Modulation of redox and insulin signaling underlie the anti-hyperglycemic and antioxidant effects of diphenyl diselenide in zebrafish.

The organic selenium compound diphenyl diselenide (DD) has been recognized as an antioxidant and neuroprotective agent, exerting an anti-hyperglycemic effect in experimental models of diabetes. However, the precise mechanisms involved in the protection are unclear. Using the zebrafish (Danio rerio) as a model organism, here we investigated biomarkers underlying the protective effects of DD against hyperglycemia, targeting in a transcriptional approach the redox and insulin-signaling pathway. Fish were fed on a diet containing DD (3 mg/kg) for 74 days. In the last 14 days, they were exposed to a 111 mM glucose solution to induce a hyperglycemic state. DD reduced blood glucose levels as well as normalized the brain mRNA transcription of four insulin receptors-coding genes (Insra1, Insra2, Insrb1, Insrb2), which were down-regulated by glucose. DD alone caused an up-regulation of relative mRNA transcription in both Insra receptors and glucose transporter 3 genes. DD counteracted hyperglycemia-induced lipid peroxidation, protein and thiol depletion. Along with the decreased activity of antioxidant enzymes SOD and GPx, the brain of hyperglycemic fish presented a reduction in mRNA transcription of FoxO3A, FoxO3B, Nrf2, GPx3A, SOD1, and SOD2 genes. Besides normalizing the transcriptional levels, DD caused an up-regulation of relative mRNAs that encode Nrf2, FoxO1A, FOXO3A, GPx4A, PTP1B, AKT and SelP. Collectively, our findings suggest that the antioxidant and anti-hyperglycemic actions of DD in a zebrafish diabetes model are likely associated with the regulation of the oxidative stress resistance and the insulin-signaling pathway and that could be related to the modulation at mRNA level of two important transcription factors, Nrf2 and FoxO.

Methyl and Ethylmercury elicit oxidative stress and unbalance the antioxidant system in Saccharomyces cerevisiae.

Methylmercury (MeHg) and Ethylmercury (EtHg) are toxic to the central nervous system. Human exposure to MeHg and EtHg results mainly from the consumption of contaminated fish and thimerosal-containing vaccines, respectively. The mechanisms underlying the toxicity of MeHg and EtHg are still elusive. Here, we compared the toxic effects of MeHg and EtHg in Saccharomyces cerevisiae (S. cerevisiae) emphasizing the involvement of oxidative stress and the identification of molecular targets from antioxidant pathways. Wild type and mutant strains with deleted genes for antioxidant defenses, namely: γ-glutamylcysteine synthetase, glutathione peroxidase, catalase, superoxide dismutase, mitochondrial peroxiredoxin, cytoplasmic thioredoxin, and redox transcription factor Yap1 were used to identify potential pathways and proteins from cell redox system targeted by MeHg and EtHg. MeHg and EtHg inhibited cell growth, decreased membrane integrity, and increased the granularity and production of reactive species (RS) in wild type yeast. The mutants were predominantly less tolerant of mercurial than wild type yeast. But, as the wild strain, mutants exhibited higher tolerance to MeHg than EtHg. Our results indicate the involvement of oxidative stress in the cytotoxicity of MeHg and EtHg and reinforce S. cerevisiae as a suitable model to explore the mechanisms of action of electrophilic toxicants.

Hyperglycemia elicits anxiety-like behaviors in zebrafish: Protective role of dietary diphenyl diselenide.

Diabetes mellitus (DM) is a chronic metabolic disease that may comorbid with various psychiatric disorders, such as anxiety and depression. The search for effective therapeutics to alleviate hyperglycemia and complications resulting from DM is continuous. Here we investigate the effects of diphenyl diselenide (DD), an organoselenium compound with several pharmacological properties, in a zebrafish model of hyperglycemia. Fish were fed for 74 days with a diet containing 3 mg/Kg DD, a concentration chosen after experiments based in a dose-response curve (DD 1, 2 and 3 mg/Kg) that did not cause overt toxicity (mortality, weight loss and neurobehavioral deficits). In the last 14 days of the experimental period, fish were concomitantly exposed to a glucose solution (111 mM). Afterwards, blood glucose levels, brain selenium (Se) content, and behavioral analysis aiming to assess anxiety-like behaviors and locomotor/exploratory activities were performed. In the novel tank diving test, glucose decreased vertical exploration and fish spent less time in the lit area when tested in the light-dark test, suggesting increased anxiety-like behavior. Moreover, DD decreased blood glucose levels in hyperglycemic fish as well as prevented the development of anxiety-related symptoms. DD diet alone did not change glycemia and behavioral parameters, but increased Se levels in the brain without affecting the cellular viability. Collectively, our findings highlight the growing utility of this zebrafish hyperglycemia model as a valuable strategy for further research in DM field and neuroprotective approaches.

Syzygium cumini leaf extract inhibits LDL oxidation, but does not protect the liproprotein from glycation.

