Damage-associated molecular patterns stimulate interleukin-33 expression in nasal polyp epithelial cells

Comprehensive evaluation of type 2 endotype and clinical features in patients with chronic rhinosinusitis with nasal polyps in Taiwan: a cross-sectional study

PURPOSE

Endotype-driven treatment has been introduced in the management of chronic rhinosinusitis with nasal polyps (CRSwNP), and an understanding of the associations between phenotypes and endotypes of CRSwNP will be beneficial in identifying responders. We aimed to determine the correlations between clinical manifestations and type 2 inflammatory mediators of sinonasal tissues.

METHODS

Adult patients undergoing endoscopic sinus surgery for bilateral CRSwNP were prospectively enrolled. Tissue eosinophilia and type 2 mediator expression in tissue homogenates were assessed and correlated with clinical features, including symptoms, comorbidities, blood eosinophil counts, specific allergen immunoglobulin (IgE) testing, computed tomography (CT) scan findings, and Sino-Nasal Outcome Test-22 scores.

RESULTS

A total of 93 subjects were recruited in our study. Fifty-nine (63.4%) cases were identified as the eosinophilic endotype, demonstrating with higher rates of comorbidity of asthma, blood eosinophilia and a high ethmoid-maxillary ratio on CT images. To correlate of phenotypes with the inflammatory mediator profile, multivariate analyses revealed the associations of IgE expression in nasal polyp tissues with allergen sensitization (p = 0.042), CT ethmoid-maxillary ratio (p = 0.001) and tissue eosinophil counts (p = 0.022); the association of interleukin (IL-5) expression with the blood eosinophil percentage (p = 0.020); and the association of IL-13 expression with white blood cell count (p = 0.002) and central compartment-type inflammation (p < 0.001).

CONCLUSION

We demonstrated associations of IgE and IL-5 expression with clinical features of eosinophilic-type inflammation and a significantly elevated level of IL-13 in patients with central-compartment-type CRSwNP. These observations may be useful when considering the use of type 2 biologic treatment and require further validation studies.

Interesting effects of interleukins and immune cells on acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) is a medical condition characterized by widespread inflammation in the lungs with consequent proportional loss of gas exchange function. ARDS is linked with severe pulmonary or systemic infection. Several factors, including secretory cytokines, immune cells, and lung epithelial and endothelial cells, play a role in the development and progression of this disease. The present study is based on Pubmed database information (1987-2022) using the words "Acute respiratory distress syndrome", "Interleukin", "Cytokines" and "Immune cells". Cytokines and immune cells play an important role in this disease, with particular emphasis on the balance between pro-inflammatory and anti-inflammatory factors. Neutrophils are one of several important mediators of Inflammation, lung tissue destruction, and malfunction during ARDS. Some immune cells, such as macrophages and eosinophils, play a dual role in releasing inflammatory mediators, recruitment inflammatory cells and the progression of ARDS, or releasing anti-inflammatory mediators, clearing the lung of inflammatory cells, and helping to improve the disease. Different interleukins play a role in the development or inhibition of ARDS by helping to activate various signaling pathways, helping to secrete other inflammatory or anti-inflammatory interleukins, and playing a role in the production and balance between immune cells involved in ARDS. As a result, immune cells and, inflammatory cytokines, especially interleukins play an important role in the pathogenesis of this disease Therefore, understanding the relevant mechanisms will help in the proper diagnosis and treatment of this disease.

IL-33 and HMGB1 modulate the progression of EAE via oppositely regulating each other

Interleukin-33 (IL-33) and high mobility group box 1 (HMGB1) have been reported to play crucial and distinct roles in experimental autoimmune encephalomyelitis (EAE). However, little is known about their interaction in the progression of EAE. In this study, the dynamic expression and release of IL-33 and HMGB1 in different stages of EAE in vivo, and their interaction in vitro were explored. We found that HMGB1 was dominant in pre-onset stage of EAE, while IL-33 was dominant in peak stage. Moreover, both blockade of extracellular HMGB1 in the central nervous system (CNS) and conditional knockout of HMGB1 in astrocytes decreased IL-33 release. HMGB1 promoted the release of IL-33, while IL-33 reduced the release of HMGB1 from primary astrocytes in vitro. Taken together, IL-33 and HMGB1 in the CNS jointly participate in the EAE progression and the inhibitory effect of IL-33 on HMGB1 may be involved in the self-limiting of EAE.

S100A8 enhances IL-1β production from nasal epithelial cells in eosinophilic chronic rhinosinusitis

BACKGROUND

Chronic rhinosinusitis is classified into eosinophilic chronic rhinosinusitis (ECRS) and non-eosinophilic chronic rhinosinusitis (NECRS). ECRS is a refractory allergic disease involving a variety of immune and epithelial cells. S100A8 is a damage-associated molecular pattern that is closely related to allergic inflammation. However, the pathological implications of S100A8 in ECRS have not been clarified.

METHODS

We evaluated the role of S100A8 in the pathogenesis of ECRS. Gene expression profiles of nasal polyps obtained from patients with ECRS or NECRS were evaluated using RNA sequencing.

RESULTS

S100A8 was identified as a significantly upregulated gene in nasal polyps associated with ECRS. Immunohistochemistry consistently revealed intense S100A8 staining in nasal polyps from patients with ECRS. Human nasal epithelial cells expressed the receptor for advanced glycation end products and Toll-like receptor 4. Recombinant S100A8 protein induced interleukin-1β secretion in human nasal epithelial cells.

CONCLUSIONS

Our data demonstrate that S100A8 results in production of interleukin-1β in the nasal epithelium, which may be involved in the pathogenesis of ECRS.

