Trx Levels Research Articles

Protective Effects of Silymarin Against D-Gal/LPS-Induced Organ Damage and Inflammation in Mice.

AimSilymarin contains various flavonoids and exhibits antioxidative, anti-inflammatory, and anticancer effects, in addition to other pharmacological properties. This study explored the alleviating effect of silymarin on multiple-organ damage induced by D-galactose/lipopolysaccharide in Kunming mice.MethodsKunming mice were injected intraperitoneally with D-galactose (30 mg/kg·BW)/LPS (3 μg/kg·BW) and then treated using silymarin with different doses (75 mg/kg·bw and 150 mg/kg·bw) via intragastric administration. Changes in organ indexes, pathological changes, liver-function index, biochemical indexes, molecular biological indexes, and genes related to the oxidation and inflammation of main organs were evaluated.ResultsAfter the mice were treated with silymarin, their body weight showed no significant change, and the liver, kidney, and lung indexes of the treated mice were higher than those of the model group; meanwhile, the corresponding histopathological formation was reduced. Compared with the model group, the silymarin-treated group showed reductions in ALT, AST, and liver function indexes in the mouse serum. Silymarin treatment also increased the SOD, CAT, GSH, GSH-Px, T-AOC, IL-10, and IL-12 levels, as well as reduced the MDA, NO, IL-6, IL-1β, TNF-α, IFN-γ levels in the mouse serum and liver tissues. In addition, quantitative polymerase chain reaction analysis indicated that the mRNA expression levels of SOD1, SOD2, CAT, GSH-Px, IL-10, Nrf2, HO-1, NQO1, Trx, and IκB-α were higher in the liver tissue of the silymarin-treated mice than in those of the model group; meanwhile, the mRNA expression levels of IL-6, IL-1β, TNF-α, IFN-γ, NF-κB, NLRP3, COX2, and p38 were lower than those in the model group.ConclusionSilymarin, which exhibits antioxidative and anti-inflammatory effects, can alleviate the liver, lung, and kidney damage induced by D-galactose/lipopolysaccharide. High-dose (150 mg/kg·bw) silymarin can more effectively inhibit organ damage, compared with low-dose silymarin (75 mg/kg·bw) in Kunming mice.

Auranofin reveals therapeutic anticancer potential by triggering distinct molecular cell death mechanisms and innate immunity in mutant p53 non-small cell lung cancer

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).

Cytotoxic, chemosensitizing and radiosensitizing effects of curcumin based on thioredoxin system inhibition in breast cancer cells: 2D vs. 3D cell culture system.

Targeting the thioredoxin/thioredoxin reductase (Trx/TrxR) system is a promising strategy to overcome cancer resistance to conventional therapy. The present study investigated the effect of curcumin on the Trx/TrxR system either alone or in combination with chemotherapy, or radiotherapy in human MCF-7 breast cancer cells seeded in 2 and 3D culture systems. Cell viability, thioredoxin reductase 1 (TrxR1) activity, and the genetic expression of Trx, TrxR1, Bcl2 and BAX genes were studied. The findings showed that the mode of culture significantly affected the response of cancer cells to different treatment modalities, as well as their gene expression patterns. Curcumin treatment resulted in a reduction of breast cancer cell proliferation and induction of apoptosis, an effect that may be mediated by manipulating Trx system components, mainly Trx expression, and to a lesser extent TrxR1 expression and concentration. Furthermore, curcumin increased the sensitivity of breast cancer cells to chemotherapy and radiotherapy by reducing Trx and TrxR1 expression levels. Thus, curcumin may have a potential role as a dose-modifying agent that can be used either to sensitize resistant cells to therapy or to reduce the dose of these therapeutic agents.

