Levels of ras oncoproteins in human plasma from 1,3-butadiene-exposed workers and controls

Chromosomal aberrations in tire plant workers and interaction with polymorphisms of biotransformation and DNA repair genes

We evaluated chromosomal aberrations in lymphocytes of 177 workers exposed to xenobiotics in a tire plant and in 172 controls, in relation to their genetic background. Nine polymorphisms in genes encoding biotransformation enzymes and nine polymorphisms in genes involved in main DNA repair pathways were investigated for possible modulation of chromosomal damage. Chromosomal aberration frequencies were the highest among exposed smokers and the lowest in non-smoking unexposed individuals (2.5+/-1.8% vs. 1.7+/-1.2%, respectively). The differences between groups (ANOVA) were borderline significant (F=2.6, P=0.055). Chromosomal aberrations were higher in subjects with GSTT1-null (2.4+/-1.7%) than in those with GSTT1-plus genotype (1.8+/-1.4%; F=7.2, P=0.008). Considering individual groups, this association was significant in smoking exposed workers (F=4.4, P=0.040). Individuals with low activity EPHX1 genotype exhibited significantly higher chromosomal aberrations (2.3+/-1.6%) in comparison with those bearing medium (1.7+/-1.2%) and high activity genotype (1.5+/-1.2%; F=4.7, P=0.010). Both chromatid- and chromosome-type aberration frequencies were mainly affected by exposure and smoking status. Binary logistic regression analysis revealed that frequencies of chromatid-type aberrations were modulated by NBS1 Glu185Gln (OR 4.26, 95%CI 1.38-13.14, P=0.012), and to a moderate extent, by XPD Lys751Gln (OR 0.16, 95%CI 0.02-1.25, P=0.081) polymorphisms. Chromosome-type aberrations were lowest in individuals bearing the EPHX1 genotype conferring the high activity (OR 0.38, 95%CI 0.15-0.98, P=0.045). Present results show that exposed individuals in the tire production, who smoke, exhibit higher chromosomal aberrations frequencies, and the extent of chromosomal damage may additionally be modified by relevant polymorphisms.

Initial study on the effects of Prestige oil on human health

The big oil tanker Prestige wrecked at 130 miles from the coast of Galicia, on the Northwest of Spain, in November 19, 2002. During the accident over 40,000 tons of oil were spilled, and along the next weeks 22,000 more reached the shore in the way of three black tides. A great number of people participated in the cleaning tasks. The objective of this study was to initially evaluate the damage caused by Prestige oil in exposed individuals both from the cytogenetic and the endocrine points of view. Exposure level was determined by analysing volatile organic compounds in the environment and heavy metals in blood. Cytogenetic damage was determined by sister chromatid exchanges (SCE), and plasmatic prolactin and cortisol levels were used as biomarkers of endocrine toxicity. Finally we have determined the possible influence of GST genetic polymorphisms (GSTM1 and GSTT1 deletion polymorphisms, GSTP1 Ala105Val) on the evaluated effects. The exposed population was classified according to the performed cleaning tasks in three groups: volunteers that collaborated for 1 week (N=25), hired manual workers (N=20) and hired high-pressure cleaner workers (N=23). The control population consisted of 42 individuals. Exposure to Prestige oil caused cytogenetic damage in exposed individuals, being its effect influenced by age, sex, tobacco consumption and GSTM1 polymorphism. With regard to endocrine toxicity, our results showed that xenobiotics present in Prestige oil induced alterations in hormonal status, and thus it may be considered as an endocrine disruptor. Therefore, the selected parameters have shown to be good indicators of toxicity related to exposure to Prestige oil. In addition, data obtained point to the importance of using protective devices in preventing the effects related to the exposure.

Lack of increased genetic damage in 1,3-butadiene-exposed Chinese workers studied in relation to EPHX1 and GST genotypes

