Selenium. Mechanistic aspects of anticarcinogenic action

Combination treatment of zinc and selenium intervention ameliorated BPA-exposed germ cell damage in SD rats: elucidation of molecular mechanisms

Bisphenol A (BPA) is a commonly used environmental toxicant, is easily exposed to the human body and causes testicular damage, sperm abnormalities, DNA damage and apoptosis, and interferes in the process spermatogenesis and steroidal hormone production along with obstruction in testes and epididymis development. Zinc (Zn), a potent regulator of antioxidant balance, is responsible for cellular homeostasis, enzymes and proteins activities during spermatogenesis for cell defence mechanisms in the testes. Selenium (Se) is required for spermatogenesis, antioxidant action and in the activities of different selenoproteins. Both Zn and Se are essential simultaneously for the proper regulation of spermatogenesis and sperm maturation as well as protection against chemical and disease-associated germ cell toxicity. Thus, the study aimed to understand the importance and beneficial effect of Zn and Se co-treatment against BPA-exposed testicular damage in rats. BPA 100 and 200 mg/kg/day was exposed through an oral gavage. Zn (3 mg/kg/day) i.p. and Se (0.5 mg/kg/day) i.p. were injected for 8 weeks. The testicular toxicity was evaluated by measuring body and organs weight, biochemical investigations, sperm parameters, testicular and epididymal histopathology, quantification DNA damage by halo assay, DNA breaks (TUNEL assay), immunohistochemistry and western blot. Results revealed that Zn and Se co-treatment ameliorated BPA-associated male gonadal toxicity in rat as revealed by decreased SGPT, SGOT and BUN levels in serum, reduced testes and epididymis tissue injury, DNA breaks, apoptosis, expressions of 8-OHdG, γ-H2AX and NFκB with an increased serum testosterone and catalase levels. These findings suggest that Zn and Se co-treatment could be a beneficial and protective option against BPA-exposed testicular and epididymal toxicity.

Association of selenium, arsenic, and other trace elements in drinking water and urine in residents of the plateau region in China

Drinking water is considered to be an important exposure pathway for humans to ingest trace elements; human urine samples are widely accepted as biometric substrates that can reflect human exposure to trace elements. The current study aimed at investigating the concentrations of trace elements including selenium (Se), arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), manganese (Mn), nickel (Ni), lead (Pb), and zinc (Zn) in drinking water and human urine in plateau region of China, determining the association among trace elements in drinking water and urine, and analyzing their associations with age and gender. The results showed that the majority of trace element concentrations were in the range of the World Health Organization (WHO 2011) guideline values, in both urine samples of male and female, and the median values were descending in the order: Zn > Cu > As > Se > Cr > Ni > Mn > Pb > Cd > Co. Selenium contributed to the excretion of As, Cr, Cu, Cd, and Zn in human body, group of 31-40 years appeared to present the greatest excretion ability in most of the trace elements. Weak positive correlations were observed between age and Mn in female urine samples, and negative correlations were observed between age and Se, As, Co, and Cu in male urine samples and between age and Co in female urine samples, respectively. Significant positive correlation was observed in As between drinking water and the whole human urine. In the same family, female seemed to show higher proportions of urinary As levels than male. This study will provide elementary information regarding trace element levels in drinking water and human urine in residents in plateau region of China and is helpful to provide reference for dietary nutrient trace element intake and effective control for local resident.

Associations of dietary intakes and serum levels of folate and vitamin B-12 with methylation of inorganic arsenic in Uruguayan children: Comparison of findings and implications for future research

BACKGROUND

In the human body, inorganic arsenic (iAs) is methylated via the one-carbon cycle to form monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA). Lower proportions of iAs and MMA, and higher proportions of DMA in urine indicate efficient methylation; formation of DMA is thought to detoxify iAs and MMA. Studies on folate, vitamin B-12 and iAs methylation yield mixed findings, depending on whether folate and vitamin B-12 were assessed from diet, supplements, or using a blood biomarker.

OBJECTIVE

First, to compare the associations of serum concentrations and estimated intake of folate and vitamin B-12 with indicators of iAs methylation. Second, to highlight the implications of these different B-vitamin assessment techniques on the emerging evidence of the impact of dietary modifications on iAs methylation.

METHODS

The study was conducted among ~7-year-old children from Montevideo, Uruguay. Serum folate and vitamin B-12 levels were measured on the Horiba ABX Pentra 400 analyzer; urinary arsenic was measured using High-Performance Liquid Chromatography on-line with Inductively Coupled Plasma Mass Spectrometry. Dietary intakes were assessed using the average of two 24-h dietary recalls. Linear regressions assessed the associations of serum levels, and dietary intakes of folate (n = 237) and vitamin B-12 (n = 217) with indicators of iAs methylation. Models were adjusted for age, sex, body mass index, total urinary arsenic, and rice intake.

RESULTS

Serum folate and vitamin B-12 levels were above the adequacy threshold for 99% of the participants. No associations were observed between serum folate, serum vitamin B-12, or vitamin B-12 intake and iAs methylation. Folate intake was inversely associated with urinary %MMA [β (95% confidence interval): -1.04 (-1.89, -0.18)].

CONCLUSION

Additional studies on the role of B-vitamins in iAs methylation are needed to develop a deeper understanding of the implications of assessing folate and vitamin B-12 intake compared to the use of biomarkers. Where possible, both methods should be employed because they reflect different exposure windows and inherent measurement error, and if used individually, will likely continue to contribute to lack of consensus.

Serum Se, Ni, and As are associated with HPV infection and CIN2+ among Uyghur women in rural China

Background

Cervical cancer incidence and mortality is high in Uyghur ethnics. Their life style and dietary habit were different from other ethnics living together. Study on the role of trace elements in HPV infection and cervical lesion of Uyghur minority is needed for future intervention and prevention work.

Methods

In total, 833 Uyghur women were randomly selected from the screening site and hospital. The concentrations of the trace elements As, Fe, Cd, Ni, Cu, Zn, Mn, and Se were determined by atomic absorption spectrophotometry and inductively coupled plasma atomic emission spectroscopy. Univariate analysis was performed with chi-squared test between the HPV-positive and HPV-negative groups and between the case group and the control group. Multivariate analysis was performed with logistic regression.

Results

An As concentration ≥ 0.02 mg/kg was a risk factor for HPV infection (OR > 1, P < 0.05), and Ni concentration ≥ 0.1232 mg/kg and Se concentration ≥ 0.02 mg/kg were protective factors (OR < 1, P < 0.05). Concentrations of Fe ≥ 6.9153 mmol/L and As ≥0.02 mg/kg were risk factors for CIN2+ (OR > 1, P < 0.05), and concentrations of Ni ≥0.0965 mg/kg and Se ≥0.02 mg/kg were protective factors (OR < 1, P < 0.05).

