Ultrafine particulate matter impairs mitochondrial redox homeostasis and activates phosphatidylinositol 3-kinase mediated DNA damage responses in lymphocytes

Association between ambient particulate matter exposure and mitochondrial DNA copy number: A systematic review and meta-analysis

BACKGROUND

Ambient particulate matter (PM) has been recognized as inducing oxidative stress, which could contribute to mitochondrial damage and dysfunction. However, studies investigating the association between ambient PM and mitochondria, particularly mitochondrial DNA copy number (mtDNA-CN), have yielded inconsistent results.

METHODS

We conducted comprehensive literature searches to identify observational studies published before July 17, 2023, examining the association between ambient PM exposure and mtDNA-CN. Meta-analysis using random effects model was employed to calculate the pooled effect estimates for general individual exposures, as well as for prenatal exposure with specific trimester. Additionally, the quality and level of evidence for each exposure-outcome pair was evaluated.

RESULTS

A total of 10 studies were included in the systematic review and meta-analysis. The results indicated that general individual exposure to PM2.5 (β = -0.084, 95 % CI: -0.521, 0.353; I2 = 93 %) and PM10 (β = 0.035, 95 % CI: -0.129, 0.199; I2 = 95 %) did not significantly affect mtDNA-CN. Prenatal exposure to PM2.5 (β = 0.023, 95 % CI: -0.087, 0.133; I2 = 0 %) and PM10 (β = 0.006, 95 % CI: -0.135; 0.147; I2 = 51 %) were also not significantly associated with mtDNA-CN in offspring. The level of evidence for each tested exposure-outcome pair was assessed as "inadequate."

CONCLUSIONS

The findings of this systematic review and meta-analysis indicate that there is an "inadequate" strength of evidence for the association between general individual or prenatal exposure to ambient PM and mtDNA-CN. Future research necessitates studies with more rigorous design, enhanced control of confounding factors, and improved measures of exposure to substantiate our findings.

Toxicological evaluation and concentration of airborne PM0.1 in high air pollution period in Guangzhou, China

The emissions and exposure limits for airborne PM0.1 are lacking, with limited scientific data for toxicity. Therefore, we continuously monitored and calculated the number and mass concentrations of airborne PM0.1 in December 2017, January 2018 and March 2018 during the high pollution period in Guangzhou. We collected PM0.1 from the same period and analyzed their chemical components. A549, THP-1 and A549/THP-1 co-cultured cells were selected for exposure to PM0.1, and evaluated for toxicological responses. Our aims are to 1) measure and analyze the number and mass concentrations, and chemical components of PM0.1; 2) evaluate and compare PM0.1 toxicity to different airway cells models at different time points. Guangzhou had the highest mass concentration of PM0.1 in December 2017, while the number concentration was the lowest. Chemical components in PM0.1 vary significantly at different time periods, and the correlation between the chemical composition or source of PM0.1 and the mass and number concentration of PM0.1 was dissimilar. Exposure to PM0.1 disrupted cell membranes, impaired mitochondrial function, promoted the expression of inflammatory mediators, and interfered with DNA replication in the cell cycle. The damage caused by exposure to PM0.1 at different times exhibited variations across different types of cells. PM0.1 in March 2018 stimulated co-cultured cells to secrete more inflammatory mediators, and CMA was significantly related to the expression of them. Our study indicates that it is essential to monitor both the mass and number concentrations of PM0.1 throughout all seasons annually, as conventional toxicological experiments and the internal components of PM0.1 may not effectively reveal the health damages caused by elevated number levels of PM0.1.

Disruption of phosphofructokinase activity and aerobic glycolysis in human bronchial epithelial cells by atmospheric ultrafine particulate matter

Exposure to ambient ultrafine particulate matter (UPM) causes respiratory disorders; however, the underlying molecular mechanisms remain unclear. In this study, we synthesized simulated UPM (sUPM) with controlled physicochemical properties using the spark-discharge method. Subsequently, we investigated the biological effects of sUPM using BEAS-2B human bronchial epithelial cells (HBECs) and a mouse intratracheal instillation model. High throughput RNA-sequencing and bioinformatics analyses revealed that dysregulation of the glycolytic metabolism is involved in the inhibited proliferation and survival of HBECs by sUPM treatment. Furthermore, signaling pathway and enzymatic analyses showed that the treatment of BEAS-2B cells with sUPM induces the inactivation of extracellular signal-regulated kinase (ERK) and protein kinase B (PKB, also known as AKT), resulting in the downregulation of phosphofructokinase 2 (PFK2) S483 phosphorylation, PFK enzyme activity, and aerobic glycolysis in HBECs in an oxidative stress-independent manner. Additionally, intratracheal instillation of sUPM reduced the phosphorylation of ERK, AKT, and PFK2, decreased proliferation, and increased the apoptosis of bronchial epithelial cells in mice. The findings of this study imply that UPM induces pulmonary toxicity by disrupting aerobic glycolytic metabolism in lung epithelial cells, which can provide novel insights into the toxicity mechanisms of UPM and strategies to prevent their toxic effects.

Novel insights into the role of ion channels in cellular DNA damage response

The DNA damage response (DDR) is a complex and highly regulated cellular process that detects and repairs DNA damage. The integrity of the DNA molecule is crucial for the proper functioning and survival of cells, as DNA damage can lead to mutations, genomic instability, and various diseases, including cancer. The DDR safeguards the genome by coordinating a series of signaling events and repair mechanisms to maintain genomic stability and prevent the propagation of damaged DNA to daughter cells. The study of an ion channels in the context of DDR is a promising avenue in biomedical research. Lately, it has been reported that the movement of ions through channels plays a crucial role in various physiological processes, including nerve signaling, muscle contraction, cell signaling, and maintaining cell membrane potential. Knowledge regarding the involvement of ion channels in the DDR could support refinement of our approach to several pathologies, mainly cancer, and perhaps lead to innovative therapies. In this review, we focused on the ion channel's possible role in the DDR. We present an analysis of the involvement of ion channels in DDR, their role in DNA repair mechanisms, and cellular outcomes. By addressing these areas, we aim to provide a comprehensive perspective on ion channels in the DDR and potentially guide future research in this field. It is worth noting that the interplay between ion channels and the cellular DDR is complex and multifaceted. More research is needed to fully understand the underlying mechanisms and potential therapeutic implications of these interactions.

Nano-engineered vitamins as a potential epigenetic modifier against environmental air pollutants

Air pollution has emerged as a serious threat to human health due to close association with spectrum of chronic ailments including cardiovascular disorders, respiratory diseases, nervous system dysfunctions, diabetes and cancer. Exposure to air-borne pollutants along with poor eating behaviours and inferior dietary quality irreversibly impacts epigenomic landscape, leading to aberrant transcriptional control of gene expression which is central to patho-physiology of non-communicable diseases. It is assumed that nutriepigenomic interventions such as vitamins can control such adverse effects through their immediate action on mitochondrial epigenomic-axis. Importantly, the exhaustive clinical utility of vitamins-interceded epigenetic synchronization is not well characterized. Therefore, improving the current limitations linked to stability and bioavailability issues in vitamin formulations is highly warranted. The present review not only sums up the available data on the role of vitamins as potential epigenetic modifiers but also discusses the importance of nano-engineered vitamins as potential epidrugs for dietary and pharmacological intervention to mitigate the long-term effects of air pollution toxicity.

The bio-distribution, clearance pathways, and toxicity mechanisms of ambient ultrafine particles

Ambient particles severely threaten human health worldwide. Compared to larger particles, ultrafine particles (UFPs) are highly concentrated in ambient environments, have a larger specific surface area, and are retained for a longer time in the lung. Recent studies have found that they can be transported into various extra-pulmonary organs by crossing the air-blood barrier (ABB). Therefore, to understand the adverse effects of UFPs, it is crucial to thoroughly investigate their bio-distribution and clearance pathways in vivo after inhalation, as well as their toxicological mechanisms. This review highlights emerging evidence on the bio-distribution of UFPs in pulmonary and extra-pulmonary organs. It explores how UFPs penetrate the ABB, the blood-brain barrier (BBB), and the placental barrier (PB) and subsequently undergo clearance by the liver, kidney, or intestine. In addition, the potential underlying toxicological mechanisms of UFPs are summarized, providing fundamental insights into how UFPs induce adverse health effects.

