Elevated microsomal prostaglandin-E synthase-1 in Alzheimer's disease

HIV-1 Tat Upregulates TREM1 Expression in Human Microglia

Because microglia are a reservoir for HIV and are resistant to the cytopathic effects of HIV infection, they are a roadblock for any HIV cure strategy. We have previously identified that triggering receptor expressed on myeloid cells 1 (TREM1) plays a key role in human macrophage resistance to HIV-mediated cytopathogenesis. In this article, we show that HIV-infected human microglia express increased levels of TREM1 and are resistant to HIV-induced apoptosis. Moreover, upon genetic inhibition of TREM1, HIV-infected microglia undergo cell death in the absence of increased viral or proinflammatory cytokine expression or the targeting of uninfected cells. We also show that the expression of TREM1 is mediated by HIV Tat through a TLR4, TICAM1, PG-endoperoxide synthase 2, PGE synthase, and PGE2-dependent manner. These findings highlight the potential of TREM1 as a therapeutic target to eradicate HIV-infected microglia without inducing a proinflammatory response.

Off-Label Use of Crisdesalazine (GedaCure) in Meningoencephalitis in Two Dogs

An 8-year-old, castrated male Shih-tzu dog (Case 1) showing ataxia and gait disorder was referred for neurological examination and magnetic resonance imaging. Through comprehensive examinations, the patient was tentatively diagnosed with meningoencephalitis of unknown origin (MUO) and treatment with prednisolone and cytosine arabinoside was started. The symptoms were improving with immunosuppressive treatment. However, severe bacterial cystitis occurred and we could not avoid tapering off prednisolone. Then, neurological signs recurred. Therefore, we added crisdesalazine, which allowed us to reduce the daily dosage of immunosuppressants easily. In another case, a 4-year-old, spayed female Yorkshire terrier dog (Case 2) was referred to our hospital showing a head tilt, circling, and loss of the menace reflex. The patient was tentatively diagnosed with MUO and treatment with some immunosuppressants was attempted. The clinical symptoms improved, but the alleviation was inadequate. Thus, we added crisdesalazine. The neurological signs then markedly improved. Moreover, the drugs could be tapered off more easily than before. Crisdesalazine is a novel drug that has antioxidant and anti-inflammatory action in brain disease and is used particularly for dementia. In this paper, we tried an off-label use of this drug in canine MUO patients, and found that it had, in these two patients, additional therapeutic effects on the MUO.

Update on the pathological roles of prostaglandin E2 in neurodegeneration in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease characterized by selective degeneration of upper and lower motor neurons. The pathogenesis of ALS remains largely unknown; however, inflammation of the spinal cord is a focus of ALS research and an important pathogenic process in ALS. Prostaglandin E₂ (PGE₂) is a major lipid mediator generated by the arachidonic-acid cascade and is abundant at inflammatory sites. PGE₂ levels are increased in the postmortem spinal cords of ALS patients and in ALS model mice. Beneficial therapeutic effects have been obtained in ALS model mice using cyclooxygenase-2 inhibitors to inhibit the biosynthesis of PGE₂, but the usefulness of this inhibitor has not yet been proven in clinical trials. In this review, we present current evidence on the involvement of PGE₂ in the progression of ALS and discuss the potential of microsomal prostaglandin E synthase (mPGES) and the prostaglandin receptor E-prostanoid (EP) 2 as therapeutic targets for ALS. Signaling pathways involving prostaglandin receptors mediate toxic effects in the central nervous system. In some situations, however, the receptors mediate neuroprotective effects. Our recent studies demonstrated that levels of mPGES-1, which catalyzes the final step of PGE₂ biosynthesis, are increased at the early-symptomatic stage in the spinal cords of transgenic ALS model mice carrying the G93A variant of superoxide dismutase-1. In addition, in an experimental motor-neuron model used in studies of ALS, PGE₂ induces the production of reactive oxygen species and subsequent caspase-3-dependent cytotoxicity through activation of the EP2 receptor. Moreover, this PGE₂-induced EP2 up-regulation in motor neurons plays a role in the death of motor neurons in ALS model mice. Further understanding of the pathophysiological role of PGE₂ in neurodegeneration may provide new insights to guide the development of novel therapies for ALS.

The inducible prostaglandin E synthase (mPGES-1) in neuroinflammatory disorders

The cyclooxygenase (COX)/prostaglandin E2 (PGE2) signaling pathway has emerged as a critical target for anti-inflammatory therapeutic development in neurological diseases. However, medical use of COX inhibitors in the treatment of various neurological disorders has been limited due to well-documented cardiovascular and cerebrovascular complications. It has been widely proposed that modulation of downstream microsomal prostaglandin E synthase-1 (mPGES-1) enzyme may provide more specificity for inhibiting PGE2-elicited neuroinflammation. Heightened levels of mPGES-1 have been detected in a variety of brain diseases such as epilepsy, stroke, glioma, and neurodegenerative diseases. Subsequently, elevated levels of PGE2, the enzymatic product of mPGES-1, have been demonstrated to modulate a multitude of deleterious effects. In epilepsy, PGE2 participates in retrograde signaling to augment glutamate release at the synapse leading to neuronal death. The excitotoxic demise of neurons incites the activation of microglia, which can become overactive upon further stimulation by PGE2. A selective mPGES-1 inhibitor was able to reduce gliosis and the expression of proinflammatory cytokines in the hippocampus following status epilepticus. A similar mechanism has also been observed in stroke, where the overactivation of microglia by PGE2 upregulated the expression and secretion of proinflammatory cytokines. This intense activation of neuroinflammatory processes triggered the secondary injury commonly observed in stroke, and blockade of mPGES-1 reduced infarction size and edema, suppressed induction of proinflammatory cytokines, and improved post-stroke well-being and cognition. Furthermore, elevated levels of PGE2 have been shown to intensify the proliferation of glioma cells, mediate P-glycoprotein expression at the blood-brain barrier (BBB) and facilitate breakdown of the BBB. For these reasons, targeting mPGES-1, the central and inducible enzyme of the COX cascade, may provide a more specific therapeutic strategy for treating neuroinflammatory diseases.

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.

