Genetic toxicology studies with glutaraldehyde.

Glutaraldehyde (GA; CAS no. 111-30-8) has a wide spectrum of industrial, scientific and biomedical applications, with a potential for human exposure particularly in its biocidal applications. The likelihood for genotoxic effects was investigated in vitro and in vivo. A Salmonella typhimurium reverse mutation assay showed no evidence for mutagenic activity with strains TA98, TA1535, TA1537 and TA1538, with or without metabolic activation. However, there was a weak mutagenic response (1.9-2.3-fold at the highest non-toxic concentration) with TA100 in the presence of metabolic activation. In a Chinese hamster ovary (CHO) forward gene mutation assay (HGPRT locus) there were no consistent, statistically significant, reproducible or dosage-related increases in the frequency of 6-thioguanine resistant cells. There were no reproducible or dosage-related increases in sister chromatid exchanges in an in vitro test in CHO cells. An in vitro cytogenetics study in CHO cells showed no evidence for an increase in chromosomal aberrations on treatment with GA, either in the presence or absence of metabolic activation. In vivo, a mouse peripheral blood micronucleus test showed no increase in micronucleated polychromatophils at sampling times of 30, 48 and 72 h after acute gavage dosing with GA at 40, 80 and 125 mg kg(-1) (corresponding to 25, 50 and 85% of the LD(50)). The absence of an in vivo clastogenic potential was confirmed by no increase in chromosomal aberrations in a rat bone marrow cytogenetics study with sampling at 12, 24 and 48 h after acute gavage dosing with GA (12.5, 30 or 60 mg kg(-1) with males, and 7.5, 20 or 40 mg kg(-1) with females). Thus, in this series of tests, GA produced genotoxic effects in vitro only in a bacterial reverse mutation assay with no evidence for in vivo genotoxicity.     

Detoxication Strategy of Epoxide Hydrolase��The Basis for a Novel Threshold for Definable Genotoxic Carcinogens

From our recent work on the three-dimensional structure of epoxide hydrolases we theoretically deduced the likelihood of a two-step catalytic mechanism that we and others have subsequently experimentally confirmed. Analysis of the rate of the two steps by us and by others show that the first step—responsible for removal of the reactive epoxide from the system—works extraordinarily fast (typically three orders of magnitude faster than the second step), sucking up the epoxide like a sponge. Regeneration of the free enzyme (the second step of the catalytic mechanism) is slow. This becomes a toxicological problem only at doses of the epoxide that titrate the enzyme out. Our genotoxicity work shows that indeed this generates a practical threshold below which no genotoxicity is observed. This shows that—contrary to old dogma—practical thresholds exist for definable genotoxic carcinogens.     

Genotoxicity of nitrated polycyclic aromatic hydrocarbons and related structures on Escherichia coli PQ37 (SOS chromotest)

To determine the genotoxicity of nitrated polycyclic aromatic hydrocarbons and related molecules (nPAH) we examined 24 compounds representative of nitroanthracenes, nitrofluorenes, nitronaphthalenes, nitropyrenes, and nitroquinolines for genotoxicity in Escherichia coli PQ37 (SOS-chromotest). To enhance the sensitivity of the tester strain and optimize metabolic activation we used a modified test protocol and S9-mix composition. All chemicals with the exception of 9-nitroanthracene, 1- and 2-nitronaphthalene, 2-methyl-1-nitronaphthalene, and 5-, 6-, and 8-nitroquinoline induced the SOS system of E. coli PQ37. As expected from previously referred mutagenicity studies, the highest SOS inducing potencies (SOSIP) were exhibited by the dinitropyrenes (SOSIP = 151-416), 4-nitroquinoline-N-oxide (SOSIP = 62), and 3-nitrofluoranthese (SOSIP = 16). Except for some nitronaphthalenes, the nPAHs showed their highest genotoxicity in the absence of an exogeneous metabolic activation system. The results were compared to those reported for the bacterial mutagenicity of these substances in Salmonella typhimurium TA98.     

