Estimating intestinal absorption of inorganic and organic selenium compounds by in vitro flux and biotransformation studies in Caco-2 cells and ICP-MS detection

Unveiling Green Synthesis and Biomedical Theranostic paradigms of Selenium Nanoparticles (SeNPs) - A state-of-the-art comprehensive update

The advancements in nanotechnology, pharmaceutical sciences, and healthcare are propelling the field of theranostics, which combines therapy and diagnostics, to new heights; emphasizing the emergence of selenium nanoparticles (SeNPs) as versatile theranostic agents. This comprehensive update offers a holistic perspective on recent developments in the synthesis and theranostic applications of SeNPs, underscoring their growing importance in nanotechnology and healthcare. SeNPs have shown significant potential in multiple domains, including antioxidant, anti-inflammatory, anticancer, antimicrobial, antidiabetic, wound healing, and cytoprotective therapies. The review highlights the adaptability and biocompatibility of SeNPs, which are crucial for advanced disease detection, monitoring, and personalized treatment. Special emphasis is placed on advancements in green synthesis techniques, underscoring their eco-friendly and cost-effective benefits in biosensing, diagnostics, imaging and therapeutic applications. Additionally, the appraisal scrutinizes the progressive trends in smart stimuli-responsive SeNPs, conferring their role in innovative solutions for disease management and diagnostics. Despite their promising therapeutic and prophylactic potential, SeNPs also present several challenges, particularly regarding toxicity concerns. These challenges and their implications for clinical translation are thoroughly explored, providing a balanced view of the current state and prospects of SeNPs in theranostic applications.

Investigation of selenium and selenium species in Cardamine violifolia using in vitro digestion coupled with a Caco-2 cell monolayer model

Inadequate Se intake can enhance vulnerability to certain health risks, with supplementation lessening these risks. This study investigated the bioavailability of Se and Se species in five Se compounds and in Se-rich Cardamine violifolia using in vitro digestion coupled with a Caco-2 cell monolayer model, which enabled the study of Se transport and uptake. Translocation results showed that SeCys2 and MeSeCys had high translocation rates in C. violifolia leaves (CVLs). The uptake rate of organic Se increased with time, and MeSeCys exhibited a higher uptake rate than that for SeCys2 and SeMet. The translocation mechanisms of SeMet, Se(IV), and Se(VI) were passive transport, whereas those of SeCys2 and MeSeCys were active transport. The bioavailability of organic Se was higher than that of inorganic Se, with a total Se bioavailability in CVLs of 49.11 %. This study would provide a theoretical basis for the application of C. violifolia in the functional food.

Selenium in Prostate Cancer: Prevention, Progression, and Treatment

Selenium, a trace mineral with various biological functions, has become a focal point in prostate cancer research. This review aims to present a comprehensive overview of selenium's involvement in prostate cancer, covering its impact on prevention, development, treatment, and underlying mechanisms. Observational studies have revealed a link between selenium levels and selenoproteins with prostate cancer progression. However, randomized controlled studies have shown that selenium supplementation does not prevent prostate cancer (HR: 0.95; 95% CI 0.80-1.13). This discrepancy might be attributed to selenoprotein single nucleotide polymorphisms. In the context of combinatorial therapy, selenium has demonstrated promising synergistic potential in the treatment of prostate cancer. Emerging evidence highlights the significant role of selenium and selenoproteins in prostate cancer, encompassing AR signaling, antioxidative properties, cell death, cell cycle regulation, angiogenesis, epigenetic regulation, immunoregulation, epithelial-mesenchymal transformation, and redox signal. In conclusion, selenium's diverse properties make it a promising trace mineral in prostate cancer prevention, development, and treatment and as a platform for exploring novel agents.

Nano-Sized Selenium Maintains Performance and Improves Health Status and Antioxidant Potential While Not Compromising Ultrastructure of Breast Muscle and Liver in Chickens

The poultry industry is looking for the most effective sources of selenium (Se) for commercial use. Over the past five years, nano-Se has attracted a great deal of attention in terms of its production, characterisation and possible application in poultry production. The objective of this study was to evaluate the effects of dietary levels of inorganic and organic Se, selenised yeast and nano forms of selenium on breast meat quality, liver and blood markers of antioxidants, the ultrastructure of tissue and the health status of chickens. A total of 300 one-day-old chicks Ross 308 were divided into 4 experimental groups, in 5 replications, with 15 birds per replication. Birds were fed the following treatments: a standard commercial diet containing inorganic Se in the form of inorganic Se at the level of 0.3 mg/kg diet and an experimental diet with an increased level of Se (0.5 mg/kg diet). The use of other forms of Se (nano-Se) versus sodium selenate significantly influences (p ≤ 0.05) a higher collagen content and does not impair physico-chemical properties in the breast muscle or the growth performance of the chickens. In addition, the use of other forms of selenium at an increased dose versus sodium selenate affected (p ≤ 0.01) the elongation of sarcomeres in the pectoral muscle while reducing (p ≤ 0.01) mitochondrial damage in hepatocytes and improving (p ≤ 0.05) oxidative indices. The use of nano-Se at a dose of 0.5 mg/kg feed has high bioavailability and low toxicity without negatively affecting the growth performance and while improving breast muscle quality parameters and the health status of the chickens.

