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Introduction Mast cells are regarded as a kind of classical anaphylaxis cells. However autoimmune diseases and allergic reactions have many similarities or overlaps. A large number of papers have proved that mast cells play a significant role in the pathogenesis of systemic lupus erythematosus (SLE). It is speculated that IgE, anti‐IgE antibodies, FcεRI, and anti‐FcεRI antibodies activate mast cells through autoimmune pathways and participate in the disease process of SLE. Naturally occurring protein molecules not only exist in monomer form, but also in polymer of protein molecules. Therefore, whether IgE, FcεRIα, anti‐IgE antibodies, and anti‐FcεRI antibodies also exist in polymeric forms in the natural state is worthy of further investigation. Methods The serum samples and clinical data of 131 patients with SLE were collected from Qilu Hospital (Qingdao). Sixty healthy individuals were collected as the control group. Serum FcεRIα, anti‐IgE, and anti‐FcεRI were detected by enzyme‐linked immunosorbent assay. Serum IgE was detected by rate scatter nephelometry. A Chinese hamster ovarian cancer cell line CHO3D10 transfected with human FcεRIα was cultured and the cell protein extract was prepared. The existence forms of FcεRIα in the cell protein extract were detected by the native‐page method. Results The serum FcεRIα in SLE patients was significantly higher than that in control group (3.52 [2.18, 4.71] µg/ml and 1.87 [1.52, 2.33] µg/ml, respectively; p, First, as autoimmune diseases and allergic reactions have many similarities or overlaps, we compared the differences in serum IgE, FcεRIα, anti‐IgE, and anti‐FcεRI levels of systemic lupus erythematosus group and healthy control group for the first time. The serum FcεRIα in SLE patients is significantly higher than that in the control group and anti‐IgE is significantly lower than that in the control group, which provides a new reference basis for the understanding and further discussion of the inflammatory mechanism of the disease. Second, this study has revealed that the FcεRIα has one kind of monomer and two kinds of polymers in the degeneration conditions, which is worthy of further investigation.

There is strong evidence of an association between severe anaphylaxis, especially hymenoptera venom induced, and mast cell (MC) disorders. It has been thought that intrinsic abnormalities in MCs, including the presence of the activating KIT D816V mutation in mastocytosis or of genetic trait, hereditary alpha-tryptasemia, may influence susceptibility to severe anaphylaxis. This article evaluates the potential mechanisms leading to severe MC activation, as well as the differential diagnosis of and range of symptoms attributable to MC mediator release. Also, we offer a global classification for disorders related to MC activation.

Cyclooxygenase (COX)-1-selective inhibitors have side effects such as itching and dryness of the skin. In this study, the degree of skin dryness and the onset mechanism of this condition were investigated by comparing the effects of three non-steroidal anti-inflammatory drugs (NSAIDs) in mice. Mice were orally administered either indomethacin, loxoprofen sodium, or celecoxib (n = 5 per group) once daily for four consecutive days, and blood samples as well as skin and jejunal tissues were isolated on day 5. In the mice treated with indomethacin, transepidermal water loss was significantly increased, and dry skin was observed. In addition, the expression of matrix metalloproteinase (MMP)-I, mast cells, CD163, CD23, CD21, histamine, and peroxisome proliferation-activated receptor (PPAR)γ in the skin and jejunum was increased, and the blood levels of interleukin-10 and immunoglobulin E were also increased. In contrast, the expression of collagen type I in the skin was decreased. These results show that indomethacin activates PPARγ in the skin and jejunum, changes the polarity of macrophages, increases the secretion of MMP-1 from mast cells, and decomposes collagen type I, leading to dry skin.

The diagnosis of mast cell activation syndrome (MCAS) is defined by 3 criteria: (1) typical clinical signs and symptoms of acute, recurrent (episodic), and systemic mast cell activation (MCA); (2) increase in tryptase level to >20% + 2 ng/mL within 1-4 hours after onset of the acute crisis; and (3) response of MCA symptoms to antimediator therapy. Classification of MCAS requires highly sensitive and specific methodological approaches for the assessment of clonal bone marrow mast cells at low frequencies. The Spanish Network on Mastocytosis score has been used successfully as a predictive model for selecting MCAS candidates for bone marrow studies based on a high probability of an underlying clonal mast cell disorder. In this article, we propose a diagnostic algorithm and focus on the practical evaluation and management of patients with suspected MCAS. Key words: Anaphylaxis. Antimediator therapy. Mast cell activation syndrome. Mast cell mediator release–related symptoms. Tryptase.

Objective To describe our current understanding of hereditary α-tryptasemia (HαT), how HαT fits into the evolutionary context of tryptases and contemporary framework of mast cell–associated disorders, and to discuss the future clinical and therapeutic landscape for symptomatic individuals with HαT. Data Sources Primary peer-reviewed literature. Study Selections Basic, clinical, and translational studies describing tryptase gene composition, generation, secretion, and elevation and the associated clinical impacts of HαT and treatment of such individuals were reviewed. Results HαT is a common autosomal dominant genetic trait caused by increased TPSAB1 copy number encoding α-tryptase. Approximately 1 in 20 White individuals have HαT, making it by far the most common cause for elevated basal serum tryptase levels. Although many individuals with HαT may not manifest associated symptoms, the prevalence of HαT is increased in patients with clonal and nonclonal mast cell–associated disorders wherein it is linked to more prevalent and/or severe anaphylaxis and increased mast cell mediator-associated symptoms. Increased generation of mature α/β-tryptase heterotetramers, and their unique physiochemical properties, may be responsible for some of these clinical findings. Conclusion HαT is a common modifier of mast cell–associated disorders and reactions. Nevertheless, whether HαT may be an independent cause of clinical phenotypes with which it has been associated remains unproven. Correct identification of HαT is critical to accurate interpretation of serum tryptase levels in the clinical evaluation of patients. Beyond HαT, we foresee tryptase genotyping as an important parameter in the standard workup of patients with mast cell–associated disorders and development of therapeutic modalities targeting these patients and associated clinical phenotypes.

Hymenoptera venom anaphylaxis is the most frequent cause of anaphylaxis and responsible for about 20% of all fatal anaphylaxis cases in adults. We report two cases of fatal hymenoptera venom anaphylaxis with undiagnosed underlying mastocytosis and review the risk factors for severe or fatal hymenoptera venom anaphylaxis, as well as the specificities of its association with mastocytosis. As hymenoptera venom allergic patients with underlying clonal mast cell disorder generally lack typical skin lesions of mastocytosis, its diagnosis can easily be missed, underscoring the importance and need for diagnostic strategies in order to correctly identify these patients. Predominant cardiovascular symptoms in the absence of urticaria or angioedema following an insect sting are suggestive of underlying clonal mast cell disorder, and should be distinguished from panic attack or vasovagal syncope. Similarly, an unexplained syncope or an "idiopathic" anaphylaxis might reveal mastocytosis or hereditary alpha-tryptasemia. Acute and basal serum tryptase measurements should always be integrated in the diagnostic work-up of an insect sting reaction or unexplained syncope or shock of any origin.

Background Pituitary adenylate cyclase-activating polypeptide-38 (PACAP38) and vasoactive intestinal polypeptide can provoke cluster headache attacks in up to half of cluster headache patients in their active phase. At present, it is unknown whether provoked attacks are mediated via calcitonin gene-related peptide or mast cell activation. Methods All enrolled patients with cluster headache were randomly allocated to receive a continuous infusion of either PACAP38 (10 pmol/kg/min) or vasoactive intestinal polypeptide (8 pmol/kg/min) over 20 min. We collected clinical data and measured plasma levels of calcitonin gene-related peptide and markers of mast cell activation (tryptase and histamine) at fixed time points: at baseline (T0), at the end of the infusion (T20), 10 min after the infusion (T30), and 70 min after the infusion (T90). Results Blood was collected from episodic cluster headache patients in active phase (n = 14), episodic cluster headache patients in remission (n = 15), and chronic cluster headache patients (n = 15). At baseline, plasma levels of calcitonin gene-related peptide, tryptase, and histamine were not different among the three study groups. Plasma levels of calcitonin gene-related peptide ( p = 0.7074), tryptase ( p = 0.6673), or histamine ( p = 0.4792) remained unchanged during provoked attacks compared to attack-free patients. Conclusion Cluster headache attacks provoked by either PACAP38 or vasoactive intestinal polypeptide were not accompanied by alterations of plasma calcitonin gene-related peptide, tryptase or histamine. The provoked attacks may not be mediated by calcitonin gene-related peptide or mast cell activation. Trial Registration: The study is registered at ClinicalTrials.gov (NCT03814226).

