Targeting Mast Cells Research Articles

Aurora kinase inhibitor tozasertib suppresses mast cell activation in vitro and in vivo.

Mast cells are important in allergic reactions. Here, we assessed the anti-allergic effects of the anti-cancer drug tozasertib specifically regarding regulatory effects on mast cell activation. Tozasertib effects on mast cell degranulation were determined by measuring β-hexosaminidase and histamine release and by assessing morphological changes in RBL-2H3 and mouse bone marrow-derived mast cells (BMMCs) stimulated with mouse anti-dinitrophenyl (DNP)-IgE/DNP-human serum albumin or human LAD2 cells activated with phorbol-12-myristate 13-acetate plus calcium ionophore (PMACI). Western blots were performed to detect the expression of molecules involved in NF-κB, MAPK, and Aurora kinase signalling. in vivo anti-allergic effects of tozasertib were determined in the murine IgE-mediated passive cutaneous anaphylaxis (PCA) and ovalbumin (OVA)-induced active systemic anaphylaxis (ASA) models. Tozasertib treatment decreased high-affinity IgE receptor (FcεRI) or PMACI-mediated degranulation in RBL-2H3 cells and in BMMCs or LAD2 cells as shown by β-hexosaminidase or histamine levels. Similarly, tozasertib prevented morphological changes in mast cells, such as particle release and F-actin reorganization. In addition, tozasertib markedly decreased expression of phosphorylated (p)-NF-κB p65, p-Erk1/2, p-p38, and p-Aurora A/B, indicating that tozasertib can inhibit the signalling pathway mediating mast cell activation. Tozasertib attenuated IgE/Ag-induced PCA dose-dependently, as shown by reduced Evans blue staining. Similarly, tozasertib reduced body temperature levels and serum histamine levels in OVA-challenged ASA mice. The Aurora kinase inhibitor tozasertib suppressed mast cell activation in vitro and in vivo. Tozasertib may be a potential drug, targeting mast cell activation, to treat allergic diseases or mastocytosis.

Therapeutics for Dengue

Dengue virus (DENV) infections are a global health emergency. Humans can experience multiple DENV infections, owing to the presence of four antigenically distinct DENV serotypes, DENV1–4. DENV infection results in a spectrum of disease, ranging from mild and self-limiting to severe and life-threatening illness. Currently, one dengue vaccine is approved, although with modest efficacy, so dengue-directed therapeutics are still needed to minimize the disease burden. The current standard-of-care treatment for dengue is only supportive but there is a pipeline of therapeutic treatments that are in development. In the past decade, many promising anti-dengue drug targets have been identified. Antivirals directly influencing the virus replication cycle or immune modulatory drugs with host targets that affect inflammation have been explored. Recently, targeting mast cells (MCs) or MC products has also emerged as a promising treatment option for dengue-associated vascular pathologies. Several human clinical trials have been conducted or are ongoing to test the efficacy of various therapeutics with an end-goal of treating dengue. Special emphasis is given to safe and tolerable drugs, which could be re-purposed and introduced into clinical practice quickly. This review highlights the current standard-of-care treatment for dengue and discusses various antiviral and host target drugs that are currently being pursued at various stages of preclinical and clinical development.

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).

Selective Serotonin Reuptake Inhibitors Suppress Mast Cell Function

Abstract Mast cells are tissue resident innate immune cells activated by IgE and many other ligands, including purines. Upon activation, they release histamine, cytokines, chemokines, proteases, and lipid mediators evoking allergic symptoms. New ways of targeting mast cells could greatly benefit allergic disease therapy. One plausible target is activation by purinergic receptors binding ligands such as ATP. However, there are currently no clinically available therapies targeting purinergic signaling. Because anti-depressants in the SSRI family can have off-target effects on purinergic receptors, we tested the hypothesis that SSRIs can attenuate mast cell function. We found that the SSRI fluoxetine blocks IgE- and ATP-induced cytokine production, degranulation, and calcium influx in murine bone marrow derived mast cells (BMMC). Furthermore, fluoxetine suppresses IgE-mediated anaphylaxis in vivo, and reduces ATP cellular uptake. Because adding serotonin to BMMC or deleting the serotonin transporter has no effect on fluoxetine-mediated suppression, an off-target effect seemed likely. We show that inhibitors of the ATP receptor P2X3 attenuate IgE-mediated activation similarly to fluoxetine, and combining fluoxetine with these inhibitors does not result in additive effects. Using siRNAs to knock down P2X3, we find that P2X3 is needed for suppression by fluoxetine. These data support the possibility of targeting purinergic signaling to treat allergic diseases, and suggest that this may be possible by repurposing FDA-approved SSRIs.

