Cytotoxicity of Extracts from Petiveria alliacea Leaves on Yeast.

Petiveria alliacea L. is a plant used in traditional medicine harboring pharmacological properties with anti-inflammatory, antinociceptive, hypoglycemiant and anesthetic activities. This study assessed the potential cytotoxic, genotoxic and mutagenic effects of ethanolic extract of P. alliacea on Saccharomyces cerevisiae strains. S. cerevisiae FF18733 (wild type) and CD138 (ogg1) strains were exposed to fractioned ethanolic extracts of P. alliacea in different concentrations. Three experimental assays were performed: cellular inactivation, mutagenesis (canavanine resistance system) and loss of mitochondrial function (petites colonies). The chemical analyses revealed a rich extract with phenolic compounds such as protocatechuic acid, cinnamic and catechin epicatechin. A decreased cell viability in wild-type and ogg1 strains was demonstrated. All fractions of the extract exerted a mutagenic effect on the ogg1 strain. Only ethyl acetate and n-butanol fractions increased the rate of petites colonies in the ogg1 strain, but not in the wild-type strain. The results indicate that fractions of mid-polarity of the ethanolic extract, at the studied concentrations, can induce mutagenicity mediated by oxidative lesions in the mitochondrial and genomic genomes of the ogg1-deficient S. cerevisiae strain. These findings indicate that the lesions caused by the fractions of P. alliacea ethanolic extract can be mediated by reactive oxygen species and can reach multiple molecular targets to exert their toxicity.

Influence of Ogg1 repair on the genetic stability of ccc2 mutant of Saccharomyces cerevisiae chemically challenged with 4-nitroquinoline-1-oxide (4-NQO).

In Saccharomyces cerevisiae, disruption of genes by deletion allowed elucidation of the molecular mechanisms of a series of human diseases, such as in Wilson disease (WD). WD is a disorder of copper metabolism, due to inherited mutations in human copper-transporting ATPase (ATP7B). An orthologous gene is present in S. cerevisiae, CCC2 gene. Copper is required as a cofactor for a number of enzymes. In excess, however, it is toxic, potentially carcinogenic, leading to many pathological conditions via oxidatively generated DNA damage. Deficiency in ATP7B (human) or Ccc2 (yeast) causes accumulation of intracellular copper, favouring the generation of reactive oxygen species. Thus, it becomes important to study the relative importance of proteins involved in the repair of these lesions, such as Ogg1. Herein, we addressed the influence Ogg1 repair in a ccc2 deficient strain of S. cerevisiae. We constructed ccc2-disrupted strains from S. cerevisiae (ogg1ccc2 and ccc2), which were analysed in terms of viability and spontaneous mutator phenotype. We also investigated the impact of 4-nitroquinoline-1-oxide (4-NQO) on nuclear DNA damage and on the stability of mitochondrial DNA. The results indicated a synergistic effect on spontaneous mutagenesis upon OGG1 and CCC2 double inactivation, placing 8-oxoguanine as a strong lesion-candidate at the origin of spontaneous mutations. The ccc2 mutant was more sensitive to cell killing and to mutagenesis upon 4-NQO challenge than the other studied strains. However, Ogg1 repair of exogenous-induced DNA damage revealed to be toxic and mutagenic to ccc2 deficient cells, which can be due to a detrimental action of Ogg1 on DNA lesions induced in ccc2 cells. Altogether, our results point to a critical and ambivalent role of BER mediated by Ogg1 in the maintenance of genomic stability in eukaryotes deficient in CCC2 gene.

Diversity and Karyotypic Evolution in the Genus Neacomys (Rodentia, Sigmodontinae).

Neacomys (Sigmodontinae) comprises 8 species mainly found in the Amazonian region. We describe 5 new karyotypes from Brazilian Amazonia: 2 cytotypes for N. paracou (2n = 56/FNa = 62-66), 1 for N. dubosti (2n = 64/FNa = 68), and 2 for Neacomys sp. (2n = 58/FNa = 64-70), with differences in the 18S rDNA. Telomeric probes did not show ITS. We provide a phylogeny using Cytb, and the analysis suggests that 2n = 56 with a high FNa is ancestral for the genus, as found in N. paracou, being retained by the ancestral forms of the other species, with an increase in 2n occurring independently in N. spinosus and N. dubosti. Alternatively, an increase in 2n may have occurred in the ancestral taxon of the other species, followed by independent 2n-reduction events in Neacomys sp. and in the ancestral species of N. tenuipes, N. guianae, N. musseri, and N. minutus. Finally, a drastic reduction event in the diploid number occurred in the ancestral species of N. musseri and N. minutus which exhibit the lowest 2n of the genus. The karyotypic variations found in both intra- and interspecific samples, associated with the molecular phylogeny, suggest a chromosomal evolution with amplification/deletion of constitutive heterochromatin and rearrangements including fusions, fissions, and pericentric inversions.

