DNA bulky adducts in a Mediterranean population correlate with environmental ozone concentration, an indicator of photochemical smog

Traffic-Related Air Pollution and Ground-Level Ozone Associated Global DNA Hypomethylation and Bulky DNA Adduct Formation

Studies have indicated that air pollution, including surface-level ozone (O₃), can significantly influence the risk of chronic diseases. To better understand the carcinogenic mechanisms of air pollutants and identify predictive disease biomarkers, we examined the association between traffic-related pollutants with DNA methylation alterations and bulky DNA adducts, two biomarkers of carcinogen exposure and cancer risk, in the peripheral blood of 140 volunteers-95 traffic police officers, and 45 unexposed subjects. The DNA methylation and adduct measurements were performed by bisulfite-PCR and pyrosequencing and ³²P-postlabeling assay. Airborne levels of benzo(a)pyrene [B(a)P], carbon monoxide, and tropospheric O₃ were determined by personal exposure biomonitoring or by fixed monitoring stations. Overall, air pollution exposure was associated with a significant reduction (1.41 units) in global DNA methylation (95% C.I. -2.65-0.04, p = 0.026). The decrement in ALU repetitive elements was greatest in the policemen working downtown (95% C.I. -3.23--0.49, p = 0.008). The DNA adducts were found to be significantly increased (0.45 units) in the municipal officers with respect to unexposed subjects (95% C.I. 0.02-0.88, p = 0.039), mainly in those who were controlling traffic in downtown areas (95% C.I. 0.39-1.29, p < 0.001). Regression models indicated an increment of ALU methylation at higher B(a)P concentrations (95% C.I. 0.03-0.60, p = 0.032). Moreover, statistical models showed a decrement in ALU methylation and an increment of DNA damage only above the cut-off value of 30 µg/m³ O₃. A significant increment of 0.73 units of IL-6 gene methylation was also found in smokers with respect to non-smokers. Our results highlighted the role of air pollution on epigenetic alterations and genotoxic effects, especially above the target value of 30 µg/m³ surface-level O₃, supporting the necessity for developing public health strategies aimed to reduce traffic-related air pollution molecular alterations.

Applications of Adductomics in Chemically Induced Adverse Outcomes and Major Emphasis on DNA Adductomics: A Pathbreaking Tool in Biomedical Research

Adductomics novel and emerging discipline in the toxicological research emphasizes on adducts formed by reactive chemical agents with biological molecules in living organisms. Development in analytical methods propelled the application and utility of adductomics in interdisciplinary sciences. This review endeavors to add a new dimension where comprehensive insights into diverse applications of adductomics in addressing some of society's pressing challenges are provided. Also focuses on diverse applications of adductomics include: forecasting risk of chronic diseases triggered by reactive agents and predicting carcinogenesis induced by tobacco smoking; assessing chemical agents' toxicity and supplementing genotoxicity studies; designing personalized medication and precision treatment in cancer chemotherapy; appraising environmental quality or extent of pollution using biological systems; crafting tools and techniques for diagnosis of diseases and detecting food contaminants; furnishing exposure profile of the individual to electrophiles; and assisting regulatory agencies in risk assessment of reactive chemical agents. Characterizing adducts that are present in extremely low concentrations is an exigent task and more over absence of dedicated database to identify adducts is further exacerbating the problem of adduct diagnosis. In addition, there is scope of improvement in sample preparation methods and data processing software and algorithms for accurate assessment of adducts.

Bulky DNA Adducts, Tobacco Smoking, Genetic Susceptibility, and Lung Cancer Risk

The generation of bulky DNA adducts consists of conjugates formed between large reactive electrophiles and DNA-binding sites. The term "bulky DNA adducts" comes from early experiments that employed a ³²P-DNA postlabeling approach. This technique has long been used to elucidate the association between adducts and carcinogen exposure in tobacco smoke studies and assess the predictive value of adducts in cancer risk. Molecular data showed increased DNA adducts in respiratory tracts of smokers vs nonsmokers. Experimental studies and meta-analysis demonstrated that the relationship between adducts and carcinogens was linear at low doses, but reached steady state at high exposure, possibly due to metabolic and DNA repair pathway saturation and increased apoptosis. Polymorphisms of metabolic and DNA repair genes can increase the effects of environmental factors and confer greater likelihood of adduct formation. Nevertheless, the central question remains as to whether bulky adducts cause human cancer. If so, lowering them would reduce cancer incidence. Pooled and meta-analysis has shown that smokers with increased adducts have increased risk of lung cancer. Adduct excess in smokers, especially in prospective longitudinal studies, supports their use as biomarkers predictive of lung cancer.

