IgE-dependent Mast Cell Research Articles

Butyrate, Valerate, and Niacin Ameliorate Anaphylaxis by Suppressing IgE-Dependent Mast Cell Activation: Roles of GPR109A, PGE2, and Epigenetic Regulation.

Short-chain fatty acids (SCFAs) are produced by the intestinal microbiota during the fermentation of dietary fibers as secondary metabolites. Several recent studies reported that SCFAs modulate the development and function of immune-related cells. However, the molecular mechanisms by which SCFAs regulate mast cells (MCs) remain unclear. In the current study, we analyzed the function and gene expression of mouse MCs in the presence of SCFAs invitro and invivo. We found that the oral administration of valerate or butyrate ameliorated passive systemic anaphylaxis and passive cutaneous anaphylaxis in mice. The majority of SCFAs, particularly propionate, butyrate, valerate, and isovalerate, suppressed the IgE-mediated degranulation of bone marrow-derived MCs, which were eliminated by the Gi protein inhibitor pertussis toxin and by the knockdown of Gpr109a. A treatment with the HDAC inhibitor trichostatin A also suppressed IgE-mediated MC activation and reduced the surface expression level of FcεRI on MCs. Acetylsalicylic acid and indomethacin attenuated the suppressive effects of SCFAs on degranulation. The degranulation degree was significantly reduced by PGE2 but not by PGD2. Furthermore, SCFAs enhanced PGE2 release from stimulated MCs. The SCFA-mediated amelioration of anaphylaxis was exacerbated by COX inhibitors and an EP3 antagonist, but not by an EP4 antagonist. The administration of niacin, a ligand of GPR109A, alleviated the symptoms of passive cutaneous anaphylaxis, which was inhibited by cyclooxygenase inhibitors and the EP3 antagonist. We conclude that SCFAs suppress IgE-mediated activation of MCs invivo and invitro involving GPR109A, PGE2, and epigenetic regulation.

Protective role of protease-activated receptor-2 in anaphylaxis model mice.

Anaphylaxis is a severe life-threatening hypersensitivity reaction induced by mast cell degranulation. Among the various mediators of mast cells, little is known about the role of tryptase. Therefore, we aimed to elucidate the role of protease-activating receptor-2 (PAR-2), a receptor activated by tryptase, in murine anaphylactic models using PAR-2-deficient mice and newly generated tryptase-deficient mice. Anaphylaxis was induced by IgE-dependent and IgE-independent mast cell degranulation in mice. PAR-2 deficiency exacerbated the decrease in body temperature and hypotension during anaphylaxis; however, the number of skin mast cells, degree of mast cell degranulation, and systemic and local vascular hyperpermeability were comparable in PAR-2 knockout and wild-type mice. Nitric oxide, which is produced by endothelial nitric oxide synthase (eNOS), is an indispensable vasodilator in anaphylaxis. In the lungs of anaphylactic mice, PAR-2 deficiency promoted eNOS expression and phosphorylation, suggesting a protective effect of PAR-2 against anaphylaxis by downregulating eNOS activation and expression. Based on the hypothesis that the ligand for PAR-2 in anaphylaxis is mast cell tryptase, tryptase-deficient mice were generated using CRISPR-Cas9. In wild-type mice, the PAR-2 antagonist exacerbated the body temperature drop due to anaphylaxis; however, the effect of the PAR-2 antagonist was abolished in tryptase-deficient mice. These results suggest that tryptase is a possible ligand of PAR-2 in anaphylaxis and that the tryptase/PAR-2 pathway attenuates the anaphylactic response in mice.

