Mast-cell responses in the development of asthma

Immunohistochemical expression of estrogen receptor alpha in the maxillary sinus, pulp, and periodontal ligament of adjacent teeth in late pregnancy in rats

This study aimed to assess the histological changes in the maxillary sinus and its adjacent dental tissues as pulp and periodontal ligament during pregnancy and investigate the role of estrogen hormone in these changes through the detection of estrogen receptors in these tissues. Sixteen adult female rats were used and were allocated into two groups: control non-pregnant (n = 8) and pregnant (n = 8). They were sacrificed and their heads were prepared for histological and immunohistochemical examination for estrogen receptor alpha. Our results revealed that pregnant rats revealed inflammatory changes in the sinus as thick epithelial lining, loss of cilia, swollen goblet cells, intraepithelial and interstitial edema. The lamina propria demonstrated considerable infiltration of inflammatory cells, glandular hyperplasia with vacuolar degeneration, and vascular congestion. Periodontal ligament and pulp revealed hyperemia and vascular congestion. Immunohistochemical examination of estrogen receptor alpha in the maxillary sinus and adjacent dental tissues (Periodontal ligament and pulp) in pregnant rats revealed a significant increase in its expression in all examined tissues. In conclusion, there was an increase in expression of ERα in the sinus mucosa and dental tissues during pregnancy together with slight inflammatory changes in these tissues. Hence, dentists should be aware of the effect of these changes on the pregnant women avoiding teeth extraction due to misdiagnosis of dental, periodontal or sinus pain after exclusion of true pathologies.

Lung-specific MCEMP1 functions as an adaptor for KIT to promote SCF-mediated mast cell proliferation

Lung mast cells are important in host defense, and excessive proliferation or activation of these cells can cause chronic inflammatory disorders like asthma. Two parallel pathways induced by KIT-stem cell factor (SCF) and FcεRI-immunoglobulin E interactions are critical for the proliferation and activation of mast cells, respectively. Here, we report that mast cell-expressed membrane protein1 (MCEMP1), a lung-specific surface protein, functions as an adaptor for KIT, which promotes SCF-mediated mast cell proliferation. MCEMP1 elicits intracellular signaling through its cytoplasmic immunoreceptor tyrosine-based activation motif and forms a complex with KIT to enhance its autophosphorylation and activation. Consequently, MCEMP1 deficiency impairs SCF-induced peritoneal mast cell proliferation in vitro and lung mast cell expansion in vivo. Mcemp1-deficient mice exhibit reduced airway inflammation and lung impairment in chronic asthma mouse models. This study shows lung-specific MCEMP1 as an adaptor for KIT to facilitate SCF-mediated mast cell proliferation.

Artesunate inhibits airway remodeling in asthma via the MAPK signaling pathway

Background: Artesunate (ART), is a semi-synthetic water-soluble artemisinin derivative extracted from the plant Artemisia annua, which is often used to treating malaria. In vivo and in vitro studies suggested it may help decrease inflammation and attenuate airway remodeling in asthma. However, its underlying mechanism of action is not elucidated yet. Herein, an attempt is made to investigate the ART molecular mechanism in treating asthma.

Methods: The BALB/c female mice sensitized via ovalbumin (OVA) have been utilized to establish the asthma model, followed by carrying out ART interventions. Lung inflammation scores by Haematoxylin and Eosin (H&E), goblet cell hyperplasia grade by Periodic Acid-Schiff (PAS), and collagen fibers deposition by Masson trichrome staining have been utilized for evaluating how ART affected asthma. RNA-sequencing (RNA-seq) analyses were performed to identify differentially expressed genes (DEGs). The DEGs were analyzed by Gene Ontology (GO) terms, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways, and Protein-Protein interaction (PPI) function analyses. Hub clusters were found by Cytoscape MCODE. Subsequently, Real-Time quantitative PCR (RT-qPCR) verified the mRNA expression profiles of DEGs. Finally, immunohistochemistry (IHC) and western blots have validated the relevant genes and potential pathways.

Results: ART considerably attenuated inflammatory cell infiltration, mucus secretion, and collagen fibers deposition. KEGG pathway analysis revealed that the ART played a protective role via various pathways including the mitogen-activated protein kinase (MAPK) pathway as one of them. Moreover, ART could alleviate the overexpression of found in inflammatory zone 1(FIZZ1) as revealed by IHC and Western blot analyses. ART attenuated OVA-induced asthma by downregulating phosphorylated p38 MAPK.

Conclusion: ART exerted a protective function in a multitarget and multi-pathway on asthma. FIZZ1 was a possible target for asthma airway remodeling. The MARK pathway was one of the key pathways by which ART protected against asthma.

Tryptase and Exogenous Trypsin: Mechanisms and Ophthalmic Applications

Ocular injuries caused by inflammation, surgery or accidents are subject to a physiological healing process that ultimately restores the structure and function of the damaged tissue. Tryptase and trypsin are essential component of this process and they play a role in promoting and reducing the inflammatory response of tissues, respectively. Following injury, tryptase is endogenously produced by mast cells and can exacerbate the inflammatory response both by stimulating neutrophil secretion, and through its agonist action on proteinase-activated receptor 2 (PAR2). In contrast, exogenously introduced trypsin promotes wound healing by attenuating inflammatory responses, reducing oedema and protecting against infection. Thus, trypsin may help resolve ocular inflammatory symptoms and promote faster recovery from acute tissue injury associated with ophthalmic diseases. This article describes the roles of tryptase and exogenous trypsin in affected tissues after onset of ocular injury, and the clinical applications of trypsin injection.

Pentraxin 3 Facilitates Shrimp-Allergic Responses in IgE-Activated Mast Cells

Background. Since food avoidance is currently the only way to prevent allergic reactions to shrimp, a better understanding of molecular events in the induction and progression of allergy, including food allergy, is needed for developing strategies to inhibit allergic responses. Pentraxin 3 (PTX3) is rapidly produced directly from inflammatory or damaged tissues and is involved in acute immunoinflammatory responses. However, the role of PTX3 in the development of immediate IgE-mediated shrimp allergy remains unknown. Methods. Wild-type BALB/c mice were immunized intraperitoneally and were challenged with shrimp extract. Serum IgE and PTX3 levels were analyzed. RBL-2H3 cells were stimulated with either dinitrophenyl (DNP) or serum of shrimp-allergic mice, and markers of degranulation, proinflammatory mediators, and phosphorylation of signal proteins were analyzed. We further examined the effect of PTX3 in shrimp extract-induced allergic responses in vitro and in vivo. Results. Mice with shrimp allergy had increased PTX3 levels in the serum and small intestine compared with healthy mice. PTX3 augmented degranulation, the production of proinflammatory mediators, and activation of the Akt and MAPK signaling pathways in mast cells upon DNP stimulation. Furthermore, the expression of transcription factor CCAAT/enhancer-binding protein delta (CEBPD) was elevated in PTX3-mediated mast cell activation. Finally, the PTX3 inhibitor RI37 could attenuate PTX3-induced degranulation, proinflammatory mediator expression, and phosphorylation of the Akt and MAPK signaling. Conclusions. The results suggested that PTX3 can facilitate allergic responses. Our data provide new insight to demonstrate that PTX3 is a cause of allergic inflammation and that RI37 can serve as a therapeutic agent in shrimp allergy.

Dynamically upregulated mast cell CPA3 patterns in chronic obstructive pulmonary disease and idiopathic pulmonary fibrosis

Background

The mast cell-specific metalloprotease CPA3 has been given important roles in lung tissue homeostasis and disease pathogenesis. However, the dynamics and spatial distribution of mast cell CPA3 expression in lung diseases remain unknown.

Methods

Using a histology-based approach for quantitative spatial decoding of mRNA and protein single cell, this study investigates the dynamics of CPA3 expression across mast cells residing in lungs from control subjects and patients with severe chronic obstructive pulmonary disease (COPD) or idiopathic lung fibrosis (IPF).

Results

Mast cells in COPD lungs had an anatomically widespread increase of CPA3 mRNA (bronchioles p < 0.001, pulmonary vessels p < 0.01, and alveolar parenchyma p < 0.01) compared to controls, while granule-stored CPA3 protein was unaltered. IPF lungs had a significant upregulation of both mast cell density, CPA3 mRNA (p < 0.001) and protein (p < 0.05), in the fibrotic alveolar tissue. Spatial expression maps revealed altered mast cell mRNA/protein quotients in lung areas subjected to disease-relevant histopathological alterations. Elevated CPA3 mRNA also correlated to lung tissue eosinophils, CD3 T cells, and declined lung function. Single-cell RNA sequencing of bronchial mast cells confirmed CPA3 as a top expressed gene with potential links to both inflammatory and protective markers.

