Influence of Selenium on Mast Cell Mediator Release

Selenium supplementation still enhanced the immune response even in individuals who, according to current standards, would be considered as not being overtly selenium deficient. Mast cells are granulated cells that play a pivotal role in allergic reactions. In this study, we investigated the modulatory effect of sodium selenite on mediator release and degranulation of murine mast cell line (MC/9). Cells were pre-treated with selenium selenite (1, 2, 3 μg/ml) for 24 h and controls left untreated. Then, cells were sensitized overnight with anti-dinitrophenyl (DNP) IgE and challenged with DNP/HSA for degranulation induction. The histamine and prostaglandin D2 (PGD2) were measured by ELISA, and β-hexosaminidase was measured by spectrophotometery method. Selenium-treated cells revealed significant decrease in concentration of PGD2 (P?=?0.019) and β-hexosaminidase (P?=?0.009). In addition, a slight reduction of histamine release by the selenium-treated cells was observed, based on our intracellular and extracellular assessments. The most inhibitory effect of selenium supplementation on mediator release of MC/9 cells was obtained in the presence of 3 μg/ml of sodium selenite. The results of the present study demonstrate beneficial effects of supplemental selenium in attenuating clinical manifestations of allergy and asthma.     

The antimutagenic effect of selenium on 7,12-dimethylbenz(a)anthracene and metabolites in the amesSalmonella/microsome system

The antimutagenic effect of selenium as sodium selenite, sodium selenate, selenium dioxide, and seleno-methionine was studied in the AmesSalmonella/microsome mutagenicity test using 7,12-dimethylbenz(a)anthracene (DMBA) and some of its metabolites. Selenium (20 ppm) as sodium selenite reduced the number of histidine revertants on plates containing up to 100 μg DMBA/plate. Increasing concentrations of selenium as sodium selenite, sodium selenate, and selenium dioxide up to 40 ppm Se progressively decreased the number of revertants caused by 50 μg DMBA. DMBA and its metabolites 7-hydroxymethyl-12-methylbenz(a)anthracene, 12-hydroxymethyl-7-methylbenz(a)anthracene, and 3-hydroxy-7,12-dimethylbenz(a)anthracene were mutagenic forSalmonella typhimurium TA100 in the presence of an S-9 mixture. Selenium supplementation as Na₂SeO₃ reduced the number of revertants induced by these metabolites to background levels. The antimutagenic effect of inorganic selenium compounds cannot be explained by toxicity of selenium as determined by viability tests withSalmonella typhimurium TA100. Selenium supplementation in all forms examined, except sodium selenate, decreased the rate of spontaneous reversion. Selenium as sodium selenate was slightly mutagenic at concentrations of 4 ppm or less. Higher concentration of Na₂SeO₄ inhibited the mutagenicity of DMBA. The present studies support the anticarcinogenic potential of selenium and indicate that form and concentration are important factors in this trace element's efficacy.     

Preparation,characterization and immunomodulatory activity of selenium-enriched exopolysaccharide produced by bacterium Enterobacter cloacae Z0206

The tolerant-selenium exopolysaccharide-producing bacterial strain Enterobacter cloacae Z0206 was batch cultured in PDA medium containing optimal concentration of sodium selenite. Selenium was accumulated efficiently in Enterobacter cloacae Z0206 during cultivation with selenium. Inorganic selenite could be transformed into organic forms. Selenium-enriched exopolysaccharide (Se-ECZ-EPS-1) was purified from the fermentation liquid. Selenium content of Se-ECZ-EPS-1 was 12.962 μg/g. Se-ECZ-EPS-1 with Mw of 29,300 Ka was composed of Glc, Gal and Mann with molar ratio of 8.530:0.061:0.706. Administration of Se-ECZ-EPS-1 to cyclophosphamide (CP)-exposed animals resulted in improvement of cellular and humoral immune responses. These findings indicated that Se-ECZ-EPS-1 may act as potent immunomodulatory agents.     

