The role of IL-33 and its receptor ST2 in human nasal epithelium with allergic rhinitis

Group 2 Innate Lymphoid Cells in Allergic Rhinitis

Allergic rhinitis (AR), which presents symptoms like sneezing and a runny nose, is categorized as an upper respiratory condition of type 2. Recent progress in comprehending AR has revealed the significant role played by type 2 cytokines, specifically interleukin (IL)-13, IL-4, and IL-5. These cytokines are released by helper T cells 2 (Th2) and innate lymphoid cells (ILC2s). ILC2s have the ability to interact with various immune cells and are essential in promoting both type 2 immune response and tissue repair, contributing to normal homeostatic functions within the body. This article presents a summary of the latest advancements in comprehending the activity of ILC2s, with particular emphasis on their potential role involvement in AR. It explores how they collaborate with Th2 cells to exacerbate nasal inflammation and interact with regulatory T cells (Tregs) to counteract the suppressive role mediated by Tregs during allergic inflammation. The significance of ILC2s in allergen-specific therapy is highlighted. A comprehensive understanding of ILC2s biology establishes a robust foundation for unraveling the pathogenesis of AR and devising innovative therapeutic approaches for its management.

Necrotic Change of Tunica Media Plays a Key Role in the Development of Coronary Artery Lesions in Kawasaki Disease

BACKGROUND

Alarmins resulting from cell death or oxidative stress are involved in the development of Kawasaki disease (KD) vasculitis. In a previous study, we demonstrated the potential role of interleukin (IL)-33 as an alarmin in the development of KD vasculitis. Although edematous dissociation (necrotic change) of the tunica media is thought to be a major source of IL-33 in KD vasculitis, it has not yet been elucidated.

METHODS AND RESULTS

We investigated the impact of IL-33 released from necrotic human coronary artery smooth muscle cells (HCASMCs) on human coronary artery endothelial cells (HCAECs) using a coculture assay. Subsequently, we evaluated the anti-inflammatory effects of anti-IL-33 and anti-suppression of tumorigenicity 2 (ST2) antibodies compared with conventional therapies of KD, such as high-dose IgG or anti-tumor necrosis factor (TNF)-α antibody. Primary necrosis of HCASMCs induced significant release of IL-33. In cocultures of necrotic HCASMCs with HCAECs, the necrotic HCASMCs significantly induced the production of various proinflammatory cytokines in the HCAECs. Anti-IL-33 and anti-ST2 antibodies exhibited unique inhibitory effects on the production of platelet-derived growth factor-BB or IL-12(p70) in HCAECs.

CONCLUSIONS

There is potential involvement of edematous dissociation of the tunica media in the development of KD vasculitis. Furthermore, the distinctive anti-inflammatory effects of the anti-IL-33/ST2 axis drugs suggest novel therapeutic options for patients with refractory KD.

IL-33 Enhances the Total Production of IgG, IgG1, and IgG3 in Angiostrongylus cantonensis-Infected Mice

The purpose of this study is to clarify the role of IL-33 in the immune response to angiostrongyliasis, especially in terms of antibody production and isotype switching. In our experiment, C57BL/6 mice were each infected with 35 infectious larvae and were divided into groups that received an intraperitoneal injection of IL-33, anti-IL-33 monoclonal antibody (mAb), or anti-ST2 mAb 3 days post-infection (dpi) and were subsequently administered booster shots at 5-day intervals with the same dose. Serum samples from each group were collected weekly for ELISA assays. The levels of total IgG, IgG1, and IgG3 were significantly increased in A. cantonensis-infected mice that were treated with IL-33, and the levels decreased significantly in infected groups treated with anti-IL-33 or anti-ST2 mAb. These results suggest that IL-33 may play a critical role in the pathogenesis of human angiostrongyliasis and could be useful for understanding protective immunity against this parasitic infection.

Lack of a transcriptional response of primary bronchial epithelial cells from patients with asthma and controls to IL-33

IL-33 and IL-1RL1 are well-replicated asthma genes that act in a single pathway toward type-2 immune responses. IL-33 is expressed by basal epithelial cells, and the release of IL-33 upon epithelial damage can activate innate lymphoid cells, T helper-2 cells, basophilic granulocytes, and mast cells through a receptor complex containing IL-1RL1. However, it is unknown how bronchial epithelial cells respond to IL-33, and whether this response is increased in the disease. We aimed to characterize the IL-33-driven transcriptomic changes in cultured primary bronchial epithelial cells from patients with asthma and healthy controls. Primary bronchial epithelial cells (PBECs) were obtained by bronchial brushing from six healthy control for air-liquid interface (ALI) cultures, whereas we selected eight healthy controls and seven patients with asthma for epithelial organoid cultures. We then stimulated the cultures for 24 h with recombinant IL-33 (rhIL33) at various concentrations with 1, 10, and 50 ng/mL for the ALI cultures and 20 ng/mL and 100 ng/mL for the organoid cultures, followed by RNA-sequencing and differential gene expression analysis. We did not detect any genome-wide significant differentially expressed genes after stimulation of PBECs with IL-33, irrespective of growth in three-dimensional (3-D) epithelial organoids or after differentiation in ALI cultures. These results were identical between PBECs obtained from patients with asthma or from healthy control subjects. We detected very low levels of IL-1RL1 gene expression in these airway epithelial cell cultures. We conclude that bronchial epithelial cells do not have a transcriptional response to IL-33, independent of their differentiation state. Hence, the airway epithelium acts as a source of IL-33 but does not seem to contribute to the response upon release of the alarmin after epithelial damage.NEW & NOTEWORTHY The IL-33/IL-1RL1 pathway stands as a formidable genetic predisposition for asthma, with ongoing clinical developments of various drugs designed to mitigate its influence in patients with asthma. The absence of a transcriptomic reaction to IL-33 within the bronchial epithelium holds significance in the pursuit of identifying biomarkers that can aid in pinpointing those individuals who would derive the greatest benefit from therapies targeting the IL-33 pathway.

HDAC4 depletion ameliorates IL-13-triggered inflammatory response and mucus production in nasal epithelial cells via activation of SIRT1/NF-κB signaling

INTRODUCTION

Allergic rhinitis (AR) is frequently known as a chronic respiratory disease with a global high prevalence. The pivotal roles of histone deacetylase 4 (HDAC4) in multiple human diseases have been underlined by numerous studies. Nevertheless, whether HDAC4 is implicated in AR remains to be elaborated. The objective of the current study is to clarify the impacts of HDAC4 on AR.

METHODS

First, human nasal epithelial cells (hNECs) were pretreated by interleukin-13 (IL-13). HDAC4 expression in hNECs with the presence or absence of IL-13 treatment was tested by quantitative reverse-transcription polymerase chain reaction (RT-qPCR) and western blot. Following, after HDAC4 was depleted, levels of histamine, Immunoglobulin E (IgE) and inflammatory factors were analyzed by ELISA assay. Then, Mucin-5AC (MUC5AC) expression was examined through RT-qPCR, western blot, and IF assay. Western blot was to analyze the expression of sirtuin 1 (SIRT1)/nuclear factor-kappaB (NF-κB) signaling-related proteins. After IL-13-induced hNECs were cotransfected with HDAC4 interference plasmids and SIRT1 inhibitor EX527, the functional experiments above were conducted again.

RESULTS

The experimental data in this study presented that HDAC4 expression was increased in IL-13-induced hNECs. Silencing of HDAC4 cut down the levels of histamine, IgE and inflammatory factors and the expression of MUC5AC. Additionally, knockdown of HDAC4 led to the activation of SIRT1/NF-κB signaling. Further, the downregulated levels of histamine, IgE and inflammatory factors and the expression of MUC5AC imposed by HDAC4 interference were all reversed by EX527.

CONCLUSIONS

In short, HDAC4 inhibition activated SIRT1/NF-κB signaling to mitigate inflammatory response and mucus production in IL-13-treated nasal epithelial cells in AR.

The potential role of interleukin (IL)-25/IL-33/thymic stromal lymphopoietin (TSLP) on the pathogenesis of idiopathic pulmonary fibrosis

OBJECTIVES

Interleukin (IL)-25, IL-33, and thymic stromal lymphopoietin (TSLP) are the important drivers for excessive type-2 immunity. It has been well elucidated that IL-25/IL-33/TSLP plays an important role in allergic airway inflammation and remodeling, whereas their roles in idiopathic pulmonary fibrosis (IPF) still remained largely unclear. Herein, the aim of the review is to discuss the potential role and mechanism of IL-25/IL-33/TSLP on IPF by literature analysis and summary.

DATA SOURCE

We have done a literature search using the following terms: ("idiopathic pulmonary fibrosis" OR "IPF" OR "lung fibrosis") and (TSLP or "thymic stromal lymphopoietin" or IL-25 OR IL-17E OR IL-33) from the database of PubMed published in English up to July 2018.