Genotoxic and Cytotoxic Safety Evaluation of Papain (Carica papaya L.) Using In Vitro Assays.

Papain, a phytotherapeutic agent, has been used in the treatment of eschars and as a debriding chemical agent to remove damaged or necrotic tissue of pressure ulcers and gangrene. Its benefits in these treatments are deemed effective, since more than 5000 patients, at the public university hospital at Rio de Janeiro, Brazil, have undergone papain treatment and presented satisfactory results. Despite its extensive use, there is little information about toxic and mutagenic properties of papain. This work evaluated the toxic and mutagenic potential of papain and its potential antioxidant activity against induced-H(2)O(2) oxidative stress in Escherichia coli strains. Cytotoxicity assay, Growth inhibition test, WP2-Mutoxitest and Plasmid-DNA treatment, and agarose gel electrophoresis were used to investigate if papain would present any toxic or mutagenic potential as well as if papain would display antioxidant properties. Papain exhibited negative results for all tests. This agent presented an activity protecting cells against H(2)O(2)-induced mutagenesis.

Biological effects of rutin on the survival of Escherichia coli AB1157 and on the electrophoretic mobility of plasmid PUC 9.1 DNA.

The use of natural products as medicines is growing in the world. The rutin, a compound isolated from Ruta graveolens, is a flavonoid, which has been suggested to have antioxidant properties and to reduce the triacylglycerol levels. In this study, plasmid desoxyribonucleic acid (DNA) was exposed to rutin (0.33, 10, 20, 30 microg/ml) in presence of stannous chloride (SnCl2), a reducing agent widely used to obtain radiopharmaceuticals labeled with technetium-99m. Samples of the plasmid DNA were analyzed through agarose gel electrophoresis. E. coli AB1157 culture was also incubated with rutin (3, 30, 50, 100 microg/ml) and the survival fractions were calculated. The results show that the rutin, in these concentrations, is not capable of: i/ damaging the DNA, ii/ protecting the DNA from the SnCl2 redox action, and iii/ inactivating the E. coli AB1157 culture. The analysis of our data indicates that rutin do not present toxic activity in the evaluated systems.

Radiation induced-like effects of four home bleaching agents used for tooth whitening: effects on bacterial cultures with different capabilities of repairing deoxyribonucleic acid (DNA) damage.

"Home bleaching" methods are commonly used in dentistry to correct tooth discoloration. This technique employs carbamide peroxide, in several concentrations, where the active component is hydrogen peroxide. In patients undertaking this treatment, this exposure can cause biological effects mainly due to the activity of hydrogen peroxide. Hydrogen peroxide is associated with effects induced by chemical (natural and synthetic substances) and physical agents (ionizing radiations). We have evaluated the cytotoxic effects of four commercial dental bleaching agents: Insta-Brite, Karisma, Opalescence and Whiteness. We have studied the effects of these agents on the survival of different E. coli strains with various capabilities to repair damages on the deoxyribonucleic acid (DNA): AB1157 (wild type), AB2463 (recA) and BW9091 (xthA). To determine the effect of the bleaching agents on the survival of E. coli AB1157, AB2463 and BW9091, cultures in exponential growth-phase were incubated with the bleaching agent or with 0.9% NaCl, as a control. After plating, the survival fractions were determined. The bleaching agents tested decreased the survival fractions of all strains studied and the E. coli BW9091 was the most sensitive and, moreover, these bleaching agents are capable of inducing damage to the DNA molecule. In conclusion, our results indicate that dental bleaching agents can generate biological effects like the ionizing radiations, and we suggest that dental professionals involved in bleaching to correct tooth discoloration, should control the clinical environment strictly, thus preventing contact between the oral mucosa/gingival tissues and the bleaching agents.