Mast Cell Activation Research Articles

Water-avoidance stress aggravates prostatic inflammation in a murine model of chronic prostatitis.

To date, few studies have considered the influence of psychological factors on chronic prostatitis (PRO) models. Here, we aimed to refine a murine PRO model combining chemically induced prostatitis with psychological stress. A total of 40 mice were randomly divided into four groups: normal control (NC) group, PRO group, water avoidance stress (WAS) group, and PRO + WAS group. Ten mice were assigned to each group: five for cystometrograms (CMGs) and five for von Frey testing and histological analysis. PRO was induced through a prostatic injection of 10% paraformaldehyde. The WAS mice were placed on the middle platform for 1 h per day for 10 consecutive days. The results of the von Frey test demonstrated that both WAS and PRO induced bladder hyperalgesia in mice, and the WAS + PRO group showed significant pelvic pain symptoms either. The CMG results suggested that the PRO group, the WAS group, and the PRO + WAS group all exhibited bladder overactivity, presented as a shortened micturition interval and decreased threshold pressure evoking bladder contraction. The symptoms of the PRO group and the PRO + WAS group were more severe than those of the WAS group. The tissue staining results indicated that WAS itself caused only mild prostatic inflammation but could significantly aggravate chemical-induced prostatic inflammation, as well as the total number of mast cells and proportion of activated mast cells. Our refined murine PRO model could manifest persistent bladder overactivity, pelvic hyperalgesia and prostatic inflammation. WAS could induce mild prostatic inflammation and aggravate primary prostatic inflammation.

The role of transforming growth factor-β in lung damage in COVID-19: clinical and diagnostic parallels

BACKGROUND: Coronavirus 2 (SARS-CoV-2), which causes severe acute respiratory syndrome in COVID-19, leads to complex immune reactions, hyperactivation of immunocompetent cells, including increased degranulation activity of mast cells and the release of their secretome products. The SARS-CoV-2 virus and the subsequent strong immune and inflammatory response, as well as a violation of the regulation of coagulation and fibrinolytic pathways, cause massive activation of latent TGF-β in the lungs, as well as the latent pool of TGF-β in the blood of patients with COVID-19. AIMS: To assume the participation of transforming growth factor-β (TGF-β) in lung damage in patients with COVID-19 by determining its quantitative level in autopsy lung samples in patients with COVID-19 and to conduct a correlation analysis with clinical and laboratory parameters. MATERIALS AND METHODS: The study included samples of lung autopsy material obtained from patients who died from severe COVID-19. A correlation analysis of TGF-β-positive cells and clinical and laboratory parameters was also performed. RESULTS: Extensive representation of TGF-β-positive cells was found in lung tissues of patients who died from COVID-19.A negative correlation was revealed: between TGF-β and the content of nucleated neutrophils in the blood (r = - 0,617; p = 0,033); between TGF-β and the level of C-reactive protein (CRP) according to the results of blood biochemistry (r = - 0,491; p = 0,013). A positive correlation was revealed between TGF-β and the content of blood platelets (r = 0,384; p =0,012);TGF-β with the level of erythrocyte sedimentation rate (ESR) (r = 0,409; p = 0,025). A positive correlation was also found between TGF-β and the presence of cough in the patient at the beginning of hospitalization (r = 0,367; p = 0,046). CONCLUSIONS: Activation of TGF-β in the lungs of patients who died from severe COVID-19 correlates with the level of neutrophils, platelets, ESR, CRP and the presence of cough in the patient. Further research is needed on the activation, release of TGF-β and its interactions in larger cohorts of patients. These correlations suggest the negative involvement of the transforming growth factor and consider the therapeutic possibilities of regulatory influence on its activation.

Antidepressant-like Effects of Cannabis sativa L. Extract in an Lipopolysaccharide Model: Modulation of Mast Cell Activation in Deep Cervical Lymph Nodes and Dura Mater.