Physical exercise and persistent organic pollutants

Exposure to the legacy and emerging persistent organic pollutants (POPs) incessantly has become an important threat to individual health, which is closely related to neurodevelopment, endocrine and cardiovascular homeostasis. Exercise, on the other hand, has been consistently shown to improve physical fitness. Whereas associations between traditional air pollutants, exercise and lung function have been thoroughly reviewed, reviews on associations between persistent organic pollutants and exercise are scarce. Hence, a literature review focused on exercise, exposure to POPs, and health risk assessment was performed for studies published from 2004 to 2022. The purpose of this review is to provide an overview of exposure pathways and levels of POPs during exercise, as well as the impact of exercise on health concerns attributable to the redistribution, metabolism, and excretion of POPs in vivo. Therein lies a broader array of exercise benefits, including insulin sensitizing, mitochondrial DNA repair, lipid metabolism and intestinal microecological balance. Physical exercise is conducive to reduce POPs body burden and resistant to health hazards of POPs generally. Besides, individual lipid metabolism condition is a critical factor in evaluating potential link in exercise, POPs and health effects.

A hybrid model for estimating the number concentration of ultrafine particles based on machine learning algorithms in central Taiwan

Modeling is a cost-effective measure to estimate ultrafine particle (UFP) levels. Previous UFP estimates generally relied on land-use regression with insufficient temporal resolution. We carried out in-situ measurements for UFP in central Taiwan and developed a model incorporating satellite-based measurements, meteorological variables, and land-use data to estimate daily UFP levels at a 1-km resolution. Two sampling campaigns were conducted for measuring hourly UFP concentrations at six sites between 2008-2010 and 2017-2021, respectively, using scanning mobility particle sizers. Three machine learning algorithms, namely random forest, eXtreme gradient boosting (XGBoost), and deep neural network, were used to develop UFP estimation models. The performances were evaluated with a 10-fold cross-validation, temporal, and spatial validation. A total of 1,022 effective sampling days were conducted. The XGBoost model had the best performance with a training coefficient of determination (R²) of 0.99 [normalized root mean square error (nRMSE): 6.52%] and a cross-validation R² of 0.78 (nRMSE: 31.0%). The ten most important variables were surface pressure, distance to the nearest road, temperature, calendar year, day of the year, NO₂, meridional wind, the total length of roads, PM_2.5, and zonal wind. The UFP levels were elevated along the main roads across different seasons, suggesting that traffic emission is an important contributor to UFP. This hybrid model outperformed prior land use regression models and thus can provide more accurate estimates of UFP for epidemiological studies.

Cell-free circulating mitochondrial DNA: An emerging biomarker for airborne particulate matter associated with cardiovascular diseases

The association of airborne particulate matter exposure with the deteriorating function of the cardiovascular system is fundamentally driven by the impairment of mitochondrial-nuclear crosstalk orchestrated by aberrant redox signaling. The loss of delicate balance in retrograde communication from mitochondria to the nucleus often culminates in the methylation of the newly synthesized strand of mitochondrial DNA (mtDNA) through DNA methyl transferases. In highly metabolic active tissues such as the heart, mtDNA's methylation state alteration impacts mitochondrial bioenergetics. It affects transcriptional regulatory processes involved in biogenesis, fission, and fusion, often accompanied by the integrated stress response. Previous studies have demonstrated a paradoxical role of mtDNA methylation in cardiovascular pathologies linked to air pollution. A pronounced alteration in mtDNA methylation contributes to systemic inflammation, an etiological determinant for several co-morbidities, including vascular endothelial dysfunction and myocardial injury. In the current article, we evaluate the state of evidence and examine the considerable promise of using cell-free circulating methylated mtDNA as a predictive biomarker to reduce the more significant burden of ambient air pollution on cardiovascular diseases.

The Road to Malignant Cell Transformation after Particulate Matter Exposure: From Oxidative Stress to Genotoxicity

In cells, oxidative stress is an imbalance between the production/accumulation of oxidants and the ability of the antioxidant system to detoxify these reactive products. Reactive oxygen species (ROS), cause multiple cellular damages through their interaction with biomolecules such as lipids, proteins, and DNA. Genotoxic damage caused by oxidative stress has become relevant since it can lead to mutation and play a central role in malignant transformation. The evidence describes chronic oxidative stress as an important factor implicated in all stages of the multistep carcinogenic process: initiation, promotion, and progression. In recent years, ambient air pollution by particulate matter (PM) has been cataloged as a cancer risk factor, increasing the incidence of different types of tumors. Epidemiological and toxicological evidence shows how PM-induced oxidative stress could mediate multiple events oriented to carcinogenesis, such as proliferative signaling, evasion of growth suppressors, resistance to cell death, induction of angiogenesis, and activation of invasion/metastasis pathways. In this review, we summarize the findings regarding the involvement of oxidative and genotoxic mechanisms generated by PM in malignant cell transformation. We also discuss the importance of new approaches oriented to studying the development of tumors associated with PM with more accuracy, pursuing the goal of weighing the impact of oxidative stress and genotoxicity as one of the main mechanisms associated with its carcinogenic potential.

Particulate Matters Affecting lncRNA Dysregulation and Glioblastoma Invasiveness: In Silico Applications and Current Insights

With a reported rise in global air pollution, more than 50% of the population remains exposed to toxic air pollutants in the form of particulate matters (PMs). PMs, from various sources and of varying sizes, have a significant impact on health as long-time exposure to them has seen a correlation with various health hazards and have also been determined to be carcinogenic. In addition to disrupting known cellular pathways, PMs have also been associated with lncRNA dysregulation-a factor that increases predisposition towards the onset or progression of cancer. lncRNA dysregulation is further seen to mediate glioblastoma multiforme (GBM) progression. The vast array of information regarding cancer types including GBM and its various precursors can easily be obtained via innovative in silico approaches in the form of databases such as GEO and TCGA; however, a need to obtain selective and specific information correlating anthropogenic factors and disease progression-in the case of GBM-can serve as a critical tool to filter down and target specific PMs and lncRNAs responsible for regulating key cancer hallmarks in glioblastoma. The current review article proposes an in silico approach in the form of a database that reviews current updates on correlation of PMs with lncRNA dysregulation leading to GBM progression.

Prenatal exposure to environmental pro-oxidants induces mitochondria-mediated epigenetic changes: a cross-sectional pilot study

Mitochondria play a central role in maintaining cellular and metabolic homeostasis during vital development cycles of foetal growth. Optimal mitochondrial functions are important not only to sustain adequate energy production but also for regulated epigenetic programming. However, these organelles are subtle targets of environmental exposures, and any perturbance in the defined mitochondrial machinery during the developmental stage can lead to the re-programming of the foetal epigenetic landscape. As these modifications can be transferred to subsequent generations, we herein performed a cross-sectional study to have an in-depth understanding of this intricate phenomenon. The study was conducted with two arms: whereas the first group consisted of in utero pro-oxidant exposed individuals and the second group included controls. Our results showed higher levels of oxidative mtDNA damage and associated integrated stress response among the exposed individuals. These disturbances were found to be closely related to the observed discrepancies in mitochondrial biogenesis. The exposed group showed mtDNA hypermethylation and changes in allied mitochondrial functioning. Altered expression of mitomiRs and their respective target genes in the exposed group indicated the possibilities of a disturbed mitochondrial-nuclear cross talk. This was further confirmed by the modified activity of the mitochondrial stress regulators and pro-inflammatory mediators among the exposed group. Importantly, the disturbed DNMT functioning, hypermethylation of nuclear DNA, and higher degree of post-translational histone modifications established the existence of aberrant epigenetic modifications in the exposed individuals. Overall, our results demonstrate the first molecular insights of in utero pro-oxidant exposure associated changes in the mitochondrial-epigenetic axis. Although, our study might not cement an exposure-response relationship for any particular environmental pro-oxidant, but suffice to establish a dogma of mito-epigenetic reprogramming at intrauterine milieu with chronic illness, a hitherto unreported interaction.

