Selenoprotein Gene Nomenclature

Understanding the Roles of Selenium on Thyroid Hormone-Induced Thermogenesis in Adipose Tissue

Brown adipose tissue (BAT) and white adipose tissue (WAT) are known to regulate lipid metabolism. A lower amount of BAT compared to WAT, along with adipose tissue dysfunction, can result in obesity. Studies have shown that selenium supplementation protects against adipocyte dysfunction, decreases WAT triglycerides, and increases BAT triiodothyronine (T3). In this review, we discuss the relationship between selenium and lipid metabolism regulation through selenoprotein deiodinases and the role of deiodinases and thyroid hormones in the induction of adipose tissue thermogenesis. Upon 22 studies included in our review, we found that studies investigating the relationship between selenium and deiodinases demonstrated that selenium supplementation affects the iodothyronine deiodinase 2 (DIO2) protein and the expression of its associated gene, DIO2, proportionally. However, its effect on DIO1 is inconsistent while its effect on DIO3 activity is not detected. Studies have shown that the activity of deiodinases especially DIO2 protein and DIO2 gene expression is increased along with other browning markers upon white adipose tissue browning induction. Studies showed that thermogenesis is stimulated by the thyroid hormone T3 as its activity is correlated to the expression of other thermogenesis markers. A proposed mechanism of thermogenesis induction in selenium supplementation is by autophagy control. However, more studies are needed to establish the role of T3 and autophagy in adipose tissue thermogenesis, especially, since some studies have shown that thermogenesis can function even when T3 activity is lacking and studies related to autophagy in adipose tissue thermogenesis have contradictory results.

Targeted Restoration of GPX3 Attenuates Renal Ischemia/Reperfusion Injury by Balancing Selenoprotein Expression and Inhibiting ROS-mediated Mitochondrial Apoptosis

BACKGROUND

Renal ischemia/reperfusion (IR) injury is the leading cause of acute kidney injury in both autologous and transplanted kidneys. Low-level glutathione peroxidase 3 (GPX3) is associated with renal IR injury. The exact mechanism of targeted GPX3 restoration in renal IR injury has yet to be determined.

METHODS

The distribution of GPX3 in different tissues and organs of the body was investigated. The level of GPX3 in renal IR injury was assessed. To confirm the action of GPX3 and its mechanisms, IR models were used to introduce adeno-associated virus 9 containing GPX3, as well as hypoxia/reoxygenation-exposed normal rat kidney cells that consistently overexpressed GPX3. Reverse molecular docking was used to confirm whether GPX3 was a target of ebselen.

RESULTS

GPX3 is abundant in the kidneys and decreases in expression during renal IR injury. GPX3 overexpression reduced renal IR injury and protected tubular epithelial cells from apoptosis. Proteomics analysis revealed a strong link between GPX3 and mitochondrial signaling, cellular redox state, and different expression patterns of selenoproteins. GPX3 inhibited reactive oxygen species-induced mitochondrial apoptosis and balanced the disordered expression of selenoproteins. GPX3 was identified as a stable selenoprotein that interacts with ebselen. Ebselen enhanced the level of GPX3 and reduced IR-induced mitochondrial damage and renal dysfunction.

CONCLUSIONS

Targeted restoration of GPX3 attenuates renal IR injury by balancing selenoprotein expression and inhibiting reactive oxygen species-mediated mitochondrial apoptosis, indicating that GPX3 could be a potential therapeutic target for renal IR injury.

Iron, Copper, and Selenium: Cancer's Thing for Redox Bling

Cells require micronutrients for numerous basic functions. Among these, iron, copper, and selenium are particularly critical for redox metabolism, and their importance is heightened during oncogene-driven perturbations in cancer. In this review, which particularly focuses on iron, we describe how these micronutrients are carefully chaperoned about the body and made available to tissues, a process that is designed to limit the toxicity of free iron and copper or by-products of selenium metabolism. We delineate perturbations in iron metabolism and iron-dependent proteins that are observed in cancer, and describe the current approaches being used to target iron metabolism and iron-dependent processes.

Green Synthesis of Selenium Nanoparticles From Clove and Their Toxicity Effect and Anti-angiogenic, Antibacterial and Antioxidant Potential

Introduction  Nanoparticles, owing to their minuscule size, have become pivotal in diverse scientific endeavors, presenting unique characteristics with applications spanning medicine to environmental science. Selenium nanoparticles (SeNPs) exhibit potential in diverse biomedical uses. Aim This research investigates the potential anti-inflammatory and anticancer properties of SeNPs, which are synthesized using the green synthesis method. This eco-friendly approach aligns with sustainable practices and utilizes clove extract (Syzygium aromaticum). Materials and methods Clove extract facilitates SeNP synthesis via sodium selenite reduction. The characterization methods comprised Fourier-transform infrared (FTIR) spectroscopy, UV-VIS spectroscopy, and scanning electron microscopy (SEM). Assessments covered antioxidant properties, chorioallantoic membrane assay (CAM) assay for antiangiogenic effects, toxicity evaluation, and antibacterial assays. Results Successful synthesis of SeNPs was verified by a UV-visible absorption peak at 256 nm and FTIR peaks around 3500-500 cm -1, and the spherical morphology was confirmed by SEM analysis with EDAX, which indicated the presence of SeNPs and their unique properties. Phytochemical substances are active chemicals that contribute to the properties of SeNPs. The SeNPs exhibited antioxidant activity with an IC50 value of 0.437 µg/mL and antibacterial properties against bacterial pathogen Salmonella species, with a zone of inhibition measuring 19 mm. The CAM assay demonstrated possible antiangiogenic actions, and toxicity testing on Artemia nauplii showed biocompatibility. Conclusion This study underscores the efficient synthesis of SeNPs using clove extract, emphasizing their potential applications. The notable properties of SeNPs emphasize their promise for diverse biomedical and environmental uses.

Metabolism-related signalling pathways involved in the pathogenesis and development of metabolic dysfunction-associated steatotic liver disease

Metabolic dysfunction-associated steatotic liver disease (MASLD) which formerly known as non-alcoholic fatty liver disease (NAFLD) is one of the causes of liver cirrhosis. Currently, a growing number of liver cirrhosis cases develop on the basis of MASLD, and the pathogenesis of MASLD remains unclear. This paper reviews the research progress on the involvement of different metabolism-related signalling pathways in the pathogenesis and development of MASLD.

Current Understanding of Human Polymorphism in Selenoprotein Genes: A Review of Its Significance as a Risk Biomarker

Selenium has been proven to influence several biological functions, showing to be an essential micronutrient. The functional studies demonstrated the benefits of a balanced selenium diet and how its deficiency is associated with diverse diseases, especially cancer and viral diseases. Selenium is an antioxidant, protecting the cells from damage, enhancing the immune system response, preventing cardiovascular diseases, and decreasing inflammation. Selenium can be found in its inorganic and organic forms, and its main form in the cells is the selenocysteine incorporated into selenoproteins. Twenty-five selenoproteins are currently known in the human genome: glutathione peroxidases, iodothyronine deiodinases, thioredoxin reductases, selenophosphate synthetase, and other selenoproteins. These proteins lead to the transport of selenium in the tissues, protect against oxidative damage, contribute to the stress of the endoplasmic reticulum, and control inflammation. Due to these functions, there has been growing interest in the influence of polymorphisms in selenoproteins in the last two decades. Selenoproteins' gene polymorphisms may influence protein structure and selenium concentration in plasma and its absorption and even impact the development and progression of certain diseases. This review aims to elucidate the role of selenoproteins and understand how their gene polymorphisms can influence the balance of physiological conditions. In this polymorphism review, we focused on the PubMed database, with only articles published in English between 2003 and 2023. The keywords used were "selenoprotein" and "polymorphism". Articles that did not approach the theme subject were excluded. Selenium and selenoproteins still have a long way to go in molecular studies, and several works demonstrated the importance of their polymorphisms as a risk biomarker for some diseases, especially cardiovascular and thyroid diseases, diabetes, and cancer.