Lipopolysaccharide (LPS)-induced neuroinflammation is a well-established model for studying depression-like behavior, driven by pro-inflammatory cytokines such as TNF-α and IL-1β. Mast cells (MCs) contribute to neuroinflammation by releasing mediators that exacerbate depressive-like symptoms. This study evaluates the antidepressant-like and anti-inflammatory effects of Cannabis sativa L. inflorescence extract (CSL) in an LPS-induced neuroinflammation model. Male C57BL/6 mice were intraperitoneally injected with CSL at doses of 10, 20, and 30 mg/kg, 30 min prior to LPS (0.83 mg/kg) administration. Depressive behaviors were assessed using the sucrose preference test (SPT), tail suspension test (TST), and forced swimming test (FST). The neutrophil-to-lymphocyte ratio (NLR) was measured to assess systemic inflammation. Cytokine levels in the prefrontal cortex (PFC) were measured, and mast cell degranulation in the lymph nodes and dura mater was analyzed histologically (approval number: WKU24-64). CSL significantly improved depressive-like behaviors and decreased the NLR, indicating reduced systemic inflammation. CSL also significantly reduced TNF-α and IL-1β levels in the PFC. Furthermore, CSL inhibited MC degranulation in the deep cervical lymph nodes and dura mater, with the strongest effects observed at 30 mg/kg. CSL demonstrated antidepressant-like and anti-inflammatory effects in an LPS-induced neuroinflammation model, likely through the modulation of cytokine expression and mast cell activity. These results suggest the potential of CSL as a therapeutic option for treating inflammation-related depression.

Studies of Structure–Activity Relationship of 2-(Pyrrolidin-1ylmethyl)-1H-pyrrole-Based ST2 Inhibitors and Their Inhibition of Mast Cells Activation

Studies of Structure–Activity Relationship of 2-(Pyrrolidin-1ylmethyl)-1<i>H</i>-pyrrole-Based ST2 Inhibitors and Their Inhibition of Mast Cells Activation

Gastrointestinal symptoms in children with mastocytosis

Introduction. Mastocytosis is a heterogeneous group of diseases characterized by the abnormal accumulation of clonal mast cells (MCs) in various tissues and organs, including skin, bone marrow, liver, spleen and lymph nodes. The clinical picture of cutaneous and indolent systemic mastocytosis is formed by a wide range of symptoms associated with activation of mast cells. Single European studies have demonstrated wide variability in the frequency of gastrointestinal symptoms (GI-symptoms)) in children with mastocytosis (from 15 to 50%).Aim. To analyze the frequency of mediator-related GI-symptoms in children with different subtypes and clinical forms of mastocytosis.Materials and methods. A prospective observational study included data from 289 children aged 3 to 17 years who were under observation at the Moscow Scientific and Practical Center of Dermatovenereology and Cosmetology. Symptoms were assessed using the Pediatric grade scale of symptoms of mastocytosis. Clinical manifestations of reactions caused by mast cell degranulation were compared with data from clinical and laboratory studies. The concentrations of tryptase and histamine in the blood serum of patients were determined. The incidence of organomegaly and mesenteric lymphadenitis in children with mediating symptoms and without symptoms was determined using ultrasound.Results. 67 (23.2%) patients had GI symptoms. More than half of the patients (51.6%) indicated abdominal pain, 32.3% reported diarrhea. The severity of pain symptoms correlated with the level of serum tryptase (ρ = 0.564, p &lt; 0.01). The incidence of hepatomegaly and mesadenitis in children with GI- symptoms was 19.4% and 25.4%, respectively. In a comparative analysis in groups of children with and without GI symptoms, the differences in the number of identified cases of organomegaly and mesadenitis were statistically significant (p &lt; 0.001). An increase in histamine levels in the blood was detected in half of the patients with complaints of heartburn and nausea.Conclusion. Our results demonstrated that a study of the level of serum tryptase, ultrasound of the abdominal organs and lymph nodes should be carried out in all children with mediator-related GI-symptoms regardless of the clinical form of mastocytosis.

Decoding the Genetic Basis of Mast Cell Hypersensitivity and Infection Risk in Hypermobile Ehlers-Danlos Syndrome.

Hypermobile Ehlers-Danlos syndrome (hEDS) is a connective tissue disorder marked by joint hypermobility, skin hyperextensibility, and tissue fragility. Recent studies have linked hEDS with mast cell activation syndrome (MCAS), suggesting a genetic interplay affecting immune regulation and infection susceptibility. This study aims to decode the genetic basis of mast cell hypersensitivity and increased infection risk in hEDS by identifying specific genetic variants associated with these conditions. We conducted whole-genome sequencing (WGS) on 18 hEDS participants and 7 first-degree relatives as controls, focusing on identifying genetic variants associated with mast cell dysregulation. Participants underwent clinical assessments to document hEDS symptoms and mast cell hypersensitivity, with particular attention to past infections and antihistamine response. Our analysis identified specific genetic variants in MT-CYB, HTT, MUC3A, HLA-B and HLA-DRB1, which are implicated in hEDS and MCAS. Protein-protein interaction (PPI) network analysis revealed significant interactions among identified variants, highlighting their involvement in pathways related to antigen processing, mucosal protection, and collagen synthesis. Notably, 61.1% of the hEDS cohort reported recurrent infections compared to 28.5% in controls, and 72.2% had documented mast cell hypersensitivity versus 14.2% in controls. These findings provide a plausible explanation for the complex interplay between connective tissue abnormalities and immune dysregulation in hEDS. The identified genetic variants offer insights into potential therapeutic targets for modulating mast cell activity and improving patient outcomes. Future research should validate these findings in larger cohorts and explore the functional implications of these variants to develop effective treatment strategies for hEDS and related mast cell disorders.

