Role Of PGE2 Research Articles

The COX-2-PGE2 Pathway Promotes Tumor Evasion in Colorectal Adenomas.

These findings provide a potential explanation underlying the chemopreventive effect of NSAIDs on reducing colorectal cancer incidence during premalignancy and provide a rationale for developing EP4 antagonists for colorectal cancer prevention and treatment. Simply targeting PGE2 signaling alone may be efficacious in colorectal cancer prevention and treatment, avoiding side effects associated with NSAIDs.

The Role of PGE2 and EP Receptors on Lung's Immune and Structural Cells; Possibilities for Future Asthma Therapy

The Role of PGE2 and EP Receptors on Lung's Immune and Structural Cells; Possibilities for Future Asthma Therapy

Investigations on the potential role of prostaglandin E2 in canine uterine inertia

Prostaglandin (PG) E2 plays a crucial role in the endocrine network of canine parturition and we hypothesized that PGE2, 15-hydroxyprostaglandin dehydrogenase (HPGD) and PG-transporter (PGT) might be involved in the development of primary uterine inertia (PUI). We investigated PTGE synthase (PTGES), PTGE receptors 2/4 (PTGER2/4), HPGD and PGT expression on the mRNA- and protein-level in interplacental (IP) and uteroplacental (UP) tissues of bitches presented with dystocia undergoing emergency caesarean section. Groups were formed retrospectively based on strict criteria: PUI (n = 12; small/normal/large litter - PUI-S/N/L: n = 5/4/3), and obstructive dystocia (OD, n = 8). Respective mRNA expressions (ratio) between PUI and OD in IP and UP, between PUI dogs with different litter sizes, between PUI-N and OD in IP, and overall between IP and UP were compared. PTGES, PTGER2, PTGER4, HPGD and PGT mRNA expressions did not differ significantly between PUI and OD in IP or UP. PUI-N PTGES mRNA expression was higher than PUI-S/L (P = 0.0203/P = 0.0186) and OD (P = 0.0314). Higher PTGES (P = 0.0112) and a tendency for higher PTGER2 (P = 0.059) mRNA-expressions were detected in UP versus IP. Other than hypothesized, we did not find a difference in PGE2 production and signaling between PUI and OD, indicating that altered uterine PTGES, PTGER2, PTGER4, HPGD and PGT expression was likely not causative for PUI. However, higher PTGES expression in PUI-N compared to OD might point to a possible role of PGE2 during the course of parturition. Higher PTGES expression in PUI-N compared to PUI-S/L indicates an influence of litter size, the underlying cause and biological relevance of which remain to be clarified.

Role of PGE2 in colonic motility: PGE2 attenuates spontaneous contractions of circular smooth muscle via EP4 receptors in the rat colon

Colonic motor activity is important for the formation and propulsion of feces. The production of prostaglandins (PGs) in colonic tissue is considered to play a critical role in the generation and regulation of colonic motility. In this study, we investigated the inhibitory effects of PGE2 and selective agonists of four EP receptors on the spontaneous phasic contractions, called ‘giant contractions’ (GCs), of mucosa-free circular smooth muscle strips from the rat middle colon. Neural blockade with tetrodotoxin (TTX) increased the frequency and amplitude of the GCs by about twofold. However, inhibiting PG production with piroxicam reduced the GC frequency in the presence of TTX, but did not affect the GC amplitude. In the presence of both TTX and piroxicam, exogenous PGE2 and each EP receptor agonist were cumulatively added to the tissue bath. In this setting, PGE2, the EP2 agonist ONO-AE1-259, and the EP4 agonist ONO-AE1-329, but not the EP1 agonist ONO-AE-DI-004 or the EP3 agonist ONO-AE-248, concentration-dependently reduced the GC frequency and amplitude. The PGE2-induced inhibition of GC frequency and amplitude was inhibited by the EP4 antagonist ONO-AE3-208, but not by the EP1/2 antagonist AH6809. Immunohistochemistry revealed the EP2 and EP4 receptors were localized in perinuclear sites in circular smooth muscle cells. EP2 immunoreactivity was also located in GFAP-immunoreactive enteroglia, whereas EP4 immunoreactivity was also located in HU (embryonic lethal, abnormal vision [ELAV] protein; a marker of all myenteric neurons)-immunoreactive myenteric nerve cell bodies. These results suggest that the PGs produced in the colonic tissue inhibit the GC frequency and amplitude of circular muscle in the rat middle colon, and is mediated by EP4 receptors expressed in the smooth muscle cells.

