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.

The EP2 agonist, omidenepag, alters the physical stiffness of 3D spheroids prepared from human corneal stroma fibroblasts differently depending on the osmotic pressure.

The objective of the current study was to examine the drug-induced effects of the EP2 agonist, omidenapag (OMD), on human corneal stroma, two- and three-dimensional (2D and 3D) cultures of human corneal stroma fibroblasts (HCSFs). The drug-induced effects on 2D monolayers and 3D spheroids were characterized by examining the ultrastructures by scanning electron microscope (SEM), transendothelial electrical resistance (TEER) measurements, and fluorescein isothiocyanate (FITC)-dextran permeability. The physical properties of 3D spheroids with respect to size and stiffness were also examined. In addition, the gene expressions of extracellular matrix (ECM) molecules, including collagen (COL) 1, 4, and 6, and fibronectin (FN), a tissue inhibitor of metalloproteinase (TIMP) 1-4, matrix metalloproteinase (MMP) 2, 9, and 14, aquaporin1 (AQP1), and several endoplasmic reticulum (ER) stress-related factors were evaluated. In the 2D HCSFs, OMD induced (1) a significant increase in ECM deposits, as evidenced by SEM, the mRNA expression of COL4 and FN, and (2) a decrease in TEER values and a concentration-dependent increase in FITC-dextran permeability. In the case of 3D spheroids, OMD had no effect on size but a substantial increase in stiffness was observed. Furthermore, such OMD-induced effects on stiffness were dramatically modulated by the osmotic pressure of the system. In contrast to the above 2D cultures, among the ECM molecules and the modulators of 3D spheroids, namely, TIMPS and MMPs, the down-regulation of COL1, TIMP1 and 2 and the up-regulation of MMP9 were observed. Interestingly, such diversity in terms of OMD-induced gene expressions between 2D and 3D cultures was also recognized in AQP1 (2D; no significant change, 3D; significant up-regulation) and ER stress-related genes. The findings presented herein suggest that the EP2 agonist, OMD, alters the physical stiffness of 3D spheroids obtained from human corneal stroma fibroblasts and this alteration is dependent on the osmotic pressures. 2D and 3D cell cultures may be useful for evaluating the drug induced effects of OMD toward human corneal stroma.

Reactivities of a Prostanoid EP2 Agonist, Omidenepag, Are Useful for Distinguishing between 3D Spheroids of Human Orbital Fibroblasts without or with Graves' Orbitopathy.

BACKGROUND: To obtain new insights into the activation of the thyroid-stimulating hormone (TSH) and insulin-like growth factor 1 (IGF-1) receptors in human orbital fibroblasts (n-HOFs), the effects of the prostanoid EP2 agonist, omidenepag (OMD), and a rho-associated coiled-coil-containing protein kinase (ROCK) inhibitor, ripasudil (Rip) were evaluated using three-dimension (3D) n-HOFs spheroids in the absence and presence of the recombinant human TSH receptor antibodies, M22 and IGF-1. METHODS: The effects of 100 nM OMD or 10 µM Rip on the physical properties, size, stiffness, and mRNA expression of several extracellular matrix (ECM) molecules, their regulator, inflammatory cytokines, and endoplasmic reticulum (ER) stress-related factors were examined and compared among 3D spheroids of n-HOFs, M22-/IGF-1-activated n-HOFs and GO-related human orbital fibroblasts (GHOFs). RESULTS: The physical properties and mRNA expressions of several genes of the 3D n-HOFs spheroids were significantly and diversely modulated by the presence of OMD or Rip. The OMD-induced effects on M22-/IGF-1-activated n-HOFs were similar to the effects caused by GHOHs, but quite different from those of n-HOFs. CONCLUSIONS: The findings presented herein indicate that the changes induced by OMD may be useful in distinguishing between n-HOFs and GHOFs.

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

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

Prostaglandin E2 increases the expression of cyclooxygenase-2 in cultured rat microglia.

