Usefulness of biomarkers in population studies: from exposure to susceptibility and to prediction of cancer

Occupational health risk of working in garages: comparative study on blood pressure and hematological parameters between garage workers and Haramaya University community, Harar, eastern Ethiopia

Background

Occupational exposure to chemicals in garages causes a wide range of biological effects, depending upon the level and duration of exposure. In Ethiopia, there have been few studies conducted to assess the exposure of garage workers to chemicals. Preceding studies have not explored the effect of working in garage on blood pressure and hematological parameters. Therefore, this study aimed to assess differences in blood pressure and hematological parameters among garage workers compared to the Haramaya University community, Harar, eastern Ethiopia.

Materials and methods

A comparative cross-sectional study was conducted in Harar town, eastern Ethiopia. Thirty garage workers were selected and compared with 30 age- and sex-matched controls comprising of teachers and students. Demographic and occupational data were collected by using a structured questionnaire by a trained data collector. Blood pressure was measured using sphygmomanometry. Hematological parameters were measured with an automated hematology analyzer. Data were analyzed using Stata version 13.

Results

The majority of the garage workers did not implement effective preventive or control measures for workplace chemical exposure. Statistically significant increases were found in systolic (128.67±18.14 vs 106.33 ±9.27 mmHg, P<0.0001), diastolic blood pressure (90.33±11.29 vs 75.67 ±5.68 mmHg, P<0.0001), total white blood cells (7.9±1.51 vs 6.72±2.04×10⁹ cells/L, P=0.0138), and platelets (323.20±48.82 vs 244.1±47.3×10⁹ cells/L, P<0.0001) in garage workers compared to the control group. On the other hand, statistically significant decreases were found in red blood cells (5.13±0.38 vs 5.46±0.36×10¹² cells/L, P=0.0006), hemoglobin (14.89±0.71 vs 15.45±0.87 g/dL, P=0.0062), hematocrit (43.98%±1.99% vs 46.4%3±2.32%, P<0.0001), and mean corpuscular volume (83.19±2.93 vs 85.11±3.87 fL, P=0.0353) among garage workers compared to the control group.

Conclusion

There were significant differences in blood pressure and hematological parameters between garage workers and the control group. Therefore, appropriate and effective safety measures need to be taken by the workers to prevent possible chemical exposure during routine tasks.

[Biomonitoring in exposure to pesticides, its contribution to epidemiological surveillance of pesticide applicators in Cordoba, Argentina]

OBJECTIVE

To assess the level of exposure to pesticides and its correlation with perceived health indicators and injury biomarkers (genotoxic alterations and those caused by butyrylcholinesterase enzyme activity) in the population of pesticide applicators in extensive crops (PAEC) in Córdoba, Argentina.

METHODS

Transversal study, in PAEC (n = 47) randomly selected from a sample of 2000, and non-exposed subject controls (n = 52). The sociodemographic variables, exposure conditioning, and perceived health were surveyed by means of a self-administered questionnaire; biological indicators of genotoxicity: micronuclei, chromosomal aberrations and kite assay, and butyrylcholinesterase activity.

RESULTS

40% of PAEC have over 10 years' length of service and almost 50% of them reside less than 500 m from the sprinkled fields; they report low rates of personal protective equipment use while mixing, applying, or repairing the equipment. General, cardio-respiratory, and dermatological symptoms were greater among PAEC (p <0.05) as well as indicators of genotoxic injury (p <0.001). The butyrylcholinesterase activity was negatively associated with levels of exposure to pesticides.

CONCLUSIONS

The PAEC show an important negative impact on health linked to exposure to pesticides. The exposure scales associated to the use of biomarkers were a useful tool for monitoring pesticide applicators' health.

Meta-analysis of chromosomal aberrations as a biomarker of exposure in healthcare workers occupationally exposed to antineoplastic drugs

