Mast cell heterogeneity

Mast cells are at the interface between the external environment and the inner organism

Mast cells localized at the level of the mucosal barrier in the skin, lung, and gastrointestinal tract, intervene in the modulation of the function of the epithelial cells and are involved in innate and adaptive defensive responses. In this context, mast cells intervene in the recognition and clearance of microbial pathogens. This mini-review article discusses the role of mast cells in these barrier systems.

Acute Urticaria and Anaphylaxis: Differences and Similarities in Clinical Management

Acute urticaria is a common condition that presents with wheals and/or angioedema. However, these symptoms are also frequent in anaphylaxis, a life-threatening reaction that should be immediately diagnosed and treated. In both, mast cells play a central role in the physiopathology. Causes and triggers of acute urticaria and anaphylaxis are similar in general, but some peculiarities can be observed. The diagnostic approach may differ, accordingly to the condition, suspicious causes, age groups and regions. Adrenaline is the first-line treatment for anaphylaxis, but not for acute urticaria, where H1-antihistamines are the first choice. In this paper, we review the main aspects, similarities and differences regarding definitions, mechanisms, causes, diagnosis and treatment of acute urticaria and anaphylaxis.

Mast Cells in the Mammalian Testis and Epididymis-Animal Models and Detection Methods

Mast cells (MCs) are an evolutionary well-conserved type of cells, mediating and modulating allergic responses in innate immunity and tissue remodeling after chronic inflammation. Among other tissues, they inhabit both the testis and epididymis. In the testis, MCs usually appear in the interstitial compartment in humans, but not in other standard experimental models, like rats and mice. MCs seem to be responsible for testicular tissue fibrosis in different causes of infertility. Although experimental animal models follow the effect on MC activation or penetration to the interstitial tissue like in humans to some extent, there is an inconsistency in the available literature regarding experimental design, animal strain, and detection methods used. This comprehensive review offers an insight into the literature on MCs in mammalian testes and epididymides. We aimed to find the most suitable model for research on MC and offer recommendations for future experimental designs. When using in vivo animal models, tunica albuginea incorporation and standard histological assessment need to be included. Domesticated boar strains kept in modified controlled conditions exhibit the highest similarity to the MC distribution in the human testis. 3D testicular models are promising but need further fine-tuning to become a valid model for MC investigation.

Modern Imaging Technologies of Mast Cells for Biology and Medicine (Review)

Mast cells play an important role in the body defense against allergens, pathogens, and parasites by participating in inflammation development. However, there is evidence for their contributing to the pathogenesis of a number of atopic, autoimmune, as well as cardiovascular, oncologic, neurologic, and other diseases (allergy, asthma, eczema, rhinitis, anaphylaxis, mastocytosis, multiple sclerosis, rheumatoid arthritis, inflammatory gastrointestinal and pulmonary diseases, migraine, etc.). The diagnosis of many diseases and the study of mast cell functions in health and disease require their identification; so, the knowledge on adequate imaging techniques for mast cells in humans and different species of animals is of particular importance. The present review summarizes the data on major methods of mast cell imaging: enzyme histochemistry, immunohistochemistry, as well as histochemistry using histological stains. The main histological stains bind to heparin and other acidic mucopolysaccharides contained in mast cells and stain them metachromatically. Among these are toluidine blue, methylene blue (including that contained in May-Grünwald-Giemsa stain), thionin, pinacyanol, and others. Safranin and fluorescent dyes: berberine and avidin - also bind to heparin. Longer staining with histological dyes or alcian blue staining is needed to label mucosal and immature mast cells. Advanced techniques - enzyme histochemistry and especially immunohistochemistry - enable to detect mast cells high-selectively using a reaction to tryptases and chymases (specific proteases of these cells). In the immunohistochemical study of tryptases and chymases, species-specific differences in the distribution of the proteases in mast cells of humans and animals should be taken into account for their adequate detection. The immunohistochemical reaction to immunoglobulin E receptor (FcεRI) and c-kit receptor is not specific to mast cells, although the latter is important to demonstrate their proliferation in normal and malignant growth. Correct fixation of biological material is also discussed in the review as it is of great significance for histochemical and immunohistochemical mast cell detection. Fluorescent methods of immunohistochemistry and a multimarker analysis in combination with confocal microscopy are reported to be new technological approaches currently used to study various mast cell populations.

Decoding the intricacies of the mast cell compartment

Historically, understanding of the human mast cell (MC) compartment has lagged behind the appreciation of other cell lineages. MCs exist in vascularised tissues but do not under normal circumstances circulate in blood, and there has been no pharmacological agent identified that totally and selectively inhibits human MC function. There are no substantiated accounts of an apparently healthy individual who is severely lacking in MCs. Thus, some of the approaches employed to understand the function of a specific immune cell are not available to the MC biologist. The disease categories that have provided the greatest insight into MC biology have been monoclonal and IgE-mediated MC disorders. This has led to the categorisation of MC diseases as intrinsic or extrinsic to the MC compartment and to the recognition of the role of mediators in MC activation disorders. Mastocytosis as a clonal disorder not only impacts the MC compartment through changes intrinsic to the MC, but also by the effects of episodes of significant release of MC mediators. The availability of newer therapeutic approaches developed to treat monoclonal MC disorders offer insights into how to more selectively approach management of MC centric diseases.

Granulocyte-targeted therapies for airway diseases

The average respiration rate for an adult is 12-20 breaths per minute, which constantly exposes the lungs to allergens and harmful particles. As a result, respiratory diseases, which includes asthma, chronic obstructive pulmonary disease (COPD) and acute lower respiratory tract infections (LTRI), are a major cause of death worldwide. Although asthma, COPD and LTRI are distinctly different diseases with separate mechanisms of disease progression, they do share a common feature - airway inflammation with intense recruitment and activation of granulocytes and mast cells. Neutrophils, eosinophils, basophils, and mast cells are crucial players in host defense against pathogens and maintenance of lung homeostasis. Upon contact with harmful particles, part of the pulmonary defense mechanism is to recruit these cells into the airways. Despite their protective nature, overactivation or accumulation of granulocytes and mast cells in the lungs results in unwanted chronic airway inflammation and damage. As such, understanding the bright and the dark side of these leukocytes in lung physiology paves the way for the development of therapies targeting this important mechanism of disease. Here we discuss the role of granulocytes in respiratory diseases and summarize therapeutic strategies focused on granulocyte recruitment and activation in the lungs.

