Single-cell ICP-MS for evaluating the Se-protective effect against MeHg+-induced neurotoxicity in human neuroblastoma cell line (SH-SY5Y)

The protective effect of selenium (Se) against Hg-induced neurotoxicity has been widely investigated; however, the mechanisms behind this interaction have not been fully elucidated yet. In the current work, the role of Se against MeHg+-induced cytotoxicity in the human neuroblastoma cell line (SH-SY5Y) is reported for the first time by tracking Hg uptake and accumulation at the single-cell level by inductively coupled plasma-mass spectrometry in single-cell mode (SC-ICP-MS). The influence of different Se species (SeMet, SeMeSeCys, citrate-SeNPs, and chitosan-SeNPs) on MeHg+ cytotoxicity was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays. SeMet and SeMeSeCys exhibited protective effects against MeHg+-induced cell death, particularly at high MeHg+ concentrations (LC50). In addition, chitosan-SeNPs showed greater protection compared to citrate-SeNPs when co-exposed with MeHg+. Interestingly, SC-ICP-MS unveiled the heterogeneous distribution of Hg uptake by SH-SY5Y cells. Co-exposure of SeMet and SeMeSeCys with MeHg+ led to a reduction of the amount of Hg accumulated per individual cell, which decreased the maximum level of Hg per cell by half (from 60 fg Hg cell-1 to 30 fg Hg cell-1) when SeMet was present, along with a decrease in the percentage of cells that accumulated the highest quantity of MeHg+. All these data corroborate the protective role of Se against Hg toxicity at the cellular level.

Is selenium beneficial or detrimental to earthworm? Growth and metabolism responses of Eisenia Fetida to Na2SeO3 exposure

Se unevenly distributed in soils due to variations of geology and anthropogenic input, which results in different effects on earthworms. The effects of Se were characterized by analyzing the growth and metabolism responses of earthworms after exposure to three different concentrations of Na₂SeO₃. The results showed that except the possible growth promotion at 5 mg/kg, low and middle-level exposure to Na₂SeO₃ (0.3-10 mg/kg) did not significantly affect the growth of earthworms. While a significant inhibition effect on growth was observed in the high-level exposure group (30-70 mg/kg). There was an inflection point for Se performing promotion to inhibition effects on earthworm growth. To investigate the metabolic response of earthworms, a novel HPLC-ESI-MS (High Performance Liquid Chromatography-Electrospray Ionization-Mass Spectrometry) method was used to determine sensitive biomarkers. Selenium exposure significantly altered the metabolism of seven essential amino acids, namely tyrosine, leucine, phenylalanine, valine, alanine, glycine, and lysine, and two selenoamino acids, namely selenomethionine and methylselenocysteine. The overall metabolism level of earthworms was not affected at low exposure concentrations, but was affected at medium and high exposure concentrations. The metabolic pathways that integrated the selenocompound metabolism and the tricarboxylic acid cycle from the perspective of energy supply and demand were affected by Na₂SeO₃ exposure. The derived reactive oxygen species at high exposure concentrations were probably the reason for the growth inhibition effect of Se on earthworms. This study provides biochemical insights into the effects of Na₂SeO₃ on earthworms and suggests that an Se concentration of about 2.3 mg/kg is appropriate for soil organism health.

Effect of boiling and frying on the selenium content, speciation, and in vitro bioaccessibility of selenium-biofortified potato (Solanum tuberosum L.)

Selenium-enriched potato is a good supplement for selenium-deficient populations. This study evaluated the influence of two most common cooking methods, including boiling and frying, on selenium content, speciation, and in vitro bioaccessibility of selenium-biofortified potato tubers. After foliar application of 200 μg/mL sodium selenite, potato tubers with 1.33 μg Se/g were obtained. Peeling resulted in 53.4%-69.9% loss of selenium in tubers. The total selenium content decreased by approximately 43.3% after boiling, among which up to 38.5% of the lost selenium is found in the boiling water. Nearly 31.7% of selenium was lost via volatilization during frying. Both cooking methods significantly enhanced the bioaccessibility of Se(IV) in tubers. Whereas SeMeCys became less bioaccessible after boiling. SeMet and SeCys₂ in fired tubers were not accessible after digestion. This study suggested that boiling is more appropriate for cooking selenium-enriched potatoes.

Selenium accumulation, speciation, and its effect on nutritive value of Flammulina velutipes (Golden needle mushroom)

Flammulina velutipes is one of the most popular edible mushrooms worldwide. A selenium-biofortification method for its fruiting body was developed using selenite. This study investigated the selenium content, distribution, speciation and the effect of selenium on mushroom growth, nutritive value, and mineral accumulation. Results showed that F. velutipes accumulated nearly 108 μg/g of organic selenium under treatment with 20 μg/g selenite, which accounts for over 97% of total selenium. Most (60-74%) of selenium combined with the protein fraction, whereas 15-21% combined with the polysaccharide fraction. Selenomethionine (56.8%), selenocysteine (22.8%), and methylselenocysteine (17.3%) were the main organic selenium compounds in the fruiting body. Selenium biofortification increased the biomass yield of fruiting body and elevated the content of polysaccharides, proteins, total amino acids, essential amino acids, and several minerals, including iron, calcium, and copper. F. velutipes might become a suitable selenium supplement.

Accumulation and speciation of selenium in biofortified vegetables grown under high boron and saline field conditions

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Vegetables tolerated high B and saline soils.

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Vegetables accumulated naturally occurring Se and other essential nutrients.

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Monomethylated selenoamino acids were the primary organic forms.

Selenium (Se) biofortification, as an agronomic-based strategy, is utilized to produce Se-enriched food products for increasing Se intake in inhabitants in Se-deficient regions. This strategy can be accomplished by soil and foliar application of Se or by growing crops in soils naturally high in Se. In this study, different cruciferous vegetables were field-grown in high boron (B) and saline soils of central California containing naturally high levels of Se. We investigated whether Se biofortification occurs in salt- and B-tolerant vegetables grown in poor-quality soil. The uptake of Se and other elements occurred in all vegetables. In plant tissues, Se speciation analyses showed greatest percentages of Se-containing compounds were contained in organic Se forms (monomethylated) and as selenate in the inorganic Se forms. Selenium-enriched vegetables produced from saline soils high in B and Se can be a natural source of Se-biofortified food that can be consumed as bioactive food products.

In vitro bioaccessibility of selenoamino acids from selenium (Se)-enriched Chlorella vulgaris biomass in comparison to selenized yeast; a Se-enriched food supplement; and Se-rich foods

Selenium (Se) is an indispensable microelement in our diet and health issues resulting from deficiencies are well documented. Se-containing food supplements are available on the market including Se-enriched Chlorella vulgaris (Se-Chlorella) which accumulates Se in the form of Se-amino acids (Se-AAs). Despite its popular uses, data about the bioaccessibility of Se-AAs from Se-Chlorella are completely missing. In the present study, gastrointestinal digestion times were optimized and the in vitro bioaccessibility of Se-AAs in Se-Chlorella, Se-yeast, a commercially available Se-enriched food supplement (Se-supplement) and Se rich foods (Se-foods) were compared. Higher bioaccessibility was found in Se-Chlorella (∼49%) as compared to Se-yeast (∼21%), Se-supplement (∼32%) and Se-foods. The methods used in production of Se-Chlorella biomass were also investigated. We found that disintegration increased bioaccessibility whereas the drying process had no effect. Similarly, temperature treatment by microwave oven also increased bioaccessibility whereas boiling water did not.