Inhibitor for FcεRI expression on mast cell from Verbasucum thapsus L.

We found out 2',3'-dihydroxypuberulin from South American medicinal plant, V. thapsus L., as a candidate of an anti-allergic lead which inhibits the expression of high-affinity receptor of IgE (FcεRI) on the surface of mast cells. Furthermore, the analysis of structure-activity relationship by using synthesized 2',3'-dihydroxypuberulin analogs revealed that both hydroxy groups in the side chain and both of methyl moieties on phenolic hydroxy groups were crucial for potent activity, but absolute configuration of C-3' position wasn't. The active principle, 2',3'-dihydroxypuberulin, was disclosed to down-regulate the mRNA level of ß-chain of FcεRI, different from previous reported active natural product reducing γ-chain level.

Thymic Stromal Lymphopoietin: A Promising Target in the Treatment of Asthma? / Linfopoyetina del estroma tímico: ¿un objetivo prometedor para el tratamiento del asma?

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Gnetin H isolated from Paeonia anomala inhibits FcεRI-mediated mast cell signaling and degranulation.

ETHNOPHARMACOLOGICAL RELEVANCE: Paeonia anomala L. is used in Mongolian traditional medicine to treat various diseases including indigestion, abdominal pain, kidney disorders, inflammation, and female diseases. In this study we examined the effects of Paeonia anomala extract (PAE) and compounds derived from Paeonia anomala on immunoglobulin E (IgE)-mediated type I hypersensitivity responses in vitro. MATERIALS AND METHODS: Degranulation assay, reverse transcription PCR, enzyme-lined immunosorbent assays, western blot analyses were performed to measure allergic and proinflammatory mediators in IgE-stimulated rat basophilic leukemia (RBL)-2H3 mast cells treated with or without PAE or gnetin H. RESULTS: Seventeen compounds were isolated, and ß-hexosaminidase release from IgE-stimulated RBL-2H3 mast cells was measured. Of the seventeen isolated compounds, gnetin H, a resveratrol derivative, significantly inhibited ß-hexosaminidase release from RBL-2H3 cells with an IC50 value of 0.3 µM. Notably, Gnetin H reduced ß-hexosaminidase release at lower concentrations than resveratrol. Furthermore, PAE and gnetin H inhibited histamine secretion, decreased the production and mRNA expression of tumor necrosis factor-α and interleukin-4 and suppressed translocation of nuclear factor κB. PAE and gnetin H also reduced the expression of cyclooxygenase-2 and production of prostaglandin E2. PAE and gnetin H suppressed the phosphorylation of Syk, protein kinase C (PKC)µ, phospholipase Cγ, and the mitogen-activated protein kinases, c-Jun N-terminal kinase, p38, and extracellular signal-regulated kinase. CONCLUSIONS: These results suggest that PAE and its active compound gnetin H could be promising therapeutic agents for allergic disorders.

Inhibitors for expression of IgE receptor on human mast cell from Puerariae Flos.

Bioassay-guided separation of the extract of the medicinal plant, Puerariae Flos, disclosed the two isoflavones tectorigenin (1) and genistein (2) as the inhibitors for expression of IgE receptor (FcepsilonRI), the key molecule triggering the allergic reactions, on human mast cells. As a result of analysis of structure-activity relationship of the naturally occurring and synthesized isoflavones, 7-O-methyl glycitein (11) was disclosed as the more potent inhibitor than tectorigenin (1). These isoflavone ingredients suppressed expression of FcepsilonRI more potently than the active flavonoids found previously. In addition, tectorigenin (1) was clarified to particularly reduce generation of gamma-chain subunit to suppress expression of FcepsilonRI among the three subunits.

Pentagalloylglucose down-regulates mast cell surface FcepsilonRI expression in vitro and in vivo.

Mast cell activation by immunoglobulin E (IgE)-mediated stimuli is a central event in the pathogenesis of allergic disorders. The present report shows that treatment with pentagalloylglucose (PGG) resulted in a down-regulation of FcepsilonRI surface expression on mucosal-type murine bone marrow-derived mast cells (mBMMCs), which correlated with a reduction in IgE-mediated activation of mBMMCs. Furthermore, PGG prevented development of allergic diarrhea in a food-allergy mouse model and suppressed the up-regulated FcepsilonRI surface expression on mast cells derived from the food-allergy mouse colon. These findings on PGG suggest its therapeutic potential for allergic diseases through suppressing the FcepsilonRI surface expression.

Ecklonia cava extract suppresses the high-affinity IgE receptor, FcepsilonRI expression.

Basophils and mast cells express FcepsilonRI, a high-affinity receptor for IgE, on the cell surface and act as effector cells in allergic reactions. In this study, we investigated the inhibitory effect of Ecklonia cava (EC) methanolic extract on the expression of FcepsilonRI in human basophilic KU812F cells. Flow cytometric analysis revealed that EC extract caused a concentration-dependent reduction in the cell surface expression of FcepsilonRI. The extract was also capable of reducing the binding between IgE or serum IgE and cell surface FcepsilonRI. RT-PCR analysis revealed that EC extract reduced the mRNA expression of total cellular FcepsilonRI alpha-chain. Moreover, data obtained by fluorescence spectrophotometry showed that the extract inhibited the FcepsilonRI-mediated release of histamine in a concentration-dependent manner. These results suggest that EC extract may exert its anti-allergic activity through negative-regulation of FcepsilonRI expression and a decrease in histamine release.

