Epithelial Autoantigen-Specific IgG Antibody Enhances Eosinophil Extracellular Trap Formation in Severe Asthma

Inhibition of EETosis with an anti-citrullinated histone antibody: a novel therapeutic approach for eosinophilic inflammatory disorders

Eosinophils are a subset of granulocytes that protect the host against fungal and parasitic infection through secretion of their granular contents. In response to specific stimuli, eosinophils also undergo a type of lytic cell death, referred to as eosinophil extracellular trap (EET)-associated cell death (EETosis), where histone citrullination facilitates chromatin decondensation, cell rupture and release of pro-inflammatory, decondensed chromatin into the extracellular environment as EETs. In this study, we show the abundant presence of eosinophils and citrullinated histones in nasal polyp tissue of patients with eosinophilic chronic rhinosinusitis (ECRS). Using live imaging microscopy on purified human eosinophils, we demonstrate that physiologically relevant stimuli induce release of citrullinated EETs and the marker of eosinophil activation galectin-10. While the kinetics of release of EETs and galectin-10 are similar, inhibitors of citrullination block EETosis in a dose dependent manner but fail to inhibit galectin-10 release. The importance of citrullination is further exemplified with CIT-013, a monoclonal antibody specific for citrullinated histones H2A and H4. CIT-013 potently inhibits release of EETs (half-maximal inhibitory concentration of 2.5 nM) without inhibiting other eosinophil functions such as degranulation, adhesion, superoxide production and induction of chemokine expression. Together, this study provides new insights into the requirement of protein arginine deiminase 4 (PAD4) for EETosis, differentiates requirements of EETosis from galectin-10 release, and identifies a novel therapeutic approach for EETosis inhibition by targeting citrullinated histones in eosinophil-driven diseases such as ECRS.

Correlation Analysis of Serum 25-Hydroxyvitamin D Levels With Immune Function and Calcium-Phosphate Metabolism in Patients With Bronchial Asthma Treated With Combination Therapy

It was to investigate the clinical efficacy of the combination therapy of fluticasone propionate inhalation aerosol and vitamin D (VD) in pediatric bronchial asthma (BA) and analyze the correlation between serum 25-(OH)-D3 levels and immune function, as well as calcium-phosphorus metabolism. A total of 110 patients with BA were recruited. Regarding treatment plan, patients were randomly rolled into a single-drug treatment group (SDT, treated with fluticasone propionate inhalation aerosol alone) and a dual-drug treatment group (TDT, treated with the combination of fluticasone propionate inhalation aerosol and VD). The changes in serum 25-(OH)-D3 levels, immunoglobulins, T lymphocyte subsets, and inflammatory cytokine levels in children with BA under different treatment modalities were compared. Clinical symptom disappearance, asthma control, and quality of life (QoL) were assessed, and the total effective rate and adverse reactions (ARs) were compared. A control group consisting of 60 healthy children who underwent concurrent physical examinations was included. The differences in serum 25-(OH)-D3 levels, immunoglobulins, and T lymphocyte subset levels between children with BA and healthy controls were compared, and their correlations were analyzed. The TDT group showed a drastic reduction in the disappearance time of lung wheezing and dyspnea relative to the SDT group. Furthermore, the TDT group exhibited notable improvements in lung function parameters, including forced vital capacity (FVC), forced expiratory volume at one second (FEV1), FEV1/FVC, and peak expiratory flow (PEF). Blood gas analysis revealed a great decrease in PaCO2 and an increase in PaO2. The Childhood Asthma Control Test (C-ACT) scores for asthma control and Pediatric Asthma Quality of Life Questionnaire (PAQLQ) scores for QoL showed marked increases in the TDT group. Moreover, the TDT group demonstrated notable increases in serum 25-(OH)-D3 levels, immunoglobulins (IgA, IgG, and IgM), T lymphocyte subsets (CD4+ and CD8+), as well as blood calcium and phosphorus levels. Additionally, the TDT group exhibited a prominent increase in the anti-inflammatory cytokine interleukin (IL)-10 level and a drastic decrease in the pro-inflammatory cytokines IL-6 and tumor necrosis factor alpha (TNF-alpha) levels (all P<0.05). The total effective rates of treatment in the SDT group and TDT group were 83.64 % and 96.36 %, respectively, with AR rates of 16.36 % and 7.27 %. The TDT group exhibited a superior total effective rate and an inferior incidence of ARs to the SDT group (both P<0.05). Additionally, in contrast to the control group, the BA group showed notable decreases in serum 25-(OH)-D3 levels, immunoglobulins (IgA, IgG, and IgM), T lymphocyte subsets (CD4+, CD8+, and CD4+/CD8+), as well as blood calcium and phosphorus levels (all P<0.05). Prior to treatment, there was a positive correlation between serum 25-(OH)-D3 levels and immunoglobulins (IgA, IgG, and IgM), T lymphocyte subsets (CD4+ and CD8+), as well as blood calcium and phosphorus levels in children with BA (P<0.05). In patients with BA, combined treatment with inhaled fluticasone propionate aerosol and VD may have a regulatory effect on serum 25-hydroxyVD levels, immune function, and calcium-phosphate metabolism. The correlation between serum 25-(OH)-D3 levels and immune function, as well as calcium-phosphate metabolism, suggested that VD may play a crucial role in the immune regulation and calcium-phosphate metabolism of BA.

