Stimulation Of Mast Cells Research Articles

RUNX1 regulates KIT expression and is a novel therapeutic target in human mast-cell diseases.

Abstract Mast cells develop from hematopoietic progenitors under SCF-dependent activation of KIT encoding a type III receptor tyrosine kinase. In addition, KIT signaling also enhances release of chemical mediators from stimulated mast cells. KIT D816V mutation, a gain-of-function mutation which is often found in mastocytosis, causes SCF-independent activation of KIT, leading to autonomous mast cell survival and proliferation. ChIP-seq analysis of mouse bone marrow-derived mast cells showed that hematopoietic transcription factor RUNX1 bound to several genomic regions between KIT exon 1 and intron 1. We therefore investigated an association between RUNX1 and the transcriptional regulation of KIT in the human mast cell lines. The global gene expression profile revealed that KIT gene expression in the cells was positively linked to RUNX1 gene expression. Using ChIP assay coupled to PCR, we found RUNX1 binding at KIT intron 1 in the cells with KIT D816V mutation. RUNX1 knockdown reduced KIT expression in both cell lines with and without KIT D816V mutation, and led to a significant decrease in cell growth of those with D816V mutation. In the RUNX1-knockdown cells, PI3K-Akt pathway of KIT downstream signaling was suppressed, and G0/G1 cell-cycle arrest occurred, which was followed by apoptosis. The chlorambucil-conjugated compound that we developed to inhibit RUNX1 binding to its DNA targets successfully and effectively decreased the KIT expression of the mast cells with KIT D816V mutation, which resulted in the cell growth suppression. These findings suggested that RUNX1 upregulates KIT expression and may be a potential therapeutic target in mast-cell diseases.

IL-6 induces production of VEGF and MCP-1 from human skin mast cells.

Abstract Mast cells are the cell type responsible for IgE-mediated allergic reactions, and are involved in innate immunity against bacteria and pathogens. Interestingly, recent research has implicated mast cells in traditionally non-allergic diseases such as cancer. It has been hypothesized that in these non-allergic diseases mast cells may be activated by stimuli other than antigen, such as pro-inflammatory cytokines. Interleukin-6 (IL-6) is a pleiotropic cytokine that has been implicated in several diseases in which mast cells are also believed to contribute, suggesting that IL-6 could be the link that connects mast cells to non-allergic disease. However, the surface expression of IL-6 receptors, and the effect of IL-6 on human tissue-derived mast cells remained to be determined. Here, we show that human skin mast cells express functional membrane-bound IL-6 receptors, and address the role of IL-6 on the release of allergic and inflammatory mediators. Stimulation of skin mast cells with IL-6 resulted in a dose-dependent increase in Signal Transducer and Activator of Transcription 3 (STAT-3) phosphorylation, and increased expression of Suppressor of Cytokine Signaling 3 (SOCS3) mRNA. IL-6 had no effect on degranulation, but enhanced PGD2 biosynthesis and IL-8 production following FcɛRI crosslinking. In addition, treatment with IL-6 alone was sufficient to induce the production of monocyte chemoattractant protein (MCP-1) and vascular endothelial growth factor (VEGF). Overall, these findings clarify the effect of IL-6 on the allergic response from human tissue-derived mast cells, and reveal a potential role for IL-6 in mast cell-mediated angiogenesis.

Methoxyluteolin Inhibits Neuropeptide-stimulated Proinflammatory Mediator Release via mTOR Activation from Human Mast Cells.

