Formation of an oxidative DNA damage, 8-hydroxydeoxyguanosine, in mouse lung DNA after intratracheal instillation of diesel exhaust particles and effects of high dietary fat and beta-carotene on this process

Diesel exhaust particles dysregulate multiple immunological pathways in murine macrophages: Lessons from microarray and scRNA-seq technologies

Exposure to ambient particulate matter has been shown to promote a variety of disorders, including cardiovascular diseases predominantly of ischemic etiology. However, the mechanisms linking inhaled particulates with systemic vascular effects, resulting in worsened atherosclerosis, are not well defined. We assessed the potential role of macrophages in translating these effects by analyzing gene expression patterns in response to diesel exhaust particles (DEP) at the average cell level, using Affymetrix microarrays in peritoneal macrophages in culture (in vitro), and at the individual cell level, using single-cell RNA sequencing (scRNA-seq) in alveolar macrophages collected from exposed mice (in vivo). Peritoneal macrophages were harvested from C57BL/6J mice and treated with 25 μg/mL of a DEP methanol extract (DEPe). These cells exhibited significant (FDR < 0.05) differential expression of a large number of genes and enrichment in pathways, especially engaged in immune responses and antioxidant defense. DEPe led to marked upregulation of heme oxygenase 1 (Hmox1), the most significantly upregulated gene (FDR = 1.75E-06), and several other antioxidant genes. For the in vivo work, C57BL/6J mice were subjected to oropharyngeal aspiration of 200 μg of whole DEP. The gene expression profiles of the alveolar macrophages harvested from these mice were analyzed at the single-cell level using scRNA-seq, which showed significant dysregulation of a broad number of genes enriched in immune system pathways as well, but with a large heterogeneity in how individual alveolar macrophages responded to DEP exposures. Altogether, DEP pollutants dysregulated immunological pathways in macrophages that may mediate the development of pulmonary and systemic vascular effects.

Oxidatively damaged DNA in animals exposed to particles

Exposure to combustion-derived particles, quartz and asbestos is associated with increased levels of oxidized and mutagenic DNA lesions. The aim of this survey was to critically assess the measurements of oxidatively damaged DNA as marker of particle-induced genotoxicity in animal tissues. Publications based on non-optimal assays of 8-oxo-7,8-dihydroguanine by antibodies and/or unrealistically high levels of 8-oxo-7,8-dihydroguanine (suggesting experimental problems due to spurious oxidation of DNA) reported more induction of DNA damage after exposure to particles than did the publications based on optimal methods. The majority of studies have used single intracavitary administration or inhalation with dose rates exceeding the pulmonary overload threshold, resulting in cytotoxicity and inflammation. It is unclear whether this is relevant for the much lower human exposure levels. Still, there was linear dose-response relationship for 8-oxo-7,8-dihydroguanine in lung tissue without obvious signs of a threshold. The dose-response function was also dependent on chemical composition and other characteristics of the administered particles, whereas dependence on species and strain could not be equivocally determined. Roles of cytotoxicity or inflammation for oxidatively induced DNA damage could not be documented or refuted. Studies on exposure to particles in the gastrointestinal tract showed consistently increased levels of 8-oxo-7,8-dihydroguanine in the liver. Collectively, there is evidence from animal experimental models that both pulmonary and gastrointestinal tract exposure to particles are associated with elevated levels of oxidatively damaged DNA in the lung and internal organs. However, there is a paucity of studies on pulmonary exposure to low doses of particles that are relevant for hazard/risk assessment.

Nrf2 is a protective factor against oxidative stresses induced by diesel exhaust particle in allergic asthma

Epidemiological studies have shown that air pollutants, such as diesel exhaust particle (DEP), are implicated in the increased incidence of allergic airway disorders. In vitro studies of molecular mechanisms have focused on the role of reactive oxygen species generated directly and indirectly by the exposure to DEP. Antioxidants effectively reduce the allergic inflammatory effects induced by DEP both in vitro and in vivo. On the other hand, Nrf2 is a transcription factor essential for the inducible and/or constitutive expression of phase II and antioxidant enzymes. Disruption of Nrf2 enhances susceptibility to airway inflammatory responses and exacerbation of allergic inflammation induced by DEP in mice. Host responses to DEP are regulated by a balance between antioxidants and proinflammatory responses. Nrf2 may be an important protective factor against oxidative stresses induced by DEP in airway inflammation and allergic asthma and is expected to contribute to chemoprevention against DEP health effects in susceptible individuals.

Possible mechanisms for induction of oxidative stress and suppression of systemic nitric oxide production caused by exposure to environmental chemicals

The cytotoxic effects evoked by exposure to environmental chemicals having electrophilic properties are often attributable to covalent attachment to intracellular macromolecules through sulfhydryl groups or enzyme-mediated redox cycling, leading to the generation of reactive oxygen species (ROS). When huge amounts of ROS form they overwhelm antioxidant defenses resulting in the induction of oxidative stress. Nitric oxide (NO) which plays a crucial role in vascular tone, is formed by endothelial NO synthase (eNOS). Since a decrease in systemic NO production is implicated in the pathophysiological actions of vascular diseases, dysfunction of eNOS by environmental chemicals is associated with cardiopulmonary-related diseases and mortality. In this review, we introduce the mechanism-based toxicities (covalent attachment and redox cycling) of electrophiles. Therefore, this review will focus on the possible mechanisms for the induction of oxidative stress and impairment of NO production caused by environmental chemicals.

Increase of urinary concentrations of 8-hydroxy-2'-deoxyguanosine in diesel exhaust emission inspector exposed to polycyclic aromatic hydrocarbons

PURPOSE

The objectives of this study were to explore the factors influencing urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG) levels in diesel engine exhaust emission inspectors (inspectors), the association between polycyclic aromatic hydrocarbons (PAHs) exposure and fine particulate matter (PM(2.5)) levels in diesel exhaust particles (DEPs), and the PAHs exposure levels in diesel vehicle emission inspection stations (inspection stations).

METHODS

Twenty-eight inspectors and a control group of thirty-eight individuals matched by age and gender were recruited for this study. Fifteen ambient air samples and eighty-four personal air samples were monitored during 3-day work periods using a repeated-measures study design in each inspection station. Airborne samples were analyzed with a fluorescence detector and by high-performance liquid chromatography. Urinary 8-OHdG was measured in 168 pre- and post-work urine samples from inspectors, and in 38 urine samples from controls.

RESULTS

The concentrations of PAHs in DEP(2.5) (PM(2.5) in DEPs) were significantly and positively related to urinary log(10) 8-OHdG levels after adjusting for smoking status and BMI. Statistically, there was a significant correlation between air log(10) PAHs and air log(10) PM(2.5) concentrations in inspectors. Fifteen PAHs compounds within DEP(2.5) revealed the concentrations ranged from 5.18 to 22.93 ng/m(3) in ambient air monitoring and 1.03 to 12.60 ng/m(3) in personal air monitoring.

CONCLUSIONS

This study is the first to indicate an association between occupational PAHs exposure from DEP(2.5) at an inspection station and an increased excretion of urinary 8-OHdG in inspectors. In addition, this study also found smoking is not a confounder in inspectors exposed to PAHs in DEP(2.5).