Conclusions

Low serum concentrations of Se and Ni and a high serum concentration of As might be related to HPV infection and CIN2+ in Uyghur women in rural China.

Total arsenic, inorganic arsenic, and other elements concentrations in Italian rice grain varies with origin and type

Rice is comparatively efficient at assimilating inorganic arsenic (Asi), a class-one, non-threshold carcinogen, into its grain, being the dominant source of this element to mankind. Here it was investigated how the total arsenic (Ast) and Asi content of Italian rice grain sourced from market outlets varied by geographical origin and type. Total Cr, Cd Se, Mg, K, Zn, Ni were also quantified. Ast concentration on a variety basis ranged from means of 0.18 mg kg(-1) to 0.28 mg kg(-1), and from 0.11 mg kg(-1) to 0.28 mg kg(-1) by production region. For Asi concentration, means ranged from 0.08 mg kg(-1) to 0.11 mg kg(-1) by variety and 0.10 mg kg(-1) to 0.06 mg kg(-1) by region. There was significant geographical variation for both Ast and Asi; total Se and Ni concentration; while the total concentration of Zn, Cr, Ni and K were strongly influenced by the type of rice.

Protective Effects of Selenium, Calcium, and Magnesium Against Arsenic-Induced Oxidative Stress in Male Rats

Inorganic arsenic is a potent carcinogen and environmental pollutant. More than one hundred million people are reported to be exposed to elevated concentrations of arsenic mainly via drinking water. Essential trace elements can affect toxicity of metals by interacting with metals at the primary site of action and can also modify the body's response to toxic metals by altering their metabolism and transport. This study investigates the effects of concomitant administration of selenium, magnesium, and calcium with arsenic on blood biochemistry and oxidative stress. Selenium was the most effective in reducing arsenic-induced inhibition of blood δ-aminolevulinic acid dehydratase (ALAD) activity and liver oxidative stress. Calcium and magnesium also showed favourable effects on haematological and other biochemical parameters. Because selenium was the most effective, it should be added to chelation therapy to achieve the best protective effects against arsenic poisoning in humans.

Disposition kinetics of selenium in healthy volunteers following therapeutic shampoo treatment

This study was aimed at documenting the kinetic time courses of selenium (Se) in accessible biological matrices of volunteers following controlled applications of therapeutic shampoo containing Se, to better elucidate the mechanisms by which shampoo-Se accumulates in hair and hence estimate the contribution of this source to total Se body burden. Ten healthy volunteers were exposed to Se-shampoo three times a week over a month. Blood, hair and toenail concentrations along with daily urinary excretions were repeatedly measured over an 18-month period following the onset of application. Over the entire study period, blood concentrations of Se (range: 127-233μg/l) and daily urinary excretions (range: 11.9-150μg/d) remained within baseline range of the general population. Conversely, during shampoo application, mean Se concentrations in hair reached transitional levels of 89μg/g while, following cessation of treatment, a mono-exponential decrease was observed with a mean half-life of 4.5 weeks. Two of the volunteers also exhibited an increase in toenail concentrations of Se during the study period. Results show that Se-shampoo does not contribute significantly to total Se body burden, as assessed from blood and urine levels. Differences observed between blood and urine time courses as compared to hair profiles and the presence of Se on hair grown before treatment indicates an adsorption on hair; however, the gradual decrease in Se concentrations in successive centimeters of hair grown following the application period suggests a concomitant absorption from the scalp during treatment with subsequent excretion in hair.

Transport pathways for arsenic and selenium: a minireview

Arsenic and selenium are metalloids found in the environment. Arsenic is considered to pose the most significant potential threat to human health based on frequency of occurrence, toxicity and human exposure. Selenium, on the other hand, ranks only 147th in toxicity but, in contrast to arsenic, is a required micronutrient. Whether a toxin or micronutrient, their metabolism requires that cells to accumulate these metalloids. In this review we discuss the membrane proteins that transport arsenic and selenium into cells, from bacteria to humans, as well as some of the efflux proteins involved in detoxification.

Effects on lipid peroxidation and antioxidative enzymes of Euonymus alatus in cultured rat hepatocytes

The Euonymus alatus (Thunb.) Sieb. has long been used as a crude drug. In this paper, we investigate the effects of E. alatus on cultured hepatocyte cell system and lipid peroxidation in hydrogen peroxide (H(2)O(2)) treatment conditions. The study covers the physiological activity (the antioxidative activity and the nitrite-scavenging effect) of E. alatus. H(2)O(2) that can produce intracellular free radical was used for inducer of the peroxidation of cellular lipids. Treatment of E. alatus attenuated in cell killing enhanced by increasing concentrations of H(2)O(2). The increased malondialdehyde level induced by H(2)O(2) treatment was reduced by pre-treatment of E. alatus. Furthermore, addition of E. alatus in cell culture medium significantly reduced cell killing and content of intracellular antioxidants. Changes in nitrite-scavenging effect of E. alatus at various concentrations (5-25 mg/ml) and various pH levels (pH 1.2, 4.2 and 6.0) were also observed. The present study was also done to investigate the effects of E. alatus on cultured hepatocyte cell system, H(2)O(2)-induced cytotoxicity and antioxidative enzyme activities, including catalase, superoxide dismutase, glutathione peroxidase and glutathione S-transferase in H(2)O(2 )treatment conditions. E. alatus treatment had significant protective or elevating activities on these antioxidative enzyme activities compared to a normal group. The results indicate that E. alatus provides a strong antioxidant protection of cells against H(2)O(2)-induced oxidative stress.

A selenium-deficient Caco-2 cell model for assessing differential incorporation of chemical or food selenium into glutathione peroxidase

Assessing the ability of a selenium (Se) sample to induce cellular glutathione peroxidase (GPx) activity in Se-deficient animals is the most commonly used method to determine Se bioavailability. Our goal is to establish a Se-deficient cell culture model with differential incorporation of Se chemical forms into GPx, which may complement the in vivo studies. In the present study, we developed a Se-deficient Caco-2 cell model with a serum gradual reduction method. It is well recognized that selenomethionine (SeMet) is the major nutritional source of Se; therefore, SeMet, selenite, or methylselenocysteine (SeMSC) was added to cell culture media with different concentrations and treatment time points. We found that selenite and SeMSC induced GPx more rapidly than SeMet. However, SeMet was better retained as it is incorporated into proteins in place of methionine; compared with 8-, 24-, or 48-h treatment, 72-h Se treatment was a more sensitive time point to measure the potential of GPx induction in all tested concentrations. Based on induction of GPx activity, the cellular bioavailability of Se from an extract of selenobroccoli after a simulated gastrointestinal digestion was comparable with that of SeMSC and SeMet. These in vitro data are, for the first time, consistent with previous published data regarding selenite and SeMet bioavailability in animal models and Se chemical speciation studies with broccoli. Thus, Se-deficient Caco-2 cell model with differential incorporation of chemical or food forms of Se into GPx provides a new tool to study the cellular mechanisms of Se bioavailability.

