Cyclooxygenases, microsomal prostaglandin E synthase-1, and cardiovascular function

Differential Impact In Vivo of Pf4-ΔCre-Mediated and Gp1ba-ΔCre-Mediated Depletion of Cyclooxygenase-1 in Platelets in Mice

BACKGROUND

Low-dose aspirin is widely used for the secondary prevention of cardiovascular disease. The beneficial effects of low-dose aspirin are attributable to its inhibition of platelet Cox (cyclooxygenase)-1-derived thromboxane A2. Until recently, the use of the Pf4 (platelet factor 4) Cre has been the only genetic approach to generating megakaryocyte/platelet ablation of Cox-1 in mice. However, Pf4-ΔCre displays ectopic expression outside the megakaryocyte/platelet lineage, especially during inflammation. The use of the Gp1ba (glycoprotein 1bα) Cre promises a more specific, targeted approach.

METHODS

To evaluate the role of Cox-1 in platelets, we crossed Pf4-ΔCre or Gp1ba-ΔCre mice with Cox-1flox/flox mice to generate platelet Cox-1-/- mice on normolipidemic and hyperlipidemic (Ldlr-/-; low-density lipoprotein receptor) backgrounds.

RESULTS

Ex vivo platelet aggregation induced by arachidonic acid or adenosine diphosphate in platelet-rich plasma was inhibited to a similar extent in Pf4-ΔCre Cox-1-/-/Ldlr-/- and Gp1ba-ΔCre Cox-1-/-/Ldlr-/- mice. In a mouse model of tail injury, Pf4-ΔCre-mediated and Gp1ba-ΔCre-mediated deletions of Cox-1 were similarly efficient in suppressing platelet prostanoid biosynthesis. Experimental thrombogenesis and attendant blood loss were similar in both models. However, the impact on atherogenesis was divergent, being accelerated in the Pf4-ΔCre mice while restrained in the Gp1ba-ΔCres. In the former, accelerated atherogenesis was associated with greater suppression of PGI2 biosynthesis, a reduction in the lipopolysaccharide-evoked capacity to produce PGE2 (prostaglandin E) and PGD2 (prostanglandin D), activation of the inflammasome, elevated plasma levels of IL-1β (interleukin), reduced plasma levels of HDL-C (high-density lipoprotein receptor-cholesterol), and a reduction in the capacity for reverse cholesterol transport. By contrast, in the latter, plasma HDL-C and α-tocopherol were elevated, and MIP-1α (macrophage inflammatory protein-1α) and MCP-1 (monocyte chemoattractant protein 1) were reduced.

CONCLUSIONS

Both approaches to Cox-1 deletion similarly restrain thrombogenesis, but a differential impact on Cox-1-dependent prostanoid formation by the vasculature may contribute to an inflammatory phenotype and accelerated atherogenesis in Pf4-ΔCre mice.

Prostanoids in Cardiac and Vascular Remodeling

Prostanoids are biologically active lipids generated from arachidonic acid by the action of the COX (cyclooxygenase) isozymes. NSAIDs, which reduce the biosynthesis of prostanoids by inhibiting COX activity, are effective anti-inflammatory, antipyretic, and analgesic drugs. However, their use is limited by cardiovascular adverse effects, including myocardial infarction, stroke, hypertension, and heart failure. While it is well established that NSAIDs increase the risk of atherothrombotic events and hypertension by suppressing vasoprotective prostanoids, less is known about the link between NSAIDs and heart failure risk. Current evidence indicates that NSAIDs may increase the risk for heart failure by promoting adverse myocardial and vascular remodeling. Indeed, prostanoids play an important role in modulating structural and functional changes occurring in the myocardium and in the vasculature in response to physiological and pathological stimuli. This review will summarize current knowledge of the role of the different prostanoids in myocardial and vascular remodeling and explore how maladaptive remodeling can be counteracted by targeting specific prostanoids.

The Emerging Therapeutic Role of Prostaglandin E2 Signaling in Pulmonary Hypertension

Mild-to-moderate pulmonary hypertension (PH) is a common complication of chronic obstructive pulmonary disease (COPD). It is characterized by narrowing and thickening of the pulmonary arteries, resulting in increased pulmonary vascular resistance (PVR) and ultimately leading to right ventricular dysfunction. Pulmonary vascular remodeling in COPD is the main reason for the increase of pulmonary artery pressure (PAP). The pathogenesis of PH in COPD is complex and multifactorial, involving chronic inflammation, hypoxia, and oxidative stress. To date, prostacyclin and its analogues are widely used to prevent PH progression in clinical. These drugs have potent anti-proliferative, anti-inflammatory, and stimulating endothelial regeneration properties, bringing therapeutic benefits to the slowing, stabilization, and even some reversal of vascular remodeling. As another well-known and extensively researched prostaglandins, prostaglandin E2 (PGE2) and its downstream signaling have been found to play an important role in various biological processes. Emerging evidence has revealed that PGE2 and its receptors (i.e., EP1-4) are involved in the regulation of pulmonary vascular homeostasis and remodeling. This review focuses on the research progress of the PGE2 signaling pathway in PH and discusses the possibility of treating PH based on the PGE2 signaling pathway.

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.

The anti-inflammatory and vasoprotective properties of mPGES-1 inhibition offer promising therapeutic potential

INTRODUCTION

Prostaglandin E2 (PGE2) is produced by cyclooxygenases (COX-1/2) and the microsomal prostaglandin E synthase 1 (mPGES-1). PGE2 is pro-inflammatory in diseases such as rheumatoid arthritis, cardiovascular disorders, and cancer. While Nonsteroidal anti-inflammatory drugs (NSAIDs) targeting COX can effectively reduce inflammation, their use is limited by gastrointestinal and cardiovascular side effects resulting from the blockade of all prostanoids. To overcome this limitation, selective inhibition of mPGES-1 is being explored as an alternative therapeutic strategy to inhibit PGE2 production while sparing or even upregulating other prostaglandins. However, the exact timing and location of PGH2 conversion to PGD2, PGI2, TXB2 or PGF2α, and whether it hinders or supports the therapeutic effect of mPGES-1 inhibition, is not fully understood.

AREAS COVERED

The article briefly describes prostanoid history and metabolism with a strong focus on the vascular effects of prostanoids. Recent advances in mPGES-1 inhibitor development and results from pre-clinical and clinical studies are presented. Prostanoid shunting after mPGES-1 inhibition is highlighted and particularly discussed in the context of cardiovascular diseases.

EXPERT OPINION

The newest research demonstrates that inhibition of mPGES-1 is a potent anti-inflammatory treatment strategy and beneficial and safer regarding cardiovascular side effects compared to NSAIDs. Inhibitors of mPGES-1 hold great potential to advance to the clinic and there are ongoing phase-II trials in endometriosis.

Renal Function Underpins the Cyclooxygenase-2: Asymmetric Dimethylarginine Axis in Mouse and Man

Introduction

Through the production of prostacyclin, cyclooxygenase (COX)-2 protects the cardiorenal system. Asymmetric dimethylarginine (ADMA), is a biomarker of cardiovascular and renal disease. Here we determined the relationship between COX-2/prostacyclin, ADMA, and renal function in mouse and human models.

Methods

We used plasma from COX-2 or prostacyclin synthase knockout mice and from a unique individual lacking COX-derived prostaglandins (PGs) because of a loss of function mutation in cytosolic phospholipase A2 (cPLA2), before and after receiving a cPLA2-replete transplanted donor kidney. ADMA, arginine, and citrulline were measured using ultra-high performance liquid-chromatography tandem mass spectrometry. ADMA and arginine were also measured by enzyme-linked immunosorbent assay (ELISA). Renal function was assessed by measuring cystatin C by ELISA. ADMA and prostacyclin release from organotypic kidney slices were also measured by ELISA.

Results

Loss of COX-2 or prostacyclin synthase in mice increased plasma levels of ADMA, citrulline, arginine, and cystatin C. ADMA, citrulline, and arginine positively correlated with cystatin C. Plasma ADMA, citrulline, and cystatin C, but not arginine, were elevated in samples from the patient lacking COX/prostacyclin capacity compared to levels in healthy volunteers. Renal function, ADMA, and citrulline were returned toward normal range when the patient received a genetically normal kidney, capable of COX/prostacyclin activity; and cystatin C positively correlated with ADMA and citrulline. Levels of ADMA and prostacyclin in conditioned media of kidney slices were not altered in tissue from COX-2 knockout mice compared to wildtype controls.

Conclusion

In human and mouse models, where renal function is compromised because of loss of COX-2/PGI2 signaling, ADMA levels are increased.