Evaluation of Selenomethionine Entrapped in Nanoparticles for Oral Supplementation Using In Vitro, Ex Vivo and In Vivo Models

Selenium methionine (SeMet) is an essential micronutrient required for normal body function and is associated with additional health benefits. However, oral administration of SeMet can be challenging due to its purported narrow therapeutic index, low oral bioavailability, and high susceptibility to oxidation. To address these issues, SeMet was entrapped in zein-coated nanoparticles made from chitosan using an ionic gelation formulation. The high stability of both the SeMet and selenomethionine nanoparticles (SeMet-NPs) was established using cultured human intestinal and liver epithelial cells, rat liver homogenates, and rat intestinal homogenates and lumen washes. Minimal cytotoxicity to Caco-2 and HepG2 cells was observed for SeMet and SeMet-NPs. Antioxidant properties of SeMet were revealed using a Reactive Oxygen Species (ROS) assay, based on the observation of a concentration-dependent reduction in the build-up of peroxides, hydroxides and hydroxyl radicals in Caco-2 cells exposed to SeMet (6.25–100 μM). The basal apparent permeability coefficient (Papp) of SeMet across isolated rat jejunal mucosae mounted in Ussing chambers was low, but the Papp was increased when presented in NP. SeMet had minimal effects on the electrogenic ion secretion of rat jejunal and colonic mucosae in Ussing chambers. Intra-jejunal injections of SeMet-NPs to rats yielded increased plasma levels of SeMet after 3 h for the SeMet-NPs compared to free SeMet. Overall, there is potential to further develop SeMet-NPs for oral supplementation due to the increased intestinal permeability, versus free SeMet, and the low potential for toxicity.

Single-cell ICP-MS to address the role of trace elements at a cellular level

The heterogeneity properties shown by cells or unicellular organisms have led to the development of analytical methods at the single-cell level. In this sense, considering the importance of trace elements in these biological systems, the inductively coupled plasma mass spectrometer (ICP-MS) configured for analyzing single cell has presented a high potential to assess the evaluation of elements in cells. Moreover, advances in instrumentation, such as coupling laser ablation to the tandem configuration (ICP-MS/MS), or alternative mass analyzers (ICP-SFMS and ICP-TOFMS), brought significant benefits, including sensitivity improvement, high-resolution imaging, and the cell fingerprint. From this perspective, the single-cell ICP-MS has been widely reported in studies involving many fields, from oncology to environmental research. Hence, it has contributed to finding important results, such as elucidating nanoparticle toxicity at the cellular level and vaccine development. Therefore, in this review, the theory of single-cell ICP-MS analysis is explored, and the applications in this field are pointed out. In addition, the instrumentation advances for single-cell ICP-MS are addressed.

Selenium Forms and Dosages Determined Their Biological Actions in Mouse Models of Parkinson's Disease

Selenium (Se), an essential antioxidant trace element, is reported to play a role in Parkinson's disease (PD). However, there is a lack of systematic studies on different Se forms against PD. Our study is designed to compare the neuroprotective effects of inorganic and organic Se in two classical PD mice models and investigate the underlying mechanisms for their potentially differential actions against PD. In this study, different dosages of inorganic sodium selenite (Se-Na) or organic seleno-L-methionine (Se-Met) were fed to either acute or chronic PD mice models, and their neuroprotective effects and mechanisms were explored and compared. Se-Na provided better neuroprotective effects in PD mice than Se-Met administered at the same but at a relatively low Se dosage. Se-Na treatment could influence GPX activities but not their mRNA expressions in the midbrains of PD mice. The enhanced GPX activities caused by Se-Na, but not Se-Met, in PD mice could be the major reason for the positive actions of inorganic Se to prevent dopaminergic neuronal loss in this study. In vivo bio-distribution experiments found MPTP injection greatly changed Se bio-distribution in mice, which led to reversed alterations in the bioavailability of Se-Met and Se-Na. Se-Na had higher bioavailability than Se-Met in PD mice, which could explain its better neuroprotective effects compared to Se-Met. Our results proved that Se forms and dosages determined their biological actions in mouse models of PD. Our study will provide valuable scientific evidence to researchers and/or medical professionals in using Se for PD prevention or therapy.

