Syk inhibitors as treatment for allergic rhinitis

SYK identified by bioinformatics analysis promotes the proliferation of multiple myeloma

BACKGROUND

Despite recent advancements, the pathogenesis of multiple myeloma (MM) remains incompletely elucidated, with relapse and therapy resistance persisting as major clinical challenges, underscoring the imperative to identify novel therapeutic targets.

RESEARCH DESIGN AND METHODS

Differentially expressed genes were initially screened from the GSE6477 and GSE6691 datasets. Subsequent functional annotation and pathway enrichment analyses were conducted utilizing the DAVID bioinformatics platform. A protein-protein interaction network was constructed via the STRING database, followed by module analysis and hub genes identification through CytoHubba plugin. The biological significance of candidate genes was ultimately validated through ex vivo cellular functional assays and in vivo xenograft tumorigenesis experiments in murine models.

RESULTS

Bioinformatics analysis identified spleen tyrosine kinase (SYK) as the most prognostically significant candidate gene (p = 0.027). The SYK-specific inhibitor BAY61-3606 demonstrated time- (p < 0.05) and dose- (p < 0.01) dependent inhibition of MM cell viability, concomitant induction of G2/M phase cell cycle arrest (p < 0.001), and significant promotion of apoptosis (p < 0.05). In vivo experiments utilizing MM xenograft models demonstrated that BAY61-3606 administration significantly attenuated tumor growth kinetics (p < 0.05).

CONCLUSIONS

Our findings establish SYK as a therapeutic target in MM, thereby facilitating the development of innovative treatment strategies.

Ubiquitin-specific protease 13 regulates FcεRI-mediated mast cell activation and allergic inflammation via SYK protein modulation

Mast cells (MCs) are therapeutic targets for high-affinity IgE Fc receptors (FcεRI)-mediated allergic responses. Deubiquitinating enzymes (DUBs), including ubiquitin-specific protease 13 (USP13), are involved in multiple inflammatory processes. This study aims to reveal USP13's role in FcεRI-mediated MC activation and its underlying mechanisms. Our results showed USP10/13 inhibitor spautin-1 inhibited IgE-mediated MC activation, as evidenced by a reduction in the release of β-hexosaminidase (β-hex) and histamine and decreased expression and secretion of inflammatory cytokines. Spautin-1 also attenuated inflammatory processes in IgE-mediated passive cutaneous anaphylaxis (PCA) and ovalbumin (OVA)-induced active systemic anaphylaxis (ASA) models. Furthermore, knockdown of USP13 by short hairpin (sh)RNA diminished IgE-induced MC activation. Protein-protein interactions assays showed that USP13 interacted with the co-immunoprecipitated protein spleen tyrosine kinase (SYK) and deubiquitinated SYK. USP13 bound the kinase domain of SYK and removed its K63-linked polyubiquitination chain, yielding a more stable SYK protein. Importantly, 2-methoxyestradiol (2-Meth) was identified as a potential inhibitor of USP13 and inhibited FcεRI-mediated MC activation effectively in vitro and in vivo. In conclusion, it elucidated the molecular mechanism by which USP13 regulated SYK stability in MCs. The USP13-SYK axis may serve as a therapeutic target for treating FcεRI-mediated activation of MCs and associated inflammatory responses.

Terpenoids, a Rising Star in Bioactive Constituents for Alleviating Food Allergy: A Review about the Potential Mechanism, Preparation, and Application

Food allergies affect approximately 2.5% of the global population, with a notable increase in prevalence observed each year. Terpenoids, a class of natural bioactive constituents, have been widely utilized in the management of immune- and inflammation-related disorders, and their potential in alleviating food allergies is increasingly being recognized. This article summarizes various terpenoids derived from plant, fungal, and marine sources. Among them, triterpenoids, such as oleanolic acid, ursolic acid, and lupeol, possess the highest proportion and bioactivity in alleviating food allergy. Additionally, the mechanisms by which terpenoids may mitigate allergic diseases were categorically outlined, focusing on their roles in epithelial mucosal barrier function, immunomodulatory effects during the sensitization phase, inhibition of effector cells, oxidative stress, and regulation of microbial homeostasis. Finally, the advantages and limitations of natural extraction and artificial synthesis methods were compared, and the application of terpenoids in the food industry were also discussed. This article serves as a useful reference for the development of methods or functional foods based on terpenoids, which could represent a promising avenue for alleviating food allergy.

Chemical proteomics reveals the target landscape of 1,000 kinase inhibitors

Medicinal chemistry has discovered thousands of potent protein and lipid kinase inhibitors. These may be developed into therapeutic drugs or chemical probes to study kinase biology. Because of polypharmacology, a large part of the human kinome currently lacks selective chemical probes. To discover such probes, we profiled 1,183 compounds from drug discovery projects in lysates of cancer cell lines using Kinobeads. The resulting 500,000 compound-target interactions are available in ProteomicsDB and we exemplify how this molecular resource may be used. For instance, the data revealed several hundred reasonably selective compounds for 72 kinases. Cellular assays validated GSK986310C as a candidate SYK (spleen tyrosine kinase) probe and X-ray crystallography uncovered the structural basis for the observed selectivity of the CK2 inhibitor GW869516X. Compounds targeting PKN3 were discovered and phosphoproteomics identified substrates that indicate target engagement in cells. We anticipate that this molecular resource will aid research in drug discovery and chemical biology.

Aiming to IgE: Drug development in allergic diseases

The incidence of allergic disease significantly increases in recent decades, causing it become a major public health problem all over the world. The common allergic diseases such as allergic dermatitis, allergy rhinitis, allergic asthma and food allergy are mediated, at least in part, by immunoglobulin E (IgE), and so IgE acts as a central role in allergic diseases. IgE can interact with its high-affinity receptor (FcεRⅠ) which is primarily expressed on tissue-resident mast cells and circulating basophils, initiating intracellular signal transduction and then causing the activation and degranulation of mast cells and basophils. On the other hand, IgE interaction with its low-affinity receptor (CD23), can regulate various IgE-mediated immune responses including IgE-allergen complex presentation, IgE synthesis, the growth and differentiation of both B and T cells, and the secretion of pro-inflammatory mediators. With the deeper mechanism research for allergic diseases, new therapeutic strategies for interfering IgE are developed and receive a great attention. In this review, we summarize a current profile of therapeutic strategies for interfering IgE in allergic diseases. Besides, we suggest that targeting memory B cells (including long-lived plasma cells and (or) IgE⁺ memory B cells) may help to completely control allergic diseases, and highlight that the development of drugs synergistically aiming to multiple targets can be a better choice for improving treatment efficacy which results from allergic diseases as the systemic disorders caused by an impaired immune system.

