Mast Cell-mediated Responses Research Articles

TAK1 signaling activity links the mast cell cytokine response and degranulation in allergic inflammation.

Mast cells drive the inappropriate immune response characteristic of allergic inflammatory disorders via release of pro-inflammatory mediators in response to environmental cues detected by the IgE-FcεRI complex. The role of TGF-β-activated kinase 1 (TAK1), a participant in related signaling in other contexts, remains unknown in allergy. We detect novel activation of TAK1 at Ser412 in response to IgE-mediated activation under SCF-c-kit potentiation in a mast cell-driven response characteristic of allergic inflammation, which is potently blocked by TAK1 inhibitor 5Z-7-oxozeaenol (OZ). We, therefore, interrogated the role of TAK1 in a series of mast cell-mediated responses using IgE-sensitized murine bone marrow-derived mast cells, stimulated with allergen under several TAK1 inhibition strategies. TAK1 inhibition by OZ resulted in significant impairment in the phosphorylation of MAPKs p38, ERK, and JNK; and mediation of the NF-κB pathway via IκBα. Impaired gene expression and near abrogation in release of pro-inflammatory cytokines TNF, IL-6, IL-13, and chemokines CCL1, and CCL2 was detected. Finally, a significant inhibition of mast cell degranulation, accompanied by an impairment in calcium mobilization, was observed in TAK1-inhibited cells. These results suggest that TAK1 acts as a signaling node, not only linking the MAPK and NF-κB pathways in driving the late-phase response, but also initiation of the degranulation mechanism of the mast cell early-phase response following allergen recognition and may warrant consideration in future therapeutic development.

Deciphering the role of Interleukin-33, a Janus-Faced cytokine, in mast cell-mediated responses in allergic asthma using systems immunological methodologies

Abstract The prevalence of Allergy and Asthma has been increasing over the past decade, and about 300 million people suffer from these diseases worldwide. Interleukin-33 (IL-33), an Interleukin-1 family of cytokine, binds with the IL-33 receptor (IL-33R) to elicit an array of molecular and cellular processes in immune cells. Here, we have studied the role of IL-33 in mast cell-mediated responses and its impact on allergic asthma using systems immunological methodologies. We have obtained all the microarray datasets from the Gene Expression Omnibus (GEO) related to the IL-33 treated mast cells and allergic asthma. The datasets were analyzed using Genespring GX12.6 (Agilent Technologies, USA) to classify the differentially expressed genes (P<0.05) compared to untreated controls. The ingenuity pathway analysis (Qiagen, USA) of the IL-33 triggered differentially expressed genes in mast cells have revealed that the canonical pathways such as T-helper cell differentiation, the role of macrophages, fibroblasts, endothelial cells in autoimmunity, and chemokine signaling were significantly (P<0.05) upregulated. Besides, in-depth analyses of the IL-33 induced differentially expressed genes in mast cells and allergic asthma, using the comparison analysis module in IPA, showed a significant attenuation in HCK and other related signaling networks. However, the stimulation of both Th1 and Th2 associated cytokines by IL-33 could differentially regulate allergic asthma. Thus, IL-33 is a Janus-Faced cytokine in mast cell mediated allergic responses and, hence, requires further in vitro and in vivo studies to evaluate the therapeutic importance.

The role of individual protein kinase C isoforms in mouse mast cell function and their targeting by the immunomodulatory parasitic worm product, ES-62

ES-62, a glycoprotein secreted by the filarial nematode Acanthocheilonema viteae, has been shown to modulate the immune system through subversion of signal transduction pathways operating in various immune system cells. With respect to human bone marrow-derived mast cells (BMMCs), ES-62 was previously shown to inhibit FcϵRI-mediated mast cell functional responses such as degranulation and pro-inflammatory cytokine release through a mechanism involving the degradation of PKC-α. At the same time, it was noted that the worm product was able to degrade certain other PKC isoforms but the significance of this was uncertain. In this study, we have employed PKC isoform KO mice to investigate the role of PKC-α, -β -ϵ, and -θ in mouse BMMCs in order to establish their involvement in mast cell-mediated responses and also, if their absence impacts on ES-62’s activity. The data obtained support that in response to antigen cross-linking of IgE bound to FcϵRI, pro-inflammatory cytokine release is controlled in part by a partnership between one conventional and one novel isoform with PKC-α and -θ acting as positive regulators of IL-6 and TNF-α production, while PKC-β and ϵ act as negative regulators of such cytokines. Furthermore, ES-62 appears to target certain other PKC isoforms in addition to PKC-α to inhibit cytokine release and this may enable it to more efficiently inhibit mast cell responses.