Many antineoplastic drugs used to treat cancer, particularly alkylating agents and topoisomerase inhibitors, are known to induce genetic damage in patients. Elevated levels of chromosomal aberrations, micronuclei, and DNA damage have been documented in cancer patients. Elevations in these same biomarkers of genetic damage have been reported in numerous studies of healthcare workers, such as nurses and pharmacists, who routinely handle these drugs, but results vary across studies. To obtain an overall assessment of the exposure effect, we performed a meta-analysis on data obtained from peer-reviewed publications reporting chromosomal aberration levels in healthcare workers exposed to antineoplastic drugs. A literature search identified 39 studies reporting on occupational exposure to antineoplastic drugs and measurement of chromosomal aberrations in healthcare workers. After applying strict inclusion criteria for data quality and presentation, data from 17 studies included in 16 publications underwent meta-analysis using Hedges' bias-corrected g and a random-effects model. Results showed the level of chromosomal aberrations in healthcare workers exposed to antineoplastic drugs was significantly higher than in controls. The standardized mean differences (difference of means divided by within sd) from all studies were pooled, yielding a value 1.006 (unitless) with p<0.001. Thus, in addition to the documented genotoxic effects of antineoplastic drugs in cancer patients, this meta-analysis confirmed a significant association between occupational exposure to antineoplastics during the course of a normal work day and increases in chromosomal aberrations in healthcare workers. Based on the studies reviewed, we were unable to accurately assess whether appropriate use of protective measures might reduce the incidence of genetic damage in healthcare workers. However, given the potential for increased cancer risk linked to increases in chromosomal aberrations, the results of this study support the need to limit occupational exposure of healthcare workers to antineoplastic drugs as much as possible.

The use of genotoxicity biomarkers in molecular epidemiology: applications in environmental, occupational and dietary studies

Molecular epidemiology is an approach increasingly used in the establishment of associations between exposure to hazardous substances and development of disease, including the possible modulation by genetic susceptibility factors. Environmental chemicals and contaminants from anthropogenic pollution of air, water and soil, but also originating specifically in occupational contexts, are potential sources of risk of development of disease. Also, diet presents an important role in this process, with some well characterized associations existing between nutrition and some types of cancer. Genotoxicity biomarkers allow the detection of early effects that result from the interaction between the individual and the environment; they are therefore important tools in cancer epidemiology and are extensively used in human biomonitoring studies. This work intends to give an overview of the potential for genotoxic effects assessment, specifically with the cytokinesis blocked micronucleus assay and comet assay in environmental and occupational scenarios, including diet. The plasticity of these techniques allows their inclusion in human biomonitoring studies, adding important information with the ultimate aim of disease prevention, in particular cancer, and so it is important that they be included as genotoxicity assays in molecular epidemiology.

Predictive and Prognostic Biomarkers of Respiratory Diseases due to Particulate Matter Exposure

Air pollution is getting severe and concerns about its toxicity effects on airway and lung disease are also increasing. Particulate matter (PM) is major component of air pollutant. It causes respiratory diseases, such as asthma, chronic obstructive pulmonary disease, lung cancer, and so on. PM particles enter the airway and lung by inhalation, causing damages to them. Especially, PM_2.5 can penetrate into the alveolus and pass to the systemic circulation. It can affect the cardiopulmonary system and cause cardiopulmonary disorders. In this review, we focused on PM-inducing toxicity mechanisms in the framework of oxidative stress, inflammation, and epigenetic changes. We also reviewed its correlation with respiratory diseases. In addition, we reviewed biomarkers related to PM-induced respiratory diseases. These biomarkers might be used for disease prediction and early diagnosis. With recent trend of using genomic analysis tools in the field of toxicogenomics, respiratory disease biomarkers associated with PM will be continuously investigated. Effective biomarkers derived from earlier studies and further studies might be utilized to reduce respiratory diseases.

Improving the International Agency for Research on Cancer's consideration of mechanistic evidence

BACKGROUND

The International Agency for Research on Cancer (IARC) recently developed a framework for evaluating mechanistic evidence that includes a list of 10 key characteristics of carcinogens. This framework is useful for identifying and organizing large bodies of literature on carcinogenic mechanisms, but it lacks sufficient guidance for conducting evaluations that fully integrate mechanistic evidence into hazard assessments.

OBJECTIVES

We summarize the framework, and suggest approaches to strengthen the evaluation of mechanistic evidence using this framework.

DISCUSSION

While the framework is useful for organizing mechanistic evidence, its lack of guidance for implementation limits its utility for understanding human carcinogenic potential. Specifically, it does not include explicit guidance for evaluating the biological significance of mechanistic endpoints, inter- and intra-individual variability, or study quality and relevance. It also does not explicitly address how mechanistic evidence should be integrated with other realms of evidence. Because mechanistic evidence is critical to understanding human cancer hazards, we recommend that IARC develop transparent and systematic guidelines for the use of this framework so that mechanistic evidence will be evaluated and integrated in a robust manner, and concurrently with other realms of evidence, to reach a final human cancer hazard conclusion.

CONCLUSIONS

IARC does not currently provide a standardized approach to evaluating mechanistic evidence. Incorporating the recommendations discussed here will make IARC analyses of mechanistic evidence more transparent, and lead to assessments of cancer hazards that reflect the weight of the scientific evidence and allow for scientifically defensible decision-making.

