Prostaglandin D2 as a mediator of allergic asthma

The effect of anti-IgE treatment on in vitro leukotriene release in children with seasonal allergic rhinitis

BACKGROUND

Binding of allergens with IgE to the IgE receptors on mast cells and basophils results in the release of inflammatory mediators as sulfidoleukotrienes (SLTs), triggering allergic cascades that result in allergic symptoms, such as asthma and rhinitis.

OBJECTIVE

We sought to investigate whether anti-IgE (Oma-lizumab), a humanized monoclonal anti-IgE antibody, in addition to specific immunotherapy (SIT) affects the leukotriene pathway.

METHODS

Ninety-two children (age range, 6-17 years) with sensitization to birch and grass pollens and with seasonal allergic rhinitis were included in a phase III, placebo- controlled, multicenter clinical study. All subjects were randomized to one of 4 treatment groups. Two groups subcutaneously received birch SIT and 2 groups received grass SIT for at least 14 weeks before the start of the birch pollen season. After 12 weeks of SIT titration, placebo or anti-IgE was added for 24 weeks. The primary clinical efficacy variable was symptom load (ie, the sum of daily symptom severity score and rescue medication score during pollen season). Blood samples taken at baseline and at the end of study treatment after the grass pollen season were used for separation of leukocytes in this substudy. After in vitro stimulation of the blood cells with grass and birch pollen allergens, SLT release (LTC4, LTD4, and LTE4) was quantified by using the ELISA technique.

RESULTS

Before the study treatment, SLT release to birch and grass pollen exposure did not differ significantly among the 4 groups. Under treatment with anti-IgE + SIT-grass (n = 23), a lower symptom load occurred during the pollen season compared to placebo + SIT-grass (n = 24, P =.012). The same applied to both groups receiving birch SIT (n = 23 and n = 22, respectively; P =.03). At the end of treatment, the combination of anti-IgE plus grass SIT, as well as anti-IgE plus birch SIT, resulted in significantly lower SLT release after stimulation with the corresponding allergen (416 ng/L [5th-95th percentile, 1-1168] and 207 ng/L [1-860 ng/L], respectively) compared with placebo plus SIT (2490 ng/L [384-6587 ng/L], P =.001; 2489 ng/L [1-5670 ng/L], P =.001). In addition, treatment with anti-IgE was also followed by significantly lower SLT releases to the allergens unrelated to SIT (grass SIT: 300 ng/L [1-2432 ng/L] in response to birch allergen; birch SIT: 1478 ng/L [1-4593 ng/L] in response to grass pollen) in comparison with placebo (grass SIT: 1850 ng/L [1-5499 ng/L], P =.001; birch SIT: 2792 ng/L [154-5839 ng/L], P =.04].

CONCLUSION

Anti-IgE therapy reduces leukotriene release of peripheral leukocytes stimulated with allergen in children with allergic rhinitis undergoing allergen immunotherapy independent of the type of SIT allergen used.

Augmentation of allergic inflammation in prostanoid IP receptor deficient mice

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.

A comparative study of eicosanoid concentrations in sputum and urine in patients with aspirin-intolerant asthma

BACKGROUND

Although many studies have assumed that the overproduction of cysteinyl- leukotrienes (cys-LTs) and an imbalance of arachidonic acid metabolism may be plausible causes for the pathogenesis of aspirin-intolerant asthma (AIA), there has been little experimental evidence to substantiate this notion in lower airways of patients with AIA.

OBJECTIVES

The purpose of this study was to compare the eicosanoid concentrations in sputum and urine from patients with AIA.

METHODS

The concentrations of sputum cys-LTs, prostaglandin E2 (PGE2), PGF2alpha, PGD2 and thromboxane B2 were measured to assess local concentrations of eicosanoids in patients with AIA and in those with aspirin-tolerant asthma (ATA). The concentrations of two urinary metabolites, leukotriene E4 (LTE4) and 9alpha11betaPGF2, were also measured to corroborate the relationship between the eicosanoid biosynthesis in the whole body and that in lower airways.

RESULTS

The concentration of PGD2 in sputum was significantly higher in patients with AIA than in those with ATA (median, 5.3 pg/mL vs. 3.1 pg/mL, P < 0.05), but there was no significant difference in the concentration of the corresponding metabolite, 9alpha11betaPGF2, between the two groups. No differences were noted in the concentrations of other prostanoids in sputum between the two groups. The sputum cys-LT concentrations showed no differences between the two groups, in spite of the observation that the concentration of urinary LTE4 was significantly higher in patients with AIA than in those with ATA (median, 195.2 pg/mg-cre vs. 122.1 pg/mg-cre, P < 0.05). There was a significant correlation among the concentration of cys-LTs, the number of eosinophils and the concentration of eosinophil-derived neurotoxin (EDN) in sputum.

CONCLUSION

The urinary concentration of LTE4 does not necessary reflect cys-LT biosynthesis in lower airways. A significantly higher concentration of PGD2 in sputum from patients with AIA suggests the possible ongoing mast cell activation in lower airways.

PGD(2) modulates fibroblast-mediated native collagen gel contraction

Repair of tissues is a necessary step in restoring tissue function following injury consequent to inflammation. Many inflammatory mediators are capable of modulating not only the activity of "inflammatory cells" but also of modulating functions of parenchymal cells that may contribute to repair. Disordered repair is believed to contribute to tissue dysfunction in many inflammatory diseases, including bronchial asthma. The current study evaluated the ability of prostaglandin D(2) (PGD(2)) to modulate fibroblast repair using the in vitro contraction of three-dimensional native collagen gels as a model system. PGD(2) stimulated gel contraction in a concentration- and time-dependent manner. In contrast, the PGD(2) analog BW245C inhibited contraction. Both effects were blocked by a DP-receptor blocker (AH6809). Neither TP receptor blocker SQ29548 nor protein kinase (PK) A antagonist KT5720 hand an effect on PGD(2)-stimulated contraction, suggesting action through a novel prostaglandin D receptor. PKC inhibitor calphostin-C (10(-6) M) blocked the PGD(2) stimulation of gel contraction. A calcium-independent PKC-epsilon inhibitor (Ro31-8220), but not calcium-dependent PKC-alpha and -beta inhibitors, also blocked the PGD(2) effect on contraction, implying a role for a calcium-independent pathway. This study, therefore, supports a role for PGD(2) in tissue repair and remodeling. These effects of PGD(2) appear to be mediated through receptor-signal transduction pathways different from the cAMP-PKA pathways mediating the proinflammatory activity of PGD(2), creating the possibility for selective therapeutic manipulation.

[Functional molecules in allergic bronchial asthma]

Bronchial asthma is considered to be a chronic airway inflammatory disease, characterized by airway obstruction, airway eosinophilic inflammation, and airway hyperresponsiveness (AHR) to a variety of stimuli. AHR is thought to be an important symptom, because the severity of the disease is generally correlated with the degree of AHR. Recent clinical studies have demonstrated the involvement of airway inflammation in the development of allergen-induced AHR, although, the mechanism of allergen-induced AHR has not been fully elucidated and remains controversial. In vivo animal models might provide important information on this point. We have established a mouse model of allergic asthma, which is characterized by airway eosinophilia, IgE production, T helper type 2 (Th2) cytokine production in the airway, and AHR, and investigated the role of inflammatory cells and functional molecules. Results from gene-knockout and mutant mice demonstrated the involvement of T cells, mast cells, prostanoids, and Th2 cytokines including interleukin (IL)-4 and IL-5 in the development of allergen-induced airway inflammation and AHR. In contrast, treatment with anti-IL-4 monoclonal antibody (mAb) or anti-IL-5 mAb during allergen inhalation did not inhibit allergen-induced AHR, although the combination of these mAbs clearly inhibited the enhanced responsiveness. These data indicate that it is a better strategy for control of the disease to inhibit or suppress multifunctional molecules like corticosteroids rather than to inhibit a single factor, because bronchial asthma is a multifactorial disease.

