Oxidant-induced epithelial alarmin pathway mediates lung inflammation and functional decline following ultrafine carbon and ozone inhalation co-exposure

The effect of tropospheric low-value ozone exposure on the mortality risk of ischemic heart disease and stroke on the example of Yibin (southwestern China)

The association of low-level ozone (O3) exposure with the mortality risk of ischemic heart disease (IHD) and stroke remains to be investigated. This study aimed to investigate the relationship between low-level O3 exposure and mortality risk of IHD and stroke in Yibin, a city in southwestern China. A Poisson distribution lagged nonlinear model was used to assess the effect of O3 exposure on IHD and stroke mortality and to explore the susceptible population according to gender and age subgroups and the susceptible season according to seasonal subgroups and to analyse the health effects under low O3 exposure compared with high O3 exposure. The mean O3 exposure concentration from 2014 to 2020 was approximately 48.3 μg/m3. There was a major lagged effect of O3 exposure on IHD and stroke. For every 10.0 μg/m3 increase in O3 concentration, the cumulative risks of death for the two diseases were 1.0211 (95% Confidence Interval [CI]: 1.0064, 1.0358) and 1.0211 (95% CI: 1.0064, 1.0357), respectively. The mortality risks of IHD and stroke for women were 1.0064 (95% CI: 1.0016, 1.0113) and 1.0030 (95% CI: 1.0008, 1.0051), and for those aged > 65 years, they were 1.0082 (95% CI: 1.0026, 1.0139) and 1.0018 (95% CI: 1.0002, 1.0034), and the mortality risks in the warm season were 1.0043 (95% CI: 1.0007, 1.0080) and 1.0038 (95% CI: 1.0005, 1.0072), respectively. The introduction of other pollutants (PM2.5, PM10, NO2, CO) to construct a dual-pollutant model showed that the effect of O3 on the mortality risk of IHD and stroke remained statistically significant. This study consolidates the evidence for a positive correlation between low-level O3 exposure and the mortality risk of IHD and stroke. The findings provide preliminary exploratory insights into the potential impact of air pollution on these diseases, offering a valuable reference for future research.

Air Pollution and Effects of Tropospheric Ozone (O3) on Public Health

Air pollution is a significant and widespread issue that presents serious challenges for both human health and the environment because of the presence of a variety of harmful substances in the air, such as tropospheric ozone (O3), particulate matter (PM10), nitrogen oxides (NOx), sulfur dioxide (SO2), and carbon monoxide (CO). In this research, the aim is to evaluate the current evidence for the harmful effects of air pollution on human health, focusing on tropospheric ozone, and to highlight the need for further research in the future. The objective is to evaluate recent data on the respiratory and cardiovascular risks caused by air pollution, the potential association between climate change due to air pollution and human disorders, and the subsequent economic burden. A systematic search of the literature is conducted using PubMed, Scopus, Web of Science, and regulatory reports (EPA), focusing on peer-reviewed studies, epidemiological analyses, and clinical and experimental studies. The key findings indicate that O3 exposure contributes to inflammatory lung injury and to the worsening of preexisting conditions like asthma and COPD, is associated with cancer, and also has numerous negative impacts on neurological, metabolic, and reproductive health, combined with increased healthcare costs. These findings highlight the significance of O3 pollution as a major public health concern, emphasizing the need for immediate measures to decrease emissions and effective policies to protect the climate and the health of the individuals.

Short-Term Effect of Ozone Exposure on Small Airway Function in Adult Asthma Patients with PM2.5 Exacerbating the Effect

Ambient ozone (O3) has been associated with asthma symptoms and exacerbations. The impairment of small airway function leads to worse control, more frequent exacerbations and increased bronchial hyperresponsiveness in asthma patients. However, the impact of O3 on small airway function in asthma remains underexplored. Our longitudinal observational study enrolled 312 adult asthma patients and collected a total of 399 lung function records. We applied a linear mixed-effects model to analyze the associations between ambient O3 exposure at different lag days (from lag0 to lag7) and small airway function parameters, including forced expiratory flow (FEF) at 50%, 75% and 25-75% of forced vital capacity (FVC) predicted (FEF50%pred, FEF75%pred and FEF25-75%pred). Significant associations were found between ambient O3 levels and reductions in FEF50%pred, FEF75%pred and FEF25-75%pred, with the effects being most pronounced for exposure at lag0. Further analysis indicated that fine particulate matter (PM2.5) and its main components, including black carbon, organic matter, sulfate, nitrate and ammonium, exacerbated the detrimental effects of O3 on small airway function. Additionally, stronger O3 effects were found in asthma patients aged over 40 years, those with a body mass index ≥ 25 kg/m2, and individuals with allergic asthma. These results provide new insights into the impact of O3 on small airway function, offering fresh insights into asthma exacerbation mechanisms and underscoring the critical need to address composite pollutants for more effective asthma management.