Allergy therapy: The therapeutic potential of targeting sphingosine kinase signalling in mast cells

Mast cell activation is a central event in allergic diseases, and investigating the signalling pathways triggered during mast cell activation may lead to the discovery of novel therapeutic targets. Mast cells can be activated by a multitude of stimuli including antibodies/antigen, cytokines/chemokines and neuropeptides, resulting in a variety of responses including the immediate release of potent inflammatory mediators. Moreover, recent data suggest that mast cell-mediated responses are also influenced by the differential sphingolipids/sphingosine to sphingosine-1-phosphate ratio. The importance of sphingolipids as potent biological mediators of both intracellular and extracellular responses is being increasingly recognized and accepted; it is now appreciated that activation of mast cells, via the high-affinity IgE-receptor (FcepsilonRI) leads to the activation of sphingosine kinases (SphK), resulting in increased formation of sphingosine-1-phosphate. Furthermore, FcepsilonRI activates SphK-dependent calcium mobilization in mast cells, leading to degranulation, cytokine, and eicosanoid production, and chemotaxis. In the past two years a critical role for SphK in allergic responses in vivo has emerged. In this review, I focus on the current understanding of the role of sphingosine kinases during mast cell signalling in vitro and their role during hypersensitivity responses in vivo, and discuss the potential of these enzymes as novel therapeutic targets to treat allergic diseases.

Cosensitivity of vagal mucosal afferents to histamine and 5-HT in the rat jejunum.

A complex sensitivity of afferent nerves in the mesentery of the rat jejunum to systemic administration of histamine has recently been demonstrated. In the present study, we aimed to characterize subpopulations of mesenteric afferents that mediate this afferent nerve response. Multiunit afferent discharge was recorded from mesenteric nerves supplying the proximal jejunum in anesthetized rats. The majority of mesenteric bundles (84%) exhibited biphasic responses to histamine (8 micromol/kg), and these bundles also responded to 2-methyl-5-HT (2m5HT). In contrast, monophasic responses lacked a short-latency component, and these bundles failed to respond to 2m5HT. Single-unit analysis revealed a population of afferents that possessed cosensitivity for 2m5HT and histamine. This population of afferents was absent in chronically vagotomized animals, whereas mucosal anesthesia with luminal lidocaine reversibly converted the biphasic profile to a monophasic one. Ondansetron (500 microg/kg) blocked the response to 2m5HT with no effect on the profile of the histamine response, whereas pyrilamine (5 mg/kg) blocked the histamine response without affecting the response to 2m5HT. We conclude that histamine-sensitive afferents exist in the rat proximal jejunum that also respond to 5-HT via the 5-HT3 receptor. These fibers appear to be vagal afferents originating in the intestinal mucosa and may be involved in the organization of mast cell-mediated responses.

Immunologic mast cell-mediated responses and histamine release are attenuated by heparin.

Heparin has been shown to act as a competitive inhibitor of inositol 1,4,5-triphosphate (InsP3) receptors in various cell types. Because InsP3 is one of the second messengers involved in stimulus-secretion coupling in mast cells, it is possible that heparin may inhibit mast cell-mediated reactions. Therefore, in allergic sheep, we tested this hypothesis in two mast cell-mediated reactions induced by immunologic and nonimmunologic stimuli: immediate cutaneous reaction (ICR) and acute bronchoconstrictor response (ABR). In 12 sheep allergic to Ascaris suum antigen, the surface area of the skin wheal was determined 20 min after intradermal injection (0.05 ml) of increasing concentrations of specific antigen, compound 48/80, and histamine, without and after pretreatment with heparin (100, 300, or 1,000 U/kg i.v.). Antigen, compound 48/80, and histamine produced concentration-dependent increases in ICR. Heparin "partially" inhibited the ICR to antigen and compound 48/80 in a dose-dependent manner without modifying the ICR to histamine. The heparin preservative benzyl alcohol was ineffective. In 11 additional sheep, specific lung resistance was measured before and after inhalation challenges with antigen, compound 48/80, and histamine without and with aerosol heparin pretreatment (1,000 U/kg). Heparin blocked the antigen- and compound 48/80-induced bronchoconstriction without modifying the airway effects of histamine. In isolated human uterine mast cells, heparin inhibited the anti-immunoglobulin E- but not the calcium ionophore- (A23187) induced histamine release. These data suggest that heparin inhibits the ICR and ABR induced by stimuli that produce immunologic and nonimmunologic mast cell degranulation without attenuating the effects of histamine.(ABSTRACT TRUNCATED AT 250 WORDS)