Eicosanoid regulation of debris-stimulated metastasis.

Cancer therapy reduces tumor burden via tumor cell death ("debris"), which can accelerate tumor progression via the failure of inflammation resolution. Thus, there is an urgent need to develop treatment modalities that stimulate the clearance or resolution of inflammation-associated debris. Here, we demonstrate that chemotherapy-generated debris stimulates metastasis by up-regulating soluble epoxide hydrolase (sEH) and the prostaglandin E2 receptor 4 (EP4). Therapy-induced tumor cell debris triggers a storm of proinflammatory and proangiogenic eicosanoid-driven cytokines. Thus, targeting a single eicosanoid or cytokine is unlikely to prevent chemotherapy-induced metastasis. Pharmacological abrogation of both sEH and EP4 eicosanoid pathways prevents hepato-pancreatic tumor growth and liver metastasis by promoting macrophage phagocytosis of debris and counterregulating a protumorigenic eicosanoid and cytokine storm. Therefore, stimulating the clearance of tumor cell debris via combined sEH and EP4 inhibition is an approach to prevent debris-stimulated metastasis and tumor growth.

Prostaglandin E2 stimulates cAMP signaling and resensitizes human leukemia cells to glucocorticoid-induced cell death.

Glucocorticoid (GC) resistance remains a clinical challenge in pediatric acute lymphoblastic leukemia where response to GC is a reliable prognostic indicator. To identify GC resistance pathways, we conducted a genome-wide, survival-based, short hairpin RNA screen in murine T-cell acute lymphoblastic leukemia (T-ALL) cells. Genes identified in the screen interfere with cyclic adenosine monophosphate (cAMP) signaling and are underexpressed in GC-resistant or relapsed ALL patients. Silencing of the cAMP-activating Gnas gene interfered with GC-induced gene expression, resulting in dexamethasone resistance in vitro and in vivo. We demonstrate that cAMP signaling synergizes with dexamethasone to enhance cell death in GC-resistant human T-ALL cells. We find the E prostanoid receptor 4 expressed in T-ALL samples and demonstrate that prostaglandin E2 (PGE2) increases intracellular cAMP, potentiates GC-induced gene expression, and sensitizes human T-ALL samples to dexamethasone in vitro and in vivo. These findings identify PGE2 as a target for GC resensitization in relapsed pediatric T-ALL.

Prostaglandin receptor EP4 expression by Th17 cells is associated with high disease activity in ankylosing spondylitis.

BACKGROUND: Th17 cells are involved in the pathogenesis of ankylosing spondylitis (AS). However, the mechanism underlying enhanced Th17 cell accumulation in AS remains unknown. The prostaglandin E2 receptor EP2/EP4 signaling pathway plays a critical role in the development of autoimmune Th17 cells. Interestingly, recent genome-wide association studies (GWAS) have identified five risk alleles for AS in PTGER4, the gene encoding for EP4. The aim of this study was to reveal a possible link between EP4 and disease activity in patients with AS. METHODS: Th17 cells from patients with AS were analyzed for the transcriptional expression of prostaglandin receptor genes by quantitative RT-PCR. Th17 cells from patients with rheumatoid arthritis (RA) and from healthy individuals served as controls. EP4 receptor expression in Th17 cells was assessed ex vivo by flow cytometry and by western blot. Functional analysis using EP4-specific agonists was performed to reveal how EP4 regulates Th17 cells. RESULTS: EP4 is significantly overexpressed in Th17 cells from patients with AS compared to Th17 cells from healthy individuals or patients with RA or psoriatic arthritis (PsA). EP4 upregulation is unique to Th17 cells and is not found in other CD4+ T cell subsets. Specific activation of EP4 drives Th17 cell development and promotes EP4 expression in a positive feedback loop in AS but not in RA or PsA. Mechanistically, EP4 acts via upregulation of the interleukin-23 receptor (IL-23R), by suppressing the RORγt inhibitor FoxO1 and by enhancing STAT3 phosphorylation. Increased EP4 expression levels in Th17 cells from AS patients correlate with high disease activity as defined by a Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) score ≥ 4 (r = 0.7591, p = 0.0016). CONCLUSIONS: EP4 is a potential marker of disease activity in patients with AS. Aberrant EP4 expression might contribute to pathogenic Th17 cell accumulation and represent a new target for the treatment of AS.