Microsomal prostaglandin E synthase-1 inhibition promotes shunting in arachidonic acid metabolism during inflammatory responses in vitro

Microsomal Prostaglandin E Synthase 1 (mPGES-1) is the key enzyme for the generation of the pro-inflammatory lipid mediator prostaglandin E₂ (PGE₂), which contributes to several pathological features of many diseases. Inhibition of mPGES-1 has been shown to be a safe and effective therapeutic strategy in various pre-clinical studies. In addition to reduced PGE₂ formation, it is also suggested that the potential shunting into other protective and pro-resolving prostanoids may play an important role in resolution of inflammation. In the present study, we analysed the eicosanoid profiles in four in vitro inflammation models and compared the effects of mPGES-1 inhibition with those of cyclooxygenase-2 (Cox-2) inhibition. Our results showed a marked shift to the PGD₂ pathway under mPGES-1 inhibition in A549 cells, RAW264.7 cells and mouse bone marrow-derived macrophages (BMDMs), whereas enhanced prostacyclin production was observed in rheumatoid arthritis synovial fibroblasts (RASFs) treated with an mPGES-1 inhibitor. As expected, Cox-2 inhibition completely suppressed all prostanoids. This study suggests that the therapeutic effects of mPGES-1 inhibition may be mediated by modulation of other prostanoids in addition to PGE₂ reduction.

Effects of Atherogenic Factors on Endothelial Cells: Bioinformatics Analysis of Differentially Expressed Genes and Signaling Pathways

(1) Background: Atherosclerosis is a serious medical condition associated with high morbidity and mortality rates. It develops over many years as a complex chain of events in the vascular wall involving various cells and is influenced by many factors of clinical interest. (2) Methods: In this study, we performed a bioinformatic analysis of Gene Expression Omnibus (GEO) datasets to investigate the gene ontology of differentially expressed genes (DEGs) in endothelial cells exposed to atherogenic factors such as tobacco smoking, oscillatory shear, and oxidized low-density lipoproteins (oxLDL). DEGs were identified using the limma R package, and gene ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment, and protein-protein interaction (PPI) network analysis were performed. (3) Results: We studied biological processes and signaling pathways involving DEGs in endothelial cells under the influence of atherogenic factors. GO enrichment analysis demonstrated that the DEGs were mainly involved in cytokine-mediated signaling pathway, innate immune response, lipid biosynthetic process, 5-lipoxygenase activity, and nitric-oxide synthase activity. KEGG pathway enrichment analysis showed that common pathways included tumor necrosis factor signaling pathway, NF-κB signaling pathway, NOD-like receptor signaling pathway, lipid and atherosclerosis, lipoprotein particle binding, and apoptosis. (4) Conclusions: Atherogenic factors such as smoking, impaired flow, and oxLDL contribute to impaired innate immune response, metabolism, and apoptosis in endothelial cells, potentially leading to the development of atherosclerosis.

Analgesic effects of a highly selective mPGES-1 inhibitor

The growing opioid use and overdose crisis in the US is closely related to the abuse of pain medications. Particularly for postoperative pain (POP), ~ 310 million major surgeries are performed globally per year. Most patients undergoing surgical procedures experience acute POP, and ~ 75% of those with POP report the severity as moderate, severe, or extreme. Opioid analgesics are the mainstay for POP management. It is highly desirable to develop a truly effective and safe non-opioid analgesic to treat POP and other forms of pain. Notably, microsomal prostaglandin E2 (PGE₂) synthase-1 (mPGES-1) was once proposed as a potentially promising target for a next generation of anti-inflammatory drugs based on studies in mPGES-1 knockouts. However, to the best of our knowledge, no studies have ever been reported to explore whether mPGES-1 is also a potential target for POP treatment. In this study, we demonstrate for the first time that a highly selective mPGES-1 inhibitor can effectively relieve POP as well as other forms of pain through blocking the PGE₂ overproduction. All the data have consistently demonstrated that mPGES-1 is a truly promising target for treatment of POP as well as other forms of pain.

Mechanism of platelet activation and potential therapeutic effects of natural drugs

BACKGROUND

Cardiovascular disease is one of the most concerning chronic diseases in the world. Many studies have shown that platelet overactivation is a very important factor in the occurrence and development of cardiovascular diseases. At present, the widely used antiplatelet drugs have some defects, such as drug resistance and adverse reactions.

PURPOSE

The purpose of this article is to summarize the main mechanisms and pathways of platelet activation, the main targets of antiplatelet aggregation, and the antiplatelet aggregation components of natural drugs and their mechanisms of action to provide new research ideas for the development and application of antiplatelet drugs.

STUDY DESIGN AND METHODS

In this review, we systematically searched the PubMed, Google Scholar, Web of Science, and CNKI databases and selected studies based on predefined eligibility criteria. We then assessed their quality and extracted data.

RESULTS

ADP, AA, THR, AF, collagen, SDF-1α, and Ca²⁺ can induce platelet aggregation and trigger thrombosis. Natural drugs have a good inhibitory effect on platelet activation. More than 50 kinds of natural drugs and over 120 kinds of chemical compounds, including flavonoids, alkaloids, saponins, terpenoids, coumarins, and organic acids, have significantly inhibited platelet activation activity. The MAPK pathway, cGMP-PKG pathway, cAMP-PKA pathway, PI3K-AKT pathway, PTK pathway, PLC pathway, and AA pathway are the main mechanisms and pathways of platelet activation.

CONCLUSION

Natural drugs and their active ingredients have shown good activity and application prospects in anti-platelet aggregation. We hope that this review provides new research ideas for the development and application of antiplatelet drugs.

In Silico, In Vitro, and In Vivo Analysis of Tanshinone IIA and Cryptotanshinone from Salvia miltiorrhiza as Modulators of Cyclooxygenase-2/mPGES-1/Endothelial Prostaglandin EP3 Pathway

Tanshinone IIA (TIIA) and cryptotanshinone (CRY) from Salvia miltiorrhiza Bunge were investigated for their inhibitory activity against the cyclooxygenase-2 (COX-2)/microsomal prostaglandin E synthase-1 (mPGES-1)/endothelial prostaglandin 3 (EP3) pathway using in silico, in vitro, in vivo, and ex vivo assays. From the analysis of the docking poses, both diterpenoids were able to interact significantly with COX-2, 5-lipoxygenase (5-LO), platelet-activating factor receptor (PAFR), and mPGES-1. This evidence was further corroborated by data obtained from a cell-free assay, where CRY displayed a significant inhibitory potency against mPGES-1 (IC50 = 1.9 ± 0.4 µM) and 5-LO (IC50 = 7.1 µM), while TIIA showed no relevant inhibition of these targets. This was consistent with their activity to increase mice bleeding time (CRY: 2.44 ± 0.13 min, p ≤ 0.001; TIIA: 2.07 ± 0.17 min p ≤ 0.01) and with the capability to modulate mouse clot retraction (CRY: 0.048 ± 0.011 g, p ≤ 0.01; TIIA: 0.068 ± 0.009 g, p ≤ 0.05). For the first time, our results show that TIIA and, in particular, CRY are able to interact significantly with the key proteins involved not only in the onset of inflammation but also in platelet activity (and hyper-reactivity). Future preclinical and clinical investigations, together with this evidence, could provide the scientific basis to consider these compounds as an alternative therapeutic approach for thrombotic- and thromboembolic-based diseases.

Analysis of Sex-Specific Prostanoid Production Using a Mouse Model of Selective Cyclooxygenase-2 Inhibition

Background:

Prostanoids are a family of lipid mediators formed from arachidonic acid by cyclooxygenase enzymes and serve as biomarkers of vascular function. Prostanoid production may be different in males and females indicating that different therapeutic approaches may be required during disease.

Objectives:

We examined sex-dependent differences in COX-related metabolites in genetically modified mice that produce a cyclooxygenase-2 (COX2) enzyme containing a tyrosine 385 to phenylalanine (Y385F) mutation. This mutation renders the COX2 enzyme unable to form a key intermediate radical required for complete arachidonic acid metabolism and provides a model of selective COX2 inhibition.

Design and Methods:

Mice heterozygous for the Y385F mutation in COX2 were mated to produce cohorts of wild-type, heterozygous, and COX2 mutant mice. We investigated whether the genotype distribution followed Mendelian genetics and studied whether sex-specific differences could be found in certain prostanoid levels measured in peritoneal macrophages and in urinary samples.

