The Role of Interleukin-33 in Pathogenesis of Bronchial Asthma. New Experimental Data

Chemical chaperone TUDCA selectively inhibits production of allergen-specific IgE in a low-dose model of allergy

The cellular response to endoplasmic reticulum (ER) stress accompanies plasma cell maturation and is one of triggers and cofactors of the local inflammatory response. Chemical chaperones, low-molecular substances that eliminate pathological ER stress, are proposed as means of treating pathologies associated with ER stress. The aim of this study was to evaluate the effect and mechanisms of influence of chemical chaperones on the humoral response in a low-dose model of allergy. The allergic immune response was induced in BALB/c mice by repeated administration of ovalbumin at a dose of 100 ng for 6 weeks. Some animals were injected with both the antigen and the chemical chaperones, TUDCA (tauroursodeoxycholic acid) or 4-PBA (4-phenylbutyrate). Administration of TUDCA, but not 4-PBA, suppressed production of allergen-specific IgE (a 2.5-fold decrease in titer). None of the chemical chaperones affected the production of specific IgG1. The effect of TUDCA was associated with suppression of the switch to IgE synthesis in regional lymph nodes. This phenomenon was associated with suppressed expression of genes encoding cytokines involved in type 2 immune response, especially Il4 and Il9, which in turn could be caused by suppression of IL-33 release. In addition, TUDCA significantly suppressed expression of the cytokine APRIL, and to a lesser extent, BAFF. Thus, TUDCA inhibition of the allergy-specific IgE production is due to suppression of the release of IL-33 and a decrease in the production of type 2 immune response cytokines, as well as suppression of the expression of the cytokines APRIL and BAFF.

Strategies targeting IL-33/ST2 axis in the treatment of allergic diseases

Interleukin-33 (IL-33) and its receptor Serum Stimulation-2 (ST2, also called Il1rl1) are members of the IL-1 superfamily that plays a crucial role in allergic diseases. The interaction of IL-33 and ST2 mainly activates NF-κB signaling and MAPK signaling via the MyD88/IRAK/TRAF6 module, resulting in the production and secretion of pro-inflammatory cytokines. The IL-33/ST2 axis participates in the pathogenesis of allergic diseases, and therefore serves as a promising strategy for allergy treatment. In recent years, strategies blocking IL-33/ST2 through targeting regulation of IL-33 and ST2 or targeting the molecules involved in the signal transduction have been extensively studied mostly in animal models. These studies provide various potential therapeutic agents other than antibodies, such as small molecules, nucleic acids and traditional Chinese medicines. Herein, we reviewed potential targets and agents targeting IL-33/ST2 axis in the treatment of allergic diseases, providing directions for further investigations on treatments for IL-33 induced allergic diseases.

Role and Molecular Mechanisms of Alternative Splicing of Th2-Cytokines IL-4 and IL-5 in Atopic Bronchial Asthma

Bronchial asthma (BA) is a heterogeneous chronic inflammatory disease of the respiratory tract. Allergic (atopic) asthma is the most common (up to 80% of cases) phenotype developing through the Th2-dependent mechanisms involving cytokines: IL-4, IL-5, IL-9, and IL-13. The genes encoding Th2-cytokines have a mosaic structure (encode exons and introns). Therefore, several mature mRNA transcripts and protein isoforms can be derived from a single mRNA precursor through alternative splicing, and they may contribute to BA pathogenesis. Analysis of the published studies and databases revealed existence of the alternative mRNA transcripts for IL-4, IL-5, and IL-13. The alternative transcripts of IL-4 and IL-5 carry open reading frames and therefore can encode functional proteins. It was shown that not only alternative mRNA transcripts exist for IL-4, but alternative protein isoforms, as well. Natural protein isoform (IL-4δ2) lacking the part encoded by exon-2 was identified. Similarly, alternative mRNA transcript with deleted exon-2 (IL-5δ2) was also identified for IL-5. In this review, we summarize current knowledge about the identified alternative mRNA transcripts and protein isoforms of Th2-cytokinins, first of all IL-4 and IL-5. We have analyzed biological properties of the alternative variants of these cytokines, their possible role in the allergic asthma pathogenesis, and considered their diagnostic and therapeutic potential.

