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PubMed1999

Levels of major selenoproteins in T cells decrease during HIV infection and low molecular mass selenium compounds increase.

It has been observed previously that plasma selenium and glutathione levels are subnormal in HIV-infected individuals, and plasma glutathione peroxidase activity is decreased. Under these conditions the survival rate of AIDS patients is reduced significantly. In the present study, using 75Se-labeled human Jurkat T cells, we show that the levels of four 75Se-containing proteins are lower in HIV-infected cell populations than in uninfected cells. These major selenoproteins migrated as 57-, 26-, 21-, and 15-kDa species on SDS/PAGE gels. In our earlier studies, the 57-kDa protein was purified from T cells and identified as a subunit of thioredoxin reductase. The 26- and 21-kDa proteins were identified in immunoblot assays as the glutathione peroxidase (cGPX or GPX1) subunit and phospholipid hydroperoxide glutathione peroxidase (PHGPX or GPX4), respectively. We recently purified the 15-kDa protein and characterized it as a selenoprotein of unknown function. In contrast to selenoproteins, low molecular mass [75Se]compounds accumulated during HIV infection and migrated as a diffuse band near the front of SDS/PAGE gels.

Acquired Immunodeficiency Syndrome↗
PubMed2006

Speciation of selenium compounds by open tubular capillary electrochromatography-inductively coupled plasma mass spectrometry.

We introduce a T-type interface and a crossflow nebulizer to find ways to combine CEC with inductively coupled plasma MS (ICP-MS) detection for selenium speciation. For CEC separation, we employed a macrocyclic polyamine-bonded phase capillary as the separation column and a bare fused-silica capillary filled with the make-up liquid (0.05 M HNO3). The effect of nebulizer gas flow rate, make-up liquid flow, type, concentration and pH of the mobile phase on the separation have been studied. Tris buffer of 50 mM at pH 8.50 gave the best performance for selenium speciation. The reproducibility of the retention time indicated that sample injection by electrokinetic and nebulizer gas flow was better than that by self-aspiration alone. The detection limits for selenate, selenite, selenocystine and selenomethionine were found to be 2.40, 3.53, 12.86 and 11.25 ng/mL, respectively. Due to the high sensitivity and element-specific detection, as well as the high selectivity of the bonded phase, quantitative analysis of selenium speciation in urine was also achieved.

Buffers↗
PubMed2005

Speciation of cationic selenium compounds in Brassica juncea leaves by strong cation-exchange chromatography with inductively coupled plasma mass spectrometry.

Strong cation-exchange chromatography (SCX-HPLC) was used in conjunction with inductively coupled plasma mass spectrometry (ICP-MS) to investigate cationic selenium species present in leaf extract of wild-type Brassica juncea supplemented with selenite. Total amount of Se accumulated by the leaves was found to be 352 microg g(-1). Cation-exchange solid-phase extraction (SCX-SPE) was used to pre-concentrate the cationic species present in the leaf extract. Methylselenomethionine (MeSeMet) and dimethylselenoniumproprionate (DMSeP) were synthesized and characterized by electrospray quadrupole time-of-flight MS (ESI-QTOF-MS). Laboratory synthesized and commercially available standards were used in chromatographic studies to identify the Se species in the leaf extract through retention time comparisons and standard addition method. Major cationic selenium species identified in the present study were MeSeMet and methylselenocysteine (MeSeCys) while selenomethionine (SeMet) was found in minor quantities.

Chemical Fractionation↗
PubMed1991

Effect of selenium compounds and thiols on human mammary tumor cells.

The effect on cell viability and growth rate of sodium selenite, selenocystine, sodium selenate, and selenomethionine at selenium concentrations of 6.25 and 12.5 uM was studied in vitro on cells of the human mammary tumor cell line HTB123/DU4475. Selenite and selenocystine affected both cell viability and growth rate of the tumor cells at these selenium concentrations. Selenite and selenocystine decreased intracellular glutathione concentrations, but did not affect tumor cell glutathione peroxidase activity. After six days of exposure to either selenate or selenomethionine, the viability of tumor cells remained stable, but cell growth, as measured by numbers of cells, was retarded. Neither selenate nor selenomethionine produced changes in concentrations of intracellular glutathione. The toxic effect of selenite on tumor cells was enhanced by addition of 0.25 mM glutathione to the growth medium. Preincubation of the tumor cells with 62.5 uM buthionine sulfoximine decreased cellular glutathione to 15% of controls at 24 h and enhanced the toxicity of selenite toward the tumor cells. Glutathione, 2-mercaptoethanol, and L-cysteine were all toxic to the tumor cells in a dose-dependent manner.

Aged↗
PubMed1995

Toxicity studies of a new selenium compound, Selol, in rats.

