Urban particulate matter increases human airway epithelial cell IL-1β secretion following scratch wounding and H1N1 influenza A exposurein vitro

Particulate Matter Exposure and Viral Infections: Relevance to Highly Polluted Settings such as Ulaanbaatar, Mongolia

PURPOSE OF REVIEW

Particulate matter (PM), a ubiquitous significant component of the ambient air pollution mixture, significantly contributes to increased global risk for chronic cardiopulmonary diseases, acute hospitalizations, and deaths. One of the causes of this increased risk is because PM exposure increases the incidence and severity of respiratory infections. The respiratory system is particularly vulnerable to air pollution and its impact on infection as it is a key site for exposure both to inhaled pollutants and infectious microbes or viruses. This review examines the current understanding of how PM affects antiviral host defense responses and possible underlying mechanisms.

RECENT FINDINGS

While numerous studies have associated adverse health outcomes with combined or sequential exposure to inhaled pollutants and viruses, defining causal relationships and mechanisms remains limited. Particularly limited, are contemporary data focuses on low- and middle-income countries, including heavily polluted regions such as Ulaanbaatar, Mongolia. This manuscript focuses on how (1) PM, serving as a carrier for viruses, enhances the transmission of viruses; (2) PM impairs immune defense to viruses; and (3) PM impacts epithelial cell functions to exacerbate viral infections. Given the significant public health hazards on PM, particularly in heavily polluted regions such as Southeast Asia, Middle East and Africa, it is critical to define specific mechanisms of PM on respiratory infection and how their impact may differ in these highly polluted regions. Ultimately, this could devise future public health measures and interventions to limit this substantial public health risk.

Airway epithelial cells as drivers of severe asthma pathogenesis

Our understanding of the airway epithelium's role in driving asthma pathogenesis has evolved over time. From being regarded primarily as a physical barrier that could be damaged via inflammation, the epithelium is now known to actively contribute to asthma development through interactions with the immune system. The airway epithelium contains multiple cell types with specialized functions spanning barrier action, mucociliary clearance, immune cell recruitment, and maintenance of tissue homeostasis. Environmental insults may cause direct or indirect injury to the epithelium leading to impaired barrier function, epithelial remodelling, and increased release of inflammatory mediators. In severe asthma, the epithelial barrier repair process is inhibited and the response to insults is exaggerated, driving downstream inflammation. Genetic and epigenetic mechanisms also maintain dysregulation of the epithelial barrier, adding to disease chronicity. Here, we review the role of the airway epithelium in severe asthma and how targeting the epithelium can contribute to asthma treatment.

Ambient PM2.5 and specific sources increase inflammatory cytokine responses to stimulators and reduce sensitivity to inhibitors

Ambient exposure to fine particulate matter (PM2.5) is associated with increased morbidity and mortality from multiple diseases. Recent observations suggest the hypothesis that trained immunity contributes to these risks, by demonstrating that ambient PM2.5 sensitizes innate immune cells to mount larger inflammatory response to subsequent bacterial stimuli. However, little is known about how general and durable this sensitization phenomenon is, and whether specific sources of PM2.5 are responsible. Here we consider these issues in a longitudinal study of children. The sample consisted of 277 children (mean age 13.92 years; 63.8% female; 38.4% Black; 32.2% Latinx) who completed baseline visits and were re-assessed two years later. Fasting whole blood was ex vivo incubated with 4 stimulating agents reflecting microbial and sterile triggers of inflammation, and with 2 inhibitory agents, followed by assays for IL-1β, IL-6, IL-8, and TNF-α. Blood also was assayed for 6 circulating biomarkers of low-grade inflammation: C-reactive protein, interleukin-6, -8, and -10, tumor necrosis factor-α, and soluble urokinase-type plasminogen activator receptor. Using machine learning, levels of 15 p.m.2.5 constituents were estimated for a 50 m grid around children's homes. Models were adjusted for age, sex, race, pubertal status, and household income. In cross-sectional analyses, higher neighborhood PM2.5 was associated with larger cytokine responses to the four stimulating agents. These associations were strongest for constituents released by motor vehicles and soil/crustal dust. In longitudinal analyses, residential PM2.5 was associated with declining sensitivity to inhibitory agents; this pattern was strongest for constituents from fuel/biomass combustion and motor vehicles. By contrast, PM2.5 constituents were not associated with the circulating biomarkers of low-grade inflammation. Overall, these findings suggest the possibility of a trained immunity scenario, where PM2.5 heightens inflammatory cytokine responses to multiple stimulators, and dampens sensitivity to inhibitors which counter-regulate these responses.

Outdoor air pollution as a risk factor for testing positive for SARS-CoV-2: A nationwide test-negative case-control study in the Netherlands

Air pollution is a known risk factor for several diseases, but the extent to which it influences COVID-19 compared to other respiratory diseases remains unclear. We performed a test-negative case-control study among people with COVID-19-compatible symptoms who were tested for SARS-CoV-2 infection, to assess whether their long- and short-term exposure to ambient air pollution (AAP) was associated with testing positive (vs. negative) for SARS-CoV-2. We used individual-level data for all adult residents in the Netherlands who were tested for SARS-CoV-2 between June and November 2020, when only symptomatic people were tested, and modeled ambient concentrations of PM10, PM2.5, NO2 and O3 at geocoded residential addresses. In long-term exposure analysis, we selected individuals who did not change residential address in 2017-2019 (1.7 million tests) and considered the average concentrations of PM10, PM2.5 and NO2 in that period, and different sources of PM (industry, livestock, other agricultural activities, road traffic, other Dutch sources, foreign sources). In short-term exposure analysis, individuals not changing residential address in the two weeks before testing day (2.7 million tests) were included in the analyses, thus considering 1- and 2-week average concentrations of PM10, PM2.5, NO2 and O3 before testing day as exposure. Mixed-effects logistic regression analysis with adjustment for several confounders, including municipality and testing week to account for spatiotemporal variation in viral circulation, was used. Overall, there was no statistically significant effect of long-term exposure to the studied pollutants on the odds of testing positive vs. negative for SARS-CoV-2. However, significant positive associations of long-term exposure to PM10 and PM2.5 from specifically foreign and livestock sources, and to PM10 from other agricultural sources, were observed. Short-term exposure to PM10 (adjusting for NO2) and PM2.5 were also positively associated with increased odds of testing positive for SARS-CoV-2. While these exposures seemed to increase COVID-19 risk relative to other respiratory diseases, the underlying biological mechanisms remain unclear. This study reinforces the need to continue to strive for better air quality to support public health.

