An update on anaphylaxis and urticaria

Association between immune cells and urticaria: a bidirectional Mendelian randomization study

Urticaria is characterized by transient itchy symptoms on the skin, usually accompanied by swelling, which is caused by mast cell activation leading to increased vascular permeability and dilation of the dermis. Urticaria involves recurrent activation of mast cells, T cells, eosinophils, and other immune cells around lesioned venules, with complex regulatory systems affecting mast cell functions, potentially contributing to urticaria pathogenesis. The direct causal relationship between immune cells and urticaria is currently unclear. To address this, our study utilized a bidirectional Mendelian randomization analysis, employing instrumental variables (IVs) associated with immune cells and urticaria, to investigate this causal relationship. First, by utilizing Genome-wide Association Study (GWAS) data, we identified 31 immunophenotypes associated with urticaria risk, with 18 increasing and 13 decreasing the risk. Through rigorous criteria, we identified 4 immunophenotypes that have a strong causal relationship with urticaria. Notably, HLA DR+ CD4+AC, CD45 on CD8br, and HLA DR on plasmacytoid dendritic cells were associated with an increased risk, while CD8dim NKT %lymphocyte was identified as a protective factor. Sensitivity analyses, including the MR-Egger intercept test, scatter plots, funnel plots, and leave-one-out analysis, supported the robustness of the findings. Reverse MR analysis suggested an inverse causal effect of urticaria on CD8dim NKT %lymphocyte, reinforcing the potential bidirectional nature of the relationship between urticaria and immune cell phenotypes. Our research substantiates the bidirectional causal relationship between immune cells and urticaria, thus benefiting for urticaria-targeted therapy development.

N-demethylsinomenine metabolite and its prototype sinomenine activate mast cells via MRGPRX2 and aggravate anaphylaxis

Sinomenine hydrochloride (SH) is commonly used in the treatment of rheumatoid arthritis. It activates mast cells and induces anaphylaxis in the clinical setting. Adverse drug reactions can be caused by activation of MAS-associated G protein-coupled receptor X2 (MRGPRX2) on mast cells. Because the ligand binding site of MRGPRX2 is easily contacted in dilute solvents, it can be activated by many opioid drug structures. N-Demethylsinomenine (M-3) has a similar chemical structure to that of the opioid scaffold and is a major metabolite of SH. We sought to clarify whether M-3 induces anaphylaxis synergistically with its prototype in a mouse model. Molecular docking computer simulations suggested a similar binding effect between M-3 and SH. M-3 was chemically synthesized and analyzed by surface plasmon resonance to reveal its affinity for MRGPRX2. Temperature monitoring, in vivo hindlimb swelling and exudation test, and in vitro mast cell degranulation test were used to explore the mechanism of MRGPrx2 mediated allergic reaction triggered by M-3. Reduced M-3-induced inflammation was evident in MrgprB2 (the ortholog of MRGPRX2) conditional (Cpa3-Cre/MrgprB2flox) knockout (MrgprB2-CKO) mice. Additionally, LAD2 human mast cells with MRGPRX2 knockdown showed reduced degranulation. M-3 activated LAD2 cells synergistically with SH as regulated by GRK2 signaling and IP3R/PLC/PKC/P38 molecular signaling pathways. The results indicate that the M-3 metabolite can activate mast cells synergistically with its prototype SH via MRGPRX2 and aggravate anaphylaxis. These findings provide important insights into drug safety.

