Hematopoietic prostaglandin D synthase

Mast cells contribute to double-stranded RNA-induced augmentation of airway eosinophilia in a murine model of asthma

BACKGROUND

Clinical studies showed the contribution of viral infection to the development of asthma. Although mast cells have multiple roles in the pathogenesis of allergic asthma, their role of in the virus-associated pathogenesis of asthma remains unknown. Most respiratory viruses generate double-stranded (ds) RNA during their replication. dsRNA provokes innate immune responses. We recently showed that an administration of polyinocinic polycytidilic acid (poly IC), a mimetic of viral dsRNA, during allergen sensitization augments airway eosinophilia and hyperresponsiveness in mice via enhanced production of IL-13.

METHODS

The effect of poly IC on allergen-induced airway eosinophilia was investigated for mast cell-conserved Kit+/+ mice and -deficient KitW/KitW-v mice. The outcome of mast cell reconstitution was further investigated.

RESULTS

Airway eosinophilia and IL-13 production were augmented by poly IC in Kit+/+ mice but not in KitW/KitW-v mice. When KitW/KitW-v mice were reconstituted with bone marrow-derived mast cells (BMMCs), the augmentation was restored. The augmentation was not induced in the mice systemically deficient for TIR domain-containing adaptor-inducing IFN-β (TRIF) or interferon regulatory factor (IRF)-3, both mediate dsRNA-triggered innate immune responses. The augmentation was, however, restored in KitW/KitW-v mice reconstituted with TRIF-deficient or IRF-3-deficient BMMCs. Although leukotriene B4 and prostaglandin D2 are major lipid mediators released from activated mast cells, no their contribution was shown to the dsRNA-induced augmentation of airway eosinophilia.

CONCLUSIONS

We conclude that mast cells contribute to dsRNA-induced augmentation of allergic airway inflammation without requiring direct activation of mast cells with dsRNA or involvement of leukotriene B4 or prostaglandin D2.

Prostaglandins as PPARγ Modulators in Adipogenesis

Adipocytes and fat cells play critical roles in the regulation of energy homeostasis. Adipogenesis (adipocyte differentiation) is regulated via a complex process including coordinated changes in hormone sensitivity and gene expression. PPARγ is a ligand-dependent transcription factor and important in adipogenesis, as it enhances the expression of numerous adipogenic and lipogenic genes in adipocytes. Prostaglandins (PGs), which are lipid mediators, are associated with the regulation of PPARγ function in adipocytes. Prostacyclin promotes the differentiation of adipocyte-precursor cells to adipose cells via activation of the expression of C/EBPβ and δ. These proteins are important transcription factors in the activation of the early phase of adipogenesis, and they activate the expression of PPARγ, which event precedes the maturation of adipocytes. PGE₂ and PGF_2α strongly suppress the early phase of adipocyte differentiation by enhancing their own production via receptor-mediated elevation of the expression of cycloxygenase-2, and they also suppress the function of PPARγ. In contrast, PGD₂ and its non-enzymatic metabolite, Δ¹²-PGJ₂, activate the middle-late phase of adipocyte differentiation through both DP2 receptors and PPARγ. This paper focuses on potential roles of PGs as PPARγ modulators in adipogenesis and regulators of obesity.

Biochemical pathogenesis of aspirin exacerbated respiratory disease (AERD)

Aspirin exacerbated respiratory disease (AERD) is a distinct clinical entity characterized by eosinophilic rhinosinusitis, asthma and often nasal polyposis. Exposure to aspirin or other nonsteroid anti-inflammatory drugs (NSAIDs) exacerbates bronchospasms with asthma and rhinitis. Disease progression suggests a skewing towards TH2 type cellular response along with moderate to severe eosinophil and mast cell infiltration. Alterations in upper and lower airway cellular milieu with abnormalities in eicosanoid metabolism and altered eicosanoid receptor expression are the key features underlying AERD pathogenesis. Dysregulation of arachidonic acid (AA) metabolism, notably reduced prostaglandin E2 (PGE2) synthesis compared to their aspirin tolerant counterpart and relatively increased PGD2 production, a TH2/eosinophil chemoattractant are reported in AERD. Underproduced PGE2 is metabolized by overexpression of 15 prostaglandin dehydrogenase (15-PGDH) to inactive products further reducing PGE2 at real time. This relives the inhibitory effect of PGE2 on 5-lipoxygenase (5-LOX) resulting in overproduction of cysteinyl leukotrienes (CysLTs). Diminished formation of CysLT antagonists called lipoxins (LXs) also augments CysLTs responsiveness. Occasional intake of NSAIDs favors even more 5-LOX product formation, further narrowing the bronchoconstrictive bottle neck, resulting in acute asthmatic exacerbations along with increased mucus production. This review focuses on abnormalities in biochemical and molecular mechanisms in eicosanoid biosynthesis, eicosanoid receptor dysregulation and associated polymorphisms with special reference to arachidonic acid metabolism in AERD.

Aspirin-intolerant asthma (AIA) assessment using the urinary biomarkers, leukotriene E4 (LTE4) and prostaglandin D2 (PGD2) metabolites

The clinical syndrome of aspirin-intolerant asthma (AIA) is characterized by aspirin/nonsteroidal anti-inflammatory drug intolerance, bronchial asthma, and chronic rhinosinusitis with nasal polyposis. AIA reactions are evidently triggered by pharmacological effect of cyclooxygenase-1 inhibitors. Urine sampling is a non-invasive research tool for time-course measurements in clinical investigations. The urinary stable metabolite concentration of arachidonic acid products provides a time-integrated estimate of the production of the parent compounds in vivo. AIA patients exhibits significantly higher urinary concentrations of leukotriene E(4) (LTE(4)) and 1,15-dioxo-9α-hydroxy-2,3,4,5-tetranorprostan-1,20-dioic acid (tetranor-PGDM), a newly identified metabolite of PGD(2), at baseline. This finding suggests the possibility that increased mast cell activation is involved in the pathophysiology of AIA even in a clinically stable condition. In addition, lower urinary concentrations of primary prostaglandin E(2) and 15-epimer of lipoxin A(4) at baseline in the AIA patients suggest that the impaired anti-inflammatory elements may also contribute to the severe clinical outcome of AIA. During the AIA reaction, the urinary concentrations of LTE(4) and PGD(2) metabolites, including tetranor-PGDM significantly and correlatively increase. It is considered that mast cell activation probably is a pathophysiologic hallmark of AIA. However, despite the fact that cyclooxygenease-1 is the dominant in vivo PGD(2) biosynthetic pathway, the precise mechanism underlying the PGD(2) overproduction resulting from the pharmacological effect of cyclooxygenease-1 inhibitors in AIA remains unknown. A comprehensive analysis of the urinary concentration of inflammatory mediators may afford a new research target in elucidating the pathophysiology of AIA.

