Small-molecule inhibition of prostaglandin E receptor 2 impairs cyclooxygenase-associated malignant glioma growth

Increased Cyclic Adenosine Monophosphate Responsive Element is Closely Associated with the Pathogenesis of Drug-resistant Epilepsy

BACKGROUND

Drug-resistant epilepsy (DRE) is a refractory neurological disorder. There is ample evidence that suggest that γ-aminobutyric acid-a (GABAA) receptors could be one of the mechanisms responsible for the development of drug resistance in epilepsy. It is also known that the cAMP response element binding protein (CREB) plays a possible key role in the transcriptional regulation of GABAA.

OBJECTIVE

This study explores the role of CREB in the development of DRE and the effect of CREB on GABA-related receptors in DRE.

METHODS

The CREB expression was increased or decreased in the hippocampus of normal rats by lentiviral transfection, who then underwent the lithium-pilocarpine-induced epilepsy model. Phenobarbital (PB) sodium and carbamazepine (CBZ) were used to select a drug-resistant epileptic model. The expression levels of GABAA receptor α1, β2, and γ2 subunits and CREB protein were measured in the rat hippocampus by western blot and fluorescent quantitative PCR.

RESULTS

The frequency and duration of seizures increased in the overexpression group compared to that in the control group. In addition, the severity, frequency, and duration of seizures decreased in the group with decreased expression. The hippocampus analysis of the expression levels of the CREB protein and CREB mRNA yielded similar findings. Altering the CREB protein expression in the rat hippocampus could negatively regulate the expression and transcript levels of GABAA receptors α1, β2, and γ2, suggesting that CREB may serve as a potential target for the development of treatment protocols and drugs for epilepsy.

CONCLUSION

Our study shows that enhanced CREB expression promotes the development of DRE and negatively regulates GABAA receptor levels and that the inhibition of CREB expression may reduce the incidence of DRE.

Cytokine Profile in Development of Glioblastoma in Relation to Healthy Individuals

Cytokines play an essential role in the control of tumor cell development and multiplication. However, the available literature provides ambiguous data on the involvement of these proteins in the formation and progression of glioblastoma (GBM). This study was designed to evaluate the inflammatory profile and to investigate its potential for the identification of molecular signatures specific to GBM. Fifty patients aged 66.0 ± 10.56 years with newly diagnosed high-grade gliomas and 40 healthy individuals aged 71.7 ± 4.9 years were included in the study. White blood cells were found to fall within the referential ranges and were significantly higher in GBM than in healthy controls. Among immune cells, neutrophils showed the greatest changes, resulting in elevated neutrophil-to-lymphocyte ratio (NLR). The neutrophil count inversely correlated with survival time expressed by Spearman's coefficient rs = -0.359 (p = 0.010). The optimal threshold values corresponded to 2.630 × 103/µL for NLR (the area under the ROC curve AUC = 0.831, specificity 90%, sensitivity 76%, the relative risk RR = 7.875, the confidence intervals 95%CI 3.333-20.148). The most considerable changes were recorded in pro-inflammatory cytokines interleukin IL-1β, IL-6, and IL-8, which were approx. 1.5-2-fold higher, whereas tumor necrosis factor α (TNFα) and high mobility group B1 (HMGB1) were lower in GBM than healthy control (p < 0.001). The results of the ROC, AUC, and RR analysis of IL-1β, IL-6, IL-8, and IL-10 indicate their high diagnostics potential for clinical prognosis. The highest average RR was observed for IL-6 (RR = 2.923) and IL-8 (RR = 3.151), which means there is an approx. three-fold higher probability of GBM development after exceeding the cut-off values of 19.83 pg/mL for IL-6 and 10.86 pg/mL for IL-8. The high values of AUC obtained for the models NLR + IL-1β (AUC = 0.907), NLR + IL-6 (AUC = 0.908), NLR + IL-8 (AUC = 0.896), and NLR + IL-10 (AUC = 0.887) prove excellent discrimination of GBM patients from healthy individuals and may represent GBM-specific molecular signatures.

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.

Dysregulated lipid metabolism in TMZ-resistant glioblastoma: pathways, proteins, metabolites and therapeutic opportunities

Glioblastoma (GBM) is a highly aggressive and lethal brain tumor with limited treatment options, such as the chemotherapeutic agent, temozolomide (TMZ). However, many GBM tumors develop resistance to TMZ, which is a major obstacle to effective therapy. Recently, dysregulated lipid metabolism has emerged as an important factor contributing to TMZ resistance in GBM. The dysregulation of lipid metabolism is a hallmark of cancer and alterations in lipid metabolism have been linked to multiple aspects of tumor biology, including proliferation, migration, and resistance to therapy. In this review, we aimed to summarize current knowledge on lipid metabolism in TMZ-resistant GBM, including key metabolites and proteins involved in lipid synthesis, uptake, and utilization, and recent advances in the application of metabolomics to study lipid metabolism in GBM. We also discussed the potential of lipid metabolism as a target for novel therapeutic interventions. Finally, we highlighted the challenges and opportunities associated with developing these interventions for clinical use, and the need for further research to fully understand the role of lipid metabolism in TMZ resistance in GBM. Our review suggests that targeting dysregulated lipid metabolism may be a promising approach to overcome TMZ resistance and improve outcomes in patients with GBM.

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.

EP2 inhibition restores myeloid metabolism and reverses cognitive decline

Nonsteroidal anti-inflammatory drugs alleviate pain and inflammation by inhibiting the cyclooxygenase pathway. This pathway has various downstream effects, some of which are beneficial. Prostaglandin E2 is a key downstream product in the cyclooxygenase pathway that modulates inflammation. A correlation between aging and increased expression of the prostaglandin E2 receptor, EP2, has been associated with inflammatory processes, cognitive aging, angiogenesis, and tumorigenesis. Therefore, inhibition of EP2 could lead to therapeutic effects and be more selective than inhibiting cyclooxygenase-2. Studies suggest that inhibition of EP2 restores age-associated spatial memory deficits and synaptic proteins and impairs tumorigenesis. The data indicate that EP2 signaling is important in myeloid cell metabolism and support its candidacy as a therapeutic target.

Novel, Brain-Permeable, Cross-Species Benzothiazole Inhibitors of Microsomal Prostaglandin E Synthase-1 (mPGES-1) Dampen Neuroinflammation In Vitro and In Vivo

Microsomal prostaglandin E synthase-1 (mPGES-1) is an inducible enzyme of the cyclooxygenase (COX) cascade that generates prostaglandin E2 (PGE2) during inflammatory conditions. PGE2 is known to be a potent immune signaling molecule that mediates both peripheral and central inflammations. Inhibition of mPGES-1, rather than COX, may overcome the cardiovascular side effects associated with long-term COX inhibition by providing a more specific strategy to target inflammation. However, mPGES-1 inhibitor development is hampered by the large differences in cross-species activity due to the structural differences between the human and murine mPGES-1. Here, we report that our thiazole-based mPGES-1 inhibitors, compounds 11 (UT-11) and 19 derived from two novel scaffolds, were able to suppress PGE2 production in human (SK-N-AS) and murine (BV2) cells. The IC50 values of inhibiting PGE2 production in human and murine cells were 0.10 and 2.00 μM for UT-11 and 0.43 and 1.55 μM for compound 19, respectively. Based on in vitro and in vivo pharmacokinetic data, we selected UT-11 for evaluation in a lipopolysaccharide (LPS)-induced inflammation model. We found that our compound significantly suppressed proinflammatory cytokines and chemokines in the hippocampus but not in the kidney. Taken together, we demonstrated the potential of UT-11 in treating neuroinflammatory conditions, including epilepsy and stroke, and warrant further optimization.