Trace element concentration distributions in breast, lung and colon tissues

The concentrations of Fe, Cu, Zn and Se in cancerous and benign tissues of breast, lung and intestine (colon) have been determined. In the cases when the element concentration has not been determined in all samples the Kaplan-Meier method has been used for the reconstruction of the original concentration distributions and estimation of the true mean concentrations and medians. Finally, the log-rank test has been applied to compare the elemental concentration distributions between cancerous and benign tissues of the same organ, between cancerous tissues and between benign tissues taken from different organs. Comparing benign and malignant neoplastic tissues, statistically significant differences have been found between Fe and Se concentration distributions of breast as well as for Cu and Zn in the case of lung tissues and in the case of colon tissues for Zn. The concentrations of all elements have been found to be statistically different in cancer tissues as well as in benign ones when comparing the different organs, i.e. groups 'breast-colon' and 'breast-lung'. Concentrations of Fe and Cu have been found to be statistically different in lung and colon cancerous tissues. For benign tissues of lung and colon a statistically significant difference has been found only for Zn.

Genotoxic effects in C57Bl/6J mice chronically exposed to arsenate in drinking water and modulation of the effects by low-selenium diet

In C57Bl/6J mice chronically exposed to arsenate in drinking water at 50, 200, or 500 microg As/L, genotoxic effects in bone-marrow cells using micronucleus test and in peripheral blood leukocytes using the comet assay were determined after 3, 6 or 12 mo. To assess the modulating role of selenium in development of the effects, the animals were fed a specially prepared low-selenium diet and were supplemented with sodium selenite (200 microg Se/L) in drinking water (supplemented groups) or were without Se supplementation (nonsupplemented groups). Measurements of glutathione peroxidase activity in erythrocytes and plasma as well as selenium concentration in plasma were performed after 3, 6, and 12 mo and showed a marked decrease in values in animals in non-Se supplemented compared to Se-supplemented groups. After 3 mo of arsenic exposure in the Se-supplemented animals the level of DNA fragmentation (without Endo III and Fpg enzymes) did not differ from the control; however, increased oxidative damage of purine and pyrimidine bases was observed. In groups not supplemented with Se, an increase of DNA fragmentation was observed; however, the levels of oxidative DNA damage in these groups did not differ from the control. None of the positive effects observed in the comet assay after 3 mo was related to arsenate concentration. The levels of DNA damage after 6 and 12 mo of exposure to arsenic as well as the frequency of micronuclei after 3, 6, and 12 mo did not differ significantly between exposed and control animals, irrespective of Se supplementation status.

Short-Interfering RNA-Mediated Silencing of Thioredoxin Reductase 1 Alters the Sensitivity of HeLa Cells toward Cadmium

The mammalian thioredoxin reductase (TrxR) is a selenocysteine-containing flavoprotein that regulates the thioredoxin system, one of the major systems that maintain the intracellular redox balance. We previously reported that cytosolic TrxR (TrxR1), one of three mammalian TrxR isozymes, was induced by treatment with cadmium. In the present study, to study the role of cadmium-induced TrxR1 in cellular defense, we silenced the expression of TrxR1 in HeLa cells by using small interfering RNA and examined the effect of TrxR1 silencing on the sensitivity of the cells toward cadmium. We found that the gene silencing of TrxR1 had a dual effect on cadmium-induced cell death, depending on the concentration of cadmium. The TrxR1 silencing increased the sensitivity toward a low dose (less than 10 microM) of cadmium but decreased the sensitivity toward a high dose of cadmium. These results suggested that TrxR1 might play an important role in the cellular defense system against cadmium in two ways. TrxR1 might rescue the cells from a low dose of cadmium-induced moderate injury, while it might promote the death of cells severely injured by a high dose of cadmium.

Effects of Bambusae concretio Salicea (Chunchukhwang) on amyloid beta-induced cell toxicity and antioxidative enzymes in cultured rat neuronal astrocytes

Bambusae concretio Salicea (BCS; plant family name: Phyllostachys bambusoides Siebold et Zuccarinii) is a medicinal plant used in Korea for the treatment of various symptoms accompanying hypertension and cerebrovascular disorders. Previously, it was shown that BCS is an effective protectant against oxidative glutamate toxicity in the murine neuroblastoma cells and human neuroblastoma cells. Treatment with BCS increased the secretion of the non-amyloidogenic amyloid precursor protein fragment, and decreased the secretion of amyloid-beta (Abeta) peptides from neuronal cells [Jeong, J.C., Seo, Y.J., Kim, H.M., Lee, Y.C., Kim, C.H., 2003. Inhibitory effects of Bombusae concretio Salicea on neuronal secretion of Alzheimer's beta-amyloid peptides, a neuro-degenerative peptide. Neurochemical Research 28, 1785-1792.]. To further examine the pharmacological activity of BCS, we studied the protective effect of the water extracts on Abeta25-35 peptide-induced neuronal death by microscopic observation and lactate dehydrogenase (LDH) assay, and action on antioxidative enzymes using cultured astrocyte cells. Ten microM Abeta25-35-induced cell death was protected by the application of water extract of BCS in a dose-dependent manner, and concentrations of 1-10 microg/ml had a significant effect compared to exposure to Abeta25-35 only. When antioxidative enzyme activities such as catalase, superoxide dismutase (SOD), glutathione peroxidase (GPx) and glutathione-S-transferase (GST) were assayed after Abeta25-35 treatment, the enzymes were decreased in a similar fashion. However, those activities were enhanced by BCS treatment and this may have resulted from the potentiation of antioxidative ability by BCS. The ability of BCS to reduce cellular cytotoxicity induced by 10 microM Abeta25-35 suggests that BCS may be a protective agent for free radical generating compounds such as Abeta25-35, and that Abeta25-35 is not only a potent lipid peroxide inducer, but also causes changes in antioxidative enzymes. From the results, it was concluded that BCS has a protective effect on Abeta-induced neuronal death in cultured astrocyte cells through the inhibition of lipid peroxidation and protection of antioxidative enzymes.

