Effect of NO2 exposure on airway inflammation and oxidative stress in asthmatic mice

Air pollution, genetic factors, and chronic rhinosinusitis: A prospective study in the UK Biobank

BACKGROUND

Chronic rhinosinusitis (CRS) is a prevalent upper respiratory condition that manifests in two primary subtypes: CRS with nasal polyps (CRSwNP) and CRS without nasal polyps (CRSsNP). While previous studies indicate a correlation between air pollution and CRS, the role of genetic predisposition in this relationship remains largely unexplored. We hypothesized that higher air pollution exposure would lead to the development of CRS, and that genetic susceptibility might modify this association.

METHODS

This cohort study involving 367,298 adult participants from the UK Biobank, followed from March 2006 to October 2021. Air pollution metrics were estimated at residential locations using land-use regression models. Cox proportional hazard models were employed to explore the associations between air pollution exposure and CRS, CRSwNP, and CRSsNP. A polygenic risk score (PRS) was constructed to evaluate the joint effect of air pollution and genetic predisposition on the development of CRS.

RESULTS

We found that the risk of CRS increased under long-term exposure to PM2.5 [the hazard ratios (HRs) with 95 % CIs: 1.59 (1.26-2.01)], PM10 [1.64 (1.26-2.12)], NO2 [1.11 (1.04-1.17)], and NOx [1.18 (1.12-1.25)], respectively. These effects were more pronounced among participants with CRSwNP, although the differences were not statistically significant. Additionally, we found that the risks for CRS and CRSwNP increased in a graded manner among participants with higher PRS or higher exposure to PM2.5, PM10, or NOx concentrations. However, no multiplicative or additive interactions were observed.

CONCLUSIONS

Long-term exposure to air pollution increases the risk of CRS, particularly CRSwNP underscoring the need to prioritize clean air initiatives and environmental regulations.

High humidity and NO2 co-exposure exacerbates allergic asthma by increasing oxidative stress, inflammatory and TRP protein expressions in lung tissue

Allergic asthma is a chronic inflammatory airway disease with a high mortality rate and a rapidly increasing prevalence in recent decades that is closely linked to environmental change. Previous research found that high humidity (HH) and the traffic-related air pollutant NO2 both aggregated allergic asthma. Their combined effect and mechanisms on asthma exacerbation, however, are unknown. Our study aims to toxicologically clarify the role of HH (90%) and NO2 (5 ppm) on allergic asthma. Ninety male Balb/c mice were randomly assigned to one of six groups (n = 15 in each): saline control, ovalbumin (OVA)-sensitized, OVA + HH, OVA + NO2, OVA + HH + NO2, and OVA + HH + NO2+Capsazepine (CZP). After 38 days of treatment, the airway function, pathological changes in lung tissue, blood inflammatory cells, and oxidative stress and inflammatory biomarkers were comprehensively assessed. Co-exposure to HH and NO2 exacerbated histopathological changes and airway hyperresponsiveness, increased IgE, oxidative stress markers malonaldehyde (MDA) and allergic asthma-related inflammation markers (IL-1β, TNF-α and IL-17), and upregulated the expressions of the transient receptor potential (TRP) ion channels (TRPA1, TRPV1 and TRPV4). Our findings show that co-exposure to HH and NO2 disrupted the Th1/Th2 immune balance, promoting allergic airway inflammation and asthma susceptibility, and increasing TRPV1 expression, whereas CZP reduced TRPV1 expression and alleviated allergic asthma symptoms. Thus, therapeutic treatments that target the TRPV1 ion channel have the potential to effectively manage allergic asthma.

Fatty acids metabolism in ozone-induced pulmonary inflammatory injury: Evidence, mechanism and prevention

