Meta-analytical review of antioxidant mechanisms responses in animals exposed to herbicide 2,4-D herbicide

The 2,4-Dichlorophenoxyacetic acid (2,4-D) is a low-cost herbicide to eradicate broadleaf weeds. Since the development of 2,4-D resistant transgenic crops, it has been described as one of the most widely distributed pollutants in the world, increasing concern about its environmental impacts. This study aimed to elucidate the antioxidant system response in animals exposed to 2,4-D by different routes of exposure. It focused on determining if tissue, phylogenetic group, and herbicide formulation would influence the antioxidant mechanisms. A careful literature search of Scopus, WoS, and Science Direct retrieved 6983, 24,098, and 20,616 articles, respectively. The dataset comprised 390 control-treatment comparisons and included three routes of exposure: transgenerational, oral, and topical. The data set for transgenerational and oral exposure revealed oxidative stress through a decrease in enzymatic activities and the level of molecules of the antioxidant system. In contrast, topical exposure increased the oxidative stress. Tissue-specific analyses revealed that the transgenerational effects reduced hepatic catalase (CAT) activity. Oral exposure caused a variety of effects, including increased CAT activity in the prostate and decreased activity in various tissues. Mammals predominate in the transgenerational and oral groups, showing a significantly reduced activity of the antioxidant system. In contrast, in the topical exposure, an increased activity of oxidative stress biomarkers was observed in fish, earthworms, and mollusks. The effects of the 2,4-D formulation on oxidative stress responses showed significant differences between pure and commercial formulations, with oral exposure resulting in decreased activity and topical exposure increasing responses. In summary, orally exposed animals exhibited a clear decrease in enzyme activities, transgenerational exposure elicited tissue-specific prompted biochemical reductions, and topical exposure induced increased responses, emphasizing the need for unbiased exploration of the effects of 2,4-D on biomarkers of oxidative stress while addressing publication bias in oral and topical datasets.

Short communication: The boring sponge (Pione vastifica, Hancock, 1849) induces oxidative stress in the Pacific oyster (Magallana gigas, Thunberg, 1793)

Boring sponge infection affects growth, development and reduces the soft tissue weight of oysters. In this study, we investigated the effects of boring sponge on the activity of three antioxidant enzymes (superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GP)) in the mantle, and the production of reactive oxygen species (ROS) and potential genotoxicity in hemocytes of the Pacific oyster Magallana gigas. Our results showed a significant increase in ROS production and DNA damage in hemocytes. Notably, the activity of SOD, CAT, and GP in the mantle was not significantly affected by boring sponge infection. Collectively, these results suggest that sponge invasion may cause oxidative stress in Pacific oyster hemocytes through ROS overproduction.

Specificity and dynamics of H2O2 detoxification by the cytosolic redox regulatory network as revealed by in vitro reconstitution

The thiol redox state is a decisive functional characteristic of proteins in cell biology. Plasmatic cell compartments maintain a thiol-based redox regulatory network linked to the glutathione/glutathione disulfide couple (GSH/GSSG) and the NAD(P)H system. The basic network constituents are known and in vivo cell imaging with gene-encoded probes have revealed insight into the dynamics of the [GSH]2/[GSSG] redox potential, cellular H2O2 and NAD(P)H+H+ amounts in dependence on metabolic and environmental cues. Less understood is the contribution and interaction of the network components, also because of compensatory reactions in genetic approaches. Reconstituting the cytosolic network of Arabidopsis thaliana in vitro from fifteen recombinant proteins at in vivo concentrations, namely glutathione peroxidase-like (GPXL), peroxiredoxins (PRX), glutaredoxins (GRX), thioredoxins, NADPH-dependent thioredoxin reductase A and glutathione reductase and applying Grx1-roGFP2 or roGFP2-Orp1 as dynamic sensors, allowed for monitoring the response to a single H2O2 pulse. The major change in thiol oxidation as quantified by mass spectrometry-based proteomics occurred in relevant peptides of GPXL, and to a lesser extent of PRX, while other Cys-containing peptides only showed small changes in their redox state and protection. Titration of ascorbate peroxidase (APX) into the system together with dehydroascorbate reductase lowered the oxidation of the fluorescent sensors in the network but was unable to suppress it. The results demonstrate the power of the network to detoxify H2O2, the partially independent branches of electron flow with significance for specific cell signaling and the importance of APX to modulate the signaling without suppressing it and shifting the burden to glutathione oxidation.

Evolutionary expansion, functional diversification, and transcript profiling of plant Glutathione Peroxidases

Glutathione peroxidases (GPXs) play a crucial role in combating activated oxygen species and have been widely studied for their involvement in stress responses. In addition to their stress-related functions, GPXs exhibit diverse roles such as immunological response, and involvement in growth and development. These enzymes are found in both animals and plants, with multiple families identified in the evolutionarily diverse species. These families consist of conserved genes as well as unique members, highlighting the evolutionary diversification of GPX members. While animals have eight GPX families, plants possess five families. Notably, plant genomes undergo duplication and expansion events, leading to an increase in the number of GPX genes and the overall size of the GPX superfamily. This expansion suggests a wide range of functional roles for GPX. In this study, the evolutionary diversification, family expansion, and diverse functional roles of GPX enzymes have been investigated. Additionally, the expression profile of Arabidopsis and Oryza sativa GPX genes were analyzed in different developmental stages, tissues, and abiotic stress conditions. Further extensive research has been required to unravel the intricate interplay between GPX and other proteins, to gain the comprehensive mechanism governing the physiological and developmental roles of GPX.

Emerging role of ferroptosis in metabolic dysfunction-associated steatotic liver disease: revisiting hepatic lipid peroxidation

Metabolic dysfunction-associated steatohepatitis (MASH) is characterised by cell death of parenchymal liver cells which interact with their microenvironment to drive disease activity and liver fibrosis. The identification of the major death type could pave the way towards pharmacotherapy for MASH. To date, increasing evidence suggest a type of regulated cell death, named ferroptosis, which occurs through iron-catalysed peroxidation of polyunsaturated fatty acids (PUFA) in membrane phospholipids. Lipid peroxidation enjoys renewed interest in the light of ferroptosis, as druggable target in MASH. This review recapitulates the molecular mechanisms of ferroptosis in liver physiology, evidence for ferroptosis in human MASH and critically appraises the results of ferroptosis targeting in preclinical MASH models. Rewiring of redox, iron and PUFA metabolism in MASH creates a proferroptotic environment involved in MASH-related hepatocellular carcinoma (HCC) development. Ferroptosis induction might be a promising novel approach to eradicate HCC, while its inhibition might ameliorate MASH disease progression.

Comparative investigation of selenium-enriched Pleurotus ostreatus and Ganoderma lucidum as natural sources of selenium supplementation

Selenium (Se) is an essential trace element for human health, but its nutritional supply is insufficient in large parts of the world. Mushrooms can be enriched in selenium and can serve as alternative and natural source of selenium supplementation. In the present study, two common mushroom species (Pleurotus ostreatus and Ganoderma lucidum), were enriched with two selenium compounds (selenite and selenate) to test their suitability as natural sources of selenium supplementation. Sharp differences in the the metabolic patterns of the fortified selenium were observed. Selenium was effectively metabolized in P. ostreatus but remained in inorganic form in G. lucidum. However, mushrooms extracts were effective in enhancing selenoprotein expression in cell lines. The present study highlights the importance of employing selenium speciation analysis with an element-selective technique to examine the metabolic products following mushroom fortification for nutritional purposes due to the different toxicological profile and bioavailability of different selenium biotransformation products.

Phototoxic action of meloxicam contributes to dysregulation of redox homeostasis in normal human skin cells - Molecular and biochemical analysis of antioxidant enzymes in melanocytes and fibroblasts

The phototoxic effect of meloxicam (MLX) raises the question of the effect of the drug on the redox homeostasis of normal human skin cells. The main objective of the study was to analyze the effect of MLX and/or UVA radiation (UVAR) on the redox homeostasis of human normal skin cells - melanocytes and fibroblasts. MLX was found to affect the activity and expression of enzymes of the antioxidant system differently depending on the cell line used. The drug decreased the activity and expression of superoxide dismutase type 1 and 2 (SOD1 and SOD2), catalase (CAT) and glutathione peroxidase (GPx) in fibroblasts, while increasing the activity of these enzymes in melanocytes. UVA radiation enhanced the effects of the drug. In conclusion, MLX in combination with UVAR induces oxidative stress in melanocytes and fibroblasts, however, the analyses showed that the drug's effect the activity and expression of SOD, CAT and GPx differently, depending on the cell line. The observed dissimilarity between tested cell lines may result from the presence of melanin pigments.

The transcriptomic and biochemical responses of blood clams (Tegillarca granosa) to prolonged intermittent hypoxia

The blood clam (Tegillarca granosa), a marine bivalve of ecological and economic significance, often encounters intermittent hypoxia in mudflats and aquatic environments. To study the response of blood clam foot to prolonged intermittent hypoxia, the clams were exposed to intermittent hypoxia conditions (0.5 mg/L dissolved oxygen, with a 12-h interval) for 31 days. Initially, transcriptomic analysis was performed, uncovering a total of 698 differentially expressed genes (DEGs), with 236 upregulated and 462 downregulated. These genes show enrichments in signaling pathways related to glucose metabolism, sugar synthesis and responses to oxidative stress. Furthermore, the activity of the enzyme glutathione peroxidase (GPx) and the levels of gpx1 mRNA showed gradual increases, reaching their peak on the 13th day of intermittent hypoxia exposure. This observation suggests an indirect protective role of GPx against oxidative stress. The results of this study make a significantly contribute to our broader comprehensive of the physiological, biochemical responses, and molecular reactions governing the organization of foot muscle tissue in marine bivalves exposed to prolonged intermittent hypoxic conditions.