Eicosanoids in Cancer: New Roles in Immunoregulation.

Eicosanoids represent a family of active biolipids derived from arachidonic acid primarily through the action of cytosolic phospholipase A2-α. Three major downstream pathways have been defined: the cyclooxygenase (COX) pathway which produces prostaglandins and thromboxanes; the 5-lipoxygenase pathway (5-LO), which produces leukotrienes, lipoxins and hydroxyeicosatetraenoic acids, and the cytochrome P450 pathway which produces epoxygenated fatty acids. In general, these lipid mediators are released and act in an autocrine or paracrine fashion through binding to cell surface receptors. The pattern of eicosanoid production is cell specific, and is determined by cell-specific expression of downstream synthases. Increased eicosanoid production is associated with inflammation and a panel of specific inhibitors have been developed designated non-steroidal anti-inflammatory drugs. In cancer, eicosanoids are produced both by tumor cells as well as cells of the tumor microenvironment. Earlier studies demonstrated that prostaglandin E2, produced through the action of COX-2, promoted cancer cell proliferation and metastasis in multiple cancers. This resulted in the development of COX-2 inhibitors as potential therapeutic agents. However, cardiac toxicities associated with these agents limited their use as therapeutic agents. The advent of immunotherapy, especially the use of immune checkpoint inhibitors has revolutionized cancer treatment in multiple malignancies. However, the majority of patients do not respond to these agents as monotherapy, leading to intense investigation of other pathways mediating immunosuppression in order to develop rational combination therapies. Recent data have indicated that PGE2 has immunosuppressive activity, leading to renewed interest in targeting this pathway. However, little is known regarding the role of other eicosanoids in modulating the tumor microenvironment, and regulating anti-tumor immunity. This article reviews the role of eicosanoids in cancer, with a focus on their role in modulating the tumor microenvironment. While the role of PGE2 will be discussed, data implicating other eicosanoids, especially products produced through the lipoxygenase and cytochrome P450 pathway will be examined. The existence of small molecular inhibitors and activators of eicosanoid pathways such as specific receptor blockers make them attractive candidates for therapeutic trials, especially in combination with novel immunotherapies such as immune checkpoint inhibitors.

PECULIARITIES OF THE COURSE AND TREATMENT OF GASTROESOPHAGEAL REFLUX DISEASE IN PATIENTS WITH SYNDROME OF UNDIFFERENTIATED CONNECTIVE TISSUE DYSPLASIA. (SYSTEMATIC LITERATURE REVIEW)

PECULIARITIES OF THE COURSE AND TREATMENT OF GASTROESOPHAGEAL REFLUX DISEASE IN PATIENTS WITH SYNDROME OF UNDIFFERENTIATED CONNECTIVE TISSUE DYSPLASIA. (SYSTEMATIC LITERATURE REVIEW)

An ARC-Regulated IL1β/Cox-2/PGE2/β-Catenin/ARC Circuit Controls Leukemia-Microenvironment Interactions and Confers Drug Resistance in AML.

