[Experimental study on promotion of peripheral nerve regeneration by selenium-methylselenocysteine]

Objective

To investigate the feasibility of selenium-methylselenocysteine (SMC) to promote peripheral nerve regeneration and its mechanism of action.

Methods

Rat Schwann cells RSC96 cells were randomly divided into 5 groups, which were group A (without any treatment, control group), group B (adding 100 μmol/L H 2O 2), group C (adding 100 μmol/L H 2O 2+100 μmol/L SMC), group D (adding 100 μmol/L H 2O 2+200 μmol/L SMC), group E (adding 100 μmol/L H 2O 2+400 μmol/L SMC); the effect of SMC on cell proliferation was detected by MTT method, and the level of oxidative stress was detected by immunofluorescence for free radicals [reactive oxygen species (ROS)] after determining the appropriate dose group. Thirty-six 4-week-old male Sprague Dawley rats were randomly divided into 3 groups, namely, the sham operation group (Sham group), the sciatic nerve injury group (PNI group), and the SMC treatment group (SMC group), with 12 rats in each group; the rats in the PNI group were fed with food and water normally after modelling operation, and the rats in the SMC group were added 0.75 mg/kg SMC to the drinking water every day. At 4 weeks after operation, the sciatic nerves of rats in each group were sampled for neuroelectrophysiological detection of highest potential of compound muscle action potential (CMAP). The levels of inflammatory factors [interleukin 17 (IL-17), IL-6, IL-10 and oxidative stress factors catalase (CAT), superoxide dismutase (SOD), and malondialdehyde (MDA)] were detected by ELISA assay. The luxol fast blue (LFB) staining was used to observe the myelin density, fluorescence intensity of glial fibrillary acidic protein (GFAP) and myelin basic protein (MBP) was observed by immunofluorescence staining, and myelin morphology was observed by transmission electron microscopy with measurement of axon diameter. Western blot was used to detect the protein expressions of p38 mitogen-activated protein kinases (p38MAPK), phosphorylated p38MAPK (p-p38MAPK), heme oxygenase 1 (HO-1), and nuclear factor erythroid 2-related factor 2 (Nrf2).

Results

MTT assay showed that the addition of SMC significantly promoted the proliferation of RSC96 cells, and the low concentration could achieve an effective effect, so the treatment method of group C was selected for the subsequent experiments; ROS immunofluorescence test showed that group B showed a significant increase in the intensity of ROS fluorescence compared with that of group A, and group C showed a significant decrease in the intensity of ROS fluorescence compared with that of group B ( P<0.05). Neuroelectrophysiological tests showed that the highest potential of CMAP in SMC group was significantly higher than that in PNI and Sham groups ( P<0.05). ELISA assay showed that the levels of IL-6, IL-17, and MDA in PNI group were significantly higher than those in Sham group, and the levels of IL-10, SOD, and CAT were significantly lower; the levels of IL-6, IL-17, and MDA in SMC group were significantly lower than those in PNI group, and the levels of IL-10, SOD, and CAT were significantly higher ( P<0.05). LFB staining and transmission electron microscopy showed that the myelin density and the diameter of axons in the SMC group were significantly higher than those of the PNI group and the Sham group ( P<0.05). Immunofluorescence staining showed that the fluorescence intensity of GFAP and MBP in the SMC group were significantly stronger than those in the PNI group and Sham group ( P<0.05). Western blot showed that the relative expressions of Nrf2 and HO-1 proteins in the SMC group were significantly higher than those in the PNI group and Sham group, and the ratio of p-p38MAPK/p38MAPK proteins was significantly higher in the PNI group than that in the SMC group and Sham group ( P<0.05).

Conclusion

SMC may inhibit oxidative stress and inflammation after nerve injury by up-regulating the Nrf2/HO-1 pathway, and then inhibit the phosphorylation of p38MAPK pathway to promote the proliferation of Schwann cells, which ultimately promotes the formation of myelin sheaths and accelerates the regeneration of peripheral nerves.

Se-methylselenocysteine ameliorates mitochondrial function by targeting both mitophagy and autophagy in the mouse model of Alzheimer's disease

Background: Alzheimer's disease (AD) exerts tremendous pressure on families and society due to its unknown etiology and lack of effective treatment options. Our previous study had shown that Se-methylselenocysteine (SMC) improved the cognition and synaptic plasticity of triple-transgenic AD (3 × Tg-AD) mice and alleviated the related pathological indicators. We are dedicated to investigating the therapeutic effects and molecular mechanisms of SMC on mitochondrial function in 3 × Tg-AD mice. Methods: Transmission electron microscopy (TEM), western blotting (WB), mitochondrial membrane potential (ΔΨm), mitochondrial swelling test, and mitochondrial oxygen consumption test were used to evaluate the mitochondrial morphology and function. Mitophagy flux and autophagy flux were assessed with immunofluorescence, TEM and WB. The Morris water maze test was applied to detect the behavioral ability of mice. Results: The destroyed mitochondrial morphology and function were repaired by SMC through ameliorating mitochondrial energy metabolism, mitochondrial biogenesis and mitochondrial fusion/fission balance in 3 × Tg-AD mice. In addition, SMC ameliorated mitochondria by activating mitophagy flux via the BNIP3/NIX pathway and triggering autophagy flux by suppressing the Ras/Raf/MEK/ERK/mTOR pathway. SMC remarkably increased the cognitive ability of AD mice. Conclusions: This research indicated that SMC might exert its therapeutic effect by protecting mitochondria in 3 × Tg-AD mice.

Immunomodulatory and Anti-Inflammatory Properties of Selenium-Containing Agents: Their Role in the Regulation of Defense Mechanisms against COVID-19

The review presents the latest data on the role of selenium-containing agents in the regulation of diseases of the immune system. We mainly considered the contributions of selenium-containing compounds such as sodium selenite, methylseleninic acid, selenomethionine, and methylselenocysteine, as well as selenoproteins and selenium nanoparticles in the regulation of defense mechanisms against various viral infections, including coronavirus infection (COVID-19). A complete description of the available data for each of the above selenium compounds and the mechanisms underlying the regulation of immune processes with the active participation of these selenium agents, as well as their therapeutic and pharmacological potential, is presented. The main purpose of this review is to systematize the available information, supplemented by data obtained in our laboratory, on the important role of selenium compounds in all of these processes. In addition, the presented information makes it possible to understand the key differences in the mechanisms of action of these compounds, depending on their chemical and physical properties, which is important for obtaining a holistic picture and prospects for creating drugs based on them.

Se-methylselenocysteine stimulates migration and antioxidant response in HaCaT keratinocytes: Implications for wound healing

BACKGROUND

Se-methylselenocysteine (MSC), a natural organic selenium compound, is known for its anticancer effects. In the present study, we investigated the effects of MSC on cell migration, which is the most limiting step in the reepithelialization process of wound healing and the antioxidant response in HaCaT keratinocytes.

METHODS

HaCaT cells were treated with various concentrations of MSC. Cell migration and proliferation, the expression of proteins that are involved in the epidermal-mesenchymal transition (EMT) process, the extent of oxidative stress and the antioxidant response, and the associated signaling pathways were analyzed.

RESULTS

MSC (100-500 μM) increased HaCaT cell migration. MSC stimulated EMT, which was evidenced by a decrease in E-cadherin in the cells at the wound edge and increases in Snail, Twist, and matrix metalloproteinases. MSC increased the phosphorylation of Akt and glycogen synthase kinase 3β, which led to the stabilization and nuclear accumulation of β-catenin, a transcriptional coactivator involved in EMT. MSC caused a transient increase and then an eventual decrease in cellular reactive oxygen species, which appeared to be associated with the increase in nuclear factor erythroid 2-related factor 2, a key transcription factor for the antioxidant response.

CONCLUSION

Our results suggest that MSC can promote skin wound healing by stimulating keratinocyte migration and, moreover, can protect cells from excessive oxidative stress that often accompanies and impairs the wound healing process, particularly in chronic wounds, by stimulating an antioxidant response.

Comparative Safety and Pharmacokinetic Evaluation of Three Oral Selenium Compounds in Cancer Patients

Selenium (Se) compounds have demonstrated anticancer properties in both preclinical and clinical studies, with particular promise in combination therapy where the optimal form and dose of selenium has yet to be established. In a phase I randomised double-blinded study, the safety, tolerability and pharmacokinetic (PK) profiles of sodium selenite (SS), Se-methylselenocysteine (MSC) and seleno-l-methionine (SLM) were compared in patients with chronic lymphocytic leukaemia and a cohort of patients with solid malignancies. Twenty-four patients received 400 μg of elemental Se as either SS, MSC or SLM for 8 weeks. None of the Se compounds were associated with any significant toxicities, and the total plasma Se AUC of SLM was markedly raised in comparison to MSC and SS. DNA damage assessment revealed negligible genotoxicity, and some minor reductions in lymphocyte counts were observed. At the dose level used, all three Se compounds are well-tolerated and non-genotoxic. Further analyses of the pharmacodynamic effects of Se on healthy and malignant peripheral blood mononuclear cells will inform the future evaluation of higher doses of these Se compounds. The study is registered under the Australian and New Zealand Clinical Trials Registry No: ACTRN12613000118707.

Treatment of Caenorhabditis elegans with Small Selenium Species Enhances Antioxidant Defense Systems

SCOPE

Small selenium (Se) species play a key role in Se metabolism and act as dietary sources of the essential trace element. However, they are redox-active and trigger pro- and antioxidant responses. As health outcomes are strongly species-dependent, species-specific characteristics of Se compounds are tested in vivo.