Epithelial Cells Induce a Cyclo-Oxygenase-1-Dependent Endogenous Reduction in Airway Smooth Muscle Contractile Phenotype.

Airway smooth muscle cells (ASMCs) are phenotypically regulated to exist in either a proliferative or a contractile state. However, the influence of other airway structural cell types on ASMC phenotype is largely unknown. Although epithelial cells are known to drive ASM proliferation, their effects on the contractile phenotype are uncertain. In the current study, we tested the hypothesis that epithelial cells reduce the contractile phenotype of ASMCs. To do so, we measured force production by traction microscopy, gene and protein expression, as well as calcium release by Fura-2 ratiometric imaging. ASMCs incubated with epithelial-derived medium produced less force after histamine stimulation. We observed reduced expression of myocardin, α-smooth muscle actin, and calponin within ASMCs after coculture with epithelial cells. Peak calcium release in response to histamine was diminished, and depended on the synthesis of cyclo-oxygenase-1 products by ASM and on prostaglandin E receptors 2 and 4. Together, these in vitro results demonstrate that epithelial cells have the capacity to coordinately reduce ASM contraction by functional antagonism and by reduction of the expression of certain contractile proteins.

Inactivation of PI3-K/Akt and reduction of SP1 and p65 expression increase the effect of solamargine on suppressing EP4 expression in human lung cancer cells.

BACKGROUND: Lung cancer is the most common cause of cancer-related deaths worldwide. Natural phytochemicals from traditional medicinal plants such as solamargine have been shown to have anticancer properties. The prostaglandin E2 receptor EP4 is highly expressed in human cancer, however, the functional role of EP4 in the occurrence and progression of non small cell lung cancer (NSCLC) remained to be elucidated. METHODS: Cell viability was measured by MTT assays. Western blot was performed to measure the phosphorylation and protein expression of PI3-K downstream effector Akt, transcription factors SP1, p65, and EP4. Quantitative real-time PCR (qRT-PCR) was used to examine the mRNA levels of EP4 gene. Exogenous expression of SP1, p65, and EP4 genes was carried out by transient transfection assays. EP4 promoter activity was measured by Dual Luciferase Reporter Kit. RESULTS: We showed that solamargine inhibited the growth of lung cancer cells. Mechanistically, we found that solamargine decreased the phosphorylation of Akt, the protein, mRNA expression, and promoter activity of EP4. Moreover, solamargine inhibited protein expression of SP1 and NF-κB subunit p65, all of which were abrogated in cells transfected with exogenous expressed Akt. Intriguingly, exogenous expressed SP1 overcame the effect of solamargine on inhibition of p65 protein expression, and EP4 protein expression and promoter activity. Finally, exogenous expressed EP4 feedback reversed the effect of solamargine on phosphorylation of Akt and cell growth inhibition. CONCLUSION: Our results show that solamargine inhibits the growth of human lung cancer cells through inactivation of Akt signaling, followed by reduction of SP1 and p65 protein expression. This results in the inhibition of EP4 gene expression. The cross-talk between SP1 and p65, and the positive feedback regulatory loop of PI3-K/Akt signaling by EP4 contribute to the overall responses of solamargine in this process. This study unveils a novel mechanism by which solamargine inhibits growth of human lung cancer cells.

EP4 Receptor-Associated Protein in Macrophages Ameliorates Colitis and Colitis-Associated Tumorigenesis.

