The actinomycete Kitasatospora sp. SeTe27, subjected to adaptive laboratory evolution (ALE) in the presence of selenite, varies its cellular morphology, redox stability, and tolerance to the toxic oxyanion.

The effects of oxyanions selenite (SeO32-) in soils are of high concern in ecotoxicology and microbiology as they can react with mineral particles and microorganisms. This study investigated the evolution of the actinomycete Kitasatospora sp. SeTe27 in response to selenite. To this aim, we used the Adaptive Laboratory Evolution (ALE) technique, an experimental approach that mimics natural evolution and enhances microbial fitness for specific growth conditions. The original strain (wild type; WT) isolated from uncontaminated soil gave us a unique model system as it has never encountered the oxidative damage generated by the prooxidant nature of selenite. The WT strain exhibited a good basal level of selenite tolerance, although its growth and oxyanion removal capacity were limited compared to other environmental isolates. Based on these premises, the WT and the ALE strains, the latter isolated at the end of the laboratory evolution procedure, were compared. While both bacterial strains had similar fatty acid profiles, only WT cells exhibited hyphae aggregation and extensively produced membrane-like vesicles when grown in the presence of selenite (challenged conditions). Conversely, ALE selenite-grown cells showed morphological adaptation responses similar to the WT strain under unchallenged conditions, demonstrating the ALE strain improved resilience against selenite toxicity. Whole-genome sequencing revealed specific missense mutations in genes associated with anion transport and primary and secondary metabolisms in the ALE variant. These results were interpreted to show that some energy-demanding processes are attenuated in the ALE strain, prioritizing selenite bioprocessing to guarantee cell survival in the presence of selenite. The present study indicates some crucial points for adapting Kitasatospora sp. SeTe27 to selenite oxidative stress to best deal with selenium pollution. Moreover, the importance of exploring non-conventional bacterial genera, like Kitasatospora, for biotechnological applications is emphasized.

Carbon Monoxide Releasing Molecule-3 Alleviates Oxidative Stress and Apoptosis in Selenite-Induced Cataract in Rats via Activating Nrf2/HO-1 Pathway.

PURPOSE: This study investigated the protective effect of carbon monoxide releasing molecule-3 (CORM-3), the classical donor of carbon monoxide, on selenite-induced cataract in rats and explore its possible mechanism. METHODS: Sprague-Dawley rat pups treated with sodium selenite (Na2SeO3) were chosen as the cataract model. Fifty rat pups were randomly divided into 5 groups: Control group, Na2SeO3 (3.46 mg/kg) group, low-dose CORM-3 (8 mg/kg/d) + Na2SeO3 group, high-dose CORM-3 (16 mg/kg/d) + Na2SeO3 group, and inactivated CORM-3 (iCORM-3) (8 mg/kg/d) + Na2SeO3 group. The protective effect of CORM-3 was tested by lens opacity scores, hematoxylin and eosin staining, TdT-mediated dUTP nick-end labeling assay, and enzyme-linked immunosorbent assay. Besides, quantitative real-time PCR and western blotting were used for mechanism validation. RESULTS: Na2SeO3 induced nuclear cataract rapidly and stably, and the achievement ratio of Na2SeO3 group was 100%. CORM-3 alleviated lens opacity of selenite-induced cataract and attenuated the morphological changes of the rat lens. The levels of antioxidant enzymes GSH and SOD in rat lens were also increased by CORM-3 treatment. CORM-3 significantly reduced the ratio of apoptotic lens epithelial cells, besides, CORM-3 decreased the expression of Cleaved Caspase-3 and Bax induced by selenite and increased the expression of Bcl-2 in rat lens inhibited by selenite. Moreover, Nrf-2 and HO-1 were upregulated and Keap1 was downregulated after CORM-3 treatment. While iCORM-3 did not exert the same effect as CORM-3. CONCLUSIONS: Exogenous CO released from CORM-3 alleviates oxidative stress and apoptosis in selenite-induced rat cataract via activating Nrf2/HO-1 pathway. CORM-3 may serve as a promising preventive and therapeutic strategy for cataract.

Environmentally relevant concentrations of selenite trigger reproductive toxicity by affecting oocyte development and promoting larval apoptosis.

