Anti-Allergic Effect of 3,4-Dihydroxybenzaldehyde Isolated from Polysiphonia morrowii in IgE/BSA-Stimulated Mast Cells and a Passive Cutaneous Anaphylaxis Mouse Model.

In this study, we investigated the anti-allergic effects of 3,4-dihydroxybenzaldehyde (DHB) isolated from the marine red alga, Polysiphonia morrowii, in mouse bone-marrow-derived cultured mast cells (BMCMCs) and passive cutaneous anaphylaxis (PCA) in anti-dinitrophenyl (DNP) immunoglobulin E (IgE)-sensitized mice. DHB inhibited IgE/bovine serum albumin (BSA)-induced BMCMCs degranulation by reducing the release of ß-hexosaminidase without inducing cytotoxicity. Further, DHB dose-dependently decreased the IgE binding and high-affinity IgE receptor (FcεRI) expression and FcεRI-IgE binding on the surface of BMCMCs. Moreover, DHB suppressed the secretion and/or the expression of the allergic cytokines, interleukin (IL)-4, IL-5, IL-6, IL-13, and tumor necrosis factor (TNF)-α, and the chemokine, thymus activation-regulated chemokine (TARC), by regulating the phosphorylation of IκBα and the translocation of cytoplasmic NF-κB into the nucleus. Furthermore, DHB attenuated the passive cutaneous anaphylactic (PCA) reaction reducing the exuded Evans blue amount in the mouse ear stimulated by IgE/BSA. These results suggest that DHB is a potential therapeutic candidate for the prevention and treatment of type I allergic disorders.

Anti-allergic property of 4,8-sphingadienine stereoisomers in vivo and in vitro model.

4,8-Sphingadienines (SD), metabolites of glucosylceramides (GlcCer), are sometimes determined as key mediators of the biological activity of dietary GlcCer, and cis/trans geometries of 4,8-SD have been reported to affect its activity. Since regulating excessive activation of mast cells seems an important way to ameliorate allergic diseases, this study was focused on cis/trans stereoisomeric-dependent inhibitory effects of 4,8-SD on mast cell activation. Degranulation of RBL-2H3 was inhibited by treatment of 4-cis-8-trans- and 4-cis-8-cis-SD, and their intradermal administrations ameliorated ear edema in passive cutaneous anaphylaxis reaction, but 4-trans-8-trans- and 4-trans-8-cis-SD did not. Although the activation of mast cells depends on the bound IgE contents, those stereoisomers did not affect IgE contents on RBL-2H3 cells after the sensitization of anti-TNP IgE. These results indicated that 4-cis-8-trans- and 4-cis-8-cis-SD directly inhibit the activation of mast cells. In conclusion, it was assumed that 4,8-SD stereoisomers with cis double bond at C4-position shows anti-allergic activity by inhibiting downstream pathway after activation by the binding of IgE to mast cells.

Lactobacillus plantarum 22A-3 exerts anti-allergic activity through TGF-ß secretion in passive cutaneous anaphylaxis of mice.

Allergy is a global issue, however, medical intervention for allergy treatment is limited. Recent studies have focussed on allergy prevention with food factors. In this study, Lactobacillus plantarum 22 A-3 (LP22A3) exerted an anti-allergic effect in passive cutaneous anaphylaxis (PCA) reaction and increased transforming growth factor (TGF)-ß contents in blood. The increase of TGF-ß contents in blood by exogenous TGF-ß injection intraperitoneally decreased Evans blue release into mice ears to the same level as LP22A3 treatment in PCA reaction. LP22A3 treatment directly to RBL-2H3 cells shows no effect on ß-hexosaminidase release from RBL-2H3 but inhibited its release using the Caco-2/RBL-2H3 cells co-culture system stimulated with LP22A3 from the apical side. Moreover, TGF-ß treatment to RBL-2H3 inhibited ß-hexosaminidase release from RBL-2H3. However, ß-hexosaminidase release was cancelled by TGF-ß neutralising antibody without the influence of TGF-ß mRNA expression in Caco-2 cells. These results showed that LP22A3 ameliorates allergy by TGF-ß secretion through the intestine.

Anti-allergic actions of a Chinese patent medicine, huoxiangzhengqi oral liquid, in RBL-2H3 cells and in mice.

