Neutrophil extracellular traps and the dysfunctional innate immune response of cystic fibrosis lung disease: a review

NET-related gene signature for predicting AML prognosis

Acute Myeloid Leukemia (AML) is a malignant blood cancer with a high mortality rate. Neutrophil extracellular traps (NETs) influence various tumor outcomes. However, NET-related genes (NRGs) in AML had not yet received much attention. This study focuses on the role of NRGs in AML and their interaction with the immunological microenvironment. The gene expression and clinical data of patients with AML were downloaded from the TCGA-LAML and GEO cohorts. We identified 148 NRGs through the published article. Univariate Cox regression was used to analyze the association of NRGs with overall survival (OS). The least absolute shrinkage and selection operator were utilized to assess the predictive efficacy of NRGs. Kaplan-Meier plots visualized survival estimates. ROC curves assessed the prognostic value of NRG-based features. A nomogram, integrating clinical information and prognostic scores of patients, was constructed using multivariate logistic regression and Cox proportional hazards regression models. Twenty-seven NRGs were found to significantly impact patient OS. Six NRGs-CFTR, ENO1, PARVB, DDIT4, MPO, LDLR-were notable for their strong predictive ability regarding patient survival. The ROC values for 1-, 3-, and 5-year survival rates were 0.794, 0.781, and 0.911, respectively. In the training set (TCGA-LAML), patients in the high NRG risk group showed a poorer prognosis (p < 0.001), which was validated in two external datasets (GSE71014 and GSE106291). The 6-NRG signature and corresponding nomograms exhibit superior predictive accuracy, offering insights for pre-immune response evaluation and guiding future immuno-oncology treatments and drug selection for AML patients.

Cryo-EM analysis of Pseudomonas phage Pa193 structural components

The World Health Organization has designated Pseudomonas aeruginosa as a critical pathogen for the development of new antimicrobials. Bacterial viruses, or bacteriophages, have been used in various clinical settings, commonly called phage therapy, to address this growing public health crisis. Here, we describe a high-resolution structural atlas of a therapeutic, contractile-tailed Pseudomonas phage, Pa193. We used bioinformatics, proteomics, and cryogenic electron microscopy single particle analysis to identify, annotate, and build atomic models for 21 distinct structural polypeptide chains forming the icosahedral capsid, neck, contractile tail, and baseplate. We identified a putative scaffolding protein stabilizing the interior of the capsid 5-fold vertex. We also visualized a large portion of Pa193 ~ 500 Å long tail fibers and resolved the interface between the baseplate and tail fibers. The work presented here provides a framework to support a better understanding of phages as biomedicines for phage therapy and inform engineering opportunities.

Objective sputum colour assessment and clinical outcomes in bronchiectasis: data from the European Bronchiectasis Registry (EMBARC)

BACKGROUND

A validated 4-point sputum colour chart can be used to objectively evaluate the levels of airway inflammation in bronchiectasis patients. In the European Bronchiectasis Registry (EMBARC), we tested whether sputum colour would be associated with disease severity and clinical outcomes.

METHODS

We used a prospective, observational registry of adults with bronchiectasis conducted in 31 countries. Patients who did not produce spontaneous sputum were excluded from the analysis. The Murray sputum colour chart was used at baseline and at follow-up visits. Key outcomes were frequency of exacerbations, hospitalisations for severe exacerbations and mortality during up to 5-year follow-up.

RESULTS

13 484 patients were included in the analysis. More purulent sputum was associated with lower forced expiratory volume in 1 s (FEV1), worse quality of life, greater bacterial infection and a higher bronchiectasis severity index. Sputum colour was strongly associated with the risk of future exacerbations during follow-up. Compared to patients with mucoid sputum (reference group), patients with mucopurulent sputum experienced significantly more exacerbations (incident rate ratio (IRR) 1.29, 95% CI 1.22-1.38; p<0.0001), while the rates were even higher for patients with purulent (IRR 1.55, 95% CI 1.44-1.67; p<0.0001) and severely purulent sputum (IRR 1.91, 95% CI 1.52-2.39; p<0.0001). Hospitalisations for severe exacerbations were also associated with increasing sputum colour with rate ratios, compared to patients with mucoid sputum, of 1.41 (95% CI 1.29-1.56; p<0.0001), 1.98 (95% CI 1.77-2.21; p<0.0001) and 3.05 (95% CI 2.25-4.14; p<0.0001) for mucopurulent, purulent and severely purulent sputum, respectively. Mortality was significantly increased with increasing sputum purulence, hazard ratio 1.12 (95% CI 1.01-1.24; p=0.027), for each increment in sputum purulence.

CONCLUSION

Sputum colour is a simple marker of disease severity and future risk of exacerbations, severe exacerbations and mortality in patients with bronchiectasis.

The potential health effects associated with electronic-cigarette

A good old gateway theory that electronic-cigarettes (e-cigarettes) are widely recognized as safer tobacco substitutes. In actuality, demographics also show that vaping cannibalizes smoking, the best explanation of the data is the "common liability". However, the utilization of e-cigarette products remains a controversial topic at present. Currently, there has been a widespread and substantial growth in e-cigarette use worldwide owing to their endless new flavors and customizable characteristics. Furthermore, e-cigarette has grown widespread among smokers as well as non-smokers, including adolescents and young adults. And some studies have shown that e-cigarette users are at greater risk to start using combustible cigarettes while e-cigarettes use was also observed the potential benefits to people who want to quit smoking or not. Although it is true that e-cigarettes generally contain fewer toxic substances than combustible cigarettes, this does not mean that the chemical composition in e-cigarettes aerosols poses absolutely no risks. While concerns about toxic substances in e-cigarettes and their widespread use in the population are reasonable, it is also crucial to consider that e-cigarettes have been associated with the potential for promoting smoking cessation and the clinically relevant improvements in users with smoking-related pathologies. Meanwhile, there is still short of understanding of the health impacts associated with e-cigarette use. Therefore, in this review, we discussed the health impacts of e-cigarette exposure on oral, nasal, pulmonary, cardiovascular systems and brain. We aspire for this review to change people's previous perceptions of e-cigarettes and provide them with a more balanced perspective. Additionally, we suggest appropriate adjustments on regulation and policy for e-cigarette to gain greater public health benefits.

Small molecule modulators of cystic fibrosis transmembrane conductance regulator (CFTR): Structure, classification, and mechanisms

The advent of small molecule modulators targeting the cystic fibrosis transmembrane conductance regulator (CFTR) has revolutionized the treatment of persons with cystic fibrosis (CF) (pwCF). Presently, these small molecule CFTR modulators have gained approval for usage in approximately 90 % of adult pwCF. Ongoing drug development endeavors are focused on optimizing the therapeutic benefits while mitigating potential adverse effects associated with this treatment approach. Based on their mode of interaction with CFTR, these drugs can be classified into two distinct categories: specific CFTR modulators and non-specific CFTR modulators. Specific CFTR modulators encompass potentiators and correctors, whereas non-specific CFTR modulators encompass activators, proteostasis modulators, stabilizers, reader-through agents, and amplifiers. Currently, four small molecule modulators, all classified as potentiators and correctors, have obtained marketing approval. Furthermore, numerous novel small molecule modulators, exhibiting diverse mechanisms of action, are currently undergoing development. This review aims to explore the classification, mechanisms of action, molecular structures, developmental processes, and interrelationships among small molecule CFTR modulators.

Autoimmunity in people with cystic fibrosis

Cystic fibrosis (CF) clinicians may see patients who have difficult-to-manage symptoms that do not have a clear CF-related etiology, such as unusual gastrointestinal (GI) complaints, vasculitis, or arthritis. Alterations in immunity, inflammation and intraluminal dysbiosis create a milieu that may lead to autoimmunity, and the CF transmembrane regulator protein may have a direct role as well. While autoantibodies and other autoimmune markers may develop, these may or may not lead to organ involvement, therefore they are helpful but not sufficient to establish an autoimmune diagnosis. Autoimmune involvement of the GI tract is the best-established association. Next steps to understand autoimmunity in CF should include a more in-depth assessment of the community perspective on its impact. In addition, bringing together specialists in various fields including, but not limited to, pulmonology, gastroenterology, immunology, and rheumatology, would lead to cross-dissemination and help define the path forward in basic science and clinical practice.