As a trace element, selenium (Se) has been widely added to food to maintain the physiological homeostasis of the organism. The adverse effects of Se on the reproduction of zebrafish have been investigated, however, the effects of Se on the maturation and apoptosis of zebrafish oocytes remain unclear. In this study, zebrafish embryos (2 h post fertilization, hpf) were exposed to 0, 12.5, 25, 50, and 100 µg Se/L for 120 days. The results demonstrated that exposure to selenite decreased the gonad-somatic index (GSI) and cumulative production of eggs, inhibited oocyte maturation (OM), and increased oocyte apoptosis in females. Exposure to selenite decreased the contents of sex hormones (E2) in the serum and increased the levels of reactive oxygen species (ROS) and cyclic adenosine monophosphate (cAMP) in the ovary. Furthermore, exposure to selenite downregulated the transcription level of genes on the HPG axis, decreased the phosphorylation level of CyclinB and the protein content of cAMP-dependent protein kinase (Pka), and upregulated the expression of genes (eif2s1a and chop) and proteins (Grp78, Chop) related to endoplasmic reticulum stress (ERS) and apoptosis. Moreover, maternal exposure to selenite resulted in the apoptosis of offspring and upregulated the content of ROS and the transcription level of genes related to ERS and apoptosis.

Comparison of selenite and selenate in alleviation of drought stress in Nicotiana tabacum L.

Exogenous selenium (Se) improves the tolerance of plants to abiotic stress. However, the effects and mechanisms of different Se species on drought stress alleviation are poorly understood. This study aims to evaluate and compare the different effects and mechanisms of sodium selenate (Na2SeO4) and sodium selenite (Na2SeO3) on the growth, photosynthesis, antioxidant system, osmotic substances and stress-responsive gene expression of Nicotiana tabacum L. under drought stress. The results revealed that drought stress could significantly inhibit growth, whereas both Na2SeO4 and Na2SeO3 could significantly facilitate the growth of N. tabacum under drought stress. However, compared to Na2SeO3, Se application as Na2SeO4 induced a significant increase in the root tip number and number of bifurcations under drought stress. Furthermore, both Na2SeO4 and Na2SeO3 displayed higher levels of photosynthetic pigments, better photosynthesis, and higher concentrations of osmotic substances, antioxidant enzymes, and stress-responsive gene (NtCDPK2, NtP5CS, NtAREB and NtLEA5) expression than drought stress alone. However, the application of Na2SeO4 showed higher expression levels of the NtP5CS and NtAREB genes than Na2SeO3. Both Na2SeO4 and Na2SeO3 alleviated many of the deleterious effects of drought in leaves, which was achieved by reducing stress-induced lipid peroxidation (MDA) and H2O2 content by enhancing the activity of antioxidant enzymes, while Na2SeO4 application showed lower H2O2 and MDA content than Na2SeO3 application. Overall, the results confirm the positive effects of Se application, especially Na2SeO4 application, which is markedly superior to Na2SeO3 in the role of resistance towards abiotic stress in N. tabacum.

TRAP transporter TakP: a key player in the resistance against selenite-induced oxidative stress in Rhodobacter sphaeroides.

Almost one-third of all proteins require metal ions as an essential component in key biological processes and approximately half of all enzymes are associated with one or more metal ions. The naturally occurring selenium is very toxic at higher levels, but few bacteria can reduce it into the less toxic insoluble elemental selenium. Selenium is required for the synthesis of selenocysteine, an essential residue involved in the active sites of various enzymes. The purple non-sulphur bacteria, Rhodobacter sphaeroidesis demonstrated for its selenite reduction capacity. The exact mechanism of selenite toxicity is unknown but it reacts with glutathione to form selenodiglutathione, producing the highly toxic compounds namely, H2O2and O2-. A R. sphaeroidesstrain with mutated takP gene, a member of the TRAP (tripartite ATP-independent periplasmic) family of transporter, was reported to be showing more resistance towards selenite in the growth medium but the reason for the resistance is unknown. TRAP transporters are the best-studied family of substrate-binding protein and in our previous study it was confirmed that the gene takP in R. sphaeroides is down-regulated by a small non-coding RNA SorY, providing more resistance to the bacterium against the oxidative stress. By comparative growth analysis and sensitivity assays in the presence of 2 mM selenite, it was observed that the SorY knockout strain is more sensitive to selenite while overexpression of the sRNA conferred more resistance to the bacterium like the takP mutant strain. TakP is involved in the import of malate into the cell, which under oxidative stress needs to be down-regulated to limit malate flux into the cell. Limited malate flux leads to metabolic rearrangements in the cell to avoid excessive generation of prooxidant NADH and facilitate constant generation of antioxidant NADPH. In the presence and absence of selenite, a drastic increase in the NADPH and decrease in the NADH levels are reported respectively. Accumulation of metallic selenium in the cytoplasm was detected via atomic absorption spectrophotometer and our analysis clearly demonstrated the presence of more selenium in the electron micrographs of the SorY knockout strain compared to the takP mutant grown under dark semi-aerobic growth conditions in the presence of selenite. Hence based on our analysis, it is confirmed that lack of TakP transporter led to reduced selenite influx into the cytoplasm, relieving cells with limited generation of ROS, eventually exhibiting more resistance against selenite-induced oxidative stress.

