Selenium-containing Amino Acids Research Articles

Exposure to Selenomethionine and Selenocystine Induces Redox-Mediated ER Stress in Normal Breast Epithelial MCF-10A Cells.

Selenium is an essential trace element co-translationally incorporated into selenoproteins with important biological functions. Health benefits have long been associated with selenium supplementation. However, cytotoxicity is observed upon excessive selenium intake. The aim of this study is to investigate the metabolic pathways underlying the response to the selenium-containing amino acids selenomethionine and selenocysteine in a normal human breast epithelial cell model. We show that both selenomethionine and selenocystine inhibit the proliferation of non-cancerous MCF-10A cells in the same concentration range as cancerous MCF-7 and Hela cells, which results in apoptotic cell death. Selenocystine exposure in MCF-10A cells caused a severe depletion of free low molecular weight thiols, which might explain the observed upregulation of the expression of the oxidative stress pathway transcription factor NRF2. Both selenomethionine and selenocystine induced the expression of target genes of the unfolded protein response (GRP78, ATF4, CHOP). Using a redox-sensitive fluorescent probe targeted to the endoplasmic reticulum (ER), we show that both selenoamino acids shifted the ER redox balance towards an even more oxidizing environment. These results suggest that alteration of the redox state of the ER may disrupt protein folding and cause ER stress-induced apoptosis in MCF-10A cells exposed to selenoamino acids.

Vibrational analysis of auranofin complexes with cysteine and selenocysteine unveils distinct binding motifs and specific unimolecular reactivity

Auranofin (AF) is the most used gold(I)-containing drugs, whose mechanism of action involves targeting sulfur and selenium-containing amino acids, including cysteine (Cys) and selenocysteine (Sec). These residues are present in...

Effect of dry extract from Saccharomyces cerevisiae culture with selenium-containing amino acids on the productivity and chemical composition of meat of broiler chickens

Introduction of biologically active supplements to the diet of poultry results in maximal use of nutrients and positively influences the live weight and slaughter parameters. This promotes rational and economical use of fodders and boosts the poultry productivity. We studied a mineral feed supplement – an organic selenium compound, which has a much greater bioavailability than inorganic sources of selenium. Selenomethionine is easily digested in the organism and effectively used for synthesis of proteins. Broiler chickens of the experimental group that had been consuming the selenoamino-acid feed additive had greater live weight at the age of 14–42 days, compared with the control. Intake of the mineral supplement by the broiler chickens in the experimental group increased their mean daily increment by 8.5% and the absolute increment by 8.6%, compared with the control peers. In the experimental group of broilers, the mineral supplement increased the pre-slaughter live weight by 8.4%, weight of intact carcass by 10.1%. Also, the weight of the semi-processed carcasses (i.e. those with removed intestines and cloaca, filled crop, oviduct and ovary (in female specimens) increased by 4.3%, and the weight of the processed carcasses (the internal organs and abdominal-cavity fat and esophagus of which were removed, without head, legs and wing metacarpals) increased by 8.0%, compared with the control group of broilers. In the experimental group, the feed supplement gave 13.7% rise in the weight of the breast muscles and 14.5% increase in the weight of the thigh muscles, compared with the control group. Intake of this supplement in the experimental group promoted 7.5% increase in the weight of the gizzard by and 9.2% increase in the weight of the duodenum, as compared with the control. Usage of the selenoamino-acid feed supplement increased the protein concentration in the breast muscles of the broiler chickens by 1.9%, compared with the control. Intake of the mineral supplement increased the amounts of dry matter and fat in the thigh muscles of the experimental group, compared with the control group. Therefore, adding dry yeast extract to diet of broilers together with selenium-containing amino acids is a promising method of increasing the effectiveness of poultry farming.