Mast cells (MCs) are critical for allergic reactions but are also important in inflammatory processes. Stimulation by neuropeptides, such as substance P (SP) and neurotensin (NT), leads to release of preformed molecules stored in numerous MC secretory granules and newly synthesized proinflammatory mediators, including tumor necrosis factor, C-X-C motif chemokine ligand 8, and vascular endothelial growth factor. Here, we investigate the role of mammalian target of rapamycin (mTOR) signaling in the stimulation of cultured human LAD2 MCs by NT or SP, as well as the inhibitory effect of the natural flavonoids 3',4',5,7-tetrahydroxyflavone (luteolin) and its novel structural analog 3',4',5,7-tetramethoxyflavone (methoxyluteolin). Stimulation by NT (10 μM) or SP (1 μM) increases (P < 0.0001) gene expression (after 6 hours) and release (after 24 hours) of tumor necrosis factor, C-X-C motif chemokine ligand 8, and vascular endothelial growth factor. This occurs via activation of both mTOR complexes, as denoted by the increased phosphorylated (p) protein levels (P < 0.0001) of the downstream mTORC1 substrate pp70S6KThr389 and mTORC2 component pmTORSer2448. Pretreatment of human MCs using the mTORC1 inhibitor rapamycin, the mTORC1/mTORC2 inhibitor Torin1, or the two flavonoids decreases both gene expression and release (P < 0.0001) of all three mediators. Methoxyluteolin is a more potent human MC inhibitor than luteolin or Torin1, implicating other MC protein targets in addition to the mTOR complex. These findings indicate that mTOR is partially involved in the neuropeptide stimulation of MCs, but the novel flavonoid methoxyluteolin inhibits the response entirely, suggesting that it may be developed for treatment of allergic and inflammatory diseases.

Neuroendocrinology of mast cells: Challenges and controversies.

Mast cells (MC) are hemotopoietically derived tissue immune cells that are ubiquitous in the body, including neuroendocrine organs such as the hypothalamus, pineal, pituitary, ovaries, pancreas and uterus where their action is not well understood. Mast cells have historically been associated with allergies because of their rich content of histamine and tryptase, but more recently with regulation of immunity and inflammation due to their synthesis and release of numerous cytokines and chemokines. Mast cells are located perivascularly and express numerous receptors for diverse ligands such as allergens, pathogens, neurotransmitters, neuropeptides and hormones including acetylcholine, calcitonin gene-related peptide (CGRP), corticosteroids, corticotropin-releasing hormone (CRH), β-endorphin, epinephrine, 17β-oestradiol, gonadotrophins, hemokinin-A (HKA), leptin, melatonin, neurotensin (NT), parathyroid hormone (PTH), substance P (SP) and vasoactive intestinal peptide (VIP). Moreover, MC can synthesize and release most of their neurohormonal triggers, including adrenocorticotropin hormone (ACTH), CRH, endorphins, HKA, leptin, melatonin, NT, SP and VIP. Animal experiments have shown that diencephalic MC increase in number during courting in doves, while stimulation of brain and nasal MC leads to activation of the hypothalamic-pituitary-adrenal (HPA) axis. Recent evidence indicates that MC reactivity exhibits diurnal variations, and it is interesting that melatonin appears to regulate MC secretion. However, the way MC change their phenotype or secrete specific molecules selectively at different pathophysiological settings still remains unknown. Mast cells developed over 500million years ago and may have served as the original prototype neuroimmunoendocrine cell and then evolved into a master regulator of such interactions, especially as most of the known diseases involve neuroinflammation that worsens with stress.

Differential Activation of Itch vs Pain C‐fibers by Mast Cell Stimulation in Mouse Skin

Allergic skin reactions are often itchy, but seldom painful. We addressed the hypothesis that mast cell activation preferentially stimulates itch nerves in the mouse skin. Nerves that evoke itch in mouse skin can be identified by their expression of MrgprA3 and selective activation by chloroquine (CQ) (Cell. 2009,139:1353–65). We have developed a unique innervated isolated dorsal skin preparation in which action potential discharge in single afferent nerves terminating in the skin can be evaluated with an extracellular electrode positioned in the dorsal root ganglia. The dissected section skin includes the main arterial supply through which chemical stimuli are delivered directly to the receptive field. CQ strongly stimulated (12 ± 1Hz) only C‐fibers (0.8 ± 0.01 m/s). Among 228 C‐fibers from 138 mice, 26% were CQ and histamine sensitive; so‐called “itch C‐fibers”. Capsaicin stimulated 73% of the CQ sensitive C‐fibers. The response to CQ, but not histamine was absent in Mrgpr cluster knock out animals. The majority of capsaicin‐sensitive C‐fibers are not stimulated by CQ, but are activated by ATP or 5‐HT; a population likely comprising “pain C‐fibers”. Mice were actively sensitized to ovalbumin (OVA). OVA added to the sensitized skin activates mast cells leading to mast cell mediator release strong activation of 12 of 12 CQ‐sensitive C‐fibers (6 ± 2 Hz). Conversely OVA‐activation of mast cells did not or only very modestly activated the non‐itch, pain population of C‐fibers (1.6 ± 2 Hz, n=30). The itch fibers do not respond to 5‐HT (0 of 24 responded), so it is unlikely that 5‐HT contributes to the activation of itch nerves. CQ‐sensitive C‐fibers respond to histamine 100 μM with only 4 ± 1 Hz discharge, so it is likely that mediators in addition to histamine are involved. We have previously noted that mast cells can release MrgprC11 agonists (J Immunol. 2008, 180:2251–5). BAM8‐22, a MrgprC11 agonist, stimulated 13 of 13 CQ‐sensitive C‐fibers (12 ± 2 Hz), but not CQ‐insensitive fibers (only 3 of 29 stimulated) thereby mimicking the effect of mast cells activation. We hypothesize that mast cell mediators that stimulate Mrgpr C11 may contribute to the response.Support or Funding InformationSupprted by NIH