METHODS AND RESULTS

In the model organism Caenorhabditis elegans (C. elegans), immediate and sustained effects of selenite, selenomethionine (SeMet), and Se-methylselenocysteine (MeSeCys) are studied regarding their bioavailability, incorporation into proteins, as well as modulation of the cellular redox status. While all tested Se compounds are bioavailable, only SeMet persistently accumulates and is non-specifically incorporated into proteins. However, the protection toward chemically-induced formation of reactive species is independent of the applied Se compound. Increased thioredoxin reductase (TXNRD) activity and changes in mRNA expression levels of antioxidant proteins indicate the activation of cellular defense mechanisms. However, in txnrd-1 deletion mutants, no protective effects of the Se species are observed anymore, which is also reflected by differential gene expression data.

CONCLUSION

Se species protect against chemically-induced reactive species formation. The identified immediate and sustained systemic effects of Se species give rise to speculations on possible benefits facing subsequent periods of inadequate Se intake.

Nutraceutical formulation, characterisation, and in-vitro evaluation of methylselenocysteine and selenocystine using food derived chitosan:zein nanoparticles

Selenoamino acids (SeAAs) have been shown to possess antioxidant and anticancer properties. However, their bioaccessibility is low and they may be toxic above the recommended nutritional intake level, thus improved targeted oral delivery methods are desirable. In this work, the SeAAs, Methylselenocysteine (MSC) and selenocystine (SeCys₂) were encapsulated into nanoparticles (NPs) using the mucoadhesive polymer chitosan (Cs), via ionotropic gelation with tripolyphosphate (TPP) and the NPs produced were then coated with zein (a maize derived prolamine rich protein). NPs with optimized physicochemical properties for oral delivery were obtained at a 6: 1 ratio of Cs:TPP, with a 1:0.75 mass ratio of Cs:zein coating (diameter ~260 nm, polydispersivity index ~0.2, zeta potential >30 mV). Scanning Electron Microscopy (SEM) analysis showed that spheroidal, well distributed particles were obtained. Encapsulation Efficiencies of 80.7% and 78.9% were achieved, respectively, for MSC and SeCys₂ loaded NPs. Cytotoxicity studies of MSC loaded NPs showed no decrease in cellular viability in either Caco-2 (intestine) or HepG2 (liver) cells after 4 and 72 h exposures. For SeCys₂ loaded NPs, although no cytotoxicity was observed in Caco-2 cells after 4 h, a significant reduction in cytotoxicity was observed, compared to pure SeCys₂, across all test concentrations in HepG2 after 72 h exposure. Accelerated thermal stability testing of both loaded NPs indicated good stability under normal storage conditions. Lastly, after 6 h exposure to simulated gastrointestinal tract environments, the sustained release profile of the formulation showed that 62 ± 8% and 69 ± 4% of MSC and SeCys₂, had been released from the NPs respectively.

Effect of administration route and dose on metabolism of nine bioselenocompounds

The nutritional availability of selenium (Se) is highly dependent on its chemical form because chemical form affects absorption, distribution, metabolism, and excretion. We evaluated the effects of administration route and dose on the bioavailability of nine Se compounds found in biota, the so-called bioselenocompounds, such as selenite, selenate, selenocyanate (SeCN), Se-methylselenocysteine (MeSeCys), selenomethionine (SeMet), selenohomolanthionine (SeHLan), selenocystine (SeCys2), 1β-methylseleno-N-acetyl-d-galactosamine (SeSug1), and trimethylselenonium ion (TMSe). We determined the bioavailability of bioselenocompounds recovered as urinary selenometabolites and serum selenoproteins from urine and serum of Se-deficient rats after the administration of bioselenocompounds by speciation analysis. Urinary Se was more easily recovered than serum selenoproteins, suggesting that the speciation of urinary Se is a better tool to indicate Se status in the body. The intravenous administration of bioselenocompounds showed different Se bioavailability from the oral administration. Intestinal microflora might be involved in the bioavailability of some bioselenocompounds, such as SeCN, MeSeCys, and SeSug1.

Effects of Chinese Cooking Methods on the Content and Speciation of Selenium in Selenium Bio-Fortified Cereals and Soybeans

Cereals and soybeans are the main food sources for the majority of Chinese. This study evaluated the effects of four common cooking methods including steaming, boiling, frying, and milking on selenium (Se) content and speciation in seven selenium bio-fortified cereals and soybeans samples. The Se concentrations in the selected samples ranged from 0.91 to 110.8 mg/kg and selenomethionine (SeMet) was detected to be the main Se species. Total Se loss was less than 8.1% during the processes of cooking except milking, while 49.1% of the total Se was lost in milking soybean for soy milk due to high level of Se in residuals. It was estimated that about 13.5, 24.0, 3.1, and 46.9% of SeMet were lost during the processes of steaming, boiling, frying, and milking, respectively. Meanwhile, selenocystine (SeCys₂) and methylselenocysteine (SeMeCys) were lost completely from the boiled cereals. Hence, steaming and frying were recommended to cook Se-biofortified cereals in order to minimize the loss of Se.

Selenium accumulation and metabolism in algae

Selenium (Se) is an intriguing element because it is metabolically required by a variety of organisms, but it may induce toxicity at high doses. Algae primarily absorb selenium in the form of selenate or selenite using mechanisms similar to those reported in plants. However, while Se is needed by several species of microalgae, the essentiality of this element for plants has not been established yet. The study of Se uptake and accumulation strategies in micro- and macro-algae is of pivotal importance, as they represent potential vectors for Se movement in aquatic environments and Se at high levels may affect their growth causing a reduction in primary production. Some microalgae exhibit the capacity of efficiently converting Se to less harmful volatile compounds as a strategy to cope with Se toxicity. Therefore, they play a crucial role in Se-cycling through the ecosystem. On the other side, micro- or macro-algae enriched in Se may be used in Se biofortification programs aimed to improve Se content in human diet via supplementation of valuable food. Indeed, some organic forms of selenium (selenomethionine and methylselenocysteine) are known to act as anticarcinogenic compounds and exert a broad spectrum of beneficial effects in humans and other mammals. Here, we want to give an overview of the developments in the current understanding of Se uptake, accumulation and metabolism in algae, discussing potential ecotoxicological implications and nutritional aspects.

Selenomethionine and methyl selenocysteine: multiple-dose pharmacokinetics in selenium-replete men

According to the Nutritional Prevention of Cancer (NPC) trial, a selenized yeast supplement containing selenium, 200 mcg/day, decreased the incidence of total cancer, cancers of the prostate, colon and lung, and cancer mortality. The active agent in the selenized yeast supplement was assumed to be selenomethionine (SEMET), although the supplement had not been well speciated. The SELECT study, largely motivated by the NPC trial, enrolling nearly 40 times as many subjects, showed unequivocally that selenium 200 mcg/day, with selenium in the form of SEMET, does not protect selenium-replete men against prostate or other major cancer. The agent tested by SELECT, pure SEMET, could have been different from the selenized yeast tested in NPC. One of the selenium forms suspected of having chemopreventive effects, and which may have been present in the NPC agent, is methyl selenocysteine (MSC). This study, with 29 selenium-replete patients enrolled in a randomized, double-blind trial, compared the multiple-dose toxicity, pharmacokinetics and pharmacodynamics of MSC and SEMET. Patients were on trial for 84 days. No toxicity was observed. Although SEMET supplementation increased blood selenium concentration more than MSC did, neither form had a more than minimal impact on the two major selenoproteins: selenoprotein P(SEPP1) and glutathione peroxidase(GPX).

Evaluation of selenium in dietary supplements using elemental speciation

Selenium-enriched dietary supplements containing various selenium compounds are readily available to consumers. To ensure proper selenium intake and consumer confidence, these dietary supplements must be safe and have accurate label claims. Varying properties among selenium species requires information beyond total selenium concentration to fully evaluate health risk/benefits A LC-ICP-MS method was developed and multiple extraction methods were implemented for targeted analysis of common "seleno-amino acids" and related oxidation products, selenate, selenite, and other species relatable to the quality and/or accuracy of the labeled selenium ingredients. Ultimately, a heated water extraction was applied to recover selenium species from non-selenized yeast supplements in capsule, tablet, and liquid forms. For selenized yeast supplements, inorganic selenium was monitored as a means of assessing selenium yeast quality. A variety of commercially available selenium supplements were evaluated and discrepancies between labeled ingredients and detected species were noted.

Antioxidant Actions of Selenium in Orbital Fibroblasts: A Basis for the Effects of Selenium in Graves' Orbitopathy

BACKGROUND

A recent clinical trial has shown a beneficial effect of the antioxidant agent selenium in Graves' orbitopathy (GO). In order to shed light on the cellular mechanisms on which selenium may act, this study investigated its effects in cultured orbital fibroblasts.

METHODS

Primary cultures of orbital fibroblasts from six GO patients and six control subjects were established. Cells were treated with H₂O₂ to induce oxidative stress, after pre-incubation with selenium-(methyl)selenocysteine (SeMCys). The following assays were performed: glutathione disulfide (GSSG), as a measure of oxidative stress, glutathione peroxidase (GPX) activity, cell proliferation, hyaluronic acid (HA), and pro-inflammatory cytokines.