Conclusion

This study shows that lung tissue mast cell populations in COPD and IPF lungs have spatially complex and markedly upregulated CPA3 expression profiles that correlate with immunopathological alterations and lung function. Given the proposed roles of CPA3 in tissue homeostasis, remodeling, and inflammation, these alterations are likely to have clinical consequences.

Annexin A1 Mimetic Peptide Ac2-26 Modulates the Function of Murine Colonic and Human Mast Cells

Mast cells (MCs) are main effector cells in allergic inflammation and after activation, they release stored (histamine, heparin, proteases) and newly synthesized (lipid mediators and cytokines) substances. In the gastrointestinal tract the largest MC population is located in the lamina propria and submucosa whereas several signals such as the cytokine IL-4, seem to increase the granule content and to stimulate a remarkable expansion of intestinal MCs. The broad range of MC-derived bioactive molecules may explain their involvement in many different allergic disorders of the gastrointestinal tract. Annexin A1 (AnxA1) is a 37 KDa glucocorticoid induced monomeric protein selectively distributed in certain tissues. Its activity can be reproduced by mimetic peptides of the N-terminal portion, such as Ac2-26, that share the same receptor FPR-L1. Although previous reports demonstrated that AnxA1 inhibits MC degranulation in murine models, the effects of exogenous peptide Ac2-26 on intestinal MCs or the biological functions of the Ac2-26/FPR2 system in human MCs have been poorly studied. To determine the effects of Ac2-26 on the function of MCs toward the possibility of AnxA1-based therapeutics, we treated WT and IL-4 knockout mice with peptide Ac2-26, and we examined the spontaneous and compound 48/80 stimulated colonic MC degranulation and cytokine production. Moreover, in vitro, using human mast cell line HMC-1 we demonstrated that exogenous AnxA1 peptide is capable of interfering with the HMC-1 degranulation in a direct pathway through formyl peptide receptors (FPRs). We envisage that our results can provide therapeutic strategies to reduce the release of MC mediators in inflammatory allergic processes.

Elevated Circulating Th2 Cells in Women With Asthma and Psychological Morbidity: A New Asthma Endotype?

PURPOSE

Psychological stress shifts the immune system toward the production of T-helper (Th)-2-mediated cytokines and eosinophilia, increases the risks for both asthma and depression, and can precipitate asthma exacerbations. Th2-mediated inflammation is a characteristic of allergic asthma. We have shown that the levels of CD4⁺ Th2 cells in the peripheral blood of patients with asthma are associated with severity and/or control of the disease. To improve our understanding of the interactions between stress and asthma symptoms, we evaluated the effects of psychological comorbidity on Th2-mediated inflammation in patients with asthma.

METHODS

Sixty-six asthmatic patients were recruited from the University of Alberta Asthma Clinic after they gave informed consent. Stress-related effects on asthma and psychological morbidity were assessed using the Asthma Control Questionnaire, completed by the patients at recruitment. Venous blood was collected at recruitment and Th2-mediated immunity evaluated by flow cytometry, quantitative real-time reverse-transcription polymerase chain reaction and enzyme-linked immunosorbent assay.

FINDINGS

Patients with stress-triggered asthma (n = 12) had higher percentage of CD4⁺ T cells (P = 0.006) and Th2 cells (CD4⁺CRTh2⁺ T cells; P = 0.002) in peripheral blood compared to patients with asthma who did not experience stress-related worsening of disease (n = 54). The same was true when we analyzed patients with any form of psychological comorbidity (n = 19) compared to those without psychological comorbidities (n = 47). These differences were evident among women, but not among men. Women with psychological comorbidity also required higher doses of inhaled and oral corticosteroids compared to those without psychological comorbidity.

IMPLICATIONS

Asthma involving psychological morbidity associates with an elevated level of circulating Th2 cells and increased corticosteroid usage, and may be more prevalent in women. Larger-scale prospective studies are required for assessing whether these women constitute a new endotype of Th2-high asthma responsive to treatments aimed to improve psychological comorbidities.

Kinase inhibitors in the treatment of obstructive pulmonary diseases

Chronic pulmonary diseases, including chronic obstructive pulmonary disease (COPD) and asthma, are major causes of death and reduced quality of life. Characteristic of chronic pulmonary disease is excessive lung inflammation that occurs in response to exposure to inhaled irritants, chemicals, and allergens. Chronic inflammation leads to remodeling of the airways that includes excess mucus secretion, proliferation of smooth muscle cells, increased deposition of extracellular matrix proteins and fibrosis. Protein kinases have been implicated in mediating inflammatory signals and airway remodeling associated with reduced lung function in chronic pulmonary disease. This review will highlight the role of protein kinases in the lung during chronic inflammation and examine opportunities to use protein kinase inhibitors for the treatment of chronic pulmonary diseases.

Histamine H4 receptor mediates chemotaxis of human lung mast cells

The diverse effects of histamine are mediated by discrete histamine receptors. The principal repository of histamine in the body is the mast cell. However, the effects of histamine on mast cells, especially those of human origin, have not been fully elucidated. In this study, the expression of histamine receptors in human lung mast cells was evaluated. Moreover, the effects of histamine receptor engagement on both mediator release and chemotaxis were investigated. Mast cells were isolated and purified from human lung tissue. Histamine receptor expression was determined by RT-PCR and q-PCR. Both methods for the detection of histamine receptors were in accordance and human lung mast cells expressed mRNA for histamine H₄ and histamine H₁ receptors, variably expressed histamine H₂ receptor but did not express histamine H₃ receptor. The effects of selective histamine receptor agonists on the release of both pre-formed (histamine) and newly-synthesised (cysteinyl-leukotriene, prostaglandin D₂) mediators were investigated. None of the agonists tested had any direct effects on mediator release. None of the agonists modulated release stimulated by anti-IgE. Further studies showed that histamine induced migration of mast cells. Chemotaxis appeared to be mediated by the histamine H₄ receptor since JNJ28610244 (H₄ agonist) was chemotactic for mast cells whereas 2-(2-pyridyl) ethylamine (H₁ agonist) was not. Furthermore, the selective histamine H₄ receptor antagonist, JNJ7777120, effectively reversed the chemotaxis of mast cells induced by JNJ28610244. Overall, these experiments identify the histamine H₄ receptor as chemotactic for human lung mast cells. This mechanism might influence mast cell accumulation in the lung.

Activation of Th2 cells downregulates CRTh2 through an NFAT1 mediated mechanism

CRTh2 (encoded by PTGDR2) is a G-protein coupled receptor expressed by Th2 cells as well as eosinophils, basophils and innate lymphoid cells (ILC)2s. Activation of CRTh2, by its ligand prostaglandin (PG)D2, mediates production of type 2 cytokines (IL-4, IL-5 and IL-13), chemotaxis and inhibition of apoptosis. As such, the PGD2-CRTh2 pathway is considered important to the development and maintenance of allergic inflammation. Expression of CRTh2 is mediated by the transcription factor GATA3 during Th2 cell differentiation and within ILC2s. Other than this, relatively little is known regarding the cellular and molecular mechanisms regulating expression of CRTh2. Here, we show using primary human Th2 cells that activation (24hrs) through TCR crosslinking (αCD3/αCD28) reduced expression of both mRNA and surface levels of CRTh2 assessed by flow cytometry and qRT-PCR. This effect took more than 4 hours and expression was recovered following removal of activation. EMSA analysis revealed that GATA3 and NFAT1 can bind independently to overlapping sites within a CRTh2 promoter probe. NFAT1 over-expression resulted in loss of GATA3-mediated CRTh2 promoter activity, while inhibition of NFAT using a peptide inhibitor (VIVIT) coincided with recovery of CRTh2 expression. Collectively these data indicate that expression of CRTh2 is regulated through the competitive action of GATA3 and NFAT1. Though prolonged activation led to NFAT1-mediated downregulation, CRTh2 was re-expressed when stimulus was removed suggesting this is a dynamic mechanism and may play a role in PGD2-CRTh2 mediated allergic inflammation.

