Mast cells as "tunable" effector and immunoregulatory cells: recent advances

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.

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.

Cell-specific immune-modulation of cadmium on murine macrophages and mast cell lines in vitro

Toxic trace metals are widespread contaminants that are potentially immunotoxic even at environmentally low exposure levels. They can modulate the immunity to infections, e.g., in wildlife species living in contaminated areas. The diverse immune cell types can be differentially affected by the exposure leading to the modulation of specific protective mechanisms. Macrophages and mast cells, part of the innate immune system, trigger immune responses and perform particular effector functions. The present study compared toxicological and functional effects of cadmium in two models of murine macrophages (RAW264.7 and NR8383 cell lines) and two models of murine mast cells (MC/9 and RBL-2H3 cell lines). Cadmium was selected as a model compound because its known potential to induce reactive oxygen species and its relevance as an environmental contaminant. Mechanisms of toxicity, such as redox imbalance and apoptosis induction were measured in stationary cells, while functional outcome effects were measured in activated cells. Cadmium-depleted glutathione antioxidant in all four cell lines tested although reactive oxygen species was not significantly increased. Mast cells had full dose-response depletion of glutathione below cytotoxic levels while in macrophages the depletion was not complete. Functional endpoints tumour necrosis factor-alpha and nitrite production in lipopolysaccharide-activated macrophages were increased by cadmium exposure. In contrast, mast cell lipopolysaccharide-induced tumour necrosis factor-alpha and IgE-mediated histamine release were reduced by cadmium. These data indicate potentially differential effects of cadmium among murine innate immune cell types, where mast cells would be more susceptible to oxidative stress and their function might be at a higher risk to be modulated compared to macrophages.

Mast cells contribute to the induction of ocular mucosal alloimmunity

Beyond their historical role as the effector cells in allergic disorders, mast cells have been implicated in regulating both innate and adaptive immune responses. Possessing considerable functional plasticity, mast cells are abundant at mucosal surfaces, where the host and external environments interface. The purpose of this study was to evaluate the contribution of mast cells to allograft rejection at the ocular surface. Using a well-characterized murine model of corneal transplantation, we report that mast cells promote allosensitization. Our data show mast cell frequencies and activation are increased following transplantation. We demonstrate that mast cell inhibition (a) limits the infiltration of inflammatory cells and APC maturation at the graft site; (b) reduces allosensitization and the generation of Th1 cells in draining lymphoid tissues; (c) decreases graft infiltration of alloimmune-inflammatory cells; and (d) prolongs allograft survival. Our data demonstrate a novel function of mast cells in promoting allosensitization at the ocular surface.

Hepatic encephalopathy: Sometimes more portal than hepatic

Hepatic encephalopathy is a severe complication of both chronic and acute liver diseases. The term hepatic encephalopathy stems from the belief that hepatic insufficiency is its fundamental etiopathogenic factor. However, most clinical cases show liver failure along with mesenteric venous portal hypertension. This portal hypertension would explain the abnormal mechanical forces suffered by the digestive tract in the early stages of the disorder. These forces could regulate some gut biochemical pathological pathways in a process known as mechanotransduction. Thus, portal hypertension would begin with the establishment of a mechanotransduced afferent or sensory inflammatory gut-brain pathway, resulting in functional and structural changes in the central nervous system. In this review, we will revisit the term "hepatic encephalopathy" in light of new results where portal hypertension occurs before liver failure and is accompanied by brain changes. Moreover, we will point out cellular links that can explain the microbiota, immune, gut, and brain axis disturbances found in this disorder.

Syntaxin 3, but not syntaxin 4, is required for mast cell-regulated exocytosis, where it plays a primary role mediating compound exocytosis

Mast cells (MCs) participate in allergy, inflammation, and defense against pathogens. They release multiple immune mediators via exocytosis, a process that requires SNARE proteins, including syntaxins (Stxs). The identity of the Stxs involved in MC exocytosis remains controversial. Here, we studied the roles of Stx3 and -4 in fully developed MCs from conditional knockout mice by electrophysiology and EM, and found that Stx3, and not Stx4, is crucial for MC exocytosis. The main defect seen in Stx3-deficient MCs was their inability to engage multigranular compound exocytosis, while leaving most single-vesicle fusion events intact. We used this defect to show that this form of exocytosis is not only required to accelerate MC degranulation but also essential to achieve full degranulation. The exocytic defect was severe but not absolute, indicating that an Stx other than Stx3 and -4 is also required for exocytosis in MCs. The removal of Stx3 affected only regulated exocytosis, leaving other MC effector responses intact, including the secretion of cytokines via constitutive exocytosis. Our in vivo model of passive systemic anaphylaxis showed that the residual exocytic function of Stx3-deficient MCs was sufficient to drive a full anaphylactic response in mice.

Japanese encephalitis virus neuropenetrance is driven by mast cell chymase

Japanese encephalitis virus (JEV) is a leading cause of viral encephalitis. However, the mechanisms of JEV penetration of the blood-brain-barrier (BBB) remain poorly understood. Mast cells (MCs) are granulated innate immune sentinels located perivascularly, including at the BBB. Here we show that JEV activates MCs, leading to the release of granule-associated proteases in vivo. MC-deficient mice display reduced BBB permeability during JEV infection compared to congenic wild-type (WT) mice, indicating that enhanced vascular leakage in the brain during JEV infection is MC-dependent. Moreover, MCs promoted increased JEV infection in the central nervous system (CNS), enhanced neurological deficits, and reduced survival in vivo. Mechanistically, chymase, a MC-specific protease, enhances JEV-induced breakdown of the BBB and cleavage of tight-junction proteins. Chymase inhibition reversed BBB leakage, reduced brain infection and neurological deficits during JEV infection, and prolonged survival, suggesting chymase is a novel therapeutic target to prevent JEV encephalitis.

How Japanese encephalitis virus (JEV) penetrates the blood-brain barrier (BBB) remains unclear. Here, using a genetic mouse model and a virulent JEV strain, the authors show that perivascular mast cells (MC) mediate JEV neuroinvasion and identify the MC-protease chymase as a potential therapeutic target.

Mast Cells Initiate the Recruitment of Neutrophils Following Ocular Surface Injury

Purpose

The purpose of this study was to investigate the contribution of mast cells to early neutrophil recruitment during ocular inflammation.

Methods

In a murine model of corneal injury, the epithelium and anterior stroma were removed using a handheld motor brush. Cromolyn sodium (2% in PBS) eye drops were administered topically for mast cell inhibition. In vitro, bone marrow–derived mast cells were cultured alone or with corneal tissue. The frequencies of CD45⁺ inflammatory cells, CD11b⁺Ly6G⁺ neutrophils, and ckit⁺FcεR1⁺ mast cells in the cornea were assessed by flow cytometry. mRNA expression of CXCL2 was evaluated by real-time PCR and protein expression by ELISA. β-Hexosaminidase assays were performed to gauge mast cell activation.

