IL-4 amplifies the pro-inflammatory effect of adenosine in human mast cells by changing expression levels of adenosine receptors

Adenosine inhalation produces immediate bronchoconstriction in asthmatics but not in normal subjects. The bronchospastic effect of adenosine is largely mediated through adenosine-induced mast cell activation, the mechanism of which is poorly understood due to limitations in culturing human primary mast cells. Here, we show that human umbilical cord blood -derived mast cells incubated with the Th2 cytokine IL-4 develop increased sensitivity to adenosine. Potentiation of anti-IgE- induced and calcium ionophore/PMA-induced degranulation was augmented in mast cells cultured with IL-4, and this effect was reduced or abolished by pre-treatment with A(2B)siRNA and selective A(2B) receptor antagonists, respectively. IL-4 incubation resulted in the increased expression of A(2B) and reduced expression of A(2A) adenosine receptors on human mast cells. These results suggest that Th2 cytokines in the asthmatic lung may alter adenosine receptor expression on airway mast cells to promote increased responsiveness to adenosine.     

Th2-induced airway mucus production is dependent on IL-4Ralpha, but not on eosinophils

Mucus hyperproduction in asthma results from airway inflammation and contributes to clinical symptoms, airway obstruction, and mortality. In human asthmatics and in animal models, excess mucus production correlates with airway eosinophilia. We previously described a system in which TCR transgenic CD4 Th2 cells generated in vitro were transferred into recipient mice and activated in the respiratory tract with inhaled Ag. Th2 cells stimulated airway eosinophilia and a marked increase in mucus production, while mice that received Th1 cells exhibited airway inflammation without eosinophilia or mucus. Mucus could be induced by IL-4-/- Th2 cells at comparable levels to mucus induced by IL-4+/+ Th2 cells. In the current studies we dissect further the mechanisms of Th2-induced mucus production. When IL-4-/- Th2 cells are transferred into IL-4Ralpha-/- mice, mucus is not induced, and BAL eosinophilia is absent. These data suggest that in the absence of IL-4, IL-13 may be critical for Th2-induced mucus production and eosinophilia. To determine whether eosinophils are important in mucus production, IL-5-/- Th2 cells were transferred into IL-5-/- recipients. Eosinophilia was abolished, yet mucus staining in the epithelium persisted. These studies show definitively that IL-5, eosinophils, or mast cells are not essential, but signaling through IL-4Ralpha is critically important in Th2 cell stimulation of mucus production.     

Accumulation of peribronchial mast cells in a mouse model of ovalbumin allergen induced chronic airway inflammation: modulation by immunostimulatory DNA sequences

Few peribronchial mast cells are noted either in the lungs of naive mice or in the lungs of OVA-sensitized mice challenged acutely with OVA by inhalation. In this study, we demonstrate that OVA-sensitized mice exposed to repetitive OVA inhalation for 1-6 mo have a significant accumulation of peribronchial mast cells. This accumulation of peribronchial mast cells is associated with increased expression of the Th2 cell-derived mast cell growth factors, including IL-4 and IL-9, but not with the non-Th2 cell-derived mast cell growth factor, stem cell factor. Pretreating mice with immunostimulatory sequences (ISS) of DNA containing a CpG motif significantly inhibited the accumulation of peribronchial mast cells and the expression of IL-4 and IL-9. To determine whether mast cells express Toll-like receptor-9 (TLR-9; the receptor for ISS), TLR-9 expression by mouse bone marrow-derived mast cells (MBMMCs) was assessed by RT-PCR. MBMMCs strongly expressed TLR-9 and bound rhodamine-labeled ISS. However, incubation of MBMMCs with ISS in vitro neither inhibited MBMMC proliferation nor inhibited Ag/IgE-mediated MBMMC degranulation, but they did induce IL-6. Overall these studies demonstrate that mice exposed to repetitive OVA challenge, but not acute OVA challenge, have an accumulation of peribronchial mast cells and express increased levels of mast cell growth factors in the lung. Although mast cells express TLR-9, ISS does not directly inhibit mast cell proliferation in vitro, suggesting that ISS inhibits accumulation of peribronchial mast cells in vivo by indirect mechanism(s), which include inhibiting the lung expression of Th2 cell-derived mast cell growth factors.     