CONTEXT: Huoxiangzhengqi oral liquid (HXZQ-OL), a traditional Chinese medicine formula, has antibacterial, anti-inflammation and gastrointestinal motility regulation effects. OBJECTIVE: The study investigates the anti-allergic activity and underlying mechanism of HXZQ-OL. MATERIALS AND METHODS: IgE/Ag-mediated RBL-2H3 cells were used to evaluate the anti-allergic activity of HXZQ-OL (43.97, 439.7 and 4397 µg/mL) in vitro. The release of cytokines and eicosanoids were quantified using ELISA. RT-qPCR was used to measure the gene expression of cytokines. The level of intracellular Ca2+ was measured with Fluo 3/AM. Immunoblotting analysis was performed to investigate the mechanism of HXZQ-OL. In the passive cutaneous anaphylaxis (PCA), BALB/c mice (5 mice/group) were orally administrated with HXZQ-OL (263.8, 527.6 and 1055 mg/kg/d) or dexamethasone (5 mg/kg/d, positive control) for seven consecutive days. RESULTS: HXZQ-OL not only inhibited degranulation of mast cells (IC50, 123 µg/mL), but also inhibited the generation and secretion of IL-4 (IC50, 171.4 µg/mL), TNF-α (IC50, 88.4 µg/mL), LTC4 (IC50, 52.9 µg/mL) and PGD2 (IC50, 195.8 µg/mL). Moreover, HXZQ-OL suppressed the expression of IL-4 and TNF-α mRNA, as well as the phosphorylation of Fyn, Lyn and multiple downstream signalling proteins including MAPK and PI3K/NF-κB pathways. In addition, HXZQ-OL (527.5 mg/kg) attenuated the IgE-mediated PCA with 55% suppression of Evans blue exudation in mice. CONCLUSIONS: HXZQ-OL attenuated the activation of mast cell and PCA. Therefore, HXZQ-OL might be used as an alternative treatment for allergic diseases.

Roxithromycin inhibits compound 48/80-induced pseudo-allergy via the MrgprX2 pathway both in vitro and in vivo.

Roxithromycin (ROX) is a macrolide antibiotic with a variety of immunological effects. Mast cells (MCs) play a key role in host defense, mediating hypersensitivity and pseudo-allergic reactions. Mas-related G protein-coupled receptor X2 (MrgprX2) is the main receptor related to pseudo-allergy. In this study, we investigated the anti-pseudo-allergy effect of ROX and its underlying mechanism. The effects of ROX on passive cutaneous anaphylaxis (PCA) and active systemic allergy were examined, degranulation, Ca2+ influx, and cytokine release were studied in vivo and in vitro. Interactions between ROX and MrgprX2 protein were also detected through surface plasmon resonance. The PCA and active systemic allergy induced by compound 48/80 were inhibited by ROX. An intermolecular interaction was detected between the ROX and MrgprX2 protein. In conclusion, ROX could inhibit pseudo-allergic reactions, and this effect involves the Ca2+/PLC/IP3 pathway of MrgprX2. This study provides new insight into the anti-pseudo-allergy effects of ROX.

AGK2 ameliorates mast cell-mediated allergic airway inflammation and fibrosis by inhibiting FcεRI/TGF-ß signaling pathway.

Asthma is characterized by airway hyperresponsiveness and allergic inflammation, detrimentally affecting the patients' quality of life. The development of new drugs for the treatment of asthma is warranted to alleviate these issues. Recent studies have demonstrated that sirtuin2 (SIRT2) aggravates asthmatic inflammation by up-regulation of T-helper type 2 responses and macrophage polarization. However, effects of SIRT2 on mast cell activation remain obscure. In this study, we investigated the effects of AGK2, an inhibitor for SIRT2, on mast cell-mediated allergic airway inflammation. Pre-treatment with AGK2 inhibited degranulation of mast cells by suppressing the FcεRI signaling pathway and intracellular calcium influx. The expression of pro-inflammatory cytokines, such as tumor necrosis factor (TNF)-α, interleukin (IL)-1ß, IL-4, IL-5, IL-6, and IL-8, was inhibited via regulation of transcription factors such as NF-κB and NRF2. These effects of AGK2 were verified in passive cutaneous anaphylaxis and acute lung injury animal models. AGK2 attenuated Evans blue pigmentation by inhibiting mast cell activation and lung barrier dysfunction by inhibiting inflammatory responses in these animal models. In the ovalbumin (OVA)-induced allergic airway inflammation murine model, AGK2 alleviated allergic asthma symptoms such as lung histological changes (immune cell and mast cell infiltration, collagen deposition, and α-smooth muscle actin expression) and serum immunoglobulins (Ig) levels (IgE, OVA-specific IgE, IgG1, and IgG2a). Moreover, AGK2 reduced the levels of pro-inflammatory cytokines (TNF-α, IL-1ß, IL-4, IL-5, and IL-6) and inflammatory mediators (myeloperoxidase, eosinophil peroxidase, and tumor growth factor-α) in the bronchoalveolar lavage fluid and lung tissues. In addition, the anti-fibrotic effects of AGK2 were verified using lung epithelial cells and TGF-ß/Smad reporter stable cells. In conclusion, our findings suggest that SIRT2 plays a role in mast cell-mediated airway inflammatory disease. Therefore, AGK2 is a good potential candidate for treating allergic asthma and lung inflammation.

