Exposure to fine particulate matter causes oxidative and methylated DNA damage in young adults: A longitudinal study

Longitudinal assessment of oxidative stress markers and their relationship with exposure to PM2.5 and its bound metals in healthy participants

OBJECTIVE

Exposure to ambient PM2.5 and its bound metals poses a risk to health and disease, via, in part, oxidative stress response. A variety of oxidative stress markers have been used as markers of response, but their relevance to environmental exposure remains to be established. We evaluated, longitudinally, a battery of oxidative stress markers and their relationship with the exposure of PM2.5 and its bound metals in a panel of healthy participants.

MATERIAL AND METHODS

Levels of residence- and personal-based ambient air PM2.5 and its bound metals, as well as of lung function parameters, were assessed in a total of 58 questionnaire-administered healthy never smoker participants (male, 39.7%). Levels of urinary oxidative stress markers, including Nε-(hexanoyl)-lysine (HEL; an early lipid peroxidation product), 4-hydroxynonenal (4-HNE), N7-methylguanine (N7-meG), and 8-hydroxy-2-deoxyguanosine (8-OHdG), plasma antioxidants [superoxide dismutase (SOD) and glutathione peroxidase (GPx), and urinary metals were measured by ELISA, LC-MS, and ICP-MS, respectively. The results of three repeated measurements at two-month intervals were analyzed using the Generalized Estimating Equation (GEE).

RESULTS

After adjusting for confounders, residence- and personal-based PM2.5 levels were positively associated with HEL (β = 0.22 and 0.18) and N7-meG (β = 0.39 and 0.13). Significant correlations were observed between personal air PM2.5-Pb and urinary Pb with HEL (β = 0.08 and 0.26). While FVC, FEV1, FEV1/FVC, MMF, and PEFR predicted% were normal, a negative interaction (pollutant*time, P < 0.05) was noted for PM2.5-V, Mn, Co, Ni, Zn, As, and Pb. Additionally, a negative interaction was found for N7-meG (β = -21.35, -18.77, -23.86) and SOD (β = -26.56, -26.18, -16.48) with FEV1, FVC, and PEFR predicted%, respectively.

CONCLUSION

These findings emphasize potential links between environmental exposure, internal dose, and health effects, thereby offering valuable markers for future research on metal exposure, oxidative stress, and health outcomes.

Long-Term Exposure to PM2.5 and Mortality: A Cohort Study in China

We investigated the association of long-term exposure to atmospheric PM2.5 with non-accidental and cause-specific mortality in Yinzhou, China. From July 2015 to January 2018, a total of 29,564 individuals aged ≥ 40 years in Yinzhou were recruited for a prospective cohort study. We used the Cox proportional-hazards model to analyze the relationship of the 2-year average concentration of PM2.5 prior to the baseline with non-accidental and cause-specific mortality. The median PM2.5 concentration was 36.51 μg/m3 (range: 25.57-45.40 μg/m3). In model 4, the hazard ratios per 10 μg/m3 increment in PM2.5 were 1.25 (95%CI: 1.04-1.50) for non-accidental mortality and 1.38 (95%CI:1.02-1.86) for cardiovascular disease mortality. We observed no associations between PM2.5 and deaths from respiratory disease or cancer. In the subgroup analysis, interactions were observed between PM2.5 and age, as well as preventive measures on hazy days. The observed association between long-term exposure to atmospheric PM2.5 at a relatively moderate concentration and the risk of non-accidental and cardiovascular disease mortality among middle-aged and elderly Chinese adults could provide evidence for government decision-makers to revise environmental policies towards a more stringent standard.

Association between urinary biomarkers of polycyclic aromatic hydrocarbons and severe abdominal aortic calcification in adults: data from the National Health and Examination Nutrition Survey

OBJECTIVE

Recent studies have found that polycyclic aromatic hydrocarbons (PAHs) exposure may increase the risk of cardiovascular disease. The present study aimed to explore the association between PAHs exposure and severe abdominal aortic calcification (AAC) in adults.

METHODS

Data were collected from the 2013-2014 National Health and Nutrition Examination Survey. PAHs exposure was analyzed from urinary mono hydroxylated metabolites of PAHs. Logistic regression models and subgroup analysis were performed to explore the association of PAHs exposure with severe AAC prevalence.

RESULTS

A total of 1,005 eligible individuals were recruited into the study. After adjusting for confounding factors, those with the highest quartiles of 1-hydroxynaphthalene (1-NAP: OR 2.19, 95% CI 1.03-4.68, P_{for trend} < 0.001), 2-hydroxynaphthalene (2-NAP: OR 2.22, 95% CI 1.04-4.64, P_{for trend} < 0.001) and 1-hydroxypyrene (1-PYR: OR 2.15, 95% CI 1.06-4.33, P_{for trend} < 0.001) were associated with an increased prevalence of severe AAC in the adults compared to those who in the lowest quartile.

