Human mast cells release Interleukin-8 and induce neutrophil chemotaxis on contact with activated T cells

Role of mast cells activation in the tumor immune microenvironment and immunotherapy of cancers

The mast cell is an important cellular component that plays a crucial role in the crosstalk between innate and adaptive immune responses within the tumor microenvironment (TME). Recently, numerous studies have indicated that mast cells related to tumors play a dual role in regulating cancers, with conflicting results seemingly determined by the degranulation medium. As such, mast cells are an ignored but very promising potential target for cancer immunotherapy based on their immunomodulatory function. In this review, we present a comprehensive overview of the roles and mechanisms of mast cells in diverse cancer types. Firstly, we evaluated the infiltration density and location of mast cells on tumor progression. Secondly, mast cells are activated by the TME and subsequently release a range of inflammatory mediators, cytokines, chemokines, and lipid products that modulate their pro-or anti-tumor functions. Thirdly, activated mast cells engage in intercellular communication with other immune or stromal cells to modulate the immune status or promote tumor development. Finally, we deliberated on the clinical significance of targeting mast cells as a therapeutic approach to restrict tumor initiation and progression. Overall, our review aims to provide insights for future research on the role of mast cells in tumors and their potential as therapeutic targets for cancer treatment.

Exploiting innate immunity for cancer immunotherapy

Immunotherapies have revolutionized the treatment paradigms of various types of cancers. However, most of these immunomodulatory strategies focus on harnessing adaptive immunity, mainly by inhibiting immunosuppressive signaling with immune checkpoint blockade, or enhancing immunostimulatory signaling with bispecific T cell engager and chimeric antigen receptor (CAR)-T cell. Although these agents have already achieved great success, only a tiny percentage of patients could benefit from immunotherapies. Actually, immunotherapy efficacy is determined by multiple components in the tumor microenvironment beyond adaptive immunity. Cells from the innate arm of the immune system, such as macrophages, dendritic cells, myeloid-derived suppressor cells, neutrophils, natural killer cells, and unconventional T cells, also participate in cancer immune evasion and surveillance. Considering that the innate arm is the cornerstone of the antitumor immune response, utilizing innate immunity provides potential therapeutic options for cancer control. Up to now, strategies exploiting innate immunity, such as agonists of stimulator of interferon genes, CAR-macrophage or -natural killer cell therapies, metabolic regulators, and novel immune checkpoint blockade, have exhibited potent antitumor activities in preclinical and clinical studies. Here, we summarize the latest insights into the potential roles of innate cells in antitumor immunity and discuss the advances in innate arm-targeted therapeutic strategies.

The Role of Crosstalk of Immune Cells in Pathogenesis of Chronic Spontaneous Urticaria

Chronic spontaneous urticaria (CSU) is defined as recurrent episodes of spontaneous wheal development and/or angioedema for more than six weeks and at least twice a week. The core link in the pathogenesis of CSU is the activation of mast cells, T cells, eosinophils, and other immune cells infiltrating around the small venules of the lesion. Increased vascular permeability, vasodilatation, and recruitment of inflammatory cells directly depend on mast cell mediators’ release. Complex regulatory systems tightly influence the critical roles of mast cells in the local microenvironment. The bias toward Th2 inflammation and autoantibodies derived from B cells, histamine expressed by basophils, and initiation of the extrinsic coagulation pathway by eosinophils or monocytes exerts powerful modulatory influences on mast cells. Cell-to-cell interactions between mast cells and eosinophils/T cells also are regulators of their function and may involve CSU’s pathomechanism. This review summarizes up-to-date knowledge regarding the crosstalk between mast cells and other immune cells, providing the impetus to develop new research concepts and treatment strategies for CSU.

Cromolyn Sodium differentially regulates human mast cell and mouse leukocyte responses to control allergic inflammation

BACKGROUND

Cromolyn Sodium (CS) has been used in the past as an anti-allergy drug owing to its mast cell (MC) stabilizing properties that impair histamine release. However, additional mechanisms for its clinical actions are likely and might help to identify new roles for MCs and leukocytes in regulating inflammation. Here, using human cord blood-derived MCs (CBMCs), murine bone marrow-derived MCs (BMMCs) and eosinophils (BMEos), and in vivo mouse models of allergic inflammation (AI), additional actions of CS on MCs were determined.

METHODS

The in vitro effects of CS on IgE-activated human and mouse MCs were assessed by measuring the levels of pro-inflammatory (tryptase, LTC₄, IL-8, CD48) and pro-resolution effectors (IL-10, CD300a, Annexin A1) before and after CS treatment. The in vivo effects of daily CS injections on parameters of inflammation were assessed using mouse models of allergic peritonitis (AP) (Ovalbumin/Alum- or Ovalbumin/S. aureus enterotoxin B) and allergic airways inflammation (AAI) (house dust mite (HDM)).

RESULTS

In vitro, CS did not affect pro-inflammatory effectors but significantly increased the anti-inflammatory/pro-resolution CD300a levels and IL-10 release from IgE-activated CBMCs. BMMCs were not affected by CS. In vivo, CS injections decreased total cell and Eos numbers in the peritoneal cavity in the AP models and bronchoalveolar lavage and lungs in the AAI model. CS reduced EPX release from PAF-activated BMEos in vitro, possibly explaining the in vivo findings.

CONCLUSION

Together, these results demonstrate immunomodulatory actions for CS in AI that are broader than only MC stabilization.

Innate Cells: The Alternative Source of IL-17 in Axial and Peripheral Spondyloarthritis?

Spondyloarthritis (SpA) is a chronic inflammatory rheumatism characterized by inflammation of sacroiliac joints, peripheral joints, and spine. The Assessment of SpondyloArthritis Society describes three disease forms: axial (axSpA), peripheral, and enthesitic SpA. Each may be associated with extra-articular manifestations: psoriasis, inflammatory bowel disease, and acute anterior uveitis. Genome-wide association studies performed in axSpA and psoriatic arthritis (PsA) have shown a shared genetic background, especially the interleukin 23 (IL-23)/IL-17 pathway, which suggests pathophysiological similarities. The convincing positive results of clinical trials assessing the effect of secukinumab and ixekizumab (anti-IL-17A monoclonal antibodies) in axSpA and PsA have reinforced the speculated crucial role of IL-17 in SpA. Nevertheless, and obviously unexpectedly, the differential efficacy of anti-IL-23–targeted treatments between axSpA (failure) and PsA (success) has profoundly disrupted our presumed knowledge of disease pathogeny. The cells able to secrete IL-17, their dependence on IL-23, and their respective role according to the clinical form of the disease is at the heart of the current debate to potentially explain these observed differences in efficacy of IL-23/IL-17–targeted therapy. In fact, IL-17 secretion is usually mainly related to T helper 17 lymphocytes. Nevertheless, several innate immune cells express IL-23 receptor and can produce IL-17. To what extent these alternative cell populations can produce IL-17 independent of IL-23 and their respective involvement in axSpA and PsA are the crucial scientific questions in SpA. From this viewpoint, this is a nice example of a reverse path from bedside to bench, in which the results of therapeutic trials allow for reflecting more in depth on the pathophysiology of a disease. Here we provide an overview of each innate immunity-producing IL-17 cell subset and their respective role in disease pathogeny at the current level of our knowledge.

