Expression of E-Cadherin and Ber-EP4 in the Trophoblastic Tissues of Intrauterine and Ectopic Tubal Pregnancies.

Introduction: We investigated the role of E-cadherin and Ber-EP4 in tubal pregnancy by comparing their expressions in epithelial and trophoblastic cells both in ectopic tubal and intrauterine pregnancies. Methods: The Formalin-fixed paraffin embedded blocks of 17 intrauterine and 17 tubal pregnancies were immunohistochemically stained with E-cadherin and Ber-EP4. Results: E-cadherin was expressed in the epithelium, villous and extravillous trophoblast in tubal and intrauterine pregnancies but not in the syncytiotrophoblast. The staining intensity was lower in the extra-villous trophoblast in tubal ectopic pregnancies compared with intrauterine pregnancies. Ber-EP4 was expressed in the epithelium of tubal and intrauterine pregnancies and only in villous cytotrophoblast. The intensity of staining in tubal pregnancy was higher than in intrauterine pregnancy. Discussion: The loss of E-cadherin expression in extra-villous trophoblast and increased expression of Ber-EP4 in the villous cytotrophoblast may play a role in the formation of tubal pregnancy by allowing the blastocyst to attach to the tubal epithelium.

First-in-human study of ONO-4578, an antagonist of prostaglandin E2 receptor 4, alone and with nivolumab in solid tumors.

EP4, a prostaglandin E2 receptor, has shown an immunosuppressive activity on cancer cells. This first-in-human study evaluated ONO-4578, a highly selective EP4 antagonist, as monotherapy and in combination with nivolumab in patients with advanced or metastatic solid tumors. A daily dose ranging from 30 mg to 100 mg of ONO-4578 monotherapy and that ranging from 2 mg to 60 mg of ONO-4578 with biweekly nivolumab 240 mg were administered. A total of 31 patients were enrolled, 10 receiving monotherapy and 21 receiving combination therapy. Overall, 26 patients experienced treatment-related adverse events. Dose-limiting toxicities were observed in three patients; one of six patients receiving 100 mg monotherapy developed grade 3 duodenal ulcer and two of six patients receiving 60 mg combination therapy developed either grade 3 erythema multiforme or grade 3 increased amylase and grade 4 increased lipase. One patient with small-cell lung cancer who received 40 mg combination therapy had a partial response, and three patients with monotherapy and six patients with combination therapy had stable disease. Pharmacodynamics analyses showed that ONO-4578 had EP4 antagonistic activity at doses as low as 2 mg. In conclusion, the maximum tolerated dose of ONO-4578 alone or in combination with nivolumab was not reached. ONO-4578 was well tolerated at the tested doses and showed signs of antitumor activity. Considering safety, efficacy, and pharmacokinetics/pharmacodynamics results, ONO-4578 40 mg daily with nivolumab 240 mg biweekly was selected as the recommended dose for future clinical trials. (Registration: JapicCTI-173,496 and NCT03155061).

Prostaglandin E2/EP4 axis is upregulated in Spondyloarthritis and contributes to radiographic progression.

Ankylosing spondylitis (AS) is an inflammatory disease leading to spine ankylosis; however, the mechanisms behind new bone formation are still not fully understood. Single Nucleotide Polymorphisms (SNPs) in PTGER4, encoding for the receptor EP4 of prostaglandin E2 (PGE2), are associated with AS. Since the PGE2-EP4 axis participates in inflammation and bone metabolism, this work aims at investigating the influence of the prostaglandin-E2 axis on radiographic progression in AS. In 185 AS (97 progressors), baseline serum PGE2 predicted progression, and PTGER4 SNP rs6896969 was more frequent in progressors. Increased EP4/PTGER4 expression was observed in AS circulating immune cells, synovial tissue, and bone marrow. CD14highEP4 + cells frequency correlated with disease activity, and when monocytes were cocultured with mesenchymal stem cells, the PGE2/EP4 axis induced bone formation. In conclusion, the Prostaglandin E2 axis is involved in bone remodelling and may contribute to the radiographic progression in AS due to genetic and environmental upregulation.

A novel role for PGE2-EP4 in the developmental programming of the mouse ductus arteriosus: consequences for vessel maturation and function.

