Role of human mast cells and basophils in bronchial asthma

Mast cells and ocular surface: An update review

Mast cells (MCs), traditionally viewed as key players in IgE-mediated allergic responses, are increasingly recognized for their versatile roles. Situated at critical barrier sites such as the ocular surface, these sentinel cells participate in a broad array of physiological and pathological processes. This review presents a comprehensive update on the immune pathophysiology of MCs, with a particular focus on the mechanisms underlying innate immunity. It highlights their roles at the ocular surface, emphasizing their participation in allergic reactions, maintenance of corneal homeostasis, neovascularization, wound healing, and immune responses in corneal grafts. The review also explores the potential of MCs as therapeutic targets, given their significant contributions to disease pathogenesis and their capacity to modulate immunity. Through a thorough examination of current literature, we aim to elucidate the immune pathophysiology and multifaceted roles of MCs in ocular surface health and disease, suggesting directions for future research and therapeutic innovation.

Death Due to Anaphylactic Reaction: The Role of the Forensic Pathologist in an Accurate Postmortem Diagnosis

Background and Objectives: The diagnosis of anaphylaxis comprehensively depends on both situational information and laboratory investigations. For this purpose, serum tryptase concentration is examined as an indicator of systemic mast cell mediator release, linked to an underlying anaphylactic process. Increased levels of tryptase may occur in some events different from anaphylaxis, but usually information from crime scene investigations is lacking and autoptic findings are not specific. For legal reasons, it is required to achieve a definite diagnosis of mast cell degranulation that can lead to a certain diagnosis of death from anaphylaxis. Immunohistochemistry seems to be a relatively simple, reliable, and easily repeatable method that can assist the forensic pathologist in the differential diagnosis of death from anaphylaxis. Materials and Methods: This work provides an overview of the current literature on immunohistochemical methods useful in the determination process of anaphylactic-related deaths. A systematic search, according to the PRISMA statement, was performed in databases to identify studies investigating immunohistochemical targets related to anaphylaxis death. Results: This work underscores the importance of anaphylaxis mediators such as tryptase, CD117, and chymase in the immunohistochemical analysis of anaphylactic deaths. Conclusions: According to the reviewed literature, the diagnosis of death due to anaphylaxis should depend not just on the suspicion of an anaphylactic reaction but also on confirming mast cell degranulation through the identification of IHC positivity for inflammatory mediators, particularly in the respiratory tract.

Immunologic Basis of Type 2 Biologics for Severe Asthma

Asthma is a chronic airway inflammatory disease characterized by reversible airway obstruction and airway hyperreactivity to various environmental stimuli, leading to recurrent cough, dyspnea, and wheezing episodes. Regarding inflammatory mechanisms, type 2/eosinophilic inflammation along with activated mast cells is the major one; however, diverse mechanisms, including structural cells-derived and non-type 2/neutrophilic inflammations are involved, presenting heterogenous phenotypes. Although most asthmatic patients could be properly controlled by the guided treatment, patients with severe asthma (SA; classified as a treatment-refractory group) suffer from uncontrolled symptoms with frequent asthma exacerbations even on regular anti-inflammatory medications, raising needs for additional controllers, including biologics that target specific molecules found in asthmatic airway, and achieving the precision medicine for asthma. This review summarizes the immunologic basis of airway inflammatory mechanisms and current biologics for SA in order to address unmet needs for future targets.

Histamine 2 receptors in cardiovascular biology: A friend for the heart

Undermining new mediators involved in the development and progression of cardiovascular diseases (CVDs) is vital for better disease management. Existing studies implicate a crucial role for inflammation and inflammatory cells, particularly mast cells, in cardiac diseases. Interestingly, the mast cell mediator, histamine, and its receptors profoundly impact the pathophysiology of the heart, resulting in hypertension-induced cardiac hypertrophy and other cardiac anomalies. In this review, we provide a detailed description of mast cell activation, mediators, and histamine receptors, with a particular focus on histamine 2 receptors (H2Rs). Preclinical and clinical studies using histamine receptor antagonists report improvement in cardiac function. Insights into the precise function of histamine receptors will aid in developing novel therapies and pave the way for repurposing antihistamines for cardiovascular diseases.

Is There a Role for Basophils in Cancer?

Basophils were identified in human peripheral blood by Paul Ehrlich over 140 years ago. Human basophils represent <1% of peripheral blood leukocytes. During the last decades, basophils have been described also in mice, guinea pigs, rabbits, and monkeys. There are many similarities, but also several immunological differences between human and mouse basophils. There are currently several strains of mice with profound constitutive or inducible basophil deficiency useful to prove that these cells have specific roles in vivo. However, none of these mice are solely and completely devoid of all basophils. Therefore, the relevance of these findings to humans remains to be established. It has been known for some time that basophils have the propensity to migrate into the site of inflammation. Recent observations indicate that tissue resident basophils contribute to lung development and locally promote M2 polarization of macrophages. Moreover, there is increasing evidence that lung-resident basophils exhibit a specific phenotype, different from circulating basophils. Activated human and mouse basophils synthesize restricted and distinct profiles of cytokines. Human basophils produce several canonical (e.g., VEGFs, angiopoietin 1) and non-canonical (i.e., cysteinyl leukotriene C₄) angiogenic factors. Activated human and mouse basophils release extracellular DNA traps that may have multiple effects in cancer. Hyperresponsiveness of basophils has been demonstrated in patients with JAK2^V617F-positive polycythemia vera. Basophils are present in the immune landscape of human lung adenocarcinoma and pancreatic cancer and can promote inflammation-driven skin tumor growth. The few studies conducted thus far using different models of basophil-deficient mice have provided informative results on the roles of these cells in tumorigenesis. Much more remains to be discovered before we unravel the hitherto mysterious roles of basophils in human and experimental cancers.

