Modulation Of Mast Cell Function Research Articles

Repeated FcεRI triggering reveals modified mast cell function related to chronic allergic responses in tissue

Activation of mast cells through FcεRI plays an important role in acute allergic reactions. However, little is known about the function of mast cells in patients with chronic allergic inflammation or the effect of repeated FcεRI triggering occurring in such responses. We aimed to identify changes in mast cell function after repeated FcεRI triggering and to correlate these changes to chronic allergic responses in tissue. Human cord blood-derived mast cells were treated for 2weeks with anti-IgE. The function of naive or treated mast cells was analyzed by means of RNA sequencing, quantitative RT-PCR, flow cytometry, and functional assays. Protein secretion was measured with ELISAs and multiplex assays. We observed several changes in mast cell function after repeated anti-IgE triggering. Although the acute response was dampened, we identified 289 genes significantly upregulated after repeated anti-IgE. Most of these genes (84%) were not upregulated after a single anti-IgE stimulus, indicating a significantly different response mode characterized by increased antigen presentation, response to bacteria, and chemotaxis. Changes in mast cell function were related to changes in expression of the transcription factors RXRA and BATF and others. Importantly, we found a substantial overlap between genes upregulated after repeated anti-IgE triggering and genes upregulated in tissue from patients with chronic allergy, in particular those of patients with chronic rhinosinusitis. Our study provides evidence for intrinsic modulation of mast cell function on repeated FcεRI-mediated activation. The overlap with gene expression in tissues is suggestive of a direct link between repeated IgE-mediated activation of mast cells and chronic allergy.

AB0068 Potential Regulation of Mast Cell Function via Peroxisome Proliferator-Activated Receptor Pathway

BackgroundMast cells release important chemical mediators, including histamine, for the regulation of allergic reactions and inflammation upon activation with IgE-mediated or non IgE-mediated stimuli. Recently, we reported using a murine...

Modulation of Mast Cell Function by Amino Acids In vitro: A Potential Mechanism of Immunonutrition for Wound Healing.

Mast cells release important chemical mediators, such as histamine and interleukin (IL)-13, for the regulation of allergic reactions and inflammation. Recently, mast cell activation has been implicated in wound healing. Glutamine (Gln) and Arginine (Arg) are used as “immune nutrients” in severe infections and chronic wounds in malnourished patients, but the potential effect of these amino acids on mast cell activation is unclear. We evaluated the effect of Gln and / or Arg in culture on mast cell function. The murine mast cell line P815 was cultured in RPMI-1640 medium under different Gln and/or Arg concentrations and IL-6 stimulation. Histamine and IL-13 release into the supernatant was measured using enzyme-linked immunoassays. As a result, the amino acid concentrations affected cellular viability. Cells cultured in higher Gln concentrations produced a greater histamine response upon IL-6 stimulation while the histamine response in cells cultured in a high Arg concentration was suppressed. IL-13 production in the Gln containing medium was not significantly altered by IL-6 stimulation. In conclusion, in an inflammatory milieu, Gln and/or Arg concentrations in situ may regulate histamine and IL-13 release from mast cells. The appropriate use of functional amino acids as immune nutrients may suppress inflammation and aid in wound healing.

Modulation of mast cell function by TIM-1 signaling (177.4)

Abstract Transmembrane, immunoglobulin and mucin domain (TIM)-1 belongs to a family of transmembrane proteins with emerging roles in immune modulation. As a putative atopy susceptibility gene, polymorphisms in human and mouse TIM-1 are associated with atopic diseases, including asthma and atopic dermatitis. Antibodies targeting different extracellular domains of Tim-1 either attenuated or exacerbated airway inflammation in a mouse model of asthma. Recent studies found that Tim-1 is expressed on mast cells. Tim-1 crosslinking by its ligand Tim-4 enhanced secretion of pro-inflammatory cytokines in IgE and Ag-activated bone marrow-derived mast cells (BMMCs). However, the mechanism(s) by which Tim-1 modulates mast cell function and how Tim-1 activity may be altered by antibody treatment is unknown. We hypothesize that Tim-1 engagement provides a co-stimulatory signal to enhance mast cell degranulation and mediator release in allergic inflammation. We found that Tim-1 requires a tyrosine phosphorylation motif in its cytoplasmic tail to co-stimulate NF-AT/ AP1, NF-κB, and IL-6 promoter transcriptional activation as well as IL-6 cytokine secretion. Furthermore, IgE-Ag and Tim-1 costimulation of BMMCs using a panel of Tim-1 antibodies and its ligand Tim-4 demonstrate that IL-6 and TNF-alpha secretion can be modulated by activity of agonistic and blocking Tim-1 antibodies. These studies suggest that Tim-1 may serve as an important modulator of mast cell effector functions in atopic diseases.

