Prostanoid EP4 Research Articles

TRAP-Induced Platelet Reactivity Is Inhibited by Omega-3 Fatty Acid-Derived Prostaglandin E3 (PGE3).

Background: Prostaglandins are naturally occurring local mediators that can participate in the modulation of the cardiovascular system through their interaction with Gs/Gi-coupled receptors in different tissues and cells, including platelets. Thrombin is one of the most important factors that regulates platelet reactivity and coagulation. Clinical trials have consistently shown that omega-3 fatty acid supplementation lowers the risk for cardiovascular mortality and morbidity. Since omega-3 fatty acids are the main precursors of PGE3 in vivo, it would be relevant to investigate the effects of PGE3 on Thrombin Receptor Activating Peptide (TRAP-6)-induced platelet reactivity to determine the receptors and possible mechanisms of action of these compounds. Methods: We have measured platelet aggregation, P-selectin expression, and vasodilator-stimulated phosphoprotein (VASP) phosphorylation to evaluate platelet reactivity induced by TRAP-6 to determine the effects of PGE3 on platelet function. Results: We assessed the ability of DG-041, a selective prostanoid EP3 receptor antagonist, and of ONO-AE3-208, a selective prostanoid EP4 receptor antagonist, to modify the effects of PGE3. PGE3 inhibited TRAP-6-induced platelet aggregation and activation. This inhibition was enhanced in the presence of a Gi-coupled EP3 receptor antagonist and abolished in the presence of a Gs-coupled EP4 receptor antagonist. The effects of PGE3 were directly related to changes in cAMP, assessed by VASP phosphorylation. Conclusions: The general effects of PGE3 on human platelet reactivity are the consequence of a balance between activatory and inhibitory effects at receptors that have contrary effects on adenylate cyclase. These results indicate a potential mechanism by which omega-3 fatty acids underlie cardioprotective effects.

Inducible deletion of the prostaglandin EP3 receptor in kidney tubules of male and female mice has no major effect on water homeostasis.

The prostaglandin E2 (PGE2) receptor EP3 has been detected in the thick ascending limb (TAL) and the collecting duct of the kidney, where its actions are proposed to inhibit water reabsorption. However, EP3 is also expressed in other cell types, including vascular endothelial cells. The aim here was to determine the contribution of EP3 in renal water handling in male and female adult mice by phenotyping a novel mouse model with doxycycline-dependent deletion of EP3 throughout the kidney tubule (EP3-/- mice). RNAscope demonstrated that EP3 was highly expressed in the cortical and medullary TAL of adult mice. Compared with controls EP3 mRNA expression was reduced by >80% in whole kidney (RT-qPCR) and nondetectable (RNAscope) in renal tubules of EP3-/- mice. Under basal conditions, there were no significant differences in control and EP3-/- mice of both sexes in food and water intake, body weight, urinary output, or clinical biochemistries. No differences were detectable between genotypes in handling of an acute water load or in their response to the vasopressin analog 1-deamino-8-d-arginine-vasopressin (dDAVP). No differences in water handling were observed when PGE2 production was enhanced using 1% NaCl load. Expression of proteins involved in kidney water handling was not different between genotypes. This study demonstrates that renal tubular EP3 is not essential for body fluid homeostasis in males or females, even when PGE2 levels are high. The mouse model is a novel tool for examining the role of EP3 in kidney function independently of potential developmental abnormalities or systemic effects.NEW & NOTEWORTHY The prostanoid EP3 receptor is proposed to play a key role in the kidney tubule and antagonize the effects of vasopressin on aquaporin-mediated water reabsorption. Here, we phenotyped a kidney tubule-specific inducible knockout mouse model of the EP3 receptor. Our major finding is that, even under physiological stress, tubular EP3 plays no detectable role in renal water or solute handling. This suggests that other EP receptors must be important for renal salt and water handling.

Genetic deletion of 12/15 lipoxygenase delays vascular remodeling and limits cardiorenal dysfunction after pressure overload.