Management of Refractory Anaphylaxis: An Overview of Current Guidelines

In this review, we compare different refractory anaphylaxis (RA) management guidelines focusing on cardiovascular involvement and best practice recommendations, discuss postulated pathogenic mechanisms underlining RA and highlight knowledge gaps and research priorities. There is a paucity of data supporting existing management guidelines. Therapeutic recommendations include the need for the timely administration of appropriate doses of aggressive fluid resuscitation and intravenous (IV) adrenaline in RA. The preferred second-line vasopressor (noradrenaline, vasopressin, metaraminol and dopamine) is unknown. Most guidelines recommend IV glucagon for patients on beta-blockers, despite a lack of evidence. The use of methylene blue or extracorporeal life support (ECLS) is also suggested as rescue therapy. Despite recent advances in understanding the pathogenesis of anaphylaxis, the factors that lead to a lack of response to the initial adrenaline and thus RA are unclear. Genetic factors, such as deficiency in platelet activating factor-acetyl hydrolase or hereditary alpha-tryptasaemia, mastocytosis may modulate reaction severity or response to treatment. Further research into the underlying pathophysiology of RA may help define potential new therapeutic approaches and reduce the morbidity and mortality of anaphylaxis.

PTGS2: A potential immune regulator and therapeutic target for chronic spontaneous urticaria

AIMS

Chronic spontaneous urticaria (CSU) is a common and debilitating skin disease that is difficult to control with existing treatments, and the pathogenesis of CSU has not been fully revealed. The aim of this study was to explore the underlying mechanisms of CSU and identify potential treatments.

MATERIALS AND METHODS

Microarray datasets of CSU were obtained from Gene Expression Omnibus database. Differentially expressed genes between skin lesions of CSU and normal controls (LNS-DEGs) were identified, and the enrichment analyses of LNS-DEGs were performed. Hub genes of LNS-DEGs were selected by protein-protein interaction analysis. The co-expression and transcriptional regulatory networks of hub genes were conducted using GeneMANIA and TRRUST database, respectively. CIBERSORT was utilized for immune cell infiltration analysis. Experimental validation was performed by β-hexosaminidase release examination and passive cutaneous anaphylaxis (PCA) mouse model.

KEY FINDINGS

A total of 247 LNS-DEGs were identified, which were enriched in cell migration, cell chemotaxis, and inflammatory pathways such as TNF and interleukin (IL) -17 signaling pathway. Among LNS-DEGs, seven upregulated (PTGS2, CCL2, IL1B, CXCL1, IL6, VCAM1, ICAM1) and one downregulated hub gene (PECAM1) were selected. Immune infiltration analysis identified eight different immune cells, such as activated/resting mast cells and neutrophils. Furthermore, PTGS2, encoding cyclooxygenase 2 (COX2), was selected for further validation. COX2 inhibitor, celecoxib, significantly inhibited mast cell degranulation, and reduced vascular permeability and inflammatory cytokine expression in PCA mouse model.

SIGNIFICANCE

PTGS2 may be a potential regulator of immunity and inflammation in CSU. Targeting PTGS2 is a new perspective for CSU treatment.

A case-control study for comorbidity and laboratory factors associated with food-induced anaphylaxis

Background: Food-induced anaphylaxis (FIA) is a serious and potentially life-threatening allergic reaction triggered by food allergens. Objective: This case-control study aimed to investigate comorbidities and laboratory factors associated with FIA in the pediatric population of Israel. Methods: Retrospective data from the electronic health records of Leumit Health Care Services were used to identify 711 pediatric patients with FIA and 2560 subjects with food allergy and without anaphylaxis matched for age, gender, and ethnicity. Comorbidities were identified based on medical billing diagnosis codes, and laboratory characteristics were compared between the two groups. Results: The mean ± standard deviation age of patients with FIA was 4.1 ± 4.1 years, and 37.3% were girls. Laboratory analysis revealed increased eosinophil counts (p < 0.001), elevated immunoglobulin E (IgE) (p < 0.001), and IgA levels (p = 0.001) in the FIA group compared with the controls. With regard to comorbidities, the FIA group had higher prevalence rates of allergic diseases, including allergic rhinitis (odds ratio [OR] 1.72; p < 0.001), allergic conjunctivitis (OR 1.84; p = 0.001), asthma (OR 1.36; p < 0.001), angioedema (OR 6.37; p < 0.001), atopic dermatitis (OR 1.77; p < 0.001), and contact dermatitis (OR 1.42; p = 0.001). There was a trend toward significance for chronic spontaneous urticaria (p = 0.051). There was a significant negative association between helminthiases, particularly enterobiasis, and FIA (OR 0.76 [95% confidence interval, 0.59-0.98]; p = 0.029). Conclusion: This study provides valuable epidemiologic evidence on the associations among FIA, comorbidities, and laboratory factors in the pediatric population.

