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Ryszard Lobinski - One of the best experts on this subject based on the ideXlab platform.
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Quantification of Se-Methylselenocysteine and Its γ-Glutamyl Derivative from Naturally Se-Enriched Green Bean (Phaseolus vulgaris vulgaris) After HPLC-ESI-TOF-MS and Orbitrap MSn-Based Identification
Food Analytical Methods, 2014Co-Authors: S. Shao, Ryszard Lobinski, L. Ouerdane, J.f. García-reyes, A. Molina-díaz, A. Vass, M. DernovicsAbstract:Orthogonal liquid chromatographic (ion exchange, reversed phase, and ion pairing) and mass spectrometric [electrospray ionization (ESI)-TOF-MS, ESI-Orbitrap MS, and inductively coupled plasma mass spectrometry (ICP-MS)] methods were addressed to identify and quantify selenium species from a naturally Se-enriched green bean (Phaseolus vulgaris vulgaris) sample after proteolytic digestion. While selenomethionine (10.1 mg/kg as Se) and selenate (9.5 mg/kg as Se) could be quantified in a straightforward way by anion exchange LC-ICP-MS technique, a multistep purification protocol was required to identify Se-Methylselenocysteine and γ-glutamyl-Se-Methylselenocysteine in an unambiguous way prior to quantification by using either in-source fragmentation (LC-ESI-TOF-MS) or collision-induced dissociation (LC-ESI-Orbitrap MS). Finally, Se-Methylselenocysteine (2.6 mg/kg as Se) and γ-glutamyl-Se-Methylselenocysteine (1.2 mg/kg as Se) could contribute to the overall selenium recovery of 72 %. This sample is the first of the Faboideae subfamily and Phaseolus ssp. to be speciated to such an extent for selenium including γ-glutamyl-Se-Methylselenocysteine, a highly potential selenium species, which makes this bean material an ideal candidate for functional food purposes. © 2013 Springer Science+Business Media New York.
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Quantification of Se-Methylselenocysteine and Its γ-Glutamyl Derivative from Naturally Se-Enriched Green Bean (Phaseolus vulgaris vulgaris) After HPLC-ESI-TOF-MS and Orbitrap MSn-Based Identification
Food Analytical Methods, 2013Co-Authors: S. Shao, Ryszard Lobinski, L. Ouerdane, J.f. García-reyes, A. Molina-díaz, A. Vass, M. DernovicsAbstract:Orthogonal liquid chromatographic (ion exchange, reversed phase, and ion pairing) and mass spectrometric [electrospray ionization (ESI)-TOF-MS, ESI-Orbitrap MS, and inductively coupled plasma mass spectrometry (ICP-MS)] methods were addressed to identify and quantify selenium species from a naturally Se-enriched green bean (Phaseolus vulgaris vulgaris) sample after proteolytic digestion. While selenomethionine (10.1 mg/kg as Se) and selenate (9.5 mg/kg as Se) could be quantified in a straightforward way by anion exchange LC-ICP-MS technique, a multistep purification protocol was required to identify Se-Methylselenocysteine and γ-glutamyl-Se-Methylselenocysteine in an unambiguous way prior to quantification by using either in-source fragmentation (LC-ESI-TOF-MS) or collision-induced dissociation (LC-ESI-Orbitrap MS). Finally, Se-Methylselenocysteine (2.6 mg/kg as Se) and γ-glutamyl-Se-Methylselenocysteine (1.2 mg/kg as Se) could contribute to the overall selenium recovery of 72 %. This sample is the first of the Faboideae subfamily and Phaseolus ssp. to be speciated to such an extent for selenium including γ-glutamyl-Se-Methylselenocysteine, a highly potential selenium species, which makes this bean material an ideal candidate for functional food purposes.