The lipid metabolizing enzyme 12/15 lipoxygenase (12/15LOX) induces proinflammatory responses that may increase cardiovascular and renal complications after cardiac insult. To define the role of 12/15LOX, 8-12-week-old male C57BL/6J wild-type (WT; n=49) and 12/15LOX-/- mice (n=50) were subject to transverse aortic constriction (TAC) and monitored for 7, 28, and 56days (d) post-TAC. Compared with WT, 12/15LOX-/- mice experienced less left ventricle (LV) dysfunction with limited LV hypertrophy and lung edema post-TAC. 12/15LOX deletion decreased TAC-induced proinflammatory mediators 12-HETE and prostaglandins with modulation in mir-7a-5p, mir 26a-5p, miR-21e-5p, and miR-107-3p during chronic remodeling period (after d28). At d7 post-TAC, 12/15LOX-/- mice showed increased cardiac gene expression of Arg-1 and the prostanoid receptors EP2 and EP4. The EP4 receptor expression was consistently elevated from d7 till d56 in 12/15LOX-/- mice post-TAC compared with WT controls. Post-TAC, wheat germ agglutinin staining revealed less cardiomyocyte hypertrophy at d28 and d56 in 12/15LOX-/- mice compared with WT. TAC-induced vascular remodeling was marked by disruption in the endothelium, evident by irregular CD31 staining and increased alpha-smooth muscle actin (α-SMA) in WT mice at d28 and d56. Compared to WT, 12/15LOX-/- mice exhibited a diminished expression of NGAL in the kidney, suggesting that 12/15LOX-/- reduced cardiorenal dysfunction post-TAC. In WT-TAC mice, structural analyses of the kidney revealed glomerular swelling during the maladaptive phase of heart failure, with decreases in the capsula glomeruli space and glomerular sclerosis compared to 12/15LOX-/- mice. Overall, vascular and kidney inflammation markers were higher in WT than in 12/15LOX-/- post-TAC. Thus, deletion of 12/15LOX limits LV hypertrophy associated with perivascular inflammation and cardiorenal remodeling after pressure overload. Deficiency of 12/15 LOX serves a dual role in delaying an early adaptive interstitial remodeling with long-term protective effects on cardiac hypertrophy and cardiac fibrosis and detrimental adverse vascular remodeling during later maladaptive remodeling after pressure overload.

Cystoid macular edema associated with omidenepag isopropyl in a phakic eye with an implantable collamer lens: a case report

BackgroundCystoid macular edema is a known complication of omidenepag isopropyl usage. Omidenepag isopropyl is a selective prostanoid EP2 receptor agonist, and its association with macular edema has mainly been identified in pseudophakic eyes. Herein, we report a case of cystoid macular edema caused by omidenepag isopropyl use in a phakic eye with an implantable collamer lens.Case presentationA 38-year-old woman was diagnosed with left eye glaucoma and prescribed omidenepag isopropyl. She had undergone bilateral implantation of implantable collamer lenses approximately 12 years prior to the glaucoma diagnosis. After 9 months of using omidenepag isopropyl, she presented with blurred vision in the left eye; swept source optical coherence tomography revealed cystoid macular edema in this eye. Omidenepag isopropyl usage was discontinued, and bromfenac sodium hydrate was administered twice daily instead. After 2 months, the patient’s visual discomfort was completely ameliorated. Additionally, an optical coherence tomography examination confirmed that the macula had normalized.ConclusionsWe report a case of cystoid macular edema development after omidenepag isopropyl use in a patient with glaucoma who had undergone bilateral implantable collamer lens implantation. This case shows that the possibility of cystoid macular edema occurrence should be considered when omidenepag isopropyl is used, even in phakic eyes, after the insertion of implantable collamer lenses.

Prostanoid FP and EP2 Receptor Agonists Induce Epithelial and Subepithelial Fibrogenetic Changes in Human Conjunctival Fibroblasts in Different Manners.

