Positioning prostanoids of the D and J series in the immunopathogenic scheme

Prostanoids in Cardiac and Vascular Remodeling

Prostanoids are biologically active lipids generated from arachidonic acid by the action of the COX (cyclooxygenase) isozymes. NSAIDs, which reduce the biosynthesis of prostanoids by inhibiting COX activity, are effective anti-inflammatory, antipyretic, and analgesic drugs. However, their use is limited by cardiovascular adverse effects, including myocardial infarction, stroke, hypertension, and heart failure. While it is well established that NSAIDs increase the risk of atherothrombotic events and hypertension by suppressing vasoprotective prostanoids, less is known about the link between NSAIDs and heart failure risk. Current evidence indicates that NSAIDs may increase the risk for heart failure by promoting adverse myocardial and vascular remodeling. Indeed, prostanoids play an important role in modulating structural and functional changes occurring in the myocardium and in the vasculature in response to physiological and pathological stimuli. This review will summarize current knowledge of the role of the different prostanoids in myocardial and vascular remodeling and explore how maladaptive remodeling can be counteracted by targeting specific prostanoids.

Prostaglandin D2 regulates Escherichia coli-induced inflammatory responses through TLR2, TLR4, and NLRP3 in macrophages

Prostaglandin D2 (PGD2) synthesis is closely associated with the innate immune response mediated by pattern recognition receptors (PPRs). We determined PGD2 synthesis whether mediated by Toll-like receptor 2 (TLR2), TLR4 and Nod-like receptor pyrin domain-containing protein 3 (NLRP3) in Escherichia coli (E. coli)-, lipopolysaccharide (LPS)- and Braun lipoprotein (BLP)-stimulated macrophages. Our data demonstrate that TLR2, TLR4, and NLRP3 could regulate the synthesis of PGD2 through cyclo-oxygenase-2 (COX-2) and hematopoietic PGD synthase (H-PGDS) in E. coli-, LPS- or BLP-stimulated macrophages, suggesting that TLR2, TLR4, and NLRP3 are critical in regulating PGD2 secretion by controlling PGD2 synthetase expression in E. coli-, LPS- or BLP-stimulated macrophages. The H-PGDS (a PGD2 specific synthase) inhibitor pre-treatment could down-regulate the secretion of TNF-α, RANTES and IL-10 in LPS- and E. coli-stimulated macrophage. Meanwhile, H-PGDS inhibitor could down-regulate the secretion of TNF-α, while up-regulated RANTES and IL-10 secretion in BLP-stimulated macrophages, suggesting that PGD2 could regulate the secretion of cytokines and chemokines in E. coli-, LPS- or BLP-stimulated macrophages. Furthermore, exogenous PGD2 regulates the secretion of cytokines and chemokines through activation of MAPK and NF-κB signaling pathways after E. coli-, LPS- or BLP stimulation in macrophages. Taken together, PGD2 is found able to regulate E. coli-induced inflammatory responses through TLR2, TLR4, and NLRP3 in macrophages.

Pro- and Anti-Inflammatory Prostaglandins and Cytokines in Humans: A Mini Review

Inflammation has been described for two millennia, but cellular aspects and the paradigm involving different mediators have been identified in the recent century. Two main groups of molecules, the prostaglandins (PG) and the cytokines, have been discovered and play a major role in inflammatory processes. The activation of prostaglandins PGE2, PGD2 and PGI2 results in prominent symptoms during cardiovascular and rheumatoid diseases. The balance between pro- and anti-inflammatory compounds is nowadays a challenge for more targeted therapeutic approaches. The first cytokine was described more than a century ago and is now a part of different families of cytokines (38 interleukins), including the IL-1 and IL-6 families and TNF and TGFβ families. Cytokines can perform a dual role, being growth promotors or inhibitors and having pro- and anti-inflammatory properties. The complex interactions between cytokines, vascular cells and immune cells are responsible for dramatic conditions and lead to the concept of cytokine storm observed during sepsis, multi-organ failure and, recently, in some cases of COVID-19 infection. Cytokines such as interferon and hematopoietic growth factor have been used as therapy. Alternatively, the inhibition of cytokine functions has been largely developed using anti-interleukin or anti-TNF monoclonal antibodies in the treatment of sepsis or chronic inflammation.

Anti-inflammatory effects of the prostaglandin D2/prostaglandin DP1 receptor and lipocalin-type prostaglandin D2 synthase/prostaglandin D2 pathways in bacteria-induced bovine endometrial tissue

Dairy cows often develop different degrees of endometritis after calving and this is attributed to pathogenic bacterial infections such as by Escherichia coli and Staphylococcus aureus. Infection of the bovine endometrium causes tissue damage and increases the expression of prostaglandin D2 (PGD2), which exerts anti-inflammatory effects on lung inflammation. However, the roles of PGD2 and its DP1 receptor in endometritis in cows remain unclear. Here, we examined the anti-inflammatory roles of the lipocalin-type prostaglandin D2 synthase (L-PGDS)/PGD2 and DP1 receptor regulatory pathways in bovine endometritis. We evaluated the regulatory effects of PGD2 on inflammation and tissue damage in E. coli- and S. aureus-infected bovine endometrial cells cultured in vitro. We found that the secretion of pro-inflammatory cytokines interleukin (IL)-6, IL-1β, and tumour necrosis factor (TNF)-α as well as expression of matrix metalloproteinase (MMP)-2, platelet-activating factor receptor (PAFR), and high mobility group box (HMGB)-1 were suppressed after DP1 receptor agonist treatment. In contrast, IL-6, IL-1β, and TNF-α release and MMP-2, PAFR, and HMGB-1 expression levels were increased after treatment of bovine endometrial tissue with DP1 receptor antagonists. DP1-induced anti-inflammatory effects were dependent on cellular signal transduction. The L-PGDS/PGD2 pathway and DP1 receptor induced anti-inflammatory effects in bovine endometrium infected with S. aureus and E. coli by inhibiting the mitogen-activated protein kinase and nuclear factor-κB signalling pathways, thereby reducing tissue damage. Overall, our findings provide important insights into the pathophysiological roles of PGD2 in bovine endometritis and establish a theoretical basis for applying prostaglandins or non-steroidal anti-inflammatory drugs for treating endometrial inflammatory infertility in bovines.

Quantitative Data-Independent Acquisition Mass Spectrometry Proteomics and Weighted Correlation Network Analysis of Plasma Samples for the Discovery of Chronic Kidney Disease-Specific Atherosclerosis Risk Factors

Chronic kidney disease (CKD) accelerates atherosclerosis. The mechanism of CKD-related atherosclerosis is complex, and CKD-specific risk factors may contribute to this process in addition to traditional risk factors such as hypertension, diabetes, and hypercholesterolemia. In the present study, to discover CKD-specific atherosclerosis risk factors, a total of 62 patients with different stages of kidney function were enrolled. All patients underwent coronary angiographies and the severity of coronary atherosclerosis was defined by the SYNTAX score. Patients were divided into different groups according to their kidney function levels and coronary atherosclerosis severity. Data-independent acquisition mass spectrometry was used to identify differentially expressed proteins (DEPs) in the plasma samples, and weighted correlation network analysis (WGCNA) was employed to identify significant protein modules and hub proteins related to CKD-specific atherosclerosis. The results showed that 10 DEPs associated with atherosclerosis were found in the comparative groups with modest and severe CKD. Through WGCNA, 1768 proteins were identified and 8 protein modules were established. Enrichment analyses of protein modules revealed functional clusters mainly associated with inflammation and the complement and coagulation cascade as atherosclerosis developed under CKD conditions. The results may help to better understand the mechanisms of CKD-related atherosclerosis and guide future research on developing treatments for CKD-related atherosclerosis.

