The role of mast cells in asthma

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.

Understanding fibroblast-immune cell interactions via co-culture models and their role in asthma pathogenesis

Asthma is a chronic lung disease involving airway inflammation and fibrosis. Fibroblasts are the main effector cells important for lung tissue production which becomes abnormal in asthmatics and is one of the main contributors to airway fibrosis. Although fibroblasts were traditionally viewed solely as structural cells, they have been discovered to be highly active, and involved in lung inflammatory and fibrotic processes in asthma. In line with this, using 2D and 3D in vitro co-culture models, a complex interaction between lung fibroblasts and various immune cells important for the pathogenesis of asthma have been recently uncovered. Hence, in this review, we provide the first-ever summary of various studies that used 2D and 3D in vitro co-culture models to assess the nature of aberrant immune cell-fibroblast interactions and their contributions to chronic inflammation and fibrotic mechanisms in asthma pathogenesis.

Mast cell regranulation requires a metabolic switch involving mTORC1 and a glucose-6-phosphate transporter

Mast cells (MCs) are granulated cells implicated in inflammatory disorders because of their capacity to degranulate, releasing prestored proinflammatory mediators. As MCs have the unique capacity to reform granules following degranulation in vitro, their potential to regranulate in vivo is linked to their pathogenesis. It is not known what factors regulate regranulation, let alone if regranulation occurs in vivo. We report that mice can undergo multiple bouts of MC regranulation following successive anaphylactic reactions. mTORC1, a nutrient sensor that activates protein and lipid synthesis, is necessary for regranulation. mTORC1 activity is regulated by a glucose-6-phosphate transporter, Slc37a2, which increases intracellular glucose-6-phosphate and ATP during regranulation, two upstream signals of mTOR. Additionally, Slc37a2 concentrates extracellular metabolites within endosomes, which are trafficked into nascent granules. Thus, the metabolic switch associated with MC regranulation is mediated by the interactions of a cellular metabolic sensor and a transporter of extracellular metabolites into MC granules.

Mast cells within cellular networks

Mast cells are highly versatile in terms of their mode of activation by a host of stimuli and their ability to flexibly release a plethora of biologically highly active mediators. Within the immune system, mast cells can best be designated as an active nexus interlinking innate and adaptive immunity. Here we try to draw an arc from initiation of acute inflammatory reactions to microbial pathogens to development of adaptive immunity and allergies. This multifaceted nature of mast cells is made possible by interaction with multiple cell types of immunologic and nonimmunologic origin. Examples for the former include neutrophils, eosinophils, T cells, and professional antigen-presenting cells. These interactions allow mast cells to orchestrate inflammatory innate reactions and complex adaptive immunity, including the pathogenesis of allergies. Important partners of nonimmunologic origin include cells of the sensory neuronal system. The intimate association between mast cells and sensory nerve fibers allows bidirectional communication, leading to neurogenic inflammation. Evidence is accumulating that this mast cell/nerve crosstalk is of pathophysiologic relevance in patients with allergic diseases, such as asthma.

Cytological Evaluation of the Influence of High and Low Doses of Bisphenol a on an Erythroblastic Cell Line of Porcine Bone Marrow

Introduction

Bisphenol A (BPA) is a substance widely used in industry for the production of polycarbonates and epoxy resins used in packaging and containers for beverages, contact lenses, compact discs (CDs), window panes, and many other elements. This compound belongs to the group of polyphenols and xenoestrogens commonly found in the human environment. What we know about BPA is still insufficient to enable us to protect our health against its adverse effects, and current knowledge of the influence of BPA on erythroblastic cell lines in bone marrow is rather fragmentary. The aim of the experiment was to assess the effect of two doses of BPA (0.05 mg/kg and 0.5 mg/kg b.w. per day) on myeloid haematopoiesis.

Material and Methods

During this experiment, the number of all types of cells in the erythroblastic cell line was evaluated in porcine bone marrow before and after BPA administration.

Results

The obtained results clearly indicate changes in haematopoietic activity of the bone marrow, which was demonstrated by a decrease in erythroblastic cell line production in both experimental groups. The haematological effects of the bone marrow changes were anaemia, caused by a number of erythrocytes which was depressed due to their immaturity, and a significant decrease in mean cellular volume in both groups.

Conclusion

The harmful effect of high and low doses of BPA on haematopoietic processes was proved.

Subdiuretic dose of furosemide enhances albuterol effects in asthmatic mice rather than bumetanide

BACKGROUND

One of the loop diuretics, furosemide, was found useful in bronchial asthma. It enhanced anti-asthmatic effects of albuterol. The underlying mechanism is still unclear.

OBJECTIVE

This study was planned to investigate whether the enhancing effect of furosemide for albuterol in ovalbumin-induced asthmatic BALB/c mice is diuretic-related or not.

METHODS

Two sets of experiments were performed. In the first, effects of inhaled subdiuretic doses of furosemide and bumetanide (another loop diuretic) were compared. Treatments (mg/mL) were given as 15 minute-inhalation before final ovalbumin provocation as follows: albuterol (2.5), furosemide (0.08), bumetanide (0.005), (albuterol+furosemide, 2.5+0.08), and (albuterol+bumetanide, 2.5+0.005). Airway hyperreactivity (AHR) to inhaled methacholine, levels of IL-6, TNF-α, and differential white blood cells in bronchoalveolar lavage fluid (BALF), and lung histopathology were evaluated. In the second set, effects of oral diuretic doses (mg/kg) of furosemide (10) and bumetanide (0.25) were given before final ovalbumin provocation. Urine volume and asthma parameters were measured.

RESULTS

Ovalbumin-asthmatic mice showed significant increases in AHR, levels of IL-6, TNF-α, and inflammatory cells in BALF, and lung inflammatory cell infiltration. Inhaled furosemide significantly decreased these changes while inhaled bumetanide failed. Albuterol and albuterol+bumetanide significantly decreased these changes more than furosemide while albuterol+furosemide produced the most significant decreases. Both oral furosemide and bumetanide exerted equivalent diuretic effects but failed to improve asthma.

CONCLUSIONS

Inhaled subdiuretic dose of furosemide enhanced effects of albuterol more in ovalbumin-asthmatic mice rather than bumetanide, while oral diuretic doses of both drugs failed to improve asthma, indicating that this enhancing effect is not diuretic-related.

Effects of particulate matter on allergic respiratory diseases

The health impact of airborne particulate matter (PM) has long been a concern to clinicians, biologists, and the general public. With many epidemiological studies confirming the association of PM with allergic respiratory diseases, an increasing number of follow-up empirical studies are being conducted to investigate the mechanisms underlying the toxic effects of PM on asthma and allergic rhinitis. In this review, we have briefly introduced the characteristics of PM and discussed its effects on public health. Subsequently, we have focused on recent studies to elucidate the association between PM and the allergic symptoms of human respiratory diseases. Specifically, we have discussed the mechanism of action of PM in allergic respiratory diseases according to different subtypes: coarse PM (PM2.5-10), fine PM (PM2.5), and ultrafine PM.

