The role of IL-33 and mast cells in allergy and inflammation

Clinical and Immunological Features of Bronchial Asthma Comorbid Chronic Urticaria: A Retrospective Study

INTRODUCTION

Asthma and chronic urticaria (CU) are two high prevalent diseases and often coexist. The underlying relationship and potential immunological mechanism between the two diseases are still unclear. The objective of this study was to investigate the clinical and immunological feature of asthma comorbid with CU.

METHODS

A retrospective study was conducted. Fifty patients with asthma comorbid CU, 50 patients with asthma, and 50 patients with CU alone were included. Age and sex of the patients enrolled were matched. Data of demographic characteristics, clinical manifestations including disease severity (frequency of symptoms, age of onset, disease duration, symptom score, complication with allergic rhinitis) as well as serum immunological index including total IgE (tIgE), allergen-specific IgE (sIgE), and food-specific IgG4 (FS-IgG4), were collected and analyzed.

RESULTS

No significant differences in the frequency of symptoms, age of onset, and disease duration were found among the three groups. The score of asthma control test (ACT) in patients with asthma comorbid CU was significantly lower than that of asthma (p = 0.005); however, compared with patients with CU, the 7-day urticaria activity score (UAS7) of patients with asthma comorbid CU did not show obvious differences. Immunological index showed that the positive rates of tIgE, house dust mite (HDM)-sIgE, and FS-IgG4 were different among the three groups (p < 0.05). Patients with asthma comorbid CU had the highest rate of positive tIgE, moderate and severe positive sIgE to HDM. Egg-specific IgG4 (egg-sIgG4) had the highest positive rate in all groups. Patients of asthma comorbid CU obtained the highest rate of severe positive of egg-sIgG4.

CONCLUSION

Our results demonstrated that patients with asthma comorbid CU have lower control level of asthma symptoms, higher tIgE and HDM-sIgE level, and highest rate of severe positive egg-sIgG4. These results indicate that comorbidity of CU in asthma obviously increases the severity of allergens.

A Narrative Review of the IL-18 and IL-37 Implications in the Pathogenesis of Atopic Dermatitis and Psoriasis: Prospective Treatment Targets

Atopic dermatitis and psoriasis are prevalent inflammatory skin conditions that significantly impact the quality of life of patients, with diverse treatment options available. Despite advances in understanding their underlying mechanisms, recent research highlights the significance of interleukins IL-18 and IL-37, in Th1, Th2, and Th17 inflammatory responses, closely associated with the pathogenesis of psoriasis and atopic dermatitis. Hence, IL-18 and IL-37 could potentially become therapeutic targets. This narrative review synthesizes knowledge on these interleukins, their roles in atopic dermatitis and psoriasis, and emerging treatment strategies. Findings of a literature search up to 30 May 2024, underscore a research gap in IL-37-targeted therapies. Conversely, IL-18-focused treatments have demonstrated promise in adult-onset Still's Disease, warranting further exploration for their potential efficacy in psoriasis and atopic dermatitis.

IL-10 Differentially Promotes Mast Cell Responsiveness to IL-33, Resulting in Enhancement of Type 2 Inflammation and Suppression of Neutrophilia

Mast cells (MCs) play critical roles in the establishment of allergic diseases. We recently demonstrated an unexpected, proinflammatory role for IL-10 in regulating MC responses. IL-10 enhanced MC activation and promoted IgE-dependent responses during food allergy. However, whether these effects extend to IgE-independent stimuli is not clear. In this article, we demonstrate that IL-10 plays a critical role in driving IL-33-mediated MC responses. IL-10 stimulation enhanced MC expansion and degranulation, ST2 expression, IL-13 production, and phospho-relA upregulation in IL-33-treated cells while suppressing TNF-α. These effects were partly dependent on endogenous IL-10 and further amplified in MCs coactivated with both IL-33 and IgE/Ag. IL-10's divergent effects also extended in vivo. In a MC-dependent model of IL-33-induced neutrophilia, IL-10 treatment enhanced MC responsiveness, leading to suppression of neutrophils and decreased TNF-α. In contrast, during IL-33-induced type 2 inflammation, IL-10 priming exacerbated MC activity, resulting in MC recruitment to various tissues, enhanced ST2 expression, induction of hypothermia, recruitment of eosinophils, and increased MCPT-1 and IL-13 levels. Our data elucidate an important role for IL-10 as an augmenter of IL-33-mediated MC responses, with implications during both allergic diseases and other MC-dependent disorders. IL-10 induction is routinely used as a prognostic marker of disease improvement. Our data suggest instead that IL-10 can enhance ST2 responsiveness in IL-33-activated MCs, with the potential to both aggravate or suppress disease severity depending on the inflammatory context.

Endothelial cell dynamics in sepsis-induced acute lung injury and acute respiratory distress syndrome: pathogenesis and therapeutic implications

Sepsis, a prevalent critical condition in clinics, continues to be the leading cause of death from infections and a global healthcare issue. Among the organs susceptible to the harmful effects of sepsis, the lungs are notably the most frequently affected. Consequently, patients with sepsis are predisposed to developing acute lung injury (ALI), and in severe cases, acute respiratory distress syndrome (ARDS). Nevertheless, the precise mechanisms associated with the onset of ALI/ARDS remain elusive. In recent years, there has been a growing emphasis on the role of endothelial cells (ECs), a cell type integral to lung barrier function, and their interactions with various stromal cells in sepsis-induced ALI/ARDS. In this comprehensive review, we summarize the involvement of endothelial cells and their intricate interplay with immune cells and stromal cells, including pulmonary epithelial cells and fibroblasts, in the pathogenesis of sepsis-induced ALI/ARDS, with particular emphasis placed on discussing the several pivotal pathways implicated in this process. Furthermore, we discuss the potential therapeutic interventions for modulating the functions of endothelial cells, their interactions with immune cells and stromal cells, and relevant pathways associated with ALI/ARDS to present a potential therapeutic strategy for managing sepsis and sepsis-induced ALI/ARDS.

IL-33 Induces Cellular and Exosomal miR-146a Expression as a Feedback Inhibitor of Mast Cell Function

IL-33 is an inflammatory cytokine that promotes allergic disease by activating group 2 innate lymphoid cells, Th2 cells, and mast cells. IL-33 is increased in asthmatics, and its blockade suppresses asthma-like inflammation in mouse models. Homeostatic control of IL-33 signaling is poorly understood. Because the IL-33 receptor, ST2, acts via cascades used by the TLR family, similar feedback mechanisms may exist. MicroRNA (miR)-146a is induced by LPS-mediated TLR4 signaling and serves as a feedback inhibitor. Therefore, we explored whether miR-146a has a role in IL-33 signaling. IL-33 induced cellular and exosomal miR-146a expression in mouse bone marrow-derived mast cells (BMMCs). BMMCs transfected with a miR-146a antagonist or derived from miR-146a knockout mice showed enhanced cytokine expression in response to IL-33, suggesting that miR-146a is a negative regulator of IL-33-ST2 signaling. In vivo, miR-146a expression in plasma exosomes was elevated after i.p. injection of IL-33 in wild-type but not mast cell-deficient KitW-sh/W-sh mice. Finally, KitW-sh/W-sh mice acutely reconstituted with miR-146a knockout BMMCs prior to IL-33 challenge had elevated plasma IL-6 levels compared with littermates receiving wild-type BMMCs. These results support the hypothesis that miR-146a is a feedback regulator of IL-33-mediated mast cell functions associated with allergic disease.

Mast cells in the autonomic nervous system and potential role in disorders with dysautonomia and neuroinflammation

Mast cells (MC) are ubiquitous in the body, and they are critical for not only in allergic diseases but also in immunity and inflammation, including having potential involvement in the pathophysiology of dysautonomias and neuroinflammatory disorders. MC are located perivascularly close to nerve endings and sites such as the carotid bodies, heart, hypothalamus, the pineal gland, and the adrenal gland that would allow them not only to regulate but also to be affected by the autonomic nervous system (ANS). MC are stimulated not only by allergens but also many other triggers including some from the ANS that can affect MC release of neurosensitizing, proinflammatory, and vasoactive mediators. Hence, MC may be able to regulate homeostatic functions that seem to be dysfunctional in many conditions, such as postural orthostatic tachycardia syndrome, autism spectrum disorder, myalgic encephalomyelitis/chronic fatigue syndrome, and Long-COVID syndrome. The evidence indicates that there is a possible association between these conditions and diseases associated with MC activation. There is no effective treatment for any form of these conditions other than minimizing symptoms. Given the many ways MC could be activated and the numerous mediators released, it would be important to develop ways to inhibit stimulation of MC and the release of ANS-relevant mediators.

