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

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

PGE2 limits effector expansion of tumour-infiltrating stem-like CD8+ T cells.

Cancer-specific TCF1+ stem-like CD8+ T cells can drive protective anticancer immunity through expansion and effector cell differentiation1-4; however, this response is dysfunctional in tumours. Current cancer immunotherapies2,5-9 can promote anticancer responses through TCF1+ stem-like CD8+ T cells in some but not all patients. This variation points towards currently ill-defined mechanisms that limit TCF1+CD8+ T cell-mediated anticancer immunity. Here we demonstrate that tumour-derived prostaglandin E2 (PGE2) restricts the proliferative expansion and effector differentiation of TCF1+CD8+ T cells within tumours, which promotes cancer immune escape. PGE2 does not affect the priming of TCF1+CD8+ T cells in draining lymph nodes. PGE2 acts through EP2 and EP4 (EP2/EP4) receptor signalling in CD8+ T cells to limit the intratumoural generation of early and late effector T cell populations that originate from TCF1+ tumour-infiltrating CD8+ T lymphocytes (TILs). Ablation of EP2/EP4 signalling in cancer-specific CD8+ T cells rescues their expansion and effector differentiation within tumours and leads to tumour elimination in multiple mouse cancer models. Mechanistically, suppression of the interleukin-2 (IL-2) signalling pathway underlies the PGE2-mediated inhibition of TCF1+ TIL responses. Altogether, we uncover a key mechanism that restricts the IL-2 responsiveness of TCF1+ TILs and prevents anticancer T cell responses that originate from these cells. This study identifies the PGE2-EP2/EP4 axis as a molecular target to restore IL-2 responsiveness in anticancer TILs to achieve cancer immune control.

PGE2 inhibits TIL expansion by disrupting IL-2 signalling and mitochondrial function.

Expansion of antigen-experienced CD8+ T cells is critical for the success of tumour-infiltrating lymphocyte (TIL)-adoptive cell therapy (ACT) in patients with cancer1. Interleukin-2 (IL-2) acts as a key regulator of CD8+ cytotoxic T lymphocyte functions by promoting expansion and cytotoxic capability2,3. Therefore, it is essential to comprehend mechanistic barriers to IL-2 sensing in the tumour microenvironment to implement strategies to reinvigorate IL-2 responsiveness and T cell antitumour responses. Here we report that prostaglandin E2 (PGE2), a known negative regulator of immune response in the tumour microenvironment4,5, is present at high concentrations in tumour tissue from patients and leads to impaired IL-2 sensing in human CD8+ TILs via the PGE2 receptors EP2 and EP4. Mechanistically, PGE2 inhibits IL-2 sensing in TILs by downregulating the IL-2Rγc chain, resulting in defective assembly of IL-2Rß-IL2Rγc membrane dimers. This results in impaired IL-2-mTOR adaptation and PGC1α transcriptional repression, causing oxidative stress and ferroptotic cell death in tumour-reactive TILs. Inhibition of PGE2 signalling to EP2 and EP4 during TIL expansion for ACT resulted in increased IL-2 sensing, leading to enhanced proliferation of tumour-reactive TILs and enhanced tumour control once the cells were transferred in vivo. Our study reveals fundamental features that underlie impairment of human TILs mediated by PGE2 in the tumour microenvironment. These findings have therapeutic implications for cancer immunotherapy and cell therapy, and enable the development of targeted strategies to enhance IL-2 sensing and amplify the IL-2 response in TILs, thereby promoting the expansion of effector T cells with enhanced therapeutic potential.

EP2 and EP4 blockade prevents tumor-induced suppressive features in human monocytic myeloid-derived suppressor cells.

