The prostaglandin E2 E-prostanoid 4 receptor exerts anti-inflammatory effects in brain innate immunity

Rethinking the role of microglia in obesity

Microglia are the macrophages of the central nervous system (CNS), implying their role in maintaining brain homeostasis. To achieve this, these cells are sensitive to a plethora of endogenous and exogenous signals, such as neuronal activity, cellular debris, hormones, and pathological patterns, among many others. More recent research suggests that microglia are highly responsive to nutrients and dietary variations. In this context, numerous studies have demonstrated their significant role in the development of obesity under calorie surfeit. Because many reviews already exist on this topic, we have chosen to present the state of our reflections on various concepts put forth in the literature, bringing a new perspective whenever possible. Our literature review focuses on studies conducted in the arcuate nucleus of the hypothalamus, a key structure in the control of food intake. Specifically, we present the recent data available on the modifications of microglial energy metabolism following the consumption of an obesogenic diet and their consequences on hypothalamic neuron activity. We also highlight the studies unraveling the mechanisms underlying obesity-related sexual dimorphism. The review concludes with a list of questions that remain to be addressed in the field to achieve a comprehensive understanding of the role of microglia in the regulation of body energy metabolism. This article is part of the Special Issue on "Microglia".

Primary microglia cell cultures in translational research: Strengths and limitations

Microglia are the resident macrophages in the central nervous system, accounting for 10-15% of the cell mass in the brain. Next to their physiological role in development, monitoring neuronal function and the maintenance of homeostasis, microglia are crucial in the brain's immune defense. Brain injury and chronic neurological disorders are associated with neuroinflammation, in which microglia activation is a central element. Microglia acquire a wide spectrum of activation states in the diseased or injured brain, some of which are neurotoxic. The investigation of microglia (patho)physiology and therapeutic interventions targeting neuroinflammation is a substantial challenge. In addition to in vivo approaches, the application of in vitro model systems has gained significant ground and is essential to complement in vivo work. Primary microglia cultures have proved to be a useful tool. Microglia cultures have offered the opportunity to explore the mechanistic, molecular elements of microglia activation, the microglia secretome, and the efficacy of therapeutic treatments against neuroinflammation. As all model systems, primary microglia cultures have distinct strengths and limitations to be weighed when experiments are designed and when data are interpreted. Here, we set out to provide a succinct overview of the advantages and pitfalls of the use of microglia cultures, which instructs the refinement and further development of this technique to remain useful in the toolbox of microglia researchers. Since there is no conclusive therapy to combat neurotoxicity linked to neuroinflammation in acute brain injury or neurodegenerative disorders, these research tools remain essential to explore therapeutic opportunities.

Arachidonic acid-derived lipid mediators in multiple sclerosis pathogenesis: fueling or dampening disease progression?

BACKGROUND

Multiple sclerosis (MS) is a chronic autoimmune disease of the central nervous system (CNS), characterized by neuroinflammation, demyelination, and neurodegeneration. Considering the increasing prevalence among young adults worldwide and the disabling phenotype of the disease, a deeper understanding of the complexity of the disease pathogenesis is needed to ultimately improve diagnosis and personalize treatment opportunities. Recent findings suggest that bioactive lipid mediators (LM) derived from ω-3/-6 polyunsaturated fatty acids (PUFA), also termed eicosanoids, may contribute to MS pathogenesis. For example, disturbances in LM profiles and especially those derived from the ω-6 PUFA arachidonic acid (AA) have been reported in people with MS (PwMS), where they may contribute to the chronicity of neuroinflammatory processes. Moreover, we have previously shown that certain AA-derived LMs also associated with neurodegenerative processes in PwMS, suggesting that AA-derived LMs are involved in more pathological events than solely neuroinflammation. Yet, to date, a comprehensive overview of the contribution of these LMs to MS-associated pathological processes remains elusive.

MAIN BODY

This review summarizes and critically evaluates the current body of literature on the eicosanoid biosynthetic pathway and its contribution to key pathological hallmarks of MS during different disease stages. Various parts of the eicosanoid pathway are highlighted, namely, the prostanoid, leukotriene, and hydroxyeicosatetraenoic acids (HETEs) biochemical routes that include specific enzymes of the cyclooxygenases (COXs) and lipoxygenases (LOX) families. In addition, cellular sources of LMs and their potential target cells based on receptor expression profiles will be discussed in the context of MS. Finally, we propose novel therapeutic approaches based on eicosanoid pathway and/or receptor modulation to ultimately target chronic neuroinflammation, demyelination and neurodegeneration in MS.

SHORT CONCLUSION

The eicosanoid pathway is intrinsically linked to specific aspects of MS pathogenesis. Therefore, we propose that novel intervention strategies, with the aim of accurately modulating the eicosanoid pathway towards the biosynthesis of beneficial LMs, can potentially contribute to more patient- and MS subtype-specific treatment opportunities to combat MS.

Receptors on Microglia

Microglial cells are the most receptive cells in the central nervous system (CNS), expressing several classes of receptors reflecting their immune heritage and newly acquired neural specialisation. Microglia possess, depending on the particular context, receptors to neurotransmitters and neuromodulators as well as immunocompetent receptors. This rich complement allows microglial cells to monitor the functional status of the nervous system, contribute actively to the regulation of neural activity and plasticity and homeostasis, and guard against pathogens as well as other challenges to the CNS's integrity and function.

Exploring the Potential Molecular Mechanism of the Shugan Jieyu Capsule in the Treatment of Depression through Network Pharmacology, Molecular Docking, and Molecular Dynamics Simulation

BACKGROUND

Shugan Jieyu Capsule (SJC) is a pure Chinese medicine compound prepared with Hypericum perforatum and Acanthopanacis senticosi. SJC has been approved for the clinical treatment of depression, but the mechanism of action is still unclear.

OBJECTIVES

Network pharmacology, molecular docking, and molecular dynamics simulation (MDS) were applied in the present study to explore the potential mechanism of SJC in the treatment of depression.

METHODS

TCMSP, BATMAN-TCM, and HERB databases were used, and related literature was reviewed to screen the effective active ingredients of Hypericum perforatum and Acanthopanacis senticosi. TCMSP, BATMAN-TCM, HERB, and STITCH databases were used to predict the potential targets of effective active ingredients. GeneCards database, DisGeNET database, and GEO data set were used to obtain depression targets and clarify the intersection targets of SJC and depression. STRING database and Cytoscape software were used to build a protein-protein interaction (PPI) network of intersection targets and screen the core targets. The enrichment analysis on the intersection targets was conducted. Then the receiver operator characteristic (ROC) curve was constructed to verify the core targets. The pharmacokinetic characteristics of core active ingredients were predicted by SwissADME and pkCSM. Molecular docking was performed to verify the docking activity of the core active ingredients and core targets, and molecular dynamics simulations were performed to evaluate the accuracy of the docking complex.