Inflammasomes in epithelial innate immunity: front line warriors

Our epithelium represents a battle ground against a variety of insults including pathogens and danger signals. It encodes multiple sensors that detect and respond to such insults, playing an essential role in maintaining and defending tissue homeostasis. One key set of defense mechanisms is our inflammasomes which drive innate immune responses including, sensing and responding to pathogen attack, through the secretion of pro-inflammatory cytokines and cell death. Identification of physiologically relevant triggers for inflammasomes has greatly influenced our ability to decipher the mechanisms behind inflammasome activation. Furthermore, identification of patient mutations within inflammasome components implicates their involvement in a range of epithelial diseases. This review will focus on exploring the roles of inflammasomes in epithelial immunity and cover: the diversity and differential expression of inflammasome sensors amongst our epithelial barriers, their ability to sense local infection and damage and the contribution of the inflammasomes to epithelial homeostasis and disease.

Acute and subchronic exposure to urban atmospheric pollutants aggravate acute respiratory failure in infants

Urban air pollution is a major factor that affects the respiratory health of children and adolescents. Less studied is exposure during the first two years of life. This study analyzed the influence of acute and subchronic exposure to urban air pollutants on the severity of acute respiratory failure (ARF) in the first two years of life. This population-based study included 7364 infants hospitalized with ARF. Acute exposure was considered to have occurred 1, 3 and 7 days before hospitalization and subchronic exposure was considered the mean of the last 30 and 60 days. We found that for acute exposure, significant increases in days of hospitalization (LOS) occurred at lag 1 day for NO2 (0.24), SO2 (6.64), and CO (1.86); lag 3 days for PM10 (0.30), PM2.5 (0.37), SO2 (10.8), and CO (0.71); and lag 7 days for NO2 (0.16), SO2 (5.07) and CO (0.87). Increases in the risk of death occurred at lag 1 day for NO2 (1.06), SO2 (3.64), and CO (1.28); and lag 3 days for NO2 (1.04), SO2 (2.04), and CO (1.19). Subchronic exposures at 30 and 60 days occurred for SO2 (9.18, 3.77) and CO (6.53, 2.97), respectively. The associations were more pronounced with higher temperatures and lower relative humidity levels. We concluded that acute and subchronic exposure to higher atmospheric concentrations of all the pollutants studied were associated with greater severity of ARF. The greatest increases in LOS and risk of death occurred with hot and dry weather.

Risk Factors for Respiratory Viral Infections: A Spotlight on Climate Change and Air Pollution

Climate change has both direct and indirect effects on human health, and some populations are more vulnerable to these effects than others. Viral respiratory infections are most common illnesses in humans, with estimated 17 billion incident infections globally in 2019. Anthropogenic drivers of climate change, chiefly the emission of greenhouse gases and toxic pollutants from burning of fossil fuels, and the consequential changes in temperature, precipitation, and frequency of extreme weather events have been linked with increased susceptibility to viral respiratory infections. Air pollutants like nitrogen dioxide, particulate matter, diesel exhaust particles, and ozone have been shown to impact susceptibility and immune responses to viral infections through various mechanisms, including exaggerated or impaired innate and adaptive immune responses, disruption of the airway epithelial barrier, altered cell surface receptor expression, and impaired cytotoxic function. An estimated 90% of the world's population is exposed to air pollution, making this a topic with high relevance to human health. This review summarizes the available epidemiologic and experimental evidence for an association between climate change, air pollution, and viral respiratory infection.

Molecular Mechanisms of RSV and Air Pollution Interaction: A Scoping Review

RSV is one of the major infectious agents in paediatrics, and its relationship with air pollution is frequently observed. However, the molecular basis of this interaction is sparsely reported. We sought to systematically review the existing body of literature and identify the knowledge gaps to answer the question: which molecular mechanisms are implied in the air pollutants-RSV interaction? Online databases were searched for original studies published before August 2022 focusing on molecular mechanisms of the interaction. The studies were charted and a narrative synthesis was based upon three expected directions of influence: a facilitated viral entry, an altered viral replication, and an inappropriate host reaction. We identified 25 studies published between 1993 and 2020 (without a noticeable increase in the number of studies) that were performed in human (n = 12), animal (n = 10) or mixed (n = 3) models, and analysed mainly cigarette smoke (n = 11), particulate matter (n = 4), nanoparticles (n = 3), and carbon black (n = 2). The data on a damage to the epithelial barrier supports the hypothesis of facilitated viral entry; one study also reported accelerated viral entry upon an RSV conjugation to particulate matter. Air pollution may result in the predominance of necrosis over apoptosis, and, as an effect, an increased viral load was reported. Similarly, air pollution mitigates epithelium function with decreased IFN-γ and Clara cell secretory protein levels and decreased immune response. Immune response might also be diminished due to a decreased viral uptake by alveolar macrophages and a suppressed function of dendritic cells. On the other hand, an exuberant inflammatory response might be triggered by air pollution and provoke airway hyperresponsiveness (AHR), prolonged lung infiltration, and tissue remodeling, including a formation of emphysema. AHR is mediated mostly by increased IFN-γ and RANTES concentrations, while the risk of emphysema was related to the activation of the IL-17 → MCP-1 → MMP-9 → MMP-12 axis. There is a significant lack of evidence on the molecular basics of the RSV-air pollution interaction, which may present a serious problem with regards to future actions against air pollution effects. The major knowledge gaps concern air pollutants (mostly the influence of cigarette smoke was investigated), the mechanisms facilitating an acute infection or a worse disease course (since it might help plan short-term, especially non-pharmacological, interventions), and the mechanisms of an inadequate response to the infection (which may lead to a prolonged course of an acute infection and long-term sequelae). Thus far, the evidence is insufficient regarding the broadness and complexity of the interaction, and future studies should focus on common mechanisms stimulated by various air pollutants and a comparison of influence of the different contaminants at various concentrations.