Selenium Nanoparticles in Protecting the Brain from Stroke: Possible Signaling and Metabolic Mechanisms

Strokes rank as the second most common cause of mortality and disability in the human population across the world. Currently, available methods of treating or preventing strokes have significant limitations, primarily the need to use high doses of drugs due to the presence of the blood-brain barrier. In the last decade, increasing attention has been paid to the capabilities of nanotechnology. However, the vast majority of research in this area is focused on the mechanisms of anticancer and antiviral effects of nanoparticles. In our opinion, not enough attention is paid to the neuroprotective mechanisms of nanomaterials. In this review, we attempted to summarize the key molecular mechanisms of brain cell damage during ischemia. We discussed the current literature regarding the use of various nanomaterials for the treatment of strokes. In this review, we examined the features of all known nanomaterials, the possibility of which are currently being studied for the treatment of strokes. In this regard, the positive and negative properties of nanomaterials for the treatment of strokes have been identified. Particular attention in the review was paid to nanoselenium since selenium is a vital microelement and is part of very important and little-studied proteins, e.g., selenoproteins and selenium-containing proteins. An analysis of modern studies of the cytoprotective effects of nanoselenium made it possible to establish the mechanisms of acute and chronic protective effects of selenium nanoparticles. In this review, we aimed to combine all the available information regarding the neuroprotective properties and mechanisms of action of nanoparticles in neurodegenerative processes, especially in cerebral ischemia.

Sodium Selenite Prevents Matrine-Induced Nephrotoxicity by Suppressing Ferroptosis via the GSH-GPX4 Antioxidant System

Matrine (MT), an active ingredient derived from Sophor flavescens Ait, is used as a therapeutic agent to treat liver disease and cancer. However, the serious toxic effects of MT, including nephrotoxicity, have limited its clinical application. Here, we explored the involvement of ferroptosis in MT-induced kidney injury and evaluated the potential efficacy and underlying mechanism of sodium selenite (SS) in attenuating MT-induced nephrotoxicity. We found that MT not only disrupts renal structure in mice but also induces the death of NRK-52E cells. Additionally, MT treatment resulted in significant elevations in ferrous iron, reactive oxygen species (ROS) and lipid peroxidation levels, accompanied by decreases in glutathione (GSH) and glutathione peroxidase (GPx) levels. SS effectively mitigated the alterations in ferroptosis-related indicators caused by MT and prevented MT-induced nephrotoxicity as effectively as Fer-1 in vivo and in vitro. SS also reversed the MT-induced reduction in GPX4, CTH and xCT protein levels. However, the glutathione peroxidase 4 (GPX4) inhibitor RSL3 and knockdown of GPX4, CTH, or xCT via siRNA abolished the protective effect of SS against MT-induced nephrotoxicity, indicating that SS exhibited antiferroptotic effects via the GSH-GPX4 antioxidant system. Overall, MT-induced ferroptosis triggers nephrotoxicity, and SS is a promising therapeutic drug for alleviating MT-induced renal injury by activating the GSH-GPX4 axis.

Ameliorating Effect of Sodium Selenite on Developmental and Molecular Response of Bovine Cumulus-Oocyte Complexes Matured in Vitro Under Heat Stress Condition

Selenium (Se), an essential trace element, plays an important role in the antioxidative defense mechanism, and it has been proven to improve fertility and reproductive efficiency in dairy cattle. The present study evaluated the potential protective action of Se supplement of in vitro maturation (IVM) media on the maturation and subsequent development of bovine cumulus-oocyte complexes (COCs) exposed to heat stress (HS). The treatment with Se improved the viability of cumulus cells (CCs) and oocytes (P < 0.05). The proportion of oocytes reached metaphase II (MII) and those arrested at metaphase I (MI) was greater and lower in treatment than control respectively (P < 0.05). Supplementation with Se increased the percentage of cleaved embryos, total blastocysts, and blastocyst/cleavage ratio (P < 0.05). Moreover, the upregulation of CCND1, SEPP1, GPX-4, SOD, CAT, and downregulation of GRP78, CHOP, and BAX in both Se-treated CCs and oocytes were recorded. The upregulation of NRF2 was detected in Se-treated CCs other than in oocytes, which showed upregulation of IGF2R and SOX-2 as the markers of quality as well. Se supplement in IVM media improved the viability, maturation, and the level of transcripts related to antioxidant defense and quality of heat-treated oocytes, which coincided with greater subsequent development outcomes. Se ameliorated the viability of CCs along with upregulation of antioxidative candidate gene expression and downregulation of apoptosis-related ones to support their protective role on restoring the quality of oocytes against compromising effects of HS.

Biology and Roles in Diseases of Selenoprotein I Characterized by Ethanolamine Phosphotransferase Activity and Antioxidant Potential

Selenoprotein I (SELENOI) has been demonstrated to be an ethanolamine phosphotransferase (EPT) characterized by a nonselenoenzymatic domain and to be involved in the main synthetic branch of phosphatidylethanolamine (PE) in the endoplasmic reticulum. Therefore, defects of SELENOI may affect the health status through the multiple functions of PE. On the other hand, selenium (Se) is covalently incorporated into SELENOI as selenocysteine (Sec) in its peptide, which forms a Sec-centered domain as in the other members of the selenoprotein family. Unlike other selenoproteins, Sec-containing SELENOI was formed at a later stage of animal evolution, and the high conservation of the structural domain for PE synthesis across a wide range of species suggests the importance of EPT activity in supporting the survival and evolution of organisms. A variety of factors, such as species characteristics (age and sex), diet and nutrition (dietary Se and fat intakes), SELENOI-specific properties (tissue distribution and rank in the selenoproteome), etc., synergistically regulate the expression of SELENOI in a tentatively unclear interaction. The N- and C-terminal domains confer 2 distinct biochemical functions to SELENOI, namely PE regulation and antioxidant potential, which may allow it to be involved in numerous physiological processes, including neurological diseases (especially hereditary spastic paraplegia), T cell activation, tumorigenesis, and adipocyte differentiation. In this review, we summarize advances in the biology and roles of SELENOI, shedding light on the precise regulation of SELENOI expression and PE homeostasis by dietary Se intake and pharmaceutical or transgenic approaches to modulate the corresponding pathological status.

Selenium metabolism heterogeneity in pan-cancer: insights from bulk and single-cell RNA sequencing

BACKGROUND

Selenium, a natural microelement with both nutritional and toxicological properties, is intertwined with tumorigenesis and progression. However, it is not fully understood how selenium metabolism affects immune response and cancer biology.

METHODS

We estimated selenium metabolism by Gene Set Enrichment Analysis (GSEA) to delineate the selenium metabolism landscape using The Cancer Genome Atlas (TCGA), Genotype-Tissue Expression (GTEx), Cancer Cell Line Encyclopedia (CCLE) and a integrated pan-cancer single-cell dataset. We systematically explored the prognostic implications of selenium metabolism and selenium-related regulatory patterns. The therapeutic value of selenium metabolism was explored through machine learning and examined in several immunotherapy cohorts. The heterogeneity and underlying mechanism of selenium metabolism were investigated by cell‒cell communication analysis at the single-cell level.

RESULTS

A GSEA analysis based on 86 genes was used to evaluate the selenium metabolism landscape. The selenium metabolism score exhibited prognostic value in predicting the lower risk of mortality, possibly due to its correlation with multiple cancer hallmarks, including a positive correlation with complement (R = 0.761, P < 0.001), inflammatory response (R = 0.663, P < 0.001), apoptosis (R = 0.626, P < 0.001), hypoxia (R = 0.587, P < 0.001), reactive oxygen species (ROS) (R = 0.558, P < 0.001), and interferon gamma response (R = 0.539, P < 0.001). We also observed heterogeneity in the relationship between selenium metabolism and immunity across different cancers. Based on selenium-related genes, we constructed a machine learning model with area under the ROC curve (AUC) of 0.82 in predicting immune checkpoint inhibitor (ICI)-based immunotherapy response. Single-cell selenium metabolism quantification revealed that adjacent and tumor tissues had higher selenium metabolism compared with normal tissues, especially in epithelial cells, fibroblasts and macrophages. The communication between high-selenium epithelium and high-selenium fibroblast was significantly higher than other cells, especially in cytokines, chemokines, collagen, Wnt, VEGF, IGF and FGF pathways.