PGD synthase and PGD2 in immune resposne

PGD₂ is formed from arachidonic acid by successive enzyme reactions: oxygenation of arachidonic acid to PGH₂, a common precursor of various prostanoids, catalyzed by cyclooxygenase, and isomerization of PGH₂ to PGD₂ by PGD synthases (PGDSs). PGD₂ can be either pro- or anti-inflammatory depending on disease process and etiology. The anti-inflammatory and immunomodulatory attributes of PGDS/PGD₂ provide opportunities for development of novel therapeutic approaches for resistant infections and refractory inflammatory diseases. This paper highlights the role of PGD synthases and PGD2 in immune inflammatory response.

The Sigma class glutathione transferase from the liver fluke Fasciola hepatica

Background

Liver fluke infection of livestock causes economic losses of over US$ 3 billion worldwide per annum. The disease is increasing in livestock worldwide and is a re-emerging human disease. There are currently no commercial vaccines, and only one drug with significant efficacy against adult worms and juveniles. A liver fluke vaccine is deemed essential as short-lived chemotherapy, which is prone to resistance, is an unsustainable option in both developed and developing countries. Protein superfamilies have provided a number of leading liver fluke vaccine candidates. A new form of glutathione transferase (GST) family, Sigma class GST, closely related to a leading Schistosome vaccine candidate (Sm28), has previously been revealed by proteomics in the liver fluke but not functionally characterised.

Methodology/Principal Findings

In this manuscript we show that a purified recombinant form of the F. hepatica Sigma class GST possesses prostaglandin synthase activity and influences activity of host immune cells. Immunocytochemistry and western blotting have shown the protein is present near the surface of the fluke and expressed in eggs and newly excysted juveniles, and present in the excretory/secretory fraction of adults. We have assessed the potential to use F. hepatica Sigma class GST as a vaccine in a goat-based vaccine trial. No significant reduction of worm burden was found but we show significant reduction in the pathology normally associated with liver fluke infection.

Conclusions/Significance

We have shown that F. hepatica Sigma class GST has likely multi-functional roles in the host-parasite interaction from general detoxification and bile acid sequestration to PGD synthase activity.

Combating neglected parasitic diseases is of paramount importance to improve the health of human populations and/or their domestic animals. Uncovering key roles in host-parasite interactions may support the vaccine potential portfolio of a parasite protein. Fasciola hepatica causes global disease in humans and their livestock but no commercial vaccines are available. Members of the Sigma class glutathione transferase (GST) family have long been highlighted as vaccine candidates towards parasitic flatworms. To this end, a Sigma class GST is currently undergoing phase II clinical trials to protect against infection from the schistosomes. In this study we characterise the protein from F. hepatica following four work pathways that 1) confirm its designation as a Sigma class GST using substrate profiling, 2) assess prostaglandin synthase activity and its effect on host immune cells, 3) localise the Sigma GST within adult fluke and between ontogenic stages and 4) measure its potential as a vaccine candidate. The work presented here shows F. hepatica Sigma class GST to have key host-parasite roles and we suggest, warrants further investigation for inclusion into vaccine formulations.

Omega-3 fatty acids cause dramatic changes in TLR4 and purinergic eicosanoid signaling

Dietary fish oil containing ω3 fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), elicit cardioprotective and anti-inflammatory effects through unresolved mechanisms that may involve competition and inhibition at multiple levels. Here, we report the effects of arachidonic acid (AA), EPA, and DHA supplementation on membrane incorporation, phospholipase A(2) catalyzed release, and eicosanoid production in RAW264.7 macrophages. Using a targeted lipidomics approach, we observed that Toll-like receptor 4 and purinergic receptor activation of supplemented cells leads to the release of 22-carbon fatty acids that potently inhibit cyclooxygenase pathways. This inhibition was able to shunt metabolism of AA to lipoxygenase pathways, augmenting leukotriene and other lipoxygenase mediator synthesis. In resident peritoneal macrophages, docosapentaenoic acid (DPA) was responsible for cyclooxygenase inhibition after EPA supplementation, offering fresh insights into how EPA exerts anti-inflammatory effects indirectly through elongation to 22-carbon DPA.

Local inflammatory events induced by Bothrops atrox snake venom and the release of distinct classes of inflammatory mediators

Bothrops atrox is responsible for most accidents involving snakes in the Brazilian Amazon and its venom induces serious systemic and local effects. The local effects are not neutralized effectively by commercial antivenoms, resulting in serious sequelae in individuals bitten by this species. This study investigates the local inflammatory events induced in mice by B. atrox venom (BaV), such as vascular permeability, leukocyte influx and the release of important inflammatory mediators such as cytokines, eicosanoids and the chemokine CCL-2, at the injection site. The effect of BaV on cyclooxygenase (COX-1 and COX-2) expression was also investigated. The results showed that intraperitoneal (i.p.) injection of BaV promoted a rapid and significant increase in vascular permeability, which reached a peak 1 h after venom administration. Furthermore, BaV caused leukocyte infiltration into the peritoneal cavity between 1 and 8 h after i.p. injection, with mononuclear leukocytes (MNs) predominating in the first 4 h, and polymorphonuclear leukocytes (PMNs) in the last 4 h. Increased protein expression of COX-2, but not of COX-1, was detected in leukocytes recruited in the first and fourth hours after injection of BaV. The venom caused the release of eicosanoids PGD₂, PGE₂, TXA₂ and LTB₄, cytokines TNF-α, IL-6, IL-10 and IL-12p70, but not IFN-γ, and chemokine CCL-2 at different times. The results show that BaV is able to induce an early increase in vascular permeability and a leukocyte influx to the injection site consisting mainly of MNs initially and PMNs during the later stages. These phenomena are associated with the production of cytokines, the chemokine CCL-2 and eicosanoids derived from COX-1 and COX-2.

PGH1, the precursor for the anti-inflammatory prostaglandins of the 1-series, is a potent activator of the pro-inflammatory receptor CRTH2/DP2

Prostaglandin H₁ (PGH₁) is the cyclo-oxygenase metabolite of dihomo-γ-linolenic acid (DGLA) and the precursor for the 1-series of prostaglandins which are often viewed as “anti-inflammatory”. Herein we present evidence that PGH₁ is a potent activator of the pro-inflammatory PGD₂ receptor CRTH2, an attractive therapeutic target to treat allergic diseases such as asthma and atopic dermatitis. Non-invasive, real time dynamic mass redistribution analysis of living human CRTH2 transfectants and Ca²⁺ flux studies reveal that PGH₁ activates CRTH2 as PGH₂, PGD₂ or PGD₁ do. The PGH₁ precursor DGLA and the other PGH₁ metabolites did not display such effect. PGH₁ specifically internalizes CRTH2 in stable CRTH2 transfectants as assessed by antibody feeding assays. Physiological relevance of CRTH2 ligation by PGH₁ is demonstrated in several primary human hematopoietic lineages, which endogenously express CRTH2: PGH₁ mediates migration of and Ca²⁺ flux in Th2 lymphocytes, shape change of eosinophils, and their adhesion to human pulmonary microvascular endothelial cells under physiological flow conditions. All these effects are abrogated in the presence of the CRTH2 specific antagonist TM30089. Together, our results identify PGH₁ as an important lipid intermediate and novel CRTH2 agonist which may trigger CRTH2 activation in vivo in the absence of functional prostaglandin D synthase.