Results

Neutrophil infiltration of the cornea was observed within 1 hour of injury, with neutrophil frequencies increasing over subsequent hours. Concurrent expansion of mast cell frequencies at the cornea were observed, with mast cell activation (assessed by β-hexosaminidase levels) peaking at 6 hours after injury. Evaluation of CXCL2 mRNA and protein expression levels demonstrated augmented expression by injured corneal tissue relative to naïve corneal tissue. Mast cells were observed to constitutively express CXCL2, with significantly higher expression of CXCL2 protein compared with naïve corneal tissue. Culture with harvested injured corneas further amplified CXCL2 expression by mast cells. In vivo, mast cell inhibition was observed to decrease CXCL2 expression, limit early neutrophil infiltration, and reduce inflammatory cytokine expression by the cornea.

Conclusions

Our data suggest that mast cell activation after corneal injury amplifies their secretion of CXCL2 and promotes the initiation of early neutrophil recruitment.

Imaging of mast cells

Mast cells are a part of the innate immune system implicated in allergic reactions and the regulation of host-pathogen interactions. The distribution, morphology and biochemical composition of mast cells has been studied in detail in vitro and on tissue sections both at the light microscopic and ultrastructural level. More recently, the development of fluorescent reporter strains and intravital imaging modalities has enabled first glimpses of the real-time behavior of mast cells in situ. In this review, we describe commonly used imaging approaches to study mast cells in cell culture as well as within normal and diseased tissues. We further describe the interrogation of mast cell function via imaging by providing a detailed description of mast cell-nerve plexus interactions in the intestinal tract. Together, visualizing mast cells has expanded our view of these cells in health and disease.

Mast cells as sources of cytokines, chemokines, and growth factors

Mast cells are hematopoietic cells that reside in virtually all vascularized tissues and that represent potential sources of a wide variety of biologically active secreted products, including diverse cytokines and growth factors. There is strong evidence for important non-redundant roles of mast cells in many types of innate or adaptive immune responses, including making important contributions to immediate and chronic IgE-associated allergic disorders and enhancing host resistance to certain venoms and parasites. However, mast cells have been proposed to influence many other biological processes, including responses to bacteria and virus, angiogenesis, wound healing, fibrosis, autoimmune and metabolic disorders, and cancer. The potential functions of mast cells in many of these settings is thought to reflect their ability to secrete, upon appropriate activation by a range of immune or non-immune stimuli, a broad spectrum of cytokines (including many chemokines) and growth factors, with potential autocrine, paracrine, local, and systemic effects. In this review, we summarize the evidence indicating which cytokines and growth factors can be produced by various populations of rodent and human mast cells in response to particular immune or non-immune stimuli, and comment on the proven or potential roles of such mast cell products in health and disease.

Human mast cells and basophils-How are they similar how are they different?

Mast cells and basophils are key contributors to allergies and other inflammatory diseases since they are the most prominent source of histamine as well as numerous additional inflammatory mediators which drive inflammatory responses. However, a closer understanding of their precise roles in allergies and other pathological conditions has been marred by the considerable heterogeneity that these cells display, not only between mast cells and basophils themselves but also across different tissue locations and species. While both cell types share the ability to rapidly degranulate and release histamine following high-affinity IgE receptor cross-linking, they differ markedly in their ability to either react to other stimuli, generate inflammatory eicosanoids or release immunomodulating cytokines and chemokines. Furthermore, these cells display considerable pharmacological heterogeneity which has stifled attempts to develop more effective anti-allergic therapies. Mast cell- and basophil-specific transcriptional profiling, at rest and after activation by innate and adaptive stimuli, may help to unravel the degree to which these cells differ and facilitate a clearer understanding of their biological functions and how these could be targeted by new therapies.

Changing the threshold-Signals and mechanisms of mast cell priming

Mast cells play a key role in allergy and other inflammatory diseases involving engagement of multivalent antigen with IgE bound to high-affinity IgE receptors (FcεRIs). Aggregation of FcεRIs on mast cells initiates a cascade of signaling events that eventually lead to degranulation, secretion of leukotrienes and prostaglandins, and cytokine and chemokine production contributing to the inflammatory response. Exposure to pro-inflammatory cytokines, chemokines, bacterial and viral products, as well as some other biological products and drugs, induces mast cell transition from the basal state into a primed one, which leads to enhanced response to IgE-antigen complexes. Mast cell priming changes the threshold for antigen-mediated activation by various mechanisms, depending on the priming agent used, which alone usually do not induce mast cell degranulation. In this review, we describe the priming processes induced in mast cells by various cytokines (stem cell factor, interleukins-4, -6 and -33), chemokines, other agents acting through G protein-coupled receptors (adenosine, prostaglandin E₂ , sphingosine-1-phosphate, and β-2-adrenergic receptor agonists), toll-like receptors, and various drugs affecting the cytoskeleton. We will review the current knowledge about the molecular mechanisms behind priming of mast cells leading to degranulation and cytokine production and discuss the biological effects of mast cell priming induced by several cytokines.

Targeting mast cell as a neuroprotective strategy

Background: Mast cells (MCs) are perivascularly located immune cells of haematopoietic origin. Emerging evidences suggest that the activation of MCs play important roles in the pathogenesis of blood brain barrier disruption, neuroinflammation, and neurodegeneration. Objectives: In this review, we aimed to discuss the detrimental effects of MCs in response to various types of brain injury, as well as the therapeutic potential and neuroprotective effects of targeting the activation and degranulation of MCs, particularly in the management of the acute phase. Methods: An extensive online literature search was conducted through Pubmed/Central on March 2018. Then, we comprehensively summarized the effects of the activation of brain MCs in acute brain injury along with current pharmacological strategies targeting at the activation of MCs. Results: The review of the current literature indicated that the activation and degranulation of brain MCs significantly contribute to the acute pathological process following different types of brain injury including focal and global cerebral ischaemia, intracerebral haemorrhage, subarachnoid haemorrhage, and traumatic brain injury. Conclusions: Brain MCs significantly contribute to the acute pathological processes following brain injury. In that regard, targeting brain MCs may provide a novel strategy for neuroprotection.

Prostaglandin D2 receptor antagonists in allergic disorders: safety, efficacy, and future perspectives

INTRODUCTION

Prostaglandin D₂ (PGD₂) is a major cyclooxygenase mediator that is synthesized by activated human mast cells and other immune cells. The biological effects of PGD₂ are mediated by D-prostanoid (DP₁), DP₂ (CRTH2) and thromboxane prostanoid (TP) receptors that are expressed on several immune and non-immune cells involved in allergic inflammation. PGD₂ exerts various proinflammatory effects relevant to the pathophysiology of allergic disorders. Several selective, orally active, DP₂ receptor antagonists and a small number of DP₁ receptor antagonists are being developed for the treatment of allergic disorders.

AREAS COVERED

The role of DP₂ and DP₁ receptor antagonists in the treatment of asthma and allergic rhinitis.

EXPERT OPINION

Head-to-head studies that compare DP₁ antagonists with the standard treatment for allergic rhinitis are necessary to verify the role of these novel drugs as mono- or combination therapies. Further clinical trials are necessary to verify whether DP₂ antagonists as monotherapies or, more likely, as add-on therapies, will be effective for the treatment of different phenotypes of adult and childhood asthma. Long-term studies are necessary to evaluate the safety of targeted anti-PGD₂ treatments.

