Polycyclic Aromatic hydrocarbon-DNA Adducts Research Articles

Relative genotoxicity of polycyclic aromatic hydrocarbons inferred from free energy perturbation approaches

Utilizing molecular dynamics and free energy perturbation, we examine the relative binding affinity of several covalent polycyclic aromatic hydrocarbon - DNA (PAH-DNA) adducts at the central adenine of NRAS codon-61, a mutational hotspot implicated in cancer risk. Several PAHs classified by the International Agency for Research on Cancer as probable, possible, or unclassifiable as to carcinogenicity are found to have greater binding affinity than the known carcinogen, benzo[a]pyrene (B[a]P). van der Waals interactions between the intercalated PAH and neighboring nucleobases, and minimal disruption of the DNA duplex drive increases in binding affinity. PAH-DNA adducts may be repaired by global genomic nucleotide excision repair (GG-NER), hence we also compute relative free energies of complexation of PAH-DNA adducts with RAD4-RAD23 (the yeast ortholog of human XPC-RAD23) which constitutes the recognition step in GG-NER. PAH-DNA adducts exhibiting the greatest DNA binding affinity also exhibit the least RAD4-RAD23 complexation affinity and are thus predicted to resist the GG-NER machinery, contributing to their genotoxic potential. In particular, the fjord region PAHs dibenzo[a,l]pyrene, benzo[g]chrysene, and benzo[c]phenanthrene are found to have greater binding affinity while having weaker RAD4-RAD23 complexation affinity than their respective bay region analogs B[a]P, chrysene, and phenanthrene. We also find that the bay region PAHs dibenzo[a,j]anthracene, dibenzo[a,c]anthracene, and dibenzo[a,h]anthracene exhibit greater binding affinity and weaker RAD4-RAD23 complexation affinity than B[a]P. Thus, the study of PAH genotoxicity likely needs to be substantially broadened, with implications for public policy and the health sciences. This approach can be broadly applied to assess factors contributing to the genotoxicity of other unclassified compounds.

Interaction of polycyclic aromatic hydrocarbon DNA adducts and telomere length on missed abortion

Objective: To analyze the contribution and interaction of polycyclic aromatic hydrocarbons (PAH)-DNA adducts and changes of telomere length (TL) on missed abortion. Methods: From March to December 2019, patients with missed abortion in the First Hospital of Shanxi Medical University and pregnant women with normal pregnancy but voluntary abortion in the same department during the same period were selected and divided into a case group and a control group. Questionnaire was used to investigate the general situation and the pregnancy situation of the subjects. The abortion villi were collected and the content of PAH-DNA adducts and TL was detected. Logistic regression model was used to analyze the associated factors of missed abortion. R epiR package and Mediation package were used to analyze the effect and relationship between PAH-DNA adducts and TL on missed abortion. Results: The age of the subjects was(29.92±5.69)years old. The M(Q1,Q3)of PAH-DNA adducts was 453.75(404.61, 504.72) pg/ml. The M(Q1,Q3)of TL was 1.21(0.77, 1.72). The content of PAH-DNA adducts in the case group was higher than that in the control group (Z=-2.10, P=0.036), while the TL was lower than that in the control group (Z=-4.05, P<0.001). Multivariate logistic regression showed that low, medium and high levels of PAH-DNA adducts (OR=3.17,95%CI:1.41-7.14;OR=2.85,95%CI:1.25-6.52;OR=2.46,95%CI:1.07-5.64), and long, medium and short levels of TL (OR=2.50,95%CI:1.11-5.63;OR=3.32,95%CI:1.45-7.56;OR=3.22,95%CI:1.42-7.26) were all risk factors for missed abortion. The medium level of PAH-DNA adducts had a 2.76-fold higher risk of shortened TL than those with the lowest level, and no mediating role of TL was found. The stratified analysis showed that when the TL level was longer (>1.21), the low and high levels of PAH-DNA adducts were associated with missed abortion (all P<0.05); when the TL level was shorter (<1.21), the medium level of PAH-DNA adducts was associated with abortion (P=0.025). At lower levels of PAH-DNA adducts, no effect of TL on missed abortion was observed, while, at higher levels, TL was strongly associated with missed abortion (OR=7.50,95%CI:1.95-28.82;OR=6.04,95%CI:1.54-23.65;OR=9.05,95%CI:2.34-35.04). The interaction analysis found that the AP was 0.72 (95%CI: 0.46-0.99), and the SI was 5.21 (95%CI: 2.30-11.77). Conclusion: The high level of PAH-DNA adducts and shortened TL may increase the risk of missed abortion, and there may be a positive additive interaction between the two factors on missed abortion.

