Mast Cell Mediator Secretion Research Articles

Research progress of mast cell activation syndrome

Mast cells are the main effector cells in allergic diseases. Allergic diseases are mostly a direct result of mast cell mediator release effects, while allergen activation is only one of many triggers for mast cell mediator secretion. Increased mast cell number, high mast cell reactivity, or both can lead to abnormal mast cell activation. Mast cell activated syndrome (MCAS) refers to a group or a"spectrum"of mediator-related, symptomatically similar diseases in which mast cells are stimulated by multiple factors. The symptoms and signs of mast cell disease overlap with allergic diseases, but the etiology is different, which requires clinical attention. This article summarizes the research progress on mast cell activation syndrome in recent years thus increase awareness of the differential diagnosis.

Calpain-1 contributes to IgE-mediated mast cell activation.

Mast cells play a central role in allergy through secretion of both preformed and newly synthesized mediators. Mast cell mediator secretion is controlled by a complex network of signaling events. Despite intensive studies, signaling pathways in the regulation of mast cell mediator secretion remain incompletely defined. In this study, we examined the role of calpain in IgE-dependent mast cell activation. IgE-mediated activation of mouse bone marrow-derived mast cells enhanced calpain activity. Inhibition of calpain activity by a number of calpain inhibitors reduced IgE-mediated mast cell degranulation both in vitro and in vivo. Calpain inhibitors blocked IgE-mediated TNF and IL-6 production in vitro and reduced late-phase allergic response in vivo. Importantly, mouse calpain-1 null bone marrow-derived mast cells showed reduced IgE-mediated mast cell degranulation in vitro and in vivo, diminished cytokine and chemokine production in vitro, and impaired late-phase allergic response in vivo. Further studies revealed that calpain-1 deficiency led to specific attenuation of IκB-NF-κB pathway and IKK-SNAP23 pathway, whereas calcium flux, MAPK, Akt, and NFAT pathway proceed normally in IgE-activated calpain-1 null mast cells. Thus, calpain-1 is identified as a novel regulator in IgE-mediated mast cell activation and could serve as a potential therapeutic target for the management of allergic inflammation.

Stem cell factor induces AP-1-dependent mast cell IL-6 production via MAPK kinase 3 activity

Mast cells are critical immune effectors abundant in tissues interfacing with the environment and have major roles in allergen-induced inflammation and host responses to infection. SCF is a regulator of mast cell function and growth. However, the critical mechanisms in SCF-directed events remain incompletely defined. Here, we have investigated the role of MKK3 in mast cell SCF signaling-dependent functions by using BMMCs from MKK3-deficient mice. MKK3 was phosphorylated rapidly and persistently following SCF-induced activation and contributed to mast cell proliferation but not survival or migration in response to SCF. Analysis of SCF-induced mast cell mediator secretion demonstrated that IL-6 production is specifically dependent on MKK3 signals, both independently and in concert with IgE. Analysis of SCF-induced signaling showed that sustained p38 phosphorylation was impaired in MKK3-deficient mast cells, where as early JNK and IκBα activation were enhanced. Notably, SCF-inducible expression and activation of c-Jun, a component of the AP-1 transcription factor, was significantly dependent on MKK3. Accordingly, AP-1 DNA-binding activity and interaction with the IL6 gene promoter was markedly impaired in MKK3-deficient mast cells, whereas transcription factors of the Egr family, NF-κB, and NFAT retained near-full activity. These results designate MKK3 as a novel, positive regulator of SCF-induced mast cell proliferation and a critical signaling protein for AP-1-dependent IL-6 production.

