Type I interferon limits mast cell-mediated anaphylaxis by controlling secretory granule homeostasis

Autoantibodies to type I interferons in patients with systemic mastocytosis

Background

Autoantibodies to type I interferons have been identified in association with a variety of inflammatory and autoimmune diseases. Type I interferons have demonstrated inhibitory effects on mast cell proliferation and degranulation. Systemic mastocytosis (SM) is a disease characterized by increased mast cell burden and mediator release. Whether autoantibodies to type I interferon are present in the sera of patients with SM, and if so, whether they correlate with characteristics of disease, is unknown.

Objective

The purpose of this study was to determine whether autoantibodies to type I interferons are observed in the sera of patients with SM, and if so, whether they correlate with biomarkers of disease severity.

Methods

We analyzed sera from 89 patients with SM for concentrations of autoantibodies to type I interferon by using a multiplex particle-based assay and signal neutralization capacity by using a STAT1 activity assay and then compared these measurements with those in a database of information on 1284 healthy controls.

Results

Our cohort was predominantly female (57.3%), with a median age of 56 years. Of the cohort members, 13 produced autoantibodies to IFN-β, 3 to IFN-ω, and 0 to IFN-α. None of the 13 sera demonstrated signal neutralization. Neither autoantibody concentration nor signaling inhibition measurements correlated with tryptase concentrations or D816V allele burden.

Conclusion

Although a small subpopulation of patients with SM have autoantibodies to type I interferons, there was no correlation between autoantibody production and signaling inhibition. These data are consistent with the conclusion that autoantibodies to type I interferon do not play a significant role in the pathogenesis or severity of SM.

Activity-dependent FosB gene expression negatively regulates mast cell functions

Mast cells are innate immune cells that play a crucial role in numerous physiological processes across tissues by releasing pre-stored and newly synthesized mediators in response to stimuli, an activity largely driven by changes in gene expression. Given their widespread influence, dysfunction in mast cells can contribute to a variety of pathologies including allergies, long COVID, and autoimmune and neuroinflammatory disorders. Despite this, the specific transcriptional mechanisms that control mast cell mediator release remain poorly understood, significantly hindering the development of effective therapeutic strategies. We found that the two proteins encoded by the transcription factor FosB, FOSB and the highly stable variant ΔFOSB, are robustly expressed upon stimulation in both murine and human mast cell progenitors. Motivated by these findings, we generated a novel mouse model with targeted ablation of FosB gene expression specifically in mast cells (MC FosB- ) by crossing a mast cell-specific Cre reporter line (Mcpt5-Cre) with a Cre-dependent floxed FosB mouse lines. We found that mast cell progenitors derived from MC FosB- mice, compared to wild types (WT), exhibit baseline increased histamine content and vesicle numbers. Additionally, they show enhanced calcium mobilization, degranulation, and histamine release following allergy-related IgE-mediated stimulation, along with heightened IL-6 release in response to infection-like LPS stimulation. In vivo experiments with IgE- mediated and LPS challenges revealed that MC FosB- mice experience greater drops in body temperature, heightened activation of tissue-resident mast cells, and increased release of pro-inflammatory mediators compared to their WT counterparts. These findings suggest that FosB products play a crucial regulatory role in moderating stimulus-induced mast cell activation in response to both IgE and LPS stimuli. Lastly, by integrating CUT&RUN and RNAseq data, we identified several genes targeted by ΔFOSB that could mediate these observed effects, including Mir155hg, CLCF1, DUSP4, and Trib1. Together, this study provides the first evidence that FOSB/ΔFOSB modulate mast cell functions and provides a new possible target for therapeutic interventions aimed at ameliorating mast cell-related diseases.

Associations of Gut and Circulating Microbiota with Circulating Vitamin D3, Type I Interferon, and Systemic Inflammation in Chronic Spontaneous Urticaria Patients

Objective

To analyze the associations of the gut and circulating microbiota with circulating vitamin D3 (VD3), type I interferon (IFNI), systemic inflammation, and clinical profiles in chronic spontaneous urticaria (CSU) patients.