Computational investigations of the excited state dynamics and quenching mechanisms of polycyclic aromatic hydrocarbon DNA adducts in solution

Synthetically modified fluorescent nucleotides (SFNs) are highly popular in a variety of experiments to explore biochemistry in molecular imaging, but the connection between their photodynamics and quenching mechanisms to their molecular structure remain relatively unstudied computationally. We combine various levels of theory, including classical force field dynamics and excited state quantum mechanic/molecular mechanic Born–Oppenheimer dynamics to characterize a set of polycyclic aromatic hydrocarbon based substituents bound to cytidine (dC) and guanine (dG) nucleobases. We specifically focus on perylene (P) bound to C5 and C6 of dC, and the naturally occurring benzo[a]pyrene diol epoxide (B[a]PDE) on dG. We find that specific angles of the connection points between them modulate mechanisms of intramolecular charge transfer, where an electron moves from P to dC and dG to B[a]PDE once an optimal angle is reached. Functionalization location and flexibility of the substituent affect access to these angles and, therefore, the amount of rapid charge transfer quenching of the fluorescence that we observe. This work demonstrates that the choice of functionalization location for SFNs changes the accessibility of charge transfer mechanisms via steric hindrance, and suggest that this feature can be applied for future tuning of fluorescence properties.

Interaction between adverse pregnancy history and polycyclic aromatic hydrocarbon-DNA adducts on missed abortion

Interaction between adverse pregnancy history and polycyclic aromatic hydrocarbon-DNA adducts on missed abortion

Nucleotide Excision Repair Pathway Activity Is Inhibited by Airborne Particulate Matter (PM10) through XPA Deregulation in Lung Epithelial Cells.

Airborne particulate matter with a diameter size of ≤10 µm (PM10) is a carcinogen that contains polycyclic aromatic hydrocarbons (PAH), which form PAH–DNA adducts. However, the way in which these adducts are managed by DNA repair pathways in cells exposed to PM10 has been partially described. We evaluated the effect of PM10 on nucleotide excision repair (NER) activity and on the levels of different proteins of this pathway that eliminate bulky DNA adducts. Our results showed that human lung epithelial cells (A549) exposed to 10 µg/cm2 of PM10 exhibited PAH–DNA adducts as well as an increase in RAD23 and XPD protein levels (first responders in NER). In addition, PM10 increased the levels of H4K20me2, a recruitment signal for XPA. However, we observed a decrease in total and phosphorylated XPA (Ser196) and an increase in phosphatase WIP1, aside from the absence of XPA–RPA complex, which participates in DNA-damage removal. Additionally, an NER activity assay demonstrated inhibition of the NER functionality in cells exposed to PM10, indicating that XPA alterations led to deficiencies in DNA repair. These results demonstrate that PM10 exposure induces an accumulation of DNA damage that is associated with NER inhibition, highlighting the role of PM10 as an important contributor to lung cancer.

Regularization of least squares problems in CHARMM parameter optimization by truncated singular value decompositions.

We examine the use of the truncated singular value decomposition and Tikhonov regularization in standard form to address ill-posed least squares problems Ax = b that frequently arise in molecular mechanics force field parameter optimization. We illustrate these approaches by applying them to dihedral parameter optimization of genotoxic polycyclic aromatic hydrocarbon-DNA adducts that are of interest in the study of chemical carcinogenesis. Utilizing the discrete Picard condition and/or a well-defined gap in the singular value spectrum when A has a well-determined numerical rank, we are able to systematically determine truncation and in turn regularization parameters that are correspondingly used to produce truncated and regularized solutions to the ill-posed least squares problem at hand. These solutions in turn result in optimized force field dihedral terms that accurately parameterize the torsional energy landscape. As the solutions produced by this approach are unique, it has the advantage of avoiding the multiple iterations and guess and check work often required to optimize molecular mechanics force field parameters.

