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To investigate the effect of flavonoids on the activation of p72(syk) (Syk) protein tyrosine kinase which plays a pivotal role in the high affinity IgE receptor-mediated degranulation of mast cells, we picked out 10 flavonoids, classified them into 4 series, and examined their effects on the activation of Syk and on the degranulation of human mast cells. Flavones and flavonols showed clear inhibition, whereas flavanones and isoflavones had either weak or no effect on Syk enzymatic activity induced by amino acid peptide corresponding to the activation loop domain and on IgE-dependent degranulation of human cultured mast cells (HCMC). On the basis of calculated logP (ClogP) values as a prediction of compound lipophilicity, some flavonoids were speculated to have low lipophilicity, the reason for poor cell permeability. A significant relationship was observed between the inhibition of Syk activity and HCMC degranulation attributable to flavonoids when the ClogP values of the compounds were taken into account (r(2)=0.89). These results suggested that the impairment of mast cell degranulation by several flavonoids classified into flavones and flavonols might be mediated via inhibition of the intracellular activation of Syk.

Coculture of mouse bone marrow-derived immature mast cells (BMMC) with Swiss 3T3 fibroblasts in the presence of stem cell factor (SCF) promotes morphological and functional maturation toward a connective tissue mast cell (CTMC)-like phenotype, which is accompanied by increased expression of several unique genes. Here we report the molecular identification of one of them, mast cell maturation-associated inducible gene (MMIG)-1. The MMIG-1 cDNA encodes a 117-kDa cytosolic protein that comprises an N-terminal PYRIN domain, a central nucleotide-binding domain, and nine C-terminal leucine-rich repeats. MMIG-1 shows >85% sequence similarity to human cryopyrin/PYPAF1, a causal gene for familial cold urticaria and Muckle-Wells syndrome. MMIG-1 was distributed in the cytosol of CTMC-like differentiated BMMC. MMIG-1 underwent alternative splicing in the leucine-rich repeats and each variant was induced differently in BMMC during coculture. Moreover, its expression was increased in the ears of mice with experimental atopic dermatitis. Thus, MMIG-1, a likely mouse PYPAF1 ortholog, may play a role in mast cell-directed inflammatory diseases.

Recently, we demonstrated that prostaglandin (PG)I2 has a regulatory role in allergic responses through the receptor, IP; however, the role of PGI2 in airway remodeling associated with chronic airway inflammation has not been elucidated. In the present study, we examined the role of PGI2 in allergen-induced airway remodeling using IP gene-deficient mice. Mice were sensitized to ovalbumin (OVA) with alum, and exposed daily for 3 wk to aerosolized OVA. Twenty-four hours after the final antigen inhalation, bronchoalveolar lavage, biochemical, and histopathologic examinations were performed. In wild-type mice, prolonged allergen exposure in sensitized animals induced the increases in the numbers of inflammatory leukocytes (including eosinophils and lymphocytes), levels of T helper type 2 (Th2) cytokines (interleukin [IL]-4, IL-5, and IL-13), levels of OVA-specific immunoglobulin (Ig)E and IgG1 in serum, and amount of hydroxyproline in the right lungs associated with transforming growth factor-beta1 levels in bronchoalveolar lavage fluid. Moreover, goblet cell hyperplasia and subepithelial fibrosis were also appreciated after repeated allergen challenge. In contrast, the disruption of IP gene significantly augmented all these parameters. These findings suggest that PGI2 has a regulatory role in allergen-induced airway remodeling as well as airway eosinophilic inflammation, Th2 cytokine production and IgE production, and that a PGI2 agonist is a therapeutic approach for the treatment of airway remodeling in allergic asthma.

The effects of 4-[4-[5,5,6,6,6-pentafluoro-1-(4-fluorobenzene-sulfonamido)hexyl]phenyl]butyric acid (RS-601), a novel leukotriene D(4) (LTD(4))/thromboxane A(2) (TxA(2)) dual receptor antagonist, on bronchial asthmatic responses in guinea pigs were examined. The effects were compared with those of pranlukast (LTD(4) receptor antagonist) and S-1452 (TxA(2) receptor antagonist). RS-601 inhibited the increase in airway resistance caused by LTD(4) and TxA(2) mimetic compound, U-46619, but not by histamine. RS-601 and pranlukast but not S-1452 inhibited an antigen-induced late asthmatic response. In addition, RS-601 inhibited an antigen-induced airway hyperresponsiveness (AHR), whereas pranlukast and S-1452 had no effect on the AHR. The antigen-induced increase in inflammatory cells in airway was not affected by all examined agents. Furthermore, bacterial lipopolysaccharide-induced AHR in guinea pigs was clearly suppressed by RS-601 but not by pranlukast and S-1452. The increase in airway inflammatory cells caused by lipopolysaccharide was not affected by all three drugs. These findings indicate that RS-601 has a potent antiasthmatic efficacy, especially on AHR, but does not affect accumulation of eosinophils in the airways., (Copyright 2003 S. Karger AG, Basel)

