Discovering Biomarkers of Neutrophilic Asthma: A Clinician's Perspective

TGF-β, IL-1β, IL-6 levels and TGF-β/Smad pathway reactivity regulate the link between allergic diseases, cancer risk, and metabolic dysregulations

The risk of cancer is higher in patients with asthma compared to those with allergic rhinitis for many types of cancer, except for certain cancers where a contrasting pattern is observed. This study offers a potential explanation for these observations, proposing that the premalignant levels of circulating transforming growth factor-β (TGF-β), IL-1β, and IL-6 as well as the reactivity of the TGF-β/Smad signaling pathway at the specific cancer site, are crucial factors contributing to the observed disparities. Circulating TGF-β, IL- β and IL-6 levels also help clarify why asthma is positively associated with obesity, Type 2 diabetes, hypertension, and insulin resistance, whereas allergic rhinitis is negatively linked to these conditions. Furthermore, TGF-β/Smad pathway reactivity explains the dual impact of obesity, increasing the risk of certain types of cancer while offering protection against other types of cancer. It is suggested that the association of asthma with cancer and metabolic dysregulations is primarily linked to the subtype of neutrophilic asthma. A binary classification of TGF-β activity as either high (in the presence of IL-1β and IL-6) or low (in the presence or absence of IL-1β and IL-6) is proposed to differentiate between allergy patients prone to cancer and metabolic dysregulations and those less prone. Glycolysis and oxidative phosphorylation, the two major metabolic pathways utilized by cells for energy exploitation, potentially underlie this dichotomous classification by reprogramming metabolic pathways in immune cells.

ST2-Mediated Neutrophilic Airway Inflammation: A Therapeutic Target for Patients With Uncontrolled Asthma

PURPOSE

Suppression of tumorigenicity 2 (ST2) has been proposed as the receptor contributing to neutrophilic inflammation in patients with type 2-low asthma. However, the exact role of ST2 in neutrophil activation remains poorly understood.

METHODS

A total of 105 asthmatic patients (classified into 3 groups according to control status: the controlled asthma [CA], partly-controlled asthma [PA], and uncontrolled asthma [UA] groups), and 104 healthy controls were enrolled to compare serum levels of soluble ST2 (sST2) and interleukin (IL)-33. Moreover, the functions of ST2 in neutrophils and macrophages (Mϕ) were evaluated ex vivo and in vivo.

RESULTS

Serum sST2 levels were significantly higher in the UA group than in the CA or PA groups (P < 0.05 for all) with a negative correlation between serum sST2 and forced expiratory volume in 1 second % (r = -0.203, P = 0.038). Significantly higher expression of ST2 receptors on peripheral neutrophils was noted in the UA group than in the PA or CA groups. IL-33 exerted its effects on the production of reactive oxygen species, the formation of extracellular traps from neutrophils, and Mϕ polarization/activation. In neutrophilic asthmatic mice, treatment with anti-ST2 antibody significantly suppressed proinflammatory cytokines (tumor necrosis factor-alpha and IL-17A) as well as the numbers of immune cells (neutrophils, Mϕ, and group 3 innate lymphoid cells) in the lungs.

CONCLUSIONS

These results suggest that IL-33 induces the activation of neutrophils and Mϕ via ST2 receptors, leading to neutrophilic airway inflammation and poor control status of asthma. ST2 could be a therapeutic target for neutrophilic airway inflammation in patients with UA.

MUC1 attenuates neutrophilic airway inflammation in asthma by reducing NLRP3 inflammasome-mediated pyroptosis through the inhibition of the TLR4/MyD88/NF-κB pathway

BACKGROUND

Neutrophilic airway inflammation is a challenge in asthma management and is associated with poor patient prognosis. Mucin 1 (MUC1), which contains a cytoplasmic tail (MUC1-CT), has been found to mediate glucocorticoid sensitivity in asthma; however, its role in modulating neutrophilic airway inflammation in asthma remains unknown.

METHODS

Human-induced sputum cells were collected from healthy participants (n = 12), patients with mild-to-moderate asthma (n = 34), and those with severe asthma (n = 18). In vitro human lung bronchial 1 epithelial cell line (BEAS-2B) was transfected with small interfering RNA against MUC1 (MUC1-siRNA) and then stimulated by lipopolysaccharide (LPS), where some cells were pretreated with a TLR4 inhibitor (TAK-242). In vivo mouse model of asthmatic neutrophil airway inflammation was induced by ovalbumin (OVA)/LPS. Some groups were intraperitoneally injected with MUC1-CT inhibitor (GO-203) and/or TAK-242 .