STUDY SELECTION

We have totally found 58 articles by using the retrieval terms mentioned above. By careful title and abstract reading, 10 original research articles of high quality were enrolled for the full text reading and analysis. Two additional relevant studies were also included during the course of literature readings.

RESULTS

IL-25/IL-33/TSLP and their corresponding receptors, that is, IL-17BR/ST2L/TSLPR, are shown to be up-regulated both in IPF patients and bleomycin (BLM)-induced lung fibrosis mice model. IL-25 may promote lung fibrosis by activating IL-17BR+fibroblast and IL-17BR+ILC2 (type 2 innate lymphoid cell). Full length (fl)-IL-33, as a transcription factor mainly in the cell nucleus, mediated non-atopic lung inflammation and fibrosis by modulating expressions of several pro-fibrotic mediators, including transforming growth factor (TGF)-b1. By contrast, mature (m)-IL-33 potentiates lung fibrosis by recruiting ST2L+M2 macrophages and ST2L+ILC2 to enlarge type 2 immunity. TSLP was shown to directly promote CCL2 expression in primary human lung fibroblasts (pHLFs).

CONCLUSION

IL-25/IL-33/TSLP contributes to non-allergic lung fibrosis by mediating persistent abnormal epithelial-mesenchymal crosstalk. IL-25/IL-33/TSLP may serve the promising novel target for the treatment of IPF.

Schistosoma mansoni infection decreases IL-33-mRNA expression and increases CXCL9 and CXCL10 production by peripheral blood cells

Schistosoma mansoni infections, particularly egg antigens, induce Th2-dominant granulomatous responses accompanied by remarkable immunoregulatory mechanisms that avoid intense fibrosis. Interleukin (IL)-33 is a cytokine that stimulates the early activation of Th2 responses, and its soluble ST2 receptor (sST2) avoids granulomatous response, as well as CXCL9 and CXCL10 chemokines that have antifibrotic activity. However, in schistosomiasis, these molecules have not been suitably studied. Therefore, this study aimed to measure IL-33 and sST2 RNA, cytokines, and chemokines in peripheral blood cultures from individuals living in schistosomiasis-endemic areas. Peripheral blood cells from individuals with S. mansoni (n = 34) and non-infected individuals (n = 31) were cultured under mitogen stimulation. Supernatant chemokines and cytokines were evaluated using a cytometric bead array, and IL-33 and sST2 mRNA expression was measured using qPCR. Infected individuals showed higher levels of CXCL8, CXCL9, CXCL10, IFN-γ, TNF-α, IL-6, IL-2, IL-4, and IL-10; there was a lower expression of IL-33 mRNA and similar expression of sST2mRNA in infected than non-infected individuals. In conclusion, for the first time, we demonstrated lower IL-33mRNA expression and high levels of the antifibrotic chemokines CXCL9 and CXCL10 in schistosomiasis mansoni, which could control exacerbations of the disease in individuals from endemic areas.

Differences in Inflammatory Cytokine Profile in Obesity-Associated Asthma: Effects of Weight Loss

Obesity and asthma are associated with systemic inflammation maintained by mediators released by adipose tissue and lung. This study investigated the inflammatory serum mediator profile in obese subjects (O) (n = 35), non-obese asthma (NOA) patients (n = 14), obese asthmatics (OA) (n = 21) and healthy controls (HC) (n = 33). The effect of weight loss after bariatric surgery (BS) was examined in 10 OA and 31 O subjects. We analyzed serum markers including leptin, adiponectin, TGF-β1, TNFR2, MCP-1, ezrin, YKL-40, ST2, IL-5, IL-9, and IL-18. Compared with HC subjects, the O group showed increased levels of leptin, TGF-β1, TNFR2, MCP-1, ezrin, YKL-40, and ST2; the OA group presented increased levels of MCP-1, ezrin, YKL-40, and IL-18, and the NOA group had increased levels of ezrin, YKL-40, IL-5, and IL-18. The higher adiponectin/leptin ratio in NOA with respect to OA subjects was the only significant difference between the two groups. IL-9 was the only cytokine with significantly higher levels in OA with respect to O subjects. TNFR2, ezrin, MCP-1, and IL-18 concentrations significantly decreased in O subjects after BS. O, OA, and NOA showed distinct patterns of systemic inflammation. Leptin and adiponectin are regulated in asthma by obesity-dependent and -independent mechanisms. Combination of asthma and obesity does not result in significant additive effects on circulating cytokine levels.

Increased expression of IL1-RL1 is associated with type 2 and type 1 immune pathways in asthma

Background

Asthma is a common chronic airway disease in the world. The purpose of this study was to explore the expression of IL1-RL1 in sputum and its correlation with Th1 and Th2 cytokines in asthma.

Methods

We recruited 132 subjects, detected IL1-RL1 protein level in sputum supernatant by ELISA, and analyzed the correlation between the expression level of IL1-RL1 and fraction of exhaled nitric oxide (FeNO), IgE, peripheral blood eosinophil count (EOS#), and Th2 cytokines (IL-4, IL-5, IL-10, IL-13, IL-33 and TSLP) and Th1 cytokines (IFN-γ, IL-2, IL-8). The diagnostic value of IL1-RL1 was evaluated by ROC curve. The expression of IL1-RL1 was further confirmed by BEAS-2B cell in vitro.

Results

Compared with the healthy control group, the expression of IL1-RL1 in sputum supernatant, sputum cells and serum of patients with asthma increased. The AUC of ROC curve of IL1-RL1 in sputum supernatant and serum were 0.6840 (p = 0.0034), and 0.7009 (p = 0.0233), respectively. IL1-RL1 was positively correlated with FeNO, IgE, EOS#, Th2 cytokines (IL-4, IL-5, IL-10, IL-13, IL-33 and TSLP) and Th1 cytokines (IFN-γ, IL-2, IL-8) in induced sputum supernatant. Four weeks after inhaled glucocorticoids (ICS) treatment, the expression of IL1-RL1 in sputum supernatant and serum was increased. In vitro, the expression of IL1-RL1 in BEAS-2B was increased after stimulated by IL-4 or IL-13 for 24 h.

Conclusion

The expression of IL1-RL1 in sputum supernatant, sputum cells and serum of patients with asthma was increased, and was positively correlated with some inflammatory markers in patients with asthma. IL1-RL1 may be used as a potential biomarker for the diagnosis and treatment of asthma.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12865-022-00499-z.

TLR Signals in Epithelial Cells in the Nasal Cavity and Paranasal Sinuses

The respiratory tract is constantly at risk of invasion by microorganisms such as bacteria, viruses, and fungi. In particular, the mucosal epithelium of the nasal cavity and paranasal sinuses is at the very forefront of the battles between the host and the invading pathogens. Recent studies have revealed that the epithelium not only constitutes a physical barrier but also takes an essential role in the activation of the immune system. One of the mechanisms equipped in the epithelium to fight against microorganisms is the Toll-like receptor (TLR) response. TLRs recognize common structural components of microorganisms and activate the innate immune system, resulting in the production of a plethora of cytokines and chemokines in the response against microbes. As the epithelia-derived cytokines are deeply involved in the pathogenesis of inflammatory conditions in the nasal cavity and paranasal sinuses, such as chronic rhinosinusitis (CRS) and allergic rhinitis (AR), the molecules involved in the TLR response may be utilized as therapeutic targets for these diseases. There are several differences in the TLR response between nasal and bronchial epithelial cells, and knowledge of the TLR signals in the upper airway is sparse compared to that in the lower airway. In this review, we provide recent evidence on TLR signaling in the upper airway, focusing on the expression, regulation, and responsiveness of TLRs in human nasal epithelial cells (HNECs). We also discuss how TLRs in the epithelium are involved in the pathogenesis of, and possible therapeutic targeting, for CRS and AR.

High Mobility Group Box-1 Protein and Interleukin 33 Expression in Allergic Rhinitis

BACKGROUND

Allergic rhinitis (AR) is characterized by an inflammatory reaction. High mobility group box 1 (HMGB1) protein and interleukin (IL)-33 are damage-associated molecular pattern molecules and have many characteristics similar to pro-inflammatory cytokines. However, the role of IL-33 and HMGB1 in AR remains unclear. The aim of this study is to explore the role of HMGB1 and IL-33 in AR.

METHODS

Twenty patients with AR (AR group) and 10 normal controls (normal group) were enrolled in this study. HMGB1 and IL-33 expression were analyzed by immunohistochemistry in epithelial cells of the inferior turbinate mucosa samples. Then, the human nasal mucosa epithelial cells (HNECs) were cultured in vitro, and the house dust mite allergen (Derp1) was used to stimulate the cells. Quantitative real-time PCR and ELISA assay were performed to detect HMGB1 and IL-33 expression in HNECs.

RESULTS

The expression of HMGB1 and IL-33 in the nasal mucosa was higher in the AR group than in the normal group, with a statistically significant difference (p < 0.05). In HNECs of AR, the expression of both HMGB1 and IL-33 in stimulated groups was higher than that in non-stimulated groups. The differences were statistically significant (p < 0.05). In addition, they increased gradually with the prolonging time and the concentration of the added Derp1.