Allergic rhinitis (AR) is a common allergic inflammatory and chronic reactive disease caused by allergen-induced immunoglobulin E (IgE). Tanshinone IIA (Tan IIA) is one of the active ingredients in Salvia miltiorrhiza Bunge (Danshen) and plays a vital role in inhibiting inflammation. Thus, we hypothesized that Tan IIA has anti-allergic effects and studied the function of Tan IIA in mast cells and an AR animal model. We induced RBL-2H3 cell sensitization with monoclonal anti-2,4,6-dinitrophenyl-immunoglobulin (Ig) E/human serum albumin (DNP-IgE/HSA) and constructed an ovalbumin (OVA)-induced AR model in mice. The role of Tan IIA in AR progression was studied using the MTT assay, ELISA, western blot, toluidine blue staining, HE staining, and Alcian blue and safranin O (A&S) staining. Tan IIA treatment significantly increased IgE/HSA-induced cell viability. However, Tan IIA treatment markedly downregulated the expression levels of β-hexosaminidase, histamine, tumor necrosis factor (TNF-α), interleukin 1β (IL-1β), IL-4, and IL-5 in IgE/HSA-induced cells. Furthermore, Tan IIA improved typical symptoms in the OVA-induced AR model mice by inhibiting the phospholipase Cγ1 (PLCγ1)/protein kinase C (PKC)/IP3R pathway. Additionally, Tan IIA effectively improved the degranulation of RBL-2H3 cells and OVA-induced AR in mice. Together, these results suggest that Tan IIA may be a potential drug for the treatment of AR in the future.

Mast cell activation disease (MCAD) includes single organ disease such as asthma, urticaria, and gastroenteritis, as well as multiorgan system involvement such as mast cell activation syndrome and anaphylaxis. Reports link MCAD with hypermobile Ehlers-Danlos syndrome (hEDS), hypermobility spectrum disorder (HSD), and with primary immune deficiencies such as complement and immunoglobulin deficiencies (Ig Def). This study assesses the concurrence of these syndromes. We undertook a cohort analysis of patients seen in a community-based Allergy/Immunology clinic from 2015 to 2019. We searched for diagnostic codes for Ig Def disorders, hypermobility syndrome, hypermobile/Ehlers-Danlos syndrome, and MCADs. Of 974 patients with suspected MCAD, 449 (46%) had a diagnosis of MCAD; 496 (51%) of cases had a combination of at least two of hEDS/HSD, MCAD, and Ig Def. Ig Def was present in 417 (43%) of patients; 188 (19.3%) had hEDS/HSD with an Ig Def with or without MCAD and accounted for 45% of all the cases with Ig Def. Of 974 cases, 101 (10%) had hEDS/HSD and MCAD; 207 (21%) had Ig Def and MCAD; 7 (0.7%) had Ig Def and hEDS/HSD; and 181 (19%) had a combination of all three syndromes. Most patients (74%) with these comorbidities were female. The presence of MCAD and Ig Def should be explored in patients with hEDS/HSD. Identifying underlying contributors to recurrent/chronic inflammation and tissue injury is needed to tailor and personalize therapies. This, in turn, can reduce tissue damage, iatrogenic intervention, and optimize health outcomes.

4,8-Sphingadienines (SD), metabolites of glucosylceramides (GlcCer), are sometimes determined as key mediators of the biological activity of dietary GlcCer, and cis/trans geometries of 4,8-SD have been reported to affect its activity. Since regulating excessive activation of mast cells seems an important way to ameliorate allergic diseases, this study was focused on cis/trans stereoisomeric-dependent inhibitory effects of 4,8-SD on mast cell activation. Degranulation of RBL-2H3 was inhibited by treatment of 4-cis-8-trans- and 4-cis-8-cis-SD, and their intradermal administrations ameliorated ear edema in passive cutaneous anaphylaxis reaction, but 4-trans-8-trans- and 4-trans-8-cis-SD did not. Although the activation of mast cells depends on the bound IgE contents, those stereoisomers did not affect IgE contents on RBL-2H3 cells after the sensitization of anti-TNP IgE. These results indicated that 4-cis-8-trans- and 4-cis-8-cis-SD directly inhibit the activation of mast cells. In conclusion, it was assumed that 4,8-SD stereoisomers with cis double bond at C4-position shows anti-allergic activity by inhibiting downstream pathway after activation by the binding of IgE to mast cells.

A senile male captive bush dog (Speothos venaticus) presented a small perianal cutaneous nodule. Histologically, there was an ulcerated round cell tumor composed of well differentiated mast cells with abundant intracytoplasmic purple Giemsa-positive granules, with a diffuse eosinophilic infiltrate. Immunohistochemistry revealed that 30% of the neoplastic cells were positive for Kit in the cytoplasm and cell membrane, and all neoplastic cells were negative for MAC and CD3. Less than 10% of the neoplastic cells were positive for Ki67. At necropsy other primary tumors were identified in this animal, including an intestinal adenoma, an adrenal cortex adenoma and a testicular interstitial cell tumor. RESUMO Um cachorro-vinagre (Speothos venaticus) apresentou um nódulo cutâneo pequeno na região perianal. Histologicamente havia neoplasia cutânea de células redondas e ulcerada, constituída por mastócitos bem diferenciados, com abundantes grânulos citoplasmáticos metacromáticos na coloração de Giemsa e infiltrado eosinofílico difuso. A imuno-histoquímica demonstrou que 30% das células neoplásicas eram positivas para a proteína Kit no citoplasma e na membrana celular. As células foram negativas para MAC e CD3. Menos de 10% das células neoplásicas foram positivas para Ki67. Durante a necropsia, foram identificados outros tumores primários, como adenoma intestinal, adenoma cortical da adrenal e tumor de células intersticiais do testículo.

Mast cells have crucial roles in allergic and other inflammatory diseases. Preclinical approaches provide circumstantial evidence for mast cell involvement in many diseases, but these studies have major limitations — for example, there is still a lack of suitable mouse models for some mast cell-driven diseases such as urticaria. Some approaches for studying mast cells are invasive or can induce severe reactions, and very few mediators or receptors are specific for mast cells. Recently, several drugs that target human mast cells have been developed. These include monoclonal antibodies and small molecules that can specifically inhibit mast cell degranulation via key receptors (such as FceRI), that block specific signal transduction pathways involved in mast cell activation (for example, BTK), that silence mast cells via inhibitory receptors (such as Siglec-8) or that reduce mast cell numbers and prevent their differentiation by acting on the mast/stem cell growth factor receptor KIT. In this Review, we discuss the existing and emerging therapies that target mast cells, and we consider how these treatments can help us to understand mast cell functions in disease. Kolkhir and colleagues discuss how therapies targeting human mast cells in both allergic and non-allergic disease settings have provided crucial insights into the functions of these cells.