Methods

A total of 36 CSU patients with VD3 insufficiency (VDI; serum 25(OH)VD3 <30 ng/mL) and 36 sex-, age-, and body mass index-matched CSU patients with non-VDI were enrolled. Fecal and serum bacteria were identified through 16S rRNA sequencing, and serum 25(OH)VD3 and inflammation biomarkers were assessed using ELISA kits. IFNI response was determined by measuring the stimulatory activity of serum on IFNI-stimulated response element in HEK293 cells in vitro with luciferase assays.

Results

Higher urticarial activity score over 7 days (UAS7), higher frequency of levocetirizine resistance, and more severe proinflammation but weaker IFNI response were observed in VDI than non-VDI patients (all P<0.05). IFNI response was strongly positively associated with serum 25(OH)VD3 level in both groups (P<0.001). Compared to non-VDI patients, abundance of the fecal genera Prevotella 9, Escherichia-Shigella, and Klebsiella was significantly increased, while Bacteroides, Faecalibacterium, and Agathobacter were remarkably reduced in VDI patients (all P<0.05). Burkholderia-Caballeronia-Paraburkholderia (40.95%), Acinetobacter (3.05%), and Aquabacterium (2.37%) were the top three bacteria in sera from VDI patients. Both serum 25(OH)VD3 level and IFNI response were positively associated with fecal Bacteroides in the two groups (P<0.05). In non-VDI patients, there were moderately positive associations between IFNI response and fecal Lachnoclostridium, unclassified_f__Lachnospiraceae, and Phascolarctobacterium and between serum 25(OH)VD3 level and fecal Lachnoclostridium (all P<0.01). Circulating microbiota in VDI patients was closely related only to proinflammation and UAS7 (both P<0.05).

Conclusion

Changes in gut but not circulating microbiota composition are associated with serum 25(OH)VD3 insufficiency and impaired IFNI homeostasis, which points to greater disease severity (UAS7) and systemic proinflammation in CSU patients.

The Role Played by Autophagy in FcεRI-Dependent Activation of Mast Cells

The significant role of mast cells in the development of allergic and inflammatory diseases is well-established. Among the various mechanisms of mast cell activation, the interaction of antigens/allergens with IgE and the subsequent binding of this complex to the high-affinity IgE receptor FcεRI stand out as the most studied and fundamental pathways. This activation process leads to the rapid exocytosis of granules containing preformed mediators, followed by the production of newly synthesized mediators, including a diverse array of cytokines, chemokines, arachidonic acid metabolites, and more. While conventional approaches to allergy control primarily focus on allergen avoidance and the use of antihistamines (despite their associated side effects), there is increasing interest in exploring novel methods to modulate mast cell activity in modern medicine. Recent evidence suggests a role for autophagy in mast cell activation, offering potential avenues for utilizing low-molecular-weight autophagy regulators in the treatment of allergic diseases. More specifically, mitochondria, which play an important role in the regulation of autophagy as well as mast cell activation, emerge as promising targets for drug development. This review examines the existing literature regarding the involvement of the molecular machinery associated with autophagy in FcεRI-dependent mast cell activation.

Dysregulated early transcriptional signatures linked to mast cell and interferon responses are implicated in COVID-19 severity

Background

Dysregulated immune responses to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection are thought to underlie the progression of coronavirus disease 2019 (COVID-19) to severe disease. We sought to determine whether early host immune-related gene expression could predict clinical progression to severe disease.

Methods

We analysed the expression of 579 immunological genes in peripheral blood mononuclear cells taken early after symptom onset using the NanoString nCounter and compared SARS-CoV-2 negative controls with SARS-CoV-2 positive subjects with mild (SARS+ Mild) and Moderate/Severe disease to evaluate disease outcomes. Biobanked plasma samples were also assessed for type I (IFN-α2a and IFN-β), type II (IFN-γ) and type III (IFN-λ1) interferons (IFNs) as well as 10 additional cytokines using multiplex immunoassays.

