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PubMed2001

Protective effects of vitamins and selenium compounds in yeast.

Antimutagens and anticarcinogens are known to play an important role in decreasing damages induced by oxidants. In this study, we investigated the genotoxic and antimutagenic potential of two selenium compounds (sodium selenite: Na(2)SeO(3); seleno-DL-methionine: C(5)H(11)NO(2)Se) and Vitamins A and E in yeast cells of Saccharomyces cerevisiae. An oxidative mutagen (hydrogen peroxide (H(2)O(2)), HP) was chosen as positive control. We determined the enzymatic activities involved in the protection against oxidative damages (catalase: CAT; superoxide dismutase: SOD; glutathione peroxidase: GPx) in the cytosolic extract of yeast cells. The results demonstrated that selenium compounds exerted both mutagenic and antimutagenic effect at different concentrations. Antimutagenesis was evident both in stationary and in logarithmic phase cells. Catalase, SOD, and GPx were significantly increased in the presence of all the compounds assayed. Vitamins A (retinol) and E (alpha-tocopherol) did not have toxic or mutagenic action.

Antimutagenic Agents↗
PubMed1978

Gas-liquid chromatographic determination of selenium in biological materials, using 4-bromo- and 4-chloro 1,2-diaminobenzene as derivatizing reagents.

A method is described for the gas-liquid chromatographic determination of traces of selenium in marine biological materials. The method is based on the reaction of Se(IV) with bromo- and chloro-substituted 1,2-diaminobenzenes. The benzoselenadiazoles so formed are sensitive to electron capture detection. The sample is digested in a nitric-perchloric acid mixture and selenium is reduced to the IV oxidation state. Different aliquots of the digest solution are reacted with either 4-bromo- or 4-chloro-1,2-diaminobenzene to quantitatively form the corresponding 2,1,3-benzoselenadiazole. Recovery of added selenite to a fish meal sample was 95% for the bromo derivative and 101% for the chloro derivative. Different portions of a well mixed fish meal sample were analyzed in independent laboratories by the fluorometric method and by atomic absorption spectrophotometry (hydride generation). The following mean values (microgram/g) were found: present method 1.89, fluorometric method 1.91, atomic absorption method 2.1. The lower limit of detection for the method described was 13 ng, using the bromo derivative, and 27 ng, using the chloro derivative.

Aniline Compounds↗
PubMed1998

Antimycobacterial activities of dehydrocostus lactone and its oxidation products.

In an attempt to study the structural dependence of antimycobacterial activity of the guaianolide dehydrocostus lactone and its derivatives, m-chloroperoxybenzoic acid oxidations of dehydrocostus lactone (1a) were performed. Three new monoepoxides, one previously synthesized diepoxide, and two new diepoxides were obtained. Two of the monoepoxides are C-10 epimers (3a, 3b), while the 4(15)-monoepoxide (2) has the 4alpha-O-configuration. The known diepoxide (4a) contains a C-10 alpha-epoxide and a beta-epoxide at C-4. The diepoxides 4b and 4c, each with a C-4 alpha-epoxy group, differ in the configuration of the epoxide ring at C-10. Allylic oxidation of dehydrocostus lactone (1a) with selenium dioxide/tert-butyl hydroperoxide afforded the known 3-epizaluzanin C (1b). The relative configurations of compounds 1b-4c were established by 1D and 2D NMR techniques (1H, 13C, COSY, NOESY, HMQC, and HMBC) as well as comparison with literature data. The molecular structures of lactones 1b, 4a, and 4c were determined by single-crystal X-ray diffraction. In radiorespirometric bioassays against Mycobacterium tuberculosis and Mycobacterium avium, dehydrocostus lactone (1a) exhibited minimum inhibitory concentrations of 2 and 16 microgram/mL, respectively. In contrast, its monoepoxides (2, 3a, and 3b) and diepoxides (4a-c), as well as its hydrogenated derivatives and other analogues (1b, 1c, 5, and 6), showed significantly lower activities against M. tuberculosis.

Antitubercular Agents↗
PubMed2006

Analysis of proline reduction in the nosocomial pathogen Clostridium difficile.