The apoptosis repressor with caspase recruitment domain (ARC) protein is a strong independent adverse prognostic marker in acute myeloid leukemia (AML). We previously reported that ARC regulates leukemia-microenvironment interactions through the NFκB/IL1β signaling network. Malignant cells have been reported to release IL1β, which induces PGE2 synthesis in mesenchymal stromal cells (MSC), in turn activating β-catenin signaling and inducing the cancer stem cell phenotype. Although Cox-2 and its enzymatic product PGE2 play major roles in inflammation and cancer, the regulation and role of PGE2 in AML are largely unknown. Here, we report that AML-MSC cocultures greatly increase Cox-2 expression in MSC and PGE2 production in an ARC/IL1β-dependent manner. PGE2 induced the expression of β-catenin, which regulated ARC and augmented chemoresistance in AML cells; inhibition of β-catenin decreased ARC and sensitized AML cells to chemotherapy. NOD/SCIDIL2RγNull-3/GM/SF mice transplanted with ARC-knockdown AML cells had significantly lower leukemia burden, lower serum levels of IL1β/PGE2, and lower tissue human ARC and β-catenin levels, prolonged survival, and increased sensitivity to chemotherapy than controls. Collectively, we present a new mechanism of action of antiapoptotic ARC by which ARC regulates PGE2 production in the tumor microenvironment and microenvironment-mediated chemoresistance in AML.Significance: The antiapoptotic protein ARC promotes AML aggressiveness by enabling detrimental cross-talk with bone marrow mesenchymal stromal cells.

Role of PGE-2 and Other Inflammatory Mediators in Skin Aging and Their Inhibition by Topical Natural Anti-Inflammatories

Human skin aging is due to two types of aging processes, “intrinsic” (chronological) aging and “extrinsic” (external factor mediated) aging. While inflammatory events, triggered mainly by sun exposure, but also by pollutants, smoking and stress, are the principle cause of rapid extrinsic aging, inflammation also plays a key role in intrinsic aging. Inflammatory events in the skin lead to a reduction in collagen gene activity but an increase in activity of the genes for matrix metalloproteinases. Inflammation also alters proliferation rates of cells in all skin layers, causes thinning of the epidermis, a flattening of the dermo-epidermal junction, an increase in irregular pigment production, and, finally, an increased incidence of skin cancer. While a large number of inflammatory mediators, including IL-1, TNF-alpha and PGE-2, are responsible for many of these damaging effects, this review will focus primarily on the role of PGE-2 in aging. Levels of this hormone-like mediator increase quickly when skin is exposed to ultraviolet radiation (UVR), causing changes in genes needed for normal skin structure and function. Further, PGE-2 levels in the skin gradually increase with age, regardless of whether or not the skin is protected from UVR, and this smoldering inflammation causes continuous damage to the dermal matrix. Finally, and perhaps most importantly, PGE-2 is strongly linked to skin cancer. This review will focus on: (1) the role of inflammation, and particularly the role of PGE-2, in accelerating skin aging, and (2) current research on natural compounds that inhibit PGE-2 production and how these can be developed into topical products to retard or even reverse the aging process, and to prevent skin cancer.

T cell–intrinsic prostaglandin E2-EP2/EP4 signaling is critical in pathogenic TH17 cell–driven inflammation