Metabolism and Anticancer Mechanisms of Selocompounds: Comprehensive Review

Selenium (Se) is an essential micronutrient with several functions in cellular and molecular anticancer processes. There is evidence that Se depending on its chemical form and the dosage use could act as a modulator in some anticancer mechanisms. However, the metabolism of organic and inorganic forms of dietary selenium converges on the main pathways. Different selenocompounds have been reported to have crucial roles as chemopreventive agents, such as antioxidant activity, activation of apoptotic pathways, selective cytotoxicity, antiangiogenic effect, and cell cycle modulation. Nowadays, great interest has arisen to find therapies that could enhance the antitumor effects of different Se sources. Herein, different studies are reported related to the effects of combinatorial therapies, where Se is used in combination with proteins, polysaccharides, chemotherapeutic agents or as nanoparticles. Another important factor is the presence of single nucleotide polymorphisms in genes related to Se metabolism or selenoprotein synthesis which could prevent cancer. These studies and mechanisms show promising results in cancer therapies. This review aims to compile studies that have demonstrated the anticancer effects of Se at molecular levels and its potential to be used as chemopreventive and in cancer treatment.

Effect of Selenium Sources on Laying Performance, Egg Quality Characteristics, Intestinal Morphology, Microbial Population and Digesta Volatile Fatty Acids in Laying Hens

The use of toxic and less bioavailable inorganic selenium can now be supplemented with an alternative organic source from bacterial species in nutrition for human and animal benefit. This study investigated the effects of selenium sources on laying performance, egg quality characteristics, intestinal morphology, caecum microbial population, and digesta volatile fatty acids in laying hens. One hundred and forty-four Lohman Brown Classic laying hens, at 23 weeks of age, were divided into four experimental groups (36 hens in each), differing in form of Se supplementation: no Se supplementation (Con), 0.3 mg/kg of inorganic Se in the form of sodium selenite (Na2SeO3), 0.3 mg/kg of organic Se from selenium yeast (Se-Yeast), and 0.3 mg/kg of organic Se from Stenotrophomonas maltophilia (bacterial organic Se, ADS18). The results showed that different dietary Se sources significantly affected laying rate, average egg weight, daily egg mass, feed conversion ratio (FCR), and live bodyweight (LBW) (p < 0.05). However, average daily feed intake and shell-less and broken eggs were unaffected (p > 0.05) among the treatment groups. The findings revealed that selenium sources had no (p > 0.05) effect on egg quality (external and internal) parameters. However, eggshell breaking strength and Haugh unit were significantly (p < 0.05) improved with organic (ADS18 or Se-yeast) Se-fed hens compared to the control group. In addition, egg yolk and breast tissue Se concentrations were higher (p < 0.05) in the dietary Se supplemented group compared to the control. Intestinal histomorphology revealed that hens fed ADS18 or Se-Yeast groups had significantly (p < 0.05) higher villi height in the duodenum and jejunum compared to those fed Na2SeO3 or a basal diet. However, when compared to organic Se fed (ADS18 or Se-Yeast) hens, the ileum villus height was higher (p < 0.05) in the basal diet group; with the lowest in the SS among the treatment groups. A significant increase (p < 0.05) of Lactobacilli spp. and Bifidobacteria spp., and a decrease of Escherichia coli and Salmonella spp. population were observed in the organic (ADS18 or Se-yeast) compared to inorganic supplemented and control hens. The individual digesta volatile fatty acid (VFA) was significantly different, but with no total VFA differences. Thus, bacterial selenoprotein or Se-yeast improved the performance index, egg quality characteristics, egg yolk and tissue Se contents, and intestinal villus height in laying hens. Moreover, caecum beneficial microbes increased with a decrease in the harmful microbe population and affected individual cecal volatile fatty acids without affecting the total VFA of the laying hens digesta.

Effect of Sodium Selenite, Selenium Yeast, and Bacterial Enriched Protein on Chicken Egg Yolk Color, Antioxidant Profiles, and Oxidative Stability