Assessing the impact of pollution on the Japaratuba river in Brazil using the Drosophila wing spot test

The Drosophila melanogaster somatic mutation and recombination test (SMART) was used to assess the genotoxicity of surface (S) and bottom (B) water and sediment samples collected from Sites 1 and 2 on the Japaratuba River (Sergipe, Brazil), an area impacted by a petrochemical industrial complex that indirectly discharges treated effluent (produced water) into the river. The genotoxicity tests were performed in standard (ST) cross and high bioactivation (HB) cross flies and were conducted on samples taken in March (dry season) and in July (rainy season) of 2003. Mutant spot frequencies found in treatments with unprocessed water and sediment samples from the test sites were compared with the frequencies observed for similar samples taken from a clean reference site (the Jacarecica River in Sergipe, Brazil) and those of negative (ultrapure water) controls. While samples from the Japaratuba River generally produced greater responses than those from the Jacarecica River, positive responses were detected for both the test and reference site samples. All the water samples collected in March 2003 were genotoxic. In July 2003, the positive responses were restricted to water samples collected from Sites 1 B and 2 S in the ST cross. The genotoxicity of the water samples was due to mitotic recombination, and the samples produced similar genotoxic responses in ST and HB flies. The spot frequencies found in the July water samples were considerably lower than those for the March water samples, suggesting a seasonal effect. The only sediment samples that were genotoxic were from Site 1 (March and July) and from the Jacarecica River (March). The genotoxins in these samples produced both somatic mutation (limited to the Site 1 sample in HB flies) and recombination. The results of this study indicate that samples from both the Japaratuba and Jacarecica Rivers were genotoxic, with the most consistently positive responses detected with Site 1 samples, the site closest to the putative pollution source.     

River water genotoxicity evaluation using micronucleus assay in fish erythrocytes

The quality of Caí river water (Rio Grande do Sul State) in an area under the influence of a petrochemical complex was studied using the micronucleus assay in erythrocytes from peripheral blood of the fathead minnow Pimephales promelas. This cytogenetic in vivo assay was performed to evaluate the effects of petrochemical effluents on the stream. Organisms were exposed to samples collected at four sites, during an 11-month period. Three different exposure periods were used (7, 14, and 21 days) to evaluate their influence in genotoxic detection. The 14-day exposure period was most effective in detecting genotoxicity in samples from this area. The presence of substances with clastogenic and/or aneugenic potential could be detected at the different sites analyzed. This in vivo assay allowed the detection of genotoxicity in the area studied, indicating the potential for environmental genotoxicity monitoring.     

两种荧光波长CdSeS/ZnS-COOH合金量子点微核组学效应特征的比较研究

目的:比较两种荧光波长CdSeS/ZnS-COOH合金量子点对细胞微核组效应遗传毒作用的特征。方法:采用L5178Y细胞胞质分裂阻滞微核细胞组学试验,490和540 nm两种荧光波长的合金量子点CdSeS/ZnS-COOH受试浓度均为0.062 5、0.125、0.25、0.5和0.1 mg/mL,观察其微核组效应、剂量-效应和时间-效应关系。结果:与阴性对照组相比,两种波长的CdSeS/ZnS-COOH合金量子点在0.062 5 mg/mL剂量时均可诱导微核率增加(P<0.05);两者都能诱导Ⅰ型微核、Ⅱ型微核和核芽效应,但490 nm合金量子点不能诱导核质桥效应,而540 nm合金量子点能诱导核质桥效应。490 nm合金量子点在0.062 5 mg/mL可诱导产生总微核、Ⅰ型微核和核芽,而540 nm合金量子点在此浓度仅可诱导产生Ⅰ型微核;两者均随着剂量进一步增加诱导产生其他效应;各种微核组效应有明显的剂量-效应关系(P<0.05)。490 nm量子点在9 h首先出现核质桥,540 nm量子点在9 h首先出现总微核和Ⅱ型微核数增加;随时间延长进一步出现其他效应,27 h各效应值达到峰值,此后下降。结论:两种荧光波长CdSeS/ZnS-COOH合金量子点均可诱导微核组学效应,但在相同剂量的效应谱、剂量-效应和时间-效应方面均有差异,表明两者的遗传毒作用特点有差异。     