Polycyclic Aromatic Hydrocarbon-DNA Adducts in Gulf of Mexico Sperm Whale Skin Biopsies Collected in 2012.

The northern Gulf of Mexico has a long history of polycyclic aromatic hydrocarbon (PAH) contamination from anthropogenic activities, natural oil seepages, and the 2010 Deepwater Horizon explosion and oil spill. The continental shelf of the same area is a known breeding ground for sperm whales (Physeter macrocephalus). To evaluate PAH-DNA damage, a biomarker for potential cancer risk, we compared skin biopsies collected from Gulf of Mexico sperm whales in 2012 with skin biopsies collected from sperm whales in areas of the Pacific Ocean in 1999-2001. All samples were obtained by crossbow and comprised both epidermis and subcutaneous blubber. To evaluate exposure, 7 carcinogenic PAHs were analyzed in lipids extracted from Pacific Ocean sperm whale blubber, pooled by sex, and location. To evaluate PAH-DNA damage, portions of all tissue samples were formalin-fixed, paraffin-embedded, sectioned, and examined for PAH-DNA adducts by immunohistochemistry (IHC) using an antiserum elicited against benzo[a]pyrene-modified DNA, which crossreacts with several high molecular weight carcinogenic PAHs bound to DNA. The IHC showed widespread epidermal nuclear localization of PAH-DNA adducts in the Gulf of Mexico whales (n = 15) but not in the Pacific Ocean whales (n = 4). A standard semiquantitative scoring system revealed significantly higher PAH-DNA adducts in the Gulf of Mexico whales compared to the whales from the Pacific Ocean study (p = .0002).

Arsenic exposures alter clinical indicators of anemia in a male population of smokers and non-smokers in Bangladesh

Drinking water arsenic (WAs) exposure has been linked to a number of detrimental health outcomes including anemia, primarily among pregnant women. Little is known about the effects of arsenic (As) on hematological disorders among men. We have examined the role of As exposure on hematological indicators of anemia in a group of men exposed to a wide range of As in their drinking water. We conducted a cross-sectional investigation among 119 healthy men in the Health Effects of As Longitudinal Study (HEALS) cohort, in rural Bangladesh. The participants are part of an ongoing study focused on evaluating the influence of As and smoking on immune function. Samples were collected at recruitment and analyzed for water As, urinary As (UAs) and UAs metabolites to assess As exposure. Blood samples were also collected at recruitment and assayed immediately for hematological parameters. We found that increased WAs levels were associated with decreased red blood cell counts [β=−0.13, p<0.0001] as well as hematocrit packed cell volumes [β=−0.68, p=0.008] following adjustment for age, smoking, body mass index and polycyclic aromatic hydrocarbon-DNA adducts. Other measures of As exposure (UAs and its metabolites) demonstrated similar associations. Slightly stronger effects were observed among smokers. We also observed an effect of As on hemoglobin among smokers in relation to UAs [β=−0.54, p<0.05]. Our analysis revealed effects of As exposure on hematological indicators of anemia in a group of healthy male smokers and non-smokers.

DNA adducts induced by in vitro activation of extracts of diesel and biodiesel exhaust particles

Context: Biodiesel and biodiesel-blend fuels offer a renewable alternative to petroleum diesel, but few data are available concerning the carcinogenic potential of biodiesel exhausts.Objectives: We compared the formation of covalent DNA adducts by the in vitro metabolic activation of organic extracts of diesel-exhaust particles (DEP) from petroleum diesel and soy biodiesel and correlated DNA adduct levels and mutagenicity in Salmonella TA100.Methods: We examined two different DEP from petroleum diesel (C-DEP and B0), one from soy bean oil biodiesel (B100) and one from combustion of a blend of 20% B100 and 80% B0 (B20) for in vitro DNA adduct-forming potential under oxidative or nitroreductive conditions in the presence of calf thymus DNA as well as in vivo in Salmonella TA100. The modified DNA was hydrolyzed and analyzed by 32P-postlabeling using either butanol extraction or nuclease P1 pre-enrichment.Results: Multiple DNA adducts were produced with chromatographic mobilities consistent with PAH and nitro-PAH adducts. The types and quantities of DNA adducts produced by the two independent petroleum diesel DEP were similar, with both polycyclic aromatic hydrocarbon (PAH)- and nitro-PAH-derived adducts formed. Relative potencies for S9-mediated DNA adduct formation, either per mass of particulate or per MJth energy consumed were B100 > B0 > B20.Conclusions: Soy biodiesel emissions induced DNA damage in the form of presumptive PAH and nitro-PAH DNA adducts that correlated with mutagenicity in Salmonella. B20 is the soy biodiesel used most commonly in the US, and it produced the lowest DNA adduct-emission factor, ∼50% that of petroleum diesel.

