for the treatment of OC.

The selenoprotein from selenium-rich glutinous rice improves spleen immune protection by inhibiting the NF-κB pathway

Moderate amounts of selenium supplementation have a positive effect on the immune response. Selenium deficiency status can lead to reduced immunity, but the benefits of a natural selenium-rich diet for selenium deficiency are unknown. In this experiment, low selenium feed (0.02 mg Se/kg diet) was given to the mice for 5 weeks and selenium supplementation with selenoprotein (SeP) for 4 weeks, and the selenium-deficient mouse model was successfully established. SeP supplementation had significant protective effects, including increased antioxidant capacity and alleviation of inflammatory damage. SeP markedly elevated the activities of thioredoxin reductase (TrxR) and glutathione peroxidase (GSH-Px) in the serum, kidney, liver, and spleen of selenium-deficient mice. SeP can restore the condition of damaged spleen tissue, raise the spleen index in mice, and encourage an increase in immunoglobulin (IgA, IgG, and IgM) content. The levels of catalase (CAT), total antioxidant capacity (T-AOC), GSH-Px, and cytokines (IL-1β, IL-6, and TNF-α) were all significantly elevated by SeP. SeP showed superior immunomodulatory effects over inorganic selenium (Na2SeO3). Together, these results suggest that SeP may be a potential dietary selenium supplement that can reduce symptoms of spleen damage caused by selenium deficiency.

Melatonin antagonizes oxidative stress-induced apoptosis in retinal ganglion cells through activating the thioredoxin-1 pathway.

This study aimed to explore the role of melatonin in oxidative stress-induced injury on retinal ganglion cells and the underlying mechanisms. The immortalized RGC-5 cells were treated with H2O2 to induce oxidative injury. Cell viability was measured by Cell Counting Kit-8, and apoptosis was determined by flow cytometry and western blot assays. Reactive oxygen species (ROS), lactate dehydrogenase (LDH), and malondialdehyde (MDA) levels were examined to evaluate oxidative stress levels. In addition, Thioredoxin-1 (Trx1) was silenced in RGC-5 cells using small interfering RNA followed by signaling pathway examination to explore the underlying mechanisms of melatonin in alleviating oxidative injury. Melatonin pre-treatment significantly alleviated H2O2-induced apoptosis in RGC-5 cells. Melatonin also markedly reversed the upregulation of cleaved-caspase 3, cleaved-caspase 9, and Bax expression and downregulation of Bcl-2 expression induced by H2O2. Further analyses presented that melatonin significantly attenuated the increase of ROS, LDH, and MDA levels in RGC-5 cells after H2O2 treatment. Melatonin also abolished the downregulated expression of Superoxide dismutase type 1, Trx1, and Thioredoxin reductase 1, and the reduced activity of thioredoxin reductase in RGC-5 cells after H2O2 treatment. Notably, Trx1 knockdown significantly mitigated the protective effect of melatonin in alleviating H2O2-induced apoptosis and oxidative stress, while administration of compound C, a common inhibitor of c-Jun N-terminal kinase (JNK) signaling, partially reversed the effect of Trx1 silencing, thereby ameliorating the apoptosis and oxidative injury induced by H2O2 in RGC-5 cells. Melatonin could significantly alleviate oxidative stress-induced injury of retinal ganglion cells via modulating Trx1-mediated JNK signaling pathway.

Gold(i) and gold(iii) carbene complexes from the marine betaine norzooanemonin: inhibition of thioredoxin reductase, antiproliferative and antimicrobial activity.

The natural marine betaine norzooanemonin (1,3-dimethylimidazolim-4-carboxylate) and its methyl and ethyl esters were used as ligand precursors to prepare a systematic series (12 members) of neutral monocarbene gold(i/iii) and cationic dicarbene gold(i/iii) complexes. The complexes were evaluated as inhibitors of bacterial thioredoxin reductase and for their antiproliferative and antimicrobial activities. While gold complexes with the parent norzooanemonin scaffold resulted in overall poor performance, the more lipophilic esters proved to be highly bioactive agents, related to their higher cellular uptake. The monocarbene gold(i/iii) complexes showed significant potency as inhibitors of bacterial thioredoxin reductase. In most assays, the efficacy of both gold(i) and gold(iii) analogues was found to be comparable. The cytotoxicity of dicarbene gold(i/iii) complexes against cancer cells was strong, in some cases exceeding that of the standard reference auranofin.