Abstract PS3-25: Quantitation of serum thioredoxin 1 could mitigate difficulty to detect breast cancer from dense breasts by mammography

Abstract Background: Even though almost half of women have dense breasts (DB), the density of breasts has been an obstacle to detect breast cancer (BC) correctly by the gold standard of screening, mammography. It is strongly recommended to take consideration of breast density in analyzing mammogram. We have reported the possibility of serum level of thioredoxin 1 (Trx1) as a novel means to assess the risk of BC regardless of various conditions of breasts. In present study, we have evaluated how serum level of Trx1 can mitigate the difficulty to detect BC from dense breast by mammography. Methods: We have generated monoclonal antibodies against Trx1 and developed an ELISA kit that quantitates Trx1 in serum. The level of Trx1 was determined in each serum from BC patients (n=106) who had been confirmed as BC by various examinations including mammography as well as surgery. Each Trx1 level was analyzed with corresponding patient’s mammography results such as patterns, asymmetry, shapes, margin, and density. The analyzed results were compared with those from other biomarker tests including CA15-5 and CEA to evaluate the clinical validity of Trx1 in this study. Each test was duplicated two times, and test results were analyzed by ROC analysis, one-way ANOVA tests, and unpaired t-tests.Results: Most of BC patients (82.6%, n=86) was classified as mammography pattern 3 and 4, and BI-RADS score higher than 4 (74.0%, n=77). More than half of patients’ breast density was in high density group (54.8%, n=57), whereas 5.8% of iso density (n=6) and 39.4% of not determined (n=41). The blood Trx1 levels of patients were higher than the cut-off value of 14 U/ml indicating BC regardless of characteristics of breasts. Although other breast cancer biomarker tests such as CA15-3 and CEA could not identify BC, Trx1 level could correctly detect BC even in the cases that mammography could not show the mass clearly. The sensitivity/specificity of mammography and Trx1 test were 75.2%/74.0% and 96.2%/99.0%, respectively. When mammography and Trx1 test were combined, the whole sensitivity/specificity was 99.3%/100.0%. Conclusion: Even though it is obvious that larger size of further study necessary, the serum Trx1 level showed that it could identify BC in dense breasts easily. These results indicated that serum Trx1 level could efficiently mitigate the difficulty to detect BC from dense breasts by mammography. Keywords: Thioredoxin 1, Breast cancer, Dense breast, Diagnostics, Sensitivity, Specificity, Blood Citation Format: Kyoung Hoon Suh, Bo Bae Choi, Youn Ju Lee, Je Ryoong Kim, Jin Sun Lee, Young Kim. Quantitation of serum thioredoxin 1 could mitigate difficulty to detect breast cancer from dense breasts by mammography [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS3-25.

The Serum Selenium Level, the Activity of Some Selenodependent Enzymes and the Lipid Profile in Childhood Obesity

Oxidative stress and dyslipidemia are present in childhood obesity. Selenoproteins are important antioxidants. Glutathione peroxidase and thioredoxin reduce the level of peroxides while the conversion of the tyroid hormon T4 to T3 needs also a selenoenzyme. Selenium deficiency can reduce the selenoproteins activity. The aim of this study was to determine the serum: selenium (Se), thioredoxin level (Trx) and activity of glutathione peroxidase (GPx) in obese children with dysmetabolism. The lipid profile, the hormones (free T4 and TSH), serum Se, serum Trx and GPx activity and atherogenic indexes (TG/HDLc, total cholesterol/HDLc, apoB/apoA-I ) were determined in 20 healthy children (10-16 years old) versus 41 overweight/obese children, same age, in an observational study. Spectro-photometer and ELISA methods were used. The GPx activity and the serum Se level had similar values in the studied groups , while the serum Trx level was lower in the obese children. The GPx activity was positively correlated with atherogenic indexes, negatively correlated with apo A-I (r= -0.74) and Se was positively correlated with apo B (r=0.52). The obese children had TSH and freeT4 in the normal range, but freeT4 was significantly higher in comparison with the values observed in the normal weight children. In conclusion, in childhood obesity, the normal serum range values for selenium or for selenium dependent proteins can �hide�a dysmetabolism of selenium because there are significant differences for the values of these parameters versus the ones from normal weight children. In childhood obesity, serum GPx activity and selenium values were strongly correlated with the atherogenic indexes.

Small molecules inhibitors of the heterogeneous ribonuclear protein A18 (hnRNP A18): a regulator of protein translation and an immune checkpoint.