Prenatal exposure to polycyclic aromatic hydrocarbons/aromatics, BDNF and child development

ObjectivesWithin a New York City (NYC) birth cohort, we assessed the associations between polycyclic aromatic hydrocarbon (PAH) and other aromatic DNA adducts and brain derived neurotrophic factor (BDNF) concentrations in umbilical cord blood, and neurodevelopment at age 2 years and whether BDNF is a mediator of the associations between PAH/aromatic-DNA adducts and neurodevelopment. MethodsPAH/aromatic-DNA adduct concentrations in cord blood were measured in 505 children born to nonsmoking African-American and Dominican women residing in NYC, and a subset was assessed for neurodevelopment at 2 years using the Bayley Scales of Infant Development Mental Development Index (MDI). A spectrum of PAH/aromatic-DNA adducts was measured using the 32P-postlabeling assay; DNA adducts formed by benzo[a]pyrene (B[a]P), a representative PAH, were measured by High Performance Liquid Chromatography (HPLC)/fluorescence. BDNF mature protein in cord blood plasma was quantified by an ELISA. Multivariate regression analysis, adjusting for potential confounders, was conducted. ResultsPAH/aromatic-DNA adduct concentration measured by postlabeling was inversely associated with BDNF concentration (p=0.02) and with MDI scores at 2 years (p=0.04). BDNF level was positively associated with MDI scores (p=0.003). Restricting to subjects having all three measures (PAH/aromatic-DNA adducts by postlabeling, MDI, and BDNF), results were similar but attenuated (p=0.13, p=0.05, p=0.01, respectively). Associations between B[a]P-DNA adducts and BDNF and B[a]P-DNA adducts and MDI at age 2 years were not significant. At age 3 years, the positive association of BDNF with MDI was not observed. ConclusionsThe results at age 2 suggest that prenatal exposure to a spectrum of PAH/aromatic pollutants may adversely affect early neurodevelopment, in part by reducing BDNF levels during the fetal period. However, the same relationship was not seen at age 3.

Levels of PAH–DNA adducts in cord blood and cord tissue and the risk of fetal neural tube defects in a Chinese population

IntroductionMaternal exposure to polycyclic aromatic hydrocarbons (PAHs) has been shown to be associated with an elevated risk for neural tube defects (NTDs). In the human body, PAHs are bioactivated and the resultant reactive epoxides can covalently bind to DNA to form PAH–DNA adducts, which may, in turn, cause transcription errors, changes in gene expression or altered patterns of apoptosis. During critical developmental phases, these changes can result in abnormal morphogenesis. ObjectivesWe aimed to examine the relationship between the levels of PAH–DNA adducts in cord blood and cord tissue and the risk of NTDs. MethodsFrom 2010 to 2012, 60 NTD cases and 60 healthy controls were recruited from a population-based birth defects surveillance system in five counties of Shanxi Province in Northern China, where the emission of PAHs remains one of the highest in the country and PAHs exposure is highly prevalent. PAH–DNA adducts in cord blood of 15 NTD cases and 15 control infants, and in cord tissue of 60 NTD cases and 60 control infants were measured using the 32P-postlabeling method. ResultsPAH–DNA adduct levels in cord blood tend to be higher in the NTD group (28.5 per 108 nucleotides) compared with controls (19.7 per 108 nucleotides), although the difference was not statistically significant (P=0.377). PAH–DNA adducts in cord tissue were significantly higher in the NTD group (24.6 per 106 nucleotides) than in the control group (15.3 per 106 nucleotides), P=0.010. A positive dose-response relationship was found between levels of PAH–DNA adducts in cord tissue and the risk of NTDs (P=0.009). When the lowest tertile was used as the referent and potential confounding factors were adjusted for, a 1.03-fold (95% CI, 0.37–2.89) and 2.96-fold (95% CI, 1.16–7.58) increase in the risk of NTDs was observed for fetuses whose cord tissue PAH–DNA adduct levels were in the second and highest tertile, respectively. ConclusionsHigh levels of PAH–DNA adducts in fetal tissues were associated with increased risks of NTDs.