RESULTS

H₂O₂ induced an increase in cell GSSG and fibroblast proliferation, which were reduced by SeMCys. Incubation of H₂O₂-treated cells with SeMCys was followed by an increase in glutathione peroxidase activity, one of the antioxidant enzymes into which selenium is incorporated. At the concentrations used (5 μM), H₂O₂ did not significantly affect HA release, but it was reduced by SeMCys. H₂O₂ determined an increase in endogenous cytokines involved in the response to oxidative stress and GO pathogenesis, namely tumor necrosis factor alpha, interleukin 1 beta, and interferon gamma. The increases in tumor necrosis factor alpha and interferon gamma were blocked by SeMCys. While the effects of SeMCys on oxidative stress and cytokines were similar in GO and control fibroblasts, they were exclusive to GO fibroblasts in terms of inhibiting proliferation and HA secretion.

CONCLUSIONS

Selenium, in the form of SeMCys, abolishes some of the effects of oxidative stress in orbital fibroblasts, namely increased proliferation and secretion of pro-inflammatory cytokines. SeMCys reduces HA release in GO fibroblasts in a manner that seems at least in part independent from H₂O₂-induced oxidative stress. Some effects of SeMCys are specific for GO fibroblasts. These findings reveal some cellular mechanisms by which selenium may act in patients with GO.

Selenium Plays a Protective Role in Staphylococcus aureus-Induced Endometritis in the Uterine Tissue of Rats

The essential trace element selenium (Se) modulates the functions of many regulatory proteins in signal transduction, conferring benefits in inflammatory diseases. Endometritis is a reproductive obstacle disease both in humans and animals. Staphylococcus aureus is the major pathogen that causes endometritis. The present study analyzes the protection and mechanism of Se-methylselenocysteine (MSC) and methylseleninic acid (MSA) on S. aureus-induced endometritis. An atomic fluorescence spectrophotometry study showed that the uterine Se content increased with the addition of MSC and MSA. Histopathology observation and TUNEL detection showed that Se supplementation displayed a greater defense against uterine inflammatory damage. The quantitative PCR (qPCR) and ELISA analyses showed that the expressions of tumor necrosis factor alpha (TNF-α) and interleukin-6 (IL-6) increased with S. aureus infection and decreased with the addition of MSC and MSA. The Toll-like receptor 2 (TLR2) expression showed the same status as the inflammatory cytokines. The Western blot results showed that the increased phosphorylation of IκBα and NF-κB p65 was also reduced by the addition of MSC and MSA. The qPCR and Western blot results also showed that the transcription expressions and the protein dissociation of caspase-9, caspase-3, caspase-7, caspase-6, and poly(ADP-ribose) polymerase (PARP), which were increased by S. aureus infection, were inhibited by Se supplementation. All of the results displayed that the protection conferred by MSC was stronger than MSA. The present study indicated the Se supplementation might be a potential prevention and control measure for S. aureus-induced endometritis.

[Production effect comparison of SEPP and GPx between HepG2 and Hela cells with different selenocompounds]

OBJECTIVE

To compare the effect of several selenocompounds on the productions of SEPP and GPx in HepG2 and Hela cells.

METHODS

The cultured HepG2 and Hela cells were divided into the control, Na2SeO3, SeMet and MeSeCys groups. After adding the selected selenocompounds (with the respective concentration 0.01 and 0.1 μmol/L), the experimental groups were then incubated for 48 h and 72 h. Finally, the cell culture supernatants and homogenates were collected for the SEPP and GPx concentrations detection by a double-antibody sandwich enyme-linked immuno-sorbent-assay (ELISA).

RESULTS

The SEPP and GPx concentrations in Hela cells treated with 0.1 μmol/L SeMet and MeSeCys were significantly higher than that in the control group (P < 0.05). The SEPP and GPx concentrations in HepG2 cell treated with 0.1 μmol/L selenocompounds were significantly higher than that in Hela cells (P < 0.05).

CONCLUSION

HepG2 cells are more beneficial to the production of selenoproteins than Hela cells.

Methylselenocysteine preventing castration-resistant progression of prostate cancer

BACKGROUND

Castration-resistant progression of prostate cancer after androgen deprivation therapy remains a critical challenge in the clinical management of prostate cancer. Resurgent androgen receptor activity is an established driver of castration-resistant progression, and upregulation of androgen receptor expression has been implicated to contribute to the resurgent androgen receptor activity. We reported previously that methylselenocysteine can decrease the expression and activity of androgen receptor. Here we investigated the ability of methylselenocysteine to inhibit castration-resistant progression of prostate cancer.

METHODS

The regrowth of LNCaP prostate cancer xenografts after castration was monitored. The levels of prostate-specific antigen in mouse serum were measured by ELISA. Tumor cell proliferation and apoptosis were analyzed via Ki-67 immunohistochemistry and TUNEL assay, respectively. Intratumoral angiogenesis was assessed by immunohistochemistry staining of vascular endothelial growth factor and CD31.

RESULTS

We showed that methylselenocysteine delayed castration-resistant regrowth of LNCaP xenograft tumors after androgen deprivation. This was accompanied by decreased serum levels of prostate-specific antigen, inhibition of prostate cancer cell proliferation and tumor angiogenesis, as well as downregulation of androgen receptor and induction of apoptosis in the relapsed tumors.

CONCLUSIONS

The present study represents the first to show the preclinical efficacy of methylselenocysteine in delaying castration-resistant progression of prostate cancer. The findings provide a rationale for evaluating the clinical application of combining methylselenocysteine with androgen deprivation therapy for the treatment of advanced prostate cancer.

Se-Methyl-L-selenocysteine Induces Apoptosis via Endoplasmic Reticulum Stress and the Death Receptor Pathway in Human Colon Adenocarcinoma COLO 205 Cells

Selenomethionine (SeMet) and Se-methyl-L-selenocysteine (MSeC) are natural organoselenium compounds found in garlic, onion, and broccoli. In addition, these compounds have lower toxicity and better anticancer activities than inorganic Se. This study investigated the effects of MSeC treatment on the growth of COLO 205 human colorectal adenocarcinoma cells and evaluated the mechanisms related to the MSeC-induced effects. When COLO 205 cells were treated with 200 μM MSeC for 24 h, MSeC caused 80% apoptosis in cells. MSeC increased the expression of Fas and FasL, followed by the cleavage of caspase-3, caspase-8, DNA fragmentation factor (DFF45), and poly(ADP-ribose) polymerase (PARP). MSeC also increased the levels of Bax protein and decreased the levels of Bid and Bcl-2 proteins. However, MSeC did not cause apoptosis through reactive oxygen species (ROS) stress but instead through endoplasmic reticulum (ER) stress. The cleavage of caspase-12 and caspase-9 was shown to increase the growth arrest and protein levels of DNA-damage inducible genes (GADD) 153 and 45. MSeC also downregulated the ERK1/2 and PI3K/AKT protein levels and upregulated the p38 and JNK protein levels in COLO 205 cells. These results showed that the mechanism by which MSeC induced apoptosis in COLO 205 cells involved caspase activation, the extrinsic apoptotic pathway, and the regulation of ER-stress-induced apoptosis.

[Effects of selenium compounds on proliferation, migration and adhesion of HeLa cells]

OBJECTIVE

To explore the effects of methylseleninic acid (MeSeA), selenomethionine (SeMet) and methylselenocysteine (MeSeCys) on proliferation, migration and adhesion of HeLa cells.

METHODS

HeLa cells were cultured and treated with MeSeA, SeMet and MeSeCys for 12 - 72 h respectively. MTT assay, healing assay and in vitro cell Matrigel adhesion assay were used to detect the proliferation, migration and adhesion of HeLa cells.

RESULTS

Compared to the control group, the proliferation of HeLa cells was remarkably inhibited by MeSeA (P <0. 01). The migration of HeLa cells in MeSeA group was inhibited by 34% (P < 0. 05) and 26% (P < 0. 05) in 4 h and 8 h, respectively. However, the migration of HeLa cells with inhibitions of 18% and 13% was in SeMet group in 4 h and 8 h. The inhibitions of HeLa cell migration in MeSeCys group was 28% (P < 0.05) and 5% in 4 h and 8 h, respectively. In addition, the adhesive function of HeLa cells in the MeSeA group, the SeMet group as well as the MeSeCys group were inhibited by 36% (P < 0. 01), 25% and 49% (P < 0. 01).

CONCLUSION

The proliferation and migration of HeLa cell were effectively inhibited by MeSeA, while the adhesive function of HeLa cell was remarkably inhibited by MeSeCys.

Synergistic effect of Se-methylselenocysteine and vitamin E in ameliorating the acute ethanol-induced oxidative damage in rat

The present study was conduced to investigate the synergistic effects of combined treatments with Se-methylselenocysteine (SeMSC) and vitamin E (Vit E) in reversing oxidative stress induced by ethanol in serum and different tissues of rats. Sixty female rats were randomly divided into six groups for 30 days' consecutive pretreatments as followed: control (I), physiological saline (II), 2.8μgkg(-1) Se as SeMSC (III), 2.8μgkg(-1) Se as sodium selenite (Na2SeO3, IV), 5mgkg(-1) α-tocopherol as α-tocopherol acetate (Vit E, V), 5mgkg(-1) α-tocopherol as α-tocopherol acetate and 2.8μgkg(-1) Se as SeMSC (VI). All animals in groups II-VI were treated by ethanol treatment to cause oxidative stress. After 6h of ethanol treatment, the activities of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), the contents of total antioxidant capacity (T-AOC), malondialdehyde (MDA), glutathione (GSH) and carbonyl protein (CP) in the serum, liver, heart and kidney were measured. The result showed that the individual SeSMC, Na2SeO3 and vitamin E could effectively increase the SOD, T-AOC, GSH-Px and GSH contents as well as significantly decrease the MDA and CP concentrations in the tissues of ethanol-induced rats. At the same dose on different forms of Se, SeMSC showed greater antioxidant activity than Na2SeO3. Moreover, group VI (SeMSC and α-tocopherol acetate) showed much better antioxidant activity than individual group III (SeMSC) and V (α-tocopherol acetate) due to the synergistic effect.

