Preclinical Evaluation of Sodium Selenite in Mice: Toxicological and Tumor Regression Studies after Striatum Implantation of Human Glioblastoma Stem Cells.

Glioblastoma (GBM) is the most aggressive malignant glioma, with a very poor prognosis; as such, efforts to explore new treatments and GBM's etiology are a priority. We previously described human GBM cells (R2J-GS) as exhibiting the properties of cancer stem cells (growing in serum-free medium and proliferating into nude mice when orthotopically grafted). Sodium selenite (SS)-an in vitro attractive agent for cancer therapy against GBM-was evaluated in R2J-GS cells. To go further, we launched a preclinical study: SS was given orally, in an escalation-dose study (2.25 to 10.125 mg/kg/day, 5 days on, 2 days off, and 5 days on), to evaluate (1) the absorption of selenium in plasma and organs (brain, kidney, liver, and lung) and (2) the SS toxicity. A 6.75 mg/kg SS dose was chosen to perform a tumor regression assay, followed by MRI, in R2J-GS cells orthotopically implanted in nude mice, as this dose was nontoxic and increased brain selenium concentration. A group receiving TMZ (5 mg/kg) was led in parallel. Although not reaching statistical significance, the group of mice treated with SS showed a slower tumor growth vs. the control group (p = 0.08). No difference was observed between the TMZ and control groups. We provide new insights of the mechanisms of SS and its possible use in chemotherapy.

Optimization of elemental selenium (Se(0)) determination in yeasts by anion-exchange HPLC-ICP-MS.

An analytical method was developed for the speciation of elemental selenium (Se(0)) in selenized yeasts by anion-exchange HPLC-ICP-MS after its chemical transformation into SeSO32- by reaction with sodium sulfite. The presence of Se(0) in the yeasts was further confirmed by single-particle ICP-MS. Indeed, Se nanoparticles, if present, are expected to be, at least partly, Se(0). X-ray photoelectron spectroscopy, a well-recognized technique for chemical element speciation in the solid state, was also used with this objective. Both methods were able to confirm the presence of Se(0) in the selenized yeasts but failed to provide reliable quantitative results. Analytical performances of the HPLC-ICP-MS method were then evaluated for Se(0) determination. Quantification limits of 1 mg/kg were reached. The recovery levels from an added quantity comprised between 93 and 101%. Within-run and between-run precisions were both below 8%. The procedure developed was finally applied to quantify Se(0) content in a series of seven yeast batches from different suppliers. Se(0) was found to be present in all the studied yeasts and represented on average 10-15% of the total Se.

Total Selenium Quantification in Biological Samples by Inductively Coupled Plasma Mass Spectrometry (ICP-MS).

Selenium (Se) is an element readily absorbed during the intestinal tract, distributed in the body by means of blood and excreted mainly by urine or feces. Here, we describe the method allowing the determination of the total Se content in biological tissues and fluids by Inductively Coupled Plasma Mass Spectrometry (ICP MS).

Determination of Zn-, Cu- and Mn-glycinate complexes in feed samples and in-vitro and in-vivo assays to assess their bioaccessibility in feed samples.

A method was developed for the quantification of Zn-, Cu- and Mn-glycinates in supplemented feed samples. The coupling of capillary electrophoresis (CE) with ICP MS detection after purification of the extract by ultrafiltration was shown to be efficient for the quantitative recovery of glycinates. The method developed was then applied to evaluate the bioaccessibility of glycinates using a sequential enzymolysis approach. The data obtained indicated a strong bioaccessibility of each element (79-94%). A new complex was also found to be formed during the digestion process. Bioavailability was then evaluated by analyzing plasma samples of horses supplemented with glycinates-rich feed. Intact glycinates could not be detected in plasma samples but a Cu-containing molecule was found more abundant after CuGly treatment.

Comparative study of a new organic selenium source v. seleno-yeast and mineral selenium sources on muscle selenium enrichment and selenium digestibility in broiler chickens.