Preclinical development of an EP2 antagonist for post-seizure cognitive deficits

Cognitive comorbidities can substantially reduce quality of life in people with epilepsy. Inflammation is a component of all chronic diseases including epilepsy, as well as acute events like status epilepticus (SE). Neuroinflammation is the consequence of several broad signaling cascades including cyclooxygenase-2 (COX-2)-associated pathways. Activation of the EP2 receptor for prostaglandin E2 appears responsible for blood-brain barrier leakage and much of the inflammatory reaction, neuronal injury and cognitive deficit that follows seizure-provoked COX-2 induction in brain. Here we show that brief exposure of mice to TG11-77, a potent, selective, orally available and brain permeant EP2 antagonist, eliminates the profound cognitive deficit in Y-maze performance after SE and reduces delayed mortality and microgliosis, with a minimum effective i.p. dose (as free base) of 8.8 mg/kg. All in vitro studies required to submit an investigational new drug (IND) application for TG11-77 have been completed, and non-GLP dose range-finding toxicology in the rat identified no overt, organ or histopathology signs of toxicity after 7 days of oral administration at 1000 mg/kg/day. Plasma exposure in the rat was dose-linear between 15 and 1000 mg/kg dosing. TG11-77 thus appears poised to continue development towards the initial clinical test of the hypothesis that EP2 receptor modulation after SE can provide the first preventive treatment for one of the chief comorbidities of epilepsy.

Neuroinflammatory mediators in acquired epilepsy: an update

Epilepsy is a group of chronic neurological disorders that have diverse etiologies but are commonly characterized by spontaneous seizures and behavioral comorbidities. Although the mechanisms underlying the epileptic seizures mostly remain poorly understood and the causes often can be idiopathic, a considerable portion of cases are known as acquired epilepsy. This form of epilepsy is typically associated with prior neurological insults, which lead to the initiation and progression of epileptogenesis, eventually resulting in unprovoked seizures. A convergence of evidence in the past two decades suggests that inflammation within the brain may be a major contributing factor to acquired epileptogenesis. As evidenced in mounting preclinical and human studies, neuroinflammatory processes, such as activation and proliferation of microglia and astrocytes, elevated production of pro-inflammatory cytokines and chemokines, blood-brain barrier breakdown, and upregulation of inflammatory signaling pathways, are commonly observed after seizure-precipitating events. An increased knowledge of these neuroinflammatory processes in the epileptic brain has led to a growing list of inflammatory mediators that can be leveraged as potential targets for new therapies of epilepsy and/or biomarkers that may provide valued information for the diagnosis and prognosis of the otherwise unpredictable seizures. In this review, we mainly focus on the most recent progress in understanding the roles of these inflammatory molecules in acquired epilepsy and highlight the emerging evidence supporting their candidacy as novel molecular targets for new pharmacotherapies of acquired epilepsy and the associated behavioral deficits.

Pleiotropic effects of the COX-2/PGE2 axis in the glioblastoma tumor microenvironment

Glioblastoma (GBM) is the most common and aggressive form of malignant glioma. The GBM tumor microenvironment (TME) is a complex ecosystem of heterogeneous cells and signaling factors. Glioma associated macrophages and microglia (GAMs) constitute a significant portion of the TME, suggesting that their functional attributes play a crucial role in cancer homeostasis. In GBM, an elevated GAM population is associated with poor prognosis and therapeutic resistance. Neoplastic cells recruit these myeloid populations through release of chemoattractant factors and dysregulate their induction of inflammatory programs. GAMs become protumoral advocates through production a variety of cytokines, inflammatory mediators, and growth factors that can drive cancer proliferation, invasion, immune evasion, and angiogenesis. Among these inflammatory factors, cyclooxygenase-2 (COX-2) and its downstream product, prostaglandin E2 (PGE2), are highly enriched in GBM and their overexpression is positively correlated with poor prognosis in patients. Both tumor cells and GAMs have the ability to signal through the COX-2 PGE2 axis and respond in an autocrine/paracrine manner. In the GBM TME, enhanced signaling through the COX-2/PGE2 axis leads to pleotropic effects that impact GAM dynamics and drive tumor progression.

Transient inhibition of microsomal prostaglandin E synthase-1 after status epilepticus blunts brain inflammation and is neuroprotective

Status epilepticus (SE) in humans is characterized by prolonged convulsive seizures that are generalized and often difficult to control. The current antiseizure drugs (ASDs) aim to stop seizures quickly enough to prevent the SE-induced brain inflammation, injury, and long-term sequelae. However, sole reliance on acute therapies is imprudent because prompt treatment may not always be possible under certain circumstances. The pathophysiological mechanisms underlying the devastating consequences of SE are presumably associated with neuroinflammatory reactions, where prostaglandin E2 (PGE2) plays a pivotal role. As the terminal synthase for pathogenic PGE2, the microsomal prostaglandin E synthase-1 (mPGES-1) is rapidly and robustly induced by prolonged seizures. Congenital deletion of mPGES-1 in mice is neuroprotective and blunts gliosis following chemoconvulsant seizures, suggesting the feasibility of mPGES-1 as a potential antiepileptic target. Herein, we investigated the effects of a dual species mPGES-1 inhibitor in a mouse pilocarpine model of SE. Treatment with the mPGES-1 inhibitor in mice after SE that was terminated by diazepam, a fast-acting benzodiazepine, time-dependently abolished the SE-induced PGE2 within the brain. Its negligible effects on cyclooxygenases, the enzymes responsible for the initial step of PGE2 biosynthesis, validated its specificity to mPGES-1. Post-SE inhibition of mPGES-1 also blunted proinflammatory cytokines and reactive gliosis in the hippocampus and broadly prevented neuronal damage in a number of brain areas. Thus, pharmacological inhibition of mPGES-1 by small-molecule inhibitors might provide an adjunctive strategy that can be implemented hours after SE, together with first-line ASDs, to reduce SE-provoked brain inflammation and injury.

Targeting EP2 receptor with multifaceted mechanisms for high-risk neuroblastoma

Prostaglandin E₂ (PGE₂) promotes tumor cell proliferation, migration, and invasion, fostering an inflammation-enriched microenvironment that facilitates angiogenesis and immune evasion. However, the PGE₂ receptor subtype (EP1–EP4) involved in neuroblastoma (NB) growth remains elusive. Herein, we show that the EP2 receptor highly correlates with NB aggressiveness and acts as a predominant Gα_s-coupled receptor mediating PGE₂-initiated cyclic AMP (cAMP) signaling in NB cells with high-risk factors, including 11q deletion and MYCN amplification. Knockout of EP2 in NB cells blocks the development of xenografts, and its conditional knockdown prevents established tumors from progressing. Pharmacological inhibition of EP2 by our recently developed antagonist TG6-129 suppresses the growth of NB xenografts in nude mice and syngeneic allografts in immunocompetent hosts, accompanied by anti-inflammatory, antiangiogenic, and apoptotic effects. This proof-of-concept study suggests that the PGE₂/EP2 signaling pathway contributes to NB malignancy and that EP2 inhibition by our drug-like compounds provides a promising strategy to treat this deadly pediatric cancer.