BackgroundIL-23 is the key cytokine for generation of pathogenic IL-17–producing helper T (TH17) cells, which contribute critically to autoimmune diseases. However, how IL-23 generates pathogenic TH17 cells remains to be elucidated.ObjectivesWe sought to examine the involvement, molecular mechanisms, and clinical implications of prostaglandin (PG) E2–EP2/EP4 signaling in induction of IL-23–driven pathogenic TH17 cells.MethodsThe role of PGE2 in induction of pathogenic TH17 cells was investigated in mouse TH17 cells in culture in vitro and in an IL-23–induced psoriasis mouse model in vivo. Clinical relevance of the findings in mice was examined by using gene expression profiling of IL-23 and PGE2-EP2/EP4 signaling in psoriatic skin from patients.ResultsIL-23 induces Ptgs2, encoding COX2 in TH17 cells, and produces PGE2, which acts back on the PGE receptors EP2 and EP4 in these cells and enhances IL-23–induced expression of an IL-23 receptor subunit gene, Il23r, by activating signal transducer and activator of transcription (STAT) 3, cAMP-responsive element binding protein 1, and nuclear factor κ light chain enhancer of activated B cells (NF-κB) through cyclic AMP–protein kinase A signaling. This PGE2 signaling also induces expression of various inflammation-related genes, which possibly function in TH17 cell–mediated pathology. Combined deletion of EP2 and EP4 selectively in T cells suppressed accumulation of IL-17A+ and IL-17A+IFN-γ+ pathogenic Th17 cells and abolished skin inflammation in an IL-23–induced psoriasis mouse model. Analysis of human psoriatic skin biopsy specimens shows positive correlation between PGE2 signaling and the IL-23/TH17 pathway.ConclusionsT cell–intrinsic EP2/EP4 signaling is critical in IL-23–driven generation of pathogenic TH17 cells and consequent pathogenesis in the skin.

The prostaglandin E2 receptor EP3 controls CC-chemokine ligand 2–mediated neuropathic pain induced by mechanical nerve damage

Prostaglandin (PG) E2 is an important lipid mediator that is involved in several pathophysiological processes contributing to fever, inflammation, and pain. Previous studies have shown that early and continuous application of nonsteroidal anti-inflammatory drugs significantly reduces pain behavior in the spared nerve injury (SNI) model for trauma-induced neuropathic pain. However, the role of PGE2 and its receptors in the development and maintenance of neuropathic pain is incompletely understood but may help inform strategies for pain management. Here, we sought to define the nociceptive roles of the individual PGE2 receptors (EP1-4) in the SNI model using EP knockout mice. We found that PGE2 levels at the site of injury were increased and that the expression of the terminal synthase for PGE2, cytosolic PGE synthase was up-regulated in resident positive macrophages located within the damaged nerve. Only genetic deletion of the EP3 receptor affected nociceptive behavior and reduced the development of late-stage mechanical allodynia as well as recruitment of immune cells to the injured nerve. Importantly, EP3 activation induced the release of CC-chemokine ligand 2 (CCL2), and antagonists against the CCL2 receptor reduced mechanical allodynia in WT but not in EP3 knockout mice. We conclude that selective inhibition of EP3 might present a potential approach for reducing chronic neuropathic pain.

The Role of PGE2 in Alveolar Epithelial and Lung Microvascular Endothelial Crosstalk

Disruption of the blood-air barrier, which is formed by lung microvascular endothelial and alveolar epithelial cells, is a hallmark of acute lung injury. It was shown that alveolar epithelial cells release an unidentified soluble factor that enhances the barrier function of lung microvascular endothelial cells. In this study we reveal that primarily prostaglandin (PG) E2 accounts for this endothelial barrier-promoting activity. Conditioned media from alveolar epithelial cells (primary ATI-like cells) collected from BALB/c mice and A549 cells increased the electrical resistance of pulmonary human microvascular endothelial cells, respectively. This effect was reversed by pretreating alveolar epithelial cells with a cyclooxygenase-2 inhibitor or by blockade of EP4 receptors on endothelial cells, and in A549 cells also by blocking the sphingosine-1-phosphate1 receptor. Cyclooxygenase-2 was constitutively expressed in A549 cells and in primary ATI-like cells, and was upregulated by lipopolysaccharide treatment. This was accompanied by enhanced PGE2 secretion into conditioned media. Therefore, we conclude that epithelium-derived PGE2 is a key regulator of endothelial barrier integrity via EP4 receptors under physiologic and inflammatory conditions. Given that pharmacologic treatment options are still unavailable for diseases with compromised air-blood barrier, like acute lung injury, our data thus support the therapeutic potential of selective EP4 receptor agonists.