Two experiments were conducted on broiler chickens to compare the effect of a new organic Se source, 2-hydroxy-4-methylselenobutanoic acid (HMSeBA; SO), with two practical Se additives, sodium selenite (SS) and Se yeast (SY). The relative bioavailability of the different Se sources was compared on muscle (pectoralis major) total Se, selenomethionine (SeMet) and selenocysteine (SeCys) concentrations and apparent digestibility of total Se (ADSe). In the first experiment, from day (d) 0 to d21, Se sources were tested at different supplied levels and compared with an unsupplemented diet (NC). No significant effects were observed on growth performance during the experimental period. However, the different Se sources and levels improved muscle Se concentration compared with the NC, with a significant source effect in the following order: SS < SY < SO (P<0·05). Seleno-amino acids speciation results for NC, SY and SO at 0·3 mg Se/kg feed indicated that muscle Se was only present as SeMet or SeCys, showing a full conversion of Se by the bird. The second experiment (d0-d24) compared SS, SY or SO at 0·3 mg Se/kg feed. The ADSe measurements carried out between d20 and d23 were 24, 46 and 49% for SS, SY and SO, respectively, with significant differences between the organic and mineral Se sources (P<0·05). These results confirmed the higher bioavailability of organic Se sources compared with the mineral source and demonstrated a significantly better efficiency of HMSeBA compared with SY for muscle Se enrichment.

Characterization of metal glycinate complexes by electrospray Q-TOF-MS/MS and their determination by capillary electrophoresis-ICP-MS: application to premix samples.

A method was developed for the determination of metal complexes with glycine (glycinates, [M(Gly)(x)(H(2)O)(y)(SO(4))(z)](n), where M denotes Zn, Cu, Mn and Fe) in premix samples used for the preparation of animal feeds enriched in essential trace elements. The method was based on the extraction of the glycinates with 10 mM ammonium acetate (pH 7.4) followed by their determination using capillary electrophoresis with ICP MS detection. The stability of the glycinates in solution was verified by electrospray TOF-MS. Each supplement was shown to be a mixture of complexes, with polymerization degrees ranging from n = 1 to n = 4 (depending on the metal), that were fully or partially dehydrated. The metal glycine complex moiety was found to be preserved during capillary electrophoresis. The detection limits, calculated as three times the standard deviation of the blank plus the blank, were between 0.05 and 0.2 microg mL(-1) (as the metal), and the calibration curves were linear, allowing the analysis of premix samples. Repeatability for glycinate standards was below 12%, and analytical precision was typically within 15%.

Determination of selenocysteine and selenomethionine in edible animal tissues by 2D size-exclusion reversed-phase HPLC-ICP MS following carbamidomethylation and proteolytic extraction.

A method was developed for the simultaneous determination of selenomethionine (SeMet) and selenocysteine (SeCys) in meat (chicken and lamb muscles) and different offal tissues (heart, liver, kidney). The analytical procedure was based on the protein extraction with urea under reducing conditions (dithiothreitol), derivatization of SeCys and SeMet by carbamidomethylation with iodoacetamide (IAM) followed by quantitative proteolysis. The mixture of the derivatized Se-amino acids was purified by size-exclusion liquid chromatography (LC) and analysed by ion-paring reversed-phase HPLC-inductively coupled plasma mass spectroscopy (ICP MS). The quantification of SeCys and SeMet was carried out by the method of standard additions. (77)SeMet was used to control the SeMet derivatization efficiency and recovery. The method was validated by the determination of the Se mass balance. The Se-amino acids accounted for 91 +/- 8% of the total selenium (mean of 95 samples of seven tissues analysed over a period of 18 months). The method was applied to the discrimination of the contribution of selenoproteins (containing SeCys) and other Se-containing proteins (containing SeMet) in tissues of animals during supplementation studies (dose-effect and tolerance).