SHIP represses Th2 skewing by inhibiting IL-4 production from basophils

We report that SHIP(-/-) mice, compared to SHIP(+/+) mice, are Th2 skewed with elevated serum IgE and twice as many splenic CD4(+) Th2 cells that, when stimulated with anti-CD3, produce more IL-4 and less IFN-γ. Exploring the reason for this Th2 skewing, we found that freshly isolated SHIP(-/-) splenic and bone marrow basophils are present in elevated numbers and secrete far more IL-4 in response to IL-3 or to FcεRI stimulation than do WT basophils. These SHIP(-/-) basophils markedly skew wild-type macrophage colony stimulating factor-derived macrophages toward an M2 phenotype, stimulate OT-II CD4(+) Th cells to differentiate into Th2 cells, and trigger SHIP(+/+) B cells to become IgE-producing cells. All these effects are completely abrogated with neutralizing anti-IL-4 Ab. Exploring the cell signaling pathways responsible for hyperproduction of IL-4 by SHIP(-/-) basophils, we found that IL-3-induced activation of the PI3K pathway is significantly enhanced and that PI3K inhibitors, especially a p110α inhibitor, dramatically suppresses IL-4 production from these cells. In vivo studies, in which basophils were depleted from mast cell-deficient SHIP(+/+) and SHIP(-/-) mice, confirmed the central role that basophils play in the Th2 skewing of naive SHIP-deficient mice. Taken together, these studies demonstrate that SHIP is a potent negative regulator of IL-4 production from basophils and thus may be a novel therapeutic target for Th1- and Th2-related diseases.     

Identification of a novel cytokine, ML-1, and its expression in subjects with asthma

A novel gene, designated ML-1, was identified from a human genomic DNA clone and human T cell cDNA sequences. The second exon of ML-1 gene shares significant sequence identity with the gene encoding IL-17 (IL-17). ML-1 gene expression was up-regulated in activated PBMCs, CD4(+) T cells, allergen-specific Th0, Th1, and Th2 clones, activated basophils, and mast cells. Increased expression of the ML-1 gene, but not IL-17, was seen following allergen challenge in four asthmatic subjects, suggesting its role in allergic inflammatory responses. ML-1 from transiently transfected COS-7 cells was able to induce gene expression and protein production for IL-6 and IL-8 (at 10 ng/ml of ML-1: for IL-6, 599.6 +/- 19.1 pg/ml; for IL-8, 1724.2 +/- 132.9 pg/ml; and at 100 ng/ml of ML-1: for IL-6, 1005.3 +/- 55.6 pg/ml; for IL-8, 4371.4 +/- 280.5 pg/ml; p < 0.05 for both doses vs baseline) in primary bronchial epithelial (PBE) cells. Furthermore, increased expression of ICAM-1 was found in ML-1-stimulated PBE cells (mean fluorescence intensity (MFI) = 31.42 +/- 4.39 vs baseline, MFI = 12.26 +/- 1.77, p < 0.05), a functional feature distinct from IL-17 (MFI = 11.07 +/- 1.22). This effect was not inhibited by a saturating amount of IL-17. These findings demonstrate that ML-1 is a novel cytokine with a distinct function, and suggest a different receptor for ML-1 on PBE cells.     

BLT2 Is upregulated in allergen-stimulated mast cells and mediates the synthesis of Th2 cytokines