Toll-like receptor-mediated involvement of innate immune cells in asthma disease

BACKGROUND

Innate immune cells as the first line of defense are adept at recognizing and triggering appropriate response against various pathogens. Apart from the protective functions, the innate immunity plays an essential role in mediation of allergic responses. Dendritic cells (DCs) and airway epithelial cells (AECs) along with other innate cells such as granulocytes, natural killer cells (NKs), natural killer T cells (NKTs), and alternatively activated macrophages (AAMs) are able to orchestrate allergic responses, especially asthma. Chronic stimulation of TLRs by airway stimuli induces local inflammation which gradually results in the recruitment and settling of innate cells around airways.

SCOPE OF REVIEW

This review discusses how recruitment and accumulation of the inflammatory cells in the site of insult facilitate hypersensitivity reactions and initiate airway inflammation. We indicate that these cells are well equipped to highly sensitive receptors known as toll-like receptors (TLRs) making them fit to prime adaptive immune response. Based on emerging findings, we highlight the pivotal role of TLRs in regulation of innate cells function in the context of asthma disease.

MAJOR CONCLUSIONS

Stimulation of the TLRs of innate cells by allergens has been found to accelerate and regulate allergic airway inflammation. In fact, the sophisticated interaction between environmental allergens and TLRs leads to release of various pro-inflammatory mediators from innate cells supporting asthma development.

GENERAL SIGNIFICANCE

This review highlights that TLRs have a substantial role in priming innate cells and cytokine release, suggesting that the involvement of TLRs of innate immune cells can modulate the function of these cells in asthma disease.

Interaction Between Helminths and Toll-Like Receptors: Possibilities and Potentials for Asthma Therapy

Toll-like receptors (TLRs) are essential components of the innate immune system. They play an important role in the pathogenesis of allergic diseases, especially asthma. Since TLRs significantly orchestrate innate and adaptive immune response, their manipulation has widely been considered as a potential approach to control asthma symptoms. It is well established that helminths have immunoregulatory effects on host immune responses, especially innate immunity. They release bioactive molecules such as excretory-secretory (ES) products manipulating TLRs expression and signaling. Thus, given the promising results derived from preclinical studies, harnessing helminth-derived molecules affecting TLRs can be considered as a potential biological therapy for allergic diseases. Prospectively, the data that are available at present suggest that, in the near future, it is possible that helminth antigens will offer new therapeutic strategies and druggable targets for fighting allergic diseases. This review describes the interactions between helminths and TLRs and discusses the potential possibilities for asthma therapy. In this opinion paper, the authors aimed to review the updated literatures on the interplay between helminths, TLRs, and asthma with a view to proposing helminth-based asthma therapy.

9α,11β-PGF2, a Prostaglandin D2 Metabolite, as a Marker of Mast Cell Activation in Bee Venom-Allergic Patients

Mast cell (MC) mediators, among them prostaglandin D₂ (PGD₂) and 9α,11β-PGF₂, PGD₂’s metabolite, play a key role in allergic reactions, including bee venom anaphylaxis (BVA). Assessment of these mediators has never been performed in BVA. The aim of the study was to assess the activation of MC during in vivo provocation with bee venom (BV) and to measure PGD₂ and 9α,11β-PGF₂ in the course of an allergen challenge. The second aim was to determine if assessment of these mediators could be useful for predicting adverse events during venom immunotherapy (VIT). In 16 BV-VIT patients and 12 healthy subjects, levels of PGD₂ and 9α,11β-PGF₂ were assessed during BV provocation by means of the skin chamber method. Chamber fluids, collected at 5 and 15 min, were analyzed for both mediators by gas chromatography mass spectrometry negative ion chemical ionization. BVA in comparison to non-allergic patients had a significantly higher ratio of 9α,11β-PGF₂ in allergen-challenged chambers to 9α,11β-PGF₂ in allergen-free chambers after 15 min of provocation (p = 0.039). Allergen challenge resulted in a significant increase of 9α,11β-PGF₂ levels between 5 and 15 min after provocation only in BVA patients (p < 0.05). Analysis of log-transformed PGD2 levels showed significant difference between changes in PGD₂ concentration between BVA and healthy subjects. No study patient developed adverse reactions during. 9α,11β-PGF₂ is actively generated during the early allergic response to BV. Skin chamber seems to be a promising, non-invasive and safe model of in vivo allergen provocation in BV-allergic patients. High or low levels of both mediators do not predict occurrence of adverse events during VIT.

Mast cell activation syndrome: a review

Mast cell activation syndrome (MCAS) is a condition with signs and symptoms involving the skin, gastrointestinal, cardiovascular, respiratory, and neurologic systems. It can be classified into primary, secondary, and idiopathic. Earlier proposed criteria for the diagnosis of MCAS included episodic symptoms consistent with mast cell mediator release affecting two or more organ systems with urticaria, angioedema, flushing, nausea, vomiting, diarrhea, abdominal cramping, hypotensive syncope or near syncope, tachycardia, wheezing, conjunctival injection, pruritus, and nasal stuffiness. Other criteria included a decrease in the frequency, severity, or resolution of symptoms with anti-mediator therapy including H(1) and H(2)histamine receptor antagonists, anti-leukotrienes, or mast cell stabilizers. Laboratory data that support the diagnosis include an increase of a validated urinary or serum marker of mast cell activation (MCA), namely the documentation of an increase of the marker above the patient's baseline value during symptomatic periods on more than two occasions, or baseline serum tryptase levels that are persistently above 15 ng/ml, or documentation of an increase of the tryptase level above baseline value on one occasion. Less specific assays are 24-h urine histamine metabolites, PGD(2) (Prostaglandin D(2)) or its metabolite, 11-β-prostaglandin F(2) alpha. A recent global definition, criteria, and classification include typical clinical symptoms, a substantial transient increase in serum total tryptase level or an increase in other mast cell derived mediators, such as histamine or PGD2 or their urinary metabolites, and a response of clinical symptoms to agents that attenuate the production or activities of mast cell mediators.

Do mast cells link obesity and asthma?

Asthma is a chronic inflammatory disease of the lungs. Both the number of cases and severity of asthma have been increasing without a clear explanation. Recent evidence suggests that obesity, which has also been increasing alarmingly, may worsen or precipitate asthma, but there is little evidence of how obesity may contribute to lung inflammation. We propose that mast cells are involved in both asthma and obesity by being the target and source of adipocytokines, 'alarmins' such as interleukin-9 (IL-9) and interleukin-33 (IL-33), and stress molecules including corticotropin-releasing hormone (CRH) and neurotensin (NT), secreted in response to the metabolic burden. In particular, CRH and NT have synergistic effects on mast cell secretion of vascular endothelial growth factor (VEGF). IL-33 augments VEGF release induced by substance P (SP) and tumor necrosis factor (TNF) release induced by NT. Both IL-9 and IL-33 also promote lung mast cell infiltration and augment allergic inflammation. These molecules are also expressed in human mast cells leading to autocrine effects. Obese patients are also less sensitive to glucocorticoids and bronchodilators. Development of effective mast cell inhibitors may be a novel approach for the management of both asthma and obesity. Certain flavonoid combinations may be a promising new treatment approach.

Characterization of syk expression in human lung mast cells: relationship with function

BACKGROUND

Previous studies indicate that the protein tyrosine kinase, syk, is critical in transducing FcɛRI-mediated signals. In human basophils, 'releasability' has been linked to the extent of syk expression. Human lung mast cells, like basophils, are also found to be variably responsive to IgE-dependent activation.

OBJECTIVE

The aim of the present study was to determine whether the wide variability in human lung mast cell responses, following IgE-dependent activation, has a relationship with syk expression.

METHODS

Mast cells were isolated from human lung tissue and 'releasability' was determined by activating the cells with a maximal releasing concentration of anti-IgE. Syk levels in mast cells were determined by immunoblotting and flow cytometry.

RESULTS

Histamine release from mast cells, challenged with a maximal releasing concentration of anti-IgE, ranged from 0% to 69% (mean±SEM, 24±2%, n=53). A proportion of these preparations (nine out of 53) released very low levels of histamine (5%) in response to anti-IgE. Flow cytometry of a subset of preparations indicated that a weak response to anti-IgE was not related to a lack of surface IgE. Immunoblotting and flow cytometry studies demonstrated that, compared with mononuclear cells, human lung mast cells express low and variable levels of syk. However, there was no correlation between syk expression and mast cell releasability. Nonetheless, a number of putative inhibitors of syk including NVP-QAB205 (EC₅₀, 0.2 μm) effectively attenuated the IgE-dependent release of histamine from mast cells.