Maintaining tissue selenium species distribution as a potential defense mechanism against methylmercury toxicity in juvenile white sturgeon (Acipenser transmontanus)

Selenium (Se) has been shown to antagonize mercury (Hg) toxicity. We have previously demonstrated that orally intubated selenomethionine (SeMet) and methylmercury (MeHg) reduced tissue Se accumulation, as well as blood and kidney Hg concentrations in juvenile white sturgeon (Acipenser transmontanus). However, the form of Se accumulated is not known. In this study, three organoseleniums: selenocysteine (Sec), Se-methyl-selenocysteine (MSeCys), and SeMet and two inorganic Se species: selenate and selenite were determined and quantified in the blood at different post-intubation periods (12, 24, 48h) and in the muscle, liver, and kidneys at 48h in white sturgeon orally intubated with a single dose of control (carrier), SeMet (500μg Se/kg body weight; BW), MeHg (850μg Hg/kg BW), and both (Se+Hg; at 500μg Se/kg and 850μg Hg/kg BW). When only SeMet was intubated, the accumulative/unmodified pathway took precedent in the blood, white muscle, liver, and kidneys. In the presence of MeHg, however, active metabolic transformation and de novo synthesis of biologically active Se forms are seen in the liver and kidneys, as indicated by a gradual increase in blood Sec:SeMet ratios and Se metabolites. In the white muscle, mobilization of endogenous Se storage by MeHg is supported by the absence of tissue SeMet and detectable levels of blood SeMet. In contrast, co-intubation with SeMet increased muscle SeMet. The high levels of unknown Se metabolites and detectable levels of selenite in the kidney reflect its role as the major excretory organ for Se. Selenium metabolism is highly regulated in the kidneys, as Se speciation was not affected by MeHg or by its co-intubation with SeMet. In the Se+Hg group, the proportion of SeMet in the liver has decreased to nearly 1/8th of that of the SeMet only group, resulting in a more similar selenocompound distribution profile to that of the MeHg only group. This is likely due to the increased need for Se metabolites necessary for MeHg demethylation in the liver. Our study demonstrated that in the presence of MeHg, regulating tissue Se speciation, hence, Se bioavailability, is more an important strategy than maintaining total Se levels in major organs of juvenile white sturgeon.

Large-scale, protection-free synthesis of Se-adenosyl-L-selenomethionine analogues and their application as cofactor surrogates of methyltransferases

S-adenosyl-L-methionine (SAM) analogues have previously demonstrated their utility as chemical reporters of methyltransferases. Here we describe the facile, large-scale synthesis of Se-alkyl Se-adenosyl-L-selenomethionine (SeAM) analogues and their precursor, Se-adenosyl-L-selenohomocysteine (SeAH). Comparison of SeAM analogues with their equivalent SAM analogues suggests that sulfonium-to-selenonium substitution can enhance their compatibility with certain protein methyltransferases, favoring otherwise less reactive SAM analogues. Ready access to SeAH therefore enables further application of SeAM analogues as chemical reporters of diverse methyltransferases.

Effects of selenium on development, survival, and accumulation in the honeybee (Apis mellifera L.)

Apis mellifera L. (Hymenoptera: Apidae) is an important agricultural pollinator in the United States and throughout the world. In areas of selenium (Se) contamination, honeybees may be at risk because of the biotransfer of Se from plant products such as nectar and pollen. Several forms of Se can occur in accumulating plants. In the present study, the toxicity of 4 compounds (selenate, selenite, methylselenocysteine, and selenocystine) to honeybee adult foragers and larvae was assessed using dose-response bioassays. Inorganic forms were more toxic than organic forms for both larvae (lethal concentration [LC50] selenate = 0.72 mg L(-1) , LC50 selenite = 1.0 mg L(-1) , LC50 methylselenocysteine = 4.7 mg L(-1) , LC50 selenocystine = 4.4 mg L(-1) ) and foragers (LC50 selenate = 58 mg L(-1) , LC50 selenite = 58 mg L(-1) , LC50 methylselenocysteine = 161 mg L(-1) , LC50 selenocystine = 148 mg L(-1) ). Inorganic forms of Se caused rapid mortality, and organic forms had sublethal effects on development. Larvae accumulated substantial amounts of Se only at the highest doses, whereas foragers accumulated large quantities at all doses. The present study documented very low larval LC50 values for Se; even modest transfer to brood will likely cause increased development times and mortality. The toxicities of the various forms of Se to honeybee larvae and foragers are discussed in comparison with other insect herbivores and detritivores.

Assessment of the anticancer compounds Se-methylselenocysteine and glucosinolates in Se-biofortified broccoli (Brassica oleracea L. var. italica) sprouts and florets

Broccoli (Brassica oleracea L. var. italica) is a rich source of chemopreventive compounds. Here, we evaluated and compared the effect of selenium (Se) treatment on the accumulation of anticancer compounds Se-methylselenocysteine (SeMSCys) and glucosinolates in broccoli sprouts and florets. Total Se and SeMSCys content in sprouts increased concomitantly with increasing Se doses. Selenate was superior to selenite in inducing total Se accumulation, but selenite is equally effective as selenate in promoting SeMSCys synthesis in sprouts. Increasing sulfur doses reduced total Se and SeMSCys content in sprouts treated with selenate, but not in those with selenite. Examination of five broccoli cultivars reveals that sprouts generally have better fractional ability than florets to convert inorganic Se into SeMSCys. Distinctive glucosinolate profiles between sprouts and florets were observed, and sprouts contained approximately 6-fold more glucoraphanin than florets. In contrast to florets, glucosinolate content was not affected by Se treatment in sprouts. Thus, Se-enriched broccoli sprouts are excellent for simultaneous accumulation of chemopreventive compounds SeMSCys and glucoraphanin.

Chemical characterisation and speciation of organic selenium in cultivated selenium-enriched Agaricus bisporus

The selenium concentration in Agaricus bisporus cultivated in growth compost irrigated with sodium selenite solution increased by 28- and 43-fold compared to the control mushroom irrigated solely with water. Selenium contents of mushroom proteins increased from 13.8 to 60.1 and 14.1 to 137 μgSe/g in caps and stalks from control and selenised mushrooms, respectively. Selenocystine (SeCys; detected as [SeCys]2 dimer), selenomethionine (SeMet), and methyl-selenocysteine (MeSeCys) were separated, identified and quantified by liquid chromatography-electrospray ionisation-mass spectrometry from water solubilised and acetone precipitated proteins, and significant increases were observed for the selenised mushrooms. The maximum selenoamino acids concentration in caps and stalks of control/selenised mushrooms was 4.16/9.65 μg/g dried weight (DW) for SeCys, 0.08/0.58 μg/g DW for SeMet, and 0.031/0.10 μg/g DW for MeSeCys, respectively. The most notable result was the much higher levels of SeCys accumulated by A. bisporus compared to SeMet and MeSeCys, for both control and selenised A. bisporus.

Combination effects of dietary soy and methylselenocysteine in a mouse model of prostate cancer

BACKGROUND

High dietary intake of soy or selenium (Se) is associated with decreased risk of prostate cancer. Soy constituents and various chemical forms of Se have each been shown to downregulate expression of the androgen receptor (AR) and AR-regulated genes in the prostate. We hypothesized that downregulation of AR and AR-regulated genes by the combination of these dietary components would inhibit tumorigenesis in the TRansgenic Adenocarcinoma of Mouse Prostate (TRAMP) mouse.

METHODS

Male mice were exposed from conception to stock diets high or low in soy, with or without a supplement of Se-methylseleno-L-cysteine (MSC) in a 2 × 2 factorial design. Mice were sacrificed at 18 weeks. Prostate histopathology, urogenital tract (UGT) weight, hepatic activity of androgen-metabolizing enzymes, and expression of AR, AR-regulated, and AR-associated FOX family genes, in the dorsolateral prostate were examined.

RESULTS

High soy intake decreased activity of hepatic aromatase and 5α-reductase, expression of AR, AR-regulated genes, FOXA1, UGT weight, and tumor progression, and upregulated protective FOXO3. Supplemental MSC upregulated AKR1C14, which reduces 5α-dihydrotestosterone.

CONCLUSIONS

Soy is an effective pleiotropic dietary agent for prevention of prostate cancer. The finding of effects of soy on FOX family gene expression in animals is novel. Combination effects of supplemental MSC may depend upon the soy content of the basal diet to which it is added.

Selenium metabolism in cancer cells: the combined application of XAS and XFM techniques to the problem of selenium speciation in biological systems

Determining the speciation of selenium in vivo is crucial to understanding the biological activity of this essential element, which is a popular dietary supplement due to its anti-cancer properties. Hyphenated techniques that combine separation and detection methods are traditionally and effectively used in selenium speciation analysis, but require extensive sample preparation that may affect speciation. Synchrotron-based X-ray absorption and fluorescence techniques offer an alternative approach to selenium speciation analysis that requires minimal sample preparation. We present a brief summary of some key HPLC-ICP-MS and ESI-MS/MS studies of the speciation of selenium in cells and rat tissues. We review the results of a top-down approach to selenium speciation in human lung cancer cells that aims to link the speciation and distribution of selenium to its biological activity using a combination of X-ray absorption spectroscopy (XAS) and X-ray fluorescence microscopy (XFM). The results of this approach highlight the distinct fates of selenomethionine, methylselenocysteine and selenite in terms of their speciation and distribution within cells: organic selenium metabolites were widely distributed throughout the cells, whereas inorganic selenium metabolites were compartmentalized and associated with copper. New data from the XFM mapping of electrophoretically-separated cell lysates show the distribution of selenium in the proteins of selenomethionine-treated cells. Future applications of this top-down approach are discussed.