CONCLUSION

This study found that urinary 1-NAP, 2-NAP and 1-PYR were positively associated with severe AAC prevalence in adults.

Association between atmospheric pollutant levels and oxidative stress in pregnant women and newborns in Urumqi

BACKGROUND

Frequent heavy air pollution occurred during the winter heating season of northern China. Particulate air pollution is a serious concern in Urumqi during heating season. Exposure to air pollution is known to increase adverse health outcomes, particularly oxidative damage. This study aimed to evaluate the impact of air pollution on oxidative damage around pregnant women and newborns in Urumqi.

METHODS

This prospective observational study enrolled pregnant women in the Fifth Affiliated Hospital of Xinjiang Medical University between January 2019 and October 2019. Pregnant women and newborns were allocated into a heating season group (January - end of April 2019, October 2019) or non-heating season group (June 2019 - end of September) according to the specific delivery time. Venous blood, urine from the women and cord blood from their newborns were collected to measure the levels of PAHs and 8-deoxyguanosine (8-OHdG), a measure of oxidative stress.

RESULTS

A total of 200 pregnant women and newborns were enrolled, with 100 pregnant women and newborns in the heating season group. Compared to the non-heating season group, the total contents of 8-OHdG in maternal urine, PAHs and 8-OHdG in maternal plasma and neonatal cord blood were higher in the heating season group (all P < 0.001). The average values for AQI, PM_2.5, PM₁₀, SO₂, NO₂, and CO were higher in the heating season group (all P < 0.001). Maternal and neonatal PAHs were correlated with 8-OHdG measurements in maternal urine (r = 0.288, P < 0.001 and r = 0.336, P < 0.001) and neonatal umbilical cord blood (r = 0.296, P < 0.001 and r = 0.252, P < 0.001). There was also a positive relationship between PAHs, 8-OHdG levels in pregnant women and their newborns and proximate air pollutant concentrations (all P < 0.05). Based on the results of multiple linear regression analysis, it was found that air pollutants(PM₁₀, 0₃) had a great influence on the level of 8-OHdG in neonatal cord blood, and the contribution rate was high(R² = 0.320). Based on the epidemiological questionnaire, a multiple linear regression model was established(R² = 0.496). We found that 8-OHdG levels in neonatal umbilical cord blood were mainly affected by two aspects: (1) Biological samples collected during heating had higher levels of 8-OHdG in neonatal umbilical cord blood. (2) Study may suggest that in neonates, males are more sensitive to oxidative damage.

CONCLUSION

Particulate air pollution may increase PAHs exposure and oxidative DNA damage in pregnant women and newborns.

Occupational exposure of vehicular emissions and cardiorespiratory risk among urban metropolitan bus drivers: A cross-sectional comparative study

BACKGROUND

Vehicular emissions on long-term exposure predispose metropolitan bus drivers to cardiorespiratory ailments.

OBJECTIVE

To evaluate the cardiorespiratory risk of urban metropolitan bus drivers related to vehicular emission exposure.

METHODS

Bus drivers (with service >5 years, n = 254) and their administrative controls (primarily engaged in indoor white collared jobs, n = 73) were recruited. Demographic, occupational and clinical details were collected through pre-validated standardized format. Pulmonary Function Test (PFT) and lipid profile were carried out with standard protocol. Risk for cardiovascular events for preceding 10-years was estimated with WHO/ISH risk prediction chart and QRISK3 score. Exposure assessments for particulate matter (PM) were performed for both groups while duty hours.

RESULTS

Exposure of drivers to PM2.5 six times and PM10 five times higher in comparison to administration staff (PM2.5- 970.9 v/s 145.0μg/m3 TWA and PM10- 1111.7 v/s 233.8μg/m3 TWA). Bus drivers exhibited significantly higher prevalence of respiratory symptoms (dyspnea-25% v/s 6.8% and cough-20.1% v/s 9.8%) and compromised PFT (obstructive-21% v/s 5.7% and restrictive-4.2% v/s 2.9%) in comparison to controls. Multivariate regression statistics reveal a significant decline for FEV1/FVC and FEV25-75 % among bus drivers compared to controls, controlling the influence of physiological and environmental factors. The difference between predicted cardiac age and their respective chronological age was twice higher (8.3 v/s 4.3 years) among drivers compared to their administration staff.

CONCLUSION

Bus drivers were exposed to high levels of outdoor air pollutants. Further, the drivers exhibited higher risk for ischemic attack and obstructive airway diseases as compared to administration staff.