Sargassum horneri as a Functional Food Ameliorated IgE/BSA-Induced Mast Cell Activation and Passive Cutaneous Anaphylaxis in Mice.

Sargassum horneri (S. horneri), an edible brown alga, has been proposed as a functional food with an improvement effect on abnormal skin immune responses. The present study investigates the anti-allergic effect of an ethanol extract from S. horneri (SHE) on immunoglobulin E (IgE)/bovine serum albumin (BSA)-mediated activation in bone marrow-derived cultured-mast cells (BMCMCs) and passive cutaneous anaphylaxis (PCA) reaction in mice. SHE markedly and dose-dependently suppressed the degranulation of BMCMCs by reducing the ß-hexosaminidase and histamine release without cytotoxicity. In addition, SHE significantly decreased the FcεRI expression on the surface of BMCMCs and its IgE binding. Moreover, SHE reduced the mRNA expression and the production of allergic cytokines; interleukin (IL)-1ß, IL-4, IL-5, IL-6, IL-10, IL-13; interferon (IFN)-γ and/or tumor necrosis factor (TNF)-α; and a chemokine, thymus and activation-regulated chemokine (TARC), by suppressing the activation of Src-family kinases and nuclear factor (NF)-κB signaling. In further study, the application of SHE reduced the PCA reaction in an IgE/BSA-induced type I allergic mice model. Taken together, we suggest that SHE has an anti-allergic effect in type I allergic responses.

Extract of Boehmeria nivea Suppresses Mast Cell-Mediated Allergic Inflammation by Inhibiting Mitogen-Activated Protein Kinase and Nuclear Factor-κB.

Mast cells are effector cells that initiate allergic inflammatory immune responses by inducing inflammatory mediators. Boehmeria nivea (Linn.) Gaudich is a natural herb in the nettle family Urticaceae that possesses numerous pharmacological properties. Despite the various pharmacological benefits of Boehmeria nivea, its effects on allergic inflammation have not yet been determined. Here, we investigated the effect of the ethanol extract of Boehmeria nivea (BNE) on degranulation rat basophilic leukemia (RBL)-2H3 mast cells stimulated with anti-dinitrophenyl (anti-DNP) and bovine serum albumin (BSA) during immunoglobulin E (IgE)-mediated allergic immune response. The results showed inhibition of the release of ß-hexosaminidase and histamine from the cells. BNE suppressed pro-inflammatory cytokines (Tumor necrosis factor (TNF)-α, Interleukin (IL)-1ß, and IL-6) and reduced T helper (Th)2 cytokine IL-4 expression and/or secretion correlated with the downregulation of p38, extracellular signal-regulated kinases (ERK) mitogen-activated protein kinase (MAPK), and nuclear factor-κB (NF-κB) signaling pathways in treated RBL-2H3 mast cells. In passive cutaneous anaphylaxis, treatment with BNE during IgE-mediated local allergic reaction triggered a reduction in mouse ear pigmentation and thickness. Taken together, these results indicated that BNE suppressed mast cell-mediated inflammation, suggesting that BNE might be a candidate for the treatment of various allergic disorders.

Wheat Bran Extract Regulates Mast Cell-Mediated Allergic Responses In Vitro and In Vivo.