1,3-Butadiene (BD) is an important industrial chemical and pollutant. Its ability to induce genetic damage and cause hematological malignancies in humans is controversial. We have examined chromosome damage by fluorescence in situ hybridization (FISH) and mutations in the HPRT gene in the blood of Chinese workers exposed to BD. Peripheral blood samples were collected and cultured from 39 workers exposed to BD (median level 2 ppm, 6 h time-weighted average) and 38 matched controls in Yanshan, China. No difference in the level of aneuploidy or structural changes in chromosomes 1, 7, 8, and 12 was detected in metaphase cells from exposed subjects in comparison with matched controls, nor was there an increase in the frequency of HPRT mutations in the BD-exposed workers. Because genetic polymorphisms in glutathione S-transferase (GST) enzymes and microsomal epoxide hydrolase (EPHX1) may affect the genotoxic effects of BD and its metabolites, we also related chromosome alterations and gene mutations to GSTT1, GSTM1 and EPHX1 genotypes. Overall, there was no effect of variants in these genotypes on numerical or structural changes in chromosomes 1, 7, 8 and 12 or on HPRT mutant frequency in relation to BD exposure, but the GST genotypes did influence background levels of both hyperdiploidy and HPRT mutant frequency. In conclusion, our data show no increase in chromosomal aberrations or HPRT mutations among workers exposed to BD, even in potentially susceptible genetic subgroups. The study is, however, quite small and the levels of BD exposure are not extremely high, but our findings in China do support those from a similar study conducted in the Czech Republic. Together, these studies suggest that low levels of occupational BD exposure do not pose a significant risk of genetic damage.

Exploring environmental causes of altered ras effects: fragmentation plus integration?

Mutations in ras genes are the most common abnormality of oncogenes in human cancer and a major example of activation by point mutation. Experimental and epidemiological studies support the notion that Ki-ras activation and expression may be chemically related. We discuss the potential role of several environmental compounds in the induction or promotion of ras mutations in humans, with a focus on exocrine pancreatic cancer, the human tumor with the highest prevalence at diagnosis of Ki-ras mutations. Organochlorine compounds, organic solvents, and coffee compounds may play an indirect role in causing Ki-ras mutations, rather than as direct inducers of the mutations. Although for some organochlorine compounds the induction of point mutations in ras oncogenes cannot be excluded, it seems more likely that the effects of these compounds are mediated through nongenomic or indirectly genotoxic mechanisms of action. Organic solvents also may act via enzymatic induction of ras mutagens or by providing a proliferation advantage to ras-mutated cell clones. In exocrine pancreatic cancer, caffeine, other coffee compounds, or other factors with which coffee drinking is associated could modulate Ki-ras activation by interfering with DNA repair, cell-cycle checkpoints, and apoptosis. Asbestos, cigarette smoking, and some dietary factors also may be involved in the initiation or the promotion of Ki-ras mutations in lung and colon cancers. Further development of the mechanistic scenarios proposed here could contribute to a meaningful integration of biological, clinical, and environmental knowledge on the causes of altered ras effects.

Expression of ras (p21) protein in plasma from exposed workers and from patients with lung disease

Oncogenes are involved with the regulation of cellular proliferation and thus could be important in the development of many cancers. Cells transformed in culture by ras genes can be activated either by the introduction of specific point mutations or by overexpression of the normal proto-oncogene. The ras genes encode a protein of 189 amino acids (molecular mass 21 kDa) designated as p21. ras p21 proteins are contained in all eukaryotic cells on the inner surface of the plasma membrane. We measured ras p21 proteins in lung cancer patients, patients with chronic obstructive pulmonary disease (COPD) and workers exposed to emissions from petrochemical plants and 1,3-butadiene and 1,3-butadiene/styrene. Proteins were separated by gel electrophoresis, transferred to a nitrocellulose membrane by Western blotting and detected by chemiluminescence. A monoclonal pan-ras antibody was used as the primary antibody. Optical densities of the peak area of the protein bands were calculated and values which were two standard deviations above negative control means were considered positive. Many of the cancer patients and some of the COPD patients gave positive responses, whilst exposed worker groups did not show statistically significant increases by comparison with the controls. Thus, an increase in ras oncoproteins could be a biomarker for cancer or the disease state in general, but it cannot be ruled out that it is a biomarker for exposure since many of the individuals examined were smokers exposed to cigarette smoke.

