Accessing the transcriptional status of selenoproteins in skin cancer-derived cell lines.

BACKGROUND: Selenoproteins are selenocysteine (Sec)-containing proteins that exhibit numerous physiological functions, mainly antioxidative activities. Studies have suggested that several human selenoproteins play an important role in tumor initiation and progression, including melanoma. METHODS: Using RNA-seq data set from Sequence Reads Archive (SRA) experiments published at the National Center for Biotechnology Information (NCBI), we determined and compared the transcriptional levels of the 25 selenoproteins-coding sequences found in 16 human-derived melanoma cell lines and compared to four melanocyte controls. RESULTS: 15 selenoprotein-coding genes were found to be expressed in melanoma and normal melanocyte cells, and their mRNA levels varied among the cell lines. All melanoma cells analyzed with BRAF or NRAS mutations presented upregulated levels of SELENOI, TXNRD1, and SELENOT transcripts and downregulated levels of SELENOW and SELENON transcripts in comparison with melanocytes controls. Moreover, SELENOW, SELENON, SELENOI, TXNRD1, and SELENOT-coding transcripts were affected when BRAF-mutated A375 cells were treated with CPI203, A771726 or Vorinostat drugs. CONCLUSION: Our results indicate that melanoma cells can modify, in a different manner, the selenoprotein transcript levels, as a possible mechanism to control tumor progression. We suggest that the usage of diet and supplements containing selenium should be carefully used for patients with melanoma.

Safety profile of AZT derivatives: Organoselenium moieties confer different cytotoxic responses in fresh human erythrocytes during in vitro exposures.

INTRODUCTION: The incorporation of selenium in the structure of nucleosides is a promising strategy to develop novel therapeutic molecules. OBJECTIVE: To assess the toxic effects of three AZT derivatives containing organoselenium moieties on human erythrocytes. METHODOLOGY: Freshly human erythrocytes were acutely treated with AZT and selenium derivatives SZ1 (chlorophenylseleno), SZ2 (phenylseleno) and SZ3 (methylphenylseleno) at concentrations ranging from 10 to 500 µM. Afterwards, parameters related to membrane damage, redox dyshomeostasis and eryptosis were determined in the cells. RESULTS: The effects of AZT and derivatives toward erythrocytes differed considerably. Overall, the SZ3 exhibited similar effect profiles to the prototypal AZT, without causing cytotoxicity. Contrary, the derivative SZ1 induced hemolysis and increased the membrane fragility of cells. Reactive species generation, lipid peroxidation and thiol depletion were also substantially increased in cells after exposure to SZ1. δ-ALA-D and Na+/K+-ATPase activities were inhibited by derivatives SZ1 and SZ2. Additionally, both derivatives caused eryptosis, promoting cell shrinkage and translocation of phosphatidylserine at the membrane surface. The size and granularity of erythrocytes were not modified by any compound. CONCLUSION: The insertion of either chlorophenylseleno or, in a certain way, phenylseleno moietes in the structure of AZT molecule was harmful to erythrocytes and this effect seems to involve a pro-oxidant activity. This was not true for the derivative encompassing methylphenylseleno portion, making it a promising candidate for pharmacological studies.

Peumus boldus attenuates copper-induced toxicity in Drosophila melanogaster.

Peumus boldus (P. boldus) is a medicinal plant popularly used in the treatment of gastrointestinal disorders. P. boldus aqueous extract is rich in phenolic compounds and alkaloids that possess antiinflammatory and antioxidant effects. In the present study, the potential protective effect of P. boldus against Cu2+-induced toxicity was investigated. Adult Drosophila melanogaster were exposed to Cu2+ (1mM and 3mM) and/or P. boldus aqueous extract (5mg/mL) in the food during 4days. Cu2+-fed flies had impairment in the negative geotaxis performance (i.e. motor climbing capability) as well as a higher incidence of mortality when compared to the control group. P. boldus co-treatment afforded protection against the Cu2+-induced toxicity. Acetylcholinesterase (AChE) and glutathione S-transferase (GST) activity decreased significantly in D. melanogaster after Cu2+ exposure. P. boldus co-exposure for 4days restored enzyme activities to control levels. In addition, Cu2+ exposure caused a significant increase in the mRNA levels of antioxidant enzymes, superoxide dismutase (Sod1), catalase (Cat), thioredoxin reductase (TrxR1) and nuclear factor erythroid 2-related factor 2 (Nrf2), as well as increased the mRNA levels of acetylcholinesterase (Ace). The expression of P-type ATPase (Atp7A) and copper uptake protein 1 (Ctr1A) mRNAs were up-regulated in D. melanogaster exposed to Cu2+. The co-treatment with P. boldus blunted Cu2+-induced up-regulation of Atp7A and down-regulated Ctr1A mRNA expression. These findings suggest that P. boldus extracts reduce Cu2+-induced toxicity but not Cu2+ absorption in D. melanogaster. Consequently, P. boldus can be a potential therapeutical alternative for modulating Cu2+-associated toxicity.

Protective effect of (-)-α-bisabolol on rotenone-induced toxicity in Drosophila melanogaster.