Deficiency of BMAL1 promotes ROS generation and enhances IgE-dependent degranulation in mast cells

BackgroundBmal1 (Brain and muscle arnt-like, or Arntl) is a bHLH/PAS domain transcription factor central to the transcription/translation feedback loop of the circadian clock. Mast cells are crucial for effector functions in allergic reaction and their activity follows a circadian rhythm. However, the functional roles of Bmal1 in mast cells remain to be determined. PurposeThis study aimed to elucidate the specific roles of Bmal1 in IgE-dependent mast cell degranulation. ResultsIgE-dependent degranulation was enhanced in bone marrow–derived mast cells (BMMCs) derived from Bmal1-deficient mice (Bmal1-KO mice) compared to that in BMMCs derived from wild-type mice (WT mice) in the absence of 2-Mercaptoethanol (2-ME) in culture. Mast cell–deficient KitW-sh mice reconstituted with Bmal1-KO BMMCs showed more robust passive cutaneous anaphylactic (PCA) reactions, an in vivo model of IgE-dependent mast cell degranulation, than KitW-sh mice reconstituted with WT BMMCs. In the absence of 2-ME in culture, the mRNA expression of the anti-oxidative genes NF-E2-related factor 2 (Nrf2), superoxide dismutase 2 (SOD2), and heme oxygenase-1 (HO-1) was lower and reactive oxygen species (ROS) generation was higher in Bmal1-KO BMMCs than in WT BMMCs at steady state. The IgE-dependent ROS generation and degranulation were enhanced in Bmal1-KO BMMCs compared to WT BMMCs in the absence of 2-ME in culture. The addition of 2-ME into the culture abrogated or weakened the differences in anti-oxidative gene expression, ROS generation, and IgE-dependent degranulation between WT and Bmal1-KO BMMCs. ConclusionThe current findings suggest that Bmal1 controls the expression of anti-oxidative genes in mast cells and Bmal1 deficiency enhanced IgE-dependent degranulation associated with promotion of ROS generation. Thus, Bmal1 may function as a key molecule that integrates redox homeostasis and effector functions in mast cells.

MITF Downregulation Induces Death in Human Mast Cell Leukemia Cells and Impairs IgE-Dependent Degranulation.

Activating mutations in KIT (CD117) have been associated with several diseases, including gastrointestinal stromal tumors and mastocytosis. Rapidly progressing pathologies or drug resistance highlight the need for alternative treatment strategies. Previously, we reported that the adaptor molecule SH3 binding protein 2 (SH3BP2 or 3BP2) regulates KIT expression at the transcriptional level and microphthalmia-associated transcription factor (MITF) expression at the post-transcriptional level in human mast cells and gastrointestinal stromal tumor (GIST) cell lines. Lately, we have found that the SH3BP2 pathway regulates MITF through miR-1246 and miR-5100 in GIST. In this study, miR-1246 and miR-5100 were validated by qPCR in the SH3BP2-silenced human mast cell leukemia cell line (HMC-1). MiRNA overexpression reduces MITF and MITF-dependent target expression in HMC-1. The same pattern was observed after MITF silencing. In addition, MITF inhibitor ML329 treatment reduces MITF expression and affects the viability and cell cycle progression in HMC-1. We also examine whether MITF downregulation affected IgE-dependent mast cell degranulation. MiRNA overexpression, MITF silencing, and ML329 treatment reduced IgE-dependent degranulation in LAD2- and CD34+-derived mast cells. These findings suggest MITF may be a potential therapeutic target for allergic reactions and deregulated KIT mast-cell-mediated disorders.

TH9-derived IL-9 promotes CCR2-dependent mast cell accumulation in the allergic lung