The ductus arteriosus (DA) is a vascular shunt that allows oxygenated blood to bypass the developing lungs in utero. Fetal DA patency requires vasodilatory signaling via the prostaglandin E2 (PGE2) receptor EP4. However, in humans and mice, disrupted PGE2-EP4 signaling in utero causes unexpected patency of the DA (PDA) after birth, suggesting another role for EP4 during development. We used EP4-knockout (KO) mice and acute versus chronic pharmacological approaches to investigate EP4 signaling in DA development and function. Expression analyses identified EP4 as the primary EP receptor in the DA from midgestation to term; inhibitor studies verified EP4 as the primary dilator during this period. Chronic antagonism recapitulated the EP4 KO phenotype and revealed a narrow developmental window when EP4 stimulation is required for postnatal DA closure. Myography studies indicate that despite reduced contractile properties, the EP4 KO DA maintains an intact oxygen response. In newborns, hyperoxia constricted the EP4 KO DA but survival was not improved, and permanent remodeling was disrupted. Vasomotion and increased nitric oxide (NO) sensitivity in the EP4 KO DA suggest incomplete DA development. Analysis of DA maturity markers confirmed a partially immature EP4 KO DA phenotype. Together, our data suggest that EP4 signaling in late gestation plays a key developmental role in establishing a functional term DA. When disrupted in EP4 KO mice, the postnatal DA exhibits signaling and contractile properties characteristic of an immature DA, including impairments in the first, muscular phase of DA closure, in addition to known abnormalities in the second permanent remodeling phase.NEW & NOTEWORTHY EP4 is the primary EP receptor in the ductus arteriosus (DA) and is critical during late gestation for its development and eventual closure. The "paradoxical" patent DA (PDA) phenotype of EP4-knockout mice arises from a combination of impaired contractile potential, altered signaling properties, and a failure to remodel associated with an underdeveloped immature vessel. These findings provide new mechanistic insights into women who receive NSAIDs to treat preterm labor, whose infants have unexplained PDA.

Seasonal expressions of COX-1, COX-2, and EP4 in the scent glands of muskrats (Ondatra zibethicus).

Prostaglandins (PGs) serve as signaling molecules that regulate various physiological processes, including inflammation, immune response, blood clotting, and reproduction. The aim of this study was to investigate the immunolocalizations and expression patterns of prostaglandin-E2 (PGE2), cyclooxygenase (COX)-1, and COX-2, as well as its receptor subtypes 4 (EP4) in the scent glands of muskrats (Ondatra zibethicus) during the breeding and nonbreeding periods. There were significant seasonal differences in the scent glandular mass, with higher values in the breeding season and relatively low in the nonbreeding season. PGE2, EP4, COX-1, and COX-2 have been immunolocalized in the scent glandular and epithelial cells in both breeding and nonbreeding seasons, whereas no immunostaining was observed in the interstitial cells. The protein and mRNA expression levels of EP4, COX-1, and COX-2 were higher in the scent glands of the breeding season than those of the nonbreeding season. The mean mRNA levels of EP4, COX-1, and COX-2 were positively correlated with the scent glandular weights. The circulating follicle-stimulating hormone (FSH), luteinizing hormone (LH), testosterone (T), and PGE2, as well as scent glandular PGE2 and dihydrotestosterone (DHT) concentrations, were also significantly higher in the breeding season. In addition, the transcriptomic study in the scent glands identified that differentially expressed genes might be related to fatty carboxylic monocarboxylic acid, steroidogenic-related pathways, and prostanoid metabolic processes. These findings suggested that prostaglandin-E2 might play an essential autocrine or paracrine role in regulating seasonal changes in the scent glandular functions of the muskrats.

Discovery of NXT-10796, an orally active, intestinally restricted EP4 agonist prodrug for the treatment of inflammatory bowel disease.

A property-focused optimization strategy was employed to modify the carboxylic acid head group of a class of EP4 agonists in order to minimize its absorption upon oral administration. The resulting oxalic acid monohydrazide-derived carboxylate isostere demonstrated utility as a class of prodrug showing colon-targeted delivery of parent agonist 2, with minimal exposure observed in the plasma. Oral administration of NXT-10796 demonstrated tissue specific activation of the EP4 receptor through modulation of immune genes in the colon, without modulation of EP4 driven biomarkers in the plasma compartment. Although further in depth understanding of the conversion of NXT-10796 is required for further assessment of the developability of this series of prodrugs, using NXT-10796 as a tool molecule has allowed us to confirm that tissue-specific modulation of an EP4-modulated gene signature is possible, which allows for further evaluation of this therapeutic modality in rodent models of human disease.