Prostaglandin E2 (PGE2) plays pivotal roles in controlling microglial activation with the EP2 receptor, a PGE2 receptor subtype. Activated microglia are often reported to increase cyclooxygenase (COX)-2 expression, followed by PGE2 production, but it is unclear whether extracellular PGE2 is involved in microglial PGE2 synthesis. In the present study, we report that PGE2 increases COX-2 protein in microglia. In a culture system, PGE2 at 10-6 M for 3 h increased COX-2 and microsomal PGE synthase (mPGES)-1 mRNA levels, and reduced mPGES-2, but did not affect COX-1 or cytosolic PGE synthase (cPGES) in microglia. PGE2 at 10-6 M for 3 h also increased the COX-2 protein level, but did not affect COX-1, mPGES-1, mPGES-2, or cPGES. An EP2 agonist, ONO-AE1-259-01, also increased COX-2 and mPGES-1 mRNA levels, and reduced mPGES-2, but did not affect COX-1 or cPGES, whereas an EP1 agonist, ONO-DI-004, an EP3 agonist, ONO-AE-248, and an EP4 agonist, ONO-AE1-329, had no effect. Similar to PGE2, ONO-AE1-259-01 increased the COX-2 protein level, but did not affect COX-1, mPGES-1, mPGES-2, or cPGES. In addition, the effects of PGE2 were inhibited by an EP2 antagonist, PF-04418948, but not by an EP1 antagonist, ONO-8713, an EP3 antagonist, ONO-AE3-240, or an EP4 antagonist, ONO-AE3-208, at 10-6 M. On the other hand, lipopolysaccharide (LPS) increased PGE2 production, but the LPS-induced PGE2 production was not affected by ONO-8713, PF-04418948, ONO-AE3-240, or ONO-AE3-208. These results indicate that PGE2 increases COX-2 protein in microglia through the EP2 receptor supporting the idea that extracellular PGE2 has a triggering aspect for microglial activation.

Effects of selective EP2 receptor agonist, omidenepag, on trabecular meshwork cells, Schlemm's canal endothelial cells and ciliary muscle contraction.

This study investigated the effects of omidenepag (OMD), a novel selective EP2 receptor agonist, on human trabecular meshwork (HTM) cells, monkey Schlemm's canal endothelial (SCE) cells, and porcine ciliary muscle (CM) to clarify the mechanism of intraocular pressure (IOP) reduction involving conventional outflow pathway. In HTM and SCE cells, the effects of OMD on transforming growth factor-ß2 (TGF-ß2)-induced changes were examined. The expression of actin cytoskeleton and extracellular matrix (ECM) proteins, myosin light chain (MLC) phosphorylation in HTM cells were evaluated using real-time quantitative PCR, immunocytochemistry, and western blotting. The expression of barrier-related proteins, ZO-1 and ß-catenin, and permeability of SCE cells were evaluated using immunocytochemistry and transendothelial electrical resistance. The CM contraction was determined by contractibility assay. OMD significantly inhibited expression of TGF-ß2 induced mRNA, protein, and MLC-phosphorylation on cytoskeletal and ECM remodeling in the HTM dose dependently. In SCE cells, OMD suppressed TGF-ß2-induced expression of the barrier-related proteins and decreased SCE monolayer permeability. OMD at 3 µM significantly inhibited CM contraction, however, the effect was not significant at lower concentrations. IOP lowering effect of OMD through conventional outflow pathway is exerted by increasing outflow facilities with the modulation of TM cell fibrosis and SCE cell permeability.

Addition of EP2 agonists to an FP agonist additively and synergistically modulates adipogenesis and the physical properties of 3D 3T3-L1 sphenoids.