The IL-33/ST2 axis is protective against acute inflammation during the course of periodontitis

Periodontitis, which is induced by repeated bacterial invasion and the ensuing immune reactions that follow, is the leading cause of tooth loss. Periodontal tissue is comprised of four different components, each with potential role in pathogenesis, however, most studies on immune responses focus on gingival tissue. Here, we present a modified ligature-induced periodontitis model in male mice to analyze the pathogenesis, which captures the complexity of periodontal tissue. We find that the inflammatory response in the peri-root tissues and the expression of IL-6 and RANKL by Thy-1.2- fibroblasts/stromal cells are prominent throughout the bone destruction phase, and present already at an early stage. The initiation phase is characterized by high levels of ST2 (encoded by Il1rl1) expression in the peri-root tissue, suggesting that the IL-33/ST2 axis is involved in the pathogenesis. Both Il1rl1- and Il33-deficient mice exhibit exacerbated bone loss in the acute phase of periodontitis, along with macrophage polarization towards a classically activated phenotype and increased neutrophil infiltration, indicating a protective role of the IL-33/ST2 axis in acute inflammation. Thus, our findings highlight the hidden role of the peri-root tissue and simultaneously advance our understanding of the etiology of periodontitis via implicating the IL-33/ST2 axis.

Communication between Mast Cells and Group 2 Innate Lymphoid Cells in the Skin

The skin is a dynamic organ with a complex immune network critical for maintaining balance and defending against various pathogens. Different types of cells in the skin, such as mast cells (MCs) and group 2 innate lymphoid cells (ILC2s), contribute to immune regulation and play essential roles in the early immune response to various triggers, including allergens. It is beneficial to dissect cell-to-cell interactions in the skin to elucidate the mechanisms underlying skin immunity. The current manuscript concentrates explicitly on the communication pathways between MCs and ILC2s in the skin, highlighting their ability to regulate immune responses, inflammation, and tissue repair. Furthermore, it discusses how the interactions between MCs and ILC2s play a crucial role in various skin conditions, such as autoimmune diseases, dermatological disorders, and allergic reactions. Understanding the complex interactions between MCs and ILC2s in different skin conditions is crucial to developing targeted treatments for related disorders. The discovery of shared pathways could pave the way for novel therapeutic interventions to restore immunological balance in diseased skin tissues.

Serum levels of interleukin-33, soluble ST2 and IgE in patients with asthma: a case-control study

INTRODUCTION

Interleukins play a very important role in the pathophysiology of asthma. Interleukin-33 (IL-33) is a partially explored cytokine in asthma. It binds with a specific receptor called suppression of tumorigenicity 2 (ST2). The study aims to evaluate the serum levels of IL-33, sST2 and IgE in asthmatic patients and healthy controls and its further association with the forced expiratory volume in one second (FEV 1%) and absolute eosinophil count.

MATERIALS AND METHODS

We enrolled 100 asthmatic patients and 57 healthy subjects for the study. We measured serum levels of IgE, IL-33, and sST2. Based on serum IgE levels, patients were divided into allergic and non-allergic groups. Statistical analysis was done by using Graph pad prism software 8.

RESULTS

We found significantly elevated levels of IL-33 and IgE in asthmatic patients as compared to healthy subjects. However, sST2 levels were significantly lower in asthmatic patients than in healthy subjects. FEV1% values were decreased in uncontrolled asthmatic patients. In addition, serum levels of IL-33 were significantly correlated with the IgE. Furthermore, we found a significant correlation between IL-33 and AEC in allergic asthmatic patients.

CONCLUSION

In this study, we reported elevated IL-33 and IgE levels and decreased sST2 levels in asthmatic patients compared to healthy controls. IL-33 and sST2 may act as inflammatory biomarkers for allergic diseases such as asthma.

Potential Role of IL-37 in Atopic Dermatitis

Interleukin 37 (IL-37) is a recently discovered member of the IL-1 cytokine family that appears to have anti-inflammatory and immunosuppressive effects in various diseases. IL-37 acts as a dual-function cytokine, exerting its effect extracellularly by forming a complex with the receptors IL-18 α (IL-18Rα) and IL-1R8 and transmitting anti-inflammatory signals, as well as intracellularly by interacting with Smad3, entering the nucleus, and inhibiting the transcription of pro-inflammatory genes. Consequently, IL-37 is linked to IL-18, which plays a role in the pathogenesis of atopic dermatitis (AD), consistent with our studies. Some isoforms of IL-37 are expressed by keratinocytes, monocytes, and other skin immune cells. IL-37 has been found to modulate the skewed T helper 2 (Th2) inflammation that is fundamental to the pathogenesis of AD. This review provides an up-to-date summary of the function of IL-37 in modulating the immune system and analyses its potential role in the pathogenesis of AD. Moreover, it speculates on IL-37's hypothetical value as a therapeutic target in the treatment of AD.

IL-33 priming and antigenic stimulation synergistically promote the transcription of proinflammatory cytokine and chemokine genes in human skin mast cells

BACKGROUND

Antigenic stimulation through cross-linking the IgE receptor and epithelial cell-derived cytokine IL-33 are potent stimuli of mast cell (MC) activation. Moreover, IL-33 primes a variety of cell types, including MCs to respond more vigorously to external stimuli. However, target genes induced by the combined IL-33 priming and antigenic stimulation have not been investigated in human skin mast cells (HSMCs) in a genome-wide manner. Furthermore, epigenetic changes induced by the combined IL-33 priming and antigenic stimulation have not been evaluated.

RESULTS

We found that IL-33 priming of HSMCs enhanced their capacity to promote transcriptional synergy of the IL1B and CXCL8 genes by 16- and 3-fold, respectively, in response to combined IL-33 and antigen stimulation compared to without IL-33 priming. We identified the target genes in IL-33-primed HSMCs in response to the combined IL-33 and antigenic stimulation using RNA sequencing (RNA-seq). We found that the majority of genes synergistically upregulated in the IL-33-primed HSMCs in response to the combined IL-33 and antigenic stimulation were predominantly proinflammatory cytokine and chemokine genes. Moreover, the combined IL-33 priming and antigenic stimulation increase chromatin accessibility in the synergy target genes but not synergistically. Transcription factor binding motif analysis revealed more binding sites for NF-κB, AP-1, GABPA, and RAP1 in the induced or increased chromatin accessible regions of the synergy target genes.

CONCLUSIONS

Our study demonstrates that IL-33 priming greatly potentiates MCs' ability to transcribe proinflammatory cytokine and chemokine genes in response to antigenic stimulation, shining light on how epithelial cell-derived cytokine IL-33 can cause exacerbation of skin MC-mediated allergic inflammation.

RORα overexpression reduced interleukin-33 expression and prevented mast cell degranulation and inflammation by inducing autophagy in allergic rhinitis

BACKGROUND

Retinoid acid receptor related orphan receptor α (RORα) is a nuclear receptor that along with other bioactive factors regulates cell proliferation, differentiation, and immunomodulation in vivo.

AIMS

The objective of this study was to explore the function and mechanism of RORα in allergic rhinitis (AR).

MATERIALS AND METHODS

Derp1 was used to construct an AR cell model in HNEpC cells, and RORα was overexpressed or silenced in the AR HNEpC cells. Next, LAD2 cells were co-cultured with the Derp1-treated HNEpC cells. Additionally, an AR mouse model was established using by OVA, and a RORα Adenovirus was delivered by nebulizing. Pathological tissue structures were evaluated by hematoxylin-eosin staining, and the levels of RORα, interleukin-33 (IL-33), and other proteins were analyzed immunohistochemistry, western blotting, and immunofluorescence staining. IL-33, IL-4, IL-5, and IL-13 levels were detected using enzyme-linked immunosorbent assay kits and cell migration was assessed by Transwell assays.

RESULTS

Our data showed that RORα was downregulated in the nasal mucosa tissues of AR patients. Derp1 treatment could cause a downregulation of RORα, upregulation of IL-33, the induction of NLRP3 inflammasomes, and cell migration in HNEpC cells. Furthermore, RORα overexpression dramatically attenuated IL-33 levels, NLRP3 inflammasome activity, and the migration of AR HNEpC cells induced with Derp1. Moreover, RORα in AR HNEpC cells could prevent mast cell (MC) degranulation and inflammation by accelerating autophagy, RORα overexpression inhibited MC degranulation and NLRP3-induced inflammation in the AR model mice. RORα overexpression reduced IL-33 expression in nasal epithelial cells, and also suppressed MC degranulation and inflammation by promoting autophagy.

CONCLUSION

RORα inhibits NLRP3 inflammasome in HNEpC, and attenuated mast cells degranulation and inflammation through autophagy in AR.