CONCLUSION AND CLINICAL RELEVANCE

These studies indicate that although syk may play an important role in mediating degranulation, the relative level of syk expression does not govern human lung mast cell releasability. Identification of the mechanisms that govern IgE-dependent activation of human lung mast cells is likely to be of wider clinical significance, given the central role that mast cells play in the development of allergic asthma.

Increased expression of leukotriene C4 synthase and predominant formation of cysteinyl-leukotrienes in human abdominal aortic aneurysm

Leukotrienes (LTs) are arachidonic acid-derived lipid mediators involved in the pathogenesis and progression of diverse inflammatory disorders. The cysteinyl-leukotrienes LTC(4), LTD(4), and LTE(4) are important mediators of asthma, and LTB(4) has recently been implicated in atherosclerosis. Here we report that mRNA levels for the three key enzymes/proteins in the biosynthesis of cysteinyl-leukotrienes, 5-lipoxygenase (5-LO), 5-LO-activating protein (FLAP), and LTC(4) synthase (LTC(4)S), are significantly increased in the wall of human abdominal aortic aneurysms (AAAs). In contrast, mRNA levels of LTA(4) hydrolase, the enzyme responsible for the biosynthesis of LTB(4), are not increased. Immunohistochemical staining of AAA wall revealed focal expression of 5-LO, FLAP, and LTC(4)S proteins in the media and adventitia, localized in areas rich in inflammatory cells, including macrophages, neutrophils, and mast cells. Human AAA wall tissue converts arachidonic acid and the unstable epoxide LTA(4) into significant amounts of cysteinyl-leukotrienes and to a lesser extent LTB(4). Furthermore, challenge of AAA wall tissue with exogenous LTD(4) increases the release of matrix metalloproteinase (MMP) 2 and 9, and selective inhibition of the CysLT1 receptor by montelukast blocks this effect. The increased expression of LTC(4)S, together with the predominant formation of cysteinyl-leukotrienes and effects on MMPs production, suggests a mechanism by which LTs may promote matrix degradation in the AAA wall and identify the components of the cysteinyl-leukotriene pathway as potential targets for prevention and treatment of AAA.

Amelioration of skewed Th1/Th2 balance in tumor-bearing and asthma-induced mice by oral administration of Agaricus blazei extracts

We showed in a previous study that hot-water extracts of Agaricus blazei (Agaricus extracts) had anti-tumor activity to Meth A fibrosarcoma, but it remains unclear whether the Agaricus extracts ameliorate the skewed balance of type-1 T helper (Th1) and type-2 T helper (Th2) cells. We examined whether Agaricus extracts effect the skewed Th1/Th2 balance in tumor-bearing and asthma-induced mice. When Meth A-bearing mice were given orally either Agaricus extracts or water once a day starting 5 days after tumor implantation, spleen T cells, prepared from tumor-bearing mice treated with Agaricus extracts, in response to anti-CD3 monoclonal antibody produced significantly higher levels of interferon gamma (IFN-gamma) than that of controls. The mRNA expression of IFN-gamma-inducing protein 10 and the frequency of CD69(+) or CD49d(+) cells, among activated T cells infiltrated into tumors, significantly increased in Agaricus-treated mice, compared with those of tumor-controls. In asthma-induced mice, treatment with the Agaricus extracts caused significant downregulation of OVA-specific antibody responses of IgG1 and IgE but not of IgG2a, and significantly decreased total cell numbers, levels of interleukin 5, and eosinophil numbers in bronchial alveolar lavage fluids. IFN-gamma production by anti-CD3-stimulated spleen cells, obtained from Agaricus-treated mice, significantly increased. Our results strongly suggest that oral administration of Agaricus extracts ameliorates the Th1/Th2 balance from the Th2-skewed conditions.

Stable overexpression of miRNAs in bone marrow-derived murine mast cells using lentiviral expression vectors

MicroRNAs (miRNAs) constitute a class of molecules regulating gene expression in many different cell types, including cells of the mammalian immune system. Indeed, changes in miRNA expression patterns have been implicated in various physiological and pathological processes. Mast cells (MCs) are hematopoietic cells that originate in the bone marrow and migrate into the tissues, where they mature and reside. They have an important immunoregulatory and effector role in IgE-associated allergic disorders, as well as in certain innate and adaptive immune responses. An effective way to explore the functions of miRNAs in murine MCs includes the modification of miRNA expression in primary bone marrow-derived mast cells (BMMCs), followed by the analysis of the phenotypic consequences of such perturbation. In this chapter, we describe how to differentiate BMMCs and transduce them with lentiviruses. As an example, we expressed miR-221 and miR-222, which showed stable expression in BMMCs and acted as post-transcriptional regulators of c-Kit expression.

Genetic deficiency and pharmacological stabilization of mast cells reduce diet-induced obesity and diabetes in mice

Although mast cell functions classically relate to allergic responses1–3, recent studies indicate that these cells contribute to other common diseases such as multiple sclerosis, rheumatoid arthritis, atherosclerosis, aortic aneurysm, and cancer4–8. This study presents evidence that mast cells contribute importantly to diet-induced obesity and diabetes. White adipose tissues (WAT) from obese humans and mice contain more mast cells than WAT from their lean counterparts. Genetically determined mast cell deficiency and pharmacological stabilization of mast cells in mice reduce body weight gain and levels of inflammatory cytokines, chemokines, and proteases in serum and WAT, in concert with improved glucose homeostasis and energy expenditure. Mechanistic studies reveal that mast cells contribute to WAT and muscle angiogenesis and associated cell apoptosis and cathepsin activity. Adoptive transfer of cytokine-deficient mast cells established that these cells contribute to mice adipose tissue cysteine protease cathepsin expression, apoptosis, and angiogenesis, thereby promoting diet-induced obesity and glucose intolerance by production of IL6 and IFN-γ. Mast cell stabilizing agents in clinical use reduced obesity and diabetes in mice, suggesting the potential of developing novel therapies for these common human metabolic disorders.

The long-acting beta-adrenoceptor agonist, indacaterol, inhibits IgE-dependent responses of human lung mast cells

BACKGROUND AND PURPOSE

The long-acting beta(2)-adrenoceptor agonist, indacaterol, has been developed as a bronchodilator for the therapeutic management of respiratory diseases. The aim of the present study was to determine whether indacaterol has any anti-inflammatory activity. To this end, the effects of indacaterol on human lung mast cell responses were investigated.

EXPERIMENTAL APPROACH

The effects of indacaterol, and the alternative long-acting beta-agonists formoterol and salmeterol, were investigated on the IgE-dependent release and generation of histamine, cysteinyl-leukotrienes and prostaglandin D(2) from human lung mast cells. Moreover, the extent to which long-term (24-72 h) incubation of mast cells with long-acting beta-agonists impaired the subsequent ability of beta-agonists to inhibit mast cell responses was assessed.

KEY RESULTS

Indacaterol was as potent and as efficacious as the full agonist, isoprenaline (EC(50), approximately 4 nmol x L(-1)), at inhibiting the IgE-dependent release of histamine from mast cells. Formoterol was a full agonist whereas salmeterol was a partial agonist as inhibitors of histamine release. All three long-acting beta-agonists were effective inhibitors of the IgE-dependent generation of cysteinyl-leukotrienes and prostaglandin D(2). Long-term incubation of mast cells with long-acting beta-agonists led to a reduction in the subsequent ability of beta-agonists to stabilize mast cell responses. This tendency to induce functional desensitization was least evident for indacaterol.

CONCLUSIONS AND IMPLICATIONS

Indacaterol is an effective inhibitor of the release of mediators from human lung mast cells. This suggests that, as well as bronchodilation, mast cell stabilization may constitute an additional therapeutic benefit of indacaterol.

Ablation of type I hypersensitivity in experimental allergic conjunctivitis by eotaxin-1/CCR3 blockade

The immune response is regulated, in part, by effector cells whose activation requires multiple signals. For example, T cells require signals emanating from the T cell antigen receptor and co-stimulatory molecules for full activation. Here, we present evidence indicating that IgE-mediated hypersensitivity reactions in vivo also require cognate signals to activate mast cells. Immediate hypersensitivity reactions in the conjunctiva are ablated in mice deficient in eotaxin-1, despite normal numbers of tissue mast cells and levels of IgE. To further define the co-stimulatory signals mediated by chemokine receptor 3 (CCR3), an eotaxin-1 receptor, effects of CCR3 blockade were tested with an allergic conjunctivitis model and in ex vivo isolated connective tissue-type mast cells. Our results show that CCR3 blockade significantly suppresses allergen-mediated hypersensitivity reactions as well as IgE-mediated mast cell degranulation. We propose that a co-stimulatory axis by CCR3, mainly stimulated by eotaxin-1, is pivotal in mast cell-mediated hypersensitivity reactions.

