Constitutive internalisation of EP2 differentially regulates G protein signalling.

The prostanoid G protein-coupled receptor (GPCR) EP2 is widely expressed and implicated in endometriosis, osteoporosis, obesity, pre-term labour and cancer. Internalisation and intracellular trafficking are critical for shaping GPCR activity, yet little is known regarding the spatial programming of EP2 signalling and whether this can be exploited pharmacologically. Using three EP2-selective ligands that favour activation of different EP2 pathways, we show that EP2 undergoes limited agonist-driven internalisation but is constitutively internalised via dynamin-dependent, ß-arrestin-independent pathways. EP2 was constitutively trafficked to early and very early endosomes (VEE), which was not altered by ligand activation. APPL1, a key adaptor and regulatory protein of the VEE, did not impact EP2 agonist-mediated cAMP. Internalisation was required for ~70% of the acute butaprost- and AH13205-mediated cAMP signalling, yet PGN9856i, a Gαs-biased agonist, was less dependent on receptor internalisation for its cAMP signalling, particularly in human term pregnant myometrial cells that endogenously express EP2. Inhibition of EP2 internalisation partially reduced calcium signalling activated by butaprost or AH13205 and had no effect on PGE2 secretion. This indicates an agonist-dependent differential spatial requirement for Gαs and Gαq/11 signalling and a role for plasma membrane-initiated Gαq/11-Ca2+-mediated PGE2 secretion. These findings reveal a key role for EP2 constitutive internalisation in its signalling and potential spatial bias in mediating its downstream functions. This, in turn, could highlight important considerations for future selective targeting of EP2 signalling pathways.

Proliferation of bovine endometrial epithelial cells is promoted by prostaglandin E2-PTGER2 signaling through cell cycle regulation.

It is known that prostaglandin E2 (PGE2) induces proliferation of epithelia in bovine endometrial explants, however, the detailed mechanism of regulation of PGE2 in inducing bovine endometrial epithelial cell (bEEC) proliferation is unclear. In this study, we determined whether proliferation of bEECs is promoted by PGE2-prostaglandin E receptor 2 (PTGER2) signaling activation through cell cycle regulation. The results demonstrated that bEECs proliferation was induced by treatment of PGE2 and PTGER2 agonist butaprost. These processes were down-regulated by PTGER2 antagonist AH6809 and CDK inhibitors (LEE011, CDK2 Inhibitor II and Ro 3306). PGE2 and butaprost induced cyclins (A, B1, D1, D3 and E2), cyclin-dependent kinases (CDKs, 1, 2, 4 and 6), and epidermal growth factor (EGF) expression were inhibited by AH6809 treatment in bEECs. Moreover, proliferating cell nuclear antigen (PCNA), cyclooxygenase-1 (COX-1), cyclooxygenase-2 (COX-2), and PTGER2 expression in bEECs were up-regulated by PGE2 and butaprost treatment. Our data demonstrate that PGE2-PTGER2 signaling activation has a direct molecular association with cell cycle regulation and cell proliferation in bEECs. Collectively, these findings will improve our understanding of the roles for PGE2-PTGER2 signaling activation in the physiological and pharmacological processes of bovine endometrium.

Effects of Sodium Selenite Injection on Serum Metabolic Profiles in Women Diagnosed with Breast Cancer-Related Lymphedema-Secondary Analysis of a Randomized Placebo-Controlled Trial Using Global Metabolomics.