Persistence of Breakage in Specific Chromosome Bands 6 Years after Acute Exposure to Oil

BACKGROUND

The identification of breakpoints involved in chromosomal damage could help to detect genes involved in genetic disorders, most notably cancer. Until now, only one published study, carried out by our group, has identified chromosome bands affected by exposure to oil from an oil spill. In that study, which was performed two years after the initial oil exposure in individuals who had participated in clean-up tasks following the wreck of the Prestige, three chromosomal bands (2q21, 3q27, 5q31) were found to be especially prone to breakage. A recent follow-up study, performed on the same individuals, revealed that the genotoxic damage had persisted six years after oil exposure.

OBJECTIVES

To determine whether there exist chromosome bands which are especially prone to breakages and to know if there is some correlation with those detected in the previous study. In addition, to investigate if the DNA repair problems detected previously persist in the present study.

DESIGN

Follow-up study performed six years after the Prestige oil spill.

SETTING

Fishermen cooperatives in coastal villages.

PARTICIPANTS

Fishermen highly exposed to oil spill who participated in previous genotoxic study six years after the oil.

MEASUREMENTS

Chromosome damage in peripheral lymphocytes. For accurate identification of the breakpoints involved in chromosome damage of circulating lymphocytes, a sequential stain/G-banding technique was employed. To determine the most break-prone chromosome bands, two statistical methods, the Fragile Site Multinomial and the chi-square tests (where the bands were corrected by their length) were used. To compare the chromosome lesions, structural chromosome alterations and gaps/breaks between two groups of individuals we used the GEE test which takes into account a possible within-individual correlation. Dysfunctions in DNA repair mechanisms, expressed as chromosome damage, were assessed in cultures with aphidicolin by the GEE test.

RESULTS

Cytogenetic analyses were performed in 47 exposed individuals. A total of 251 breakpoints in exposed individuals) were identified, showing a non-uniform distribution in the human ideogram. Ten chromosome bands were found to be especially prone to breakage through both statistical methods. By comparing these bands with those observed in certain exposed individuals who had already participated the previous study, it was found in both studies that four bands (2q21, 3q27, 5q31 and 17p11.2) are particularly sensitive to breakage. Additionally, the dysfunction in DNA repair mechanisms was not significantly higher in oil-exposed individuals than in non-exposed individuals.

LIMITATIONS

The sample size and the possibility of some kind of selection bias should be considered. Genotoxic results cannot be extrapolated to the high number of individuals who participated occasionally in clean-up tasks.

CONCLUSION

Our findings show the existence of at least four target bands (2q21, 3q27, 5q31 and 17p11.2) with a greater propensity to break over time after an acute exposure to oil. The breaks in these bands, which are commonly involved in hematological cancer, may explain the increase of cancer risk reported in chronically benzene-exposed individuals. In addition, a more efficiency of the DNA repair mechanisms has been detected six years after in fishermen who were highly exposed to the oil spill. To date, only this study, performed by our group on the previous and present genotoxic effects, has analyzed the chromosomal regions affected by breakage after an acute oil exposure.

The role of oxidative DNA damage and GSTM1, GSTT1, and hOGG1 gene polymorphisms in coronary artery disease risk

Objective:

Atherosclerotic coronary artery disease (CAD) appears to be a multifactorial process caused by the interaction of environmental risk factors with multiple predisposing genes. Therefore, in this study we aimed to determine the role of oxidative DNA damage and some variations in glutathione S-transferase (GSTM1 and GSTT1) and DNA repair (hOGG1) genes in CAD risk.

Methods:

A case-control study was conducted on 59 individuals who had undergone coronary angiographic evaluation. Of these, 29 were patients diagnosed with CAD (mean age =61.5±10.3) and 30 were controls examined for reasons other than suspected CAD and who had angiographically documented normal coronary arteries (mean age =60.4±11.6). Basal DNA damage as well as pyrimidine and purine base damage were evaluated in peripheral blood lymphocytes using the modified comet assay. Polymerase chain reaction-restriction length polymorphism (PCR-RFLP)-based assay was used for genotyping.

Results:

Basal DNA damage levels in patients [9.16 (3.26)] were significantly higher than those in controls [7.59 (3.23); p=0.017], and basal DNA and pyrimidine base damage levels were significantly correlated with disease severity based on Gensini scoring (r=0.352, p=0.006; r=0.318, p=0.014, respectively). However, no significant differences were observed in terms of oxidized DNA bases between patients and controls. The frequencies of studied genotypes (GSTM1, GSTT1, and hOGG1) were similar between groups.