Prostaglandin D2 regulates joint inflammation and destruction in murine collagen-induced arthritis

OBJECTIVE

Prostaglandin D2 (PGD2) may exert proinflammatory or antiinflammatory effects in different biologic systems. Although this prostanoid and the enzymes responsible for its synthesis are up-regulated by interleukin-1β (IL-1β) in human chondrocytes in vitro, the role of PGD2 in arthritis remains unclear. This study was undertaken to investigate the role of PGD2 in the inflammatory response and in joint destruction during the development of collagen-induced arthritis (CIA) in mice.

METHODS

PGD2 and cytokine levels in mice with CIA were determined by enzyme-linked immunosorbent assay. Expression of hematopoietic PGD synthase (h-PGDS), lipocalin-type PGD synthase (l-PGDS), and DP1 and DP2 receptors was analyzed by immunohistochemical methods. PGE2 levels were determined by radioimmunoassay.

RESULTS

The arthritic process up-regulated the expression of h-PGDS, l-PGDS, DP1, and DP2 in articular tissue. PGD2 was produced in the joint during the early phase of arthritis, and serum PGD2 levels increased progressively throughout the arthritic process, reaching a maximum during the late stages of CIA. Treatment of arthritic mice with the DP1 antagonist MK0524 soon after the onset of disease increased the incidence and severity of CIA as well as the local levels of IL-1β, CXCL-1, and PGE2, whereas IL-10 levels were reduced. The administration of the DP2 antagonist CAY10595 did not modify the severity of arthritis. The injection of PGD2 into the paw, as well as the administration of the DP1 agonist BW245C, significantly lowered the incidence of CIA, the inflammatory response, and joint damage.

CONCLUSION

Our findings indicate that PGD2 is produced in articular tissue during the development of CIA and plays an antiinflammatory role, acting through the DP1 receptor.

Eosinophils as a novel cell source of prostaglandin D2: autocrine role in allergic inflammation

PGD(2) is a key mediator of allergic inflammatory diseases that is mainly synthesized by mast cells, which constitutively express high levels of the terminal enzyme involved in PGD(2) synthesis, the hematopoietic PGD synthase (H-PGDS). In this study, we investigated whether eosinophils are also able to synthesize, and therefore, supply biologically active PGD(2). PGD(2) synthesis was evaluated within human blood eosinophils, in vitro differentiated mouse eosinophils, and eosinophils infiltrating inflammatory site of mouse allergic reaction. Biological function of eosinophil-derived PGD(2) was studied by employing inhibitors of synthesis and activity. Constitutive expression of H-PGDS was found within nonstimulated human circulating eosinophils. Acute stimulation of human eosinophils with A23187 (0.1-5 μM) evoked PGD(2) synthesis, which was located at the nuclear envelope and was inhibited by pretreatment with HQL-79 (10 μM), a specific H-PGDS inhibitor. Prestimulation of human eosinophils with arachidonic acid (10 μM) or human eotaxin (6 nM) also enhanced HQL-79-sensitive PGD(2) synthesis, which, by acting on membrane-expressed specific receptors (D prostanoid receptors 1 and 2), displayed an autocrine/paracrine ability to trigger leukotriene C(4) synthesis and lipid body biogenesis, hallmark events of eosinophil activation. In vitro differentiated mouse eosinophils also synthesized paracrine/autocrine active PGD(2) in response to arachidonic acid stimulation. In vivo, at late time point of the allergic reaction, infiltrating eosinophils found at the inflammatory site appeared as an auxiliary PGD(2)-synthesizing cell population. Our findings reveal that eosinophils are indeed able to synthesize and secrete PGD(2), hence representing during allergic inflammation an extra cell source of PGD(2), which functions as an autocrine signal for eosinophil activation.

Lipid-cytokine-chemokine cascades orchestrate leukocyte recruitment in inflammation

Chemoattractants are pivotal mediators of host defense, orchestrating the recruitment of immune cells into sites of infection and inflammation. Chemoattractants display vast chemical diversity and include bioactive lipids, proteolytic fragments of serum proteins, and chemokines (chemotactic cytokines). All chemoattractants induce chemotaxis by activating seven-transmembrane-spanning GPCRs expressed on immune cells, establishing the concept that all chemoattractants are related in function. However, although chemoattractants have overlapping functions in vitro, recent in vivo data have revealed that they function, in many cases, nonredundantly in vivo. The chemically diverse nature of chemoattractants contributes to the fine control of leukocyte trafficking in vivo, with sequential chemoattractant use guiding immune cell recruitment into inflammatory sites. Lipid mediators frequently function as initiators of leukocyte recruitment, attracting the first immune cells into tissues. These initial responding immune cells produce cytokines locally, which in turn, induce the local release of chemokines. Local chemokine production then markedly amplifies subsequent waves of leukocyte recruitment. These new discoveries establish a paradigm for leukocyte recruitment in inflammation--described as lipid-cytokine-chemokine cascades--as a driving force in the effector phase of immune responses.

Rapid degradation of cyclooxygenase-1 and hematopoietic prostaglandin D synthase through ubiquitin-proteasome system in response to intracellular calcium level

Cyclooxygenase (COX)-1 and hematopoietic prostaglandin (PG) D synthase (H-PGDS) proteins, which are both involved in the arachidonate cascade, were stable in human megakaryocytic MEG-01 cells. In contrast, once the intracellular calcium level was increased by treatment with a calcium ionophore, both protein levels rapidly decreased with a half-life of less than 30 and 120 min for COX-1 and H-PGDS, respectively. In the presence of a proteasome inhibitor, COX-1 and H-PGDS proteins accumulated within 10 and 30 min, respectively, and concurrently appeared as the high-molecular-mass ubiquitinated proteins within 30 and 60 min, respectively, after an increase in the intracellular calcium level. The ubiquitination of these proteins was also observed when ADP, instead of a calcium ionophore, was used as an inducer to elevate the intracellular calcium level. When the entry of calcium ion into the cells was inhibited by ethylene glycol tetraacetic acid (EGTA), the ubiquitination of COX-1 and H-PGDS was clearly suppressed; and the addition of CaCl(2) to the medium cleared the EGTA-mediated suppression of the ubiquitination. These results indicate that COX-1 and H-PGDS were rapidly ubiquitinated and degraded through the ubiquitin-proteasome system in response to the elevation of the intracellular calcium level.