Degradation of low-density polyethylene by the bacterium Rhodococcus sp. C-2 isolated from seawater

Low-density polyethylene (LDPE), which accounts for 20% of the global plastic production, is discharged in great quantities into the ocean, threatening marine life and ecosystems. Marine microorganisms have previously been reported to degrade LDPE plastics; however, the exploration of strains and enzymes that degrade LDPE is still limited. Here, an LDPE-degrading bacterium was isolated from seawater of the Changjiang Estuary, China and identified as Rhodococcus sp. C-2, the relative abundance of which was dramatically enhanced during PE-degrading microbial enrichment. The strain C-2 exhibited the degradation of LDPE films, leading to their morphological deterioration, reduced hydrophobicity and tensile strength, weight loss, as well as the formation of oxygen-containing functional groups in short-chain products. Sixteen bacterial enzymes potentially involved in LDPE degradation were screened using genomic, transcriptomic, and degradation product analyses. Thereinto, the glutathione peroxidase GPx with exposed active sites catalyzed the LDPE depolymerization with the cooperation of its dissociated superoxide anion radicals. Furthermore, an LDPE degradation model involving multiple enzymes was proposed. The present study identifies a novel PE-degrading enzyme (PEase) for polyethylene bioremediation and promotes the understanding of LDPE degradation.

Age-Dependent Developmental Changes of Selenium Content and Selenoprotein Expression and Content in Longissimus Dorsi Muscle and Liver of Duroc Pigs

The trace element selenium (Se) plays a key role in development and various physiological processes, mainly through its transformation into selenoproteins. To investigate the developmental patterns of Se content and expression of selenoproteins, the liver and longissimus dorsi (LD) muscle of Duroc pigs were collected at 1, 21, 80, and 185 days of age (7 pigs each age) for the determination of Se content, mRNA expression of selenoproteins, and concentrations of glutathione peroxidase (GPX), thioredoxin reductase (TrxR or TXNRD), and selenoprotein P (SELP). The results showed that age significantly affected the expression of GPX1, GPX2, GPX3, TXNRD1, TXNRD2, TXNRD3, iodothyronine deiodinases 2 (DIO2), DIO3, SELF, SELH, SELM, SELP, SELS, SELW, and selenophosphate synthetase2 (SPS2) in the liver, as well as GPX3, GPX4, TXNRD1, TXNRD2, DIO2, DIO3, SELF, SELN, SELP, SELR, SELS, and SELW in the LD muscle of Duroc pigs. The concentrations of GPX, TrxR, and SELP showed an increasing trend with age, and they were positively correlated with Se content at 1, 21, and 185 days of age and negatively correlated at 80 days of age, both in the liver and LD muscle. The Se content decreased at the age of 80 days, especially in the LD muscle. In summary, our study revealed developmental changes in Se content and expression of selenoproteins in the liver and LD muscle of Duroc pigs at different growth stages, which provided a theoretical basis for further study of Se nutrition and functions of selenoproteins.

Arsenic exposure and increased C-reactive protein are independently associated with lower erythrocyte glutathione peroxidase activity in Bangladeshi children

Toxic metal contaminants present in food and water have widespread effects on health and disease. Chalcophiles, such as arsenic, cadmium, and mercury, show a high affinity to selenium and exposure to these metals could have a modulating effect on enzymes dependent on selenocysteine in their active sites. The aim of this study was to assess the influence of these metals on the activity of the selenoprotein glutathione peroxidase 1 (GPX1) in erythrocytes of 100 children residing in rural Bangladesh, where drinking water often contains arsenic. GPX1 expression, as measured using high-throughput immunoblotting, showed little correlation with GPX activity (rs = 0.02, p = 0.87) in blood samples. Toxic metals and selenium measured in erythrocytes using inductively coupled plasma mass spectrometry (ICP-MS) and C-reactive protein (CRP) measured in plasma, were all considered as effectors of this divergence in GPX enzymatic activity. Arsenic concentrations in erythrocytes were most influential for GPX1 activity (rs = -0.395, p < 0.0001), and CRP levels also negatively impacted GPX1 activity (rs = -0.443, p < 0.0001). These effects appear independent of each other as arsenic concentrations and CRP showed no correlation (rs = 0.124, p = 0.2204). Erythrocyte selenium, cadmium, and mercury did not show any correlation with GPX1 activity, nor with CRP or arsenic. Our findings suggest that childhood exposure to inorganic arsenic, as well as inflammation triggering the release of CRP, may negatively affect GPX1 activity in erythrocytes.

Genome-wide identification of Glutathione peroxidase (GPX) family genes and silencing TaGPX3.2A reduced disease resistance in wheat

Glutathione peroxidase (GPX) is a crucial enzyme that scavenges reactive oxygen species in plants, playing a vital role in enhancing plant stress resistance. In this study, we identified 14 glutathione peroxidase genes (TaGPXs) from common hexaploid wheat (Triticum aestivum L.). These genes were subsequently categorized into three distinct groups based on their phylogenetic relationships. Simultaneously, a preliminarily analysis was conducted on the protein characteristics, chromosome localization, gene structure, cis-regulatory elements and transcriptome. Using reverse transcription quantitative PCR to analyze the expression patterns of five GPX genes that were investigated under various exogenous hormone treatments. According to the qRT-PCR analysis, it indicated that TaGPX genes have the distinct expression patterns. The enzyme activities in transiently overexpressed Nicotiana benthamiana (TaGPX3.2A and TaGPX3.4A) leaves were measured under salt and drought stresses, showed that peroxidase (POD) exhibited higher enzyme activity under stresses. Silencing TaGPX3.2A by virus-induced gene silencing (VIGS) led to reduced resistance of wheat to Fusarium graminearum, indicating that TaGPX3.2A plays a crucial role in enhancing wheat resistance against F. graminearum. This research provides a foundational basis for further investigations on the functional characterization of TaGPXs family members. And in the future it is provides valuable resources for genetic improvement of wheat resistance.

Low Antioxidant Enzyme Levels and Oxidative Stress in Laryngopharyngeal Reflux (LPR) Patients

OBJECTIVE

Laryngopharyngeal reflux disease (LPR) is a characterized by symptoms different from gastroesophageal reflux disease (GERD). LPR can causes chronic mucosal inflammation which may lead to an increase in cytokine production, and a systemic decrease in antioxidant enzyme levels. Our aim in this study is to evaluate antioxidant enzyme levels in patients with LPR.

METHODS

Reflux Symptom Index (RSI) questionnaire, extraesophageal symptom questionnaire which is included in RSI and Reflux Finding Score (RFS) evaluation with 70° rigid laryngoscope were performed to patients who applied to the otolaryngology clinic with a typical LPR complaint, and 60 patients who had an RSI score above 13 and an RFS score above 7 were included in the study. Thirty people consisting of healthy volunteers were included in the control group. Antioxidant enzyme SOD, GSH-Px and CAT levels were measured in the blood serum of the patients and compared with the control group. Results obtained from biochemical tests were expressed as mean ± SE. Descriptive statistical methods (mean ± standard error) were used for the independent t test for the control and study group. P < 0.05 was considered statistically significant.

RESULTS

In the LPR group, 28 (46%) were women, 32 (53%) were men, and age range was 21-60, average age was 36.45 ± 1.147.There was no significant difference between LPR and control group in terms of age, gender and Body Mass Index (BMI). In the LPR group, the lowest score for RSI was 14 and the highest score was 39. The average RSI was 23.67. RFS ranges from 8-22. The mean RFS was 13.50. A highly significant statistical correlation was observed between RSI and total RFS (P < 0.001). There was a significant difference between the antioxidant enzyme levels of the control group and the LPR group. Antioxidant enzyme levels of the control group were SOD 274.10 ± 26.836 U / L, GSH-Px 174.20 ± 20.699 µU / mL and CAT 42.2898 ± 20.699 KU / L. Antioxidant enzyme level results of the LPR group were SOD 147 ± 14.022 U / L (P < 0.01), GSH-Px 88.28 ± 9.113 µU / mL (P < 0.01) and CAT 12.67 ± 0.799 KU / L (P < 0.001). The RSI results ranges from 4 to 39 and the RFS from 8 to 22. Antioxidant enzyme levels demonstrated fairly consistent reliability with individual variables from both RFS and RFS. There was also a highly significant statistical correlation between RSI and RFS.

CONCLUSION

We found that the antioxidant enzymes SOD, GPX and catalase enzyme levels were significantly lower in LPR patients. Treatment modalities to reduce oxidative stress (OS) in LPR should be investigated.

Evaluation of cyto-genotoxicity biomarkers, changes in histology and antioxidant defense system of Oreochromis niloticus induced by the industrial effluents

Aquatic pollution mainly by industrial effluents has been a major concern since a few decades. The current study evaluated cyto-genotoxicity of industrial effluents on Oreochromis niloticus exposed to sublethal levels by hematotoxicity, blood biochemistry analysis, micronucleus assay, antioxidants and cerebral toxicity. The significant elevation in differential leukocytes of exposed fish was indicative of infections and compromised immune system. The acute and chronic industrial effluent exposure caused significant decline in aspartame transaminase (AST) and alanine transaminase (ALT) and renal function enzymes. Necrosis, hyperplastic growth, hypertrophy and toxicant accumulation exhibited cerebral toxicity potential of industrial toxicants. A significant decrease in antioxidants, GSH, SOD and catalase (0.14, 0.66 and 1549 unit/mg protein) in chronic exposure group in comparison to 0.18, 2.83, 7680 and 6200.8 values of GSH, SOD, GPx and CAT, respectively. Results showed that acute and chronic industrial effluent exposure caused genotoxicity with higher frequencies of formation of micronuclei and cytokaryotic fusion.

