Selenium and cancer: some nutritional aspects

Selenium Ameliorates Acetaminophen-Induced Oxidative Stress via MAPK and Nrf2 Pathways in Mice

Overdose of acetaminophen (paracetamol), a widely used non-prescriptive analgesic and antipyretic medication, is one of the main causes of drug-induced acute liver failure around the world. Oxidative stress contributes to this hepatotoxicity. Antioxidants are known to protect the liver from oxidative stress. Selenium, a potent antioxidant, is a commonly used micronutrient. Here, we evaluated the protective effect of selenium on acetaminophen-induced hepatotoxicity. Treating Wistar albino mice with sodium selenite (1 mg/kg) before or after inducing hepatotoxicity with acetaminophen (150 mg/kg) significantly reduced the levels of liver injury biomarkers such as serum glutamate oxaloacetate transaminase and serum glutamate pyruvate transaminase. In addition, selenium-treated mice showed decreased levels of oxidative stress markers such as protein carbonyls and myeloperoxidase. Acetaminophen treatment stimulated all three mitogen-activated protein kinases (MAPKs) and Keap1 and decreased the expression of nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 in liver and in isolated mouse peritoneal macrophages, which was reversed by selenium treatment. Our findings suggest that the reactive oxygen species-mediated Nrf2 and MAPK pathways are critical players in acetaminophen-induced hepatotoxicity. These key findings offer an alternative therapeutic target for addressing acetaminophen-induced hepatotoxicity.

Analysis of phosphorus and sulfur effect on soil selenium bioavailability based on diffusive gradients in thin films technique and sequential extraction

Human intake of selenium (Se) mainly occurs through the food chain, and is largely dependent on the bioavailability of soil Se. Sulfur (S) and phosphorus (P) also as essential nutrients for plants, their antagonistic with Se effects on Se bioavailability should be considered. We conducted pot experiments to investigate the interaction effect on the bioavailability of Se in the soil using a sequential extraction method and diffusive gradients in thin films (DGT). The results showed that the root and shoot Se of pak choi increased at most 340%-360% with S and P application, while the Se uptake by pak choi was slightly inhibited when S and P application was 100 mg kg^-1. With high S and P application, pak choi Se had a high bioaccumulation factor (BAF) and low translocation factor (TF), and soil Soluble-Se (SOL-Se) increased 178%-299%, which due to the competitive adsorption of S, P with Se and changes in soil pH that lead to the transformation of soil Se fractions. In addition, the available Se concentration in soil measured by the DGT (C_DGT-Se) increased by 866% with exogenous S and P application, and its source was HA-Se. However, C_DGT-Se failed to show a good linear relationship with the Se content of pak choi. The application of DGT to assess the bioavailability of Se in soils where Se is present in the steady state needs to be further explored. We discuss the effect of S and P application on the bioavailability of soil Se and provide evidence for agricultural production and rational fertilizer use on Se-rich land.

Speciation of inorganic selenium in natural water by in situ solid-phase extraction using functionalized silica

Functionalized adsorbents with poly-(4,9-dioxododecane-1,12-guanidine) (SiO₂-PDDG) and mercaptophenyl groups (MPhS) were used for the separation of Se(VI) and Se(IV) for the first time. Fixation of PDDG was characterized by capillary electrophoresis and TGA/DSC. The quantitative extraction of Se(VI) proceeded due to anion exchange at pH 3-7. The adsorption capacity of SiO₂-PDDG for Se(VI) was 28 μmol g^-1. Silicas with mercaptophenyl groups were used for the extraction of Se(IV) from solutions in the range of 2 M HCl - pH 6.5. The adsorption capacity of MPhS was 35 μmol g^-1. A system of columns containing synthesized adsorbents was proposed for the separation of Se(VI) and Se(IV) and their subsequent determination by ICP-MS. Optimal parameters of adsorption include a flow rate of 1 mL min^-1, pH of 5, and sample volume of 200 mL. Se(IV) was desorbed with 5 mL of 0.25 M 2,3-dimercapto-1-propanesulphonic acid and Se(VI) with 5 mL of 1 M HNO₃. The preconcentration factor was 40. The limits of detection (3s) were 0.75 and 1.25 ng L^-1 for Se(VI) and Se(IV), respectively. The proposed method (SPE-ICPMS) was used to determine selenium species in natural water and certified reference materials. The separation was carried out directly at the sampling site.