Counteractive Effects of IL-33 and IL-37 on Inflammation in Osteoarthritis

Osteoarthritis (OA) is a chronic inflammatory disease where pro-inflammatory cytokines, damage-associated molecular patterns (DAMPs), and macrophages play a crucial role. However, the interactive role of these mediators, the exact cause precipitating OA and definitive treatment for OA are not known yet. Moreover, the interactive role of interleukin (IL)-33 and IL-37 with other factors in the pathogenesis of OA has not been discussed elaborately. In this study, we analyzed the expression of IL-33 and IL-37 in human OA knee and hip joint cartilage tissues. The effect of increased DAMPs, IL-33, and IL-37 on IL-6, tumor necrosis factor (TNF)-α, toll-like receptors (TLRs), and matrix metalloproteinases (MMPs) expression was delineated using human normal and osteoarthritic chondrocytes. The effect of anti-inflammatory cytokine IL-37 on various mediators of inflammation in the presence of IL-33, rHMGB-1, and LPS was investigated to delineate the effects of IL-37. Further, the effects of blocking IL-33 downstream signaling and the effects of IL-33 and IL-37 on macrophage polarization were assessed along with examining the macrophage phenotypes in human OA cartilage tissues. The results of this study revealed increased expression of IL-33 in OA cartilage and that IL-33 increases IL-6, TNF-α, TLRs, and MMPs expression and favors phenotypic conversion towards the M1 phenotype, while IL-37 and blocking IL-33 receptor ST2 have opposite effects. Overall, the results suggest that blocking IL-33 and increasing IL-37 act synergistically to attenuate inflammation and might serve as potential therapeutics in OA.

IL-33, IL-37, and Vitamin D Interaction Mediate Immunomodulation of Inflammation in Degenerating Cartilage

Chronic joint inflammation due to increased secretion of pro-inflammatory cytokines, the accumulation of inflammatory immune cells (mainly macrophages), and vitamin D deficiency leads to cartilage degeneration and the development of osteoarthritis (OA). This study investigated the effect of vitamin D status on the expression of mediators of inflammation including interleukin (IL)-33, IL-37, IL-6, tumor necrosis factor (TNF)-α, toll-like receptors (TLRs), damage-associated molecular patterns (DAMPs), and matrix metalloproteinases (MMPs) in degenerating the cartilage of hyperlipidemic microswine. Additionally, in vitro studies with normal human chondrocytes were conducted to investigate the effect of calcitriol on the expression of IL-33, IL-37, IL-6, TNF-α, TLRs, DAMPs, and MMPs. We also studied the effects of calcitriol on macrophage polarization using THP-1 cells. The results of this study revealed that vitamin D deficiency is associated with an increased expression of IL-33, IL-37, IL-6, TNF-α, TLRs, DAMPs, and MMPs, while vitamin D supplementation is associated with a decreased expression of the former. Additionally, vitamin D deficiency is associated with increased M1, while vitamin D-supplemented microswine cartilage showed increased M2 macrophages. It was also revealed that calcitriol favors M2 macrophage polarization. Taken together, the results of this study suggest that modulating expression of IL-33, IL-6, TNF-α, TLRs, DAMPs, and MMPs with vitamin D supplementation may serve as a novel therapeutic to attenuate inflammation and cartilage degeneration in osteoarthritis.

Role of P2X7R in eosinophilic and non‑eosinophilic chronic rhinosinusitis with nasal polyps

Chronic rhinosinusitis with nasal polyps (CRSwNP) is an inflammation‑mediated disease of the nasal mucosa. P2X7R has been reported to be a potential biomarker for inflammation. The aim of the present study was to explore the role of P2X7R in CRSwNP, and the interaction between P2X7R and the NLRP3 inflammasome in the development of CRSwNP. Firstly, the expression profiles of P2X7R in nasal mucosa were investigated using western blotting (WB), polymerase chain reaction (PCR) and immunofluorescence (IF) staining. Next, the effect of inflammatory stimulation with lipopolysaccharides (LPS) combined with 2'(3')‑O‑(4‑benzoylbenzoyl) adenosine 5'‑triphosphate triethylammonium salt (BzATP) on primary human nasal epithelial cells (HNECs) was determined. Then, the therapeutic effect of the selective P2X7R antagonist, A740003, on P3X7R, NOD‑like receptor pyrin domain containing 3 (NLRP3) inflammasome and IL‑1β alterations in HNECs was explored using enzyme‑linked immunosorbent assay, WB and PCR. It was found that P2X7R was overexpressed in CRSwNP, especially in eosinophilic CRSwNP, the expression of P2X7R, NLRP3 and IL‑1β were upregulated in HNECs after induction by LPS combined with BzATP; but the expression of NLRP3 and IL‑1β were downregulated after stimulation with A740003. The aforementioned results indicate that P2X7R‑mediated NLRP3 inflammasome activation may have a role in the pathogenesis of CRSwNP.

International consensus statement on allergy and rhinology: rhinosinusitis 2021

I.

EXECUTIVE SUMMARY

BACKGROUND: The 5 years since the publication of the first International Consensus Statement on Allergy and Rhinology: Rhinosinusitis (ICAR-RS) has witnessed foundational progress in our understanding and treatment of rhinologic disease. These advances are reflected within the more than 40 new topics covered within the ICAR-RS-2021 as well as updates to the original 140 topics. This executive summary consolidates the evidence-based findings of the document.

METHODS

ICAR-RS presents over 180 topics in the forms of evidence-based reviews with recommendations (EBRRs), evidence-based reviews, and literature reviews. The highest grade structured recommendations of the EBRR sections are summarized in this executive summary.

RESULTS

ICAR-RS-2021 covers 22 topics regarding the medical management of RS, which are grade A/B and are presented in the executive summary. Additionally, 4 topics regarding the surgical management of RS are grade A/B and are presented in the executive summary. Finally, a comprehensive evidence-based management algorithm is provided.

CONCLUSION

This ICAR-RS-2021 executive summary provides a compilation of the evidence-based recommendations for medical and surgical treatment of the most common forms of RS.

Clinical characteristics and cytokine profiles of central-compartment-type chronic rhinosinusitis

BACKGROUND

The clinical characteristics of central-compartment-type chronic rhinosinusitis (CRS) in East Asian individuals are not clear. We sought to investigate the clinical features and the cytokine profiles of central-compartment-type CRS in our patient group.

METHODS

Adult patients diagnosed with bilateral CRS were recruited, and patients who had previously undergone sinus surgery and pansinusitis (Lund-Mackay scores >23) were excluded. Central-compartment-type CRS was defined by both endoscopic and radiological features. The symptoms, inhalant allergen sensitization status, endoscopic findings, and radiological assessments were recorded and compared between patients with central-compartment-type CRS and other types of CRS. We also examined the extent of tissue eosinophilia and specific cytokine protein levels (eosinophil cationic protein [ECP], myeloperoxidase [MPO], immunoglobulin E [IgE], interleukin [IL]-4, IL-5, and IL-13) in the sinonasal tissues.