Anti-Allergic Potential of Cinnamaldehyde via the Inhibitory Effect of Histidine Decarboxylase (HDC) Producing Klebsiella pneumonia

Allergy is an immunological disorder that develops in response to exposure to an allergen, and histamines mediate these effects via histidine decarboxylase (HDC) activity at the intracellular level. In the present study, we developed a 3D model of Klebsiella pneumoniae histidine decarboxylase (HDC) and analyzed the HDC inhibitory potential of cinnamaldehyde (CA) and subsequent anti-allergic potential using a bacterial and mammalian mast cell model. A computational and in vitro study using K. pneumonia revealed that CA binds to HDC nearby the pyridoxal-5'-phosphate (PLP) binding site and inhibited histamine synthesis in a bacterial model. Further study using a mammalian mast cell model also showed that CA decreased the levels of histamine in the stimulated RBL-2H3 cell line and attenuated the release of β-hexoseaminidase and cell degranulation. In addition, CA treatment also significantly suppressed the levels of pro-inflammatory cytokines TNF-α and IL-6 and the nitric oxide (NO) level in the stimulated mast cells. A gene expression and Western blotting study revealed that CA significantly downregulated the expressions of MAPKp38/ERK and its downstream pro-allergic mediators that are involved in the signaling pathway in mast cell cytokine synthesis. This study further confirms that CA has the potential to attenuate mast cell activation by inhibiting HDC and modifying the process of allergic disorders.

The anti-allergic potential of tea: a review of its components, mechanisms and risks

Allergy is an immune-mediated disease with increasing prevalence worldwide. Regular treatment with glucocorticoids and antihistamine drugs for allergy patients is palliative rather than permanent. Daily use of dietary anti-allergic natural products is a superior way to prevent allergy and alleviate the threat. Tea, as a health-promoting beverage, has multiple compounds with immunomodulatory ability. Persuasive evidence has shown the anti-allergic ability of tea against asthma, food allergy, atopic dermatitis and anaphylaxis. Recent advances in potential anti-allergic ability of tea and anti-allergic compounds in tea have been reviewed in this paper. Tea exerts its anti-allergic effect mainly by reducing IgE and histamine levels, decreasing FcεRI expression, regulating the balance of Th1/Th2/Th17/Treg cells and inhibiting related transcription factors. Further research perspectives are also discussed.

Emerging Roles of Mast Cells in the Regulation of Lymphatic Immuno-Physiology

Mast cells (MCs) are abundant in almost all vascularized tissues. Furthermore, their anatomical proximity to lymphatic vessels and their ability to synthesize, store and release a large array of inflammatory and vasoactive mediators emphasize their significance in the regulation of the lymphatic vascular functions. As a major secretory cell of the innate immune system, MCs maintain their steady-state granule release under normal physiological conditions; however, the inflammatory response potentiates their ability to synthesize and secrete these mediators. Activation of MCs in response to inflammatory signals can trigger adaptive immune responses by dendritic cell-directed T cell activation. In addition, through the secretion of various mediators, cytokines and growth factors, MCs not only facilitate interaction and migration of immune cells, but also influence lymphatic permeability, contractility, and vascular remodeling as well as immune cell trafficking through the lymphatic vessels. In summary, the consequences of these events directly affect the lymphatic niche, influencing inflammation at multiple levels. In this review, we have summarized the recent advancements in our understanding of the MC biology in the context of the lymphatic vascular system. We have further highlighted the MC-lymphatic interaction axis from the standpoint of the tumor microenvironment.

Mast Cells Are Directly Activated by Cancer Cell-Derived Extracellular Vesicles by a CD73- and Adenosine-Dependent Mechanism

We have recently shown that mast cells (MCs), which constitute an important part of the tumor microenvironment (TME), can be directly activated by cancer cells under conditions that recapitulate cell to cell contact. However, MCs are often detected in the tumor periphery rather than intratumorally. Therefore, we investigated the possibility of MC activation by cancer cell–derived extracellular vesicles (EVs). Here we show that exposure of MCs to EVs derived from pancreatic cancer cells or non–small cell lung carcinoma results in MC activation, evident by the increased phosphorylation of the ERK1/2 MAP kinases. Further, we show that, similarly to activation by cancer cell contact, activation by EVs is dependent on the ecto enzyme CD73 that mediates extracellular formation of adenosine and on signaling by the A3 adenosine receptor. Finally, we show that activation by either cell contact or EVs upregulates expression of angiogenic and tissue remodeling genes, including IL8, IL6, VEGF, and amphiregulin. Collectively, our findings indicate that both intratumorally localized MCs and peripheral MCs are activated and reprogrammed in the TME either by contact with the cancer cells or by their released EVs.

Recent advances in our understanding of mast cell activation - or should it be mast cell mediator disorders?

INTRODUCTION

An increasing number of patients present with multiple symptoms affecting many organs including the brain due to multiple mediators released by mast cells. These unique tissue immune cells are critical for allergic reactions triggered by immunoglobulin E (IgE), but are also stimulated (not activated) by immune, drug, environmental, food, infectious, and stress triggers, leading to secretion of multiple mediators often without histamine and tryptase. The presentation, diagnosis, and management of the spectrum of mast cell disorders are very confusing. As a result, neuropsychiatric symptoms have been left out, and diagnostic criteria made stricter excluding most patients. Areas covered: A literature search was performed on papers published between January 1990 and November 2018 using MEDLINE. Terms used were activation, antihistamines, atopy, autism, brain fog, heparin, KIT mutation, IgE, inflammation, IL-6, IL-31, IL-37, luteolin, mast cells, mastocytosis, mediators, mycotoxins, release, secretion, tetramethoxyluteolin, and tryptase. Expert opinion: Conditions associated with elevated serum or urine levels of any mast cell mediator, in the absence of comorbidities that could explain elevated levels, should be considered 'Mast Cell Mediator Disorders (MCMD).' Emphasis should be placed on the identification of unique mast cell mediators, and development of drugs or supplements that inhibit their release.