Lung toxicity of particulates and gaseous pollutants using ex-vivo airway epithelial cell culture systems

Air pollution consists of a multi-faceted mix of gases and ambient particulate matter (PM) with diverse organic and non-organic chemical components that contribute to increasing morbidity and mortality worldwide. In particular, epidemiological and clinical studies indicate that respiratory health is adversely affected by exposure to air pollution by both causing and worsening (exacerbating) diseases such as chronic obstructive pulmonary disease (COPD), asthma, interstitial pulmonary fibrosis and lung cancer. The molecular mechanisms of air pollution-induced pulmonary toxicity have been evaluated with regards to different types of PM of various sizes and concentrations with single and multiple exposures over different time periods. These data provide a plausible interrelationship between cellular toxicity and the activation of multiple biological processes including proinflammatory responses, oxidative stress, mitochondrial oxidative damage, autophagy, apoptosis, cell genotoxicity, cellular senescence and epithelial-mesenchymal transition. However, these molecular changes have been studied predominantly in cell lines rather than in primary bronchial or nasal cells from healthy subjects or those isolated from patients with airways disease. In addition, they have been conducted under different cell culture conditions and generally in submerged culture rather than the more relevant air-liquid interface culture and with a variety of air pollutant exposure protocols. Cell types may respond differentially to pollution delivered as an aerosol rather than being bathed in media containing agglomerations of particles. As a result, the actual pathophysiological pathways activated by different PMs in primary cells from the airways of healthy and asthmatic subjects remains unclear. This review summarises the literature on the different methodologies utilised in studying the impact of submicron-sized pollutants on cells derived from the respiratory tract with an emphasis on data obtained from primary human cell. We highlight the critical underlying molecular mechanisms that may be important in driving disease processes in response to air pollution in vivo.

Association of Ambient Particulate Matter Pollution of Different Sizes With In-Hospital Case Fatality Among Stroke Patients in China

BACKGROUND AND OBJECTIVES

To characterize the association of ambient particulate matter (PM) pollution of different sizes (PM ≤1 µm in aerodynamic diameter [PM1], PM2.5, and PM10) with in-hospital case fatality among patients with stroke in China.

METHODS

We collected hospitalizations due to stroke in 4 provinces in China from 2013 to 2019. Seven-day and annual averages of PM prior to hospitalization were estimated using bilinear interpolation and residential addresses. Associations with in-hospital case fatality were estimated using random-effects logistic regression models. Potential reducible fraction and the number of fatalities attributed to PM were estimated using a counterfactual approach.

RESULTS

Among 3,109,634 stroke hospitalizations (mean age 67.23 years [SD 12.22]; 1,765,644 [56.78%] male), we identified 32,140 in-hospital stroke fatalities (case fatality rate 1.03%). Each 10 µg/m3 increase in 7-day average (short-term) exposure to PM was associated with increased in-hospital case fatality: odds ratios (ORs) were 1.058 (95% CI 1.047-1.068) for PM1, 1.037 (95% CI 1.031-1.043) for PM2.5, and 1.025 (95% CI 1.021-1.029) for PM10. Similar but larger ORs were observed for annual averages (long-term): 1.240 (95% CI 1.217-1.265) for PM1, 1.105 (95% CI 1.094-1.116) for PM2.5, and 1.090 (95% CI 1.082-1.099) for PM10. In counterfactual analyses, PM10 was associated with the largest potential reducible fraction in in-hospital case fatality (10% [95% CI 8.3-11.7] for short-term exposure and 21.1% [19.1%-23%] for long-term exposure), followed by PM1 and PM2.5.

DISCUSSION

PM pollution is a risk factor for in-hospital stroke-related deaths. Strategies that target reducing PM pollution may improve the health outcomes of patients with stroke.

LSEA Evaluation of Lipid Mediators of Inflammation in Lung and Cortex of Mice Exposed to Diesel Air Pollution

Airborne ultrafine particle (UFP) exposure is a great concern as they have been correlated to increased cardiovascular mortality, neurodegenerative diseases and morbidity in occupational and environmental settings. The ultrafine components of diesel exhaust particles (DEPs) represent about 25% of the emission mass; these particles have a great surface area and consequently high capacity to adsorb toxic molecules, then transported throughout the body. Previous in-vivo studies indicated that DEP exposure increases pro- and antioxidant protein levels and activates inflammatory response both in respiratory and cardiovascular systems. In cells, DEPs can cause additional reactive oxygen species (ROS) production, which attacks surrounding molecules, such as lipids. The cell membrane provides lipid mediators (LMs) that modulate cell-cell communication, inflammation, and resolution processes, suggesting the importance of understanding lipid modifications induced by DEPs. In this study, with a lipidomic approach, we evaluated in the mouse lung and cortex how DEP acute and subacute treatments impact polyunsaturated fatty acid-derived LMs. To analyze the data, we designed an ad hoc bioinformatic pipeline to evaluate the functional enrichment of lipid sets belonging to the specific biological processes (Lipid Set Enrichment Analysis-LSEA). Moreover, the data obtained correlate tissue LMs and proteins associated with inflammatory process (COX-2, MPO), oxidative stress (HO-1, iNOS, and Hsp70), involved in the activation of many xenobiotics as well as PAH metabolism (Cyp1B1), suggesting a crucial role of lipids in the process of DEP-induced tissue damage.

Mitochondria and traffic-related air pollution linked coronary artery calcification: exploring the missing link

The continuing increase in the exposure to Traffic-related air pollution (TRAP) in the general population is predicted to result in a higher incidence of non-communicable diseases like cardiovascular disease. The chronic exposure of air particulate matter from TRAP upon the vascular system leads to the enhancement of deposition of calcium in the vasculature leading to coronary artery calcification (CAC), triggered by inflammatory reactions and endothelial dysfunction. This calcification forms within the intimal and medial layers of vasculature and the underlying mechanism that connects the trigger from TRAP is not well explored. Several local and systemic factors participate in this active process including inflammatory response, hyperlipidemia, presence of self-programmed death bodies and high calcium-phosphate concentrations. These factors along with the loss of molecules that inhibit calcification and circulating nucleation complexes influence the development of calcification in the vasculature. The loss of defense to prevent osteogenic transition linked to micro organelle dysfunction that includes deteriorated mitochondria, elevated mitochondrial oxidative stress, and defective mitophagy. In this review, we examine the contributory role of mitochondria involved in the mechanism of TRAP linked CAC development. Further we examine whether TRAP is an inducer or trigger for the enhanced progression of CAC.

Association between preconceptional air pollution exposure and medical purposes for selective termination of pregnancy

BACKGROUND

Exposure to air pollutants is associated with adverse pregnancy outcomes. But evidence on the effects of preconceptional air pollution exposure on the risk of termination of pregnancy (TOP) caused by pregnancy losses and congenital malformations is lacking.

METHODS

The distributed lag nonlinear model (DLNM) was used to evaluate the impact of short-term air pollutants exposure on the risk of TOP. Stratified analyses by age (<35 years old, ≥ 35 years old) and season (warm season, cold season) were further conducted. Relative risk (RR) and 95 % confidential interval (95 % CI) were calculated for per interquartile range (IQR) increment in air pollutants during the study period.

RESULTS

PM_2.5, PM₁₀, and O₃ exposure were significantly associated with elevated risk of TOP. The risk of TOP was associated with PM_2.5 exposure from lag11 to lag15 in the single-pollutant model, and the strongest association was observed at lag13 (RR = 1.021, 95%CI:1.002-1.040). PM₁₀ exposure from lag10 to lag15 was associated with increased TOP risk, with the corresponding peak association being at lag13 (RR = 1.020, 95%CI: 1.004-1.037). For O₃, the single-day lag association appeared to be statistically significant from lag26 to lag27, with the highest RR of TOP cases being at lag27 (RR = 1.044, 95%CI: 1.005-1.084). Similar results were observed for pregnancy losses (PL). However, no significantly association between air pollution exposure and the risk of congenital malformations (CM) was found in this study. Stratified analyses showed that pregnant women with more advanced ages were more susceptible to PM_2.5, PM₁₀, and O₃ exposure. The effect of PM_2.5 exposure was statistically significant in cold season subgroups.

CONCLUSION

The findings suggest that exposure to PM_2.5, PM₁₀, and O₃ before pregnancy are associated with the risk of TOP in Lu'an, China, reflecting the significance of preconceptional environmental exposure in the development of adverse pregnancy outcomes.

