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The etiology and pathophysiology of allergic diseases remain incompletely understood. Current immunological paradigms, while insightful, often fall short in fully elucidating the mechanisms underlying allergic and autoimmune disorders. Under the protein–homeostasis–system (PHS) hypothesis, allergic diseases have etiological substances, and immune reactions against them are responsible for clinical manifestations of allergic diseases. The etiological substances are mainly external in origin and very small with each biochemical property and react to target cells in various organ tissues. Eosinophils, mast cells, and immunoglobulin Es as major immune effectors in allergic diseases control toxic substances according to the chemical or biochemical properties of these substances. Mast cells in the central nervous system may be associated with allergic episodes through connection to peripheral mast cells, and this connection is proposed as the mast cell-associated network. The toxic and/or bioactive proteins/peptides and other non-protein substances, which are derived from injured cells caused by allergic reactions, induce activation of adaptive and innate immune components for controlling the substances. New insights into the etiology and pathophysiology of allergic diseases are introduced with the PHS hypothesis. Full article

MRGPRX2 (Mas-related G protein-coupled receptor member X2) is implicated in mast cell (MC)-driven disorders due to its ability to bind diverse ligands, which may be G-protein-biased or balanced, with the latter activating both G-proteins and the β-arrestin pathway. Icatibant, a peptide drug, produces injection-site reactions in most patients and is used experimentally to probe MRGPRX2 function in skin tests. While reported to be G-protein-biased, it is unknown how skin MCs respond to icatibant, although these are the primary target cells during therapy. We therefore compared responses to icatibant with those induced by the balanced agonist substance P (SP) in skin MCs. Degranulation and desensitization were assessed via β-hexosaminidase release, receptor internalization by flow cytometry, and downstream signaling by immunoblotting. Skin MCs degranulated in response to SP and icatibant, relying on Gi proteins and calcium channels; Gq and PI3K (Phosphoinositide 3-kinase) contributed more strongly to exocytosis following icatibant, while JNK (c-Jun n-terminal kinase) was more relevant for SP. Both agonists activated ERK, PI3K/AKT, and (weakly) p38. Surprisingly, and in contrast to the LAD2 (Laboratory of Allergic Diseases 2 mast cell line) MC line, icatibant was at least as potent as SP in eliciting MRGPRX2 internalization and (cross-)desensitization in skin MCs. These findings suggest that icatibant functions differently in primary versus transformed MCs, acting as a fully balanced ligand in the former by triggering not only degranulation but also receptor internalization and desensitization. Therefore, not only the ligand but also the MRGPRX2-expressing cell plays a decisive role in whether a ligand is balanced or biased. These findings are relevant to our understanding of icatibant’s clinical effects on edema and itch. Full article

In addition to its role in angiotensin II (Ang II) production, chymase exhibits various functions, including activation of latent transforming growth factor beta 1 (TGF-β1) and pro-matrix metalloproteinases (MMPs). However, the extent to which these Ang II-independent functions contribute to pathological conditions remains unclear. In this study, we investigated the Ang II-independent roles of chymase in cardiac remodeling and dysfunction. Eighteen male Syrian hamsters, aged 6 weeks and weighing 90–110 g, were used. Exogenous Ang II was administered to a hamster model that mirrors the human chymase-dependent Ang II production pathway, via subcutaneous osmotic mini pumps (2 mg/kg/day) for 4 weeks. A chymase-specific inhibitor, TY-51469 (10 mg/kg/day), was given daily starting 1 day after commencement of Ang II infusion. Evaluation showed that while systolic blood pressure increased significantly, only diastolic dysfunction developed over time. Ang II treatment led to elevated cardiac expression of chymase, TGF-β1, and MMP-2, and increased the number of chymase-positive mast cells, resulting in notable cardiac hypertrophy and fibrosis. TY-51469 effectively suppressed these molecular changes and improved both cardiac structure and diastolic dysfunction, despite continued Ang II exposure. These results suggest that chymase promotes cardiac remodeling and dysfunction not only through Ang II generation but also by activating profibrotic and matrix-degrading factors, such as TGF-β1 and MMP-2. Full article