Mast cells function as an alternative modulator of adipogenesis through 15-deoxy-delta-12, 14-prostaglandin J2

Mast cells are one of the major producers of prostaglandins (PGs). The final metabolite of PGs 15-deoxy-delta-12,14-PGJ(2) (15-deoxy-delta PGJ(2)) is the endogenous ligand of the peroxisome proliferator-activated receptor (PPAR) γ. PPARγ modulates adipocyte differentiation; therefore, we attempted to investigate whether PGs derived from mast cells influenced on adipogenesis. We found the increase of mast cell numbers in fat tissue of obese mice fed with a high-fat diet allowed us to speculate contributions of mast cells to adipogenesis. Mast cell-mediated induction of adipogenesis was evaluated by using 3T3 L1 cells. Supernatants obtained from mast cells stimulated with calcium ionophore or the high-glucose condition contained 15-deoxy-delta PGJ(2) and induced adipogenesis of 3T3 L1 cells. Agonistic activity of PGJ(2) from the supernatants on PPARγ was confirmed by a reporter gene assay. Culture medium collected from calcium ionophore-stimulated bone marrow-derived cultured mast cells (BMCMC) activated PPAR-responsive element in NIH3T3 fibroblasts, and the specific inhibitor of PPARγ canceled the activation. Contribution of mast cells to obesity was evaluated by using mast cell-deficient mice fed with a Western diet. Weight gain of mast cell-deficient mice during high-fat feeding was impaired compared with their littermate wild-type mice; on the other hand, transplantation of bone marrow-derived cultured mast cells to mast cell-deficient mice restored the weight gain by intake of a high-fat diet. In this study, we clearly demonstrated that mast cells produced PGs in response to the high-glucose condition and induced adipocyte differentiation and possibly obesity. This is the first study that provides evidence for a novel role of mast cells in adipogenesis via PPARγ activation.

Hematopoietic prostaglandin D synthase (HPGDS): a high stability, Val187Ile isoenzyme common among African Americans and its relationship to risk for colorectal cancer

Intestinal tumors in Apc(Min/+) mice are suppressed by over-production of HPGDS, which is a glutathione transferase that forms prostaglandin D(2) (PGD(2)). We characterized naturally occurring HPGDS isoenzymes, to see if HPGDS variation is associated with human colorectal cancer risk. We used DNA heteroduplex analysis and sequencing to identify HPGDS variants among healthy individuals. HPGDS isoenzymes were produced in bacteria, and their catalytic activities were tested. To determine in vivo effects, we conducted pooled case-control analyses to assess whether there is an association of the isoenzyme with colorectal cancer. Roughly 8% of African Americans and 2% of Caucasians had a highly stable Val187lle isoenzyme (with isoleucine instead of valine at position 187). At 37°C, the wild-type enzyme lost 15% of its activity in 1h, whereas the Val187Ile form remained >95% active. At 50°C, the half life of native HPGDS was 9min, compared to 42 min for Val187Ile. The odds ratio for colorectal cancer among African Americans with Val187Ile was 1.10 (95% CI, 0.75-1.62; 533 cases, 795 controls). Thus, the Val187Ile HPGDS isoenzyme common among African Americans is not associated with colorectal cancer risk. Other approaches will be needed to establish a role for HPGDS in occurrence of human intestinal tumors, as indicated by a mouse model.

Functional studies of single-nucleotide polymorphic variants of human glutathione transferase T1-1 involving residues in the dimer interface

Glutathione transferase T1-1 catalyses detoxication and bioactivation processes in which glutathione conjugates are formed from endogenous and xenobiotic substrates, including alkylating agents and halogenated alkanes. Although the common null polymorphism of the human GSTT1 gene has been studied extensively, little is known about the consequences of GSTT1 single-nucleotide polymorphisms (SNPs). Here, we have examined the effects of two SNPs that alter amino acid residues in the dimer interface of the GST T1-1 protein and one that causes a conservative substitution in the core of the subunit. Variant proteins were expressed in an Escherichia coli strain in which the metabolism of ethylene dibromide to a glutathione conjugate leads to lacZ reversion mutations. We measured the kinetic properties of the enzymes with the characteristic substrate 1,2-epoxy-3-(p-nitrophenoxy)propane (EPNP) and determined the specific activities with several other substrates. Circular dichroism spectroscopy was used to measure protein thermal denaturation profiles. Variant T104P, which has been reported as inactive, showed weak but detectable activity with each substrate. Variant R76S was expressed at lower levels and showed much-reduced thermal stability. The results are interpreted in the context of the three-dimensional structure of human GST T1-1.

FcεRI, but not FcγR, signals induce prostaglandin D2 and E2 production from basophils

Prostaglandin (PG) D2 and PGE2 are arachidonic acid metabolites that are generated though an isomerization reaction catalyzed by PG synthases. PGs have been implicated in immunologic reactions in addition to a wide range of physiological functions. It has long been thought that basophils, in contrast to mast cells, do not synthesize PGs, although they do release leukotrienes and platelet-activating factor. Here, we show that basophils function as a source of PGD2 and PGE2. In vitro-cultured basophils from mouse bone marrow produced both PGD2 and PGE2 in response to IgE + antigen (Ag), but not to IgG + Ag. Release of PGs was almost completely abrogated in cultured basophils from FcRγ-chain(-/-) mice, indicating the involvement of FcεRI. Basophils freshly isolated from bone marrow cells (primary basophils) were also capable of secreting PGD2 and PGE2. Although the amount of PGD2 released from primary basophils was lower than that from mast cells, the capability of primary basophils to generate PGE2 was more potent than that of mast cells. Transcripts and proteins for both hematopoietic-type PGD synthase and PGE synthase were detected in basophils. In addition, human basophils, like mouse basophils, also produced PGD2 through IgE-mediated stimulation. Thus, basophils could be an important source of PGD2/PGE2 and may contribute to allergic inflammation and immune responses.

Role of hematopoietic prostaglandin D synthase in biphasic nasal obstruction in guinea pig model of experimental allergic rhinitis

We investigated the role of hematopoietic prostaglandin D synthase (H-PGDS) in biphasic nasal obstruction in allergic rhinitis using a new specific inhibitor, (N-methoxy-N-methyl)-4-(5-benzoylbenzimidazole-2-yl)-3,5-dimethylpyrrole-2-carboxamide hydrochloride (TAS-204). First, we developed a novel guinea pig model of allergic rhinitis. Guinea pigs sensitized to ovalbumin without adjuvant were challenged with intranasal exposure to ovalbumin once a week. After the 3rd antigen challenge, they exhibited biphasic nasal obstruction. Additionally, analysis of nasal lavage fluid revealed an increase in the level of prostaglandin D(2) in both early and late phases. Treatment with oral TAS-204 for 15 days during the period of antigen challenges suppressed increases in nasal airway resistance in both phases. It is noteworthy that the late phase nasal obstruction was almost completely abrogated by inhibiting H-PGDS alone. Eosinophil infiltration in nasal lavage fluid and nasal hyperresponsiveness to histamine was also reduced by TAS-204 administration. These findings suggest that H-PGDS plays a critical role in the development of allergic rhinitis, especially in the induction of late phase nasal obstruction.

