Association Between Prostaglandin E Receptor Subtype EP4 Overexpression and Unstable Phenotype in Atherosclerotic Plaques in Human

Prostaglandin E2 in the Tumor Microenvironment, a Convoluted Affair Mediated by EP Receptors 2 and 4

The involvement of the prostaglandin E2 (PGE2) system in cancer progression has long been recognized. PGE2 functions as an autocrine and paracrine signaling molecule with pleiotropic effects in the human body. High levels of intratumoral PGE2 and overexpression of the key metabolic enzymes of PGE2 have been observed and suggested to contribute to tumor progression. This has been claimed for different types of solid tumors, including, but not limited to, lung, breast, and colon cancer. PGE2 has direct effects on tumor cells and angiogenesis that are known to promote tumor development. However, one of the main mechanisms behind PGE2 driving cancerogenesis is currently thought to be anchored in suppressed antitumor immunity, thus providing possible therapeutic targets to be used in cancer immunotherapies. EP2 and EP4, two receptors for PGE2, are emerging as being the most relevant for this purpose. This review aims to summarize the known roles of PGE2 in the immune system and its functions within the tumor microenvironment. SIGNIFICANCE STATEMENT: Prostaglandin E2 (PGE2) has long been known to be a signaling molecule in cancer. Its presence in tumors has been repeatedly associated with disease progression. Elucidation of its effects on immunological components of the tumor microenvironment has highlighted the potential of PGE2 receptor antagonists in cancer treatment, particularly in combination with immune checkpoint inhibitor therapeutics. Adjuvant treatment could increase the response rates and the efficacy of immune-based therapies.

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.

Leveraging Lymphatic System Targeting in Systemic Lupus Erythematosus for Improved Clinical Outcomes

The role of advanced drug delivery strategies in drug repositioning and minimizing drug attrition rates, when applied early in drug discovery, is poised to increase the translational impact of various therapeutic strategies in disease prevention and treatment. In this context, drug delivery to the lymphatic system is gaining prominence not only to improve the systemic bioavailability of various pharmaceutical drugs but also to target certain specific diseases associated with the lymphatic system. Although the role of the lymphatic system in lupus is known, very little is done to target drugs to yield improved clinical benefits. In this review, we discuss recent advances in drug delivery strategies to treat lupus, the various routes of drug administration leading to improved lymph node bioavailability, and the available technologies applied in other areas that can be adapted to lupus treatment. Moreover, this review also presents some recent findings that demonstrate the promise of lymphatic targeting in a preclinical setting, offering renewed hope for certain pharmaceutical drugs that are limited by efficacy in their conventional dosage forms. These findings underscore the potential and feasibility of such lymphatic drug-targeting approaches to enhance therapeutic efficacy in lupus and minimize off-target effects of the pharmaceutical drugs. SIGNIFICANCE STATEMENT: The World Health Organization estimates that there are currently 5 million humans living with some form of lupus. With limited success in lupus drug discovery, turning to effective delivery strategies with existing drug molecules, as well as those in the early stage of discovery, could lead to better clinical outcomes. After all, effective delivery strategies have been proven to improve treatment outcomes.

The Link between Prostanoids and Cardiovascular Diseases

Cardiovascular diseases are the leading cause of global deaths, and many risk factors contribute to their pathogenesis. In this context, prostanoids, which derive from arachidonic acid, have attracted attention for their involvement in cardiovascular homeostasis and inflammatory processes. Prostanoids are the target of several drugs, but it has been shown that some of them increase the risk of thrombosis. Overall, many studies have shown that prostanoids are tightly associated with cardiovascular diseases and that several polymorphisms in genes involved in their synthesis and function increase the risk of developing these pathologies. In this review, we focus on molecular mechanisms linking prostanoids to cardiovascular diseases and we provide an overview of genetic polymorphisms that increase the risk for cardiovascular disease.

Plasma Cyclooxygenase-2 as a Potential Biomarker for Early Diagnosis of Kawasaki Disease

Background: Previous research demonstrated the association between cyclooxygenase-2 (COX-2) gene polymorphisms and susceptibility to Kawasaki disease (KD). This study aims to detect the plasma concentration of COX-2 in different phases of KD patients and evaluate the relationship between COX-2 level and coronary artery lesion formation, therapeutic response to intravenous immunoglobulin. Methods: Plasma COX-2 levels were measured by enzyme-linked immunosorbent assay in KD patients during the acute (a-KD, n = 52), subacute (s-KD, n = 46), and convalescent (c-KD, n = 43) phase. Results: The concentration of COX-2 in the a-KD group was significantly higher than that in the s-KD, c-KD, healthy control or febrile control group, respectively. There was no difference in the levels of COX-2 between the KD with or without coronary artery lesion subgroups, intravenous immunoglobulin resistant, and sensitive subgroups in the a-KD group, respectively. Conclusions: The plasma concentration of COX-2 might be a novel potential biomarker of acute KD.

The Predictive Values of MMP-9, PLTs, ESR, and CRP Levels in Kawasaki Disease with Cardiovascular Injury

Objective

To explore the levels of matrix metalloproteinase-9 (MMP-9), platelets (PLTs), C reactive protein (CRP), and erythrocyte sedimentation rate (ESR) and their predictive values in Kawasaki disease (KD) with cardiovascular injury.

Methods

128 children were diagnosed with KD in the Lanzhou University Second Hospital. 75 patients had coronary artery lesion (CAL), while 53 patients did not. The levels of MMP-9, PLTs, and CRP and ESR in the two groups were determined. The area under the curve (AUC) of the receiver-operating characteristic (ROC) curve and the Youden index (YI) were used to evaluate the efficacy of MMP-9, PLTs, ESR, and CRP for predicting CALs in KD.

Results

The mean age of the patients was 2.7 ± 2.03 years (range, 2 months to 11 years). There were 87 boys (67.97%) and 41 girls (32.03%). In contrast to the NCAL group, the CAL group had obviously higher levels of MMP-9, PLTs, and CRP and an obviously higher ESR (P < 0.05). MMP-9 showed a linear positive correlation with ESR (P < 0.05) and CRP (P < 0.05). The AUC of the combined detection of the four indicators was 0.877, the sensitivity was 85.07% and the specificity was 78.95%.

Conclusion

MMP-9, PLTs, ESR, and CRP are important indicators for a CAL in KD. The efficacy of the combined detection of MMP-9, PLTs, ESR and CRP is better than that of any single indicator for predicting a CAL in KD.

Effects of Arachidonic Acid Metabolites on Cardiovascular Health and Disease

Arachidonic acid (AA) is an essential fatty acid that is released by phospholipids in cell membranes and metabolized by cyclooxygenase (COX), cytochrome P450 (CYP) enzymes, and lipid oxygenase (LOX) pathways to regulate complex cardiovascular function under physiological and pathological conditions. Various AA metabolites include prostaglandins, prostacyclin, thromboxanes, hydroxyeicosatetraenoic acids, leukotrienes, lipoxins, and epoxyeicosatrienoic acids. The AA metabolites play important and differential roles in the modulation of vascular tone, and cardiovascular complications including atherosclerosis, hypertension, and myocardial infarction upon actions to different receptors and vascular beds. This article reviews the roles of AA metabolism in cardiovascular health and disease as well as their potential therapeutic implication.