We have identified chemical probes that simultaneously inhibit cancer cell progression and an immune checkpoint. Using the computational Site Identification by Ligand Competitive Saturation (SILCS) technology, structural biology and cell-based assays, we identify small molecules that directly and selectively bind to the RNA Recognition Motif (RRM) of hnRNP A18, a regulator of protein translation in cancer cells. hnRNP A18 recognizes a specific RNA signature motif in the 3′UTR of transcripts associated with cancer cell progression (Trx, VEGF, RPA) and, as shown here, a tumor immune checkpoint (CTLA-4). Post-transcriptional regulation of immune checkpoints is a potential therapeutic strategy that remains to be exploited. The probes target hnRNP A18 RRM in vitro and in cells as evaluated by cellular target engagement. As single agents, the probes specifically disrupt hnRNP A18–RNA interactions, downregulate Trx and CTLA-4 protein levels and inhibit proliferation of several cancer cell lines without affecting the viability of normal epithelial cells. These first-in-class chemical probes will greatly facilitate the elucidation of the underexplored biological function of RNA Binding Proteins (RBPs) in cancer cells, including their effects on proliferation and immune checkpoint activation.

Thioredoxin down-regulation in the cytosol in thioredoxin 2 transgenic mice did not have beneficial effects to extend lifespan in male C57BL/6 mice

Background: This study was conducted to test the effects of thioredoxin (Trx)1 down-regulation in Trx2 transgenic [Tg(TXN2)+/0] mice on lifespan and age-related diseases. Our previous study with Tg(TXN2)+/0 mice showed that mitochondrial Trx overexpression produced minimal life-extending effects with a slightly elevated severity of lymphoma and another study with a limited number of Trx1KO mice showed that there was a slight reduction of neoplastic lesions. Thus, this study was aimed to test if reduced Trx1 expression in combination with elevated Trx2 has beneficial effects on lifespan in mice by attenuating age-related diseases, specifically cancer. Methods: Trx2 hemizygous transgenic and Trx1 heterozygous knockout mice [Tg(TXN2)+/0 x Trx1KO] were generated for survival and cross-sectional pathology experiments. Results: Tg(TXN2)+/0 x Trx1KO mice showed significantly higher (approximately 1.5- to 3-fold) Trx2 levels and significantly less (approximately 50% less) Trx1 levels in all of the tissues we examined compared to wildtype (WT) littermates. Trx1 down-regulation along with Trx2 overexpression did not change the levels of glutathione or other major antioxidant enzymes. Male Tg(TXN2)+/0 x Trx1KO mice demonstrated only a slight extension of lifespan in the early part of life and no significant effects on the later part of life were observed,which was similar to our previous study with Tg(TXN2)+/0 mice. Tg(TXN2)+/0 x Trx1KO mice had similar tumor burden, disease burden, incidence and severity of lymphoma, and severity of glomerulonephritis compared to WT mice at 22-26 months. Conclusions: Our findings suggest that the combined Trx down-regulation in cytosol along with upregulation in mitochondria of Tg(TXN2)+/0 x Trx1KO mice did not provide beneficial effects on aging, i.e., extend the lifespan or reduce age-related pathology compared to WT mice. Keywords: Thioredoxin, transgenic mouse, knockout mouse, aging, cancer

Dexmedetomidine Protects against Myocardial Ischemia/Reperfusion Injury by Ameliorating Oxidative Stress and Cell Apoptosis through the Trx1-Dependent Akt Pathway.

Dexmedetomidine (Dex) was reported to reduce oxidative stress and protect against myocardial Ischemia/Reperfusion (I/R) injury. However, the molecular mechanism involved in its antioxidant property is not fully elucidated. The present study was aimed at investigating whether the Trx1/Akt pathway participated in the cardioprotective effect of Dex. In the present study, I/R-induced myocardial injury in isolated rat hearts and OGD/R-induced injury in H9c2 cardiomyocytes were established. Our findings suggested that Dex ameliorated myocardial I/R injury by improving cardiac function, reducing myocardial apoptosis and oxidative stress, which was manifested by increased GSH and SOD contents, decreased ROS level, and MDA generation in both the isolated rat hearts and OGD/R-treated H9C2 cells. More importantly, it was found that the level of Trx1 was preserved, and Akt phosphorylation was significantly upregulated by Dex treatment. However, these effects of Dex were abolished by PX-12 (a specific Trx1 inhibitor) administration. Taken together, this study suggests that Dex plays a protective role in myocardial I/R injury, improves cardiac function, and relieves oxidative stress and cell apoptosis. Furthermore, our results present a novel signaling mechanism that the cardioprotective effect of Dex is at least partly achieved through the Trx1-dependent Akt pathway.