In our previous study, intravenous (IV) injection of selenium alleviated breast cancer-related lymphedema (BCRL). This secondary analysis aimed to explore the metabolic effects of selenium on patients with BCRL. Serum samples of the selenium-treated (SE, n = 15) or the placebo-controlled (CTRL, n = 14) groups were analyzed by ultra-high-performance liquid chromatography with Q-Exactive Orbitrap tandem mass spectrometry (UHPLC-Q-Exactive Orbitrap/MS). The SE group showed a lower ratio of extracellular water to segmental water (ECW/SW) in the affected arm to ECW/SW in the unaffected arm (arm ECW/SW ratio) than the CTRL group. Metabolomics analysis showed a valid classification at 2-weeks and 107 differential metabolites were identified. Among them, the levels of corticosterone, LTB4-DMA, and PGE3-which are known anti-inflammatory compounds-were elevated in the SE group. Pathway analysis demonstrated that lipid metabolism (glycerophospholipid metabolism, steroid hormone biosynthesis, or arachidonic acid metabolism), nucleotide metabolism (pyrimidine or purine metabolism), and vitamin metabolism (pantothenate and CoA biosynthesis, vitamin B6 metabolism, ascorbate and aldarate metabolism) were altered in the SE group compared to the CTRL group. In addition, xanthurenic acid levels were negatively associated with whole blood selenium level (WBSe) and positively associated with the arm ECW/SW. In conclusion, selenium IV injection improved the arm ECW/SW ratio and altered the serum metabolic profiles in patients with BCRL, and improved the anti-inflammatory process in lipid, nucleotide and vitamin pathways, which might alleviate the symptoms of BCRL.

Relationship between the n-3 index, serum metabolites and breast cancer risk.

The present study aimed to investigate the relationship between the n-3 index, serum metabolites and breast cancer risk. A total of 104 newly diagnosed breast cancer patients and 70 healthy controls were recruited. The erythrocyte phospholipid fatty acid composition was determined by gas-liquid chromatography, and the n-3 index was calculated with the percentage of eicosapentaenoic acid plus docosahexaenoic acid in total fatty acids. Serum metabolomic profiles were analyzed by UHPLC-Q-Exactive Orbitrap/MS. The results showed that the erythrocyte phospholipid n-3 index was significantly lower in breast cancer patients than in healthy controls, and it was inversely associated with breast cancer risk (OR = 0.60; 95% CI: 0.36-0.84). Metabolomics analyses showed that serum 16α-hydroxy dehydroepiandrosterone (DHEA) 3-sulfate, lysophatidylethanolamines (LPE) 22:0/0:0 and hexanoylcarnitine were significantly higher, while thromboxane B3, prostaglandin E3 (PGE3) and 18ß-glycyrrhetinic acid were significantly lower in breast cancer patients than those in healthy controls. In addition, serum 16α-hydroxy DHEA 3-sulfate was inversely correlated with the n-3 index (r = -0.412, p = 0.036). In conclusion, our findings suggest that the lack of n-3 PUFAs might be a potential risk factor for breast cancer, and the serum metabolite 16α-hydroxy DHEA 3-sulfate may play an important role in linking n-3 PUFA deficiency and breast disease etiology.

Prostaglandin E3 attenuates macrophage-associated inflammation and prostate tumour growth by modulating polarization.

Alternative polarization of macrophages regulates multiple biological processes. While M1-polarized macrophages generally mediate rapid immune responses, M2-polarized macrophages induce chronic and mild immune responses. In either case, polyunsaturated fatty acid (PUFA)-derived lipid mediators act as both products and regulators of macrophages. Prostaglandin E3 (PGE3 ) is an eicosanoid derived from eicosapentaenoic acid, which is converted by cyclooxygenase, followed by prostaglandin E synthase successively. We found that PGE3 played an anti-inflammatory role by inhibiting LPS and interferon-γ-induced M1 polarization and promoting interleukin-4-mediated M2 polarization (M2a). Further, we found that although PGE3 had no direct effect on the growth of prostate cancer cells in vitro, PGE3 could inhibit prostate cancer in vivo in a nude mouse model of neoplasia. Notably, we found that PGE3 significantly inhibited prostate cancer cell growth in a cancer cell-macrophage co-culture system. Experimental results showed that PGE3 inhibited the polarization of tumour-associated M2 macrophages (TAM), consequently producing indirect anti-tumour activity. Mechanistically, we identified that PGE3 regulated the expression and activation of protein kinase A, which is critical for macrophage polarization. In summary, this study indicates that PGE3 can selectively promote M2a polarization, while inhibiting M1 and TAM polarization, thus exerting an anti-inflammatory effect and anti-tumour effect in prostate cancer.