Role of lipid mediators and control of lymphocyte responses in type 2 immunopathology

Type 2 immunopathology is a cardinal feature of allergic diseases and involves cooperation between adaptive immunity and innate effector responses. Virtually all cell types relevant to this pathology generate leukotriene and/or prostaglandin mediators that derive from arachidonic acid, express receptors for such mediators, or both. Recent studies highlight prominent functions for these mediators in communication between the innate and adaptive immune systems, as well as amplification or suppression of type 2 effector responses. This review focuses on recent advances and insights, and highlights existing and potential therapeutic applications of drugs that target these mediators or their receptors, with a special emphasis on their regulation of the innate and adaptive lymphocytes relevant to type 2 immunopathology.

1,6-O,O-Diacetylbritannilactone suppresses activation of mast cell and airway hyper-responsiveness

Mast cells play critical roles in allergic disorders such as atopic dermatitis and allergic asthma. The aim of this study was to investigate the anti-inflammatory and anti-asthmatic activities of 1,6-O,O-diacetylbritannilactone (OODBL) isolated from Inula japonica Thunb. (I. japonica) in a murine asthma model and bone marrow-derived mast cells (BMMCs). In an ovalbumin-induced asthma model, OODBL administration attenuated the airway hyper-responsiveness induced by aerosolized methacholine and serum IgE level in asthmatic mice. In vitro system, we found that OODBL reduced leukotriene C₄ production and degranulation through the suppression of cytosolic phospholipase A₂ phosphorylation and phospholipase Cγ-mediated Ca²⁺ influx in IgE/antigen-stimulated BMMCs. Taken together, OODBL may have therapeutic potential in the treatment of allergic diseases such as asthma.

KOTMIN13, a Korean herbal medicine alleviates allergic inflammation in vivo and in vitro

Background

The ethanol extract of KOTMIN13, composed of Inula japonica Flowers, Trichosanthes kirilowii Semen, Peucedanum praeruptorum Radix, and Allium macrostemon Bulbs, was investigated for its anti-asthmatic and anti-allergic activities.

Methods

The anti-asthmatic effects of KOTMIN13 were evaluated on ovalbumin (OVA)-induced murine asthma model. Anti-allergic properties of KOTMIN13 in bone-marrow derived mast cells (BMMC) and passive cutaneous anaphylaxis (PCA) in vivo were also examined.

Results

In asthma model, KOTMIN13 effectively suppressed airway hyperresponsiveness induced by aerosolized methacholine when compared to the levels of OVA-induced mice. KOTMIN13 treatment reduced the total leukocytes, eosinophil percentage, and Th2 cytokines in the bronchoalveolar lavage fluids in OVA-induced mice. The increased levels of eotaxin and Th2 cytokines in the lung as well as serum IgE were decreased by KOTMIN13. The histological analysis shows that the increased inflammatory cell infiltration and mucus secretion were also reduced. In addition, the degranulation and leukotriene C₄ production were inhibited in BMMC with IC₅₀ values of 3.9 μg/ml and 1.7 μg/ml, respectively. Furthermore, KOTMIN13 treatment attenuated mast-mediated PCA reaction.

Conclusions

These results demonstrate that KOTMIN13 has anti-asthmatic and anti-allergic effects in vivo and in vitro models.

Effect of fruits of Opuntia elatior Mill on mast cell degranulation

Background:

The presence of potentially active nutrients and their multifunctional properties make prickly pear a perfect candidate for the production of phytopharmaceutical products. Among the numerous Opuntia species, bioactive compounds have been isolated and characterized primarily from Opuntia ficus-indica, Opuntia polycantha, Opuntia stricta, Opuntia dilleni for various medicinal properties.

Objective:

Based on the traditional use of prickly pear for enhancement of immune function, the objective of the present study to evaluate the effect of prickly pear on mast cell degranulation function.

Materials and Methods:

The Opuntia fruit juice (OFJ) (10-200 μl/ml) were studied for the effect on sensitized rat peritoneal mast cell degranulation induced by immunological (egg albumin), and nonimmunological (compound 48/80) stimuli and compared with that of the reference standard, sodium cromoglycate and ketotifen (10 μg/ml).

Results and Conclusion:

The OFJ exhibited significantly (P < 0.001) concentration dependent inhibition of mast cell degranulation. The IC₅₀ value of OFJ was found 12.24 and 18 μl/ml for immunological and nonimmunological induced mast cell degranulation, respectively. The betacyanin is an active principle compound in prickly pear that may responsible for mast cell stabilizing action.

Assessment of various second-line medications in addition to inhaled corticosteroid in asthma patients: a randomized controlled trial

Many patients with persistent asthma cannot achieve the treatment goal for asthma with a single controller medication. The aim of the present study was to assess lung function and rescue medication use in asthma patients receiving four different categories of drugs in combination with an inhaled corticosteroid. Patients recruited to the study were randomized into four groups to receive budesonide with either formoterol, doxofylline, montelukast or tiotropium for a period of 3 months. Lung function (i.e. forced expiratory volume in 1 s (FEV1 )) and rescue medication use were determined at baseline and on Day 15, 30, 45, 60 and 90 of treatment. A total of 297 patients completed the study. At baseline, no significant differences (P > 0.05) were observed in any of the outcome measures. Significant within-group improvement in FEV1 was observed in all groups. On Day 90, between-group differences showed that the improvement in FEV1 was significantly (P < 0.05) higher for patients receiving budesonide + formoterol, followed by budesonide + montelukast and budesonide + doxofylline, and least for those receiving budesonide + tiotropium. Similarly, within- and between-group comparisons showed significant (P < 0.05) reductions in rescue medication use in all groups. However, the magnitude of the decrease was greater in the budesonide + formoterol group, followed by the budesonide + montelukast, budesonide + doxofylline and budesonide + tiotropium groups. Based on our findings, among the second-line treatment regimens, budesonide with either montelukast or doxofylline was found to be better than budesonide + tiotropium in patients with mild-to-moderate persistent asthma. Further studies with a longer duration are likely to be useful.