Neuroaxonal and cellular damage/protection by prostanoid receptor ligands, fatty acid derivatives and associated enzyme inhibitors

Cellular and mitochondrial membrane phospholipids provide the substrate for synthesis and release of prostaglandins in response to certain chemical, mechanical, noxious and other stimuli. Prostaglandin D₂, prostaglandin E₂, prostaglandin F_2α, prostaglandin I₂ and thromboxane-A₂ interact with five major receptors (and their sub-types) to elicit specific downstream cellular and tissue actions. In general, prostaglandins have been associated with pain, inflammation, and edema when they are present at high local concentrations and involved on a chronic basis. However, in acute settings, certain endogenous and exogenous prostaglandins have beneficial effects ranging from mediating muscle contraction/relaxation, providing cellular protection, regulating sleep, and enhancing blood flow, to lowering intraocular pressure to prevent the development of glaucoma, a blinding disease. Several classes of prostaglandins are implicated (or are considered beneficial) in certain central nervous system dysfunctions (e.g., Alzheimer’s, Parkinson’s, and Huntington’s diseases; amyotrophic lateral sclerosis and multiple sclerosis; stroke, traumatic brain injuries and pain) and in ocular disorders (e.g., ocular hypertension and glaucoma; allergy and inflammation; edematous retinal disorders). This review endeavors to address the physiological/pathological roles of prostaglandins in the central nervous system and ocular function in health and disease, and provides insights towards the therapeutic utility of some prostaglandin agonists and antagonists, polyunsaturated fatty acids, and cyclooxygenase inhibitors.

Gut microbiota regulate Alzheimer's disease pathologies and cognitive disorders via PUFA-associated neuroinflammation

OBJECTIVE

This study is to investigate the role of gut dysbiosis in triggering inflammation in the brain and its contribution to Alzheimer's disease (AD) pathogenesis.

DESIGN

We analysed the gut microbiota composition of 3×Tg mice in an age-dependent manner. We generated germ-free 3×Tg mice and recolonisation of germ-free 3×Tg mice with fecal samples from both patients with AD and age-matched healthy donors.

RESULTS

Microbial 16S rRNA sequencing revealed Bacteroides enrichment. We found a prominent reduction of cerebral amyloid-β plaques and neurofibrillary tangles pathology in germ-free 3×Tg mice as compared with specific-pathogen-free mice. And hippocampal RNAseq showed that inflammatory pathway and insulin/IGF-1 signalling in 3×Tg mice brain are aberrantly altered in the absence of gut microbiota. Poly-unsaturated fatty acid metabolites identified by metabolomic analysis, and their oxidative enzymes were selectively elevated, corresponding with microglia activation and inflammation. AD patients' gut microbiome exacerbated AD pathologies in 3×Tg mice, associated with C/EBPβ/asparagine endopeptidase pathway activation and cognitive dysfunctions compared with healthy donors' microbiota transplants.

CONCLUSIONS

These findings support that a complex gut microbiome is required for behavioural defects, microglia activation and AD pathologies, the gut microbiome contributes to pathologies in an AD mouse model and that dysbiosis of the human microbiome might be a risk factor for AD.

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.

Systematic review of human post-mortem immunohistochemical studies and bioinformatics analyses unveil the complexity of astrocyte reaction in Alzheimer's disease

AIMS

Reactive astrocytes in Alzheimer's disease (AD) have traditionally been demonstrated by increased glial fibrillary acidic protein (GFAP) immunoreactivity; however, astrocyte reaction is a complex and heterogeneous phenomenon involving multiple astrocyte functions beyond cytoskeletal remodelling. To better understand astrocyte reaction in AD, we conducted a systematic review of astrocyte immunohistochemical studies in post-mortem AD brains followed by bioinformatics analyses on the extracted reactive astrocyte markers.

METHODS

NCBI PubMed, APA PsycInfo and WoS-SCIE databases were interrogated for original English research articles with the search terms 'Alzheimer's disease' AND 'astrocytes.' Bioinformatics analyses included protein-protein interaction network analysis, pathway enrichment, and transcription factor enrichment, as well as comparison with public human -omics datasets.

RESULTS

A total of 306 articles meeting eligibility criteria rendered 196 proteins, most of which were reported to be upregulated in AD vs control brains. Besides cytoskeletal remodelling (e.g., GFAP), bioinformatics analyses revealed a wide range of functional alterations including neuroinflammation (e.g., IL6, MAPK1/3/8 and TNF), oxidative stress and antioxidant defence (e.g., MT1A/2A, NFE2L2, NOS1/2/3, PRDX6 and SOD1/2), lipid metabolism (e.g., APOE, CLU and LRP1), proteostasis (e.g., cathepsins, CRYAB and HSPB1/2/6/8), extracellular matrix organisation (e.g., CD44, MMP1/3 and SERPINA3), and neurotransmission (e.g., CHRNA7, GABA, GLUL, GRM5, MAOB and SLC1A2), among others. CTCF and ESR1 emerged as potential transcription factors driving these changes. Comparison with published -omics datasets validated our results, demonstrating a significant overlap with reported transcriptomic and proteomic changes in AD brains and/or CSF.

CONCLUSIONS

Our systematic review of the neuropathological literature reveals the complexity of AD reactive astrogliosis. We have shared these findings as an online resource available at www.astrocyteatlas.org.

A Study to Decipher the Potential Effects of Butylphthalide against Central Nervous System Diseases Based on Network Pharmacology and Molecular Docking Integration Strategy

Background

Butylphthalide (NBP), approved by the China National Medical Products Administration (NMPA) for the treatment of ischemic stroke (IS), showed pleiotropic potentials against central nervous system (CNS) diseases, including neuroprotection and cognitive deficits improvement. However, the effects and corresponding modes of action were not fully explored. This study was designed to investigate the potential of NBP against IS-associated CNS diseases based on network pharmacology (NP) and molecular docking (MD).

Methods

IS was inputted as the index disease to retrieve the “associated diseases” in DisGeNET. Three-database-based IS genes were obtained and integrated (DisGeNET, Malacards, and OMIM). Then, IS-associated genes were identified by combining these genes. Meanwhile, PubMed references and online databases were applied to identify NBP target genes. The IS-related disease-disease association (DDA) network and NBP-disease regulation network were constructed and analyzed in Cytoscape. In silico MD and references were used to validate the binding affinity of NBP with critical targets and the potential of NBP against certain IS-related CNS disease regulation.

Results

175 NBP target genes were obtained, while 312 IS-related disease genes were identified. 36 NBP target genes were predicted to be associated with IS-related CNS diseases, including Alzheimer's disease (AD), epilepsy, major depressive disorder (MDD), amyotrophic lateral sclerosis (ALS), and dementia. Six target genes (i.e., GRIN1, PTGIS, PTGES, ADRA1A, CDK5, and SULT1E1) indicating disease specificity index (DSI) >0.5 showed certain to good degree binding affinity with NBP, ranging from −9.2 to −6.7 kcal/mol. And the binding modes may be mainly related to hydrogen bonds and hydrophobic “bonds.” Further literature validations inferred that these critical NBP targets had a tight association with AD, epilepsy, ALS, and depression.

