Ilce Mara de Syllos Cólus

Polymorphisms in glutathione-related genes modify mercury concentrations and antioxidant status in subjects environmentally exposed to methylmercury

Methylmercury (MeHg) toxicity may vary widely despite similar levels of exposure. This is hypothetically related to genetic differences in enzymes metabolizing MeHg. MeHg causes oxidative stress in experimental models but little is known about its effects on humans. The aims of the present study was to evaluate the effects of polymorphisms in glutathione (GSH)-related genes (GSTM1, GSTT1, GSTP1 and GCLM) on Hg concentrations in blood and hair, as well as MeHg-related effects on catalase (CAT) and glutathione-peroxidase (GPx) activity and GSH concentrations. Study subjects were from an Amazonian population in Brazil chronically exposed to MeHg from fish. Hg in blood and hair were determined by ICP-MS, CAT, GPx and GSH were determined by spectrophotometry, and multiplex PCR (GSTM1 and GSTT1) and TaqMan assays (GSTP1 and GCLM) were used for genotyping. Mean Hg concentrations in blood and hair were 48±36 μg/L and 14±10 μg/g. Persons with the GCLM-588 TT genotype had lower blood and hair Hg than did C-allele carriers (linear regression for Hg in blood β=-0.32, p=0.017; and hair β=-0.33; p=0.0090; adjusted for fish intake, age and gender). GSTM1*0 homozygous had higher blood (β=0.20; p=0.017) and hair Hg (hair β=0.20; p=0.013). Exposure to MeHg altered antioxidant status (CAT: β=-0.086; GSH: β=-0.12; GPx: β=-0.16; all p<0.010; adjusted for gender, age and smoking). Persons with GSTM1*0 had higher CAT activity in the blood than those with GSTM1. Our data thus indicate that some GSH-related polymorphisms, such as GSTM1 and GCLM may modify MeHg metabolism and Hg-related antioxidant effects.

Oral carcinoma epidemiology in Paraná State, Southern Brazil

Oral carcinoma is the sixth most frequent type of cancer in the world and the seventh most common in Brazil (the country with the highest incidence in Latin America). Mean five-year survival remains one of the lowest among the main cancers, thus justifying studies that contribute to the development of preventive strategies. The aim of this study was to compare the epidemiological, clinical, and histological characteristics of 91 patients with oral carcinoma. Mean age was 58.62 +/- 10.46 years, and male-to-female ratio was 6.6:1.0 (79 men and 12 women). European descendants predominated with 79 patients (86.8%). Eighty-five individuals (93.4%) smoked and 70 (76.9%) consumed alcohol regularly. Anatomical distribution of tumors was: 27 (29.7%) tongue; 18 (19.8%) floor of mouth; 11 (12.1%) oropharynx; and 11 (12.1%) oral mucosa. Fifty-seven patients (62.6%) presented lymph node involvement and three (3.3%) had distant metastases. Surgery and radiotherapy were used in 43.2% of patients. With the exception of the male/female ratio (which was higher), our data are consistent with previous studies on oral carcinoma patients.

Micronucleus frequencies in Astyanax bimaculatus (Characidae) treated with cyclophosphamide or vinblastine sulfate

Abstract Two known mutagenic drugs, cyclophosphamide and vinblastine sulfate, were tested using the micronucleus test in the native fish species,Astyanax bimaculatus , in order to determine which of these drugs and the doses which would be the most adequate for use as positivecontrols in this species. This Brazilian fish species was chosen because few toxicity studies have used native fish species and this particularspecies is widely consumed in various regions of Brazil. Three thousand erythrocytes per specimen were scored. Doses of 16 and 8 mg/kg body weight of cyclophosphamide and vinblastine sulfate, respectively, were the most effective in causing micronuclei. Cyclo phospha-mide was the most mutagenic of the two drugs and is recommended for use as a positive control in A. bimaculatus . Departamento de Biologia Geral, Centro de Ciencias Biologicas, Universidade Estadual de Londrina,86051-970 Londrina, PR, Brasil. Send correspondence to I.M.S.C. Fax: +55-43-371-4207. E-mail: colus@sercomtel.com.br

Cytogenetic and molecular biomonitoring of agricultural workers exposed to pesticides in Brazil