Genetic and reproductive toxicity of butadiene and isoprene

Butadiene (BD) and its 2-methyl analogue, isoprene, have been extensively studied in animals and BD in population studies. Both chemicals are metabolised by liver cytochrome P450 dependent monogenases to monoepoxide and diepoxide intermediates. The diepoxide intermediates of both compounds were mutagenic in Salmonella typhimurium. However, unlike the monoepoxide of BD, the monoepoxides of isoprene were not mutagenic. It appears that they have no alkylating capacity. BD did not induce somatic cell mutation and recombination or sex-linked recessive lethal mutation in Drosophila melanogaster and isoprene produced no increase in chromosomal aberrations in CHO cells in vitro. Comparative concentrations of haemoglobin adducts in the blood of mice and rats after exposure to BD indicated that reaction with blood may decrease the levels of reactive intermediates available to tissues in rats, but not in mice contributing to greater potency of BD in the mouse. For isoprene, the adducts reach approximately the same concentrations in both species. DNA adducts have also been detected in testicular and lung cells of mice after BD exposure. The level of epoxybutene haemoglobin adducts was significantly elevated in BD-exposed workers, but lower than in rats and mice. In conjunction with the toxicology and carcinogenesis studies for BD and isoprene, additional mice were included for the evaluation of cytogenetic effects. Both chemicals produced increases in sister chromatid exchanges in bone marrow cells and in the frequency of micronuclei in normochromatic and polychromatic erythrocytes, but only BD produced an increase in the percent of bone marrow cells with chromosomal aberrations. At similar doses, the effects with BD were 2-3 times larger than with isoprene. There were also increased hprt mutation frequencies in rats and mice after BD exposure. Biomonitoring studies with hprt mutations in lymphocytes showed conflicting results, with both positive and negative findings. BD has been shown to be positive in one human cytogenetic biomonitoring study and not in three others, but chromosomal aberrations were increased in BD-exposed workers after challenge with gamma rays. Re-analysis of GSTTI null individuals showed positive results. There was an increase in spermatid micronuclei in mice by BD and its metabolites and in rats only by its metabolites. The cytotoxic response of germ cells in mice is greater than in rats. Dominant lethal mutations have been induced by BD and diepoxybutane, but not by epoxybutene. There was some evidence of congenital malformations in mice after BD exposure and there was a linear concentration-related induction of heritable translocations in mice. There was no induction of dominant lethal mutations or congenital malformations in rats. Using the heritable translocation data in mice, it has been determined that if a worker is continually exposed over 5 or 6 weeks to 20-25 ppm of BD, the risk of producing a child with a balanced reciprocal translocation is twice as high as the background risk. Since genetic damage cannot be measured directly in human germ cells, risk to such cells can also be estimated from germ cells and somatic cells of the mouse and human somatic cells using the parallelogram approach. Using doubling doses, the fourth corner of the parallelogram was calculated as a doubling dose for human germ cells of 4390 ppm/h. However, it is still questioned if man is more like rat than mouse in terms of sensitivity to exposure. Similar germ cell data do not exist for isoprene. In conventional developmental studies, where rats and mice were exposed to BD, maternal toxicity was shown in rats but there was no evidence of developmental toxicity or teratogenic effects and there was a small effect on sperm morphology. After exposure to isoprene, there was no adverse effect on rat dams or other reproductive indices. In mice, there was reduced foetal body weight and decreased maternal weight gain and isoprene also affected ovarian follicles. There was a reduction in testicular function parameters such as testicular weight and sperm motility.

A review of the genetic and related effects of 1,3-butadiene in rodents and humans

In this paper, the metabolism and genetic toxicity of 1,3-butadiene (BD) and its oxidative metabolites in humans and rodents is reviewed with attention to newer data that have been published since the latest evaluation of BD by the International Agency for Research on Cancer (IARC). The oxidative metabolism of BD in mice, rats and humans is compared with emphasis on the major pathways leading to the reactive intermediates 1,2-epoxy-3-butene (EB), 1,2:3, 4-diepoxybutane (DEB), and 3,4-epoxy-1,2-butanediol (EBdiol). Results from recent studies of DNA and hemoglobin adducts indicate that EBdiol may play a more significant role in the toxicity of BD than previously thought. All three metabolites are capable of reacting with macromolecules, such as DNA and hemoglobin, and have been shown to induce a variety of genotoxic effects in mice and rats as well as in human cells in vitro. DEB is clearly the most potent of these genotoxins followed by EB, which in turn is more potent than EBdiol. Studies of mutations in lacI and lacZ mice and of the Hprt mutational spectrum in rodents and humans show that mutations at G:C base pairs are critical events in the mutagenicity of BD. In-depth analyses of the mutational spectra induced by BD and/or its oxidative metabolites should help to clarify which metabolite(s) are associated with specific mutations in each animal species and which mutational events contribute to BD-induced carcinogenicity. While the quantitative relationship between exposure to BD, its genotoxicity, and the induction of cancer in occupationally exposed humans remains to be fully established, there is sufficient data currently available to demonstrate that 1,3-butadiene is a probable human carcinogen.