Tumors educate their environment to prime the occurrence of suppressive cell subsets, which enable tumor evasion and favors tumor progression. Among these, there are the myeloid-derived suppressor cells (MDSCs), their presence being associated with the poor clinical outcome of cancer patients. Tumor-derived prostaglandin E2 (PGE2) is known to mediate MDSC differentiation and the acquisition of pro-tumor features. In myeloid cells, PGE2 signaling is mediated via E-prostanoid receptor type 2 (EP2) and EP4. Although the suppressive role of PGE2 is well established in MDSCs, the role of EP2/4 on human MDSCs or whether EP2/4 modulation can prevent MDSCs suppressive features upon exposure to tumor-derived PGE2 is poorly defined. In this study, using an in vitro model of human monocytic-MDSCs (M-MDSCs) we demonstrate that EP2 and EP4 signaling contribute to the induction of a pro-tumor phenotype and function on M-MDSCs. PGE2 signaling via EP2 and EP4 boosted M-MDSC ability to suppress T and NK cell responses. Combined EP2/4 blockade on M-MDSCs during PGE2 exposure prevented the occurrence of these suppressive features. Additionally, EP2/4 blockade attenuated the suppressive phenotype of M-MDSCs in a 3D coculture with colorectal cancer patient-derived organoids. Together, these results identify the role of tumor-derived PGE2 signaling via EP2 and EP4 in this human M-MDSC model, supporting the therapeutic value of targeting PGE2-EP2/4 axis in M-MDSCs to alleviate immunosuppression and facilitate the development of anti-tumor immunity.

Surface CD52, CD84, and PTGER2 mark mature PMN-MDSCs from cancer patients and G-CSF-treated donors.

Precise molecular characterization of circulating polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs) is hampered by their mixed composition of mature and immature cells and lack of specific markers. Here, we focus on mature CD66b+CD10+CD16+CD11b+ PMN-MDSCs (mPMN-MDSCs) from either cancer patients or healthy donors receiving G-CSF for stem cell mobilization (GDs). By RNA sequencing (RNA-seq) experiments, we report the identification of a distinct gene signature shared by the different mPMN-MDSC populations under investigation, also validated in mPMN-MDSCs from GDs and tumor-associated neutrophils (TANs) by single-cell RNA-seq (scRNA-seq) experiments. Analysis of such a gene signature uncovers a specific transcriptional program associated with mPMN-MDSC differentiation and allows us to identify that, in patients with either solid or hematologic tumors and in GDs, CD52, CD84, and prostaglandin E receptor 2 (PTGER2) represent potential mPMN-MDSC-associated markers. Altogether, our findings indicate that mature PMN-MDSCs distinctively undergo specific reprogramming during differentiation and lay the groundwork for selective immunomonitoring, and eventually targeting, of mature PMN-MDSCs.

PGE2-EP4 signaling steers cDC2 maturation toward the induction of suppressive T-cell responses.

Dendritic cells (DCs) shape adaptive immunity in response to environmental cues such as cytokines or lipid mediators, including prostaglandin E2 (PGE2). In cancer, tumors are known to establish an enriched PGE2 microenvironment. Tumor-derived PGE2 primes regulatory features across immune cells, including DCs, facilitating tumor progression. PGE2 shapes DC function by providing signaling via its two so-called E-prostanoid receptors (EPs) EP2 and EP4. Although studies with monocyte-derived DCs have shown the importance of PGE2 signaling, the role of PGE2-EP2/EP4 on conventional DCs type 2 (cDC2s), is still poorly defined. In this study, we investigated the function of EP2 and EP4 using specific EP antagonists on human cDC2s. Our results show that EP2 and EP4 exhibit different functions in cDC2s, with EP4 modulating the upregulation of activation markers (CD80, CD86, CD83, MHC class II) and the production of IL-10 and IL-23. Furthermore, PGE2-EP4 boosts CCR type 7-based migration as well as a higher T-cell expansion capacity, characterized by the enrichment of suppressive rather than pro-inflammatory T-cell populations. Our findings are relevant to further understanding the role of EP receptors in cDC2s, underscoring the benefit of targeting the PGE2-EP2/4 axis for therapeutic purposes in diseases such as cancer.

Design of Dual EP2/EP4 Antagonists through Scaffold Merging of Selective Inhibitors.