Protective Effect of Low-Dose Alcohol Consumption against Post-Ischemic Neuronal Apoptosis: Role of L-PGDS

Ischemic stroke is one of the leading causes of permanent disability and death in adults worldwide. Apoptosis is a major element contributing to post-ischemic neuronal death. We previously found that low-dose alcohol consumption (LAC) protects against neuronal apoptosis in the peri-infarct cortex following transient focal cerebral ischemia. Lipocalin-type prostaglandin D2 synthase (L-PGDS), which is mainly localized in the central nervous system (CNS), was previously shown to inhibit neuronal apoptosis. Therefore, we determined whether L-PGDS is involved in the protective effect of LAC against post-ischemic neuronal apoptosis. Wild-type (WT), CaMKIIα^CreERT2/+/L-PGDS^+/+, and CaMKIIα^CreERT2/+/L-PGDS^flox/flox mice on a C57BL/6J background were gavage fed with ethanol or volume-matched water once a day for 8 weeks. Tamoxifen (2 mg/day) was given intraperitoneally to CaMKIIα^CreERT2/+/L-PGDS^+/+ and CaMKIIα^CreERT2/+/L-PGDS^flox/flox mice for 5 days during the fourth week. AT-56 (30 mg/kg/day), a selective inhibitor of L-PGDS, was given orally to AT-56-treated WT mice from the fifth week for four weeks. Cerebral ischemia/reperfusion (I/R) injury, TUNEL-positive neurons, and cleaved caspase-3-positive neurons were measured at 24 h of reperfusion after a 90 min unilateral middle cerebral artery occlusion (MCAO). We found that 0.7 g/kg/day but not 2.8 g/kg/day ethanol significantly upregulated L-PGDS in the cerebral cortex. In addition, 0.7 g/kg/day ethanol diminished cerebral ischemia/reperfusion (I/R) injury and TUNEL-positive and cleaved caspase-3-positive neurons in the peri-infarct cortex in WT and CaMKIIα^CreERT2/+/L-PGDS^+/+ mice. Furthermore, the neuroprotective effect of 0.7 g/kg/day ethanol was alleviated in AT-56-treated WT and CaMKIIα^CreERT2/+/L-PGDS^flox/flox mice. Our findings suggest that LAC may protect against cerebral I/R injury by suppressing post-ischemic neuronal apoptosis via an upregulated L-PGDS.

15-Deoxy-Δ-12,14-prostaglandin J2 effects in vascular smooth muscle cells: Implications in vascular smooth muscle cell proliferation and contractility

15-Deoxy-Δ-^12,14-prostaglandin J2 (15d-PGJ2) is an endogenous agonist of the ligand dependent transcriptional factor, peroxisome proliferator-activated receptor -gamma (PPAR-γ). Although PPAR-γ mediates some actions of 15d-PGJ2, many actions of 15d-PGJ2 are independent of PPAR-γ. The PPAR-γ signaling pathway has beneficial effects on tumor progression, inflammation, oxidative stress, and angiogenesis in numerous studies. In this review, various studies were analyzed to understand the effects of 15d-PGJ2 in vascular smooth muscle cells (VSMC)s. 15d-PGJ2 inhibits proliferation of VSMCs during vascular remodeling and it alters the expression of contractile proteins and inflammatory components within these cells as well. However, the effects of 15d-PGJ2 as well as its ability to induce PPAR-γ activation remains controversial as contradictory effects of this prostaglandin in VSMCs exist. Understanding the mechanisms by which 15d-PGJ2 elicit beneficial actions whether by PPAR-γ activation or independently, will aid in developing new therapeutic strategies for diseases such as hypertension with an inflammatory component. Although great advances are being made, more research is needed to reach definitive conclusions.

Prostanoids and Resolution of Inflammation - Beyond the Lipid-Mediator Class Switch

Bioactive lipid mediators play a major role in regulating inflammatory processes. Herein, early pro-inflammatory phases are characterized and regulated by prostanoids and leukotrienes, whereas specialized pro-resolving mediators (SPM), including lipoxins, resolvins, protectins, and maresins, dominate during the resolution phase. While pro-inflammatory properties of prostanoids have been studied extensively, their impact on later phases of the inflammatory process has been attributed mainly to their ability to initiate the lipid-mediator class switch towards SPM. Yet, there is accumulating evidence that prostanoids directly contribute to the resolution of inflammation and return to homeostasis. In this mini review, we summarize the current knowledge of the resolution-regulatory properties of prostanoids and discuss potential implications for anti-inflammatory, prostanoid-targeted therapeutic interventions.

Deletion of Alox15 improves kidney dysfunction and inhibits fibrosis by increased PGD2 in the kidney

BACKGROUND

Lipid-metabolizing enzymes and their metabolites affect inflammation and fibrosis, but their roles in chronic kidney disease (CKD) have not been completely understood.

METHODS

To clarify their role in CKD, we measured the mRNA levels of major lipid-metabolizing enzymes in 5/6 nephrectomized (Nx) kidneys of C57BL/6 J mice. Mediator lipidomics was performed to reveal lipid profiles of CKD kidneys.

RESULTS

In 5/6 Nx kidneys, both mRNA and protein levels of Alox15 were higher when compared with those in sham kidneys. With respect to in situ hybridization, the mRNA level of Alox15 was higher in renal tubules of 5/6 Nx kidneys. To examine the role of Alox15 in CKD pathogenesis, we performed 5/6 Nx on Alox15-/- mice. Alox15-/- CKD mice exhibited better renal functions than wild-type mice. Interstitial fibrosis was also inhibited in Alox15-/- CKD mice. Mediator lipidomics revealed that Alox15-/- CKD mouse kidneys had significantly higher levels of PGD2 than the control. To investigate the effects of PGD2 on renal fibrosis, we administered PGD2 to TGF-β1-stimulated NRK-52E cells and HK-2 cells, which lead to a dose-dependent suppression of type I collagen and αSMA in both cell lines.

CONCLUSION

Increased PGD2 in Alox15-/- CKD mouse kidneys could inhibit fibrosis, thereby resulting in CKD improvement. Thus, Alox15 inhibition and PGD2 administration may be novel therapeutic targets for CKD.

Bioactive Lipids in MSCs Biology: State of the Art and Role in Inflammation

Lipidomics is a lipid-targeted metabolomics approach that aims to the comprehensive analysis of lipids in biological systems in order to highlight the specific functions of lipid species in health and disease. Lipids play pivotal roles as they are major structural components of the cellular membranes and energy storage molecules but also, as most recently shown, they act as functional and regulatory components of intra- and intercellular signaling. Herein, emphasis is given to the recently highlighted roles of specific bioactive lipids species, as polyunsaturated fatty acids (PUFA)-derived mediators (generally known as eicosanoids), endocannabinoids (eCBs), and lysophospholipids (LPLs), and their involvement in the mesenchymal stem cells (MSCs)-related inflammatory scenario. Indeed, MSCs are a heterogenous population of multipotent cells that have attracted much attention for their potential in regulating inflammation, immunomodulatory capabilities, and reparative roles. The lipidomics of the inflammatory disease osteoarthritis (OA) and the influence of MSCs-derived lipids have also been addressed.

