Frequency and size distribution of micronuclei in lymphocytes stimulated with phytohemagglutinin and pokeweed mitogen in workers exposed to piperazine

Assessment of genetic effects and pesticide exposure of farmers in NW Greece

The present study aims at evaluating potential genotoxic and cytotoxic effects caused by the occupational exposure of farmers to pesticide mixtures in the Aitoloakarnania Prefecture (Greece). The aforementioned assessment was conducted through in vivo Cytokinesis Block Micronucleus assay (CBMN assay) in peripheral blood lymphocytes, in relation to chemical analysis of pesticide residues in blood samples. The exposure of the farmers' population studied to different combinations of pesticides induced significant differences in the frequencies of micronuclei (MN) compared to those of the control group. Furthermore, our results indicated a possible clastogenic and aneugenic effect of pesticides on the genetic material of the farmers exposed. Five pesticides (trifluralin, chlorpyriphos methyl, metolachlor, fenthion and dimethoate) and three metabolites (fenthion sulfone, fenthion sulfoxide and 4,4' DDE) were detected in the 62.5% of blood samples, with mean concentrations ranging from 0.4 ng/ml to 48 ng/ml. Since the farmers studied probably exhibit detectable levels of systematic exposure to the pesticides applied, continuous educational programs focused on the rational and safe use of pesticides, together with implementation of risk communication strategies among farmers are highly recommended.

Necrosis is increased in lymphoblastoid cell lines from children with autism compared with their non-autistic siblings under conditions of oxidative and nitrosative stress

Autism spectrum disorders are a heterogeneous group of neurodevelopmental conditions characterised by impairments in reciprocal social interaction, communication and stereotyped behaviours. As increased DNA damage events have been observed in a range of other neurological disorders, it was hypothesised that they would be elevated in lymphoblastoid cell lines (LCLs) obtained from children with autism compared with their non-autistic siblings. Six case-sibling pairs of LCLs from children with autistic disorder and their non-autistic siblings were obtained from the Autism Genetic Resource Exchange (AGRE) and cultured in standard RPMI-1640 tissue culture medium. Cells were exposed to medium containing either 0, 25, 50, 100 and 200 µM hydrogen peroxide (an oxidative stressor) or 0, 5, 10, 20 and 40 µM s-nitroprusside (a nitric oxide producer) for 1h. Following exposure, the cells were microscopically scored for DNA damage, cytostasis and cytotoxicity biomarkers as measured using the cytokinesis-block micronucleus cytome assay. Necrosis was significantly increased in cases relative to controls when exposed to oxidative and nitrosative stress (P = 0.001 and 0.01, respectively). Nuclear division index was significantly lower in LCLs from children with autistic disorder than their non-autistic siblings when exposed to hydrogen peroxide (P = 0.016), but there was no difference in apoptosis, micronucleus frequency, nucleoplasmic bridges or nuclear buds. Exposure to s-nitroprusside significantly increased the number of micronuclei in non-autistic siblings compared with cases (P = 0.003); however, other DNA damage biomarkers, apoptosis and nuclear division did not differ significantly between groups. The findings of this study show (i) that LCLs from children with autism are more sensitive to necrosis under conditions of oxidative and nitrosative stress than their non-autistic siblings and (ii) refutes the hypothesis that children with autistic disorder are abnormally susceptible to DNA damage.

Induction of micronuclei on Greek hairdressers occupationally exposed to chemical mixtures

Since the early 20th century, hairdressers (HD) have been exposed to a wide range of harmful chemical products. To determine the possible genetic damage to HD, as a result of their occupational exposure to combinations of different chemical factors, we applied the micronucleus assay on their peripheral blood lymphocytes cultures. The micronucleus assay was performed on blood samples from 20 Greek female HD and 20 control women, having no connection with the occupation, from the same area. In the results analysis, parameters included were age, smoking habits, and duration of occupational exposure. The results of our study showed a significant increase in HD micronuclei (MN) frequency, compared to the controls (13.4 ± 1.00 vs. 8.05 ± 0.65). The frequency of large-size MN was significantly higher in the HD and presented potential correlation with the phenomenon of aneuploidy. A statistically significant difference in the frequency of MN between HD and controls who smoked was observed, while this was not the case with the non smoker groups. However, multiple regression analysis showed no significant correlation between smoking habits and MN frequency. The observed increase of the frequency of MN in HD is attributed to the long-term occupational exposure of HD in combination with different chemical factors. Since in the literature there are very few similar studies, further combined studies are suggested on a larger number of HD from different countries, combining biological and molecular techniques, as well as chemical analytical methods of determining and tracing the chemical factors in both the occupational environment and their organisms.