Differential Transcriptional Changes in Mice Exposed to Chemically Distinct Diesel Samples

Epidemiological studies have linked exposure to ambient particulate matter (PM) with increased asthmatic symptoms. Diesel exhaust particles (DEP) are a predominant source of vehicle derived ambient PM, and experimental studies have demonstrated that they may have adjuvant potential when given with an antigen. We previously compared 3 DEP samples: N-DEP, A-DEP, and C-DEP in a murine ovalbumin (OVA) mucosal sensitization model and reported the adjuvant activity to be: C-DEP ≈ A-DEP > N-DEP. The present study analyzed gene expression changes from the lungs of these mice. Transcription profiling demonstrated that all the DEP samples altered cytokine and toll-like receptor pathways regardless of type, with or without antigen sensitization. Further analysis of DEP exposure with OVA showed that all DEP treatments altered networks involved in immune and inflammatory responses. The A- and C-DEP/OVA treatments induced differential expression of apoptosis pathways in association with stronger adjuvant responses, while expression of cell cycle control and DNA damage pathways were also altered in the C-DEP/OVA treatment. This comprehensive approach using gene expression analysis to examine changes at a pathway level provides detailed information on events occurring in the lung after DEP exposure, and confirms that the most bioactive sample induced many more individual genes and changes in immunoregulatory and homeostatic pathways.

Role of oxidative damage in toxicity of particulates

Particulates are small particles of solid or liquid suspended in liquid or air. In vitro studies show that particles generate reactive oxygen species, deplete endogenous antioxidants, alter mitochondrial function and produce oxidative damage to lipids and DNA. Surface area, reactivity and chemical composition play important roles in the oxidative potential of particulates. Studies in animal models indicate that particles from combustion processes (generated by combustion of wood or diesel oil), silicate, titanium dioxide and nanoparticles (C60 fullerenes and carbon nanotubes) produce elevated levels of lipid peroxidation products and oxidatively damaged DNA. Biomonitoring studies in humans have shown associations between exposure to air pollution and wood smoke particulates and oxidative damage to DNA, deoxynucleotides and lipids measured in leukocytes, plasma, urine and/or exhaled breath. The results indicate that oxidative stress and elevated levels of oxidatively altered biomolecules are important intermediate endpoints that may be useful markers in hazard characterization of particulates.

Analysis of 8-hydroxydeoxyguanosine among workers exposed to diesel particulate exhaust: Comparison with urinary metabolites and PAH air monitoring

Oxidative DNA damage and repair, as measured by 8-hydroxy-2'-deoxyguanosine (8-OHdG) in urine and DNA samples were studied in association with work-related diesel exhaust exposure among garage and waste collection workers. Seasonal variations of the urinary 8-OHdG levels in pre- and two post-workshift urine samples of 29 exposed workers and 36 control persons were evaluated. The mean+/-SE levels of post-workshift 8-OHdG (mumol/mol crea) were 1.52+/-0.44 in winter and 1.61+/-0.33 in summer for the exposed workers, and 1.56+/-0.61 in winter and 1.43+/-0.49 in summer for the controls, respectively. No significant difference in the urinary 8-OHdG levels between exposed workers and control subjects in winter (p=0.923) and summer (p=0.350) was observed. A linear mixed model, adjusted for years of employment, age, ex/non-smoking and BMI, indicated no significant dose exposure-relationships between the urinary 8-OHdG and 15 PAH air concentrations nor between the 8-OHdG and 7 PAH monohydroxy-metabolites analyzed in the same workers. 8-OHdG was also analyzed in the mononuclear cell DNA of 19 exposed and 18 control subjects. The mean value of 8-OHdG/non-modified 2'-deoxyguanosine (8-OHdG/105 dG+/-SE) were 4.89+/-0.17 for the exposed and 4.11+/-0.16 for the control persons, which showed no correlation with the urinary 8-OHdG levels (r=0.01, n=28, P=0.96). The PAH exposure at workplaces was mainly composed of volatile compounds, particularly naphthalene, suggesting low exposure through the respiratory tract and a low effect of PAH in ROS induction.

Repeated inhalations of diesel exhaust particles and oxidatively damaged DNA in young oxoguanine DNA glycosylase (OGG1) deficient mice

DNA repair may prevent increased levels of oxidatively damaged DNA from prolonged oxidative stress induced by, e.g. exposure to diesel exhaust particles (DEP). We studied oxidative damage to DNA in broncho-alveolar lavage cells, lungs, and liver after 4 x 1.5 h inhalations of DEP (20 mg/m3) in Ogg1-/- and wild type (WT) mice with similar extent of inflammation. DEP exposure increased lung levels of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) in Ogg1-/- mice, whereas no effect on 8-oxodG or oxidized purines in terms of formamidopyrimidine DNA glycosylase (FPG) sites was observed in WT mice. In both unexposed and exposed Ogg1-/- mice the level of FPG sites in the lungs was 3-fold higher than in WT mice. The high basal level of FPG sites in Ogg1-/- mice probably saturated the assay and prevented detection of DEP-generated damage. In conclusion, Ogg1-/- mice have elevated pulmonary levels of FPG sites and accumulate genomic 8-oxodG after repeated inhalations of DEP.

8-hydroxy-2' -deoxyguanosine (8-OHdG): A critical biomarker of oxidative stress and carcinogenesis

There is extensive experimental evidence that oxidative damage permanently occurs to lipids of cellular membranes, proteins, and DNA. In nuclear and mitochondrial DNA, 8-hydroxy-2' -deoxyguanosine (8-OHdG) or 8-oxo-7,8-dihydro-2' -deoxyguanosine (8-oxodG) is one of the predominant forms of free radical-induced oxidative lesions, and has therefore been widely used as a biomarker for oxidative stress and carcinogenesis. Studies showed that urinary 8-OHdG is a good biomarker for risk assessment of various cancers and degenerative diseases. The most widely used method of quantitative analysis is high-performance liquid chromatography (HPLC) with electrochemical detection (EC), gas chromatography-mass spectrometry (GC-MS), and HPLC tandem mass spectrometry. In order to resolve the methodological problems encountered in measuring quantitatively 8-OHdG, the European Standards Committee for Oxidative DNA Damage was set up in 1997 to resolve the artifactual oxidation problems during the procedures of isolation and purification of oxidative DNA products. The biomarker 8-OHdG or 8-oxodG has been a pivotal marker for measuring the effect of endogenous oxidative damage to DNA and as a factor of initiation and promotion of carcinogenesis. The biomarker has been used to estimate the DNA damage in humans after exposure to cancer-causing agents, such as tobacco smoke, asbestos fibers, heavy metals, and polycyclic aromatic hydrocarbons. In recent years, 8-OHdG has been used widely in many studies not only as a biomarker for the measurement of endogenous oxidative DNA damage but also as a risk factor for many diseases including cancer.

Involvement of alveolar macrophages in the formation of 8-oxodeoxyguanosine associated with exogenous particles in human lungs

Lung specimens were collected from 161 non-smoking male patients with carcinoma to determine the deposition of carbon particles and oxidative damage in lung tissues. Morphologically, carbon particles deposited in human lungs with carcinoma were similar to those of diesel exhaust like particles, and mass of particles showed a significant increase with the increasing age of the patients. An increasing age of patient with carcinomas was also associated with 8-oxodeoxy-guanosine (8-oxo-dG) formation, which was analyzed using the HPLC-electrochemical detector method. In addition, it was found that 8-oxo-dG increased in cancerous tissues rather than in non-cancerous ones. To determine whether particles in lung tissues were associated with 8-oxo-dG formation, carbon particles deposited in lung tissues were partially purified by cycling of alkali fusion with 1 M KOH; mutagenic chemicals in particles were extracted and excluded by removal with an equal volume of benzene/methanol and dichloromethane. It was also found that 8-oxo-dG was formed by non-mutagenic particles, and enhanced in the in vivo test using mouse rather than in the in vitro using RAW 254.7 tissue cultured cells. The 8-oxo-dG formation in vivo was due to the fact that hydroxyl radicals might be involved with phagocytosis of non-mutagenic particles in inflammatory cells, and the mutation was induced by hydroxylation of guanine residue on DNA. These results were also demonstrated by the occurrence of alveolar macrophages and neutrophils after intratracheal instillation of particles. These observations suggest that small particles from lung cancer patients further promote oxidative damage when used to treat the mouse lung. Especially, particles from which organic chemicals were removed were highly reactive to oxidative damage and formed 8-oxo-dG.