Spleen tyrosine kinase (Syk) tyrosine kinase plays essential roles in receptors for Fc portion of immunoglobulins and B cell receptor complex signaling in various inflammatory cells; therefore, inhibitors of Syk kinase may show potential as antiasthmatic/allergic therapeutics. We identified 2-[7-(3,4-dimethoxyphenyl)-imidazo[1,2-c]pyrimidin-5-ylamino]-nicotinamide dihydrochloride (BAY 61-3606), a potent (Ki = 7.5 nM) and selective inhibitor of Syk kinase. BAY 61-3606 inhibited not only degranulation (IC50 values between 5 and 46 nM) but also lipid mediator and cytokine synthesis in mast cells. BAY 61-3606 was highly efficacious in basophils obtained from healthy human subjects (IC50 = 10 nM) and seems to be at least as potent in basophils obtained from atopic (high serum IgE) subjects (IC50 = 8.1 nM). B cell receptor activation and receptors for Fc portion of IgG signaling in eosinophils and monocytes were also potently suppressed by BAY 61-3606. Oral administration of BAY 61-3606 to rats significantly suppressed antigen-induced passive cutaneous anaphylactic reaction, bronchoconstriction, and bronchial edema at 3 mg/kg. Furthermore, BAY 61-3606 attenuated antigen-induced airway inflammation in rats. Based on these anti-inflammatory effects of BAY 61-3606 both in vitro and in vivo, it was demonstrated that Syk may play a very critical role in the pathogenesis of allergic reactions.

Physical interaction of T cells and dendritic cells (DCs) is essential for T cell proliferation and differentiation, but it has been unclear how this interaction is regulated physiologically. Here we show that DCs produce thromboxane A2 (TXA2), whereas naive T cells express the thromboxane receptor (TP). In vitro, a TP agonist enhances random cell movement (chemokinesis) of naive but not memory T cells, impairs DC-T cell adhesion, and inhibits DC-dependent proliferation of T cells. In vivo, immune responses to foreign antigens are enhanced in TP-deficient mice, which also develop marked lymphadenopathy with age. Similar immune responses were seen in wild-type mice treated with a TP antagonist during the sensitization period. Thus, TXA2-TP signaling modulates acquired immunity by negatively regulating DC-T cell interactions.

Glucocorticoids are effective drugs for the treatment of allergic skin diseases. In the present study, we observed the effects of prednisolone on the cutaneous reaction and skin barrier function in mice treated with a hapten, 2,4-dinitrofluorobenzene. Repeated hapten application onto the mouse ear resulted in a potent ear swelling with an elevation of specific serum IgE. The ear swelling appeared following the second application of the hapten and peaked at 24 h after each application. Specific serum IgE was detected first after the fourth hapten application. Topical treatment with prednisolone apparently suppressed the swelling, whereas it failed to affect the serum specific IgE level. The hapten application caused an increase in transepidermal water loss, which was potently inhibited by prednisolone, although the water content was not affected. Amounts of triglyceride and cholesterol in the ear skin increased after repeated hapten applications, whereas the relative amount of free fatty acid and ceramide diminished. Prednisolone exhibited an inhibitory effect on the changes in lipid content. Thus prednisolone apparently inhibits the alteration of skin barrier function caused by hapten application as well as the cutaneous reaction.

(1) To clarify the involvement of Th2 responses in the development of allergen-induced airway remodelling, we investigated the effect of anti-CD4 monoclonal antibody (mAb) and anti-CD8 mAb, and the responses of IL-4 gene-knockout (KO) mice in a murine model of allergic asthma. (2) Mice were immunized twice by intraperitoneal injections of ovalbumin (OA), and exposed to aeroallergen (OA, 1% w v(-1)) for 3 weeks. Twenty-four hours after the final challenge, airway responsiveness to acetylcholine was measured, and bronchoalveolar lavage (BAL) and histological examinations were carried out. (3) Anti-CD4 mAb (1 mg kg(-1)) clearly inhibited allergen-induced increases in airway responsiveness to acetylcholine, the number of eosinophils in BAL fluid, serum OA-specific IgE levels, IL-13 and transforming growth factor-beta1 levels in BAL fluid, and amount of hydroxyproline in the lung by 100, 99, 100, 100, 84, and 60%, respectively. Furthermore, the antibody (1 mg kg(-1)) also attenuated allergen-induced goblet cell hyperplasia in the epithelium and subepithelial fibrosis by 72 and 83%, respectively. In contrast, anti-CD8 mAb (1 mg kg(-1)) showed no effect on each parameter. Furthermore, all these parameters were attenuated in IL-4KO mice by 57, 93, 100, 45, 84 and 60%, and also 72 and 83%, respectively. (4) These findings suggest that Th2 responses play a critical role for the development of allergen-induced airway remodelling, and that the inhibition of Th2 responses, e.g. using anti-CD4 mAb, is a therapeutic approach for the treatment of airway remodelling in asthma.