Dual functions of prostaglandin D2 in murine contact hypersensitivity via DP and CRTH2

Prostaglandin D2 (PGD2) exerts its effects through two distinct receptors: the chemoattractant receptor-homologous molecule expressed on Th2 cells (CRTH2) and the D prostanoid (DP) receptor. Our previous study demonstrated that CRTH2 mediates contact hypersensitivity (CHS) in mice. However, the function of DP receptor remains to be fully established. In this study, we examine the pathophysiological roles of PGD2 using DP-deficient (DP(-/-)) and CRTH2/DP-deficient (CRTH2(-/-)/DP(-/-)) mice to elucidate receptor-mediated PGD2 action in CHS. We observed profound exacerbation of CHS in DP(-/-) mice. CRTH2(-/-)/DP(-/-) mice showed similar exacerbation, but to a lesser extent. These symptoms were accompanied by increased production of interferon-γ and IL-17. The increase in IL-17 producing γδ T cells was marked and presumably contributed to the enhanced CHS. DP deficiency promoted the in vivo migration of dendritic cells to regional lymph nodes. A DP agonist added to DCs in vitro was able to inhibit production of IL-12 and IL-1β. Interestingly, production of IL-10 in dendritic cells was elevated via the DP pathway, but it was lowered by the CRTH2 pathway. Collectively, PGD2 signals through CRTH2 to mediate CHS inflammation, and conversely, DP signals to exert inhibitory effects on CHS. Thus, we report opposing functions for PGD2 that depend on receptor usage in allergic reactions.

Knockout and transgenic mice in glutathione transferase research

Glutathione transferases (GSTs) are a multigene family of ubiquitously expressed, polymorphic enzymes responsible for the metabolism of a wide range of both endogenous and exogenous substrates, play a central role in the adaptive response to chemical and oxidative stress, and are subject to regulation by a range of structurally unrelated chemicals. In this review, we present a current summary of knockout mouse models in the GST field, discussing some of the issues pertaining to orthologous proteins between mice and humans, the potential confounding issues related to genetic background, and also cover new transgenic models in the increasingly important area of humanization.

Hematopoietic-Prostaglandin D2 synthase through PGD2 production is involved in the adult ovarian physiology

Background

The prostaglandin D2 (PGD2) pathway is involved in numerous biological processes and while it has been identified as a partner of the embryonic sex determining male cascade, the roles it plays in ovarian function remain largely unknown. PGD2 is secreted by two prostaglandin D synthases (Pgds); the male-specific lipocalin (L)-Pgds and the hematopoietic (H)-Pgds.

Methods

To study the expression of the Pgds in the adult ovary, in situ hybridization were performed. Then, to evaluate the role of H-Pgds produced PGD2 in the ovarian physiology, adult female mice were treated with HQL-79, a specific inhibitor of H-Pgds enzymatic activity. The effects on expression of the gonadotrophin receptors FshR and LhR, steroidogenic genes Cyp11A1, StAR and on circulating progesterone and estradiol, were observed.

Results

We report the localization of H-Pgds mRNA in the granulosa cells from the primary to pre-ovulatory follicles. We provide evidence of the role of H-Pgds-produced PGD2 signaling in the FSH signaling through increased FshR and LhR receptor expression. This leads to the activation of steroidogenic Cyp11A1 and StAR gene expression leading to progesterone secretion, independently on other prostanoid-synthetizing mechanisms. We also identify a role whereby H-Pgds-produced PGD2 is involved in the regulation of follicular growth through inhibition of granulosa cell proliferation in the growing follicles.

Conclusions

Together, these results show PGD2 signaling to interfere with FSH action within granulosa cells, thus identifying an important and unappreciated role for PGD2 signaling in modulating the balance of proliferation, differentiation and steroidogenic activity of granulosa cells.

Mast cell phenotype, location, and activation in severe asthma. Data from the Severe Asthma Research Program

RATIONALE

Severe asthma (SA) remains poorly understood. Mast cells (MC) are implicated in asthma pathogenesis, but it remains unknown how their phenotype, location, and activation relate to asthma severity.

OBJECTIVES

To compare MC-related markers measured in bronchoscopically obtained samples with clinically relevant parameters between normal subjects and subjects with asthma to clarify their pathobiologic importance.

METHODS

Endobronchial biopsies, epithelial brushings, and bronchoalveolar lavage were obtained from subjects with asthma and normal subjects from the Severe Asthma Research Program (N = 199). Tryptase, chymase, and carboxypeptidase A (CPA)3 were used to identify total MC (MC(Tot)) and the MC(TC) subset (MCs positive for both tryptase and chymase) using immunostaining and quantitative real-time polymerase chain reaction. Lavage was analyzed for tryptase and prostaglandin D2 (PGD2) by ELISA.

MEASUREMENTS AND MAIN RESULTS

Submucosal MC(Tot) (tryptase-positive by immunostaining) numbers were highest in "mild asthma/no inhaled corticosteroid (ICS) therapy" subjects and decreased with greater asthma severity (P = 0.002). In contrast, MC(TC) (chymase-positive by immunostaining) were the predominant (MC(TC)/MC(Tot) > 50%) MC phenotype in SA (overall P = 0.005). Epithelial MC(Tot) were also highest in mild asthma/no ICS, but were not lower in SA. Instead, they persisted and were predominantly MC(TC). Epithelial CPA3 and tryptase mRNA supported the immunostaining data (overall P = 0.008 and P = 0.02, respectively). Lavage PGD2 was higher in SA than in other steroid-treated groups (overall P = 0.02), whereas tryptase did not differentiate the groups. In statistical models, PGD2 and MC(TC)/MC(Tot) predicted SA.

CONCLUSIONS

Severe asthma is associated with a predominance of MC(TC) in the airway submucosa and epithelium. Activation of those MC(TC) may contribute to the increases in PGD2 levels. The data suggest an altered and active MC population contributes to SA pathology.

Divergent responses to peptidoglycans derived from different E. coli serotypes influence inflammatory outcome in trout, Oncorhynchus mykiss, macrophages

Background

Pathogen-associated molecular patterns (PAMPs) are structural components of pathogens such as lipopolysaccharide (LPS) and peptidoglycan (PGN) from bacterial cell walls. PAMP-recognition by the host results in an induction of defence-related genes and often the generation of an inflammatory response. We evaluated both the transcriptomic and inflammatory response in trout (O. mykiss) macrophages in primary cell culture stimulated with DAP-PGN (DAP; meso-diaminopimelic acid, PGN; peptidoglycan) from two strains of Escherichia coli (PGN-K12 and PGN-O111:B4) over time.

Results

Transcript profiling was assessed using function-targeted cDNA microarray hybridisation (n = 36) and results show differential responses to both PGNs that are both time and treatment dependent. Wild type E. coli (K12) generated an increase in transcript number/diversity over time whereas PGN-O111:B4 stimulation resulted in a more specific and intense response. In line with this, Gene Ontology analysis (GO) highlights a specific transcriptomic remodelling for PGN-O111:B4 whereas results obtained for PGN-K12 show a high similarity to a generalised inflammatory priming response where multiple functional classes are related to ribosome biogenesis or cellular metabolism. Prostaglandin release was induced by both PGNs and macrophages were significantly more sensitive to PGN-O111:B4 as suggested from microarray data.