硒对H2O2诱导的人甲状腺细胞凋亡和超微结构改变的影响

目的：观察硒对H2O2诱导的人甲状腺上皮细胞凋亡和超微结构改变的影响。方法：取良性甲状腺腺瘤旁正常组织进行细胞培养。加硒（10^-7mol／L）或不加硒后加入不同浓度H2O2（0～800μmol／L）刺激单层培养的甲状腺细胞,流式细胞术（FCM）检测甲状腺细胞凋亡率并在电镜下观察其超微结构的改变.结果：经过H2O2作用24h的人甲状腺细胞,随H2O2浓度升高,细胞凋亡率逐渐升高;电镜下甲状腺细胞超微结构呈损伤型改变,甚至出现凋亡、死亡。预先加入10^-7mol／L硒可降低细胞凋亡率,可明显减轻亚细胞结构损伤。结论：硒可减轻H2O2诱发的人甲状腺细胞的氧化损伤,拮抗其导致的细胞凋亡。     

Dimethylsulfoxide maintains human thyroid cells in suspension culture, facilitating synthesis and release of thyroid hormone

Usually, human thyrocytes in primary culture rapidly lose their thyroid function and fail to synthesize or release thyroid hormone after 3-5 days of culture. By culturing thyroid follicles obtained from patients with Graves' disease in medium supplemented with TSH and a low concentration of fetal calf serum (1%), thyrocytes can maintain thyroid function for several days. We have found that the addition of dimethylsulfoxide to culture medium (1.7%) furthermore enhanced and maintained thyroid function (de novo synthesis and release of [125I] thyroxine) for more than 13 days, probably by inhibiting dedifferentiation of thyrocytes. The present bioassay will be also useful for detecting thyroid stimulating immunoglobulin in patients with Graves' disease.     

Effect of fertilization on selenium content of tea and the nutritional function of Se-enriched tea in rats

The present study examined the effect of fertilization with sodium selenite on the selenium content of tea and the nutritional function of Se-enriched tea. Selenium content of tea leaves was increased up to 0.36 g g^–1 by the application of sodium selenite to soil at 0.5 and 1.0 kg Se ha^–1. Application by a Se-enriched organic manure at a rate of 0.5 kg Se ha^–1 provided a higher biological availability of selenium for plant uptake compared with a similar amount of sodium selenite. Foliar spray of sodium selenite at 50–100 g Se ha^–1 increased the selenium content to 0.32–1.45 g g^–1 in tea leaves sampled at the 8–26 days after spraying. Selenium content in the blood and liver, glutathione peroxidase activity in blood of rats were significantly enhanced by feeding of an extracted solution of Se-enriched tea leaves and sodium selenite. Glutathione peroxidase activity in liver of rats fed with Se-enriched tea was higher than that fed with sodium selenite, indicating that the selenium in Se-enriched tea leaves is a more effective Se source than sodium selenite. Increasing the Se level in food products through the application of a selenium fertilizer is a safe, effective and feasible means of increasing the selenium intake of human and animals in low selenium areas of China.     

Efficient Preparation of Selenium/Glutathione-Enriched Candida utilis and Its Biological Effects on Rats

The main purpose of this study was to prepare selenium/glutathione-enriched Candida utilis and investigate its effect on growth performance, antioxidant capacity, and immune response in rats. The preparation of the selenium/glutathione-enriched yeast was conducted using fed-batch culture for high cell density. The optimal culture conditions for increased intracellular organic selenium and glutathione contents were as follows: the concentrated medium was fed beginning at 12?h using a polynomial feeding strategy until a total glucose concentration of 150?g/l was reached, and sodium selenite was continuously added together with glucose to a total concentration of 60?mg/l. As a result, 81?% of sodium selenite was assimilated and transformed into organic selenium by C. utilis under optimal conditions, which in turn resulted in greater glutathione accumulation and lower malondialdehyde cellular content in the yeast. To investigate and compare the effects of the prepared selenized C. utilis and other dietary supplements, 40 female rats were divided into five groups of eight rats each, following a randomized block design. Experimental feeding was conducted for a period of 6?weeks. Selenium supplementation with inorganic selenium (sodium selenite) and organic selenium (selenized C. utilis) showed better results than the control and other groups supplemented with yeast with or without glutathione. The body mass of rats, selenium deposition, and oxidative enzymes activities in both serum and liver samples, and immunity responses were all significantly improved by selenium supplementation, and between the two sources, organic selenium was more effective than inorganic selenium.     