RESULTS

We obtained 15 active ingredients and 308 potential drug targets with quercetin, kaempferol, luteolin, and hyperforin as the core active ingredients. We obtained 3598 targets of depression and 193 intersection targets of SJC and depression. A total of 9 core targets (AKT1, TNF, IL6, IL1B, VEGFA, JUN, CASP3, MAPK3, PTGS2) were screened with Cytoscape 3.8.2 software. A total of 442 GO entries and 165 KEGG pathways (p <0.01) were obtained from the enrichment analysis of the intersection targets, mainly enriched in IL-17, TNF, and MAPK signaling pathways. The pharmacokinetic characteristics of the 4 core active ingredients indicated that they could play a role in SJC antidepressants with fewer side effects. Molecular docking showed that the 4 core active components could effectively bind to the 8 core targets (AKT1, TNF, IL6, IL1B, VEGFA, JUN, CASP3, MAPK3, PTGS2), which were related to depression by the ROC curve. MDS showed that the docking complex was stable.

CONCLUSION

SJC may treat depression by using active ingredients such as quercetin, kaempferol, luteolin, and hyperforin to regulate targets such as PTGS2 and CASP3 and signaling pathways such as IL-17, TNF, and MAPK, and participate in immune inflammation, oxidative stress, apoptosis, neurogenesis, etc.

Prostaglandin E2 and myocarditis; friend or foe?

This review article summarizes the role of prostaglandin E2 (PGE2) and its receptors (EP1-EP4) as it relates to the inflammatory cardiomyopathy, myocarditis. During the COVID-19 pandemic, the onset of myocarditis in a subset of patients prompted a debate on the use of nonsteroidal anti-inflammatory drugs (NSAIDs), like ibuprofen, which act to inhibit the actions of prostaglandins. This review aims to further understanding of the role of PGE2 in the pathogenesis or protection of the myocardium in myocarditis. Inflammatory cardiomyopathies encompass a broad spectrum of disorders, all characterized by cardiac inflammation. Therefore, for the purpose of this review, the authors have placed particular emphasis on etiologies of myocarditis where effects of PGE2 have been documented.

Bacteroides Fragilis in the gut microbiomes of Alzheimer's disease activates microglia and triggers pathogenesis in neuronal C/EBPβ transgenic mice

Gut dysbiosis contributes to Alzheimer's disease (AD) pathogenesis, and Bacteroides strains are selectively elevated in AD gut microbiota. However, it remains unknown which Bacteroides species and how their metabolites trigger AD pathologies. Here we show that Bacteroides fragilis and their metabolites 12-hydroxy-heptadecatrienoic acid (12-HHTrE) and Prostaglandin E2 (PGE2) activate microglia and induce AD pathogenesis in neuronal C/EBPβ transgenic mice. Recolonization of antibiotics cocktail-pretreated Thy1-C/EBPβ transgenic mice with AD patient fecal samples elicits AD pathologies, associated with C/EBPβ/Asparaginyl endopeptidase (AEP) pathway upregulation, microglia activation, and cognitive disorders compared to mice receiving healthy donors' fecal microbiota transplantation (FMT). Microbial 16S rRNA sequencing analysis shows higher abundance of proinflammatory Bacteroides fragilis in AD-FMT mice. Active components characterization from the sera and brains of the transplanted mice revealed that both 12-HHTrE and PGE2 activate primary microglia, fitting with poly-unsaturated fatty acid (PUFA) metabolites enrichment identified by metabolomics. Strikingly, recolonization with live but not dead Bacteroides fragilis elicited AD pathologies in Thy1-C/EBPβ transgenic mice, so did 12-HHTrE or PGE2 treatment alone. Collectively, our findings support a causal role for Bacteroides fragilis and the PUFA metabolites in activating microglia and inducing AD pathologies in Thy1- C/EBPβ transgenic mice.

Role of neuroinflammation in neurodegeneration development

Studies in neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease and Amyotrophic lateral sclerosis, Huntington's disease, and so on, have suggested that inflammation is not only a result of neurodegeneration but also a crucial player in this process. Protein aggregates which are very common pathological phenomenon in neurodegeneration can induce neuroinflammation which further aggravates protein aggregation and neurodegeneration. Actually, inflammation even happens earlier than protein aggregation. Neuroinflammation induced by genetic variations in CNS cells or by peripheral immune cells may induce protein deposition in some susceptible population. Numerous signaling pathways and a range of CNS cells have been suggested to be involved in the pathogenesis of neurodegeneration, although they are still far from being completely understood. Due to the limited success of traditional treatment methods, blocking or enhancing inflammatory signaling pathways involved in neurodegeneration are considered to be promising strategies for the therapy of neurodegenerative diseases, and many of them have got exciting results in animal models or clinical trials. Some of them, although very few, have been approved by FDA for clinical usage. Here we comprehensively review the factors affecting neuroinflammation and the major inflammatory signaling pathways involved in the pathogenicity of neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, and Amyotrophic lateral sclerosis. We also summarize the current strategies, both in animal models and in the clinic, for the treatment of neurodegenerative diseases.

The effect of neuroinflammation on the cerebral metabolism at baseline and after neural stimulation in neurodegenerative diseases

Neuroinflammation is a reaction of nervous tissue to an attack caused by an infection, a toxin, or a neurodegenerative disease. It involves brain metabolism adaptation in order to meet the increased energy needs of glial cell activation, but the nature of these adaptations is still unknown. Increasing interest concerning neuroinflammation leads to the identification of its role in neurodegenerative diseases. Few reports studied the effect of metabolic alteration on neuroinflammation. Metabolic damage initiates a pro-inflammatory response by microglial activation. Moreover, the exact neuroinflammation effect on cerebral cell metabolism remains unknown. In this study, we reviewed systematically the neuroinflammation effect in animal models' brains. All articles showing the relationship of neuroinflammation with brain metabolism, or with neuronal stimulation in neurodegenerative diseases were considered. Moreover, this review examines also the mitochondrial damage effect in neurodegeneration diseases. Then, different biosensors are classified regarding their importance in the determination of metabolite change. Finally, some therapeutic drugs inhibiting neuroinflammation are cited. Neuroinflammation increases lymphocyte infiltration and cytokines' overproduction, altering cellular energy homeostasis. This review demonstrates the importance of neuroinflammation as a mediator of disease progression. Further, the spread of depolarization effects pro-inflammatory genes expression and microglial activation, which contribute to the degeneration of neurons, paving the road to better management and treatment of neurodegenerative diseases.