Results

We identified 19 significantly deregulated genes in 62 SARS-CoV-2 positive subject samples within 5 days of symptom onset and 58 SARS-CoV-2 negative controls and found that type I interferon (IFN) signalling (MX1, IRF7, IFITM1, IFI35, STAT2, IRF4, PML, BST2, STAT1) and genes encoding proinflammatory cytokines (TNF, TNFSF4, PTGS2 and IL1B) were upregulated in both SARS+ groups. Moreover, we found that FCER1, involved in mast cell activation, was upregulated in the SARS+ Mild group but significantly downregulated in the SARS+ Moderate/Severe group. In both SARS+ groups we discovered elevated interferon type I IFN-α2a, type II IFN and type III IFN λ1 plasma levels together with higher IL-10 and IL-6. These results indicate that those with moderate or severe disease are characterised by deficiencies in a mast cell response together with IFN hyper-responsiveness, suggesting that early host antiviral immune responses could be a cause and not a consequence of severe COVID-19.

Conclusions

This study suggests that early host immune responses linking defects in mast cell activation with host interferon responses correlates with more severe outcomes in COVID-19. Further characterisation of this pathway could help inform better treatment for vulnerable individuals.

New Mechanistic Advances in FcεRI-Mast Cell-Mediated Allergic Signaling

Mast cells originate from the CD34⁺/CD117⁺ hematopoietic progenitors in the bone marrow, migrate into circulation, and ultimately mature and reside in peripheral tissues. Microbiota/metabolites and certain immune cells (e.g., Treg cells) play a key role in maintaining immune tolerance. Cross-linking of allergen-specific IgE on mast cells activates the high-affinity membrane-bound receptor FcεRI, thereby initiating an intracellular signal cascade, leading to degranulation and release of pro-inflammatory mediators. The intracellular signal transduction is intricately regulated by various kinases, transcription factors, and cytokines. Importantly, multiple signal components in the FcεRI-mast cell–mediated allergic cascade can be targeted for therapeutic purposes. Pharmacological interventions that include therapeutic antibodies against IgE, FcεRI, and cytokines as well as inhibitors/activators of several key intracellular signaling molecues have been used to inhibit allergic reactions. Other factors that are not part of the signal pathway but can enhance an individual’s susceptibility to allergen stimulation are referred to as cofactors. Herein, we provide a mechanistic overview of the FcεRI-mast cell–mediated allergic signaling. This will broaden our scope and visions on specific preventive and therapeutic strategies for the clinical management of mast cell–associated hypersensitivity reactions.

Intrahepatic transcriptomics reveals gene signatures in chronic hepatitis B patients responded to interferon therapy

Chronic hepatitis B virus (HBV) infection remains a substantial public health burden worldwide. Alpha-interferon (IFNα) is one of the two currently approved therapies for chronic hepatitis B (CHB), to explore the mechanisms underlying IFNα treatment response, we investigated baseline and 24-week on-treatment intrahepatic gene expression profiles in 21 CHB patients by mRNA-seq. The data analyses demonstrated that PegIFNα treatment significantly induced antiviral responses. Responders who achieved HBV DNA loss and HBeAg or HBsAg seroconversion displayed higher fold change and larger number of up-regulated interferon-stimulated genes (ISGs). Interestingly, lower expression levels of certain ISGs were observed in responders in their baseline biopsy samples. In HBeAg+ patients, non-responders had relative higher baseline HBeAg levels than responders. More importantly, HBeAg− patients showed higher HBsAg loss rate than HBeAg+ patients. Although a greater fold change of ISGs was observed in HBeAg− patients than HBeAg+ patients, upregulation of ISGs in HBeAg+ responders exceeded HBeAg− responders. Notably, PegIFNα treatment increased monocyte and mast cell infiltration, but decreased CD8 T cell and M1 macrophage infiltration in both responders and non-responders, while B cell infiltration was increased only in responders. Moreover, co-expression analysis identified ribosomal proteins as critical players in antiviral response. The data also indicate that IFNα may influence the production of viral antigens associated with endoplasmic reticulum. Collectively, the intrahepatic transcriptome analyses in this study enriched our understanding of IFN-mediated antiviral effects in CHB patients and provided novel insights into the development of potential strategies to improve IFNα therapy.

