Detection of benzo[a]pyrene-diol-epoxide-DNA adducts in white blood cells of psoriatic patients treated with coal tar

BaP Metabolism and DNA-adduct Formation in Cultured Human Lymphocytes TreatedIn Vitrowith BaP and (-)-BaP-7,8-dihydrodiol

Nine samples of human lymphocytes from six healthy subjects were treated in vitro for 24 hours with [3H]-benzo[a]pyrene (BaP) and unlabelled (-)-BaP-7,8-dihydrodiol; 1μg/ml and 0.5μg/ml, respectively. The separation by HPLC of BaP-DNA adducts showed a significant formation of syn-BaPDE-dGuo adducts in five out of the nine human lymphocyte samples treated in vitro with [3H]-BaP. BaP-(7,10/8,9) tetrol and BaP-(7/8,9,10) tetrol derived from (+)-anti-BaPDE were the predominant isomers extracted from the culture medium of all the lymphocyte samples treated with (-)-BaP-7,8-dihydrodiol (mean ratio of anti-BaPDE/syn-BaPDE tetrols 5.6 + 1.2), suggesting that the metabolic activation of (-)-BaP-7,8-dihydrodiol occurred by its epoxidation to (+)-anti-BaPDE much more frequently (4–8 times) than by epoxidation to the (-)-syn-BaPDE form. In contrast to the predominant formation of anti-BaPDE tetrols, the analysis by HPLC of DNA adducts in the five subjects examined also revealed the significant formation of syn-BaPDE-DNA adducts (mean adduct ratio of (+)-anti-/(-)-syn-BaPDE-DNA = 2.6 ± 0.7). In six human lymphocyte samples treated in vitro with anti-BaPDE and syn-BaPDE, the anti-BaPDE bound to DNA 2–5 times more efficiently than did the syn-BaPDE. However, after 24 hours, the level of anti-BaPDE-DNA adducts significantly decreased almost to the level of the syn-BaPDE-DNA adducts, suggesting that a stereoselective repair mechanism could have preferentially removed the anti-BaPDE-DNA adducts.

Prenatal exposure to particulate matter and ozone: Bulky DNA adducts, plasma isoprostanes, allele risk variants, and neonate susceptibility in the Mexico City Metropolitan Area

Mexico City's Metropolitan Area (MCMA) includes Mexico City and 60 municipalities of the neighbor states. Inhabitants are exposed to emissions from over five million vehicles and stationary sources of air pollutants such as particulate matter (PM) and ozone. MCMA PM contains elemental carbon and organic carbon (OC). OCs include polycyclic aromatic hydrocarbons (PAHs), many of which induce mutagenic and carcinogenic DNA adducts. Gestational exposure to air pollution has been associated with increased risk of intrauterine growth restriction, preterm birth or low birth weight risk, and PAH-DNA adducts. These effects also depend on the presence of risk alleles. We investigated the presence of bulky PAH-DNA adducts, plasma 8-iso-PGF_2α (8-iso-prostaglandin F_2α ) and risk allele variants in neonates cord blood and their non-smoking mothers' leucocytes from families that were living in a highly polluted area during 2014-2015. The presence of adducts was significantly associated with both PM_2.5 and PM₁₀ levels, mainly during the last trimester of gestation in both neonates and mothers, while the last month of pregnancy was significant for the association between ozone levels and maternal plasma 8-iso-PGF_2α . Fetal CYP1B1*3 risk allele was associated with increased adduct levels in neonates while the presence of the maternal allele significantly reduced the levels of fetal adducts. Maternal NQO1*2 was associated with lower maternal levels of adducts. Our findings suggest the need to reduce actual PM limits in MCMA. We did not observe a clear association between PM and/or adduct levels and neonate weight, length, body mass index, Apgar or Capurro score. Environ. Mol. Mutagen. 60:428-442, 2019. © 2019 Wiley Periodicals, Inc.