Selenoneine-inspired selenohydantoins with glutathione peroxidase-like activity

Chronic diseases such as cystic fibrosis, inflammatory bowel diseases, rheumatoid arthritis, and cardiovascular illness have been linked to a decrease in selenium levels and an increase in oxidative stress. Selenium is an essential trace element that exhibits antioxidant properties, with selenocysteine enzymes like glutathione peroxidase being particularly effective at reducing peroxides. In this study, a series of synthetic organoselenium compounds were synthesized and evaluated for their potential antioxidant activities. The new selenohydantoin molecules were inspired by selenoneine and synthesized using straightforward methods. Their antioxidant potential was evaluated and proven using classical radical scavenging and metal-reducing methods. The selenohydantoin derivatives exhibited glutathione peroxidase-like activity, reducing hydroperoxides. Theoretical calculations using Density Functional Theory (DFT) revealed the selenone isomer to be the only one occurring in solution, with selenolate as a possible tautomeric form in the presence of a basic species. Cytocompatibility assays indicated that the selenohydantoin derivatives were non-toxic to primary human aortic smooth muscle cells, paving the way for further biological evaluations of their antioxidant activity. The results suggest that selenohydantoin derivatives with trifluoro-methyl (-CF3) and chlorine (-Cl) substituents have significant activities and could be potential candidates for further biological trials. These compounds may contribute to the development of effective therapies for chronic diseases such cardiovascular diseases.

TaGPX1-D overexpression provides salinity and osmotic stress tolerance in Arabidopsis

Glutathione peroxidases (GPXs) are known to play an essential role in guarding cells against oxidative stress by catalyzing the reduction of hydrogen peroxide and organic hydroperoxides. The current study aims functional characterization of the TaGPX1-D gene of bread wheat (Triticum aestivum) for salinity and osmotic stress tolerance. To achieve this, we initially performed the spot assays of TaGPX1-D expressing yeast cells. The growth of recombinant TaGPX1-D expressing yeast cells was notably higher than the control cells under stress conditions. Later, we generated transgenic Arabidopsis plants expressing the TaGPX1-D gene and investigated their tolerance to various stress conditions. The transgenic plants exhibited improved tolerance to both salinity and osmotic stresses compared to the wild-type plants. The higher germination rates, increased antioxidant enzymes activities, improved chlorophyll, carotenoid, proline and relative water contents, and reduced hydrogen peroxide and MDA levels in the transgenic lines supported the stress tolerance mechanism. Overall, this study demonstrated the role of TaGPX1-D in abiotic stress tolerance, and it can be used for improving the tolerance of crops to environmental stressors, such as salinity and osmotic stress in future research.

Improving Catalytic Activity, Acid-Tolerance, and Thermal Stability of Glutathione Peroxidase by Systematic Site-Directed Selenocysteine Incorporation

Glutathione peroxidase (GPx) is an important antioxidant enzyme. Selenocysteine (Sec)-containing GPxs (Sec-GPxs) are usually superior to their conventional cysteine-containing counterparts (Cys-GPxs), which make up the majority of the natural GPxs but display unsuitable activity and stability for industrial applications. This study first heterologously expressed and characterized a Cys-GPx from Lactococcus lactis (LlGPx), systematically exchanged all the three Cys to Sec and introduced an extra Sec. The results showed that the insertion of Sec at the active site could effectively increase the enzyme activity and confer a lower optimal pH value on the mutants. The double mutant C36U/L157U increased by 2.65 times (5.12 U/mg). The thermal stability of the C81U mutant was significantly improved. These results suggest that site-directed Sec incorporation can effectively improve the enzymatic properties of LlGPx, which may be also used for the protein engineering of other industrial enzymes containing catalytic or other functional cysteine residues.

Matched analysis of circulating selenium with the breast cancer selenotranscriptome: a multicentre prospective study

INTRODUCTION

Low serum selenium and altered tumour RNA expression of certain selenoproteins are associated with a poor breast cancer prognosis. Selenoprotein expression stringently depends on selenium availability, hence circulating selenium may interact with tumour selenoprotein expression. However, there is no matched analysis to date.

METHODS

This study included 1453 patients with newly diagnosed breast cancer from the multicentric prospective Sweden Cancerome Analysis Network - Breast study. Total serum selenium, selenoprotein P and glutathione peroxidase 3 were analysed at time of diagnosis. Bulk RNA-sequencing was conducted in matched tumour tissues. Fully adjusted Cox regression models with an interaction term were employed to detect dose-dependent interactions of circulating selenium with the associations of tumour selenoprotein mRNA expression and mortality.

RESULTS

237 deaths were recorded within ~ 9 years follow-up. All three serum selenium biomarkers correlated positively (p < 0.001). All selenoproteins except for GPX6 were expressed in tumour tissues. Single cell RNA-sequencing revealed a heterogeneous expression pattern in the tumour microenvironment. Circulating selenium correlated positively with tumour SELENOW and SELENON expression (p < 0.001). In fully adjusted models, the associations of DIO1, DIO3 and SELENOM with mortality were dose-dependently modified by serum selenium (p < 0.001, p = 0.020, p = 0.038, respectively). With increasing selenium, DIO1 and SELENOM associated with lower, whereas DIO3 expression associated with higher mortality. Association of DIO1 with lower mortality was only apparent in patients with high selenium [above median (70.36 µg/L)], and the HR (95%CI) for one-unit increase in log(FPKM + 1) was 0.70 (0.50-0.98).

CONCLUSIONS

This first unbiased analysis of serum selenium with the breast cancer selenotranscriptome identified an effect-modification of selenium on the associations of DIO1, SELENOM, and DIO3 with prognosis. Selenium substitution in patients with DIO1-expressing tumours merits consideration to improve survival.

Autoantibodies to selenoprotein P in chronic fatigue syndrome suggest selenium transport impairment and acquired resistance to thyroid hormone

Chronic Fatigue Syndrome (CFS) presents with symptoms of hypothyroidism, including mental and physical fatigue, poor sleep, depression, and anxiety. However, thyroid hormone (TH) profiles of elevated thyrotropin and low thyroxine (T4) are not consistently observed. Recently, autoantibodies to the Se transporter SELENOP (SELENOP-aAb) have been identified in Hashimoto's thyroiditis and shown to impair selenoprotein expression. We hypothesized that SELENOP-aAb are prevalent in CFS, and associate with reduced selenoprotein expression and impaired TH deiodination. Se status and SELENOP-aAb prevalence was compared by combining European CFS patients (n = 167) and healthy controls (n = 545) from different sources. The biomarkers total Se, glutathione peroxidase (GPx3) and SELENOP showed linear correlations across the samples without reaching saturation, indicative of Se deficiency. SELENOP-aAb prevalence was 9.6-15.6% in CFS versus 0.9-2.0% in controls, depending on cut-off for positivity. The linear correlation between Se and GPx3 activity was absent in SELENOP-aAb positive patients, suggesting impaired Se supply of kidney. A subgroup of paired control (n = 119) and CSF (n = 111) patients had been characterized for TH and biochemical parameters before. Within this subgroup, SELENOP-aAb positive patients displayed particularly low deiodinase activity (SPINA-GD index), free T3 levels, total T3 to total T4 (TT3/TT4) and free T3 to free T4 (FT3/FT4) ratios. In 24 h urine, iodine concentrations were significantly lower in SELENOP-aAb positive than in SELENOP-aAb negative patients or controls (median (IQR); 43.2 (16.0) vs. 58.9 (45.2) vs. 89.0 (54.9) μg/L). The data indicate that SELENOP-aAb associate with low deiodination rate and reduced activation of TH to active T3. We conclude that a subset of CFS patients express SELENOP-aAb that disturb Se transport and reduce selenoprotein expression in target tissues. Hereby, TH activation decreases as an acquired condition not reflected by thyrotropin and T4 in blood. This hypothesis opens new diagnostic and therapeutic options for SELENOP-aAb positive CFS, but requires clinical evidence from intervention trials.

The effect of micronutrient supplementation on bioavailability, antioxidants activity, and weight gain in response to Infectious Bursal Disease vaccination in commercial broilers

The effect of supplementing organic selenium and zinc on bioavailability, oxidative stress, weight gain in commercial broilers was studied. A total of 180-day-old chicks were divided into six groups: NSUV (Not supplemented, unvaccinated), NSV (Not supplemented, vaccinated), VS (vaccinated, supplemented selenium), VZ (vaccinated supplemented zinc), VSZ (vaccinated supplemented selenium and zinc), UVSZ (unvaccinated supplemented selenium and zinc). 1 mg/kg selenium and 60 mg/kg zinc were added to the feed of supplemented groups. The concentration of selenium (0.05 ± 0.00 mg/L) in VS and zinc (0.66 ± 0.13 mg/L) in VZ were lower on day 27 post-vaccination compared to day 10 (VS= 0.07 ± 0.01 mg/L; VZ= 1.46 ± 0.30 mg/L). Glutathione peroxidase and catalase concentrations were highest in the supplemented groups compared to unsupplemented groups on day 27 post vaccination, expressing a similar trend with the micronutrients. There was no difference (P ≥ 0.05) in the glutathione concentration between all groups except on day 27 post vaccination where SZV group was significantly higher (P=0.02) compared to the NSV group. Catalase concentration was significantly decreased in the NSV group compared to SZV (P=0.04) on day 27 post vaccination. The NSV group (1.64 ± 0.13 kg) weighed significantly lower (P=0.02) than the VSZ (2.00 ± 0.12 kg) in the fifth week, while on the sixth week, the SZV group gained the highest weight (2.04 ± 0.18 kg). The supplementation of organic selenium and zinc in broilers increased the serum micronutrients bioavailability, decreased oxidative stress, increased weight gain, thus, enhancing immunity in the broilers.