Oral route lipopolysaccharide as a potential dementia preventive agent inducing neuroprotective microglia

In today's aging society, dementia is an urgent problem to be solved because no treatment or preventive methods have been established. This review focuses on oral administration of lipopolysaccharide (LPS), an outer membrane component of Gram-negative bacteria, as a novel preventive drug for dementia. LPS is also called endotoxin and is well known to induce inflammation when administered systemically. On the other hand, although we humans routinely ingest LPS derived from symbiotic bacteria of edible plants, the effect of oral administration of LPS has hardly been studied. Recently, oral administration of LPS was reported to prevent dementia by inducing neuroprotective microglia. Furthermore, it has been suggested that colony stimulating factor 1 (CSF1) is involved in the dementia prevention mechanism by oral administration of LPS. Thus, in this review, we summarized the previous studies of oral administration of LPS and discussed the predicted dementia prevention mechanism. In addition, we showed the potential of oral LPS administration as a preventive drug for dementia by highlighting research gaps and future issues for clinical application development.

Prostaglandin PGE2 Receptor EP4 Regulates Microglial Phagocytosis and Increases Susceptibility to Diet-Induced Obesity

In rodents, susceptibility to diet-induced obesity requires microglial activation, but the molecular components of this pathway remain incompletely defined. Prostaglandin PGE2 levels increase in the mediobasal hypothalamus during high-fat-diet (HFD) feeding, and the PGE2 receptor EP4 regulates microglial activation state and phagocytic activity, suggesting a potential role for microglial EP4 signaling in obesity pathogenesis. To test the role of microglial EP4 in energy balance regulation, we analyzed the metabolic phenotype in a microglia-specific EP4 knockout (MG-EP4 KO) mouse model. Microglial EP4 deletion markedly reduced weight gain and food intake in response to HFD feeding. Corresponding with this lean phenotype, insulin sensitivity was also improved in HFD-fed MG-EP4 KO mice, though glucose tolerance remained surprisingly unaffected. Mechanistically, EP4-deficient microglia showed an attenuated phagocytic state marked by reduced CD68 expression and fewer contacts with pro-opiomelanocortin (POMC) neuron processes. These cellular changes observed in the MG-EP4 KO mice corresponded with an increased density of POMC neurites extending into the paraventricular nucleus (PVN). These findings reveal that microglial EP4 signaling promotes body weight gain and insulin resistance during HFD feeding. Furthermore, the data suggest that curbing microglial phagocytic function may preserve POMC cytoarchitecture and PVN input to limit overconsumption during diet-induced obesity.

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.

Role of prostaglandin E2 in macrophage polarization: Insights into atherosclerosis

Atherosclerosis, a trigger of cardiovascular disease, poses grave threats to human health. Although atherosclerosis depends on lipid accumulation and vascular wall inflammation, abnormal phenotypic regulation of macrophages is considered the pathological basis of atherosclerosis. Macrophage polarization mainly refers to the transformation of macrophages into pro-inflammatory (M1) or anti-inflammatory (M2) phenotypes, which has recently become a much-discussed topic. Increasing evidence has shown that M2 macrophage polarization can alleviate atherosclerosis progression. PGE₂ is a bioactive lipid that has been observed to be elevated in atherosclerosis and to play a pro-inflammatory role, yet recent studies have reported that PGE₂ promotes anti-inflammatory M2 macrophage polarization and mitigates atherosclerosis progression. However, the mechanisms by which PGE₂ acts remain unclear. This review summarizes current knowledge of PGE₂ and macrophages in atherosclerosis. Additionally, we discuss potential PGE₂ mechanisms of macrophage polarization, including CREB, NF-κB, and STAT signaling pathways, which may provide important therapeutic strategies based on targeting PGE₂ pathways to modulate macrophage polarization for atherosclerosis treatment.

Higher serum PGE2 is a predicative biomarker for postoperative delirium following elective orthopedic surgery in elderly patients

Background

Postoperative delirium (POD), one of the most common complications following major surgery, imposes a heavy burden on patients and society. The objective of this exploratory study was to conduct a secondary analysis to identify whether there exist novel and reliable serum biomarkers for the prediction of POD.

Methods

A total of 131 adult patients (≥ 65 years) undergoing lower extremity orthopedic surgery with were enrolled in this study. Cognitive function was assessed preoperatively with Mini-Mental State Examination (MMSE). Delirium was diagnosed according to the Confusion Assessment Method (CAM) criteria on preoperative day and postoperative days 1–3. The preoperative serum levels of a panel of 16 biochemical parameters were measured by ELISA.

Results

Thirty-five patients developed POD, with an incidence of 26.7%. Patients in POD group were older (P = 0.001) and had lower preoperative MMSE scores (P = 0.001). Preoperative serum levels of prostaglandin E2 (PGE2, P < 0.001), S100β (P < 0.001), glial fibrillary acidic protein (P < 0.001) and neurofilament light (P = 0.002) in POD group were significantly increased. Logistic regression analysis showed that advanced age (OR = 1.144, 95%CI: 1.008 ~ 1.298, P = 0.037), higher serum neurofilament light (OR = 1.003, 95%CI: 1.000 ~ 1.005, P = 0.036) and PGE2 (OR = 1.031, 95%CI: 1.018 ~ 1.044, P < 0.001) levels were associated with the development of POD. In addition, serum level of PGE2 yielded an area under the ROC curve (AUC) of 0.897 to predict POD (P < 0.001), with a sensitivity of 80% and a specificity of 83.3%.

Conclusions

Our study showed that higher preoperative serum PGE2 level might be a biomarker to predict the occurrence of POD in elderly patients undergoing elective orthopedic surgery.

Trial registration

NCT03792373 www.clinicaltrials.gov.

Exploring lipophilic compounds that induce BDNF secretion in astrocytes beyond the BBB using a new multi-cultured human in vitro BBB model

Brain-derived neurotrophic factor (BDNF) cannot cross the blood-brain barrier (BBB) when administered peripherally, which hinders its therapeutic potential. We utilized an in vitro BBB model-a tri-culture of a human endothelial cell line, a pericyte cell line, and an astrocyte cell line-to study the effect of twenty candidate lipophilic compounds on stimulating BDNF secretion in pericytes and astrocytes. The prostaglandin E2 receptor 4 agonist and sphingosine-1-phosphate receptor 5 agonist facilitated secretion of BDNF in the astrocyte, but did not decrease the transendothelial electrical resistance. These compounds may be promising agents for neurodegenerative and neuroinflammatory diseases.