Ozone-induced lung injury and inflammation: Pathways and therapeutic targets for pulmonary diseases caused by air pollutants

Exposure to ambient Ozone (O3) air pollution directly causes by its oxidative properties, respiratory epithelial cell injury, and cell death, which promote inflammation and hyperreactivity, posing a significant public health concern. Recent clinical and experimental studies have made strides in elucidating the mechanisms underlying O3-induced epithelial cell injury, inflammation, and airway hyperreactivity, which are discussed herein. The current data suggest that O3-induced oxidative stress is a central event-inducing oxeiptotic cell death pathway. O3-induced epithelial barrier damage and cell death, triggering the release of alarmins and damage-associated molecular patterns (DAMPs), with subsequent endogenous activation of Toll-like receptors (TLRs), DNA sensing pathways, and inflammasomes, activating interleukin-1-Myd88 inflammatory pathway with the production of a range of chemokines and cytokines. This cascade orchestrates lung tissue-resident cell activation in response to O3 in leukocyte and non-leukocyte populations, driving sterile innate immune response. Chronic inflammatory response to O3, by repeated exposures, supports a mixed phenotype combining asthma and emphysema, in which their exacerbation by other particulate pollutants potentially culminates in respiratory failure. We use data from lung single-cell transcriptomics to map genes of O3-damage sensing and signaling pathways to lung cells and thereby highlight potential hotspots of O3 responses. Deeper insights into these pathological pathways might be helpful for the identification of novel therapeutic targets and strategies.

Synergistic Toxicity of Fine Particulate Matter and Ozone and Their Underlying Mechanisms

The co-occurrence of fine particulate matter (PM2.5) and ozone has emerged as a critical environmental challenge in recent years. The individual harmful impacts of PM2.5 and ozone exposure have been well studied; however, their combined toxicity under co-exposure conditions remains mechanistically undefined. This paper provides an extensive evaluation of the current pollution levels, epidemiological investigation, and new findings on the toxicological mechanisms of combined exposure to PM2.5 and ozone. The synergistic toxicity of PM2.5 and ozone depends on different factors, including the physicochemical properties of PM2.5, the dose and duration of exposure, and the specific target organs. Through extensive research, we identified the main targets of toxic responses to PM2.5 and ozone exposure and summarized their synergistic toxic mechanisms. Given the current research priorities, there is an urgent need to improve scientific research regarding PM2.5 and ozone co-exposure with priority given to characterizing their properties and toxicological responses while updating relevant guidelines and standards.

Health effects associated with ozone in China: A systematic review

As the ozone (O3) pollution becomes severe in China, it poses a threat to human health. Currently, studies on the impacts of O3 on different regions and groups are limited. This review systematically summarizes the relationship between O3 pollution and mortality and morbidity across the nation, regions, and cities in China, with a focus on the regional and group-specific studies. Then, we clarify the overall limitations in the research data, methods, and subjects. In addition, we briefly discuss the mechanisms by which O3 exposure affects human health, analyzing the effects of O3 on human health under heatwaves (temperature) condition, multi-pollutant modeling, and future climate scenarios. Finally, we give some suggestions for future research directions. Studies found that increased risks of premature mortality and morbidity of respiratory and cardiovascular diseases are closely associated with high concentration O3 exposure. Besides, the old and children are sensitive groups, more studies are needed estimate the risk of their health associated with O3 pollution. Severe O3 pollution in Northern and Eastern China, has significantly increased premature mortality. O3 pollution has led to decreased lung function in the elderly in East China, and a higher asthma risk among young people in South China. Comparing with other regions, less research studied the relationship between O3 pollution and health of local people in Southwest, Central, Northeast, and Northwest Regions. Therefore, it is necessary to enhance research in these regions, with a particular emphasis on the distinctive health consequences of O3 pollution in these regions. Given the diversity of regions and research groups, comprehensive comparison is crucial for determining the impact of O3 pollution on human health in China.