Mast Cells Induce Blood Brain Barrier Damage in SCD by Causing Endoplasmic Reticulum Stress in the Endothelium.

Endothelial dysfunction underlies the pathobiology of cerebrovascular disease. Mast cells are located in close proximity to the vasculature, and vasoactive mediators released upon their activation can promote endothelial activation leading to blood brain barrier (BBB) dysfunction. We examined the mechanism of mast cell-induced endothelial activation via endoplasmic reticulum (ER) stress mediated P-selectin expression in a transgenic mouse model of sickle cell disease (SCD), which shows BBB dysfunction. We used mouse brain endothelial cells (mBECs) and mast cells-derived from skin of control and sickle mice to examine the mechanisms involved. Compared to control mouse mast cell conditioned medium (MCCM), mBECs incubated with sickle mouse MCCM showed increased, structural disorganization and swelling of the ER and Golgi, aggregation of ribosomes, ER stress marker proteins, accumulation of galactose-1-phosphate uridyl transferase, mitochondrial dysfunction, reactive oxygen species (ROS) production, P-selectin expression and mBEC permeability. These effects of sickle-MCCM on mBEC were inhibited by Salubrinal, a reducer of ER stress. Histamine levels in the plasma, skin releasate and in mast cells of sickle mice were higher compared to control mice. Compared to control BBB permeability was increased in sickle mice. Treatment of mice with imatinib, Salubrinal, or P-selectin blocking antibody reduced BBB permeability in sickle mice. Mast cells induce endothelial dysfunction via ER stress-mediated P-selectin expression. Mast cell activation contributes to ER stress mediated endothelial P-selectin expression leading to increased endothelial permeability and impairment of BBB. Targeting mast cells and/or ER stress has the potential to ameliorate endothelial dysfunction in SCD and other pathobiologies.

The roles of mast cells in radiation-induced damage are still an enigma

Mast cells are immune cells that mature within the host tissue. The acquired phenotype is dictated by the tissue microenvironment, giving rise to diverse tissue-dependent phenotypes and functions. The lack of cellular models reflecting phenotypes found in vivo and important differences between human and rodent mast cells are obstacles to the understanding of their exact role in several pathophysiological processes. Studies published over the past few years showed that mast cells' role lies far beyond their involvement in allergy and anaphylaxis. Studies demonstrating their participation in innate immune responses as well as tissue scaring and vascular pathologies allowed the understanding of their role in several diseases, but also gave contradictory results, especially concerning tissue response to ionizing radiations. Nevertheless, therapeutic tools exist to target mast cells, such as degranulation inhibitors, antihistamine, protease inhibitors or tyrosine kinase receptors antagonists, and may offer some interesting new therapeutic perspectives to manage acute and chronic after-effects of radiation therapy.

Building and Crossing the Translational Bridge: 2016Alopecia Areata Research Summit Highlights.

Alopecia areata (AA) is a common autoimmune skin disease that results in the loss of hair on the scalp and elsewhere on the body and affects over 146 million people worldwide at some point in their lives. Founded in 1981, the National Alopecia Areata Foundation is a nonprofit organization that supports research to find a cure or acceptable treatment for AA, supports those with the disease, and educates the public about AA. The National Alopecia Areata Foundation conducts research summits every 2 years to review progress and create new directions in its funded and promoted research. The Foundation brings together scientists from all disciplines to get a broad and varied perspective. These AA research summits are part of the Foundation's main strategic initiative, the AA Treatment Development Program, to enhance the understanding of AA and accelerate progress toward a viable treatment.

