Mast Cell-associated Diseases Research Articles

Cannabidiol Inhibits IgE-Mediated Mast Cell Degranulation and Anaphylaxis in Mice.

Cannabidiol (CBD), the most abundant non-psychoactive constituent of the plant Cannabis sativa, is known to possess immune modulatory properties. This study investigates the effects of CBD on mast cell degranulation in human and mouse primary mast cells and passive cutaneous anaphylaxis in mice. Mouse bone marrow-derived mast cells and human cord-blood derived mast cellsare generated. CBD suppressed antigen-stimulated mast cell degranulation in a concentration-dependent manner. Mechanistically, CBD inhibited both the phosphorylation of FcεRI downstream signaling molecules and calcium mobilization in mast cells, while exerting no effect on FcεRI expression and IgE binding to FcεRI. These suppressive effectsare preserved in the mast cells thatare depleted of type 1 (CB1) and type 2 (CB2) cannabinoid receptors, as well as in the presence of CB1 agonist, CB2 agonist, CB1 inverse agonist, and CB2 inverse agonist. CBD also inhibited the development of mast cells in a long-term culture. The intraperitoneal administration of CBD suppressed passive cutaneous anaphylaxis in mice as evidenced by a reduction in ear swelling and decrease in the number of degranulated mast cells. Based on these results, the administration of CBD is a new therapeutic intervention in mast cell-associated anaphylactic diseases.

Identification of MOD000001, A Novel Highly Selective and Orally Available KIT Inhibitor Designed for Treatment of Mast Cell-Associated Disorders

Stem cell factor (SCF) and its receptor KIT play crucial roles in the differentiation, proliferation, survival, migration, and activation of mast cells. Therefore, highly selective, orally available KIT inhibitors would be beneficial for mast cell-associated diseases.

Sex Differences in Mast Cell-Associated Disorders: A Life Span Perspective.

Mast cells are critical innate immune effectors located throughout the body that are crucial for host defense mechanisms via orchestrating immune responses to a variety of host and environmental stimuli necessary for survival. The role of mast cells in brain development and behavior, meningeal function, and stress-related disorders has also been increasingly recognized. While critical for survival and development, excessive mast cell activation has been linked with an increasing number of inflammatory, stress-associated, and neuroimmune disorders including allergy/anaphylaxis, autoimmune diseases, migraine headache, and chronic pain disorders. Further, a strong sex bias exists for mast cell-associated diseases with females often at increased risk. Here we review sex differences in human mast cell-associated diseases and animal models, and the underlying biological mechanisms driving these sex differences, which include adult gonadal sex hormones as well the emerging organizational role of perinatal gonadal hormones on mast cell activity and development.

Loss of isoprenylation significantly reduces IgE mediated mast cell activation

Abstract Allergic disease is the 6th leading cause of chronic illness in the US and accounts for billions of dollars in healthcare costs annually. Mast cells are tissue resident innate immune cells linked to allergic disease and activated by IgE and other ligands. Upon activation they release histamine, cytokines, chemokines, proteases, and lipid mediators evoking allergic symptoms. New ways of targeting mast cells could greatly benefit allergic disease therapy. Previous findings showed repurposing of statin drugs, such as Fluvastatin, reduced allergic symptoms in vitro and in vivo. We found that Fluvastatin suppresses IgE-mediated mast cell activation by inhibiting isoprenylation of proteins. However, statin effects were dependent on genetic background. To avert genetic background dependency, we tested the hypothesis that a dual farnesyl and geranylgeranyl transferase inhibitor (FGTI 2734) would suppress allergic disease withoutgenetic background limitations. We show that FGTI 2734 reduced IgE-mediated degranulation and cytokine production by bone marrow derived mast cells from multiple genetic backgrounds. Similarly, FGTI 2734 also suppressed IgE-mediated anaphylaxis on multiple genetic backgrounds. These in vivo effects extended to an allergic asthma model, in which FGTI 2734 inhibited pulmonary inflammation. Finally, we show that FGTI-2734 can significantly reduce IgE-induced cytokine production from human skin mast cells. These data show that dual farnesyl and geranylgeranyl transferase inhibitors may be an effective therapeutic treatment for mast cell-associated diseases. Supported by NIH (1RO1AI101153)

Resveratrol Treatment Prevents Increase of Mast Cells in Both Murine OVA Enteritis and IL-10-/- Colitis.