Conclusion:

The results of this study pointed out the role of DNA damage in CAD and its severity. However, GSTM1, GSTT1, and hOGG1 gene polymorphisms seemed to have no effect on individual susceptibility for disease progression. (Anatol J Cardiol 2016; 16: 931-8)

Aldehyde dehydrogenase induction in arsenic-exposed rat bladder epithelium

Arsenic is widely distributed in the environment. Many human cancers, including urothelial carcinoma (UC), show a dose-dependent relationship with arsenic exposure in the south-west coast of Taiwan (also known as the blackfoot disease (BFD) areas). However, the molecular mechanisms of arsenic-mediated UC carcinogenesis has not yet been defined. In vivo study, the rat bladder epithelium were exposed with arsenic for 48 h. The proteins were extracted from untreated and arsenic-treated rat bladder cells and utilized two-dimensional gel electrophoresis and mass spectrometry. Selected peptides were extracted from the gel and identified by quadrupole-time of flight (Q-TOF) Ultima-Micromass spectra. The significantly difference expression of proteins in arsenic-treated groups as compared with untreated groups was confirmed by immunohistochemistry (IHC) and western blotting. We found that thirteen proteins were down-regulated and nine proteins were up-regulated in arsenic-treated rat bladder cells when compared with untreated groups. The IHC and western blotting results confirmed that aldehyde dehydrogenase (ALDH) protein was up-regulated in arsenic-treated rat bladder epithelium. Expression of ALDH protein was significantly higher in UC patients from BFD areas than those from non-BFD areas using IHC (p=0.018). In conclusion, the ALDH protein expression could be used as molecular markers for arsenic-induced transformation.

DNA damage assessment in the lymphocytes of construction painters by comet assay

BACKGROUND

Exposure to chemicals is inevitable for certain occupational groups, particularly in industrial countries. Some cytogenetic tests such as comet assay are effectively utilized to screen genotoxic effects of these chemicals in humans. The purpose of this study has been to assess the DNA damage in construction painters' lymphocytes using the comet assay.

METHODS

Fourteen male construction painters with 1 year of required work experience were randomly selected from the list of Painter Union in Gonabad city, Iran. In addition, 14 healthy male non-painters were randomly selected as controls. The DNA damage degree was determined using a fluorescence microscope and CometScore software. The obtained data were analyzed employing independent t-test using SPSS software v. 14 at the significant level of p < 0.05.

RESULTS

All participants were non-smokers and non-alcoholics. No significant differences were found between the two groups in terms of age, weight, height, body mass index, and systolic and diastolic blood pressure. The DNA damage in the painter group was significantly greater than that of the control group. Tail length (µm) was 12.63 ± 6.54 versus 2.90 ± 0.84, tail DNA (%) was 4.33 ± 1.84 versus 1.29 ± 0.43, and tail moment (µm) was 1.85 ± 0.98 versus 0.14 ± 0.20 in painter and control groups ( p < 0.001), respectively.

CONCLUSION

The chemicals used in oil paint may increase the DNA damage in painter blood lymphocytes.

Chromosomal bands affected by acute oil exposure and DNA repair errors

BACKGROUND

In a previous study, we showed that individuals who had participated in oil clean-up tasks after the wreckage of the Prestige presented an increase of structural chromosomal alterations two years after the acute exposure had occurred. Other studies have also reported the presence of DNA damage during acute oil exposure, but little is known about the long term persistence of chromosomal alterations, which can be considered as a marker of cancer risk.

OBJECTIVES

We analyzed whether the breakpoints involved in chromosomal damage can help to assess the risk of cancer as well as to investigate their possible association with DNA repair efficiency.

METHODS

Cytogenetic analyses were carried out on the same individuals of our previous study and DNA repair errors were assessed in cultures with aphidicolin.

RESULTS

Three chromosomal bands, 2q21, 3q27 and 5q31, were most affected by acute oil exposure. The dysfunction in DNA repair mechanisms, expressed as chromosomal damage, was significantly higher in exposed-oil participants than in those not exposed (p= 0.016).

CONCLUSION

The present study shows that breaks in 2q21, 3q27 and 5q31 chromosomal bands, which are commonly involved in hematological cancer, could be considered useful genotoxic oil biomarkers. Moreover, breakages in these bands could induce chromosomal instability, which can explain the increased risk of cancer (leukemia and lymphomas) reported in chronically benzene-exposed individuals. In addition, it has been determined that the individuals who participated in clean-up of the oil spill presented an alteration of their DNA repair mechanisms two years after exposure.