Role of Dietary Metabolites in Regulating the Host Immune Response in Gastrointestinal Disease.

The host immune response to gastrointestinal (GI) infections, hypersensitivity reactions, or GI cancers comprises numerous pathways that elicit responses on different host cells. Some of these include (1) the stimulation of mast cells via their IgE receptor, (2) the production of antibodies leading to antibody-mediated cytotoxic T/natural killer cell killing, (3) the activation of the complement pathway, and (4) the activation of the adaptive immune response via antigen-presenting cell, T cell, and B cell interactions. Within the plethora of these different responses, several host immune cells represent major key players such as those of myeloid lineage (including neutrophils, macrophages, myeloid-derived suppressor cells) or lymphoid lineage (including T and B cells). In this review, we focus on newly identified metabolites and metabolite receptors that are expressed by either myeloid or lymphoid lineages. Irrespective of their source, these metabolites can in certain instances elicit responses on a wide range of cell types. The myeloid-expressed metabolic enzymes and receptors which we will discuss in this review include arginase 2 (Arg2), indoleamine-2,3-dioxygenase 1 (IDO1), hydroxycarboxylic acid receptor 2 (Hcar2; also called GPR109A), and immunoresponsive gene 1 (Irg1). We will also review the role of the lymphoid-expressed metabolite receptor that binds to the sphingosine-1-phosphate (S1P) sphingolipid. Moreover, we will describe the synthesis and metabolism of retinoic acid, and its effect on T cell activation. The review will then discuss the function of these metabolites in the context of GI disease. The review provides evidence that metabolic pathways operate in a disease- and context-dependent manner—either independently or concomitantly—in the GI tract. Therefore, an integrated approach and combinatorial analyses are necessary to devise new therapeutic strategies that can synergistically improve prognoses.

Effect of Ocimum tenuiflorum Linn Extract on Histamine Mediated Allergic Inflammation in Human Mast Cells

Histamine induced mast cell allergic reaction is involved in many diseases such as asthma, rhinitis and sinusitis. Ocimum tenuiflorum Linn is an herb that has been traditionally used in Indian medicine for curing various diseases. In this study, we aim to investigate the anti-allergic effects of the aqueous extracts of Ocimum tenuiflorum Linn (AEOT) on histamine induced mast cell allergic model and thepossible mechanism of action. Aqueous extract of O. tenuiflorum Linn was prepared and its effect on cell cytotoxicity was checked in HMC-1 cells. In order to investigate the anti-allergic effects of AEOT on mast cell degraulation, intracellular calcium mobilization, IL-13 release by ELISA. Furthermore, the effect of AEOT on nuclear translocation of NF- κB-p65 was analysed by western blotting. We found that AEOT inhibited the histamine induced intracellular calcium level. Furthermore, AEOT also attenuated compound 48/80 stimulated mast cell degranulation and reduced histamine induced IL-13 secretion in HMC-1 cells. The inhibitory effect of AEOT on the histamine induced allergic model was found to be NF-κB dependent. Taken together, this study suggests that the aqueous extract of O. tenuiflorum Linn. might be a therapeutic candidate for allergic inflammatory diseases.