Prostaglandin E2 mediates the late phase of ischemic preconditioning in the heart via its receptor subtype EP4.

Ischemic preconditioning (IPC) describes a phenomenon wherein brief ischemia of the heart induces a potent cardioprotective mechanism against succeeding ischemic insult. Cyclooxygenase-2 (COX-2), a rate-limiting enzyme in prostanoid biosynthesis, is upregulated in the ischemic heart and contributes to IPC. Prostaglandin E2 (PGE2) protects the heart from ischemia-reperfusion (I/R) injury via its receptor subtype EP4. We sought to clarify the role of the PGE2/EP4 system in the late phase of IPC. Mice were subjected to four IPC treatment cycles, consisting of 5 min of occlusion of the left anterior descending coronary artery (LAD). We found that COX-2 mRNA was significantly upregulated in wild-type hearts at 6 h after IPC treatment. Cardiac PGE2 levels at 24 h after IPC treatment were significantly increased in both wild-type mice and mice lacking EP4 (EP4-/-). At 24 h after IPC treatment, I/R injury was induced by 30 min of LAD occlusion followed by 2 h of reperfusion and the cardiac infarct size was determined. The infarct size was significantly reduced by IPC treatment in wild-type mice; a reduction was not observed in EP4-/- mice. AE1-329, an EP4 agonist, significantly reduced infarct size and significantly ameliorated deterioration of cardiac function in wild-type mice subjected to I/R without IPC treatment. Furthermore, AE1-329 significantly enhanced the I/R-induced activation of Akt, a pro-survival kinase. We demonstrated that the PGE2/EP4 system in the heart plays a critical role in the late phase of IPC, partly by augmenting Akt-mediated signaling. These findings clarify the mechanism of IPC and may contribute to the development of therapeutic strategies for ischemic heart disease.

Tailored PGE2 Immunomodulation of moDCs by Nano-Encapsulated EP2/EP4 Antagonists.

Prostaglandin E2 (PGE2) is an important maturation mediator for dendritic cells (DCs). However, increased PGE2 levels in the tumor exert immunosuppressive effects on DCs by signaling through two E-Prostanoid (EP) receptors: EP2 and EP4. Blocking EP-receptor signaling of PGE2 with antagonists is currently being investigated for clinical applications to enhance anti-tumor immunity. In this study, we investigated a new delivery approach by encapsulating EP2/EP4 antagonists in polymeric nanoparticles. The nanoparticles were characterized for size, antagonist loading, and release. The efficacy of the encapsulated antagonists to block PGE2 signaling was analyzed using monocyte-derived DCs (moDCs). The obtained nanoparticles were sized between 210 and 260 nm. The encapsulation efficacy of the EP2/EP4 antagonists was 20% and 17%, respectively, and was further increased with the co-encapsulation of both antagonists. The treatment of moDCs with co-encapsulation EP2/EP4 antagonists prevented PGE2-induced co-stimulatory marker expression. Even though both antagonists showed a burst release within 15 min at 37 °C, the nanoparticles executed the immunomodulatory effects on moDCs. In summary, we demonstrate the functionality of EP2/EP4 antagonist-loaded nanoparticles to overcome PGE2 modulation of moDCs.

Prostaglandin E2-Induced Immune Suppression via Cytotoxic T-Lymphocyte Antigen 4 in Paratuberculosis.

Paratuberculosis is a chronic enteritis of ruminants caused by the facultative intracellular pathogen Mycobacterium avium subsp. paratuberculosis. The Th1 response inhibits the proliferation of M. avium subsp. paratuberculosis during the early subclinical stage. However, we have previously shown that immune inhibitory molecules, such as prostaglandin E2 (PGE2), suppress M. avium subsp. paratuberculosis-specific Th1 responses as the disease progresses. To date, the mechanism underlying immunosuppression during M. avium subsp. paratuberculosis infection has not been elucidated. Therefore, in the present study, we investigated the function of cytotoxic T-lymphocyte antigen 4 (CTLA-4) expressed by peripheral blood mononuclear cells (PBMCs) from cattle with paratuberculosis because CTLA-4 expression is known to be elevated in T cells under an M. avium subsp. paratuberculosis experimental infection. M. avium subsp. paratuberculosis antigen induced CTLA-4 expression in T cells from cattle experimentally infected with M. avium subsp. paratuberculosis. Interestingly, both PGE2 and an E prostanoid 4 agonist also induced CTLA-4 expression in T cells. In addition, a functional assay with a bovine CTLA-4-immunogobulin fusion protein (CTLA-4-Ig) indicated that CTLA-4 inhibited gamma interferon (IFN-γ) production in M. avium subsp. paratuberculosis-stimulated PBMCs, while blockade by anti-bovine CTLA-4 monoclonal antibody increased the secretion of IFN-γ and tumor necrosis factor alpha production in these PBMCs. These preliminary findings show that PGE2 has immunosuppressive effects via CTLA-4 to M. avium subsp. paratuberculosis. Therefore, it is necessary to clarify in the future whether CTLA-4-mediated immunosuppression facilitates disease progression of paratuberculosis in cattle.