T Cell-Mediated Modulation of Mast Cell Function: Heterotypic Adhesion-Induced Stimulatory or Inhibitory Effects

Close physical proximity between mast cells and T cells has been demonstrated in several T cell mediated inflammatory processes such as rheumatoid arthritis and sarcoidosis. However, the way by which mast cells are activated in these T cell-mediated immune responses has not been fully elucidated. We have identified and characterized a novel mast cell activation pathway initiated by physical contact with activated T cells, and showed that this pathway is associated with degranulation and cytokine release. The signaling events associated with this pathway of mast cell activation have also been elucidated confirming the activation of the Ras mitogen-activated protein kinase systems. More recently, we hypothesized and demonstrated that mast cells may also be activated by microparticles released from activated T cells that are considered as miniature version of a cell. By extension, microparticles might affect the activity of mast cells, which are usually not in direct contact with T cells at the inflammatory site. Recent works have also focused on the effects of regulatory T cells (Treg) on mast cells. These reports highlighted the importance of the cytokines IL-2 and IL-9, produced by mast cells and T cells, respectively, in obtaining optimal immune suppression. Finally, physical contact, associated by OX40–OX40L engagement has been found to underlie the down-regulatory effects exerted by Treg on mast cell function.

SCF and TLR4 ligand cooperate to augment the tumor-promoting potential of mast cells.

Mast cells may have either antitumor or tumor-promoting potential. Nevertheless, mast cells in tumor microenvironment have been found to promote tumor growth. So far the mechanisms underlying the modulation of mast cell function in tumor microenvironment remains to be fully elucidated. Here, we report that tumor-promoting potential of mast cells could be augmented by molecules released from damaged tumor cells through cooperative stimulation of stem cell factor (SCF) and ligand for Toll-like receptor 4 (TLR4). Co-simulation with SCF and TLR4 ligand inhibited mast cell degranulation, but efficiently induced the production and secretion of VEGF, PDGF, and IL-10. Although TLR4 ligand alone may induce IL-12 expression in mast cells, co-stimulation with SCF and TLR4 ligand induced the expression of IL-10, but not IL-12, in mast cells. The phosphorylation of GSK3β was crucial for the effect of SCF and TLR4 ligand. In addition to inducing phosphorylation of GSK3β at Ser9 through PI3K pathway, SCF and TLR4 ligand cooperated to induce phosphorylation of GSK3β at Tyr216 by simultaneous activation of ERK and p38MAPK pathways. Both phospho-Ser9 and phospho-Tyr216 of GSK3β were required for IL-10 expression induced by SCF/TLR4 ligand, whereas suppressive effect of SCF/TLR4 ligand on mast cell degranulation was related to phospho-Tyr216. Importantly, the effect of SCF and TLR4 ligand on mast cells could be abrogated by inhibiting phosphorylation of GSK3β at Tyr216. These findings disclose the mechanisms underlying the modulation of mast cell function in tumor microenvironment, and suggest that inhibiting GSK3β in mast cells will be beneficial to the treatment of cancer.

Mast Cells: Pivotal Players in Cardiovascular Diseases

The clinical outcome of cardiovascular diseases as myocardial infarction and stroke are generally caused by rupture of an atherosclerotic plaque. However, the actual cause of a plaque to rupture is not yet established. Interestingly, pathology studies have shown an increased presence of the mast cell, an important inflammatory effector cell in allergy and host defense, in (peri)vascular tissue during plaque progression, which may point towards a causal role for mast cells. Very recent data in mouse models show that mast cells and derived mediators indeed can profoundly impact plaque progression, plaque stability and acute cardiovascular syndromes such as vascular aneurysm or myocardial infarction. In this review, we discuss recent evidence on the role of mast cells in the progression of cardiovascular disorders and give insight in the therapeutic potential of modulation of mast cell function in these processes to improve the resilience of a plaque to rupture.