Prostaglandin E2 plays important roles in the maintenance of colonic homeostasis. The recently identified prostaglandin E receptor (EP) 4-associated protein (EPRAP) is essential for an anti-inflammatory function of EP4 signaling in macrophages in vitro. To investigate the in vivo roles of EPRAP, we examined the effects of EPRAP on colitis and colitis-associated tumorigenesis. In mice, EPRAP deficiency exacerbated colitis induced by dextran sodium sulfate (DSS) treatment. Wild-type (WT) or EPRAP-deficient recipients transplanted with EPRAP-deficient bone marrow developed more severe DSS-induced colitis than WT or EPRAP-deficient recipients of WT bone marrow. In the context of colitis-associated tumorigenesis, both systemic EPRAP null mutation and EPRAP-deficiency in the bone marrow enhanced intestinal polyp formation induced by azoxymethane (AOM)/DSS treatment. Administration of an EP4-selective agonist, ONO-AE1-329, ameliorated DSS-induced colitis in WT, but not in EPRAP-deficient mice. EPRAP deficiency increased the levels of the phosphorylated forms of p105, MEK, and ERK, resulting in activation of stromal macrophages in DSS-induced colitis. Macrophages of DSS-treated EPRAP-deficient mice exhibited a marked increase in the expression of pro-inflammatory genes, relative to WT mice. By contrast, forced expression of EPRAP in macrophages ameliorated DSS-induced colitis and AOM/DSS-induced intestinal polyp formation. These data suggest that EPRAP in macrophages functions crucially in suppressing colonic inflammation. Consistently, EPRAP-positive macrophages were also accumulated in the colonic stroma of ulcerative colitis patients. Thus, EPRAP may be a potential therapeutic target for inflammatory bowel disease and associated intestinal tumorigenesis.

Salt restriction leads to activation of adult renal mesenchymal stromal cell-like cells via prostaglandin E2 and E-prostanoid receptor 4.

Despite the importance of juxtaglomerular cell recruitment in the pathophysiology of cardiovascular diseases, the mechanisms that underlie renin production under conditions of chronic stimulation remain elusive. We have previously shown that CD44+ mesenchymal-like cells (CD44+ cells) exist in the adult kidney. Under chronic sodium deprivation, these cells are recruited to the juxtaglomerular area and differentiate to new renin-expressing cells. Given the proximity of macula densa to the juxtaglomerular area and the importance of macula densa released prostanoids in renin synthesis and release, we hypothesized that chronic sodium deprivation induces macula densa release of prostanoids, stimulating renal CD44+ cell activation and differentiation. CD44+ cells were isolated from adult kidneys and cocultured with the macula densa cell line, MMDD1, in normal or low-sodium medium. Low sodium stimulated prostaglandin E2 production by MMDD1 and induced migration of CD44+ cells. These effects were inhibited by addition of a cyclooxygenase 2 inhibitor (NS398) or an E-prostanoid receptor 4 antagonist (AH23848) to MMDD1 or CD44+ cells, respectively. Addition of prostaglandin E2 to CD44+ cells increased cell migration and induced renin expression. In vivo activation of renal CD44+ cells during juxtaglomerular recruitment was attenuated in wild-type mice subjected to salt restriction in the presence of cyclooxygenase 2 inhibitor rofecoxib. Similar results were observed in E-prostanoid receptor 4 knockout mice subjected to salt restriction. These results show that the prostaglandin E2/E-prostanoid receptor 4 pathway plays a key role in the activation of renal CD44+ mesenchymal stromal cell-like cells during conditions of juxtaglomerular recruitment; highlighting the importance of this pathway as a key regulatory mechanism of juxtaglomerular recruitment.

Transforming growth factor ß2 promotes transcription of COX2 and EP4, leading to a prostaglandin E2-driven autostimulatory loop that enhances virulence of Theileria annulata-transformed macrophages.

Transforming growth factor beta (TGF-ß) is a pleiotropic cytokine known to regulate cell growth, differentiation, and motility and is a potent modulator of immune function. TGF-ß consequently plays a central role in carcinogenesis, and a dampened TGF-ß2 response by Theileria annulata-infected monocytes/macrophages underpins disease resistance to tropical theileriosis. Here, we show that concomitant with the loss of TGF-ß2 production, there is ablated expression of COX2 and EP4, which leads to a drop in cyclic AMP (cAMP) levels and, consequently, reduced activation of protein kinase A (PKA) and EPAC. This ablated phenotype can be rescued in attenuated macrophages by the addition of exogenous TGF-ß2, which reactivates the expression of COX2 and EP4 while repressing that of protein kinase inhibitor gamma (PKIG) to the levels in virulent macrophages. TGF-ß2 therefore promotes the adhesion and invasiveness of virulent macrophages by modulating COX2, EP4, and PKIG transcription to initiate a prostaglandin E2 (PGE2)-driven autostimulatory loop that augments PKA and EPAC activities. A virulence phenotype stemming from the double activation of PKA and EPAC is the induction of a CREB-mediated transcriptional program and the upregulation of JAM-L- and integrin 4αß1-mediated adhesion of Theileria-infected macrophages.