DNA damage and cytotoxicity in type II lung epithelial (A549) cell cultures after exposure to diesel exhaust and urban street particles

Background

Exposure to air pollution particles has been acknowledged to be associated with excess generation of oxidative damage to DNA in experimental model systems and humans. The use of standard reference material (SRM), such as SRM1650 and SRM2975, is advantageous because experiments can be reproduced independently, but exposure to such samples may not mimic the effects observed after exposure to authentic air pollution particles. This study was designed to compare the DNA oxidizing effects of authentic street particles with SRM1650 and SRM2975. The authentic street particles were collected at a traffic intensive road in Copenhagen, Denmark.

Results

All of the particles generated strand breaks and oxidized purines in A549 lung epithelial cells in a dose-dependent manner and there were no overt differences in their potency. The exposures also yielded dose-dependent increase of cytotoxicity (as lactate dehydrogenase release) and reduced colony forming ability with slightly stronger cytotoxicity of SRM1650 than of the other particles. In contrast, only the authentic street particles were able to generate 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) in calf thymus DNA, which might be due to the much higher level of transition metals.

Conclusion

Authentic street particles and SRMs differ in their ability to oxidize DNA in a cell-free environment, whereas cell culture experiments indicate that the particle preparations elicit a similar alteration of the level of DNA damage and small differences in cytotoxicity. Although it cannot be ruled out that SRMs and authentic street particles might elicit different effects in animal experimental models, this study indicates that on the cellular level, SRM1650 and SRM2975 are suitable surrogate samples for the study of authentic street particles.

Air pollution, oxidative damage to DNA, and carcinogenesis

There is growing concern that air pollution exposure increases the risk of lung cancer. The mechanism of action is related to particle-induced oxidative stress and oxidation of DNA. Humans exposed to urban air with vehicle emissions have elevated levels of oxidized guanine bases in blood cells and urine. Animal experimental studies show that pulmonary and gastrointestinal exposure is associated with elevated levels of oxidized guanines in the lung and other organs. Collectively, there is evidence indicating that exposure to traffic-related air pollution particles is associated with oxidative damage to DNA and this might be associated with increased risk of cancer.

Antioxidant enzyme induction: a new protective approach against the adverse effects of diesel exhaust particles

Exposure to airborne particulate pollutants such as diesel exhaust particles (DEPs) has been associated with allergic respiratory disorders, including asthma and allergic rhinitis. In this communication, we review recent advances in the mechanism by which DEPs elicit their harmful effects and the protective role of antioxidants. Reactive oxidative species (ROS) are believed to play a key role in cellular damage after exposure to DEPs. Numerous reports demonstrate that both proinflammatory and anti-inflammatory products are induced by DEPs via the activation of transcription factors. DEPs trigger multiple signaling pathways, which lead to DNA damage and cell apoptosis, inflammatory response, and antioxidant defense. Recent studies both in vitro and in mice show that antioxidants could alleviate the allergic inflammatory effects of DEPs. Human in vivo models suggest that the important phase II enzymes GSTM1 and GSTP1 modify the adjuvant effect of diesel exhaust particles on allergic inflammation. We have shown that the induction of phase II enzymes by the chemical sulforaphane can block DEP-induced enhanced immunoglobulin (Ig) E production in B cells and DEP-induced proinflammatory cytokine production in epithelial cells. These findings suggest that overexpression of antioxidant enzymes could constitute a powerful potential chemopreventive approach against adverse effects induced by oxidant pollutants such as DEPs.

Mutations in the lungs of gpt delta transgenic mice following inhalation of diesel exhaust

Diesel exhaust (DE) is a major airborne pollutant of urban areas. It contains various polycyclic aromatic hydrocarbons (PAH) and nitrated PAHs. In this study, gpt delta mice were treated with inhalation of 1 or 3 mg m(-3) DE, or a single intratracheal instillation of diesel exhaust particles (DEP) or DEP extract. In the lungs of mice treated with inhalation of 3 mg m(-3) DE for 12 weeks, the mutant frequency (MF) was 3.2-fold higher than that of the control group (1.90 x 10(-5) and 0.59 x 10(-5), respectively). An instillation of DEP and DEP extract resulted in a significant dose-dependent linear increase in MF. In mice treated with 0.5 mg DEP and 0.2 mg DEP extract, the MFs were 3.0- and 2.7-fold higher than that of the control group, respectively. The mutagenic potency (MF mg(-1)) of DEP extract (5.6 x 10(-5)) was double that of DEP (2.7 x 10(-5)), suggesting that the mutagenicity of the latter is derived primarily from compounds in the extract, which itself is responsible for ca. 50% of the weight of DEP. G:C-->A:T transitions were the predominant gpt mutation induced by all three treatments and G:C-->T:A transversions were induced by DEP and DEP extract. Guanine bases centered in nucleotide sequences such as GGA, TGA, CGG, and CGT were the major mutation targets of all three treatments. Thus, our results suggest that the mutagens contained in DEP such as PAH and nitrated PAHs induce mutations and may be responsible for carcinogenesis caused by inhalation of DE.

Reactive oxygen species: role in the development of cancer and various chronic conditions

Oxygen derived species such as superoxide radical, hydrogen peroxide, singlet oxygen and hydroxyl radical are well known to be cytotoxic and have been implicated in the etiology of a wide array of human diseases, including cancer. Various carcinogens may also partly exert their effect by generating reactive oxygen species (ROS) during their metabolism. Oxidative damage to cellular DNA can lead to mutations and may, therefore, play an important role in the initiation and progression of multistage carcinogenesis. The changes in DNA such as base modification, rearrangement of DNA sequence, miscoding of DNA lesion, gene duplication and the activation of oncogenes may be involved in the initiation of various cancers. Elevated levels of ROS and down regulation of ROS scavengers and antioxidant enzymes are associated with various human diseases including various cancers. ROS are also implicated in diabtes and neurodegenerative diseases. ROS influences central cellular processes such as proliferation a, apoptosis, senescence which are implicated in the development of cancer. Understanding the role of ROS as key mediators in signaling cascades may provide various opportunities for pharmacological intervention.

Air pollution and cancer: biomarker studies in human populations

Large cohort studies in the U.S. and in Europe suggest that air pollution may increase lung cancer risk. Biomarkers can be useful to understand the mechanisms and to characterize high-risk groups. Here we describe biomarkers of exposure, in particular DNA adducts as well as markers of early damage, including mutagenicity, other endpoints of genotoxicity and molecular biomarkers of cancer. Several studies found an association between external measures of exposure to air pollution and increased levels of DNA adducts, with an apparent levelling-off of the dose-response relationship. Also, numerous experimental studies in vitro and in vivo have provided unambiguous evidence for genotoxicity of air pollution. In addition, due to the organic extracts of particulate matter [especially various polycyclic aromatic hydrocarbon (PAH) compounds], particulate air pollution induces oxidative damage to DNA. The experimental work, combined with the data on frequent oxidative DNA damage in lymphocytes in people exposed to urban air pollution, suggests 8-oxo-dG as one of the important promutagenic lesions. Lung cancer develops through a series of progressive pathological changes occurring in the respiratory epithelium. Molecular alterations such as loss of heterozygosity, gene mutations and aberrant gene promoter methylation have emerged as potentially promising molecular biomarkers of lung carcinogenesis. Data from such studies relevant for emissions rich in PAHs are also summarized, although the exposure circumstances are not directly relevant to outdoor air pollution, in order to shed light on potential mechanisms of air pollution-related carcinogenesis.