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

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

Chorioamnionitis, Inflammation and Neonatal Apnea: Effects on Preterm Neonatal Brainstem and on Peripheral Airways: Chorioamnionitis and Neonatal Respiratory Functions

Background: The present manuscript aims to be a narrative review evaluating the association between inflammation in chorioamnionitis and damage on respiratory centers, peripheral airways, and lungs, explaining the pathways responsible for apnea in preterm babies born by delivery after chorioamnionitis. Methods: A combination of keywords and MESH words was used, including: "inflammation", "chorioamnionitis", "brainstem", "cytokines storm", "preterm birth", "neonatal apnea", and "apnea physiopathology". All identified papers were screened for title and abstracts by the two authors to verify whether they met the proper criteria to write the topic. Results: Chorioamnionitis is usually associated with Fetal Inflammatory Response Syndrome (FIRS), resulting in injury of brain and lungs. Literature data have shown that infections causing chorioamnionitis are mostly associated with inflammation and consequent hypoxia-mediated brain injury. Moreover, inflammation and infection induce apneic episodes in neonates, as well as in animal samples. Chorioamnionitis-induced inflammation favors the systemic secretion of pro-inflammatory cytokines that are involved in abnormal development of the respiratory centers in the brainstem and in alterations of peripheral airways and lungs. Conclusions: Preterm birth shows a suboptimal development of the brainstem and abnormalities and altered development of peripheral airways and lungs. These alterations are responsible for reduced respiratory control and apnea. To date, mostly animal studies have been published. Therefore, more clinical studies on the role of chorioamninitis-induced inflammation on prematurity and neonatal apnea are necessary.

Regulation of PGE2 Pathway During Cerebral Ischemia Reperfusion Injury in Rat

Stroke is an acute central nervous system disease with high morbidity and mortality rate. Cerebral ischemia reperfusion (I/R) injury is easily induced during the development or treatment of stroke and subsequently leads to more serious brain damage. Prostaglandin E2 (PGE2) is one of the most important inflammatory mediators in the brain and contributes to both physiological and pathophysiological functions. It may be upregulated and subsequently plays a key role in cerebral ischemia reperfusion injury. The synthesis and degradation of PGE2 is an extremely complex process, with multiple key stages and molecules. However, there are few comprehensive and systematic studies conducted to investigate the synthesis and degradation of PGE2 during cerebral I/R injury, which is what we want to demonstrate. In this study, qRT-PCR and immunoblotting demonstrated that the key enzymes in PGE2 synthesis, including COX-1, COX-2, mPGES-1 and mPGES-2, were upregulated during cerebral I/R injury, but 15-PGDH, the main PGE2 degradation enzyme, was downregulated. In addition, two of PGE2 receptors, EP3 and EP4, were also increased. Meanwhile, immunohistochemistry demonstrated the localization of these molecules in ischemic areas, including cortex, striatum and hippocampus, and reflected their expression patterns in different regions. Combining the results of PCR, Western blotting and immunohistochemistry, we can determine where the increase or decrease of these molecules occurs. Overall, these results further indicate a possible pathway that mediates enhanced production of PGE2, and thus that may impact production of inflammatory cytokines including IL-1β and TNF-α during cerebral I/R injury.

Prevention of Diabetes-Associated Cognitive Dysfunction Through Oral Administration of Lipopolysaccharide Derived From Pantoea agglomerans

Diabetes-related cognitive dysfunction (DRCD) is a serious complication induced by diabetes. However, there are currently no specific remedies for DRCD. Here, we show that streptozotocin-induced DRCD can be prevented without causing side effects through oral administration of lipopolysaccharide (LPS) derived from Pantoea agglomerans. Oral administration of LPS (OAL) prevented the cerebral cortex atrophy and tau phosphorylation induced by DRCD. Moreover, we observed that neuroprotective transformation of microglia (brain tissue-resident macrophages) is important for preventing DRCD through OAL. These findings are contrary to the general recognition of LPS as an inflammatory agent when injected systemically. Furthermore, our results strongly suggest that OAL promotes membrane-bound colony stimulating factor 1 (CSF1) expression on peripheral leukocytes, which activates the CSF1 receptor on microglia, leading to their transformation to the neuroprotective phenotype. Taken together, the present study indicates that controlling innate immune modulation through the simple and safe strategy of OAL can be an innovative prophylaxis for intractable neurological diseases such as DRCD. In a sense, for modern people living in an LPS-depleted environment, OAL is like a time machine that returns microglia to the good old LPS-abundant era.

Cyclopentenone Prostaglandins: Biologically Active Lipid Mediators Targeting Inflammation

Cyclopentenone prostaglandins (cyPGs) are biologically active lipid mediators, including PGA2, PGA1, PGJ2, and its metabolites. cyPGs are essential regulators of inflammation, cell proliferation, apoptosis, angiogenesis, cell migration, and stem cell activity. cyPGs biologically act on multiple cellular targets, including transcription factors and signal transduction pathways. cyPGs regulate the inflammatory response by interfering with NF-κB, AP-1, MAPK, and JAK/STAT signaling pathways via both a group of nuclear receptor peroxisome proliferator-activated receptor-gamma (PPAR-γ) dependent and PPAR-γ independent mechanisms. cyPGs promote the resolution of chronic inflammation associated with cancers and pathogen (bacterial, viral, and parasitic) infection. cyPGs exhibit potent effects on viral infections by repressing viral protein synthesis, altering viral protein glycosylation, inhibiting virus transmission, and reducing virus-induced inflammation. We summarize their anti-proliferative, pro-apoptotic, cytoprotective, antioxidant, anti-angiogenic, anti-inflammatory, pro-resolution, and anti-metastatic potential. These properties render them unique therapeutic value, especially in resolving inflammation and could be used in adjunct with other existing therapies. We also discuss other α, β -unsaturated carbonyl lipids and cyPGs like isoprostanes (IsoPs) compounds.

Arachidonic Acid Derivatives and Neuroinflammation

Neuroinflammation is characterized by dysregulated inflammatory responses localized within the brain and spinal cord. Neuroinflammation plays a pivotal role in the onset of several neurodegenerative disorders and is considered a typical feature of these disorders. Microglia perform primary immune surveillance and macrophage-like activities within the central nervous system. Activated microglia are predominant players in the central nervous system response to damage related to stroke, trauma, and infection. Moreover, microglial activation per se leads to a proinflammatory response and oxidative stress. During the release of cytokines and chemokines, cyclooxygenases and phospholipase A2 are stimulated. Elevated levels of these compounds play a significant role in immune cell recruitment into the brain. Cyclic phospholipase A2 plays a fundamental role in the production of prostaglandins by releasing arachidonic acid. In turn, arachidonic acid is biotransformed through different routes into several mediators that are endowed with pivotal roles in the regulation of inflammatory processes. Some experimental models of neuroinflammation exhibit an increase in cyclic phospholipase A2, leukotrienes, and prostaglandins such as prostaglandin E2, prostaglandin D2, or prostacyclin. However, findings on the role of the prostacyclin receptors have revealed that their signalling suppresses Th2-mediated inflammatory responses. In addition, other in vitro evidence suggests that prostaglandin E2 may inhibit the production of some inflammatory cytokines, attenuating inflammatory events such as mast cell degranulation or inflammatory leukotriene production. Based on these conflicting experimental data, the role of arachidonic acid derivatives in neuroinflammation remains a challenging issue.