The effect of 4-[3,5-bis(trimethylsilyl)benzamido] benzoic acid (TAC-101), one of the synthetic retinoids, on collagen-induced arthritis (CIA) in mice and experimental autoimmune encephalomyelitis (EAE) in rats was studied. TAC-101 at doses of 5 and 20 mg/kg clearly inhibited the development of CIA in terms of the swelling of fore- and hind-limbs and bone destruction in knee joints. TAC-101 also suppressed the production of anti-type II collagen (CII) IgG antibody and delayed-type hypersensitivity (DTH) against CII. In addition, TAC-101 delayed the onset and development of EAE but did not affect the maximum symptom of EAE in rats. The elevation of serum antimyelin basic protein (MBP) antibody and DTH to MBP on day 13 clearly suppressed by TAC-101 in EAE rats. Moreover, TAC-101 inhibited the IL-1beta-induced PGE(2) production by MG-63 cells, human osteoblast-like cells, through the suppression of cyclooxygenase II mRNA expression. These findings suggest that TAC-101 inhibits CIA in mice and EAE in rats due to the suppression of immune response to auto-antigen and the production of PGE(2)., (Copyright 2003 S. Karger AG, Basel)

Rodent mast cells (MCs) are common experimental tools but are somewhat different from their human counterparts in their responses to certain cytokines and drugs. We examined the expression of more than 10 000 distinct genes in human and mouse cultured MCs using high-density oligonucleotide probe arrays to find molecules similarly regulated and expressed by the 2 MC types. After stimulation via high-affinity Fcepsilon receptor I (FcepsilonRI), the transcriptional levels of several CC chemokines were markedly increased, and I-309 (CCL1), macrophage inflammatory protein-1alpha (MIP-1alpha) (CCL3) and MIP-1beta (CCL4) were found among the 10 most increased human and mouse transcripts from approximately 12 000 genes (including some expressed sequence tags). In addition, a costimulatory molecule that was originally found on the membrane of activated T cells, 4-1BB (CD137), was found among the 10 most increased transcripts. The FcepsilonRI-induced expression of CC chemokines and 4-1BB was also detected at the protein level in both MC types. The conservation of these responses suggests that MCs play a crucial role in recruitment of various CCR-expressing cells into the tissue in a manner dependent on immunoglobin E, and that FcepsilonRI-mediated induction of several CC chemokines and 4-1BB is highly conserved between human and mouse. Interspecies comparison studies at the whole genome expression level should be useful for the interpretation of experimental data obtained in animal models of human pathobiology.

1 To evaluate the role of prostaglandin I(2) (PGI(2)) in allergic inflammation, allergic responses in the airway, skin and T cells were studied in mice lacking the receptor for PGI(2) (the prostanoid IP receptor) through gene disruption. 2 Three inhalations of antigen caused an increase in plasma extravasation, leukocyte accumulation and cytokine (interleukin (IL)-4 and IL-5) production in the airway of sensitized mice. These airway inflammatory responses were significantly greater in IP receptor deficient mice than in wild-type mice. 3 The vascular leakage caused by passive cutaneous anaphylaxis, substance P and 5-hydroxytryptamine was markedly increased in the skin of IP receptor deficient mice, compared with comparably treated wild-type mice. 4 The inhalation of antigen in sensitized mice resulted in increased serum antigen specific IgE, total IgE and IgG levels. The magnitude of the elevations of each immunoglobulin level in IP receptor deficient mice is notably higher than that in wild-type mice. To elucidate the mechanism of an enhancement of immunoglobulin production, the activity of T cells in sensitized and non-sensitized mice was studied by means of the production of cytokines. The antigen-induced IL-4 production by spleen cells from sensitized IP receptor deficient mice was almost three times greater than that in wild-type mice. On the contrary, the anti-CD3 antibody-induced interferon-gamma production by CD4(+) T cells from non-sensitized IP receptor deficient mice was significantly lower than that in wild-type mice. 5 The present data indicate that IP receptor deficiency reinforced an allergic airway and skin inflammation by augmentation of vascular permeability increase and the T helper 2 cell function. These findings suggest a regulatory role of PGI(2) in allergic inflammation.

