Serum thioredoxin reductase levels increase in response to chemically induced acute liver injury

The C-terminal selenenylsulfide of extracellular/non-reduced thioredoxin reductase endows this protein with selectivity to small-molecule electrophilic reagents under oxidative conditions

Mammalian cytosolic thioredoxin reductase (TrxR1) serves as an antioxidant protein by transferring electrons from NADPH to various substrates. The action of TrxR1 is achieved via reversible changes between NADPH-reduced and non-reduced forms, which involves C-terminal selenolthiol/selenenylsulfide exchanges. TrxR1 may be released into extracellular environment, where TrxR1 is present mainly in the non-reduced form with active-site disulfide and selenenylsulfide bonds. The relationships between extracellular TrxR1 and tumor metastasis or cellular signaling have been discovered, but there are few reports on small-molecule compounds in targeted the non-reduced form of TrxR1. Using eight types of small-molecule thiol-reactive reagents as electrophilic models, we report that the selenenylsulfide bond in the non-reduced form of TrxR1 functions as a selector for the thiol-reactive reagents at pH 7.5. The non-reduced form of TrxR1 is resistant to hydrogen peroxide/oxidized glutathione, but is sensitive to certain electrophilic reagents in different ways. With 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB) and S-nitrosoglutathione (GSNO), the polarized selenenylsulfide bond breaks, and selenolate anion donates electron to the dynamic covalent bond in DTNB or GSNO, forming TNB-S-Se-TrxR1 complex or ON-Se-TrxR1 complex. The both complexes lose the ability to transfer electrons from NADPH to substrate. For diamide, the non-reduced TrxR1 actually prevents irreversible damage by this oxidant. This is consistent with the regained activity of TrxR1 through removal of diamide via dialysis. Diamide shows effective in the presence of human cytosolic thioredoxin (hTrx1), Cys residue(s) of which is/are preferentially affected by diamide to yield disulfide, hTrx1 dimer and the mixed disulfide between TrxR1-Cys497/Sec498 and hTrx1-Cys73. In human serum samples, the non-reduced form of TrxR1 exists as dithiothreitol-reducible polymer/complexes, which might protect the non-reduced TrxR1 from inactivation by certain electrophilic reagents under oxidative conditions, because cleavage of these disulfides can lead to regain the activity of TrxR1. The details of the selective response of the selenenylsulfide bond to electrophilic reagents may provide new information for designing novel small-molecule inhibitors (drugs) in targeted extracellular/non-reduced TrxR1.

Antioxidant, antihyperglycemic, and antihyperlipidemic properties of Chimonanthus salicifolius S. Y. Hu leaves in experimental animals: modulation of thioredoxin and glutathione systems, renal water reabsorption, and gut microbiota

Introduction

Excessive calorie intake and physical inactivity have dramatically increased nutrient overload-associated disease, becoming a global public health issue. Chimonanthus salicifolius S. Y. Hu (CHI) is a homology plant of food and medicine in China and shows several health benefits.

Methods

This work investigated the antioxidant activity, the alleviating effects, and the mechanism of action on diabetes and hyperlipidemia of CHI leaves.

Results and discussion

Results showed that CHI leaves infusion displayed in vitro antioxidant activity measured by ABTS and ferric reducing antioxidant power methods. In wild-type Kunming mice, CHI leaves infusion consumption activated the hepatic antioxidant enzymes, including glutathione reductase, glutathione S-transferase, glutathione peroxidase and thioredoxin reductase as well as thioredoxin reductase 1. In alloxan-induced type 1 diabetic mice, CHI leaves infusion ameliorated diabetic symptoms, including polyuria, polydipsia, polyphagia and hyperglycemia, in a dose-dependent and time-course manners. The mechanism involved CHI leaves up-regulating renal water reabsorption associated protein - urine transporter A1-and promoting the trafficking of urine transporter A1 and aquaporin 2 to the apical plasma membrane. Despite this, in high-fat diet-induced hyperlipidemic golden hamsters, CHI leaves powder did not significantly effect on hyperlipidemia and body weight gain. This might be attributed to CHI leaves powder increasing the calorie intake. Interestingly, we found that CHI leaves extract containing a lower dose of total flavonoid than CHI leaves powder pronouncedly reduced the levels of total cholesterol, triglyceride, and low-density lipoprotein cholesterol in serum in golden hamsters fed a high-fat diet. Furthermore, CHI leaves extract elevated the diversity of gut microbiota and the abundance of Bifidobacterium and Ruminococcaceae_UCG-014. It also decreased the abundance of Lactobacillus at the genus level in golden hamsters fed a high-fat diet. Overall, CHI leaves benefit oxidative stress prevention and metabolic syndrome amelioration in vivo.

