Search Results (74)

The IRE1α-XBP1 axis is the most conserved of the three major unfolded protein response (UPR) branches triggered by the endoplasmic reticulum (ER) stress. Although the transcription factor XBP1 is involved in the development and function of several hematopoietic lineages, its role in the activation of mast cells (MCs), which are critical in allergic responses, remains largely unknown. We identified salicylaldehyde, which suppresses IRE1α nuclease activity that is essential for XBP1 production, as an inhibitor of MC activation in our previous screening; therefore, we herein investigated the effects of additional IRE1α inhibitors, 3-methyl-6-bromo-salichylaldehyde (MBSA) and KIRA6, targeting the nuclease domain and kinase domain, respectively, on MC activation. MBSA and KIRA6 suppressed IgE-dependent degranulation of bone marrow-derived MCs (BMMCs) but did not inhibit Ca²⁺ ionophore- or compound48/80-induced degranulation. Treatments with inhibitors of two other branches of UPR, the PERK and ATF6 pathways, did not affect the IgE-induced activation of BMMCs. The intraperitoneal administration of MBSA or KIRA6 significantly suppressed IgE-induced passive anaphylaxis in mice. Furthermore, to examine the effects of XBP1, siRNA-mediated knockdown was performed. The results obtained confirmed that Xbp1 siRNA introduction reduced the IgE-dependent degranulation of BMMCs in parallel with the knockdown level of Xbp1 mRNA. Therefore, the IRE1α-XBP1 axis plays a significant role in IgE-dependent and MC-mediated allergic responses and is considered to be a therapeutic target of allergic diseases. Full article

Background/Objectives: Cardiovascular disease (CVD), particularly coronary artery disease (CAD), is increasingly linked to microvascular inflammation driven by interactions between immune, vascular, and neuroendocrine systems. Mast cells (MCs), strategically positioned near blood vessels, play pivotal roles in this process through the release of inflammatory and vasoactive mediators, contributing to increased vascular permeability, endothelial dysfunction, and tissue inflammation in conditions including ischemia–reperfusion (I/R) and CVD. This comprehensive review examines the cellular and molecular mechanisms underlying MC-mediated microvascular inflammation, with emphasis on neuroimmune regulation through the heart–brain axis, and evaluates the therapeutic potential of flavonoids. Methods: A review of in vitro, animal, and clinical studies was conducted to assess MC-mediated cardiovascular pathology and the pharmacological effects of natural flavonoids on MC activation and microvascular inflammation. Results: Psychological and physical stress activates hypothalamic corticotropin-releasing hormone (CRH) signaling, directly triggering coronary MC degranulation via CRHR-1 and CRHR-2 receptors, while co-released neuropeptides, including neurotensin and urocortin, amplify this neuroimmune cascade. Traumatic brain injury, autonomic dysregulation, and atrial fibrillation further perpetuate this bidirectional heart–brain axis, linking neurological stress to microvascular injury and adverse cardiac remodeling. An autocrine–paracrine CRH amplification loop sustains chronic coronary microvascular inflammation, contributing to heart failure with preserved ejection fraction (HFpEF) and MC activation disease (MCAD)-related cardiovascular manifestations. Natural flavonoids were found to inhibit MC activation, suppress inflammatory mediator synthesis, and protect microvascular integrity through multiple molecular targets, including calcium signaling, transcription factors, oxidative stress pathways, and CRHR-1-mediated neuroimmune signaling. Conclusions: While challenges remain regarding bioavailability and standardization, multi-compound formulations targeting multiple risk factors hold promise for preventing CVD progression. Future research directions for advancing these natural compounds toward clinical implementation are identified. Full article