Progression in migraine: Role of mast cells and pro-inflammatory and anti-inflammatory cytokines

Migraine is a common painful neurovascular disorder usually associated with several symptoms, such as photophobia, phonophobia, nausea, vomiting and inflammation, and involves immune cells. Mast cells (MCs) are immune cells derived from hematopoietic pluripotent stem cells which migrate and mature close to epithelial, blood vessels, and nerves. In almost all vascularized tissues there are MCs that produce, contain and release biologically active products including cytokines, arachidonic acid compounds, and proteases. In addition, MCs participate in innate and adaptive immune responses. Innate responses in the central nervous system (CNS) occur during neuroinflammatory phenomena, including migraine. Antigens found in the environment have a crucial role in inflammatory response, causing a broad range of diseases including migraine. They can be recognized by several innate immune cells, such as macrophages, microglia, dendritic cells and MCs, which can be activated trough Toll-like receptor (TLR) signaling. MCs reside close to primary nociceptive neurons, associate with nerves, and are capable of triggering local inflammation. MCs are involved in the pathophysiology of various tissues and organs, especially where there is an increase of angiogenesis. Activated MCs release preformed mediators include histamine, heparin, proteases (tryptase, chimase), hydrolases, cathepsin, carboxypeptidases, and peroxidase, and they also generate pro-inflammatory cytokines/chemokines. In addition, activated macrophages, microglia and MCs in the CNS release pro-inflammatory cytokines which provoke an increase of arachidonic acid product levels and lead to migraine and other neurological manifestations including fatigue, nausea, headaches and brain fog. Innate immunity and pro-inflammatory interleukin (IL)-1 cytokine family members can be inhibited by IL-37, a relatively new member of the IL-1 family. In this article, we report that some pro-inflammatory cytokines inducing migraine may be inhibited by IL-37, a natural suppressor of inflammation, and innate and acquired immunity.

Professional and 'Amateur' Antigen-Presenting Cells In Type 2 Immunity

Dendritic cells (DCs) are critical for the activation of naïve CD4⁺ T cells and are considered professional antigen-presenting cells (APCs), as are macrophages and B cells. Recently, several innate type 2 immune cells, such as basophils, mast cells (MCs), eosinophils, and innate type 2 lymphocytes (ILC2), have also emerged as harboring APC behavior. Through surface expression or transfer of peptide-loaded MHCII, expression of costimulatory and co-inhibitory molecules, as well as the secretion of polarizing cytokines, these innate cells can extensively communicate with effector and regulatory CD4⁺ T cells. An exciting new concept is that the complementary tasks of these 'amateur' APCs contribute to shaping and regulating adaptive immunity to allergens and helminths, often in collaboration with professional APCs.

Effect of Syringic acid on antioxidant biomarkers and associated inflammatory markers in mice model of asthma

Asthma is termed as the induction of chronic inflammation in the airway lumen of lungs due to accumulation of inflammatory cells which affects normal breathing process. Prolonged accumulation of inflammatory cells leads to oxidative stress and suppression of antioxidant activities. Therefore, in our present investigation, a potential phenolic compound, Syringic acid was tested for the suppression of inflammatory markers toward an antiasthmatic activity in ovalbumin (OVA)-induced asthmatic mice model. As a result, the Syringic acid treatment was found to suppress the inflammatory cells; eosinophil, neutrophil, macrophage, lymphocyte, and other inflammatory markers including IL-4, IL-5, IL-13, and TNF-α in the BALF of OVA-induced asthmatic mice. Similarly, IgE levels were significantly reduced in the blood serum of Syringic acid treated mice groups. In this context, the IFN-γ levels were found enhanced in the BALF of Syringic acid treated asthmatic mice groups, expressing an anti-inflammatory response. Enzymatic and nonenzymatic antioxidants such as SOD, CAT, and GSH levels were found high in the Syringic acid treatment than the asthmatic control group, which depicts the antioxidant response of Syringic acid on asthmatic groups. Intriguingly, the ROS, NO₂ , NO₃ , and MDA levels were inhibited in the BALF of Syringic acid treated mice groups. The airway hyper-reactivity (AHR) was comparatively normal in the Syringic acid treatment as it was severe in the case of asthmatic control group. Consequently, the effect of Syringic acid is prominent in the treatment of asthma by controlling the accumulation of inflammatory cells, other inflammatory markers along with enhancement of antioxidant markers, suppression of ROS and controlling airway hyperreactivity. Hence, Syringic acid may be recommended for clinical trials in the treatment of asthma.

Hepatic cytochrome P450 metabolism suppressed by mast cells in type 1 allergic mice

Mast cells and Kupffer cells secrete interleukin (IL)-1β, interferon (IFN)-γ, and tumor necrosis factor (TNF)-α, which stimulate excess nitric oxide (NO) producing-inducible NO synthase (iNOS). Unlike Kupffer cells, immunoglobulin E-sensitized mast cells elicit sustained NO production. We investigated the participation of mast cell-released NO and cytokine-derived iNOS activation in type 1 allergy-suppressed hepatic cytochrome P450 (CYP) metabolism. Aminoguanidine, a selective iNOS inhibitor, completely suppressed serum nitrate plus nitrite (NOx) concentrations after primary and secondary sensitization of ICR mice and markedly attenuated allergy-suppressed hepatic CYP1A2, CYP2C, CYP2E1, and CYP3A activities. In the liver, primary and secondary sensitization enhanced iNOS-stimulating IFN-γ (5-15-fold) and TNF-α (3-5-fold) mRNA levels more than IL-1β (2-fold) and F4/80-positive Kupffer cell (2-fold) mRNA levels. When mast cell-deficient (-/-) mice were sensitized, hepatic CYP activities were not suppressed. Serum NOx levels in the sensitized -/- mice were similar with those in saline-treated ICR and -/- mice. In the liver of -/- mice, secondary sensitization markedly enhanced mRNA expression of iNOS (20-fold), IFN-γ (15-fold), and TNF-α (3-fold). However, hepatic total NOS activities in -/- mice were not significantly different between saline treatment and sensitization. Similarly, primary and secondary ICR mice did not significantly enhance total NOS activities in the liver and hepatocytes. The total NOS activities observed did not relate to the high levels of iNOS, IFN-γ, and TNF-α mRNA in the liver. Hepatic c-kit-positive mast cells in sensitized ICR mice were maintained at control levels. Therefore, our data suggest that mast cell-released NO participates in type 1 allergy-suppressed CYP1A2, CYP2C, CYP2E1, and CYP3A metabolism.