Selenium(â £) alleviates chromium(â ¥)-induced toxicity in the green alga Chlamydomonas reinhardtii.

The wide range of industrial applications of chromium (Cr) has led to an increasing risk of water contamination by Cr(Ⅵ). However, efficient methods to remove or decrease the toxicity of Cr(Ⅵ) in situ are lacking. The main aim of this study was to investigate the mechanisms by which selenite alleviates chromium(Ⅵ)-induced toxicity in Chlamydomonas reinhardtii. Our results showed that K2Cr2O7 had toxic effects on both the structure and physiology of C. reinhardtii in a dose-dependent manner. Adding selenite significantly alleviated chromium accumulation and toxicity in cells. RNA-seq data showed that the expression level of selenoproteins such as SELENOH was significantly increased. Both SELENOH-amiRNA knockdown mutants and selenoh insertional mutant produced more reactive oxygen species (ROS) and grew slower than the wild type, suggesting that SELENOH can reduce chromium toxicity by decreasing the levels of ROS produced by Cr(Ⅵ). We also demonstrated that selenite can reduce the absorption of Cr(Ⅵ) by cells but does not affect the process of Cr(Ⅵ) adsorption and efflux. This information on the molecular mechanism by which selenite alleviates Cr(Ⅵ) toxicity can be used to increase the bioremediation capacity of algae and reduce the human health risks associated with Cr(Ⅵ) toxicity.

Modeling of selenite toxicity to wheat root elongation using biotic ligand model: Considering the effects of pH and phosphate anion.

It has not been well understood that the binding affinity and potential toxicity of different chemical forms of selenite (Se(IV)), which are predominant forms of selenium with plant availability. The influences of pH and major anions on Se(IV) toxicity to wheat root elongation were determined in solutions and modeled based on the biotic ligand model (BLM) and free ion activity model (FIAM) concepts. Results showed that EC50[Se(IV)]T values increased from 164 to 273 µM as the pH raised from 4.5 to 8.0, indicating the increase of pH induced weakened Se(IV) toxicity. The EC50{SeO32-} values increased from 0.019 to 71.3 µM while the EC50{H2SeO3} values sharply decreased from 2.08 µM to 0.760 nM with the pH increasing from 4.5 to 8.0. The effect of pH on Se(IV) toxicity could be explained by the changes of Se(IV) species in different pH solutions as H2SeO3, HSeO3- and SeO32- were differently toxic to wheat root elongation. The toxicity of Se(IV) decreased with increasing H2PO4- activity but not for SO42-, NO3- and Cl- activities, indicating that only H2PO4- had a competitive effect with Se(IV) on the binding sites. A site-specific BLM was developed to count in effects of pH and H2PO4-, and stability constants of H2SeO3, HSeO3-, SeO32- and H2PO4- to the binding sites were obtained: log [Formula: see text]  = 4.96, log [Formula: see text]  = 3.47, log [Formula: see text]  = 2.56 and log [Formula: see text]  = 2.00. Results implied that BLM performed much better than FIAM in the wheat root elongation prediction when coupling toxic species H2SeO3, HSeO3-, SeO32-, and the competitions of H2PO4- for the binding sites while developing the Se(IV)-BLM.

Selenate and selenite affect photosynthetic pigments and ROS scavenging through distinct mechanisms in cowpea (Vigna unguiculata (L.) walp) plants.