Genotoxicity in adult residents in mineral coal region-a cross-sectional study

The present study assessed the DNA damage in environmentally exposed volunteers living in seven municipalities in an industrial coal region, through the use of the comet assay with blood cells and the micronucleus test with buccal cells. Blood and buccal smears were collected from 320 male volunteers living in seven cities inserted in a coal region. They were ages of 18 and 50 years and also completed a questionnaire intended to identify factors associated with DNA damage through a Poisson regression analysis. The comet assay detected significant differences in DNA damage in volunteers from different municipalities, and neighboring cities (Pedras Altas, Aceguá, and Hulha Negra) had a higher level of DNA damage in relation to control city. Some of the risk factors associated with identified DNA lesions included residence time and life habits. On the other hand, the micronucleus test did not identify differences between the cities studied, but the regression analysis identified risk factors such as age and life habits (consumption of mate tea and low carbohydrates diet). We conclude that there are differences in the DNA damage of volunteers from different cities of the carboniferous region, but the presence of micronuclei in the oral mucosa does not differ between the same cities. Furthermore, we alert that some related factors may increase the risk of genotoxicity, such as residence location and time, and living and food habits. Finally, we suggest the need for continuous biomonitoring of the population, as well as for investing in health promotion in these vulnerable populations.

The relationship between prenatal exposure to airborne polycyclic aromatic hydrocarbons (PAHs) and PAH-DNA adducts in cord blood

In a birth cohort study, we have assessed the dose-response relationship between individual measurements of prenatal airborne polycyclic aromatic hydrocarbon (PAH) exposure and specific PAH-DNA adducts in cord blood adjusted for maternal blood adducts and season of birth. The study uses data from an earlier established birth cohort of children in Krakow. The final analysis included 362 pregnant women who gave birth to term babies and had complete data on personal exposure in the second trimester of pregnancy to eight airborne PAHs including benzo[a]pyrene (B[a]P), as well as DNA adducts, both in maternal and cord blood. The relation between cord blood PAH-DNA adducts and airborne prenatal PAH exposure was non-linear. Although cord blood PAH-DNA adducts were significantly associated with the B[a]P exposure categorized by tertiles (non-parametric trend z=3.50, P<0.001), the relationship between B[a]P and maternal blood adducts was insignificant (z=1.63, P=0.103). Based on the multivariable linear regression model, we estimated the effect of the prenatal airborne B[a]P on the level of cord blood adducts. In total, 14.8% of cord blood adducts variance was attributed to the level of maternal adducts and 3% to a higher prenatal B[a] exposure above 5.70 ng/m(3). The calculated fetal/maternal blood adduct ratio (FMR) linearly increased with B[a]P exposure (z=1.99, P=0.047) and was highest at B[a]P concentrations exceeding 5.70 ng/m(3). In conclusion, the results support other findings that transplacental exposure to B[a]P from maternal inhalation produces DNA damage in the developing fetus. It also confirms the heightened fetal susceptibility to prenatal PAH exposure that should be a matter of public health concern, particularly in the highly polluted areas, because DNA adducts represent a pro-carcinogenic alteration in DNA. The continuation of this birth cohort study will assess the possible health effects of fetal DNA damage on the health of children and help in establishing new protective guidelines for newborns.