The additive effects of prostaglandin (PG)-EP2 agonists on a PG-FP agonist toward adipogenesis in two- or three-dimension (2D or 3D) cultures of 3T3-L1 cells was examined by lipid staining, the mRNA expression of adipogenesis related genes, and extracellular matrixes (ECMs) including collagen molecules (Col) -1, -4 and -6, and fibronectin (Fn), and the sizes and physical properties of 3D sphenoids, as measured by a micro-squeezer. The results indicate that adipogenesis induced 1) an enlargement in the sizes of 3D sphenoids, 2) a substantial enhancement in lipid staining, the expression of the PParγ, Ap2 and Leptin genes, and 3) a significant decrease in the stiffness of the 3D sphenoids. These effects were inhibited by bimatoprost acid (BIM-A), but 4) adipogenesis induced significant down-regulation of Col1 and Fn, and the significant up-regulation of the Col4 and Col6 genes were unchanged by BIM-A. On the addition of an EP2 agonist, such as omidenepag (OMD) or butaprost (Buta), to BIM-A, 1) the sizes of the 3D sphenoids were further decreased, 2) lipid staining was decreased (2D; OMD, 3D; Buta) 3) the stiffness of the 3D sphenoids was increased by Buta, 4) the expression of PParγ was up-regulated (2D; Buta) or unchanged (3D), the expression of Ap2 was down-regulated (2D; OMD) or up-regulated (3D; Buta), and the expression of Leptin was increased (2D), 5) the expression of all four (OMD) or all except Col4 (buta) in 2D, and Col1and Col4 (OMD) in 3D were up-regulated. These collective findings indicate that the addition of an EP2 agonist, OMD or Buta significantly modulated the BIM-A induced suppression of adipogenesis as well as physical properties of 2D and 3D cultured 3T3-L1 cells in different manners.

Myeloid-Derived Suppressor Cells Dampen Airway Inflammation Through Prostaglandin E2 Receptor 4.

Emerging evidence suggests a mechanistic role for myeloid-derived suppressor cells (MDSCs) in lung diseases like asthma. Previously, we showed that adoptive transfer of MDSCs dampens lung inflammation in murine models of asthma through cyclooxygenase-2 and arginase-1 pathways. Here, we further dissected this mechanism by studying the role and therapeutic relevance of the downstream mediator prostaglandin E2 receptor 4 (EP4) in a murine model of asthma. We adoptively transferred MDSCs generated using an EP4 agonist in a murine model of asthma and studied the consequences on airway inflammation. Furthermore, pegylated human arginase-1 was used to model MDSC effector activities. We demonstrate that the selective EP4 agonist L-902,688 increased the number and suppressive activity of MDSCs through arginase-1 and nitric oxide synthase-2. These results showed that adoptive transfer of EP4-primed MDSCs, EP4 agonism alone or arginase-1 administration ameliorated lung inflammatory responses and histopathological changes in asthmatic mice. Collectively, our results provide evidence that MDSCs dampen airway inflammation in murine asthma through a mechanism involving EP4.

Simultaneous Use of ROCK Inhibitors and EP2 Agonists Induces Unexpected Effects on Adipogenesis and the Physical Properties of 3T3-L1 Preadipocytes.

To elucidate the additive effects of an EP2 agonist, omidenepag (OMD) or butaprost (Buta) on the Rho-associated coiled-coil-containing protein kinase (ROCK) inhibitor, ripasudil (Rip) on adipose tissue, two- or three-dimension (2D or 3D) cultures of 3T3-L1 cells were analyzed by lipid staining, the mRNA expression of adipogenesis-related genes, extracellular matrix (ECM) molecules including collagen (Col) -1, -4 and -6, and fibronectin (Fn), and the sizes and physical properties of 3D organoids, as measured by a micro-squeezer. The results indicate that adipogenesis induced (1) an enlargement of the 3D organoids; (2) a substantial enhancement in lipid staining as well as the expression of the Pparγ, Ap2 and Leptin genes; (3) a significant softening of the 3D organoids, the effects of which were all enhanced by Rip except for Pparγ expression; and (4) a significant downregulation in Col1 and Fn, and a significant upregulation in Col4, Col6, the effects of which were unchanged by Rip. When adding the EP2 agonist to Rip, (1) the sizes of the 3D organoids were reduced substantially; (2) lipid staining was increased (OMD), or decreased (Buta); (3) the stiffness of the 3D organoids was substantially increased in Buta; (4-1) the expression of Pparγ was suppressed (2D, OMD) or increased (2D, Buta), and the expressions of Ap2 were downregulated (2D, 3D) and Leptin was increased (2D) or decreased (3D), (4-2) all the expressions of four ECM molecules were upregulated in 2D (2D), and in 3D, the expression of Col1, Col4 was upregulated. The collective findings reported herein indicate that the addition of an EP2 agonist, OMD or Buta significantly but differently modulate the Rip-induced effects on adipogenesis and the physical properties of 2D and 3D cultured 3T3-L1 cells.