Selenium (Se) is a beneficial element to higher plants. Application of Se at low concentrations enhances the antioxidant metabolism reducing the reactive oxygen species (ROS) generated by plant membrane cells. This study aimed to evaluate how the application of Se in the forms sodium selenate and sodium selenite regulates ROS scavenging in field-grown cowpea plants. Seven Se application rates (0; 2.5; 5; 10; 20; 40 and 60 g ha-1) of each of the two Se forms were applied to plants via the soil. Photosynthetic pigments concentration, gas exchange parameters, lipid peroxidation by malondialdehyde (MDA) concentration, hydrogen peroxide concentration, activity of catalase (CAT, EC:1.11.1.6), glutathione reductase (GR, EC:1.6.4.2), ascorbate peroxidase (APX, EC:1.11.1.11) and Se concentration in leaves and grains were evaluated. In general, Se application led to a decrease in chlorophyll a concentration whilst leading to an increase in chlorophyll b, indicating conservation of total chlorophyll concentration. Application of 2.5 g ha-1 of Se as selenate provided a notable increase in total chlorophyll and total carotenoids compared to the other application rates. Selenate and selenite application decreased lipid peroxidation. However, each Se source acted in a different pathway to combat ROS. While selenate showed more potential to increase activity of APX and GR, selenite showed a higher potential to increase CAT activity. The negative correlation between CAT and GR is indicative that both pathways might be activated under distinct circumstances. The more prominent activity of CAT under high rates of selenite resulted in a negative correlation of this enzyme with chlorophyll a and carotenoids. Both selenate and selenite application increased sucrose and total sugars concentration in leaves of cowpea plants. Overall, these results indicate that application of Se in cowpea under field conditions stimulates distinct pathways to scavenge ROS. This could prove beneficial to mitigate oxidative stress during plant development.

A comparative study on the accumulation, translocation and transformation of selenite, selenate, and SeNPs in a hydroponic-plant system.

Plants can play important roles in overcoming selenium (Se) deficiency and Se toxicity in various regions of the world. Selenite (SeIV), selenate (SeVI), as well as Se nanoparticles (SeNPs) naturally formed through reduction of SeIV, are the three main Se species in the environment. The bioaccumulation and transformation of these Se species in plants still need more understanding. The aims of this study are to investigate the phytotoxicity, accumulation, and transformation of SeIV, SeVI and SeNPs in garlic, a relatively Se accumulative plant. The spatial distribution of Se in the roots were imaged using synchrotron radiation micro-focused X-ray fluorescence (SR-µXRF). The chemical forms of Se in different plant tissues were analyzed using synchrotron radiation X-ray absorption spectroscopy (SR-XAS). The results demonstrate that 1) SeNPs which has the lowest phytotoxicity is stable in water, but prone to be converted to organic Se species, such as C-Se-C (MeSeCys) upon uptake by root. 2) SeIV is prone to concentrate in the root and incorporated into C-Se-C (MeSeCys) and C-Se-R (SeCys) bonding forms; 3) SeVI with the lowest transformation probability to organic Se species has the highest phytotoxicity to plant, and is much easier to translocate from root to leaf than SeNPs and SeIV. The present work provides insights into potential impact of SeNPs, selenite and selenate on aquatic-plant ecosystems, and is beneficial for systematically understanding the Se accumulation and transformation in food chain.

A cysteinyl-tRNA synthetase variant confers resistance against selenite toxicity and decreases selenocysteine misincorporation.

Selenocysteine (Sec) is the 21st genetically encoded amino acid in organisms across all domains of life. Although structurally similar to cysteine (Cys), the Sec selenol group has unique properties that are attractive for protein engineering and biotechnology applications. Production of designer proteins with Sec (selenoproteins) at desired positions is now possible with engineered translation systems in Escherichia coli However, obtaining pure selenoproteins at high yields is limited by the accumulation of free Sec in cells, causing undesired incorporation of Sec at Cys codons due to the inability of cysteinyl-tRNA synthetase (CysRS) to discriminate against Sec. Sec misincorporation is toxic to cells and causes protein aggregation in yeast. To overcome this limitation, here we investigated a CysRS from the selenium accumulator plant Astragalus bisulcatus that is reported to reject Sec in vitro Sequence analysis revealed a rare His → Asn variation adjacent to the CysRS catalytic pocket. Introducing this variation into E. coli and Saccharomyces cerevisiae CysRS increased resistance to the toxic effects of selenite and selenomethionine (SeMet), respectively. Although the CysRS variant could still use Sec as a substrate in vitro, we observed a reduction in the frequency of Sec misincorporation at Cys codons in vivo We surmise that the His → Asn variation can be introduced into any CysRS to provide a fitness advantage for strains burdened by Sec misincorporation and selenium toxicity. Our results also support the notion that the CysRS variant provides higher specificity for Cys as a mechanism for plants to grow in selenium-rich soils.