Leucoselect Phytosome Modulates Serum Eicosapentaenoic Acid, Docosahexaenoic Acid, and Prostaglandin E3 in a Phase I Lung Cancer Chemoprevention Study.

Grape seed procyanidin extract (GSE) has been shown to exert antineoplastic properties in preclinical studies. Recently, we reported findings from a modified phase I, open-label, dose escalation clinical study conducted to evaluate the safety, tolerability, MTD, and potential chemopreventive effects of leucoselect phytosome, a standardized GSE complexed with soy phospholipids to enhance bioavailability, in heavy active and former smokers. Three months of leucoselect phytosome treatment significantly decreased bronchial Ki-67 labeling index (LI), a marker of cell proliferation on the bronchial epithelium. Because GSE is widely used as a supplement to support cardiovascular health, we evaluate the impact of oral leucoselect phytosome on the fasting serum complex lipid metabolomics profiles in our participants. One month of leucoselect phytosome treatment significantly increased eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), the omega-3 polyunsaturated fatty acids (n-3 PUFA) with well-established anticancer properties. Leucoselect phytosome also significantly increased unsaturated phosphatidylcholines (PC), likely from soy phospolipids in the phytosome and functioning as transporters for these PUFAs. Furthermore, 3-month leucoselect phytosome treatment significantly increased serum prostaglandin (PG) E3 (PGE3), a metabolite of EPA with anti-inflammatory and antineoplastic properties. Such increases in PGE3 correlated with reductions of bronchial Ki-67 LI (r = -0.9; P = 0.0374). Moreover, posttreatment plasma samples from trial participants significantly inhibited proliferation of human lung cancer cell lines A549 (adenocarcinoma), H520 (squamous cell carcinoma), DMS114 (small cell carcinoma), and 1198 (preneoplastic cell line). Our findings further support the potential utility of leucoselect phytosome in reducing cardiovascular and neoplastic risks in heavy former and active smokers. PREVENTION RELEVANCE: In this correlative study of leucoselect phytosome for lung cancer chemoprevention in heavy active and former smokers, we demonstrate for the first time, favorable modulations of n-3PUFA and downstream PGE3 in fasting serum, further supporting the chemopreventive potential of leucoselect phytosome against lung cancer.

Lumbar Spinal Stenosis and Potential Management With Prostaglandin E1 Analogs.

ABSTRACT: Lumbar spinal stenosis is one of the most commonly diagnosed spinal disorders worldwide and remains a major cause for surgery in older adults. Lumbar spinal stenosis is clinically defined as a progressive degenerative disorder with low back pain and associated neurogenic intermittent claudication. Conservative and surgical management of lumbar spinal stenosis has been shown to be minimally effective on its symptoms. A treatment option that has not been investigated in the United States is the utilization of prostaglandin E1 analogs, which have been used primarily in Japan for the treatment of lumbar spinal stenosis since the 1980s. The vasodilatory and antiplatelet aggregation effects of prostaglandin E1 presumably improve symptoms of lumbar spinal stenosis by increasing blood flow to the spinal nerve roots. This brief report examines the potential vascular pathology of lumbar spinal stenosis, reviews evidence on the use of prostaglandin E1 analog limaprost in Japan for lumbar spinal stenosis, and briefly discusses misoprostol as a possible alternative in the United States. The studies summarized in this report suggest that prostaglandin E1 analogs may provide benefit as a conservative treatment option for patients with lumbar spinal stenosis. However, higher-quality studies conducted in the United States and comparison with other currently used conservative treatments are required before it can be recommended for routine clinical use.

In Vivo Targeted Metabolomic Profiling of Prostanit, a Novel Anti-PAD NO-Donating Alprostadil-Based Drug.

