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

Progesterone suppresses rhinovirus-induced airway inflammation by inhibiting neutrophil infiltration and extracellular traps formation

BACKGROUND

The process of NETosis is observed in a range of inflammatory conditions. Progesterone (P4) has been shown to alleviate inflammation caused by viral infections such as influenza and SARS-CoV-2. However, the precise molecular mechanisms responsible for this effect are not yet fully understood. Therefore, the present investigation aims to explore whether P4 can exert its anti-inflammatory properties by inhibiting NETosis and the related molecular pathways.

METHODS

Airway inflammation caused by rhinovirus serotype-1b (RV-1b) was induced in male BALB/c mice. The inflammation was assessed through histological examination and calculation of inflammatory cells present in the bronchoalveolar lavage fluid. Flow cytometry was used to analyze the inflammatory cells and NETotic neutrophils. Western blotting analysis was conducted to detect proteins associated with NETosis, inflammasome activation, and signaling. Furthermore, confocal microscopy was utilized to observe neutrophil extracellular trap (NET) structures in vivo tissues and in vitro neutrophils, neutrophil infiltration, and inflammasome formation.

RESULTS

The administration of P4 proved to be an effective treatment for reducing airway inflammation and the production of NETs caused by RV-1b infection. The infection triggered the activation of NLRP3 inflammasomes in neutrophils, which led to the maturation of IL-1β and subsequent activation of both the NF-κB and p38 signaling pathways. The activation of NF-κB signaling resulted in the secretion of downstream chemokines CCL3 and IL-6, which led to an increase in neutrophil infiltration into the lung airways. Moreover, the activation of p38 signaling led to the generation of reactive oxygen species, resulting in NETosis. However, the administration of P4 inhibited the activation of the NLRP3 inflammasome, which subsequently led to the deactivation of both the IL-1β-NF-κB and IL-1β-p38 axes. As a result, there was a reduction in neutrophil infiltration and NETosis. Furthermore, TGF-β-activated kinase 1 (TAK1) was identified as an intermediary enzyme. P4 inhibits both the NF-κB and IL-1β-p38 pathways by suppressing the activity of TAK1.

CONCLUSION

The capacity of P4 to mitigate rhinovirus-induced airway inflammation is attributed to its ability to impede the infiltration of neutrophils and NETosis. As inflammation mediated by NETosis is widespread in diverse disorders, our findings propose that P4 could potentially function as a universal therapeutic agent in the management of such ailments.

Pregnancy Entails a Metabolic Rewiring of Maternal Circulating Neutrophils

Immunometabolism is an emerging growing field that focuses on the role of cellular metabolism in the regulation of immune cell function and fate. Thus, proliferation, differentiation, activation, and function of immune cell populations are modulated by reprogramming their fueling and metabolic pathways. Pregnancy entails a fine immune and metabolic regulation of the maternal-fetal interaction to assist the energetic demands of the fetus where trophoblast cells have a central role. Maternal neutrophil functional shaping by trophoblast cells has been proposed though their metabolic conditioning during pregnancy has not been studied yet. Here, we explored the effects of trophoblast-derived factors on the metabolic rewiring of neutrophils from nonpregnant women and its impact on central functions like reactive oxygen species (ROS) production, neutrophil extracellular trap (NET) release, and migration. In parallel, the immunometabolic status and function of neutrophils isolated from pregnant women (16-20 weeks) was compared with nonpregnant age-matched control samples. Trophoblast-derived factors induced glucose uptake and lipid droplet accumulation without activating ROS production or NET release. Conditioned media from trophoblast cells also inhibited PMA-induced NETosis partly by impairing glucose uptake in neutrophils. In turn, neutrophils from pregnant women had increased basal ROS production, lipid accumulation, and glucose uptake compared to neutrophils from nonpregnant women, accompanied by a higher release of PMA-induced NETs. Interestingly, PMA-induced NETs was blocked by a fatty acid oxidation inhibitor in neutrophils from pregnant women indicating the contribution of fatty acid metabolism to neutrophil activity during pregnancy. Results are consistent with immunometabolic mechanisms underlying the functional shaping of neutrophils during pregnancy and point out the contribution of trophoblast-derived factors to their metabolic profiling. These findings provide novel immunometabolic clues to understand immune homeostasis maintenance during pregnancy and raise the clinical potential of monitoring neutrophil metabolism during normal and complicated pregnancies.