Protective Effects of Trimetazidine in Retarding Selenite-Induced Lens Opacification.

Purpose: Cataracts are the leading cause of vision loss worldwide, and the over-production of reactive oxygen species (ROS) is the foremost underlying cause of cataracts. Reducing ROS levels can efficiently prevent lens opacification, as evidenced by many studies. Here, we inhibited ROS overproduction with trimetazidine (TMZ), which is an antioxidant, to explore the therapeutic effects of TMZ and the mechanism of lens opacification.Materials and methods: Sodium selenite-induced cataract formation resulted in a significant loss of lens transparency. This effect could be efficiently rescued by TMZ, which was further found to be an inhibitor of ROS production, as determined by assaying oxidative stress-related parameters (SOD activity, MDA, ·OH and H2O2 levels) during cataract formation. The experimental protocols involving animal research were approved by the Animal Care and Ethics Committee of Wenzhou Medical University and conducted according to the Association for Research in Vision and Ophthalmology under the guidelines of the Animal Welfare Act (SYXK 2015-0009).Results: Our study found that TMZ can retard the onset and progression of lens opacification in vivo in experiments using Sprague-Dawley (SD) suckling rats and can rescue the morphology of HLEB3 cells in vitro. The flow cytometry and DNA fragmentation assays showed that TMZ could prevent sodium selenite-induced apoptosis. The western blot analysing showed that the levels of apoptosis-associated Bcl-2 and Nrf2 were dramatically decreased following the sodium selenite treatment. In addition, the bisulfate DNA sequencing revealed that the demethylation of CpGs in the promoter region of Keap1 was stimulated, and that this demethylation could be inhibited by TMZ by rescuing the Nrf2 expression level.Conclusions: Our findings indicate that the antioxidant TMZ strongly reduces ROS production, which ultimately delays the progression of cataract formation, suggesting that treatment with TMZ represents a novel, promising antioxidant protection to retard cataract formation.

Effects of selenium on benthic macroinvertebrates and fathead minnow (Pimephales promelas) in a boreal lake ecosystem.

Selenium (Se) is a contaminant of concern in many aquatic ecosystems due to its narrow range between essentiality and toxicity in oviparous (yolk-bearing) vertebrates. The objective of the present study was to determine the effects of Se, experimentally added to in situ limnocorrals as selenite, on invertebrate communities and fathead minnow (Pimephales promelas) at environmentally realistic Se concentrations. Nine limnocorrals were deployed in a mesotrophic lake at the International Institute for Sustainable Development - Experimental Lakes Area in Ontario, Canada in May 2017. From June 1 to August 17, 2017, selenite was added to six enclosures to attain mean measured aqueous Se concentrations of 1.0 ±â€¯0.10 or 8.9 ±â€¯2.7 µg/L Se (in triplicate) and three limnocorrals were untreated controls (background mean aqueous Se = 0.12 ±â€¯0.03 µg/L). Benthic macroinvertebrates were collected throughout and at the end of the exposure period using artificial substrates to determine density, dry biomass, diversity, and taxa richness at the family level. Reproductively mature female fathead minnows (added on d 33 of the study) were collected throughout and at the end of the exposure period. After 77 d, Chironomidae and Gammaridae densities and biomass were significantly lower in the 8.9 µg/L Se treatment relative to the 1.0 µg/L Se treatment and the control. Invertebrate diversity (measured as Shannon's and Simpson's indices) significantly declined in the 1.0 µg/L and 8.9 µg/L Se treatments relative to the control (0.12 µg/L Se group). Fulton's condition factor for fathead minnow was significantly less in the 8.9 µg/L treatment compared to 0.12 and 1.0 µg/L Se experimental groups. The results of this study indicated that exposure to relatively low aqueous selenite concentrations can negatively affect invertebrate density and biomass, as well as fish condition. More research is necessary to characterize the risk of selenite exposure to aquatic invertebrates under realistic field conditions, and future risk assessments may need to consider reduced food availability as a factor that may impair the health of higher trophic level organisms in areas with elevated selenite.