Genotoxicity study of photolytically treated 2-chloropyridine aqueous solutions

2-Chloropyridine (2-CPY) has been identified as a trace organic chemical in process streams, wastewater and even drinking water. Furthermore, it appears to be formed as a secondary pollutant during the decomposition of specific insecticides. As reported in our previous work, 2-CPY was readily removed and slowly mineralised when subjected to ultraviolet (UV) irradiation at 254 nm. Moreover, 2-CPY was found to be genotoxic at 100 microg ml(-1) but it was not genotoxic at or below 50 microg ml(-1). In this work 2-CPY aqueous solutions were treated by means of UV irradiation at 254 nm. 2-CPY mineralisation history under different conditions is shown. 2-CPY was found to mineralise completely upon prolonged irradiation. Identified products of 2-CPY photolytic decomposition are presented. Solution genotoxicity was tested as a function of treatment time. Aqueous solution samples, taken at different photo-treatment times were tested in cultured human lymphocytes applying the cytokinesis block micronucleus (CBMN) assay. It was found that the solution was genotoxic even when 2-CPY had been practically removed. This shows that photo-treatment of 2-CPY produces genotoxic products. Upon prolonged irradiation solution genotoxicity values approached the control value.

Micronucleus induction in human B and T lymphocytes separated by an immunomagnetic technique

Micronuclei were induced in human lymphocytes by mitomycin C or gamma radiation. After the incubation the cells were separated in B- and T-cells by an immunomagnetic method, i.e., Dynabeads. The cultures were stimulated by PHA. The effect of different incubation times (60-110 h) as well as different doses of mitomycin C (0-100 nmol/l) and gamma radiation (0-2 Gy) at an incubation time of 72 h were studied. There were significantly higher frequencies of micronuclei in B- than in T-cells, when micronuclei were induced by mitomycin C. This was not found with gamma radiation, probably because of a cytotoxic effect of this agent on the B-cells.

Effect of dithiocarbamate pesticide zineb and its commercial formulation, azzurro. II. micronucleus induction in immunophenotyped human lymphocytes

The frequency of micronuclei was measured in human peripheral B-lymphocytes and some T-lymphocyte subpopulations exposed in vitro to 1.0-100.0 microg/ml of the dithiocarbamate pesticide zineb and its commercial formulation azzurro. The peripheral mononuclear lymphocytes were stimulated in vitro with phytohemagglutinin after pesticide treatment and B-lymphocytes and the various T-lymphocyte subsets were classified by the MAC (morphology, antibody, chromosomes) method, which allows the immunological identification of different cell lineages. An increased frequency of micronuclei in CD20(+) (P < 0.01), CD3(+) (P < 0.01), and CD8(+) lymphocytes (P < 0.01) was observed only when 25.0 microg/ml of zineb and azzurro were employed. The frequency of micronuclei in treated CD8(+) cells did not differ from treated CD20(+) lymphocytes (P > 0.05). Lower concentrations of pesticides did not increase the frequency of micronuclei from that observed in control cultures. Furthermore, for both zineb and azzurro cytotoxicity was observed at doses higher than 50.0 microg/ml. Significant increases in the proportion of CD20(+) (P < 0.01) and CD8(+) cells (P < 0.01) among mitotic and interphasic lymphocytes from both zineb- and azzurro-treated cultures were observed only when a concentration of 25.0 microg/ml was employed. In contrast, significant decreases in the proportion of CD3(+) (P < 0.01) and CD4(+) cells (P < 0.01) were found for both mitotic and interphasic lymphocytes from zineb- and azzurro-treated cultures. The MAC methodology revealed that among the different lymphocyte subpopulations analyzed (CD20, CD3, CD4, and CD8), the induction of micronuclei by zineb and its commercial formulation azzurro was restricted to CD20(+) B-cells and T-suppressor/cytotoxic CD8(+) lymphocytes.