Mast cells are involved in allergic and other inflammatory diseases. The polyphenol resveratrol is known for its anti-inflammatory properties and may be used as nutraceutical in mast cell associated diseases. We analyzed the effect of resveratrol on mast cells in vivo in ovalbumin-induced allergic enteritis as well as experimental colitis in IL-10−/− mice which received resveratrol via drinking water. Treatment with resveratrol prevented the increase in mast cells in both allergic enteritis and chronic colitis in duodenum as well as in colon. Further, it delayed the onset of diseases symptoms and ameliorated diseases associated parameters such as tissue damage as well as inflammatory cell infiltration in affected colon sections. In addition to the findings in vivo, resveratrol inhibited IgE-dependent degranulation and expression of pro-inflammatory cytokines such as TNF-α in IgE/DNP-activated as well as in LPS-activated bone marrow-derived mast cells. These results indicate that resveratrol may be considered as an anti-allergic and anti-inflammatory plant-derived component for the prevention or treatment of mast cell-associated disorders of the gastrointestinal tract.

Resveratrol Is a Natural Inhibitor of Human Intestinal Mast Cell Activation and Phosphorylation of Mitochondrial ERK1/2 and STAT3

Mast cells play a critical role as main effector cells in allergic and other inflammatory diseases. Usage of anti-inflammatory nutraceuticals could be of interest for affected patients. Resveratrol, a natural polyphenol found in red grapes, is known for its positive properties. Here, we analyzed the effects of resveratrol on FcεRI-mediated activation of mature human mast cells isolated from intestinal tissue (hiMC). Resveratrol inhibited degranulation and expression of cytokines and chemokines such as CXCL8, CCL2, CCL3, CCL4, and TNF-α in a dose-dependent manner. Further, resveratrol inhibited the phosphorylation of extracellular signal-regulated kinase (ERK) 1/2 and signal transducer and activator of transcription (STAT) 3. ERK1/2 is known to be involved in cytokine expression of hiMC and to directly interact with STAT3. Mitochondrial STAT3 is phosphorylated by ERK1/2 and contributes to mast cell degranulation. We were able to isolate mitochondrial fractions from small hiMC numbers and could show that activation of mitochondrial STAT3 and ERK1/2 in hiMC was also inhibited by resveratrol. Our results indicate that resveratrol inhibits hiMC activation by inhibiting the phosphorylation of mitochondrial and nuclear ERK1/2 and STAT3, and it could be considered as an anti-inflammatory nutraceutical in the treatment of mast cell-associated diseases.

Sirtuin 6 is a negative regulator of FcεRI signaling and anaphylactic responses

Binding IgE to a cognate allergen causes aggregation of Fcε receptor I (FcεRI) in mast cells, resulting in activation of receptor-associated Src family tyrosine kinases, including Lyn and Syk. Protein tyrosine phosphatase, receptor type C (PTPRC), also known as CD45, has emerged as a positive regulator of FcεRI signaling by dephosphorylation of the inhibitory tyrosine of Lyn. Sirtuin 6 (Sirt6), a NAD+-dependent deacetylase, exhibits an anti-inflammatory property. It remains to be determined, however, whether Sirt6 attenuates mast cell-associated diseases, including anaphylaxis. FcεRI signaling and mast cell degranulation were measured after IgE cross-linking in murine bone marrow-derived mast cells (BMMCs) and human cord blood-derived mast cells. To investigate the function of Sirt6 in mast cell activation invivo, we used mast cell-dependent animal models of passive systemic anaphylaxis (PSA) and passive cutaneous anaphylaxis (PCA). Sirt6-deficient BMMCs augmented IgE-FcεRI-mediated signaling and degranulation compared to wild-type BMMCs. Reconstitution of mast cell-deficient KitW-sh/W-sh mice with BMMCs received from Sirt6 knockout mice developed more severe PSA and PCA compared to mice engrafted with wild-type BMMCs. Similarly, genetic overexpression or pharmacologic activation of Sirt6 suppressed mast cell degranulation and blunted responses to PCA. Mechanistically, Sirt6 deficiency increased PTPRC transcription via acetylating histone H3, leading to enhanced aggregation of FcεRI in BMMCs. Finally, we recapitulated the Sirt6 regulation of PTPRC and FcεRI signaling in human mast cells. Sirt6 acts as a negative regulator of FcεRI signaling cascade in mast cells by suppressing PTPRC transcription. Activation of Sirt6 may therefore represent apromising and novel therapeutic strategy for anaphylaxis.