Association of a new-type prostaglandin D2 receptor CRTH2 with circulating T helper 2 cells in patients with atopic dermatitis

Prostaglandin D2 is known to be the major prostanoid produced by allergen-activated mast cells, but its role in the formation of allergic diseases is not well established because of complexity of its receptor system and lack of appropriate inhibitors. We have recently identified a new-type prostaglandin D2 receptor, named CRTH2. Studies with normal subjects have shown that CRTH2 appears to be selectively expressed by T helper 2 cells but not T helper 1 cells among circulating CD4+ lymphocytes. The exact correlation between CRTH2 and T helper 2 cells in various disease settings and the impact of CRTH2-mediated prostaglandin D2 activities on various T helper 2 responses in vivo still remain to be elucidated, however. In this study, we investigated the correlation between CRTH2 and T helper 2 cells among circulating CD4+ lymphocytes in normal adults and patients with atopic dermatitis, a T-helper-2-involving disease. The results showed that virtually all CRTH2+CD4+ lymphocytes had a pure T helper 2 phenotype and formed not all but a large proportion of circulating T helper 2 cells for both normal and atopic dermatitis subjects. In chemotaxis assays, peripheral blood CRTH2+CD4+ lymphocytes were significantly attracted by prostaglandin D2 as well as by a typical T-helper-2-attracting chemokine, thymus and activation regulated chemokine, whereas they showed little chemotactic migration toward typical T-helper-1-attracting chemokines, macrophage inflammatory protein 1beta and interferon-gamma-inducible protein 10. Furthermore, in atopic dermatitis patients, a preferential increase of CRTH2+ cells was noted within the disease-related cutaneous lymphocyte-associated antigen-positive, but not the cutaneous lymphocyte-associated antigen-negative, CD4+ lymphocyte compartment. Our results suggest the involvement of the prostaglandin D2/CRTH2 system in both normal and pathogenic T helper 2 responses.

Prostaglandin D2 generation by rat peritoneal mast cells stimulated with Datura stramonium agglutinin and its inhibition by haptenic sugar and wheat germ agglutinin

The production of prostaglandin D2 (PGD2) by rat peritoneal mast cells incubated with N-acetyl glucosamine (GlcNAc) oligomer-specific Datura stramonium agglutinin (DSA) for 10 min in the presence of 0.3 mM Ca2+ was examined. Previously, our group reported that the incubation of rat mast cells with DSA (5 - 100 microg/ml) under similar conditions resulted in a calcium influx and histamine release via a pertussis toxin-sensitive G-protein pathway of the mast cells, and the histamine release was inhibited by haptenic sugar chitooligosaccharides or GlcNAc-specific lectin wheat germ agglutinin (WGA) (K. Matsuda et al., Jpn J Pharmacol 66, 195 - 204 (1994)). DSA (5 - 100 microg/ml) dose-dependently stimulated the mast cells to generate PGD2. Chitooligosaccharides (1% w/v) and WGA (100 microg/ml) inhibited the production of PGD2 induced by 100 microg/ml of DSA, suggesting that the effect of DSA is sugar-specific. A prostaglandin G/H synthase inhibitor NS-398 (N-[cyclohexyloxy-4-nitrophenyl] methanesulfonamide) (10 microM) inhibited the formation of PGD2 induced by DSA (20 microg/ml). These results suggest that the binding of DSA to the corresponding sugar residues on the mast cell surface mediates the signaling of the prostaglandin G/H synthase pathway.

Roles for cytosolic phospholipase A2alpha as revealed by gene-targeted mice

Cytosolic phospholipase A2alpha (cPLA2alpha) has unique characteristics among phospholipase A2 (PLA2) family members. Under regulation by intracellular signaling system, cytosolic phospholipase A2alpha liberates arachidonic acid that can be metabolized by downstream enzymes to generate prostaglandins (PGs) and leukotrienes (LTs). Mice deficient in this enzyme have been generated by gene-targeting techniques. Cytosolic phospholipase A2alpha-deficient mice have a normal appearance and grow normally. Close examinations have revealed a renal concentration defect and intestinal ulcerative lesions. There may also be other disadvantages that are not manifested in well-regulated housing conditions. Although female mice are fertile, they become pregnant less frequently and have small litter sizes; moreover, impaired parturition results in few surviving pups. Primary cultured cells prepared from cytosolic phospholipase A2alpha-deficient mice produce significantly smaller amounts of prostaglandins and leukotrienes. Various disease models such as anaphylaxis, acute lung injury, brain injury induced by ischemia/reperfusion and neurotoxin, and polyposis have been investigated. In all these settings, cytosolic phospholipase A2alpha-deficient mice show significantly milder phenotypes. The mechanisms by which deficiencies of this enzyme exert protective effects may differ, but, a cytosolic phospholipase A2alpha inhibitor could have a wide spectrum of clinical targets. Specific functions of cytosolic phospholipase A2alpha have been clearly demonstrated using the gene-targeted mice. Also, comparisons with mice in which related enzymes and receptors have been manipulated using genetic technologies provide further insights into roles of lipid mediators in physiology and pathology.

Lipocalin-type and hematopoietic prostaglandin D synthases as a novel example of functional convergence

Prostaglandin (PG) D2 is a major PG produced in the central nervous system and is involved in the regulation of sleep and pain responses through DP receptors. It is also actively produced by mast cells, basophils, and Th2 cells, acting as an allergic mediator through DP and CRTH2 receptors. PGD2 is further dehydrated to produce PGJ2, delta12-PGJ2, and 15-deoxy-delta(12,14)-PGJ2, the last being a ligand for the nuclear receptor PPARgamma. PGD synthase (PGDS) catalyzes the isomerization of PGH2 to PGD2 in the presence of sulfhydryl compounds. Two distinct types of PGDS have been identified: one is the lipocalin-type PGDS (L-PGDS); and the other, the hematopoietic PGDS (H-PGDS). We isolated the human and mouse cDNAs and genes for L-PGDS and H-PGDS, determined their X-ray crystallographic structures, examined their tissue distribution profiles and cellular localization, and generated gene-knockout mice and human enzyme-overexpressing transgenic mice. L-PGDS and H-PGDS are quite different from each other, in terms of their amino acid sequence, tertiary structure, evolutional origin, chromosomal and cellular localization, tissue distribution, and also functional relevance. Therefore, L-PGDS and H-PGDS are considered to be a novel example of functional convergence.

Function of prostanoid receptors: studies on knockout mice

Prostanoids consisting of the prostaglandins (PGs) and the thromboxanes (TXs) are the cyclooxygenase metabolites of arachidonic acid. They exert a range of actions mediated by their respective receptors expressed in the target cells. The receptors include the DP, EP, FP, IP and TP receptors for PGD, PGE, PGF, PGI and TXA, respectively. Furthermore, EP is subdivided into four subtypes, EP1, EP2, EP3 and EP4, which are encoded by different genes and differ in their responses to various agonists and antagonists. Recent developments in the molecular biology of the prostanoid receptors have enabled the investigation of physiological roles of each receptor by disruption of the respective gene. At this point, all the eight types and subtypes of the prostanoid receptors have been individually knocked out in mice, and various phenotypes have been reported for each strain. Here, we review the findings obtained in these studies. The results from these knockout mice studies may be useful in the development of novel therapeutics that can selectively manipulate actions mediated by each receptor.