[Objective]: Mast cell (MC) activation (MCA) defines the mechanism by which certain patients have symptoms owing to the effect of a wide range of mediators released from MCs upon their activation, when triggered by different stimuli. When these symptoms are severe and recurrent, the diagnosis of MCA syndrome (MCAS) might be considered. Here, we review the relevant aspects related to the pathogenesis of MCAS, with special emphasis on the prevalence and diagnostic relevance of KIT mutations., [Data Sources]: PubMed was searched between 1980 and 2021 using the following terms: mast cell activation syndromes, mast cell activation, anaphylaxis, KIT mutations, KIT D816V, indolent systemic mastocytosis, bone marrow mastocytosis, cutaneous mastocytosis, IgE anaphylaxis, and idiopathic anaphylaxis., [Study Selections]: Only articles published in English were selected based on their relevance to MCAS or severe and recurrent anaphylaxis., [Results]: MCAS can be classified as clonal MCAS and nonclonal MCAS depending on the presence vs absence of an underlying KIT mutation (mostly KIT D816V), respectively. In contrast to clonal MCAS in which MCA is associated with a primary MC disorder (ie, primary MCAS) such as mastocytosis or monoclonal MCAS, nonclonal MCAS can be secondary to known or unidentified triggers (ie, secondary and idiopathic MCAS, respectively)., [Conclusion]: The clinical heterogeneity and complexity of the molecular assays needed for the study of patients with MCAS might lead to misdiagnosis, particularly when patients are evaluated at nonspecialized centers. Thus, referral of patients having clinical manifestations suggestive of MCAS to reference centers on mastocytosis and MC diseases is strongly recommended., This work was supported by grants from the Instituto de Salud Carlos III (Madrid, Spain), Fondos Europeos de Desarrollo Regional (reference numbers: PI19/01166 and Centro de Investigación Biomédica en Red de Cáncer, CB16/12/00400), Fundación Española de Mastocitosis (Madrid, Spain; reference number: FEM2021-SAM), and Asociación Española de Pacientes con Mastocitosis y otras Enfermedades Relacionadas (Madrid, Spain; reference number: AEDM2019-SAM).

Dysregulated mast cell-mediated inflammation and/or activation have been linked to a number of human diseases, including asthma, anaphylaxis, chronic spontaneous urticaria, and mast cell activation syndromes. As a major mast cell granule protein, tryptase is a biomarker commonly used in clinical practice to diagnose mast cell-associated disorders and -mediated reactions, but its mechanistic roles in disease pathogenesis remains incompletely understood. Here, we summarize recent advances in the understanding of human tryptase genetics and the effects that different genetic composition may have on the quaternary structure of tetrameric mature tryptases. We also discuss how these differences may impact clinical phenotypes including allergic inflammation, immediate hypersensitivity, and others seen in patients with mast cell-associated disorders. With the increased application of next-generation sequencing, we foresee that human genetic approaches will be a major focus of understanding human tryptase functions in various human mast cell disorders and in new therapeutic development.

Interactions of antigens with the mast cell FcεRI-IgE receptor complex induce degranulation and boost synthesis of pro-inflammatory lipid mediators and cytokines. Activation of spleen tyrosine kinase (Syk) functions as a central hub in this signaling. The tyrosine phosphatase SHP-1 opposes Syk activity; stimulation of NADPH oxidase by FcεRI activation results in the production of oxidants that reversibly inhibit SHP-1, up-regulating the signal from Syk. Activated AMPK can suppress Syk activation by the FcεRI receptor, possibly reflecting its ability to phosphorylate the FcεRI beta subunit. Cyclic GMP, via protein kinase G II, enhances the activity of SHP-1 by phosphorylating its C-terminal region; this may explain its inhibitory impact on mast cell activation. Hydrogen sulfide (H2S) likewise opposes mast cell activation; H2S can boost AMPK activity, up-regulate cGMP production, and trigger Nrf2-mediated induction of Phase 2 enzymes – including heme oxygenase-1, whose generation of bilirubin suppresses NADPH oxidase activity. Phycocyanobilin (PCB), a chemical relative of bilirubin, shares its inhibitory impact on NADPH oxidase, rationalizing reported anti-allergic effects of PCB-rich spirulina ingestion. Phase 2 inducer nutraceuticals can likewise oppose the up-regulatory impact of NADPH oxidase on FcεRI signaling. AMPK can be activated with the nutraceutical berberine. High-dose biotin can boost cGMP levels in mast cells via direct stimulation of soluble guanylate cyclase. Endogenous generation of H2S in mast cells can be promoted by administering N-acetylcysteine and likely by taurine, which increases the expression of H2S-producing enzymes in the vascular system. Mast cell stabilization by benifuuki green tea catechins may reflect the decreased surface expression of FcεRI.

Kimchi is a traditional Korean food, of which its constituent lactic acid bacteria have been reported to possess various physiological activities. However, few studies have investigated the immunological activity of these bacteria or their effect on atopic dermatitis (AD). We investigated whether a mixture of 6 types of lactic acid bacteria strains (LBS) isolated from kimchi has an immunomodulating effect on atopy. Mice with atopic dermatitis were orally administered LSB from kimchi for 8 weeks, and skin moisture content, scratching behavior, T-and B-cell proliferation, Th1/2 cytokines, and serum IgE and histamine levels were measured. In addition, hematoxylin and eosin and toluidine blue staining were con-ducted. Mice receiving LBS from kimchi had increased skin moisture content (164.3%) and T-cell proliferation (more than 4-fold), and decreased number of scratching behaviors (78.2%) and B-cell proliferation (63.7%) compared with the 2,4-dinitrochlorobenzene control group. In addition, LBS increased Th1 type cytokines, decreased Th2 type and pro-inflam-matory cytokines, and decreased blood IgE (70.4%), histamine (67.6%) and mast cell levels. Therefore, it suggests that LBS of kimchi may be helpful in improving AD caused by immunological imbalance.

Hyaluronic acid (HA) is the main component of the extracellular matrix (ECM) of joints, and it is important for a lubricating joint during body movement. Degradation is the main metabolic process of HA in vivo. Hyaluronidases (HAase) were known for HA degradation. The inflammation-induced HA rapid-metabolism can reduce HA viscosity and concentration in joints. Mast cells (MC) containing their specific proteases were found in synovium tissue. It is unclear if MC-proteases could be involved in HA degradation pathways. This study aims to explore the correlations between HA concentration vs mast cell proteases, or matrix metalloproteinase-2/9 (MMP-2/9) and to investigate the association of MC-specific proteases with disrupted synovial HA homeostasis in rheumatoid arthritis (RA) or collagen-induced arthritis rats. The synovial fluid samples from no-RA and RA patients were collected; the collagen-induced arthritis (CIA) rat model was established; HA concentration and the activities of MC-protease and MMP-2/9 in the samples were detected, and the correlations were analyzed. In vitro interaction experiment was carried out by mixing MC-proteases with HA to observe the degradation speed. The HA concentrations in synovial fluids were decreased in RA patients and CIA rats compared with those in no-RA subjects or normal rats respectively. The activities of mast cell proteases in synovial fluids were increased and positively correlated with MMP-9, but negatively correlated with HA concentrations. In vitro study, the addition of MC-chymase and tryptase promoted the speed in HA degradation. MC-proteases may influence HA degradation pathway.

Although hypothermia has received substantial attention as an indicator of severity in anaphylaxis, it has been neglected from the perspective of whether it could act as a disease-modifying factor in this condition. Here, the impact of naturally occurring (spontaneous) hypothermia on anaphylaxis was evaluated in a murine model of ovalbumin (OVA)-induced allergy. Nonextreme changes in the ambient temperature (Ta) were used to modulate the magnitude of spontaneous hypothermia. At a Ta of 24°C, challenge with OVA intraperitoneally or intravenously resulted in a rapid, transient fall in body core temperature, which reached its nadir 4-6°C below baseline in 30 min. This hypothermic response was largely attenuated when the mice were kept at a Ta of 34°C. The Ta-dependent attenuation of hypothermia resulted in a survival rate of only 30%, as opposed to survival of 100% in the condition that favored the development of hypothermia. The protective effect of hypothermia did not involve changes in the rate of mast cell degranulation, as assessed by the concentration of mast cell protease-1 in bodily fluids. On the other hand, hypothermia improved oxygenation of the brain and kidneys, as indicated by higher NAD+/NADH ratios. Therefore, it is plausible to propose that naturally occurring hypothermia makes organs more resistant to the anaphylactic insult.