Mast Cell Histamine-Induced Calcium Transients in Cultured Human Peritoneal Mesothelial Cells

Objective

Peritoneal inflammation results from a complex interplay of events initiated by macrophage activity in response to infection, with the stimulation of mesothelial cell cytokine release amplifying the recruitment of blood-borne defense cells to the site of injury. Resident peritoneal mast cells may add to this complexity with mast cell derived cytokines released during this cascade. This study examined the influence of histamine, a mast cell derived inflammatory mediator, on the initial activation of human peritoneal mesothelial cells (HPMC) by intracellular free calcium (Cai2+) mobilization, and changes to the actin cytoskeleton.

Design

HPMC signal transduction was examined in response to histamine (1.0 mmol/L) compared to fetal bovine serum (FBS) (0.1 %) and 4-br-A23187 (1.0 μmol/L). Intracellular free calcium was measured in fura-2 loaded cells with and without external calcium (Ca2ex+t), or Ca2ex+t with verapamil (100 μmol/L). Following treatment with agonists, HPMC actin cytoskeleton was stained using direct immunocytochemistry.

Results

HPMC responded to histamine with a twofold transient rise in Cai2+ which returned to the baseline, in contrast with FBS and A23187–induced Cai2+ transients, which returned to elevated resting values. In the absence of Ca2ex+t’ all agents produced a calcium transient indicative of calcium release from intracellular stores. Histamine induced calcium -dependent changes to the cytoskeleton and cellular organization, including increased actin stress fibers.

Conclusion

Histamine produced large specific receptor-mediated calcium transients in HPMC, which included components of calcium release from intracellular stores and receptor -mediated calcium influx processes. The observed response to histamine raises the possibility that histamine derived from resident mast cells may modulate mesothelial cell function, in part by calciumdependent pathways, and influence the performance of the peritoneal membrane during peritoneal dialysis.

Enterocolic increase of cannabinoid receptor type 1 and type 2 and clinical improvement after probiotic administration in dogs with chronic signs of colonic dysmotility without mucosal inflammatory changes

BACKGROUND

Colonic dysmotility in dogs can cause different GI signs. Sometimes, histology of enterocolic biopsies does not reveal inflammatory infiltrates or mucosal lesions that are typically associated with clinical disease activity. It is speculated that, similarly to humans, colonic dysmotility may be anxiety-based, although recent data demonstrate that irritable bowel syndrome (IBS) could result from acute infectious enteritis. Specific Lactobacillus spp. strains administered orally in humans induced the expression of μ-opioid and cannabinoid receptors in mucosal enterocytes, modulating intestinal morphine-like analgesic functions. We investigated the potential association of GI signs caused by colonic dysmotility and mucosal expression of cannabinoid receptors in intestinal epithelial cells and the number of mucosal mast cells.

METHODS

Ten to 15 endoscopic biopsies were collected from colonic mucosa of 20 dogs diagnosed with dysmotility disturbances before and after probiotic (Slab51 bacterial blend; Sivoy^® ) administration (3-month period). Number and distribution of mast cells (MCs), and cannabinoid receptor type 1 (CB1) and type 2 (CB2) were evaluated by immunohistochemistry and PCR. Results were compared to data obtained from five clinically healthy dogs (archive samples).

KEY RESULTS

Decreased numbers of MCs (P < .0001) and increased CB1- and CB2-positive epithelial cells (P < .0001) in diseased dogs were positively associated with post-treatment CCECAI scores (P < .0001).

CONCLUSIONS AND INFERENCES

Our results suggest that probiotic administration can reduce signs of colonic dysmotility, possibly due to microbiota modulation and epithelial cell receptor-mediated signaling in intestinal mucosa.

Mast cell chymase: morphofunctional characteristics

During degranulation, mast cells secrete a specific set of mediators defined as "secretome" including the preformed mediators that have already been synthesized by a cell and contained in the cytoplasmic granules. This group includes serine proteases, in particular, chymase and tryptase. Biological significance of chymase depends on the mechanisms of degranulation and is characterized by selective effects on the cellular and non-cellular components of the specific tissue microenvironment. Chymase is known to be closely involved in the mechanisms of inflammation and allergy, angiogenesis, and oncogenesis, remodeling of the extracellular matrix of the connective tissue and changes in organ histoarchitectonics. Number of chymase-positive mast cells in the intra-organ population, and the mechanisms of biogenesis and secretome degranulation appear to be the informative criteria for interpreting the state of the internal organs, characterizing not only the diagnostic efficacy but also the properties of targets of pharmacotherapy. In this review, we discussed the current state of knowledge about mast cell chymase as one of the mast cell secretome proteases. Main issues of the reviewed publications are highlighted with our microscopic images of mast cell chymase visualized using immunohistochemical staining.

Emerging Therapies in Chronic Spontaneous Urticaria

Chronic spontaneous urticaria (CSU) is characterized by typically short-lived and fleeting wheals, angioedema or both, which occur spontaneously and persist for longer than 6 weeks. This term is applied to the most common subtype of chronic urticaria. The underlying pathophysiology for CSU involves mast cell and basophil degranulation with release of histamine, leukotrienes, prostaglandins and other inflammatory mediators. Although a variety of treatments exist, many patients do not tolerate or benefit from the existing therapies and even require more effective treatments. Omalizumab is currently the only licensed biologic for antihistamine-refractory CSU, and novel drugs are under development. This article reviews its current status regarding pathogenesis and approach to treatment as well as therapeutic agents that are under development for the treatment of CSU.

Mast cell heterogeneity and anti-inflammatory annexin A1 expression in leprosy skin lesions

Mast cells (MCs) have important immunoregulatory roles in skin inflammation. Annexin A1 (ANXA1) is an endogenous anti-inflammatory protein that can be expressed by mast cells, neutrophils, eosinophils, monocytes, epithelial and T cells. This study investigated MCs heterogeneity and ANXA1 expression in human dermatoses with special emphasis in leprosy. Sixty one skin biopsies from 2 groups were investigated: 40 newly diagnosed untreated leprosy patients (18 reaction-free, 11 type 1 reaction/T1R, 11 type 2 reaction/T2R); 21 patients with other dermatoses. Tryptase/try+ and chymase/chy + phenotypic markers and toluidine blue stained intact/degranulated MC counts/mm² were evaluated. Try⁺/chy⁺ MCs and ANXA1 were identified by streptavidin-biotin-peroxidase immunostaining and density was reported. In leprosy, degranulated MCs outnumbered intact ones regardless of the leprosy form (from tuberculoid/TT to lepromatous/LL), leprosy reactions (reactional/reaction-free) and type of reaction (T1R/T2R). Compared to other dermatoses, leprosy skin lesions showed lower numbers of degranulated and intact MCs. Try⁺ MCs outnumbered chy⁺ in leprosy lesions (reaction-free/reactional, particularly in T2R), but not in other dermatoses. Compared to other dermatoses, ANXA1 expression, which is also expressed in mast cells, was higher in the epidermis of leprosy skin lesions, independently of reactional episode. In leprosy, higher MC degranulation and differential expression of try⁺/chy⁺ subsets independent of leprosy type and reaction suggest that the Mycobacterium leprae infection itself dictates the inflammatory MCs activation in skin lesions. Higher expression of ANXA1 in leprosy suggests its potential anti-inflammatory role to maintain homeostasis preventing tissue and nerve damage.