Baseline type 2 biomarker levels and response to tezepelumab in severe asthma

Background

Tezepelumab is a human monoclonal antibody that blocks activity of thymic stromal lymphopoietin (TSLP). In the phase IIb PATHWAY study (NCT02054130), tezepelumab significantly reduced annualized asthma exacerbation rates (AAERs) versus placebo in adults with severe, uncontrolled asthma. We evaluated the effects of tezepelumab in reducing type 2 (T2) inflammatory biomarker levels in the PATHWAY population, and the relationship between baseline T2 biomarker levels and AAER.

Methods

Adults with severe, uncontrolled asthma (n = 550) were randomized to tezepelumab (70 mg or 210 mg every 4 weeks, or 280 mg every 2 weeks) or placebo for 52 weeks. Blood eosinophil count, fractional exhaled nitric oxide (FeNO), and serum total immunoglobulin (Ig)E, interleukin (IL)‐5, IL‐13, periostin, thymus and activation‐regulated chemokine (TARC), and TSLP were measured at baseline and over 52 weeks. AAERs were analyzed by baseline threshold (high/low) biomarker levels.

Results

Positive correlations were observed between T2 inflammatory biomarkers (blood eosinophil count, FeNO, IL‐5, IL‐13 and periostin) at baseline. At Week 52, treatment with tezepelumab 210 mg reduced all biomarker levels measured from baseline versus placebo. Exacerbations were reduced by 55–83% in the pooled tezepelumab cohort versus placebo, irrespective of baseline blood eosinophil count, FeNO, or serum total IgE, IL‐5, IL‐13, periostin, TARC, or TSLP, when these biomarkers were assessed individually.

Conclusion

At baseline, positive correlations between specific T2 inflammatory biomarkers were observed. Tezepelumab reduced multiple T2 inflammatory biomarkers, which indicates decreased airway inflammation, and reduced exacerbations irrespective of baseline T2 biomarker profiles in patients with severe asthma.

IL-1β Promotes Expansion of IL-33+ Lung Epithelial Stem Cells Following RSV Infection During Infancy

Respiratory syncytial virus (RSV)-induced immunopathogenesis and disease severity in neonatal mice and human infants have been related to elevated pulmonary IL-33. Thus, targeting IL-33 has been suggested as a potential therapy for respiratory viral infections. Yet, the regulatory mechanisms on IL-33 during early life remain unclear. Here, using a neonatal mouse model of RSV, we demonstrate that IL-1β positively regulates but is not required for RSV-induced expression of pulmonary IL-33 in neonatal mice early after the initial infection. Exogenous IL-1β upregulates RSV-induced IL-33 expression by promoting the proliferation of IL-33pos lung epithelial stem/progenitor cells (EpiSPC). These cells are exclusively detected in RSV-infected neonatal rather than adult mice, partially explaining the IL-1β-independent IL-33 expression in RSV-infected adult mice. Furthermore, IL-1β aggravates IL-33 mediated Th2 biased immunopathogenesis upon reinfection. Collectively, our study demonstrates that IL-1β exacerbates IL-33 mediated RSV immunopathogenesis by promoting the proliferation of IL-33pos EpiSPC in early life.

Role of STAT3 Transcription Factor in Pathogenesis of Bronchial Asthma

Bronchial asthma is a heterogeneous chronic inflammatory disease of airways. The studies of molecular and cellular mechanisms of bronchial asthma have established that a wide range of immune (T and B cells, eosinophils, neutrophils, macrophages, etc.) and structural (epithelial and endothelial) cells are involved in its pathogenesis. These cells are activated in response to external stimuli (bacteria, viruses, allergens, and other pollutants) and produce pro-inflammatory factors (cytokines, chemokines, metalloproteinases, etc.), which ultimately leads to the initiation of pathological processes in the lungs. Genes encoding transcription factors of the STAT family (signal transducer and activator of transcription), that includes seven representatives, are involved in the cell activation. Recent studies have shown that the transcription factor STAT3 plays an important role in the activation of the abovementioned cells, thus contributing to the development of asthma. In animal studies, selective inhibition of STAT3 significantly reduces the severity of lung inflammation, which indicates its potential as a therapeutic target. In this review, we describe the mechanisms of STAT3 activation and its role in polarization of Th2/Th17 cells and M2 macrophages, as well as in the dysfunction of endothelial cells, which ultimately leads to development of bronchial asthma symptoms, such as infiltration of neutrophils and eosinophils into the lungs, bronchial hyperreactivity, and the respiratory tract remodeling.