Results:

The inheritance of the COX2 mutation displayed a significant deviation with respect to Mendel’s laws of genetics, with a lower-than-expected progeny of weaned COX2 mutant pups. In macrophages, prostaglandin E2 (PGE2) production following lipopolysaccharide (LPS) and interferon gamma (IFNγ) stimulation was COX2-dependent in both males and females, and data indicated that crosstalk between the nitric oxide (NO) and COX2 pathways may be sex specific. We observed significant differences in urinary PGE2 production by male and female COX2 mutant mice, with the loss of COX2 activity in male mice decreasing their ability to produce urinary PGE2. Finally, female mice across all 3 genotypes produced similar levels of urinary thromboxane (measured as 11-dehydro TxB2) at significantly higher levels than males, indicating a sex-related difference that is likely COX1-derived.

Conclusions:

Our findings clearly demonstrate that sex-related differences in COX-derived metabolites can be observed, and that other pathways (such as the NO pathway) are affected.

Microsomal Prostaglandin E Synthase-1 (mPGES-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 obesity development and in the metabolic and cardiovascular alterations associated.

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 studied by glucose and insulin tolerance tests and colorimetric assays. Vascular function, structure and mechanics were evaluated 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 and its correlation with vascular damage was determined.

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 to mPGES-1^+/+ mice. mPGES-1 knockdown prevented cardiomyocyte hypertrophy, cardiac fibrosis, endothelial dysfunction, aortic insulin resistance, and vascular inflammation and remodeling, 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 remodeling, 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 for the management of obesity and the associated cardiovascular and metabolic alterations.

Microsomal prostaglandin E2 synthase-1 and its inhibitors: Molecular mechanisms and therapeutic significance

Inflammation is closely linked to the abnormal phospholipid metabolism chain of cyclooxygenase-2/microsomal prostaglandin E₂ synthase-1/prostaglandin E₂ (COX-2/mPGES-1/PGE₂). In clinical practice, non-steroidal anti-inflammatory drugs (NSAIDs) as upstream COX-2 enzyme activity inhibitors are widely used to block COX-2 cascade to relieve inflammatory response. However, NSAIDs could also cause cardiovascular and gastrointestinal side effects due to its inhibition on other prostaglandins generation. To avoid this, targeting downstream mPGES-1 instead of upstream COX is preferable to selectively block overexpressed PGE₂ in inflammatory diseases. Some mPGES-1 inhibitor candidates including synthetic compounds, natural products and existing anti-inflammatory drugs have been proved to be effective in in vitro experiments. After 20 years of in-depth research on mPGES-1 and its inhibitors, ISC 27864 have completed phase II clinical trial. In this review, we intend to summarize mPGES-1 inhibitors focused on their inhibitory specificity with perspectives for future drug development.

Effects of microsomal prostaglandin E synthase-1 (mPGES-1) inhibition on resistance artery tone in patients with end stage kidney disease

BACKGROUND

Inhibition of the microsomal prostaglandin (PG) E₂ synthase (mPGES-1) introduces a promising anti-inflammatory treatment approach by specifically reducing PGE₂ . The microvasculature is a central target organ for early manifestations of cardiovascular disease. Therefore, a better understanding of the prostaglandin system and characterising the effects of mPGES-1 inhibition in this vascular bed are of interest.

EXPERIMENTAL APPROACH

The effects of mPGES-1 inhibition on constriction and relaxation of resistance arteries (Ø100-400μm) from patients with end stage kidney disease (ESKD) and controls (Non-ESKD) were studied using wire-myography in combination with immunological and mass-spectrometry based analyses.

KEY RESULTS

Inhibition of mPGES-1 in arteries from ESKD patients and Non-ESKD controls significantly reduced adrenergic vasoconstriction, which was not affected by the COX-2 inhibitors NS-398 and Etoricoxib or the COX-1/COX-2 inhibitor Indomethacin, tested in Non-ESKD controls. Correspondingly, a significant increase of acetylcholine-induced dilatation was observed for mPGES-1 inhibition only. In IL-1β treated arteries, inhibition of mPGES-1 significantly reduced PGE₂ levels while PGI₂ levels remained unchanged. In contrast, COX-2 inhibition blocked the formation of both prostaglandins. Blockage of PGI₂ signaling with an IP receptor antagonist did not restore the reduced constriction, neither did blocking of PGE₂ -EP4 or signaling through PPARγ. A biphasic effect was observed for PGE₂ , inducing dilatation at nmol and constriction at μmol concentrations. Immunohistochemistry demonstrated expression of mPGES-1, COX-1, PGIS, weak expression for COX-2 as well as receptor expression for PGE₂ (EP1-4), thromboxane (TP) and PGI₂ (IP) in ESKD and Non-ESKD.

CONCLUSION

Our study demonstrates vasodilating effects following mPGES-1 inhibition in human microvasculature and suggests that several pathways besides shunting to PGI₂ may be involved.

New horizons in the roles and associations of COX-2 and novel natural inhibitors in cardiovascular diseases

Age-related cardiovascular disease is the leading cause of death in elderly populations. Coxibs, including celecoxib, valdecoxib, etoricoxib, parecoxib, lumiracoxib, and rofecoxib, are selective cyclooxygenase-2 (COX-2) inhibitors used to treat osteoarthritis and rheumatoid arthritis. However, many coxibs have been discontinued due to adverse cardiovascular events. COX-2 contains cyclooxygenase (COX) and peroxidase (POX) sites. COX-2 inhibitors block COX activity without affecting POX activity. Recently, quercetin-like flavonoid compounds with OH groups in their B-rings have been found to serve as activators of COX-2 by binding the POX site. Galangin-like flavonol compounds serve as inhibitors of COX-2. Interestingly, nabumetone, flurbiprofen axetil, piketoprofen-amide, and nepafenac are ester prodrugs that inhibit COX-2. The combination of galangin-like flavonol compounds with these prodrug metabolites may lead to the development of novel COX-2 inhibitors. This review focuses on the most compelling evidence regarding the role and mechanism of COX-2 in cardiovascular diseases and demonstrates that quercetin-like compounds exert potential cardioprotective effects by serving as cofactors of COX-2.

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

Activated macrophages overexpress the folate receptor β (FR-β) 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.

Kidney damage from nonsteroidal anti-inflammatory drugs-Myth or truth? Review of selected literature

Nonsteroidal anti-inflammatory drugs (NSAIDs) are widely available drugs with anti-inflammatory and analgesic properties. Their mechanism of action is associated with the enzymes of the arachidonic acid cycle (cyclooxygenases: COX-1 and COX-2). The cyclooxygenase pathway results in the formation of prostanoids (prostaglandins [PGs], prostacyclins, and thromboxanes). It affects various structures of the human body, including the kidneys. Medical literature associates the usage of NSAIDs with acute kidney injury (AKI), tubulointerstitial nephritis (TIN), as well as nephrotic syndrome and chronic kidney disease (CKD). AKI associated with the chronic consumption of NSAIDs is mainly attributed to pharmacological polytherapy and the presence of cardiovascular or hepatic comorbidities. The pathomechanism of AKI and CKD is associated with inhibition of the biosynthesis of prostanoids involved in the maintenance of renal blood flow, especially PGE2 and PGI2. It is suggested that both COX isoforms play opposing roles in renal function, with natriuresis increased by COX-1 inhibition followed by a drop in a blood pressure, whereas COX-2 inhibition increases blood pressure and promotes sodium retention. TIN after NSAID use is potentially associated with glomerular basement membrane damage, reduction in pore size, and podocyte density. Therefore, nephrotic proteinuria and impairment of renal function may occur. The following article analyzes the association of NSAIDs with kidney disease based on available medical literature.

Low-dose Aspirin prevents hypertension and cardiac fibrosis when thromboxane A2 is unrestrained

Enhanced platelet activation has been reported in patients with essential hypertension and heart failure. The possible contribution of platelet-derived thromboxane (TX)A2 in their pathophysiology remains unclear. We investigated the systemic TXA2 biosynthesis in vivo and gene expression of its receptor TP in 22 essential hypertension patients and a mouse model of salt-sensitive hypertension. The contribution of platelet TXA2 biosynthesis on enhanced blood pressure (BP) and overload-induced cardiac fibrosis was explored in mice by treating with low-dose Aspirin, resulting in selective inhibition of platelet cyclooxygenase (COX)-1-dependent TXA2 generation. In essential hypertensive patients, systemic biosynthesis of TXA2 [assessed by measuring its urinary metabolites (TXM) reflecting predominant platelet source] was enhanced together with higher gene expression of circulating leukocyte TP and TGF-β, vs. normotensive controls. Similarly, in hypertensive mice with prostacyclin (PGI2) receptor (IP) deletion (IPKO) fed with a high-salt diet, enhanced urinary TXM, and left ventricular TP overexpression were detected vs. normotensive wildtype (WT) mice. Increased cardiac collagen deposition and profibrotic gene expression (including TGF-β) was found. Low-dose Aspirin administration caused a selective inhibition of platelet TXA2 biosynthesis and mitigated enhanced blood pressure, cardiac fibrosis, and left ventricular profibrotic gene expression in IPKO but not WT mice. Moreover, the number of myofibroblasts and extravasated platelets in the heart was reduced. In cocultures of human platelets and myofibroblasts, platelet TXA2 induced profibrotic gene expression, including TGF-β1. In conclusion, our results support tailoring low-dose Aspirin treatment in hypertensive patients with unconstrained TXA2/TP pathway to reduce blood pressure and prevent early cardiac fibrosis.