In the present study the effects and molecular mechanisms of wheat bran (WB), the hard outer layer of the wheat kernel used in food ingredients, on mast cell-mediated allergic responses in vitro and in vivo were investigated. The water extract of WB inhibited degranulation and expression of allergic and inflammatory mediators such as tumor necrosis factor-α, cyclooxygenase-2 and inducible nitric oxide synthase in antigen-stimulated RBL-2H3 cells. These anti-allergic activities of WB were mediated by the inactivation of extracellular signal-regulated kinase and p38 mitogen-activated protein kinase, which play important roles in degranulation and expression of various allergic and inflammatory molecules. In agreement with its in vitro effects, WB inhibited immunoglobulin E (IgE)/antigen-induced and compound 48/80-induced anaphylactic reactions in vivo. Taken together, these findings suggest the pharmacological potential of WB in the regulation of allergic diseases, including allergic rhinitis, atopic dermatitis, asthma and anaphylaxis.

In Vivo Anti-inflammatory and Antiallergic Activity of Pure Naringenin, Naringenin Chalcone, and Quercetin in Mice.

Flavonoids, found in almost all fruits and vegetables, belong to a class of plant secondary metabolites with a polyphenolic structure and have properties with health-improving potential. However, few experimental studies on the effects of flavonoids have been carried out in vivo after external application and using pure compounds. Aiming to fill this gap, in this study we tested the topical anti-inflammatory and antiallergic activity of three flavonoids of high purity, naringenin, naringenin chalcone, and quercetin, in mouse models. The topical anti-inflammatory effects were assessed against arachidonic acid- (AA) and tetradecanoylphorbol-13-acetate- (TPA) induced ear edema. The anti-inflammatory effect of naringenin against ear edema was noticeable at a 1% dose in the AA model and at half this dose in the TPA model. Quercetin (1.3%) did not exert any topical anti-inflammatory activity in the AA model, but its inhibitory effect in the TPA model was similar to that of naringenin (2%); in contrast, naringenin chalcone was more active against the AA-induced than TPA-induced inflammation. The flavonoid effect on IgE-mediated passive cutaneous anaphylaxis was also studied in mice, both intravenously and topically. Naringenin, naringenin chalcone, and quercetin all showed strong antiallergic activity after intravenous dosing (0.02%) and when applied topically (2%). The results of this study suggest that the flavonoids naringenin, naringenin chalcone, and quercetin may be useful alternatives for the topical treatment of inflammatory and allergic skin disorders.

Hispidulin Inhibits Mast Cell-Mediated Allergic Inflammation through Down-Regulation of Histamine Release and Inflammatory Cytokines.

Hispidulin (4',5,7-trihydroxy-6-methoxyflavone) is a natural compound derived from traditional Chinese medicinal herbs, and it is known to have an anti-inflammatory effect. Here, we investigated the effect of hispidulin on the immunoglobulin E (IgE)-mediated allergic responses in rat basophilic leukemia (RBL)-2H3 mast cells. When RBL-2H3 cells were sensitized with anti-dinitrophenyl (anti-DNP) IgE and subsequently stimulated with DNP-human serum albumin (HSA), histamine and ß-hexosaminidase were released from the cells by degranulation of activated mast cells. However, pretreatment with hispidulin before the stimulation of DNP-HSA markedly attenuated release of both in anti-DNP IgE-sensitized cells. Furthermore, we investigated whether hispidulin inhibits anti-DNP IgE and DNP-HSA-induced passive cutaneous anaphylaxis (PCA), as an animal model for Type I allergies. Hispidulin markedly decreased the PCA reaction and allergic edema of ears in mice. In addition, activated RBL-2H3 cells induced the expression of inflammatory cytokines (tumor necrosis factor-α and interleukin-4), which are critical for the pathogenesis of allergic disease, through the activation of c-Jun N-terminal kinase (JNK). Inhibition of JNK activation by hispidulin treatment reduced the induction of cytokine expression in the activated mast cells. Our results indicate that hispidulin might be a possible therapeutic candidate for allergic inflammatory diseases through the suppression of degranulation and inflammatory cytokines expression.

Design and synthesis of novel pyrimidine analogs as highly selective, non-covalent BTK inhibitors.

BTK is a promising target for the treatment of multiple diseases such as B cell malignances, asthma, and rheumatoid arthritis. Here, we report the discovery of a series of novel pyrimidine analogs as potent, highly selective, non-covalent inhibitors of BTK. Compound 25d demonstrated higher affinity to an unactivated conformation of BTK that resulted in an excellent kinase selectivity. Compound 25d showed a good oral bioavailability in mice, and significantly inhibits the PCA reaction in mice.