Final safety assessment of Coal Tar as used in cosmetics

Coal Tar is a semisolid by-product obtained in the destructive distillation of bituminous coal, which functions in cosmetic products as a cosmetic biocide and denaturant--antidandruff agent is also listed as a function, but this is considered an over-the-counter (OTC) drug use. Coal Tar is a nearly black, viscous liquid, heavier than water, with a naphthalene-like odor and a sharp burning taste, produced in cooking ovens as a by-product in the manufacture of coke. Crude Coal Tar is composed of 48% hydrocarbons, 42% carbon, and 10% water. In 2002, Coal Tar was reported to the Food and Drug Administration (FDA) to be used in four formulations, all of which appear to be OTC drug products. Coal Tar is monographed by the FDA as Category I (safe and effective) OTC drug ingredient for use in the treatment of dandruff, seborrhoea, and psoriasis. Coal Tar is absorbed through the skin of animals and humans and is systemically distributed. In short-term studies, mice fed a diet containing Coal Tar found it unpalatable, but no adverse effects were reported other than weight loss; rats injected with Coal Tar experienced malaise in one study and decreased water intake and increased liver weights in another; rabbits injected with Coal Tar residue experienced eating avoidance, respiratory difficulty, sneezing, and weight loss. In a subchronic neurotoxicity study using mice, a mixture of phenols, cresols, and xylenols at concentrations approximately equal to those expected in Coal Tar extracts produced regionally selective effects, with a rank order of corpus striatum > cerebellum > cerebral cortex. Coal Tar applied to the backs of guinea pigs increases epidermal thickness. Painting female rabbits with tar decreases the absolute and relative weights of the ovaries and decreased the number of interstitial cells in the ovary. Four therapeutic Coal Tar preparations used in the treatment of psoriasis were mutagenic in the Ames assay. Urine and blood from patients treated with Coal Tar were genotoxic in bacterial assays. Coal Tar was genotoxic in a mammalian genotoxicity assay and induced DNA adducts in various tissue types. Chronic exposure of mice to Coal Tar significantly decreased survival and liver neoplasms were seen in a significant dose-related trend; in other studies using mice lung tumors and perianal skin cancers were found. Coal Tar was comedogenic in three small clinical studies. Folliculitis is associated with the prolonged use of some tars. Several published reports describe cases of contact sensitivity to Coal Tar. Polycyclic aromatic hydrocarbons, which make up Coal Tar, are photosensitizers and cause phototoxicity by an oxygen-dependent mechanism. A retrospective study of the reproductive toxicity of Coal Tar in humans compared exposed women to controls and found little difference in spontaneous abortion and congenital disorders. Cancer epidemiology studies of patients who have received Coal Tar therapy of one form or other have failed to link treatment with an increase in the risk of cancer. Although the Cosmetic Ingredient Review (CIR) Expert Panel believes that Coal Tar use as an antidandruff ingredient in OTC drug preparations is adequately addressed by the FDA regulations, the Panel also believes that the appropriate concentration of use of Coal Tar in cosmetic formulations should be that level that does not have a biological effect in the user. Additional data needed to make a safety assessment include product types in which Coal Tar is used (other than as an OTC drug ingredient), use concentrations, and the maximum concentration that does not induce a biological effect in users.

Human respiratory disease: environmental carcinogens and lung cancer risk

Inhalatory intake of environmental agents may have adverse effects on health, the lung being the first target. Therefore, an increased risk of lung cancer and respiratory disease is in general considered as an indication of environmental health problems related to exposure to industrial emissions, traffic exhaust and smog. Classical epidemiological studies of the association between exposure to ambient air pollutants and respiratory dysfunctions and studies with laboratory animals have failed to demonstrate the distinct proof of risk for the general population that would be needed to form a basis for high impact environmental policy measures. Here, as an example, we describe the uncertainty in assessing risks of lung cancer associated with environmental exposure to polycyclic aromatic hydrocarbons. The recently introduced methodology of molecular cancer epidemiology is considered to yield more information on the relationship between exposure to environmental carcinogens and tumour development. Recent advances in the study of carcinogen (polycyclic aromatic hydrocarbon) dosimetry at the DNA level in combination with proto-oncogenic activation in humans are described.

A critical evaluation of DNA adducts as biological markers for human exposure to polycyclic aromatic compounds

The causative role of polycyclic aromatic hydrocarbons (PAH) in human carcinogenesis is undisputed. Measurements of PAH-DNA adduct levels in easily accessible white blood cells therefore represent useful early endpoints in exposure intervention or chemoprevention studies. The successful applicability of DNA adducts as early endpoints depends on several criteria: i. adduct levels in easily accessible surrogate tissues should reflect adduct levels in target-tissues, ii. toxicokinetics and the temporal relevance should be properly defined. iii. sources of interand intra-individual variability must be known and controllable, and finally iv. adduct analyses must have advantages as compared to other markers of PAHexposure. In general, higher DNA adduct levels or a higher proportion of subjects with detectable DNA adduct levels were found in exposed individuals as compared with nonexposed subjects, but saturation may occur at high exposures. Furthermore, DNA adduct levels varied according to changes in exposure, for example smoking cessation resulted in lower DNA adduct levels and adduct levels paralleled seasonal variations of air-pollution. Intraindividual variation during continuous exposure was low over a short period of time (weeks), but varied significantly when longer time periods (months) were investigated. Inter-individual variation is currently only partly explained by genetic polymorphisms in genes involved in PAH-metabolism and deserves further investigation. DNA adduct measurements may have three advantages over traditional exposure assessment: i. they can smooth the extreme variability in exposure which is typical for environmental toxicants and may integrate exposure over a longer period of time. Therefore, DNA adduct assessment may reduce the monitoring effort. ii. biological monitoring of DNA adducts accounts for all exposure routes. iii. DNA adducts may account for inter-individual differences in uptake, elimination, distribution, metabolism and repair amongst exposed individuals. In conclusion, there is now a sufficiently large scientific basis to justify the application of DNA adduct measurements as biomarkers in exposure assessment and intervention studies. Their use in risk-assessment, however, requires further investigation.