Vitamin D Influences the Activity of Mast Cells in Allergic Manifestations and Potentiates Their Effector Functions against Pathogens

Mast cells (MCs) are abundant at sites exposed to the external environment and pathogens. Local activation of these cells, either directly via pathogen recognition or indirectly via interaction with other activated immune cells and results in the release of pre-stored mediators in MC granules. The release of these pre-stored mediators helps to enhance pathogen clearance. While MCs are well known for their protective role against parasites, there is also significant evidence in the literature demonstrating their ability to respond to viral, bacterial, and fungal infections. Vitamin D is a fat-soluble vitamin and hormone that plays a vital role in regulating calcium and phosphorus metabolism to maintain skeletal homeostasis. Emerging evidence suggests that vitamin D also has immunomodulatory properties on both the innate and adaptive immune systems, making it a critical regulator of immune homeostasis. Vitamin D binds to its receptor, called the vitamin D receptor (VDR), which is present in almost all immune system cells. The literature suggests that a vitamin D deficiency can activate MCs, and vitamin D is necessary for MC stabilization. This manuscript explores the potential of vitamin D to regulate MC activity and combat pathogens, with a focus on its ability to fight viruses.

Siglecs as potential targets of therapy in human mast cell- and/or eosinophil-associated diseases

Siglecs (sialic acid-binding immunoglobulin-like lectins) are a family of vertebrate glycan-binding cell-surface proteins. The majority mediate cellular inhibitory activity once engaged by specific ligands or ligand-mimicking molecules. As a result, Siglec engagement is now of interest as a strategy to therapeutically dampen unwanted cellular responses. When considering allergic inflammation, human eosinophils and mast cells express overlapping but distinct patterns of Siglecs. For example, Siglec-6 is selectively and prominently expressed on mast cells while Siglec-8 is highly specific for both eosinophils and mast cells. This review will focus on a subset of Siglecs and their various endogenous or synthetic sialoside ligands that regulate eosinophil and mast cell function and survival. It will also summarize how certain Siglecs have become the focus of novel therapies for allergic and other eosinophil- and mast cell-related diseases.

Inhibiting Isoprenylation Suppresses FcεRI-Mediated Mast Cell Function and Allergic Inflammation

IgE-mediated mast cell activation is a driving force in allergic disease in need of novel interventions. Statins, long used to lower serum cholesterol, have been shown in multiple large-cohort studies to reduce asthma severity. We previously found that statins inhibit IgE-induced mast cell function, but these effects varied widely among mouse strains and human donors, likely due to the upregulation of the statin target, 3-hydroxy-3-methylgutaryl-CoA reductase. Statin inhibition of mast cell function appeared to be mediated not by cholesterol reduction but by suppressing protein isoprenylation events that use cholesterol pathway intermediates. Therefore, we sought to circumvent statin resistance by targeting isoprenylation. Using genetic depletion of the isoprenylation enzymes farnesyltransferase and geranylgeranyl transferase 1 or their substrate K-Ras, we show a significant reduction in FcεRI-mediated degranulation and cytokine production. Furthermore, similar effects were observed with pharmacological inhibition with the dual farnesyltransferase and geranylgeranyl transferase 1 inhibitor FGTI-2734. Our data indicate that both transferases must be inhibited to reduce mast cell function and that K-Ras is a critical isoprenylation target. Importantly, FGTI-2734 was effective in vivo, suppressing mast cell-dependent anaphylaxis, allergic pulmonary inflammation, and airway hyperresponsiveness. Collectively, these findings suggest that K-Ras is among the isoprenylation substrates critical for FcεRI-induced mast cell function and reveal isoprenylation as a new means of targeting allergic disease.

Symbiotic microbiome Staphylococcus epidermidis restricts IL-33 production in allergic nasal epithelium via limiting the cellular necroptosis

BACKGROUND

Allergic rhinitis (AR) is characterized by airway inflammation in nasal mucosa from inhaled allergens and interleukin (IL)-33 is the potent inducer of Th2 inflammation in allergic nasal epithelium. Staphylococcus epidermidis is one of the most abundant colonizers of the healthy human nasal mucosa and might impact the allergen-induced inflammatory responses in the nasal epithelium. Thus, we sought to characterize the mechanism of S. epidermidis regulating Th2 inflammation and IL-33 production in AR nasal mucosa.

RESULTS

The AR symptoms were alleviated and eosinophilic infiltration, serum IgE levels, and Th2 cytokines were significantly decreased in OVA-sensitized AR mice in response to human nasal commensal S. epidermidis. The inoculation of S. epidermidis to normal human nasal epithelial cells reduced IL-33 and GATA3 transcriptions and also reduced IL-33 and GATA3 expression in AR nasal epithelial (ARNE) cells and the nasal mucosa of AR mice. Our data exhibited that the cellular necroptosis of ARNE cells might be involved in IL-33 production and inoculation of S. epidermidis decreased the phosphorylation of necroptosis enzymes in ARNE cells, which was related to the reduction of IL-33 production.

CONCLUSIONS

We present that human nasal commensal S. epidermidis reduces allergic inflammation by suppressing IL-33 production in nasal epithelium. Our findings indicate that S. epidermidis serves a role in blocking allergen-induced cellular necroptosis in allergic nasal epithelium which might be a key mechanism of reduction of IL-33 and Th2 inflammation.

Evaluation of interleukin-33 & sST2 levels in type-2 diabetic mellitus patients with or without metabolic syndrome

Background & objectives

Diabetes mellitus (DM) is characterized by increase in blood glucose levels due to defective insulin secretion or insulin sensitivity. Interleukins (ILs) are known to play an important role in the pathogenesis of DM. The aim of this study was to investigate the serum concentration of IL-33 and its receptor soluble ST2 (sST2) in patients with diabetes and draw a correlation between their serum levels and different standard glycaemic indices of patients affected with type-2 diabetes with or without metabolic syndrome.

Methods

Thirty type-2 diabetic individuals and 30 healthy controls were recruited for this study. Serum and plasma were separated by centrifugation of blood for quantitative measurement of IL-33, sST2 and other biochemical parameters.

Results

It was observed that serum IL-33 levels were significantly less and sST2 levels were significantly high in type-2 diabetic individuals as compared to healthy controls. A significant correlation between the serum IL-33 concentration and fasting plasma glucose (FPG) and postprandial plasma glucose (PPG) levels were also found. Additionally, data also elucidated that serum levels of high-density lipoprotein, low-density lipoprotein or triglyceride in type-2 diabetics did not influence the serum levels of IL-33 and sST2, thereby excluding these factors as the major drivers of changes in serum IL-33 and sST2 concentration.

Interpretation & conclusions

This study demonstrated alteration in serum levels of IL-33 and sST2 in type-2 diabetic individuals. Further mechanistic studies, focusing on the progression of type-2 diabetes could elucidate the involvement of IL-33 in the cellular acquisition of insulin resistance as observed in type-2 diabetics.

IL-33-mediated activation of mast cells is involved in the progression of imiquimod-induced psoriasis-like dermatitis

BACKGROUND

Psoriasis is a chronic inflammatory dermatosis with an unclear pathogenesis. Mast cells (MCs) can serve as a bridge between innate and adaptive immunity and are involved in the regulation of the inflammatory state and immune homeostasis in diseases. MCs constitutively express interleukin-33 receptor T1/ST2 (IL-33R). IL-33 is a potent MCs activator that is actively secreted by keratinocytes in psoriasis. However, the regulatory role of MCs in psoriasis remains uncertain. Therefore, we hypothesised that IL-33 could promote MC activation to regulate psoriasis development.

METHODS

We performed experiments on wild-type (WT) and MC-deficient (Kit Wsh/Wsh) mice, established psoriasis-like mouse models using imiquimod (IMQ), and performed RNA sequencing and transcriptomic analysis of skin lesions. Exogenous administration was performed using recombinant IL-33. Validation and evaluation were performed using PSI scoring, immunofluorescence, immunohistochemistry, and qPCR.

RESULTS

We observed an upregulation in the number and activation of MCs in patients with psoriasis and in IMQ-induced psoriasis-like dermatitis. Deficiency of MCs ameliorates IMQ-induced psoriatic dermatitis at an early stage. IL-33 is increased and co-localized with MCs in the dermis of psoriasis-like lesions using immunofluorescence. Compared to WT mice, IMQ-induced Kit^Wsh/Wsh mice demonstrated a delayed response to exogenous IL-33.

CONCLUSIONS

MCs are activated by IL-33 in the early stages of psoriasis and exacerbate psoriasis-associated skin inflammation. The regulation of MC homeostasis may be a potential therapeutic strategy for psoriasis. Video Abstract.