Oxidative stress-induced DNA damage by particulate air pollution

Exposure to ambient air particulate matter (PM) is associated with pulmonary and cardiovascular diseases and cancer. The mechanisms of PM-induced health effects are believed to involve inflammation and oxidative stress. The oxidative stress mediated by PM may arise from direct generation of reactive oxygen species from the surface of particles, soluble compounds such as transition metals or organic compounds, altered function of mitochondria or NADPH-oxidase, and activation of inflammatory cells capable of generating ROS and reactive nitrogen species. Resulting oxidative DNA damage may be implicated in cancer risk and may serve as marker for oxidative stress relevant for other ailments caused by particulate air pollution. There is overwhelming evidence from animal experimental models, cell culture experiments, and cell free systems that exposure to diesel exhaust and diesel exhaust particles causes oxidative DNA damage. Similarly, various preparations of ambient air PM induce oxidative DNA damage in in vitro systems, whereas in vivo studies are scarce. Studies with various model/surrogate particle preparations, such as carbon black, suggest that the surface area is the most important determinant of effect for ultrafine particles (diameter less than 100 nm), whereas chemical composition may be more important for larger particles. The knowledge concerning mechanisms of action of PM has prompted the use of markers of oxidative stress and DNA damage for human biomonitoring in relation to ambient air. By means of personal monitoring and biomarkers a few studies have attempted to characterize individual exposure, explore mechanisms and identify significant sources to size fractions of ambient air PM with respect to relevant biological effects. In these studies guanine oxidation in DNA has been correlated with exposure to PM(2.5) and ultrafine particles outdoor and indoor. Oxidative stress-induced DNA damage appears to an important mechanism of action of urban particulate air pollution. Related biomarkers and personal monitoring may be useful tools for risk characterization.

Urinary 8-hydroxydeoxyguanosine in Belarussian children relates to urban living rather than radiation dose after the chernobyl accident: a pilot study

As a result of the Chernobyl accident in 1986, exposure to radioactive cesium is still a concern in the contaminated regions of Belarus. We tested the hypothesis that long-term radiation exposure from the Chernobyl accident might increase the urinary excretion of the oxidative stress marker, 8-hydroxydeoxyguanosine (8-OHdG), in Belarussian children. Urinary 8-OHdG was determined in two groups of children (-n = 31 and n = 46) -living in contaminated and uncontaminated areas of Belarus, respectively (the majority of the unexposed children lived in the capital Minsk). The children from the contaminated areas had a significantly higher annual summary effective dose but significantly lower urinary 8-OHdG levels than the children from the uncontaminated areas. Unexpectedly, children living in uncontaminated urban areas had significantly higher urinary 8-OHdG levels than children living in uncontaminated rural areas. There was no statistically significant effect of sex or body mass index on urinary 8-OHdG, but there was a weak significant inverse correlation to age as well as to the annual summary effective dose. These findings suggest that radiation from the Chernobyl accident is now a less important contributor to oxidative stress in Belarussian children than urban living.

9,10-Phenanthraquinone in diesel exhaust particles downregulates Cu,Zn-SOD and HO-1 in human pulmonary epithelial cells: intracellular iron scavenger 1,10-phenanthroline affords protection against apoptosis

9,10-Phenanthraquinone (PQ), a major quinone contained in diesel exhaust particles and atmospheric PM(2.5), undergoes one-electron reduction by flavin enzymes such as NADPH-cytochrome P450 reductase, leading to production of reactive oxygen species in vitro. We have detected an ESR signal for superoxide (O(2)(-)) and hydroxyl radicals ((.)OH) by the spin trap method when PQ was mixed with P450 reductase, NADPH, and iron(III). When we examined the effects of PQ on A549 human pulmonary epithelial cells, PQ induced apoptosis with a LC(50) of approximately 7 microM. Formation of protein carbonyls was also detected in cells after treatment with PQ, suggesting that PQ induces oxidative damage. Iron chelators such as 1,10-phenanthroline (OP), desferrioxamine mesylate, and deferiprone respectively afforded protection against the toxic effects of PQ. Furthermore, treatment of A549 cells with 10-20 microM PQ for 12 h specifically down-regulated protein levels of Cu,Zn-superoxide dismutase (Cu,Zn-SOD) and heme oxygenase-1 (HO-1) by more than 50%. Pretreatment of cells with OP (10 microM) markedly reduced the down-regulation of Cu,Zn-SOD and HO-1 and protein carbonyl formation in response to PQ. The inhibitor of Cu,Zn-SOD, diethyldithiocarbamate, enhanced the toxic effects of 5 microM PQ. The present findings suggest that PQ causes iron-mediated oxidative damage that is exacerbated by the concomitant down-regulation of Cu,Zn-SOD.

Porphyrin metabolism in lymphocytes of miners exposed to diesel exhaust at oil shale mine

The present study was carried out on the evaluation and application of new biomarkers for populations exposed to occupational diesel exhaust at oil shale mines. Since not only genotoxic effects may play an important role in the generation of tumors, the level of porphyrin metabolism was proposed as a biomarker of diesel exhaust exposure effects. The data on determination of 5-aminolevulinic acid (ALA) synthesis and heme formation in lymphocytes from groups of 50 miners exposed to diesel exhaust and 50 unexposed surface workers of oil shale mine are presented. All workers were examined and interviewed using structured questionnaires. The levels of benzene, carbon monoxide and nitric oxides in air as well as concentrations of 1-nitropyrene and elemental carbon in particulate matter were used for evaluation of exposure to diesel exhaust in mine. The levels of ALA and protoporphyrin (PP), activities of ALA synthetase (ALA-S) and ferrochelatase (FC), as well as levels of PP associated with DNA (PP/DNA) were investigated in lymphocytes spectrophotometrically. Significant differences in activity of ALA synthesis and heme formation between exposed miners and surface workers were found (207+/-23 vs. 166+/-14 pmol/10(6) lymp./30' for ALA-S and 46.1+/-3.8 vs. 54.8+/-4.1 pmol/10(6) lymp./60' for FC activities, respectively, P<0.001). ALA-S activity was higher and ALA accumulated in lymphocytes of exposed miners. Inhibition of FC activity caused PP cellular accumulation and an increase in the PP/DNA level (P<0.05). Tobacco smoking led to the increase of ALA biosynthesis in lymphocytes of both surface and underground smokers. The comparison of data obtained for non-smokers and smokers of both groups of workers has shown a significant difference (P<0.05). The work duration of underground or surface workers did not significantly influence the investigated biochemical parameters. The determination of ALA synthesis in lymphocytes could be a useful biomonitoring index of organism sensitivity to underground working. The alterations of PP levels, FC activity and PP/DNA association in peripheral lymphocytes of miners illustrate the harmful effects of exposure to diesel exhaust.