Distribution of EP4 receptor in different Atlantic salmon (Salmo salar L.) tissues.

Prostaglandin E2 (PGE2) is an important lipid mediator that plays diverse functions in mammals. Four receptor subtypes of PGE2, designated EP1-4, have been identified to mediate its signaling pathways. Extensive studies of PGE2 and its receptors have been carried out in mammals, but little is known in fish, including Atlantic salmon. In the current study, the distribution of Atlantic salmon EP4 receptor in different tissues was investigated using RT- and real-time PCR. A custom made antibody was used to investigate the distribution of this receptor in different tissues. Quantitative analysis by real-time PCR revealed that the expression was more abundant in the spleen followed by head kidney, skin and fin while it was least expressed in heart, muscles and brain. The staining intensity obtained by immunohistochemistry correlated with the RT-PCR results. EP4 expression was strongly associated with the immune cells in different tissues. To our knowledge, this is the first study to describe the distribution of EP4 receptor in Atlantic salmon tissues. Our findings suggest that EP4 may play a role in mediating immune responses as observed in mammals.

Ultraviolet radiation-induced inflammation activates ß-catenin signaling in mouse skin and skin tumors.

UVB-induced inflammation, in particular the overexpression of cyclooxygenase-2 (COX-2) and prostaglandin (PG) E2, has been implicated in photocarcinogenesis. UVB-induced COX-2 has been associated with ß-catenin signaling in keratinocytes. However, a definitive role for COX-2 in the activation of ß-catenin signaling as well as its role in UVB-induced skin tumors has not been established. We report that exposure of the skin to UVB resulted in a time- and dose-dependent activation of ß-catenin in C3H/HeN mice. This response was COX-2-dependent as UVB-exposed COX-2-deficient mice exhibited significantly lower levels of UVB-induced activation of ß-catenin. Moreover, treatment of mice with indomethacin, a COX-2 inhibitor, and an EP2 antagonist inhibited UVB-induced ß-catenin signaling. Exposure of SKH-1 hairless mice to UVB radiation (180 mJ/cm2) 3 times a week for 24 weeks resulted in activation of ß-catenin signaling in UVB-irradiated skin as well as UVB-induced skin tumors. Concomitantly, the levels of CK1α and GSK-3ß, which are responsible for ß-catenin signaling, were reduced while the levels of c-Myc and cyclin D1, which are downstream targets of ß-catenin, were increased. To further verify the role of UVB-induced inflammation in activation of ß-catenin signaling, a high-fat-diet model was used. Administration of high-fat diet exacerbated UVB-induced inflammation. Administration of the high-fat diet enhanced ß-catenin signaling and the levels of its downstream targets (c-Myc, cyclin D1, cyclin D2, MMP-2 and MMP-9) in UVB-exposed skin and skin tumors in SKH-1 mice. These data suggest that UV-induced COX-2/PGE2 stimulates ß-catenin signaling, and that ß-catenin activation may contribute to skin carcinogenesis.

PGE2/EP4 signaling in peripheral immune cells promotes development of experimental autoimmune encephalomyelitis.