Involvement of antioxidant enzymes in Parkinson's disease

Similar to many other diseases, the etiology of Parkinson's disease (PD) is multifactorial and includes both genetic and environmental factors. Exposure to pesticides and the production of reactive oxygen species (ROS) in the body, mainly in electron transporter complexes 1 and 2 in the inner mitochondrial membrane, are two primary environmental risk factors for this disease. Increased accumulation of ROS and oxidative stress (OS) trigger a series of reactions that can lead to the aggregation of misfolded proteins, DNA damage, autophagy, and apoptosis, which may adversely affect cell function. These processes cause diseases such as coronary artery disease (CAD), Alzheimer's disease (AD), and PD. As indicated in previous studies, ROS is considered a critical regulator in the progression of PD. The human body contains several antioxidant molecules, such as vitamin A, vitamin C, bilirubin, and uric acid, as well as antioxidant enzymes including paraoxonase (PON), glutathione reductase (GR), glutathione peroxidase (GPx), catalase (CAT), and superoxide dismutase (SOD). Therefore, based on the canonical function of the antioxidant enzymes in PD, In the present review, we attempted to examine the function of antioxidant enzymes in PD.

Blood Selenium and Serum Glutathione Peroxidase Levels Were Associated with Serum β-Amyloid in Older Adults

BACKGROUND

Studies have established the association between blood β-amyloid (Aβ) levels and Alzheimer's disease, but population-based studies concerning the association between selenium (Se) and Aβ levels in blood samples are very limited. Therefore, we explored the association in an elderly population with Se status and serum Aβ measures.

METHODS

A cross-sectional study on 469 elderly individuals from four rural counties with diverse soil Se levels was carried out. Fasting blood Se, serum selenoprotein P (SELENOP), and glutathione peroxidase (GPX), serum Aβ42, and Aβ40 were measured. Quantile regression models were used to determine the associations of blood Se, serum GPX, and SELENOP with Aβ levels.

RESULTS

Significant negative associations were observed between blood Se and serum Aβ42 and Aβ40 levels at all percentiles (P < 0.05). The associations were generally stronger at higher Aβ42 and Aβ40 percentiles than lower Aβ42 and Aβ40 percentiles. Blood Se was positively associated with serum Aβ42/Aβ40 ratio at 25th, 50th, and 75th percentiles. Significant positive associations were observed between serum GPX and Aβ42 and Aβ40 levels at all percentiles (P < 0.05). The positive associations were generally stronger at higher Aβ42 and Aβ40 percentiles than at lower percentiles. Serum GPX was negatively associated with Aβ42/Aβ40 ratio at 25th, 50th, 75th, and 95th percentiles. No associations with serum SELENOP and Aβ levels were observed.

CONCLUSIONS

Our results suggest that higher Se levels are associated with lower serum Aβ42 and Aβ40 levels and with higher Aβ42/Aβ40 ratio, and the results are specific for different selenoproteins.

Flavonoid glycoside fraction of Ginkgo biloba extract modulates antioxidants imbalance in vanadium-induced brain damage

Human and animal diseases have always been reported to be treated by medicinal herbs owing to their constituents. Excess sodium metavanadate is a potential environmental toxin when consumed and could induce oxidative damage leading to various neurological disorders and Parkinsons-like diseases. This study is designed to investigate the impact of the flavonoid Glycoside Fraction of Ginkgo Biloba Extract (GBE) (at 30 mg/kg body weight) on vanadium-treated rats. Animals were divided randomly into four groups: Control (Ctrl, normal saline), Ginkgo Biloba (GIBI, 30mg/kg BWT), Vanadium (VANA, 10 mg/kg BWT) and Vanadium + Ginkgo biloba (VANA + GIBI). Markers of oxidative stress (Glutathione Peroxidase and Catalase) were assessed and found to be statistically increased with GIBI when compared with CTRL and treatment groups. Results from routine staining revealed that the control and GIBI group had a normal distribution of cells and a pronounced increase in cell count respectively compared to the VANA group. When compared to the VANA group, the NeuN photomicrographs revealed that the levels of GIBI were within the normal range (***p < 0.001; ** p < 001). The treatment with GIBI showed a better response by increasing the neuronal cells in the VANA+GIBI when compared with the VANA group. The NLRP3 Inflammasome photomicrographs denoted that there was a decrease in NLRP3-positive cells in the control and GIBI groups. The treatment group shows fewer cells compared to that of the VANA group. The treatment group shows fewer cells compared to that of the VANA group. The findings of the study confirmed that ginkgo biloba extract via its flavonoid glycoside fraction has favorable impacts in modulating vanadium-induced brain damage with the potential ability to lower antioxidant levels and reduce neuroinflammation.

Hypothermia Treatment after Hypoxia-Ischemia in Glutathione Peroxidase-1 Overexpressing Mice

The developing brain is uniquely susceptible to oxidative stress, and endogenous antioxidant mechanisms are not sufficient to prevent injury from a hypoxic-ischemic challenge. Glutathione peroxidase (GPX1) activity reduces hypoxic-ischemic injury. Therapeutic hypothermia (HT) also reduces hypoxic-ischemic injury, in the rodent and the human brain, but the benefit is limited. Here, we combined GPX1 overexpression with HT in a P9 mouse model of hypoxia-ischemia (HI) to test the effectiveness of both treatments together. Histological analysis showed that wild-type (WT) mice with HT were less injured than WT with normothermia. In the GPX1-tg mice, however, despite a lower median score in the HT-treated mice, there was no significant difference between HT and normothermia. GPX1 protein expression was higher in the cortex of all transgenic groups at 30 min and 24 h, as well as in WT 30 min after HI, with and without HT. GPX1 was higher in the hippocampus of all transgenic groups and WT with HI and normothermia, at 24 h, but not at 30 min. Spectrin 150 was higher in all groups with HI, while spectrin 120 was higher in HI groups only at 24 h. There was reduced ERK1/2 activation in both WT and GPX1-tg HI at 30 min. Thus, with a relatively moderate insult, we see a benefit with cooling in the WT but not the GPX1-tg mouse brain. The fact that we see no benefit with increased GPx1 here in the P9 model (unlike in the P7 model) may indicate that oxidative stress in these older mice is elevated to an extent that increased GPx1 is insufficient for reducing injury. The lack of benefit of overexpressing GPX1 in conjunction with HT after HI indicates that pathways triggered by GPX1 overexpression may interfere with the neuroprotective mechanisms provided by HT.

The contribution of glutathione peroxidases to chloroplast redox homeostasis in Arabidopsis

Oxidizing signals mediated by the thiol-dependent peroxidase activity of 2-Cys peroxiredoxins (PRXs) plays an essential role in fine-tuning chloroplast redox balance in response to changes in light intensity, a function that depends on NADPH-dependent thioredoxin reductase C (NTRC). In addition, plant chloroplasts are equipped with glutathione peroxidases (GPXs), thiol-dependent peroxidases that rely on thioredoxins (TRXs). Despite having a similar reaction mechanism than 2-Cys PRXs, the contribution of oxidizing signals mediated by GPXs to the chloroplast redox homeostasis remains poorly known. To address this issue, we have generated the Arabidopsis (Arabidopsis thaliana) double mutant gpx1gpx7, which is devoid of the two GPXs, 1 and 7, localized in the chloroplast. Furthermore, to analyze the functional relationship of chloroplast GPXs with the NTRC-2-Cys PRXs redox system, the 2cpab-gpx1gpx7 and ntrc-gpx1gpx7 mutants were generated. The gpx1gpx7 mutant displayed wild type-like phenotype indicating that chloroplast GPXs are dispensable for plant growth at least under standard conditions. However, the 2cpab-gpx1gpx7 showed more retarded growth than the 2cpab mutant. The simultaneous lack of 2-Cys PRXs and GPXs affected PSII performance and caused higher delay of enzyme oxidation in the dark. In contrast, the ntrc-gpx1gpx7 mutant combining the lack of NTRC and chloroplast GPXs behaved like the ntrc mutant indicating that the contribution of GPXs to chloroplast redox homeostasis is independent of NTRC. Further supporting this notion, in vitro assays showed that GPXs are not reduced by NTRC but by TRX y2. Based on these results, we propose a role for GPXs in the chloroplast redox hierarchy.

Development of an assay pipeline for the discovery of novel small molecule inhibitors of human glutathione peroxidases GPX1 and GPX4

Selenoprotein glutathione peroxidases (GPX), like ubiquitously expressed GPX1 and the ferroptosis modulator GPX4, enact antioxidant activities by reducing hydroperoxides using glutathione. Overexpression of these enzymes is common in cancer and can be associated with the development of resistance to chemotherapy. GPX1 and GPX4 inhibitors have thus shown promise as anti-cancer agents, and targeting other GPX isoforms may prove equally beneficial. Existing inhibitors are often promiscuous, or modulate GPXs only indirectly, so novel direct inhibitors identified through screening against GPX1 and GPX4 could be valuable. Here, we developed optimized glutathione reductase (GR)-coupled GPX assays for the biochemical high-throughput screen (HTS) of almost 12,000 compounds with proposed mechanisms of action. Initial hits were triaged using a GR counter-screen, assessed for isoform specificity against an additional GPX isoform, GPX2, and were assessed for general selenocysteine-targeting activity using a thioredoxin reductase (TXNRD1) assay. Importantly, 70% of the GPX1 inhibitors identified in the primary screen, including several cephalosporin antibiotics, were found to also inhibit TXNRD1, while auranofin, previously known as a TXNRD1 inhibitor, also inhibited GPX1 (but not GPX4). Additionally, every GPX1 inhibitor identified (including omapatrilat, tenatoprazole, cefoxitin and ceftibuten) showed similar inhibitory activity against GPX2. Some compounds inhibiting GPX4 but not GPX1 or GPX2, also inhibited TXNRD1 (26%). Compounds only inhibiting GPX4 included pranlukast sodium hydrate, lusutrombopag, brilanestrant, simeprevir, grazoprevir (MK-5172), paritaprevir, navitoclax, venetoclax and VU0661013. Two compounds (metamizole sodium and isoniazid sodium methanesulfate) inhibited all three GPXs but not TXNRD1, while 2,3-dimercaptopropanesulfonate, PI4KIII beta inhibitor 3, SCE-2174 and cefotetan sodium inhibited all tested selenoproteins (but not GR). The detected overlaps in chemical space suggest that the counter screens introduced here should be imperative for identification of specific GPX inhibitors. With this approach, we could indeed identify novel GPX1/GPX2- or GPX4-specific inhibitors, thus presenting a validated pipeline for future identification of specific selenoprotein-targeting agents. Our study also identified GPX1/GPX2, GPX4 and/or TXNRD1 as targets for several previously developed pharmacologically active compounds.