CONCLUSION

Our study provides a comprehensive landscape of selenium metabolism levels and diverse regulatory patterns in different cancers, deepening the understanding of selenium's roles in tumorigenesis and immunity.

Reactive X (where X = O, N, S, C, Cl, Br, and I) species nanomedicine

Reactive oxygen, nitrogen, sulfur, carbonyl, chlorine, bromine, and iodine species (RXS, where X = O, N, S, C, Cl, Br, and I) have important roles in various normal physiological processes and act as essential regulators of cell metabolism; their inherent biological activities govern cell signaling, immune balance, and tissue homeostasis. However, an imbalance between RXS production and consumption will induce the occurrence and development of various diseases. Due to the considerable progress of nanomedicine, a variety of nanosystems that can regulate RXS has been rationally designed and engineered for restoring RXS balance to halt the pathological processes of different diseases. The invention of radical-regulating nanomaterials creates the possibility of intriguing projects for disease treatment and promotes advances in nanomedicine. In this comprehensive review, we summarize, discuss, and highlight very-recent advances in RXS-based nanomedicine for versatile disease treatments. This review particularly focuses on the types and pathological effects of these reactive species and explores the biological effects of RXS-based nanomaterials, accompanied by a discussion and the outlook of the challenges faced and future clinical translations of RXS nanomedicines.

Taming the Biological Activity of Pd(II) and Pt(II) Complexes with Triazolato "Protective" Groups: 1H, 77Se Nuclear Magnetic Resonance and X-ray Crystallographic Model Studies with Selenocysteine to Elucidate Differential Thioredoxin Reductase Inhibition

The biological activity of Pd(II) and Pt(II) complexes toward three different cancer cell lines as well as inhibition of selenoenzyme thioredoxin reductase (TrxR) was modulated in an unexpected way by the introduction of triazolate as a "protective group" to the inner metal coordination sphere using the iClick reaction of [M(N3)(terpy)]PF6 [M = Pd(II) or Pt(II) and terpy = 2,2':6',2″-terpyridine] with an electron-poor alkyne. In a cell proliferation assay using A549, HT-29, and MDA-MB-231 human cancer cell lines, the palladium compound was significantly more potent than the isostructural platinum analogue and exhibited submicromolar activity on the most responsive cell line. This difference was also reflected in the inhibitory efficiency toward TrxR with IC50 values of 0.1 versus 5.4 μM for the Pd(II) and Pt(II) complexes, respectively. UV/Vis kinetic studies revealed that the Pt compound binds to selenocysteine faster than to cysteine [k = (22.9 ± 0.2)·10-3 vs (7.1 ± 0.2)·10-3 s-1]. Selective triazolato ligand exchange of the title compounds with cysteine (Hcys) and selenocysteine (Hsec)─but not histidine (His) and 9-ethylguanine (9EtG)─was confirmed by 1H, 77Se, and 195Pt NMR spectroscopy. Crystal structures of three of the four ligand exchange products were obtained, including [Pt(sec)(terpy)]PF6 as the first metal complex of selenocysteine to be structurally characterized.

A homozygous mutation in the human selenocysteine tRNA gene impairs UGA recoding activity and selenoproteome regulation by selenium

The selenocysteine (Sec) tRNA (tRNA[Ser]Sec) governs Sec insertion into selenoproteins by the recoding of a UGA codon, typically used as a stop codon. A homozygous point mutation (C65G) in the human tRNA[Ser]Sec acceptor arm has been reported by two independent groups and was associated with symptoms such as thyroid dysfunction and low blood selenium levels; however, the extent of altered selenoprotein synthesis resulting from this mutation has yet to be comprehensively investigated. In this study, we used CRISPR/Cas9 technology to engineer homozygous and heterozygous mutant human cells, which we then compared with the parental cell lines. This C65G mutation affected many aspects of tRNA[Ser]Sec integrity and activity. Firstly, the expression level of tRNA[Ser]Sec was significantly reduced due to an altered recruitment of RNA polymerase III at the promoter. Secondly, selenoprotein expression was strongly altered, but, more surprisingly, it was no longer sensitive to selenium supplementation. Mass spectrometry analyses revealed a tRNA isoform with unmodified wobble nucleotide U34 in mutant cells that correlated with reduced UGA recoding activities. Overall, this study demonstrates the pleiotropic effect of a single C65G mutation on both tRNA phenotype and selenoproteome expression.

SelSA-1, a novel HDAC inhibitor demonstrates enhanced chemotherapeutic potential by redox modulation

Colorectal cancer (CRC) is a multistep disorder resulting from genetic and epigenetic genome changes. It is the third most common malignancy in developed nations accounting for roughly 600,000 deaths annually. Persistent gut inflammation, as observed in inflammatory bowel disease (IBD), is a key risk factor for CRC development. From an epigenetic viewpoint, the pharmacological inhibition of HDACs using HDAC inhibitors such as SAHA has emerged as a suitable anticancer strategy in the recent past. However, the clinical success of these strategies is limited and has risk factors associated with their uses. Thus, considering the critical involvement of epigenetic regulation of key molecular mechanisms in carcinogenesis as well as HDAC inhibitory and anti-tumorigenic properties of Selenium (Se), we aimed to explore the potentially safer and enhanced chemotherapeutic potential of a Se derivative of SAHA namely SelSA-1, in an experimental model of colitis-associated experimental cancer (CAC) model and mechanism involved therein. The in vitro study indicated improved efficiency, specificity, and better safety margin in terms of lower IC50 value of SelSA-1 than SAHA in both NIH3T3 (9.44 and 10.87 µM) and HCT 115 (5.70 and 7.49 µM) cell lines as well on primary colonocytes (5.61 and 6.30 µM) respectively. In an in vivo experimental model, SelSA-1 efficiently demonstrated amelioration of the multiple plaque lesions (MPLs), tumor burden/incidence, and modulation of various histological and morphological parameters. Further, redox-mediated alterations in apoptotic mediators suggested induction of cancer cell apoptosis by SelSA-1. These findings indicate the enhanced chemotherapeutic and pro-resolution effects of SelSA-1 in part mediated through redox modulation of multiple epigenetic and apoptotic pathways.

Effect of Organic Selenium on the Homeostasis of Trace Elements, Lipid Peroxidation, and mRNA Expression of Antioxidant Proteins in Mouse Organs

(1) In this study we determined the effect of long-term selenomethionine administration on the oxidative stress level and changes in antioxidant protein/enzyme activity; mRNA expression; and the levels of iron, zinc, and copper. (2) Experiments were performed on 4-6-week-old BALB/c mice, which were given selenomethionine (0.4 mg Se/kg b.w.) solution for 8 weeks. The element concentration was determined via inductively coupled plasma mass spectrometry. mRNA expression of SelenoP, Cat, and Sod1 was quantified using real-time quantitative reverse transcription. Malondialdehyde content and catalase activity were determined spectrophotometrically. (3) After long-term SeMet administration, the amount of Se increased by 12-fold in mouse blood, 15-fold in the liver, and 42-fold in the brain, as compared to that in the control. Exposure to SeMet decreased amounts of Fe and Cu in blood, but increased Fe and Zn levels in the liver and increased the levels of all examined elements in the brain. Se increased malondialdehyde content in the blood and brain but decreased it in liver. SeMet administration increased the mRNA expression of selenoprotein P, dismutase, and catalase, but decreased catalase activity in brain and liver. (4) Eight-week-long selenomethionine consumption elevated Se levels in the blood, liver, and especially in the brain and disturbed the homeostasis of Fe, Zn, and Cu. Moreover, Se induced lipid peroxidation in the blood and brain, but not in the liver. In response to SeMet exposure, significant up-regulation of the mRNA expression of catalase, superoxide dismutase 1, and selenoprotein P in the brain, and especially in the liver, was determined.

