Evaluation of oxidative stress and DNA damage in traffic policemen exposed to vehicle exhaust

Exocyclic DNA adducts and oxidative stress parameters: useful tools for biomonitoring exposure to aldehydes in smokers

CONTEXT

Exocyclic DNA adducts have been shown to be potential biomarkers of cancer risk related to oxidative stress and exposure to aldehydes in smokers. In fact, aldehydes potentially arise from tobacco combustion directly and endogenously through lipid peroxidation.

OBJECTIVE

This study aims to investigate the relationship between a profile of nine aldehydes-induced DNA adducts and antioxidant activities, in order to evaluate new biomarkers of systemic exposure to aldehydes.

METHODS

Using our previously published UPLC-MS/MS method, adducts levels were quantified in the blood DNA of 34 active smokers. The levels of antioxidant vitamins (A, C and E), coenzyme Q10, β-carotene, superoxide dismutase (SOD) and autoantibodies against oxidized low-density lipoprotein were measured.

RESULTS

Adducts induced by tobacco smoking-related aldehydes were quantified at levels reflecting an oxidative production from lipid peroxidation. A significant correlation between SOD and crotonaldehyde-induced adducts (p = 0.0251) was also observed. β-Carotene was negatively correlated with the adducts of formaldehyde (p = 0.0351) and acetaldehyde (p = 0.0413). Vitamin C tended to inversely correlate with acetaldehyde-induced adducts (p = 0.0584).

CONCLUSION

These results are promising, and the study is now being conducted on a larger cohort with the aim of evaluating the impact of smoking cessation programs on the evolution of adducts profile and antioxidants activities.

Exposure to environmental airborne particulate matter caused wide-ranged transcriptional changes and accelerated Alzheimer's-related pathology: A mouse study

Air pollution poses a significant threat to human health, though a clear understanding of its mechanism remains elusive. In this study, we sought to better understand the effects of various sized particulate matter from polluted air on Alzheimer's disease (AD) development using an AD mouse model. We exposed transgenic Alzheimer's mice in their prodromic stage to different sized particulate matter (PM), with filtered clean air as control. After 3 or 6 months of exposure, mouse brains were harvested and analyzed. RNA-seq analysis showed that various PM have differential effects on the brain transcriptome, and these effects seemed to correlate with PM size. Many genes and pathways were affected after PM exposure. Among them, we found a strong activation in mRNA Nonsense Mediated Decay pathway, an inhibition in pathways related to transcription, neurogenesis and survival signaling as well as angiogenesis, and a dramatic downregulation of collagens. Although we did not detect any extracellular Aβ plaques, immunostaining revealed that both intracellular Aβ1-42 and phospho-Tau levels were increased in various PM exposure conditions compared to the clean air control. NanoString GeoMx analysis demonstrated a remarkable activation of immune responses in the PM exposed mouse brain. Surprisingly, our data also indicated a strong activation of various tumor suppressors including RB1, CDKN1A/p21 and CDKN2A/p16. Collectively, our data demonstrated that exposure to airborne PM caused a profound transcriptional dysregulation and accelerated Alzheimer's-related pathology.

Chronic Occupational Exposure to Traffic Pollution Is Associated with Increased Carotid Intima-Media Thickness in Healthy Urban Traffic Control Police

Urban traffic officers in many low- and middle-income countries are exposed to high levels of traffic-related air pollutants (TRAP) while working vehicle control on heavily congested streets. The impact of chronic TRAP exposure on the cardiovascular health, including the carotid intima-media thickness (CIMT), of this outdoor occupational group remains unclear. This cross-sectional study compared the average mean and maximum CIMT measurements of two groups of relatively young, healthy traffic police (32 ± 7 years; 77% male) in Quito, Ecuador, who were without clinical evidence of serious cardiovascular or other disease. Previously published background data on PM10 (a TRAP surrogate) indicated that street levels of the pollutant were several orders of magnitude higher at the street intersections worked by traffic police compared to those working only in an office. Accordingly, officers permanently assigned to daily traffic control duties requiring them to stand 0-3 m from heavily trafficked street intersections were assigned to the high exposure group (n = 61). The control group (n = 54) consisted of officers from the same organization who were permanently assigned to office duties inside an administration building. Mean and maximum CIMT were measured with ultrasound. General linear models were used to compare the CIMT measurements of the high exposure and control groups, adjusting for covariates. The adjusted average mean and maximum CIMT measures of the high exposure group were increased by 11.5% and 10.3%, respectively, compared to the control group (p = 0.0001). These findings suggest that chronic occupational exposure to TRAP is associated with increased CIMT in traffic police. This is important since even small increases in arterial thickening over time may promote earlier progression to clinical disease and increased premature mortality risk.