Comparing the Therapeutic Efficacies of Lung Cancer: Network Meta-Analysis Approaches

BACKGROUND

In recent years, reduction of nuclear power generation and the use of coal-fired power for filling the power supply gap might have increased the risk of lung cancer. This study aims to explore the most effective treatment for different stages of lung cancer patients.

METHODS

We searched databases to investigate the treatment efficacy of lung cancer. The network meta-analysis was used to explore the top three effective therapeutic strategies among all collected treatment methodologies.

RESULTS

A total of 124 studies were collected from 115 articles with 171,757 participants in total. The results of network meta-analyses showed that the best top three treatments: (1) in response rate, for advanced lung cancer were Targeted + Targeted, Chemo + Immuno, and Targeted + Other Therapy with cumulative probabilities 82.9, 80.8, and 69.3%, respectively; for non-advanced lung cancer were Chemoradio + Targeted, Chemoradi + Immuno, and Chemoradio + Other Therapy with cumulative probabilities 69.0, 67.8, and 60.7%, respectively; (2) in disease-free control rate, for advanced lung cancer were Targeted + Others, Chemo + Immuno, and Targeted + Targeted Therapy with cumulative probabilities 93.4, 91.5, and 59.4%, respectively; for non-advanced lung cancer were Chemo + Surgery, Chemoradio + Targeted, and Surgery Therapy with cumulative probabilities 80.1, 71.5, and 43.1%, respectively.

CONCLUSION

The therapeutic strategies with the best effectiveness will be different depending on the stage of lung cancer patients.

Aryl hydrocarbon receptor activation-mediated vascular toxicity of ambient fine particulate matter: contribution of polycyclic aromatic hydrocarbons and osteopontin as a biomarker

BACKGROUND

Exposure to ambient fine particulate matter (PM_2.5) is associated with vascular diseases. Polycyclic aromatic hydrocarbons (PAHs) in PM_2.5 are highly hazardous; however, the contribution of PM_2.5-bound PAHs to PM_2.5-associated vascular diseases remains unclear. The ToxCast high-throughput in vitro screening database indicates that some PM_2.5-bound PAHs activate the aryl hydrocarbon receptor (AhR). The present study investigated whether the AhR pathway is involved in the mechanism of PM_2.5-induced vascular toxicity, identified the PAH in PM_2.5 that was the major contributor of AhR activation, and identified a biomarker for vascular toxicity of PM_2.5-bound PAHs.

RESULTS

Treatment of vascular smooth muscle cells (VMSCs) with an AhR antagonist inhibited the PM_2.5-induced increase in the cell migration ability; NF-κB activity; and expression of cytochrome P450 1A1 (CYP1A1), 1B1 (CYP1B1), interleukin-6 (IL-6), and osteopontin (OPN). Most PM_2.5-bound PAHs were extracted into the organic fraction, which drastically enhanced VSMC migration and increased mRNA levels of CYP1A1, CYP1B1, IL-6, and OPN. However, the inorganic fraction of PM_2.5 moderately enhanced VSMC migration and only increased IL-6 mRNA levels. PM_2.5 increased IL-6 secretion through NF-κB activation; however, PM_2.5 and its organic extract increased OPN secretion in a CYP1B1-dependent manner. Inhibiting CYP1B1 activity and silencing OPN expression prevented the increase in VSMC migration ability caused by PM_2.5 and its organic extract. The AhR activation potencies of seven PM_2.5-bound PAHs, reported in the ToxCast database, were strongly correlated with their capabilities of enhancing the migration ability of VSMCs. Benzo(k)fluoranthene (BkF) contributed the most to the AhR agonistic activity of ambient PM_2.5-bound PAHs. The association between PM_2.5-induced vascular toxicity, AhR activity, and OPN secretion was further verified in mice; PM_2.5-induced intimal hyperplasia in pulmonary small arteries and OPN secretion were alleviated in mice with low AhR affinity. Finally, urinary concentrations of 1-hydroxypyrene, a major PAH metabolite, were positively correlated with plasma OPN levels in healthy humans.

CONCLUSIONS

The present study offers in vitro, animal, and human evidences supporting the importance of AhR activation for PM_2.5-induced vascular toxicities and that BkF was the major contributor of AhR activation. OPN is an AhR-dependent biomarker of PM_2.5-induced vascular toxicity. The AhR activation potency may be applied in the risk assessment of vascular toxicity in PAH mixtures.