Immunobiology of Inherited Muscular Dystrophies

The immune response to acute muscle damage is important for normal repair. However, in chronic diseases such as many muscular dystrophies, the immune response can amplify pathology and play a major role in determining disease severity. Muscular dystrophies are inheritable diseases that vary tremendously in severity, but share the progressive loss of muscle mass and function that can be debilitating and lethal. Mutations in diverse genes cause muscular dystrophy, including genes that encode proteins that maintain membrane strength, participate in membrane repair, or are components of the extracellular matrix or the nuclear envelope. In this article, we explore the hypothesis that an important feature of many muscular dystrophies is an immune response adapted to acute, infrequent muscle damage that is misapplied in the context of chronic injury. We discuss the involvement of the immune system in the most common muscular dystrophy, Duchenne muscular dystrophy, and show that the immune system influences muscle death and fibrosis as disease progresses. We then present information on immune cell function in other muscular dystrophies and show that for many muscular dystrophies, release of cytosolic proteins into the extracellular space may provide an initial signal, leading to an immune response that is typically dominated by macrophages, neutrophils, helper T-lymphocytes, and cytotoxic T-lymphocytes. Although those features are similar in many muscular dystrophies, each muscular dystrophy shows distinguishing features in the magnitude and type of inflammatory response. These differences indicate that there are disease-specific immunomodulatory molecules that determine response to muscle cell damage caused by diverse genetic mutations. © 2018 American Physiological Society. Compr Physiol 8:1313-1356, 2018.

Mast cells in early rheumatoid arthritis associate with disease severity and support B cell autoantibody production

OBJECTIVES

Mast cells (MCs) are involved in the pathogenesis of rheumatoid arthritis (RA). However, their contribution remains controversial. To establish their role in RA, we analysed their presence in the synovium of treatment-naïve patients with early RA and their association and functional relationship with histological features of synovitis.

METHODS

Synovial tissue was obtained by ultrasound-guided biopsy from treatment-naïve patients with early RA (n=99). Immune cells (CD3/CD20/CD138/CD68) and their relationship with CD117⁺MCs in synovial tissue were analysed by immunohistochemistry (IHC) and immunofluorescence (IF). The functional involvement of MCs in ectopic lymphoid structures (ELS) was investigated in vitro, by coculturing MCs with naïve B cells and anticitrullinated protein antibodies (ACPA)-producing B cell clones, and in vivo in interleukin-27 receptor alpha (IL27ra)-deficient and control mice during antigen-induced arthritis (AIA).

RESULTS

High synovial MC counts are associated with local and systemic inflammation, autoantibody positivity and high disease activity. IHC/IF showed that MCs reside at the outer border of lymphoid aggregates. Furthermore, human MCs promote the activation and differentiation of naïve B cells and induce the production of ACPA, mainly via contact-dependent interactions. In AIA, synovial MC numbers increase in IL27ra deficient mice, in association with ELS and worse disease activity.

CONCLUSIONS

Synovial MCs identify early RA patients with a severe clinical form of synovitis characterised by the presence of ELS.

Positive and Negative Regulatory Roles of C-Terminal Src Kinase (CSK) in FcεRI-Mediated Mast Cell Activation, Independent of the Transmembrane Adaptor PAG/CSK-Binding Protein

C-terminal Src kinase (CSK) is a major negative regulator of Src family tyrosine kinases (SFKs) that play critical roles in immunoreceptor signaling. CSK is brought in contiguity to the plasma membrane-bound SFKs via binding to transmembrane adaptor PAG, also known as CSK-binding protein. The recent finding that PAG can function as a positive regulator of the high-affinity IgE receptor (FcεRI)-mediated mast cell signaling suggested that PAG and CSK have some non-overlapping regulatory functions in mast cell activation. To determine the regulatory roles of CSK in FcεRI signaling, we derived bone marrow-derived mast cells (BMMCs) with reduced or enhanced expression of CSK from wild-type (WT) or PAG knockout (KO) mice and analyzed their FcεRI-mediated activation events. We found that in contrast to PAG-KO cells, antigen-activated BMMCs with CSK knockdown (KD) exhibited significantly higher degranulation, calcium response, and tyrosine phosphorylation of FcεRI, SYK, and phospholipase C. Interestingly, FcεRI-mediated events in BMMCs with PAG-KO were restored upon CSK silencing. BMMCs with CSK-KD/PAG-KO resembled BMMCs with CSK-KD alone. Unexpectedly, cells with CSK-KD showed reduced kinase activity of LYN and decreased phosphorylation of transcription factor STAT5. This was accompanied by impaired production of proinflammatory cytokines and chemokines in antigen-activated cells. In line with this, BMMCs with CSK-KD exhibited enhanced phosphorylation of protein phosphatase SHP-1, which provides a negative feedback loop for regulating phosphorylation of STAT5 and LYN kinase activity. Furthermore, we found that in WT BMMCs SHP-1 forms complexes containing LYN, CSK, and STAT5. Altogether, our data demonstrate that in FcεRI-activated mast cells CSK is a negative regulator of degranulation and chemotaxis, but a positive regulator of adhesion to fibronectin and production of proinflammatory cytokines. Some of these pathways are not dependent on the presence of PAG.

Regulatory T Cells and Acute Lung Injury: Cytokines, Uncontrolled Inflammation, and Therapeutic Implications

Acute respiratory distress syndrome/acute lung injury (ALI) was described in 1967. The uncontrolled inflammation is a central issue of the syndrome. The regulatory T cells (Tregs), formerly known as suppressor T cells, are a subpopulation of T cells. Tregs indirectly limits immune inflammation-inflicted tissue damage by employing multiple mechanisms and creating the appropriate immune environment for successful tissue repair. And it plays a central role in the resolution of ALI. Accordingly, for this review, we will focus on Treg populations which are critical for inflammatory immunity of ALI, and the effect of interaction between Treg subsets and cytokines on ALI. And then explore the possibility of cytokines as beneficial factors in inflammation resolution of ALI.

Isolation of Peritoneum-derived Mast Cells and Their Functional Characterization with Ca2+-imaging and Degranulation Assays

Mast cells (MCs), as a part of the immune system, play a key role in defending the host against several pathogens and in the initiation of the allergic immune response. The activation of MCs via the cross-linking of surface IgE bound to high affinity IgE receptor (FcεRI), as well as through the stimulation of several other receptors, initiates the rise of the free intracellular Ca²⁺ level ([Ca²⁺]i) that promotes the release of inflammatory and allergic mediators. The identification of molecular constituents involved in these signaling pathways is crucial for understanding the regulation of MC function. In this article, we describe a protocol for the isolation of murine connective tissue type MCs by peritoneal lavage and cultivation of peritoneal MCs (PMCs). Cultures of MCs from various knockout mouse models by this methodology represent a useful approach to the identification of proteins involved in MC signaling pathways. In addition, we also describe a protocol for single cell Fura-2 imaging as an important technique for the quantification of Ca²⁺ signaling in MCs. Fluorescence-based monitoring of [Ca²⁺]i is a reliable and commonly used approach to study Ca²⁺ signaling events, including store-operated calcium entry, which is of utmost importance for MC activation. For the analysis of MC degranulation, we describe a β-hexosaminidase release assay. The amount of β-hexosaminidase released into the culture medium is considered as a degranulation marker for all three different secretory subsets described in MCs. β-hexosaminidase can easily be quantified by its reaction with a colorigenic substrate in a microtiter plate colorimetric assay. This highly reproducible technique is cost-effective and requires no specialized equipment. Overall, the provided protocol demonstrates a high yield of MCs expressing typical MC surface markers, displaying typical morphological and phenotypic features of MCs, and demonstrating highly reproducible responses to secretagogues in Ca²⁺-imaging and degranulation assays.