Sex-dependent compensatory mechanisms preserve blood pressure homeostasis in prostacyclin receptor-deficient mice

Inhibitors of microsomal prostaglandin E synthase 1 (mPGES-1) are in the early phase of clinical development. Deletion of mPges-1 in mice confers analgesia, restrains atherogenesis, and fails to accelerate thrombogenesis, while suppressing prostaglandin E2 (PGE2), but increasing the biosynthesis of prostacyclin (PGI2). In low-density lipoprotein receptor-deficient (Ldlr-/-) mice, this last effect represents the dominant mechanism by which mPges-1 deletion restrains thrombogenesis, while suppression of PGE2 accounts for its antiatherogenic effect. However, the effect of mPges-1 depletion on blood pressure (BP) in this setting remains unknown. Here, we show that mPges-1 depletion significantly increased the BP response to salt loading in male Ldlr-/- mice, whereas, despite the direct vasodilator properties of PGI2, deletion of the I prostanoid receptor (Ipr) suppressed this response. Furthermore, combined deletion of the Ipr abrogated the exaggerated BP response in male mPges-1-/- mice. Interestingly, these unexpected BP phenotypes were not observed in female mice fed a high-salt diet (HSD). This is attributable to the protective effect of estrogen in Ldlr-/- mice and in Ipr-/- Ldlr-/- mice. Thus, estrogen compensates for a deficiency in PGI2 to maintain BP homeostasis in response to high salt in hyperlipidemic female mice. In male mice, by contrast, the augmented formation of atrial natriuretic peptide (ANP) plays a similar compensatory role, restraining hypertension and oxidant stress in the setting of Ipr depletion. Hence, men with hyperlipidemia on a HSD might be at risk of a hypertensive response to mPGES-1 inhibitors.

Pathophysiological role of prostaglandin E synthases in liver diseases

Prostaglandin E synthases (PGESs) convert cyclooxygenase (COX)-derived prostaglandin H2 (PGH2) into prostaglandin E2 (PGE2) and comprise at least three types of structurally and biologically distinct enzymes. Two of these, namely microsomal prostaglandin E synthase-1 (mPGES-1) and mPGES-2, are membrane-bound enzymes. mPGES-1 is an inflammation-inducible enzyme that converts PGH2 into PGE2. mPGES-2 is a bifunctional enzyme that generally forms a complex with haem in the presence of glutathione. This enzyme can metabolise PGH2 into malondialdehyde and can produce PGE2 after its separation from haem. In this review, we discuss the role of PGESs, particularly mPGES-1 and mPGES-2, in the pathogenesis of liver diseases. A better understanding of the roles of PGESs in liver disease may aid in the development of treatments for patients with liver diseases.

A new trick for an old dog? Myocardial-specific roles for prostaglandins as mediators of ischemic injury and repair

The small lipid-derived paracrine signaling molecules known as prostaglandins have been recognized for their ability to modulate many facets of cardiovascular physiology since their initial discovery more than 85 years ago. Although the role of prostaglandins in the vasculature has gained significant attention across time, a handful of historical studies have also directly implicated the cardiomyocyte in both prostaglandin synthesis and release. Recently, our understanding of how prostaglandin receptor modulation impacts and contributes to myocardial structure and function has gained attention while leaving most other components of myocardial prostaglandin metabolism and signaling unexplored. This mini-review highlights both the key historical studies that underpin modern prostaglandin research in the heart, while concurrently presenting the latest findings related to how prostaglandin metabolism and signaling impact myocardial injury and repair.

Interplay Between Oxidative Stress, Cyclooxygenases, and Prostanoids in Cardiovascular Diseases

Significance: Endothelial cells lining the lumen of blood vessels play an important role in the regulation of cardiovascular functions through releasing both vasoconstricting and vasodilating factors. The production and function of vasoconstricting factors are largely elevated in hypertension, diabetes, atherosclerosis, and ischemia/reperfusion injuries. Cyclooxygenases (COXs) are the major enzymes producing five different prostanoids that act as either contracting or relaxing substances. Under conditions of increased oxidative stress, the expressions and activities of COX isoforms are altered, resulting in changes in production of various prostanoids and thus affecting vascular tone. This review briefly summarizes the relationship between oxidative stress, COXs, and prostanoids, thereby providing new insights into the pathophysiological mechanisms of cardiovascular diseases (CVDs). Recent Advances: Many new drugs targeting oxidative stress, COX-2, and prostanoids against common CVDs have been evaluated in recent years and they are summarized in this review. Critical Issues: Comprehensive understanding of the complex interplay between oxidative stress, COXs, and prostanoids in CVDs helps develop more effective measures against cardiovascular pathogenesis. Future Directions: Apart from minimizing the undesired effects of harmful prostanoids, future studies shall investigate the restoration of vasoprotective prostanoids as a means to combat CVDs. Antioxid. Redox Signal. 34, 784-799.

The Use of Aspirin in Contemporary Primary Prevention of Atherosclerotic Cardiovascular Diseases Revisited: The Increasing Need and Call for a Personalized Therapeutic Approach

The use of aspirin has been widely accepted for the secondary prevention of atherosclerotic cardiovascular disease (ASCVD) in all patient populations, as the benefits linked to the reduction of clinical events outweigh the risk of major bleeding. However, despite the undisputable, though modest, potential of aspirin to reduce atherothrombotic events, its overall efficacy and safety in primary ASCVD prevention remains debatable, despite being used for this purpose for decades. The net clinical benefit of aspirin was brought into question by three recent large contemporary randomized controlled trials evaluating its role in various primary prevention populations (individuals with diabetes [ASCEND], an elderly population [ASPREE], and middle-aged adults at high estimated cardiovascular risk [ARRIVE]) and numerous large meta-analyses published during the past year. As a result, the usual generalized recommendations for the use of aspirin in patients with estimated intermediate to high ASCVD risk but without overt ASCVD have already been removed from most international guidelines. Since the primary prevention framework encompasses heterogenous groups of subjects with variable absolute ASCVD risk, a more individualized approach based on the best possible estimated ratio between the potential health benefits from fewer atherothrombotic events and harms because of potential increases in major bleeding is warranted in clinical practice. With this compromise, clinicians can better decide on the personalized use of aspirin in patients at high risk of major adverse cardiovascular events.

Clinical data mining reveals analgesic effects of lapatinib in cancer patients

Microsomal prostaglandin E2 synthase 1 (mPGES-1) is recognized as a promising target for a next generation of anti-inflammatory drugs that are not expected to have the side effects of currently available anti-inflammatory drugs. Lapatinib, an FDA-approved drug for cancer treatment, has recently been identified as an mPGES-1 inhibitor. But the efficacy of lapatinib as an analgesic remains to be evaluated. In the present clinical data mining (CDM) study, we have collected and analyzed all lapatinib-related clinical data retrieved from clinicaltrials.gov. Our CDM utilized a meta-analysis protocol, but the clinical data analyzed were not limited to the primary and secondary outcomes of clinical trials, unlike conventional meta-analyses. All the pain-related data were used to determine the numbers and odd ratios (ORs) of various forms of pain in cancer patients with lapatinib treatment. The ORs, 95% confidence intervals, and P values for the differences in pain were calculated and the heterogeneous data across the trials were evaluated. For all forms of pain analyzed, the patients received lapatinib treatment have a reduced occurrence (OR 0.79; CI 0.70–0.89; P = 0.0002 for the overall effect). According to our CDM results, available clinical data for 12,765 patients enrolled in 20 randomized clinical trials indicate that lapatinib therapy is associated with a significant reduction in various forms of pain, including musculoskeletal pain, bone pain, headache, arthralgia, and pain in extremity, in cancer patients. Our CDM results have demonstrated the significant analgesic effects of lapatinib, suggesting that lapatinib may be repurposed as a novel type of analgesic.