Clostridium difficile, a proteolytic strict anaerobe, has emerged as a clinically significant nosocomial pathogen in recent years. Pathogenesis is due to the production of lethal toxins, A and B, members of the large clostridial cytotoxin family. Although it has been established that alterations in the amino acid content of the growth medium affect toxin production, the molecular mechanism for this observed effect is not yet known. Since there is a paucity of information on the amino acid fermentation pathways used by this pathogen, we investigated whether Stickland reactions might be at the heart of its bioenergetic pathways. Growth of C. difficile on Stickland pairs yielded large increases in cell density in a limiting basal medium, demonstrating that these reactions are tied to ATP production. Selenium supplementation was required for this increase in cell yield. Analysis of genome sequence data reveals genes encoding the protein components of two key selenoenzyme reductases, glycine reductase and d-proline reductase (PR). These selenoenzymes were expressed upon the addition of the corresponding Stickland acceptor (glycine, proline, or hydroxyproline). Purification of the selenoenzyme d-proline reductase revealed a mixed complex of PrdA and PrdB (SeCys-containing) proteins. PR utilized only d-proline but not l-hydroxyproline, even in the presence of an expressed and purified proline racemase. PR was found to be independent of divalent cations, and zinc was a potent inhibitor of PR. These results show that Stickland reactions are key to the growth of C. difficile and that the mechanism of PR may differ significantly from that of previously studied PR from nonpathogenic species.

Amino Acid Isomerases↗
PubMed2006

Effects of selenium supplementation on expression of glutathione peroxidase isoforms in cultured human lung adenocarcinoma cell lines.

Selenium is an essential nutrient, a component of several anti-oxidant enzymes, and a possible factor in cancer risk, including lung cancer. We determined the subtoxic range of selenium concentration (as sodium selenite) required to increase and maintain the expression of anti-oxidant selenoproteins gluthathione peroxidases GPX1 and GPX4 at a constant level in cultures of human lung adenocarcinoma cell lines (H460, H1703 and H1944) and in HPL1D, a non-transformed lung epithelial cell line. Selenium dose-dependently increased GPX1 protein expression 1.8-fold in HPL1D cells and approximately 40-fold in H460 and H1944 cancer cells, with maximum effects at 20-40 nM. GPX4 protein was also increased, but more so in HPL1D (five-fold) than in H460 or H1944 cells (two- to three-fold). GPX1 mRNA showed similar patterns but differences of lesser magnitude. GPX1 protein and activity level was not consistently detectable in H1703 cells, with or without Se supplementation; its mRNA was present but very low. GPX4 protein level was also low in H1703 cells, but was markedly increased by selenium supplementation (48-fold). These results confirm a role for selenium in risk of lung cancer and the independent regulation of GPX1 and GPX4. Characterization of individual tumors with regard to GPX1 and GPX4 levels and regulation might be useful for interpretation of clinical studies on effects of selenium in lung cancer risk.

Adenocarcinoma↗
PubMed1987

Differential effects of dietary selenium on hepatic and renal glutathione-related enzymes and on hepatic microsomal drug metabolism in the rat.

These studies were undertaken to assess the effect of dietary selenium on glutathione-related enzyme activities in the liver and kidney and on hepatic drug metabolism. The intent was to study underlying mechanisms of selenium-induced beneficial effects in some models of hepatoxicity and carcinogenesis. Dietary selenium, as sodium selenite, was incorporated into a torula yeast basal diet (0.02 ppm selenium) and fed to male rats at supplementation levels of 0.0-5.0 ppm selenium for periods of three or six weeks. Additionally, a commercial cereal-based diet (CD, 0.05-0.08 ppm selenium) was compared to the experimentally defined diet (DD) supplemented with approximately the same amount of selenium. Liver and kidney glutathione peroxidase activity essentially plateaued at levels of selenium of 0.1 ppm and greater. CD- and DD-fed animals had hepatic and renal glutathione peroxidase activities which were similar. Glutathione S-transferase activity in liver, but not kidney, increased with increasing supplements of selenium. Glutathione S-transferase activities in CD- and DD-fed rats were not different. Cytochrome P-450 content and associated oxidative drug metabolism activities were relatively unmodified by selenium. Overall, dietary selenium appeared to act by enhancing potential conjugative detoxication pathway, rather than by decreasing the potential activation of chemicals via the hepatic cytochrome P-450 system.