The preventive effect of Se-methylselenocysteine on γ-radiation-induced oxidative stress in rat lungs

We investigated the preventive effect of Se-methylselenocysteine (MSC) administration on γ-radiation (whole body irradiation, single 10-Gy dose)-induced oxidative damage in rat lungs. Rats were pretreated with MSC (0.75mg/rat/day) for 1 week before γ-irradiation. The MSC pretreatment prevented the irradiation-induced increase in lipid peroxidation and the concomitant decrease in cellular glutathione content. The prevention of irradiation-induced oxidative damage in MSC-pretreated rat lungs appeared to be associated with increased antioxidant capacity, particularly in the glutathione system. The 1-week MSC treatment resulted in an increase in glutathione peroxidase, glutathione reductase, and glucose 6-phosphate dehydrogenase activities, which are involved in glutathione redox cycling. An increase in catalase activity was also observed in the rat lungs. Additionally, a significantly increased level of nuclear factor erythroid 2-related factor 2 (Nrf2) was exhibited in the MSC-treated rat lungs. Heme oxygenase 1, glutathione S-transferase pi, and peroxiredoxin 1, which are known target proteins of Nrf2, were also increased in MSC-treated lungs. These results implicate Nrf2 signaling in the MSC-induced activation of the antioxidant system.

Selenium for the prevention of cutaneous melanoma

The role of selenium (Se) supplementation in cancer prevention is controversial; effects often depend on the nutritional status of the subject and on the chemical form in which Se is provided. We used a combination of in vitro and in vivo models to study two unique therapeutic windows for intervention in the process of cutaneous melanomagenisis, and to examine the utility of two different chemical forms of Se for prevention and treatment of melanoma. We studied the effects of Se in vitro on UV-induced oxidative stress in melanocytes, and on apoptosis and cell cycle progression in melanoma cells. In vivo, we used the HGF transgenic mouse model of UV-induced melanoma to demonstrate that topical treatment with l-selenomethionine results in a significant delay in the time required for UV-induced melanoma development, but also increases the rate of growth of those tumors once they appear. In a second mouse model, we found that oral administration of high dose methylseleninic acid significantly decreases the size of human melanoma xenografts. Our findings suggest that modestly elevation of selenium levels in the skin might risk acceleration of growth of incipient tumors. Additionally, certain Se compounds administered at very high doses could have utility for the treatment of fully-malignant tumors or prevention of recurrence.

A reliable solid phase microextraction-gas chromatography-triple quadrupole mass spectrometry method for the assay of selenomethionine and selenomethylselenocysteine in aqueous extracts: difference between selenized and not-enriched selenium potatoes

A new analytical approach is exploited in the assay of selenium speciation in selenized and not selenium enriched potatoes based on the widely available solid-phase microextraction (SPME) coupled to-GC-triple quadrupole mass spectrometry (SPME-GC-QqQ MS) method. The assay of selenomethionine (SeMet) and selenomethylselenocysteine (SeMeSeCys) in potatoes here reported provides clues to the effectiveness of SPME technique combined with gas chromatography-tandem mass spectrometry, which could be of general use. For the exploitation of the GC method, the selected analytes were converted into their N(O,S)-alkoxycarbonyl alkyl esters derivatives by direct treatment with alkyl chloroformate in aqueous extracts. The performance of five SPME fibers and three chloroformates were tested in univariate mode and the best results were obtained using the divinylbenzene/carboxen/polydimethylsiloxane fiber and propylchloroformate. The variables affecting the efficiency of SPME analysis were optimized by the multivariate approach of design of experiment (DoE) and, in particular, a central composite design (CCD) was applied. Tandem mass spectrometry in selected reaction monitoring (SRM) has allowed the elimination of matrix interferences, providing reconstructed chromatograms with well-resolved peaks and the achievement of very satisfactory detection and quantification limits. Both precision and recovery of the proposed protocol tested at concentration of 8 and 40 μg kg(-1) (dry matter), offered values ranging from 82.3 to 116.3% and from 8.5 to 13.1% for recovery and precision, respectively. The application of the method to commercial samples of selenized and not selenium enriched potatoes proved that the Se fertilization increases significantly the concentration of these bioavailable selenoamino acids.

Selenium is a modulator of circadian clock that protects mice from the toxicity of a chemotherapeutic drug via upregulation of the core clock protein, BMAL1

Selenium compounds are known as cancer preventive agents and are also able to ameliorate the toxicity associated with anti-cancer radiation and chemotherapy in mouse models. Sensitivity to the toxicity of chemotherapy is also modulated by the circadian clock, molecular time-keeping system that underlie daily fluctuations in multiple physiological and biochemical processes. Here we show that these two mechanisms are interconnected. By screening a library of small molecules in a cell-based reporter system, we identified L-methyl-selenocysteine as a positive regulator of the core clock protein, BMAL1. L-methyl-selenocysteine up-regulates BMAL1 at the transcriptional level both in cultured cells and in mice. We also show that in tissue culture selenium exerts its action by interfering with TIEG1-mediated repression of Bmal1 promoter. Selenium treatment fails to protect BMAL1-deficient mice from toxicity induced by the chemotherapeutic agent cyclophosphamide but does protect Clock mutant mice deficient in circadian rhythm control but having normal BMAL1. These findings define selenium as circadian modulator and indicate that the tissue protective effect of selenium results, at least in part, from up-regulation of BMAL1 expression and subsequent enhancement of CLOCK/BMAL1-mediated transcription.

Methyl selenocysteine: single-dose pharmacokinetics in men

The recently published report of the SELECT evaluation of selenium and vitamin E provided strong evidence that selenium 200 μg per day in the form of selenomethionine does not protect selenium-replete men against prostate or any other cancer. This seems to refute the result of the much smaller Nutritional Prevention of Cancer (NPC) trial of selenium. Because SELECT did not test the NPC agent, it is possible that the difference between the two trials stems partly from the use of different agents: selenomethionine in SELECT, and selenized yeast in the NPC trial. One of the organic selenium forms suspected of having strong chemopreventive effects, and which may have been present in the NPC agent, is methyl selenocysteine. This study characterizes the single-dose pharmacokinetics of methyl selenocysteine.

Chemical form of selenium affects its uptake, transport, and glutathione peroxidase activity in the human intestinal Caco-2 cell model

Determining the effect of selenium (Se) chemical form on uptake, transport, and glutathione peroxidase activity in human intestinal cells is critical to assess Se bioavailability at nutritional doses. In this study, we found that two sources of L-selenomethionine (SeMet) and Se-enriched yeast each increased intracellular Se content more effectively than selenite or methylselenocysteine (SeMSC) in the human intestinal Caco-2 cell model. Interestingly, SeMSC, SeMet, and digested Se-enriched yeast were transported at comparable efficacy from the apical to basolateral sides, each being about 3-fold that of selenite. In addition, these forms of Se, whether before or after traversing from apical side to basolateral side, did not change the potential to support glutathione peroxidase (GPx) activity. Although selenoprotein P has been postulated to be a key Se transport protein, its intracellular expression did not differ when selenite, SeMSC, SeMet, or digested Se-enriched yeast was added to serum-contained media. Taken together, our data show, for the first time, that the chemical form of Se at nutritional doses can affect the absorptive (apical to basolateral side) efficacy and retention of Se by intestinal cells; but that, these effects are not directly correlated to the potential to support GPx activity.

Biofortification of tomato (Solanum lycopersicum) fruit with the anticancer compound methylselenocysteine using a selenocysteine methyltransferase from a selenium hyperaccumulator

Methylselenocysteine (MeSeCys) is an amino acid derivative that possesses potent anticancer activity in animals. Plants that can tolerate growth on soils with high Se content, known as Se hyperaccumulators, do so by converting inorganic Se to MeSeCys by the enzyme selenocysteine methyltransferase (SMT). A cDNA encoding the SMT from a Se hyperaccumulator was overexpressed in tomato (Solanum lycopersicum). Transgenic plants were provided with selenite or selenate to the roots during fruit development, and liquid chromatography-mass spectrometry was used to show that MeSeCys accumulated in the fruit but not in the leaves. Depending on the transgenic line and Se treatment, up to 16% of the total Se in the fruit was present as MeSeCys. MeSeCys was produced more effectively from selenite on a percentage conversion basis, but greater accumulation of MeSeCys could be achieved from selenate due to its better translocation from the roots. MeSeCys was heat stable and survived processing of the fruit to tomato juice.

Lobe-specific lineages of carcinogenesis in the transgenic adenocarcinoma of mouse prostate and their responses to chemopreventive selenium

BACKGROUND

The transgenic adenocarcinoma of mouse prostate (TRAMP) model is by far the most practical transgenic model for preclinical prostate cancer chemoprevention studies. It is critical to characterize the prostate lobe-specificity of lesion lineages to consolidate the advantages of this model and minimize its limitations for chemoprevention studies.