RNA-Seq Analysis of UPM-Exposed Epithelium Co-Cultivated with Macrophages and Dendritic Cells in Obstructive Lung Diseases

Background. Elevated concentrations of airborne pollutants are correlated with an enlarged rate of obstructive lung disease morbidity as well as acute disease exacerbations. This study aimed to analyze the epithelium mRNA profile in response to airborne particulate matter in the control, asthma, and COPD groups. Results. A triple co-culture of nasal epithelium, monocyte-derived macrophages, and monocyte-derived dendritic cells obtained from the controls, asthma, and COPD were exposed to urban particulate matter (UPM) for 24 h. RNA-Seq analysis found differences in seven (CYP1B1, CYP1B1-AS1, NCF1, ME1, LINC02029, BPIFA2, EEF1A2), five (CYP1B1, ARC, ENPEP, RASD1, CYP1B1-AS1), and six (CYP1B1, CYP1B1-AS1, IRF4, ATP1B2, TIPARP, CCL22) differentially expressed genes between UPM exposed and unexposed triple co-cultured epithelium in the control, asthma, and COPD groups, respectively. PCR analysis showed that mRNA expression of BPIFA2 and ENPEP was upregulated in both asthma and COPD, while the expression of CYP1B1-AS1 and TIPARP was increased in the epithelium from COPD patients only. Biological processes changed in UPM exposed triple co-cultured epithelium were associated with epidermis development and epidermal cell differentiation in asthma and with response to toxic substances in COPD. Conclusions. The biochemical processes associated with pathophysiology of asthma and COPD impairs the airway epithelial response to UPM.

Recent Insights into Particulate Matter (PM2.5)-Mediated Toxicity in Humans: An Overview

Several epidemiologic and toxicological studies have commonly viewed ambient fine particulate matter (PM_2.5), defined as particles having an aerodynamic diameter of less than 2.5 µm, as a significant potential danger to human health. PM_2.5 is mostly absorbed through the respiratory system, where it can infiltrate the lung alveoli and reach the bloodstream. In the respiratory system, reactive oxygen or nitrogen species (ROS, RNS) and oxidative stress stimulate the generation of mediators of pulmonary inflammation and begin or promote numerous illnesses. According to the most recent data, fine particulate matter, or PM_2.5, is responsible for nearly 4 million deaths globally from cardiopulmonary illnesses such as heart disease, respiratory infections, chronic lung disease, cancers, preterm births, and other illnesses. There has been increased worry in recent years about the negative impacts of this worldwide danger. The causal associations between PM_2.5 and human health, the toxic effects and potential mechanisms of PM_2.5, and molecular pathways have been described in this review.

Adhesive-Based Fabrication Technique for Culture of Lung Airway Epithelial Cells with Applications in Cell Patterning and Microfluidics

This work describes a versatile and cost-effective cell culture method for micropatterning and growing adherent cells on porous membranes using pressure-sensitive double-sided adhesives. This technique also allows cell culture using conventional methods and their easy integration into microfluidic chip devices. Adhesives can be used to form different patterns of cultured cells, which can be used for cell proliferation and wound-healing models. To demonstrate the viability of our system, we evaluate the toxicity effect of five different adhesives on two distinct airway epithelial cell lines and show functional applications for cell patterning and microfluidic cell culture chip fabrication. We developed a sandwiched microfluidic device that enabled us to culture cells in a submerged condition and transformed it into a dynamic platform when required. The viability of cells and their inflammatory responses to IL-1β stimulation were investigated. Our technique is applicable for conventional culturing of cells, widely available in biomedical research labs, while enabling the introduction of perfusion for an advanced dynamic cell culture model when needed.

Potentiation of long-acting β2-agonist and glucocorticoid responses in human airway epithelial cells by modulation of intracellular cAMP

Introduction

Over 300 million people in the world live with asthma, resulting in 500,000 annual global deaths with future increases expected. It is estimated that around 50–80% of asthma exacerbations are due to viral infections. Currently, a combination of long-acting beta agonists (LABA) for bronchodilation and glucocorticoids (GCS) to control lung inflammation represent the dominant strategy for the management of asthma, however, it is still sub-optimal in 35–50% of moderate-severe asthmatics resulting in persistent lung inflammation, impairment of lung function, and risk of mortality. Mechanistically, LABA/GCS combination therapy results in synergistic efficacy mediated by intracellular cyclic adenosine monophosphate (cAMP).

Hypothesis

Increasing intracellular cAMP during LABA/GCS combination therapy via inhibiting phosphodiesterase 4 (PDE4) and/or blocking the export of cAMP by ATP Binding Cassette Transporter C4 (ABCC4), will potentiate anti-inflammatory responses of mainstay LABA/GCS therapy.

Methods

Expression and localization experiments were performed using in situ hybridization and immunohistochemistry in human lung tissue from healthy subjects, while confirmatory transcript and protein expression analyses were performed in primary human airway epithelial cells and cell lines. Intervention experiments were performed on the human airway epithelial cell line, HBEC-6KT, by pre-treatment with combinations of LABA/GCS with PDE4 and/or ABCC4 inhibitors followed by Poly I:C or imiquimod challenge as a model for viral stimuli. Cytokine readouts for IL-6, IL-8, CXCL10/IP-10, and CCL5/RANTES were quantified by ELISA.

Results

Using archived human lung and human airway epithelial cells, ABCC4 gene and protein expression were confirmed in vitro and in situ. LABA/GCS attenuation of Poly I:C or imiquimod-induced IL-6 and IL-8 were potentiated with ABCC4 and PDE4 inhibition, which was greater when ABCC4 and PDE4 inhibition was combined. Modulation of cAMP levels had no impact on LABA/GCS modulation of Poly I:C-induced CXCL10/IP-10 or CCL5/RANTES.

Conclusion

Modulation of intracellular cAMP levels by PDE4 or ABCC4 inhibition potentiates LABA/GCS efficacy in human airway epithelial cells challenged with viral stimuli. The data suggest further exploration of the value of adding cAMP modulators to mainstay LABA/GCS therapy in asthma for potentiated anti-inflammatory efficacy.

Viral respiratory infections and air pollutants

Air pollution is a public health issue of global importance and a risk factor for developing cardiorespiratory diseases. These contaminants induce reactive oxygen species (ROS) and increased pro-inflammatory cytokines such as IL-1β, IL-6, and IL-8, triggering the inflammatory response that alters cell and tissue homeostasis and facilitates the development of diseases. The effects of air pollutants such as ozone, particulate matter (PM10, PM2.5, and PM0.1), and indoor air pollutants on respiratory health have been widely reported. For instance, epidemiological and experimental studies have shown associations between hospital admissions for individual diseases and increased air pollutant levels. This review describes the association and relationships between exposure to air pollutants and respiratory viral infections, especially those caused by the respiratory syncytial virus and influenza virus. The evidence suggests that exposure to air contaminants induces inflammatory states, modulates the immune system, and increases molecules' expression that favors respiratory viruses' pathogenesis and affects the respiratory system. However, the mechanisms underlying these interactions have not yet been fully elucidated, so it is necessary to develop new studies to obtain information that will allow health and policy decisions to be made for the adequate control of respiratory infections, especially in the most vulnerable population, during periods of maximum air pollution.