Linking exposure to environmental pollutants with biological effects

Exposure to ambient air pollution has been associated with cancer. Ambient air contains a complex mixture of toxics, including particulate matter (PM) and benzene. Carcinogenic effects of PM may relate both to the content of PAH and to oxidative DNA damage generated by transition metals, benzene, metabolism and inflammation. By means of personal monitoring and biomarkers of internal dose, biologically effective dose and susceptibility, it should be possible to characterize individual exposure and identify air pollution sources with relevant biological effects. In a series of studies, individual exposure to PM(2.5), nitrogen dioxide (NO(2)) and benzene has been measured in groups of 40-50 subjects. Measured biomarkers included 1-hydroxypyrene, benzene metabolites (phenylmercapturic acid (PMA) and trans-trans-muconic acid (ttMA)), 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) in urine, DNA strand breaks, base oxidation, 8-oxodG and PAH bulky adducts in lymphocytes, markers of oxidative stress in plasma and genotypes of glutathione transferases (GSTs) and NADPH:quinone reductase (NQO1). With respect to benzene, the main result indicates that DNA base oxidation is correlated with PMA excretion. With respect to exposure to PM, biomarkers of oxidative damage showed significant positive association with the individual exposure. Thus, 8-oxodG in lymphocyte DNA and markers of oxidative damage to lipids and protein in plasma associated with PM(2.5) exposure. Several types of DNA damage showed seasonal variation. PAH adduct levels, DNA strand breaks and 8-oxodG in lymphocytes increased significantly in the summer period, requiring control of confounders. Similar seasonal effects on strand breaks and expression of the relevant DNA repair genes ERCC1 and OGG1 have been reported. In the present setting, biological effects of air pollutants appear mainly related to oxidative stress via personal exposure and not to urban background levels. Future developments include personal time-resolved monitors for exposure to ultrafine PM and PM(2.5,) use of GPS, as well as genomics and proteomics based biomarkers.

Formation of 8-oxo-7,8-dihydro-2'-deoxyguanosine in rat lung DNA following subchronic inhalation of carbon black

Chronic high-dose inhalation of carbon black (CB) can produce carcinomas in rat lungs. The mechanisms underlying this response are uncertain. It has been hypothesized that chronic inflammation and cell proliferation may play a role in the development of tumors after high dose, long-term contact of the particles with lung epithelial cells. In this investigation, we analyzed the formation of a known mutagenic lesion [8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxo-dG)] in the lung DNA of rats following subchronic inhalation of CB (Printex-90 and Sterling V). Briefly, female Fischer 344 rats were exposed for 6 h/day, 5 days/week for 13 weeks to 1, 7, and 50 mg/m(3) of Printex-90 (16 nm; specific surface area 300 m(2)/g) and to 50 mg/m(3) of Sterling V CB (70 nm; surface area of 37 m(2)/g). The exposure concentration of Sterling V was selected to be equivalent in terms of retained mass in the lung to the high dose of Printex-90 at the end of exposure. However, in terms of retained particle surface area, the retained lung dose of Sterling V was equivalent to the mid-dose of Printex 90. This design allows comparison of results on the basis of retained particle mass as well as retained particle surface area between the two CB particles. The formation of 8-oxo-dG in the lung DNA was assessed using a reverse phase HPLC system coupled with UV and electrochemical (EC) detection. After 13 weeks of exposure, measurements were made on lung samples obtained at the end of the exposure and a 44-week recovery period in clean air. Lung burdens of CB were determined at both time points as well as differential cell populations from bronchoalveolar lavage fluid (BAL). The results indicate that lung particle overload was achieved after exposure to 7 and 50 mg/m(3) (Printex-90) and 50 mg/m3 (Sterling V) but not at 1 mg/m(3) (Printex-90). Consistent with these results, a significant increase (P < 0.05) in 8-oxo-dG induction was observed following 13 weeks of exposure to 50 mg/m(3) Printex-90 and at 7 and 50 mg/m(3) after the 44-week recovery period. Interestingly, no increase in 8-oxo-dG was observed for Sterling V CB at either time point despite lung particle overload. Although the retained mass dose of Sterling V at the end of exposure was even higher than for Printex 90 (50 mg/m(3) exposure group) (approximately 7.6 vs 4.8 mg), the surface area of the retained Sterling V was similar to that of the retained Printex 90 of the mid-dose exposure (7 mg/m(3)) (approximately 0.2 m(2) in both groups). Since both Sterling V (50 mg/m(3)) and Printex 90 (7 mg/m(3)) did not induce significant increases in 8-oxo-dG in the lung at the end of the 13-week exposure, this finding indicates that a retained large particle mass is not always correlated with similar adverse effects but that particle surface area is a better dose parameter. The lower effect per unit mass dose seen with Sterling V is consistent with earlier studies showing that particle surface area of low toxicity particles is a more appropriate dosemetric for induction of inflammation in the lungs than particle mass (Oberdörster et al., 1994, 2001; Brown et al. 2001; Donaldson et al., 2002). An increase (p < 0.05) in lung lavage neutrophils was observed at 7 mg/m(3) (Printex-90) and 50 mg/m(3) (Printex-90 and Sterling V) at the 13-week exposure period and again at 50 mg/m(3) (Printex-90 and Sterling V, 44-week recovery period). Our current findings suggest that prolonged, high-dose exposure to CB can promote oxidative DNA damage that is consistent with the hypothesis that inflammatory cell-derived oxidants may play a role in the pathogenesis of rat lung tumors following long-term high-dose exposure to CB in rats.

Effects of occupational exposure to diesel exhaust on porphyrin metabolism in lymphocytes of workers employed at black coal and oil-shale mines

BACKGROUND

This pilot study was conducted to investigate biochemical effects of exposure to diesel engine exhaust at two mines. For this purpose, heme biosynthesis, and PP association with DNA (PP/DNA) in lymphocytes of miners exposed to diesel exhaust were determined.

METHODS

The pilot study was carried out at a black coal mine in Czech Republic, and at an oil-shale mine in Estonia. The subjects were ten drivers from each mine, who were exposed to diesel exhaust (underground workers). Control groups consisted of ten maintenance workers from each mine (surface workers). The content of 1-nitropyrene (NP) in respirable dust was measured using GC-MS. The levels of PP, PP/DNA, heme, and activity of ferrochelatase (FC) were determined by spectrophotometry.

RESULTS

The exposure to diesel exhaust evaluated as the level of NP associated to particulate matter in air. NP level was significantly higher in oil-shale mine compared with coal mine. The values of PP and PP/DNA in lymphocytes appeared to be significantly increased only in miners in the oil-shale mine. There was no difference in the levels of PP and PP/DNA and FC activity between surface workers and miners at the coal mine. The level of heme in lymphocytes of coal mine miners was significantly higher than in miners of the oil-shale mine. The activity of FC was significantly lower in underground workers compared to surface workers at this mine. High level of NP was accompanied by an increase of alterations in cells porphyrin metabolism in lymphocytes of miners.

CONCLUSIONS

Alterations of porphyrin and heme metabolism in peripheral lymphocytes may serve as biomarker in assessment of exposure to diesel exhaust effects.

Diesel exhaust particle-induced alterations of pulmonary phase I and phase II enzymes of rats

Although diesel exhaust particles (DEP) are known to produce pulmonary disorders, the xenobiotic metabolic pathways associated with DEP detoxification and bioactivation remain unclear. In this study, the effect of acute exposure of DEP on phase I and phase II enzymes of rat lung was investigated. Intratracheal administration of DEP produced an induction of cytochrome P-450 (CYP) 1A1 enzyme protein and activity at 1 d postexposure, with the enzyme level returning to control at 5 d postexposure. On the other hand, carbon black (CB), a particle control, did not show any induction of CYP1A1 protein or enzyme activity. However, both DEP and CB significantly decreased CYP2B1 protein and enzyme activity at 1 d postexposure. The decrease in CYP2B1 enzyme protein and activity by DEP or CB treatment was observed up to 7 d postexposure. DEP and CB treatments also significantly attenuated glutathione S-transferase (GST)-pi protein at 1 d postexposure. Both DEP and CB at 35 mg/kg significantly decreased the activities of GST and catalase at 1 and 7 d postexposure. DEP, but not CB, significantly induced quinone reductase (QR) activity at 7 d postexposure. This study suggests that DEP may induce CYP1A1 and QR enzymes via a chemical effect, while the carbonaceous core may be involved in the attenuation of CYP2B1, GST, and catalase proteins and enzyme activities.