Background Mastocytosis encompasses a heterogeneous group of disorders characterized by accumulation of clonal mast cells (MCs) in the skin and/or internal organs. Patients typically present with a broad variety of recurrent mediator-related clinical symptoms, including severe anaphylaxis. However, not all patients with mastocytosis experience anaphylactic reactions. Objective We sought to identify disease-specific biomarkers in plasma that could be used to predict patients with mastocytosis with increased risk of anaphylaxis. Methods Nineteen patients (≥18 years) and 2 control groups (11 subjects with allergic asthma and 13 healthy volunteers without history of atopy) were recruited. In total, 248 plasma proteins were analyzed by Proximity Extension Assay using Olink Proseek Multiplex panels. Results We identified 4 novel proteins, in addition to tryptase, E-selectin, adrenomedullin, T-cell immunoglobulin, and mucin domain 1, and CUB domain–containing protein 1/CD138 to be significantly increased in patients with mastocytosis compared with both patients with asthma and healthy controls. Furthermore, we investigated whether we could discriminate between patients with mastocytosis with or without anaphylaxis. In addition to tryptase, we identified 3 novel proteins, that is, allergin-1, pregnancy-associated plasma protein-A, and galectin-3, with significantly different levels in patients with mastocytosis with anaphylaxis compared with those without anaphylaxis. Conclusions Newly identified proteomic biomarkers may be used to predict patients with mastocytosis with increased risk of anaphylaxis.

Mast cells (MCs) are immune cells that are distributed in all tissues throughout the body, and their cytoplasm is rich in granules containing histamine and tryptase. When MCs recognize antigens through IgE bound to FceRI, they release these mediators by degranulation. Because degranulation induces various type I allergic reactions, such as anaphylactic shock and hay fever, elucidation of the control mechanism of degranulation is important to the development of a therapeutic strategy for allergic diseases. It is known that the antigen-induced degranulation response is fine-tuned by various humoral factors via the activation of G protein-coupled receptors. We found that extracellular ATP enhanced antigen-dependent and -independent MC degranulation via activation of ionotropic P2X4 receptors. P2X4 receptor activation itself had no effect on MC degranulation, but significantly enhanced antigen-triggered degranulation. Stimulation of the P2X4 receptor potentiated the FceRI-mediated tyrosine kinase signaling cascade. In addition to antigen-induced responses, P2X4 receptor signaling also affected antigen-independent MC responses. Thus, co-stimulation of ATP and Gi-coupled receptor agonists, such as prostaglandin E2 (PGE2) and adenosine, resulted in synergistic degranulation. The significance of P2X4 receptor signaling in allergic and inflammatory responses in vivo was confirmed by impaired responses of antigen-induced passive anaphylaxis and PGE2-induced increases in vascular permeability in P2rx4 knockout mice compared to that of wild-type mice. These results suggest that the P2X4 receptor is a potential therapeutic target for both antigen-dependent and -independent allergic reactions.

Mast cells express multiple metabotropic purinergic P2Y receptor (P2YR) subtypes. Few studies have evaluated their role in human mast cell (HMC) allergic response as quantified by degranulation induced by cross-linking the high-affinity IgE receptor (FcεRI). We have previously shown that extracellular nucleotides modify the FcεRI activation-dependent degranulation in HMCs derived from human lungs, but the mechanism of this action has not been fully delineated. This study was undertaken to determine the mechanism of activation of P2YRs on the degranulation of HMCs and elucidate the specific postreceptor pathways involved. Sensitized LAD2 cells, a human-derived mast cell line, were subjected to a weak allergic stimulation (WAS) using a low concentration of Ag in the absence and presence of P2YR agonists. Only the metabotropic purinergic P2Y11 receptor (P2Y11R) agonist, adenosine 5'-(3-thio)triphosphate (ATPγS), enhanced WAS-induced degranulation resulting in a net 7-fold increase in release (n = 4; p < 0.01). None of the P2YR agonists tested, including high concentrations of ATPγS (1000 μM), enhanced WAS-induced intracellular Ca2+ mobilization, an essential component of activated FcεRI-induced degranulation. Both a PI3K inhibitor and the relevant gene knockout decreased the ATPγS-induced enhancement. The effect of ATPγS was associated with enhanced phosphorylation of PI3K type δ and protein kinase B, but not the phosphoinositide-dependent kinase-1. The effects of ATPγS were dose dependently inhibited by NF157, a P2Y11R antagonist. To our knowledge, these data indicate for the first time that P2YR is linked to enhancement of allergic degranulation in HMC via the PI3K/protein kinase B pathway.

Paired acute and baseline serum or plasma tryptase sampling and determination have recently been included as a mechanistic approach in the diagnostic and management guidelines of perioperative immediate hypersensitivity and anaphylaxis. The timing of this paired sampling is clearly defined in international consensus statements, with the optimal window for acute tryptase sampling between 30 minutes and 2 hours after the initiation of symptoms, whereas baseline tryptase should be measured in a sample collected before the event (preop) or at least 24 hours after all signs and symptoms have resolved. A transient elevation of the acute tryptase level greater than [2 D (1.2 3 baseline tryptase level)] supports the involvement and activation of mast cells. Here, we provide the clinical, pathophysiological, and technical rationale for the procedure and interpretation of paired acute and baseline tryptase. Clinical examples, upto-date knowledge of hereditary alpha-tryptasemia as a frequent cause of baseline tryptase of 7 mg/L and higher, mastocytosis, other clonal myeloid disorders, cardiovascular or renal failure, and technical improvements resulting in continued lowering of the 95th percentile value are discussed. Clues for improved management of perioperative immediate hypersensitivity and anaphylaxis include (1) sustained dissemination and implementation of updated guidelines; (2) preoperative sample storage for deferred analysis; (3) referral for thorough allergy investigation, screening for mast cellerelated disorders, and recommendations for future anesthetic procedures; and (4) sustained collaboration between anesthesiologists, immunologists, and allergists. (C) 2021 American Academy of Allergy, Asthma & Immunology

BACKGROUND Allergic asthma is a common inflammatory lung disease and a major health problem worldwide. Mast cells (MCs) play a key role in the early-stage pathophysiology of allergic asthma. Substance P (SP) functions in neurogenic inflammation by activating MCs, and therefore, it may to participate in the occurrence and development of asthma. OBJECTIVE We examined the relationship between SP and lung inflammation, and also whether SP can directly trigger asthma. METHODS We measured the number of peripheral blood eosinophils, neutrophils and basophils and evaluated the levels of IgE and SP in blood samples of 86 individuals with allergic asthma. Serum IgE and SP levels were also determined in 29 healthy individuals. C57BL/6 mice were subjected to different doses of SP, and bronchoalveolar lavage fluid (BALF) was collected to count the inflammatory cells. Lung tissues were analysed using histopathological methods to evaluate lung peribronchial inflammation, fibrosis and glycogen deposition. Levels of IgE, interleukin (IL)-1, IL-2, IL-4, IL-5, IL-13, IL-17 and IFN-γ were determined in mouse serum. RESULTS Substance P levels were increased in the serum samples of patients with asthma. SP induced mouse lung peribronchial inflammation, fibrosis and glycogen deposition, with high levels of Th2-related cytokines such as IL-4, IL-5 and IL-13 observed in the BALF. Furthermore, low level of total IgE was noted in the serum, and SP had little effect on MC-deficient kitW-sh/W-sh mice. CONCLUSIONS & CLINICAL RELEVANCE Substance P levels increased significantly in serum of asthmatic patients and independently associated with the risk of asthma. Furthermore, SP induced Th2 lung inflammation in mice, which was dependent on MCs.