Mast cells are effector cells that mediate the allergic response through Ag stimulation of IgE bound to FcεRI. In allergic reactions, cross-linking of the surface receptors for IgE on mast cells results in the synthesis of Th2 cytokines such as IL-4 and IL-13, which are critical for the initiation and progression of the allergic response. Despite the important roles of these cytokines, the signaling mechanism by which Ag stimulation mediates the production of IL-4 and IL-13 in mast cells is not clearly understood. In the present study, we found that Ag-stimulated bone marrow-derived mast cells (BMMCs) highly upregulated the expression of BLT2, a leukotriene B(4) receptor, and that blockade of BLT2 with the specific antagonist LY255283 or small interfering RNA knockdown completely abolished the production of Th2 cytokines. Furthermore, BMMCs overexpressing BLT2 showed significantly enhanced production of Th2 cytokines compared with wild-type BMMCs. Additionally, we found that the generation of Nox1-derived reactive oxygen species occurs downstream of BLT2, thus mediating the synthesis of Th2 cytokines. Taken together, our results suggest that the BLT2-Nox1-reactive oxygen species cascade is a previously unsuspected mediatory signaling mechanism to Th2 cytokine production in Ag-stimulated BMMCs, thus contributing to allergic response.     

Adenosine-activated mast cells induce IgE synthesis by B lymphocytes: an A2B-mediated process involving Th2 cytokines IL-4 and IL-13 with implications for asthma

Adenosine provokes bronchoconstriction in asthmatics through acute activation of mast cells, but its potential role in chronic inflammation has not been adequately characterized. We hypothesized that adenosine up-regulates Th2 cytokines in mast cells, thus promoting IgE synthesis by B lymphocytes. We tested this hypothesis in human mast cells (HMC-1) expressing A(2A), A(2B), and A(3) adenosine receptors. The adenosine analog 5'-N-ethylcarboxamidoadenosine (NECA) (10 microM) increased mRNA expression of IL-1beta, IL-3, IL-4, IL-8, and IL-13, but not IL-2 and IFN-gamma. Up-regulation of IL-4 and IL-13 was verified using RT-PCR and ELISA; 10 microM NECA increased IL-13 concentrations in HMC-1 conditioned medium 28-fold, from 7.6 +/- 0.3 to 215 +/- 4 pg/ml, and increased IL-4 concentrations 6-fold, from 19.2 +/- 0.1 to 117 +/- 2 pg/ml. This effect was mediated by A(2B) receptors because neither the selective A(2A) agonist 2-p-(2-carboxyethyl)phenethylamino-NECA nor the selective A(3) agonist N(6)-(3-iodobenzyl)-N-methyl-5'-carbamoyladenosine reproduced it, and the selective A(2B) antagonist 3-isobutyl-8-pyrrolidinoxanthine prevented it. Constitutive expression of CD40 ligand on HMC-1 surface was not altered by NECA. Human B lymphocytes cocultured for 12 days with NECA-stimulated HMC-1 produced 870 +/- 33 pg IgE per 10(6) B cells, whereas lymphocytes cocultured with nonstimulated HMC-1, or cultured alone in the absence or in the presence of NECA, produced no IgE. Thus, we demonstrated induction of IgE synthesis by the interaction between adenosine-stimulated mast cells and B lymphocytes, and suggest that this mechanism is involved in the amplification of the allergic inflammatory responses associated with asthma.     

Identification of novel IL-4/Stat6-regulated genes in T lymphocytes

IL-4, primarily produced by T cells, mast cells, and basophiles, is a cytokine which has pleiotropic effects on the immune system. IL-4 induces T cells to differentiate to Th2 cells and activated B lymphocytes to proliferate and to synthesize IgE and IgG1. IL-4 is particularly important for the development and perpetuation of asthma and allergy. Stat6 is the protein activated by signal transduction through the IL-4R, and studies with knockout mice demonstrate that Stat6 is critical for a number of IL-4-mediated functions including Th2 development and production of IgE. In the present study, novel IL-4- and Stat6-regulated genes were discovered by using Stat6(-/-) mice and Affymetrix oligonucleotide arrays. Genes regulated by IL-4 were identified by comparing the gene expression profile of the wild-type T cells induced to polarize to the Th2 direction (CD3/CD28 activation + IL-4) to gene expression profile of the cells induced to proliferate (CD3/CD28 activation alone). Stat6-regulated genes were identified by comparing the cells isolated from the wild-type and Stat6(-/-) mice; in this experiment the cells were induced to differentiate to the Th2 direction (CD3/CD28 activation + IL-4). Our study demonstrates that a number a novel genes are regulated by IL-4 through Stat6-dependent and -independent pathways. Moreover, elucidation of kinetics of gene expression at early stages of cell differentiation reveals several genes regulated rapidly during the process, suggesting their importance for the differentiation process.     