Abstract 654: Impact of epithelial cell-specific deletion of mPGES-1 on colon carcinogenesis

Abstract Activation of the COX-2/mPGES-1/PGE2 signaling axis is a hallmark of many cancers, including colorectal cancer (CRC), prompting the implementation of cancer prevention strategies targeting COX-2 activity. We have shown that targeting the downstream terminal PGE2 synthase, mPGES-1, specifically reduces inducible PGE2 formation without disrupting synthesis of other essential prostanoids. Additionally, global deletion of mPGES-1 (gKO) confers dramatic protection against intestinal cancer development in several mouse models, including the AOM+DSS inflammation-associated colon cancer model. Understanding the role of PGE2 under inflammatory conditions, however, is complicated by the diverse cellular sources and context-dependence of inducible PGE2. To clarify the relative contribution of inducible PGE2 synthesis within distinct cell compartments in colon, we have recently created an mPGES-1 conditional knockout mouse (cKO), where exon 3 of the mPGES-1 gene (mPtges) is floxed for tissue-specific Cre-mediated deletion. To test the role of epithelial-derived PGE2 synthesis on inflammation-associated cancer, we crossed the cKO mice with carbonic anhydrase 1 (Car1)-controlled Cre mice (cKO:Car1), thereby inactivating mPGES-1 function specifically within colonic epithelial cells. Based on our recent observation that global inactivation mPGES-1 sensitizes the colonic mucosa to direct environmental injury, we first examined the sensitivity of the cKO:Car1 mice to DSS-induced acute colitis. Two days after a five-day treatment with 0, 0.5 or 1% DSS, clinical signs of colitis, including the extent of colonic ulceration were determined. Both cKO:Car1 and cKO:WT control mice showed a comparable extent of colonic ulceration, covering ∼60% of the epithelial surface. We next examined the impact of epithelial-specific deletion of mPGES-1 on DSS-induced colon carcinogenesis. KO:Car1 and cKO:WT control mice were treated with a single injection of AOM (10 mg/kg bw) followed by five days of 0, 0.5 or 1% DSS, and colons were examined five weeks after the end of DSS treatment. Surprisingly, epithelial deletion of mPGES-1 in the cKO:Car1 mice failed to provide against cancer development in comparison to the cKO:WT mice. This is the first study to show that genetic inactivation of inducible PGE2 formation within a specific cell lineage (e.g. epithelial cells) does not affect both the extent of acute colonic inflammation nor subsequent inflammation-associated carcinogenesis. Citation Format: Masako Nakanishi, Daniel W. Rosenberg. Impact of epithelial cell-specific deletion of mPGES-1 on colon carcinogenesis. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 654.

Effect of Inflammatory Cytokines on DNA Methylation and Demethylation

ObjectiveTo determine the effects of inflammatory cytokines and mediators on expression of DNMT and TET enzymes in human gingival fibroblasts isolated from patients with periodontitis as well as normal and transformed cell lines.MethodsExpression levels of DNA methylatransferase (DNMT1 and 3a) and demethylase (TET1) were examined by RT‐PCR in cells treated for up to 24 hours with IL‐1, IL‐6 or prostaglandin E2. The role of PGE2 in IL‐1 suppression of DNMT3a expression was assessed by treating cells with IL‐1 in the presence and absence of NS‐398. Global levels of DNA methylation following treatment with IL‐1 were measured in an ELISA‐like assay.ResultsTreatment of HGF with IL‐1 caused a three‐fold increase in levels of DNMT1 mRNA over 24 hours, but a two‐fold decrease in DNMT3a mRNA in the same samples. Global levels of 5mC were increased in HGF treated with IL‐1 for 72 hours relative to untreated controls. PGE2 caused a dose‐dependent decrease in levels of DNMT3a similar to IL‐1, but also slightly decreased levels of DNMT1.ConclusionThese data are consistent with the hypothesis that exposure to inflammatory cytokines or PGE2 alters levels and/or activity of enzymes involved in DNA methylation, resulting in global and possibly gene‐specific changes which can lead to changes in cellular characteristics over time. Further experiments will be aimed at testing the effects of these cytokines on expression of DNMT and TET enzymes in normal and transformed cell lines, and at elucidating mechanisms involved in cytokine regulation of these enzymes.Support or Funding InformationThis work has been supported by the Philadelphia College of Osteopathic Medicine Division of Research.

