Homologous recombination induced by doxazosin mesylate and saw palmetto in the Drosophila wing-spot test.

Benign prostatic hyperplasia (BPH) is the most common tumor in men over 40 years of age. Acute urinary retention (AUR) is regarded as the most serious hazard of untreated BPH. α-Blockers, such as doxazosin mesylate, and 5-α reductase inhibitors, such as finasteride, are frequently used because they decrease both AUR and the need for BPH-related surgery. An extract of the fruit from American saw palmetto plant has also been used as an alternative treatment for BPH. The paucity of information available concerning the genotoxic action of these compounds led us to assess their activity as inducers of different types of DNA lesions using the somatic mutation and recombination test in Drosophila melanogaster. Finasteride did not induce gene mutation, chromosomal mutation or mitotic recombination, which means it was nongenotoxic in our experimental conditions. On the other hand, doxazosin mesylate and saw palmetto induced significant increases in spot frequencies in trans-heterozygous flies. In order to establish the actual role played by mitotic recombination and by mutation in the genotoxicity observed, the balancer-heterozygous flies were also analyzed, showing no increment in the total spot frequencies in relation to the negative control, for both drugs. Doxazosin mesylate and saw palmetto were classified as specific inducers of homologous recombination in Drosophila proliferative cells, an event linked to the loss of heterozygosity.

Genetic toxicology of dental composite resin extracts in somatic cells in vivo.

The aim of this study was to assess the potential genetic toxicity associated to nine aqueous extracts from dental composite resins (Charisma, Fill Magic, Fill Magic Flow, Durafill, TPH Spectrum, Concept, Natural Look, Filtek Z250 and Filtek P60) and one random extract. Homologous mitotic recombination, point and chromosomal mutation effects were determined in somatic proliferative cells of Drosophila melanogaster exposed to aqueous extracts of the clinically used composites. Reproducible increases in clone mutant spot frequencies induced by diluted extract of Fill Magic Flow were observed. These increments were exclusively associated to the induction of homologous recombination - a genetic phenomenon involved in the loss of heterozygosis. The other eight composite resins and the random extract had no statistically significant effect on total spot frequencies - suggesting that they are non-genotoxic in the somatic mutation and recombination test assay, which agrees with the applications they have in dentistry. These findings - supported by numerous studies showing a positive correlation between carcinogenicity in man and genotoxicity in the Drosophila wing spot test - point to the potential risks some composite resins pose to the health of patients and dentistry personnel.

Mutagenic evaluation of combined paclitaxel and cisplatin treatment in somatic cells of Drosophila melanogaster.

Recent studies have added paclitaxel (PAC) to traditional cisplatin (CIS) regimen to treat squamous cell carcinoma of the head and neck. The target of these antineoplastic agents is nuclear DNA for CIS and microtubules for PAC, although it is not restricted to malignant cells. In this study, the genotoxicity of the combined treatment of PAC and CIS was investigated using the standard version of the wing Somatic Mutation and Recombination Test (SMART) in Drosophila melanogaster. Quantitative and qualitative genotoxic effects of these compounds were estimated by comparing wing spot frequencies in marker-heterozygous to balancer-heterozygous flies. Two different concentrations of PAC (0.0025 and 0.005mM) and CIS (0.025 and 0.05mM) as well as combinations of them were employed. The results demonstrated that the spindle poison PAC alone was not genotoxic in this test system, while CIS was able to induce a high incidence of DNA damage in both genotypes, mainly related to somatic recombination. The data obtained for the combined treatments showed that its genotoxicity varied with the concentrations used. In small concentrations the number of total spots induced by combination was reduced in relation to CIS 0.025mM just for marker-heterozygous flies, showing that somatic recombination was the prevalent event involved. At higher concentrations the combined treatment showed significant reductions in the frequencies of large single spots, for both genotypes, and twin spots for marker-heterozygous flies, but did not significantly reduce the total spots frequency in either genotype. The data suggest that aneugenic activity of PAC could be responsible for the reduction in the genotoxicity of CIS.

Vanillin as a modulator agent in SMART test: inhibition in the steps that precede N-methyl-N-nitrosourea-, N-ethyl-N-nitrosourea-, ethylmethanesulphonate- and bleomycin-genotoxicity.

Vanillin (VA), the world's major flavoring compound used in food industry and confectionery products - that has antimutagenic and anticarcinogenic activity against a variety of mutagenic/carcinogenic agents - was tested for the interval between the formation of premutational lesion and it is finalization as a DNA lesion. The overall findings using co-treatment protocols in SMART test suggest that VA can lead to a significant protection against the general genotoxicity of ethylmethanesulphonate (EMS), N-ethyl-N-nitrosourea (ENU), N-methyl-N-nitrosourea (MNU) and bleomycin sulphate (BLEO). Considering MNU, ENU and EMS the desmutagenic activity observed could result from VA-stimulation of detoxification, via induction of glutathione S-transferase. However, the protector effect related to BLEO could be attributed to its powerful scavenger ability, which has the potential to prevent oxidative damage induced by BLEO.

Activity of topoisomerase inhibitors daunorubicin, idarubicin, and aclarubicin in the Drosophila Somatic Mutation and Recombination Test.

Anthracyclines have been widely used as anticancer drugs against different types of human cancers. The present study evaluated the mutagenic and recombinagenic properties of two anthracycline topoisomerase II (topo II) poisons, daunorubicin (DNR) and idarubicin (IDA), as well as the related topo II catalytic inhibitor aclarubicin (ACLA), using the wing Somatic Mutation and Recombination Test (SMART) in Drosophila melanogaster. The three anthracyclines were positive in this bioassay, producing mainly mitotic homologous recombination. The results for spot-size distribution and recombinagenic activity indicate that recombinational DNA damage accounts for approximately 91, 86, and 62% of DNR, IDA, and ACLA genotoxicity, respectively. Besides being a catalytic inhibitor of topo II, ACLA is also a topoisomerase I (topo I) poison. This dual topo I and II inhibitory effect, associated with its DNA-intercalating activity, could contribute to the activity of ACLA in the SMART assay.