Purpose: To examine the effects of prostanoid FP and EP2 receptor agonists, PGF2α and Omidenepag (OMD), respectively, on the transforming growth factor beta (TGF-β2) induced conjunctival fibrogenesis. Methods: Two-dimension (2D) and three-dimension (3D) cultures of these fibroblasts were subjected to following analyses: (1) planar proliferation evaluated by transendothelial electron resistance (TEER) measurements, (2) real-time metabolic analyses, (3) subepithelial proliferation evaluated by 3D spheroid' size and stiffness measurements, and (4) the mRNA expression of extracellular matrix (ECM) molecules and their modulators. Results: TGF-β2 induced increase in the planar proliferation was significantly decreased or enhanced by PGF2α or OMD, respectively. The proportion of oxygen consumption required to drive ATP synthesis compared with that driving proton leakage was increased by PGF2α and OMD independently with TGF-β2. In contrast, maximal mitochondrial respiration was decreased by PGF2α and OMD, and the OMD-induced effect was further enhanced by the presence of TGF-β2. In addition, the TGF-β2 dependent increase in the glycolytic capacity was cancelled by PGF2α and/or OMD. Alternatively, subepithelial proliferation, as evidenced by the stiffness of the 3D spheroids, was substantially increased by both PGF2α and OMD, and these were differently modulated by TGF-β2. The expression of several related factors as above fluctuated among the conditions for both 2D and 3D and TGF-β2 untreated or treated cultures. Conclusion: The present findings indicate that the prostanoid FP or the EP2 receptor agonist may solely and differently induce the planar and subepithelial proliferation of HconF cells and these were also modulated by TGF-β2.

A phase 1 study of TPST-1495 as a single agent and in combination with pembrolizumab in patients with advanced solid tumors.

3107 Background: TPST-1495 is a novel oral therapy designed to be a selective dual antagonist of the prostanoid receptors, EP2 and EP4. Through these receptors, PGE2 stimulates tumor growth, suppresses immunity, and supports adaptive resistance to checkpoint inhibitors. In preclinical models, dual EP2/EP4 inhibition with TPST-1495 increased anti-tumor efficacy, reduced immune suppression, and activated immune effector response significantly better than single EP2 or EP4 antagonists and the COX-2 inhibitor celecoxib. Methods: In this Phase 1 study, subjects with advanced solid tumors received TPST-1495 in a modified 3+3 design optimizing dose and schedule as monotherapy and in combination with standard dose pembrolizumab. Study objectives included safety, PK/PD, recommended phase 2 dose (RP2D), anti-tumor activity and exploratory biomarkers. AEs were assessed per CTCAE v5 and efficacy per RECIST v1.1. Results: TPST-1495 monotherapy was dosed BID (n=11), QD (n=22) or QD days 1-5 every 7 days (n=17) and in combination was dosed QD only with pembrolizumab 200 mg IV q3 weeks (n=24). TPST-1495 doses ranged from 15 mg QD to 100 mg BID. Most subjects had CRC (61%) followed by endometrial (5.4%) and pancreatic (5.4%) cancer. Median prior lines of systemic therapy were 4 (2-10) in monotherapy; 3 (1-8) in combination The most common treatment related AEs (TRAEs) were diarrhea (22%), abdominal pain (20%), fatigue, and nausea (18% each) for monotherapy and nausea (29%), fatigue (21%) and diarrhea (17%) for combination therapy. The most common Gr 3 TRAEs were anemia (6.0%) in monotherapy, and ALT/ AST increased and fatigue (4.2% each) in combination. No Gr 4/5 TRAEs were reported. For mono vs combo cohorts, the median time on study was 1.9 mo (0.2 – 10.2) vs 2.7 mo (0.5 – 10.4) and the disease control rate was 43% (19/44) vs 43% (9/21) with 1 PR in a combination subject with MSS CRC. Pharmacodynamic activities included on-treatment increases in urine PGE2 metabolites and drug-dependent TNF-α rescue in an ex-vivo whole blood PGE2 challenge assay. The RP2D is 50 mg QD for mono and in evaluation for combo therapy. In a subject with endometrial cancer with 22% tumor shrinkage and 222+ days on combination therapy paired biopsies showed high COX-2 expression in the TME at baseline and increased CD8+ and CD8+GrB T cell infiltration on treatment. Conclusions: PGE2 is an important target for cancer and immunotherapy but remains ineffectively drugged. TPST-1495 is a novel oral therapy that inhibits signaling only at the tumor promoting EP2/EP4 receptors. In patients with heavily treated solid tumors, primarily MSS CRC, TPST-1495 had pharmacodynamic activity, a manageable safety profile, and a potential signal of activity consistent with the preclinical data and IO combination mechanism. A combination therapy cohort in endometrial cancer is underway. Updated results and biomarker work will be presented. Clinical trial information: NCT04344795 .