Ozone (O3) is a major air pollutant that directly threatens the respiratory system, lung fatty acid metabolism disorder is an important molecular event in pulmonary inflammatory diseases. Liver kinase B1 (LKB1) and nucleotide-binding domain leucine-rich repeat-containing protein 3 (NLRP3) inflammasome not only regulate inflammation, but also have close relationship with fatty acid metabolism. However, the role and mechanism of LKB1 and NLRP3 inflammasome in lung fatty acid metabolism, which may contribute to ozone-induced lung inflammation, remain unclear, and effective strategy for preventing O3-induced pulmonary inflammatory injury is lacking. To explore these, mice were exposed to 1.00 ppm O3 (3 h/d, 5 days), and pulmonary inflammation was determined by airway hyperresponsiveness, histopathological examination, total cells and cytokines in bronchoalveolar lavage fluid (BALF). Targeted fatty acids metabolomics was used to detect medium and long fatty acid in lung tissue. Then, using LKB1-overexpressing adenovirus and NLRP3 knockout (NLRP3-/-) mice to explore the mechanism of O3-induced lung fatty acid metabolism disorder. Results demonstrated that O3 exposure caused pulmonary inflammatory injury and lung medium and long chain fatty acids metabolism disorder, especially decreased dihomo-γ-linolenic acid (DGLA). Meanwhile, LKB1 expression was decreased, and NLRP3 inflammasome was activated in lung of mice after O3 exposure. Additionally, LKB1 overexpression alleviated O3-induced lung inflammation and inhibited the activation of NLRP3 inflammasome. And we found that pulmonary fatty acid metabolism disorder was ameliorated of NLRP3 -/- mice compared with those in wide type mice after O3 exposure. Furthermore, administrating DGLA intratracheally prior to O3 exposure significantly attenuated O3-induced pulmonary inflammatory injury. Taken together, these findings suggest that fatty acids metabolism disorder is involved in O3-induced pulmonary inflammation, which is regulated by LKB1-mediated NLRP3 pathway, DGLA supplement could be a useful preventive strategy to ameliorate ozone-associated lung inflammatory injury.

Exposure to O3 and NO2 on the interfacial chemistry of the pulmonary surfactant and the mechanism of lung oxidative damage

Exposure to ozone (O3) and nitrogen dioxide (NO2) are related to pulmonary dysfunctions and various lung diseases, but the underlying biochemical mechanisms remain uncertain. Herein, the effect of inhalable oxidizing gas pollutants on the pulmonary surfactant (PS, extracted from porcine lungs), a mixture of active lipids and proteins that plays an important role in maintaining normal respiratory mechanics, is investigated in terms of the interfacial chemistry using in-vitro experiments; and the oxidative stress induced by oxidizing gases in the simulated lung fluid (SLF) supplemented with the PS is explored. The results showed that O3 and NO2 individually increased the surface tension of the PS and reduced its foaming ability; this was accompanied by the surface pressure-area isotherms of the PS monolayers shifting toward lower molecular areas, with O3 exhibiting more severe effects than NO2. Moreover, both O3 and NO2 produced reactive oxygen species (ROS) resulting in lipid peroxidation and protein damage to the PS. The formation of superoxide radicals (O2•-) was correlated with the decomposition of O3 and the reactions of O3 and NO2 with antioxidants in the SLF. These radicals, in the presence of antioxidants, led to the formation of hydrogen peroxide and hydroxyl radicals (•OH). Additionally, the direct oxidation of unsaturated lipids by O3 and NO2 further caused an increase in the ROS content. This change in the ROS chemistry and increased •OH production tentatively explain how inhalable oxidizing gases lead to oxidative stress and adverse health effects. In summary, our results indicated that inhaled O3 and NO2 exposure can significantly alter the interfacial properties of the PS, oxidize its active ingredients, and induce ROS formation in the SLF. The results of this study provide a basis for the elucidation of the potential hazards of inhaled oxidizing gas pollutants in the human respiratory system.

Sex-specific associations between air pollutants and asthma prevalence in Japanese adults: a population-based study

This study investigated the association between air pollutants and asthma prevalence in male and female Japanese adults. In this retrospective cross-sectional analysis, annual mean exposure levels of air pollutants, specifically nitrogen dioxide (NO2) and particulate matter with a median aerodynamic diameter ≤2.5 μm (PM2.5), were assessed at a local monitoring site. Multivariable logistic regression models, adjusted for genetic and/or lifestyle factors, were used to explore the association between air pollutants and asthma, with stratification by sex. A total of 1,497 participants aged ≥40 years were included. Their mean age was 65.9 ± 12.4 years, with 847 being women. Overall, 91 participants were diagnosed with asthma. In the multivariable model, ambient exposure levels of NO2 and PM2.5 were significantly associated with asthma in women but not in men. This study highlights sex as a significant determinant of the link between air pollutants and asthma exacerbation, particularly among female Japanese adults.

β-glucan mitigates ovalbumin-induced airway inflammation by preventing oxidative stress and CD8+ T cell infiltration

BACKGROUND

Bronchial asthma is a severe respiratory condition characterized by airway inflammation, remodeling, and oxidative stress. β-Glucan (BG) is a polysaccharide found in fungal cell walls with powerful immunomodulatory properties. This study examined and clarified the mechanisms behind BG's ameliorativeactivitiesin an allergic asthma animal model.