Prooxidant activity-based guideline for a beneficial combination of (-)-epigallocatechin-3-gallate and chlorogenic acid

In the current study, the prooxidant activities of (-)-epigallocatechin-3-gallate (EGCG) and chlorogenic acid (CGA) were systematically compared both in multiple in vitro models and in mice. At equimolar concentrations in vitro and in vivo, EGCG displayed powerful prooxidant effects though CGA exhibited none. In vitro, though CGA and EGCG synergistically produced hydrogen peroxide, CGA was able to scavenge hydroxyl radicals generated by EGCG/copper. Consistent with the selective modulation of reactive oxygen species produced from EGCG, CGA lowered hepatotoxicity but did not perturb hepatic AMPK activation nor the increase of hepatic Nrf2-associated proteins induced by high-dose EGCG. CGA, along with low-dose EGCG, synergistically activated hepatic AMPK and increased hepatic Nrf2-associated proteins without causing toxicity in mice. This proof-of-principle study suggests that polyphenols with potent prooxidant activities (e.g., EGCG) together with antioxidant polyphenols with noticeably low prooxidant activities (e.g., CGA) may yield health benefits with a low risk of side effects.

Evaluation of dithiothreitol-oxidizing capacity (DOC) as a serum biomarker for chronic hepatitis B in patients exhibiting normal alanine aminotransferase levels: a pilot study towards better monitoring of disease

BACKGROUND

Alanine aminotransferase (ALT) is the most commonly used serum biomarker for chronic liver diseases (CLDs) but may not accurately reflect hepatic disorders and easily underestimates hepatic fibrosis. The previously revised upper limit of normal (ULN) of ALT (19 U/L for women and 30 U/L for men) increases its sensitivity but yields higher numbers of false-positives. Moreover, CLDs patients with ALT lower than the revised ULN may nonetheless have progression of disease. Therefore there is a need of novel biomarkers to complement the use of ALT. Here we have evaluated measurements of serum dithiothreitol-oxidizing capacity (DOC) in cohorts of chronic hepatitis B patients with different stages of disease as an exploratory pilot study for this purpose.

METHODS

Serum samples obtained from healthy persons and from chronic hepatitis B patients with normal ALT values were used for sensitivity evaluation. The hepatitis B patients encompassed end-stage liver diseases (ELD), chronic hepatitis B (CHB), CHB with persistently normal ALT (CHB-P) and inactive carriers (ICs). Sensitivity was also evaluated with samples from patients with other diseases. The study period was March 2018 to December 2020.

FINDINGS

DOC was found to be a robust biomarker that may become complementary to ALT measurements, especially in patients displaying low ALT levels. ROC analyses indicated that the AUC values of DOC reached 0.983 and 0.956 in ELD and CHB patients exhibiting normal ALT levels, respectively. Importantly, the AUC values of DOC reached 0.852 and 0.844 in CHB-P patients and ICs, respectively. Such AUC values permit screening and continued monitoring, corresponding to over 30% and 50% sensitivity with 99% and 95% specificity for CHB-P and ICs, respectively. DOC was also significantly correlated with indicators for fibrosis, assessing both APRI (Pearson r = 0.4905, P < 0.0001) and FIB-4 (Pearson r = 0.4421, P < 0.0001). Surprisingly, the AUC values of DOC in the hepatitis B patients with ALT levels lower than the revised ULN were not compromised. In examined non-liver diseases, DOC was low and normal, including in patients with acute myocardial infection displaying increased ALT levels.