(-)-α-Bisabolol (BISA) is a sesquiterpene alcohol, which has several recognized biological activities, including anti-inflammatory, anti-irritant, and antibacterial properties. In the present study, we investigated the influence of BISA (5, 25, and 250 µmol/L) on rotenone (500 µmol/L)-induced toxicity in Drosophila melanogaster for 7 days. BISA supplementation significantly decreased rotenone-induced mortality and locomotor deficits. The loss of motor function induced by rotenone correlated with a significant change in stress response factors; it decreased thiol levels, inhibited mitochondria complex I, and increased the mRNA expression of antioxidant marker proteins such as superoxide dismutase (SOD), catalase (CAT), and the keap1 gene product. Taken together, our findings indicate that the toxicity of rotenone is likely due to the direct inhibition of complex I activity, resulting in a high level of oxidative stress. Dietary supplementation with BISA affected the expression of SOD mRNA only at a concentration of 250 µmol/L, and did not affect any other parameter measured. Our results showed a protective effect of BISA on rotenone-induced mortality and locomotor deficits in Drosophila; this effect did not correlate with mitochondrial complex I activity, but may be related to the antioxidant protection afforded by eliminating superoxide generated as a result of rotenone-induced mitochondrial dysfunction.

High-sucrose diet induces diabetic-like phenotypes and oxidative stress in Drosophila melanogaster: Protective role of Syzygium cumini and Bauhinia forficata.

Diet is a key component for development and longevity of organisms. Here, the fruit fly was used to evaluate the detrimental effects caused by consumption of high-sucrose diets (HSD), namely phenotypic responses linked to insulin signaling and oxidative stress. The protective effects of extracts from medicinal plants Syzygium cumini and Bauhinia forficata were investigated. HSD intake (15% and 30%) delayed the time to pupation and reduced the number of white pupae. In adult flies, the intake of diets was associated with mortality and increased levels of glucose+trehalose, triacylglycerols and hydrogen peroxide. Indeed, 30% HSD induced body-weight loss, mitochondrial dysfunction and changes in acetylcholinesterase, δ-aminolevulinate dehydratase and antioxidant enzymes activity. Catalase, superoxide dismutase, keap1, HSP70, dILP-5 and Insulin receptor mRNA levels were over-expressed in flies emerged from 30% HSD. The extract treatments blunted the developmental alterations elicited by diets. Syzygium cumini extract was more efficient than B. forficata in reducing hyperglycaemia, redox disturbances and the changes in mRNA expression of insulin receptor.

Valeriana officinalis attenuates the rotenone-induced toxicity in Drosophila melanogaster.

In this study, we investigated the potential protective effects of Valeriana officinalis (V. officinalis) against the toxicity induced by rotenone in Drosophila melanogaster (D. melanogaster). Adult wild-type flies were concomitantly exposed to rotenone (500 µM) and V. officinalis aqueous extract (10mg/mL) in the food during 7 days. Rotenone-fed flies had a worse performance in the negative geotaxis assay (i.e. climbing capability) and open-field test (i.e. mobility time) as well as a higher incidence of mortality when compared to control group. V. officinalis treatment offered protection against these detrimental effects of rotenone. In contrast, the decreased number of crossings observed in the flies exposed to rotenone was not modified by V. officinalis. Rotenone toxicity was also associated with a marked decrease on the total-thiol content in the homogenates and cell viability of flies, which were reduced by V. officinalis treatment. Indeed, rotenone exposure caused a significant increase in the mRNA expression of antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT) and also in the tyrosine hydroxylase (TH) gene. The expression of SOD and CAT mRNAs was normalized by V. officinalis treatment. Our results suggest that V. officinalis extract was effective in reducing the toxicity induced by rotenone in D. melanogaster as well as confirm the utility of this model to investigate potential therapeutic strategies on movement disorders, including Parkinson disease (PD).

A single high dose of ascorbic acid and iron is not correlated with oxidative stress in healthy volunteers.

Fe (II) is a potential prooxidant in vivo and can induce cellular oxidative stress. Ascorbic acid (AA) is a powerful physiological antioxidant and, in the presence of free Fe (II), can exhibit prooxidant effects in vitro. However, in vivo prooxidant effects of Fe (II) and AA have not yet been indisputably demonstrated. Here we evaluate the potential toxic effect of supplementation of Fe (II) associated with AA. Nine healthy, nonsmoking male volunteers (20-31 years old) participated in the crossover study design. The volunteers were supplemented with either a dose of 2 g of AA, 150 mg of iron carbonyl or 2 g of AA plus 150 mg of iron carbonyl with a washout period of 15 days between each treatment. AA, iron, ferritin, thiobarbituric acid-reactive substances, catalase, delta-aminolevulinic dehydratase and SH thiol groups were measured in the blood of the volunteers. Plasma AA levels were increased at 2, 5 and 24 h after AA or AA plus iron ingestion. Plasma Fe levels were increased at 2 and 5 h in the AA plus iron group. Erythrocyte malondialdehyde levels decreased at 5 and 24 h after AA and 5 h after AA plus iron ingestion. Catalase activity from erythrocytes was increased 5 h after supplementation with AA plus iron. There was no significant difference between groups in the other biochemical parameters evaluated. Thus, the present study does not support the hypothesis that the combination of high plasma concentrations of AA and iron, or iron alone, could cause in vivo oxidative damage after a single supplementation dose.