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[Display omitted] A novel series of pyridone-based EP3 receptor antagonists was optimized for good physical properties and oral bioavailability in rodents. The lead compounds 3h , 3l and 4d displayed good in vitro profiles, moderate to good metabolic stability and good rodent PK profiles with low clearance, high oral exposure and acceptable half-life. [ABSTRACT FROM AUTHOR]

Stevens-Johnson syndrome (SJS)/toxic epidermal necrolysis (TEN) is an acute inflammatory vesiculobullous reaction of the mucosa of the ocular surface, oral cavity, and genitals, and of the skin. Severe ocular complications (SOC) are observed in about half of SJS/TEN patients diagnosed by dermatologists and in burn units. Ophthalmologists treat SOC, and they tend to encounter the patients not only in the acute stage, but also in the chronic stage. Our investigation of the pathogenesis of SJS/TEN with SOC led us to suspect that abnormal innate mucosal immunity contributes to the ocular surface inflammation seen in SJS/TEN with SOC. We confirmed that cold medicines such as NSAIDs and multi-ingredient cold medications are the main causative drugs for SJS/TEN with SOC. Single nucleotide polymorphism (SNP) association analysis of cold medicine-related SJS/TEN with SOC showed that the Toll-like receptor 3 ( TLR3 )-, the prostaglandin-E receptor 3 ( PTGER3 )-, and the IKZF1 gene were significantly associated with SNPs and that these genes could regulate mucocutaneous inflammation including that of the ocular surface. We also examined the tear cytokines of SJS/TEN with SOC in the chronic stage and found that IL-8, IL-6, IFN-γ, RANTES, eotaxin, and MIP-1β were significantly upregulated in SJS/TEN with SOC in the chronic stage. Only IP-10 was significantly downregulated in SJS/TEN with SOC in the chronic stage. This mini-review summarizes the pathological mechanisms that we identified as underlying the development of SJS/TEN with SOC., Competing Interests: The author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Ueta.)

Angiotensin II (ANG II) plays a key role in regulating blood pressure and inflammation. Prostaglandin E 2 (PGE 2 ) signals through four different G protein-coupled receptors, eliciting a variety of effects. We reported that activation of the EP 3 receptor reduces cardiac contractility. More recently, we have shown that overexpression of the EP 4 receptor is protective in a mouse myocardial infarction model. We hypothesize in this study that the relative abundance of EP 3 and EP 4 receptors is a major determinant of end-organ damage in the diseased heart. Thus EP 3 is detrimental to cardiac function and promotes inflammation, whereas antagonism of the EP 3 receptor is protective in an ANG II hypertension (HTN) model. To test our hypothesis, male 10- to 12-wk-old C57BL/6 mice were anesthetized with isoflurane and osmotic minipumps containing ANG II were implanted subcutaneously for 2 wk. We found that antagonism of the EP 3 receptor using L798,106 significantly attenuated the increase in blood pressure with ANG II infusion. Moreover, antagonism of the EP 3 receptor prevented a decline in cardiac function after ANG II treatment. We also found that 10- to 12-wk-old EP 3 -transgenic mice, which overexpress EP 3 in the cardiomyocytes, have worsened cardiac function. In conclusion, activation or overexpression of EP 3 exacerbates end-organ damage in ANG II HTN. In contrast, antagonism of the EP 3 receptor is beneficial and reduces cardiac dysfunction, inflammation, and HTN. NEW & NOTEWORTHY This study is the first to show that systemic treatment with an EP 3 receptor antagonist (L798,106) attenuates the angiotensin II-induced increase in blood pressure in mice. The results from this project could complement existing hypertension therapies by combining blockade of the EP 3 receptor with antihypertensive drugs.