Discovery of 2H-Indazole-3-carboxamide Derivatives as Novel Potent Prostanoid EP4 Receptor Antagonists for Colorectal Cancer Immunotherapy.

Nowadays, small-molecule drugs have become an indispensable part of tumor immunotherapy. Accumulating evidence has indicated that specifically blocking PGE2/EP4 signaling to induce robust antitumor immune response represents an attractive immunotherapy strategy. Herein, a 2H-indazole-3-carboxamide containing compound 1 was identified as a EP4 antagonist hit by screening our in-house small-molecule library. Systematic structure-activity relationship exploration leads to the discovery of compound 14, which displayed single-nanomolar EP4 antagonistic activity in a panel of cell functional assays, high subtype selectivity, and favorable drug-like profiles. Moreover, compound 14 profoundly inhibited the up-regulation of multiple immunosuppression-related genes in macrophages. Oral administration of compound 14, either as monotherapy or in combination with an anti-PD-1 antibody, significantly impaired tumor growth via enhancing cytotoxic CD8+ T cell-mediated antitumor immunity in a syngeneic colon cancer model. Thus, these results demonstrate the potential of compound 14 as a candidate for developing novel EP4 antagonists for tumor immunotherapy.

Opioid modulation of T-type Ca2+ channel-dependent neuritogenesis/neurite outgrowth through the prostaglandin E2/EP4 receptor/protein kinase A pathway in mouse dorsal root ganglion neurons

Irregular regeneration or inappropriate remodeling of the axons of the primary afferent neurons after peripheral nerve trauma could be associated with the development of neuropathic pain. We analyzed the molecular mechanisms for the neuritogenesis and neurite outgrowth caused by prostaglandin E2 (PGE2) in mouse dorsal root ganglion (DRG) neurons, and evaluated their opioid modulation. PGE2 in combination with IBMX, a phosphodiesterase inhibitor, caused neuritogenesis/neurite outgrowth in DRG cells, an effect abolished by a prostanoid EP4, but not EP2, receptor antagonist, and inhibitors of adenylyl cyclase or protein kinase A (PKA). Blockers of T-type Ca2+ channels (T-channels), that are responsible for window currents involving the sustained low-level Ca2+ entry at voltages near the resting membrane potentials and can be functionally upregulated by PKA, inhibited the neuritogenesis/neurite outgrowth caused by PGE2/IBMX or dibutylyl cyclic AMP, a PKA activator, in DRG neurons, an inhibitory effect mimicked by ZnCl2 and ascorbic acid that block Cav3.2, but not Cav3.1 or Cav3.3, T-channels. Morphine and DAMGO, μ-opioid receptor (MOR) agonists, suppressed the neuritogenesis and/or neurite outgrowth induced by PGE2/IBMX in DRG neurons and also DRG neuron-like ND7/23 cells, an effect reversed by naloxone or β-funaltrexamine, a selective MOR antagonist. Our data suggest that the EP4 receptor/PKA/Cav3.2 pathway is involved in the PGE2-induced neuritogenesis/neurite outgrowth in DRG neurons, which can be suppressed by MOR stimulation. We propose that MOR agonists including morphine in the early phase after peripheral nerve trauma might delay the axonal regeneration of the primary afferent neurons but prevent the development of neuropathic pain.

Recent Trends in Treatment and Associated Costs of Primary Angle-Closure Glaucoma: A Retrospective Cohort Study