Role of SARS-CoV-2 Spike-Protein-Induced Activation of Microglia and Mast Cells in the Pathogenesis of Neuro-COVID

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes coronavirus disease 2019 (COVID-19). About 45% of COVID-19 patients experience several symptoms a few months after the initial infection and develop post-acute sequelae of SARS-CoV-2 (PASC), referred to as "Long-COVID," characterized by persistent physical and mental fatigue. However, the exact pathogenetic mechanisms affecting the brain are still not well-understood. There is increasing evidence of neurovascular inflammation in the brain. However, the precise role of the neuroinflammatory response that contributes to the disease severity of COVID-19 and long COVID pathogenesis is not clearly understood. Here, we review the reports that the SARS-CoV-2 spike protein can cause blood-brain barrier (BBB) dysfunction and damage neurons either directly, or via activation of brain mast cells and microglia and the release of various neuroinflammatory molecules. Moreover, we provide recent evidence that the novel flavanol eriodictyol is particularly suited for development as an effective treatment alone or together with oleuropein and sulforaphane (ViralProtek®), all of which have potent anti-viral and anti-inflammatory actions.

The evolving landscape of biologic therapies for atopic dermatitis: Present and future perspective

Atopic dermatitis (AD) is one of the most common, chronic inflammatory skin diseases with a significant physical, emotional and socioeconomic burden. In recent years the understanding of AD pathogenesis has expanded from the Th2-centred perspective, with the recognition of the involvement of other immune axes. In different AD endotypes, influenced by environment, genetics and race, transcriptomic profiles have identified differing contributions of multiple immune axes such as, Th17, Th22 and Th1. The enriched pathogenic model of AD has catalysed the development of numerous biologic therapies targeting a range of key molecules implicated in disease progression. Currently, dupilumab and tralokinumab, which both target the Th2 pathway, are the only approved biologic therapies for AD in the United States and Europe. New biologic therapies in development, however, target different Th2-pathway molecules along with cytokines in other immune axes, including Th17 and Th22, offering promise for varied treatments for this heterogeneous disease. As the biologic pipeline advances, the integration into clinical practice and approval of these experimental biologics may provide more effective, tailored therapeutic solutions and illuminate on the pathologic processes of AD across a broader, more diverse patient population.

Neuroblast Differentiation-Associated Protein Derived Polypeptides: AHNAK(5758-5775) Induces Inflammation by Activating Mast Cells via ST2

Psoriasis is a chronic inflammatory skin disease. Mast cells are significantly increased and activated in psoriatic lesions and are involved in psoriatic inflammation. Some endogenous substances can interact with the surface receptors of mast cells and initiate the release of downstream cytokines that participate in inflammatory reactions. Neuroblast differentiation-associated protein (AHNAK) is mainly expressed in the skin, esophagus, kidney, and other organs and participates in various biological processes in the human body. AHNAK and its derived peptides have been reported to be involved in the activation of mast cells and other immune processes. This study aimed to investigate whether AHNAK (5758-5775), a neuroblast differentiation-associated protein-derived polypeptide, could be considered a new endogenous substance in psoriasis patients, which activates mast cells and induces the skin inflammatory response contributing to psoriasis. Wild-type mice were treated with AHNAK(5758-5775) to observe the infiltration of inflammatory cells in the skin and cytokine release in vivo. The release of inflammatory mediators by mouse primary mast cells and the laboratory of allergic disease 2 (LAD2) human mast cells was measured in vitro. Molecular docking analysis, molecular dynamics simulation, and siRNA transfection were used to identify the receptor of AHNAK(5758-5775). AHNAK(5758-5775) could cause skin inflammation and cytokine release in wild-type mice and activated mast cells in vitro. Moreover, suppression of tumorigenicity 2 (ST2) might be a key receptor mediating AHNAK(5758-5775)'s effect on mast cells and cytokine release. We propose a novel polypeptide, AHNAK(5758-5775), which induces an inflammatory reaction and participates in the occurrence and development of psoriasis by activating mast cells.

Vitamin D Receptor Expression Limits the Angiogenic and Inflammatory Properties of Retinal Endothelial Cells

The integrity of retinal endothelial cell (EC) is essential for establishing and maintaining the retinal blood barrier to ensure proper vision. Vitamin D is a hormone with known protective roles in EC function. The majority of vitamin D action is mediated through the vitamin D receptor (VDR). VDR is a nuclear receptor whose engagement by vitamin D impacts the expression of many genes with important roles in regulation of angiogenesis and inflammation. Although many studies have investigated vitamin D-VDR action in cardiovascular protection and tumor angiogenesis, its impact on retinal EC function and regulation of ocular angiogenesis and inflammation is exceedingly limited. We previously showed calcitriol, the active form of vitamin D, is a potent inhibitor of retinal neovascularization in vivo and retinal EC capillary morphogenesis in vitro. Here, using retinal EC prepared from wild-type (Vdr+/+) and VDR-deficient (Vdr-/-) mice, we show that retinal EC express VDR and its expression is induced by calcitriol. The lack of VDR expression had a significant impact on endothelial cell-cell and cell-matrix interactions. Vdr-/- retinal EC proliferated at a slower rate and were more adherent and less migratory. They also exhibited increased expression levels of inflammatory markers driven in part by sustained activation of STAT1 and NF-κB pathways and were more sensitive to oxidative challenge. These changes were attributed, in part, to down-regulation of endothelial nitric oxide synthetase, enhanced hepcidin expression, and increased intracellular iron levels. Taken together, our results indicate that VDR expression plays a fundamental role in maintaining the proper angiogenic and inflammatory state of retinal EC.

Phase 2 randomized clinical trial of astegolimab in patients with moderate to severe atopic dermatitis

BACKGROUND

The binding of IL-33 to its receptor ST2 (alias of IL1RL1) leads to the release of inflammatory mediators and may play a role in the pathogenesis of atopic dermatitis. Astegolimab is a fully human, IgG₂ mAb that binds to ST2 and inhibits IL-33 signaling.

OBJECTIVES

This study sought to assess the efficacy, safety, and pharmacokinetics of astegolimab in patients with atopic dermatitis.

METHODS

This was a randomized, placebo-controlled, phase 2 study in which adults with chronic atopic dermatitis were randomized 1:1 to receive astegolimab 490 mg every 4 weeks or placebo, for 16 weeks. The primary outcome was the percentage of change from baseline to week 16 of the Eczema Area and Severity Index score.

RESULTS

A total of 65 patients were enrolled in the study (placebo, n = 32; astegolimab, n = 33). The adjusted mean percentage of change from baseline to week 16 in the Eczema Area and Severity Index score was -51.47% for astegolimab compared with -58.24% for placebo, with a nonsignificant treatment difference of 6.77% (95% CI: -16.57-30.11; P = .5624). No differences were observed between treatment groups for secondary efficacy outcomes and in exploratory biomarkers (blood eosinophils, serum IL-5, serum CCL13). With the use of loading dose, pharmacokinetic exposure was sufficient from week 1. Astegolimab was well-tolerated, with a safety profile consistent with that observed in previous clinical trials.

CONCLUSIONS

In patients with atopic dermatitis, astegolimab did not show a significant difference compared to placebo for the primary or secondary outcomes.

Aqueous Extract from Cuminum cyminum L. Seed Alleviates Ovalbumin-Induced Allergic Rhinitis in Mouse via Balancing of Helper T Cells

Cuminum cyminum L. (cumin) seeds are widely used as a spice. Although we previously reported that the aqueous extract of cumin seeds suppresses the degranulation of rat basophilic RBL-2H3 cells, it has not been clarified whether the extract alleviates actual allergy symptoms in vivo. Therefore, in this study, we investigated the effect of oral administration of cumin seed aqueous extract (CAE) in ovalbumin (OVA)-induced allergic rhinitis. BALB/c mice were randomly divided into the following three groups: control group (five mice), OVA group (five mice), and OVA + CAE group (five mice). Allergic rhinitis was induced by sensitization (intraperitoneal, 25 μg OVA and 1.98 mg aluminum hydroxide gel) followed by challenge (intranasal, 400 μg OVA). The oral administration of CAE (25 mg/kg) reduced the sneezing frequency of OVA-induced allergic rhinitis model mice. In addition to reducing the serum immunoglobulin E and IL-4 levels, the oral administration of CAE reduced the production of T-helper type-2 (Th2) cytokines (IL-4, IL-5, IL-10, and IL-13) in the splenocytes of the model mice. Furthermore, a significant increase in the ratio of Th1 to Th2 cells was observed in the CAE-administered group. Our findings suggest that the ingestion of CAE improves T cell balance, the dominant state of Th2, and alleviates allergic rhinitis symptoms.