Transient receptor potential vanilloid 4 (TRPV4) is a polymodal cation channel that is widely expressed in sensory neurons, immune cells, and structural tissues, where it integrates mechanical, osmotic, and chemical stimuli to regulate both physiological responses and disease-associated signaling. Mast cells (MCs), key immune effector cells capable of rapid mediator release through degranulation, also express TRPV4. Increasing evidence supports TRPV4-MC signaling as an important neuroimmune interface, linking mechanical and inflammatory stimuli to tissue hypersensitivity and pain. In this review, we synthesize current evidence supporting a role for TRPV4 in MC-associated neuroimmune signaling across multiple disease contexts while distinguishing settings in which TRPV4 directly regulates MC activation from those in which MC responses arise through multicellular tissue interactions. Direct TRPV4-dependent MC activation has been described in conditions such as LL-37–driven rosacea and mechanically induced inflammation, whereas in disorders including asthma, visceral hypersensitivity, bladder pain syndromes, and osteoarthritis, TRPV4 activity in epithelial, neuronal, or stromal compartments more often influences MC function indirectly through ATP–purinergic signaling, cytokine release, and neuropeptide-mediated crosstalk. Across systems, TRPV4 emerges not as a single pathogenic switch but as part of a context-dependent signaling network whose functional consequences depend on cell type, tissue microenvironment, and disease stage. Altogether, these findings identify TRPV4 as a therapeutically actionable node within neuroimmune signaling pathways and support the development of tissue-specific and combination strategies targeting both TRPV4 activity and MC-mediated signaling in chronic inflammatory and pain disorders. Full article

Type 2 diabetes (T2D) features insulin resistance that promotes cerebrovascular injury, yet the immune signals linking metabolic stress to vascular dysfunction remain unclear. We tested the hypothesis that insulin resistance and soluble vascular cell adhesion molecule-1 (sVCAM1) act through complementary pathways in mast cells (MCs) to raise circulating histamine levels and impair cerebral vascular function. In a high-fat diet (HFD) plus low-dose streptozotocin (STZ) model, plasma histamine rose sharply after the onset of insulin resistance and remained elevated. Plasma sVCAM1 levels also increased after insulin resistance. In vitro, recombinant sVCAM1 upregulated histidine decarboxylase (HDC) in native MCs in a dose-dependent manner, indicating a shift toward histamine synthesis, but did not enhance degranulation. In contrast, pharmacological inhibition of Akt with MK2206 activated Glycogen Synthase Kinase 3 beta (GSK3β) and increased MC degranulation without affecting HDC expression. Diabetic endothelial cell monolayers exhibited a ~twofold reduction in transendothelial electrical resistance consistent with impaired blood–brain barrier (BBB) integrity. Diabetic cerebral arteries showed receptor remodeling that favored constriction with histamine H1 receptor (H1R) expression increasing in vascular smooth muscle, while endothelial H1R and histamine H2 receptor (H2R) decreased. Functionally, insulin treatment lowered HOMA2-IR in T2D mice but did not restore cerebral artery myogenic tone or improve stroke outcomes after distal middle cerebral artery occlusion (dMCAO). Neutralizing VCAM1 with a monoclonal antibody reduced circulating sVCAM1 and histamine levels, and, together with the GSK3β inhibitor Tideglusib, stabilized MCs, normalized cerebral artery tone, and reduced post-MCAO infarct size and edema. These findings identify two distinct yet complementary mast cell pathways in T2D, highlight an immune-vascular interface that drives cerebrovascular dysfunction, and propose sVCAM1 blockade plus GSK3β inhibition as rational strategies to protect cerebral vascular function in the diabetic brain. Full article

Mast cells (MCs) are innate immune cells that are derived from CD34⁺ hematopoietic stem/progenitor cells (HSPCs) and mature in peripheral tissues such as skin and mucosa. Mature human MCs can be generated from peripheral blood, but this process requires substantial blood volumes as HSPC frequencies are typically very low. The aim of this study was to validate a new in-house-developed protocol for the generation of MCs from less than 20 mL of peripheral blood. To this end, we used a magnetic bead-based procedure to isolate ‘untouched’ HSPCs from 14 to 16 mL peripheral blood (PB). In total, 12 cultures were set up with blood from seven healthy donors, wherein HSPCs were first expanded for 4 weeks, followed by another 8 weeks of culture in MC maturation-inducing medium. Flowcytometric analysis, histochemical staining, and degranulation assays were used to assess their phenotypic and functional features. Our data show comparable expression of cytoplasmic granules and cell-surface expression of MRGPRX2, FcεR1α, and CD117 in 8/12 blood-derived MCs (PB-MCs) and buffy coat-derived HSPCs (BC-MCs). PB-MCs responded to classic stimulating agents like IgE/anti-IgE and C48/80. Hence, our novel MC generation protocol yields functionally competent MCs with no compromise in their maturation or activation potential despite 12 weeks of in vitro culture. Full article