Association Between Cytokeratin 19-Specific IgG and Neutrophil Activation in Asthma

PURPOSE

Patients with non-eosinophilic asthma (NEA) are less responsive to anti-inflammatory drugs and suffer from frequent asthma exacerbations. The pathogenic mechanism of NEA is not fully understood; however, the roles of monocytes and autoimmune mechanisms targeting airway epithelial cell (AEC) antigens have been proposed.

METHODS

The effects of monocyte extracellular traps (MoETs) on cytokeratin 19 (CK19) production in AECs, as well as the impact of CK19-specific immunoglobulin (Ig) G on neutrophil and monocyte activation, were investigated both in vivo and in vitro. Sixty asthmatic patients and 15 healthy controls (HCs) were enrolled, and the levels of serum immune complexes containing CK19-specific IgG and neutrophil extracellular trap (NET)-specific IgG were measured using enzyme-linked immunoassay.

RESULTS

MoETs induced CK19 and CK19-specific IgG production. Furthermore, the levels of serum CK19-specific IgG were significantly higher in the NEA group than in the eosinophilic asthma group. Among patients with NEA, asthmatics with high levels of CK19-specific IgG had higher levels of myeloperoxidase and NET-specific IgG than those with low levels of CK19-specific IgG (P = 0.020 and P = 0.017; respectively). Moreover, the immune complexes from asthmatics with high CK19-specific IgG enhanced NET formation and reactive oxygen species production (neutrophil activation), which were suppressed by N-acetylcysteine and anti-CD16 antibody treatment.

CONCLUSIONS

These findings suggest that circulating CK19 and CK19-specific IgG may contribute to NET formation, leading to airway inflammation and steroid resistance in NEA.

Immune Cell-Mediated Autoimmune Responses in Severe Asthma

Severe asthma (SA) has heterogeneous inflammatory phenotypes characterized by persistent airway inflammation (eosinophilic and/or neutrophilic inflammation) and remodeling. Various immune cells (eosinophils, neutrophils, and macrophages) become more activated and release inflammatory mediators and extracellular traps, damaging the protective barrier of airway epithelial cells and further activating other immune and structural cells. These cells play a role in autoimmune responses in asthmatic airways, where the adaptive immune system generates autoantibodies, inducing immunoglobulin G-dependent airway inflammation. Recent studies have suggested that adult asthmatics had high titers of autoantibodies associated with asthma severity, although pathogenic factors or diagnostic criteria are not well-defined. This challenge is further compounded by asthmatics with the autoimmune responses showing therapy insensitivity or failure to current pharmacological and biological treatment. This review updates emerging mechanisms of autoimmune responses in asthmatic airways and provides insights into their roles, proposing potential biomarkers and therapeutic targets for SA.

New targets for type 2-low asthma

Asthma is characterized by airway obstruction and inflammation, and presents significant diagnostic and treatment challenges. The concept of endotypes has improved understanding of the mechanisms of asthma and has stimulated the development of effective treatment strategies. Sputum profiles may be used to classify asthma into two major inflammatory types: type 2-high (T2H) and type 2-low (T2L) asthma. T2H, characterized by elevated type 2 inflammation, has been extensively studied and several effective biologic treatments have been developed. However, managing T2L is more difficult due to the lack of reliable biomarkers for accurate diagnosis and classification. Additionally, conventional anti-inflammatory therapy does not completely control the symptoms of T2L; therefore, further research is needed to identify effective biologic treatments. This review provides new insights into the clinical characteristics and underlying mechanisms of severe T2L and investigates potential therapeutic approaches to control the disease.

Eosinophil extracellular traps in asthma: implications for pathogenesis and therapy

Asthma is a common, chronic inflammatory disease of the airways that affects millions of people worldwide and is associated with significant healthcare costs. Eosinophils, a type of immune cell, play a critical role in the development and progression of asthma. Eosinophil extracellular traps (EETs) are reticular structures composed of DNA, histones, and granulins that eosinophils form and release into the extracellular space as part of the innate immune response. EETs have a protective effect by limiting the migration of pathogens and antimicrobial activity to a controlled range. However, chronic inflammation can lead to the overproduction of EETs, which can trigger and exacerbate allergic asthma. In this review, we examine the role of EETs in asthma.

Bacterial Extracellular Vesicles: A Candidate Molecule for the Diagnosis and Treatment of Allergic Diseases

Extracellular vesicles (EVs) are an end product released from almost all living cells such as eukaryotic cells and bacteria. These membrane vesicles containing proteins, lipids, and nucleic acids are mainly involved in intracellular communications through the transfer of their components from donor to acceptor cells. Moreover, EVs have been implicated in many functions in response to environmental changes, contributing to health and disease; bacterial EVs depending on their specific parental bacterium have diverse effects on immune responses to play a beneficial or pathogenic role in patients with various allergic and immunologic diseases. As bacterial EVs are a completely new area of investigation in this field, we highlight our current understanding of bacterial EVs and discuss their diagnostic and therapeutic potentials (as immunomodulators) for targeting asthma and atopic dermatitis.