Intermittent ozone inhalation during house dust mite-induced sensitization primes for adverse asthma phenotype

The ability of air pollution to induce acute exacerbation of asthma is well documented. However, the ability of ozone (O3), the most reactive gaseous component of air pollution, to function as a modulator during sensitization is not well established. C57BL/6 J male mice were intranasally sensitized to house dust mite (HDM) (40 μg/kg) for 3 weeks on alternate days in parallel with once-a-week O3 exposure (1 ppm). Mice were euthanized 24 h following the last HDM challenge. Lung lavage, histology, lung function (both forced oscillation and forced expiration-based), immune cell profiling, inflammation (pulmonary and systemic), and immunoglobulin production were assessed. Compared to HDM alone, HDM + O3 leads to a significant increase in peribronchial inflammation (p < 0.01), perivascular inflammation (p < 0.001) and methacholine-provoked large airway hyperreactivity (p < 0.05). Serum total IgG and IgE and HDM-specific IgG1 were 3-5 times greater in HDM + O3 co-exposure compared to PBS and O3-exposed groups. An increase in activated/mature lung total and monocyte-derived dendritic cells (p < 0.05) as well as T-activated, and T memory lymphocyte subset numbers (p < 0.05) were noted in the HDM + O3 group compared to HDM alone group. Concurrent O3 inhalation and HDM sensitization also caused significantly greater (p < 0.05) lung tissue interleukin-17 pathway gene expression and mediator levels in the serum. Redox imbalance was manifested by impaired lung antioxidant defense and increased oxidants. O3 inhalation during allergic sensitization coalesces in generating a significantly worse TH17 asthmatic phenotype.

Using Rapid Prototyping to Develop a Cell-Based Platform with Electrical Impedance Sensor Membranes for In Vitro RPMI2650 Nasal Nanotoxicology Monitoring

Due to advances in additive manufacturing and prototyping, affordable and rapid microfluidic sensor-integrated assays can be fabricated using additive manufacturing, xurography and electrode shadow masking to create versatile platform technologies aimed toward qualitative assessment of acute cytotoxic or cytolytic events using stand-alone biochip platforms in the context of environmental risk assessment. In the current study, we established a nasal mucosa biosensing platform using RPMI2650 mucosa cells inside a membrane-integrated impedance-sensing biochip using exclusively rapid prototyping technologies. In a final proof-of-concept, we applied this biosensing platform to create human cell models of nasal mucosa for monitoring the acute cytotoxic effect of zinc oxide reference nanoparticles. Our data generated with the biochip platform successfully monitored the acute toxicity and cytolytic activity of 6 mM zinc oxide nanoparticles, which was non-invasively monitored as a negative impedance slope on nasal epithelial models, demonstrating the feasibility of rapid prototyping technologies such as additive manufacturing and xurography for cell-based platform development.

Molybdenum Nanodots for Acute Lung Injury Therapy

Acute respiratory disease syndrome (ARDS) is a common critical disease with high morbidity and mortality rates, yet specific and effective treatments for it are currently lacking. ARDS was especially apparent and rampant during the COVID-19 pandemic. Excess reactive oxygen species (ROS) production and an uncontrolled inflammatory response play a critical role in the disease progression of ARDS. Herein, we developed molybdenum nanodots (MNDs) as a functional nanomaterial with ultrasmall size, good biocompatibility, and excellent ROS scavenging ability for the treatment of acute lung injury (ALI). MNDs, which were administered intratracheally, significantly ameliorated lung oxidative stress, inflammatory response, protein permeability, and histological severity in ALI mice without inducing any safety issues. Importantly, transcriptomics analysis indicated that MNDs protected lung tissues by inhibiting the activation of the Nod-like receptor protein 3 (NLRP3)-dependent pyroptotic pathway. This work presents a promising therapeutic agent for patients suffering from ARDS.

Effects of Ambient O3 on Respiratory Mortality, Especially the Combined Effects of PM2.5 and O3

BACKGROUND

In China, the increasing concentration of ozone (O3) has emerged as a significant air pollution issue, leading to adverse effects on public health, particularly the respiratory system. Despite the progress made in managing air pollution in China, it is crucial to address the problem of environmental O3 pollution at present.

