New developments in mast cell biology

Emerging Roles for Serotonin in Regulating Metabolism: New Implications for an Ancient Molecule

Serotonin is a phylogenetically ancient biogenic amine that has played an integral role in maintaining energy homeostasis for billions of years. In mammals, serotonin produced within the central nervous system regulates behavior, suppresses appetite, and promotes energy expenditure by increasing sympathetic drive to brown adipose tissue. In addition to these central circuits, emerging evidence also suggests an important role for peripheral serotonin as a factor that enhances nutrient absorption and storage. Specifically, glucose and fatty acids stimulate the release of serotonin from the duodenum, promoting gut peristalsis and nutrient absorption. Serotonin also enters the bloodstream and interacts with multiple organs, priming the body for energy storage by promoting insulin secretion and de novo lipogenesis in the liver and white adipose tissue, while reducing lipolysis and the metabolic activity of brown and beige adipose tissue. Collectively, peripheral serotonin acts as an endocrine factor to promote the efficient storage of energy by upregulating lipid anabolism. Pharmacological inhibition of serotonin synthesis or signaling in key metabolic tissues are potential drug targets for obesity, type 2 diabetes, and nonalcoholic fatty liver disease (NAFLD).

Possible Involvement of Intracellular Calcium-Independent Phospholipase A2 in the Release of Secretory Phospholipases from Mast Cells-Increased Expression in Ileal Mast Cells of Crohn's Disease

Increased activity of secretory phospholipases A₂ (sPLA₂) type-II was previously observed in ileum of Crohn’s disease (CD). Our aims were to explore the involvement of calcium-independent (i)PLA₂β in the release of sPLA₂s from the human mast cell (MC) line (HMC-1) and investigate expressions of cytosolic (c)PLA₂α, iPLA₂β, sPLA₂-IIA and sPLA₂-V in MCs of CD ileum. The release of sPLA₂ was investigated in HMC-1 by immunocytochemistry and ELISA. The expression intensities of PLA₂s in mucosal MCs, and the proportion of PLA₂-positive MCs, were investigated in normal ileum and in ileum from patients with CD by immunohistochemistry. The calcium ionophore-stimulated release of sPLA₂-IIA and sPLA₂-V from HMC-1 was reduced by the iPLA₂-inhibitor bromoenol lactone. All four PLA₂s were detectable in mucosal MCs, both in normal ileum and in CD, but the proportion of iPLA₂β-containing mucosal MCs and the expression intensity of sPLA₂-IIA was increased in CD. Results indicate that iPLA₂β is involved in the secretion of sPLA₂s from HMC-1, and suggest that iPLA₂β-mediated release of sPLA₂ from intestinal MCs may contribute to CD pathophysiology. Ex vivo studies on isolated mucosal mast cells are however needed to clarify the precise role of MC PLA₂s in the inflammatory processes of CD.

Mast cells induce epithelial-to-mesenchymal transition and migration in non-small cell lung cancer through IL-8/Wnt/β-catenin pathway

Background: In the various cancer, mast cells (MCs) infiltration is correlated with a worse prognosis. There is an increasing evidence that MCs and their mediators are participated in remodeling of the tumor microenvironment and facilitate tumor growth, epithelial-to-mesenchymal transition (EMT) and metastasis.

Methods: The transwell was conducted to evaluate the correlations between MCs and non-small cell lung cancer (NSCLC) cells in vitro. The RNA interference of β-catenin was performed to further explore the signaling pathway. Lung adenocarcinoma cell line A549 and human MC (HMC-1) were subcutaneously injected into BALB/c nude mice. The conventional experiment methods (such as quantitative RT-PCR Western Blot, Immunofluorescence, and ELISA) were used in the present study.

Results: We found that high density of MCs in NSCLC correlates with worse prognosis. The NSCLC cells could release CCL5 and recruit MCs to the tumor microenvironment. Then, we explored that HMC-1 transplantation accelerated the growth of A549 cell in nude mice. Moreover, the MCs-derived factors were responsible for tumor growth. When NSCLC cells were activated, MCs produced various factors that induced EMT and migration. We also identified that CXCL8/interleukin (IL)-8 served as the major modulator containing in the activated MC conditioned medium. Furthermore, MCs and exogenous IL-8 promoted β-catenin phosphorylation in NSCLC cells. Inhibiting the Wnt/β-catenin pathway by RNA interference could revert EMT and migration of NSCLC.

Conclusions: Our study suggests that MCs are recruited into NSCLC microenvironment and improve the EMT and migration of cancer cells, thereby accelerating the growth of NSCLC.

The orphan nuclear receptor NR4A1 promotes FcεRI-stimulated mast cell activation and anaphylaxis by counteracting the inhibitory LKB1/AMPK axis

BACKGROUND

Nuclear receptor subfamily 4 group A member 1 (NR4A1), an orphan nuclear receptor, has been implicated in several biological events such as metabolism, apoptosis, and inflammation. Recent studies indicate a potential role for NR4A1 in mast cells, yet its role in allergic responses remains largely unknown.

OBJECTIVES

The aim of this study was to clarify the role of NR4A1 in mast cell activation and anaphylaxis.

METHODS

To evaluate the function of NR4A1 in mast cells, the impacts of siRNA knockdown, gene knockout, adenoviral overexpression, and pharmacological inhibition of NR4A1 on FcεRI signaling and effector functions in mouse bone marrow-derived mast cells (BMMCs) in vitro and on anaphylactic responses in vivo were evaluated.

RESULTS

Knockdown or knockout of NR4A1 markedly suppressed degranulation and lipid mediator production by FcεRI-crosslinked BMMCs, while its overexpression augmented these responses. Treatment with a NR4A1 antagonist also blocked mast cell activation to a similar extent as NR4A1 knockdown or knockout. Moreover, mast cell-specific NR4A1-deficient mice displayed dampened anaphylactic responses in vivo. Mechanistically, NR4A1 promoted FcεRI signaling by counteracting the liver kinase B1 (LKB1)/adenosine monophosphate-activated protein kinase (AMPK) axis. Following FcεRI crosslinking, NR4A1 bound to the LKB1/AMPK complex and sequestered it in the nucleus, thereby promoting FcεRI downstream signaling pathways. Silencing or knockout of LKB1/AMPK largely abrogated the effect of NR4A1 on mast cell activation. Additionally, NR4A1 facilitated spleen tyrosine kinase activation independently of LKB1/AMPK.

CONCLUSIONS

Nuclear receptor subfamily 4 group A member 1 positively regulates mast cell activation by antagonizing the LKB1-AMPK-dependent negative regulatory axis. This finding may provide a novel therapeutic strategy for the development of anti-allergic compounds.

Inhibition of degranulation in mast cells attached to a hydrogel through defective microtubule tracts

Mast cells (MCs) are important effectors of the immediate allergic response. MCs are distributed throughout various tissues and organs, and adhere to extracellular matrix (ECM) with broad stiffness in the body. Here we compared cellular responses following antigen stimulation in MCs on glass-base dishes with and without a hydrogel. We found that an antigen-induced increase in intracellular Ca²⁺ concentration was suppressed slightly in cells on hydrogel-coated dishes compared with those on non-coated dishes, whereas their subsequent degranulation was largely inhibited in cells adherent to the hydrogel. Focusing on focal adhesions (FAs), vinculin was distributed in a dot-like manner at the bottom of resting cells on non-coated dishes but not on hydrogel-coated dishes. According to antigen stimulation, phosphorylation of focal adhesion kinase and additive vinculin accumulation to FAs were promoted in cells on non-coated dishes, but were diminished on hydrogel-coated dishes. Moreover, microtubule reorganization and acetylation (which have important roles in MC degranulation) were also suppressed in activated MCs adherent to the hydrogel. These findings suggest that adhesion to a hydrogel led to failure of composition of functional FAs and microtubule tracts, which resulted in suppression of MC degranulation following antigen stimulation.