Protective Effects of Rosmarinic Acid against Selenite-Induced Cataract and Oxidative Damage in Rats.

Cataracts are the major cause of blindness and are associated with oxidative damage of the lens. In the present study, the aim was to evaluate the protective effects of rosmarinic acid on selenite-induced cataractogenesis in Sprague-Dawley rat pups. The animals were randomly divided into five groups, each of which consisted of 10 rat pups. Group I served as normal control (vehicle administration). For testing cataract induction, animals of Groups II, III, IV, and V were administered a single subcutaneous injection of sodium selenite (2.46 mg/kg body weight) on postpartum day 12. After sodium selenite intoxication, Group II served as control selenite. From the 11th day through the 17th day, Groups III-V received rosmarinic acid intraperitoneally at doses of 5, 10, and 50 mg/kg, respectively. On postpartum day 24, the rat pups were examined for cataract formation, and the lenses were isolated for further analysis of proteins and oxidative damage indicators. Selenite caused significant (p < 0.05) cataract formation. Through the effects of selenite, the protein expressions of filensin and calpain 2 were reduced, and the calcium concentrations, the level of lipid peroxidation (TBARS), and inflammation indicators (iNOS, COX-2, and NFκB) were upregulated. Furthermore, the protein expression of the antioxidant status (Nrf2, SOD, HO-1, and NQO1), the antioxidant enzymes activities (GSH-Px, GSH-Rd, and catalase), and the GSH levels were downregulated. In contrast, treatment with rosmarinic acid could significantly (p < 0.05) ameliorate cataract formation and oxidative damage in the lens. Moreover, rosmarinic acid administration significantly increased the protein expressions of filensin, calpain 2, Nrf2, SOD, HO-1, and NQO1, the antioxidant enzymes activities, and the GSH level, in addition to reducing the calcium, lipid peroxidation, and inflammation indicators in the lens. Taken together, rosmarinic acid is a prospective anti-cataract agent that probably delays the onset and progression of cataracts induced by sodium selenite.

Selenium cytotoxicity in Tetrahymena thermophila: New clues about its biological effects and cellular resistance mechanisms.

Selenium is an essential micronutrient but at high concentrations can produce severe cytotoxicity and genomic damage. We have evaluated the cytotoxicity, ultrastructural and mitochondrial alterations of the two main selenium inorganic species; selenite and selenate, in the eukaryotic microorganism Tetrahymena thermophila. In this ciliate, selenite is more toxic than selenate. Their LC50 values were calculated as 27.65 µM for Se(IV) and 56.88 mM for Se(VI). Significant levels of peroxides/hydroperoxides are induced under low-moderate selenite or selenate concentrations. Se(VI) exposures induce an immediate mitochondrial membrane depolarization. Selenium treated cells show an intense vacuolization and some of them present numerous discrete and small electrondense particles, probably selenium deposits. Mitochondrial fusion, an intense swelling in peripheral mitochondria and mitophagy are detected in selenium treated cells, especially in those exposed to Se (IV). qRT-PCR analysis of diverse genes, encoding relevant antioxidant enzymes or other proteins, like metallothioneins, involved in an environmental general stress response, have shown that they may be crucial against Se(IV) and/or Se (VI) cytotoxicity.

Topical nanodelivery system of lutein for the prevention of selenite-induced cataract.

Cataracts are responsible for half of the world blindness, surgery being the only viable treatment. Lutein, a naturally occurring carotenoid in the eye, has the potential to reduce cataract progression by protecting the eye from photo-oxidative stress. To restore the eye's natural line of defense against photo-oxidative stress, a formulation was developed using zein and poly(lactic-co-glycolic acid) nanoparticles (NPs) embedded in an optimized bioadhesive thermosensitive gel for the delivery of lutein via topical application. Cataracts were induced in Crl:WI rats via selenite injection at 13 days post-partum, followed by 7 days of treatment with free lutein or lutein-loaded NPs administered orally or topically. Cataract severity was significantly reduced in rats treated with topical applications of lutein-loaded NPs compared to the positive control, while no significant differences were observed in rats treated with other lutein formulations including oral and topically applied free lutein.

Subacute oral toxicity investigation of selenium nanoparticles and selenite in rats.