Conclusions

Our study proposed a drug-target-disease integrated method to predict the drug repurposing potentials to associated diseases by application of NP and MD, which could be an attractive alternative to facilitate the development of CNS disease therapies. NBP may be promising and showed potentials to be repurposed for treatments for AD, epilepsy, ALS, and depression, and further investigations are warranted to be carefully designed and conducted.

International Union of Basic and Clinical Pharmacology. CIX. Differences and Similarities between Human and Rodent Prostaglandin E2 Receptors (EP1-4) and Prostacyclin Receptor (IP): Specific Roles in Pathophysiologic Conditions

Prostaglandins are derived from arachidonic acid metabolism through cyclooxygenase activities. Among prostaglandins (PGs), prostacyclin (PGI2) and PGE2 are strongly involved in the regulation of homeostasis and main physiologic functions. In addition, the synthesis of these two prostaglandins is significantly increased during inflammation. PGI2 and PGE2 exert their biologic actions by binding to their respective receptors, namely prostacyclin receptor (IP) and prostaglandin E2 receptor (EP) 1-4, which belong to the family of G-protein-coupled receptors. IP and EP1-4 receptors are widely distributed in the body and thus play various physiologic and pathophysiologic roles. In this review, we discuss the recent advances in studies using pharmacological approaches, genetically modified animals, and genome-wide association studies regarding the roles of IP and EP1-4 receptors in the immune, cardiovascular, nervous, gastrointestinal, respiratory, genitourinary, and musculoskeletal systems. In particular, we highlight similarities and differences between human and rodents in terms of the specific roles of IP and EP1-4 receptors and their downstream signaling pathways, functions, and activities for each biologic system. We also highlight the potential novel therapeutic benefit of targeting IP and EP1-4 receptors in several diseases based on the scientific advances, animal models, and human studies. SIGNIFICANCE STATEMENT: In this review, we present an update of the pathophysiologic role of the prostacyclin receptor, prostaglandin E2 receptor (EP) 1, EP2, EP3, and EP4 receptors when activated by the two main prostaglandins, namely prostacyclin and prostaglandin E2, produced during inflammatory conditions in human and rodents. In addition, this comparison of the published results in each tissue and/or pathology should facilitate the choice of the most appropriate model for the future studies.

Inflammatory and immune mechanisms underlying epileptogenesis and epilepsy: From pathogenesis to treatment target

Epilepsy is a brain disease associated with epileptic seizures as well as with neurobehavioral outcomes of this condition. In the last century, inflammation emerged as a crucial factor in epilepsy etiology. Various brain insults through activation of neuronal and non-neuronal brain cells initiate a series of inflammatory events. Growing observations strongly suggest that abnormal activation of critical inflammatory processes contributes to epileptogenesis, a gradual process by which a normal brain transforms into the epileptic brain. Increased knowledge of inflammatory pathways in epileptogenesis has unveiled mechanistic targets for novel antiepileptic therapies. Molecules specifically targeting the pivotal inflammatory pathways may serve as promising candidates to halt the development of epilepsy. The present paper reviews the pieces of evidence conceptually supporting the potential role of inflammatory mechanisms and the relevant blood-brain barrier (BBB) disruption in epileptogenesis. Also, it discusses the mechanisms underlying inflammation-induced neuronal-glial network impairment and highlights innovative neuroregulatory actions of typical inflammatory molecules. Finally, it presents a brief analysis of observations supporting the therapeutic role of inflammation-targeting tiny molecules in epileptic seizures.

Microsomal Prostaglandin E2 Synthase-1 as a New Macromolecular Drug Target in the Prevention of Inflammation and Cancer

BACKGROUND

Cancer is one of the most life-threatening diseases worldwide. Since inflammation is considered to be one of the known characteristics of cancer, the activity of PGE2 has been paired with different tumorigenic steps such as increased tumor cell proliferation, resistance to apoptosis, increased invasiveness, angiogenesis and immunosuppression.

OBJECTIVE

It has been successfully demonstrated that inhibition of mPGES-1 prevented inflammation in preclinical studies. However, despite the crucial roles of mPGEs-1 and PGE2 in tumorigenesis, there is not much in vivo study on mPGES-1 inhibition in cancer therapy. The specificity of mPGEs-1 enzyme and its low expression level under normal conditions makes it a promising drug target with a low risk of side effects.

METHODS

A comprehensive literature search was performed for writing this review. An updated view on PGE2 biosynthesis, PGES isoenzyme family and its pharmacology and the latest information about inhibitors of mPGES-1 have been discussed.

RESULTS

In this study, it was aimed to highlight the importance of mPGES-1 and its inhibition in inflammationrelated cancer and other inflammatory conditions. Information about PGE2 biosynthesis, its role in inflammationrelated pathologies were also provided. We kept the noncancer-related inflammatory part short and tried to bring together promising molecules or scaffolds.

CONCLUSION

The information provided in this review might be useful to researchers in designing novel and potent mPGES-1 inhibitors for the treatment of cancer and inflammation.

Prostaglandins as the Agents That Modulate the Course of Brain Disorders

Neurologic and neuropsychiatric diseases are associated with great morbidity and mortality. Prostaglandins (PGs) are formed by sequential oxygenation of arachidonic acid in physiologic and pathologic conditions. For the production of PGs cyclooxygenase is a necessary enzyme that has two isoforms, that are named COX-1 and COX-2. COX-1 produces type 1 prostaglandins and on the other hand, COX-2 produces type 2 prostaglandins. Recent studies suggest PGs abnormalities are present in a variety of neurologic and psychiatric disorders. In a disease state, type 2 prostaglandins are mostly responsible and type 1 PGs are not so important in the disease state. In this review, the importance of prostaglandins especially type 2 in brain diseases has been discussed and their possible role in the initiation and outcome of brain diseases has been assessed. Overall the studies suggest prostaglandins are the agents that modulate the course of brain diseases in a positive or negative manner. Here in this review article, the various aspects of PGs in the disease state have discussed. It appears more studies must be done to understand the exact role of these agents in the pathophysiology of brain diseases. However, the suppression of prostaglandin production may confer the alleviation of some brain diseases.

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.