Short-chain per- and polyfluoralkyl substances (PFAS) effects on oxidative stress biomarkers in human liver, kidney, muscle, and microglia cell lines

Long-chain per- and polyfluoralkyl substances (PFAS) are ubiquitous contaminants implicated in the induction of intracellular reactive oxygen species (ROS), compromising antioxidant defense mechanisms in vitro and in vivo. While a handful of studies have assessed oxidative stress effects by PFAS, few specifically address short-chain PFAS. We conducted an evaluation of oxidative stress biomarkers in vitro following exposures to low (1 nM) and high (1 μM) concentrations of five short-chain PFAS compounds: perfluorobutanesulfonic acid (PFBS), perfluorohexanoic acid (PFHxA), [undecafluoro-2-methyl-3-oxahexanoic acid (HFPO-DA)], 6:2 fluorotelomer alcohol (6:2 FTOH) and perfluorohexanesulfonic acid (PFHxS). We conducted experiments in human kidney (HEK293-hTLR2), liver (HepaRG), microglia (HMC-3), and muscle (RMS-13) cell lines. Fluorescence microscopy measurements in HepaRG cells indicated ROS generation in cells exposed to PFBS and PFHxA for 24 h. Antioxidant enzyme activities were determined following 24 h short-chain PFAS exposures in HepaRG, HEK293-hTLR2, HMC-3, and RMS-13. Notably, exposure to PFBS for 24 h increased the activity of GPX in all four cell types at 1 μM and 1 nM in HepaRG and RMS-13 cells. Every short-chain PFAS evaluated, except for PFHxS, increased the activity of at least one antioxidant enzyme. To our knowledge, this is the first study of its kind to explore antioxidant defense alterations to microglia and muscle cell lines by PFAS. The findings of this study hold great potential to contribute to the limited understanding of short-chain PFAS mechanisms of toxicity and provide data necessary to inform the human health risk assessment process.

Influence of Dietary Selenium on the Oxidative Stress in Horses

The objective of this review was to analyze the effect of dietary selenium on oxidative stress in horses by considering past and recent bibliographic sources. Some research was done on oxidative stress, related pathologies and how selenium regulates oxidative stress. Oxidizing molecules are molecules that can accept electrons from the substances with which they react. Oxidizing These molecules, of oxidizing, are found naturally in any organism, and there are antioxidant mechanisms that regulate its activity. However, when the body is stressed, oxidizing molecules outperform the antioxidants, causing an imbalance known as oxidative stress. Among antioxidant molecules, selenium can act as an important antioxidant in the body. The antioxidant activity is based on an enzyme called glutathione peroxidase, which depends on selenium and controls the activity of oxidizing molecules.

Mitochondrial H2O2 metabolism as central event of heart complex I syndrome in early diabetes

Hydrogen peroxide is the main metabolite effective in redox regulation and it is considered an insulinomimetic agent, with insulin signalling being essential for normal mitochondrial function in cardiomyocytes. Therefore, the aim of this work was to deeply analyse the heart mitochondrial H₂O₂ metabolism, in the early stage of type 1 diabetes. Diabetes was induced by Streptozotocin (STZ, single dose, 60 mg × kg^-1, ip.) in male Wistar rats and the animals were sacrificed 10 days after injection. Mitochondrial membrane potential and ATP production, using malate-glutamate as substrates, in the heart of diabetic animals were like the ones observed in control group. Mn-SOD activity was lower (15%) in the heart of diabetic rats even though its expression was increased (29%). The increment in heart mitochondrial H₂O₂ production (117%) in diabetic animals was accompanied by an enhancement in the activities and expressions of glutathione peroxidase (26% and 42%) and of catalase (200% and 133%), with no changes in the peroxiredoxin activity, leading to [H₂O₂]_ss ∼40 nM. Heart mitochondrial lipid peroxidation and protein nitration were higher in STZ-injected animals (45% and 42%) than in control group. The mitochondrial membrane potential and ATP production preservation suggest the absence of irreversible damage at this early stage of diabetes 1. The increase in mitochondrial [H₂O₂]_ss above the physiological range, but still below supraphysiological concentration (∼100 nM) seems to be part of the adaptive response triggered in cardiomyocytes due to the absence of insulin. The signs of mitochondrial dysfunction observed in this very early stage of diabetes are consistent with the mitochondrial entity called ″complex I syndrome″.

Selenium homeostasis in human brain cells: Effects of copper (II) and Se species

BACKGROUND

Both essential trace elements selenium (Se) and copper (Cu) play an important role in maintaining brain function. Homeostasis of Cu, which is tightly regulated under physiological conditions, seems to be disturbed in Alzheimer´s (AD) and Parkinson´s disease (PD) patients. Excess Cu promotes the formation of oxidative stress, which is thought to be a major cause for development and progression of neurological diseases (NDs). Most selenoproteins exhibit antioxidative properties and may counteract oxidative stress. However, expression of selenoproteins is altered under conditions of Se deficiency. Serum Se levels are decreased in AD and PD patients suggesting Se as an important factor in the development and progression of NDs. The aim of this study was to elucidate the interactions between Cu and Se in human brain cells particularly with respect to Se homeostasis.

METHODS

Firstly, modulation of Se status by selenite or SeMet were assessed in human astrocytes and human differentiated neurons. Therefore, cellular total Se content, intra- and extracellular selenoprotein P (SELENOP) content, and glutathione peroxidase (GPX) activity were quantified. Secondly, to investigate the impact of Cu on these markers, cells were exposed to copper(II)sulphate (CuSO₄) for 48 h. In addition, putative protective effects of Se on Cu-induced toxicity, as measured by cell viability, DNA damage, and neurodegeneration were investigated.

RESULTS

Modulation of cellular Se status was strongly dependent on Se species. In detail, SeMet increased total cellular Se and SELENOP content, whereas selenite led to increased GPX activity and SELENOP excretion. Cu treatment resulted in 133-fold higher cellular Cu concentration with a concomitant decrease in Se content. Additionally, SELENOP excretion was suppressed in both cell lines, while GPX activity was diminished only in astrocytes. These effects of Cu could be partially prevented by the addition of Se depending on the cell line and Se species used. While Cu-induced oxidative DNA damage could not be prevented by addition of Se regardless of chemical species, SeMet protected against neurite network degeneration triggered by Cu.

CONCLUSION

Cu appears to negatively affect Se status in astrocytes and neurons. Especially with regard to an altered homeostasis of those trace elements during aging, this interaction is of high physiological relevance. Increasing Cu concentrations associated with decreased selenoprotein expression or functionality might be a promoting factor for the development of NDs.

Inhibition of erythrocyte's catalase, glutathione peroxidase or peroxiredoxin 2 - Impact on cytosol and membrane

Catalase (CAT), glutathione peroxidase (GPx) and Prx2 (peroxiredoxin 2) are the main antioxidant enzymatic defenses of erythrocytes. They prevent and minimize oxidative injuries in red blood cell (RBC) components, which are continuously exposed to oxidative stress (OS). The crosstalk between CAT, GPx and Prx2 is still not fully disclosed, as well as why these typically cytoplasmic enzymes bind to the RBC membrane. Our aim was to understand the interplay between CAT, GPx and Prx2 in the erythrocyte's cytosol and membrane. Under specific (partial) inhibition of each enzyme and increasing H₂O₂-induced OS conditions, we evaluated the enzyme activities and amounts, the binding of CAT, GPx and Prx2 to RBC membrane, and biomarkers of OS, such as the reduced and oxidized glutathione levels, thiobarbituric acid reactive substances (TBARS) levels, membrane bound hemoglobin and total antioxidant status. Our results support the hypothesis that when high levels of H₂O₂ get within the erythrocyte, CAT is the main player in the antioxidant protection of the cell, while Prx2 and GPx have a less striking role. Moreover, we found that CAT, appears to have more importance in the antioxidant protection of cytoplasm than of the membrane components, since when the activity of CAT is disturbed, GPx and Prx2 are both activated in the cytosol and mobilized to the membrane. In more severe OS conditions, the antioxidant activity of GPx is more significant at the membrane, as we found that GPx moves from the cytosol to the membrane, probably to protect it from lipid peroxidation.