Combined IgE neutralization and Bifidobacterium longum supplementation reduces the allergic response in models of food allergy

IgE is central to the development of allergic diseases, and its neutralization alleviates allergic symptoms. However, most of these antibodies are based on IgG1, which is associated with an increased risk of fragment crystallizable-mediated side effects. Moreover, omalizumab, an anti-IgE antibody approved for therapeutic use, has limited benefits for patients with high IgE levels. Here, we assess a fusion protein with extracellular domain of high affinity IgE receptor, FcεRIα, linked to a IgD/IgG4 hybrid Fc domain we term IgE_TRAP, to reduce the risk of IgG1 Fc-mediated side effects. IgE_TRAP shows enhanced IgE binding affinity compared to omalizumab. We also see an enhanced therapeutic effect of IgE_TRAP in food allergy models when combined with Bifidobacterium longum, which results in mast cell number and free IgE levels. The combination of IgE_TRAP and B. longum may therefore represent a potent treatment for allergic patients with high IgE levels.

IgE is a critical component of the allergic response and therapeutic targeting can alleviate symptomology. Here the authors propose the combined use of Bifidobacterium longum and a FcεRIα extracellular domain linked to a IgD/IgG4 hybrid Fc domain fusion protein called IgE_TRAP and show reduction of mast cell and IgE levels in models of food allergy.

Skin Commensal Bacteria Modulates the Immune Balance of Mice to Alleviate Atopic Dermatitis-Induced Damage

Objective

Although studies indicate that Staphylococcus epidermidis (S. epidermidis) can regulate inflammation and anti-inflammatory cytokines, there is limited evidence supporting their effects on atopic dermatitis (AD). Here, we aimed to investigate the effects and potential mechanism of skin commensal bacteria on the immunity of mice with AD.

Methods

Twenty-four female BALB/C mice were selected and divided randomly into 4 groups: normal group, atopic dermatitis model group (AD), atopic dermatitis/substrate group (AD/substrates), and atopic dermatitis/substrates/epidermidis group (AD/S. epidermidis). All the mice were given different ways. After 14 days, their skin conditions were scored, and the serum, ear tissue, and inguinal lymph node tissue were collected and analyzed. Furthermore, the flow cytometry was used to analyze the number of CD4°+°CD25°+°Foxp3°+°Treg in the mouse lymph node tissue.

Results

Compared with the AD/substrate group, the mice ear thickness and dermatitis score were significantly reduced in the AD/S. epidermidis group; skin epidermis, acanthosis, the degree of keratinization, inflammatory cell infiltration in the dermis, and the number of mast cells were declined. The serum levels of IgE, IgG1, IgG2a, and TNF-α, IFN-γ, IL-4, and Eotaxin were significantly declined in the AD/S. epidermidis compared with the AD/substrate group. The proportion of CD4°+°CD25°+°Foxp3°+°Treg cells in the lymph node tissue was significantly increased in the AD/S. epidermidis group compared with the AD/substrate group.

Conclusion

Staphylococcus epidermidis can regulate mice's immune balance to alleviate AD-induced skin damage.

AllergoOncology: Danger signals in allergology and oncology: A European Academy of Allergy and Clinical Immunology (EAACI) Position Paper

The immune system interacts with many nominal 'danger' signals, endogenous danger-associated (DAMP), exogenous pathogen (PAMP) and allergen (AAMP)-associated molecular patterns. The immune context under which these are received can promote or prevent immune activating or inflammatory mechanisms and may orchestrate diverse immune responses in allergy and cancer. Each can act either by favouring a respective pathology or by supporting the immune response to confer protective effects, depending on acuity or chronicity. In this Position Paper under the collective term danger signals or DAMPs, PAMPs and AAMPs, we consider their diverse roles in allergy and cancer and the connection between these in AllergoOncology. We focus on their interactions with different immune cells of the innate and adaptive immune system and how these promote immune responses with juxtaposing clinical outcomes in allergy and cancer. While danger signals present potential targets to overcome inflammatory responses in allergy, these may be reconsidered in relation to a history of allergy, chronic inflammation and autoimmunity linked to the risk of developing cancer, and with regard to clinical responses to anti-cancer immune and targeted therapies. Cross-disciplinary insights in AllergoOncology derived from dissecting clinical phenotypes of common danger signal pathways may improve allergy and cancer clinical outcomes.

Potential roles of non-lymphocytic cells in the pathogenesis of IgG4-related disease

Studies have confirmed the involvement of a variety of lymphocyte subsets, including type 2 helper T lymphocytes (Th2) and IgG4⁺ B lymphocytes, in the pathogenesis of IgG4-related disease (IgG4-RD). Those lymphocytes contribute to the major pathogenetic features of IgG4-RD. However, they are not the only cellular components in the immunoinflammatory environment of this mysterious disease entity. Recent studies have suggested that various non-lymphocytic components, including macrophages and fibroblasts, may also play an important role in the pathogenetic process of IgG4-RD in terms of contributing to the chronic and complex progress of the disease. Therefore, the potential role of non-lymphocyte in the pathogenesis of IgG4-RD is worth discussing.

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.

Immunological signature of chronic spontaneous urticaria (Review)

Chronic urticaria (CU) is a condition characterized by intensely pruritic, edematous, erythematous papules lasting for more than 6 weeks. Over half of the cases have concomitant swelling of deeper tissues, known as angioedema. The socio-economic burden of the disease is significant. Unfortunately, patients with severe CU, refractory to conventional treatment, have limited and expensive therapeutic options. The pathogenesis of CU is not yet completely understood. Therefore, elucidating the pathophysiological mechanisms involved would potentially identify new therapeutic targets. It has been accepted in recent years that mast cells and their activation, followed by excessive degranulation represent the key pathophysiological events in chronic spontaneous urticaria (CSU). The triggering events and the complexity of the effector mechanisms, however, remain intensely debated topics with conflicting studies. One pathogenetic mechanism incriminated in chronic spontaneous urticaria is the response mediated by the high-affinity receptor for IgE (FcεRI) expressed on mast cells. Increasing recognition of chronic spontaneous urticaria as an autoimmune disease linked to the cytokine-chemokine network imbalance resulting from alteration of innate immune response is another pathogenetic explanation. It is likely that these different pathological mechanisms are more interconnected, both acting synergistically, rather than separately, to produce the clinical expression of CU. The discovery and understanding of pathogenic mechanisms represent the premise for the development of safe and effective immunomodulators and targeted biological treatment for severe, refractory CU.

Enhanced expression of endogenous retroviruses and of TRIM28 and SETDB1 in children with food allergy

Background

Human endogenous retroviruses (HERVs) represent 8% of our genome. They originate from ancestral infections and although no longer contagious they can regulate transcription of adjacent cellular genes, produce viral RNAs sensed as non‐self by pattern recognition receptors, and encode viral proteins, such as Syncytin (SYN) 1 and 2, that exhibit potent immunomodulatory properties. Based on this, HERVs have been studied and proposed as relevant cofactors in several chronic inflammatory and immune‐mediated diseases. HERV transcription is regulated by host TRIM28 and SET domain bifurcated histone lysine methyltransferase 1 (SETDB1), which in turn exert crucial regulatory functions on the host immune system. No studies explored the expression of HERVs, TRIM28, and SETDB1 in allergic patients.

Methods

We assessed, through a polymerase chain reaction real time Taqman amplification assay, the transcription levels of pol genes of HERV‐H, HERV‐K, HERV‐W, and of env genes of SYN1 and SYN2, as well as of TRIM28 and SETDB1 in whole blood from 32 children with IgE‐mediated food allergy, 19 with food protein‐induced enterocolitis syndrome (FPIES), and in healthy control children.

Results

The expression levels of pol genes of HERV‐H, ‐K, and ‐W were significantly enhanced in patients with IgE‐mediated FA or FPIES as compared to control subjects, while the mRNA concentrations of SYN1 and SYN2 were comparable in each group of children. Both TRIM28 and SETDB1 mRNA levels were significantly higher in allergic patients.

Conclusions

Given the influence of HERVs and of TRIM28 and SETDB1 on innate and adaptive immune responses, their transcriptional activation in children with food allergies suggest that they might play important roles in the development of these diseases.

Gut Barrier Dysfunction and Type 2 Immunity: Implications for Compulsive Behavior

To date, much of the focus of gut-brain axis research has been on gut microbiota regulation of anxiety and stress-related behaviors. Much less attention has been directed to potential connections between gut microbiota and compulsive behavior. Here, we discuss a potential link between gut barrier dysfunction and compulsive behavior that is mediated through "type 2" rather than "type 1" inflammation. We examine connections between compulsive behavior and type 2 inflammation in Tourette syndrome, obsessive-compulsive disorder, autism, addiction, and post-traumatic stress disorder. Next, we discuss potential connections between gut barrier dysfunction, type 2 inflammation, and compulsive behavior. We posit a potential mechanism whereby gut barrier dysfunction-associated type 2 inflammation may drive compulsive behavior through histamine regulation of dopamine neurotransmission. Finally, we discuss the possibility of exploiting the greater accessibility of the gut relative to the brain in identifying targets to treat compulsive behavior disorders.