Populations of northern pike (Esox lucius) and pumpkinseed (Lepomis gibbosus) from the Mrežnica River were found to be infected with the tapeworm Triaenophorus nodulosus. In both species, the mean intensity of infection was low, suggesting a well-balanced host–parasite relationship. This study investigates pathological changes caused by adult T. nodulosus in its definitive host, the northern pike, and the associated intestinal immune response. The infection had no detectable adverse effects on either the northern pike population or the host’s body condition index. Histological examination revealed lesions both at the site of tapeworm attachment and in areas adjacent to the free strobila, involving the lamina propria and submucosa. A moderate, multifocal, ulcerative, and necrotizing enteritis was observed, accompanied by an increased number of mast cells (MCs), which were identified as the predominant immune cells involved in the E. lucius–T. nodulosus interaction. MCs, mostly degranulated, were found in the lamina propria and superficial submucosa at the attachment site. Immunofluorescence revealed a subpopulation of piscidin 1-positive MCs in the same layers, with a higher number at the attachment site compared to unaffected intestinal areas. This represents the first evidence of piscidin 1 involvement in intestinal host defence against cestode infections in teleosts. Full article

Cutaneous melanoma remains one of the most aggressive tumors, yet the role innate immunity plays in its progression remains poorly understood. Effector elements with high regulatory potential, capable of both promoting and inhibiting tumor growth—mast cells (MCs), are of particular interest. This includes quantitatively characterizing the interactions between tryptase-positive mast cells (MCs) with atypical Melanin—A⁺ cells and describing their spatial phenotype, in relation to the stage of cutaneous melanoma. A retrospective analysis was carried out on samples retrieved from 128 patients with cutaneous melanoma (AJCC 8th edition: IA–IIID). Histological analysis, histochemistry (toluidine blue, Giemsa), and diplex /multiplex IHC for tryptase and Melan-A were performed; as well as Fluorescence imaging, 3D reconstructions and quantitative mapping in QuPath v 0.6.0. Proximity was assessed by the nucleus-to-nucleus distance: <10 μm (contact), 10–20 μm (paracrine zone), >20 μm (out of interaction). The relative amount of MCs in the intratumoral zone was lower than in the intact dermis, with a simultaneous increase in their absolute density per mm² in the melanoma microenvironment, maximum in the peritumoral area and most pronounced at stage II. Three types of interactions were identified: (i) juxtaposition without secretion, (ii) degranulation of MCs directed to tumor cells, (iii) melanosecretion of Melanin—A⁺ cells directed towards MCs, followed by phagocytosis of melanocores. An inverse intratumoral connection between the number of MCs and the number of Melanin—A⁺ cells was noted; MCs with elongated forms, extensive contacts and polarized tryptase secretion, including granule localization near/at the nuclei of adjacent cells, were frequently observed. The obtained data indicate stage-region-dependent bidirectional cross-talk between melanin and MCs, forming tissue spatial signals, potentially useful as biomarkers and targets for personalized therapy. Full article