Abstract Allergic asthma is a chronic lung disease characterized by airway hyperresponsiveness and cellular infiltration that is exacerbated by IgE-dependent mast cell activation. Our work in mouse models of allergic airway inflammation identified interleukin-9 (IL-9)-producing T helper 9 (TH9) cells as important effector cells in promoting mast cell accumulation in the lungs. However, the precise mechanism of IL-9-mediated mast cell expansion remains unclear. Here, we demonstrate that intranasal recombinant IL-9 expands, while blockade of IL-9 reduces, mast cell progenitor numbers in the lungs and the bone marrow. These findings suggests that there are systemic effects of local IL-9 production in the allergic lung. Using adoptive transfer models and newly generated mice with an inactivation of the IL-9 gene restricted to T cells generated by CD4-Cre/loxP-mediated targeting of the IL-9 gene, we show that TH9 cells promote mast cell progenitor and mature mast cell recruitment from the bone marrow to the lungs in a chemokine receptor 2-dependent manner. Our research further demonstrates that T cell-derived IL-9 is critical for mast cell-mediated airway hyperresponsiveness. Together, these findings define a contribution of T cell-derived IL-9 in promoting mast cell expansion and function in allergic airway inflammation. Therefore, IL-9 may be a promising therapeutic target for targeting mast cell-specific pathologies. Supported by grants from NIH (R01 AI129241, T32 AI060519)

The regulatory mechanisms of IgE-dependent and independent mast cell activation and allergic responses

The regulatory mechanisms of IgE-dependent and independent mast cell activation and allergic responses

Tuning IgE: IgE-Associating Molecules and Their Effects on IgE-Dependent Mast Cell Reactions

The recent emergence of anti-immunoglobulin E (IgE) drugs and their candidates for humans has endorsed the significance of IgE-dependent pathways in allergic disorders. IgE is distributed locally in the tissues or systemically to confer a sensory mechanism in a domain of adaptive immunity to the otherwise innate type of effector cells, namely, mast cells and basophils. Bound on the high-affinity IgE receptor FcεRI, IgE enables fast memory responses against revisiting threats of venoms, parasites, and bacteria. However, the dysregulation of IgE-dependent reactions leads to potentially life-threatening allergic diseases, such as asthma and anaphylaxis. Therefore, reactivity of the IgE sensor is fine-tuned by various IgE-associating molecules. In this review, we discuss the mechanistic basis for how IgE-dependent mast cell activation is regulated by the IgE-associating molecules, including the newly developed therapeutic candidates.

Nanoparticles Displaying Allergen and Siglec-8 Ligands Suppress IgE-FcεRI-Mediated Anaphylaxis and Desensitize Mast Cells to Subsequent Antigen Challenge.

Siglec-8 is an inhibitory receptor expressed on eosinophils and mast cells. In this study, we took advantage of a novel Siglec-8 transgenic mouse model to assess the impact of modulating IgE-dependent mast cell degranulation and anaphylaxis using a liposomal platform to display an allergen with or without a synthetic glycan ligand for Siglec-8 (Sig8L). The hypothesis is that recruitment of Siglec-8 to the IgE-FcεRI receptor complex will inhibit allergen-induced mast cell degranulation. Codisplay of both allergen and Sig8L on liposomes profoundly suppresses IgE-mediated degranulation of mouse bone marrow-derived mast cells or rat basophilic leukemia cells expressing Siglec-8. In contrast, liposomes displaying only Sig8L have no significant suppression of antigenic liposome-induced degranulation, demonstrating that the inhibitory activity by Siglec-8 occurs only when Ag and Sig8L are on the same particle. In mouse models of anaphylaxis, display of Sig8L on antigenic liposomes completely suppresses IgE-mediated anaphylaxis in transgenic mice with mast cells expressing Siglec-8 but has no protection in mice that do not express Siglec-8. Furthermore, mice protected from anaphylaxis remain desensitized to subsequent allergen challenge because of loss of Ag-specific IgE from the cell surface and accelerated clearance of IgE from the blood. Thus, although expression of human Siglec-8 on murine mast cells does not by itself modulate IgE-FcεRI-mediated cell activation, the enforced recruitment of Siglec-8 to the FcεRI receptor by Sig8L-decorated antigenic liposomes results in inhibition of degranulation and desensitization to subsequent Ag exposure.