A strong genotoxic effect in mouse skin of a single painting of coal tar in hairless mice and in MutaMouse

The dorsal skin of C3H/Tif/hr hairless mice was painted with coal tar, pharmacological grade. Epidermal cells and hepatocytes were isolated after 4, 24, 48 and 96 h and DNA strand breaks were determined as tail moment by the alkaline comet assay. The tail moment of epidermal cells was significantly greater at the time points 4, 24, 48 and 96 h after exposure compared to the controls, with the most DNA strand breaks at 24 h. The DNA strand breaks in epidermal cells increased linearly with the dose of coal tar. In hepatocytes, no difference in DNA strand breaks was found between exposed animals and controls. DNA adducts were determined by the 32P-postlabeling assay. For epidermal cells, the mean DNA adduct level was 12-fold greater in coal tar painted mice after 24 h than in controls. Again, a linear dose/response relationship was seen 24 h after painting. For liver DNA, the mean DNA adduct level was 3-fold greater than for controls. The mutation frequency in epidermal and liver cells was examined in lambdalacZ transgenic mice (MutaMouse). Thirty-two days after painting, the mutation frequency in epidermal cells was 16-fold greater in coal tar treated mice compared to controls. No effect was detected in hepatocytes. We found that a single painting of coal tar resulted in strong genotoxic effects in the murine epidermis, evidenced by induction of DNA strand breaks and DNA adducts in hairless mice and lambdalacZ mutations in the MutaMouse. This demonstrates that it is possible to detect genotoxic effects of mixtures with high sensitivity in mouse skin by these end-points.

HPLC/fluorescence determination of anti-BPDE-DNA adducts in mononuclear white blood cells from PAH-exposed humans

The aim of this study was to compare (+/-)-r-7,t-8-dihydroxy-t-9,10-oxy-7,8,9,10-tetrahydrobenzo[a]pyrene (anti-BPDE)-DNA adduct levels in groups of humans subjected to various levels of polycyclic aromatic hydrocarbon (PAH) (benzo[a]pyrene) exposure. An HPLC/fluorescence method was applied to detect specifically anti-BPDE-DNA adducts in mononuclear white blood cells [lymphocyte plus monocyte fraction (LMF)] from humans exposed to PAHs. A total of 130 subjects comprised the sample population: 26 psoriatic patients (3 days after clinical coal tar treatment of the skin), 15 coke oven workers, 19 chimney sweeps, 36 aluminium anode plant workers and 34 non-occupationally PAH-exposed subjects (controls). PAH exposure was assessed in each group by means of the urinary excretion of 1-pyrenol (mean group levels: 1.2, 0.7, 0.3, 65.0 and 0.1 micromol/mol creatinine in coke oven workers, chimney sweeps, aluminium plant anode workers, psoriatic patients and non-occupationally PAH-exposed subjects, respectively). HPLC/fluorescence analysis of BPDE-DNA adducts showed that the percentage of subjects with adduct levels exceeding the 95 percentile control subject value (8.9 adducts/10(8) nucleotides) was significantly high in coke oven workers (46.7%) and chimney sweeps (21.0%) (chi2 test, P < 0.01 and P < 0.05, respectively) but not in aluminium plant workers (11.1%) and psoriatic patients (0%). The increase in BPDE-DNA adduct levels in LMF (Ln values) was significantly related to chronic inhalatory and high PAH exposure (linear multiple regression analysis, F = 6.37, P < 0.01; t = 4.2, P < 0.001). Skin acute (or short-term) and high PAH exposure, charcoal-grilled meat consumption and smoking habit did not seem to influence BPDE-DNA adduct formation in LMF.