The chicken egg is one of nature's flawlessly preserved biological products, recognized as an excellent source of nutrients for humans. Selenium (Se) is an essential micro-element that plays a key role in biological processes. Organic selenium can be produced biologically by the microbial reduction of inorganic Se (sodium selenite). Therefore, the possibility of integrating Se enriched bacteria as a supplement in poultry feed can provide an interesting source of organic Se, thereby offering health-related advantages to humans. In this study, bacterial selenoproteins from Stenotrophomonas maltophilia was used as a dietary supplement with other Se sources in Lohman brown Classic laying hens to study the egg yolk color, egg yolk and breast antioxidant profile, oxidative stability, and storage effect for fresh and stored egg yolk at 4 ± 2 °C for 14-days. The results showed that dietary Se supplementation significantly (p < 0.05) improved egg yolk color, the antioxidant profile of egg yolk, and breast meat (total carotenoid and phenol content). When the Se treated groups were compared to control groups, there was a significant (p < 0.05) decrease in total cholesterol in fresh and stored egg yolk and breast muscle. In hens that were fed ADS18-Se, the primary oxidation products (MDA) concentrations in the eggs, breast, and thigh muscle, and plasma were significantly (p < 0.05) lower. However, the MDA content increased (p < 0.05) with an extended storage time in egg yolk. In comparison to inorganic Se and basal diets, egg yolk from hens fed organic Se remained fresh for two weeks. The egg yolk color, antioxidant profile, and oxidative status of egg yolk and tissue improve with dietary Se organic supplementation (ADS18 > Se-Yeast). The source of supplemented organic Se is critical for egg enrichment and antioxidant properties. As a result, ''functional eggs'' enriched with organic Se becomes possible to produce.

Selenium in cereals: Insight into species of the element from total amount

Selenium (Se) is a trace mineral micronutrient essential for human health. The diet is the main source of Se intake. Se-deficiency is associated with many diseases, and up to 1 billion people suffer from Se-deficiency worldwide. Cereals are considered a good choice for Se intake due to their daily consumption as staple foods. Much attention has been paid to the contents of Se in cereals and other foods. Se-enriched cereals are produced by biofortification. Notably, the gap between the nutritional and toxic levels of Se is fairly narrow. The chemical structures of Se compounds, rather than their total contents, contribute to the bioavailability, bioactivity, and toxicity of Se. Organic Se species show better bioavailability, higher nutritional value, and less toxicity than inorganic species. In this paper, we reviewed the total content of Se in cereals, Se speciation methods, and the biological effects of Se species on human health. Selenomethionine (SeMet) is generally the most prevalent and important Se species in cereal grains. In conclusion, Se species should be considered in addition to the total Se content when evaluating the nutritional and toxic values of foods such as cereals.

The mixed application of organic and inorganic selenium shows better effects on incubation and progeny parameters

This experiment aims to study the effects of dietary selenium (Se) sources on the production performance, reproductive performance, and maternal effect of breeder laying hens. A total of 2,112 Hyline brown breeder laying hens of 42 wk of age were selected and randomly divided into 3 groups, with 8 repeats in each group and 88 chickens per repeat. The sources of dietary Se were sodium selenite (SS, added at 0.3 mg/kg), L-selenomethionine (L-SM, added at 0.2 mg/kg), and combination of SS and L-SM (SS 0.15 mg/kg + L-SM 0.15 mg/kg). The pretest period was 7 d, and the breeding period was 49 d. Compared with 0.3 mg/kg SS, the addition of 0.2 mg/kg L-SM in the diet significantly increased the hatchability (P < 0.05) and the Se content (P < 0.05) in egg yolk and chicken embryo tissues and improved the activity of yolk glutathione peroxidase (GSH-px) effectively (P < 0.05). Treatment with 0.2 mg/kg L-SM also reduced the content of yolk malondialdehyde (P < 0.05) and significantly improved the antioxidant performance of 1-day-old chicks, as manifested by increased activity of antioxidant enzymes (GSH-px, total antioxidant capacity and the ability to inhibit hydroxyl radicals) in serum, pectoral, heart, and liver (P < 0.05). This treatment decreased the malondialdehyde content (P < 0.05) and increased the expression of liver glutathione peroxidase 4 and deiodinase 1 mRNA (P < 0.05). Adding L-SM to the diets of chickens increased the hatchability of breeder eggs as well as the amount of Se deposited and antioxidant enzyme activity in breeder eggs and embryos. Compared with SS, L-SM was more effectively transferred from the mother to the embryo and offspring, showing efficient maternal nutrition. For breeder diets, the combination of organic and inorganic Se (0.15 mg/kg SS + 0.15 mg/kg L-SM) is an effective nutrient supplementation technology program for effectively improving the breeding performance of breeders and the antioxidant performance and health level of offspring chicks.

Methylation of selenocysteine catalysed by thiopurine S-methyltransferase

BACKGROUND

Methylation driven by thiopurine S-methylatransferase (TPMT) is crucial for deactivation of cytostatic and immunosuppressant thiopurines. Despite its remarkable integration into clinical practice, the endogenous function of TPMT is unknown.