METHOD

BG was extracted from Chaga mushroom and characterized using FT-IR, UV-visible, zeta potential, and 1H NMR analysis. The mice were divided into five groups, including control, untreated asthmatic, dexamethasone (Dexa)-treated (1 mg/kg), and BG (30 and 100 mg/kg)-treated groups.

RESULTS

BG treatment reduced nasal scratching behavior, airway-infiltrating inflammatory cells, and serum levels of IgE significantly. Additionally, BG attenuated oxidative stress biomarkers by lowering malonaldehyde (MDA) concentrations and increasing the levels of reduced glutathione (GSH), glutathione peroxidase (GPx), and catalase (CAT). Immunohistochemical and flow cytometric analyses have confirmed the suppressive effect of BG on the percentage of airway-infiltrating cytotoxic CD8+ T cells.

CONCLUSION

The findings revealed the role of CD8+ T cells in the pathogenesis of asthma and the role of BG as a potential therapeutic agent for asthma management through the suppression of airway inflammation and oxidative stress.

The Associations of Prenatal Exposure to Fine Particulate Matter and Its Chemical Components with Allergic Rhinitis in Children and the Modification Effect of Polyunsaturated Fatty Acids: A Birth Cohort Study

BACKGROUND

Polyunsaturated fatty acids (PUFAs) have been shown to protect against fine particulate matter < 2.5 μ m in aerodynamic diameter (PM 2.5 )-induced hazards. However, limited evidence is available for respiratory health, particularly in pregnant women and their offspring.

OBJECTIVES

We aimed to investigate the association of prenatal exposure to PM 2.5 and its chemical components with allergic rhinitis (AR) in children and explore effect modification by maternal erythrocyte PUFAs.

METHODS

This prospective birth cohort study involved 657 mother-child pairs from Guangzhou, China. Prenatal exposure to residential PM 2.5 mass and its components [black carbon (BC), organic matter (OM), sulfate (SO 4 2 - ), nitrate (NO 3 - ), and ammonium (NH 4 + )] were estimated by an established spatiotemporal model. Maternal erythrocyte PUFAs during pregnancy were measured using gas chromatography. The diagnosis of AR and report of AR symptoms in children were assessed up to 2 years of age. We used Cox regression with the quantile-based g-computation approach to assess the individual and joint effects of PM 2.5 components and examine the modification effects of maternal PUFA levels.

RESULTS

Approximately 5.33 % and 8.07% of children had AR and related symptoms, respectively. The average concentration of prenatal PM 2.5 was 35.50 ± 5.31   μ g / m 3 . PM 2.5 was positively associated with the risk of developing AR [hazard ratio ( HR ) = 1.85 ; 95% confidence interval (CI): 1.16, 2.96 per 5   μ g / m 3 ] and its symptoms (HR = 1.79 ; 95% CI: 1.22, 2.62 per 5   μ g / m 3 ) after adjustment for confounders. Similar associations were observed between individual PM 2.5 components and AR outcomes. Each quintile change in a mixture of components was associated with an adjusted HR of 3.73 (95% CI: 1.80, 7.73) and 2.69 (95% CI: 1.55, 4.67) for AR and AR symptoms, with BC accounting for the largest contribution. Higher levels of n-3 docosapentaenoic acid and lower levels of n-6 linoleic acid showed alleviating effects on AR symptoms risk associated with exposure to PM 2.5 and its components.

CONCLUSION

Prenatal exposure to PM 2.5 and its chemical components, particularly BC, was associated with AR/symptoms in early childhood. We highlight that PUFA biomarkers could modify the adverse effects of PM 2.5 on respiratory allergy. https://doi.org/10.1289/EHP13524.

Different Impacts of Traffic-Related Air Pollution on Early-Onset and Late-Onset Asthma

Background

Early-onset asthma (EOA) and late-onset asthma (LOA) are two distinct phenotypes. Air pollution has been associated with an increase in poorer asthma outcomes. The objective of this study was to examine the effects of traffic-related air pollution (TRAP) on asthma outcomes in EOA and LOA patients.

Methods

A cross-sectional study was conducted on 675 asthma patients (LOA: 415) recruited from a major medical center in Taiwan. The land-use regression (LUR) model was used to estimate the level of exposure to PM10, PM2.5, NO2, and O3 on an individual level. We investigated the association between TRAP and asthma outcomes in EOA and LOA patients, stratified by allergic sensitization status, using a regression approach.