The role of PGE2 and PGF2a in follicle wall rupture and their implications in the development and treatment of luteinized unruptured follicles

The role of PGE2 and PGF2a in follicle wall rupture and their implications in the development and treatment of luteinized unruptured follicles

Prostaglandin E2 inhibits neutrophil extracellular trap formation through production of cyclic AMP

Upon stimulation, neutrophils release their nuclear contents called neutrophil extracellular traps (NETs), which contain unfolded chromatin and lysosomal enzymes. NETs have been demonstrated to play a critical role in host defence, although the role of PGE2 , a bioactive substance generated in inflammatory tissues, in the formation of NETs remains unclear. The effects of PGE2 , agonists and antagonists of its receptors, and modulators of the cAMP-PKA pathway on the formation of NETs were examined in vitro in isolated neutrophils and in vivo in a newly established mouse model. PGE2 inhibited PMA-induced NET formation in vitro through EP2 and EP4 Gαs-coupled receptors. Incubation with a cell-permeable cAMP analogue, dibutyryl cAMP, or various inhibitors of a cAMP-degrading enzyme, PDE, also suppressed NET formation. In the assay established here, where an agarose gel was s.c. implanted in mice and NET formation was detected on the surface of the gel, the extent of the NET formed was inhibited in agarose gels containing rolipram, a PDE4 inhibitor, and butaprost, an EP2 receptor agonist. PGE2 inhibits NET formation through the production of cAMP. These findings will contribute to the development of novel treatments for NETosis-related diseases.

WS13.2 The role of PGE2 in cystic fibrosis (CF) lung inflammation and the potential association with ivacaftor therapy and treatment response

Objectives CF causes recurrent lung infections and inflammation which causes lung damage and pulmonary decline. The cyclooxgenase signalling pathway and its major metabolite PGE 2 have been shown to increase lung inflammation. PGE 2 signals through four different receptor subtypes, EP1–EP4. Exact mechanisms underpinning mode of action of new therapies such as ivacaftor may be multifactorial with potential downstream signaling consequences. Methods PGE 2 plasma levels were detected in clinically stable CF patients (n = 25) with a G551D mutation pre and post ivacaftor treatment. CF bronchial epithelial cells (DF508 homozygote, CFBE41o-) and human bronchial epithelial cells (16HBEo-) were seeded at2×10 5 cells/ml. EP1 receptor expression was determined by qRT-PCR. Cells were stimulated with PGE 2 or EP1 receptor antagonist and cell supernatant harvested. Cell proliferation was determined and changes in cytokine levels of IL-6, IL-8 and TNFa following PGE 2 stimulation and IL-6 following EP1 receptor antagonism were detected by ELISA. Results Treatment of CF patients with ivacaftor significantly reduced PGE 2 plasma levels (p 2 stimulation significantly increased expression of IL-6, IL-8 and TNFα in CFBE41o-cells compared to 16HBEo- in vitro. EP1 receptor antagonism significantly reduced IL-6 secretion in CFBE41o- cells. No significant change in cell proliferation was detected. Conclusion The findings underscore the value of unravelling the mechanisms regulating PGE 2 signalling, potentially advancing our understanding of the mechanisms of action of existing novel therapies in CF.