Evaluating the relationship between the respiratory exposure to the benzene with the primary damages of deoxyribonucleic acid and total antioxidant capacity in one of the oil companies in Iran

Benzene is a carcinogenic chemical substance which causes the injuries and damages through producing the free radicals in DNA (deoxyribonucleic acid) and the antioxidants are the agents which reduce the impacts of DNA damages by inhibiting the free radicals. This study was conducted aiming at determination of primary damages of DNA and level of plasma oxidative stress markers resulting from the respiratory exposure to the benzene found in petroleum compounds among the workers at loading platforms of a petroleum products distribution center. This study was an analytical (case control) research conducted among the workers in a working shift serving at the loading platforms of petroleum products. The exposure group included the workers with a history of contact with benzene and the control group was composed of the persons with no history of exposure to benzene. To investigate the level of the personnel's exposure to benzene, NIOSH-1501 method was utilized; to analyze the samples taken from the air, GC mass (gas chromatography-mass spectrometry) was applied; and to determine the average of DNA primary damages, comet assay was used. Total antioxidant capacity was determined by a photometric method. Results indicated that tail length (TL), tail density (TD), tail momentum (TM), percentage of tail in the DNA (%DNA), and %TAC in control group were 78.59, 8.35, 1.20, 10.05, and 25.58 and in the exposure group were 59.21, 75.74, 57.74, 3.5, and 16.58, respectively. The previously mentioned results showed a decrease in the TL, %DNA, and %TAC values among the workers already exposed to benzene while an increase in the TD and TM values of the same group compared to the control non-exposed group. In comparing the averages between two studied groups, all study variables had statistically meaningful difference (p < 0.05). More studies are recommended to be conducted on using the methods which identify the special places of breakage and damage in DNA chain due to the exposure to benzene and consequently prevent the complications and consequences.

Derivation of an occupational exposure limit for benzene using epidemiological study quality assessment tools

This paper derives an occupational exposure limit for benzene using quality assessed data. Seventy-seven genotoxicity and 36 haematotoxicity studies in workers were scored for study quality with an adapted tool based on that of Vlaanderen et al., 2008 (Environ Health. Perspect. 116 1700-5). These endpoints were selected as they are the most sensitive and relevant to the proposed mode of action (MOA) and protecting against these will protect against benzene carcinogenicity. Lowest and No- Adverse Effect Concentrations (LOAECs and NOAECs) were derived from the highest quality studies (i.e. those ranked in the top tertile or top half) and further assessed as being "more certain" or "less certain". Several sensitivity analyses were conducted to assess whether alternative "high quality" constructs affected conclusions. The lowest haematotoxicity LOAECs showed effects near 2 ppm (8 h TWA), and no effects at 0.59 ppm. For genotoxicity, studies also showed effects near 2 ppm and showed no effects at about 0.69 ppm. Several sensitivity analyses supported these observations. These data define a benzene LOAEC of 2 ppm (8 h TWA) and a NOAEC of 0.5 ppm (8 h TWA). Allowing for possible subclinical effects in bone marrow not apparent in studies of peripheral blood endpoints, an OEL of 0.25 ppm (8 h TWA) is proposed.

Effect of particulate matter 2.5 exposure to urinary malondialdehyde levels of public transport drivers in Jakarta

Background People who work long hours on the road are intensively exposed to high levels of fine particulate matters (PM2.5) which may lead to oxidative stress mechanisms in the human body that cause deleterious health problems. Malondialdehyde (MDA) is the major metabolite produced during lipid peroxidation metabolism that serves as a reliable biomarker for oxidative stress in cells. Objectives To identify the association between PM2.5 exposure and other characteristics with urinary MDA levels among public transport drivers in Jakarta. Methods A cross-sectional design was implemented by involving 130 public transport drivers of nine trajectories from Kampung Melayu Terminal, Jakarta. The continuous PM2.5 data were collected in personal measurement during one round trip of driving. Weight and height measurements were obtained to calculate body mass index (BMI) and structured questionnaires were completed to identify other characteristics. MDA levels were examined from the driver's urine right after driving and evaluated using TBARS analysis. Results The average of PM2.5 exposure was 91.56 ± 20.05 μg/m3 and MDA levels were 2.23 ± 1.57 nmoL/mL. Drivers with overweight and obese BMI had significantly higher MDA levels (2.66 ± 1.65 nmoL/mL) compared to those with normal and underweight BMI status (1.97 ± 1.47 nmoL/mL). Multiple linear regression analysis demonstrated low PM2.5 exposure, normal and underweight BMI status, and a long period of working as drivers were associated with MDA levels (p<0.05). Contrary to the prior study, PM2.5 exposure was negatively associated with MDA levels due to most drivers' BMI status being normal and underweight. Conclusion Our study suggests that the drivers who were obese and overweight should lose weight to lower the risk of increased MDA levels. We also suggest the drivers to consider maintaining their vehicle's ventilation system or using personal protection equipment (PPE) to avoid high PM2.5 exposure while driving.