CONCLUSIONS

The expression of HMGB1 and IL-33 were both increased in AR. HMGB1 and IL-33 may have a close relationship in AR.

IL-33, an Alarmin of the IL-1 Family Involved in Allergic and Non Allergic Inflammation: Focus on the Mechanisms of Regulation of Its Activity

Interleukin-33 (IL-33) is a member of the interleukin-1 (IL-1) family that is expressed in the nuclei of endothelial and epithelial cells of barrier tissues, among others. It functions as an alarm signal that is released upon tissue or cellular injury. IL-33 plays a central role in the initiation and amplification of type 2 innate immune responses and allergic inflammation by activating various target cells expressing its ST2 receptor, including mast cells and type 2 innate lymphoid cells. Depending on the tissue environment, IL-33 plays a wide variety of roles in parasitic and viral host defense, tissue repair and homeostasis. IL-33 has evolved a variety of sophisticated regulatory mechanisms to control its activity, including nuclear sequestration and proteolytic processing. It is involved in many diseases, including allergic, inflammatory and infectious diseases, and is a promising therapeutic target for the treatment of severe asthma. In this review, I will summarize the literature around this fascinating pleiotropic cytokine. In the first part, I will describe the basics of IL-33, from the discovery of interleukin-33 to its function, including its expression, release and signaling pathway. The second part will be devoted to the regulation of IL-33 protein leading to its activation or inactivation.

Targeting the P2Y13 Receptor Suppresses IL-33 and HMGB1 Release and Ameliorates Experimental Asthma

RATIONALE

The alarmins IL-33 and HMGB1 (high mobility group box 1) contribute to type-2 inflammation and asthma pathogenesis.

OBJECTIVES

To determine whether P2Y13 receptor (P2Y13-R), a purinergic G protein-coupled receptor (GPCR) and risk allele for asthma, regulates the release of IL-33 and HMGB1.

METHODS

Bronchial biopsies were obtained from healthy and asthmatic subjects. Primary human airway epithelial cells (AECs), primary mouse (m)AECs, or C57Bl/6 mice were inoculated with various aeroallergens or respiratory viruses, and the nuclear-to-cytoplasmic translocation and release of alarmins measured by immunohistochemistry and ELISA. The role of P2Y13-R in AEC function and in the onset, progression, and an exacerbation of experimental asthma, was assessed using pharmacological antagonists and P2Y13-R gene-deleted mice.

MEASUREMENTS AND MAIN RESULTS

Aeroallergen-exposure induced the extracellular release of ADP and ATP, nucleotides that activate P2Y13-R. ATP, ADP, aeroallergen (house dust mite, cockroach or Alternaria) or virus exposure induced the nuclear-to-cytoplasmic translocation and subsequent release of IL-33 and HMGB1, and this response was ablated by genetic deletion or pharmacological antagonism of P2Y13. In mice, prophylactic or therapeutic P2Y13-R blockade attenuated asthma onset, and critically, ablated the severity of a rhinovirus-associated exacerbation in a high-fidelity experimental model of chronic asthma. Moreover, P2Y13-R antagonism derepressed antiviral immunity, increasing IFN-λ production and decreasing viral copies in the lung.

CONCLUSIONS

We identify P2Y13-R as a novel gatekeeper of the nuclear alarmins IL-33 and HMGB1, and demonstrate that the targeting of this GPCR via genetic deletion or treatment with a small-molecule antagonist protects against the onset and exacerbations of experimental asthma.

Breast cancer in schizophrenia could be interleukin-33-mediated

Recent epidemiological and genetic studies have revealed an interconnection between schizophrenia and breast cancer. The mutual underlying pathophysiological mechanisms may be immunologically driven. A new cluster of molecules called alarmins may be involved in sterile brain inflammation, and we have already reported the potential impact of interleukin-33 (IL-33) on positive symptoms onset and the role of its soluble trans-membranes full length receptor (sST2) on amelioration of negative symptoms in schizophrenia genesis. Furthermore, these molecules have already been shown to be involved in breast cancer etiopathogenesis. In this review article, we aim to describe the IL-33/suppressor of tumorigenicity 2 (ST2) axis as a crossroad in schizophrenia-breast cancer comorbidity. Considering that raloxifene could be tissue-specific and improve cognition and that tamoxifen resistance in breast carcinoma could be improved by strategies targeting IL-33, these selective estrogen receptor modulators could be useful in complementary treatment. These observations could guide further somatic, as well as psychiatric therapeutical protocols by incorporating what is known about immunity in schizophrenia.

Asthma-associated genetic variants induce IL33 differential expression through an enhancer-blocking regulatory region

Genome-wide association studies (GWAS) have implicated the IL33 locus in asthma, but the underlying mechanisms remain unclear. Here, we identify a 5 kb region within the GWAS-defined segment that acts as an enhancer-blocking element in vivo and in vitro. Chromatin conformation capture showed that this 5 kb region loops to the IL33 promoter, potentially regulating its expression. We show that the asthma-associated single nucleotide polymorphism (SNP) rs1888909, located within the 5 kb region, is associated with IL33 gene expression in human airway epithelial cells and IL-33 protein expression in human plasma, potentially through differential binding of OCT-1 (POU2F1) to the asthma-risk allele. Our data demonstrate that asthma-associated variants at the IL33 locus mediate allele-specific regulatory activity and IL33 expression, providing a mechanism through which a regulatory SNP contributes to genetic risk of asthma.

Susceptibility to asthma and severity of symptoms are regulated by a number of different genomic regions. Here the authors characterise a 5kb regulatory region and demonstrate genetic and topological regulation of IL33 and association with disease in different human cohorts.

IL-1β promotes immunoregulatory responses in human blood basophils

Human basophils are essential effector cells of chronic allergic inflammation. IL-1 family cytokines such as interleukin (IL)-33 and IL-1β are elevated in serum and bronchoalveolar lavage fluid of allergic asthmatics. IL-33 is known to be a critical regulator of basophil's T2 immune responses. However, the effect of IL-1β on the function of basophils has not been well investigated. Here, we elucidate whether IL-1β regulates the function of human basophils and compared the effects of IL-1β and IL-33 on basophils of healthy and allergic subjects. We found that IL-1β activates the p38 MAPK signaling pathway and promotes IL-8 release in basophils of healthy donors, while FcεRI-mediated LCT₄ and histamine secretion is not affected. Strikingly, in the presence of IL-3, IL-1β shows more potency than IL-33, as evidenced by the enhanced p38 phosphorylation and NF-κB activation, as well as the release of both IL-13 and IL-8. We found that the enhanced basophil responsiveness is achieved through IL-3-induced IL-1RI surface expression. Importantly, basophils of allergic donors release significantly higher amounts of IL-8 compared to those from healthy donors upon IL-33 and IL-1β stimulation. Consistently, we detected increased IL-1RI and decreased IL-3 receptor alpha-chain (CD123) and CCR3 expression on basophils of allergic subjects compared to healthy controls, suggesting an in vivo IL-3 priming in allergic donors. In summary, our results suggest enhanced sensitivity of basophils toward IL-33 and IL-1β in allergic subjects compared to those from healthy controls.

It is no skin off my nose: The relationship between the skin and allergic rhinitis

OBJECTIVE

Evidence supports the relationship between the skin barrier and allergic conditions. This narrative review evaluates what role the cutaneous barrier may play in the pathogenesis, disease course, and management of allergic rhinitis (AR).

DATA SOURCES

A literature review of the MEDLINE (PubMed), Embase, Cochrane, and SCOPUS Sciverse databases was conducted to identify available evidence. Reference lists of pertinent papers were searched using a snowball technique.

STUDY SELECTIONS

Papers published in English from all years until December 2020 were included. Papers that did not address the relationship between AR and the skin and hypothesis papers were excluded.

RESULTS

The cutaneous barrier shares histologic characteristics with the sinonasal epithelial barrier, which may explain commonalities between AR and atopic dermatitis. A disruption in the epithelial barrier could be a common pathway in the development of multiple allergic conditions. The skin is a common target for the treatment of AR. Available data that look at the relationship between the skin and AR often include other topics such as other atopic disorders and the role of the epithelial barrier. Increased understanding of how the cutaneous barrier affects AR may lead to new innovations in its management.

CONCLUSION

The connection between the cutaneous barrier and AR holds possibilities for further investigation, and these may lead to a better understanding and future innovations for all atopic diseases.