Drug delivery targets and strategies to address mast cell diseases

INTRODUCTION

Current and developing mast cell therapeutics are reliant on small molecule drugs and biologics, but few are truly selective for mast cells. Most have cellular and disease-specific limitations that require innovation to overcome longstanding challenges to selectively targeting and modulating mast cell behavior. This review is designed to serve as a frame of reference for new approaches that utilize nanotechnology or combine different drugs to increase mast cell selectivity and therapeutic efficacy.

AREAS COVERED

Mast cell diseases include allergy and related conditions as well as malignancies. Here, we discuss the targets of existing and developing therapies used to treat these disease pathologies, classifying them into cell surface, intracellular, and extracellular categories. For each target discussed, we discuss drugs that are either the current standard of care, under development, or have indications for potential use. Finally, we discuss how novel technologies and tools can be used to take existing therapeutics to a new level of selectivity and potency against mast cells.

EXPERT OPINION

There are many broadly and very few selectively targeted therapeutics for mast cells in allergy and malignant disease. Combining existing targeting strategies with technology like nanoparticles will provide novel platforms to treat mast cell disease more selectively.

Recent Progress in Traditional Chinese Medicines and Their Mechanism in the Treatment of Allergic Rhinitis

Objective

To conduct a systematic review on the mechanism of action and use of traditional Chinese medicines (TCM) in allergic rhinitis treatment.

Background

Allergic rhinitis (AR) is a type I allergic disease of the immune system induced by immunoglobulin E mediated inflammation and is characterized by sneezing, nasal itching, paroxysmal nasal obstruction, mucosal edema, cough, and rhinorrhea. More than 500 million people have been affected by rhinitis worldwide in the past 20 years, leading to negative effects on health, quality of life, and social relationships. Currently, the trending medicines used in the case of AR include intranasal corticosteroids and oral H1 antihistamines, which are given as combinatorial medicines supplemented with immune therapy. These medications have been found to be very effective in either the short term or long term; however, they have been found to possess some serious side effects. Search Methodology. The information in this article on classical and traditional Chinese medications used to treat AR was derived from original papers and reviews published in Chinese and English language journals. Two Chinese databases (Wanfang and CNKI) and three English databases (Cochrane Library, PubMed, and Embase) were utilized for data gathering.

Results

Traditional Chinese remedies have been identified to influence the production of cytokines such as IL-5 and IL-6, which are key mediators of eosinophilic inflammation, TNF-α, which stimulates TH2 cells at the site of inflammation, and NF-кB, which is required for cytokine and IgE antibody production. TCM has also been shown to be successful in lowering histamine levels, preserving histological changes by decreasing the thickness of the lamina propria, and downregulating the expression of Orai1, STIM1, and TRYC1, showing low expression of Ca⁺² channel proteins.

Conclusion

In this review, we discussed a series of classical, traditional Chinese medications, including Centipeda minima, Scutellaria baicalensis, licorice root (Glycyrrhiza uralensis), and others, as potential antiallergic agents and investigate their in vivo effect upon the production of cytokines and release of histamines for allergic rhinitis treatment.

A SYK/SHC1 pathway regulates the amount of CFTR in the plasma membrane

Mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene cause the recessive genetic disease cystic fibrosis, where the chloride transport across the apical membrane of epithelial cells mediated by the CFTR protein is impaired. CFTR protein trafficking to the plasma membrane (PM) is the result of a complex interplay between the secretory and membrane recycling pathways that control the number of channels present at the membrane. In addition, the ion transport activity of CFTR at the PM is modulated through post-translational protein modifications. Previously we described that spleen tyrosine kinase (SYK) phosphorylates a specific tyrosine residue in the nucleotide-binding domain 1 domain and this modification can regulate the PM abundance of CFTR. Here we identified the underlying biochemical mechanism using peptide pull-down assays followed by mass spectrometry. We identified in bronchial epithelial cells that the adaptor protein SHC1 recognizes tyrosine-phosphorylated CFTR through its phosphotyrosine-binding domain and that the formation of a complex between SHC1 and CFTR is induced at the PM in the presence of activated SYK. The depletion of endogenous SHC1 expression was sufficient to promote an increase in CFTR at the PM of these cells. The results identify a SYK/SHC1 pathway that regulates the PM levels of CFTR channels, contributing to a better understanding of how CFTR-mediated chloride secretion is regulated.

Identification of a novel series of azabenzimidazole-derived inhibitors of spleen tyrosine kinase

Spleen Tyrosine Kinase (SYK) is a well-studied enzyme with therapeutic applications in oncology and autoimmune diseases. We identified an azabenzimidazole (ABI) series of SYK inhibitors by mining activity data of 86,000 compounds from legacy biochemical assays with SYK and other homologous kinases as target enzymes. A structure-based design and hybridization approach was then used to improve the potency and kinase selectivity of the hits. Lead compound 23 from this novel ABI series has a SYK IC₅₀ = 0.21 nM in a biochemical assay and inhibits growth of SUDHL-4 cells at a GI₅₀ = 210 nM.