Development of a co-culture model of mouse primary hepatocytes and splenocytes to evaluate xenobiotic genotoxicity using the medium-throughput Comet assay

To date, only a limited number of toxicological studies have focused on the establishment and validation of in vitro genotoxicity screening systems using primary hepatocytes, and the results of these studies have been inconsistent. Therefore, the aim of this study was to develop an effective co-culture model of mouse-derived primary hepatocytes and splenocytes for screening chemicals for genotoxicity using the medium-throughput Comet assay. This cocultured model was constructed and verified using known genotoxic and non-genotoxic compounds as positive and negative controls, respectively. Cytotoxicity was measured using Cell Counting Kit-8 and lactate dehydrogenase methods. DNA damage was detected using both alkaline and formamidopyrimidine DNA glycosylase (FPG) Comet assays. Compared with the controls, DNA strand breaks and FPG-sensitive sites showed significant concentration-dependent increases in genotoxic-agent-treated groups. In contrast, DNA damage remained unchanged in non-genotoxic-agent-treated groups. In addition, different types of genotoxic agents resulted in different time-dependent DNA lesions. Our results indicated that the % tail DNA indicating both DNA strand breaks and FPG-sensitive sites might be effective markers for predicting chemical-induced DNA damage and oxidative DNA damage using the cocultured model of hepatocytes and splenocytes. Collectively, these findings provide reliable experimental data for the establishment of in vitro genotoxicity screening methods.

Coarse particulate matter (PM2.5-10) in Los Angeles Basin air induces expression of inflammation and cancer biomarkers in rat brains

Air pollution is linked to brain inflammation, which accelerates tumorigenesis and neurodegeneration. The molecular mechanisms that connect air pollution with brain pathology are largely unknown but seem to depend on the chemical composition of airborne particulate matter (PM). We sourced ambient PM from Riverside, California, and selectively exposed rats to coarse (PM_2.5–10: 2.5–10 µm), fine (PM_<2.5: <2.5 µm), or ultrafine particles (UFPM: <0.15 µm). We characterized each PM type via atomic emission spectroscopy and detected nickel, cobalt and zinc within them. We then exposed rats separately to each PM type for short (2 weeks), intermediate (1–3 months) and long durations (1 year). All three metals accumulated in rat brains during intermediate-length PM exposures. Via RNAseq analysis we then determined that intermediate-length PM_2.5–10 exposures triggered the expression of the early growth response gene 2 (EGR2), genes encoding inflammatory cytokine pathways (IL13-Rα1 and IL-16) and the oncogene RAC1. Gene upregulation occurred only in brains of rats exposed to PM_2.5–10 and correlated with cerebral nickel accumulation. We hypothesize that the expression of inflammation and oncogenesis-related genes is triggered by the combinatorial exposure to certain metals and toxins in Los Angeles Basin PM_2.5–10.

Urinary biomarkers of exposure and of oxidative damage in children exposed to low airborne concentrations of benzene

The aim of this work was to evaluate the oxidative damage to nucleic acids in children (5-11 years) associated with exposure to environmental pollutants and tobacco smoke (ETS). For each subject, urinary sampling was done twice (evening and next morning) to measure by tandem LC-MS-MS such oxidated products of nucleic acids as 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo), 8-oxo-7,8-dihydroguanosine (8-oxoGuo), and 8-oxo-7,8-dihydroguanine (8-oxoGua). Methyl tert-butyl ether (U-MTBE), benzene (U-Benz), and its metabolites (t,t-muconic and S-phenylmercapturic acids, t,t-MA and S-PMA, respectively) were determined as biomarkers of exposure to air pollution, and cotinine as a biomarker of exposure to ETS. Biomarkers of exposure (S-PMA and U-MTBE) and of DNA oxidation (8-oxodGuo) were dependent on the urbanization and industrialization levels and increased in the evening sample as compared to next morning (p<0.05). In both evening and next morning samples, 8-oxodGuo and 8-oxoGuo correlated with each other (r=0.596 and r=0.537, respectively, p<0.01) and with biomarkers of benzene exposure, particularly S-PMA (r=0.59 and r=0.45 for 8-oxodGuo and r=0.411 and r=0.383 for 8-oxoGuo, p<0.01). No such correlations were observed for U-MTBE and cotinine. Multiple linear regression analyses showed that 8-oxodGuo was positively associated with S-PMA at both sampling times (β=0.18 and β=0.14 for evening and next morning sampling, respectively; p<0.02) and weakly with U-MTBE (β=0.07, p=0.020) only in the evening urines. These results suggest that the selected biomarkers of exposure to benzene, particularly S-PMA, are good tracers of exposure to complex mixtures of oxidative pollutants and that the associated oxidative damage to nucleic acids is detectable even at very low levels of exposure.