Modern View of Neutrophilic Asthma Molecular Mechanisms and Therapy

For a long time asthma was commonly considered as a homogeneous disease. However, recent studies provide increasing evidence of its heterogeneity and existence of different phenotypes of the disease. Currently, classification of asthma into several phenotypes is based on clinical and physiological features, anamnesis, and response to therapy. This review describes five most frequently identified asthma phenotypes. Neutrophilic asthma (NA) deserves special attention, since neutrophilic inflammation of the lungs is closely associated with severity of the disease and with the resistance to conventional corticosteroid therapy. This review focuses on molecular mechanisms of neutrophilic asthma pathogenesis and on the role of Th1- and Th17-cells in the development of this type of asthma. In addition, this review presents current knowledge of neutrophil biology. It has been established that human neutrophils are represented by at least three subpopulations with different biological functions. Therefore, total elimination of neutrophils from the lungs can result in negative consequences. Based on the new knowledge of NA pathogenesis and biology of neutrophils, the review summarizes current approaches for treatment of neutrophilic asthma and suggests new promising ways to treat this type of asthma that could be developed in future.

Respiratory syncytial virus upregulates IL-33 expression in mouse model of virus-induced inflammation exacerbation in OVA-sensitized mice and in asthmatic subjects

BACKGROUND

Bronchial asthma (BA) is a chronic disease of the airways. The great majority of BA exacerbations are associated with respiratory viral infections. Recent findings point out a possible role of proinflammatory cytokine interleukin-33 (IL-33) in the development of atopic diseases. Although, little is known about the role of IL-33 in virus-induced BA exacerbations.

METHODS

We used mouse models of RSV (respiratory syncytial virus)-induced inflammation exacerbation in OVA-sensitized mice and RSV infection alone in adult animals to characterize expression of il33 in the mouse lungs. Moreover, we studied the influence of il33 knockdown with intranasally administrated siRNA on the development of RSV-induced inflammation exacerbation. In addition, we evaluated the expression of IL33 in the ex vivo stimulated PBMCs from allergic asthma patients and healthy subjects with and without confirmed acute respiratory viral infection.

RESULTS

Using mouse models, we found that infection with RSV drives enhanced il33 mRNA expression in the mouse lung. Treatment with anti-il33 siRNA diminishes airway inflammation in the lungs (we found a decrease in the number of inflammatory cells in the lungs and in the severity of histopathological alterations) of mice with RSV-induced inflammation exacerbation, but do not influence viral load. Elevated level of the IL33 mRNA was detected in ex vivo stimulated blood lymphocytes of allergic asthmatics infected with respiratory viruses. RSV and rhinovirus were the most detected viruses in volunteers with symptoms of respiratory infection.

CONCLUSION

The present study provides additional evidence of the crucial role of the IL-33 in pathogenesis of RSV infection and virus-induced allergic bronchial asthma exacerbations.

The Impact of Interleukin (IL)-33 Gene Polymorphisms and Environmental Factors on Risk of Asthma in the Iranian Population

BACKGROUND

Airway epithelial cells secrete Interleukin-33 in response to the different allergens. Several single nucleotide polymorphisms (SNP) of this cytokine have been reported to be involved in the development of asthma. We conducted this study to evaluate the impact of the two most common SNPs of the IL-33 gene (rs1342326 and rs3939286) and environmental factors on the susceptibility to asthma in the Iranian population.

SUBJECTS AND METHODS

In this study, we enrolled 126 asthmatics patients and 300 age, sex-matched controls. Genotyping was performed by real-time PCR using the TaqMan SNP genotyping assay. Moreover, total serum IgE level, eosinophil count, and skin prick test were accomplished and complete history was taken from all the participants.

RESULTS

The frequencies of mutant genotypes in both SNPs were significantly higher in asthmatics than controls. C/C genotype of rs1342326 [OR (95% CI) 2.50 (1.33-4.69)] and A/A genotype of rs3939286 [OR (95% CI) 2.18 (1.05-4.52)] were associated with higher risk of asthma development. While A/C+C/C genotype of rs1342326 was more prevalent in mild asthma [OR (95% CI) 2.36 (1.14-4.89)], G/A+A/A genotype of rs3939286 was associated with increased risk of moderate and severe asthma [OR (95% CI) 2.53 (1.30-4.94)].