Induction of Human Lung Mast Cell Apoptosis by Granule Permeabilization: A Novel Approach for Targeting Mast Cells.

Mast cells are implicated as detrimental players in inflammatory lung diseases, particularly asthma. Mast cells respond to activating stimuli by releasing a wide panel of pro-inflammatory compounds that can contribute profoundly to the pathology, and there is currently an unmet need for strategies that efficiently ameliorate harmful effects of mast cells under such conditions. Here, we sought to evaluate a novel concept for targeting human lung mast cells, by assessing the possibility of selectively depleting the lung mast cells by induction of apoptosis. For this purpose, we used lysosomotropic agents, i.e., compounds that are known to permeabilize the secretory granules of mast cells, thereby releasing the contents of the granules into the cytosol. Either intact human lung tissue, purified human lung mast cells or mixed populations of human lung cells were incubated with the lysosomotropic agents mefloquine or siramesine, followed by measurement of apoptosis, reactive oxygen species (ROS) production, and release of cytokines. We show that human lung mast cells were highly susceptible to apoptosis induced by this strategy, whereas other cell populations of the lung were largely refractory. Moreover, we demonstrate that apoptosis induced by this mode is dependent on the production of ROS and that the treatment of lung tissue with lysosomotropic agents causes a decrease in the release of pathogenic cytokines. We conclude that selective apoptosis of human lung mast cells can be accomplished by administration of lysosomotropic agents, thus introducing the possibility of using such drugs as novel therapeutics in the treatment of inflammatory lung disorders such as asthma.

Neurogenic mediators contribute to local edema induced by Micrurus lemniscatus venom.

Background/AimsMicrurus is one of the four snake genera of medical importance in Brazil. Coral snakes have a broad geographic distribution from the southern United States to Argentina. Micrurine envenomation is characterized by neurotoxic symptoms leading to dyspnea and death. Moreover, various local manifestations, including edema formation, have been described in patients bitten by different species of Micrurus. Thus, we investigated the ability of Micrurus lemniscatus venom (MLV) to induce local edema. We also explored mechanisms underlying this effect, focusing on participation of neuropeptides and mast cells.Methodology/Principal findingsIntraplantar injection of MLV (1–10 μg/paw) in rats caused dose- and time-dependent edema with a peak between 15 min and 1 h after injection. MLV also induced degranulation of peritoneal mast cells (MCs). MC depletion by compound 48/80 markedly reduced MLV-induced edema. Pre-treatment (30 min) of rats with either promethazine a histamine H1 receptor antagonist or methysergide, a nonselective 5-HT receptor antagonist, reduced MLV-induced edema. However, neither thioperamide, a histamine H3/H4 receptor antagonist, nor co-injection of MLV with HOE-140, a BK2 receptor antagonist, altered the response. Depletion of neuropeptides by capsaicin or treatment of animals with NK1- and NK2-receptor antagonists (SR 140333 and SR 48968, respectively) markedly reduced MLV-induced edema.Conclusions/SignificanceIn conclusion, MLV induces paw edema in rats by mechanisms involving activation of mast cells and substance P-releasing sensory C-fibers. Tachykinins NKA and NKB, histamine, and serotonin are major mediators of the MLV-induced edematogenic response. Targeting mast cell- and sensory C-fiber-derived mediators should be considered as potential therapeutic approaches to interrupt development of local edema induced by Micrurus venoms.

Research on the effect of RNA interference on mast cells in respiratory allergic diseases

Respiratory allergic disease has become a major health problem in the 21st century.Mast cells are key effector cells of the respiratory anaphylaxis, and can form a variety of features of allergic inflammation by producting large numbers of inflammatory mediators.RNAi can affect the disease process by silencing gene expression, and has made significant process in the study of many diseases, but the research of targeting mast cells for the treatment of respiratory allergic diseases is rare.This review focuses on recent advances of the application of RNA interference on mast cell in respiratory allergic diseases, aming to further understand its application in the respiratory allergic diseases and research status, and broaden new ideas of treating respiratory allergies.