Prostanit is a novel drug developed for the treatment of peripheral arterial diseases. It consists of a prostaglandin E1 (PGE1) moiety with two nitric oxide (NO) donor fragments, which provide a combined vasodilation effect on smooth muscles and vascular spastic reaction. Prostanit pharmacokinetics, however, remains poorly investigated. Thus, the object of this study was to investigate the pharmacokinetics of Prostanit-related and -affected metabolites in rabbit plasma using the liquid chromatography-mass spectrometry (LC-MS) approach. Besides, NO generation from Prostanit in isolated rat aorta and human smooth muscle cells was studied using the Griess method. In plasma, Prostanit was rapidly metabolized to 1,3-dinitroglycerol (1,3-DNG), PGE1, and 13,14-dihydro-15-keto-PGE1. Simultaneously, the constant growth of amino acid (proline, 4-hydroxyproline, alanine, phenylalanine, etc.), steroid (androsterone and corticosterone), and purine (adenosine, adenosine-5 monophosphate, and guanosine) levels was observed. Glycine, aspartate, cortisol, and testosterone levels were decreased. Ex vivo Prostanit induced both NO synthase-dependent and -independent NO generation. The observed pharmacokinetic properties suggested some novel beneficial activities (i.e., effect prolongation and anti-inflammation). These properties may provide a basis for future research of the effectiveness and safety of Prostanit, as well as for its characterization from a clinical perspective.

Crosstalk between EP2 and PPARα Modulates Hypoxic Signaling and Myopia Development in Guinea Pigs.

Purpose: Cyclic adenosine monophosphate (cAMP) and peroxisome proliferator-activated receptor alpha (PPARα) levels mediate extracellular matrix (ECM) changes by altering the levels of hypoxia-inducible factor 1-alpha (HIF-1α) in various tissues. We aimed to determine, in the sclera of guinea pigs, whether a prostanoid receptor (EP2)-linked cAMP modulation affects PPARα and HIF-1α signaling during myopia. Methods: Three-week-old guinea pigs (n = 20 in each group), were monocularly injected with either an EP2 agonist (butaprost 1 µmol/L/10 µmol/L), an antagonist (AH6809 10 µmol/L/30 µmol/L) or a vehicle solution for two weeks during normal ocular growth. Separate sets of animals received these injections and underwent form deprivation (FD) simultaneously. Refraction and axial length (AL) were measured at two weeks, followed by scleral tissue isolation for quantitative PCR (qPCR) analysis (n = 10) and cAMP detection (n = 10) using a radioimmunoassay. Results: Butaprost induced myopia development during normal ocular growth, with proportional increases in AL and cAMP levels. FD did not augment the magnitude of myopia or cAMP elevations in these agonist-injected eyes. AH6809 suppressed cAMP increases and myopia progression during FD, but had no effect in a normal visual environment. Of the diverse set of 27 genes related to cAMP, PPARα and HIF-1α signaling and ECM remodeling, butaprost differentially regulated 15 of them during myopia development. AH6809 injections during FD negated such differential gene expressions. Conclusion: EP2 agonism increased cAMP and HIF-1α signaling subsequent to declines in PPARα and RXR mRNA levels, which in turn decreased scleral fibrosis and promoted myopia. EP2 antagonism instead inhibited each of these responses. Our data suggest that EP2 suppression may sustain scleral ECM structure and inhibit myopia development.

cAMP signaling primes lung endothelial cells to activate caspase-1 during Pseudomonas aeruginosa infection.