The Role of Eicosanoids in Alzheimer's Disease

Alzheimer's disease (AD) is one of the most common neurodegenerative disorders known. Estimates from the Alzheimer's Association suggest that there are currently 5.8 million Americans living with the disease and that this will rise to 14 million by 2050. Research over the decades has revealed that AD pathology is complex and involves a number of cellular processes. In addition to the well-studied amyloid-β and tau pathology, oxidative damage to lipids and inflammation are also intimately involved. One aspect all these processes share is eicosanoid signaling. Eicosanoids are derived from polyunsaturated fatty acids by enzymatic or non-enzymatic means and serve as short-lived autocrine or paracrine agents. Some of these eicosanoids serve to exacerbate AD pathology while others serve to remediate AD pathology. A thorough understanding of eicosanoid signaling is paramount for understanding the underlying mechanisms and developing potential treatments for AD. In this review, eicosanoid metabolism is examined in terms of in vivo production, sites of production, receptor signaling, non-AD biological functions, and known participation in AD pathology.

Calcium Ions Stimulate the Hyperphosphorylation of Tau by Activating Microsomal Prostaglandin E Synthase 1

Alzheimer’s disease (AD) is reportedly associated with the accumulation of calcium ions (Ca²⁺), and this accumulation is responsible for the phosphorylation of tau. Although several lines of evidence demonstrate the above phenomenon, the inherent mechanisms remain unknown. Using APP/PS1 Tg mice and neuroblastoma (N)2a cells as in vivo and in vitro experimental models, we observed that Ca²⁺ stimulated the phosphorylation of tau by activating microsomal PGE synthase 1 (mPGES1) in a prostaglandin (PG) E₂-dependent EP receptor-activating manner. Specifically, the highly accumulated Ca²⁺ stimulated the expression of mPGES1 and the synthesis of PGE₂. Treatment with the inhibitor of Ca²⁺ transporter, NMDAR, attenuated the expression of mPGES1 and the production of PGE₂ were attenuated in S(+)-ketamine-treated APP/PS1 Tg mice. Elevated levels of PGE₂ were responsible for the hyperphosphorylation of tau in an EP-1-, EP-2-, and EP-3-dependent but not EP4-dependent cyclin-dependent kinase (Cdk) 5-activating manner. Reciprocally, the knockdown of the expression of mPGES1 ameliorated the expected cognitive decline by inhibiting the phosphorylation of tau in APP/PS1 Tg mice. Moreover, CDK5 was found to be located downstream of EP1-3 to regulate the phosphorylation of tau though the cleavage of p35 to p25. Finally, the phosphorylation of tau by Ca²⁺ contributed to the cognitive decline of APP/PS1 Tg mice.

Structure-based discovery of mPGES-1 inhibitors suitable for preclinical testing in wild-type mice as a new generation of anti-inflammatory drugs

Human mPGES-1 is recognized as a promising target for next generation of anti-inflammatory drugs without the side effects of currently available anti-inflammatory drugs, and various inhibitors have been reported in the literature. However, none of the reported potent inhibitors of human mPGES-1 has shown to be also a potent inhibitor of mouse or rat mPGES-1, which prevents using the well-established mouse/rat models of inflammation-related diseases for preclinical studies. Hence, despite of extensive efforts to design and discover various human mPGES-1 inhibitors, the promise of mPGES-1 as a target for the next generation of anti-inflammatory drugs has never been demonstrated in any wild-type mouse/rat model using an mPGES-1 inhibitor. Here we report discovery of a novel type of selective mPGES-1 inhibitors potent for both human and mouse mPGES-1 enzymes through structure-based rational design. Based on in vivo studies using wild-type mice, the lead compound is indeed non-toxic, orally bioavailable, and more potent in decreasing the PGE₂ (an inflammatory marker) levels compared to the currently available drug celecoxib. This is the first demonstration in wild-type mice that mPGES-1 is truly a promising target for the next generation of anti-inflammatory drugs.

Structure-based discovery of mPGES-1 inhibitors suitable for preclinical testing in wild-type mice as a new generation of anti-inflammatory drugs

Human mPGES-1 is recognized as a promising target for next generation of anti-inflammatory drugs without the side effects of currently available anti-inflammatory drugs, and various inhibitors have been reported in the literature. However, none of the reported potent inhibitors of human mPGES-1 has shown to be also a potent inhibitor of mouse or rat mPGES-1, which prevents using the well-established mouse/rat models of inflammation-related diseases for preclinical studies. Hence, despite of extensive efforts to design and discover various human mPGES-1 inhibitors, the promise of mPGES-1 as a target for the next generation of anti-inflammatory drugs has never been demonstrated in any wild-type mouse/rat model using an mPGES-1 inhibitor. Here we report discovery of a novel type of selective mPGES-1 inhibitors potent for both human and mouse mPGES-1 enzymes through structure-based rational design. Based on in vivo studies using wild-type mice, the lead compound is indeed non-toxic, orally bioavailable, and more potent in decreasing the PGE₂ (an inflammatory marker) levels compared to the currently available drug celecoxib. This is the first demonstration in wild-type mice that mPGES-1 is truly a promising target for the next generation of anti-inflammatory drugs.

The Role of mPGES-1 in Inflammatory Brain Diseases

Prostaglandin E₂ (PGE₂) has been thought to be an important mediator of inflammation in peripheral tissues, but recent studies clearly show the involvement of PGE₂ in inflammatory brain diseases. In some animal models of brain disease, the genetic disruption and chemical inhibition of cyclooxygenase (COX)-2 resulted in the reduction of PGE₂ and amelioration of symptoms, and it had been thought that PGE₂ produced by COX-2 may be involved in the progression of injuries. However, COX-2 produces not only PGE₂, but also some other prostanoids, and thus the protective effects of COX-2 inhibition, as well as severe side effects, may be caused by the inhibition of prostanoids other than PGE₂. Therefore, to elucidate the role of PGE₂, studies of microsomal prostaglandin E synthase-1 (mPGES-1), an inducible terminal enzyme for PGE₂ synthesis, have recently been an active area of research. Studies from mPGES-1 deficient mice provide compelling evidence for its role in a variety of inflammatory brain diseases, such as ischemic stroke, Alzheimer's disease and epilepsy, and clues for developing new therapeutic treatments for brain diseases by targeting mPGES-1. Considering that COX inhibitors may non-selectively suppress the production of many types of prostanoids that are essential for normal physiological functioning of the brain and peripheral tissues, as well as induce gastro-intestinal, renal and cardiovascular complications, mPGES-1 inhibitors are expected to be injury-selective and have fewer side-effects when treating human brain diseases. Thus, this paper focuses on recent studies that have demonstrated the involvement of mPGES-1 in pathological brain diseases.