Hou et al. discover that prostaglandin receptor EP2 highly correlates with the aggressiveness of neuroblastoma, where it acts as the primary PGE₂ receptor mediating cAMP signaling. EP2 deficiency or inhibition suppresses neuroblastoma with high-risk factors including 11q deletion and MYCN amplification, demonstrating EP2 as a promising therapeutic target for neuroblastoma.

Reduced tumor growth in EP2 knockout mice is related to signaling pathways favoring an increased local anti‑tumor immunity in the tumor stroma

Inflammatory signaling through prostaglandin E2 receptor subtype 2 (EP2) is associated with malignant tumor growth in both experimental models and cancer patients. Thus, the absence of EP2 receptors in host tissues appears to reduce tumor growth and systemic inflammation by inducing major alterations in gene expression levels across tumor tissue compartments. However, it is not yet well‑established how signaling pathways in tumor tissue relate to simultaneous signaling alterations in the surrounding tumor‑stroma, at conditions of reduced disease progression due to decreased host inflammation. In the present study, wild‑type tumor cells, producing high levels of prostaglandin E2 (MCG 101 cells, EP2+/+), were inoculated into EP2 knockout (EP2‑/‑) and EP2 wild‑type (EP2+/+) mice. Solid tumors were dissected into tumor‑ and tumor‑stroma tissue compartments for RNA expression microarray screening, followed by metabolic pathway analyses. Immunohistochemistry was used to confirm adequate dissections of tissue compartments, and to assess cell proliferation (Ki‑67), prostaglandin enzymes (cyclooxygenase 2) and immunity biomarkers (CD4 and CD8) at the protein level. Microarray analyses revealed statistically significant alterations in gene expression in the tumor‑stroma compartment, while significantly less pathway alterations occurred in the tumor tissue compartment. The host knockout of EP2 receptors led to a significant downregulation of cell cycle regulatory factors in the tumor‑stroma compartment, while interferon γ‑related pathways, chemokine signaling pathways and anti‑tumor chemokines [chemokine (C‑X‑C motif) ligand 9 and 10] were upregulated in the tumor compartment. Thus, such gene alterations were likely related to reduced tumor growth in EP2‑deficient hosts. On the whole, pathway analyses of both tumor‑ and tumor‑stroma compartments suggested that absence of host EP2 receptor signaling reduces 'remodeling' of tumor microenvironments and increase local immunity, probably by decreased productions of stimulating growth factors, perhaps similar to well‑recognized physiological observations in wound healing.

Reprogramming of arachidonate metabolism confers temozolomide resistance to glioblastoma through enhancing mitochondrial activity in fatty acid oxidation

Background

Sp1 is involved in the recurrence of glioblastoma (GBM) due to the acquirement of resistance to temozolomide (TMZ). Particularly, the role of Sp1 in metabolic reprogramming for drug resistance remains unknown.

Methods

RNA-Seq and mass spectrometry were used to analyze gene expression and metabolites amounts in paired GBM specimens (primary vs. recurrent) and in paired GBM cells (sensitive vs. resistant). ω-3/6 fatty acid and arachidonic acid (AA) metabolism in GBM patients were analyzed by targeted metabolome. Mitochondrial functions were determined by Seahorse XF Mito Stress Test, RNA-Seq, metabolome and substrate utilization for producing ATP. Therapeutic options targeting prostaglandin (PG) E2 in TMZ-resistant GBM were validated in vitro and in vivo.

Results

Among the metabolic pathways, Sp1 increased the prostaglandin-endoperoxide synthase 2 expression and PGE2 production in TMZ-resistant GBM. Mitochondrial genes and metabolites were obviously increased by PGE2, and these characteristics were required for developing resistance in GBM cells. For inducing TMZ resistance, PGE2 activated mitochondrial functions, including fatty acid β-oxidation (FAO) and tricarboxylic acid (TCA) cycle progression, through PGE2 receptors, E-type prostanoid (EP)1 and EP3. Additionally, EP1 antagonist ONO-8713 inhibited the survival of TMZ-resistant GBM synergistically with TMZ.

Conclusion

Sp1-regulated PGE2 production activates FAO and TCA cycle in mitochondria, through EP1 and EP3 receptors, resulting in TMZ resistance in GBM. These results will provide us a new strategy to attenuate drug resistance or to re-sensitize recurred GBM.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12929-022-00804-3.

Pharmacological antagonism of EP2 receptor does not modify basal cardiovascular and respiratory function, blood cell counts, and bone morphology in animal models

The EP2 receptor has emerged as a therapeutic target with exacerbating role in disease pathology for a variety of peripheral and central nervous system disorders. We and others have recently demonstrated beneficial effects of EP2 antagonists in preclinical models of neuroinflammation and peripheral inflammation. However, it was earlier reported that mice with global EP2 knockout (KO) display adverse phenotypes on fertility and blood pressure. Other studies indicated that EP2 activation with an agonist has a beneficial effect of healing fractured bone in animal models. These results impeded the development of EP2 antagonists, and EP2 antagonism as therapeutic strategy. To determine whether treatment with EP2 antagonist mimics the adverse phenotypes of the EP2 global KO mouse, we tested two EP2 antagonists TG11-77. HCl and TG6-10-1 in mice and rats while they are on normal or high-salt diet, and by two different administration protocols (acute and chronic). There were no adverse effects of the antagonists on systolic and diastolic blood pressure, heart rate, respiratory function in mice and rats regardless of rodents being on a regular or high salt diet. Furthermore, chronic exposure to TG11-77. HCl produced no adverse effects on blood cell counts, bone-volume and bone-mineral density in mice. Our findings argue against adverse effects on cardiovascular and respiratory systems, blood counts and bone structure in healthy rodents from the use of small molecule reversible antagonists for EP2, in contrast to the genetic ablation model. This study paves the way for advancing therapeutic applications of EP2 antagonists against diseases involving EP2 dysfunction.

Second-Generation Prostaglandin Receptor EP2 Antagonist, TG8-260, with High Potency, Selectivity, Oral Bioavailability, and Anti-Inflammatory Properties

EP2, a G-protein-coupled prostaglandin-E₂ receptor, has emerged as a seminal biological target for drug discovery. EP2 receptor activation is typically proinflammatory; therefore, the development of EP2 antagonists to mitigate the severity and disease pathology in a variety of inflammation-driven central nervous system and peripheral disorders would be a novel strategy. We have recently developed a second-generation EP2 antagonist TG8-260 and shown that it reduces hippocampal neuroinflammation and gliosis after pilocarpine-induced status epilepticus in rats. Here, we present details of synthesis, lead optimization on earlier leads that resulted in TG8-260, potency and selectivity evaluations using cAMP-driven time-resolved fluorescence resonance energy-transfer (TR-FRET) assays and [H³]-PGE2-binding assays, absorption, distribution, metabolism, and excretion (ADME), and pharmacokinetics. TG8-260 (2f) showed Schild K _B = 13.2 nM (3.6-fold more potent than the previous lead TG8-69 (1c)) and 500-fold selectivity to EP2 against other prostanoid receptors. Pharmacokinetic data indicated that TG8-260 has a plasma half-life of 2.14 h (PO) and excellent oral bioavailability (77.3%). Extensive ADME tests indicated that TG8-260 is a potent inhibitor of CYP450 enzymes. Further, we show that TG8-260 displays antagonistic activity on the induction of EP2 receptor-mediated inflammatory gene expression in microglia BV2-hEP2 cells; therefore, it can serve as a tool for investigating anti-inflammatory pathways in peripheral inflammatory disease animal models.