RESULTS

The mRNA expression of MUC1 was downregulated in the induced sputum of patients with asthma and correlated with asthmatic neutrophilic airway inflammation. The mRNA expressions of TLR4, MyD88, nucleotide-binding oligomerization domain-like pyrin domain-containing protein 3 (NLRP3), caspase-1, interleukin (IL)-18, and IL-1β in induced sputum cells of patients with asthma were upregulated and related to the mRNA expression of MUC1. LPS activated the TLR4 pathway and NLRP3-mediated pyroptosis in BEAS-2B cells in vitro, which were significantly aggravated after MUC1-siRNA transfection. Furthermore, MUCl-CT interacted with TLR4, and the interaction between TLR4 and MyD88 was significantly increased after MUCl-siRNA transfection. Moreover, TAK-242 ameliorated TLR4/MyD88/nuclear factor kappa B (NF-κB) pathway activation, NLRP3 inflammasome-mediated pyroptosis, and neutrophilic inflammation exacerbated by MUC1 downregulation. GO-203 exacerbated TLR4/MyD88/NF-κB pathway activation in vivo, and NLRP3 inflammasome-mediated pyroptosis reduced in a mouse model of asthmatic neutrophil airway inflammation induced by OVA/LPS; these pathological changes were partially alleviated after TAK-242 application.

CONCLUSION

This study revealed that MUC1 downregulation plays an important role in asthmatic neutrophilic airway inflammation. MUC1-CT reduces NLRP3 inflammasome-mediated pyroptosis by inhibiting the activation of the TLR4/MyD88/NF-κB pathway, thereby attenuating neutrophil airway inflammation in patients with asthma.

Special Issue on ‘Asthma and Allergic Inflammation’

Asthma is a chronic inflammatory airway disease, driven by either allergic or non-allergic stimuli, which usually manifests as wheezing, reversible airflow limitation, and bronchial hyperresponsiveness [...]

Tiotropium Bromide Improves Neutrophilic Asthma by Recovering Histone Deacetylase 2 Activity

BACKGROUND

The value of tiotropium bromide (TIO) in neutrophilic asthma was meaningful in previous study. We hypothesized that TIO's mechanism of action is associated with histone deacetylase 2 (HDAC2) activity, which is key for controlling the transcription of inflammatory cytokines and usually downregulated in neutrophilic asthma.

METHODS

The effects of TIO and dexamethasone (DEX) on HDAC2 activity, nuclear factor kappa B (NF-κB), and C-X-C motif chemokine ligand 1 (CXCL1) were evaluated in neutrophilic asthma mouse model (C57BL, 6-week-old). An in-vitro study was conducted using primary human bronchial/tracheal epithelial (HBE) cells from asthma patients. Western blot analyses were performed for phospho-phospholipase Cγ-1 (PLCγ-1) and inositol trisphosphate (IP₃) receptors (IP₃R) with treating lipopolysaccharide (LPS) and TIO.

RESULTS

Ovalbumin was used to induce eosinophilic inflammation in this study. After neutrophilic asthma was induced by LPS (O+L group), HDAC2 activity was diminished with increased NF-κB activity and CXCL1 compared to the control group. TIO significantly improved NF-κB activity, CXCL1, and HDAC2 activity compared with the O+L group in in-vivo study (P < 0.05, each). Western blot analyses showed that LPS treated HBE cells from asthma patients increased PLCγ-1 and diminished IP₃ receptor levels. After TIO treatment, recovery of IP₃R and improved PLCγ-1 levels were observed.

CONCLUSION

These results support the hypothesis that TIO modulates inflammation by recovering HDAC2 activity from the acetylcholine-stimulated inflammation cascade in neutrophilic asthma. The detailed inflammation cascade of recovering HDAC2 activity by TIO might be associated with PLCγ-1-IP₃-IP₃R mediated intracellular calcium ion pathway.

Extracellular Traps: A Novel Therapeutic Target for Severe Asthma

Asthma is a complicated disease defined by a combination of clinical symptoms and physiological characteristics. Typically, asthma is diagnosed by the presence of episodic cough, wheezing, or dyspnea triggered by variable environmental factors (allergens and respiratory infections), and reversible airflow obstruction. To date, the majority of asthmatic patients have been adequately controlled by anti-inflammatory/bronchodilating agents, but those with severe asthma (SA) have not been sufficiently controlled by high-dose inhaled corticosteroids-long-acting beta-agonists plus additional controllers including leukotriene modifiers. Accordingly, these uncontrolled patients provoke a special issue, because they consume high healthcare resources, requiring innovative precision medicine solutions. Recently, phenotyping based on biomarkers of airway inflammation has led to elucidating the pathophysiological mechanism of SA, where emerging evidence has highlighted the significance of eosinophil or neutrophil extracellular traps contributing to the development of SA. Here, we aimed to provide current findings about extracellular traps as a novel therapeutic target for asthma to address medical unmet needs.

Evolving Concept of Severe Asthma: Transition From Diagnosis to Treatable Traits

In recent decades, the concept of severe asthma has evolved from an umbrella term encompassing patients with high-intensity treatment needs to a clinical syndrome with heterogeneous, albeit distinct, pathophysiological processes. Biased and unbiased cluster approaches have been used to identify several clinical phenotypes. In parallel, cellular and molecular approaches allow for the development of biological therapies, especially targeting type 2 (T2) cytokine pathways. Although T2-biologics have significantly improved clinical outcomes for patients with severe asthma in real-world practice, questions on the proper use of biologics remain open. Furthermore, a subset of severe asthma patients remains poorly controlled. The unmet needs require a new approach. The “treatable traits” concept has been suggested to address a diversity of pathophysiological factors in severe asthma and overcome the limitations of existing treatment strategies. With a tailored therapy that targets the treatable traits in individual patients, better personalized medical care and outcomes should be achieved.