Anti-Inflammatory Small Molecules To Treat Seizures and Epilepsy: From Bench to Bedside

As a crucial component of brain innate immunity, neuroinflammation initially contributes to neuronal tissue repair and maintenance. However, chronic inflammatory processes within the brain and associated blood-brain barrier (BBB) impairment often cause neurotoxicity and hyperexcitability. Mounting evidence points to a mutual facilitation between inflammation and epilepsy, suggesting that blocking the undesired inflammatory signaling within the brain might provide novel strategies to treat seizures and epilepsy. Neuroinflammation is primarily characterized by the upregulation of proinflammatory mediators in epileptogenic foci, among which cyclooxygenase-2 (COX-2)/prostaglandin E2 (PGE2), interleukin-1β (IL-1β), transforming growth factor-β (TGF-β), toll-like receptor 4 (TLR4), high-mobility group box 1 (HMGB1), and tumor necrosis factor-α (TNF-α) have been extensively studied. Small molecules that specifically target these key proinflammatory perpetrators have been evaluated for antiepileptic and antiepileptogenic effects in animal models. These important preclinical studies provide new insights into the regulation of inflammation in epileptic brains and guide drug discovery efforts aimed at developing novel anti-inflammatory therapies for seizures and epilepsy.

Pathophysiological Roles of Cyclooxygenases and Prostaglandins in the Central Nervous System

Cyclooxygenases (COXs) oxidize arachidonic acid to prostaglandin (PG) G2 and H2 followed by PG synthases that generates PGs and thromboxane (TX) A2. COXs are divided into COX-1 and COX-2. In the central nervous system, COX-1 is constitutively expressed in neurons, astrocytes, and microglial cells. COX-2 is upregulated in these cells under pathophysiological conditions. In hippocampal long-term potentiation, COX-2, PGE synthase, and PGE2 are induced in post-synaptic neurons. PGE2 acts pre-synaptic EP2 receptor, generates cAMP, stimulates protein kinase A, modulates voltage-dependent calcium channel, facilitates glutamatergic synaptic transmission, and potentiates long-term plasticity. PGD2, PGE2, and PGI2 exhibit neuroprotective effects via Gs-coupled DP1, EP2/EP4, and IP receptors, respectively. COX-2, PGD2, PGE2, PGF2α, and TXA2 are elevated in stroke. COX-2 inhibitors exhibit neuroprotective effects in vivo and in vitro models of stroke, Alzheimer's disease, Parkinson's disease, multiple sclerosis, amyotrophic lateral sclerosis, epilepsy, and schizophrenia, suggesting neurotoxicities of COX products. PGE2, PGF2α, and TXA2 can contribute to the neurodegeneration via EP1, FP, and TP receptors, respectively, which are coupled with Gq, stimulate phospholipase C and cleave phosphatidylinositol diphosphate to produce inositol triphosphate and diacylglycerol. Inositol triphosphate binds to inositol triphosphate receptor in endoplasmic reticulum, releases calcium, and results in increasing intracellular calcium concentrations. Diacylglycerol activates calcium-dependent protein kinases. PGE2 disrupts Ca(2+) homeostasis by impairing Na(+)-Ca(2+) exchange via EP1, resulting in the excess Ca(2+) accumulation. Neither PGE2, PGF2α, nor TXA2 causes neuronal cell death by itself, suggesting that they might enhance the ischemia-induced neurodegeneration. Alternatively, PGE2 is non-enzymatically dehydrated to a cyclopentenone PGA2, which induces neuronal cell death. Although PGD2 induces neuronal apoptosis after a lag time, neither DP1 nor DP2 is involved in the neurotoxicity. As well as PGE2, PGD2 is non-enzymatically dehydrated to a cyclopentenone 15-deoxy-Δ(12,14)-PGJ2, which induces neuronal apoptosis without a lag time. However, neurotoxicities of these cyclopentenones are independent of their receptors. The COX-2 inhibitor inhibits both the anchorage-dependent and anchorage-independent growth of glioma cell lines regardless of COX-2 expression, suggesting that some COX-2-independent mechanisms underlie the antineoplastic effect of the inhibitor. PGE2 attenuates this antineoplastic effect, suggesting that the predominant mechanism is COX-dependent. COX-2 or EP1 inhibitors show anti-neoplastic effects. Thus, our review presents evidences for pathophysiological roles of cyclooxygenases and prostaglandins in the central nervous system.

SAR-studies of γ-secretase modulators with PPARγ-agonistic and 5-lipoxygenase-inhibitory activity for Alzheimer's disease

We present the design, synthesis and biological evaluation of compounds containing a 2-(benzylidene)hexanoic acid scaffold as multi-target directed γ-secretase-modulators. Broad structural variations were undertaken to elucidate the structure-activity-relationships at the 5-position of the aromatic core. Compound 13 showed the most potent activity profile with IC50 values of 0.79μM (Aβ42), 0.3μM (5-lipoxygenase) and an EC50 value of 4.64μM for PPARγ-activation. This derivative is the first compound exhibiting low micromolar to nanomolar activities for these three targets. Combining γ-secretase-modulation, PPARγ-agonism and inhibition of 5-lipoxygenase in one compound could be a novel disease-modifying multi-target-strategy for Alzheimer's disease to concurrently address the causative amyloid pathology and secondary pathologies like chronic brain inflammation.

The effect of manganese on the olfactory bulb of adult male albino rat and the role of meloxicam: A histological and immunohistochemical study

Manganese (Mn) is an essential metal commonly found in the environment and is used for industrial purposes. Exposure to excessively high Mn levels may induce neurotoxicity referred to as manganism. This work was conducted to study the effect of manganese on the olfactory bulb of adult male albino rat and the possible protective role of meloxicam. Forty adult male albino rats were equally divided into four groups: control group, meloxicam-treated group (5 mg/kg/day orally for 4 weeks), MnCl₂-treated group (10 mg/kg/day orally for 4 weeks), and the fourth group received both meloxicam and MnCl₂ at the same doses and duration. Specimens of the olfactory bulbs were prepared for light and electron microscopy. An immunohistochemical study with a quantitative morphometry was performed using antibodies against glial fibrillary acidic protein (GFAP). The control group and meloxicam-treated group showed the same normal structure. MnCl₂-treated group showed shrinkage of mitral nerve cells with dark peripheral nuclei as well as disorganization of mitral and granule nerve cells. The surrounding neuropil showed vacuolar spaces. Ultrastructurally, the mitral cells showed accumulation of lysosomes, swelling of mitochondria and irregularity of the nuclei. The nerve fibers contained swollen mitochondria with splitting and irregularity of the surrounding myelin sheaths. GFAP immunoreaction showed a highly significant increase compared to control group. On the other hand, the group that received both meloxicam and MnCl₂ showed less marked histological changes. It was concluded that manganese induced structural changes in the olfactory bulb of albino rat that were ameliorated by concomitant use of meloxicam.