Rethinking the Pathogenesis of Asthma

Asthma research has focused primarily on allergic pathways on the basis that the majority of asthma is associated with atopy, the recruitment of the Th2-type T cell, the cytokines, and the chemokines that are released on exposure to allergens, and the IgE pathway. However, despite considerable investment by industry, targeting these pathways has not resulted in new treatments being developed beyond blockade of cysteinyl leukotrienes and IgE and improvements in inhaled corticosteroids and beta(2)-adrenoceptor bronchodilators. Increasingly, it is recognized that asthma is a heterogeneous disorder, and while important, allergen sensitization is only one component of the disease, with many other environmental and genetic factors playing a role. In addition, these factors act locally on a susceptible airway epithelium that is both structurally and functionally deficient. It may be worthwhile to focus on increasing the resilience of the airways to environmental insults in addition to improving strategies that modify adaptive immunity or suppress inflammation.

The Early Growth Response Factor-1 Is Involved in Stem Cell Factor (SCF)-induced Interleukin 13 Production by Mast Cells, but Is Dispensable for SCF-dependent Mast Cell Growth

The stem cell factor (SCF) plays a central role in the regulation of mast cell function and growth. However, roles of transcription factors involved in these processes remain incompletely defined. The early growth response factor-1 (Egr-1) is a member of the zinc finger transcription factor family. A role for Egr-1 in SCF-induced mast cell activation and growth was investigated in mouse bone marrow-derived mast cells (BMMC). The stimulation of BMMC with SCF induced a strong expression of Egr-1 mRNA. SCF-induced Egr-1 nuclear translocation and DNA binding were demonstrated by electrophoretic mobility shift assay (EMSA) and immunofluorescence assay. SCF-induced IL-13 expression was significantly reduced at both mRNA and protein levels in Egr-1-deficient BMMC. In addition, the synergy between IgE and SCF on IL-13 and IL-4 production was reduced in Egr-1-deficient mast cells. Interestingly, Egr-1 deficiency had little effect on SCF-induced mast cell growth. SCF-induced Egr activation likely requires tyrosine phosphorylation because a tyrosine kinase inhibitor PP2 blocked SCF-induced nuclear protein binding to Egr probe as determined by EMSA. Thus, Egr-1 is required for SCF-induced IL-13 expression, but not mast cell growth. Egr-1 represents a novel mechanism for SCF-induced mast cell activation.

Phosphatase inhibition potentiates IL-6 production by mast cells in response to FcepsilonRI-mediated activation: involvement of p38 MAPK.

Mast cells are crucial effector cells in the immune response through mediator secretion and release of cytokines. A coordinated balance between protein kinases and phosphatases plays an essential role in the regulation of mast cell mediator secretion. We have previously shown that treatment of mast cells with okadaic acid (OA), a protein phosphatase 2A (PP2A) inhibitor, results in a dose-dependent increase in interleukin (IL)-6 production. We show here for the first time a synergism between OA and immunoglobulin E (IgE)-mediated IL-6 secretion by murine bone marrow-derived mast cells (BMMC). Selective p38 mitogen-activated protein kinase (p38 MAPK) inhibition reduces OA and IgE-mediated IL-6 production. Regulation of p38 MAPK by PP2A was demonstrated, as OA treatment caused a dose-dependent increase in p38 MAPK phosphorylation. Antigen-mediated activation of murine mast cells also resulted in an increase in p38 MAPK phosphorylation, which was potentiated by cotreatment of the cells with OA. Lastly, in two mast cell lines (human mast cell-1 5C6 and murine MC/9) and primary-cultured murine BMMC, we show by coimmunoprecipitation an interaction between p38 MAPK and PP2A. These data support a role for PP2A through interaction with p38 MAPK in the regulation of IgE-dependent mast cell activation.

Effect of Substance P on Histamine Secretion from Gut Mucosa in Inflammatory Bowel Disease