Intravenous Infusion of High Dose Selenite in End-Stage Cancer Patients: Analysis of Systemic Exposure to Selenite and Seleno-Metabolites

Cancer is one of the main causes of human death globally and novel chemotherapeutics are desperately required. As a simple selenium oxide, selenite is a very promising chemotherapeutic because of pronounced its dose-dependent tumor-specific cytotoxicity. We previously published a first-in-man systematic phase I clinical trial in patients with cancer (from IV to end-stage) (the SECAR trial) showing that selenite is safe and tolerable with an unexpectable high maximum tolerated dose (MTD) and short half-life. In the present study, we analyzed the selenium species in plasma samples, from the patients participating in the SECAR trial and from various time points and dose cohorts using LC-ICP-MS. In conclusion, selenite, selenosugars, and 1-2 unidentified peaks that did not correspond to any standard, herein denoted ui-selenium, were detected in the plasma. However, trimethylated selenium (trimethylselenonoium) was not detected. The unidentified ui-selenium was eluting close to the selenium-containing amino acids (selenomethionine and selenocysteine) but was not part of a protein fraction. Our data demonstrate that the major metabolite detected was selenosugar. Furthermore, the identification of selenite even long after the administration is remarkable and unexpected. The kinetic analysis did not support that dosing per the body surface area would reduce interindividual variability of the systemic exposure in terms of trough concentrations.

Enantioselective organocatalytic syntheses of α-selenated α- and β-amino acid derivatives.

Selenium-containing amino acids are valuable targets but methods for the stereoselective α-selenation of simple amino acid precursors are rare. We herein report the enantioselective electrophilic α-selenation of azlactones (masked α-amino acid derivatives) and isoxazolidin-5-ones (masked β-amino acids) using Cinchona alkaloids as easily accessible organocatalysts. A variety of differently substituted derivatives was accessed with reasonable levels of enantioselectivities and further studies concerning the stability and suitability of these compounds for further manipulations have been carried out as well.

Nanostructured selenium-containing amino acids: properties and applications in the production of functional foods

The paper presents the properties of nanostructured Sel-Plex; self-organization and particle sizes are determined using the NTA method. It is shown that the average size of nanocapsules does not significantly depend on the nature of the shell and is 217–245 nm. It is proposed to use nanostructured Sel-Plex as a selenium-containing preparation in the production of marmalade and bakery products.

Adaptive Thermogenesis in a Mouse Model Lacking Selenoprotein Biosynthesis in Brown Adipocytes.

Selenoproteins are a class of proteins with the selenium-containing amino acid selenocysteine (Sec) in their primary structure. Sec is incorporated into selenoproteins via recoding of the stop codon UGA, with specific cis and trans factors required during translation to avoid UGA recognition as a stop codon, including a Sec-specific tRNA, tRNA[Ser]Sec, encoded in mice by the gene Trsp. Whole-body deletion of Trsp in mouse is embryonically lethal, while targeted deletion of Trsp in mice has been used to understand the role of selenoproteins in the health and physiology of various tissues. We developed a mouse model with the targeted deletion of Trsp in brown adipocytes (Trspf/f-Ucp1-Cre+/−), a cell type predominant in brown adipose tissue (BAT) controlling energy expenditure via activation of adaptive thermogenesis, mostly using uncoupling protein 1 (Ucp1). At room temperature, Trspf/f-Ucp1-Cre+/− mice maintain oxygen consumption and Ucp1 expression, with male Trspf/f-Ucp1-Cre+/− mice accumulating more triglycerides in BAT than both female Trspf/f-Ucp1-Cre+/− mice or Trspf/f controls. Acute cold exposure neither reduced core body temperature nor changed the expression of selenoprotein iodothyronine deiodinase type II (Dio2), a marker of adaptive thermogenesis, in Trspf/f-Ucp1-Cre+/− mice. Microarray analysis of BAT from Trspf/f-Ucp1-Cre+/− mice revealed glutathione S-transferase alpha 3 (Gsta3) and ELMO domain containing 2 (Elmod2) as the transcripts most affected by the loss of Trsp. Male Trspf/f-Ucp1-Cre+/− mice showed mild hypothyroidism while downregulating thyroid hormone-responsive genes Thrsp and Tshr in their BATs. In summary, modest changes in the BAT of Trspf/f-Ucp1-Cre +/− mice implicate a mild thyroid hormone dysfunction in brown adipocytes.