Characterization of mast cell populations using different methods for their identification

Mast cells are ubiquitous throughout the human tissues and play an essential role in physiology and pathology. For evaluation of patients with pathological conditions, mast cells were primarily detected using metachromatic staining with toluidine blue. In the last decades, the staining arsenal of pathologists was enriched with enzyme histochemical and immunohistochemical methods, and it was established that depending on species and tissue localization mast cells are not similar both in appearance and function. The aim of this study was to characterize different mast cell populations using the up-to-date methods of their identification. We compared standard metachromatic method for mast cells with enzyme histochemical detection of chloroacetyl esterase and with immunohistochemical detection of tryptase and chymase in human and rodent tissues. Combination of these methods allowed us to assay quantitatively mast cell populations in different organs of humans and rodents. Furthermore, we assessed the appropriate implementation of each of these methods for mast cell identification in diagnostic labs.

Allergies: diseases closely related to cancer

Allergies are hypersensitivity reactions that occur through specific type Th2 immunological mechanisms characterized by different soluble mediators, as well as specific cells of the immune system. In recent decades, evidence has emerged relating this disease with cancer development. However, most of the results of epidemiology studies have been controversial and contradictory. There are mainly two trends. While the first indicates that allergies can reduce the risk of cancer, the other indicates that they may increase this risk. The first trend can be explained by the immunosurveillance hypothesis, which states that the increased immune surveillance after the immune hyper-responsiveness can inhibit or exert a protective effect against the development of cancer. Similarly, the prophylaxis hypothesis suggests that the physical effects of allergy symptoms can prevent cancer by removing potential carcinogens. In contrast, the opposing hypothesis propose that there is a deviation of the immune response toward Th2, which favors the development of cancer, or that the process of chronic inflammation favors the generation of mutations, and therefore the development of cancer. With the purpose of understanding more about these two hypotheses, the main soluble and cellular factors of allergic diseases that could be playing a key role in the development or inhibition of cancer were considered in this review.

Mast cell phenotype, TNFα expression and degranulation status in non-small cell lung cancer

Mast cell infiltration of tumour islets represents a survival advantage in non-small cell lung cancer (NSCLC). The phenotype and activation status of these mast cells is unknown. We investigated the mast cell phenotype in terms of protease content (tryptase-only [MC_T], tryptase + chymase [MC_TC]) and tumour necrosis factor-alpha (TNFα) expression, and extent of degranulation, in NSCLC tumour stroma and islets. Surgically resected tumours from 24 patients with extended survival (ES; mean survival 86.5 months) were compared with 25 patients with poor survival (PS; mean survival 8.0 months) by immunohistochemistry. Both MC_T and MC_TC in tumour islets were higher in ES (20.0 and 5.6 cells/mm² respectively) compared to PS patients (0.0 cells/mm²) (p < 0.0001). Both phenotypes expressed TNFα in the islets and stroma. In ES 44% of MC_T and 37% of MC_TC expressed TNFα in the tumour islets. MC_T in the ES stroma were more degranulated than in those with PS (median degranulation index = 2.24 versus 1.73 respectively) (p = 0.0022), and ES islet mast cells (2.24 compared to 1.71, p < 0.0001). Since both MC_T and MC_TC infiltrating tumour islets in ES NSCLC patients express TNFα, the cytotoxic activity of this cytokine may confer improved survival in these patients. Manipulating mast cell microlocalisation and functional responses in NSCLC may offer a novel approach to the treatment of this disease.

Emerging concepts: mast cell involvement in allergic diseases

In a process known as overt degranulation, mast cells can release all at once a diverse array of products that are preformed and present within cytoplasmic granules. This occurs typically within seconds of stimulation by environmental factors and allergens. These potent, preformed mediators (ie, histamine, heparin, serotonin, and serine proteases) are responsible for the acute symptoms experienced in allergic conditions such as allergic conjunctivitis, allergic rhinitis, allergy-induced asthma, urticaria, and anaphylaxis. Yet, there is reason to believe that the actions of mast cells are important when they are not degranulating. Mast cells release preformed mediators and inflammatory cytokines for periods after degranulation and even without degranulating at all. Mast cells are consistently seen at sites of chronic inflammation, including nonallergic inflammation, where they have the ability to temper inflammatory processes and shape tissue morphology. Mast cells can trigger actions and chemotaxis in other important immune cells (eg, eosinophils and the newly discovered type 2 innate lymphocytes) that then make their own contributions to inflammation and disease. In this review, we will discuss the many known and theorized contributions of mast cells to allergic diseases, focusing on several prototypical allergic respiratory and skin conditions: asthma, chronic rhinosinusitis, aspirin-exacerbated respiratory disease, allergic conjunctivitis, atopic dermatitis, and some of the more common medication hypersensitivity reactions. We discuss traditionally accepted roles that mast cells play in the pathogenesis of each of these conditions, but we also delve into new areas of discovery and research that challenge traditionally accepted paradigms.

miRNA-221-3p Enhances the Secretion of Interleukin-4 in Mast Cells through the Phosphatase and Tensin Homolog/p38/Nuclear Factor-kappaB Pathway

Mast cells play a central role in asthma. Moreover, serum miRNA-221-3p (miR-221) has been shown to be markedly increased in children with asthma. In the current study, we aimed to examine miR-221 expression in an asthma model and elucidate the mechanisms regulating interleukin (IL)-4 secretion in mast cells. Using polymerase chain reaction, we found that miR-221 was upregulated in a murine asthma model and in P815 mast cells after lipopolysaccharide (LPS) stimulation. Moreover, miR-221 upregulated IL-4 secretion from P815 cells, as shown by enzyme-linked immunosorbent assays. Bioinformatics analysis, luciferase reporter gene assays, and western blotting showed that phosphatase and tensin homolog (PTEN) was a target of miR-221 and could block IL-4 secretion stimulated by miR-221. The phosphorylation of p38 (protein) and activity of nuclear factor-kappaB (NF-κB) were increased after overexpression of miR-221, as shown by electrophoretic mobility shift assays. Finally, treatment with specific inhibitors could block IL-4 secretion. In conclusion, miR-221, which was overexpressed in a murine asthma model, stimulated IL-4 secretion in mast cells through a pathway involving PTEN, p38, and NF-κB.