Particulate Matter-Induced Cardiovascular Dysfunction: A Mechanistic Insight

Air pollution and particulate matter (PM) are significant factors for adverse health effects most prominently cardiovascular disease (CVD). PM is produced from various sources, which include both natural and anthropogenic. It is composed of biological components, organic compounds, minerals, and metals, which are responsible for inducing inflammation and adverse health effects. However, the adverse effects are related to PM size distribution. Finer particles are a significant cause of cardiovascular events. This review discusses the direct and indirect mechanisms of PM-induced CVD like myocardial infarction, the elevation of blood pressure, cardiac arrhythmias, atherosclerosis, and thrombosis. The two potential mechanisms are oxidative stress and systemic inflammation. Prenatal exposure has also been linked with cardiovascular outcomes later in life. Moreover, we also mentioned the epidemiological studies that strongly associate PM with CVD.

Emerging role of mitochondria in airborne particulate matter-induced immunotoxicity

The immune system is one of the primary targets of airborne particulate matter. Recent evidence suggests that mitochondria lie at the center of particulate matter-induced immunotoxicity. Particulate matter can directly interact with mitochondrial components (proteins, lipids, and nucleic acids) and impairs the vital mitochondrial processes including redox mechanisms, fusion-fission, autophagy, and metabolic pathways. These disturbances impede different mitochondrial functions including ATP production, which acts as an important platform to regulate immunity and inflammatory responses. Moreover, the mitochondrial DNA released into the cytosol or in the extracellular milieu acts as a danger-associated molecular pattern and triggers the signaling pathways, involving cGAS-STING, TLR9, and NLRP3. In the present review, we discuss the emerging role of mitochondria in airborne particulate matter-induced immunotoxicity and its myriad biological consequences in health and disease.

Association between short-term exposure to ambient particulate air pollution and biomarkers of oxidative stress: A meta-analysis

BACKGROUND

Exposure to ambient particulate air pollution contributes substantially to the mortality and morbidity due to cardiovascular diseases (CVD), respiratory diseases and neurodegenerative diseases. Several hypothetical mechanisms have been proposed to explain these associations, particularly oxidative stress. Malondialdehyde (MDA), 8-hydroxy-2'-deoxyguanosine (8-OHdG), and Superoxide Dismutase (SOD) are typical biomarkers of oxidative stress and have been frequently investigated. However, the association between exposure to ambient particulate matter (PM) and these biomarkers has not been well established.

OBJECTIVES

Evaluate the association between ambient particulate air pollution and biomarkers of oxidative stress based on existing epidemiological studies.

METHODS

A systematic literature search was conducted in databases of Science Direct, PubMed, Web of Science, and Scopus up to April 24, 2020 to summarize epidemiological studies reporting the association between exposure to ambient PM (PM_2.5, PM₁₀, or both) and biomarkers of oxidative stress, and a meta-analysis was performed for the associations reported in individual studies using a random-effect model.

RESULTS

This meta-analysis included 23 epidemiological studies (13 identified for 8-OHdG, 11 identified for MDA and 5 identified for SOD). A 10 μg/m³ increase in short-term exposure to ambient PM_2.5 was associated with pooled percent changes of 2.10% (95% CIs: -0.13%, 4.38%), 1.60% (95% CIs: 0.21%, 3.01%) and -0.61% (95% CIs: -1.92%, 0.72%) in 8-OHdG, MDA and SOD, respectively.

CONCLUSION

Short-term exposure to ambient PM_2.5 was associated with a significantly increased level of MDA, indicating that ambient particulate air pollution may contribute to increased oxidative stress.

Distribution, sources, risks, and vitro DNA oxidative damage of PM2.5-bound atmospheric polycyclic aromatic hydrocarbons in Urumqi, NW China

Research has focused on the impacts of polycyclic aromatic hydrocarbons (PAHs) in the atmosphere due to their potential carcinogenicity. In this study, we investigated the seasonal variation, sources, incremental lifetime cancer risks (ILCR_S), and vitro DNA oxidative damage of PAHs in Urumqi in NW China. A total of 72 atmospheric samples from Urumqi were collected over a year (September 2017-September 2018) and were analyzed for 16 PAHs that are specifically prioritized by the U.S Environmental Protection Agency (U·S EPA). The highest PAHs concentrations were in winter (1032.66 ng m^-3) and lowest in spring (146.00 ng m^-3). Middle molecular weight PAHs with four rings were the most abundant species (45.28-61.19% of the total). The results of the diagnostic ratio and positive matrix factorization inferred that the major sources of atmospheric PAHs in Urumqi were biomass burning, coking, and petrogenic sources (52.9%), traffic (30.1%), coal combustion (8.9%), and the plastics recycling industry (8.1%). ILCR_S assessment and Monte Carlo simulations suggested that for all age groups PAHs cancer risks were mainly associated with ingestion and dermal contact and inhalation was negligible. The plasmid scission assay results showed a positive dose-response relationship between PAHs concentrations and DNA damage rates, demonstrating that toxic PAHs was the primary cause for PM_2.5-induced DNA damage in the air of Urumqi.