Inhibition of mPGES-1 attenuates efficient resolution of acute inflammation by enhancing CX3CL1 expression

Despite the progress to understand inflammatory reactions, mechanisms causing their resolution remain poorly understood. Prostanoids, especially prostaglandin E2 (PGE2), are well-characterized mediators of inflammation. PGE2 is produced in an inducible manner in macrophages (Mϕ) by microsomal PGE2-synthase-1 (mPGES-1), with the notion that it also conveys pro-resolving properties. We aimed to characterize the role of mPGES-1 during resolution of acute, zymosan-induced peritonitis. Experimentally, we applied the mPGES-1 inhibitor compound III (CIII) once the inflammatory response was established and confirmed its potent PGE2-blocking efficacy. mPGES-1 inhibition resulted in an incomplete removal of neutrophils and a concomitant increase in monocytes and Mϕ during the resolution process. The mRNA-seq analysis identified enhanced C-X3-C motif receptor 1 (CX3CR1) expression in resident and infiltrating Mϕ upon mPGES-1 inhibition. Besides elevated Cx3cr1 expression, its ligand CX3CL1 was enriched in the peritoneal lavage of the mice, produced by epithelial cells upon mPGES-1 inhibition. CX3CL1 not only increased adhesion and survival of Mϕ but its neutralization also completely reversed elevated inflammatory cell numbers, thereby normalizing the cellular, peritoneal composition during resolution. Our data suggest that mPGES-1-derived PGE2 contributes to the resolution of inflammation by preventing CX3CL1-mediated retention of activated myeloid cells at sites of injury.

Urinary 8-iso PGF2α and 2,3-dinor-8-iso PGF2α can be indexes of colitis-associated colorectal cancer in mice

Early diagnosis of colorectal cancer is needed to reduce the mortal consequence by cancer. Lipid mediators play critical role in progression of colitis and colitis-associated colon cancer (CAC) and some of their metabolites are excreted in urine. Here, we attempted to find novel biomarkers in urinary lipid metabolite of a murine model of CAC. Mice were received single administration of azoxymethane (AOM) and repeated administration of dextran sulfate sodium (DSS). Lipid metabolites in their urine was measured by liquid chromatography mass spectrometry and their colon was collected to perform morphological study. AOM and DSS caused inflammation and tumor formation in mouse colon. Liquid chromatography mass spectrometry-based comprehensive analysis of lipid metabolites showed that cyclooxygenase-mediated arachidonic acid (AA) metabolites, prostaglandins, and reactive oxygen species (ROS)-mediated AA metabolites, isoprostanes, were predominantly increased in the urine of tumor-bearing mice. Among that, urinary prostaglandin (PG)E2 metabolite tetranor-PGEM and PGD2 metabolite tetranor-PGDM were significantly increased in both of urine collected at the acute phase of colitis and the carcinogenesis phase. On the other hand, two F2 isoprostanes (F2-IsoPs), 8-iso PGF2α and 2,3-dinor-8-iso PGF2α, were significantly increased only in the carcinogenesis phase. Morphological study showed that infiltrated monocytes into tumor mass strongly expressed ROS generator NADPH (p22phox). These observations suggest that urinary 8-iso PGF2α and 2,3-dinor-8-iso PGF2α can be indexes of CAC.

Targeting microsomal prostaglandin E synthase 1 to develop drugs treating the inflammatory diseases

Microsomal prostaglandin E synthase 1 (mPGES-1) is the terminal synthase of prostaglandin E2 (PGE2) which plays a crucial role in inflammatory diseases. Thus, mPGES-1 inhibitors are promising agents for their better specificity in blocking the production of PGE2, a potent inflammatory mediator, compared with non-steroidal anti-inflammatory drugs (NSAIDs). Currently, two mPGES-1 inhibitors are undergoing clinical trials and more novel inhibitors are being developed. In this review, we focus on the advances in the development of mPGES-1 inhibitors and the potential of these inhibitors to treat different inflammatory diseases, and discuss the existing challenges. The insights from this review will increase the understanding on the current status of mPGES-1-targeted anti-inflammatory drug development and the potential of these drugs in treating inflammation in diseases.

Structure-based, multi-targeted drug discovery approach to eicosanoid inhibition: Dual inhibitors of mPGES-1 and 5-lipoxygenase activating protein (FLAP)

BACKGROUND

Due to the importance of both prostaglandins (PGs) and leukotrienes (LTs) as pro-inflammatory mediators, and the potential for eicosanoid shunting in the presence of pathway target inhibitors, we have investigated an approach to inhibiting the formation of both PGs and LTs as part of a multi-targeted drug discovery effort.

METHODS

We generated ligand-protein X-ray crystal structures of known inhibitors of microsomal prostaglandin E2 synthase-1 (mPGES-1) and the 5-Lipoxygenase Activating Protein (FLAP), with their respective proteins, to understand the overlapping pharmacophores. We subsequently used molecular modeling and structure-based drug design (SBDD) to identify hybrid structures intended to inhibit both targets.

RESULTS

This work enabled the preparation of compounds 4 and 5, which showed potent in vitro inhibition of both targets.

SIGNIFICANCE

Our findings enhance the structural understanding of mPGES-1 and FLAP's unique ligand binding pockets and should accelerate the discovery of additional dual inhibitors for these two important integral membrane protein drug targets.

MicroRNA-214 targets COX-2 to antagonize indoxyl sulfate (IS)-induced endothelial cell apoptosis

Cardiovascular disease (CVD) serves as the major cause of mortality in chronic kidney disease (CKD) patients. The injury of endothelium associated with the long-term challenge of uremic toxins including the toxic indoxyl sulfate (IS) is one of key pathological factors leading to CVD. However, the mechanisms of uremic toxins, especially the IS, resulting in endothelial injury, remain unclear. miR-214 was reported to contribute to the pathogenesis of cardiovascular diseases, while its role in IS-induced endothelial cell apoptosis is unknown. In this study, we investigated the role of microRNA-214 (miR-214) in IS-induced endothelial cell apoptosis and the underlying mechanisms using mouse aortic endothelial cells (MAECs). Following IS treatment, miR-214 was significantly downregulated in MAECs in line with enhanced cell apoptosis. Meanwhile, COX-2 was upregulated at both mRNA and protein levels along with increased secretion of PGE₂ in medium. To define the role of miR-214 in IS-induced endothelial cell apoptosis, we modulated miR-214 level in MAECs and found that overexpression of miR-214 markedly attenuated endothelial cell apoptosis, while antagonism of miR-214 deteriorated cell death after IS challenge. Further analyses confirmed that COX-2 is a target gene of miR-214, and the inhibition of COX-2 by a specific COX-2 inhibitor NS-398 strikingly attenuated IS-induced endothelial cell apoptosis along with a significant blockade of PGE₂ secretion. In conclusion, this study demonstrated an important role of miR-214 in protecting against endothelial cell damage induced by IS possibly by direct downregulation of COX-2/PGE₂ axis.

Mechanistic definition of the cardiovascular mPGES-1/COX-2/ADMA axis

AIMS

Cardiovascular side effects caused by non-steroidal anti-inflammatory drugs (NSAIDs), which all inhibit cyclooxygenase (COX)-2, have prevented development of new drugs that target prostaglandins to treat inflammation and cancer. Microsomal prostaglandin E synthase-1 (mPGES-1) inhibitors have efficacy in the NSAID arena but their cardiovascular safety is not known. Our previous work identified asymmetric dimethylarginine (ADMA), an inhibitor of endothelial nitric oxide synthase, as a potential biomarker of cardiovascular toxicity associated with blockade of COX-2. Here, we have used pharmacological tools and genetically modified mice to delineate mPGES-1 and COX-2 in the regulation of ADMA.

METHODS AND RESULTS

Inhibition of COX-2 but not mPGES-1 deletion resulted in increased plasma ADMA levels. mPGES-1 deletion but not COX-2 inhibition resulted in increased plasma prostacyclin levels. These differences were explained by distinct compartmentalization of COX-2 and mPGES-1 in the kidney. Data from prostanoid synthase/receptor knockout mice showed that the COX-2/ADMA axis is controlled by prostacyclin receptors (IP and PPARβ/δ) and the inhibitory PGE2 receptor EP4, but not other PGE2 receptors.

CONCLUSION

These data demonstrate that inhibition of mPGES-1 spares the renal COX-2/ADMA pathway and define mechanistically how COX-2 regulates ADMA.

miR-214 Protects Against Uric Acid-Induced Endothelial Cell Apoptosis

Background: Uric acid (UA) has been reported to be an important risk factor for cardiovascular diseases and can cause endothelial cell apoptosis through unclear mechanisms. Accumulating evidence has demonstrated that miR-214 plays a pivotal role in the pathogenesis of cardiovascular diseases. This study was to investigate the role of miR-214 in UA-induced endothelial cell apoptosis and the underlying mechanism.

Material and methods: We enrolled 30 patients with hyperuricemia and 32 healthy controls and analyzed the levels of miR-214 in the serum of the participants. Then mouse aorta endothelial cells (MAECs) were treated with UA to induce cell apoptosis. An miR-214 mimic and a specific COX-2 inhibitor (NS398) were used to confirm the roles of these molecules in mediating UA-induced MAEC apoptosis or COX-2/PGE₂ cascade activation.