Bioeffects of selenite on the growth of Spirulina platensis and its biotransformation

The bioeffects of selenium on the growth of Spirulina platensis and the selenium distribution were investigated. S. platensis was batch cultured in Zarrouk medium containing increasing concentrations of sodium selenite. The biotransformation characteristic of selenium was analysed by the determination of the detailed selenium distribution forms. At 35 degrees C, 315.2 microEm(-2) x s(-1), sodium selenite concentrations below 400 mg x l(-1) were found to stimulate algal growth, especially in the range of 0.5-40 mg x l(-1). However, above 500 mg x l(-1) sodium selenite was toxic to this alga with the toxicity being related to the sulfite level in the medium. S. platensis was found to resist higher selenite by reducing toxic Se(IV) to nonsoluble Se(0). Selenium was accumulated efficiently in S. platensis during cultivation with accumulated selenium increasing with selenite concentration in the medium. It was demonstrated that inorganic selenite could be transformed into organic forms through binding with protein, lipids and polysaccharides and other cell components. The organic selenium accounted for 85.1% of the total accumulated selenium and was comprised of 25.2% water-soluble protein-bound, 10.6% lipids-bound and 2.1% polysaccharides-bound selenium. Among the organic fractions lipid possessed the strongest ability to accumulate Se (6.47 mg x kg(-1)). The 14.9% inorganic selenium in S. platensis was composed of Se(IV) (13.7%) and Se(VI) (1.2%).     

Selenoprotein P Is the Major Selenium Transport Protein in Mouse Milk

Selenium is transferred from the mouse dam to its neonate via milk. Milk contains selenium in selenoprotein form as selenoprotein P (Sepp1) and glutathione peroxidase-3 (Gpx3) as well as in non-specific protein form as selenomethionine. Selenium is also present in milk in uncharacterized small-molecule form. We eliminated selenomethionine from the mice in these experiments by feeding a diet that contained sodium selenite as the source of selenium. Selenium-replete dams with deletion of Sepp1 or Gpx3 were studied to assess the effects of these genes on selenium transfer to the neonate. Sepp1 knockout caused a drop in milk selenium to 27% of the value in wild-type milk and a drop in selenium acquisition by the neonates to 35%. In addition to decreasing milk selenium by eliminating Sepp1, deletion of Sepp1 causes a decline in whole-body selenium, which likely also contributes to the decreased transfer of selenium to the neonate. Deletion of Gpx3 did not decrease milk selenium content or neonate selenium acquisition by measurable amounts. Thus, when the dam is fed selenium-adequate diet (0.25 mg selenium/kg diet), milk Sepp1 transfers a large amount of selenium to neonates but the transfer of selenium by Gpx3 is below detection by our methods.     

Selenium homeostasis and induction of thioredoxin reductase during long term selenite supplementation in the rat

Selenium is a candidate treatment for liver tumour prevention in chronic liver disease. In this study, we have studied selenium uptake, distribution and accumulation in rats provided with water containing tumour-preventive doses of sodium selenite for 10 weeks. Male Fischer 344 rats were given drinking water containing 1 μg/mL or 5 μg/mL sodium selenite. Selenium levels were monitored in serum and liver tissue over the 10-week period, and the kinetics of induction of the redox-active cytosolic selenoenzyme thioredoxin reductase were followed. Selenite exposure via drinking water caused a dose-dependent increase in blood and liver selenium levels, with plateaus at 6 and 8 weeks, respectively. These plateaus were reached at the same level of selenium regardless of dose, and no further accumulation was observed. A selenium-dependent increase in the activity of TrxR1 in parallel with the increase in liver selenium levels was also seen, and the induction of TrxR1 mRNA was seen only during the first three days of treatment, when the levels of selenium in the liver were increasing. Sodium selenite at 1 and 5 μg/mL did not affect body weight or relative liver mass. We concluded that long-term treatment with selenite did not cause accumulation of selenium and that the activity of TrxR1 in the liver rose with the selenium levels. We therefore suggest that sodium selenite at doses up to 5 μg/mL could be used for long-term tumour prevention.     

Ascorbate interacts with sodium selenite to increase glutathione peroxidase activity in selenium-deficient chick duodena cultured in vitro

Duodena from Selenium (Se)/vitamin E-depleted 19 d chick embryos were cultured in vitro for 0-30 h. The addition of sodium selenite to the culture medium was associated with increased selenium-dependent glutathione peroxidase (SeGSHpx) activity after 24 h of incubation. In the absence of Se or in the presence of sodium ascorbate supplementation alone, SeGSHpx activity showed a gradual decline over the same time period. When ascorbate was added, along with sodium selenite, SeGSHpx activity was increased earlier and to a greater extent than in the presence of Se alone. These observations show that ascorbate can influence the metabolism of sodium selenite, resulting in increased SeGSHpx activity.     