Animals↗
PubMed2005

Selenium uptake, translocation, assimilation and metabolic fate in plants.

The chemical and physical resemblance between selenium (Se) and sulfur (S) establishes that both these elements share common metabolic pathways in plants. The presence of isologous Se and S compounds indicates that these elements compete in biochemical processes that affect uptake, translocation and assimilation throughout plant development. Yet, minor but crucial differences in reactivity and other metabolic interactions infer that some biochemical processes involving Se may be excluded from those relating to S. This review examines the current understanding of physiological and biochemical relationships between S and Se metabolism by highlighting their similarities and differences in relation to uptake, transport and assimilation pathways as observed in Se hyperaccumulator and non-accumulator plant species. The exploitation of genetic resources used in bioengineering strategies of plants is illuminating the function of sulfate transporters and key enzymes of the S assimilatory pathway in relation to Se accumulation and final metabolic fate. These strategies are providing the basic framework by which to resolve questions relating to the essentiality of Se in plants and the mechanisms utilized by Se hyperaccumulators to circumvent toxicity. In addition, such approaches may assist in the future application of genetically engineered Se accumulating plants for environmental renewal and human health objectives.

Animals↗
PubMed1998

Biochemical characterization of selenium-containing catalytic antibody as a cytosolic glutathione peroxidase mimic.

A selenium-containing catalytic antibody (Se-4A4), prepared by converting reactive serine residues of a monoclonal antibody (4A4) raised against a GSH derivative into selenocysteines, acts as a mimic of cytosolic glutathione peroxidase (cGPX). To clarify the mechanism of action of this catalytic antibody, detailed studies on kinetic behaviour and biological activity were carried out. A rate of acceleration (kcat/Km/kuncat) 10(7)-fold that of the uncatalytic reaction is observed. Under similar conditions, the turnover number (kcat) of Se-4A4 is 42% of that of the natural rabbit liver cGPX. The Se-4A4 reaction involves a Ping Pong mechanism, which is the same as that of the natural cGPX. The selenocysteine residue is located in the binding site of the antibody and is shown to be crucial for this activity. Of the thiol compounds tested, only GSH is able to serve as substrate for Se-4A4. It was demonstrated, using the free-radical-damage system (hypoxanthine/xanthine oxidase) of cardiac mitochondria, that Se-4A4 can protect mitochondria from free-radical damage at least 10(4)-fold more effectively than the natural cGPX.

Antibodies, Catalytic↗
PubMed2005

Characterization of sediment bacteria involved in selenium reduction.

Bacterial reduction of selenium (Se) oxyanions (Se[VI] and Se[IV]) to elemental Se (Se[0]) is one of the major biogeochemical processes removing Se from agricultural drainage water and depositing Se in the sediment. This study was conducted to characterize Se-reducing bacterial populations in Lost Hills evaporation pond sediment and to observe their response to Se(VI) and organic C amendments. Se(VI) was removed from the dissolved phase in the sediment slurries amended with organic C with a decrease in redox potential (Eh). Se(VI) concentrations decreased from 2137 to 79 microg L-1 after 9 days of incubation in a 5% soil slurry. Upon our screening process, 9 Se(VI)- and 14 Se(IV)-reducing bacteria were isolated from sediment slurries and identified by amplification and sequencing of 16S rDNA. Bacillus strains appeared to be dominant in the bacterial assemblages active in Se(VI) and Se(IV) reduction in the sediment. Halomonas pacifica and Staphylococcus warneri were also identified as Se(IV)-reducers. Indigenous bacteria have a significant role in the biogeochemical cycling of Se and may be stimulated by addition of a suitable organic source for Se reduction. The bacterial strains isolated from salt-affected and Se-contaminated Lost Hills evaporation pond sediment may have potential application in removing Se from high salt drainage water.

Bacillaceae↗
PubMed2004

Potential roles of flavin-containing monooxygenases in sulfoxidation reactions of l-methionine, N-acetyl-l-methionine and peptides containing l-methionine.