Dasatinib Inhibits Lyn and Fyn Src-Family Kinases in Mast Cells to Suppress Type I Hypersensitivity in Mice

Mast cells (MCs) are systemically distributed and secrete several allergic mediators such as histamine and leukotrienes to cause type I hypersensitivity. Dasatinib is a type of anti-cancer agent and it has also been reported to inhibit human basophils. However, dasatinib has not been reported for its inhibitory effects on MCs or type I hypersensitivity in mice. In this study, we examined the inhibitory effect of dasatinib on MCs and MC-mediated allergic response in vitro and in vivo. in vitro, dasatinib inhibited the degranulation of MCs by antigen stimulation in a dose-dependent manner (IC50, ~34 nM for RBL-2H3 cells; ~52 nM for BMMCs) without any cytotoxicity. It also suppressed the secretion of inflammatory cytokines IL-4 and TNF-α by antigen stimulation. Furthermore, dasatinib inhibited MC-mediated passive cutaneous anaphylaxis (PCA) in mice (ED50, ~29 mg/kg). Notably, dasatinib significantly suppressed the degranulation of MCs in the ear tissue. As the mechanism of its effect, dasatinib inhibited the activation of Syk and Syk-mediated downstream signaling proteins, LAT, PLCγ1, and three typical MAP kinases (Erk1/2, JNK, and p38), which are essential for the activation of MCs. Interestingly, in vitro tyrosine kinase assay, dasatinib directly inhibited the activities of Lyn and Fyn, the upstream tyrosine kinases of Syk in MCs. Taken together, dasatinib suppresses MCs and PCA in vitro and in vivo through the inhibition of Lyn and Fyn Src-family kinases. Therefore, we suggest the possibility of repositioning the anti-cancer drug dasatinib as a treatment for various MC-mediated type I hypersensitive diseases.

The role of myricetin from Rhodomyrtus tomentosa (Aiton) Hassk fruits on downregulation of FcɛRI-mediated mast cell activation

Rhodomyrtus tomentosa was reported to contain various bioactive metabolites, especially phenolic compounds. In the present study, the suppressive activity of phenolic compound from R. tomentosa fruits on mast cell activation was investigated in vitro. The result showed that myricetin was isolated from R. tomentosa fruits and its characterization was identified by nuclear magnetic resonance spectroscopy. Notably, myricetin was found to be effective in inhibition of mast cell degranulation by attenuating the release of β-hexosaminidase and the elevation of intracellular calcium. Moreover, myricetin exhibited inhibitory effect on the production of IL-4 and Tumor necrosis factor alpha (TNF-α) in a concentration-dependent manner. Furthermore, high antioxidant activity of myricetin due to scavenging 1,1-diphenyl-2-picryl-hydrazyl (DPPH) and ABTS⁺ radicals was also evidenced. Notably, the activation of FcɛRI-mediated signaling molecules including Syk, PLCγ, and NF-κB was also suppressed by myricetin treatment. Accordingly, myricetin from R. tomentosa fruits could be suggested as a functional food for the amelioration of allergic diseases. PRACTICAL APPLICATIONS: Polyphenol have been shown to exert various biological activities and health beneficial effects. Results from the present study revealed that myricetin from R. tomentosa fruits possesses the inhibitory effect on allergic response in mast cells. Therefore, myricetin from R. tomentosa fruits could be developed as a functional ingredient for the amelioration of allergic diseases.

Ang-(1-7)/ MAS1 receptor axis inhibits allergic airway inflammation via blockade of Src-mediated EGFR transactivation in a murine model of asthma

The angiotensin-(1–7) [Ang-(1–7)]/MAS1 receptor signaling axis is a key endogenous anti-inflammatory signaling pathway. However, the mechanisms by which its mediates the anti-inflammatory effects are not completely understood. Using an allergic murine model of asthma, we investigated whether Ang-1(1–7)/MAS1 receptor axis a): inhibits allergic inflammation via modulation of Src-dependent transactivation of the epidermal growth factor receptor (EGFR) and downstream signaling effectors such as ERK1/2, and b): directly inhibits neutrophil and/or eosinophil chemotaxis ex vivo. Ovalbumin (OVA)-induced allergic inflammation resulted in increased phosphorylation of Src kinase, EGFR, and ERK1/2. In addition, OVA challenge increased airway cellular influx, perivascular and peribronchial inflammation, fibrosis, goblet cell hyper/metaplasia and airway hyperresponsiveness (AHR). Treatment with Ang-(1–7) inhibited phosphorylation of Src kinase, EGFR, ERK1/2, the cellular and histopathological changes and AHR. Ang-(1–7) treatment also inhibited neutrophil and eosinophil chemotaxis ex vivo. These changes were reversed following pre-treatment with A779. These data show that the anti-inflammatory actions of Ang-(1–7)/ MAS1 receptor axis are mediated, at least in part, via inhibition of Src-dependent transactivation of EGFR and downstream signaling molecules such as ERK1/2. This study therefore shows that inhibition of the Src/EGRF/ERK1/2 dependent signaling pathway is one of the mechanisms by which the Ang-(1–7)/ MAS1 receptor axis mediates it anti-inflammatory effects in diseases such as asthma.

GSK2646264, a spleen tyrosine kinase inhibitor, attenuates the release of histamine in ex vivo human skin

BACKGROUND AND PURPOSE

Chronic spontaneous urticaria presents as a heterogeneous syndrome characterised by wheals, angioedema, or both for greater than 6 weeks. Spleen tyrosine kinase mediates allergen-induced mast cell degranulation via the IgE signalling pathway, a central component of wheal formation and inflammation. In this study, we investigated the effects of perfused or topically administered GSK2646264 on IgE-mediated histamine release from mast cells in an ex vivo human skin model.

EXPERIMENTAL APPROACH

Using a novel SkiP device, ex vivo human skin from mastectomy surgeries was challenged with anti-IgE, complement 5a (C5a), and buffer to induce histamine release from skin mast cells. Histamine was collected via microdialysis fibres and measured fluorometrically. GSK2646264 was delivered via perfusion either using microdialysis fibres or topically in a cream. Drug concentrations in the skin were measured by LC-MS, and a pharmacokinetic/ pharmacodynamic (PK/PD) relationship developed.

KEY RESULTS

Perfused GSK2646264 significantly inhibited anti-IgE (but not C5a)-induced histamine release in a concentration-dependent manner. The 0.5, 1, and 3% cream delivered GSK2646264 to the dermis above the IC₉₀ and dose-dependently attenuated anti-IgE-induced histamine release.

CONCLUSIONS AND IMPLICATIONS

GSK2646264 administered topically or direct to the dermis blocked histamine release from in situ skin mast cells. A PK/PD relationship curve suggests that dermal concentrations above 6.8 μM should lead to approximately 90% inhibition of histamine release from skin mast cells following activation of the Fc fragment of IgE receptor 1a, implicating a potential use for the compound in skin mast cell diseases such as urticaria.