Significance of RNA N6-Methyladenosine Regulators in the Diagnosis and Subtype Classification of Childhood Asthma Using the Gene Expression Omnibus Database

RNA N6-methyladenosine (m6A) regulators play important roles in a variety of biological functions. Nonetheless, the roles of m6A regulators in childhood asthma remain unknown. In this study, 11 significant m6A regulators were selected using difference analysis between non-asthmatic and asthmatic patients from the Gene Expression Omnibus GSE40888 dataset. The random forest model was used to screen five candidate m6A regulators (fragile X mental retardation 1, KIAA1429, Wilm's tumor 1-associated protein, YTH domain-containing 2, and zinc finger CCCH domain-containing protein 13) to predict the risk of childhood asthma. A nomogram model was established based on the five candidate m6A regulators. Decision curve analysis indicated that patients could benefit from the nomogram model. The consensus clustering method was performed to differentiate children with asthma into two m6A patterns (clusterA and clusterB) based on the selected significant m6A regulators. Principal component analysis algorithms were constructed to calculate the m6A score for each sample to quantify the m6A patterns. The patients in clusterB had higher m6A scores than those in clusterA. Furthermore, we found that the patients in clusterA were linked to helper T cell type 1 (Th1)-dominant immunity while those in clusterB were linked to Th2-dominant immunity. In summary, m6A regulators play nonnegligible roles in the occurrence of childhood asthma. Our investigation of m6A patterns may be able to guide future immunotherapy strategies for childhood asthma.

ST2 expression and release by the bronchial epithelium is downregulated in asthma

BACKGROUND

The airway epithelium plays an important role in wound repair, host defense and is involved in the immunopathogenesis of asthma. Genome wide association studies have described associations between ST2/Interleukin (IL)-33 genes in asthma, but its role in bronchial epithelium is unclear.

METHODS

ST2 expression was examined in subjects with asthma and healthy controls in bronchial epithelium from biopsies (n = 27 versus n = 9) and brushings (n = 34 versus n = 20) by immunohistochemistry and RNA-Seq. In human primary bronchial epithelial cells ST2 mRNA and protein expression were assessed by qPCR, flow cytometry, Western blotting, and immunofluorescence. IL-33 function in epithelial cells was examined by intracellular calcium measurements, wound healing assays, and synthetic activation by gene array and ELISA.

RESULTS

Bronchial epithelial ST2 protein expression was significantly decreased in biopsies in subjects with asthma compared to healthy controls (P = .039). IL1RL1 gene expression in bronchial brushes was not different between health and disease. In vitro primary bronchial epithelial cells expressed ST2 and IL-33 stimulation led to an increase in intracellular calcium, altered gene expression, but had no effect upon wound repair. Epithelial cells released sST2 spontaneously, which was reduced following stimulation with TNFα or poly-IC. Stimulation by TNFα or poly-IC did not affect the total ST2 expression by epithelial cell whereas surface ST2 decreased in response to TNFα, but not poly-IC.

CONCLUSION

In asthma, bronchial epithelium protein expression of ST2 is decreased. Our in vitro findings suggest that this decrease might be a consequence of the pro-inflammatory environment in asthma or in response to viral infection.

Single-nucleotide polymorphisms and haplotypes in the interleukin-33 gene are associated with a risk of allergic rhinitis in the Chinese population

Allergic rhinitis (AR) is a common upper airway disease attributed to a variety of risk factors, such as environmental exposures and genetic susceptibility. The commonly observed comorbidity of asthma and AR in the clinic suggests the presence of shared genetic risk factors and biological mechanisms between these diseases. Interleukin (IL)-33 has been indicated to be an important factor driving asthma susceptibility and pathogenesis using both genome-wide association studies and functional studies in model animals. Although previous studies have reported the putative association of this gene with AR, evidence for the association of genetic variations of IL-33 with the disease is still missing. To examine whether variations in the IL-33 gene confer a genetic risk of AR, a total of 769 patients with AR and 769 age- and sex-matched healthy controls were recruited among Han Chinese residents in the Hubei province, and 14 single-nucleotide polymorphisms (SNPs) spanning the IL-33 gene were examined for their association with the risk of AR. The results indicated that five SNPs, which were in a moderate linkage disequilibrium and were located in the 5'-flanking region of IL-33, exhibited significant associations with the risk of AR, and these associations were additionally supported by genotypic and haplotypic analyses. Notably, three of the five IL-33 SNPs have been previously reported to exhibit genome-wide associations with asthma, and their alleles were also revealed to confer an increased risk of AR in the present study. In summary, the results of the current study suggested that certain variations in the IL-33 gene represent a potential risk for AR, and indicated a shared genetic basis between AR and asthma.

Contributions of IL-33 in Non-hematopoietic Lung Cells to Obstructive Lung Disease

Interleukin (IL)-33 plays important roles in pulmonary immune responses and lung diseases including asthma and chronic obstructive pulmonary disease (COPD). There is substantial interest in identifying and characterizing cellular sources vs. targets of IL-33, and downstream signaling pathways involved in disease pathophysiology. While epithelial and immune cells have largely been the focus, in this review, we summarize current knowledge of expression, induction, and function of IL-33 and its receptor ST2 in non-hematopoietic lung cells in the context of health and disease. Under basal conditions, epithelial cells and endothelial cells are thought to be the primary resident cell types that express high levels of IL-33 and serve as ligand sources compared to mesenchymal cells (smooth muscle cells and fibroblasts). Under inflammatory conditions, IL-33 expression is increased in most non-hematopoietic lung cells, including epithelial, endothelial, and mesenchymal cells. In comparison to its ligand, the receptor ST2 shows low expression levels at baseline but similar to IL-33, ST2 expression is upregulated by inflammation in these non-hematopoietic lung cells which may then participate in chronic inflammation both as sources and autocrine/paracrine targets of IL-33. Downstream effects of IL-33 may occur via direct receptor activation or indirect interactions with the immune system, overall contributing to lung inflammation, airway hyper-responsiveness and remodeling (proliferation and fibrosis). Accordingly from a therapeutic perspective, targeting IL-33 and/or its receptor in non-hematopoietic lung cells becomes relevant.

Association between IL-33 Gene Polymorphism (Rs7044343) and Risk of Allergic Rhinitis

BACKGROUND

Allergic rhinitis (AR) is a T helper type 2 (Th2)-mediated upper airways disease in which genetics factors including cytokine genes play a prominent role. Interleukin-33 (IL-33) is a major cytokine for naive T cells polarization into Th2 phenotype as well as enhances the secretion of Th2 cytokines. The aim of the present study was to investigate the relationship between IL-33 single nucleotide polymorphisms (SNPs) and IL-33 serum level with Allergic rhinitis.

METHODS

Blood samples were collected from 130 AR patients and 130 healthy individuals. SNPs (rs7044343 C > T, rs1929992 A > G, rs12551256 A > G) of IL-33 gene were determined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Serum level of IL-33 was measured by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Statistical analysis showed that the TT genotype (OR = 1.996, CI: 1.168-3.412, P = .01), as well as the T allele (OR = 0.675, CI: 0.476-0.957, P = .02) of rs7044343 C > T were significantly associated with reduced risk of AR. In addition, individuals carrying the TT genotype were associated with lower levels of IL-33 compared to subjects with CC and CT genotypes; however, these differences were not statistically significant. No association was found between rs1929992 and rs12551256 variants and risk of AR, but the GG genotype from rs1929992 A > G was associated with increased serum levels of IL-33 in control group (p = .01). Furthermore, serum IL-33 levels were not significantly different between AR patients and healthy controls (p > .05).

CONCLUSION

Our results suggest that the TT genotype of rs7044343 C > T may act as a protective agent against allergic rhinitis.

The Effects of Interleukin-33 (IL-33) on Osteosarcoma Cell Viability, Apoptosis, and Epithelial-Mesenchymal Transition are Mediated Through the PI3K/AKT Pathway

Background

Osteosarcoma is the most common primary tumor of bone. Interleukin-33 (IL-33) is a pro-inflammatory cytokine that also participates in tumor progression. This study aimed to investigate the role of IL-33 in human osteosarcoma cell viability, proliferation, apoptosis, and epithelial-mesenchymal transition (EMT) in vitro and the molecular mechanisms involved.

Material/Methods

The normal osteoblast cell line, hFOB 1.19, and the human osteosarcoma cell lines SOSP-9607, SAOS2, MG63, and U2OS were studied. The expression of IL-33 mRNA and protein in human osteosarcoma cell lines were detected using quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot, respectively. The effects of IL-33 on human osteosarcoma cell viability, apoptosis, EMT, and the signaling pathways were studied using the MTT assay, flow cytometry, qRT-PCR, and Western blot.

Results

IL-33 was upregulated in human osteosarcoma cell lines, including U2OS cells. The use of an IL-33 gene plasmid promoted osteosarcoma cell viability, inhibited cell apoptosis, increased the expression of Bcl-2, and reduced the expression of Bax. IL-33 reduced the level of E-cadherin and increased the levels of N-cadherin and matrix metalloproteinase-9 (MMP-9) in osteosarcoma cells at the mRNA and protein level. The use of the IL-33 plasmid increased the protein expression levels of p-AKT and the p-AKT/AKT ratio in osteosarcoma cells, and IL-33 siRNA reversed these findings.