Analysis of essential elements in Pragya-peya—a herbal drink and its constituents by neutron activation

Ayurvedic herbal formulations are a good source of several nutrient elements essential for metabolic processes. Pragya-peya, a herbal drink and its 12 herbal constituents have been analyzed for 7 minor (Al, Ca, Cl, Mg, Na, K, P) and 15 trace (Ba, Br, Co, Cr, Cs, Fe, Hg, La, Mn, Rb, Sc, Se, Th, V, Zn) elements by instrumental neutron activation analysis (INAA). The method involves thermal neutron irradiation in a reactor followed by counting at several intervals. Also Cd, Cu, Ni and Pb contents were determined by atomic absorption spectrometry (AAS). Elemental data were validated by simultaneously analysing reference materials (RMs) such as mixed Polish herbs (INCT-MPH-2) and peach leaves (SRM-1547). Sample homogeneity was tested by analysing samples from three different batches collected at different intervals. Pragya-peya has been found to be especially rich in several nutrient elements such as Ca, K, V, Fe, Mn, Se and Zn whereas no single constituent is enriched in all the nutrient elements. Concentrations of elements are discussed vis-a-vis their medicinal/therapeutic uses. Several elements such as Na, K, P, Ca, Fe, Co, and Zn seem to be well correlated in 12 constituent herbs.

Selenium-based drug design: rationale and therapeutic potential

The wide media coverage given recently to a study correlating higher selenium levels with a reduced risk of advanced prostate cancer is but the latest addition to a growing body of epidemiological findings which link dietary selenium deficiency to diseases as diverse as cancer, heart disease, arthritis and AIDS. Indeed, selenium has a long history of association with human health and disease. Moreover, direct evidence is now emerging for specific beneficial effects of dietary selenium supplementation. Thus, the pharmacology, biology and biochemistry of selenium metabolism have become subjects of intense current interest. At the molecular level, selenium (as selenocysteine) is an essential component of the active sites of the enzymes glutathione peroxidase, iodothyronine 5'-deiodinase and mammalian thioredoxin reductase, and is also present in several other mammalian selenoproteins. Both glutathione peroxidase and thioredoxin reductase catalyse reactions essential to the protection of cellular components against oxidative and free radical damage. As a consequence of the growing recognition of the important biological role of selenium, a number of novel pharmaceutical agents, either selenium-based or which target specific aspects of selenium metabolism, are under development. Among these are orally active selenium-based antihypertensive agents, anticancer, antiviral, immunosuppressive and antimicrobial agents, and organoselenium compounds which reduce oxidative tissue damage and oedema. It can be anticipated that as our understanding of the basic biology and biochemistry of selenium increases, future efforts will uncover even more sophisticated approaches for the rational development of new selenium-based pharmaceutical agents.

Characteristics of selenazolidine prodrugs of selenocysteine: toxicity, selenium levels, and glutathione peroxidase induction in A/J mice

We have previously reported the synthesis and characterization of two new classes of selenazolidine-4(R)-carboxylic acids (2-oxo and 2-methyl-SCAs) (OSCA and MSCA, respectively), as well as the "parent" compound, selenazolidine-4(R)-carboxylic acid (SCA, selenaproline). These compounds were designed as prodrugs of L-selenocysteine with potential application in cancer chemoprevention or other clinical uses. We will be exploring the chemopreventive activity of the new compounds in the well-established A/J mouse model of tobacco-induced lung carcinogenesis. The objectives of the present study were to investigate several fundamental biochemical endpoints after selenazolidine administration compared with other selenium-containing agents. Groups of mice were fed either AIN-76A diet alone or the diet supplemented with the following selenium compounds (ppm Se): sodium selenite (5), L-selenomethionine (3.75), L-selenocystine (15), Se-methyl-L-selenocysteine (3), MSCA (5, 10, or 15), OSCA (5, 10, or 15), or SCA (5, 10, or 15). After 28 days of supplementation, toxicity of the selenazolidines was not evident, as measured by outward appearance and behavior, body and organ weight changes, and histological evaluation of liver and lung tissue. Select treatment groups showed significant increases in selenium levels in blood and tissues. Increased activity of selenium-dependent glutathione peroxidase (GPx) in blood and liver illustrated that the selenazolidines provided a source of biologically-available selenium.

Copper may interact with selenite extracellularly in cultured HT-29 cells

Previous studies have demonstrated that copper (15.7 micromol/L) can inhibit selenite (12.6 micromol/L)-induced cytotoxicity and apoptosis in HT-29 cells. However, the exact nature of the interactions between selenium and copper is not fully understood. In this study, the effect of copper on the cell cycle arrest induced by selenite or selenocystine was examined. Both selenite and selenocystine were effective in inhibition of cell growth and cell cycle progression. Cell cycle analysis revealed that selenite (3-5 micromol/L) caused a decrease in G1 phase cells that corresponded with an increase in S and G2 phase cells, and that 0.625 or 1.25 micromol/L copper sufficiently inhibited selenite-induced cell cycle arrest. In contrast, selenocystine caused an increase in G1 phase cells that corresponded with a decrease in S and G2 phase cells. Interestingly, 0.625 or 1.25 micromol/L copper did not inhibit selenocystine-induced cell cycle arrest. In addition, cell free gel shift assay demonstrated that selenite suppressed the inhibitory effect of copper on SP-1 DNA binding. Furthermore, although 5 micromol/L selenite in culture media significantly increased the intracellular selenium content, 1.25 micromol/L copper sulfate blocked this increase of the intracellular selenium content. Collectively, these data demonstrate that selenite and selenocystine cause cell cycle arrest via distinct mechanisms, and suggest that copper may interact with selenite extracellularly, which represents the basis of antagonism between copper sulfate and selenite.

Human prostate cancer risk factors

Prostate cancer has the highest prevalence of any nonskin cancer in the human body, with similar likelihood of neoplastic foci found within the prostates of men around the world regardless of diet, occupation, lifestyle, or other factors. Essentially all men with circulating androgens will develop microscopic prostate cancer if they live long enough. This review is a contemporary and comprehensive, literature-based analysis of the putative risk factors for human prostate cancer, and the results were presented at a multidisciplinary consensus conference held in Crystal City, Virginia, in the fall of 2002. The objectives were to evaluate known environmental factors and mechanisms of prostatic carcinogenesis and to identify existing data gaps and future research needs. The review is divided into four sections, including 1) epidemiology (endogenous factors [family history, hormones, race, aging and oxidative stress] and exogenous factors [diet, environmental agents, occupation and other factors, including lifestyle factors]); 2) animal and cell culture models for prediction of human risk (rodent models, transgenic models, mouse reconstitution models, severe combined immunodeficiency syndrome mouse models, canine models, xenograft models, and cell culture models); 3) biomarkers in prostate cancer, most of which have been tested only as predictive factors for patient outcome after treatment rather than as risk factors; and 4) genotoxic and nongenotoxic mechanisms of carcinogenesis. The authors conclude that most of the data regarding risk relies, of necessity, on epidemiologic studies, but animal and cell culture models offer promise in confirming some important findings. The current understanding of biomarkers of disease and risk factors is limited. An understanding of the risk factors for prostate cancer has practical importance for public health research and policy, genetic and nutritional education and chemoprevention, and prevention strategies.