Inducible Prostaglandin E Synthase as a Pharmacological Target for Ischemic Stroke

As the inducible terminal enzyme for prostaglandin E2 (PGE2) synthesis, microsomal PGE synthase-1 (mPGES-1) contributes to neuroinflammation and secondary brain injury after cerebral ischemia via producing excessive PGE2. However, a proof of concept that mPGES-1 is a therapeutic target for ischemic stroke has not been established by a pharmacological strategy mainly due to the lack of drug-like mPGES-1 inhibitors that can be used in relevant rodent models. To this end, we recently developed a series of novel small-molecule compounds that can inhibit both human and rodent mPGES-1. In this study, blockade of mPGES-1 by our several novel compounds abolished the lipopolysaccharide (LPS)-induced PGE2 and pro-inflammatory cytokines interleukin 1β (IL-1β), IL-6, and tumor necrosis factor α (TNF-α) in mouse primary brain microglia. Inhibition of mPGES-1 also decreased PGE2 produced by neuronal cells under oxygen-glucose deprivation (OGD) stress. Among the five enzymes for PGE2 biosynthesis, mPGES-1 was the most induced one in cerebral ischemic lesions. Systemic treatment with our lead compound MPO-0063 (5 or 10 mg/kg, i.p.) in mice after transient middle cerebral artery occlusion (MCAO) improved post-stroke well-being, decreased infarction and edema, suppressed induction of brain cytokines (IL-1β, IL-6, and TNF-α), alleviated locomotor dysfunction and anxiety-like behavior, and reduced the long-term cognitive impairments. The therapeutic effects of MPO-0063 in this proof-of-concept study provide the first pharmacological evidence that mPGES-1 represents a feasible target for delayed, adjunct treatment - along with reperfusion therapies - for acute brain ischemia.

N-2-(phenylamino) benzamide derivatives as novel anti-glioblastoma agents: Synthesis and biological evaluation

Glioblastoma is one of the most lethal brain tumors. The crucial chemotherapy is mainly alkylating agents with modest clinical success. Given this desperate need and inspired by the encouraging results of a phase II trial via concomitant Topo I inhibitor plus COX-2 inhibitor, we designed a series of N-2-(phenylamino) benzamide derivatives as novel anti-glioblastoma agents based on structure modification on 1,5-naphthyridine derivatives (Topo I inhibitors). Notably, the target compounds I-1 (33.61 ± 1.15 μM) and I-8 (45.01 ± 2.37 μM) were confirmed to inhibit COX-2, while a previous reported compound (1,5-naphthyridine derivative) resulted nearly inactive towards COX-2 (IC₅₀ > 150 μM). Besides, I-1 and I-8 exhibited higher anti-proliferation, anti-migration, anti-invasion effects than the parent compound 1,5-naphthyridine derivative, suggesting the success of modification based on the parent. Moreover, I-1 obviously repressed tumor growth in the C6 glioma orthotopic model (TGI = 66.7%) and U87MG xenograft model (TGI = 69.4%). Besides, I-1 downregulated PGE₂, VEGF, MMP-9, and STAT3 activation, upregulated E-cadherin in the orthotopic model. More importantly, I-1 showed higher safety than temozolomide and different mechanism from temozolomide in the C6 glioma orthotopic model. All the evidence demonstrated that N-2-(phenylamino) benzamide derivatives as novel anti-glioblastoma agents could be promising for the glioma management.

EP2 Antagonists (2011-2021): A Decade's Journey from Discovery to Therapeutics

In the wake of health disasters associated with the chronic use of cyclooxygenase-2 (COX-2) inhibitor drugs, it has been widely proposed that modulation of downstream prostanoid synthases or receptors might provide more specificity than simply shutting down the entire COX cascade for anti-inflammatory benefits. The pathogenic actions of COX-2 have long been thought attributable to the prostaglandin E2 (PGE2) signaling through its Gαs-coupled EP2 receptor subtype; however, the truly selective EP2 antagonists did not emerge until 2011. These small molecules provide game-changing tools to better understand the EP2 receptor in inflammation-associated conditions. Their applications in preclinical models also reshape our knowledge of PGE2/EP2 signaling as a node of inflammation in health and disease. As we celebrate the 10-year anniversary of this breakthrough, the exploration of their potential as drug candidates for next-generation anti-inflammatory therapies has just begun. The first decade of EP2 antagonists passes, while their future looks brighter than ever.

Role of Inflammatory Mediators, Macrophages, and Neutrophils in Glioma Maintenance and Progression: Mechanistic Understanding and Potential Therapeutic Applications

Gliomas are the most common, highly malignant, and deadliest forms of brain tumors. These intra-cranial solid tumors are comprised of both cancerous and non-cancerous cells, which contribute to tumor development, progression, and resistance to the therapeutic regimen. A variety of soluble inflammatory mediators (e.g., cytokines, chemokines, and chemotactic factors) are secreted by these cells, which help in creating an inflammatory microenvironment and contribute to the various stages of cancer development, maintenance, and progression. The major tumor infiltrating immune cells of the tumor microenvironment include TAMs and TANs, which are either recruited peripherally or present as brain-resident macrophages (microglia) and support stroma for cancer cell expansion and invasion. These cells are highly plastic in nature and can be polarized into different phenotypes depending upon different types of stimuli. During neuroinflammation, glioma cells interact with TAMs and TANs, facilitating tumor cell proliferation, survival, and migration. Targeting inflammatory mediators along with the reprogramming of TAMs and TANs could be of great importance in glioma treatment and may delay disease progression. In addition, an inhibition of the key signaling pathways such as NF-κB, JAK/STAT, MAPK, PI3K/Akt/mTOR, and TLRs, which are activated during neuroinflammation and have an oncogenic role in glioblastoma (GBM), can exert more pronounced anti-glioma effects.

Metabolic Remodeling in Glioma Immune Microenvironment: Intercellular Interactions Distinct From Peripheral Tumors

During metabolic reprogramming, glioma cells and their initiating cells efficiently utilized carbohydrates, lipids and amino acids in the hypoxic lesions, which not only ensured sufficient energy for rapid growth and improved the migration to normal brain tissues, but also altered the role of immune cells in tumor microenvironment. Glioma cells secreted interferential metabolites or depriving nutrients to injure the tumor recognition, phagocytosis and lysis of glioma-associated microglia/macrophages (GAMs), cytotoxic T lymphocytes, natural killer cells and dendritic cells, promoted the expansion and infiltration of immunosuppressive regulatory T cells and myeloid-derived suppressor cells, and conferred immune silencing phenotypes on GAMs and dendritic cells. The overexpressed metabolic enzymes also increased the secretion of chemokines to attract neutrophils, regulatory T cells, GAMs, and dendritic cells, while weakening the recruitment of cytotoxic T lymphocytes and natural killer cells, which activated anti-inflammatory and tolerant mechanisms and hindered anti-tumor responses. Therefore, brain-targeted metabolic therapy may improve glioma immunity. This review will clarify the metabolic properties of glioma cells and their interactions with tumor microenvironment immunity, and discuss the application strategies of metabolic therapy in glioma immune silence and escape.