Online monitoring of volatile organic compounds emitted from human bronchial epithelial cells as markers for oxidative stress

Particulate air pollution is associated with adverse respiratory effects and is a major factor for premature deaths. In-vitro assays are commonly used for investigating the direct cytotoxicity and inflammatory impacts due to particulate matter (PM) exposure. However, biological tests are often labor-intensive, destructive and limited to endpoints measured offline at single time points, making it impossible to observe the progression of cell response upon exposure. Here we explored the potential of a high-resolution proton transfer reaction mass spectrometer (PTR-MS) to detect the volatile organic compounds (VOCs) emitted by human bronchial epithelial cells (BEAS-2B) upon exposure to PM. Cells were exposed to single components (1,4-naphthoquinone and Cu(II)) known to induce oxidative stress. We also tested filter extracts of aerosols generated in a smog chamber, including fresh and aged wood burning emissions, as well as α-pinene secondary organic aerosol (SOA). We found that 1,4-naphthoquinone was rapidly internalized by the cells. Exposing cells to each of these samples induced the emission of VOCs, which we tentatively assigned to acetonitrile, benzaldehyde and dimethylbenzaldehyde, respectively. Emission rates upon exposure to fresh and aged organic aerosol from α-pinene oxidation and from biomass burning significantly exceeded those observed after exposure to similar doses of Cu(II), a proxy for transition metals with high oxidative potential. Emission rates of biomarkers from cell exposure to α-pinene SOA exhibited a statistically significant, but weak dose dependence. The emission rates of benzaldehyde scaled with cell death, estimated by measuring the apical release of cytosolic lactate dehydrogenase. Particle mass doses delivered to the BEAS-2B cells match those deposited in the human tracheobronchial tract after several hours of inhalation at elevated ambient air pollution. The results presented here show that our method has the potential to determine biomarkers of PM induced pulmonary damage in toxicological and epidemiological research on air pollution.

Research on PM2.5 concentration based on dissipative structure theory: a case study of Xi'an, China

PM_2.5 pollution has become a serious urban environmental problem, especially in developing countries with increasing urbanization. Understanding the proportion of PM_2.5 generation sources has laid a foundation for better PM_2.5 concentration reduction This paper used Point of Interesting (POI)data, building profile data of Xi'an, PM_2.5 concentration and wind monitoring data of five provinces near Xi'an as the basic data. And this paper studied the spatial distribution of various buildings in Xi'an, the temporal and spatial distribution of PM_2.5 in Xi'an and the five provinces, and found that the spatial distribution of PM_2.5 concentration in Xi'an and the building distribution in Xi'an does not match. Based on this, a quantitative model of PM_2.5 concentration in Xi'an, energy consumption, wind, and other factors is established through the qualitative and quantitative analysis of PM_2.5 concentration in Xi'an. Entropy theory and dissipative structure theory are applied to analyze this phenomenon. The results show PM_2.5 in Xi'an mainly comes from the spread of PM_2.5 in the five provinces. The PM_2.5 generated by energy consumption in Xi'an is not enough to cause serious PM_2.5 pollution. And further suggestions on how to reduce PM_2.5 concentration in Xi'an are put forward.

Receptor for advanced glycation end products in relation to exposure to metal fumes and polycyclic aromatic hydrocarbon in shipyard welders

Advanced glycation end products (AGE) and the receptor for AGE (RAGE) have been found to be pivotal biomarkers to predict the risk of inflammation and oxidative stress. Limited evidence focuses on the influence of occupational exposure to polycyclic aromatic hydrocarbon (PAH) and metal fumes on AGE and RAGE in shipyard welders. Our aim was to determine the relationships among PAH, metal exposure, and inflammatory biomarkers. From September 1 to December 31, 2017, 53 welding workers (exposed group) and 29 office workers (control group) were enrolled in the study. Comprehensive workups included demographic characteristics, laboratory data, AGE, RAGE, Interleukin-6 (IL-6), tumor necrosis factor-α, PAH, and urinary metal concentrations. RAGE levels were measured by flow cytometric analysis. Urinary 1-hydroxypyrene (1-OHP) was used as a biomarker of exposure to PAH. Several metals were elevated in the personal fine particulate matter (PM_2.5) samples, including Mn, Fe, V, Co, Zn, and Cu. The exposed group had significantly higher exposure to PM_2.5 (p = 0.015), RAGE (p = 0.020), IL-6 (p = 0.008) than the control group. After adjusting for pertinent variables, there was still a significant and positive association between Ni level and AGE (β = 0.101; 95% CI, 0.031-0.172). Significant relationship between Cr and Cd levels and RAGE was observed (β = 0.173; 95% CI, 0.017-0.329; β = 0.084; 95% CI, 0.011-0.157, respectively). Participants with elevated 1-OHP level had higher odds of high RAGE level in the model 1 (OR = 3.466, 95% CI, 1.053-11.412) and model 2 (OR = 3.454, 95% CI, 1.034-11.536). The RAGE expression of participants was significantly associated with IL-6 levels in the fully adjusted model (β = 0.294; 95% CI, 0.083-0.732). Our findings highlighted that urinary metal levels and PAH were associated with increased AGE and RAGE formation in shipyard workers. Elevated serum RAGE might induce the production of proinflammatory cytokines and trigger ensuing inflammatory cascades.