Cutting edge: The ST2 ligand IL-33 potently activates and drives maturation of human mast cells

IL-33, the natural ligand of the IL-1 receptor family member ST2L, is known to enhance experimental allergic-type inflammatory responses by costimulating the production of cytokines from activated Th2 lymphocytes. Although ST2L has long been known to be expressed by mast cells, its role in their biology has not been explored. In this study we report that IL-33 directly stimulates primary human mast cells (MCs) to produce several proinflammatory cytokines and chemokines and also exerts a permissive effect on the MCs response to thymic stromal lymphopoietin, a recently described potent MCs activator. IL-33 also acts both alone and in concert with thymic stromal lymphopoietin to accelerate the in vitro maturation of CD34(+) MC precursors and induce the secretion of Th2 cytokines and Th2-attracting chemokines. Taken together, these results suggest that IL-33 may play an important role in mast cell-mediated inflammation and further emphasize the role of innate immunity in allergic diseases.     

Interleukin (IL)-33 induces the release of pro-inflammatory mediators by mast cells

IL-33 (or IL-1F11) was recently identified as a ligand for the previously orphaned IL-1 family receptor T1/ST2. Previous studies have established that IL-33 and T1/ST2 exert key functions in Th2 responses. In this study, we demonstrate that IL-33 induces the production of pro-inflammatory mediators in mast cells. IL-33 dose and time-dependently stimulated IL-6 secretion by P815 mastocytoma cells and primary mouse bone marrow-derived mast cells (BMMC). This effect was dependent on T1/ST2 binding. In addition, IL-33 also induced IL-1β, TNF-α, MCP-1, and PGD2 production in BMMC. By RNase protection assay, we demonstrated that IL-33 increased IL-6 and IL-1β mRNA expression. These effects of IL-33 appeared to occur independently of mast cell degranulation, The results of this study show for the first time that IL-33, a novel member of the IL-1 family of cytokines, stimulates the production of pro-inflammatory mediators by mast cells in addition to its effect on T helper 2 responses. These findings open new perspectives for the treatment of inflammatory diseases by targeting IL-33.     

IL-33 induces Th17-mediated airway inflammation via mast cells in ovalbumin-challenged mice

Allergic asthma is characterized by infiltration of eosinophils, elevated Th2 cytokine levels, airway hyperresponsiveness, and IgE. In addition to eosinophils, mast cells, and basophils, a variety of cytokines are also involved in the development of allergic asthma. The pivotal role of eosinophils in the progression of the disease has been a subject of controversy. To determine the role of eosinophils in the progression of airway inflammation, we sensitized and challenged BALB/c wild-type (WT) mice and eosinophil-deficient ΔdblGATA mice with ovalbumin (OVA) and analyzed different aspects of inflammation. We observed increased eosinophil levels and a Th2-dominant response in OVA-challenged WT mice. In contrast, eosinophil-deficient ΔdblGATA mice displayed an increased proportion of mast cells and a Th17-biased response following OVA inhalation. Notably, the levels of IL-33, an important cytokine responsible for Th2 immune deviation, were not different between WT and eosinophil-deficient mice. We also demonstrated that mast cells induced Th17-differentiation via IL-33/ST2 stimulation in vitro. These results indicate that eosinophils are not essential for the development of allergic asthma and that mast cells can skew the immune reaction predominantly toward Th17 responses via IL-33 stimulation.     