Na+/H+ exchanger regulatory factor 1 (NHERF1) enhances MRGPRX2-mediated mast cell anaphylaxis

Abstract Anaphylaxis is a severe life-threatening allergic reaction that is caused by mast cell hyperactivity. Two different mast cell receptors play critical roles in mediating anaphylaxis: 1) the IgE receptor that is stimulated by IgE-bound allergen and 2) the MRGPRX2 receptor that can bind to several cationic molecules and FDA-approved drugs resulting in mast cell activation. Activated mast cells degranulate to release proinflammatory mediators. We have recently identified that Na+/H+ exchanger regulatory factor 1 (NHERF1) regulates IgE-dependent mast cell activation in vitro and promotes passive cutaneous anaphylaxis (PCA) and passive systemic anaphylaxis (PSA) in vivo. In the current study, we investigated the role of this adapter molecule in affecting IgE-independent mast cell activation via the MrgprB2 (mouse orthologue of human MRGPRX2) receptor using a novel mouse strain, Cpa3-Cre+ NHERF1fl/fl that lacks NHERF1 in mast cells. PCA and PSA to compound 48/80 (a known MrgprB2 agonist) were significantly attenuated in the Cpa3-Cre+ NHERF1fl/fl mice as compared to control Cpa3-Cre− NHERF1fl/fl mice. In agreement with our in vivo data, peritoneal mast cells isolated from Cpa3-Cre+ NHERF1fl/fl mice showed a significant reduction in mast cell degranulation to the MrgprB2 ligands, compound 48/80 and substance P. Additionally, NHERF1-silenced human LAD2 mast cells showed decreased degranulation to these ligands as well. Collectively, our data suggests that NHERF1 promotes mast cell activation though the MRGPRX2/MrgprB2 receptor and determining the mechanisms through which NHERF1 modulates MRGPRX2 responses will lend insights into the development of new therapeutics for anaphylaxis and other allergic diseases.

Blocking of mast cell-mediated passive anaphylaxis to peanut using covalent heterobivalent inhibitor in a humanized mouse model

Abstract Anaphylaxis to peanut allergen is a severe hypersensitive allergic reaction characterized by life-threatening symptoms. Anaphylaxis is mediated by IgE-dependent mast cell activation that leads to the release of inflammatory mediators. In a previous report, we described the design of a covalent heterobivalent inhibitor (cHBI) that selectively forms covalent bonds with allergen specific-IgE (sIgE) on mast cells and abates allergic reactions in ex-vivo peanut challenges. Here, we utilized a humanized mouse model to recapitulate key features of anaphylaxis to peanut in humans, and we examined the efficacy of cHBI in blocking the anaphylactic reaction in this model. NSGS (NOD-scid Il2rgnull IL-3/GM-CSF/SCF) mice engrafted with human hematopoietic stem cells were treated with an allergen-specific human IgE monoclonal antibody and then challenged with a peanut allergen. We found that the peanut-challenged humanized mice can develop rapid anaphylaxis and mast cell degranulation following challenge. The anaphylactic reaction was characterized by a substantial decline of core body temperatures and upregulation of human mast cell degranulation markers. Additionally, we found that the severity of the anaphylactic reaction is hIgE dose-dependent. Most importantly, cHBI protected the mice from developing an anaphylactic reaction demonstrating the ability of cHBI to block IgE-mediated allergic reactions in the humanized mice. Overall, our results show that the humanized mouse model is a novel model to study human mast cell IgE-mediated allergic reactions and demonstrate that cHBI is an effective potential therapeutic inhibitor for food allergy.

MALT1 Protease Plays a Dual Role in the Allergic Response by Acting in Both Mast Cells and Endothelial Cells.