Cardiopulmonary Impact of Electronic Cigarettes and Vaping Products: A Scientific Statement From the American Heart Association

Vaping and electronic cigarette (e-cigarette) use have grown exponentially in the past decade, particularly among youth and young adults. Cigarette smoking is a risk factor for both cardiovascular and pulmonary disease. Because of their more limited ingredients and the absence of combustion, e-cigarettes and vaping products are often touted as safer alternative and potential tobacco-cessation products. The outbreak of e-cigarette or vaping product use-associated lung injury in the United States in 2019, which led to >2800 hospitalizations, highlighted the risks of e-cigarettes and vaping products. Currently, all e-cigarettes are regulated as tobacco products and thus do not undergo the premarket animal and human safety studies required of a drug product or medical device. Because youth prevalence of e-cigarette and vaping product use was as high as 27.5% in high school students in 2019 in the United States, it is critical to assess the short-term and long-term health effects of these products, as well as the development of interventional and public health efforts to reduce youth use. The objectives of this scientific statement are (1) to describe and discuss e-cigarettes and vaping products use patterns among youth and adults; (2) to identify harmful and potentially harmful constituents in vaping aerosols; (3) to critically assess the molecular, animal, and clinical evidence on the acute and chronic cardiovascular and pulmonary risks of e-cigarette and vaping products use; (4) to describe the current evidence of e-cigarettes and vaping products as potential tobacco-cessation products; and (5) to summarize current public health and regulatory efforts of e-cigarettes and vaping products. It is timely, therefore, to review the short-term and especially the long-term implications of e-cigarettes and vaping products on cardiopulmonary health. Early molecular and clinical evidence suggests various acute physiological effects from electronic nicotine delivery systems, particularly those containing nicotine. Additional clinical and animal-exposure model research is critically needed as the use of these products continues to grow.

Electronic Nicotine Delivery System: End to Smoking or Just a New Fancy Cigarette

Smoking and tobacco chewing are the predominant causes of oral cancer. Tobacco is the second-most widely consumed psychoactive substance. There are numerous ways to quit smoking, of which one is electronic cigarettes (e-cigarettes). E-cigarette use is a brand-new, global trend. E-cigarette is a battery-operated device that heats a liquid to create a vapor that the consumer inhales. Several countries have acknowledged that the first step toward electronic nicotine delivery system (ENDS) management is a precise classification of ENDS within the limits of current legislation. Countries have currently categorized ENDS into four generations. People's perceptions about tobacco products have altered recently as a consequence of the advertising of ENDS. The likelihood of starting to smoke cigarettes was four times higher in adolescents who used ENDS, and the probability of quitting was reduced and often prolonged in those who used ENDS. In addition, ENDS normalizes smoking-like actions including inhaling in and exhaling smoke. Adverse marketing via geographic locations and social media platforms, as well as nicotine's irreversible effects on growing adolescent and young adult brains that predispose individuals to addicted behaviors, may be responsible for their rising appeal among teenagers. Despite this, ENDS use has risen among young individuals who have never smoked and undoubtedly face more health risks than those who do not use ENDS. The oral cavity is the first to encounter ENDS in individuals and where it initially affects the human system. As a known contributor to cardiovascular diseases, neurological conditions, and cancers, nicotine seems to be a serious cause for concern. This review provides a concise summary of the research on the components, mode of action, applications, and effects of e-cigarettes on oral as well as systemic systems.

Immune Checkpoint Inhibitors, Small-Molecule Immunotherapies and the Emerging Role of Neutrophil Extracellular Traps in Therapeutic Strategies for Head and Neck Cancer

Immune checkpoint inhibitor (ICI) therapy has revolutionized the treatment of many cancer types, including head and neck cancers (HNC). When checkpoint and partner proteins bind, these send an "off" signal to T cells, which prevents the immune system from destroying tumor cells. However, in HNC, and indeed many other cancers, more people do not respond and/or suffer from toxic effects than those who do respond. Hence, newer, more effective approaches are needed. The challenge to durable therapy lies in a deeper understanding of the complex interactions between immune cells, tumor cells and the tumor microenvironment. This will help develop therapies that promote lasting tumorlysis by overcoming T-cell exhaustion. Here we explore the strengths and limitations of current ICI therapy in head and neck squamous cell carcinoma (HNSCC). We also review emerging small-molecule immunotherapies and the growing promise of neutrophil extracellular traps in controlling tumor progression and metastasis.

Diabetic complications and prospective immunotherapy

The incidence of Diabetes Mellitus is increasing globally. Individuals who have been burdened with diabetes for many years often develop complications as a result of hyperglycemia. More and more research is being conducted highlighting inflammation as an important factor in disease progression. In all kinds of diabetes, hyperglycemia leads to activation of alternative glucose metabolic pathways, resulting in problematic by-products including reactive oxygen species and advanced glycation end products. This review takes a look into the pathogenesis of three specific diabetic complications; retinopathy, nephropathy and neuropathy as well as their current treatment options. By considering recent research papers investigating the effects of immunotherapy on relevant conditions in animal models, multiple strategies are suggested for future treatment and prevention of diabetic complications with an emphasis on molecular targets associated with the inflammation.

Variability of Clinical Presentation in Patients Heterozygous for the F508del Cystic Fibrosis Variant: A Series of Three Cases and a Review of the Literature

Cystic fibrosis (CF) is a genetic disease that affects the lung, pancreas, and other organs caused by the presence of biallelic CF-causing variants in the cystic fibrosis conductance regular gene (CFTR). CFTR variants can also be found in CFTR-related disorders (CFTR-RD), which present milder symptoms. Increasing access to next-generation sequencing has demonstrated that both CF and CFTR-RD have a broader array of genotypes than formerly thought. Here we present three patients who carry the most common CFTR pathogenic variant - F508del - but express a wide array of phenotypes. These cases open discussion on the role of concurrent variants in CFTR, the importance of early diagnosis and treatment, and the contribution of lifestyle factors in CF and CFTR-RD presentation.

Synthetic neutrophil extracellular traps dissect bactericidal contribution of NETs under regulation of α-1-antitrypsin

Deciphering the complex interplay of neutrophil extracellular traps (NETs) with the surrounding environment is a challenge with notable clinical implications. To bridge the gap in knowledge, we report our findings on the antibacterial activity against Pseudomonas aeruginosa of synthetic NET-mimetic materials composed of nanofibrillated DNA-protein complexes. Our synthetic system makes component-by-component bottom-up analysis of NET protein effects possible. When the antimicrobial enzyme neutrophil elastase (NE) is incorporated into the bactericidal DNA-histone complexes, the resulting synthetic NET-like structure exhibits an unexpected reduction in antimicrobial activity. This critical immune function is rescued upon treatment with alpha-1-antitrypsin (AAT), a physiological tissue-protective protease inhibitor. This suggests a direct causal link between AAT inhibition of NE and preservation of histone-mediated antimicrobial activity. These results help better understand the complex and, at times, contradictory observations of in vivo antimicrobial effects of NETs and AAT by excluding neutrophil, cytokine, and chemoattractant contributions.

The Role of MMPs in the Era of CFTR Modulators: An Additional Target for Cystic Fibrosis Patients?

Cystic fibrosis (CF) is a high-prevalence disease characterized by significant lung remodeling, responsible for high morbidity and mortality worldwide. The lung structural changes are partly due to proteolytic activity associated with inflammatory cells such as neutrophils and macrophages. Matrix metalloproteases (MMPs) are the major proteases involved in CF, and recent literature data focused on their potential role in the pathogenesis of the disease. In fact, an imbalance of proteases and antiproteases was observed in CF patients, resulting in dysfunction of protease activity and loss of lung homeostasis. Currently, many steps forward have been moved in the field of pharmacological treatment with the recent introduction of triple-combination therapy targeting the CFTR channel. Despite CFTR modulator therapy potentially being effective in up to 90% of patients with CF, there are still patients who are not eligible for the available therapies. Here, we introduce experimental drugs to provide updates on therapy evolution regarding a proportion of CF non-responder patients to current treatment, and we summarize the role of MMPs in pathogenesis and as future therapeutic targets of CF.