Vascular endothelial growth factor-activated basophils in asthmatics

Introduction

Vascular endothelial growth factor (VEGF) is an angiogenic cytokine and a potential stimulator of permeability and lung neovascularization in asthmatics. It also plays an important role in the development of airway remodelling and in activation of many cells, including basophils.

Aim

To reveal the possible role of VEGF in the activation of basophils in asthmatics – subgroups with and without irreversible bronchoconstriction. Protein CD203c on the basophils surface was used as the activation marker. To define the possible pathway of basophils VEGF-activation, the influence of a genetic factor (polymorphism del18/ins -2549 -2567 in the VEGF-promoter region) was also considered.

Material and methods

Our study involved 82 patients with asthma (40 patients without and 42 patients with irreversible bronchoconstriction) and a group of 40 controls. The flow cytometric methods with anti-CD203c in the samples of basophils with increasing concentrations of VEGF was used for analysis of their activity. Genotyping for VEGF-promoter region was performed by PCR-based methods.

Results

Patients with asthma and del/del genotype showed more significant differences in the basophils activation after stimulation with increasing concentrations of VEGF than asthmatics with ins/ins and ins/del genotype (p = 0.023) and controls with del/del genotype (p = 0.0006).

Conclusions

Raised basophils VEGF-activation is characteristic for examined patients with asthma and might be associated with presence of polymorphism del18/ins -2549 -2567 in the VEGF-promoter region. Furthermore, it may contribute to the development of airways remodelling – this pathway has not been considered yet.

Thymoquinone attenuates IgE-mediated allergic response via pi3k-Akt-NFκB pathway and upregulation of the Nrf2-HO1 axis

IgE-dependent reactions mediate the majority of allergic diseases. This study explores the effects of thymoquinone (Tq) on IgE-mediated allergic response in activated mast cells, basophils, and neutrophils. Tq treatment resulted in a dose-dependent decrease in levels of TNF-α and IL-4 in activated RBL-2H3 cells. Tq inhibited the degranulation of these cells with an IC₅₀ value of 56.37 µM. Moreover, the compound suppressed basophil activation induced through FcεRI receptors with an IC₅₀ value of 45.76 µM in heparinized human whole blood. Likewise, neutrophil migration and elastase activity were dose-dependently reduced. While Tq decreased the phosphorylation of Akt and NFκB in activated RBL-2H3 cells, it increased nuclear Nrf2 and HO-1 antioxidant proteins. Our results indicate that Tq possesses demonstrable activity in cellular models of IgE-mediated allergic reactions. PRACTICAL APPLICATIONS: The current study sheds light on the mechanistic pathways of Tq on IgE-based response in activated mast cells, basophils, and neutrophils. The output of this preclinical in vitro study may be translated into better chemotherapeutic applications of Tq and its analogs in the treatment of allergic inflammation. However, a detailed investigation of in vivo models is recommended.

Interleukin-1β provided by KIT-competent mast cells is required for KRAS-mutant lung adenocarcinoma

Mast cells (MC) have been identified in human lung adenocarcinoma (LADC) tissues, but their functional role has not been investigated in vivo. For this, we applied three mouse models of KRAS-mutant LADC to two different MC-deficient mouse strains (cKit^Wsh and Cpa3.Cre). Moreover, we derived MC gene signatures from murine bone marrow-derived MC and used them to interrogate five human cohorts of LADC patients. Tumor-free cKit^Wsh and Cpa3.Cre mice were deficient in alveolar and skin KIT-dependent (KIT+) MC, but cKit^Wsh mice retained normal KIT-independent (KIT-) MC in the airways. Both KIT+ and KIT- MC infiltrated murine LADC to varying degrees, but KIT+ MC were more abundant and promoted LADC initiation and progression through interleukin-1β secretion. KIT+ MC and their transcriptional signature were significantly enriched in human LADC compared to adjacent normal tissue, especially in the subset of patients with KRAS mutations. Importantly, MC density increased with tumor stage and high overall expression of the KIT+ MC signature portended poor survival. Collectively, our results indicate that KIT+ MC foster LADC development and represent marked therapeutic targets.

Histamine Release from Mast Cells and Basophils

Mast cells and basophils represent the most relevant source of histamine in the immune system. Histamine is stored in cytoplasmic granules along with other amines (e.g., serotonin), proteases, proteoglycans, cytokines/chemokines, and angiogenic factors and rapidly released upon triggering with a variety of stimuli. Moreover, mast cell and basophil histamine release is regulated by several activating and inhibitory receptors. The engagement of different receptors can trigger different modalities of histamine release and degranulation. Histamine released from mast cells and basophils exerts its biological activities by activating four G protein-coupled receptors, namely H1R, H2R, H3R (expressed mainly in the brain), and the recently identified H4R. While H1R and H2R activation accounts mainly for some mast cell- and basophil-mediated allergic disorders, the selective expression of H4R on immune cells is uncovering new roles for histamine (possibly derived from mast cells and basophils) in allergic, inflammatory, and autoimmune disorders. Thus, the in-depth knowledge of mast cell and basophil histamine release and its biologic effects is poised to uncover new therapeutic avenues for a wide spectrum of disorders.

