Attenuation of adjuvant-induced arthritis with carnosic acid by inhibiting mPGES-1, COX-2, and bone loss in male SD rats.

OBJECTIVE: Rheumatoid arthritis (RA), a chronic inflammatory disease, is characterized by joint swelling, cartilage erosion, and bone destruction. This study investigated the therapeutic efficacy of Carnosic acid (CA), a natural compound with anti-inflammatory and antioxidant properties, in an adjuvant-induced arthritis model. METHODS: Paw swelling and arthritis index were measured. Oxidative stress markers, including lipid peroxidation and antioxidant enzyme levels, were assessed. Synovial tissue was analyzed for pro-inflammatory markers using real-time Q-PCR and Western blotting. The expression of mPGES-1 was determined by Western blotting. Peripheral neuropathic pain was assessed using cold and mechanical allodynia tests. Bone loss was quantitatively assessed through microcomputed tomography (µCT) scanning of femurs and X-ray radiography. Indomethacin-induced gastric ulcers were evaluated. Molecular docking studies were conducted to analyze the binding affinity of CA to mPGES-1. RESULTS: The CA treatment not only demonstrated a significant reduction in joint inflammation and paw swelling but also mitigated oxidative stress and improved the antioxidant defence system. CA inhibited microsomal prostaglandin E synthase-1 (mPGES-1) expression and the expression of pro-inflammatory molecules such as inducible nitric oxide synthase (iNOS) and cyclooxygenases-2 (COX-2), thus attenuating the arthritis symptoms without severe gastrointestinal side effects. Additionally, it inhibited the expression of pro-inflammatory molecules such as iNOS and COX-2, contributing to the reduction of arthritis symptoms. Notably, CA treatment prevented the common side effects of traditional RA treatments like corticosteroids and non-steroidal anti-inflammatory drugs (NSAIDs), including weight loss, bone degradation, and gastric ulcers. CONCLUSIONS: These findings suggest that CA, through specific enzyme inhibition, offers a compelling alternative therapeutic approach for RA. Further research is warranted to explore the potential of CA in other arthritis models and its suitability for human RA treatment.

CA significantly reduces inflammation in FCA induced arthritis model.CA treatment inhibits key pro-inflammatory molecules, including mPGES-1 and COX-2In silico docking studies confirm the affinity of CA to mPGES-1.CA prevents bone loss and avoids side effects seen with standard treatments.Antioxidant properties of CA counteract oxidative stress related to chronic inflammation.

Activation of the PGE2-EP2 pathway as a potential drug target for treating eosinophilic rhinosinusitis.

Current treatments of eosinophilic chronic rhinosinusitis (ECRS) involve corticosteroids with various adverse effects and costly therapies such as dupilumab, highlighting the need for improved treatments. However, because of the lack of a proper mouse ECRS model that recapitulates human ECRS, molecular mechanisms underlying this disease are incompletely understood. ECRS is often associated with aspirin-induced asthma, suggesting that dysregulation of lipid mediators in the nasal mucosa may underlie ECRS pathology. We herein found that the expression of microsomal PGE synthase-1 (encoded by PTGES) was significantly lower in the nasal mucosa of ECRS patients than that of non-ECRS subjects. Histological, transcriptional, and lipidomics analyses of Ptges-deficient mice revealed that defective PGE2 biosynthesis facilitated eosinophil recruitment into the nasal mucosa, elevated expression of type-2 cytokines and chemokines, and increased pro-allergic and decreased anti-allergic lipid mediators following challenges with Aspergillus protease and ovalbumin. A nasal spray containing agonists for the PGE2 receptor EP2 or EP4, including omidenepag isopropyl that has been clinically used for treatment of glaucoma, markedly reduced intranasal eosinophil infiltration in Ptges-deficient mice. These results suggest that the present model using Ptges-deficient mice is more relevant to human ECRS than are previously reported models and that eosinophilic inflammation in the nasal mucosa can be efficiently blocked by activation of the PGE2-EP2 pathway. Furthermore, our findings suggest that drug repositioning of omidenepag isopropyl may be useful for treatment of patients with ECRS.