Enantioselective Synthesis of Hydantoin and Diketopiperazine-Fused Tetrahydroisoquinolines via Pictet-Spengler Reaction

An enantioselective synthesis of iso-, isothio-, and isoselenohydantoin and diketopiperazine-fused tetrahydroisoquinolines from l-Dopa was reported. The route consists of an Pictet-Spengler reaction of ( S)-2-amino-3-(3,4-dimethoxyphenyl)propanoates with various aldehydes to afford diastereomeric tetrahydroisoquinolines. Next step, the tetrahydroisoquinolines were further reacted with iso-, isothio-, or isoselenocyanates to construct hydantoin. Similarly, the diketopiperazine moiety was constructed by subjecting tetrahydroisoquinolines to a condensation reaction with chloroacetyl chloride followed by nucleophilic addition with various primary amines.

A Facial Synthesis of 7-Selenodaunomycinone Derivatives

7-selenodaunomycinone derivatives 3a–e were synthesised by condensation of daunomycinone 2 with aryl selenols catalysed by trifluoroacetic acid in dichloromethane at room temperature. When the concentration of aryl selenol exceeds 2 to 2–3 times, 7-deoxydaunomycinone 4 can be obtained. Also 7 S-configuration of 3a can turn into 7 R-isomer catalysed by boron trifluoride-etherate.

Ultrastructural changes in the mycelium of Hericium erinaceum (Bull.; Fr.) Pers. under selenium-induced oxidative stress

BACKGROUND

In this study we examined the influence of various forms of selenium (organic and inorganic) on the vivacity of Hericium erinaceum mycelium and structural changes and ultrastructure occurring during its development in submerged culture.

RESULTS

The mycelium was grown on sodium selenite (Na₂SeO₃), Selol (with 20 and 50 g kg⁻¹ Se, respectively) and a mixture of Na₂SeO₃ and Selol. Samples of the mycelium were collected on day 3 and day 24 of the incubation and viewed under an electron microscope. Selol at concentration 20 g kg⁻¹ did not cause any damage to the cell ultrastructure, but it contributed to the thickening of the cell wall, which implied an influence on polysaccharide production. In the other cases, degradation changes appeared in the protoplasm and the thickness of the cell wall did not increase.

CONCLUSION

The nature of the effect exerted by various sources of selenium in the culture medium on the formation of polysaccharides probably results from the differences in their chemical composition and differences in the toxicity of these compounds towards the cells, but is also connected with the decomposition of the wall surrounding degraded fungal cells.

Influence of inorganic and organic selenium on number of living mycelial cells and their ultrastructure in culture of Hericium erinaceum (Bull.: Fr. Pers.)

Mycelium of the white-rot fungus (Hericium erinaceum (Bull.: Fr. Pers.) produces polysaccharides showing anticancer and immunostimulating activity. In our previous works, we have shown that organic selenitetriglycerides (Selol) contribute to the increase of biosynthesis of exopolysaccharides (EPS) having antioxidative properties and containing large amounts of selenium. The present work is a study of influence of inorganic and organic form of selenium on viability of H. erinaceum mycelium and on ultrastructural changes taking place during its development in submerged culture. The mycelium was grown on media containing sodium selenite (Na2SeO3), a mixture of Na2SeO3 + Selol2% and on control medium (no selenium added). It was shown that mycelium cultured for 3 days in control conditions on standard media contained almost 100% of living cells, with over 80% after 24 days. Treatment with 100 ppm of Na2SeO3 lowered the number of viable cells to 11.8% and 9.1% after 3 and 24 days, respectively. The addition of 2% Selol caused the amounts of living cells to remain at ca 90%. Apparently, Selol helped the cells to cope with the toxic activity of inorganic selenium ions. The addition of sodium selenite induced degradative changes in cell organelles. Such changes were not observed in the case of Na2SeO3 + Selol mixture, in which case cells contained numerous ribosomes and small lipid bodies.

Novel structural insights for imidoselenocarbamates with antitumoral activity related to their ability to generate methylselenol

In the search for molecules with potential antiangiogenic activity we found that several imidoselenocarbamate derivatives, which have pro-apoptotic and antiproliferative activities, under hypoxic conditions release methylselenol, a volatile and highly reactive gas that was considered to be responsible for the observed biological activity. The kinetic for the liberation of methylselenol is highly dependent on the nature of the overall structure and correlate with their proven pro-apoptotic activity in lung cancer cell line H157. The preliminary structure-activity relationships allow us to select as the basic structural element a scaffold constructed with an imidoselenocarbamate fragment decorated with a methyl residue on the Se central atom and two heteroaromatic lateral rings. These imidoselenocarbamate derivatives may be of interest both for their antitumoral activities and because they have a structure that can be considered as a template for the design of new derivatives with apoptotic activity. This activity is related to the controlled delivery of methylselenol and makes this an interesting approach to develop new antitumoral agents.