The impact of the prostaglandin D2 receptor 2 and its downstream effects on the pathophysiology of asthma

Current research suggests that the prostaglandin D₂ (PGD₂ ) receptor 2 (DP₂ ) is a principal regulator in the pathophysiology of asthma, because it stimulates and amplifies the inflammatory response in this condition. The DP₂ receptor can be activated by both allergic and nonallergic stimuli, leading to several pro-inflammatory events, including eosinophil activation and migration, release of the type 2 cytokines interleukin (IL)-4, IL-5 and IL-13 from T helper 2 (Th2) cells and innate lymphoid cells type 2 (ILCs), and increased airway smooth muscle mass via recruitment of mesenchymal progenitors to the airway smooth muscle bundle. Activation of the DP₂ receptor pathway has potential downstream effects on asthma pathophysiology, including on airway epithelial cells, mucus hypersecretion, and airway remodelling, and consequently might impact asthma symptoms and exacerbations. Given the broad distribution of DP₂ receptors on immune and structural cells involved in asthma, this receptor is being explored as a novel therapeutic target.

Targeting lipid mediators in asthma: time for reappraisal

PURPOSE OF REVIEW

In the past decades, cysteinyl leukotrienes (CysLTs) and prostaglandin D2 have been recognized as key mediators of asthma and comorbid conditions for their potent broncho-active and proinflammatory properties. However, both the development and initial positioning of small molecules targeting these lipid mediators [i.e., leukotriene-synthesis inhibitors, CysLT-antagonists, and chemoattractant receptor homologous molecule on T-helper2-cells (CRTH2) antagonists] experienced drawbacks by lacking adequate biomarkers to define potential responders.

RECENT FINDINGS

New insights into the mechanisms of airway inflammation in asthma including the interaction of leukotrienes and prostanoids has uncovered potential therapeutic targets. Emerging application of biomarkers in more recent clinical studies helped identify responders to therapies targeting lipid mediators and demonstrated their clinical efficacy in distinct asthma phenotypes and endotypes.

SUMMARY

Interest in small molecules targeting lipid mediators in asthma and related conditions is emerging. Several clinical trials evaluating the efficacy and safety of CRTH2 (Prostaglandin D2 receptor 2) antagonists are ongoing. There is an urgent need for sensitive biomarkers to identify responders to such therapies and for monitoring of (long-term) effects. Furthermore, evaluation of effectiveness of combining different agents targeting lipid mediators or combining them with available or emerging biologics may uncover other potential benefits in certain asthma populations warranting future research.

A structure-function approach identifies L-PGDS as a mediator responsible for glucocorticoid-induced leptin expression in adipocytes

Leptin is an adipokine predominantly secreted by adipocytes and has many physiological roles, including in energy homeostasis. We identified that AM630, a cannabinoid receptor 2 (CB2) antagonist, down-regulated leptin expression in mature adipocytes differentiated from either stromal vascular fractions isolated from inguinal fat pads of C57BL/6J mice or 3T3-L1 preadipocytes. However, the leptin-suppressive effects of AM630 preserved in CB2-deficient adipocytes indicated the off-target activity of AM630 in leptin expression. Pharmacological and genetic studies, cheminformatics, and docking simulation were applied to identify the potential protein target of AM630 that modulates leptin expression in differentiated primary preadipocytes. Screening of the reported off-targets of AM630 identified a synthetic cannabinoid WIN55212-2 exerting the same function. Target deconvolution and docking simulation suggested that AM630 and WIN55212-2 were both inhibitors of lipocalin-type prostaglandin D2 synthase (L-PGDS). Further studies showed that L-PGDS positively regulates leptin expression. Although glucocorticoid and aldosterone were previously reported to induce expression of both L-PGDS and leptin, our data demonstrated that L-PGDS mediates only glucocorticoid-induced leptin expression in differentiated primary preadipocytes. No effect was observed after aldosterone treatment. This newly discovered glucocorticoid - L-PGDS - leptin pathway may provide insights into current clinical use of glucocorticoid and management of their undesired effects such as obesity.

Expression of Sigma-Class Glutathione-S-Transferase in Fetal and Pediatric Filum Terminale Samples: A Comparative Study

Background and objectives: The pathophysiology of tethered cord syndrome (TCS) in children is not well elucidated. An inelastic filum terminale (FT) is the main factor underlying the stretching of the spinal cord in TCS. Our study aimed to investigate the expression of glutathione-S-transferase (GST) in children and fetal FT samples in order to understand the relationship between this enzyme expression and the development of TCS. Materials and Methods: FT samples were obtained from ten children with TCS (Group 1) and histological and immunohistochemical examinations were performed. For comparison, FT samples from fifteen normal human fetuses (Group 2) were also analyzed using the same techniques. Statistical comparison was made using a Chi-square test. Results: Positive GST-sigma expression was detected in eight (80%) of 10 samples in Group 1. The positive GST-sigma expression was less frequent in nine (60%) of 15 samples from Group 2. No statistically significant difference was detected between the two groups (p = 0.197). Conclusions: Decreased FT elasticity in TCS may be associated with increased GST expression in FT. More prospective studies are needed to clarify the mechanism of the GST-TCS relationship in children.

Global Transcriptomic Analysis of the Canine corpus luteum (CL) During the First Half of Diestrus and Changes Induced by in vivo Inhibition of Prostaglandin Synthase 2 (PTGS2/COX2)

The canine luteal phase exhibits several peculiarities compared with other species. In early diestrus, the corpus luteum (CL) is, at least in part, independent of gonadotropins, and prostaglandins (PGs) appear to be among its main regulators. This was also observed with the inhibition in vivo of COX2, when also transcriptional capacity, vascularization and immune-related factors were affected. Here, we aimed to further investigate the potential effects of PGs withdrawal on the CL transcriptome by performing deep RNA sequencing (RNA-Seq). Samples from a previous in vivo study were used; bitches were treated for 5, 10, 20, or 30 days after ovulation with firocoxib (Previcox®), a PTGS2/COX2 inhibitor, or a placebo. Analysis of results was performed with SUSHI (framework from FGCZ) and with pathways and functional networks analyzers. Time-dependent effects were also investigated and used for quality control. More highly represented differentially expressed genes (DEGs, P < 0.01, FDR < 0.1) in the early CL (days 5 and 10) referred to proliferation and immune system, while in the mature CL (days 20 and 30) they were related with steroidogenesis. The absence of genes concomitantly affected by the treatment at all time-points suggested stage-dependency in the observed effects. Little effect was observed on days 5 and 10. Day 20 had the highest number of DEGs (n = 1,741), related with increased immune response. On day 30, DEGs found (n = 552) referred to decreased steroidogenesis and vascularization. Our results suggest the presence of strong compensatory effects in the early CL and multidirectional effects toward gonadotropin-dependency of the CL after COX2 inhibition.

Prostaglandin D2 Levels Regulate CD103+ Conventional Dendritic Cell Activation in Neonates During Respiratory Viral Infection

During respiratory viral infection, conventional dendritic cells (cDCs) take up antigen and migrate to the draining lymph nodes to present viral antigen and activate cytotoxic T lymphocytes; however, regulation of cDC activation and migration may be age dependent. In this study, we used a mouse model of paramyxoviral infection (Sendai virus) and demonstrated that cDCs, which have migrated from lungs to the draining lymph nodes, are delayed in expressing activation markers in neonatal mice compared with adults. Neonatal lung cDCs expressed reduced levels of MHC Class II (major histocompatibility complex II) and CCR7 (chemokine receptor type 7) on postinfection days 3 and 5, respectively. The level of the CCR7 ligand CCL19 was significantly reduced in neonatal lungs during the course of viral infection. Interestingly, the arachidonic acid metabolite prostaglandin D₂ (PGD₂) was present at significantly higher levels in neonatal bronchoalveolar lavage fluid compared with adults. This was associated with increased expression of lipocalin PGD₂ synthase mRNA levels in neonatal lungs and in isolated neonatal tracheal epithelial cells. Although thymic stromal lymphopoietin (TSLP) expression has been associated with increased PGD₂ production, we found that TSLP levels were reduced in neonatal lungs. Importantly, blocking PGD₂ function using a prostaglandin D₂ receptor 1 (DP1) antagonist restored cDC activation in neonates. Together, these data suggest that cDC activation in neonates is delayed by a PGD₂ mechanism and associated decreased chemokine signals.