METHODS

To address the role of TPMT in methylation of selenium compounds, we established the research on saturation transfer difference (STD) and ⁷⁷Se NMR spectroscopy, fluorescence measurements, as well as computational molecular docking simulations.

RESULTS

Using STD NMR spectroscopy and fluorescence measurements of tryptophan residues in TPMT, we determined the binding of selenocysteine (Sec) to human recombinant TPMT. By comparing binding characteristics of Sec in the absence and in the presence of methyl donor, we confirmed S-adenosylmethionine (SAM)-induced conformational changes in TPMT. Molecular docking analysis positioned Sec into the active site of TPMT with orientation relevant for methylation reaction. Se-methylselenocysteine (MeSec), produced in the enzymatic reaction, was detected by ⁷⁷Se NMR spectroscopy. A direct interaction between Sec and SAM in the active site of rTPMT and the formation of both products, MeSec and S-adenosylhomocysteine, was demonstrated using NMR spectroscopy.

CONCLUSIONS

The present study provides evidence on in vitro methylation of Sec by rTPMT in a SAM-dependant manner.

GENERAL SIGNIFICANCE

Our results suggest novel role of TPMT and demonstrate new insights into enzymatic modifications of the 21st amino acid.

Nano in nano: Biosynthesized gold and iron nanoclusters cargo neoplastic exosomes for cancer status biomarking

Timely detection is crucial for successful treatment of cancer. The current study describes a new approach that involves utilization of the tumor cell environment for bioimaging with in-situ biosynthesized nanoscale gold and iron probes and subsequent dissemination of Au-Fe nanoclusters from cargo exosomes within the circulatory system. We have isolated the Au-Fe cargo exosomes from the blood of the treated murine models after in situ biosyntheses from their respective pre-ionic solutions (HAuCl₄, FeCl₂), whereas Na₂SeO₃ supplementation added into Au lethal effect. The microarray data of various differentially expressed genes revealed the up-regulated tumor ablation and metal binding genes in SGC-7901 cell lines after treatment with Au-Fe-Se triplet ionic solution. The isolation of Au-Fe nanoclusters cargo exosomes (nano in nano) after secretion from deeply seated tumors may help in early diagnosis and reveal the tumor ablation status during and after the relevant treatment like radio-chemo therapies et al.

Effect of sodium selenite and selenium yeast on performance, egg quality, antioxidant capacity, and selenium deposition of laying hens

This study compared the effects of sodium selenite and selenium yeast and their combination on laying performance, egg quality, antioxidant capacity, and selenium (Se) contents in tissues and eggs. Two-hundred-eighty-eight Jing Hong layers that were similar in laying rate (87.5 ± 0.38%) and body weight (1.70 ± 0.02 kg) were randomly distributed into 4 treatments for 11 wk (from 203 d old to 279 d old) with 9 replicates of 8 hens per replicate. The diets (corn-soybean meal diet) were supplemented with 0 [blank control (BC)], 0.3 mg/kg Se from sodium selenite (SS), 0.15 mg/kg Se from sodium selenite and 0.15 mg/kg Se from Se yeast (SS+SY), or 0.3 mg/kg Se from Se yeast (SY). Results showed that the laying rate of the SS+SY group increased significantly (P < 0.05) compared to the BC and SY groups. There were no differences (P > 0.05) in egg quality between the Se-supplemented diets and the BC diet. The serum glutathione peroxidase (GSH-Px) activity was increased (P < 0.01) in hens fed Se-supplemented diets compared to the BC diet. The liver superoxide dismutase (SOD) activity of the SY group was increased significantly (P < 0.05) compared to the BC group. Significant increase (P < 0.01) due to SY supplementation was noted in the serum vitamin E content compared to BC and SS. Layers fed Se-supplemented diets had higher (P < 0.01) contents of Se in the serum, liver, and kidney compared to the BC diet. Compared to BC, Se content in eggs was significantly increased (P < 0.05) by feeding supplementary Se. In conclusion, the effects of SS and Se yeast were approximately equal in promoting antioxidant capacity of laying hens, while Se yeast is easier to deposit into eggs and tissues. The diet with added equal amounts of the 2 sources of Se was more cost effective and affordable than a comparable amount of Se yeast to obtain the promising production performance and nearly similar Se deposition.