Selenoprotein Gene mRNA Expression Evaluation During Renal Ischemia-Reperfusion Injury in Rats and Ebselen Intervention Effects

Effects of selenoproteins on many renal diseases have been reported. However, their role in renal ischemia-reperfusion (I/R) injury is unclear. The present study was performed to investigate the impact of ebselen and renal I/R injury on the expression of selenoproteins. Sprague-Dawley rats were pretreated with or without ebselen (10 mg/kg) through a daily single oral administration from 3 days before renal I/R surgery. RT-qPCR (real-time quantitative PCR) was performed to determine the mRNA expression of 25 selenoprotein genes in the renal tissues. The expression levels of two selenoproteins, including GPX3 (glutathione peroxidase 3) and DIO1 (iodothyronine deiodinase 1), were evaluated by Western blot or/and IHF (immunohistofluorescence) assays. Furthermore, renal function, renal damage, oxidative stress, and apoptosis were assessed. The results showed that in renal I/R injury, the mRNA levels of 15 selenoprotein genes (GPX1, GPX3, GPX4, DIO1, DIO2, TXNRD2, TXNRD3, SEPHS2, MSRB1, SELENOF, SELENOK, SELENOO, SELENOP, SELENOS, and SELENOT) were decreased, whereas those of eight selenoprotein genes (GPX2, GPX6, DIO3, TXNRD1, SELENOH, SELENOM, SELENOV, and SELENOW) were increased. I/R also induced a reduction in the expression levels of GPX3 and DIO1 proteins. In addition, our results indicated that ebselen reversed the changes in those selenoprotein genes, excluding SELENOH, SELENOM, SELENOP, and SELENOT, in renal I/R injury and alleviated I/R-induced renal dysfunction, tissue damage, oxidative stress, and apoptosis. To our knowledge, this is the first study to investigate the changes of 25 mammalian selenoprotein genes in renal I/R injury kidneys. The present study also provided more evidence for the roles of ebselen against renal I/R injury.

Use of Microbial Consortia in Bioremediation of Metalloid Polluted Environments

Metalloids are released into the environment due to the erosion of the rocks or anthropogenic activities, causing problems for human health in different world regions. Meanwhile, microorganisms with different mechanisms to tolerate and detoxify metalloid contaminants have an essential role in reducing risks. In this review, we first define metalloids and bioremediation methods and examine the ecology and biodiversity of microorganisms in areas contaminated with these metalloids. Then we studied the genes and proteins involved in the tolerance, transport, uptake, and reduction of these metalloids. Most of these studies focused on a single metalloid and co-contamination of multiple pollutants were poorly discussed in the literature. Furthermore, microbial communication within consortia was rarely explored. Finally, we summarized the microbial relationships between microorganisms in consortia and biofilms to remove one or more contaminants. Therefore, this review article contains valuable information about microbial consortia and their mechanisms in the bioremediation of metalloids.

A Novel Glucose-6-Phosphate Isomerase Exists in Chicken Breast Meat: A Selenium-Containing Enzyme that Should Be Re-recognized Through New Eyes

Glucose-6-phosphate isomerase (GPI) is a highly conserved glycolytic enzyme in nature, and less information was available for GPI from hens. In this study a newly discovered selenocysteine (Sec)-containing GPI in common chicken breast meat was first isolated, purified and identified. Data about LC-MS/MS, FTIR and Se species analyses show that the molecular weight of the enzyme is 62,091 Da and only one Sec is inserted at the 403rd position in the highly conserved primary domain SIS_PGI with sugar conversion function. The enzyme shows excellent activity against hydroxyl radicals as vitamin C (Vc) in vitro. It is deduced that the Sec-containing GPI in the chicken meat may depend on Sec in its molecular structure to resist reactive oxygen species (ROS) stress produced by the accompanying biochemical reactions in cells, to protect its stability and maintain its efficient function that catalyzes the conversion of glucose-6-phosphate to fructose-6-phosphate in the critical glycolytic pathway.

Selenium, Stroke, and Infection: A Threefold Relationship; Where Do We Stand and Where Do We Go?

Stroke is currently the second most common cause of death worldwide and a major cause of serious long-term morbidity. Selenium is a trace element with pleotropic effects on human health. Selenium deficiency has been associated with a prothrombotic state and poor immune response, particularly during infection. Our aim was to synthesize current evidence on the tripartite interrelationship between selenium levels, stroke, and infection. Although evidence is contradictory, most studies support the association between lower serum selenium levels and stroke risk and outcomes. Conversely, limited evidence on the role of selenium supplementation in stroke indicates a potentially beneficial effect of selenium. Notably, the relationship between stroke risk and selenium levels is bimodal rather than linear, with higher levels of serum selenium linked to disturbances of glucose metabolism and high blood pressure, morbidities which are, in turn, substrates for stroke. Another such substrate is an infection, albeit forming a bidirectional relationship with both stroke and the consequences of impaired selenium metabolism. Perturbed selenium homeostasis leads to impaired immune fitness and antioxidant capacity, which both favor infection and inflammation; specific pathogens may also contend with the host for transcriptional control of the selenoproteome, adding a feed-forward loop to this described process. Broader consequences of infection such as endothelial dysfunction, hypercoagulation, and emergent cardiac dysfunction both provide stroke substrates and further feed-forward feedback to the consequences of deficient selenium metabolism. In this review, we provide a synthesis and interpretation of these outlined complex interrelationships that link selenium, stroke, and infection and attempt to decipher their potential impact on human health and disease. Selenium and the unique properties of its proteome could provide both biomarkers and treatment options in patients with stroke, infection, or both.

Distinct Roles of SELENOF in Different Human Cancers

SELENOF, previously known as SEP15, is a selenoprotein that contains selenium in the form of the amino acid selenocysteine. Like other selenoproteins, the role for SELENOF in carcinogenesis has been investigated due to its altered expression compared to the corresponding normal tissue, its molecular function, and the association of genetic variations in the SELENOF gene to cancer risk or outcome. This review summarizes SELENOF’s discovery, structure, cellular localization, and expression. SELENOF belongs to a new family of thioredoxin-like proteins. Published data summarized here indicate a likely role for SELENOF in redox protein quality control, and in the regulation of lipids, glucose, and energy metabolism. Current evidence indicates that loss of SELENOF contributes to the development of prostate and breast cancer, while its loss may be protective against colon cancer. Additional investigation into SELENOF’s molecular mechanisms and its impact on cancer is warranted.

Both selenium deficiency and excess impair male reproductive system via inducing oxidative stress-activated PI3K/AKT-mediated apoptosis and cell proliferation signaling in testis of mice

Selenium (Se) deficiency or excess impairs testicular development and spermatogenesis, while the underlying mechanisms in this regard remain unclear. This study was designed to explore the molecular biology of Se deficiency or excess in spermatogenesis in mice. Three-week-old male mice (n = 10 mice/diet) were fed with Se-deficient diet (SeD, 0.02 mg Se/kg), adequate-Se diet (SeA, 0.2 mg Se/kg), or excess-Se diet (SeE, 2.0 mg Se/kg) for 5 months. Compared with SeA, SeD reduced (P < 0.05) the body weight (10.4%) and sperm density (84.3%) but increased (P < 0.05) sperm deformity (32.8%); SeE decreased (P < 0.05) the sperm density (78.5%) and sperm motility (35.9%) of the mice. Meanwhile, both SeD and SeE increased (P < 0.05) serum FSH concentrations (10.4-25.6%) and induced testicular damage in mice in comparison with the SeA. Compared with SeA, SeD increased (P < 0.05) the 8-OHdG concentration by 25.5%; SeE increased (P < 0.05) both MDA and 8-OHdG concentrations by 118.8-180.3% in testis. Furthermore, transcriptome analysis showed that there 1325 and 858 transcripts were altered (P < 0.05) in the testis by SeD and SeE, respectively, compared with SeA. KEGG pathway analysis revealed that these differentially expressed genes were mainly enriched in the PI3K-AKT signaling pathway, which is regulated by oxidative stress. Moreover, western blotting analysis revealed that SeD and SeE dysregulated PI3K-AKT-mediated apoptosis and cell proliferation signaling, including upregulating (P < 0.05) caspase 3, cleaved-caspase 3, BCL-2 and (or) P53 and downregulating (P < 0.05) PI3K, p-AKT, p-mTOR, 4E-BP1, p-4E-BP1 and (or) p-p70S6K in the testis of mice compared with SeA. Additionally, compared with SeA, both SeD and SeE increased (P < 0.05) GPX3 and SELENOO; SeD decreased (P < 0.05) GPX1, TXRND3 and SELENOW, but SeE increased (P < 0.05) production of three selenoproteins in the testis. Conclusively, both Se deficiency and excess impairs male reproductive system in mice, potentially with the induction of oxidative stress and activation of PI3K/AKT-mediated apoptosis and cell proliferation signaling in the testis.