The dual effect of the particulate and organic components of diesel exhaust particles on the alteration of pulmonary immune/inflammatory responses and metabolic enzymes

Exposure to diesel exhaust particles (DEP) is an environmental and occupational health concern. This review examines the cellular actions of the organic and the particulate components of DEP in the development of various lung diseases. Both the organic and the particulate components cause oxidant lung injury. The particulate component is known to induce alveolar epithelial damage, alter thiol levels in alveolar macrophages (AM) and lymphocytes, and activate AM in the production of reactive oxygen species (ROS) and pro-inflammatory cytokines. The organic component, on the other hand, is shown to generate intracellular ROS, leading to a variety of cellular responses including apoptosis. There are a number of differences between the biological actions exerted by these two components. The organic component is responsible for DEP induction of cytochrome P450 family 1 enzymes that are critical to the polycyclic aromatic hydrocarbons (PAH) and nitro-PAH metabolism in the lung as well as in the liver. The particulate component, on the other hand, causes a sustained down-regulation of CYP2B1 in the rat lung. The significance of this effect on pulmonary metabolism of xenobiotics and endobiotics remains to be seen, but may prove to be an important factor governing the interplay of the pulmonary metabolic and inflammatory systems. Long-term exposures to various particles including DEP, carbon black (CB), TiO2, and washed DEP devoid of the organic content, have been shown to produce similar tumorigenic responses in rodents. There is a lack of correlation between tumor development and DEP chemical-derived DNA adduct formation. But the organic component has been shown to generate ROS that produce 8-hydroxydeoxyguanosine (8-OHdG) in cell culture. The organic, but not the particulate, component of DEP suppresses the production of pro-inflammatory cytokines by AM and the development of Th1 cell-mediated immunity. The mechanism for this effect is not yet clear, but may involve the induction of heme oxygenase-1 (HO-1), a cellular genetic response to oxidative stress. Both the organic and the particulate components of DEP enhance respiratory allergic sensitization. Part of the DEP effects may be due to a depletion of glutathione in lymphocytes. The organic component, which is shown to induce IL-4 and IL-10 productions, may skew the immunity toward Th2 response, whereas the particulate component may stimulate both the Th1 and Th2 responses. In conclusion, the literature shows that the particulate and organic components of DEP exhibit different biological actions but both involve the induction of cellular oxidative stress. Together, these effects inhibit cell-mediated immunity toward infectious agents, exacerbate respiratory allergy, cause DNA damage, and under long-term exposure, induce the development of lung tumors.

The effect of Au injection on the ceruloplasmin, metallothionein and 8-hydroxydeoxyguanosine of rat serum, kidney and liver

The present study was carried out to investigate the effect of gold (Au) injection on copper (Cu) and two types of ceruloplasmin (Cp), total Cp (ID1) and active Cp (ID2), metallothionein (MT) in the serum, kidney and liver, and 8-hydroxydeoxyguanosine (8-OHdG) in the rat kidney. The Cu contents in sera and kidneys of Au-injected rats were 1.7 and 5.5 times higher than those in sera and kidneys of control rats, respectively. The most of Cu in the sera of the control rats or Au-injected rats were observed in the Cp fractions from a Sephacryl S-200 column. The Cu concentration in the Cp fractions was increased by Au injection. Significant increases of ID1 and ID2 were found in the sera of the control rats and Au-injected rats, while there was no significant difference in those concentrations of livers or kidneys between the control rats and Au-injected rats. Our results indicated that the most of Cp existed as active ID1. The immunoreactivity of 8-OHdG was located in the cortex of the Au-injected rat. These results indicated that the oxidative DNA damage occurred in the renal cortex of the Au-injected rat and the localization of DNA damage did not coincide with that of Cu-MT. These findings suggest that the oxidative DNA damage in the kidneys of rats injected with Au is associated with Cu except Cu-MT.

Human 8-oxoguanine DNA glycosylase 1 mRNA expression as an oxidative stress exposure biomarker of cooking oil fumes

Epidemiological studies have indicated that the exposure to carcinogenic components formed during the cooking of food might be associated with lung cancer risk of Chinese women. Previous studies have confirmed that cooking oil fumes from frying fish (COF) contained relatively high amount of benzo[a]pyrene, 2-methyl-3,8-dimethylimidazo[4,5-f] qunoxaline, benzene, and 1,3-butadiene, reported in fumes from heated soybean oil. Thus, we consider that oxidative stress induced by COF may play a role in lung cancer development among Chinese women. To verify whether the oxidative DNA damage was induced by COF, high-performance liquid chromatography (HPLC) analysis data showed that the levels of 8-hydroxydeoxyguanine (8-OH dG) were increased in a dose-dependent manner when calf thymus DNA reacted with various concentrations of COF. Since human 8-oxoguanine DNA glycosylase 1 (hOGG1) was a repair enzyme for removing 8- OH dG from damaged DNA, we hypothesized that hOGG1 mRNA may be used to assess the risk of oxidative damage induced by the exposure of COF. The results from reverse-transcription polymerase chain reaction showed that the hOGG1 mRNA expression was induced by hydrogen peroxide (H2O2) and COF in human lung adenocarcinoma CL-3 cells. To elucidate whether hOGG1 mRNA expression was an exposure biomarker of COF, a cross-sectional study of 238 subjects including 94 professional cooks, 43 housewives, and 101 COF-nonexposed control subjects was conducted. The hOGG1 mRNA expression frequencies of COF-exposed cooks (27 of 94, 28.7%) and housewives (6 of 43, 14%) were significantly higher than those of control subjects (4 of 101, 4%). After adjusting for age, sex, and smoking and drinking status, the odds risks (ORs) of housewives versus control and cooks versus control were 3.94 (95% confidence interval [CI] = 0.95-16.62) and 10.12 (95% CI = 2.83-36.15), respectively. These results indicated that hOGG1 may be adequate to act as an exposure biomarker to assess the oxidative DNA damage induced by COF. This also suggests that oxidative stress induced by COF may play a role in lung cancer development among Chinese women.

Quantitative changes in glycosaminoglycans in the lungs of rats exposed to diesel exhaust

Exposure to diesel exhaust (DE) induces lesions in lung epithelium by generation of reactive oxygen species. Glycosaminoglycans (GAG), components of extracellar matrix, are thought to play important roles in cell proliferation and differentiation in the repair process of injured tissue. We investigated how GAG are related to the recovery of lung tissue from injury. Using high-performance liquid chromatography analysis, we determined the amounts of GAG, such as chondroitin sulfate (CS), dermatan sulfate (DS), and hyaluronan (HA) in the lungs of rats exposed to DE for 4 weeks at concentrations of 0.3 or 3 mg/m(3) as suspended particulate matter, or to filtered air. The contents of CS and HA in the surroundings of the bronchi were significantly increased after exposure to DE. In addition, immunohistochemical staining showed that the number of 8-hydroxydeoxyguanosine-positive cells as a marker of cell damage, and proliferating cell nuclear antigen-positive cells also increased in the same areas in which the levels of GAG were elevated in the lungs of rats exposed to 3 mg/m(3) DE. These results suggest that CS and HA in the lung contribute to cell proliferation and remodeling in the process of recovery from injury caused by exposure to DE.