INTERPRETATIONS

The results suggest that DOC can be promising as a complementary biomarker used in addition to ALT for monitoring of disease in chronic hepatitis B patients, especially when ALT levels are normal. DOC should be further evaluated for possible clinical use as biomarker also in other CLDs.

FUNDING

This study was funded by the National Natural Science Foundation of China (Grant numbers: 31771971 and 32001013).

SARS-CoV-2 suppresses mRNA expression of selenoproteins associated with ferroptosis, endoplasmic reticulum stress and DNA synthesis

Higher selenium status has been shown to improve the clinical outcome of infections caused by a range of evolutionally diverse viruses, including SARS-CoV-2. However, the impact of SARS-CoV-2 on host-cell selenoproteins remains elusive. The present study investigated the influence of SARS-CoV-2 on expression of selenoprotein mRNAs in Vero cells. SARS-CoV-2 triggered an inflammatory response as evidenced by increased IL-6 expression. Of the 25 selenoproteins, SARS-CoV-2 significantly suppressed mRNA expression of ferroptosis-associated GPX4, DNA synthesis-related TXNRD3 and endoplasmic reticulum-resident SELENOF, SELENOK, SELENOM and SELENOS. Computational analysis has predicted an antisense interaction between SARS-CoV-2 and TXNRD3 mRNA, which is translated with high efficiency in the lung. Here, we confirmed the predicted SARS-CoV-2/TXNRD3 antisense interaction in vitro using DNA oligonucleotides, providing a plausible mechanism for the observed mRNA knockdown. Inhibition of TXNRD decreases DNA synthesis which is thereby likely to increase the ribonucleotide pool for RNA synthesis and, accordingly, RNA virus production. The present findings provide evidence for a direct inhibitory effect of SARS-CoV-2 replication on the expression of a specific set of selenoprotein mRNAs, which merits further investigation in the light of established evidence for correlations between dietary selenium status and the outcome of SARS-CoV-2 infection.

The polysaccharides from the Grifola frondosa fruiting body prevent lipopolysaccharide/d-galactosamine-induced acute liver injury via the miR-122-Nrf2/ARE pathways

The polysaccharides from Grifola frondosa fruiting body can be used as a potential hepatoprotective agent in the treatment of acute liver injury.

A mouse model of subacute liver failure with ascites induced by step-wise increased doses of (-)-epigallocatechin-3-gallate

Acute liver failure is divided into hyperacute, acute and subacute liver failure. Ascites is a common complication of subacute liver failure. Although animal models of acute liver failure have been established, the study of the pathogenesis of subacute liver failure with ascites complication is hampered by the lack of experimental animal model. The present study aimed at providing a mouse model of subacute liver failure with ascites complication. Kunming mice were intraperitoneally injected with (-)-epigallocatechin-3-gallate (EGCG), a redox-active polyphenol from green tea, for 32 consecutive days with step-wise increased dosage. The EGCG treatment resulted in liver failure as evidenced by extensive hepatocyte necrosis observed histologically along with significant elevation of serum alanine aminotransferase, aspartate aminotransferase, total bilirubin and direct bilirubin levels as well as significant reduction of serum albumin. Liver fibrosis was not observed by Masson staining and fibrosis-associated proteins were not increased. The mortality was less than 12% and the survival mice developed noticeable ascites. Hepatic thioredoxin and glutathione systems were activated by the EGCG. These adaptive responses might render most mice tolerable to the EGCG treatment. The EGCG treatment significantly up-regulated renal urea transporter A1 and promoted its trafficking to apical membrane. These alterations, known to increase water reabsorption, may be responsible, at least in part, for the formation of the ascites. Overall, the mice treated with gradually elevated doses of EGCG exhibits some of the features observed in patients with subacute liver failure, especially ascites. This mouse model is a useful tool for investigating the pathogenesis of subacute liver failure with ascites complication.