The use of agricultural chemicals without correct protection may lead to alterations in the genetic material of cells and the possible development of several types of tumors. The individual genetic variability in the enzymes which metabolize agricultural chemicals is also involved in this process, such as when the enzymes are not efficient in the detoxifying process of the organism, the metabolic subproducts accumulate, contributing to the tumorigenic process. Cytogenetic monitoring was carried out on a group of 20 male workers occupationally exposed to a mixture of pesticides in the town of São Jerônimo da Serra, PR (Brazil). Students t = test and Wilcoxons test showed, respectively, that there was no significant difference between the chromosome aberration frequencies between the exposed and control groups and between the paired individuals. However, there was a significant difference in the two analyses regarding the mitotic index of the sampled individuals. Smoking and time of exposure to agricultural chemicals did not influence the cytogenetic responses obtained, but the mitotic index of the control individuals was higher than that of the exposed individuals from the different age groups. The GSTM1 gene polymorphism was 33% null. When statistical tests were carried out to assess the relationship of the GSTM1 genotypes with the chromosome aberrations and mitotic indexes, there was no significant difference. The CA frequencies found in this study were low, making it difficult to associate it with the GSTM1 gene polymorphism. Teratogenesis Carcinog. Mutagen. 20:161-170, 2000.

Mutagenicity of Mouriri pusa Gardner and Mouriri elliptica Martius.

Mouriri pusa Gardner and Mouriri elliptica Martius are fruit-bearing plants of the Melastomataceae family, popularly known in Brazil as puçá-preto or jaboticaba-do-cerrado, and they are used in folk medicine for the treatment of gastric ulcers. In this study, we employ the Ames test to assess the mutagenicity of compounds obtained from the leaves of these species. The methanol extract of the M. pusa was mutagenic to the Salmonella typhimurium strains TA98, TA97a and TA100, with or without metabolic activation. The methanol extract of M. elliptica induced mutagenic activity in TA98 when metabolized with S9 fraction and TA97a with and without S9, but with lower mutagenicity index (MI) and potencies values than those for M. pusa. Enriched fractions of flavonoids and tannins of M. pusa were also evaluated and they demonstrated positive mutagenicity. The highest values of MI and potency were obtained with the flavonoid fraction, which contains large amounts of quercetin, quercetin glycosides and myricetin. These compounds are probably related to the mutagenicity observed in the Ames test. The dichloromethane extract was not mutagenic in any of the test conditions employed.

In vivo assessment of DNA damage and protective effects of extracts from Miconia species using the comet assay and micronucleus test

The genus Miconia comprises approximately 1000 species belonging to the Melastomataceae family. Several crude plant extracts from Miconia and their isolated compounds have shown biological activities, such as analgesic and anti-neoplastic action; however, no studies concerning their effects on DNA are available. The present study aimed to evaluate, in vivo, the genotoxic and mutagenic effects of four species of plants from Miconia genus using the comet assay and micronucleus test. Their possible protective effects were also evaluated in experiments associating the plant extracts with cyclophosphamide (CPA). The methanolic extracts of Miconia albicans, Miconia cabucu, Miconia rubiginosa, Miconia stenostachya and the chloroformic extract of M. albicans were investigated. For genotoxic and mutagenic evaluations, three concentrations were tested, 200, 400 and 540 mg/kg body weight (bw), based on the solubility limit of the extract in distilled water. For the protective effects, only the highest dose was evaluated against 40 mg/kg bw of CPA. Blood was removed from mice tails pre- (T0) and post-treatment (T1-30 h) for the micronucleus test and 24 h post-treatment for the comet assay. The Students t-test was used to compare data obtained at T0 and T1, the analysis of variance-Tukey test was used to compare between groups in the micronucleus test and the Kruskal-Wallis and Dunns test were used to compare different groups in the comet assay. All the extracts induced alterations in DNA migration (comet assay); however, no mutagenic effect was observed in the micronucleus assay. All extracts showed a protective effect against CPA in both assays. Our study showed that the use of crude extracts could be more advantageous than the use of isolated compounds. The interaction between phytochemicals in the extracts showed efficacy in reducing mutagenicity and improving the protective effects.

CYP1A1 and GSTP1 polymorphisms in an oral cancer case-control study

CYP1A1 and GSTP1 polymorphisms have been associated with a higher risk to develop several cancers, including oral squamous cell carcinoma (OSCC), which is closely related to tobacco and alcohol consumption. Both genes code for enzymes that have an important role in activating or detoxifying carcinogenic elements found in tobacco and other compounds, and polymorphic variants of these genes may result in alterations of the enzymatic activity. The CYP1A1 gene codes for the enzyme aryl hydrocarbon hydroxylase, which is responsible for the metabolism of polycyclic aromatic hydrocarbons. The investigated polymorphism, Ile/Val, seems to increase the activity of the enzyme in homozygous individuals, leading to an accumulation of carcinogens. The Ile/Val polymorphism occurs because of an A->G transition at exon 7, resulting in the CYP1A1*2B allele. The GSTP1*B variant shows an A->G transition at exon 5, changing the amino acid Ile to Val, with a reduced catalytic activity of the enzyme. Due to this reduction, the carriers of mutant alleles lost the capability to metabolize carcinogens, which could be responsible for a higher susceptibility to cancer. We conducted a case-control study in a group of 72 cases with newly diagnosed OSCC and 60 healthy controls matched for age, gender, smoking habits, and ethnicity. We used PCR methods to identify the allelic variants CYP1A1*2B and GSTP1*B. The data obtained showed no statistically significant association of allelic or genotypic variants of CYP1A1*2B (OR = 1.06; 95% CI = 0.49-2.29) and GSTP1*B (OR = 1.40; 95% CI = 0.70-2.79) with OSCC.