PARP14 regulates EP4 receptor expression in human colon cancer HCA-7 cells.

E type prostanoid 4 (EP4) receptors and their signaling pathways have been implicated in the development and malignant transformation of colorectal cancer. We herein demonstrated that the mono(ADP-ribosyl)ation of histone deacetylase (HDAC)1 and HDAC2 by poly(ADP-ribose) polymerase 14 (PARP14) may be required to induce the expression of EP4 receptors. The suppression of PARP14 activity by siRNA and/or its inhibitors reduced the mRNA expression of EP4 receptors. Thus, the expression of their proteins to approximately 50-80% in human colon cancer HCA-7 cells, however, which retained the activities of EP4 receptors to some extent. Since the expression levels of EP4 receptors are important factors for the maintenance of homeostasis, the adequate inhibition of PARP14 activity will be a good target for the prevention of colon cancer and/or as an alternative therapy for this disease. Since non-steroidal anti-inflammatory drugs (NSAIDs) are associated with a risk of heart attacks and stroke, novel PARP14 inhibitors will supersede NSAIDs without causing heart attacks and stroke, while maintaining appropriate EP4 receptor-mediated intestinal homeostasis.

Cyclooxygenase-2 contributes to diabetic nephropathy through glomerular EP4 receptor.

Diabetic nephropathy (DN) is a major microvascular complication of diabetes and the leading cause of mortality in diabetic patients. Cyclooxygenase (COX) and COX-derived prostanoids are documented to participate in the pathogenesis of diabetic nephropathy. Herein, we found an increased COX2 expression level in diabetic kidneys of STZ-induced DBA mice. The COX2 inhibitor significantly attenuated albuminuria and histological lesions, accompanied by up-regulation of the renal angiopoietin-1/tie-2 system. This finding is consistent with the presence of an angiogenic signature in endothelial cells during the development of DN. Prostaglandin E2 (PGE2) is the most abundant prostanoid in the kidney, and its receptor EP4 is expressed in the glomerulus, as determined by in situ hybridization. To test the hypothesis that diabetes-associated COX2 overexpression induces renal PGE2 production and endothelial dysfunction by activating glomerular EP4 receptors, the effect of an EP4 antagonist on Akita/DBA mice was investigated. Our results showed that blockade of EP4 receptor significantly reduced albuminuria in diabetic mice. Owing to the established adverse effect of COX2 inhibitors, our study provided new insight into meaningful renal benefits for diabetic nephropathy by targeting the EP4 receptor.

TNF-α impairs EP4 signaling through the association of TRAF2-GRK2 in primary fibroblast-like synoviocytes.

Our previous study showed that chronic treatment with tumor necrosis factor-α (TNF-α) decreased cAMP concentration in fibroblast-like synoviocytes (FLSs) of collagen-induced arthritis (CIA) rats. In this study we investigated how TNF-α impairs cAMP homeostasis, particularly clarifying the potential downstream molecules of TNF-α and prostaglandin receptor 4 (EP4) signaling that would interact with each other. Using a cAMP FRET biosensor PM-ICUE3, we demonstrated that TNF-α (20 ng/mL) blocked ONO-4819-triggered EP4 signaling, but not Butaprost-triggered EP2 signaling in normal rat FLSs. We showed that TNF-α (0.02-20 ng/mL) dose-dependently reduced EP4 membrane distribution in normal rat FLS. TNF-α significantly increased TNF receptor 2 (TNFR2) expression and stimulated proliferation in human FLS (hFLS) via ecruiting TNF receptor-associated factor 2 (TRAF2) to cell membrane. More interestingly, we revealed that TRAF2 interacted with G protein-coupled receptor kinase (GRK2) in the cytoplasm of primary hFLS and helped to bring GRK2 to cell membrane in response of TNF-α stimulation, the complex of TRAF2 and GRK2 then separated on the membrane, and translocated GRK2 induced the desensitization and internalization of EP4, leading to reduced production of intracellular cAMP. Silencing of TRAF2 by siRNA substantially diminished TRAF2-GRK2 interaction, blocked the translocation of GRK2, and resulted in upregulated expression of membrane EP4 and intracellular cAMP. In CIA rats, administration of paroxetine to inhibit GRK2 effectively improved the symptoms and clinic parameters with significantly reduced joint synovium inflammation and bone destruction. These results elucidate a novel form of cross-talk between TNFR (a cytokine receptor) and EP4 (a typical G protein-coupled receptor) signaling pathways. The interaction between TRAF2 and GRK2 may become a potential new drug target for the treatment of inflammatory diseases.