Epicutaneous allergen immunotherapy induces a profound and selective modulation in skin dendritic cell subsets

BACKGROUND

Epicutaneous immunotherapy (EPIT) protocols have recently been developed to restore tolerance in patients with food allergy (FA). The mechanisms by which EPIT protocols promote desensitization rely on a profound immune deviation of pathogenic T and B cell responses.

OBJECTIVE

To date, little is known about the contribution of skin dendritic cells (skDCs) to T cell remodeling and EPIT efficacy.

METHODS

We capitalized on a preclinical model of food allergy to ovalbumin (OVA) to characterize the phenotype and functions of OVA⁺ skDCs throughout the course of EPIT.

RESULTS

Our results showed that both Langerhans cells (LCs) and dermal conventional cDC1 and cDC2 subsets retained their ability to capture OVA in the skin and to migrate toward the skin-draining lymph nodes during EPIT. However, their activation/maturation status was significantly impaired, as evidenced by the gradual and selective reduction of CD86, CD40, and OVA protein expression in respective subsets. Phenotypic changes during EPIT were also characterized by a progressive diversification of single cell gene signatures within each DC subset. Interestingly, we observed that OVA⁺ LCs progressively lost their capacity to prime CD4⁺ T_EFF, but gained T_REG stimulatory properties. In contrast, cDC1 were inefficient in priming CD4⁺ T_EFF or in reactivating T_MEMin vitro, while cDC2 retained moderate stimulatory properties, and progressively biased type-2 immunity toward type-1 and type-17 responses.

CONCLUSIONS

Our results therefore emphasize that the acquisition of distinct phenotypic and functional specializations by skDCs during EPIT is at the cornerstone of the desensitization process.

The COVID-19 Pandemic Affects Male Patients With Chronic Spontaneous Urticaria More Than Female Patients

Introduction

The COVID-19 pandemic dramatically disrupts health care for patients with chronic diseases including chronic spontaneous urticaria (CSU). As of now, it is unknown if the effects of the pandemic in CSU are different than in other chronic diseases. We also do not know, if different groups of CSU patients, for example female and male patients, are affected differently.

Aim

To understand how CSU patients and subgroups are affected by the COVID-19 pandemic in their disease activity and control and treatment, using psoriasis as control.

Patients and Methods

We analyzed 399 patients (450 visits) with CSU or psoriasis assessed during August 2019, i.e. before the pandemic, or August 2020, i.e. during the pandemic, for changes in disease activity, disease control, and the treatment they used, and how these changes are linked to age, gender, and disease duration.

Results

Male but not female patients with CSU had markedly increased disease activity during the pandemic. CSU patients’ age or disease duration were not linked to changes. Male and female patients with psoriasis showed similar increases in disease activity and decreases in disease control. The rate of omalizumab treatment, during the pandemic, was unchanged in male patients and increased in female patients with CSU. The efficacy of omalizumab treatment, during the pandemic, was reduced in male patients but not female patients with CSU.

Conclusion

Male but not female CSU patients, during the COVID-19 pandemic, show loss of disease control linked to loss of omalizumab efficacy. The reasons for this need to be investigated.