METHODS

We dissected dorsolateral (DLP), ventral (VP), and anterior prostate (AP) lobes, and macroscopic tumors from 90 male C57BL/6J TRAMP mice at 22-24 weeks of age (WOA) and analyzed lesions by histological, biochemical and proteomic approaches. To determine whether methylseleninic acid (MSeA) led to a deletion of initiated cells, we gave oral MSeA to TRAMP mice from 5 to 23 WOA or from 5 to 15 WOA and analyzed lesions at 23 WOA.

RESULTS

All tumors (n = 18) were T-antigen(+), synaptophysin (SYP)(+), androgen-receptor(-), and E-cadherin(-) poorly differentiated neuroendocrine carcinomas (NE-Ca). They were traceable most frequently to VP (66.7%) and rarely to DLP (11.1%) and AP (5.6%) with an estimated life-time incidence of 1 out of 3 mice. In DLP, epithelial lesions ranged from mild-to-severe atypical hyperplasia, with T-antigen(+), SYP(-), androgen-receptor(+), and E-cadherin(+). Proteomic profiling revealed many molecular differences between VP and DLP. In MSeA experiment, 6 out of 19 (31.5%) mice developed NE-Ca in the control group, only 2 in each MSeA group of 17-18 mice (11.1-11.8%) bore a detectable NE-Ca.

CONCLUSION

The C57BL/6J TRAMP mouse represents at least two lineages of prostate carcinogenesis. Chemoprevention studies should incorporate this knowledge for efficacy assessment and molecular target validations.

Distribution of Se and its species in Myriophyllum spicatum and Ceratophyllum demersum growing in water containing Se (VI)

The uptake of Se (VI) by two aquatic plants, Myriophyllum spicatum L. and Ceratophyllum demersum L., and its effects on their physiological characteristics have been studied. Plants were cultivated outdoors under semi-controlled conditions and in two concentrations of Na selenate solution (20 μg Se L(-1) and 10 mg Se L(-1)). The higher dose of Se reduced the photochemical efficiency of PSII in both species, while the lower dose had no effect on PSII. Addition of Se had no effect on the amounts of chlorophyll a and b. The concentration of Se in plants grown in 10 mg Se L(-1), averaged 212 ± 12 μg Seg(-1) DM in M. spicatum (grown from 8-13 d), and 492 ± 85 μg Se g(-1) DM in C. demersum (grown for 31 d). Both species could take up a large amount of Se. The amount of soluble Se compounds in enzyme extracts ranged from 16% to 26% in control, and in high Se solution from 48% to 36% in M. spicatum and C. demersum, respectively. Se-species were determined using HPLC-ICP-MS. The main soluble species in both plants was selenate (∼37%), while SeMet and SeMeSeCys were detected at trace levels.

The von Hippel-Lindau (VHL) tumor-suppressor gene is down-regulated by selenium deficiency in Caco-2 cells and rat colon mucosa

To test the hypothesis that selenium affects DNA methylation and hence gene regulation, we employed a methylation array (Panomics) in the human colonic epithelial Caco-2 cell model. The array profiles DNA methylation from promoter regions of 82 human genes. After conditioning cells to repeatedly reduced concentrations of fetal bovine serum, a serum-free culture was established. Se-methylselenocysteine (SeMSC) was added at 0 (deficient Se) or 250 (control Se) nM to cells maintained in DMEM. After 7 days, cells were collected and stored at -80 °C until analysis; experiments were replicated three times. Glutathione peroxidase activity was significantly decreased in cells grown in low SeMSC. Cells grown in 250 nM SeMSC had maximal GPx activity. Genomic DNA from cells grown in the low-SeMSC media and media containing 250 nM SeMSC was incubated with methylation-binding protein followed by isolation of methylated DNA. The methylated DNA was labeled with biotin and hybridized to the methylation array. Thus, genes with promoter methylation will produce a higher chemiluminescence signal than those genes with no promoter methylation. Of the genes profiled, the von Hippel-Lindau (VHL) gene was most different as indicated by quantification following chemiluminescence detection demonstrating that the promoter region of VHL was hypermethylated in cells from the low-SeMSC media. To determine whether promoter methylation affected transcription, we isolated RNA from replicate samples and performed real-time RT PCR. VHL (mRNA) was down-regulated (fold change significantly <1) in cells grown in low SeMSC compared to cells grown in 250 nM SeMSC (control; fold change = 1). We also show that (mRNA) Vhl expression is significantly reduced in mucosa from rats fed a diet deficient in Se. Our results suggest that low Se status affects DNA promoter region methylation and that this can result in down-regulation of the tumor suppressor gene VHL.

Anti-hemolytic and peroxyl radical scavenging activity of organoselenium compounds: an in vitro study

Selenium-containing amino acids, selenocystine (CysSeSeCys), methylselenocysteine (MeSeCys), and selenomethionine (SeMet) have been examined for anti-hemolytic and peroxyl radical scavenging ability. Effect of these compounds on membrane lipid peroxidation, release of hemoglobin, and loss of intracellular K(+) ion as a consequence of peroxyl radicals-induced oxidation of human red blood cells were used to evaluate their anti-hemolytic ability. The peroxyl radicals were generated from thermal degradation of 2,2'-azobis(2-methylpropionamidine) dihydrochloride. Significant delay (t(eff)) was observed in oxidative damage in the presence of the selenium compounds. From the IC(50) values for the inhibition of hemolysis, lipid peroxidation, and K(+) ion leakage, the relative anti-hemolytic ability of the compounds were found to be in the order of CysSeSeCys > MeSeCys > SeMet. The anti-hemolytic abilities of the compounds, when compared with sodium selenite (Na(2)SeO(3)) under identical experimental conditions, were found to be better than Na(2)SeO(3). Relative rate constants estimated for the reaction of MeSeCys and SeMet with peroxyl radicals by competition kinetics using ABTS(2-) as a reference confirmed that all the compounds are efficient peroxyl radical scavengers. Comparison of the GPx-like activity of these compounds, by NADPH-GSH reductase coupled assay, indicated that CysSeSeCys exhibits the highest activity. Based on these results, it is concluded that among the compounds examined, CysSeSeCys, possessing the ability to reduce peroxyl radicals and hydroperoxides showed efficient anti-hemolytic activity.

Magnetic resonance and fluorescence-protein imaging of the anti-angiogenic and anti-tumor efficacy of selenium in an orthotopic model of human colon cancer

Tumor progression and angiogenesis are intimately related. To understand the interrelationship between these two processes, real-time imaging can make a major contribution. In this report, fluorescent protein imaging (FPI) and magnetic resonance imaging (MRI) were utilized to demonstrate the effects of selenium on tumor progression and angiogenesis in an orthotopic model of human colon cancer. GEO (well-differentiated human colon carcinoma) cells transfected with green fluorescent protein (GFP) were implanted orthotopically into the colon of athymic nude mice. Beginning at five days post implantation, whole-body FPI was performed to monitor tumor growth in vivo. Upon successful visualization of tumor growth by FPI, animals were randomly assigned to either a control group or a treatment group. Treatment consisted of daily oral administration of the organoselenium compound, methyl-selenocysteine (MSC; 0.2 mg/day × five weeks). Dynamic contrast-enhanced MRI was performed to examine the change in tumor blood volume following treatment. CD31 immunostaining of tumor sections was also performed to quantify microvessel density (MVD). While T1- and T2-weighted MRI provided adequate contrast and volumetric assessment of GEO tumor growth, GFP imaging allowed for high-throughput visualization of tumor progression in vivo. Selenium treatment resulted in a significant reduction in blood volume and microvessel density of GEO tumors. A significant inhibition of tumor growth was also observed in selenium-treated animals compared to untreated control animals. Together, these results highlight the usefulness of multimodal imaging approaches to demonstrate antitumor and anti-angiogenesis efficacy and the promise of selenium treatment of colon cancer.

Interleukin-10 delivery via mesenchymal stem cells: a novel gene therapy approach to prevent lung ischemia-reperfusion injury

Ischemia-reperfusion (IR) injury is an important cause of primary graft failure in lung transplantation. In this study, viral interleukin-10 (vIL-10)-engineered mesenchymal stem cells (MSCs) were tested for their ability to prevent lung IR injury. Bone marrow-derived MSCs were transduced with rvIL-10-retrovirus. After 120 min of warm left lung ischemia, rats received approximately 15 x 10(6) vIL-10-engineered MSCs (MSC-vIL-10), empty vector-engineered MSCs (MSC-vec), or saline intravenously. Mean blood oxygenation (PaO(2)/FiO(2) ratio, mmHg) was measured at 4 hr, 24 hr, 72 hr, and 7 days. As early as 4 hr post-IR injury with MSC-vIL-10 treatment, blood oxygenation was significantly (p < 0.05) improved (319 +/- 94; n = 7) compared with untreated (saline) controls (63 +/- 19; n = 6). At 24 hr post-IR injury, in the MSC-vIL-10-treated group there was a further increase in blood oxygenation (353 +/- 105; n = 10) compared with the MSC-vec group (138 +/- 86; n = 9) and saline group (87 +/- 39; n = 10). By 72 hr, oxygenation reached normal (475 +/- 55; n = 9) in the MSC-vIL-10-treated group but not in the saline-treated and MSC-vec-treated groups. At 4 hr after IR injury, lungs with MSC-vIL10 treatment had a lower (p < 0.05) injury score (0.9 +/- 0.4) compared with lungs of the untreated (saline) group (2.5 +/- 1.4) or MSC-vec-treated group (2 +/- 0.4). Lung microvascular permeability and wet-to-dry weight ratios were markedly lower in the MSC-vIL10 group compared with untreated (saline) controls. ISOL (in situ oligonucleotide ligation for DNA fragmentation detection) and caspase-3 staining demonstrated significantly (p < 0.05) fewer apoptotic cells in MSC-vIL10-treated lungs. Animals that received MSC-vIL10 therapy had fewer (p < 0.05) CD4(+) and CD8(+) T cells in bronchoalveolar lavage fluid compared with untreated control animals. A therapeutic strategy using vIL-10-engineered MSCs to prevent IR injury in lung transplantation seems promising.