Genetic effects of petroleum fuels: cytogenetic monitoring of gasoline station attendants

Workers in the petroleum distribution trades experience relatively high-level exposures to fuel vapours whose consequences have not been fully elucidated. In this study, the possible relationship between occupational exposure to petroleum fuels and cytogenetic damages in peripheral lymphocytes was investigated. Twenty-three male, non-smoking workers from the area of Rome were enrolled in the study, together with age-paired controls with no occupational exposure to fuels. Peripheral lymphocyte cultures were set up for the analysis of structural chromosome aberrations (CAs), sister chromatid exchanges (SCEs) and micronuclei (MN) in cytokinesis-blocked lymphocytes. Frequencies of CAs, SCEs and MN were compared between exposed and control groups, and evaluated in relation to blood lead level (as an indicator of engine exhausts exposure) for the whole group under study, and to yearly averaged exposure to benzene (8-h time weighted averages, as determined by repeated personal sampling) for fillingstation attendants only. Both CAs and SCEs were slightly increased in station attendants: 1.97 versus 1.46 aberrations per 100 cells, and 4.73 +/- 0.15 versus 4.48 +/- 0.11 SCEs/cell in exposed and control individuals, respectively. The difference between cumulative CA rates in the exposed and control populations was of borderline statistical significance (p = 0.066). However, when the exposed population was dichotomized for benzene exposure, a significant (p = 0.018) correlation of CAs with benzene exposure was found. The analysis of SCE data highlighted a significant increase of cells with more than 6 exchanges (HFCs), corresponding to the 75 degrees percentile of the overall distribution, in fillingstation attendants (relative risk (RR) = 1.3, 95% CI = 1.1-1.5) in comparison with controls. In the pooled population, the frequency of HFCs showed a statistically significant upward trend at increasing blood lead levels (chi 2 for trend = 27.8, p < 0.0001). A complex relationship between SCEs and benzene exposure was observed, with an increased frequency of HFCs in the medium exposure intensity class (RR = 1.5, 95% CI = 1.2-1.7), and no difference for exposure to higher benzene levels (RR = 1.0, 95% CI = 0.9-1.2), compared to reference subjects. Finally, the analysis of MN in both phytohemagglutinin- and pokeweed-stimulated cell cultures did not show significant excess of MN in binucleated lymphocytes of exposed workers with respect to the age-paired controls.

Increased frequency of micronuclei in lymphocytes of Swedish chimney sweeps

Forty-five Swedish chimney sweeps and 49 controls were investigated with micronuclei stimulated by phytohemagglutinin and pokeweed mitogen and by analysis of lymphocyte subgroups and neutrophilic leukocytes. There was a statistically significant effect among sweeps with respect to both micronuclei variables and neutrophilic leukocytes. The effect on lymphocyte micronuclei was most prominent in pokeweed mitogen-stimulated cells, which may imply that the T4 lymphocytes were preferentially damaged by the occupational exposure.

Micronuclei and mitotic index in B-, T4- and T8-cells treated with mitomycin C and gamma-irradiation

Lymphocytes were treated in vitro with mitomycin C and gamma-radiation at different doses (0-250 nmol/l and 0-2 Gy, respectively). After incubation in RPMI 1640 medium and stimulation with phytohemagglutinin for 72 h, the lymphocyte subgroups T4 (CD4), T8 (CD8) and B (CD19) were separated by an immunomagnetic method and analyzed for the presence of micronuclei. With mitomycin C the highest levels were found in T4- and B-cells. When micronuclei were induced by irradiation the T4-cells showed the highest frequencies and the B-cells the lowest. The outcome of B-cells with gamma-irradiation was probably due to a pronounced cytotoxic reaction in this cell type, which could be measured as a decrease in mitotic index.