Role of Mast Cell-Derived Adenosine in Cancer

Accumulating evidence has highlighted the accumulation of mast cells (MCs) in tumors. However, their impact on tumor development remained controversial. Indeed, cumulative data indicate an enigmatic role for MCs in cancer, whereby depending on the circumstances, which still need to be resolved, MCs function to promote or restrict tumor growth. By responding to multiple stimuli MCs release multiple inflammatory mediators, that contribute to the resolution of infection and resistance to envenomation, but also have the potency to promote or inhibit malignancy. Thus, MCs seem to possess the power to define tumor projections. Given this remarkable plasticity of MC responsiveness, there is an urgent need of understanding how MCs are activated in the tumor microenvironment (TME). We have recently reported on the direct activation of MCs upon contact with cancer cells by a mechanism involving an autocrine formation of adenosine and signaling by the A3 adenosine receptor. Here we summarized the evidence on the role of adenosine signaling in cancer, in MC mediated inflammation and in the MC-cancer crosstalk.

Mast cells: A double-edged sword in cancer

Mast cells (MCs), a type of innate immune cells, are derived from myeloid stem cells, sometimes known as mastocytes or labrocytes, and contain many granules rich in histamine and heparin. The mentioned cells are able to release various mediators such as cytokines, leukotrienes, and a large number of proteases into the environment. Many studies and experiments have established the infiltration of MCs into the tumor site. However, the findings are highly controversial to determine whether these immune cells contribute to the growth and development of the tumor or cause anti-tumor immune responses. Various studies have revealed that MCs have a pro-tumorigenic or anti-tumorigenic role depending on the type of cancer, the degree of tumor progression, and the location of these immune cells in the tumor bulk. Although these types of immune cells cause angiogenesis and tumor progression in some cancers, they have a significant anti-tumor role in some other types of cancers. In general, although a number of studies have specified the protective role of MCs in cancers, the increased number of MCs in the blood and microenvironment of tumors, as well as the increased level of angiogenesis and tumor progression, has been indicated in another array of studies. The function of MCs against or in favor of the cancers still requires further investigations to more accurately and specifically determine the role of MCs in the cancers. The function of MCs in tumors and their various roles in case of exposure to the cancer cells have been addressed in the present review. The concluding section of the present study recommends a number of methods for modification of MCs in cancer immunotherapy.

Mast cells within cellular networks

Mast cells are highly versatile in terms of their mode of activation by a host of stimuli and their ability to flexibly release a plethora of biologically highly active mediators. Within the immune system, mast cells can best be designated as an active nexus interlinking innate and adaptive immunity. Here we try to draw an arc from initiation of acute inflammatory reactions to microbial pathogens to development of adaptive immunity and allergies. This multifaceted nature of mast cells is made possible by interaction with multiple cell types of immunologic and nonimmunologic origin. Examples for the former include neutrophils, eosinophils, T cells, and professional antigen-presenting cells. These interactions allow mast cells to orchestrate inflammatory innate reactions and complex adaptive immunity, including the pathogenesis of allergies. Important partners of nonimmunologic origin include cells of the sensory neuronal system. The intimate association between mast cells and sensory nerve fibers allows bidirectional communication, leading to neurogenic inflammation. Evidence is accumulating that this mast cell/nerve crosstalk is of pathophysiologic relevance in patients with allergic diseases, such as asthma.

Increase in mast cell marker expression in the synovium of obese patients with osteoarthritis of the knee

Purpose: While research suggests that obesity is a risk factor for knee osteoarthritis (KOA), the mechanisms are not fully understood. Mast cell (MC) numbers are increased in the osteoarthritic synovium and in the adipose tissue of obese individuals. We hypothesized that MC numbers are increased in the synovium of obese KOA patients. This study investigated MC marker and MC-generated cytokine/growth factor expression in the synovium of obese KOA patients. Patients and methods: Patients radiographically diagnosed with KOA (male: 38, female: 132) were allocated to three groups based on their body mass index (BMI): normal (<25 kg/m²), overweight (25-29.99 kg/m²) and obese (≥30 kg/m²), according to the World Health Organization BMI classification. We used real-time polymerase chain reaction to compare the expression of MC markers (CD117, CD203c) and growth factors/cytokines (FGF2, VEGFA, TNFA, and IL8) in patients' synovium among the groups. Results: CD117 expression was significantly higher in the obese group than in the normal and overweight groups. CD203c and FGF2 expression were higher in the obese group than in the normal group. FGF2 expression levels were significantly correlated with those of CD117 (ρ=0.487) and CD203c (ρ=0.751). Conclusion: MC markers CD117 and CD203c, and FGF2 were highly expressed in the synovium of obese KOA patients. Further investigations are needed to reveal the role of MCs in the relationship between obesity and osteoarthritis pathology.

Chondroitin sulfate inhibits secretion of TNF and CXCL8 from human mast cells stimulated by IL-33

Glycosaminoglycans (GAGs) are linear, highly negatively charged carbohydrate chains present in connective tissues. Chondroitin sulfate (CS) and heparin (Hep) are also found in the numerous secretory granules of mast cells (MC), tissue immune cells involved in allergic and inflammatory reactions. CS and Hep may inhibit secretion of histamine from rat connective tissue MC, but their effect on human MC remains unknown. Human LAD2 MC were pre-incubated with CS, Hep, or dermatan sulfate (DS) before being stimulated by either the peptide substance P (SP, 2 μM) or the cytokine IL-33 (10 ng/mL). Preincubation with CS had no effect on MC degranulation stimulated by SP, but inhibited TNF (60%) and CXCL8 (45%) secretion from LAD2 cells stimulated by IL-33. Fluorescein-conjugated CS (CS-F) was internalized by LAD2 cells only at 37 °C, but not 4 °C, indicating it occurred by endocytosis. DS and Hep inhibited IL-33-stimulated secretion of TNF and CXCL8 to a similar extent as CS. None of the GAGs tested inhibited IL-33-stimulated gene expression of either TNF or CXCL8. There was no effect of CS on ionomycin-stimulated calcium influx. There was also no effect of CS on surface expression of the IL-33 receptor, ST2. Neutralization of the hyaluronan receptor CD44 did not affect the internalization of CS-F. The findings in this article show that CS inhibits secretion of TNF and CXCL8 from human cultured MC stimulated by IL-33. CS could be formulated for systemic or topical treatment of allergic or inflammatory diseases, such as atopic dermatitis, cutaneous mastocytosis, and psoriasis. © 2018 BioFactors, 45(1):49-61, 2019.