Prostaglandin E2 (PGE2) plays a key role in various stages of cancer. PGE2 signals through the EP2 and the EP4 receptors, promoting tumorigenesis, metastasis, and/or immune suppression. Dual inhibition of both the EP2 and the EP4 receptors has the potential to counteract the effect of PGE2 and to result in antitumor efficacy. We herein disclose for the first time the structure of dual EP2/EP4 antagonists. By merging the scaffolds of EP2 selective and EP4 selective inhibitors, we generated a new chemical series of compounds blocking both receptors with comparable potency. In vitro and in vivo profiling suggests that the newly identified compounds are promising lead structures for further development into dual EP2/EP4 antagonists for use in cancer therapy.

N6-methyladenosine Methyltransferase METTL3 Enhances PTGER2 Expression to Increase Ovarian Cancer Stemness and Chemoresistance.

BACKGROUND: Ovarian cancer is the second leading cause of gynecologic cancer-associated deaths. Cancer stemness and chemoresistance are responsible for ovarian cancer metastasis and the poor prognosis of patients. In this study, we determined the function of N6-methyladenine (m6A) RNA methylation and prostaglandin E receptor 2 (PTGER2) in ovarian cancer progression. METHODS: The m6A RNA methylation-associated PTGER2 in ovarian cancer was identified using bioinformatics analysis. The role of PTGER2 in ovarian cancer was elucidated in cell lines and clinical samples with cellular and molecular experiments. RESULTS: In this investigation, bioinformatics analysis based on a public cancer database was used to elucidate the impact of m6A modification on the prognosis of patients with ovarian cancer. Moreover, PTGER2 was identified as a potential oncogene associated with the distant metastasis of ovarian cancer and poor patient prognosis. Interestingly, PTGER2 expression was experimentally shown to be enhanced by N6-adenosine-methyltransferase 70 kDa subunit (METTL3)-mediated m6A modification. In addition, PTGER2 enhanced cancer stem cell self-renewal properties, the epithelial-mesenchymal transition, and DNA damage repair, thus potentiating cell stemness, therapy resistance to carboplatin, proliferation, and metastasis of ovarian cancer. Importantly, PTGER2 expression in clinical samples was associated with distant metastasis, predicted poor patient prognosis, and independently served as a prognostic predictor in ovarian cancer. CONCLUSIONS: Our work defines PTGER2 as an oncogene and reveals that PTGER2 is a prognostic predictor and novel therapeutic target for the management of ovarian cancer.

Dual Blockade of EP2 and EP4 Signaling is Required for Optimal Immune Activation and Antitumor Activity Against Prostaglandin-Expressing Tumors.

While the role of prostaglandin E2 (PGE2) in promoting malignant progression is well established, how to optimally block the activity of PGE2 signaling remains to be demonstrated. Clinical trials with prostaglandin pathway targeted agents have shown activity but without sufficient significance or dose-limiting toxicities that have prevented approval. PGE2 signals through four receptors (EP1-4) to modulate tumor progression. EP2 and EP4 signaling exacerbates tumor pathology and is immunosuppressive through potentiating cAMP production. EP1 and EP3 signaling has the opposite effect through increasing IP3 and decreasing cAMP. Using available small-molecule antagonists of single EP receptors, the cyclooxygenase-2 (COX-2) inhibitor celecoxib, or a novel dual EP2/EP4 antagonist generated in this investigation, we tested which approach to block PGE2 signaling optimally restored immunologic activity in mouse and human immune cells and antitumor activity in syngeneic, spontaneous, and xenograft tumor models. We found that dual antagonism of EP2 and EP4 together significantly enhanced the activation of PGE2-suppressed mouse and human monocytes and CD8+ T cells in vitro as compared with single EP antagonists. CD8+ T-cell activation was dampened by single EP1 and EP3 antagonists. Dual EP2/EP4 PGE2 receptor antagonists increased tumor microenvironment lymphocyte infiltration and significantly reduced disease burden in multiple tumor models, including in the adenomatous polyposis coli (APC)min+/- spontaneous colorectal tumor model, compared with celecoxib. These results support a hypothesis that redundancy of EP2 and EP4 receptor signaling necessitates a therapeutic strategy of dual blockade of EP2 and EP4. Here we describe TPST-1495, a first-in-class orally available small-molecule dual EP2/EP4 antagonist. Significance: Prostaglandin (PGE2) drives tumor progression but the pathway has not been effectively drugged. We demonstrate significantly enhanced immunologic potency and antitumor activity through blockade of EP2 and EP4 PGE2 receptor signaling together with a single molecule.