Selenium-Containing Amino Acids Protect Dextran Sulfate Sodium-Induced Colitis via Ameliorating Oxidative Stress and Intestinal Inflammation

BackgroundInflammatory bowel disease (IBD) is characterized by chronic relapsing inflammation of the gastrointestinal tract. Oxidative stress plays a pivotal role in the pathogenesis of IBD. Selenium-containing amino acids reportedly have anti-oxidative and anti-inflammatory properties, but it remains unknown if selenium-containing amino acids can be used to treat IBD. This study aimed to investigate the effects of two selenium-containing amino acids – selenocysteine and selenocystine – on oxidative stress and chronic inflammation in a mouse model of dextran sulfate sodium (DSS)-induced IBD.MethodologyC57BL/6 mice were randomly assigned to the following six groups: control, DSS, DSS+selenocysteine, DSS+selenocystine, DSS+sodium selenite, and DSS+N-acetylcysteine (NAC). IBD was induced by 3% DSS. Pro-inflammatory cytokines [interleukin-1β (IL-1β), monocyte chemotactic protein 1 (MCP-1), IL-6, and tumor necrosis factor-α (TNF-α)] and markers for oxidative and anti-oxidative stress [malondialdehyde (MDA), reactive oxygen species (ROS), superoxide dismutase (SOD), and glutathione peroxidase (GPx)] were measured using immunohistochemical analysis.ResultsSelenocysteine and selenocystine significantly attenuated IBD-related symptoms, including preventing weight loss, decreasing disease activity index (DAI) scores, and increasing colon length. Selenocysteine and selenocystine significantly ameliorated the DSS-induced oxidative stress, as demonstrated by a reduction in ROS and MDA activity and an increase in SOD and GPx activity. IL-1, MCP-1, IL-6, and TNF-α levels were significantly increased in the IBD mice, while treatment with the selenium-containing amino acids significantly reduced the levels of these pro-inflammatory cytokines. In vivo safety analysis showed minimal side effects of the selenium-containing amino acids.ConclusionWe found that selenocysteine and selenocystine ameliorated DSS-induced IBD via reducing oxidative stress and intestinal inflammation, indicating that selenium-containing amino acids could be a novel therapeutic option for patients with IBD.

Breeding Buckwheat for Increased Levels and Improved Quality of Protein.

Tartary buckwheat (Fagopyrum tataricum (L.) Gaertn.) and common buckwheat (Fagopyrum esculentum Moench) are important sources of proteins with balanced amino-acid compositions, and thus of high nutritional value. The polyphenols naturally present in Tartary buckwheat and common buckwheat lower the true digestibility of the proteins. Digestion-resistant peptides are a vehicle for fecal excretion of steroids, and in this way, for bile acid elimination and reduction of cholesterol concentrations in serum. Buckwheat proteins are more effective compared to soy proteins for the prevention of gallstone formation. Tartary and common buckwheat grain that contains appropriate amounts of selenium-containing amino acids can be produced as functional food products. The protein-rich by-products of buckwheat are a good source of bioactive substances that can suppress colon carcinogenesis by reducing cell proliferation. The grain embryo is a rich source of proteins, so breeding buckwheat with larger embryos is a possible strategy to increase protein levels in Tartary and common buckwheat grain. However, chemical analysis of the grain is the most relevant criterion for assessing grain protein levels and quality.

Selenium Incorporation to Amino Acids in Chlorella Cultures Grown in Phototrophic and Heterotrophic Regimes.

Microalgae accumulate bioavailable selenium-containing amino acids (Se-AAs), and these are useful as a food supplement. While this accumulation has been studied in phototrophic algal cultures, little data exists for heterotrophic cultures. We have determined the Se-AAs content, selenium/sulfur (Se/S) substitution rates, and overall Se accumulation balance in photo- and heterotrophic Chlorella cultures. Laboratory trials revealed that heterotrophic cultures tolerate Se doses ∼8-fold higher compared to phototrophic cultures, resulting in a ∼2-3-fold higher Se-AAs content. In large-scale experiments, both cultivation regimes provided comparable Se-AAs content. Outdoor phototrophic cultures accumulated up to 400 μg g-1 of total Se-AAs and exhibited a high level of Se/S substitution (5-10%) with 30-60% organic/total Se embedded in the biomass. A slightly higher content of Se-AAs and ratio of Se/S substitution was obtained for a heterotrophic culture in pilot-scale fermentors. The data presented here shows that heterotrophic Chlorella cultures provide an alternative for Se-enriched biomass production and provides information on Se-AAs content and speciation in different cultivation regimes.

Role of Selenoproteins in Bacterial Pathogenesis.