Flavin-containing monooxygenases (FMOs) are microsomal enzymes that catalyze the NADPH-dependent oxidation of a large number of sulfur-, selenium-, and nitrogen-containing compounds. Five active isoforms (FMO1-5) have been identified and shown to be differently expressed in various mammalian tissues. Previous work from this laboratory has shown l-methionine to be S-oxidized by rat, rabbit and human FMO1-4, with FMO3 exhibiting the highest stereoselectivity for the formation of the d-diastereomer of methionine sulfoxide. In this report, we describe new studies aimed at determining if N-acetyl-l-methionine and peptides containing l-methionine can be substrates for FMOs. Experiments were carried out using either rabbit liver microsomes or human cDNA-expressed FMOs. The results show that while N-acetyl-l-methionine and peptides with a modified methionine amino group may not function as substrates for FMOs, peptides containing a free N-terminal methionine may act as FMO substrates. With human cDNA-expressed FMO1, FMO3, and FMO5, both FMO1 and FMO3 exhibited activity with the active peptides whereas FMO5 was inactive. With FMO3, the activity measured with methionine was similar (1 mM) or higher (5 mM) than the activity measured with H-Met-Val-OH and H-Met-Phe-OH. With FMO1, H-Met-Phe-OH and methionine exhibited similar activities whereas activity with H-Met-Val-OH was much lower. Collectively, the results show that FMOs can oxidize peptides containing a free N-terminal methionine. Thus, the role of FMOs in the oxidation of methionine in larger peptides or proteins warrants further investigation.

Chromatography, High Pressure Liquid↗
PubMed2001

Dietary and blood antioxidants in patients with chronic heart failure. Insights into the potential importance of selenium in heart failure.

BACKGROUND: Chronic heart failure (CHF) seems to be associated with increased oxidative stress. However, the hypothesis that antioxidant nutrients may contribute to the clinical severity of the disease has never been investigated. AIMS: To examine whether antioxidant nutrients influence the exercise capacity and left ventricular function in patients with CHF. METHODS: Dietary intake and blood levels of major antioxidant nutrients were evaluated in 21 consecutive CHF patients and in healthy age- and sex-matched controls. Two indexes of the severity of CHF, peak exercise oxygen consumption (peak VO2) and left ventricular ejection fraction (LVEF), were measured and their relations with antioxidants were analysed. RESULTS: Whereas plasma alpha-tocopherol and retinol were in the normal range, vitamin C (P=0.005) and beta-carotene (P=0.01) were lower in CHF. However, there was no significant association between vitamins and either peak VO2 or LVEF. Dietary intake (P<0.05) and blood levels of selenium (P<0.0005) were lower in CHF. Peak VO2 (but not LVEF) was strongly correlated with blood selenium: r=0.76 by univariate analysis (polynomial regression) and r=0.87 (P<0.0005) after adjustment for age, sex and LVEF. CONCLUSIONS: Antioxidant defences are altered in patients with CHF. Selenium may play a role in the clinical severity of the disease, rather than in the degree of left ventricular dysfunction. Further studies are warranted to confirm the data in a large sample size and to investigate the mechanisms by which selenium and other antioxidant nutrients are involved in CHF.

Adult↗
PubMed2004

Organoselenium compounds as potential therapeutic and chemopreventive agents: a review.

Selenium is an essential trace element. It is, however toxic at concentration little above which is required for health. Selenium is incorporated into proteins as selenocysteine, the 21(st) amino acid. Selenoproteins are found in bacteria, archaea and eukaryotes. Biochemical and physicochemical properties of selenium result in the unique redox characteristics of selenocysteine and its use in antioxidant enzymes. In this context of a redox reaction is the reduction of reactive oxygen metabolites by glutathione peroxidases, helping to maintain membrane integrity, reduces the oxidative damage to lipids, lipoproteins, and DNA. Selenium has structural and enzymatic roles. Selenium influences a number of endocrine processes, most notably, those involved in thyroid hormone synthesis and metabolism. Se is needed for the proper functioning of the immune system, a role in viral suppression, AIDS, and also is implicated in delaying the aging process. Its deficiency has been linked to a number of disorders such as heart disease, diabetes, and diseases of the liver, and it is required for sperm motility and may reduce the risk of miscarriage. Se supplementation has recently moved from the realm of correcting nutritional deficiencies to one of pharmacological intervention, especially in the clinical domain of cancer chemoprevention. During the last few years, a tremendous effort has been directed toward the synthesis of stable organoselenium compounds that could be used as antioxidants, enzyme modulators, antitumor, antimicrobials, antihypertensive agents, antivirals and cytokine inducers. The biochemistry and pharmacology of selenium-based compounds are subjects of intense current interest, especially from the point of view of public heath. The purpose of this review is to discuss the recent pharmacological applications of organoselenium compounds as therapeutic agents in the treatment of several diseases.