Role of PGE2/EP2 Receptor Signaling on The Effects of Neonatal Hyperoxia on Airway Smooth Muscle

It was shown that neonatal hyperoxic‐exposure associates with airway hyperresponsiveness and impaired nonadrenergic noncholinergic relaxation. It was demonstrated that reduced relaxant responses were associated with an impairment of prostaglandin E2 (PGE2) release from airway smooth muscle (ASM). In this study we tested the hypothesis that supplementation of PGE2 or EP2 agonists to ASM restore relaxant responses. Tracheal cylinders were obtained from 12 days rat pups exposed to hyperoxia or room air for seven days. These cylinders were used to study contractile and relaxant responses. In hyperoxic tracheal preparations the contractile responses to bethanechol were enhanced as compared to room air controls. These enhanced contractile responses were attenuated by pre‐incubation of tissues with PGE2 (1µM). Similar effect was showed by using an EP2 agonist. This effect of PGE2 and EP2 agonist was reversed by an EP2 antagonist. PGE2 and EP2 induced dose response relaxations of ASM, which were reduced by an EP2 antagonist.We conclude that PGE2 induces relaxation of airways via EP2 receptors, and the use of EP2 agonists may serve as a therapeutic approach to overcome the adverse effects of neonatal hyperoxia on relaxant responses of ASM.Support by MEST

Role of PGE2/EP4 Receptor Signaling on The Effects of Hyperoxia on Airway Smooth Muscle

It was shown that neonatal hyperoxic‐exposure associates with airway hyperresponsiveness and impaired nonadrenergic noncholinergic relaxation. It was demonstrated that reduced relaxant responses were associated with an impairment of prostaglandin E2 (PGE2) release from airway smooth muscle (ASM). In this study we tested the hypothesis that supplementation of PGE2 or EP4 agonists to ASM restore relaxant responses. Tracheal cylinders were obtained from 12 days rat pups exposed to hyperoxia or room air for seven days. These cylinders were used to study contractile and relaxant responses. In hyperoxic trachea the contractile responses to bethanechol were enhanced as compared to room air controls. These enhanced contractile responses were attenuated by pre‐incubation of tissues with PGE2 (1µM). Similar effect showed an EP4 agonist. This effect of PGE2 and EP4 agonist was reversed by an EP4 antagonist. PGE2 and EP4 induced dose response relaxations of ASM, which were reduced by an EP4 antagonist.We conclude that PGE2 induces relaxation of airways via EP4 receptors, and the use of EP4 agonists may serve as a therapeutic approach to overcome the adverse effects of neonatal hyperoxia on relaxant responses of ASM.Supported by MEST

Role of gamma-secretase in human umbilical-cord derived mesenchymal stem cell mediated suppression of NK cell cytotoxicity.

BackgroundMesenchymal stem cells (MSCs) are increasingly considered to be used as biological immunosuppressants in hematopoietic stem cell transplantation (HSCT). In the early reconstitution phase following HSCT, natural killer (NK) cells represent the major lymphocyte population in peripheral blood and display graft-vs-leukemia (GvL) effects. The functional interactions between NK cells and MSCs have the potential to influence the leukemia relapse rate after HSCT. Until date, MSC-NK cell interaction studies are largely focussed on bone marrow derived (BM)-MSCs. Umbilical cord derived (UC)-MSCs might be an alternative source of therapeutic MSCs. Thus, we studied the interaction of UC-MSCs with unstimulated allogeneic NK cells.ResultsUC-MSCs could potently suppress NK cell cytotoxicity in overnight cultures via soluble factors. The main soluble immunosuppressant was identified as prostaglandin (PG)-E2. Maximal PGE2 release involved IL-1β priming of MSCs after close contact between the NK cells and UC-MSCs. Interestingly, blocking gamma-secretase activation alleviated the immunosuppression by controlling PGE2 production. IL-1 receptor activation and subsequent downstream signalling events were found to require gamma-secretase activity.ConclusionAlthough the role of PGE2 in NK cell-MSC has been reported, the requirement of cell-cell contact for PGE2 induced immunosuppression remained unexplained. Our findings shed light on this puzzling observation and identify new players in the NK cell-MSC crosstalk.Electronic supplementary materialThe online version of this article (doi:10.1186/s12964-014-0063-9) contains supplementary material, which is available to authorized users.