The Inducible Role of Ambient Particulate Matter in Cancer Progression via Oxidative Stress-Mediated Reactive Oxygen Species Pathways: A Recent Perception

Simple Summary

Particulate matter, especially the fine fraction PM2.5, is officially stated as carcinogenic to human. There are compelling evidences on the association between PM2.5 exposure and lung cancer, and there are also some preliminary data reporting the significant links between this fraction with non-lung cancers. The underlying mechanisms remain unclear. Further studies related to such scope are highly required. The purpose of this work is to systemically analyze recent findings concerning the relationship between PM2.5 and cancer, and to thoroughly present the oxidative stress pathways mediated by reactive oxygen species as the key mechanism for carcinogenesis induced by PM2.5. This will provide a more comprehensive and updated knowledge regarding carcinogenic capacity of PM2.5 to both clinicians and public health workers, contributing to preventive and therapeutic strategies to fight against cancer in human.

Abstract

Cancer is one of the leading causes of premature death and overall death in the world. On the other hand, fine particulate matter, which is less than 2.5 microns in aerodynamic diameter, is a global health problem due to its small diameter but high toxicity. Accumulating evidence has demonstrated the positive associations between this pollutant with both lung and non-lung cancer processes. However, the underlying mechanisms are yet to be elucidated. The present review summarizes and analyzes the most recent findings on the relationship between fine particulate matter and various types of cancer along with the oxidative stress mechanisms as its possible carcinogenic mechanisms. Also, promising antioxidant therapies against cancer induced by this poison factor are discussed.

Unrepaired DNA damage in macrophages causes elevation of particulate matter- induced airway inflammatory response

The inflammatory cascade can be initiated with the recognition of damaged DNA. Macrophages play an essential role in particulate matter (PM)-induced airway inflammation. In this study, we aim to explore the PM induced DNA damage response of macrophages and its function in airway inflammation. The DNA damage response and inflammatory response were assessed using bone marrow-derived macrophages following PM treatment and mouse model instilled intratracheally with PM. We found that PM induced significant DNA damage both in vitro and in vivo and simultaneously triggered a rapid DNA damage response, represented by nuclear RPA, 53BP1 and γH2AX foci formation. Genetic ablation or chemical inhibition of the DNA damage response sensor amplified the production of cytokines including Cxcl1, Cxcl2 and Ifn-γ after PM stimulation in bone marrow-derived macrophages. Similar to that seen in vitro, mice with myeloid-specific deletion of RAD50 showed higher levels of airway inflammation in response to the PM challenge, suggesting a protective role of DNA damage sensor during inflammation. These data demonstrate that PM exposure induces DNA damage and activation of DNA damage response sensor MRN complex in macrophages. Disruption of MRN complex lead to persistent, unrepaired DNA damage that causes elevated inflammatory response.

Short-term exposure to ambient air pollution and daily atherosclerotic heart disease mortality in a cool climate

The associations between exposure to short-term ambient air pollution and daily atherosclerotic heart disease (ASHD) mortality in cool climate have not been established. We performed a time-series analysis in Shenyang, the largest city of Northeastern China. We identified 7659 ASHD deaths and obtained deaths, ambient air pollution levels, and meteorological data for Shenyang during 2014-2017. The impact of ambient air pollution on daily ASHD deaths was analyzed using generalized additive models (GAMs). Cumulative lag effects were investigated using distributed lag non-linear models (DLNM). We found ASHD deaths significantly increased during days with higher air pollution. Particulate matter with diameter < 2.5 μm (PM_2.5), PM₁₀, and sulfur dioxide (SO₂) were positively associated with ASHD deaths among the total population. Both single- and multi-pollutants models indicated that PM_2.5, PM₁₀, and sulfur dioxide (SO₂) were positively associated with the deaths of women with AHSD, whereas only SO₂ was significant in men. This suggests significant gender-based differences in the fatal effects of ambient air pollution. Up to 28 days of single-day lag effects were observed for PM_2.5 and PM₁₀ in women. The cumulative lag effects of PM_2.5 and PM₁₀ showed increasing trends in both men and women; however, exposure to higher pollutant concentrations did not necessarily translate to greater risks. The ERRs differences between women and men were larger in cold days than in hot days, suggesting that lower temperature may exacerbate the adverse effects of air pollution on vulnerable women.