Animals↗
PubMed1997

Dietary selenium increases cellular glutathione peroxidase activity and reduces the enhanced susceptibility to lipid peroxidation of plasma and low-density lipoprotein in kidney transplant recipients.

The glutathione system plays a major role in the protection of cells against oxidative stress in humans. The aim of the present study was to find out the relationship between the glutathione system and plasma lipid peroxidation in six renal transplant recipients (who are under oxidative stress and thus at high risk for atherosclerosis), by using dietary selenium to activate the glutathione system. 2,2'-Azobis-2-amidinopropane hydrochloride (AAPH)-induced plasma lipid peroxidation was increased (by 60%) in all six patients in comparison to normal subjects. A similar pattern of increased plasma lipid peroxidation was found even in the basal state (in the absence of added AAPH). CuSO4-induced low-density lipoprotein (LDL) oxidation measured by peroxide formation was also significantly increased by 2.3-fold in the patients' LDL in comparison to normal LDL. Even in the absence of CuSO4, the LDL oxidation state was also increased in the patients' LDL in comparison to normal LDL. We thus analyzed the effect of dietary selenium (0.2 mg/day for a period of 3 months, followed by an additional 3 months on placebo) on plasma and on LDL lipid peroxidation. Selenium treatment resulted in a 50% reduction in AAPH-induced plasma lipid peroxidation. The susceptibility of the patients' plasma to lipid peroxidation returned toward baseline values 3 months after termination of the selenium treatment. Similar results, although less pronounced (only 15% reduction), were obtained for CuSO4-induced LDL oxidation. Analyses of the patients' red blood cell (RBC) glutathione system revealed low levels of reduced glutathione and decreased activities of RBC glutathione peroxidase and glutathione reductase by 23%, 18%, and 20%, respectively, in comparison to normal RBC. Selenium treatment resulted in a significant elevation of RBC glutathione peroxidase and glutathione reductase activities and in reduced glutathione content by 64%, 57%, and 11%, respectively; this effect was also paralleled by a 39% reduction in the RBC oxidized glutathione content. On termination of the selenium treatment, and after 3 months on placebo, all of these values of the glutathione system elements returned toward baseline levels. We thus conclude that dietary selenium, which activates the glutathione system, is a potent antioxidant against plasma and LDL lipid peroxidation in renal transplant recipients, and may thus be considered antiatherogenic.

Adult↗
PubMed2006

Selenium for alleviating the side effects of chemotherapy, radiotherapy and surgery in cancer patients.