Prorelaxant E-type Prostanoid Receptors Functionally Partition to Different Procontractile Receptors in Airway Smooth Muscle.

Prostaglandin E2 imparts diverse physiological effects on multiple airway cells through its actions on four distinct E-type prostanoid (EP) receptor subtypes (EP1-EP4). Gs-coupled EP2 and EP4 receptors are expressed on airway smooth muscle (ASM), yet their capacity to regulate the ASM contractile state remains subject to debate. We used EP2 and EP4 subtype-specific agonists (ONO-259 and ONO-329, respectively) in cell- and tissue-based models of human ASM contraction-magnetic twisting cytometry (MTC), and precision-cut lung slices (PCLSs), respectively-to study the EP2 and EP4 regulation of ASM contraction and signaling under conditions of histamine or methacholine (MCh) stimulation. ONO-329 was superior (<0.05) to ONO-259 in relaxing MCh-contracted PCLSs (log half maximal effective concentration [logEC50]: 4.9 × 10-7 vs. 2.2 × 10-6; maximal bronchodilation ± SE, 35 ± 2% vs. 15 ± 2%). However, ONO-259 and ONO-329 were similarly efficacious in relaxing histamine-contracted PCLSs. Similar differential effects were observed in MTC studies. Signaling analyses revealed only modest differences in ONO-329- and ONO-259-induced phosphorylation of the protein kinase A substrates VASP and HSP20, with concomitant stimulation with MCh or histamine. Conversely, ONO-259 failed to inhibit MCh-induced phosphorylation of the regulatory myosin light chain (pMLC20) and the F-actin/G-actin ratio (F/G-actin ratio) while effectively inhibiting their induction by histamine. ONO-329 was effective in reversing induced pMLC20 and the F/G-actin ratio with both MCh and histamine. Thus, the contractile-agonist-dependent differential effects are not explained by changes in the global levels of phosphorylated protein kinase A substrates but are reflected in the regulation of pMLC20 (cross-bridge cycling) and F/G-actin ratio (actin cytoskeleton integrity, force transmission), implicating a role for compartmentalized signaling involving muscarinic, histamine, and EP receptor subtypes.

EP4 Receptor Conformation Sensor Suited for Ligand Screening and Imaging of Extracellular Prostaglandins.

Prostaglandins are important lipid mediators with a wide range of functions in the human body. They act mainly via plasma membrane localized prostaglandin receptors, which belong to the G-protein coupled receptor class. Due to their localized formation and short lifetime, it is important to be able to measure the distribution and abundance of prostaglandins in time and/or space. In this study, we present a Foerster resonance energy transfer (FRET)-based conformation sensor of the human prostaglandin E receptor subtype 4 (EP4 receptor), which was capable of detecting prostaglandin E2 (PGE2)-induced receptor activation in the low nanomolar range with a good signal-to-noise ratio. The sensor retained the typical selectivity for PGE2 among arachidonic acid products. Human embryonic kidney cells stably expressing the sensor did not produce detectable amounts of prostaglandins making them suitable for a coculture approach allowing us, over time, to detect prostaglandin formation in Madin-Darby canine kidney cells and primary mouse macrophages. Furthermore, the EP4 receptor sensor proved to be suited to detect experimentally generated PGE2 gradients by means of FRET-microscopy, indicating the potential to measure gradients of PGE2 within tissues. In addition to FRET-based imaging of prostanoid release, the sensor allowed not only for determination of PGE2 concentrations, but also proved to be capable of measuring ligand binding kinetics. The good signal-to-noise ratio at a commercial plate reader and the ability to directly determine ligand efficacy shows the obvious potential of this sensor interest for screening and characterization of novel ligands of the pharmacologically important human EP4 receptor. SIGNIFICANCE STATEMENT: The authors present a biosensor based on the prostaglandin E receptor subtype 4, which is well suited to measure extracellular prostaglandin E2 (PGE2) concentration with high temporal and spatial resolution. It can be used for the imaging of PGE2 levels and gradients by means of Foerster resonance energy transfer microscopy, and for determining PGE2 release of primary cells as well as for screening purposes in a plate reader setting.