The components of the AhR-molecular chaperone complex differ depending on whether the ligands are toxic or non-toxic.

The aryl hydrocarbon receptor (AhR) forms a complex with the HSP90-XAP2-p23 molecular chaperone when the cells are exposed to toxic compounds. Recently, 1,4-dihydroxy-2-naphthoic acid (DHNA) was reported to be an AhR ligand. Here, we investigated the components of the molecular chaperone complex when DHNA binds to AhR. Proteins eluted from the 3-Methylcolanthrene-affinity column were AhR-HSP90-XAP2-p23 complex. The AhR-molecular chaperone complex did not contain p23 in the eluents from the DHNA-affinity column. In 3-MC-treated cells, AhR formed a complex with HSP90-XAP2-p23 and nuclear translocation occurred within 30 min, while in DHNA-treated cells, AhR formed a complex with AhR-HSP90-XAP2, and translocation was slow from 60 min. Thus, the AhR activation mechanism may differ when DHNA is the ligand compared to toxic ligands.

Genetic or pharmacologic blockade of mPGES-2 attenuates renal lipotoxicity and diabetic kidney disease by targeting Rev-Erbα/FABP5 signaling.

Diabetic kidney disease (DKD) is one of the most common complications of diabetes, and no specific drugs are clinically available. We have previously demonstrated that inhibiting microsomal prostaglandin E synthase-2 (mPGES-2) alleviated type 2 diabetes by enhancing ß cell function and promoting insulin production. However, the involvement of mPGES-2 in DKD remains unclear. Here, we aimed to analyze the association of enhanced mPGES-2 expression with impaired metabolic homeostasis of renal lipids and subsequent renal damage. Notably, global knockout or pharmacological blockage of mPGES-2 attenuated diabetic podocyte injury and tubulointerstitial fibrosis, thereby ameliorating lipid accumulation and lipotoxicity. These findings were further confirmed in podocyte- or tubule-specific mPGES-2-deficient mice. Mechanistically, mPGES-2 and Rev-Erbα competed for heme binding to regulate fatty acid binding protein 5 expression and lipid metabolism in the diabetic kidney. Our findings suggest a potential strategy for treating DKD via mPGES-2 inhibition.

A highly selective mPGES-1 inhibitor to block abdominal aortic aneurysm progression in the angiotensin mouse model.

Abdominal aortic aneurysm (AAA) is a deadly, permanent ballooning of the aortic artery. Pharmacological and genetic studies have pointed to multiple proteins, including microsomal prostaglandin E2 synthase-1 (mPGES-1), as potentially promising targets. However, it remains unknown whether administration of an mPGES-1 inhibitor can effectively attenuate AAA progression in animal models. There are still no FDA-approved pharmacological treatments for AAA. Current research stresses the importance of both anti-inflammatory drug targets and rigor of translatability. Notably, mPGES-1 is an inducible enzyme responsible for overproduction of prostaglandin E2 (PGE2)-a well-known principal pro-inflammatory prostanoid. Here we demonstrate for the first time that a highly selective mPGES-1 inhibitor (UK4b) can completely block further growth of AAA in the ApoE-/- angiotensin (Ang)II mouse model. Our findings show promise for the use of a mPGES-1 inhibitor like UK4b as interventional treatment of AAA and its potential translation into the clinical setting.

Expression of mPGES1 and p16 in feline and human oral squamous cell carcinoma: A comparative oncology approach.