BACKGROUND: Selenium supplements are frequently used by cancer patients. Selenium is an essential trace element and is involved in antioxidant protection and redox-regulation in humans. Several adverse effects of radiotherapy and chemotherapy in cancer patients as well as cellular processes that maintain chronic lymphoedema have been linked to oxidative cell damage in the human body. Selenium has recently been investigated as a remedy against chemotherapy and radiotherapy-associated side effects as well as its effects on lymphoedema. OBJECTIVES: This review assessed the effects of supplementary selenium on adverse effects of conventional radiotherapy, chemotherapy, or surgery, in oncologic patients and on quality of life or performance status during and after oncologic treatment. SEARCH STRATEGY: We searched the Cochrane Pain, Palliative & Supportive Care Trials Register, the Cochrane Database of Systematic Reviews (The Cochrane Library , Issue 2, 2004), Medline (1966 - Sep 2004), Embase (1980 - 2004 week 12), SIGLE (October 2004), Cancerlit (October 2004), Clinical Contents in Medicine CCMed (October 2004), the German Register of Cancer Studies (October 2004), the NCI Clinical Trials Register (October 2004), the International Standard Randomised Controlled Trial Number Register ISRCTN (October 2004) and the Meta-Register of Controlled Trials mRCT (October 2004), reference lists and the archive of our working group. We contacted manufacturers of selenium supplements and investigators. SELECTION CRITERIA: Randomised-controlled trials of selenium mono-supplements in cancer patients undergoing tumour specific therapy such as chemotherapy, radiotherapy or surgery. DATA COLLECTION AND ANALYSIS: Two review authors independently checked trials for eligibility, extracted data and assessed trial quality. We sought additional information from investigators when required. MAIN RESULTS: Two trials have been included, a randomised controlled trial with 60 participants at the beginning of the study investigating secondary lymphoedema and an ongoing trial with preliminary results of 63 participants investigating radiotherapy induced diarrhoea as a secondary outcome. Both trials had drawbacks with regard to study quality and reporting. The trial on secondary lymphoedema reported a decreased number of recurrent erysipela infections in the selenium supplementation group compared to placebo. However, results must be interpreted with caution and cannot be generalised to other populations. The ongoing trial on radiotherapy associated diarrhoea preliminarily reported a lower incidence of diarrhoea in patients receiving selenium supplementation concomitant to pelvic radiation, however, no data were presented. Publication of final results must be awaited to discuss these findings in detail. No randomised controlled trials were found studying the effect of selenium supplementation on other therapy-associated toxicities or quality of life or performance status in cancer patients. AUTHORS' CONCLUSIONS: There is insufficient evidence at present that selenium supplementation alleviates the side effects of tumour specific chemotherapy or radiotherapy treatments. Or, that it improves the after effects of surgery, or improves quality of life in cancer patients or reduces secondary lymphoedema. To date research findings do not provide a basis for any recommendation in favour or against selenium supplementation in cancer patients. Potential hazards of supplementing a trace mineral should be kept in mind.

Antineoplastic Agents↗
PubMed2001

Glutathione peroxidase-1 gene knockout on body antioxidant defense in mice.

To determine the in vivo role of cellular glutathione peroxidase (E.C.1.11.1.9, GPX1), we challenged the GPX1 knockout [GPX1(-/-)], the GPX1 overexpressing [GPX1(+)], and their respective wild-type (WT) mice of different Se and vitamin E status with acute oxidative stress. After these mice were injected with pro-oxidants paraquat or diquat at 12 to 125 mg/kg of body weight, their survival rate and time were a function of their GPX1 activity levels. The GPX1 protection was associated with attenuation of NADPH and NADH oxidation, protein carbonyl and F(2)-isoprostanes formation, and alanine transaminase release in various tissues, and was irreplaceable by high levels of dietary vitamin E or other selenoproteins. The GPX1 expression was also protective against moderate oxidative stress induced by low levels of paraquat or diquat, particularly in the Se-deficient mice. Alteration of GPX1 expression showed no impact on the expression of other selenoproteins and antioxidant enzymes in unstressed mice. Total Se content in liver of the Se-adequate GPX1(-/-) mice was reduced by 60% the WT controls. In conclusion, normal expression of GPX1 is essential and overexpression of GPX1 is beneficial to protect mice against acute oxidative stress.

Animals↗
PubMed1993

Synthesis of some new heterocyclic systems derived from 2-acetylbenzimidazole.

The named compound was reacted with thiosemicarbazide and/or semicarbazide to produce the corresponding condensation products II and V respectively. Reaction of II with chloroacetic acid in ethanol containing anhydrous sodium acetate yielded III. Condensation of III with aromatic aldehydes yielded the corresponding arylidene derivatives (IV). Oxidation of the semicarbazone V with selenium dioxide gave 2-(1,2,3-selenadiazole-4-yl)benzimidazole (VIa, b) while with thionyl chloride it gave 2-(1,2,3-thiadiazole-4-yl)benzimidazole (VIIa, b). The chalcones of 2-acetyl and/or 1-methyl-2-acetylbenzimidazole were condensed with hydrazine hydrate, phenylhydrazine and/or hydroxylamine to produce 2-(5-aryl-1(H)-pyrazolin-3-yl)-, 2-(5-aryl-1-phenyl-2-pyrazolin-3-yl)- and 2-(5-aryl-2-isoxazolin-3-yl)benzimidazole (IX, X, XI) respectively.

Azoles↗