Eosinophils and tissue remodeling: Relevance to airway disease

Endotyping Chronic Respiratory Diseases: T2 Inflammation in the United Airways Model

Over the past 15 years, the paradigm of viewing the upper and lower airways as a unified system has progressively shifted the approach to chronic respiratory diseases (CRDs). As the global prevalence of CRDs continues to increase, it becomes evident that acknowledging the presence of airway pathology as an integrated entity could profoundly impact healthcare resource allocation and guide the implementation of pharmacological and rehabilitation strategies. In the era of precision medicine, endotyping has emerged as another novel approach to CRDs, whereby pathologies are categorized into distinct subtypes based on specific molecular mechanisms. This has contributed to the growing acknowledgment of a group of conditions that, in both the upper and lower airways, share a common type 2 (T2) inflammatory signature. These diverse pathologies, ranging from allergic rhinitis to severe asthma, frequently coexist and share diagnostic and prognostic biomarkers, as well as therapeutic strategies targeting common molecular pathways. Thus, T2 inflammation may serve as a unifying endotypic trait for the upper and lower airways, reinforcing the practical significance of the united airways model. This review aims to summarize the literature on the role of T2 inflammation in major CRDs, emphasizing the value of common biomarkers and integrated treatment strategies targeting shared molecular mechanisms.

Eosinophil-Epithelial Cell Interactions in Asthma

BACKGROUND

Eosinophils have numerous roles in type 2 inflammation depending on their activation states in the blood and airway or after encounter with inflammatory mediators. Airway epithelial cells have a sentinel role in the lung and, by instructing eosinophils, likely have a foundational role in asthma pathogenesis.

SUMMARY

In this review, we discuss various topics related to eosinophil-epithelial cell interactions in asthma, including the influence of eosinophils and eosinophil products, e.g., granule proteins, on epithelial cell function, expression, secretion, and plasticity; the effects of epithelial released factors, including oxylipins, cytokines, and other mediators on eosinophils, e.g., on their activation, expression, and survival; possible mechanisms of eosinophil-epithelial cell adhesion; and the role of intra-epithelial eosinophils in asthma.

KEY MESSAGES

We suggest that eosinophils and their products can have both injurious and beneficial effects on airway epithelial cells in asthma and that there are bidirectional interactions and signaling between eosinophils and airway epithelial cells in asthma.

Relationship between triglyceride-glucose index and blood eosinophils among asthmatic individuals in the USA

BACKGROUND

Presently, the majority of investigations primarily evaluate the correlation between triglyceride-glucose index (TyGI) with lung diseases, such as asthma. However, they did not delve into the correlation between TyGI and inflammatory responses related to the disease. Few studies have explored the association between TyGI and blood eosinophil count (BEOC). Thus, National Health and Nutrition Examination Survey (NHANES) data were used in this study to evaluate the correlation between TyGI and BEOC in individuals with asthma.

METHODS

This study investigated 3902 individuals with asthma. Linear regression analysis was performed to investigate the association between TyGI and BEOC in patients with asthma. Subsequently, the GAM and threshold effect models were used to validate the presence of either a nonlinear or linear association between TyGI and BEOC. Finally, stratified analyses were conducted to ascertain the correlations between different subgroups.

RESULTS

Four linear regression models confirmed a positive linear correlation between TyGI and BEOC in patients with asthma. In Model D, which controlled for all covariates, BEOC increased by 12.44 cells/uL for every extra unit of TyGI. The GAM and threshold effect models further verified the positive linear correlation between TyGI and BEOC. The XGBoost model indicated that the six most significant variables influencing BEOC, in order of relative importance, were age, cholesterol level, body mass index (BMI), poverty-to-income ratio (PIR), BNEUC, and TyGI.

CONCLUSIONS

In patients with asthma, the study discovered a linear positive correlation between TyGI and BEOC. This indicates a potential connection between TyGI and alterations in the immune status of individuals with asthma, which may help detect abnormalities in a timely manner and provide a reference for clinical decision-making. This study offers fresh insights for the future exploration of the management and treatment of asthma.