Experimental autoimmune encephalomyelitis (EAE) is a T cell-mediated inflammatory autoimmune disease model of multiple sclerosis (MS). The inflammatory process is initiated by activation and proliferation of T cells and monocytes and by their subsequent migration into the central nervous system (CNS), where they induce demyelination and neurodegeneration. Prostaglandin E2 (PGE2) - synthesized by cyclooxygenase 2 (COX-2) - has both pro- and anti-inflammatory potential, which is translated via four different EP receptors. We hypothesized that PGE2 synthesized in the preclinical phase by peripheral immune cells exerts pro-inflammatory properties in the EAE model. To investigate this, we used a bone marrow transplantation model, which enables PGE2 synthesis or EP receptor expression to be blocked specifically in peripheral murine immune cells. Our results reveal that deletion of COX-2 or its EP4 receptor in bone marrow-derived cells leads to a significant delay in the onset of EAE. This effect is due to an impaired preclinical inflammatory process indicated by a reduced level of the T cell activating interleukin-6 (IL-6), reduced numbers of T cells and of the T cell secreted interleukin-17 (IL-17) in the blood of mice lacking COX-2 or EP4 in peripheral immune cells. Moreover, mice lacking COX-2 or EP4 in bone marrow-derived cells show a reduced expression of matrix metalloproteinase 9 (MMP9), which results in decreased infiltration of monocytes and T cells into the CNS. In conclusion, our data demonstrate that PGE2 synthesized by monocytes in the early preclinical phase promotes the development of EAE in an EP4 receptor dependent manner.

Significance of divergent expression of prostaglandin EP4 and EP3 receptors in human prostate cancer.

PGE2 has been implicated in prostate cancer tumorigenesis. We hypothesized that abnormal prostaglandin receptor (EPR) expression may contribute to prostate cancer growth. Twenty-six archived radical prostatectomy specimens were evaluated by immunohistochemistry (IHC) and Western blotting for the expression of EP1, EP2, EP3, and EP4. As a corollary, EPR expression in one normal (PZ-HPV7) and four prostate cancer cell lines (CA-HPV10, LNCaP, PC3, and Du145) were assessed by Western blotting. Prostate cancer and normal cell growth were compared in vitro after EPR blockade, siRNA EPR knockdown, or overexpression. EP1, EP2, EP3, and EP4 receptors were detected by IHC in all areas of benign tissue within the clinical prostate cancer specimens. In areas of prostate cancer, EP4 and EP2 were overexpressed in 85% (22 of 26) and 75% (18 of 24) and EP3 expression was reduced in all (26 of 26, 100%) specimens (P < 0.05 vs. benign tissue). EP1 showed no specific differential expression pattern. Increased EP4 and reduced EP3 was confirmed by Western blotting in fresh clinical specimens and in prostate cancer cell lines (CA-HPV10, LNCaP, PC3, and Du145) compared with the normal prostate cell line (PZ-HPV7). EP2 and EP4 siRNA knockdown resulted in reduced in vitro growth and metastasis-related gene expression (MMP9 and Runx2) of prostate cancer lines, and in vitro migration was inhibited by EP4 antagonists. As a corollary, EP3-overexpressing PC3 cells displayed impaired growth in vitro. Human prostate cancer is associated with EP4 and EP2 overexpression and reduced EP3 expression. These data suggest that targeting specific EPR may represent a novel therapeutic approach for prostate cancer.

PGE2 differentially regulates monocyte-derived dendritic cell cytokine responses depending on receptor usage (EP2/EP4).

Dendritic cells (DCs) are central players in coordinating immune responses, both innate and adaptive. While the role of lipid mediators in the immune response has been the subject of many investigations, the precise role of prostaglandins has often been plagued by contradictory studies. In this study, we examined the role of PGE(2) on human DC function. Although studies have suggested that PGE(2) specifically plays a role in DC motility and cytokine release profile, the precise receptor usage and signaling pathways involved remain unclear. In this report we found that irrespective of the human donor, monocyte-derived dendritic cells (MoDCs) express three of the four PGE(2) receptor subtypes (EP(2-4)), although only EP(2) and EP(4) were active with respect to cytokine production. Using selective EP receptor antagonists and agonists, we demonstrate that PGE(2) coordinates control of IL-23 release (a promoter of Th17, an autoimmune associated T cell subset) in a dose-dependent manner by differential use of EP(2) and EP(4) receptors in LPS-activated MoDCs. This is in contrast to IL-12, which is dose dependently inhibited by PGE(2) through both receptor subtypes. Low concentrations (∼1-10nM) of PGE(2) promoted IL-23 production via EP(4) receptors, while at higher (>50 nM), but still physiologically relevant concentrations, IL-23 is suppressed by an EP(2) dependent mechanism. These results can be explained by differential regulation of the common subunit, IL-12p40, and IL-23p19, by EP(2) and EP(4). By these means, PGE(2) can act as a regulatory switch of immune responses depending on its concentration in the microenvironment. In addition, we believe these results may also explain why seemingly conflicting biological functions assigned to PGE(2) have been reported in the literature, as the concentration of ligand (PGE(2)) fundamentally alters the nature of the response. This finding also highlights the potential of designing therapeutics which differentially target these receptors.