In vitro diagnostics of drug allergies.

In vitro diagnostics for drug hypersensitivity reactions distinguish between serological and cellular-based tests. A serological test used for the diagnosis of immediate type reactions is the detection of specific IgE antibodies. The cellular tests include the basophil activation test for immediate type reactions and the lymphocyte transformation test, which is mainly used to detect delayed type hypersensitivity reactions. Further cellular-based tests are the CAST-ELISA and the mast cell activation test. None of the above-mentioned tests can definitively exclude an allergy if the result is negative. In addition, it is important to note that even a positive test result is not necessarily associated with an allergy but has to be interpreted in the clinical context.

Progression of Mast Cell Activation Syndrome to Systemic Mastocytosis

Abstract Introduction/Objective Mast cell activation syndrome (MCAS) is characterized by the abnormal release of mast cell mediators, leading to symptoms such as flushing, abdominal pain, and allergic reactions. In some cases, MCAS progresses to systemic mastocytosis (SM), a mast cell disorder marked by organ infiltration and dysfunction. However, predictors of MCAS progression to SM remain poorly understood, and long-term prognosis data are limited. Methods/Case Report We conducted a retrospective study of patients diagnosed with MCAS at Penn Medicine from January 1, 2019, through December 30, 2021. The primary endpoint was progression to SM, defined by World Health Organization criteria, with a secondary endpoint set for September 24, 2023. Results (if a Case Study enter NA) We identified 47 patients with MCAS (Table 1). Of these, 11 patients (23.4%) progressed to SM. Notably, all five patients with c-KIT mutations progressed to SM (100%, 5/5), while six out of 22 patients without c-KIT mutations also progressed (27.2%). Additionally, baseline serum tryptase levels were identified as a significant predictor of progression at two years. Conclusion The relative risk of progression varied depending on the subtype of MCAS, with higher rates observed in those with KIT D816V presence. Compared to the incidence of SM in the general population, our findings suggest a higher risk of progression from MCAS to SM, even without a c-KIT mutation. Identification of prognostic factors, such as specific genetic mutations and baseline serum tryptase levels, may aid in risk stratification and early intervention strategies for individuals with MCAS. HaT mutation testing should be considered in future studies on this topic. Our findings have important implications for the clinical management and understanding of MCAS progression to SM. Additionally, our data imply the importance of recognizing MCAS in the early phase and proper monitoring, considering the low rate of MCAS diagnosis. Patients with MCAS may need annual monitoring, including serum tryptase levels, to detect progression to SM and related complications. Early detection and intervention may improve outcomes and quality of life for individuals with MCAS.

Identification of novel biomarkers for atherosclerosis using single-cell RNA sequencing and machine learning.

Atherosclerosis (AS) is a predominant etiological factor in numerous cardiovascular diseases, with its associated complications such as myocardial infarction and stroke serving as major contributors to worldwide mortality rates. Here, we devised dependable AS-related biomarkers through the utilization of single-cell RNA sequencing, weighted co-expression network (WGCNA), and differential expression analysis. Furthermore, we employed various machine learning techniques (LASSO and SVM-RFE) to enhance the identification of AS biomarkers, subsequently validating them using the GEO dataset. Following this, CIBERSORT was employed to investigate the correlation between biomarkers and infiltrating immune cells. Consequently, 256 differentially expressed genes (DEGs) were selected in samples of AS and normal. GO and KEGG analyses indicated that these DEGs may be related to the negative regulation of leukocyte-mediated immunity, leukocyte cell-cell adhesion, and immune system processes. Notably, C1QC and COL1A1 were pinpointed as potential diagnostic markers for AS, a finding that was further validated in the GSE21545 dataset. Moreover, the area under the curve (AUC) values for these markers exceeded 0.8, underscoring their diagnostic utility. Analysis of immune cell infiltration revealed that the expression of C1QC was correlated with M0 macrophages, gamma delta T cells, activated mast cells and memory B cells. Similarly, COL1A1 expression was linked to M0 macrophages, memory B cells, activated mast cells, gamma delta T cells, and CD4 native T cells. Finally, these results were validated using mice and human samples through immunofluorescence, immunohistochemistry, and ELISA analysis. Overall, C1QC and COL1A1 would be potential biomarkers for AS diagnosis, and that would provides novel perspectives on the diagnosis and treatment of AS.