Selinidin suppresses IgE-mediated mast cell activation by inhibiting multiple steps of Fc epsilonRI signaling.

IgE-mediated mast cell activation is critical for development of allergic inflammation. We have recently found that selinidin, one of the coumarin derivatives isolated from Angelica keiskei, attenuates mast cell degranulation following engagement of the high-affinity receptor for IgE (Fc epsilonRI) with IgE and antigen. In the present study, we investigated the effects of selinidin on intracellular signaling and mast cell activation employing bone marrow-derived mast cells. Here, we report that selinidin attenuates the release of beta-hexosaminidase, synthesis of leukotriene C4, and production of tumor necrosis factor-alpha without affecting IgE-Fc epsilonRI binding. Furthermore, biochemical analyses of the Fc epsilonRI-mediated signaling pathway demonstrated that selinidin decreases phosphorylation of phospholipase C-gamma1, p38 mitogen-activated protein kinase, and IkappaB-alpha upon FcepsilonRI stimulation. These results suggest that this compound suppresses IgE-mediated mast cell activation by inhibiting multiple steps of FcepsilonRI-dependent signaling pathways and would be beneficial for the prevention of allergic inflammation.

Regulation of the human Fc epsilon RI alpha-chain distal promoter.

The alpha-chain of the high affinity receptor for IgE (Fc epsilon RI) is essential for cell surface expression of Fc epsilon RI and binding of the IgE Ab. The human alpha-chain gene possesses two promoters: the proximal promoter, which is highly conserved with that of rodent; and the distal promoter, the structure and role of which are largely unknown. Transcriptional regulation of the alpha-chain distal promoter was investigated in this study. Transient reporter assay revealed critical region for transcription activity located within -27/-17. EMSA identified Elf-1, YY1, and PU.1 as transcription factors binding to this region. In contrast to the proximal promoter, which was trans-activated by YY1 and PU.1, these transcription factors exhibited repressive function on this promoter. Addition of IL-4 caused a marked increase in transcription from the distal promoter and subsequently increased the intracellular production of the alpha-chain. These results indicate that IL-4-dependent up-regulation of the human alpha-chain was due to enhancement of distal promoter activity and suggests that the two promoters have different regulatory mechanisms for alpha-chain expression.

The ex vivo effect of the herbal medicine sho-saiko-to on histamine release from rat mast cells.

A traditional Japanese herbal medicine, Shosaiko-to (SST), has been used orally to treat several chronic diseases. Since these have included allergic rhinitis and bronchial asthma, we investigated the effect of SST on histamine release and the intracellular Ca2+ response in mast cells ex vivo. A single dose of 1.0 g/kg SST was administered orally to immunized rats 2-12 h before death. Mast cells were then separated from peritoneal lavages and stimulated with antigen. SST at 3 h after oral administration most significantly inhibited histamine release. This inhibitory effect was dose-dependent and was weaker than that of tranilast. In contrast, SST at 3 h had no effect on the antigen-induced Ca2+ response of the mast cells and failed to inhibit compound 48/80-induced histamine release. Our findings show that SST indeed has an active anti-allergic effect. We suggest that SST inhibits IgE receptor-associated protein phosphorylation in the histamine release pathway.

Characterization of a mobile Stat6 activation motif in the human IL-4 receptor.

The IL-4R induces proliferation and gene expression through the use of conserved tyrosine residues located in growth and gene regulation domains, respectively. We demonstrate that residues surrounding these conserved tyrosines (juxtatyrosine residues) are essential for the proper activation of the signaling molecules IRS-2 and Stat6, as well as for IL-4-induced gene expression. Further, we found that the IL-4R gene regulation domain (amino acids 557-657) contains a tyrosine-based sequence (EAGYKAF) that can convey Stat6 DNA binding and gene expression activities to a minimally active IL-4R mutant, delta 557. Thus, this tyrosine-based sequence can function as a mobile Stat6 activation cassette. However, mutants bearing this sequence induced CD23 expression much less efficiently than did wild-type IL-4R, requiring 150-fold more IL-4 to reach maximal CD23 expression. Our results indicate the importance of juxtatyrosine residues in IL-4R signaling and argue for an essential role of extended domain structure in the recognition and function of juxtatyrosine sequences.

Efficacy of traditional Chinese herbal therapy in vitro. A model system for atopic eczema: inhibition of CD23 expression on blood monocytes.

Recently, there has been growing interest in the use of traditional Chinese herbal therapy (TCHT) decoctions for the treatment of atopic eczema (AE). The mode of action of this treatment is still unknown, and in order to investigate this we have analysed the effect of an extract of these herbs (TCHTE) on interleukin 4 (IL-4)-induced CD23 expression on peripheral blood monocytes from non-atopic subjects. We found that TCHTE inhibited CD23 expression up to 60% (P < 0.001), whereas the placebo extract had no significant effect on CD23 expression. This inhibition was dose-dependent, and TCHTE was effective at a concentration of 250 micrograms/ml (P = 0.001). If TCHTE or placebo was added after IL-4, the action of TCHTE could still be seen at 12 h. This inhibition was not due to cell death, as peripheral blood mononuclear cells (PBMCs) cultured with TCHTE or placebo at a concentration used in these experiments had a similar viability to control cultures. Down-regulation of the low affinity receptors for IgE on antigen-presenting cells in patients with AE may contribute to the benefit observed following treatment with TCHT.