Results: A significant reduction in circulating miR-214 in the hyperuricemia patients compared with the healthy controls, along with a negative correlation with UA levels was observed. In the MAECs, UA treatment strikingly increased apoptosis as shown by the upregulation of BAX and cleaved Caspase-3 and the increased number of apoptotic cells. Interestingly, the expression of COX-2 was also upregulated at both the protein and mRNA levels during UA-induced cell apoptosis. In addition, an miR-214 mimic blocked UA-induced MAEC apoptosis, COX-2 induction and PGE₂ secretion. The inhibition of COX-2 markedly ameliorated UA-induced apoptotic response and PGE₂ production in MAECs. Luciferase activity assays further confirmed that COX-2 is a target gene of miR-214 in endothelial cells.

Conclusion: We concluded that miR-214 could alleviate UA-induced MAEC apoptosis possibly by inhibiting the COX-2/PGE₂ cascade.

Microsomal Prostaglandin E2 Synthase-1 Deletion Attenuates Isoproterenol-Induced Myocardial Fibrosis in Mice

Deletion of microsomal prostaglandin E₂ synthase-1 (mPGES-1) inhibits inflammation and protects against atherosclerotic vascular diseases but displayed variable influence on pathologic cardiac remodeling. Overactivation of β-adrenergic receptors (β-ARs) causes heart dysfunction and cardiac remodeling, whereas the role of mPGES-1 in β-AR-induced cardiac remodeling is unknown. Here we addressed this question using mPGES-1 knockout mice, subjecting them to isoproterenol, a synthetic nonselective agonist for β-ARs, at 5 or 15 mg/kg per day to induce different degrees of cardiac remodeling in vivo. Cardiac structure and function were assessed by echocardiography 24 hours after the last of seven consecutive daily injections of isoproterenol, and cardiac fibrosis was examined by Masson trichrome stain in morphology and by real-time polymerase chain reaction for the expression of fibrosis-related genes. The results showed that deletion of mPGES-1 had no significant effect on isoproterenol-induced cardiac dysfunction or hypertrophy. However, the cardiac fibrosis was dramatically attenuated in the mPGES-1 knockout mice after either low-dose or high-dose isoproterenol exposure. Furthermore, in vitro study revealed that overexpression of mPGES-1 in cultured cardiac fibroblasts increased isoproterenol-induced fibrosis, whereas knocking down mPGES-1 in cardiac myocytes decreased the fibrogenesis of fibroblasts. In conclusion, mPGES-1 deletion protects against isoproterenol-induced cardiac fibrosis in mice, and targeting mPGES-1 may represent a novel strategy to attenuate pathologic cardiac fibrosis, induced by β-AR agonists. SIGNIFICANCE STATEMENT: Inhibitors of microsomal prostaglandin E₂ synthase-1 (mPGES-1) are being developed as alternative analgesics that are less likely to elicit cardiovascular hazards than cyclooxygenase-2 selective nonsteroidal anti-inflammatory drugs. We have demonstrated that deletion of mPGES-1 protects inflammatory vascular diseases and promotes post-myocardial infarction survival. The role of mPGES-1 in β-adrenergic receptor-induced cardiomyopathy is unknown. Here we illustrated that deletion of mPGES-1 alleviated isoproterenol-induced cardiac fibrosis without deteriorating cardiac dysfunction. These results illustrated that targeting mPGES-1 may represent an efficacious approach to the treatment of inflammatory cardiovascular diseases.

Interplay between platelets and coagulation

Haemostasis stops bleeding at the site of vascular injury and maintains the integrity of blood vessels through clot formation. This regulated physiological process consists of complex interactions between endothelial cells, platelets, von Willebrand factor and coagulation factors. Haemostasis is initiated by a damaged vessel wall, followed with a rapid adhesion, activation and aggregation of platelets to the exposed subendothelial extracellular matrix. At the same time, coagulation factors aggregate on the procoagulant surface of activated platelets to consolidate the platelet plug by forming a mesh of cross-linked fibrin. Platelets and coagulation mutually influence each other and there are strong indications that, thanks to the interplay between platelets and coagulation, haemostasis is far more effective than the two processes separately. Clinically this is relevant because impaired interaction between platelets and coagulation may result in bleeding complications, while excessive platelet-coagulation interaction induces a high thrombotic risk. In this review, platelets, coagulation factors and the complex interaction between them will be discussed in detail.

DREAM-in-CDM Approach and Identification of a New Generation of Anti-inflammatory Drugs Targeting mPGES-1

Microsomal prostaglandin E2 synthase-1 (mPGES-1) is known as an ideal target for next generation of anti-inflammatory drugs without the side effects of currently available anti-inflammatory drugs. However, there has been no clinically promising mPGES-1 inhibitor identified through traditional drug discovery and development route. Here we report a new approach, called DREAM-in-CDM (Drug Repurposing Effort Applying Integrated Modeling-in vitro/vivo-Clinical Data Mining), to identify an FDA-approved drug suitable for use as an effective analgesic targeting mPGES-1. The DREAM-in-CDM approach consists of three steps: computational screening of FDA-approved drugs; in vitro and/or in vivo assays; and clinical data mining. By using the DREAM-in-CDM approach, lapatinib has been identified as a promising mPGES-1 inhibitor which may have significant anti-inflammatory effects to relieve various forms of pain and possibly treat various inflammation conditions involved in other inflammation-related diseases such as the lung inflammation caused by the newly identified COVID-19. We anticipate that the DREAM-in-CDM approach will be used to repurpose FDA-approved drugs for various new therapeutic indications associated with new targets.

Bmal1 Deletion in Myeloid Cells Attenuates Atherosclerotic Lesion Development and Restrains Abdominal Aortic Aneurysm Formation in Hyperlipidemic Mice

OBJECTIVE

Although the molecular components of circadian rhythms oscillate in discrete cellular components of the vasculature and many aspects of vascular function display diurnal variation, the cellular connections between the molecular clock and inflammatory cardiovascular diseases remain to be elucidated. Previously we have shown that pre- versus postnatal deletion of Bmal1 (brain and muscle aryl hydrocarbon receptor nuclear translocator-like 1), the nonredundant core clock gene has contrasting effects on atherogenesis. Here we investigated the effect of myeloid cell Bmal1 deletion on atherogenesis and abdominal aortic aneurysm formation in mice. Approach and Results: Mice lacking Bmal1 in myeloid cells were generated by crossing Bmal1 flox/flox mice with lysozyme 2 promoter-driven Cre recombinase mice on a hyperlipidemic low-density lipoprotein receptor-deficient background and were fed on a high-fat diet to induce atherosclerosis. Atherogenesis was restrained, concomitant with a reduction of aortic proinflammatory gene expression in myeloid cell Bmal1 knockout mice. Body weight, blood pressure, blood glucose, triglycerides, and cholesterol were unaltered. Similarly, myeloid cell depletion of Bmal1 also restrained Ang II (angiotensin II) induced formation of abdominal aortic aneurysm in hyperlipidemic mice. In vitro, RNA-Seq analysis demonstrated a proinflammatory response in cultured macrophages in which there was overexpression of Bmal1.

CONCLUSIONS

Myeloid cell Bmal1 deletion retards atherogenesis and restrains the formation of abdominal aortic aneurysm and may represent a potential therapeutic target for inflammatory cardiovascular diseases.

Development and evaluation of a simultaneous and efficient quantification strategy for final prostanoid metabolites in urine

Prostanoids (PNs) play critical roles in various physiological and pathological processes. Therefore, it is important to understand the alternation of PN expression profiles. However, a simultaneous and efficient quantification system for final PN metabolites in urine has not yet been established. Here, we developed and evaluated a novel method to quantify all final PN metabolites. By purification using a reverse phase solid phase extraction (SPE) column, the matrix effects against the final PGD₂, PGE₂, and PGF_2α metabolites were low, and their accuracies were nearly 100%. The matrix effects against the final PGI₂ and TXA₂ metabolites were high using reverse phase SPE column purification alone. By applying a tandem SPE method that combined reverse phase and ion exchange SPE columns, the matrix effects decreased so that the accuracy was nearly 100%. To validate the reliability of the method, each final metabolite was quantified from mouse urine to which the PNs (PGD₂, PGE₂, and PGI₂) were intravenously administered. As a result, the amounts of PN metabolites were correlated with those of the PNs administered to the blood in a dose-dependent manner. To validate the method using human samples, the urinary metabolites of Crohn's disease (CD, a PN-related disease) patients and healthy individuals were quantified. All five metabolites were successfully quantified. Only final PGE₂ metabolite levels were significantly higher in CD patients than those in healthy individuals, so that the urinary metabolite profiles of CD patients is determined. In conclusion, we developed a novel method to quantify all final PN metabolites simultaneously and efficiently and demonstrated the practicality of the method using human CD patient samples.