Phospholipase A2 enzymes

Phospholipase A2 (PLA2) catalyzes the hydrolysis of the sn-2 position of membrane glycerophospholipids to liberate arachidonic acid (AA), a precursor of eicosanoids including prostaglandins and leukotrienes. The same reaction also produces lysophosholipids, which represent another class of lipid mediators. So far, at least 19 enzymes that possess PLA2 activity have been identified and cloned in mammals. The secretory PLA2 (sPLA2) family, in which 10 isozymes have been identified, consists of low-molecular weight, Ca2+-requiring secretory enzymes that have been implicated in a number of biological processes, such as modification of eicosanoid generation, inflammation, and host defense. The cytosolic PLA2 (cPLA2) family consists of three enzymes, among which cPLA2alpha has been paid much attention by researchers as an essential component of the initiation of AA metabolism. The activation of cPLA2alpha is tightly regulated by Ca2+ and phosphorylation. The Ca2+-independent PLA2 (iPLA2) family contains two enzymes and may play a major role in phospholipid remodeling. The platelet-activating factor (PAF) acetylhydrolase (PAF-AH) family contains four enzymes that exhibit unique substrate specificity toward PAF and/or oxidized phospholipids. Degradation of these bioactive phospholipids by PAF-AHs may lead to the termination of inflammatory reaction and atherosclerosis.

Effects of the prostanoids on the proliferation or hypertrophy of cultured murine aortic smooth muscle cells

Effects of the prostanoids on the growth of cultured aortic vascular smooth muscle cells (VSMCs) were examined using mice lacking prostanoid receptors. Proliferation of VSMCs was assessed by measuring [(3)H]-thymidine incorporation and the cell number, and their hypertrophy by [(14)C]-leucine incorporation and protein content. In VSMCs from wild-type mice, expressions of mRNAs for the EP(4) and TP were most abundant, followed by those for the IP, EP(3) and FP, when examined by competitive reverse transcriptase-PCR. Those for the EP(1), EP(2) and DP, however, could not be detected. AE1-329, an EP(4) agonist, and cicaprost, an IP agonist, inhibited platelet derived growth factor (PDGF)-induced proliferation of VSMCs from wild-type mice; these inhibitory effects disappeared completely in VSMCs from EP(4)(-/-) and IP(-/-) mice, respectively. In accordance with these effects, AE1-329 and cicaprost stimulated cAMP production in VSMCs from wild-type mice, which were absent in VSMCs from EP(4)(-/-) and IP(-/-) mice, respectively. Effects of PGE(2) on cell proliferation and adenylate cyclase were almost similar with those of AE1-329 in VSMCs from wild-type mice, which disappeared in VSMCs from EP(4)(-/-) mice. PGD(2) inhibited PDGF-induced proliferation of VSMCs from both wild-type and DP(-/-) mice to a similar extent. This action of PGD(2) was also observed in VSMCs from EP4(-/-) and IP(-/-) mice. In VSMCs from wild-type mice, I-BOP, a TP agonist, showed potentiation of PDGF-induced hypertrophy. I-BOP failed to show this action in VSMCs from TP(-/-) mice. The specific agonists for the EP(1), EP(2) or EP(3), and PGF(2)alpha showed little effect on the growth of VSMCs. These results show that PGE(2), PGI(2) and TXA(2) modulate PDGF-induced proliferation or hypertrophy of VSMCs via the EP(4), IP and TP, respectively, and that the inhibitory effect of PGD(2) on PDGF-induced proliferation is not mediated by the DP, EP(4) or IP.

EC-SOD and the response to inflammatory reactions and aging in mouse lung

The lung is exposed to high oxygen tension and oxygen free radicals have been implicated in many pathologies of the organ. Extracellular superoxide dismutase occurs in high concentration in the lung and protects against hyperoxia-induced inflammation. We hypothesized that the enzyme might ameliorate other types of inflammation as well as aging-related changes of the organ. Tracheal instillation of endotoxin plus zymosan into extracellular superoxide dismutase knockout and wild-type mice resulted in a marked neutrophilic inflammation and increases in inflammatory cytokines, protein, and lactate dehydrogenase activity in the bronchoalveolar lavage fluid. There were no significant differences between the genotypes. Repeated challenges with ovalbumin caused an allergic inflammation with increases in eosinophils, interleukin-5, protein, and lactate dehydrogenase activity in the bronchoalveolar lavage fluid. Only minimal differences between the genotypes were found. In lungs from 2-year-old mice, marginal increases in inflammatory variables and fibrosis were found in the knockout mice. In conclusion, extracellular superoxide dismutase had a negligible role in the present inflammation and allergy models and for the long-term integrity of the organ.

Prostaglandin D2 and reproduction

This review highlights recent studies investigating the role of prostaglandin (PG)D2 in reproduction. PGD2 induces sleep, allergic responses, inhibition of platelet aggregation, and relaxation of vascular and non-vascular smooth muscle, and has some roles in reproduction. Two types of PGD2 synthase are known. Lipocalin-type PGD synthase is present in cerebrospinal fluid, seminal plasma and may play an important role in male reproduction. Another PGD synthase, hematopoietic PGD synthase is present in the spleen, fallopian tube, endometrial gland cells, extravillous trophoblasts and villous trophoblasts, and perhaps plays an important role in female reproduction. Recent studies demonstrate that PGD2 is probably involved in multiple aspects of inflammation through its dual receptor systems, DP and CRTH2. CRTH2 but not DP is a chemo-attractant receptor for PGD2. Interestingly, CRTH2 is a most reliable marker for the detection of human T helper type 2 (Th2) and T cytotoxic type 2 (Tc2) cells, and the percentages of CRTH expressing CD4+-T cells and CD8+-T cells were significantly higher in the decidua especially at the implantation site, suggesting that Th2 and Tc2 cells recruit into the materno-fetal interface, in a PGD2-mediated manner. PGD2 has a very unique effect to inhibit antigen presentation by inhibition of dendritic cell (DC) migration through DP but not CRTH2. PGD2 might appear to contribute to the maintenance of pregnancy by controlling the Th1/Th2 balance and antigen presentation by DCs through its dual receptor systems, CRTH2 and DP.

Selective cyclooxygenase-1 and -2 inhibitors each increase allergic inflammation and airway hyperresponsiveness in mice

Nonselective cyclooxygenase (COX) inhibition during allergic sensitization with ovalbumin in a murine model leads to an increase in the Type 2 cytokines interleukin-5 (IL-5) and IL-13; however, the effect of selective COX-1 and COX-2 inhibitors on these cytokines is unknown. We found that COX-1 protein was constitutively expressed in lung tissue. Expression of COX-1 protein did not increase with ovalbumin sensitization, but expression of COX-2 protein did. Ovalbumin-sensitized mice treated with either selective COX-1 inhibitor SC58560 (OVA-COX-1 inhibitor) or selective COX-2 inhibitor SC58236 (OVA-COX-2 inhibitor) had significantly greater airway hyperresponsiveness (p < 0.05) and higher levels of IL-13 (p < 0.05) in lung supernatants than did untreated mice that were ovalbumin sensitized (OVA). Lung mRNA levels for the chemokine receptors CCR1 through CCR5 (expressed on eosinophils, basophils, lymphocytes, and dendritic cells) were increased in the OVA-COX-2 inhibitor and OVA-indomethacin groups. We conclude that in the BALB/c mouse, COX inhibition with either a COX-1 or COX-2 inhibitor during allergen sensitization augments production of IL-13 and increases airway hyperresponsiveness.