Loss of NFE2L3 protects against inflammation-induced colorectal cancer through modulation of the tumor microenvironment

We investigated the role of the NFE2L3 transcription factor in inflammation-induced colorectal cancer. Our studies revealed that Nfe2l3^−/− mice exhibit significantly less inflammation in the colon, reduced tumor size and numbers, and skewed localization of tumors with a more pronounced decrease of tumors in the distal colon. CIBERSORT analysis of RNA-seq data from normal and tumor tissue predicted a reduction in mast cells in Nfe2l3^−/− animals, which was confirmed by toluidine blue staining. Concomitantly, the transcript levels of Il33 and Rab27a, both important regulators of mast cells, were reduced and increased, respectively, in the colorectal tumors of Nfe2l3^−/− mice. Furthermore, we validated NFE2L3 binding to the regulatory sequences of the IL33 and RAB27A loci in human colorectal carcinoma cells. Using digital spatial profiling, we found that Nfe2l3^−/− mice presented elevated FOXP3 and immune checkpoint markers CTLA4, TIM3, and LAG3, suggesting an increase in Treg counts. Staining for CD3 and FOXP3 confirmed a significant increase in immunosuppressive Tregs in the colon of Nfe2l3^−/− animals. Also, Human Microbiome Project (HMP2) data showed that NFE2L3 transcript levels are higher in the rectum of ulcerative colitis patients. The observed changes in the tumor microenvironment provide new insights into the molecular differences regarding colon cancer sidedness. This may be exploited for the treatment of early-onset colorectal cancer as this emerging subtype primarily displays distal/left-sided tumors.

Evaluation of serum interleukin-33 and soluble suppression of tumorigenicity 2 (sST2) receptors in patients with and without periodontal disease

Context

: Interleukin-33 and its receptor soluble suppression of tumorigenicity 2.

(

sST2) play an important role in inflammation and its role in periodontal disease is yet unclear. The role of both IL-33 and sST2 together in periodontal disease as biomarkers has never been studied.

Aim

: To assess the levels of IL-33 and sST2 in serum samples of patients with periodontitis and healthy subjects.

Methods

: A total of 71 subjects (30 healthy subjects and 41 patients with periodontal disease) were included in the cross-sectional study. Community Periodontal Index (CPI) was used to assess periodontal health by utilizing a mouth mirror and a CPI probe. Venous blood was collected and serum was separated. Serum levels of IL-33 and sST2 were determined by the enzyme-linked immunosorbent assay (ELISA) assay.

Statistical Analysis

Graph Pad Prism 5 was used for statistical analysis. Mann Whitney test was applied to compare the two groups.

Results

: The level of IL-33 was not found to be elevated among healthy subjects and sST2 was found elevated among patients with periodontal disease. The serum concentration of IL-33 was found at 472 ± 114 pg/ml and 282 ± 77 pg/ml among healthy subjects and patients with periodontal disease respectively. Significantly higher values of sST2 at 28 ± 2 ng/ml were found among periodontal patients as compared to healthy subjects with values of 18 ± 1 ng/ml. No significant differences were noted between mild to moderate and severe periodontitis for IL-33 and sST2 between the two groups.

Conclusion

This study shows alteration in serum levels of IL-33 and sST2 in periodontitis patients. IL-33 and sST2 may be potential inflammatory markers of periodontitis. Further studies are required on a large sample size for better understanding. This pilot study is the first to assess the serum levels of both IL-33 and sST2 together among patients with and without periodontal disease.

Development of an ultra-sensitive human IL-33 biomarker assay for age-related macular degeneration and asthma drug development

Background

Over the past decade, human Interleukin 33 (hIL-33) has emerged as a key contributor to the pathogenesis of numerous inflammatory diseases. Despite the existence of several commercial hIL-33 assays spanning multiple platform technologies, their ability to provide accurate hIL-33 concentration measurements and to differentiate between active (reduced) and inactive (oxidized) hIL-33 in various matrices remains uncertain. This is especially true for lower sample volumes, matrices with low hIL-33 concentrations, and matrices with elevated levels of soluble Interleukin 1 Receptor-Like 1 (sST2), an inactive form of ST2 that competes with membrane bound ST2 for hIL-33 binding.

Results

We tested the performance of several commercially available hIL-33 detection assays in various human matrices and found that most of these assays lacked the sensitivity to accurately detect reduced hIL-33 at biologically relevant levels (sub-to-low pg/mL), especially in the presence of human sST2 (hsST2), and/or lacked sufficient target specificity. To address this, we developed and validated a sensitive and specific enzyme-linked immunosorbent assay (ELISA) capable of detecting reduced and total hIL-33 levels even in the presence of high concentrations of sST2. By incorporating the immuno-polymerase chain reaction (iPCR) platform, we further increased the sensitivity of this assay for the reduced form of hIL-33 by ~ 52-fold. Using this hIL-33 iPCR assay, we detected hIL-33 in postmortem human vitreous humor (VH) samples from donors with age-related macular degeneration (AMD) and found significantly increased hIL-33 levels when compared to control individuals. No statistically significant difference was observed in aqueous humor (AH) from AMD donors nor in plasma and nasosorption fluid (NF) from asthma patients compared to control individuals.

Conclusions

Unlike existing commercial hIL-33 assays, our hIL-33 bioassays are highly sensitive and specific and can accurately quantify hIL-33 in various human clinical matrices, including those with high levels of hsST2. Our results provide a proof of concept of the utility of these assays in clinical trials targeting the hIL-33/hST2 pathway.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-021-03189-3.

Tanshinone IIA improves degranulation of mast cells and allergic rhinitis induced by ovalbumin by inhibiting the PLCγ1/PKC/IP3R pathway

Allergic rhinitis (AR) is a common allergic inflammatory and chronic reactive disease caused by allergen-induced immunoglobulin E (IgE). Tanshinone IIA (Tan IIA) is one of the active ingredients in Salvia miltiorrhiza Bunge (Danshen) and plays a vital role in inhibiting inflammation. Thus, we hypothesized that Tan IIA has anti-allergic effects and studied the function of Tan IIA in mast cells and an AR animal model. We induced RBL-2H3 cell sensitization with monoclonal anti-2,4,6-dinitrophenyl-immunoglobulin (Ig) E/human serum albumin (DNP-IgE/HSA) and constructed an ovalbumin (OVA)-induced AR model in mice. The role of Tan IIA in AR progression was studied using the MTT assay, ELISA, western blot, toluidine blue staining, HE staining, and Alcian blue and safranin O (A&S) staining. Tan IIA treatment significantly increased IgE/HSA-induced cell viability. However, Tan IIA treatment markedly downregulated the expression levels of β-hexosaminidase, histamine, tumor necrosis factor (TNF-α), interleukin 1β (IL-1β), IL-4, and IL-5 in IgE/HSA-induced cells. Furthermore, Tan IIA improved typical symptoms in the OVA-induced AR model mice by inhibiting the phospholipase Cγ1 (PLCγ1)/protein kinase C (PKC)/IP3R pathway. Additionally, Tan IIA effectively improved the degranulation of RBL-2H3 cells and OVA-induced AR in mice. Together, these results suggest that Tan IIA may be a potential drug for the treatment of AR in the future.

Hyperactivity of Innate Immunity Triggers Pain via TLR2-IL-33-Mediated Neuroimmune Crosstalk

The innate immune system responds to infections that give rise to pain. How the innate immune system interacts with the sensory nervous system and contributes to pain is poorly understood. Here we report that hyperactivity of innate immunity primes and initiates pain states via the TLR2-interleukin-33 (IL-33) axis. Toll-like receptors (TLRs) are upregulated in the complete Freund's adjuvant (CFA) pain model, and knockout of TLR2 abolishes CFA-induced pain. Selective activation of TLR2/6 triggers acute pain via upregulation of IL-33 in the hindpaw, dorsal root ganglia (DRG), and spinal cord in an NLRP3-dependent manner. The IL-33 increase further initiates priming of nociceptive neurons and pain states. Finally, blocking IL-33 receptors at the spinal level mediates analgesia during acute and chronic inflammatory pain, underscoring an important function of IL-33 in pain signaling. Collectively, our data reveal a critical role of the TLR2-IL-33 axis in innate immune activation for pain initiation and maintenance.