Altered Epithelial Gene Expression in Peripheral Airways of Severe Asthma

Management of severe asthma remains a challenge despite treatment with glucocorticosteroid therapy. The majority of studies investigating disease mechanisms in treatment-resistant severe asthma have previously focused on the large central airways, with very few utilizing transcriptomic approaches. The small peripheral airways, which comprise the majority of the airway surface area, remain an unexplored area in severe asthma and were targeted for global epithelial gene expression profiling in this study. Differences between central and peripheral airways were evaluated using transcriptomic analysis (Affymetrix HG U133 plus 2.0 GeneChips) of epithelial brushings obtained from severe asthma patients (N = 17) and healthy volunteers (N = 23). Results were validated in an independent cohort (N = 10) by real-time quantitative PCR. The IL-13 disease signature that is associated with an asthmatic phenotype was upregulated in severe asthmatics compared to healthy controls but was predominantly evident within the peripheral airways, as were genes related to mast cell presence. The gene expression response associated with glucocorticosteroid therapy (i.e. FKBP5) was also upregulated in severe asthmatics compared to healthy controls but, in contrast, was more pronounced in central airways. Moreover, an altered epithelial repair response (e.g. FGFBP1) was evident across both airway sites reflecting a significant aspect of disease in severe asthma unadressed by current therapies. A transcriptomic approach to understand epithelial activation in severe asthma has thus highlighted the need for better-targeted therapy to the peripheral airways in severe asthma, where the IL-13 disease signature persists despite treatment with currently available therapy.

Targeting mast cells: Uncovering prolific therapeutic role in myriad diseases

The mast cells are integral part of immune system and they have pleiotropic physiological functions in our body. Any type of abnormal stimuli causes the mast cells receptors to spur the otherwise innocuous mast cells to degranulate and release inflammatory mediators like histamine, cytokines, chemokines and prostaglandins. These mediators are involved in various diseases like allergy, asthma, mastocytosis, cardiovascular disorders, etc. Herein, we describe the receptors involved in degranulation of mast cells and are broadly divided into four categories: G-protein coupled receptors, ligand gated ion channels, immunoreceptors and pattern recognition receptors. Although, activation of pattern recognition receptors do not cause mast cell degranulation, but result in cytokines production. Degranulation itself is a complex process involving cascade of events like membrane fusion events and various proteins like VAMP, Syntaxins, DOCK5, SNAP-23, MARCKS. Furthermore, we described these mast cell receptors antagonists or agonists useful in treatment of myriad diseases. Like, omalizumab anti-IgE antibody is highly effective in asthma, allergic disorders treatment and recently mechanistic insight of IgE uncovered; matrix mettaloprotease inhibitor marimistat is under phase III trial for inflammation, muscular dystrophy diseases; ZPL-389 (H4 receptor antagonist) is in Phase 2a Clinical Trial for atopic dermatitis and psoriasis; JNJ3851868 an oral H4 receptor antagonist is in phase II clinical development for asthma, rheumatoid arthritis. Therefore, research is still in inchoate stage to uncover mast cell biology, mast cell receptors, their therapeutic role in myriad diseases.

Childhood asthma is associated with mutations and gene expression differences of ORMDL genes that can interact

BACKGROUND

Genomewide association studies identified ORMDL3 as a plausible asthma candidate gene. ORMDL proteins regulate sphingolipid metabolism and ceramide homeostasis and participate in lymphocyte activation and eosinophil recruitment. Strong sequence homology between the three ORMDL genes and ORMDL protein conservation among different species suggest that they may have shared functions. We hypothesized that if single nucleotide polymorphisms (SNPs) in ORMDL3 alter its gene expression and play a role in asthma, variants in ORMDL1 and ORMDL2 might also be associated with asthma.

METHODS

Asthma associations of 44 genotyped SNPs were determined in at least 1303 subjects (651 asthmatics). ORMDL expression was evaluated in peripheral blood mononuclear cells (PBMC) from 55 subjects (eight asthmatics) before and after allergen stimulation, and in blood (n = 60, 5 asthmatics). Allele-specific cis-effects on ORMDL expression were assessed. Interactions between human ORMDL proteins were determined in living cells.

RESULTS

Sixteen SNPs in all three ORMDLs were associated with asthma (14 in ORMDL3). Baseline expression of ORMDL1 (P = 1.7 × 10(-6) ) and ORMDL2 (P = 4.9 × 10(-5) ) was significantly higher in PBMC from asthmatics, while induction of ORMDLs upon stimulation was stronger in nonasthmatics. Disease-associated alleles (rs8079416, rs4795405, rs3902920) alter ORMDL3 expression. ORMDL proteins formed homo- and heterooligomers and displayed similar patterns of interaction with SERCA2 and SPT1.

CONCLUSIONS

Polymorphisms in ORMDL genes are associated with asthma. Asthmatics exhibit increased ORMDL levels, suggesting that ORMDLs contribute to asthma. Formation of heterooligomers and similar interaction patterns with proteins involved in calcium homeostasis and sphingolipid metabolism could indicate shared biological roles of ORMDLs, influencing airway remodeling and hyperresponsiveness.

Histamine induces human lung fibroblast-mediated collagen gel contraction via histamine H1 receptor

BACKGROUND

Airway remodeling is implicated in irreversible airflow limitation of refractory asthma, which includes increased smooth muscle mass and subepithelial fibrosis. Activated fibroblasts acquire contractile phenotype to participate in tissue contraction and structural alteration of extracellular matrices. Histamine is a potent mediator of allergic inflammation, substantially involved in asthmatic pathophysiology.

OBJECTIVE

We hypothesized that histamine might play a role in airway remodeling, and investigated its effect on fibroblast-mediated collagen gel contraction.