Transcriptome-wide profiling discover: PM2.5 aggravates airway dysfunction through epithelial barrier damage regulated by Stanniocalcin 2 in an OVA-induced model

BACKGROUND

Epidemiologic evidence suggests that PM2.5 exposure aggravates asthma, but the molecular mechanisms are not fully discovered.

METHODS

Ovalbumin (OVA)-induced mice exposed to PM2.5 were constructed. Pathological staining and immunofluorescence were performed in in vivo study. Gene set enrichment analysis (GSEA) was performed to identify the pathway involved in asthma severity by using U-BIOPRED data (human bronchial biopsies) and RNA-seq data (Beas-2B cells treated with PM2.5). Lentiviruses transfection, Real-time qPCR, immunofluorescence staining and trans-epithelial electrical resistance (TEER) measurement were performed for mechanism exploration in vitro.

RESULTS

PM2.5 exposure aggravated airway inflammation and mucus secretion in OVA-induced mice. Based on transcriptome analysis of mild-to-severe asthma from human bronchial biopsies, gene set enrichment analysis (GSEA) showed that up-regulated reactive oxygen species (ROS) pathway gene set and down-regulated apical junction gene set correlated with asthma severity. Consistent with the analysis of mild-to-severe asthma, after PM2.5 exposure, the ROS pathway in Beas-2B cells was up-regulated with the down-regulation of apical junction. The expression levels of genes involved in the specific gene sets were validated by using qPCR. The mRNA levels of junction genes, ZO-1, E-cadherin and Occludin, were significantly decreased in cells exposed to PM2.5. Moreover, it confirmed that inhibition of ROS recovered the expression levels of E-cadherin, Occludin and ZO-1, and ameliorated inflammation and mucus secretion in airway in OVA-induced mice exposed to PM2.5. Meanwhile, ROS level was elevated by PM2.5. By checking trans-epithelial electrical resistance (TEER) value, we also found that epithelial barrier was damaged after PM2.5 exposure. Importantly, Stanniocalcin 2 (STC2) was identified as a key gene in regulation of epithelial barrier. It showed that STC2 expression was up-regulated by PM2.5, which was recovered by NAC as well. Over-expression of STC2 could decrease the expression levels of ZO-1, Occludin and E-cadherin. Contrarily, suppression of STC2 could increase the expression levels of ZO-1, Occludin and E-cadherin reduced by PM2.5.

CONCLUSIONS

By using transcriptome analysis, we revealed that STC2 played a key role in PM2.5 aggravated airway dysfunction through regulation of epithelial barrier in OVA-induced mice.

Biological effect of PM10 on airway epithelium-focus on obstructive lung diseases

Recently, a continuous increase in environmental pollution has been observed. Despite wide-scale efforts to reduce air pollutant emissions, the problem is still relevant. Exposure to elevated levels of airborne particles increased the incidence of respiratory diseases. PM₁₀ constitute the largest fraction of air pollutants, containing particles with a diameter of less than 10 μm, metals, pollens, mineral dust and remnant material from anthropogenic activity. The natural airway defensive mechanisms against inhaled material, such as mucus layer, ciliary clearance and macrophage phagocytic activity, may be insufficient for proper respiratory function. The epithelium layer can be disrupted by ongoing oxidative stress and inflammatory processes induced by exposure to large amounts of inhaled particles as well as promote the development and exacerbation of obstructive lung diseases. This review draws attention to the current state of knowledge about the physical features of PM₁₀ and its impact on airway epithelial cells, and obstructive pulmonary diseases.

Polluted Air Exposure Compromises Corneal Immunity and Exacerbates Inflammation in Acute Herpes Simplex Keratitis

Air pollution is a serious environmental issue worldwide in developing countries’ megacities, affecting the population’s health, including the ocular surface, by predisposing or exacerbating other ocular diseases. Herpes simplex keratitis (HSK) is caused by the herpes simplex virus type 1 (HSV-1). The primary or recurring infection in the ocular site causes progressive corneal scarring that may result in visual impairment. The present study was designed to study the immunopathological changes of acute HSK under urban polluted air, using the acute HSK model combined with an experimental urban polluted air exposure from Buenos Aires City. We evaluated the corneal clinical outcomes, viral DNA and pro-inflammatory cytokines by RT-PCR and ELISA assays, respectively. Then, we determined the innate and adaptive immune responses in both cornea and local lymph nodes after HSV-1 corneal by immunofluorescence staining and flow cytometry. Our results showed that mice exposed to polluted air develop a severe form of HSK with increased corneal opacity, neovascularization, HSV-1 DNA and production of TNF-α, IL-1β, IFN-γ, and CCL2. A high number of corneal resident immune cells, including activated dendritic cells, was observed in mice exposed to polluted air; with a further significant influx of bone marrow-derived cells including GR1+ cells (neutrophils and inflammatory monocytes), CD11c+ cells (dendritic cells), and CD3+ (T cells) during acute corneal HSK. Moreover, mice exposed to polluted air showed a predominant Th1 type T cell response over Tregs in local lymph nodes during acute HSK with decreased corneal Tregs. These findings provide strong evidence that urban polluted air might trigger a local imbalance of innate and adaptive immune responses that exacerbate HSK severity. Taking this study into account, urban air pollution should be considered a key factor in developing ocular inflammatory diseases.

SARS-CoV-2 infection, COVID-19 pathogenesis, and exposure to air pollution: What is the connection?

Exposure to air pollutants has been previously associated with respiratory viral infections, including influenza, measles, mumps, rhinovirus, and respiratory syncytial virus. Epidemiological studies have also suggested that air pollution exposure is associated with increased cases of SARS-CoV-2 infection and COVID-19-associated mortality, although the molecular mechanisms by which pollutant exposure affects viral infection and pathogenesis of COVID-19 remain unknown. In this review, we suggest potential molecular mechanisms that could account for this association. We have focused on the potential effect of exposure to nitrogen dioxide (NO2 ), ozone (O3 ), and particulate matter (PM) since there are studies investigating how exposure to these pollutants affects the life cycle of other viruses. We have concluded that pollutant exposure may affect different stages of the viral life cycle, including inhibition of mucociliary clearance, alteration of viral receptors and proteases required for entry, changes to antiviral interferon production and viral replication, changes in viral assembly mediated by autophagy, prevention of uptake by macrophages, and promotion of viral spread by increasing epithelial permeability. We believe that exposure to pollutants skews adaptive immune responses toward bacterial/allergic immune responses, as opposed to antiviral responses. Exposure to air pollutants could also predispose exposed populations toward developing COIVD-19-associated immunopathology, enhancing virus-induced tissue inflammation and damage.