Anti-allergic properties of curine, a bisbenzylisoquinoline alkaloid

Curine is a bisbenzylisoquinoline alkaloid isolated from Chondrodendron platyphyllum (Menispermaceae). Recent findings have shed light on the actions of curine in different models of allergy and inflammation. Here we review the properties and mechanisms of action of curine focusing on its anti-allergic effects. Curine pre-treatment significantly inhibited the scratching behavior, paw edema and systemic anaphylaxis induced by either ovalbumin (OVA) in sensitized animals or compound 48/80, through mechanisms of mast cell stabilization and inhibition of mast cell activation to generate lipid mediators. In addition, oral administration of curine significantly inhibited eosinophil recruitment and activation, as well as, OVA-induced airway hyper-responsiveness in a mouse model of asthma, through inhibition of the production of IL-13 and eotaxin, and of Ca²⁺ influx. In conclusion, curine exhibit anti-allergic effects in models of lung, skin and systemic allergy in the absence of significant toxicity, and as such has the potential for anti-allergic drug development.

Curine inhibits mast cell-dependent responses in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Curine is a bisbenzylisoquinoline alkaloid and the major constituent isolated from Chondrodendron platyphyllum, a plant that is used to treat inflammatory diseases in Brazilian folk medicine. This study investigates the effectiveness of curine on mast cell-dependent responses in mice.

MATERIALS AND METHODS

To induce mast cell-dependent responses, Swiss mice were subcutaneously sensitized with ovalbumin (OVA-12 μg/mouse) and Al(OH)3 in a 0.9% NaCl solution. Fifteen days later, the animals were challenged with OVA through different pathways. Alternatively, the animals were injected with compound 48/80 or histamine, and several parameters, including anaphylaxis, itching, edema and inflammatory mediator production, were analyzed. Promethazine, cromoglycate, and verapamil were used as control drugs, and all of the treatments were performed 1h before the challenges.

RESULTS

Curine pre-treatment significantly inhibited the scratching behavior and the paw edema induced by either compound 48/80 or OVA, and this protective effect was comparable in magnitude with those associated with treatment with either cromoglycate or verapamil. In contrast, curine was a weak inhibitor of histamine-induced paw edema, which was completely inhibited by promethazine. Curine and verapamil significantly inhibited pleural protein extravasations and prostaglandin D2 (PGD2) and cysteinyl leukotrienes (CysLTs) production following allergen-induced pleurisy. Furthermore, like verapamil, curine inhibited the anaphylactic shock caused by either compound 48/80 or an allergen. In in vitro settings, these treatments also inhibited degranulation as well as PGD2 and CysLT production through IgE-dependent activation of the mast cell lineage RBL-2H3.

CONCLUSION

Curine significantly inhibited immediate allergic reactions through mechanisms more related to mast cell stabilization and activation inhibition than interference with the pro-inflammatory effects of mast cell products. These findings are in line with the hypothesis that the alkaloid curine may be beneficial for the treatment of allergic disorders.

Margaritaria discoidea (Euphorbiaceae) stem bark extract attenuates allergy and Freund's adjuvant-induced arthritis in rodents

Background:

Various parts of Margaritaria discoidea find use in traditional medicine in the treatment of pain and oedema. This study evaluated the anti-allergic, anti-inflammatory and anti-arthritic effects of a 70% (v/v) aqueous ethanol extract of the stem bark of Margaritaria discoidea, MDE in rodents.

Materials and Methods:

Systemic anaphylaxis was induced by the injection of compound 48/80 into mice and their survival rate was monitored to evaluate the anti-allergic action of the extract. The effect of MDE assessed on the maximal and total oedema responses in the mouse carrageenan-induced paw oedema was used to evaluate the anti-inflammatory action of the extract while the Freund's adjuvant-induced arthritis model was employed to study the anti-arthritic effects of MDE.

Results:

MDE dose-dependently increased the time for compound 48/80-induced mortality in mice. MDE suppressed the mean maximal swelling and the total paw swellings induced over 6 h in the carrageenan-induced paw oedema when administered either prophylactically or therapeutically. MDE caused a reduction in serum levels of TNFα and IL-6 and significantly suppressed Freund's adjuvant-induced arthritis.

Conclusion:

Margaritaria discoidea suppresses allergy and exhibits anti-inflammatory activity in mice. In addition it attenuates Freund's adjuvant-induced arthritis through a reduction in serum levels of TNFα and IL-6 in rats.

Pulmonary function assessment in mild to moderate persistent asthma patients receiving montelukast, doxofylline, and tiotropium with budesonide: a randomized controlled study

BACKGROUND

There is no comparative study among asthma patients receiving first-line versus various second-line treatment regimens for mild to moderate persistent asthma.

OBJECTIVE

We assessed the pulmonary function in asthma patients receiving montelukast, doxofylline, and tiotropium with budesonide in a pilot group.

METHODS

Patients were recruited as per the study criteria and randomly allocated to 4 groups to receive budesonide (400 µg) with formoterol (12 µg), doxofylline (400 mg), montelukast (10 mg), or tiotropium (18 µg) for a period of 3 months. Outcomes included forced expiratory volume in 1 second (FEV1) and rescue medication use.

RESULTS

A total of 167 patients were recruited; among them, 123 patients completed the study. At baseline, no significant difference (P > 0.05) was observed in any of the outcome measures. Significant within-group improvement in FEV1 was observed in all the groups. At day 90, between-group difference revealed that improvement in FEV1 was significantly (P < 0.05) high for budesonide plus formoterol followed by budesonide plus doxofylline, budesonide plus montelukast, and, lastly, budesonide plus tiotropium. Similarly, within-group comparison revealed a significant (P < 0.05) reduction in rescue medication use in all the groups. The intensity in decrease was more in budesonide plus formoterol group followed by budesonide plus doxofylline, budesonide plus montelukast, and budesonide plus tiotropium groups.

CONCLUSION

On the basis of our findings, among the second-line treatment regimens, budesonide plus doxofylline and budesonide plus montelukast was found to be better than budesonide plus tiotropium in patients with mild to moderate persistent asthma. Further studies with a larger sample size are likely to be useful.

Novel polyhydroxylated steroids from the East China Sea gorgonian Echinogorgia sassapo reticulata with suppressive activity of leukotriene C4 generation and degranulation in bone marrow-derived mast cells

The gorgonian Echinogorgia sassapo reticulata contains two new bioactive polyhydroxylated steroids, sassapols A (1), B (2), and five related known compounds (3-7). Compound 6 has been encountered for the first time in natural sources. The structures of these new compounds were defined by spectroscopic analysis. All the compounds (1-7) isolated from E. sassapo reticulata were tested for anti-inflammatory activity. Compounds 1, 3, 5, and 7 inhibited both the generation of leukotriene C₄ and the degranulation reaction in mouse bone marrow-derived mast cells.

