Pulmonary surfactant phosphatidylcholines induce immunological adaptation of alveolar macrophages

"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.

Nutraceutical formulation for immune system modulation: Active constituents, in vitro antibacterial and immunomodulatory activity, and metabolomics analysis

There is a large demand for nutraceuticals in the market and studies related to their action are needed. In this paper, the antimicrobial activity and the immunomodulatory effect of a nutraceutical formulation containing 14.39% of ascorbic acid, 7.17% of coenzyme Q10, 1.33% of Echinacea polyphenols, 0.99% of pine flavan-3-ols, 0.69% of resveratrol and 0.023% of Echinacea alkylamides were studied using in vitro assays and cell-based metabolomics. Chromatographic analysis allowed us to study the nutraceutical composition. The antibacterial activity was evaluated on S. aureus, K. pneumoniae, P. aeruginosa, E. coli, H. influenzae, S. pyogenes, S. pneumoniae and M. catarrhalis. The immunomodulatory activity was assessed on human macrophages and dendritic cells. The production of IL-1β, IL-12p70, IL-10 and IL-8 was evaluated on culture medium by ELISA and the activation/maturation of dendritic cells with cytofluorimetric analysis. Treated and untreated macrophages and dendritic cell lysates were analysed by liquid chromatography coupled with high-resolution mass spectrometry, and results were compared using multivariate data analysis to identify biological markers related to the treatment with the food supplement. The food supplement decreased K. pneumoniae, P. aeruginosa, E. coli, Methicillin-resistant Staphylococcus aureus (MRSA) and M. catharralis growth, reduced the inflammatory response in macrophages exposed to lipopolysaccharide (LPS) and modulated the activation and maturation of the dendritic cells. Oxidized phospholipids were identified as the main biological markers of treated cell lysates, compared with controls.

Respiratory syncytial virus infection disrupts pulmonary microbiota to induce microglia phenotype shift

The lung-brain axis is an emerging biological pathway that is being investigated in relation to microbiome medicine. Increasing evidence suggests that pulmonary viral infections can lead to distinct pathological imprints in the brain, so there is a need to explore and understand this mechanism and find possible interventions. This study used respiratory syncytial virus (RSV) infection in mice as a model to establish the potential lung-brain axis phenomenon. We hypothesized that RSV infection could disrupt the lung microbiota, compromise immune barriers, and induce a significant shift in microglia phenotype. One week old mice were randomized into the control, Ampicillin, RSV, and RSV+Ampicillin treated groups (n = 6 each). Seven days after the respective treatments, the mice were anaesthetized. Immunofluorescence and real-time qRT-PCR was used to detect virus. Hematoxylin-eosin staining was used to detect histopathology. Malondialdehyde and superoxide dismutase were used to determine oxidative stress and antioxidant capacity. Real-time qRT-PCR and enzyme-linked immunosorbent assay (ELISA) were used to measure Th differentiation in the lung. Real-time qRT-PCR, ELISA, and confocal immunofluorescence were used to determine the microglia phenotype. 16S DNA technology was used to detect lung microflora. RSV infection induces elevated oxidative stress, reduced antioxidant, and significant dysbacteriosis in the lungs of mice. Pulmonary microbes were found to enhance Th1-type immunoreactivity induced by RSV infection and eventually induced M1-type dominant microglia in the brains of mice. This study was able to establish a correlation between the pulmonary microbiome and brain function. Therefore, we recommend a large sample size study with robust data analysis for the long-term effects of antibiotics and RSV infection on brain physiology.

Inflammation resolution in environmental pulmonary health and morbidity

Inflammation and resolution are dynamic processes comprised of inflammatory activation and neutrophil influx, followed by mediator catabolism and efferocytosis. These critical pathways ensure a return to homeostasis and promote repair. Over the past decade research has shown that diverse mediators play a role in the active process of resolution. Specialized pro-resolving mediators (SPMs), biosynthesized from fatty acids, are released during inflammation to facilitate resolution and are deficient in a variety of lung disorders. Failed resolution results in remodeling and cellular deposition through pro-fibrotic myofibroblast expansion that irreversibly narrows the airways and worsens lung function. Recent studies indicate environmental exposures may perturb and deregulate critical resolution pathways. Environmental xenobiotics induce lung inflammation and generate reactive metabolites that promote oxidative stress, injuring the respiratory mucosa and impairing gas-exchange. This warrants recognition of xenobiotic associated molecular patterns (XAMPs) as new signals in the field of inflammation biology, as many environmental chemicals generate free radicals capable of initiating the inflammatory response. Recent studies suggest that unresolved, persistent inflammation impacts both resolution pathways and endogenous regulatory mediators, compromising lung function, which over time can progress to chronic lung disease. Chronic ozone (O3) exposure overwhelms successful resolution, and in susceptible individuals promotes asthma onset. The industrial contaminant cadmium (Cd) bioaccumulates in the lung to impair resolution, and recurrent inflammation can result in chronic obstructive pulmonary disease (COPD). Persistent particulate matter (PM) exposure increases systemic cardiopulmonary inflammation, which reduces lung function and can exacerbate asthma, COPD, and idiopathic pulmonary fibrosis (IPF). While recurrent inflammation underlies environmentally induced pulmonary morbidity and may drive the disease process, our understanding of inflammation resolution in this context is limited. This review aims to explore inflammation resolution biology and its role in chronic environmental lung disease(s).