Activation of the inflammasome-caspase-1 axis in lung endothelial cells is emerging as a novel arm of the innate immune response to pneumonia and sepsis caused by Pseudomonas aeruginosa. Increased levels of circulating autacoids are hallmarks of pneumonia and sepsis and induce physiological responses via cAMP signaling in targeted cells. However, it is unknown whether cAMP affects other functions, such as P. aeruginosa-induced caspase-1 activation. Herein, we describe the effects of cAMP signaling on caspase-1 activation using a single cell flow cytometry-based assay. P. aeruginosa infection of cultured lung endothelial cells caused caspase-1 activation in a distinct population of cells. Unexpectedly, pharmacological cAMP elevation increased the total number of lung endothelial cells with activated caspase-1. Interestingly, addition of cAMP agonists augmented P. aeruginosa infection of lung endothelial cells as a partial explanation underlying cAMP priming of caspase-1 activation. The cAMP effect(s) appeared to function as a priming signal because addition of cAMP agonists was required either before or early during the onset of infection. However, absolute cAMP levels measured by ELISA were not predictive of cAMP-priming effects. Importantly, inhibition of de novo cAMP synthesis decreased the number of lung endothelial cells with activated caspase-1 during infection. Collectively, our data suggest that lung endothelial cells rely on cAMP signaling to prime caspase-1 activation during P. aeruginosa infection.

Synergetic Effect of EP1 Receptor Antagonist and (-)-Epigallocatechin-3-gallate in Hepatocellular Carcinoma.

Epigallocatechin-3-gallate (EGCG), the principal catechin of green tea, modulates different molecular mechanisms underlying hepatocellular carcinoma (HCC). Accumulating studies showed that the activation of prostaglandin (PG) receptor EP1 promotes cell migration and invasion in different cancers, which could be inverted by blocking the EP1 receptor. This study investigated the synergetic effects of EP1-selective antagonist ONO-8711 and EGCG treatment on HCC to better understand the potential strategy to treat HCC. We found that EGCG significantly inhibited PGE2 and EP1-selective agonist induced migration of HCC cells and increased the ratio of Bax/Bcl-2 even in the presence of ONO-DI-004 or PGE2. ONO-8711 significantly inhibited PGE2-induced HCC proliferation while increased the inhibitory effect of EGCG on HCC cell viability and migration ability compared with EGCG alone. These findings suggest that a combination of ONO-8711 and EGCG is a potential treatment for HCC therapy.

Activation of the prostaglandin E2 EP2 receptor attenuates renal fibrosis in unilateral ureteral obstructed mice and human kidney slices.

AIM: Renal fibrosis plays a pivotal role in the development and progression of chronic kidney disease, which affects 10% of the adult population. Previously, it has been demonstrated that the cyclooxygenase-2 (COX-2)/prostaglandin (PG) system influences the progression of renal injury. Here, we evaluated the impact of butaprost, a selective EP2 receptor agonist, on renal fibrosis in several models of kidney injury, including human tissue slices. METHODS: We studied the anti-fibrotic efficacy of butaprost using Madin-Darby Canine Kidney (MDCK) cells, mice that underwent unilateral ureteral obstruction and human precision-cut kidney slices. Fibrogenesis was evaluated on a gene and protein level by qPCR and Western blotting. RESULTS: Butaprost (50 µM) reduced TGF-ß-induced fibronectin (FN) expression, Smad2 phosphorylation and epithelial-mesenchymal transition in MDCK cells. In addition, treatment with 4 mg/kg/day butaprost attenuated the development of fibrosis in mice that underwent unilateral ureteral obstruction surgery, as illustrated by a reduction in the gene and protein expression of α-smooth muscle actin, FN and collagen 1A1. More importantly, a similar anti-fibrotic effect of butaprost was observed in human precision-cut kidney slices exposed to TGF-ß. The mechanism of action of butaprost appeared to be a direct effect on TGF-ß/Smad signalling, which was independent of the cAMP/PKA pathway. CONCLUSION: In conclusion, this study demonstrates that stimulation of the EP2 receptor effectively mitigates renal fibrogenesis in various fibrosis models. These findings warrant further research into the clinical application of butaprost, or other EP2 agonists, for the inhibition of renal fibrosis.

Limaprost or Pregabalin: Preoperative and Postoperative Medication for Pain due to Lumbar Spinal Stenosis.