Alzheimer's Disease and Protein Kinases

Alzheimer's disease (AD) is the most common neurodegenerative disorder and accounts for more than 60-80% of all cases of dementia. Loss of pyramidal neurons, extracellular amyloid beta (Abeta) accumulated senile plaques, and neurofibrillary tangles that contain hyperphosphorylated tau constitute the main pathological alterations in AD.Synaptic dysfunction and extrasynaptic N-methyl-D-aspartate receptor (NMDAR) hyperactivation contributes to excitotoxicity in patients with AD. Amyloid precursor protein (APP) and Abeta promoted neurodegeneration develop through the activation of protein kinase signaling cascade in AD. Furthermore, ultimate neuronal death in AD is under control of protein kinases-related signaling pathways. In this chapter, critical check-points within the cross-talk between neuron and protein kinases have been defined regarding the initiation and progression of AD. In this context, amyloid cascade hypothesis, neuroinflammation, oxidative stress, granulovacuolar degeneration, loss of Wnt signaling, Abeta-related synaptic alterations, prolonged calcium ions overload and NMDAR-related synaptotoxicity, damage signals hypothesis and type-3 diabetes are discussed briefly.In addition to clinical perspective of AD pathology, recommendations that might be effective in the treatment of AD patients have been reviewed.

Scavenging Reactive Lipids to Prevent Oxidative Injury

Oxidative injury due to elevated levels of reactive oxygen species is implicated in cardiovascular diseases, Alzheimer's disease, lung and liver diseases, and many cancers. Antioxidant therapies have generally been ineffective at treating these diseases, potentially due to ineffective doses but also due to interference with critical host defense and signaling processes. Therefore, alternative strategies to prevent oxidative injury are needed. Elevated levels of reactive oxygen species induce lipid peroxidation, generating reactive lipid dicarbonyls. These lipid oxidation products may be the most salient mediators of oxidative injury, as they cause cellular and organ dysfunction by adducting to proteins, lipids, and DNA. Small-molecule compounds have been developed in the past decade to selectively and effectively scavenge these reactive lipid dicarbonyls. This review outlines evidence supporting the role of lipid dicarbonyls in disease pathogenesis, as well as preclinical data supporting the efficacy of novel dicarbonyl scavengers in treating or preventing disease.

Simple hypertrophic tonsils have more active innate immune and inflammatory responses than hypertrophic tonsils with recurrent inflammation in children

Background

Tonsil hypertrophy has negative impact on children’s health, but its pathogenesis remains obscure despite the fact that numerous bacteriological studies have been carried out. Understanding the innate immune and inflammatory states of hypertrophic tonsils with different clinical manifestations is of great significance for defining the pathogenesis of tonsil hypertrophy and establishing treatment strategies. The present study was undertaken to examine the characteristics of innate immunity and inflammation in children with hypertrophic palatine tonsils and different clinical manifestations.

Methods

Tonsil tissues were surgically removed from the patients and classified based on the patients’ clinical manifestations. The patients were divided into three groups: 1) Control group; 2) Tonsil Hypertrophy (TH) group; and 3) Tonsil Hypertrophy combined with Recurrent Infection (TH + RI) group. The immune and inflammatory statuses of these tissues were characterized using qRT-PCR and ELISA methods.

Results

Viral protein 1 (VP1) was highly expressed in TH group, but not in TH + RI group. In TH group, elevated expression was observed in the innate immune mediators, including retinoic acid-inducible gene I (RIG-I), interferon alpha (IFN-α), mitochondrial antiviral-signaling protein (MAVS), NLR family pyrin domain containing 3 (NLRP3), toll-like receptor (TLR) 4 and TLR7. Consistent with the innate immune profile, the expression of inflammatory markers (IL-1β, NF-κB and IL-7) was also significantly elevated in TH group. Meanwhile, the COX-2/PGE2/EP4 signaling pathway was found to be involved in the inflammatory response and the formation of fibroblasts.

Conclusions

Innate immune and inflammatory responses are more active in simple hypertrophic tonsils, rather than hypertrophic tonsils with recurrent inflammation. A local relative immune deficiency in the hypertrophic tonsils may be a causative factor for recurrent tonsillitis in TH + RI. These differences, together with the patient’s clinical manifestations, suggest that tonsillar hypertrophy might be regulated by diverse immune and/or inflammatory mechanism through which novel therapeutic strategies might be created.

Chronic Peripheral Inflammation Causes a Region-Specific Myeloid Response in the Central Nervous System

Systemic immune dysregulation contributes to the development of neuropsychiatric and neurodegenerative diseases. The precise effect of chronic peripheral immune stimulation on myeloid cells across anatomical brain regions is unclear. Here, we demonstrate brain-region-specific differences in myeloid responses induced by chronic peripheral inflammation. This shift in the myeloid compartment is associated with the appearance of an inflammatory myeloid subpopulation in the cortex, striatum, and thalamus accompanied by regional transcriptomic fingerprints that include induction of chemokines, complement factors, and endothelial adhesion molecules. In contrast, myeloid immune responses within the hippocampus and cerebellum are subtle or absent. Treatment with the anti-tumor necrosis factor α (anti-TNF-α) antibody infliximab ablates the region-specific inflammatory response. A region-specific myeloid cell response to chronic peripheral inflammation is observed in postmortem brains from individuals with rheumatoid arthritis. Our data suggest that chronic peripheral inflammation has heterogeneous effects on the brain, as evidenced by the spectrum of myeloid cell responses observed across brain regions.

Deep proteome profiling reveals novel pathways associated with pro-inflammatory and alcohol-induced microglial activation phenotypes

Microglia, the resident immune cells of the brain, can exhibit a broad range of activation phenotypes, many of which have been implicated in several diseases and disorders of the central nervous system including those related to alcohol abuse. Given the complexity of global-scale molecular changes that define microglial activation, accurate phenotypic classification in the context of alcohol exposure is still lacking. We employed an optimized method for deep, quantitative proteome profiling of primary microglia in order to characterize their response to acute exposure to alcohol (ethanol) as well as the pro-inflammatory driver and TLR4 agonist, LPS. From this analysis, 5,062 total proteins were identified where 4,857 and 4,928 of those proteins were quantifiable by label-free quantitation in ethanol and LPS treatment groups, respectively. This study highlights the subtle, yet significant proteomic changes that occur in ethanol-treated microglia, which do not align with the robust pro-inflammatory phenotype induced by TLR4 activation. Specifically, our results indicate inhibition of several upstream regulators associated with inflammation, opposing effects on pathways such as phagocytosis upon comparison to TLR4-mediated pro-inflammatory phenotype, and a potential metabolic shift associated with increased expression of proteins related to OXPHOS and lipid homeostasis. Data are available via ProteomeXchange with identifier PXD14466. SIGNIFICANCE: Alcohol abuse has a significant impact on the central nervous system, which includes the pathophysiological mechanisms resulting from glial cell activation. Microglia, in particular, are the resident immune cells of the brain and exhibit a broad range of activation phenotypes. The molecular changes that drive microglial activation phenotype are complex and have yet to be fully characterized in the context of alcohol exposure. Our study highlights the first and most comprehensive characterization of alcohol-induced proteomic changes in primary microglia to date and has shed light on novel immune-related and metabolic pathways that are altered due to alcohol exposure. The results from this study provide an important foundation for future work aimed to understand the complexity of alcohol-induced microglial activation in vivo and other translational models of acute and chronic alcohol exposure.