Neutrophil diversity and function in health and disease

Neutrophils, the most abundant type of granulocyte, are widely recognized as one of the pivotal contributors to the acute inflammatory response. Initially, neutrophils were considered the mobile infantry of the innate immune system, tasked with the immediate response to invading pathogens. However, recent studies have demonstrated that neutrophils are versatile cells, capable of regulating various biological processes and impacting both human health and disease. Cytokines and other active mediators regulate the functional activity of neutrophils by activating multiple receptors on these cells, thereby initiating downstream signal transduction pathways. Dysfunctions in neutrophils and disruptions in neutrophil homeostasis have been implicated in the pathogenesis of numerous diseases, including cancer and inflammatory disorders, often due to aberrant intracellular signaling. This review provides a comprehensive synthesis of neutrophil biological functions, integrating recent advancements in this field. Moreover, it examines the biological roles of receptors on neutrophils and downstream signaling pathways involved in the regulation of neutrophil activity. The pathophysiology of neutrophils in numerous human diseases and emerging therapeutic approaches targeting them are also elaborated. This review also addresses the current limitations within the field of neutrophil research, highlighting critical gaps in knowledge that warrant further investigation. In summary, this review seeks to establish a comprehensive and multidimensional model of neutrophil regulation, providing new perspectives for potential clinical applications and further research.

Bone morphogenetic protein 4 inhibits corneal neovascularization by blocking NETs-induced disruption to corneal epithelial barrier

Corneal neovascularization (CoNV) is the second leading cause of visual impairment worldwide, and current drugs have certain limitations. Inflammatory response is the core pathological process of CoNV. Neutrophil extracellular traps (NETs) are generated after neutrophil activation, which promotes neovascularization. Prior studies demonstrated that bone morphogenetic protein 4 (BMP4) could significantly reduce inflammation and CoNV formation, its exact molecular mechanism remains unclear. Therefore, we stimulated human peripheral blood neutrophils with phorbol myristate acetate (PMA) or deoxyribonuclease I (DNase I) to induce or inhibit NETs formation. By using corneal sutures and subconjunctival injections of NETs or DNase I, rat CoNV models were established. Compared with the suture group, NETs formation and inflammatory cell infiltration in the corneal stroma were significantly increased, corneal edema was aggravated, and the length, area and diameter of CoNV were significantly enhanced in the NETs group. Furthermore, by curetting the corneal epithelial apical junctional complexes (AJCs), a crucial component in preserving the function of the corneal epithelial barrier, we discovered that the damage of AJCs had a significant role in inducing CoNV formation. NETs could induce CoNV formation by injuring corneal epithelial AJCs. Finally, by comparing the aforementioned indicators after the intervention of BMP4, BMP4 inhibitor Noggin and NADPH oxidase (NOX) inhibitor, we finally demonstrated that BMP4 could inhibit NETs-induced inflammation and corneal epithelial AJC injury, repair corneal epithelial barrier function and eventually inhibit CoNV formation by blocking NOX-2-dependent NETs formation.

Molecular mechanism of Jianpiyifei II granules in the treatment of chronic obstructive pulmonary disease: Network pharmacology analysis, molecular docking, and experimental assessment

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is defined by persistent airway and lung inflammation, excessive mucus production, remodeling of the airways, and damage to the alveolar tissue. Based on clinical experience, it has been observed that Jianpiyifei II (JPYF II) granules exhibit a significant therapeutic impact on individuals suffering from stable COPD. Nevertheless, the complete understanding of JPYF II's potential mode of action against COPD remains to be further clarified.