Bulky DNA adducts and breast cancer risk in the prospective EPIC-Italy study

The role of environmental carcinogen exposure in breast cancer development has long been suspected, but no specific association has been identified so far. A few molecular epidemiology studies reported that DNA adducts detected by different methods are associated with a modest increase of breast cancer risk. We aimed to evaluate the association between bulky DNA adducts, detected by the (32)P-postlabelling method in peripheral leukocytes, and the risk of developing breast cancer in the female Italian cohorts of the EPIC (European Prospective Investigation into Cancer and nutrition) study. By using a nested case-control design, breast cancer cases identified in the follow-up of over 30,000 women of EPIC-Italy study have been matched to controls by specific criteria. We measured the levels of bulky DNA adducts by the (32)P-postlabelling method in peripheral leukocytes donated at enrolment. Conditional regression analyses adjusted for selected potential confounders were used. Results on DNA adduct levels were available for 292 cases and 292 matched controls. The mean DNA adduct levels were similar in both groups (P=0.62). Multivariate regression analyses failed to show any significant association between bulky DNA adducts and breast cancer. Our results do not support any association of breast cancer risk with exposure to environmental carcinogens as measured through the levels of bulky DNA adducts in pre-diagnostic white blood cells. Larger studies by using different methods and/or biomarkers are needed to better evaluate the role of specific environmental carcinogens in breast carcinogenesis.

DNA adducts and PM(10) exposure in traffic-exposed workers and urban residents from the EPIC-Florence City study

Air pollution and particulate matter in urban areas have been associated with increased mortality from cardiovascular and respiratory diseases and increased cancer risk. Carcinogenic effects of particulate matter have been related to the contents of specific compounds, such as polycyclic aromatic hydrocarbons. The latter may form bulky DNA adducts, that may be considered as candidate markers of cancer risk. We have recently shown that traffic-exposed workers and the general population in Florence have divergent levels of DNA adducts, possibly related to different levels of exposure to genotoxic agents from vehicle emissions. In the current study, in a series of 214 Florence City healthy adults enrolled in a prospective study in the period 1993-1998 (152 residents / 62 traffic-exposed workers), we investigated the correlation between individual levels of DNA bulky adducts and PM(10) exposure scores based on daily environmental measures provided by the local Environmental Protection Agency for the whole study period, by two types of urban monitoring stations (high- and low-traffic). We found that PM(10) cumulative scores from high-traffic stations over the last 1-2 weeks prior to blood drawing significantly correlated (r=0.58, p=0.02) with DNA adduct levels among non-smoking traffic-exposed workers (but not among residents with no occupational exposure to vehicle emissions). A multivariate regression analysis adjusted for possible confounders confirmed these findings. PM(10) scores from low-traffic stations did not show any correlation. These results show that DNA adduct levels in non-smoking workers reflect the average levels of exposure to PM(10) in high-traffic urban areas experienced over a time period of 1-2 weeks. Since DNA adduct levels have been found predictive of lung cancer risk, our findings provide clues relevant to the reduction of genotoxic damage and possibly cancer risk among traffic-exposed urban workers.

Determinants of anti-benzo[a]pyrene diol epoxide-DNA adduct formation in lymphomonocytes of the general population

We evaluated determinants of anti-benzo[a]pyrenediolepoxide-(B[a]PDE)-DNA adduct formation (adduct induced by the ultimate carcinogenic metabolite of B[a]P) in lymphomonocytes of subjects environmentally exposed to low doses of polycyclic aromatic hydrocarbons (PAHs) (B[a]P). Our study population consisted of 585 Caucasian subjects, all municipal workers living in North-East Italy and recruited during their periodic check-ups after informed consent. PAH (B[a]P) exposure was assessed by questionnaire. Anti-B[a]PDE-DNA levels were measured by HPLC fluorescence analysis. We found that cigarette smoking (smokers (22%) versus non-smokers, p<0.0001), dietary intake of PAH-rich meals (> or =52 (38%) versus <52 times/year, p<0.0001), and outdoor exposure (> or =4 (19%) versus <4h/day; p=0.0115) significantly influenced adduct levels. Indoor exposure significantly increased the frequency of positive subjects (> or =0.5 adducts/10(8) nucleotides; chi(2) for linear trend, p=0.051). In linear multiple regression analysis the major determinants of increased DNA adduct levels (ln values) were smoking (t=6.362, p<0.0001) and diet (t=4.035, p<0.0001). In this statistical analysis, indoor and outdoor exposure like other factors of PAH exposure had no influence. In non-smokers, the influence of diet (p<0.0001) and high indoor exposure (p=0.016) on anti-B[a]PDE-DNA adduct formation became more evident, but not that of outdoor exposure, as was confirmed by linear multiple regression analysis (diet, t=3.997, p<0.0001 and high indoor exposure, t=2.522, p=0.012). This study indicates that anti-B[a]PDE-DNA adducts can be detected in the general population and are modulated by PAH (B[a]P) exposure not only with smoking - information already known from studies with limited number of subjects - but also with dietary habits and high indoor exposure. In non-smokers, these two factors are the principal determinants of DNA adduct formation. The information provided here seems to be important, since DNA adduct formation in surrogate tissue is an index of genotoxic exposure also in target organs (e.g., lung) and their increase may also be predictive of higher risk for PAH-related cancers.