High Affinity Aptamer for the Detection of the Biogenic Amine Histamine

The importance of histamine in various physiological functions and its involvement in allergenic responses make this small molecule one of the most studied biogenic amines. Even though a variety of chromatography-based methods have been described for its analytical determination, the disadvantages they present in terms of cost, analysis time, and low portability limit their suitability for in situ routine testing. In this work, we sought to identify histamine-binding aptamers that could then be exploited for the development of rapid, facile, and sensitive assays for histamine detection suitable for point-of-need analysis. A classic SELEX process was designed employing magnetic beads for target immobilization and the selection was completed after ten rounds. Following Next Generation Sequencing of the last selection rounds from both positive and counter selection magnetic beads, several sequences were identified and initially screened using an apta-PCR affinity assay (APAA). Structural and functional characterization of the candidates resulted in the identification of the H2 aptamer. The high binding affinity of the H2 aptamer to histamine was validated using four independent assays ( K_D of 3-34 nM). Finally, the H2 aptamer was used for the development of a magnetic beads-based competitive assay for the detection of histamine in both buffer and synthetic urine, achieving very low limits of detection of 18 pM and 76 pM, respectively, while no matrix effects were observed. These results highlight the suitability of the strategy followed for identifying small molecule-binding aptamers and the compatibility of the selected H2 aptamer with the analysis of biological samples, thus facilitating the development of point-of-care devices for routine testing. Ongoing work is focused on extending the application of the H2 aptamer to the detection of spoilage in meat, fish, and beverages, as well as evaluating the affinity of truncated forms of the aptamer.

The Role of Mast Cells in Stroke

Mast cells (MCs) are densely granulated perivascular resident cells of hematopoietic origin. Through the release of preformed mediators stored in their granules and newly synthesized molecules, they are able to initiate, modulate, and prolong the immune response upon activation. Their presence in the central nervous system (CNS) has been documented for more than a century. Over the years, MCs have been associated with various neuroinflammatory conditions of CNS, including stroke. They can exacerbate CNS damage in models of ischemic and hemorrhagic stroke by amplifying the inflammatory responses and promoting brain–blood barrier disruption, brain edema, extravasation, and hemorrhage. Here, we review the role of these peculiar cells in the pathophysiology of stroke, in both immature and adult brain. Further, we discuss the role of MCs as potential targets for the treatment of stroke and the compounds potentially active as MCs modulators.

Mast Cell Cytonemes as a Defense Mechanism against Coxiella burnetii

Mast cells (MCs) are found in tissues that are in close contact with external environment, such as skin, lungs, or intestinal mucosa but also in the placenta during pregnancy. If their role in mediating allergic conditions is established, several studies now highlight their importance during infection with extracellular pathogens. This study showed a new and effective antimicrobial mechanism of MCs against Coxiella burnetii, an intracellular bacterium whose infection during pregnancy is associated with abortion, preterm labor, and stillbirth. The data reveal that in response to C. burnetii, MCs release extracellular actin filaments that contain antimicrobial agents and are capable to trap and kill bacteria. We show that this mechanism is dependent on the cooperation of two membrane receptors, CD36 and Toll-like receptor 4, and may occur in the placenta during pregnancy by using ex vivo placental MCs. Overall, this study reports an unexpected role for MCs during infection with intracellular bacteria and suggests that MC response to C. burnetii infection is a protective defense mechanism during pregnancy.

Mast cells (MCs) are critical mediators of inflammation; however, their microbicidal activity against invading pathogens remains largely unknown. Here, we describe a nonpreviously reported antibacterial mechanism used by MCs against Coxiella burnetii, the agent of Q fever. We show that C. burnetii interaction with MCs does not result in bacterial uptake but rather induces the formation of extracellular actin filaments named cytonemes. MC cytonemes express cathelicidin and neutrophil elastase and mediate the capture and destruction of entrapped bacteria. We provide evidence that MC cytoneme formation and microbicidal activity are dependent on the cooperation of the scavenger receptor CD36 and Toll-like receptor 4. Taken together, our results suggest that MCs use an extracellular sophisticated mechanism of defense to eliminate intracellular pathogens, such as C. burnetii, before their entry into host cells.

Regulation of Microtubule Nucleation in Mouse Bone Marrow-Derived Mast Cells by Protein Tyrosine Phosphatase SHP-1

The antigen-mediated activation of mast cells initiates signaling events leading to their degranulation, to the release of inflammatory mediators, and to the synthesis of cytokines and chemokines. Although rapid and transient microtubule reorganization during activation has been described, the molecular mechanisms that control their rearrangement are largely unknown. Microtubule nucleation is mediated by γ-tubulin complexes. In this study, we report on the regulation of microtubule nucleation in bone marrow-derived mast cells (BMMCs) by Src homology 2 (SH2) domain-containing protein tyrosine phosphatase 1 (SHP-1; Ptpn6). Reciprocal immunoprecipitation experiments and pull-down assays revealed that SHP-1 is present in complexes containing γ-tubulin complex proteins and protein tyrosine kinase Syk. Microtubule regrowth experiments in cells with deleted SHP-1 showed a stimulation of microtubule nucleation, and phenotypic rescue experiments confirmed that SHP-1 represents a negative regulator of microtubule nucleation in BMMCs. Moreover, the inhibition of the SHP-1 activity by inhibitors TPI-1 and NSC87877 also augmented microtubule nucleation. The regulation was due to changes in γ-tubulin accumulation. Further experiments with antigen-activated cells showed that the deletion of SHP-1 stimulated the generation of microtubule protrusions, the activity of Syk kinase, and degranulation. Our data suggest a novel mechanism for the suppression of microtubule formation in the later stages of mast cell activation.

A Transcriptomic Insight into the Impact of Colon Cancer Cells on Mast Cells

Mast cells (MCs) are one of the first immune cells recruited to a tumor. It is well recognized that MCs accumulate in colon cancer lesion and their density is associated with the clinical outcomes. However, the molecular mechanism of how colon cancer cells may modify MC function is still unclear. In this study, primary human MCs were generated from CD34⁺ progenitor cells and a 3D coculture model was developed to study the interplay between colon cancer cells and MCs. By comparing the transcriptomic profile of colon cancer-cocultured MCs versus control MCs, we identified a number of deregulated genes, such as MMP-2, VEGF-A, PDGF-A, COX2, NOTCH1 and ISG15, which contribute to the enrichment of cancer-related pathways. Intriguingly, pre-stimulation with a TLR2 agonist prior to colon cancer coculture induced upregulation of multiple interferon-inducible genes as well as MHC molecules in MCs. Our study provides an alternative approach to study the influence of colon cancer on MCs. The transcriptome signature of colon cancer-cocultured MCs may potentially reflect the mechanism of how colon cancer cells educate MCs to become pro-tumorigenic in the initial phase and how a subsequent inflammatory signal—e.g., TLR2 ligands—may modify their responses in the cancer milieu.

Protein kinase Ds promote tumor angiogenesis through mast cell recruitment and expression of angiogenic factors in prostate cancer microenvironment

Background

Mast cells are being increasingly recognized as critical components in the tumor microenvironment. Protein Kinase D (PKD) is essential for the progression of prostate cancer, but its role in prostate cancer microenvironment remains poorly understood.

Methods

The expression of PKD, mast cells and microvessel density were examined by IHC. The clinical significance was determined by statistical analyses. The biological function of PKD and the underlying mechanisms were investigated using in vitro and in vivo models.