PURPOSE

To further investigate the underlying mechanism of JPYF II for treating COPD and clarify the role of the IL-17 pathway in the treatment.

METHODS

A variety of databases were utilized to acquire JPYF II's bioactive components, as well as related targets of JPYF II and COPD. Cytoscape was utilized to establish multiple interaction networks for the purpose of topological analyses and core-target screening. The Metascape was utilized to identify the function of target genes and crucial signaling pathways. To evaluate the interactions between bioactive ingredients and central target proteins, molecular docking simulations were conducted. Following that, a sequence of experiments was conducted both in the laboratory and in living organisms, which included analyzing the cell counts in bronchoalveolar lavage fluid (BALF), examining lung tissue for histopathological changes, conducting immunohistochemistry, RT‒qPCR, ELISA, and Western blotting.

RESULTS

In JPYF II, 88 bioactive ingredients were predicted to have a total of 342 targets. After conducting Venn analysis, it was discovered that 284 potential targets of JPYF II were linked to the provision of defensive benefits against COPD. The PPI network yielded a total of twenty-four core targets. The findings from the analysis of enrichment and gene‒pathway network suggested that JPYF II targeted Hsp90, MAPKs, ERK, AP-1, TNF-α, IL-6, COX-2, CXCL8, and MMP-9 as crucial elements for COPD treatment through the IL-17 pathway. Additionally, JPYF II might modulate MAPK signaling pathways and the downstream transcription factor AP-1 via IL-17 regulation. According to the findings from molecular docking, it was observed that the 24 core target proteins exhibited robust binding affinities towards the top 10 bioactive compounds. Furthermore, the treatment of COPD through the regulation of MAPKs in the IL-17 pathway was significantly influenced by flavonoids and sterols found in JPYF II. In vitro, these observations were further confirmed. In vivo results demonstrated that JPYF II reduced inflammatory cell infiltration in pulmonary tissues and the quantity of inflammatory cells in BALF obtained from LPS- and CS-stimulated mice. Moreover, the administration of JPYF II resulted in the inhibition of IL-17 mRNA and protein levels, phosphorylation levels of MAPK proteins, and expression of phosphorylated AP-1 proteins. It also suppressed the expression of downstream effector genes and proteins associated with the IL-17/MAPK/AP-1 signaling axis in lung tissues and BALF.

CONCLUSION

This research reveals that JPYF II improves COPD by controlling the IL-17/MAPK/AP-1 signaling axis within the IL-17 pathway for the first time. These findings offer potential approaches for the creation of novel medications that specifically target IL-17 and proteins involved in the IL-17 pathway to address COPD.

Targeting Neutrophil Extracellular Traps in Gouty Arthritis: Insights into Pathogenesis and Therapeutic Potential

Gouty arthritis (GA) is an immune-mediated disorder characterized by severe inflammation due to the deposition of monosodium urate (MSU) crystals in the joints. The pathophysiological mechanisms of GA are not yet fully understood, and therefore, the identification of effective therapeutic targets is of paramount importance. Neutrophil extracellular traps (NETs), an intricate structure of DNA scaffold, encompassing myeloperoxidase, histones, and elastases - have gained significant attention as a prospective therapeutic target for gouty arthritis, due to their innate antimicrobial and immunomodulatory properties. Hence, exploring the therapeutic potential of NETs in gouty arthritis remains an enticing avenue for further investigation. During the process of gouty arthritis, the formation of NETs triggers the release of inflammatory cytokines, thereby contributing to the inflammatory response, while MSU crystals and cytokines are sequestered and degraded by the aggregation of NETs. Here, we provide a concise summary of the inflammatory processes underlying the initiation and resolution of gouty arthritis mediated by NETs. Furthermore, this review presents an overview of the current pharmacological approaches for treating gouty arthritis and summarizes the potential of natural and synthetic product-based inhibitors that target NET formation as novel therapeutic options, alongside elucidating the intrinsic challenges of these inhibitors in NETs research. Lastly, the limitations of HL-60 cell as a suitable substitute of neutrophils in NETs research are summarized and discussed. Series of recommendations are provided, strategically oriented towards guiding future investigations to effectively address these concerns. These findings will contribute to an enhanced comprehension of the interplay between NETs and GA, facilitating the proposition of innovative therapeutic strategies and novel approaches for the management of GA.