Antioxidant and Pro-Oxidant Activities of Melatonin in the Presence of Copper and Polyphenols In Vitro and In Vivo

Melatonin is a well-documented antioxidant. Physicochemical analysis using the density functional theory suggests that melatonin is a copper chelating agent; however, experimental evidence is still in demand. The present study investigated the influence of melatonin on reactive oxygen species (ROS) generated from polyphenol autoxidation in the presence of copper. Surprisingly, we found that melatonin paradoxically enhanced ROS formation in a redox system containing low concentrations of copper and quercetin (Que) or (−)-epigallocatechin-3-gallate (EGCG), due to reduction of cupric to cuprous ion by melatonin. Addition of DNA to this system inhibited ROS production, because DNA bound to copper and inhibited copper reduction by melatonin. When melatonin was added to a system containing high concentrations of copper and Que or EGCG, it diminished hydroxyl radical formation as expected. Upon addition of DNA to high concentrations of copper and Que, this pro-oxidative system generated ROS and caused DNA damage. The DNA damage was not prevented by typical scavengers of hydroxyl radical DMSO or mannitol. Under these conditions, melatonin or bathocuproine disulfonate (a copper chelator) protected the DNA from damage by chelating copper. When melatonin was administered intraperitoneally to mice, it inhibited hepatotoxicity and DNA damage evoked by EGCG plus diethyldithiocarbamate (a copper ionophore). Overall, the present study demonstrates the pro-oxidant and antioxidant activities of melatonin in the redox system of copper and polyphenols. The pro-oxidant effect is inhibited by the presence of DNA, which prevents copper reduction by melatonin. Interestingly, in-vivo melatonin protects against copper/polyphenol-induced DNA damage probably via acting as a copper-chelating agent rather than a hydroxyl radical scavenger. Melatonin with a dual function of scavenging hydroxyl radical and chelating copper is a more reliable DNA guardian than antioxidants that only have a single function of scavenging hydroxyl radical.

Targeting the Thioredoxin System as a Strategy for Cancer Therapy

Thioredoxin reductase (TrxR) participates in the regulation of redox reactions in organisms. It works mainly via its substrate molecule, thioredoxin, to maintain the redox balance and regulate signal transduction, which controls cell proliferation, differentiation, death, and other important physiological processes. In recent years, increasing evidence has shown that the overactivation of TrxR is related to the development of tumors. The exploration of TrxR-targeted antitumor drugs has attracted wide attention and is expected to provide new therapies for cancer treatment. In this perspective, we highlight the specific relationship between TrxR and apoptotic signaling pathways. The cytoplasm and mitochondria both contain TrxR, resulting in the activation of apoptosis. TrxR activity influences reactive oxygen species (ROS) and further regulates the inflammatory signaling pathway. In addition, we discuss representative TrxR inhibitors with anticancer activity and analyze the challenges in developing TrxR inhibitors as anticancer drugs.

Boldine Supplementation Regulates Mitochondrial Function and Oxidative Stress in a Rat Model of Hepatotoxicity

Background: The xenobiotics-induced liver injury is a clinical complication. Hence, finding new hepatoprotective strategies has clinical value. Oxidative stress and its subsequent complications are major mechanisms involved in xenobiotics-induced hepatotoxicity. Boldine is one of the most potent antioxidant molecules widely investigated for its protective properties in different experimental models. In the current study, the hepatoprotective properties of boldine and its potential mechanisms of hepatoprotection have been investigated. Methods: Rats received thioacetamide (TAA; 200 mg/kg, i.p) as a model of acute liver injury. Boldine (5, 10, 1nd 20 mg/kg; 24 hours intervals; oral) was administered as the hepatoprotective agent. Results: Liver injury was evident in TAA-treated animals (48 hours after TAA exposure) as a severe increase in serum level of liver injury biomarkers and histopathological alterations. Moreover, markers of oxidative stress were increased in liver tissue of TAA-treated rats. Assessment of mitochondrial indices of functionality revealed a significant decrease in mitochondrial dehydrogenases activity, the collapse of mitochondrial membrane potential, mitochondrial swelling and depletion of ATP content. It was found that boldine supplementation mitigated liver tissue markers of oxidative stress and improved mitochondrial indices of functionality in TAA-treated animals. Conclusion: The hepatoprotective properties of boldine might primarily rely on antioxidant and mitochondria protecting effects of this alkaloid.