Selol is a new organoselenium compound synthesized in the Department of Drug Analysis, Warsaw. The general acute and cumulative toxicities of Selol were tested in rats. The compound did not display any toxic effects after parenteral administration up to 500 mg/kg-1 s.c. and 100 mg/kg-1 i.p. However, given orally it exhibited high toxicity. LD50 value after a single oral administration amounted to 100 mg/kg-1 and after administration in an increasing-dose schedule to 80 mg/kg-1. On the basis of these results the authors conclude that Selol may be converted to a more toxic product during digestion. Therefore, Selol as a source of selenium is safer given by the parenteral route.

Administration, Oral↗
PubMed1996

Insulin-like vs. non-insulin-like stimulation of glucose metabolism by vanadium, tungsten, and selenium compounds in rat muscle.

The direct impact of vanadate, tungstate, selenate, and selenite on glucose metabolism of isolated rat soleus muscle was investigated. All compounds stimulated glucose transport, but only vanadate exerted an insulin-like effect on glycogen synthesis (mumol glucose into glycogen*g-1*h-1: control 1.43 +/- 0.11 vs. 1 mmol/l vanadate, 2.08 +/- 0.11, p < 0.0001), which was more distinct in the presence of 1 mmol/l H2O2 (control, 1.44 +/- 0.13 vs. 1 mmol/l vanadate, 3.49 +/- 0.12, p < 0.001). Glucose handling of muscles exposed to tungstate, selenate, or selenite resembled that of hypoxic muscle, i.e. the induced rise in glucose uptake was inhibited by dantrolene and associated with high rates of glycolysis and rapid glycogen depletion (glycogen content after incubation, mumol glucosyl units/g: control, 16.2 +/- 0.7 vs. hypoxia, 2.7 +/- 0.5, p < 0.0001; control, 17.0 +/- 0.5 vs. 100 mmol/l tungstate, 5.5 +/- 0.4, p < 0.001; control, 16.2 +/- 0.7 vs. 100 mmol/l selenate, 1.5 +/- 0.3, and vs. 300 mumol/l selenite, 1.7 +/- 0.3, p < 0.0001 each). The results suggest that vanadate (and more pronounced it's peroxides) exerts true insulin-like action on isolated muscle glucose metabolism, whereas tungsten and selenium salts trigger glucose transport in association with a catabolic response, which may represent an unspecific response to toxic/osmotic stress.

Androstadienes↗
PubMed2004

Prevention against oxidative stress of eukaryotic cell membranes by selenium compounds of the rat.

By a combination of trace techniques and various biochemical methods, information about the characteristics of a 15-kDa selenoprotein was obtained. After labeling of rats in vivo with [(75)Se]selenite, subcellular fractionation of the homogenates of the prostate, lung, brain, thyroid gland, and large intestine, and gel electrophoretic separation of the proteins and subcellular fractionation, 15-kDa (75)Se was found in the cytosols of the tissues prostate > brain > lung > thyroid gland > large intestine after autoradiography. After coelectrophoresis of the separated 15-kDa labeled band obtained from each cytosolic fraction, the 15-kDa (75)Se band migrated in the same way as the combined bands isolated from the five tissue cytosols. After proteolytic cleavage in the gel of the 15-kDa labeled band obtained from the cytosol of each tissue and re-electrophoresis, the same labeled peptide pattern was found in each gel slice after autoradiography. By means of reversed-phase HPLC, we characterized a selenocysteine-containing protein that has enzymatic activity like that of glutathione peroxidase.

Animals↗
PubMed2001

Speciation of arsenic and selenium compounds by ion-pair reversed-phase chromatography with electrothermic atomic absorption spectrometry. Application of experimental design for chromatographic optimisation.

An off-line system is proposed consisting of ion-pair reversed-phase liquid chromatography, collections of fractions at the outflow of the column and furnace atomic absorption spectrometry. The so-called system allowed determination of both arsenic and selenium species mainly found in the environment and in mammals (arsenite, arsenate, monomethylarsonate, dimethylarsinate, selenite, selenate, selenocystamine, selenocystine, selenomethionine and selenoethionine). In order to study the retention behaviour of these compounds and to estimate the optimal conditions for the chromatographic separation, central composite designs were used to evaluate the influence of the eluent parameters such as pH, tetrabutylammonium phosphate (TBA) concentration and sodium hydrogenphosphate amounts. The retention factors of each species and the selectivity were established as response criteria. Response surfaces and isoresponse curves were drawn from the mathematical models and enabled one to determine the optimal conditions and to visualise the method robustness. The predicted optimal zone was situated at pH 5.5-6.5, 4.0 mM Na2HPO4 and 3.0-4.0 mM TBA. Regression models suggested linearity for the studied compounds in the range 25-200 microg selenium and arsenic per litre investigated.

Arsenic↗
PubMed1993

Kinetics of glucose oxidase catalyzed electron transfer mediated by sulfur and selenium compounds.