Comparative cancer studies help us determine if discoveries in one species apply to another. Feline and human oral squamous cell carcinoma (FOSCC and HOSCC) are invasive tumours in which inflammation and abnormal p16 expression are reported. Immunohistochemistry was used to determine the expression of p16 and microsomal prostaglandin E2 synthase 1 (mPGES1) in 42 HOSCC and 45 FOSCC samples with known expression of cyclooxygenase 2 (COX2) and cluster of differentiation 147 (CD147). High p16 expression was more common in HOSCC tumour cells compared to adjacent stroma and oral epithelium (p < .05), with a similar but statistically nonsignificant pattern in FOSCC. Interestingly, high mPGES1 expression in FOSCC was more common in the adjacent epithelium compared to the other compartments (p < .05). In HOSCC, mPGES1 was more similar between compartments but was numerically more common in the tumour compartment (p > .05). There were nominal (p > 0.05) differences in marker expression between high and low mPGES1 expressing tumours in both species, including high p16 observed more commonly in high mPGES1 tumours, and COX-2 positive tumours being more common in low mPGES1 tumours. High CD147 HOSCC tumours were more common in the high mPGES1 HOSCC group (p < .05). In the FOSCC cohort, where there was no statistical difference in CD147 expression between high and low mPGES1 tumours, there were numerically higher CD147 cases in the high mPGES1group. Different expression patterns in FOSCC and HOSCC could be related to different risk factors. For example, p16 is a marker of papillomavirus-driven HOSCC, but a causal relationship between papillomaviruses and FOSCC has yet to be definitively demonstrated. The significance of high P16 expression in the absence of papillomavirus infection deserves further study, and the relative contributions of COX2 and mPGES1 to tumour inflammation and progression should be explored. The findings reveal potential similarities in FOSCC and HOSCC biology, while also demonstrating differences that may relate to risk factors and pathogenesis that are unique to each species.

Inhibiting cholesterol de novo synthesis promotes hepatocellular carcinoma progression by upregulating prostaglandin E synthase 2-mediated arachidonic acid metabolism under high fatty acid conditions.

Inhibition of cholesterol de novo synthesis (DNS) by statins has controversial effects on the treatment of hepatocellular carcinoma (HCC). High fatty acid conditions have been reported to limit the effect of statins on metabolism diseases. Whether high fatty acid conditions interfere with the effect of statins on HCC remains unclear. Here, we reported that inhibiting cholesterol DNS with atorvastatin promoted the oncogenic capabilities of diethylnitrosamine (DEN) in mice fed high fatty acid diets (HFD). The combined analysis of metabolomics and transcriptomics revealed that arachidonic acid (AA) metabolism was the most significant changed pathway between mice with and without atorvastatin treatment. In vitro, in the presence of AA precursor linoleic acid (LA), atorvastatin promoted the proliferation and migration ability of HCC cell lines. However, in the absence of LA, these phenomena disappeared. TCGA and tissue microarray examination revealed that prostaglandin e synthase 2 (PTGES2), a key enzyme in AA metabolism, was associated with the poor outcome of HCC patients. Overexpression of PTGES2 promoted the proliferation and migration of HCC cell lines, and knockdown of PTGES2 inhibited the proliferation and migration of cells. Additionally, atorvastatin upregulated PTGES2 expression by enhancing Sterol-regulatory element binding protein 2 (SREBP2)-mediated transcription. Knockdown of PTGES2 reversed the proliferation and migration ability enhanced by atorvastatin. Overall, our study reveals that a high fatty acid background is one of the possible conditions limiting the application of statins in HCC, under which statins promote the progression of HCC by enhancing SREBP2-mediated PTGES2 transcription.

Alpinia katsumadai Hayata Volatile Oil Is Effective in Treating 5-Fluorouracil-Induced Mucositis by Regulating Gut Microbiota and Modulating the GC/GR Pathway and the mPGES-1/PGE2/EP4 Pathways.

This study was aimed to investigate the therapeutic effect and mechanism of AKHO on 5-fluorouracil (5-FU)-induced intestinal mucositis in mice. Mouse body weight, diarrhea score, and H&E staining were applied to judge the therapeutic effect of AKHO. 16S rDNA and nontargeted metabolomics have been used to study the mechanism. WB, ELISA, and immunohistochemistry were adopted to validate possible mechanisms. The results demonstrated that AKHO significantly reduced diarrhea scores and intestinal damage induced by 5-FU in mice. AKHO lowered the serum levels of LD and DAO, and upregulated the expressions of ZO-1 and occludin in the ileum. Also, AKHO upregulated the abundance of Lactobacillus in the gut and suppressed KEGG pathways such as cortisol synthesis and secretion and arachidonic acid metabolism. Further validation studies indicated that AKHO downregulated the expressions of prostaglandin E2 (PGE2), microsomal prostaglandin E synthase-1 (mPGES-1), and PGE2 receptor EP4, as well as upregulated the expression of glucocorticoid (GC) receptor (GR), leading to improved intestinal epithelial barrier function. Taken together, AKHO elicited protective effects against 5-FU-induced mucositis by regulating the expressions of tight junction proteins via modulation of GC/GR and mPGES-1/PGE2/EP4 pathway, providing novel insights into the utilization and development of this pharmaceutical/food resource.