Results

PKD2/3 contributed to MCs recruitment and tumor angiogenesis in the prostate cancer microenvironment. Clinical data showed that increased activation of PKD at Ser744/748 in prostate cancer was correlated with mast cell infiltration and microvascular density. PKD2/3 silencing of prostate cancer cells markedly decreased MCs migration and tube formation of HUVEC cells. Moreover, PKD2/3 depletion not only reduced SCF, CCL5 and CCL11 expression in prostate cancer cells but also inhibited angiogenic factors in MCs. Conversely, exogenous SCF, CCL5 and CCL11 reversed the effect on MCs migration inhibited by PKD2/3 silencing. Mechanistically, PKD2/3 interacted with Erk1/2 and activated Erk1/2 or NF-κB signaling pathway, leading to AP-1 or NF-κB binding to the promoter of scf, ccl5 and ccl11. Finally, PKD-specific inhibitor significantly reduced tumor volume and tumor growth in mice bearing RM-1 prostate cancer cells, which was attributed to attenuation of mast cell recruitment and tumor angiogenesis.

Conclusions

These results demonstrate a novel PKDs function that contributes to tumor angiogenesis and progression through mast cells recruitment in prostate cancer microenvironment.

Electronic supplementary material

The online version of this article (10.1186/s13046-019-1118-y) contains supplementary material, which is available to authorized users.

Purinergic implication in amyotrophic lateral sclerosis-from pathological mechanisms to therapeutic perspectives

Amyotrophic lateral sclerosis (ALS) is a clinically heterogeneous disorder characterized by degeneration of upper motor neurons in the brainstem and lower motor neurons in the spinal cord. Multiple mechanisms of motor neuron injury have been implicated, including more than 20 different genetic factors. The pathogenesis of ALS consists of two stages: an early neuroprotective stage and a later neurotoxic. During early phases of disease progression, the immune system through glial and T cell activities provides anti-inflammatory factors that sustain motor neuron viability. As the disease progresses and motor neuron injury accelerates, a rapidly succeeding neurotoxic phase develops. A well-orchestrated purine-mediated dialog among motor neurons, surrounding glia and immune cells control the beneficial and detrimental activities occurring in the nervous system. In general, low adenosine triphosphate (ATP) concentrations protect cells against excitotoxic stimuli through purinergic P2X4 receptor, whereas high concentrations of ATP trigger toxic P2X7 receptor activation. Finally, adenosine is also involved in ALS progression since A2A receptor antagonists prevent motor neuron death. Given the complex cellular cross-talk occurring in ALS and the recognized function of extracellular nucleotides and adenosine in neuroglia communication, the comprehensive understanding of purinome dynamics might provide new research perspectives to decipher ALS and help to design more efficient and targeted drugs. This review will focus on the purinergic players involved in ALS etiology and disease progression and current therapeutic strategies to enhance neuroprotection and suppress neurotoxicity.

Increased intratumoral mast cells foster immune suppression and gastric cancer progression through TNF-α-PD-L1 pathway

Background

Mast cells are prominent components of solid tumors and exhibit distinct phenotypes in different tumor microenvironments. However, the nature, regulation, function, and clinical relevance of mast cells in human gastric cancer (GC) are presently unknown.

Methods

Flow cytometry analyses were performed to examine level and phenotype of mast cells in samples from 114 patients with GC. Multivariate analysis of prognostic factors for overall survival was performed using the Cox proportional hazards model. Kaplan-Meier plots for patient survival were performed using the log-rank test. Mast cells, T cells and tumor cells were isolated or generated, stimulated and/or cultured for in vitro and in vivo function assays.

Results

Patients with GC showed a significantly higher mast cell infiltration in tumors. Mast cell levels increased with tumor progression and independently predicted reduced overall survival. These tumor-infiltrating mast cells accumulated in tumors by CXCL12-CXCR4 chemotaxis. Intratumoral mast cells expressed higher immunosuppressive molecule programmed death-ligand 1 (PD-L1), and mast cells induced by tumors strongly express PD-L1 proteins in both time-dependent and dose-dependent manners. Significant correlations were found between the levels of PD-L1⁺ mast cells and pro-inflammatory cytokine TNF-α in GC tumors, and tumor-derived TNF-α activated NF-κB signaling pathway to induce mast cell expression of PD-L1. The tumor-infiltrating and tumor-conditioned mast cells effectively suppressed normal T-cell immunity through PD-L1 in vitro, and tumor-conditioned mast cells contributed to the suppression of T-cell immunity and the growth of human GC tumors in vivo; the effect could be reversed by blocking PD-L1 on these mast cells.

Conclusion

Thus, our results illuminate novel immunosuppressive and protumorigenic roles of mast cells in GC, and also present a novel mechanism in which PD-L1 expressing mast cells link the proinflammatory response to immune tolerance in the GC tumor milieu.

Electronic supplementary material

The online version of this article (10.1186/s40425-019-0530-3) contains supplementary material, which is available to authorized users.

CD33 recruitment inhibits IgE-mediated anaphylaxis and desensitizes mast cells to allergen

Allergen immunotherapy for patients with allergies begins with weekly escalating doses of allergen under medical supervision to monitor and treat IgE mast cell-mediated anaphylaxis. There is currently no treatment to safely desensitize mast cells to enable robust allergen immunotherapy with therapeutic levels of allergen. Here, we demonstrated that liposomal nanoparticles bearing an allergen and a high-affinity glycan ligand of the inhibitory receptor CD33 profoundly suppressed IgE-mediated activation of mast cells, prevented anaphylaxis in Tg mice with mast cells expressing human CD33, and desensitized mice to subsequent allergen challenge for several days. We showed that high levels of CD33 were consistently expressed on human skin mast cells and that the antigenic liposomes with CD33 ligand prevented IgE-mediated bronchoconstriction in slices of human lung. The results demonstrated the potential of exploiting CD33 to desensitize mast cells to provide a therapeutic window for administering allergen immunotherapy without triggering anaphylaxis.

Platelets expressing IgG receptor FcγRIIA/CD32A determine the severity of experimental anaphylaxis

Platelets are key regulators of vascular integrity; however, their role in anaphylaxis, a life-threatening systemic allergic reaction characterized by the loss of vascular integrity and vascular leakage, remains unknown. Anaphylaxis is a consequence of inappropriate cellular responses triggered by antibodies to generally harmless antigens, resulting in a massive mediator release and rapidly occurring organ dysfunction. Human platelets express receptors for immunoglobulin G (IgG) antibodies and can release potent mediators, yet their contribution to anaphylaxis has not been previously addressed in mouse models, probably because mice do not express IgG receptors on platelets. We investigated the contribution of platelets to IgG-dependent anaphylaxis in human IgG receptor-expressing mouse models and a cohort of patients suffering from drug-induced anaphylaxis. Platelet counts dropped immediately and markedly upon anaphylaxis induction only when they expressed the human IgG receptor FcγRIIA/CD32A. Platelet depletion attenuated anaphylaxis, whereas thrombocythemia substantially worsened its severity. FcγRIIA-expressing platelets were directly activated by IgG immune complexes in vivo and were sufficient to restore susceptibility to anaphylaxis in resistant mice. Serotonin released by activated platelets contributed to anaphylaxis severity. Data from a cohort of patients suffering from drug-induced anaphylaxis indicated that platelet activation was associated with anaphylaxis severity and was accompanied by a reduction in circulating platelet numbers. Our findings identify platelets as critical players in IgG-dependent anaphylaxis and provide a rationale for the design of platelet-targeting strategies to attenuate the severity of anaphylactic reactions.