TNF-α Regulates Mast Cell Functions by Inhibiting Cell Degranulation

Background/Aims: The aim of this study was to investigate the involvement of inducible co-stimulatory ligand (ICOSL) expression in stimulation of mast cells (MCs) by TNF-α and the ability of TNF-α stimulation of MCs to influence CD4+ T cell differentiation and function. The mechanisms underlying TNF-α stimulation of MCs were also explored. Methods: Mast cells and CD4⁺ T cells were prepared from C57BL/6 mice (aged 6–8 weeks). ICOSL expression by MCs was measured by real-time PCR and flow cytometry, and levels of IL-4, IL-10 and IFN-γ were measured by ELISA. Results: ICOSL expression by MCs was increased by TNF-α stimulation, and resulted in interaction with CD4+ T cells. The IL-4 and IL-10 levels in the co-culture system increased, while IFN-γ levels decreased. Furthermore, CD4+CD25+Foxp3+ T cell proliferation was induced by co-culture with TNF-α-stimulated MCs. The mechanism by which TNF-α stimulated MCs was dependent on the activation of the MAPK signaling pathway. Conclusion: TNF-α upregulated the expression of ICOSL on mast cells via a mechanism that is dependent on MAPK phosphorylation. TNF-α-treated MCs promoted the differentiation of regulatory T cells and induced a shift in cytokine expression from a Th1 to a Th2 profile by up-regulation ICOSL expression and inhibition of MC degranulation. Our study reveals a novel mechanism by which mast cells regulate T cell function.

The Mast Cell Antibody-Dependent Degranulatory Synapse.

Mast cells are key effector cells in inflammation that can be activated by specific antigens via IgE or IgG binding on their FcR. Aggregation of mast cell Fc receptors by cell-bound antigens induces mast cell polarized degranulation toward the stimulatory cell, a process named antibody-dependent degranulatory synapse (ADDS). This polarized degranulation allows mast cells to expose bioactive material embedded in the granule matrix toward the antibody-targeted cell and is accompanied by the formation of a signaling area at the cell-cell contact site. In this chapter, we describe (1) how to stimulate mast cells with cell-bound antigens and (2) how to monitor ADDS formation and to investigate ADDS characteristics by confocal microscopy.

5 nm Silver Nanoparticles Amplify Clinical Features of Atopic Dermatitis in Mice by Activating Mast Cells.

The triggering effect of silver nanoparticles (NPs) on the induction of allergic reactions is evaluated, by studying the activation of mast cells and the clinical features of atopic dermatitis in a mouse model. Granule release is induced in RBL-2H3 mast cells by 5 nm, but not 100 nm silver NPs. Increases in the levels of reactive oxygen species (hydrogen peroxide and mitochondrial superoxide) and intracellular Ca++ in mast cells are induced by 5 nm silver NPs. In a mouse model of atopic dermatitis induced by a mite allergen, the skin lesions are more severe and appear earlier in mice treated simultaneously with 5 nm silver NPs and allergen compared with mice treated with allergen alone or 100 nm silver NPs and allergen. The histological findings reveal that number of tryptase-positive mast cells and total IgE levels in the serum increase in mice treated with 5 nm silver NPs and allergen. The results in this study indicate that cotreatment with 5 nm silver NPs stimulates mast cell degranulation and induces earlier and more severe clinical alterations in allergy-prone individuals.

How mast cells make decisions.

Mast cells (MCs) are present in various tissues and are responsible for initiating many of the early inflammatory responses to extrinsic challenges. Recent studies have demonstrated that MCs can tailor their responses, depending on the stimulus encountered and the tissue in which they are stimulated. In this issue of the JCI, Gaudenzio and colleagues examine the mechanistic differences between MC responses observed after engagement of Fcε receptor I and those seen after MC stimulation via the recently identified G protein-coupled receptor MRGPRX2. By showing that discrete cellular activation patterns affect the phenotype of the MC response in vivo and in vitro, the authors provide important information about how MCs differentially process various stimuli into distinct degranulation programs.