Selenium hyperaccumulation offers protection from cell disruptor herbivores

BACKGROUND

Hyperaccumulation, the rare capacity of certain plant species to accumulate toxic trace elements to levels several orders of magnitude higher than other species growing on the same site, is thought to be an elemental defense mechanism against herbivores and pathogens. Previous research has shown that selenium (Se) hyperaccumulation protects plants from a variety of herbivores and pathogens. Selenium hyperaccumulating plants sequester Se in discrete locations in the leaf periphery, making them potentially more susceptible to some herbivore feeding modes than others. In this study we investigate the protective function of Se in the Se hyperaccumulators Stanleya pinnata and Astragalus bisulcatus against two cell disrupting herbivores, the western flower thrips (Frankliniella occidentalis) and the two-spotted spider mite (Tetranychus urticae).

RESULTS

Astragalus bisulcatus and S. pinnata with high Se concentrations (greater than 650 mg Se kg(-1)) were less subject to thrips herbivory than plants with low Se levels (less than 150 mg Se kg(-1)). Furthermore, in plants containing elevated Se levels, leaves with higher concentrations of Se suffered less herbivory than leaves with less Se. Spider mites also preferred to feed on low-Se A. bisulcatus and S. pinnata plants rather than high-Se plants. Spider mite populations on A. bisulcatus decreased after plants were given a higher concentration of Se. Interestingly, spider mites could colonize A. bisulcatus plants containing up to 200 mg Se kg(-1) dry weight, concentrations which are toxic to many other herbivores. Selenium distribution and speciation studies using micro-focused X-ray fluorescence (μXRF) mapping and Se K-edge X-ray absorption spectroscopy revealed that the spider mites accumulated primarily methylselenocysteine, the relatively non-toxic form of Se that is also the predominant form of Se in hyperaccumulators.

CONCLUSIONS

This is the first reported study investigating the protective effect of hyperaccumulated Se against cell-disrupting herbivores. The finding that Se protected the two hyperaccumulator species from both cell disruptors lends further support to the elemental defense hypothesis and increases the number of herbivores and feeding modes against which Se has shown a protective effect. Because western flower thrips and two-spotted spider mites are widespread and economically important herbivores, the results from this study also have potential applications in agriculture or horticulture, and implications for the management of Se-rich crops.

Selenium, but not lycopene or vitamin E, decreases growth of transplantable dunning R3327-H rat prostate tumors

Background

Lycopene, selenium, and vitamin E are three micronutrients commonly consumed and supplemented by men diagnosed with prostate cancer. However, it is not clear whether consumption of these compounds, alone or in combination, results in improved outcomes.

Methodology/Principal Findings

We evaluated the effects of dietary lycopene (250 mg/kg diet), selenium (methylselenocysteine, 1 mg/kg diet), and vitamin E (γ-tocopherol, 200 mg/kg diet) alone and in combination on the growth of androgen-dependent Dunning R3327-H rat prostate adenocarcinomas in male, Copenhagen rats. AIN-93G diets containing these micronutrients were prefed for 4 to 6 weeks prior to tumor implantation by subcutaneous injection. Tumors were allowed to grow for ∼18 weeks. Across diet groups, methylselenocysteine consumption decreased final tumor area (P = 0.003), tumor weight (P = 0.003), and the tumor weight/body weight ratio (P = 0.003), but lycopene and γ-tocopherol consumption intake did not alter any of these measures. There were no significant interactions among nutrient combinations on tumor growth. Methylselenocysteine consumption also led to small, but significant decreases in body weight (P = 0.007), food intake (P = 0.012), and body weight gain/food intake ratio (P = 0.022). However, neither body weight nor gain/food intake ratio was correlated with tumor weight. Methylselenocysteine, lycopene, and γ-tocopherol consumed alone and in combination did not alter serum testosterone or dihydrotestosterone concentrations; tumor proliferation or apoptosis rates. In addition, the diets also did not alter tumor or prostate androgen receptor, probasin, selenoprotein 15, selenoprotein P, or selenium binding protein 2 mRNA expression. However, using castration and finasteride-treated tissues from a previous study, we found that androgen ablation altered expression of these selenium-associated proteins.

Conclusions

Of the three micronutrients tested, only methylselenocysteine consumption reduced growth of transplantable Dunning R3327-H prostate tumors, albeit through an unresolved mechanism.

Differential apoptotic response of human cancer cells to organoselenium compounds

PURPOSE

Selenium (Se) compounds are well known to inhibit cell proliferation and induce cell death in human cancer cells. Respective chemical forms of Se are intracellularly metabolized via complicated pathways, which target distinct molecules and exhibit varying degrees of anti-carcinogenicity in different cancer types; however, the precise mechanisms by which Se activates apoptosis remain poorly understood.

METHODS

The effects of Se compounds, Se-methylselenocysteine (MSC), selenomethionine (SeMet), and selenite on cell proliferation, apoptosis and its pathway in established human carcinoma cell lines (HSC-3, -4, A549, and MCF-7) were investigated. Cancer cells were treated with each Se compound during different periods. Cell apoptosis, caspase activity and ER stress markers were analyzed by flow cytometric or immunoblotting analysis, respectively.

RESULTS

We examined four cell lines for their sensitivity to MSC and SeMet in comparison with selenite. SeMet increased apoptotic cells in p53-positive A549 cells, whereas MSC increased apoptotic cells in p53-mutated HSC-3 cells. High activities of caspase-3, -8 and -9 were observed during apoptosis, and a pan-caspase inhibitor, z-VAD-fmk, rescued the cell viability of HSC-3 cells exposed to MSC. In addition, the occurrence of endoplasmic reticulum (ER) stress was suggested by the observation that levels of phosphorylated eIF2alpha and caspase-12 activity are increased in Se-treated cells. Selenite and MSC were accompanied with the concurrent reduction of phosphorylated Akt levels, and the inhibitory effects of these Se compounds on vascular endothelial growth factor expression were observed with identical patterns.

CONCLUSION

The present findings demonstrate that Se-induced apoptosis in carcinoma cells is basically a caspase-dependent process involving complicated mechanisms. Activation of both the intrinsic apoptotic pathway and ER stress pathway plays a major and concurrent role, while p53 activation seems to have only a functional role in SeMet.

In vitro radioprotection studies of organoselenium compounds: differences between mono- and diselenides

Organoselenium compounds belonging to the class of monoselenides, such as selenomethionine (SeM) and methylselenocysteine (MSeCys) and diselenides including selenocystine (SeCys) and selenopropionic acid (SePA), were examined for their comparative radioprotective effects using in vitro models. Effects of these compounds on the inhibition of gamma-radiation induced lipid peroxidation in liposomes, protein carbonylation in bovine serum albumin (BSA) and strand breaks in pBR322 plasmid DNA, assessed, respectively, by the formation of thiobarbituric acid reactive substances, formation of 2,2'-dinitrophenyl hydrazine (DNPH) carbonyl complex and horizontal gel electrophoresis, were used to compare their radioprotective ability. The IC 50 values for SeCys, SePA, SeM and MSeCys for lipid peroxidation were 27 +/- 1, 33 +/- 2, 200 +/- 8 and 163 +/- 4 microM, respectively, and the values for inhibition of protein carbonylation were >200, 300 +/- 6, 464 +/- 8 and 436 +/- 3 microM, respectively. Inhibition of DNA strand break formation was tested at 200 microM for all the compounds and SePA and SeCys exhibited a protective effect on DNA, while SeM and MSeCys did not lead to any protection. The in vitro cytotoxicity studies in normal and tumor cells revealed that MSeCys and SeM were not cytotoxic to lymphocytes and EL4 tumor cells at the concentrations employed. In contrast, SeCys was toxic, with a higher effect on tumor cells than lymphocytes. Our studies suggest that the non-toxic diselenides like SePA should be explored as protective agents against gamma-irradiation induced damage.

Organic and inorganic selenium compounds produce different protein patterns in the blood plasma of rats

Some selenium compounds offer important health benefits when administered at supranutritional doses, such as improvement of the immune system and of male fertility, and the prevention of some types of cancer. The traditional selenium indexes do not account for the metabolic status of this element among replete individuals. As a consequence, there is a need for new indexes that distinguish between repletion statuses of selenium. The aim of this work was to identify some plasmatic proteins that respond to supranutritional doses of selenium, which could be proposed as new protein markers of selenium intake. The effect on rats of dietary supplementation with either selenomethylselenocysteine (SMSeC) or sodium-selenate on some blood plasma proteins was investigated. Two experimental groups consisting of six rats each were fed a basic diet supplemented with either SMSeC or sodium-selenate at 1.9 microg-Se / g-diet for ten weeks. The control group was fed a diet that contained the recommended selenium dose (0.15 microg-Se / g-diet). The changes in the abundance of a group of plasmatic proteins were quantified and analysed statistically. Haptoglobin, apolipoprotein E and transthyretin increased their abundance after diet supplementation with either form of selenium. HNF6 was responsive only to SMSeC, whereas fibrinogen responded only to sodium-selenate. We postulate that the protein patterns observed in this work could be proposed as new molecular biology-based markers of selenium intake.