Associations between air pollution exposure and birth defects: a time series analysis

Air pollution is a serious environmental problem in China. Birth defects are particularly vulnerable to outdoor air pollution. Our study was to evaluate the association between short-term exposure to air pollutants and the risk of birth defects. Daily data including the air pollutants, meteorological characteristics, and birth records were obtained in Hefei, China, during January 2013 to December 2016. The findings showed that PM_2.5, PM₁₀, SO₂, NO₂, and O₃ exposures were positively correlated with the risk of birth defects. Maternal exposure to PM_2.5 and SO₂ during the 4th to 13th gestational weeks was observed to have a significant association with the risk of birth defects, with the maximum effect in the 7th or 8th week for PM_2.5 and the maximum effect in the 7th week for SO₂. The positively significant exposure windows were the 4th to 14th weeks for PM₁₀, the 4th to 12th weeks for NO₂, and the 26th to 35th weeks for O₃, respectively. The strongest associations were observed in the 8th week for PM₁₀, the 7th week for NO₂, and in the 31st or 32nd week for O_3. The findings of this study demonstrate that air pollutants increase the risk of birth defects among women during pregnancy in Hefei, China, which provide evidence for improving the health of pregnant women and neonates in developing countries, and uncovered potential opportunities to reduce or prevent birth defects by proactive measures during pregnancy.

Airborne particulate matter induces oxidative damage, DNA adduct formation and alterations in DNA repair pathways

Air pollution, which includes particulate matter (PM), is classified in group 1 as a carcinogen to humans by the International Agency for Research in Cancer. Specifically, PM exposure has been associated with lung cancer in patients living in highly polluted cities. The precise mechanism by which PM is linked to cancer has not been completely described, and the genotoxicity induced by PM exposure plays a relevant role in cell damage. In this review, we aimed to analyze the types of DNA damage and alterations in DNA repair pathways induced by PM exposure, from both epidemiological and toxicological studies, to comprehend the contribution of PM exposure to carcinogenesis. Scientific evidence supports that PM exposure mainly causes oxidative stress by reactive oxygen species (ROS) and the formation of DNA adducts, specifically by polycyclic aromatic hydrocarbons (PAH). PM exposure also induces double-strand breaks (DSBs) and deregulates the expression of some proteins in DNA repair pathways, precisely, base and nucleotide excision repairs and homologous repair. Furthermore, specific polymorphisms of DNA repair genes could lead to an adverse response in subjects exposed to PM. Nevertheless, information about the effects of PM on DNA repair pathways is still limited, and it has not been possible to conclude which pathways are the most affected by exposure to PM or if DNA damage is repaired properly. Therefore, deepening the study of genotoxic damage and alterations of DNA repair pathways is needed for a more precise understanding of the carcinogenic mechanism of PM.

Air pollution-induced epigenetic changes: disease development and a possible link with hypersensitivity pneumonitis

Air pollution is a serious threat to our health and has become one of the major causes of many diseases including cardiovascular disease, respiratory disease, and cancer. The association between air pollution and various diseases has long been a topic of research interest. However, it remains unclear how air pollution actually impacts health by modulating several important cellular functions. Recently, some evidence has emerged about air pollution-induced epigenetic changes, which are linked with the etiology of various human diseases. Among several epigenetic modifications, DNA methylation represents the most prominent epigenetic alteration underlying the air pollution-induced pathogenic mechanism. Several other types of epigenetic changes, such as histone modifications, miRNA, and non-coding RNA expression, have also been found to have been linked with air pollution. Hypersensitivity pneumonitis (HP), one of the most prevalent forms of interstitial lung diseases (ILDs), is triggered by the inhalation of certain organic and inorganic substances. HP is characterized by inflammation in the tissues around the lungs' airways and may lead to irreversible lung scarring over time. This review, in addition to other diseases, attempts to understand whether certain pollutants influence HP development through such epigenetic modifications.

Maternal Particulate Matter Exposure Impairs Lung Health and Is Associated with Mitochondrial Damage

Relatively little is known about the transgenerational effects of chronic maternal exposure to low-level traffic-related air pollution (TRAP) on the offspring lung health, nor are the effects of removing such exposure before pregnancy. Female BALB/c mice were exposed to PM_2.5 (PM_2.5, 5 µg/day) for 6 weeks before mating and during gestation and lactation; in a subgroup, PM was removed when mating started to model mothers moving to cleaner areas during pregnancy to protect their unborn child (Pre-exposure). Lung pathology was characterised in both dams and offspring. A subcohort of female offspring was also exposed to ovalbumin to model allergic airways disease. PM_2.5 and Pre-exposure dams exhibited airways hyper-responsiveness (AHR) with mucus hypersecretion, increased mitochondrial reactive oxygen species (ROS) and mitochondrial dysfunction in the lungs. Female offspring from PM_2.5 and Pre-exposure dams displayed AHR with increased lung inflammation and mitochondrial ROS production, while males only displayed increased lung inflammation. After the ovalbumin challenge, AHR was increased in female offspring from PM_2.5 dams compared with those from control dams. Using an in vitro model, the mitochondria-targeted antioxidant MitoQ reversed mitochondrial dysfunction by PM stimulation, suggesting that the lung pathology in offspring is driven by dysfunctional mitochondria. In conclusion, chronic exposure to low doses of PM_2.5 exerted transgenerational impairment on lung health.

Mitochondrial-induced Epigenetic Modifications: From Biology to Clinical Translation

Mitochondria are maternally inherited semi-autonomous organelles that play a central role in redox balance, energy metabolism, control of integrated stress responses, and cellular homeostasis. The molecular communication between mitochondria and the nucleus is intricate and bidirectional in nature. Though mitochondrial genome encodes for several key proteins involved in oxidative phosphorylation, several regulatory factors encoded by nuclear DNA are prominent contributors to mitochondrial biogenesis and function. The loss of synergy between this reciprocal control of anterograde (nuclear to mitochondrial) and retrograde (mitochondrial to nuclear) signaling, triggers epigenomic imbalance and affects mitochondrial function and global gene expressions. Recent expansions of our knowledge on mitochondrial epigenomics have offered novel perspectives for the study of several non-communicable diseases including cancer. As mitochondria are considered beacons for pharmacological interventions, new frontiers in targeted delivery approaches could provide opportunities for effective disease management and cure through reversible epigenetic reprogramming. This review focuses on recent progress in the area of mitochondrial-nuclear cross-talk and epigenetic regulation of mitochondrial DNA methylation, mitochondrial micro RNAs, and post-translational modification of mitochondrial nucleoid-associated proteins that hold major opportunities for targeted drug delivery and clinical translation.

Toxic effect and mechanism of ultrafine carbon black on mouse primary splenocytes and two digestive enzymes

This paper investigated the toxic effect and mechanism of ultrafine carbon black (UFCB) on splenocytes and enzymes in the digestive system. It was found that the toxicity of UFCB to splenocytes was dose-dependent. UFCB with a low concentration (<15 μg/mL) had no significant effect on splenocytes while UFCB with high concentration (>15 μg/mL) induced significant oxidative damage with increased content of reactive oxygen species (ROS) (134%) and malonaldehyde (MDA) (222.3%) along with the decreased activity of superoxide dismutase (SOD) (55.63%) and catalase (CAT) (87.73%). Analysis combined cellular and molecular levels indicated that UFCB induced splenocyte toxicity through oxidative stress. The interactions of UFCB with two important digestive enzymes, α-amylase and lipase, were also studied respectively. Results showed that the interaction of UFCB and the two enzymes altered the particle size and fluorescence intensity in both experimental systems. The formation of protein corona also resulted in the contraction of the polypeptide skeleton in both enzymes, which further inhibited their activity. Our work provided basic data on the toxicity of UFCB in the spleen and digestive system and fills the gap in the study of UFPs toxicity. CAPSULE: UFCB induced splenocyte toxicity and enzyme dysfunction through oxidative stress and protein corona formation respectively.

Role of Mitochondrial DNA in Inflammatory Airway Diseases

The mitochondrial genome is a small, circular, and highly conserved piece of DNA which encodes only 13 protein subunits yet is vital for electron transport in the mitochondrion and, therefore, vital for the existence of multicellular life on Earth. Despite this importance, mitochondrial DNA (mtDNA) is located in one of the least-protected areas of the cell, exposing it to high concentrations of intracellular reactive oxygen species (ROS) and threat from exogenous substances and pathogens. Until recently, the quality control mechanisms which ensured the stability of the nuclear genome were thought to be minimal or nonexistent in the mitochondria, and the thousands of redundant copies of mtDNA in each cell were believed to be the primary mechanism of protecting these genes. However, a vast network of mechanisms has been discovered that repair mtDNA lesions, replace and recycle mitochondrial chromosomes, and conduct alternate RNA processing for previously undescribed mitochondrial proteins. New mtDNA/RNA-dependent signaling pathways reveal a mostly undiscovered biochemical landscape in which the mitochondria interface with their host cells/organisms. As the myriad ways in which the function of the mitochondrial genome can affect human health have become increasingly apparent, the use of mitogenomic biomarkers (such as copy number and heteroplasmy) as toxicological endpoints has become more widely accepted. In this article, we examine several pathologies of human airway epithelium, including particle exposures, inflammatory diseases, and hyperoxia, and discuss the role of mitochondrial genotoxicity in the pathogenesis and/or exacerbation of these conditions. © 2021 American Physiological Society. Compr Physiol 11:1485-1499, 2021.