Senescent cell clearance by the immune system: Emerging therapeutic opportunities

Senescent cells (SCs) arise from normal cells in multiple organs due to inflammatory, metabolic, DNA damage, or tissue damage signals. SCs are non-proliferating but metabolically active cells that can secrete a range of pro-inflammatory and proteolytic factors as part of the senescence-associated secretory phenotype (SASP). Senescent cell anti-apoptotic pathways (SCAPs) protect SCs from their own pro-apoptotic SASP. SCs can chemo-attract immune cells and are usually cleared by these immune cells. During aging and in multiple chronic diseases, SCs can accumulate in dysfunctional tissues. SCs can impede innate and adaptive immune responses. Whether immune system loss of capacity to clear SCs promotes immune system dysfunction, or conversely whether immune dysfunction permits SC accumulation, are important issues that are not yet fully resolved. SCs may be able to assume distinct states that interact differentially with immune cells, thereby promoting or inhibiting SC clearance, establishing a chronically pro-senescent and pro-inflammatory environment, leading to modulation of the SASP by the immune cells recruited and activated by the SASP. Therapies that enhance immune cell-mediated clearance of SCs could provide a lever for reducing SC burden. Such therapies could include vaccines, small molecule immunomodulators, or other approaches. Senolytics, drugs that selectively eliminate SCs by transiently disabling their SCAPs, may prove to alleviate immune dysfunction in older individuals and thereby accelerate immune-mediated clearance of SCs. The more that can be understood about the interplay between SCs and the immune system, the faster new interventions may be developed to delay, prevent, or treat age-related dysfunction and the multiple senescence-associated chronic diseases and disorders.

Nothofagin suppresses mast cell-mediated allergic inflammation

Mast cells play a major role in immunoglobulin E-mediated allergic inflammation, which is involved in asthma, atopic dermatitis, and allergic rhinitis. Nothofagin has been shown to ameliorate various inflammatory responses such as the septic response and vascular inflammation. In this study, we assessed the inhibitory effect of nothofagin on allergic inflammation using cultured/isolated mast cells and an anaphylaxis mouse model. Nothofagin treatment prevented histamine and β-hexosaminidase release by reducing the influx of calcium into the cytosol in a concentration-dependent manner. Nothofagin also inhibited the gene expression and secretion of pro-inflammatory cytokines such as tumor necrosis factor-α and interleukin-4 by downregulating the phosphorylation of Lyn, Syk, Akt and nuclear translocation of nuclear factor-κB. To confirm these effects of nothofagin in vivo, we used a passive cutaneous anaphylaxis mouse model. Topical administration of nothofagin suppressed local pigmentation and ear thickness. Taken together, these results suggest nothofagin as a potential candidate for the treatment of mast cell-involved allergic inflammatory diseases.

Epigenetic Regulation via Altered Histone Acetylation Results in Suppression of Mast Cell Function and Mast Cell-Mediated Food Allergic Responses

Mast cells are highly versatile cells that perform a variety of functions depending on the immune trigger, context of activation, and cytokine stimulus. Antigen-mediated mast cell responses are regulated by transcriptional processes that result in the induction of numerous genes contributing to mast cell function. Recently, we also showed that exposure to dietary agents with known epigenetic actions such as curcumin can suppress mast cell-mediated food allergy, suggesting that mast cell responses in vivo may be epigenetically regulated. To further assess the effects of epigenetic modifications on mast cell function, we examined the behavior of bone marrow-derived mast cells (BMMCs) in response to trichostatin A (TSA) treatment, a well-studied histone deacetylase inhibitor. IgE-mediated BMMC activation resulted in enhanced expression and secretion of IL-4, IL-6, TNF-α, and IL-13. In contrast, pretreatment with TSA resulted in altered cytokine secretion. This was accompanied by decreased expression of FcεRI and mast cell degranulation. Interestingly, exposure to non-IgE stimuli such as IL-33, was also affected by TSA treatment. Furthermore, continuous TSA exposure contributed to mast cell apoptosis and a decrease in survival. Further examination revealed an increase in I-κBα and a decrease in phospho-relA levels in TSA-treated BMMCs, suggesting that TSA alters transcriptional processes, resulting in enhancement of I-κBα transcription and decreased NF-κB activation. Lastly, treatment of wild-type mice with TSA in a model of ovalbumin-induced food allergy resulted in a significant attenuation in the development of food allergy symptoms including decreases in allergic diarrhea and mast cell activation. These data therefore suggest that the epigenetic regulation of mast cell activation during immune responses may occur via altered histone acetylation, and that exposure to dietary substances may induce epigenetic modifications that modulate mast cell function.

Comparative Analysis of Bone Marrow-derived Mast Cell Differentiation in C57BL/6 and BALB/c Mice

Allergic diseases have increased in the last three decades. Mast cells play a critical role in allergic diseases along with allergen-specific immunoglobulin E (IgE). Following mast cell degranulation elicited by ligation of the IgE-FcεRI receptor complex with allergen, allergic reactions are followed by various symptoms such as vascular hyperpermeability, mucous secretion, itching, sneezing, wheezing, rashes, fever, and anaphylactic shock. Susceptibility or inclination to allergy varies depending on individual genetic traits and living environment, and it has long been believed that such an inclination is determined by an immunologic balance of T helper cell types. Mouse strains also have different susceptibilities to allergy. Similar to T helper cells and macrophages, it is not known whether mast cells can also be divided into two different types between mouse strains. In this study, we prepared bone marrow-derived mast cells from BALB/c and C57BL/6 mice and examined their cellular properties. Cellular response to IL-3 and the process of mast cell differentiation from bone marrow cells were different on the basis of cell surface marker molecules. BALB/c-derived cells more efficiently exhibited degranulation than did C57BL/6-derived cells following both calcium ionophore and receptor crosslinking. These functional differences persisted even after a longer cell culture for 8 weeks, suggesting a difference in cell-autonomous characteristics. These results support the concept that mast cells also have different cell types dependent on their genetic background. Abbreviations: Ab: antibody; BMMC: bone marrow-derived mast cell; DNP: dinitrophenyl; FACS: fluorescence-activated cell sorter; FCS: fetal calf serum; FITC: fluorescein isothiocyanate; FSC: forward scatter; HRP: horseradish peroxidase; HSA: human serum albumin; Ig: immunoglobulin; IL: interleukin; MIP-2: macrophage inflammatory protein-2; MCP: mast cell protease; PE: phycoerythrin; PerCP: Peridinin chlorophyll protein complex; SNP: single nucleotide polymorphisms; SSC: side scatter; Th: T helper; TNF-α: tumor necrosis factor alpha.

Role of Mast Cells in Regulation of T Cell Responses in Experimental and Clinical Settings

Mast cells secrete a wide spectrum of stored or newly synthesized pro-inflammatory, anti-inflammatory, and/or immunosuppressive mediators and express several costimulatory and inhibitory surface molecules. Mast cells finely tune activities of T cells, B cells, and regulatory cells and effectively contribute to the development of different T cell-associated responses by influencing their recruitment, activation, proliferation, and differentiation. The interaction between mast cells and T cells, with regard to cellular functionality and immune responses, can be assessed in both activating and inhibitory regulations. While Th2 cytokines, including IL-5 and IL-9, stimulate stem cell factor (SCF)-dependent proliferation of mast cells, Th1 cytokine IFN-γ suppresses SCF-mediated differentiation of mast cell progenitors. Mast cell mediators such as CCL5 have a role in the recruitment of CD8+ T cells to viral infection sites where their ability in clearance of viral reservoirs is needed. The capacity of mast cells in presenting antigens by classes I and II MHC molecules to CD4+ and CD8+ T cells respectively is considered one of the main antigen-dependent interactions of mast cells with T cells. Interestingly, Tregs recruit mast cells to different sites through secretion of IL-9, while the OX40L (expressed on mast cell)-OX40(expressed on T cell) interaction inhibits the extent of the mast cell degranulation. Recently, the capability of exosomes to carry regulatory receptors of the mast cell surface and their role in T cell activation has been investigated. Functional interplay between mast cells and T cell subsets has been suggested primarily by investigating their co-localization in inflamed tissues and involvement of mast cells in autoimmune diseases. In this review, the interactions of mast cells with T cells are reviewed in cell-to-cell, cytokine, and exosome categories.