Although recognized to have an in vivo vasodepressor effect blunted by the vasoconstrictor effect of E-prostanoid receptor-3 (EP3), prostaglandin E 2 (PGE 2 ) evokes contractions of many vascular beds that are sensitive to antagonizing the thromboxane prostanoid receptor (TP). This study aimed to determine the direct effect of PGE 2 on renal arteries and/or the whole renal vasculature and how each of these two receptors is involved in the responses. Experiments were performed on isolated vessels and perfused kidneys of wild-type mice and/or mice with deficiency in TP (TP -/- ), EP3 (EP3 -/- ), or both TP and EP3 (TP -/- /EP3 -/- ). Here we show that PGE 2 (0.001-30 μM) evoked not only contraction of main renal arteries, but also a decrease of flow in perfused kidneys. EP3 -/- diminished the response to 0.001-0.3 μM PGE 2 , while TP -/- reduced that to the prostanoid of higher concentrations. In TP -/- /EP3 -/- vessels and perfused kidneys, PGE 2 did not evoke contraction but instead resulted in vasodilator responses. These results demonstrate that PGE 2 functions as an overall direct vasoconstrictor of the mouse renal vasculature with an effect reflecting the vasoconstrictor activities outweighing that of dilation. Also, our results suggest that EP3 dominates the vasoconstrictor effect of PGE 2 of low concentrations (≤0.001-0.3 μM), but its effect is further added by that of TP, which has a higher efficacy, although activated by higher concentrations (from 0.01 μM) of the same prostanoid PGE 2 ., (© 2019 Federation of American Societies for Experimental Biology.)

Prostaglandin E2 (PGE2) interacts with tyrosine kinases receptor signaling in both tumor and stromal cells supporting tumor progression. Here we demonstrate that in non-small cell lung carcinoma (NSCLC) cells, A549 and GLC82, PGE2 promotes nuclear translocation of epidermal growth factor receptor (nEGFR), affects gene expression and induces cell growth. Indeed, cyclin D1, COX-2, iNOS and c-Myc mRNA levels are upregulated following PGE2 treatment. The nuclear localization sequence (NLS) of EGFR as well as its tyrosine kinase activity are required for the effect of PGE2 on nEGFR and downstream signaling activities. PGE2 binds its bona fide receptor EP3 which by activating SRC family kinases, induces ADAMs activation which, in turn, releases EGFR-ligands from the cell membrane and promotes nEGFR. Amphiregulin (AREG) and Epiregulin (EREG) appear to be involved in nEGFR promoted by the PGE2/EP3-SRC axis. Pharmacological inhibition or silencing of the PGE2/EP3/SRC-ADAMs signaling axis or EGFR ligands i.e. AREG and EREG expression abolishes nEGFR induced by PGE2. In conclusion, PGE2 induces NSCLC cell proliferation by EP3 receptor, SRC-ADAMs activation, EGFR ligands shedding and finally, phosphorylation and nEGFR. Since nuclear EGFR is a hallmark of cancer aggressiveness, our findings reveal a novel mechanism for the contribution of PGE2 to tumor progression.

We examined the involvement of adipocyte cyclooxygenase-2 (COX-2) and prostaglandin E2 (PGE2)-prostaglandin E receptor (EP)3-mediated signaling during hypertrophy and hypoxia in the development of obesity-associated adipose tissue (AT) inflammation and insulin resistance. The experiments were conducted with high-fat diet (HFD)-induced obese rats, db/db mice, human subjects, and 3T3-L1 and the human Simpson-Golabi-Behmel syndrome (SGBS) adipocytes; the groups were treated with selective inhibitors of COX-2 [celecoxib 30 mg/kg, half maximal inhibitory concentration (IC50) ≈ 0.04 µM] and EP3 (L-798106 100 µg/kg, IC50 ≈ 0.5 µM) or a short interfering RNA. There were strong, positive correlations between adipocyte COX-2 and EP3 gene expressions and the AT TNF-α and monocyte chemotactic protein-1 contents and the homeostatic model assessment for insulin resistance in HFD-induced obese rats, as well as body mass index in human subjects. Treatment with COX-2 and EP3 inhibitors significantly reversed AT inflammatory gene and protein expressions (-50%) and impaired glucose and insulin tolerance in db/db mice. COX-2 inhibition diminished the chemotaxis of adipocytes isolated from HFD rats to macrophages and T cells. Targeting inhibition of adipocyte COX-2 and EP3 during hypertrophy and hypoxia reversed the release of the augmented proinflammatory adipokines and the diminished adiponectin and also suppressed NF-κB and hypoxia-inducible factor-1α transcription activation. These findings suggest that adipocyte COX-2 PGE2-EP3-mediated signaling is crucially involved in the development of obesity-associated AT inflammation and insulin resistance.-Chan, P.-C., Hsiao, F.-C., Chang, H.-M., Wabitsch, M., Hsieh, P. S. Importance of adipocyte cyclooxygenase-2 and prostaglandin E2-prostaglandin E receptor 3 signaling in the development of obesity-induced adipose tissue inflammation and insulin resistance., (© FASEB.)