Potential therapeutic use of IL-37: a key suppressor of innate immunity and allergic immune responses mediated by mast cells

The host response to either exogenous or endogenous insults produces a series of changes, characterized by alterations in immunological functions and generation of mediators called cytokines which include the interleukin-1 (IL-1) family members. IL-1 acts as a hormone mediating the host responses to infection and inflammation. Blocking inflammatory IL-1 family members can be effective against inflammatory disorders, including allergies. IL-37, (formerly IL-1 family member 7), emerges as an inhibitor of innate and adaptive immunity by reducing circulating and organ cytokine levels. IL-37, mainly expressed in dendritic cells, monocytes, and plasma cells after TIR ligand activation, inhibits inflammatory cytokines and augments the level of anti-inflammatory IL-10. IL-37 is involved in allergic reaction and its expression in dendritic cells causes tollerogenicity and inhibits inflammatory response. Mast cells (MCs) are ubiquitous in the body, reside in numerous mucosal tissues, and are mediators of allergic reaction, and innate and adaptive immunity. MCs are important regulators of cytokine generation in the course of inflammatory responses and allergy, and are implicated in the pathophysiology of allergic asthma. Cysteine protease caspase-1 activation leads to the cleavage of pro-form of IL-1 into active mature IL-1 which is present in stimulated and unstimulated inflammatory MCs. Inflammatory cytokine inhibition, along with the augmentation of anti-inflammatory IL-10 by IL-37, is certainly beneficial and improves the pathogenesis of allergic disorders. However, in these studies, the exact mechanism(s) of IL-37-induced anti-inflammatory and anti-allergic activity along with its side effect(s) remain to be determined.

Mast cells participate in allograft rejection: can IL-37 play an inhibitory role?

OBJECTIVE

The aim of this study was to evaluate the role of mast cells (MCs) in allograft rejection, eventually inhibited by IL-37. Immune cells including MCs participate in allograft rejection by generating IL-1, IL-33, TNF and other cytokines.

METHODS

We evaluated allograft rejection on the experience of our experimental data and using the relevant literature.

RESULTS

MCs are involved in initiation and regulation of innate and adaptive immune responses-pathways. MCs are important pro-inflammatory cells which express high-affinity receptor FceRI and can be activated by IgE and some pro-inflammatory cytokines, such as IL-1 and IL-33. The cross-linkage of high affinity IgE receptor on MCs by antigen ligation has a crucial role in allergy, asthma, anaphylaxis, cancer and allograft rejection. MCs mediate immunity in organ transplant, leading to the activation of allospecific T cells implicated in the rejection and generate pro-inflammatory cytokines/chemokines. IL-1 pro-inflammatory cytokine family members released by MCs mediate allograft rejection and inflammation. IL-37 is also an IL-1 family member generated by macrophage cell line in small amounts, which binds to IL-18Rα and produces an anti-inflammatory effect. IL-37 provokes the inhibition of TLR signaling, TLR-induced mTOR and (MyD88)-mediated responses, suppressing pro-inflammatory IL-1 family members and increasing IL-10.

CONCLUSION

IL-37 inhibition offers the opportunity to immunologically modulate MCs, by suppressing their production of IL-1 family members and reducing the risk of allograft rejection, resulting as a potential good therapeutic new cytokine. Here, we report the relationship between inflammatory MCs, allograft rejection and pro-inflammatory and anti-inflammatory IL-37.

Approaches to target IgE antibodies in allergic diseases

IgE is the antibody isotype found at the lowest concentration in the circulation. However IgE can undeniably play an important role in mediating allergic reactions; best exemplified by the clinical benefits of anti-IgE monoclonal antibody (omalizumab) therapy for some allergic diseases. This review will describe our current understanding of the interactions between IgE and its main receptors FcεRI and CD23 (FcεRII). We will review the known and potential functions of IgE in health and disease: in particular, its detrimental roles in allergic diseases and chronic spontaneous urticaria, and its protective functions in host defense against parasites and venoms. Finally, we will present an overview of the drugs that are in clinical development or have therapeutic potential for IgE-mediated allergic diseases.

Genetic and Imaging Approaches Reveal Pro-Inflammatory and Immunoregulatory Roles of Mast Cells in Contact Hypersensitivity

Contact hypersensitivity (CHS) is a common T cell-mediated skin disease induced by epicutaneous sensitization to haptens. Mast cells (MCs) are widely deployed in the skin and can be activated during CHS responses to secrete diverse products, including some with pro-inflammatory and anti-inflammatory functions. Conflicting results have been obtained regarding pathogenic versus protective roles of MCs in CHS, and this has been attributed in part to the limitations of certain models for studying MC functions in vivo. This review discusses recent advances in the development and analysis of mouse models to investigate the roles of MCs and MC-associated products in vivo. Notably, fluorescent avidin-based two-photon imaging approaches enable in vivo selective labeling and simultaneous tracking of MC secretory granules (e.g., during MC degranulation) and MC gene activation by real-time longitudinal intravital microscopy in living mice. The combination of such genetic and imaging tools has shed new light on the controversial role played by MCs in mouse models of CHS. On the one hand, they can amplify CHS responses of mild severity while, on the other hand, can limit the inflammation and tissue injury associated with more severe or chronic models, in part by representing an initial source of the anti-inflammatory cytokine IL-10.

Repositioning of anti-cancer drug candidate, AZD7762, to an anti-allergic drug suppressing IgE-mediated mast cells and allergic responses via the inhibition of Lyn and Fyn

Mast cells are critical effector cells in IgE-mediated allergic responses. The aim of this study was to investigate the anti-allergic effects of 3-[(aminocarbonyl)amino]-5-(3-fluorophenyl)-N-(3S)-3-piperidinyl-2-thiophenecarboxamide (AZD7762) in vitro and in vivo. AZD7762 inhibited the antigen-stimulated degranulation from RBL-2H3 (IC₅₀, ∼27.9 nM) and BMMCs (IC₅₀, ∼99.3 nM) in a dose-dependent manner. AZD7762 also inhibited the production of TNF-α and IL-4. As the mechanism of its action, AZD7762 inhibited the activation of Syk and its downstream signaling proteins, such as Linker of activated T cells (LAT), phospholipase (PL) Cγ1, Akt, and mitogen-activated protein (MAP) kinases (Erk1/2, p38, and JNK) in mast cells. In in vitro protein kinase assay, AZD7762 inhibited the activity of Lyn and Fyn kinases, which are important for the activation of Syk in mast cells. Furthermore, AZD7762 also suppressed the degranulation of LAD2 human mast cells (IC₅₀, ∼49.9 nM) and activation of Syk in a dose-dependent manner. As observed in experiments with mast cells in vitro, AZD7762 inhibited antigen-mediated passive cutaneous anaphylaxis in mice (ED₅₀, ∼35.8 mg/kg). Altogether, these results suggest that AZD7762 could be used as a new therapeutic agent for mast cell-mediated allergic diseases.