Targeting Mast Cells as a Viable Therapeutic Option in Endometriosis

Endometriosis is a chronic condition that affects ˜10% of young women worldwide. Pain and infertility are the two most common features of the disease. The condition appears to be sex hormone-dependent, although a subset of females with the condition still experience symptoms post-menopause. The aetiology of endometriosis induction still remains elusive, and surgery to remove the lesions often fails to cure the condition, as the lesions often reappear. The lesions contain stromal cells, blood vessels, nerves, and numerous mast cells. In some respects, endometrial lesions resemble a chronic fibrotic scar-like tissue that does not resolve. Studies in other fibrotic abnormal healing conditions have revealed that targeting mast cells, as a central component of what is called a ‘neural–mast cell–fibroblast’ axis, by repurposing asthma drugs can prevent induction of the abnormal healing phenotype. Given the similarities between conditions with abnormal healing phenotypes and endometrial lesions, it is postulated that taking a similar approach to target endometrial lesion mast cells could exert a benefit for patients with endometriosis. This review also outlines approaches to assess the likelihood that targeting mast cells could lead to clinical trials using such ‘repurposed’ mast cell targeted drugs.

MAST CELL HYPERACTIVATION INDUCES BEHAVIORAL DEFICITS AND CEREBRAL PERFUSION REDUCTION IN MICE

There is growing evidence that mast cells are involved in Alzheimer's disease (AD). In humans they are associated with amyloid lesions, are degranulated by β-amyloid in mouse tissue culture and brain slices, and their increased presence is associated with later appearance of amyloid plaques in mice [1 and refs within]. Additionally, an AD clinical trial targeting mast cells with the inhibitor Masitinib (AB Science) stabilized cognitive scores [2]. To test directly if their overactivation can cause AD-like symptoms, we evaluated the KitD814V mouse model of mast cell hyperactivation [3], previously uncharacterized for CNS effects. KitD814V mice under the control of the mature-onset promoter Mctp5 (n=11) and their Mcpt5-only controls (n=7) were used. Due to likely variable age-related penetrance [3] and uncertain gender dimorphism, both groups included males and females 6–12 months old (equal per-group distribution). Mice were evaluated by MRI for brain morphology and cerebral perfusion, and behaviorally for anxiety/risk assessing (6 min elevated plus maze) and 24hr displacement activity (Noldus PhenoTyper). Statistics are presented as mean±SEM; p-values are from t-tests, with the significance threshold set at p≤0.05. Mcpt5-KitD814V mice, when compared to Mcpt5-only controls, exhibited a deficit in cerebral perfusion (112±13 vs. 155±12 ml 100g-1 min-1, p=0.026) though not one in brain volume (422±6 vs. 440±7 mm3, p=0.075). Behaviorally, deficits were also seen in elevated plus maze head dip total duration (risk-assessing behavior; 3.57±1.55 vs. 10.61±2.57 seconds, p=0.040) and 24hr displacement activity (294±40 vs. 494±54 meters, p=0.036). Mast cell hyperactive mice suffer behavioral deficits and exhibit perfusion reduction, a human biomarker of AD. This provides further evidence of the potential role of mast cells in dementia, and highlights the potential value of the KitD814V mouse as a model of it.

Are Mast Cells MASTers in Cancer?

Prolonged low-grade inflammation or smoldering inflammation is a hallmark of cancer. Mast cells form a heterogeneous population of immune cells with differences in their ultra-structure, morphology, mediator content, and surface receptors. Mast cells are widely distributed throughout all tissues and are stromal components of the inflammatory microenvironment that modulates tumor initiation and development. Although canonically associated with allergic disorders, mast cells are a major source of pro-tumorigenic (e.g., angiogenic and lymphangiogenic factors) and antitumorigenic molecules (e.g., TNF-α and IL-9), depending on the milieu. In certain neoplasias (e.g., gastric, thyroid and Hodgkin’s lymphoma) mast cells play a pro-tumorigenic role, in others (e.g., breast cancer) a protective role, whereas in yet others they are apparently innocent bystanders. These seemingly conflicting results suggest that the role of mast cells and their mediators could be cancer specific. The microlocalization (e.g., peritumoral vs intratumoral) of mast cells is another important aspect in the initiation/progression of solid and hematologic tumors. Increasing evidence in certain experimental models indicates that targeting mast cells and/or their mediators represent a potential therapeutic target in cancer. Thus, mast cells deserve focused consideration also as therapeutic targets in different types of tumors. There are many unanswered questions that should be addressed before we understand whether mast cells are an ally, adversary, or innocent bystanders in human cancers.