RESULTS

Central-compartment-type CRS was found in 16 (23.9%) patients, and non-central-compartment-type CRS was found in 51 (76.1%) patients. Hyposmia or anosmia as the major symptom was more common in the central-compartment-type CRS group. The numbers of eosinophils in tissue and serum were significantly higher in the central-compartment-type CRS patients. The presence of allergen sensitization was not significantly different between groups. The levels of IL-5 and IL-13 were increased in middle turbinate tissues of patients with central-compartment-type CRS.

CONCLUSION

Central-compartment-type CRS was associated with hyposmia or anosmia, eosinophilic subtypes, and elevated levels of IL-5 and IL-13 in middle turbinate tissues but not necessarily correlated with allergic disease in our patients.

Serum amyloid A is a soluble pattern recognition receptor that drives type 2 immunity

The molecular basis for the propensity of a small number of environmental proteins to provoke allergic responses is largely unknown. Herein, we report that mite group 13 allergens of the fatty acid-binding protein (FABP) family are sensed by an evolutionarily conserved acute-phase protein, serum amyloid A1 (SAA1), that promotes pulmonary type 2 immunity. Mechanistically, SAA1 interacted directly with allergenic mite FABPs (Der p 13 and Blo t 13). The interaction between mite FABPs and SAA1 activated the SAA1-binding receptor, formyl peptide receptor 2 (FPR2), which drove the epithelial release of the type-2-promoting cytokine interleukin (IL)-33 in a SAA1-dependent manner. Importantly, the SAA1-FPR2-IL-33 axis was upregulated in nasal epithelial cells from patients with chronic rhinosinusitis. These findings identify an unrecognized role for SAA1 as a soluble pattern recognition receptor for conserved FABPs found in common mite allergens that initiate type 2 immunity at mucosal surfaces.

p38 MAPK signalling regulates cytokine production in IL-33 stimulated Type 2 Innate Lymphoid cells

Type 2 Innate lymphoid cells (ILC2s) are implicated in helminth infections and asthma where they play a role in the production of Th2-type cytokines. ILC2s express the IL-33 receptor and are a major cell type thought to mediate the effects of this cytokine in vivo. To study the signalling pathways that mediate IL-33 induced cytokine production, a culture system was set up to obtain pure populations of ILC2s from mice. Inhibitors of the p38α/β and ERK1/2 MAPK pathways reduced the production of IL-5, IL-6, IL-9, IL-13 and GM-CSF by ILC2 in response to IL-33, with inhibition of p38 having the greatest effect. MK2 and 3 are kinases activated by p38α; MK2/3 inhibitors or knockout of MK2/3 in mice reduced the production of IL-6 and IL-13 (two cytokines implicated in asthma) but not IL-5, IL-9 or GM-CSF in response to IL-33. MK2/3 inhibition also suppressed IL-6 and IL-13 production by human ILC2s. MK2/3 were required for maximal S6 phosphorylation, suggesting an input from the p38α-MK2/3 pathway to mTOR1 activation in ILC2s. The mTORC1 inhibitor rapamycin also reduced IL-6 and IL-13 production, which would be consistent with a model in which MK2/3 regulate IL-6 and IL-13 via mTORC1 activation in ILC2s.

House dust mite allergens induce interleukin 33 (IL-33) synthesis and release from keratinocytes via ATP-mediated extracellular signaling

In atopic diseases, the epithelium releases cytokines and chemokines that initiate skin inflammation. Atopic dermatitis (AD) is characterized by a disrupted epidermal barrier and is triggered or exacerbated by environmental stimuli such as house dust mite (HDM) allergens. The proinflammatory cytokine interleukin 33 (IL-33) plays an important role in the pathogenesis of AD, but how IL-33 production in keratinocytes is elicited by HDM is unknown. To that end, here we stimulated monolayer-cultured human keratinocytes and human living skin equivalents with Dermatophagoides pteronyssinus HDM extract to investigate its effects on IL-33 production from keratinocytes. The HDM extract induced intracellular expression of IL-33 and modulated its processing and maturation, triggering rapid IL-33 release from keratinocytes. Group 1 HDM allergen but not group 2 HDM allergen elicited IL-33 production. An ATP assay of keratinocyte culture supernatants revealed an acute and transient accumulation of extracellular ATP immediately after the HDM extract stimulation. Using the broad-spectrum P2 antagonist suramin, the specific purinergic receptor P2Y2 (P2RY2) antagonist AR-C118925XX, and P2RY2-specific siRNA, we discovered that the HDM extract-induced IL-33 expression was mainly dependent on extracellular ATP/P2Y2 signaling mediated by transactivation of epidermal growth factor receptor, followed by activation of the ERK kinase signaling pathway. Moreover, HDM extract-induced release of 25-kDa IL-33 from the keratinocytes depended on an extracellular ATP/P2 signaling-mediated intracellular Ca²⁺ increase. Our study demonstrates the new mechanism controlling the induction and maturation of keratinocyte-produced IL-33 by HDM allergens, an innate immune process that might play a role in AD development or severity.

Key role of the epithelium in chronic upper airways diseases

The respiratory epithelium of the upper airways is a first-line defence against inhaled irritants, pathogens and allergens. It ensures a physical barrier provided by apical junctions and mucociliary clearance to avoid excessive activation of the immune system. The epithelium also forms a chemical and immunological barrier, extensively equipped to protect the airways against external aggressions before the adaptive immune system is required. Under normal circumstances, the epithelium is capable of recovering rapidly after damage. This manuscript reviews these main properties of the upper airway epithelium as well as its reported impairments in chronic inflammatory diseases. The knowledge on normal epithelial functions and their dysregulation in upper airway diseases should help to design new epithelial-targeted treatments.

Contributions of Innate Lymphoid Cells in Chronic Rhinosinusitis

PURPOSE OF REVIEW

To review innate lymphoid cells (ILCs) and their role in chronic rhinosinusitis (CRS).