The trace element selenium is an essential micronutrient that plays an important role in maintaining homeostasis of several tissues including the immune system of mammals. The vast majority of the biological functions of selenium are mediated via selenoproteins, proteins which incorporate the selenium-containing amino acid selenocysteine. Several bacterial infections of humans and animals are associated with decreased levels of selenium in the blood and an adjunct therapy with selenium often leads to favorable outcomes. Many pathogenic bacteria are also capable of synthesizing selenocysteine suggesting that selenoproteins may have a role in bacterial physiology. Interestingly, the composition of host microbiota is also regulated by dietary selenium levels. Therefore, bacterial pathogens, microbiome, and host immune cells may be competing for a limited supply of selenium. Elucidating how selenium, in particular selenoproteins, may regulate pathogen virulence, microbiome diversity, and host immune response during a bacterial infection is critical for clinical management of infectious diseases.

The Synthesis and Biological Activity of 3,3'-Dimethyl-L-Selenocystine, a New Selenocystine Derivative

Using the known synthesis of L-selenocystine,3,3'-diseleno-bis (2-aminopropionic acid), from β‑chloroalanine, a structural analog of natural sulfur-containing amino acids capable of accumulating selenium in the body, we synthesized a new selenium-containing amino acid 3,3'-dimethyl-L-selenocystine ( ) from α-amino-β-chlorobutyric acid. It was shown that, similarly to the selenium released from natural L-selenocystine, the selenium from 3,3'-dimethyl-L-selenocystine accumulated in rat liver, muscles, and serum, where its concentration exceeded that of the control by 40.63, 14.07 and 22.98%, respectively. A close degree of selenium accumulation in the tissues implied a similar metabolic pathway of the amino acids and biological availability of the trace element from the synthesized amino acid. L-Selenocystine and 3,3'‑dimethyl-L-selenocystine decreased concentrations of free amino acids in rat serum by 12.17 and 11.78%, respectively. The most significant reduction, by 74.6 and 66.4% respectively, was observed for proline, a marker of organism stress. Accumulation of selenium in liver and serum indicated close metabolism of L‑selenocystine and its derivative 3,3'-dimethyl-L-selenocystine.

Selenium strikes back at fungi.

Computational analysis of fungal genomes revealed that some early-branching fungi use selenocysteine, the selenium-containing amino acid, that was thought to be missing from proteins in this lineage.

Stability constant determination of sulfur and selenium amino acids with Cu(II) and Fe(II)

Sulfur- and selenium-containing amino acids are of great biological importance, but their metal-binding properties with biologically-relevant metal ions are not well investigated. Stability constants of the methionine, selenomethionine, methylcysteine, and methylselenocysteine with Cu(II) and Fe(II) were determined by potentiometric titration. Stability constants of Cu(II) with these thio- and selenoether amino acids are in the range of 8.0–8.2 ([CuL]+) and 14.5–14.7 (CuL2) (L = amino acid). Fe(II) interactions with the same thio- and selenoether amino acids are much weaker, with stability constants between 3.5 and 3.8 ([FeL]+) and −4.9 and −5.7 (FeL(OH)). Stability of Fe(II) with penicillamine, a thiol-containing amino acid, is much higher (FeL = 7.48(7) and [FeL]2− = 13.74(2)). For both copper and iron complexes, thio- and selenoether amino acid coordination occurs through the carboxylate and the amine groups as confirmed by infrared spectroscopy, with no stability afforded by thio- or selenoether coordination. The first single-crystal structure of Cu(II) with a selenium-containing amino acid, Cu(SeMet)2, also confirms binding through only the amine and carboxylate groups. The measured Cu(II)-amino-acid stability constants confirm that nearly 100% of the available Cu(II) can be coordinated by these amino acids at pH 7, but very little Fe(II) is bound under these conditions. The relative instability of Fe(II) complexes with thio- and selenoether amino acids is consistent with their inability to prevent metal-mediated oxidative DNA damage. In contrast, the stability constants of these amino acids with Cu(II) weakly correlate to their ability to inhibit DNA damage inhibition.