Exon skipping of FcεRIβ eliminates expression of the high-affinity IgE receptor in mast cells with therapeutic potential for allergy

Allergic diseases are driven by activation of mast cells and release of mediators in response to IgE-directed antigens. However, there are no drugs currently available that can specifically down-regulate mast cell function in vivo when chronically administered. Here, we describe an innovative approach for targeting mast cells in vitro and in vivo using antisense oligonucleotide-mediated exon skipping of the β-subunit of the high-affinity IgE receptor (FcεRIβ) to eliminate surface high-affinity IgE receptor (FcεRI) expression and function, rendering mast cells unresponsive to IgE-mediated activation. As FcεRIβ expression is restricted to mast cells and basophils, this approach would selectively target these cell types. Given the success of exon skipping in clinical trials to treat genetic diseases such as Duchenne muscular dystrophy, we propose that exon skipping of FcεRIβ is a potential approach for mast cell-specific treatment of allergic diseases.

367 Targeting mast cells and basophils by FcγRIIB specific IgE: New treatment strategy for type I allergies?

367 Targeting mast cells and basophils by FcγRIIB specific IgE: New treatment strategy for type I allergies?

IL-33 promotes food anaphylaxis in epicutaneously sensitized mice by targeting mast cells

Cutaneous exposure to food allergens predisposes to food allergy, which is commonly associated with atopic dermatitis (AD). Levels of the epithelial cytokine IL-33 are increased in skin lesions and serum of patients with AD. Mast cells (MCs) play a critical role in food-induced anaphylaxis and express the IL-33 receptor ST2. The role of IL-33 in patients with MC-dependent food anaphylaxis is unknown. We sought to determine the role and mechanism of action of IL-33 in patients with food-induced anaphylaxis in a model of IgE-dependent food anaphylaxis elicited by oral challenge of epicutaneously sensitized mice. Wild-type, ST2-deficient, and MC-deficient KitW-sh/W-sh mice were epicutaneously sensitized with ovalbumin (OVA) and then challenged orally with OVA. Body temperature was measured by means of telemetry, Il33 mRNA by means of quantitative PCR, and IL-33, OVA-specific IgE, and mouse mast cell protease 1 by means of ELISA. Bone marrow-derived mast cell (BMMC) degranulation was assessed by using flow cytometry. Il33 mRNA expression was upregulated in tape-stripped mouse skin and scratched human skin. Tape stripping caused local and systemic IL-33 release in mice. ST2 deficiency, as well as ST2 blockade before oral challenge, significantly reduced the severity of oral anaphylaxis without affecting the systemic TH2 response to the allergen. Oral anaphylaxis was abrogated in KitW-sh/W-sh mice and restored by means of reconstitution with wild-type but not ST2-deficient BMMCs. IL-33 significantly enhanced IgE-mediated degranulation of BMMCs invitro. IL-33 is released after mechanical skin injury, enhances IgE-mediated MC degranulation, and promotes oral anaphylaxis after epicutaneous sensitization by targeting MCs. IL-33 neutralization might be useful in treating food-induced anaphylaxis in patients with AD.

Identification of Biological and Pharmaceutical Mast Cell‐ and Basophil‐Related Targets

Identification of Biological and Pharmaceutical Mast Cell‐ and Basophil‐Related Targets

Mast Cells and Irritable Bowel Syndrome: From the Bench to the Bedside.