Destabilization of TNF-α mRNA by Rapamycin

Stimulation of mast cells through the high affinity IgE receptor (FcεRI) induces degranulation, lipid mediator release, and cytokine secretion leading to allergic reactions. Although various signaling pathways have been characterized to be involved in the FcεRI-mediated responses, little is known about the precious mechanism for the expression of tumor necrosis factor-α (TNF-α) in mast cells. Here, we report that rapamycin, a specific inhibitor of mammalian target of rapamycin (mTOR), reduces the expression of TNF-α in rat basophilic leukemia (RBL-2H3) cells. IgE or specific antigen stimulation of RBL-2H3 cells increases the expression of TNF-α and activates various signaling molecules including S6K1, Akt and p38 MAPK. Rapamycin specifically inhibits antigen-induced TNF-α mRNA level, while other kinase inhibitors have no effect on TNF-α mRNA level. These data indicate that mTOR signaling pathway is the main regulation mechanism for antigen-induced TNF-α expression. TNF-α mRNA stability analysis using reporter construct containing TNF-α adenylate/uridylate-rich elements (AREs) shows that rapamycin destabilizes TNF-α mRNA via regulating the AU-rich element of TNF-α mRNA. The antigen-induced activation of S6K1 is inhibited by specific kinase inhibitors including mTOR, PI3K, PKC and Ca²⁺chelator inhibitor, while TNF-α mRNA level is reduced only by rapamycin treatment. These data suggest that the effects of rapamycin on the expression of TNF-α mRNA are not mediated by S6K1 but regulated by mTOR. Taken together, our results reveal that mTOR signaling pathway is a novel regulation mechanism for antigen-induced TNF-α expression in RBL-2H3 cells.

Perinatal bisphenol A exposures increase production of pro-inflammatory mediators in bone marrow-derived mast cells of adult mice

Bisphenol A (BPA) is a widely used monomer of polycarbonate plastics and epoxide resin that has been implicated in asthma pathogenesis when exposure occurs to the developing fetus. However, few studies have examined the relationship between perinatal BPA exposure and asthma pathogenesis in adulthood. This study used an isogenic mouse model to examine the influence of perinatal BPA exposure via maternal diet on inflammatory mediators associated with asthma in 6-month-old adult offspring by measuring bone marrow-derived mast cell (BMMC) production of lipid mediators (cysteinyl leukotrienes and prostaglandin D2), cytokines (interleukin [IL]-4, IL-5, IL-6, IL-13, and tumor necrosis factor [TNF]-α), and histamine. Global DNA methylation levels in BMMCs from adult offspring were determined to elucidate a potential regulatory mechanism linking perinatal exposure to mast cell phenotype later in life. Four BPA exposure doses were tested: low (50 ng BPA/kg diet, n = 5), medium (50 μg BPA/kg diet, n = 4), high (50 mg BPA/kg diet, n = 4), and control (n = 3). Following BMMC activation, increases in cysteinyl leukotriene (p < 0.01) and TNFα (p < 0.05) production were observed in all BPA-exposure groups, and increases in prostaglandin D2 (p < 0.01) and IL-13 (p < 0.01) production were observed in the high exposure group. Additionally, BMMCs from adult mice in all exposure groups displayed a decrease in global DNA methylation compared to control animals. Thus, perinatal BPA exposure displayed a long-term influence on mast cell-mediated production of pro-inflammatory mediators associated with asthma and global DNA methylation levels, suggesting a potential for mast cell dysregulation, which could affect pulmonary inflammation associated with allergic airway disease into adulthood.

Adenosine signaling in airways: toward a promising antiasthmatic approach

Adenosine participates to asthma physiopathology by signaling through more than just one receptor subtype. Defining the role of each receptor is complicated by evidence that often results obtained on rodents do not coincide with human studies, but what emerges is that an important condition to establish hyperresponsiveness to adenosine in any species of sensitized animals is the exposure to allergen; this feature appears to be very similar to the human situation, since allergic humans regularly undergo exposure to allergen. Furthermore, A₂B in humans, but A₃ receptor in rodents, would mediate, indirectly, the bronchoconstriction in response to adenosine and would play the main role in adenosine-induced airway inflammation and airway hyperreactivity. On the other hand, A₁ receptor over-expressed on asthmatic airways would mediate a direct adenosine bronchoconstrictor effect. Antagonists and agonists to adenosine receptors have been considered as antiasthmatic drugs but often their development has been limited by unwanted effects. Preventing adenosine accumulation in airways should be considered as a novel promising antiasthmatic strategy.

Bisphenol A at concentrations relevant to human exposure enhances histamine and cysteinyl leukotriene release from bone marrow-derived mast cells

Bisphenol A (BPA), a monomer of polycarbonate plastics and epoxide resin, acts as an endocrine-active compound and has been shown to enhance the inflammatory response to allergen challenge. Previous reports in rodents have demonstrated that perinatal BPA exposure alters airway inflammation following sensitization and challenge to ovalbumin in juvenile and adult offspring. Additionally, a high concentration of BPA has been shown to enhance mediator release in mast cell lines. This study aimed to determine if short-term BPA exposure, at levels relevant to human exposure, enhances mast cell release of histamine and cysteinyl leukotrienes (CysLTs). Primary murine bone marrow-derived mast cells (BMMC) produced from the femurs of female C57BL/6 mice were stimulated with BPA or estradiol (E2) in vitro. It was observed that both BPA and E2 increased BMMC histamine release over a range of nanomolar concentrations (1-1000 nM). The estrogen receptor (ER) antagonist ICI 182,780 partially blocked the ability of E2, but not BPA, to elevate histamine release. BPA also increased CysLT release, which was not abrogated by ER inhibition. It was also observed that the ability of BPA to enhance histamine and CysLT release was inhibited by blocking the extracellular signal-regulated kinase (ERK) pathway with U0126 or by chelating extracellular calcium (Ca(2+)) using EGTA. In summary, these experiments are the first to demonstrate that acute BPA exposure enhances mast cell histamine and CysLT release in vitro--an effect that is not dependent on an ER-mediated mechanism. Instead, BPA-induced mast cell histamine and CysLT release may be mediated, in part, by the ERK pathway and extracellular Ca(2+) concentrations. These data suggest that exposure to BPA at levels relevant to human exposure may provoke an acute inflammatory response in atopic individuals via enhanced mast cell activation.

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.

Gene-by-environment effect of house dust mite on purinergic receptor P2Y12 (P2RY12) and lung function in children with asthma

BACKGROUND

Distinct receptors likely exist for leukotriene (LT)E(4), a potent mediator of airway inflammation. Purinergic receptor P2Y12 is needed for LTE(4)-induced airways inflammation, and P2Y12 antagonism attenuates house dust mite-induced pulmonary eosinophilia in mice. Although experimental data support a role for P2Y12 in airway inflammation, its role in human asthma has never been studied.

OBJECTIVE

To test for association between variants in the P2Y12 gene (P2RY12) and lung function in human subjects with asthma, and to examine for gene-by-environment interaction with house dust mite exposure.