International Union of Basic and Clinical Pharmacology. CIX. Differences and Similarities between Human and Rodent Prostaglandin E2 Receptors (EP1-4) and Prostacyclin Receptor (IP): Specific Roles in Pathophysiologic Conditions

Prostaglandins are derived from arachidonic acid metabolism through cyclooxygenase activities. Among prostaglandins (PGs), prostacyclin (PGI2) and PGE2 are strongly involved in the regulation of homeostasis and main physiologic functions. In addition, the synthesis of these two prostaglandins is significantly increased during inflammation. PGI2 and PGE2 exert their biologic actions by binding to their respective receptors, namely prostacyclin receptor (IP) and prostaglandin E2 receptor (EP) 1-4, which belong to the family of G-protein-coupled receptors. IP and EP1-4 receptors are widely distributed in the body and thus play various physiologic and pathophysiologic roles. In this review, we discuss the recent advances in studies using pharmacological approaches, genetically modified animals, and genome-wide association studies regarding the roles of IP and EP1-4 receptors in the immune, cardiovascular, nervous, gastrointestinal, respiratory, genitourinary, and musculoskeletal systems. In particular, we highlight similarities and differences between human and rodents in terms of the specific roles of IP and EP1-4 receptors and their downstream signaling pathways, functions, and activities for each biologic system. We also highlight the potential novel therapeutic benefit of targeting IP and EP1-4 receptors in several diseases based on the scientific advances, animal models, and human studies. SIGNIFICANCE STATEMENT: In this review, we present an update of the pathophysiologic role of the prostacyclin receptor, prostaglandin E2 receptor (EP) 1, EP2, EP3, and EP4 receptors when activated by the two main prostaglandins, namely prostacyclin and prostaglandin E2, produced during inflammatory conditions in human and rodents. In addition, this comparison of the published results in each tissue and/or pathology should facilitate the choice of the most appropriate model for the future studies.

Genetic Deletion or Pharmacological Inhibition of Cyclooxygenase-2 Reduces Blood-Brain Barrier Damage in Experimental Ischemic Stroke

Cyclooxygenase (COX)-2 and matrix metalloproteinase (MMP)-9 are two crucial mediators contributing to blood-brain barrier (BBB) damage during cerebral ischemia. However, it is not known whether MMP-9 activation is involved in COX-2-mediated BBB disruption in ischemic stroke. In this study, we hypothesized that genetic deletion or pharmacological inhibition of COX-2 reduces BBB damage by reducing MMP-9 activity in a mouse model of ischemic stroke. Male COX-2 knockout (COX-2^-/-) and wild-type (WT) mice were subjected to 60 min of middle cerebral artery occlusion (MCAO) followed by 24 h of reperfusion. Genetic deletion of COX-2 or post-ischemic treatment with CAY10404, a highly selective COX-2 inhibitor, significantly reduced BBB damage and hemorrhagic transformation, as assessed by immunoglobulin G (IgG) extravasation and brain hemoglobin (Hb) levels, respectively. Immunoblotting analysis showed that tight junction proteins (TJPs) zonula occludens (ZO)-1 and occludin as well as junctional adhesion molecule-A (JAM-A) and the basal lamina protein collagen IV were dramatically reduced in the ischemic brain. Stroke-induced loss of these BBB structural proteins was significantly attenuated in COX-2^-/- mice. Similarly, stroke-induced loss of ZO-1 and occludin was significantly attenuated by CAY10404 treatment. Ischemia-induced increase in MMP-9 protein levels in the ipsilateral cerebral cortex was significantly reduced in COX-2^-/- mice. Stroke induced a dramatic increase in MMP-9 enzymatic activity in the ischemic cortex, which was markedly reduced by COX-2 gene deficiency or pharmacological inhibition with CAY10404. Levels of myeloperoxidase (MPO, an indicator of neutrophil infiltration into the brain parenchyma), neutrophil elastase (NE), and lipocalin-2 (LCN2, also known as neutrophil gelatinase-associated lipocalin), measured by western blot and specific ELISA kits, respectively, were markedly increased in the ischemic brain. Increased levels of markers for neutrophil infiltration were significantly reduced in COX-2^-/- mice compared with WT controls following stroke. Altogether, neurovascular protective effects of COX-2 blockade are associated with reduced BBB damage, MMP-9 expression/activity and neutrophil infiltration. Our study shows for the first time that MMP-9 is an important downstream effector contributing to COX-2-mediated neurovascular damage in ischemic stroke. Targeting the COX-2/MMP-9 pathway could represent a promising strategy to reduce neuroinflammatory events in order to preserve the BBB integrity and ameliorate ischemic stroke injury.

Bioactive lipids, inflammation and chronic diseases

Endogenous bioactive lipids are part of a complex network that modulates a plethora of cellular and molecular processes involved in health and disease, of which inflammation represents one of the most prominent examples. Inflammation serves as a well-conserved defence mechanism, triggered in the event of chemical, mechanical or microbial damage, that is meant to eradicate the source of damage and restore tissue function. However, excessive inflammatory signals, or impairment of pro-resolving/anti-inflammatory pathways leads to chronic inflammation, which is a hallmark of chronic pathologies. All main classes of endogenous bioactive lipids - namely eicosanoids, specialized pro-resolving lipid mediators, lysoglycerophopsholipids and endocannabinoids - have been consistently involved in the chronic inflammation that characterises pathologies such as cancer, diabetes, atherosclerosis, asthma, as well as autoimmune and neurodegenerative disorders and inflammatory bowel diseases. This review gathers the current knowledge concerning the involvement of endogenous bioactive lipids in the pathogenic processes of chronic inflammatory pathologies.

Inhibition of prostaglandin E2 receptor 4 by lnc000908 to promote the endothelial-mesenchymal transition participation in cardiac remodelling

Long non‐coding RNAs (lncRNAs) have emerged as potent regulators of cardiac disease; however, the role of lncRNA in cardiac fibrosis remains partially understood. In this study, we identified a cardiac endothelial‐enriched lncRNA‐lnc000908, which was markedly up‐regulated in rats with cardiac fibrosis. In addition, the expression of prostaglandin E2 receptor 4 (EP4) was decreased in cardiac fibrosis. In vivo lnc000908 silencing by lentivirus increased the EP4 level, decreased endothelial‐mesenchymal transition (EndMT) and improved cardiac fibrosis and cardiac function. Consistently, the lnc000908 knockdown also up‐regulated EP4 and suppressed transforming growth factor‐beta (TGF‐β)‐induced EndMT in cardiac microvascular endothelial cells. In contrast, the lnc000908 overexpression by lentivirus decreased the EP4 level and induced EndMT. Of note, these pro‐ or anti‐EndMT effects were reversed by the EP4 overexpression or the EP4 antagonist AH‐23848, respectively. This study demonstrates that lnc000908 is a novel regulator of cardiac fibrosis by modulating the EP4 expression and EndMT.