Conclusions

IL-33 was highly expressed in human osteosarcoma cells. Down-regulation of IL-33 reduced cell viability and EMT of osteosarcoma cells, and induced cell apoptosis through activation of the PI3K/AKT signaling pathway.

Epithelial cells expressed IL-33 to promote degranulation of mast cells through inhibition on ST2/PI3K/mTOR-mediated autophagy in allergic rhinitis

Nasal epithelial cells are the first barrier against allergen infiltration in allergic rhinitis (AR), and the relationship between nasal epithelial cells and mast cell-mediated hypersensitivity remains unclear. This study aimed to investigate the possible association between allergen-challenged nasal epithelial cells (AR-HNEpC) and mast cell degranulation in AR. Our data revealed that calcium influx and degranulation were increased in AR-HNEpC-co-cultured mast cells. Expression of IL-33, a factor that binds to ST2 receptors on mast cells and regulates their degranulation, was elevated in AR-HNEpC. Blocking IL-33/ST2 pathway activated autophagy and inhibited degranulation and inflammatory factor release in mast cells. Furthermore, PI3K/mTOR was increased in IL-33-treated mast cells. Inhibition on PI3K/mTOR pathway enhanced autophagy and inhibited degranulation. Analysis using an in vivo AR model supported the above findings. In conclusion, IL-33 from epithelial cells promotes degranulation of mast cells in AR through inhibition on ST2/PI3K/mTOR-mediated autophagy, which provides a potential therapeutic target for the disease.Abbreviations: AR: allergic rhinitis; IL: interleukin; TNF-α: tumor necrosis factor-alpha; INF-γ: interferon-gamma; HNEpC: human nasal epithelial cell line; ATCC: American Type Culture Collection; C48/80: compound 48/80; 3-MA: 3-methyladenine; qPCR: quantitative PCR; AR-HNEpC: dust mite allergen-treated nasal epithelial cells; IgE: immunoglobulin E; Atg7: autophagy-related gene 7.

Physical and immunological barrier of human primary nasal epithelial cells from non-allergic and allergic donors

The epithelial cell-derived cytokine milieu has been discussed as a “master switch” in the development of allergic disease.

To understand the role of innate immune response in nasal epithelial cells during allergic inflammation, we created and established a fast and minimally invasive method to isolate and culture human nasal epithelial cells from clinically and immunologically well characterized patients. Human nasal epithelial cells from non-atopic volunteers and from allergic rhinitis patients were compared in respect to their growth, barrier integrity, pattern recognition, receptor expression, and immune responses to allergens and an array of pathogen-associated molecular patterns and inflammasome activators.

Cells from nasal scrapings were clearly identified as nasal epithelial cells by staining of pan-Cytokeratin, Cytokeratin-14 and Tubulin. Additionally, Mucin 5AC staining revealed the presence of goblet cells, while staining of tight-junction protein Claudin-1, Occludin and ZO-1 showed the ability of the cells to form a tight barrier. Cells of atopic donors grew slower than cells of non-atopic donors. All nasal epithelial cells expressed TLR1-6 and 9, yet the expression of TLR-9 was lower in cells from allergic rhinitis (AR) donors. Additionally, epithelial cells from AR donors responded with a different TLR expression pattern to stimulation with TLR ligands. TLR-3 was the most potent modulator of cytokine and chemokine secretion in all human nasal epithelial cells (HNECs). The secretion of IL-1β, CCL-5, IL-8, IL-18 and IL-33 was elevated in HNECs of AR donors as compared to cells of non-atopic donors. This was observed in the steady-state (IL-18, IL-33) as well as under stimulation with TLR ligands (IL-18, IL-33, CCL-5, IL-8), aqueous pollen extracts (IL-18, IL-33), or the inflammasome activator Nigericin (IL-1β).

In conclusion, nasal epithelial cells of AR donors show altered physical barrier responses in steady-state and in response to allergen stimulation. Cells of AR donors show increased expression of pro-inflammatory and IL-1 family cytokines at baseline and under stimulation, which could contribute to a micromilieu which is favorable for Th2.

Synergistic relationship between TSLP and IL-33/ST2 signaling pathways in allergic rhinitis and the effects of hypoxia

BACKGROUND

The World Health Organization (WHO) has noted that allergic diseases are a major health problem of the 21st century. Allergic rhinitis (AR) is a type I allergic disease characterized by nasal mucosa and immune system abnormalities. AR is mediated by various inflammatory cells and is mainly characterized by altered secretion of cytokines. Thymic stromal lymphopoietin (TSLP) and the interleukin-33/stimulation-expressed gene 2 (IL-33/ST2) signaling pathway are cytokines that play pivotal roles in many inflammatory responses and allergic reactions. There have been reports of interactions between the 2 pathways in many diseases. Hypoxia is a common pathologic manifestation of AR. The aim of this study was to explore the relationship and expressions and biologic functions of TSLP and IL-33/ST2 in AR, and also to determine the effects of hypoxia on these cytokines.

METHODS

The rat nasal mucosal epithelium was obtained from Wistar rats. Cells were cultured in groups under hypoxia and normoxia conditions. Identification of rat nasal epithelial cell (RNEpC) and protein expressions was done by immunohistochemistry and immunofluorescence methods. Cell proliferation and migration were examined using the cell counting kit-8 (CCK-8) and Transwell kit. Detection of apoptosis was tested using a fluorescence apoptosis kit. Enzyme-linked immunoassay (ELISA) and Western blot analysis ELISA were used to measure cell secretion and protein expressions. For these experiments, TSLP was knocked down by lentivirus transfection and IL-33 blocked with its antagonist.

RESULTS

TSLP, IL-33, and ST2 expressions were significantly higher in nasal mucosa epithelial cells from AR rats than in those from control rats. Hypoxia further promoted their expression. Increased TSLP and IL-33/ST2 promoted cell proliferation, inhibited cell apoptosis, and enhanced cell migration. In addition, the downregulation of TSLP expression effectively attenuated expression of the IL-33/ST2 axis and, through use of IL-33 antagonists, could also reduce TSLP expression, a synergistic effect more obvious under hypoxia.

CONCLUSION

Our data indicate that TSLP and IL-33/ST2 signaling pathways interact with each other in the pathogenesis and pathologic development of AR. TSLP inhibition is a key factor in AR treatment. Inhibiting hypoxia-induced pathologic processes could represent a therapeutic effect by inhibiting IL-33/ST2 expression via downregulating TSLP.

Effects of a Cloth Panel Containing a Specific Ore Powder on Patients with Japanese Cedar Pollen Allergy During the Pollen Dispersal Season

Pollen allergy remains a big problem in contemporary societies. We have shown in previous studies that a cloth containing a special natural ore powder (CCSNOP) is effective in relieving symptoms in patients with pollen allergies. However, in that study, subjects were exposed to CCSNOP for only one hour. In the present study, CCSNOP or control (non-woven cloth; NWC) panels were placed in the bedrooms of pollen allergy patients for two weeks during the pollen dispersal season in 2018, and the effects were investigated. Twenty-one subjects were exposed to CCSNOP panels and 10 subjects were exposed to NWC panels. Our investigations showed that use of CCSNOP resulted in relief of symptoms and reduced use of therapeutics. Moreover, the ratio of eosinophil count decrease during exposure was higher in the CCSNOP group. Furthermore, a formula for measuring various cytokines and other parameters was established and clearly showed a distinction between the CCSNOP and NWC groups. In this formula, Granulocyte Macrophage colony-stimulating Factor (GM-SCF), Interleukin (IL)-12p40, Immunoglobulin (Ig) G4 and eosinophil count were extracted. These results indicated that CCNSNOP has a beneficial effect on pollen allergy patients. Future studies shall engage in long-term monitoring of pollen allergy patients who will utilize this mineral powder for at least one year.

Phase 2a randomized, placebo-controlled study of anti-IL-33 in peanut allergy

BACKGROUNDIL-33, found in high levels in participants with allergic disorders, is thought to mediate allergic reactions. Etokimab, an anti-IL-33 biologic, has previously demonstrated a good safety profile and favorable pharmacodynamic properties in many clinical studies.METHODSIn this 6-week placebo-controlled phase 2a study, we evaluated the safety and the ability of a single dose of etokimab to desensitize peanut-allergic adults. Participants received either etokimab (n = 15) or blinded placebo (n = 5). Clinical tests included oral food challenges and skin prick tests at days 15 and 45. Blood samples were collected for IgE levels and measurement of ex vivo peanut-stimulated T cell cytokine production.RESULTSEfficacy measurements for active vs. placebo participants at the day 15 and 45 food challenge (tolerating a cumulative 275 mg of peanut protein, which was the food challenge outcome defined in this paper) demonstrated, respectively, 73% vs. 0% (P = 0.008) to 57% vs. 0% (ns). The etokimab group had fewer adverse events compared with placebo. IL-4, IL-5, IL-9, IL-13, and ST2 levels in CD4+ T cells were reduced in the active vs. placebo arm upon peanut-induced T cell activation (P = 0.036 for IL-13 and IL-9 at day 15), and peanut-specific IgE was reduced in active vs. placebo (P = 0.014 at day 15).CONCLUSIONThe phase 2a results suggest etokimab is safe and well tolerated and that a single dose of etokimab could have the potential to desensitize peanut-allergic participants and possibly reduce atopy-related adverse events.TRIAL REGISTRATIONClinicalTrials.gov NCT02920021.FUNDINGThis work was supported by NIH grant R01AI140134, AnaptysBio, the Hartman Vaccine Fund, and the Sean N. Parker Center for Allergy and Asthma Research at Stanford University.

