Role of Macrophages in Air Pollution Exposure Related Asthma

Impact of swine influenza A virus on porcine reproductive and respiratory syndrome virus infection in alveolar macrophages

Porcine respiratory disease complex represents a major challenge for the swine industry, with swine influenza A virus (swIAV) and porcine reproductive and respiratory syndrome virus (PRRSV) being major contributors. Epidemiological studies have confirmed the co-circulation of these viruses in pig herds, making swIAV-PRRSV co-infections expected. A couple of in vivo co-infection studies have reported replication interferences between these two viruses. Herein, using a reductionist in vitro model, we investigated the potential mechanisms of these in vivo interferences. We first examined the impact of swIAV on porcine alveolar macrophages (AMs) and its effects on AMs co-infection by PRRSV. This was done either in monoculture or in co-culture with respiratory tracheal epithelial cells to represent the complexity of the interactions between the viruses and their respective target cells (epithelial cells for swIAV and AMs for PRRSV). AMs were obtained either from conventional or specific pathogen-free (SPF) pigs. SwIAV replication was abortive in AMs, inducing cell death at high multiplicity of infections. In AMs from three out of four conventional animals, swIAV showed no impact on PRRSV replication. However, inhibition of PRRSV multiplication was observed in AMs from one animal, accompanied by an early increase in the expression of interferon (IFN)-I and IFN-stimulated genes. In AMs from six SPF pigs, swIAV inhibited PRRSV replication in all animals, with an early induction of antiviral genes. Co-culture experiments involving tracheal epithelial cells and AMs from either SPF or conventional pigs all showed swIAV-induced inhibition of PRRSV replication, together with early induction of antiviral genes. These findings highlight the complex interactions between swIAV and PRRSV in porcine AMs, and would suggest a role of host factors, such as sanitary status, in modulating viral propagation. Our co-culture experiments demonstrated that swIAV inhibits PRRSV replication more effectively in the presence of respiratory tracheal epithelial cells, suggesting a synergistic antiviral response between AMs and epithelial cells, consistent with in vivo experiments.

Signalling Pathways of Inflammation and Cancer in Human Mononuclear Cells: Effect of Nanoparticle Air Pollutants

Fine inhalable particulate matter (PM) triggers an inflammatory response in the airways and activates mononuclear cells, mediators of tissue homeostasis, and tumour-promoting inflammation. We have assessed ex vivo responses of human monocytes and monocyte-derived macrophages to standardised air pollutants: carbon black, urban dust, and nanoparticulate carbon black, focusing on their pro-inflammatory and DNA-damaging properties. None of the PM (100 μg/mL/24 h) was significantly toxic to the cells, aside from inducing oxidative stress, fractional DNA damage, and inhibiting phagocytosis. TNFα was only slightly increased. PM nanoparticles increase the expression and activate DNA-damage-related histone H2A.X as well as pro-inflammatory NF-κB. We have shown that the urban dust stimulates the pathway of DNA damage/repair via the selective post-translational phosphorylation of H2A.X while nanoparticulate carbon black increases inflammation via activation of NF-κB. Moreover, the inflammatory response to lipopolysaccharide was significantly stronger in macrophages pre-exposed to urban dust or nanoparticulate carbon black. Our data show that airborne nanoparticles induce PM-specific, epigenetic alterations in the subsets of cultured mononuclear cells, which may be quantified using binary fluorescence scatterplots. Such changes intercede with inflammatory signalling and highlight important molecular and cell-specific epigenetic mechanisms of tumour-promoting inflammation.