Conclusion

Responses at the level of the transcriptome and the inflammatory outcome (prostaglandin synthesis) highlight the different sensitivity of the macrophage to slight differences (serotype) in peptidoglycan structure. Such divergent responses are likely to involve differential receptor sensitivity to ligands or indeed different receptor types. Such changes in biological response will likely reflect upon pathogenicity of certain serotypes and the development of disease.

Development and characterization of new inhibitors of the human and mouse hematopoietic prostaglandin D(2) synthases

The hematopoietic prostaglandin D(2) synthase has a proinflammatory effect in a range of diseases, including allergic asthma, where its product prostaglandin D(2) (PGD(2)) has a role in regulating many of the hallmark disease characteristics. Here we describe the development and characterization of a novel series of hematopoietic prostaglandin D(2) synthase inhibitors with potency similar to that of known inhibitors. Compounds N-benzhydryl-5-(3-hydroxyphenyl)thiophene-2-carboxamide (compound 8) and N-(1-amino-1-oxo-3-phenylpropan-2-yl)-6-(thiophen-2-yl)nicotinamide (compound 34) demonstrated low micromolar potency in the inhibition of the purified enzyme, while only 34 reduced Toll-like receptor (TLR) inducible PGD(2) production in both mouse primary bone marrow-derived macrophages and the human megakaryocytic cell line MEG-01S. Importantly, 34 demonstrated a greater selectivity for inhibition of PGD(2) synthesis versus other eicosanoids that lie downstream of PGH(2) (PGE(2) and markers of prostacyclin (6-keto PGF(1alpha)) and thromboxane (TXB(2))) when compared to the known inhibitors HQL-79 (compound 1) and 2-phenyl-5-(1H-pyrazol-3-yl)thiazole (compound 2). Compound 34 therefore represents a selective hematopoietic prostaglandin D(2) synthase inhibitor.

High-quality crystals of human haematopoietic prostaglandin D synthase with novel inhibitors

Human haematopoietic prostaglandin D synthase (H-PGDS; EC 5.3.99.2) produces prostaglandin D(2), an allergic and inflammatory mediator, in mast cells and Th2 cells. H-PGDS has been crystallized with novel inhibitors with half-maximal inhibitory concentrations (IC(50)) in the low nanomolar range by the counter-diffusion method onboard the Russian Service Module on the International Space Station. The X-ray diffraction of a microgravity-grown crystal of H-PGDS complexed with an inhibitor with an IC(50) value of 50 nM extended to 1.1 A resolution at 100 K using SPring-8 synchrotron radiation, which is one of the highest resolutions obtained to date for this protein.

Discovery of an Oral Potent Selective Inhibitor of Hematopoietic Prostaglandin D Synthase (HPGDS)

Hematopoietic prostaglandin D synthase (HPGDS) is primarly expressed in mast cells, antigen-presenting cells, and Th-2 cells. HPGDS converts PGH2 into PGD2, a mediator thought to play a pivotal role in airway allergy and inflammatory processes. In this letter, we report the discovery of an orally potent and selective inhibitor of HPGDS that reduces the antigen-induced response in allergic sheep.

Mast cell-derived prostaglandin D2 controls hyaluronan synthesis in human orbital fibroblasts via DP1 activation: implications for thyroid eye disease

Thyroid eye disease (TED) is a debilitating disorder characterized by the accumulation of adipocytes and hyaluronan (HA). Production of HA by fibroblasts leads to remarkable increases in tissue volume and to the anterior displacement of the eyes. Prostaglandin D(2) (PGD(2)), mainly produced by mast cells, promotes orbital fibroblast adipogenesis. The mechanism by which PGD(2) influences orbital fibroblasts and their synthesis of HA is poorly understood. We report here that mast cell-derived PGD(2) is a key factor that promotes HA biosynthesis by orbital fibroblasts. Primary orbital fibroblasts from TED patients were isolated and used to test the effects of PGD(2), prostaglandin J(2), as well as prostaglandin D receptor (DP) agonists and antagonists on HA synthesis. The expression of HA synthase (HAS), hyaluronidase, DP1, and DP2 mRNA levels was assessed by PCR. Small interfering RNAs against HAS1 or HAS2 were used to assess the importance of HAS isoforms on HA production. Treatment of human orbital fibroblasts with PGD(2) and PGJ(2) increased HA synthesis and HAS mRNA. HAS2 was the dominant isoform responsible for HA production by PGD(2). The effect of PGD(2) on HA production was mimicked by the selective DP1 agonist BW245C. The DP1 antagonist MK-0524 completely blocked PGD(2)-induced HA synthesis. Human mast cells (HMC-1) produced PGD(2). Co-culture of HMC-1 cells with orbital fibroblasts induced HA production and inhibition of mast cell-derived PGD(2) prevented HA synthesis. Mast cell-derived PGD(2) increased HA production via activation of DP1. Selectively targeting the production of PGD(2) and/or activation of DP1 may prevent pathological changes associated with TED.

Integrative meta-analysis of differential gene expression in acute myeloid leukemia

Background

Acute myeloid leukemia (AML) is a heterogeneous disease with an overall poor prognosis. Gene expression profiling studies of patients with AML has provided key insights into disease pathogenesis while exposing potential diagnostic and prognostic markers and therapeutic targets. A systematic comparison of the large body of gene expression profiling studies in AML has the potential to test the extensibility of conclusions based on single studies and provide further insights into AML.

Methodology/Principal Findings

In this study, we systematically compared 25 published reports of gene expression profiling in AML. There were a total of 4,918 reported genes of which one third were reported in more than one study. We found that only a minority of reported prognostically-associated genes (9.6%) were replicated in at least one other study. In a combined analysis, we comprehensively identified both gene sets and functional gene categories and pathways that exhibited significant differential regulation in distinct prognostic categories, including many previously unreported associations.

Conclusions/Significance

We developed a novel approach for granular, cross-study analysis of gene-by-gene data and their relationships with established prognostic features and patient outcome. We identified many robust novel prognostic molecular features in AML that were undetected in prior studies, and which provide insights into AML pathogenesis with potential diagnostic, prognostic, and therapeutic implications. Our database and integrative analysis are available online (http://gat.stamlab.org).