The prostaglandin receptor EP4 suppresses colitis, mucosal damage and CD4 cell activation in the gut

We used mice deficient in each of the eight types and subtypes of prostanoid receptors and examined the roles of prostanoids in dextran sodium sulfate-induced (DSS-induced) colitis. Among the prostanoid receptor-deficient mice, only EP4-deficient mice and not mice deficient in either DP, EP1, EP2, EP3, FP, IP, or TP developed severe colitis with 3% DSS treatment, which induced only marginal colitis in wild-type mice. This phenotype was mimicked in wild-type mice by administration of an EP4-selective antagonist (AE3-208). The EP4 deficiency impaired mucosal barrier function and induced epithelial loss, crypt damage, and aggregation of neutrophils and lymphocytes in the colon. Conversely, administration of an EP4-selective agonist (AE1-734) to wild-type mice ameliorated severe colitis normally induced with 7% DSS, while that of AE3-208 suppressed recovery from colitis and induced significant proliferation of CD4+ T cells. In vitro AE3-208 enhanced and AE1-734 suppressed the proliferation and Th1 cytokine production of lamina propria mononuclear cells from the colon. DNA microarray analysis revealed elevated expression of genes associated with immune response and reduced expression of genes with mucosal repair and remodeling in the colon of EP4-deficient mice. We conclude that EP4 maintains intestinal homeostasis by keeping mucosal integrity and downregulating immune response.

[The roles of the prostanoids played in the body]

The actions of prostanoids in various physiological and pathophysiological conditions have been examined using mice lacking the prostanoid receptors. PGD2 was found to be a mediator of allergic asthma. Prostaglandin (PG) I2 worked not only as a mediator of inflammation but also as an antithrombotic and cardio-protective agent. Several important actions of PGE2 are brought out via the PGE2-receptor subtype EP3; PGE2 participated in the regulation of platelet function, and it worked as a mediator of febrile responses to both endogenous and exogenous pyrogens. These novel findings on the roles of the prostanoids would contribute to the development of drugs targeting the prostanoid receptors.

The prostaglandin receptor EP4 suppresses colitis, mucosal damage and CD4 cell activation in the gut

We used mice deficient in each of the eight types and subtypes of prostanoid receptors and examined the roles of prostanoids in dextran sodium sulfate-induced (DSS-induced) colitis. Among the prostanoid receptor-deficient mice, only EP4-deficient mice and not mice deficient in either DP, EP1, EP2, EP3, FP, IP, or TP developed severe colitis with 3% DSS treatment, which induced only marginal colitis in wild-type mice. This phenotype was mimicked in wild-type mice by administration of an EP4-selective antagonist (AE3-208). The EP4 deficiency impaired mucosal barrier function and induced epithelial loss, crypt damage, and aggregation of neutrophils and lymphocytes in the colon. Conversely, administration of an EP4-selective agonist (AE1-734) to wild-type mice ameliorated severe colitis normally induced with 7% DSS, while that of AE3-208 suppressed recovery from colitis and induced significant proliferation of CD4+ T cells. In vitro AE3-208 enhanced and AE1-734 suppressed the proliferation and Th1 cytokine production of lamina propria mononuclear cells from the colon. DNA microarray analysis revealed elevated expression of genes associated with immune response and reduced expression of genes with mucosal repair and remodeling in the colon of EP4-deficient mice. We conclude that EP4 maintains intestinal homeostasis by keeping mucosal integrity and downregulating immune response.

15-Deoxy-delta 12,14-prostaglandins D2 and J2 are potent activators of human eosinophils

15-Deoxy-Delta(12,14)-PDJ(2) (15d-PGJ(2)) is a degradation product of PGD(2) that has been proposed as an anti-inflammatory compound because of its various inhibitory effects, some of which are mediated by peroxisome proliferator-activated receptor-gamma. In contrast to its reported inhibitory effects on macrophages and other cells, we found that this compound is a potent activator of eosinophils, inducing calcium mobilization, actin polymerization, and CD11b expression. It is selective for eosinophils, having little or no effect on neutrophils or monocytes. 15d-PGJ(2) has an EC(50) of approximately 10 nM, similar to that of its precursor, PGD(2). The concentrations of 15d-PGJ(2) required to activate eosinophils are thus much lower than those required for its anti-inflammatory effects (usually micromolar). 15-Deoxy-Delta(12,14)-prostaglandin D(2) (15d-PGD(2)) is also a potent activator of eosinophils, with an EC(50) about the same as that of PGD(2), whereas Delta(12)-PGJ(2) is slightly less potent. Eosinophils pretreated with PGD(2) no longer respond to 15d-PGJ(2), and vice versa, but in both cases the cells still respond to another eicosanoid proinflammatory mediator, 5-oxo-6,8,11,14-eicosatetraenoic acid. This indicates that the effects of 15d-PGJ(2) are mediated by the DP(2)/chemoattractant receptor-homologous molecule expressed on Th2 cells that has recently been identified in eosinophils. 15d-PGJ(2) is selective for the DP(2) receptor, in that it has no effect on DP(1) receptor-mediated adenylyl cyclase activity in platelets. We conclude that 15d-PGJ(2) and 15d-PGD(2) are selective DP(2) receptor agonists that activate human eosinophils with potencies at least 100 times greater than those for the proposed anti-inflammatory effects of 15d-PGJ(2) on other cells.

Mouse models for the genetic dissection of atopy

Atopic disorders are complex traits with a significant contribution of heritability. Several mouse models for atopic phenotypes such as allergen-induced and intrinsic asthma, atopic dermatitis and immediate cutaneous hypersensitivity have been used to systematically dissect the genetics of these diseases. Many of the chromosomal regions identified in genome-wide screens colocalize with linkage regions of autoimmune phenotypes suggesting common regulatory genes in combination (or addition) to disease-specific genes. Moreover, many of these regions correspond to regions found in the human system, thus strengthening the likelihood of a gene contributing to the phenotype. The role of individual candidate genes has been vigorously pursued in genetically modified mice by destruction or overexpression of the candidate gene. The complex interactions of multiple contributing genes may further be elucidated in randomly mutated mouse strains. Thus mouse models can contribute largely to the elucidation of disease genes.

Sexually dimorphic development of mouse primordial germ cells: switching from oogenesis to spermatogenesis

During embryogenesis, primordial germ cells (PGCs) have the potential to enter either spermatogenesis or oogenesis. In a female genital ridge, or in a non-gonadal environment, PGCs develop as meiotic oocytes. However, male gonadal somatic cells inhibit PGCs from entering meiosis and direct them to a spermatogenic fate. We have examined the ability of PGCs from male and female embryos to respond to the masculinising environment of the male genital ridge, defining a temporal window during which PGCs retain a bipotential fate. To help understand how PGCs respond to the male gonadal environment, we have identified molecular differences between male PGCs that are committed to spermatogenesis and bipotential female PGCs. Our results suggest that one way in which PGCs respond to this masculinising environment is to synthesise prostaglandin D2. We show that this signalling molecule can partially masculinise female embryonic gonads in culture, probably by inducing female supporting cells to differentiate into Sertoli cells. In the developing testis, prostaglandin D2 may act as a paracrine factor to induce Sertoli cell differentiation. Thus part of the response of PGCs to the male gonadal environment is to generate a masculinising feedback loop to ensure male differentiation of the surrounding gonadal somatic cells.