Gut-derived memory γδ T17 cells exacerbate sepsis-induced acute lung injury in mice

Sepsis is a critical global health concern linked to high mortality rates, often due to acute lung injury (ALI)/acute respiratory distress syndrome (ARDS). While the gut-lung axis involvement in ALI is recognized, direct migration of gut immune cells to the lung remains unclear. Our study reveals sepsis-induced migration of γδ T17 cells from the small intestine to the lung, triggering an IL-17A-dominated inflammatory response in mice. Wnt signaling activation in alveolar macrophages drives CCL1 upregulation, facilitating γδ T17 cell migration. CD44+ Ly6C- IL-7Rhigh CD8low cells are the primary migratory subtype exacerbating ALI. Esketamine attenuates ALI by inhibiting pulmonary Wnt/β-catenin signaling-mediated migration. This work underscores the pivotal role of direct gut-to-lung memory γδ T17 cell migration in septic ALI and clarifies the importance of localized IL-17A elevation in the lung.

Research progress on the relationship between phenotype and signaling pathways of pulmonary macrophages and asthma

OBJECTIVE

The purpose of this study is to systematically investigate the different phenotypes and functional analyses of macrophages in lung tissue.

DATA SOURCES

A search was performed using three databases (Web of Science, Science Direct, and MEDLINE) for all relevant studies published from January 1, 2019, to December 31, 2023.

STUDY SELECTIONS

This systematic review complied with the PRlSMA document's requirements, including studies related to the signaling pathway relationship between pulmonary macrophages and asthma phenotype. The search includedstudies published in English or French lanquage, and was based on title, abstract, and complete textDocuments not meeting inclusion requirements were excluded.

RESULTS

We have identified studies published within the past five years that meet the criteria for inclusion in this review. We found that asthma is a heterogeneous chronic inflammatory lung disease, and lung tissue macrophages are important immune cells in the respiratory tract. Pulmonary macrophages are also heterogeneous, as they have different subgroups with varying effector functions depending on the environment. They have different phenotypes and biological functions in different disease environments. The phenotypic changes of pulmonary macrophages occur during asthma, and the study of the different phenotypes and functions of macrophages in lung tissue is of great significance for treatment.

CONCLUSIONS

This review summarizes current literature and provides a detailed introduction to the role of macrophages as key inflammatory mediators in the pathogenesis of asthma, as well as existing knowledge gaps. In addition, we propose that regulatory macrophages may prevent the development of asthma by producing IL-10, and regulating the polarization of pulmonary macrophages may be a new direction for asthma treatment.

Correlation between Exposure to UFP and ACE/ACE2 Pathway: Looking for Possible Involvement in COVID-19 Pandemic

The overlap between the geographic distribution of COVID-19 outbreaks and pollution levels confirmed a correlation between exposure to atmospheric particulate matter (PM) and the SARS-CoV-2 pandemic. The RAS system is essential in the pathogenesis of inflammatory diseases caused by pollution: the ACE/AngII/AT1 axis activates a pro-inflammatory pathway, which is counteracted by the ACE2/Ang(1-7)/MAS axis, which activates an anti-inflammatory and protective pathway. However, ACE2 is also known to act as a receptor through which SARS-CoV-2 enters host cells to replicate. Furthermore, in vivo systems have demonstrated that exposure to PM increases ACE2 expression. In this study, the effects of acute and sub-acute exposure to ultrafine particles (UFP), originating from different anthropogenic sources (DEP and BB), on the levels of ACE2, ACE, COX-2, HO-1, and iNOS in the lungs and other organs implicated in the pathogenesis of COVID-19 were analyzed in the in vivo BALB/c male mice model. Exposure to UFP alters the levels of ACE2 and/or ACE in all examined organs, and exposure to sub-acute DEP also results in the release of s-ACE2. Furthermore, as evidenced in this and our previous works, COX-2, HO-1, and iNOS levels also demonstrated organ-specific alterations. These proteins play a pivotal role in the UFP-induced inflammatory and oxidative stress responses, and their dysregulation is linked to the development of severe symptoms in individuals infected with SARS-CoV-2, suggesting a heightened vulnerability or a more severe clinical course of the disease. UFP and SARS-CoV-2 share common pathways; therefore, in a "risk stratification" concept, daily exposure to air pollution may significantly increase the likelihood of developing a severe form of COVID-19, explaining, at least in part, the greater lethality of the virus observed in highly polluted areas.