Up-regulation of COX-2 and mPGES-1 by 27-hydroxycholesterol and 4-hydroxynonenal: A crucial role in atherosclerotic plaque instability

Atherosclerosis is currently understood to be mainly the consequence of a complicated inflammatory process at the different stages of plaque development. Among the several inflammatory molecules involved, up-regulation of the functional cyclooxygenase 2/membrane-bound prostaglandin E synthase 1 (COX-2/mPGES-1) axis plays a key role in plaque development. Excessive production of oxidized lipids, following low-density lipoprotein (LDL) oxidation, is a characteristic feature of atherosclerosis. Among the oxidized lipids of LDLs, the oxysterol 27-hydroxycholesterol (27-OH) and the aldehyde 4-hydroxynonenal (HNE) substantially accumulate in the atherosclerotic plaque, contributing to its progression and instability through a variety of processes. This study shows that 27-OH and HNE promote up-regulation of both the inducible enzymes COX-2 and mPGES-1, leading to increased production of prostaglandin (PG) E₂ and inducible nitric oxide synthase, and the subsequent release of nitric oxide in human promonocytic U937 cells. The study also examined the potential involvement of the functionally coupled COX-2/mPGES-1 in enhancing the production of certain pro-inflammatory cytokines and of matrix metalloproteinase 9 by U937 cells. This enhancement is presumably due to the induction of PGE₂ synthesis, as a result of the up-regulation of the COX-2/mPGES-1, stimulated by the two oxidized lipids, 27-OH and HNE. Induction of PGE₂ synthesis might thus be a mechanism of plaque instability and eventual rupture, contributing to matrix metalloproteinase production by activated macrophages.

Inhibition of cytokine-mediated JNK signalling by purinergic P2Y11 receptors, a novel protective mechanism in endothelial cells

Previous research from our laboratory has demonstrated a novel phenomenon whereby GPCRs play a role in inhibiting cytokine-mediated c-Jun N-terminal kinase (JNK) signalling. So far this novel phenomenon seems to have been vastly overlooked, with little research in the area. Therefore, in this study we explored this further; by assessing the potential of P2YRs to mediate inhibition of cytokine-mediated JNK signalling and related functional outcomes in human endothelial cells. We utilised primary endothelial cells, and employed the use of endogenous activators of P2YRs and well characterised pharmacological inhibitors, to assess signalling parameters mediated by P2YRs, Interleukin-1β (IL-1β), TNFα and JNK. Activation of P2YRs with adenosine tri-phosphate (ATP) resulted in a time- and concentration-dependent inhibition of IL-1β-mediated phosphorylation of JNK and associated kinase activity. The effect was specific for cytokine-mediated JNK signalling, as ATP was without effect on JNK induced by other non-specific activators (e.g. sorbitol, anisomycin), nor effective against other MAPK pathways such as p38 and the canonical NFκB cascade. Pharmacological studies demonstrated a role for the P2Y₁₁ receptor in mediating this effect, but not the P2Y₁ nor the adenosine receptors (A1, A2A, A2B & A3). The novel Gα_q/11 inhibitor YM254890 and a protein kinase A (PKA) inhibitor H89 both partially reversed ATP-mediated inhibition of IL-1β-stimulated JNK indicating involvement of both Gα_q/11 and Gα_s mediated pathways. ATP also partially reversed IL-1β-mediated induction of cyclo‑oxygenase-2 (COX-2) and E-selectin. Collectively, these studies indicate the potential for activation of purinergic receptors to protect the endothelium from inflammatory driven JNK activation and may be a new target for inflammatory disease therapy.

Research Progress on the Risk Factors and Outcomes of Human Carotid Atherosclerotic Plaques

Objective:

Atherosclerosis is an inflammatory process that results in complex lesions or plaques that protrude into the arterial lumen. Carotid atherosclerotic plaque rupture, with distal atheromatous debris embolization, causes cerebrovascular events. This review aimed to explore research progress on the risk factors and outcomes of human carotid atherosclerotic plaques, and the molecular and cellular mechanisms of human carotid atherosclerotic plaque vulnerability for therapeutic intervention.

Data Sources:

We searched the PubMed database for recently published research articles up to June 2016, with the key words of “risk factors”, “outcomes”, “blood components”, “molecular mechanisms”, “cellular mechanisms”, and “human carotid atherosclerotic plaques”.

Study Selection:

The articles, regarding the latest developments related to the risk factors and outcomes, atherosclerotic plaque composition, blood components, and consequences of human carotid atherosclerotic plaques, and the molecular and cellular mechanisms of human carotid atherosclerotic plaque vulnerability for therapeutic intervention, were selected.

Results:

This review described the latest researches regarding the interactive effects of both traditional and novel risk factors for human carotid atherosclerotic plaques, novel insights into human carotid atherosclerotic plaque composition and blood components, and consequences of human carotid atherosclerotic plaque.

Conclusion:

Carotid plaque biology and serologic biomarkers of vulnerability can be used to predict the risk of cerebrovascular events. Furthermore, plaque composition, rather than lesion burden, seems to most predict rupture and subsequent thrombosis.

Decreased vasorelaxation induced by iloprost during acute inflammation in human internal mammary artery

Cyclooxygenase-2 (COX-2) induction in human internal mammary arteries (IMA) under inflammatory conditions has been associated with attenuated norepinephrine (NE)-induced vasoconstriction. This effect was associated with increased prostaglandin (PG) E₂ and prostacyclin (PGI₂) releases. The present study was designed to assess the role of these PG and their receptors (EP and IP, respectively) on the vascular reactivity during acute inflammation. Isolated IMA were cultured in the absence (Control conditions) or presence (Inflammatory conditions) of both interleukin-1 beta (IL-1β) and lipopolysaccharide (LPS). The vasorelaxation and the increased content of cyclic adenosine monophosphate (cAMP) induced by iloprost, a PGI₂ analogue, were significantly reduced under inflammatory conditions and restored in preparations cultured with the IP antagonist (CAY10441). Decreased cAMP levels under inflammatory conditions are due to at least increased phosphodiesterase (PDE) 4B expression. On the other hand, PGE₂, thromboxane analogues and EP agonists-induced vasoconstrictions were not affected under inflammatory conditions. No vasorelaxation was observed with PGD₂, PGE₂ or the EP2/4 agonists in pre-contracted IMA. Finally, using RT-qPCR and immunohistochemistry, the COX-2, IP receptor and PGI₂ synthase (PGIS) were detected. A significant increase of COX-2 and moderate increase of IP mRNA expression was observed under inflammatory conditions, whereas PGIS mRNA level was not affected. This study demonstrates that PGI₂/IP receptor signalling and PGI₂-induced relaxation are impaired in human IMA during acute inflammation, whereas the responses induced by other prostanoids are not affected. These results could explain some of the mechanisms of vascular dysfunction reported in inflammatory conditions.