Chemical pollution and ecotoxicological effects of high-density polyethylene microplastics in Mytilus galloprovincialis from two Italian lagoon ecosystems

Transitional water ecosystems have low water exchanges and can trap chemicals and microplastics (MPs). In this study, MPs, trace elements, polycyclic aromatic hydrocarbon-PHAs levels and the oxidative stress response were assessed in Mytilus galloprovincialis from two Italian lagoon ecosystems (Orbetello and Varano). In addition, the ecotoxicological effects induced by the exposure of M. galloprovincialis to high-density polyethylene-HDPE MPs were also determined. Levels of trace elements were almost always comparable among the sites, whereas MPs were found only in mussels from Orbetello. PAHs were always under the limit of quantification. Glutathione peroxidase and malondialdehyde levels were significantly higher in mussels from Varano. As regard the exposure test, it was found a significant effect of treatment, site and their interaction on mortality and biochemical biomarkers in both fed and unfed mussels. However, principal component analysis suggests similar effects of both color and nourishment condition on biochemical biomarkers. These findings warrant further investigation.

Targeting the nervous system of the parasitic worm, Haemonchus contortus with quercetin

Prevalence of infection, limited choice of drugs, and emerging resistance against contemporary medications lead to a pressing need to develop new anthelmintic drugs and drug targets. However, little understanding of worms' physiology has substantially delayed the process. Here, we are reporting the tissue morphology of Haemonchus contortus, intestinal parasitic helminths found in small ruminants, and targeting its nervous system with quercetin, a naturally occurring flavonoid. Quercetin showed anthelmintic activity against all of the developmental stages of H. contortus. Further, histological analysis demonstrated damage to various body parts, including isthmus, brut, pseudocoele, and other organs. Mechanistic studies revealed the generation of oxidative stress and alterations in the activities of the stress response enzymes, such as catalase, superoxide dismutase, and glutathione peroxidase. Moreover, the time-dependent imaging of reactive oxygen species (ROS) generated due to quercetin treatment disclosed neuropils as the primary targets of quercetin in adult worms, which eventually lead to the paralysis and death of the worms. Thus, this work demonstrates that the nervous system of the parasitic helminth, H. contortus, is a novel target of the drug quercetin.

Study of the inhibition effects on glutathione peroxidase immobilized on MNPs using a stopped-flow microfluidic system

A stopped-flow microfluidic system to monitor glutathione peroxidase (GPx) activity and evaluate potential inhibitors of the enzyme has been developed based on the integration of the microfluidic chip in the reaction/detection zone. This integration supposes the physical alignment at the optimal location of the microfluidic channel, both the magnetically retained enzyme microreactor (MREµR) and the remote luminescence detection using a focused bifurcated fiber optic bundle (BFOB) connected to a conventional spectrofluorometer detector. The method is based on the coupling of two competitive oxidative chemical reactions, in which glutathione (GSH) and homovanillic acid (HVA) competed for their interaction with hydrogen peroxide in the presence of the magnetically retained GPx-MNPs. The biocatalytic reaction was followed by monitoring the fluorescence of the biphenyl-HVA dimer formed. The dynamic range of the calibration graph was 0.45-10 µmol L^-1, expressed as GSH concentration with a detection limit of 0.1 µmol L^-1 (r² = 0.9954, n = 10, r = 3). The precision expressed as the relative standard deviation (RSD%) was between 0.5 and 3.9%. The stopped-flow microfluidic system showed a sampling frequency of 25 h^-1. The method was applied to the study of GPx inhibition provided by three inhibitory compounds, two metallic ions Hg(II) and Cu(II) and t-butyl hydroperoxide, and their presence in liquid samples, as water, milk, and edible oil. Recovery values between 88.7 and 99.4% were achieved in all instances.

The antioxidant glutathione

Reduced glutathione (GSH) is an essential non-enzymatic antioxidant in mammalian cells. GSH can act directly as an antioxidant to protect cells against free radicals and pro-oxidants, and as a cofactor for antioxidant and detoxification enzymes such as glutathione peroxidases, glutathione S-transferases, and glyoxalases. Glutathione peroxidases detoxify peroxides by a reaction that is coupled to GSH oxidation to glutathione disulfide (GSSG). GSSG is converted back to GSH by glutathione reductase and cofactor NADPH. GSH can regenerate vitamin E following detoxification reactions of vitamin E with lipid peroxyl radicals (LOO). GSH is a cofactor for GST during detoxification of electrophilic substances and xenobiotics. Dicarbonyl stress induced by methylglyoxal and glyoxal is alleviated by glyoxalase enzymes and GSH. GSH regulates redox signaling through reversible oxidation of critical protein cysteine residues by S-glutathionylation. GSH is involved in other cellular processes such as protein folding, protecting protein thiols from oxidation and crosslinking, degradation of proteins with disulfide bonds, cell cycle regulation and proliferation, ascorbate metabolism, apoptosis and ferroptosis.

Side-by-side comparison of recombinant human glutathione peroxidases identifies overlapping substrate specificities for soluble hydroperoxides

Five out of eight human glutathione peroxidases (GPXs) are selenoproteins, representing proteins that contain selenium as part of the amino acid selenocysteine. The GPXs are important for reducing hydroperoxides in a glutathione-consuming manner and thus regulate cellular redox homeostasis. GPX1, GPX2, and GPX4 represent the three main cytosolic GPXs, but they differ in their expression patterns with GPX1 and GPX4 being expressed ubiquitously, whereas GPX2 is mainly expressed in epithelial cells. GPX1 and GPX2 have been described to reduce soluble hydroperoxides, while GPX4 reduces complex lipid hydroperoxides, thus protecting cells from lipid peroxidation and ferroptosis. But most of these data are derived from cells that are devoid of one of the isoforms and thus, compensation or other cellular effects might affect the conclusions. So far, the use of isolated recombinant human selenoprotein glutathione peroxidases in pure enzyme assays has not been employed to study their substrate specificities side by side. Using recombinant GPX1, GPX2, and GPX4 produced in E. coli we here assessed their GPX activities by a NADPH-consuming glutathione reductase-coupled assay with 17 different peroxides (all at 50 μM) as substrates. GPX4 was clearly the only isoform able to reduce phosphatidylcholine hydroperoxide. In contrast, small soluble hydroperoxides such as H₂O₂, cumene hydroperoxide, and tert-butyl hydroperoxide were reduced by all three isoforms, but with approximately 10-fold higher efficiency for GPX1 in comparison to GPX2 and GPX4. Also, several fatty acid-derived hydroperoxides were reduced by all three isoforms and again GPX1 had the highest activity. Interestingly, the stereoisomerism of the fatty acid-derived hydroperoxides clearly affected the activity of the GPX enzymes. Overall, distinct substrate specificity is obvious for GPX4, but not so when comparing GPX1 and GPX2. Clearly GPX1 was the most potent isoform of the three GPXs in terms of turnover in reduction of soluble and fatty-acid derived hydroperoxides.

Antioxidant effects of Se-glutathione peroxidase in alcoholic liver disease

Oxidative damage induced by ethanol and its metabolites is one of the factors that fuels the development of alcoholic liver disease (ALD). Selenium (Se) is an effective cofactor for glutathione peroxidase (GPx), and has antioxidant effects that improve ALD. In patients with ALD, ethanol-induced oxidative damage inhibits the synthesis of related Se-containing proteins such as: selenoprotein P (Sepp1), albumin (ALB), and GPx in the liver, thus decreasing the overall Se level in patients. Both Se deficiency and excess can affect the expression of GPx, resulting in damage to the antioxidant defense system. This damage enhances oxidative stress by increasing the levels of reactive oxygen species (ROS) in the body, which aggravates the inflammatory response, lipid metabolism disorder, and lipid peroxidation and worsens ALD symptoms. A cascade of oxidative damages caused by ALD will deplete selenium deposition in the body, stimulate the expression of Gpx1, Sepp1, and Gpx4, and thus mobilize systemic selenoproteins, which can restore GPx activity in the hepatocytes of ALD patients, reduce the levels of reactive oxygen species and alleviate oxidative stress, the inflammatory response, lipid metabolism disorder, and lipid peroxidation, thus helping to mitigate ALD. This review provides a reference for future ALD studies that evaluate the regulation of Se levels and contributes to studies on the potential pathological mechanisms of Se imbalance in ALD.

Plant thiol peroxidases as redox sensors and signal transducers in abiotic stress acclimation

The temporal and spatial patterns of reactive oxygen species (ROS) in cells and tissues decisively determine the plant acclimation response to diverse abiotic and biotic stresses. Recent progress in developing dynamic cell imaging probes provides kinetic information on changes in parameters like H₂O₂, glutathione (GSH/GSSG) and NAD(P)H/NAD(P)⁺, that play a crucial role in tuning the cellular redox state. Central to redox-based regulation is the thiol-redox regulatory network of the cell that integrates reductive information from metabolism and oxidative ROS signals. Sensitive proteomics allow for monitoring changes in redox-related posttranslational modifications. Thiol peroxidases act as sensitive peroxide and redox sensors and play a central role in this signal transduction process. Peroxiredoxins (PRX) and glutathione peroxidases (GPX) are the two main thiol peroxidases and their function in ROS sensing and redox signaling in plants is emerging at present and summarized in this review. Depending on their redox state, PRXs and GPXs act as redox-dependent binding partners, direct oxidants of target proteins and oxidants of thiol redox transmitters that in turn oxidize target proteins. With their versatile functions, the multiple isoforms of plant thiol peroxidases play a central role in plant stress acclimation, e.g. to high light or osmotic stress, but also in ROS-mediated immunity and development.