Intermolecular interaction of chloroquine with peptide-bonded-(N)-ethyl selenol-(C)-ethanethiol

Chloroquine (CQ) interacts with peptide bonded-ethyl selenol and ethanethiol through electrostatic interactions with a protonated triethylamine moiety and inhibits the oxidoreductase activity of thioredoxin reductase (TrxR).

Inhibition of thioredoxin reductase and upregulation of apoptosis genes for effective anti-tumor sono-chemotherapy using a meso-organosilica nanomedicine.

The thioredoxin system is involved in cancer development and therefore is a promising target for cancer chemotherapy. Thioredoxin reductase (TrxR) is a key component of the thioredoxin (Trx) system, and is overexpressed in many cancers to inhibit apoptosis-related proteins. Alternatively, inhibition of thioredoxin reductase and upregulation of apoptosis factors provide a therapeutic strategy for anti-tumor treatment. In this study, an ultrasound-activatable meso-organosilica nanomedicine was prepared by integrating chloroquine (CQ) into hollow mesoporous organosilica (CQ@MOS). The meso-organosilica nanomedicine can inhibit the activity of thioredoxin reductase, elevate cellular reactive oxygen species (ROS) levels, upregulate the pro-apoptotic factors in the c-Jun N-terminal kinase (JNK) apoptosis pathway and induce autophagy inhibition, further resulting in mitochondrial membrane potential (MMP) depolarization and cellular ATP content decrease, ultimately causing significant damage to tumor cells. Moreover, CQ@MOS can efficiently deliver chloroquine into cancer cells and promote an enhanced sonodynamic effect for effective anti-tumor chemotherapy and sonodynamic therapy. This study may enlighten us on a new anti-tumor strategy and suggest its promising applications in cancer treatments.

The architecture of redox microdomains: Cascading gradients and peroxiredoxins’ redox-oligomeric coupling integrate redox signaling and antioxidant protection

In the cytosol of human cells under low oxidative loads, hydrogen peroxide is confined to microdomains around its supply sites, due to its fast consumption by peroxiredoxins. So are the sulfenic and disulfide forms of the 2-Cys peroxiredoxins, according to a previous theoretical analysis [Travasso et al., Redox Biology 15 (2017) 297]. Here, an extended reaction-diffusion model that for the first time considers the differential properties of human peroxiredoxins 1 and 2 and the thioredoxin redox cycle predicts important new aspects of the dynamics of redox microdomains. The peroxiredoxin 1 sulfenates and disulfides are more localized than the corresponding peroxiredoxin 2 forms, due to the former peroxiredoxin's faster resolution step. The thioredoxin disulfides are also localized. As the H2O2 supply rate (vsup) approaches and then surpasses the maximal rate of the thioredoxin/thioredoxin reductase system (V), these concentration gradients become shallower, and then vanish. At low vsup the peroxiredoxin concentration determines the H2O2 concentrations and gradient length scale, but as vsup approaches V, the thioredoxin reductase activity gains influence. A differential mobility of peroxiredoxin disulfide dimers vs. reduced decamers enhances the redox polarity of the cytosol: as vsup approaches V, reduced decamers are preferentially retained far from H2O2 sources, attenuating the local H2O2 buildup. Substantial total protein concentration gradients of both peroxiredoxins emerge under these conditions, and the concentration of reduced peroxiredoxin 1 far from the H2O2 sources even increases with vsup. Altogether, the properties of 2-Cys peroxiredoxins and thioredoxin are such that localized H2O2 supply induces a redox and functional polarization between source-proximal regions (redox microdomains) that facilitate peroxiredoxin-mediated signaling and distal regions that maximize antioxidant protection.