Genetic Deletion Of mPGES-1 Research Articles

Microsomal prostaglandin E synthase-1 is a critical factor in dopaminergic neurodegeneration in Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disorder of uncertain pathogenesis characterized by the loss of nigrostriatal dopaminergic neurons. Although increased production of prostaglandin E2 (PGE2) has been implicated in tissue damage in several pathological settings, the role of microsomal prostaglandin E synthase-1 (mPGES-1), an inducible terminal enzyme for PGE2 synthesis, in dopaminergic neurodegeneration remains unclear. Here we show that mPGES-1 is up-regulated in the dopaminergic neurons of the substantia nigra of postmortem brain tissue from PD patients and in neurotoxin 6-hydroxydopamine (6-OHDA)-induced PD mice. The expression of mPGES-1 was also up-regulated in cultured dopaminergic neurons stimulated with 6-OHDA. The genetic deletion of mPGES-1 not only abolished 6-OHDA-induced PGE2 production but also inhibited 6-OHDA-induced dopaminergic neurodegeneration both in vitro and in vivo. Nigrostriatal projections, striatal dopamine content, and neurological functions were significantly impaired by 6-OHDA administration in wild-type (WT) mice, but not in mPGES-1 knockout (KO) mice. Furthermore, in cultured primary mesencephalic neurons, addition of PGE2 to compensate for the deficiency of 6-OHDA-induced PGE2 production in mPGES-1 KO neurons recovered 6-OHDA toxicity to almost the same extent as that seen in WT neurons. These results suggest that induction of mPGES-1 enhances 6-OHDA-induced dopaminergic neuronal death through excessive PGE2 production. Thus, mPGES-1 may be a valuable therapeutic target for treatment of PD.

Increased lethality and defective pulmonary clearance of Streptococcus pneumoniae in microsomal prostaglandin E synthase-1-knockout mice.

The production of prostaglandin E2 (PGE2) increases dramatically during pneumococcal pneumonia, and this lipid mediator impairs alveolar macrophage (AM)-mediated innate immune responses. Microsomal prostaglandin E synthase-1 (mPGES-1) is a key enzyme involved in the synthesis of PGE2, and its expression is enhanced during bacterial infections. Genetic deletion of mPGES-1 in mice results in diminished PGE2 production and elevated levels of other prostaglandins after infection. Since PGE2 plays an important immunoregulatory role during bacterial pneumonia we assessed the impact of mPGES-1 deletion in the host defense against pneumococcal pneumonia in vivo and in AMs in vitro. Wild-type (WT) and mPGES-1 knockout (KO) mice were challenged with Streptococcus pneumoniae via the intratracheal route. Compared with WT animals, we observed reduced survival and increased lung and spleen bacterial burdens in mPGES-1 KO mice 24 and 48 h after S. pneumoniae infection. While we found modest differences between WT and mPGES-1 KO mice in pulmonary cytokines, AMs from mPGES-1 KO mice exhibited defective killing of ingested bacteria in vitro that was associated with diminished inducible nitric oxide synthase expression and reduced nitric oxide (NO) synthesis. Treatment of AMs from mPGES-1 KO mice with an NO donor restored bacterial killing in vitro. These results suggest that mPGES-1 plays a critical role in bacterial pneumonia and that genetic ablation of this enzyme results in diminished pulmonary host defense in vivo and in vitro. These results suggest that specific inhibition of PGE2 synthesis by targeting mPGES-1 may weaken host defense against bacterial infections.

Proteome analysis reveals an upregulation of heat-shock proteins in LPS-induced peritoneal macrophages from mPGES-1 knock-out mice

BackgroundMicrosomal prostaglandin E synthase-1 (mPGES-1) is the terminal enzyme in the induced PGE2 production at the sites of inflammation and well-recognised target for the development of novel anti-inflammatory drugs that...