RECENT FINDINGS

The immune system consists of the innate and adaptive response. Until the recognition of ILCs, chronic inflammatory diseases were characterized by cytokines linked only to T helper cells. However, these immune responses are now described more broadly to include contributions from both the innate and adaptive immunity. In CRS, focus had been on ILC2s in CRS with nasal polyps. These studies also highlight the importance of epithelial cell-derived cytokines in coordinating these responses. In addition to indirect crosstalk via cytokines, ILCs and T helper cells can utilize the OX40/OX40 ligand and major histocompatibility complex class II pathways to directly interact and coordinate responses. In addition to T helper cells, ILCs contribute to the inflammatory response associated with CRS. The understanding of these cells along with pathways that activate and perpetuate these cells leads to new potential therapeutic targets for CRS treatment.

Dysregulated invertebrate tropomyosin-dectin-1 interaction confers susceptibility to allergic diseases

The key factors underlying the development of allergic diseases-the propensity for a minority of individuals to develop dysfunctional responses to harmless environmental molecules-remain undefined. We report a pathway of immune counter-regulation that suppresses the development of aeroallergy and shrimp-induced anaphylaxis. In mice, signaling through epithelially expressed dectin-1 suppresses the development of type 2 immune responses through inhibition of interleukin-33 (IL-33) secretion and the subsequent recruitment of IL-13-producing innate lymphoid cells. Although this homeostatic pathway is functional in respiratory epithelial cells from healthy humans, it is dramatically impaired in epithelial cells from asthmatic and chronic rhinosinusitis patients, resulting in elevated IL-33 production. Moreover, we identify an association between a single-nucleotide polymorphism (SNP) in the dectin-1 gene loci and reduced pulmonary function in two cohorts of asthmatics. This intronic SNP is a predicted eQTL (expression quantitative trait locus) that is associated with reduced dectin-1 expression in human tissue. We identify invertebrate tropomyosin, a ubiquitous arthropod-derived molecule, as an immunobiologically relevant dectin-1 ligand that normally serves to restrain IL-33 release and dampen type 2 immunity in healthy individuals. However, invertebrate tropomyosin presented in the context of impaired dectin-1 function, as observed in allergic individuals, leads to unrestrained IL-33 secretion and skewing of immune responses toward type 2 immunity. Collectively, we uncover a previously unrecognized mechanism of protection against allergy to a conserved recognition element omnipresent in our environment.

Interleukin-33 contributes to ILC2 activation and early inflammation-associated lung injury during abdominal sepsis

Sepsis is defined as infection with organ dysfunction due to a dysregulated immune response. The lung is one of the most vulnerable organs at the onset of sepsis. Interleukin (IL)-33 can be released by injured epithelial and endothelial cells in the lung and regulate immune activation and infiltration. Therefore, we postulated that IL-33 would contribute to the immune response in the lung during sepsis. Using the cecal ligation and puncture (CLP) sepsis model, we show here that IL-33 contributes significantly to both sepsis-induced inflammation in the lung and systemic inflammatory response in the early phase of sepsis. Despite the higher intra-peritoneal bacterial burden, the absence of IL-33 resulted in less infiltration of neutrophils and monocytes into the lungs in association with lower circulating, lung and liver cytokine levels as well as reduced lung injury at 6 h after sepsis. IL-33 was required for the upregulation of IL-5 in type 2 Innate Lymphoid Cells (ILC2), while IL-5 neutralization suppressed neutrophil and monocyte infiltration in the lungs during CLP sepsis. This reduction in leukocyte infiltration in IL-33-deficient mice was reversed by administration of recombinant IL-5. These results indicate that IL-33 plays a major role in the local inflammatory changes in the lung, in part, by regulating IL-5 and this axis contributes to lung injury early after the onset of sepsis.

Sentinels at the wall: epithelial-derived cytokines serve as triggers of upper airway type 2 inflammation

Recent evidence has demonstrated an expanding role of respiratory epithelial cells in immune surveillance and modulation. Studies have been focusing on the earliest events that link epithelial injury to downstream inflammatory responses. Cytokines produced by and released from respiratory epithelial cells are among these early trigger signals. Epithelial-derived cytokines, namely thymic stromal lymphopoietin (TSLP), interleukin (IL)-25, and IL-33, have come to the forefront of recent investigations. Each of these 3 cytokines has been implicated in chronic rhinosinusitis (CRS), asthma, and atopy. Herein we review studies elucidating the roles of epithelial-derived cytokines in the pathobiology of upper airway disease, with particular emphasis on type 2 inflammatory conditions.

Oxygen matters: hypoxia as a pathogenic mechanism in rhinosinusitis

The airway epithelium is the first place, where a defense mechanism is initiated against environmental stimuli. Mucociliary transport (MCT), which is the defense mechanism of the airway and the role of airway epithelium as mechanical barriers are essential in innate immunity. To maintain normal physiologic function, normal oxygenation is critical for the production of energy for optimal cellular functions. Several pathologic conditions are associated with a decrease in oxygen tension in airway epithelium and chronic sinusitis is one of the airway diseases, which is associated with the hypoxic condition, a potent inflammatory stimulant. We have observed the overexpression of the hypoxia-inducible factor 1 (HIF-1), an essential factor for oxygen homeostasis, in the epithelium of sinus mucosa in sinusitis patients. In a series of previous reports, we have found hypoxia-induced mucus hyperproduction, especially by MUC5AC hyperproduction, disruption of epithelial barrier function by the production of VEGF, and down-regulation of junctional proteins such as ZO-1 and E-cadherin. Furthermore, hypoxia-induced inflammation by HMGB1 translocation into the cytoplasm results in the release of IL-8 through a ROS-dependent mechanism in upper airway epithelium. In this mini-review, we briefly introduce and summarize current progress in the pathogenesis of sinusitis related to hypoxia. The investigation of hypoxia-related pathophysiology in airway epithelium will suggest new insights on airway inflammatory diseases, such as rhinosinusitis for clinical application and drug development.