Cardiovascular Consequences of Prostanoid I Receptor Deletion in Microsomal Prostaglandin E Synthase-1-Deficient Hyperlipidemic Mice

BACKGROUND

Inhibitors of cyclooxygenase-2 alleviate pain and reduce fever and inflammation by suppressing the biosynthesis of prostacyclin (PGI2) and prostaglandin E2. However, suppression of these prostaglandins, particularly PGI2, by cyclooxygenase-2 inhibition or deletion of its I prostanoid receptor also predisposes to accelerated atherogenesis and thrombosis in mice. By contrast, deletion of microsomal prostaglandin E synthase 1 (mPGES-1) confers analgesia, attenuates atherogenesis, and fails to accelerate thrombogenesis, while suppressing prostaglandin E2, but increasing biosynthesis of PGI2.

METHODS

To address the cardioprotective contribution of PGI2, we generated mice lacking the I prostanoid receptor together with mPges-1 on a hyperlipidemic background (low-density lipoprotein receptor knockouts).

RESULTS

mPges-1 depletion modestly increased thrombogenesis, but this response was markedly further augmented by coincident deletion of the I prostanoid receptor (n=10-18). By contrast, deletion of the I prostanoid receptor had no effect on the attenuation of atherogenesis by mPGES-1 deletion in the low-density lipoprotein receptor knockout mice (n=17-21).

CONCLUSIONS

Although suppression of prostaglandin E2 accounts for the protective effect of mPGES-1 deletion in atherosclerosis, augmentation of PGI2 is the dominant contributor to its favorable thrombogenic profile. The divergent effects on these prostaglandins suggest that inhibitors of mPGES-1 may be less likely to cause cardiovascular adverse effects than nonsteroidal anti-inflammatory drugs specific for inhibition of cyclooxygenase-2.

An Update of Microsomal Prostaglandin E Synthase-1 and PGE2 Receptors in Cardiovascular Health and Diseases

Nonsteroidal anti-inflammatory drugs (NSAIDs), especially cyclooxygenase-2 (COX-2) selective inhibitors, are among the most widely used drugs to treat pain and inflammation. However, clinical trials have revealed that these inhibitors predisposed patients to a significantly increased cardiovascular risk, consisting of thrombosis, hypertension, myocardial infarction, heart failure, and sudden cardiac death. Thus, microsomal prostaglandin E (PGE) synthase-1 (mPGES-1), the key terminal enzyme involved in the synthesis of inflammatory prostaglandin E2 (PGE2), and the four PGE2 receptors (EP1-4) have gained much attention as alternative targets for the development of novel analgesics. The cardiovascular consequences of targeting mPGES-1 and the PGE2 receptors are substantially studied. Inhibition of mPGES-1 has displayed a relatively innocuous or preferable cardiovascular profile. The modulation of the four EP receptors in cardiovascular system is diversely reported as well. In this review, we highlight the most recent advances from our and other studies on the regulation of PGE2, particularly mPGES-1 and the four PGE2 receptors, in cardiovascular function, with a particular emphasis on blood pressure regulation, atherosclerosis, thrombosis, and myocardial infarction. This might lead to new avenues to improve cardiovascular disease management strategies and to seek optimized anti-inflammatory therapeutic options.

Molecular Characterization of E-Type Prostanoid Receptor 4 (EP4) from Ayu (Plecoglossus altivelis) and Its Functional Analysis in the Monocytes/Macrophages

Prostaglandin E2 (PGE2) plays an important role in a broad spectrum of physiological and pathological processes by interacting with E-type prostanoid receptors (EPs). EP4 is one of four EP subtypes known to mediate the immune response in mammalian monocytes/macrophages. However, the precise function and characteristics of EP4 in fish remain unclear. In this study, we characterized a novel EP4-like (PaEP4L) gene from ayu, Plecoglossus altivelis. The cDNA sequence of PaEP4L is 2781 nucleotides (nts) in length, encoding a polypeptide of 459 amino acid residues with a calculated molecular weight of 51.17 kDa. Sequence comparison and phylogenetic tree analysis showed that PaEP4L shared 76% amino acid identity with that of the Atlantic salmon (Salmo salar). PaEP4L mRNA was detected by real-time quantitative PCR (QPCR) in all tested tissues and head kidney-derived monocytes/macrophages (MO/MФ). It varied greatly in liver, spleen and MO/MФ upon Vibrio anguillarum infection. Western blot analysis revealed a significant increase of PaEP4L in cell homogenates from ayu MO/MФ upon V. anguillarum infection. Moreover, anti-PaEP4L IgG reversed the down-regulation of interleukin 1β (IL-1β) and tumor necrosis factor α (TNF-α) mRNA expression as well as phagocytosis in ayu MO/MФ caused by PGE2. There were no significant differences in the respiratory burst response between PGE2 treated and untreated cells. We further found that cAMP mediated PGE2/PaEP4L signal in ayu MO/MФ. In conclusion, our results indicate that PaEP4L mediates PGE2 effects on ayu MO/MФ function, revealing that EP4 also plays a role in the modulation of cells of the fish’s innate immune system.

Dose-dependent effects of prostaglandin E2 in macrophage adhesion and migration

Macrophage migration to the focus of infection is a hallmark of the innate immune response. Macrophage spreading, adhesion, and migration through the extracellular matrix require dynamic remodeling of the actin cytoskeleton associated to integrin clustering in podosomes and focal adhesions. Here, we show that prostaglandin E2 (PGE2 ), the main prostaglandin produced by macrophages during inflammation, promote the distinctive dose-dependent formation of podosomes or focal adhesions in macrophages. Low concentrations of PGE2 increased p110γ PI3K expression, phosphorylation of actin-related protein 2, and formation of podosomes, which enhanced macrophage migration in response to chemokines. However, high doses of PGE2 increased phosphorylation of paxillin and focal adhesion kinase, the expression of serine/threonine protein kinase 1, and promoted focal adhesion formation and macrophage adhesion, reducing macrophage chemotaxis. In summary, we describe the dual role of PGE2 as a promoter of macrophage chemotaxis and adhesion, proposing a new model of macrophage migration to the inflammatory focus in the presence of a gradient of PGE2 .

Effect of tocopherol on atherosclerosis, vascular function, and inflammation in apolipoprotein E knockout mice with subtotal nephrectomy

BACKGROUND/AIMS

Inflammation and endothelial dysfunction contribute to cardiovascular disease, prevalent in chronic kidney disease (CKD). Antioxidant supplements such as tocopherols may reduce inflammation and atherosclerosis. This study aimed to investigate the effect of tocopherol supplementation on vascular function, aortic plaque formation, and inflammation in apolipoprotein E(-/-) mice with 5/6 nephrectomy as a model of combined cardiovascular and kidney disease.