Alveolar macrophages: Achilles' heel of SARS-CoV-2 infection

The coronavirus disease 2019 (COVID-19) pandemic has caused more than 6.3 million deaths to date. Despite great efforts to curb the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), vaccines and neutralizing antibodies are in the gloom due to persistent viral mutations and antiviral compounds face challenges of specificity and safety. In addition, vaccines are unable to treat already-infected individuals, and antiviral drugs cannot be used prophylactically. Therefore, exploration of unconventional strategies to curb the current pandemic is highly urgent. Alveolar macrophages (AMs) residing on the surface of alveoli are the first immune cells that dispose of alveoli-invading viruses. Our findings demonstrate that M1 AMs have an acidic endosomal pH, thus favoring SARS-CoV-2 to leave endosomes and release into the cytosol where the virus initiates replication; in contrast, M2 AMs have an increased endosomal pH, which dampens the viral escape and facilitates delivery of the virus for lysosomal degradation. In this review, we propose that AMs are the Achilles’ heel of SARS-CoV-2 infection and that modulation of the endosomal pH of AMs has the potential to eliminate invaded SARS-CoV-2; the same strategy might also be suitable for other lethal respiratory viruses.

Characterization of the Structural Diversity and Structure-Specific Behavior of Oxidized Phospholipids by LC-MS/MS

Polyunsaturated fatty acids (PUFAs), esterified to phospholipids, are susceptible to oxidation. They form oxidized phospholipids (OxPLs) by oxygenases or reactive oxygen species (ROS), or both. These OxPLs are associated with various diseases, such as atherosclerosis, pulmonary injuries, neurodegenerative diseases, cancer, and diabetes. Since many types of OxPLs seem to be generated in vivo, precise determination of their structural diversity is required to understand their potential structure-specific functions. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) is a powerful method to quantitatively measure the structural diversity of OxPLs present in biological samples. This review outlines recent advances in analytical methods for OxPLs and their physiological relevance in health and diseases.

Potential Therapeutic Applications of Pulmonary Surfactant Lipids in the Host Defence Against Respiratory Viral Infections

Pulmonary surfactant is a complex and highly surface-active material. It covers the alveolar epithelium and consists of 90% lipids and 10% proteins. Pulmonary surfactant lipids together with pulmonary surfactant proteins facilitate breathing by reducing surface tension of the air-water interface within the lungs, thereby preventing alveolar collapse and the mechanical work required to breathe. Moreover, pulmonary surfactant lipids, such as phosphatidylglycerol and phosphatidylinositol, and pulmonary surfactant proteins, such as surfactant protein A and D, participate in the pulmonary host defense and modify immune responses. Emerging data have shown that pulmonary surfactant lipids modulate the inflammatory response and antiviral effects in some respiratory viral infections, and pulmonary surfactant lipids have shown promise for therapeutic applications in some respiratory viral infections. Here, we briefly review the composition, antiviral properties, and potential therapeutic applications of pulmonary surfactant lipids in respiratory viral infections.

Ozone-Induced Oxidative Stress, Neutrophilic Airway Inflammation, and Glucocorticoid Resistance in Asthma

Despite recent advances in using biologicals that target Th2 pathways, glucocorticoids form the mainstay of asthma treatment. Asthma morbidity and mortality remain high due to the wide variability of treatment responsiveness and complex clinical phenotypes driven by distinct underlying mechanisms. Emerging evidence suggests that inhalation of the toxic air pollutant, ozone, worsens asthma by impairing glucocorticoid responsiveness. This review discusses the role of oxidative stress in glucocorticoid resistance in asthma. The underlying mechanisms point to a central role of oxidative stress pathways. The primary data source for this review consisted of peer-reviewed publications on the impact of ozone on airway inflammation and glucocorticoid responsiveness indexed in PubMed. Our main search strategy focused on cross-referencing "asthma and glucocorticoid resistance" against "ozone, oxidative stress, alarmins, innate lymphoid, NK and γδ T cells, dendritic cells and alveolar type II epithelial cells, glucocorticoid receptor and transcription factors". Recent work was placed in the context from articles in the last 10 years and older seminal research papers and comprehensive reviews. We excluded papers that did not focus on respiratory injury in the setting of oxidative stress. The pathways discussed here have however wide clinical implications to pathologies associated with inflammation and oxidative stress and in which glucocorticoid treatment is essential.