PURPOSE: We aimed to evaluate the incidence of (and risk factors for) postoperative pregabalin and/or limaprost to treat persistent numbness and/or pain of the lower extremities after lumbar spinal stenosis (LSS) surgery. METHODS: Medical records of 329 patients (168 men, 161 women; average age 70 years) were retrospectively reviewed for data on the duration of LSS diagnosis; LSS disease; preoperative medication (limaprost, pregabalin, or combined limaprost/pregabalin; duration); symptoms; preoperative/postoperative intermittent claudication (IC); operation type; and postoperative medication and period. RESULTS: Limaprost, pregabalin, and combined limaprost/pregabalin were prescribed preoperatively for 43%, 7%, and 5% of patients, respectively. At an average of 21 months postoperatively, limaprost, pregabalin, and combined therapy were prescribed in 11%, 8%, 4% of patients, respectively. Medication requirement was significantly lower postoperatively than preoperatively (P < 0.0001). Significant risk factors for required postoperative medication were required preoperative medication (odds ratio [OR] 3.088, 95% confidence interval [CI] 1.679 to 5.681]; postoperative period (OR 1.063, 95% CI 1.031 to 1.096); and postoperative IC (OR 3.868, 95% CI 1.481 to 10.103). A negative impact from postoperative medication was seen in patients who had undergone decompression surgery (OR 0.589, 95% CI 0.377 to 0.918). CONCLUSIONS: Overall, 23% of LSS patients required medication for pain and/or numbness at 21 months postoperatively. Significant factors portending required postoperative medication were preoperative medication, longer postoperative period, and postoperative IC. A negative influence from postoperative medication was seen in patients who had undergone decompression surgery without fusion.

The prostaglandin E2 receptor PTGER2 and prostaglandin F2α receptor PTGFR mediate oviductal glycoprotein 1 expression in bovine oviductal epithelial cells.

Oviductal glycoprotein 1 (OVGP1), an oviductin, is involved in the maintenance of sperm viability and motility and contributes to sperm capacitation in the oviduct. In this study, the regulatory effects exerted by prostaglandin E2 (PGE2) and F2α (PGF2α) on OVGP1 expression via their corresponding receptors in bovine oviductal epithelial cells (BOECs) were investigated. BOECs were cultured in vitro, and their expression of receptors of PGE2 (PTGER1, PTGER2, PTGER3, and PTGER4) and PGF2α (PTGFR) was measured using RT-qPCR. Ca2+ concentration was determined with a fluorescence-based method and cAMP was quantified by enzyme-linked immunosorbent assays to verify activation of PTGER2 and PTGFR by their corresponding agonists in these cells. OVGP1 mRNA and protein expression was measured using RT-qPCR and western blotting, respectively, following PTGER2 and PTGFR agonist-induced activation. PTGER1, PTGER2, PTGER4, and PTGFR were found to be present in BOECs; however, PTGER3 expression was not detected. OVGP1 expression was significantly promoted by 10-6 M butaprost (a PTGER2 agonist) and decreased by 10-6 M fluprostenol (a PTGFR agonist). In addition, 3 µM H-89 (a PKA inhibitor) and 3 µM U0126 (an ERK inhibitor) effectively inhibited PGE2-induced upregulation of OVGP1, and 5 µM chelerythrine chloride (a PKC inhibitor) and 3 µM U0126 negated OVGP1 downregulation by PGF2α. In conclusion, this study demonstrates that OVGP1 expression in BOECs is enhanced by PGE2 via PTGER2-cAMP-PKA signaling, and reduced by PGF2α through the PTGFR-Ca2+-PKC pathway.

Investigation on the regulatory effect of PGE2 on ESCC cells through the trans-activation of EGFR by EP2 and the relevant mechanism.