Unusually high electron transfer rates in Aspergillus niger glucose oxidase catalyzed oxidation of glucose using 5,6:11,12-Bis(dithio)tetracene (TTT), 1,2-dimethyltetraselenafulvalene (DMTSF) and tetrathiafulvalene (TTF) were observed. At pH 7.0 oxidation rate constants (TN/Km) in the range from 1.0.10(7) to 8.7.10(7) M.s-1 were deduced from experimental data. One of the investigated mediators, DMTSF, has been used for electrocatalytical glucose oxidation on graphite at a potential of 0.3 V vs. a standard calomel electrode (SCE). The prepared bioelectrodes have a sensitivity of 1.3 microA/(cm2.mM), a pH optimum at 6.5-7.0, and a linear range which covers the relevant range for monitoring physiological levels of glucose. The bioelectrodes are stable for more than one month.

Aspergillus niger↗
PubMed1996

Organic and inorganic selenium compounds inhibit mouse mammary cell growth in vitro by different cellular pathways.

Selenium, both organic and inorganic forms, inhibit mammary tumorigenesis in vivo and mammary cell growth in vitro. In the present study, sodium selenite was compared to methylselenocysteine (MSC) for their individual effects on cell growth, cdc2/cdk2 kinase activities and the levels of cyclins D1, E and A bound to cdk2 in a mouse mammary epithelial cell culture model. Selenite arrested the growth of cells in S-G2-M phase in contrast to MSC which arrested or delayed the cells in G1. In MSC-treated cells there was a 57% drop in the cdk2 kinase activity accompanied by a 73.5% decrease in cyclin E-cdk2 content as compared to the control cells. Selenite treatment increased the cdk2 kinase activity by 30% without any appreciable change in either of the cyclins D1, E or A bound to cdk2 when compared to the control cells. These data support the hypothesis that selenite and MSC have distinct modes of action in the inhibition of cell growth in vitro. Selenite has a strong genotoxic effect on the tumor cells; in contrast, MSC appears to inhibit cell growth via specific inhibition of cell cycle regulatory proteins.

Animals↗
PubMed1993

Generation of reactive oxygen species from the reaction of selenium compounds with thiols and mammary tumor cells.

Sodium selenite, sodium selenate, selenocystine and selenomethionine were tested for their abilities to generate superoxide by the oxidation of glutathione and other thiols in the absence and presence of cells of the human mammary tumor cell line HTB123/DU4475. Free radical generation was measured by lucigenin- or luminol-amplified chemiluminescence. In the absence of tumor cells, lucigenin-dependent chemiluminescence was observed from the reaction of selenite with the thiols glutathione, 2-mercaptoethanol and L-cysteine, but not with oxidized glutathione. Superoxide dismutase, catalase, and glutathione peroxidase all suppressed the observed chemiluminescence; but when these enzymes were heat inactivated they had little suppressive inhibition on chemiluminescence. Luminol-dependent chemiluminescence from the reaction of selenite with glutathione was much less than that observed by lucigenin-amplified chemiluminescence. In the presence of the HTB123/DU4475 mammary tumor cells, lucigenin-dependent chemiluminescence was observed from the reactions of selenite and selenocystine with glutathione which were 5 and 23 times greater than their respective reactions with glutathione in the absence of tumor cells. The enhanced chemiluminescence generated by selenite and selenocystine in the presence of the tumor cells was also suppressed by superoxide dismutase, catalase and glutathione peroxidase. These data suggest that a free radical, the superoxide anion (O2-), and H2O2 are produced from the reaction of selenite and selenocystine with glutathione. These free radical reactions may account for the toxicity of selenite and selenocystine in vitro in comparison to a near absence of acute tumor cell toxicity and superoxide generation by selenate and selenomethionine with thiols. Enhanced chemiluminescence in the presence of tumor cells may be an expression of cellular selenium metabolism and the capability of cells to form selenium metabolites that more easily oxidize glutathione and other thiols producing reactive free radicals and peroxides.

Catalase↗
PubMed1986

Selenium compounds in the fathead minnow (Pimephales promelas)--I. Uptake, distribution, and elimination of orally administered selenate, selenite and l-selenomethionine.

Treatment of fathead minnows (Pimephales promelas) with either [75Se]selenate, -selenite or -l-selenomethionine by gavage at 20 ng Se/g resulted in organ uptake and early distribution patterns which differed significantly between compounds. The greatest differences in uptake between compounds was observed in liver tissue which accumulated much less [75Se]selenate than either selenite or l-selenomethionine. The 75Se burdens and relative distribution among the various organs were nearly identical during the elimination phase for [75Se]selenate and -selenite. This suggests that selenium derived from these compounds converge to a common metabolic pool. The whole body T1/2, rate of 75Se uptake and magnitude of 75Se accumulation were generally greater for [75Se]selenomethionine than the inorganic forms. Selenium-75 was present in the bile following the oral administration of each compound. The partitioning of selenate and selenite into the plasma and cellular fraction of blood differs with both the compound and time following exposure.

Animals↗