VSMC-specific EP4 deletion exacerbates angiotensin II-induced aortic dissection by increasing vascular inflammation and blood pressure.

Prostaglandin E2 (PGE2) plays an important role in vascular homeostasis. Its receptor, E-prostanoid receptor 4 (EP4) is essential for physiological remodeling of the ductus arteriosus (DA). However, the role of EP4 in pathological vascular remodeling remains largely unknown. We found that chronic angiotensin II (AngII) infusion of mice with vascular smooth muscle cell (VSMC)-specific EP4 gene knockout (VSMC-EP4-/-) frequently developed aortic dissection (AD) with severe elastic fiber degradation and VSMC dedifferentiation. AngII-infused VSMC-EP4-/- mice also displayed more profound vascular inflammation with increased monocyte chemoattractant protein-1 (MCP-1) expression, macrophage infiltration, matrix metalloproteinase-2 and -9 (MMP2/9) levels, NADPH oxidase 1 (NOX1) activity, and reactive oxygen species production. In addition, VSMC-EP4-/- mice exhibited higher blood pressure under basal and AngII-infused conditions. Ex vivo and in vitro studies further revealed that VSMC-specific EP4 gene deficiency significantly increased AngII-elicited vasoconstriction of the mesenteric artery, likely by stimulating intracellular calcium release in VSMCs. Furthermore, EP4 gene ablation and EP4 blockade in cultured VSMCs were associated with a significant increase in MCP-1 and NOX1 expression and a marked reduction in α-SM actin (α-SMA), SM22α, and SM differentiation marker genes myosin heavy chain (SMMHC) levels and serum response factor (SRF) transcriptional activity. To summarize, the present study demonstrates that VSMC EP4 is critical for vascular homeostasis, and its dysfunction exacerbates AngII-induced pathological vascular remodeling. EP4 may therefore represent a potential therapeutic target for the treatment of AD.

The Enhanced Cytotoxic Effects in B-Cell Leukemia and Lymphoma Following Activation of Prostaglandin EP4 Receptor and Targeting of CD20 Antigen by Monoclonal Antibodies.

Anti-CD20 monoclonal antibodies (MAbs) have revolutionized the treatment of B-cell leukemia and lymphoma. However, many patients do not respond to such treatment due to either deficiency of the complementary immune response or resistance to apoptosis. Other currently available treatments are often inadequate or induce major side effects. Therefore, there is a constant need for improved therapies. The prostaglandin E2 receptor 4 (EP4) receptor has been identified as a promising therapeutic target for hematologic B-cell malignancies. Herein, we report that EP4 receptor agonists PgE1-OH and L-902688 have exhibited enhanced cytotoxicity when applied together with anti-CD20 MAbs rituximab, ofatumumab and obinutuzumab in vitro in Burkitt lymphoma cells Ramos, as well as in p53-deficient chronic lymphocytic leukemia (CLL) cells MEC-1. Moreover, the enhanced cytotoxic effects of EP4 receptor agonists and MAbs targeting CD20 have been identified ex vivo on primary lymphocytes B obtained from patients diagnosed with CLL. Incubation of cells with PgE1-OH and L-902688 preserved the expression of CD20 molecules, further confirming the anti-leukemic potential of EP4 receptor agonists in combination with anti-CD20 MAbs. Additionally, we demonstrated that the EP4 receptor agonist PgE-1-OH induced apoptosis and inhibited proliferation via the EP4 receptor triggering in CLL. This work has revealed very important findings leading towards the elucidation of the anticancer potential of PgE1-OH and L-902688, either alone or in combination with MAbs. This may contribute to the development of potential therapeutic alternatives for patients with B-cell malignancies.