Degranulation of mast cells induced by gastric cancer-derived adrenomedullin prompts gastric cancer progression

Mast cells are prominent components of solid tumors and exhibit distinct phenotypes in different tumor microenvironments. However, their precise mechanism of communication in gastric cancer remains largely unclear. Here, we found that patients with GC showed a significantly higher mast cell infiltration in tumors. Mast cell levels increased with tumor progression and independently predicted reduced overall survival. Tumor-derived adrenomedullin (ADM) induced mast cell degranulation via PI3K-AKT signaling pathway, which effectively promoted the proliferation and inhibited the apoptosis of GC cells in vitro and contributed to the growth and progression of GC tumors in vivo, and the effect could be reversed by blocking interleukin (IL)-17A production from these mast cells. Our results illuminate a novel protumorigenic role and associated mechanism of mast cells in GC, and also provide functional evidence for these mast cells to prevent, and to treat this immunopathogenesis feature of GC.

Raf kinase inhibitor protein negatively regulates FcεRI-mediated mast cell activation and allergic response

The signaling cascades triggered by the cross-linkage of immunoglobulin E (IgE) with its high-affinity receptor (FcεRI) on mast cells contribute to multiple allergic disorders, such as asthma, rhinitis, and atopic dermatitis. Restraint of intracellular signals for mast cell activation is essential to restore homeostasis. In this study, we found that Raf kinase inhibitor protein (RKIP) negatively regulated mast cell activation. RKIP-deficient mast cells showed greater IgE-FcεRI-mediated activation than wild-type mast cells. Consistently, RKIP deficiency in mast cells rendered mice more sensitive to IgE-FcεRI-mediated allergic responses and ovalbumin-induced airway inflammation. Mechanistically, RKIP interacts with the p85 subunit of PI3K, prevents it from binding to GRB2-associated binding protein 2 (Gab2), and eventually inhibits the activation of the PI3K/Akt/NF-κB complex and its downstream signaling. Furthermore, the expression of RKIP was significantly down-regulated in the peripheral blood of asthma patients and in the IgE-FcεRI-stimulated mast cells. Collectively, our findings not only suggest that RKIP plays an important role in controlling mast cell-mediated allergic responses but also provide insight into therapeutic targets for mast cell-related allergic diseases.

Oral administration of Cervus nippon mantchuricus extract suppresses 2,4-dinitrochlorobenzene-induced atopic dermatitis in BALB/c mice and inflammatory effects in mast cells

Cervus nippon mantchuricus extract, known as nok‑gol (NGE) in Korean, is useful for the treatment of various inflammatory diseases, including bone resorption and neutropenia. However, NGE has not been widely investigated, and its efficacy and safety remain to be fully elucidated. In the present study, histological analysis, blood analysis, reverse transcription‑semi-quantitative polymerase chain reaction analysis and enzyme‑linked immunosorbent assays were performed to verify the inhibitory effect of NGE on atopic dermatitis (AD) in BALB/c mice and on inflammatory effects in HMC‑1 human mast cells. NGE suppressed the development of AD in mice, and decreased the infiltration of inflammatory cells, mast cells and CD4+ T cells into AD skin lesions. NGE also decreased leukocyte levels induced by 2,4‑dinitrochlorobenzene (DNCB). NGE alleviated AD‑like inflammatory symptoms in mice by suppressing the production of CD4+ T cells. NGE downregulated the mRNA expression of inflammatory cytokines induced by DNCB. It also decreased the serum immunoglobulin E concentration and inflammatory cytokine levels in DNCB‑treated BALB/c mice. The in vitro experiments demonstrated that NGE reduced the phorbol 12‑myristate 13‑acetate + ionomycin‑induced expression of pro‑inflammatory cytokines interleukin (IL)‑4, IL‑13, tumor necrosis factor‑α, and IL‑6 in HMC‑1 cells. Taken together, the results of the present study indicated that NGE suppressed the progression of DNCB‑induced AD in BALB/c mice and reduced inflammatory effects in HMC‑1 cells. This suggests that NGE may be a useful drug for the treatment of AD.

The anti-anaphylactoid effects of hydroxysafflor yellow A on the suppression of mast cell Ca2+ influx and degranulation

BACKGROUND

Anaphylaxis is a type of potentially fatal hypersensitivity reaction resulting from the activation of mast cell mediators, especially histamine and lipid mediators. Non-IgE-mediated anaphylaxis can occur because of the direct activation of mast cells. Hydroxysafflor yellow A (HSYA) is the main chemical component of safflower (Carthamus tinctorius) and has been reported to have pharmacological activities. However, the anti-anaphylactoid effect of HSYA has not yet been investigated.

PURPOSE

The aims of this study were to evaluate the anti-anaphylactoid activity of HSYA in vivo and to investigate the underlying mechanism in vitro.

METHODS

The anti-anaphylactoid activity of HSYA was evaluated in a mouse model of hindpaw extravasation. Calcium imaging was used to assess intracellular Ca²⁺ mobilization. The levels of cytokines and chemokines released by stimulated mast cells were measured using enzyme immunoassay kits. Western blotting was used to explore the related molecular signaling pathways.

RESULTS

HSYA markedly inhibited mast cell degranulation by suppressing the activation of intracellular Ca²⁺ mobilization and preventing the release of cytokines and chemokines from mast cells in a dose-dependent manner via the PKC-PLCγ-IP3R signaling pathway.

CONCLUSION

In summary, HSYA has anti-anaphylactoid pharmacological activity, which makes it a potential candidate for the development of a novel agent to suppress drug-induced anaphylactoid reactions.

Differential effects of functionally different histamine H4 receptor ligands on acute irritant dermatitis in mice

The anti-inflammatory effects of histamine H4 receptor (H4R) antagonists opened new therapeutic options for the treatment of inflammatory/allergic diseases, but the role of H4R in inflammation is far from being solved. Aim of the present study was to investigate the role of structurally related H4R ligands of the aminopyrimidine class with different efficacies and functionalities (neutral antagonist ST-994, partial agonist ST-1006, inverse agonist ST-1012, and partial inverse agonist ST-1124) on croton oil-induced ear edema and pruritus in mice. The H4R ligands were administered subcutaneously before topical application of croton oil. While ST-1006 and ST-1124 were ineffective at any dose tested (10-100 mg/kg), both ST-994 and ST-1012 (30 and 100 mg/kg) significantly reduced croton oil-induced ear edema. Moreover, ST-994, ST-1006, and ST-1124, but not ST-1012, significantly inhibited croton oil-induced ear pruritus at 30 mg/kg. In accordance with results obtained with the reference H4R antagonist JNJ7777120 (100 mg/kg), histological examination of inflamed ear tissue indicated that treatment with ST-994 (30 mg/kg) led to a significant reduction in the inflammatory severity score and in the number of eosinophils infiltrating the tissue, while the number of degranulated mast cells in inflamed tissues was increased in comparison with the number of intact mast cells. These data indicate that croton oil-induced ear inflammation and pruritus seem to be clearly, but variably, affected by the H4R ligands tested. The potential advantage of dual effect of the H4R neutral antagonist ST-994 has to be carefully considered as a new therapeutic approach to the treatment of inflammatory diseases.