Neutrophil extracellular traps in influenza infection

Despite recent progress in developing novel therapeutic approaches and vaccines, influenza is still considered a global health threat, with about half a million mortality worldwide. This disease is caused by Influenza viruses, which are known for their rapid evolution due to different genetical mechanisms that help them develop new strains with the ability to evade therapies and immunization. Neutrophils are one of the first immune effectors that act against pathogens. They use multiple mechanisms, including phagocytosis, releasing the reactive oxygen species, degranulation, and the production of neutrophil extracellular traps. Neutrophil extracellular traps are used to ensnare pathogens; however, their dysregulation is attributed to inflammatory and infectious diseases. Here, we discuss the effects of these extracellular traps in the clinical course of influenza infection and their ability to be a potential target in treating influenza infection.

Exploring key genes associated with neutrophil function and neutrophil extracellular traps in heart failure: a comprehensive analysis of single-cell and bulk sequencing data

Background: Heart failure (HF) is a complex and heterogeneous manifestation of multiple cardiovascular diseases that usually occurs in the advanced stages of disease progression. The role of neutrophil extracellular traps (NETs) in the pathogenesis of HF remains to be explored. Methods: Bioinformatics analysis was employed to investigate general and single-cell transcriptome sequencing data downloaded from the GEO datasets. Differentially expressed genes (DEGs) associated with NETs in HF patients and healthy controls were identified using transcriptome sequencing datasets and were subsequently subjected to functional enrichment analysis. To identify potential diagnostic biomarkers, the random forest algorithm (RF) and the least absolute shrinkage and selection operator (LASSO) were applied, followed by the construction of receiver operating characteristic (ROC) curves to assess accuracy. Additionally, single-cell transcriptome sequencing data analysis identified key immune cell subpopulations in TAC (transverse aortic constriction) mice potentially involved in NETs regulation. Cell-cell communication analysis and trajectory analysis was then performed on these key cell subpopulations. Results: We identified thirteen differentially expressed genes (DEGs) associated with NET through differential analysis of transcriptome sequencing data from HF (heart failure) samples. Utilizing the Random Forest and Lasso algorithms, along with experimental validation, we successfully pinpointed four diagnostic markers (CXCR2, FCGR3B, VNN3, and FPR2) capable of predicting HF risk. Furthermore, our analysis of intercellular communication, leveraging single-cell sequencing data, highlighted macrophages and T cells as the immune cell subpopulations with the closest interactions with neutrophils. Pseudo-trajectory analysis sheds light on the differentiation states of distinct neutrophil subpopulations. Conclusion: In this study, we conducted an in-depth investigation into the functions of neutrophil subpopulations that infiltrate cardiac tissue in TAC mice. Additionally, we identified four biomarkers (CXCR2, FCGR3B, VNN3, and FPR2) associated with NETs in HF. Our findings enhance the understanding of immunology in HF.

Neutrophils in COVID-19: recent insights and advances

Coronavirus disease 2019 (COVID-19) is an acute respiratory disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which can lead to acute respiratory distress syndrome (ARDS), multi-organ failure and death, posing significant threat to human health. Studies have found that pathological mechanisms, such as cytokine storms caused by uncontrolled innate immune system activation, release of damage-associated molecular patterns during tissue injury and a high incidence of thrombotic events, are associated with the function and dysfunction of neutrophils. Specifically, the increased formation of low-density neutrophils (LDNs) and neutrophil extracellular traps (NETs) has been shown to be closely linked with the severity and poor prognosis in patients with COVID-19. Our work focuses on understanding the increased number, abnormal activation, lung tissue infiltration, and elevated neutrophil-to-lymphocyte ratio in the pathogenesis of COVID-19. We also explore the involvement of NETs and LDNs in disease progression and thrombosis formation, along with potential therapeutic strategies targeting neutrophil and NETs formation.

