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.

Genotoxicity of organoselenium compounds in human leukocytes in vitro.

DNA damage and cell viability of human leukocytes cells were examined as simple tests for screening the potential toxicity of organoselenium compounds. Leukocytes were incubated with different organoselenium compounds at 4, 10, 40 and 100 microM or vehicle (DMSO) for 3h at 37 degrees C before of in vitro assays. Cell viability was determined by Trypan blue exclusion. DNA damage was assessed using the alkaline comet assay with silver staining. The exposure of leukocytes to (S)-tert-butyl 1-diselenide-3-methylbutan-2-ylcarbamate, (S)-tert-butyl 1-diselenide-3-phenylpropan-2-ylcarbamate, (S)-2-amino-1-diselenide-3-methylpropanyl, (S)-2-amino-1-diselenide-3-phenylpropanyl, 3',3-ditrifluoromethyl diphenyl diselenide, 4',4-dimethoxy diphenyl diselenide, 4',4-dichloro diphenyl diselenide and 2',2,4',4,6',6-hexamethyl diphenyl diselenide, in the range of 10-100muM, induced a significant increase in Damage Index (DI). The genotoxic effect of all compounds was associated with high frequencies of cells with damage level 4 and all compounds caused a decrease in cell viability. Our results suggest that the selenium compounds tested were genotoxic and cytotoxic to human leukocytes cells in vitro and that the organoselenium amino acid derivatives ((S)-tert-butyl 1-diselenide-3-methylbutan-2-ylcarbamate, (S)-tert-butyl 1-diselenide-3-phenylpropan-2-ylcarbamate, (S)-2-amino-1-diselenide-3-methylpropanyl and (S)-2-amino-1-diselenide-3-phenylpropanyl) were more genotoxic than aromatic derivatives (3',3-ditrifluoromethyl diphenyl diselenide, 4',4-dimethoxy diphenyl diselenide, 4',4-dichloro diphenyl diselenide and 2',2,4',4,6',6-hexamethyl diphenyl diselenide). These effects may be linked to the pro-oxidant activity exhibited by selenium compounds when used in relatively high concentrations.