Liver Proteome of Mice with Distinct Genetic Susceptibilities to Fluorosis Treated with Different Concentrations of F in the Drinking Water

Appropriate doses of fluoride (F) have therapeutic action against dental caries, but higher levels can cause disturbances in soft and mineralized tissues. Interestingly, the susceptibility to the toxic effects of F is genetically determined. This study evaluated the effects of F on the liver proteome of mice susceptible (A/J) or resistant (129P3/J) to the effects of F. Weanling male A/J (n = 12) and 129P3/J (n = 12) mice were housed in pairs and assigned to two groups given low-F food and drinking water containing 15 or 50 ppm F for 6 weeks. Liver proteome profiles were examined using nano-LC-ESI-MS/MS. Difference in expression among the groups was determined using the PLGS software. Treatment with the lower F concentration provoked more pronounced alterations in fold change in liver proteins in comparison to the treatment with the higher F concentration. Interestingly, most of the proteins with fold change upon treatment with 15 ppm F were increased in the A/J mice compared with their 129P3/J counterparts, suggesting an attempt of the former to fight the deleterious effects of F. However, upon treatment with 50 ppm F, most proteins with fold change were decreased in the A/J mice compared with their 129P3/J counterparts, especially proteins related to oxidative stress and protein folding, which might be related to the higher susceptibility of the A/J animals to the deleterious effects of F. Our findings add light into the mechanisms underlying genetic susceptibility to fluorosis.

Selenium nanoparticles are more efficient than sodium selenite in producing reactive oxygen species and hyper-accumulation of selenium nanoparticles in cancer cells generates potent therapeutic effects

We have previously demonstrated that selenium nanoparticles (SeNPs) administered via oral route possess similar capacities of increasing selenoenzyme activities as the extensively examined sodium selenite, selenomethionine and methylselenocysteine, and yet display the lowest toxicity among these selenium compounds in mouse models. However, the low toxicity of SeNPs found in mammalian systems would lead to the interpretation that the punctate distribution of elemental selenium found in cultured cancer cells subjected to selenite treatment that triggers marked cytotoxicity represents a detoxifying mechanism. The present study found that SeNPs could be reduced by the thioredoxin- or glutaredoxin-coupled glutathione system to generate ROS. Importantly, ROS production by SeNPs in these systems was more efficient than by selenite, which has been recognized as the most redox-active selenium compound for ROS production. This is because multiple steps of reduction from selenite to selenide anion are required; whereas only a single step reduction from the elemental selenium atom to selenide anion is needed to trigger redox cycling with oxygen to produce ROS. We thus speculated that accumulation of SeNPs in cancer cells would result in a strong therapeutic effect, rather than serves a detoxification function. Indeed, we showed herein that preformed SeNPs generated a potent therapeutic effect in a mouse model due to rapid, massive and selective accumulation of SeNPs in cancer cells. Overall, for the first time, we demonstrate that SeNPs have a stronger pro-oxidant property than selenite and hyper-accumulation of SeNPs in cancer cells can generate potent therapeutic effects.

Synergistic toxicity of epigallocatechin-3-gallate and diethyldithiocarbamate, a lethal encounter involving redox-active copper

Dithiocarbamates (DTC) are widely used in agricultural, industrial and therapeutic domains. There are ample opportunities for human exposure to DTC. Green tea extracts, with epigallocatechin-3-gallate (EGCG) being the most abundant constituent, have been used as dietary supplements for body weight reduction. Our hypothesis is that DTC can act as a copper ionophore to increase hepatic levels of redox-active copper which promotes EGCG auto-oxidation to produce oxidative stress and toxicity. The results of the present study in a mouse model is consistent with this hypothesis, showing that co-administration of EGCG and diethyldithiocarbamate - a metabolite of disulfiram (a drug for alcohol aversion therapy), both at tolerable levels, caused lethality. The liver was the major organ site of toxicity. The co-administration drastically increased lipid peroxidation, DNA damage and cell apoptosis as well as caused deleterious transcriptional responses including basal and Nrf2 antioxidant systems in the liver. The results suggest that exposure to DTC reduces toxic threshold of dietary polyphenols from green tea and possibly other plants, and vice versa. This novel hypothesis is important to human health, and the dose-response relationship of this synergistic toxicity needs to be further characterized.