Typical murine models of allergic inflammation are induced by the combination of ovalbumin and aluminum hydroxide. However, accumulating evidence indicates that, in models of asthma and atopic dermatitis, allergic inflammation can be generated in the absence of aluminum hydroxide. Moreover, co-administration of Staphylococcus aureus enterotoxin B with ovalbumin can enhance inflammation. The objective of this study was to establish a rapid and mast cell-dependent murine model of allergic inflammation by inducing allergic peritonitis using ovalbumin and S. aureus enterotoxin B. Allergic peritonitis was induced in C57BL/6 mice by subcutaneous sensitization and intraperitoneal challenge with ovalbumin and S. aureus enterotoxin B. Disease characteristics were assessed by flow cytometry, enzyme-linked immunosorbent assay (ELISA), trypan blue exclusion and colorimetric assays. The time–course of the allergic peritonitis revealed a peak of peritoneal inflammation 48 h after challenge, as assessed by total cells and eosinophil counts. The decrease of cell numbers started 96 h post-challenge, with complete clearance within 168 h. Moreover, significantly higher levels of tryptase and increased vascular permeability were found 30 min following challenge. Allergic inflammation induction by ovalbumin and S. aureus enterotoxin B was impaired in mast cell-deficient mice and partially restored by mice reconstitution with bone marrow-derived mast cells, indicating the mast cell role in this model. We present a novel model of allergic peritonitis that is mast cell-dependent, simple and robust. Moreover, the use of S. aureus enterotoxin B better resembles human allergic inflammation, which is known to be characterized by the colonization of S. aureus.

(-)-Epigallocatechin-3-O-(3-O-methyl) gallate (1, EGCG3″Me), an antiallergic O-methylated catechin, is present in high quantities in the green tea cultivar "Benifuuki" (Camellia sinensis L.). Previous studies have shown that EGCG3″Me inhibited basophil degranulation mediated through the cell-surface 67-kDa laminin receptor (67LR), but the mechanisms are not fully elucidated. This study aimed to investigate the mechanisms underlying the inhibitory effect of EGCG3″Me on IgE/antigen (Ag)-mediated degranulation and the combined effect of EGCG3″Me with eriodictyol (2), a bioactive flavanone. EGCG3″Me inhibited β-hexosaminidase release from the rat basophilic/mast cell line RBL-2H3 stimulated by IgE/Ag and induced acid sphingomyelinase (ASM) activity. This induction was inhibited by anti-67LR antibody treatment. The ASM-specific inhibitor desipramine inhibited EGCG3″Me-induced suppression of degranulation. The soluble guanylate cyclase (sGC) inhibitor NS2028 weakened the potency of EGCG3″Me, and the sGC activator BAY41-2272 suppressed degranulation. The ability of EGCG3″Me to induce ASM activity and inhibit degranulation was amplified by eriodictyol. Furthermore, oral administration of the lemon-peel-derived eriodyctiol-7-O-glucoside (3) potentiated the suppressive effect of EGCG3″Me-rich "Benifuuki" green tea on the IgE/Ag-induced passive cutaneous anaphylaxis (PCA) reaction in BALB/c mice. These results suggest that EGCG3″Me inhibits IgE/Ag-mediated degranulation by inducing the 67LR/sGC/ASM signaling pathway, and eriodictyol amplifies this signaling.

Hereditary alpha-tryptasemia (HαT) is an autosomal dominant genetic trait found in 4% to 6% of the general population and defined by excess copies of alpha-tryptase at TPSAB1. Elevated basal serum tryptase (sBT >8 ng/mL) is a defining feature of HαT and appears to result from increased pro-alpha-tryptase synthesis and secretion rather than mast cell activation. It is estimated that approximately one-third of individuals with HαT have associated symptoms, including cutaneous, gastrointestinal, atopic, musculoskeletal, autonomic, and neuropsychiatric manifestations. HαT is found at a disproportionately high rate in systemic mastocytosis and idiopathic anaphylaxis, and is a modifying factor that independently increases the incidence and severity of anaphylaxis. The varied phenotypes associated with HαT may, in part, result from coinheritance of other genetic variants, increased expression of α-/s-tryptase heterotetramers, and/or overexpression of pro-alpha-tryptase, although further studies are needed. There is an accurate diagnostic test available to confirm HαT in patients that can be used in combination with sBT to help risk-stratify individuals in whom bone marrow biopsy is being considered. There is no specific treatment for symptoms associated with HαT, and management is focused on controlling clinical manifestations with mast cell mediator antagonists, aspirin, inhalers, epinephrine, omalizumab, and involvement of other specialists.

Background Mast cells (MCs) are known to contribute to both acute and chronic inflammation. Bronchial epithelial cells are the first line of defence against pathogens and a deficient anti-viral response has been suggested to play a role in the pathogenesis of asthma exacerbations. However, effects of MC mediators on bronchial epithelial immune response have been less studied. The aim of this study is to investigate the direct effects of stimulation with MC proteases, tryptase and chymase, on inflammatory and anti-viral responses in human bronchial epithelial cells (HBECs). Method Cultured BEAS-2b cells and primary HBECs from 3 asthmatic patients were stimulated with tryptase or chymase (0.1 to 0.5 μg/ml) for 1, 3, 6 and 24 h. To study the effects of MC mediators on the anti-viral response, cells were stimulated with 10 μg/ml of viral mimic Poly (I:C) for 3 and 24 h following pre-treatment with 0.5 μg/ml tryptase or chymase for 3 h. Samples were analysed for changes in pro-inflammatory and anti-viral mediators and receptors using RT-qPCR, western blot and Luminex. Results Tryptase and chymase induced release of the alarmin ATP and pro-inflammatory mediators IL-8, IL-6, IL-22 and MCP-1 from HBECs. Moreover, tryptase and chymase decreased the expression of E-cadherin and zonula occludens-1 expression from HBECs. Pre-treatment of HBECs with tryptase and chymase further increased Poly (I:C) induced IL-8 release at 3 h. Furthermore, tryptase significantly reduced type-I and III interferons (IFNs) and pattern recognition receptor (PRR) expression in HBECs. Tryptase impaired Poly (I:C) induced IFN and PRR expression which was restored by treatment of a serine protease inhibitor. Similar effects of tryptase on inflammation and anti-viral responses were also confirmed in primary HBECs from asthmatic patients. Conclusion MC localization within the epithelium and the release of their proteases may play a critical role in asthma pathology by provoking pro-inflammatory and alarmin responses and downregulating IFNs. Furthermore, MC proteases induce downregulation of epithelial junction proteins which may lead to barrier dysfunction. In summary, our data suggests that mast cells may contribute towards impaired anti-viral epithelial responses during asthma exacerbations mediated by the protease activity of tryptase.

The activation and degranulation of mast cells is critical in the pathogenesis of allergic inflammation and modulation of inflammation. Recently, we demonstrated that the unconventional long-tailed myosin, MYO1F, localizes with cortical F-actin and mediates adhesion and migration of mast cells. In this study, we show that knockdown of MYO1F by short hairpin RNA reduces human mast cell degranulation induced by both IgE crosslinking and by stimulation of the Mas-related G protein–coupled receptor X2 (MRGPRX2), which has been associated with allergic and pseudoallergic drug reactions, respectively. Defective degranulation was accompanied by a reduced reassembly of the cortical actin ring after activation but reversed by inhibition of actin polymerization. Our data show that MYO1F is required for full Cdc42 GTPase activation, a critical step in exocytosis. Furthermore, MYO1F knockdown resulted in less granule localization in the cell membrane and fewer fissioned mitochondria along with deficient mitochondria translocation to exocytic sites. Consistent with that, AKT and DRP1 phosphorylation are diminished in MYO1F knockdown cells. Altogether, our data point to MYO1F as an important regulator of mast cell degranulation by contributing to the dynamics of the cortical actin ring and the distribution of both the secretory granules and mitochondria.