METHODS

Nineteen single nucleotide polymorphisms (SNPs) in P2RY12 were genotyped in 422 children with asthma and their parents (n = 1266). Using family based methods, we tested for associations between these SNPs and five lung function measures. We performed haplotype association analyses and tested for gene-by-environment interactions using house dust mite exposure. We used the false discovery rate to account for multiple comparisons.

RESULTS

Five SNPs in P2RY12 were associated with multiple lung function measures (P-values 0.006–0.025). Haplotypes in P2RY12 were also associated with lung function (P-values 0.0055–0.046). House dust mite exposure modulated associations between P2RY12 and lung function, with minor allele homozygotes exposed to house dust mite demonstrating worse lung function than those unexposed (significant interaction P-values 0.0028–0.040).

CONCLUSIONS AND CLINICAL RELEVANCE

The P2RY12 variants were associated with lung function in a large family-based asthma cohort. House dust mite exposure caused significant gene-by-environment effects. Our findings add the first human evidence to experimental data supporting a role for P2Y12 in lung function. P2Y12 could represent a novel target for asthma treatment.

Contribution of stress to asthma worsening through mast cell activation

OBJECTIVE

To review the available evidence linking stress to asthma and to investigate whether mast cells contribute to the effect of stress through activation by corticotropin-releasing hormone (CRH).

DATA SOURCE

The PubMed database was searched for articles (1998-2011) using the keywords anxiety, asthma, exacerbation, inflammation, mast cells, socioeconomic status, stress, violence, and worsening.

STUDY SELECTION

Articles were selected based on their relevance to the topic, with emphasis on clinical or epidemiologic data linking stress to asthma and studies that offered possible explanations for how stress may affect asthma.

RESULTS

Many articles point to an association between stress (socioeconomic status, interpersonal conflicts, emotional distress, terrorism) and asthma exacerbations but without any distinct pathogenetic mechanism. A few articles have reported reduced circulating cortisol and/or sensitivity to corticosteroids. We propose that mast cells, known to be involved in the pathophysiology of asthma, can be activated by CRH, which is secreted under stress in the lungs, leading to selective release of proinflammatory mediators. This effect may be augmented by neuropeptides or cytokines. CRH also reduces T-regulatory cell production of interleukin 10, which in known to inhibit allergic mast cell activation.

CONCLUSION

More studies are required to investigate lung levels of CRH and selective mast cell mediators. Reducing stress and using CRH receptor antagonists and/or mast cell blockers may serve as possible new therapeutic approaches for asthma.

Eosinophils as a novel cell source of prostaglandin D2: autocrine role in allergic inflammation

PGD(2) is a key mediator of allergic inflammatory diseases that is mainly synthesized by mast cells, which constitutively express high levels of the terminal enzyme involved in PGD(2) synthesis, the hematopoietic PGD synthase (H-PGDS). In this study, we investigated whether eosinophils are also able to synthesize, and therefore, supply biologically active PGD(2). PGD(2) synthesis was evaluated within human blood eosinophils, in vitro differentiated mouse eosinophils, and eosinophils infiltrating inflammatory site of mouse allergic reaction. Biological function of eosinophil-derived PGD(2) was studied by employing inhibitors of synthesis and activity. Constitutive expression of H-PGDS was found within nonstimulated human circulating eosinophils. Acute stimulation of human eosinophils with A23187 (0.1-5 μM) evoked PGD(2) synthesis, which was located at the nuclear envelope and was inhibited by pretreatment with HQL-79 (10 μM), a specific H-PGDS inhibitor. Prestimulation of human eosinophils with arachidonic acid (10 μM) or human eotaxin (6 nM) also enhanced HQL-79-sensitive PGD(2) synthesis, which, by acting on membrane-expressed specific receptors (D prostanoid receptors 1 and 2), displayed an autocrine/paracrine ability to trigger leukotriene C(4) synthesis and lipid body biogenesis, hallmark events of eosinophil activation. In vitro differentiated mouse eosinophils also synthesized paracrine/autocrine active PGD(2) in response to arachidonic acid stimulation. In vivo, at late time point of the allergic reaction, infiltrating eosinophils found at the inflammatory site appeared as an auxiliary PGD(2)-synthesizing cell population. Our findings reveal that eosinophils are indeed able to synthesize and secrete PGD(2), hence representing during allergic inflammation an extra cell source of PGD(2), which functions as an autocrine signal for eosinophil activation.

Janus kinase-3 dependent inflammatory responses in allergic asthma

Allergic asthma is a chronic inflammatory condition of the lung characterized by reversible airway obstruction, high serum immunoglobulin (Ig) E levels, and chronic airway inflammation. A number of cells including mast cells, T cells, macrophages and dendritic cells play a role in the pathogenesis of the disease. Janus kinase (JAK)-3, a non-receptor protein tyrosine kinase, traditionally known to mediate cytokine signaling, also regulates functional responses of these cells. In this review the role of JAK-3 in regulating various pathogenic processes in allergic asthma is discussed. We propose that targeting JAK-3 is a rationale approach to control the inflammatory responses of multiple cell types responsible for the pathogenesis of allergic asthma.

Renin-angiotensin system in human coronavirus pathogenesis

Although initially considered relatively harmless pathogens, human coronaviruses (HCoVs) are nowadays known to be associated with more severe clinical complications. Still, their precise pathogenic potential is largely unknown, particularly regarding the most recently identified species HCoV-NL63 and HCoV-HKU1. HCoVs need host cell proteins to successively establish infections. Proteases of the renin–angiotensin system serve as receptors needed for entry into target cells; this article describes the current knowledge on the involvement of this system in HCoV pathogenesis.

Mouse mast cell protease 4 is the major chymase in murine airways and has a protective role in allergic airway inflammation

It is widely established that mast cells (MCs) have a harmful role in asthma, for example by secreting various proinflammatory substances stored within their secretory granule. However, in this study, we show that one of the substances stored within MC granule, chymase, in fact has a protective role in allergic airway inflammation, indicating that MCs may possess both harmful and protective activities in connection with this type of disease. Wild-type (WT) mice and mice lacking mouse MC protease 4 (mMCP-4), a chymase that is functionally homologous to human chymase, were sensitized and challenged with OVA, followed by the assessment of airway physiology and inflammatory parameters. Our results show that the airway hyperresponsiveness was significantly higher in mMCP-4(-/-) as compared with WT mice. Moreover, the degree of lung tissue inflammation was markedly higher in mice lacking mMCP-4 than in WT controls. Histological analysis revealed that OVA sensitization/challenge resulted in a marked increased in the thickness of the smooth muscle cell (SMC) layer and, notably, that the degree of SMC layer thickening was more pronounced in mMCP-4(-/-) animals than in WT controls, thus indicating that chymase may have an effect on airway SMCs. In support of this, mMCP-4-positive MCs were located in the close vicinity of the SMC layer, mainly in the upper airways, and mMCP-4 was shown to be the major chymase expressed in these MCs. Taken together, our results indicate that chymase present in the upper airways protects against allergic airway responses, possibly by regulating SMCs.

