Browsing by Author "Rueff, José"
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- Genetic toxicology of flavonoids : the role of metabolic conditions in the induction of reverse mutation, SOS functions and sister-chromatid exchangesPublication . Rueff, José; Laires, António; Borba, Helena; Chaveca, Teresa; Gomes, Maria Inácia; Hapern, ManuelGlycosides of flavonols such as quercetin, are found in the edible portions of most food vegetables. Flavonols present in plants as glycosides can be freed during fermentation. We have compared the DNA-damaging activity of quercetin, rutin (3-o-rutinoside of quercetin) and a fermented flavonoid-containing beverage, red wine, for different genetic end-points under different metabolic conditions. The genotoxicity of quercetin, rutin and commercial red wine has been studied for the induction of: (i) reverse mutation in the Ames assay; (ii) SOS functions in the SOS Chromotest; (iii) sister-chro-matid exchanges (SCEs) in human lymphocytes. While in the Ames assay the mutagenicity of quercetin is enhanced by the presence of rat liver microsomal enzymes (S9) or the respective cytosolic fraction (S100), genotoxicity is reduced when the induction of SOS responses is assessed using the SOS Chromotest. Similarly, the induction of SCEs is lowered when testing in the presence of liver enzymes. Rutin has no activity whatsoever. Detection of activity of red wine in the three assays is not dependent upon hydrolysis by glycosidases and its content of quercetin accounts almost entirely for the levels of genotoxicity detected. The results suggest that the putative genotoxic metabolites of quercetin vary for different genetic end-points considered and that the metabolic fate of flavonoids might partly account for the conflicting data about their genotoxicity in vivo and carcinogenic activity.
- Oxidative injury in V79 Chinese hamster cells: protectivePublication . Fernandes, Ana S.; Serejo, João; Gaspar, Jorge; Cabral, Fátima; Bettencourt, Ana F.; Rueff, José; Castro, Matilde; Costa, Judite; Oliveira, Nuno G.Oxidative cell injury could be induced by different reactive oxygen species (ROS) operating in multiple pathways. The present work is focused on three different models of oxidative stress: the xanthine/xanthine oxidase system (XXO), an extracellular superoxide anion generator; tert-butylhydroperoxide (TBHP), an analogue of lipid hydroperoxides; and doxorubicin (Dox), an anticancer drug. Superoxide and peroxyl radicals, among other ROS, could be effectively scavenged by MnTM-4-PyP, a polyfunctional catalytic antioxidant. In this report, we have addressed the role of MnTM-4-PyP on the protection against the cytotoxicity induced by the three aforementioned oxidants. The effect of MnTM-4-PyP (0.1–100 μM) was evaluated in V79 fibroblasts using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide reduction and the crystal violet assays, as well as the mitotic index. Also, the generation of intracellular ROS was studied by the fluorescent probe dihydroethidium. MnTM-4-PyP has shown significant protective effects against the cytotoxicity of XXO and TBHP, increasing the cell viability in approximately 40% and reducing the intracellular level of ROS. However, no considerable protection occurred against Dox. The three oxidants caused a mitotic index reduction that was not altered by MnTM-4-PyP. In summary, MnTM-4-PyP appears to be a promising agent for the protection against oxidative injury. However, it has shown differential responses, reinforcing the need to study different experimental models for the adequate evaluation of its potentialities as a catalytic antioxidant.
- The role of poly(ADP-ribose)polymerase in the induction of sister chromatid exchanges and micronuclei by mitomycin C in Down's syndrome cells as compared to euploid cellsPublication . Caria, Helena; Quintas, Ana; Chaveca, Teresa; Rueff, JoséInhibitors of poly(ADP-ribose)polymerase (PARP; EC 2.4.2.30), such as 3-aminobenzamide (3-AB), can be used to assess the role of the enzyme in the induction of DNA lesions in euploid cells as compared to cells of genetic conditions known to exhibit increased susceptibility to chemical or physical mutagens, such as Down’s syndrome (DS) lymphocytes. We report in this work on the effect of PARP inhibition by 3-AB in the induction of sister chromatid exchanges (SCE) and micronuclei (MN) in DS lymphocytes as compared to iymphocytes from normal controls exposed in vitro to a gradient of mitomycin C (MMC). For both tvpes of cells, DS and normal lymphocytes. MMC induces a significant increase in frequencies of SCE and MN in the absence and in the presence of 3-AB. In the presence of 3-AB the yield of SCE and MN induced by MMC was significantly higher in normal lymphocytes as compared to lymphocytes from DS patients. The molecular mechanisms by which 3-AB affects the yield of SCE and MN remains to be fully elucidated: however, it seems clear that DS patients display a diftèrent behavior in what concerns poly(ADP-ribosyl)ation as compared to normal individuais.