Comorbid asthma is associated with rhinitis severity in children exposed to air pollutants

BACKGROUND

The impact of asthma on the severity of rhinitis when children with allergic rhinitis (AR) are exposed to air pollutants has not been studied.

METHODS

Children with AR (65 with asthma, 208 without asthma), aged 6-13 years, were recruited from a hospital in Taichung, Taiwan, between 2007 and 2011. Correlations between Pediatric-Rhinoconjunctivitis-Quality-of-Life score, nasal peak expiratory flow, and air pollutants were compared. With the same age, research time, and form the same city, children with AR (660 with asthma, 3174 without asthma) were selected from a database. Correlations between clinical visit times for AR and air pollutants were compared.

RESULTS

In male children with AR and asthma, both clinical and database studies revealed a correlation between higher rhinitis discomfort (quality-of-life score), higher visit times for AR, and higher PM10, PM2.5, NO2, NMHC concentrations. Correlations between higher nasal inflammation/obstruction (lower expiratory flow) and higher air pollutant concentrations were observed in male children with AR and asthma.

CONCLUSION

In children with AR, comorbid asthma was associated with increased rhinitis severity when they were exposed to air pollutants, and the association was only noted in males. Increased nasal obstruction/inflammation from exposure to air pollutants may be the mechanisms underlying this association.

IMPACT STATEMENT

The influence of asthma on the severity of rhinitis when children with allergic rhinitis (AR) are exposed to air pollutants has not been studied. In children with AR, the correlation between higher rhinitis discomfort, higher number of clinical visits for AR, and higher PM10, PM2.5, NO2, NMHC concentrations were only noted in those who also had asthma. The correlation was only noted in male. Comorbid asthma was associated with higher rhinitis severity when children with AR are exposed to air pollutants The association was only noted in male.

Effect of Air Pollutants on Allergic Inflammation in Structural Cells of the Nasal Mucosa

OBJECTIVES

Air pollution is an increasing global concern, and its effect on allergic inflammation has attracted the attention of many researchers. Particulate matter (PM) is a major component of ambient air pollution, and heavy metals are the primary toxic constituents of PM. As previous studies on the impact of air pollutants on allergic inflammation did not adequately mimic real-world atmospheric exposure, we developed an experimental model to investigate the effects of aerosolized air pollutants on nasal epithelial cells and fibroblasts.

METHODS

We collected particulate matter 2.5 (PM2.5) samples from ambient 24-hour air samples obtained in Seoul from August 2020 to August 2022, and then conducted component analysis for metallic constituents. Primary nasal epithelial cells and nasal fibroblasts, obtained and cultured from the turbinate tissues of human participants, were treated with PM2.5. The associations of heavy metals identified from the component analysis with cytokine expression were investigated. A three-dimensional (3D)-hybrid culture model, consisting of co-culture of an air-liquid interface and nasal fibroblast spheroids, was constructed to observe the impact of aerosolized air pollutants.

RESULTS

Among the heavy metals, Si was the predominant component of PM2.5, and Zn showed the highest correlation with the concentration of PM2.5 in Seoul. PM2.5, Zn, and Si increased the production of epithelial cell-derived cytokines, and PM2.5 and Zn exhibited similar trends with one another. Exposure of the 3D-hybrid model to aerosolized PM2.5 and Zn resulted in elevated periostin, alpha-smooth muscle actin, and fibronectin expression in fibroblast spheroids, and those without an epithelial barrier exhibited a similar increase in periostin expression.

CONCLUSION

Ambient air pollutants in the form of aerosols increase the expression of allergic inflammatory cytokines in both nasal epithelial cells and fibroblasts. Regulations on air pollution will help reduce the global burden of allergic diseases in the future.