Indication of immune activation in patients with perceived food hypersensitivity

Majority of the patients with perceived food hypersensitivity have irritable bowel syndrome (IBS), and a significant proportion of IBS patients also attribute their gastrointestinal complaints to food items. Different factors such as disturbed intestinal fermentation, enteric dysmotility, post-infectious changes and altered microbial flora in the colon as well as psychological disturbances likely play a role in the pathophysiology and symptoms generation in patients with food hypersensitivity. In addition, a number of studies in these patient groups indicate that local, systemic and mucosal immune systems are activated. The question now is no longer intestinal immune activation, but how the immune system is activated in these patients. In the following review, the potential pathogenetic role of the immune system and evidence of immune activation are reported in patients with perceived food hypersensitivity.

β-Defensins activate human mast cells via Mas-related gene X2

Human β-defensins (hBDs) stimulate degranulation in rat peritoneal mast cells in vitro and cause increased vascular permeability in rats in vivo. In this study, we sought to determine whether hBDs activate murine and human mast cells and to delineate the mechanisms of their regulation. hBD2 and hBD3 did not induce degranulation in murine peritoneal or bone marrow-derived mast cells (BMMC) in vitro and had no effect on vascular permeability in vivo. By contrast, these peptides induced sustained Ca(2+) mobilization and substantial degranulation in human mast cells, with hBD3 being more potent. Pertussis toxin (PTx) had no effect on hBD-induced Ca(2+) mobilization, but La(3+) and 2-aminoethoxydiphenyl borate (a dual inhibitor of inositol 1,4,5-triphosphate receptor and transient receptor potential channels) caused substantial inhibition of this response. Interestingly, degranulation induced by hBDs was substantially inhibited by PTx, La(3+), or 2-aminoethoxydiphenyl borate. Whereas human mast cells endogenously express G protein-coupled receptor, Mas-related gene X2 (MrgX2), rat basophilic leukemia, RBL-2H3 cells, and murine BMMCs do not. Silencing the expression of MrgX2 in human mast cells inhibited hBD-induced degranulation, but had no effect on anaphylatoxin C3a-induced response. Furthermore, ectopic expression of MrgX2 in RBL-2H3 and murine BMMCs rendered these cells responsive to hBDs for degranulation. This study demonstrates that hBDs activate human mast cells via MrgX2, which couples to both PTx-sensitive and insensitive signaling pathways most likely involving Gαq and Gαi to induce degranulation. Furthermore, murine mast cells are resistant to hBDs for degranulation, and this reflects the absence of MrgX2 in these cells.

Double expression of CD34 and CD117 on bone marrow progenitors is a hallmark of the development of functional mast cell of Callithrix jacchus (common marmoset)

Mast cells (MCs) are developed from hematopoietic progenitor cells and play an important role in inflammation. Study of the kinetics of development and accumulation of primate MC in vivo is crucial for the control of human inflammatory diseases, as evolution of the immune system is quite rapid and inflammation including MC response is considered to be different between mouse and human. In the present study, we examined the development of MC from hematopoietic progenitors of Callithrix jacchus (common marmoset), an experimental animal of nonhuman primates. Bone marrow cells were fractionated for the expression of CD34 and CD117 by cell sorting. MCs were developed in vitro or by transplanting the cells to NOD/SCID/IL-2γc knockout (NOG) mice. In vitro culture of CD34(+)CD117(+) (double positive, DP) cells with stem cell factor could generate high-affinity Fc epsilon receptor (FcεR)-expressing CD117(+) cells with typical granules. The developed MC released β-hexosaminidase and produced leukotriene C(4) after the stimulation of FcεRI. Transplantation of DP cells gave rise to a marked expansion of CD34(-)CD45(+)CD117(+)FcεR(+) cells in NOG mice. They expressed transcripts encoding chymase 1 and tryptase β. Differentiation of CD34(-)CD117(+) cells to MCs was relatively limited compared with the DP cells, similarly to human MCs. These results suggest that this marmoset system provides a good model for human MC development.

Mast cell phenotypes and microvessels in non-small cell lung cancer and its prognostic significance

The impact of interstitial inflammatory cells, such as mast cells, and angiogenesis on the prognosis of cancer patients has been reported in many solid tumors, although there is disagreement about their role. We undertook a retrospective study with tissue samples from 65 patients with stage I and II non-small cell lung cancer to assess the clinical pathologic role and prognostic significance of mast cells. Mast cell phenotypes were identified by immunohistochemistry for tryptase and chymase. In addition, we identified microvessels using the endothelial marker CD34. Mast cell and microvessel density was quantified by assessing immunopositive cells in the intratumoral and peritumoral zones of tumor specimens. Both mast cell and microvessel density was higher in the peritumoral zone than the intratumoral zone (P <or= .05). A positive correlation between mast cell (tryptase-chymase phenotype) and microvessel densities was observed in the intratumoral zone (P <or= .05), supporting the involvement of mast cells in the angiogenic process. Regarding survival, a subset of stage I patients had a worse prognosis at five years when low mast cell (tryptase-chymase phenotype) density was found in the peritumoral zone (median survival in months [range]: 27 [1-60] versus 46 [1-60]). Multivariate Cox analysis indicated that this parameter may be an independent prognostic factor (P <or= .05) useful for selecting candidates for earlier treatment.

Time-related changes of the intestinal morphology of Atlantic salmon, Salmo salar L., at two different soybean meal inclusion levels

Abstract Soybean meal (SBM) induces enteritis in the distal intestine of Atlantic salmon. The present study assesses the effects of SBM concentrations on the kinetics of the enteritis process. Fish of 300 g, kept at 12 degrees C, were fed diets with different SBM inclusions: 0%, 10% and 20% SBM for 57 days. Samples of the distal intestine of five fish per treatment were taken for histological and electron microscopical analysis. A semi-quantitative scoring system was used to assess the degree of the morphological changes induced by SBM feeding in the distal intestinal epithelium. The first signs of enteritis appeared earlier in the salmon fed the 20SBM diet than in those fed the 10SBM diet. Thereafter, the condition increased steadily, displaying no signs of recovery. Furthermore, at the lower concentration, the process marking the onset of enteritis began more gradually than at the higher concentration and it displayed a tendency to stabilize after 13-20 days of continuous feeding. Electron microscopy indicated that the endocytosis process was hampered at day 3 of 20SBM and at 7 days of 10SBM. Furthermore, a strong reduction of microvilli was already evident after 7 days of 20SBM feeding, thus indicating a decreased uptake capacity of the distal enterocytes. In addition, transformation and migration of eosinophilic granulocytes was observed, which, in combination with the lysozyme C immunoreactivity supports their protective role during the inflammatory process in the distal gut of Atlantic salmon. It can be concluded that the severity of enteritis and its kinetics are concentration-dependent, showing no signs of recovery during feeding with diets containing SBM.