Results

An increase in PM10 was associated with younger age of onset, increased asthma duration, and decreased lung function in EOA patients (p<0.05). An increase in PM10 was associated with older age of onset, and decreased asthma duration, eosinophil count, and Asthma Control Test (ACT) score in LOA patients. An increase in PM2.5 was associated with younger age of onset, increased asthma duration, decreased eosinophil count, and lung function in EOA patients (p<0.05). An increase in PM2.5 was associated with decreased lung function and ACT score in LOA patients. An increase in NO2 was associated with increased eosinophil count and decreased lung function in EOA patients (p<0.05). An increase in O3 was associated with decreased lung function in LOA patients (p<0.05). In addition, associations of TRAP with age of onset and eosinophil counts were mainly observed in both EOA and LOA patients with allergic sensitization, and an association with ACT was mainly observed in LOA patients without allergic sensitization.

Conclusion

The impact of TRAP on age of onset, eosinophil count, and lung function in EOA patients, and ACT in LOA patients, was affected by the status of allergic sensitization.

"Air That Once Was Breath" Part 1: Wildfire-Smoke-Induced Mechanisms of Airway Inflammation - "Climate Change, Allergy and Immunology" Special IAAI Article Collection: Collegium Internationale Allergologicum Update 2023

BACKGROUND

Wildfires are a global concern due to their wide-ranging environmental, economic, and public health impacts. Climate change contributes to an increase in the frequency and intensity of wildfires making smoke exposure a more significant and recurring health concern for individuals with airway diseases. Some of the most prominent effects of wildfire smoke exposure are asthma exacerbations and allergic airway sensitization. Likely due to the delayed recognition of its health impacts in comparison with cigarette smoke and industrial or traffic-related air pollution, research on the composition, the mechanisms of toxicity, and the cellular/molecular pathways involved is poor or non-existent.

SUMMARY

This review discusses potential underlying pathological mechanisms of wildfire-smoke-related allergic airway disease and asthma. We focused on major gaps in understanding the role of wildfire smoke composition in the development of airway disease and the known and potential mechanisms involving cellular and molecular players of oxidative injury at the epithelial barrier in airway inflammation. We examine how PM2.5, VOCs, O3, endotoxin, microbes, and toxic gases may affect oxidative stress and inflammation in the respiratory mucosal barrier. We discuss the role of AhR in mediating smoke's effects in alarmin release and IL-17A production and how glucocorticoid responsiveness may be impaired by IL-17A-induced signaling and epigenetic changes leading to steroid-resistant severe airway inflammation.

KEY MESSAGE

Effective mitigation of wildfire-smoke-related respiratory health effects would require comprehensive research efforts aimed at a better understanding of the immune regulatory effects of wildfire smoke in respiratory health and disease.

Mediation of the JNC/ILC2 pathway in DBP-exacerbated allergic asthma: A molecular toxicological study on neuroimmune positive feedback mechanism

BACKGROUND

Dibutyl phthalate (DBP), a commonly used plasticizer, has been found to be strongly linked to a consistently high prevalence of allergic diseases, particularly allergic asthma. Previous animal experiments have demonstrated that exposure to DBP can worsen asthma by triggering the production of calcitonin gene-related peptide (CGRP), a neuropeptide in the lung tissue. However, the precise neuroimmune mechanism and pathophysiology of DBP-exacerbated allergic asthma with the assistance of CGRP remain unclear.

OBJECTIVE

The present study was to investigate the potential pathophysiological mechanism in DBP-exacerbated asthma from the perspective of neural-immune interactions.

METHODS AND RESULTS

C57BL/6 mice were orally exposed to different concentrations (0.4, 4, 40 mg/kg) of DBP for 28 days. They were then sensitized with OVA and nebulized with OVA for 7 consecutive excitations. To investigate whether DBP exacerbates allergic asthma in OVA induced mice, we analyzed airway hyperresponsiveness and lung histopathology. To investigate the activation of JNC and TRPV1 neurons and the release of CGRP by JNC cells, we measured the levels of TRPV1 channels, calcium inward flow, and downstream neuropeptide CGRP. Results showed that TRPV1 expression, inward calcium flux, and CGRP levels were significantly elevated in the lung tissues of the 40DBP + OVA group, suggesting the release of CGRP by JNC cells. To counteract the detrimental effects of DBP mediated by CGRP, we employed olcegepant (also known as BIBN-4096), a CGRP receptor specific antagonist. Results revealed that 40DBP + OVA + olcegepant led to notable decreases in TRPV1, calcium inward flow, and CGRP expression in lung tissues compare with 40DBP + OVA, further supporting the efficacy of olcegepant. Additionally, we also conducted ILC2 flow sorting and observed that neuropeptide CGRP-activated ILC2 cells have a crucial role as key effector cells in DBP-induced neuroimmune positive feedback regulation. Finally, we examined the protein expression of CGRP, GATA3 and P-GATA3, and found that significant upregulations of CGRP and P-GATA3 in the 40DBP + OVA group, suggest that GATA3 acted as a key regulator of CGRP-activated ILC2.