Antiproliferative effect of 1,4-phenylenebis(methylene)selenocyanate (p-XSC) on colonic epithelium of patients with adenomatous polyps in vitro

We have consistently shown that the organoselenium compound 1,4-phenylenebis(methylene)selenocyanate (p-XSC) is a superior cancer chemopreventive agent and less toxic than selenite or certain naturally-occurring selenoamino acids. To elucidate the effects of p-XSC on human colonic mucosa, biopsies from endoscopically normal sigmoid colon of 30 patients with adenomatous polyps were incubated with p-XSC at concentrations of 1, 2 and 5 micromol/l dissolved in dimethylsulphoxide (DMSO). Biopsies incubated with DMSO or pure culture medium served as a control. Proliferating cells were labelled by bromodeoxyuridine immunohistochemistry and the labelling index (LI) was computed. Upper crypt labelling index (LI of crypt compartments 4+5) and Phih value, which are both discriminators of the expansion of the proliferative zone, were significantly lower after incubation with 1 and 5 micromol/l p-XSC, respectively (LI 4+5: 0.8 and 1.0; Phih value: 2.1 and 2.4), as compared with DMSO (LI 4+5: 3.6 and 4.5; Phih value: 7.0 and 8.3) or culture medium (LI 4+5: 3.3 and 4.5; Phih value: 7.2 and 8.1) (P<0.005 and P<0.05 by Friedman's block test). A trend towards lower levels of LI 4+5 (P=0.059) and Phih value (P=0.075) were seen after 2 micromol/l p-XSC incubation compared with DMSO. Since hyperproliferation of colonic crypt cells with expansion of the proliferative zone is regarded as a biomarker of increased cancer risk, the antiproliferative effects of p-XSC especially on upper crypt LI and Phih value may indicate a possible protective effect of this organoselenium compound in the prevention of human colon cancer development.

Determinants of inorganic arsenic methylation capability among residents of the Lanyang Basin, Taiwan: arsenic and selenium exposure and alcohol consumption

The objective of this study was to assess individual variation in inorganic arsenic methylation capability and the association between selenium levels in urine and blood, and inorganic arsenic methylation capability among residents of the Lanyang Basin who drank groundwater and were exposed to high concentrations of inorganic arsenic. According to the arsenic concentration of their drinking water, they were equally and randomly classified into four groups of 252 persons. It turned out that the higher the concentration of arsenic in well water was and thus the cumulative arsenic exposure, the higher the total inorganic arsenic metabolites in urine (total As(i)) and the overall inorganic and organic arsenic in urine (overall As(i+o)) were. The percentage of inorganic arsenic significantly decreased and the DMA percentage significantly increased as the concentration of urinary selenium and serum alpha-tocopherol increased. It appeared that urinary selenium levels increased the metabolism by methylation of arsenic, a finding that requires further investigation.

Interactions betweenN-acetylcysteine and sodium selenite in modulating the clastogenicity of urethane and 2-acetylaminofluorene in mice

Combined treatment with different agents represents a promising approach in cancer chemoprevention. Therefore, it is useful to assess in preclinical models the efficacy of combinations that are selected by taking into account mechanistic considerations. We designed 2 studies evaluating the interaction between N-acetylcysteine (NAC) and sodium selenite (Se), both given with the drinking water to Balb/c mice, in modulating clastogenic effects in bone marrow polychromatic erythrocytes. In a first study, a single i.p. injection of urethane considerably enhanced the frequency of micronucleated cells. While NAC produced a significant inhibition, Se further enhanced urethane clastogenicity. When given in combination at the same doses, NAC prevented the adverse effect of Se. In a second study, a single i.p. injection of 2-acetylaminofluorene enhanced the frequency of micronucleated cells. Se did not reduce this effect to a significant extent, while NAC produced a dose-dependent inhibition. When tested at the lower dose in combination with Se, the protective effect of NAC was unchanged. Especially in association with Se, NAC also prevented the toxicity of 2-acetylaminofluorene by normalizing the ratio of polychromatic to normochromatic erythrocytes. In conclusion, NAC attenuated the clastogenicity of both urethane and 2-acetylaminofluorene and the toxicity of this aromatic amine. In addition, NAC prevented the clastogenic and toxic effects resulting from the interaction of Se with urethane. Together with the findings of previous studies, it appears that, besides its intrinsic protective properties in carcinogenesis, NAC is capable of attenuating the adverse effects of several cytotoxic drugs and chemopreventive agents.

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

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.

Selenium supplementation in rheumatoid arthritis investigated in a double blind, placebo-controlled trial

INTRODUCTION

Selenium is an essential trace element with antioxidant properties. Trials with selenium have been conducted in rheumatoid arthritis (RA) to correct impaired selenium status and increase defences against deleterious oxidant species.

AIM OF THE STUDY

To investigate in a double blind multi-centric placebo-controlled study the effects of selenium supplementation in RA.

METHODS

Fifty five patients with moderate RA received during 90 days either capsules containing selenium-enriched yeast (200 microg/d) or a placebo.

RESULTS

The visual analog scale, the Ritchie index, the number of swollen and painful joints, and morning stiffness significantly decreased with time in both groups (p<0.001), but no difference between groups could be identified. When examining the quality of life a significant (p<0.01) improvement in arm movements and health feeling was evidenced in selenium-treated patients.

CONCLUSION

Selenium treatment did not show clinical benefit on RA. Interestingly, the improval in both groups demonstrated a placebo effect of the intervention trial.