This narrative review explains the history of anaphylactic or hypersensitivity reactions, their connection to the cardiovascular system, and Kounis syndrome, which is linked to hypersensitivity. Additional subjects discussed include immunoglobulin E and serum tryptase, common pathways of allergic and nonallergic cardiovascular events, current perspectives on Kounis syndrome, allergic myocardial infarction, allergic angina, and the impact of COVID-19 and its vaccination on Kounis syndrome. Kounis syndrome is a distinct kind of acute vascular disease that affects the coronary, cerebral, mesenteric, peripheral, and venous systems. Kounis syndrome is currently used to describe coronary symptoms linked to disorders involving mast cell activation and inflammatory cell interactions, such as those involving T-lymphocytes and macrophages, which further induce allergic, hypersensitive, anaphylactic, or anaphylactic insults. Platelet activating factor, histamine, neutral proteases like tryptase and chymase, arachidonic acid products, and a range of cytokines and chemokines released during the activation process are among the inflammatory mediators that cause it. Proinflammatory cytokines are primarily produced by mast cells in COVID-19 infections. Mast cell-derived proteases and eosinophil-associated mediators are also more prevalent in the lung tissues and sera of COVID-19 patients. As a modern global threat to civilization, COVID-19 is linked to chemical patterns that can activate mast cells; therefore, allergic stimuli are usually the reason. Virus-associated molecular patterns can activate mast cells, but allergic triggers are typically the cause. By activating SARS-CoV-2 and other toll-like receptors, a variety of proinflammatory mediators, including IL-6 and IL-1β, are released, potentially contributing to the pathology of COVID-19. Full article

Atopic dermatitis (AD) is a chronic inflammatory disorder with immune imbalance, including elevated IgE levels and mast cell activation mediated by Th2 cytokines, leading to allergic inflammation and impaired skin barrier function. Current treatment limitations highlight the need for safer and more effective AD alternatives. We aimed to evaluate the therapeutic effects of multi-strain probiotics, BCL-2 (comprising Lactiplantibacillus plantarum LRCC5264 and Bifidobacterium longum RAPO), in alleviating AD clinical signs and elucidate its underlying immunomodulatory mechanisms. In vitro, BCL-2 treatment significantly reduced IL-4 secretion in RBL-2H3 cells, with higher inhibitory effects than single-strain treatment. In vivo, BCL-2 (10⁶–10⁸ CFU/day) was orally administered for 28 days to AD-induced Nc/Nga mice. BCL-2 treatment improved the clinical signs and histopathological features of AD, including epidermal hypertrophy, hyperkeratosis, and mast cell infiltration (p < 0.05). It also reduced neutrophil and eosinophil counts and modulated cytokine and chemokine profiles, notably decreasing IL-17, IL-5, IL-6, TNF-α, IL-1β, TARC, and eotaxin, while increasing IL-10, IFN-γ, and IL-12 (p < 0.05). Among the tested concentrations, 10⁷ CFU exhibited the most effective immune modulation with no adverse effects on body weight. These findings demonstrate the therapeutic potential of BCL-2 in AD; however, further studies are required to validate its clinical relevance. Full article

Emerging evidence suggests a critical role of the gut microbiome in modulating systemic immune responses, with increasing relevance in dermatological diseases. Chronic spontaneous urticaria (CSU), traditionally viewed as an isolated cutaneous disorder, is now recognized as a systemic immune condition involving complex interactions between innate and adaptive immunity, mast cell dysregulation, and non-IgE-mediated pathways. This review explores the gut–skin axis as a unifying concept linking intestinal dysbiosis to inflammatory skin diseases, including atopic dermatitis, psoriasis, rosacea, and acne. Special emphasis is placed on CSU, where altered gut microbial composition, characterized by reduced diversity, depletion of short-chain fatty acid-producing bacteria, and expansion of Proteobacteria, may contribute to increased intestinal permeability, systemic immune activation via toll-like receptors, and heightened mast cell sensitivity. We discuss findings from animal models demonstrating that gut microbiota modulation can attenuate mast cell hyperreactivity and reduce urticarial symptoms. In parallel, we examine clinical evidence supporting the potential role of probiotics, prebiotics, dietary interventions, and fecal microbiota transplantation as adjunctive strategies in CSU management. Despite promising findings, challenges remain in translating microbiome research into effective therapies due to interindividual variability, the complexity of host–microbiome interactions, and a lack of standardized protocols. Future research should focus on identifying predictive microbial patterns and developing personalized microbiome-targeted interventions. Understanding the bidirectional gut–skin relationship may open new therapeutic avenues beyond symptomatic treatment, positioning the microbiome as a novel target in CSU and related inflammatory dermatoses. Full article