DNA single-strand breaks and DNA repair in the lymphocytes of wooden furniture workers

DNA single-strand breaks (DNA SSB) in peripheral lymphocytes of wooden furniture workers and a control group, including smokers and nonsmokers, were detected by the microfiltration method. Our results show that cigarette smoking significantly increases the fragmentation of DNA single strands in the wooden furniture workers (by nearly two times) but not in the control group. Moreover, occupational exposure to wood dust and other wooden plant substances significantly induced DNA SSB only in the lymphocytes of smokers (by about two times). DNA repair in the lymphocytes was investigated as 3H incorporation into DNA. High 3H incorporation in the unstimulated lymphocytes of both smoking and nonsmoking workers, as compared to the references, suggests that besides DNA SSB other DNA damage can be caused by occupational exposure in the wooden plant. Since DNA repair is not always perfect, the possibility is high that the low level of DNA repair in the study group may lead to irreversible DNA damage. We think that the workers exposed to wood dust and the substances emitted by furniture coating materials in the plant may be at higher risk for mutagenesis and/or carcinogenesis than the unexposed population.

Coal tar therapy. Is it carcinogenic?

Epidemiological studies indicate that occupational exposure to coal tar may lead to an increased risk of lung, scrotum and skin cancer. Furthermore, studies with laboratory rodents show carcinogenicity of coal tar after dermal application. This effect may be attributable to polycyclic aromatic hydrocarbons (PAH), which are ubiquitous coal tar constituents. Absorbed PAH can be metabolised to reactive derivatives that bind to DNA. These PAH-DNA binding products are thought to be involved in PAH-induced carcinogenesis. However, no clearly increased skin cancer incidences have been reported in psoriasis patients who have been exposed to therapeutically high doses of coal tar. To determine whether patients treated with coal tar actually have an altered risk of cutaneous malignancies, we suggest that further controlled studies and experiments are necessary. Future research should also focus on the possibility of increased risks of developing internal malignancies.

A sensitive color ELISA for detecting polycyclic aromatic hydrocarbon-DNA adducts in human tissues

Human exposure to polycyclic aromatic hydrocarbons (PAHs) has been determined by measurement of DNA adducts in human tissues. Competitive enzyme-linked immunosorbent assays (ELISAs) using antisera recognizing benzo[a]pyrenediol-epoxide-modified DNA (BPDE-I-DNA) and color of fluorescence endpoint detection have been used extensively for quantifying PAH-DNA adducts. The fluorescence ELISA (limit of detection 1 adduct/10(8) nucleotides) was previously reported to be more sensitive than the color ELISA (1/10(7)) for measuring PAH adducts (Santella et al. (1988) Carcinogenesis, 9, 1265-1269). However, the fluorescence assay has the disadvantages of greater variation among the replicates and higher background levels than the color assay. Using a newly developed antiserum against BPDE-I-DNA, we have modified the color of ELISA so that it has the same sensitivity as the fluorescence ELISA and requires only 33% of the sample quantity needed for the fluorescence ELISA. The modifications included preincubation of the antiserum with the samples, using microtiter plates with half-size, flat bottom wells, and optimizing the assay conditions. The improved color ELISA was used to analyze DNA samples from human autopsy tissues, including heart, lung, liver, kidney, spleen, pancreas and stomach from smokers and nonsmokers. With the exception of spleen and stomach, all tissues from smokers showed higher PAH-DNA adducts (ranging from 0.3 to 19.0 adducts/10(7) nucleotides) than the tissues from the nonsmokers (0.3 to 3.7 adducts/10(7) nucleotides) in two separate experiments. Among the tissues from smokers, heart showed the highest level of DNA adducts. This study demonstrates that a stable color ELISA with high sensitivity can be useful in assessing human exposure to PAH.

