Interactions between NCR+ILC3s and the Microbiome in the Airways Shape Asthma Severity

Decoding innate lymphoid cells and innate-like lymphocytes in asthma: pathways to mechanisms and therapies

Asthma is a chronic inflammatory lung disease driven by a complex interplay between innate and adaptive immune components. Among these, innate lymphoid cells (ILCs) and innate-like lymphocytes have emerged as crucial players in shaping the disease phenotype. Within the ILC family, group 2 ILCs (ILC2s), in particular, contribute significantly to type 2 inflammation through their rapid production of cytokines such as IL-5 and IL-13, promoting airway eosinophilia and airway hyperreactivity. On the other hand, innate-like lymphocytes such as invariant natural killer T (iNKT) cells can play either pathogenic or protective roles in asthma, depending on the stimuli and lung microenvironment. Regulatory mechanisms, including cytokine signaling, metabolic and dietary cues, and interactions with other immune cells, play critical roles in modulating their functions. In this review, we highlight current findings on the role of ILCs and innate-like lymphocytes in asthma development and pathogenesis. We also examine the underlying mechanisms regulating their function and their interplay with other immune cells. Finally, we explore current therapies targeting these cells and their effector cytokines for asthma management.

The Role of Biodiversity in the Development of Asthma and Allergic Sensitization: A State-of-the-Science Review

BACKGROUND

Changes in land use and climate change have been reported to reduce biodiversity of both the environment and human microbiota. These reductions in biodiversity may lead to inadequate and unbalanced stimulation of immunoregulatory circuits and, ultimately, to clinical diseases, such as asthma and allergies.

OBJECTIVE

We summarized available empirical evidence on the role of inner (gut, skin, and airways) and outer (air, soil, natural waters, plants, and animals) layers of biodiversity in the development of asthma, wheezing, and allergic sensitization.

METHODS

We conducted a systematic search in SciVerse Scopus, PubMed MEDLINE, and Web of Science up to 5 March 2024 to identify relevant human studies assessing the relationships between inner and outer layers of biodiversity and the risk of asthma, wheezing, or allergic sensitization. The protocol was registered in PROSPERO (CRD42022381725).

RESULTS

A total of 2,419 studies were screened and, after exclusions and a full-text review of 447 studies, 82 studies were included in the comprehensive, final review. Twenty-nine studies reported a protective effect of outer layer biodiversity in the development of asthma, wheezing, or allergic sensitization. There were also 16 studies suggesting an effect of outer layer biodiversity on increasing asthma, wheezing, or allergic sensitization. However, there was no clear evidence on the role of inner layer biodiversity in the development of asthma, wheezing, and allergic sensitization (13 studies reported a protective effect and 15 reported evidence of an increased risk).

CONCLUSIONS

Based on the reviewed literature, a future systematic review could focus more specifically on outer layer biodiversity and asthma. It is unlikely that association with inner layer biodiversity would have enough evidence for systematic review. Based on this comprehensive review, there is a need for population-based longitudinal studies to identify critical periods of exposure in the life course into adulthood and to better understand mechanisms linking environmental exposures and changes in microbiome composition, diversity, and/or function to development of asthma and allergic sensitization. https://doi.org/10.1289/EHP13948.

The IL-31/TRPV1 pathway mediates allergic asthma exacerbated by DINP dermal exposure in OVA-sensitized Balb/c mice

BACKGROUND

The potential role of dermal exposure diisononyl phthalate (DINP) as an adjuvant in allergic inflammation and asthma has been suggested. However, the current findings do not provide enough evidence to support this claim.

OBJECTIVES

The purpose of this investigation was to examine the impact and mechanisms of allergic asthma exacerbation through the dermal exposure to DINP.

METHODS

The study was undertaken using OVA-sensitized mice. Lung histopathology and airway hyperreactivity (AHR) were assessed. Expression levels of immunoglobulins (t-IgE, OVA-IgE and OVA-IgG1), cytokines (IL-31, IL-4, IL-5, IL-6, IL-13 and INF-γ), and TRPV1 were measured. To investigate the mechanism by which allergic asthma worsens due to dermal exposure to DINP, the blockade analysis using the IL-31 antagonist SB-431542 and the TRPV1 antagonist capsazepine (CZP) were performed.

RESULTS

The findings of the study revealed that the simultaneous exposure to DINP and OVA resulted in an increase in inspiratory resistance (Ri) and expiratory resistance (Re), a decrease in the minimum value of lung dynamic compliance (Cldyn), and worsened airway remodeling. Additionally, it was found that this exposure led to an increase in the levels of IL-31 and TRPV1, which are biomarkers of Th2 cytokines (IL-4, IL-5, IL-6, and IL-13), as well as immunoglobulins (Total IgE, OVA-lgE, and OVA-IgG1), while decreasing the biomarker of Th1 cytokines (IFN-γ). However, these impairments showed improvement after the administration of SB-431542 or CZP.