Toll-like receptor 9 ligands increase type I interferon induced B-cell activating factor expression in chronic rhinosinusitis with nasal polyposis

B-cell activating factor (BAFF) has been proposed to play a crucial role in the pathogenesis of chronic rhinosinusitis with nasal polyp (CRSwNP). The aim of this study was to evaluate the role of toll-like receptor (TLR) 9-mediated BAFF activation on the pathogenesis of CRSwNP. NP and uncinate tissue (UT) were obtained from patients with CRSwNP or CRS without NP, and control subjects. The expression of TLR9, high mobility group box-1 protein (HMGB1), type I interferon (IFN), BAFF, and anti-double stranded DNA (dsDNA) antibody were examined in the tissues and the cultured dispersed NP cells (DNPCs). The expression of TLR9, HMGB1, type I IFN, BAFF, and anti-dsDNA antibody were elevated in NP tissue compared to the UTs. Exposure to TLR9 agonist increased the type I IFN expression in vitro, which further increased BAFF production. In conclusion, we provided a novel therapeutic potential of TLR9 agonist in CRSwNP.

Emerging roles of innate lymphoid cells in inflammatory diseases: Clinical implications

Innate lymphoid cells (ILC) represent a group of lymphocytes that lack specific antigen receptors and are relatively rare as compared to adaptive lymphocytes. ILCs play important roles in allergic and nonallergic inflammatory diseases due to their location at barrier surfaces within the airways, gut, and skin, and they respond to cytokines produced by activated cells in their local environment. Innate lymphoid cells contribute to the immune response by the release of cytokines and other mediators, forming a link between innate and adaptive immunity. In recent years, these cells have been extensively characterized and their role in animal models of disease has been investigated. Data to translate the relevance of ILCs in human pathology, and the potential role of ILCs in diagnosis, as biomarkers and/or as future treatment targets are also emerging. This review, produced by a task force of the Immunology Section of the European Academy of Allergy and Clinical Immunology (EAACI), encompassing clinicians and researchers, highlights the role of ILCs in human allergic and nonallergic diseases in the airways, gastrointestinal tract, and skin, with a focus on new insights into clinical implications, therapeutic options, and future research opportunities.

Characterization of a novel, papain-inducible murine model of eosinophilic rhinosinusitis

BACKGROUND

Eosinophilic chronic rhinosinusitis (ECRS) is a disease characterized by eosinophilic inflammatory infiltrate and a local type 2 cytokine milieu. Current animal models fail to recapitulate many of the innate and adaptive immunologic hallmarks of the disease, thus hindering the development of effective therapeutics. In the present study, mice were exposed intranasally to the cysteine protease papain, which shares functional similarities with parasitic proteases and aeroallergens, to generate a rapidly inducible murine model of eosinophilic rhinosinusitis.

METHODS

C57BL/6 mice were intranasally instilled with 20 μg papain or heat-inactivated papain (HP) on days 0-2 and days 7-10, and then euthanized on day 11. Nasal lavage fluid (NALF) was analyzed to quantify eosinophils and inflammatory cytokine secretion. Sinonasal tissue was sectioned and stained for goblet cells or homogenized to analyze cytokine levels. Serum samples were assayed for immunoglobulin E (IgE) by enzyme-linked immunoassay. Sinonasal mucosal tissue was dissociated and analyzed by flow cytometry.

RESULTS

Compared with HP treatment, papain induced significant eosinophilia in NALF, goblet cell hyperplasia, innate and adaptive immune cell infiltration, type 2 cytokine production, and IgE responses. Flow cytometric analysis of sinonasal tissues revealed significant inflammatory cell infiltration and interleukin-13-producing cell populations.

CONCLUSION

In this study, we demonstrated that the cysteine protease papain induces allergic sinonasal eosinophilic rhinosinusitis and resembles T-helper 2 cell inflammation and innate immune characteristics of ECRS. This model permits further study into the molecular mechanisms underlying ECRS pathology and provides a model system for the evaluation of potential pharmacologic interventions.

Cyclic stretch induced IL-33 production through HMGB1/TLR-4 signaling pathway in murine respiratory epithelial cells

Interleukin 33 (IL-33), an inflammatory and mechanically responsive cytokine, is an important component of a TLR4-dependent innate immune process in mucosal epithelium. Although TLR4 also plays a role in sensing biomechanical stretch, a pathway of stretch-induced TLR4-dependent IL-33 biosynthesis has not been revealed. In the current study, we show that short term (6 h) cyclic stretch (CS) of cultured murine respiratory epithelial cells (MLE-12) increased intracellular IL-33 expression in a TLR4 dependent fashion. There was no detectable IL-33 in conditioned media in this interval. CS, however, increased release of the notable alarmin, HMGB1, and a neutralizing antibody (2G7) to HMGB1 completely abolished the CS mediated increase in IL-33. rHMGB1 increased IL-33 synthesis and this was partially abrogated by silencing TLR4 suggesting additional receptors for HMGB1 are involved in its regulation of IL-33. Collectively, these data reveal a HMGB1/TLR4/IL-33 pathway in the response of respiratory epithelium to mechanical stretch.

Innate Immune Responses to Fungal Allergens

PURPOSE OF REVIEW

In this review, we describe innate immunity to fungi and the ability of pattern recognition receptors (PRRs) to recognize fungal-associated molecular patterns (FAMPs) and danger-associated molecular patterns (DAMPs).

RECENT FINDINGS

Protective responses against fungal antigens can be divided into two parts: innate immunity and adaptive immunity. Detection of foreign substance by the innate immune system is mediated by a variety of genetically encoded receptors known as pattern recognition receptors (PRRs). These PRRs bind to PAMPs (pathogen-associated molecular patterns) and more specifically to fungal-associated molecular patterns or FAMPs on target microorganisms. They also bind to DAMPs (damage-associated molecular patterns) which are substances released due to tissue and cell damage. PRRs can be divided into several families including Toll-like receptors (TLRs), nucleotide-oligomerization domain (NOD)-like receptors (NLRs), and C-type lectin receptors. Fungal PRRs can respond to internal and external components found in fungi. In addition, a number of fungal products, including some fungal allergens, seem to mimic or represent DAMPs. Collectively, activation of these fungal PRRs alerts the innate immune system to the presence of fungal exposure and can promote both innate and adaptive immune responses.