Assessment of individual susceptibility to baseline DNA and cytogenetic damage in a healthy Turkish population: evaluation with lifestyle factors

BACKGROUND

Cytogenetic biomarkers are most frequently used well-established endpoints in human population studies with their sensitivity for measuring exposure to genotoxic agents. They have an important role as early predictors of cancer risk. Identification of individual genotypes of metabolic gene polymorphisms helps to understand the modulation of cancer susceptibility by environmental exposures, such as cigarette smoking and other lifestyle factors.

AIM

To evaluate individual susceptibility to chemicals, we determined individual DNA damage related to glutathione S-transferase (GST) genotypes (GSTM1, GSTT1, and GSTP1) in a Turkish population.

METHODS

Peripheral blood lymphocytes (PBL) and DNA samples of 127 subjects were analyzed for the presence of DNA damage, using single-cell gel electrophoresis (the Comet assay), and for cytogenetic parameters (chromosomal aberrations [CAs], bleomycin-induced CA, and a cytokinesis-blocked micronucleus assay), and the polymerase chain reaction/restriction fragment length polymorphism method, respectively.

RESULTS

Individuals carrying a GSTT1-null allele showed higher frequencies of CA and micronucleus (MN) (p=0.026, p=0.003, respectively), whereas the GSTM1-null and GSTP1 mutant genotypes did not show any differences in cytogenetic parameters. Our findings demonstrated that none of the lifestyle factors (smoking, alcohol drinking, dietary habits, vitamin intake, and physical activity), except for vitamin intake (p=0.002), were significantly associated with the studied cytogenetic parameters.

CONCLUSION

Our results suggest that the GSTT1 gene polymorphism may influence the baseline cytogenetic frequency in a healthy population.

Categorizing biomarkers of the human exposome and developing metrics for assessing environmental sustainability

The concept of maintaining environmental sustainability broadly encompasses all human activities that impact the global environment, including the production of energy, use and management of finite resources such as petrochemicals, metals, food production (farmland, fresh and ocean waters), and potable water sources (rivers, lakes, aquifers), as well as preserving the diversity of the surrounding ecosystems. The ultimate concern is how one can manage Spaceship Earth in the long term to sustain the life, health, and welfare of the human species and the planet's flora and fauna. On a more intimate scale, one needs to consider the human interaction with the environment as expressed in the form of the exposome, which is defined as all exogenous and endogenous exposures from conception onward, including exposures from diet, lifestyle, and internal biology, as a quantity of critical interest to disease etiology. Current status and subsequent changes in the measurable components of the exposome, the human biomarkers, could thus conceivably be used to assess the sustainability of the environmental conditions with respect to human health. The basic theory is that a shift away from sustainability will be reflected in outlier measurements of human biomarkers. In this review, the philosophy of long-term environmental sustainability is explored in the context of human biomarker measurements and how empirical data can be collected and interpreted to assess if solutions to existing environmental problems might have unintended consequences. The first part discusses four conventions in the literature for categorizing environmental biomarkers and how different types of biomarker measurements might fit into the various grouping schemes. The second part lays out a sequence of data management strategies to establish statistics and patterns within the exposome that reflect human homeostasis and how changes or perturbations might be interpreted in light of external environmental stressors. The underlying concept is to identify probative outliers from the "unremarkable exposome" in individuals or subpopulations that could be used for discerning deviations from the healthy environment, much like current diagnostic medicine uses batteries of blood and urine tests to screen for preclinical disease conditions. Such empirically derived human in vivo data could subsequently be integrated into high-throughput in vitro and in silico testing of environmental and manufactured chemicals to support real-world toxicity evaluations.

Cytogenetic methods in human biomonitoring: principles and uses

Cellular phenotypes can be applied as biomarkers to differentiate normal from abnormal biological -conditions. Several cytogenetic methods have been developed and allow the accurate detection of such phenotypic changes.Based on their mechanisms of formation, cellular phenotypes may be used either as biomarkers of exposure or as biomarkers of effect. Therefore, it is important that cytogenetic methods implemented in human biomonitoring should be based on a good knowledge of these mechanisms.In this chapter, we aim to review the mechanistic basis, the methodology, and the use in human biomonitoring studies of four major cytogenetic endpoints: sister chromatid exchanges (SCEs), high frequency cells (HFCs), chromosomal aberrations (CAs), and micronuclei (MN). In addition, an overview of potential confounding factors on the induction of these cytogenetic makers is presented. Furthermore, the combination of cytogenetics with molecular methods, which allows chromosome and gene identification on metaphase as well as in interphase cells with high resolution, is discussed. Finally, practical recommendations for an efficient application of these cytogenetic assays and a correct interpretation of the results on the basis of cellular phenotype(s) assessment in human biomonitoring are highlighted.