Granule formation in NGF-cultured mast cells is associated with expressions of pyruvate kinase type M2 and annexin I proteins

BACKGROUND

Nerve growth factor (NGF) is a potent mediator, which regulates characteristics of mast cells, but its biological function is not well characterized. This study aimed to screen proteins associated with the maturation of human mast cells-1 (HMC-1) or mouse bone marrow-derived mast cells (BMMCs) cultured with NGF, and to examine the functions of proteins involved.

METHODS

NGF (10 ng/ml) was added to cell culture medium every other day for 10 days for HMC-1 or twice a week for 5 weeks for BMMCs. Granule formation was determined by electron microscopy or May-Grunwald-Giemsa staining, TNF-alpha by ELISA, expressions of various proteins by two-dimensional gel electrophoresis (2-DE), siRNA transfection by Lipofectamine 2000, and the expressions of pyruvate kinase and annexin I by immunoblotting.

RESULTS

After NGF treatment, granule formation and total amounts of granular mediator, TNF-alpha increased in both mast cells. This TNF-alpha was released by calcium ionophore or by antigen/antibody reaction. Expressions of pyruvate kinase and annexin I obtained by 2-DE were confirmed by immunoblotting and siRNA-transfected HMC-1 cells. Expressions of proteins, granule formation and TNF-alpha content were blocked by both the TrkA inhibitor, K252a, and the ERK inhibitor, PD98059, but not by the PI3 kinase inhibitors, LY294002 and wortmannin.

CONCLUSION

These data suggest that pyruvate kinase and annexin I expressed by NGF contribute to granule formation containing TNF-alpha as well as other mediators in mast cells, which play a major role in allergic diseases via a TrkA/ERK pathway.

FcepsilonRI- and Fcgamma receptor-mediated production of reactive oxygen species by mast cells is lipoxygenase- and cyclooxygenase-dependent and NADPH oxidase-independent

We investigated the enzymes responsible for FcepsilonRI-dependent production of reactive oxygen species (ROS) and the influence of ROS on mast cell secretory responses. 5-Lipoxygenase (5-LO) was the primary enzyme involved in ROS production by human mast cells (huMC) and mouse bone marrow-derived mast cells (mBMMC) following FcepsilonRI aggregation because incubation with 5-LO inhibitors (AA861, nordihydroguaiaretic acid, zileuton) but not a flavoenzyme inhibitor (diphenyleneiodonium) completely abrogated Ag-induced dichlorodihydrofluorescein (DCF) fluorescence. Furthermore, 5-LO-deficient mBMMC had greatly reduced FcepsilonRI-dependent DCF fluorescence compared with wild type mBMMC or those lacking a functional NADPH oxidase (i.e., gp91(phox)- or p47(phox)-deficient cells). A minor role for cyclooxygenase (COX)-1 in FcepsilonRI-dependent ROS production was demonstrated by inhibition of Ag-mediated DCF fluorescence by a COX-1 inhibitor (FR122047) and reduced DCF fluorescence in COX-1-deficient mBMMC. Complete abrogation of FcepsilonRI-dependent ROS production in mast cells had no effect on degranulation or cytokine secretion. In response to the NADPH oxidase-stimulating agents including PMA, mBMMC and huMC produced negligible ROS. IgG-coated latex beads did stimulate ROS production in huMC, and in this experiment 5-LO and COX again appeared to be the enzymatic sources of ROS. In contrast, IgG-coated latex bead-induced ROS production in human polymorphonuclear leukocytes occurred by the NADPH oxidase pathway. Thus mBMMC and huMC generate ROS by 5-LO and COX-1 in response to FcepsilonRI aggregation; huMC generate ROS upon exposure to IgG-coated latex beads by 5-LO and COX; and ROS appear to have no significant role in FcepsilonRI-dependent degranulation and cytokine production.

Lower airways inflammation in allergic rhinitics: a comparison with asthmatics and normal controls

BACKGROUND

Allergic rhinitis (AR) and asthma represent a continuum of atopic disease. AR is believed to pre-dispose an individual to asthma. Compared with asthmatics and normal controls, the inflammatory response in the lower airways of rhinitics is not fully elucidated. To test the hypothesis that the inflammatory response in the airways of subjects with AR is at a level intermediate between that in normal controls and asthmatics, we have characterized bronchial inflammation and cytokine mRNA levels in non-asthmatic allergic rhinitics and compared it with subjects with allergic asthma and with normal controls.

METHODS

Endobronchial mucosal biopsies were obtained at bronchoscopy from 14 allergic rhinitics, 16 asthmatics and 21 normal controls. Biopsies were embedded into glycol methacrylate resin for immunohistochemical analysis of cellular inflammation and snap frozen for semi-quantitative PCR analysis of cytokine mRNA levels.

RESULTS

Airway inflammation in rhinitic subjects was characterized by an increase in submucosal eosinophils, mast cells and the mRNA expression of TNF-alpha, at an intermediate level between healthy and asthmatics. In addition, CD3(+) and CD8(+) lymphocytes in the epithelium, the endothelial expression of vascular adhesion molecule-1 and IL-1 beta mRNA were higher in the allergic rhinitics compared with both normal controls and asthmatics, whereas growth-related oncogene alpha-mRNA was decreased in AR compared with both healthy and asthmatics. Airway inflammation in the asthmatic group was characterized by higher numbers of eosinophils and mast cells, together with an increase in TNF-alpha-mRNA compared with both healthy and rhinitics. IFN-gamma mRNA was the highest in normal controls and lowest in the asthmatics.

CONCLUSIONS

In individuals with AR the present data suggest an intermediate state of airway inflammation between that observed in normal individuals and subjects with clinical asthma. It is also indicated that IFN-gamma production by CD8(+) T lymphocytes could be protective against the development of airway hyperresponsiveness. Further work is needed to evaluate this hypothesis.

Anti-IgE antibodies for the treatment of IgE-mediated allergic diseases

The pharmacological purposes of the anti-IgE therapy are to neutralize IgE and to inhibit its production to attenuate type I hypersensitivity reactions. The therapy is based on humanized IgG1 antibodies that bind to free IgE and to membrane-bound IgE on B cells, but not to IgE bound by the high-affinity IgE.Fc receptors on basophils and mast cells or by the low-affinity IgE.Fc receptors on B cells. After nearly 20 years since inception, therapeutic anti-IgE antibodies (anti-IgE) have been studied in about 30 Phase II and III clinical trials in many allergy indications, and a lead antibody, omalizumab, has been approved for treating patients (12 years and older) with moderate-to-severe allergic asthma. Anti-IgE has confirmed the roles of IgE in the pathogenesis of asthma and helped define the concept "allergic asthma" in clinical practice. It has been shown to be safe and efficacious in treating pediatric allergic asthma and treating allergic rhinitis and is being investigated for treating peanut allergy, atopic dermatitis, latex allergy, and others. It has potential for use to combine with specific and rush immunotherapy for increased safety and efficacy. Anti-IgE thus appears to provide a prophylactic and therapeutic option for moderate to severe cases of many allergic diseases and conditions in which IgE plays a significant role. This chapter reviews the evolution of the anti-IgE concept and the clinical studies of anti-IgE on various disease indications, and presents a comprehensive analysis on the multiple intricate immunoregulatory pharmacological effects of anti-IgE. Finally, it reviews other approaches that target IgE or IgE-expressing B cells.