Novel association between TGFA, TGFB1, IRF1, PTGS2 and IKBKB single-nucleotide polymorphisms and occurrence, severity and treatment response of major depressive disorder

Background

Activation of the immune system might affect the severity of depressive episodes as well as response to the antidepressant treatment. The purpose of this study was to investigate whether the occurrence of variant alleles of analyzed SNPs are involved in prevalence and progression of depression. Moreover, selected genes and SNPs have not been investigated in context of the disease severity and treatment. Therefore, six polymorphisms were selected: g.41354391A>G-TGFB1 (rs1800469), g.132484229C>A-IRF (rs2070729), g.186643058A>G-PTGS2 (rs5275), g.186640617C>T-PTGS2 (rs4648308), g.70677994G>A-TGFA (rs2166975) and g.42140549G>T-IKBKB (rs5029748).

Methods

A total of 360 (180 patients and 180 controls) DNA samples were genotyped using TaqMan probes.

Results

We observed that A/G of the rs2166975 TGFA, A/C of rs2070729 IRF1 and G/T of rs5029748 IKBKB were associated with an increased risk of depression development while the T/T of rs5029748 IKBKB, T/T of rs4648308 PTGS2 and G/G of rs2166975 TGFA reduced this risk. We also stratified the study group according to gender and found that genotype A/G and allele G of the rs2166975 TGFA, G/T of rs5029748 IKBKB as well as C allele of rs4648308 PTGS2, homozygote A/A and allele A of rs5275 PTGS2 were associated with increased risk of depression development in men while homozygote G/G of rs5275 PTGS2 decreased this risk. Moreover, C/T of rs4648308 PTGS2 and A/G of rs5275 PTGS2 was positively correlated with the risk of the disease occurrence in women. Furthermore, a gene-gene analysis revealed a link between studied polymorphisms and depression. In addition, A/A of rs1800469 TGFB1 was associated with earlier age of onset of the disease while G/G of this SNP increased severity of the depressive episode. Interestingly, A/C of rs2070729 IRF1 and T/T of rs5029748 IKBKB may modulate the effectiveness of selective serotonin reuptake inhibitors therapy. In conclusion, studied SNPs may modulate the risk of occurrence, age of onset, severity of the disease and response to the antidepressant treatment.

A joint study of whole exome sequencing and structural MRI analysis in major depressive disorder

BACKGROUND

Major depressive disorder (MDD) is a leading cause of disability worldwide and influenced by both environmental and genetic factors. Genetic studies of MDD have focused on common variants and have been constrained by the heterogeneity of clinical symptoms.

METHODS

We sequenced the exome of 77 cases and 245 controls of Han Chinese ancestry and scanned their brain. Burden tests of rare variants were performed first to explore the association between genes/pathways and MDD. Secondly, parallel Independent Component Analysis was conducted to investigate genetic underpinnings of gray matter volume (GMV) changes of MDD.

RESULTS

Two genes (CSMD1, p = 5.32×10-6; CNTNAP5, p = 1.32×10-6) and one pathway (Neuroactive Ligand Receptor Interactive, p = 1.29×10-5) achieved significance in burden test. In addition, we identified one pair of imaging-genetic components of significant correlation (r = 0.38, p = 9.92×10-6). The imaging component reflected decreased GMV in cases and correlated with intelligence quotient (IQ). IQ mediated the effects of GMV on MDD. The genetic component enriched in two gene sets, namely Singling by G-protein coupled receptors [false discovery rate (FDR) q = 3.23×10-4) and Alzheimer Disease Up (FDR q = 6.12×10-4).

CONCLUSIONS

Both rare variants analysis and imaging-genetic analysis found evidence corresponding with the neuroinflammation and synaptic plasticity hypotheses of MDD. The mediation of IQ indicates that genetic component may act on MDD through GMV alteration and cognitive impairment.

Evaluation of Microglia/Macrophage Cells from Rat Striatum and Prefrontal Cortex Reveals Differential Expression of Inflammatory-Related mRNA after Methamphetamine

RNA sequencing (RNAseq) can be a powerful tool in the identification of transcriptional changes after drug treatment. RNAseq was utilized to determine expression changes in Fluorescence-activated cell sorted (FACS) CD11b/c+ cells from the striatum (STR) and prefrontal cortex (PFC) of male Sprague-Dawley rats after a methamphetamine (METH) binge dosing regimen. Resident microglia and infiltrating macrophages were collected 2 h or 3 days after drug administration. Gene expression changes indicated there was an increase toward an overall pro-inflammatory state, or M1 polarization, along with what appears to be a subset of cells that differentiated toward the anti-inflammatory M2 polarization. In general, there were significantly more mRNA expression changes in the STR than the PFC and more at 2 h post-binge METH than at 3 days post-binge METH. Additionally, Ingenuity^® Pathway Analysis along with details of RNA expression changes revealed cyclo-oxygenase 2 (COX2)-driven prostaglandin (PG) E2 synthesis, glutamine uptake, and the Nuclear factor erythroid2-related factor 2 (NRF2) canonical pathway in microglia were associated with the binge administration regimen of METH.

Inflammation markers in the saliva of infants born from Zika-infected mothers: exploring potential mechanisms of microcephaly during fetal development

Zika virus (ZIKV) has emerged as one of the most medically relevant viral infections of the past decades; the devastating effects of this virus over the developing brain are a major matter of concern during pregnancy. Although the connection with congenital malformations are well documented, the mechanisms by which ZIKV reach the central nervous system (CNS) and the causes of impaired cortical growth in affected fetuses need to be better addressed. We performed a non-invasive, metabolomics-based screening of saliva from infants with congenital Zika syndrome (CZS), born from mothers that were infected with ZIKV during pregnancy. We were able to identify three biomarkers that suggest that this population suffered from an important inflammatory process; with the detection of mediators associated with glial activation, we propose that microcephaly is a product of immune response to the virus, as well as excitotoxicity mechanisms, which remain ongoing even after birth.