Human mast cells promote colon cancer growth via bidirectional crosstalk: studies in 2D and 3D coculture models

Chronic inflammation drives the development of colorectal cancer (CRC), where tumor-infiltrating immune cells interact with cancer cells in a dynamic crosstalk. Mast cells (MC), one of earliest recruited immune cells, accumulate in CRC tissues and their density is correlated with cancer progression. However, the exact contribution of MC in CRC and their interaction with colon cancer cells is poorly understood. Here, we investigated the impact of primary human MC and their mediators on colon cancer growth using 2D and 3D coculture models. Primary human MC were generated from peripheral CD34⁺ stem cells. Transwell chambers were used to analyze MC chemotaxis to colon cancer. Colon cancer cells HT29 and Caco2 differentially recruited MC by releasing CCL15 or SCF, respectively. Using BrdU proliferation assays, we demonstrated that MC can directly support colon cancer proliferation and this effect was mediated by their cellular crosstalk. 3D coculture models with cancer spheroids further confirmed the pro-tumor effect of MC on colon cancer growth, where direct cell-cell contact is dispensable and increased production of multiple soluble mediators was detected. Moreover, TLR2 stimulation of MC promoted stronger growth of colon cancer spheroids. By examining the transcriptome profile of colon cancer-cocultured MC versus control MC, we identified several MC marker genes, which were deregulated in expression. Our study provides an advanced in vitro model to investigate the role of human MC in cancer. Our data support the detrimental role of MC in CRC development and provide a molecular insight into the cellular crosstalk between MC and colon cancer cells.

Biological and epidemiological evidence of anti-allergic effects of traditional Japanese food ume (Prunus mume)

Japanese apricot (Prunus mume; ume) is a traditional food in Japan that has been shown to have various beneficial health effects. There is some evidence to suggest that ume is also effective against allergic disease. Here, we conducted a cross-sectional epidemiological pilot study to examine the association between ume intake frequency and allergic symptoms including rhinitis in 563 adults (288 men and 275 women) who resided in Wakayama, Japan. After adjusting for age, present illness and medication, women with high ume intake had significantly lower odds ratio (OR) for the presence of symptoms of allergy [OR: 0.49 with 95% confidence interval (CI): 0.25-0.97]. Therefore, we investigated the anti-allergic effect of ume on passive cutaneous anaphylaxis (PCA) reaction in immunoglobulin E (IgE)-sensitized mice. The animal study demonstrated that oral administration of ume extract attenuated the PCA reaction and mast cell degranulation. Furthermore, RBL-2H3 mast cells were used to identify anti-allergic ume compounds. The following ume compounds inhibited IgE-mediated mast cell degranulation: vanillin, syringic acid, protocatechuic aldehyde, lyoniresinol and p-coumaric acid. These results suggested that ume has the potential to inhibit mast cell degranulation and may be associated with reduced risk of allergic symptoms in women.

Spinacetin Suppresses the Mast Cell Activation and Passive Cutaneous Anaphylaxis in Mouse Model

We previously reported the anti-inflammatory and anti-asthmatic activities of the extract of the Inula japonica Thunb. Aiming for discovery of a novel anti-inflammatory compound, we isolated spinacetin from the extract and investigated its in vitro and in vivo anti-inflammatory effect and the related mechanism. Effect of spinacetin on the Syk signaling pathway was studied in bone marrow-derived mast cells (BMMCs), and that on the nuclear factor-κB (NF-κB) and mitogen-activated protein kinases (MAPKs) was investigated in Rat basophilic leukemia (RBL)-2H3 cells and human mast cell line (HMC-1). The in vivo anti-inflammatory activity was assessed with passive cutaneous anaphylaxis (PCA) reaction assay. Spinacetin significantly inhibited the release of histamine, and production of inflammatory mediators such as leukotriene C₄ (LTC₄) and interlukin-6 (IL-6) in IgE/Ag stimulated BMMCs. Analysis of the signaling pathways demonstrated that spinacetin inhibited activation of Syk, linker of activated T cells (LAT), phospholipase Cγ (PLCγ), cytosolic phospholipase A₂ (cPLA₂), MAPKs, Akt/NF-κB, and intracellular Ca²⁺ mobilization but with no effect on Fyn and Lyn. On the other hand, spinacetin suppressed IgE/Ag-induced activation of RBL-2H3 cells with inhibition against phosphorylation of extracellular signal regulated-protein kinase (ERK), c-Jun-NH₂-terminal kinase (JNK), p38 MAPKs, PLCγ, translocation of cPLA₂, and Akt/IκBα/NF-κB signal. However, spinacetin had no effect on PMA and A23187-induced activation of HMC-1. Furthermore, oral administration of spinacetin dose-dependently attenuated IgE/Ag-mediated PCA reaction in mouse model. Taken together, spinacetin showed the activities in preventing inflammatory processes, which might be at least partially attributed to the abolishment of Syk-dependent activation of IgE/Ag-mediated mast cells.

Video-Rate Bioluminescence Imaging of Degranulation of Mast Cells Attached to the Extracellular Matrix

Degranulation refers to the secretion of inflammatory mediators, such as histamine, serotonin, and proteases, that are stored within the granules of mast cells and that trigger allergic reactions. The amount of these released mediators has been measured biochemically using cell mass. To investigate degranulation in living single cells, fluorescence microscopy has traditionally been used to observe the disappearance of granules and the appearance of these discharged granules within the plasma membrane by membrane fusion and the movement of granules inside the cells. Here, we developed a method of video-rate bioluminescence imaging to directly detect degranulation from a single mast cell by measuring luminescence activity derived from the enzymatic reaction between Gaussia luciferase (GLase) and its substrate coelenterazine. The neuropeptide Y (NPY), which was reported to colocalize with serotonin in the secretory granules, fused to GLase (NPY-GLase) was efficiently expressed in rat basophilic leukemia (RBL-2H3) cells, a mast-cell line, using a preferred human codon-optimized gene. Bioluminescence imaging analysis of RBL-2H3 cells expressing NPY-GLase and adhered on a glass-bottomed dish showed that the luminescence signals from the resting cells were negligible, while the luminescence signals of the secreted NPY-GLase were repeatedly detected after the addition of an antigen. In addition, this imaging method was applicable for observing degranulation in RBL-2H3 cells that adhered to the extracellular matrix (ECM). These results indicated that video-rate bioluminescence imaging using GLase will be a useful tool for detecting degranulation in single mast cells adhered to a variety of ECM proteins.

An Inflammation-Centric View of Neurological Disease: Beyond the Neuron

Inflammation is a complex biological response fundamental to how the body deals with injury and infection to eliminate the initial cause of cell injury and effect repair. Unlike a normally beneficial acute inflammatory response, chronic inflammation can lead to tissue damage and ultimately its destruction, and often results from an inappropriate immune response. Inflammation in the nervous system (“neuroinflammation”), especially when prolonged, can be particularly injurious. While inflammation per se may not cause disease, it contributes importantly to disease pathogenesis across both the peripheral (neuropathic pain, fibromyalgia) and central [e.g., Alzheimer disease, Parkinson disease, multiple sclerosis, motor neuron disease, ischemia and traumatic brain injury, depression, and autism spectrum disorder] nervous systems. The existence of extensive lines of communication between the nervous system and immune system represents a fundamental principle underlying neuroinflammation. Immune cell-derived inflammatory molecules are critical for regulation of host responses to inflammation. Although these mediators can originate from various non-neuronal cells, important sources in the above neuropathologies appear to be microglia and mast cells, together with astrocytes and possibly also oligodendrocytes. Understanding neuroinflammation also requires an appreciation that non-neuronal cell—cell interactions, between both glia and mast cells and glia themselves, are an integral part of the inflammation process. Within this context the mast cell occupies a key niche in orchestrating the inflammatory process, from initiation to prolongation. This review will describe the current state of knowledge concerning the biology of neuroinflammation, emphasizing mast cell-glia and glia-glia interactions, then conclude with a consideration of how a cell's endogenous mechanisms might be leveraged to provide a therapeutic strategy to target neuroinflammation.