Wound healing is a delicately regulated pathophysiological process based on molecular, cellular, and tissue interactions. Mast cells (MCs) are involved in the reparative process in all phases of wound healing, which indicates their general significance in reparative processes. The structural and functional changes in the MCs during the healing process correspond to the phase of the wound process and determine its course. In the inflammatory phase, rapid whole-granular degranulation of MCs with the secretion of biologically active proinflammatory substances that have a stimulating effect on inflammatory cells prevailed. In the proliferation phase, the maximum number of MCs per unit area of wound tissue and the maximum degranulation index were noted. In the phase of granulated tissue remodeling, the amount and functional activity of MCs sharply decrease, which contributes to the completion of the healing process with the formation of a fully fledged normotrophic scar. The gradual degranulation of MCs was characteristic of the proliferation and remodeling phases. The treatment of purulent wounds with a drug from the polyhexamethylene guanidine group with the antiseptic polyhexanide 0.1% contributed to a temporary shift in the phases of the wound process while maintaining its general patterns, while the activation of the process occurred at an earlier time than in the control group of animals without local treatment. The results obtained showed that the use of a drug from the polyhexamethylene guanidine group with the antiseptic polyhexanide 0.1% for the treatment of purulent wounds quickly stops the inflammatory response and creates conditions for the development of the reparative abilities of granulation tissue cells, and primarily, mast cells. Full article

This study explores immunophenotypic and angiogenic profiles in salivary gland tumors (SGTs), focusing on epithelial–mesenchymal dynamics and immune–stromal interactions. Immunohistochemical analysis of E-cadherin, Vimentin, mast cell tryptase (MCT), CD300a, CK18, CD31, and vascular endothelial growth factor (VEGF) was performed in normal salivary tissue, pleomorphic adenomas (PA), and squamous cell carcinomas (SCCs) to assess epithelial plasticity, mast cell (MC) involvement, and vascular remodeling. Normal glands showed compartmentalized E-cadherin (epithelial) and Vimentin (mesenchymal) expression, with stromal MCs positive for MCT and CD300a. PA exhibited reduced E-cadherin, increased Vimentin, and atypical co-localization of CK18 with MCT/CD300a in ductal cells, indicating immune–epithelial plasticity. SCC displayed epithelial–mesenchymal transition (EMT), architectural disruption, and reduced MCT/CD300a. Notably, diminished MCT may reflect either decreased MCs density or prior degranulation, with possible diffuse MCT in stroma. Angiogenic profiling showed maximal CD31 in PA and minimal in SCC, while VEGF peaked in normal tissue, suggesting deregulated angiogenesis. SGT progression involves immune–epithelial plasticity, vascular deregulation, and stromal reprogramming. Immune marker localization within epithelial cells challenges histogenetic models and may inform prognostic assessment and targeted therapeutic strategies. Full article

Pancreatic inflammation and subsequent fibrosis drive serious disease complications. However, the pathogenesis of this process and the mechanisms underlying excessive extracellular matrix (ECM) deposition remain poorly understood. Our aim was to study intercellular interactions and ultrastructural changes in mast cells, pancreatic stellate cells, and telocytes, as well as in the extracellular matrix in various degrees of pancreatic fibrosis. Histological, immunohistochemical, and electron microscopic (EM) studies were performed on surgical materials from 17 patients. Mapping of fibrosis fields was performed on scanned images using the QuPath software v0.6.0. The IHC study was performed using a panel of antibodies: CD34, CD117, and SMA. Fluorescent IHC was performed using a panel of antibodies: CD34 and CD117. The EM study was performed on ultrathin sections with a thickness of 100–120 nm. The functional activity of mast cells (MCs) increased in pancreatic fibrosis. Most of the MCs were in a degranulation state, with the formation of intercellular contacts. The activation of pancreatic stellate cells (PaSCs), which underwent ultrastructural and functional changes in pancreatic fibrosis that developed as a result of chronic pancreatitis (CP), was noted. Multiple plasmolemma discontinuities, telopode shortenings, and nuclear fragmentations were observed among telocytes (TCs). The presence of MCs in the inflammatory infiltrate, as well as the destruction of TCs with the activation of exosomal transport, plays an important role in the pathogenesis of fibrosis in CP and provides a promising therapeutic target for the treatment of this pathology. Full article