Listeria monocytogenes induces mast cell extracellular traps

Mast cells play an essential role in different immunological phenomena including allergy and infectious diseases. Several bacteria induce mast cell activation leading to degranulation and the production of several cytokines and chemokines. However, mast cells also have different microbicidal activities such as phagocytosis and the release of DNA with embedded granular proteins known as Mast Cell Extracellular Traps (MCETs). Although previous reports indicate that extracellular bacteria are able to induce MCETs little is known if intracellular bacteria can induce these structures. In this work, we evaluated MCETs induction by the intracellular bacteria Listeria monocytogenes. We found that mast cells released DNA after stimulation with L. monocytogenes, and this DNA was complexed to histone and tryptase. Before extracellular DNA release, L. monocytogenes induced modifications to the mast cell nuclear envelope and DNA was detected outside the nucleus. L. monocytogenes stimulated mast cells to produce significant amounts of reactive oxygen species (ROS) and blocking NADPH oxidase diminished DNA release by mast cells. Finally, MCETs showed antimicrobial activity against L. monocytogenes that was partially blocked when β-hexosaminidase activity was inhibited. These results show that L. monocytogenes induces mast cells to produce microbicidal MCETs, suggesting a role for mast cells in containing infection beyond the induction of inflammation.

Neuroendocrinology of the skin.

The skin is considered the mirror of the soul and is affected by neurohormonal triggers, especially stress. Hair follicles, keratinocytes, mast cells, melanocytes, and sebocytes all express sex and stress hormones implicating them in a local "hypothalamic-pituitary-adrenal axis." In particular, the peptides corticotropin-releasing hormone (CRH) and neurotensin (NT) have synergistic action stimulating mast cells and are uniquely elevated in the serum of patients with skin diseases exacerbated by stress. Addressing the neurohormonal regulation of skin function could lead to new targets for effective treatment of inflammatory skin diseases.

Activated brain mast cells contribute to postoperative cognitive dysfunction by evoking microglia activation and neuronal apoptosis.

BackgroundNeuroinflammation plays a key role in the occurrence and development of postoperative cognitive dysfunction (POCD). Microglia, the resident immune cells in the brain, has been increasingly recognized to contribute to neuroinflammation. Although brain mast cells (MCs) are the “first responder” in the brain injury rather than microglia, little is known about the functional aspects of MCs-microglia interactions.MethodsMale Sprague-Dawley (SD) rats were injected intracerebroventricular with MC stabilizer Cromolyn (100 μg/μl), MC stimulator C48/80 (1 μg/μl), or sterile saline 30 min before open tibial fracture surgery, and the levels of neuroinflammation and memory dysfunction were tested 1 and 3 days after surgery. In addition, the effect of activated MCs on microglia and neurons was determined in vitro.ResultsTibial fracture surgery induced MCs degranulation, microglia activation, and inflammatory factors production, which initiated the acute brain inflammatory response and neuronal death and exhibited cognitive deficit. Site-directed preinjection of the “MCs stabilizer” disodium cromoglycate (Cromolyn) inhibited this effect, including decrease of inflammatory cytokines, reduced MCs degranulation, microglia activation, neuronal death, and improved cognitive function 24 h after the surgery. In vitro study, we found that the conditioned medium from lipopolysaccharide (LPS)-stimulated mast cells line (P815) could induce primary microglia activation through mitogen-activated protein kinase (MAPK) pathway signaling and subsequent production of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6). In addition, the activated P815 could directly induce neuronal apoptosis and synapse injury with microglia independently. Cromolyn could inhibit P815 activation following improved microglia activation and neuronal loss.ConclusionsThese results implicate that activated MCs could trigger microglia activation and neuronal damage, resulting in central nervous system (CNS) inflammation, and communications of MCs with microglia and neuron could constitute a new and unique therapeutic target for CNS immune inflammation-related diseases.