Invited review: Mineral absorption mechanisms, mineral interactions that affect acid-base and antioxidant status, and diet considerations to improve mineral status

Several minerals are required for life to exist. In animals, 7 elements (Ca, P, Mg, Na, K, Cl, and S) are required to be present in the diet in fairly large amounts (grams to tens of grams each day for the dairy cow) and are termed macrominerals. Several other elements are termed microminerals or trace minerals because they are required in much smaller amounts (milligrams to micrograms each day). In most cases the mineral in the diet must be absorbed across the gastrointestinal mucosa and enter the blood if it is to be of value to the animal. The bulk of this review discusses the paracellular and transcellular mechanisms used by the gastrointestinal tract to absorb each of the various minerals needed. Unfortunately, particularly in ruminants, interactions between minerals and other substances within the diet can occur within the digestive tract that impair mineral absorption. The attributes of organic or chelated minerals that might permit diet minerals to circumvent factors that inhibit absorption of more traditional inorganic forms of these minerals are discussed. Once absorbed, minerals are used in many ways. One focus of this review is the effect macrominerals have on the acid-base status of the animal. Manipulation of dietary cation and anion content is commonly used as a tool in the dry period and during lactation to improve performance. A section on how the strong ion theory can be used to understand these effects is included. Many microminerals play a role in the body as cofactors of enzymes involved in controlling free radicals within the body and are vital to antioxidant capabilities. Those same minerals, when consumed in excess, can become pro-oxidants in the body, generating destructive free radicals. Complex interactions between minerals can compromise the effectiveness of a diet in promoting health and productivity of the cow. The objective of this review is to provide insight into some of these mechanisms.

The Epidemiology of Selenium and Human Cancer

The relation between selenium and cancer has been one of the most hotly debated topics in human health over the last decades. Early observational studies reported an inverse relation between selenium exposure and cancer risk. Subsequently, randomized controlled trials showed that selenium supplementation does not reduce the risk of cancer and may even increase it for some types, including advanced prostate cancer and skin cancer. An increased risk of diabetes has also been reported. These findings have been consistent in the most methodologically sound trials, suggesting that the early observational studies were misleading. Other studies have investigated selenium compounds as adjuvant therapy for cancer. Though there is currently insufficient evidence regarding the utility and safety of selenium compounds for such treatments, this issue is worthy of further investigation. The study of selenium and cancer is complicated by the existence of a diverse array of organic and inorganic selenium compounds, each with distinct biological properties, and this must be taken into consideration in the interpretation of both observational and experimental human studies.

Selenium: an element for life

This review aims to illustrate the importance of selenium (Se) for maintenance of overall health, especially for the thyroid, immunity, and homeostasis. Furthermore, it outlines the role of Se in reproduction and in virology and discusses the effects of Se supplementation in critical illness. The multifaceted aspects of this essential nutrient have attracted worldwide clinical and research interest in the last few decades. Se exerts its activity in the form of the aminoacid selenocysteine incorporated in selenoproteins. The impact of Se administration should be considered in relation to its apparent U shaped effects, i.e., exhibiting major advantages in Se-deficient individuals but specific health risks in those with Se excess. Addition of selenium to the administration of levothyroxine may be useful in patients with low Se intake and with mild-form or early-stage Hashimoto's thyroiditis (HT). Serum Se concentration (possibly also at tissue level) decreases in inflammatory conditions and may vary with the severity and duration of the inflammatory process. In such cases, the effect of Se supplementation seems to be useful and rational. Meanwhile, Se's ability to improve the activity of T cells and the cytotoxicity of natural killer cells could render it effective in viral disease. However, the evidence, and this should be stressed, is at present conflicting as to whether Se supplementation is of benefit in patients with HT, though there are indications that it is advantageous in cases of mild/moderate Graves' Orbitopathy. The role of Se in type 2 diabetes mellitus (T2DM) is ambiguous, driven by both Se intake and serum levels. The evidence that insulin and glycaemia influence the transport and activity of Se, via regulatory activity on selenoproteins, and that high serum Se may have a diabetogenic effect suggests a 'Janus-effect' of Se in T2DM. Though the evidence is not as yet clear-cut, the organic form (selenomethionine), due to its pharmacokinetics, is likely to be more advantageous in long-term prevention, and supplementation efforts, while the inorganic form (sodium selenite) has proven effective in an acute, e.g., sepsis, clinical setting. Recent data indicate that functional selenoprotein single-nucleotide polymorphisms (SNPs) may interfere with Se utilization and effectiveness.