To describe recent trends in the treatment for primary angle-closure glaucoma (PACG) and its associated costs in a clinical setting. A retrospective cohort study. We included patients with PACG from 2011 to 2020 using a large-scale administrative claims database in Japan. We calculated the frequencies and costs of antiglaucoma drugs, ophthalmic examinations, and glaucoma-related surgeries, stratified by fiscal years and age groups. Frequencies and costs of antiglaucoma drugs, ophthalmic examinations, and glaucoma-related surgeries. We identified 5654 patients with PACG (15 338 patient-years). Prostanoid FP receptor agonist, nonselective β-blocker, and topical carbonic anhydrase inhibitor use decreased, whereas prostanoid EP2 receptor agonist, α-2 adrenergic agonist, Rho-associated protein kinase inhibitor, and fixed-combination eyedrops use increased. The total amount of drug per patient-year significantly decreased. In recent years, the frequency of cataract surgery increased, whereas that of laser peripheral iridotomy decreased. Visual field testing, slit-lamp examination, intraocular pressure measurement, and funduscopy were performed 0.83, 6.65, 5.15, and 4.61 times/patient-year, respectively. The total cost of drugs, examinations, and surgeries was 60 338 yen per patient-year. Patients with PACG spent more than twice the money on surgeries and examinations than they did on antiglaucoma drugs. The amount of antiglaucoma drugs dispensed decreased, and the proportion of fixed-combination and newly introduced eyedrops increased. Frequency of cataract surgery increased whereas that of laser peripheral iridotomy decreased in recent years. Surgeries and examinations were the major cost drivers for PACG treatment. The current results would be valuable information for future economic analyses and policy making. The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Role of Prostaglandins in Nitric Oxide-Induced Glial Cell-Mediated Vasodilation in Rat Retina.

We previously identified that NO derived from neuronal cells acts on glial cells and causes vasodilation in the healthy rat retina via the release of epoxyeicosatrienoic acids (EETs) and prostaglandins (PGs) by activation of the arachidonic acid cascade. However, it is not clear which PG types are involved in these responses. The aim of the present study was to identify prostanoid receptors involved in glial cell-derived vasodilation induced by NO in rat retina. Male Wistar rats were used to examine the effects of intravitreal pretreatment with indomethacin, a cyclooxygenase inhibitor; PF-04418948, a prostanoid EP2 receptor antagonist; and CAY10441, a prostanoid IP receptor antagonist, on the changes in the retinal arteriolar diameter induced by intravitreal administration of NOR3, an NO donor. Retinal arteriolar diameters were measured using ocular fundus images captured with a high-resolution digital camera in vivo. The increase in the retinal arteriolar diameter induced by intravitreal injection of NOR3 was significantly suppressed by intravitreal pretreatment with indomethacin and PF-04418948, but not by CAY10441. The dose of PF-04418948 and CAY10441 injected intravitreally in the present study significantly reduced the increase in the retinal arteriolar diameter induced by prostaglandin E2 (PGE2) and prostaglandin I2 (PGI2), respectively. These results suggest that activation of the arachidonic acid cascade and subsequent stimulation of prostanoid EP2 receptors are involved in rat retinal vasodilatory responses evoked by NO-induced glial cell stimulation. Therefore, glial cell-derived PGE2, similar to EETs, may play an important role in retinal vasodilatory mechanisms.

Abstract P062: Interaction Of Cytochrome P450 1B1 And 12/15 Lipoxygenase In Paraventricular Nucleus In The Regulation Of Angiotensin II-induced Hypertension In Female Mice