PGE2-EP2/EP4 signaling elicits mesoCAR T cell immunosuppression in pancreatic cancer.

Introduction: For many years, surgery, adjuvant and combination chemotherapy have been the cornerstone of pancreatic cancer treatment. Although these approaches have improved patient survival, relapse remains a common occurrence, necessitating the exploration of novel therapeutic strategies. CAR T cell therapies are now showing tremendous success in hematological cancers. However, the clinical efficacy of CAR T cells in solid tumors remained low, notably due to presence of an immunosuppressive tumor microenvironment (TME). Prostaglandin E2, a bioactive lipid metabolite found within the TME, plays a significant role in promoting cancer progression by increasing tumor proliferation, improving angiogenesis, and impairing immune cell's function. Despite the well-established impact of PGE2 signaling on cancer, its specific effects on CAR T cell therapy remain under investigation. Methods: To address this gap in knowledge the role of PGE2-related genes in cancer tissue and T cells of pancreatic cancer patients were evaluated in-silico. Through our in vitro study, we manufactured fully human functional mesoCAR T cells specific for pancreatic cancer and investigated the influence of PGE2-EP2/EP4 signaling on proliferation, cytotoxicity, and cytokine production of mesoCAR T cells against pancreatic cancer cells. Results: In-silico investigations uncovered a significant negative correlation between PGE2 expression and gene signature of memory T cells. Furthermore, in vitro experiments demonstrated that the activation of PGE2 signaling through EP2 and EP4 receptors suppressed the proliferation and major antitumor functions of mesoCAR T cells. Interestingly, the dual blockade of EP2 and EP4 receptors effectively reversed PGE2-mediated suppression of mesoCAR T cells, while individual receptor antagonists failed to mitigate the PGE2-induced suppression. Discussion: In summary, our findings suggest that mitigating PGE2-EP2/EP4 signaling may be a viable strategy for enhancing CAR T cell activity within the challenging TME, thereby improving the efficacy of CAR T cell therapy in clinical settings.

Targeting EP2 Receptor for Drug Discovery: Strengths, Weaknesses, Opportunities, and Threats (SWOT) Analysis.

Cyclooxygenase-1 and -2 (COX1 and COX2) derived endogenous ligand prostaglandin-E2 (PGE2) triggers several physiological and pathological conditions. It mediates signaling through four G-protein coupled receptors, EP1, EP2, EP3, and EP4. Among these, EP2 is expressed throughout the body including the brain and uterus. The functional role of EP2 has been extensively studied using EP2 gene knockout mice, cellular models, and selective small molecule agonists and antagonists for this receptor. The efficacy data from in vitro and in vivo animal models indicate that EP2 receptor is a major proinflammatory mediator with deleterious functions in a variety of diseases suggesting a path forward for EP2 inhibitors as the next generation of selective anti-inflammatory and antiproliferative agents. Interestingly in certain diseases, EP2 action is beneficial; therefore, EP2 agonists seem to be clinically useful. Here, we highlight the strengths, weaknesses, opportunities, and potential threats (SWOT analysis) for targeting EP2 receptor for therapeutic development for a variety of unmet clinical needs.

Single hormone or synthetic agonist induces Gs/Gi coupling selectivity of EP receptors via distinct binding modes and propagating paths.