Therapeutic inhibition of spleen tyrosine kinase in inflammatory macrophages using PLGA nanoparticles for the treatment of non-alcoholic steatohepatitis

Non-alcoholic steatohepatitis (NASH) is the leading cause of cirrhosis worldwide and the most rapidly growing indication for liver transplantation. Macrophages are the important cellular component in the inflammatory milieu in NASH. Inflammatory and pro-fibrotic mediators produced by macrophages causes significant tissue injury in many inflammatory diseases. Therefore, inhibition of the inflammatory macrophages would be a promising approach to attenuate NASH. In this study, we studied the implication of SYK pathway in NASH, and investigated PLGA nanoparticles-based delivery of SYK pathway inhibitor as an effective and promising therapeutic approach for the treatment of NASH. We found positive correlation between SYK expression with the pathogenesis of NASH and alcoholic hepatitis in patients. Importantly, SYK expression was significantly induced in M1-differentiated inflammatory macrophages. To inhibit SYK pathway specifically, we used a small-molecule inhibitor R406 that blocks Fc-receptor signaling pathway and reduces immune complex-mediated inflammation. R406 dose-dependently inhibited nitric-oxide release and M1-specific markers in M1-differentiated macrophages. Thereafter, we synthesized PLGA nanoparticles to deliver R406 to increase the drug pharmacokinetics for the efficient treatment of NASH. We investigated the therapeutic efficacy of R406-PLGA in-vitro in differentiated macrophages, and in-vivo in Methionine-Choline-deficient (MCD)-diet induced NASH mouse model. R406-PLGA inhibited M1-specific differentiation markers in RAW and bone-marrow-derived macrophages. In-vivo, R406 and more strongly R406-PLGA ameliorated fibrosis, inflammation and steatosis in mice. R406 and more significantly R406-PLGA reduced ALT, AST, cholesterol and triglyceride plasma levels. These results suggest that delivery of SYK inhibitor using PLGA nanoparticles can be a potential therapeutic approach for the treatment of Non-alcoholic steatohepatitis.

JTE-852, a novel spleen tyrosine kinase inhibitor, blocks antigen-induced allergic reactions in rats

Conventional clinical treatments for allergy management remain suboptimal; new, orally available medications that improve a wide range of allergic signs have been desired. We previously demonstrated that JTE-852, a novel spleen tyrosine kinase inhibitor, potently and simultaneously suppresses secretion of granule contents, arachidonate metabolites, and cytokines from mast cells stimulated by immunoglobulin E-crosslinking. In the present study, we investigated the effects of JTE-852 in four rat models (sneezing, rhinorrhea, airway constriction, and airway inflammation) as representatives of allergy models. Rats were sensitized and challenged with antigen. Allergic reactions developed after challenge were detected. JTE-852 and current anti-allergic drugs (ketotifen, pranlukast, and prednisolone) were administered orally before challenge. JTE-852 showed significant blocking effects on antigen-induced allergic reactions in all models, indicating that JTE-852 in oral dosage form would improve a wide range of allergic signs. The current anti-allergic drugs, on the other hand, failed to display significant suppression in several models. Because JTE-852 suppresses the secretion of all three groups of allergic mediators from mast cells, it would be capable of targeting signs that current drugs cannot sufficiently relieve. We anticipate JTE-852 to be a promising new anti-allergic drug that is potentially more effective than conventional drugs.

Syk inhibitors in clinical development for hematological malignancies

Spleen tyrosine kinase (Syk) is a cytosolic non-receptor protein tyrosine kinase (PTK) and is mainly expressed in hematopoietic cells. Syk was recognized as a critical element in the B-cell receptor signaling pathway. Syk is also a key component in signal transduction from other immune receptors like Fc receptors and adhesion receptors. Several oral Syk inhibitors including fostamatinib (R788), entospletinib (GS-9973), cerdulatinib (PRT062070), and TAK-659 are being assessed in clinical trials. The second generation compound, entospletinib, showed promising results in clinical trials against B-cell malignancies, mainly chronic lymphoid leukemia. Syk inhibitors are being evaluated in combination regimens in multiple malignancies.

Mast cells in asthma--state of the art

Mast cells (MCs) play a central role in tissue homoeostasis, sensing the local environment through numerous innate cell surface receptors. This enables them to respond rapidly to perceived tissue insults with a view to initiating a co-ordinated programme of inflammation and repair. However, when the tissue insult is chronic, the ongoing release of multiple pro-inflammatory mediators, proteases, cytokines and chemokines leads to tissue damage and remodelling. In asthma, there is strong evidence of ongoing MC activation, and their mediators and cell-cell signals are capable of regulating many facets of asthma pathophysiology. This article reviews the evidence behind this.

15,16-Dihydrotanshinone I suppresses IgE-Ag stimulated mouse bone marrow-derived mast cell activation by inhibiting Syk kinase

ETHNOPHARMACOLOGICAL RELEVANCE

15,16-Dihydrotanshinone I (DHT-I), isolated from the dried root of Salvia miltiorrhiza Bung, which is traditionally used to treat cardiovascular and inflammatory diseases agent in Chinese medicine. DHT-I has been reported to have a broad range of biological activities, including antibacterial activity, and has been used to treat circulatory disorders, hepatitis, inflammation, cancer, and neurodegenerative diseases.

AIM OF THE STUDY

The aim of this study was to evaluate the anti-allergic inflammatory effects of DHT-I on degranulation and on the generation of eicosanoids, such as, prostaglandin D2 (PGD2) and leukotriene C4 (LTC4), in IgE/Ag-stimulated bone marrow-derived mast cells (BMMCs).

MATERIALS AND METHODS

The anti-allergic inflammatory activity of DHT-I was evaluated using BMMCs. The effects of DHT-I on mast cell activation were investigated by following degranulation and eicosanoid generation using ELISA and immunoblotting and immunoprecipitation techniques.