Inhibition of Matrix Metalloproteinase-3 and -13 Synthesis Induced by IL-1β in Chondrocytes from Mice Lacking Microsomal Prostaglandin E Synthase-1

Joint destruction in arthritis is in part due to the induction of matrix metalloproteinase (MMP) expression and their inhibitors, especially MMP-13 and -3, which directly degrade the cartilage matrix. Although IL-1β is considered as the main catabolic factor involved in MMP-13 and -3 expression, the role of PGE(2) remains controversial. The goal of this study was to determine the role of PGE(2) on MMP synthesis in articular chondrocytes using mice lacking microsomal PGE synthase-1 (mPGES-1), which catalyses the rate-limiting step of PGE(2) synthesis. MMP-3 and MMP-13 mRNA and protein expressions were assessed by real-time RT-PCR, immunoblotting, and ELISA in primary cultures of articular chondrocytes from mice with genetic deletion of mPGES-1. IL-1β-induced PGE(2) synthesis was dramatically reduced in mPGES-1(-/-) and mPGES-1(+/-) compared with mPGES-1(+/+) chondrocytes. A total of 10 ng/ml IL-1β increased MMP-3 and MMP-13 mRNA, protein expression, and release in mPGES-1(+/+) chondrocytes in a time-dependent manner. IL-1β-induced MMP-3 and MMP-13 mRNA expression, protein expression, and release decreased in mPGES-1(-/-) and mPGES-1(+/-) chondrocytes compared with mPGES-1(+/+) chondrocytes from 8 up to 24 h. Otherwise, MMP inhibition was partially reversed by addition of 10 ng/ml PGE(2) in mPGES-1(-/-) chondrocytes. Finally, in mPGES-1(-/-) chondrocytes treated by forskolin, MMP-3 protein expression was significantly decreased compared with wild-type, suggesting that PGE(2) regulates MMP-3 expression via a signaling pathway dependent on cAMP. These results demonstrate that PGE(2) plays a key role in the induction of MMP-3 and MMP-13 in an inflammatory context. Therefore, mPGES-1 could be considered as a critical target to counteract cartilage degradation in arthritis.

Abstract 2461: Gene deletion of mPGES-1 results in a significant reduction in tumor stage and burden in the BBN mouse model of bladder cancer

Abstract Introduction and Objective: Prostaglandins (PG) play a critical role in the development of solid tumors. Inhibition of cyclooxygenase-2 (COX-2), the committed step in PG synthesis, has been shown to impact tumor development in the BBN mouse model of bladder cancer. However, clinical translation has been impeded by the well documented cardiovascular problems with COX-2 inhibitors. Inhibition of other synthases downstream of COX-2 in the PG cascade may prove useful for chemoprevention or chemotherapy. In the following study, we evaluated the impact of gene deletion of membrane-associated prostaglandin synthase-1 (mPGES-1), the terminal synthase in the generation of PGE2, in the BBN mouse model. Methods: Two month old male C57Bl/6 mice with global homozygous deletion for Ptges (mPGES-1 KO) and wild-type (WT) were treated with and without BBN in drinking water (n=5/grp) for 23 weeks. Bladders were harvested, weighed, fixed, step sectioned and evaluated by H&E for pathologic stage and grade and percent involvement of tissue by tumor. Urine was collected prior to sacrifice and evaluated for PGE-2 metabolites (PGEM) by ELISA. Results: All animals had high-grade cancer at the time of euthanasia. WT bladders were significantly heavier than KO bladders (mean 0.18 vs 0.04 g respectively; p=0.03). Four of 5 WT mice had pT3 and one pT2 disease. Three of 5 KO mice had pT1 and 2 had pT2 disease. % tissue involvement was significantly less in the KO animals as well (54 vs 87%, p=0.03). Pearson's correlation for bladder weight and percent tumor involvement was 0.73 (p=0.02). Pathologic stage was dependant on genotype by Wilcoxon Rank Sum Test (p=0.02). Urine metabolites were reduced 50% in the KO compared to WT animals (mean 18.9 vs 45.2 pg/ml respectively; p<0.01). Conclusions: Genetic deletion of mPGES-1 resulted in significant decreases in PGE-2 as evidenced by lower urinary PGEM and in pathologic stage and % tissue involvement by tumor. Increased bladder weights in the WT mice compared to KO mice were directly related to the increased tumor burden. These results suggest that inhibitors of mPGES-1 may prove to be an alternative to COX inhibition and possibly prove useful in the management of high-grade bladder cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2461.