METABOLISM AND MECHANISM OF TOXICITY OF SELENIUM-CONTAINING SUPPLEMENTS USED FOR OPTIMIZING HUMAN SELENIUM STATUS

The work presents a review devoted to the metabolism and the mechanism of toxicity of seleniumcontaining supplements: elemental selenium, sodium selenite, diacetophenonyl selenide, selenopyrane, ebselen, dimethyl dipyrasolyl selenide and selenium-containing amino acids used for correction of selenium deficiency. Elemental selenium penetrating through cell walls, but not through transport channels demonstrates poorly predicted and difficultly regulated bioavailability. Sodium selenate is known to be the most toxic form of selenium in food. The metabolism of xenobiotic diacetophenonyl selenide resembles that of sodium selenide. The xenobiotic reacts with thiols, for instance, with the reduced form of glutathione leading to the formation of hydrogen selenide. Ebselen is not considered to be a well bioavailable form of selenium and thus possesses low toxicity. Xenobiotic selenopyrane eliminates selenium only in processes of xenobiotic liver exchange, and in our investigations - partially in acid-catalyzed hydrolysis. The metabolism of xenobiotic dimethyl dipyrasolyl selenide having low toxicity is poorly investigated. The toxicity of high doses of selenomethionine is determined by the possibility of incorporation in proteins and vitally important enzymes with dramatic changes of protein quaternary structure. The toxicity of high doses of methylselenocysteine seems to be caused by the lack of an exchange pool in the body and quick regeneration of hydrogen selenide from methylselenol which is formed as a result of enzymatic destruction of this amino acid. Also the issue of the most prospect selenium donor is discussed. The physiological compatibility, the low toxicity, the presence of an exchangeable pool in the organism, the antioxidantal properties and the simplicity of production indicate selenocystine as an optimal selenium donor.

77Se-NMR Probes the Protein Environment of Selenomethionine

77Se NMR is highly sensitive to its chemical environment and can report on the interactions and degrees of freedom available for selenium-containing amino acids in biological systems. Particularly, selenomethionine can be used as a probe for methionine environment, an amino acid which is often found in protein-protein interfaces and in ligand binding sites. Yet, for these larger and more complex biological systems, reliable data interpretation that systematically connects variations of system variables to changes in the NMR spectra is still lacking. To build a biological 77Se magnetic resonance databank, we thus constructed a library of GB1 variants with a single selenomethionine at different locations within the protein. The structure of five of such GB1 variants was solved to 1.2 Å, allowing the conformation of the selenomethionine to be unambiguously determined. We recorded the isotropic 77Se chemical shift for six GB1 variants along with their T1 relaxation times and line width. For four of the GB1 variants we were able to determine the chemical shielding tensor of SeM by 77Se solid-state NMR. Finally, we combine solution and solid-state NMR with the structural information to arrive at general recommendations for the use of selenomethionine as NMR probe in biological systems.

Selenocysteine antagonizes oxygen glucose deprivation-induced damage to hippocampal neurons.

Designing and/or searching for novel antioxidants against oxygen glucose deprivation (OGD)-induced oxidative damage represents an effective strategy for the treatment of human ischemic stroke. Selenium is an essential trace element, which is beneficial in the chemoprevention and chemotherapy of cerebral ischemic stroke. The underlying mechanisms for its therapeutic effects, however, are not well documented. Selenocysteine (SeC) is a selenium-containing amino acid with neuroprotective potential. Studies have shown that SeC can reduce irradiation-induced DNA apoptosis by reducing DNA damage. In this study, the in vitro protective potential and mechanism of action of SeC against OGD-induced apoptosis and neurotoxicity were evaluated in HT22 mouse hippocampal neurons. We cultured HT22 cells in a glucose-free medium containing 2 mM Na2S4O2, which formed an OGD environment, for 90 minutes. Findings from MTT, flow cytometry and TUNEL staining showed obvious cytotoxicity and apoptosis in HT22 cells in the OGD condition. The activation of Caspase-7 and Caspase-9 further revealed that OGD-induced apoptosis of HT22 cells was mainly achieved by triggering a mitochondrial-mediated pathway. Moreover, the OGD condition also induced serious DNA damage through the accumulation of reactive oxygen species and superoxide anions. However, SeC pre-treatment for 6 hours effectively inhibited OGD-induced cytotoxicity and apoptosis in HT22 cells by inhibiting reactive oxygen species-mediated oxidative damage. Our findings provide evidence that SeC has the potential to suppress OGD-induced oxidative damage and apoptosis in hippocampal neurons.