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detection and identification of hydrophilic selenium compounds in selenium rich yeast by size exclusion microbore normal phase hplc with the on line icp ms and electrospray q tof ms detection
Analytica Chimica Acta, 2010Co-Authors: Hugues Preudhomme, Ryszard LobinskiAbstract:Abstract Normal-phase HPLC and hydrophilic interaction HPLC (HILIC) were investigated for the separation of selenometabolites in a water extract of Se-rich yeast prior to their detection by ICP–MS and identification by electrospray MS/MS. The targeted fraction was a low-abundant fraction co-eluting with salt and sulfur analogues in size-exclusion chromatography which has so far been inaccessible to Se speciation studies. The optimization of the separation conditions resulted in the highest separation efficiency when HILIC was used and elution was carried out isocratically with a low concentration ammonium acetate buffer (1 mM ammonium acetate/10 mM acetic acid) in 80% acetonitrile. Out of 15 peaks observed with the Se-specific ICP–MS detection 12 was identified by electrospray Q-TOF MS/MS (2,3-dihydroxypropionyl (DHP)-Se-Methylselenocysteine [M+H] + : 272, Se-methyl-γ-glutamyl-selenocysteinylglycine dioxide [M+H] + : 402, γ-glutamyl-Se-Methylselenocysteine [M+H] + : 313; isomers of γ-glutamylselenocystathionine [M+H] + : 400; Se-methyl-selenoglutathione [M+H] + : 370, isomers of N-acetylselenocystathionine [M+H] + : 313, 2,3-DHP-selenohomolanthionine [M+H] + : 373, isomers of 2,3-DHP-selenocystathionine [M+H] + : 359, 2,3-DHP-selenolanthionine [M+H] + : 345 and selenohomolanthionine [M+H] + : 285).
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Detection and identification of hydrophilic selenium compounds in selenium-rich yeast by size exclusion-microbore normal-phase HPLC with the on-line ICP-MS and electrospray Q-TOF-MS detection
Analytica Chimica Acta, 2010Co-Authors: J. Far, Hugues Preud'homme, Ryszard LobinskiAbstract:Normal-phase HPLC and hydrophilic interaction HPLC (HILIC) were investigated for the separation of selenometabolites in a water extract of Se-rich yeast prior to their detection by ICP-MS and identification by electrospray MS/MS. The targeted fraction was a low-abundant fraction co-eluting with salt and sulfur analogues in size-exclusion chromatography which has so far been inaccessible to Se speciation studies. The optimization of the separation conditions resulted in the highest separation efficiency when HILIC was used and elution was carried out isocratically with a low concentration ammonium acetate buffer (1 mM ammonium acetate/10 mM acetic acid) in 80% acetonitrile. Out of 15 peaks observed with the Se-specific ICP-MS detection 12 was identified by electrospray Q-TOF MS/MS (2,3-dihydroxypropionyl (DHP)-Se-Methylselenocysteine [M+H]+: 272, Se-methyl-γ-glutamyl-selenocysteinylglycine dioxide [M+H]+: 402, γ-glutamyl-Se-Methylselenocysteine [M+H]+: 313; isomers of γ-glutamylselenocystathionine [M+H]+: 400; Se-methyl-selenoglutathione [M+H]+: 370, isomers of N-acetylselenocystathionine [M+H]+: 313, 2,3-DHP-selenohomolanthionine [M+H]+: 373, isomers of 2,3-DHP-selenocystathionine [M+H]+: 359, 2,3-DHP-selenolanthionine [M+H]+: 345 and selenohomolanthionine [M+H]+: 285). © 2009 Elsevier B.V. All rights reserved.
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Speciation analysis of selenium in garlic by two-dimensional high-performance liquid chromatography with parallel inductively coupled plasma mass spectrometric and electrospray tandem mass spectrometric detection
Analytica Chimica Acta, 2000Co-Authors: S. Mcsheehy, Ryszard Lobinski, W. Yang, F. Pannier, J. Szpunar, J. Auger, M. Potin-gautierAbstract:Speciation of selenium in garlic harvested in naturally seleniferous soil was investigated. The sample was leached with water and the aqueous extract was fractionated by preparative size-exclusion chromatography. Selenium was found in only one (low-molecular mass) fraction. The chromatographic purity of the fraction was verified by reversed-phase chromatography with inductively coupled mass spectrometric detection. Again, one major signal accounting for more than 95% of the total selenium was observed. The heartcut fraction containing this compound produced an intense peak in an electrospray mass spectrum with the selenium pattern centered at m/z 313 (80Se). Protonated molecular ions corresponding to the four Se isotopes gave rich fragmentation patterns by collision induced dissociation that allowed the identification of the selenium species to be ?-glutamyl-Se-Methylselenocysteine without the need for an authentic standard. Copyright (C) 2000 Elsevier Science B.V.
Ted W Reid - One of the best experts on this subject based on the ideXlab platform.