EGR3-HDAC6-IL-27 Axis Mediates Allergic Inflammation and Is Necessary for Tumorigenic Potential of Cancer Cells Enhanced by Allergic Inflammation-Promoted Cellular Interactions

The objective of this study was to investigate mechanisms of allergic inflammation both in vitro and in vivo in details. For this, RNA sequencing was performed. Early growth response 3 gene (Egr3) was one of the most highly upregulated genes in rat basophilic leukemia (RBL2H3) cells stimulated by antigen. The role of Egr3 in allergic inflammation has not been studied extensively. Egr3 was necessary for passive cutaneous anaphylaxis (PCA) and passive systemic anaphylaxis (PSA). Egr3 promoter sequences contained potential binding site for NF-κB p65. NF-κB p65 directly regulated Egr3 expression and mediated allergic inflammation in vitro. Histone deacetylases (HDACs) is known to be involved in allergic airway inflammation. HDAC6 promoter sequences contained potential binding site for EGR3. EGR3 showed binding to promoter sequences of HDAC6. EGR3 was necessary for increased expression of histone deacetylase 6 (HDAC6) in antigen-stimulated RBL2H3 cells. HDAC6 mediated allergic inflammation in vitro and PSA. TargetScan analysis predicted that miR-182-5p was a negative regulator of EGR3. Luciferase activity assay confirmed that miR-182-5p was a direct regulator of EGR3. MiR-182-5p mimic inhibited allergic inflammation both in vitro and in vivo. Cytokine array showed that HDAC6 was necessary for increased interleukin-27 (IL-27) expression in BALB/C mouse model of PSA. Antigen stimulation did not affect expression of EBI3, another subunit of IL-27 in RBL2H3 cells or BALB/C mouse model of PCA or PSA. IL-27 receptor alpha was shown to be able to bind to HDAC6. IL-27 p28 mediated allergic inflammation in vitro, PCA, and PSA. Mouse recombinant IL-27 protein promoted features of allergic inflammation in an antigen-independent manner. HDAC6 was necessary for tumorigenic and metastatic potential enhanced by PSA. PSA enhanced the metastatic potential of mouse melanoma B16F1 cells in an IL-27-dependent manner. Experiments employing culture medium and mouse recombinant IL-27 protein showed that IL-27 mediated and promoted cellular interactions involving B16F1 cells, lung macrophages, and mast cells during allergic inflammation. IL-27 was present in exosomes of antigen-stimulated RBL2H3 cells. Exosomes from antigen-stimulated RBL2H3 cells enhanced invasion of B16F1 melanoma cells in an IL-27-dependemt manner. These results present evidence that EGR3-HDAC6-IL-27 axis can regulate allergic inflammation by mediating cellular interactions.

Anaphylaxis: Focus on Transcription Factor Activity

Anaphylaxis is a severe allergic reaction, rapid in onset, and can lead to fatal consequences if not promptly treated. The incidence of anaphylaxis has risen at an alarming rate in past decades and continues to rise. Therefore, there is a general interest in understanding the molecular mechanism that leads to an exacerbated response. The main effector cells are mast cells, commonly triggered by stimuli that involve the IgE-dependent or IgE-independent pathway. These signaling pathways converge in the release of proinflammatory mediators, such as histamine, tryptases, prostaglandins, etc., in minutes. The action and cell targets of these proinflammatory mediators are linked to the pathophysiologic consequences observed in this severe allergic reaction. While many molecules are involved in cellular regulation, the expression and regulation of transcription factors involved in the synthesis of proinflammatory mediators and secretory granule homeostasis are of special interest, due to their ability to control gene expression and change phenotype, and they may be key in the severity of the entire reaction. In this review, we will describe our current understanding of the pathophysiology of human anaphylaxis, focusing on the transcription factors' contributions to this systemic hypersensitivity reaction. Host mutation in transcription factor expression, or deregulation of their activity in an anaphylaxis context, will be updated. So far, the risk of anaphylaxis is unpredictable thus, increasing our knowledge of the molecular mechanism that leads and regulates mast cell activity will enable us to improve our understanding of how anaphylaxis can be prevented or treated.