Lipocalin-Like Prostaglandin D Synthase but Not Hemopoietic Prostaglandin D Synthase Deletion Causes Hypertension and Accelerates Thrombogenesis in Mice

Prostaglandin (PG) D₂ is formed by two distinct PGD synthases (PGDS): lipocalin-type PGDS (L-PGDS), which acts as a PGD₂-producing enzyme and as extracellular lipophilic transporter, and hematopoietic PGDS (H-PGDS), a σ glutathione-S-transferase. PGD₂ plays an important role in the maintenance of vascular function; however, the relative contribution of L-PGDS– and H-PGDS–dependent formation of PGD₂ in this setting is unknown. To gain insight into the function played by these distinct PGDS, we assessed systemic blood pressure (BP) and thrombogenesis in L-Pgds and H-Pgds knockout (KO) mice. Deletion of L-Pgds depresses urinary PGD₂ metabolite (PGDM) by ∼35%, whereas deletion of H-Pgds does so by ∼90%. Deletion of L-Pgds, but not H-Pgds, elevates BP and accelerates the thrombogenic occlusive response to a photochemical injury to the carotid artery. HQL-79, a H-PGDS inhibitor, further depresses PGDM in L-Pgds KO mice, but has no effect on BP or on the thrombogenic response. Gene expression profiling reveals that pathways relevant to vascular function are dysregulated in the aorta of L-Pgds KOs. These results indicate that the functional impact of L-Pgds deletion on vascular homeostasis may result from an autocrine effect of L-PGDS–dependent PGD₂ on the vasculature and/or the L-PGDS function as lipophilic carrier protein.

Non-steroidal Anti-inflammatory Drugs in Newborns and Infants

Nonsteroidal antiinflammatory drugs (NSAIDs) and acetaminophen are used in young infants and newborns for pain and fever control, patent ductus closure, prevention of intraventricular hemorrhage, and potentially for prevention of retinopathy of prematurity. These drugs inhibit cyclooxygenase 1 (COX-1), COX-2, and peroxidases, thus, blocking prostaglandin (PG) synthesis. PGs are eicosanoids that regulate several physiologic, pathologic, and cellular processes, including vasomotor tone, platelet aggregation, sensitization of neurons to pain, and many molecular events critical to physiologic homeostasis. NSAIDs inhibit caspases and cell death. Increasing knowledge of these molecular entities may allow targeted drug development to prevent or minimize neonatal morbidities.

Prostaglandin D2 elicits the reversible neurite retraction in hypothalamic cell line

Prostaglandins (PGs) play important roles in diverse physiological processes in the central nervous system. PGD2 is the most abundant PG in the brain and acts through specific receptors, DP1 and CRTH2. We investigated the effects of PGD2 on the morphology of the hypothalamic cell line mHypoE-N37 (N37). In N37 cells, serum starvation induced neurite outgrowth and PGD2 elicited neurite retraction, although we failed to detect transcripts for DP1 and CRTH2. Such an effect of PGD2 was efficiently mimicked by its metabolite, 15-deoxy-Δ(12,14)-prostaglandin J2. N-acetyl cysteine completely abolished the effect of PGD2, and reactive oxygen species (ROS) were considered to be important. Notably, neurite outgrowth was restored by PGD2 removal. These results suggest that PGD2 induces reversible neurite retraction in a ROS-mediated mechanism that does not involve any known receptor.

Vascular endothelial cell Toll-like receptor pathways in sepsis

The endothelium forms a vast network that dynamically regulates vascular barrier function, coagulation pathways and vasomotor tone. Microvascular endothelial cells are uniquely situated to play key roles during infection and injury, owing to their widespread distribution throughout the body and their constant interaction with circulating blood. While not viewed as classical immune cells, endothelial cells express innate immune receptors, including the Toll-like receptors (TLRs), which activate intracellular inflammatory pathways mediated through NF-κB and the MAP kinases. TLR agonists, including LPS and bacterial lipopeptides, directly upregulate microvascular endothelial cell expression of inflammatory mediators. Intriguingly, TLR activation also modulates microvascular endothelial cell permeability and the expression of coagulation pathway intermediaries. Microvascular thrombi have been hypothesized to trap microorganisms thereby limiting the spread of infection. However, dysregulated activation of endothelial inflammatory pathways is also believed to lead to coagulopathy and increased vascular permeability, which together promote sepsis-induced organ failure. This article reviews vascular endothelial cell innate immune pathways mediated through the TLRs as they pertain to sepsis, highlighting links between TLRs and coagulation and permeability pathways, and their role in healthy and pathologic responses to infection and sepsis.

Eicosapentaenoic acid suppression of systemic inflammatory responses and inverse up-regulation of 15-deoxyΔ(12,14) prostaglandin J2 production

BACKGROUND AND PURPOSE

Eicosapentaenoic acid (EPA) has been shown to suppress immune cell responses, such as cytokine production and downstream PG production in vitro. Studies in vivo, however, have used EPA as a minor constituent of fish oil with variable results. We investigated the effects of EPA on systemic inflammatory responses as pure EPA has not been evaluated on immune/inflammatory responses in vivo.

EXPERIMENTAL APPROACH

Rabbits were administered polyinosinic: polycytidylic acid (poly I:C) i.v. before and after oral treatment with EPA for 42 days (given daily). The responses to IL-1β and TNF-α were also studied. Immediately following administration of poly I:C, body temperature was continuously monitored and blood samples were taken. Plasma levels of IL-1β, PGE2 (PGE2), and 15-deoxy-Δ(12,14)-PGJ2 (15d-PGJ2) were measured by enzyme immunoassay.

KEY RESULTS

Following EPA treatment, the fever response to poly I:C was markedly suppressed compared with pretreatment responses. This was accompanied by a parallel reduction in the poly I:C-stimulated elevation in plasma levels of IL-1β and PGE2. Paradoxically, the levels of 15d-PGJ2 were higher following EPA treatment. EPA treatment did not significantly alter the fever response or plasma levels of PGE2 in response to either IL-1β or TNF-α.

CONCLUSION AND IMPLICATIONS

Oral treatment with EPA can suppress immune/inflammatory responses in vivo via a suppression of upstream cytokine production resulting in a decreased fever response and indirectly reducing circulating levels of PGE2. EPA also enhances the production of the cytoprotective prostanoid 15d-PGJ2 indicating the therapeutic benefit of EPA.

Multiple roles of the prostaglandin D2 signaling pathway in reproduction

Prostaglandins signaling molecules are involved in numerous physiological processes. They are produced by several enzyme-limited reactions upon fatty acids, which are catalyzed by two cyclooxygenases and prostaglandin synthases. In particular, the prostaglandins E2(PGE2), D2(PGD2), and F2(PGF2α) have been shown to be involved in female reproductive mechanisms. Furthermore, widespread expression of lipocalin- and hematopoietic-PGD2synthases in the male reproductive tract supports the purported roles of PGD2in the development of both embryonic and adult testes, sperm maturation, and spermatogenesis. In this review, we summarize the putative roles of PGD2signaling and the roles of both PGD2synthases in testicular formation and function. We review the data reporting the involvement of PGD2signaling in the differentiation of Sertoli and germ cells of the embryonic testis. Furthermore, we discuss the roles of lipocalin-PGD2synthase in steroidogenesis and spermatogenesis, in terms of lipid molecule transport and PGD2production. Finally, we discuss the hypothesis that PGD2signaling may be affected in certain reproductive diseases, such as infertility, cryptorchidism, and testicular cancer.