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Methioninase and selenomethionine but not Se-Methylselenocysteine generate methylselenol and superoxide in an in vitro chemiluminescent assay: implications for the nutritional carcinostatic activity of selenoamino acids
Biochemical pharmacology, 2004Co-Authors: Julian E. Spallholz, Vince P. Palace, Ted W ReidAbstract:Abstract Methylselenol from selenium metabolism is postulated to be and most experimental evidence now indicates that it is the selenium metabolite responsible for the dietary chemoprevention of cancers. Using the recombinant enzyme methioninase, methylselenol-generating chemiluminesence by superoxide (O2 −) is shown to be catalytically produced from l -selenomethionine and d , l -selenoethionine, but not from methionine or l -Se-Methylselenocysteine (SeMC). Methylselenol enzymaticaly generated by methioninase activity from the substrate selenomethionine arises from an initial putative selenium radical as measured by chemiluminesence in the absence of glutathione (GSH). In the presence of GSH, superoxide was generated as measured by chemiluminesence and superoxide dismutase inhibition of chemiluminescence. Ascorbic acid also quenched the chemiluminesence from the activity of methioninase with selenomethionine. Methylselenol and other redox cycling selenium compounds are almost assuredly accountable for inducing cell-cycle arrest and apoptosis in cancer cells in vitro and in vivo. Methylselenol generated from selenomethionine by methioninase is catalytic alone in oxidizing thiols, i.e. GSH, generating superoxide and inducing oxidative stress in direct proportion to its concentration. Se-Methylselenocysteine in vivo is very likely carcinostatic in like manner to selenomethionine by generating methylselenol from other enzymatic activity, i.e. beta-lyase or amino acid oxidases.
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dimethyldiselenide and methylseleninic acid generate superoxide in an in vitro chemiluminescence assay in the presence of glutathione implications for the anticarcinogenic activity of l selenomethionine and l se Methylselenocysteine
Nutrition and Cancer, 2001Co-Authors: Julian E. Spallholz, Brent J Shriver, Ted W ReidAbstract:The reduction of cancer incidence by dietary supplementation with L-selenomethionine, L-Se-Methylselenocysteine, and other methylated selenium compounds and metabolites is believed to be due to the metabolic generation of the monomethylated selenium species methylselenol. Dimethyldiselenide and methylseleninic acid were reduced by glutathione in an in vitro chemiluminescent assay in the presence of lucigenin for the detection of superoxide (O2-.). The methylselenol produced on reduction of dimethyldiselenide and methylseleninic acid was found to be highly catalytic, continuously generating a steady state of O2-. The O2-. detected by the chemiluminescence generated by methylselenol was fully quenched by superoxide dismutase, causing a complete cessation of chemiluminescence. In contrast, dimethyldisulfide in the presence of glutathione was not catalytic to any measurable extent and did not generate any superoxide. These in vitro results suggest that methylselenol catalysis is possible in vivo, and if metabolism generates sufficient concentrations of methlylselenol from L-selenomethionine or L-Se-Methylselenocysteine in vivo, it could change the redox status of cells and oxidatively induce cellular apoptosis.
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Dimethyldiselenide and methylseleninic acid generate superoxide in an in vitro chemiluminescence assay in the presence of glutathione: implications for the anticarcinogenic activity of L-selenomethionine and L-Se-Methylselenocysteine.
Nutrition and cancer, 2001Co-Authors: Julian E. Spallholz, Brent J Shriver, Ted W ReidAbstract:The reduction of cancer incidence by dietary supplementation with L-selenomethionine, L-Se-Methylselenocysteine, and other methylated selenium compounds and metabolites is believed to be due to the metabolic generation of the monomethylated selenium species methylselenol. Dimethyldiselenide and methylseleninic acid were reduced by glutathione in an in vitro chemiluminescent assay in the presence of lucigenin for the detection of superoxide (O2 - ). The methylselenol produced on reduction of dimethyldiselenide and methylseleninic acid was found to be highly catalytic, continuously generating a steady state of O2 - . The O2 - detected by the chemiluminescence generated by methylselenol was fully quenched by superoxide dismutase, causing a complete cessation of chemiluminescence. In contrast, dimethyldisulfide in the presence of glutathione was not catalytic to any measurable extent and did not generate any superoxide. These in vitro results suggest that methylselenol catalysis is possible in vivo, and if me...
Julian E. Spallholz - One of the best experts on this subject based on the ideXlab platform.
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Selenomethionine and Methioninase: Selenium Free Radical Anticancer Activity.