Air pollution effects on fetal and child development: A cohort comparison in China

In Tongliang, China, a coal-fired power plant was the major pollution source until its shutdown in 2004. We enrolled two cohorts of nonsmoking women and their newborns before and after the shutdown to examine the relationship between prenatal exposure to polycyclic aromatic hydrocarbons (PAHs) and fetal and child growth and development. PAHs were used to measure exposure to air pollution generated by the power plant. Using PAH–DNA adduct levels as biomarkers for the biologically effective dose of PAH exposure, we examined whether PAH–DNA adduct levels were associated with birth outcome, growth rate, and neurodevelopment. Head circumference was greater in children of the second cohort, compared with the first (p = 0.001), consistent with significantly reduced levels of cord blood PAH–DNA adducts in cohort II (p < 0.001) and reduced levels of ambient PAHs (p = 0.01).

Bulky DNA adducts in human sperm associated with semen parameters and sperm DNA fragmentation in infertile men: a cross-sectional study

BackgroundDNA adducts are widely used marker of DNA damage induced by environmental pollutants. The present study was designed to explore whether sperm polycyclic aromatic hydrocarbon-DNA adducts were associated with sperm DNA integrity and semen quality.MethodsA total of 433 Han Chinese men were recruited from an infertility clinic. Immunofluorescence was applied to analyze sperm PAH-DNA adducts. Sperm DNA fragmentation was detected by terminal deoxynucleotidyl transferase (Tdt)-mediated dUTP nick end labelling (TUNEL) assay.ResultsAfter adjustment for potential confounders using linear regression, sperm PAH-DNA adducts were negatively associated with sperm concentration, total sperm count, sperm motility, and curvilinear velocity (VCL). In addition, a positive relationship between sperm PAH-DNA adducts and sperm DNA fragmentation was found.ConclusionsOur findings suggested an inverse association between sperm PAH-DNA adducts and semen quality, and provided the first epidemiologic evidence of an adverse effect of PAH-DNA adducts on sperm DNA integrity.

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.

Functional effect of polymorphisms in 15q25 locus on CHRNA5 mRNA, bulky DNA adducts andTP53mutations

Genome-wide association studies have demonstrated that genetic polymorphisms influence the risk of developing lung cancer. Nicotinic acetylcholine receptor alpha3, alpha5 and beta4 genes (CHRNA3, CHRNA5 and CHRNB4) cluster at the 15q25.1 lung cancer susceptibility locus. We genotyped 310 patients with non-small cell lung cancer and a control group of 348 cancer-free individuals for seven sequence variants located in CHRNA3 and CHRNA5 genes. Two of the polymorphisms (rs3829787 and rs3841324) statistically influenced the risk of developing lung cancer. We found that four of the variants (rs3829787, rs3841324, rs588765 and rs3743073) were associated with differential levels of genetic alterations measured as the levels of hydrophobic DNA adducts in the adjacent histologically normal tissue of the lung cancer patients and as TP53 mutations in their lung tumors. The seven sequence variants formed three haplotypes with a frequency above 5%. The two most frequent haplotypes were associated with the risk of developing lung cancer and with smoking-related DNA alterations. We also found an association between CHRNA5 mRNA levels and the sequence variants or haplotypes. In conclusion, our results showed that several of the polymorphisms and their haplotypes in CHRNA5/CHRNA3 genes may have functional effects on (i) CHRNA5 mRNA levels, (ii) polycyclic aromatic hydrocarbon-DNA adduct levels, (iii) TP53 mutations and (iv) susceptibility to lung cancer.