Genotoxic damage in auto body shop workers

Some studies have shown increased DNA damage among car painters, but other professionals working in auto body and paint shops have not been extensively assessed. The aim of this study was to assess DNA damage in different types of auto body shop workers by measuring micronucleus (MN) levels in exfoliated buccal cells. The mean number of cells with MN per 2000 exfoliated buccal cells was analyzed in three groups of male workers: auto body repair technicians, painters, and office workers (control group). All participants answered a questionnaire inquiring about age, smoking habits, alcohol consumption, work practices, occupational exposure time, job activities, and use of protective equipment. The mean number of cells with MN was 3.50 ± 1.50 in auto body painters, 3.91 ± 2.10 in auto body repair technicians, and 0.80 ± 0.78 in office workers, with a significant difference between the control group and the two other groups (p = 0.0001). Age, occupational exposure time, use of protective masks, alcohol consumption, and smoking habit did not affect MN results. The findings indicate that technicians and painters working in auto body shops are at risk for genotoxic damage, while office workers seem to be protected.

The role of oxidative DNA damage, DNA repair, GSTM1, SOD2 and OGG1 polymorphisms in individual susceptibility to Barrett’s esophagus

Determination of the genetic alterations, which play a role in the etiology of Barrett’s esophagus (BE), could help identify high-risk individuals for esophageal adenocarcinoma (EA). The aim of the present study was to investigate the role of oxidative DNA damage, glutathione (GSH) concentration as oxidative stress parameters and DNA repair capacity, GSTM1, SOD1 Ala16Val and OGG1 Ser326Cys genetic polymorphisms as individual susceptibility parameters in the etiology of BE. The study groups comprised BE patients who were clinically diagnosed (n = 40) and a healthy control group (n = 40). Basal DNA damage, pyrimidine and purine base damage after H2O2 induction, H 2O2 sensitivity, DNA repair capacity, oxidized pyrimidine and purine base damage repair were evaluated in peripheral blood lymphocytes with a modified comet assay using specific endonucleases (Endo III and Fpg). Polymerase chain reaction—restriction length polymorphism (PCR-RFLP)-based assays were used for genotyping. The patient group showed elevated levels of basal DNA damage, pyrimidine base damage and H2O2 sensitivity as compared to controls (p < .05). DNA repair capacity, oxidized pyrimidine and purine base damage repair capacity, were not statistically different between patients and controls. GSH concentration was found to be significantly lower in smoking patients than in the controls (p < .05). None of the genetic variations changed the risk of having BE disease. However, patients carrying the variant OGG1 Cys allele showed elevated levels of pyrimidine base damage as compared to patients carrying the wild-type OGG1 Ser (p < .05). The results of this study point to a role of oxidative DNA damage in BE. However, DNA repair capacity, GSTM1, SOD1 Ala16Val and OGG1 Ser326Cys genetic polymorphisms appeared to play no role in the individual susceptibility to this disease.

Evaluation of a suitable DNA damage biomarker for human biomonitoring of exposed workers

The objective of this study was to identify a sensitive and noninvasive biomarker of early genotoxic effects, for health risk assessment of workers exposed to mixtures of low doses of xenobiotics. We studied 30 workers exposed to antineoplastic drugs, 57 workers exposed to different mixtures of polycyclic aromatic hydrocarbons (PAHs) (41 airport workers and 16 paving workers) and 76 controls. Comet and micronucleus (MN) tests were performed on lymphocytes and exfoliated buccal cells. The MN assay on lymphocytes did not show significant differences between exposed and controls, while the MN assay on exfoliated buccal cells showed higher values in workers exposed to antineoplastics as compared with controls (0.85 vs. 0.48, P = 0.042). The comet assay on lymphocytes showed a higher comet percentage value (18.11 vs. 11.24 in controls, P = 0.001) and mean tail moment (TM) value (21.84 vs. 16.72 in controls, P = 0.003) in individuals exposed to PAHs as compared with controls; no significant differences were found in exposed to antineoplastics. The comet assay on exfoliated buccal cells did not show significant differences between exposed and control groups for comet percentages, whereas the TM value was higher in workers exposed to PAHs (55.1 vs. 32.31 for controls, P < 0.001). These results show that exfoliated buccal cells, obtained by a noninvasive procedure, represent robust target cells to assess the occupational exposure to inhalable mixture of chemicals at low doses. The comet assay seems to be suitable to promptly evaluate the genotoxic effects of PAHs mixtures that also contain volatile substances. The MN test is suitable to evaluate the effects of antineoplastics. Inc.