Histological and biochemical biomarkers analysis reveal strong toxicological impacts of pollution in hybrid sparrow (Passer domesticus × Passer hispaniolensis) in southern Tunisia

Environmental pollution is a great concern worldwide. Our aim was to investigate the histopathological injuries and oxidative stress induced by exposure to contaminants in liver tissues of hybrid sparrows (Passer domesticus × Passer hispaniolensis) living in Gabès city, which is one of the most polluted hot spot in Tunisia. Our results show evidence of a pronounced impairment in liver function which is confirmed by histopathological changes as well as remarkable blood chemical alterations in sparrows living near the Gabès-Ghannouche factory complex of phosphate treatment. Moreover, a significant decrease in the hepatic activities of superoxide dismutase (SOD) and catalase (CAT) was observed in birds from Ghannouche when compared to other distant areas. Our study revealed also a significant increase in the liver levels of thiobarbituric acid reactive substances (TBARS), in sparrows living in Ghannouche, indicating oxidative damage to membrane lipids. Overall, our results suggest that the hybrid sparrow offers a suitable model for biomonitoring programs of atmosphere pollutants and the selected biomarkers may function as useful tool to evaluate the effects of pollutants on living organisms.

Elevated Levels of Selenium Species in Cerebrospinal Fluid of Amyotrophic Lateral Sclerosis Patients with Disease-Associated Gene Mutations

BACKGROUND

Although an increasing role of genetic susceptibility has been recognized, the role of environmental risk factors in amyotrophic lateral sclerosis (ALS) etiology is largely uncertain; among neurotoxic chemicals, epidemiological and biological plausibility has been provided for pesticides, the heavy metal lead, the metalloid selenium, and other persistent organic pollutants. Selenium involvement in ALS has been suggested on the basis of epidemiological studies, in vitro investigations, and veterinary studies in which selenium induced a selective toxicity against motor neurons.

OBJECTIVE

Hypothesizing a multistep pathogenic mechanism (genetic susceptibility and environmental exposure), we aimed to study selenium species in ALS patients carrying disease-associated gene mutations as compared to a series of hospital controls.

METHODS

Using advanced analytical techniques, we determined selenium species in cerebrospinal fluid sampled at diagnosis in 9 ALS patients carrying different gene mutations (C9ORF72, SOD1, FUS, TARDBP, ATXN2, and TUBA4A) compared to 42 controls.

RESULTS

In a patient with the tubulin-related TUBA4A mutation, we found highly elevated levels (in μg/L) of glutathione-peroxidase-bound selenium (32.8 vs. 1.0) as well as increased levels of selenoprotein-P-bound selenium (2.4 vs. 0.8), selenite (1.8 vs. 0.1), and selenate (0.9 vs. 0.1). In the remaining ALS patients, we detected elevated selenomethionine-bound selenium levels (0.38 vs. 0.06).

CONCLUSIONS

Selenium compounds can impair tubulin synthesis and the cytoskeleton structure, as do tubulin-related gene mutations. The elevated selenium species levels in the TUBA4A patient may have a genetic etiology and/or represent a pathogenic pathway through which this mutation favors disease onset, though unmeasured confounding cannot be excluded. The elevated selenomethionine levels in the other patients are also of interest due to the toxicity of this nonphysiological selenium species. Our study is the first to assess selenium exposure in genetic ALS, suggesting an interaction between this environmental factor and genetics in triggering disease onset.

Epigallocatechin-3-gallate enhances key enzymatic activities of hepatic thioredoxin and glutathione systems in selenium-optimal mice but activates hepatic Nrf2 responses in selenium-deficient mice