ETNOPHARMACOLOGICAL RELEVANCE: Syzygium cumini (L.) Skeels is a plant widely used in folk medicine to treat diabetes mellitus (DM). The tea from its leaves is frequently used by diabetics for lowering hyperglycemia. There is a close relationship between DM and atherosclerosis, a chronic immuno-inflammatory disease, were the early stages encompass oxidative and glycative modifications in the structure of low density lipoprotein (LDL). AIM OF THIS STUDY: To investigate the potential protective effects of aqueous-leaf extract from Syzygium cumini (S.cExt) against CuSO4-induced oxidation and methylglyoxal (MG)-induced glycation of human LDL in vitro. MATERIALS AND METHODS: LDL oxidative changes were evaluated by measuring conjugated dienes (CD) formation, thiobarbituric acid reactive substances (TBARS) levels, quenching of tryptophan (Trp) fluorescence and structural modifications in LDL particle. In LDL glycated by MG (glyLDL), we determined the levels of fluorescent advanced glycation end products (AGEs) and mobility by agarose gel electrophoresis. RESULTS: S.cExt blocked oxidative events induced by CuSO4 in human LDL, plasma and serum. Fourier transform infrared spectroscopy (FT-IR) revealed that specific regions of apoB100 were oxidized by CuSO4 in human LDL and that S.cExt reduced these oxidations. Unlike, the increased AGEs levels and eletrophoretic mobility observed in LDL MG-glycated were not modified by S.cExt. CONCLUSION: The findings herein indicate that S.cExt could be tested in atherogenesis models as potential protective agent against LDL oxidation.

N-Acetylcysteine does not protect behavioral and biochemical toxicological effect after acute exposure of diphenyl ditelluride.

Diphenyl ditelluride (PhTe)2 is a versatile molecule used in the organic synthesis and it is a potential prototype for the development of novel biologically active molecules. The mechanism(s) involved in (PhTe)2 toxicity is(are) elusive, but thiol oxidation of critical proteins are important targets. Consequently, the possible remedy of its toxicity by thiol-containing compounds is of experimental and clinical interest. The present study aimed to investigate putative mechanisms underlying the toxicity of (PhTe)2 in vivo. We assessed behavioral and oxidative stress parameters in mice, including the modulation of antioxidant enzymatic defense systems. In order to mitigate such toxicity, N-acetylcysteine (NAC) was administered before (3 d) and simultaneously with (PhTe)2 (7 d). Mice were separated into six groups receiving daily injections of (1) TFK (2.5 ml/kg, intraperitonealy (i.p.)) plus canola oil (10 ml/kg, subcutaneously (s.c.)), (2) NAC (100 mg/kg, i.p.) plus canola oil s.c., (3) TFK i.p. plus (PhTe)2 (10 µmol/kg, s.c.), (4) TFK i.p. plus (PhTe)2 (50 µmol/kg, s.c.), (5) NAC plus (PhTe)2 (10 µmol/kg, s.c.), and (6) NAC plus (PhTe)2 (50 µmol/kg, s.c.). (PhTe)2 treatment started on the fourth day of treatment with NAC. Results demonstrated that (PhTe)2 induced behavioral alterations and inhibited important selenoenzymes (thioredoxin reductase and glutathione peroxidase). Treatments produced no or minor effects on the activities of antioxidant enzymes catalase and glutathione reductase. Contrary to expected, NAC co-administration did not protect against the deleterious effects of (PhTe)2. Other low-molecular-thiol containing molecules should be investigated to determine whether or not they can be effective against ditellurides.

Evaluation of in vitro antioxidant effect of new mono and diselenides.

This study was designed to examine the antioxidant activity in vitro of novel mono- and diselenide compounds. We compared whether the formation of p-methyl-selenol from compounds 1-phenyl-3-(p-tolylselanyl)propan-2-amine (C1) and 1,2-dip-tolyldiselenide (C4) and o-methoxy-selenol from compounds 1-(2-methoxyphenylselanyl)-3-phenylpropan-2-amine (C2) and 1,2-bis(2-methoxyphenyl)diselenide (C3) may be involved in their antioxidant effects. The compounds were tested against Fe(II) and sodium nitroprusside (SNP)-induced lipid peroxidation in rat brain and liver homogenates. Likewise, the antioxidant capacity of the compounds was assessed by their ability to decolorize the DPPH radical as well as the Fe(II) chelating assay through the reduction of molybdenum(VI) (Mo6+) to molybdenum(V) (Mo5+). This colorimetric assay was also used to quantify thiol peroxidase (GPx) and oxidase activity and thioredoxin reductase (TrxR) activity. The results showed that the novel selenide compounds inhibit the thiobarbituric acid reactive species (TBARS) induced by different pro-oxidants, but the monoselenides effects were significant only at concentrations higher than the concentrations of the diselenides. Similarly, the total antioxidant activity was higher in the diselenides. Moreover, GPx and TrxR activity was only observed for the diselenides, which indicates that these compounds are more stable selenol molecules than monoselenides.