The signaling protein MALT1 plays a key role in promoting NF-κB activation in Ag-stimulated lymphocytes. In this capacity, MALT1 has two functions, acting as a scaffolding protein and as a substrate-specific protease. MALT1 is also required for NF-κB-dependent induction of proinflammatory cytokines after FcεR1 stimulation in mast cells, implicating a role in allergy. Because MALT1 remains understudied in this context, we sought to investigate how MALT1 proteolytic activity contributes to the overall allergic response. We compared bone marrow-derived mast cells from MALT1 knockout (MALT1-/-) and MALT1 protease-deficient (MALTPD/PD) mice to wild-type cells. We found that MALT1-/- and MALT1PD/PD mast cells are equally impaired in cytokine production following FcεRI stimulation, indicating that MALT1 scaffolding activity is insufficient to drive the cytokine response and that MALT1 protease activity is essential. In addition to cytokine production, acute mast cell degranulation is a critical component of allergic response. Intriguingly, whereas degranulation is MALT1-independent, MALT1PD/PD mice are protected from vascular edema induced by either passive cutaneous anaphylaxis or direct challenge with histamine, a major granule component. This suggests a role for MALT1 protease activity in endothelial cells targeted by mast cell-derived vasoactive substances. Indeed, we find that in human endothelial cells, MALT1 protease is activated following histamine treatment and is required for histamine-induced permeability. We thus propose a dual role for MALT1 protease in allergic response, mediating 1) IgE-dependent mast cell cytokine production, and 2) histamine-induced endothelial permeability. This dual role indicates that therapeutic inhibitors of MALT1 protease could work synergistically to control IgE-mediated allergic disease.

Resveratrol inhibits IL-33\u2013mediated mast cell activation by targeting the MK2/3\u2013PI3K/Akt axis

Interleukin-33 (IL-33)/ST2–mediated mast cell activation plays important roles in the pathophysiology of allergic diseases. Hence, pharmacologically targeting the IL-33/ST2 pathway in mast cells could help to treat such diseases. We found that resveratrol inhibits IL-33/ST2–mediated mast cell activation. Resveratrol suppressed IL-33–induced IL-6, IL-13, and TNF-α production in mouse bone marrow–derived mast cells (BMMCs), mouse fetal skin–derived mast cells, and human basophils. Resveratrol also attenuated cytokine expression induced by intranasal administration of IL-33 in mouse lung. IL-33–mediated cytokine production in mast cells requires activation of the NF-κB and MAPK p38–MAPK-activated protein kinase-2/3 (MK2/3)–PI3K/Akt pathway, and resveratrol clearly inhibited IL-33–induced activation of the MK2/3–PI3K/Akt pathway, but not the NF-κB pathway, without affecting p38 in BMMCs. Importantly, resveratrol inhibited the kinase activity of MK2, and an MK2/3 inhibitor recapitulated the suppressive effects of resveratrol. Resveratrol and an MK2/3 inhibitor also inhibited IgE-dependent degranulation and cytokine production in BMMCs, concomitant with suppression of the MK2/3–PI3K/Akt pathway. These findings indicate that resveratrol inhibits both IL-33/ST2–mediated and IgE-dependent mast cell activation principally by targeting the MK2/3–PI3K/Akt axis downstream of p38. Thus, resveratrol may have potential for the prevention and treatment of broad ranges of allergic diseases.

Gender differences in anaphylaxis.

Is sexual dimorphism also true in anaphylaxis as described in other allergic diseases? Possible gender differences in the epidemiology, triggers, severity, outcomes of anaphylaxis as well as in the pathogenesis of the disease are discussed. Hormonal status and the X-chromosome-coded factors deeply involved in the regulation of T-cell and B-cell responses may influence the gender difference noticed in allergic diseases, such as asthma and rhinitis. Little is known if sex is also relevant for anaphylaxis, although the description of catamenial anaphylaxis is intriguing. However, epidemiologic bias, lack of reliable animal models for the human disease, differences into diagnostic codes and not harmonized clinical grading unfortunately represent hurdles to obtain meaningful information on this topic. The female sex predisposes to a dysregulation of the immune response as suggested by the increased prevalence of autoimmunity and atopy. In anaphylaxis, pathomechanisms are not fully disclosed, triggers are numerous and IgE-dependent mast cell degranulation only represents a part of the story. Improvement into the definition of the disease including a more careful coding system and better investigations about triggers seem the only way to allow a more precise assessment of the possible different risk for women to develop anaphylaxis.