The properties, functions, and use of selenium compounds in living organisms

Selenium occurs in the environment in inorganic and organic compounds. For many years it was regarded as a toxic element, causing numerous illnesses and diseases. But research in the past 50 years has revealed a "bright side" to this element, especially as a component of selenoproteins, selenium makes a significant contribution to the health of humans and animals. The selenium content in an organism depends on its concentration and bioavailability in the soil, and the differences between its deficiency, appropriate intake, and excess are very slight. This article gathers information from the literature on: • the consequences of a deficiency and an excess of selenium in the body, as well as the health-promoting mechanisms of selenium, including the functions of selenoproteins • the uptake and transformation of selenium compounds by plants, because of the fact that selenium is better assimilated from plant food and also the classification of plants with respect to their ability to take up selenium from the soil and to accumulate it.

Effects of cadmium chloride and sodium selenite alone or in combination on the liver of male Sprague-Dawley rats assessed by different assays

This study assessed the impact of either cadmium chloride (Cd) or sodium selenite (Se) alone or in combination on male Sprague-Dawley rats. For this purpose, body and liver weights, comet and TUNEL assays, histological analysis and levels of lipid peroxidation and antioxidants in liver were determined in four groups of male Sprague-Dawley rats. The rats were given subcutaneous doses of 1 mg/kg body weight (BW) of either normal saline (control=Ct) or Cd or Se or Cd plus Se (Cd+Se) on alternate days for 4 weeks. The Cd group showed increased DNA damage, apoptosis and hepatic levels of lipid peroxidation and altered histology. Conversely, the antioxidant levels in this group were decreased as compared with the control group. The Se group also showed DNA damage, apoptosis and altered histology and reduced catalase activity, but it was less severe than the Cd group. In the Cd+Se group, ameliorating effects of Se on Cd-induced changes were observed. While the Se was able to curtail the toxic effect of Cd, the Cd or Se alone were genotoxic and cytotoxic for rats receiving a high pharmacological but non-fatal dose of 1 mg/kg BW.

Altered expression of selenium-binding protein 1 in gastric carcinoma and precursor lesions

Selenium-binding protein 1 (SBP1) has been shown to be greatly reduced in various human cancers. The purpose of this study was to evaluate the expression of SBP1 in precursor lesions and gastric carcinoma (GC) and to discuss the specific role of SBP1 in gastric carcinogenesis. Using tissue microarray (TMA) technology and immunohistochemical (IHC) survey, SBP1 expressions were evaluated based on a semi-quantitative scoring system developed for this study in 25 paired of GC and corresponding nonneoplastic epithelia tissues, 21 gastric ulcer, 13 gastric polyp, 19 chronic atrophic gastritis, 20 intestinal metaplasia, and 16 dysplasia tissues. We found abundant expression of SBP1 in most precursor lesions in addition to the nonneoplastic epithelia tissues. However, the expression of SBP1 was severely suppressed in most of the GC tissues (P=0.000). Although no statistical differences were found between the expressions of SBP1 in gastric tissues with different levels of intestinal metaplasia or dysplasia (P>0.05), the reduction in SBP1 seems to be correlated with clinical stage of GC (P=0.044). Thus, SBP1 can be supposed as a diagnosis marker of GC. The suppression of SBP1 may be a late event in gastric carcinogenesis.

Reduced selenium-binding protein 1 is associated with poor survival rate in gastric carcinoma

Human selenium-binding protein 1 (SBP1) is known to play a key role in the development and progression of many cancers. The role of SBP1 expression in gastric carcinoma (GC) is far from being fully established. The aim of the present study was to evaluate the expression of SBP1 in GC and correlate the findings with several clinicopathological features and prognosis. Tissue samples from 65 patients treated by gastric resection for GC with clinical stage II and III were used. Each sample was matched with the corresponding nonneoplastic epithelia tissues removed during the same surgery. Reverse transcriptase-polymerase chain reaction, immunostaining and Western blot analyses were used to detect the expression of SBP1 at the mRNA and protein levels, respectively. The associations between SBP1 expressions and clinicopathological features were analyzed. Expressions of SBP1 at both mRNA and protein levels were significantly lower in GC than those in the corresponding nonneoplastic epithelia tissues (P = 0.000). SBP1-negative expression had a significant relationship with high clinical stage (P = 0.038). Prognosis of SBP1-negative patients was significantly poorer than that of SBP1-positive patients (P = 0.001), and multivariate analysis further confirmed that SBP1 was an independent prognostic factor (P = 0.004). Thus, down-regulation of SBP1 may play a key role in the tumorigenic process of human GC. The correlation of SBP1 reduction in GC with clinical stage and survival proposes a prognostic role in GC.