Cutting edge: agonistic effect of indomethacin on a prostaglandin D2 receptor, CRTH2

Indomethacin is a widely used nonsteroidal anti-inflammatory drug and is generally known to exhibit its multiple biological functions by inhibiting cyclooxygenases or activating peroxisome proliferator-activated receptors. In this study, we present evidence demonstrating that the novel PGD(2) receptor chemoattractant receptor-homologous molecule expressed on Th2 cells (CRTH2) is another functional target for indomethacin. Indomethacin induced Ca(2+) mobilization in CRTH2-transfected K562 cells at submicromolar concentrations (approximate EC(50), 50 nM) in a G(alphai)-dependent manner as PGD(2) did. Other nonsteroidal anti-inflammatory drugs (aspirin, sulindac, diclofenac, and acemetacin) had no such effect even at micromolar concentrations. In chemotaxis assay, three CRTH2-expressing cell types, Th2 cells, eosinophils, and basophils, were all significantly attracted by indomethacin (EC(50), 50-500 nM) as well as by PGD(2) (EC(50), 2-20 nM), and the effects of indomethacin were blocked by anti-CRTH2 mAb. These results suggest the involvement of CRTH2 in mediating some of therapeutic and/or unwanted side effects of indomethacin, independently of cyclooxygenases and peroxisome proliferator-activated receptors.

Molecular genetic studies on sleep-wake regulation, with special emphasis on the prostaglandin D(2) system

To elucidate the exact role of the PGD(2) system in sleep-wake regulation in vivo, the sleep behavior of knockout mice, generated in the author's and other laboratories, was examined for lipocalin-type PGD synthase (L-PGDS), PGD receptor, adenosine A(2A) receptor, and histamine H(1) receptor; transgenic mice overexpressing the human L-PGDS gene, generated in the author's laboratory, were also examined. The circadian profiles of sleep patterns of wild-type and the genetically manipulated mice were essentially identical, indicating the possibility that the deficiency of one system may be effectively compensated by some other systems during development. Available evidence indicated that the PGD(2) system is involved in the homeostatic regulation of non-rapid eye movement sleep and that the arousal effect of orexin A is mediated by the histamine H(1) receptor system.

Cyclooxygenase-2 expression during allergic inflammation in guinea-pig lungs

Prostaglandins and thromboxanes are important modulators of airway physiology. The synthesis of these mediators depends on two isoforms of cyclooxygenase (COX), constitutive COX-1 and inducible COX-2. COX-2 expression has been observed in various inflammatory diseases, but not all aspects of the expression and the role of COX-2 in conditions of allergic inflammation such as asthma are clear. In the present study, we examined the 72-h kinetics of the expression of COX-isoform mRNA in ovalbumin-sensitized and -challenged guinea-pig lungs. The sensitized animals showed a robust and transient induction of COX-2 mRNA expression within 1 h after ovalbumin challenge, whereas their COX-1 mRNA levels remained unchanged. Upregulation of the level and activity of COX-2 protein followed the induction of COX-2 mRNA. Lung slices harvested from ovalbumin-challenged animals released more prostaglandin D(2) and prostaglandin E(2) spontaneously or in response to A23187 (10 microM) ex vivo than did those from unchallenged animals. This response was significantly blocked by the COX-2 selective inhibitors, NS-398 and JTE-522. In vivo administration of NS-398 significantly inhibited the accumulation of eosinophils and neutrophils in the lungs. In conclusion, de novo COX-2 expression during allergic inflammation modifies prostanoid synthesis in the lung and airway pathophysiology.

The Th2 lymphocyte products IL-4 and IL-13 rapidly induce airway hyperresponsiveness through direct effects on resident airway cells

Airway inflammation and airway hyperresponsiveness (AHR) are hallmarks of asthma. Cytokines produced by T helper type 2 (Th2) lymphocytes have been implicated in both processes. There is strong support for the idea that Th2 cytokines can produce AHR indirectly by promoting the recruitment of inflammatory cells. Less attention has been given to the possibility that Th2 cytokines might induce AHR by acting directly on resident airway cells. To investigate this, we polarized and activated CD4(+) T cells in vitro and analyzed airway function after administration of lymphocyte-conditioned media to the airways of naive mice. Th2-lymphocyte-conditioned medium induced AHR within 6 h. This finding was reproduced in mast-cell-deficient and in T- and B-lymphocyte-deficient mice. AHR did not occur when Th2-lymphocyte-conditioned medium was administered to mice lacking the IL-4 receptor alpha subunit or Stat6, suggesting a critical role for interleukin (IL)-4 and/or IL-13. This was confirmed by the finding that recombinant IL-4 and IL-13 both induced AHR within 6 h. The induction of AHR occurred in the absence of inflammatory cell recruitment or mucus production. These results strongly suggest that products of activated Th2 lymphocytes can rapidly perturb airway function through direct effects on resident airway cells.

Regulation of prostaglandin endoperoxide synthase-2 and IL-6 expression in mouse bone marrow-derived mast cells by exogenous but not endogenous prostanoids

Mouse bone marrow-derived mast cells (BMMC), stimulated with stem cell factor, IL-1beta, and IL-10, secrete IL-6 and demonstrate a delayed phase of PGD(2) generation that is dependent upon the induced expression of PG endoperoxide synthase (PGHS)-2. We have examined the potential for exogenous prostanoids, acting in a paracrine fashion, and endogenous prostanoids, acting in an autocrine fashion, to regulate PGHS-2 induction and IL-6 secretion in mouse BMMC. Exogenous PGE(2), which acts through G protein-coupled receptors, and 15-deoxy-Delta(12,14)-PGJ(2), which is a ligand for peroxisome proliferator-activated receptor (PPAR)gamma, elicited a 2- to 3-fold amplification of PGHS-2 induction, delayed-phase PGD(2) generation, and IL-6 secretion in response to stem cell factor, IL-1beta, and IL-10. The effect of PGE(2) was reproduced by the E prostanoid (EP)1 receptor agonist 17-trinor-PGE(2), and the EP1/EP3 agonist, sulprostone, but not the EP2 receptor agonist, butaprost. Although BMMC express PPARgamma, the effects of 15-deoxy-Delta(12,14)-PGJ(2) were not reproduced by the PPARgamma agonists, troglitazone and ciglitazone. PGHS-2 induction, but not IL-6 secretion, was impaired in cPLA(2)-deficient BMMC. However, there was no impairment of PGHS-2 induction in BMMC deficient in hematopoietic PGD synthase or PGHS-1 in the presence or absence of the PGHS-2 inhibitor, NS-398. Thus, although exogenous prostanoids may contribute to amplification of the inflammatory response by augmenting PGD(2) generation and IL-6 secretion from mast cells, endogenous prostanoids do not play a role.

Lipocalin-type prostaglandin d synthase in essential hypertension

Lipocalin-type prostaglandin D synthase (L-PGDS) reportedly well predicts cardiovascular injuries in humans. However, little is known about the implications of L-PGDS in hypertension. In the present study, we investigated the alterations of serum and urinary L-PGDS in hypertensive patients with or without renal dysfunction. A total of 111 patients with hypertension (EHT; 65 with normoalbuminuria, 23 with microalbuminuria, 12 with macroalbuminuria, 11 with renal failure) and 102 normotensive, nomoalbuminuric subjects (NT) were studied. L-PGDS was measured by enzyme-linked immunosorbent assay, and L-PGDS in the kidney was localized using immunohistochemical methods. Blood pressure was higher in EHT groups than in the NT group (P<0.0001). There were no differences in age, gender, BMI, TC, TG, and HbA1c levels among the groups. Serum creatinine and urinary albumin levels were higher in the group with renal failure. Serum levels of L-PGDS were increased in EHT with normoalbuminuria, as compared with NT (0.88 +/- 0.05 versus 0.65 +/- 0.02 microg/mL; P<0.001). Serum levels of L-PGDS increased with the renal function worsened and positively correlated with serum creatinine, particularly in patients with renal impairments (r=0.76, P<0.0001). Similarly, the urinary L-PGDS excretions in EHT with normoalbuminuria were higher than that in NT (2.31 +/- 0.29 versus 1.16 +/- 0.14 mg/gCr, P<0.001), whereas there were no differences in urinary albumin excretion between the 2 groups. Moreover, urinary L-PGDS excretion increased dramatically with an increase in albuminuria or proteinuria. L-PGDS was stained in the tubules and the interstitium of the kidney in nephrosclerosis. In conclusion, patients with hypertension exhibited a higher level of L-PGDS in serum and urine, and this became increasingly obvious along with advance in renal dysfunction. These data suggest that L-PGDS metabolism is related to blood pressure and kidney injuries associated with hypertension.