Noninvasive detection of hydroxyl radical generation in lung by diesel exhaust particles

Diesel exhaust particles (DEP) induce pulmonary tumors, asthma-like symptoms, and the like in experimental animals. The involvement of reactive oxygen species (ROS) is suggested in the injuries induced by DEP, though the generation of ROS has not been proven. The present study provided the first direct evidence of *OH generation in the lungs of living mice after intratracheal instillation of DEP, using noninvasive L-band ESR spectroscopy and a membrane-impermeable nitroxyl probe. *OH generation is confirmed with the enhancement of in vivo ESR signal decay rate of the probe. The decay rate at mid-thorax was significantly enhanced in DEP-treated mice compared to that in vehicle-treated mice. The enhancement was completely suppressed by the administration of either *OH scavengers, catalase, or desferrioxamine, while the administration of SOD further increased the rate. The administration of Fenton's reagents into the lung also enhanced the decay rate of the probe at mid-thorax of mice. These results clearly provided evidence that the intratracheal exposure to DEP in mice produced *OH in the lung through an iron-catalyzed reaction of superoxide/H(2)O(2). This first direct evidence of *OH generation in DEP-treated mice lung may be utilized to determine treatments for DEP-induced lung injury.

Anti-8-oxo-2'-deoxyguanosine phage antibodies: isolation, characterization, and relationship to disease states

We have used human single chain Fv (scFv) phage display antibody libraries to isolate recombinant antibodies against the DNA adduct 8-oxo-2'-deoxyguanosine (8-oxodG). One of these scFvs (175G) bound to several 8-oxodG-containing oligonucleotides whilst demonstrating no cross-reactivity with G-containing control oligonucleotides, and bound to 8-oxodG lesions introduced into DNA by treatment with methylene blue and white light. In addition, 175G inhibited the cleavage of an 8-oxodG-containing oligonucleotide by the Escherichia coli enzyme formamidopyrimidine-DNA glycosylase (Fpg). The nucleotide sequence of the 175G V(H) gene segment was 98% homologous to the published V(H) sequence of a human hybridoma derived from a patient with systemic lupus erythematosus (SLE). Sera from two SLE patients bound to damaged DNA, and this binding could be inhibited by 175G. The use of human scFv phage display libraries has thus produced a unique reagent with specificity for 8-oxodG, which may have a role in damage detection and quantitation and in modifying DNA repair activity. 175G also offers support to the hypothesis that SLE might be associated with oxidative damage to DNA.

Early oxidative DNA damages and late development of lung cancer in diesel exhaust-exposed rats

To demonstrate DNA damages in the early stage of diesel exhaust exposure, an inhalation study of 1 through 12 months was conducted. The lung burden of diesel soot increased with increase in exposure duration. Histologically, hyperplastic foci of alveolar epithelia were found at 6-month exposure and became prominent at the 12th month, with slight nuclear atypia and positive p53 staining. The level of 8-OH-hydroxyguanosine (8-OH-dG) in the exposed rat lungs showed an increase from 1 month of exposure, followed by a gradual increase, reaching almost a plateau level at the 9th month. An in vitro experiment demonstrated significant 8-OH-dG formation when diesel particles and H(2)O(2) were added to the DNA solution. The level of bulky aromatic DNA adducts peaked at the 1st month of exposure, followed by a decrease. By the end of the observation period of 30 months, lung tumors developed even in the 6-month exposure group, and the earliest lung tumors were found only in rats that survived longer than 18 months. In conclusion, persisting oxidative stress on DNA induced in the early phase of diesel exhaust exposure, together with inflammation, seems to play an important role in carcinogenesis at advance ages after a long latent period.

Action of chlorogenic acid in vegetables and fruits as an inhibitor of 8-hydroxydeoxyguanosine formation in vitro and in a rat carcinogenesis model

Various plant extracts, such as carrot, burdock (gobou), apricot and prune, showed inhibitory effects in an in vitro assay of lipid peroxide-induced 8-hydroxydeoxyguanosine (8-OH-dG) formation. The major inhibitor purified from various plants extracts was identified as chlorogenic acid (CA), on the basis of UV- and mass-spectra and comparison with a standard sample. To examine whether CA also inhibits 8-OH-dG formation in animal organs, an oxygen radical-forming carcinogen, 4-nitroquinoline-1-oxide, was administered to rats, with or without CA. The 8-OH-dG level in the DNA of the rat tongue, the target organ, was significantly reduced in the CA-treated group.

Increase in mutation frequency in lung of Big Blue rat by exposure to diesel exhaust

Exposure to diesel exhaust (DE) is known to cause lung tumors in rats. To clarify the mutagenicity of DE, we estimated mutant frequency (MF) and determined the mutation spectra in rat lung after exposure to DE using lambda/lacI transgenic rats (Big Blue system). Male Big Blue rats (6 weeks old) were exposed for 4 weeks to 1 or 6 mg/m(3) DE, which contains suspended particulate matter. Control rats were maintained in filtered clean air. After exposure to 6 mg/m(3) DE, MF in lung was 4.8-fold higher than in control rats (P < 0.01), but no increase in MF was observed in rats exposed to 1 mg/m(3) DE. Sixty-nine mutants were identified after exposure to 6 mg/m(3) DE. The major mutations were A:T-->G:C (18 mutations) and G:C-->A:T (19 mutations) transitions. Remarkably, G-->T transversion of the lacI gene at site 221 was a hot-spot induced by exposure to DE, and there were complex mutations in which multiple mutations occurred in a single mutant, especially in the rats exposed to 6 mg/m(3) DE. DNA adducts formed by DE were analyzed using a (32)P-post-label TLC method and the amount of 8-hydroxydeoxyguanosine (8-OHdG) was measured using HPLC. Relative adduct level and amount of 8-OHdG were significantly increased in the rats exposed to 6 mg/m(3) DE compared with the controls (3.0- and 2.2-fold, respectively; P < 0.01). The level of cytochrome P450 1A1 mRNA was shown by northern blot analysis to be significantly increased in the lungs of rats exposed to 6 mg/m(3) DE (5.5-fold; P < 0.01). These results indicate that DE causes lesions in genomic DNA and acts as a mutagen in rat lung.

Oxidants and antioxidants in breast cancer

Although a number of risk factors have been identified for breast cancer, mechanisms by which they increase risk of the disease are not clear. Breast cancer etiology could, in part, be related to oxidative stress. Recognized risk factors for breast cancer include a family history of the disease. BRCA1 is needed for post-transcriptional repair of oxidative damage, indicating that oxidative stress may be an important risk factor for women with a family history of the disease. Reproductive and hormonal factors that result in greater exposure to circulating estrogens also increase risk, and steroid hormones are metabolized to reactive quinones and hydroquinones, which can directly damage DNA. Alcohol consumption is associated with increased risk, and the metabolism of alcohol results in production of DNA-damaging reactive oxygen species (ROS). Finally, the inverse relationship noted with consumption of fruits and vegetables could be related to their being a source of antioxidant vitamins. Endogenous factors may play an equally important role in the effects of oxidative stress on breast carcinogenesis. Genetic variability in enzymes that result in increased production of ROS and those that protect the cell from oxidative stress could also have an impact for risk of the disease. In this review, a rationale is given for linking breast cancer risk factors to oxidative stress. The possible role of genetic polymorphisms in a number of enzymes that may be important in affecting levels of ROS to which the cell is exposed, as well as those that protect the cell from oxidative stress, is discussed.

Mechanisms of action of poorly soluble particulates in overload-related lung pathology

For reasons that are unclear, poorly soluble particulates are associated with the development of inflammation, fibrogenesis, and carcinogenesis in the rat. The pathogenesis of these changes may be triggered by distinct or species-specific cellular responses to inhaled particulates in a manner similar to known fibrogenic and carcinogenic fibers, such as asbestos. Data reviewed here suggest that generation of oxidants by poorly soluble particulates is a key factor in the initiation of inflammation and generation of chemokines and cytokines in the rat. These substances then cause hyperplasia of epithelial cells and fibroblasts. The diminished or lack of proliferative responses by poorly soluble particulates in mice and primates, in comparison to rats, may be reflected by intrinsic differences in their oxidant-generating capacities or repair after oxidant injury or DNA damage.