Mobilization of Selenite by Ralstonia metallidurans CH34

Ralstonia metallidurans CH34 (formerly Alcaligenes eutrophus CH34) is a soil bacterium characteristic of metal-contaminated biotopes, as it is able to grow in the presence of a variety of heavy metals. R. metallidurans CH34 is reported now to resist up to 6 mM selenite and to reduce selenite to elemental red selenium as shown by extended X-ray absorption fine-structure analysis. Growth kinetics analysis suggests an adaptation of the cells to the selenite stress during the lag-phase period. Depending on the culture conditions, the medium can be completely depleted of selenite. Selenium accumulates essentially in the cytoplasm as judged from electron microscopy and energy-dispersive X-ray analysis. Elemental selenium, highly insoluble, represents a nontoxic storage form for the bacterium. The ability of R. metallidurans CH34 to reduce large amounts of selenite may be of interest for bioremediation processes targeting selenite-polluted sites.     

还原亚硒酸盐产生红色单质硒光合细菌菌株的筛选与鉴定

从实验室保藏的光合细菌中筛选出一株对亚硒酸钠还原效率较高的菌株S3,其亚硒酸钠还原产物通过透射电子显微镜及EDX(Electron-Dispersive X-ray)分析确定为红色单质硒。菌株S3的形态学特征、生理生化特征及光合色素扫描结果与固氮红细菌(Rhodobacter azotoformans)的特征基本一致;16S rDNA序列(GenBank登录号为DQ402051)在系统发育树中与固氮红细菌同属一个类群,序列同源性为99%。根据上述结果将菌株S3鉴定为固氮红细菌。初步研究了该菌株还原亚硒酸钠的特性,首次报道固氮红细菌具有还原亚硒酸盐产生红色单质硒的能力,为今后利用微生物方法治理环境中硒污染、利用微生物方法获得活性红色单质硒以及对微生物还原亚硒酸盐产生红色单质硒的机理研究奠定了良好的基础。     

Biochemical and morphological characteristics of selenite-induced apoptosis in human hepatoma hep G2 cells

Selenium is a cellular growth inhibitor in many mammary tumor cells. To comprehend the mechanism for the selenium-induced cell death, we examined the effects of sodium selenite, which has been one of the most extensively investigated selenium compounds, in human hepatoma Hep G2 cells. Cell viability gradually decreased after treatment with sodium selenite within the concentration range of 10–50 μM. Low (10 μM) selenite has shown a high-percentage laddering pattern compared to the high (25 μM) cytotoxic selenium concentration in agarose gel electrophoresis. G₂M-phase enrichment was also concentration dependent. The most consistent transmission electron microscopic finding was the existence of large lysosomes. Based on these data, we hypothesize that sodium selenite predominantly shows its apoptotic effect over hydrogen selenite accumulation.     

Detection of Selenium Deposits in Escherichia coli by Electron Microscopy

Cells of Escherichia coli will reduce sodium selenite to elemental selenium. Examination by electron microscopy of E. coli cultures grown in the presence of sodium selenite show selenium deposited on the cell membrane and cell wall but not in the cytoplasm.     

Effect of increasing selenite concentrations, vitamin E supplementation and different fetal calf serum content on GPx1 activity in primary cultured rabbit hepatocytes

Primary rabbit hepatocytes from 6 week old female New Zealand White rabbits (3.0 x 10(6) viable hepatocytes per treatment) were incubated for 24 h or 48 h with two basic variants of the selenium and vitamin E free DMEM/F12-HAM nutrition medium containing 2.5% or 10% fetal calf serum (FCS). Selenium and vitamin E concentrations of the media were varied by the addition of 0, 10, 50 and 100 ng Se/mL medium as sodium selenite and 100 microg alpha-tocopheryl acetate/mL. Lactic dehydrogenase (LDH) leakage of the hepatocytes was not influenced by the various selenium concentrations of the media, whereas vitamin E addition significantly inhibited LDH release. The activity of cellular glutathione peroxidase (GPx1) was markedly induced by increasing the selenium supplementation of the culture media. Vitamin E supply further enhanced GPx1 induction. In hepatocytes cultivated at the lower serum concentration (2.5% FCS), increasing the selenite concentration of the media raised GPx1 and reduced the intracellular levels of the reduced tripeptide glutathione (GSH). No vectored relation between the selenium concentration of the media and the activity of superoxide dismutase (SOD) could be observed. After both incubation periods (24 h and 48 h) SOD activity was significantly higher in the cytosol of hepatocytes grown in media containing 10% FCS as compared to cells incubated at the 2.5% FCS level. Furthermore, SOD activity was reduced by the addition of vitamin E to the media. In conclusion the results indicate an effective metabolism of rabbit hepatocytes for selenite even in amounts as low as nanograms. A general cytoprotective role for vitamin E can be shown by its ability to decrease LDH leakage and by the reduction of SOD activity.     

