Ozone impairs endogenous compensatory responses in allergic asthma

Oxidative Stress in Pediatric Asthma: Sources, Mechanisms, and Therapeutic Potential of Antioxidants

Pediatric asthma is a common respiratory condition in children, characterized by a complex interplay of environmental and genetic factors. Evidence shows that the airways of stimulated asthmatic patients have increased oxidative stress, but the exact mechanisms through which this stress contributes to asthma progression are not fully understood. Oxidative stress originates from inflammatory cells in the airways, producing significant amounts of reactive oxygen species (ROS) and reactive nitrogen species (RNS). External factors such as cigarette smoke, particulate matter, and atmospheric pollutants also contribute to ROS and RNS levels. The accumulation of these reactive species disrupts the cellular redox balance, leading to heightened oxidative stress, which activates cellular signaling pathways and modulates the release of inflammatory factors, worsening asthma inflammation. Therefore, understanding the sources and impacts of oxidative stress in pediatric asthma is crucial to developing antioxidant-based treatments. This review examines the sources of oxidative stress in children with asthma, the role of oxidative stress in asthma development, and the potential of antioxidants as a therapeutic strategy for pediatric asthma.

The health impact of PM2.5 and O3 in Beijing modified by infiltration factors from 2014 to 2022

PM2.5 and O3 are significant threats to the health of residents and modern residents spend more than 80% of their time indoors, so quantifying indoor exposure of residents has a positive influence on formulating policies and improving health indicators. Analysis of monitoring data shows a consistent decrease in the annual average concentration of outdoor PM2.5 in Beijing from 90.1 to 30.4 μg/m3, and the equivalent human exposure concentration also declined from 55.2 to 18.6 μg/m3 modified by infiltration factors from 2014 to 2022, while during the peak season, the average value of O3-8 h concentration in Beijing has consistently remained between 159.3 and 225.3 μg/m3; the equivalent human exposure concentration remained between 64.7 and 92.3 μg/m3 modified by infiltration factors from 2014 to 2023. The equivalent exposure concentration is calculated by weighting the concentration of indoor and outdoor pollutants, the proportion of indoor and outdoor activity time of the population, and the permeability coefficient of outdoor pollutants into the room, so as to quantify the actual concentration of pollutants exposed to the human body in a certain time. Previous studies have primarily focused on the impact of annual changes in pollutant concentrations on health estimates, often neglecting indoor concentrations and behavior patterns. This limitation should be addressed. Therefore, this study utilized equivalent human exposure concentration and AirQ + , the authoritative software released by the World Health Organization (WHO), to evaluate quantitatively the impact of PM2.5 and O3 on the health of Beijing residents by combining pollutant concentration, annual population, and mortality of various diseases and other indicators to enhance the credibility of the study. The number of deaths related to PM2.5 has decreased from 28,182 people in 2014 to 10,250 people in 2022 (age ≥ 30). The number of premature deaths in 2022 was only 36.4 percent of that in 2014 and was decreasing by 1992 per year. The number of deaths related to O3 varies between 550 and 3358 people. Lowering PM2.5 and O3 concentrations can effectively reduce natural premature death as well as cardiovascular and respiratory diseases caused by air pollution. The government should persist in enhancing the regulation of PM2.5 and accord significance to the oversight of O3. Concurrently, there is a need to reinforce the cooperative regulation addressing both PM2.5 and O3.

scRNA-seq identifies unique macrophage population in murine model of ozone induced asthma exacerbation

Ozone (O 3 ) inhalation triggers asthmatic airway hyperresponsiveness (AHR), but the mechanisms by which this occurs are unknown. Previously, we developed a murine model of dust mite, ragweed, and aspergillus (DRA)-induced allergic lung inflammation followed by O 3 exposure for mechanistic investigation. The present study used single cell RNA-sequencing for unbiased profiling of immune cells within the lungs of mice exposed to DRA, O 3 , or DRA+O 3 , to identify the components of the immune cell niche that contribute to AHR. Alveolar macrophages (AMs) had the greatest number of differentially expressed genes following DRA+O 3 , most of which were unique to the 2-hit exposure. Following DRA+O 3 , AMs activated transcriptional pathways related to cholesterol biosynthesis, degradation of the extracellular matrix, endosomal TLR processing, and various cytokine signals. We also identified AM and monocyte subset populations that were unique to the DRA+O 3 group. These unique AMs activated gene pathways related to inflammation, sphingolipid metabolism, and bronchial constriction. The unique monocyte population had a gene signature that suggested phospholipase activation and increased degradation of the extracellular matrix. Flow cytometry analysis of BAL immune cells showed recruited monocyte-derived AMs after DRA and DRA+O 3 , but not after O 3 exposure alone. O 3 alone increased BAL neutrophils but this response was attenuated in DRA+O 3 mice. DRA-induced changes in the airspace immune cell profile were reflected in elevated BAL cytokine/chemokine levels following DRA+O 3 compared to O 3 alone. The present work highlights the role of monocytes and AMs in the response to O 3 and suggests that the presence of distinct subpopulations following allergic inflammation may contribute to O 3 -induced AHR.

"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.

Bronchial Asthma, Airway Remodeling and Lung Fibrosis as Successive Steps of One Process

Bronchial asthma is a heterogeneous disease characterized by persistent respiratory system inflammation, airway hyperreactivity, and airflow obstruction. Airway remodeling, defined as changes in airway wall structure such as extensive epithelial damage, airway smooth muscle hypertrophy, collagen deposition, and subepithelial fibrosis, is a key feature of asthma. Lung fibrosis is a common occurrence in the pathogenesis of fatal and long-term asthma, and it is associated with disease severity and resistance to therapy. It can thus be regarded as an irreversible consequence of asthma-induced airway inflammation and remodeling. Asthma heterogeneity presents several diagnostic challenges, particularly in distinguishing between chronic asthma and other pulmonary diseases characterized by disruption of normal lung architecture and functions, such as chronic obstructive pulmonary disease. The search for instruments that can predict the development of irreversible structural changes in the lungs, such as chronic components of airway remodeling and fibrosis, is particularly difficult. To overcome these challenges, significant efforts are being directed toward the discovery and investigation of molecular characteristics and biomarkers capable of distinguishing between different types of asthma as well as between asthma and other pulmonary disorders with similar structural characteristics. The main features of bronchial asthma etiology, pathogenesis, and morphological characteristics as well as asthma-associated airway remodeling and lung fibrosis as successive stages of one process will be discussed in this review. The most common murine models and biomarkers of asthma progression and post-asthmatic fibrosis will also be covered. The molecular mechanisms and key cellular players of the asthmatic process described and systematized in this review are intended to help in the search for new molecular markers and promising therapeutic targets for asthma prediction and therapy.