METHODS

Nephrectomized mice were assigned to a normal chow diet group (normal chow), a group receiving 1000 mg/kg diet of α-tocopherol supplementation or a group receiving 1000 mg/kg diet mixed-tocopherol (60% γ-tocopherol).

RESULTS

Following 12 weeks, in vitro aortic endothelial-independent relaxation was enhanced with both α-tocopherol and mixed-tocopherol (P < 0.05), while mixed-tocopherol enhanced aortic contraction at noradrenaline concentrations of 3 × 10(-7) M to 3 × 10(-5) M (P < 0.05), when compared to normal chow. Supplementation with α- and mixed-tocopherol reduced systemic concentrations of IL-6 (P < 0.001 and P < 0.001, respectively) and IL-10 (P < 0.05 and P < 0.001, respectively), while α-tocopherol also reduced MCP-1 (P < 0.05) and tumor necrosis factor (TNF)-α (P < 0.05). Aortic sinus plaque area was significantly reduced with α-tocopherol supplementation when compared to normal chow (P < 0.01).

CONCLUSION

Tocopherol supplementation favorably influenced vascular function and cytokine profile, while it was also effective in reducing atherosclerosis in the apolipoprotein E(-/-) mouse with CKD.

Inhibition of differentiation of monocyte to macrophages in atherosclerosis by oligomeric proanthocyanidins -In-vivo and in-vitro study

Monocyte to macrophage differentiation is a key event in the progression of atherosclerosis. An understanding on the fundamental molecular mechanisms and the identification of regulatory mechanisms behind this differentiation may aid in the identification of new therapeutic strategies. Inhibition of this phenomenon will form first line of defense in the prevention and treatment of atherosclerosis. In the current study we explored hypercholesterolemia induced monocyte to macrophage differentiation in-vivo (Wistar rats) leading to atherosclerosis and OxyLDL, M-CSF induced monocyte differentiation in-vitro (U937 cells). Oligomeric proanthocyanidin (OPC) isolated from Crataegus oxyacantha was tested for its efficacy in downregulating this differentiation and in preventing atherogenic disturbances. Cholesterol cholic acid diet induced an increased monocyte to macrophage differentiation by upregulating MCP1 and VCAM1 which induced the inflammatory cytokines that further substantiated the monocyte conversion and infiltration into the vascular walls. On addition of OxyLDL and M-CSF to U937 cells, macrophage markers CD36 and CD 68, PPARγ, MMP2 and 9 were elevated, suggesting differentiation. OPC downregulated this differentiation and thus could prevent the initiation of atherosclerosis.

Vascular extracellular matrix in atherosclerosis

The extracellular matrix (ECM) is an essential component of the human body that is responsible for the proper function of various organs. Changes in the ECM have been implicated in the pathogenesis of several cardiovascular conditions including atherosclerosis, restenosis, and heart failure. Matrix components, such as collagens and noncollagenous proteins, influence the function and activity of vascular cells, particularly vascular smooth muscle cells and macrophages. Matrix proteins have been shown to be implicated in the development of atherosclerotic complications, such as plaque rupture, aneurysm formation, and calcification. ECM proteins control ECM remodeling through feedback signaling to matrix metalloproteinases (MMPs), which are the key players of ECM remodeling in both normal and pathological conditions. The production of MMPs is closely related to the development of an inflammatory response and is subjected to significant changes at different stages of atherosclerosis. Indeed, blood levels of circulating MMPs may be useful for the assessment of the inflammatory activity in atherosclerosis and the prediction of cardiovascular risk. The availability of a wide variety of low-molecular MMP inhibitors that can be conjugated with various labels provides a good perspective for specific targeting of MMPs and implementation of imaging techniques to visualize MMP activity in atherosclerotic plaques and, most interestingly, to monitor responses to antiatheroslerosis therapies. Finally, because of the crucial role of ECM in cardiovascular repair, the regenerative potential of ECM could be successfully used in constructing engineered scaffolds and vessels that mimic properties of the natural ECM and consist of the native ECM components or composite biomaterials. These scaffolds possess a great promise in vascular tissue engineering.

Decreased PGE₂ content reduces MMP-1 activity and consequently increases collagen density in human varicose vein

Varicose veins are elongated and dilated saphenous veins. Despite the high prevalence of this disease, its pathogenesis remains unclear.

AIMS

In this study, we investigated the control of matrix metalloproteinases (MMPs) expression by prostaglandin (PG)E₂ during the vascular wall remodeling of human varicose veins.

METHODS AND RESULTS

Varicose (small (SDv) and large diameter (LDv)) and healthy saphenous veins (SV) were obtained after surgery. Microsomal and cytosolic PGE-synthases (mPGES and cPGES) protein and mRNA responsible for PGE₂ metabolism were analyzed in all veins. cPGES protein was absent while its mRNA was weakly expressed. mPGES-2 expression was similar in the different saphenous veins. mPGES-1 mRNA and protein were detected in healthy veins and a significant decrease was found in LDv. Additionally, 15-hydroxyprostaglandin dehydrogenase (15-PGDH), responsible for PGE₂ degradation, was over-expressed in varicose veins. These variations in mPGES-1 and 15-PGDH density account for the decreased PGE₂ level observed in varicose veins. Furthermore, a significant decrease in PGE₂ receptor (EP4) levels was also found in SDv and LDv. Active MMP-1 and total MMP-2 concentrations were significantly decreased in varicose veins while the tissue inhibitors of metalloproteinases (TIMP -1 and -2), were significantly increased, probably explaining the increased collagen content found in LDv. Finally, the MMP/TIMP ratio is restored by exogenous PGE₂ in varicose veins and reduced in presence of an EP4 receptor antagonist in healthy veins.

CONCLUSIONS

In conclusion, PGE₂ could be responsible for the vascular wall thickening in human varicose veins. This mechanism could be protective, strengthening the vascular wall in order to counteract venous stasis.

Oxidized low-density lipoprotein suppresses expression of prostaglandin E receptor subtype EP3 in human THP-1 macrophages

EP3, one of four prostaglandin E2 (PGE2) receptors, is significantly lower in atherosclerotic plaques than in normal arteries and is localized predominantly in macrophages of the plaque shoulder region. However, mechanisms behind this EP3 expression pattern are still unknown. We investigated the underlying mechanism of EP3 expression in phorbol 12-myristate 13-acetate (PMA)-differentiated THP-1 macrophages with oxidized low-density lipoprotein (oxLDL) treatment. We found that oxLDL decreased EP3 expression, in a dose-dependent manner, at both the mRNA and protein levels. Moreover, oxLDL inhibited nuclear factor-κB (NF-κB)-dependent transcription of the EP3 gene by the activation of peroxisome proliferator-activated receptor-γ (PPAR-γ). Finally, chromatin immunoprecipitation revealed decreased binding of NF-κB to the EP3 promoter with oxLDL and PPAR-γ agonist treatment. Our results show that oxLDL suppresses EP3 expression by activation of PPAR-γ and subsequent inhibition of NF-κB in macrophages. These results suggest that down-regulation of EP3 expression by oxLDL is associated with impairment of EP3-mediated anti-inflammatory effects, and that EP3 receptor activity may exert a beneficial effect on atherosclerosis.