Inhibition of colon cancer growth by methylselenocysteine-induced angiogenic chemomodulation is influenced by histologic characteristics of the tumor

Despite an armamentarium that is wide in range, scope of action, and target, chemotherapy has limited success in colorectal cancer (CRC). Novel approaches are needed to overcome tumor barriers to chemotherapy that includes an abnormal tumor vasculature constituting a poor drug delivery system. We have previously shown that 5-methylselenocysteine (MSC) enhances therapeutic efficacy of irinotecan in various human tumor xenografts. We have recently demonstrated that MSC through vascular normalization leads to better tumor vascular function in vivo. In this study, we examined the role of MSC on tumor vasculature, interstitial fluid pressure (IFP) and drug delivery in 2 histologically distinct CRC xenografts, HCT-8 (uniformly poorly differentiated) and HT-29 (moderately differentiated tumor with avascular glandular regions). The presence of specific histologic structures as a barrier to therapy in these xenografts and their clinical relevance was studied using tissue microarray of human surgical samples of CRC. MSC led to a significant tumor growth inhibition, a reduced microvessel density, and a more normalized vasculature in both colorectal xenografts. While IFP was found to be significantly improved in HCT-8, an improved intratumoral doxorubicin delivery seen in both xenografts could explain the observed increase in therapeutic efficacy. Differentiated, glandular, avascular and hypoxic regions that contribute to tumor heterogeneity in HT-29 were also evident in the majority of surgical samples of CRC. Such regions constitute a physical barrier to chemotherapy and can confer drug resistance. Our results indicate that MSC could enhance chemotherapeutic efficacy in human CRC, especially in CRC with few or no hypoxic regions.

Accumulation of an organic anticancer selenium compound in a transgenic Solanaceous species shows wider applicability of the selenocysteine methyltransferase transgene from selenium hyperaccumulators

Tolerance to high selenium (Se) soils in Se-hyperaccumulating plant species is correlated with the ability to biosynthesise methylselenocysteine (MeSeCys), due to the activity of selenocysteine methyltransferase (SMT). In mammals, inclusion of MeSeCys in the diet reduces the incidence of certain cancers, so increasing the range of crop plants that can produce this compound is an attractive biotechnology target. However, in the non-Se accumulator Arabidopsis, overexpression of SMT does not result in biosynthesis of MeSeCys from selenate because the rate at which selenate is reduced to selenite by ATP sulfurylase (ATPS) is low. This limitation is less problematic in other species of the Brassicaceae that can produce MeSeCys naturally. We investigated the potential for biosynthesis of MeSeCys in other plant families using Nicotiana tabacum L., a member of the Solanaceae. When plants were watered with 200 microM selenate, overexpression of a SMT transgene caused a 2- to 4-fold increase in Se accumulation (resulting in increased numbers of leaf lesions and areas of necrosis), production of MeSeCys (up to 20% of total Se) and generation of volatile dimethyl diselenide derived directly from MeSeCys. Despite the greatly increased accumulation of total Se, this did not result in increased Se toxicity effects on growth. Overexpression of ATPS did not increase Se accumulation from selenate. Accordingly, lines overexpressing both ATPS and SMT did not show a further increase in total Se accumulation or in leaf toxicity symptoms relative to overexpression of SMT alone, but directed a greater proportion of Se into MeSeCys. This work demonstrates that the production of the cancer-preventing compound MeSeCys in plants outside the Brassicaceae is possible. We conclude that while the SMT gene from Se hyperaccumulators can probably be utilised universally to increase the metabolism of Se into MeSeCys, the effects of enhancing ATPS activity will vary depending on the species involved.

Separation and determination of seleno amino acids using gas chromatography hyphenated with inductively coupled plasma mass spectrometry after hollow fiber liquid phase microextraction

A new derivatization-extraction method for preconcentration of seleno amino acids using hollow fiber liquid phase microextraction (HF-LPME) was developed for the separation and determination of seleno amino acids in biological samples by gas chromatography-inductively coupled plasma mass spectrometry (GC-ICP-MS). Derivatization was performed with ethyl chloroformate (ECF) to improve the volatility of seleno amino acids. Parameters influencing microextraction, including extraction solvent, pH of sample solution, extraction time, stirring speed, and inorganic salt concentration have been investigated. Under the optimal conditions, the limits of detection (LODs) obtained for Se-methyl-selenocysteine (SeMeCys), selenomethionine (SeMet), and selenoethionine (SeEth) were 23, 15, and 11 ng Se l(-1), respectively. The relative standard deviations (RSDs) were 14.6%, 16.4%, and 19.4% for SeMeCys, SeMet, and SeEth (c = 1.0 ng ml(-1), n = 7), respectively, and the RSDs for SeMeCys, SeMet could be improved obviously if SeEth was utilized as the internal standard. The proposed method was applied for the determination of seleno amino acids in extracts of garlic, cabbage, and mushroom samples, and the recoveries for the spiked samples were in the range of 96.8-108% and 93.4-115% with and without the use of SeEth as internal standard. The developed method was also applied to the analysis of SeMet in a certified reference material of SELM-1 yeast and the determined value is in good agreement with the certified value.

Se-methylselenocysteine sensitized TRAIL-mediated apoptosis via down-regulation of Bcl-2 expression

Recent studies establish a critical role of selenium in cancer prevention in vitro and in vivo. Selenium may sensitize TRAIL-mediated apoptosis in human renal cancer cells and increase therapeutic efficacy. In this study, we demonstrate that concomitant administration of TRAIL and Se-methylselenocysteine (Se-MSC) produces synergistic effects on the induction of apoptosis in Caki cells. Se-MSC rapidly and specifically down-regulates expression of the Bcl-2 at transcriptional level. The forced expression of Bcl-2 attenuated Se-MSC plus TRAIL-mediated apoptosis, suggesting that the lessened Bcl-2 expression caused by Se-MSC treatment is critical to the increased sensitivity to TRAIL in renal cancer cells. In addition, we demonstrate that the synergistic effects of Se-MSC and TRAIL result from the activation of the caspase-dependent pathways. Co-administration of HA14-1, a small molecule Bcl-2 inhibitor and TRAIL increased apoptosis in Caki cells. Taken together, Se-MSC-mediated down-regulation of Bcl-2 is able to sensitize Caki cells for TRAIL-induced apoptosis. Thus, selenium-based dietary compounds may help to overcome resistance to TRAIL-mediated apoptosis in renal cancer cells.

[Effects of Se-methylselenocysteine on biological behavior of and matrix metalloproteinase-2 expression in human breast cancer MDA-MB-231 cells]

BACKGROUND & OBJECTIVE

Se-methylselenocysteine (MSC), a natural organoselenium compound, has functions on chemoprevention and treatment of many tumors, but the mechanism remains unclear. This study was to investigate the effects of MSC on the biological behavior of and matrix metalloproteinase-2 (MMP-2) expression in human breast cancer MDA-MB-231 cells.

METHODS

After treatment of MSC, the proliferation and apoptosis of MDA-MB-231 cells were detected with light microscope and Cell Counting Kit-8 (CCK-8), cell cycle and apoptosis were determined by flow cytometry, malignant phenotype was determined by soft agarose growth assay, and the expression of MMP-2 was determined by reverse transcription-polymerase chain reaction (RT-PCR) and Western blot. The concentration of MMP-2 protein in culture supernatant was measured with enzyme-linked immunosorbent assay (ELISA).

RESULTS

MSC induced S phase arrest and apoptosis, inhibited the proliferation and colony formation of MDA-MB-231 cells. When treated with 50 mumol/L MSC for 48 h and 72 h, the mRNA levels of MMP-2 were up-regulated by 32.2% and 47.1%, whereas its protein levels were down-regulated by 42.4% and 50.8%, its concentrations in culture supernatant were down-regulated by 56.7% and 75.2%. When treated with 100 mumol/L MSC for 48 h and 72 h, the mRNA levels of MMP-2 were up-regulated by 52.6% and 61.3%, whereas its protein levels were down-regulated by 72.9% and 81.4%, and its concentrations in culture supernatant were down-regulated by 68.5% and 80.9%.

CONCLUSIONS

MSC could inhibit proliferation, and induce apoptosis and S phase arrest in MDA-MB-231 cells. MSC could also up-regulate the mRNA level of MMP-2 while down-regulate its protein level and secretion in the cells.

Elemental selenium at nano size (Nano-Se) as a potential chemopreventive agent with reduced risk of selenium toxicity: comparison with se-methylselenocysteine in mice

Selenium (Se) is an essential trace element with a narrow margin between beneficial and toxic effects. As a promising chemopreventive agent, its use requires consumption over the long term, so the toxicity of Se is always a crucial concern. Based on clinical findings and recent studies in selenoprotein gene-modified mice, it is likely that the antioxidant function of one or more selenoproteins is responsible for the chemopreventive effect of Se. Furthermore, upregulation of phase 2 enzymes by Se has been implicated as a possible chemopreventive mechanism at supranutritional dietary levels. Se-methylselenocysteine (SeMSC), a naturally occurring organic Se product, is considered as one of the most effective chemopreventive selenocompounds. The present study revealed that, as compared with SeMSC, elemental Se at nano size (Nano-Se) possessed equal efficacy in increasing the activities of glutathione peroxidase, thioredoxin reductase, and glutathione S-transferase, but had much lower toxicity as indicated by median lethal dose, acute liver injury, survival rate, and short-term toxicity. Our results suggest that Nano-Se can serve as a potential chemopreventive agent with reduced risk of Se toxicity.