The effect of probiotic-fermented soy milk on enhancing the NO-mediated vascular relaxation factors.

BACKGROUND: Soy milk is one of the common soy-based foods in Asia. In this study the effects of soy milk fermented with selected probiotics on nitric oxide (NO)-mediated vascular relaxation factors in cell model systems were investigated. RESULTS: Soy milk fermented with Lactobacillus plantarum TWK10 or Streptococcus thermophilus BCRC 14085 for 48 h showed a greater transformation of glucoside isoflavones to aglycone isoflavones (P < 0.05). An increase in aglycone isoflavones in ethanol extracts from fermented soy milk stimulated NO production and endothelial NO synthase (eNOS) activity in human umbilical vein endothelial cells. It also had a stimulating effect on superoxide anion scavenging and prostaglandin E2 production. In addition, it enhanced mRNA expression of the E-prostanoid 4 receptor in rat thoracic aorta smooth muscle cells. Moreover, a small amount of O2⁻ induced by water extracts from fermented soy milk at low concentration (1 mg mL⁻¹) increased the content of calcium ions and activated eNOS, thereby promoting NO production and the coupling state of eNOS. CONCLUSION: Soy milk fermented with selected probiotics promotes the relaxation factors of vascular endothelial cells and can be applied in the development of functional foods.

Immunolocalization of adipocytes and prostaglandin E2 and its four receptor proteins EP1, EP2, EP3, and EP4 in the caprine cervix during spontaneous term labor.

The mechanisms of cervical ripening and dilation in mammals remain obscure. Information is lacking about the localization of prostaglandin E(2) (PGE(2))-producing cells and PGE(2) receptors (EP) in intrapartum cervix and whether cervical dilation at parturition is an active process. To reveal these mechanisms, immunolocalization of EP1-EP4 (official gene symbols PTGER1-PTGER4) and PGE(2)-producing cells in caprine cervix during nonpregnancy, pregnancy, and parturition was assayed by immunohistochemistry (IHC); the mRNA expression levels of PTGS2, PTGER2 (EP2), and PTGER4 (EP4) were determined using quantitative PCR; and the existence of adipocytes in the cervix at various stages was demonstrated with Oil Red O staining and IHC of perilipin A. The results suggested that in intrapartum caprine cervix staining of the PGE(2) was observed in the overall tissues, for example, blood vessels, canal or glandular epithelia, serosa, circular and longitudinal muscles, and stroma in addition to adipocytes; EP2 was detectable in all the tissues other than glandular epithelia; EP4 was strongly expressed in all the tissues other than serosa; EP1 was detected mainly in arterioles and canal or glandular epithelia; and EP3 was poorly expressed only in stroma, canal epithelia, and circular muscles. Little or no expression of EP2, EP3, and EP4 as well as PGE(2) in all cervical tissues was observed during nonpregnancy and pregnancy except for the strong expression of EP1 in canal or glandular epithelia during pregnancy. The mRNA expression levels of PTGS2, PTGER2, and PTGER4 were significantly higher in intrapartum than nonpregnant and midpregnant cervices (P < 0.01). Adipocytes appear only in the intrapartum cervix. These results support the concept that PGE(2) modulates specific functions in various anatomical structures of the caprine cervix at labor and the appearance of adipocytes at labor is likely related to caprine cervical dilation.

Bladder outlet obstruction induced expression of prostaglandin E2 receptor subtype EP4 in the rat bladder: a possible counteractive mechanism against detrusor overactivity.