OBJECTIVE: To determine whether the combination of prostaglandin E2 (PGE2) and EP2, the subtype receptor of PGE2, could trans-activate the epidermal growth factor receptor (EGFR). PATIENTS AND METHODS: In this experiment, we selected epithelial cells from normal esophageal mucosa as the negative control group, and the ESCC EC109 and TE-1 cell strain as the observation group. Real-time PCR and Western-blotting were used to detect the expression of EP2, EGFR and phosphorylated EGFR (p-EGFR). The pre-treatment of ESCC cell strains was carried out using Butaprost (special agonist of PGE2 and EP2) and RNAi of EP2, and we observed the expression of EP2, EGFR, and p-EGFR. WST-8 (CCK-8) was applied for the detection of the cell proliferation rate. The transwell invasion experiment was conducted for the detection of the invasion capability of cells. The expression of MMP-9 (matrix metalloproteinase-9), VEGF (vascular endothelial growth factor), pro-inflammatory factors (IL-6 and TNF-α) in the cell supernatant were detected using ELISA. RESULTS: The high mRNA and protein expression of EP2, EGFR, and p-EGFR were found in the EC109 and TE-1 cell strains in the observation group, which were higher than those in the control group (p < 0.05). After the intervention of PGE2, EP2 expression was decreased and the p-EGFR expression was increased (p < 0.05). There was no variation found in the expression of EGFR (p > 0.05). After cells were intervened using Butaprost, the expressions of EP2 and p-EGFR were increased (p < 0.05), and there were no changes identified in the expression of EGFR (p > 0.05). After the intervention of RNAi, the expression of EP2 and p-EGFR was decreased (p < .05), and no changes were identified in the expression of EGFR (p > 0.05). After the intervention of PGE2 and Butaprost, great increases were seen in the cell proliferation rate, invasion capability, and the expression of MMP-9, VEGF, IL-6, and TNF-α in EC109 and TE-1 cell strains (p < 0.05), however, the intervention of RNAi could reduce above indexes (p < 0.05). CONCLUSIONS: Through cell experiments, we verified that the combination of prostaglandin E2 (PGE2) and EP2, the subtype receptor of PGE2, could trans-activate the epidermal growth factor receptor (EGFR) to regulate the proliferation and invasion capability of esophageal squamous cell carcinoma (ESCC) cells, and secrete and express multiple cytokines, thus discovering the pathological mechanism of inflammation to carcinoma transition in the occurrence of ESCC, and providing the experimental evidence for the search of new target in the treatment of ESCC. ESCC cells can highly express the receptor subtype EP2 of PGE2 that can transactivate the EGFR, through which PGE2 is involved in the transition mechanism from inflammation to cancer.

Prostaglandin E2 facilitates neurite outgrowth in a motor neuron-like cell line, NSC-34.

Prostaglandin E2 (PGE2) exerts various biological effects by binding to E-prostanoid receptors (EP1-4). Although recent studies have shown that PGE2 induces cell differentiation in some neuronal cells such as mouse DRG neurons and sensory neuron-like ND7/23 cells, it is unclear whether PGE2 plays a role in differentiation of motor neurons. In the present study, we investigated the mechanism of PGE2-induced differentiation of motor neurons using NSC-34, a mouse motor neuron-like cell line. Exposure of undifferentiated NSC-34 cells to PGE2 and butaprost, an EP2-selective agonist, resulted in a reduction of MTT reduction activity without increase the number of propidium iodide-positive cells and in an increase in the number of neurite-bearing cells. Sulprostone, an EP1/3 agonist, also significantly lowered MTT reduction activity by 20%; however, no increase in the number of neurite-bearing cells was observed within the concentration range tested. PGE2-induced neurite outgrowth was attenuated significantly in the presence of PF-0441848, an EP2-selective antagonist. Treatment of these cells with dibutyryl-cAMP increased the number of neurite-bearing cells with no effect on cell proliferation. These results suggest that PGE2 promotes neurite outgrowth and suppresses cell proliferation by activating the EP2 subtype, and that the cAMP-signaling pathway is involved in PGE2-induced differentiation of NSC-34 cells.

Prostaglandin E2 restrains human Treg cell differentiation via E prostanoid receptor 2-protein kinase A signaling.