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.

Urban Aerosol Particulate Matter Promotes Necrosis and Autophagy via Reactive Oxygen Species-Mediated Cellular Disorders that are Accompanied by Cell Cycle Arrest in Retinal Pigment Epithelial Cells

Urban particulate matter (UPM) is recognized as a grave public health problem worldwide. Although a few studies have linked UPM to ocular surface diseases, few studies have reported on retinal dysfunction. Thus, the aim of the present study was to evaluate the influence of UPM on the retina and identify the main mechanism of UPM toxicity. In this study, we found that UPM significantly induced cytotoxicity with morphological changes in ARPE-19 human retinal pigment epithelial (RPE) cells and increased necrosis and autophagy but not apoptosis. Furthermore, UPM significantly increased G2/M arrest and simultaneously induced alterations in cell cycle regulators. In addition, DNA damage and mitochondrial dysfunction were remarkably enhanced by UPM. However, the pretreatment with the potent reactive oxygen species (ROS) scavenger N-acetyl-L-cysteine (NAC) effectively suppressed UPM-mediated cytotoxicity, necrosis, autophagy, and cell cycle arrest. Moreover, NAC markedly restored UPM-induced DNA damage and mitochondrial dysfunction. Meanwhile, UPM increased the expression of mitophagy-regulated proteins, but NAC had no effect on mitophagy. Taken together, although further studies are needed to identify the role of mitophagy in UPM-induced RPE injury, the present study provides the first evidence that ROS-mediated cellular damage through necrosis and autophagy is one of the mechanisms of UPM-induced retinal disorders.

PCR-Based Determination of Mitochondrial DNA Copy Number in Multiple Species

Mitochondrial DNA (mtDNA) copy number is a critical component of overall mitochondrial health. In this chapter, we describe methods for simultaneous isolation of mtDNA and nuclear DNA (nucDNA), and measurement of their respective copy numbers using quantitative PCR. Methods differ depending on the species and cell type of the starting material, and availability of specific PCR reagents. We also briefly describe factors that affect mtDNA copy number and discuss caveats to its use as a biomarker.

Associations of blood lead levels with multiple genotoxic biomarkers among workers in China: A population-based study

Carcinogenic effects from low doses of lead (Pb) exposure to populations have been suspected but not concluded. Therefore, a large-scale cross-sectional study was conducted by us to investigate genotoxic effects from Pb exposure during 2016-2018 in North China. Blood lead levels (BLLs) and cumulative blood lead levels (CBLLs) were measured. Multiple relevant biomarkers were used to assess genotoxicity of Pb: mitochondrial DNA copy number (mtDNAcn, n = 871), Comet Tail Intensity (n = 872), γ-H2AX (n = 345), relative telomere length (rTL, n = 757), micronuclei (MN, n = 934) and phosphatidylinositol glycan class A mutation (PIG-A, n = 362). The BLL data show right-skewed distribution, with increase of the median (P25, P75) from 17.4 (8.9, 26.4) μg/dl in 2016 to 18.5 (10.5, 27.2) μg/dl in 2017, and to 20.8 (11.3, 31.0) μg/dl in 2018. Multivariate regression analyses show that mtDNAcn was non-linearly associated with BLLs or CBLLs, i.e. decreased at low levels but increased at the higher levels. Comet and Micronuclei data show positive dose-response relationships with BLLs as well as CBLLs. γ-H2AX data show an overall increased trend with BLLs while rTL data show a shortening trend. No associations were found for PIG-A mutation with Pb exposure. Our findings indicate that current low dose exposure to Pb can still cause health hazards to occupational populations, and the mechanism may be via the induction of DNA & chromosome damage rather than via the mutagenesis pathway.

Effects of air pollution particles (ultrafine and fine particulate matter) on mitochondrial function and oxidative stress - Implications for cardiovascular and neurodegenerative diseases

Environmental pollution is a major cause of global mortality and burden of disease. All chemical pollution forms together may be responsible for up to 12 million annual excess deaths as estimated by the Lancet Commission on pollution and health as well as the World Health Organization. Ambient air pollution by particulate matter (PM) and ozone was found to be associated with an all-cause mortality rate of up to 9 million in the year 2015, with the majority being of cerebro- and cardiovascular nature (e.g. stroke and ischemic heart disease). Recent evidence suggests that exposure to airborne particles and gases contributes to and accelerates neurodegenerative diseases. Especially, airborne toxic particles contribute to these adverse health effects. Whereas it is well established that air pollution in the form of PM may lead to dysregulation of neurohormonal stress pathways and may trigger inflammation as well as oxidative stress, leading to secondary damage of cardiovascular structures, the mechanistic impact of PM-induced mitochondrial damage and dysfunction is not well established. With the present review we will discuss similarities between mitochondrial damage and dysfunction observed in the development and progression of cardiovascular disease and neurodegeneration as well as those adverse mitochondrial pathomechanisms induced by airborne PM.

Comparative profiling of epigenetic modifications among individuals living in different high and low air pollution zones: A pilot study from India.. [DOI: 10.1101/2020.09.15.20194928] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Epigenetic modifications act as an important bridge to regulate the complex network of gene-environment interaction. As these mechanisms determines the gene-expression patterns via regulating the transcriptomic machinery, environmental stress induced epigenetic modifications may interrupt distinct cellular functions resulting into generation of diseased phenotypes. In the present study, we used a multi-city approach to compare the epigenomic signatures of individuals living in two tiers of Indian cities categorized as low-risk and high-risk air pollution zones. The high-risk group reported marked changes in the expression levels of epigenetic modifiers (DNMT1, DNMT3a, EZH2, EHMT2 and HAT), that maintains the levels of specific epigenetic marks essential for appropriate gene functioning. These results also coincided with the observed alterations in the levels of DNA methylation (LINE-1 and % 5mC), and histone modifications (H3 and H4), among the high-risk group. In addition, higher degree of changes reported in the expression profile of a selected miRNA panel in the high-risk group indicated the probability of deregulated transcriptional machinery. This was further confirmed by the analysis of a target gene panel involved in various signalling pathways, which revealed differential expression of the gene transcripts regulating cell cycle, inflammation, cell survival, apoptosis and cell adhesion. Together, our results provide first insights of epigenetic modifications among individuals living in different high and low levels of air pollution zones of India. However, further steps to develop a point-of-care epigenomic assay for human bio-monitoring may be immensely beneficial to reduce the health burden of air pollution especially in lower-middle-income countries.

Clostridium perfringens phospholipase C impairs innate immune response by inducing integrated stress response and mitochondrial-induced epigenetic modifications

Clostridium perfringens, a rod-shaped, gram-positive, anaerobic, spore-forming bacterium is one of the most widely occurring bacterial pathogens, associated with a spectrum of diseases in humans. A major virulence factor during its infection is the enzyme phospholipase C encoded by the plc gene, known as Clostridium perfringens phospholipase C (CpPLC). The present study was designed to understand the role of CpPLC in inducing survival mechanisms and mitochondrial-induced epigenetic changes in a human lymphocyte cell culture model. Following exposure to CpPLC, a significant generation of mitochondrial reactive oxygen species was observed, which coincided with the changes in the expression of vital components of MAP/ERK/RTK signaling cascade that regulates the downstream cellular functions. These disturbances further led to alterations in the mitochondrial genome and functioning. This was supported by the observed upregulation in the expression of mitochondrial fission genes Drp1, Fis1, and Mff, and mitochondrial fusion genes MFN1, MFN2, and OPA1 following CpPLC exposure. CpPLC exposed cells showed upregulation of OMA1, DELE1, and HRI genes involved in the integrated stress response (ISR), which suggests that it may induce the ISR that provides a pro-survival mechanism to the host cell. CpPLC also initiated immune patho-physiologic mechanisms including mitochondrial-induced epigenetic modifications through a mitochondrial-ROS driven signaling pathway. Interestingly, epigenetic machinery not only play a pivotal role in lymphocyte homeostasis by contributing to cell-fate decisions but thought to be one of the mechanisms by which intracellular pathogens survive within the host cells. Importantly, the impairment of mtDNA repair among the CpPLC exposed cells, induced alterations within mtDNA methylation, and led to the deregulation of MT-CO1, MT-ND6, MT-ATPase 6, and MT-ATPase8 gene expression profiles that are important for mitochondrial bioenergetics and subsequent metabolic pathways. This was further confirmed by the changes in the activity of mitochondrial electron chain complexes (complex I, II, III, IV and V). The altered mtDNA methylation profile was also found to be closely associated with the varied expression of mitomiRs and their targets. CpPLC exposed cells showed up-regulation of miR24 expression and down-regulation of miR34a, miR150, and miR155, while the increased expression of mitomiR target genes i.e. of K-Ras, MYC, EGFR, and NF-kβ was also observed in these cells. Altogether, our findings provide novel insights into the derailment of redox signaling machinery in CpPLC treated lymphocytes and its role in the induction of survival mechanisms and mitochondrial-induced epigenetic modifications.