Early onset airway obstruction in response to organic dust in the horse

Equine recurrent airway obstruction (RAO) has been used as a naturally occurring model of human asthma. However, it is unknown whether there is an early-phase response in RAO. The aim of this study was to determine whether exposure to organic dust induces immediate changes in lung function in RAO-affected horses, which could be mediated by airway mast cells. Six RAO-affected horses in remission and six control horses were challenged with hay-straw dust suspension by nebulization. Total respiratory resistance at 1 Hz, measured by forced oscillation, was increased from 0.62 ± 0.09 cmH2O·l−1·s (mean ± SE) to 1.23 ± 0.20 cmH2O·l−1·s 15 min after nebulization in control horses ( P = 0.023) but did not change significantly in the RAO group. Total respiratory reactance at 1 Hz ( P = 0.005) was significantly lower in the control horses (−0.77 ± 0.07 cmH2O·l−1·s) than in the RAO group (−0.49 ± 0.04 cmH2O·l−1·s) 15 min after nebulization. Bronchoalveolar lavage fluid (BALF) histamine concentration was significantly elevated 10 and 20 min postnebulization in control horses but not in RAO horses. Minimum reactance at 1 Hz in the early postnebulization period significantly correlated with both prechallenge BALF mast cell numbers ( r = −0.65, P = 0.02) and peak BALF histamine concentration postnebulization ( r = −0.61, P = 0.04). In conclusion, RAO horses, unlike human asthmatic patients, do not exhibit an early-phase response. However, healthy control horses do demonstrate a mild but significant early (<20 min) phase response to inhaled organic dust. This response may serve to decrease the subsequent dose of dust inhaled and as such provide a protective mechanism, which may be compromised in RAO horses.

Phospholipase C gamma negatively regulates Rac/Cdc42 activation in antigen-stimulated mast cells

The Rho GTPases Rac and Cdc42 play a central role in the regulation of secretory and cytoskeletal responses in antigen-stimulated mast cells. In this study, we examine the kinetics and mechanism of Rac and Cdc42 activation in the rat basophilic leukemia RBL-2H3 cells. The activation kinetics of both Rac and Cdc42 show a biphasic profile, consisting of an early transient peak at 1 min and a late sustained activation phase at 20-40 min. The inhibition of phospholipase C (PLC)gamma causes a twofold increase in Rac and Cdc42 activation that coincides with a dramatic production of atypical filopodia-like structures. Inhibition of protein kinase C using bisindolylmaleimide mimics the effect of PLCgamma inhibition on Rac activation, but not on Cdc42 activation. In contrast, depletion of intracellular calcium leads to a complete inhibition of the early activation peak of both Rac and Cdc42, without significant effects on the late sustained activation. These data suggest that PLCgamma is involved in a negative feedback loop that leads to the inhibition of Rac and Cdc42. They also suggest that the presence of intracellular calcium is a prerequisite for both Rac and Cdc42 activation.

Regulation of mast cells by beta-agonists

The human lung mast cell is known to be a critical effector cell in the mediation of asthma. Activation of the mast cell by allergens and other stimuli leads to the release and generation of a wide variety of autacoids that cause bronchoconstriction, promote inflammation, and may influence airway remodeling. Therefore, the stabilization of mast cells has obvious value in the prevention of asthma. Among the drugs used to treat asthma, only beta-agonists are effective stabilizers of mast cells. Both short- and long-acting beta-agonists are effective against mast cells, but there are differences between agonists regarding the extent of inhibitory activity attained. Consequently, the type of beta-agonist prescribed influences the degree of mast cell stabilization possible. Despite the potential value of attenuating mast cell activity with beta-agonists, this benefit may diminish with time because of the development of tolerance. Both short- and long-acting beta-agonists can induce tolerance to mast cell stabilization, and generally, higher efficacy agonists tend to induce greater levels of tolerance; however, weaker agonists induce greater levels of tolerance than might be expected. Tolerance to the mast-cell-stabilizing effects of beta- agonists may be an issue clinically, because this occurs more readily than tolerance to smooth muscle relaxation. This could lead to a situation in which beta-agonists fail to prevent the release of mediators from mast cells but can still effectively relax airway smooth muscle. The continued ability to bronchodilate could mask the unfavorable consequences of unchecked mediator release from mast cells.

Prostaglandin E2 activates EP2 receptors to inhibit human lung mast cell degranulation

The prostanoid, PGE2, is known to inhibit human lung mast cell activity. The aim of the present study was to characterize the EP receptor that mediates this effect. PGE2 (pEC(50), 5.8+/-0.1) inhibited the IgE-mediated release of histamine from mast cells in a concentration-dependent manner. Alternative EP receptor agonists were studied. The EP2-selective agonist, butaprost (pEC50, 5.2+/-0.2), was an effective inhibitor of mediator release whereas the EP1/EP3 receptor agonist, sulprostone, and the EP1-selective agonist, 17-phenyl-trinor-PGE2, were ineffective. The DP agonist PGD2, the FP agonist PGF(2alpha), the IP agonist iloprost and the TP agonist U-46619 were ineffective inhibitors of IgE-mediated histamine release from mast cells. PGE2 induced a concentration-dependent increase in intracellular cAMP levels in mast cells. The effects of the EP1/EP2 receptor antagonist, AH6809, and the EP4 receptor antagonist, AH23848, on the PGE2-mediated inhibition of histamine release were determined. AH6809 (pK(B), 5.6+/-0.1) caused a modest rightward shift in the PGE2 concentration-response curve, whereas AH23848 was ineffective. Long-term (24 h) incubation of mast cells with either PGE2 or butaprost (EP2 agonist), but not sulprostone (EP1/EP3 agonist), caused a significant reduction in the subsequent ability of PGE2 to inhibit histamine release. Collectively, these data suggest that PGE2 mediates effects on human lung mast cells by interacting with EP2 receptors.

A role for the Mycoplasma pneumoniae adhesin P1 in interleukin (IL)-4 synthesis and release from rodent mast cells

Mycoplasma pneumoniae is a respiratory tract pathogen associated with exacerbations in patients with chronic asthma, yet relatively little is known about the potential role of this organism in asthma pathogenesis. Our previous studies demonstrated that RBL-2H3 mast cells co-cultured with M. pneumoniae released preformed inflammatory mediators, synthesized multiple cytokine mRNA species, and released IL-4 protein. In this study, we sought to determine the mechanism by which M. pneumoniae activates mast cell cytokine production. Cytokine mRNA upregulation and IL-4 protein production in RBL cells were induced almost exclusively by plastic-adherent M. pneumoniae cultures (MpA). Organisms grown under non-adherent conditions (MpN) were unable to induce cytokine responses efficiently. Western blots demonstrated that MpA was enriched for P1, the major M. pneumoniae adhesin, compared to MpN. M. pneumoniae-induced IL-4 release from RBL cells was inhibited >85% by anti-P1 monoclonal antibodies. Additionally, a P1-deficient strain of the bacteria was unable to efficiently induce IL-4 release. Desialation of RBL cell surface glycoproteins by neuraminidase treatment eliminated IL-4 release. We conclude that P1 plays an important role in M. pneumoniae-induced cytokine responses in RBL mast cells and that direct contact between the organism and sialated residues on the RBL surface mediates this activation.

Human airway epithelial cell determinants of survival and functional phenotype for primary human mast cells

Mast cells (MCs) are found in increased numbers at airway mucosal surfaces in asthmatic patients. Because human airway epithelial cells (HAECs) actively participate in airway inflammatory responses and are in direct contact with MCs in the mucosa, we hypothesized that HAEC-MC interactions may contribute to the differentiation and survival of MCs in the airway mucosa. Here, we show that HAECs express mRNA and protein for soluble and membrane-bound stem cell factor, releasing soluble stem cell factor into the cell culture supernatant at a concentration of 5.9 +/- 0.1 ng per 10(6) HAEC. HAECs were able to support MC survival in coculture in the absence of any exogenous cytokines for at least 4 d. Before the initiation of coculture, MCs were uniformly tryptase and chymase (MC(TC)) double positive, but by 2 d of coculture the majority of MCs expressed tryptase (MC(T)) alone. MCs supported in coculture generated low amounts of cysteinyl-leukotrienes (cys-LT) after FcepsilonRI-dependent activation (0.2 +/- 0.1 ng of cys-LT per 10(6) cells) and required priming with IL-4 and IL-3 during coculture to achieve a quantity of cys-LT generation within the range expected for human lung mucosal MC (26.5 +/- 16 ng of cys-LT per 10(6) cells). In these culture conditions, HAECs were able to direct mucosal MC protease phenotype, but T cell-derived Th2 cytokines were required for the expression of a functional airway MC eicosanoid phenotype. Thus, distinct cell types may direct unique aspects of reactive mucosal MC phenotype in the airways.