Thioredoxin 1 is upregulated in the bone and bone marrow following experimental myocardial infarction: evidence for a remote organ response

Ischemia and reperfusion events, such as myocardial infarction (MI), are reported to induce remote organ damage severely compromising patient outcomes. Tissue survival and functional restoration relies on the activation of endogenous redox regulatory systems such as the oxidoreductases of the thioredoxin (Trx) family. Trxs and peroxiredoxins (Prxs) are essential for the redox regulation of protein thiol groups and for the reduction of hydrogen peroxide, respectively. Here, we determined whether experimental MI induces changes in Trxs and Prxs in the heart as well as in secondary organs. Levels and localization of Trx1, TrxR1, Trx2, Prx1, and Prx2 were analyzed in the femur, vertebrae, and kidneys of rats following MI or sham surgery. Trx1 levels were significantly increased in the heart (P = 0.0017) and femur (P < 0.0001) of MI animals. In the femur and lumbar vertebrae, Trx1 upregulation was detected in bone-lining cells, osteoblasts, megakaryocytes, and other hematopoietic cells. Serum levels of Trx1 increased significantly 2 days after MI compared to sham animals (P = 0.0085). Differential regulation of Trx1 in the bone was also detected by immunohistochemistry 1 month after MI. N-Acetyl-cysteine treatment over a period of 1 month induced a significant reduction of Trx1 levels in the bone of MI rats compared to sham and to MI vehicle. This study provides first evidence that MI induces remote organ upregulation of the redox protein Trx1 in the bone, as a response to ischemia–reperfusion injury in the heart.

Resveratrol Regulates Nrf2-Mediated Expression of Antioxidant and Xenobiotic Metabolizing Enzymes in Pesticides-Induced Parkinsonism.

Combined maneb (MB) and paraquat (PQ), two widely used pesticides, increases oxidative stress leading to Parkinsonism. Xenobiotic metabolizing enzymes, cytochrome P450 (CYP) 2D6 and its mouse ortholog Cyp2d22 protect against Parkinsonism. Resveratrol, an antioxidant, restores antioxidant defense system through the activation of nuclear factor erythroid 2- related factor 2 (Nrf2). However, a crosstalk between Cyp2d22/CYP2D6-mediated protection and resveratrol-induced Nrf2 activation leading to neuroprotection is not yet elucidated. The study aimed to decipher the effect of resveratrol on Nrf2 activation and expression of its downstream mediators, nicotinamide adenine dinucleotide phosphate quinone oxidoreductase 1 (NQO1) and thioredoxin 1 (Trx1) along with Cyp2d22/CYP2D6 activity in combined MB and PQ mouse model of Parkinsonism and differentiated neuroblastoma cells. MB and PQ reduced the dopamine content (mouse) and Cyp2d22/CYP2D6 activity (mouse/neuroblastoma cells) and increased the nuclear translocation of Nrf2 and expression of NQO1 and Trx1 (both). Resveratrol ameliorated pesticides-induced changes in dopamine content and Cyp2d22/CYP2D6 activity. It was found to promote nuclear translocation of Nrf2 and expression of NQO1 and Trx1 proteins. Since Cyp2d22/CYP2D6 inhibitor (ketoconazole/quinidine) per se reduced Cyp2d22/CYP2D6 activity and dopamine content, it was found to substantially increase the pesticides-induced reduction in Cyp2d22/CYP2D6 activity and dopamine content. Inhibitors normalized the pesticides induced changes in Nrf2 translocation and NQO1 and Trx1 levels in pesticides treated groups. The results suggest that resveratrol promotes the catalytic activity of xenobiotic metabolizing enzyme, Cyp2d22/CYP2D6, which partially contributes to Nrf2 activation in pesticides- induced Parkinsonism.

Relationships between diabetic nephropathy and insulin resistance, inflammation, Trx, Txnip, CysC and serum complement levels.