METHODS

The connection between O3 exposure and respiratory mortality in Shenyang, China, from 2014 to 2018 was analyzed by a time-series generalized additive regression model (GAM) with quasi-Poisson regression. Additionally, the potential combined effects of fine particulate matter (PM2.5) and O3 were investigated using the synergy index (SI).

RESULTS

Our findings indicate that each 10 μg/m3 increase in O3 at lag 2 days was associated with a maximum relative risk (RR) of 1.0150 (95% CI: 1.0098-1.0202) for respiratory mortality in the total population. For individuals aged ≥55 years, unmarried individuals, those engaged in indoor occupations, and those with low educational attainment, each 10 μg/m3 increase in O3 at lag 07 days was linked to RR values of 1.0301 (95% CI: 1.0187-1.0417), 1.0437 (95% CI: 1.0266-1.0610), 1.0317 (95% CI: 1.0186-1.0450), and 1.0346 (95% CI: 1.0222-1.0471), respectively. Importantly, we discovered a synergistic effect of PM2.5 and O3, resulting in an SI of 2.372 on the occurrence of respiratory mortality.

CONCLUSIONS

This study confirmed a positive association between O3 exposure and respiratory mortality. Furthermore, it highlighted the interaction between O3 and PM2.5 in exacerbating respiratory deaths.

Effect of altered human exposome on the skin and mucosal epithelial barrier integrity

Pollution in the world and exposure of humans and nature to toxic substances is continuously worsening at a rapid pace. In the last 60 years, human and domestic animal health has been challenged by continuous exposure to toxic substances and pollutants because of uncontrolled growth, modernization, and industrialization. More than 350,000 new chemicals have been introduced to our lives, mostly without any reasonable control of their health effects and toxicity. A plethora of studies show exposure to these harmful substances during this period with their implications on the skin and mucosal epithelial barrier and increasing prevalence of allergic and autoimmune diseases in the context of the "epithelial barrier hypothesis". Exposure to these substances causes an epithelial injury with peri-epithelial inflammation, microbial dysbiosis and bacterial translocation to sub-epithelial areas, and immune response to dysbiotic bacteria. Here, we provide scientific evidence on the altered human exposome and its impact on epithelial barriers.

Lung-gut axis of microbiome alterations following co-exposure to ultrafine carbon black and ozone

BACKGROUND

Microbial dysbiosis is a potential mediator of air pollution-induced adverse outcomes. However, a systemic comparison of the lung and gut microbiome alterations and lung-gut axis following air pollution exposure is scant. In this study, we exposed male C57BL/6J mice to inhaled air, CB (10 mg/m3), O3 (2 ppm) or CB + O3 mixture for 3 h/day for either one day or four consecutive days and were euthanized 24 h post last exposure. The lung and gut microbiome were quantified by 16 s sequencing.

RESULTS

Multiple CB + O3 exposures induced an increase in the lung inflammatory cells (neutrophils, eosinophils and B lymphocytes), reduced absolute bacterial load in the lungs and increased load in the gut. CB + O3 exposure was more potent as it decreased lung microbiome alpha diversity just after a single exposure. CB + O3 co-exposure uniquely increased Clostridiaceae and Prevotellaceae in the lungs. Serum short chain fatty acids (SCFA) (acetate and propionate) were increased significantly only after CB + O3 co-exposure. A significant increase in SCFA producing bacterial families (Ruminococcaceae, Lachnospiraceae, and Eubacterium) were also observed in the gut after multiple exposures. Co-exposure induced significant alterations in the gut derived metabolite receptors/mediator (Gcg, Glp-1r, Cck) mRNA expression. Oxidative stress related mRNA expression in lungs, and oxidant levels in the BALF, serum and gut significantly increased after CB + O3 exposures.

CONCLUSION

Our study confirms distinct gut and lung microbiome alterations after CB + O3 inhalation co-exposure and indicate a potential homeostatic shift in the gut microbiome to counter deleterious impacts of environmental exposures on metabolic system.

