Nilza Nascimento Guimarães

Genotoxicity testing of combined treatment with cisplatin, bleomycin, and 5-fluorouracil in somatic cells of Drosophila melanogaster.

The simultaneous treatment with the cross-linking agent cisplatin, the radiomimetic antitumoral drug bleomycin, and the anti-metabolite drug 5-fluorouracil has been used as a regimen to treat patients with squamous cell carcinoma of the head and neck. Considering that these drugs interact directly with DNA, one of the important late-occurring complications from treatment of primary malignancies is the therapy-related secondary cancers as a result of the genotoxic activity of the drugs on normal cells. In this sense, the genotoxicity of this combination was evaluated using the wing somatic mutation and recombination test in Drosophila melanogaster. The mutant spots observed in marker-heterozygous and balancer-heterozygous flies were compared in order to quantitatively and qualitatively estimate the genotoxic effect of these drugs. Cisplatin (0.003 and 0.006mM), bleomycin (0.005 and 0.01mM), and both combinations preferentially induced recombinational events, while mutation is the major event regarding the genetic toxicity of 5-fluorouracil (0.025 and 0.05mM). The combination of these drugs produced synergistic and antagonistic genotoxic effects, depending on the concentrations used, which could impose a higher risk of secondary effects associated with their genotoxic effects, emphasizing the importance of long-term monitoring in patients being treated with these drugs.

Mutagenic and recombinagenic effects of lamivudine and stavudine antiretrovirals in somatic cells of Drosophila melanogaster

Lamivudine (3TC) and stavudine (d4T) are nucleoside analogue reverse transcriptase inhibitors employed in antiretroviral therapies. The mutational and recombinational potential as well as the total genetic toxicity was determined for both compounds at concentrations allowing at least 30% survival using the standard version of wing SMART assay. The standardized clone induction frequency per mg/ml for mwh/flr(3) genotype were approximately 2 and approximately 33 mutant clones/10(5) cells/(mg/ml) for d4T and 3TC, respectively. Comparing these results with those obtained in the mwh/TM3 genotype, it was possible to quantify the recombinagenic action of each drug. Approximately 86% of the mutant clones induced by 3TC and approximately 76% of the d4T induced clones were related to their mitotic recombination action. Our results indicate that both 3TC and d4T have high recombinagenic potential, and suggest that exposure to the drugs could cause genomic instability and loss of heterozygosity. This may be due to the fact that these genetic alterations play a primary role in carcinogenesis, and are also involved in secondary and subsequent steps of carcinogenesis by which recessive oncogenic mutations are revealed.

Antimutagenic and antirecombinagenic activities of noni fruit juice in somatic cells of Drosophila melanogaster

Noni, a Hawaiian name for the fruit of Morinda citrifolia L., is a traditional medicinal plant from Polynesia widely used for the treatment of many diseases including arthritis, diabetes, asthma, hypertension and cancer. Here, a commercial noni juice (TNJ) was evaluated for its protective activities against the lesions induced by mitomycin C (MMC) and doxorrubicin (DXR) using the Somatic Mutation and Recombination Test (SMART) in Drosophila melanogaster. Three-day-old larvae, trans-heterozygous for two genetic markers (mwh and flr3 ), were co-treated with TNJ plus MMC or DXR. We have observed a reduction in genotoxic effects of MMC and DXR caused by the juice. TNJ provoked a marked decrease in all kinds of MMC- and DXR-induced mutant spots, mainly due to its antirecombinagenic activity. The TNJ protective effects were concentration-dependent, indicating a dose-response correlation, that can be attributed to a powerful antioxidant and/or free radical scavenger ability of TNJ.

Comparative analysis of genetic toxicity of antiretroviral combinations in somatic cells of Drosophila melanogaster

Nucleoside reverse-transcriptase inhibitor (NRTI) drugs are a major component of highly-active antiretroviral therapy (HAART). NRTI combinations have been demonstrated as producing a sustained reduction in plasma viremia with an increased CD4 count, thereby showing clear clinical benefits. Therefore, the secondary effects caused by the combination of two NRTIs, mainly those related to amplification of genotoxic effects, due to increased risk of DNA damage caused by these drugs, should be carefully examined. We employed the standard version of the wing SMART in Drosophila melanogaster to obtain more detailed knowledge about the genotoxic profile of NRTI combinations of AZT+ddI, AZT+3TC and AZT+d4T. Our results showed that all combinations increased the frequencies of induction of mutant spots. The combinations AZT+ddI and AZT+3TC were shown to induce recombination rates ranging from 86.38% to 98.36% while AZT+d4T showed a large discrepancy between recombination and mutation percentages. The combination index demonstrated that 3TC and d4T produced antagonism while ddI showed synergistic effects in combination with AZT.