Bicarbonate Effects on Antibacterial Immunity and Mucus Glycobiology in the Cystic Fibrosis Lung: A Review With Selected Experimental Observations

The primary defect in cystic fibrosis (CF) is abnormal chloride and bicarbonate transport in the cystic fibrosis transmembrane conductance regulator (CFTR) epithelial ion channel. The apical surface of the respiratory tract is lined by an airway surface liquid layer (ASL) composed of mucin comprising mainly MUC5A and MUC5B glycoproteins. ASL homeostasis depends on sodium bicarbonate secretion into the airways and secretion deficits alter mucus properties leading to airway obstruction, inflammation, and infections. Downstream effects of abnormal ion transport in the lungs include altered intrinsic immune defenses. We observed that neutrophils killed Pseudomonas aeruginosa more efficiently when it had been exposed to sodium bicarbonate, and formation of neutrophil extracellular traps (NETs) by neutrophils was augmented in the presence of increasing bicarbonate concentrations. Physiological levels of bicarbonate sensitized P. aeruginosa to the antimicrobial peptide cathelicidin LL-37, which is present in both lung ASL and in NETs. Sodium bicarbonate has various uses in clinical medicine and in the care of CF patients, and could be further explored as a therapeutic adjunct against Pseudomonas infections.

Macrophage Lysosomal Alkalinization Drives Invasive Aspergillosis in a Mouse Cystic Fibrosis Model of Airway Transplantation

Cystic fibrosis (CF) lung transplant recipients (LTRs) exhibit a disproportionately high rate of life-threatening invasive aspergillosis (IA). Loss of the cystic fibrosis transmembrane conductance regulator (CFTR-/-) in macrophages (mφs) has been associated with lyosomal alkalinization. We hypothesize that this alkalinization would persist in the iron-laden post-transplant microenvironment increasing the risk of IA. To investigate our hypothesis, we developed a murine CF orthotopic tracheal transplant (OTT) model. Iron levels were detected by immunofluorescence staining and colorimetric assays. Aspergillus fumigatus (Af) invasion was evaluated by Grocott methenamine silver staining. Phagocytosis and killing of Af conidia were examined by flow cytometry and confocal microscopy. pH and lysosomal acidification were measured by LysoSensorTM and LysotrackerTM, respectively. Af was more invasive in the CF airway transplant recipient compared to the WT recipient (p < 0.05). CFTR-/- mφs were alkaline at baseline, a characteristic that was increased with iron-overload. These CFTR-/- mφs were unable to phagocytose and kill Af conidia (p < 0.001). Poly(lactic-co-glycolic acid) (PLGA) nanoparticles acidified lysosomes, restoring the CFTR-/- mφs’ ability to clear conidia. Our results suggest that CFTR-/- mφs’ alkalinization interacts with the iron-loaded transplant microenvironment, decreasing the CF-mφs’ ability to kill Af conidia, which may explain the increased risk of IA. Therapeutic pH modulation after transplantation could decrease the risk of IA.

One Size Does Not Fit All: The Past, Present and Future of Cystic Fibrosis Causal Therapies

Cystic fibrosis (CF) is the most common monogenic disorder, caused by mutations in the CF transmembrane conductance regulator (CFTR) gene. Over the last 30 years, tremendous progress has been made in understanding the molecular basis of CF and the development of treatments that target the underlying defects in CF. Currently, a highly effective CFTR modulator treatment (Kalydeco™/Trikafta™) is available for 90% of people with CF. In this review, we will give an extensive overview of past and ongoing efforts in the development of therapies targeting the molecular defects in CF. We will discuss strategies targeting the CFTR protein (i.e., CFTR modulators such as correctors and potentiators), its cellular environment (i.e., proteostasis modulation, stabilization at the plasma membrane), the CFTR mRNA (i.e., amplifiers, nonsense mediated mRNA decay suppressors, translational readthrough inducing drugs) or the CFTR gene (gene therapies). Finally, we will focus on how these efforts can be applied to the 15% of people with CF for whom no causal therapy is available yet.

Role of Cellular Metabolism in the Formation of Neutrophil Extracellular Traps in Airway Diseases

Neutrophil extracellular traps (NETs) are a recently described mechanism of neutrophils that play an important role in health and disease. NETs are an innate defense mechanism that participate in clearance of pathogens, but they may also cause collateral damage in unrelated host tissues. Neutrophil dysregulation and NETosis occur in multiple lung diseases, such as pathogen-induced acute lung injury, pneumonia, chronic obstructive pulmonary disease (COPD), severe asthma, cystic fibrosis, and recently, the novel coronavirus SARS-CoV-2. More recently, research into immunometabolism has surged due to the possibility of reprogramming metabolism in order to modulate immune functions. The present review analyzes the different metabolic pathways associated with NETs formation, and how these impact on pathologies of the airways.

Neutrophil dysfunction in the pathogenesis of cystic fibrosis

Polymorphonuclear neutrophils (PMNs) figure prominently in host defense against infection and in noninfectious inflammation. Mobilized early in an inflammatory response, PMNs mediate immediate cellular defense against microbes and orchestrate events that culminate in cessation of inflammation and restoration of homeostasis. Failure to terminate the inflammatory response and its causes can fuel exuberant inflammation characteristic of many human diseases, including cystic fibrosis (CF), an autosomal recessive genetic disease caused by mutations in the CF transmembrane conductance regulator. CF affects multiple end organs, with persistent bacterial infection and chronic neutrophilic inflammation in airways predominating the clinical picture. To match the diverse microbial challenges that they may encounter, PMNs possess a variety of antimicrobial systems to slow or kill invading microorganisms confined in their phagosomes. Prominent among PMN defense systems is their ability to generate hypochlorous acid, a potent microbicide, by reacting oxidants generated by the NADPH oxidase with myeloperoxidase (MPO) released from azurophilic granules in the presence of chloride (Cl-). Products of the MPO-H2O2-Cl system oxidize susceptible biomolecules and support robust antimicrobial action against many, but not all, potential human pathogens. Underscoring that the MPO-H2O2-Cl system is integral to optimal host defense and proper regulation of inflammation, individuals with defects in any component of this system, as seen in chronic granulomatous disease or MPO deficiency, incur increased rates or severity of infection and signs of dysregulated inflammatory responses. We focus attention in this review on the molecular basis for and the clinical consequences of defects in the MPO-H2O2-Cl system because of the compromised Cl transport seen in CF. We will discuss first how the MPO-H2O2-Cl system in healthy PMNs participates in host defense and resolution of inflammation and then review how a defective MPO-H2O2-Cl system contributes to the increased susceptibility to infection and dysregulated inflammation associated with the clinical manifestations of CF.

The Effect of CFTR Modulators on Airway Infection in Cystic Fibrosis

The advent of Cystic fibrosis transmembrane receptor (CFTR) modulators in 2012 was a critical event in the history of cystic fibrosis (CF) treatment. Unlike traditional therapies that target downstream effects of CFTR dysfunction, CFTR modulators aim to correct the underlying defect at the protein level. These genotype-specific therapies are now available for an increasing number of CF patients, transforming the way we view the condition from a life-limiting disease to one that can be effectively managed. Several studies have demonstrated the vast improvement CFTR modulators have on normalization of sweat chloride, CFTR function, clinical endpoints, and frequency of pulmonary exacerbation. However, their impact on other aspects of the disease, such as pathogenic burden and airway infection, remain under explored. Frequent airway infections as a result of increased susceptibility and impaired innate immune response are a serious problem within CF, often leading to accelerated decline in lung function and disease progression. Current evidence suggests that CFTR modulators are unable to eradicate pathogenic organisms in those with already established lung disease. However, this may not be the case for those with relatively low levels of disease progression and conserved microbial diversity, such as young patients. Furthermore, it remains unknown whether the restorative effects exerted by CFTR modulators extend to immune cells, such as phagocytes, which have the potential to modulate the response of people with CF (pwCF) to infection. Throughout this review, we look at the potential impact of CFTR modulators on airway infection in CF and their ability to shape impaired pulmonary defences to pathogens.