Nonlinear cancer response at ultralow dose: a 40800-animal ED(001) tumor and biomarker study

Assessment of human cancer risk from animal carcinogen studies is severely limited by inadequate experimental data at environmentally relevant exposures and by procedures requiring modeled extrapolations many orders of magnitude below observable data. We used rainbow trout, an animal model well-suited to ultralow-dose carcinogenesis research, to explore dose-response down to a targeted 10 excess liver tumors per 10000 animals (ED(001)). A total of 40800 trout were fed 0-225 ppm dibenzo[a,l]pyrene (DBP) for 4 weeks, sampled for biomarker analyses, and returned to control diet for 9 months prior to gross and histologic examination. Suspect tumors were confirmed by pathology, and resulting incidences were modeled and compared to the default EPA LED(10) linear extrapolation method. The study provided observed incidence data down to two above-background liver tumors per 10000 animals at the lowest dose (that is, an unmodeled ED(0002) measurement). Among nine statistical models explored, three were determined to fit the liver data well-linear probit, quadratic logit, and Ryzin-Rai. None of these fitted models is compatible with the LED(10) default assumption, and all fell increasingly below the default extrapolation with decreasing DBP dose. Low-dose tumor response was also not predictable from hepatic DBP-DNA adduct biomarkers, which accumulated as a power function of dose (adducts = 100 x DBP(1.31)). Two-order extrapolations below the modeled tumor data predicted DBP doses producing one excess cancer per million individuals (ED(10)(-6)) that were 500-1500-fold higher than that predicted by the five-order LED(10) extrapolation. These results are considered specific to the animal model, carcinogen, and protocol used. They provide the first experimental estimation in any model of the degree of conservatism that may exist for the EPA default linear assumption for a genotoxic carcinogen.

Challenge assay: A functional biomarker for exposure-induced DNA repair deficiency and for risk of cancer

A variety of biomarkers have been used to monitor exposed populations to determine potential health hazards from their exposure to environmental toxic agents. However, the majority of these biomarkers have been focused onto the identification of biological damage from the exposure. Therefore, there is a need to develop functional biomarkers that can identify exposure-induced functional deficiencies. More importantly, these deficiencies should be positioned along pathways that are responsible for the development of specific diseases. One of such pathways belongs to the extensive and complex DNA-repair machinery. The machinery thus becomes a large target for damage from environmental toxic agents. The hypothesis is that damage to any component of a repair pathway will interfere with the pathway-specific repair activities. Therefore, when cells from exposed populations are challenged with a DNA-damaging agent in vitro, the in vivo exposure-induced repair deficiency will be dramatically amplified and the deficiency will be detectable in a challenge assay as increased chromosome aberrations, micronuclei or un-repaired DNA strand breaks. The challenge assay has been used in different laboratories to show that a variety of exposed populations (with exposure to air pollutants, arsenic, benzene, butadiene, cigarette smoke, incense smoke, lead, mercury, pesticides, uranium or xylene but not to low concentrations of air pollutants or butadiene) expressed abnormal challenge response. The predicted health consequences of some of these studies have also been validated. Therefore, the challenge assay is a useful functional biomarker for population studies. Details of the challenge assay and its application will be presented in this review.

Biomarkers in population studies: environmental mutagenesis and risk for cancer

Biomarkers of exposure and biological effects have frequently been used to monitor populations for their exposure to toxic substances and for the prediction of disease risk, such as cancer. Current interest is focused on improving the use of biomarkers to better understand biological mechanisms for improved risk assessment. Such improvements involve the understanding of inter-individual variations in response to exposure, integration of genomic and proteomic technologies into biomarker studies, development of functional biomarkers, and the use of high tech procedures like biosensors and lab-on-a-chip approaches. The latter two approaches can provide unique contributions by providing specific and real-time reporting of excessive exposure. Based on the generation of more reliable information regarding exposure-specific effects, biological mechanisms, and health risk, more realistic prevention and intervention protocols have been implemented. The usefulness and application of these biomarkers and technologies will be presented.

