Interleukin-1α Is a Critical Mediator of the Response of Human Bronchial Fibroblasts to Eosinophilic Inflammation

The Causal Role of Immune Cell Phenotypes and Inflammatory Factors in Childhood Asthma: Evidence From Mendelian Randomization

OBJECTIVE

This study utilizes Mendelian randomization (MR) to explore the causal relationship between immune cell phenotypes, inflammatory factors, and childhood asthma, aiming to enhance our understanding and management of the disease.

METHODS

A two-sample MR approach was used to explore the causal relationships between 731 immune cell phenotypes, 91 inflammatory factors, and childhood asthma. The main analysis was performed using inverse variance weighting (IVW), with additional methods like weighted median, MR-Egger, and weighted mode. Statistical significance was further assessed using false discovery rate (FDR) correction. Sensitivity analyses assessed heterogeneity (Cochran's Q test) and pleiotropy (MR-Egger, MR-PRESSO), while reverse causality was evaluated using the Steiger test. Findings were further validated through cohort studies and meta-analyses to ensure robustness.

RESULTS

Among 91 inflammatory factors, DNER, IL-18 R1, and Osteoprotegerin increased childhood asthma risk, while CDCP1 and VEGF-A were protective (p < 0.05). Of 731 immune cell phenotypes, 45 showed significant links to asthma, with protective effects from CD45RA+ CD8+ T cells and HLA-DR+ NK cells, and increased risk from IgD-CD38- B cells and CD8dim T cells (p < 0.05). Specific SSC-A parameters and higher MFI values for CD19, CD28, and CD3 were protective, while elevated MFI for CCR2 on monocytes and CD86 on myeloid dendritic cells increased risk. However, after further FDR correction, no statistically significant results were identified. Nonetheless, sensitivity and replication analyses, including meta-analysis, confirmed the robustness of these associations.

CONCLUSIONS

This study provides a comprehensive investigation into the complex interplay between immune system dysregulation and childhood asthma. By identifying specific inflammatory factors and immune cell phenotypes linked to asthma risk and protection, the findings offer valuable insights into disease pathogenesis. While these results highlight potential targets for precision-based therapeutic interventions, further research is needed to validate these associations and translate them into clinical applications.

Biomarkers Reflecting the Severity of Bronchial Asthma in Children

Background

Bronchial asthma, the most prevalent chronic inflammatory airway disease in children, exhibits a concerning rise in both incidence and prevalence. Asthma biomarkers hold promise for stratifying patients into distinct clinical phenotypes, paving the way for targeted and personalized treatment approaches.

Aim of Study

This study aimed to evaluate the association between novel and non-established semi-invasive circulating and well-known exhaled inflammatory biomarkers in two distinct pediatric asthma populations stratified by disease severity.

Materials and Methods

Forty-four asthmatic children aged 8-12 years meeting inclusion criteria were recruited from hospitalized patients. The first group (n=15, mean age 9.8 years) consisted of patients with mild persistent asthma who did not require regular inhaled corticosteroids (ICS). The second group (n=29, mean age 9.8 years) consisted of children with moderate to persistent asthma who received regular ICS treatment. Serum levels of interleukins (IL-13, IL-1β), eosinophil-derived neurotoxin (EDN), and surfactant protein D (SPD) were measured by ELISA in all participants. In addition, exhaled nitric oxide (FeNO) and blood eosinophil counts were evaluated.

Results

No significant differences were observed in the baseline plasma concentrations of inflammatory markers (IL-13, IL-1β, SPD, and EDN) or exhaled FeNO between the ICS-treated and non-ICS-treated groups. Further inter-individual analysis confirmed significant positive correlations between IL-13, SPD, and IL-1β (Pearson's r = 0.591-0.781) in both groups of patients. Interestingly, the ICS-treated group compared to the nontreated group showed an exclusive moderate negative correlation between FeNO and IL-1β. In contrast, FeNO exhibited a positive correlation with EDN and a strong association with eosinophil count in all the study groups.

Conclusion

Our findings highlight the complex and unresolved role of asthma biomarkers in routine clinical practice for the management of childhood asthma, particularly in predicting exacerbations. By comparing the relationships of carefully selected biomarkers, we can achieve a greater clinical predictive value.

Integrative Cross-Talk in Asthma: Unraveling the Complex Interactions Between Eosinophils, Immune, and Structural Cells in the Airway Microenvironment

Asthma is a chronic inflammatory process that leads to airway narrowing, causing breath loss followed by spasms, wheezing, and shortness of breath. Within the asthmatic lungs, interaction among various immune cells and structural cells plays a significant role in orchestrating an inflammatory response in which eosinophils hold central importance. In these settings, allergens or other environmental exposures commonly drive the immune response to recruit eosinophils to the airways. The appearance of eosinophils in the airways indicates a dynamic interplay of various cell types within lung tissue and does not represent a passive effect of inflammation. The cellular cross-talk causes the persistence of eosinophilic inflammation, and if left untreated, it results in long-term damage to the airway structure and function. Further exacerbation of the condition occurs because of this. We discuss how this complex interplay of eosinophils, immune, and structural cells within the airway microenvironment leads to the distinct pathophysiological features in asthma, the variability in disease severity, and the response to biological treatments.