MAST CELLS INDUCE ACTIVATION OF HUMAN LUNG FIBROBLASTS IN VITRO

Mast cells are able to induce proliferation of skin fibroblasts; however, their effect on lung fibroblasts has not been clearly established. Using in vitro cocultures of rat or human mast cells with lung fibroblasts, the authors determined whether mast cells alter proliferation, collagen synthesis, and metalloproteinase production from lung fibroblasts. Mast cells enhanced the proliferation of human fibroblasts (mean +/- SEM: 90% +/- 4.7% increase, P < .001) while inhibiting fibroblast collagen synthesis (48.1% +/- 4.2% decrease, P < .001). Histamine, but not tryptase, significantly enhanced fibroblast proliferation: 92% +/- 5.8% (P < .001) and 39.2% +/- 4.3% (P > 0.05), respectively. Rat mast cell sonicate added to lung fibroblasts induced the activation of metalloproteinase-9 while inhibiting that of metaloproteinase-2. The addition of lipopolysaccharide (LPS)-stimulated lung macrophage supernatant further enhanced the poliferative effect of mast cells on fibroblasts (by 60% +/- 7.8%, P < .001) and induced synthesis of collagen from these cells (190% +/- 28% increase versus control, P < .05). This study demonstrates that mast cells influence several aspects of lung fibroblast function in vitro.

MITF-CM, a newly identified isoform of microphthalmia-associated transcription factor, is expressed in cultured mast cells

The microphthalmia-associated transcription factor (MITF) gene encodes a basic helix-loop-helix and leucin zipper protein. In this study, we identified a novel MITF isoform, MITF-CM, which possesses a unique amino terminus. Exon 1CM is located 84 kb upstream of the exon encoding the B1b domain. MITF-CM was expressed in the human mast cell line HMC-1, the human basophilic cell line KU812, and CB-derived mast cells cultured for 10 weeks as well as bone marrow mononuclear cells. Transient transfection of MITF-CM cDNA in COS-7 cells resulted in the expression of a 64-kDa protein, detected by Western blotting, and nuclear localization of the protein, detected by immunostaining. The transient cotransfection of a luciferase construct under the control of the tyrosinase promoter and MITF-CM cDNA increased luciferase activity threefold. In contrast, none of the MITF isoforms transactivated both the tryptase and chymase gene promoters, indicating differences in the gene transactivation system between humans and mice.

Immunology

The concept of forbidden foods that should not be eaten goes back to the Garden of Eden and apart from its religious meanings it may also have foreshadowed the concept of foods that can provoke adverse reactions. Thus we could say that allergic diseases have plagued mankind since the beginning of life on earth. The prophet Job was affected by a condition that following the rare symptoms described by the Holy Bible might be identified as a severe form of atopic dermatitis (AD). The earliest record of an apparently allergic reaction is 2621 B.C., when death from stinging insects was first described by hieroglyphics carved into the walls of the tomb of Pharaoh Menes depicting his death following the sting of a wasp. In 79 A.D., the death of the Roman admiral Pliny the Elder was ascribed to the SO₂-rich gases emanating from the eruption of Mount Vesuvius. Hippocrates (460–377 B.C.) was probably the first to describe how cow’s milk (CM) could cause gastric upset and hives, proposing dietetic measures including both treatment and prevention for CM allergy.

Ocular allergy in pediatric practice

Allergies occur frequently in all pediatric age groups, affecting up to 40% of children. Allergic conjunctivitis is the most common ocular allergy syndrome among children, with atopic keratoconjunctivitis and vernal keratoconjunctivitis comprising less common, but potentially more severe, forms of ocular allergy. In this article, we review the impact, diagnosis, potential complications, and treatment of these ocular allergic pediatric conditions. Early detection is necessary to prevent potentially serious consequences of pediatric ocular allergy. Involvement of pediatric ophthalmologists may be necessary to avoid preventable vision loss in severe cases.

Mast Cells in the Salivary Glands and Tongue of the Ferret: Demonstration and Some Histochemical Observations

Previous investigations failed to demonstrate mast cells in the alimentary tract and extraparietal glands of the ferret. It was decided therefore to test this and assess factors that may be of influence. Major salivary glands and tongues of mature ferrets, which had been fixed in formalin-calcium, were examined by means of light microscopical histochemistry. Staining of paraffin sections with techniques depending on basic dyes or esterolytic activity was carried out for conventional times with and without previous oxidation, hot acid hydrolysis, and trypsin and beta-glucuronidase digestion. Aldehyde fuchsin and high iron diamine consistently revealed the presence of few mast cells in interstitial stroma of salivary glands and lingual musculature, and in the lamina propria of lingual mucosa. Alcian blue at 0.5 M MgCl2 and safranin produced less consistent results, and even fewer metachromatic mast cells were detected. No staining of mast cells was obtained with the technique for naphthol AS-D chloroacetate esterase. Pretreatment did not increase the numbers and/or staining reactions of mast cells. The results refute the previous misconception and suggest that ferret is a species with a low incidence of mast cells largely expressing a connective-tissue phenotype.

Inflammation, proteases and cancer

Tumours are complex tissues composed of ever-evolving neoplastic cells, matrix proteins that provide structural support and sequester biologically active molecules, and a cellular stromal component. Reciprocal interactions between neoplastic cells, activated host cells and the dynamic micro-environment in which they live enables tumour growth and dissemination. It has become evident that early and persistent inflammatory responses observed in or around developing neoplasms regulates many aspects of tumour development (matrix remodelling, angiogenesis, malignant potential) by providing diverse mediators implicated in maintaining tissue homeostasis, e.g., soluble growth and survival factors, matrix remodelling enzymes, reactive oxygen species and other bioactive molecules. This review highlights recent insights into the role of chronic inflammation associated with cancer development and examines proteolytic pathways activated by infiltrating leukocytes during neoplastic programming of tissues.