Air pollution and respiratory infections: the past, present, and future

Air pollution levels across the globe continue to rise despite government regulations. The increase in global air pollution levels drives detrimental human health effects, including 7 million premature deaths every year. Many of these deaths are attributable to increased incidence of respiratory infections. Considering the COVID-19 pandemic, an unprecedented public health crisis that has claimed the lives of over 6.5 million people globally, respiratory infections as a driver of human mortality is a pressing concern. Therefore, it is more important than ever to understand the relationship between air pollution and respiratory infections so that public health measures can be implemented to ameliorate further morbidity and mortality. This article aims to review the current epidemiologic and basic science research on interactions between air pollution exposure and respiratory infections. The first section will present epidemiologic studies organized by pathogen, followed by a review of basic science research investigating the mechanisms of infection, and then conclude with a discussion of areas that require future investigation.

The Cultivation Modality and Barrier Maturity Modulate the Toxicity of Industrial Zinc Oxide and Titanium Dioxide Nanoparticles on Nasal, Buccal, Bronchial, and Alveolar Mucosa Cell-Derived Barrier Models

As common industrial by-products, airborne engineered nanomaterials are considered important environmental toxins to monitor due to their potential health risks to humans and animals. The main uptake routes of airborne nanoparticles are nasal and/or oral inhalation, which are known to enable the transfer of nanomaterials into the bloodstream resulting in the rapid distribution throughout the human body. Consequently, mucosal barriers present in the nose, buccal, and lung have been identified and intensively studied as the key tissue barrier to nanoparticle translocation. Despite decades of research, surprisingly little is known about the differences among various mucosa tissue types to tolerate nanoparticle exposures. One limitation in comparing nanotoxicological data sets can be linked to a lack of harmonization and standardization of cell-based assays, where (a) different cultivation conditions such as an air-liquid interface or submerged cultures, (b) varying barrier maturity, and (c) diverse media substitutes have been used. The current comparative nanotoxicological study, therefore, aims at analyzing the toxic effects of nanomaterials on four human mucosa barrier models including nasal (RPMI2650), buccal (TR146), alveolar (A549), and bronchial (Calu-3) mucosal cell lines to better understand the modulating effects of tissue maturity, cultivation conditions, and tissue type using standard transwell cultivations at liquid-liquid and air-liquid interfaces. Overall, cell size, confluency, tight junction localization, and cell viability as well as barrier formation using 50% and 100% confluency was monitored using trans-epithelial-electrical resistance (TEER) measurements and resazurin-based Presto Blue assays of immature (e.g., 5 days) and mature (e.g., 22 days) cultures in the presence and absence of corticosteroids such as hydrocortisone. Results of our study show that cellular viability in response to increasing nanoparticle exposure scenarios is highly compound and cell-type specific (TR146 6 ± 0.7% at 2 mM ZnO (ZnO) vs. ~90% at 2 mM TiO2 (TiO2) for 24 h; Calu3 93.9 ± 4.21% at 2 mM ZnO vs. ~100% at 2 mM TiO2). Nanoparticle-induced cytotoxic effects under air-liquid cultivation conditions declined in RPMI2650, A549, TR146, and Calu-3 cells (~0.7 to ~0.2-fold), with increasing 50 to 100% barrier maturity under the influence of ZnO (2 mM). Cell viability in early and late mucosa barriers where hardly influenced by TiO2 as well as most cell types did not fall below 77% viability when added to Individual ALI cultures. Fully maturated bronchial mucosal cell barrier models cultivated under ALI conditions showed less tolerance to acute ZnO nanoparticle exposures (~50% remaining viability at 2 mM ZnO for 24 h) than the similarly treated but more robust nasal (~74%), buccal (~73%), and alveolar (~82%) cell-based models.

Aerosol physicochemical determinants of carbon black and ozone inhalation co-exposure induced pulmonary toxicity