Mechanistic Implications of Biomass-Derived Particulate Matter for Immunity and Immune Disorders

Particulate matter (PM) is a major and the most harmful component of urban air pollution, which may adversely affect human health. PM exposure has been associated with several human diseases, notably respiratory and cardiovascular diseases. In particular, recent evidence suggests that exposure to biomass-derived PM associates with airway inflammation and can aggravate asthma and other allergic diseases. Defective or excess responsiveness in the immune system regulates distinct pathologies, such as infections, hypersensitivity, and malignancies. Therefore, PM-induced modulation of the immune system is crucial for understanding how it causes these diseases and highlighting key molecular mechanisms that can mitigate the underlying pathologies. Emerging evidence has revealed that immune responses to biomass-derived PM exposure are closely associated with the risk of diverse hypersensitivity disorders, including asthma, allergic rhinitis, atopic dermatitis, and allergen sensitization. Moreover, immunological alteration by PM accounts for increased susceptibility to infectious diseases, such as tuberculosis and coronavirus disease-2019 (COVID-19). Evidence-based understanding of the immunological effects of PM and the molecular machinery would provide novel insights into clinical interventions or prevention against acute and chronic environmental disorders induced by biomass-derived PM.

Inflammatory effects of particulate matter air pollution

Air pollution is an important cause of non-communicable diseases globally with particulate matter (PM) as one of the main air pollutants. PM is composed of microscopic particles that contain a mixture of chemicals and biological elements that can be harmful to human health. The aerodynamic diameter of PM facilitates their deposition when inhaled. For instance, coarse PM having a diameter of < 10 μm is deposited mainly in the large conducting airways, but PM of < 2.5 μm can cross the alveolar-capillary barrier, traveling to other organs within the body. Epidemiological studies have shown the association between PM exposure and risk of disease, namely those of the respiratory system such as lung cancer, asthma, and chronic obstructive pulmonary disease (COPD). However, cardiovascular and neurological diseases have also been reported, including hypertension, atherosclerosis, acute myocardial infarction, stroke, loss of cognitive function, anxiety, and Parkinson's and Alzheimer's diseases. Inflammation is a common hallmark in the pathogenesis of many of these diseases associated with exposure to a variety of air pollutants, including PM. This review focuses on the main effects of PM on human health, with an emphasis on the role of inflammation.

Particulate matter (PM10) enhances RNA virus infection through modulation of innate immune responses

Sensing of pathogens by specialized receptors is the hallmark of the innate immunity. Innate immune response also mounts a defense response against various allergens and pollutants including particulate matter present in the atmosphere. Air pollution has been included as the top threat to global health declared by WHO which aims to cover more than three billion people against health emergencies from 2019 to 2023. Particulate matter (PM), one of the major components of air pollution, is a significant risk factor for many human diseases and its adverse effects include morbidity and premature deaths throughout the world. Several clinical and epidemiological studies have identified a key link between the PM existence and the prevalence of respiratory and inflammatory disorders. However, the underlying molecular mechanism is not well understood. Here, we investigated the influence of air pollutant, PM10 (particles with aerodynamic diameter less than 10 μm) during RNA virus infections using Highly Pathogenic Avian Influenza (HPAI) - H5N1 virus. We thus characterized the transcriptomic profile of lung epithelial cell line, A549 treated with PM10 prior to H5N1infection, which is known to cause severe lung damage and respiratory disease. We found that PM10 enhances vulnerability (by cellular damage) and regulates virus infectivity to enhance overall pathogenic burden in the lung cells. Additionally, the transcriptomic profile highlights the connection of host factors related to various metabolic pathways and immune responses which were dysregulated during virus infection. Collectively, our findings suggest a strong link between the prevalence of respiratory illness and its association with the air quality.

ABCF1 Regulates dsDNA-induced Immune Responses in Human Airway Epithelial Cells

Background: The airway epithelium represents a critical component of the human lung that helps orchestrate defenses against respiratory tract viral infections, which are responsible for more than 2.5 million deaths/year globally. Innate immune activities of the airway epithelium rely on Toll-like receptors (TLRs), nucleotide binding and leucine-rich-repeat pyrin domain containing (NLRP) receptors, and cytosolic nucleic acid sensors. ATP Binding Cassette (ABC) transporters are ubiquitous across all three domains of life—Archaea, Bacteria, and Eukarya—and expressed in the human airway epithelium. ABCF1, a unique ABC family member that lacks a transmembrane domain, has been defined as a cytosolic nucleic acid sensor that regulates CXCL10, interferon-β expression, and downstream type I interferon responses. We tested the hypothesis that ABCF1 functions as a dsDNA nucleic acid sensor in human airway epithelial cells important in regulating antiviral responses.

Methods: Expression and localization experiments were performed using in situ hybridization and immunohistochemistry in human lung tissue, while confirmatory transcript and protein expression was performed in human airway epithelial cells. Functional experiments were performed with siRNA methods in a human airway epithelial cell line. Complementary transcriptomic analyses were performed to explore the contributions of ABCF1 to gene expression patterns.

Results: Using archived human lung and human airway epithelial cells, we confirm expression of ABCF1 gene and protein expression in these tissue samples, with a role for mediating CXCL10 production in response to dsDNA viral mimic challenge. Although, ABCF1 knockdown was associated with an attenuation of select genes involved in the antiviral responses, Gene Ontology analyses revealed a greater interaction of ABCF1 with TLR signaling suggesting a multifactorial role for ABCF1 in innate immunity in human airway epithelial cells.

Conclusion: ABCF1 is a candidate cytosolic nucleic acid sensor and modulator of TLR signaling that is expressed at gene and protein levels in human airway epithelial cells. The precise level where ABCF1 protein functions to modulate immune responses to pathogens remains to be determined but is anticipated to involve IRF-3 and CXCL10 production.