CP-25 reverses prostaglandin E4 receptor desensitization-induced fibroblast-like synoviocyte dysfunction via the G protein-coupled receptor kinase 2 in autoimmune arthritis

Paeoniflorin-6'-O-benzene sulfonate (CP-25) is a novel compound derived from paeoniflorin that has been demonstrated to have therapeutic effects in a rat model of rheumatoid arthritis (RA). However, the underlying mechanism has not been elucidated to date. We explored this mechanism in the present study by treating rats with adjuvant arthritis (AA) with CP-25. We found that the membrane EP4 protein level was downregulated; whereas, GRK2 was upregulated, in fibroblast-like synoviocyte (FLS)s of AA rats. Prostaglandin (PGE)2 stimulated FLS proliferation and enhanced the membrane EP4 receptor protein level; the latter was reversed by the administration of an EP4 receptor agonist, whereas the membrane GRK2 protein level gradually increased. The changes in the EP4 receptor and GRK2 expression were enhanced by TNF-α, and the former was accompanied by an alteration in the cyclic (c)AMP level. The EP4 receptor agonist stimulation increased the association between GRK2 and the EP4 receptor. GRK2 knockdown abrogated the abnormalities in FLS proliferation. The CP-25 treatment (100 mg/kg) suppressed joint inflammation with an efficacy that was similar to that of methotrexate. This finding was associated with EP4 upregulation and GRK2 downregulation in FLSs. Thus, GRK2 plays an important role in the abnormal FLS proliferation observed in AA possibly by promoting EP4 receptor desensitization and decreasing the cAMP level. Our results demonstrate that CP-25 has therapeutic potential for the treatment of human RA via GRK2 regulation.

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.

Lipopolysaccharide-Induced Neuroinflammation as a Bridge to Understand Neurodegeneration

A large body of experimental evidence suggests that neuroinflammation is a key pathological event triggering and perpetuating the neurodegenerative process associated with many neurological diseases. Therefore, different stimuli, such as lipopolysaccharide (LPS), are used to model neuroinflammation associated with neurodegeneration. By acting at its receptors, LPS activates various intracellular molecules, which alter the expression of a plethora of inflammatory mediators. These factors, in turn, initiate or contribute to the development of neurodegenerative processes. Therefore, LPS is an important tool for the study of neuroinflammation associated with neurodegenerative diseases. However, the serotype, route of administration, and number of injections of this toxin induce varied pathological responses. Thus, here, we review the use of LPS in various models of neurodegeneration as well as discuss the neuroinflammatory mechanisms induced by this toxin that could underpin the pathological events linked to the neurodegenerative process.

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.

PGE2 signaling via the neuronal EP2 receptor increases injury in a model of cerebral ischemia

The inflammatory prostaglandin E2 (PGE₂) EP2 receptor is a master suppressor of beneficial microglial function, and myeloid EP2 signaling ablation reduces pathology in models of inflammatory neurodegeneration. Here, we investigated the role of PGE₂ EP2 signaling in a model of stroke in which the initial cerebral ischemic event is followed by an extended poststroke inflammatory response. Myeloid lineage cell-specific EP2 knockdown in Cd11bCre;EP2^lox/lox mice attenuated brain infiltration of Cd11b⁺CD45^hi macrophages and CD45⁺Ly6G^hi neutrophils, indicating that inflammatory EP2 signaling participates in the poststroke immune response. Inducible global deletion of the EP2 receptor in adult ROSA26-CreER^T2 (ROSACreER);EP2^lox/lox mice also reduced brain myeloid cell trafficking but additionally reduced stroke severity, suggesting that nonimmune EP2 receptor-expressing cell types contribute to cerebral injury. EP2 receptor expression was highly induced in neurons in the ischemic hemisphere, and postnatal deletion of the neuronal EP2 receptor in Thy1Cre;EP2^lox/lox mice reduced cerebral ischemic injury. These findings diverge from previous studies of congenitally null EP2 receptor mice where a global deletion increases cerebral ischemic injury. Moreover, ROSACreER;EP2^lox/lox mice, unlike EP2^-/- mice, exhibited normal learning and memory, suggesting a confounding effect from congenital EP2 receptor deletion. Taken together with a precedent that inhibition of EP2 signaling is protective in inflammatory neurodegeneration, these data lend support to translational approaches targeting the EP2 receptor to reduce inflammation and neuronal injury that occur after stroke.

[Roles of macrophages in formation and progression of intracranial aneurysms]

Studies have shown that chronic inflammatory response plays a key role in intracranial aneurysms (IA) formation and progression, and macrophages regulate the formation and progression of IA through a variety of pathways. Bone marrow monocyte-derived macrophages and resident-tissue macrophages infiltrate the vessel wall, after infiltration macrophages are polarized into various polarization phenotypes dominated by M1-like and M2-like cells. Polarized phenotypes of macrophages can regulate the formation and progression of intracranial aneurysms by releasing cytokines and regulating the inflammatory response of other immune cells, as well as release different cytokines to regulate the process of extracellular matrix remodeling. Some important progresses have been made in the clinical detection and treatment in targeting macrophages. This review provides a summary on the pathogenesis of IA and potential drug targets to prevent the formation and rupture of intracranial aneurysms.

IDO, COX and iNOS have an important role in the proliferation of Neospora caninum in neuron/glia co-cultures

Central nervous system (CNS) is the main site for encystment of Neospora caninum in different animal species. In this tissue, glial cells (astrocytes and microglia) modulate responses to aggression in order to preserve homeostasis and neuronal function. Previous data showed that when primary cultures of glial cells are infected with N. caninum, they develop gliosis and the immune response is characterized by the release of TNF and IL-10, followed by the control of parasite proliferation. In order to elucidate this control, three enzymatic systems involved in parasite-versus-host interactions were observed on a model of neuron/glia co/cultures obtained from rat brains. Indoleamine 2,3-dioxygenase (IDO), induced nitric oxide synthase (iNOS) responsible for the catabolism of tryptophan and arginine, respectively, and cycloxigenase (COX) were studied comparing their modulation by respective inhibitors with the number of tachyzoites or the immune response measured by the release of IL-10 and TNF. Cells were treated with the inhibitors of iNOS (1.5 mM L-NAME), IDO (1 mM 1-methyl tryptophan), COX-1 (1 μM indomethacin) and COX-2 (1 μM nimesulide) before infection with tachyzoites of N. caninum (1:1 cell: parasite). After 72 h of infection, immunocytochemistry showed astrogliosis and a significant increase in the number and length of neurites, compared with uninfected co-cultures, while an increase of IL-10 and TNF was verified. N. caninum did not change iNOS activity, but the inhibition of the basal levels of this enzyme stimulated parasite proliferation. Additionally, a significant increase of about 40% was verified in the IDO activity, whose inhibition caused 1.2-fold increase in parasitic growth. For COX-2 activity, infection of cultures stimulated a significant increase in release of PGE₂ and its inhibition by nimesulide allowed the parasitic growth. These data indicate that iNOS, IDO and COX-2 control the proliferation of N. caninum in this in vitro model. On the other hand, the release of IL-10 by glia besides modulating the inflammation also allow the continuity of parasitism.