To investigate the relationships between diabetic nephropathy (DN) and insulin resistance, inflammation, thioredoxin (Trx), thioredoxin-interacting protein (Txnip), Cystatin C (CysC) and serum complement levels. A total of 119 patients with type 2 diabetes mellitus (T2DM) treated in the Endocrinology Department of our hospital from January 2017 to December 2017 were enrolled as the experiment group, while 30 healthy volunteers were selected as the control group. The expression levels of inflammatory factors, Trx, Txnip, CysC and serum complements in every subject were detected. In addition, the type 2 diabetic nephropathy rat model was established via high-fat diet and injection of low-dose streptozotocin. Blood glucose, insulin resistance indexes and 24h-urinary albumin excretion were measured, and the histomorphological characteristics of the kidney in animals were observed. In clinical subjects, Trx level was notably lower in the simple DM group, early DN group and clinical DN group in comparison with that in the control group. The levels of Txnip and CysC in the simple DM group, early DN group and clinical DN group were remarkably higher than those in the control group. Moreover, the expression levels of TNF-α and IL-6 in the clinical DN group were significantly elevated compared with those in the simple DM group and early DN group. In addition, C1q expression in the clinical DN group was higher than that in the simple DM group and early DN group. In model rats, HOMA-IR was distinctly higher in the DM group and DN group than that in the control group. The ratio of kidney weight to body weight (KW/BW) was evidently higher in the DN group in comparison with that in the control group and DM group. Insulin resistance, inflammatory factors, and levels of Trx, Txnip, CysC and serum complement C1q are related to the progression of DM.

Thioredoxin protects mitochondrial structure, function and biogenesis in myocardial ischemia-reperfusion via redox-dependent activation of AKT-CREB- PGC1α pathway in aged mice.

Aging is an independent risk factor for cardiovascular diseases, such as myocardial infarction due to ischemia-reperfusion injury (I/R) of the heart. Cytosolic thioredoxin (Trx) is a multifunctional redox protein which has antioxidant and protein disulfide reducing properties. We hypothesized that high levels of Trx will protect against multifactorial disease such as myocardial infarction due to I/R injury in aged mice. Aged mice overexpressing human Trx (Trx-Tg), mice expressing redox-inactive mutant of human Trx (dnTrx-Tg) and non-transgenic litter-mates (NT) were subjected to I/R (60/30 min), and cardiac function, mitochondrial structure and function, and biogenesis involving PGC1α pathway were evaluated in these mice. While aged Trx-Tg mice were protected from I/R-induced reduction in ejection fraction (EF) and fractional shortening (FS), had smaller infarct with decreased apoptosis and preserved mitochondrial function, aged dnTrx-Tg mice showed enhanced myocardial injury and mitochondrial dysfunction. Further, Trx-Tg mice were protected from I/R induced loss of PGC1α, ACO2, MFN1 and MFN2 in the myocardium. The dnTrx-Tg mice were highly sensitive to I/R induced apoptosis. Overall, our study demonstrated that the loss of Trx redox balance in I/R in aged NT or dnTrx-Tg mice resulted in decreased PGC1α expression that decreased mitochondrial gene expression with increased myocardial apoptosis. High levels of Trx, but not mitochondrial thioredoxin (Trx-2) maintained Trx redox balance in I/R resulting in increased PGC1α expression via AKT/CREB activation upregulating mitochondrial gene expression and protection against I/R injury.

NK cells in the tumor microenvironment and thioredoxin activity.

NK cells are responsible for defense against viral infections and cancer. Although activated NK cells are armed to combat tumors, the tumor microenvironment (TME) contains ROS, which suppress NK cell antitumor activity. In this issue of the JCI, Yang, Neo, and colleagues explored NK cell resistance to oxidative stress in vitro and in human non-small-cell lung cancer (NSCLC). High surface thiol density and elevated expression of the ROS scavenger thioredoxin (Trx1) protected NK cells from ROS. Trx1 and thiol levels were higher in IL-15- than in IL-2-primed NK cells. Tumor-infiltrating Trx1+ NK cells were present in patients with NSCLC with elevated ROS levels in the tumor. Smokers scored higher for the ROS signature, which predicted poor prognosis, compared with nonsmokers. This study explains how activated NK cells survive in the ROS-rich TME and suggests that smokers with lung cancer may benefit from therapies using IL-15-primed NK cells.