METHODS

Fibroblast-mediated collagen gel contraction was studied. Histamine's regulation of collagen gel contraction was characterized by using specific histamine-receptor antagonists, an IP3 receptor antagonist and a PKC inhibitor.

RESULTS

Histamine induced contraction of collagen gels embedded with human lung fibroblasts, in a time-dependent manner, and at the concentration more than 10(-6) M, both in four primary cultured adult lung fibroblasts and three fetal lung fibroblast cell lines. This effect was attenuated by H1 receptor antagonist, whereas those for H2 to H4 receptors failed to show an inhibitory effect. Furthermore, IP3 receptor-mediated Ca(2+) mobilization was implicated in histamine's action on collagen gel contraction.

CONCLUSIONS

Our results suggest that histamine is involved in airway remodeling through its action on lung fibroblasts, and antihistamine drugs, especially H1 receptor antagonists, might be potentially beneficial for a subset of asthmatic patients.

Mast cells and basophils are essential for allergies: mechanisms of allergic inflammation and a proposed procedure for diagnosis

The current definition of allergy is a group of IgE-mediated diseases. However, a large portion of patients with clinical manifestations of allergies do not exhibit elevated serum levels of IgE (sIgEs). In this article, three key factors, ie soluble allergens, sIgEs and mast cells or basophils, representing the causative factors, messengers and primary effector cells in allergic inflammation, respectively, were discussed. Based on current knowledge on allergic diseases, we propose that allergic diseases are a group of diseases mediated through activated mast cells and/or basophils in sensitive individuals, and allergic diseases include four subgroups: (1) IgE dependent; (2) other immunoglobulin dependent; (3) non-immunoglobulin mediated; (4) mixture of the first three subgroups. According to our proposed definition, pseudo-allergic-reactions, in which mast cell or basophil activation is not mediated via IgE, or to a lesser extent via IgG or IgM, should be non-IgE-mediated allergic diseases. Specific allergen challenge tests (SACTs) are gold standard tests for diagnosing allergies in vivo, but risky. The identification of surface membrane activation markers of mast cells and basophils (CD203c, CCR3, CD63, etc) has led to development of the basophil activation test (BAT), an in vitro specific allergen challenge test (SACT). Based on currently available laboratory allergy tests, we here propose a laboratory examination procedure for allergy.

Intranasal curcumin and its evaluation in murine model of asthma

Curcumin, a phytochemical present in turmeric, rhizome of Curcuma longa, has been shown to have a wide variety of pharmacological activities including anti-inflammatory, anti-allergic and anti-asthmatic properties. Curcumin is known for its low systemic bioavailability and rapid metabolization through oral route and has limited its applications. Over the recent decades, the interest in intranasal delivery as a non-invasive route for drugs has increased as target tissue for drug delivery since nasal mucosa offers numerous benefits. In this study, we evaluated intranasal curcumin following its absorption through nasal mucosa by a sensitive and validated high-performance liquid chromatography (HPLC) method for the determination of intranasal curcumin in mouse blood plasma and lung tissue. Intranasal curcumin has been detected in plasma after 15 min to 3 h at pharmacological dose (5 mg/kg, i.n.), which has shown anti-asthmatic potential by inhibiting bronchoconstriction and inflammatory cell recruitment to the lungs. At considerably lower doses has proved better than standard drug disodium cromoglycate (DSCG 50 mg/kg, i.p.) by affecting inflammatory cell infiltration and histamine release in mouse model of asthma. HPLC detection revealed that curcumin absorption in lungs has started after 30 min following intranasal administration and retained till 3h then declines. Present investigations suggest that intranasal curcumin (5.0 mg/kg, i.n.) has effectively being absorbed and detected in plasma and lungs both and suppressed airway inflammations at lower doses than the earlier doses used for detection (100-200 mg/kg, i.p.) for pharmacological studies (10-20 mg/kg, i.p.) in mouse model of asthma. Present study may prove the possibility of curcumin as complementary medication in the development of nasal drops to prevent airway inflammations and bronchoconstrictions in asthma without any side effect.

Identification of basophils as a major source of hepatocyte growth factor in chronic myeloid leukemia: a novel mechanism of BCR-ABL1-independent disease progression

Chronic myeloid leukemia (CML) is a hematopoietic neoplasm characterized by the Philadelphia chromosome and the related BCR-ABL1 oncoprotein. Acceleration of CML is usually accompanied by basophilia. Several proangiogenic molecules have been implicated in disease acceleration, including the hepatocyte growth factor (HGF). However, little is known so far about the cellular distribution and function of HGF in CML. We here report that HGF is expressed abundantly in purified CML basophils and in the basophil-committed CML line KU812, whereas all other cell types examined expressed only trace amounts of HGF or no HGF. Interleukin 3, a major regulator of human basophils, was found to promote HGF expression in CML basophils. By contrast, BCR-ABL1 failed to induce HGF synthesis in CML cells, and imatinib failed to inhibit expression of HGF in these cells. Recombinant HGF as well as basophil-derived HGF induced endothelial cell migration in a scratch wound assay, and these effects of HGF were reverted by an anti-HGF antibody as well as by pharmacologic c-Met inhibitors. In addition, anti-HGF and c-Met inhibitors were found to suppress the spontaneous growth of KU812 cells, suggesting autocrine growth regulation. Together, HGF is a BCR-ABL1-independent angiogenic and autocrine growth regulator in CML. Basophils are a unique source of HGF in these patients and may play a more active role in disease-associated angiogenesis and disease progression than has so far been assumed. Our data also suggest that HGF and c-Met are potential therapeutic targets in CML.