Prostaglandin EP4 antagonists

Prostaglandin antagonists, with their pharmacological effects, are well-known drugs capable of treating widely diffused illnesses, including pain and inflammation disorders. In recent years, a major research focus has been devoted to the identification of agents able to selectively antagonize each receptor with which prostaglandins interact. This review attempts to give a broad overview of molecules capable of selectively blocking the prostaglandin PGE2 EP4 receptor. Further therapeutic applications and uses have also been disccussed, including the first drug candidate to have reached clinical trials within the last few years.

Depression after myocardial infarction: TNF-α-induced alterations of the blood-brain barrier and its putative therapeutic implications

Patients experiencing an acute myocardial infarction (AMI) have a three times higher chance to develop depression. Vice versa, depressive symptoms increase the risk of cardiovascular events. The co-existence of both conditions is associated with substantially worse prognosis. Although the underlying mechanism of the interaction is largely unknown, inflammation is thought to be of pivotal importance. AMI-induced peripheral cytokines release may cause cerebral endothelial leakage and hence induces a neuroinflammatory reaction. The neuroinflammation may persist even long after the initial peripheral inflammation has subsided. Among those selected brain regions that are prone to blood-brain barrier dysfunction, the paraventricular nucleus of the hypothalamus (PVN), a major center for cardiovascular autonomic regulation, is indicated to play a mediating role. Optimal cardiovascular therapy improves cardiovascular prognosis without major effects on depression. By the same token, antidepressant therapy in cardiovascular disease is associated with modest improvement in depressive symptoms, however without improvement in cardiac outcome. The failure of current antidepressants and the growing number of patients suffering from both conditions legitimize the search for better antidepressive therapies, from patients as well as society perspectives. Though we appreciate the mutual character of the interaction between depression and AMI, the present review focuses on the side of AMI induced depression and discusses the role of inflammation, represented by the proinflammatory cytokine TNF-α, as potential underlying mechanism. It is conceivable that inhibition of the inflammatory response post-AMI, through targeted anti-inflammatory pharmacotherapeutical agents may prevent the development of depressive symptoms and ultimately may improve cardiovascular outcomes.

Bioactive lipid mediators in skin inflammation and immunity

The skin is the primary barrier from the outside environment, protecting the host from injury, infectious pathogens, water loss and solar ultraviolet radiation. In this role, it is supported by a highly organized system comprising elements of innate and adaptive immunity, responsive to inflammatory stimuli. The cutaneous immune system is regulated by mediators such as cytokines and bioactive lipids that can initiate rapid immune responses with controlled inflammation, followed by efficient resolution. However, when immune responses are inadequate or mounted against non-infectious agents, these mediators contribute to skin pathologies involving unresolved or chronic inflammation. Skin is characterized by active lipid metabolism and fatty acids play crucial roles both in terms of structural integrity and functionality, in particular when transformed to bioactive mediators. Eicosanoids, endocannabinoids and sphingolipids are such key bioactive lipids, intimately involved in skin biology, inflammation and immunity. We discuss their origins, role and influence over various cells of the epidermis, dermis and cutaneous immune system and examine their function in examples of inflammatory skin conditions. We focus on psoriasis, atopic and contact dermatitis, acne vulgaris, wound healing and photodermatology that demonstrate dysregulation of bioactive lipid metabolism and examine ways of using this insight to inform novel therapeutics.

Inhibition of EP4 signaling attenuates aortic aneurysm formation

Background

Aortic aneurysm is a common but life-threatening disease among the elderly, for which no effective medical therapy is currently available. Activation of prostaglandin E₂ (PGE₂) is known to increase the expression of matrix metalloproteinase (MMP) and the release of inflammatory cytokines, and may thus exacerbate abdominal aortic aneurism (AAA) formation. We hypothesized that selective blocking of PGE₂, in particular, EP4 prostanoid receptor signaling, would attenuate the development of AAA.

Methods and Findings

Immunohistochemical analysis of human AAA tissues demonstrated that EP4 expression was greater in AAA areas than that in non-diseased areas. Interestingly, EP4 expression was proportional to the degree of elastic fiber degradation. In cultured human aortic smooth muscle cells (ASMCs), PGE₂ stimulation increased EP4 protein expression (1.4±0.08-fold), and EP4 stimulation with ONO-AE1-329 increased MMP-2 activity and interleukin-6 (IL-6) production (1.4±0.03- and 1.7±0.14-fold, respectively, P<0.05). Accordingly, we examined the effect of EP4 inhibition in an ApoE^−/− mouse model of AAA infused with angiotensin II. Oral administration of ONO-AE3-208 (0.01–0.5 mg/kg/day), an EP4 antagonist, for 4 weeks significantly decreased the formation of AAA (45–87% reduction, P<0.05). Similarly, EP4^+/−/ApoE^−/− mice exhibited significantly less AAA formation than EP4^+/+/ApoE^−/− mice (76% reduction, P<0.01). AAA formation induced by periaortic CaCl₂ application was also reduced in EP4^+/− mice compared with wild-type mice (73% reduction, P<0.001). Furthermore, in human AAA tissue organ cultures containing SMCs and macrophages, doses of the EP4 antagonist at 10–100 nM decreased MMP-2 activation and IL-6 production (0.6±0.06- and 0.7±0.06-fold, respectively, P<0.05) without increasing MMP-9 activity or MCP-1 secretion. Thus, either pharmacological or genetic EP4 inhibition attenuated AAA formation in multiple mouse and human models by lowering MMP activity and cytokine release.

Conclusion

An EP4 antagonist that prevents the activation of MMP and thereby inhibits the degradation of aortic elastic fiber may serve as a new strategy for medical treatment of AAA.