ITCH regulates oxidative stress induced by high glucose through thioredoxin interacting protein in cultured human lens epithelial cells.

Thioredoxin (Trx) is an important protein that controls oxidative damage in almost all eukaryotic cells. Trx interaction protein (Txnip) has been reported to negatively regulate the bioavailability of Trx and inhibit its biological function. The E3 ubiquitin ligase ITCH can specifically degrade Txnip via ubiquitination. The apoptosis of human lens epithelial cells (HLECs), which are highly sensitive to redox caused by oxidative stress, is a significant factor for the development of sugar cataract in a high-glucose environment. However, whether Trx, Txnip and ITCH contribute to the progression of sugar cataracts and the underlying mechanisms remain unknown, and thus, identifying these were the aims of the present study. The present results suggested that the expression levels of Trx, Txnip and ITCH in HLECs cultured with different glucose concentrations were detected by reverse transcription-quantitative PCR and western blotting, and the apoptotic rate of the cells was detected by flow cytometry and superoxide detection assay. The interaction between ITCH and Txnip was determined by co-localization immunofluorescence and co-immunoprecipitation. In addition, a vector and small interfering RNA of ITCH were transfected to overexpress and knockdown ITCH, respectively, to alter the expression of downstream proteins and cell apoptosis. It was found that Txnip was highly expressed in cultured HLECs in high-glucose environment, and the antioxidative function of Trx was restricted and suppressed, thus promoting apoptosis. The overexpression of ITCH increased the expression of Trx and decreased oxidative stress and apoptosis by decreasing Txnip in cultured HLECs, while downregulation of ITCH significantly decreased the expression of Trx and enhanced oxidative stress and apoptosis. Therefore, the present results indicated that ITCH could regulate the apoptosis of HLECs that were cultured in high-glucose concentration and that it may be a treatment target for sugar cataract.

Thioredoxin Decreases Anthracycline Cardiotoxicity, But Sensitizes Cancer Cell Apoptosis

Cardiotoxicity is a major limitation for anthracycline chemotherapy although anthracyclines are potent antitumor agents. The precise mechanism underlying clinical heart failure due to anthracycline treatment is not fully understood, but is believed to be due, in part, to lipid peroxidation and the generation of free radicals by anthracycline-iron complexes. Thioredoxin (Trx) is a small redox-active antioxidant protein with potent disulfide reductase properties. Here, we present evidence that cancer cells overexpressing Trx undergo enhanced apoptosis in response to daunomycin. In contrast, cells overexpressing redox-inactive mutant Trx were not effectively killed. However, rat embryonic cardiomyocytes (H9c2 cells) overexpressing Trx were protected against daunomycin-mediated apoptosis, but H9c2 cells with decreased levels of active Trx showed enhanced apoptosis in response to daunomycin. We further demonstrate that increased level of Trx is specifically effective in anthracycline toxicity, but not with other topoisomerase II inhibitors such as etoposide. Collectively these data demonstrate that whereas high levels of Trx protect cardiomyocytes against anthracycline toxicity, it potentiates toxicity of anthracyclines in cancer cells.

Abstract 2962: Molecular mechanisms underlying the sensitizing effect of mutant p53 protein expression for Auranofin treatment of NSCLC and PDAC cells