Early Life Represents a Vulnerable Time Window for IL-33-Induced Peripheral Lung Pathology

IL-33, an IL-1 family cytokine, is constitutively expressed in mucosal tissues and other organs in healthy humans and animals, and expression levels increase in inflammatory conditions. Although IL-33-mediated promotion of type 2 immune responses has been well established, a gap in our knowledge regarding the functional diversity of this pleiotropic cytokine remains. To address this gap, we developed a new IL-33 transgenic mouse model in which overexpression of full-length IL-33 is induced in lung epithelial cells under conditional control. In adult mice, an ∼3-fold increase in the steady-state IL-33 levels produced no pathologic effects in the lungs. When exposed to airborne allergens, adult transgenic mice released more IL-33 extracellularly and exhibited robust type 2 immune responses. In neonatal transgenic mice, up to postnatal day 14, a similar increase in steady-state IL-33 levels resulted in increased mortality, enlarged alveolar spaces resembling bronchopulmonary dysplasia, and altered expression of genes associated with tissue morphogenesis. Processed 25-kDa IL-33 protein was detected in bronchoalveolar lavage fluids without any exogenous stimuli, and pathologic changes were abolished in mice deficient in the IL-33 receptor ST2. These findings suggest that adult lungs are relatively resistant to IL-33 overexpression unless they encounter environmental insults, whereas developing lungs are highly susceptible, with IL-33 overexpression resulting in detrimental and pathologic outcomes.

The interleukin-33-mediated inhibition of expression of two key genes implicated in atherosclerosis in human macrophages requires MAP kinase, phosphoinositide 3-kinase and nuclear factor-κB signaling pathways

Atherosclerosis, a chronic inflammatory disorder of the walls of arteries, causes more deaths worldwide than any other disease. Cytokines, which are present at high levels in atherosclerotic plaques, play important roles in regulating the initiation and the progression of the disease. Previous studies using animal and cell culture model systems revealed protective, anti-atherogenic effects of the cytokine interleukin-33 (IL-33). The action of this cytokine involves both the induction and suppression of expression of many genes. Unfortunately, the signaling pathways that are responsible for the inhibition of gene expression by this cytokine are poorly understood. Further studies are required given the important roles of genes whose expression is inhibited by IL-33 in key cellular processes associated with atherosclerosis such as monocyte recruitment, foam cell formation and lipoprotein metabolism. We have investigated here the roles of various known IL-33 activated signaling pathways in such inhibitory actions using RNA interference-mediated knockdown assays and monocyte chemotactic protein-1 and intercellular adhesion molecule-1 as model genes. Key roles were identified for extracellular signal-regulated kinase-1/2, p38α kinase, c-Jun N-terminal kinase-1/2, phosphoinositide 3-kinase-γ, and p50 and p65 nuclear factor-κB in such inhibitory action of IL-33. These studies provide new insights on the signaling pathways through which IL-33 inhibits the macrophage expression of key atherosclerosis-associated genes.

MicroRNA-21 abrogates palmitate-induced cardiomyocyte apoptosis through caspase-3/NF-κB signal pathways

Objective:

The aim of the study was to investigate the role of microRNA-21 (miR-21) in cardiomyocyte apoptosis and to determine a possible mechanism.

Methods:

H9c2 embryonic rat heart-derived cells were used in the study. Cell viability was determined using the 3-(4.5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) assay, and flow cytometry was used to evaluate cell apoptosis. Reverse transcription-polymerase chain reaction and western blot assays were used to detect mRNA and protein expression of the apoptosis-related proteins and miR-21. ELISA was used to detect reactive oxygen species (ROS).

Results:

Palmitate exposure greatly reduced miR-21 expression in cardiomyocytes. Apoptosis increased when miR-21 was inhibited with or without palmitate exposure. Consistently, reduced apoptosis was observed when miR-21 was overexpressed in cardiomyocytes. Caspase-3 activity was reduced after palmitate exposure. Bcl-2 protein expression was increased in H9c2 cells when transfected with the miR-21 mimic. MiR-21 overexpression alone did not induce ROS or DNA fragmentation; however, in conjunction with palmitate exposure, miR-21 mimic reduced ROS and DNA fragmentation. Moreover, palmitate administration overcame the antioxidant effect of 3 mM N-acetylcysteine to significantly inhibit apoptosis, DNA fragmentation, and caspase-3 activity. The exposure to palmitate greatly reduced p65 and p-p38 expression in the nucleus. A p38 inhibitor had no effect on the expression of Bcl-2 and cleaved caspase-3 in H9c2 cells alone; however, when combined with exposure to palmitate the p38 inhibitor induced Bcl-2 expression and inhibited caspase-3 activity. The p38 inhibitor by itself did not induce apoptosis, ROS production, or DNA fragmentation in H9c2 cells, but when palmitate was included with the p38 inhibitor, apoptosis, ROS production, and DNA fragmentation were reduced.

Conclusion:

miR-21 protects cardiomyocytes from apoptosis that is induced by palmitate through the caspase-3/NF-κB signal pathways.

ST2 and the ST2/IL-33 signalling pathway-biochemistry and pathophysiology in animal models and humans

ST2 is an interleukin (IL)-1 receptor family member with transmembrane (ST2L) and soluble (sST2) isoforms. Structurally, the ST2 gene products are very similar in mice and humans. In humans and in mice, alternative promoter activation and splicing produce ST2L and sST2. ST2L represents the longest transcript, whereas sST2 is the truncated, soluble isoform. ST2L is the biological receptor for IL-33, a member of the IL-1 family. IL-33 is the functional ligand of ST2L and signals the presence of tissue damage to local immune cells. IL-33/ST2L signalling leads to the production of inflammatory cytokines/chemokines and to the induction of the immune response. Conversely, sST2 functions as a decoy receptor for IL-33, inhibiting the effects of IL-33/ST2L signalling. Animal studies have allowed the investigation of ST2 and the IL-33/ST2L signalling pathway at multiple levels. However, clinical studies have mainly focused on the determination of sST2 in the circulation. In humans, plasma concentrations of sST2 increase in several diseases, such as heart disease, pulmonary disease, burn injury and graft-versus-host disease. Consequently, increased plasma concentrations of sST2 are not specific for a single disorder in humans and are thus of limited value for diagnostic purposes. However, increased plasma concentrations of sST2 have been linked to a worse prognosis in numerous diseases. Nevertheless, the major source of circulating sST2 in healthy and diseased humans is currently not fully established. In addition, whether the downregulation of sST2 can improve the outcome of patients in the clinical setting has not been elucidated. The aim of the present review was to provide an update on the findings regarding the biochemistry and pathophysiology of ST2 and the sST2 signalling pathway in humans and experimental models.

Role of innate lymphoid cells in allergic diseases

Background: Over the past decade, there has been increasing interest and research into understanding the type 2 immune responses by the epithelium-derived cytokines interleukin (IL) 33, IL-25, and thymic stromal lymphopoietin. Innate lymphoid cells (ILC) are a unique family of effector immune cells that functionally resemble T cells but lack clonal distributed antigen receptors. Group 2 ILCs, ILC2s, are known for their capability to secrete proallergic cytokines, including IL-5 and IL-13. ILC2s are enriched at mucosal barriers in lung, gut, and skin, and their activation has been associated with a variety of allergic disorders. Objective: To study the role of ILC2 in different allergic disorders, including allergic rhinitis, asthma, atopic dermatitis, and food allergies. Methods: A MEDLINE search was performed for articles that reported on ILC2 in allergic disorders, including allergic rhinitis, asthma, atopic dermatitis, and food allergies. Results: A review of the literature revealed an important role of ILC2 in various allergic disorders. Conclusion: Identification of ILC2s in patients with allergic rhinitis, asthma, and atopic dermatitis indicates that these cells may represent a new therapeutic target. In this review, we discussed the current understanding of ILC2 biology and its function and regulation in various allergic diseases.

Bioinformatics-Based Approaches Predict That MIR-17-5P Functions in the Pathogenesis of Seasonal Allergic Rhinitis Through Regulating ABCA1 and CD69

OBJECTIVE

As the most prevalent type of rhinitis, allergic rhinitis is consisted of seasonal allergic rhinitis (SAR) and perennial allergic rhinitis. This study is carried out for revealing the mechanisms of SAR.