Selenium as an alternative peptide label - comparison to fluorophore-labelled penetratin

In the present study, the impact on peptide properties of labelling peptides with the fluorophore TAMRA or the selenium (Se) containing amino acid SeMet was evaluated. Three differently labelled variants of the cell-penetrating peptide (CPP) penetratin (Pen) were synthesized, PenM(Se), TAMRA-PenM(Se) and TAMRA-Pen. The labelled peptides were characterized in terms of hydrodynamic radius, secondary structure during peptide-membrane interaction, effect on membrane leakage induction, uptake efficiency in HeLa cells. Furthermore, stability of peptides and identities of degradation products in cell media and cell lysate were evaluated. TAMRA-labelling increased the hydrodynamic radius of Pen and PenM(Se) significantly. Labelling with Se caused no or minimal changes in size, secondary structure and membrane leakage induction in concentration levels relevant for cellular uptake studies. Similar degradation patterns of all labelled peptides were observed in HBSS media; degradation was mainly due to oxidation. Cellular uptake was significantly higher for the TAMRA labelled peptides as compared to Se-labelled Pen. Extensive degradation was observed in media during cellular uptake studies, however, in all cell lysates, primarily the intact peptide (PenM(Se), TAMRA-PenM(Se) or TAMRA-Pen) was observed. Selenium labelling caused minimal alteration of the physicochemical properties of the peptide and allowed for absolute quantitative determination of cellular uptake by inductively coupled plasma mass spectrometry. Selenium is thus proposed as a promising alternative label for quantification of peptides in general, altering the properties of the peptide to a minor extent as compared to commonly used peptide labels.

Differential protein expression of Caco-2 cells treated with selenium nanoparticles compared with sodium selenite and selenomethionine

The study was designed to determine the differential protein expression of Caco-2 cells treated with different forms of selenium including sodium selenite, selenomethionine (Se-Met), and selenium nanoparticles (nano-Se). Two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) and mass spectrometry (MS) were used to identify the differentially expressed proteins. The results indicated that seven protein spots, ubiquitin-conjugating enzyme E2 (E2), glutathione synthetases (GS), triosephosphate isomerase (TSP), T-complex protein 1 subunit zeta (TCPZ), lamin-B1, heterogeneous nuclear ribonucleoprotein F (hnRNP F), and superoxide dismutase [Cu-Zn] (Cu, Zn-SOD) were significantly different among all the groups. According to the order of control, sodium selenite, Se-Met, and Nano-Se, the expression levels of two proteins (E2 and GS) increased and the other differential proteins were reverse. Except for E2, there were no significant differences in other protein expressions between the groups treated with nano-Se and Se-Met.

Quantification of pharmaceutical peptides using selenium as an elemental detection label

Se-labelling of pharmaceutical biomolecules provides detailed quantitative and qualitative information on the fate of the biomolecule in cell uptake studies.

Long-term selenium supplementation in HaCaT cells: importance of chemical form for antagonist (protective versus toxic) activities

The beneficial effect of selenium (Se) on cancer is known to depend on the chemical form, the dose and the duration of the supplementation. The aim of this work was to explore long term antagonist (antioxidant versus toxic) effects of an inorganic (sodium selenite, Na2SeO3) and an organic (seleno-L-methionine, SeMet) forms in human immortalized keratinocytes HaCaT cells. HaCaT cells were supplemented with Na2SeO3 or SeMet at micromolar concentrations for 144 h, followed or not by UVA radiation. Se absorption, effects of UVA radiation, cell morphology, antioxidant profile, cell cycle processing, DNA fragmentation, cell death triggered and caspase-3 activity were determined. At non-toxic doses (10 μM SeMet and 1 μM Na2SeO3), SeMet was better absorbed than Na2SeO3. The protection of HaCaT from UVA-induced cell death was observed only with SeMet despite both forms increased glutathione peroxidase-1 (GPX1) activities and selenoprotein-1 (SEPW1) transcript expression. After UVA irradiation, malondialdehyde (MDA) and SH groups were not modulated whatever Se chemical form. At toxic doses (100 μM SeMet and 5 μM Na2SeO3), Na2SeO3 and SeMet inhibited cell proliferation associated with S-G2 blockage and DNA fragmentation leading to apoptosis caspase-3 dependant. SeMet only led to hydrogen peroxide production and to a decrease in mitochondrial transmembrane potential. Our study of the effects of selenium on HaCaT cells reaffirm the necessity to take into account the chemical form in experimental and intervention studies.

The need for a reassessment of the safe upper limit of selenium in drinking water

Results of recent epidemiologic studies suggest the need to reassess the safe upper limit in drinking water of selenium, a metalloid with both toxicological and nutritional properties. Observational and experimental human studies on health effects of organic selenium compounds consumed through diet or supplements, and of inorganic selenium consumed through drinking water, have shown that human toxicity may occur at much lower levels than previously surmised. Evidence indicates that the chemical form of selenium strongly influences its toxicity, and that its biological activity may differ in different species, emphasizing the importance of the few human studies on health effects of the specific selenium compounds found in drinking water. Epidemiologic studies that investigated the effects of selenate, an inorganic selenium species commonly found in drinking water, together with evidence of toxicity of inorganic selenium at low levels in from in vitro and animal studies, indicate that health risks may occur at exposures below the current European Union and World Health Organization upper limit and guideline of 10 and 40 μg/l, respectively, and suggest reduction to 1 μg/l in order to adequately protect human health. Although few drinking waters are currently known to have selenium concentrations exceeding this level, the public health importance of this issue should not be overlooked, and further epidemiologic research is critically needed in this area.

