Mutation Research\/environmental Mutagenesis and Related Subjects最新文献

Pleural mesothelioma, lung cancer, pleural calcification and fibrosis have been observed among inhabitants of the villages in Ivriz-Zanapa valley in Turkey. Earlier reports have stated that these endemic pathological conditions are caused by the inhalation of actinolite asbestos, a mineral commonly used indiscriminately to paint the walls and floors of houses. In the present study, 40 inhabitants in Yassikaya village in Ivriz-Zanapa valley and 20 controls were further investigated. The peripheral blood lymphocytes were cultured and harvested at 72 h for sister chromatid exchange (SCE) frequency. Inhabitants had a raised mean SCE rate compared with a control population.

The purpose of the present study was to investigate the range of micronucleated erythrocytes (MNE) in peripheral blood from splenectomized patients with and without genotoxic chemotherapy. The erythrocytes were stained with Wright and Giemsa for microscopic observation. To estimate the number of MNE, two series of 10 000 erythrocytes per sample were analyzed and averaged. The results expressed as mean ± standard deviation were as follows: control patients with genotoxic chemotherapy (n=6) 2.5 ± 1.5 (range 1 to 5 MNE); splenectomized patients with genotoxic chemotherapy (n=7) 65.2 ± 17.7 (range: 47–108) MNE and splenectomized patients without genotoxic chemotherapy (n=13) 29.5 ± 5.8 MNE; (range: 18.5–35.6). The MNE number in the patients treated with genotoxic chemotherapy depended on the type of drugs utilized: cyclophosphamide, mitoxantrone, vincristine, busulphan, cytosine arabinoside and hydroxyurea. Upon these results, it is suggested that splenectomized people could be useful in monitoring exposures, and the baseline MNE level would serve as each person's pre-exposure control when either chronic or acute exposure to environmental mutagens is investigated.

The ability of metalaxyl, whose mutagenic/cocarcinogenic activity has as yet not been clarified, to affect specific biomarkers related to non-genotoxic cocarcinogenesis, was investigated. Several CYP-dependent reactions have been studied in liver, kidney and lung microsomes derived from male and female Swiss Albino CD1 mice treated i.p. with single (200 or 400 mg/kg b.w.) or repeated (200 mg/kg b.w., 3 days) administrations of fungicide. No significant changes in both absolute and relative liver, kidney and lung weights were observed after metalaxyl treatment. Although a single dose did not significantly affect the considered monooxygenases, a clear example of selective CYP3A induction was recorded in different tissues after repeated treatment. A 3 ∼ -fold increase in CYP3A isozymes, probed by N-demethylation of aminopyrine, was observed in the liver (both sexes). Again, a 5 ∼-fold increase (averaged between male and female) in this oxidase activity was present in the kidney. No significant change of the selected biomarkers was observed in the lung. A weak, but significant reduction of CYP2B1 isoform in liver (male) was also recorded. Liver and kidney CYP3A overexpression was corroborated by means of Western immunoblotting analysis using rabbit polyclonal antibodies anti-CYP3A1/2. Northern blotting analysis with CYP3A cDNA biotinylated probe showed that, in the liver, the expression of this isozyme is regulated at the mRNA level. On the whole, these data seem to indicate the cotoxic and cocarcinogenic potential of this fungicide.

A collaborative study of chemically-induced mutagenicity was performed using the four bacterial strains Salmonella typhimurium TA102 and TA2638 and Escherichia coli WP2/pKM101 and WP2 urA/pKM101 in order to compare the specific spectrum of response to chemicals among the four strains and to determine the usefulness (sensitivity) of each strain. Twenty laboratories participated in this study. As the first step, 29 compounds were tested for mutagenicity using the plate incorporation method with or without metabolic activation. The compounds consisted of 12 chemicals judged previously positive only in E. coli WP2 uvrA/pKM101, 15 of their derivatives, and the 2 well-known mutagens hydrazine and formaldehyde. The strains and the chemicals were sent from a central source to each laboratory. The tests were performed in two laboratories per chemical. Concerning the result with each strain, the number of chemicals which showed mutagenic activity were 10, 7, 9 and 17 in TA102, TA2638, WP2/pKM101 and WP2 uvrA/pKM101, respectively. Among these 29 compounds tested, no qualitative difference in the response to chemicals among the four strains was observed with 17 compounds, being 12 negative chemicals and 5 positive chemicals. The remaining 12 compounds showed varying results among the four strains. On the comparison of TA102 and WP2 uvrA/pKM101, the same qualitative response to chemicals was observed with 22 compounds. Thus, although compounds tested in this study were selected, partly based on a previously-judged positive response only in E. coli WP2 uvrA/pKM101, 76% of test chemicals showed the same sensitivity in TA102, 7 chemicals (24%) were only positive in the E. coli strains. Of these 7 chemicals, 5 were the acrylic acid ester derivatives and the chloroacetic acid ester derivatives possessing a common structure of a functional group esterized between acid and alcohol with two or more carbon radicals.

The antimutagenic effects of green tea catechins, (−)-epicatechin gallate (ECg) and (−)-epigallocatechin gallate (EGCg) on induction of 6-thioguanine (6TG)-resistant mutations induced by 4-nitroquinolin 1-oxide (4NQO) were found in cultured Chinese hamster V79 cells. The antimutagenic activity of catechins was found only when cells were post-treated with catechins during the mutation expression time after treatment with 4NQO, and not found by simultaneous treatments with 4NQO and catechins. This bioantimutagenic activity of catechins were not observed in ethyl methanesulfonate (EMS)-induced mutations. This suggests that the antimutagenic effects of catechins may act intracellularly as bio-antimutagenic blocking agent or suppressive agent. These catechins had no effects on the cytotoxic activity of 4NQO in V79 cells, whether catechins were used in simultaneous treatment with or in post-treatment after 4NQO. This indicates that the antimutagenicity and anticytotoxicity to 4NQO may be caused by different mechanism(s).