The Effect of Selenium Supplementation on Clinical Outcomes, Metabolic Profiles, and Pulsatility Index of the Uterine Artery in High-Risk Mothers in Terms of Preeclampsia Screening with Quadruple Test: a Randomized, Double-Blind, Placebo-Controlled Clinical Trial : Selenium and preeclampsia

Data on the effects of selenium (Se) supplementation on clinical outcomes, metabolic profiles, and pulsatility index (PI) in high-risk mothers in terms of preeclampsia (PE) screening with quadruple tests are scarce. This study evaluated the effects of Se supplementation on clinical outcomes, metabolic profiles, and uterine artery PI on Doppler ultrasound in high-risk mothers in terms of PE screening with quad marker. The current randomized, double-blind, placebo-controlled trial was conducted among 60 high-risk pregnant women screening for PE with quad tests. Participants were randomly allocated into two groups (30 participants each group), received either 200 µg/day Se supplements (as Se amino acid chelate) or placebo from 16 to 18 weeks of pregnancy for 12 weeks. Clinical outcomes, metabolic profiles, and uterine artery PI were assessed at baseline and at the end of trial. Se supplementation resulted in a significant elevation in serum Se levels (β 22.25 µg/dl; 95% CI, 18.3, 26.1; P < 0.001) compared with the placebo. Also, Se supplementation resulted in a significant elevation in total antioxidant capacity (β 82.88 mmol/L; 95% CI, 3.03, 162.73; P = 0.04), and total glutathione (β 71.35 µmol/L; 95% CI, 5.76, 136.94; P = 0.03), and a significant reduction in high-sensitivity C-reactive protein levels (β - 1.52; 95% CI, - 2.91, - 0.14; P = 0.03) compared with the placebo. Additionally, Se supplementation significantly decreased PI of the uterine artery in Doppler ultrasound (β - 0.09; 95% CI, - 0.14, - 0.04; P = 0.04), and a significant improvement in depression (β - 5.63; 95% CI, - 6.97, - 4.28; P < 0.001), anxiety (β - 1.99; 95% CI, - 2.56, - 1.42; P < 0.001), and sleep quality (β - 1.97; 95% CI, - 2.47, - 1.46; P < 0.001). Se supplementation for 12 weeks in high-risk pregnant women in terms of PE screening with quad marker had beneficial effects on serum Se level, some metabolic profiles, uterine artery PI, and mental health. IRCT Registration: htpp:// www.irct.ir ; identifier IRCT20200608047701N1.

Treatments of Mycobacterium tuberculosis and Toxoplasma gondii with Selenium Nanoparticles

Toxoplasma gondii and Mycobacterium tuberculosis are pathogens that are harmful to humans. When these diseases interact in humans, the result is typically fatal to the public health. Several investigations on the relationship between M. tuberculosis and T. gondii infections have found that there is a strong correlation between them with each infection having a reciprocal effect on the other. TB may contribute to the reactivation of innate toxoplasmosis or enhance susceptibility to a new infection, and toxoplasma co-infection may worsen the severity of pulmonary tuberculosis. As a consequence, there is an earnest and urgent necessity to generate novel therapeutics that can subdue these challenges. Selenium nanostructures' compelling properties have been shown to be a successful treatment for Mycobacterium TB and Toxoplasma gondii. Despite the fact that selenium (Se) offers many health advantages for people, it also has a narrow therapeutic window; therefore, consuming too much of either inorganic or organic compounds based on selenium can be hazardous. Compared to both inorganic and organic Se, Se nanoparticles (SeNPs) are less hazardous. They are biocompatible and excellent in selectively targeting specific cells. As a consequence, this review conducted a summary of the efficacy of biogenic Se NPs in the treatment of tuberculosis (TB) and toxoplasmosis. Mycobacterium tuberculosis, Toxoplasma gondii, and their co-infection were all briefly described.

Selenoprotein S: A versatile disordered protein

Selenoprotein S (selenos) is a small, intrinsically disordered membrane protein that is associated with various cellular functions, such as inflammatory processes, cellular stress response, protein quality control, and signaling pathways. It is primarily known for its contribution to the ER-associated degradation (ERAD) pathway, which governs the extraction of misfolded proteins or misassembled protein complexes from the ER to the cytosol for degradation by the proteasome. However, selenos's other cellular roles in signaling are equally vital, including the control of transcription factors and cytokine levels. Consequently, genetic polymorphisms of selenos are associated with increased risk for diabetes, dyslipidemia, and cardiovascular diseases, while high expression levels correlate with poor prognosis in several cancers. Its inhibitory role in cytokine secretion is also exploited by viruses. Since selenos binds multiple protein complexes, however, its specific contributions to various cellular pathways and diseases have been difficult to establish. Thus, the precise cellular functions of selenos and their interconnectivity have only recently begun to emerge. This review aims to summarize recent insights into the structure, interactome, and cellular roles of selenos.

Selenium and Redox Enzyme Activity in Pregnant Women Exposed to Methylmercury

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

Selenocompounds and Sepsis-Redox Bypass Hypothesis: Part B-Selenocompounds in the Management of Early Sepsis

Significance: Endothelial barrier damage, which is in part caused by excess production of reactive oxygen, halogen and nitrogen species (ROHNS), especially peroxynitrite (ONOO^-), is a major event in early sepsis and, with leukocyte hyperactivation, part of the generalized dysregulated immune response to infection, which may even become a complex maladaptive state. Selenoenzymes have major antioxidant functions. Their synthesis is related to the need to limit deleterious oxidant redox cycling by small selenocompounds, which may be of therapeutic cytotoxic interest. Plasma selenoprotein-P is crucial for selenium transport from the liver to the tissues and for antioxidant endothelial protection, especially against ONOO^-. Above micromolar concentrations, sodium selenite (Na₂SeO₃) becomes cytotoxic, with a lower cytotoxicity threshold in activated cells, which has led to cancer research. Recent Advances: Plasma selenium (<2% of total body selenium) is mainly contained in selenoprotein-P, and concentrations decrease rapidly in the early phase of sepsis, because of increased selenoprotein-P binding and downregulation of hepatic synthesis and excretion. At low concentrations, Na₂SeO₃ acts as a selenium donor, favoring selenoprotein-P synthesis in physiology, but probably not in the acute phase of sepsis. Critical Issues: The cytotoxic effects of Na₂SeO₃ against hyperactivated leukocytes, especially the most immature forms that liberate ROHNS, may be beneficial, but they may also be harmful for activated endothelial cells. Endothelial protection against ROHNS by selenoprotein-P may reduce Na₂SeO₃ toxicity, which is increased in sepsis. Future Direction: The combination of selenoprotein-P for endothelial protection and the cytotoxic effects of Na₂SeO₃ against hyperactivated leukocytes may be a promising intervention for early sepsis. Antioxid. Redox Signal. 37, 998-1029.

The Effects of BSA-Stabilized Selenium Nanoparticles and Sodium Selenite Supplementation on the Structure, Oxidative Stress Parameters and Selenium Redox Biology in Rat Placenta

The chemical element selenium (Se) is a nonmetal that is in trace amounts indispensable for normal cellular functioning. During pregnancy, a low Se status can increase the risk of oxidative stress. However, elevated concentrations of Se in the body can also cause oxidative stress. This study aimed to compare the effects of BSA-stabilized Se nanoparticles (SeNPs, Se0) (BSA-bovine serum albumin) and inorganic sodium selenite (NaSe, Se+4) supplementation on the histological structure of the placenta, oxidative stress parameters and the total placental Se concentration of Wistar rats during pregnancy. Pregnant females were randomized into four groups: (i) intact controls; (ii) controls that were dosed by daily oral gavage with 8.6% bovine serum albumin (BSA) and 0.125 M vit C; (iii) the SeNP group that was administered 0.5 mg of SeNPs stabilized with 8.6% BSA and 0.125 M vit C/kg bw/day by oral gavage dosing; (iv) the NaSe group, gavage dosed with 0.5 mg Na2SeO3/kg bw/day. The treatment of pregnant females started on gestational day one, lasted until day 20, and on day 21 of gestation, the fetuses with the placenta were removed from the uterus. Our findings show that the mode of action of equivalent concentrations of Se in SeNPs and NaSe depended on its redox state and chemical structure. Administration of SeNPs (Se0) increased fetal lethality and induced changes in the antioxidative defense parameters in the placenta. The accumulation of Se in the placenta was highest in SeNP-treated animals. All obtained data indicate an increased bioavailability of Se in its organic nano form and Se0 redox state in comparison to its inorganic sodium selenite form and Se+4 redox state.