Influence of model resolution on geometric simulations of antibody aggregation

SUMMARYIt is estimated that allergies afflict up to 40% of the world's population. A primary mediator for allergies is the aggregation of antigens and IgE antibodies bound to cell-surface receptors, FcεRI. Antibody/antigen aggregate formation causes stimulation of mast cells and basophils, initiating cellular degranulation and releasing immune mediators which produce an allergic or anaphylactic response. Understanding the shape and structure of these aggregates can provide critical insights into the allergic response. We have previously developed methods to geometrically model, simulate and analyze antibody aggregation inspired by rigid body robotic motion simulations. Our technique handles the large size and number of molecules involved in aggregation, providing an advantage over traditional simulations such as molecular dynamics (MD) and coarse-grained energetic models. In this paper, we study the impact of model resolution on simulations of geometric structures using both our previously developed Monte Carlo simulation and a novel application of rule-based modeling. These methods complement each other, the former providing explicit geometric detail and the latter providing a generic representation where multiple resolutions can be captured. Our exploration is focused on two antigens, a man-made antigen with three binding sites, DF3, and a common shrimp allergen (antigen), Pen a 1. We find that impact of resolution is minimal for DF3, a small globular antigen, but has a larger impact on Pen a 1, a rod-shaped molecule. The volume reduction caused by the loss in resolution allows more binding site accessibility, which can be quantified using a rule-based model with implicit geometric input. Clustering analysis of our simulation shows good correlation when compared with available experimental results. Moreover, collisions in all-atom reconstructions are negligible, at around 0.2% at 90% reduction.

Inhibitory effect of Pterocarpus indicus Willd water extract on IgE/Ag-induced mast cell and atopic dermatitis-like mouse models.

Pterocarpus indicus Willd has been widely used as a traditional medicine to treat edema, cancer, and hyperlipidemia, but its antiallergic properties and underlying mechanisms have not yet been studied. The purpose of this study was to evaluate the antiallergic activity of Pterocarpus indicus Willd water extract (PIW) using activated mast cells and an atopic dermatitis (AD)-like mouse model. PIW decreased IgE/Ag-induced mast cell degranulation and the phosphorylation of Syk and downstream signaling molecules such as PLC-γ, Akt, Erk 1/2, JNK compared to stimulated mast cells. In DNCB-induced AD-like mice, PIW reduced IgE level in serum, as well as AD-associated scratching behavior and skin severity score. These results indicate that PIW inhibits the allergic response by reducing mast cell activation and may have clinical potential as an antiallergic agent for disorders such as AD.

When signals get crossed: the consequences of dual allergen- and influenza-mediated signaling in mast cells

Abstract Despite the many advances in our understanding of viral infections, influenza A virus (IAV) continues to impose a significant heath burden and presents a serious threat for a worldwide pandemic. Severe IAV infection is characterized by a cytokine storm. Recent evidence indicates mast cell activation is a key initiator of this cytokine storm during severe IAV infection. During the 2009 H1N1 pandemic, asthma was the most common co-morbidity among hospitalized individuals suggesting a potential interplay between pre-existing mast cell disease and IAV infection. Experimental data examining the cross-talk that can occur during dual FcɛRI and IAV stimulation of mast cells is lacking. Here we show that signaling through FcɛRI concurrent with IAV infection (A/WSN/33) augments the mast cell response resulting in a highly synergist enhancement of cytokine synthesis and release by these cells in vitro. Surprisingly, while IAV induced cytokine production by A/WSN/33 is dependent on the MAVS pathway, using bone marrow cultured mast cells from MAVS and STING knockout mice, we determined this synergistic effect can occur independent of MAVS signaling and the STING adaptor. Furthermore, the synergy can be observed as early as 1 hour PI, prior to significant viral replication. These data suggest an early signaling event is responsible for the synergy. Our data supports a role for the lipid mediator sphingosine-1-phosphate, which is known to be important during allergen stimulation, and as our data demonstrates, is essential for proper IAV activation of mast cells. Taken together, our data suggest that IAV may incite asthmatic exacerbation through enhanced cytokine production from mast cells receiving two distinct stimuli simultaneously.

Citrus peel polymethoxyflavones nobiletin and tangeretin suppress LPS- and IgE-mediated activation of human intestinal mast cells.