Air pollution and risk of lung cancer in a prospective study in Europe

To estimate the relationship between air pollution and lung cancer, a nested case-control study was set up within EPIC (European Prospective Investigation on Cancer and Nutrition). Cases had newly diagnosed lung cancer, accrued after a median follow-up of 7 years among the EPIC ex-smokers (since at least 10 years) and never smokers. Three controls per case were matched. Matching criteria were gender, age (+/-5 years), smoking status, country of recruitment and time elapsed between recruitment and diagnosis. We studied residence in proximity of heavy traffic roads as an indicator of exposure to air pollution. In addition, exposure to air pollutants (NO(2), PM10, SO(2)) was assessed using concentration data from monitoring stations in routine air quality monitoring networks. Cotinine was measured in plasma. We found a nonsignificant association between lung cancer and residence nearby heavy traffic roads (odds ratio = 1.46, 95% confidence interval, CI, 0.89-2.40). Exposure data for single pollutants were available for 197 cases and 556 matched controls. For NO(2) we found an odds ratio of 1.14 (95% CI, 0.78-1.67) for each increment of 10 microg/m(3), and an odds ratio of 1.30 (1.02-1.66) for concentrations greater than 30 microg/m(3). The association with NO(2) did not change after adjustment by cotinine and additional potential confounders, including occupational exposures. No clear association was found with other pollutants.

DNA adducts and lung cancer risk: a prospective study

Objectives were to investigate prospectively the ability of DNA adducts to predict cancer and to study the determinants of adducts, especially air pollutants. DNA adducts were measured in a case-control study nested in the European Prospective Investigation into Cancer and Nutrition (EPIC) investigation. Cases included newly diagnosed lung cancer (n = 115), upper respiratory cancers (pharynx and larynx; n = 82), bladder cancer (n = 124), leukemia (n = 166), and chronic obstructive pulmonary disease or emphysema deaths (n = 77) accrued after a median follow-up of 7 years among the EPIC former smokers and never-smokers. Three controls per case were matched for questionnaire analyses and two controls per case for laboratory analyses. Matching criteria were gender, age, smoking status, country of recruitment, and follow-up time. Individual exposure to air pollution was assessed using concentration data from monitoring stations in routine air quality monitoring networks. Leukocyte DNA adducts were analyzed blindly using 32P postlabeling technique. Adducts were associated with the subsequent risk of lung cancer, with an odds ratio (OR) of 1.86 [95% confidence interval (95% CI), 0.88-3.93] when comparing detectable versus nondetectable adducts. The association with lung cancer was stronger in never-smokers (OR, 4.04; 95% CI, 1.06-15.42) and among the younger age groups. After exclusion of the cancers occurring in the first 36 months of follow-up, the OR was 4.16 (95% CI, 1.24-13.88). A positive association was found between DNA adducts and ozone (O3) concentration. Our prospective study suggests that leukocyte DNA adducts may predict lung cancer risk of never-smokers. Besides, the association of DNA adduct levels with O3 indicates a possible role for photochemical smog in determining DNA damage.

Specific plant DNA adducts as molecular biomarkers of genotoxic atmospheric environments

The general purpose of this study was to determine whether the formation of DNA addition products ('adducts') in plants could be a valuable biomarker of genotoxic air pollution. Plants from several species were exposed to ambient atmosphere at urban and suburban sites representative of different environmental conditions. The levels of NO2 and of the quantitatively major genotoxic air pollutants benzene, toluene, and xylene were monitored in parallel with plant exposure. DNA adducts were measured in bean (Phaseolus vulgaris), rye-grass (Lolium perenne), and tobacco (Nicotiana tabacum) seedlings by means of the [32P]-postlabeling method. Whereas, no correlation was found between the levels of the major genotoxic air pollutants and the total amounts of DNA adducts, individual analyses revealed site-specific and plant species-specific adduct responses, both at the qualitative and quantitative level. Among these, the amount of a specific rye-grass DNA adduct (rgs1) correlated with benzene/toluene/xylene levels above a threshold. For further characterization, rye-grass seedlings were treated in controlled conditions with benzene, toluene, xylene or their derivatives. On the other hand, in vitro DNA adduct formation assays were developed involving benzene, toluene, xylene, or their derivatives, and plant microsomes or purified peroxidase. Although in some cases, these approaches produced specific adduct responses, they failed to generate the rgs1 DNA adduct, which appeared to be characteristic for on-site test-plant exposure. Our studies have thus identified an interesting candidate for further analysis of environmental biomarkers of genotoxicity.