RESULTS

DHT-I at a concentration of 20μM markedly inhibited degranulation and the generation of PGD2 and LTC4 in IgE/Ag-stimulated BMMCs (about 90% inhibitions, respectively). Analyses of FcεRI-mediated signaling pathways demonstrated that DHT-I inhibited the phosphorylations of spleen tyrosine kinase (Syk) and linker for activation of T cells (LAT), and inhibited downstream signaling process, including [Ca(2+)]i mobilization induced by the phosphorylation of phospholipase Cγ1 (PLCγ1), and the activations of mitogen-activated protein kinases (MAPKs) and the Akt-nuclear factor-κB (NF-κB) pathway.

CONCLUSIONS

DHT-1 inhibits the release of allergic inflammatory mediators from IgE/Ag-stimulated mast cells by suppressing a FcεRI-mediated Syk-dependent signal pathway. This result suggests DHT-I offers a novel developmental basis for drugs targeting allergic inflammatory diseases.

Mast cell stabilisers

Mast cells play a critical role in type 1 hypersensitivity reactions. Indeed, mast cell mediators are implicated in many different conditions including allergic rhinitis, conjunctivitis, asthma, psoriasis, mastocytosis and the progression of many different cancers. Thus, there is intense interest in the development of agents which prevent mast cell mediator release or which inhibit the actions of such mediators once released into the environment of the cell. Much progress into the design of new agents has been made since the initial discovery of the mast cell stabilising properties of khellin from Ammi visnaga and the clinical approval of cromolyn sodium. This review critically examines the progress that has been made in the intervening years from the design of new agents that target a specific signalling event in the mast cell degranulation pathway to those agents which have been developed where the precise mechanism of action remains elusive. Particular emphasis is also placed on clinically used drugs for other indications that stabilise mast cells and how this additional action may be harnessed for their clinical use in disease processes where mast cells are implicated.

An indoxyl compound 5-bromo-4-chloro-3-indolyl 1,3-diacetate, CAC-0982, suppresses activation of Fyn kinase in mast cells and IgE-mediated allergic responses in mice

Mast cells, constituents of virtually all organs and tissues, are critical cells in IgE-mediated allergic responses. The aim of this study was to investigate the effect and mechanism of an indoxyl chromogenic compound, 5-bromo-4-chloro-3-indolyl 1,3-diacetate, CAC-0982, on IgE-mediated mast cell activation and allergic responses in mice. CAC-0982 reversibly suppressed antigen-stimulated degranulation in murine mast cells (IC50, ~3.8μM) and human mast cells (IC50, ~3.0μM). CAC-0982 also inhibited the expression and secretion of IL-4 and TNF-α in mast cells. Furthermore, CAC-0982 suppressed the mast cell-mediated allergic responses in mice in a dose-dependent manner (ED50 27.9mg/kg). As for the mechanism, CAC-0982 largely suppressed the phosphorylation of Syk and its downstream signaling molecules, including LAT, Akt, Erk1/2, p38, and JNK. Notably, the tyrosine kinase assay of antigen-stimulated mast cells showed that CAC-0982 inhibited Fyn kinase, one of the upstream tyrosine kinases for Syk activation in mast cells. Taken together, these results suggest that CAC-0982 may be used as a new treatment for regulating IgE-mediated allergic diseases through the inhibition of the Fyn/Syk pathway in mast cells.

Twenty-first century mast cell stabilizers

Mast cell stabilizing drugs inhibit the release of allergic mediators from mast cells and are used clinically to prevent allergic reactions to common allergens. Despite the relative success of the most commonly prescribed mast cell stabilizer, disodium cromoglycate, in use for the preventative treatment of bronchial asthma, allergic conjunctivitis and vernal keratoconjunctivitis, there still remains an urgent need to design new substances that are less expensive and require less frequent dosing schedules. In this regard, recent developments towards the discovery of the next generation of mast cell stabilizing drugs has included studies on substances isolated from natural sources, biological, newly synthesized compounds and drugs licensed for other indications. The diversity of natural products evaluated range from simple phenols, alkaloids, terpenes to simple amino acids. While in some cases their precise mode of action remains unknown it has nevertheless sparked interest in the development of synthetic derivatives with improved pharmacological properties. Within the purely synthetic class of inhibitors, particular attention has been devoted to the inhibition of important signalling molecules including spleen TK and JAK3. The statin class of cholesterol-lowering drugs as well as nilotinib, a TK inhibitor, are just some examples of clinically used drugs that have been evaluated for their anti-allergic properties. Here, we examine each approach under investigation, summarize the test data generated and offer suggestions for further preclinical evaluation before their therapeutic potential can be realized.

Immunopharmacological modulation of mast cells

Mast cells produce a wide spectrum of mediators and they have been implicated in several physiopathological conditions (e.g. allergic reactions and certain tumors). Pharmacologic agents that modulate the release of mediators from mast cells has helped to elucidate the biochemical mechanisms by which immunological and non-immunological stimuli activate these cells. Furthermore, the study of surface receptors and signaling pathways associated with mast cell activation revealed novel pharmacologic targets. Thus, the development of pharmacologic agents based on this new wave of knowledge holds promise for the treatment of several mast cell-mediated disorders.

Britanin Suppresses IgE/Ag-Induced Mast Cell Activation by Inhibiting the Syk Pathway

The aim of this study was to determine whether britanin, isolated from the flowers of Inula japonica (Inulae Flos), modulates the generation of allergic inflammatory mediators in activated mast cells. To understand the biological activity of britanin, the authors investigated its effects on the generation of prostaglandin D₂ (PGD₂), leukotriene C₄ (LTC₄), and degranulation in IgE/Ag-induced bone marrow-derived mast cells (BMMCs). Britanin dose dependently inhibited degranulation and the generations of PGD₂ and LTC₄ in BMMCs. Biochemical analyses of IgE/Ag-mediated signaling pathways demonstrated that britanin suppressed the phosphorylation of Syk kinase and multiple downstream signaling processes, including phospholipase Cγ1 (PLCγ1)-mediated calcium influx, the activation of mitogen-activated protein kinases (MAPKs; extracellular signal-regulated kinase 1/2, c-Jun NH₂-terminal kinase and p38), and the nuclear factor-κB (NF-κB) pathway. Taken together, the findings of this study suggest britanin suppresses degranulation and eicosanoid generation by inhibiting the Syk-dependent pathway and britanin might be useful for the treatment of allergic inflammatory diseases.