Cannabinoids reduce granuloma‐associated angiogenesis in rats by controlling transcription and expression of mast cell protease‐5

Chronic inflammatory conditions, such as granulomas, are associated with angiogenesis. Mast cells represent the main cell type orchestrating angiogenesis, through the release of their granule content. Therefore, compounds able to modulate mast cell behaviour may be considered as a new pharmacological approach to treat angiogenesis-dependent events. Here, we tested the effect of selective cannabinoid (CB) receptor agonists in a model of angiogenesis-dependent granuloma formation induced by lambda-carrageenin in rats. Granulomas were induced by lambda-carrageenin-soaked sponges implanted subcutaneously on the back of male Wistar rats. After 96 h, implants were removed and granuloma formation was measured (wet weight); angiogenesis was evaluated by histological analysis and by the measurement of haemoglobin content. Mast cells in the granulomas were evaluated histologically and by RT-PCR and immunoblotting analysis for mast cell-derived proteins (rat mast cell protease-5 (rMCP-5) and nerve growth factor). Selective CB1 and CB2 receptor agonists(,) ACEA and JWH-015 (0.001-0.1 mg mL(-1)), were given locally only once, at the time of implantation. The CB1 and CB2 receptor agonists decreased the weight and vascularization of granulomas after 96 h. This treatment also reduced mast cell number and activation in granulomatous tissue. Specifically, these compounds prevented the transcription and expression of rMCP-5, a protein involved in sprouting and advance of new blood vessels. Modulation of mast cell function by cannabinoids reduced granuloma formation and associated angiogenesis. Therefore cannabinoid-related drugs may be useful in the management of granulomatous diseases accompanied by angiogenesis.

IL-4 gene expression up-regulated by mercury in rat mast cells: a role of oxidant stress in IL-4 transcription.

In the Brown Norway (BN) rat, chemical compounds [mercuric chloride (HgCl2), D-penicillamine or gold salts] induce a T(h)2-dominated autoimmune syndrome with tissue injury in the form of a vasculitis and arthritis. An early phase of vasculitis in the model occurs within 24 h of an injection of HgCl2, is alphabeta T cell independent and involves the mast cell. In addition, HgCl2 induces IL-4 mRNA in mast cells from BN rats. Our recent work has demonstrated that the balance of oxidative/antioxidative influences plays an important role in the modulation of mast cell function (degranulation) in chemically induced autoimmunity. The aim of this study was to determine, in mast cells, whether oxidative status influences IL-4 transcription and translation, which is required for the development of a T(h)2 response. Exposure of the mast cell line RBL-2H3 to HgCl2 enhanced both IL-4 mRNA and its promoter activity. Oxidative stress by hydrogen peroxide mimicked the effects of HgCl2 in enhancing IL-4 promoter activity. The enhancement of IL-4 gene expression by HgCl2 was significantly reduced by antioxidants (both sulphydryl and non-sulphydryl containing). The same pattern of regulation was also observed on IL-4 protein expression in the mast cells. These data suggest a novel mechanism of IL-4 transcriptional up-regulation by oxidative stress. Our results provide evidence to support our hypothesis that alterations in intracellular reactive oxygen species production modulate both IL-4 gene expression and mast cell function.

Human mast cells transmigrate through human umbilical vein endothelial monolayers and selectively produce IL-8 in response to stromal cell-derived factor-1 alpha.

Mature mast cells are generally considered to be less mobile cells residing within tissue sites. However, mast cell numbers are known to increase in the context of inflammation, and mast cells are recognized to be important in regulating local neutrophil infiltration. CXC chemokines may play a critical role in this process. In this study two human mast cell-like lines, HMC-1 and KU812, and human cord blood-derived primary cultured mast cells were employed to examine role of stromal cell-derived factor-1 (SDF-1) in regulating mast cell migration and mediator production. It was demonstrated that human mast cells constitutively express mRNA and protein for CXCR4. Stimulation of human mast cells with SDF-1, the only known ligand for CXCR4, induced a significant increase in intracellular calcium levels. In vitro, SDF-1 alpha mediated dose-dependent migration of human cord blood-derived mast cells and HMC-1 cells across HUVEC monolayers. Although SDF-1 alpha did not induce mast cell degranulation, it selectively stimulated production of the neutrophil chemoattractant IL-8 without affecting TNF-alpha, IL-1beta, IL-6, GM-CSF, IFN-gamma, or RANTES production, providing further evidence of the selective modulation of mast cell function by this chemokine. These findings provide a novel, SDF-1-dependent mechanism for mast cell transendothelial migration and functional regulation, which may have important implications for the local regulation of mast cells in disease.

Alterations in intracellular reactive oxygen species generation and redox potential modulate mast cell function.