Cardiovascular Biology of Prostanoids and Drug Discovery

Prostanoids are a group of bioactive lipids that are synthesized de novo from membrane phospholipid-released arachidonic acid and have diverse functions in normal physiology and disease. NSAIDs (non-steroidal anti-inflammatory drugs), which are among the most commonly used medications, ameliorate pain, fever, and inflammation by inhibiting COX (cyclooxygenase), which is the rate-limiting enzyme in the biosynthetic cascade of prostanoids. The use of NSAIDs selective for COX-2 inhibition increases the risk of a thrombotic event (eg, myocardial infarction and stroke). All NSAIDs are associated with an increased risk of heart failure. Substantial variation in clinical responses to aspirin exists and is associated with cardiovascular risk. Limited clinical studies suggest the involvement of prostanoids in vascular restenosis in patients who received angioplasty intervention. mPGES (microsomal PG [prostaglandin] E synthase)-1, an alternative target downstream of COX, has the potential to be therapeutically targeted for inflammatory disease, with diminished thrombotic risk relative to selective COX-2 inhibitors. mPGES-1-derived PGE₂ critically regulates microcirculation via its receptor EP (receptor for prostanoid E) 4. This review summarizes the actions and associated mechanisms for modulating the biosynthesis of prostanoids in thrombosis, vascular remodeling, and ischemic heart disease as well as their therapeutic relevance.

Pharmacological Characterization of the Microsomal Prostaglandin E2 Synthase-1 Inhibitor AF3485 In Vitro and In Vivo

Rationale

The development of inhibitors of microsomal prostaglandin (PG)E₂ synthase-1 (mPGES-1) was driven by the promise of attaining antiinflammatory agents with a safe cardiovascular profile because of the possible diversion of the accumulated substrate, PGH₂, towards prostacyclin (PGI₂).

Objectives

We studied the effect of the human mPGES-1 inhibitor, AF3485 (a benzamide derivative) on prostanoid biosynthesis in human whole blood in vitro. To characterize possible off-target effects of the compound, we evaluated: i)the impact of its administration on the systemic biosynthesis of prostanoids in a model of complete Freund's adjuvant (CFA)-induced monoarthritis in rats; ii) the effects on cyclooxygenase (COX)-2 expression and the biosynthesis of prostanoids in human monocytes and human umbilical vein endothelial cells (HUVECs) in vitro.

Methods

Prostanoids were assessed in different cellular models by immunoassays. The effect of the administration of AF3485 (30 and 100 mg/kg,i.p.) or celecoxib (20mg/kg, i.p.), for 3 days, on the urinary levels of enzymatic metabolites of prostanoids, PGE-M, PGI-M, and TX-M were assessed by LC-MS.

Results

In LPS-stimulated whole blood, AF3485 inhibited PGE₂ biosynthesis, in a concentration-dependent fashion. At 100μM, PGE₂ levels were reduced by 66.06 ± 3.30%, associated with a lower extent of TXB₂ inhibition (40.56 ± 5.77%). AF3485 administration to CFA-treated rats significantly reduced PGE-M (P < 0.01) and TX-M (P < 0.05) similar to the selective COX-2 inhibitor, celecoxib. In contrast, AF3485 induced a significant (P < 0.05) increase of urinary PGI-M while it was reduced by celecoxib. In LPS-stimulated human monocytes, AF3485 inhibited PGE₂ biosynthesis with an IC₅₀ value of 3.03 µM (95% CI:0.5–8.75). At 1μM, AF3485 enhanced TXB₂ while at higher concentrations, the drug caused a concentration-dependent inhibition of TXB₂. At 100 μM, maximal inhibition of the two prostanoids was associated with the downregulation of COX-2 protein by 86%. These effects did not involve AMPK pathway activation, IkB stabilization, or PPARγ activation. In HUVEC, AF3485 at 100 μM caused a significant (P < 0.05) induction of COX-2 protein associated with enhanced PGI₂ production. These effects were reversed by the PPARγ antagonist GW9662.

Conclusions

The inhibitor of human mPGES-1 AF3485 is a novel antiinflammatory compound which can also modulate COX-2 induction by inflammatory stimuli. The compound also induces endothelial COX-2-dependent PGI₂ production via PPARγ activation, both in vitro and in vivo, which might translate into a protective effect for the cardiovascular system.

Druggable Prostanoid Pathway

Prostanoids (prostaglandins, prostacyclin and thromboxane) belong to the oxylipin family of biologically active lipids generated from arachidonic acid (AA). Protanoids control numerous physiological and pathological processes. Cyclooxygenase (COX) is a rate-limiting enzyme involved in the conversion of AA into prostanoids. There are two COX isozymes: the constitutive COX-1 and the inducible COX-2. COX-1 and COX-2 have similar structures, catalytic activities, and subcellular localizations but differ in patterns of expression and biological functions. Non-selective COX-1/2 or traditional, non-steroidal anti-inflammatory drugs (tNSAIDs) target both COX isoforms and are widely used to relieve pain, fever and inflammation. However, the use of NSAIDs is associated with various side effects, particularly in the gastrointestinal tract. NSAIDs selective for COX-2 inhibition (coxibs) were purposefully designed to spare gastrointestinal toxicity, but predisposed patients to increased cardiovascular risks. These health complications from NSAIDs prompted interest in the downstream effectors of the COX enzymes as novel drug targets. This chapter describes various safety issues with tNSAIDs and coxibs, and discusses the current development of novel classes of drugs targeting the prostanoid pathway, including nitrogen oxide- and hydrogen sulfide-releasing NSAIDs, inhibitors of prostanoid synthases, dual inhibitors, and prostanoid receptor agonists and antagonists.

Biological characterization of new inhibitors of microsomal PGE synthase-1 in preclinical models of inflammation and vascular tone

BACKGROUND AND PURPOSE

Microsomal PGE synthase-1 (mPGES-1), the inducible synthase that catalyses the terminal step in PGE₂ biosynthesis, is of high interest as therapeutic target to treat inflammation. Inhibition of mPGES-1 is suggested to be safer than traditional NSAIDs, and recent data demonstrate anti-constrictive effects on vascular tone, indicating new therapeutic opportunities. However, there is a lack of potent mPGES-1 inhibitors lacking interspecies differences for conducting in vivo studies in relevant preclinical disease models.

EXPERIMENTAL APPROACH

Potency was determined based on the reduction of PGE₂ formation in recombinant enzyme assays, cellular assay, human whole blood assay, and air pouch mouse model. Anti-inflammatory properties were assessed by acute paw swelling in a paw oedema rat model. Effect on vascular tone was determined with human ex vivo wire myography.

KEY RESULTS

We report five new mPGES-1 inhibitors (named 934, 117, 118, 322, and 323) that selectively inhibit recombinant human and rat mPGES-1 with IC₅₀ values of 10-29 and 67-250 nM respectively. The compounds inhibited PGE₂ production in a cellular assay (IC₅₀ values 0.15-0.82 μM) and in a human whole blood assay (IC₅₀ values 3.3-8.7 μM). Moreover, the compounds blocked PGE₂ formation in an air pouch mouse model and reduced acute paw swelling in a paw oedema rat model. Human ex vivo wire myography analysis showed reduced adrenergic vasoconstriction after incubation with the compounds.

CONCLUSION AND IMPLICATIONS

These mPGES-1 inhibitors can be used as refined tools in further investigations of the role of mPGES-1 in inflammation and microvascular disease.

Ellagitannins from Punica granatum leaves suppress microsomal prostaglandin E synthase-1 expression and induce lung cancer cells to undergo apoptosis

Prostaglandin E₂ (PGE₂), which is a potent pro-inflammatory lipid mediator, is biosynthesized from arachidonic acid by cyclooxygenase-2 (COX-2) and microsomal PGE synthase-1 (mPGES-1). Non-steroidal anti-inflammatory drugs (NSAIDs) are used clinically as COX inhibitors, but they have gastrointestinal and cardiovascular side-effects. Thus, the terminal enzyme mPGES-1 holds promise as the next therapeutic target. In this study, we found that the ellagitannins granatin A and granatin B isolated from pomegranate leaves, and geraniin, which is their structural analog, selectively suppressed mPGES-1 expression without affecting COX-2 in non-small cell lung carcinoma A549 cells. The ellagitannins also down-regulated tumor necrosis factor α, inducible nitric oxide synthase, and anti-apoptotic factor B-cell chronic lymphocytic leukemia/lymphoma 2, and induced A549 cells to undergo apoptosis. These findings indicate that the ellagitannins have anti-inflammatory and anti-carcinogenic effects, due to their specific suppression of mPGES-1.Abbreviations: Bcl-2: B-cell chronic lymphocytic leukemia/lymphoma 2; COX: cyclooxygenase; CRE: cAMP response element; DHHDP: dehydrohexahydroxydiphenoyl; Et₂O: diethyl ether; EtOAc: ethyl acetate; GAPDH: glyceraldehyde 3-phosphate dehydrogenase; iNOS: inducible nitric oxide synthase; mPGES-1: microsomal prostaglandin E synthase-1; n-BuOH: water-saturated n-butanol; NSAIDs: non-steroidal anti-inflammatory drugs; NF-κB: nuclear factor-κB; PG: prostaglandin; TNF: tumor necrosis factor; TUNEL: terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling.