Molecular targets for selenium in cancer prevention

Mounting evidence reveals that selenium is a dietary constituent with anticarcinogenic and antitumorigenic properties. Various forms of selenium appear to be effective in bringing about these effects, although preclinical studies suggest that differences may arise as the quantity provided is reduced. The literature also documents the greater sensitivity of neoplastic cells to selenium than their nonneoplastic counterparts. Unfortunately, the minimal amount needed to bring about a positive effect in humans remains elusive. If there is a positive response to exaggerated intakes, it will likely be dependent on many factors, including the consumption of other dietary constituents, as well as variation in a host of genetic pathways involved with cancer. Although the biological basis of the reduction in cancer risk ascribed to selenium remains to be established, its consistency in retarding various experimentally induced tumors and suppressing the growth of various types of neoplasms in vitro and in vivo suggests that several mechanisms are involved. Depressed carcinogen bioactivation, reduced cell proliferation, and increased apoptosis raise the possibility that selenium works at a number of specific molecular targets involved with the cancer process. This review will focus on molecular targets involved with cell proliferation and apoptosis as possible mechanisms by which selenium might alter the cancer process.

Bombycis corpus extract prevents amyloid-beta-induced cytotoxicity and protects superoxide dismutase activity in cultured rat astrocytes

Bombycis corpus(BC) or Bombyx Batryticatus, a batryticated silkworm and white-stiff silkworm, is a drug consisting of the dried larva of silkworm, Mobyz mori L., dead and stiffened due to the infection of Beauveria (Bals.) Vuill. In the present study, we have examined the protective effect of the water extracts against Amyloid- beta(A beta) 25-35 peptide-induced cytotoxicity by microscopic observation and LDH assay, and its action on antioxidative enzymes using cultured astrocyte cells. A beta 25-35-induced cell death was protected by the application of water extract of BC in a dose-dependent manner, and concentrations of 10(-6)to 10(-7)g ml(-1)showed a significant effect compared to exposure of A beta 25-35 alone. When antioxidative enzyme activities such as catalase, superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and glutathione-S transferase (GST) were assayed after A beta 25-35 treatment, most enzyme activities were decreased in a similar fashion. BC treatment of A beta 25-35-treated astrocytes did not affect the enzyme activities of catalase, GSH-Px and GST. However, only SOD activity was enhanced by BC treatment and this may result from the potentiation of the antioxidative ability of BC. The protective effect of BC against cytotoxicity induced by Abeta 25-35 strongly indicates that BC could be a protective agent for free radical generating compounds, and that Abeta 25-35 is not only a potent lipid peroxide inducer, but can also cause changes in antioxidative enzymes. From the results, it was concluded that BC has a protective effect against Abeta -induced cytotoxicity in cultured astrocyte cells through the inhibition of lipid peroxidation and protection of antioxidative enzymes.

Chromosome damage induced by selenium salts in human peripheral lymphocytes

Two inorganic salts of selenium, sodium selenite (Na(2)SeO(3)) and sodium selenate (Na(2)SeO(4)), were screened for damage to chromosome and cell division following exposure to human lymphocyte cultures. In vitro exposure of human peripheral blood lymphocytes to high concentration of two inorganic salts of selenium-sodium selenite (2.9 x 10(-5) M) and sodium selenate (2.65 x 10(-5) M)-was found to be lethal; no blast cells being formed. Lower concentrations of both salts, 5.8 x 10(-6) M and 1.06 x 10(-5) M, respectively, were highly mitostatic. Lower concentrations of sodium selenite (2.9 x 10(-6) M, 1.16 x 10(-6) M and 2.32 x 10(-7) M) and sodium selenate (5.3 x 10(-6) M, 2.65 x 10(-6) M and 1.06 x 10(-6) M), respectively, induced chromosomal aberrations and reduced cell division in proportions directly related to the dose. Sodium selenite was considerably more clastogenic than sodium selenate.

Selenium and cancer: some nutritional aspects

The level of selenium in cancer patients is lower than that in control subjects. However, low selenium levels in body fluids can be due to the malnutrition observed in these patients. There is evidence from epidemiologic studies that high dietary selenium intakes and high selenium status in people are associated with lower cancer mortality. However, contradictory information has been found in some prospective studies. The presence of other nutrients in selenium-rich foods can influence the role of the selenium in cancer etiology. Therefore, there are selenium antagonistic elements that inhibit the anticarcinogenic effects of selenium and other antioxidant micronutrients such as ascorbic acid, retinol, beta-carotene, alpha-tocopherol, and some other elements have a synergistic effect on the prevention of cancer.

Confounding variables in the environmental toxicology of arsenic

Arsenic is one of the most important global environmental toxicants. For example, in regions of West Bengal and Inner Mongolia, more than 100000 persons are chronically exposed to well water often strongly contaminated with As. Unfortunately, a toxicologically safe risk assessment and standard setting, especially for long-term and low-dose exposures to arsenic, is not possible. One reason is that the key mechanism of arsenic's tumorigenicity still is not elucidated. Experimental data indicate that either DNA repair inhibition or DNA methylation status alteration may be causal explanations. Moreover, when comparing epidemiological data, it cannot be ruled out that the susceptibility to arsenic's carcinogenicity may be different between Mexican and Taiwanese people. Some other studies indicate that some Andean populations do not develop skin cancer after long-term exposure to As. It is not known yet how this resistance could be mediated. Finally, the situation is even more complicated when taking into consideration that there are several compounds suspected to modulate the chronic environmental toxicity of arsenic, variables that may either enhance or suppress the in vivo genotoxicity and carcinogenicity of the metalloid. Among them are nutritional factors like selenium and zinc as well as drinking water co-contaminants like antimony. Further, yet unidentified factors influencing the body burden and/or the excretion of arsenic are possibly prevailing: preliminary data from own human biomonitoring studies showed a peaking of As in urine samples of non-exposed people which was not caused by elevated exposure to As through seafood consumption. The relevance of these putative confounding variables cannot be finally evaluated yet. Further experimental as well as epidemiological studies are needed to answer these questions. This would help to conduct a toxicologically improved risk assessment, especially for low-dose and long-term exposures to arsenic.

Trace element status (Se, Cu, Zn) and serum lipid profile in Portuguese subjects of San Miguel Island from Azores'archipelago

Data on selenium, copper and zinc in serum of Portuguese inhabitants of the city of Ponta Delgada-Azores Archipelago are reported for the first time. The subjects are of both sexes, aged 20 to 60 years, and non-abusers of alcohol, tobacco or drugs. Serum concentrations of these elements are in the same range than those found for populations of Lisbon and of some other European countries. Differences between sexes are observed, with serum selenium and zinc levels being higher in males than in females, and the copper levels being higher in females as compared to males. These results can be explained by the hormonal status and/or oral contraceptive steroids intake, particularly for copper. Concerning lipid profile, the majority of individuals have serum lipid parameters within the normal range. In addition, no difference in trace element levels between normo and hyperlipidemic individuals is observed and no conclusive results about the relationship of all evaluated parameters to alcohol, tobacco and drug consumption are observed, in agreement with data obtained in the population of Lisbon.