Reduced mast cell and basophil numbers and function in Cpa3-Cre; Mcl-1fl/fl mice

It has been reported that the intracellular antiapoptotic factor myeloid cell leukemia sequence 1 (Mcl-1) is required for mast cell survival in vitro, and that genetic manipulation of Mcl-1 can be used to delete individual hematopoietic cell populations in vivo. In the present study, we report the generation of C57BL/6 mice in which Cre recombinase is expressed under the control of a segment of the carboxypeptidase A3 (Cpa3) promoter. C57BL/6-Cpa3-Cre; Mcl-1(fl/fl) mice are severely deficient in mast cells (92%-100% reduced in various tissues analyzed) and also have a marked deficiency in basophils (58%-78% reduced in the compartments analyzed), whereas the numbers of other hematopoietic cell populations exhibit little or no changes. Moreover, Cpa3-Cre; Mcl-1(fl/fl) mice exhibited marked reductions in the tissue swelling and leukocyte infiltration that are associated with both mast cell- and IgE-dependent passive cutaneous anaphylaxis (except at sites engrafted with in vitro-derived mast cells) and a basophil- and IgE-dependent model of chronic allergic inflammation, and do not develop IgE-dependent passive systemic anaphylaxis. Our findings support the conclusion that Mcl-1 is required for normal mast cell and basophil development/survival in vivo in mice, and also suggest that Cpa3-Cre; Mcl-1(fl/fl) mice may be useful in analyzing the roles of mast cells and basophils in health and disease.

Benzene metabolites inhibit the release of proinflammatory mediators and cytokines from human basophils

Benzene and its metabolites have been involved in the pathogenesis of chronic lung inflammation and allergic disorders such as bronchial asthma. However, the effects of these xenobiotics on human basophils, key cells in the development of respiratory allergy, have not been investigated. We examined the effects of hydroquinone (HQ) and benzoquinone (BQ), two important chemicals implicated in benzene toxicity, on the release of preformed (histamine) and de novo synthesized mediators (cysteinyl leukotriene C4, LTC4, and IL-4) from human basophils. Preincubation of basophils purified from normal donors with HQ (3-100 microM) inhibited up to 30% histamine release induced by anti-IgE and up to 55% of that induced by the Ca2+ ionophore A23187. HQ had no effect on histamine release induced by formyl-methionyl-leucyl-phenylalanine (f-Met-Leu-Phe). Preincubation of basophils with BQ (3-100 microM) resulted in the concentration-dependent inhibition of histamine release (up to 70%) induced by anti-IgE, A23187 and f-Met-Leu-Phe. HQ completely suppressed the de novo synthesis of LTC4 from basophils challenged with anti-IgE or f-Met-Leu-Phe and the production of IL-4 in cells stimulated with anti-IgE. These results indicate that two major benzene metabolites, HQ and BQ, inhibit the release of proinflammatory mediators and Th2-promoting cytokines from basophils activated by different stimuli. These results suggest that benzene metabolites interfere with multiple intracellular signals involved in the activation of human basophils.

Mast cells have a protumorigenic role in human thyroid cancer

In different human carcinoma types, mast cell infiltrate increases with respect to normal tissue and mast cell density correlates with a bad prognosis. To assess the role of mast cells in human thyroid cancer, we compared the density of tryptase-positive mast cells in 96 papillary thyroid carcinomas (PTCs) versus normal thyroid tissue from 14 healthy individuals. Mast cell density was higher in 95% of PTCs (n=91) than in control tissue. Mast cell infiltrate correlated with extrathyroidal extension (P=0.0005) of PTCs. We show that thyroid cancer cell-line-derived soluble factors induce mast cell activation and chemoattraction in vitro. Different mast cell lines (HMC-1 and LAD2) and primary human lung mast cells induced thyroid cancer cell invasive ability, survival and DNA synthesis in vitro. The latter effect was mainly mediated by three mast-cell-derived mediators: histamine, and chemokines CXCL1/GROα and CXCL10/IP10. We show that xenografts of thyroid carcinoma cells (8505-C) could recruit mast cells injected into the tail vein of mice. Co-injection of human mast cells accelerated the growth of thyroid cancer cell (8505-C) xenografts in athymic mice. This effect was mediated by increased tumor vascularization and proliferation, and was reverted by treating mice with sodium cromoglycate (Cromolyn), a specific mast cell inhibitor. In conclusion, our study data suggest that mast cells are recruited into thyroid carcinomas and promote proliferation, survival and invasive ability of cancer cells, thereby contributing to thyroid carcinoma growth and invasiveness.

Angiogenesis and lymphangiogenesis in bronchial asthma

Neovascularization plays a prominent role in inflammation and tissue remodeling in several chronic inflammatory disorders. Vessel number and size, vascular surface area and vascular leakage are all increased in biopsies from patients with asthma. High levels of VEGF and other angiogenic factors have been detected in tissues and biological samples of patients with asthma and correlate with disease activity and inversely with airway hyper-responsiveness. Inflammation in the lung stimulates the growth of new blood vessels and these contribute to the airway obstruction or airway hyper-responsiveness, or both. Effector cells of inflammation (human lung mast cells, basophils, eosinophils, macrophages, etc.) are major sources of a vast array of angiogenic and lymphangiogenic factors. Inhaled corticosteroids reduce vascularity and growth factor expression and might modulate bronchial vascular remodeling in asthma. Specific antagonists to VEGF and other angiogenic factors and their receptors might help to control chronic airway inflammation and vascular remodeling and offer a novel approach for the treatment of chronic inflammatory lung disorders.