Tuberculosis (TB) is still a major worldwide health threat and primarily a lung disease. The innate immune response against Mycobacterium tuberculosis (Mtb) is orchestrated by dendritic cells, macrophages, neutrophils, natural killer cells and apparently mast cells (MCs). MCs are located at mucosal sites including the lungs and contribute in host-defence against pathogens, but little is known about their role during Mtb infection. This study investigates the location and characteristics of MCs in TB lesions to assess their contribution to TB pathology. To this purpose, number, location and phenotype of MCs was studied in 11 necropsies of pulmonary TB and 3 necropsies of non-TB infected lungs that were used as controls. MCs were localised at pneumonic areas, in the granuloma periphery and particularly abundant in fibrotic tissue. Furthermore, MCs displayed intracellular Mtb and IL-17A and TGF-β immunostaining. These findings were validated by analysing, post-mortem lung tissue microarrays from 44 individuals with pulmonary TB and 25 control subjects. In affected lungs, increased numbers of MCs expressing intracellularly both tryptase and chymase were found at fibrotic sites. Altogether, our data suggest that MCs are recruited at the inflammatory site and that actively produce immune mediators such as proteases and TGF-β that may be contributing to late fibrosis in TB lesions.

Background Mast cells (MCs) are key regulators of IgE-mediated allergic inflammation. Cell-derived extracellular vesicles (EVs) contain bioactive compounds such as microRNAs. EVs can transfer signals to recipient cells, thus using a novel mechanism of cell-to-cell communication. However, whether MC-derived EVs are involved in FceRI-mediated allergic inflammation is unclear. Objective We sought to investigate the effect of EVs derived from FceRI-aggregated human MCs on the function of human group 2 innate lymphoid cells (ILC2s). Methods Human cultured MCs were sensitized with and without IgE for 1 hour and then incubated with anti-IgE antibody, IL-33, or medium alone for 24 hours. EVs in the MC supernatant were isolated by using ExoQuick-TC. Results Coculture of ILC2s with EVs derived from the FceRI-aggregated MCs significantly enhanced IL-5 production and sustained upregulation of IL-5 mRNA expression in IL-33–stimulated ILC2s, but IL-13 production and IL-13 mRNA expression were unchanged. miR103a-3p expression was upregulated in IL-33–stimulated ILC2s that had been cocultured with EVs derived from anti-IgE antibody–stimulated MCs. Transduction of an miR103a-3p mimic to ILC2s significantly enhanced IL-5 production by IL-33–stimulated ILC2s. miR103a-3p promoted demethylation of an arginine residue of GATA3 by downregulating protein arginine methyltransferase 5 (PRMT5) mRNA. Reduction of protein arginine methyltransferase 5 expression in ILC2s by using a small interfering RNA technique resulted in upregulation of IL-5 production by IL-33–stimulated ILC2s. Furthermore, the level of miR103a-3p expression was significantly higher in EVs from sera of patients with atopic dermatitis than in EVs from nonatopic healthy control subjects. Conclusion Eosinophilic allergic inflammation may be exacerbated owing to ILC2 activation by MC-derived miR103a-3p.

Imidazolidinyl urea (IU) is used as an antimicrobial preservative in cosmetic and pharmaceutical products. IU induces allergic contact dermatitis, however, the mechanism has not yet been elucidated. Mas-related G protein-coupled receptor-X2 (MRGPRX2) triggers drug-induced pseudo-allergic reactions. The aims of this study were to determine whether IU activated mast cells through MRGPRX2 to further trigger contact dermatitis. Wild-type (WT) and KitW-sh/HNihrJaeBsmJNju (MUT) mice were treated with IU to observe its effects on local inflammation and mast cells degranulation in vivo. Laboratory of allergic disease 2 cells were used to detect calcium mobilization and release of inflammatory mediators in vitro. WT mice showed a severe local inflammatory response and contact dermatitis, whereas only slight inflammatory infiltration was observed in MUT mice. Thus, MRGPRX2 mediated the IU-induced activation of mast cells. However, histamine, a typical allergen, was not involved in this process. Tryptase expressed by mast cells was the major non-histaminergic inflammatory mediator of contact dermatitis. IU induced anaphylactic reaction via MRGPRX2 and further triggering non-histaminergic contact dermatitis, which explained why antihistamines are clinically ineffective against some chronic dermatitis.

Anaphylaxis is a rapidly evolving, acute, life-threatening reaction that occurs rapidly on contact with a trigger. Anaphylaxis is classically defined as an allergen-driven process that induces specific IgE and the activation of mast cells and basophils through the cross-linking of IgE receptors. However, it is clear that non-IgE-mediated pathways can induce symptoms indistinguishable from those of classic anaphylaxis, and their activation could explain the severity of IgE-mediated anaphylaxis. Indeed, mast cells and basophils can be activated by antibodies against IgE or their receptors, by molecules such as anaphylatoxins, or through G-coupled receptors. Some other allergens can induce antibodies of class IgG that can activate neutrophils to produce a molecule similar to histamine to induce anaphylaxis. Finally, some inflammatory mediators such as bradykinin or prostaglandin can also modulate mast cell and basophil activation as well as directly cause vasodilation and bronchoconstriction, resulting in anaphylaxis-like reactions.

Herbal products are the most representative alternative medicine, but most herbal drugs are taken orally and these can cause allergic reactions in the gastrointestinal tract such as food allergies. To confirm whether herbal proteins can cause allergic reaction by binding to human serum immunoglobulin E (IgE), we selected sera from 800 randomized human sera using Allergy-Q tests and investigated the allergenic reactivity of Cnidium officinale (CO) Makinoe extract with positive sera in HMC-1 cells. The proteins derived from CO extract were separated by SDS-PAGE, and identified these proteins using LC–MS/MS. The human sera IgE binding proteins were estimated at the four different predicted proteins such as FAR1-related sequence 5-like protein, a carrier protein, a hypothetical protein, and a predicted protein. The number of positive sera reacted with CO extract was 18 in 800 donor blood (2.25%). In HMC-1 cells, a co-treatment of the positive sera containing CO-specific IgE with CO extract induced synergy effects in ERK/NF-kB activation compared with a sole treatment of human sera, but negative sera did not show a significant change. This results imply that herbal allergens can cause allergic reaction through the crosslinking with human serum IgE, and it may trigger hypersensitivity of body immune system.

The Mas-related G protein-coupled receptor X2 (MRGPRX2) is a multiligand receptor responding to various exogenous and endogenous stimuli. Being highly expressed on skin mast cells, MRGPRX2 triggers their degranulation and release of proinflammatory mediators, and it promotes multicellular signaling cascades, such as itch induction and transmission in sensory neurons. The expression of MRGPRX2 by skin mast cells and the levels of the MRGPRX2 agonists (eg, substance P, major basic protein, eosinophil peroxidase) are upregulated in the serum and/or skin of patients with inflammatory and pruritic skin diseases, such as chronic spontaneous urticaria or atopic dermatitis. Therefore, MRGPRX2 and its agonists might be potential biomarkers for the progression of cutaneous inflammatory diseases and the response to treatment. In addition, they may represent promising targets for prevention and treatment of signs and symptoms in patients with skin diseases or drug reactions. To assess this possibility, this review explores the role and relevance of MRGPRX2 and its activators in cutaneous inflammatory disorders and chronic pruritus.