Endocrine regulation of menstruation

In women, endometrial morphology and function undergo characteristic changes every menstrual cycle. These changes are crucial for perpetuation of the species and are orchestrated to prepare the endometrium for implantation of a conceptus. In the absence of pregnancy, the human endometrium is sloughed off at menstruation over a period of a few days. Tissue repair, growth, angiogenesis, differentiation, and receptivity ensue to prepare the endometrium for implantation in the next cycle. Ovarian sex steroids through interaction with different cognate nuclear receptors regulate the expression of a cascade of local factors within the endometrium that act in an autocrine/paracrine and even intracrine manner. Such interactions initiate complex events within the endometrium that are crucial for implantation and, in the absence thereof, normal menstruation. A clearer understanding of regulation of normal endometrial function will provide an insight into causes of menstrual dysfunction such as menorrhagia (heavy menstrual bleeding) and dysmenorrhea (painful periods). The molecular pathways that precipitate these pathologies remain largely undefined. Future research efforts to provide greater insight into these pathways will lead to the development of novel drugs that would target identified aberrations in expression and/or of local uterine factors that are crucial for normal endometrial function.

Structural and functional comparison of mast cells in the pregnant versus nonpregnant human uterus

OBJECTIVE

To characterize uterine mast cells and investigate uterine muscle strips contractile responses to challenge with an allergen in nonpregnant and pregnant women.

STUDY DESIGN

A double-antibody labeling technique was used to identify tryptase positive or chymase-tryptase-positive mast cells in uterine samples from term pregnant and nonpregnant women. Longitudinal myometrial strips were prepared from biopsies of hysterectomy specimens from patients undergoing procedures for benign indications and women who had elective cesarean sections. Responses to ragweed antigen were compared in uterine tissues from allergic and nonallergic patients and with passively sensitized tissues in the absence or presence of H1 receptor antagonist and a cyclooxygenase inhibitor.

RESULTS

Tryptase-chymase-positive mast cells were predominant in nonpregnant myometrium, whereas tryptase-positive cells were dominant in pregnant myometrium. Mast cell density was significantly higher in tissue from pregnant women than those of nonpregnant women. Studies in tissues from patients with known allergy to ragweed, as well as in passively sensitized tissues, showed an immediate and substantial increase in the frequency and force of myometrial contraction after a challenge with ragweed antigen. A similar response was observed to histamine. There was no contractile response to antigen challenge in tissues from nonallergic patients. An H1 receptor antagonist partially inhibited the response to antigen, whereas a cyclooxygenase inhibitor had no effect.

CONCLUSION

Sensitized isolated pregnant and nonpregnant human uterine tissue is capable of responding to antigen challenge with strong myometrial contractions. This ability, along with the increased density of mast cells in pregnant tissues as compared with nonpregnant tissues, indicates a possible role for mast cells in mediating uterine contractility in pregnancy.

Mast cell stabilization and anti-histamine effects of olopatadine ophthalmic solution: a review of pre-clinical and clinical research

BACKGROUND

Histamine receptor activation and degranulation of mast cells are the mechanisms by which the ocular itching, hyperemia, chemosis, eyelid swelling, and tearing of seasonal allergic conjunctivitis are induced. Some of the topical solutions available as anti-allergy therapies are intended to interfere with these mechanisms, and the body of research regarding the capabilities of these therapeutic molecules continues to expand.

OBJECTIVE

To review the currently available literature regarding one topical ophthalmic anti-allergy agent, olopatadine (Patanol), and its anti-histaminic and mast cell stabilizing actions, both in pre-clinical and clinical settings.

DESIGN AND METHODS

Relevant research of laboratory, animal model, and clinical trial studies performed using olopatadine was reviewed. MEDLINE literature searches were conducted and supplemented by additional reports which furthered relevant discussion or were necessary to verify the information resulting from original searches.

RESULTS

Olopatadine demonstrates unique properties both pre-clinically and clinically which differentiate it from other therapeutic molecules in its class of dual action mast cell stabilizer/anti-histamine. Its non-perturbation of cell membranes, human conjunctival mast cell stabilization in vivo and in vitro, and superior efficacy as compared to other topical anti-allergic medications including mast cell stabilizers, anti-histamines, and dual action agents, all contribute to olopatadine's profile.

CONCLUSIONS

Peer-reviewed literature suggests that olopatadine is clinically superior to the other anti-allergic molecules because of its strong anti-histaminic qualities and its unique ocular mast cell stabilizing properties.

Simultaneous labeling of mast cell proteases and protease mRNAs at the bone-implant interface of aseptically loosened hip implants

Human mast cells (MC) exhibit two distinct phenotypes based on the protease content of their secretory granules. MC(TC) cells express tryptase, chymase, cathepsin G, and mast cell carboxypeptidase, while MC(T) cells express only tryptase. Both mast cell phenotypes were assessed near regions of osteolysis in uninfected failed joint implants by immunohistochemistry with antibodies to tryptase and chymase, and by in situ hybridization with anti-sense RNA probes for the respective mRNA molecules. Specimens from the interface membrane of 32 aseptically loosened total hip implants were studied, 28 of which had mast cells of the MC(TC) type. Most of these mast cells were aligned along the bone-prosthesis interface adjacent to loosened implants, suggesting involvement in the chronic inflammatory response that leads to bone resorption. Further ultrastructural evidence of mast cells in tissues from failed joint interface membranes was shown by transmission electron microscopy, and detection by staining after magnetic activated cell sorting. The presence of MC at the periprosthetic interface of eroded bone suggests MC degranulation and activity are associated with osteolysis in failed joint prostheses.

Immunohistochemical study on distribution of mast cell phenotypes in human laryngeal mucosa: evidence for laryngeal type I allergy

It is controversial whether or not type I allergic reactions can occur in the human laryngeal mucosa. To clarify this issue, we studied the distribution of mast cell phenotypes in the human laryngeal mucosa using the immunohistochemical staining method with antihuman tryptase and chymase antibodies. A large number of mast cells are present in the superficial layer of subepithelial connective tissue (SECT) of the epiglottis, arytenoid, and subglottis. Although mast cells containing both tryptase and chymase are predominant in the deep layer of the SECT, the majority of mast cells containing tryptase alone are located in both the epithelial layer and the superficial layer of the SECT. We conclude that the human laryngeal mucosa has the potential to induce type I allergic reaction.

Ocular allergy treatment comparisons: azelastine and olopatadine

Azelastine hydrochloride 0.05% and olopatadine hydrochloride 0.1% are topical ocular allergy treatments that have demonstrated multiple pharmacologic actions, including antihistamine, mast cell stabilization, and inhibition of proinflammatory mediators. In this article, the mechanisms of action, efficacy, and tolerability of these two agents on ocular signs and symptoms are examined. By studying the various target sites of drug action, an enhanced clinical response algorithm of these topical ocular agents can be implemented to maximize the response for patients suffering from ocular allergy.