The organic selenium compound selenomethionine modulates bleomycin-induced DNA damage and repair in human leukocytes

The objective of this work was to evaluate the effects of selenomethionine (SeMet) on the induction, repair, and persistence of DNA damage in human leukocytes challenged with bleomycin (BLM). Comet assay was used to determine DNA strand breaks and hOGG1 for the specific recognition of oxidative damage. Leukocytes were (A) stimulated with phytohemagglutinin, (B) damaged with BLM, and (C) incubated to allow DNA repair. Comet assay was performed after each phase. SeMet (50 microM) was supplemented either during phase A, B, or C, or AB, or ABC. Treatment with SeMet decreased BLM-induced stand breaks when added during phase AB. Results obtained after the repair period indicate that SeMet favors repair of DNA damage especially when applied during phase AB. The comparison between DNA damage before and after repair showed that BLM-induced damage was repaired better in the presence of SeMet. Our results showed antigenotoxic effect of SeMet on BLM-induced DNA and also on repair and persistence of this damage when applied before and simultaneously with BLM.

Study on the raw fish oil purification from PCDD/F and dl-PCB-industrial tests

The results of tests for the purification of fish oils with activated carbon for industrial use are presented. The optimum parameters for the process of purification (granulation of the activated carbon, its dosage, the oil temperature, and the duration of mixing the oil with activated carbon) were previously established for the laboratory scale. The optimization of the process consisted of selecting purification parameters that would allow for maximum reduction of the toxic polychlorinated dibenzo-para-dioxins and polychlorinated dibenzofurans (PCDD/Fs) content, while retaining the favorable high fatty acid content [C20:5 n-3, eicosapentaenoic acid (EPA) and C22:6 n-3, docosahexaenoic acid (DHA)]. The use of that optimum parameters in industrial conditions confirmed the satisfactory results obtained in laboratory tests. Five types of oil derived from various Baltic fish were purified. Reduction in the PCDD/Fs content was 77.0-93.6% on average, whereas in the dioxin-like polychlorinated biphenyls (dl-PCBs)-it was 42.7-50.5% on average, with insignificant changes in the total amount of EPA and DHA content. Furthermore, a significant reduction in the content of arsenic was noted (by about 62% on average), with insignificant changes in the content of organochlorine pesticides (OCPs), and marker polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), cadmium, lead, and mercury. Purification provided fish oil having standardized parameters that allow for its use as feed additives, whilst retaining its favorable fatty acid content.

Evaluation of the microelement profile of Turkish hazelnut (Corylus avellana L.) varieties for human nutrition and health

In this study, the levels of boron (B), cobalt (Co), copper (Cu), chromium (Cr), iron (Fe), lithium (Li), nickel (Ni), selenium (Se) and zinc (Zn) microelements in 16 hazelnut samples were determined by inductively coupled plasma mass spectrometry and atomic absorption spectroscopy after microwave digestion, and are discussed for human nutrition and health. Significant differences were observed between the microelement contents of the 16 varieties (P < 0.01). The average microelements concentrations in the varieties varied in the following ranges: B, 13.63-23.87; Co, 0.47-0.82; Cr, 0.22-0.52; Cu, 16.23-32.23; Fe, 31.60-51.60; Li, 0.035-0.042; Ni, 0.58-2.58; Se, 0.96-1.39; and Zn, 22.03-44.03 mg/kg. These results showed that hazelnuts can be an important microelement source for human nutrition and health. According to our trace element data, a daily consumption of 50 g hazelnut can supply easily about 6% for B, 9% for Co, 19% for Fe, 9% for Ni and 16% for Zn of the recommended daily allowance. On the other hand, Se, Cu and Cr levels of 50 g hazelnuts are higher than the respective daily requirements, but slight overdoses of these elements are non-toxic for human health.

Antioxidant defense markers modulated by glutathione S-transferase genetic polymorphism: results of lung cancer case-control study

Oxidative stress and xenobiotic metabolizing enzymes are suspected to be related to carcinogenesis by different cellular mechanisms. Hence, our study aimed at identifying potential relationships between antioxidant defense parameters measured in blood and glutathione S-transferase (GST) genetic polymorphisms of four GST izoenzymes in lung cancer patients and reference individuals. The case-control study included 404 lung cancer patients and 410 non-cancer subjects as controls, matched by age, gender and place of living (central Poland). In control subjects with GSTM3*A/*A, GSTT1 null, GSTM1 null + GSTT1 null, GSTM3*A/*A + GSTT1 null genotype, glutathione peroxidase activity was significantly higher (P < 0.05) than in controls possessing respective potential protective GST genotypes. Controls with GSTM3*A/*A + GSTP1*B genotype presented significantly higher ceruloplasmin activity (P < 0.05) than GSTM3*B + GSTP1*A/*A carriers. Zinc level was significantly higher (P < 0.05) in controls and cases with GSTP1*B + GSTT1 null genotype and in cases with GSTM1 null + GSTP1*B genotype, when compared with respective potential protective GST genotypes. This case-control study indicates that particular defective GST genotypes may enhance the defense against oxidative stress. The potential relationship between the investigated antioxidative enzymes and microelements, and common functional genetic polymorphism of GST was observed mostly in control subjects.