Design, synthesis and biological evaluation of N-anthraniloyl tryptamine derivatives as pleiotropic molecules for the therapy of malignant glioma

COX-2 and STAT3 are two key culprits in the glioma microenvironment. Herein, to inhibit COX-2 and block STAT3 signaling, we disclosed 27 N-anthraniloyl tryptamine compounds based on the combination of melatonin derivatives and N-substituted anthranilic acid derivatives. Among them, NP16 showed the best antiproliferative activity and moderate COX-2 inhibition. Of note, NP16 decreased the level of p-JAK2 and p-STAT3, and blocked the nuclear translocation of STAT3 in GBM cell lines. Moreover, NP16 downregulated the MMP-9 expression of BV2 cells in a co-culture system of BV2 and C6 glioma cells, abrogated the proliferative/invasive/migratory abilities of GBM cells, induced apoptosis by ROS and the Bcl-2-regulated apoptotic pathway, and induced obvious G₂/M arrest in glioma cells in vitro. Furthermore, NP16 displayed favorable pharmacokinetic profiles covering long half-life (11.43 ± 0.43 h) and high blood-brain barrier permeability. Finally, NP16 effectively inhibited tumor growth, promoted the survival rate, increased the expression of E-cadherin and reduced overproduction of PGE₂, MMP-9, VEGF-A and the level of p-STAT3 in tumor tissue, and improved the anxiety-like behavior in C6 glioma model. All these evidences demonstrated N-anthraniloyl tryptamine derivatives as multifunctional anti-glioma agents with high potency could drain the swamp to beat glioma.

Cancer-associated-platelet-inspired nanomedicines for cancer therapy

Platelets, with hemostasis and thrombosis activities, are one of the key components in the blood circulation. As a guard, they rapidly respond to any abnormal blood vessel injury signal and release their granules' contents, which induce their adhesion and aggregation on wound site for hemostasis. Recently, increasing evidence has indicated that platelets are critically involved in the growth and metastasis of cancer cells by releasing a variety of cytokines and chemokines to stimulate cancer cell proliferation and various angiogenic regulators to accelerate tumor angiogenesis. Platelets also secrete active transforming growth factor beta (TGF-β) to promote the epithelial-mesenchymal transition of cancer cells and their extravasation from primary site, and form microthrombus on the surface of cancer cells to protect them from immune attack and high-speed shear force in the circulation. Therefore, blocking platelet-cancer cell interaction may be an attractive strategy to treat primary tumor and/or prevent cancer metastasis. However, systemic inhibition or depletion of platelets brings risk of severe bleeding complication. Cancer-associated-platelets-targeted nanomedicines and biomimetic nanomedicines coated with platelet membrane can be used for targeted anticancer drug delivery, due to their natural targeting ability to tumor cells and platelets. In the current review, we first summarized the platelet mechanisms of action in physiological condition and their multiple roles in cancer progression and conventional antiplatelet therapeutics. We then highlighted the recent progress on the design and fabrication of cancer-associated-platelet-targeted nanomedicines and platelet membrane coating nanomedicines for cancer therapy. Finally, we discussed opportunities and challenges and offered our thoughts for the future development. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Biology-Inspired Nanomaterials > Lipid-Based Structures.

PGE2 receptors in detrusor muscle: Drugging the undruggable for urgency

Overactive bladder (OAB) syndrome is a prevalent condition of the lower urinary tract that causes symptoms, such as urinary frequency, urinary urgency, urge incontinence, and nocturia, and disproportionately affects women and the elderly. Current medications for OAB merely provide symptomatic relief with considerable limitations, as they are no more than moderately effective, not to mention that they may cause substantial adverse effects. Identifying novel molecular targets to facilitate the development of new medical therapies with higher efficacy and safety for OAB is in an urgent unmet need. Although the molecular mechanisms underlying the pathophysiology of OAB largely remain elusive and are likely multifactorial, mounting evidence from preclinical studies over the past decade reveals that the pro-inflammatory pathways engaging cyclooxygenases and their prostanoid products, particularly the prostaglandin E2 (PGE₂), may play essential roles in the progression of OAB. The goals of this review are to summarize recent progresses in our knowledge on the pathogenic roles of PGE₂ in the OAB and to provide new mechanistic insights into the signaling pathways transduced by its four G-protein-coupled receptors (GPCRs), i.e., EP1-EP4, in the overactive detrusor smooth muscle. We also discuss the feasibility of targeting these GPCRs as an emerging strategy to treat OAB with better therapeutic specificity than the current medications.

Prostaglandin E2 and Cancer: Insight into Tumor Progression and Immunity

The involvement of inflammation in cancer progression has been the subject of research for many years. Inflammatory milieu and immune response are associated with cancer progression and recurrence. In different types of tumors, growth and metastatic phenotype characterized by the epithelial mesenchymal transition (EMT) process, stemness, and angiogenesis, are increasingly associated with intrinsic or extrinsic inflammation. Among the inflammatory mediators, prostaglandin E2 (PGE2) supports epithelial tumor aggressiveness by several mechanisms, including growth promotion, escape from apoptosis, transactivation of tyrosine kinase growth factor receptors, and induction of angiogenesis. Moreover, PGE2 is an important player in the tumor microenvironment, where it suppresses antitumor immunity and regulates tumor immune evasion, leading to increased tumoral progression. In this review, we describe the current knowledge on the pro-tumoral activity of PGE2 focusing on its role in cancer progression and in the regulation of the tumor microenvironment.

Small molecules targeting cyclooxygenase/prostanoid cascade in experimental brain ischemia: Do they translate?

Acute brain ischemia accounts for most of stroke cases and constitutes a leading cause of deaths among adults and permanent disabilities in survivors. Currently, the intravenous thrombolysis is the only available medication for ischemic stroke; mechanical thrombectomy is an emerging alternative treatment for occlusion of large arteries and has shown some promise in selected subsets of patients. However, the overall narrow treatment window and potential risks largely limit the patient eligibility. New druggable targets are needed to innovate the treatment of brain ischemia. As the rate-limiting enzyme in the biosyntheses of prostanoids, cyclooxygenase (COX), particularly the inducible isoform COX-2, has long been implicated in mechanisms of acute stroke-induced brain injury and inflammation. However, the notion of therapeutically targeting COX has been diminished over the past two decades due to significant complications of the cardiovascular and cerebrovascular systems caused by long-term use of COX-2 inhibitor drugs. New treatment strategies targeting the downstream prostanoid signaling receptors regulating the deleterious effects of COX cascade have been proposed. As such, a large number of selective small molecules that negatively or positively modulate these important inflammatory regulators have been evaluated for neuroprotection and other beneficial effects in various animal models of brain ischemia. These timely preclinical studies, though not yet led to clinical innovation, provided new insights into the regulation of inflammatory reactions in the ischemic brain and could guide drug discovery efforts aiming for novel adjunctive strategies, along with current reperfusion therapy, to treat acute brain ischemia with higher specificity and longer therapeutic window.