Inductively coupled plasma-MS in drug development: bioanalytical aspects and applications

The vast majority of today's modern bioanalytical methods for pharmacokinetic, pharmacodynamic and immunogenicity purposes are based on LC-MS/MS and immunoanalytical approaches. Indeed, these methodologies are suitable for a wide range of molecules from small to large. For a smaller but not insignificant group of compounds, LC-MS/MS is not suitable - or in some cases much less suitable - as a reliable bioanalytical methodology, and inductively coupled plasma (ICP)-MS is a more appropriate methodology. ICP-MS is one of these less widely used techniques in drug development. This methodology is predominantly used for elemental bioanalysis for pharmacokinetics, for imaging purposes, for mass-balance, food-effect and biomarker studies. In addition, in the last couple of years an increasing number of applications has been published, where ICP-MS and its various hyphenations (LC-ICP-MS, CE-ICP-MS) have been used for speciation/metabolism and proteomics studies. Here, the analytical potential, the quantitative bioanalytical aspects, the various modes of operation and the challenges of the application of ICP-MS in life sciences applications are given. This includes an overview of recent applications in this area in scientific literature, the various hyphenation possibilities and their application areas and the analysis of the various sample matrices applicable to these fields. It also provides a brief outlook of where the potential of this technique lies in the future of regulated bioanalysis and drug development.

Human urinary excretion and metabolism of (82)Se-enriched selenite and selenate determined by LC-ICP-MS

Urinary excretion of selenium after ingestion of isotope labeled selenite and selenate was studied in seven healthy volunteers, 4 men and 3 women (age 28-50 years). An aqueous solution containing 330 μL (82)Se-selenate (corresponding to 74.3 μg (82)Se) was given orally and urine samples were subsequently collected during the following 24 hours. The scheme was repeated four weeks later with a 280 μL (82)Se-selenite solution (corresponding to 74.4 μg (82)Se). The amount of total Se in the urine samples was determined by inductively coupled mass spectrometry. The mean total urinary excretion of (82)Se following (82)Se-selenate administration was 33.7% (range 15.6-42.5%) while the mean total excretion of (82)Se after (82)Se-selenite administration was 3.2% (range 2.8-3.9%) of the ingested amount. LC-ICPMS analysis of the urine samples showed that the majority of the selenium excreted after selenate ingestion was unchanged selenate for 6 of the individuals while one individual had metabolized a fraction (approx. 20%) of the selenate to selenosugar. Ingestion of 10 times larger doses of selenite in two individuals resulted in 13-23% excretion primarily excreted as selenosugar. These results show that the human metabolic pathways of selenite and selenate are different and indicate that not all selenate, although well absorbed, may be available for the beneficial health effects.

Catalytic activity of selenomethionine in removing amino acid, peptide, and protein hydroperoxides

Selenium is a critical trace element, with deficiency associated with numerous diseases including cardiovascular disease, diabetes, and cancer. Selenomethionine (SeMet; a selenium analogue of the amino acid methionine, Met) is a major form of organic selenium and an important dietary source of selenium for selenoprotein synthesis in vivo. As selenium compounds can be readily oxidized and reduced, and selenocysteine residues play a critical role in the catalytic activity of the key protective enzymes glutathione peroxidase and thioredoxin reductase, we investigated the ability of SeMet (and its sulfur analogue, Met) to scavenge hydroperoxides present on amino acids, peptides, and proteins, which are key intermediates in protein oxidation. We show that SeMet, but not Met, can remove these species both stoichiometrically and catalytically in the presence of glutathione (GSH) or a thioredoxin reductase (TrxR)/thioredoxin (Trx)/NADPH system. Reaction of the hydroperoxide with SeMet results in selenoxide formation as detected by HPLC. Recycling of the selenoxide back to SeMet occurs rapidly with GSH, TrxR/NADPH, or a complete TrxR/Trx/NADPH reducing system, with this resulting in an enhanced rate of peroxide removal. In the complete TrxR/Trx/NADPH system loss of peroxide is essentially stoichiometric with NADPH consumption, indicative of a highly efficient system. Similar reactions do not occur with Met under these conditions. Studies using murine macrophage-like J774A.1 cells demonstrate a greater peroxide-removing capacity in cells supplemented with SeMet, compared to nonsupplemented controls. Overall, these findings demonstrate that SeMet may play an important role in the catalytic removal of damaging peptide and protein oxidation products.