A flavanone derivative from the Asian medicinal herb (Perilla frutescens) potently suppresses IgE-mediated immediate hypersensitivity reactions.

Perilla frutescens is a dietary leafy herb consumed as a traditional Japanese condiment as well as used for Chinese medicine with anti-inflammatory activity. Here we report a hitherto-unrecognized P. frutescens phytochemical that potently suppresses IgE-mediated type I hypersensitivity reactions. Structural analysis reveals that the purified anti-allergic compound (Perilla-derived methoxyflavanone, PDMF) is identified as 8-hydroxy-5,7-dimethoxyflavanone. PDMF significantly inhibits IgE-mediated histamine release from RBL-2H3 rat basophilic leukemia cells as compared with those seen in known P. frutescens-derived anti-inflammatory polyphenols. We also show that oral administration of PDMF not only suppresses passive cutaneous anaphylaxis, but also prevents allergic rhinitis-like nasal symptoms in a murine model of Japanese cedar pollinosis. Mechanistically, PDMF negatively regulates Akt phosphorylation and intracellular Ca2+ influx, both of which are essential for mast cell secretory granule translocation and its exocytosis upon high-affinity IgE receptor (FcεRI) cross-linking. These results represent PDMF as a new potent anti-allergic phytochemical useful for prevention of IgE-driven hypersensitivity reactions.

Anti-allergic activity of 2,4,6-trihydroxy-3-geranylacetophenone (tHGA) via attenuation of IgE-mediated mast cell activation and inhibition of passive systemic anaphylaxis.

tHGA, a geranyl acetophenone compound originally isolated from a local shrub called Melicope ptelefolia, has been previously reported to prevent ovalbumin-induced allergic airway inflammation in a murine model of allergic asthma by targeting cysteinyl leukotriene synthesis. Mast cells are immune effector cells involved in the pathogenesis of allergic diseases including asthma by releasing cysteinyl leukotrienes. The anti-asthmatic properties of tHGA could be attributed to its inhibitory effect on mast cell degranulation. As mast cell degranulation is an important event in allergic responses, this study aimed to investigate the anti-allergic effects of tHGA in cellular and animal models of IgE-mediated mast cell degranulation. For in vitro model of IgE-mediated mast cell degranulation, DNP-IgE-sensitized RBL-2H3 cells were pre-treated with tHGA before challenged with DNP-BSA to induce degranulation. For IgE-mediated passive systemic anaphylaxis, Sprague Dawley rats were sensitized by intraperitoneal injection of DNP-IgE before challenged with DNP-BSA. Both in vitro and in vivo models showed that tHGA significantly inhibited the release of preformed mediators (ß-hexosaminidase and histamine) as well as de novo mediators (interleukin-4, tumour necrosis factor-α, prostaglandin D2 and leukotriene C4). Pre-treatment of tHGA also prevented IgE-challenged RBL-2H3 cells and peritoneal mast cells from undergoing morphological changes associated with mast cell degranulation. These findings indicate that tHGA possesses potent anti-allergic activity via attenuation of IgE-mediated mast cell degranulation and inhibition of IgE-mediated passive systemic anaphylaxis. Thus, tHGA may have the potential to be developed as a mast cell stabilizer for the treatment of allergic diseases in the future.

The bacterial quorum-sensing molecule, N-3-oxo-dodecanoyl-L-homoserine lactone, inhibits mediator release and chemotaxis of murine mast cells.

OBJECTIVE: Bacterial colonization relies on communication between bacteria via so-called "quorum-sensing molecules", which include the acyl-homoserine lactone group. Certain acyl-homoserine lactones can modulate mammalian cell function and are thought to contribute to bacterial pathogenicity. Given the role of mast cells in host defense, we investigated the ability of acyl-homoserine lactones to modulate mast cell function. METHODS: We utilized murine primary mast cell cultures to assess the effect of acyl-homoserine lactones on degranulation and cytokine release in response to different stimuli. We also assessed cell migration in response to chemoattractants. The effect of acyl-homoserine lactones in vivo was tested using a passive cutaneous anaphylaxis model. RESULTS: Two of the tested quorum-sensing molecules, N-3-oxo-dodecanoyl-L-homoserine lactone and N-Dodecanoyl-L-homoserine lactone, inhibited IgE dependent and independent degranulation and mediator release from primary mast cells. Further testing of N-3-oxo-dodecanoyl-L-homoserine lactone, the most potent inhibitor and a product of Pseudomonas aeruginosa, revealed that it also attenuated chemotaxis and LPS induced cytokine production. In vivo, N-3-oxo-dodecanoyl-L-homoserine lactone inhibited the passive cutaneous anaphylaxis response in mice. CONCLUSION: The ability of N-3-oxo-dodecanoyl-L-homoserine lactone to stabilize mast cells may contribute to the pathogenicity of P. aeruginosa but could potentially be exploited therapeutically in allergic disease.