Short-term influence of Immufen™ on mild allergic rhinitis: a randomized, double-blind, placebo-controlled study.

Allergic rhinitis (AR) is an IgE-mediated reaction to inhaled allergens, and is a prominent health concern affecting approximately 400 million people worldwide. A comprehensive understanding of AR's pathophysiology is imperative for developing novel therapies, especially considering its frequent co-morbidity with asthma and conjunctivitis. The escalating prevalence of AR is correlated with increased urbanization and environmental pollutants, recognized as prominent contributing factors. Dysregulation in immune networks, Th1/Th2 cytokine imbalance, activation of mast cells and eosinophils are implicated in AR progression. Classic AR symptoms include nasal congestion, nasal itching, rhinorrhea, and sneezing which significantly impact the quality of life, social interactions, and workplace productivity. This randomized, double-blind, placebo-controlled, three-arm, three-sequence study was aimed to assess the efficacy of supplementation of a co-delivery form of turmeric extract with ashwagandha extract (CQAB) in comparison with a bioavailable curcumin (CGM) and placebo in alleviating AR symptoms and enhancing the quality of life in individuals with mild AR. Participants received either placebo, CGM, or CQAB twice/day for 28 days, and subjective measures were recorded at the baseline and at the end of study. CQAB supplementation demonstrated a significant (P < 0.05) improvement in Total Nasal Symptom Score (TNSS) compared to placebo and CGM. Furthermore, CQAB administration resulted in enhanced sleep quality (P < 0.05) as evaluated by the BIS questionnaire, heightened energy levels, and decreased fatigue and overall mood disturbance (POMS-SF) compared to both placebo and CGM. The results suggests that CQAB has the potential to be used as a dietary supplement in alleviating AR discomforts. https://ctri.nic.in/Clinicaltrials/login.php; Identifier CTRI/2021/01/030355.

Integrated machine learning and Mendelian randomization reveal PALMD as a prognostic biomarker for nonspecific orbital inflammation

Background: Nonspecific Orbital Inflammation (NSOI) remains a perplexing enigma among proliferative inflammatory disorders. Its etiology is idiopathic, characterized by distinctive and polymorphous lymphoid infiltration within the orbital region. Preliminary investigations suggest that PALMD localizes within the cytosol, potentially playing a crucial role in cellular processes, including plasma membrane dynamics and myogenic differentiation. The potential of PALMD as a biomarker for NSOI warrants meticulous exploration. Methods: PALMD was identified through the intersection analysis of common DEGs from datasets GSE58331 and GSE105149 from the GEO database, alongside immune-related gene lists from the ImmPort database, using Lasso regression and SVM-RFE analysis. GSEA and GSVA were conducted with gene sets co-expressed with PALMD. To further investigate the correlation between PALMD and immune-related biological processes, the CIBERSORT algorithm and ESTIMATE method were employed to evaluate immune microenvironment characteristics of each sample. The expression levels of PALMD were subsequently validated using GSE105149. Results: Among the 314 DEGs identified, several showed significant differences. Lasso and SVM-RFE algorithms pinpointed 15 hub genes. Functional analysis of PALMD emphasized its involvement in cell-cell adhesion, leukocyte migration, and leukocyte-mediated immunity. Enrichment analysis revealed that gene sets positively correlated with PALMD were enriched in immune-related pathways. Immune infiltration analysis indicated that resting dendritic cells, resting mast cells, activated NK cells, and plasma cells positively associate with PALMD expression. Conversely, naive B cells, activated dendritic cells, M0 and M1 macrophages, activated mast cells, activated CD4 memory T cells, and naive CD4 T cells showed a negative correlation with PALMD expression. PALMD demonstrated significant diagnostic potential in differentiating NSOI. Conclusions: This study identifies PALMD as a potential biomarker linked to NSOI, providing insights into its pathogenesis and offering new avenues for tracking disease progression.