Mast cells play a pivotal role in ischaemia reperfusion injury to skeletal muscles

Ischaemia reperfusion (IR) injury is a serious complication of cardiovascular disease, transplantation and replantation surgery. Once established there is no effective method of treatment. Although studies using mast cell-depleted (Wf/Wf) mice implicate mast cells in this pathology, they do not exclude a contribution by other deficiencies expressed in Wf/Wf mice. In order to obtain conclusive evidence for the role of mast cells, we engrafted cultured bone marrow-derived mast cells (BMMC) from normal mice into their Wf/Wf littermates. After 12 weeks, the hind limbs of Wf/Wf, engrafted Wf/Wf and normal littermates were subjected to IR injury. Muscle viability was assessed by both morphology and by nitroblue tetrazolium histochemical assay. Here, we present conclusive evidence for a causal role of mast cells in IR injury. Our data show that muscles from Wf/Wf mice subjected to IR have a significantly greater proportion of viable fibres than normal littermates subjected to identical injury (78.9+/-5.2 vs 27.2+/-3.7%, respectively). When Wf/Wf IR-resistant mice were engrafted with BMMC from normal littermates and subjected to IR, the proportion of viable muscle fibres was significantly reduced (78.9+/-5.2 vs 37.0+/-6.5%). Thus, engraftment of BMMC into Wf/Wf mice restores the susceptibility of skeletal muscle to IR injury irrespective of other abnormalities in Wf/Wf mice. In this model, the numerical density of mast cells undergoes a significant decrease within 1 h of reperfusion, indicating extensive mast cell degranulation. We conclude that mast cells are pivotal effector cells in the pathogenesis of IR injury of murine skeletal muscle.

Molecular cloning and biological characterization of novel antimicrobial peptides, pilosulin 3 and pilosulin 4, from a species of the Australian ant genus Myrmecia

Venom of an Australian ant species of the Myrmecia pilosula species complex (mss. name Myrmecia banksi Taylor) contains two major allergenic peptides, pilosulin 1 and pilosulin 2. To obtain novel cDNA clones that encode the pilosulin-related bioactive peptides, mRNA of another Myrmecia species was subjected to RT-PCR in which the forward primer corresponds to a nucleotide sequence in the leader sequences of pilosulin 1 and pilosulin 2. As a result, we isolated cDNA clones encoding the novel antimicrobial peptides pilosulin 3 and pilosulin 4. The nucleotide and the amino acid sequences of all four pilosulins have high homology except for the mature peptide coding regions. Synthetic pilosulin 3 and pilosulin 4 peptides displayed antimicrobial activity with histamine-releasing and low hemolytic activities.

Mast cells in human periodontal disease

Recently, mast cells have been shown to produce cytokines which can direct the development of T-cell subsets. The aim of the present study was to determine the relationship between mast cells and the Th1/Th2 response in human periodontal disease. Tryptase+ mast cell numbers were decreased in chronic periodontitis tissues compared with healthy/gingivitis lesions. Lower numbers of c-kit+ cells, which remained constant regardless of clinical status, indicate that there may be no increased migration of mast cells into periodontal disease lesions. While there were no differences in IgG2+ or IgG4+ cell numbers in healthy/gingivitis samples, there was an increase in IgG4+ cells compared with IgG2+ cells in periodontitis lesions, numbers increasing with disease severity. This suggests a predominance of Th2 cells in periodontitis, although mast cells may not be the source of Th2-inducing cytokines.

Development of both human connective tissue-type and mucosal-type mast cells in mice from hematopoietic stem cells with identical distribution pattern to human body

The transplantation of primitive human cells into sublethally irradiated immune-deficient mice is the well-established in vivo system for the investigation of human hematopoietic stem cell function. Although mast cells are the progeny of hematopoietic stem cells, human mast cell development in mice that underwent human hematopoietic stem cell transplantation has not been reported. Here we report on human mast cell development after xenotransplantation of human hematopoietic stem cells into nonobese diabetic severe combined immunodeficient (NOD/SCID)/gamma(c)(null) (NOG) mice with severe combined immunodeficiency and interleukin 2 (IL-2) receptor gamma-chain allelic mutation. Supported by the murine environment, human mast cell clusters developed in mouse dermis, but they required more time than other forms of human cell reconstitution. In lung and gastric tract, mucosal-type mast cells containing tryptase but lacking chymase located on gastric mucosa and in alveoli, whereas connective tissue-type mast cells containing both tryptase and chymase located on gastric submucosa and around major airways, as in the human body. Mast cell development was also observed in lymph nodes, spleen, and peritoneal cavity but not in the peripheral blood. Xenotransplantation of human hematopoietic stem cells into NOG mice can be expected to result in a highly effective model for the investigation of human mast cell development and function in vivo.

In vitro inhibition of human conjunctival mast-cell degranulation by ketotifen

Ketotifen relieves the symptoms of allergic conjunctivitis through multiple mechanisms of action. One such mechanism may involve stabilization of conjunctival mast cells. Because of inter- and intra-species variation, however, this hypothesis cannot be adequately tested using mast cells from animals or other human tissues. We therefore employed human conjunctival mast cells. The mast cells were prepared using human conjunctival tissues obtained from US eye banks. Cell suspensions were sensitized with human IgE and incubated with ketotifen fumarate or control. After antigenic challenge of sensitized cells with anti-IgE, levels of histamine and tryptase, two mast-cell granule markers, were measured in the supernatant fluid. Cell viability was assessed with a Trypan Blue assay. Ketotifen at concentrations of approximately 10(-11) to 10(-4) M inhibited mast-cell histamine release by 90% or more. Similarly, ketotifen at approximately 10(-10) to 10(-4) M inhibited tryptase release by 90% or more (apart from a single anomalous reading). At all ketotifen concentrations that stabilized mast cells, cell viability was preserved. Moreover, ketotifen did not impair cell viability unless concentrations were increased above the clinically relevant range, i.e., above the order of magnitude of 10(-4) M. These data demonstrate that ketotifen can stabilize human conjunctival mast cells, without impairing cell viability.

Mast cell heterogeneity in B-cell non-Hodgkin's lymphomas: an ultrastructural study

Mast cells (MC) are critical for a number of pathological conditions, including acute and chronic inflammation and tumor angiogenesis. We have previously demonstrated that in B-cell non-Hodgkin's lymphoma (B-NHL) angiogenesis is correlated with total methachromatic and tryptase-positive MC and that both counts increase in step with the increase in malignancy, whereas the role of MC in malignant lymph nodes is not fully clear. An extensive ultrastructural study has been made of representative samples of 30 B-NHL and 10 benign lymphadenopathies. A heterogeneous population of MC characterized by the presence of granules with a semilunar aspect and containing scrolls was observed. The former are the expression of a slow but progressive release of angiogenic factors due to chronic, progressive stimulation of MC degranulation, while the latter contain tryptase, an angiogenic factor. These two ultrastructural data confirm the important role played by MC in the angiogenesis associated with progression in B-NHL.