Investigation of genotoxic activity of trans-dehydrocrotonin, a clerodane diterpene from Croton cajucara.

The genotoxic action of three doses of trans-dehydrocrotonin (t-DCTN), an active ingredient obtained from the bark extracts of an Amazon native plant, Croton cajucara, were examined in Swiss mouse bone marrow cells in vivo, submitted to acute intraperitoneal treatment, by micronucleus (MN) and chromosomal aberration (CA) tests. The statistical tests (Anova and Tukey) made to compare the results obtained in each of the three doses of t-DCTN with the negative-control group showed that the frequencies of MN and mitotic index were equal to the negative-control and that the frequencies of CA were lower than that observed in the negative-control. Therefore, based on our results it can be said that t-DCTN is not genotoxic nor cytotoxic to mouse bone marrow cells, submitted to acute intraperitoneal treatment in vivo. Teratogenesis Carcinog. Mutagen. 19:377-384, 1999.

Evaluation of the influence of polymorphic variants CYP1A1 2B, CYP1B1 2, CYP3A4 1B, GSTM1 0, and GSTT1 0 in prostate cancer.

BACKGROUND/OBJECTIVE Genetic polymorphisms in cytochrome P-450 (CYPs) and glutathione S-transferase (GSTs) genes can influence the appearance of tumors by the formation of new enzymes with altered activities. In the present study, 5 polymorphic variants were examined in 154 patients with prostate carcinoma and in 154 controls. MATERIALS AND METHODS DNA analysis was carried out through PCR-based methods. The statistical methods used were odds ratio and confidence interval (95% CI), χ(2), Fisher, and Mann-Whitney. RESULTS The study showed absence of association for CYP1A1 2B, CYP1B1 2, GSTM1 0, and GSTT1 0. The statistical analysis implied a positive association of variant CYP3A4 1B for prostate cancer. The combined analysis of CYP1A1 2B, CYP1B1 2, and CYP3A4 1B genotypes showed positive association. The analysis of histopathologic parameters detected statistically significant differences for Gleason score and biochemistry recurrence risk. The presence of the GSTT1 0 genotype in red meat consumers increased the risk for this disease. CONCLUSION Some polymorphic variants analyzed can influence the development and the progression of prostate cancer.

Allelic variants of XRCC1 and XRCC3 repair genes and susceptibility of oral cancer in Brazilian patients.

BACKGROUND The capacity for DNA repair is essential in maintaining cellular functions and homeostasis; however, this capacity can be altered based on DNA sequence variations in DNA repair genes, which may contribute to the onset of cancer. Many single-nucleotide polymorphisms (SNPs) in repair genes have been found to be associated with oral cancer. The aim of this study was to investigate the relationship between the presence of allelic variants Arg194Trp (rs:1799782) and Arg399Gln (rs: 25487) of XRCC1 gene and Thr241Met (rs: 861539) of XRCC3 gene and susceptibility to oral cancer. We also attempted to correlate the frequencies obtained for each of the SNPs to histopathological parameters. METHODS A case-control study was conducted with genomic DNA from 150 patients with oral squamous cell carcinomas and 150 controls. SNPs were genotyped by RFLP-PCR. RESULTS The presence of the polymorphic variants of the XRCC1 gene within codon 194 (OR 0.82, 95% CI: 0.44-1.51) and codon 399 (OR 0.94, 95% CI: 0.59-1.50) and within the XRCC3 gene (OR 0.72; 95% CI: 0.45-1.16) were not associated with an increased risk of oral cancer. A combinational analysis of SNPs in both genes indicated no association. The presence of the allelic variants of these two genes had no statistically significant effect on tumor differentiation, lymph node invasion or tumor size. CONCLUSIONS These results suggest that allelic variants of XRCC1 and XRCC3 are not suitable markers for susceptibility to carcinomas of the oral cavity and are also not related to the later stages of such tumors.