B- and T-lymphocyte micronuclei in chimney sweeps with respect to genetic polymorphism for CYP1A1 and GST1 (class Mu)

Epidemiological studies have shown an increased incidence of lung cancer, bladder cancer, and esophageal cancer in chimney sweeps, probably due to their exposure to PAH in soot. The work environment for sweeps has, however, improved during the last decades. It was thus important to assess whether the present exposure still may cause genotoxic effects. A further objective was to assess whether genetic polymorphisms in metabolic enzyme activities could explain some of the variation in the parameters of genotoxicity. Venous blood samples were drawn from 71 chimney sweeps and 59 control subjects. Micronuclei were analyzed in activated peripheral B- and T-lymphocytes with preserved cytoplasm. Polymorphisms for CYP1A1 and GST1 in the sweeps were analyzed by a PCR technique. The sweeps did not have higher frequencies of micronuclei in B- or T-lymphocytes than the control subjects, when allowance was made for age and smoking in a multiple regression analysis. Further, there was no association between years of active work as a sweep and any of the two micronucleus parameters. None of the sweeps had the rare CYP1A1 genotype val/val and only one individual had the m2/m2 genotype. The presence of at least one GST1 allele (GST1+) was observed in 36 subjects (51.4%). Thirteen individuals (18.6%) were of the m1/m2 or m2/m2 genotype. And among those only seven had the combined GST1- and m1/m2 genotype. No difference was observed in B- or T-lymphocyte micronucleus frequencies between sweeps with the rare CYP1A1 genotypes m1/m2, m2/m2 or ile/val compared to individuals with the m1/m1 and ile/ile genotypes. Moreover, the GST1 deficient sweeps (GST1-) did not show any altered micronucleus frequency compared to the GST1 positive sweeps. A possible reason for the lack of genotoxic effect in sweeps is the improved hygienic conditions and change in fuels, which has decreased the exposure levels for PAH. Host polymorphisms for metabolizing enzymes did not influence the micronucleus frequencies. As the sweeps did not differ from the control subjects, with respect to micronucleus frequencies, no conclusion on the importance of host polymorphisms for genotoxic risk can be drawn.

Radiation induced micronuclei in subpopulations of human lymphocytes

The micronucleus expression in T-helper, T-suppressor and B lymphocytes of the peripheral blood was studied after in vitro exposure to high (2.5 Gy and 5 Gy) and low (0.5 Gy and 1 Gy) doses of ionizing radiation. Investigations were carried out by combining the micronucleus assay with immunofluorescence staining using subpopulation specific antibodies. While in the higher dose range B cell proliferation was inhibited nearly completely-so that micronuclei could not be expressed-we found after exposure to lower doses that B cells were the lymphocyte subpopulation which was most sensitive to micronucleus induction. Among the T cell population, the T-suppressor subset revealed a higher yield of micronuclei than T-helper cells, whereas with regard to the effect of radiation on proliferative ability, T-helper cells reacted more sensitivity than the T-suppressor lymphocytes. Our studies provide insight into the effect of radiation exposure on the micronucleus expression of lymphocyte subpopulations and new information which may be useful for the further development of biological dosimetry.

In vitro micronucleus bioassay of human peripheral lymphocytes for adriamycin in the presence of cyclophosphamide and urines of patients administered anticancer drugs