Cytokines regulate development of human mast cells from hematopoietic progenitors

Combination of stem cell factor (SCF) and interleukin-6 (IL-6) significantly promoted proliferation of human mast cells from cord blood CD34+ cells. Most of the cells, cultured in the presence of SCF and IL-6 for 10 weeks, expressed c-kit and contained a significant amount of histamine and tryptase and a low amount of chymase. Both tryptase-positive chymase-negative mast cells (MC(T)) and tryptase-positive chymase-positive mast cells (MC(TC)) were found in the same colony derived from a single cord blood CD34+ cell, suggesting that MC(T) and MC(TC) develop from common precursor cells. Single-cell culture of CD34+ cells revealed that committed mast cell progenitors are included in CD34+CD38+HLA-DR- cells. IL-4 significantly enhanced high-affinity immunoglobulin E (IgE) receptor (FcepsilonRI) alpha-chain messenger RNA expression and induced FcepsilonRI on SCF-dependent cord blood-derived human mast cells, resulting in high histamine-releasing activity upon cross-linking of FcepsilonRI. Another factor that up-regulated FcepsilonRI was IgE, and a combination of IL-4 and IgE markedly augmented FcepsilonRI expression on the mast cells. IL-4 and IgE may enhance FcepsilonRI expression by distinct mechanisms; IL-4 promotes FcepsilonRI alpha-chain gene transcription and thus increases alpha-chain protein synthesis in the cells, whereas the binding of IgE may anchor the FcepsilonRI on the cell surface, resulting in suppression of internalization of FcepsilonRI. Mast cells are progeny of hematopoietic stem cells. Recent discovery of a xenotransplantation model revealed that human hematopoietic stem cells can proliferate and differentiate into mature mast cells in the mouse skin 3 months after transplantation of human cord blood CD34+ cells, suggesting that this model may pave the way to clarification of the functions of human mast cells in vivo.

Human mast cell and airway smooth muscle cell interactions: implications for asthma

Asthma is characterized by inflammation, hyperresponsiveness, and remodeling of the airway. Human mast cells (HMCs) play a central role in all of these changes by releasing mediators that cause exaggerated bronchoconstriction, induce human airway smooth muscle (HASM) cell proliferation, and recruit and activate inflammatory cells. Moreover, the number of HMCs present on asthmatic HASM is increased compared with that on nonasthmatic HASM. HASM cells also have the potential to actively participate in the inflammatory process by synthesizing cytokines and chemokines and expressing surface molecules, which have the capacity to perpetuate the inflammatory mechanisms present in asthma. This review specifically examines how the mediators of HMCs have the capacity to modulate many functions of HASM; how the synthetic function of HASM, particularly through the release and expression of stem cell factor, has the potential to influence HMC number and activation in an extraordinarily potent and proinflammatory manner; and how these interactions between HMCs and HASM have potential consequences for airway structure and inflammation relevant to the disease process of asthma.

Possible involvement of mast-cell activation in aspirin provocation of aspirin-induced asthma

BACKGROUND

Although there is increasing evidence of the importance of cysteinyl leukotrienes (LT) as mediators of aspirin-induced bronchoconstriction in aspirin-sensitive asthma, the cellular origin of the LT is not yet clear.

METHODS

Urinary concentrations of leukotriene E4 (LTE4), 11-dehydrothromboxane B2, 9alpha,11beta-prostaglandin F2, and Ntau-methylhistamine were measured during the 24 h following cumulative intravenous administration of increasing doses of lysine aspirin to asthmatic patients. In addition, the urinary concentrations of these metabolites were measured on 5 consecutive days in a patient who suffered an asthma attack after percutaneous administration of nonsteroidal anti-inflammatory drugs.

RESULTS

In aspirin-induced asthma patients (AIA, n=10), the basal concentration of urinary LTE4, but not the other metabolites, was significantly higher than that in aspirin-tolerant asthma patients (ATA, n=10). After intravenous aspirin provocation, the AIA group showed a 13.1-fold (geometric mean) increase in excretion of LTE4 during the first 3 h, and 9alpha,11beta-prostaglandin F2 also increased in the AIA group during the first 0-3 h and the 3-6 h collection period. Ntau-methylhistamine excretion was also increased, but to a lesser degree. Administration of aspirin caused significant suppression of 11-dehydrothromboxane B2 excretion in both the AIA and ATA groups. When the percentage of maximum increase of each metabolite from the baseline concentrations was compared between the AIA group and the ATA group, a significantly higher increase in excretion of LTE4, 9alpha,11beta-prostaglandin F2, and Ntau-methylhistamine was observed in the AIA group than the ATA group. An increased excretion of LTE4 and 9alpha,11beta-prostaglandin F2 has been detected in a patient who suffered an asthma attack after percutaneous administration of nonsteroidal anti-inflammatory drugs.

CONCLUSIONS

Considering that human lung mast cells are capable of producing LTC4, prostaglandin D2, and histamine, our present results support the concept that mast cells, at least, may participate in the development of aspirin-induced asthma.

Degranulation of mast cells provokes a massive inflammatory reaction in the tympanic membrane

OBJECTIVE

The pars flaccida is extremely rich in mast cells. On stimulation the mast cells release preformed and de novo synthesized inflammatory substances. The purpose of this study was to examine how these mast cell substances provoke inflammatory changes in the tympanic membrane.

STUDY DESIGN

In vivo, murine model.

METHODS

In a rat model, the mast cell secretagogue compound 48/80 was applied locally to the tympanic membrane on 4 consecutive days and the ensuing inflammatory changes were evaluated by otological, light, and electron microscopy 3, 6, 9, 12, 18, 24, 36, and 48 hours and 4, 6, and 8 days later.

RESULTS

Degranulation of the mast cells occurred within 3 hours of applying compound 48/80. Release of the mast cell substances coincided with an inflammatory event characterized by a two-stage reaction: an edema stage, peaking 6 hours after application, followed by a massive invasion of inflammatory cells, peaking at 24 and 48 hours. Pars flaccida and pars tensa were both involved, pars flaccida showing the earliest changes. Pars tensa exhibited the same biphasic reaction as pars flaccida, but approximately 6 hours later.

CONCLUSIONS

The mast cells of the pars flaccida have the capacity to elicit an intense inflammation of the tympanic membrane. The biphasic reaction pattern resembles that observed in experimental otitis media, suggesting involvement of the mast cells in this inflammatory condition of the middle ear.