Blocking dephosphorylation at Serine 120 residue in t-SNARE SNAP-23 leads to massive inhibition in exocytosis from mast cells

Mast cells (MCs) respond to allergen challenge by release of pre-stored inflammatory mediators from their secretory granules, on cross-linking of Fc(epsilon) receptor I (Fc(epsilon)RI) receptors. The target-SNARE (t-SNARE) SNAP-23 has been shown to play an important role in MC exocytosis and undergoes transient phosphorylation at Serine 95 (S95) and Serine 120 (S120), concomitant with mediator release. During current study we explored the importance of transient nature of phosphorylation at S120 in MC exocytosis. A phosphomimetic SNAP-23-S120D mutant of rodent SNAP-23 was cloned into EGFP vector and its effect on the exocytosis and the mechanisms involved was studied in RBL-2H3 MC line. Secretion reporter assay with SNAP-23-S120D transfected MCs revealed a very significant inhibition of exocytosis, and reduced ruffling in response to Fc(epsilon)RI cross-linking. Further, the effect of this mutation on localization of SNAP-23 in MCs was studied. Immunofluorescence microscopy studies and membrane-cytosol fractionation of green fluorescent protein-tagged SNAP- 23-S120D (GFP-SNAP-23-S120D) transfected MCs showed that a large proportion of GFP-SNAP-23-S120D was residing in cytosol unlike wild-type SNAP-23, in resting and activated MCs and even the membrane associated portion was on internal lysosomal membranes than plasma membrane. These studies imply that dephosphorylation of S120 is important for SNAP-23 membrane association dynamics and subsequently MC degranulation.

The Autoimmune Skin Disease Bullous Pemphigoid: The Role of Mast Cells in Autoantibody-Induced Tissue Injury

Bullous pemphigoid (BP) is an autoimmune and inflammatory skin disease associated with subepidermal blistering and autoantibodies directed against the hemidesmosomal components BP180 and BP230. Animal models of BP were developed by passively transferring anti-BP180 IgG into mice, which recapitulates the key features of human BP. By using these in vivo model systems, key cellular and molecular events leading to the BP disease phenotype are identified, including binding of pathogenic IgG to its target, complement activation of the classical pathway, mast cell degranulation, and infiltration and activation of neutrophils. Proteinases released by infiltrating neutrophils cleave BP180 and other hemidesmosome-associated proteins, causing DEJ separation. Mast cells and mast cell-derived mediators including inflammatory cytokines and proteases are increased in lesional skin and blister fluids of BP. BP animal model evidence also implicates mast cells in the pathogenesis of BP. However, recent studies questioned the pathogenic role of mast cells in autoimmune diseases such as multiple sclerosis, rheumatoid arthritis, and epidermolysis bullosa acquisita. This review highlights the current knowledge on BP pathophysiology with a focus on a potential role for mast cells in BP and mast cell-related critical issues needing to be addressed in the future.

Diverse exocytic pathways for mast cell mediators

Mast cells play pivotal roles in innate and adaptive immunities but are also culprits in allergy, autoimmunity, and cardiovascular diseases. Mast cells respond to environmental changes by initiating regulated exocytosis/secretion of various biologically active compounds called mediators (e.g. proteases, amines, and cytokines). Many of these mediators are stored in granules/lysosomes and rely on intricate degranulation processes for release. Mast cell stabilizers (e.g. sodium cromoglicate), which prevent such degranulation processes, have therefore been clinically employed to treat asthma and allergic rhinitis. However, it has become increasingly clear that different mast cell diseases often involve multiple mediators that rely on overlapping but distinct mechanisms for release. This review illustrates existing evidence that highlights the diverse exocytic pathways in mast cells. We also discuss strategies to delineate these pathways so as to identify unique molecular components which could serve as new drug targets for more effective and specific treatments against mast cell-related diseases.

Corilagin Attenuates Allergy and Anaphylactic Reaction by Inhibiting Degranulation of Mast Cells

Background

This study evaluated the anti-allergic activity of corilagin and also postulates the possible mechanism of its action.

Material/Methods

Corilagin was given orally at dose of 10, 20, and 40 mg/kg/day. All the animals (guinea pigs, rats, and mice) were sensitized for allergy such as eosinophilia and leukocytosis induced by milk; degranulation of mast cell by compound 48/80; and passive and active anaphylaxis. Moreover, the antagonistic effect was determined by estimating the effect of corilagin on contraction of guinea pig tracheal chain and ileum induced by Ach and histamine, respectively.

Result

There was a significant decrease in the leukocyte and eosinophil counts in the corilagin-treated group compared to the negative control group. Treatment with corilagin significantly protects the degranulation of mast cells, and it also has significant anti-muscarinic and antihistaminic activity by reducing the muscle contraction induced by Acetylcholine (Ach) and histamine in guinea pig tracheal chain and ileum.

Conclusions

Corilagin possess anti-anaphylactic and anti-allergic activity by inhibiting the release of mediators from mast cells and by decreasing the serum concentration of immunoglobulin E (IgE).

Mast cells, basophils and eosinophils: From allergy to cancer

Basophils, eosinophils and mast cells were first recognized by Paul Ehrlich in the late 19th century. These cells have common, but non-redundant roles, in the pathogenesis of allergic diseases and in the protection against parasites. Nevertheless, in virtue of their shared-adeptness to produce a huge variety of immunological mediators and express membrane-bound receptors, they are able to interact with immune and non-immune components of the tissue microenvironment, contributing to the regulation of tissue homeostasis and immune response while participating to further deregulation of tissues transforming into neoplasia.

Mast cells and sphingosine-1-phosphate underlie prelesional remodeling in a mouse model of eczema

BACKGROUND

Atopic dermatitis (AD) is a chronic skin inflammation that affects children and adults worldwide, but its pathogenesis remains ill-understood.

METHODS

We show that a single application of OVA to mouse skin initiates remodeling and cellular infiltration of the hypodermis measured by a newly developed computer-aided method.

RESULTS

Importantly, we demonstrate that skin mast cell (MC) activation and local sphingosine-1-phosphate (S1P) are significantly augmented after OVA treatment in mice. Deficiency in sphingosine kinase (SphK)1, the S1P-producing enzyme, or in MC, remarkably mitigates all signs of OVA-mediated remodeling and MC activation. Furthermore, skin S1P levels remain unchanged in MC-deficient mice exposed to OVA. LPS-free OVA does not recapitulate any of the precursor signs of AD, supporting a triggering contribution of LPS in AD that, per se, suffice to activate local MC and elevate skin S1P.

CONCLUSION

We describe MC and S1P as novel pathogenic effectors that initiate remodeling in AD prior to any skin lesions and reveal the significance of LPS in OVA used in most studies, thus mimicking natural antigen (Ag) exposure.

ROCK1 via LIM kinase regulates growth, maturation and actin based functions in mast cells

Understanding mast cell development is essential due to their critical role in regulating immunity and autoimmune diseases. Here, we show how Rho kinases (ROCK) regulate mast cell development and can function as therapeutic targets for treating allergic diseases. Rock1 deficiency results in delayed maturation of bone marrow derived mast cells (BMMCs) in response to IL-3 stimulation and reduced growth in response to stem cell factor (SCF) stimulation. Further, integrin-mediated adhesion and migration, and IgE-mediated degranulation are all impaired in Rock1-deficient BMMCs. To understand the mechanism behind altered mast cell development in Rock1-/- BMMCs, we analyzed the activation of ROCK and its downstream targets including LIM kinase (LIMK). We observed reduced activation of ROCK, LIMK, AKT and ERK1/2 in Rock1-deficient BMMCs in response to SCF stimulation. Further, loss of either Limk1 or Limk2 also demonstrated altered BMMC maturation and growth; combined deletion of both Limk1 and Limk2 resulted in further reduction in BMMC maturation and growth. In passive cutaneous anaphylaxis model, deficiency of Rock1 or treatment with ROCK inhibitor Fasudil protected mice against IgE-mediated challenge. Our results identify ROCK/LIMK pathway as a novel therapeutic target for treating allergic diseases involving mast cells.