ß-eudesmol suppresses allergic reactions via inhibiting mast cell degranulation.

The regulatory effect of ß-eudesmol, which is an active constituent of Pyeongwee-San (KMP6), is evaluated for allergic reactions induced by mast cell degranulation. Phorbol 12-myristate 13-acetate (PMA) plus calcium ionophore A23187-stimulated human mast cell line, HMC-1 cells, and compound 48/80-stimulated rat peritoneal mast cells (RPMCs) are used as the in vitro models; mice models of systemic anaphylaxis, ear swelling, and IgE-dependent passive cutaneous anaphylaxis (PCA) are used as the in vivo allergic models. The results demonstrate that ß-eudesmol suppressed the histamine and tryptase releases from the PMA plus calcium ionophore A23187-stimulated HMC-1 cells. ß-eudesmol inhibits the expression and activity of histidine decarboxylase in the activated HMC-1 cells. In addition, ß-eudesmol inhibits the levels of histamine and tryptase released from the compound 48/80-stimulated RPMCs. Furthermore, ß-eudesmol decreases the intracellular calcium level in the activated RPMCs. ß-eudesmol also decreases the compound 48/80-induced mortality and ear swelling response. ß-eudesmol suppresses the serum levels of histamine, IgE, interleukin (IL)-1ß, IL-4, IL-5, IL-6, IL-13, and vascular endothelial growth factor (VEGF) under PCA mice as well as PCA reactions. Therefore, the results from this study indicate the potential of ß-eudesmol as an anti-allergic drug with respect to its pharmacological properties against mast cell-mediated allergic reactions.

Davallia mariesii Moore Improves FcεRI-Mediated Allergic Responses in the Rat Basophilic Leukemia Mast Cell Line RBL-2H3 and Passive Cutaneous Anaphylaxis in Mice.

Davallia mariesii Moore (Drynaria rhizome extract (DRE)) is widely known for its efficacy in treating inflammation, arteriosclerosis, and bone injuries. This study evaluated whether treatment with DRE inhibited FcɛRI-mediated allergic responses in the RBL-2H3 mast cells and investigated the early- and late-phase mechanisms by which DRE exerts its antiallergic effects. IgE anti-DNP/DNP-HSA-sensitized RBL-2H3 mast cells were tested for cytotoxicity to DRE, followed by the assessment of ß-hexosaminidase release. We measured the amounts of inflammatory mediators (e.g., histamine, PGD2, TNF-α, IL-4, and IL-6) and examined the expression of genes involved in arachidonate and FcεRI signaling pathways. In addition, we confirmed the antiallergic effects of DRE on passive cutaneous anaphylaxis (PCA) in mice. DRE inhibited RBL-2H3 mast cell degranulation and production of allergic mediators in them. In early allergic responses, DRE reduced expression of FcεRI signaling-related genes (e.g., Syk, Lyn, and Fyn) and extracellular signal-regulated kinase phosphorylation in mast cells. In late allergic responses, DRE reduced PGD2 release and COX-2 expression and cPLA2 phosphorylation in FcɛRI-mediated mast cells. Lastly, 250-500 mg/kg DRE significantly attenuated the IgE-induced PCA reaction in mice. These findings provide novel information on the molecular mechanisms underlying the antiallergic effects of DRE in FcɛRI-mediated allergic responses.

Extracellular superoxide dismutase ameliorates house dust mite-induced atopic dermatitis-like skin inflammation and inhibits mast cell activation in mice.