Prostaglandins, especially prostaglandin E2 (PGE2), and COX-2 play an important role in carcinogenesis of many tumors including bladder cancer (BCA). The PGE2 receptors EP1-4 regulate tumor cell growth, invasion and migration in different tumor entities but EP expression in BCA remains to be determined. In the present study we examined the expression of EP1-4 in non-muscle invasive bladder cancer (NMIBC), muscle invasive bladder cancer (MIBC) and normal urothelial tissue (NU) using immunohistochemistry. Nuclear and cytoplasmic EP1-4 expression was correlated with clinicopathological parameters and survival of BCA patients. EP1, EP2 and EP3 were significantly less expressed in the cytoplasm und nucleus of NMIBC and MIBC than in NU; EP4 cytoplasmic staining in MIBC was significantly higher compared to NU. The cytoplasmic staining was significantly more abundant in MIBC than in NMIBC in all investigated receptors except EP2. The level of EP staining in NMIBC was correlated with staging and grading, especially cytoplasmic EP1. Nuclear staining of EP1 was an independent predictor of BCA recurrence-free survival in NMIBC patients. EP receptors are dysregulated in BCA. The increase of EP1 may be used as prognostic parameter in NMIBC patients and its dysregulation could be targeted by specific EP1 inhibitors.

Rationale: Vascular smooth muscle cell (VSMC) migration and proliferation are the hallmarks of restenosis pathogenesis after angioplasty. Cyclooxygenase (COX)-derived prostaglandin (PG) E₂ is implicated in the vascular remodeling response to injury. However, its precise molecular role remains unknown., Objective: This study investigates the impact of COX-2-derived PGE₂ on neointima formation after injury., Methods and Results: Vascular remodeling was induced by wire injury in femoral arteries of mice. Both neointima formation and the restenosis ratio were diminished in COX-2 knockout mice as compared with controls, whereas these parameters were enhanced in COX-1>COX-2 mice, in which COX-1 is governed by COX-2 regulatory elements. PG profile analysis revealed that the reduced PGE₂ by COX-2 deficiency, but not PGI2, could be rescued by COX-1 replacement, indicating COX-2-derived PGE₂ enhanced neointima formation. Through multiple approaches, the EP3 receptor was identified to mediate the VSMC migration response to various stimuli. Disruption of EP3 impaired VSMC polarity for directional migration by decreasing small GTPase activity and restricted vascular neointimal hyperplasia, whereas overexpression of EP3α and EP3β aggravated neointima formation. Inhibition or deletion of EP3α/β, a Gαi protein-coupled receptor, activated the cAMP/protein kinase A pathway and decreased activation of RhoA in VSMCs. PGE₂ could stimulate phosphatidylinositol 3-kinase/Akt/glycogen synthase kinase3β signaling in VSMCs through Gβγ subunits on EP3α/β activation. Ablation of EP3 suppressed phosphatidylinositol 3-kinase signaling and reduced GTPase activity in VSMCs and altered cell polarity and directional migration., Conclusions: COX-2-derived PGE₂ facilitated the neointimal hyperplasia response to injury through EP3α/β-mediated cAMP/protein kinase A and phosphatidylinositol 3-kinase pathways, indicating EP3 inhibition may be a promising therapeutic strategy for percutaneous transluminal coronary angioplasty.

Although numerous epidemiological studies show aspirin to reduce risk of prostate cancer, the mechanism of this effect is unclear. Here, we first confirmed that aspirin downregulated androgen receptor (AR) and prostate-specific antigen in prostate cancer cells. We also found that aspirin upregulated prostaglandin receptor subtype EP3 but not EP2 or EP4. The EP3 antagonist L798106 and EP3 knockdown increased AR expression and cell proliferation, whereas the EP3 agonist sulprostone decreased them, indicating that EP3 affects AR expression. Additionally, EP3 (PTGER3) transcript levels were significantly decreased in human prostate cancer tissues compared with those in normal human prostate tissues, suggesting that EP3 is important to prostate carcinogenesis. Decreased EP3 expression was also seen in castration-resistant subtype CxR cells compared with parental LNCaP cells. Finally, we found that aspirin and EP3 modulators affected prostate cancer cell growth. Taken together, aspirin suppressed LNCaP cell proliferation via EP3 signaling activation; EP3 downregulation contributed to prostate carcinogenesis and to progression from androgen-dependent prostate cancer to castration-resistant prostate cancer by regulating AR expression. In conclusion, cyclooxygenases and EP3 may represent attractive therapeutic molecular targets in androgen-dependent prostate cancer.