Impact of Fungi on Immune Responses

Spores and fungal fragments found in indoor and outdoor environments originate from opportunistic fungi and they can contribute to inflammatory responses, causing a broad range of symptoms. Papers were selected and reviewed with an emphasis on the molecular mechanisms involved in the effect of fungi on immune cells, especially mast cells (MCs). Fungi can bind to antibodies and complement them, allowing them to be recognized by cells of the innate immune system, including macrophages, dendritic cells, and MCs, which are then stimulated via Toll-like receptor signaling. Fungi can cause diseases mediated by MCs and aggravate allergic inflammation. Immunosuppressed subjects can be particularly susceptible to developing diseases caused by opportunistic fungi. Mold also liberates mycotoxins that could be on volatile spores and stimulate MCs to secrete pro-inflammatory cytokines/chemokines, but this mechanism is not known. Fungi can activate the immune system directly or through mycotoxins, leading to stimulation of immune cells and chronic neuroinflammatory symptoms. Some of these processes may be inhibited by the new anti-inflammatory cytokine interleukin 37.

Controlling Mast Cell Activation and Homeostasis: Work Influenced by Bill Paul That Continues Today

Mast cells are tissue resident, innate immune cells with heterogenous phenotypes tuned by cytokines and other microenvironmental stimuli. Playing a protective role in parasitic, bacterial, and viral infections, mast cells are also known for their role in the pathogenesis of allergy, asthma, and autoimmune diseases. Here, we review factors controlling mast cell activation, with a focus on receptor signaling and potential therapies for allergic disease. Specifically, we will discuss our work with FcεRI and FγR signaling, IL-4, IL-10, and TGF-β1 treatment, and Stat5. We conclude with potential therapeutics for allergic disease. Much of these efforts have been influenced by the work of Bill Paul. With many mechanistic targets for mast cell activation and different classes of therapeutics being studied, there is reason to be hopeful for continued clinical progress in this area.

Platelet-Activating Factor-Induced Reduction in Contact Hypersensitivity Responses Is Mediated by Mast Cells via Cyclooxygenase-2-Dependent Mechanisms

Platelet-activating factor (PAF) stimulates numerous cell types via activation of the G protein-coupled PAF receptor (PAFR). PAFR activation not only induces acute proinflammatory responses, but it also induces delayed systemic immunosuppressive effects by modulating host immunity. Although enzymatic synthesis and degradation of PAF are tightly regulated, oxidative stressors, such as UVB, chemotherapy, and cigarette smoke, can generate PAF and PAF-like molecules in an unregulated fashion via the oxidation of membrane phospholipids. Recent studies have demonstrated the relevance of the mast cell (MC) PAFR in PAFR-induced systemic immunosuppression. The current study was designed to determine the exact mechanisms and mediators involved in MC PAFR-mediated systemic immunosuppression. By using a contact hypersensitivity model, the MC PAFR was not only found to be necessary, but also sufficient to mediate the immunosuppressive effects of systemic PAF. Furthermore, activation of the MC PAFR induces MC-derived histamine and PGE₂ release. Importantly, PAFR-mediated systemic immunosuppression was defective in mice that lacked MCs, or in MC-deficient mice transplanted with histidine decarboxylase- or cyclooxygenase-2-deficient MCs. Lastly, it was found that PGs could modulate MC migration to draining lymph nodes. These results support the hypothesis that MC PAFR activation promotes the immunosuppressive effects of PAF in part through histamine- and PGE₂-dependent mechanisms.

Ovarian mast cells migrate toward ovary-fimbria connection in neonatal MRL/MpJ mice

MRL/MpJ mice have abundant ovarian mast cells (MCs) as compared with other strains at postnatal day 0 (P0); however, they sharply decrease after birth. These ovarian MCs, particularly beneath the ovarian surface epithelium (SE), which express mucosal MC (MMC) marker, might participate in early follicular development. This study investigated the changes in spatiotemporal distribution of MCs in the perinatal MRL/MpJ mouse ovaries. At P0 to P7, the MCs were densely localized to the ovary, especially their caudomedial region around the ovary-fimbria connection. The neonatal ovarian MCs showed intermediate characteristics of MMC and connective tissue MC (CTMC), and the latter phenotype became evident with aging. However, the expression ratio of the MMC to CTMC marker increased from P0 to P4 in the MRL/MpJ mouse ovary. Similarly, the ratio of MCs facing SE to total MC number increased with aging, although the number of ovarian MCs decreased, indicating the relative increase in MMC phenotypes in the early neonatal ovary. Neither proliferating nor apoptotic MCs were found in the MRL/MpJ mouse ovaries. The parenchymal cells surrounding MCs at ovary-fimbria connection showed similar molecular expression patterns (E-cadherin⁺/Foxl2^-/Gata4⁺) as that of the ovarian surface epithelial cells. At P2, around the ovary-fimbria connection, c-kit^- immature oocytes formed clusters called nests, and some MCs localized adjacent to c-kit^- oocytes within the nests. These results indicated that in postnatal MRL/MpJ mice, ovarian MCs changed their distribution by migrating toward the parenchymal cells composing ovary-fimbria connection, which possessed similar characteristics to the ovarian surface epithelium. Thus, we elucidated the spatiotemporal alterations of the ovarian MCs in MRL/MpJ mice, and suggested their importance during the early follicular development by migrating toward the ovary-fimbria connection. MRL/MpJ mice would be useful to elucidate the relationship between neonatal immunity and reproductive systems.

Innate defense regulator IDR-1018 activates human mast cells through G protein-, phospholipase C-, MAPK- and NF-ĸB-sensitive pathways

Host defense (antimicrobial) peptides not only display antimicrobial activities against numerous pathogens but also exert a broader spectrum of immune-modulating functions. Innate defense regulators (IDRs) are a class of host defense peptides synthetically developed from natural or endogenous cationic host defense peptides. Of the IDRs developed to date, IDR-1018 is more efficient not only in killing bacteria but also in regulating the various functions of macrophages and neutrophils and accelerating the wound healing process. Because mast cells intimately participate in wound healing and a number of host defense peptides involved in wound healing are also known to activate mast cells, this study aimed to investigate the effects of IDR-1018 on mast cell activation. Here, we showed that IDR-1018 induced the degranulation of LAD2 human mast cells and caused their production of leukotrienes, prostaglandins and various cytokines and chemokines, including granulocyte-macrophage colony-stimulating factor, interleukin-8, monocyte chemoattractant protein-1 and -3, macrophage-inflammatory protein-1α and -1β, and tumor necrosis factor-α. Furthermore, IDR-1018 increased intracellular calcium mobilization and induced mast cell chemotaxis. The mast cell activation was markedly suppressed by pertussis toxin, U-73122, U0126, SB203580, JNK inhibitor II, and NF-κB activation inhibitor II, suggesting the involvement of G-protein, phospholipase C, ERK, p38, JNK and NF-κB pathways, respectively, in IDR-1018-induced mast cell activation. Notably, we confirmed that IDR-1018 caused the phosphorylation of MAPKs and IκB. Altogether, the current study suggests a novel immunomodulatory role of IDR-1018 through its ability to recruit and activate human mast cells at the sites of inflammation and wounds.