Refractory Chronic Rhinosinusitis with Nasal Polyposis

Chronic rhinosinusitis with nasal polyposis (CRSwNP) represents a subset of chronic sinusitis with various causes. Some forms of the disease are driven by allergy, often in association with asthma. Refractory CRSwNP can be associated with cystic fibrosis and other clinical syndromes. More recent literature is presented regarding roles of innate immunity and superantigens. Effective treatment of CRSwNP requires careful endoscopic sinus surgery followed by an individualized treatment plan that often includes oral and topical steroids. Recidivism of polyps is common, and patients require long-term follow-up.

Nuclear erythroid 2-related factor 2 activation inhibits house dust mite-induced sinonasal epithelial cell barrier dysfunction

BACKGROUND

Dysregulated sinonasal epithelial cell (SNEC) barrier function has been proposed to contribute to the pathogenesis of sinonasal inflammatory conditions such as allergic rhinitis (AR) and chronic rhinosinusitis (CRS). Allergens such as house dust mite (HDM) have been reported to disrupt SNEC barrier integrity. We have recently identified nuclear erythroid 2-related factor 2 (Nrf2) activation via sulforaphane (SFN) stimulation to stabilize SNEC barrier function. The purpose of this study was to explore whether Nrf2 activation could ameliorate HDM-induced SNEC barrier dysfunction.

METHODS

Human SNECs (HSNECs) were grown from patients at the air-liquid interface (ALI). HSNECs were stimulated with HDM with or without pharmacologic activation of Nrf2 with SFN. HSNECs were then stained for the epithelial cell junction protein zonula occludens-1 (ZO-1) and cell surface localization was evaluated by confocal microscopy. Transepithelial electrical resistance (TER) and paracellular fluorescein isothiocyanate (FITC)-dextran permeability was measured in response to stimulation with HDM and SFN.

RESULTS

HDM stimulation caused a global disruption of the protein ZO-1 along with an associated decrease in TER (p < 0.001) and increased FITC-dextran paracellular permeability (p < 0.0001). Enhancing Nrf2 activation through treatment with SFN prior to stimulation with HDM was associated with increased localization of ZO-1 at the cell surface and statistically significant increases in TER (p < 0.05) and decrease in paracellular FITC-dextran permeability (p < 0.001).

CONCLUSION

This is the first study to demonstrate that HDM-induced SNEC barrier dysfunction may be preventable by Nrf2 activation. The Nrf2 antioxidant pathway may represent a potential therapeutic target for allergen-induced sinonasal inflammation.

HMGB1-TLR4 signaling contributes to the secretion of interleukin 6 and interleukin 8 by nasal epithelial cells

BACKGROUND

Alarmins play important roles in the pathogenesis of inflammatory and autoimmune diseases. However, the role of the alarmin protein high-mobility group box 1 (HMGB1) in upper airway inflammation is unclear.

OBJECTIVE

To determine if HMGB1 is present in the nasal mucosa and, if so, to elucidate its role in upper airway inflammation.

METHODS

Nasal secretions were collected from a total of 32 patients with chronic rhinosinusitis with nasal polyp, allergic rhinitis, and control subjects. The concentration of HMGB1 in nasal secretions and its tissue and cellular localization were examined by enzyme immunoassays and immunofluorescent staining of nasal polyps and cultured nasal epithelial cells. We then examined whether nasal epithelial cells secrete HMGB1 after inflammatory stimulation by tumor necrosis factor (TNF) α. The effects of HMGB1 on the production and secretion of interleukin (IL) 6 and IL-8 were also examined in cultured nasal epithelial cells.

RESULTS

Significantly higher concentrations of HMGB1 were found in nasal secretions from patients with chronic rhinosinusitis with nasal polyp or allergic rhinitis compared with the control subjects. HMGB1 expression was localized in the nuclei of epithelial cells and other constitutive cells in nasal polyps and in the nuclei of cultured nasal epithelial cells. TNF-α stimulated the production and secretion of HMGB1 by cultured nasal epithelial cells. HMGB1 stimulated the production and secretion of IL-6 and IL-8 by cultured nasal epithelial cells, and anti-toll-like receptor 4 blocking antibody significantly inhibited HMGB1-induced secretion of IL-6 and IL-8.

CONCLUSIONS

Nasal secretions contain substantial amounts of HMGB1. TNF-α stimulates the production of HMGB1, which, in turn, upregulates the production and secretion of IL-6 and IL-8 by nasal epithelial cells via toll-like receptor 4, which indicated that HMGB1 plays an important role in the pathogenesis of upper airway inflammation.

HMGB1 in the Pathogenesis of Nasal Inflammatory Diseases and its Inhibition as New Therapeutic Approach: A Review from the Literature

Introduction  This study is a systematic review on recent developments about the importance of HMGB1 protein in the pathogenesis of rhino-sinusal inflammatory diseases. We also report data on the use of 18-β-glycyrrhetic acid (GA), which has been shown able to inhibit the pro-inflammatory activities of HMGB1, in young patients affected by allergic rhinitis and complaining of nasal obstruction as main symptom.

Objectives  The objective of this study was to review the literature to demonstrate the importance of HMGB1 in the pathogenesis of nasal inflammatory disorders and understand whether the inhibition of this protein may be an efficacious and innovative therapeutic strategy for patients with rhino-sinusal inflammation.

Data Synthesis  Authors searched for pertinent articles indexed in PubMed, Scopus, and other health journals between 2004 and 2015.

In total, the authors gathered 258 articles: 219 articles through Pubmed and 39 articles from other search engines. The search terms used were as follows: HMGB1 AND “respiratory epithelium,” “airway inflammation,” “rhinitis,” “allergic rhinitis,” “rhinosinusitis,” “nasal polyposis,” “glycyrrhetic acid,” “children.”

Conclusions  Patients with severe symptoms have the highest serum levels and the highest extracellular expression of HMGB1. GA inhibits HMGB1 chemotactic and mitogenic function by a scavenger mechanism on extracellular HMGB1 accumulation stimulated by lipopolysaccharides in vitro. Treatment of allergic rhinitis with GA is not associated with local or systemic side effects in children and adults.