Elevated polycyclic aromatic hydrocarbon-DNA adducts in benign prostate and risk of prostate cancer in African Americans.

Carcinogen-DNA adducts, a marker of DNA damage, are capable of inducing mutations in oncogenes and tumor suppressor genes, resulting in carcinogenesis. We have shown previously that polycyclic aromatic hydrocarbon (PAH)-DNA adduct levels in prostate cancer cases vary by cellular histology and that higher adduct levels are associated with biochemical recurrence. A nested case-control study was conducted in a historical cohort of 6692 men with histopathologically benign prostate specimens. PAH-DNA adduct levels were determined by immunohistochemistry in benign prostate specimens from 536 prostate cancer case-control pairs (59% White and 41% African American). We estimated the overall and race-stratified risk of subsequent prostate cancer associated with higher adduct levels. Prostate cancer risk for men with elevated adduct levels (defined as greater than control group median) was slightly increased [odds ratio (OR) = 1.28, 95% confidence interval (CI) = 0.98-1.67, P = 0.07]. After race stratification, elevated adduct levels were significantly associated with increased risk in African American men (OR = 1.56, CI = 1.00-2.44, *P = 0.05) but not White men (OR = 1.14, CI = 0.82-1.59, P = 0.45). Elevated PAH-DNA adduct levels were significantly associated with 60% increased risk of prostate cancer among cases diagnosed 1-4 years after cohort entry (OR = 1.60, CI = 1.07-2.41) with a greater risk observed in African Americans within the first 4 years of follow-up (OR = 4.71, CI = 1.97-11.26, ***P = 0.0005). Analyses stratified by age or tumor grade revealed no additional significant heterogeneity in risk. Increased prostate cancer risk associated with high PAH-DNA adduct levels in benign prostate was found only in African Americans; risk was greatest within 4 years of follow-up, possibly reflecting a carcinogenic process not yet histologically detectable.

Neighborhood socioeconomic status modifies the association between individual smoking status and PAH‐DNA adduct levels in prostate tissue

Interactions between smoking and neighborhood-level socioeconomic status (SES) as risk factors for higher polycyclic aromatic hydrocarbon (PAH) DNA adduct levels in prostate tissue were investigated. PAH-DNA adducts were measured by immunohistochemistry with staining intensity measured in optical density units by semiquantitative absorbance image analysis in tumor adjacent tissue from 400 prostatectomy specimens from the Henry Ford Health System in Detroit. For each subject, their U.S. Census tract of residence was classified as being of higher or lower SES using the median value of the distribution of the proportion of tract residents with a high-school education. Generalized estimating equation models were used to assess interactions between neighborhood-level SES and smoking status, adjusting for race, age, education level, tumor volume, primary Gleason grade and prostate specific antigen (PSA) at diagnosis. There was a statistical interaction (P = 0.004) between tract-level SES and smoking status. In lower SES tracts smoking status was not associated with adduct staining, but in higher SES tracts adduct staining intensity was 13% (P = 0.01) higher in ever-smokers as compared to never-smokers. Among never-smokers, living in a lower SES tract was associated with a 25% higher mean staining intensity (P < 0.001). Neighborhood SES modifies the association between individual smoking status and PAH-DNA adduct levels in prostate tissue.

Prenatal Exposure to Polycyclic Aromatic Hydrocarbons, Benzo[ a ]pyrene–DNA Adducts, and Genomic DNA Methylation in Cord Blood