Genome-wide DNA methylation analysis reveals significant impact of long-term ambient air pollution exposure on biological functions related to mitochondria and immune response

Exposure to long-term ambient air pollution is believed to have adverse effects on human health. However, the mechanisms underlying these impacts are poorly understood. DNA methylation, a crucial epigenetic modification, is susceptible to environmental factors and likely involved in these processes. We conducted a whole-genome bisulfite sequencing study on 120 participants from a highly polluted region (HPR) and a less polluted region (LPR) in China, where the HPR had much higher concentrations of five air pollutants (PM_2.5, PM₁₀, SO₂, NO₂, and CO) (fold difference 1.6 to 6.6 times; P value 1.80E-07 to 3.19E-23). Genome-wide methylation analysis revealed 371 DMRs in subjects from the two areas and these DMRs were located primarily in gene regulatory elements such as promoters and enhancers. Gene enrichment analysis showed that DMR-related genes were significantly enriched in diseases related to pulmonary disorders and cancers and in biological processes related to mitochondrial assembly and cytokine production. Further, HPR participants showed a higher mtDNA copy number. Of those identified DMRs, 15 were significantly correlated with mtDNA copy number. Finally, cytokine assay indicated that an increased plasma interleukin-5 level was associated with greater air pollution. Taken together, our findings suggest that exposure to long-term ambient air pollution can lead to alterations in DNA methylation whose functions relate to mitochondria and immune responses.

Association of particulate matter air pollution with leukocyte mitochondrial DNA copy number

BACKGROUND

Ambient particulate matter (PM) has been associated with mitochondrial damage and dysfunction caused by excessive oxidative stress, but the associations between long-term PM exposure and leukocyte mitochondrial DNA copy number (mtDNAcn), a biomarker of mitochondrial dysfunction due to oxidative stress, are less studied.

OBJECTIVES

To investigate the associations between short-, intermediate- and long-term exposure (1-, 3- and 12-months) to different size fractions of PM (PM2.5, PM2.5-10 and PM10) and leukocyte mtDNAcn in a cross-sectional study.

METHODS

The associations between each of the PM exposure metrics with z scores of log-transformed mtDNAcn were examined using generalized linear regression models in 2758 female participants from the Nurses' Health Study (NHS). Monthly exposures to PM were estimated from spatio-temporal prediction models matched to each participants' address history. Potential effect modification by selected covariates was examined using multiplicative interaction terms and subgroup analyses.

RESULTS

In single-size fraction models, increases in all size fractions of PM were associated with decreases in mtDNAcn, although only models with longer averages of PM2.5 reached statistical significance. For example, an interquartile range (IQR) increase in 12-month average ambient PM2.5 (5.5 μg/m3) was associated with a 0.07 [95% confidence interval (95% CI): -0.13, -0.01; p-value = 0.02] decrease in mtDNAcn z score in both basic- and multivariable-adjusted models. Associations for PM2.5 were stronger after controlling for PM2.5-10 in two size-fraction models.

CONCLUSIONS

Our study suggests that long-term exposure to ambient PM2.5 is associated with decreased mtDNAcn in healthy women.

Mitochondrial superoxide mediates PM2.5-induced cytotoxicity in human pulmonary lymphatic endothelial cells

Exposure to airborne fine particulate matter (PM_2.5) is associated with a variety of respiratory health effects and contributes to premature mortality. Lymphatic vessels are instrumental in facilitating the transport of toxic materials away from the lung to maintain alveolar clearance and have been shown to play important roles in lung injury and repair. Despite intense research efforts in delineating the effects of PM_2.5 on blood vascular endothelial cells, the impacts of PM_2.5 on lymphatic endothelial cells (LECs), a specialized subset of endothelial cells that comprise lymphatic vessels, remain enigmatic. Here, we conducted MTT assay and show that treatment of human pulmonary LECs with PM_2.5 suppresses cell viability in a time- and dose-dependent manner. We subsequently performed Annexin V/propidium iodide labeling and demonstrate that PM_2.5 induces LECs apoptosis and necrosis. Furthermore, we found that manganese superoxide dismutase (SOD2) expression and mitochondrial SOD activity were profoundly reduced following PM_2.5 exposure. Mechanistically, we provide compelling evidence that PM_2.5 reduces SOD2 expression through activation of Akt pathway, which leads to a disruption of mitochondrial redox homeostasis characterized by increased accumulation of mitochondrial superoxide. Conversely, mitochondria-targeted SOD mimetic (MitoTEMPO) corrects the disturbed oxidative milieu in PM_2.5-treated LECs. Additionally, MitoTEMPO ameliorates the deleterious impacts of PM_2.5 on mitochondrial DNA integrity and preserves the viability of LECs. Taken together, these novel data support a critical role for mitochondrial superoxide in the pathogenesis of PM_2.5-induced LECs injury and identity mitochondrial-targeted antioxidants as promising therapeutic options to treat environmental lung diseases. Our findings are limited to experimental studies with primary LECs, and future investigations in animal models are warranted to shed light on the precise pathophysiology of lymphatic system in response to PM exposure.

Ambient particulate matter triggers dysfunction of subcellular structures and endothelial cell apoptosis through disruption of redox equilibrium and calcium homeostasis

Ambient particulate matter (APM) is becoming a global environmental problem that seriously jeopardizes public health. Previous evidence hinted that APM correlates to cardiovascular diseases. As a potential target, equilibrium of endothelial cell is a prerequisite for vascular health which could be vulnerably attacked by particles, but the specific mechanisms whereby APM damages endothelial cells have not been fully elucidated. In the current study, based on two classical mechanisms of oxidative stress and intracellular calcium overload, we aimed to explore their roles in APM-induced endothelial cell apoptosis from the perspective of subcellular levels, including endoplasmic reticulum (ER) stress and mitochondrial dysfunction. As a result, PM SRM1648a results in oxidative stress and calcium overload in EA.hy926 cells. Additionally, ERs and mitochondria could be severely disturbed by particles in morphology and function, characterized by swelling ERs, mitochondrial fission and disappearance of cristae, coupled with ER damage, mtROS overproduction and significant reduction in mitochondrial membrane potential (MMP). Adverse effects on these organelles are the prime culprits of following apoptosis in endothelial cells. Fortunately, additional antioxidants and calcium inhibitors could mitigate cellular lesion through improvement of subcellular function. Intriguingly, antioxidants relieve cell stress via both mitochondrial and ER stress-mediated pathways, whereas the role of calcium modulators in cell apoptosis is independent of the mitochondrial pathway but could be explained by amelioration of ER stress. In conclusion, our data basically revealed that internalized PM SRM1648a triggers oxidative stress and calcium influx in EA.hy926 endothelial cells, followed by multiple subcellular damage and eventually contributes to cell death, during which antioxidants and calcium inhibitors confer protective effects.