Loss of isoprenylation significantly reduces IgE mediated mast cell activation

Abstract Allergic disease a leading cause of chronic illness in the US and accounts for billions of dollars in healthcare costs annually. Mast cells are tissue resident innate immune cells linked to allergic disease and activated by IgE and other ligands. Upon activation they release histamine, cytokines, chemokines, proteases, and lipid mediators evoking allergic symptoms. New ways of targeting mast cells could greatly benefit allergic disease therapy. Repurposing statin drugs such as Fluvastatin as a therapeutic treatment of allergic disease showed reduced allergic symptoms using in vitro and in vivo mouse models. We found the Fluvastatin suppresses IgE mediated mast cell activation by inhibiting protein isoprenylation. However, statin suppression is dependent on genetic background. To avert genetic background dependency, we tested the hypothesis that a dual farnesyl and geranylgeranyl transferase inhibitor (FGTI 2734) would consistently suppress mast cell function. We show that FGTI 2734 reduced IgE-mediated degranulation and cytokine production similar to Fluvastatin effects, but maintained efficacy on fluvastatin-resistant genetic backgrounds. FGTI 2734 also suppressed IgE-mediated anaphylaxis in vivo on multiple genetic backgrounds. Finally, inhibition of Ras, a known target of prenylation, can mimic statin effects on IgE-mediated mast cell function. These data support the hypothesis that dual farnesyl and geranylgeranyl transferase inhibitors may be an effective therapeutic treatment for mast cell-associated diseases.

Discovery, Function, and Therapeutic Targeting of Siglec-8.

Siglecs (sialic acid-binding immunoglobulin-like lectins) are single-pass cell surface receptors that have inhibitory activities on immune cells. Among these, Siglec-8 is a CD33-related family member selectively expressed on human mast cells and eosinophils, and at low levels on basophils. These cells can participate in inflammatory responses by releasing mediators that attract or activate other cells, contributing to the pathogenesis of allergic and non-allergic diseases. Since its discovery in 2000, initial in vitro studies have found that the engagement of Siglec-8 with a monoclonal antibody or with selective polyvalent sialoglycan ligands induced the cell death of eosinophils and inhibited mast cell degranulation. Anti-Siglec-8 antibody administration in vivo to humanized and transgenic mice selectively expressing Siglec-8 on mouse eosinophils and mast cells confirmed the in vitro findings, and identified additional anti-inflammatory effects. AK002 (lirentelimab) is a humanized non-fucosylated IgG1 antibody against Siglec-8 in clinical development for mast cell- and eosinophil-mediated diseases. AK002 administration has safely demonstrated the inhibition of mast cell activity and the depletion of eosinophils in several phase 1 and phase 2 trials. This article reviews the discovery and functions of Siglec-8, and strategies for its therapeutic targeting for the treatment of eosinophil- and mast cell-associated diseases.

A Potent Mimetic of the Siglec-8 Ligand 6'-Sulfo-Sialyl Lewisx.

Siglecs are members of the immunoglobulin gene family containing sialic acid binding N-terminal domains. Among them, Siglec-8 is expressed on various cell types of the immune system such as eosinophils, mast cells and weakly on basophils. Cross-linking of Siglec-8 with monoclonal antibodies triggers apoptosis in eosinophils and inhibits degranulation of mast cells, making Siglec-8 a promising target for the treatment of eosinophil- and mast cell-associated diseases such as asthma. The tetrasaccharide 6'-sulfo-sialyl Lewisx has been identified as a specific Siglec-8 ligand in glycan array screening. Here, we describe an extended study enlightening the pharmacophores of 6'-sulfo-sialyl Lewisx and the successful development of a high-affinity mimetic. Retaining the neuraminic acid core, the introduction of a carbocyclic mimetic of the Gal moiety and a sulfonamide substituent in the 9-position gave a 20-fold improved binding affinity. Finally, the residence time, which usually is the Achilles tendon of carbohydrate/lectin interactions, could be improved.