Synthesis, function, and regulation of sterol and nonsterol isoprenoids

Cholesterol, the bulk end-product of the mevalonate pathway, is a key component of cellular membranes and lipoproteins that transport lipids throughout the body. It is also a precursor of steroid hormones, vitamin D, and bile acids. In addition to cholesterol, the mevalonate pathway yields a variety of nonsterol isoprenoids that are essential to cell survival. Flux through the mevalonate pathway is tightly controlled to ensure cells continuously synthesize nonsterol isoprenoids but avoid overproducing cholesterol and other sterols. Endoplasmic reticulum (ER)-localized 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase (HMGCR), the rate limiting enzyme in the mevalonate pathway, is the focus of a complex feedback regulatory system governed by sterol and nonsterol isoprenoids. This review highlights transcriptional and post-translational regulation of HMGCR. Transcriptional regulation of HMGCR is mediated by the Scap-SREBP pathway. Post-translational control is initiated by the intracellular accumulation of sterols, which causes HMGCR to become ubiquitinated and subjected to proteasome-mediated ER-associated degradation (ERAD). Sterols also cause a subfraction of HMGCR molecules to bind the vitamin K₂ synthetic enzyme, UbiA prenyltransferase domain-containing protein-1 (UBIAD1). This binding inhibits ERAD of HMGCR, which allows cells to continuously synthesize nonsterol isoprenoids such as geranylgeranyl pyrophosphate (GGPP), even when sterols are abundant. Recent studies reveal that UBIAD1 is a GGPP sensor, dissociating from HMGCR when GGPP thresholds are met to allow maximal ERAD. Animal studies using genetically manipulated mice disclose the physiological significance of the HMGCR regulatory system and we describe how dysregulation of these pathways contributes to disease.

Selenoprotein P - Selenium transport protein, enzyme and biomarker of selenium status

The habitual intake of selenium (Se) varies strongly around the world, and many people are at risk of inadequate supply and health risks from Se deficiency. Within the human organism, efficient transport mechanisms ensure that organs with a high demand and relevance for reproduction and survival are preferentially supplied. To this end, selenoprotein P (SELENOP) is synthesized in the liver and mediates Se transport to essential tissues such as the endocrine glands and the brain, where the "SELENOP cycle" maintains a privileged Se status. Mouse models indicate that SELENOP is not essential for life, as supplemental Se supply was capable of preventing the development of severe symptoms. However, knockout mice died under limiting supply, arguing for an essential role of SELENOP in Se deficiency. Many clinical studies support this notion, pointing to close links between health risks and low SELENOP levels. Accordingly, circulating SELENOP concentrations serve as a functional biomarker of Se supply, at least until a saturated status is achieved and SELENOP levels reach a plateau. Upon toxic intake, a further increase in SELENOP is observed, i.e., SELENOP provides information about possible selenosis. The SELENOP transcripts predict an insertion of ten selenocysteine residues. However, the decoding is imperfect, and not all these positions are ultimately occupied by selenocysteine. In addition to the selenocysteine residues near the C-terminus, one selenocysteine resides central within an enzyme-like environment. SELENOP proved capable of catalyzing peroxide degradation in vitro and protecting e.g. LDL particles from oxidation. An enzymatic activity in the intact organism is unclear, but an increasing number of clinical studies provides evidence for a direct involvement of SELENOP-dependent Se transport as an important and modifiable risk factor of disease. This interaction is particularly strong for cardiovascular and critical disease including COVID-19, cancer at various sites and autoimmune thyroiditis. This review briefly highlights the links between the growing knowledge of Se in health and disease over the last 50 years and the specific advances that have been made in our understanding of the physiological and clinical contribution of SELENOP to the current picture.

Selenium and mercury concentrations in biological samples from patients with COVID-19

BACKGROUND

Coronavirus disease 2019 (COVID-19) is a systemic disease affecting multiple organs. Furthermore, viral infection depletes several trace elements and promotes complex biochemical reactions in the body. Smoking has been linked to the incidence of COVID-19 and associated mortality, and it may impact clinical effects, viral and bacterial conversion, and treatment outcomes.

OBJECTIVES

To study the relationship between severe acute respiratory syndrome coronavirus type 2 and the elemental concentrations of selenium (Se) and mercury (Hg) in biological samples from smokers and nonsmokers infected with the virus and in healthy individuals.

METHOD

We evaluated changes in the concentrations of essential (Se) and toxic (Hg) elements in biological samples (blood, nasal fluid, saliva, sputum, serum, and scalp hair) collected from male smokers and nonsmokers (aged 29-59 years) infected with COVID-19 and from healthy men in the same age group. The patients lived in different cities in Sindh Province, Pakistan. The Se and Hg concentrations were determined using atomic absorption spectrophotometry.

RESULTS

Se concentrations in all types of biological samples from smokers and nonsmokers with COVID-19 were lower than those of healthy smokers and nonsmokers. Hg concentrations were elevated in both smokers and nonsmokers with COVID-19.

CONCLUSIONS

In the current study, persons infected with COVID-19 had higher concentrations of toxic Hg, which could cause physiological disorders, and low concentrations of essential Se, which can also cause weakness. COVID-19 infection showed positive correlations with levels of mercury and selenium. Thus, additional clinical and experimental investigations are essential.

Emerging roles of ER-resident selenoproteins in brain physiology and physiopathology

The brain has a very high oxygen consumption rate and is particularly sensitive to oxidative stress. It is also the last organ to suffer from a loss of selenium (Se) in case of deficiency. Se is a crucial trace element present in the form of selenocysteine, the 21st proteinogenic amino acid present in selenoproteins, an essential protein family in the brain that participates in redox signaling. Among the most abundant selenoproteins in the brain are glutathione peroxidase 4 (GPX4), which reduces lipid peroxides and prevents ferroptosis, and selenoproteins W, I, F, K, M, O and T. Remarkably, more than half of them are proteins present in the ER and recent studies have shown their involvement in the maintenance of ER homeostasis, glycoprotein folding and quality control, redox balance, ER stress response signaling pathways and Ca2+ homeostasis. However, their molecular functions remain mostly undetermined. The ER is a highly specialized organelle in neurons that maintains the physical continuity of axons over long distances through its continuous distribution from the cell body to the nerve terminals. Alteration of this continuity can lead to degeneration of distal axons and subsequent neuronal death. Elucidation of the function of ER-resident selenoproteins in neuronal pathophysiology may therefore become a new perspective for understanding the pathophysiology of neurological diseases. Here we summarize what is currently known about each of their molecular functions and their impact on the nervous system during development and stress.

COVID-19 and Selenium Deficiency: a Systematic Review

Several studies have indicated that selenium deficiency may be detrimental in the context of various viral disorders, and in the case of COVID-19, several studies have reported heterogeneous results concerning the association of selenium deficiency with the severity of disease. To summarize the available data surrounding the association of body selenium levels with the outcomes of COVID-19, a systematic search was performed in the Medline database (PubMed), Scopus, Cochrane Library, Embase, and Web of Science using keywords including "SARS-CoV-2," "COVID-19," and "selenium," Studies evaluating the association of COVID-19 with body selenium levels were included. Among 1,862 articles viewed in the database search, 10 articles were included after title, abstract, and full-text review. One study was further included after searching the literature again for any newly published articles. Out of 11 included studies, 10 studies measured serum selenium level, and one study investigated urinary selenium level. Three of 10 studies measured serum SELENOP level as well as selenium level. Glutathione peroxidase-3 level in serum was also assessed in one study. The reported outcomes were severity, mortality, and risk of COVID-19. Nine studies indicated that a lower serum selenium level is associated with worse outcomes. Two studies reported no significant association between serum selenium level and COVID-19. In one study, urinary selenium level was reported to be higher in severe and fatal cases compared to non-severe and recovered patients, respectively. In most cases, selenium deficiency was associated with worse outcomes, and selenium levels in COVID-19 patients were lower than in healthy individuals. Thus, it could be concluded that cautious selenium supplementation in COVID-19 patients may be helpful to prevent disease progression. However, randomized clinical trials are needed to confirm this.