Functional roles of Syk in macrophage-mediated inflammatory responses

Inflammation is a series of complex biological responses to protect the host from pathogen invasion. Chronic inflammation is considered a major cause of diseases, such as various types of inflammatory/autoimmune diseases and cancers. Spleen tyrosine kinase (Syk) was initially found to be highly expressed in hematopoietic cells and has been known to play crucial roles in adaptive immune responses. However, recent studies have reported that Syk is also involved in other biological functions, especially in innate immune responses. Although Syk has been extensively studied in adaptive immune responses, numerous studies have recently presented evidence that Syk has critical functions in macrophage-mediated inflammatory responses and is closely related to innate immune response. This review describes the characteristics of Syk-mediated signaling pathways, summarizes the recent findings supporting the crucial roles of Syk in macrophage-mediated inflammatory responses and diseases, and discusses Syk-targeted drug development for the therapy of inflammatory diseases.

Mast cell mediator responses and their suppression by pathogenic and commensal microorganisms

Mast cells (MCs) are selectively found at the host environment interface and are capable of secreting a wide array of pharmacologically active mediators, many of which are prepackaged in granules. Over the past two decades, it has become clear that these cells have the capacity to recognize a range of infectious agents allowing them to play a key role in initiating and modulating early immune responses to infectious agents. However, a number of pathogenic and commensal microbes appear to have evolved distinct mechanisms to suppress MC mediator release to avoid elimination in the host. Understanding how these microbes suppress MC functions may have significant therapeutic value to relieve inflammatory disorders mediated by MCs.

Salmonella typhimurium impedes innate immunity with a mast-cell-suppressing protein tyrosine phosphatase, SptP

The virulence of Salmonella is linked to its invasive capacity and suppression of adaptive immunity. This does not explain, however, the rapid dissemination of the pathogen after it breaches the gut. In our study, S. Typhimurium suppressed degranulation of local mast cells (MCs), resulting in limited neutrophil recruitment and restricting outflow of vascular contents into infection sites, thus facilitating bacterial spread. MC suppression was mediated by secreted effector protein (SptP), which shares structural homology with Yersinia YopH. SptP functioned by dephosphorylating the vesicle fusion protein N-ethylmalemide-sensitive factor and by blocking phosphorylation of Syk. Without SptP, orally challenged S. Typhimurium failed to suppress MC degranulation and exhibited limited colonization of the mesenteric lymph nodes. Administration of SptP to sites of E. coli infection markedly enhanced its virulence. Thus, SptP-mediated inactivation of local MCs is a powerful mechanism utilized by S. Typhimurium to impede early innate immunity.

Inhibitors of switch kinase 'spleen tyrosine kinase' in inflammation and immune-mediated disorders: a review

Spleen tyrosine kinase (Syk), a member of Syk family of non-receptor protein tyrosine kinases plays a significant role in the immune cell signaling in B cells, mast cells, macrophages and neutrophils. Anomalous regulation of this kinase can lead to different allergic disorders and antibody-mediated autoimmune diseases such as rheumatoid arthritis, asthma, psoriasis and allergic rhinitis. Being involved in the growth and survive mechanism of B cells, its inhibition can be beneficial in B-cell lymphoma. Thus, Syk can be sited as a therapeutically relevant target for various allergic and autoimmune disorders. This review article describes the structure of Syk and its role in B-cell signaling. In addition to this, data regarding small molecule inhibitors of Syk has also been reviewed from different papers and patents published.

Morus bombycis extract suppresses mast cell activation and IgE-mediated allergic reaction in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Morus bombycis Koidzumi (MB) is widely distributed throughout Korea, where it is used as a traditional folk remedy for the treatment of allergic diseases including asthma. However, the pharmacological effect and the mechanistic study of MB have not been investigated. We aimed to investigate the anti-allergic activity of MB in vitro and in vivo and the mechanism of its action on mast cells.

MATERIALS AND METHODS

The anti-allergic activity of MB extract (MBE) was assessed using passive cutaneous anaphylaxis (PCA) in mice and mouse bone marrow-derived mast cells (BMMCs) in vitro. The effects of MBE on mast cell activation were evaluated by using the β-hexosaminidase release assay, reverse transcriptase-polymerase chain reaction, enzyme-linked immunosorbent assay, and western blotting analysis.

RESULTS

MBE reversibly inhibited degranulation and generation of cytokines (TNF-α and IL-4) in antigen-stimulated mast cells. With regard to its mechanism of action, MBE inhibited the activation of Lyn and Syk, which have essential roles in degranulation and the production of various inflammatory cytokines. MBE also inhibited the activating phosphorylation of mitogen-activated protein (MAP) kinases, Erk1/2, p38, JNK, and Akt. In agreement with its in vitro effect, MBE significantly inhibited mast cell-mediated PCA reactions in IgE-sensitized mice.

CONCLUSIONS

The present results strongly suggest that MBE exerts an anti-allergic effect, both in vitro and in vivo by inhibiting the Lyn and Syk pathways in mast cells. Therefore, MBE may be useful for the treatment of allergic diseases, including atopic dermatitis and allergic asthma.

Targeting the SYK-BTK axis for the treatment of immunological and hematological disorders: recent progress and therapeutic perspectives

Spleen Tyrosine Kinase (SYK) and Bruton's Tyrosine Kinase (BTK) are non-receptor cytoplasmic tyrosine kinases that are primarily expressed in cells of hematopoietic lineage. Both are key mediators in coupling activated immunoreceptors to downstream signaling events that affect diverse biological functions, from cellular proliferation, differentiation and adhesion to innate and adaptive immune responses. As such, pharmacological inhibitors of SYK or BTK are being actively pursued as potential immunomodulatory agents for the treatment of autoimmune and inflammatory disorders. Deregulation of SYK or BTK activity has also been implicated in certain hematological malignancies. To date, from a clinical perspective, pharmacological inhibition of SYK activity has demonstrated encouraging efficacy in patients with rheumatoid arthritis (RA), while patients with relapsed or refractory chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma (SLL) have benefited from covalent inhibitors of BTK in early clinical studies. Here, we review and discuss recent insights into the emerging role of the SYK-BTK axis in innate immune cell function as well as in the maintenance of survival and homing signals for tumor cell progression. The current progress on the clinical development of SYK and BTK inhibitors is also highlighted.