Mast cells, their subtypes, and relation to asthma phenotypes

Mast cells (MCs) are among the first cell types associated with allergies and asthma. Studies in human asthma have identified their presence in the lung submucosa and smooth muscle and also in the airway epithelium. As our understanding of the distribution and location of these MCs in the human airway has increased, it is clear that much remains to be understood regarding the presence and subtype of these MCs in relationship to asthma phenotypes, defined both clinically and on the basis of immunologic pathways. Human MCs have traditionally been divided into two major subtypes based on the protease granule content, with tryptase representing total MCs. There is emerging evidence that in the epithelium, MCs of an altered subtype (with tryptase, chymase, and/or carboxypeptidase A3) may play a role in the pathophysiology of poorly controlled, severe, Th2-associated asthma.

PACAP27 prevents Parkinson-like neuronal loss and motor deficits but not microglia activation induced by prostaglandin J2

Neuroinflammation is a major risk factor in Parkinson's disease (PD). Alternative approaches are needed to treat inflammation, as anti-inflammatory drugs such as NSAIDs that inhibit cyclooxygenase-2 (COX-2) can produce devastating side effects, including heart attack and stroke. New therapeutic strategies that target factors downstream of COX-2, such as prostaglandin J2 (PGJ2), hold tremendous promise because they will not alter the homeostatic balance offered by COX-2 derived prostanoids. In the current studies, we report that repeated microinfusion of PGJ2 into the substantia nigra of non-transgenic mice, induces three stages of pathology that mimic the slow-onset cellular and behavioral pathology of PD: mild (one injection) when only motor deficits are detectable, intermediate (two injections) when neuronal and motor deficits as well as microglia activation are detectable, and severe (four injections) when dopaminergic neuronal loss is massive accompanied by microglia activation and motor deficits. Microglia activation was evaluated in vivo by positron emission tomography (PET) with [(11)C](R)PK11195 to provide a regional estimation of brain inflammation. PACAP27 reduced dopaminergic neuronal loss and motor deficits induced by PGJ2, without preventing microglia activation. The latter could be problematic in that persistent microglia activation can exert long-term deleterious effects on neurons and behavior. In conclusion, this PGJ2-induced mouse model that mimics in part chronic inflammation, exhibits slow-onset PD-like pathology and is optimal for testing diagnostic tools such as PET, as well as therapies designed to target the integrated signaling across neurons and microglia, to fully benefit patients with PD.

Immune cells and metabolic dysfunction

Throughout evolution, effective nutrient sensing and control of systemic energy homeostasis have relied on a close physical and functional interaction between immune and metabolically active cells. However, in today's obesogenic environment, this fine-tuned immunometabolic interface is perturbed. As a consequence, chronic inflammatory conditions and aberrant activation of immune cells have emerged as key features of obesity-related metabolic disorders, including insulin resistance, cardiovascular complications, and type 2 diabetes, whereas a major research focus has been placed on the adipocyte-macrophage interaction in the context of metabolic dysfunction; recent studies have not only expanded the scope of relevant immune cells in this setting but also highlight the impact of distinct metabolic organs, including the liver, on immunometabolic control, metabolic disease development, and potential anti-inflammatory therapeutic options in obesity-driven pathologies. This review will thus summarize recent progress in this emerging area of metabolic research.

Proinflammatory and immunoregulatory roles of eicosanoids in T cells

Eicosanoids are inflammatory mediators primarily generated by hydrolysis of membrane phospholipids by phospholipase A2 to ω-3 and ω-6 C20 fatty acids that next are converted to leukotrienes (LTs), prostaglandins (PGs), prostacyclins (PCs), and thromboxanes (TXAs). The rate-limiting and tightly regulated lipoxygenases control synthesis of LTs while the equally well-controlled cyclooxygenases 1 and 2 generate prostanoids, including PGs, PCs, and TXAs. While many of the classical signs of inflammation such as redness, swelling, pain, and heat are caused by eicosanoid species with vasoactive, pyretic, and pain-inducing effects locally, some eicosanoids also regulate T cell functions. Here, we will review eicosanoid production in T cell subsets and the inflammatory and immunoregulatory functions of LTs, PGs, PCs, and TXAs in T cells.

Cyclooxygenase-2 inhibition blocks M2 macrophage differentiation and suppresses metastasis in murine breast cancer model

Tumor cells are often associated with abundant macrophages that resemble the alternatively activated M2 subset. Tumor-associated macrophages (TAMs) inhibit anti-tumor immune responses and promote metastasis. Cyclooxygenase-2 (COX-2) inhibition is known to prevent breast cancer metastasis. This study hypothesized that COX-2 inhibition affects TAM characteristics potentially relevant to tumor cell metastasis. We found that the specific COX-2 inhibitor, etodolac, inhibited human M2 macrophage differentiation, as determined by decreased CD14 and CD163 expressions and increased TNFα production. Several key metastasis-related mediators, such as vascular endothelial growth factor-A, vascular endothelial growth factor-C, and matrix metalloproteinase-9, were inhibited in the presence of etodolac as compared to untreated M2 macrophages. Murine bone marrow derived M2 macrophages also showed enhanced surface MHCII IA/IE and CD80, CD86 expressions together with enhanced TNFα expressions with etodolac treatment during differentiation. Using a BALB/c breast cancer model, we found that etodolac significantly reduced lung metastasis, possibly due to macrophages expressing increased IA/IE and TNFα, but decreased M2 macrophage-related genes expressions (Ym1, TGFβ). In conclusion, COX-2 inhibition caused loss of the M2 macrophage characteristics of TAMs and may assist prevention of breast cancer metastasis.

Suppressive effects of antimycotics on thymic stromal lymphopoietin production in human keratinocytes

BACKGROUND

Thymic stromal lymphopoietin (TSLP) is produced by epidermal keratinocytes, and it induces Th2-mediated inflammation. TSLP expression is enhanced in lesions with atopic dermatitis, and is a therapeutic target. Antimycotic agents improve the symptoms of atopic dermatitis.

OBJECTIVE

The objective of this study was to examine whether antimycotics suppress TSLP expression in human keratinocytes.

METHODS

Normal human keratinocytes were incubated with polyinosinic-polycytidylic acid (poly I:C) plus IL-4 in the presence of antimycotics. TSLP expression was analyzed by ELISA and real time PCR. Luciferase assays were performed to analyze NF-κB activity. IκBα degradation was analyzed by Western blot analysis.

RESULTS

Poly I:C plus IL-4 increased the secretion and mRNA levels of TSLP, which was suppressed by an NF-κB inhibitor, and also enhanced NF-κB transcriptional activities and induced the degradation of IκBα in keratinocytes. The antimycotics itraconazole, ketoconazole, luliconazole, terbinafine, butenafine, and amorolfine suppressed the secretion and mRNA expression of TSLP, NF-κB activity, and IκBα degradation induced by poly I:C plus IL-4. These suppressive effects were similarly manifested by 15-deoxy-Δ-(12,14)-PGJ2 (15d-PGJ2), a prostaglandin D2 metabolite. Antimycotics increased the release of 15d-PGJ2 from keratinocytes and decreased the release of thromboxane B2, a thromboxane A2 metabolite. Antimycotic-induced suppression of TSLP production and NF-κB activity was counteracted by an inhibitor of lipocalin type-prostaglandin D synthase.

