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 共查询到10条相似文献,搜索用时 281 毫秒
1.
BACKGROUND AND PURPOSE: M2-type pyruvate kinase (M2PK) was found to interact directly with the 'ITAM' region of the gamma chain of the high-affinity IgE receptor (FcvarepsilonRI). Our hypothesis was that mast cell degranulation might require the FcvarepsilonRI-mediated inhibition of M2PK activity. EXPERIMENTAL APPROACH: In rat basophilic leukaemia (RBL-2H3) cells, the effects of directly inhibiting M2PK or preventing the FcvarepsilonRI-mediated inhibition of M2PK (disinhibition) on degranulation was measured by hexosaminidase release. Effects of blocking the FcvarepsilonRI-mediated inhibition of M2PK was also assessed in vivo in a mouse model of allergen-induced airway hyper-responsiveness. KEY RESULTS: Activation of FcvarepsilonRI in RBL-2H3 cells caused the rapid phosphorylation of tyrosine residues in M2PK, associated with a decrease in M2PK enzymatic activity. There was an inverse correlation between M2PK activity and mast cell degranulation. FcvarepsilonRI-mediated inhibition of M2PK involved Src kinase, phosphatidylinositol 3-kinase, PKC and calcium. Direct inhibition of M2PK potentiated FcvarepsilonRI-mediated degranulation and prevention of the FcvarepsilonRI-mediated inhibition of M2PK attenuated mast cell degranulation. Transfection of RBL-2H3 cells with M1PK which prevents FcvarepsilonRI-induced inhibition of M2PK, markedly reduced their degranulation and exogenous M1PK (i.p.) inhibited ovalbumin-induced airway hyper-responsiveness in vivo. CONCLUSIONS AND IMPLICATIONS: We have identified a new control point and a novel biochemical pathway in the process of mast cell degranulation. Our study suggests that the FcvarepsilonRI-mediated inhibition of M2PK is a crucial step in responses to allergens. Moreover, the manipulation of glycolytic processes and intermediates could provide novel strategies for the treatment of allergic diseases.  相似文献   

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

3.
Houttuynia cordata has been used as a traditional medicine in Korea and is known to have antioxidant, anti-cancer and anti-allergic activities. The precise effect of H. cordata, however, remains unknown. In this study, we investigated the effects of H. cordata water extract (HCWE) on passive cutaneous anaphylaxis (PCA) in mice and on IgE-mediated allergic response in rat mast RBL-2H3 cells. Oral administration of HCWE inhibited IgE-mediated systemic PCA in mice. HCWE also reduced antigen (DNP-BSA)-induced release of β-hexosaminidase, histamine, and reactive oxygen species in IgE-sensitized RBL-2H3 cells. In addition, HCWE inhibited antigen-induced IL-4 and TNF-α production and expression in IgE-sensitized RBL-2H3 cells. HCWE inhibited antigen-induced activation of NF-κB and degradation of IκB-α. To investigate the inhibitory mechanism of HCWE on degranulation and cytokine production, we examined the activation of intracellular FcεRI signaling molecules. HCWE suppressed antigen-induced phosphorylation of Syk, Lyn, LAT, Gab2, and PLC γ2. Further downstream, antigen-induced phosphorylation of Akt and MAP kinases (ERK1/2 and JNK1/2 but not p38 MAP kinase) were inhibited by HCWE. Taken together, the in vivo/in vitro anti-allergic effect of HCWE suggests possible therapeutic applications of this agent in inflammatory allergic diseases through inhibition of cytokines and multiple events of FcεRI-dependent signaling cascades in mast cells.  相似文献   

4.
The purpose of this study was to investigate the protective effects of saponins isolated from the root of Platycodi Radix (Changkil saponins: CKS) anti-allergic effects in mice and mast cells. Oral administration of CKS inhibited the dinitrophenyl (DNP)–IgE antibody-induced systemic PCA reaction in mice. CKS reduced the β-hexosaminidase and histamine release from anti-DNP–IgE-sensitized RBL–2H3 cells. In addition, CKS inhibited the IgE antibody-induced increases in IL-4 and TNF-α production and expression in RBL-2H3 cells. In order to explore the inhibitory mechanism of CKS in PCA and mast cell degranulation, we examined the activation of intracellular signaling molecules. CKS suppressed DNP–IgE antibody-induced Syk phosphorylation. Further downstream, CKS also inhibited the phosphorylation of Akt and MAP kinases. Taken together, the in vivo/in vitro anti-allergic effects of CKS suggest possible therapeutic applications for this agent in allergic diseases through the inhibition of inflammatory cytokines and Syk-dependent signaling cascades.  相似文献   

5.
Importance of the field: Ocular allergic diseases are characterized by specific activation of conjunctival mast cells with subsequent release of preformed and newly formed mediators. Mast cells are thus the first therapeutic target of ocular anti-allergic treatments.

Areas covered in this review: In this review, a Medline literature search was conducted on conjunctival mast cells, their role in ocular allergy and mast cell stabilization by ocular anti-allergic compounds.

What the reader will gain: Olopatadine hydrochloride, a mast cell stabilizer and histamine receptor antagonist, has been shown to inhibit mast cell activation in an in vitro model of human mast cell culture, reducing histamine and TNF-α release and upregulating proinflammatory mediators in conjunctival epithelial cells. In the in vivo conjunctival allergen challenge (CAC) model in allergic subjects, combined with objective evaluations of tear mediators and cytology, olopatadine reduced histamine tear levels and all aspects of allergic inflammation, confirming the positive clinical effects observed in active allergic patients.