Microglial polarization and plasticity: evidence from organotypic hippocampal slice cultures

Increasing evidence indicates that "functional plasticity" is not solely a neuronal attribute but a hallmark of microglial cells, the main brain resident macrophage population. Far from being a univocal phenomenon, microglial activation can originate a plethora of functional phenotypes, encompassing the classic M1 proinflammatory and the alternative M2 anti-inflammatory phenotypes. This concept overturns the popular view of microglial activation as a synonym of neurotoxicity and neurogenesis failure in brain disorders. The characterization of the alternative programs is a matter of intense investigation, but still scarce information is available on the course of microglial activation, on the reversibility of the different commitments and on the capability of preserving molecular memory of previous priming stimuli. By using organotypic hippocampal slice cultures as a model, we developed paradigms of stimulation aimed at shedding light on some of these aspects. We show that persistent stimulation of TLR4 signaling promotes an anti-inflammatory response and microglial polarization toward M2-like phenotype. Moreover, acute and chronic preconditioning regimens permanently affect the capability to respond to a later challenge, suggesting the onset of mechanisms of molecular memory. Similar phenomena could occur in the intact brain and differently affect the vulnerability of mature and newborn neurons to noxious signals.

CCAAT/enhancer binding protein β regulates prostaglandin E synthase expression and prostaglandin E2 production in activated microglial cells

The eicosanoid prostaglandin E2 (PGE2 ) plays important roles in neuroinflammation and it is produced by the sequential action of the enzymes cyclooxygenase-2 (COX-2) and prostaglandin E synthase (PTGES). The expression of both enzymes and the production of PGE2 are increased in neuroinflammation. The objective of this study was to elucidate whether the transcription factor CCAAT/enhancer binding protein β (C/EBPβ) regulates the expression of prostaglandin synthesis enzymes in neuroinflammation. To this aim, the expression of these enzymes in wild-type and C/EBPβ-null mice was analyzed in vitro and in vivo. In mixed glial cultures, lipopolysaccharide (LPS) ± interferon γ (IFN-γ) induced C/EBPβ binding to COX-2 and PTGES promoters. LPS ± IFN-γ-induced increases in PTGES expression and in PGE2 production in mixed glial and microglial cultures were abrogated in the absence of C/EBPβ. Also, increased brain PTGES expression induced by systemic LPS administration was markedly reduced in C/EBPβ-null mice. In contrast to PTGES, the induction of COX-2 expression in vitro or in vivo was not markedly affected by the absence of C/EBPβ. These results demonstrate that C/EBPβ regulates PTGES expression and PGE2 production by activated microglial cells in vitro and point to C/EBPβ as a regulator of PTGES expression in vivo in the inflamed central nervous system. Altogether, these findings strengthen the proposed role of C/EBPβ as a key player in the orchestration of neuroinflammatory gene response.

Putative role of prostaglandin receptor in intracerebral hemorrhage

Each year, approximately 795,000 people experience a new or recurrent stroke. Of all strokes, 84% are ischemic, 13% are intracerebral hemorrhage (ICH) strokes, and 3% are subarachnoid hemorrhage strokes. Despite the decreased incidence of ischemic stroke, there has been no change in the incidence of hemorrhagic stroke in the last decade. ICH is a devastating disease 37–38% of patients between the ages of 45 and 64 die within 30 days. In an effort to prevent ischemic and hemorrhagic strokes we and others have been studying the role of prostaglandins and their receptors. Prostaglandins are bioactive lipids derived from the metabolism of arachidonic acid. They sustain homeostatic functions and mediate pathogenic mechanisms, including the inflammatory response. Most prostaglandins are produced from specific enzymes and act upon cells via distinct G-protein coupled receptors. The presence of multiple prostaglandin receptors cross-reactivity and coupling to different signal transduction pathways allow differentiated cells to respond to prostaglandins in a unique manner. Due to the number of prostaglandin receptors, prostaglandin-dependent signaling can function either to promote neuronal survival or injury following acute excitotoxicity, hypoxia, and stress induced by ICH. To better understand the mechanisms of neuronal survival and neurotoxicity mediated by prostaglandin receptors, it is essential to understand downstream signaling. Several groups including ours have discovered unique roles for prostaglandin receptors in rodent models of ischemic stroke, excitotoxicity, and Alzheimer disease, highlighting the emerging role of prostaglandin receptor signaling in hemorrhagic stroke with a focus on cyclic-adenosine monophosphate and calcium (Ca²⁺) signaling. We review current ICH data and discuss future directions notably on prostaglandin receptors, which may lead to the development of unique therapeutic targets against hemorrhagic stroke and brain injuries alike.

Role of the blood-cerebrospinal fluid barrier transporter as a cerebral clearance system for prostaglandin E₂ produced in the brain

An increasing level of prostaglandin (PG) E(2) is involved in the progression of neuroinflammation induced by ischemia and bacterial infection. Although an imbalance in the rates of production and clearance of PGE(2) under these pathological conditions appears to affect the concentration of PGE(2) in the cerebrospinal fluid (CSF), the regulatory system remains incompletely understood. The purpose of this study was to investigate the cellular system of PGE(2) production via microsomal PGE synthetase-1 (mPGES-1), the inducible PGE(2) -generating enzyme, and PGE(2) elimination from the CSF via the blood-CSF barrier (BCSFB). Immunohistochemical analysis revealed that mPGES-1 was expressed in the soma and perivascular sheets of astrocytes, pia mater, and brain blood vessel endothelial cells, suggesting that these cells are local production sites of PGE(2) in the CSF. The in vivo PGE(2) elimination clearance from the CSF was eightfold greater than that of d-mannitol, which is considered to reflect CSF bulk flow. This process was inhibited by the simultaneous injection of unlabeled PGE(2) and β-lactam antibiotics, such as benzylpenicillin, cefazolin, and ceftriaxone, which are substrates and/or inhibitors of organic anion transporter 3 (OAT3). The characteristics of PGE(2) uptake by the isolated choroid plexus were at least partially consistent with those of OAT3. OAT3 was able to mediate PGE(2) transport with a Michaelis-Menten constant of 4.24 μM. These findings indicate that a system regulating the PGE(2) level in the CSF involves OAT3-mediated PGE(2) uptake by choroid plexus epithelial cells, acting as a cerebral clearance pathway via the BCSFB of locally produced PGE(2) .