A Novel Small Molecular Prostaglandin Receptor EP4 Antagonist, L001, Suppresses Pancreatic Cancer Metastasis.

Metastatic pancreatic cancer remains a major clinical challenge, emphasizing the urgent need for the exploitation of novel therapeutic approaches with superior response. In this study, we demonstrate that the aberrant activation of prostaglandin E2 (PGE2) receptor 4 (EP4) is a pro-metastatic signal in pancreatic cancer. To explore the therapeutic role of EP4 signaling, we developed a potent and selective EP4 antagonist L001 with single-nanomolar activity using a panel of cell functional assays. EP4 antagonism by L001 effectively repressed PGE2-elicited cell migration and the invasion of pancreatic cancer cells in a dose-dependent manner. Importantly, L001 alone or combined with the chemotherapy drug gemcitabine exhibited remarkably anti-metastasis activity in a pancreatic cancer hepatic metastasis model with excellent tolerability and safety. Mechanistically, EP4 blockade by L001 abrogated Yes-associated protein 1 (YAP)-driven pro-metastatic factor expression in pancreatic cancer cells. The suppression of YAP's activity was also observed upon L001 treatment in vivo. Together, these findings support the notions that EP4-YAP signaling axis is a vital pro-metastatic pathway in pancreatic cancer and that EP4 inhibition with L001 may deliver a therapeutic benefit for patients with metastatic pancreatic cancer.

15-Keto-PGE2 acts as a biased/partial agonist to terminate PGE2-evoked signaling.

Prostaglandin E2 (PGE2) is well-known as an endogenous proinflammatory prostanoid synthesized from arachidonic acid by the activation of cyclooxygenase-2. E type prostanoid (EP) receptors are cognates for PGE2 that have four main subtypes: EP1 to EP4. Of these, the EP2 and EP4 prostanoid receptors have been shown to couple to Gαs-protein and can activate adenylyl cyclase to form cAMP. Studies suggest that EP4 receptors are involved in colorectal homeostasis and cancer development, but further work is needed to identify the roles of EP2 receptors in these functions. After sufficient inflammation has been evoked by PGE2, it is metabolized to 15-keto-PGE2 Thus, 15-keto-PGE2 has long been considered an inactive metabolite of PGE2 However, it may have an additional role as a biased and/or partial agonist capable of taking over the actions of PGE2 to gradually terminate reactions. Here, using cell-based experiments and in silico simulations, we show that PGE2-activated EP4 receptor-mediated signaling may evoke the primary initiating reaction of the cells, which would take over the 15-keto-PGE2-activated EP2 receptor-mediated signaling after PGE2 is metabolized to 15-keto-PGE2 The present results shed light on new aspects of 15-keto-PGE2, which may have important roles in passing on activities to EP2 receptors from PGE2-stimulated EP4 receptors as a "switched agonist." This novel mechanism may be significant for gradually terminating PGE2-evoked inflammation and/or maintaining homeostasis of colorectal tissues/cells functions.

Prostaglandin E receptor subtype 4 protects against diabetic cardiomyopathy by modulating cardiac fatty acid metabolism via FOXO1/CD36 signalling.

BACKGROUND: Cardiac fatty acid metabolism is essential for maintaining normal cardiac function at baseline and in response to various disease stress, like diabetes. EP4 is widely expressed in cardiomyocytes and has been demonstrated to play a role in cardio function. However, its function in regulating cardiac fatty acid metabolism is remained unknown. METHODS: Mice were fed with standard chow or high-fat for eight weeks. The effects of EP4 deficiency on cardiac function, cardiomyocytes hypertrophy and myocardial fibrosis were studied. The possible regulatory mechanisms were further investigated. RESULTS: EP4-/- mice exhibited concentric hypertrophy and myocardial fibrosis with cardiac energy deprivation due to reduction of fatty acid uptake and inhibition of ATP generation mediated by FOXO1/CD36 signalling. Moreover, pharmacologically activated EP4 alleviated impaired fatty acid transport and insufficient ATP generation in cardiomyocytes. CONCLUSION: EP4 tightly coordinates the rates of cardiac fatty acid uptake and ATP generation via FOXO1/CD36 signalling axis. Our study provides evidences for the link between EP4 and cardiac fatty acid transport and further pointed out that EP4 could be a potential target for modulating fatty acid metabolism and curbing cardiac tissue-specific impairment of function following diabetes.