Recently, we showed that 17β-estradiol (E2)-cytochrome P450 (CYP) 1B1-generated metabolite 2-methoxyestradiol (2-ME) in the paraventricular nucleus (PVN) protects from angiotensin (Ang) II-induced hypertension. Moreover, we showed that 2-ME produces this action by inhibiting the cytosolic phospholipase (cPLA) 2 α/arachidonic acid (AA)-cyclooxygenase (COX)-generated metabolites prostaglandin (PG)E 2 and thromboxane (TX)A 2 exerting prohypertensive effects via prostanoid receptors EP1, EP3, and TP, respectively, in female mice. 12/15 lipoxygenase (ALOX15), which also metabolizes AA, is present in the brain in neural tissue, endothelial cells, microglia, and astrocytes. This study was conducted to determine the contribution of central 12/15 lipoxygenase (ALOX15) and its relationship to CYP1B1 in Ang II-induced hypertension in the female mice. ALOX15 knockdown in the PVN by transduction with adenovirus (Ad)-ALOX15-short hairpin (sh)RNA (200 nL, bilaterally 7.04х10 11 pfu/mL) but not its control Ad-scrambled (Scr)-shRNA (6.4х10 11 pfu/mL) produced a greater reduction in systolic blood pressure (SBP, mmHg) measured by tail-cuff in response to Ang II (700 ng/kg/min, subcutaneous, osmotic pump, two weeks) in intact Cyp1b1 knockout (KO, E2 present but lacking 2-ME) than wild-type (WT, endogenous E2 and 2-ME present) female mice (Day 12: 177±4 vs 143±1 and 133±3 vs 124±1, respectively, P<0.05, n=4/group). Moreover, administration of ALOX15-generated AA metabolite 12(S)-hydroxyeicosatetraenoic acid (HETE) in a dose (50 ng/ 2 μL/ every 3rd day, intracerebroventricularly) that did not alter the mean arterial pressure (MAP) alone produced a greater increase in MAP in response to Ang II in ovariectomized (both E2 and 2-ME are lacking) than intact Alox15 KO female mice (Day 0 vs Day 12: 103±4 vs 167±2 and 103±2 vs 128±1, respectively, P<0.05, n=4/group). These results suggest that E2, via its CYP1B1-derived metabolite 2-ME, inhibits the generation of ALOX15/AA metabolite 12(S)-HETE in the brain to protect against Ang II-induced hypertension in female mice. Thus, 2-ME and/or ALOX15/12(S)-HETE inhibitors could be useful for treating hypertension and its pathogenesis in females.

In vivo and In silico Anti Inflammatory Studies of Alstonia scholaris Bark Extract

The present research is focused on screening In vivo anti-inflammatory activity using carrageen and formalin induced paw edema model in rodents and In silico approaches like docking studies (mcule), Ramchandran plot (procheck) and PASS. The extract significantly inhibited inflammation caused by carrageenan and formalin at doses of 200 mg and 400 mg/kg body weight which is compared to the the effect of the standard drugs meloxicam and indomethacin. Docking studies for natural compounds were carried out against PDB ID: 2AZ5, PDB ID: 1IBC, PDB ID: 6COX, and PDB ID: 4NOS in order to assess the ligand-binding affinity of the active principles of the extract. The docking results showed that the phytoconstituents from the extract and standard drugs meloxicam and indomethacin had shown highest glide scores with all the selected proteins which indicate a greater affinity for binding between receptor and ligand. From the PASS results the possible interventions of selected active constituents of Alstonia scholaris were found to be anti- inflammatory intestinal, Prostaglandin-E2 9-reductase inhibitor, TNF expression inhibitor, Cyclooxygenase 1 and 2 inhibitors, NOS2 expression inhibitor, and Interleukin1 and 6 antagonists. From the prediction results of adverse effects the constituents like Stigmasterol, Diospyrolide, D-Friedoolean-14-en-3-one and Lupeol acetate were found to be free from any adverse effects. All the constituents of Alstonia scholaris were found to have interventions either as direct targets or possible targets with Histamine H2 receptor, Arachidonate 5-lipoxygenase, Interleukin-1 receptor-associated kinase 3 TNF-alpha, Cyclooxygenase 1, Prostanoid EP2 receptor, Prostaglandin E synthase, and Serotonin 1e (5-HT1e) receptor. From In vivo and In silico results it is evident that ethanolic bark extract of Alstonia scholaris possessed significant anti-inflammatory activity.

Effects of NP-1815-PX, a P2X4 Receptor Antagonist, on Contractions in Guinea Pig Tracheal and Bronchial Smooth Muscles.