Microsomal Prostaglandin E2 Synthase-1

The prostanoids and leukotrienes (LTs) formed from arachidonic acid (AA) via the cyclooxygenase (COX)-1/2 and 5-lipoxygenase (5-LO) pathway, respectively, mediate inflammatory responses, chronic tissue remodelling, cancer, asthma and autoimmune disorders, but also possess homeostatic functions in the gastrointestinal tract, uterus, brain, kidney, vasculature and host defence. Based on the manifold functions of these eicosanoids, the clinical use of non-steroidal anti-inflammatory drugs (NSAIDs), a class of drugs that block formation of all prostanoids, is hampered by severe side-effects including gastrointestinal injury, renal irritations and cardiovascular risks. Therefore, anti-inflammatory agents interfering with eicosanoid biosynthesis require a well-balanced pharmacological profile to minimize these on-target side-effects. Current anti-inflammatory research aims at identifying compounds that can suppress the massive formation of pro-inflammatory prostaglandin (PG)E2 without affecting homeostatic PGE2 and PGI2 synthesis. The inducible microsomal prostaglandin E2 synthase-1 (mPGES-1) is one promising target enzyme. We will give an overview about the structure, regulation and function of mPGES-1 and then present novel inhibitors of mPGES-1 that may possess a promising pharmacological profile.

Role of prostaglandins in neuroinflammatory and neurodegenerative diseases

Increasing data demonstrates that inflammation participates in the pathophysiology of neurodegenerative diseases. Among the different inflammatory mediators involved, prostaglandins play an important role. The effects induced by prostaglandins might be mediated by activation of their known receptors or by nonclassical mechanisms. In the present paper, we discuss the evidences that link prostaglandins, as well as the enzymes that produce them, to some neurological diseases.

Concurrent blockade of free radical and microsomal prostaglandin E synthase-1-mediated PGE2 production improves safety and efficacy in a mouse model of amyotrophic lateral sclerosis

While free radicals and inflammation constitute major routes of neuronal injury occurring in amyotrophic lateral sclerosis (ALS), neither antioxidants nor non-steroidal anti-inflammatory drugs have shown significant efficacy in human clinical trials. We examined the possibility that concurrent blockade of free radicals and prostaglandin E(2) (PGE(2))-mediated inflammation might constitute a safe and effective therapeutic approach to ALS. We have developed 2-hydroxy-5-[2-(4-trifluoromethylphenyl)-ethylaminobenzoic acid] (AAD-2004) as a derivative of aspirin. AAD-2004 completely removed free radicals at 50 nM as a potent spin-trapping molecule and inhibited microsomal PGE(2) synthase-1 (mPGES-1) activity in response to both lipopolysaccharide-treated BV2 cell with IC(50) of 230 nM and recombinant human mPGES-1 protein with IC(50) of 249 nM in vitro. In superoxide dismutase 1(G93A) transgenic mouse model of ALS, AAD-2004 blocked free radical production, PGE(2) formation, and microglial activation in the spinal cords. As a consequence, AAD-2004 reduced autophagosome formation, axonopathy, and motor neuron degeneration, improving motor function and increasing life span. In these assays, AAD-2004 was superior to riluzole or ibuprofen. Gastric bleeding was not induced by AAD-2004 even at a dose 400-fold higher than that required to obtain maximal therapeutic efficacy in superoxide dismutase 1(G93A). Targeting both mPGES-1-mediated PGE(2) and free radicals may be a promising approach to reduce neurodegeneration in ALS and possibly other neurodegenerative diseases.

Expression of microsomal prostaglandin E synthase-1 in the spinal cord in a transgenic mouse model of amyotrophic lateral sclerosis

Prostaglandin E(2) (PGE(2)) is a key molecule involved in the neuroinflammatory processes that characterize amyotrophic lateral sclerosis (ALS). Although PGE(2) synthesis is regulated by PGE(2) synthases (PGESs), the pathological role of PGESs in ALS still remains unknown. Experiments were performed to elucidate the expression of PGESs and the localization of microsomal PGES-1 (mPGES-1) in neurons and glial cells in the spinal cord of ALS model (G93A) mice. Neurological symptom was observed in G93A mice from 14 weeks by the tail suspension test, and rotarod performances were decreased at 16 weeks and older. Western blotting revealed that the level of mPGES-1 was increased in G93A mice at 15 weeks and older. In contrast, the levels of cytosolic PGES and mPGES-2 did not change at any age. Immunohistochemical analysis demonstrated that age-dependent expression of mPGES-1 was found in motor neurons in G93A mice at 11 and 15 weeks. Immunoreactivity of mPGES-1 was also co-localized in Iba1-positive microglia in G93A mice at 15 weeks. These results suggest that mPGES-1 in motor neurons may play a role in the pathogenesis of ALS and that mPGES-1 may work sequentially in motor neurons and activated microglia to produce ALS symptoms in G93A mice.

Induction of COX-2 enzyme and down-regulation of COX-1 expression by lipopolysaccharide (LPS) control prostaglandin E2 production in astrocytes

Pathological conditions and pro-inflammatory stimuli in the brain induce cyclooxygenase-2 (COX-2), a key enzyme in arachidonic acid metabolism mediating the production of prostanoids that, among other actions, have strong vasoactive properties. Although low basal cerebral COX-2 expression has been reported, COX-2 is strongly induced by pro-inflammatory challenges, whereas COX-1 is constitutively expressed. However, the contribution of these enzymes in prostanoid formation varies depending on the stimuli and cell type. Astrocyte feet surround cerebral microvessels and release molecules that can trigger vascular responses. Here, we investigate the regulation of COX-2 induction and its role in prostanoid generation after a pro-inflammatory challenge with the bacterial lipopolysaccharide (LPS) in astroglia. Intracerebral administration of LPS in rodents induced strong COX-2 expression mainly in astroglia and microglia, whereas COX-1 expression was predominant in microglia and did not increase. In cultured astrocytes, LPS strongly induced COX-2 and microsomal prostaglandin-E(2) (PGE(2)) synthase-1, mediated by the MyD88-dependent NFκB pathway and influenced by mitogen-activated protein kinase pathways. Studies in COX-deficient cells and using COX inhibitors demonstrated that COX-2 mediated the high production of PGE(2) and, to a lesser extent, other prostanoids after LPS. In contrast, LPS down-regulated COX-1 in an MyD88-dependent fashion, and COX-1 deficiency increased PGE(2) production after LPS. The results show that astrocytes respond to LPS by a COX-2-dependent production of prostanoids, mainly vasoactive PGE(2), and suggest that the coordinated down-regulation of COX-1 facilitates PGE(2) production after TLR-4 activation. These effects might induce cerebral blood flow responses to brain inflammation.