Reversal of cigarette smoke extract-induced sinonasal epithelial cell barrier dysfunction through Nrf2 Activation

BACKGROUND

Environmental factors such as inhaled pollutants like cigarette smoke may play a significant role in diseases of the upper airway including chronic rhinosinusitis (CRS). Recent studies have shown that cigarette smoke causes impaired airway epithelial cell barrier function likely through environmental oxidative stress related pathways. The purpose of this study is to explore whether enhancing nuclear factor erythroid 2 [NF-E2]-related factor 2 [Nrf2], the body's master antioxidant system, can ameliorate cigarette smoke-induced sinonasal epithelial cell (SNEC) barrier dysfunction.

METHODS

Human SNECs (HSNECs) were grown from control patients at the air-liquid interface (ALI). HSNECs were stimulated with cigarette smoke extract (CSE) with and without pharmacologic activation of Nrf2. HSNECs were then stained for the epithelial cell junctional proteins zonula occludens 1 (ZO-1) and junctional adhesion molecule A (JAM-A) using confocal microscopy. In addition, transepithelial electrical resistance (TER) was measured in cultures before and after stimulation with CSE.

RESULTS

CSE stimulation caused a global disruption of the epithelial junctional proteins ZO-1 and JAM-A along with an associated decrease in TER levels. Enhancing Nrf2 levels prior to stimulation with CSE was associated with increased localization of ZO-1 and JAM-A levels at the cell surface and statistically significant increases in TER levels.

CONCLUSION

This is the first study to demonstrate that cigarette smoke induced SNEC barrier dysfunction is reversible by Nrf2 activation. The Nrf2 antioxidant pathway may represent a potential therapeutic target for cigarette smoke-associated sinonasal inflammation.

HMGB1 regulates IL-33 expression in acute respiratory distress syndrome

The development and progression of acute respiratory distress syndrome (ARDS) has been shown to be regulated by cytokines. IL-33 and HMGB1 are conventionally considered as nuclear proteins and have a proinflammatory role. Studies have confirmed that HMGB1 has a significant role in ARDS, but few studies have provided direct evidence to confirm that IL33 is involved in ARDS. The purpose of our study was to determine whether IL-33 is elevated in ARDS and the relationship between IL-33 and HMGB1 in ARDS. We established a mouse model of LPS-induced lung inflammation/injury. Serum, bronchoalveolar lavage fluid (BALF) and lung tissues were obtained to determine the related indicators. IL-33 levels in both the serum, BALF and lungs were significantly increased at 24h after LPS administration compared to the control group. We also found that HMGB1 and other Th1 cytokine/chemokine levels in serum and BALF were also significantly elevated, but the Th2 cytokine levels in serum and BALF didn't increase. To further study the relationship between IL-33 and HMGB1, mice were pretreated with glycyrrhizin (an inhibitor of HMGB1) prior to LPS administration. We found that the expression of IL-33 and HMGB1 were markedly lower than those in the LPS group and the lung injury was ameliorated. The levels of other Th1 cytokines and chemokines in serum and BALF were also significantly decreased. The results showed that IL-33 is likely a major factor in ARDS, and the release of HMGB1 may be correlated with up-regulation of IL-33 expression.

Drivers of chronic rhinosinusitis: Inflammation versus infection

Studies of the underlying cause or causes of chronic rhinosinusitis (CRS) over the past 20 or more years have expanded from a focus on systemic immune and allergic mechanisms to an intense search for the underlying drivers of mucosal inflammation. These drivers involve mucosal inflammatory pathways that become activated by allergens, microbial stimuli, or poorly understood exogenous or endogenous stimuli. The holy grail in the study of CRS is to identify specific drivers of mucosal inflammation and translate these into more effective treatment for CRS. Certain deficiencies in local innate immunity have been described in patients with CRS that predispose to increased sinus mucosal bacterial colonization/infection, including deficient local production of antimicrobial lactoferrin and deficient functioning of the bitter taste receptor TAS2R38. Conversely, certain innate factors, namely IL-25, IL-33, and thymic stromal lymphopoietin (TSLP), are elaborated by sinus epithelial cells in response to microbial stimulation or airway injury and promote local TH2 inflammation. The precise physiologic role of these factors in innate or adaptive immunity is unclear, although IL-33 might function as an alarmin triggered by damage-associated molecular patterns. The cytokines IL-25 and TSLP, similarly promote proinflammatory tissue responses. Another feature of epithelial dysregulation in patients with CRS is overproduction of eosinophil-promoting C-C chemokines by sinus epithelium, perhaps driven in part through innate stimuli, as well as TH2 cytokines, such as IL-13. Strategies to reduce the microbial stimulation of maladaptive TH2 inflammation or to suppress the local elaboration of TH2-promoting epithelial factors, such as IL-33, have potential therapeutic benefit in patients with CRS, although the extent to which this is realized in patient care remains limited at present. This rostrum will summarize my views on the major microbial drivers of mucosal inflammation and dysregulation of innate TH2-promoting factors in patients with CRS based on recent experimental data.

Innate and Adaptive Immune Response to Fungal Products and Allergens

Exposure to fungi and their products is practically ubiquitous, yet most of this is of little consequence to most healthy individuals. This is because there are a number of elaborate mechanisms to deal with these exposures. Most of these mechanisms are designed to recognize and neutralize such exposures. However, in understanding these mechanisms it has become clear that many of them overlap with our ability to respond to disruptions in tissue function caused by trauma or deterioration. These responses involve the innate and adaptive immune systems usually through the activation of nuclear factor kappa B and the production of cytokines that are considered inflammatory accompanied by other factors that can moderate these reactivities. Depending on different genetic backgrounds and the extent of activation of these mechanisms, various pathologies with resulting symptoms can ensue. Complicating this is the fact that these mechanisms can bias toward type 2 innate and adaptive immune responses. Thus, to understand what we refer to as allergens from fungal sources, we must first understand how they influence these innate mechanisms. In doing so it has become clear that many of the proteins that are described as fungal allergens are essentially homologues of our own proteins that signal or cause tissue disruptions.

P-glycoprotein regulates Staphylococcus aureus enterotoxin B-stimulated interleukin-5 and thymic stromal lymphopoietin secretion in organotypic mucosal explants

BACKGROUND

T-helper 2 (Th2) inflammation is a hallmark of chronic rhinosinusitis with nasal polyps (CRSwNP) although the pathogenesis is poorly understood. P-glycoprotein (permeability glycoprotein, P-gp) is an efflux pump that is capable of regulating cytokine transport and is expressed within sinonasal mucosa. The purpose of this study was to examine if the oversecretion of interleukin 5 (IL-5) and thymic stromal lymphopoietin (TSLP) in CRSwNP could be explained through P-gp-mediated secretory pathways.