Clinical characteristics and immune profiles of patients with immune-mediated alopecia associated with COVID-19 vaccinations

BACKGROUND

The clinical characteristics and pathomechanism for immune-mediated alopecia following COVID-19 vaccinations are not clearly characterized.

OBJECTIVE

We investigated the causality and immune mechanism of COVID-19 vaccines-related alopecia areata (AA).

STUDY DESIGN

27 new-onset of AA patients after COVID-19 vaccinations and 106 vaccines-tolerant individuals were enrolled from multiple medical centers for analysis.

RESULTS

The antinuclear antibody, total IgE, granulysin, and PARC/CCL18 as well as peripheral eosinophil count were significantly elevated in the patients with COVID-19 vaccines-related AA compared with those in the tolerant individuals (P = 2.03 × 10-5-0.039). In vitro lymphocyte activation test revealed that granulysin, granzyme B, and IFN-γ released from the T cells of COVID-19 vaccines-related AA patients could be significantly increased by COVID-19 vaccine excipients (polyethylene glycol 2000 and polysorbate 80) or spike protein (P = 0.002-0.04).

CONCLUSIONS

Spike protein and excipients of COVID-19 vaccines could trigger T cell-mediated cytotoxicity, which contributes to the pathogenesis of immune-mediated alopecia associated with COVID-19 vaccines.

Characteristics of immune response profile in patients with immediate allergic and autoimmune urticarial reactions induced by SARS-CoV-2 vaccines

Severe allergic reactions following SARS-COV-2 vaccination are generally rare, but the reactions are increasingly reported. Some patients may develop prolonged urticarial reactions following SARS-COV-2 vaccination. Herein, we investigated the risk factors and immune mechanisms for patients with SARS-COV-2 vaccines-induced immediate allergy and chronic urticaria (CU). We prospectively recruited and analyzed 129 patients with SARS-COV-2 vaccine-induced immediate allergic and urticarial reactions as well as 115 SARS-COV-2 vaccines-tolerant individuals from multiple medical centers during 2021-2022. The clinical manifestations included acute urticaria, anaphylaxis, and delayed to chronic urticaria developed after SARS-COV-2 vaccinations. The serum levels of histamine, IL-2, IL-4, IL-6, IL-8, IL-17 A, TARC, and PARC were significantly elevated in allergic patients comparing to tolerant subjects (P-values = 4.5 × 10^-5-0.039). Ex vivo basophil revealed that basophils from allergic patients could be significantly activated by SARS-COV-2 vaccine excipients (polyethylene glycol 2000 and polysorbate 80) or spike protein (P-values from 3.5 × 10^-4 to 0.043). Further BAT study stimulated by patients' autoserum showed positive in 81.3% of patients with CU induced by SARS-COV-2 vaccination (P = 4.2 × 10^-13), and the reactions could be attenuated by anti-IgE antibody. Autoantibodies screening also identified the significantly increased of IgE-anti-IL-24, IgG-anti-FcεRI, IgG-anti-thyroid peroxidase (TPO), and IgG-anti-thyroid-related proteins in SARS-COV-2 vaccines-induced CU patients comparing to SARS-COV-2 vaccines-tolerant controls (P-values = 4.6 × 10^-10-0.048). Some patients with SARS-COV-2 vaccines-induced recalcitrant CU patients could be successfully treated with anti-IgE therapy. In conclusion, our results revealed that multiple vaccine components, inflammatory cytokines, and autoreactive IgG/IgE antibodies contribute to SARS-COV-2 vaccine-induced immediate allergic and autoimmune urticarial reactions.