Development of a beta-trace protein based formula for estimation of glomerular filtration rate

Beta-trace protein (BTP) is a novel marker of glomerular filtration rate (GFR). To date, no pediatric formula for calculating GFR based on BTP has been developed. We measured GFR, serum creatinine and BTP in 387 children who underwent 474 (99m)Tc-diethylene triamine pentaacetic acid renal scans. A BTP-based formula for estimating GFR was derived using stepwise linear regression analysis. A separate control group of 116 measurements in 99 children was used to validate the novel formula. A formula was also developed for each gender. The novel formula is: [formula: see text]. The Spearman rank correlation coefficient between the BTP-derived GFR estimate and the measured GFR was 0.80 [95% confidence interval (CI) 0.76-0.83], which is substantially better than that derived with the Schwartz formula (r = 0.70, 95% CI 0.65-0.74). The Bland-Altman analysis revealed a mean bias of 1.21% [standard deviation (SD) 28%] in the formula development dataset, which was virtually identical to the 1.03% mean bias (29.5% SD) in the validation group and no different from the Schwartz formula bias. The percentage of values within 10% (33.0 vs. 28.3%) and 30% deviation (76.8 vs. 72.6%) were better for BTP-based formula than for the Schwartz formula. Separate formulas according to gender did not perform better than that for the pediatric population. This BTP-based formula was found to estimate GFR with reasonable precision and provided improved accuracy over the Schwartz GFR formula.

Increased expression and cellular localization of lipocalin-type prostaglandin D synthase in Helicobacter pylori-induced gastritis

Immunological responses in the host can result in different disease outcomes of Helicobacter pylori-induced gastritis. Prostaglandin E2 derived from cyclooxygenase (COX) and prostaglandin E synthase contribute to gastric protection. Recently, prostaglandin D2 was shown to be involved in host immunity by chemotactic activity through chemoattractant receptor-homologous molecule expressed on Th2 cells (CRTH2), but its role in H. pylori-induced gastritis has not been clarified. We determined the expression levels of mRNAs for haematopoietic PGD synthase (H-PGDS) and lipocalin-type PGDS (L-PGDS), MIP-1 alpha, IFN-gamma, IL-4, and CDX2 in H. pylori-induced gastritis mucosa by quantitative RT-PCR. We found that L-PGDS was constitutively expressed in the epithelium of the glandular base. L-PGDS, but not H-PGDS, was induced on fibroblasts close to infiltrating cells in the H. pylori-infected gastric mucosa. These fibroblasts co-expressed COX-2. The level of L-PGDS mRNA expression decreased as gastritis became more severe. In most of the H. pylori-infected gastric mucosa, CCR5(+) cells had more actively infiltrated than had CRTH2(+) cells. However, the expression level of IFN-gamma was lower in the mucosa of the CRTH2(+) cells-dominantly infiltrating group than that of the less CRTH2-infiltrating group. Exogenously added PGD2 decreased the H. pylori-induced expression of IFN-gamma in peripheral blood mononuclear cells in vitro. The data suggest that PGD2 derived from the gastric mucosa and fibroblasts plays protective roles against inflammatory changes in H. pylori-induced gastritis.

Pronounced adipogenesis and increased insulin sensitivity caused by overproduction of prostaglandin D2 in vivo

Lipocalin-type prostaglandin (PG) D synthase is expressed in adipose tissues and involved in the regulation of glucose tolerance and atherosclerosis in type 2 diabetes. However, the physiological roles of PGD(2) in adipogenesis in vivo are not clear, as lipocalin-type prostaglandin D synthase can also act as a transporter for lipophilic molecules, such as retinoids. We generated transgenic (TG) mice overexpressing human hematopoietic PGDS (H-PGDS) and investigated the in vivo functions of PGD(2) in adipogenesis. PGD(2) production in white adipose tissue of H-PGDS TG mice was increased approximately seven-fold as compared with that in wild-type (WT) mice. With a high-fat diet, H-PGDS TG mice gained more body weight than WT mice. Serum leptin and insulin levels were increased in H-PGDS TG mice, and the triglyceride level was decreased by about 50% as compared with WT mice. Furthermore, in the white adipose tissue of H-PGDS TG mice, transcription levels of peroxisome proliferator-activated receptor gamma, fatty acid binding protein 4 and lipoprotein lipase were increased approximately two-fold to five-fold as compared with those of WT mice. Finally, H-PGDS TG mice showed clear hypoglycemia after insulin clamp. These results indicate that TG mice overexpressing H-PGDS abundantly produced PGD(2) in adipose tissues, resulting in pronounced adipogenesis and increased insulin sensitivity. The present study provides the first evidence that PGD(2) participates in the differentiation of adipocytes and in insulin sensitivity in vivo, and the H-PGDS TG mice could constitute a novel model mouse for diabetes studies.

Comparison of PGH2 binding site in prostaglandin synthases

BACKGROUND

Prostaglandin H2 (PGH2) is a common precursor for the synthesis of five different Prostanoids via specific Prostanoid Synthases. The binding of this substrate with these Synthases is not properly understood. Moreover, currently no crystal structure of complexes bound with PGH2 has been reported. Hence, understanding the interactions of PGH2 and characterizing its binding sites in these synthases is crucial for developing novel therapeutics based on these proteins as targets.

RESULTS

Shape and physico-chemical properties of the PGH2 binding sites of the four prostanoid synthases were analyzed and compared in order to understand the molecular basis of the specificity. This study provides models with predicted pockets for the binding of PGH2 with PGD, PGE, PGF and PGI Synthases. The results closely match with available experimental data. The comparison showed seven physico-chemical features that are common to the four PGH2 binding sites. However this common pattern is not statistically unique and is not specific enough to distinguish between proteins that can or cannot bind PGH2. A large scale search in ASTRAL data bank, a non redundant Protein Data Bank, for a similar pattern showed the uniqueness of each of the PGH2 binding site in these Synthases.

CONCLUSION

The binding pockets in PGDS, PGES, PGFS and PGIS are unique and do not share significant commonality which can be characterized as a PGH2 binding site. Local comparison of these protein structures highlights a case of convergent evolution in analogous functional sites.

Dendritic cells express hematopoietic prostaglandin D synthase and function as a source of prostaglandin D2 in the skin

Prostaglandin D2 (PGD2), an arachidonic acid metabolite, has been implicated in allergic responses. A major source of PGD2 in the skin is mast cells that express hematopoietic PGD synthase (H-PGDS). In this study, we show the expression of H-PGDS in human dendritic cells (DCs) and the regulatory mechanisms by which DCs produce PGD2. We detected H-PGDS in epidermal Langerhans cells, dermal DCs, plasmacytoid DCs, and myeloid DCs. Monocyte-derived DCs rapidly secreted PGD2 when stimulated with the calcium ionophore A23187. More importantly, pretreatment of monocyte-derived DCs with PMA (phorbol 12-myrisate 13-acetate) synergistically enhanced the rapid PGD2 secretion induced by A23187, whereas PMA alone did not induce PGD2 secretion. Lipopolysaccharide (LPS) reduced H-PGDS expression, but interferon-gamma followed by LPS induced significant PGD2 production in a delayed time course at 6 hours. This effect was associated with inhibition of LPS-induced H-PGDS reduction. Interestingly, an irritant compound, SDS, also induced a rapid PGD2 release. PGD2 synergistically enhanced CCL22/macrophage-derived chemokine synthesis in interferon-gamma-treated human keratinocytes. In addition, bone marrow-derived DCs from wild-type mice stimulated lymph node cells to produce higher amounts of interleukin-17 than did DCs from mice lacking the H-PGDS gene. Thus, DCs could be an important source of skin PGD2 and may mediate or regulate skin inflammation by releasing PGD2 in response to various stimuli, contributing to the innate and/or acquired immune responses.