CONCLUSIONS

Antimycotics itraconazole, ketoconazole, luliconazole, terbinafine, butenafine, and amorolfine may suppress poly I:C plus IL-4-induced production of TSLP by inhibiting NF-κB via increasing 15d-PGJ2 production in keratinocytes. These antimycotics may block the overexpression of TSLP in lesions with atopic dermatitis.

Yin-Yang regulation of prostaglandins and nitric oxide by PGD2 in human arthritis: reversal by celecoxib

The role of PGD2 has been recognized in allergy, innate immunity and inflammation. Western blot analysis identified 21 kDa lipocalin (L)-prostaglandin D2 (PGD2) synthase (S) in human osteoarthritis (OA)-affected cartilage, whose expression was increased by IL-1β and TNFα. Similarly, PGD2 was spontaneously released by human OA-affected cartilage (and upregulated by IL-β) in ex vivo conditions and could be inhibited by indomethacin. Addition of PGD2 to human OA-affected cartilage significantly increased accumulation of PGE2, PGF1α, PGF2α, TXB2, but inhibited LTB4 and nitric oxide (NO) accumulation. Similarly, PGD2 (but not 13,14-dihydro-15-keto PGD2) augmented IL-1β induced PGE2 but inhibited IL-β induced nitric oxide (NO) in human chondrocytes. Celecoxib (10 μM) inhibits COX-1 mediated PGD2, and nitric oxide synthase (NOS) mediated NO in human OA-affected cartilage. Furthermore, celecoxib (1 μM) counter balances (IL-1β induced+PGD2 modulated) levels of NO and PGE2 in human OA-affected cartilage and chondrocytes to basal levels. These results show concentration-dependent, pro- and anti-inflammatory activity of PGD2 in human chondrocytes and cartilage, which can be neutralized by celecoxib. In view of the broad prostaglandin dependent and independent mechanism of action of celecoxib, these observations further reaffirm the broader role of celecoxib as a "Disease Modifying Drug" for human Osteoarthritis.

Prostaglandin D₂ pathway upregulation: relation to asthma severity, control, and TH2 inflammation

BACKGROUND

Bronchoalveolar lavage (BAL) fluid prostaglandin D₂(PGD₂) levels are increased in patients with severe, poorly controlled asthma in association with epithelial mast cells (MCs). PGD₂, which is generated by hematopoietic prostaglandin D synthase (HPGDS), acts on 3 G protein-coupled receptors, including chemoattractant receptor-homologous molecule expressed on TH2 lymphocytes (CRTH2) and PGD₂ receptor 1 (DP1). However, much remains to be understood regarding the presence and activation of these pathway elements in asthmatic patients.

OBJECTIVE

We sought to compare the expression and activation of PGD₂ pathway elements in bronchoscopically obtained samples from healthy control subjects and asthmatic patients across a range of disease severity and control, as well as in relation to TH2 pathway elements.

METHODS

Epithelial cells and BAL fluid were evaluated for HPGDS (quantitative real-time PCR/immunohistochemistry [IHC]) and PGD₂ (ELISA/liquid chromatography mass spectrometry) in relation to levels of MC proteases. Expression of the 2 inflammatory cell receptors DP1 and CRTH2 was evaluated on luminal cells. These PGD₂ pathway markers were then compared with asthma severity, level of control, and markers of TH2 inflammation (blood eosinophils and fraction of exhaled nitric oxide).

RESULTS

Confirming previous results, BAL fluid PGD₂ levels were highest in patients with severe asthma (overall P = .0001). Epithelial cell compartment HPGDS mRNA and IHC values differed among groups (P = .008 and P < .0001, respectively) and correlated with MC protease mRNA. CRTH2 mRNA and IHC values were highest in patients with severe asthma (P = .001 and P = .0001, respectively). Asthma exacerbations, poor asthma control, and TH2 inflammatory markers were associated with higher PGD₂, HPGDS, and CRTH2 levels.

CONCLUSION

The current study identifies coordinated upregulation of the PGD₂ pathway in patients with severe, poorly controlled, TH2-high asthma despite corticosteroid use.

Resolution of inflammation as a novel chemopreventive strategy

Acute inflammation, a physiologic response to protect cells from microbial infection and other noxious stimuli, is automatically terminated by endogenous anti-inflammatory and pro-resolving mediators to restore homeostatic conditions. However, if timely resolution of inflammation is failed, inflammation persists and can progress to a chronic inflammation which has long been thought as a predisposing factor to carcinogenesis. Excessive and pathologic inflammation causes DNA damage, genomic instability, epigenetic dysregulation, and alteration of intracellular signaling, all of which are involved in neoplastic transformation. To prevent chronic inflammation and resulting inflammation-promoted cancer development, understanding the process that resolves inflammation is essential. Resolution of inflammation is an active coordinated process regulated by distinct anti-inflammatory and pro-resolving endogenous lipid mediators, such as resolvins and lipoxins. The role of pro-inflammatory signaling in carcinogenesis has become more and more evident and well characterized, but the potential role of pro-resolving mediators in cancer prevention remains still elusive. In searching for an efficacious way to prevent chronic inflammation-associated cancer, the pro-resolving signal transduction pathways and their regulators should be unraveled.

Gene transcription and biomarker responses in the clam Ruditapes philippinarum after exposure to ibuprofen

Pharmaceuticals are a class of emerging environmental contaminants that continuously enter aquatic environments. Presently, little information is available about the effects of these substances on non-target organisms, such as bivalves. We investigated the effects of ibuprofen (IBU) on the clam Ruditapes philippinarum. Clams were exposed for 1, 3, 5 and 7 days to 0, 100 and 1000 μgIBU/L, and established biomarker responses (haemolymph lysozyme, gill acetylcholinesterase and digestive gland superoxide dismutase activities) as well as digestive gland transcriptome were evaluated. A two-way ANOVA revealed significant effects of both "IBU concentration" and "exposure duration" on biomarker responses. Overall, the enzyme activities were generally lower in IBU-exposed clams than in controls. Although limited knowledge of the mollusc transcriptome makes it difficult to interpret the effects of IBU on clams, the gene transcription analysis using DNA microarrays enabled the identification of the putative molecular mode of action of the IBU. The functional analysis of differentially transcribed genes suggests that IBU can interfere with various signalling pathways in clams, such as arachidonic acid metabolism, apoptosis, peroxisomal proliferator-activated receptors, and nuclear factor-kappa B. In addition, several genes involved in the metabolism of xenobiotics (e.g., glutathione S-transferase, sulfotransferase, cytochrome P450) were also found to be significantly affected by IBU exposure. In summary, the integrated approach of gene transcription analysis and biomarker responses facilitated the elucidation of the putative mechanisms of action of IBU in non-target species.