New polymorphisms of haematopoietic prostaglandin D synthase and human prostanoid DP receptor genes

BACKGROUND

Prostaglandin D2 (PGD2), a major cyclo-oxygenase metabolite of arachidonic acid in mast cells, induces bronchoconstriction in the human lung. It has been reported that mice lacking PGD receptor fail to develop the bronchial hyper-responsiveness upon ovalbumin challenge, suggesting that PGD2 functions as a mediator of allergic asthma.

OBJECTIVE

To determine if there are any mutations associated with the development of asthma in the haematopoietic prostaglandin D synthase (H-PGDS) gene and the human prostanoid DP receptor (PTGDR) gene.

METHODS AND RESULTS

We screened the 5'flanking and coding regions of the H-PGDS gene and the PTGDR gene by direct sequence. We identified one variant in intron 2 (IVS2 + 11 A > C) and one variant in intron 3 (IVS3 + 13T > C) of the H-PGDS gene, and two variants in the 5'flanking region of the PTGDR gene (-197T > C and -2C > T). The IVS3 + 13T > C and -197T > C variants were rare, appearing only once in 48 subjects. transmission disequilibrium test (TDT) analysis of 144 asthmatic families revealed that the IVS2 + 11 A allele of the H-PGDS gene was significantly transmitted preferentially to asthma-affected children (P = 0.0056), but no association was observed between -2C/T polymorphism of the PTGDR gene and asthma (P > 0.05).

CONCLUSION

Our results suggest that the IVS2 + 11A/C allele may be involved in the development of asthma in the Japanese population.

Pronounced eosinophilic lung inflammation and Th2 cytokine release in human lipocalin-type prostaglandin D synthase transgenic mice

PGD(2) is a major lipid mediator released from mast cells, but little is known about its role in the development of allergic reactions. We used transgenic (TG) mice overexpressing human lipocalin-type PGD synthase to examine the effect of overproduction of PGD(2) in an OVA-induced murine asthma model. The sensitization of wild-type (WT) and TG mice was similar as judged by the content of OVA-specific IgE. After OVA challenge, PGD(2), but not PGE(2), substantially increased in the lungs of WT and TG mice with greater PGD(2) increment in TG mice compared with WT mice. The numbers of eosinophils and lymphocytes in the bronchoalveolar lavage (BAL) fluid were significantly greater in TG mice than in WT mice on days 1 and 3 post-OVA challenge, whereas the numbers of macrophages and neutrophils were the same in both WT and TG mice. The levels of IL-4, IL-5, and eotaxin in BAL fluid were also significantly higher in TG mice than in WT mice, although the level of IFN-gamma in the BAL fluid of TG mice was decreased compared with that in WT mice. Furthermore, lymphocytes isolated from the lungs of TG mice secreted less IFN-gamma than those from WT mice, whereas IL-4 production was unchanged between WT and TG mice. Thus, overproduction of PGD(2) caused an increase in the levels of Th2 cytokines and a chemokine, accompanied by the enhanced accumulation of eosinophils and lymphocytes in the lung. These results indicate that PGD(2) plays an important role in late phase allergic reactions in the pathophysiology of bronchial asthma.

Production of prostaglandins and leukotrienes by pathogenic fungi

These studies demonstrate that pathogenic fungi (dermatophytic, subcutaneous, and systemic) have the ability to produce eicosanoids both from simple metabolites and from arachidonic acid. Host-derived eicosanoids have been previously demonstrated to enhance fungal colonization and atopic disease development. Thus, fungus-derived eicosanoids represent a potential class of novel virulence factors.

Selective modulation of chemokinesis, degranulation, and apoptosis in eosinophils through the PGD2 receptors CRTH2 and DP

BACKGROUND

PGD(2) is the major prostanoid released by mast cells during an allergic response. Its role in the allergic response, however, remains unclear.

OBJECTIVE

Because the accumulation of eosinophils is a feature of allergic reactions, we investigated the role of PGD(2) in the modulation of eosinophil function.

METHODS

Circulating human eosinophils were isolated and challenged with PGD(2). The effects of PGD(2) on various eosinophil functions were then analyzed.

RESULTS

PGD(2) binds with high affinity preferentially to 2 receptors, DP and chemoattractant receptor-homologous molecule expressed on T(H)2 cells (CRTH2). We show that both DP and CRTH2 are detectable on circulating eosinophils. We demonstrate that PGD(2) (1-10 nmol/L) induces a rapid change in human eosinophil morphology and an increase in chemokinesis and promotes eosinophil degranulation. These effects are induced by the CRTH2-selective agonist 13-14-dihydro-15-keto-PGD(2) (DK-PGD(2)) but not by the DP-selective agonist BW245C. These results suggest a role for CRTH2 in the modulation of eosinophil movement and in triggering the release of cytotoxic proteins. Finally, we demonstrate that BW245C, but not DK-PGD(2), can delay the onset of apoptosis in cultured eosinophils, presumably through interaction with DP.

CONCLUSION

These data support the hypothesis that PGD(2) controls eosinophil functions through 2 pharmacologically distinct receptors with independent functions. Blockade of PGD(2)-mediated effects on human eosinophils may reduce the damage caused by these cells during an allergic response, but inhibition of both receptors may be required.

CTLA4-IgG reverses asthma manifestations in a mild but not in a more "severe" ongoing murine model

We investigated whether CTLA4-Ig can reverse established asthma manifestations in a novel murine model of ongoing disease. In BALB/c mice, sensitized to ovalbumin (OVA) without adjuvant, airway inflammation was induced by a first series of OVA aerosol challenges. Murine CTLA4-IgG was then administered, followed by a second series of OVA inhalations. In control-treated mice, two series of OVA challenges induced upregulation of OVA-specific IgE in serum, eosinophils in the bronchoalveolar lavage fluid (BALF), and IL-5 production by lung lymphocytes upon OVA restimulation in vitro, compared with saline-challenged mice. CTLA4-IgG significantly inhibited all of these parameters in OVA-challenged mice. Importantly, mCTLA4-IgG performed better than the gold-standard dexamethasone because this corticosteroid did not inhibit the upregulation of OVA-specific IgE in serum. In a more "severe" ongoing model, induced by sensitization to OVA emulsified in aluminum hydroxide, resulting in airway hyperresponsiveness to methacholine and stronger inflammatory responses, mCTLA4-IgG was less effective in that only the number of eosinophils in the BALF was reduced (P = 0.053), whereas dexamethasone inhibited both BALF eosinophilia and cytokine production by lung lymphocytes. Thus, CTLA4-Ig might be an effective alternative therapy in established allergic asthma, especially in situations of mild disease.