Examination of ras oncoproteins in human plasma from healthy controls and workers exposed to petroleum emissions, including benzene-related compounds

Ras oncoproteins in blood plasma from workers exposed to petroleum emissions and unexposed controls were examined from Polish and Estonian samples. Twenty-four workers and 35 unexposed controls were examined from Poland and 97 exposed and 40 unexposed controls from Estonia. Of the Estonian workers, 50 were exposed to benzene in a benzene production plant and 47 to polyaromatic hydrocarbons and benzene in a cokery. Blood plasma proteins were separated by gel electrophoresis, transferred to a nitrocellulose membrane by Western blotting and detected by chemiluminescence using a monoclonal antibody as the primary antibody. There were no statistically significant differences between the exposed and the control groups in either the Polish or the Estonian samples.

Butadiene: species comparison for metabolism and genetic toxicology

The synthetic monomer 1,3-butadiene and its metabolites have been reviewed in various in vitro and in vivo metabolic studies and in genetic toxicology assays. The species differences have been compared.

Ras p21 protein levels in human plasma from patients with chronic obstructive pulmonary disease (COPD) compared with lung cancer patients and healthy controls

To explore the value of an increase in ras p21 proteins in plasma as a biomarker for the carcinogenic process or for the general disease state, we have directly analysed for ras p21 proteins, plasma samples from Polish human patients with chronic obstructive pulmonary disease (COPD). They were compared with appropriate controls and also with the Polish lung cancer patients previously examined before treatment [D. Anderson, J.A. Hughes, A. Cebulska-Wasilewska, E. Nizankowska, B. Graca, Ras oncoproteins in human plasma from lung cancer patients and healthy controls, Mutat. Res. 349 (1996) 121-126]. An elevated level of ras p21 proteins was considered to be greater than 2 standard deviations (SD) above the mean negative control values. Nine out of 20 COPD patients (mean age = 65.9 years) had increased ras p21 protein levels when compared with 20 age-matched (mean age = 62.4 years) controls of the present study with a mean + 2 SD of 0.70. Eighteen out of 40 lung cancer patients (mean age = 60.1 years) had increased ras p21 protein levels compared with their concurrent controls (mean age = 40.2 years) with a mean + 2 SD of 2.53. However when compared with the age-matched controls of this present study, there were 35 out of 40 (87.5%) with increased levels. When the COPD patients and lung cancer patients were compared with 101 historical controls (age range 25-76 years, of those whose age was recorded) from unexposed healthy populations from Poland, Estonia and Spain with a mean + 2 SD of 1.83, then 4 out of 20 (20%) COPD patients and 30 out of 40 (75%) lung cancer patients had increased levels. Whether using concurrent controls, age-matched controls or historical controls, the data would suggest that an increase in ras p21 protein levels in plasma from lung cancer patients could be a possible prognostic marker or biomarker for lung cancer. COPD patients when compared with historical controls or age-matched controls had lower ras p21 protein values than cancer patients. Their ras p21 protein values might also be a biomarker for cancer. It is possible that some of these COPD patients were in the process of developing cancer or perhaps would die from COPD before cancer develops. It cannot be ruled out that the increases could be a biomarker of exposure since many of the lung cancer patients and most of the COPD patients were smokers.

Examination of ras (P21) proteins in plasma from workers exposed to benzene emissions from petrochemical plants and healthy controls

Exposure of workers to benzene and polyaromatic hydrocarbons has been documented to be at relatively high levels in the production of benzene and in the coking process at a petrochemical plant in the oil shale area in Estonia. Altogether 97 plasma samples from workers and 40 from unexposed matched referents from two samplings in different seasons were analyzed for the presence of ras (P21) proteins; of the workers 50 were exposed to benzene in the benzene production plant and 47 to polyaromatic hydrocarbons and benzene in a cokery. Proteins were separated by gel electrophoresis, transferred to a nitrocellulose membrane by Western blotting and detected by chemiluminescence, using a monoclonal antibody as the primary antibody. There were no statistically significant differences between the exposed and the referent groups. The results are thus in keeping with the lack of exposure related cytogenetic effects for this same workforce.