Prostaglandin E2 promotes Staphylococcus aureus infection via EP4 receptor in bovine endometrium.

Prostaglandin E2 (PGE2) enhances Staphylococcus aureus infection but its mechanism is not well understood. Here, we examined the effect of PGE2 on Staphylococcal Protein A (SPA) expression in bovine endometrium and determined the role of select PGE2 receptors (i.e., EP2 and EP4) in adhesion and internalization of S. aureus. S. aureus isolate SA113 was used for in vitro infection of bovine endometrial tissues and epithelial cells, with treatment conditions consisting of untreated control, SA113 treatment, SA113 + PGE2, SA113 + PGE2 + EP2 receptor antagonist (AH-6809), and SA113 + PGE2 + EP4 receptor antagonist (AH-23848). Immunofluorescence assay revealed that PGE2 could promote SPA expression in S. aureus-infected bovine endometrial tissues. PGE2 also enhanced the adhesion and internalization of S. aureus in bovine endometrial cells. The addition of EP4 antagonist, but not the EP2 antagonist, abrogated the ability of PGE2 to promote S. aureus SPA expression, adhesion, and internalization in endometrial cells. Our findings suggest that S. aureus infection in the endometrium is enhanced by PGE2 through the EP4 receptor. This result is essential for the development of new approach to treating S. aureus infection, such as the application of EP4 antagonist as an adjunct drug treatment.

Prostaglandin E2 promotes pathological retinal neovascularisation via EP4R-EGFR-Gab1-AKT signaling pathway.

Proliferative retinopathies, such as proliferative diabetic retinopathy (PDR) and retinopathy of prematurity (ROP) are major causes of visual impairment and blindness in industrialized countries. Prostaglandin E2 (PGE2) is implicated in cellular proliferation and migration via E-prostanoid receptor (EP4R). The aim of this study was to investigate the role of PGE2/EP4R signaling in the promotion of retinal neovascularisation. In a streptozotocin (STZ)-induced diabetic model and an oxygen-induced retinopathy (OIR) model, rats received an intravitreal injection of PGE2, cay10598 (an EP4R agonist) or AH23848 (an EP4R antagonist). Optical coherence tomography, retinal histology and biochemical markers were assessed. Treatment with PGE2 or cay10598 accelerated pathological retinal angiogenesis in STZ and OIR-induced rat retina, which was ameliorated in rats pretreated with AH23848. Serum VEGF-A was upregulated in the PGE2-treated diabetic rats vs non-treated diabetic rats and significantly downregulated in AH23848-treated diabetic rats. PGE2 or cay10598 treatment also significantly accelerated endothelial tip-cell formation in new-born rat retina. In addition, AH23848 treatment attenuated PGE2-or cay10598-induced proliferation and migration by repressing the EGF receptor (EGFR)/Growth factor receptor bound protein 2-associated binder protein 1 (Gab1)/Akt/NF-κB/VEGF-A signaling network in human retinal microvascular endothelial cells (hRMECs). PGE2/EP4R signaling network is thus a potential therapeutic target for pathological intraocular angiogenesis.

Intestinal host defense outcome is dictated by PGE2 production during efferocytosis of infected cells.

Inflammatory responses are terminated by the clearance of dead cells, a process termed efferocytosis. A consequence of efferocytosis is the synthesis of the antiinflammatory mediators TGF-ß, PGE2, and IL-10; however, the efferocytosis of infected cells favors Th17 responses by eliciting the synthesis of TGF-ß, IL-6, and IL-23. Recently, we showed that the efferocytosis of apoptotic Escherichia coli-infected macrophages by dendritic cells triggers PGE2 production in addition to pro-Th17 cytokine expression. We therefore examined the role of PGE2 during Th17 differentiation and intestinal pathology. The efferocytosis of apoptotic E. coli-infected cells by dendritic cells promoted high levels of PGE2, which impaired IL-1R expression via the EP4-PKA pathway in T cells and consequently inhibited Th17 differentiation. The outcome of murine intestinal Citrobacter rodentium infection was dependent on the EP4 receptor. Infected mice treated with EP4 antagonist showed enhanced intestinal defense against C. rodentium compared with infected mice treated with vehicle control. Those results suggest that EP4 signaling during infectious colitis could be targeted as a way to enhance Th17 immunity and host defense.