Selenium (Se) nanoparticles have been proposed as food supplements. However, the particle formulation may exert unexpected toxicity. The aim was therefore to compare toxicity of low doses of Se nanoparticles and the dissolved, ionized Se species selenite. Female rats were dosed orally for 28 d with either: 0.05, 0.5, or 4 mg Se/kg body weight (bw)/day as 20 nm Se nanoparticles or 0.05 or 0.5 mg Se/kg bw/day as sodium selenite. Male rats were dosed 4 mg Se/kg bw/day as Se nanoparticles. Body weight and clinical appearance were recorded throughout the experiment. At necropsy, blood samples were taken for hematological and clinical chemistry analyses; organ weights were recorded. At the high-dose of Se nanoparticles, overt toxicity occurred and the female animals had to be euthanized prematurely, whereas the male animals were reduced in dose. At all doses of Se nanoparticles and at 0.5 mg Se/kg bw/day as selenite, a lower body weight gain as compared to vehicle occurred. Relative liver weight was increased for both Se formulations at 0.5 mg Se/kg bw/day. Creatinine clearance and urinary pH were affected in some Se dosed groups. There were no effects among dosed groups on brain neurotransmitters or on hematological parameters compared with controls. There were no histological changes in the livers of animals exposed to Se nanoparticles or to selenite. Based on effects on body weight and liver weight, selenium nanoparticles and ionic Se exerted similar toxicity. This suggests that a nanoparticle-specific toxicity of Se did not occur.

Inhibition of bacteriochlorophyll biosynthesis in the purple phototrophic bacteria Rhodospirillumrubrum and Rhodobacter capsulatus grown in the presence of a toxic concentration of selenite.

Background In many works, the chemical composition of bacterially-produced elemental selenium nanoparticles (Se0-nanoparticles) was investigated using electron dispersive X-ray analysis. The results suggest that these particles should be associated with organic compounds. However, a complete analysis of their chemical composition is still missing. Aiming at identifying organic compounds associated with the Se0-nanoparticles produced by the purple phototrophic bacteria Rhodospirillum rubrum and Rhodobacter capsulatus (α group of the proteobacteria), we used MALDI-TOF spectrometry.Results This technic revealed that numerous signals obtained from particles produced by both species of bacteria were from metabolites of the photosynthetic system. Furthermore, not only bacteriochlorophyll a, bacteriopheophytin a, and bacteriopheophorbide a, which are known to accumulate in stationary phase cultures of these bacteria grown phototrophically in the absence of selenite, were identified. The particles were also associated with intermediary metabolites of the bacteriochlorophyll a biosynthesis pathway such as protoporphyrin IX, protoporphyrin IX monomethyl ester, bacteriochlorophyllide a and, most likely, Mg-protoporphyrin IX-monomethyl ester, as well as with oxidation products of the substrates of protochlorophyllide reductase and chlorin reductase.Conclusion Accumulation of intermediary metabolites of the bacteriochlorophyll biosynthesis pathway in these purple phototrophic bacteria was attributed to inhibition of oxygen-sensitive enzymes involved in this pathway. Consistent with this interpretation it has been reported that these bacteria reduce selenite intracellularly, that they contain high levels of glutathione and that the reduction of selenite with glutathione is a very fast reaction accompanied by the production of reactive oxygen species. As many enzymes involved in the biosynthesis of bacteriochlorophyll contain [Fe-S] clusters in their active site, which are known to be degraded in the presence of reactive oxygen species as well as in the presence of molecular oxygen, we concluded that the substrates of these enzymes accumulate in cells during selenite reduction.Association of metabolites of bacteriochlorophyll biosynthesis and degradation with the Se0-nanoparticles produced by Rhodospirillum rubrum and Rhodobacter capsulatus is proposed to result from coating of the nanoparticles with the intracytoplasmic membrane of these bacteria, where the photochemical apparatus is concentrated.

Acute toxicity of selenate and selenite and their impacts on oxidative status, efflux pump activity, cellular and genetic parameters in earthworm Eisenia andrei.