Effects of Ultrafine Particles in Ambient Air on Primary Health Care Consultations for Diabetes in Children and Elderly Population in Ljubljana, Slovenia: A 5-Year Time-Trend Study

Epidemiological studies indicate that exposure to ultrafine particles (UFP) in ambient air represents an important environmental public health issue. The aim of this study was to determine the association between UFP in ambient air and the daily number of consultations in the primary health care unit due to diabetes mellitus in children and elderly population of the Municipality of Ljubljana. A 5-year time-trend ecological study was carried out for the period between 1 January 2013 and 31 December 2017. The daily number of primary health care consultations due to diabetes mellitus among children and elderly population was observed as the health outcome. Daily mean UFP concentrations (different size from 10 to 100 nm) were measured and calculated. Poisson regression analysis was used to investigate the association between the observed outcome and the daily UFP, particulate matter fine fraction (PM_2.5), and particulate matter coarse fraction (PM₁₀) concentrations, adjusted to other covariates. The results show that the daily number of consultations due to diabetes mellitus were highly significantly associated with the daily concentrations of UFP (10 to 20 nm; p ≤ 0.001 and 20 to 30 nm; p ≤ 0.001) in all age groups and in the elderly population. In observed the population of children, we did not confirm the association. Findings indicate that specified environmental challenges should be addressed by comprehensive public health strategies leading to the coordinated cross-sectoral measures for the reduction of UFP in ambient air and the mitigation of adverse health effects.

Mapping the Mitochondrial Regulation of Epigenetic Modifications in Association With Carcinogenic and Noncarcinogenic Polycyclic Aromatic Hydrocarbon Exposure

Polycyclic aromatic hydrocarbons (PAHs) refer to a ubiquitous group of anthropogenic air pollutants that are generated through incomplete carbon combustion. Although the immunotoxic nature of PAHs has been previously reported, the underlying molecular mechanisms of this effect are not fully understood. In the present study, we investigated the mitochondrial-mediated epigenetic regulation of 2 PAHs, carcinogenic (benzo[a]pyrene; BaP) and noncarcinogenic (anthracene [ANT]), in peripheral lymphocytes. While ANT exposure triggered mitochondrial oxidative damage, no appreciable epigenetic modifications were observed. On the other hand, exposure to BaP perturbed the mitochondrial redox machinery and initiated cascade of epigenetic modifications. Cells exposed to BaP showed prominent changes in the expression of mitochondrial microRNAs (miR-24, miR-34a, miR-150, and miR-155) and their respective gene targets (NF-κβ, MYC, and p53). The exposure of BaP also caused significant alterations in the expression of epigenetic modifiers (DNMT1, HDAC1, HDAC7, KDM3a, EZH2, and P300) and hypomethylation within nuclear and mitochondrial DNA. This further induced methylation of histone tails, which play a crucial role in the regulation of chromatin structure. Overall, our study provides novel mechanistic insights into the mitochondrial regulation of epigenetic modifications in association with PAH-induced immunotoxicity.

Urban air particulate matter induces mitochondrial dysfunction in human olfactory mucosal cells

BACKGROUND

The adverse effects of air pollutants including particulate matter (PM) on the central nervous system is increasingly reported by epidemiological, animal and post-mortem studies in the last decade. Oxidative stress and inflammation are key consequences of exposure to PM although little is known of the exact mechanism. The association of PM exposure with deteriorating brain health is speculated to be driven by PM entry via the olfactory system. How air pollutants affect this key entry site remains elusive. In this study, we investigated effects of urban size-segregated PM on a novel cellular model: primary human olfactory mucosal (hOM) cells.

RESULTS

Metabolic activity was reduced following 24-h exposure to PM without evident signs of toxicity. Results from cytometric bead array suggested a mild inflammatory response to PM exposure. We observed increased oxidative stress and caspase-3/7 activity as well as perturbed mitochondrial membrane potential in PM-exposed cells. Mitochondrial dysfunction was further verified by a decrease in mitochondria-dependent respiration. Transient suppression of the mitochondria-targeted gene, neuronal pentraxin 1 (NPTX1), was carried out, after being identified to be up-regulated in PM2.5-1 treated cells via RNA sequencing. Suppression of NPTX1 in cells exposed to PM did not restore mitochondrial defects resulting from PM exposure. In contrast, PM-induced adverse effects were magnified in the absence of NPTX1, indicating a critical role of this protein in protection against PM effects in hOM cells.

CONCLUSION

Key mitochondrial functions were perturbed by urban PM exposure in a physiologically relevant cellular model via a mechanism involving NPTX1. In addition, inflammatory response and early signs of apoptosis accompanied mitochondrial dysfunction during exposure to PM. Findings from this study contribute to increased understanding of harmful PM effects on human health and may provide information to support mitigation strategies targeted at air pollution.

Cross organelle stress response disruption promotes gentamicin-induced proteotoxicity

Gentamicin is a nephrotoxic antibiotic that causes acute kidney injury (AKI) primarily by targeting the proximal tubule epithelial cell. The development of an effective therapy for gentamicin-induced renal cell injury is limited by incomplete mechanistic insight. To address this challenge, we propose that RNAi signal pathway screening could identify a unifying mechanism of gentamicin-induced cell injury and suggest a therapeutic strategy to ameliorate it. Computational analysis of RNAi signal screens in gentamicin-exposed human proximal tubule cells suggested the cross-organelle stress response (CORE), the unfolded protein response (UPR), and cell chaperones as key targets of gentamicin-induced injury. To test this hypothesis, we assessed the effect of gentamicin on the CORE, UPR, and cell chaperone function, and tested the therapeutic efficacy of enhancing cell chaperone content. Early gentamicin exposure disrupted the CORE, evidenced by a rise in the ATP:ADP ratio, mitochondrial-specific H2O2 accumulation, Drp-1-mediated mitochondrial fragmentation, and endoplasmic reticulum-mitochondrial dissociation. CORE disruption preceded measurable increases in whole-cell oxidative stress, misfolded protein content, transcriptional UPR activation, and its untoward downstream effects: CHOP expression, PARP cleavage, and cell death. Geranylgeranylacetone, a therapeutic that increases cell chaperone content, prevented mitochondrial H2O2 accumulation, preserved the CORE, reduced the burden of misfolded proteins and CHOP expression, and significantly improved survival in gentamicin-exposed cells. We identify CORE disruption as an early and remediable cause of gentamicin proteotoxicity that precedes downstream UPR activation and cell death. Preserving the CORE significantly improves renal cell survival likely by reducing organelle-specific proteotoxicity during gentamicin exposure.

The cellular effects of PM2.5 collected in Chinese Taiyuan and Guangzhou and their associations with polycyclic aromatic hydrocarbons (PAHs), nitro-PAHs and hydroxy-PAHs

Numerous studies have demonstrated adverse effects on human health after exposure to fine particulate matter (PM_2.5). However, it is still not clear how the toxicological effects and the health risks vary among PM samples of different compositions and concentrations. In this study, we examined effects of region- and season-dependent differences of PM_2.5 on cytotoxicity, and the contributions of PAHs, nitro-PAHs (N-PAHs) and hydroxy-PAHs (OH-PAHs) to PM_2.5 toxicity by determining different toxicological indicators in three lung cell lines. The results illustrated significant differences in components concentrations and biological responses elicited by PM_2.5 collected in different cities and seasons. The concentrations of most PAHs, N-PAHs and OH-PAHs were much higher in Taiyuan than in Guangzhou. PM_2.5 from Taiyuan exhibited lower cell viability and higher reactive oxygen species (ROS) and interleukin-6 (IL-6) release on lung cells than those from Guangzhou. Specifically, PM_2.5 collected in summer from Taiyuan caused higher levels of pro-inflammatory responses and oxidative potential than those collected in winter. The correlation analysis between 19 PAHs, 17 N-PAHs and 12 OH-PAHs and the measured indicators demonstrated that PAHs were more related to PM_2.5-induced CCK-8 cytotoxicity and IL-6 release in Taiyuan while N-PAHs and OH-PAHs were more related to PM_2.5-induced CCK-8 cytotoxicity and dithiothreitol (DTT)-based redox activity in Guangzhou, suggesting that the toxicity of PM_2.5 from Taiyuan was mostly correlated with PAHs while the toxicity of PM_2.5 from Guangzhou was closely associated with N-PAHs and OH-PAHs. These results revealed that composition differences in PM_2.5 from different regions and seasons significantly accounted for the differences of their toxicological effects.