Epithelial-neuronal-immune cell interactions: Implications for immunity, inflammation, and tissue homeostasis at mucosal sites

The epithelial lining of the respiratory tract and intestine provides a critical physical barrier to protect host tissues against environmental insults, including dietary antigens, allergens, chemicals, and microorganisms. In addition, specialized epithelial cells communicate directly with hematopoietic and neuronal cells. These epithelial-immune and epithelial-neuronal interactions control host immune responses and have important implications for inflammatory conditions associated with defects in the epithelial barrier, including asthma, allergy, and inflammatory bowel diseases. In this review, we discuss emerging research that identifies the mechanisms and impact of epithelial-immune and epithelial-neuronal cross talk in regulating immunity, inflammation, and tissue homeostasis at mucosal barrier surfaces. Understanding the regulation and impact of these pathways could provide new therapeutic targets for inflammatory diseases at mucosal sites.

AIM2 participates in house dust mite (HDM)-induced epithelial dysfunctions and ovalbumin (OVA)-induced allergic asthma in infant mice

Objective: Allergen sensitization and high rates of concomitant allergic diseases are characteristic of severe pediatric asthma. The present study was aimed to explore the mechanism of allergic asthma via bioinformatics and experiment investigation. Methods: The GSE27011 dataset contained the expression profiles of normal and pediatric asthma white blood cells was downloaded for analyzing the different expression genes and function enrichment. The allergic asthma model in infant mice was established by ovalbumin (OVA) stimulation. The cellular model was established by house dust mite (HDM)-stimulation in human bronchial epithelial cells. The absent in melanoma 2 (AIM2) knockdown was achieved by intranasal lentivirus injection or cell infection. The bronchoalveolar lavage fluid (BALF) was collected for cell counting and ELISA assessment of cytokines. Lung tissues were collected for HE staining and immunohistochemical (IHC) staining. Real-time PCR and immunoblotting were used for the determination of key gene expressions in mouse and cell models. Results: upregulation of AIM2 gene expression was observed in pediatric asthma patients based on GSE27011 and OVA-induced infant mouse allergic asthma model. AIM2 knockdown ameliorated OVA caused elevation in airway hyper-responsiveness (AHR), elevation in cell quantities (eosinophils, neutrophils, lymphocytes), and levels of cytokines (IL-4, IL-13, TNF-α, and OVA-specific IgE) in BALF. Moreover, AIM2 knockdown relieved OVA-caused histopathological alterations in mouse lungs, up-regulation of AIM2 levels, and NOD1 and receptor-interacting protein 2 (RIP2) protein levels, as well as p65 phosphorylation. In the cell model, AIM2 knockdown partially ameliorated HDM-induced epithelial dysfunctions by promoting cell viability, down-regulating inflammatory cytokines levels, and decreasing the protein levels of AIM2, NOD1, RIP2, and phosphorylated p65. Conclusion: AIM2 participates in HDM-induced epithelial dysfunctions and OVA-induced allergic asthma progression. AIM2 could be a promising target for pediatric allergic asthma treatment regimens, which warrants further in vivo investigations.

Upper and lower airway interactions in children

PURPOSE OF REVIEW

The aim of the present review was to highlight the interactions between rhinitis, rhinosinusitis and asthma in children and to discuss the most relevant scientific progresses in the pathophysiology and treatment of these combined conditions.

RECENT FINDINGS

Advances in understanding the mechanisms underlying the relationship between upper and lower airways have provided valuable insights into the role of eosinophils in the pathophysiology of inflammatory events and have further delineated the concept of united airway disease. Studies addressed to evaluate the burden of sinonasal system on asthma outcomes showed a parallel severity of upper and lower airway diseases. Histopathology of sinonasal tissue in patients with chronic rhinosinusitis is different in adults and children. Targeted administration of biological agents represents an effective treatment in patients with severe uncontrolled asthma, but specific trials are awaited in children with chronic sinonasal disease.

SUMMARY

Allergic rhinitis and rhinosinusitis are important comorbidities in patients with asthma. Improved knowledge of pathogenic mechanisms of inflammation and remodelling in the sinonasal system and the lung has led to new therapeutic approaches in patients with united airway disease and opened interesting perspectives for personalized drug therapies.