The aim of this study was to develop an in vitro human peripheral lymphocyte micronucleus bioassay involving phytohemagglutinin stimulant for urines containing adriamycin (ADR) and cyclophosphamide (CP). In vitro studies with defined concentrations of ADR, CP, and fresh urine showed that mitotic indices and micronuclei counts/1,000 cells had to be log (X + 1) transformed to be able to use parametric statistics and that a specific micronucleus assay for ADR in the presence of CP and urine for 5-15 ng ADR/mL had been developed. Whereas CP alone could be detected between 196-522 micrograms/mL, this effect was abolished in the presence of 15 ng ADR/mL. Interdonor variabilities relative to ADR sensitivity and CP linear dynamic range were marked, but intradonor variability was small. The MN bioassay tolerated < 10% urine. Results for urines from nine patients receiving antineoplastic drugs (CP, all; ADR, 3; 5-fluorouracil, 3; methotrexate, 3; vincristine, 4; procarbazine, 1; and megestrol acetate, 1) showed that only 1/3 patients given ADR were detected, and two others not given ADR were positive. All frozen urines from the 12 control subjects and the nine patients exhibited depressed mitotic index, with, however, no control patient urines inducing increased micronuclei. Two patients had urines of undefined genotoxic potential since undepressed mitotic indices were not attainable by dilution. The effects of combination chemotherapy in addition to freezing and storage influences were complex. More research is required to be able to interpret the results.

Cytogenetic effects in rotogravure printers exposed to toluene (and benzene)

Comparing 21 rotogravure printers exposed to toluene (medians: time-weighted air level 150 mg/m3, blood toluene 1.6 mumole/l) and 21 unexposed controls (median blood toluene less than or equal to 0.01 mumole/l) there was a significant increase in the frequency of micronuclei (MN) in pokeweed mitogen (PWM)-stimulated peripheral blood lymphocytes in the printers, as compared to the controls (2.8% vs. 1.5%; p = 0.03; all p adjusted for age and smoking). The frequency of small MN (size ratio MN/main nucleus less than or equal to 0.03) in PWM-stimulated lymphocytes was associated with the exposure (1% vs. 0.3%; p = 0.05). Furthermore, among the exposed subjects there was an association between blood toluene and small MN (0.17% per mumole/l; p = 0.0005). Small MN in phytohemagglutinin (PHA) cultures displayed no association with any exposure parameter. However, in the printers, an estimated cumulative exposure index was weakly correlated with the frequency of total MN in PHA-stimulated cells (0.00003% per mg/m3 x year; p = 0.07). Among the printers, chromosomal breaks in PHA-stimulated cells were associated with the duration of earlier benzene exposure (0.03% per year; p = 0.01). The results of this study strongly indicate that toluene causes a clastogenic effect on the B-cells even at low exposure levels. Further, earlier benzene exposure seems to have caused chromosomal breaks in T-cells.

Gasoline pump mechanics had increased frequencies and sizes of micronuclei in lymphocytes stimulated by pokeweed mitogen

Fifteen gasoline pump mechanics and 15 controls were investigated with the lymphocyte micronucleus assay and also with differential count of leukocytes in the peripheral blood. The lymphocytes were stimulated with phytohemagglutinin and pokeweed mitogen in parallel cultures. The pump mechanics had increased frequencies and sizes of micronuclei in the pokeweed mitogen-stimulated cultures but not in those stimulated with phytohemagglutinin. The difference in effect between the 2 mitogens is probably due to an increased sensitivity of the B-lymphocytes to mutagens. The leukocyte count was significantly higher in the gasoline-exposed group. The effect of the occupational exposure was probably caused by the benzene content of the gasoline. The time-weighted average for 8 h was around 1 mg/m3 of benzene, but there were peak levels of 20 mg/m3.

Micronucleus formation in different lymphocyte subpopulations in peplomycin-treated and control cultures

Spontaneous micronucleus formation and micronucleus induction by peplomycin in B and T lymphocytes was studied by a recently developed MAC (Morphology, Antibody, Chromosomes) method allowing the immunologic identification of different cell lineages. Blood samples from 3 healthy donors were cultured in the presence of phytohaemagglutinin and pokeweed mitogen. An increased frequency of micronuclei was observed in peplomycin cultures compared with controls. B cells were found to be more sensitive to peplomycin induction than were T lymphocytes. In control cultures, pokeweed mitogen yielded a higher frequency of micronuclei than did phytohaemagglutinin. In both pokeweed- and phytohaemagglutinin-stimulated cultures, B cells showed a higher frequency of micronuclei than did T cells. The relative proportion of mitotic B cells was equal in pokeweed and phytohaemagglutinin cultures. In peplomycin cultures, the proportion of B cells decreased as compared with control cultures.