To accomplish concerted physiological reactions, nature has diversified functions of a single hormone at at least two primary levels: 1) Different receptors recognize the same hormone, and 2) different cellular effectors couple to the same hormone-receptor pair [R.P. Xiao, Sci STKE 2001, re15 (2001); L. Hein, J. D. Altman, B.K. Kobilka, Nature 402, 181-184 (1999); Y. Daaka, L. M. Luttrell, R. J. Lefkowitz, Nature 390, 88-91 (1997)]. Not only these questions lie in the heart of hormone actions and receptor signaling but also dissecting mechanisms underlying these questions could offer therapeutic routes for refractory diseases, such as kidney injury (KI) or X-linked nephrogenic diabetes insipidus (NDI). Here, we identified that Gs-biased signaling, but not Gi activation downstream of EP4, showed beneficial effects for both KI and NDI treatments. Notably, by solving Cryo-electron microscope (cryo-EM) structures of EP3-Gi, EP4-Gs, and EP4-Gi in complex with endogenous prostaglandin E2 (PGE2)or two synthetic agonists and comparing with PGE2-EP2-Gs structures, we found that unique primary sequences of prostaglandin E2 receptor (EP) receptors and distinct conformational states of the EP4 ligand pocket govern the Gs/Gi transducer coupling selectivity through different structural propagation paths, especially via TM6 and TM7, to generate selective cytoplasmic structural features. In particular, the orientation of the PGE2 ω-chain and two distinct pockets encompassing agonist L902688 of EP4 were differentiated by their Gs/Gi coupling ability. Further, we identified common and distinct features of cytoplasmic side of EP receptors for Gs/Gi coupling and provide a structural basis for selective and biased agonist design of EP4 with therapeutic potential.

Complementary roles of EP2 and EP4 receptors in malignant glioma.

BACKGROUND AND PURPOSE: Glioblastoma (GBM) is the most aggressive brain tumour in the central nervous system, but the current treatment is very limited and unsatisfactory. PGE2 -initiated cAMP signalling via EP2 and EP4 receptors is involved in the tumourigenesis of multiple cancer types. However, whether or how EP2 and EP4 receptors contribute to GBM growth largely remains elusive. EXPERIMENTAL APPROACH: We performed comprehensive data analysis of gene expression in human GBM samples and determined their expression correlations through multiple bioinformatics approaches. A time-resolved fluorescence energy transfer (TR-FRET) assay was utilized to characterize PGE2 -mediated cAMP signalling via EP2 and EP4 receptors in human glioblastoma cells. Using recently reported potent and selective small-molecule antagonists, we determined the effects of inhibition of EP2 and EP4 receptors on GBM growth in subcutaneous and intracranial tumour models. KEY RESULTS: The expression of both EP2 and EP4 receptors was upregulated and highly correlated with a variety of tumour-promoting cytokines, chemokines, and growth factors in human gliomas. Further, they were heterogeneously expressed in human GBM cells, where they compensated for each other to mediate PGE2 -initiated cAMP signalling and to promote colony formation, cell invasion and migration. Inhibition of EP2 and EP4 receptors revealed that these receptors might mediate GBM growth, angiogenesis, and immune evasion in a compensatory manner. CONCLUSION AND IMPLICATIONS: The compensatory roles of EP2 and EP4 receptors in GBM development and growth suggest that concurrently targeting these two PGE2 receptors might represent a more effective strategy than inhibiting either alone for GBM treatment.

The discovery of cyclic γ-AApeptides as the promising ligands targeting EP2.

EP2 is a G protein-coupled receptor for prostaglandin E2 (PGE2) derived from cell membrane-released arachidonic acid upon various harmful and injurious stimuli. It is commomly upregulated in tumors and injured brain tissues, as its activation by PGE2 is widely believed to be involved in the pathophysiological mechanisms underlying these conditions via promoting pro-inflammatory reactions. Herein, we report the discovery of two novel macrocyclic peptidomimetics based on the screening of a cyclic γ-AApeptides combinatorial library. These two cyclic γ-AApeptides showed excellent binding affinity with the EP2 protein, and they may lead to the development of novel therapeutic agents and/or molecular probes to modulate the PGE2/EP2 signaling.

Prostaglandin E2-Transporting Pathway and Its Roles via EP2/EP4 in Cultured Human Dental Pulp.