Emerging drugs for perennial allergic rhinitis

INTRODUCTION

Allergic rhinitis (AR) is a high-prevalence disease, sustained by an IgE-triggered reaction with histamine release, followed by an inflammatory response which involves cells, mediators, cytokines and adhesion molecules. According to its duration, AR can be either intermittent or persistent. In the persistent form, the inflammatory component usually predominates.

AREAS COVERED

The current therapeutic strategy is based on antihistamines, antileukotrienes and on corticosteroids (which broadly act on inflammation). Allergen-specific immunotherapy is a biological response modifier that affects the immune response to allergens in a broad sense. The available pharmacotherapy is overall effective in controlling symptoms and inflammation, but safety concerns may be present (especially for prolonged treatments), and a proportion of patients remain uncontrolled. The available therapeutic innovations, as derived from the most recent literature are reviewed herein.

EXPERT OPINION

In the last years there have been very few innovative approaches to optimize the management of AR. These include new histamine receptor antagonists, combination therapy and strategies to selectively block relevant signaling pathways of the allergic reaction. Some more promising advances have been shown for allergen immunotherapy, where a number of new strategies are currently under development.

Spleen tyrosine kinase inhibition attenuates airway hyperresponsiveness and pollution-induced enhanced airway response in a chronic mouse model of asthma

BACKGROUND

Asthma is a chronic inflammatory disease characterized by airways hyperresponsiveness (AHR), reversible airflow obstruction, airway remodeling, and episodic exacerbations caused by air pollutants, such as particulate matter (PM; PM <2.5 μm in diameter [PM(2.5)]) and ozone (O(3)). Spleen tyrosine kinase (Syk), an immunoregulatory kinase, has been implicated in the pathogenesis of asthma.

OBJECTIVE

We sought to evaluate the effect of Syk inhibition on AHR in a chronic mouse model of allergic airways inflammation and pollutant exposure.

METHODS

We used a 12-week chronic ovalbumin (OVA) sensitization and challenge mouse model of airways inflammation followed by exposure to PM(2.5) plus O(3). Respiratory mechanics and methacholine (MCh) responsiveness were assessed by using the flexiVent system. The Syk inhibitor NVP-QAB-205 was nebulized intratracheally by using a treatment-based protocol 15 minutes before assessment of MCh responsiveness.

RESULTS

Syk expression increased significantly in the airway epithelia of OVA-sensitized and OVA-challenged (OVA/OVA) mice compared with OVA-sensitized but PBS-challenged (OVA/PBS) control mice. OVA/OVA mice exhibited AHR to MCh, which was attenuated by a single administration of NVP-QAB-205 (0.3 and 3 mg/kg). PM(2.5) plus O(3) significantly augmented AHR to MCh in the OVA/OVA mice, which was abrogated by NVP-QAB-205. Total inflammatory cell counts were significantly higher in the bronchoalveolar lavage fluid from OVA/OVA than OVA/PBS mice and were unaffected by PM(2.5) plus O(3) or NVP-QAB-205.

CONCLUSION

NVP-QAB-205 reduced AHR and the enhanced response to PM(2.5) plus O(3) to normal levels in an established model of chronic allergic airways inflammation, suggesting that Syk inhibitors have promise as a therapy for asthma.

Gene transcription abnormalities in canine atopic dermatitis and related human eosinophilic allergic diseases

Canine atopic dermatitis (AD) is clinically similar to human AD, implicating it as a useful model of human eosinophilic allergic disease. To identify cutaneous gene transcription changes in relatively early inflammation of canine AD, microarrays were used to monitor transcription in normal skin (n=13) and in acute lesional AD (ALAD) and nearby visibly nonlesional AD (NLAD) skin (n=13) from dogs. Scanning the putative abnormally transcribed genes, several potentially relevant genes, some abnormally transcribed in both NLAD and ALAD (e.g. IL6, NFAM1, MSRA, and SYK), were observed. Comparison for abnormally transcribed genes common to two related human diseases, human AD and asthmatic chronic rhinosinusitis with nasal polyps (aCRSwNP), further identified genes or gene sets likely relevant to eosinophilic allergic inflammation. These included: (1) genes associated with alternatively activated monocyte-derived cells, including members of the monocyte chemotactic protein (MCP) gene cluster, (2) members of the IL1 family gene cluster, (3) eosinophil-associated seven transmembrane receptor EMR1 and EMR3 genes, (4) interferon-inducible genes, and (5) keratin genes associated with hair and nail formation. Overall, numerous abnormally transcribed genes were observed only in canine AD; however, many others are common to related human eosinophilic allergic diseases and represent therapeutic targets testable in dogs with AD.

Spleen tyrosine kinase mediates high glucose-induced transforming growth factor-β1 up-regulation in proximal tubular epithelial cells

The role of spleen tyrosine kinase (Syk) in high glucose-induced intracellular signal transduction has yet to be elucidated. We investigated whether Syk is implicated in high glucose-induced transforming growth factor-β1 (TGF-β1) up-regulation in cultured human proximal tubular epithelial cells (HK-2 cell). High glucose increased TGF-β1 gene expression through Syk, extracellular signal-regulated kinase (ERK), AP-1 and NF-κB. High glucose-induced AP-1 DNA binding activity was decreased by Syk inhibitors and U0126 (an ERK inhibitor). Syk inhibitors suppressed high glucose-induced ERK activation, whereas U0126 had no effect on Syk activation. High glucose-induced NF-κB DNA binding activity was also decreased by Syk inhibitors. High glucose increased nuclear translocation of p65 without serine phosphorylation of IκBα and without degradation of IκBα, but with an increase in tyrosine phosphorylation of IκBα that may account for the activation of NF-κB. Both Syk inhibitors and Syk-siRNA attenuated high glucose-induced IκBα tyrosine phosphorylation and p65 nuclear translocation. Depletion of p21-activated kinase 2 (Pak2) by transfection of Pak2-siRNA abolished high glucose-induced Syk activation. In summary, high glucose-induced TGF-β1 gene transcription occurred through Pak2, Syk and subsequent ERK/AP-1 and NF-κB pathways. This suggests that Syk might be implicated in the diabetic kidney disease.