Take home message: Mast cells play a central role in the pathogenesis of ocular allergy. The CAC model is ideal for assessing the mast cell stabilizing effects of anti-allergic compounds. This review of clinical studies demonstrates the superiority of olopatadine compared with other topical allergic drugs.  相似文献   

6.
7.
Reactive oxygen species (ROS) are produced in various cells and affect many biologic processes. In this study, we examined the effects of 2-methyl-1,4-naphtoquinone (menadione; vitamin K3) on signal transduction in mast cells. Several lines of evidence suggest that H2O2 affects the antigen-induced responses in mast cells but its mechanism is not clearly understood. Unlike H2O2, menadione produces ROS only inside cells. Thus, it is possible to investigate the effects of ROS produced intracellularly. Pretreatment of mast cells (RBL-2H3) with menadione inhibited exocytotic secretion (degranulation) induced by antigen stimulation dose dependently. Menadione also inhibited the intracellular Ca2+ increase induced by antigen stimulation. Menadione did not inhibit the Ca2+ increase due to Ca2+ release from the intracellular calcium store in the absence of extracellular Ca2+, but inhibited the Ca2+ influx from the extracellular medium. These results suggest that reactive oxygen generated inside RBL cells by menadione inhibited degranulation by decreasing Ca2+ influx through the store operated Ca2+ channel on the plasma membrane.  相似文献   

8.
The present study was designed to investigate the effect of sinomenine (SIN), an alkaloid extracted from sinomenium acutum, on the antigen-induced activation of RBL-2H3. For this investigation, the RBL-2H3 cells were sensitized with dinitrophenyl (DNP)-specific IgE overnight in 1.0 ml of Eagle's MEM (EMEM), and varying doses of SIN were added to the culture medium for 30 min and challenged with dinitrophenyl-human serum albumin (DNP-HSA) to induce mast cell degranulation before supernatants were collected. The effects of SIN on antigen-induced release of beta-hexosaminidase were measured by enzymatic assay, calcium influx by FACS, cytokines by ELISA, and signaling events by immunoblotting. The results showed that treatment with SIN was followed by a decrease in FcepsilonRI-mediated mast cell release of beta-hexosaminidase, production of IL-4 and TNF-alpha, phosphorylation of Gab2 (Scaffolding adapter Grb2-associated binder 2), Akt and p38 mitogen-activated protein kinase (MAPK). In addition, SIN had no effect on the phosphorylation of LAT and no significant difference on calcium mobilization was observed between control and SIN treated group. These results suggested that SIN might suppress the antigen-induced activation of RBL-2H3 cells via a Ca2+ independent pathway.  相似文献   

9.
1. To determine the role of actin assembly in the Ca(2+) signalling of mast cells activated by cross-linking of FcepsilonRI, we examined the effects of cytochalasin D, an inhibitor of actin polymerization. 2. In the RBL-2H3 cells, F-actin content was increased by sensitization with anti-dinitrophenol (DNP) IgE. In these cells, cytochalasin D induced oscillatory increases in cytosolic Ca(2+) ([Ca(2+)](i)); these increase were inhibited by jasplakinolide, a stabilizer of actin filaments. 3. In the IgE-sensitized RBL-2H3 cells, DNP-human serum albumin (DNP-HSA) augmented actin assembly. DNP-HSA also increased the production of IP(3), [Ca(2+)](i) and degranulation. Cytochalasin D enhanced all of these DNP-HSA-induced effects. 4. In a Ca(2+)-free solution, DNP-HSA induced a transient increase in [Ca(2+)](i), and this increase was accelerated by cytochalasin D. After cessation of the DNP-HSA-induced Ca(2+) release, the re-addition of Ca(2+) induced a sustained increase in [Ca(2+)](i) through capacitative Ca(2+) entry (CCE), and this increase was enhanced by cytochalasin D. 5 The effect of cytochalasin D in enhancing the CCE activity was prevented by xestospongin C. 6. In contrast, neither the Ca(2+) release nor the CCE activation that was induced by thapsigargin was affected by cytochalasin D. 7. These results suggest that actin de-polymerization stimulates the FcepsilonRI-mediated signalling to augment the release of Ca(2+) from the endoplasmic reticulum in RBL-2H3 cells.  相似文献   

10.
Human mast cells express the G protein coupled receptor (GPCR) for C5a (CD88). Previous studies indicated that C5a could cause mast cell degranulation, at least in part, via a mechanism similar to that proposed for basic neuropeptides such as substance P, possibly involving Mas-related gene 2 (MrgX2). We therefore sought to more clearly define the receptor specificity for C5a-induced mast cell degranulation. We found that LAD2, a human mast cell line, and CD34(+) cell-derived primary mast cells express functional MrgX1 and MrgX2 but the immature human mast cell line HMC-1 does not. A potent CD88 antagonist, PMX-53 (10 nM) inhibited C5a-induced Ca(2+) mobilization in HMC-1 cells, but at higher concentrations (≥30 nM) it caused degranulation in LAD2 mast cells, CD34(+) cell-derived mast cells, and RBL-2H3 cells stably expressing MrgX2. PMX-53 did not, however, activate RBL-2H3 cells expressing MrgX1. Although C5a induced degranulation in LAD2 and CD34(+) cell-derived mast cells, it did not activate RBL-2H3 cells expressing MrgX1 or MrgX2. Replacement of Trp with Ala and Arg with dArg abolished the ability of PMX-53 to inhibit C5a-induced Ca(2+) mobilization in HMC-1 cells and to cause degranulation in RBL-2H3 cells expressing MrgX2. These findings demonstrate that C5a does not use MrgX1 or MrgX2 for mast cell degranulation. Moreover, it reveals the novel finding that PMX-53 functions as a potent CD88 antagonist and a low-affinity agonist for MrgX2. Furthermore, Trp and Arg residues are required for the ability of PMX53 to act as both a CD88 antagonist and a MrgX2 agonist.  相似文献   

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