Application of bis-2-(trimethylsilyl)ethyl diselenide to the synthesis of selenium-containing amino acid derivatives

Selenium-containing amino acids play a pivotal role as biomaterials for the synthesis of Se-dependent enzymes and repair proteins. Especially, selenocysteine and selenoglutathione are prominently involved in fundamental biological processes. In this study, a series of selenocysteine (Sec) and selenoglutathione (GSeH) derivatives were synthesized via 2-(trimethylsilyl)ethylselenation as a key step. Our findings suggested the relevance and application of a 2-(trimethylsilyl)ethylselenyl group to the Se-containing amino acid synthesis.

Effect of organic and mineral selenium sources on production performance and selected physiological indicators in swine

The study was conducted on sows (hybrids of wbp × pbz breeds) and their offspring (until day 75 of life) kept on a farm. The aim of the experiment was to compare the effects of different sources of selenium (Se) on the production performance of the animals, Se content in their blood, the level of Se in sow’s colostrum, as well as Gpx, haptoglobin and immunoglobulin levels in the serum of sows and their offspring. Experimental feed mixtures for pregnant sows (LP), lactating sows (LK) and piglets (prestarter and starter) in each treatment had an identical basic composition, differing only in the type of selenium forms. Group I received a mineral form of Se in an amount of 0.2 mg/kg; group II received a mixture of a Se amino acid chelate and the mineral form of Se (0.1 mg/kg of each); group III received a Se amino acid chelate (0.2 mg/kg), and group IV received Se-enriched yeasts (0.2 mg/kg). Beneficial effects of the organic forms of Se were evident already in the lactation period. Sows, especially those from group II receiving 0.2 mg/kg of organic Se, had a higher feed intake, which was related to a higher milk production during lactation. As a result, on the weaning day, piglets from this group were significantly heavier than the other piglets. After weaning, as well, the piglets in this group were significantly heavier. These results were confirmed by parameters of blood serum and whey colostrum. Selenium as a chelate was more available than the mineral and enriched yeast forms. For this reason, the animals receiving the chelate were healthier (fewer inflammations were noted). The animals in this group also showed a better feed conversion compared with the others. The Gpx level in sows’ serum varied depending on the treatment. The highest level of this parameter was determined in sows from group III (receiving 0.2 mg/kg of organic Se), and it differed significantly from its value in the control group. The results showed that the Gpx level was related to the Se concentration in blood serum, which was also confirmed by a higher production of selenocysteine (a part of Gpx). Cells of the animals from this group were better protected against free radicals. Administration of 0.1 mg/kg of organic Se positively affects the performance of animals, but the recommended level in feed is 0.2 mg/kg of a selenium-containing amino acid....

Mass Spectrometry Uncovers Molecular Reactivities of Coordination and Organometallic Gold(III) Drug Candidates in Competitive Experiments That Correlate with Their Biological Effects.

The reactivity of three cytotoxic organometallic gold(III) complexes with cyclometalated C,N,N and C,N ligands (either six- or five-membered metallacycles), as well as that of two representative gold(III) complexes with N-donor ligands, with biological nucleophiles has been studied by ESI-MS on ion trap and time-of-flight instruments. Specifically, the gold compounds were reacted with mixtures of nucleophiles containing l-histidine (imine), l-methionine (thioether), l-cysteine (thiol), l-glutamic acid (carboxylic acid), methylseleno-l-cysteine (selenoether), and in situ generated seleno-l-cysteine (selenol) to judge the preference of the gold compounds for binding to selenium-containing amino acid residues. Moreover, the gold compounds' reactivity was studied with proteins and nucleic acid building blocks. These experiments revealed profound differences between the coordination and organometallic families and even within the family of organometallics, which allowed insights to be gained into the compounds mechanisms of action. In particular, interactions with seleno-l-cysteine appear to reflect well the compounds' inhibition properties of the seleno-enzyme thioredoxin reductase and to a certain extent their antiproliferative effects in vitro. Therefore, mass spectrometry is successfully applied for linking the molecular reactivity and target preferences of metal-based drug candidates to their biological effects. Finally, this experimental setup is applicable to any other metallodrug that undergoes ligand substitution reactions and/or redox changes as part of its mechanism of action.