Selenoprotein expression is regulated at multiple levels in prostate cells

Selenium supplementation in a population with low basal blood selenium levels has been reported to decrease the incidence of several cancers including prostate cancer. Based on the clinical findings, it is likely that the antioxidant function of one or more selenoproteins is responsible for the chemopreventive effect, although low molecular weight seleno-compounds have also been posited to selectively induce apoptosis in transformed cells. To address the effects of selenium supplementation on selenoprotein expression in prostate cells, we have undertaken an analysis of antioxidant selenoprotein expression as well as selenium toxicity in non-tumorigenic prostate epithelial cells （RWPE- 1 ） and prostate cancer cells （LNCaP and PC-3）. Our results show that two of the glutathione peroxidase family members （GPX1 and GPX4） are highly induced by supplemental selenium in prostate cancer cells but only slightly induced in RWPE-1 cells. In addition, GPX 1 levels are dramatically lower in PC-3 cells as compared to RWPE- 1 or LNCaP cells. GPX2 protein and mRNA, however, are only detectable in RWPE-1 cells. Of the three selenium compounds tested （sodium selenite, sodium selenate and selenomethionine）, only sodium selenite shows toxicity in a physiological range of selenium concentrations. Notably and in contrast to previous studies, RWPE-1 cells were significantly more sensitive to selenite than either of the prostate cancer cell lines. These results demonstrate that selenoproteins and selenium metabolism are regulated at multiple levels in prostate cells.     

Production of Selenium-Enriched Biomass by Enterococcus durans

Selenium (Se) is an essential micronutrient for several organisms, and there is an increased interest about adequate sources for dietary selenium supplementation. The aim of this study was to evaluate the selenium bioaccumulation capacity of an Enterococcus strain. The isolate LAB18s was identified as Enterococcus durans by the VITEK® 2 system and analysis of both 16S rDNA gene sequence (JX503528) and the 16S-23S rDNA intergenic spacer (ITS). After 24-h incubation, E. durans LAB18s bioaccumulated elevated Se(IV) concentrations, reaching 2.60 and 176.97 mg/g in media containing initial amounts of 15 and 240 mg/l sodium selenite, respectively. The isolate grew optimally and had high selenium bioaccumulation at initial pH of 7.0 and 30 °C. Time course studies showed that E. durans LAB18s displayed the highest bioaccumulation of Se(IV) after 6 h of incubation. Analyses from scanning electron microscopy (SEM) demonstrated the presence of filaments connecting the cells of E. durans LAB18s cultivated in the presence of sodium selenite. It was demonstrated that a considerable amount of Se(IV) was absorbed by E. durans LAB18s. Therefore, this strain may represent an alternative source of organic dietary selenium.     

Biosynthesis of selenium-containing polysaccharides with antioxidant activity in liquid culture of Hericium erinaceum

The effects of inorganic selenium (sodium selenite) and Selol containing selenitetriglycerides synthesized from sunflower oil on mycelial growth and selenium-containing extracellular (EPS) and intracellular (IPS) polysaccharides production were examined in shake flask cultures of Hericium erinaceum.Unlike sodium selenite which inhibited mycelial growth, Selol increased in biomass production in a dose-dependent manner. Selol also dramatically enhanced EPS formation to 2.25 g/L which is 2.5–fold higher than in the control. Selenium content in EPS and IPS obtained from Selol-enriched medium reached a maximum of 4.89 and 4.69 mg/g, respectively.The in vitro antioxidant activities of polysaccharides were evaluated by reducing power, inhibition of lipid peroxidation, and 1,1-diphenyl-dipicrylhydrazyl radicals scavenging assays. The selenium-containing EPS showed an excellent antioxidant activity correlated well with increasing concentrations.The results suggested that selenium-containing EPS from H. erinaceum submerged culture should be explored as a novel selenium source in dietary supplements, with potent antioxidant properties.