Anticlastogenic and antigenotoxic effects of selenomethionine on doxorubicin-induced damage in vitro in human lymphocytes

The use of antioxidants during chemotherapy has been shown to reduce or prevent the undesirable effects experienced by healthy cells. Micronutrient selenium is well known for its antioxidant properties; however, selenium exhibits a bimodal nature in that both its beneficial and toxic properties lie within a limited and narrow dose range. The present study investigated the possible protective effects of selenomethionine (SM) on the cytotoxicity, genotoxicity and clastogenicity of the chemotherapic doxorubicin (DXR), a key chemotherapic used in cancer treatment. Human peripheral lymphocytes were treated in vitro with varying concentrations of SM (0.25 microM, 0.5 microM, 1.0 microM and 2.0 microM), tested in combination with DXR (0.15 microg/mL). SM alone was not cytotoxic and when combined with DXR treatment, reduced the DNA damage index significantly, the frequency of chromosomal aberrations, the number of aberrant metaphases and the frequency of apoptotic cells. The mechanism of chemoprotection of SM may be related to its antioxidant properties as well as its ability to interfere with DNA repair pathways. Therefore this study showed that SM is effective in reducing the genetic damage induced by the antitumoral agent DXR.

Vicia root-mirconucleus and sister chromatid exchange assays on the genotoxicity of selenium compounds

Selenium (Se) is an important metalloid with industrial, environmental, biological and toxicological significance. Excessive selenium in soil and water may contribute to environmental selenium pollution, and affect plant growth and human health. By using Vicia faba micronucleus (MN) and sister chromatid exchange (SCE) tests, possible genotoxicity of sodium selenite and sodium biselenite was evaluated in this study. The results showed that sodium selenite, at concentrations from 0.01 to 10.0mg/L, induced a 1.9-3.9-fold increase in MN frequency and a 1.5-1.6-fold increase in SCE frequency, with a statistically significantly difference from the control (P<0.05 and 0.01, respectively). Sodium selenite also caused mitotic delay and a 15-80% decrease in mitotic indices (MI), but at the lowest concentration (0.005mg/L), it slightly stimulated mitotic activity. Similarly, the frequencies of MN and SCE also increased significantly in sodium biselenite treated samples, with MI decline only at relatively higher effective concentrations. Results of the present study suggest that selenite is genotoxic to V. faba root cells and may be a genotoxic risk to human health.

4-Methyl-1,2,3-selenadiazole-5-carboxylic acid amides: Antitumor action and cytotoxic effect correlation

Synthesis and cytotoxic activity of a series of 4-methyl-1,2,3-selenadiazole-5-carboxylic acid amides on human fibrosarcoma HT-1080, mouse hepatoma MG-22A, and mouse fibroblasts 3T3 cell lines are described. The correlation between compound LD(50) and 3T3 fibroblast cell line morphology was shown. In vivo evaluation of amides on mouse sarcoma S-180 confirms high antitumor activity (58-85%).

Efficacy of increasing the therapeutic index of irinotecan, plasma and tissue selenium concentrations is methylselenocysteine dose dependent

This study was designed to understand the basis for the efficacy of methylselenocysteine (MSC) in increasing the therapeutic index of irinotecan against human tumor xenografts. Nude mice bearing human head and neck squamous cells carcinoma xenografts (FaDu and A253) were treated orally with different doses of MSC and irinotecan. Plasma, tumor and normal tissue samples were collected at different times after MSC treatments and were analyzed for selenium (Se) concentration using electrothermal atomic absorption spectrophotometry. MSC is highly effective in modulating the therapeutic index of irinotecan. Enhanced irinotecan efficacy was greater in FaDu tumors (100% CR) than in A253 tumors (60% CR), and depended on MSC dose with a minimum effective dose of 0.01 mg/dx28. The highest plasma Se concentration was achieved 1h after a single dose and 28 d after daily treatments of MSC. The ability of FaDu tumors to retain Se was significantly better than A253 tumors, and the highest Se concentration in normal tissue was achieved in the liver. Peak plasma and tissue Se concentrations were functions of the dose and duration of MSC treatment. The MSC-dependent increase in Se level in normal tissues may contribute to the protective effect against irinotecan toxicity observed in those tissues. Intratumoral total Se concentration was not found to be predictive of the combination therapy response rates. There is a critical need to develop a method to measure the active metabolite of MSC, rather than total Se.