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.

Additive Intraocular Pressure-Lowering Effects of a Novel Selective EP2 Receptor Agonist, Omidenepag Isopropyl, Combined with Existing Antiglaucoma Agents in Conscious Ocular Normotensive Monkeys.

Purpose: To investigate the intraocular pressure (IOP)-lowering effects of omidenepag isopropyl (OMDI), a potent and highly selective prostanoid EP2 receptor agonist, as a potential first-line ocular hypotensive agent when combined with existing antiglaucoma agents in conscious ocular normotensive monkeys. Methods: Male cynomolgus monkeys were examined under conscious conditions. OMDI ophthalmic solution alone was topically applied to an eye or combined with other ophthalmic solutions at 5-min intervals. The contralateral eye was left untreated. IOP was measured before and at 2, 4, 6, and 8 h after instillation. Results: Topical application of OMDI to the eye resulted in statistically significant IOP reduction, which lasted for at least 6 h. The IOP-lowering effects of OMDI concomitantly administered with any of the tested antiglaucoma agents (timolol, brinzolamide, netarsudil, ripasudil, and brimonidine) were greater than those of OMDI alone. Furthermore, these enhanced IOP responses to their concomitant use were statistically significant compared with those of the tested antiglaucoma agents alone. Any combination of OMDI with the tested agents did not lead to serious abnormalities either systemically or locally in the eye. Conclusions: We demonstrated that OMDI has additive IOP-lowering effects when administered in combination with various antiglaucoma agents, namely, ß-adrenergic antagonist, carbonic anhydrase inhibitor, Rho-associated coiled-coil containing protein kinase inhibitors, and α2-adrenergic agonist. These results suggest that OMDI provides additional clinical benefits because of its unique mechanisms of action when combination therapy is required.

Prostaglandin F2α and EP2 agonists, and a ROCK inhibitor modulate the formation of 3D organoids of Grave's orbitopathy related human orbital fibroblasts.

3D organoid cultures were used to elucidate the periocular effects of several anti-glaucoma drugs including a prostaglandin F2α analogue (bimatoprost acid; BIM-A), EP2 agonist (omidenepag; OMD) or a Rho-associated coiled-coil containing protein kinase (ROCK) inhibitor (ripasudil; Rip) on Grave's orbitopathy (GO) related orbital fatty tissue. 3D organoids were prepared from GO related human orbital fibroblasts (GHOFs) obtained from patients with GO. The effects of either 100 nM BIM-A, 100 nM OMD or 10 µM Rip on the 3D GHOFs organoids were examined with respect to organoid size, physical properties by a micro-squeezer, and the mRNA expression of extracellular matrix (ECM) proteins including collagen (COL) 1, COL 4, COL 6, and fibronectin (FN), ECM regulatory genes including lysyl oxidase (LOX), Connective Tissue Growth Factor (CTGF) and inflammatory cytokines including interleukin-1ß (IL1ß) and interleukin-6 (IL6). The size of the 3D GHOFs organoids decreased substantially in the presence of BIM-A, but also increased substantially in the presence of the others (OMD or Rip). The physical stiffness of the 3D GHOFs organoids was significantly decreased by Rip. BIM-A caused significantly the down-regulation of three ECM genes, Col 1, Col 6 and Fn, and two ECM regulatory genes and the up-regulation of IL6. In the presence of OMD, two ECM genes, Col 1 and Fn, and LOX were significantly down-regulated but IL1ß and IL6 were significantly up-regulated. In the case of Rip, Col 1, FN and CTGF were significant down-regulated. Our present findings indicate that anti-glaucoma drugs modulate the structures and physical properties 3D GHOFs organoids in different manners by modifying the gene expressions of ECM, ECM regulatory factors and inflammatory cytokines. The results indicate that the benefits and demerits of anti-glaucoma medications need to be scrutinized carefully, in cases of patients with GO.