Selective Serotonin Reuptake Inhibitors Suppress IL-33-Mediated Mast Cell Function

Abstract Interleukin-33 (IL-33) is an inflammatory cytokine that promotes allergic disease by activating ILC2, Th2 cells, and mast cells. IL-33 is increased in asthmatics, and its blockade suppresses asthma-like inflammation in mouse models. Therefore, clinical interventions targeting IL-33 may be beneficial for allergic disease. We have sought ways of re-purposing FDA-approved drugs for use in allergic inflammation. Because drugs in the selective serotonin reuptake inhibitor class (SSRIs) have documented anti-inflammatory effects, we tested the hypothesis that SSRIs can attenuate mast cell function. We show that the SSRI fluoxetine inhibits IL-33-mediated cytokine production in mouse bone marrow derived mast cells in vitro and reduces IL-33-induced peritonitis in vivo. These data indicate that fluoxetine may be an effective therapeutic for IL-33- and mast cell-associated diseases.

Effect of Dietary Fiber and Metabolites on Mast Cell Activation and Mast Cell-Associated Diseases.

Many mast cell-associated diseases, including allergies and asthma, have seen a strong increase in prevalence during the past decades, especially in Western(ized) countries. It has been suggested that a Western diet may contribute to the prevalence and manifestation of allergies and asthma through reduced intake of dietary fiber and the subsequent production of their metabolites. Indeed, dietary fiber and its metabolites have been shown to positively influence the development of immune disorders via changes in microbiota composition and the regulation of B- and T-cell activation. However, the effects of these dietary components on the activation of mast cells, key effector cells of the inflammatory response in allergies and asthma, remain poorly characterized. Due to their location in the gut and vascularized tissues, mast cells are exposed to high concentrations of dietary fiber and/or its metabolites. Here, we provide a focused overview of current findings regarding the direct effects of dietary fiber and its various metabolites on the regulation of mast cell activity and the pathophysiology of mast cell-associated diseases.

Selective Serotonin Reuptake Inhibitors Suppress Mast Cell Function

Abstract There is considerable evidence of links between depression and inflammation. Selective serotonin reuptake inhibitors (SSRIs) are effective anti-depressants with well documented off-target effects. Because SSRI also has anti-inflammatory effects, we tested the hypothesis that SSRIs can attenuate mast cell function. We show that SSRIs reduce IgE-mediated degranulation and cytokine production in mouse bone marrow derived and peritoneal mast cells in vitro, and suppress IgE-mediated anaphylaxis in vivo. Since exogenous serotonin had no effect on IgE-induced mast cell activation, we suspected an SSRI mechanism independent of serotonin inhibition. We show that inhibiting the purinergic receptors P2X3 and P2X7 mimic SSRI effects, and combining these inhibitors and SSRIs has no additive effects. SSRIs blocked ATP-induced activation and ATP uptake in mouse mast cells, further suggesting SSRIs are targeting P2X signaling. Because IgE induces ATP release, we postulate that SSRIs suppress an IgE-ATP positive feedback response by limiting P2X signaling. These data indicate that SSRIs may be effective therapeutics for mast cell-associated diseases.

Frontline Science: Corticotropin-releasing factor receptor subtype 1 is a critical modulator of mast cell degranulation and stress-induced pathophysiology.

Life stress is a major risk factor in the onset and exacerbation of mast cell-associated diseases, including allergy/anaphylaxis, asthma, and irritable bowel syndrome. Although it is known that mast cells are highly activated upon stressful events, the mechanisms by which stress modulates mast cell function and disease pathophysiology remains poorly understood. Here, we investigated the role of corticotropin-releasing factor receptor subtype 1 (CRF1) in mast cell degranulation and associated disease pathophysiology. In a mast cell-dependent model of IgE-mediated passive systemic anaphylaxis (PSA), prophylactic administration of the CRF1-antagonist antalarmin attenuated mast cell degranulation and hypothermia. Mast cell-deficient KitW-sh/W-sh mice engrafted with CRF1-/- bone marrow-derived mast cells (BMMCs) exhibited attenuated PSA-induced serum histamine, hypothermia, and clinical scores compared with wild-type BMMC-engrafted KitW-sh/W-sh mice. KitW-sh/W-sh mice engrafted with CRF1-/- BMMCs also exhibited suppressed in vivo mast cell degranulation and intestinal permeability in response to acute restraint stress. Genetic and pharmacologic experiments with murine BMMCs, rat RBL-2H3, and human LAD2 mast cells demonstrated that although CRF1 activation did not directly induce MC degranulation, CRF1 signaling potentiated the degranulation responses triggered by diverse mast cell stimuli and was associated with enhanced release of Ca2+ from intracellular stores. Taken together, our results revealed a prominent role for CRF1 signaling in mast cells as a positive modulator of stimuli-induced degranulation and in vivo pathophysiologic responses to immunologic and psychologic stress.