Objective: This study aims to identify clinically relevant lactylation-related biomarkers in chronic obstructive pulmonary disease (COPD) and investigate their potential mechanistic roles in COPD pathogenesis. Methods: Differentially expressed genes (DEGs) were identified from the GSE21359 dataset, followed by weighted gene co-expression network analysis (WGCNA) to detect COPD-associated modules. Least absolute shrinkage and selection operator (LASSO) regression and support vector machine–recursive feature elimination (SVM–RFE) algorithms were applied to screen lactylation-related biomarkers, with diagnostic performance evaluated through the ROC curve. Candidates were validated in the GSE76925 dataset for expression and diagnostic robustness. Immune cell infiltration patterns were exhibited using EPIC deconvolution. Single-cell transcriptomics (from GSE173896) were processed via the ‘Seurat’ package encompassing quality control, dimensionality reduction, and cell type annotation. Cell-type-specific markers and intercellular communication networks were delineated using the ‘FindAllMarkers’ package and the ‘CellChat’ R package, respectively. In vitro validation was conducted using a cigarette smoke extract (CSE)-induced COPD model. Results: Integrated transcriptomic approaches and multi-algorithm screening (LASSO/Boruta/SVM–RFE) revealed carbonyl reductase 1 (CBR1) and peroxiredoxin 1 (PRDX1) as core COPD biomarkers enriched in oxidation–reduction and inflammatory pathways, with high diagnostic accuracy (AUC > 0.85). Immune profiling and scRNA-seq delineated macrophage and cancer-associated fibroblasts (CAFs) infiltration with oxidative-redox transcriptional dominance in COPD. CBR1 was significantly upregulated in T cells, neutrophils, and mast cells; and PRDX1 showed significant upregulation in endothelial, macrophage, and ciliated cells. Experimental validation in CSE-induced models confirmed significant upregulation of both biomarkers via transcription PCR (qRT-PCR) and immunofluorescence. Conclusions: CBR1 and PRDX1 are lactylation-associated diagnostic markers, with lactylation-driven redox imbalance implicated in COPD progression. Full article

Background/Objectives: Fasting-induced elevation of blood ketone body levels suppresses allergic reactions; however, the underlying mechanism remains unclear. This study investigated whether elevated ketone body levels affect allergic contact dermatitis (ACD) and explored nutritional interventions that effectively increase β-hydroxybutyrate (BHB) levels. Additionally, we examined the role of GPR109A, a receptor for β-hydroxybutyrate (BHB), in ketone body-induced allergy suppression through ingestion of a ketogenic substrate. Methods: To evaluate the effects of ketone body precursors, medium-chain triglyceride (MCT) oil or 1,3-butanediol (BD) was administered as a single oral dose (2 g/kg body weight) under fed conditions. Blood BHB concentrations were measured at the time of euthanasia. ACD was induced using 2,4-dinitrofluorobenzene (DNFB), and its severity was assessed by measuring ear swelling and mast cell (MC) degranulation. To determine whether GPR109A mediates ketone body-induced allergy suppression, mepenzolate bromide (MPN), a GPR109A antagonist, was subcutaneously administered before BD treatment. Results: Both MCT oil and BD significantly increased the blood BHB levels. Elevated BHB concentrations were accompanied by reduced ear swelling and MC degranulation in DNFB-treated mice. The anti-allergic effects of BD were abolished by MPN administration, indicating that these effects were mediated by GPR109A activation. Conclusions: Nutritional supplementation with ketogenic substrates, such as MCT oil and BD, may serve as a dietary intervention for ACD by elevating blood BHB levels. GPR109A activation appears to be involved in ketone body-induced allergy suppression, suggesting a mechanistic link between ketone metabolism and immunomodulation. Full article

Objectives: Atopic dermatitis (AD) is a long-term, recurring inflammatory skin condition characterized by impaired epidermal barrier function and abnormal immune system regulation. Pine pollen has traditionally been used for dermatological treatments, though its active components remain unclear. The primary objective of this study was to pinpoint the active constituents of pine pollen and elucidate its therapeutic effects against AD. Methods: The safety concentration ranges and protective efficacy of nine pine pollen constituents against 2,4-dinitrochlorobenzene (DNCB)-induced HaCaT cell damage were evaluated using the CCK-8 assay. Furthermore, models of DNCB-induced damage were established both in vitro (HaCaT cells) and in vivo (BALB/c mice) to explore the protective effects of the key functional component. Results: Our findings identified pine pollen polysaccharides (PPPS) as the principal bioactive constituent, characterized by a unique infrared absorption spectral profile and a sponge-like architecture with three-dimensional interconnected porous networks. In vitro, PPPS inhibited DNCB-induced decreases in cell viability, morphological abnormalities, oxidative stress, and apoptosis. In vivo, PPPS alleviated DNCB-induced skin lesions by attenuating epidermal hyperplasia, suppressing mast cell infiltration, inhibiting cell apoptosis, and downregulating the expression of IL-4 and IL-17A. Conclusions: This study provides evidence that PPPS from pine pollen can alleviate epidermal damage in AD, offering a novel therapeutic strategy for AD treatment. Full article