Selenium, apoptosis, and colorectal adenomas

BACKGROUND

Selenium is an essential trace element found in cereals, wheat, dairy products, meat, and fish. This micronutrient may prevent carcinogenesis through several biochemical pathways; one suggested pathway is enhanced apoptosis.

OBJECTIVES

The relation between selenium and colorectal adenomas was evaluated because the colorectal adenoma is the established precursor lesion of most colorectal cancers. Apoptosis was a pathway of interest because decreased apoptosis has been associated with an increased prevalence of adenomas. Our objectives were as follows: to investigate the association between (a) selenium and colorectal adenomas and (b) selenium and apoptosis.

METHODS

The study population was assembled for the Diet and Health Study III (n = 803), a cross-sectional study conducted at the University of North Carolina Hospital (Chapel Hill, NC). There were 451 participants in the analysis of selenium and adenoma prevalence and 351 participants in the analysis of selenium and apoptosis. Selenium was measured from serum collected at the time of colonoscopy. Apoptosis was measured in biopsies from normal rectal epithelium obtained during the colonoscopy procedure.

RESULTS

Participants in the highest fifth of serum selenium were less likely to have adenomas in comparison with those in the lowest fifth (prevalence ratio, 0.6; 95% confidence interval, 0.4-1.1). Selenium and apoptosis (>2.76 cells per crypt) were not strongly related, but results collectively suggested a roughly inverse association.

CONCLUSIONS

High selenium was associated with a reduced prevalence of colorectal adenomas. Apoptosis, however, did not seem to be the mechanism by which selenium was related to adenoma prevalence in our data.

Synthesis and study of the cancer cell growth inhibitory properties of α-, γ-tocopheryl and γ-tocotrienyl 2-phenylselenyl succinates

Vitamin E succinate selenium-conjugated molecules were synthesized and their apoptogenic properties were evaluated. 4-Methyl-2-phenylselenyl succinate (4) was prepared by the reaction of sodium benzeneselenolate with 2-bromosuccinic anhydrite in methanol solution. The methyl ester was converted to the acid (5) by hydrolysis with aqueous hydrochloric acid. Reaction of the 2-phenylselenyl succinic anhydrite (6) with alpha-tocopherol (1a), gamma-tocopherol (1c), and gamma-tocotrienol (2c) in acidic conditions gave the respective esters. The free radical scavenging properties of alpha-tocopheryl-2-phenylselenyl succinate (7), gamma-tocopheryl-2-phenylselenyl succinate (8), and gamma-tocotrienyl-2-phenylselenyl succinate (9) were evaluated in comparison with those of alpha-tocopheryl succinate (10), gamma-tocopheryl succinate (11), and gamma-tocotrienyl succinate (12), respectively, and the free tocopherols and gamma-tocotrienol. Compounds 7-9 induced a statistically significant decrease in prostate cancer cell viability compared to 10-12, respectively, or 5, exhibiting features of apoptotic cell death and associated with caspase-3 activation. These data show that structural modifications of vitamin E components by 5 enhance their apoptogenic properties in cancer cells.

Direct determination of selenium in urine samples by electrothermal atomic absorption spectrometry using a Zr plus Rh-treated graphite tube and co-injection of Rh as chemical modifier

Different chemical modifiers for use with electrothermal atomic absorption spectrometry (ET AAS) were investigated in relation to determining the selenium in human urine samples. The samples were diluted in a solution containing 1% v/v HNO3 and 0.02% m/v cetyltrimethylammonium chloride (CTAC). Studying the modifiers showed that the use of either Ru or Ir as the permanent modifier gave low sensitivity to Se and the peak shape was very noisy, while Zr or Rh gave no peak at all. The same occurred when Zr was used in solution. For mixtures of permanent modifiers, Ir plus Rh or Zr plus Rh gave very low sensitivity, Zr plus Rh with co-injection of Ir in solution was also not efficient, Zr plus Rh in solution gave good sensitivity, but the best results were obtained with a mixture of Zr and Rh as the permanent modifier and co-injection of Rh in solution. Using this last modifier, the following dilutions with the HNO3 and CTAC were studied: 1:1, 1:2, 1:3 and 1:4. The best dilution was 1:1, which promoted good sensitivity and a more defined peak shape and made it possible to correct for the background using a deuterium arc lamp. Under these conditions, a characteristic mass of 26+/-0.2 pg was obtained for Se in aqueous solution. Six certified urine samples were analyzed using matrix matching calibration and the measured concentrations were in agreement with the certified values, according to a t-test at the 95% confidence level. Recovery tests were carried out and the recoveries were in the range 100-103%, with relative standard deviation better than 9%. The limit of detection (LOD, 3 sd, n = 10) was 3.0 microg L(-1) in the sample. The treated graphite tube could be used for at least 600 atomization cycles without significant alteration of the analytical signal.