STAT5b Controls IgE-mediated Mast Cell Functions In Vitro and In Vivo

Abstract Signal Transducers and Activators of Transcription (STATs) are latent transcription factors that mediate a number of cellular responses including but not limited to cell survival, proliferation and differentiation. This protein family consists of seven members, STATs 1 – 6 including two closely related molecules, STAT5a and STAT5b, that show 96% amino acid sequence homology and are critical for lymphoid, myeloid, and erythroid cell development and function. We recently identified Stat5b as the critical regulator of IgE-mediated cytokine production in mast cells. STAT5b knockout (KO) cells show decreased cytokine production in vitro. In vivo STAT5b KO mice demonstrate decreased sensitivity to IgE-mediated passive systemic anaphylaxis accompanied with decreased production of IL-6 and IL-13 compared to wildtype counterparts. There was no difference in MAR-1-mediated passive systemic anaphylaxis or mast cell number and distribution. Interestingly STAT5b KO mice demonstrate elevated levels of serum IgE and an exacerbated response to histamine-mediated passive systemic anaphylaxis. We previously found that Fyn-mediated Stat5 tyrosine phosphorylation is critical for Stat5-dependent effects. The current work demonstrates that Stat5b is also phosphorylated on serine residues during IgE signaling in mast cells, via a Src-independent pathway requiring PI3-kinase function. Preliminary data show that STAT5b tyrosine and serine phosphorylation either independently or in tandem regulate IgE-induced cytokine production. Elucidating the role of STAT5b in the inflammatory response as well as the key players in STAT5b serine phosphorylation will yield new targets for mast cell-associated diseases.

Anti-allergic mechanisms of Japanese herbal medicine, yokukansan on mast cells.

We previously reported that the addition of orally administered yokukansan (YKS), a traditional Japanese herbal medicine, to the standard regimen using histamine H1-receptor inhibitors was effective in controlling refractory chronic urticaria, but the mechanism remained unknown. YKS has also been reported to be effective on inhibiting the development of atopic dermatitis-like skin lesions in NC/Nga mice. As known, the release of various chemical mediators including histamine from degranulated mast cells is strongly related to the mechanism of these diseases. Thus the purpose of this study was to examine the mechanisms behind the medicinal effects of YKS on mast cells using an in vitro system and rat basophil leukemia (RBL-2H3) cells. The degree of degranulation was measured by β-hexosaminidase secretion assay and intracellular calcium influx assay. ELISA for cytokines (TNF-α and IL-4) was also conducted using cell culture media. Furthermore, we investigated the effects of YKS on the expression of adhesion molecules (ICAM-1, VCAM-1, E-selectin) and cytokine production (IL-8) in human dermal microvascular endothelial cells using gene-transcriptional- and immunohisotoligical analysis. We found that YKS inhibited secretion of β-hexosaminidase, intracellular calcium increase, production of TNF-α and ICAM-1 expression, and that several YKS ingredients may be the key effectors. In conclusion, YKS may suppress several mast cell functions such as degranulation and calcium increase that eventually inhibits the release of proinflammatory cytokines. Furthermore, YKS suppresses ICAM-1 expression on human microvascular endothelial cells. These findings may promote our understanding of the beneficial effects of YKS on mast cell-associated allergic diseases.

IgE receptor induces Stat5b serine phosphorylation in mast cells (HYP3P.346)

Abstract Signal Transducers and Activators of Transcription (STATs) are latent transcription factors that mediate a number of cellular responses including but not limited to cell survival, proliferation and differentiation. This protein family consists of seven members, STAT1-6 including two closely related molecules, STAT5a and STAT5b, that show 96% amino acid sequence homology and are critical for lymphoid, myeloid, and erythroid cell development and function. We recently identified Stat5b as the critical regulator of IgE-mediated cytokine production in mast cells. We found that Fyn-mediated Stat5 tyrosine phosphorylation is critical for Stat5-dependent effects. Our recent work demonstrates that Stat5b is also phosphorylated on serine residues during IgE signaling in mast cells. We find that STAT5b serine phosphorylation occurs through a Src-independent pathway requiring PI3-kinase function. Understanding the pathways leading to Stat5b serine phosphorylation and its role in the inflammatory response will yield new targets for mast cell-associated diseases.