IL-33 synergizes with IgE-dependent and IgE-independent agents to promote mast cell and basophil activation

OBJECTIVE

Mast cell and basophil activation contributes to inflammation, bronchoconstriction, and airway hyperresponsiveness in asthma. Because IL-33 expression is inflammation inducible, we investigated IL-33-mediated effects in concert with both IgE-mediated and IgE-independent stimulation.

METHODS

Because the HMC-1 mast cell line can be activated by GPCR and RTK signaling, we studied the effects of IL-33 on these pathways. The IL-33- and SCF-stimulated HMC-1 cells were co-cultured with human lung fibroblasts and airway smooth muscle cells in a collagen gel contraction assay. IL-33 effects on IgE-mediated activation were studied in primary mast cells and basophils.

RESULT

IL-33 synergized with adenosine, C5a, SCF, and NGF receptor activation. IL-33-stimulated and SCF-stimulated HMC-1 cells demonstrated enhanced collagen gel contraction when cultured with fibroblasts or smooth muscle cells. IL-33 also synergized with IgE receptor activation of primary human mast cells and basophils.

CONCLUSION

IL-33 amplifies inflammation in both IgE-independent and IgE-dependent responses.

Siglec-8 on human eosinophils and mast cells, and Siglec-F on murine eosinophils, are functionally related inhibitory receptors

Siglecs (sialic acid-binding, Ig-like lectins) are a family of single-pass transmembrane cell surface proteins found predominantly on leucocytes. Their unique structural characteristics include an N-terminal carbohydrate-binding ('lectin') domain that binds sialic acid, followed by a variable number of Ig-like domains, hence these structures are a subset of the Ig gene superfamily. Another unique feature of Siglecs is that most, but not all, possess so-called immunoreceptor tyrosine-based inhibitory motifs in their cytoplasmic domains, suggesting that these molecules function in an inhibitory capacity. Siglec-8, the eighth member identified at the time, was discovered as part of an effort initiated almost a decade ago to identify novel human eosinophil and mast cell proteins. Since that time, its selective expression on human eosinophils and mast cells has been confirmed. On eosinophils, Siglec-8 engagement results in apoptosis, whereas on mast cells, inhibition of FcepsilonRI-dependent mediator release, without apoptosis, is seen. It has subsequently been determined that the closest functional paralog in the mouse is Siglec-F, selectively expressed by eosinophils but not expressed on mast cells. Despite only modest homology, both Siglec-8 and Siglec-F preferentially recognize a sulphated glycan ligand closely related to sialyl Lewis X, a common ligand for the selectin family of adhesion molecules. Murine experiments in normal, Siglec-F-deficient mice and hypereosinophilic mice have resulted in similar conclusions that Siglec-F, like Siglec-8, plays a distinctive and important role in regulating eosinophil accumulation and survival in vivo. Given the resurgent interest in eosinophil-directed therapies for a variety of disorders, plus its unique additional ability to also target the mast cell, therapies focusing on Siglec-8 could some day prove to be a useful adjunct to our current armamentarium for the treatment of asthma, allergies and related disorders where overproduction and overactivity of eosinophils and mast cells is occurring.

Toll-like receptor-expressing cells for antiallergy compound screening

BACKGROUND

Regulation of type 2 helper T cell (TH2) polarization by toll-like receptors (TLRs) has triggered great interest in new antiallergic therapeutics. In addition to being involved in the regulation of co-stimulation by antigen-presenting cells, they are expressed on other immune and non-immune cells.

OBJECTIVE

To review the expression and function of TLRs on these cells and their potential to regulate TH2-associated responses.

METHODS

We focused on human cells that can be used for in vitro testing of TLR agonists.

RESULTS/CONCLUSION

Many cells involved in the allergic reaction have the capacity to respond to TLR agonists. Therefore, one needs to be cautious in extrapolating the antiallergic effect of a TLR agonist from the response analyzed in one cell type. Therefore, it is suggested that several cell types should be studied.

Inhibition of FcepsilonRI-dependent mediator release and calcium flux from human mast cells by sialic acid-binding immunoglobulin-like lectin 8 engagement

BACKGROUND

Sialic acid-binding immunoglobulin-like lectins (Siglecs) are a family of glycan-binding inhibitory receptors, and among them, Siglec-8 is selectively expressed on human eosinophils, basophils, and mast cells. On eosinophils, Siglec-8 engagement induces apoptosis, but its function on mast cells is unknown.

OBJECTIVE

We sought to study the effect of Siglec-8 engagement on human mast cell survival and mediator release responses.

METHODS

Human mast cells were generated from CD34+ precursors. Apoptosis was studied by using flow cytometry. Mast cell mediator release or human lung airway smooth muscle contraction was initiated by FcepsilonRI cross-linking with or without preincubation with Siglec-8 or control antibodies, and release of mediators was analyzed along with Ca++ flux. RBL-2H3 cells transfected with normal and mutated forms of Siglec-8 were used to study how Siglec-8 engagement alters mediator release.

RESULTS

Siglec-8 engagement failed to induce human mast cell apoptosis. However, preincubation with Siglec-8 mAbs significantly (P < .05) inhibited FcepsilonRI-dependent histamine and prostaglandin D(2) release, Ca++ flux, and anti-IgE-evoked contractions of human bronchial rings. In contrast, release of IL-8 was not inhibited. Siglec-8 ligation was also shown to inhibit beta-hexosaminidase release and Ca++ flux triggered through FcepsilonRI in RBL-2H3 cells transfected with full-length human Siglec-8 but not in cells transfected with Siglec-8 containing a tyrosine to phenylalanine point mutation in the membrane-proximal immunoreceptor tyrosine-based inhibitory motif domain.