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.

The role of selenoprotein P in the determining the sensitivity of cervical cancer patients to concurrent chemoradiotherapy: A metabonomics-based analysis

BACKGROUND

The effect of selenoprotein P (SELENOP) levels on the sensitivity of cervical cancer patients to concurrent chemoradiotherapy (CCRT) has not been reported. In this study, the effects of the variations in plasma SELENOP levels on the sensitivity of cervical cancer patients to CCRT were investigated using metabonomics.

METHODS

Two patient groups were evaluated, i.e., the case group: 11 patients with intermediate to advanced primary squamous cervical cancer, who developed resistance against CCRT, and the sensitivity group: 11 patients who did not develop resistance were matched in a 1:1 ratio (controls). Blood samples were collected before and after CCRT, and the plasma SELENOP levels were measured by ELISA. The different metabolites present in the plasma were analyzed by UPLC-MS-MS.

RESULTS

SELENOP levels exhibited a significant reduction in both the resistant and sensitive groups after CCRT (F = 50.705, P < 0.001), and interaction effects between sensitivity and pre-and post-treatment on SELENOP levels were observed (F = 7.414, P = 0.013). Further, a more significant reduction in the SELENOP levels was observed in the CCRT-resistant group (mean reduction, 0.028 µg/mL; P < 0.001) than in the sensitive group (mean reduction, 0.013 µg/mL; P = 0.006). Four metabolic biomarkers, i.e., C18, C19, C20 sphingomyelin, and phosphatidylcholine 20:2/22:6, were shown to be differentially expressed between the resistant and sensitive groups pre-and post-treatment. C20 sphingomyelin levels exhibited a significant correlation with SELENOP levels (r = -0.326, P = 0.031).

CONCLUSION

The levels of plasma SELENOP in the CCRT-resistant group decreased significantly, suggesting that SELENOP might affect the sensitivity by modulating lipid synthesis and metabolism.

Selenoproteins in brain development and function

Expression of selenoproteins is widespread in neurons of the central nervous system. There is continuous evidence presented over decades that low levels of selenium or selenoproteins are linked to seizures and epilepsy indicating a failure of the inhibitory system. Many developmental processes in the brain depend on the thyroid hormone T3. T3 levels can be locally increased by the action of iodothyronine deiodinases on the prohormone T4. Since deiodinases are selenoproteins, it is expected that selenoprotein deficiency may affect development of the central nervous system. Studies in genetically modified mice or clinical observations of patients with rare diseases point to a role of selenoproteins in brain development and degeneration. In particular selenoprotein P is central to brain function by virtue of its selenium transport function into and within the brain. We summarize which selenoproteins are essential for the brain, which processes depend on selenoproteins, and what is known about genetic deficiencies of selenoproteins in humans. This review is not intended to cover the potential influence of selenium or selenoproteins on major neurodegenerative disorders in human.

Voyage of selenium from environment to life: Beneficial or toxic?

Selenium (Se), a naturally occurring metalloid, is an essential micronutrient for life as it is incorporated as selenocysteine in proteins. Although beneficial at low doses, Se is hazardous at high concentrations and poses a serious threat to various ecosystems. Due to this contrasting 'dual' nature, Se has garnered the attention of researchers wishing to unravel its puzzling properties. In this review, we describe the impact of selenium's journey from environment to diverse biological systems, with an emphasis on its chemical advantage. We describe the uneven distribution of Se and how this affects the bioavailability of this element, which, in turn, profoundly affects the habitat of a region. Once taken up, the subsequent incorporation of Se into proteins as selenocysteine and its antioxidant functions are detailed here. The causes of improved protein function due to the incorporation of redox-active Se atom (instead of S) are examined. Subsequently, the reasons for the deleterious effects of Se, which depend on its chemical form (organo-selenium or the inorganic forms) in different organisms are elaborated. Although Se is vital for the function of many antioxidant enzymes, how the pro-oxidant nature of Se can be potentially exploited in different therapies is highlighted. Furthermore, we succinctly explain how the presence of Se in biological systems offsets the toxic effects of heavy metal mercury. Finally, the different avenues of research that are fundamental to expand our understanding of selenium biology are suggested.

Pituitary and liver selenoprotein transcriptome profiles of grazing steers and their sensitivity to the form of selenium in vitamin-mineral mixes

Many supplemental Se-dependent metabolic effects are mediated through the function of selenoproteins. The full complement and relative abundance of selenoproteins expressed by highly metabolic cattle tissues have not been characterized in cattle. The complement and number of selenoprotein mRNA transcripts expressed by the pituitary and liver of healthy growing beef steers (n = 7 to 8) was characterized using NanoString methodology (Study 1). Of the 25 known bovine selenoproteins, 24 (all but SELENOH) were expressed by the pituitary and 23 (all but SELENOH and SELENOV) by the liver. Transcript abundance ranged (P ≤ 0.05) over 5 orders of magnitude in the pituitary (&gt; 10,000 for GPX3, &lt; 10 for DIO1 and GPX2) and liver (&gt; 35,000 for SELENOP, &lt; 10 for DIO2). Also unknown is the sensitivity of the selenoprotein transcriptome to the form of supplemental Se. The effect of form of supplemental Se on the relative content of selenoprotein mRNA species in the pituitary and liver of steers grazing a Se-deficient (0.07 ppm Se) tall fescue pasture and consuming 85 g/d of a basal vitamin-mineral mix that contained 35 ppm Se as either ISe (n = 6), organically-bound Se (SELPLEX; OSe, n = 7 to 8), or a 1:1 blend of ISe and OSe (MIX, n = 7 to 8) was determined by RT-PCR after sequence-validating the 25 bovine selenoprotein cDNA products (Study 2). In the pituitary, Se form affected (P &lt; 0.05) the relative content of 9 selenoprotein mRNAs and 2 selenoprotein P receptor mRNAs in a manner consistent with a greater capacity to manage against oxidative damage, maintain cellular redox balance, and have a better control of protein-folding in the pituitaries of OSe and MIX versus ISe steers. In the liver, expression of 5 selenoprotein mRNA was affected (P ≤ 0.05) in a manner consistent with MIX steers having greater redox signaling capacity and capacity to manage oxidative damage than ISe steers. We conclude that inclusion of 3 mg Se/d as OSe or MIX versus ISe, forms of supplemental Se in vitamin-mineral mixes alters the selenoprotein transcriptome in a beneficial manner in both the pituitary and liver of growing steers consuming toxic endophyte-infected tall fescue.

Breast cancer vaccines: New insights into immunomodulatory and nano-therapeutic approaches

Breast cancer (BC) is known to be a highly heterogeneous disease that is clinically subdivided into four primary molecular subtypes, each having distinct morphology and clinical implications. These subtypes are principally defined by hormone receptors and other proteins involved (or not involved) in BC development. BC therapeutic vaccines [including peptide-based vaccines, protein-based vaccines, nucleic acid-based vaccines (DNA/RNA vaccines), bacterial/viral-based vaccines, and different immune cell-based vaccines] have emerged as an appealing class of cancer immunotherapeutics when used alone or combined with other immunotherapies. Employing the immune system to eliminate BC cells is a novel therapeutic modality. The benefit of active immunotherapies is that they develop protection against neoplastic tissue and readjust the immune system to an anti-tumor monitoring state. Such immunovaccines have not yet shown effectiveness for BC treatment in clinical trials. In recent years, nanomedicines have opened new windows to increase the effectiveness of vaccinations to treat BC. In this context, some nanoplatforms have been designed to efficiently deliver molecular, cellular, or subcellular vaccines to BC cells, increasing the efficacy and persistence of anti-tumor immunity while minimizing undesirable side effects. Immunostimulatory nano-adjuvants, liposomal-based vaccines, polymeric vaccines, virus-like particles, lipid/calcium/phosphate nanoparticles, chitosan-derived nanostructures, porous silicon microparticles, and selenium nanoparticles are among the newly designed nanostructures that have been used to facilitate antigen internalization and presentation by antigen-presenting cells, increase antigen stability, enhance vaccine antigenicity and remedial effectivity, promote antigen escape from the endosome, improve cytotoxic T lymphocyte responses, and produce humoral immune responses in BC cells. Here, we summarized the existing subtypes of BC and shed light on immunomodulatory and nano-therapeutic strategies for BC vaccination. Finally, we reviewed ongoing clinical trials on BC vaccination and highlighted near-term opportunities for moving forward.