CFTR-mediated monocyte/macrophage dysfunction revealed by cystic fibrosis proband-parent comparisons

Cystic fibrosis (CF) is an inherited disorder caused by biallelic mutations of the CF transmembrane conductance regulator (CFTR) gene. Converging evidence suggests that CF carriers with only 1 defective CFTR copy are at increased risk for CF-related conditions and pulmonary infections, but the molecular mechanisms underpinning this effect remain unknown. We performed transcriptomic profiling of peripheral blood mononuclear cells (PBMCs) of CF child-parent trios (proband, father, and mother) and healthy control (HC) PBMCs or THP-1 cells incubated with the plasma of these participants. Transcriptomic analyses revealed suppression of cytokine-enriched immune-related genes (IL-1β, CXCL8, CREM), implicating lipopolysaccharide tolerance in innate immune cells (monocytes) of CF probands and their parents. These data suggest that a homozygous as well as a heterozygous CFTR mutation can modulate the immune/inflammatory system. This conclusion is further supported by the finding of lower numbers of circulating monocytes in CF probands and their parents, compared with HCs, and the abundance of mononuclear phagocyte subsets, which correlated with Pseudomonas aeruginosa infection, lung disease severity, and CF progression in the probands. This study provides insight into demonstrated CFTR-related innate immune dysfunction in individuals with CF and carriers of a CFTR mutation that may serve as a target for personalized therapy.

Molecular Prerequisites for Neutrophil Extracellular Trap Formation and Evasion Mechanisms of Staphylococcus aureus

NETosis is a multi-facetted cellular process that promotes the formation of neutrophil extracellular traps (NETs). NETs as web-like structures consist of DNA fibers armed with granular proteins, histones, and microbicidal peptides, thereby exhibiting pathogen-immobilizing and antimicrobial attributes that maximize innate immune defenses against invading microbes. However, clinically relevant pathogens often tolerate entrapment and even take advantage of the remnants of NETs to cause persistent infections in mammalian hosts. Here, we briefly summarize how Staphylococcus aureus, a high-priority pathogen and causative agent of fatal diseases in humans as well as animals, catalyzes and concurrently exploits NETs during pathogenesis and recurrent infections. Specifically, we focus on toxigenic and immunomodulatory effector molecules produced by staphylococci that prime NET formation, and further highlight the molecular and underlying principles of suicidal NETosis compared to vital NET-formation by viable neutrophils in response to these stimuli. We also discuss the inflammatory potential of NET-controlled microenvironments, as excessive expulsion of NETs from activated neutrophils provokes local tissue injury and may therefore amplify staphylococcal disease severity in hospitalized or chronically ill patients. Combined with an overview of adaptation and counteracting strategies evolved by S. aureus to impede NET-mediated killing, these insights may stimulate biomedical research activities to uncover novel aspects of NET biology at the host-microbe interface.

Mucosal Immunity in Cystic Fibrosis

The highly complex and variable genotype-phenotype relationships observed in cystic fibrosis (CF) have been an area of growing interest since the discovery of the CF transmembrane conductance regulator (CFTR) gene >30 y ago. The consistently observed excessive, yet ineffective, activation of both the innate and adaptive host immune systems and the establishment of chronic infections within the lung, leading to destruction and functional decline, remain the primary causes of morbidity and mortality in CF. The fact that both inflammation and pathogenic bacteria persist despite the introduction of modulator therapies targeting the defective protein, CFTR, highlights that we still have much to discover regarding mucosal immunity determinants in CF. Gene modifier studies have overwhelmingly implicated immune genes in the pulmonary phenotype of the disease. In this context, we aim to review recent advances in our understanding of the innate and adaptive immune systems in CF lung disease.

Cystic Fibrosis: Systems Biology Analysis from Homozygous p.Phe508del Variant Patients' Samples Reveals Perturbations in Tissue-Specific Pathways

Cystic fibrosis (CF) is an autosomal recessive disorder, caused by diverse genetic variants for the CF transmembrane conductance regulator (CFTR) protein. Among these, p.Phe508del is the most prevalent variant. The effects of this variant on the physiology of each tissue remains unknown. This study is aimed at predicting cell signaling pathways present in different tissues of fibrocystic patients, homozygous for p.Phe508del. The study involved analysis of two microarray datasets, E-GEOD-15568 and E-MTAB-360 corresponding to the rectal and bronchial epithelium, respectively, obtained from the ArrayExpress repository. Particularly, differentially expressed genes (DEGs) were predicted, protein-protein interaction (PPI) networks were designed, and centrality and functional interaction networks were analyzed. The study reported that p.Phe508del-mutated CFTR-allele in homozygous state influenced the whole gene expression in each tissue differently. Interestingly, gene ontology (GO) term enrichment analysis revealed that only “neutrophil activation” was shared between both tissues; however, nonshared DEGs were grouped into the same GO term. For further verification, functional interaction networks were generated, wherein no shared nodes were reported between these tissues. These results suggested that the p.Phe508del-mutated CFTR-allele in homozygous state promoted tissue-specific pathways in fibrocystic patients. The generated data might further assist in prediction diagnosis to define biomarkers or devising therapeutic strategies.

Hexavalent chromium inhibits the formation of neutrophil extracellular traps and promotes the apoptosis of neutrophils via AMPK signaling pathway

As the most common heavy metal pollutant, hexavalent chromium [Cr(VI)] has caused serious environmental pollution and health damage. Although the toxic effect of Cr(VI) has been widely studied, and oxidative stress has been confirmed to be the main mechanism of its cytotoxicity, the toxicity of Cr(VI) to human immune system remains to be elucidated. Neutrophil extracellular traps (NETs) participate in the innate immune response, and the release of NETs is considered to be the most important part of the extracellular killing mechanism. We demonstrated in this study that Cr(VI) inhibited the formation of NETs in rat peripheral blood and induced neutrophils apoptosis by inhibiting the AMP-activated protein kinase (AMPK) signaling pathway. Cr(VI)-induced inhibition of NETs was accompanied by down-regulated myeloperoxidase (MPO)/Histones-3 (H3) protein expressions and decreased NETs-associated intracellular and extracellular DNA levels in the neutrophils. Metformin (Met), as an AMPK activator, triggered autophagy and thus alleviated the inhibitory effect of Cr(VI) on NETs. At the same time, Met can reduce the intracellular reactive oxygen species (ROS) level by activating the AMPK/nuclear factor erythroid-2 related factor 2 (Nrf2) signaling pathway, thus alleviating Cr(VI)-induced neutrophils apoptosis. In conclusion, this study elucidated the mechanism of Cr(VI)-induced neutrophils toxicity and the role of AMPK as a key regulatory signal, which could provide valuable experimental basis for the prevention and treatment of related diseases in Cr(VI)-exposed populations.

Increased Prevalence of Celiac Disease in Patients with Cystic Fibrosis: A Systematic Review and Meta-Analysis

Objectives: Immune regulation seems to be altered in cystic fibrosis (CF), thus potentially predisposing patients to developing autoimmune diseases (AID). In this meta-analysis, we aimed to evaluate the prevalence of celiac disease (CeD) among CF patients as by far the most commonly reported autoimmune disease in this population and, secondly, to review the observations on other, less frequently studied autoimmune diseases. Methods: We conducted a systematic literature search for studies that discussed AIDs among CF patients. Following standard selection and data collection, we calculated pooled raw prevalence with 95% confidence intervals (CI) for biopsy-verified CeD and seropositivity. Results: Out of the 21 eligible studies, 15 reported on CeD. Pooled prevalence of biopsy-verified CeD was 1.8% (CI 1.1–2.7%) according to a homogeneous dataset from six prospective, consecutive screening studies, while it proved to be 2.3% (CI 1.1–4.7%) according to a heterogeneous dataset from the other studies. Tissue transglutaminase IgA positivity was detected in 4.5% of CF cases (CI 2.8–6.9%), while tissue transglutaminase IgA–endomysial antibody IgA double positivity was found in 2.4% of them (CI 1.5–3.9%). Findings on other AIDs were strongly limited. Conclusions: The pooled prevalence of CeD in CF seemed to be more than twice as high compared to the global prevalence; therefore, routine screening of CeD could be considered in CF.