Understanding fibroblast-immune cell interactions via co-culture models and their role in asthma pathogenesis

Asthma is a chronic lung disease involving airway inflammation and fibrosis. Fibroblasts are the main effector cells important for lung tissue production which becomes abnormal in asthmatics and is one of the main contributors to airway fibrosis. Although fibroblasts were traditionally viewed solely as structural cells, they have been discovered to be highly active, and involved in lung inflammatory and fibrotic processes in asthma. In line with this, using 2D and 3D in vitro co-culture models, a complex interaction between lung fibroblasts and various immune cells important for the pathogenesis of asthma have been recently uncovered. Hence, in this review, we provide the first-ever summary of various studies that used 2D and 3D in vitro co-culture models to assess the nature of aberrant immune cell-fibroblast interactions and their contributions to chronic inflammation and fibrotic mechanisms in asthma pathogenesis.

Development of Adaptive Immunity and Its Role in Lung Remodeling

Asthma is characterized by airflow limitations resulting from bronchial closure, which can be either reversible or fixed due to changes in airway tissue composition and structure, also known as remodeling. Airway remodeling is defined as increased presence of mucins-producing epithelial cells, increased thickness of airway smooth muscle cells, angiogenesis, increased number and activation state of fibroblasts, and extracellular matrix (ECM) deposition. Airway inflammation is believed to be the main cause of the development of airway remodeling in asthma. In this chapter, we will review the development of the adaptive immune response and the impact of its mediators and cells on the elements defining airway remodeling in asthma.

An open microfluidic coculture model of fibroblasts and eosinophils to investigate mechanisms of airway inflammation

Interactions between fibroblasts and immune cells play an important role in tissue inflammation. Previous studies have found that eosinophils activated with interleukin-3 (IL-3) degranulate on aggregated immunoglobulin G (IgG) and release mediators that activate fibroblasts in the lung. However, these studies were done with eosinophil-conditioned media that have the capacity to investigate only one-way signaling from eosinophils to fibroblasts. Here, we demonstrate a coculture model of primary normal human lung fibroblasts (HLFs) and human blood eosinophils from patients with allergy and asthma using an open microfluidic coculture device. In our device, the two types of cells can communicate via two-way soluble factor signaling in the shared media while being physically separated by a half wall. Initially, we assessed the level of eosinophil degranulation by their release of eosinophil-derived neurotoxin (EDN). Next, we analyzed the inflammation-associated genes and soluble factors using reverse transcription quantitative polymerase chain reaction (RT-qPCR) and multiplex immunoassays, respectively. Our results suggest an induction of a proinflammatory fibroblast phenotype of HLFs following the coculture with degranulating eosinophils, validating our previous findings. Additionally, we present a new result that indicate potential impacts of activated HLFs back on eosinophils. This open microfluidic coculture platform provides unique opportunities to investigate the intercellular signaling between the two cell types and their roles in airway inflammation and remodeling.

Airway fibrin formation cascade in allergic asthma exacerbation: implications for inflammation and remodeling

BACKGROUND

Airway remodeling in patients with asthma, which leads to a decline in pulmonary function, is likely the result of repeated exacerbations often provoked by aeroallergen exposures. Aeroallegen exposure triggers a stereotypic response orchestrated by growth factor cytokines and other protein mediators. This results in a late-phase allergic reaction characterized by vascular permeability, recruitment of activated leukocytes, and activation of structural cells of the airway. The spectrum of protein mediators and their functions are incompletely understood.

METHODS

Bronchoalveolar lavage fluid (BALF) samples were obtained from 12 volunteers who exhibited robust eosinophilic recruitment following segmental bronchial provocation with allergen (SBP-Ag). We systematically identified and quantified proteins in BALF using high-performance liquid chromatography-high-resolution mass spectrometry (LC-MS/MS) followed by pathway analysis and correlations with airway physiology.

RESULTS

Pairwise analysis of protein abundance in BALF pre- vs post-SBP-Ag revealed that 55 proteins were upregulated and 103 proteins were downregulated. We observed enrichment of groups of proteins mapping to hemostasis/fibrin clot, platelet activation, lipoprotein assembly, neutrophil degranulation proteins, and acute-phase inflammation-airway remodeling pathways. The abundances of F2 and Fibrinogen γ (FGG) correlated with eosinophil numbers, whereas SERPINA3 negatively correlated with change in FeNO. The coagulation proteins F2 and KNG negatively correlated with FN1 an index of airway remodeling. Interestingly, patients with lower FEV1 showed distinct allergen-induced patterns of 8 BALF proteins, including MUC1, alarmins (HSPB1), and actin polymerization factors.

CONCLUSIONS

Protein abundance of the fibrin formation cascade, platelet activation and remodeling are associated with late-phase leukocyte numbers and markers of remodeling. Patients with lower FEV1 have distinct dynamic responses to allergen.

Role of amygdala in stress-induced upregulation of airway IL-1 signaling in asthma

Psychological stress, an important contributor to asthma morbidity, potentiates the immune response to allergen, but the brain mechanisms mediating this response are not fully understood. The amygdala is likely to play an important role, given its sensitivity to threat and connectivity with descending immune modulatory pathways. In this study, we recruited thirty asthmatic participants and examined glucose metabolism in the amygdala, using [F-18]fluorodeoxyglucose positron emission tomography, during a laboratory stressor. Stress hormone and airway inflammatory measurements were also acquired. Results showed that activity in the amygdala was significantly increased during the stressor, compared to a matched control task (p < .05 corrected). Moreover, the increase in amygdala activity was associated with a greater increase in sputum IL-1R1 mRNA and alpha amylase response (p < .05 corrected), which were also positively correlated (p = .01). These findings suggest that heightened amygdala reactivity may contribute to asthma morbidity via descending proinflammatory sympathetic signaling pathways.