METHODS

Microarray data set GSE43523 (including 7 SAR nasal epithelial cells and 5 nonallergic control nasal epithelial cells) was extracted from Gene Expression Omnibus database. Based on limma package, differential expression analysis for the 2 groups was performed to obtain differentially expressed genes (DEGs). Using Multifaceted Analysis Tool for Human Transcriptome online tool, the functions involving the DEGs were predicted by enrichment analysis. Combined with Cytoscape software, protein-protein interaction (PPI) network was built and a significant network module was acquired. In addition, transcription factor (TF)-target and miRNA-target pairs were predicted using WebGestalt tool, and then TF-miRNA-target regulatory network was built by Cytoscape software.

RESULTS

There were 274 DEGs between rhinitis and control samples, including 144 upregulated genes and 130 downregulated genes. After PPI for the DEGs was built, a significant network module was identified. In the TF-miRNA-target regulatory network, ABCA1, CPEB4, CD69, MIR-17-5P, and CREB had higher degrees. Furthermore, both ABCA1 and CD69 were targeted by MIR-17-5P in the regulatory network.

CONCLUSION

CPEB4 and CREB might be implicated in the pathogenesis of SAR. Besides, MIR-17-5P might also act in SAR via targeting ABCA1 and CD69.

Do Alarmins Have a Potential Role in Autism Spectrum Disorders Pathogenesis and Progression?

Autism spectrum disorders (ASDs) represent a disabling condition in early childhood. A number of risk factors were proposed in order to explain their pathogenesis. A multifactorial model was proposed, and data supported the implication of genetic and environmental factors. One of the most accepted speculations is the existence of an imbalance of the immune system. Altered levels of cytokines, chemokines and immunoglobulins were demonstrated in patients with ASDs; in particular, proinflammatory mediators were significantly increased. Alarmins are a multifunctional heterogeneous group of proteins, structurally belonging to specific cells or incorporated by them. They are released in the surrounding tissues as a consequence of cell damage or inflammation. Their functions are multiple as they could activate innate immunity or recruit and activate antigen-presenting cells stimulating an adaptive response. Alarmins are interesting both for understanding the inflammatory process and for diagnostic purposes as biomarkers. Moreover, recent studies, separately, showed that alarmins like interleukin (IL)-33, high-mobility group box 1 (HMGB1), heat-shock protein (HSP) and S100 protein (S100) could play a relevant role in the pathogenesis of ASDs. According to the literature, some of these alarmins could be suitable as biomarkers of inflammation in ASD. Other alarmins, by interfering with the immune system blocking pro-inflammatory mediators, could be the key for ameliorating symptoms and behaviours in autistic disorders.

Potential Role of Interleukin-25/Interleukin-33/Thymic Stromal Lymphopoietin-Fibrocyte Axis in the Pathogenesis of Allergic Airway Diseases

Objective:

Allergic airway diseases (AADs) are a group of heterogeneous disease mediated by T-helper type 2 (Th2) immune response and characterized with airway inflammation and remodeling, including allergic asthma, allergic rhinitis, and chronic rhinosinusitis with allergic background. This review aimed to discuss the abnormal epithelial-mesenchymal crosstalk in the pathogenesis of AADs.

Data Sources:

Articles referred in this review were collected from the database of PubMed published in English up to January 2018.

Study Selection:

We had done a literature search using the following terms “allergic airway disease OR asthma OR allergic rhinitis OR chronic sinusitis AND IL-25 OR IL-33 OR thymic stromal lymphopoietin OR fibrocyte”. Related original or review articles were included and carefully analyzed.

Results:

It is now believed that abnormal epithelial-mesenchymal crosstalk underlies the pathogenesis of AADs. However, the key regulatory factors and molecular events involved in this process still remain unclear. Epithelium-derived triple cytokines, including interleukin (IL)-25, IL-33, and thymic stromal lymphopoietin (TSLP), are shown to act on various target cells and promote the Th2 immune response. Circulating fibrocyte is an important mesenchymal cell that can mediate tissue remodeling. We previously found that IL-25-circulating fibrocyte axis was significantly upregulated in patients with asthma, which may greatly contribute to asthmatic airway inflammation and remodeling.

Conclusions:

In view of the redundancy of cytokines and “united airway” theory, we propose a new concept that IL-25/IL-33/TSLP-fibrocyte axis may play a vital role in the abnormal epithelial-mesenchymal crosstalk in some endotypes of AADs. This novel idea will guide potential new intervention schema for the common treatment of AADs sharing common pathogenesis in the future.

Identification of specifically reduced Th2 cell subsets in allergic rhinitis patients after sublingual immunotherapy

BACKGROUND

Although Th2 cells are well known to play important roles in allergic diseases including allergic rhinitis (AR), the factors that induce and sustain the pathogenesis of AR remain unclear. The recent development of sublingual immunotherapy (SLIT) is expected to allow changes to the underlying pathogenesis of AR. However, which Th2 cell subsets are important in house dust mite-induced AR (HDM-AR), the influence of SLIT on the pathogenic Th2 cells, and the association of Th2 cell subsets with SLIT efficacy have not been clarified.

METHODS

The cytokine production and frequency of HDM-reactive T-cell subsets in peripheral blood mononuclear cells (PBMCs) were evaluated using flow cytometry in 89 HDM-AR patients (placebo [n = 43] and HDM 300 IR [n = 46]) who participated in a placebo-controlled study of SLIT with HDM tablets. All patients provided samples both before treatment as a baseline and at the end of the 52-week study. The PBMCs were stained with CellTrace™ Violet (CTV) before culture with HDM extract, and HDM-reactive T cells were detected as the proliferated cells with diminished CTV.

RESULTS

HDM-reactive IL-5⁺ IL-13⁺ CD27^- CD161⁺ CD4⁺ cells and ST2⁺ CD45RO⁺ CD4⁺ cells were observed in the peripheral blood from each patient with HDM-AR; these cells significantly decreased after SLIT in the group treated with active tablets. HDM-reactive ST2⁺ CD45RO⁺ CD4⁺ cells were significantly lower in active-responders.

CONCLUSION

Allergen-reactive ST2⁺ CD45RO⁺ CD4⁺ cells or those combined with IL-5⁺ IL-13⁺ CD27^- CD161⁺ CD4⁺ cells may be useful as markers indicating the successful treatment of SLIT. These cells may play a crucial role in the pathogenesis of AR as pathogenic memory Th2 cells.

Soluble ST2 suppresses IL-5 production by human basophilic KU812 cells, induced by epithelial cell-derived IL-33

BACKGROUND

Epithelial cell-derived IL-33 has an important role in the initiation and activation of innate allergic inflammation. IL-33 acts as a cytokine through the ST2 receptor (ST2L) and it stimulates the production of Th2 cytokines. Soluble ST2 (sST2) may regulate Th2 responses by neutralizing the activity of IL-33. Basophils express ST2L and produce IL-5 in response to IL-33. However, the role of the epithelial cell-basophil interaction and sST2 in IL-5 production remains unclear.

METHODS

Cultured human bronchial epithelial (hBE33) cells, that contained the human IL-33 gene (i.e., hBE33 cells) and a human basophilic cell line, KU812 cells, were used to study the epithelial cell-basophil interaction in the production of IL-5 induced by HDM.

RESULTS

At 15 min after incubation, HDM stimulated the rapid release of IL-33 from cultured hBE33 cells. IL-33 and the supernatant of HDM-treated hBE33 cells stimulated IL-5 production from KU812 cells. Anti-IL-33 antibody and anti-ST2 antibody treatment of KU812 cells suppressed IL-5 production, which had been induced by the supernatant of HDM-treated hBE33 cells. The hBE33 cells secreted sST2 in a time-dependent manner. The production of sST2 by KU812 cells co-cultured with hBE33 cells was significantly increased, compared with KU812 cells cultured with the supernatant of hBE33 cells. Soluble ST2 suppressed IL-5 production by KU812 cells, which was induced by the supernatant of HDM-treated hBE33 cells.

CONCLUSIONS

Epithelial cell-derived IL-33 promoted IL-5 production by KU812 cells. The subsequently produced sST2 has important roles in regulating Th2 responses.

Interleukin-33: Its Emerging Role in Allergic Diseases

Allergic diseases, which include asthma, allergic rhinitis (AR), chronic rhinosinusitis (CRS), atopic dermatitis (AD), food allergy (FA), allergic keratoconjunctivitis, seriously affect the quality of life of people all over the world. Recently, interleukin-33 (IL-33) has been found to play an important role in these refractory disorders, mainly by inducing T helper (Th) 2 immune responses. This article reviews the mobilization and biological function of IL-33 in allergic disorders, providing novel insights for addressing these hypersensitive conditions.

IL-33/s-ST2 ratio, systemic symptoms, and basophil activation in Pru p 3-sensitized allergic patients

BACKGROUND

Although IL-33/ST2 axis is involved in the development of allergic diseases, its contribution in food allergy is still unknown.