Abstract 4193: Prostaglandin E2 activates an okadaic acid-sensitive Ser/Thr phosphatase that leads to transient inhibition of the ERK 1/2 pathway in glioblastoma multiforme cells

Abstract Prostaglandin E2, the most abundant prostaglandin produced by tumor cells and by the tumor microenvironment, plays a critical role in regulation of tumor cell functions by activating signaling pathways that ultimately lead to increased tumor growth, proliferation, invasion, and survival. We previously demonstrated a growth regulatory role of PGE2 in the established glioblastoma multiforme cell line U87-MG. Unexpectedly, stimulation of U87-MG cells by PGE2 resulted in inhibition of the ERK 1/2 pathway. The present study was, therefore, undertaken to characterize PGE2-induced inhibition of ERK 1/2 and elucidate the underlying signaling mechanisms. We demonstrate that ERK 1/2 phosphorylation was transiently inhibited by PGE2 in a time-dependent manner. Dephosphorylation of ERK1/2 was detected at 5 min exposure to PGE2, reached maximum levels between 20-180 min and was sustained for 6 h. Levels of phosphorylated ERK 1/2 increased thereafter and at 24-48 h were higher than those found in unstimulated cells. Raf-1 phosphorylation was also transiently inhibited by PGE2. Desphosphorylation of Raf-1 at Ser338 was detected at 10 min exposure to PGE2 and followed thereafter kinetics identical to those of ERK 1/2. Receptor tyrosine kinase dependent- (EGF) and independent (TPA)- phosphorylation of ERK and Raf-1 were also attenuated by PGE2. PGE2-induced dephosphorylation of ERK1/2 and Raf-1 was not unique to U87-MG cells, as it was detected in other glioma cell lines, including T98G, U118-MG, but not in primary astrocytes or brain endothelial cells. Stimulation of U87-MG cells with other prostaglandins, including prostaglandin D2, had no effect on Raf-1 and ERK dephosphorylation. Pretreatment of U87-MG with okadaic acid (OA), an inhibitor of several Ser/Thr phosphatases, including PP2A, PP2B, PP1 and PP5, rescued Raf-1 and ERK dephosphorylation detected at 20 min exposure to PGE2, while an inactive analogue of OA had no effect. In contrast, fostriecin, a selective inhibitor of PP2A and PP1, failed to rescue PGE2-induced ERK 1/2 and Raf-1 dephosphorylation. Sodium orthovanadate, a tyrosine phosphatase inhibitor, had no effect on PGE2-induced ERK 1/2 dephosphorylation. RNAi-mediated silencing of PP5, but not PP2A, and forced expression of the TPR domain of PP5, which acts as a dominant negative PP5 construct, partially rescued PGE2-induced Raf-1 and ERK-dephosphorylation. Taken together, these results demonstrate that PGE2 transiently dephosphorylates Raf-1 and ERK 1/2 via an okadaic acid-sensitive pathway involving activation of PP5 and suggest the potential involvement or cooperation of additional Ser/Thr phosphatases. We speculate that transient inhibition of Raf-1 and ERK 1/2 activation by PGE2 could represent a mechanism by which glioma cells escape apoptosis caused by sustained activation of the ERK 1/2 pathway. (Supported by NIH Grant RO3 NS076765 to M.T.R). Citation Format: Maria Teresa Rizzo, Wilmer Mata-Castro, Yoo Seung Ko, Aaron Cohen-Gadol. Prostaglandin E2 activates an okadaic acid-sensitive Ser/Thr phosphatase that leads to transient inhibition of the ERK 1/2 pathway in glioblastoma multiforme cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4193. doi:10.1158/1538-7445.AM2014-4193