HIGHLIGHTS

We report that IDR-1018 stimulates various functions of human mast cells. IDR-1018-induced mast cell activation is mediated through G protein, PLC, MAPK and NF-κB pathways. IDR-1018 will be a useful therapeutic agent for wound healing.

Intestinal mast cells and their function

Mast cells develop from the CD34⁺ precursor cells in bone marrow, are activated in the gut, and can release a variety of bioactive mediators, including histamine, 5-hydroxytryptamine, and tryptase. They play a crucial role in intestinal innate and adaptive immunity because of their diverse secretory granules and unique mature characteristics. Many studies have shown that a variety of intestinal diseases have close relationship with mast cells, especially inflammatory bowel disease, irritable bowel syndrome, and intestinal allergic diseases, which has attracted extensive attention. In this paper, we review the function and mechanism of intestinal mast cells and their role in the treatment of related clinical diseases.

Inhibitory effects of methamphetamine on mast cell activation and cytokine/chemokine production stimulated by lipopolysaccharide in C57BL/6J mice

Previous studies have demonstrated that methamphetamine (MA) influences host immunity; however, the effect of MA on lipopolysaccharide (LPS)-induced immune responses remains unknown. Mast cells (MCs) are considered to serve an important role in the innate and acquired immune response, but it remains unknown whether MA modulates MC activation and LPS-stimulated cytokine production. The present study aimed to investigate the effect of MA on LPS-induced MC activation and the production of MC-derived cytokines in mice. Markers for MC activation, including cluster of differentiation 117 and the type I high affinity immunoglobulin E receptor, were assessed in mouse intestines. Levels of MC-derived cytokines in the lungs and thymus were also examined. The results demonstrated that cytokines were produced in the bone marrow-derived mast cells (BMMCs) of mice. The present study demonstrated that MA suppressed the LPS-mediated MC activation in mouse intestines. MA also altered the release of MC cytokines in the lung and thymus following LPS stimulation. In addition, LPS-stimulated cytokines were decreased in the BMMCs of mice following treatment with MA. The present study demonstrated that MA may regulate LPS-stimulated MC activation and cytokine production.

The 100 most influential publications in asthma from 1960 to 2017: A bibliometric analysis

BACKGROUND

The area of asthma medicine has produced a large volume of important clinical and scientific papers that can be found in those most influential journals. The purpose of our study was to identify the 100 most cited papers in asthma research and to analyze their characteristics.

METHODS

We used the Institute for Scientific Information Web of Knowledge Database to identify the most frequently cited articles published from 1960 to December 2017. Original articles and reviews were included in the study. The 100 top-cited articles were then analyzed with regard to number of citations, publication year, journals, institution, research type and field, authors and countries of authors of publications.

RESULTS

The 100 top-cited articles in asthma were published between 1960 and 2011 with a median of 933 citations per article (range, 701-2947). The number of citations per article was greatest for articles published in the 1990s. The United States of America contributed most of the classic articles, followed by England. The leading institutions were Imperial College London, McMaster University, Erasmus University Rotterdam. The 100 top-cited articles were published in twenty-five journals, led by The New England Journal of Medicine (21 articles), followed by American Journal of Respiratory and Critical Care Medicine (19 articles), Lancet (11 articles), respectively. Among the 100 classics, 50% articles were clinical research articles.

CONCLUSIONS

Our study provides a historical perspective on the progress of research on asthma. Studies conducted in well-developed European countries and North America, published in high-impact journals had the highest citations.

Mast cells in neuropathic pain: an increasing spectrum of their involvement in pathophysiology

Mast cells are immunological cells that are diversely distributed in different parts of the body. Their role in various pathological conditions such as hypersensitivity, atherosclerosis, pulmonary hypertension, and male infertility has been reported by different scientists. Apart from these, a number of studies have shown their important role in pathogenesis of neuropathic pain of diverse aetiology. They have been found to release active mediators, primarily histamine and serotonin on degranulation in response to different stimuli including chemical, nerve damage, toxin or disease-related conditions. The mast cells stabilizer has shown pain attenuating effects by preventing degranulation of mast cells. Similarly, compound 48/80 (first dose 200 μg/100 g and after 6-h interval, second dose of 500 μg/100 g) caused the degranulation of the accumulated endoneurial histamine and 5-HT antagonists have shown pain relieving effects by attenuating the effects of histamine and serotonin, respectively. On the other hand, the mast cell degranulator compound 48/80 has shown dual action depending on its time of administration. The present review discusses the critical role of mast cells in the generation and maintenance of neuropathic pain in experimental models.

Ginsenoside Rg3 suppresses mast cell-mediated allergic inflammation via mitogen-activated protein kinase signaling pathway

Background

Ginsenoside Rg3 (G-Rg3) is the major bioactive ingredient of Panax ginseng and has many pharmacological effects, including antiadipogenic, antiviral, and anticancer effects. However, the effect of G-Rg3 on mast cell–mediated allergic inflammation has not been investigated.

Method

The antiallergic effects of G-Rg3 on allergic inflammation were evaluated using the human and rat mast cell lines HMC-1 and RBL-2H3. Antiallergic effects of G-Rg3 were detected by measuring cyclic adenosine monophosphate (cAMP), detecting calcium influx, and using real-time reverse transcription polymerase chain reaction, enzyme-linked immunosorbent assay, Western blotting, and in vivo experiments.

Results

G-Rg3 decreased histamine release from activated mast cells by enhancing cAMP levels and calcium influx. Proinflammatory cytokine production was suppressed by G-Rg3 treatment via regulation of the mitogen-activated protein kinases/nuclear factor-kappa B and receptor-interacting protein kinase 2 (RIP2)/caspase-1 signaling pathway in mast cells. Moreover, G-Rg3 protected mice against the IgE-mediated passive cutaneous anaphylaxis reaction and compound 48/80-induced anaphylactic shock.

Conclusion

G-Rg3 may serve as an alternative therapeutic agent for improving allergic inflammatory disorders.

Allergens displayed on virus-like particles are highly immunogenic but fail to activate human mast cells

BACKGROUND

The goal of allergen-specific immunotherapy is the induction of protective immune responses in the absence of anaphylactic reactions. We have previously shown that Fel d 1, the major cat allergen, displayed in a repetitive fashion on virus-like particles (VLPs) may fulfill these criteria. Specifically, Fel d 1 on VLPs induced strongly increased protective IgG responses compared to free allergen in mice while anaphylactic reactions were essentially abolished. Here we extend these findings to human mast cells and offer a mechanistic explanation for the reduced anaphylactic activity.

METHODS

We differentiated human mast cells in vitro from blood-derived stem cell progenitors and sensitized the cells with a monoclonal Fel d 1-specific IgE. We compared the capability of Fel d 1 to induce mast cell activation in its free form versus displayed on VLPs and we performed allergen binding studies by surface plasmon resonance as well as flow cytometry.

RESULTS

We show that free Fel d 1 induces degranulation of IgE-sensitized mast cells whereas Fel d 1 displayed on VLPs fails to induce mast cell activation. We demonstrate that this inability to activate mast cells is based on a biophysical as well as a biochemical mechanism. Firstly, Fel d 1 on VLPs showed a strongly impaired ability to bind to surface-bound IgE. Secondly, despite residual binding, repetitively displayed allergen on VLPs failed to cause mast cell activation.