Contribution of organokines in the development of NAFLD/NASH associated hepatocellular carcinoma

Globally the incidence of hepatocellular carcinoma (HCC) is on an upsurge. Evidence is accumulating that liver disorders like nonalcoholic fatty liver disease (NAFLD) and its more progressive form nonalcoholic steatohepatitis (NASH) are associated with increased risk of developing HCC. NAFLD has a prevalence of about 25% and 50%-90% in obese population. With the growing burden of obesity epidemic worldwide, HCC presents a major healthcare burden. While cirrhosis is one of the major risk factors of HCC, available literature suggests that NAFLD/NASH associated HCC also develops in minimum or noncirrhotic livers. Therefore, there is an urgent need to understand the pathogenesis and risk factors associated with NAFLD and NASH related HCC that would help in early diagnosis and favorable prognosis of HCC secondary to NAFLD. Adipokines, hepatokines and myokines are factors secreted by adipocytes, hepatocytes and myocytes, respectively, playing essential roles in cellular homeostasis, energy balance and metabolism with autocrine, paracrine and endocrine effects. In this review, we endeavor to focus on the role of these organokines in the pathogenesis of NAFLD/NASH and its progression to HCC to augment the understanding of the factors stimulating hepatocytes to acquire a malignant phenotype. This shall aid in the development of novel therapeutic strategies and tools for early diagnosis of NAFLD/NASH and HCC.

Selenium Status and Its Antioxidant Role in Metabolic Diseases

Selenium (Se), in the form of selenoproteins, is an essential micronutrient that plays an important role in human health and disease. To date, there are at least 25 selenoproteins in humans involved in a wide variety of biological functions, including mammalian development, metabolic progress, inflammation response, chemoprotective properties, and most notably, oxidoreductase functions. In recent years, numerous studies have reported that low Se levels are associated with increased risk, poor outcome, and mortality of metabolic disorders, mainly related to the limited antioxidant defense resulting from Se deficiency. Moreover, the correlation between Se deficiency and Keshan disease has received considerable attention. Therefore, Se supplementation as a therapeutic strategy for preventing the occurrence, delaying the progression, and alleviating the outcomes of some diseases has been widely studied. However, supranutritional levels of serum Se may have adverse effects, including Se poisoning. This review evaluates the correlation between Se status and human health, with particular emphasis on the antioxidant benefits of Se in metabolic disorders, shedding light on clinical treatment.

Association between Selenium Status and Chronic Kidney Disease in Middle-Aged and Older Chinese Based on CHNS Data

Background: The association between selenium and chronic kidney disease (CKD) remains controversial. Population studies with large samples facilitate the reliability of conclusions. Objective: In this study, we aimed to describe the prevalence of a CKD association with selenium intake in middle-aged and older Chinese. Methods: Data for this study were obtained from the China Health and Nutrition Survey (CHNS). A total of 5381 participants (aged ≥ 45) with biochemical test data were included in the study. Logistic regression models were used to examine the association between diet selenium intake (quartile) and the prevalence of CKD. Results: A total of 942 (17.01%) participants had CKD. The prevalence of CKD was 23.33%, 20.32%, 14.98%, and 9.25% among participants with average selenium intakes of 21.5 ± 4.82, 33.1 ± 2.79, 43.8 ± 3.70, and 67.0 ± 13.97 µg/day, respectively. In the fully adjusted model (Model 3), across the quartiles of selenium intake, the ORs for the prevalence of CKD were 1.00, 1.09 (95% CI 0.69–1.73), 0.82 (95% CI 0.49–1.38), and 0.43 (95% CI 0.22–0.85). The protein intake had a certain diagnostic significance for the selenium intake. Conclusions: An adequate selenium intake may have a positive effect on CKD. The influence of individual weight and location on the effect of selenium on CKD needs to be further explored.

The Roles and Pathogenesis Mechanisms of a Number of Micronutrients in the Prevention and/or Treatment of Chronic Hepatitis, COVID-19 and Type-2 Diabetes Mellitus

A trace element is a chemical element with a concentration (or other measures of an amount) that is very low. The essential TEs, such as copper (Cu), selenium (Se), zinc (Zn), iron (Fe) and the electrolyte magnesium (Mg) are among the most commonly studied micronutrients. Each element has been shown to play a distinctive role in human health, and TEs, such as iron (Fe), zinc (Zn) and copper (Cu), are among the essential elements required for the organisms' well-being as they play crucial roles in several metabolic pathways where they act as enzyme co-factors, anti-inflammatory and antioxidant agents. Epidemics of infectious diseases are becoming more frequent and spread at a faster pace around the world, which has resulted in major impacts on the economy and health systems. Different trace elements have been reported to have substantial roles in the pathogenesis of viral infections. Micronutrients have been proposed in various studies as determinants of liver disorders, COVID-19 and T2DM risks. This review article sheds light on the roles and mechanisms of micronutrients in the pathogenesis and prevention of chronic hepatitis B, C and E, as well as Coronavirus-19 infection and type-2 diabetes mellitus. An update on the status of the aforementioned micronutrients in pre-clinical and clinical settings is also briefly summarized.

Dietary Selenium Across Species

This review traces the discoveries that led to the recognition of selenium (Se) as an essential nutrient and discusses Se-responsive diseases in animals and humans in the context of current understanding of the molecular mechanisms of their pathogeneses. The article includes a comprehensive analysis of dietary sources, nutritional utilization, metabolic functions, and dietary requirements of Se across various species. We also compare the function and regulation of selenogenomes and selenoproteomes among rodents, food animals, and humans. The review addresses the metabolic impacts of high dietary Se intakes in different species and recent revelations of Se-metabolites, means of increasing Se status, and the recycling of Se in food systems and ecosystems. Finally, research needs are identified for supporting basic science and practical applications of dietary Se in food, nutrition, and health across species. Expected final online publication date for the Annual Review of Nutrition, Volume 42 is August 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Comparative Proteomic Analysis Reveals the Effect of Selenoprotein W Deficiency on Oligodendrogenesis in Fear Memory

The essential trace element selenium plays an important role in maintaining brain function. Selenoprotein W (SELENOW), the smallest selenoprotein that has been identified in mammals, is sensitive to selenium levels and abundantly expressed in the brain. However, its biological role in the brain remains to be clarified. Here, we studied the morphological and functional changes in the brain caused by SELENOW deficiency using its gene knockout (KO) mouse models. Histomorphological alterations of the amygdala and hippocampus, specifically in the female SELENOW KO mice, were observed, ultimately resulting in less anxiety-like behavior and impaired contextual fear memory. Fear conditioning (FC) provokes rapidly intricate responses involving neuroplasticity and oligodendrogenesis. During this process, the females generally show stronger contextual FC than males. To characterize the effect of SELENOW deletion on FC, specifically in the female mice, a Tandem mass tag (TMT)-based comparative proteomic approach was applied. Notably, compared to the wildtype (WT) no shock (NS) mice, the female SELENOW KO NS mice shared lots of common differentially expressed proteins (DEPs) with the WT FC mice in the hippocampus, enriched in the biological process of ensheathment and oligodendrocyte differentiation. Immunostaining and Western blotting analyses further confirmed the proteomic results. Our work may provide a holistic perspective of gender-specific SELENOW function in the brain and highlighted its role in oligodendrogenesis during fear memory.