Extracellular superoxide dismutase (EC-SOD) is an enzyme that catalyses the dismutation of superoxide anions. It has multiple functions, such as reactive oxygen species scavenging, anti-angiogenic, anti-inflammatory, antichemotatic and antitumor activities. Recently, we demonstrated that EC-SOD inhibits ovalbumin-induced allergic airway inflammation in mice. However, the anti-allergic effect of EC-SOD on skin tissue and the role of EC-SOD in mast cells, which are important for allergic responses, have not been well studied. In this study, we investigated whether EC-SOD can alleviate atopic dermatitis in mice and inhibit mast cell activation. Treatment with human recombinant EC-SOD ameliorated house dust mite-induced atopic dermatitis in mice. Furthermore, the levels of pro-allergic cytokine gene expression and histamine release increased in EC-SOD KO mast cells and decreased in EC-SOD overexpressing mast cells, suggesting that EC-SOD inhibits mast cell activation. Consistently, a passive cutaneous anaphylaxis experiment showed more blood leakage from EC-SOD KO mouse ear skin, implying that the lack of EC-SOD increases allergic responses. These results suggest that EC-SOD inhibits mast cell activation and atopic dermatitis and that the loss of EC-SOD causes more severe allergic responses, implying that EC-SOD might be a good drug candidate for treatment of allergic disorders, such as atopic dermatitis.

Spiraeoside inhibits mast cells activation and IgE-mediated allergic responses by suppressing phospholipase C-γ-mediated signaling.

Mast cells are responsible for IgE-mediated allergic responses through the secretion of various inflammatory cytokines and mediators. Therefore, the pharmacological regulation of mast cell activation is an important goal in the development of novel anti-allergic drugs. In this study, we found that spiraeoside (SP) inhibits mast cell activation and allergic responses in vivo. SP dose-dependently inhibited the degranulation induced by IgE-antigen (Ag) stimulation in RBL-2H3 mast cells without cytotoxic effects. At the molecular level, SP reduced the Ag-induced phosphorylation and subsequent activation of phospholipase C-γ2 (PLC-γ2). Moreover, SP inhibited the phosphorylation of spleen tyrosine kinase (Syk), linker for activation of T cells (LAT), and downstream MAPKs, such as ERK1/2, p38, and JNK, eventually attenuating expression of TNF-α and IL-4. Finally, we found that SP significantly inhibited IgE-mediated passive cutaneous anaphylaxis (PCA) in mice. Taken together, our results strongly suggest that SP suppresses IgE-mediated mast cell activation and allergic responses by inhibiting Lyn-induced PLC-γ2/MAPK signaling in mast cells.

Rhamnus davurica leaf extract inhibits Fyn activation by antigen in mast cells for anti-allergic activity.

BACKGROUND: Complementary and alternative herbal medicines are recently considered as a promising approach for treating various diseases. We screened approximately 100 plant extracts for anti-allergic activity. Rhamnus davurica leaf extract showed the most potent inhibitory effect on the activation of RBL-2H3 mast cells. Although Rhamnus davurica extract has been used to treat pruritus, dysuresia, and constipation as a traditional herbal medicine in some Asian countries, an anti-allergic effect of Rhamnus davurica has not yet been demonstrated. We aimed to investigate the effect and mechanism of the leaf extract of Rhamnus davurica (LERD) on mast cells in vitro and allergic responses in vivo. METHODS: The effects of LERD on the activation of mast cells and mast cell-mediated passive cutaneous anaphylaxis (PCA) were measured in mice and two types of mast cells, mouse bone marrow-derived mast cells (BMMCs) and RBL-2H3 cells in vitro. A mechanistic study of its inhibitory effect was performed by using degranulation assay, reverse transcriptase-polymerase chain reaction, enzyme-linked immunosorbent assay, and western blotting analysis. RESULTS: LERD reversibly suppressed antigen-stimulated degranulation in BMMCs and RBL-2H3 cells, and also inhibited mRNA expression and secretion of TNF-α and IL-4 in a dose-dependent manner. In a PCA animal model, LERD significantly inhibited antigen-induced allergic response and degranulation of ear tissue mast cells. As for the mechanism of action, LERD inhibited the activation of Syk, which is the pivotal signaling protein for mast cell activation by antigen. Furthermore, LERD also impeded the activations of well-known downstream proteins such as LAT, Akt and three MAP kinases (Erk, p38 and JNK). In an in vitro kinase assay, LERD suppressed the activation of Fyn in antigen-stimulated mast cells. CONCLUSION: This study demonstrated for the first time that LERD has anti-allergic effects through inhibiting the Fyn/Syk pathway in mast cells. Therefore, this study provides scientific evidence for LERD to be used as an herbal medicine or health food for patients with allergic diseases.