Administration of a P2X4 receptor antagonist to asthma model mice improved asthma symptoms, suggesting that P2X4 receptor antagonists may be new therapeutics for asthma. However, the effects of these antagonists on tracheal/bronchial smooth muscle (TSM and BSM) have not been investigated. This study examined the effects of NP-1815-PX, a selective P2X4 receptor antagonist, on guinea pig TSM and BSM contractions. In epithelium-intact TSM, NP-1815-PX (10-5 M) strongly suppressed ATP-induced contractions. ATP-induced contractions were strongly suppressed by indomethacin (3 × 10-6 M) and ONO-8130 (a prostanoid EP1 receptor antagonist, 10-7 M). ATP-induced contractions were partially suppressed by SQ 29,548 (a prostanoid TP receptor antagonist, 3 × 10-7 M), although the difference was not significant. In contrast, ATP-induced contractions were not affected by AL 8810 (a prostanoid FP receptor antagonist, 10-5 M) or L-798,106 (a prostanoid EP3 receptor antagonist, 10-8 M). NP-1815-PX (10-5-10-4 M) strongly suppressed U46619 (a TP receptor agonist)- and prostaglandin F2α (PGF2α)-induced epithelium-denuded TSM and BSM contractions, which were largely inhibited by SQ 29,548. Additionally, NP-1815-PX (10-5-10-4 M) strongly suppressed the U46619-induced increase in intracellular Ca2+ concentrations in human TP receptor-expressing cells. However, NP-1815-PX (10-4 M) did not substantially inhibit the TSM/BSM contractions induced by carbachol, histamine, neurokinin A, or 50 mM KCl. These findings indicate that NP-1815-PX inhibits guinea pig TSM and BSM contractions mediated through the TP receptor, in addition to the P2X4 receptor, whose stimulation mainly induces EP1 receptor-related mechanisms. Thus, these findings support the usefulness of NP-1815-PX as a therapeutic drug for asthma.

Scaffold Hopping Strategy to Identify Prostanoid EP4 Receptor Antagonists for Cancer Immunotherapy.

Cancer cells can effectively suppress the natural immune response in humans, and prostaglandin E2 (PGE2) is a key mediator in the development of tumor cell resistance to immunotherapy. As a major contributor to PGE2-elicited immunosuppressive activity, the EP4 receptor promotes tumor development and progression in the tumor microenvironment, and the development of selective and potent EP4 receptor antagonists should have promising potential for tumor immunotherapy. Aiming at improving the drug-like properties, a series of 4,7-dihydro-5H-thieno[2,3-c]pyran derivatives were designed and synthesized through a scaffold hopping strategy. The most promising compound 47 exhibited good EP4 antagonistic activity and excellent subtype selectivity, as well as favorable drug-like properties. It effectively suppressed the expression of multiple immunosuppression-related genes in macrophages. Meanwhile, oral administration of compound 47, alone or in combination with anti-PD-1 antibody, significantly enhanced the antitumor immune response and inhibited tumor growth in the mouse CT26 colon carcinoma model.

The Gαs-protein-mediated pathway may be steadily stimulated by prostanoid EP2 receptors, but not by EP4 receptors.

EP2 and EP4 prostanoid receptors have long been considered to have similar roles, since they are known to couple with Gαs‐protein and activate cAMP‐mediated signaling pathways. In this study, we re‐evaluated the results of cAMP assays with or without phosphodiesterase (PDE) inhibitor pretreatment. Here, we show that in the absence of PDE inhibitor pretreatment, prostaglandin E2 causes accumulation of cAMP in EP2 receptors, whereas markedly low levels of cAMP accumulated in EP4 receptors. By applying the Black/Leff operational model calculation, we found that EP2 receptors have a biased ability to intrinsically activate the Gαs‐protein‐mediated pathway, whereas EP4 receptors have strong biased activity for the Gαi‐protein‐mediated pathway. Thus, EP2 and EP4 receptors may not be similar Gαs‐coupled receptors but instead substantially different receptors with distinct roles.

One amino acid mutation of prostanoid EP4 receptor altered its signaling profiles.

One amino acid mutation of prostanoid EP4 receptor altered its signaling profiles.

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.

Twenty-Four-Hour Intraocular Pressure Control with Omidenepag Isopropyl 0.002% in Patients with Glaucoma and Ocular Hypertension.