Particulate Matter and Its Impact on Macrophages: Unraveling the Cellular Response for Environmental Health

Particulate matter (PM) imposes a significant impact to environmental health with deleterious effects on the human pulmonary and cardiovascular systems. Macrophages (Mφ), key immune cells in lung tissues, have a prominent role in responding to inhaled cells, accommodating inflammation, and influencing tissue repair processes. Elucidating the critical cellular responses of Mφ to PM exposure is essential to understand the mechanisms underlying PM-induced health effects. The present review aims to give a glimpse on literature about the PM interaction with Mφ, triggering the cellular events causing the inflammation, oxidative stress (OS) and tissue damage. The present paper reviews the different pathways involved in Mφ activation upon PM exposure, including phagocytosis, intracellular signaling cascades, and the release of pro-inflammatory mediators. Potential therapeutic strategies targeting Mφ-mediated responses to reduce PM-induced health effects are also discussed. Overall, unraveling the complex interplay between PM and Mφ sheds light on new avenues for environmental health research and promises to develop targeted interventions to reduce the burden of PM-related diseases on global health.

Nootkatone attenuates airway inflammation in asthmatic mice through repressing ROS-induced NLRP3 inflammasome activation

Nootkatone (NKT) exhibits potential pharmacological activities including anti-oxidation and anti-inflammation. Nevertheless, little is known about the roles of NKT in asthmatic airway inflammation. In the study, mice were sensitized and challenged with ovalbumin (OVA) to establish experimental allergic asthma model. After treatment with NKT, lung tissues, peripheral blood, and bronchoalveolar lavage fluid (BALF) were collected to assess inflammatory cytokines, oxidative stress, and pathological alternations. The effects of NKT on regulating reactive oxygen species (ROS)-induced NLR family pyrin domain containing 3 (NLRP3) inflammasome activation was assessed in IL-13-treated BEAS-2B cell model. We found that NKT treatment decreased the production of Th2 inflammatory cytokines (IL-4, IL-5, and IL-13) in BALF and IgE levels in serum, and alleviated inflammatory cell penetration, goblet cell proliferation, collagen accumulation, and mucus hypersecretion in lung tissues. NKT treatment mitigated oxidative stress and NLRP3 inflammasome activation in asthmatic mice. IL-13 treatment induced oxidative stress and NLRP3-mediated pyroptosis in BEAS-2B bronchial epithelial cells, whereas these effects were blocked by NKT. NKT protected against airway remodeling, as indicated by decreased epithelial-mesenchymal transition. Taken together, these results demonstrate that NKT mitigates asthmatic airway inflammation by inhibiting ROS-triggered NLRP3 activation and may be a potential agent for treating asthma.

Emerging role of macrophages in non-infectious diseases: An update

In the past three decades, a huge body of evidence through various research studies conducted on animal models, has demonstrated that the macrophages are centralized of all the leukocytes involved in diseases and, particularly, their role in non-infectious diseases has been studied extensively for which they have also been referred to as the "double-edged swords". The most versatile of all immunocytes, macrophages play a key role in health and diseases. Various experimental models have demonstrated the conventional paradigms such as the M1/M2 dichotomy, which is not as obvious and presents a complex characterization of the macrophages in the disease immunology. In human diseases, this M1-M2 continuum shows a complex web of mechanisms, which are majorly divided into the pro-inflammatory roles (derived mainly by the cytokines: IL-1, IL-6, IL-12, IL-23, and tumor necrosis factor) and anti-inflammatory roles (CCl-17, CCl-22, CCL-2, transforming growth factor (TGF), and interleukin-10), which are involved in the wound healing and pathogen-suppression. The conventional division of these macrophages as M1 and M2 is derived from the opposing functions of these macrophages; where M1 is involved in the tissue damage and pro-inflammatory roles and M2 promotes cell proliferation and the resolution of inflammation. Both these pathways down-regulate each other in diseases through a plethora of enzymatic and cytokine mediators.