Role and mechanism of REG2 depletion in insulin secretion augmented by glutathione peroxidase-1 overproduction

We previously reported a depletion of murine regenerating islet-derived protein 2 (REG2) in pancreatic islets of glutathione peroxidase-1 (Gpx1) overexpressing (OE) mice. The present study was to explore if and how the REG2 depletion contributed to an augmented glucose stimulated insulin secretion (GSIS) in OE islets. After we verified a consistent depletion (90%, p < 0.05) of REG2 mRNA, transcript, and protein in OE islets compared with wild-type (WT) controls, we treated cultured and perifused OE islets (70 islets/sample) with REG2 (1 μg/ml or ml · min) and observed 30-40% (p < 0.05) inhibitions of GSIS by REG2. Subsequently, we obtained evidences of co-immunoprecipitation, cell surface ligand binding, and co-immunofluorescence for a ligand-receptor binding between REG2 and transmembrane, L-type voltage-dependent Ca2+ channel (CaV1.2) in beta TC3 cells. Mutating the C-type lectin binding domain of REG2 or deglycosylating CaV1.2 removed the inhibition of REG2 on GSIS and(or) the putative binding between the two proteins. Treating cultured OE and perifused WT islets with REG2 (1 μg/ml or ml · min) decreased (p < 0.05) Ca2+ influx triggered by glucose or KCl. An intraperitoneal (ip) injection of REG2 (2 μg/g) to OE mice (6-month old, n = 10) decreased their plasma insulin concentration (46%, p < 0.05) and elevated their plasma glucose concentration (25%, p < 0.05) over a 60 min period after glucose challenge (ip, 1 g/kg). In conclusion, our study identifies REG2 as a novel regulator of Ca2+ influx and insulin secretion, and reveals a new cascade of GPX1/REG2/CaV1.2 to explain how REG2 depletion in OE islets could decrease its binding to CaV1.2, resulting in uninhibited Ca2+ influx and augmented GSIS. These findings create new links to bridge redox biology, tissue regeneration, and insulin secretion.

Diphenyl diselenide modulate antioxidant status, inflammatory and redox-sensitive genes in diesel exhaust particle-induced neurotoxicity

This study seeks to determine the influence of diphenyl diselenide (DPDSe) on redox status, inflammatory and redox-sensitive genes in diesel exhaust particle (DEP)-induced neurotoxicity in male albino rats. Male Wistar albino rats were administered nasally with DEP (30 and 60 μg/kg) and treated with intraperitoneal administration of 10 mg/kg DPDSe. Non-enzymatic (lipid peroxidation and conjugated diene concentrations) and enzymatic (catalase, superoxide dismutase, glutathione peroxidase) antioxidant indices and activity of acetylcholinesterase enzyme were evaluated in brain tissues of the rats. Furthermore, the expression of genes linked to oxidative stress (HO-1, Nrf2), pro-inflammatory (NF-KB, IL-8, TNF-α) anti-inflammatory (IL-10) and brain-specific (GFAP, ENO-2) genes were also determined. The results indicated that DPDSe caused a notable reduction in the high levels of thiobarbituric acid reactive substances and conjugated diene observed in the brain of DEP-administered rats. DPDSe also reversed the observed reduction in catalase, superoxide dismutase and glutathione peroxidase enzyme activities in the brain of DEP-administered rats. Lastly, the downregulation of genes associated with redox homeostasis, anti-inflammatory and brain-specific genes and upregulation of pro-inflammatory genes observed in the DEP-treated groups were ameliorated by DPDSe. The immediate restoration of altered biochemical conditions and molecular expression in the brain of DEP-treated rats by DPDSe further validates its use as a promising therapeutic candidate for restoring neurotoxicity linked with DEP-induced oxidative stress.

Genetic polymorphism impact superoxide dismutase and glutathione peroxidase activity in charcoal workers

BACKGROUND

Incomplete combustion of wood releases toxic chemicals. Exposure to these chemicals during charcoal production can modulate redox status of cellular system which may further lead to genomic instability and of antioxidant enzymes. Genetic polymorphism may alter the functioning properties of these enzymes and modulate the response to oxidative stress.

METHODS

In this study, we analyzed the link between genetic polymorphism and enzyme activity for antioxidant enzymes: MnSOD and GPx-1 in charcoal workers and control population. This study included 77 charcoal workers and 79 demographically matched healthy control subjects. This association was studied using multiple linear regression, adjusted for confounding factors viz. age, consumption habits and exposure duration.

RESULTS

SOD activity was lower for TT genotype (3.47 ± 0.66; 5.92 ± 1.08) versus CC genotype (3.47 ± 0.66; 6.67 ± 1.60) in control and charcoal workers respectively. Significant lower GPx-1 activity was found in leu/leu genotype (7.25 ± 0.38; 3.59 ± 0.57) when compared to pro/pro genotype (7.78 ± 0.59; 4.28 ± 0.71) and pro/leu genotype (8.48 ± 0.34; 4.30 ± 0.76) in control population and charcoal workers respectively. A significant difference in the levels of 1-Hydroxypyrene (biomarker of exposure) and SOD and GPx-1 activity (biomarkers of oxidative stress) was evident in exposed group in comparison to the control one.

CONCLUSION

Collectively, our findings suggested that PAH influenced the mode of action of SOD and GPx-1 which were impacted by polymorphism in SOD and GPx-1 gene. Hence, polymorphism of MnSOD and GPx-1 genes were found to play a modulatory role in human susceptibility to oxidative damage induced by wood smoke in charcoal workers.

New insights on selenoproteins and neuronal function

Fifty years have passed since the discovery of the first selenoprotein by Rotruck and colleagues. In that time, the essential nature of selenium has come to light including the dependence of the brain on selenium to function properly. Animal models have shown that a lack of certain selenoproteins in the brain is detrimental for neuronal health, sometimes leading to neurodegeneration. There is also potential for selenoprotein-mediated redox balance to impact neuronal activity, including neurotransmission. Important insights on these topics have been gained over the past several years. This review briefly summarizes the known roles of specific selenoproteins in the brain while highlighting recent advancements regarding selenoproteins in neuronal function. Hypothetical models of selenoprotein function and emerging topics in the field are also provided.

Delayed increase of plasma selenoproteins and absence of side effect induced by infusion of pharmacological dose of sodium selenite in septic shock: Secondary analysis of a multicenter, randomized controlled trial

BACKGROUND

In sepsis, neutrophil respiratory bursts participate in endothelium damage, the first step to multiple organ failure. In plasma two antioxidant selenoenzymes, which protect the endothelium, decrease: selenoprotein-P, and to a lesser extent glutathione peroxidase (GPX3). Sodium selenite (Na₂SeO₃) is a Se donor, but also an oxidant chemotherapy drug depending on its concentration. In a previous published study, Na₂SeO₃ continuous infusion in septic shock patients at a pharmacological dose of 4 mg¹ Se/day on day-1, followed by a high nutritional dose of 1 mg Se/day during 9 days, showed no beneficial effect on weaning of catecholamine nor on survival. In this ancillary study, we report clinical and biological effects of such continuous infusion of Na₂SeO_3. METHODS: This was a multicenter, placebo-controlled, double-blind study on 60 patients. Na₂SeO₃ or placebo in continuous infusion as described above. Evolution with time of plasma Se, selenoprotein-P, GPX3, Organ dysfunction (sequential organ failure assessment SOFA scores, including PaO2/FiO2, for respiratory failure, and plasma lactate) and quality of life at 6 months (by SF36 scores) were analyzed using two-way (time, treatment) non-parametric repeated-measures analysis of variance (Friedman test).

MAIN RESULTS

At baseline, plasma Se was about a quarter of reference values. From baseline to day-4 plasma Se, selenoprotein-P and GPX3 significantly increased by 3.9, 2.7 and 1.8 respectively in the Na₂SeO₃ group as compared with placebo and remained elevated by 2.3, 2.7 and 2.1 at day-14 respectively (p < 0.001). Na₂SeO₃ did not affect global and organ by organ SOFA Scores and plasma lactate concentration at day-1 and later up to day-14. The evolution of PaO2/FiO2 until day-14 was similar in the two groups. Quality of life in the surviving patients at 6 months was similar between the two groups.

CONCLUSION

Continuous infusion of Na₂SeO₃ at 4 mg Se at day-1 seems to have neither beneficial nor toxic effect at day-1 or later and induces a late increase of selenoprotein-P at day-4. Preclinical studies are required to confirm the use of Na₂SeO₃ as a cytotoxic drug against neutrophils and protection of the endothelium by selenoprotein-P.

Characteristics of glutathione peroxidase gene and its responses to ammonia-N stress in razor clam Sinonovacula constricta

Glutathione peroxidase (GPX) is a crucial enzyme in the antioxidant defense system. However, the previous studies on the structure and functions of mollusk GPX genes are still very limited. Here, we investigated the GPX gene from Sinonovacula constricta (Sc-GPX), and its expression profiles, protein localization, gene function and association with ammonia tolerance. The full length of sequence of Sc-GPX was 1781 bp, containing an open reading frame (ORF) of 588 bp encoding 195 amino acids. Quantitative expression of seven adult tissues showed that Sc-GPX was most abundant in hepatopancreas, followed by gills. Furthermore, the enzyme activity of Sc-GPX in hepatopancreas increased significantly under different ammonia concentrations (100, 140, and 180 mg/L) (P < 0.01). Further, we explored the mRNA expression level, histological structure and histo-cellular localization in gills and hepatopancreas of Sc-GPX under 140 mg/L ammonia stress. The mRNA expression level in gills and hepatopancreas of Sc-GPX increased significantly (P < 0.05) and immunohistochemistry results suggested that the columnar cells of gills filaments and the endothelial cells of hepatopancreas were the major sites for the action of Sc-GPX protein. In addition, we performed western blotting (WB), RNA interference (RNAi) and single nucleotide polymorphisms (SNPs) in the hepatopancreas of Sc-GPX under ammonia stress (140 mg/L). WB results indicated that the protein expression of Sc-GPX increased significantly (P < 0.01) after ammonia challenge. In addition, expression of Sc-GPX mRNA were significantly downregulated at 24 and 48 h after RNAi (P < 0.01). The association analysis between ammonia-tolerance group and control group identified six SNPs in coding sequence (CDS) of Sc-GPX from 449 individuals. Among them, c.162A > C was missense mutation, which lead to the amino acid change from Lys to Asn. These findings revealed that Sc-GPX may play a critical role in clam ammonia detoxification.