PURPOSE: Prostaglandins have been implicated as endogenous modulators of bladder function under physiological and pathological conditions. We examined how the expression of each EP receptor subtype changed in association with bladder outlet obstruction and focused on the functional role of EP4 receptor subtype in the bladder with outlet obstruction. MATERIALS AND METHODS: We assessed the gene expression of EP receptor subtypes by reverse transcriptase-polymerase chain reaction. EP4 protein localization was determined by immunohistochemistry. The effect of the selective EP4 agonist ONO-AE1-329 on 50 mM KCl induced contraction of rat bladder strips was examined in vitro. Continuous infusion cystometrograms were done to examine the effect of intravesical perfusion of ONO-AE1-329 on the micturition reflex in urethane anesthetized rats. RESULTS: EP4 receptor genes were largely expressed in bladders with outlet obstruction but absent in controls. EP4 receptor proteins were clearly detected in obstructed bladder detrusor smooth muscle and epithelium. ONO-AE1-329 (100 µM) significantly relaxed KCl induced contraction of bladder strips from rats with bladder outlet obstruction. A significant correlation was found between the relaxant effect of ONO-AE1-329 and whole bladder weight. In rats with bladder outlet obstruction intravesical infusion of 10 µM ONO-AE1-329 significantly increased bladder capacity without changing micturition pressure while it had no effect in controls. CONCLUSIONS: Activation of the EP4 receptors expressed in bladders with outlet obstruction may suppress detrusor muscle contraction and afferent activity. This might be a compensatory mechanism to counteract the deterioration of storage function in bladders with outlet obstruction.

Function of prostaglandin E2 EP receptors in the acute outcome of rodent hypoxic ischemic encephalopathy.

Neonatal hypoxic-ischemic encephalopathy (HIE) is a leading cause of severe and permanent neurologic disability after birth. The inducible cyclooxygenase COX-2, which along with COX-1 catalyzes the first committed step in prostaglandin (PG) synthesis, elicits significant brain injury in models of cerebral ischemia; however its downstream PG receptor pathways trigger both toxic and paradoxically protective effects. Here, we investigated the function of PGE(2) E-prostanoid (EP) receptors in the acute outcome of hypoxic-ischemic (HI) injury in the neonatal rat. We determined the temporal and cellular expression patterns of the EP1-4 receptors before and after HIE and tested whether modulation of EP1-4 receptor function could protect against cerebral injury acutely after HIE. All four EP receptors were expressed in forebrain neurons and were induced in endothelial cells after HIE. Inhibition of EP1 signaling with the selective antagonist SC-51089 or co-activation of EP2-4 receptors with the agonist misoprostol significantly reduced HIE cerebral injury 24 h after injury. These receptor ligands also protected brain endothelial cells subjected to oxygen glucose deprivation, suggesting that activation of EP receptor signaling is directly cytoprotective. These data indicate that the G-protein coupled EP receptors may be amenable to pharmacologic targeting in the acute setting of neonatal HIE.

Prostaglandin E2 regulates renal cell carcinoma invasion through the EP4 receptor-Rap GTPase signal transduction pathway.

Prognosis for patients with early stage kidney cancer has improved, but the treatment options for patients with locally advanced disease and metastasis remain few. Understanding the molecular mechanisms that regulate invasion and metastasis is critical for developing successful therapies to treat these patients. Proinflammatory prostaglandin E(2) plays an important role in cancer initiation and progression via activation of cognate EP receptors that belong to the superfamily of G protein-coupled receptors. Here we report that prostaglandin E(2) promotes renal cancer cell invasion through a signal transduction pathway that encompasses EP4 and small GTPase Rap. Inactivation of Rap signaling with Rap1GAP, like inhibition of EP4 signaling with ligand antagonist or knockdown with shRNA, reduces the kidney cancer cell invasion. Human kidney cells evidence increased EP4 and decreased Rap1GAP expression levels in the malignant compared with benign samples. These results support the idea that targeted inhibition of EP4 signaling and restoration of Rap1GAP expression constitute a new strategy to control kidney cancer progression.