METHODS

In this study, we assessed the serum levels of IL-33 and its s-ST2 receptor in 53 control patients (without allergic diseases), 47 peach (Pru p 3)-sensitized allergic patients (SAP), and in 68 non-Pru p 3-SAP. Basophil activation test (BAT) was used to assess the basophil activation due to allergen exposure before and after the addition of s-ST2 to the blood samples from 5 Pru p 3-SAP.

RESULTS

IL-33 levels in Pru p 3-SAP were higher than in non-Pru p 3-SAP and in normal controls. Lower s-ST2 levels were found in Pru p 3-SAP than in non-Pru p 3-SAP. IL-33/s-ST2 ratio was higher in Pru p 3-SAP than in both non-Pru p 3-SAP and controls. Higher IL-33/s-ST2 ratio was observed in Pru p 3-SAP with severe than in those with mild systemic symptoms. BAT analysis in Pru p 3-SAP showed a decrease in basophil activation due to Pru p 3 exposure after the addition of s-ST2 to the blood samples.

CONCLUSIONS

An imbalance in the baseline levels of IL-33/ST2 pathway is present in Pru p 3-SAP. The measurement of this pathway might be helpful to detect patients at a higher risk of developing severe systemic symptoms.

IL-33 and Its Receptor ST2 after Inhaled Allergen Challenge in Allergic Asthmatics

BACKGROUND

Previous murine models have demonstrated interleukin (IL)-33 to be an important mediator of type-2 inflammation and to promote airway hyperresponsiveness in allergic asthma. A number of inflammatory cells produce IL-33 and eosinophils express ST2 mRNA. The relationship between IL-33 and eosinophils in allergic asthma, however, remains unclear.

OBJECTIVE

The aim of this work was to evaluate in vitro the effect of allergen inhalation on IL-33 levels and expression of its receptor (ST2L) on eosinophils in allergic asthmatics, and the effect of IL-33 stimulation on eosinophil activity.

METHODS

Plasma and sputum IL-33, soluble ST2 (sST2) levels, and ST2L expression on eosinophils were measured in 10 healthy controls and 10 allergic asthmatics. Asthmatics underwent allergen and diluent inhalation challenges. Blood and sputum samples were collected to measure IL-33, sST2, and ST2L eosinophil expression before and 24 h after allergen inhalation. Purified blood eosinophils from allergic asthmatics were incubated overnight with IL-33 to assess ST2 and intracellular IL-5 expression.

RESULTS

Baseline levels of IL-33 in sputum and sST2 in plasma and sputum were similar in allergic asthmatics compared to healthy controls. In addition, there was no difference in blood or sputum eosinophil ST2L expression in healthy controls versus allergic asthmatics. Eosinophil ST2L expression was significantly increased 24 h postallergen inhalation in allergic asthmatics. In vitro stimulation of human eosinophils with IL-33 and LPS significantly increased eosinophil ST2L expression and IL-33 stimulation increased intracellular IL-5 expression, which was attenuated by treatment with sST2 and ST2 blockade.

CONCLUSION AND CLINICAL RELEVANCE

In mild asthmatics, there was a significant upregulation of ST2 surface expression on eosinophils from blood and sputum following allergen inhalation challenge. In vitro, IL-33 stimulation of eosinophils increases both ST2 membrane expression and IL-5 production. These results support a role for IL-33 in causing allergen-induced eosinophilia. Blockade of IL-33 and ST2 signaling may present a novel therapeutic avenue for asthma treatment.

The Allergic Rhinitis Clinical Investigator Collaborative (AR-CIC): verification of nasal allergen challenge procedures in a study utilizing an investigational immunotherapy for cat allergy

Background

The Allergic Rhinitis Clinical Investigator Collaborative (AR-CIC) is a network of experienced Allergic Rhinitis (AR) researchers developing better research tools based on the nasal allergen challenge (NAC). A key objective of such is the ability to detect efficacy in a small population. AR-CIC sought to test its NAC protocol as a secondary objective in two small mechanistic research trials of a novel form of immunotherapy [Cat Peptide Antigen Desensitisation (Cat-PAD)] for which efficacy had previously been demonstrated. The primary objective (not presented here) was to identify potential biomarkers of efficacy for peptide immunotherapy, and this provided an ideal opportunity to corroborate the NAC protocol. We aim to clinically validate the AR-CIC NAC methodology in a pooled analysis of secondary endpoints measured in two open label mechanistic studies of cat allergic participants treated with Cat-PAD.

Methods

Cat allergic AR sufferers with ongoing cat exposure were included. Participants had to demonstrate a total nasal symptom score (TNSS) of at least 8 (max 12) and/or achieve a reduction in peak nasal inspiratory flow (PNIF) of ≥ 50% during a screening titrated NAC. Eligible participants then underwent a baseline NAC visit with the allergen dose that produced a positive challenge at screening, followed by four monthly injections of 6 nmol Cat-PAD. A follow up NAC visit documented changes in nasal response 1 month following the completion of treatment.

Results

Nineteen subjects completed the study protocol in the two studies combined. Four injections of Cat-PAD resulted in a significant reduction in TNSS responses generated via NAC following allergen challenge (15 min p < 0.05, 30 min p < 0.05, 1 h p < 0.01, 2 h p < 0.05). There was modest correlation between symptom scores and PNIF measurements.

Conclusions

This study supports the validity of the AR-CIC’s optimised NAC protocol for conducting research of the potential efficacy of novel therapeutics in multi-centre studies.

Trial registration Both studies reported herein were registered clinicaltrials.gov (NCT01383590 and NCT01383603)

IL-33: biological properties, functions, and roles in airway disease

Interleukin (IL)-33 is a key cytokine involved in type 2 immunity and allergic airway diseases. Abundantly expressed in lung epithelial cells, IL-33 plays critical roles in both innate and adaptive immune responses in mucosal organs. In innate immunity, IL-33 and group 2 innate lymphoid cells (ILC2s) provide an essential axis for rapid immune responses and tissue homeostasis. In adaptive immunity, IL-33 interacts with dendritic cells, Th2 cells, follicular T cells, and regulatory T cells, where IL-33 influences the development of chronic airway inflammation and tissue remodeling. The clinical findings that both the IL-33 and ILC2 levels are elevated in patients with allergic airway diseases suggest that IL-33 plays an important role in the pathogenesis of these diseases. IL-33 and ILC2 may also serve as biomarkers for disease classification and to monitor the progression of diseases. In this article, we reviewed the current knowledge of the biology of IL-33 and discussed the roles of the IL-33 in regulating airway immune responses and allergic airway diseases.

Research highlights from the 2017 ERS International Congress: airway diseases in focus

For another year, high-quality research studies from around the world transformed the annual ERS International Congress into a vivid platform to discuss trending research topics, to produce new research questions and to further push the boundaries of respiratory medicine and science. This article reviews only some of the high-quality research studies on asthma, chronic obstructive pulmonary disease (COPD), bronchiectasis and chronic cough that were presented during the congress through the Airway Diseases Assembly (ERS Assembly 5) and places them into the context of current knowledge and research challenges.

Members of the @ERStalk Airway Diseases Assembly discuss clinical highlights from #ERSCongress 2017http://ow.ly/G51Y30i7fMR

Interleukin-33 induces interleukin-8 expression via JNK/c-Jun/AP-1 pathway in human umbilical vein endothelial cells

Interleukin (IL)-33 is a member of the IL-1 cytokine family with dual functions as a traditional cytokine and as a transcriptional regulator. We recently reported that IL-33 up-regulated growth regulated oncogene (GRO)-α/CXCL1 expression in human vascular endothelial cells. The aim of this study was to investigate the effect of IL-33 on the expression of IL-8/CXCL8, another member of the CXC-chemokine family, and to elucidate its signaling pathways in human umbilical vein endothelial cells (HUVECs). Immunocytochemical staining and Western immunoblot analysis revealed that IL-33 augmented IL-8 protein expression in HUVECs. Real time reverse transcription-polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA) showed that IL-33 significantly increased IL-8 mRNA and secretion in a dose- and time-dependent manner. IL-33 preferentially stimulated proliferating subconfluent cells, and increased IL-8 secretion to a higher level compared with confluent cells. IL-33 also stimulated phosphorylations of c-Jun N-terminal kinase (JNK) and c-Jun, and enhanced activator protein (AP)-1 DNA-binding activity, all of which were suppressed by SP600125, a JNK inhibitor. Moreover, IL-33-induced IL-8 mRNA and secretion were also suppressed by SP600125. Transfection of c-Jun small interfering RNA into cultured HUVECs significantly reduced the IL-33-induced increase in IL-8 secretion from HUVECs. The present study demonstrates that IL-33 induces IL-8 expression via JNK/c-Jun/AP-1 pathway in human vascular endothelial cells, and provides a new insight into the role of IL-33-induced IL-8 in the pathophysiology of atherosclerosis and vascular inflammation.