Methods in molecular biology (Clifton N.J.), 2019Co-Authors: Julian E. SpallholzAbstract:Colloidal selenium, was first used to treat cancer as early as 1911 in both humans and mice. Selenium was identified as the toxic component in forage plants of sheep, cattle, and horses in the 1930s. The animal toxicity of selenium compounds was determined to be from the metabolism by animals of the elevated concentrations of Se-Methylselenocysteine and selenomethionine in plants. The metabolism of both Se-Methylselenocysteine and selenomethionine by animals gives rise to the metabolite, methylselenide (CH3Se-), which if in sufficient concentration oxidizes thiols and generates superoxide and other reactive oxygen species. Cancer cells that may overly express methionine gamma-lyase, or beta-lyase (methioninase), by induced viral genomic expression, are susceptible to free radical-induced apoptosis from selenomethionine or Se-Methylselenocysteine supplementation.
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General, Applied and Systems Toxicology - Toxicity of Selenium Compounds and Nano‐Selenium Particles
General Applied and Systems Toxicology, 2011Co-Authors: Jinsong Zhang, Julian E. SpallholzAbstract:Selenium is a necessary dietary constituent of at least 25 human selenoproteins and enzymes all containing selenocysteine. In excessive amounts, all selenium compounds become toxic in a dose-dependent fashion to cells in vitro and to the primary target tissue of chronic selenium toxicity, the liver. Elemental selenium of zero valence state has long been considered to be biologically inert. With bovine serum albumin or other dispersant agents such as polysaccharide, biologically active nano-selenium particles (Nano-Se) are formed from sodium selenite and glutathione. Different from the biologically inert black elemental selenium with coarse size, red Nano-Se manifests toxicity which conforms to the concern of nanotoxicity. However, compared with selenium compounds such as sodium selenite, selenomethionine and Se-Methylselenocysteine, Nano-Se is not compromised in increasing the activities of selenoenzymes including glutathione peroxidase and thioredoxin reductase at nutritional levels and phase 2 detoxification enzymes such as glutathione S-transferase at supranutritional levels, but exhibits much lower toxicities. Nano-Se is thus a potential selenium source with a prominent characteristic of lower toxicity for supplementation. Keywords: toxicity; selenite; selenomethionine; Se-Methylselenocysteine; nano-selenium particles
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Methioninase and selenomethionine but not Se-Methylselenocysteine generate methylselenol and superoxide in an in vitro chemiluminescent assay: implications for the nutritional carcinostatic activity of selenoamino acids
Biochemical pharmacology, 2004Co-Authors: Julian E. Spallholz, Vince P. Palace, Ted W ReidAbstract:Abstract Methylselenol from selenium metabolism is postulated to be and most experimental evidence now indicates that it is the selenium metabolite responsible for the dietary chemoprevention of cancers. Using the recombinant enzyme methioninase, methylselenol-generating chemiluminesence by superoxide (O2 −) is shown to be catalytically produced from l -selenomethionine and d , l -selenoethionine, but not from methionine or l -Se-Methylselenocysteine (SeMC). Methylselenol enzymaticaly generated by methioninase activity from the substrate selenomethionine arises from an initial putative selenium radical as measured by chemiluminesence in the absence of glutathione (GSH). In the presence of GSH, superoxide was generated as measured by chemiluminesence and superoxide dismutase inhibition of chemiluminescence. Ascorbic acid also quenched the chemiluminesence from the activity of methioninase with selenomethionine. Methylselenol and other redox cycling selenium compounds are almost assuredly accountable for inducing cell-cycle arrest and apoptosis in cancer cells in vitro and in vivo. Methylselenol generated from selenomethionine by methioninase is catalytic alone in oxidizing thiols, i.e. GSH, generating superoxide and inducing oxidative stress in direct proportion to its concentration. Se-Methylselenocysteine in vivo is very likely carcinostatic in like manner to selenomethionine by generating methylselenol from other enzymatic activity, i.e. beta-lyase or amino acid oxidases.