Genotoxicity of trichloroethylene in the natural milieu

Trichloroethylene (TCE) is a suspected genotoxic and carcinogenic compound which is usually present in the air, soil and water as pollutant. To estimate the genotoxic potential of TCE in a pure chemical form as well as an ingredient of the complex sample, Ames fluctuation test using TA98 and TA100 strains and Allium cepa genotoxicity assay were performed. For the genotoxicity analysis of TCE in natural milieu, the above mentioned tests were performed on the waste waters collected from two different stations of northern India namely Saharanpur and Aligarh, U.P., and these waste waters were supplemented with 50 and 100 mg/l of trichloroethylene. TCE alone was found to be non-genotoxic by both the testing system up to the range of 1000 mg/l concentration (data not shown). However, the test water samples supplemented with 100 mg/l of TCE, exhibited a significant increase in the genotoxicity compared with control by both the testing systems. In Ames fluctuation test, Mi(f) value was found to be increased by 41% and 53% with 100 mg/l of TCE supplemented Saharanpur and Aligarh waste water samples respectively, in the presence of S9 fraction compared with their respective controls. Allium cepa genotoxicity test also showed around 25% increase in total chromosomal aberration frequency following 100 mg/l TCE supplementation. However, supplementation of 50 mg/l TCE to the test water samples could not enhance the genotoxicity to a significant extent. From these results, we can conclude that TCE itself was non-genotoxic but it may promote mutation and/or DNA damage at a concentration of 100 mg/l under certain environmental conditions. We suggest that some chemicals in the test water samples might be interacting with TCE and/or metabolite(s) to cause the enhancement in genotoxicity. The mechanism of these synergistic effects should be explored further.     

壬基酚对红鲫、草鱼和鲢鱼的毒性及组织蓄积研究

目的了解不同鱼种对壬基酚的毒性差异。方法选择红鲫、草鱼和鲢鱼鱼苗,4-壬基酚换水式染毒进行96h急性毒性试验、12周亚慢性毒性试验、外周血红细胞微核试验,高效液相色谱法测定组织中4-壬基酚。结果①4-壬基酚对红鲫、草鱼和鲢鱼的96h LC50分别为251.30、155.84和187.01μg/L。②染毒12周,红鲫高剂量组肝胰脏系数降低,中、高剂量组卵巢系数增高(P<0.05);草鱼中剂量组肾脏系数降低(P<0.05);鲢鱼高剂量组肝胰脏系数降低(P<0.05)。③染毒4周时,红鲫和鲢鱼中、高剂量组及草鱼高剂量组微核细胞率与对照组相比显著增高(P<0.05);染毒8周及以后,受试鱼各剂量组微核细胞率均增高(P<0.05);④受试鱼肌肉、脑和肝胰脏等组织样品中均有4-壬基酚检出,其中肝胰脏的生物浓缩系数最高;红鲫对4-壬基酚的生物浓缩系数高于草鱼和鲢鱼。结论红鲫对壬基酚较敏感。     

Mitochondria-derived reactive intermediate species mediate asbestos-induced genotoxicity and oxidative stress-responsive signaling pathways

Background: The incidence of asbestos-induced human cancers is increasing worldwide, and considerable evidence suggests that reactive oxygen species (ROS) are important mediators of these diseases. Our previous studies suggested that mitochondria might be involved in the initiation of oxidative stress in asbestos-exposed mammalian cells.Objective: We investigated whether mitochondria are a potential cytoplasmic target of asbestos using a mitochondrial DNA–depleted (ρ⁰) human small airway epithelial (SAE) cell model: ρ⁰ SAE cells lack the capacity to produce mitochondrial ROS.Methods: We examined nuclear DNA damage, micronuclei (MN), intracellular ROS production, and the expression of inflammation-related nuclear genes in both parental and ρ⁰ SAE cells in response to asbestos treatment.Results: Asbestos induced a dose-dependent increase in nuclear DNA oxidative damage and MN in SAE cells. Furthermore, there was a significant increase in intracellular oxidant production and activation of genes involved in nuclear factor κB and proinflammatory signaling pathways in SAE cells. In contrast, the effects of asbestos were minimal in ρ⁰ SAE cells.Conclusions: Mitochondria are a major cytoplasmic target of asbestos. Asbestos may initiate mitochondria-associated ROS, which mediate asbestos-induced nuclear mutagenic events and inflammatory signaling pathways in exposed cells. These data provide new insights into the molecular mechanisms of asbestos-induced genotoxicity.     

空气中高浓度二氯乙烷对蚕豆根尖细胞遗传毒性研究

目的探讨将蚕豆根尖微核检测系统(micronucleus,MCN)应用于空气污染物致突变性检测的可行性。方法以市售蚕豆为材料,在密闭容器中模拟室内空气的高浓度二氯乙烷污染,对蚕豆进行染毒。结果随着浓度的递增,平均微核率、染色体畸变率逐步上升,有丝分裂指数有下降趋势,表现出明显的剂量效应关系。结论在实验浓度下,1,2-二氯乙烷有对蚕豆根尖细胞产生遗传毒害效应。应用蚕豆根尖微核技术检测室内高浓度1,2-二氯乙烷污染物是可行的。