Environmental monitoring and the developmental origins of health and disease

Early-life chronic exposure to environmental contaminants, such as bisphenol-A, particulate matter air pollution, organophosphorus pesticides, and pharmaceutical drugs, among others, may affect central tissues, such as the hypothalamus, and peripheral tissues, such as the endocrine pancreas, causing inflammation and apoptosis with severe implications to the metabolism. The Developmental Origins of Health and Disease (DOHaD) concept articulates events in developmental phases of life, such as intrauterine, lactation, and adolescence, to later-life metabolism and health. These developmental phases are more susceptible to environmental changes, such as those caused by environmental contaminants, which may predispose individuals to obesity, metabolic syndrome, and chronic noncommunicable diseases later in life. Alterations in the epigenome are explored as an underlying mechanism to the programming effects on metabolism, as the expression of key genes related with central and peripheral metabolic functions may be altered in response to environmental disturbances. Studies show that environmental contaminants may affect gene expressions in mammals, especially when exposed to during the developmental phases of life, leading to metabolic disorders in adulthood. In this review, we discuss the current obesity epidemics, the DOHaD concept, pollutants' toxicology, environmental control, and the role of environmental contaminants in the central and peripheral programming of obesity and metabolic syndrome. Improving environmental monitoring may directly affect the quality of life of the population and help protect the future generations from metabolic diseases.

Personal exposure to PM2.5 in Chinese rural households in the Yangtze River Delta

High levels of PM_2.5 exposure and associated health risks are of great concern in rural China. For this study, we used portable PM_2.5 monitors for monitoring concentrations online, recorded personal time-activity patterns, and analyzed the contribution from different microenvironments in rural areas of the Yangtze River Delta, China. The daily exposure levels of rural participants were 66 μg/m³ (SD 40) in winter and 65 μg/m³ (SD 16) in summer. Indoor exposure levels were usually higher than outdoor levels. The exposure levels during cooking in rural kitchens were 140 μg/m³ (SD 116) in winter and 121 μg/m³ (SD 70) in summer, the highest in all microenvironments. Winter and summer values were 252 μg/m³ (SD 103) and 204 μg/m³ (SD 105), respectively, for rural people using biomass for fuel, much higher than those for rural people using LPG and electricity. By combining PM_2.5 concentrations and time spent in different microenvironments, we found that 92% (winter) and 85% (summer) of personal exposure to PM_2.5 in rural areas was attributable to indoor microenvironments, of which kitchens accounted for 24% and 27%, respectively. Consequently, more effective policies and measures are needed to replace biomass fuel with LPG or electricity, which would benefit the health of the rural population in China.

Air pollution associated epigenetic modifications: Transgenerational inheritance and underlying molecular mechanisms

Air pollution is one of the leading causes of deaths in Southeast Asian countries including India. Exposure to air pollutants affects vital cellular mechanisms and is intimately linked with the etiology of a number of chronic diseases. Earlier work from our laboratory has shown that airborne particulate matter disturbs the mitochondrial machinery and causes significant damage to the epigenome. Mitochondrial reactive oxygen species possess the ability to trigger redox-sensitive signaling mechanisms and induce irreversible epigenomic changes. The electrophilic nature of reactive metabolites can directly result in deprotonation of cytosine at C-5 position or interfere with the DNA methyltransferases activity to cause alterations in DNA methylation. In addition, it also perturbs level of cellular metabolites critically involved in different epigenetic processes like acetylation and methylation of histone code and DNA hypo or hypermethylation. Interestingly, these modifications may persist through downstream generations and result in the transgenerational epigenomic inheritance. This phenomenon of subsequent transfer of epigenetic modifications is mainly associated with the germ cells and relies on the germline stability of the epigenetic states. Overall, the recent literature supports, and arguably strengthens, the contention that air pollution might contribute to transmission of epimutations from gametes to zygotes by involving mitochondrial DNA, parental allele imprinting, histone withholding and non-coding RNAs. However, larger prospective studies using innovative, integrated epigenome-wide metabolomic strategy are highly warranted to assess the air pollution induced transgenerational epigenetic inheritance and associated human health effects.