Selenium (Se) is an essential element for humans, animals, and certain lower plants, but can be toxic at high concentration. Even though Se is potentially toxic, little information is available about the effects of Se on soil animals. The aim of this study was to assess the impact of different concentrations of two Se forms, selenate and selenite, on earthworm Eisenia andrei. In order to obtain comprehensive overview on the Se effects, different parameters were measured. Namely, acute toxicity, apoptosis, efflux pump activity, different enzymatic and non-enzymatic biomarkers (acetylcholinesterase, carboxylesterase, glutathione S-transferase, catalase, glutathione reductase and superoxide dismutase activities, lipid peroxidation level and GSH/GSSG ratio) and expression of genes involved in oxidative and immune response have been investigated. Additionally, measurement of metallothioneins concentration and concentration of Se in exposed earthworms has been also performed. The assessment of acute toxicity showed a greater sensitivity of E. andrei to selenite exposure, whereas Se concentration measurements in earthworms showed higher accumulation of selenate form. Both Se forms caused inhibition of the efflux pump activity. Decrease in superoxide dismutase activity and increase in lipid peroxidation and glutathione reductase activity indicate that Se has a significant impact on the oxidative status of earthworms. Selenate exposure caused an apoptotic-like cell death in the coelomocytes of exposed earthworms, whereas decreased mRNA levels of stress-related genes and antimicrobial factors were observed upon the exposure to selenite. The obtained data give insight into the effects of two most common forms of Se in soil on the earthworm E. andrei.

Effect of hesperetin derivatives on the development of selenite­induced cataracts in rats.

Cataracts are a major cause of blindness worldwide. As anti­cataract pharmaceutical therapies require long­term treatment, identifying anti­cataract compounds that are ubiquitous in the human diet, have no adverse effects and are affordable, is of paramount importance. The present study focused on hesperetin and its derived compounds, hesperetin stearic acid ester (Hes­S) and hesperetin oleic acid ester (Hes­O), in order to investigate their therapeutic potential to treat cataracts in a selenite animal model. Thirteen­day­old Sprague Dawley rats were divided into 12 groups. Animals in groups 1 and 7 were subcutaneously injected with vehicle, those in groups 2 and 8 were administered hesperetin, those in groups 3 and 9 received stearic acid, those in groups 4 and 10 were injected with oleic acid, those in groups 5 and 11 were administered Hes­S, and those in groups 6 and 12 received Hes­O (10 nmol/kg body weight on days 0, 1 and 2). Animals in groups 7 to 12 were treated with sodium selenite (20 µmol/kg body weight given 4 h following the test compound treatment on day 0) to induce cataract. On day 6, rats had less severe central opacities and lower stage cataracts than rats in the selenite treatment­only control groups. The levels of glutathione (GSH) and ascorbic acid (AsA) in lenses with selenite­induced cataracts declined to one­third of that of controls, and the reduction in GSH and AsA levels was rescued following hesperetin, Hes­S or Hes­O treatment, with concentrations remaining to 70­80% of that of controls. However, there were no changes in the plasma levels of GSH and AsA following treatments. Administration of either hesperetin or hesperetin­derived compounds prevented the reduction of chaperone activity in the lens, and rats treated with Hes­S or Hes­O treatment had significantly greater chaperone activity than hesperetin­treated rats. Collectively, these results suggested that hesperetin and hesperetin­derived compounds may be novel drug compounds that have the potential to prevent or delay the onset of cataracts.

Selenium accumulation and the effects on the liver of topmouth gudgeon Pseudorasbora parva exposed to dissolved inorganic selenium.

Selenite(IV) and selenate(VI) are the major forms of Se in aquatic ecosystem. In this study, Pseudorasbora parva were exposed to 10, 200 and 1000 µg L-1 selenite and selenate for 28 days. Selenium accumulation, antioxidant enzyme levels, glutathione concentrations, lipid peroxidation and histology were evaluated in livers following exposure. Our results showed that Se(IV) and Se(VI) caused different accumulation patterns in the liver, with a more rapid accumulation of Se with Se(IV) treatment. Both Se species increased hepatic lipid peroxidation after 14 and 28 d (~ 30%). Among the antioxidants examined, the activity of SOD (except day 28) and the cellular levels of GSH were induced by 72-137% at lower concentrations, while the activity of GST was at least 24% lower than that of the control at 200 and 1000 µg L-1 for both Se species at all sampling points. Both forms of Se reduced the hepatosomatic index at 1000 µg L-1 after 28 d. In addition, marked histopathological alterations (10-31%) were observed in the liver of P. parva after exposure to both Se species, with higher frequency in the Se(IV) exposed fish. Liver local necrosis was observed only in the liver of fish exposed to 1000 µg L-1 of Se(IV) (~ 20%). Our results suggest that the ecological impacts of dissolved Se in this freshwater species may also contribute to overall toxicity.