CONCLUSION

The aforementioned studies indicate that exposure to DBP can exacerbate allergic asthma, leading to airway inflammation. This exacerbation occurs through the activation of TRPV1 in JNC, resulting in the release of CGRP. The excessive release of CGRP further promotes the release of Th2 cytokines by inducing the activation of ILC2 through GATA phosphorylation. Consequently, this process contributes to the development of airway inflammation and allergic asthma. The increased production of Th2 cytokines also triggers the production of IgE, which interacts with FcεRI on JNC neurons, thereby mediating neuro-immune positive feedback regulation.

Sperm quality decline associated with gaseous pollutant exposure: Evidence from a large cohort multicenter study

BACKGROUND

Poor sperm quality is a prevalent cause of male infertility, and the association between gaseous ambient air pollutants exposure and semen quality remains unclear.

OBJECTIVES

To examine the relationship between gaseous air pollution exposure with semen quality in a large-scale and multi-center study.

METHODS

We analyzed 78,952 samples corresponding to 33,234 study subjects from 2014 to 2020. The high-resolution grid pollution dataset was used to estimate personal exposures to CO, SO2, NO2 and O3 across entire stage of semen formation and three crucial stages. The linear mixed models were performed to evaluate the relationships.

RESULTS

The results showed that sperm count was inversely related to SO2 exposure (-0.0070, -0.0128 to -0.0011). Decreased sperm concentration was associated with SO2 (-0.0083, -0.0142 to -0.0024), NO2 (-0.0162, -0.0320 to -0.0005) and O3 (-0.0306, -0.0480 to -0.0133) during 0-90 lag days, respectively. Additionally, we observed significant decline of PR and total motility with SO2 exposure. Similar trends were observed for SO2 and CO exposure during 3 key periods.

CONCLUSIONS

Our findings suggest that exposure to gaseous air pollutants may have negative impacts on sperm quality. These findings highlight the importance that critical periods of sperm development should be considered when implementing protective measures.

Mediation of endoplasmic reticulum stress and NF-κB signaling pathway in DINP-exacerbated allergic asthma: A toxicological study with Balb/c mice

Epidemiological evidence indicates a significant relationship between exposure to diisononyl phthalate and allergic asthma. Despite this, the mechanism underlying this association remains unclear. Previous toxicological researches have suggested that the development of allergic asthma may involve the activation of endoplasmic reticulum stress (ERS) and the nuclear factor κ-B (NF-κB) pathways. Nevertheless, it is currently unknown whether these specific signaling pathways are implicated in diisononyl phthalate (DINP)-induced allergic asthma. The objective of this research was to understand how DINP exacerbates allergic asthma in Balb/c mice through ERS and NF-κB pathways. To systematically examine the aggravated effects of DINP in Balb/c mice, we measured airway hyperresponsiveness (AHR), lung tissue pathology, cytokines, and ERS and NF-κB pathway biomarkers. Additionally, we applied the ERS antagonist phenylbutyric acid (4-PBA) or the NF-κB antagonist pyrrolidine dithiocarbamate (PDTC) to verify the mediating effects of ERS and NF-κB on DINP-exacerbated allergic asthma. The results of our experiment show that oral DINP exposure may exacerbate airway hyperresponsiveness and airway remodeling. This deterioration is accompanied by an imbalance in immunoglobulin levels, Th17/Treg cells, ERS, and NF-κB biomarkers, leading to the activation of pro-inflammatory pathways. Furthermore, our study found that the blocking effect of 4-PBA or PDTC can inhibit the Th17/Treg imbalance and effectively alleviate symptoms resembling allergic asthma. In conclusion, ERS and NF-κB signaling pathways play an important role in regulating DINP-induced allergic asthma exacerbations.