CONCLUSION

These data represent the first reported inhibitory effects of Siglec engagement on human mast cells.

Mast cells: versatile regulators of inflammation, tissue remodeling, host defense and homeostasis

The possible roles of mast cells in heath and disease have been a topic of interest for over 125 years. Many adaptive or pathological processes affecting the skin or other anatomical sites have been associated with morphological evidence of mast cell activation, and/or with changes in mast cell numbers or phenotype. Such observations, taken together with the known functions of the diverse mediators, cytokines and growth factors which can be secreted by mast cells, have suggested many potential functions for mast cells in health and disease. Definitively identifying the importance of mast cells in biological responses in humans is difficult. However, mutant mice which are profoundly mast cell-deficient, especially those which can undergo engraftment with wild-type or genetically altered mast cells, provide an opportunity to investigate the importance of mast cells, and specific mast cell functions or products, in various adaptive or pathological responses in mice. Such work has shown that mast cells can significantly influence multiple features of inflammatory or immune responses, through diverse effects that can either promote or, surprisingly, suppress, aspects of these responses. Through such functions, mast cells can significantly influence inflammation, tissue remodeling, host defense and homeostasis.

Pretreatment of cromolyn sodium prior to reperfusion attenuates early reperfusion injury after the small intestine ischemia in rats

AIM: To investigate the effects of Cromolyn Sodium (CS) pretreated prior to reperfusion on the activity of intestinal mucosal mast cells (IMMC) and mucous membrane of the small intestine in ischemia-reperfusion (IR) injury of rats.

METHODS: Thirty-two Sprague-Dawley (SD) rats were randomly divided into four groups: sham group (group S), model group (group M), high and low dosage of CS groups, (treated with CS 50 mg/kg or 25 mg/kg, group C1 and C2). Intestinal IR damage was induced by clamping the superior mesenteric artery for 45 min followed by reperfusion for 60 min. CS was intravenouly administrated 15 min before reperfusion. Ultrastructure and counts of IMMC, intestinal structure, the expression of tryptase, levels of malondisldehyde (MDA), TNF-α, histamine and superoxide dismutase (SOD) activity of the small intestine were detected at the end of experiment.

RESULTS: The degranulation of IMMC was seen in group M and was attenuated by CS treatment. Chiu’s score of group M was higher than the other groups. CS could attenuate the up-regulation of the Chiu’s score, the levels of MDA, TNF-α, and expression of tryptase and the down-regulation of SOD activity and histamine concentration. The Chiu’s score and MDA content were negatively correlated, while SOD activity was positively correlated to the histamine concentration respectively in the IR groups.

CONCLUSION: Pretreated of CS prior to reperfusion protects the small intestine mucous from ischemia-reperfusion damage, the mechanism is inhibited IMMC from degranulation.

Genome-wide profiling identifies epithelial cell genes associated with asthma and with treatment response to corticosteroids

Airway inflammation and epithelial remodeling are two key features of asthma. IL-13 and other cytokines produced during T helper type 2 cell-driven allergic inflammation contribute to airway epithelial goblet cell metaplasia and may alter epithelial-mesenchymal signaling, leading to increased subepithelial fibrosis or hyperplasia of smooth muscle. The beneficial effects of corticosteroids in asthma could relate to their ability to directly or indirectly decrease epithelial cell activation by inflammatory cells and cytokines. To identify markers of epithelial cell dysfunction and the effects of corticosteroids on epithelial cells in asthma, we studied airway epithelial cells collected from asthmatic subjects enrolled in a randomized controlled trial of inhaled corticosteroids, from healthy subjects and from smokers (disease control). By using gene expression microarrays, we found that chloride channel, calcium-activated, family member 1 (CLCA1), periostin, and serine peptidase inhibitor, clade B (ovalbumin), member 2 (serpinB2) were up-regulated in asthma but not in smokers. Corticosteroid treatment down-regulated expression of these three genes and markedly up-regulated expression of FK506-binding protein 51 (FKBP51). Whereas high baseline expression of CLCA1, periostin, and serpinB2 was associated with a good clinical response to corticosteroids, high expression of FKBP51 was associated with a poor response. By using airway epithelial cells in culture, we found that IL-13 increased expression of CLCA1, periostin, and serpinB2, an effect that was suppressed by corticosteroids. Corticosteroids also induced expression of FKBP51. Taken together, our findings show that airway epithelial cells in asthma have a distinct activation profile and identify direct and cell-autonomous effects of corticosteroid treatment on airway epithelial cells that relate to treatment responses and can now be the focus of specific mechanistic studies.

Mast cells in the promotion and limitation of chronic inflammation

Observations of increased numbers of mast cells at sites of chronic inflammation have been reported for over a hundred years. Light and electron microscopic evidence of mast cell activation at such sites, taken together with the known functions of the diverse mediators, cytokines, and growth factors that can be secreted by appropriately activated mast cells, have suggested a wide range of possible functions for mast cells in promoting (or suppressing) many features of chronic inflammation. Similarly, these and other lines of evidence have implicated mast cells in a variety of adaptive or pathological responses that are associated with persistent inflammation at the affected sites. Definitively characterizing the importance of mast cells in chronic inflammation in humans is difficult. However, mice that genetically lack mast cells, especially those which can undergo engraftment with wildtype or genetically altered mast cells, provide a means to investigate the importance of mast cells and specific mast cell functions or products in diverse models of chronic inflammation. Such work has confirmed that mast cells can significantly influence multiple features of chronic inflammatory responses, through diverse effects that can either promote or, perhaps more surprisingly, suppress aspects of these responses.