Diverse patterns of cyclooxygenase-independent metalloproteinase gene regulation in human monocytes

BACKGROUND AND PURPOSE Matrix metalloproteinase (MMP) production from monocyte/macrophages is implicated in matrix remodelling and modulation of inflammation. However, knowledge of the patterns and mechanisms of gene regulation of MMPs and their endogenous tissue inhibitors (TIMPs) is fragmentary. MMP up-regulation may be a target for cyclooxygenase (COX) and prostaglandin (PG) receptor inhibition, but the extent and mechanisms of COX-independent MMP up-regulation are unclear. EXPERIMENTAL APPROACH We studied MMP mRNA expression and selected protein levels in human peripheral blood monocytes before and after adhesion, upon stimulation with bacterial lipopolysaccharide (LPS), PGE(2) or forskolin and after culturing with monocyte colony-stimulating factor on plastic or human fibronectin for up to 7 days. KEY RESULTS Monocyte adherence for 2 h transiently up-regulated COX-2, MMP-1, MMP-7 and MMP-10 mRNAs, and persistently up-regulated MMP-2, MMP-9, MMP-14 and MMP-19 mRNAs. LPS, PGE(2) or forskolin selectively increased MMP-1, MMP-9, MMP-10, MMP-12 and MMP-14 mRNAs. LPS increased PGE(2) production through COX but up-regulated MMP levels independently of COX. Differential dependence on inhibition of p42/44 and p38 mitogen-activated protein kinases, c-jun N-terminal kinase and inhibitor of κB kinase2 paralleled the diverse patterns of MMP stimulation by LPS. Differentiation on plastic increased mRNA levels of MMP-7, MMP-9, MMP-12 and MMP-14 and TIMP-2 and TIMP-3 independently of COX; fibronectin accelerated MMP but not TIMP up-regulation. CONCLUSIONS AND IMPLICATIONS Adhesion, LPS stimulation and maturation of human monocytes lead to selective, COX-independent MMP and TIMP gene regulation, which is a potential target for selective inhibition by signalling kinase inhibitors.

Matrix metalloproteinase-dependent microsomal prostaglandin E synthase-1 expression in macrophages: role of TNF-α and the EP4 prostanoid receptor

Matrix metalloproteinase (MMP)-9 contributes to the pathogenesis of chronic inflammatory diseases and cancer. Thus, identifying targetable components of signaling pathways that regulate MMP-9 expression may have broad therapeutic implications. Our previous studies revealed a nexus between metalloproteinases and prostanoids whereby MMP-1 and MMP-3, commonly found in inflammatory and neoplastic foci, stimulate macrophage MMP-9 expression via the release of TNF-α and subsequent induction of cyclooxygenase-2 and PGE(2) engagement of EP4 receptor. In the current study, we determined whether MMP-induced cyclooxygenase-2 expression was coupled to the expression of prostaglandin E synthase family members. We found that MMP-1- and MMP-3-dependent release of TNF-α induced rapid and transient expression of early growth response protein 1 in macrophages followed by sustained elevation in microsomal prostaglandin synthase 1 (mPGES-1) expression. Metalloproteinase-induced PGE(2) levels and MMP-9 expression were markedly attenuated in macrophages in which mPGES-1 was silenced, thereby identifying mPGES-1 as a therapeutic target in the regulation of MMP-9 expression. Finally, the induction of mPGES-1 was regulated, in part, through a positive feedback loop dependent on PGE(2) binding to EP4. Thus, in addition to inhibiting macrophage MMP-9 expression, EP4 antagonists emerge as potential therapy to reduce mPGES-1 expression and PGE(2) levels in inflammatory and neoplastic settings.

Synthesis, pharmacophore modeling and in vitro activity of 10,11-dihydrodibenzo[b,f]oxepine-4-carboxamide derivatives as novel and potent antagonists of the prostaglandin EP4 receptor

The construction of a EP(4) antagonists pharmacophore model and the discovery of a highly potent oxepinic series of EP(4) antagonists is discussed. Compound 1a exhibits an excellent selectivity profile toward EP(2) receptor subtype and low cytochrome P450 inhibition potential.

Tobacco smoke regulates the expression and activity of microsomal prostaglandin E synthase-1: role of prostacyclin and NADPH-oxidase

Tobacco smoke (TS) interacts with interleukin-1β (IL-1β) to modulate generation of reactive oxygen species (ROS) and expression of cyclooxygenase-2. We explored molecular mechanisms by which TS/IL-1β alters expression and activity of microsomal-prostaglandin E synthase-1 (mPGES-1) and of prostacyclin synthase (PGIS) in mouse cardiac endothelial cells. TS (EC(50) ∼5 puffs/L) interacting with IL-1β (2 μg/L) up-regulates PGE(2) production and mPGES-1 expression, reaching a plateau at 4-6 h, but down-regulates prostacyclin (PGI(2)) release by increasing IL-1β-mediated PGIS tyrosine nitration. Inhibition of NADPH-oxidase, achieved pharmacologically and/or by silencing its catalytic subunit p47phox, or exogenous PGI(2) (carbaprostacyclin; IC(50) ∼5 μM) prevents production of both ROS and PGE(2), and negatively modulates mPGES-1 expression induced by TS/IL-1β. Moreover, inhibiting PGI(2), either using PGIS siRNA and/or CAY10441 (EC(50) ∼20 nM), a PGI(2) receptor antagonist, increases NADPH-oxidase activation, mPGES-1 synthesis, and PGE(2) production. Finally, lower PGI(2) levels associated with higher PGIS tyrosine nitration, p47phox translocation to the membrane (an index of activation of NADPH-oxidase), and mPGES-1 expression and activity were detected in cardiovascular tissues of ApoE(-/-) mice exposed to cigarette smoke compared to control mice. In conclusion, cigarette smoke in association with cytokines alters the balance between PGI(2)/PGE(2), reducing PGI(2) production and increasing synthesis and activity of mPGES-1 via NADPH-oxidase activation, predisposing to development of pathological conditions.

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.

Lack of microsomal prostaglandin E synthase-1 reduces cardiac function following angiotensin II infusion

Our laboratory previously reported that inducible PGE(2) synthase, mPGES-1, contributes to micromolar production of PGE(2) in neonatal ventricular myocytes in vitro, which stimulates their growth. We therefore hypothesized that mPGES-1 contributes to cardiac hypertrophy following angiotensin II (ANG II) infusion. To test this hypothesis, we used 10- to 12-wk-old mPGES-1 knockout mice (mPGES-1 KO) and C57Bl/6 control mice infused for 8 wk with either 1.4 mg · kg(-1) · day(-1) ANG II or vehicle subcutaneously. Blood pressure [systolic blood pressure (SBP)] was measured throughout the study, and cardiac function was assessed by M-mode echocardiography at baseline and at 8 wk of infusion. At the conclusion of the study, immunohistochemistry was used to evaluate collagen fraction, myocyte cross-sectional area (MCSA), and apoptosis. At baseline, there was no difference in SBP between mPGES-1 KO mice and C57BL/6 controls. ANG II infusion increased SBP to similar levels in both strains. In control mice, infusion of ANG II increased MCSA and posterior wall thickness at diastole (PWTd) but had little effect on cardiac function, consistent with compensatory hypertrophy. In contrast, cardiac function was worse in mPGES-1 KO mice after ANG II treatment. Ejection fraction declined from 76.2 ± 2.7 to 63.3 ± 3.4% after ANG II, and left ventricular dimension at systole and diastole increased from 1.29 ± 0.02 to 1.78 ± 0.15 mm and from 2.57 ± 0.03 to 2.90 ± 0.13 mm, respectively. Infusion of ANG II increased both the LV-to-body weight and the mass-to-body weight ratios to a similar extent in both strains. However, PWTd increased by a lesser extent in KO mice, suggesting an impaired hypertrophic response. ANG II infusion increased collagen staining similarly in both strains, but TdT-dUTP nick end labeling staining was greater in mPGES-1 KO mice. Overall, these results are consistent with a beneficial effect for mPGES-1 in the maintenance of cardiac function in ANG II-dependent hypertension.