8-Hydroxyguanosine formed in human lung tissues and the association with diesel exhaust particles

Diesel exhaust particles consist of various organic chemicals, heavy metals, and carbon particles. Knowledge of the fate of organic chemicals and carbon particles in the lungs is important to determine the mechanisms responsible for lung tumors. In the present study, diesel particle extracts were found to show mutagenicity for YG3003, a sensitive strain to some oxidative mutagens, as well as other mutant strains, and those of lung tissues obtained from lung cancer patients exhibited potent mutagenicity. Formation of 8-hydroxyguanosine (8-OHdG) as a biomarker of oxidative damage was analyzed with in vitro and in vivo assay systems. The 8-OHdG was detected in all 22 cases of lung tissues with carcinomas tested and their levels increased with the increasing age of the patients, suggesting a correlation between age and the presence of carbon particles in lung tissues. Therefore, the formation of 8-OHdG due to diesel exhaust particles was investigated via intratracheal injections into mice. 8-OHdG formation was elevated when carboneceous particles, after removal of organic chemicals with various solvents, were administered to mice, but it was not elevated when polyaromatic compounds such as benzo[a]pyrene, 1,8-dinitropyrene, and 1-nitropyrene were used in the same procedure in mice. The carboneceous particles were formed from a giant particle that was aggregated by micro-particles with diameters of 1.47 +/- 1.34 to 1.05 +/- 0.83 microm. These results suggest that carboneceous particles, but not mutagens and carcinogens, promote the formation of 8-OHdG, and that as a mechanism, alveolar macrophages may be involved in oxidative damage. The oxidative damage may be due to the fact that the mutation is involved with the generation of a hydroxyl radical during phagocytosis, and the hydroxyl radical leads to hydroxylation at the C-8 position of the deoxyguanosine residue in the DNA.

Modeling the interactions of particulates with epithelial lining fluid antioxidants

Oxidative stress may be a fundamental mode of injury associated with inspired particles. To examine this, we determined the ability of three carbon black particles (CBPs; M120, M880, and R250) and two forms of silicon dioxide, amorphous (Cabosil) and crystalline (DQ12) quartz, to deplete epithelium lining fluid antioxidant defenses. Single and composite antioxidant solutions of uric acid, ascorbic acid (AA), and reduced glutathione (GSH) were examined in the presence of particle concentrations of 150 microgram/ml. Uric acid was not depleted by any particle considered. AA was depleted in a near-linear fashion with time by the three different CBPs; however, AA depletion rates varied markedly with CBP type and decreased in the presence of metal chelators. An initially high GSH depletion rate was noted with all CBPs, and this was always accompanied by the appearance of oxidized glutathione. Exposure to Cabosil or DQ12 did not result in the loss of GSH. Together, these data demonstrate that particle type, size, and surface area are all important factors when considering particle-antioxidant interactions in the airways.

Generation of reactive oxygen species and 8-hydroxy-2'-deoxyguanosine formation from diesel exhaust particle components in L1210 cells

The generation of the reactive oxygen species during the interaction of diesel exhaust particles (DEP) with NADPH-cytochrome P450 reductase (P450 reductase) was investigated by electron spin resonance using the spin-trap 5,5'-dimethyl-1-pyrroline-N-oxide (DMPO). Addition of DEP extract to an incubation mixture of mouse lung microsomes in the presence of NADPH resulted in a time-dependent NADPH oxidation and acetylated-cytochrome c reduction. Using purified P450 reductase as the enzyme source, superoxide radicals which were detected as the spin adduct (DMPO-OOH) while metabolized by P450 reductase were dependent upon both DEP and enzyme concentrations. The ELISA method using a specific monoclonal antibody revealed that DEP produced 8-hydroxy-2'-deoxyguanosine (8-OHdG), which is formed from deoxyguanosine in DNA by hydroxyl radicals, in the culture medium of L1210 cells. Active oxygen scavengers such as superoxide dismutase and catalase effectively blocked the formation of 8-OHdG in culture medium, and deferoxamine, which inhibits hydroxyl radicals production by chelating iron, was also effective in inhibiting the DEP-produced 8-OHdG formation. These results indicate that DEP components produce 8-OHdG through the hydroxyl radical formation via superoxide by redox cycling of P450 reductase.

Increased urinary excretion of 8-oxo-2'-deoxyguanosine, a biomarker of oxidative DNA damage, in urban bus drivers

Oxidative damage to DNA could be involved in the increased risk of cancer associated with exposure to polluted urban air, which contains a number of oxidants. CYP1A2 is induced by and metabolizes polyaromatic hydrocarbons (PAH) and aromatic amines and could modify effects of exposure to ambient air pollution. Similarly, DNA repair may be influenced by occupational and other exposures as well as modify the effect of DNA damaging agents. As part of a large investigation of the genotoxic burden to diesel exposed workers in transport sectors we studied oxidative DNA damage in 57 non-smoking bus drivers from the greater Copenhagen area. The drivers were studied on a workday and on a day off work. Comparisons were made between drivers from the central (n=30) and rural/suburban (n=27) areas of Copenhagen. The rate of oxidative DNA damage was estimated from 24 h urinary excretion of 8-oxo-2'-deoxyguanosine (8-oxodG), a repair product of the highly mutagenic oxidation of guanine in DNA or the cellular pool of GTP. CYP1A2 activity was estimated from the urinary excretion of metabolites of dietary caffeine. The DNA repair was estimated by unscheduled DNA synthesis (UDS) in mononuclear cells isolated on the workday. Repeated measures ANOVA and multifactorial ANCOVA with CYP1A2 activity, age and UDS as covariates were used for statistical evaluation. On the workday, the 8-oxodG excretion was 190+/-108 and 146+/-89 pmol/kg 24 h in the bus drivers from central and the suburban/rural areas Copenhagen, respectively (p<0.05). The 8-oxodG excretion was not significantly different between the workday and the day off. CYP1A2 activity was not affected by driving area but was correlated with the 8-oxodG excretion on the workday (r=0.53; p<0.05). UDS was not significantly affected by driving area or correlated with the 8-oxodG excretion. The increased excretion of 8-oxodG in bus drivers from central Copenhagen as compared with drivers from rural/suburban greater Copenhagen suggests that exposure to ambient air pollution causes oxidative damage to DNA. This effect may be modified by the activity of CYP1A2 or a coregulated enzyme.

Dietary fat and prostate cancer: current status

Efforts to elucidate the causes of prostate cancer have met with little success to date. All that is known with certainty is that the incidence increases exponentially with age, varies by geography and by race or ethnicity, and is higher among men whose father or brother had the disease. Because the incidence changes in migrants and their offspring, exogenous factors certainly contribute to the risk of prostate cancer. Early epidemiologic studies implicated dietary fat as a likely causal factor for this cancer. However, scientific support for such an association has diminished in recent years as more epidemiologic evidence has accrued. Accordingly, we reviewed the relevant English language literature on this topic, including epidemiologic and animal studies, as well as current concepts regarding the involvement of fat in carcinogenesis to re-examine the fat-prostate cancer hypothesis. We conclude that dietary fat may indeed be related to prostate cancer risk, although the specific fat components that are responsible are not yet clear. Given the diverse effects of fatty acids on cellular biology and chemistry, it seems likely that the relationship is complex, involving the interplay of fat with other dietary factors, such as antioxidant vitamins and minerals, or with genetic factors that influence susceptibility. Some suggestions for further research are offered.