The IL-27 receptor (WSX-1) is an inhibitor of innate and adaptive elements of type 2 immunity

Although previous studies have investigated the role of IL-27/WSX-1 interactions in the regulation of Th1 responses, little is known about their role in regulating Th2-type responses. Studies presented in this work identify a direct role for IL-27/WSX-1 interactions in the negative regulation of type 2 responses independent of effects on type 1 cytokines. WSX-1-/- mice infected with the gastrointestinal helminth Trichuris muris displayed accelerated expulsion of parasites and the development of exaggerated goblet cell hyperplasia and mastocytosis in the gut due to increased production of Th2 cytokines. Enhanced mast cell activity in the absence of WSX-1 was consistent with the ability of wild-type mast cells to express this receptor. In addition, IL-27 directly suppressed CD4+ T cell proliferation and Th2 cytokine production. Together, these studies identify a novel role for IL-27/WSX-1 in limiting innate and adaptive components of type 2 immunity at mucosal sites.     

婴儿双歧杆菌对花生过敏小鼠模型肠道Th2反应的调节

目的研究婴儿型双歧杆菌对花生过敏小鼠肠道Th2型反应的调节作用。方法通过应用花生蛋白诱导肠道的Th2型反应,建立食物过敏小鼠模型。过敏小鼠灌胃给予婴儿型双歧杆菌（ATCC菌或CGMCC0313-2）或不做处理。然后分离小鼠小肠黏膜CD4＋T细胞或DC,另取肠黏膜组织进行石蜡包埋甲苯胺蓝染色肥大细胞计数,HE染色进行嗜酸细胞和单个核细胞计数,流式细胞检测CD4＋T中Th2（CD4＋IL4＋T）细胞和Treg（CD4＋CD25＋Foxp3＋T）比例,另取CD4＋T进行CFSE标记,与DC共培养4d后流式细胞检测CD4＋T增殖反应,收集细胞培养液ELISA检测IL-4、IL-5和IL—13分泌水平。结果过敏组小鼠Th2型细胞数,CD4＋T细胞增殖反应,IL4、IL-5和IL-13水平,肠黏膜中肥大细胞、嗜酸性细胞和单个核细胞数均明显高于对照组（P〈0．01）,而Treg数目低于对照组（P〈0．01）,婴儿双歧杆菌干预后,婴儿双歧杆菌组Th2型细胞数,IL4、IL-5和IL-13水平,肠黏膜中肥大细胞、嗜酸性细胞和单个核细胞数均明显低于过敏组（P〈0．01）,而Treg数目高于过敏组（P〈0．01）。结论口服婴儿型双歧杆菌可以抑制花生过敏导致的肠道Th2型反应。     

Murine abortion is associated with enhanced interleukin-6 levels at the feto-maternal interface

CBA/JXDBA/2J murine abortion is known to be associated with increased local and peripheral Th1-cytokines levels. The role of the pro-inflammatory interleukin-6 (IL-6) in murine abortion remains unclear. In humans, IL-6 was reported to be elevated at the onset of spontaneous abortion. The aim of our study was to evaluate the levels of IL-6 during murine pregnancy in (1) the normal murine pregnancy combination CBA/JXBALB/c and in (2) the CBA/JXDBA/2J abortion prone mating combination. We measured IL-6 serum levels by ELISA and local (placental and decidual) IL-6 levels by flow cytometry and immunohistochemistry. The expression of the IL-6 receptor gp80 was further analyzed. We additionally evaluated the number of mast cells and macrophages at the feto-maternal interface as a putative IL-6 source in reproductive tissues. IL-6 and gp80 were expressed in decidual cells as well as in different trophoblast types. Flow cytometry analysis showed increased numbers of IL-6+ cells in abortion placentas and deciduas compared to control pregnant mice. We observed an elevated number of mast cells and macrophages at the feto-maternal interface from abortion mice in comparison to control mice. Interestingly, we found very high numbers of mast cells, macrophages and IL-6+ cells in resorption tissue compared to control tissues. Flow cytometry studies confirmed that macrophages are being an important source of IL-6 at the feto-maternal interface. The mRNA IL-6 levels were also enhanced in placenta and decidua from mice with high abortion rate compared to normal pregnant mice, as analyzed by RT-PCR. Our results suggest that IL-6 produced not only by immunocompetent cells such as macrophages and mast cells, but also by trophoblasts and decidua cells, is directly involved in the pathology of abortion.