Mast Cells as Targets of Pimecrolimus

Mast cells, the multi-functional secretory cells, are the pivotal effector cells in immune response, and contribute to the pathogenesis of many diverse diseases, like asthma and mastocytosis, by releasing numerous proinflammatory mediators. Pimecrolimus (SDZ ASM 981) is a derivative of the macrolactam ascomycin and is a member of the calcineurin inhibitor class of immunosuppressors. It inhibits the calcineurin-dependent activation of nuclear factor of activated T cells and the expression of a number of proinflammatory cytokines in turn. Pimecrolimus has high and selective anti-inflammatory activity within the skin, and with much lower potential to affect local and systemic immune responses. Therefore it has been widely used for treatment of various inflammatory skin diseases. It has a cellselective mode of action, and mast cells are its specific target cells. Pimecrolimus inhibits the release of both preformed and de novo synthesized mediators from activated mast cells and inhibits accumulation of mast cells by inducing apoptosis. Several experimental and clinical reports have demonstrated the successful application of pimecrolimus and other calcineurin inhibitors, such as tacrolimus and cyclosporine A, to treat mastocytosis, a spectrum of disorders characterized by mast cell hyperplasia, especially cutaneous mastocytosis. These new findings suggest that pimecrolimus and other calcineurin inhibitors may be a novel and effective therapeutic approach for mast cell-associated diseases such as asthma and mastocytosis.

The BH3-Mimetic ABT-737 Induces Mast Cell Apoptosis In Vitro and In Vivo: Potential for Therapeutics

Mast cells and their mediators are implicated in the pathogenesis of many different diseases. One possible therapeutic intervention in mast cell-associated diseases can be to reduce the number of tissue mast cells by inducing mast cell apoptosis. In this study, we demonstrate that mast cells exhibit a high sensitivity to ABT-737, a BH3-only mimetic molecule that induces apoptosis through high-affinity binding to the prosurvival proteins, Bcl-2, Bcl-XL, and Bcl-w. Primary mast cells as well as mast cell lines tested succumbed to apoptosis in response to the inhibitor at varying but seemingly low concentrations compared with other leukocytes investigated. I.p. injections of ABT-737 in mice resulted in a total abolishment of mast cells in the peritoneum. Confocal microscopy analysis of peritoneal cells revealed apoptotic bodies of mast cells being phagocytosed by macrophages. In addition, ex vivo treatment of human skin biopsies with ABT-737 demonstrated increased mast cell apoptosis. The data we present in this article show exceptional mast cell sensitivity to ABT-737, a selective inhibitor of antiapoptotic proteins, rendering a possible application for BH3-only mimetic compounds like ABT-737 in mast cell-associated diseases, such as mastocytosis, allergy, asthma, and other chronic inflammations.

Stat5 is Activated by FceRI via Fyn Kinase (86.7)

Abstract We have recently found that the transcription factor Stat5 is rapidly activated by IgE crosslinkage, and that its expression is critical to IgE-mediated degranulation, LTB4 production, cytokine secretion, and survival signals. Stat5KO mast cells induced cytokine mRNAs normally following IgE crosslinkage, but these mRNAs were not sustained over time, and were degraded at twice the rate observed in wild type cells. We find that Stat5 is associated with the IgE receptor after antigen-mediated activation. Moreover, cholesterol depletion or Fyn kinase deletion prevents Stat5 tyrosine phosphorylation in response to IgE crosslinkage. In contrast, the Lyn, Syk, MAPK, and PI-3 kinase pathways do not appear to regulate Stat5 tyrosine phosphorylation via the IgE receptor. We also find that Stat5 is serine phosphorylated during IgE signaling. These data suggest that Stat5 is activated through a lipid raft- and Fyn-dependent pathway. Our work demonstrates that Stat5 is a critical factor in IgE-induced mast cell activation that could provide a new clinical target for mast cell-associated inflammatory diseases.