Comparative analysis of genetic toxicity of AZT and ddI antiretrovirals in somatic cells of Drosophila melanogaster

Antiretroviral therapies based on nucleoside reverse transcriptase inhibitors, like zidovudine (3′‐azido‐3′‐deoxythymidine; AZT) and didanosine (2′,3′‐dideoxyinosine; ddI), markedly reduce human immunodeficiency virus loads. The Somatic Mutation And Recombination Test in Drosophila melanogaster (wing SMART), in its standard version, was applied to compare AZT and ddI genetic toxicity expressed as point and chromosomal mutation as well as homologous mitotic recombination. The present findings provide evidence that the mechanistic basis underlying the genetic toxicity of these antiretrovirals is mainly related to mitotic recombination. However, a genotoxic pattern can correspondingly be discerned: AZT is able to induce recombination (∼85%) and mutation (∼15%), and ddI causes only homologous recombination (100%) in the wing SMART assay. Another point to be considered is the fact that ddI is 3.8 times less active to induce mutant clones per mg/ml unit as compared to AZT. The clinical significance of these observations has to be interpreted in the light of data obtained from long‐term toxicity in patients treated with the above mentioned agents. Environ. Mol. Mutagen., 2008.

Genetic toxicity of dillapiol and spinosad larvicides in somatic cells of Drosophila melanogaster.

BACKGROUND Higher rates of diseases transmitted from insects to humans led to the increased use of organophosphate insecticides, proven to be harmful to human health and the environment. New, more effective chemical formulations with minimum genetic toxicity effects have become the object of intense research. These formulations include larvicides derived from plant extracts such as dillapiol, a phenylpropanoid extracted from Piper aduncum, and from microorganisms such as spinosad, formed by spinosyns A and D derived from the Saccharopolyspora spinosa fermentation process. This study investigated the genotoxicity of dillapiol and spinosad, characterising and quantifying mutation events and chromosomal and/or mitotic recombination using the somatic mutation and recombination test (SMART) in wings of Drosophila melanogaster. RESULTS Standard cross larvae (72 days old) were treated with different dillapiol and spinosad concentrations. Both compounds presented positive genetic toxicity, mainly as mitotic recombination events. Distilled water and doxorubicin were used as negative and positive controls respectively. CONCLUSION Spinosad was 14 times more genotoxic than dillapiol, and the effect was found to be purely recombinogenic. However, more studies on the potential risks of insecticides such as spinosad and dillapiol are necessary, based on other experimental models and methodologies, to ensure safe use.

Assessment of complex genomic alterations induced by AZT, 3TC, and the combination AZT +3TC

Abstract Highly active antiretroviral therapy (HAART) regimens are based on the use of nucleoside reverse transcriptase inhibitors (NRTIs), which are the main drugs used by patients infected with the human immunodeficiency virus (HIV). The use of NRTIs combinations has afforded clear clinical benefits to patients undergoing HAART. However, the combination of two NRTIs may increase the risk of genomic instability in comparison with the drugs administered individually. We analyzed the ability of zidovudine (AZT) and lamivudine (3TC), and the combination AZT +3TC to induce complex genomic alterations using the cytokinesis-block micronucleus (CBMN) assay in Chinese hamster ovary (CHO)-K1 cells. The 24-h cell treatment with individual NRTIs showed that AZT increased micronucleus frequencies and nucleoplasmic bridges (NPBs). No significant differences were observed for any parameters investigated after exposure of CHO-K1 cells to 3TC. The combination AZT +3TC significantly increased micronucleus frequencies. Analysis of interaction between these drugs suggested that antagonism occurs in all AZT +3TC concentrations. These results highlight the importance to investigate the genotoxic profile of NRTIs to develop safer intervention strategies in antiretroviral treatment protocols.