Lipopolysaccharide-induced expression of microsomal prostaglandin E synthase-1 mediates late-phase PGE2 production in bone marrow derived macrophages

Cyclooxygenase (COX)-2 expression and release of prostaglandins (PGs) by macrophages are consistent features of lipopolysaccharide (LPS)-induced macrophage inflammation. The two major PGs, PGE₂ and PGD₂, are synthesized by the prostanoid isomerases, PGE synthases (PGES) and PGD synthases (PGDS), respectively. Since the expression profile and the individual role of these prostanoid isomerases-mediated inflammation in macrophages has not been defined, we examined the LPS-stimulated PGs production pattern and the expression profile of their synthases in the primary cultured mouse bone marrow derived macrophages (BMDM). Our data show that LPS induced both PGE₂ and PGD₂ production, which was evident by ∼8 hrs and remained at a similar ratio (∼1∶1) in the early phase (≤12 hrs) of LPS treatment. However, PGE₂ production continued increase further in the late phase (16–24 hrs); whereas the production of PGD₂ remained at a stable level from 12 to 24 hrs post-treatment. In response to LPS-treatment, the expression of both COX-2 and inducible nitric oxide synthase (iNOS) was detected within 2 to 4 hrs; whereas the increased expression of microsomal PGES (mPGES)-1 and a myeloid cell transcription factor PU.1 did not appear until later phase (≥12 hrs). In contrast, the expression of COX-1, hematopoietic-PGDS (H-PGDS), cytosolic-PGES (c-PGES), or mPGES-2 in BMDM was not affected by LPS treatment. Selective inhibition of mPGES-1 with either siRNA or isoform-selective inhibitor CAY10526, but not mPGES-2, c-PGES or PU.1, attenuated LPS-induced burst of PGE₂ production indicating that mPGES-1 mediates LPS-induced PGE₂ production in BMDM. Interestingly, selective inhibition of mPGES-1 was also associated with a decrease in LPS-induced iNOS expression. In summary, our data show that mPGES-1, but not mPGES-2 or c-PGES isomerase, mediates LPS-induced late-phase burst of PGE₂ generation, and regulates LPS-induced iNOS expression in BMDM.

Prostaglandin D2 induces apoptosis of human osteoclasts by activating the CRTH2 receptor and the intrinsic apoptosis pathway

Prostaglandin D(2) (PGD(2)) is a lipid mediator synthesized from arachidonic acid that directly activates two specific receptors, the D-type prostanoid (DP) receptor and chemoattractant receptor homologous molecule expressed on T-helper type 2 cells (CRTH2). PGD(2) can affect bone metabolism by influencing both osteoblast and osteoclast (OC) functions, both cells involved in bone remodeling and in in vivo fracture repair as well. The objective of the present study was to determine the effects of PGD(2), acting through its two specific receptors, on human OC apoptosis. Human OCs were differentiated in vitro from peripheral blood mononuclear cells in the presence of receptor activator for nuclear factor κB ligand (RANKL) and macrophage-colony stimulating factor (M-CSF), and treated with PGD(2), its specific agonists and antagonists. Treatment with PGD(2) for 24hours in the presence of naproxen (10μM) to inhibit endogenous prostaglandin production increased the percentage of apoptotic OCs in a dose-dependent manner, as did the specific CRTH2 agonist compound DK-PGD(2) but not the DP agonist compound BW 245C. In the absence of naproxen, the CRTH2 antagonist compound CAY 10471 reduced OC apoptosis rate but the DP antagonist BW A868C had no effect. The induction of PGD(2)-CRTH2 dependent apoptosis was associated with the activation of caspase-9, but not caspase-8, leading to caspase-3 cleavage. These data show that PGD(2) induces human OC apoptosis through activation of CRTH2 and the apoptosis intrinsic pathway.

Microarray expression analysis and identification of serum biomarkers for Niemann-Pick disease, type C1

Niemann-Pick disease type C (NPC) is a lysosomal storage disorder characterized by liver disease and progressive neurodegeneration. Deficiency of either NPC1 or NPC2 leads to the accumulation of cholesterol and glycosphingolipids in late endosomes and early lysosomes. In order to identify pathological mechanisms underlying NPC and uncover potential biomarkers, we characterized liver gene expression changes in an Npc1 mouse model at six ages spanning the pathological progression of the disease. We identified altered gene expression at all ages, including changes in asymptomatic, 1-week-old mice. Biological pathways showing early altered gene expression included: lipid metabolism, cytochrome P450 enzymes involved in arachidonic acid and drug metabolism, inflammation and immune responses, mitogen-activated protein kinase and G-protein signaling, cell cycle regulation, cell adhesion and cytoskeleton remodeling. In contrast, apoptosis and oxidative stress appeared to be late pathological processes. To identify potential biomarkers that could facilitate monitoring of disease progression, we focused on a subset of 103 differentially expressed genes that encode secreted proteins. Further analysis identified two secreted proteins with increased serum levels in NPC1 patients: galectin-3 (LGALS3), a pro-inflammatory molecule, and cathepsin D (CTSD), a lysosomal aspartic protease. Elevated serum levels of both proteins correlated with neurological disease severity and appeared to be specific for NPC1. Expression of Lgals3 and Ctsd was normalized following treatment with 2-hydroxypropyl-β-cyclodextrin, a therapy that reduces pathological findings and significantly increases Npc1(-/-) survival. Both LGALS3 and CTSD have the potential to aid in diagnosis and serve as biomarkers to monitor efficacy in therapeutic trials.

Resolution of inflammation by N-arachidonoylglycine

N-arachidonoylglycine (NAgly) is an endogenous signaling lipid that is a member of the eicosanoid super family and is related to anandamide. It shows anti-inflammatory activity in vivo in the mouse peritonitis model where it reduces migration of inflammatory leukocytes following injection of pro-inflammatory agents into the peritoneal cavity. Using cell culture models, including GPR18 transfected HEK-293 cells, evidence is presented that the orphan receptor GPR18 is involved in this action. Increases in free arachidonic acid, and robust stimulation of anti-inflammatory eicosanoids were observed at low micromolar concentrations. These included 15-deoxy-delta-13,14-PGJ(2) and lipoxin A(4) both of which are believed to mediate the resolution stage of inflammation. It was further shown that NAgly might act via GPR18 activation in promoting the number of Trypan Blue stained cells, a possible indicator of programmed cell death. Thus, we hypothesize that NAgly induces the death of inflammatory cells, a process that is considered to be important for the resolution of inflammation.

Different roles of mast cells in obesity and diabetes: lessons from experimental animals and humans

Mast cells (MCs) play an important role in allergic hyperresponsiveness and in defending microorganism infections. Recent studies of experimental animals and humans have suggested that MCs participate in obesity and diabetes. MC distribution and activities in adipose tissues may vary, depending on the locations of different adipose tissues. In addition to releasing inflammatory mediators to affect adipose tissue extracellular matrix remodeling and to promote inflammatory cell recruitment and proliferation, MCs directly and indirectly interact and activate adipose tissue cells, including adipocytes and recruited inflammatory cells. Plasma MC protease levels are significantly higher in obese patients than in lean subjects. Experimental obese animals lose body weight after MC inactivation. MC functions in diabetes are even more complicated, and depend on the type of diabetes and on different diabetic complications. Both plasma MC proteases and MC activation essential immunoglobulin E levels are significant risk factors for human pre-diabetes and diabetes mellitus. MC stabilization prevents diet-induced diabetes and improves pre-established diabetes in experimental animals. MC depletion or inactivation can improve diet-induced type 2 diabetes and some forms of type 1 diabetes, but also can worsen other forms of type 1 diabetes, at least in experimental animals. Observations from animal and human studies have suggested beneficial effects of treating diabetic patients with MC stabilizers. Some diabetic patients may benefit from enhancing MC survival and proliferation – hypotheses that merit detailed basic researches and clinical studies.

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.