Nutrient-derived signals regulate eosinophil adaptation to the small intestine

Eosinophils are well recognized as effector cells of type 2 immunity, yet they also accumulate in many tissues under homeostatic conditions. However, the processes that govern homeostatic eosinophil accumulation and tissue-specific adaptation, and their functional significance, remain poorly defined. Here, we investigated how eosinophils adapt to the small intestine (SI) microenvironment and the local signals that regulate this process. We observed that eosinophils gradually migrate along the crypt-villus axis, giving rise to a villus-resident subpopulation with a distinct transcriptional signature. Retinoic acid signaling was specifically required for maintenance of this subpopulation, while IL-5 was largely dispensable outside of its canonical role in eosinophil production. Surprisingly, we found that a high-protein diet suppressed the accumulation of villus-resident eosinophils. Purified amino acids were sufficient for this effect, which was a consequence of accelerated eosinophil turnover within the tissue microenvironment and was not due to altered development in the bone marrow. Our study provides insight into the process of eosinophil adaptation to the SI, highlighting its reliance on nutrient-derived signals.

Temperature influences commensal-pathogen dynamics in a nasal epithelial cell co-culture model

Chronic rhinosinusitis (CRS) is an inflammatory disease of the paranasal sinuses, and microbial dysbiosis associated with CRS is thought to be a key driver of host inflammation that contributes to disease progression. Staphylococcus aureus is a common upper respiratory tract (URT) pathobiont associated with higher carriage rates in CRS populations, where S. aureus-secreted toxins can be identified in CRS tissues. Although many genera of bacteria colonize the URT, few account for the majority of sequencing reads. These include S. aureus and several species belonging to the genus Corynebacterium, including Corynebacterium propinquum and Corynebacterium pseudodiphtheriticum, which are observed at high relative abundance in the healthy URT. Studies have examined bacterial interactions between major microbionts of the URT and S. aureus, but few have done so in the context of a healthy versus diseased URT environment. Here, we examine the role of temperature in commensal, pathogen, and epithelial dynamics using an air-liquid interface cell culture model mimicking the nasal epithelial environment. Healthy URT temperatures change from the nares to the nasopharynx and are increased during disease. Temperatures representative of the healthy URT increase persistence and aggregate formation of commensal C. propinquum and C. pseudodiphtheriticum, reduce S. aureus growth, and lower epithelial cytotoxicity compared to higher temperatures correlating with the diseased CRS sinus. Dual-species colonization revealed species-specific interactions between Corynebacterium species and S. aureus dependent on temperature. Our findings suggest URT mucosal temperature plays a significant role in mediating polymicrobial and host-bacterial interactions that may exacerbate microbial dysbiosis in chronic URT diseases.IMPORTANCEChronic rhinosinusitis is a complex inflammatory disease with a significant healthcare burden. Although presence of S. aureus and microbial dysbiosis are considered mediators of inflammation in CRS, no studies have examined the influence of temperature on S. aureus interactions with the nasal epithelium and the dominant genus of the healthy URT, Corynebacterium. Interactions between Corynebacterium species and S. aureus have been documented in several studies, but none to date have examined how environmental changes in the URT may alter their interactions with the epithelium or each other. This study utilizes a polarized epithelial cell culture model at air-liquid interface to study the colonization and spatial dynamics of S. aureus and clinical isolates of Corynebacterium from people with CRS to characterize the role temperature has in single- and dual-species dynamics on the nasal epithelium.

Eosinophils-from cradle to grave: An EAACI task force paper on new molecular insights and clinical functions of eosinophils and the clinical effects of targeted eosinophil depletion

Over the past years, eosinophils have become a focus of scientific interest, especially in the context of their recently uncovered functions (e.g. antiviral, anti-inflammatory, regulatory). These versatile cells display both beneficial and detrimental activities under various physiological and pathological conditions. Eosinophils are involved in the pathogenesis of many diseases which can be classified into primary (clonal) and secondary (reactive) disorders and idiopathic (hyper)eosinophilic syndromes. Depending on the biological specimen, the eosinophil count in different body compartments may serve as a biomarker reflecting the underlying pathophysiology and/or activity of distinct diseases and as a therapy-driving (predictive) and monitoring tool. Personalized selection of an appropriate therapeutic strategy directly or indirectly targeting the increased number and/or activity of eosinophils should be based on the understanding of eosinophil homeostasis including their interactions with other immune and non-immune cells within different body compartments. Hence, restoring as well as maintaining homeostasis within an individual's eosinophil pool is a goal of both specific and non-specific eosinophil-targeting therapies. Despite the overall favourable safety profile of the currently available anti-eosinophil biologics, the effect of eosinophil depletion should be monitored from the perspective of possible unwanted consequences.