Surfactant protein D decreases pollen-induced IgE-dependent mast cell degranulation

Mast cells play a key role in allergy and asthma. They reside at the host-environment interface and are among the first cells to make contact with inhaled microorganisms and particulate antigens. Pulmonary surfactant proteins A and D (SP-A and SP-D) function in lung host defense by enhancing microbe phagocytosis and mediating other immune cell functions, but little is known about their effects on mast cells. We hypothesized that SP-A and/or SP-D modulate IgE-dependent mast cell functions. Pollen starch granules (PSG) extracted from Dactylis glomerata and coated with trinitrophenol (TNP) were used as a model of an inhaled organic particulate allergen. Our data revealed that SP-D inhibited by 50% the release of beta-hexosaminidase by peritoneal mast cells sensitized with IgE anti-TNP and stimulated with TNP-PSG. In contrast, SP-A had no effect. Furthermore, SP-D aggregated PSG in a dose-dependent manner, and this aggregation was mediated by SP-D's carbohydrate recognition domain. A single arm SP-D mutant (RrSP-Dser15,20) neither aggregated PSG nor inhibited degranulation, suggesting that multimerization of SP-D is required for maximal PSG aggregation and inhibition of PSG-induced mast cell degranulation. This study is the first to demonstrate that SP-D modulates IgE-mediated mast cell functions, which are important in asthma and allergic inflammation.

Ultrastructure of bronchial biopsies from patients with allergic and non-allergic asthma

Epithelial damage is commonly found in airways of asthma patients. The aim of this study was to investigate epithelial damage in allergic and non-allergic asthma at the ultrastructural level. Bronchial biopsies obtained from patients with allergic asthma (n=11), non-allergic asthma (n=7), and healthy controls (n=5) were studied by transmission electron microscopy. Epithelial damage was found to be extensive in both asthma groups. Both in basal and in columnar cells, relative desmosome length was reduced by 30-40%. In columnar cells, half-desmosomes (i.e., desmosomes of which only one side was present) were frequently noticed. Eosinophils showing piece-meal degranulation were commonly observed in allergic asthma. Degranulating mast cells were more often observed in allergic asthma. Goblet cell hyperplasia was only found in allergic asthma. Lymphocytes were increased in both groups. In both groups, the lamina densa of the basal lamina was thicker than the control by about 40-50%. In allergic asthma the lamina densa was irregular with focal thickening. While there was always a tendency for changes (epithelial damage, desmosomes, degranulating mast cells, basal lamina) to be more extensive in allergic asthma compared to non-allergic asthma, there was no significant difference between the two groups in this respect. Reduced desmosomal contact may be an important factor in the epithelial shedding observed in patients with asthma.

Dual effects of acetylsalicylic acid on mast cell degranulation, expression of cyclooxygenase-2 and release of pro-inflammatory cytokines

Several studies have demonstrated that nonsteroidal anti-inflammatory drugs, such as acetylsalicylic acid (ASA), can have inhibitory or enhancing effects on inflammatory cell function. These effects seem independent of cyclooxygenase activity and prostaglandin synthesis inhibition. Here, we examined the effect of ASA on bone marrow-derived mast cells in more detail. ASA blocked the expression of cyclooxygenase-2, the production of tumor necrosis factor-alpha and interleukin-6, and the release of granule mediators from mast cells in a concentration-dependent fashion. Concomitantly, ASA inhibited nuclear factor (NF)-kappaB activity, as well as the phosphorylation and breakdown of the inhibitory protein IkappaB-alpha. We thus propose that the anti-inflammatory effects of ASA in mast cells are due to suppression of IkappaB kinase activity, thereby inhibiting subsequent phosphorylation and degradation of IkappaB-alpha, activation of NF-kappaB, and transcription of proinflammatory cytokines. The inhibition of BMMC degranulation was independent of NF-kappaB activation, however. Interestingly, the expression of cyclooxygenase-2 was not inhibited at 1mM ASA, but was even enhanced significantly. The latter might contribute to the adverse effects of ASA in ASA-sensitive asthmatics.

Inhibition of mast cells by interleukin-10 gene transfer contributes to protection against acute myocarditis in rats

Progression of acute myocarditis involves a variety of inflammatory events. Mast cells have been implicated as the source of various cytokines, chemokines and histamine in acute inflammation and fibrosis. Interleukin (IL)-10 has well-known immunomodulatory actions that are exerted during the recovery phase of myocarditis. In this study, 9-week-old male Lewis rats were immunized with cardiac myosin. A plasmid vector expressing mouse IL-10 cDNA (800 mug per rat) was then transferred three times (7, 12 and 17 days after immunization) into the tibialis anterior muscles of the rats by electroporation. Microscopic examination of mast cells was carried out on toluidine blue-stained transverse sections of the mid ventricles. Mouse IL-10 gene transfer significantly reduced mast cell density, cardiac histamine concentration and mast cell growth, and prevented mast cell degranulation. Furthermore, improvement in both myocardial function and the overall condition of the rats was evident from the reduction in the heart weight-to-body weight ratio and inflammatory infiltration as well as improvement in hemodynamic and echocardiographic parameters. These findings suggest that IL-10 gene transfer by electroporation protected against myocarditis via mast cell inhibition.

Urinary leukotriene E4 and 9 alpha, 11 beta-prostaglandin F concentrations in mild, moderate and severe asthma, and in healthy subjects

BACKGROUND

Airway inflammation in asthma is associated with cysteinyl leukotriene and prostaglandin D(2) production. Measurement of urinary metabolites of these eicosanoids may be useful for monitoring asthma patients. However, the influence of asthma phenotype and severity on basal urinary excretion of these metabolites is unknown.

OBJECTIVE

To compare urinary leukotriene (LT)E(4) and 9 alpha, 11 beta-prostaglandin (PG)F(2) concentrations in large groups of mild, moderate and severe asthmatic patients and healthy control subjects.

METHODS

Asthma severity, treatment and aspirin sensitivity were assessed by questionnaire in 168 asthmatic patients. Basal LTE(4) and 9 alpha, 11 beta-PGF(2) concentrations were measured in urine samples from these patients and from 175 control subjects using enzyme immunoassays.

RESULTS

Urinary LTE(4) was correlated with 9 alpha, 11 beta-PGF(2) in both control subjects and asthmatic patients (P<0.002). Median LTE(4) and 9 alpha, 11 beta-PGF(2) concentrations in patients with severe asthma were significantly reduced compared with mild asthmatic patients (P<0.05 and <0.001, respectively). Urinary 9 alpha, 11 beta-PGF(2), but not LTE(4) was lower in asthmatic patients using inhaled corticosteroids (P<0.02). Multiple regression analysis indicated that urinary 9 alpha, 11 beta-PGF(2) concentration was negatively correlated with asthma severity (P=0.003) and also with % predicted FEV(1) (forced expiratory volume in 1 s) (P=0.005).

CONCLUSIONS

Baseline urinary LTE(4) and 9 alpha, 11 beta-PGF(2) concentrations are of limited value in discriminating between patients with different severities of asthma. Reduced urinary LTE(4) and 9 alpha, 11 beta-PGF(2) in patients with severe asthma suggest that direct or indirect effects of high-dose corticosteroid therapy combined with other factors associated with severe asthma may influence eicosanoid production. However, the negative association of urinary 9 alpha, 11 beta-PGF(2) with lung function suggests an adverse effect of chronic PGD(2) production on lung function in asthma, irrespective of severity.

Gene expression of cardiac mast cell chymase and tryptase in a murine model of heart failure caused by viral myocarditis

This study examined the gene expression of mouse mast cell proteases to clarify their role in the pathophysiology of viral myocarditis. Male DBA/2 mice were inoculated intraperitoneally with the encephalomyocarditis virus and the gene expression of mast cell chymase, mouse mast cell protease (mMCP)-4 and -5, and tryptase, mMCP-6, matrix metalloproteinase (MMP)-9 and type-I procollagen was measured by real-time quantitative RT-PCR analysis. The gene expression of mMCP-4, -5 and -6 mRNA was increased at 5 days, and continued to increase to day 14, coinciding with a prominent inflammatory reaction and extensive myocardial necrosis and fibrosis. The gene expression of MMP-9 was also increased, and there was a significant correlation between upregulation of mast cell proteases and MMP-9. The gene expression of type-I procollagen was increased at 5 days and continued to increase to day 14, suggesting that a fibrotic process had already begun during the acute stage of viral myocarditis. These findings suggest that mast cell chymase and tryptase participate in the acute inflammation and remodeling process of viral myocarditis.