Genetic Deletion of mPGES-1 Suppresses Intestinal Tumorigenesis

Elevated levels of prostaglandin E(2) (PGE(2)) are often found in colorectal cancers. Thus, nonsteroidal anti-inflammatory drugs, including selective cyclooxygenase-2 (COX-2) inhibitors, are among the most promising chemopreventive agents for colorectal cancer. However, their long-term use is restricted by the occurrence of adverse events believed to be associated with a global reduction in prostaglandin production. In the present study, we evaluated the chemopreventive efficacy of targeting the terminal synthase microsomal PGE(2) synthase 1 (mPGES-1), which is responsible for generating PGE(2), in two murine models of intestinal cancer. We report for the first time that genetic deletion of mPGES-1 in Apc-mutant mice results in marked and persistent suppression of intestinal cancer growth by 66%, whereas suppression of large adenomas (>3 mm) was almost 95%. This effect occurred despite loss of Apc heterozygosity and beta-catenin activation. However, we found that mPGES-1 deficiency was associated with a disorganized vascular pattern within primary adenomas as determined by CD31 immunostaining. We also examined the effect of mPGES-1 deletion on carcinogen-induced colon cancer. The absence of mPGES-1 reduced the size and number of preneoplastic aberrant crypt foci (ACF). Importantly, mPGES-1 deletion also blocked the nuclear accumulation of beta-catenin in ACF, confirming that beta-catenin is a critical target of PGE(2) procarcinogenic signaling in the colon. Our data show the feasibility of targeting mPGES-1 for cancer chemoprevention with the potential for improved tolerability over traditional nonsteroidal anti-inflammatory drugs and selective COX-2 inhibitors.

Microsomal Prostaglandin E Synthase-1 Deficiency Is Associated with Elevated Peroxisome Proliferator-activated Receptor γ: REGULATION BY PROSTAGLANDIN E2 VIA THE PHOSPHATIDYLINOSITOL 3-KINASE AND AKT PATHWAY

mPGES-1 (microsomal PGE synthase-1) is an inducible enzyme that acts downstream of cyclooxygenase (COX) and specifically catalyzes the conversion of prostaglandin (PG) H(2) to PGE(2) under basal as well as inflammatory conditions. In this study, using mouse embryo fibroblasts (MEFs) isolated from mice genetically deficient for the mPges-1 gene, we show basal elevation of peroxisome proliferator-activated receptor gamma (PPARgamma) expression (protein and mRNA) and transcriptional activity associated with reduced basal PGE(2). We further show that basal mPGES-1-derived PGE(2) suppresses the expression of PPARgamma through a cAMP-independent pathway involving phosphatidylinositol 3-kinase and Akt signaling. Using specific PPARgamma agonist (rosiglitazone), PPARgamma ligand (15-deoxy-Delta12,14-PGJ(2)), and PPARgamma inhibitor (GW9662), we confirm that activation of PPARgamma blocks interleukin-1beta-induced up-regulation of COX-2, mPGES-1, and their derived PGE(2). Furthermore, we demonstrate that up-regulation of PPARgamma upon genetic deletion of mPGES-1 is responsible for reduced COX-2 expression under basal as well as interleukin-1beta-stimulated conditions. This study provides evidence for the first time that mPGES-1 deletion not only decreases proinflammatory PGE(2) but also up-regulates anti-inflammatory PPARgamma, which has the ability to suppress COX-2 and mPGES-1 expression and PGE(2) production. Thus, mPGES-1 inhibition may limit inflammation by multiple mechanisms and is a potential therapeutic target.