METHODS

Fifteen ethmoid mucosal explants were harvested from patients with CRS (n = 10) and CRSwNP (n = 10) and stimulated with Staphylococcus aureus enterotoxin B (SEB). P-gp was inhibited using zosuquidar trihydrochloride (herein Zosuquidar). P-gp expression was measured using real-time polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA). IL-5, IL-8, and TSLP secretion were quantified using ELISA.

RESULTS

P-gp protein was overexpressed in CRSwNP (28.32 ± 25.94 ng/mL per mg explant) as compared to CRS (10.74 ± 8.61; p = 0.01, 2-tailed Mann-Whitney U test). There was no difference in messenger RNA (mRNA) expression. SEB induced a significant increase in IL-5 and TSLP but not IL-8 secretion relative to control in the CRSwNP explants only. Subsequent P-gp inhibition significantly reduced IL-5 and TSLP secretion (p = 0.04 for both, 2-tailed Student t test) to control levels. The concentration of IL-5 and TSLP secretion were strongly and significantly correlated to the concentration of P-gp within the same explant (IL-5: r = 0.791, p = 0.001; TSLP: r = 0.687, p = 0.003; 2-tailed Spearman's rank-order correlation).

CONCLUSION

P-gp protein is expressed at higher concentrations in CRSwNP as compared to CRS. This overexpression directly contributes to the relative hypersecretion of IL-5 and TSLP. These findings suggest a novel mechanism for Th2 skewing in CRSwNP.

Pathogenesis of nasal polyposis

Chronic rhinosinusitis with nasal polyps (CRSwNP) is a complex inflammatory condition that affects a large proportion of the population world-wide and is associated with high cost of management and significant morbidity. Yet, there is a lack of population-based epidemiologic studies using current definitions of CRSwNP, and the mechanisms that drive pathogenesis in this disease remain unclear. In this review, we summarize the current evidence for the plethora of factors that likely contribute to CRSwNP pathogenesis. Defects in the innate function of the airway epithelial barrier, including diminished expression of antimicrobial products and loss of barrier integrity, combined with colonization by fungi and bacteria likely play a critical role in the development of chronic inflammation in CRSwNP. This chronic inflammation is characterized by elevated expression of many key inflammatory cytokines and chemokines, including IL-5, thymic stromal lymphopoietin and CCL11, that help to initiate and perpetuate this chronic inflammatory response. Together, these factors likely combine to drive the influx of a variety of immune cells, including eosinophils, mast cells, group 2 innate lymphoid cells and lymphocytes, which participate in the chronic inflammatory response within the nasal polyps. Importantly, however, future studies are needed to demonstrate the necessity and sufficiency of these potential drivers of disease in CRSwNP. In addition to the development of new tools and models to aid mechanistic studies, the field of CRSwNP research also needs the type of robust epidemiologic data that has served the asthma community so well. Given the high prevalence, costs and morbidity, there is a great need for continued research into CRS that could facilitate the development of novel therapeutic strategies to improve treatment for patients who suffer from this disease.

Physiologic concentrations of HMGB1 have no impact on cytokine-mediated eosinophil survival or chemotaxis in response to Eotaxin-2 (CCL24)

HMGB1 is an alarmin that can stimulate the innate immune system alone or in a complex with other inflammatory mediators. Given the recent interest in HMGB1 with respect to the pathogenesis of eosinophil-associated disorders, including asthmatic inflammation and chronic rhinosinusitis, we have explored the role of this mediator and in promoting eosinophil activation. HMGB1 receptors RAGE and TLR4 but not TLR2 were detected on freshly isolated human eosinophils from healthy donors. Physiologic and relevant pathophysiologic levels of biologically-active HMGB1 had no effect on survival of human eosinophils alone or in combination with pro-survival cytokines IL-5, IL-3, or GM-CSF, and increasing concentrations of HMGB1 had no impact on surface expression of RAGE, TLR2 or TLR4. Similarly, HMGB1 did not elicit chemotaxis of human eosinophils alone and had no effect in combination with the eosinophil chemotactic agent, eotaxin-2 (CCL24). However, surface expression of TLR2 and TLR4 increased in response to cell stress, notably on eosinophils that remain viable after 48 hours without IL-5. As such, HMGB1 signaling on eosinophils may be substantially more detailed, and may involve complex immunostimulatory pathways other than or in addition to those evaluated here.

Level of secreted HMGB1 correlates with severity of inflammation in chronic rhinosinusitis

OBJECTIVE

High mobility group box 1 (HMGB1) protein is a chromatin protein that functions as a proinflammatory cytokine when secreted in response to inflammatory stimuli. The purpose of this study was to determine the relationship between the HMGB1 level in nasal secretions and the severity of inflammation in chronic rhinosinusitis.

STUDY DESIGN

This was a cross-sectional study.

METHODS

Nasal secretions were obtained by irrigation of the affected sinonasal cavities with normal saline. Total 63 nasal lavage fluid samples were collected from 38 patients with chronic rhinosinusitis who underwent endoscopic sinus surgery. Levels of HMGB1 and tumor necrosis factor alpha, interleukin (IL)-1β, and IL-8 were determined by enzyme-linked immunoassay. Severity of inflammation was assessed by the Lund-Mackay scoring system, which is based on preoperative computed tomography scans. Concurrent medical disorders, presence of nasal polyps, septal deviation, and allergic rhinitis were also investigated.

RESULTS

The level of HMGB1 in nasal lavage fluid was positively correlated with the Lund-Mackay score. The score was the only factor associated with HMGB1 by univariate and multivariate analysis. Other cytokines, with the exception of IL-8, were not correlated with the Lund-Mackay score.

CONCLUSION

Our results showed that HMGB1 is secreted into the extracellular area space in the upper airway, and HMGB1 levels in nasal lavage fluid correlate with severity of inflammation, as assessed by the Lund-Mackay staging system for chronic rhinosinusitis. These results provide evidence for HMGB1 as an inflammatory mediator associated with the severity of chronic rhinosinusitis.