Dampening of mast cell secondary responses to allergen involves specific signalling and epigenetic changes

Allergic diseases are increasing worldwide. Allergen and IgE dependent mast cell (MC) activation is the major initiator of these clinical symptoms. During this study, the effect of multiple exposures to the same allergen, on MC degranulation was studied. First, MC recovery in terms of surface expression of high affinity receptor FcεRI, and granule content after a primary allergen challenge was confirmed. Overall, previous exposure of MCs to allergen challenge led to a significant reduction in pre-stored mediator release during the secondary challenge at various time points and with various doses of allergen in vitro. The dampened response was not due to any defects in very early steps in signalling involving FcεRI activation. Inhibition of dampening response during secondary challenge by various inhibitors like wortmannin, tranylcypromine and pargyline, indicated the involvement of PI3K signalling and chromatin modifications. Our study provides insight into new therapeutic avenues for treating allergic disorders targeting MCs.

IgE-mediated mast cell activation promotes inflammation and cartilage destruction in osteoarthritis.

This article has been through an editorial process in which the authors decide how to respond to the issues raised during peer review. The Reviewing Editor's assessment is that all the issues have been addressed (see decision letter).

Histamine-releasing factor (HRF) is a novel alarmin

Abstract Objective We are investigating how HRF secretion is regulated during allergic conditions. Results HRF interacts with a subset of IgE molecules. HRF dimer and oligomers, but not monomer, enhance the antigen sensitivity and magnitude of IgE-dependent mast cell activation. We found that BEAS-2B human bronchial epithelial cells constitutively secrete various forms of HRF (monomer, disulfide-linked dimer/oligomers). Secretion of these forms of HRF was enhanced by allergens such as house dust mites (HDM). HDM-mediated HRF secretion was dramatically enhanced by epithelial-derived cytokines (IL-25, IL-33, TSLP), Th2 cytokines (IL-4, IL-5, IL-13), and proinflammatory cytokines (IL-1b, IL-6, TNF), although the cytokines alone had much less effects. Mechanical injury of BEAS-2B cells and its byproducts (i.e., adenosine and ATP) also enhanced HRF secretion. In contrast, papain and bromelain (occupational allergens) as well as uric acid (NLRP3 inflammasome activator) exhibited limited effects on HRF secretion. Several high-molecular-weight forms (≥150 kDa) of HRF were found in body fluids. Interestingly, rhinovirus infection in humans and nasal instillation of HDM in mice, conditions predisposing asthma exacerbation, induced secretion of these HRF forms into airways. These results suggest that disulfide-linked HRF dimer/oligomers are involved in asthma exacerbation. Conclusion HRF dimer/oligomers secreted by epithelial and other cells enhance allergic inflammation as a novel alarmin.

Recruiting CD33 on mast cells to inhibit IgE-mediated mast cell-dependent anaphylaxis.

IgE-mediated activation of mast cells is a hallmark of an anaphylactic reaction to allergen. In this issue of the JCI, Duan et al. describe an approach for suppressing IgE-dependent mast cell activation, thereby suppressing anaphylaxis. Specifically, the authors show that delivery of liposomes containing both the specific antigen recognized by the mast cell-bound IgE and a high-affinity glycan ligand of the inhibitory receptor CD33 (CD33L) to targeted mast cells inhibits antigen-induced, FcεRI-dependent spleen tyrosine kinase (Syk) phosphorylation and downstream protein tyrosine kinase (PTK) phosphorylation, Ca++ flux, and β-hexosaminidase release (i.e., degranulation). However, this strategy only worked if both the antigen (reactive with the mast cell-bound IgE) and CD33L were on the same liposome. This approach promises to rapidly reduce IgE-dependent mast cell activation in response to challenge with offending allergens.

Mas-Related G Protein-Coupled Receptor-X2 (MRGPRX2) in Drug Hypersensitivity Reactions.