Competitive enzymatic interactions determine the relative amounts of prostaglandins E2 and D2

Prostaglandins (PGs) are a family of cellular messengers exerting diverse homeostatic and pathophysiologic effects. Recently, several studies reported significant increases of PGI(2) and PGF(2α) after the inhibition of microsomal PGE synthase-1 (mPGES-1) expression, which indicated that PGH(2) metabolism might be redistributed when the PGE(2) pathway is blocked. To address the determinants that govern the relative amounts of PGs, we developed an in vitro cell-free method, based on liquid chromatography-tandem mass spectrometry, to measure the exact amounts of these PGs formed in response to the addition of recombinant isomerases and their selective inhibitors. Our in vitro cell-free assay results were confirmed in cells using bone marrow-derived macrophage. Initially, we determined the in vitro stability of PGH(2) and noted that there was spontaneous nonenzymatic conversion to PGD(2) and PGE(2). mPGES-1 markedly increased the conversion to PGE(2) and decreased conversion to PGD(2). Reciprocally, the addition of hematopoietic or lipocalin PGD synthase resulted in a relative increase of PGD(2) and decrease of PGE(2). A detailed titration study showed that the ratio of PGE(2)/PGD(2) was closely correlated with the ratio of PGE synthase/PGD synthase. Our redistribution results also provide the foundation for understanding how PGH(2) metabolism is redistributed by the presence of distal isomerases or by blocking the major metabolic outlet, which could determine the relative benefits and risks resulting from interdiction in nonrated-limiting components of PG synthesis pathways.

The contribution of prostaglandins versus prostacyclin in ventricular remodeling during heart failure

Although the role of Cox-2 in the heart's response to physiologic stress remains controversial (i.e. expression in myocytes versus other resident myocardial cells) the ever expanding role of prostanoids in multiple models of heart failure cannot be denied. Due to the fact that prostanoids are metabolized rather quickly (half life of seconds to minutes) it is believed these signaling mediators act in a paracrine fashion at the site of production. Evidence to date is quite convincing that these bioactive lipid derivatives are involved in physiologic homeostatic regulation as well as beneficial and maladaptive ventricular remodeling in heart failure. Thus, this review will assess the direct contribution of each PG on remodeling in the left ventricle (e.g. hypertrophy, functional effects, and fibrosis).

Discovery of selective indole-based prostaglandin D₂ receptor antagonist

A series of N-benzoyl-2-methylindole-3-acetic acids were synthesized and biologically evaluated as prostaglandin (PG) D₂ receptor antagonists. Some of the selected compounds significantly inhibited OVA-induced vascular permeability in guinea pig conjunctiva after oral dosing. Structure-activity relationship study is presented.

International Union of Basic and Clinical Pharmacology. LXXXIII: classification of prostanoid receptors, updating 15 years of progress

It is now more than 15 years since the molecular structures of the major prostanoid receptors were elucidated. Since then, substantial progress has been achieved with respect to distribution and function, signal transduction mechanisms, and the design of agonists and antagonists (http://www.iuphar-db.org/DATABASE/FamilyIntroductionForward?familyId=58). This review systematically details these advances. More recent developments in prostanoid receptor research are included. The DP(2) receptor, also termed CRTH2, has little structural resemblance to DP(1) and other receptors described in the original prostanoid receptor classification. DP(2) receptors are more closely related to chemoattractant receptors. Prostanoid receptors have also been found to heterodimerize with other prostanoid receptor subtypes and nonprostanoids. This may extend signal transduction pathways and create new ligand recognition sites: prostacyclin/thromboxane A(2) heterodimeric receptors for 8-epi-prostaglandin E(2), wild-type/alternative (alt4) heterodimers for the prostaglandin FP receptor for bimatoprost and the prostamides. It is anticipated that the 15 years of research progress described herein will lead to novel therapeutic entities.

Prostaglandins and inflammation

Prostaglandins are lipid autacoids derived from arachidonic acid. They both sustain homeostatic functions and mediate pathogenic mechanisms, including the inflammatory response. They are generated from arachidonate by the action of cyclooxygenase isoenzymes, and their biosynthesis is blocked by nonsteroidal antiinflammatory drugs, including those selective for inhibition of cyclooxygenase-2. Despite the clinical efficacy of nonsteroidal antiinflammatory drugs, prostaglandins may function in both the promotion and resolution of inflammation. This review summarizes insights into the mechanisms of prostaglandin generation and the roles of individual mediators and their receptors in modulating the inflammatory response. Prostaglandin biology has potential clinical relevance for atherosclerosis, the response to vascular injury and aortic aneurysm.

Selenoprotein-dependent up-regulation of hematopoietic prostaglandin D2 synthase in macrophages is mediated through the activation of peroxisome proliferator-activated receptor (PPAR) gamma

The plasticity of macrophages is evident from their dual role in inflammation and resolution of inflammation that are accompanied by changes in the transcriptome and metabolome. Along these lines, we have previously demonstrated that the micronutrient selenium increases macrophage production of arachidonic acid (AA)-derived anti-inflammatory 15-deoxy-Δ(12,14)-prostaglandin J(2) (15d-PGJ(2)) and decreases the proinflammatory PGE(2). Here, we hypothesized that selenium modulated the metabolism of AA by a differential regulation of various prostaglandin (PG) synthases favoring the production of PGD(2) metabolites, Δ(12)-PGJ(2) and 15d-PGJ(2). A dose-dependent increase in the expression of hematopoietic-PGD(2) synthase (H-PGDS) by selenium and a corresponding increase in Δ(12)-PGJ(2) and 15d-PGJ(2) in RAW264.7 macrophages and primary bone marrow-derived macrophages was observed. Studies with organic non-bioavailable forms of selenium and the genetic manipulation of cellular selenium incorporation machinery indicated that selenoproteins were necessary for H-PGDS expression and 15d-PGJ(2) production. Treatment of selenium-deficient macrophages with rosiglitazone, a peroxisome proliferator-activated receptor γ ligand, up-regulated H-PGDS. Furthermore, electrophoretic mobility shift assays indicated the presence of an active peroxisome proliferator-activated receptor-response element in murine Hpgds promoter suggesting a positive feedback mechanism of H-PGDS expression. Alternatively, the expression of nuclear factor-κB-dependent thromboxane synthase and microsomal PGE(2) synthase was down-regulated by selenium. Using a Friend virus infection model of murine leukemia, the onset of leukemia was observed only in selenium-deficient and indomethacin-treated selenium-supplemented mice but not in the selenium-supplemented group or those treated with 15d-PGJ(2). These results suggest the importance of selenium in the shunting of AA metabolism toward the production of PGD(2) metabolites, which may have clinical implications.

Molecular evolution and the role of oxidative stress in the expansion and functional diversification of cytosolic glutathione transferases

Background

Cytosolic glutathione transferases (cGST) are a large group of ubiquitous enzymes involved in detoxification and are well known for their undesired side effects during chemotherapy. In this work we have performed thorough phylogenetic analyses to understand the various aspects of the evolution and functional diversification of cGSTs. Furthermore, we assessed plausible correlations between gene duplication and substrate specificity of gene paralogs in humans and selected species, notably in mammalian enzymes and their natural substrates.

Results

We present a molecular phylogeny of cytosolic GSTs that shows that several classes of cGSTs are more ubiquitous and thus have an older ancestry than previously thought. Furthermore, we found that positive selection is implicated in the diversification of cGSTs. The number of duplicate genes per class is generally higher for groups of enzymes that metabolize products of oxidative damage.

Conclusions

1) Protection against oxidative stress seems to be the major driver of positive selection in mammalian cGSTs, explaining the overall expansion pattern of this subfamily;

2) Given the functional redundancy of GSTs that metabolize xenobiotic chemicals, we would expect the loss of gene duplicates, but by contrast we observed a gene expansion of this family, which likely has been favored by: i) the diversification of endogenous substrates; ii) differential tissue expression; and iii) increased specificity for a particular molecule;

3) The increased availability of sequence data from diversified taxa is likely to continue to improve our understanding of the early origin of the different cGST classes.

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.