The administration of mercuric chloride (HgCl2), gold compounds, or D-penicillamine to Brown Norway (BN) rats causes a T helper (Th)2 cell-associated autoimmune syndrome characterized by the production of a number of autoantibodies, marked elevation of serum IgE concentration, and tissue injury in the form of a vasculitis and arthritis. We have recently shown that the same compounds in vitro sensitize BN rat peritoneal mast cells for IgE-triggered mediator release and interleukin-4 mRNA production. We wished to test the hypothesis that these agents influence mast cell function via an effect on intracellular reactive oxygen species (ROS) production/redox balance. Mast cells were obtained from BN rats by peritoneal washout. Incubation with HgCl2, gold compounds or D-penicillamine (the latter only in the presence of copper ions) led to the intracellular production of ROS as shown by the oxidative production of the fluorescent compound 2',7'-dichlorofluorescein. Mast cells were more sensitive than splenocytes to this effect. Direct oxidative stress (exposure to H2O2) produced a similar sensitization for mediator release to that caused by HgCl2. Inhibition of ROS formation by desferrioxamine or catalase diminished the enhancement of IgE-mediated serotonin release caused by HgCl2, as did replenishment of intracellular glutathione. 2-Mercaptoethanol exacerbated the toxicity of HgCl2, perhaps due to the formation of a lipophilic complex that enhanced HgCl2 uptake. Blocking of glutathione synthesis increased the toxicity of HgCl2, but also abolished any sensitizing effect on mediator release. These results support three main predictions of our hypothesis: (1) the compounds known to influence mast cell function all lead to the generation of ROS within the mast cell; (2) direct oxidative stress causes sensitization for mediator release by the mast cell; and (3) modulation of ROS production/redox balance within the mast cell modulates the effects of these compounds on mast cell function. The balance of oxidative/antioxidative influences may play an important role in the modulation of mast cell function, particularly in the context of chemically induced autoimmunity.

Effect of Recombinant Human c-kit Receptor Ligand on Mediator Release from Human Skin Mast Cells.

We studied the activity of recombinant human stem cell factor (rhSCF) on the release of mediators from human skin mast cells. High concentrations of rhSCF (1 ng/ml-1 μg/ml) induced a rapid and sustained rise in intracellular Ca2+ levels that was accompanied by release of histamine and prostaglandin D2 (PGD2). A brief incubation (10 min) with lower concentrations of rhSCF (0.1 pg/ml-1 ng/ml) enhanced anti-IgE-induced histamine release, but not the release of PGD2. Since some of the effects of rhSCF on mast cell mediator release in vitro occur at concentrations of cytokine similar to those found in the serum of normal subjects it is possible that SCF contributes to the modulation of mast cell function under physiological conditions.

Lipid metabolism during mediator release from mast cells: studies of the role of arachidonic acid metabolism in the control of phospholipid metabolism.

Recent studies indicate that both arachidonic acid (AA) metabolism and phospholipid (PL) metabolism are markedly stimulated during the release of mediators from mast cells. The relationship between stimulated AA metabolism and stimulated PL metabolism in isolated rat mast cells was investigated and then correlated with the secretory process. ETYA (5,8,11,14-eicosatetraynoic acid, a known inhibitor of cyclooxygenase and lipoxygenase pathways of AA metabolism) inhibited 32PO4 incorporation into phosphatidic acid (PA), phosphatidylinositol (PI), and phoshodidylcholine (PC) in both unstimulated mast cells and mast cells stimulated by cross-linking of surface IgE molecules. ID50 values for inhibition of mediator release and of basal and stimulated 32PO4 incorporation into PL were 50 to 60 microM ETYA. Indomethacin (1 to 10 microM) and aspirin (10 to 100 microM) had no significant effect on 32PO4 incorporation or on mediator release. AA (10 microM) inhibited PL labeling in resting mast cells and rendered the cells less responsive to secretory signals. Preincubation of the cells with indomethacin (1 microM) blocked both of these AA effects. When AA was added to stimulated mast cells, however, both PL labeling and mediator release were enhanced. Thus, each of the alterations in AA metabolism caused parallel changes in mast cell PL metabolism and in mediator release. Since both basal and stimulated PL metabolism were modified by ETYA and AA, some form of direct regulation of mast cell PL metabolism by AA metabolites seems likely. The close parallelism of effects on mediator release and on PL metabolism suggests that modulation of mast cell function by AA metabolites may be mediated at lest in part by effects on lipid metabolism.