Somatic and germ cell effects in rats and mice after treatment with 1,3-butadiene and its metabolites, 1,2-epoxybutene and 1,2,3,4-diepoxybutane

1,3-Butadiene is produced in large quantities for use in the manufacture of synthetic rubber. It is also an environmental pollutant. There is concern about exposure to 1,3-butadiene as it has been shown to produce tumours in rats, mice and an increased risk of leukaemia in humans. It has also been shown to produce germ cell effects in mice. Differences in responses to 1,3-butadiene have been reported in rats and mice, possibly due to different metabolic capabilities. The present study thus investigated somatic and germ cell effects of 1,3-butadiene in mice and its metabolites in both rats and mice to help determine species differences using different endpoints for genotoxic effects. These included DNA strand breakage as measured in the single cell gel electrophoresis (Comet assay) in bone marrow and testicular cells, and micronuclei in bone marrow cells using both the acridine orange and Giemsa staining methods. Unscheduled DNA synthesis (UDS) was also measured in the testes of mice. CD-1 mice were exposed to 1,3-butadiene by inhalation for 6 h/day for 4 weeks, and CD-1 mice and Sprague-Dawley rats to the metabolites after i.p. injection. 1,3-Butadiene did not affect liver, bone marrow and testicular cells in mice as measured in the Comet assay. After treatment with 1,2-epoxybutene in the Comet assay, there was a response in the testes in mice but not in rats and there was little or no effect in the bone marrow assay in mice but there was in rats. After treatment with 1,2,3,4-diepoxybutane in the Comet assay in mice, there was a response in the bone marrow cells but not in the testicular cells, and in rats there was also a response only in bone marrow cells. There was an increase in micronuclei in both rats and mice with both metabolites, but clastogenicity was stronger with 1,2,3,4-diepoxybutane, occurring at lower doses, than with 1,2-epoxybutene. In the UDS assay in the testes of mice, there was an increase in response with 1,2,3,4-diepoxybutane treatment but not with 1,2-epoxybutene. These studies would appear to confirm a species difference of CD-1 mice and Sprague-Dawley rats, where mice were sensitive at lower doses than rats.

Monitoring of occupational exposure to cytostatic anticancer agents

Many anticancer agents have been shown to be carcinogenic, mutagenic and teratogenic in experimental animals and in in vitro test systems. Epidemiological data on the association of second neoplasms with a specific chemotherapy treatment is available on some 30 agents, and in the case of 10 compounds the overall evidence on human carcinogenicity has been evaluated to be conclusive (Group 1: IARC, 1987 and 1990). The primary source of human exposure to anticancer drugs is from their use in therapy of cancer. However, persons employed in the manufacture, preparation and administration of the drugs to patients and in nursing patients may also be exposed. Safe handling of anticancer drugs, since the introduction of various general handling guidelines, is now good practice in hospitals, pharmacies and drug manufacturing companies of most developed countries. Careless handling of cancer chemotherapeutic agents may lead to exposure of the personnel in amounts detectable with chemical or biological methods in the body fluids or cell samples of the subjects. The exposure is typically to mixed compounds over long-term and to low exposure levels with accidental peaks. Therefore, the use of biological exposure markers is appropriate for the monitoring of such exposure patterns. The biological markers/methods for exposure assessment are either non-specific (e.g., cytogenetic damage, point mutations or 32P-post-labelling adducts in peripheral blood lymphocytes, urinary mutagenicity) or specific for a given compound (immunological methods for DNA adducts, specific analytical methods). Studies have revealed minor amounts of cyclophosphamide in the urine of pharmacy technicians and nurses handling the drug even when taking special safety precautions (Sessink et al. (1994a) J. Occup. Med., 36, 79; Sessink et al. (1994b) Arch. Env. Health, 49, 165). Another study showed surface wipe samples with measurable cyclophosphamide even away from the handling site (McDevitt et al. (1993) J. Occup. Med., 5, 57). These studies strongly implicate the importance of skin absorption as an exposure route. Also accidental spillage is never completely avoidable (Sorsa et al. (1988) Mutation Res., 204, 465-479). The potential confounders (smoking etc.), toxicokinetics of the agent(s) to be assessed and individual working practices should be carefully considered in any exposure assessment studies using human body fluid samples. Environmental monitoring on indicator cytostatics should be combined into studies designed to identify potential occupational exposure situations to anticancer agents. A properly performed study should also include dissemination of information to the workers to create a psychologically positive atmosphere for this important work.