Nuclear import of N-terminal FAK by activation of the FcepsilonRI receptor in RBL-2H3 cells

As FAK integrates membrane receptor signalling, yet is also found in the nucleus, we investigated whether nuclear FAK is regulated by membrane receptor activation. Activation of the mast cell FcepsilonRI receptor leads to the release and synthesis of inflammatory mediators as well as increased proliferation and survival. Using RBL-2H3 basophilic leukaemia cells, FAK and the FcepsilonRI receptor were co-localised following cross-linking of IgE with antigen. This also resulted in a significant increase in the nucleus of several N-terminal FAK fragments, the largest of which included the kinase domain but not the focal adhesion targeting domain. This was confirmed using cells that stably expressed recombinant EGFP-FAK. Furthermore, treatment of EGFP-FAK expressing cells with Leptomycin B, an inhibitor of nuclear export, resulted in increased nuclear localisation of EGFP-FAK. Therefore, FAK can shuttle between the nuclear and cytoplasmic compartments and the cellular distribution of N-terminal FAK is regulated by membrane receptor activation.

Neurotrophins and neurotrophin receptors in allergic asthma

The neurotrophins nerve growth factor, brain-derived neurotrophic factor, neurotrophin-3 (NT-3) and NT-4 play a pivotal role in the development of the nervous system. Despite their well-known effects on neurons, elevated neurotrophin concentrations have been observed under pathological conditions in sera of patients with inflammatory disorders. Patients with asthma feature both airway inflammation and an abnormal airway reactivity to many unspecific stimuli, referred to as airway hyperresponsiveness, which is, at least partly, neuronally controlled. Interestingly, these patients show increased levels of neurotrophins in the blood as well as locally in the lung. It has been demonstrated that neurotrophin release from immune cells is triggered by allergen contact. The presence of neurotrophins and the neurotrophin receptors p75 (p75NTR), tyrosine kinase A (TrkA), TrkB and TrkC have been described in several immune cells. There is strong evidence for an involvement of neurotrophins in regulation of hematopoiesis and, in addition, in modulation of immune cell function in mature cells circulating in blood or resting in lymphatic organs and peripheral tissues. The aim of this review is to demonstrate possible roles of neurotrophins during an allergic reaction in consideration of the temporospatial compartimentalization.

Bronchial mast cells are the dominating LTC4S-expressing cells in aspirin-tolerant asthma

The increased bronchial production of leukotriene C4 (LTC4) in asthma is assumed to derive from infiltrating eosinophils expressing LTC4-synthase (LTC4S). Multicolor immunohistofluorescence examination of bronchial cryosections from 30 treated, untreated, or bronchial antigen-provoked aspirin-tolerant individuals with asthma and nine control subjects revealed that the dominating LTC4S-expressing cells were mast cells (> 80%), and not eosinophils. Whereas 95% of the mast cells expressed high levels of LTC4S, only 8-27% of the eosinophils expressed low levels. Image analysis revealed a significantly higher LTC4S expression levels in mast cells than in eosinophils. The bronchial mRNA levels for LTC4S did not correlate with the densities of LTC4S-positive eosinophils or mast cells. Treated individuals with asthma with more than 12% reversibility had significantly higher density of LTC4S-positive mast cells than those with less reversibility, and it correlated significantly with reduction in lung function (FEV1-predicted), both before and after salbutamol inhalation. Thus, mucosal mast cells, and not eosinophils, were the dominating LTC4S-containing cells in both untreated and treated aspirin-tolerant asthma. The density of LTC4S-positive mast cells correlated, moreover, with both the reduction in lung function and the degree of reversibility in treated asthma.

Human cord blood-derived mast cells synthesize and release I-309 in response to IgE

Mast cells are the central mediating cells of allergic reactions. Binding of allergen specific IgE to high affinity IgE receptor (Fcepsilon RI) and subsequent binding of allergen by the IgE causes receptor cross-linking and activation. In a study examining the differential gene expression in human cord blood-derived mast cells (CBMCs) mediated by activation of Fcepsilon RI both with IgE and IgE followed by cross-linking with alpha-IgE, the chemokine I-309 was found to be upregulated. I-309 is the ligand for the CCR8 receptor and is responsible for chemoattraction of TH2 type T-cells. Interestingly, I-309 RNA and protein levels were elevated not only in response to IgE/alpha-IgE activation but also by IgE alone. In addition, the I-309 levels were augmented by growth of the CBMCs in the presence of the proinflammatory cytokine IL-4. GM-CSF and MIP-1alpha secretion was also induced by IgE. These results suggest that IgE, through the production and release of cytokines such as I-309, GM-CSF and MIP-1alpha could promote an inflammatory reaction in the absence of antigen stimulation of mast cells.

Airway tissue mast cells in persistent asthma: predictor of treatment failure when patients discontinue inhaled corticosteroids

STUDY OBJECTIVES

To determine if persistent airway tissue mast cells are associated with treatment failure when patients discontinue inhaled corticosteroids (ICS).

DESIGN

Double-blind, randomized, placebo-controlled trial.

SETTING

Multicenter, tertiary referral centers.

PATIENTS OR PARTICIPANTS

Forty-five subjects with asthma recruited from six medical centers in the United States.

INTERVENTIONS

The Asthma Clinical Research Network undertook a 28-week, randomized, multicenter, double-blind, placebo-controlled trial of 164 subjects with clinically stable, persistent asthma. A subset of subjects (n = 45) underwent bronchoscopy with endobronchial biopsy and BAL at the end of a 6-week run-in period, during which all subjects received triamcinolone acetonide (TAA), 400 microg bid. Airway tissue mast cells, eosinophils, neutrophils, macrophages, and T cells were quantified morphometrically along with determination of BAL tryptase. At the end of the run-in period, subjects were then randomized to receive salmeterol (42 micro g bid), placebo, or continue TAA for 16 weeks followed by a second bronchoscopy.

MEASUREMENTS AND RESULTS

Outcome variables included airway tissue mast cells, eosinophils, neutrophils, macrophages, and T cells that were quantified morphometrically and BAL tryptase. Thirty-five subjects completed the treatment phase; an additional 10 subjects, who were randomized to either salmeterol or placebo after the run-in, had treatment failure. When the bronchoscopy results performed at the end of the run-in, prior to randomization, were analyzed, the treatment failure group demonstrated significantly more tissue mast cells as compared to the nontreatment failure group despite 6 weeks of therapy with TAA (p = 0.04). BAL tryptase was also significantly higher in the treatment failure group (p < 0.0001). Of those subjects who completed the study, tissue mast cells and BAL tryptase did not change significantly within any of the treatment groups during the treatment phase (p > 0.05).

CONCLUSIONS

Persistent elevations in airway tissue mast cells and BAL tryptase after treatment with TAA predict treatment failure in patients for whom discontinuation of ICS is being considered.

Distinct phosphoinositide 3-kinases mediate mast cell degranulation in response to G-protein-coupled versus FcepsilonRI receptors

Phosphoinositide (PI) 3-kinases are critical regulators of mast cell degranulation. The Class IA PI 3-kinases p85/p110beta and p85/p110delta but not p85/p110alpha are required for antigen-mediated calcium flux in RBL-2H3 cells (Smith, A. J., Surviladze, Z., Gaudet, E. A., Backer, J. M., Mitchell, C. A., and Wilson, B. S. et al., (2001) J. Biol. Chem. 276, 17213-17220). We now examine the role of Class IA PI 3-kinases isoforms in degranulation itself, using a single-cell degranulation assay that measures the binding of fluorescently tagged annexin V to phosphatidylserine in the outer leaflet of the plasma membrane of degranulated mast cells. Consistent with previous data, antibodies against p110delta and p110beta blocked FcepsilonR1-mediated degranulation in response to FcepsilonRI ligation. However, antigen-stimulated degranulation was also inhibited by antibodies against p110alpha, despite the fact that these antibodies have no effect on antigen-induced calcium flux. These data suggest that p110alpha mediates a calcium-independent signal during degranulation. In contrast, only p110beta was required for enhancement of antigen-stimulated degranulation by adenosine, which augments mast cell-mediated airway inflammation in asthma. Finally, we examined carbachol-stimulated degranulation in RBL2H3 cells stably expressing the M1 muscarinic receptor (RBL-2H3-M1 cells). Surprisingly, carbachol-stimulated degranulation was blocked by antibody-mediated inhibition of the Class III PI 3-kinase hVPS34 or by titration of its product with FYVE domains. Antibodies against Class IA PI 3-kinases had no effect. These data demonstrate: (a) a calcium-independent role for p110alpha in antigen-stimulated degranulation; (b) a requirement for p110beta in adenosine receptor signaling; and (c) a requirement for hVPS34 during M1 muscarinic receptor signaling. Elucidation of the intersections between these distinct pathways will lead to new insights into mast cell degranulation.