Irritable bowel syndrome (IBS) is traditionally defined as a functional disorder since it lacks demonstrable pathological abnormalities. However, in recent years, low grade inflammatory infiltration, often rich in mast cells, in both the small and large bowel, has been observed in some patients with IBS. The close association of mast cells with major intestinal functions, such as epithelial secretion and permeability, neuroimmune interactions, visceral sensation, and peristalsis, makes researchers and gastroenterologists to focus attention on the key roles of mast cells in the pathogenesis of IBS. Numerous studies have been carried out to identify the mechanisms in the development, infiltration, activation, and degranulation of intestinal mast cells, as well as the actions of mast cells in the processes of mucosal barrier disruption, mucosal immune dysregulation, visceral hypersensitivity, dysmotility, and local and central stress in IBS. Moreover, therapies targeting mast cells, such as mast cell stabilizers (cromoglycate and ketotifen) and antagonists of histamine and serotonin receptors, have been tried in IBS patients, and have partially exhibited considerable efficacy. This review focuses on recent advances in the role of mast cells in IBS, with particular emphasis on bridging experimental data with clinical therapeutics for IBS patients.

Mast Cell Targeted Chimeric Toxin Can Be Developed as an Adjunctive Therapy in Colon Cancer Treatment.

The association of colitis with colorectal cancer has become increasingly clear with mast cells being identified as important inflammatory cells in the process. In view of the relationship between mast cells and cancer, we studied the effect and mechanisms of mast cells in the development of colon cancer. Functional and mechanistic insights were gained from ex vivo and in vivo studies of cell interactions between mast cells and CT26 cells. Further evidence was reversely obtained in studies of mast cell targeted Fcε-PE40 chimeric toxin. Experiments revealed mast cells could induce colon tumor cell proliferation and invasion. Cancer progression was found to be related to the density of mast cells in colonic submucosa. The activation of MAPK, Rho-GTPase, and STAT pathways in colon cancer cells was triggered by mast cells during cell-to-cell interaction. Lastly, using an Fcε-PE40 chimeric toxin we constructed, we confirmed the promoting effect of mast cells in development of colon cancer. Mast cells are a promoting factor of colon cancer and thus also a potential therapeutic target. The Fcε-PE40 chimeric toxin targeting mast cells could effectively prevent colon cancer in vitro and in vivo. Consequently, these data may demonstrate a novel immunotherapeutic approach for the treatment of tumors.

IL-33 Promotes Food Anaphylaxis in Epicutaneously-Sensitized Mice By Targeting Mast Cells

Cutaneous exposure to food allergens predisposes to food allergy, which is commonly associated with atopic dermatitis (AD). The levels of the epithelial cytokine IL-33 are increased in skin lesions and serum of AD patients. Mast cells (MC) play a critical role in food anaphylaxis and express the IL-33 receptor ST2. The role of IL-33 in MC-dependent food anaphylaxis is unknown.We aim to determine the role and mechanism of action of IL-33 in food anaphylaxis in a model of IgE-dependent food anaphylaxis elicited by oral challenge of epicutaneously (EC)-sensitized mice. WT, ST2-deficient and MC-deficient KitW-sh/W-sh mice were EC sensitized with ovalbumin (OVA) then challenged orally with OVA. Body temperature was measured by telemetry, Il33 mRNA by qPCR, and IL-33, OVA-specific IgE and mouse mast cell protease 1 (mMCP-1) by ELISA. Bone marrow-derived MCs (BMMCs) degranulation was assessed by flow cytometry. Il33 mRNA expression was upregulated in tape-stripped mouse skin and scratched human skin, and tape stripping caused local and systemic IL-33 release in mice. ST2 deficiency, as well as ST2 blockade prior to oral challenge, significantly reduced the severity of oral anaphylaxis without affecting antigen-specific IgE or Th2 responses. Oral anaphylaxis was abrogated in KitW-sh/W-sh mice, and restored by reconstitution with WT, but not ST2-deficient, BMMCs. IL-33 significantly enhanced IgE-mediated degranulation of BMMCs in vitro. IL-33 is released following mechanical skin injury, enhances IgE-mediated MC degranulation, and promotes oral anaphylaxis following EC sensitization by targeting MCs. IL-33 neutralization may be useful in treating food anaphylaxis in AD patients.