Inhibition of Microsomal Prostaglandin E2 Synthase Reduces Collagen Deposition in Melanoma Tumors and May Improve Immunotherapy Efficacy by Reducing T-cell Exhaustion.

The arachidonic acid pathway participates in immunosuppression in various types of cancer. Our previous observation detailed that microsomal prostaglandin E2 synthase 1 (mPGES-1), an enzyme downstream of cyclooxygenase 2 (COX-2), limited antitumor immunity in melanoma; in addition, genetic depletion of mPGES-1 specifically enhanced immune checkpoint blockade therapy. The current study set out to distinguish the roles of mPGES-1 from those of COX-2 in tumor immunity and determine the potential of mPGES-1 inhibitors for reinforcing immunotherapy in melanoma. Genetic deletion of mPGES-1 showed different profiles of prostaglandin metabolites from that of COX-2 deletion. In our syngeneic mouse model, mPGES-1-deficient cells exhibited similar tumorigenicity to that of COX-2-deficient cells, despite a lower ability to suppress PGE2 synthesis by mPGES-1 depletion, indicating the presence of factors other than PGE2 that are likely to regulate tumor immunity. RNA-sequencing analysis revealed that mPGES-1 depletion reduced the expressions of collagen-related genes, which have been found to be associated with immunosuppressive signatures. In our mouse model, collagen was reduced in mPGES-1-deficient tumors, and phenotypic analysis of tumor-infiltrating lymphocytes indicated that mPGES-1-deficient tumors had fewer TIM3+ exhausted CD8+ T cells compared with COX-2-deficient tumors. CAY10678, an mPGES-1 inhibitor, was equivalent to celecoxib, a selective COX-2 inhibitor, in reinforcing anti-PD-1 treatment. Our study indicates that mPGES-1 inhibitors represent a promising adjuvant for immunotherapies in melanoma by reducing collagen deposition and T-cell exhaustion. Significance: Collagen is a predominant component of the extracellular matrix that may influence the tumor immune microenvironment for cancer progression. We present here that mPGES-1 has specific roles in regulating tumor immunity, associated with several collagen-related genes and propose that pharmacologic inhibition of mPGES-1 may hold therapeutic promise for improving immune checkpoint-based therapies.

LDL-Dependent Regulation of TNFα/PGE2 Induced COX-2/mPGES-1 Expression in Human Macrophage Cell Lines.

Inflammation is a hallmark in severe diseases such as atherosclerosis and non-alcohol-induced steatohepatitis (NASH). In the development of inflammation, prostaglandins, especially prostaglandin E2 (PGE2), are major players alongside with chemo- and cytokines, like tumor-necrosis-factor alpha (TNFα) and interleukin-1 beta (IL-1ß). During inflammation, PGE2 synthesis can be increased by the transcriptional induction of the two key enzymes: cyclooxygenase 2 (COX-2), which converts arachidonic acid to PGH2, and microsomal prostaglandin E2 synthase 1 (mPGES-1), which synthesizes PGE2 from PGH2. Both COX-2 and mPGES-2 were induced by a dietary intervention where mice were fed a fatty acid-rich and, more importantly, cholesterol-rich diet, leading to the development of NASH. Since macrophages are the main source of PGE2 synthesis and cholesterol is predominantly transported as LDL, the regulation of COX-2 and mPGES-1 expression by native LDL was analyzed in human macrophage cell lines. THP-1 and U937 monocytes were differentiated into macrophages, through which TNFα and PGE-2 induced COX-2 and mPGES-1 expression by LDL could be analyzed on both mRNA and protein levels. In addition, the interaction of LDL- and EP receptor signal chains in COX-2/mPGES-1 expression and PGE2-synthesis were analyzed in more detail using EP receptor specific agonists. Furthermore, the LDL-mediated signal transduction in THP-1 macrophages was analyzed by measuring ERK and Akt phosphorylation as well as transcriptional regulation of transcription factor Egr-1. COX-2 and mPGES-1 were induced in both THP-1 and U937 macrophages by the combination of TNFα and PGE2. Surprisingly, LDL dose-dependently increased the expression of mPGES-1 but repressed the expression of COX-2 on mRNA and protein levels in both cell lines. The interaction of LDL and PGE2 signal chains in mPGES-1 induction as well as PGE2-synthesis could be mimicked by through simultaneous stimulation with EP2 and EP4 agonists. In THP-1 macrophages, LDL induced Akt-phosphorylation, which could be blocked by a PI3 kinase inhibitor. Alongside blocking Akt-phosphorylation, the PI3K inhibitor inhibited LDL-mediated mPGES-1 induction; however, it did not attenuate the repression of COX-2 expression. LDL repressed basal ERK phosphorylation and expression of downstream transcription factor Egr-1, which might lead to inhibition of COX-2 expression. These findings suggest that simultaneous stimulation with a combination of TNFα, PGE2, and native LDL-activated signal chains in macrophage cell lines leads to maximal mPGES-1 activity, as well repression of COX-2 expression, by activating PI3K as well as repression of ERK/Egr-1 signal chains.