Interleukin-8 in cancer pathogenesis, treatment and follow-up

Interleukin-8 (CXCL8) was originally described asa chemokine whose main function is the attraction of a polymorphonuclear inflammatory leukocyte infiltrate acting on CXCR1/2. Recently, it has been found that tumors very frequently coopt the production of this chemokine, which in this malignant context exerts different pro-tumoral functions. Reportedly, these include angiogenesis, survival signaling for cancer stem cells and attraction of myeloid cells endowed with the ability to immunosuppress and locally provide growth factors. Given the fact that in cancer patients IL-8 is mainly produced by tumor cells themselves, its serum concentration has been shown to correlate with tumor burden. Thus, IL-8 serum concentrations have been shown to be useful asa pharmacodynamic biomarker to early detect response to immunotherapy. Finally, because of the roles that IL-8 plays in favoring tumor progression, several therapeutic strategies are being developed to interfere with its functions. Such interventions hold promise, especially for therapeutic combinations in the field of cancer immunotherapy.

Mast cells are directly activated by contact with cancer cells by a mechanism involving autocrine formation of adenosine and autocrine/paracrine signaling of the adenosine A3 receptor

Mast cells (MCs) constitute an important part of the tumor microenvironment (TME). However, their underlying mechanisms of activation within the TME remain poorly understood. Here we show that recapitulating cell-to-cell contact interactions by exposing MCs to membranes derived from a number of cancer cell types, results in MC activation, evident by the increased phosphorylation of the ERK1/2 MAP kinases and Akt, in a phosphatidylinositol 3-kinase dependent fashion. Activation is unidirectional since MC derived membranes do not activate cancer cells. Stimulated ERK1/2 phosphorylation is strictly dependent on the ecto enzyme CD73 that mediates autocrine formation of adenosine, and is inhibited by knockdown of the A3 adenosine receptor (A3R) as well as by an A3R antagonist or by agonist-stimulated down-regulation of the A3R. We also show that cancer cell mediated triggering upregulates expression and stimulates secretion of interleukin 8 from the activated MCs. These findings provide evidence for a novel mode of unidirectional crosstalk between MCs and cancer cells implicating direct activation by cancer cells in MC reprogramming into a pro tumorigenic profile.

SNAP23-Dependent Surface Translocation of Leukotriene B4 (LTB4) Receptor 1 Is Essential for NOX2-Mediated Exocytotic Degranulation in Human Mast Cells Induced by Trichomonas vaginalis-Secreted LTB4

Trichomonas vaginalis is a sexually transmitted parasite that causes vaginitis in women and itself secretes lipid mediator leukotriene B₄ (LTB₄). Mast cells are important effector cells of tissue inflammation during infection with parasites. Membrane-bridging SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) complexes are critical for fusion during exocytosis. Although T. vaginalis-derived secretory products (TvSP) have been shown to induce exocytosis in mast cells, information regarding the signaling mechanisms between mast cell activation and TvSP is limited. In this study, we found that SNAP23-dependent surface trafficking of LTB₄ receptor 1 (BLT1) is required for nicotinamide adenine dinucleotide phosphate oxidase 2 (NOX2)-mediated exocytotic degranulation of mast cells induced by TvSP. First, stimulation with TvSP induced exocytotic degranulation and reactive oxygen species (ROS) generation in HMC-1 cells. Next, TvSP-induced ROS generation and exocytosis were strongly inhibited by transfection of BLT1 small interfering RNA (siRNA). TvSP induced trafficking of BLT1 from the cytosol to the plasma membrane. We also found that knockdown of SNAP23 abrogated TvSP-induced ROS generation, exocytosis, and surface trafficking of BLT1 in HMC-1 cells. By coimmunoprecipitation, there was a physical interaction between BLT1 and SNAP23 in TvSP-stimulated HMC-1 cells. Taken together, our results suggest that SNAP23-dependent surface trafficking of BLT1 is essential for exocytosis in human mast cells induced by T. vaginalis-secreted LTB₄ Our data collectively demonstrate a novel regulatory mechanism for SNAP23-dependent mast cell activation of T. vaginalis-secreted LTB₄ involving surface trafficking of BLT1. These results can help to explain how the cross talk mechanism between parasite and host can govern deliberately tissue inflammatory responses.

Use of neutrophil to lymphocyte ratio for predicting histopathological grade of canine mast cell tumours

Canine mast cell tumours (MCTs) are variable in their biological behaviour and treatment decisions depend heavily on the histopathological grade. Biomarkers such as neutrophil to lymphocyte ratio (NLR) and albumin to globulin ratio are used to predict the biological behaviour of human neoplasms, but have not been widely studied in dogs. A retrospective analysis identified 62 cases of gross MCT (14 high-grade, 48 low-grade tumours). Median NLR was significantly different between high- and low-grade MCT and tumours at different locations. A multivariable model identified increasing NLR (OR 2.0) and age (OR 1.7) to be associated with an increased risk of high-grade MCT. Receiver operating characteristic curve analysis identified an NLR threshold value of 5.67 (sensitivity 85.7 per cent; specificity 54.2 per cent) for predicting a high-grade MCT. An NLR threshold of 5.67 could be useful alongside existing tools (appearance, location, etc.) to help to predict the grade of MCT. With further validation, this biomarker could be used to guide clinical decisions before obtaining a histopathological diagnosis.

The novel flavone tetramethoxyluteolin is a potent inhibitor of human mast cells

BACKGROUND

Mast cells (MCs) are hematopoietic cells that mature in tissues and are involved in allergy, immunity, and inflammation by secreting multiple mediators. The natural flavone luteolin has anti-inflammatory actions and inhibits human mast cells (MCs).

OBJECTIVE

We sought to investigate the ability of luteolin and its novel structural analog 3',4',5,7-tetramethoxyluteolin (methlut) to inhibit human MC mediator expression and release in vitro and in vivo.

METHODS

Human LAD2 cells and umbilical primary human cord blood-derived cultured mast cells were stimulated with substance P (SP) or IgE/anti-IgE with or without preincubation with luteolin, methlut, or cromolyn (1-100 μmol/L) for 2 or 24 hours, after which mediator secretion was measured. The effect of the compounds on MC intracellular calcium levels and nuclear factor κB activation was also investigated. Pretreatment with methlut was also studied in mice passively sensitized with dinitrophenol-human serum albumin and challenged intradermally.

RESULTS

Methlut is a more potent inhibitor than luteolin or cromolyn for β-hexosaminidase and histamine secretion from LAD2 cells stimulated by either SP or IgE/anti-IgE, but only methlut and luteolin significantly inhibit preformed TNF secretion. Methlut is also a more potent inhibitor than luteolin of de novo-synthesized TNF from LAD2 cells and of CCL2 from human cord blood-derived cultured MCs. This mechanism of action for methlut might be due to its ability to inhibit intracellular calcium level increases, as well as nuclear factor κB induction, at both the transcriptional and translational levels in LAD2 cells stimulated by SP without affecting cell viability. Intraperitoneal treatment with methlut significantly decreases skin vascular permeability of Evans blue dye in mice passively sensitized to dinitrophenol-human serum albumin and challenged intradermally.