Regulatory T cells (Treg cells) belong to a class of immunosuppressive cells that control the pathological changes of autoimmunity and inflammation. Prostaglandin E2 (PGE2) is a potent lipid mediator of immune inflammation including rheumatoid arthritis (RA) that exerts its effects via four subtypes of G-protein-coupled receptors (EP1-4). The ability of PGE2 to regulate human Treg differentiation has not yet been reported. In the current study, we investigated the effects of PGE2 on the differentiation of naïve T cells from healthy and RA patients into Treg cells and the intracellular signaling involved in this process in vitro. Our data indicate that PGE2 negatively influenced the percentage of Treg cells and Foxp3 mRNA expression. The regulatory effects of PGE2 were associated with increased intracellular cAMP levels and PKA activity. EP2 receptors may mediate the inhibitory role of PGE2, since PGE2 actions were mimicked by EP2 agonist (Butaprost) and cAMP agonist (Sp-8-CPT-cAMPS) but were reversed by an EP2 antagonist (PF-04418948) and a PKA inhibitor (H-89). PGE2 negatively modulated the expression of cytotoxic T lymphocyte antigen-4 (CTLA-4) and glucocorticoid-induced tumor necrosis factor receptor-related protein (GITR), as well as the production of interleukin (IL)-10 by Treg cells via EP2 receptors and cAMP/PKA signaling. All these findings indicate that PGE2 can inhibit Treg differentiation mediated through the EP2-cAMP/PKA signaling pathway, and suggest novel immune-based therapies for use in RA treatment.

PTGER2 activation induces PTGS-2 and growth factor gene expression in endometrial epithelial cells of cattle.

The prostaglandin E2 receptor 2 (PTGER2) is present in the endometrium and its gene expression is accompanied with endometrial growth, however, it is unknown whether there is endometrial repair through stimulation of growth factor gene expression that is promoted by PTGER2 activation in cattle. The aim of this study was to investigate whether PTGER2 activation can induce prostaglandin-endoperoxide synthase-2 (PTGS-2) and growth factor gene expression by activating PKA and ERK signaling pathways in endometrial epithelial cells of cattle. Results demonstrated that the PTGER2 agonist, butaprost, induced cAMP/PKA and ERK activation and up-regulated PTGS-2, VEGF, CTGF, TGF-ß1 and IL-8 gene expression. These activations were less after PTGER2 antagonist, AH6809, treatment. Data suggested that PTGS-2 gene expression was induced by PTGER2 activation through the PKA and ERK pathways. Furthermore, PTGER2 activation promoted several growth factor gene expressions in endometrial epithelial cells. One potential implication of this finding is that PTGER2 activation in the endometrium of cattle could induce endometrial repair by stimulating VEGF, CTGF, TGF-ß1 and IL-8 gene expression.

PGE1 and E3 show lower efficacies than E2 to ß-catenin-mediated activity as biased ligands of EP4 prostanoid receptors.

The 2-series of prostaglandin E (PGE2 ) is regarded as a pro-cancer prostanoid, whereas the 1-series (PGE1 ) and the 3-series (PGE3 ) are considered to act as anti-cancer prostanoids. In the present study, we provide possible reasons why PGE1 and PGE3 , but not PGE2 , exert anti-cancer effects by focusing on each diverged E-type prostanoid (EP)4 receptor-mediated signaling pathway. PGE1 , PGE2 and PGE3 function as full agonists in terms of Gαs - and Gαi -protein-mediated signaling. However, PGE1 and PGE3 function as partial agonists of T-cell factor (TCF)/ß-catenin (ß-cat)-mediated activity, the well-known cancer-related signaling pathway. Furthermore, pretreatment with PGE1 or PGE3 almost completely reduces PGE2 -induced TCF/ß-cat activity. These results provide a plausible reason why PGE1 and PGE3 function as anti-cancer prostanoids as a result of novel biased activity for EP4 receptors.