The diphenyl ditelluride (DPDT) is a prototype for the development of new biologically active molecules. In previous studies, DPDT showed an elevated cytotoxicity in Chinese hamster fibroblast (V79) cells but the mechanisms for reduction of cell viability still remain unknown. DPDT showed mutagenic properties by induction of frameshift mutations in bacterium Salmonella typhimurium and yeast Saccharomyces cerevisiae. This organotelluride also induced DNA strand breaks in V79 cells. In this work, we investigated the mechanism of DPDT cytotoxicity by evaluating the effects of this compound on cell cycle progression, apoptosis induction and topoisomerase I inhibition. Significant decrease of V79 cell viability after DPDT treatment was revealed by MTT assay. Morphological analysis showed induction of apoptosis and necrosis by DPDT in V79 cells. An increase of caspase 3/7 activity confirmed apoptosis induction. The cell cycle analysis showed an increase in the percentage of V79 cells in S phase and sub-G1 phase. The yeast strain deficient in topoisomerase I (Topo I) showed higher tolerance to DPDT compared with the isogenic wild-type strain, suggesting that the interaction with this enzyme could be involved in DPDT toxicity. The sensitivity to DPDT found in top3Δ strain indicates that yeast topoisomerase 3 (Top3p) could participate in the repair of DNA lesions induced by the DPDT. We also demonstrated that DPDT inhibits human DNA topoisomerase I (Topo I) activity by DNA relaxation assay. Therefore, our results suggest that the DPDT-induced cell cycle arrest and reduction in cell viability could be attributed to interaction with topoisomerase I enzyme.

The clinical manifestations of Lonomia obliqua caterpillar envenomation are systemic hemorrhage and acute kidney injury. In an effort to better understand the physiopathological mechanisms of envenomation, a rat model was established to study systemic tissue damage during L. obliqua envenomation. An array of acute venom effects was characterized, including biochemical, hematological, histopathological, myotoxic and genotoxic alterations. Rapid increases in serum alanine and aspartate transaminases, γ-glutamyl transferase, lactate dehydrogenase, hemoglobin, bilirubin, creatinine, urea and uric acid were observed, indicating that intravascular hemolysis and liver and kidney damage had occurred. Treatment with a specific antivenom (antilonomic serum) for up to 2 h post-venom injection neutralized the biochemical alterations. However, treatment after 6 h post-venom injection failed to normalize all biochemical parameters, despite its efficacy in reversing coagulation dysfunction. The hematological findings were consistent with hemolytic anemia and neutrophilic leukocytosis. The histopathological alterations were mainly related to hemorrhage and inflammation in the subcutaneous tissue, lung, heart and kidneys. Signs of congestion and hemosiderosis were evident in the spleen, and hemoglobin and/or myoglobin casts were also detected in the renal tubules. Increased levels of creatine kinase and creatine kinase-MB were correlated with the myocardial necrosis observed in vivo and confirmed the myotoxicity detected in vitro in isolated extensor digitorum longus muscles. Significant DNA damage was observed in the kidneys, heart, lung, liver and lymphocytes. The majority of the DNA lesions in the kidney were due to oxidative damage. The results presented here will aid in understanding the pathology underlying Lonomia's envenomation.

The organoselenium compound, dicholesteroyl diselenide (DCDS) is a structural analogue of diphenyl diselenide (DPDS) and may be considered as a promising antioxidant drug in vivo. Nevertheless, little is known about the toxicological properties of DCDS. In the present study we evaluated the cytotoxic, genotoxic and mutagenic properties of DCDS in Chinese hamster lung fibroblasts (V79) and in strains of the yeast Saccharomyces cerevisiae, proficient and deficient in several DNA-repair pathways. The results with V79 cells show that DCDS induced cytotoxicity, GSH depletion and elevation of lipid peroxidation at lower concentrations than did DPDS. DCDS also generated single- and double-strand DNA breaks in V79 cells, both in the presence and in the absence of metabolic activation, as revealed by alkaline and neutral comet assays. Moreover, the induction of oxidative DNA base-damage was demonstrated by means of a modified comet assay with formamidopyrimidine-DNA glycosylase and endonuclease III. Treatment with DCDS also induced micronucleus formation in V79 cells as well as point and frame-shift mutations in a haploid wild-type strain of S. cerevisiae. Yeast mutants defective in base excision-repair proteins were the most sensitive to DCDS. Pre-incubation with N-acetylcysteine reduced DCDS's oxidative, genotoxic and mutagenic effects in yeast and in V79 cells. Our findings indicate that the presence of cholesteroyl substituents in DCDS results in elevation of its cytotoxic and genotoxic potential compared with that of DPDS in yeast and in V79 cells. However, due to dose-dependent contrasting behaviour of organoselenium compounds and differences in their toxicity in in vitro and in vivo systems, further studies are needed in order to establish the non-toxic concentration range for treatment in mammals.