PM2.5-bound polycyclic aromatic hydrocarbons and nitro-polycyclic aromatic hydrocarbons inside and outside a primary school classroom in Beijing: Concentration, composition, and inhalation cancer risk

PM_2.5 samples were collected inside and outside a primary school classroom in Beijing in 2015 and analysed for 11 polycyclic aromatic hydrocarbons (PAHs) and 10 nitro-PAHs (NPAHs). In the sampling period in the heating season (namely, the heating period), the median concentrations of indoor and outdoor PAHs were 223 ng/m³ and 264 ng/m³, respectively, and those of indoor and outdoor NPAHs were 3.61 ng/m³ and 5.12 ng/m³, respectively. The concentrations of PAHs and NPAHs were consistently higher in the heating period than those (indoor PAHs: 8.75 ng/m³, outdoor PAHs: 8.95 ng/m³, indoor NPAHs: 0.25 ng/m³, outdoor NPAHs: 0.40 ng/m³) in the sampling period in the non-heating season (namely, the non-heating period). In both periods, total PAHs and total NPAHs in indoor PM_2.5, as well as most individual PAHs and NPAHs, were positively correlated with the outdoor PAH and NPAH concentrations (p < 0.05). This finding suggests that indoor PAHs and NPAHs are largely dependent on outdoor inputs. It is inferred from the diagnostic ratios that PAHs and NPAHs in indoor and outdoor PM_2.5 were affected jointly by coal combustion and vehicular emission in the heating period and mainly derived from vehicle exhaust in the non-heating period. Both indoor and outdoor PM_2.5 showed considerable benzo[a]pyrene equivalent toxicity (BaP_eq), especially in the heating period. Benzo[c]fluorene (BcFE) had relatively low concentrations but large contributions to BaP_eq in both periods. This is the first report of PM_2.5-bound BcFE inside and outside classrooms in Beijing. This result indicates that neglecting PAHs with low abundance but high toxicity leads to a significant underestimation of the overall PAH toxicity. The inhalation cancer risk (CR) of PAHs and NPAHs in PM_2.5 during the primary school year exceeded the acceptable level as defined by the U.S. EPA, emphasizing its impact on the lifetime CR in schoolchildren.

Biomarkers of exposure, effect, and susceptibility in occupational exposure to traffic-related air pollution: A review

There is a well-recognized association between environmental air pollution exposure and several human diseases. However, the relationship between diseases related to occupational air pollution exposure on roads and high levels of traffic-related air pollutants (TRAPs) is less substantiated. Biomarkers are essential tools in environmental and occupational toxicology, and studies on new biomarkers are increasingly relevant due to the need to determine early biomarkers to be assessed in exposure conditions. This review aimed to investigate the main advances in the biomonitoring of subjects occupationally exposed to air pollution, as well as to summarize the biomarkers of exposure, effect, and susceptibility. Furthermore, we discuss how biomarkers could be used to complement the current application of methods used to assess occupational exposures to xenobiotics present in air pollution. The databases used in the preparation of this review were PubMed, Scopus, and Science Direct. Considering the significant deleterious effects on health associated with chronic occupational exposure to xenobiotics, this topic deserves attention. As it is difficult to avoid occupational exposure to TRAPs, biomonitoring should be applied as a strategy to reduce the toxic effects of workplace exposure.

Urban PM2.5 Induces Cellular Toxicity, Hormone Dysregulation, Oxidative Damage, Inflammation, and Mitochondrial Interference in the HRT8 Trophoblast Cell Line

Objective: Epidemiological studies have found air pollution to be a driver of adverse pregnancy outcomes, including gestational diabetes, low term birth weight and preeclampsia. It is unknown what biological mechanisms are involved in this process. A first trimester trophoblast cell line (HTR-8/SVneo) was exposed to various concentrations of PM2.5 (PM2.5) in order to elucidate the effect of urban particulate matter (PM) of size <2.5 μm on placental function. Methods: PM2.5 were collected at a site representative of urban traffic and dispersed in cell media by indirect and direct sonication. The HTR-8 cells were grown under standard conditions. Cellular uptake was studied after 24 and 48 h of exposure by transmission electron microscopy (TEM). The secretion of human chorionic gonadotropin (hCG), progesterone, and Interleukin-6 (IL-6) was measured by ELISA. Changes in membrane integrity and H₂O₂ production were analyzed using the CellTox^TM Green Cytotoxicity and ROSGlo^TM assays. Protease activity was evaluated by MitoTox^TM assay. Mitochondrial function was assessed through high resolution respirometry in an Oroboros O2k-FluoRespirometer, and mitochondrial content was quantified by citrate synthase activity. Results: TEM analysis depicted PM2.5 cellular uptake and localization of the PM2.5 to the mitochondria after 24 h. The cells showed aggregated cytoskeleton and generalized necrotic appearance, such as chromatin condensation, organelle swelling and signs of lost membrane integrity. The mitochondria displayed vacuolization and disruption of cristae morphology. At 48 h exposure, a significant drop in hCG secretion and a significant increase in progesterone secretion and IL-6 production occurred. At 48 h exposure, a five-fold increase in protease activity and a significant alteration of H₂O₂ production was observed. The HTR-8 cells exhibited evidence of increased cytotoxicity with increasing exposure time and dose of PM2.5. No significant difference in mitochondrial respiration or mitochondrial mass could be demonstrated. Conclusion: Following exposure to air pollution, intracellular accumulation of PM may contribute to the placental dysfunction associated with pregnancy outcomes, such as preeclampsia and intrauterine growth restriction, through their direct and indirect effects on trophoblast protein secretion, hormone regulation, inflammatory response, and mitochondrial interference.

Deciphering the Code between Air Pollution and Disease: The Effect of Particulate Matter on Cancer Hallmarks

Air pollution has been recognized as a global health problem, causing around 7 million deaths worldwide and representing one of the highest environmental crises that we are now facing. Close to 30% of new lung cancer cases are associated with air pollution, and the impact is more evident in major cities. In this review, we summarize and discuss the evidence regarding the effect of particulate matter (PM) and its impact in carcinogenesis, considering the “hallmarks of cancer” described by Hanahan and Weinberg in 2000 and 2011 as a guide to describing the findings that support the impact of particulate matter during the cancer continuum.

Exposure to ultrafine particulate matter induces NF-κβ mediated epigenetic modifications

Exposure to ultrafine particulate matter (PM0.1) is positively associated with the etiology of different acute and chronic disorders; however, the in-depth biological imprints that link these submicron particles with the disturbances in the epigenomic machinery are not well defined. Earlier, we showed that exposure to these particles causes significant disturbances in the mitochondrial machinery and triggers PI-3-kinase mediated DNA damage responses. In the present study, we aimed to further understand the epigenomic insights of the ultrafine PM exposure. The higher levels of intracellular reactive oxygen species and depleted Nrf-2 in ultrafine PM exposed cells reconfirmed its potential to induce oxidative stress. Importantly, the observed increase in the levels of NF-κβ and associated cytokines among exposed cells suggested the activation of NF-κβ mediated inflammatory loop which potentially serves as a platform for initiating epigenetic insinuations. This fact was strongly supported by the altered miRNA expression profile of the ultrafine PM exposed cells. These NF-κβ induced miRNA alterations were also found to be associated with other epigenetic targets as the exposed cells showed higher expression levels of DNA methyltransferases which positively corresponded with the global changes in DNA methylation levels. Upon further analysis, significant alterations in histone code were also reported in ultrafine PM exposed cells. Conclusively our results suggested that NF-κβ acts as an inflammatory switch that possesses the potential to induce genome-wide epigenetic modification upon ultrafine PM exposure.

In Vivo Comparative Study on Acute and Sub-acute Biological Effects Induced by Ultrafine Particles of Different Anthropogenic Sources in BALB/c Mice

Exposure to ultrafine particles (UFPs) leads to adverse effects on health caused by an unbalanced ratio between UFPs deposition and clearance efficacy. Since air pollution toxicity is first direct to cardiorespiratory system, we compared the acute and sub-acute effects of diesel exhaust particles (DEP) and biomass burning-derived particles (BB) on bronchoalveolar Lavage Fluid (BALf), lung and heart parenchyma. Markers of cytotoxicity, oxidative stress and inflammation were analysed in male BALB/c mice submitted to single and repeated intra-tracheal instillations of 50 μg UFPs. This in-vivo study showed the activation of inflammatory response (COX-2 and MPO) after exposure to UFPs, both in respiratory and cardiovascular systems. Exposure to DEP results also in pro- and anti-oxidant (HO-1, iNOS, Cyp1b1, Hsp70) protein levels increase, although, stress persist only in cardiac tissue under repeated instillations. Statistical correlations suggest that stress marker variation was probably due to soluble components and/or mediators translocation of from first deposition site. This mechanism, appears more important after repeated instillations, since inflammation and oxidative stress endure only in heart. In summary, chemical composition of UFPs influenced the activation of different responses mediated by their components or pro-inflammatory and pro-oxidative molecules, indicating DEP as the most damaging pollutant in the comparison.