Helicobacter pylori (Hp), a widespread gastric pathogen, has long been studied for its role in upper gastrointestinal disorders. While its involvement in gastritis, peptic ulcer disease, and gastric cancer is well established, its impact on esophageal diseases remains an area of ongoing investigation. Nevertheless, some data indicate that Hp may be involved in the pathogenesis of gastroesophageal reflux disease–Barrett’s esophagus–esophageal adenocarcinoma sequence. Similarly, the Hp-related mast cell activation—an essential immunological event—may also play a crucial role in the progression from gastroesophageal reflux disease to Barrett’s esophagus and esophageal adenocarcinoma. The underlying mechanisms include immune modulation, cytokine cascades, and microbial interactions that collectively shape the esophageal microenvironment. This review provides an in-depth analysis of these pathways, highlighting the potential role of Hp-induced, mast cell-driven inflammation in esophageal disease progression and discussing emerging therapeutic strategies. Full article

Amirthalingamia macracantha (Joyeux and Baer, 1935) larvae, a member of the Gryporhynchidae family (Cestoda: Cyclophyllidea), are commonly found in a variety of African fish species, including Nile tilapia (Oreochromis niloticus, Linnaeus, 1758). Nonetheless, little is known regarding their existence in native Egyptian fish species. Two hundred O. niloticus were examined in the current investigation, using standard parasitological techniques to detect the presence of these larvae in different fish organs. According to this study’s findings, A. macracantha larvae were found in 35% of the microscopically examined samples as red nodules, attaching to the serosa of both the anterior and posterior sections of the intestine and stomach, respectively. The mean abundance of the infection was 3.5 ± 0.05 (CI 95% 3.4–3.5), and its mean intensity was 10 ± 1.7 (CI 95% 8.2–11.7). The existence of two rows of twenty rostellar hooks of varying lengths is the main characteristic of the parasite. The upper row consisted of four large hooks and six smaller ones, while the lower row contained smaller hooks of consistent length. According to histopathological analysis, the larvae with a hook-and-spiny rostellum were affixed to the stomach serosa of O. niloticus. Additionally, there was a notable presence of degranulated mast cells and lymphocytes of varying sizes within the stomach’s lamina propria, submucosa, and blood vessels, as well as a loss of gastric epithelium, fibrosis, and enlargement of submucosal lymph vessels. This study offers a succinct description of this larval stage, representing the first reported occurrence of its presence in Egyptian O. niloticus. Full article

Microglia, the brain’s resident innate immune cells, play a fundamental role in maintaining neural homeostasis and mediating responses to injury or infection. Upon activation, microglia undergo morphological and functional changes, including phenotypic switching between pro- and anti-inflammatory types and the release of different inflammatory mediators. These processes contribute to neuroprotection and the pathogenesis of various central nervous system (CNS) disorders. Mast cells, although sparsely located in the brain, exert a significant influence on neuroinflammation through their interactions with microglia. Through degranulation and secretion of different mediators, mast cells disrupt the blood–brain barrier and modulate microglial responses, including alteration of microglial phenotypes. Notably, mast cell-derived factors, such as histamine, interleukins, and tryptase, activate microglia through various pathways including protease-activated receptor 2 and purinergic receptors. These interactions amplify inflammatory cascades via various signaling pathways. Previous studies have revealed an exceedingly complex crosstalk between mast cells and microglia suggesting a bidirectional regulation of CNS immunity, implicating their cooperation in both neurodegenerative progression and repair mechanisms. Here, we review some of the diverse communication pathways involved in this complex interplay. Understanding this crosstalk may offer novel insights into the cellular dynamics of neuroinflammation and highlight potential therapeutic targets for a variety of CNS disorders. Full article