The human ortholog MRGPRX2 and the mice ortholog, Mrgprb2 are activated by basic secretagogues and neurokinins. A number of commonly used small-molecule drugs (e.g., neuromuscular blocking agents, fluoroquinolones, vancomycin) have been recently shown to activate these receptors under in vitro experimental conditions, what results in mast cell degranulation. The above drugs are also known to cause IgE-mediated anaphylactic reactions in allergic patients. The new findings on mechanisms of drug-induced mast cell degranulation may modify the current management of drug hypersensitivity reactions. Clinical interpretation of mild drug-provoked hypersensitivity reactions, interpretation of skin test with a drug of interest or further recommendations for patients suspected of drug allergy are likely to be reconsidered. In the paper we discussed future directions in research on identification and differentiation of MRGPRX2-mediated and IgE-dependent mast cell degranulation in patients presenting clinical features of drug-induced hypersensitivity reactions.

323 NecroX-5 Ameliolates Atopic dermatitis like Skin Lesions of NC/Nga Mice

NecroX-5 is a cell permeable necrosis inhibitor with cytoprotective effects. Although it has been reported to be a novel anti-allergic agent that inhibits mast cell degranulation and suppresses IgE-dependent mast cell signaling, its action on atopic dermatitis (AD) is unclear. In this study, we examined whether NecroX-5 could suppress AD-like skin lesions of NC/Nga mice. In this study, we examined whether NecroX-5 could have the potential to suppress the AD-like skin lesions in NC/Nga mice.2, 4-dinitrochlorobenzene (DNCB) was repeatedly applied to the ear skin of NC/Nga mice to induce AD-like skin lesions. NecroX- 5 cream (1μg/ml, once a day for 5 consecutive days/week) was applied topically for four weeks for the evaluation of its therapeutic effects. NecroX-5 cream significantly reduced the clinical severity score of AD-like skin lesions, compared to the control (p < 0.005). A histopathological analysis revealed that NecroX-5 cream significantly decreased mononuclear cell infiltration as well as the mast cell infiltration, compared to the control (p < 0.005). We also showed that NecroX-5 cream significantly reduced the expression of TSLP, IL-4, IL-5, IL-13, and IFN-γ, compared to the control (p < 0.005). These results suggest that NecroX-5 might be a potential candidate which regulates the inflammatory reaction as well as allergic reaction of AD.

IL-10 enhances IgE-independent IL-33-mediated mast cell cytokine production

Abstract IgE antibodies play a critical role in antigen-mediated mast cell activation. However, mast cells can be activated via IgE-independent mechanisms including signaling via the IL-33 receptor ST2. We have previously shown that the Th2-derived cytokine IL-10 can enhance IgE-dependent mucosal mast cell activation and promote mast cell function and survival. However, whether the effects of IL-10 on mast cells are global in nature and not limited to IgE-mediated signaling is not clear. To determine whether IL-10 can prime the activation of mast cells mediated by IgE-independent signals such as IL-33, we assessed the effects of rIL-10 exposure on IL-33-stimulated mast cells and their subsequent activation via IgE. Bone marrow-derived mast cells (BMMCs) from wild-type (WT) and IL-10−/− mice were cultured with rIL-33 with or without rIL-10 and activated with DNP-IgE and antigen. Exposure to IL-10 enhanced cytokine production in both WT and IL-10−/− BMMCs, and this was significantly increased after activation via IgE. IL-10−/−BMMCs exhibited decreased cytokine production, but this was restored upon culture with rIL-10. Interestingly, IL-33 stimulation (and subsequent activation with IgE) induced comparably enhanced levels of cytokine production, specifically IL-13 and IL-6, in both WT and IL-10−/−cells, suggesting that ST2-mediated signals can overcome the lack of IL-10. However, the addition of exogenous IL-10 to IL-33-stimulated cultures further enhanced the levels of these cytokines not only in IgE-activated cells, but also in cells stimulated with IL-33 alone. Our observations therefore suggest that IL-10 can play critical roles in enhancing mast cell function both via IgE-dependent and independent mechanisms.