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

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

Intraocular pressure-lowering effect of omidenepag isopropyl in latanoprost non-/low-responder patients with primary open-angle glaucoma or ocular hypertension: the FUJI study.

PURPOSE: Omidenepag isopropyl (OMDI) is the prodrug of omidenepag, a selective, non-prostaglandin, prostanoid EP2 receptor agonist, which has been shown to lower intraocular pressure (IOP) in patients with glaucoma and ocular hypertension (OHT). This study evaluated the efficacy and safety of OMDI ophthalmic solution 0.002% in patients with primary open-angle glaucoma or OHT who were non-/low responders to latanoprost. STUDY DESIGN: Open-label, multicenter, Phase 3 study (NCT02822742). METHODS: Following 1-4-week washout, patients were treated with latanoprost ophthalmic solution 0.005% during an 8-week run-in period. Patients with ≤15% IOP reduction at the end of the run-in (indicating non-/low response) received OMDI 0.002% (one drop once daily for 4 weeks). The primary endpoint was the change from baseline in mean diurnal IOP at Week 4. RESULTS: In total, 26 patients were treated with OMDI; two withdrew owing to lack of efficacy. The mean diurnal IOP at baseline (end of latanoprost run-in) was 23.1 mmHg (7.6% IOP reduction from end of washout) indicating non-/low response to latanoprost. After 4 weeks of OMDI treatment, mean diurnal IOP was significantly reduced from baseline (-2.99 mmHg; P < 0.0001). No serious adverse events were reported. Adverse events occurred in five patients (19.2%); adverse drug reactions (anterior chamber cell, conjunctival hyperemia, and erythema of eyelid) occurred in two patients (7.7%) and were mild in severity. CONCLUSIONS: In this study, OMDI 0.002% demonstrated a clinically significant reduction in IOP and was well tolerated in patients with primary open-angle glaucoma and OHT who were non-/low responders to latanoprost.

Generation of Cellular Reactive Oxygen Species by Activation of the EP2 Receptor Contributes to Prostaglandin E2-Induced Cytotoxicity in Motor Neuron-Like NSC-34 Cells.

Amyotrophic lateral sclerosis (ALS) is a devastating motor neuron disease characterized by progressive degeneration of motor neurons in the central nervous system. Prostaglandin E2 (PGE2) plays a pivotal role in the degeneration of motor neurons in human and transgenic models of ALS. We have shown previously that PGE2 directly induces neuronal death through activation of the E-prostanoid (EP) 2 receptor in differentiated NSC-34 cells, a motor neuron-like cell line. In the present study, to clarify the mechanisms underlying PGE2-induced neurotoxicity, we focused on generation of intracellular reactive oxygen species (ROS) and examined the effects of N-acetylcysteine (NAC), a cell-permeable antioxidant, on PGE2-induced cell death in differentiated NSC-34 cells. Dichlorofluorescein (DCF) fluorescence analysis of PGE2-treated cells showed that intracellular ROS levels increased markedly with time, and that this effect was antagonized by a selective EP2 antagonist (PF-04418948) but not a selective EP3 antagonist (L-798,106). Although an EP2-selective agonist, butaprost, mimicked the effect of PGE2, an EP1/EP3 agonist, sulprostone, transiently but significantly decreased the level of intracellular ROS in these cells. MTT reduction assay and lactate dehydrogenase release assay revealed that PGE2- and butaprost-induced cell death were each suppressed by pretreatment with NAC in a concentration-dependent manner. Western blot analysis revealed that the active form of caspase-3 was markedly increased in the PGE2- and butaprost-treated cells. These increases in caspase-3 protein expression were suppressed by pretreatment with NAC. Moreover, dibutyryl-cAMP treatment of differentiated NSC-34 cells caused intracellular ROS generation and cell death. Our data reveal the existence of a PGE2-EP2 signaling-dependent intracellular ROS generation pathway, with subsequent activation of the caspase-3 cascade, in differentiated NSC-34 cells, suggesting that PGE2 is likely a key molecule linking inflammation to oxidative stress in motor neuron-like NSC-34 cells.