COX-2/PGE2 axis regulates hippocampal BDNF/TrkB signaling via EP2 receptor after prolonged seizures

OBJECTIVE

The objective of this study was to identify the signaling pathway that is immediately triggered by status epilepticus (SE) and in turn contributes to the excessive brain-derived neurotrophic factor (BDNF)/tropomyosin-related kinase receptor B (TrkB) signaling within the hippocampus.

METHODS

We used quantitative PCR, enzyme-linked immunosorbent assay, and Western blot analysis to examine gene expression at both mRNA and protein levels in the hippocampus following prolonged SE in mice and rats. Three classical animal models of SE were utilized in the present study to avoid any model- or species-specific findings.

RESULTS

We showed that both cyclooxygenase-2 (COX-2) and BDNF in the hippocampus were rapidly upregulated after SE onset; however, the induction of COX-2 temporally preceded that of BDNF. Blocking COX-2 activity by selective inhibitor SC-58125 prevented BDNF elevation in the hippocampus following SE; prostaglandin E2 (PGE2), a major product of COX-2 in the brain, was sufficient to stimulate hippocampal cells to secrete BDNF, suggesting that a PGE2 signaling pathway might be directly involved in hippocampal BDNF production. Inhibiting the Gαs-coupled PGE2 receptor EP2 by our recently developed selective antagonist TG6-10-1 decreased the SE-triggered phosphorylation of the cAMP response element-binding protein (CREB) and activation of the BDNF/TrkB signaling in the hippocampus.

SIGNIFICANCE

The molecular mechanisms whereby BDNF/TrkB signaling is upregulated in the hippocampus by SE largely remain unknown. Our findings suggest that COX-2 via the PGE2/EP2 pathway regulates hippocampal BDNF/TrkB activity following prolonged seizures. EP2 inhibition by our bioavailable and brain-permeable antagonists such as TG6-10-1 might therefore provide a novel strategy to suppress the abnormal TrkB activity, an event that can sufficiently trigger pathogenic processes within the brain including acquired epileptogenesis.

Aspirin Induced Glioma Apoptosis through Noxa Upregulation

Clinically, high cyclooxygenase-2 expression in malignant glioma correlates well with poor prognosis and the use of aspirin is associated with a reduced risk of glioma. To extend the current understanding of the apoptotic potential of aspirin in most cell types, this study provides evidence showing that aspirin induced glioma cell apoptosis and inhibited tumor growth, in vitro and in vivo. We found that the human H4 glioma cell-killing effects of aspirin involved mitochondria-mediated apoptosis accompanied by endoplasmic reticulum (ER) stress, Noxa upregulation, Mcl-1 downregulation, Bax mitochondrial distribution and oligomerization, and caspase 3/caspase 8/caspase 9 activation. Genetic silencing of Noxa or Bax attenuated aspirin-induced viability loss and apoptosis, while silencing Mcl-1 augmented the effects of aspirin. Data from genetic and pharmacological studies revealed that the axis of ER stress comprised an apoptotic cascade leading to Noxa upregulation and apoptosis. The apoptotic programs and mediators triggered by aspirin in H4 cells were duplicated in human U87 glioma cell line as well as in tumor-bearing BALB/c nude mice. The involvement of ER stress in indomethacin-induced Mcl-1 downregulation was reported in our previous study on glioma cells. Therefore, the aforementioned phenomena indicate that ER stress may be a valuable target for intervention in glioma apoptosis.

An Agonist Dependent Allosteric Antagonist of Prostaglandin EP2 Receptors

All reported prostaglandin EP2 receptor antagonists have a purely orthosteric, competitive mode of action. Herein, we report the characterization of compound 1 (pubchem CID 664888) as the first EP2 antagonist that features a reversible, agonist dependent allosteric mode of action. Compound 1 displayed an unsurmountable inhibition of cAMP accumulation stimulated by different EP2 agonists in C6 glioma cells overexpressing human EP2 (C6G-hEP2). The degree of reduction of agonist potency and efficacy depended on the agonist employed. Negative allosteric modulation was not observed in C6G cells overexpressing human EP4, IP, or DP1 receptors. Moreover, in the murine microglial cell line that stably expresses human EP2 receptors (BV2-hEP2), compound 1 reduced the EP2 agonist-induced elevation of interleukin 6 (IL-6), IL-1β, and hEP2 mRNA levels and increased that of tumor necrosis factor (TNF)-α. Compound 1 was docked into a homology model of hEP2. The predicted binding site on the cytoplasmic receptor surface was similar to that of allosteric inhibitors of the β2-adrenergic, CC chemokine receptor 9 (CCR9), and CC chemokine receptor 2 (CCR2) receptors, which supports the notion of a conserved G-protein-coupled receptor (GPCR) binding pocket for allosteric inhibitors. As the first agonist dependent negative allosteric modulator of EP2 receptor, the structure of this compound may provide a basis for developing improved allosteric modulators of EP2 receptors.

Radiosensitivity enhancement by Co-NMS-mediated mitochondrial impairment in glioblastoma

We investigated the radiosensitizing effects of Co-NMS, a derivative of nimesulide based on a cobalt carbonyl complex, on malignant glioma cells. In the zebrafish exposed to Co-NMS ranging from 5 to 20 μM, cell death and heat shock protein 70 expression in the brain and neurobehavioral performance were evaluated. Our data showed that Co-NMS at 5 μM did not cause the appreciable neurotoxicity, and thereby was given as a novel radiation sensitizer in further study. In the U251 cells, Co-NMS combined with irradiation treatment resulted in significant inhibition of cell growth and clonogenic capability as well as remarkable increases of G2/M arrest and apoptotic cell population compared to the irradiation alone treatment. This demonstrated that the Co-NMS administration exerted a strong potential of sensitizing effect on the irradiated cells. With regard to the tumor radiosensitization of Co-NMS, it could be primarily attributed to the Co-NMS-derived mitochondrial impairment, reflected by the loss of mitochondrial membrane potential, the disruption of mitochondrial fusion and fission balance as well as redox homeostasis. Furthermore, the energy metabolism of the U251 cells was obviously suppressed by cotreatment with Co-NMS and irradiation through repressing mitochondrial function. Taken together, our findings suggested that Co-NMS could be a desirable drug to enhance the radiotherapeutic effects in glioblastoma patients.