Background: Mast cell hyperplasia in the gut is a feature of inflammatory bowel disease (IBD), but the role of mast cells in this disease is still unclear. Since mast cell-nerve interactions might have some impact on intestinal inflammation, the present study investigated whether the neuropeptide substance P causes histamine secretion from human gut mucosal mast cells. Methods: Four hundred and eighteen colorectal endoscopic samples from 20 patients with IBD and 10 controls were studied. Colorectal biopsy samples were cultured in an oxygenated medium for spontaneous histamine release or were stimulated with substance P, anti-human immunoglobulin E, and a combination of substance P and anti-human immunoglobulin E. Histamine release was measured using a highly sensitive and specific radioimmunoassay. Results: Substance P failed to induce mast cell activation in histologically normal mucosa from controls. In contrast, mucosal specimens taken from inflamed IBD tissue or from uninvolved Crohn disease tissue showed a considerably enhanced rate of histamine secretion towards substance P, alone or in combination with anti-IgE. Unaffected mucosa with ulcerative colitis appeared insensitive towards substance P. Conclusions: The neuropeptide substance P was shown to preferentially enhance mucosal mast cell mediator secretion in active IBD. Thus, it appears likely that mast cell-nerve interactions are involved in as yet uninvestigated neurovegetative histamine-releasing processes of the gut in IBD.

Effect of colonoscopy premedication containing diazepam and pethidine on the release of mast cell mediators in gut mucosal samples.

To date there is no information available on whether drugs that are commonly used in premedication for colonoscopy procedures, such as diazepam and pethidine, may activate intestinal mast cells and thereby give rise to adverse effects. Since opioids such as pethidine are well-known for their ability to induce histamine release from several mast cell subtypes, the present study investigated the effect of diazepam and pethidine, intravenously administered as premedication for colonoscopy, on mast cell mediator secretion from colonic and rectal mucosa. The secretion of the mast cell mediators histamine and tryptase was followed from biopsies of patients with and without premedication for 30 minutes in an air-bubbled incubation medium (mucosa oxygenation). The mediator release and tissue histamine content were studied prospectively in 17 control persons (histologically normal mucosa) as well as in 71 patients with inflammatory bowel disease (IBD) (histologically uninvolved and involved tissue). Although a significant accumulation of histamine was found in inflamed IBD-tissue, the results indicate, however, that this premedication does not enhance the release of histamine or tryptase from gut mucosal samples, neither in the histologically normal mucosa of control persons nor in tissue unaffected or affected by inflammatory bowel disease. This study demonstrates that colonoscopy premedication with diazepam and pethidine is safe in terms of gut mucosal mast cell activation.

Inhibition of mast cell mediator secretion induced by protoporphyrin plus long-wave ultraviolet light: A morphometric and ultrastructural analysis

It has been shown that treatment of rat peritoneal mast cells with protoporphyrin plus long-wave ultraviolet light (UVA) irradiation can suppress mediator secretion. In this study we conducted a morphometric and ultrastructural analysis of rat peritoneal mast cells to investigate possible alterations produced by this treatment before or after stimulation with calcium ionophore. Protoporphyrin plus UVA, at doses causing inhibition of mediator release, had no effect on either cell size or viability but increased cellular sphericity. There was a 43% reduction of the cell surface area, and qualitative inspection of the cells revealed that this change was associated with a reduction in microfolds on the cell surface. After 1 minute of incubation with calcium ionophore A23187 (1 μmol/L), both cells that were pretreated with protoporphyrin plus UVA and control cells showed dramatic changes in granule structure. Although treated cells had an unchanged tendency to have granules that closely approached the plasma membrane, there was an inhibition of granule extrusion in response to ionophore stimulation. These observations may be relevant to the inhibitory effect of protoporphyrin plus UVA on the generation and release of mast cell mediators.

Is inhibition of mast cell mediator release relevant to the clinical activity of anti-allergic drugs?

The introduction of SCG for the treatment of bronchial asthma was viewed by many as the advent of a new era, the era of the antiallergic drug which acted by suppressing the release of inflammatory mediators from mast cells. However, some 17 years on, SCG is the only drug of its type on the market. Efforts to improve its efficacy by chemical modification have not succeeded. As it is now clear that all of the beneficial effects of SCG in asthma cannot be attributed to its effects on mast cell mediator secretion, it is not surprising that mast cell models are not predictive of clinical activity. Perhaps a clearer understanding of the basic bio-chemical mechanisms of SCG and its actions in animals and man may lead to development of more relevant models and to a more potent drug.