Proteomic alteration in lung tissue of rats exposed to cigarette smoke

Cigarette smoke has been widely investigated in terms of epidemiological and pathological studies in relation to human lung diseases. In this study, we conducted a proteomic analysis to characterize the differential protein expression in lung tissue of rats exposed to cigarette smoke. Wistar rats were exposed to cigarette smoke twice a day, 30 min each for 1, 2 and 4 months, respectively. The total protein of lung tissue was extracted for two-dimensional electrophoresis (2-DE) and analyzed with ImageMaster 2D Platinum software. A total of 28 differentially expressed proteins between the control and the smoke-exposed groups were screened and of which 18 were identified by matrix assistant laser desorption ion-top of flight-mass spectrometry (MALDI-TOF-MS) or MALDI- TOF-TOF analysis, revealing 10 up-regulated and 8 down-regulated proteins. The up-regulated expression of two proteins, receptor for advanced glycation endpoints (RAGE) and thioredoxin (Trx), were validated by immunoblotting and found to be consistent with the proteomic analysis. The results presented in this study demonstrate the identification of proteomic pattern as an early indicator of lung damages induced by cigarette smoke. The differentially expressed proteins may be applied as exposure biomarkers in future experimental as well as epidemiologic investigations upon confirmation by a greater sample size and more validate study design for the proteomic research.

Human biomonitoring: State of the art

Human biomonitoring (HBM) of dose and biochemical effect nowadays has tremendous utility providing an efficient and cost effective means of measuring human exposure to chemical substances. HBM considers all routes of uptake and all sources which are relevant making it an ideal instrument for risk assessment and risk management. HBM can identify new chemical exposures, trends and changes in exposure, establish distribution of exposure among the general population, identify vulnerable groups and populations with higher exposures and identify environmental risks at specific contaminated sites with relatively low expenditure. The sensitivity of HBM methods moreover enables the elucidation of human metabolism and toxic mechanisms of the pollutants. So, HBM is a tool for scientists as well as for policy makers. Blood and urine are by far the most approved matrices. HBM can be done for most chemical substances which are in the focus of the worldwide discussion of environmental medicine. This especially applies for metals, PAH, phthalates, dioxins, pesticides, as well as for aromatic amines, perfluorinated chemicals, environmental tobacco smoke and volatile organic compounds. Protein adducts, especially Hb-adducts, as surrogates of DNA adducts measuring exposure as well as biochemical effect very specifically and sensitively are a still better means to estimate cancer risk than measuring genotoxic substances and their metabolites in human body fluids. Using very sophisticated but nevertheless routinely applicable analytical procedures Hb-adducts of alkylating agents, aromatic amines and nitro aromatic compounds are determined routinely today. To extend the spectrum of biochemical effect monitoring further methods should be elaborated which put up with cleavage and separation of the adducted protein molecules as a measure of sample preparation. This way all sites of adduction as well as further proteins, like serum albumin could be used for HBM. DNA-adducts indicate the mutagenicity of a chemical substance as well as an elevated cancer risk. DNA-adducts therefore would be ideal parameters for HBM. Though there are very sensitive techniques for DNA adduct monitoring like P32-postlabelling and immunological methods they lack specificity. For elucidating the mechanism of carcinogenesis and for a broad applicability and comparability in epidemiological studies analytical methods must be elaborated which are strictly specific for the chemical structure of the DNA-adduct. Current analytical possibilities however meet their borders. In HBM studies with exposure to genotoxic chemicals especially the measurement of DNA strand breaks in lymphocytes and 8-hydroxy-2'-deoxyguanosine (8-OHdG) in white blood cells has become very popular. However, there is still a lack of well-established dose-response relations between occupational or environmental exposures and the induction of 8-OHdG or formation of strand breaks which limits the applicability of these markers. Most of the biomarkers used in population studies are covered by standard operating procedures (SOPs) as well as by internal and external quality assessment schemes. Therefore, HBM results from the leading laboratories worldwide are analytically reliable and comparable. Newly upcoming substances of environmental relevance like perfluorinated compounds can rapidly be assessed in body fluids because there are very powerful laboratories which are able to elaborate the analytical prerequisites in due time. On the other hand, it is getting more and more difficult for the laboratories to keep up with a progress in instrumental analyses. In spite of this it will pay to reach the ultimate summit of HBM because it is the only way to identify and quantify human exposure and risk, elucidate the mechanism of toxic effects and to ultimately decide if measures have to be taken to reduce exposure. Risk assessment and risk management without HBM lead to wrong risk estimates and cause inadequate measures. In some countries like in USA and in Germany, thousands of inhabitants are regularly investigated with respect to their internal exposure to a broad range of environmentally occurring substances. For the evaluation of HBM results the German HBM Commission elaborates reference- and HBM-values.