On the pathogenesis of COVID-19: the role of transforming growth factor beta

Proteins of the transforming growth factor beta (TGF-β) family regulate numerous cellular processes that are essential in the pathogenesis of acute respiratory distress syndrome (ARDS), contributing to increased alveolar epithelial permeability, activation of fibroblasts, and extracellular matrix remodeling. TGF-β is involved in the pathogenesis of inflammatory respiratory diseases during the development of COVID-19. SARS-CoV-2 leads to complex immune responses that include the release of inflammatory cytokines, increased activity of mast cells, and the release of mast cell secretome, in particular profibrotic enzymes and cytokines, including TGF-β.Tryptaseand chymase-positive mast cells play a major role in pulmonary fibrosis and embolism in COVID-19. Mast cell chymase is angiotensin-converting enzyme 2-independent due to extracellular formation of angiotensin II in the interstitium; it also activates TGF-β and other molecules, thereby playing a role in tissue remodeling. Mast cell β-tryptase increases the secretion of TGF-β1 by airway smooth muscle tissue and the expression of α-smooth muscle actin (α-SMA). TGF-β also induces the generation of mitochondrial reactive oxygen species (ROS), which enhances the production of ROS in lung fibroblasts. TGF-β is crucial for induing the synthesis of extracellular matrix components by fibroblasts.The review is devoted to the structure of TGF-β, the sources of its secretion and functions, the mechanism of its involvement in the pathogenesis of COVID-19, and the possibility of its use as a prognostic marker of COVID-19 severity.

Ursolic acid attenuates pseudo-allergic reactions via reducing MRGPRX2-mediated mast cell degranulation

Mas-related G protein–coupled receptor X2 (MRGPRX2) is a newly identified receptor on mast cells that contribute to IgE-independent pseudo-allergy. Ursolic acid (UA), a pentacyclic triterpenoid, has been reported for its anti-allergy effects. However, the protective mechanism against pseudo-allergic reactions remains unclear. This study aims to investigate the effects of UA on pseudo-allergic reactions both in vivo and in vitro, focusing on the therapeutical mechanism underlying its effect on mast cells. In present study, UA reduced degranulation and chemokines production induced by MRGPRX2 agonists, including compound 48/80 (C48/80) and substance P (SP), in LAD2 cells in vitro. UA also alleviated C48/80 and SP-induced systemic anaphylaxis and passive cutaneous anaphylaxis (PCA) in vivo. Furthermore, UA demonstrated strong binding affinity to the MRGPRX2 protein, leading to a decrease in calcium influx in both LAD2 cells and MRGPRX2-HEK293 cells stimulated with C48/80 and SP. Moreover, UA effectively suppressed phosphorylation levels within phospholipase C-γ (PLCγ) pathway and nuclear factor kappa-B (NF-κB) pathway of MRGPRX2 downstream proteins. Our findings indicated that UA exerts an attenuating effect in pseudo-allergic reactions by suppressing MRGPRX2-mediated mast cell activation, targeting PLCγ pathway and NF-κB pathway. These results suggest that UA may serve as a promising therapeutic agent for MRGPRX2-dependent pseudo-allergic reactions.

Differential MRGPRX2-dependent activation of human mast cells by polymyxins and octapeptins

The emergence of multi-drug resistant Gram-negative bacteria has led to renewed interest in the antimicrobial activity of polymyxins and novel polymyxin analogues (e.g. nonapeptides and octapeptin). In some individuals, clinically used polymyxins can cause acute hypersensitivity reactions through mast cell activation, with a recent study attributing this effect to activation of the MAS-related G protein-coupled receptor X2 (MRGPRX2). In the present study, HEK293 cells expressing human MRGPRX2 and the human mast cell line LAD2 were used to characterize the activity of the broader family of polymyxins. Octapeptin C4, polymyxin B and colistin produced concentration-dependent calcium mobilization, degranulation, and CCL-2 (MCP-1) release in LAD2 mast cells, with the former being highly potent. CRISPR-Cas9 knockdown of MRGPRX2 in LAD2 cells and a MRGPRX2 inverse agonist caused a significant reduction in calcium mobilization, degranulation, and CCL-2 release, demonstrating dependency on MRGPRX2 expression. In contrast, polymyxin nonapeptides were far less potent calcium mobilisers and failed to induce functional degranulation in LAD2 cells. Our results confirm that activation of mast cells induced by polymyxin-related antibiotics is MRGPRX2-dependent and reveal that octapeptin C4 might be more liable, whilst nonapeptides are less liable, to trigger immediate hypersensitivity reactions clinically. The mechanism underpinning the difference in MRGPRX2 activation between polymyxin-related antibiotics is important to better understand as it may help design new, safer polymyxins and guide the optimal clinical use of existing polymyxin drugs.