Gene expression and in situ protein profiling of candidate SARS-CoV-2 receptors in human airway epithelial cells and lung tissue

In December 2019, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged, causing the coronavirus disease 2019 (COVID-19) pandemic. SARS-CoV, the agent responsible for the 2003 SARS outbreak, utilises angiotensin-converting enzyme 2 (ACE2) and transmembrane serine protease 2 (TMPRSS2) host molecules for viral entry. ACE2 and TMPRSS2 have recently been implicated in SARS-CoV-2 viral infection. Additional host molecules including ADAM17, cathepsin L, CD147 and GRP78 may also function as receptors for SARS-CoV-2.To determine the expression and in situ localisation of candidate SARS-CoV-2 receptors in the respiratory mucosa, we analysed gene expression datasets from airway epithelial cells of 515 healthy subjects, gene promoter activity analysis using the FANTOM5 dataset containing 120 distinct sample types, single cell RNA sequencing (scRNAseq) of 10 healthy subjects, proteomic datasets, immunoblots on multiple airway epithelial cell types, and immunohistochemistry on 98 human lung samples.We demonstrate absent to low ACE2 promoter activity in a variety of lung epithelial cell samples and low ACE2 gene expression in both microarray and scRNAseq datasets of epithelial cell populations. Consistent with gene expression, rare ACE2 protein expression was observed in the airway epithelium and alveoli of human lung, confirmed with proteomics. We present confirmatory evidence for the presence of TMPRSS2, CD147 and GRP78 protein in vitro in airway epithelial cells and confirm broad in situ protein expression of CD147 and GRP78 in the respiratory mucosa.Collectively, our data suggest the presence of a mechanism dynamically regulating ACE2 expression in human lung, perhaps in periods of SARS-CoV-2 infection, and also suggest that alternative receptors for SARS-CoV-2 exist to facilitate initial host cell infection.

Gene expression and in situ protein profiling of candidate SARS-CoV-2 receptors in human airway epithelial cells and lung tissue

In December 2019, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged, causing the coronavirus disease 2019 (COVID-19) pandemic. SARS-CoV, the agent responsible for the 2003 SARS outbreak, utilises angiotensin-converting enzyme 2 (ACE2) and transmembrane serine protease 2 (TMPRSS2) host molecules for viral entry. ACE2 and TMPRSS2 have recently been implicated in SARS-CoV-2 viral infection. Additional host molecules including ADAM17, cathepsin L, CD147 and GRP78 may also function as receptors for SARS-CoV-2.To determine the expression and in situ localisation of candidate SARS-CoV-2 receptors in the respiratory mucosa, we analysed gene expression datasets from airway epithelial cells of 515 healthy subjects, gene promoter activity analysis using the FANTOM5 dataset containing 120 distinct sample types, single cell RNA sequencing (scRNAseq) of 10 healthy subjects, proteomic datasets, immunoblots on multiple airway epithelial cell types, and immunohistochemistry on 98 human lung samples.We demonstrate absent to low ACE2 promoter activity in a variety of lung epithelial cell samples and low ACE2 gene expression in both microarray and scRNAseq datasets of epithelial cell populations. Consistent with gene expression, rare ACE2 protein expression was observed in the airway epithelium and alveoli of human lung, confirmed with proteomics. We present confirmatory evidence for the presence of TMPRSS2, CD147 and GRP78 protein in vitro in airway epithelial cells and confirm broad in situ protein expression of CD147 and GRP78 in the respiratory mucosa.Collectively, our data suggest the presence of a mechanism dynamically regulating ACE2 expression in human lung, perhaps in periods of SARS-CoV-2 infection, and also suggest that alternative receptors for SARS-CoV-2 exist to facilitate initial host cell infection.

Effects of air pollutants on the transmission and severity of respiratory viral infections

Particulate matter, sulfur dioxide, nitrogen oxides, ozone, carbon monoxide, volatile organic compounds (VOCs) and polycyclic aromatic hydrocarbons (PAHs) are among the outdoor air pollutants that are major factors in diseases, causing especially adverse respiratory effects in humans. On the other hand, the role of respiratory viruses in the pathogenesis of severe respiratory infections is an issue of great importance. The present literature review was aimed at assessing the potential effects of air pollutants on the transmission and severity of respiratory viral infections. We have reviewed the scientific literature regarding the association of outdoor air pollution and respiratory viruses on respiratory diseases. Evidence supports a clear association between air concentrations of some pollutants and human respiratory viruses interacting to adversely affect the respiratory system. Given the undoubted importance and topicality of the subject, we have paid special attention to the association between air pollutants and the transmission and severity of the effects caused by the coronavirus named SARS-CoV-2, which causes the COVID-19. Although to date, and by obvious reasons, the number of studies on this issue are still scarce, most results indicate that chronic exposure to air pollutants delays/complicates recovery of patients of COVID-19 and leads to more severe and lethal forms of this disease. This deserves immediate and in-depth experimental investigations.

Epithelial-interleukin-1 inhibits collagen formation by airway fibroblasts: Implications for asthma

In asthma, the airway epithelium has an impaired capacity to differentiate and plays a key role in the development of airway inflammation and remodeling through mediator release. The study objective was to investigate the release of (IL)-1 family members from primary airway epithelial-cells during differentiation, and how they affect primary airway fibroblast (PAF)-induced inflammation, extracellular matrix (ECM) production, and collagen I remodeling. The release of IL-1α/β and IL-33 during airway epithelial differentiation was assessed over 20-days using air-liquid interface cultures. The effect of IL-1 family cytokines on airway fibroblasts grown on collagen-coated well-plates and 3-dimensional collagen gels was assessed by measurement of inflammatory mediators and ECM proteins by ELISA and western blot, as well as collagen fiber formation using non-linear optical microscopy after 24-hours. The production of IL-1α is elevated in undifferentiated asthmatic-PAECs compared to controls. IL-1α/β induced fibroblast pro-inflammatory responses (CXCL8/IL-8, IL-6, TSLP, GM-CSF) and suppressed ECM-production (collagen, fibronectin, periostin) and the cell’s ability to repair and remodel fibrillar collagen I via LOX, LOXL1 and LOXL2 activity, as confirmed by inhibition with β-aminopropionitrile. These data support a role for epithelial-derived-IL-1 in the dysregulated repair of the asthmatic-EMTU and provides new insights into the contribution of airway fibroblasts in inflammation and airway remodeling in asthma.