The Antiglaucoma Agent and EP2 Receptor Agonist Omidenepag Does Not Affect Eyelash Growth in Mice.

Purpose: The present study investigated the effects of the antiglaucoma agent and selective E2 receptor agonist omidenepag isopropyl (OMDI) on eyelash growth in comparison with a prostaglandin analog (prostamide receptor agonist) in mice. Methods: Four-week-old female mice (C57BL/6J) were divided into 3 groups of n = 10 each. The groups were administered 3 µL of 0.003% OMDI solution, the vehicle (negative control), or a 0.03% bimatoprost solution (positive control) on the upper eyelids of the right eyes once daily for 14 days. On the 15th day, all animals were euthanized, and the upper eyelids with eyelashes were fixed with 10% neutral formalin. Eyelashes were evaluated for number, length, and thickness using a stereomicroscope. Specimens were then paraffin-embedded and stained with hematoxylin and eosin, followed by microscopic examination to assess eyelash morphology and growth cycle. Results: Eyelash number (143.5 ± 6.7/eyelid), thickness, and percentage of dermal papilla in the anagen phase in the OMDI group were similar to those observed in the vehicle group (eyelash number, 144.2 ± 5.7/eyelid). In contrast, eyelash number (166.7 ± 7.0/eyelid), thickness, and the percentage of dermal papilla in the anagen phase were significantly greater in the bimatoprost group compared with those of the vehicle group. Conclusions: Unlike existing prostaglandin analogs, our findings indicate that OMDI has no effect on eyelash growth in mice, suggesting that it may be a promising antiglaucoma agent with a reduced number of adverse effects.

Effects of the Selective EP2 Receptor Agonist Omidenepag on Adipocyte Differentiation in 3T3-L1 Cells.

Purpose: We aimed at comparing the effects of omidenepag (OMD) with those of prostaglandin F (FP) receptor agonists (FP agonists) on adipogenesis in mouse 3T3-L1 cells. Methods: To evaluate the agonistic activities of OMD against the mouse EP2 (mEP2) receptor, we determined cAMP contents in mEP2 receptor-expressing CHO cells by using radioimmunoassays. Overall, 3T3-L1 cells were cultured in differentiation medium for 10 days and adipocyte differentiation was assessed according to Oil Red O-stained cell areas. Changes in expression levels of the adipogenic transcription factors Pparg, Cebpa, and Cebpb were determined by using real-time polymerase chain reaction (PCR). OMD at 0.1, 1, 10, and 40 µmol/L, latanoprost free acid (LAT-A) at 0.1 µmol/L, or prostaglandin F2α (PGF2α), at 0.1 µmol/L were added to cell culture media during adipogenesis. Oil Red O-stained areas and expression patterns of transcription factor targets of OMD or FP agonists were compared with those of untreated controls. Results: The 50% effective concentration (EC50) of OMD against the mEP2 receptor was 3.9 nmol/L. Accumulations of Oil Red O-stained lipid droplets were observed inside control cells on day 10. LAT-A and PGF2α significantly inhibited the accumulation of lipid droplets; however, OMD had no effect on this process even at concentrations up to 40 µmol/L. LAT-A and PGF2α significantly suppressed Pparg, Cebpa, and Cebpb gene expression levels during adipocyte differentiation. Conversely, OMD had no obvious effects on the expression levels of these genes. Conclusions: A selective EP2 receptor agonist, OMD, did not affect the adipocyte differentiation in 3T3-L1 cells, whereas FP agonists significantly inhibited this process.

Agonist-specific desensitization of PGE2-stimulated cAMP signaling due to upregulated phosphodiesterase expression in human lung fibroblasts.