Mast cell-derived TNF contributes to airway hyperreactivity, inflammation, and TH2 cytokine production in an asthma model in mice

BACKGROUND

Mast cells, IgE, and TNF, which have been implicated in human atopic asthma, contribute significantly to the allergic airway inflammation induced by ovalbumin (OVA) challenge in mice sensitized with OVA without alum. However, it is not clear to what extent mast cells represent a significant source of TNF in this mouse model.

OBJECTIVE

We investigated the importance of mast cell-derived TNF in a mast cell-dependent model of OVA-induced airway hyperreactivity (AHR) and allergic airway inflammation.

METHODS

Features of this model of airway inflammation were analyzed in C57BL/6J-wild-type mice, mast cell-deficient C57BL/6J-Kit(W-sh)(/W-sh) mice, and C57BL/6J Kit(W-sh/W-sh) mice that had been systemically engrafted with bone marrow-derived cultured mast cells from C57BL/6J-wild-type or C57BL/6J-TNF(-/-) mice.

RESULTS

Ovalbumin-induced AHR and airway inflammation were significantly reduced in mast cell-deficient Kit(W-sh/W-sh) mice versus wild-type mice. By contrast, Kit(W-sh/W-sh) mice that had been engrafted with wild-type but not with TNF(-/-) bone marrow-derived cultured mast cells exhibited responses very similar to those observed in wild-type mice. Mast cells and mast cell-derived TNF were not required for induction of OVA-specific memory T cells in the sensitization phase, but significantly enhanced lymphocyte recruitment and T(H)2 cytokine production in the challenge phase.

CONCLUSION

Mast cell-derived TNF contributes significantly to the pathogenesis of mast cell-dependent and IgE-dependent, OVA-induced allergic inflammation and AHR in mice, perhaps in part by enhancing lymphocyte recruitment and T(H)2 cytokine production.

CLINICAL IMPLICATIONS

Our findings in mice support the hypothesis that mast cell-derived TNF can promote allergic inflammation and AHR in asthma.

Mast cells--key effector cells in immune responses

Mast cells are best known for their potent effector functions in allergic disorders. In recent years, however, mast cells have been identified to be involved in a surprisingly complex range of immune functions that go far beyond allergies and include the development of autoimmune disorders and peripheral tolerance, and the initiation and maintenance of adaptive and innate host responses. Here, we review the key signals and effector mechanisms that have lately been identified for mast cell functions in these immune responses.

Role of mast cells in allergic and non-allergic immune responses: comparison of human and murine data

The versatile role of mast cells in allergy, in innate immune responses and in the regulation of tissue homeostasis is well recognized. However, it is often not made clear that most mast-cell data derive solely from experiments in mice or rats, species that obviously never suffer from allergic and most other mast-cell-associated human diseases. Data on human mast cells are limited, and the mast-cell source and species from which findings derive are frequently not indicated in the titles and summaries of research publications. This Review summarizes recent data on human mast cells, discusses differences with murine mast cells, and describes new tools to study this increasingly meaningful cell type in humans.

Expression and functions of the vascular endothelial growth factors and their receptors in human basophils

Angiogenesis is a multistep complex phenomenon critical for several inflammatory and neoplastic disorders. Basophils, normally confined to peripheral blood, can infiltrate the sites of chronic inflammation. In an attempt to obtain insights into the mechanism(s) underlying human basophil chemotaxis and its role in inflammation, we have characterized the expression and function of vascular endothelial growth factors (VEGFs) and their receptors in these cells. Basophils express mRNA for three isoforms of VEGF-A (121, 165, and 189) and two isoforms of VEGF-B (167 and 186). Peripheral blood and basophils in nasal polyps contain VEGF-A localized in secretory granules. The concentration of VEGF-A in basophils was 144.4 +/- 10.8 pg/10(6) cells. Immunologic activation of basophils induced the release of VEGF-A. VEGF-A (10-500 ng/ml) induced basophil chemotaxis. Supernatants of activated basophils induced an angiogenic response in the chick embryo chorioallantoic membrane that was inhibited by an anti-VEGF-A Ab. The tyrosine kinase VEGFR-2 (VEGFR-2/KDR) mRNA was expressed in basophils. These cells also expressed mRNA for the soluble form of VEGFR-1 and neuropilin (NRP)1 and NRP2. Flow cytometric analysis indicated that basophils express epitopes recognized by mAbs against the extracellular domains of VEGFR-2, NRP1, and NRP2. Our data suggest that basophils could play a role in angiogenesis and inflammation through the expression of several forms of VEGF and their receptors.

Effector and potential immunoregulatory roles of mast cells in IgE-associated acquired immune responses

Mast cells are best known as critical effector cells in anaphylaxis and other examples of IgE-associated immediate hypersensitivity reactions. However, mast cells also can contribute to the development of the late-phase responses that occur in some sensitized subjects hours after initial exposure to specific antigen, and can promote many of the features of chronic allergic inflammation, including tissue remodeling and functional changes in the affected organs. In addition to such effector cell functions in IgE-associated immune responses, recent evidence indicates that mast cells can importantly influence the sensitization phase of at least some acquired immune responses, and can contribute to the pathology of autoimmune disorders and to the expression of peripheral tolerance.