Prostaglandin E2 reduces amyloid beta-induced phagocytosis in cultured rat microglia

Treatment with amyloid beta(1-42) (Abeta(1-42)) at 1microM for 60min increased phagocytosis of latex beads by cultured rat microglia. This increase was reduced dose-dependently by prostaglandin E(2) (PGE(2)), but PGD(2), PGF(2alpha), iloprost, or U-46619 had no effects. PGE(2) also reduced the phagocytosis of fluorescent-labeled Abeta(1-42). Abeta(1-42)-induced phagocytosis was reduced by butaprost but not by 17-phenyl trinor PGE(2), sulprostone, or PGE(1) alcohol. The reduction effect of PGE(2) on phagocytosis was reversed by AH6809, an E-prostanoid receptor 2 (EP2) antagonist, which inhibited cyclic adenosine monophosphate (AMP) accumulation induced by PGE(2). Butaprost, but not 17-phenyl trinor PGE(2), sulprostone, or PGE(1) alcohol increased intracellular cyclic AMP accumulation. In western blotting analysis, EP2-like immunoreactivity was detected in the crude membrane fraction of microglia. On the other hand, Abeta(1-42)-induced phagocytosis was not affected by SC-560, a cyclooxygenase-1 (COX-1) inhibitor, NS-398, a COX-2 inhibitor, or ibuprofen, a non-specific COX inhibitor. Abeta(1-42) or PGE(2) had little effect on the expression levels of COX-1 or COX-2. These results indicate that Abeta(1-42)-induced microglial phagocytosis is reduced by PGE(2) through EP2.

Resveratrol inhibits prostaglandin formation in IL-1beta-stimulated SK-N-SH neuronal cells

Resveratrol, a polyphenol present in grapes and red wine, has been studied due to its vast pharmacological activity. It has been demonstrated that resveratrol inhibits production of inflammatory mediators in different in vitro and in vivo models. Our group recently demonstrated that resveratrol reduced the production of prostaglandin (PG) E₂ and 8-isoprostane in rat activated microglia. In a microglial-neuronal coculture, resveratrol reduced neuronal death induced by activated microglia. However, less is known about its direct roles in neurons. In the present study, we investigated the effects of resveratrol on interleukin (IL)-1β stimulated SK-N-SH cells. Resveratrol (0.1-5 μM) did not reduce the expression of cyclooxygenase (COX)-2 and microsomal PGE₂ synthase-1 (mPGES-1), although it drastically reduced PGE₂ and PGD₂ content in IL-1β-stimulated SK-N-SH cells. This effect was due, in part, to a reduction in COX enzymatic activity, mainly COX-2, at lower doses of resveratrol. The production of 8-iso-PGF_2α, a marker of cellular free radical generation, was significantly reduced by resveratrol. The present work provides evidence that resveratrol reduces the formation of prostaglandins in neuroblastoma cells by reducing the enzymatic activity of inducible enzymes, such as COX-2, and not the transcription of the PG synthases, as demonstrated elsewhere.

Prostaglandin E(2) synthase inhibition as a therapeutic target

BACKGROUND

Most NSAIDs function by inhibiting biosynthesis of PGE(2) by inhibition of COX-1 and/or COX-2. Since COX-1 has a protective function in the gastro-intestinal tract (GIT), non-selective inhibition of both cycloxy genases leads to moderate to severe gastro-intestinal intolerance. Attempts to identify selective inhibitors of COX-2, led to the identification of celecoxib and rofecoxib. However, long-term use of these drugs has serious adverse effects of sudden myocardial infarction and thrombosis. Drug-mediated imbalance in the levels of prostaglandin I(2) (PGI(2)) and thromboxane A(2) (TXA(2)) with a bias towards TXA(2) may be the primary reason for these events. This resulted in the drugs being withdrawn from the market, leaving a need for an effective and safe anti-inflammatory drug.

METHODS

Recently, the focus of research has shifted to enzymes downstream of COX in the prosta glandin biosynthetic pathway such as prostaglandin E(2) synthases. Microsomal prostaglandin E(2) synthase-1 (mPGES-1) specifically isomerizes PGH(2) to PGE(2), under inflammatory conditions. In this review, we examine the biology of mPGES-1 and its role in disease. Progress in designing molecules that can selectively inhibit mPGES-1 is reviewed.

CONCLUSION

mPGES-1 has the potential to be a target for anti-inflammatory therapy, devoid of adverse GIT and cardiac effects and warrants further investigation.

Microsomal prostaglandin E synthase-2: cellular distribution and expression in Alzheimer's disease

Nonsteroidal anti-inflammatory drugs, such as cyclooxygenase (COX)-2 inhibitors, have been unsuccessful in slowing or reversing Alzheimer's disease (AD). Thus, understanding the expression patterns of the downstream effectors for the regulation of prostaglandin synthesis may be important for understanding the pathological processes involved in AD and formulating more effective pharmacotherapeutics for this disease. In this study, we used immunofluorescence, immunohistochemistry, and Western blot analysis to compare patterns of microsomal prostaglandin E synthase (mPGES)-2 expression in the middle frontal gyrus (MFG) of AD patients and age-matched controls. In control human brain sections, mPGES-2 immunoreactivity was observed in neurons, activated microglia, and endothelium, but not in resting microglia, astrocytes, or smooth muscle cells. Microsomal PGES-2 immunoreactivity was particularly elevated in the pyramidal neurons of brains from three of five sporadic and four of five familial AD patients compared with four of five age-matched control brains that showed minimal immunoreactivity. In contrast, Western blot analysis revealed no difference in mPGES-2 levels between end-stage AD brain tissue and control brain tissue. These results suggest that in human cortex, mPGES-2 is constitutive in neurons and endothelium and induced in activated microglia. Furthermore, the high immunoreactivity of mPGES-2 in pyramidal neurons of AD brains indicates that it might have a potential role in the functional replacement of cytosolic PGES or inactive mPGES-1 in later stages of AD.