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dimethyldiselenide and methylseleninic acid generate superoxide in an in vitro chemiluminescence assay in the presence of glutathione implications for the anticarcinogenic activity of l selenomethionine and l se Methylselenocysteine
Nutrition and Cancer, 2001Co-Authors: Julian E. Spallholz, Brent J Shriver, Ted W ReidAbstract:The reduction of cancer incidence by dietary supplementation with L-selenomethionine, L-Se-Methylselenocysteine, and other methylated selenium compounds and metabolites is believed to be due to the metabolic generation of the monomethylated selenium species methylselenol. Dimethyldiselenide and methylseleninic acid were reduced by glutathione in an in vitro chemiluminescent assay in the presence of lucigenin for the detection of superoxide (O2-.). The methylselenol produced on reduction of dimethyldiselenide and methylseleninic acid was found to be highly catalytic, continuously generating a steady state of O2-. The O2-. detected by the chemiluminescence generated by methylselenol was fully quenched by superoxide dismutase, causing a complete cessation of chemiluminescence. In contrast, dimethyldisulfide in the presence of glutathione was not catalytic to any measurable extent and did not generate any superoxide. These in vitro results suggest that methylselenol catalysis is possible in vivo, and if metabolism generates sufficient concentrations of methlylselenol from L-selenomethionine or L-Se-Methylselenocysteine in vivo, it could change the redox status of cells and oxidatively induce cellular apoptosis.
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Dimethyldiselenide and methylseleninic acid generate superoxide in an in vitro chemiluminescence assay in the presence of glutathione: implications for the anticarcinogenic activity of L-selenomethionine and L-Se-Methylselenocysteine.
Nutrition and cancer, 2001Co-Authors: Julian E. Spallholz, Brent J Shriver, Ted W ReidAbstract:The reduction of cancer incidence by dietary supplementation with L-selenomethionine, L-Se-Methylselenocysteine, and other methylated selenium compounds and metabolites is believed to be due to the metabolic generation of the monomethylated selenium species methylselenol. Dimethyldiselenide and methylseleninic acid were reduced by glutathione in an in vitro chemiluminescent assay in the presence of lucigenin for the detection of superoxide (O2 - ). The methylselenol produced on reduction of dimethyldiselenide and methylseleninic acid was found to be highly catalytic, continuously generating a steady state of O2 - . The O2 - detected by the chemiluminescence generated by methylselenol was fully quenched by superoxide dismutase, causing a complete cessation of chemiluminescence. In contrast, dimethyldisulfide in the presence of glutathione was not catalytic to any measurable extent and did not generate any superoxide. These in vitro results suggest that methylselenol catalysis is possible in vivo, and if me...
Howard E. Ganther - One of the best experts on this subject based on the ideXlab platform.
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Se-Methylselenocysteine: A New Compound for Chemoprevention of Breast Cancer
Nutrition and cancer, 2001Co-Authors: Daniel Medina, Henry J. Thompson, Howard E. GantherAbstract:Selenium compounds have attracted renewed interest as chemopreventive agents for human cancer on the basis of the pioneering intervention study by Clark and co-workers. The rodent mammary gland has been used extensively as a model for examining the chemopreventive activities of inorganic and organic selenium compounds. This review summarizes the rationale and results for use of a new organic selenium compound, Se-Methylselenocysteine, which exhibits greater efficacy as a chemopreventive agent than several previously used selenium compounds in experimental models of breast cancer and has potential for use in human populations.
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In Vitro and in Vivo Studies of Methylseleninic Acid: Evidence That a Monomethylated Selenium Metabolite Is Critical for Cancer Chemoprevention
Cancer research, 2000Co-Authors: Henry J. Thompson, Zongjian Zhu, Howard E. GantherAbstract:Previous research suggested that the β-lyase-mediated production of a monomethylated selenium metabolite from Se-Methylselenocysteine is a key step in cancer chemoprevention by this agent. In an attempt to affirm the concept, the present study was designed to evaluate the activity of methylseleninic acid, a compound that represents a simplified version of Se-Methylselenocysteine without the amino acid moiety, thereby obviating the need for β-lyase action. The in vitro experiments showed that methylseleninic acid was more potent than Se-Methylselenocysteine in inhibiting cell accumulation and inducing apoptosis in TM12 (wild-type p53) and TM2H (nonfunctional p53) mouse mammary hyperplastic epithelial cells, and these effects were not attributable to DNA damage, as determined by the comet assay. In general, methylseleninic acid produced a more robust response at one-tenth the concentration of Se-Methylselenocysteine. It is possible that these cell lines may have only a modest ability to generate a monomethylated selenium species from Se-Methylselenocysteine via theβ -lyase enzyme. In contrast, methylseleninic acid already serves as a preformed active monomethylated metabolite, and this could be an underlying reason why methylseleninic acid acts more rapidly and exerts a more powerful effect than Se-Methylselenocysteine in vitro . Interestingly, the distinction between these two compounds disappeared in vivo, where their cancer chemopreventive efficacies were found to be very similar to each other[ in both methylnitrosourea and dimethylbenz( a )anthracene rat mammary tumor models]. The β-lyase enzyme is present in many tissues; thus, animals have an ample capacity to metabolize Se-Methylselenocysteine systemically. Therefore, Se-Methylselenocysteine would be expected to behave like methylseleninic acid if β-lyase is no longer a limiting factor. Taken together, the present in vitro and in vivo results provide strong evidence in support of our earlier hypothesis that a monomethylated selenium metabolite is important for cancer chemoprevention. Methylseleninic acid could be an excellent tool, especially for molecular mechanism studies in cell culture, and some of these attributes are discussed.