CONCLUSION

Methlut is a promising MC inhibitor for the treatment of allergic and inflammatory conditions.

Isoflavones inhibit poly(I:C)-induced serum, brain, and skin inflammatory mediators - relevance to chronic fatigue syndrome

Background

Chronic Fatigue Syndrome (CFS) is a neuroimmunoendocrine disease affecting about 1% of the US population, mostly women. It is characterized by debilitating fatigue for six or more months in the absence of cancer or other systemic diseases. Many CFS patients also have fibromyalgia and skin hypersensitivity that worsen with stress. Corticotropin-releasing hormone (CRH) and neurotensin (NT), secreted under stress, activate mast cells (MC) necessary for allergic reactions to release inflammatory mediators that could contribute to CFS symptoms.

Objective

To investigate the effect of isoflavones on the action of polyinosinic:polycytidylic acid (poly(I:C)), with or without swim stress, on mouse locomotor activity and inflammatory mediator expression, as well as on human MC activation.

Methods

Female C57BL/6 mice were randomly divided into four groups: (a) control/no-swim, (b) control/swim, (c) polyinosinic:polycytidylic acid (poly(I:C))/no swim, and (d) polyinosinic:polycytidylic acid (poly(I:C))/swim. Mice were provided with chow low or high in isoflavones for 2 weeks prior to ip injection with 20 mg/kg poly(I:C) followed or not by swim stress for 15 minutes. Locomotor activity was monitored overnight and animals were sacrificed the following day. Brain and skin gene expression, as well as serum levels, of inflammatory mediators were measured. Data were analyzed using the non-parametric Mann-Whitney U-test.

Results

Poly(I:C)-treated mice had decreased locomotor activity over 24 hours, and increased serum levels of TNF-α, IL-6, KC (IL-8/CXCL8 murine homolog), CCL2,3,4,5, CXCL10, as well as brain and skin gene expression of TNF, IL-6, KC (Cxcl1, IL8 murine homolog), CCL2, CCL4, CCL5 and CXCL10. Histidine decarboxylase (HDC) and NT expression were also increased, but only in the skin, over the same period. High isoflavone diet reversed these effects.

Conclusion

Poly(I:C) treatment decreased mouse locomotor activity and increased serum levels and brain and skin gene expression of inflammatory mediators. These effects were inhibited by isoflavones that may prove useful in CFS.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-014-0168-5) contains supplementary material, which is available to authorized users.

Oral administration of herbal mixture extract inhibits 2,4-dinitrochlorobenzene-induced atopic dermatitis in BALB/c mice

CP001 is four traditional herbal medicine mixtures with anti-inflammatory properties. In this study, we investigated the effect of oral administration of CP001 ethanol extract on the 2,4-dinitrochlorobenzene- (DNCB-) induced AD mouse models. For that purpose, we observed the effects of oral administration of CP001 on skin inflammatory cell infiltration, skin mast cells, production of serum IgE, and expression of Th2 cytokine mRNA in the AD skin lesions of DNCB treated BALB/c mice. Histological analyses demonstrated that CP001 decreased dermis and epidermis thickening as well as dermal infiltration induced by inflammatory cells. In addition, CP001 decreased mast cell infiltration in count as well as dermal infiltration induced by inflammatory cells. In the skin lesions, mRNA expression of interleukin- (IL-) 4 and IL-13 was inhibited by CP001. CP001 also reduced the production of IgE level in mouse plasma. In addition, we investigated the effect of CP001 on the inflammatory allergic reaction using human mast cells (HMC-1). In HMC-1, cytokine production and mRNA levels of IL-4, IL-13, IL-6, and IL-8 were suppressed by CP001. Taken together, our results showed that oral administration of CP001 exerts beneficial effects in AD symptoms, suggesting that CP001 might be a useful candidate for the treatment of AD.

Spectrum of mast cell activation disorders

Mast cell (MC) activation disorders present with multiple symptoms including flushing, pruritus, hypotension, gastrointestinal complaints, irritability, headaches, concentration/memory loss and neuropsychiatric issues. These disorders are classified as: cutaneous and systemic mastocytosis with a c-kit mutation and clonal MC activation disorder, allergies, urticarias and inflammatory disorders and mast cell activation syndrome (MCAS), idiopathic urticaria and angioedema. MCs are activated by IgE, but also by cytokines, environmental, food, infectious, drug and stress triggers, leading to secretion of multiple mediators. The symptom profile and comorbidities associated with these disorders, such as chronic fatigue syndrome and fibromyalgia, are confusing. We propose the use of the term 'spectrum' and highlight the main symptoms, useful diagnostic tests and treatment approaches.

Mast cells as targets for immunotherapy of solid tumors

Mast cells have historically been studied mainly in the context of allergic disease. In recent years, we have come to understand the critical importance of mast cells in tissue remodeling events and their role as sentinel cells in the induction and development of effective immune responses to infection. Studies of the role of mast cells in tumor immunity are more limited. The pro-tumorigenic role of mast cells has been widely reported. However, mast cell infiltration predicts improved prognosis in some cancers, suggesting that their prognostic value may be dependent on other variables. Such factors may include the nature of local mast cell subsets and the various activation stimuli present within the tumor microenvironment. Experimental models have highlighted the importance of mast cells in orchestrating the anti-tumor events that follow immunotherapies that target innate immunity. Mast cells are long-lived tissue resident cells that are abundant around many solid tumors and are radiation resistant making them unique candidates for combined treatment modalities. This review will examine some of the key roles of mast cells in tumor immunity, with a focus on potential immunotherapeutic interventions that harness the sentinel role of mast cells.

Mast cells: multitalented facilitators of protection against bacterial pathogens

Mast cells are crucial effector cells evoking immune responses against bacterial pathogens. The positioning of mast cells at the host-environment interface, and the multitude of pathogen-recognition receptors and preformed mediator granules make these cells potentially the earliest to respond to an invading pathogen. In this review, the authors summarize the receptors used by mast cells to recognize invading bacteria and discuss the function of immune mediators released by mast cells in control of bacterial infection. The interaction of mast cells with other immune cells, including macrophages, dendritic cells and T cells, to induce protective immunity is highlighted. The authors also discuss mast cell-based vaccine strategies and the potential application in control of bacterial disease.