Mast Cells Mediate Acute Inflammatory Responses After Glenoid Labral Tears and Can Be Inhibited With Cromolyn in a Rat Model.

Injuries to the glenoid labrum have been recognized as a source of joint pain and discomfort, which may be associated with the inflammatory responses that lead to the deterioration of labral tissue. However, it is unclear whether the torn labrum prompts mast cell (MC) activation, resulting in synovial inflammatory responses that lead to labral tissue degeneration. To determine the potential influence of activated MC on synovial inflammatory responses and subsequent labral tissue degeneration and shoulder function deterioration in a rat model by monitoring MC behavior and sequential inflammatory responses within the synovial tissue and labral tissue after injury, suture repair, and MC stabilizer administration. Controlled laboratory study. Anteroinferior glenoid labral tears were generated in the right shoulder of rats (n = 20) and repaired using a tunneled suture technique. Synovial tissue inflammatory responses were modulated in some rats with intraperitoneal administration of an MC stabilizer-cromolyn (n = 10). At weeks 1 and 3, MC activation, synovial inflammatory responses, and labral degeneration were histologically evaluated. Simultaneously, gait analysis was performed before and after surgical repair to assess the worsening of the shoulder function after the injury and treatment. Resident MC degranulation after labral injury (50.48% ± 8.23% activated at week 1) contributed to the initiation of synovial tissue inflammatory cell recruitment, inflammatory product release, matrix metalloproteinase-13, and subsequent labral tissue extracellular matrix degeneration. The administration of cromolyn, an MC stabilizer, was found to significantly diminish injury-mediated inflammatory responses (inflammatory cell infiltration and subsequent proinflammatory product secretion) and improve shoulder functional recovery. MC activation is responsible for labral tear-associated synovial inflammation and labral degeneration. The administration of cromolyn can significantly diminish the cascade of inflammatory reactions after labral injury. Our findings support the concept that MC stabilizers may be used as a complementary therapeutic option in the treatment and repair of labral tears.

Characterization of the cellular components of mouse collecting lymphatic vessels reveals that lymphatic muscle cells are the innate pacemaker cells regulating lymphatic contractions.

Collecting lymphatic vessels (cLVs) exhibit spontaneous contractions with a pressure-dependent frequency, but the identity of the lymphatic pacemaker cell is still debated. By analogy to pacemakers in the GI and lower urinary tracts, proposed cLV pacemaker cells include interstitial cells of Cajal like cells (ICLC) or the lymphatic muscle (LMCs) cells themselves. Here we combined immunofluorescence and scRNAseq analyses with electrophysiological methods to examine the cellular constituents of the mouse cLV wall and assess whether any cell type exhibited morphological and functional processes characteristic of pacemaker cells: a continuous if not contiguous network integrated into the electrical syncytium; spontaneous Ca2+ transients; and depolarization-induced propagated contractions. We employed inducible Cre (iCre) mouse models routinely used to target these specific cell populations including: c-kitCreER T2 to target ICLC; PdgfrβCreER T2 to target pericyte-like cells; PdgfrαCreER ™ to target CD34+ adventitial cells and ICLC; and Myh11CreER T2 to target LMCs directly. These specific inducible Cre lines were crossed to the fluorescent reporter ROSA26mT/mG, the genetically encoded Ca2+ sensor GCaMP6f, and the light-activated cation channel rhodopsin2 (ChR2). c-KitCreER T2 labeled both a sparse population of LECs and round adventitial cells that responded to the mast cell activator compound 48-80. PdgfrβCreER T2 drove recombination in both adventitial cells and LMCs, limiting its power to discriminate a pericyte-specific population. PdgfrαCreER ™ labeled a large population of interconnected, oak leaf-shaped cells primarily along the adventitial surface of the vessel. Of these cells, only LMCs consistently, but heterogeneously, displayed spontaneous Ca2+ events during the diastolic period of the contraction cycle, and whose frequency was modulated in a pressure-dependent manner. Optogenetic depolarization through the expression of ChR2 under control of Myh11CreER T2 , but not PdgfrαCreER ™ or c-KitCreER T2 , resulted in propagated contractions upon photo-stimulation. Membrane potential recordings in LMCs demonstrated that the rate of diastolic depolarization significantly correlated with contraction frequency. These findings support the conclusion that LMCs, or a subset of LMCs, are responsible for mouse cLV pacemaking.