A review on mPGES-1 inhibitors: From preclinical studies to clinical applications

Prostaglandin E₂ (PGE₂) is a lipid mediator of inflammation and cancer progression. It is mainly formed via metabolism of arachidonic acid by cyclooxygenases (COX) and the terminal enzyme microsomal prostaglandin E synthase-1 (mPGES-1). Widely used non-steroidal anti-inflammatory drugs (NSAIDs) inhibit COX activity, resulting in decreased PGE₂ production and symptomatic relief. However, NSAIDs block the production of many other lipid mediators that have important physiological and resolving actions, and these drugs cause gastrointestinal bleeding and/or increase the risk for severe cardiovascular events. Selective inhibition of downstream mPGES-1 for reduction in only PGE₂ biosynthesis is suggested as a safer therapeutic strategy. This review covers the recent advances in characterization of new mPGES-1 inhibitors in preclinical models and their future clinical applications.

Cyclooxygenase-2, Asymmetric Dimethylarginine, and the Cardiovascular Hazard From Nonsteroidal Anti-Inflammatory Drugs

BACKGROUND

Large-scale, placebo-controlled trials established that nonsteroidal anti-inflammatory drugs confer a cardiovascular hazard: this has been attributed to depression of cardioprotective products of cyclooxygenase (COX)-2, especially prostacyclin. An alternative mechanism by which nonsteroidal anti-inflammatory drugs might constrain cardioprotection is by enhancing the formation of methylarginines in the kidney that would limit the action of nitric oxide throughout the vasculature.

METHODS

Targeted and untargeted metabolomics were used to investigate the effect of COX-2 deletion or inhibition in mice and in osteoarthritis patients exposed to nonsteroidal anti-inflammatory drugs on the l-arginine/nitric oxide pathway.

RESULTS

Analysis of the plasma and renal metabolome was performed in postnatal tamoxifen-inducible Cox-2 knockout mice, which exhibit normal renal function and blood pressure. This revealed no changes in arginine and methylarginines compared with their wild-type controls. Moreover, the expression of genes in the l-arginine/nitric oxide pathway was not altered in the renal medulla or cortex of tamoxifen inducible Cox-2 knockout mice. Therapeutic concentrations of the selective COX-2 inhibitors, rofecoxib, celecoxib, and parecoxib, none of which altered basal blood pressure or renal function as reflected by plasma creatinine, failed to elevate plasma arginine and methylarginines in mice. Finally, plasma arginine or methylarginines were not altered in osteoarthritis patients with confirmed exposure to nonsteroidal anti-inflammatory drugs that inhibit COX-1 and COX-2. By contrast, plasma asymmetrical dimethylarginine was increased in mice infused with angiotensin II sufficient to elevate blood pressure and impair renal function. Four weeks later, blood pressure, plasma creatinine, and asymmetrical dimethylarginine were restored to normal levels. The increase in asymmetrical dimethylarginine in response to infusion with angiotensin II in celecoxib-treated mice was also related to transient impairment of renal function.

CONCLUSIONS

Plasma methylarginines are not altered by COX-2 deletion or inhibition but rather are elevated coincident with renal compromise.

Cell-Specific Gene Deletion Reveals the Antithrombotic Function of COX1 and Explains the Vascular COX1/Prostacyclin Paradox

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Endothelial cells (ECs) and platelets, which respectively produce antithrombotic prostacyclin and prothrombotic thromboxane A₂, both express COX1 (cyclooxygenase1). Consequently, there has been no way to delineate any antithrombotic role for COX1-derived prostacyclin from the prothrombotic effects of platelet COX1. By contrast, an antithrombotic role for COX2, which is absent in platelets, is straightforward to demonstrate. This has resulted in an incomplete understanding of the relative importance of COX1 versus COX2 in prostacyclin production and antithrombotic protection in vivo.

Inhibition of mPGES-1 or COX-2 Results in Different Proteomic and Lipidomic Profiles in A549 Lung Cancer Cells

Pharmacological inhibition of microsomal prostaglandin E synthase (mPGES)-1 for selective reduction in prostaglandin E₂ (PGE₂) biosynthesis is protective in experimental models of cancer and inflammation. Targeting mPGES-1 is envisioned as a safer alternative to traditional non-steroidal anti-inflammatory drugs (NSAIDs). Herein, we compared the effects of mPGES-1 inhibitor Compound III (CIII) with the cyclooxygenase (COX)-2 inhibitor NS-398 on protein and lipid profiles in interleukin (IL)-1β-induced A549 lung cancer cells using mass spectrometry. Inhibition of mPGES-1 decreased PGE₂ production and increased PGF_2α and thromboxane B₂ (TXB₂) formation, while inhibition of COX-2 decreased the production of all three prostanoids. Our proteomics results revealed that CIII downregulated multiple canonical pathways including eIF2, eIF4/P70S6K, and mTOR signaling, compared to NS-398 that activated these pathways. Moreover, pathway analysis predicted that CIII increased cell death of cancer cells (Z = 3.8, p = 5.1E-41) while NS-398 decreased the same function (Z = -5.0, p = 6.5E-35). In our lipidomics analyses, we found alterations in nine phospholipids between the two inhibitors, with a stronger alteration in the lysophospholipid (LPC) profile with NS-398 compared to CIII. Inhibition of mPGES-1 increased the concentration of sphinganine and dihydroceramide (C_16:0DhCer), while inhibition of COX-2 caused a general decrease in most ceramides, again suggesting different effects on cell death between the two inhibitors. We showed that CIII decreased proliferation and potentiated the cytotoxic effect of the cytostatic drugs cisplatin, etoposide, and vincristine when investigated in a live cell imaging system. Our results demonstrate differences in protein and lipid profiles after inhibition of mPGES-1 or COX-2 with important implications on the therapeutic potential of mPGES-1 inhibitors as adjuvant treatment in cancer. We encourage further investigations to illuminate the clinical benefit of mPGES-1 inhibitors in cancer.

Efficacy between low and high dose aspirin for the initial treatment of Kawasaki disease: Current evidence based on a meta-analysis

Background

Kawasaki disease (KD) is now the leading cause of acquired heart disease in children in developed countries. Intravenous immunoglobulin (IVIG) and aspirin were considered as the standard initial treatment of KD for decades. However, the optimal dose of aspirin has remained controversial. In recent years, many studies compared the efficacy of low-dose with high-dose aspirin in the acute phase of KD, but the results have not always been consistent. Therefore, we performed this meta-analysis to evaluate the efficacy of low-dose aspirin compared with high-dose for the initial treatment of KD.

Methods

Studies related to aspirin therapy for KD were selected from PubMed, EMBASE, the Cochrane Central Register of Controlled Trials, China National Knowledge Infrastructure, and Google scholar through Mar 25^th, 2019. Data were analyzed using STATA Version 15.1. Additionally, publication bias and sensitivity analysis were also performed by STATA version 15.1.

Results

Six studies were included in our analysis of the rate of coronary artery lesion (CAL), five reports for IVIG-resistant KD (rKD), and four for the duration of fever and hospitalization. However, no significant differences were found between low-dose and high-dose aspirin groups in the incidence of CAL (risk ratio (RR), 0.85; 95%CI (0.63, 1.14); P = 0.28), the risk of rKD (RR, 1.39; 95%CI (1.00, 1.93); P = 0.05), and duration of fever and hospitalization (the mean standard deviation (SMD), 0.03; 95%CI (-0.16, 0.22); P = 0.78).

Conclusion

Low-dose aspirin (3–5 mg·kg^-1·d^-1) may be as effective as the use of high-dose aspirin (≥30 mg·kg^-1·d^-1) for the initial treatment of KD. Further well-designed randomized clinical trials are needed to evaluate the efficacy of low-dose aspirin for the initial treatment of KD.