Angiopoietin 1 release from human neutrophils is independent from neutrophil extracellular traps (NETs)

Background

Neutrophils induce the synthesis and release of angiopoietin 1 (Ang1), a cytosolic growth factor involved in angiogenesis and capable of inducing several pro-inflammatory activities in neutrophils. Neutrophils also synthesize and release neutrophil extracellular traps (NETs), comprised from decondensed nuclear DNA filaments carrying proteins such as neutrophil elastase (NE), myeloperoxidase (MPO), proteinase 3 (PR3) and calprotectin (S100A8/S100A9), which together, contribute to the innate immune response against pathogens (e.g., bacteria). NETs are involved in various pathological conditions through pro-inflammatory, pro-thrombotic and endothelial dysfunction effects and have recently been found in heart failure (HF) and type 2 diabetes (T2DM) patients. The aim of the present study was to investigate the role of NETs on the synthesis and release of Ang1 by the neutrophils in patients with T2DM and HF with preserved ejection fraction (HFpEF) (stable or acute decompensated; ADHFpEF) with or without T2DM.

Results

Our data show that at basal level (PBS) and upon treatment with LPS, levels of NETs are slightly increased in patients suffering from T2DM, HFpEF ± T2DM and ADHF without (w/o) T2DM, whereas this increase was significant in ADHFpEF + T2DM patients compared to healthy control (HC) volunteers and ADHFpEF w/o T2DM. We also observed that treatments with PMA or A23187 increase the synthesis of Ang1 (from 150 to 250%) in HC and this effect is amplified in T2DM and in all cohorts of HF patients. Ang1 is completely released (100%) by neutrophils of all groups and does not bind to NETs as opposed to calprotectin.

Conclusions

Our study suggests that severely ill patients with HFpEF and diabetes synthesize and release a greater abundance of NETs while Ang1 exocytosis is independent of NETs synthesis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12865-021-00442-8.

Anti-Inflammatory Influences of Cystic Fibrosis Transmembrane Conductance Regulator Drugs on Lung Inflammation in Cystic Fibrosis

Cystic fibrosis (CF) is caused by a defect in the cystic fibrosis transmembrane conductance regulator protein (CFTR) which instigates a myriad of respiratory complications including increased vulnerability to lung infections and lung inflammation. The extensive influx of pro-inflammatory cells and production of mediators into the CF lung leading to lung tissue damage and increased susceptibility to microbial infections, creates a highly inflammatory environment. The CF inflammation is particularly driven by neutrophil infiltration, through the IL-23/17 pathway, and function, through NE, NETosis, and NLRP3-inflammasome formation. Better understanding of these pathways may uncover untapped therapeutic targets, potentially reducing disease burden experienced by CF patients. This review outlines the dysregulated lung inflammatory response in CF, explores the current understanding of CFTR modulators on lung inflammation, and provides context for their potential use as therapeutics for CF. Finally, we discuss the determinants that need to be taken into consideration to understand the exaggerated inflammatory response in the CF lung.

Neutrophil extracellular traps in cancer: not only catching microbes

Neutrophils are the most abundant type of white blood cells circulating throughout the bloodstream and are often considered the frontline defenders in innate immunity. However, neutrophils are increasingly being recognized as having an important role in tumorigenesis and carcinogenesis due to their aberrant activation by molecules released into the tumor microenvironment. One defensive response of neutrophils that is aberrantly triggered during the neoplastic process is called NETosis, where activated neutrophils expel their DNA and intracellular contents in a web-like structure known as a neutrophil extracellular trap (NET). In cancer, NETosis has been linked to increased disease progression, metastasis, and complications such as venous thromboembolism. NET structures released by neutrophils can also serve as a scaffold for clot formation, shining new light on the role of neutrophils and NETosis in coagulation-mediated diseases.

Here, we review current available knowledge regarding NET and the related NETosis process in cancer patients, with an emphasis on pre-clinical and clinical data fostering the identification and validation of biomarkers of NET with a predictive/prognostic role in cancer patients treated with immunotherapy agents. NETosis biomarkers, e.g., citH3, may integrate correlates of immunogenicity currently available (e.g., PD-L1 expression, TMB, TILs) and help select the subsets of patients who may most benefit from the use of the therapeutic weapons under discussion.

Peptide inhibition of neutrophil-mediated injury after in vivo challenge with supernatant of Pseudomonas aeruginosa and immune-complexes

Neutrophils are recognized for their role in host defense against pathogens as well as inflammatory conditions mediated through many mechanisms including neutrophil extracellular trap (NET) formation and generation of reactive oxygen species (ROS). NETs are increasingly appreciated as a major contributor in autoimmune and inflammatory diseases such as cystic fibrosis. Myeloperoxidase (MPO), a key neutrophil granule enzyme mediates generation of hypochlorous acid which, when extracellular, can cause host tissue damage. To better understand the role played by neutrophils in inflammatory diseases, we measured and modulated myeloperoxidase activity and NETs in vivo, utilizing a rat peritonitis model. RLS-0071 is a 15 amino acid peptide that has been shown to inhibit myeloperoxidase activity and NET formation in vitro. The rat model of inflammatory peritonitis was induced with intraperitoneal injection of either P. aeruginosa supernatant or immune-complexes. After euthanasia, a peritoneal wash was performed and measured for myeloperoxidase activity and free DNA as a surrogate for measurement of NETs. P. aeruginosa supernatant caused a 2-fold increase in MPO activity and free DNA when injected IP. Immune-complexes injected IP increased myeloperoxidase activity and free DNA 2- fold. RLS-0071 injection decreased myeloperoxidase activity and NETs in the peritoneal fluid generally to baseline levels in the presence of P. aeruginosa supernatant or immune-complexes. Taken together, RLS-0071 demonstrated the ability to inhibit myeloperoxidase activity and NET formation in vivo when initiated by different inflammatory stimuli including shed or secreted bacterial constituents as well as immune-complexes.

Neutrophil, Extracellular Matrix Components, and Their Interlinked Action in Promoting Secondary Pathogenesis After Spinal Cord Injury

Secondary pathogenesis following primary mechanical damage to the spinal cord is believed to be the ultimate reason for the limitation of currently available therapies. Precisely, the complex cascade of secondary events-mediated scar formation is the sole hurdle in the recovery process due to its inhibitory effect on axonal regeneration, plasticity, and remyelination. Neutrophils initiate this secondary injury along with other extracellular matrix components such as matrix metalloproteinase (MMPs), and chondroitin sulfate proteoglycans (CSPGs). Together, they mediate inflammation, necrosis, apoptosis, lesion, and scar formation at the injury site. Activated neutrophil releases several proteases, cytokines, and chemokines that cause complete tissue destruction. Thus, neutrophil activation and infiltration in the acute phase of injury act as a roadmap for inducing tissue destruction. MMPs, are extracellular proteolytic enzymes that degrade the ECM proteins, increases vascular permeability, and are predominantly released by neutrophils. These MMPs, in turn, cleave NG2 proteoglycan, a subtype of CSPG, into the active form. This active or shed form is involved in both the fibrotic as well as glial scar formation. Since neutrophils and ECM components are closely associated with each other in pathological conditions. Herein, we emphasize the interaction of neutrophils and their influence on ECM protein expression during the acute and chronic phases to identify a promising targets for designing a therapeutic approach in spinal cord injury.