Mast cells are tissue-resident immune cells that play pivotal roles in initiating and amplifying allergic/anaphylactic reactions in humans. Their activation occurs via multiple mechanisms, which include cross-linking of the IgE-bound, high-affinity IgE receptors (FcεRI) by allergens or Ags and the binding of anaphylatoxins such as C3a to its receptor, C3aR. We have previously demonstrated that the Na+/H+ exchanger regulatory factor 1 (NHERF1) promotes C3aR functions in human mast cells. In the current study, we show that NHERF1 regulates mast cell response following FcεRI stimulation. Specifically, intracellular Ca2+ mobilization, activation of the MAPKs (ERK1/2 and P38), and production of cytokines (IL-13 and IL-6) following exposure to IgE/Ag were significantly reduced in mast cells from NHERF1+/‒ mice. In agreement with our in vitro data, mast cell–mediated passive cutaneous anaphylaxis and passive systemic anaphylaxis were reduced in NHERF1+/‒ mice and mast cell–deficient KitW-sh/W-sh mice engrafted with NHERF1+/‒ mast cells. Mechanistically, the levels of microRNAs (miRNAs) that regulate mast cell responses, miRNA 155-3p and miRNA 155-5p, were altered in mast cells from NHERF1+/‒ mice. Moreover, NHERF1 rapidly localized to the nucleus of mast cells following FcεRI stimulation. In summary, our results suggest that the NHERF1 acts as an adapter molecule and promotes IgE/Ag-induced mast cell activation. Further elucidating the mechanisms through which NHERF1 modulates mast cell responses will lend insights into the development of new therapeutic strategies to target mast cells during anaphylaxis or other allergic diseases.

Galectins are a family of proteins that bind β-galactosides and play key roles in a variety of cellular processes including host defence. They have been well studied in hosts but less so in gastrointestinal nematodes. Both host and parasite galectins are present in the gastrointestinal tract following infection. Parasite galectins can both bind antibody, especially highly glycosylated IgE and be bound by antibody. Parasite galectins may act as molecular sponges that soak up antibody. Host galectins promote mast cell degranulation while parasite galectins inhibit degranulation. Host and parasite galectins can also bind mucins and influence mucus viscosity. As the protective response against gastrointestinal nematode infection is partly dependent on IgE mediated mast cell degranulation and mucus, the interactions between host and parasite galectins play key roles in determining the outcome of infection.

Mast cells cyclically synthesize and excrete a wide range of biogenesis products with different biological activities into the extracellular matrix and are regulators of local homeostasis both in normal conditions and in pathology – inflammation, oncogenesis, etc. The relative specificity of classical histochemical methods for detecting mast cells in relation to chromogenic to substrates causes certain difficulties in the selective study of the components of the secretome of mast cells, for example, heparin, histamine, chymase or tryptase. Therefore, immunomorphological techniques have become very popular, which identify specific substrates and allow differentiation of the components of the mast cell secretome. Mediators produced by mast cells promote neoangiogenesis, fibrillogenesis and re-epithelialization during the repair process.The aim of our work was to study the tryptase profile of the mast cell population of rat skin during the wound processusing an original combined method of immunohistochemical staining.Material and methods. The experiment involved 12 Wistar rats divided into two groups – intact (n=6) and with the existing wound process of the skin in the withers (n=6). The tryptase profile of mast cells was assessed on the 7th day of the wound process in comparison with the control group.Results. The results obtained showed a significant increase in the number of tryptase-positive mast cells on the 7th day of the wound process in the skin against the background of a general increase in the population of mast cells. Intragranular tryptase reserve was significantly increased. In contrast to the control, where mast cells with single tryptase-positive granules dominated, during the wound process, cells of this type were practically not detected in the skin (43.69±2.9% and 8.55±0.9%). The content of tryptase-positive mast cells with complete filling of the cytoplasm in the control group and the group of animals with a wound process was 14.24±1.2% and 38.03±2.9%, respectively.Conclusion. Thus, when modeling a wound, an increase in tryptase synthesis is detected both in individual MCs and within the entire MC population. This fact indicates that mast cell proteases can become a potential therapeutic target for improving wound regeneration by correcting immunogenesis, inflammation and fiber formation.

Mastocytosis is a hematopoietic neoplasm characterized by expansion of KIT D816V-mutated clonal mast cells in various organs and severe or even life-threatening anaphylactic reactions. Recently, hereditary α-tryptasemia (HαT) has been described as a common genetic trait with increased copy numbers of the α-tryptase encoding gene, TPSAB1, and associated with an increased basal serum tryptase level and a risk of mast cell activation. The purpose of our study was to elucidate the clinical relevance of HαT in patients with mastocytosis. TPSAB1 germline copy number variants were assessed by digital polymerase chain reaction in 180 mastocytosis patients, 180 sex-matched control subjects, 720 patients with other myeloid neoplasms, and 61 additional mastocytosis patients of an independent validation cohort. α-Tryptase encoding TPSAB1 copy number gains, compatible with HαT, were identified in 17.2% of mastocytosis patients and 4.4% of the control population (P < .001). Patients with HαT exhibited higher tryptase levels than patients without HαT (median tryptase in HαT+ cases: 49.6 ng/mL vs HαT− cases: 34.5 ng/mL, P = .004) independent of the mast cell burden. Hymenoptera venom hypersensitivity reactions and severe cardiovascular mediator-related symptoms/anaphylaxis were by far more frequently observed in mastocytosis patients with HαT than in those without HαT. Results were confirmed in an independent validation cohort. The high prevalence of HαT in mastocytosis hints at a potential pathogenic role of germline α-tryptase encoding TPSAB1 copy number gains in disease evolution. Together, our data suggest that HαT is a novel emerging robust biomarker in mastocytosis that is useful for determining the individual patient´s risk of developing severe anaphylaxis.

Skin wounds are an important clinical problem which affects millions of people worldwide. The search for new therapeutic approaches to improve wound healing is needed. The present study aimed to evaluate the effects of the oral treatment with the skin-related probiotics Lactobacillus johnsonii LA1 (LJ), L. paracasei ST11 (LP), and L. rhamnosus LPR (LR) in a model of excisional skin wounds in Swiss mice. The animals received daily oral gavage of PBS or 1 × 107 colony-forming units of LJ, LP, or LR, singly, beginning just after the creation of wounds until euthanasia. Blood flow was evaluated by laser Doppler perfusion imaging. Myeloperoxidase and N-acetyl-β-D-glucosaminidase activities were used to assess the accumulation of neutrophils and macrophages, respectively. The wound tissue was also collected for histological analyses (H&E, Toluidine blue, and Picrosirius red staining). The macroscopic wound closure rate was faster only in mice treated with LR, but not with LJ and LP, when compared to mice treated with PBS. Histological evaluations showed that treatment with LR stimulated wound epithelization when compared to PBS. Further analyses showed that wounds from LR-treated mice presented a significant decrease in macrophage (p

A comparative study of the nerve structures and the density of mast cells in the heart of rats aged 3–4 and 23 months was carried out with histological and histochemical methods and the immunohistochemical markers PGP 9.5, tyrosine hydroxylase (TH), and synaptophysin. It was found that tissues innervation decreases with aging in all studied heart areas, particularly, sympathetic innervation. A decrease in sympathetic plexus density and the presence of dystrophic and degenerative changes in TH-immunopositive axon terminals were registered. It was also demonstrated that the mast cell population in old animals increases in the connective tissue of the pericardial, in the epicardium, and the myocardium of atria and ventricles region upon a decrease in sympathetic innervation. It is suggested that the increase in the number of mast cells in the heart during aging occurs in response to a deficiency in catecholamines and is related to the mast-cell secretion of biologically active substances (heparin, histamine, and serotonin), which help maintain local tissue homeostasis and adaptive and compensatory reactions of the animal heart.

Asthma is a chronic obstructive lung disease characterized by recurrent episodes of bronchoconstriction and wheezing. Conventional asthma treatment involves the suppression of airway inflammation or improving airway flow. Rosmarinus officialis, also known as rosemary, is a Mediterranean plant that is used for the treatment of inflammatory diseases. Carnosol, a diterpenoid found in rosemary extracts, has been known to exhibit anti-inflammatory, anti-tumor, and anti-oxidant effects. The effect of carnosol on allergic responses has not been tested yet. The effect of carnosol on a murine allergic asthma model were investigated. Carnosol inhibited the degranulation of RBL-2H3 mast cells. Carnosol treatment inhibited the increase in the number of eosinophils in the bronchoalveolar lavage fluids (BALF) of mice treated with ovalbumin. Carnosol treatment also inhibited inflammatory responses and mucin production in histologic studies. Carnosol treatment inhibited the increases of IL-4 and IL-13 cytokines expression in both BALF and the lungs. These results suggest that carnosol may have a potential for allergic asthma therapy.