Inverse Agonism of Cannabinoid Receptor Type 2 Confers Anti-inflammatory and Neuroprotective Effects Following Status Epileptics

Prolonged status epilepticus (SE) in humans causes high mortality and brain inflammation-associated neuronal injury and morbidity in survivors. Currently, the only effective treatment is to terminate the seizures swiftly to prevent brain damage. However, reliance on acute therapies alone would be imprudent due to the required short response time. Follow-on therapies that can be delivered well after the SE onset are in an urgent need. Cannabinoid receptor type 2 (CB2), a G protein-coupled receptor that can be expressed by activated brain microglia, has emerged as an appealing anti-inflammatory target for brain conditions. In the current study, we reported that the CB2 inverse agonism by our current lead compound SMM-189 largely prevented the rat primary microglia-mediated inflammation and showed moderate neuroprotection against N-methyl-D-aspartic acid (NMDA) receptor-mediated excitotoxicity in rat primary hippocampal cultures containing both neurons and glia. Using a classical mouse model of epilepsy, in which SE was induced by systemic administration of kainate (30 mg/kg, i.p.) and proceeded for 1 h, we demonstrated that SE downregulated the CB1 but slightly upregulated CB2 receptor in the hippocampus. Transient treatment with SMM-189 (6 mg/kg, i.p., b.i.d.) after the SE was interrupted by diazepam (10 mg/kg, i.p.) prevented the seizure-induced cytokine surge in the brain, neuronal death, and behavioral impairments 24 h after SE. Our results suggest that CB2 inverse agonism might provide an adjunctive anti-inflammatory therapy that can be delivered hours after SE onset, together with NMDA receptor blockers and first-line anti-convulsants, to reduce brain injury and functional deficits following prolonged seizures.

Multi-omic analysis reveals HIP-55-dependent regulation of cytokines release

HIP-55 (HPK1 [hematopoietic progenitor kinase 1] -interacting protein of 55 kDa) contains an actin-depolymerizing factor homology (ADF-H) domain at the N-terminus and a src homology 3 (SH3) domain at the C-terminus, which plays an important role in the T cell receptor (TCR) and B-cell receptor (BCR) signaling and immune system. In our previous studies, HIP-55 was found to be highly expressed in several types of tumors and function as a novel oncogenic signaling hub that regulates tumor progression and metastasis through defined functional domains, actin-binding and SH3 modules. However, the wider functions and mechanisms of HIP-55 are still unclear. Here, multi-omic analysis revealed that one of the main biofunctions of HIP-55 is the regulation of cytokines release. Furthermore, to investigate the role of HIP-55 in the cytokine production, a series Cytokine Antibody Arrays were performed to detect differentially expressed cytokines between control and HIP-55 knockdown cells. A total of 97 differentially expressed cytokines were identified from 300 cytokines in A549 cell. Bioinformatics analysis showed these differentially cytokines were mainly enriched in cancer signal pathways and IL-6 is the most critical hub in the integrated network. Analysis of RNAseq data from lung cancer patients showed that there is a strong negative correlation between HIP-55 and interleukin-6 (IL-6) in samples from lung adenocarcinoma patients. Our data indicated that HIP-55 may participate in cancer progression and metastasis via regulating cytokines release.

Selective EP2 and Cox-2 inhibition suppresses cell migration by reversing epithelial-to-mesenchymal transition and Cox-2 overexpression and E-cadherin downregulation are implicated in neck metastasis of hypopharyngeal cancer

Cyclooxygenase-2 (Cox-2) has been shown to promote cancer initiation and progression through pleiotropic functions including induction of epithelial-to-mesenchymal transition (EMT) via its predominant product prostaglandin E₂ that binds to the cognate receptor EP2. Hence, pharmacological inhibition at the level of EP2 is assumed to be a more selective alternative with less risk to Cox-2 inhibition. However, little is known regarding the anti-cancer effect of an EP2 antagonist on the malignant properties of cancers including hypopharyngeal squamous cell carcinoma (HPSCC). The present study found that both the Cox-2 inhibitor celecoxib and the EP2 antagonist PF-04418948 upregulated CDH-1 expression, restored membranous localization of E-cadherin, and reduced vimentin expression, by downregulating the transcriptional repressors of E-cadherin in BICR6 and FaDu cells. Such Cox-2 or EP2 inhibition-induced EMT reversal led to repressed migration ability in both cells. Immunohistochemical analysis of surgical HPSCC specimens demonstrated an inverse relationship in expression between Cox-2 and E-cadherin both in the context of statistics (P = 0.028) and of reciprocal immunolocalization in situ. Multivariate logistic regression revealed that overexpression of Cox-2 (P < 0.001) and downregulation of E-cadherin (P = 0.016) were both independently predictive of neck metastasis. These results suggest that suppression of cell migration ability via reversing EMT by inhibiting the Cox-2/EP2 signaling may contribute to preventing the development and progression of lymphatic metastasis. Collectively, targeting Cox-2/EP2, especially using EP2 antagonist, can be a promising therapeutic strategy by exerting an anti-metastatic effect via EMT reversal for improving the treatment outcomes of patients with various cancers including HPSCC.

Targeting prostaglandin receptor EP2 for adjunctive treatment of status epilepticus

Status epilepticus (SE) is an emergency condition that can cause permanent brain damage or even death when generalized convulsive seizures last longer than 30 min. Controlling the escalation and propagation of seizures quickly and properly is crucial to the prevention of irreversible neuronal death and the associated morbidity. However, SE often becomes refractory to current anticonvulsant medications, which primarily act on ion channels and commonly impose undesired effects. Identifying new molecular targets for SE might lead to adjunctive treatments that can be delivered even when SE is well established. Recent preclinical studies suggest that prostaglandin E2 (PGE₂) is an essential inflammatory mediator for the brain injury and morbidity following prolonged seizures via activating four G protein-coupled receptors, namely, EP1-EP4. Given that EP2 receptor activation has been identified as a common culprit in several inflammation-associated neurological conditions, such as strokes and neurodegenerative diseases, selective small-molecule antagonists targeting EP2 have been recently developed and utilized to suppress PGE₂-mediated neuroinflammation. Transient inhibition of the EP2 receptor by these bioavailable and brain-permeable antagonists consistently showed marked anti-inflammatory and neuroprotective effects in several rodent models of SE yet had no noticeable effect on seizures per se. This review provides overviews and perspectives of the EP2 receptor as an emerging target for adjunctive treatment, together with the current first-line anti-seizure drugs, to prevent acute brain inflammation and damage following SE.

Lipid mechanisms in hallmarks of cancer

Excess adiposity is a risk factor for several cancer types. This is likely due to complex mechanisms including alterations in the lipid milieu that plays a pivotal role in multiple aspects of carcinogenesis. Here we consider the direct role of lipids in regulating well-known hallmarks of cancer. Furthermore, we suggest that obesity-associated remodelling of membranes and organelles drives cancer cell proliferation and invasion. Identification of cancer-related lipid-mediated mechanisms amongst the broad metabolic disturbances due to excess adiposity is central to the identification of novel and more efficacious prevention and intervention strategies.