Selenium-enriched Agaricus bisporus mushrooms suppress 7,12-dimethlybenz[a]anthracene bioactivation in mammary tissue

The present studies compared dietary Se (1.0 microg/g) when provided as either fortified Agaricus bisporus mushrooms, or sodium selenite on the in vivo metabolism of 7,12-dimethylbenz(a)anthracene (DMBA). Dietary addition of Se unenriched A. bisporus mushrooms at 2% did not alter the occurrence of DMBA induced DNA adducts or the activity of glutathione S-transferase (GST). However, the addition of Se as enriched mushrooms, or as selenite, significantly increased both liver and mammary GST activity. Providing sodium selenite, or enriched mushrooms also significantly reduced total and anti-3,4-dihydrodiol-1,2-epoxide-deoxyguanosine adducts compared to feeding the basal diet (P < 0.05). These investigations provide evidence that Se enriched mushrooms can be used as an effective method to retard chemically induced tumors.

Inhibition of selenite-induced cytotoxicity and apoptosis in human colonic carcinoma (HT-29) cells by copper

Selenite catalytically oxidizes reduced glutathione (GSH) with subsequent generation of superoxide. Our laboratory has previously shown that this selenite-catalyzed generation of superoxide is strongly inhibited by copper [as copper(II) sulfate]. In the present study we have demonstrated that exposure of human colonic carcinoma cells (HT-29) to selenite resulted in the induction of apoptosis, DNA fragmentation, an increase in intracellular levels of the antioxidant GSH, and cytotoxicity. Selenite-induced apoptosis, DNA fragmentation, increases in GSH levels, and cytotoxicity were inhibited by copper(II) sulfate. Copper only protected cells from selenite cytotoxicity when cells were exposed to selenite and copper simultaneously, not when cells were pretreated with copper, then washed before selenite exposure. This suggests that copper elicits its protective effect extracellularly. Previous data reported by this laboratory clearly demonstrated that copper inhibited selenite-catalyzed superoxide generation. Collectively, these data suggest that reactive oxygen species may play a role in selenite-induced cytotoxicity, apoptosis, and DNA fragmentation.

Enhancement of selenium excretion in bile by sulfobromophthalein: elucidation of the mechanism

This work was intended to explore the mechanism whereby sulfobromophthalein (BSP), an electrophilic and cholephilic organic acid, increases the biliary excretion of selenium in rats injected with sodium [75Se]selenite. In such animals, neither BSP-glutathione conjugate nor dibromosulfophthalein, nonelectrophilic congeners of BSP, enhanced the hepatobiliary transport of selenium, suggesting that reaction of nucleophilic selenite metabolites formed in vivo with the injected BSP may be involved. Indeed, HPLC analysis of bile from rats receiving [75Se]selenite and BSP revealed two peaks (X and Y) that were simultaneously detected both by absorbance as BSP metabolites and by radioactivity as [75Se] metabolites, indicating that these represent selenium-containing BSP metabolites. Pretreatment of rats with inhibitors of selenium methylation, such as periodate-oxidized adenosine (PAD) and ethionine, drastically diminished the size of peak X, while increasing (PAD) or not influencing (ethionine) the size of peak Y. This finding indicates that production of metabolite X, but not Y, is dependent on formation of methylated selenium metabolites. A compound chromatographically indistinguishable from that in peak X was formed in vitro during incubation of BSP with methylselenol, suggesting that biliary metabolite X is identical to the reaction product of BSP and selenite-derived methylselenol. Incubation of BSP with selenite in the presence of a thiol, namely glutathione, cysteine or N-acetylcysteine (which convert selenite into nucleophilic products, i.e. the respective selenopersulfides and hydrogen selenide) resulted in product(s) chromatographically identical to the biliary selenium-containing BSP metabolite(s) of peak Y, irrespective of the nature of the thiol used. Thus, biliary metabolite(s) Y may be reaction products of BSP and hydrogen selenide. Finally, BSP significantly diminished exhalation of dimethyl selenide in selenite-injected rats, purportedly because it reacted with precursors of dimethyl selenide, that include hydrogen selenide and methylselenol. In summary, BSP increases biliary excretion of selenium in rats receiving selenite because it forms selenium-containing BSP metabolites that are readily transported into bile. It is suggested that the in vivo reaction of nucleophilic selenite metabolites with electrophilic compounds may influence the fate of selenium and may contribute to some of the effects of this essential and anticarcinogenic metalloid.

Human exposures to arsenic from consumption of well water in West Bengal, India

The authors visited the State of West Bengal, India, in August 1996, as consultants to the World Health Organization (WHO). The general mandate of the mission was to formulate recommendations to the Government of India regarding its efforts to assist the Government of West Bengal in remedying health problems arising from the presence of arsenic in groundwater in excess of the WHO guideline limit of 0.05 mg/L in eight districts of the State. The authors held discussions with Government of India and Government of West Bengal officials, as well as scientists, engineers, and physicians studying the analytic, medical, engineering, and hydrogeologic facets of the problem. They conducted field visits to arsenic-affected villages; inspected health centers, including the laboratories conducting the analytic and clinical studies; and interviewed and examined local lay people, including many arsenic-poisoned patients. This overview of the arsenic contamination problem in West Bengal is based upon a review of the scientific literature and government reports and the authors direct, firsthand assessment. The authors hope that their recommendations will assist in the development of a comprehensive infrastructure and plan of action, which are necessary to control the epidemic of chronic arsenic poisoning now afflicting West Bengal.

Symptomatic treatment of brain tumor patients with sodium selenite, oxygen, and other supportive measures

Patients (16 women and 16 men) with brain tumors previously treated conservatively by surgery, radiation, and/or chemotherapy with typical symptoms of increased intracranial pressure were consecutively enrolled to test the effects of pharmacological dosages of sodium selenite (selenase) in conjunction with other supportive therapies (biological response modifiers, detoxification, chemotherapy, immunotherapy, oxygen therapy). The rationale for the use of sodium selenite was that the whole-blood selenium levels were subnormal in 70% of the patients on admission. Patients also frequently presented abnormal levels of other minerals, especially lowered sodium and elevated potassium levels, which appears to be characteristic of brain tumor patients. Sodium selenite was administered by infusion at dosages of 1000 microg Se in physiological saline/d for 4-8 wk. In 76% of the patients, a definite, and in 24% a slight improvement of the general condition and a decrease in symptoms, such as nausea, emesis, headache, vertigo, unsteady gait, speech disorders, and Jacksonian seizures, were observed. In all treated patients, improvements of erythrocyte, hemoglobin, and thrombocyte counts were observed. Additional beneficial effects were noted in the patients receiving the oxygen therapy. It is concluded that the sodium selenite can be employed with oxygen therapy and other supportive measures in the management of brain tumor patients.