Expression of ADAMs ("a disintegrin and metalloprotease") in the human lung

In view of the associations of "a disintegrin and metalloprotease" (ADAM) with respiratory diseases, we assessed the expression of various ADAMs in human lung tissue. Lung tissue was obtained from nine individuals who underwent surgery for lung cancer or underwent lung transplantation for emphysema. Also, 16HBE 14o- (human bronchial epithelial) and A549 (alveolar type II epithelium-like) cell lines were used. Immunohistochemistry was performed with antibodies recognizing different ADAM domains. The ADAMs were typically distributed over the bronchial epithelium. ADAM8 and ADAM10 were expressed diffusely in all layers of the epithelium. ADAM9, ADAM17, and ADAM19 were predominantly expressed in the apical part of the epithelium, and ADAM33 was predominantly and strongly expressed in basal epithelial cells. In smooth muscle, ADAM19 and ADAM17 were strongly expressed, as was ADAM33, though this expression was weaker. ADAM33 was strongly expressed in vascular endothelium. All ADAMs were generally expressed in inflammatory cells. The typical distribution of ADAMs in the lung, especially in the epithelium, is interesting and suggests a localized function. As most ADAMs are involved in release of (pro-) inflammatory mediators and growth factors, they may play an important role in the first line of defense and in initiation of repair events in the airways.

Mast cells in tumor growth: angiogenesis, tissue remodelling and immune-modulation

There is a growing acceptance that tumor-infiltrating myeloid cells play an active role in tumor growth and mast cells are one of the earliest cell types to infiltrate developing tumors. Mast cells accumulate at the boundary between healthy tissues and malignancies and are often found in close association with blood vessels within the tumor microenvironment. They express many pro-angiogenic compounds, and may play an early role in angiogenesis within developing tumors. Mast cells also remodel extracellular matrix during wound healing, and this function is subverted in tumor growth, promoting tumor spread and metastasis. In addition, mast cells modulate immune responses by dampening immune rejection or directing immune cell recruitment, depending on local stimuli. In this review, we focus on key roles for mast cells in angiogenesis, tissue remodelling and immune modulation and highlight recent findings on the integral role that mast cells play in tumor growth. New findings suggest that mast cells may serve as a novel therapeutic target for cancer treatment and that inhibiting mast cell function may lead to tumor regression.

Interaction between prostaglandin D and chemoattractant receptor-homologous molecule expressed on Th2 cells mediates cytokine production by Th2 lymphocytes in response to activated mast cells

The mechanisms by which immunologically activated mast cells stimulate the production of proinflammatory cytokines by T helper type 2 (Th2) lymphocytes were investigated in a human cell culture system. Supernatants collected from cord blood-derived mast cells after treatment with immunoglobulin E (IgE)/anti-IgE contained an activity that stimulated the production of interleukin (IL)-4, IL-5 and IL-13 (both mRNA and protein) by Th2 lymphocytes. This activity was not detected in supernatants from unactivated mast cells and its production was inhibited by treatment of activated mast cells with the cyclo-oxygenase inhibitor diclofenac. The concentration of diclofenac used inhibited completely the production of prostaglandin D(2) (PGD(2)) but did not inhibit the release of histamine or leukotriene C(4). The effect of supernatants from activated mast cells was mimicked by exogenous PGD(2) at concentrations similar to those detected in the cultures of activated mast cells, and addition of exogenous PGD(2) to supernatants from diclofenac-treated mast cells restored their ability to stimulate Th2 cytokine production. The ability of the mast cell supernatants to stimulate production of Th2 cytokines was not affected by addition of diclofenac to the Th2 cells directly, indicating that the production, but not the action, of the factor was sensitive to diclofenac treatment. Inhibition of chemoattractant receptor-homologous molecule expressed on Th2 cells (CRTH2) abolished the effect of the mast cell supernatants on Th2 cytokine production. These data indicate that mast cells have the ability to stimulate Th2 cells to elaborate cytokines independently of T cell receptor activation or co-stimulation and this response is mediated by PGD(2) acting upon CRTH2 expressed by Th2 cells.

A new chemical tool (C0036E08) supports the role of adenosine A(2B) receptors in mediating human mast cell activation

Asthma is a chronic inflammatory disease of the airways that involves many cell types, amongst which mast cells are known to be important. Adenosine, a potent bronchoconstricting agent, exerts its ability to modulate adenosine receptors of mast cells thereby potentiating derived mediator release, histamine being one of the first mediators to be released. The heterogeneity of sources of mast cells and the lack of highly potent ligands selective for the different adenosine receptor subtypes have been important hurdles in this area of research. In the present study we describe compound C0036E08, a novel ligand that has high affinity (pK(i) 8.46) for adenosine A(2B) receptors, being 9 times, 1412 times and 3090 times more selective for A(2B) receptors than for A(1), A(2A) and A(3) receptors, respectively. Compound C0036E08 showed antagonist activity at recombinant and native adenosine receptors, and it was able to fully block NECA-induced histamine release in freshly isolated mast cells from human bronchoalveolar fluid. C0036E08 has been shown to be a valuable tool for the identification of adenosine A(2B) receptors as the adenosine receptors responsible for the NECA-induced response in human mast cells. Considering the increasing interest of A(2B) receptors as a therapeutic target in asthma, this chemical tool might provide a base for the development of new anti-asthmatic drugs.

Serotonin and histamine storage in mast cell secretory granules is dependent on serglycin proteoglycan

BACKGROUND

Serotonin and histamine are components of human and rodent mast cell secretory granules.

OBJECTIVE

Serotonin and histamine are stored in the same compartment as serglycin proteoglycan. Here we addressed the possibility that serglycin may be involved in their storage and/or release.

METHODS

The storage and release of histamine and serotonin was studied in bone marrow-derived mast cells (BMMCs) and in peritoneal mast cells from wild-type or serglycin-/- mice.

RESULTS

Both serotonin and histamine storage in BMMCs was positively correlated with the degree of mast cell differentiation, and the amount of stored amine was reduced in serglycin-/- BMMCs compared with wild-type controls. The amounts of histamine/serotonin stored were reflected by the expression levels of histidine decarboxylase and tryptophan hydroxylase 1, respectively. Calcium ionophore activation resulted in serotonin/histamine release both from wild-type and serglycin-/- BMMCs. Interestingly, serotonin release was induced in cells lacking intracellular stores of serotonin, suggesting de novo synthesis. The knockout of serglycin affected the levels of stored and released mast cell serotonin and histamine to an even larger extent in in vivo-derived mast cells than in BMMCs.