Air pollution accounts for more than 7 million premature deaths worldwide. Using ultrafine carbon black (CB) and ozone (O3) as a model for an environmental co-exposure scenario, the dose response relationships in acute pulmonary injury and inflammation were determined by generating, characterizing, and comparing stable concentrations of CB aerosols (2.5, 5.0, 10.0 mg/m3), O3 (0.5, 1.0, 2.0 ppm) with mixture CB + O3 (2.5 + 0.5, 5.0 + 1.0, 10.0 + 2.0). C57BL6 male mice were exposed for 3 h by whole body inhalation and acute toxicity determined after 24 h. CB itself did not cause any alteration, however, a dose response in pulmonary injury/inflammation was observed with O3 and CB + O3. This increase in response with mixtures was not dependent on the uptake but was due to enhanced reactivity of the particles. Benchmark dose modeling showed several-fold increase in potency with CB + O3 compared with CB or O3 alone. Principal component analysis provided insight into response relationships between various doses and treatments. There was a significant correlation in lung responses with charge-based size distribution, total/alveolar deposition, oxidant generation, and antioxidant depletion potential. Lung tissue gene/protein response demonstrated distinct patterns that are better predicted by either particle dose/aerosol responses (interleukin-1β, keratinocyte chemoattractant, transforming growth factor beta) or particle reactivity (thymic stromal lymphopoietin, interleukin-13, interleukin-6). Hierarchical clustering showed a distinct signature with high dose and a similarity in mRNA expression pattern of low and medium doses of CB + O3. In conclusion, we demonstrate that the biological outcomes from CB + O3 co-exposure are significantly greater than individual exposures over a range of aerosol concentrations and aerosol characteristics can predict biological outcome.

Redox imbalance in COVID-19 pathophysiology

Background

The pathophysiologic significance of redox imbalance is unquestionable as numerous reports and topic reviews indicate alterations in redox parameters during corona virus disease 2019 (COVID-19). However, a more comprehensive understanding of redox-related parameters in the context of COVID-19-mediated inflammation and pathophysiology is required.

Methods

COVID-19 subjects (n = 64) and control subjects (n = 19) were enrolled, and blood was drawn within 72 h of diagnosis. Serum multiplex assays and peripheral blood mRNA sequencing was performed. Oxidant/free radical (electron paramagnetic resonance (EPR) spectroscopy, nitrite-nitrate assay) and antioxidant (ferrous reducing ability of serum assay and high-performance liquid chromatography) were performed. Multivariate analyses were performed to evaluate potential of indicated parameters to predict clinical outcome.

Results

Significantly greater levels of multiple inflammatory and vascular markers were quantified in the subjects admitted to the ICU compared to non-ICU subjects. Gene set enrichment analyses indicated significant enhancement of oxidant related pathways and biochemical assays confirmed a significant increase in free radical production and uric acid reduction in COVID-19 subjects. Multivariate analyses confirmed a positive association between serum levels of VCAM-1, ICAM-1 and a negative association between the abundance of one electron oxidants (detected by ascorbate radical formation) and mortality in COVID subjects while IL-17c and TSLP levels predicted need for intensive care in COVID-19 subjects.

Conclusion

Herein we demonstrate a significant redox imbalance during COVID-19 infection affirming the potential for manipulation of oxidative stress pathways as a new therapeutic strategy COVID-19. However, further work is requisite for detailed identification of oxidants (O₂^•-, H₂O₂ and/or circulating transition metals such as Fe or Cu) contributing to this imbalance to avoid the repetition of failures using non-specific antioxidant supplementation.

Whole-body inhalation of nano-sized carbon black: a surrogate model of military burn pit exposure

OBJECTIVE

Chronic multisymptom illness (CMI) is an idiopathic disease affecting thousands of U.S. Veterans exposed to open-air burn pits emitting aerosolized particulate matter (PM) while serving in Central and Southwest Asia and Africa. Exposure to burn pit PM can result in profound biologic consequences including chronic fatigue, impaired cognition, and respiratory diseases. Dysregulated or unresolved inflammation is a possible underlying mechanism for CMI onset. We describe a rat model of whole-body inhalation exposure using carbon black nanoparticles (CB) as a surrogate for military burn pit-related exposure. Using this model, we measured biomarkers of inflammation in multiple tissues.

RESULTS

Male Sprague Dawley rats were exposed to CB aerosols by whole body inhalation (6 ± 0.83 mg/m3). Proinflammatory biomarkers were measured in multiple tissues including arteries, brain, lung, and plasma. Biomarkers of cardiovascular injury were also assayed in plasma. CB inhalation exposure increased CMI-related proinflammatory biomarkers such as IFN-γ and TNFα in multiple tissue samples. CB exposure also induced cardiovascular injury markers (adiponectin, MCP1, sE-Selectin, sICam-1 and TIMP1) in plasma. These findings support the validity of our animal exposure model for studies of burn pit-induced CMI. Future studies will model more complex toxicant mixtures as documented at multiple burn pit sites.