Naphthalene/quinoline amides and sulfonylureas as potent and selective antagonists of the EP4 receptor

Two new series of EP(4) antagonists based on naphthalene/quinoline scaffolds have been identified as part of our on-going efforts to develop treatments for inflammatory pain. One series contains an acidic sulfonylurea pharmacophore, whereas the other is a neutral amide. Both series show subnanomolar intrinsic binding potency towards the EP(4) receptor, and excellent selectivity towards other prostanoid receptors. While the amide series generally displays poor pharmacokinetic parameters, the sulfonylureas exhibit greatly improved profile. MF-592, the optimal compound from the sulfonylurea series, has a desirable overall preclinical profile that suggests it is suitable for further development.

Grape seed extract ameliorates tumor necrosis factor-α-induced inflammatory status of human umbilical vein endothelial cells

BACKGROUND

Inflammation has played a key role in the causation of atherosclerosis. However, the effects of grape seed extract (GSE) on the pro-inflammatory intracellular signaling, enzyme activity, and inflammatory mediators of endothelial cells have not been sufficiently studied, and less information exists on the comparison between GSE and vitamin C, a well-known antioxidant compound, on their anti-inflammatory properties.

PURPOSE

We investigated the effects of GSE and vitamin C on the cell viability, oxidative stress, monocyte adhesion, the expression of nuclear factor-κB inhibitor (IκB), intercellular adhesion molecule-1 (ICAM-1) and cyclooxygenase-2 (COX-2), and the production of prostaglandin E(2) (PG E(2)) in TNF-α-treated human umbilical vein endothelial cells (HUVECs).

METHODS

Cell viability was measured by MTT assay. The adhesion of THP-1 to HUVECs was evaluated by cell adhesion assay. The oxidized nucleoside 8-hydroxydeoxyguanosine (8-OHdG) (an indicator of oxidative damage to DNA), ICAM-1, and PG E(2) were measured by ELISA. IκB and COX-2 expression were evaluated by western blot analysis.

RESULTS

TNF-α (10, 20, and 50 ng/mL), GSE (50 and 200 μg/mL), or vitamin C (100 μM) did not affect cell viability. GSE (50-100 μg/mL) attenuated TNF-α (20 ng/mL)-induced 8-OHdG production, THP-1 adhesion, the expression of IκB degradation, ICAM-1 and COX-2, and the production of PGE(2) in a dose-dependent manner. Vitamin C (100 μM) also showed significant antioxidative and anti-inflammatory effects.

CONCLUSIONS

GSE effectively ameliorates TNF-α-induced inflammatory status of HUVECs. The findings of the present study suggest that consumption of GSE may be beneficial to inflammatory atherosclerosis.

Deletion of EP4 on bone marrow-derived cells enhances inflammation and angiotensin II-induced abdominal aortic aneurysm formation

OBJECTIVE

To examine whether a lack of prostaglandin E receptor 4 (EP4) on bone marrow-derived cells would increase local inflammation and enhance the formation of abdominal aortic aneurysm (AAA) in vivo.

METHODS AND RESULTS

Prostaglandin E(2) (PGE(2)) through activation of EP4, can mute inflammation. Hypercholesterolemic low-density lipoprotein receptor knockout (LDLR(-/-)) mice transplanted with either EP4(+/+) (EP4(+/+)/LDLR(-/-)) or EP4(-/-) (EP4(-/-)/LDLR(-/-)) bone marrow received infusions of angiotensin II to induce AAA. Deficiency of EP4 on bone marrow-derived cells increased the incidence (50% of male EP4(+/+)/LDLR(-/-) mice versus 88.9% of male EP4(-/-)/LDLR(-/-) mice developed AAA; and 22% of female EP4(+/+)/LDLR(-/-) mice versus 83.3% of female EP4(-/-)/LDLR(-/-) mice developed AAA) and severity of AAA, increased monocyte chemoattractant protein-1 (2.72-fold in males and 1.64-fold in females), and enhanced infiltration of macrophages (3.8-fold in males and 2.44-fold in females) and T cells (1.88-fold in males and 1.66-fold in females) into AAA lesions. Lack of EP4 on bone marrow-derived cells augmented elastin fragmentation, increased apoptotic markers, and decreased smooth muscle cell accumulation within AAA lesions.

CONCLUSIONS

Deficiency of EP4 on bone marrow-derived cells boosted inflammation and AAA formation induced by angiotensin II in hyperlipidemic mice. This study affirms the pathophysiologic importance of PGE(2) signaling through EP4 as an endogenous anti-inflammatory pathway involved in experimental aneurysm formation.

Scalable synthesis of a prostaglandin EP4 receptor antagonist

The evolution of scalable, economically viable synthetic approaches to the potent and selective prostaglandin EP4 antagonist 1 is presented. The chromatography-free synthesis of multikilogram quantities of 1 using a seven-step sequence (six in the longest linear sequence) is described. This approach has been further modified in an effort to identify a long-term manufacturing route. Our final synthesis involves no step requiring cryogenic (< -25 degrees C) conditions; comprises a total of four steps, only three of which are in the longest linear synthesis; and features the use of two consecutive iron-catalyzed Friedel-Crafts substitutions.

Lack of EP4 receptors on bone marrow-derived cells enhances inflammation in atherosclerotic lesions

AIM

prostaglandin E(2), by ligation of its receptor EP4, suppresses the production of inflammatory cytokines and chemokines in macrophages in vitro. Thus, activation of EP4 may constitute an endogenous anti-inflammatory pathway. This study investigated the role of EP4 in atherosclerosis in vivo, and particularly its impact on inflammation.

METHODS AND RESULTS

Ldlr(-/-) mice transplanted with EP4(+/+) or EP4(-/-) bone marrow consumed a high-fat diet for 5 or 10 weeks. Allogenic bone marrow transplantation promoted exacerbation of atherosclerosis irrespective of EP4 genotype, compatible with prior observations of exacerbated atherogenesis by allogenicity. EP4 deficiency had little effect on plaque size or morphology in early atherosclerosis, but at the later time point, mice deficient in EP4 displayed enhanced inflammation in their atherosclerotic plaques. Expression of monocyte chemoattractant protein-1 and interferon-γ inducible protein 10 increased, and there was a corresponding increase in macrophage and T-cell infiltration. These plaques also contained fewer smooth muscle cells. Despite these changes, mice deficient in EP4 in bone marrow-derived cells at an advanced stage had similar lesion size (in both aorta and aortic root) as mice with EP4.

CONCLUSION

this study shows that in advanced atherosclerosis, EP4 deficiency did not alter atherosclerotic lesion size, but yielded plaques with exacerbated inflammation and altered lesion composition.