Selenium participates in the antioxidant defense mainly through a class of selenoproteins, including thioredoxin reductase. Epigallocatechin-3-gallate (EGCG) is the most abundant and biologically active catechin in green tea. Depending upon the dose and biological systems, EGCG may function either as an antioxidant or as an inducer of antioxidant defense via its pro-oxidant action or other unidentified mechanisms. By manipulating the selenium status, the present study investigated the interactions of EGCG with antioxidant defense systems including the thioredoxin system comprising of thioredoxin and thioredoxin reductase, the glutathione system comprising of glutathione and glutathione reductase coupled with glutaredoxin, and the Nrf2 system. In selenium-optimal mice, EGCG increased hepatic activities of thioredoxin reductase, glutathione reductase and glutaredoxin. These effects of EGCG appeared to be not due to overt pro-oxidant action because melatonin, a powerful antioxidant, did not influence the increase. However, in selenium-deficient mice, with low basal levels of thioredoxin reductase 1, the same dose of EGCG did not elevate the above-mentioned enzymes; intriguingly EGCG in turn activated hepatic Nrf2 response, leading to increased heme oxygenase 1 and NAD(P)H:quinone oxidoreductase 1 protein levels and thioredoxin activity. Overall, the present work reveals that EGCG is a robust inducer of the Nrf2 system only in selenium-deficient conditions. Under normal physiological conditions, in selenium-optimal mice, thioredoxin and glutathione systems serve as the first line defense systems against the stress induced by high doses of EGCG, sparing the activation of the Nrf2 system.

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EGCG increases hepatic activities of TrxR, GR and Grx in selenium-optimal mice.

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EGCG fails to manipulate the above-mentioned enzymes in selenium-deficient mice.

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EGCG in turn activates hepatic Nrf2 response in selenium-deficient mice.

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Selenium deficiency does not increase EGCG toxicity due to potent Nrf2 response.

Thioredoxin reductase: a novel, independent prognostic marker in patients with hepatocellular carcinoma

Here we found that hepatocellular carcinoma (HCC) patients with recurrence outcome and nonsurvivors had significantly increased thioredoxin reductase (TrxR) serum levels on reoperation (P < 0.0001 and P < 0.0001). Multivariate regression analysis adjusted for common risk factors showed that TrxR was an independent predictor of recurrence (hazard ratios [HR] = 4.19; 95% confidence intervals [CI]: 3.21-7.08) and overall survival (HR = 5.56; 95% CI: 3.42-10.21). The area under the receiver operating characteristic curve of TrxR was 0.837 (95% CI, 0.794-0.881) for recurrence outcome and 0.901 (95% CI, 0.869-0.933) for mortality, which was superior to high-sensitivity-C-reactive protein and a-fetoprotein (P < 0.001). The preoperative serum TrxR level is an independent and significant indicator predictive of poor prognosis and early recurrence in patients with HCC, which offering reliable information for predicting survival.

Predicting the Cytotoxic Potency of Cigarette Smoke by Assessing the Thioredoxin Reductase Inhibitory Capacity of Cigarette Smoke Extract

The present study investigated the influence of the cigarette smoke extract (CSE) on mammalian thioredoxin reductase (TrxR) activity. TrxR is a selenoenzyme with a selenocysteine (Sec) residue exposed on the enzyme’s surface. This unique Sec residue is particularly susceptible to modification by numerous types of electrophiles, leading to inactivation of TrxR and consequent cytotoxicity. Cigarette smoke contains various electrophiles, and the present study showed that CSE could inhibit intracellular TrxR through causing crosslinking and alkylation of TrxR1. TrxR inhibitory capacities of various CSEs were evaluated by using mouse-liver homogenate. Among the CSEs prepared from 18 commercial cigarette brands, TrxR inhibitory capacities of the maximum and the minimum had a 2.5-fold difference. Importantly, CSE’s inhibitory capacity greatly paralleled its cytotoxic potency in all cell lines used. Compared to cytotoxic assays, which have been widely used for evaluating cigarette toxicity but are not suitable for simultaneously examining a large number of cigarette samples, the present method was simple and rapid with a high-throughput feature and thus could be used as an auxiliary means to predict the cytotoxicity of a large number of cigarette samples, making it possible to extensively screen numerous agricultural and industrial measures that potentially affect cigarette safety.

Thioredoxin as a marker for severity and prognosis of aneurysmal subarachnoid hemorrhage

OBJECTIVE

Circulating levels of thioredoxin (Trx), a potent anti-oxidant that modulates inflammation, cell growth and apoptosis, are increased in various critical care conditions. The purpose of this study was to establish the relationship between serum Trx levels and prognosis of aneurysmal subarachnoid hemorrhage (aSAH).