Background: Patients with mastocytosis may present with exacerbated respiratory symptoms and lung diseases resulting from mast cell mediator release. However, their prevalence and severity level remain under debate. The study aims to analyze the prevalence of respiratory symptoms and the usefulness of lung function tests like spirometry, diffusing capacity of the lung for carbon monoxide (DLCO), and high-resolution computed tomography (HRCT) of the chest in mastocytosis patients presenting with dyspnea, cough, and exercise intolerance. Methods: We included 104 patients with mastocytosis and 71 healthy controls. Data collection encompassed patient interview, clinical examination, spirometry, DLCO, and chest HRCT. Diagnosis of mastocytosis included bone marrow biopsies and serum tryptase measurements. Results: Compared to controls, patients with mastocytosis exhibited significantly lower values in FEV1/VC ratio, absolute DLCO/VA, predicted DLCO/VA, absolute DLCOcSB, and predicted DLCOcSB (p < 0.001). Commonly reported respiratory symptoms included dyspnea (36.5%), chest tightness (22.1%), and wheezing (9.6%). Airway obstruction was identified in 7.7% of patients; however, it appeared to be independent of the mastocytosis subtype. A decreased DLCO/VA ratio was observed in 4.8% of patients, but HRCT did not reveal any evidence of underlying lung disease. Conclusions: Mastocytosis appears to be a risk factor for the occurrence and exacerbation of respiratory symptoms. However, airway obstruction and impairment of the alveolar–capillary membrane seem to occur independently of the clinical subtype of mastocytosis. Additionally, the causal relationship between pulmonary involvement, mast cell infiltration of the alveolar–capillary membrane, and the systemic circulation of mast cell mediators remains unclear and requires further research. Full article

Patients with Inflammatory Bowel Disease (IBD) exhibit a dysregulated immune response that may be further exacerbated by bioactive compounds, such as histamine. Current dietary guidelines for IBD primarily focus on symptom management and flare-up prevention, yet targeted nutritional strategies addressing histamine metabolism remain largely unexplored. This narrative review aims to summarize the existing literature on the complex interplay between IBD and histamine metabolism and propose a novel dietary framework for managing IBD progression in patients with histamine intolerance (HIT). Relevant studies were identified through a comprehensive literature search of PubMed/MEDLINE, Google Scholar, ScienceDirect, Scopus, and Web of Science. The proposed low-histamine diet (LHD) aims to reduce the overall histamine burden in the body through two primary strategies: (1) minimizing exogenous intake by limiting high-histamine and histamine-releasing foods and (2) reducing endogenous histamine production by modulating gut microbiota composition, specifically targeting histamine-producing bacteria. In parallel, identifying individuals who are histamine-intolerant and understanding the role of histamine-degrading enzymes, such as diamine oxidase (DAO) and histamine-N-methyltransferase (HNMT), are emerging as important areas of focus. Despite growing interest in the role of histamine and mast cell activation in gut inflammation, no clinical trials have investigated the effects of a low-histamine diet in IBD populations. Therefore, future research should prioritize the implementation of LHD interventions in IBD patients to evaluate their generalizability and clinical applicability. Full article

Atopic dermatitis (AD) is a common chronic inflammatory skin disorder characterized by immune dysregulation and skin barrier impairment. This study evaluated the anti-inflammatory and immunomodulatory effects of Camellia japonica extract in a 2,4-dinitrochlorobenzene (DNCB)-induced AD mouse model using SKH-1 hairless mice. Topical application of Camellia japonica extract for four weeks significantly alleviated AD-like symptoms by reducing epidermal thickness, mast cell infiltration, and overall skin inflammation. Hematological analysis revealed a marked decrease in total white blood cell (WBC) and neutrophil counts. Furthermore, the Camellia japonica extract significantly decreased oxidative stress, as evidenced by reduced serum reactive oxygen species (ROS) and nitric oxide (NO) levels, while enhancing the activity of antioxidant enzymes such as catalase. Importantly, allergic response markers including serum immunoglobulin E (IgE), histamine, and thymic stromal lymphopoietin (TSLP), were also downregulated. At the molecular level, Camellia japonica extract suppressed the expression of key pro-inflammatory cytokines, including tumor necrosis factor-alpha (TNF-α), interleukin (IL)-1β, and T helper 2 (Th2)-type cytokines such as IL-4 and IL-5, while slightly upregulating the anti-inflammatory cytokine IL-10. Collectively, these findings suggest that Camellia japonica extract effectively modulates immune responses, suppresses allergic responses, attenuates oxidative stress, and promotes skin barrier recovery. Therefore, application of Camellia japonica extract holds the promising effect as a natural therapeutic agent for the prevention and treatment of AD-like skin conditions. Full article