Mast cells promote choroidal neovascularization in a model of age-related macular degeneration

‘Wet’ age-related macular degeneration (AMD) is characterized by pathologic choroidal neovascularization (CNV) that destroys central vision. Abundant evidence points to inflammation and immune cell dysfunction in the progression of CNV in AMD. Mast cells are resident immune cells that control the inflammatory response. Mast cells accumulate and degranulate in the choroid of patients with AMD, suggesting they play a role in CNV. Activated mast cells secrete various biologically active mediators, including inflammatory cytokines and proteolytic enzymes such as tryptase. We investigated the role of mast cells in AMD using a model of CNV. Conditioned media from activated mast cells exerts proangiogenic effects on choroidal endothelial cells and choroidal explants. Laser-induced CNV in vivo was markedly attenuated in mice genetically depleted of mast cells (KitW−sh/W−sh) and in wild-type mice treated with mast cell stabilizer, ketotifen fumarate. Tryptase was found to elicit pronounced choroidal endothelial cell sprouting, migration and tubulogenesis; while tryptase inhibition diminished CNV. Transcriptomic analysis of laser-treated RPE/choroid complex revealed collagen catabolism and extracellular matrix (ECM) reorganization as significant events correlated in clusters of mast cell activation. Consistent with these analyses, compared to wildtype mice choroids of laser-treated mast cell-deficient mice displayed less ECM remodelling evaluated using collagen hybridizing peptide tissue binding. Findings herein provide strong support for mast cells as key players in the progression of pathologic choroidal angiogenesis and as potential therapeutic targets to prevent pathological neovascularization in ‘wet’ AMD.

Altered B-cell, plasma cell and antibody immune profiles in blood of systemic mastocytosis

Systemic mastocytosis (SM) is a heterogeneous disease characterised by an expansion of KIT-mutated constitutively activated mast cells (MC) which release MC mediators that might act on the tumour microenvironment including other immune cells. Here we investigated the blood distribution of B-cell, plasma cell (PC) and antibody-isotype compartments in SM. We used spectral flow cytometry and the EuroFlow Immunomonitoring panel and Lymphocyte Screening Tube to quantify B-cells, PC and their subsets in blood of 108 SM patients - 35 bone marrow mastocytosis (BMM), 64 indolent SM (ISM), 9 aggressive SM (ASM)- vs 117 age-matched healthy donors (HD) and paired bone marrow (BM) samples of 31 SM vs 17 controls, respectively. In parallel, immunoglobulin (Ig) M, IgD, IgG, IgA and IgE plasma levels of were measured. Compared to HD, SM patients showed an increased immature B-cell production in BM (P=0.003) associated with a greater release of pre-germinal center immature (P<0.001) and naive CD5+ B-lymphocytes (P<0.001) to blood, but a pronounced decrease in PC counts of all different IgH-isotypes and subclasses (P≤0.001) together with overall increased IgM (P=0.001) and IgD (P<0.001) plasma levels. Of note, different immune profiles were found per diagnostic subtype of the disease with progressively greater counts in blood of immature B-lymphocytes together with decreased IgMD+, IgG2+, IgA1+ and IgA2+ MBC (P≤0.032) and elevated IgM (P=0.017) plasma levels in ASM cases, increased IgM (P=0.001) and IgD (P=0.001) plasma levels in ISM patients and exacerbated IgE (P<0.001) with decreased IgG (P=0.008) plasma levels in BMM cases. Our results reveal a significant dysregulation of the B-cell and PC compartments in blood of SM patients, consistent with distinctly altered antibody-isotype profiles in plasma of BMM vs ISM vs ASM patients.

Involvement of interferon γ-producing mast cells in immune responses against melanocytes in vitiligo requires MrgX2 activation.