Leukotriene and prostanoid pathway enzymes in bronchial biopsies of seasonal allergic asthmatics

Cysteinyl-leukotrienes and prostaglandin D2 generated by the 5-lipoxygenase (5-LO) and cyclooxygenase (COX) pathways, respectively, cause bronchoconstriction, leukocyte recruitment, and bronchial hyperresponsiveness in asthma. We characterized the cellular expression of 5-LO and COX enzymes using immunohistochemistry on bronchial biopsies from 12 allergic asthmatic patients before and during seasonal exposure to birch pollen. Bronchial responsiveness (p = 0.004) and symptoms (p < 0.005) increased and peak expiratory flow (PEF; p < or = 0.02) decreased in the pollen season. In-season biopsies had 2-fold more cells immunostaining for 5-LO (p = 0.02), 5-LO-activating protein (FLAP; p = 0.04), and leukotriene (LT)A4 hydrolase (p = 0.05), and 4-fold more for the terminal enzyme for cysteinyl-leukotriene synthesis, LTC4 synthase (p = 0.02). Immunostaining for COX-1, COX-2, and PGD2 synthase was unchanged. Increased staining for LTC4 synthase was due to increased eosinophils (p = 0.035) and an increased proportion of eosinophils expressing the enzyme (p = 0.047). Macrophages also increased (p = 0.019), but mast cells and T-lymphocyte subsets were unchanged. Inverse correlations between PEF and 5-LO(+) cell counts link increased expression of 5-LO pathway enzymes in eosinophils and macrophages within the bronchial mucosa to deterioration of lung function during seasonal allergen exposure.

Mammalian class Sigma glutathione S-transferases: catalytic properties and tissue-specific expression of human and rat GSH-dependent prostaglandin D2 synthases

GSH-dependent prostaglandin D(2) synthase (PGDS) enzymes represent the only vertebrate members of class Sigma glutathione S-transferases (GSTs) identified to date. Complementary DNA clones encoding the orthologous human and rat GSH-dependent PGDS (hPGDS and rPGDS, respectively) have been expressed in Escherichia coli, and the recombinant proteins isolated by affinity chromatography. The purified enzymes were both shown to catalyse specifically the isomerization of prostaglandin (PG) H(2) to PGD(2). Each transferase also exhibited GSH-conjugating and GSH-peroxidase activities. The ability of hPGDS to catalyse the conjugation of aryl halides and isothiocyanates with GSH was found to be less than that of the rat enzyme. Whilst there is no difference between the enzymes with respect to their K(m) values for 1-chloro-2,4-dinitrobenzene, marked differences were found to exist with respect to their K(m) for GSH (8 mM versus 0.3 mM for hPGDS and rPGDS, respectively). Using molecular modelling techniques, amino acid substitutions have been identified in the N-terminal domain of these enzymes that lie outside the proposed GSH-binding site, which may explain these catalytic differences. The tissue-specific expression of PGDS also varies significantly between human and rat; amongst the tissues examined, variation in expression between the two species was most apparent in spleen and bone marrow. Differences in catalytic properties and tissue-specific expression of hPGDS and rPGDS appears to reflect distinct physiological roles for class Sigma GST between species. The evolution of divergent functions for the hPGDS and rPGDS is discussed in the context of the orthologous enzyme from chicken.

PGRL is a major CD81-associated protein on lymphocytes and distinguishes a new family of cell surface proteins

CD81 exerts a range of interesting effects on T cells including early thymocyte differentiation, LFA-1 activation, and provision of costimulation. To better understand the mechanisms by which CD81 influences T cell function we evaluated CD81 molecular complexes on T cells. The most prominent CD81-associated cell surface protein on thymocytes as well as a number of T cell and B cell lines has an apparent molecular mass of 75 kDa. The 75-kDa protein was purified and analyzed by matrix-assisted laser desorption ionization time-of-flight mass spectrometry followed by postsource-decay profiling. p75 is a novel type I transmembrane protein of the Ig superfamily which is most similar to FPRP. We cloned and sequenced both human and mouse PG regulatory-like protein (PGRL) and characterized mouse PGRL expression in both lymphocytes and nonlymphoid tissues. The discovery of PGRL allows for the clustering of a small family of related proteins including PGRL, FPRP, V7/CD101, and IGSF3. Expression constructs containing various domains of PGRL with an epitope tag were coexpressed with CD81 and used to determine that the interaction of CD81 with PGRL requires the membrane distal Ig3-Ig4 domains of PGRL. Although it remains to be determined whether PGRL possesses PG regulatory functions, transwell chamber experiments show that PGs and CD81 coordinately regulate T cell motility.

Requirements for allergen-induced airway inflammation and hyperreactivity in CD4-deficient and CD4-sufficient HLA-DQ transgenic mice

BACKGROUND

Airway inflammation is central to the pathogenesis of allergic asthma, and molecules that mediate this process obviously represent targets for therapy.

OBJECTIVE

To study the role of CD4(+) T cells and/or HLA-DQ molecules in allergic asthma, we have generated and characterized models of short ragweed allergen (SRW)-induced inflammation using transgenic mice with HLA-DQ (DQ6 or DQ8), human CD4 (hCD4), or both on a genetic background that lacks mouse MHC II and CD4 (Abeta(0)/mCD4(0)).

METHODS

Mice were actively sensitized and later challenged intranasally with SRW allergenic extract. Bronchoalveolar lavage fluid composition, airway inflammation and hyperresponsiveness, blood eosinophil levels, and cell proliferation were examined.

RESULTS

In response to SRW treatment, both DQ6 and DQ8 transgenic mice expressing hCD4 developed pulmonary eosinophilia and associated lung tissue damage with increase in eosinophil peroxidase and T(H)2 cytokines in bronchoalveolar lavage fluid, strong airway hyperreactivity, and persistent blood eosinophilia. The response was independent of mast cells/histamine pathway and was mediated by DQ-restricted hCD4(+) T cells. Interestingly, lungs of CD4-deficient DQ6 transgenic mice showed an eosinophilic inflammation without local increase in cytokines and eosinophil peroxidase. The allergic reaction was absent in double-knockout mice and mice expressing either DQ8 or hCD4 alone.

CONCLUSIONS

DQ6 molecules are critical to SRW-induced allergy and can operate in the presence or absence of CD4. However, both DQ antigens and CD4 molecules are critical for full manifestation of allergen-induced asthma in transgenic mice.

Prostanoid receptors: ontogeny and implications in vascular physiology

Prostanoids exert significant effects on circulatory beds. They play a role in the response of the vasculature to adjustments in perfusion pressure and oxygen and carbon dioxide tension, and they mediate the actions of numerous factors. The role of prostanoids in governing circulation of the perinate is suggested to surpass that in the adult. Prostanoids are abundantly generated in the perinate. They have been implicated in autoregulation of blood flow as studied in brain and eyes. Prostaglandins are also dominant regulators of ductus arteriosus tone. The effects of these autacoids are mediated through specific G protein-coupled receptors. In addition to the pharmacological characterization of the prostanoid receptors, important advances in understanding the biology of these receptors have been made in the last decade. Their cloning and the development of animals with disrupted genes of these receptors have been very informative. The involvement of prostanoid receptors in the developing subject, especially on brain and ocular vasculature and on ductus arteriosus, has also begun to be investigated; the expression of these receptors changes with development. Some but not all of the ontogenic changes in these receptors are attributed to homologous regulation. Interestingly, in the process of elucidating their effects, functional perinuclear prostaglandin E2 receptors have been uncovered. This article reviews prostanoid receptors and addresses implications on the developing subject with attention to vascular physiology.