Current perspectives on the role of interleukin-1 signalling in the pathogenesis of asthma and COPD

Asthma and chronic obstructive pulmonary disease (COPD) cause significant morbidity and mortality worldwide. In the context of disease pathogenesis, both asthma and COPD involve chronic inflammation of the lung and are characterised by the abnormal release of inflammatory cytokines, dysregulated immune cell activity and remodelling of the airways. To date, current treatments still only manage symptoms and do not reverse the primary disease processes. In recent work, interleukin (IL)-1α and IL-1β have been suggested to play important roles in both asthma and COPD. In this review, we summarise overwhelming pre-clinical evidence for dysregulated signalling of IL-1α and IL-1β contributing to disease pathogenesis and discuss the paradox of IL-1 therapeutic studies in asthma and COPD. This is particularly important given recent completed and ongoing clinical trials with IL-1 biologics that have had varying degrees of failure and success as therapeutics for disease modification in asthma and COPD.

Particulate matters induce acute exacerbation of allergic airway inflammation via the TLR2/NF-κB/NLRP3 signaling pathway

BACKGROUND

Exposure to particulate matters (PMs) can lead to an acute exacerbation of allergic airway diseases, increasing the severity of symptoms and mortality. However, little is known about the underlying molecular mechanism. This study aimed to investigate the effects of PMs on acute exacerbation of allergic airway inflammation and seek potential therapeutic targets.

METHODS

Non-allergic control and ovalbumin (OVA)-allergic wide-type (WT) and Toll-like receptor 2 knockout (Tlr2-/-) mice were exposed to 100 μg of PM (diameter 5.85 μm) or saline by the oropharyngeal instillation. The responses were examined three days after exposure. In the RAW264.7 macrophage cell line, Tlr2 was knocked down by small-interfering RNA or the NF-κB inhibitor JSH-23 was used, and then the cells were stimulated with PMs for 12 h before comparison of the inflammatory responses.

RESULTS

PM exposure led to increased inflammatory cell recruitment and airway intensity of PAS + staining in OVA-allergic WT mice, accompanied with an accumulation of inflammatory cells and elevated inflammatory cytokines, such as IL-6 and IL-18, in the bronchoalveolar lavage fluid (BALF). Furthermore, the protein levels of TLR2 and the NLRP3 inflammasome were elevated concomitantly with the airway inflammation post-OVA/PMs challenge. Tlr2 deficiency effectively inhibited the airway inflammation, including pulmonary inflammatory cell recruitment, mucus secretion, serum OVA-specific immunoglobulin E (IgE), and BALF inflammatory cytokine production. Additionally, the P-induced NLRP3 activation in the RAW 264.7 cell line was diminished by the knockdown of Tlr2 or JSH-23 treatment in vitro.

CONCLUSION

Our results indicated that PMs exacerbate the allergic airway inflammation mediated by the TLR2/ NF-κB/NLRP3 signaling pathway. Inhibition of NF-κB seems to be a possible treatment.

[The impact of sugarcane burning on hospitalization due to respiratory diseases]

The scope of this article is to evaluate the impact of emissions from sugarcane burning on hospital admission numbers for respiratory diseases in a sugarcane region. Hospital admission records for respiratory diseases were acquired from the database of the Hospital Information System of the Unified Health System (SIH-SUS) in the period from March 28, 2011 to December 28, 2012. Levels of PM10, NO2, O3, Temperature and Relative Humidity were recorded. Logistic regression models were created to analyze the association between the total number of hospitalizations, atmospheric pollutants and meteorological variables. A total of 1,179 hospitalization admissions were recorded, with a significant increase in cases of pneumonia in the burning period (p = 0.005). Likewise, it was observed that the cluster of PM10 and NO2 was influenced 67.9% (95% CI: 11.111-2.537) followed by cluster PM10, NO2, O3 and Temperature that influenced 91.1% (95% CI: 1.116; 3.271) in the total number of hospitalization admissions. During the sugarcane burning period there were more hospitalization admissions due to respiratory tract diseases, mainly pneumonia, where the influence of air pollutants and temperature in the process of illness in the population was detected.

Silica nanoparticles as an enhancer in the IL-1β-induced inflammation cycle of A549 cells

Objective: The industrial production and combustion of coal can produce silica nanoparticles (nano-SiO₂). It enters the human body mainly through the respiratory tract and exerts a toxic effect. However, whether nano-SiO₂ can increase the IL-1β-induced inflammatory expression in A549 cells has not been tested. Therefore, the synergistic toxicity of nano-SiO₂ and IL-1β to A549 was observed in our study. Materials and methods: We exposed A549 cells to nano-SiO₂ (0, 100, 500, and 1000 μg/ml) for 12 and 24 h. The effect of nano-SiO₂ on the viability of A549 cells was observed by the CCK-8 method. The A549 cells were exposed to nano-SiO₂ (1 mg/mL) and cytokine IL-1β (10 ng/mL) for 4 h, and we detected the expression of IL-1β and IL-6 cytokines by real time quantitative polymerase chain (RT-qPCR) and enzyme linked immunosorbent assay (ELISA). The expression of β-Actin, I-κB, phospho-ERK_1/2 (P-ERK_1/2), total-ERK_1/2 (T-ERK_1/2), phospho-JNK (P-JNK), total-JNK (T-JNK), phospho-P38 (P-P38), and total-P38 (T-P38) in A549 cells was detected by the Western Blot method. Results: The nano-SiO₂ treatment resulted in a time-dependent decrease in the viability of A549 cells. The synergistic effect of nano-SiO₂ and IL-1β was observed on the new production of IL-1β and IL-6 in A549 cells. The Western blot results showed that nano-SiO₂ can increase the expression of IL-1β and IL-6 by promoting the phosphorylation of ERK_1/2 and elevating the phosphorylation of I-κB by IL-1β. IL-1β and IL-6 were induced by nano-SiO₂, and the IL-1β treatment with 20 μM of I-κBα phosphorylation inhibitor (PD98059) and 20 μM of ERK_1/2 inhibitor (BAY11-7082) for 1 h was significantly lower than that of the control group in A549 cells. Discussion and conclusion: These results indicated that nano-SiO₂ had a toxic effect on A549 cells, and this effect could increase IL-1β on the A549 cell-induced inflammatory response. The results suggested that the release of IL-1β and IL-6 in A549 was enhanced by the synergistic IL-1β-induced phosphorylation of ERK_1/2 and I-κB. This process is similar to a snowball, and it is possible that IL-1β is continuously produced and repeatedly superimposed in A549 cells to produce an inflammatory effect; then, a vicious circle occurs, and an inflammatory storm is accelerated.