Background: Polycyclic aromatic hydrocarbons (PAHs) are carcinogenic environmental pollutants generated during incomplete combustion. After exposure and during metabolism, PAHs can form reactive epoxides that can covalently bind to DNA. These PAH–DNA adducts are established markers of cancer risk. PAH exposure has been associated with epigenetic alterations, including genomic cytosine methylation. Both global hypomethylation and hypermethylation of specific genes have been associated with cancer and other diseases in humans. Experimental evidence suggests that PAH–DNA adduct formation may preferentially target methylated genomic regions. Early embryonic development may be a particularly susceptible period for PAH exposure, resulting in both increased PAH–DNA adducts and altered DNA methylation.Objective: We explored whether prenatal exposure to PAHs is associated with genomic DNA methylation in cord blood and whether methylation levels are associated with the presence of detectable PAH–DNA adducts.Methods: In a longitudinal cohort study of nonsmoking women in New York City, we measured PAH exposure during pregnancy using personal air monitors, assessed PAH internal dose using prenatal urinary metabolites (in a subset), and quantified benzo[a]pyrene–DNA adducts and genomic DNA methylation in cord blood DNA among 164 participants.Results: Prenatal PAH exposure was associated with lower global methylation in umbilical cord white blood cells (p = 0.05), but global methylation levels were positively associated with the presence of detectable adducts in cord blood (p = 0.01).Conclusions: These observations suggest that PAH exposure was adequate to alter global methylation in our study population. Additional epidemiologic studies that can measure site-specific cytosine methylation and adduct formation will improve our ability to understand this complex molecular pathway in vivo.

Influence of immunization with non-genotoxic PAH–KLH conjugates on the resistance of organisms exposed to benzo( a)pyrene

Polycyclic aromatic hydrocarbons (PAH) are recognized as common environmental pollutants released into the environment from many natural as well as man-made sources, and some have been classified as potent carcinogens. The main representative of the carcinogenic PAH is benzo( a)pyrene (B( a)P) which is known to induce genotoxic effects in vitro and in vivo, detected as PAH–DNA adducts. Long-term PAH exposure may be accompanied by an immunological response with the formation of antibodies against PAH as well as against PAH–DNA adducts. This paper describes the use of four PAH–keyhole-limpet haemocyanin (KLH) conjugates for the induction of specific and cross-reactive anti-PAH antibodies and focuses on the potential protective effects of anti-PAH antibodies produced after immunization of mice. In the in vitro experiments with HepG-2 cells, the genotoxicity of the PAH–KLH conjugates and the neutralizing effect of induced anti-PAH antibodies were evaluated. The titer of specific anti-PAH antibodies in sera and the amounts of DNA adducts in liver homogenates from immunized mice were investigated in vivo. The results show that anti-PAH antibodies of class IgG were induced during immunization. All the PAH–KLH conjugates tested were non-genotoxic and did not induce detectable DNA adducts in HepG2 cells or in the liver of immunized mice. The results show that only B( a)P-specific and B( a)P cross-reactive antibodies are able to neutralize B( a)P or its activated metabolites, which was revealed by a sudden decrease in the titer of anti-B( a)P antibodies in mouse sera after exposure to B( a)P. Furthermore, the anti-B( a)P antibodies produced by immunization were effective in reducing the amount of DNA adducts in mouse livers after intraperitoneal ( i.p.) exposure to B( a)P. The results suggest that immunization with PAH–KLH conjugates can protect organisms against the adverse effects of carcinogenic PAH.

Polycyclic Aromatic Hydrocarbon (PAH) Exposure and DNA Adduct Semi-Quantitation in Archived Human Tissues

Polycyclic aromatic hydrocarbons (PAHs) are combustion products of organic materials, mixtures of which contain multiple known and probable human carcinogens. PAHs occur in indoor and outdoor air, as well as in char-broiled meats and fish. Human exposure to PAHs occurs by inhalation, ingestion and topical absorption, and subsequently formed metabolites are either rendered hydrophilic and excreted, or bioactivated and bound to cellular macromolecules. The formation of PAH-DNA adducts (DNA binding products), considered a necessary step in PAH-initiated carcinogenesis, has been widely studied in experimental models and has been documented in human tissues. This review describes immunohistochemistry (IHC) studies, which reveal localization of PAH-DNA adducts in human tissues, and semi-quantify PAH-DNA adduct levels using the Automated Cellular Imaging System (ACIS). These studies have shown that PAH-DNA adducts concentrate in: basal and supra-basal epithelium of the esophagus, cervix and vulva; glandular epithelium of the prostate; and cytotrophoblast cells and syncitiotrophoblast knots of the placenta. The IHC photomicrographs reveal the ubiquitous nature of PAH-DNA adduct formation in human tissues as well as PAH-DNA adduct accumulation in specific, vulnerable, cell types. This semi-quantative method for PAH-DNA adduct measurement could potentially see widespread use in molecular epidemiology studies.