[6]-Shogaol inhibits the production of proinflammatory cytokines via regulation of NF-κB and phosphorylation of JNK in HMC-1 cells

[6]-Shogaol is a major bioactive component of Zingiber officinale. Although [6]-shogaol has a number of pharmacological activities including antipyretic, analgesic, antitussive and anti-inflammatory effects, the specific mechanisms of its anti-allergic effects have not been studied. In this study, we present the effects of [6]-shogaol on mast cell-mediated allergic reactions in vivo and in vitro. Sprague-Dawley rats received intradermal injections of anti-DNP IgE was injected into dorsal skin sites. After 48 h, [6]-shogaol was administered orally 1 h prior to challenge with DNP-HSA in saline containing 4% Evans blue through the dorsal vein of the penis. In addition, rat peritoneal mast cells (RPMCs) were cultured and purified to investigate histamine release. In vitro, we evaluated the regulatory effects of [6]-shogaol on the level of inflammatory mediators in phorbol 12-myristate 13-acetate plus calcium ionomycin A23187-stimulated human mast cells (HMC-1). [6]-Shogaol reduced the passive cutaneous anaphylaxis reaction compared to the control group, and histamine release decreased significantly following the treatment of RPMCs with [6]-shogaol. In HMC-1 cells, [6]-shogaol inhibited the production of TNF-α, IL-6 and IL-8, as well as the activation of nuclear factor-κB (NF-κB) and phosphorylation of JNK in compound 48/80-induced HMC-1 cells. [6]-shogaol inhibited mast cell-mediated allergic reactions by inhibiting the release of histamine and the production of proinflammatory cytokines with the involvement of regulation of NF-κB and phosphorylation of JNK.

Interacting mast cells and eosinophils acquire an enhanced activation state in vitro

BACKGROUND

Mast cells (MCs) and eosinophils (Eos), the key effector cells in allergy, are abundantly co-localized particularly in the late and chronic stages of allergic inflammation. Recent evidence has outlined a specialized 'allergic effector unit' in which MCs and Eos communicate via both soluble mediators and physical contact. However, the functional impact of this bi-directional crosstalk on the cells' effector activities has not yet been revealed. We aimed to investigate whether MC/eosinophil interactions can influence the immediate and late activation phenotypes of these cells.

METHODS

Human and murine MCs and Eos were co-cultured under various conditions for 1-2 h or 1-3 days, and in selected experiments cell-cell contact was blocked. Cell migration and mediator release were examined, and flow cytometry was applied to stain intracellular signaling molecules and surface receptors.

RESULTS

Eosinophils enhanced basal MCs mediator release and co-stimulated IgE-activated MCs through physical contact involving CD48-2B4 interactions. Reciprocally, resting and IgE-stimulated MCs led to eosinophil migration and activation through a paracrine-dependent mechanism. Increased phosphorylation of activation-associated signaling molecules, and enhanced release of tumor necrosis factor α, was observed in long-term co-cultures. Eosinophils also showed enhanced expression of intercellular adhesion molecule 1, which depended on direct contact with MCs.

CONCLUSIONS

Our findings reveal a new role for MC/eosinophil interplay in augmenting short- and long-term activation in both cells, in a combined physical/paracrine manner. This enhanced functional activity may thus critically contribute to the perpetuation of the inflammatory response in allergic conditions.

Mast cell activation and neutrophil recruitment promotes early and robust inflammation in the meninges in EAE

The meninges are often considered inert tissues that house the CSF and provide protection for the brain and spinal cord. Yet emerging data demonstrates that they are also active sites of immune responses. Furthermore, the blood-CSF barrier surrounding meningeal blood vessels, together with the blood-brain barrier (BBB), is postulated to serve as a gateway for the pathological infiltration of immune cells into the CNS in multiple sclerosis (MS). Our previous studies using mast cell-deficient (Kit(W/Wv)) mice demonstrated that mast cells resident in the dura mater and pia mater exacerbate experimental autoimmune encephalomyelitis (EAE), a rodent model of MS, by facilitating CNS inflammatory cell influx. Here we examined the underlying mechanisms that mediate these effects. We demonstrate that there are dramatic alterations in immune associated gene expression in the meninges in pre-clinical disease, including those associated with mast cell and neutrophil function. Meningeal mast cells are activated within 24 h of disease induction, but do not directly compromise CNS vascular integrity. Rather, through production of TNF, mast cells elicit an early influx of neutrophils, cells known to alter vascular permeability, into the meninges. These data add to the growing evidence that inflammation in the meninges precedes CNS immune cell infiltration and establish that mast cells are among the earliest participants in these disease-initiating events. We hypothesize that mast cell-dependent neutrophil recruitment and activation in the meninges promotes early breakdown of the local BBB and CSF-blood barrier allowing initial immune cell access to the CNS.

Mast Cells are Important Modifiers of Autoimmune Disease: With so Much Evidence, Why is There Still Controversy?

There is abundant evidence that mast cells are active participants in events that mediate tissue damage in autoimmune disease. Disease-associated increases in mast cell numbers accompanied by mast cell degranulation and elaboration of numerous mast cell mediators at sites of inflammation are commonly observed in many human autoimmune diseases including multiple sclerosis, rheumatoid arthritis, and bullous pemphigoid. In animal models, treatment with mast cell stabilizing drugs or mast cell ablation can result in diminished disease. A variety of receptors including those engaged by antibody, complement, pathogens, and intrinsic danger signals are implicated in mast cell activation in disease. Similar to their role as first responders in infection settings, mast cells likely orchestrate early recruitment of immune cells, including neutrophils, to the sites of autoimmune destruction. This co-localization promotes cellular crosstalk and activation and results in the amplification of the local inflammatory response thereby promoting and sustaining tissue damage. Despite the evidence, there is still a debate regarding the relative role of mast cells in these processes. However, by definition, mast cells can only act as accessory cells to the self-reactive T and/or antibody driven autoimmune responses. Thus, when evaluating mast cell involvement using existing and somewhat imperfect animal models of disease, their importance is sometimes obscured. However, these potent immune cells are undoubtedly major contributors to autoimmunity and should be considered as important targets for therapeutic disease intervention.

Microarray analysis of the gene expression profile of HMC-1 mast cells following Schizonepeta tenuifolia Briquet treatment

It has long been believed that mast cells play a crucial role in the development of many physiological changes during immediate allergic responses. This study was conducted to evaluate the anti-inflammation mechanism of Schizonepeta tenuifolia (ST) extract and ST purified chemicals on the PMA plus A23187-induced stimulation of HMC-1 human mast cells. ST, rosmarinic acid, pulegone, and 2α,3α,24-thrihydrooxylen-12en-28oic acid treatment of HMC-1 cells led to significant suppression of pro-inflammatory cytokines (IL-6, IL-8, and TNF-α) in a dose dependent manner. In addition, the results of the microarray and real-time RT-PCR analyses revealed that ST regulates several pathways, including the cytokine-cytokine receptor interaction (CCRI), MAPK, and the Toll-like receptor (TLR) signaling pathways. ST may be useful for the treatment of inflammation disease via anti-inflammation activity that occurs through inhibition of the CCRI, MAPK, and TLR signaling pathways.