Pulmonary fibrosis is characterized by fibroblasts persisting in an activated form, producing excessive fibrous material that destroys alveolar structure. The second messenger molecule cyclic 3',5'-adenosine monophosphate (cAMP) has antifibrotic properties, and prostaglandin E2 (PGE2) can stimulate cAMP production through prostaglandin E (EP)2 and EP4 receptors. Although EP receptors are attractive therapeutic targets, the effects of long-term exposure to PGE2 have not been characterized. To determine the effects of long-term exposure of lung fibroblasts to PGE2, human fetal lung (HFL)-1 cells were treated for 24 h with 100 nM PGE2 or other cAMP-elevating agents. cAMP levels stimulated by acute exposure to PGE2 were measured using a fluorescent biosensor. Pretreatment for 24 h with PGE2 shifted the concentration-response curve to PGE2 rightward by approximately 22-fold but did not affect responses to the beta-adrenoceptor agonist isoproterenol. Neither isoproterenol nor forskolin pretreatment altered PGE2 responses, implying that other cAMP-elevating agents do not induce desensitization. Use of EP2- and EP4-selective agonists and antagonists suggested that PGE2-stimulated cAMP responses in HFL-1 cells are mediated by EP2 receptors. EP2 receptors are resistant to classical mechanisms of agonist-specific receptor desensitization, so we hypothesized that increased PDE activity mediates the loss of signaling after PGE2 pretreatment. PGE2 treatment upregulated messenger RNA for PDE3A, PDE3B, PDE4B, and PDE4D and increased overall PDE activity. The PDE4 inhibitor rolipram partially reversed PGE2-mediated desensitization and PDE4 activity was increased, but rolipram did not alter responses to isoproterenol. The PDE3 inhibitor cilostazol had minimal effect. These results show that long-term exposure to PGE2 causes agonist-specific desensitization of EP2 receptor-stimulated cAMP signaling through the increased expression of PDE isozymes, most likely of the PDE4 family.

Pharmacokinetics, Safety, and Intraocular Pressure-Lowering Profile of Omidenepag Isopropyl, a Selective, Nonprostaglandin, Prostanoid EP2 Receptor Agonist, in Healthy Japanese and Caucasian Volunteers (Phase I Study).

Purpose: Omidenepag isopropyl (OMDI) is a prodrug of OMD, a selective, nonprostaglandin, prostanoid EP2 receptor agonist. This phase I study aimed to investigate the pharmacokinetic properties, safety, and intraocular pressure (IOP)-lowering efficacy of OMDI. Methods: Fourteen healthy male volunteers (7 Japanese and 7 Caucasian) 20-35 years of age received 1 drop of OMDI 0.0025% at 9:00 h in both eyes for 7 days. Blood samples were taken predose and up to 8 h postdose on days 1, 3, and 7. The plasma concentration of OMD was determined using high-performance liquid chromatography-tandem mass spectrometry. Pharmacokinetic parameters measured included the maximum plasma concentration (Cmax) and the half-life (t½) of OMD. IOP, adverse events (AEs), ophthalmic examinations, vital signs, and laboratory values were assessed. Results:Cmax for all subjects was reached after 10-15 min and decreased with a t½ of ∼30 min. Ad hoc statistical analyses found significant differences in some pharmacokinetic parameters between Japanese and Caucasian subjects, likely due to differences in body weight. These differences reduced over 7 days of dosing and were not thought to be clinically meaningful. There was no OMD accumulation after 7 days of repeated dosing. Mean IOP was reduced by ∼4-5 mmHg between baseline and 2 h postdose, remaining stable from day 3 onward. All AEs were mild and considered treatment related. Conclusions: Pharmacokinetic parameters of OMD were similar between Japanese and Caucasian subjects. There was no accumulation of OMD after 7 days of dosing. OMDI was well tolerated and demonstrated clinically significant IOP reductions.

Antiglaucoma EP2 Agonists: A Long Road That Led Somewhere.

For >2 decades, EP2 agonists have been the subject of antiglaucoma research and development by scientists in industry and academia around the world. The road has led to the recent approval of the first drug of this class. This article reviews the development of EP2 agonists from conception to clinical approval, discussing pharmacology, structure, biodistribution, therapeutics, and drug delivery. An extensive list of source references is provided for the reader's benefit.