Dominant localization of prostaglandin D receptors on arachnoid trabecular cells in mouse basal forebrain and their involvement in the regulation of non-rapid eye movement sleep

Infusion of prostaglandin (PG) D(2) into the lateral ventricle of the brain induced an increase in the amount of non-rapid eye movement sleep in wild-type (WT) mice but not in mice deficient in the PGD receptor (DP). Immunofluorescence staining of WT mouse brain revealed that DP immunoreactivity was dominantly localized in the leptomeninges (LM) of the basal forebrain but that PGD synthase immunoreactivity was widely distributed in the LM of the entire brain. Electron microscopic observation indicated that DP-immunoreactive particles were predominantly located on the plasma membranes of arachnoid trabecular cells of the LM. The region with the highest DP immunoreactivity was clearly defined as bilateral wings in the LM of the basal forebrain located lateral to the optic chiasm in the proximity of the ventrolateral preoptic area, one of the putative sleep centers, and the tuberomammillary nucleus, one of the putative wake centers. The LM of this region contained DP mRNA 70-fold higher than that in the cortex as judged from the results of quantitative reverse transcription-PCR. PGD(2) infusion into the subarachnoid space of this region increased the extracellular adenosine level more than 2-fold in WT mice but not in the DP-deficient mice. These results indicate that DPs in the arachnoid trabecular cells of the basal forebrain mediate an increase in the extracellular adenosine level and sleep induction by PGD(2).

Prostaglandin D2 is a potent chemoattractant for human eosinophils that acts via a novel DP receptor

Prostaglandin D2 (PGD2) is released following exposure of asthmatics to allergen and acts via the adenylyl cyclase-coupled receptor for PGD2 (DP receptor). In this study, it is reported that human eosinophils possess this receptor, which would be expected to inhibit their activation. In contrast, it was found that prostaglandin D2 is a potent stimulator of eosinophil chemotaxis, actin polymerization, CD11b expression, and L-selectin shedding. These responses are specific for eosinophils, as neutrophils display little or no response to prostaglandin D2. They were not due to interaction with receptors for other prostanoids, as prostaglandins E2 and F(2alpha), U46619 (a thromboxane A2 analogue), and carbaprostacyclin (a prostacyclin analogue) displayed little or no activity. Furthermore, they were not shared by the selective DP receptor agonist BW245C and were not prevented by the selective DP receptor antagonist BWA868C, indicating that they were not mediated by DP receptors. In contrast, the prostaglandin D2 metabolite 13,14-dihydro-15-oxoprostaglandin D2 induced eosinophil activation but did not stimulate DP receptor-mediated adenosine 3',5'-cyclic monophosphate (cAMP) formation. These results indicate that in addition to the classic inhibitory DP1 receptor, eosinophils possess a second, novel DP2 receptor that is associated with PGD2-induced cell activation. These 2 receptors appear to interact to regulate eosinophil responses to PGD2, as blockade of DP1 receptor-mediated cAMP production by BWA868C resulted in enhanced DP2 receptor-mediated stimulation of CD11b expression. The balance between DP1 and DP2 receptors could determine the degree to which prostaglandin D2 can activate eosinophils and may play a role in eosinophil recruitment in asthma.

Genetics of allergen-induced asthma

Antigen-induced airway hyperresponsiveness and airway inflammation are features of both human asthma and animal models of this disease. The genesis of these key asthma phenotypes represents the summation of a complex cascade of immune responses. It is hypothesized that multiple cell types are involved in the induction, propagation, and maintenance of these immune processes. Several molecules have been reported to be essential for cell-cell interactions, inflammatory cell recruitment, and effector functions leading to the overall expression of the asthmatic phenotype. This review summarizes the genetic evidence supporting a role for these molecules in antigen-driven airway hyperresponsiveness and inflammation.

Acute effects of prostaglandin D2 to induce airflow obstruction and airway microvascular leakage in guinea pigs: role of thromboxane A2 receptors

BACKGROUND

Although prostaglandin D2 (PGD2), a mast cell-derived inflammatory mediator, may trigger allergic airway inflammation, its potency and the mechanism by which it induces airway microvascular leakage, a component of airway inflammation, is not clear.

OBJECTIVE

We wanted to evaluate the relative potency of PGD2 to cause microvascular leakage as compared to airflow obstruction, because both responses were shown to occur simultaneously in allergic airway diseases such as asthma. The role of thromboxane A2 receptors (TP receptors) in inducing these airway responses was also examined.

METHODS

Anesthetized and mechanically ventilated guinea pigs were given i.v. Evans blue dye (EB dye) and, 1 min later, PGD2 (30, 100, 300 or 1,000 nmol/kg). For comparison, the effect of 150 nmol/kg histamine or 2 nmol/kg leukotriene D4 (LTD4) was also examined. Lung resistance (R(L)) was measured for 6 min (or 25 min for selected animals) and the lungs were removed to calculate the amount of extravasated EB dye into the airways as a marker of leakage. In some of the animals, specific TP receptor antagonists, S-1452 (10 microg/kg) or ONO-3708 (10 mg/kg), or a thromboxane A2 synthase inhibitor, OKY-046 (30 mg/kg), was pretreated before giving PGD2.

RESULTS

Injection of PGD2 produced an immediate and dose-dependent increase in RL (peaking within 1 min), which was significant at all doses studied. At 1,000 nmol/kg, PGD2 induced a later increase in R(L), starting at 3 min and reaching a second peak at 8 min. By contrast, only PGD2 at doses of 300 and 1,000 nmol/kg produced a significant increase in EB dye extravasation. The relative potency of 1,000 nmol/kg PGD2 to induce leakage as compared to airflow obstruction was comparable to histamine at most of airway levels, but less than LTD4. Both responses caused by PGD2 were completely abolished by S-1452 and ONO-3708, but not by OKY-046.

CONCLUSION

PGD2 may induce airway microvascular leakage by directly stimulating TP receptors without generating TXA2 in guinea pigs. Microvascular leakage may play a role in the development of allergic airway inflammation caused by PGD2.

Inhibitory effects of capsaicinoids on fatty acid desaturation in a rat liver cell line

The inhibitory effects of such vanillylamides as capsaicin and nine capsaicinoids on fatty acid desaturation in liver cells were investigated by using the cultured rat liver cell line, BRL-3A. When capsaicin was added to the medium, it had a relatively strong inhibitory effect on delta6 desaturation and clear inhibitory effects on delta5 and C24delta16 desaturation (delta16 desaturation of C24-polyunsaturated fatty acids). Capsaicinoids with side carbon chain lengths of C10:0 and C12:0 expressed the maximum inhibitory effects of the nine capsaicinoids on fatty acid desaturation in the BRL-3A cells. The inhibitory effects of the capsaicinoids were not correlated with their pungency.

Drugs for the treatment of allergic diseases

Many kinds of drugs are used for the treatment of allergic diseases. Glucocorticoids are the most efficacious drugs and widely used for the treatment of allergic diseases. Recently, effectiveness of inhaled glucocorticoids for the treatment of bronchial asthma has been established. Beclomethasone dipropionate and fluticasone propionate, which are degraded easily after absorption, are applied by inhalation. Histamine is one of the most important mediators in allergic reactions and antihistamines have widely been applied for the treatment of allergic skin diseases. In Japan, over 20 antiallergic drugs, such as mediator release inhibitors, mediator antagonists and mediator synthesis inhibitors, have been developed. Recently developed compounds such as pranlukast and suplatast are very effective. To relieve the asthmatic attack, bronchodilators such as beta2-adrenoceptor agonists, theophylline and anti-cholinergic drugs are used. Clinical application of tacrolimus ointment has just started for the treatment of atopic dermatitis. Recently the number of allergic patients has increased. The onset and development of allergic diseases are considered to be dependent on both the genetic factors and the environmental factors. For the successful treatment of patients with allergic diseases, it is also important to consider the control of environmental factors.