Increasing evidence indicates that oxidative stress and interferon γ (IFNγ)-driven cellular immune responses are responsible for the pathogenesis of vitiligo. However, the connection between oxidative stress and the local production of IFNγ in early vitiligo remains unexplored. The aim of this study was to identify the mechanism underlying the production of IFNγ by mast cells and its impact on vitiligo pathogenesis. Skin specimens from the central, marginal, and perilesional skin areas of active vitiligo lesions were collected to characterize changes of mast cells, CD8+ T cells, and IFNγ-producing cells. Cell supernatants from hydrogen peroxide (H2O2)-treated keratinocytes (KCs) were harvested to measure levels of soluble stem cell factor (sSCF) and matrix metalloproteinase (MMP)-9. A murine vitiligo model was established using Mas-related G protein-coupled receptor-B2 (MrgB2, mouse ortholog of human MrgX2) conditional knockout (MrgB2-/-) mice to investigate IFNγ production and inflammatory cell infiltrations in tail skin following the challenge with tyrosinase-related protein (Tyrp)-2 180 peptide. Potential interactions between the Tyrp-2 180 peptide and MrgX2 were predicted using molecular docking. The siRNAs targeting MrgX2 and the calcineurin inhibitor FK506 were also used to examine the signaling pathways involved in mast cell activation. IFNγ-producing mast cells were closely aligned with the recruitment of CD8+ T cells in the early phase of vitiligo skin. sSCF released by KCs through stress-enhanced MMP9-dependent proteolytic cleavage recruited mast cells into sites of inflamed skin (Perilesion vs. lesion, 13.00 ± 4.00/HPF vs. 26.60 ± 5.72/HPF, P <0.05). Moreover, IFNγ-producing mast cells were also observed in mouse tail skin following challenge with Tyrp-2 180 (0 h vs. 48 h post-recall, 0.00 ± 0.00/HPF vs. 3.80 ± 1.92/HPF, P <0.05). The IFNγ+ mast cell and CD8+ T cell counts were lower in the skin of MrgB2-/-mice than in those of wild-type mice (WT vs. KO 48 h post-recall, 4.20 ± 0.84/HPF vs. 0.80 ± 0.84/HPF, P <0.05). Mast cells activated by MrgX2 serve as a local IFNγ producer that bridges between innate and adaptive immune responses against MCs in early vitiligo. Targeting MrgX2-mediated mast cell activation may represent a new strategy for treating vitiligo.

Neoadjuvant chemotherapy induces phenotypic mast cell changes in high grade serous ovarian cancer

BackgroundHigh grade serous ovarian cancer (HGSOC) is the most lethal gynecologic malignancy in which patients have still yet to respond meaningfully to clinically available immunotherapies. Hence, novel immune targets are urgently needed. Our past work has identified that mast cells are significantly upregulated at the mRNA level in HGSOC patient tumors following neoadjuvant chemotherapy (NACT) exposure. Therefore, in this current investigation we sought to characterize intratumoral mast cell phenotypic changes as a result of NACT exposure and determine how these adaptations are associated with patient clinical outcomes.MethodsHematologic immunohistochemistry was employed to determine mast cell levels in 36 matched pre- and post-NACT HGSOC patient tumors. Fluorescent Immunohistochemistry was utilized to identify Tryptase+(carboxypeptidase A3 (CPA3) + mast cells as well as histamine levels in 29 and 20, respectively, matched pre- and post-NACT HGSOC patient tumors. Finally, human immortalized mast cells, LUVA were stimulated with carboplatin and paclitaxel and genomic changes were analyzed by quantitative PCR.ResultsHematologic labeled intratumoral mast cells were significantly upregulated in the intraepithelial and stromal regions of the tumor, post-NACT. Lower levels of pre-NACT mast cells were significantly associated with an improved progression-free survival (PFS). Histamine, a marker of mast cell degranulation was similarly upregulated in post-NACT exposed tumors. Through the characterization of mast cell specific proteases Tryptase and CPA3, it was found that Tryptase+/ CPA3 + mast cells were significantly upregulated both in the intraepithelial and stromal compartments of the tumor, while Tryptase + cells were significantly upregulated in the stromal regions of the tumor. Lower post-NACT treated levels with Tryptase+/ CPA3 + cells were significantly associated with improved overall survival (OS) and PFS while higher Tryptase + mast cells were associated with improved OS. Finally, following chemotherapy exposure mast cell activating factors AREG and CCL2 were significantly upregulated while TGFB1, an inhibitor of mast cell activation was downregulated in LUVA cells.ConclusionsEnhanced mast cell numbers, as well as activation and degranulation are a consequence of NACT exposure. Post-NACT mast cells displayed differing associations with survival outcomes that was dependent upon granule classification. Ultimately, mast cells represent a clinically relevant putative HGSOC immune target.