Native SodB Overexpression of Synechocystis sp. PCC 6803 Improves Cell Growth Under Alcohol Stresses Whereas Its Gpx2 Overexpression Impacts on Growth Recovery from Alcohol Stressors

To overcome the limited resistance to alcohol stress, genetically engineered Synechocystis sp. PCC 6803 strains with overexpressions of genes related with the ROS detoxification system (sodB and gpx2, which encode superoxide dismutase and glutathione peroxidase, respectively) were developed. Three engineered strains including a sodB-overexpressing strain (OE + S), a gpx2-overexpressing strain (OE + G), and a sodB/gpx2-overexpressing strain (OE + SG) grew similarly as wild-type control under normal condition. When compared to wild-type control, OE + S and OE + SG strains grew faster for 4 days under 2.0% (v/v) ethanol and 0.3% (v/v) n-butanol conditions, as well as having higher chlorophyll a levels. On the other hand, the prominent growth recovery of OE + G and OE + SG was noted within 4 days in normal BG₁₁ medium after treating cells with high alcohol stresses for 1 h, in particular 15% ethanol and 2.5% n-butanol. Under 4 days of recovery from butanol stress, specific levels of intracellular pigments including chlorophyll a and carotenoids were dramatically increased in all modified strains. The overexpression of antioxidant genes then revealed a significant improvement of alcohol tolerance in Synechocystis sp. PCC 6803.

Cold stratification-induced dormancy removal in apple (Malus domestica Borkh.) seeds is accompanied by an increased glutathione pool in embryonic axes

A reduced form of glutathione (GSH) is an essential metabolite that participates in the control of reactive oxygen species (ROS) levels in cells. GSH plays a pivotal role in seed biology as a modulator of seed viability and germination. The GSH:GSSG ratio and half-cell reduction potential (E_GSSG/2GSH) serve as indicators of the oxidative status in seeds. Apple (Malus domestica Borkh.) seeds are deeply dormant, and this state is removed by long-term cold stratification. The aim of our work was to examine the modification of GSH and GSSG content, GSH:GSSG ratio and E_GSSG/2GSH in the embryonic axes isolated from apple seeds subjected to cold stratification for 7, 14, 21 and 40 d. Our data indicated that cold stratification increased the generation of free radicals in the embryonic axes, which correlated with an alteration in the expression of genes encoding Rboh, particularly RbohC. GSH and GSSG levels increased during prolonged cold stratification of apple seeds. This was accompanied by the modification of glutathione reductase and glutathione peroxidase-like activities, which did not match their transcript levels. The steady-state GSH:GSSG ratio and E_GSSG/2GSH in the axes of embryos subjected to cold stratification indicated no impact of the dormancy removal treatment on apple seed viability. We suggest that the glutathione system is an important component of the redox network and is involved in the management of the seed transition from dormant to nondormant states.

Gene expression and alterations of antioxidant enzymes in spleen of rats exposed to fluoride

BACKGROUND

Fluorosis is a slow and progressive process causing metabolic, functional and structural damages affecting many tissues particularly musculoskeletal, dental systems, kidney, liver and brain. It can be rapidly absorbed by passive diffusion through the stomach, small intestine, mouth and skin. Endemic fluorosis is connected to the high concentration of fluoride in drinking water. The present study aimed to evaluate the toxic effects of sodium fluoride (NaF) on splenic activity at the biochemical and molecular level.

MATERIALS AND METHODS

Wistar albino rats were randomly assigned to three groups. The control rats were given 1 ml deionized water orally for 40 days. Groups II and III were administered 300 and 600 mg NaF/kg b.w. /day for the same period. Animals were sacrificed under ether anaesthesia. The spleen tissue was excised and used for biochemical and real-time PCR analysis. The level of fluoride, malondialdehyde (MDA), reduced glutathione (GSH) and activities of different antioxidant enzymes such as cytosolic copper/zinc superoxide dismutase (Cu/Zn SOD), glutathione peroxidase (GPx) and catalase (CAT) were determined. The analysis of gene expression of Cu/Zn SOD, GPx and CAT in spleen was done using Real-time PCR.

RESULTS

The levels of fluoride and MDA were significantly (P < 0.0001) increased where as GSH content decreased significantly (P < 0.0001) in the spleen of fluoridated rats. The activities of antioxidant enzymes viz; Cu/Zn SOD, GPx and CAT declined significantly (P < 0.0001) compared to the control. Pearson's bivariate correlation and simple linear regression analysis exhibited strong positive correlation between levels of splenic tissue fluoride and MDA(r = 0.985) while negative correlations existed in GSH (r = -0.907) as well as activities of Cu/Zn SOD (r = -0.982), GPx (r = -0.966), and CAT (r = -0.935). The gene expression of Cu/Zn SOD, GPx and CAT were significantly (P < 0.0001) reduced in fluorotic rats.

CONCLUSION

It is concluded that fluoride intoxication leads to the development of oxidative stress and damaging the cellular metabolism resulting in the declined ability of free radical scavengers along with increased level of MDA and decreased expression level of antioxidant genes which helps to understand the possible mechanism of fluoride-induced toxicity at the molecular level.

Elevated Selenoprotein P Levels in Thalassemia Major Patients

INTRODUCTION

Previous studies have measured selenium levels and glutathione peroxidase 3 (GPX3) activity in patients with thalassemia major (TM). However, Selenoprotein P (SEPP), which is responsible for the storage and transport of selenium, has not been studied in thalassemia patients. This study aims to correlate thyroid functions of TM patients with their SEPP and GPX3 levels.

MATERIALS AND METHODS

Eighty subjects (40 controls, 40 TM patients) were included in this study. GPX3 and SEPP concentrations were measured in all subjects using sandwich ELISA. Iron, ferritin, urinary iodine, thyroxine (T₄), triiodothyronine (T₃), thyrotropin (TSH), anti-thyroid peroxidase (anti-TPO), and anti-human thyroglobulin (anti-hTG) concentrations were also measured.

RESULTS

Mean SEPP concentration was higher in the TM group compared to the control group. A slight elevation in GPX3 levels was also observed in thalassemia patients, yet it was not statistically significant. In both TM patients and controls, ferritin was inversely correlated with free T₄ concentration and GPX3 was inversely correlated with free T₄ and T₃ concentrations. There was also a negative correlation between SEPP and TSH concentrations in healthy subjects.

CONCLUSION

This is the first study, which has measured SEPP concentrations in thalassemia patients. SEPP levels were higher in TM patients compared to controls. Correlations between thyroid hormones and selenoproteins may indicate that selenium is necessary for thyroid function. Detailed studies are required to elaborate the role of SEPP in thyroid metabolism in thalassemia patients.

Genome-wide mining of gpx gene family provides new insights into cadmium stress responses in common carp (Cyprinus carpio)

Glutathione peroxidase (Gpx) is an important member of antioxidant enzymes, which can play a vital role in metabolizing reactive oxygen species (ROS) and in maintaining cell homeostasis. In order to study the evolutionary dynamics of gpx gene family in allotetraploid fish species, we identified a total of 14 gpx genes in common carp Cyprinus carpio, while 9 gpx genes were discovered in the diploid progenitor-like species Poropuntius huangchuchieni. Comparative genomic analysis and phylogenetic analysis revealed that the common carp gpx genes had significant expansion and were divided into five distinct subclades. Exon-intron distribution patterns and conserved motif analysis revealed highly conserved evolutionary patterns. Transcript profiles suggested that different gpx genes had specific patterns of regulation during early embryonic development. In adult tissues, gpx genes had a relatively broad expression distribution, most of which were highly expressed in the gills, intestines, and gonads. RT-qPCR studies showed that most gpx genes were downregulated during the initial cd²⁺ treatment stage. Dietary supplementation of Bacillus coagulans at different concentrations (Group 2 of 1.0 × 10⁷ cfu/g, Group 3 of 1.0 × 10⁸ cfu/g, and Group 4 of 1.0 × 10⁹ cfu/g) induced different regulatory responses of gpx subclades. This result suggested that the appropriate concentration of B. coagulans can improve gpx gene expression when exposed to heavy metal cadmium treatment, which may play a vital role in the resistance to oxidative stress and immune responses. This study has expanded our understanding of the functional evolution of the gpx gene family in common carp.

Antioxidant Activities and Selenogene Transcription in the European Sea Bass (Dicentrarchus labrax) Liver Depend, in a Non-linear Manner, on the Se/Hg Molar Ratio of the Feeds

Feeding 3.9 and 6.7 mg Hg/kg (Se/Hg molar ratios of 0.8 and 0.4, respectively) for 14 days negatively affected Dicentrarchus labrax growth and total DNTB- and thioredoxin-reductase (TrxR) activities and the transcription of four redox genes (txn1, gpx1, txnrd3, and txnrd2) in the liver, but a diet with 0.5 mg Hg/kg (Se/Hg molar ratio 6.6) slightly increased both reductase activities and the transcription of txn1, gpx1, and txnrd2. Feeding 6.7 mg Hg/kg for 53 days downregulated the genes of the thioredoxin system (txn1, txnrd3, and txnrd2) but upregulated gpx1, confirming the previously proposed complementarity among the antioxidant systems. Substitution of 20% of the feed by thawed white fish (hake) slightly counteracted the negative effects of Hg. The effects were not statistically significant and were dependent, in a non-linear manner, on the Se/Hg molar ratio of the feed but not on its Hg concentration. These results stress the need to consider the Se/Hg molar ratio of the feed/food when evaluating the toxicity of Hg.