Endoplasmic Reticulum Stress Contributes to Indomethacin-Induced Glioma Apoptosis

The dormancy of cellular apoptotic machinery has been highlighted as a crucial factor in therapeutic resistance, recurrence, and poor prognosis in patients with malignancy, such as malignant glioma. Increasing evidence indicates that nonsteroidal anti-inflammatory drugs (NSAIDs) confer chemopreventive effects, and indomethacin has been shown to have a novel chemotherapeutic application targeting glioma cells. To extend these findings, herein, we studied the underlying mechanisms of apoptosis activation caused by indomethacin in human H4 and U87 glioma cells. We found that the glioma cell-killing effects of indomethacin involved both death receptor- and mitochondria-mediated apoptotic cascades. Indomethacin-induced glioma cell apoptosis was accompanied by a series of biochemical changes, including reactive oxygen species generation, endoplasmic reticulum (ER) stress, apoptosis signal-regulating kinase-1 (Ask1) activation, p38 hyperphosphorylation, protein phosphatase 2A (PP2A) activation, Akt dephosphorylation, Mcl-1 and FLICE-inhibiting protein (FLIP) downregulation, Bax mitochondrial distribution, and caspases 3/caspase 8/caspase 9 activation. Data on pharmacological inhibition related to oxidative stress, ER stress, free Ca²⁺, and p38 revealed that the axis of oxidative stress/ER stress/Ask1/p38/PP2A/Akt comprised an apoptotic cascade leading to Mcl-1/FLIP downregulation and glioma apoptosis. Since indomethacin is an emerging choice in chemotherapy and its antineoplastic effects have been demonstrated in glioma tumor-bearing models, the findings further strengthen the argument for turning on the aforementioned axis in order to activate the apoptotic machinery of glioma cells.

Cyclooxygenase 2 Promotes Proliferation and Invasion in Ovarian Cancer Cells via the PGE2/NF-κB Pathway

Ovarian cancer is the leading cause of death among gynecological malignancies. Cyclooxygenase 2 is widely expressed in various cancer cells and participates in the occurrence and development of tumors by regulating a variety of downstream signaling pathways. However, the function and molecular mechanisms of cyclooxygenase 2 remain unclear in ovarian cancer. Here, we demonstrated that cyclooxygenase 2 was highly expressed in ovarian cancer and the expression level was highly correlated with ovarian tumor grades. Further, ovarian cancer cells with high expression of cyclooxygenase 2 exhibit enhanced proliferation and invasion abilities. Specifically, cyclooxygenase 2 promoted the release of prostaglandin E2 upregulated the phosphorylation levels of phospho-nuclear factor-kappa B p65. Celecoxib, AH6809, and BAY11-7082 all can inhibit the promoting effect of cyclooxygenase 2 on SKOV3 and OVCAR3 cell proliferation and invasion. Besides, celecoxib inhibited SKOV3 cell growth in the xenograft tumor model. These data suggest that high expression of cyclooxygenase 2 promotes the proliferation and invasion of ovarian cancer cells through the prostaglandin E2/nuclear factor-kappa B signaling pathway. Cyclooxygenase 2 may be a potential therapeutic target for the treatment of ovarian cancer.

G protein-coupled receptors in acquired epilepsy: Druggability and translatability

As the largest family of membrane proteins in the human genome, G protein-coupled receptors (GPCRs) constitute the targets of more than one-third of all modern medicinal drugs. In the central nervous system (CNS), widely distributed GPCRs in neuronal and nonneuronal cells mediate numerous essential physiological functions via regulating neurotransmission at the synapses. Whereas their abnormalities in expression and activity are involved in various neuropathological processes. CNS conditions thus remain highly represented among the indications of GPCR-targeted agents. Mounting evidence from a large number of animal studies suggests that GPCRs play important roles in the regulation of neuronal excitability associated with epilepsy, a common CNS disease afflicting approximately 1-2% of the population. Surprisingly, none of the US Food and Drug Administration (FDA)-approved (>30) antiepileptic drugs (AEDs) suppresses seizures through acting on GPCRs. This disparity raises concerns about the translatability of these preclinical findings and the druggability of GPCRs for seizure disorders. The currently available AEDs intervene seizures predominantly through targeting ion channels and have considerable limitations, as they often cause unbearable adverse effects, fail to control seizures in over 30% of patients, and merely provide symptomatic relief. Thus, identifying novel molecular targets for epilepsy is highly desired. Herein, we focus on recent progresses in understanding the comprehensive roles of several GPCR families in seizure generation and development of acquired epilepsy. We also dissect current hurdles hindering translational efforts in developing GPCRs as antiepileptic and/or antiepileptogenic targets and discuss the counteracting strategies that might lead to a potential cure for this debilitating CNS condition.

Small-molecule inhibition of prostaglandin E receptor 2 impairs cyclooxygenase-associated malignant glioma growth

BACKGROUND AND PURPOSE

An up-regulation of COX-2 in malignant gliomas causes excessive synthesis of PGE₂ , which is thought to facilitate brain tumour growth and invasion. However, which downstream PGE₂ receptor subtype (i.e., EP₁ -EP₄ ) directly contributes to COX activity-promoted glioma growth remains largely unknown.

EXPERIMENTAL APPROACH

Using a publicly available database from The Cancer Genome Atlas research network, we compared the expression of PGE₂ signalling-associated genes in human lower grade glioma and glioblastoma multiforme (GBM) samples. The Kaplan-Meier analysis was performed to determine the relationship between their expression and survival probability. A time-resolved FRET method was used to identify the EP subtype that mediates COX-2/PGE₂ -initiated cAMP signalling in human GBM cells. Taking advantage of a recently identified novel selective bioavailable brain-permeable small-molecule antagonist, we studied the effect of pharmacological inhibition of the EP₂ receptor on glioma cell growth in vitro and in vivo.

KEY RESULTS

The EP₂ receptor is a key Gα_s -coupled receptor that mediates COX-2/PGE₂ -initiated cAMP signalling pathways in human malignant glioma cells. Inhibition of EP₂ receptors reduced COX-2 activity-driven GBM cell proliferation, invasion, and migration and caused cell cycle arrest at G0-G1 and apoptosis of GBM cells. Glioma cell growth in vivo was also substantially decreased by post-treatment with an EP₂ antagonist in both subcutaneous and intracranial tumour models.

CONCLUSION AND IMPLICATIONS

Taken together, our results suggest that PGE₂ signalling via the EP₂ receptor increases the malignant potential of human glioma cells and might represent a novel therapeutic target for GBM.

Suppressing pro-inflammatory prostaglandin signaling attenuates excitotoxicity-associated neuronal inflammation and injury

Glutamate receptor-mediated excitotoxicity is a common pathogenic process in many neurological conditions including epilepsy. Prolonged seizures induce elevations in extracellular glutamate that contribute to excitotoxic damage, which in turn can trigger chronic neuroinflammatory reactions, leading to secondary damage to the brain. Blocking key inflammatory pathways could prevent such secondary brain injury following the initial excitotoxic insults. Prostaglandin E2 (PGE₂) has emerged as an important mediator of neuroinflammation-associated injury, in large part via activating its EP2 receptor subtype. Herein, we investigated the effects of EP2 receptor inhibition on excitotoxicity-associated neuronal inflammation and injury in vivo. Utilizing a bioavailable and brain-permeant compound, TG6-10-1, we found that pharmacological inhibition of EP2 receptor after a one-hour episode of kainate-induced status epilepticus (SE) in mice reduced seizure-promoted functional deficits, cytokine induction, reactive gliosis, blood-brain barrier impairment, and hippocampal damage. Our preclinical findings endorse the feasibility of blocking PGE₂/EP2 signaling as an adjunctive strategy to treat prolonged seizures. The promising benefits from EP2 receptor inhibition should also be relevant to other neurological conditions in which excitotoxicity-associated secondary damage to the brain represents a pathogenic event.