CONCLUSION

This study revealed that both IL-33 SNPs were associated with an increased risk of asthma. The rs1342326 was associated with atopic, mild and adult-onset asthma and a higher level of eosinophils in peripheral blood. However, rs3939286 was more frequent in moderate and severe asthma. Moreover, rs3939286 was associated with non-atopic and childhood-onset asthma.

IL-33 stimulates human mast cell release of CCL5 and CCL2 via MAPK and NF-κB, inhibited by methoxyluteolin

Mast Cells (MCs) are critical for allergic reactions but also play important roles in inflammation, following stimulation by non-allergic triggers such as cytokines. Upon stimulation, MCs secrete numerous newly synthesized mediators, but the mechanism of the release of chemokines, which are important in the pathogenesis of allergic and inflammatory diseases, remains unknown. IL-33 is an "alarmin", known to augment allergic stimulation of MCs, but its effect on the release of chemokines is not known. The present work investigated the action of IL-33 on the release of the chemokines CCL5 and CCL2 from human MCs, as well as the inhibitory effect of the flavonoid 3',4',5,7-tetramethoxyflavone (methoxyluteolin). Stimulation of cultured human MCs (LAD2) and primary MCs (hCBMCs) by IL-33 (1-100 ng/ml) increased the gene expression and the release of CCL5 (P < 0.0001) and CCL2 (P < 0.01). Stimulation with IL-33 (10 ng/ml) activated MAPK components, as shown by phosphorylation of p38α MAPK, JNK, and c-Jun using Western blot analysis. Inhibition of these responses by known inhibitors confirmed that CCL5 and CCL2 are stimulated by the activation of p38α MAPK, JNK, and IκB-α. The gene expression and the release of CCL5 and CCL2 stimulated by IL-33 were significantly inhibited by 2 h pre-treatment with methoxyluteolin (10, 50, 100  μM). The inhibition by methoxyluteolin (50 μM) was not mediated via MAPK inhibition as phosphorylated p38α MAPK and JNK expression were not affected. In conclusion, IL-33 plays an important role in chemokine release from human MCs and that is by activation of more than one signaling pathway. The inhibitory effect of methoxyluteolin may indicate that it can be developed as a novel treatment for inflammatory diseases.

Decreased circulating interleukin-33 concentration in Helicobacter pylori-infected patients with peptic ulcer: Evaluation of its association with a cytokine gene polymorphism, gender of patients and bacterial virulence factor CagA

IL-33 has powerful immunoregulatory activities such as reinforcement of Th2 cell responses. The aim was to assess the circulating IL-33 levels and IL-33 rs1929992 polymorphism in H. pylori-infected peptic ulcer (PU) patients and asymptomatic (AS) subjects. Blood samples were obtained from 100 PU patients, 100 AS subjects and 100 uninfected individuals. Circulating IL-33 levels were detected by ELISA. After DNA extraction, the IL-33 rs1929992 polymorphism was determined using PCR-RFLP method. Serum IL-33 quantities were significantly lower in PU patients compared with AS and uninfected groups. IL-33 levels were higher in AS subjects compared with uninfected group. In PU, AS and uninfected groups, IL-33 levels were significantly higher in women than men. In PU and AS groups, the CagA⁺H. pylori-infected subjects exhibit higher IL-33 levels compared with carriers of CagA^-H. pylori strains. In PU patients, the frequency of genotype GG and allele G at IL-33 rs1929992 was significantly higher compared with all healthy subjects (AS + uninfected groups). The presence of genotypes GG and AG, and allele G in rs1929992 conferred greater risk for PU. In whole H. pylori-infected population (PU + AS groups), IL-33 levels in individuals with genotype AA or allele A at rs1929992 were higher than subjects with GG genotype or allele G. The reduced IL-33 production could contribute to the PU development during H. pylori infection. The IL-33 levels may be affected by individual gender, rs1929992 polymorphism, and the CagA status of bacteria. The rs1929992-related GG genotype and G allele may be associated with PU development.