Chronic bacterial pulmonary infections in advanced cystic fibrosis differently affect the level of sputum neutrophil elastase, IL-8 and IL-6

Advanced cystic fibrosis (CF) lung disease is commonly characterized by a chronic Pseudomonas aeruginosa infection and destructive inflammation caused by neutrophils. However, the lack of convincing evidence from most informative biomarkers of severe lung dysfunction (SLD-CF) has hampered the formulation of a conclusive, targeted diagnosis of CF. The aim of this study was to determine whether SLD-CF is related to the high concentration of sputum inflammatory mediators and the presence of biofilm-forming bacterial strains. Forty-one patients with advanced CF lung disease were studied. The severity of pulmonary dysfunction was defined by forced expiratory volume in 1 second (FEV1) < 40%. C-reactive protein (CRP) and NLR (neutrophil-lymphocyte ratio) were examined as representative blood-based markers of inflammation. Expectorated sputum was collected and analysed for cytokines and neutrophil-derived defence proteins. Isolated sputum bacteria were identified and their biofilm-forming capacity was determined. There was no association between FEV1% and total number of sputum bacteria. However, in the high biofilm-forming group the median FEV1 was < 40%. Importantly, high density of sputum bacteria was associated with increased concentrations of neutrophil elastase and interleukin (IL)-8 and low concentrations of IL-6 and IL-10. The low concentration of sputum IL-6 is unique for CF and distinct from that observed in other chronic pulmonary inflammatory diseases. These findings strongly suggest that expectorated sputum is an informative source of pulmonary biomarkers representative for advanced CF and may replace more invasive bronchoalveolar lavage analysis to monitor the disease. We recommend to use of the following inflammatory biomarkers: blood CRP, NLR and sputum elastase, IL-6, IL-8 and IL-10.

The contact system in liver injury

Coagulation is controlled by a delicate balance of prothrombotic and antithrombotic mechanisms, to prevent both excessive blood loss from injured vessels and pathologic thrombosis. The liver plays a pivotal role in hemostasis through the synthesis of plasma coagulation factors and their inhibitors that, in addition to thrombosis and hemostasis, orchestrates an array of inflammatory responses. As a result, impaired liver function has been linked with both hypercoagulability and bleeding disorders due to a pathologic balance of pro- and anticoagulant plasma factors. At sites of vascular injury, thrombus propagation that finally may occlude the blood vessel depends on negatively charged biopolymers, such as polyphosphates and extracellular DNA, that provide a physiological surface for contact activation of coagulation factor XII (FXII). FXII initiates the contact system that drives both the intrinsic pathway of coagulation, and formation of the inflammatory mediator bradykinin by the kallikrein–kinin system. Moreover, FXII facilitates receptor-mediated signalling, thereby promoting mitogenic activities, angiogenesis, and neutrophil stimulation with implications for liver diseases. Here, we summarize current knowledge on the FXII-driven contact system in liver diseases and review therapeutic approaches to target its activities during impaired liver function.

Neutrophil dysfunction in bronchiectasis: an emerging role for immunometabolism

Bronchiectasis is a heterogenous disease with multiple underlying causes. The pathophysiology is poorly understood but neutrophilic inflammation and dysfunctional killing of pathogens is believed to be key. There are, however, no licensed therapies for bronchiectasis that directly target neutrophilic inflammation. In this review, we discuss our current understanding of neutrophil dysfunction and therapeutic targeting in bronchiectasis. Immunometabolic reprogramming, a process through which inflammation changes inflammatory cell behaviour by altering intracellular metabolic pathways, is increasingly recognised across multiple inflammatory and autoimmune diseases. Here, we show evidence that much of the neutrophil dysfunction observed in bronchiectasis is consistent with immunometabolic reprogramming. Previous attempts at developing therapies targeting neutrophils have focused on reducing neutrophil numbers, resulting in increased frequency of infections. New approaches are needed and we propose that targeting metabolism could theoretically reverse neutrophil dysfunction and dysregulated inflammation. As an exemplar, 5' adenosine monophosphate (AMP)-activated protein kinase (AMPK) activation has already been shown to reverse phagocytic dysfunction and neutrophil extracellular trap (NET) formation in models of pulmonary disease. AMPK modulates multiple metabolic pathways, including glycolysis which is critical for energy generation in neutrophils. AMPK activators can reverse metabolic reprogramming and are already in clinical use and/or development. We propose the need for a new immunomodulatory approach, rather than an anti-inflammatory approach, to enhance bacterial clearance and reduce bronchiectasis disease severity.

Diesel Exhaust Particulates Enhances Susceptibility of LPS-Induced Acute Lung Injury through Upregulation of the IL-17 Cytokine-Derived TGF-β1/Collagen I Expression and Activation of NLRP3 Inflammasome Signaling in Mice

Diesel exhaust particulates (DEP) adversely affect the respiratory system and exacerbate lung diseases, resulting in high mortality rates. However, its pathogenesis is complicated, and the mechanisms involved are incompletely understood. We investigated the effects of DEP pre-exposure on lipopolysaccharide (LPS)-induced acute lung injury (ALI) and identified the roles of interleukin (IL)-17 in mice. Mice were divided into vehicle control, DEP, LPS, and DEP pre-exposed and LPS-instilled groups. Pre-exposure to DEP enhanced the number of total cells, neutrophils, and lymphocytes in the BAL fluid of LPS-instilled mice. Pre-exposure to DEP synergistically exacerbated pulmonary acute lung inflammation and granulomatous inflammation/pulmonary fibrosis, concomitant with the enhanced expression of inflammatory cytokines in the BAL fluid and of collagen I and TGF-β1 in the lungs of LPS-instilled mice. The number of TGF-β1-positive cells in the DEP pre-exposed and LPS-instilled group was higher than that in the LPS group. The expression of NLR family pyrin domain containing 3 (NLRP3) inflammasome components was markedly increased in the DEP pre-exposed and LPS-instilled group. IL-17 levels in the BAL fluid and IL-17-positive cells in the lungs were significantly increased by pre-exposure to DEP in the LPS-induced group compared to that in the DEP or LPS group. These results suggest that DEP predominantly contributes to fibrotic lung disease in LPS-related acute lung injury by upregulating IL-17 cytokine-mediated collagen I and TGF-β1 and, at least in part, by activating LPS-induced NLRP3 inflammasome signaling. The study should be useful in devising better strategies for prevention and management of ALI.

Electronic Cigarette Users' Perspective on the COVID-19 Pandemic: Observational Study Using Twitter Data

BACKGROUND

Previous studies have shown that electronic cigarette (e-cigarette) users might be more vulnerable to COVID-19 infection and could develop more severe symptoms if they contract the disease owing to their impaired immune responses to viral infections. Social media platforms such as Twitter have been widely used by individuals worldwide to express their responses to the current COVID-19 pandemic.

OBJECTIVE

In this study, we aimed to examine the longitudinal changes in the attitudes of Twitter users who used e-cigarettes toward the COVID-19 pandemic, as well as compare differences in attitudes between e-cigarette users and nonusers based on Twitter data.

METHODS

The study dataset containing COVID-19-related Twitter posts (tweets) posted between March 5 and April 3, 2020, was collected using a Twitter streaming application programming interface with COVID-19-related keywords. Twitter users were classified into two groups: Ecig group, including users who did not have commercial accounts but posted e-cigarette-related tweets between May 2019 and August 2019, and non-Ecig group, including users who did not post any e-cigarette-related tweets. Sentiment analysis was performed to compare sentiment scores towards the COVID-19 pandemic between both groups and determine whether the sentiment expressed was positive, negative, or neutral. Topic modeling was performed to compare the main topics discussed between the groups.

RESULTS

The US COVID-19 dataset consisted of 4,500,248 COVID-19-related tweets collected from 187,399 unique Twitter users in the Ecig group and 11,479,773 COVID-19-related tweets collected from 2,511,659 unique Twitter users in the non-Ecig group. Sentiment analysis showed that Ecig group users had more negative sentiment scores than non-Ecig group users. Results from topic modeling indicated that Ecig group users had more concerns about deaths due to COVID-19, whereas non-Ecig group users cared more about the government's responses to the COVID-19 pandemic.

CONCLUSIONS

Our findings show that Twitter users who tweeted about e-cigarettes had more concerns about the COVID-19 pandemic. These findings can inform public health practitioners to use social media platforms such as Twitter for timely monitoring of public responses to the COVID-19 pandemic and educating and encouraging current e-cigarette users to quit vaping to minimize the risks associated with COVID-19.

