Evaluation of the biological effects of (S)-dimethyl 2-(3-(phenyltellanyl) propanamido) succinate, a new telluroamino acid derivative of aspartic acid

Diselenoamino acid derivatives as GPx mimics and as substrates of TrxR: in vitro and in silico studies

Excessive production of reactive species in living cells usually has pathological effects. Consequently, the synthesis of compounds which can mimic the activity of antioxidant enzymes has inspired great interest. In this study, a variety of diselenoamino acid derivatives from phenylalanine and valine were tested to determine whether they could be functional mimics of glutathione peroxidase (GPx) and substrates for liver thioredoxin reductase (TrxR). Diselenides C and D showed the best GPx mimicking properties when compared with A and B. We suppose that the catalytic activity of diselenide GPx mimics depends on the steric effects, which can be influenced by the number of carbon atoms between the selenium atom and the amino acid residue and/or by the amino acid lateral residue. Compounds C and D stimulated NADPH oxidation in the presence of partially purified hepatic mammalian TrxR, indicating that they are substrates for TrxR. Our study indicates a possible dissociation between the two pathways for peroxide degradation (i.e., via a substrate for TrxR or via mimicry of GPx) for compounds tested in this study, except for PhSeSePh, and the antioxidant activity of diselenoamino acids can also be attributed to their capacity to mimic GPx and to be a substrate for mammalian TrxR.

The potential toxicological insights about the anti-HIV drug azidothymidine-derived monoselenides in human leukocytes: Toxicological insights of new selenium-azidothymidine analogs

Acquired immunodeficiency syndrome (AIDS) is a worldwide disease characterized by impairments of immune function. AIDS can be associated with oxidative stress (OS) that can be linked to selenium (Se) deficiency. Se is fundamental for the synthesis of selenoproteins, such as glutathione peroxidase and thioredoxin reductase. These enzymes catalyze the decomposition of reactive oxygen species and contribute to maintain equilibrium in cell redox status. Literature data indicate that organoselenium compounds, such as ebselen and diphenyl diselenide, have antioxidant properties in vitro and in vivo models associated with OS. Nevertheless, selenocompounds can also react and oxidize thiols groups, inducing toxicity in mammals. Here, we tested the potential cytotoxic and genotoxic properties of six analogs of the prototypal anti-HIV drug azidothymidine (AZT) containing Se (5′-Se-(phenyl)zidovudine; 5′-Se-(1,3,5-trimethylphenyl)zidovudine; 5′-Se-(1-naphtyl)zidovudine; 5′-Se-(4-chlorophenyl)zidovudine) (C4); 5′-Se-(4-methylphenyl)zidovudine (C5); and 5′-(4-methylbenzoselenoate)zidovudine). C5 increased the rate of dithiothreitol oxidation (thiol oxidase activity) and C2-C4 and C6 (at 100 µM) increased DNA damage index (DI) in human leukocytes. Moreover, C5 (200 µM) decreased human leukocyte viability to about 50%. Taken together, these results indicated the low in vitro toxicity in human leukocytes of some Se-containing analogs of AZT.

Differential genotoxicity of diphenyl diselenide (PhSe)2 and diphenyl ditelluride (PhTe)2

Organoselenium compounds have been pointed out as therapeutic agents. In contrast, the potential therapeutic aspects of tellurides have not yet been demonstrated. The present study evaluated the comparative toxicological effects of diphenyl diselenide (PhSe)₂ and diphenyl ditelluride (PhTe)₂ in mice after in vivo administration. Genotoxicity (as determined by comet assay) and mutagenicicity were used as end-points of toxicity. Subcutaneous administration of high doses of (PhSe)₂ or (PhTe)₂ (500 µmol/kg) caused distinct genotoxicity in mice. (PhSe)₂ significantly decreased the DNA damage index after 48 and 96 h of its injection (p < 0.05). In contrast, (PhTe) caused a significant increase in DNA damage (p < 0.05) after 48 and 96 h of intoxication. (PhSe)₂ did not cause mutagenicity but (PhTe)₂ increased the micronuclei frequency, indicating its mutagenic potential. The present study demonstrated that acute in vivo exposure to ditelluride caused genotoxicity in mice, which may be associated with pro-oxidant effects of diphenyl ditelluride. In addition, the use of this compound and possibly other related tellurides must be carefully controlled.

An in vivo insight to the toxicological profile of various organotellurides

In this study we have examined the in vivo toxic effects of various organochalcogens on hepatic, renal, glycemic and lipid profile. Diorganotellurium dichloride phosphonate (C1) at all tested doses did not modify serum alanine aminotransferase (ALT) activity in mice. While, 2-butyltellurium furan (C2) and dinaphthalene ditelluride (C3) at a dose of 0.75 and 0.125 mmol/kg caused an increase in aspartate aminotransferase (AST) and ALT activities. Our data showed that C1 caused an increase in urea content at different doses while treatment with C2 and C3 did not modify urea content. Treatment with C2 caused a significant alteration in serum glucose and fructosamine levels which explains the possible toxicity of these compounds. No significant changes were observed for cholesterol and triglycerides levels. These results suggest that organochalcogen compounds presented liver and renal toxicity and also altered glycemic profile which may leads to various clinical complications.

Sub-acute administration of (S)-dimethyl 2-(3-(phenyltellanyl) propanamido) succinate induces toxicity and oxidative stress in mice: unexpected effects of N-acetylcysteine

The organic tellurium compound (S)-dimethyl 2-(3-(phenyltellanyl) propanamide) succinate (TeAsp) exhibits thiol-peroxidase activity that could potentially offer protection against oxidative stress. However, data from the literature show that tellurium is a toxic agent to rodents. In order to mitigate such toxicity, N-acetylcysteine (NAC) was administered in parallel with TeAsp during 10 days. Mice were separated into four groups receiving daily injections of (A) vehicle (PBS 2.5 ml/kg, i.p. and DMSO 1 ml/kg, s.c.), (B) NAC (100 mg/kg, i.p. and DMSO s.c.), (C) PBS i.p. and TeAsp (92.5 μmol/kg, s.c), or (D) NAC plus TeAsp. TeAsp treatment started on the fourth day. Vehicle or NAC-treated animals showed an increase in body weight whereas TeAsp caused a significant reduction. Contrary to expected, NAC co-administration potentiated the toxic effect of TeAsp, causing a decrease in body weight. Vehicle, NAC or TeAsp did not affect the exploratory and motor activity in the open-field test at the end of the treatment, while the combination of NAC and TeAsp produced a significant decrease in these parameters. No DNA damage or alterations in cell viability were observed in leukocytes of treated animals. Treatments produced no or minor effects on the activities of antioxidant enzymes catalase, glutathione peroxidase and glutathione reductase, whereas the activity of the thioredoxin reductase was decreased in the brain and increased the liver of the animals in the groups receiving TeAsp or TeAsp plus NAC. In conclusion, the toxicity of TeAsp was potentiated by NAC and oxidative stress appears to play a central role in this process.