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Selenium modulation of cell proliferation and cell cycle biomarkers in normal and premalignant cells of the rat mammary gland.
Cancer epidemiology biomarkers & prevention : a publication of the American Association for Cancer Research cosponsored by the American Society of Pre, 2000Co-Authors: Henry J. Thompson, Howard E. GantherAbstract:The present study was designed to assess the effect of Se -Methylselenocysteine or triphenylselenonium chloride treatment on cell proliferation [bromodeoxyuridine (BrdUrd) labeling] and cell cycle biomarkers [proliferating cell nuclear antigen (PCNA), cyclin D1, and p27/Kip 1] in the intact mammary gland of rats. Immunohistochemical assays of the above end points were carried out in different morphological structures: ( a ) terminal end bud cells and alveolar cells of a maturing mammary gland undergoing active differentiation; and ( b ) premalignant mammary intraductal proliferations (IDPs) identified at 6 weeks after carcinogen dosing. Neither compound was found to affect BrdUrd labeling or the expression of cell cycle biomarkers in the normal terminal-end bud cells and alveolar cells. Se -Methylselenocysteine reduced the total number of IDP lesions by ∼60%. Interestingly, this was not accompanied by decreases in BrdUrd labeling or the proportion of IDP cells expressing PCNA and cyclin D1. An enhancement in the fraction of p27/Kip 1-positive IDP cells, however, was detected as a result of Se -Methylselenocysteine treatment. Although triphenylselenonium chloride did not reduce the total number of IDPs, there were more of the smaller-sized lesions and fewer of the larger-sized lesions compared with those found in the control group. Triphenylselenonium chloride also significantly decreased the proportion of IDP cells incorporating the BrdUrd label or expressing PCNA and cyclin D1. The above findings suggest that early transformed cells are sensitive to selenium intervention, whereas normal proliferating cells are not. It is possible that Se -Methylselenocysteine blocks carcinogenesis by a pathway that may not involve cell growth inhibition as a primary response; in contrast, triphenylselenonium chloride is likely to act by a cytostatic mechanism. The data also imply that selenium efficacy testing in intervention trials is possible with the use of biomarkers, provided that the appropriate biomarkers are matched with the selenium compound of interest and that the pathological characteristics of the cell population to be evaluated are taken into consideration.
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Comparison of selenium and sulfur analogs in cancer prevention.
Carcinogenesis, 1992Co-Authors: Howard E. GantherAbstract:Several organoselenium compounds have been shown to have powerful anticarcinogenic activity. In view of certain similarities between selenium and sulfur biochemistry, we have evaluated the chemopreventive efficacy of three pairs of analogs using the 7,12-dimethylbenz[a]anthracene (DMBA)-induced mammary tumor model in rats. The compounds tested were selenocystamine/cysteamine, SeMethylselenocysteine/S-methylcysteine, selenobetaine/sulfobetaine. In the first study, each agent was added to the basal AIN-76A diet and was given before and continued after DMBA treatment until the end. All three selenium compounds were active; a 50% inhibition was achieved at approximately 25 x 10(-6) mol/kg with Se-Methylselenocysteine and selenobetaine and at approximately 40 x 10(-6) mol/kg with selenocystamine. In the sulfur series, only cysteamine and S-methylcysteine produced anticancer activity, and the levels required for comparable responses were 500- to 750-fold higher compared to the corresponding selenium analogs. Sulfobetaine was inactive even when present at near maximally tolerated levels. In the second study, Se-Methylselenocysteine and S-methylcysteine were chosen for further examination during the initiation and post-initiation phases of mammary carcinogenesis. Se-Methylselenocysteine was effective when it was given either before or after DMBA administration. In contrast, S-methylcysteine was effective only after DMBA treatment. Thus, compared to the sulfur structural analogs, selenium compounds are much more active in cancer protection and may have a multi-modal mechanism in preventing cellular transformation as well as in delaying or inhibiting the expression of malignancy after carcinogen exposure.