Targeted lipidomics reveals mPGES-1-PGE2 as a therapeutic target for multiple sclerosis

The arachidonic acid (AA) cascade produces eicosanoids, such as prostaglandins (PGs), that regulate physiological and pathological functions. Although various nonsteroidal anti-inflammatory drugs have been developed, blocking upstream components (cyclooxygenase-1 and -2) of the AA cascade leads to severe side effects, including gastrointestinal ulcers and cardiovascular events, respectively, due to the complexity of the AA cascade. Here, using an AA cascade-targeted lipidomics approach, we report that microsomal PGE synthase 1 (mPGES-1) plays a key role in experimental autoimmune encephalomyelitis (EAE). Eicosanoids (mainly PGD(2)) are produced constitutively in the spinal cord of naive mice. However, in EAE lesions, the PGE(2) pathway is favored and the PGD(2), PGI(2), and 5-lipoxygenase pathways are attenuated. Furthermore, mPGES-1(-/-) mice showed less severe symptoms of EAE and lower production of IL-17 and IFN-gamma than mPGES-1(+/+) mice. Expression of PGE(2) receptors (EP1, EP2, and EP4) was elevated in EAE lesions and correlated with clinical symptoms. Immunohistochemistry on central nervous systems of EAE mice and multiple sclerosis (MS) patients revealed overt expression of mPGES-1 protein in microglia/macrophages. Thus, the mPGES-1-PGE(2)-EPs axis of the AA cascade may exacerbate EAE pathology. Our findings have important implications for the design of therapies for MS.

On the mechanism of microsomal prostaglandin E synthase type-2--a theoretical study of endoperoxide reaction with MeS(-)

The reaction pathways of deprotonation versus nucleophilic substitution involving mPGES-2 enzyme catalysis were investigated by ab initio molecular orbital theory calculations for the reaction of methylthiolate with the endoperoxide core of PGH(2) and by the combined quantum mechanical molecular mechanical methods. The calculations showed that deprotonation mechanism is energetically more favorable than the nucleophilic substitution pathway.

Identification and characterisation of new inhibitors for the human hematopoietic prostaglandin D2 synthase

Prostaglandin D(2) synthesised by the hematopoietic prostaglandin D(2) synthase has a pro-inflammatory effect in allergic asthma, regulating many hallmark characteristics of the disease. Here we describe identification of hematopoietic prostaglandin D(2) synthase inhibitors including cibacron blue, bromosulfophthalein and ethacrynic acid. Expansion around the drug-like ethacrynic acid identified a novel inhibitor, nocodazole, and a fragment representing its aromatic core. Nocodazole binding was further characterised by docking calculations in combination with conformational strain analysis. The benzyl thiophene core was predicted to be buried in the active site, binding in the putative prostaglandin binding site, and a likely hydrogen bond donor site identified. X-ray crystallographic studies supported the predicted binding mode.

Prostaglandin D(2) sustains the pyrogenic effect of prostaglandin E(2)

Prostaglandin D(2) (PGD(2)) is involved in a variety of physiological and pathophysiological processes, but its role in fever is poorly understood. Here we investigated the effects of central PGD(2) administration on body temperature and prostaglandin levels in the cerebrospinal fluid (CSF) of rats. Administration of PGD(2) into the cisterna magna (i.c.m) evoked a delayed fever response that was paralleled by increased levels of prostaglandin E(2) (PGE(2)) in the CSF. The elevated PGE(2) levels were not caused by an increased expression of cyclooxygenase 2 or microsomal prostaglandin E synthase-1 in the hypothalamus. Interestingly, i.c.m. pretreatment of animals with PGD(2) considerably sustained the pyrogenic effects of i.c.m. administered PGE(2). These data indicate that PGD(2) might control the availability of PGE(2) in the CSF and suggest that centrally produced PGD(2) may play a role in the maintenance of fever.

Effects of Bothrops asper snake venom on the expression of cyclooxygenases and production of prostaglandins by peritoneal leukocytes in vivo, and by isolated neutrophils and macrophages in vitro

In this study, the ability of Bothrops asper snake venom (BaV) to increase the production of prostaglandins PGE(2) and PGD(2) was assessed in a mouse model in vivo and in inflammatory cells in vitro. In addition, the expressions of COX-1 and COX-2 were assessed. BaV induced an increment in the in vivo synthesis of PGE(2) and PGD(2), together with an enhanced expression of COX-2, but not of COX-1. However, enzymatic activities of COX-1 and COX-2 were increased. Incubation of isolated macrophages and neutrophils with a sub-cytotoxic concentration of BaV in vitro resulted in increased release of PGE(2) and PGD(2) by macrophages and PGE(2) by neutrophils, concomitantly with an increment in the expression of COX-2, but not of COX-1 by both cell types. Our results demonstrate the ability of BaV to promote the expression of COX-2 and to induce the synthesis of proinflammatory prostaglandins. Macrophages and neutrophils may be important targets for this venom under in vivo situation.

Role of prostaglandin D(2) and its receptors in the pathophysiology of asthma

Prostaglandin D(2) (PGD(2)) is one of the most abundant lipid mediators present in the airways of asthmatics. However, little was known of the role it plays in the pathophysiology of asthma, until the identification of DP (DP1, PTGDR) and CRTH2 (DP2), two PGD(2)-specific transmembrane receptors with different distribution and intracellular signaling. Pharmacological tools, such as receptor-specific agonists and antagonists, and genetically-engineered mice, which lack either DP or CRTH2, have helped understand the complex effects of PGD(2) in allergic inflammation of the airways. Furthermore, genetic association studies have shown a positive linkage of the genetic polymorphisms in DP and CRTH2, with asthma phenotypes from specific ethnic backgrounds, further highlighting the importance of PGD(2) and its receptors in the pathophysiology of asthma.

Prostanoid function and cardiovascular disease

Prostanoids, including prostaglandins (PGs) and thromboxanes (TXs) are synthesized from arachidonic acid by the combined action of cyclooxygenases (COXs) and PG and TX synthases. Finally after their synthesis, prostanoids are quickly released to the extracellular medium exerting their effects upon interaction with prostanoid receptors present in the neighbouring cells. These agents exert important actions in the cardiovascular system, modulating vascular homeostasis and participating in the pathogenesis of vascular diseases as thrombosis and atherosclerosis. Among prostanoids, Tromboxane (TX)A(2), a potent platelet activator and vasoconstrictor and prostacyclin (PGI2), a platelet inhibitor and vasodilator, are the most important in controlling vascular homeostasis. Although multiple studies using pharmacological inhibitors and genetically deficient mice have demonstrated the importance of prostanoid-mediated actions on cardiovascular physiology, further analysis on the prostanoid mediated actions in the vascular system are required to better understand the benefits and risks for the use of COX inhibitors in cardiovascular diseases.