INTRODUCTION: Prostaglandin E2 (PGE2) exerts biological actions through its transport pathway involving intracellular synthesis, extracellular transport, and receptor binding. This study aimed to determine the localization of the components of the PGE2-transporting pathway in human dental pulp and explore the relevance of PGE2 receptors (EP2/EP4) to angiogenesis and dentinogenesis. METHODS: Protein localization of microsomal PGE2 (mPGES)synthase, PGE2 transporters (multidrug resistance-associated protein-4 [MRP4] and prostaglandin transporter [PGT]), and EP2/EP4 was analyzed using double immunofluorescence staining. Tooth slices from human third molars were cultured with or without butaprost (EP2 agonist) or rivenprost (EP4 agonist) for 1 week. Morphometric analysis of endothelial cell filopodia was performed to evaluate angiogenesis, and real-time polymerase chain reaction was performed to evaluate angiogenesis and odontoblast differentiation markers. RESULTS: MRP4 and PGT were colocalized with mPGES and EP2/EP4 in odontoblasts and endothelial cells. Furthermore, MRP4 was colocalized with mPGES and EP4 in human leukocyte antigen-DR-expressing dendritic cells. In the tooth slice culture, EP2/EP4 agonists induced significant increases in the number and length of filopodia and mRNA expression of angiogenesis markers (vascular endothelial growth factor and fibroblast growth factor-2) and odontoblast differentiation markers (dentin sialophosphoprotein and collagen type 1). CONCLUSIONS: PGE2-producing enzyme (mPGES), transporters (MRP4 and PGT), and PGE2-specific receptors (EP2/EP4) were immunolocalized in various cellular components of the human dental pulp. EP2/EP4 agonists promoted endothelial cell filopodia generation and upregulated angiogenesis- and odontoblast differentiation-related genes, suggesting that PGE2 binding to EP2/EP4 is associated with angiogenic and dentinogenic responses.

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

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

Studies in Zebrafish and Rat Models Support Dual Blockade of EP2 and EP4 (Prostaglandin E2 Receptors Type 2 and 4) for Renoprotection in Glomerular Hyperfiltration and Albuminuria.

BACKGROUND: Glomerular hyperfiltration (GH) is an important mechanism in the development of albuminuria in hypertension. Upregulation of COX2 (cyclooxygenase 2) and prostaglandin E2 (PGE2) was linked to podocyte damage in GH. We explored the potential renoprotective effects of either separate or combined pharmacological blockade of EP2 (PGE2 receptor type 2) and EP4 (PGE2 receptor type 4) in GH. METHODS: We conducted in vivo studies in a transgenic zebrafish model (Tg[fabp10a:gc-EGFP]) suitable for analysis of glomerular filtration barrier function and a genetic rat model with GH, albuminuria, and upregulation of PGE2. Similar pharmacological interventions and primary outcome analysis on albuminuria phenotype development were conducted in both model systems. RESULTS: Stimulation of zebrafish embryos with PGE2 induced an albuminuria-like phenotype, thus mimicking the suggested PGE2 effects on glomerular filtration barrier dysfunction. Both separate and combined blockade of EP2 and EP4 reduced albuminuria phenotypes in zebrafish and rat models. A significant correlation between albuminuria and podocyte damage in electron microscopy imaging was identified in the rat model. Dual blockade of both receptors showed a pronounced synergistic suppression of albuminuria. Importantly, this occurred without changes in arterial blood pressure, glomerular filtration rate, or tissue oxygenation in magnetic resonance imaging, while RNA sequencing analysis implicated a potential role of circadian clock genes. CONCLUSIONS: Our findings confirm a role of PGE2 in the development of albuminuria in GH and support the renoprotective potential of combined pharmacological blockade of EP2 and EP4 receptors. These data support further translational research to explore this therapeutic option and a possible role of circadian clock genes.

The role of PGE2 and EP receptors on lung's immune and structural cells; possibilities for future asthma therapy.

Asthma is the most common airway chronic disease with treatments aimed mainly to control the symptoms. Adrenergic receptor agonists, corticosteroids and anti-leukotrienes have been used for decades, and the development of more targeted asthma treatments, known as biological therapies, were only recently established. However, due to the complexity of asthma and the limited efficacy as well as the side effects of available treatments, there is an urgent need for a new generation of asthma therapies. The anti-inflammatory and bronchodilatory effects of prostaglandin E2 in asthma are promising, yet complicated by undesirable side effects, such as cough and airway irritation. In this review, we summarize the most important literature on the role of all four E prostanoid (EP) receptors on the lung's immune and structural cells to further dissect the relevance of EP2/EP4 receptors as potential targets for future asthma therapy.