METHODS

An enzyme-linked immunosorbent assay measurement of Trx was performed in serum from 132 patients and 132 healthy volunteers. Clinical outcomes included 6-month mortality and unfavorable outcome (Glasgow outcome scale score of 1-3).

RESULTS

The serum Trx levels were significantly higher in patients than in controls (23.4±12.2 ng/mL vs.8.5±4.0 ng/mL, P<0.001) and had close relation to the World Federation of Neurological Surgeons (WFNS) scores (r=0.461, P<0.001) and modified Fisher scores (r=0.459, P<0.001). Trx was an independent predictor for 6-month mortality (Odds ratio, 1.386; 95% confidence interval, 1.015-2.161; P<0.001) and 6-month unfavorable outcome (Odds ratio, 1.297; 95% confidence interval, 1.012-2.002; P<0.001). Based on receiver operating characteristic curve, TRX had similar prognostic value compared with WFNS scores and modified Fisher scores and also significantly improved their prognostic value for 6-month unfavorable outcome, but not for 6-month mortality.

CONCLUSIONS

Elevated plasma Trx levels are correlated with the severity and poor prognosis, substantializing Trx as a potential prognostic predictive biomarker following aSAH.

Fluoride-induced oxidative stress is involved in the morphological damage and dysfunction of liver in female mice

Fluoride (F), one of the most toxic environmental and industrial pollutants, is known to exert hepatotoxicity. The contribution of oxidative stress to the F tolerance of liver remains largely unknown. In this study, the morphological and ultrastructural characteristics of liver were observed using hematoxylin and eosin staining and transmission electron microscopy (TEM), respectively. Oxidative-stress participations was analysed and the mRNA expression levels of catalase (Cat), glutathione peroxidase 1 (GSH-Px1), nitric oxide synthase 2 (NOS2), and superoxide dismutase 1 (SOD1) were investigated by real-time PCR. Changes in liver-function parameters were also detected. Results showed that the reactive content of reactive oxygen species increased significantly, whereas SOD and GSH-Px activities, as well as total anti-oxidising capability (T-AOC), decreased significantly, with increased nitric oxide (NO) and malondialdehyde (MDA) contents in liver and serum after 70days of F treatment. The mRNA expression levels of Cat, GSH-Px1, and SOD were significantly downregulated, whereas NOS2 mRNA expression level was up upregulated, after F treatment for 70days. Light microscopy also revealed that hepatocytes were fused into pieces; cell boundaries were unclear, and nuclei were lightly stained. TEM further showed that hepatocytes were characterised by vague nuclear and mitochondrial membranes, dilated endoplasmic reticulum, and aggravated vacuolar degeneration. Activities of alanine transaminase, aspartate aminotransferase, alkaline phosphatase and lactate dehydrogenase, as well as the level of total bilirubin in serum increased. Overall, these results indicated that F interfered with the balance of antioxidase activity and morphological changes in liver, which were involved in mouse liver dysfunction.

Selenium and Human Health: Witnessing a Copernican Revolution?

In humans, selenium was hypothesized to lower the risk of several chronic diseases, mainly due to the antioxidant activity of selenium-containing proteins. Recent epidemiologic and laboratory studies, however, are changing our perception of the biological effects of this nutritionally essential trace element. We reviewed the most recent epidemiologic and biochemical literature on selenium, synthesizing the findings from these studies into a unifying view. Randomized trials have shown that selenium did not protect against cancer and other chronic diseases, but even increased the risk of specific neoplasms such as advanced prostate cancer and skin cancer, in addition to type 2 diabetes. Biochemical studies indicate that selenium may exert a broad pattern of toxic effects at unexpectedly low concentrations. Furthermore, its upregulation of antioxidant proteins (selenium-dependent and selenium-independent) may be a manifestation of self-induced oxidative stress. In conclusion, toxic effects of selenium species occur at lower concentrations than previously believed. Those effects may include a large range of proteomic changes and adverse health effects in humans. Since the effects of environmental exposure to this element on human health still remain partially unknown, but are potentially serious, the toxicity of selenium exposure should be further investigated and considered as a public health priority.