Group IID secretory phospholipase A(2) (sPLA(2)-IID), a heparin-binding sPLA(2) that is closely related to sPLA(2)-IIA, augments stimulus-induced cellular arachidonate release in a manner similar to sPLA(2)-IIA. Here we identified the residues of sPLA(2)-IID that are responsible for heparanoid binding, are and therefore essential for cellular function. Mutating four cationic residues in the C-terminal portion of sPLA(2)-IID resulted in abolition of its ability to associate with cell surface heparan sulfate and to enhance stimulus-induced delayed arachidonate release, cyclooxygenase-2 induction, and prostaglandin generation in 293 cell transfectants. As compared with several other group II subfamily sPLA(2)s, which were equally active on A23187- and IL-1-primed cellular membranes, sPLA(2)-IID showed apparent preference for A23187-primed membranes. Several human colon carcinoma cell lines expressed sPLA(2)-IID and sPLA(2)-X constitutively, the former of which was negatively regulated by IL-1. sPLA(2)-IID, but not other sPLA(2) isozymes, was expressed in human cord blood-derived mast cells. The expression of sPLA(2)-IID was significantly altered in several tissues of mice with experimental inflammation. These results indicate that sPLA(2)-IID may be involved in inflammation in cell- and tissue-specific manners under particular conditions.

Here we report the cellular arachidonate (AA)-releasing function of group IIF secretory phospholipase A(2) (sPLA(2)-IIF), a sPLA(2) enzyme uniquely containing a longer C-terminal extension. sPLA(2)-IIF increased spontaneous and stimulus-dependent release of AA, which was supplied to downstream cyclooxygenases and 5-lipoxygenase for eicosanoid production. sPLA(2)-IIF also enhanced interleukin 1-stimulated expression of cyclooxygenase-2 and microsomal prostaglandin E synthase. AA release by sPLA(2)-IIF was facilitated by oxidative modification of cellular membranes. Cellular actions of sPLA(2)-IIF occurred independently of the heparan sulfate proteoglycan glypican, which acts as a functional adaptor for other group II subfamily sPLA(2)s. Confocal microscopy revealed the location of sPLA(2)-IIF on the plasma membrane. The unique C-terminal extension was crucial for its plasma membrane localization and optimal cellular functions. sPLA(2)-IIF expression was increased in various tissues from lipopolysaccharide-treated mice and in ears of mice with experimental atopic dermatitis. In human rheumatoid arthritic joints, sPLA(2)-IIF was detected in synovial lining cells, capillary endothelial cells, and plasma cells. These results suggest that sPLA(2)-IIF is a potent regulator of AA metabolism and participates in the inflammatory process under certain conditions.

The heparin-binding group II subfamily of secretory phospholipase A(2)s (sPLA(2)s), such as sPLA(2)-IIA and -IID, augments stimulus-induced arachidonic acid (AA) release through the cellular heparan sulfate proteoglycan (HSPG)-dependent pathway when transfected into HEK293 cells. Here we show that the closest homolog, sPLA(2)-IIE, also promotes stimulus-induced AA release and prostaglandin (PG) production similar to those elicited by HSPG-dependent sPLA(2)s. Confocal laser microscopic analysis demonstrates the location of sPLA(2)-IIE in cytoplasmic punctate compartments. sPLA(2)-IIE also enhances leukotriene (LT) production and granule exocytosis by RBL-2H3 mastocytoma cells. Expression of sPLA(2)-IIE was highly upregulated in mice injected with lipopolysaccharide (LPS) and in mice with experimental atopic dermatitis. These observations suggest that this enzyme plays a role in the inflammatory process, as proposed for other group II subfamily sPLA(2)s.

Interleukin (IL)-5 is thought to play important roles in asthma and to be a potential therapeutic target. An intratracheal injection of murine recombinant IL-5 (3-30 microg/animal) induced a dose-dependent increase in the number of eosinophils in the bronchoalveolar lavage fluid of Brown Norway (BN) rats 24 h after administration. Bovine serum albumin (30pg/animal), used as reference material, did not cause any change. The reaction was not observed in F344 rats. The increase in the number of eosinophils did not accompany bronchial hyperreactivity in BN or F344 rats. Prednisolone (3-10 mg/kg, i.p.) and emedastine (30 mg/kg, p.o.) reduced the increased number of eosinophils induced by the IL-5 challenge. These results suggest that IL-5 is a potent inducer of eosinophils in the airway of BN rats. Prednisolone and emedastine are effective against IL-5-induced eosinophilia.