Observations of, and Insights into, Cystic Fibrosis Mucus Heterogeneity in the Pre-Modulator Era: Sputum Characteristics, DNA and Glycoprotein Content, and Solubilization Time

Airway obstruction with chronic inflammation and infection are major contributors to the lung damage and mortality of cystic fibrosis (CF). A better understanding of the congested milieu of CF airways will aid in improving therapeutic strategies. This article retrospectively reports our observations, and discusses insights gained in the handling and analysis of CF sputa. CF and non-CF mucus samples were surveyed for morphological features by electron microscopy and analyzed for the macromolecular dry weight (MDW), total protein, lipid, carbohydrate, and DNA. Mucus character was investigated with chemical solubilization time as a comparative tool. CF mucus appeared distinctly thick, viscous, and heterogeneous, with neutrophils as the dominant immune cell. CF sputum DNA content varied markedly for and between individuals (~1–10% MDW), as did solubilization times (~1–20 h). CF Sputum DNA up to 7.1% MDW correlated positively with solubilization time, whereas DNA >7.1% MDW correlated negatively. 3D analysis of CF sputa DNA, GP, and solubilization times revealed a dynamic and predictive relationship. Reflecting on the heterogeneous content and character of CF mucus, and the possible interplay in space and time in the respiratory tract of polymeric DNA and mucous glycoproteins, we highlight it’s potential to affect infection-related airway pathologies and the success of therapeutic interventions.

Pirfenidone regulates LPS mediated activation of neutrophils

Excessive inflammation or its absence may result in impaired wound healing. Neutrophils are among the first innate immune cells to arrive at the injury site. They participate in infection control and debris removal to initiate healing. If not timely resolved, neutrophils can cause excessive tissue inflammation and damage. Drugs with anti-inflammatory and anti-fibrotic effects are of promise for improving healing by balancing the primary defensive functions and excessive tissue damage actions. Of interest, pirfenidone (Pf), an FDA approved anti-fibrotic drug to treat idiopathic pulmonary fibrosis, has been shown to ameliorate inflammation in several animal models including mouse deep partial-thickness burn wounds. However, there is a lack of mechanistic insights into Pf drug action on inflammatory cells such as neutrophils. Here, we examined the treatment effects of Pf on LPS-stimulated neutrophils as a model of non-sterile inflammation. Firstly, Pf reduced chemotaxis and production of pro-inflammatory ROS, cytokines, and chemokines by LPS-activated neutrophils. Secondly, Pf increased anti-inflammatory IL-1RA and reduced neutrophil degranulation, phagocytosis, and NETosis. Thirdly, Pf affected downstream signaling kinases which might directly or indirectly influence neutrophil responses to LPS. In conclusion, the results suggest that Pf lessens the inflammatory phenotypes of LPS-activated neutrophils.

Development of a vaccine against Staphylococcus aureus invasive infections: Evidence based on human immunity, genetics and bacterial evasion mechanisms

Invasive Staphylococcus aureus infections are a leading cause of morbidity and mortality in both hospital and community settings, especially with the widespread emergence of virulent and multi-drug resistant methicillin-resistant S. aureus strains. There is an urgent and unmet clinical need for non-antibiotic immune-based approaches to treat these infections as the increasing antibiotic resistance is creating a serious threat to public health. However, all vaccination attempts aimed at preventing S. aureus invasive infections have failed in human trials, especially all vaccines aimed at generating high titers of opsonic antibodies against S. aureus surface antigens to facilitate antibody-mediated bacterial clearance. In this review, we summarize the data from humans regarding the immune responses that protect against invasive S. aureus infections as well as host genetic factors and bacterial evasion mechanisms, which are important to consider for the future development of effective and successful vaccines and immunotherapies against invasive S. aureus infections in humans. The evidence presented form the basis for a hypothesis that staphylococcal toxins (including superantigens and pore-forming toxins) are important virulence factors, and targeting the neutralization of these toxins are more likely to provide a therapeutic benefit in contrast to prior vaccine attempts to generate antibodies to facilitate opsonophagocytosis.

Quantification of bronchoalveolar neutrophil extracellular traps and phagocytosis in murine pneumonia

The past two decades have witnessed a resurgence in neutrophil research, inspired in part by the discovery of neutrophil extracellular traps (NETs) and their myriad roles in health and disease. Within the lung, dysregulation of neutrophils and NETosis have been linked to an array of diseases including pneumonia, cystic fibrosis, acute respiratory distress syndrome (ARDS), chronic obstructive pulmonary disease (COPD), and severe asthma. However, our understanding of pathologic neutrophil responses in the lung remains incomplete. Two methodologic issues have contributed to this gap: first, an emphasis on studying neutrophils from blood rather than the lung and second, the technical difficulties of interrogating neutrophil responses in mice, which has largely restricted basic murine research to specialized laboratories. To address these limitations, we have developed a suite of techniques for studying neutrophil effector functions specifically in the mouse lung. These include ex vivo assays for phagocytosis and NETosis using bronchoalveolar neutrophils and in situ evaluation of NETosis in a murine model of pneumonia. Throughout, we have prioritized technical ease and robust, quantitative readouts. We hope these assays will help to standardize research on lung neutrophils and improve accessibility to this burgeoning field.

Neutrophil Extracellular Traps Impair Intestinal Barrier Function during Experimental Colitis

Aberrant neutrophil extracellular trap (NET) formation and the loss of barrier integrity in inflamed intestinal tissues have long been associated with inflammatory bowel disease (IBD). However, whether NETs alter intestinal epithelium permeability during colitis remains elusive. Here, we demonstrated that NETs promote the breakdown in intestinal barrier function for the pathogenesis of intestinal inflammation in mouse models of colitis. NETs were abundant in the colon of mice with colitis experimentally induced by dextran sulfate sodium (DSS) or 2,4,6-trinitrobenzene sulfonic acid (TNBS). Analysis of the intestinal barrier integrity revealed that NETs impaired gut permeability, enabling the initiation of luminal bacterial translocation and inflammation. Furthermore, NETs induced the apoptosis of epithelial cells and disrupted the integrity of tight junctions and adherens junctions. Intravenous administration of DNase I, an enzyme that dissolves the web-like DNA filaments of NETs, during colitis restored the mucosal barrier integrity which reduced the dissemination of luminal bacteria and attenuated intestinal inflammation in both DSS and TNBS models. We conclude that NETs serve a detrimental factor in the gut epithelial barrier function leading to the pathogenesis of mucosal inflammation during acute colitis.

E-cigarettes and respiratory health: the latest evidence

The E-cigarette market continues to expand at an alarming rate with thousands of flavours available for purchase and continuously evolving devices. Now that it is a multi-billion dollar industry and one without stringent regulation, there is rising concern over the safety of vaping products. Since June 2019, over 2800 cases of E-cigarette-associated acute lung toxicity have been reported in the USA, over 60 of which resulted in death. Many argue that E-cigarettes offer a safer alternative to smoking, but we are evidently far from fully understanding the potential hazards that they pose to respiratory health. Although the risk of an outbreak in the UK has been considered low due to tighter E-cigarette regulations, we cannot fully eliminate the possibility of similar events occurring in the future. With evidence frequently emerging of the harmful effects of E-cigarettes to pulmonary health, there is an urgent need to define the long-term implications of vaping. Studies show that E-cigarette exposure can disrupt pulmonary homeostasis, with reports of gas exchange disturbance, reduced lung function, increased airway inflammation and oxidative stress, downregulation of immunity, and increased risk of respiratory infection. In this review, the latest research on the effect of E-cigarette use on respiratory health will be presented.

The role of inflammation in cystic fibrosis pulmonary exacerbations

INTRODUCTION

Cystic Fibrosis pulmonary exacerbations are critical events in the lives of people with CF that have deleterious effects on lung function, quality of life, and life expectancy. There are significant unmet needs in the management of exacerbations. We review here the associated inflammatory changes that underlie these events and are of interest for the development of biomarkers of exacerbation.

AREAS COVERED

Inflammatory responses in CF are abnormal and contribute to a sustained proinflammatory lung microenvironment, abundant in proinflammatory mediators and deficient in counter-regulatory mediators that terminate and resolve inflammation. There is increasing interest in these inflammatory pathways to discover novel biomarkers for pulmonary exacerbation management. In this review, we explore the inflammatory changes occurring during intravenous antibiotic therapy for exacerbation and how they may be applied as biomarkers to guide exacerbation therapy. A literature search was conducted using the PubMed database in February 2020.