Role of Leukotriene B4 Receptor-2 in Mast Cells in Allergic Airway Inflammation

Mast cells are effector cells in the immune system that play an important role in the allergic airway inflammation. Recently, it was reported that BLT2, a low-affinity leukotriene (LT) B₄ receptor, plays a pivotal role in the pathogenesis of allergic airway inflammation through its action in mast cells. We observed that highly elevated expression levels of BLT2 are critical for the pathogenesis leading to allergic airway inflammation, and that if BLT2 expression is downregulated by siBLT2-mediated knockdown, allergic inflammation is dramatically alleviated. Furthermore, we demonstrated that BLT2 mediates the synthesis of vascular endothelial growth factor (VEGF) and Th2 cytokines, such as interleukin (IL)-13, in mast cells during allergic inflammation. Based on the critical roles of BLT2 in mast cells in allergic inflammation, anti-BLT2 strategies could contribute to the development of new therapies for allergic airway inflammation.

IL33: Roles in Allergic Inflammation and Therapeutic Perspectives

Interleukin (IL)-33 belongs to IL-1 cytokine family which is constitutively produced from the structural and lining cells including fibroblasts, endothelial cells, and epithelial cells of skin, gastrointestinal tract, and lungs that are exposed to the environment. Different from most cytokines that are actively secreted from cells, nuclear cytokine IL-33 is passively released during cell necrosis or when tissues are damaged, suggesting that it may function as an alarmin that alerts the immune system after endothelial or epithelial cell damage during infection, physical stress, or trauma. IL-33 plays important roles in type-2 innate immunity via activation of allergic inflammation-related eosinophils, basophils, mast cells, macrophages, and group 2 innate lymphoid cells (ILC2s) through its receptor ST2. In this review, we focus on the recent advances of the underlying intercellular and intracellular mechanisms by which IL-33 can regulate the allergic inflammation in various allergic diseases including allergic asthma and atopic dermatitis. The future pharmacological strategy and application of traditional Chinese medicines targeting the IL-33/ST2 axis for anti-inflammatory therapy of allergic diseases were also discussed.

Dysregulation of IL-33/ST2 signaling and myocardial periarteriolar fibrosis

Microvascular dysfunction in the heart and its association with periarteriolar fibrosis may contribute to the diastolic dysfunction seen in heart failure with preserved ejection fraction. Interleukin-33 (IL-33) prevents global myocardial fibrosis in a pressure overloaded left ventricle by acting via its receptor, ST2 (encoded by the gene, Il1rl1); however, whether this cytokine can also modulate periarteriolar fibrosis remains unclear. We utilized two approaches to explore the role of IL-33/ST2 in periarteriolar fibrosis. First, we studied young and old wild type mice to test the hypothesis that IL-33 and ST2 expression change with age. Second, we produced pressure overload in mice deficient in IL-33 or ST2 by transverse aortic constriction (TAC). With age, IL-33 expression increased and ST2 expression decreased. These alterations accompanied increased periarteriolar fibrosis in aged mice. Mice deficient in ST2 but not IL-33 had a significant increase in periarteriolar fibrosis following TAC compared to wild type mice. Thus, loss of ST2 signaling rather than changes in IL-33 expression may contribute to periarteriolar fibrosis during aging or pressure overload, but manipulating this pathway alone may not prevent or reverse fibrosis.

The Combination Therapy of Dietary Galacto-Oligosaccharides With Budesonide Reduces Pulmonary Th2 Driving Mediators and Mast Cell Degranulation in a Murine Model of House Dust Mite Induced Asthma

Background: Dietary non-digestible galacto-oligosaccharides (GOS) suppress allergic responses in mice sensitized and challenged with house dust mite (HDM). Budesonide is the standard therapy for allergic asthma in humans but is not always completely effective.

Aim: To compare the efficacy of budesonide or different doses of GOS alone or with a combination therapy of budesonide and GOS on HDM-allergic responses in mice.

Methods:BALB/c mice were sensitized and challenged with HDM, while fed a control diet or a diet supplemented with 1 or 2.5 w/w% GOS, and either or not oropharyngeally instilled with budesonide. Systemic and local inflammatory markers, such as mucosal mast cell protease-1 (mMCP-1) in serum, pulmonary CCL17, CCL22, and IL-33 concentrations and inflammatory cell influx in the bronchoalveolar lavage fluid (BALF) were determined.