The cochlea is susceptible to damage from ototoxic agents such as cisplatin, yet the mechanisms underlying cochlear injury remain incompletely understood. Mast cells (MCs), key immune players in allergic and inflammatory responses, have recently been identified in the rodent cochlea and implicated in cisplatin-induced ototoxicity. Our study investigated the role of MC degranulation in cochlear damage and evaluated the activation capacity of cochlear-resident MCs. Bone marrow-derived MCs (BMMCs) were cultured and induced to degranulate via IgE-anti-DNP/DNP stimulation, and the supernatants were applied to cochlear explants. Cochlear explants were also treated with Compound 48/80 (CP48/80) or cisplatin to assess MC activation. Morphological changes were assessed and hair cells (HC) quantified via phalloidin staining, while ELISA measured mediator release. Supernatants from degranulated BMMC induced a dose-dependent HC loss and tissue damage. A significant chymase and tryptase release was triggered by CP48/80 from cochlear MCs, with chymase elevation detected even at low concentrations. Cochlear MCs were rapidly activated by cisplatin exposure, elevating chymase and histamine levels, and the effects were attenuated by the MC stabilizer sodium cromolyn. Notably, tryptase remained undetectable post-cisplatin treatment, suggesting tissue-specific MC responses. These findings establish MC degranulation as an early event in cisplatin-induced cochlear injury, mediated by chymase and histamine. Our study highlights MCs as potential therapeutic targets for mitigating ototoxicity and underscores the need to explore MC-driven pathways in hearing loss. 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

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

Globally, bladder cancer is the sixth most frequently diagnosed cancer among men. Despite the increasing availability of immunomodulatory treatments for bladder cancer, the survival rates are still low, which calls for potential new drug-repurposing targets. This study aimed to investigate the effects of cromolyn, a mast cell (MC) stabilizer in allergic reactions, on a subcutaneous tumor model with a syngeneic mouse MB49 bladder cancer cell line. A concentration of 50 mg/kg of cromolyn was daily administered intraperitoneally in a 4-day therapeutic protocol to mice with established tumors and in a continuous 11-day protocol which started one day prior to the subcutaneous injection of tumor cells. Therapeutic treatment demonstrated a marked downregulation of genes related to angiogenesis and upregulation of genes related to cytotoxic T-cell and NK cell activity. Conversely, continuous cromolyn treatment suppressed genes involved in immune cell recruitment and activation, as well as apoptotic and necroptotic pathways, leading to a greater tumor burden (+142.4 mg [95CI + 28.42, +256.4], p = 0.0158). The same pro-tumorigenic effect was found in mast cell-deficient mice (Kit^W-sh/W-sh + 301.7 mg [95CI + 87.99, 515.4], p = 0.0079; Cpa3^Cre/+ +107.2 mg [95CI − 39.37, +253.57], p = 0.1423), indicating that continuous cromolyn treatment mostly acts through the inhibition of mast cell degranulation. In summary, our results demonstrate the distinct effects of cromolyn on tumor progression, which depend on the protocol of cromolyn administration. Full article

Although mast cells have long been known, they are not yet fully understood. They are traditionally recognized for their role in allergic reactions through the IgE/FcεRI axis, but different groups of surface receptors have since been characterized, which appear to be involved in the manifestation of peculiar clinical features. In particular, MRGPRX2 has emerged as a crucial receptor involved in degranulating human skin mast cells. Because of mast cells’ close proximity to peripheral nerve endings, it may play a key role in neuroimmune interactions. This paper provides an overview of mast cell contributions to hypersensitivity and so-called “pseudoallergic” reactions, as well as an update on neuroinflammatory implications in the main models of airway and skin allergic diseases. In particular, the main cellular characteristics and the most relevant surface receptors involved in MC pathophysiology have been reappraised in light of recent advancements in MC research. Molecular and clinical aspects related to MC degranulation induced by IgE or MRGPRX2 have been analyzed and compared, along with their possible repercussions and limitations on future therapeutic perspectives. Full article