Simultaneous determination of arsenic and selenium in biological samples by HG-AFS

A new method is proposed for simultaneous determination of traces of arsenic (As) and selenium (Se) in biological samples by hydride-generation double-channel non-dispersive atomic-fluorescence spectrometry (HG-AFS) from tartaric acid media. The effects of analytical conditions on fluorescence signal intensity were investigated and optimized. Interferences from coexisting ions were evaluated. Under optimum conditions linear response ranges above 20 microg L(-1) for As and 32 microg L(-1) for Se were obtained with detection limits of 0.13 and 0.12 microg L(-1), respectively. The precision for eleven-fold determination of As at the 4 microg L(-1) level and of Se at the 8 microg L(-1) level were 2.7 and 1.9% (RSD), respectively. Recoveries of 92.5-95.5% for As and 101.2-108.4% for Se were obtained for four biological samples and two certified biological reference materials. The proposed method has the advantages of simple operation, high sensitivity, and high efficiency; it was successfully used for simultaneous determination of As and Se in biological samples.

Chiral Speciation and Determination of DL-Selenomethionine Enantiomers on a Novel Chiral Ligand-Exchange Stationary Phase

A new type of chiral ligand-exchange stationary phase (CLES) was successfully synthesized by treating silica gel with beta-(3,4-epoxycyclohexyl)ethyltrimethoxy silane and opening the epoxy ring by L-isoleucine. The chiral speciation of DL-selenomethionine (DL-SeMet) by high-performance liquid chromatography (HPLC) with UV absorbance on the CLES column was studied. The influences of the contents of copper ion and methanol as well as the pH value in the mobile phase and temperature of the column on the efficiency of resolution of DL-SeMet were investigated in detail. DL-SeMet could be completely resolved within 40 min under the optimal operating conditions of 0.1 mmol/L Cu2+ at 0.05 mol/L KH2PO4 buffer (pH = 5.5) and 35 degrees C temperature of the column. The limits of detection of D- and L-SeMet were 255 ppb and 286 ppb, respectively. This method was applied to determine the D- and L-enantiomers of DL-SeMet in real samples, such as selenized yeast powder and garlic.

Clinical pharmacokinetics of antioxidants and their impact on systemic oxidative stress

Dietary antioxidants play a major role in maintaining the homeostasis of the oxidative balance. They are believed to protect humans from disease and aging. Vitamin C (ascorbic acid), vitamin E (tocopherol), beta-carotene and other micronutrients such as carotenoids, polyphenols and selenium have been evaluated as antioxidant constituents in the human diet. This article addresses data provided from clinical trials, highlighting the clinical pharmacokinetics of vitamin C, vitamin E, beta-carotene, lycopene, lutein, quercetin, rutin, catechins and selenium. The bioavailability of vitamin C is dose-dependent. Saturation of transport occurs with dosages of 200-400 mg/day. Vitamin C is not protein-bound and is eliminated with an elimination half-life (t((1/2))) of 10 hours. In Western populations plasma vitamin C concentrations range from 54-91 micro mol/L. Serum alpha- and gamma-tocopherol range from 21 micro mol/L (North America) to 27 micro mol/L (Europe) and from 3.1 micro mol/L to 1.5 micro mol/L, respectively. alpha-Tocopherol is the most abundant tocopherol in human tissue. The bioavailability of all-rac-alpha-tocopherol is estimated to be 50% of R,R,R-alpha-tocopherol. The hepatic alpha-tocopherol transfer protein (alpha-TTP) together with the tocopherol-associated proteins (TAP) are responsbile for the endogenous accumulation of natural alpha-tocopherol. Elimination of alpha-tocopherol takes several days with a t((1/2)) of 81 and 73 hours for R,R,R-alpha-tocopherol and all-rac-alpha-tocopherol, respectively. The t((1/2)) of tocotrienols is short, ranging from 3.8-4.4 hours for gamma- and alpha-tocotrienol, respectively. gamma-Tocopherol is degraded to 2, 7, 8-trimethyl-2-(beta-carboxyl)-6-hyrdoxychroman by the liver prior to renal elimination. Blood serum carotenoids in Western populations range from 0.28-0.52 micro mol/L for beta-carotene, from 0.2-0.28 for lutein, and from 0.29-0.60 for lycopene. All-trans-carotenoids have a better bioavailability than the 9-cis-forms. Elimination of carotenoids takes several days with a t((1/2)) of 5-7 and 2-3 days for beta-carotene and lycopene, respectively. The bioconversion of beta-carotene to retinal is dose-dependent, and ranges between 27% and 2% for a 6 and 126mg dose, respectively. Several oxidised metabolites of carotenoids are known. Flavonols such as quercetin glycosides and rutin are predominantly absorbed as aglycones, bound to plasma proteins and subsequently conjugated to glucuronide, sulfate, and methyl moieties. The t((1/2)) ranges from 12-19 hours. The bioavailabillity of catechins is low and they are eliminated with a t((1/2)) of 2-4 hours. Catechins are degraded to several gamma-valerolactone derivatives and phase II conjugates have also been identified. Only limited clinical pharmacokinetic data for other polyphenols such as resveratrol have been reported to date.