PurposeTo clarify the intraocular pressure (IOP)-lowering effect of a selective prostanoid EP2 receptor agonist, omidenepag isopropyl (OMDI) during a 24-hour period.Patients and MethodsSubjects aged ≥20 years and with diagnosed, untreated primary open-angle glaucoma or ocular hypertension were enrolled. IOP measurements were performed every 4 hours over a 24-hour period using a Goldmann applanation tonometer (GAT) and Icare PRO tonometer (PRO). The baseline 24-hour IOP was measured in untreated subjects. After the baseline measurements, participants were given OMDI 1 drop once daily at night for 4 weeks. At week 4, the IOP measurement was repeated under the same conditions. Diurnal (9 am, 1 pm, 5 pm) and nocturnal (9 pm, 1 am, 5 am) IOP measurements were compared between baseline and treatment with OMDI. Safety measures included adverse events, slit-lamp biomicroscopy, visual acuity, heart rate and blood pressure.ResultsOf 27 participants enrolled, 25 patients (20 males and 5 females, average age 52.2 ± 8.5 years) completed the study. In the sitting position, the baseline diurnal and nocturnal mean IOPs (GAT) were 19.1 ± 2.1 mmHg and 18.2 ± 2.6 mmHg, respectively, the diurnal and nocturnal mean IOP reduction from baseline were –2.8 ± 2.6 mmHg (p < 0.0001) and –3.3 ± 2.9 mmHg (p < 0.0001), respectively, mean 24-hour IOP (GAT) was significantly lower with the OMDI treatment (−3.1 ± 2.5 mmHg, p < 0.0001). In the supine position, the baseline nocturnal mean IOP (PRO) was 17.99 ± 2.22 mmHg, and the nocturnal mean IOP reduction from baseline was −1.78 ± 2.37 mmHg (p = 0.0009) after 4 weeks of the treatment. Nine adverse events were observed in 8 patients including mild conjunctival hyperemia (n = 8) and mild iritis (n=1). There were no significant effects on systemic safety.ConclusionOnce daily OMDI treatment was able to produce stable 24-hour IOP reduction.

Prostaglandin E2 Dilates Intracerebral Arterioles When Applied to Capillaries: Implications for Small Vessel Diseases.

Prostaglandin E2 (PGE2) has been widely proposed to mediate neurovascular coupling by dilating brain parenchymal arterioles through activation of prostanoid EP4 receptors. However, our previous report that direct application of PGE2 induces an EP1-mediated constriction strongly argues against its direct action on arterioles during neurovascular coupling, the mechanisms sustaining functional hyperemia. Recent advances have highlighted the role of capillaries in sensing neuronal activity and propagating vasodilatory signals to the upstream penetrating parenchymal arteriole. Here, we examined the effect of capillary stimulation with PGE2 on upstream arteriolar diameter using an ex vivo capillary-parenchymal arteriole preparation and in vivo cerebral blood flow measurements with two-photon laser-scanning microscopy. We found that PGE2 caused upstream arteriolar dilation when applied onto capillaries with an EC50 of 70 nM. The response was inhibited by EP1 receptor antagonist and was greatly reduced, but not abolished, by blocking the strong inward-rectifier K+ channel. We further observed a blunted dilatory response to capillary stimulation with PGE2 in a genetic mouse model of cerebral small vessel disease with impaired functional hyperemia. This evidence casts previous findings in a different light, indicating that capillaries are the locus of PGE2 action to induce upstream arteriolar dilation in the control of brain blood flow, thereby providing a paradigm-shifting view that nonetheless remains coherent with the broad contours of a substantial body of existing literature.

Prostanoid receptor agonists for glaucoma treatment.

Intraocular pressure reduction is the only available and evidence-based medical therapy for glaucoma. Currently, the first-line eye drops are prostaglandin analogues including latanoprost, travoprost, bimatoprost, and tafluprost. These drugs stimulate intraocular prostanoid false positive (FP) receptors and reduce intraocular pressure by increasing mainly uveoscleral aqueous outflow. For 2 decades since latanoprost was launched, no drug has been comparable in its efficacy. In 2018, a prostanoid EP2 agonist, omidenepag, was launched in Japan. Current FP agonists and EP2 agonists indicate comparable intraocular pressure reduction by stimulating prostanoid FP or EP2 receptors. However, their safety profiles are quite different because of the differences between the intracellular signaling pathways through their own receptors. Including these commercially available FP and EP2 receptor agonists, prostanoid receptors have a large potential to control intraocular pressure. In this review I will trace the history and development of FP and EP2 receptor agonists from their original function, and explain their potential as first-line drugs including elucidation of their efficacy and safety.