Air-Liquid interface cultures to model drug delivery through the mucociliary epithelial barrier

Epithelial cells from mucociliary portions of the airways can be readily grown and expanded in vitro. When grown on a porous membrane at an air-liquid interface (ALI) the cells form a confluent, electrically resistive barrier separating the apical and basolateral compartments. ALI cultures replicate key morphological, molecular and functional features of the in vivo epithelium, including mucus secretion and mucociliary transport. Apical secretions contain secreted gel-forming mucins, shed cell-associated tethered mucins, and hundreds of additional molecules involved in host defense and homeostasis. The respiratory epithelial cell ALI model is a time-proven workhorse that has been employed in various studies elucidating the structure and function of the mucociliary apparatus and disease pathogenesis. It serves as a critical milestone test for small molecule and genetic therapies targeting airway diseases. To fully exploit the potential of this important tool, numerous technical variables must be thoughtfully considered and carefully executed.

Anti-citrullinated histone monoclonal antibody CIT-013, a dual action therapeutic for neutrophil extracellular trap-associated autoimmune diseases

Neutrophil extracellular traps (NETs) contribute to the pathophysiology of multiple inflammatory and autoimmune diseases. Targeting the NETosis pathway has demonstrated significant therapeutic potency in various disease models. Here, we describe a first-in-class monoclonal antibody (CIT-013) with high affinity for citrullinated histones H2A and H4, which inhibits NETosis and reduces tissue NET burden in vivo with significant anti-inflammatory consequences. We provide a detailed understanding of the epitope selectivity of CIT-013. Detection of CIT-013 epitopes in rheumatoid arthritis (RA) synovium provides evidence that RA is an autoimmune disease with excessive citrullinated NETs that can be targeted by CIT-013. We show that CIT-013 acts upon the final stage of NETosis, binding to its chromatin epitopes when plasma membrane integrity is compromised to prevent NET release. Bivalency of CIT-013 is necessary for NETosis inhibition. In addition, we show that CIT-013 binding to NETs and netting neutrophils enhance their phagocytosis by macrophages in an Fc-dependent manner. This is confirmed using a murine neutrophilic airway inflammation model where a mouse variant of CIT-013 reduced tissue NET burden with significant anti-inflammatory consequences. CIT-013's therapeutic activity provides new insights for the development of NET antagonists and indicates the importance of a new emerging therapy for NET-driven diseases with unmet therapeutic needs.

Impact of CFTR Modulators on the Impaired Function of Phagocytes in Cystic Fibrosis Lung Disease

Cystic fibrosis (CF), the most common genetically inherited disease in Caucasian populations, is a multi-systemic life-threatening autosomal recessive disorder caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. In 2012, the arrival of CFTR modulators (potentiators, correctors, amplifiers, stabilizers, and read-through agents) revolutionized the therapeutic approach to CF. In this review, we examined the physiopathological mechanism of chronic dysregulated innate immune response in the lungs of CF patients with pulmonary involvement with particular reference to phagocytes, critically analyzing the role of CFTR modulators in influencing and eventually restoring their function. Our literature review highlighted that the role of CFTR in the lungs is crucial not only for the epithelial function but also for host defense, with particular reference to phagocytes. In macrophages and neutrophils, the CFTR dysfunction compromises both the intricate process of phagocytosis and the mechanisms of initiation and control of inflammation which then reverberates on the epithelial environment already burdened by the chronic colonization of pathogens leading to irreversible tissue damage. In this context, investigating the impact of CFTR modulators on phagocytic functions is therefore crucial not only for explaining the underlying mechanisms of pleiotropic effects of these molecules but also to better understand the physiopathological basis of this disease, still partly unexplored, and to develop new complementary or alternative therapeutic approaches.