PGE2 pathway mediates oxidative stress-induced ferroptosis in renal tubular epithelial cells.

Prostaglandin E2 (PGE2) is one of the most abundant prostaglandins and has been implicated in various diseases. Here, we aimed to explore the role of the PGE2 pathway in mediating ferroptosis during acute kidney injury. When renal tubular epithelial cells stimulated by H2 O2 , the contents of glutathione (GSH) and glutathione peroxidase 4 (GPX4) decreased, whereas the level of lipid peroxide increased. Ferrostatin-1 can effectively attenuate these changes. In this process, the expression levels of cyclooxygenase (COX)-1 and COX-2 were up-regulated. Meanwhile, the expression of microsomal prostaglandin E synthase-2 was elevated, whereas the expression of microsomal prostaglandin E synthase-1 and cytosolic prostaglandin E synthase were down-regulated. Furthermore, the expression of 15-hydroxyprostaglandin dehydrogenase decreased. An excessive accumulation of PGE2 promoted ferroptosis, whereas the PGE2 inhibitor pranoprofen minimized the changes for COX-2, GSH, GPX4 and lipid peroxides. A decrease in the levels of the PGE2 receptor E-series of prostaglandin 1/3 partially restored the decline of GSH and GPX4 levels and inhibited the aggravation of lipid peroxide. Consistent with the in vitro results, increased PGE2 levels led to increased levels of 3,4-methylenedioxyamphetamine, Fe2+ accumulation and decreased GSH and GPX4 levels during renal ischaemia/reperfusion injury injury in mice. Our results indicate that the PGE2 pathway mediated oxidative stress-induced ferroptosis in renal tubular epithelial cells.

Mechanisms by which dupilumab normalizes eicosanoid metabolism and restores aspirin-tolerance in AERD: A hypothesis.

Aspirin-exacerbated respiratory disease (AERD) is associated with overproduction of proinflammatory cysteinyl leukotrienes (CysLTs), defective generation of anti-inflammatory prostaglandin E2 (PGE2), and reduced expression of the EP2 receptor for PGE2. Reduced PGE2 synthesis results from the downregulation of inducible COX-2. Because PGE2 signaling via EP2 inhibits the 5-lipoxygenase/leukotriene C4 synthase-dependent pathway, the deficient levels of both PGE2 and EP2 likely contribute to the excessive baseline production of cysteinyl leukotrienes in patients with AERD compared with in patients with aspirin-tolerant asthma. The COX-2 pathway is regulated by an autocrine metabolic loop involving IL-1ß, IL-1 receptor type I, EP2, COX-2, membrane-bound PGE2 prostaglandin E2 synthase-1, and PGE2. Previous studies reported that this metabolic loop is dysregulated in patients with AERD. When the downexpressed EP2 receptor is normalized, the entire loop returns to its normal function. Cotreatment of airway cells from healthy subjects with IL-4 and IFN-γ induces alterations in the metabolic loop similar to those seen in patients with AERD. In these patients, IL-4, which is produced in excess in airways of patients with AERD, likely contributes to the alteration of normal functioning of the autocrine metabolic loop involving IL-1ß, IL-1 receptor type I, EP2, COX-2, membrane-bound PGE2 prostaglandin E2 synthase-1, and PGE2. We hypothesized that by blocking IL-4 action, dupilumab normalizes EP2 expression and restores the normal functioning of the COX-2 pathway autocrine metabolic loop, thereby normalizing the synthesis of PGE2 and restoring aspirin tolerance.