Abstract Introduction: Auranofin (AF) is an orally available, organogold compound that is FDA-approved for its use in rheumatoid arthritis. AF gained interest as an anti-cancer agent since it acts as a thioredoxin reductase (TrxR) inhibitor. Data extracted from The Cancer Genome Atlas show that TXNRD1 is abundantly expressed in lung adenocarcinoma patients and negatively affects their outcome, making TrxR1 an attractable target in non-small cell lung cancer (NSCLC) patients. The goal of this study was to determine if mutant p53 expression can be used as a predictive biomarker for the treatment of AF in NSCLC. In addition, we aimed to obtain a profound understanding of the molecular mechanisms that govern the sensitizing effect of mutant p53 towards AF-treated NSCLC cells by investigating the type of cell death. Material and methods: We determined IC50-values using the sulforhodamine-B assay for AF in a panel of NSCLC and pancreatic ductal adenocarcinoma (PDAC) cell lines with different p53 mutations and expression levels. In addition, we correlated these IC50-values to baseline expression levels of different antioxidant related proteins. Results were confirmed in the NSCLC cell line NCI-H1299 (p53 deletion, null) and its two isogenic derivates (mutant p53 R175H or R273H knock-in). mRNA-Seq of the isogenic cell line panel was performed after exposure to a medium dose of AF. Finally, the IncuCyte ZOOM system was used to determine the percentage of AF-induced cell death by the means of the Cytotox Green reagent after pretreatment of the tumor cells with a panel of apoptosis, necroptosis and ferroptosis inhibitors. Results: A strong inverse correlation was observed between mutant p53 protein expression and AF IC50-values and baseline Trx levels in the NSCLC and PDAC cells, indicating that mutant p53 can sensitize cancer cells for AF. This sensitizing effect was confirmed in the p53Mutant isogenic NSCLC cells. Transcriptome analysis revealed the up- and downregulation of specific genes involved in ferroptosis. More specifically, AF induced cell death through various mechanisms, including apoptosis and ferroptosis, which were dependent on the expression levels of p53 rather than the type of p53 mutation. In cells with high expression levels of mutant p53, AF induced ferroptosis and lipid peroxidation. At lower expression levels of p53, the apoptosis pathway was triggered by AF with an increase in caspase-3/7 positive cells and inhibition of cell death by the caspase inhibitor Z-VAD-FMK. Conclusion: Mutant p53 protein expression renders NSCLC and PDAC cells more susceptible to AF. In an isogenic setting, medium levels of mutant p53 sensitize NSCLC cells for apoptosis while cells with higher levels are effectively killed through ferroptosis. Altogether, AF presents a potential novel therapeutic strategy to efficiently kill p53 mutated NSCLC tumor cells by various types of cell death. Citation Format: Laurie Freire Boullosa, Filip Lardon, Evelien Smits, Christophe Deben. Molecular mechanisms underlying the sensitizing effect of mutant p53 protein expression for Auranofin treatment of NSCLC and PDAC cells [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2962.

Oxidation of apoptosis-inducing factor (AIF) to disulfide-linked conjugates

Apoptosis-inducing factor (AIF) is a flavoprotein and essential partner of the CHCHD4 redox protein during the mitochondrial intermembrane space import machinery. Mammalian AIF has three cysteine residues, which have received little attention. Previous reports have evidenced a redox interaction between AIF and thioredoxin 1 (Trx1), particularly after oxidant conditions. Therefore, we asked whether the cysteine residues of the human AIF could be oxidized. Our data showed that endogenous AIF could be oxidized to disulfide-linked conjugates (DLC). Overexpressed WT AIF in HEK293T cells, as well as recombinant WT AIF, formed DLC. Expression of C256S, C317S or C441S AIF mutants severely inhibited DLC formation in cells exposed to oxidants. In vitro, DLC formation was completely precluded with C256S and C441S AIF mutants and partially inhibited with the C317S mutant. DLC was shown to enhance cellular susceptibility to apoptosis induced by staurosporine, likely by preventing AIF to maintain mitochondrial oxidative phosphorylation. Cells with decreased expression of Trx1 produced more AIF DLC than those with normal Trx1 levels, and in vitro, Trx1 was able to decrease the amount of AIF DLC. Finally, confocal analysis, as well as immunoblotting of mitochondrial fraction, indicated that a fraction of Trx1 is present in mitochondria. Overall, these data provide evidence that all three cysteine residues of AIF can be oxidized to DLC, which can be disrupted by mitochondrial Trx1.

Protective Antioxidant Effects of Amentoflavone and Total Flavonoids from Hedyotis diffusa on H2 O2 -Induced HL-O2 Cells through ASK1/p38 MAPK Pathway.