Polycyclic aromatic hydrocarbon-DNA and protein adducts in coal tar treated patients and controls and their relationship to glutathione S-transferase genotype

Coal tar treated psoriasis patients were used as a model population to evaluate a panel of immunoassays for monitoring exposure to benzo[a]pyrene (BP) and related polycyclic aromatic hydrocarbons (PAH). The assays included measurement of PAH diol epoxide-DNA adducts in white blood cells by competitive enzyme-linked immunosorbent assay (ELISA) with fluorescence endpoint detection, PAH-albumin adducts by competitive ELISA with color endpoint detection and serum levels of antibodies recognizing BP diol epoxide-DNA adducts by noncompetitive color ELISA. PAH-DNA adducts by ELISA were elevated in patients (mean 6.77 +/- 12.05/10(8)) compared to controls (4.90 +/- 8.81/10(8), p = 0.12). There was no difference in PAH-albumin adducts between patients (mean 0.61 +/- 0.31 fmol/micrograms) and controls (0.63 +/- 0.30 fmol/micrograms). Glutathione S-transferase M1 genotype was also determined but no relationship was found between presence of the gene and either DNA or protein adduct levels. About 30% of both patients and controls had measurable titer of antibodies recognizing BPDE-I-DNA adducts. Measurement of white blood cell DNA adducts by ELISA was the most sensitive method for detecting PAH exposure in coal tar-treated psoriasis patients.

Is dermatologic usage of coal tar carcinogenic? A review of the literature

BACKGROUND

Coal tar ointments have been used for decades in the treatment of various dermatoses, most notably eczema and psoriasis. Occupational exposure to coal tar poses an increased risk of developing cutaneous malignancies. The evidence of an increased risk of skin cancer in humans, as a result of dermatologic usage of tar, however, is conflicting.

OBJECTIVE

A consensus on the carcinogenicity of tar is sought.

METHODS

The existing literature (in vitro, animal, and human studies) on this subject is reviewed.

RESULTS

The carcinogenicity of coal tar has clearly been demonstrated by in vitro and animal studies, and appears to be potentiated by concomitant use of ultraviolet radiation. Systemic absorption of mutagens from topically applied tar has been demonstrated in humans. Epidemiologic studies in humans, however, have not definitively shown an increase in skin cancer with therapeutic use of tar.

CONCLUSIONS

Conclusive evidence for the carcinogenicity of tar used in dermatologic practice is lacking. Further controlled studies are necessary.

Cigarette smoking protects mononuclear blood cells of carcinogen exposed workers from additional work exposure-induced DNA single strand breaks

DNA single-strand breaks in mononuclear blood cells (MNC) of taxi drivers, painters, ethylene oxide-exposed sterilization workers, metal workers, and car mechanics were detected by alkaline filter elution and compared to smoking and non-smoking control persons. Cigarette smoking caused a small but statistically significant increase in control persons (13.5%). In all occupationally exposed groups except the car mechanics, statistically significant increases of DNA single-strand breaks were detected in non-smokers compared to non-smoking controls or comparing groups with high and low exposure. For non-smoking workers the increase in DNA single-strand breaks was found to be 22% for taxi drivers, 60% for painters, 70% for ethylene oxide-exposed workers, and 69% for metal workers compared to control persons. For smokers, however, the increase in DNA single-strand breaks caused by additional occupational exposure was smaller and did not reach statistical significance in any of the occupational groups investigated in this study. Since a high level of glutathione may help to detoxify electrophilic DNA-damaging agents we measured the concentration of total glutathione in MNC of smoking and non-smoking control persons. The glutathione concentration was 13% higher in smokers, but statistical significance was weak (p < 0.05; t-test). Thus cigarette smoking, which represents a highly significant risk factor in carcinogenesis by itself, protects on the other hand against some additional genotoxic insults.

Adducts to macromolecules in the biological monitoring of workers exposed to polycyclic aromatic hydrocarbons

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous contaminants. Human exposure occurs through diet, smoking, and polluted air. In some groups of workers exposed to PAHs, epidemiological studies have revealed an increased mortality risk for neoplasms. This paper reviews the principal methods that have been developed recently for the detection of PAH adducts to white blood cell DNA and blood proteins (hemoglobin, albumin) and summarizes observations made on occupationally exposed subjects.