The microsomal prostaglandin E synthase-1/prostaglandin E2 axis induces recovery from ischaemia via recruitment of regulatory T cells.

AIMS: Microsomal prostaglandin E synthase-1 (mPGES-1)/prostaglandin E2 (PGE2) induces angiogenesis through the prostaglandin E2 receptor (EP1-4). Among immune cells, regulatory T cells (Tregs), which inhibit immune responses, have been implicated in angiogenesis, and PGE2 is known to modulate the function and differentiation of Tregs. We hypothesized that mPGES-1/PGE2-EP signalling could contribute to recovery from ischaemic conditions by promoting the accumulation of Tregs. METHODS AND RESULTS: Wild-type (WT), mPGES-1-deficient (mPges-1-/-), and EP4 receptor-deficient (Ep4-/-) male mice, 6-8 weeks old, were used. Hindlimb ischaemia was induced by femoral artery ligation. Recovery from ischaemia was suppressed in mPges-1-/- mice and compared with WT mice. The number of accumulated forkhead box protein P3 (FoxP3)+ cells in ischaemic muscle tissue was decreased in mPges-1-/- mice compared with that in WT mice. Expression levels of transforming growth factor-ß (TGF-ß) and stromal cell derived factor-1 (SDF-1) in ischaemic tissue were also suppressed in mPges-1-/- mice. The number of accumulated FoxP3+ cells and blood flow recovery were suppressed when Tregs were depleted by injecting antibody against folate receptor 4 in WT mice but not in mPges-1-/- mice. Recovery from ischaemia was significantly suppressed in Ep4-/- mice compared with that in WT mice. Furthermore, mRNA levels of Foxp3 and Tgf-ß were suppressed in Ep4-/- mice. Moreover, the number of accumulated FoxP3+ cells in ischaemic tissue was diminished in Ep4-/- mice compared with that in Ep4+/+ mice. CONCLUSION: These findings suggested that mPGES-1/PGE2 induced neovascularization from ischaemia via EP4 by promoting the accumulation of Tregs. Highly selective EP4 agonists could be useful for the treatment of peripheral artery disease.

The Role of mPGES-1 in Promoting Granulation Tissue Angiogenesis Through Regulatory T-cell Accumulation.

BACKGROUND/AIM: Microsomal prostaglandin E synthase-1 (mPGES-1) is an enzyme, which catalyzes the final step of prostaglandin E2 (PGE2) synthesis. PGE2 in involved in wound-induced angiogenesis. Regulatory T cells (Tregs) regulate not only immune tolerance but also tissue repair and angiogenesis. We examined whether the mPGES-1/PGE2 axis contributes to wound-induced angiogenesis and granulation tissue formation through Treg accumulation. MATERIALS AND METHODS: The dorsal subcutaneous tissues of male mPGES-1-deficient (mPGES-1-/-) and C57BL/6 wild-type (WT) mice were implanted with polyurethane sponge disks. Angiogenesis was estimated by determining the wet weight of sponge tissues and the expression of proangiogenic factors including CD31, vascular endothelial growth factor (VEGF), and transforming growth factor ß (TGF-ß) in granulation tissues. RESULTS: Angiogenesis was suppressed in mPGES-1-/- mice compared with WT mice, which was associated with attenuated forkhead box P3 (Foxp3) expression and Foxp3+ Treg accumulation. The number of cells double-positive for Foxp3/TGFß and Foxp3/VEGF were lower in mPGES-1-/- mice than in WT mice. Neutralizing Tregs with antibodies (Abs) against CD25 or folate receptor 4 (FR4) inhibited the Foxp3+ Treg angiogenesis and accumulation in WT mice, but not in mPGES-1-/- mice. The topical application of PGE2 into the implanted sponge enhanced angiogenesis and accumulation of Tregs expressing TGFß and VEGF in WT and mPGES-1-/- mice. CONCLUSION: Tregs producing TGFß and VEGF accumulate in wounds and contribute to angiogenesis through mPGES-1-derived PGE2 mPGES-1 induction may control angiogenesis in skin wounds by recruiting Tregs.