Presentation serum selenium predicts for overall survival, dose delivery, and first treatment response in aggressive non-Hodgkin's lymphoma

PURPOSE

This study was undertaken to test the hypothesis that serum selenium concentration at presentation correlates with dose delivery, first treatment response, and overall survival in patients with aggressive B-cell non-Hodgkin's lymphoma.

PATIENTS AND METHODS

The patients presented between July 1986 and March 1999 and received anthracycline-based chemotherapy, radiotherapy, or both. The total selenium content was retrospectively analyzed in 100 sera, frozen at presentation, using inductively coupled plasma mass spectrometry.

RESULTS

The serum selenium concentration ranged from 0.33 to 1.51 micromol/L (mean, 0.92 micromol/L; United Kingdom adult reference range, 1.07 to 1.88 micromol/L). Serum selenium concentration correlated closely with performance status but with no other clinical variable. Multivariate analysis revealed that increased dose delivery, summarized by an area under the curve, correlated positively with younger age (P <.001), advanced stage (P =.001), and higher serum selenium concentration (P =.032). Selenium level also correlated positively with response (odds ratio, 0.62; 95% confidence interval [CI], 0.43 to 0.90; P =.011) and achievement of long-term remission after first treatment (log-rank test, 4.38; P =.036). On multivariate analysis, selenium concentration was positively predictive of overall survival (hazard ratio [HR], 0.76 for 0.2 micromol/L increase; 95% CI, 0.60 to 0.95; P =.018), whereas age indicated negative borderline significance (HR, 1.09; 95% CI, 0.99 to 1.18; P =.066).

CONCLUSION

Serum selenium concentration at presentation is a prognostic factor, predicting positively for dose delivery, treatment response, and long-term survival in aggressive non-Hodgkin's lymphoma. Unlike most existing prognostic factors in aggressive non-Hodgkin's lymphoma, selenium supplementation may offer a novel therapeutic strategy in this frequently curable malignancy.

Organoammonium hydroselenites: antitumor action through radical balance regulation

Organoammonium hydroselenites were synthesized and investigated as potential selective, anticancer prodrugs. These compounds were studied in vitro on human fibrosarcoma (HT-1080), hamster kidney endothelial (BHK 21) and normal mouse embryonic fibroblasts (NIH 3T3). Most of them were very active against HT-1080 (0.6-5.3 g/ml). Amino acid hydroselenites readily increased the nitric oxide (NO) concentration in the culture medium of HT-1080 cells (up to TG(100)=1500%); however, 4-amidohydroximinomethylpyridinium hydroselenite (TG(100)=24%) and o-phenanthrolinium hydroselenite (TG(100)=50%) were free radical inhibitors. All compounds were glutathione peroxidase inhibitors; some of them could also prevent hydrogen peroxide degradation by inhibition of catalase. The influence of the investigated ammonium hydroselenites on tumor cell (HT-1080) morphology was examined. The substances studied were also active in vivo against sarcoma S-180. The role of organoammonium hydroselenites as free radical regulators and their therapeutic antitumor are discussed.

Design, synthesis and antitumor activities of novel 7-arylseleno-7-deoxydaunomycinone derivatives

7-Arylseleno-7-deoxydaunomycinone derivatives 3a-e and 7-thiophenyl-7-deoxydaunomycinones (7 and 8) were synthesized and the antitumor activities of them were evaluated against human stomach cancer SGC-7901 and human leukaemia HL60. The cytotoxic assay show that seleno daunomycinone derivatives are much better inhibitory activity than thiodaunomycinone and the structure-activity relationship was discussed. 7-Deoxydaunomycinone 4 was obtained when selenophenols were used in excess and the possible mechanism was proposed.