Allergic diseases with mast cells (MC) as main effector cells show an increased prevalence. MC also play an essential role in other inflammatory conditions. Therapeutical use of anti-inflammatory nutraceuticals directly targeting MC activation could be of interest for afflicted patients. Nobiletin and tangeretin are citrus peel polymethoxyflavones, a group of citrus flavonoids, possessing anticancer, antimetastatic, and anti-inflammatory activities. Here, we analyzed the effects of nobiletin/tangeretin on LPS- and IgE-mediated stimulation of human intestinal mast cells (hiMC). MC isolated from human intestinal tissue were treated with different concentrations of nobiletin or tangeretin prior to stimulation via LPS/sCD14 or IgE-dependently. Degranulation, pro-inflammatory cytokine expression and phosphorylation of ERK1/2 were examined. Expression of CXCL8, CCL3, CCL4 and IL-1β in response to LPS-mediated stimulation was inhibited by nobiletin/tangeretin. hiMC activated IgE-dependently showed a reduced release of β-hexosaminidase and cysteinyl LTC4 in response to nobiletin, but not in response to tangeretin. Expression of CXCL8, CCL2, CCL3, CCL4 and TNF in IgE-dependently activated hiMC was decreased in a dose-dependent manner following treatment with nobiletin/tangeretin. IL-1β expression was only reduced by tangeretin. Compared to treatment with NF-κB inhibitor BMS345541 or MEK-inhibitor PD98059, nobiletin and tangeretin showed similar effects on mediator production. Phosphorylation of ERK1/2 upon IgE-mediated antigen stimulation was significantly suppressed by nobiletin and tangeretin. Nobiletin and, to a lesser extent, tangeretin could be considered as anti-inflammatory nutraceuticals by reducing release and production of proinflammatory mediators in MC.

Possible Involvement of the Inhibition of NF-κB Factor in Anti-Inflammatory Actions That Melatonin Exerts on Mast Cells.

Melatonin is a molecule endogenously produced in a wide variety of immune cells, including mast cells (RBL-2H3). It exhibits immunomodulatory, anti-inflammatory and anti-apoptotic properties. The physiologic mechanisms underlying these activities of melatonin have not been clarified in mast cells. This work is designed to determine the anti-inflammatory effect and mechanism of action of melatonin on activated mast cells. RBL-2H3 were pre-treated with exogenous melatonin (MELx) at physiological (100nM) and pharmacological (1 mM) doses for 30 min, washed and activated with PMACI (phorbol 12-myristate 13-acetate plus calcium ionophore A23187) for 2 h and 12 h. The data shows that pre-treatment of MELx in stimulated mast cells, significantly reduced the levels of endogenous melatonin production (MELn), TNF-α and IL-6. These effects are directly related with the MELx concentration used. MELx also inhibited IKK/NF-κB signal transduction pathway in stimulated mast cells. These results indicate a molecular basis for the ability of melatonin to prevent inflammation and for the treatment of allergic inflammatory diseases through the down-regulation of mast cell activation. J. Cell. Biochem. 117: 1926-1933, 2016. © 2016 Wiley Periodicals, Inc.

Brain Fires in Autism Spectrum Disorders

Autism spectrum disorders (ASD) is characterized by social and communicative deficits, severe anxiety, and stereotypic movements. Despite affecting as many as 1 in 45 US children in the USA, the pathogenesis of ASD is still unknown. Recent epidemiological studies indicated a strong statistical correlation between risk for maternal / infant atopic diseases and ASD suggesting the possible involvement and activation of mast cells (MC). These unique immune cells are located close to blood vessels in all tissues, including the thalamus and hypothalamus in the brain, which regulate emotions known to be dysfunctional in ASD. Moreover, MCs are stimulated by two brain peptides, corticotropin-releasing hormone (CRH) and neurotensin (NT), which we showed to be high in the blood of children with ASD. Stimulated MCs then secrete inflammatory molecules that activate brain microglia, which proliferate and “choke off” nerve communication. These inflammatory molecules are increased in the brain and serum of patients with ASD and also lead to disruption of the protective blood brain barrier (BBB), which is regulated by MCs, permitting the entry of circulating white blood cells and toxins contributing to brain. We further reported that the elevated blood levels of two inflammatory molecules, IL-6 and TNF, identify a subgroup of children with ASD, who benefit most from a promising treatment with the natural flavonoid luteolin that combats brain inflammation. Extinguishing inflammation (“Brain fires”) may be the best hope for curing ASD.