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Chemical form of selenium, critical metabolites, and cancer prevention.
Cancer research, 1991Co-Authors: Cassandra Hayes, Rose Marie Budnick, Howard E. GantherAbstract:Methylated selenides are prominent metabolites at the dietary levels used for obtaining anticarcinogenic effects with selenium. The present study reports the chemopreventive activities of 2 novel selenium compounds, Se-Methylselenocysteine and dimethyl selenoxide, in the rat dimethylbenz(a)anthracene-induced mammary tumor model. Other treatment groups were supplemented with either selenite or selenocystine for comparative purposes. Each selenium compound was tested at different levels and was given to the animal starting 1 week before dimethylbenz(a)anthracene administration and continued until sacrifice. Results of the carcinogenesis experiments showed that the relative efficacy with the four compounds was Se-Methylselenocysteine greater than selenite greater than selenocystine greater than dimethyl selenoxide. In correlating the chemical form and metabolism of these selenium compounds with their anticarcinogenic activity, it is concluded that: (a) selenium compounds that are able to generate a steady stream of methylated metabolites, particularly the monomethylated species, are likely to have good chemopreventive potential; (b) anticarcinogenic activity is lower for selenoamino acids, such as selenocysteine following conversion from selenocystine, which have an escape mechanism via random, nonstoichiometric incorporation into proteins; and (c) forms of selenium, as exemplified by dimethyl selenoxide, which are metabolized rapidly and quantitatively to dimethyl selenide and trimethylselenonium and excreted, are likely to be poor choices. We also undertook a separate bioavailability study using Se-Methylselenocysteine, dimethyl selenoxide, and trimethylselenonium as the starting compounds for delivering selenium with one, two, or three methyl groups, and measured the ability of these compounds to restore glutathione peroxidase activity in selenium-depleted animals. All three compounds were able to fully replete this enzyme, although with a wide range of efficiency (Se-Methylselenocysteine greater than dimethyl selenoxide greater than trimethylselenonium), suggesting that complete demethylation to inorganic selenium is a normal process of selenium metabolism. However, the degree to which this occurs under chemoprevention conditions would argue against the involvement of selenoproteins in the anticarcinogenic action of these selenium compounds.
Hugh H Harris - One of the best experts on this subject based on the ideXlab platform.
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Methylselenocysteine treatment leads to diselenide formation in human cancer cells: evidence from X-ray absorption spectroscopy studies.
Biochemistry, 2012Co-Authors: Claire M. Weekley, Jade B. Aitken, Ian F. Musgrave, Hugh H HarrisAbstract:The selenoamino acids Methylselenocysteine (MeSeCys) and selenomethionine (SeMet) have disparate efficacies as anticancer agents. Herein, we use X-ray absorption spectroscopy to determine the chemical form of selenium in human neuroblastoma cells. Cells treated with MeSeCys contain a significant diselenide component, which is absent from SeMet-treated cells and suggests that metabolites of MeSeCys are capable of altering the redox status of the cells. The differences in the speciation of Se in the selenoamino acid-treated cells may provide insight into the differing anticancer activities of MeSeCys and SeMet.
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Methylselenocysteine Treatment Leads to Diselenide Formation in Human Cancer Cells: Evidence from X-ray Absorption Spectroscopy Studies
2012Co-Authors: Claire M. Weekley, Jade B. Aitken, Ian F. Musgrave, Hugh H HarrisAbstract:The selenoamino acids Methylselenocysteine (MeSeCys) and selenomethionine (SeMet) have disparate efficacies as anticancer agents. Herein, we use X-ray absorption spectroscopy to determine the chemical form of selenium in human neuroblastoma cells. Cells treated with MeSeCys contain a significant diselenide component, which is absent from SeMet-treated cells and suggests that metabolites of MeSeCys are capable of altering the redox status of the cells. The differences in the speciation of Se in the selenoamino acid-treated cells may provide insight into the differing anticancer activities of MeSeCys and SeMet
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() Growth of SMT over-producing and empty vector control plants in soil treated with selenite
2011Co-Authors: Danielle R Ellis, Thomas G Sors, Dennis G Brunk, Carrie Albrecht, Brett Lahner, Karl V Wood, Hugh H Harris, Ingrid J Pickering, Cindy S. Orser, David E SaltAbstract:Copyright information: Taken from "Production of Se-Methylselenocysteine in transgenic plants expressing selenocysteine methyltransferase"BMC Plant Biology 2004;4():1-1.Published online 28 Jan 2004PMCID:PMC343276.Copyright © 2004 Ellis et al; licensee BioMed Central Ltd. This is an Open Access article: verbatim copying and redistribution of this article are permitted in all media for any purpose, provided this notice is preserved along with the article's original URL. () Relative selenite tolerance in soil grown plants is positively correlated with the concentration of Methylselenocysteine, and () total shoot Se concentration. Relative tolerance is quantified as the percent fresh weight of selenite treated plants relative to the same line grown in the absence of selenite. Data represents averages (± SE) from between 10 – 16 individual plants from each line.