Interactions between selenium and group Va-metalloids (arsenic, antimony and bismuth) in the biliary excretion

The interrelationship between the biliary excretion of exogenous group Va-metalloids (arsenic, antimony and bismuth) and selenium, as well as endogenous glutathione has been studied in rats injected intravenously with sodium selenite and one of the group Va-metalloids. Arsenic, antimony and bismuth appeared in the bile of rats together with large amounts of non-protein thiols (NPSH, representing glutathione and its SH-containing degradation products) and, with the exception of bismuth, they caused choleresis. Significant interactions were observed in the hepatobiliary disposition between selenium and each of the group Va-metalloids, however, their outcomes were not uniform. When coadministered with sodium arsenite or arsenate, selenite enhanced the initial biliary excretion of arsenic 2- and 8-fold, respectively, without further increasing the concomitant excretion of NPSH or the choleretic effect of arsenicals. However, selenite augmented neither the excretion of antimony or bismuth, nor the simultaneous biliary release of NPSH. In turn, arsenite, arsenate and antimony potassium tartrate increased the initial biliary excretion of selenium more than 10-fold and enhanced the accumulation of selenium in blood (exclusively in the erythrocytes). In contrast, administration of bismuth ammonium citrate diminished both the biliary excretion and the erythrocytic accumulation of selenium, while causing retention of selenium in the blood plasma. In rats receiving arsenic or antimony with selenite, the time courses of the biliary excretion of these group Va-metalloids, selenium and NPSH were similar. It is hypothesised that incorporation of selenol metabolites of selenite into the glutathione complexes of arsenic and antimony, resulting in cholephilic ternary complexes, accounts for the arsenic- and antimony-induced augmentation of the hepatobiliary transport of selenium. However, additional chemical and/or dispositional mechanisms are thought to be responsible for the selenite-induced increase in biliary excretion of arsenic.

Trace element correlations in the blood of Indian women with breast cancer

Fourteen minor (Na, K, P, Fe) and trace (Br, Co, Cr, Cs, Hg, Rb, Sb, Se, Sr, Zn) elements have been determined in pre- and postoperative blood samples of 10 breast-cancer-affected. Indian women and compared with controls. The study showed elevation of Cr, Hg, Fe, Rb, Sb, and Zn and lowering of Se, K, P, and Sr contents in the blood of cancer patients. Most elemental contents in pre- and postoperative stages remain unaltered except Br, Co, and Sb. Statistical significance of Fe, Se, Zn, and Hg levels has been tested by box plots. Lowering of Se in blood (-54.4%) is correlated with its enhancement in cancerous breast tissue (94.7%) of various clinical stages. Se/Zn and Se/Fe ratios are lowered in the blood of cancer patients, whereas Na/K ratio is only marginally enhanced. An attempt has been made to correlate Se levels with the dietary intake and breast cancer risk vis-a-vis American and Japanese women.

Induction of differentiation and apoptosis by sodium selenite in human colonic carcinoma cells (HT29)

To explore the mechanism(s) by which selenium (Se) exerts its cancer chemopreventive activity, we studied the effect of selenite (0-100 microM) on cell growth, viability, differentiation, detachment, DNA fragmentation and apoptosis in human colonic carcinoma cells (HT29). Selenite (>5 microM) decreased cell growth, increased cell detachment and decreased intracellular levels of reduced glutathione (GSH), whereas >10 microM selenite induced cell differentiation and apoptosis. The chemopreventive effects of selenite may be related in part to the generation of reactive oxygen species (ROS) resulting from the reaction between selenite and GSH.

Effects of selenium on gallbladder carcinogenesis induced by an intracholecystic 3-methylcholanthrene beeswax pellet in female Syrian golden hamsters

This study represents the first report of the effects of selenium (Se) on chemically induced gallbladder carcinogenesis in hamsters. A total of 100 female Syrian golden hamsters was randomly assigned to four groups, which groups of 25 hamsters were given ad libitum drinking water containing either 0.0, 0.5, 2.0 or 4.0 ppm Se (as sodium selenite) for 24 weeks. Initiation was performed at week 4 by the insertion of a Beeswax pellet containing 3-methylcholanthrene (3-MC) into the gallbladder. The incidence of total malignant tumors at the end of the study (24 weeks) was 88, 75, 81 and 82% in the 0.0, 0.5, 2.0 and 4.0 ppm Se groups, respectively. All the cases of carcinoma but two were considered to develop through the sequence from dysplasia to carcinoma in situ (CIS) and from CIS to adenocarcinoma of invasive type. The incidence of CIS was significantly lower in hamsters treated without Se than in those treated with Se (P < 0.05). On the other hand, the incidence of invasive adenocarcinoma was significantly higher in the former than in the latter (P < 0.05). These results were summarized that Se might retard the progression of hamster gallbladder carcinogenesis induced by a 3-MC beeswax pellet.

Selenium status of healthy Turkish children

Selenium concentrations, in blood plasma, red blood cells, hair of 61 healthy children, ages 0-14 yr, were determined using hydride generation atomic absorption spectrometry. Starting from late lactation period, selenium concentrations in all these matrices were found to be increasing with age. A good correlation was found between erythrocyte and plasma, hair and plasma, and hair and erythrocyte selenium concentrations. Although plasma, erythrocyte, and hair selenium concentrations of girls seemed to be higher than that of boys (only in erythrocytes), selenium concentrations of girls were found to be significantly (p < 0.002) higher than that of boys, 71 +/- 9 ng/mL, vs 65 +/- 10 ng/mL, respectively. Selenium status of Turkish children is found to be lower than that found in the literature; marginal selenium deficiency could be important in the development of some selenium deficiency related diseases. There is a need for extension of this study to healthy children from different regions in Turkey and to different disease states.

Apoptosis induced by selenium in human glioma cell lines

Several studies have shown that selenium can inhibit tumorigenesis in tissues. However, little is known about the mechanism and the effect of selenium on DNA, especially in brain tumor cells. In this study we examined the biological effect of selenium on human glioma cell lines (A172 and T98G). Selenium exhibited an antiproliferative effect on these cell lines (and induced the typical ladder pattern of DNA fragmentation commonly found in apoptosis), which were prevented by catalase. Few effects of selenium on NT14 fibroblasts were found. These findings demonstrate that selenium may induce, by apoptosis, cell death of human glioma cell lines, which are resulting from free radical oxygen forming.