Selenium scientific update |
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Folia Microbiol (Praha). 2004;49(3):301-5.
Belicova A, Krizkova L, Dobias J, Krajcovic J, Ebringer L.
Institute of Cell Biology, Faculty of Science, Comenius University, 811 07 Bratislava, Slovakia.
Synergic activity of selenium and probiotic bacterium Enterococcus faecium M-74 against selected mutagens in Salmonella assay.
Concentrated extracts of MRS (De Man-Rogosa-Sharpe) media in which probiotic bacterium Enterococcus faecium strain M-74 was grown exerted different antimutagenic activity against ofloxacin-, N-methyl, N'-nitro-N-nitrosoguanidine- and sodium 5-nitro-2-furylacrylate-induced mutagenicity in Salmonella typhimurium assay depending on the presence (+Se) or absence of disodium selenite pentahydrate (-Se). The antimutagenicity of MRS(+Se) extract was higher than that of MRS(-Se) extract. Selenium enhanced also the antimutagenic effect of both live and killed cells of E. faecium M-74, respectively. The live bacteria decreased the mutagenicity of selected substances more than killed cells. Synergic activity of selenium with the bacterium was also manifested.
Environ Res. 2004 Sep;96(1):51-61.
Kantola M, Purkunen R, Kroger P, Tooming A, Juravskaja J, Pasanen M, Seppanen K, Saarikoski S, Vartiainen T.
Department of Chemistry, University of Kuopio, Kuopio, Finland.
Selenium in pregnancy: is selenium an active defective ion against environmental chemical stress?
Transportation of selenium from mother to fetus and its possible effects on mother's zinc, copper, cadmium, and mercury levels were studied together during the first trimester and at term in 216 mothers. Mothers came from three geographical places with different selenium intakes. The role of selenium as a biomarker for the vital function was estimated by studying the associations between tissue or blood selenium content and placental cytochrome P450 enzyme activities and the newborn's birth weight. Regardless of the selenium intake of the mothers, higher concentrations were found in the cord blood than in mother's blood reflecting active transportation of selenium to the fetus. Active smoking was associated with higher placental selenium concentrations like it is associated with higher placental zinc concentrations. When the cadmium concentrations were high in placenta, as in smokers, the transfer of selenium from blood to placenta was increased, decreasing the selenium levels in blood. On the other hand, the high selenium concentrations in blood were connected to lower cadmium concentrations in placenta also in nonsmokers. Selenium had correlations with copper and zinc. ECOD activity in placental tissue, mercury in mothers' hair, mothers' age, and selenium concentrations in cord blood and placental selenium all seem to have connections with xenobiotic-metabolizing enzymes linked effects among mothers. These data suggest that selenium has an active role in the mother's defense systems against the toxicity of environmental pollutants and the constituents of cigarette smoke.
Eur J Biochem. 2004 Aug;271(15):3190-9.
Blessing H, Kraus S, Heindl P, Bal W, Hartwig A.
Institute of Food Chemistry and Toxicology, University of Karlsruhe, Germany.
Interaction of selenium compounds with zinc finger proteins involved in DNA repair.
As an essential element, selenium is present in enzymes from several families, including glutathione peroxidases, and is thought to exert anticarcinogenic properties. A remarkable feature of selenium consists of its ability to oxidize thiols under reducing conditions. Thus, one mode of action recently suggested is the oxidation of thiol groups of metallothionein, thereby providing zinc for essential reactions. However, tetrahedral zinc ion complexation to four thiolates, similar to that found in metallothionein, is present in one of the major classes of transcription factors and other so-called zinc finger proteins. Within this study we investigated the effect of selenium compounds on the activity of the formamidopyrimidine-DNA glycosylase (Fpg), a zinc finger protein involved in base excision repair, and on the DNA-binding capacity and integrity of xeroderma pigmentosum group A protein (XPA), a zinc finger protein essential for nucleotide excision repair. The reducible selenium compounds phenylseleninic acid, phenylselenyl chloride, selenocystine, ebselen, and 2-nitrophenylselenocyanate caused a concentration-dependent decrease of Fpg activity, while no inhibition was detected with fully reduced selenomethionine, methylselenocysteine or some sulfur-containing analogs. Furthermore, reducible selenium compounds interfered with XPA-DNA binding and released zinc from the zinc finger motif, XPAzf. Zinc release was even evident at high glutathione/oxidised glutathine ratios prevailing under cellular conditions. Finally, comparative studies with metallothionein and XPAzf revealed similar or even accelerated zinc release from XPAzf. Altogether, the results indicate that zinc finger motifs are highly reactive towards oxidizing selenium compounds. This could affect gene expression, DNA repair and, thus, genomic stability.
Anticancer Res. 2004 May-Jun;24(3a):1401-8.
Smith ML, Lancia JK, Mercer TI, Ip C.
Indiana University School of Medicine, Department of Microbiology and Walther Oncology Center, Indianapolis, IN 46202, USA.
Selenium compounds regulate p53 by common and distinctive mechanisms.
Selenium compounds show much promise in the prevention of prostate and other human cancers. Various selenium chemical forms have been shown to differ widely in their anticancer properties. The main dietary form is selenomethionine, which we showed modulated p53 activity by causing redox regulation of key p53 cysteine residues. In the current study we included other selenium chemical forms, sodium selenite and methyl-seleninic acid. All three forms are relevant selenium sources in human populations. All three forms can affect p53 activity defined as trans-activation of a p53-dependent reporter gene. In addition to the reduction of cysteine sulfhydryl groups, p53 phosphorylation was also affected in cells treated with selenium compounds. Methyl-seleninic acid caused phosphorylation of one or more p53 threonine residues, but did not affect any known serine phosphorylation sites. By contrast sodium selenite caused phosphorylation of p53 serines 20, 37 and 46 known to mediate apoptosis. Selenomethionine did not cause detectable phosphorylation of p53 serines or threonines. Our data show that, although p53 modulation may be a common denominator of selenium compounds, specific mechanisms of p53 activation differ among selenium chemical forms. Post-translational modifications of p53 are determinants of p53 activity and probably affect the threshold for p53-mediated functions. Different selenium chemical forms may differentially modify p53 for DNA repair or apoptosis in conjunction with a given level of endogenous or exogenous DNA damage.
Neurotoxicol Teratol. 2005 Mar-Apr;27(2):241-4. Epub 2004 Dec 08.
Pamphlett R, Eide R, Danscher G.
Department of Pathology D06, The University of Sydney, Sydney, New South Wales 2006, Australia.
Does selenium deficiency unmask mercury toxicity in motor neurons?
OBJECTIVE: Inorganic mercury enters in particular motor neurons and has been implicated in motor neuron diseases. One way that cells protect themselves from mercury toxicity is via selenium, so we sought to determine whether the motor neurons of mice on a low selenium diet would be more susceptible to mercury toxicity. METHODS: Recently weaned mouse pups were placed on diets containing either low, normal or high levels of selenium. Twenty days later, half were exposed to mercury vapor. Ninety days after exposure, their spinal motor neurons and phrenic motor axons were examined histologically. Mercury in the spinal cord was sought using autometallography. RESULTS: Neither low nor high selenium diets combined with mercury vapor had any clinical effect on the mice. Mercury was seen within the spinal motor neurons of all exposed mice. Spinal motor neurons and phrenic motor axons however appeared normal in morphology and size across the groups. CONCLUSION: Diets low or high in selenium did not damage motor neurons with or without mercury. This suggests that changes in the selenium environment are unlikely to precipitate mercury toxicity in motor neurons.
Selenium description...
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Drug category:Antioxidants and Vitamines
 Selenium scientific update
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