Comparative genotoxic effect of vincristine, vinblastine, and vinorelbine in somatic cells of Drosophila melanogaster.

In this study, the vinca alkaloids vincristine (VCR), vinblastine (VBL) and vinorelbine (VNR) were investigated for genotoxicity in the wing Somatic Mutation and Recombination Test (SMART) of Drosophila. Our in vivo experiments demonstrated that all drugs assessed induced genetic toxicity, causing increments in the incidence of mutational events, as well as in somatic recombination. Another point to be considered is the fact that VNR was able to induce, respectively, approximately 13.0 and 1.7 times more mutant clones per millimolar exposure unit as their analogues VCR and VBL. The replacement of a CH(3) attached to vindoline group in VBL by a CHO in VCR seems to be responsible for the approximately seven times higher potency of the former. In contrast, the structural modifications on VNR's catharantine group could be related to its higher genotoxic potency, as well as its similar mutagenic and recombinagenic action.

Comparison of camptothecin derivatives presently in clinical trials: genotoxic potency and mitotic recombination.

The genotoxicity of camptothecin (CPT) and its clinical antineoplastic analogues irinotecan (CPT-11) and topotecan (TPT) were evaluated using the wing somatic mutation and recombination test (SMART) in Drosophila melanogaster. These compounds stabilize and trap the topoisomerase I-DNA complex, preventing the religation step of the breakage/rejoining reaction mediated by the enzyme. The standard version of the wing SMART was used to evaluate the three compounds and to compare the wing spots induced in marker-heterozygous and balancer-heterozygous flies. The results demonstrate that all compounds tested have a significant genotoxic effect in both genotypes analysed. At the same time, a comparison of the clone induction frequencies in marker-heterozygous and balancer-heterozygous flies shows that mitotic recombination is the prevalent mechanism through which the three compounds induce all categories of wing spots (78-93% recombination). TPT was the most genotoxic compound, probably because substitutions of amino groups for the 9-carbon of the CPT A ring leads to compounds with greater in vivo activity. CPT and CPT-11 induced, respectively, about 7 and 28 times fewer mutant clones per millimolar exposure unit than TPT.

Somatic recombination: a major genotoxic effect of two pyrimidine antimetabolitic chemotherapeutic drugs in Drosophila melanogaster.

Two deoxycytidine analogues, 1-beta-D-arabinofuranosylcytosine (cytosine arabinoside, citarabine, araC) and 5-aza-2'-deoxycytidine (decitabine, DAC, 5-aza-dC), are the drugs of choice in the treatment of acute myeloid leukaemia. The araC-induced cytotoxicity is a direct result of its interference with nucleic acids synthesis, whereas 5-aza-dC is a potent suppressor of DNA methylation. We employed the standard version of the wing somatic mutation and recombination test (SMART) in Drosophila melanogaster to evaluate the genotoxic potential of these two antimetabolites as a function of exposure concentration. In addition, we determined the relative contributions of mutational and recombinational events to total genotoxicity. The compounds were administered by chronic feeding of 3-day-old larvae. Our results indicate that recombinagenicity is the major genotoxic effect of araC and 5-aza-dC (approximately, 77 and 81%, respectively, recombination). The standardised clone induction frequencies (per mM concentration per cell per cell division) show that 5-aza-dC is 85 times more powerful then araC (inducing approximately 58 mutant clones per 10(5) cells per mM). The high recombinagenic activity of these two drugs suggests that--despite their therapeutic effects against cancer--a question is raised whether these drugs should be considered for adverse effects in cancer chemotherapy.

Effect of caffeine on the radioresistance and radiosensitivity of Drosophila melanogaster

Foi analisado o efeito do pré-tratamento com cafeína na induçäo de letais na linhagem radiorresistente CO3 e na sensível RC1. Os resultados obtidos mostraram que o tratamento isolado com cafeína näo tem um efeito mutagênico, tanto na linhagem resistente quanto na sensível. No entanto, o pré-tratamento com cafeína aumentou a freqüência de letais induzidos por radiaçäo na linhagem resistente (até o nivel da sensível näo pré-tratada), mas näo modificou a freqüência de letais na linhagem sensível, de modo que desaparecem as diferenças significativas na induçäo de letais existentes entre elas quando do tratamento isolado com radiaçäo. Dois tipos de resultados foram obtidos na análise do efeito da cafeína em combinaçäo com o EMS: quando da freqüência de letais induzidos foi baixa, o pré-tratamento com a cafeína aumentou a freqüência em ambas as linhagens; quando a freqüência foi alta, observou-se um pequeno aumento na resistente e uma pequena diminuiçäo na sensível. Estes resultados, tomados em conjunto, estäo de acordo com a sugestäo de que a diferença de sensibilidade observada entre as duas linhagens seja devido a diferenças no reparo do dano pré-mutacional. Apoio adicional a esta conclusäo foi obtido pela verificaçäo de que o pré-tratamento com cafeína aumentou de maneira significativa a freqüência de mutaçäo induzida em espermatozóides e espermátides e diminuiu a de espermatócitos tratados com EMS. Por outro lado, a observaçäo de que o efeito na linhagem resistente foi muito maior que o obtido na linhagem sensível, apoia a sugestäo da existência de diferenças nos níveis de reparo das duas linhagens analisadas