Sinomenine increases the methylation level at specific GCG site in mPGES-1 promoter to facilitate its specific inhibitory effect on mPGES-1.

Prostaglandin E2 (PGE2) in cancer and inflammatory diseases is a key mediator of disease progression. Non-steroidal anti-inflammatory drugs (NSAIDs) are widely used to inhibit the expression of PGE2 by depressing cyclooxygenase (COX) in inflammatory treatments. However, the inhibition to COXs may cause serious side effects. Thus, it is urgent to develop new anti-inflammatory drugs aiming new targets to inhibit PGE2 production. Microsomal prostaglandin E synthase 1 (mPGES-1) catalyzes the final step of PGE2 biosynthesis. Therefore, the selective inhibition of mPGES-1 has become a promising strategy in the treatments of cancer and inflammatory diseases. Our previous studies confirmed that sinomenine (SIN) is a specific mPGES-1 inhibitor. However, the exact mechanism by which SIN inhibits mPGES-1 remains unknown. This study aimed to explain the regulation effect of SIN to mPGES-1 gene expression by its DNA methylation induction effect. We found that the demethylating agent 5-azacytidine (5-AzaC) reversed the inhibitory effect of SIN to mPGES-1. Besides, SIN selectively increased the methylation level of the promoter region in the mPGES-1 gene while the pretreatment of 5-AzaC suppressed this effect. The results also shows that pretreatment with SIN increased the methylation level of specific GCG sites in the promoter region of mPGES-1. This specific methylation site may become a new biomarker for predicting and diagnosing RA and cancer with high expression of mPGES-1. Also, our research provides new ideas and solutions for clinical diagnosis and treatment of diseases related to mPGES-1 and for targeted methylation strategy in drug development.

mPGES-2 blockade antagonizes ß-cell senescence to ameliorate diabetes by acting on NR4A1.

ß-cell dysfunction is a hallmark of type 1 and type 2 diabetes. Type 2 diabetes is strongly associated with ageing-related ß-cell abnormalities that arise through unknown mechanisms. Here we show better ß-cell identity, less ß-cell senescence, enhanced glucose-stimulated insulin secretion and improved glucose homeostasis in global microsomal prostaglandin E synthase-2 (mPGES-2)-deficient mice challenged with a high-fat diet or bred with a genetic model of type 2 diabetes (db/db mice). Furthermore, the function of mPGES-2 in ß-cells is validated using mice with ß-cell-specific mPGES-2 deficiency or overexpression. Mechanistically, the protective role of mPGES-2 deletion is induced by antagonizing ß-cell senescence via interference of the PGE2-EP3-NR4A1 signalling axis. We also discover an inhibitor of mPGES-2, SZ0232, which protects against ß-cell dysfunction and diabetes, similar to mPGES-2 deletion. We conclude that mPGES-2 contributes to ageing-associated ß-cell senescence and dysfunction via the PGE2-EP3-NR4A1 signalling axis. Pharmacologic blockade of mPGES-2 might be effective for treating ageing-associated ß-cell dysfunction and diabetes.

Disruption of Prostaglandin E2 Signaling in Cancer-Associated Fibroblasts Limits Mammary Carcinoma Growth but Promotes Metastasis.