The inflammasomes, immune guardians at defence barriers

As a result of its strategic location, the epithelium is constantly exposed to a wide variety of pathogen and danger signals. Traditionally, the epithelium has been perceived as a defensive but passive barrier; however, it has now become evident that the epithelium senses and actively responds to these signals in order to maintain barrier homeostasis and contributes to the inflammatory response. One way it does this is by producing pro-inflammatory cytokines including interleukin-1β (IL-1β) and IL-18. These two cytokines are synthesized as inactive precursors, the maturation of which is mediated by pro-inflammatory caspases after the activation and assembly of macromolecular complexes called inflammasomes. Epithelial cells express a large panel of inflammasome components, and although the molecular mechanisms underlying the activation of these complexes in haematopoietic cells are well understood, how epithelial cells react to danger signals to activate the inflammasome remains unclear. We review and discuss how different inflammasomes contribute to barrier homeostasis and inflammation at several barrier sites, their mechanisms and how their aberrant regulation contributes to disease at the different epithelia.

Regulation of xanthine dehydrogensase gene expression and uric acid production in human airway epithelial cells

Introduction

The airway epithelium is a physical and immunological barrier that protects the pulmonary system from inhaled environmental insults. Uric acid has been detected in the respiratory tract and can function as an antioxidant or damage associated molecular pattern. We have demonstrated that human airway epithelial cells are a source of uric acid. Our hypothesis is that uric acid production by airway epithelial cells is induced by environmental stimuli associated with chronic respiratory diseases. We therefore examined how airway epithelial cells regulate uric acid production.

Materials and methods

Allergen and cigarette smoke mouse models were performed using house dust mite (HDM) and cigarette smoke exposure, respectively, with outcome measurements of lung uric acid levels. Primary human airway epithelial cells isolated from clinically diagnosed patients with asthma and chronic obstructive pulmonary disease (COPD) were grown in submerged cultures and compared to age-matched healthy controls for uric acid release. HBEC-6KT cells, a human airway epithelial cell line, were grown under submerged monolayer conditions for mechanistic and gene expression studies.

Results

HDM, but not cigarette smoke exposure, stimulated uric acid production in vivo and in vitro. Primary human airway epithelial cells from asthma, but not COPD patients, displayed elevated levels of extracellular uric acid in culture. In HBEC-6KT, production of uric acid was sensitive to the xanthine dehydrogenase (XDH) inhibitor, allopurinol, and the ATP Binding Cassette C4 (ABCC4) inhibitor, MK-571. Lastly, the pro-inflammatory cytokine combination of TNF-α and IFN-γ elevated extracellular uric acid levels and XDH gene expression in HBEC-6KT cells.

Conclusions

Our results suggest that the active production of uric acid from human airway epithelial cells may be intrinsically altered in asthma and be further induced by pro-inflammatory cytokines.

Predictive and Prognostic Biomarkers of Respiratory Diseases due to Particulate Matter Exposure

Air pollution is getting severe and concerns about its toxicity effects on airway and lung disease are also increasing. Particulate matter (PM) is major component of air pollutant. It causes respiratory diseases, such as asthma, chronic obstructive pulmonary disease, lung cancer, and so on. PM particles enter the airway and lung by inhalation, causing damages to them. Especially, PM_2.5 can penetrate into the alveolus and pass to the systemic circulation. It can affect the cardiopulmonary system and cause cardiopulmonary disorders. In this review, we focused on PM-inducing toxicity mechanisms in the framework of oxidative stress, inflammation, and epigenetic changes. We also reviewed its correlation with respiratory diseases. In addition, we reviewed biomarkers related to PM-induced respiratory diseases. These biomarkers might be used for disease prediction and early diagnosis. With recent trend of using genomic analysis tools in the field of toxicogenomics, respiratory disease biomarkers associated with PM will be continuously investigated. Effective biomarkers derived from earlier studies and further studies might be utilized to reduce respiratory diseases.

Novel flow cytometry approach to identify bronchial epithelial cells from healthy human airways

Sampling various compartments within the lower airways to examine human bronchial epithelial cells (HBEC) is essential for understanding numerous lung diseases. Conventional methods to identify HBEC in bronchoalveolar lavage (BAL) and wash (BW) have throughput limitations in terms of efficiency and ensuring adequate cell numbers for quantification. Flow cytometry can provide high-throughput quantification of cell number and function in BAL and BW samples, while requiring low cell numbers. To date, a flow cytometric method to identify HBEC recovered from lower human airway samples is unavailable. In this study we present a flow cytometric method identifying HBEC as CD45 negative, EpCAM/pan-cytokeratin (pan-CK) double-positive population after excluding debris, doublets and dead cells from the analysis. For validation, the HBEC panel was applied to primary HBEC resulting in 98.6% of live cells. In healthy volunteers, HBEC recovered from BAL (2.3% of live cells), BW (32.5%) and bronchial brushing samples (88.9%) correlated significantly (p = 0.0001) with the manual microscopy counts with an overall Pearson correlation of 0.96 across the three sample types. We therefore have developed, validated, and applied a flow cytometric method that will be useful to interrogate the role of the respiratory epithelium in multiple lung diseases.

The NLRP3 inflammasome in pathogenic particle and fibre-associated lung inflammation and diseases

The concept of the inflammasome, a macromolecular complex sensing cell stress or danger signals and initiating inflammation, was first introduced approximately a decade ago. Priming and activation of these intracellular protein platforms trigger the maturation of pro-inflammatory chemokines and cytokines, most notably, interleukin-1β (IL-1β) and IL-18, to promulgate innate immune defenses. Although classically studied in models of gout, Type II diabetes, Alzheimer's disease, and multiple sclerosis, the importance and mechanisms of action of inflammasome priming and activation have recently been elucidated in cells of the respiratory tract where they modulate the responses to a number of inhaled pathogenic particles and fibres. Most notably, inflammasome activation appears to regulate the balance between tissue repair and inflammation after inhalation of pathogenic pollutants such as asbestos, crystalline silica (CS), and airborne particulate matter (PM). Different types of fibres and particles may have distinct mechanisms of inflammasome interaction and outcome. This review summarizes the structure and function of inflammasomes, the interplay between various chemokines and cytokines and cell types of the lung and pleura after inflammasome activation, and the events leading to the development of non-malignant (allergic airway disease and chronic obstructive pulmonary disease (COPD), asbestosis, silicosis) and malignant (mesothelioma, lung cancer) diseases by pathogenic particulates. In addition, it emphasizes the importance of communication between cells of the immune system, target cells of these diseases, and components of the extracellular matrix (ECM) in regulation of inflammasome-mediated events.