Background Allergic reactions have been observed following both direct centipede bites and the clinical use of centipede-containing medicines, such as traditional Chinese medicines utilizing Scolopendra subspinipes mutilans; however, no natural centipede allergen has yet been characterized. Methods An allergen was purified from S. s. mutilans venom using Superdex 75 gel filtration and RESOURCE S ion chromatography, and its primary structure was determined via a combination of LC-MS-MS, MALDI-TOF/TOF and protein sequencing techniques. Its potential allergenicity was evaluated by immunoblotting, ELISAs, skin prick tests (SPTs) and mast cell activation assays. Results A novel allergen Sco m 5 (210 amino acids long) was successfully purified from crude S. s. mutilans venom. Sco m 5 could promote the degranulation of a human mast cell line, HMC-1. Among centipede-allergic patients, Sco m 5 showed an 83.3% IgE-binding frequency and a 66.7% positive reaction frequency, as detected by immunoblotting and SPTs, respectively. Sco m 5 IgE-binding frequencies of common Chinese population was found to be 9%–16%. Sera positive for Sco m 5 IgE-binding was cross-reactive against venom from the wasp Vespa mandaeinia. Conclusions The present study isolated and characterized a novel allergen termed as Sco m 5 from the centipede S. s. mutilans. The use of Sco m 5 to identify centipede-allergic individuals could be important, given the high potential allergenicity of Sco m 5 among the general Chinese population, along with the likely possibility of cross-reactivity against wasp venom among centipede-allergic patients.

Atopic dermatitis (AD, eczema) is an inflammatory skin condition whose histopathology involves remodeling. Few preclinical AD studies are performed using male mice. The histopathological mechanisms underlying AD development were investigated here in male mice at a pre-lesional stage using a human AD-like mouse model. Hypodermal cellular infiltration without thickening of skin layers was observed after one epicutaneous exposure to antigen ovalbumin (OVA), compared to controls. In contrast to our previous report using female mice, OVA treatment did not activate skin mast cells (MC) or elevate sphingosine-1-phosphate (S1P) levels while increasing systemic but not local levels of CCL2, CCL3 and CCL5 chemokines. In contrast to the pathogenic AD mechanisms we recently uncovered in female, S1P-mediated skin MC activation with subsequent local chemokine production is not observed in male mice, supporting sex differences in pre-lesional stages of AD. We are proposing that differential involvement of the MC/S1P axis in early pathogenic skin changes contributes to the well documented yet still incompletely understood sex-dimorphic susceptibility to AD in humans.

Introduction: Mast cells and their major protein, the serine proteinase tryptase, can be involved in cutaneous photodamage and carcinogenesis. The serum test of tryptase (S-tryptase) measures total tryptase protein (active tryptase and inactive protryptases), and S-tryptase is elevated in a variety of diseases, for example, in mastocytosis and α-tryptasemia. Objectives: The objective of this study is to study whether S-tryptase is a marker of cutaneous photodamage and carcinogenesis. Methods: Adult subjects (n = 399, aged 21–79) evaluated to be at risk for skin cancers were recruited at the dermatological policlinic and examined for photodamage severity, mole count, actinic keratoses (AKs), skin cancers, and immunosuppression (IS). A blood sample was analyzed for S-tryptase using the ImmunoCAP® Tryptase fluoroenzymeimmunoassay. Results: There was no difference in S-tryptase between non-IS (n = 321) and IS (n = 78) subjects or between genders. S-tryptase correlated slightly to photodamage and AKs in 321 non-IS subjects, and this association can be related, in part, to the age of subjects. In 34 subjects, S-tryptase was elevated (≥13.5 ng/mL), and in 20 males, but not in 14 females, the photodamage level was significantly (p = 0.031) more severe than in 179 males with normal S-tryptase. In contrast, there were more frequently subjects (n = 12) with past or present skin cancer (basal or squamous cell carcinoma or melanoma) in 14 females with elevated S-tryptase than in 186 female controls. So far, no explanation has been found for the elevated S-tryptase. Conclusion: There are significant associations between elevated S-tryptase and skin carcinogenesis, but the molecular mechanisms are unclear and gender differences can exist.

Epithelial damage and increase of intraepithelial mast cells (MC) are characteristics of asthma. The role of MC mediator tryptase and the protease-activated receptor-2 (PAR2) on epithelial wound healing is not fully investigated. Stimulation of bronchial epithelial cells (BECs) with tryptase promoted gap closure, migration and cellular speed compared to controls. Stimulated BECs had higher expression of migration marker CD151 compared to controls. Proliferation marker KI67 was upregulated in tryptase-stimulated BECs compared to controls. Treatment with PAR2 antagonist I-191 reduced gap closure, migration and cell speed compared to BECs stimulated with tryptase. We found that tryptase enhances epithelial wound healing by increased migration and proliferation, which is in part regulated via PAR2. Our data suggest that tryptase might be beneficial in tissue repair under baseline conditions. However, in a pathological context such as asthma with increased numbers of activated MCs, it might lead to epithelial remodeling and loss of function.

Background:Chronic idiopathic urticaria (CIU) represents a common skin disorder often characterized by mast cell activation and secretion of histamine and other proinflammatory factors. E-selectin (SELE) has been implicated in the pathogenesis of common inflammatory cutaneous disorders, while the role of SELE in CIU is yet to be fully understood. Thus, we aimed to investigate the mechanism by which SELE influences CIU in connection with the involvement of mast cells. Methods: SELE expression was measured in blood samples obtained from CIU patients and normal individuals. A CIU mouse model was subsequently established by intradermally injecting a normal saline solution with ovalbumin IgE antiserum into the mice. Loss- and gain-of-function investigations were conducted on the mouse models. The number of degranulated mast cells and the amount of histamine release in vitro were determined. The levels of SELE, tumor necrosis factor (TNF)-α, homologous restriction factor (HRF), and interleukin (IL)-6 levels were determined. Results: The CIU clinical samples exhibited upregulated SELE, while the CIU mice showed increased mast cell degranulation and an increased rate of histamine directional release, as well as an elevated expression of SELE, TNF-α, HRF, and IL-6. SELE silencing was found to decrease the number of degranulated mast cells and reduce the rate of histamine directional release, along with suppressed TNF-α, HRF, and IL-6 expression, in the serum of CIU mice. Ketotifen was observed to rescue the increased expression of TNF-α, HRF, and IL-6 caused by SELE overexpression. Conclusions:This study highlights the potential of SELE downregulation to repress inflammatory factor secretion caused by the accumulation of mast cells, which ultimately inhibits the development of CIU.

Despite significant advances in understanding the role of the immune response in Opisthorchis viverrini-associated carcinogenesis, little is known about how infection induces gall bladder disease. This study investigated whether mast cells are activated in cholecystitis associated with O. viverrini, gall bladder specimens from ninety-two patients who had undergone cholecystectomy at the Khon Kaen Regional Hospital, Khon Kaen, Thailand. Two representative sections from the body of fresh gall bladder tissue were fixed in Carnoy’s solution and embedded in paraffin wax. The paraffin sections were stained for mast cells and IgE plasma cells by the double histochemical and immunohistochemical method. The cells in the epithelium, lamina propria, muscular layer, and subserosa were counted and expressed as cells per square millimeter. The gall bladder bile was examined for the presence of O. viverrini eggs. Significantly higher mean mast cell numbers were found in the lamina propria (221.41 ± 16.01 vs 116.97 ± 14.61 cells per mm2; P < 0.005) of egg positive compared to egg negative groups, respectively. No comparable differences in mast cell number were observed in other layers. IgE plasma cells were rarely seen. The results suggest that mast cell hyperplasia occurs during cholecystitis in association with opisthorchiasis and may play a role in the pathogenesis of the disease.