Activation of spleen tyrosine kinase is required for TNF-α-induced endothelin-1 upregulation in human aortic endothelial cells

Endothelin-1 (ET-1) promotes atherosclerosis. We tested whether spleen tyrosine kinase (Syk) mediates tumor necrosis factor-α (TNF-α)-induced ET-1 upregulation in human aortic endothelial cells (HAECs) and sought to identify the signal pathways involved. TNF-α-induced reactive oxygen species (ROS) activated Syk and phosphatidylinositol 3-kinase (PI3K), which was required for the activation of AP-1 and subsequent ET-1 gene transcription. ROS mediated c-Jun NH(2)-terminal kinase (JNK) is also required for AP-1 activation, but Syk and PI3K regulated AP-1 activation independently of JNK. Through regulation of ET-1 production, Syk could be implicated in atherosclerosis.

Emodin, a naturally occurring anthraquinone derivative, suppresses IgE-mediated anaphylactic reaction and mast cell activation

The high-affinity receptor for IgE (FcɛRI)-mediated activation of mast cells plays an important role in allergic diseases such as asthma, allergic rhinitis and atopic dermatitis. Emodin, a naturally occurring anthraquinone derivative in oriental herbal medicines, has several beneficial pharmacologic effects, such as anti-cancer and anti-diabetic activities. However, the anti-allergic effect of emodin has not yet been investigated. To assess the anti-allergic activity of emodin, in vivo passive anaphylaxis animal model and in vitro mouse bone marrow-derived mast cells were used to investigate the mechanism of its action on mast cells. Our results showed that emodin inhibited degranulation, generation of eicosanoids (prostaglandin D(2) and leukotriene C(4)), and secretion of cytokines (TNF-α and IL-6) in a dose-dependent manner in IgE/Ag-stimulated mast cells. Biochemical analysis of the FcɛRI-mediated signaling pathways demonstrated that emodin inhibited the phosphorylation of Syk and multiple downstream signaling processes including mobilization of intracellular Ca(2+) and activation of the mitogen-activated protein kinase, phosphatidylinositol 3-kinase, and NF-κB pathways. When administered orally, emodin attenuated the mast cell-dependent passive anaphylactic reaction in IgE-sensitized mice. Thus, emodin inhibits mast cell activation and thereby the anaphylactic reaction through suppression of the receptor-proximal Syk-dependent signaling pathways. Therefore, emodin might provide a basis for development of a novel anti-allergic drug.

Tyrosine kinase syk non-enzymatic inhibitors and potential anti-allergic drug-like compounds discovered by virtual and in vitro screening

In the past decade, the spleen tyrosine kinase (Syk) has shown a high potential for the discovery of new treatments for inflammatory and autoimmune disorders. Pharmacological inhibitors of Syk catalytic site bearing therapeutic potential have been developed, with however limited specificity towards Syk. To address this topic, we opted for the design of drug-like compounds that could impede the interaction of Syk with its cellular partners while maintaining an active kinase protein. To achieve this challenging task, we used the powerful potential of intracellular antibodies for the modulation of cellular functions in vivo, combined to structure-based in silico screening. In our previous studies, we reported the anti-allergic properties of the intracellular antibody G4G11. With the aim of finding functional mimics of G4G11, we developed an Antibody Displacement Assay and we isolated the drug-like compound C-13, with promising in vivo anti-allergic activity. The likely binding cavity of this compound is located at the close vicinity of G4G11 epitope, far away from the catalytic site of Syk. Here we report the virtual screen of a collection of 500,000 molecules against this new cavity, which led to the isolation of 1000 compounds subsequently evaluated for their in vitro inhibitory effects using the Antibody Displacement Assay. Eighty five compounds were selected and evaluated for their ability to inhibit the liberation of allergic mediators from mast cells. Among them, 10 compounds inhibited degranulation with IC₅₀ values ≤ 10 µM. The most bioactive compounds combine biological activity, significant inhibition of antibody binding and strong affinity for Syk. Moreover, these molecules show a good potential for oral bioavailability and are not kinase catalytic site inhibitors. These bioactive compounds could be used as starting points for the development of new classes of non-enzymatic inhibitors of Syk and for drug discovery endeavour in the field of inflammation related disorders.

Spleen tyrosine kinase inhibition in the treatment of autoimmune, allergic and autoinflammatory diseases

Spleen tyrosine kinase (Syk) is involved in the development of the adaptive immune system and has been recognized as being important in the function of additional cell types, including platelets, phagocytes, fibroblasts, and osteoclasts, and in the generation of the inflammasome. Preclinical studies presented compelling evidence that Syk inhibition may have therapeutic value in the treatment of rheumatoid arthritis and other forms of arthritis, systemic lupus erythematosus, autoimmune cytopenias, and allergic and autoinflammatory diseases. In addition, Syk inhibition may have a place in limiting tissue injury associated with organ transplant and revascularization procedures. Clinical trials have documented exciting success in the treatment of patients with rheumatoid arthritis, autoimmune cytopenias, and allergic rhinitis. While the extent and severity of side effects appear to be limited so far, larger studies will unravel the risk involved with the clinical benefit.

Adapters in the organization of mast cell signaling

Mast cells are pivotal in innate immunity and play an important role in amplifying adaptive immunity. Nonetheless, they have long been known to be central to the initiation of allergic disorders. This results from the dysregulation of the immune response whereby normally innocuous substances are recognized as non-self, resulting in the production of IgE antibodies to these 'allergens'. Preformed and newly synthesized inflammatory (allergic) mediators are released from the mast cell following allergen-mediated aggregation of allergen-specific IgE bound to the high-affinity receptors for IgE (FcepsilonRI). Thus, the process by which the mast cell is able to interpret the engagement of FcepsilonRI into the molecular events necessary for release of their allergic mediators is of considerable therapeutic interest. Unraveling these molecular events has led to the discovery of a functional class of proteins that are essential in organizing activated signaling molecules and in coordinating and compartmentalizing their activity. These so-called 'adapters' bind multiple signaling proteins and localize them to specific cellular compartments, such as the plasma membrane. This organization is essential for normal mast cell responses. Here, we summarize the role of adapter proteins in mast cells focusing on the most recent advances toward understanding how these molecules work upon FcepsilonRI engagement.