In this study, total flavonoids and total triterpenoid acid were extracted with ethyl acetate from Hedyotis diffusa Willd, and hepatoprotective activities of them and five compounds from total flavonoids against H2 O2 induced hepatocyte damage on HL-02 cells were determined. In particular, amentoflavone and total flavonoids had influence on the leakage of ALT, AST, LDH, the activities of SOD and the content of MDA. They effectively reduced the loss of MMP, the release of Cyt C, and then inhibited activation of caspase-3/caspase-9 cascade in hepatotoxic cells. The contents of ROS were significantly reduced to inhibit p38 in amentoflavone and flavonoids groups which decreased ASK1 and p-p38 levels through increasing thioredoxin Trx1 and reductase TrxR1. These results suggesting that the antioxidant protection of amentoflavone and flavonoids might be reducing ROS to inhibit the H2 O2 -induced upstream of pathway via increasing levels of Trx1 and TrxR1, which were pivotal in blocking the down streaming effectors of ASK1/p38 MAPK pathway and alleviating hepatotoxicity.

The quantitation of thioredoxin 1 from serum as a novel means to detect breast cancer (BC).

557 Background: Breast cancer (BC) is the most common cancer and the second leading cause of cancer death in women. Enormous effort has been conducted without success to develop a means to detect BC using the blood. We have reported that the level of thioredoxin 1 (Trx1) in serum could be a novel standard to evaluate the risk of BC. Therefore, we have investigated the clinical utility of Trx1 as a biomarker to detect BC by testing sera from normal women, women with BC, women with five other types of cancer. Methods: We have developed an ELISA kit that quantitates Trx1 in sera. The level of Trx1 was determined in each serum from normal healthy women (n = 114), as well as patients with BC (n = 106), cervical cancer (n = 17), lung cancer (n = 14), stomach cancer (n = 9), and thyroid cancer (n = 4). BC patients were recruited according to their age and cancer stage. Each test was duplicated more than three times, and test results were analyzed by ROC analysis, one-way ANOVA tests, and unpaired t-tests. Results: The mean value of Trx1 from normal women was 5.60±4.39(±SD) and that from BC was 22.25±7.07. The Trx1 level was effective to distinguish BC serum from healthy serum with a sensitivity of 94.3% and specificity of 93.9% (AUC 0.985, p&lt; 0.001). The levels of Trx1 from BC patients were higher than the cut-off value of 14.13 U/ml regardless of age, stage, histological grade, type, ER/PR/HER2 expression profile, and proliferation activity of BC cells. The levels of Trx1 from the other five types of cancers (2.34±1.82 - 3.64±2.99) were low enough to be distinguishable from BC. Especially, Trx1 levels could rescue patients whose mammography resulted in a false judgement. Conclusions: These results indicated that the blood level of Trx1 is an effective and accurate method to detect breast cancer, and particularly as a complement to mammography.

Paracrine regulation and improvement of β-cell function by thioredoxin

The failure of insulin-producing β-cells is the underlying cause of hyperglycemia in diabetes mellitus. β-cell decay has been linked to hypoxia, chronic inflammation, and oxidative stress. Thioredoxin (Trx) proteins are major actors in redox signaling and essential for signal transduction and the cellular stress response. We have analyzed the cytosolic, mitochondrial, and extracellular Trx system proteins in hypoxic and cytokine-induced stress using β-cell culture, isolated pancreatic islets, and pancreatic islet transplantation modelling low oxygen supply.Protein levels of cytosolic Trx1 and Trx reductase (TrxR) 1 significantly decreased, while mitochondrial Trx2 and TrxR2 increased upon hypoxia and reoxygenation. Interestingly, Trx1 was secreted by β-cells during hypoxia. Moreover, murine and human pancreatic islet grafts released Trx1 upon glucose stimulation. Survival of transplanted islets was substantially impaired by the TrxR inhibitor auranofin.Since a release was prominent upon hypoxia, putative paracrine effects of Trx1 on β-cells were examined. In fact, exogenously added recombinant hTrx1 mitigated apoptosis and preserved glucose sensitivity in pancreatic islets subjected to hypoxia and inflammatory stimuli, dependent on its redox activity. Human subjects were studied, demonstrating a transient increase in extracellular Trx1 in serum after glucose challenge. This increase correlated with better pancreatic islet function. Moreover, hTrx1 inhibited the migration of primary murine macrophages.In conclusion, our study offers evidence for paracrine functions of extracellular Trx1 that improve the survival and function of pancreatic β-cells.