CONCLUSION

These findings indicate that repetitively displaying allergens on VLPs increases their immunogenicity while reducing their potential to cause anaphylactic reactions by essentially eliminating IgE-mediated activation of mast cells.

Activated Mast Cells Mediate Low-Grade Inflammation in Type 2 Diabetes: Interleukin-37 Could Be Beneficial

Mast cells (MCs) promote guest immune responses to parasites and play a critical role in allergic and inflammatory reactions. Once they have been activated, MCs release highly inflammatory compounds that can provoke serious pathologic signs that can lead to death. MCs generate a number of preformed, de novo synthesized compounds and inflammatory cytokine/chemokine synthesis in response to the high-affinity (Kd=10^-10 M) immunoglobulin E receptor triggering. Circulating MC progenitors migrate into arterial intima and develop lesions, mediating inflammation. They are involved in several disorders, including metabolic diseases, such as type 2 diabetes mellitus, in which endothelial cells release several inflammatory compounds during acute and chronic vascular damage. Certain inflammatory cytokines, such as interleukin (IL)-1 and IL-33, not only are produced by MCs but also may activate them. These effects mediate systemic inflammatory responses in metabolic disorders. Proinflammatory cytokines, such as tumor necrosis factor, IL-33 and IL-6, secreted by MCs and other immune cells, contribute to insulin resistance by activating kinases. IL-37 (IL-1 family member 7), one of the latest cytokines discovered, binds the IL-18 receptor alpha (IL-18Rα) chain and suppresses innate and acquired immunity, with a therapeutic effect. It also inhibits cytokine levels, including IL-6, IL-18, IL-33, tumor necrosis factor and IL-1, and may improve insulin production and, therefore, the pathogenesis of diabetes, stroke and cardiovascular health. This describes a new concept of inhibition of and cure for inflammatory diseases. However, the safety, dosage and tolerability of this novel therapeutic agent, IL-37, still remains to be determined.

Activation of mast cells in skin abscess induced by Staphylococcus aureus (S. aureus) infection in mice

The skin abscess is a common inflammatory disease that occurs following the ubiquitous S. aureus infection. In our study, a skin abscess murine model was established and the dynamics of mast cells chemotaxing was evaluated. In the S. aureus-infected mice, severe infiltration of inflammatory cells in the dermis were observed, and mast cells were markedly accumulated in the skins. Besides, tryptase, the marker for mast cells activation, has a positive correlation with mast cell activity. The mast cells identified in the tissues were likely to be activated since they were associated with cell degranulation and the presence of tryptase. Our results suggested that mast cells and its mediator tryptase contribute to the inflammation of skin abscess induced by S. aureus infection.

Ameliorative effects of type-A procyanidins polyphenols from cinnamon bark in compound 48/80-induced mast cell degranulation

Allergic diseases are a significant health concern in developing countries. Type-A procyanidin polyphenols from cinnamon (Cinnamomum zeylanicum Blume) bark (TAPP-CZ) possesses antiasthmatic and antiallergic potential. The present study was aimed at the possible anti-allergic mechanism of TAPP-CZ against the compound 48/80 (C48/80)–induced mast cell degranulation in isolated rat peritoneal mast cells (RPMCs). TAPP-CZ (1, 3, 10, and 30 µg/ml) was incubated for 3 hours with isolated, purified RPMCs. The C48/80 (1 µg/ml) was used to induce mast cell degranulation. The mast cell viability was assessed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay whereas histamine, β-hexosaminidase (β-HEX), and interleukin-4 (IL-4) levels were determined in RPMCs. TAPP-CZ (3, 10, and 30 µg/ml) showed significant and dose-dependent decrease in a number of degranulated cells and levels of markers (histamine, β-HEX, and IL-4) as compared with C48/80 control. In conclusion, TAPP-CZ stabilizes mast cell and cause inhibition of the allergic markers such as histamine, IL-4, and β-HEX in IgE-mediated manner. The present study supports mast cell stabilization as a possible mechanism of action of TAPP-CZ against immune respiratory disorders such as asthma and allergic rhinitis.

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.

Palmitoylethanolamide Supplementation during Sensitization Prevents Airway Allergic Symptoms in the Mouse

One important risk factor for the development of asthma is allergen sensitization. Recent increasing evidence suggests a prominent role of mast cells in asthma pathophysiology. Since Palmitoylethanolamide (PEA), an endogenous lipid mediator chemically related to - and co-released with- the endocannabinoid anandamide, behaves as a local autacoid down-regulator of mast cell activation and inflammation, we explored the possible contribution of PEA in allergic sensitization, by using ovalbumin (OVA) as sensitizing agent in the mouse. PEA levels were dramatically reduced in the bronchi of OVA-treated animals. This effect was coupled to a significant up-regulation of CB₂ and GPR55 receptors, two of the proposed molecular PEA targets, in bronchi harvested from allergen-sensitized mice. PEA supplementation (10 mg/kg, 15 min before each allergen exposure) prevented OVA-induced bronchial hyperreactivity, but it did not affect IgE plasma increase. On the other hand, PEA abrogated allergen-induced cell recruitment as well as pulmonary inflammation. Evaluation of pulmonary sections evidenced a significant inhibitory action of PEA on pulmonary mast cell recruitment and degranulation, an effect coupled to a reduction of leukotriene C₄ production. These findings demonstrate that allergen sensitization negatively affects PEA bronchial levels and suggest that its supplementation has the potential to prevent the development of asthma-like features.

Contribution of Adipose Tissue to Development of Cancer

Solid tumor growth and metastasis require the interaction of tumor cells with the surrounding tissue, leading to a view of tumors as tissue-level phenomena rather than exclusively cell-intrinsic anomalies. Due to the ubiquitous nature of adipose tissue, many types of solid tumors grow in proximate or direct contact with adipocytes and adipose-associated stromal and vascular components, such as fibroblasts and other connective tissue cells, stem and progenitor cells, endothelial cells, innate and adaptive immune cells, and extracellular signaling and matrix components. Excess adiposity in obesity both increases risk of cancer development and negatively influences prognosis in several cancer types, in part due to interaction with adipose tissue cell populations. Herein, we review the cellular and noncellular constituents of the adipose "organ," and discuss the mechanisms by which these varied microenvironmental components contribute to tumor development, with special emphasis on obesity. Due to the prevalence of breast and prostate cancers in the United States, their close anatomical proximity to adipose tissue depots, and their complex epidemiologic associations with obesity, we particularly highlight research addressing the contribution of adipose tissue to the initiation and progression of these cancer types. Obesity dramatically modifies the adipose tissue microenvironment in numerous ways, including induction of fibrosis and angiogenesis, increased stem cell abundance, and expansion of proinflammatory immune cells. As many of these changes also resemble shifts observed within the tumor microenvironment, proximity to adipose tissue may present a hospitable environment to developing tumors, providing a critical link between adiposity and tumorigenesis. © 2018 American Physiological Society. Compr Physiol 8:237-282, 2018.