Mast Cell Activation in Brain Injury, Stress, and Post-traumatic Stress Disorder and Alzheimer's Disease Pathogenesis

Mast cells are localized throughout the body and mediate allergic, immune, and inflammatory reactions. They are heterogeneous, tissue-resident, long-lived, and granulated cells. Mast cells increase their numbers in specific site in the body by proliferation, increased recruitment, increased survival, and increased rate of maturation from its progenitors. Mast cells are implicated in brain injuries, neuropsychiatric disorders, stress, neuroinflammation, and neurodegeneration. Brain mast cells are the first responders before microglia in the brain injuries since mast cells can release prestored mediators. Mast cells also can detect amyloid plaque formation during Alzheimer's disease (AD) pathogenesis. Stress conditions activate mast cells to release prestored and newly synthesized inflammatory mediators and induce increased blood-brain barrier permeability, recruitment of immune and inflammatory cells into the brain and neuroinflammation. Stress induces the release of corticotropin-releasing hormone (CRH) from paraventricular nucleus of hypothalamus and mast cells. CRH activates glial cells and mast cells through CRH receptors and releases neuroinflammatory mediators. Stress also increases proinflammatory mediator release in the peripheral systems that can induce and augment neuroinflammation. Post-traumatic stress disorder (PTSD) is a traumatic-chronic stress related mental dysfunction. Currently there is no specific therapy to treat PTSD since its disease mechanisms are not yet clearly understood. Moreover, recent reports indicate that PTSD could induce and augment neuroinflammation and neurodegeneration in the pathogenesis of neurodegenerative diseases. Mast cells play a crucial role in the peripheral inflammation as well as in neuroinflammation due to brain injuries, stress, depression, and PTSD. Therefore, mast cells activation in brain injury, stress, and PTSD may accelerate the pathogenesis of neuroinflammatory and neurodegenerative diseases including AD. This review focusses on how mast cells in brain injuries, stress, and PTSD may promote the pathogenesis of AD. We suggest that inhibition of mast cells activation and brain cells associated inflammatory pathways in the brain injuries, stress, and PTSD can be explored as a new therapeutic target to delay or prevent the pathogenesis and severity of AD.

Review of various molecular targets on mast cells and its relation to obesity: A future perspective

Mast cells are stimulatory factors in prognosis of various immunogenic and allergic diseases in human body. These cells play an important role in various immunological and metabolic diseases. The aim of present article is to explore the molecular targets to suppress the over expression of mast cells in obesity. The last 20 years literature were searched by various bibliographic data bases like Pubmed, google Scholar, Scopus and web of Science. The data were collected by keywords like "Mast Cell" "obesity" and "role of mast cell or role in obesity". Articles and their abstract were reviewed with a counting of 827 publications, in which 87 publications were considered for study and remaining was excluded because of its specificity to the subject. This review explains the characteristics, molecular targets and role of mast cells in obesity and existing research with mast cells to the area of metabolic diseases.

Immunomodulation: A definitive role of microRNA-142

Majority of microRNAs are evolutionarily conserved in vertebrates. This is suggestive of their similar roles in regulation of gene networks. In addition to their conserved mature sequences and regulatory roles, a few microRNAs show very cell or tissue specific expression. These microRNAs are highly enriched in some cell types or organs. One such microRNA is microRNA-142 (miR-142). The classical stem-loop structure of miR142 encodes for two species of mature microRNAs; miR142-5p and miR142-3p. MiR-142 is abundant in cells of hematopoietic origin, and therefore, aptly plays a role in lineage differentiation of hematopoietic cells. Interestingly, over the years, miR-142 has gained considerable attention for its quintessential role in regulating immune response. This mini-review discusses the important functional roles of miR-142 in inflammatory and immune response in different physiological and disease setting.

Rifampicin Alleviates Atopic Dermatitis-Like Response in vivo and in vitro

Atopic dermatitis (AD) is a common inflammatory skin disorder mediated by inflammatory cells, such as macrophages and mast cells. Rifampicin is mainly used for the treatment of tuberculosis. Recently, it was reported that rifampicin has anti-inflammatory and immune-suppressive activities. In this study, we investigated the effect of rifampicin on atopic dermatitis in vivo and in vitro. AD was induced by treatment with 2, 4-dinitrochlorobenzene (DNCB) in NC/Nga mice. A subset of mice was then treated with rifampicin by oral administration. The severity score and scratching behavior were alleviated in the rifampicin-treated group. Serum immunoglobulin E (IgE) and interleukin-4 (IL-4) levels were also ameliorated in mice treated with rifampicin. We next examined whether rifampicin has anti-atopic activity via suppression of mast cell activation. Rifampicin suppressed the release of β-hexosaminidase and histamine from human mast cell (HMC)-1 cultures stimulated with compound 48/80. Treatment with rifampicin also inhibited secretion of inflammatory mediators, such tumor necrosis factor-α (TNF-α) and prostaglandin D₂ (PGD₂), in mast cells activated by compound 48/80. The mRNA expression of cyclooxygenase 2 (COX-2) was reduced in the cells treated with rifampicin in a concentration-dependent manner. These results suggest that rifampicin can be used to treat atopic dermatitis.

Mast cell involvement in glucose tolerance impairment caused by chronic mild stress with sleep disturbance

We have developed a chronic mild stress (MS) mouse model by simply rearing mice on a wire net for 3 weeks and investigated the effects of MS on glucose homeostasis and sleep. MS mice showed impaired glucose tolerance and disturbed sleep. One-week treatment with a histamine H1 receptor antagonist (H1RA) ameliorated the glucose intolerance and improved sleep quality in MS mice. MS mice showed an increased number of mast cells in both adipose tissue and the brain. Inhibition of mast cell function ameliorated the impairment in both glucose tolerance and sleep. Together, these findings indicate that mast cells may represent an important pathophysiological mediator in sleep and energy homeostasis.

Interaction of DJ-1 with Lyn is essential for IgE-mediated stimulation of human mast cells

BACKGROUND

DJ-1 is a redox-sensitive protein with multiple roles in cell homeostasis, levels of which are altered in patients with mast cell (MC)-related disorders. However, whether DJ-1 can regulate human MC function is unknown.

OBJECTIVE

We sought to investigate the potential role of DJ-1 in the responses of human MCs to antigen stimulation.

METHODS

DJ-1 was silenced in human CD34⁺-derived MCs and in the LAD2 MC line by using lentiviral short hairpin RNA constructs. Release of β-hexosaminidase, prostaglandin D₂, and GM-CSF and changes in reactive oxygen species levels were measured after FcεRI engagement. Enzymatic assays, sucrose density gradient centrifugation, immunoprecipitation, dot and Western blotting, and confocal imaging were performed for signaling, cellular localization, and coassociation studies.

RESULTS

DJ-1 knockdown substantially reduced mediator release, as well as Lyn kinase and spleen tyrosine kinase activation and signaling through mechanisms that appeared largely unrelated to DJ-1 antioxidant activity. Following FcεRI activation, nonoxidized rather than oxidized DJ-1 translocated to lipid rafts, where it associated with Lyn, an interaction that appeared critical for maximal Lyn activation and initiation of signaling. Using purified recombinant proteins, we demonstrated that DJ-1 directly bound to Lyn but not to other Src kinases, and this interaction was specific for human but not mouse proteins. In addition, DJ-1 reduced Src homology 2 domain-containing phosphatase 2 phosphatase activity by scavenging reactive oxygen species, thus preventing spleen tyrosine kinase dephosphorylation and perpetuating MC signaling.

CONCLUSION

We demonstrate a novel role for DJ-1 in the early activation of Lyn by FcεRI, which is essential for human MC responses and provides the basis for an alternative target in allergic disease therapy.