T cell-mediated modulation of mast cell function: heterotypic adhesion-induced stimulatory or inhibitory effects

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

Ethyl acetate extract of Psidium guajava inhibits IgE-mediated allergic responses by blocking FcεRI signaling

Psidium guajava (P. guajava) is an important food crop and medicinal plant with antioxidant, anti-inflammatory, and anti-allergic activities, supporting its traditional uses. However, its precise effects remain unknown. We investigated the effects of P. guajava ethyl acetate extract (PGEA) on IgE-mediated allergic responses in rat mast RBL-2H3 cells. PGEA reduced antigen (DNP-BSA)-induced release of β-hexosaminidase and histamine in IgE-sensitized RBL-2H3 cells. In addition, it inhibited antigen-induced IL-4 and TNF-α mRNA expression and protein production in IgE-sensitized RBL-2H3 cells. PGEA also suppressed antigen-induced COX-2 mRNA and protein expression in these cells, as well as antigen-induced activation of NFAT and reactive oxygen species. Moreover, it inhibited antigen-induced activation of NF-κB and degradation of IκB-α. To identify the mechanisms underpinning the inhibition of degranulation and cytokine production by PGEA, we examined the activation of intracellular FcεRI signaling molecules. PGEA suppressed antigen-induced phosphorylation of Syk, LAT, Gab2, and PLCγ2 but not Lyn, and inhibited antigen-induced phosphorylation of downstream signaling intermediates including MAP kinases and Akt. Collectively, the anti-allergic effects of PGEA in vitro suggest its possible therapeutic application to inflammatory allergic diseases, in which its inhibition of inflammatory cytokine production and FcεRI-dependent signaling events in mast cells may be hugely beneficial.

Pharmacotherapy of systemic sclerosis

IMPORTANCE OF THE FIELD

Systemic sclerosis (SSc) is an uncommon autoimmune disease with variable degrees of fibroproliferation in blood vessels and certain organs of the body. There is currently no cure. The purpose of this article is to review the current literature regarding pathogenesis and treatment of complications of SSc.

AREAS COVERED IN THIS REVIEW

All available articles regarding research related to SSc pathogenesis and treatment listed in the PubMed database were searched; relevant articles were then reviewed and used as sources of information for this review.

WHAT THE READER WILL GAIN

This review attempts to highlight for the reader some current thought regarding mechanisms of SSc pathogenesis and how autoimmunity relates to vascular changes and fibrogenesis of the disease, as well as providing a review of results of completed clinical trials and current ongoing clinical trials that address organ-specific or global therapies for this disease. This can aid physicians who provide medical care for patients with SSc.

TAKE HOME MESSAGE

SSc is a complex autoimmune disease, the pathogenesis of which, although not completely understood, is under active study; new insights into pathogenesis are continually being discovered. Although there is no effective disease-modifying treatment for patients with SSc, quality of life, morbidity and mortality can be improved by using targeted therapy directed at affecting the consequences of damage to lungs, blood vessels, kidneys and the gastrointestinal tract. Innovative approaches to treating SSc are under intense investigation.

Characterization of ERK activation in human mast cells stimulated by contact with T cells

Close physical proximity between mast cells and T cells has been demonstrated in several human conditions. We have identified and characterized a novel mast cell activation pathway initiated by contact with T cells, and showed that this pathway is associated with cytokine release. It has been shown recently that Ras is activated in this pathway. Thus, in the present study we further explore the downstream events associated with Ras activation and cytokine release in human mast cells stimulated by contact with T cells. ERK activation in human mast cells stimulated by either contact with T cells or by crosslinking the FC epsilon receptor was studied. Photobleaching experiments were used to study ERK localization. Enzyme linked immunosorbent assay was used to study the cytokine release by human mast cells. We show that stimulation of human mast cells by contact with activated T cells results is sustained ERK activation. Furthermore, sustained ERK activation in these cells is associated with increased dwell time at the nucleus and with IL-8 release. Interestingly, when mast cells were stimulated by crosslinking the FC epsilon receptor I, ERK activation was transient. ERK activation was associated with a shorter dwell time at the nucleus and with TNF-alpha release. Thus, retaining ERK in the nucleus might be a mechanism utilized by human mast cells to generate different cytokines from a single signaling cascade.

Meningeal mast cells affect early T cell central nervous system infiltration and blood-brain barrier integrity through TNF: a role for neutrophil recruitment?

Mast cells contribute to the pathogenesis of experimental autoimmune encephalomyelitis, a rodent model of the human demyelinating disease multiple sclerosis. Yet their site and mode of action is unknown. In both diseases, myelin-specific T cells are initially activated in peripheral lymphoid organs. However, for disease to occur, these cells must enter the immunologically privileged CNS through a breach in the relatively impermeable blood-brain barrier. In this study, we demonstrate that a dense population of resident mast cells in the meninges, structures surrounding the brain and spinal cord, regulate basal CNS barrier function, facilitating initial T cell CNS entry. Through the expression of TNF, mast cells recruit an early wave of neutrophils to the CNS. We propose that neutrophils in turn promote the blood-brain barrier breach and together with T cells lead to further inflammatory cell influx and myelin damage. These findings provide specific targets for intervention in multiple sclerosis as well as other immune-mediated CNS diseases.

Autism: an emerging 'neuroimmune disorder' in search of therapy

BACKGROUND

Autism spectrum disorders (ASDs) are neurodevelopmental disorders characterized by difficulties in communication and by repetitive and stereotypic behaviors, as well as by social impairment, attention, cognitive, and learning defects. ASDs present in early childhood and their prevalence has increased significantly to 1/150 children. Despite a number of theories, the actual reasons for this increase are still not clear. There is no reliable screening test, and no definite pathogenesis or curative therapy. Consequently, there is a major gap hampering development of effective treatments.

OBJECTIVE

To review recent publications on ASDs pathogenesis and treatment with emphasis on neuroimmune processes and new therapeutic approaches.

METHODS

Mostly original papers (450) on epidemiology, possible pathogenesis or treatment of ASDs in Medline from 1990 to May 2009 were reviewed. All authors contributed to this review.