Results: Budesonide or GOS alone suppressed the number of eosinophils in the BALF of HDM allergic mice whereas budesonide either or not combined with GOS lowered both eosinophil and lymphocyte numbers in the BALF of HDM-allergic mice. Both 1 w/w% and 2.5 w/w% GOS and/or budesonide suppressed serum mMCP-1 concentrations. However, budesonide nor GOS alone was capable of reducing Th2 driving chemokines CCL17, CCL22 and IL-33 protein levels in supernatants of lung homogenates of HDM allergic mice, whereas the combination therapy did. Moreover, IL-13 concentrations were only significantly suppressed in mice treated with budesonide while fed GOS. A similar tendency was observed for the frequency of GATA3⁺CD4⁺ Th2 and CD4⁺RORγt⁺ Th17 cells in the lungs of the allergic mice.

Conclusion: Dietary intervention using GOS may be a novel way to further improve the efficacy of anti-inflammatory drug therapy in allergic asthma by lowering Th2 driving mediators and mast cell degranulation.

Gallic acid attenuates allergic airway inflammation via suppressed interleukin-33 and group 2 innate lymphoid cells in ovalbumin-induced asthma in mice

BACKGROUND

Asthma is an inflammatory disease characterized by airway hyperresponsiveness. Gallic acid is a powerful anti-inflammatory agent. In this study we aimed to investigate the efficacy of gallic acid in asthma treatment and its mechanisms.

METHODS

An ovalbumin-induced asthma mouse model was generated. Pro-inflammatory cell infiltration and T helper (Th2)-associated cytokine release in the bronchoalveolar lavage fluid (BALF) were analyzed to reflect the severity of asthma in mice. An interleukin-33 (IL-33)-induced asthma mouse model was also generated to study the mechanism by which gallic acid could improve asthma. Group 2 lymphoid cells (ILC2s) were identified using flow cytometry. Proteins were detected using Western blotting.

RESULTS

Ovalbumin significantly increased the infiltration of pro-inflammatory cells, including eosinophils, macrophages, lymphocytes, and neutrophils, accompanied by enhanced airway hyperesponsiveness. Gallic acid reduced pro-inflammatory cell infiltration and improved airway hyperresponsiveness. Meanwhile, gallic acid reduced IL-5 and IL-13 levels in BALF and decreased expression of IL-33 in the lungs. Mechanistically, gallic acid inhibited MyD88 expression and downregulated nuclear factor (NF)-κB signaling to decrease IL-33 expression.

CONCLUSIONS

Gallic acid can mollify ovalbumin-induced asthma in mice, possibly by inhibiting IL-33-mediated ILC2 activation and subsequent Th2 cytokine release via downregulation of the MyD88/NF-κB signaling pathway. ©2018 ARSAAOA, LLC.

Increased serum interleukin-33 concentrations predict worse prognosis of aneurysmal subarachnoid hemorrhage

BACKGROUND

Interleukin-33 (IL-33) is an inflammatory biomarker. We elucidated the relationship between serum IL-33 concentrations, severity and prognosis in aneurysmal subarachnoid hemorrhage (aSAH).

METHODS

We prospectively recruited 175 controls and 175 aSAH patients. Serum IL-33 concentrations were gauged using an enzyme-linked immunosorbent assay. Clinical and radiological severity was assessed by World Federation of Neurological Surgeons (WFNS) scale and modified Fisher grading scale respectively. Poor outcome was defined as Glasgow Outcome Scale score of 1-3.

RESULTS

Serum IL-33 concentrations were significantly higher in patients than in controls. IL-33 concentrations were significantly increased with increasing WFNS scores, modified Fisher scores and serum C-reactive protein concentrations. Serum IL-33 emerged as an independent predictor for 6-month mortality and poor outcome. Under receiver operating characteristic curve, the prognostic predictive ability of serum IL-33 was equivalent to those of WFNS scores and modified Fisher scores. Moreover, serum IL-33 significantly improved the prognostic predictive performance of WFNS scores and modified Fisher scores.

CONCLUSIONS

High serum IL-33 concentrations have close relation to the inflammation, severity and poor outcome in aSAH, indicating IL-33 might have the potential to be an inflammatory biomarker for assessing severity and reflecting prognosis of aSAH.