Mechanisms for Alternaria alternata Function in the Skin During Induction of Peanut Allergy in Neonatal Mice With Skin Barrier Mutations

Neonatal mice with heterozygous mutations in genes encoding the skin barrier proteins filaggrin and mattrin (flaky tail mice [FT^+/-]) exhibit oral peanut-induced anaphylaxis after skin sensitization. As we have previously reported, sensitization in this model is achieved via skin co- exposure to the environmental allergen Alternaria alternata (Alt), peanut extract (PNE), and detergent. However, the function of Alt in initiation of peanut allergy in this model is little understood. The purpose of this study was to investigate candidate cytokines induced by Alt in the skin and determine the role of these cytokines in the development of food allergy, namely oncostatin M (Osm), amphiregulin (Areg), and IL-33. RT-qPCR analyses demonstrated that skin of FT^+/- neonates expressed Il33 and Osm following Alt or Alt/PNE but not PNE exposure. By contrast, expression of Areg was induced by either Alt, PNE, or Alt/PNE sensitization in FT^+/- neonates. In scRNAseq analyses, Osm, Areg, and Il33 were expressed by several cell types, including a keratinocyte cluster that was expanded in the skin of Alt/PNE-exposed FT^+/- pups as compared to Alt/PNE-exposed WT pups. Areg and OSM were required for oral PNE-induced anaphylaxis since anaphylaxis was inhibited by administration of neutralizing anti-Areg or anti-OSM antibodies prior to each skin sensitization with Alt/PNE. It was then determined if intradermal injection of recombinant IL33 (rIL33), rAreg, or rOSM in the skin could substitute for Alt during skin sensitization to PNE. PNE skin sensitization with intradermal rIL33 was sufficient for oral PNE-induced anaphylaxis, whereas skin sensitization with intradermal rAreg or rOSM during skin exposure to PNE was not sufficient for anaphylaxis to oral PNE challenge. Based on these studies a pathway for IL33, Areg and OSM in Alt/PNE sensitized FT^+/- skin was defined for IgE induction and anaphylaxis. Alt stimulated two pathways, an IL33 pathway and a pathway involving OSM and Areg. These two pathways acted in concert with PNE to induce food allergy in pups with skin barrier mutations.

A Mechanistic Site-Of-Action Model: A Tool for Informing Right Target, Right Compound, And Right Dose for Therapeutic Antagonistic Antibody Programs

Quantitative modeling is increasingly utilized in the drug discovery and development process, from the initial stages of target selection, through clinical studies. The modeling can provide guidance on three major questions–is this the right target, what are the right compound properties, and what is the right dose for moving the best possible candidate forward. In this manuscript, we present a site-of-action modeling framework which we apply to monoclonal antibodies against soluble targets. We give a comprehensive overview of how we construct the model and how we parametrize it and include several examples of how to apply this framework for answering the questions postulated above. The utilities and limitations of this approach are discussed.

Ways to Address Perinatal Mast Cell Activation and Focal Brain Inflammation, including Response to SARS-CoV-2, in Autism Spectrum Disorder

The prevalence of autism spectrum disorder (ASD) continues to increase, but no distinct pathogenesis or effective treatment are known yet. The presence of many comorbidities further complicates matters, making a personalized approach necessary. An increasing number of reports indicate that inflammation of the brain leads to neurodegenerative changes, especially during perinatal life, "short-circuiting the electrical system" in the amygdala that is essential for our ability to feel emotions, but also regulates fear. Inflammation of the brain can result from the stimulation of mast cells-found in all tissues including the brain-by neuropeptides, stress, toxins, and viruses such as SARS-CoV-2, leading to the activation of microglia. These resident brain defenders then release even more inflammatory molecules and stop "pruning" nerve connections, disrupting neuronal connectivity, lowering the fear threshold, and derailing the expression of emotions, as seen in ASD. Many epidemiological studies have reported a strong association between ASD and atopic dermatitis (eczema), asthma, and food allergies/intolerance, all of which involve activated mast cells. Mast cells can be triggered by allergens, neuropeptides, stress, and toxins, leading to disruption of the blood-brain barrier (BBB) and activation of microglia. Moreover, many epidemiological studies have reported a strong association between stress and atopic dermatitis (eczema) during gestation, which involves activated mast cells. Both mast cells and microglia can also be activated by SARS-CoV-2 in affected mothers during pregnancy. We showed increased expression of the proinflammatory cytokine IL-18 and its receptor, but decreased expression of the anti-inflammatory cytokine IL-38 and its receptor IL-36R, only in the amygdala of deceased children with ASD. We further showed that the natural flavonoid luteolin is a potent inhibitor of the activation of both mast cells and microglia, but also blocks SARS-CoV-2 binding to its receptor angiotensin-converting enzyme 2 (ACE2). A treatment approach should be tailored to each individual patient and should address hyperactivity/stress, allergies, or food intolerance, with the introduction of natural molecules or drugs to inhibit mast cells and microglia, such as liposomal luteolin.

Citric acid and enzyme-assisted modification of flavonoids from celery (Apium graveolens) extract and their anti-inflammatory activity in HMC-1.2 cells

Apium graveolens (celery) of the family Apiaceae contains bioactive compounds including luteolin and apigenin. The purpose of this study was to increase the extraction yield of apigenin and luteolin in celery extract using green technology and to evaluate their biological activities. The results showed that CA and β-glucosidase-assisted celery extraction transformed apiin in the celery to apigenin with an increase in luteolin concentration. The CA and β-glucosidase-treated celery extract (CAGE) improved the anti-inflammatory properties of celery extract by inhibiting the expression and production of inflammatory cytokines (IL-6, IL-8, IL-31, and TNF-α) in IL-33-stimulated mast cells (HMC-1.2 cells). Their mechanism of action was tied to the inhibition of ERK, JNK, IKKα, IκBα, and NF-κB activation by CAGE in the stimulated cells. In conclusion, CA and enzyme treatment can be considered as a useful biotechnology tool for the improvement of bioactive compounds in celery and hence improve on their bioactivity. PRACTICAL APPLICATIONS: Apium graveolens commonly called celery is an edible agricultural product cultivated throughout the world and known as a "superfood." Celery contains bioactive compounds including apigenin and luteolin that contribute to their described biological activities. However, extracting celery using normal extraction procedures such as hot water and ethanol methods yields only a small amount of apigenin and luteolin. In the present study, we introduced an eco-friendly method using citric and β-glucosidase to obtain apigenin and luteolin-rich celery extract with improved anti-inflammatory activities. The present work will spark studies on the conversion of less biologically active compounds in functional food materials to more active compounds using CA and β-glucosidase, and the development of functional food with specifically enriched bioactive substances at the industrial levels.

G Protein-Coupled Receptor Kinase 2 (GRK2) Regulates T Cell Response in a Murine Model of House Dust Mite-Induced Asthma

G protein-coupled receptor kinase 2 (GRK2) is an adapter protein that modulates G protein-coupled receptor (GPCR) signaling. It also regulates the functions and activity of other intracellular proteins in many cell types. Accordingly, GRK2 is thought to contribute to disease progression by a variety of mechanisms related to its multifunctional roles. Indeed, GRK2 levels are enhanced in patient samples as well as in preclinical models of several diseases. We have previously shown that GRK2 regulates mast cell functions, and thereby contributes to exacerbated inflammation during allergic reactions. In the current study, we observed that GRK2 levels are enhanced in the lungs of human asthma patients and in mice sensitized to house dust mite extract (HDME) allergen. Consistent with these findings, interleukin (IL)-4 and IL-13 levels were reduced in the lungs of GRK2+/- mice in a HMDE mouse model of asthma. Because Th2 cells are the major source of these cytokines during asthma, we determined the role of GRK2 in regulating T cell-specific responses in our HMDE mouse model. We observed a significant reduction of airway hyperresponsiveness (AHR), lung eosinophil and lymphocyte counts, serum IgE, Th2 cytokines (IL-4 and IL-13), goblet cell hyperplasia and mucus production in mice that had reduced GRK2 expression specifically in T cells. Collectively, our studies reveal an important role for GRK2 in regulating T cell response during asthma pathogenesis and further elucidation of the mechanisms through which GRK2 modulates airway inflammation will lead to the development of new therapeutic strategies for asthma.