CONCLUSION

These results establish a previously assumed, but not proven, role of serglycin in storage of histamine and, further, establish for the first time that serotonin storage in mast cells is dependent on serglycin proteoglycan.

Mast cell renin and a local renin-angiotensin system in the airway: role in bronchoconstriction

We previously reported that mast cells express renin, the rate-limiting enzyme in the renin-angiotensin cascade. We have now assessed whether mast cell renin release triggers angiotensin formation in the airway. In isolated rat bronchial rings, mast cell degranulation released enzyme with angiotensin I-forming activity blocked by the selective renin inhibitor BILA2157. Local generation of angiotensin (ANG II) from mast cell renin elicited bronchial smooth muscle contraction mediated by ANG II type 1 receptors (AT(1)R). In a guinea pig model of immediate type hypersensitivity, anaphylactic mast cell degranulation in bronchial rings resulted in ANG II-mediated constriction. As in rat bronchial rings, bronchoconstriction (BC) was inhibited by a renin inhibitor, an AT(1)R blocker, and a mast cell stabilizer. Anaphylactic release of renin, histamine, and beta-hexosaminidase from mast cells was confirmed in the effluent from isolated, perfused guinea pig lung. To relate the significance of this finding to humans, mast cells were isolated from macroscopically normal human lung waste tissue specimens. Sequence analysis of human lung mast cell RNA showed 100% homology between human lung mast cell renin and kidney renin between exons 1 and 10. Furthermore, the renin protein expressed in lung mast cells was enzymatically active. Our results demonstrate the existence of an airway renin-angiotensin system triggered by release of mast-cell renin. The data show that locally produced ANG II is a critical factor governing BC, opening the possibility for novel therapeutic targets in the management of airway disease.

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

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

A dominant role for chemoattractant receptor-homologous molecule expressed on T helper type 2 (Th2) cells (CRTH2) in mediating chemotaxis of CRTH2+ CD4+ Th2 lymphocytes in response to mast cell supernatants

Human cultured mast cells, immunologically activated with immunoglobuin E (IgE)/anti-IgE, released a factor(s) that promoted chemotaxis of human CRTH2+ CD4+ T helper type 2 (Th2) lymphocytes. Mast cell supernatants collected at 20 min, 1 hr, 2 hr and 4 hr after activation caused a concentration-dependent increase in the migration of Th2 cells. The effect of submaximal dilutions of mast-cell-conditioned media was inhibited in a dose-dependent manner by ramatroban (IC50 = 96 nm), a dual antagonist of both the thromboxane-like prostanoid (TP) receptor and the chemoattractant receptor-homologous molecule expressed on Th2 cells (CRTH2), but not by the selective TP antagonist SQ29548, implicating CRTH2 in mediating the chemotactic response of these Th2 cells. The effect of mast-cell-conditioned media was mimicked by prostaglandin D2 (PGD2) and this eicosanoid was detected in the conditioned media from activated mast cells in concentrations sufficient to account for the activity of the mast cell supernatants. Treatment of the mast cells with the cyclo-oxygenase inhibitor diclofenac (10 microm) inhibited both the production of PGD2 and the CRTH2+ CD4+ Th2-stimulatory activity, while addition of exogenous PGD2 to conditioned media from diclofenac-treated mast cells restored the ability of the supernatants to promote chemotaxis of these Th2 cells. The degree of inhibition caused by diclofenac treatment of the mast cells was concordant with the degree of inhibition of chemotactic responses afforded by CRTH2 blockade. These data suggest that PGD2, or closely related metabolites of arachidonic acid, produced from mast cells may play a central role in the activation of CRTH2+ CD4+ Th2 lymphocytes through a CRTH2-dependent mechanism.

Mast cells can promote the development of multiple features of chronic asthma in mice

Bronchial asthma, the most prevalent cause of significant respiratory morbidity in the developed world, typically is a chronic disorder associated with long-term changes in the airways. We developed a mouse model of chronic asthma that results in markedly increased numbers of airway mast cells, enhanced airway responses to methacholine or antigen, chronic inflammation including infiltration with eosinophils and lymphocytes, airway epithelial goblet cell hyperplasia, enhanced expression of the mucin genes Muc5ac and Muc5b, and increased levels of lung collagen. Using mast cell-deficient (Kit(W-sh/W-sh) and/or Kit(W/W-v)) mice engrafted with FcRgamma+/+ or FcRgamma-/- mast cells, we found that mast cells were required for the full development of each of these features of the model. However, some features also were expressed, although usually at less than wild-type levels, in mice whose mast cells lacked FcRgamma and therefore could not be activated by either antigen- and IgE-dependent aggregation of Fc epsilonRI or the binding of antigen-IgG1 immune complexes to Fc gammaRIII. These findings demonstrate that mast cells can contribute to the development of multiple features of chronic asthma in mice and identify both Fc Rgamma-dependent and Fc Rgamma-independent pathways of mast cell activation as important for the expression of key features of this asthma model.

Regulation of allergic airway inflammation through Toll-like receptor 4-mediated modification of mast cell function

In a mouse experimental asthma model, the administration of bacterial lipopolysaccharide (LPS), particularly at low doses, enhances the levels of ovalbumin (OVA)-induced eosinophilic airway inflammation. In an effort to clarify the cellular and molecular basis for the LPS effect, we demonstrate that the OVA-induced eosinophilic inflammation in the lung is dramatically increased by the administration of LPS in wild-type mice, whereas such increase was not observed in mast-cell-deficient mice or Toll-like receptor (TLR)4-deficient mice. Adoptive transfer of bone-marrow-derived mast cells (BMMCs) from wild-type, but not from TLR4-deficient, mice restored the increased eosinophilic inflammation in mast-cell-deficient mice. Wild-type BMMCs pretreated with LPS in vitro also reconstituted the eosinophilic inflammation. Moreover, in vitro analysis revealed that the treatment of BMMCs with LPS resulted in NF-kappaB activation, sustained up-regulation of GATA1 and -2 expression, and increased the capability to produce IL-5 and -13. Dramatic increases in the expression of IL-5 and -13 and Eotaxin 2 were detected in LPS-treated BMMCs after costimulation with LPS and IgE/Ag. Overexpression of GATA1, but not GATA2, in MC9 mast cells resulted in increased transcriptional activity of IL-4, -5, and -13. Furthermore, the levels of transcription of Th2 cytokines in BMMCs were decreased by the introduction of small interfering RNA for GATA1. Thus, mast cells appear to control allergic airway inflammation after their activation and modulation through TLR4-mediated induction of GATA1 and subsequent increase in Th2 cytokine production.