Okadaic acid (OA), a toxin involved in diarrhetic shellfish poisoning (DSP), has been shown to be a potent tumor promoter in mouse skin and glandular stomach. However, more recent studies tended to show that OA can also act as a genotoxic. In this study, using the ³²P-postlabelling method, DNA adduct formation was obtained in two cell lines (BHK21 C13 fibroblasts and HESV keratinocytes) after treatment by OA for 24 h with a dose range between 0.01 and 5 nM. Nineteen adducts were observed with BHK21 C13 cells and 15 with HESV ones. Low doses did not show adduct formation. Intermediate doses have given the most important number of adducts and with higher doses, the number of adducts decreased dose dependently. Ten adducts were similar in the two strains while 9 were specific of BHK21 C13 cell line and 5 of HESV one. The highest total DNA adduct level from origin parts was estimated at 95.6 adducts/10⁹ nucleotides for BHK21 C13 fibroblasts (1 nM OA treatment) and 31.1 adducts/10⁹ nucleotides for HESV keratinocytes (0.5 nM OA treatment). In this case, the major adduct (number 3) represented 20% for the fibroblastic cell line and 30% for the keratinocytic strain. The genotoxic effect of OA showed in this study should lead to a more careful survey of DSP outbreaks.

We have carried out analysis of the number of blood erythrocytes and lymphocytes with micronuclei in the inhabitants of four settlements located near the place of the accident which happened at the atomic power station of the Siberian chemical plant (Tomsk-7) on April 6, 1993. In all cases, the people examined showed a considerable increase in the number of cells with micronuclei as compared with the control. We observed the same people for 2 years and found a gradual decrease in the number of cells with micronuclei. This study shows that people born between1963–1970 have a much higher level of cells9 with micronuclei, which we tend to see as a result of the radiation accident at the Siberian chemical plant in 1963. The data we have obtained allow us to conclude that penetration of radionuclides into the human organism in the prenatal and early postnatal periods can lead to the formation of stable clones of erythroid cells with micronuclei and a higher level of erythrocytes with micronuclei which can remain in the blood for a long time.

Aromatic amines are activated into mutagens by both animal and plant systems. For plant-activated aromatic amines an important step in this process involves peroxidase enzymes. 4-nitro-o-phenylenediamine (NOP) is a well known direct-acting mutagen that can be enhanced in mutagenic potency by intact plant cells andalso by isolated peroxidase enzymes. This activation process is inhibited by several different chemical agents including potassium cyanide (KCn), a known peroxidase inhibitor, and (+)-catechin. In our laboratory both KCn and (+)-catechin inhibited peroxidase-mediated NOP activation into a Salmonella mutagen. However, while KCn demonstrated strong peroxidase enzyme inhibition (as measured biochemically), (+)-catechin showed only minimal inhibition of peroxidase. Experiments comparing NOP direct and plant-activated mutagenic activity to different Salmonella strains (in the presence and absence of (+)-catechin) suggest that (+)-catechin may inhibit the mutagenic process by limiting O-acetyltransferase (OAT) activity in Salmonella. OAT activity in Salmonella is a required process for mutations to be induced following treatment with NOP and other aromatic amines.

Review of the literature shows that such cytokines as human interferons α and γ, tumor necrosis factor α, epidermal growth factor and interleukin-2 may exhibit genotoxic properties in human peripheral blood lymphocyte cultures. For all above cytokines, except interleukin-2, parabolic-like relationship between the dose and the frequency of sister chromatid exchanges was found. Although the mechanisms of these genotoxic actions remain largely unknown, generation of free radicals or interaction with enzymes such as DNA topoisomerase II may be suspected. Human interferon α also may be considered as an antimutagenic compound in human cells. Human tumor necrosis factor α has been reported to enhance cytotoxicity and DNA fragmentation produced by DNA topoisomerase II-targeted anticancer drugs. At the same time, it has some radio- and chemoprotective properties in vitro and in vivo. Despite these facts, the question about genotoxicity of cytokines is not answered. Some problems must be resolved before receiving the final answer. First, much more cytokines must be tested for their genotoxic activity. Second, appropriate test-systems must be designed. Third, genotoxicity studies of cytokines must account for cytokine interaction in the cytokine network as well as for such cytokine-induced effects as cytotoxicity and apoptosis. Fourth, in each case, it is necessary to have experimental evidence that observed genotoxic effects were caused by cytokine under investigation and not by the other factors.

Chinese hamster lung fibroblasts (V79 cells) were challenged with respirable silica particles using an in vitro genotoxicity assay. Two particle sizes of crystalline quartz and a non-crystalline silica were assayed for induction of micronuclei (MN) in V79 cells. Some of the silica dusts used were pretreated with simulated pulmonary surfactant to model in vivo exposure conditions. The results showed that both crystalline and non-crystalline silica dispered in medium (MEM) induced MN formation in a dose-dependent manner. Crystalline silica was more active in this assay than non-crystalline silica on a mass basis. The results also show that the frequency of micronucleated cells in cultures treated with surfactant-coated silica was not significantly different from that of the non-treated control cultures. These results seem to indicate that silica can cause chromosomal aberrations and/ or aneuploidies in V79 cells; however, pretreatment of silica particles with simulated pulmonary surfactant reduces or delays genotoxicity in this assay.