Cytokines Stimulated by IL-33 in Human Skin Mast Cells: Involvement of NF-κB and p38 at Distinct Levels and Potent Co-Operation with FcεRI and MRGPRX2

The IL-1 family cytokine IL-33 activates and re-shapes mast cells (MCs), but whether and by what mechanisms it elicits cytokines in MCs from human skin remains poorly understood. The current study found that IL-33 activates CCL1, CCL2, IL-5, IL-8, IL-13, and TNF-α, while IL-1β, IL-6, IL-31, and VEGFA remain unaffected in cutaneous MCs, highlighting that each MC subset responds to IL-33 with a unique cytokine profile. Mechanistically, IL-33 induced the rapid (1–2 min) and durable (2 h) phosphorylation of p38, whereas the phosphorylation of JNK was weaker and more transient. Moreover, the NF-κB pathway was potently activated, as revealed by IκB degradation, increased nuclear abundance of p50/p65, and vigorous phosphorylation of p65. The activation of NF-κB occurred independently of p38 or JNK. The induced transcription of the cytokines selected for further study (CCL1, CCL2, IL-8, TNF-α) was abolished by interference with NF-κB, while p38/JNK had only some cytokine-selective effects. Surprisingly, at the level of the secreted protein products, p38 was nearly as effective as NF-κB for all entities, suggesting post-transcriptional involvement. IL-33 did not only instruct skin MCs to produce selected cytokines, but it also efficiently co-operated with the allergic and pseudo-allergic/neurogenic activation networks in the production of IL-8, TNF-α, CCL1, and CCL2. Synergism was more pronounced at the protein than at the mRNA level and appeared stronger for MRGPRX2 ligands than for FcεRI. Our results underscore the pro-inflammatory nature of an acute IL-33 stimulus and imply that especially in combination with allergens or MRGPRX2 agonists, IL-33 will efficiently amplify skin inflammation and thereby aggravate inflammatory dermatoses.

Long-COVID syndrome-associated brain fog and chemofog: Luteolin to the rescue

COVID-19 leads to severe respiratory problems, but also to long-COVID syndrome associated primarily with cognitive dysfunction and fatigue. Long-COVID syndrome symptoms, especially brain fog, are similar to those experienced by patients undertaking or following chemotherapy for cancer (chemofog or chemobrain), as well in patients with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) or mast cell activation syndrome (MCAS). The pathogenesis of brain fog in these illnesses is presently unknown but may involve neuroinflammation via mast cells stimulated by pathogenic and stress stimuli to release mediators that activate microglia and lead to inflammation in the hypothalamus. These processes could be mitigated by phytosomal formulation (in olive pomace oil) of the natural flavonoid luteolin.

Baicalin suppresses type 2 immunity through breaking off the interplay between mast cell and airway epithelial cell

ETHNOPHARMACOLOGICAL RELEVANCE

The traditional Japanese herbal medicine Shin'iseihaito was reported to ameliorate the airway type 2 inflammatory response in clinical and experimental studies. Airway type 2 inflammatory diseases, including bronchial asthma and eosinophilic chronic rhinosinusitis (ECRS), often coexist and interact with each other. However, it is still unclear how Shin'iseihaito exerts its pharmacological effects on cells involved in airway mucosa.

AIM OF THE STUDY

This study aims to examine the direct effect of baicalin, a representative bioactive compound of Shin'iseihaito, on type 2 immune responses in human airway epithelial cells and mast cells.

MATERIAL AND METHODS

We measured the plasma pharmacokinetics of flavonoids derived from Shin'iseihaito and investigated the effects of baicalin on type 2 immune responses in human airway epithelial cells and human mast cells.

RESULTS

Baicalin, wogonin, and wogonoside were detected in the plasma. The maximum plasma concentration of baicalin was highest at 1610 ng/ml (3.6 μM). In the normal human bronchial epithelial cells treated with baicalin, with or without stimulation by IFN-γ, the IL-33 expression was significantly downregulated. However, baicalin treatment did not affect the levels of thymic stromal lymphopoietin and IL-25. We noted that IL-33-dependent expression of tryptase mRNA in mast cells was significantly inhibited by baicalin. Also, the expression of IL-5 in mast cells enhanced by stimulation with TSLP plus IL-1β was significantly downregulated by baicalin treatment. Moreover, the enhancement of IL-13 expression in mast cells by IL-33 simulation was also significantly inhibited by baicalin.

CONCLUSIONS

Our results prove that by breaking off the vicious circle of mast cells and airway epithelial cells, baicalin may be an effective alternative therapeutic option for the treatment of type 2 inflammatory diseases, such as ECRS and comorbid asthma.

Active smoking effect in allergic rhinitis

Background

Tobacco smoke has been described as causing increased prevalence of rhinitis symptoms and decreased atopy. Furthermore, these nasal symptoms and quality of life in smokers with Allergic Rhinitis (AR) were not significantly different to non-smokers. As a result of this duality, a comparison study between the quality of life and inflammatory markers of atopy among active smokers and non-smokers having AR was put forward.

Material and methods

Cross-sectional study in adult smokers and non-smokers, with a clinical diagnosis of AR and positive Skin Prick Test (SPT). Smoking status was confirmed by salivary cotinine measurements. Functional respiratory evaluation was performed, and quality of life between groups was compared using Mini-RQLQ questionnaire. Immunological markers in serum and nasal washes (IgE, IL-4, IL 5, IL 13, IL 17, IL 33) were evaluated, while samples from a third group of passive smokers was incorporated for serological comparison exclusively. The statistical analysis included Student T test, x2, Mann Whitney U (Anova 2-way), and Kruskal Wallis for 3 groups analysis. Values of P < 0.05 were considered significant.

Results

Twenty-two patients per group with similar demographics and allergen sensitivity were studied. Regarding inflammatory markers, a reduction of IL 33 in the serum of smokers (P < 0.001) was the only statistically significant different parameter revealed, showing a remarkable trend in nasal lavage. Salivary cotinine levels were absolutely different (P < 0.0001), but pulmonary function evaluations were not statistically significant after multiple adjusting. There were no significant differences in quality of life parameters.

Conclusions

In our study of AR, active smokers do not demonstrate impaired nasal related quality of life or impact on atopic inflammatory parameters, compared to non-smokers. Reduced levels of IL33 could explain a lack of symptoms alerting smokers of the harmful consequences of smoking.

GATA2 regulates mast cell identity and responsiveness to antigenic stimulation by promoting chromatin remodeling at super-enhancers

Mast cells are critical effectors of allergic inflammation and protection against parasitic infections. We previously demonstrated that transcription factors GATA2 and MITF are the mast cell lineage-determining factors. However, it is unclear whether these lineage-determining factors regulate chromatin accessibility at mast cell enhancer regions. In this study, we demonstrate that GATA2 promotes chromatin accessibility at the super-enhancers of mast cell identity genes and primes both typical and super-enhancers at genes that respond to antigenic stimulation. We find that the number and densities of GATA2- but not MITF-bound sites at the super-enhancers are several folds higher than that at the typical enhancers. Our studies reveal that GATA2 promotes robust gene transcription to maintain mast cell identity and respond to antigenic stimulation by binding to super-enhancer regions with dense GATA2 binding sites available at key mast cell genes.

Signal Transduction Pathways Activated by Innate Immunity in Mast Cells: Translating Sensing of Changes into Specific Responses

Mast cells (MCs) constitute an essential cell lineage that participates in innate and adaptive immune responses and whose phenotype and function are influenced by tissue-specific conditions. Their mechanisms of activation in type I hypersensitivity reactions have been the subject of multiple studies, but the signaling pathways behind their activation by innate immunity stimuli are not so well described. Here, we review the recent evidence regarding the main molecular elements and signaling pathways connecting the innate immune receptors and hypoxic microenvironment to cytokine synthesis and the secretion of soluble or exosome-contained mediators in this cell type. When known, the positive and negative control mechanisms of those pathways are presented, together with their possible implications for the understanding of mast cell-driven chronic inflammation. Finally, we discuss the relevance of the knowledge about signaling in this cell type in the recognition of MCs as central elements on innate immunity, whose remarkable plasticity converts them in sensors of micro-environmental discontinuities and controllers of tissue homeostasis.

Emerging mechanisms contributing to mast cell-mediated pathophysiology with therapeutic implications

Mast cells are tissue-resident immune cells that play key roles in the initiation and perpetuation of allergic inflammation, usually through IgE-mediated mechanisms. Mast cells are, however, evolutionary ancient immune cells that can be traced back to urochordates and before the emergence of IgE antibodies, suggesting their involvement in antibody-independent biological functions, many of which are still being characterized. Herein, we summarize recent advances in understanding the roles of mast cells in health and disease, partly through the study of emerging non-IgE receptors such as the Mas-related G protein-coupled receptor X2, implicated in pseudo-allergic reactions as well as in innate defense and neuronal sensing; the mechano-sensing adhesion G protein-coupled receptor E2, variants of which are associated with familial vibratory urticaria; and purinergic receptors, which orchestrate tissue damage responses similarly to the IL-33 receptor. Recent evidence also points toward novel mechanisms that contribute to mast cell-mediated pathophysiology. Thus, in addition to releasing preformed mediators contained in granules and synthesizing mediators de novo, mast cells also secrete extracellular vesicles, which convey biological functions. Understanding their release, composition and uptake within a variety of clinical conditions will contribute to the understanding of disease specific pathology and likely lead the way to novel therapeutic approaches. We also discuss recent advances in the development of therapies targeting mast cell activity, including the ligation of inhibitory ITIM-containing receptors, and other strategies that suppress mast cells or responses to mediators for the management of mast cell-related diseases.