Markers of Oxidative Stress in the Exhaled Breath Condensate of Workers Handling Nanocomposites

Researchers in nanocomposite processing may inhale a variety of chemical agents, including nanoparticles. This study investigated airway oxidative stress status in the exhaled breath condensate (EBC). Nineteen employees (42.4 ± 11.4 y/o), working in nanocomposites research for 18.0 ± 10.3 years were examined pre-shift and post-shift on a random workday, together with nineteen controls (45.5 ± 11.7 y/o). Panels of oxidative stress biomarkers derived from lipids, nucleic acids, and proteins were analyzed in the EBC. Aerosol exposures were monitored during three major nanoparticle generation operations: smelting and welding (workshop 1) and nanocomposite machining (workshop 2) using a suite of real-time and integrated instruments. Mass concentrations during these operations were 0.120, 1.840, and 0.804 mg/m³, respectively. Median particle number concentrations were 4.8 × 10⁴, 1.3 × 10⁵, and 5.4 × 10⁵ particles/cm³, respectively. Nanoparticles accounted for 95, 40, and 61%, respectively, with prevailing Fe and Mn. All markers of nucleic acid and protein oxidation, malondialdehyde, and aldehydes C₆⁻C13 were elevated, already in the pre-shift samples relative to controls in both workshops. Significant post-shift elevations were documented in lipid oxidation markers. Significant associations were found between working in nanocomposite synthesis and EBC biomarkers. More research is needed to understand the contribution of nanoparticles from nanocomposite processing in inducing oxidative stress, relative to other co-exposures generated during welding, smelting, and secondary oxidation processes, in these workshops.

Concentration characteristics, source apportionment, and oxidative damage of PM2.5-bound PAHs in petrochemical region in Xinjiang, NW China

Polycyclic aromatic hydrocarbons (PAHs) are of considerable concern due to their potential as human carcinogens. Thus, determining the characteristics, potential source, and examining the oxidative capacity of PAHs to protect human health is essential. This study investigated the PM_2.5-bound PAHs at Dushanzi, a large petrochemical region in Xinjiang as well as northwest China. A total of 33 PM_2.5 samples with 13 PAHs, together with molecular tracers (levoglucosan, and element carbon), were analyzed during the non-heating and heating periods. The results showed that the PM_2.5 concentrations were 70.22 ± 22.30 and 95.47 ± 61.73 μg/m³, while that of total PAHs were 4.07 ± 2.03 and 60.33 ± 30.80 ng/m³ in sampling period, respectively. The fluoranthene, pyrene, chrysene, benzo[b]fluoranthene, and benzo[k]fluoranthene were the most abundant (top five) PAHs, accounting for 71.74 and 72.80% of total PAH mass during non-heating and heating periods. The BaP equivalent (BaPeq) concentration exceeded 1 ng/m³ as recommended by National Ambient Air Quality Standards during heating period. The diagnostic ratios and positive matrix factorization indicated that oil industry, biomass burning, coal combustion, and vehicle emissions are the primary sources. The coal combustion remarkably increased during heating period. The plasmid scission assay (PSA) results showed that higher DNA damage rate was observed during heating period. PAHs in PM_2.5 such as Chr, BaP, and IcdP were found to have significantly positive correlations with the plasmid DNA damage rates. Additionally, the relationship among BaPeq and DNA damage rate suggested that synergistic reaction may modify the toxicity of PAHs.

Exposure to traffic-related air pollution and acute bronchitis in children: season and age as modifiers

Background

Acute bronchitis (AB) is one of the principal causes of childhood morbidity. Increasing number of studies has shown that air pollution is an important environmental contributor of respiratory disease. However, evidence so far is scarce regarding the effects of air pollution on childhood AB, and it also remains unclear how the risk of AB will change by season and age.

Methods

Data on hospital visits for AB in children, air pollution and meteorological factors from 1 January 2015 to 31 December 2016 were collected in Hefei, China. Time-series analysis was applied to assess the short-term effects of traffic-related air pollution on childhood AB outpatient visits. A Poisson generalised linear regression model combined with a distributed lag non-linear model was used to estimate the relationships, controlling for long-term trends, seasonal patterns, meteorological factors and other possible confounders.

Results

We found that an IQR increase in concentrations of nitrogen dioxide, particulate matter <2.5 µm and carbon monoxide significantly increased the daily hospital visits for childhood AB with 4-day cumulative effect estimates (relative risks: 1.03, 95% CI 1.01 to 1.05; 1.09, 95% CI 1.07 to 1.11; 1.07, 95% CI 1.05 to 1.09). Notably, the risk estimates during the cold season are pronounced; however, no significant association was observed during the warm season. Interestingly, children aged 6–14 years were more vulnerable to air pollutants than children aged less than 1 year and within 1–5 years. However, no gender difference was observed.

Conclusion

A significant association of traffic-related air pollution and increased department visits for childhood AB was observed, notably in school-age children and during the cold season.