Targeted chiral lipidomics analysis

Genomics, transcriptomics, and proteomics are proving to be very useful techniques, which have impacted significantly on our understanding mechanisms of human disease. However, this systems biology approach has several drawbacks than can be overcome by the integration of metabonomics and lipidomics. We have developed a targeted lipidomics approach that makes it possible to directly analyze chiral lipids generated in cellular systems. Bioactive lipids are usually present in trace amounts as enanatiomers and regioisomers that require separation before they can be analyzed by mass spectrometry. Normal phase chiral chromatography is generally used to resolve bioactive lipid enanatiomers. However, conventional electrospray and atmospheric pressure chemical ionization/tandem mass spectrometry have limited sensitivity when normal phase solvents are used, which makes it difficult to conduct studies when only trace amounts of the bioactive lipids are present. The use of electron capture atmospheric pressure chemical ionization/tandem mass spectrometry overcomes this problem. Enantiomers and regioisomers of targeted bioactive lipids can be quantified using stable isotope dilution methodology coupled with normal phase chiral chromatography and electron capture atmospheric chemical ionization/tandem mass spectrometry. A targeted lipidomics profile from rat epithelial cells transfected with cyclooxygenase-2 and maintained in culture was obtained. Inhibition with the non-selective cyclooxygenase inhibitor aspirin increased the formation of 15(R)-hydroxyeicosatetraenoic acid in the cells although it completely inhibited formation of the 15(S)-enantiomer and prostaglandin E2. New mass spectrometry instrumentation with an improved atmospheric pressure chemical ionization source was found to be an order of magnitude more sensitive than existing instruments for analysis of bioactive lipids using electron capture methodology. This type of mass spectrometer will permit a more detailed analysis of cellular bioactive lipid production than has been possible previously. It will also permit in vivo targeted lipidomics studies to be conducted using biological fluids derived from animal models and human subjects.

Evaluation of the toll-like receptor 6 Ser249Pro polymorphism in patients with asthma, atopic dermatitis and chronic obstructive pulmonary disease

Background

For allergic disorders, the increasing prevalence over the past decade has been attributed in part to the lack of microbial burden in developed countries ('hygiene hypothesis'). Variation in genes encoding toll-like receptors (TLRs) as the receptor system for the first innate immune response to microbial stimuli has been implicated in various inflammatory diseases. We evaluated here the role of a coding variation, Ser249Pro, in the TLR6 gene in the pathogenesis of asthma, atopic dermatitis (AD) and chronic obstructive pulmonary disease (COPD).

Methods

Genotyping of the Ser249Pro polymorphism in 68 unrelated adult patients and 132 unrelated children with asthma, 185 unrelated patients with COPD, 295 unrelated individuals with AD and 212 healthy control subjects was performed by restriction enzyme digestion.

Results

We found a weak association of the 249Ser allele with childhood asthma (p = 0.03). Yet, significance was lost after Bonferroni correction. No association was evident for AD or COPD.

Conclusion

Variation in TLR6 might play a role in the pathogenesis of childhood asthma.

Antibody-antigen interaction in the airway drives early granulocyte recruitment through BLT1

Antibody-antigen interactions in the airway initiate inflammation in acute asthma exacerbations. This inflammatory response is characterized by the recruitment of granulocytes into the airways. In murine models of asthma, granulocyte recruitment into the lung contributes to the development of airway hyperresponsiveness (AHR), mucus production, and airway remodeling. Leukotriene B4 is a mediator released following antigen challenge that has chemotactic activity for granulocytes, mediated through its receptor, BLT1. We investigated the role of BLT1 in granulocyte recruitment following antigen challenge. Wild-type mice and BLT1-/- mice were sensitized and challenged with ovalbumin (OVA) to induce acute allergic airway inflammation. In addition, to explore the relevance to antibody-antigen interactions, we injected OVA bound to anti-OVA IgG1 or anti-OVA IgE intratracheally into naïve wild-type and BLT1-/- mice. Cell composition of the lungs, cytokine levels, histology, and AHR were determined. After sensitization and challenge with ovalbumin, there was significantly reduced neutrophil and eosinophil recruitment into the airways of BLT1-/- mice compared with wild-type animals after one or two daily antigen challenges, but this difference was not seen after three or four daily antigen challenges. Mucus production and AHR were not affected. Intratracheal injection of OVA bound to IgG1 or IgE induced neutrophil recruitment into the airways in wild-type mice but not in the BLT1-/- mice. We conclude that BLT1 mediates early recruitment of granulocytes into the airway in response to antigen-antibody interactions in a murine model of acute asthma.

High-resolution tracking of cell division demonstrates differential effects of TH1 and TH2 cytokines on SCF-dependent human mast cell production in vitro: correlation with apoptosis and Kit expression

T-helper 1 (TH1) (interferon-gamma [IFN-gamma]) and TH2 (interleukin-4 [IL-4] and IL-5) cytokines have been variably reported to alter human mast cell numbers in complex culture systems. The effects of these cytokines on the kinetics of cell division and cell death are unknown, and their effect on mast cell behavior is relevant to anticipate the consequences of in vivo strategies that alter cytokine levels. To determine the effect of these cytokines on stem cell factor (SCF)-dependent human mast cell production, we used high-resolution tracking of cell division and correlated the results with cell apoptosis, expression of Kit, and mast cell degranulation. When IFN-gamma, IL-5, or IL-4 was administered over 8 weeks, we found each cytokine decreased the mast number through a different mechanism. IFN-gamma inhibited early progenitor cell division, IL-4 down-regulated early Kit expression, and IL-5 blocked later cell division. Further, IL-4 and IFN-gamma had the greatest suppressive effect on degranulation and FcepsilonRI expression. When these cytokines were administered to mature mast cells, IFN-gamma and IL-5 had no effect on degranulation and cell division, but IL-4 induced division and potentiated FcepsilonRI-mediated degranulation. Thus, exposure of human mast cells to IL-4, IL-5, and IFN-gamma during growth and differentiation generally down-regulated mast cell number and function, whereas IL-4 increased mature mast cell division and degranulation.

Mast cells in inflammatory arthritis

Mast cells are present in limited numbers in normal human synovium, but in rheumatoid arthritis and other inflammatory joint diseases this population can expand to constitute 5% or more of all synovial cells. Recent investigations in a murine model have demonstrated that mast cells can have a critical role in the generation of inflammation within the joint. This finding highlights the results of more than 20 years of research indicating that mast cells are frequent participants in non-allergic immune responses as well as in allergy. Equipped with a diversity of surface receptors and effector capabilities, mast cells are sentinels of the immune system, detecting and delivering a first response to invading bacteria and other insults. Accumulating within inflamed tissues, mast cells produce cytokines and other mediators that may contribute vitally to ongoing inflammation. Here we review some of the non-allergic functions of mast cells and focus on the potential role of these cells in murine and human inflammatory arthritis.