CONCLUSION

The findings of this research indicate that the IL-31/TRPV1 pathway plays a moderating function in OVA-induced allergic asthma worsened by dermal exposure to DINP.

Winds of change a tale of: asthma and microbiome

The role of the microbiome in asthma is highlighted, considering its influence on immune responses and its connection to alterations in asthmatic patients. In this context, we review the variables influencing asthma phenotypes from a microbiome perspective and provide insights into the microbiome's role in asthma pathogenesis. Previous cohort studies in patients with asthma have shown that the presence of genera such as Bifidobacterium, Lactobacillus, Faecalibacterium, and Bacteroides in the gut microbiome has been associated with protection against the disease. While, the presence of other genera such as Haemophilus, Streptococcus, Staphylococcus, and Moraxella in the respiratory microbiome has been implicated in asthma pathogenesis, indicating a potential link between microbial dysbiosis and the development of asthma. Furthermore, respiratory infections have been demonstrated to impact the composition of the upper respiratory tract microbiota, increasing susceptibility to bacterial diseases and potentially triggering asthma exacerbations. By understanding the interplay between the microbiome and asthma, valuable insights into disease mechanisms can be gained, potentially leading to the development of novel therapeutic approaches.

Microbiome and Asthma: Microbial Dysbiosis and the Origins, Phenotypes, Persistence, and Severity of Asthma

The importance of the microbiome, and of the gut-lung axis in the origin and persistence of asthma, is an ongoing field of investigation. The process of microbial colonisation in the first three years of life is fundamental for health, with the first hundred days of life being critical. Different factors are associated with early microbial dysbiosis, such as caesarean delivery, artificial lactation and antibiotic therapy, among others. Longitudinal cohort studies on gut and airway microbiome in children have found an association between microbial dysbiosis and asthma at later ages of life. A low α-diversity and relative abundance of certain commensal gut bacterial genera in the first year of life are associated with the development of asthma. Gut microbial dysbiosis, with a lower abundance of Phylum Firmicutes, could be related with increased risk of asthma. Upper airway microbial dysbiosis, especially early colonisation by Moraxella spp., is associated with recurrent viral infections and the development of asthma. Moreover, the bacteria in the respiratory system produce metabolites that may modify the inception of asthma and is progression. The role of the lung microbiome in asthma development has yet to be fully elucidated. Nevertheless, the most consistent finding in studies on lung microbiome is the increased bacterial load and the predominance of proteobacteria, especially Haemophilus spp. and Moraxella catarrhalis. In this review we shall update the knowledge on the association between microbial dysbiosis and the origins of asthma, as well as its persistence, phenotypes, and severity.

Micrococcus luteus-derived extracellular vesicles attenuate neutrophilic asthma by regulating miRNAs in airway epithelial cells

Bacterial extracellular vesicles (EVs) have been shown to regulate various pulmonary diseases, but their functions in asthma remain uncertain. To demonstrate the clinical significance of Micrococcus luteus-derived EVs (MlEVs) in asthma, we enrolled 45 asthmatic patients (20 patients with neutrophilic asthma [NA], 25 patients with eosinophilic asthma [EA]) and 40 healthy controls (HCs). When the prevalence of IgG1 and IgG4 specific to MlEVs was evaluated in serum by ELISA, lower levels of MlEV-specific IgG4 (but not IgG1) were noted in asthmatic patients than in HCs. Among asthmatic patients, significantly lower levels of MIEV-specific IgG4 were noted in patients with NA than in those with EA. Moreover, there was a positive correlation between serum MlEV-specific IgG4 levels and FEV₁ (%) values. In asthmatic C57BL/6 mice, MlEVs significantly attenuated neutrophilic airway inflammation by reducing the production of IL-1β and IL-17 in bronchoalveolar lavage fluid as well as the number of group 3 innate lymphoid cells (ILC3s) in lung tissues. To clarify the functional mechanism of MlEVs in NA, the effect of MlEVs on airway epithelial cells (AECs) and immune cells was investigated ex vivo. According to microarray analysis, MlEVs upregulated hsa-miR-4517 expression in AECs. Moreover, this miRNA could suppress IL-1β production by monocytes, resulting in the inhibition of ILC3 activation and neutrophil recruitment. These findings suggest that MlEVs could be a novel therapeutic agent for managing unresolved NA by regulating miRNA expression in AECs.