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Production of Se-Methylselenocysteine in transgenic plants expressing selenocysteine methyltransferase
BMC Plant Biology, 2004Co-Authors: Danielle R Ellis, Thomas G Sors, Dennis G Brunk, Carrie Albrecht, Cindy Orser, Brett Lahner, Karl V Wood, Hugh H Harris, Ingrid J Pickering, David E SaltAbstract:Background It has become increasingly evident that dietary Se plays a significant role in reducing the incidence of lung, colorectal and prostate cancer in humans. Different forms of Se vary in their chemopreventative efficacy, with Se -Methylselenocysteine being one of the most potent. Interestingly, the Se accumulating plant Astragalus bisulcatus (Two-grooved poison vetch) contains up to 0.6% of its shoot dry weight as Se -Methylselenocysteine. The ability of this Se accumulator to biosynthesize Se -Methylselenocysteine provides a critical metabolic shunt that prevents selenocysteine and selenomethionine from entering the protein biosynthetic machinery. Such a metabolic shunt has been proposed to be vital for Se tolerance in A. bisulcatus . Utilization of this mechanism in other plants may provide a possible avenue for the genetic engineering of Se tolerance in plants ideally suited for the phytoremediation of Se contaminated land. Here, we describe the overexpression of a selenocysteine methyltransferase from A. bisulcatus to engineer Se -Methylselenocysteine metabolism in the Se non-accumulator Arabidopsis thaliana (Thale cress). Results By over producing the A. bisulcatus enzyme selenocysteine methyltransferase in A. thaliana , we have introduced a novel biosynthetic ability that allows the non-accumulator to accumulate Se -Methylselenocysteine and γ-glutamylMethylselenocysteine in shoots. The biosynthesis of Se -Methylselenocysteine in A. thaliana also confers significantly increased selenite tolerance and foliar Se accumulation. Conclusion These results demonstrate the feasibility of developing transgenic plant-based production of Se -Methylselenocysteine, as well as bioengineering selenite resistance in plants. Selenite resistance is the first step in engineering plants that are resistant to selenate, the predominant form of Se in the environment.
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production of se Methylselenocysteine in transgenic plants expressing selenocysteine methyltransferase
BMC Plant Biology, 2004Co-Authors: Danielle R Ellis, Thomas G Sors, Dennis G Brunk, Carrie Albrecht, Cindy Orser, Brett Lahner, Karl V Wood, Hugh H Harris, Ingrid J PickeringAbstract:Background It has become increasingly evident that dietary Se plays a significant role in reducing the incidence of lung, colorectal and prostate cancer in humans. Different forms of Se vary in their chemopreventative efficacy, with Se-Methylselenocysteine being one of the most potent. Interestingly, the Se accumulating plant Astragalus bisulcatus (Two-grooved poison vetch) contains up to 0.6% of its shoot dry weight as Se-Methylselenocysteine. The ability of this Se accumulator to biosynthesize Se-Methylselenocysteine provides a critical metabolic shunt that prevents selenocysteine and selenomethionine from entering the protein biosynthetic machinery. Such a metabolic shunt has been proposed to be vital for Se tolerance in A. bisulcatus. Utilization of this mechanism in other plants may provide a possible avenue for the genetic engineering of Se tolerance in plants ideally suited for the phytoremediation of Se contaminated land. Here, we describe the overexpression of a selenocysteine methyltransferase from A. bisulcatus to engineer Se-Methylselenocysteine metabolism in the Se non-accumulator Arabidopsis thaliana (Thale cress).