Transcriptomics of single dose and repeated carbon black and ozone inhalation co-exposure highlight progressive pulmonary mitochondrial dysfunction

BACKGROUND

Air pollution is a complex mixture of particles and gases, yet current regulations are based on single toxicant levels failing to consider potential interactive outcomes of co-exposures. We examined transcriptomic changes after inhalation co-exposure to a particulate and a gaseous component of air pollution and hypothesized that co-exposure would induce significantly greater impairments to mitochondrial bioenergetics. A whole-body inhalation exposure to ultrafine carbon black (CB), and ozone (O3) was performed, and the impact of single and multiple exposures was studied at relevant deposition levels. C57BL/6 mice were exposed to CB (10 mg/m3) and/or O3 (2 ppm) for 3 h (either a single exposure or four independent exposures). RNA was isolated from lungs and mRNA sequencing performed using the Illumina HiSeq. Lung pathology was evaluated by histology and immunohistochemistry. Electron transport chain (ETC) activities, electron flow, hydrogen peroxide production, and ATP content were assessed.

RESULTS

Compared to individual exposure groups, co-exposure induced significantly greater neutrophils and protein levels in broncho-alveolar lavage fluid as well as a significant increase in mRNA expression of oxidative stress and inflammation related genes. Similarly, a significant increase in hydrogen peroxide production was observed after co-exposure. After single and four exposures, co-exposure revealed a greater number of differentially expressed genes (2251 and 4072, respectively). Of these genes, 1188 (single exposure) and 2061 (four exposures) were uniquely differentially expressed, with 35 mitochondrial ETC mRNA transcripts significantly impacted after four exposures. Both O3 and co-exposure treatment significantly reduced ETC maximal activity for complexes I (- 39.3% and - 36.2%, respectively) and IV (- 55.1% and - 57.1%, respectively). Only co-exposure reduced ATP Synthase activity (- 35.7%) and total ATP content (30%). Further, the ability for ATP Synthase to function is limited by reduced electron flow (- 25%) and translation of subunits, such as ATP5F1, following co-exposure.

CONCLUSIONS

CB and O3 co-exposure cause unique transcriptomic changes in the lungs that are characterized by functional deficits to mitochondrial bioenergetics. Alterations to ATP Synthase function and mitochondrial electron flow underly a pathological adaptation to lung injury induced by co-exposure.

Oxidized carbon black nanoparticles induce endothelial damage through C-X-C chemokine receptor 3-mediated pathway

Oxidation of engineered nanomaterials during application in various industrial sectors can alter their toxicity. Oxidized nanomaterials also have widespread industrial and biomedical applications. In this study, we evaluated the cardiopulmonary hazard posed by these nanomaterials using oxidized carbon black (CB) nanoparticles (CBox) as a model particle. Particle surface chemistry was characterized by X-ray photo electron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FTIR). Colloidal characterization and in vitro dosimetry modeling (particle kinetics, fate and transport modeling) were performed. Lung inflammation was assessed following oropharyngeal aspiration of CB or oxidized CBox particles (20 μg per mouse) in C57BL/6J mice. Toxicity and functional assays were also performed on murine macrophage (RAW 264.7) and endothelial cell lines (C166) with and without pharmacological inhibitors. Oxidant generation was assessed by electron paramagnetic resonance spectroscopy (EPR) and via flow cytometry. Endothelial toxicity was evaluated by quantifying pro-inflammatory mRNA expression, monolayer permeability, and wound closure. XPS and FTIR spectra indicated surface modifications, the appearance of new functionalities, and greater oxidative potential (both acellular and in vitro) of CBox particles. Treatment with CBox demonstrated greater in vivo inflammatory potentials (lavage neutrophil counts, secreted cytokine, and lung tissue mRNA expression) and air-blood barrier disruption (lavage proteins). Oxidant-dependent pro-inflammatory signaling in macrophages led to the production of CXCR3 ligands (CXCL9,10,11). Conditioned medium from CBox-treated macrophages induced significant elevation in endothelial cell pro-inflammatory mRNA expression, enhanced monolayer permeability and impairment of scratch healing in CXCR3 dependent manner. In summary, this study mechanistically demonstrated an increased biological potency of CBox particles and established the role of macrophage-released chemical mediators in endothelial damage.