RESULTS/CONCLUSION

Increased oxidative stress and immune dysregulation are present in ASDs. Mast-cell activation may contribute to gut-blood-brain barrier disruption and brain inflammation. No effective treatments have emerged. Well-designed clinical trials with nonpsychotropic drugs were few and ASD characteristics varied considerably, making conclusions difficult. Psychotropic drugs are often used for stereotypic and aggressive behaviors. Unique combinations with antioxidant and anti-inflammatory flavonoids hold promise. New potential translational research areas and possible treatments are suggested.

Immunomodulatory responses of peripheral blood mononuclear cells from multiple sclerosis patients upon in vitro incubation with the flavonoid luteolin: additive effects of IFN-beta

The study is aimed to determine the role of luteolin (3',4',5,7-tetrahydroxyflavone), alone and in combination with human interferon-beta (IFN-beta), in modulating the immune response(s) of peripheral blood mononuclear cells (PBMCs) isolated from multiple sclerosis (MS) patients. PBMC proliferation in the presence or absence of these drugs was determined and the production of pro-inflammatory cytokines (IL-1beta, TNF-alpha), and the ratio of cell migration mediator MMP-9, and its inhibitor, TIMP-1 was assessed in the culture supernatants. Luteolin reduced, in a dose-dependent manner, the proliferation of PBMCs, and modulated the levels of IL-1beta and TNF-alpha released by PBMCs in the culture supernatants. Luteolin reduced the MMP-9/TIMP-1 ratio via lowering MMP-9 production. In the majority of cases, luteolin, when combined with IFN-beta, had additive effects in modulating cell proliferation, IL-1beta, TNF-alpha, MMP-9 and TIMP-1.

The hydroxyflavone, fisetin, suppresses mast cell activation induced by interaction with activated T cell membranes

BACKGROUND AND PURPOSE

Cell-to-cell interactions between mast cells and activated T cells are increasingly recognized as a possible mechanism in the aetiology of allergic or non-allergic inflammatory disorders. To determine the anti-allergic effect of fisetin, we examined the ability of fisetin to suppress activation of the human mast cell line, HMC-1, induced by activated Jurkat T cell membranes.

EXPERIMENTAL APPROACH

HMC-1 cells were incubated with or without fisetin for 15 min and then co-cultured with Jurkat T cell membranes activated by phorbol-12-myristate 13-acetate for 16 h. We determined gene expression in activated HMC-1 cells by DNA microarray and quantitative reverse transcription (RT)-PCR analysis. We also examined activation of the transcription factor NF-kappaB and MAP kinases (MAPKs) in activated HMC-1 cells.

KEY RESULTS

Fisetin suppresses cell spreading and gene expression in HMC-1 cells stimulated by activated T cell membranes. Additionally, we show that these stimulated HMC-1 cells expressed granzyme B. The stimulatory interaction also induced activation of NF-kappaB and MAPKs; these activations were suppressed by fisetin. Fisetin also reduced the amount of cell surface antigen CD40 and intercellular adhesion molecule-1 (ICAM-1) on activated HMC-1 cells.

CONCLUSIONS AND IMPLICATIONS

Fisetin suppressed activation of HMC-1 cells by activated T cell membranes by interfering with cell-to-cell interaction and inhibiting the activity of NF-kappaB and MAPKs and thereby suppressing gene expression. Fisetin may protect against the progression of inflammatory diseases by limiting interactions between mast cells and activated T cells.

Rupatadine inhibits proinflammatory mediator secretion from human mast cells triggered by different stimuli

BACKGROUND

Mast cells are involved in allergy and inflammation by secreting multiple mediators including histamine, cytokines and platelet-activating factor. Certain histamine 1 receptor antagonists have been reported to inhibit histamine secretion, but the effect on cytokine release from human mast cells triggered by allergic and other stimuli is not well known. We investigated the ability of rupatadine, a potent histamine 1 receptor antagonist that also blocks platelet-activating factor actions, to also inhibit mast cell mediator release.

METHODS

Rupatadine (1-50 microM) was used before stimulation by: (1) interleukin (IL)-1 to induce IL-6 from human leukemic mast cells (HMC-1 cells), (2) substance P for histamine, IL-8 and vascular endothelial growth factor release from LAD2 cells, and (3) IgE/anti-IgE for cytokine release from human cord blood-derived cultured mast cells. Mediators were measured in the supernatant fluid by ELISA or by Milliplex microbead arrays.

RESULTS

Rupatadine (10-50 microM) inhibited IL-6 release (80% at 50 microM) from HMC-1 cells, whether added 10 min or 24 h prior to stimulation. Rupatadine (10-50 microM for 10 min) inhibited IL-8 (80%), vascular endothelial growth factor (73%) and histamine (88%) release from LAD2 cells, as well as IL-6, IL-8, IL-10, IL-13 and tumor necrosis factor release from human cord blood-derived cultured mast cells.

CONCLUSION

Rupatadine can inhibit histamine and cytokine secretion from human mast cells in response to allergic, immune and neuropeptide triggers. These actions endow rupatadine with unique properties in treating allergic inflammation, especially perennial rhinitis and idiopathic urticaria.

Stimulation of CCL2 (MCP-1) and CCL2 mRNA by substance P in LAD2 human mast cells

Chemokines are cytokines with chemotactic properties on inflammatory cells and other cell types. Chemokine (C-C motif) ligand 2 (CCL2), which is also called monocyte chemotactic protein 1 (MCP-1), is a potent chemotactic molecule that attracts lymphocytes, monocytes, mast cells, and memory T cells, but not neutrophils. CCL2/MCP-1 represents a link between the activation of monocytes, lymphocytes, basophils, mast cells, and eosinophils in inflammatory disorders, such as the late-phase allergic reaction. This C-C chemokine also plays a role in regulating Th-cell cytokine production and leukocyte trafficking. Laboratory of allergic diseases (LAD) cells is the first reported human mast cell line that closely resembles a primary culture of CD34+-derived human mast cells. These cells were cultured in vitro and treated with different concentrations of substance P (SP) for the production of CCL2/MCP-1. We used calcium ionophore as a positive control for stimulating transcription and translation of CCL2/MCP-1. The stimulation of SP on CCL2/MCP-1 was statistically significant (P < 0.05) compared with the control (untreated cells). In this study, we determined the expression and secretion of CCL2/MCP-1 from SP-activated LAD2 human mast cells in vitro. The levels of CCL2/MCP-1 from SP-activated LAD2 human mast cells were higher at 10 microM and at 18 h incubation compared with controls. This effect was also revealed on CCL2/MCP-1 messenger RNA (mRNA) expression, as determined by reverse transcriptase polymerase chain reaction (RT-PCR) analysis. Our data suggest that SP is an important neurotransmitter that can stimulate the chemokine CCL2, which plays a fundamental role in inflammation by recruiting inflammatory cells to specific cites.