The activation and differentiation of cancer-associated fibroblasts (CAF) are involved in tumor progression. Here, we show that the tumor-promoting lipid mediator prostaglandin E2 (PGE2) plays a paradoxical role in CAF activation and tumor progression. Restricting PGE2 signaling via knockout of microsomal prostaglandin E synthase-1 (mPGES-1) in PyMT mice or of the prostanoid E receptor 3 (EP3) in CAFs stunted mammary carcinoma growth associated with strong CAF proliferation. CAF proliferation upon EP3 inhibition required p38 MAPK signaling. Mechanistically, TGFß-activated kinase-like protein (TAK1L), which was identified as a negative regulator of p38 MAPK activation, was decreased following ablation of mPGES-1 or EP3. In contrast with its effects on primary tumor growth, disruption of PGE2 signaling in CAFs induced epithelial-to-mesenchymal transition in cancer organoids and promoted metastasis in mice. Moreover, TAK1L expression in CAFs was associated with decreased CAF activation, reduced metastasis, and prolonged survival in human breast cancer. These data characterize a new pathway of regulating inflammatory CAF activation, which affects breast cancer progression. SIGNIFICANCE: The inflammatory lipid prostaglandin E2 suppresses cancer-associated fibroblast expansion and activation to limit primary mammary tumor growth while promoting metastasis.

Microsomal prostaglandin E synthase-1 is involved in the metabolic and cardiovascular alterations associated with obesity.

BACKGROUND AND PURPOSE: Microsomal prostaglandin E synthase-1 (mPGES-1) is an inducible isomerase responsible for prostaglandin E2 production in inflammatory conditions. We evaluated the role of mPGES-1 in the development and the metabolic and cardiovascular alterations of obesity. EXPERIMENTAL APPROACH: mPGES-1+/+ and mPGES-1-/- mice were fed with normal or high fat diet (HFD, 60% fat). The glycaemic and lipid profile was evaluated by glucose and insulin tolerance tests and colorimetric assays. Vascular function, structure and mechanics were assessed by myography. Histological studies, q-RT-PCR, and western blot analyses were performed in adipose tissue depots and cardiovascular tissues. Gene expression in abdominal fat and perivascular adipose tissue (PVAT) from patients was correlated with vascular damage. KEY RESULTS: Male mPGES-1-/- mice fed with HFD were protected against body weight gain and showed reduced adiposity, better glucose tolerance and insulin sensitivity, lipid levels and less white adipose tissue and PVAT inflammation and fibrosis, compared with mPGES-1+/+ mice. mPGES-1 knockdown prevented cardiomyocyte hypertrophy, cardiac fibrosis, endothelial dysfunction, aortic insulin resistance, and vascular inflammation and remodelling, induced by HFD. Obesity-induced weight gain and endothelial dysfunction of resistance arteries were ameliorated in female mPGES-1-/- mice. In humans, we found a positive correlation between mPGES-1 expression in abdominal fat and vascular remodelling, vessel stiffness, and systolic blood pressure. In human PVAT, there was a positive correlation between mPGES-1 expression and inflammatory markers. CONCLUSIONS AND IMPLICATIONS: mPGES-1 inhibition might be a novel therapeutic approach to the management of obesity and the associated cardiovascular and metabolic alterations.

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

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

Targeted delivery of mPGES-1 inhibitors to macrophages via the folate receptor-ß for inflammatory pain.

Activated macrophages overexpress the folate receptor ß (FR-ß) that can be used for targeted delivery of drugs conjugated to folic acid. FR-expressing macrophages contribute to arthritis progression by secreting prostaglandin E2 (PGE2). Non-steroidal anti-inflammatory drugs (NSAIDs) block PGs and thromboxane by inhibiting the cyclooxygenase (COX) enzymes and are used for chronic pain and inflammation despite their well-known toxicity. New NSAIDs target an enzyme downstream of COXs, microsomal prostaglandin E synthase-1 (mPGES-1). Inhibition of mPGES-1 in inflammatory macrophages promises to retain NSAID efficacy while limiting toxicity. We conjugated a potent mPGES-1 inhibitor, MK-7285, to folate, but the construct released the drug inefficiently. Folate conjugation to the primary alcohol of MK-7285 improved the construct's stability and the release of free drug. Surprisingly, the drug-folate conjugate potentiated PGE2 in FR-positive KB cells, and reduced PGE2 in macrophages independently of the FR. Folate conjugation of NSAIDs is not an optimal strategy for targeting of macrophages.