EXPERT OPINION

Heterogeneity in inflammatory responses to treatment of a pulmonary exacerbation, a disease process with complex pathophysiology, limits the clinical utility of individual biomarkers. Biomarker panels may be a more successful strategy to capture informative changes within the CF population to improve pulmonary exacerbation management and outcomes.

The Biology of Lactoferrin, an Iron-Binding Protein That Can Help Defend Against Viruses and Bacteria

Lactoferrin is a nutrient classically found in mammalian milk. It binds iron and is transferred via a variety of receptors into and between cells, serum, bile, and cerebrospinal fluid. It has important immunological properties, and is both antibacterial and antiviral. In particular, there is evidence that it can bind to at least some of the receptors used by coronaviruses and thereby block their entry. Of importance are Heparan Sulfate Proteoglycans (HSPGs) and the host receptor angiotensin-converting enzyme 2 (ACE2), as based on other activities lactoferrin might prevent severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) from attaching to the host cells. Lactoferrin (and more specifically enteric-coated LF because of increased bioavailability) may consequently be of preventive and therapeutic value during the present COVID-19 pandemic.

The role of neutrophils in host defense and disease

Neutrophils, the most abundant circulating leukocyte, are critical for host defense. Granulopoiesis is under the control of transcriptional factors and culminates in mature neutrophils with a broad armamentarium of antimicrobial pathways. These pathways include nicotinamide adenine dinucleotide phosphate oxidase, which generates microbicidal reactive oxidants, and nonoxidant pathways that target microbes through several mechanisms. Activated neutrophils can cause or worsen tissue injury, underscoring the need for calibration of activation and resolution of inflammation when infection has been cleared. Acquired neutrophil disorders are typically caused by cytotoxic chemotherapy or immunosuppressive agents. Primary neutrophil disorders typically result from disabling mutations of individual genes that result in impaired neutrophil number or function, and provide insight into basic mechanisms of neutrophil biology. Neutrophils can also be activated by noninfectious causes, including trauma and cellular injury, and can have off-target effects in which pathways that typically defend against infection exacerbate injury and disease. These off-target effects include acute organ injury, autoimmunity, and variable effects on the tumor microenvironment that can limit or worsen tumor progression. A greater understanding of neutrophil plasticity in these conditions is likely to pave the way to new therapeutic approaches.

Viral strategies predisposing to respiratory bacterial superinfections

Acute respiratory infections are amongst the leading causes of childhood morbidity and mortality globally. Viruses are the predominant cause of such infections, but mixed etiologies with bacteria has for decades raised the question of the interplay between them in causality and determination of the outcome of such infections. In this review, we examine recent microbiological, biochemical, and immunological advances that contribute to elucidating the mechanisms by which infections by specific viruses enable bacterial infections in the airway, and exacerbate them. We analyze specific domains in which viruses play such facilitating role including enhancement of bacterial adhesion by unmasking cryptic receptors and upregulation of adhesion proteins, disruption of tight junction integrity favoring paracellular transmigration of bacteria and loss of epithelial barrier integrity, increased availability of nutrient, such as mucins and iron, alteration of innate and adaptive immune responses, and disabling defense against bacteria, and lastly, changes in airway microbiome that render the lung more vulnerable to pathogens. Separate exhaustive analysis of each domain focuses on individuals with cystic fibrosis (CF), in whom viruses may play a key role in paving the way for the primary injury that leads to permanence of bacterial pathogens, viruses may then serve as triggers for "CF exacerbations"; these constituting the signature and ultimately the outcome determinants of these patients.

The Brain Entangled: The Contribution of Neutrophil Extracellular Traps to the Diseases of the Central Nervous System

Under normal conditions, neutrophils are restricted from trafficking into the brain parenchyma and cerebrospinal fluid by the presence of the brain–blood barrier (BBB). Yet, infiltration of the central nervous system (CNS) by neutrophils is a well-known phenomenon in the course of different pathological conditions, e.g., infection, trauma or neurodegeneration. Different studies have shown that neutrophil products, i.e., free oxygen radicals and proteolytic enzymes, play an important role in the pathogenesis of BBB damage. It was recently observed that accumulating granulocytes may release neutrophil extracellular traps (NETs), which damage the BBB and directly injure surrounding neurons. In this review, we discuss the emerging role of NETs in various pathological conditions affecting the CNS.

High Nuclease Activity of Long Persisting Staphylococcus aureus Isolates Within the Airways of Cystic Fibrosis Patients Protects Against NET-Mediated Killing

Staphylococcus aureus is one of the first and most prevalent pathogens cultured from the airways of cystic fibrosis (CF) patients, which can persist there for extended periods. Airway infections in CF patients are characterized by a strong inflammatory response of highly recruited neutrophils. One killing mechanism of neutrophils is the formation of neutrophil extracellular traps (NETs), which capture and eradicate bacteria by extracellular fibers of neutrophil chromatin decorated with antimicrobial granule proteins. S. aureus secretes nuclease, which can degrade NETs. We hypothesized, that S. aureus adapts to the airways of CF patients during persistent infection by escaping from NET-mediated killing via an increase of nuclease activity. Sputum samples of CF patients with chronic S. aureus infection were visualized by confocal microscopy after immuno-fluorescence staining for NET-specific markers, S. aureus bacteria and overall DNA structures. Nuclease activity was analyzed in sequential isogenic long persisting S. aureus isolates, as confirmed by whole genome sequencing, from an individual CF patient using a FRET-based nuclease activity assay. Additionally, some of these isolates were selected and analyzed by qRT-PCR to determine the expression of nuc1 and regulators of interest. NET-killing assays were performed with clinical S. aureus isolates to evaluate killing and bacterial survival depending on nuclease activity. To confirm the role of nuclease during NET-mediated killing, a clinical isolate with low nuclease activity was transformed with a nuclease expression vector (pCM28nuc). Furthermore, two sputa from an individual CF patient were subjected to RNA-sequence analysis to evaluate the activity of nuclease in vivo. In sputa, S. aureus was associated to extracellular DNA structures. Nuclease activity in clinical S. aureus isolates increased in a time-and phenotype-dependent manner. In the clinical isolates, the expression of nuc1 was inversely correlated to the activity of agr and was independent of saeS. NET-mediated killing was significantly higher in S. aureus isolates with low compared to isolates with high nuclease activity. Importantly, transformation of the clinical isolate with low nuclease activity with pCM28nuc conferred protection against NET-mediated killing confirming the beneficial role of nuclease for protection against NETs. Also, nuclease expression in in vivo sputa was high, which underlines the important role of nuclease within the highly inflamed CF airways. In conclusion, our data show that S. aureus adapts to the neutrophil-rich environment of CF airways with increasing nuclease expression most likely to avoid NET-killing during long-term persistence.

What are the respiratory effects of e-cigarettes?

Electronic cigarettes (e-cigarettes) are alternative, non-combustible tobacco products that generate an inhalable aerosol containing nicotine, flavors, propylene glycol, and vegetable glycerin. Vaping is now a multibillion dollar industry that appeals to current smokers, former smokers, and young people who have never smoked. E-cigarettes reached the market without either extensive preclinical toxicology testing or long term safety trials that would be required of conventional therapeutics or medical devices. Their effectiveness as a smoking cessation intervention, their impact at a population level, and whether they are less harmful than combustible tobacco products are highly controversial. Here, we review the evidence on the effects of e-cigarettes on respiratory health. Studies show measurable adverse biologic effects on organ and cellular health in humans, in animals, and in vitro. The effects of e-cigarettes have similarities to and important differences from those of cigarettes. Decades of chronic smoking are needed for development of lung diseases such as lung cancer or chronic obstructive pulmonary disease, so the population effects of e-cigarette use may not be apparent until the middle of this century. We conclude that current knowledge of these effects is insufficient to determine whether the respiratory health effects of e-cigarette are less than those of combustible tobacco products.