Discovery of 2-Piperidinyl Phenyl Benzamides and Trisubstituted Pyrimidines as Positive Allosteric Modulators of the Prostaglandin Receptor EP2

Prostaglandin E2 (PGE2) via its Gαs-coupled EP2 receptor protects cerebral cortical neurons from excitotoxic and anoxic injury, though EP2 receptor activation can also cause secondary neurotoxicity in chronic inflammation. We performed a high-throughput screen of a library of 292 000 small molecules and identified several compounds that have a 2-piperidinyl phenyl benzamide or trisubstituted pyrimidine core as positive modulators for human EP2 receptor. The most active compounds increased the potency of PGE2 on EP2 receptor 4-5-fold at 20 μM without altering efficacy, indicative of an allosteric mechanism. These compounds did not augment the activity of the other Gαs-coupled PGE2 receptor subtype EP4 and showed neuroprotection against N-methyl-d-aspartate (NMDA)-induced excitotoxicity. These newly developed compounds represent second-generation allosteric potentiators for EP2 receptor and shed light on a promising neuroprotective strategy. They should prove valuable as molecular tools to achieve a better understanding of the dichotomous action of brain EP2 receptor activation.

Protective Effects of L-902,688, a Prostanoid EP4 Receptor Agonist, against Acute Blood-Brain Barrier Damage in Experimental Ischemic Stroke

Ischemic stroke occurs when a clot forms in the brain vasculature that starves downstream tissue of oxygen and nutrients resulting in cell death. The tissue immediately downstream of the blockage, the core, dies within minutes, but the surrounding tissue, the penumbra is potentially salvageable. Prostaglandin E₂ binds to four different G-protein coupled membrane receptors EP1–EP4 mediating different and sometimes opposing responses. Pharmacological activation of the EP4 receptor has already been established as neuroprotective in stroke, but the mechanism(s) of protection are not well-characterized. In this study, we hypothesized that EP4 receptor activation reduces ischemic brain injury by reducing matrix metalloproteinase (MMP)-3/-9 production and blood-brain barrier (BBB) damage. Rats underwent transient ischemic stroke for 90 min. Animals received an intravenous injection of either the vehicle or L-902,688, a highly specific EP4 agonist, at the onset of reperfusion. Brain tissue was harvested at 24 h. We established a dose-response curve and used the optimal dose that resulted in the greatest infarct reduction to analyze BBB integrity compared to vehicle-treated rats. The presence of IgG, a blood protein, in the brain parenchyma is a marker of BBB damage, and L-902,688 (1 mg/kg; i.v.) dramatically reduced IgG extravasation (P < 0.05). Consistent with these data, we assessed zona occludens-1 and occludin, tight junction proteins integral to the maintenance of the BBB, and found reduced degradation with L-902,688 administration. With immunoblotting, qRT-PCR, and/or a fluorescence resonance energy transfer (FRET)-based activity assay, we next measured MMP-3/-9 since they are key effectors of BBB breakdown in stroke. In the cerebral cortex, not only was MMP-3 activity significantly decreased (P < 0.05), but L-902,688 treatment also reduced MMP-9 mRNA, protein, and enzymatic activity (P < 0.001). In addition, post-ischemic administration of the EP4 agonist significantly reduced pro-inflammatory cytokines IL-1β (P < 0.05) and IL-6 (P < 0.01) in the ischemic cerebral cortex. Most importantly, one injection of L-902,688 (1 mg/kg; i.v) at the onset of reperfusion significantly reduces neurological deficits up to 3 weeks later (P < 0.05). Our data show for the first time that pharmacological activation of EP4 with L-902,688 is neuroprotective in ischemic stroke by reducing MMP-3/-9 and BBB damage.

The Consequences of Preterm Birth and Chorioamnionitis on Brainstem Respiratory Centers: Implications for Neurochemical Development and Altered Functions by Inflammation and Prostaglandins

Preterm birth is a major cause for neonatal morbidity and mortality, and is frequently associated with adverse neurological outcomes. The transition from intrauterine to extrauterine life at birth is particularly challenging for preterm infants. The main physiological driver for extrauterine transition is the establishment of spontaneous breathing. However, preterm infants have difficulty clearing lung liquid, have insufficient surfactant levels, and underdeveloped lungs. Further, preterm infants have an underdeveloped brainstem, resulting in reduced respiratory drive. These factors facilitate the increased requirement for respiratory support. A principal cause of preterm birth is intrauterine infection/inflammation (chorioamnionitis), and infants with chorioamnionitis have an increased risk and severity of neurological damage, but also demonstrate impaired autoresuscitation capacity and prevalent apnoeic episodes. The brainstem contains vital respiratory centers which provide the neural drive for breathing, but the impact of preterm birth and/or chorioamnionitis on this brain region is not well understood. The aim of this review is to provide an overview of the role and function of the brainstem respiratory centers, and to highlight the proposed mechanisms of how preterm birth and chorioamnionitis may affect central respiratory functions.

Reactive astrocyte COX2-PGE2 production inhibits oligodendrocyte maturation in neonatal white matter injury

Inflammation is a major risk factor for neonatal white matter injury (NWMI), which is associated with later development of cerebral palsy. Although recent studies have demonstrated maturation arrest of oligodendrocyte progenitor cells (OPCs) in NWMI, the identity of inflammatory mediators with direct effects on OPCs has been unclear. Here, we investigated downstream effects of pro-inflammatory IL-1β to induce cyclooxygenase-2 (COX2) and prostaglandin E2 (PGE2) production in white matter. First, we assessed COX2 expression in human fetal brain and term neonatal brain affected by hypoxic-ischemic encephalopathy (HIE). In the developing human brain, COX2 was expressed in radial glia, microglia, and endothelial cells. In human term neonatal HIE cases with subcortical WMI, COX2 was strongly induced in reactive astrocytes with "A2" reactivity. Next, we show that OPCs express the EP1 receptor for PGE2, and PGE2 acts directly on OPCs to block maturation in vitro. Pharmacologic blockade with EP1-specific inhibitors (ONO-8711, SC-51089), or genetic deficiency of EP1 attenuated effects of PGE2. In an IL-1β-induced model of NWMI, astrocytes also exhibit "A2" reactivity and induce COX2. Furthermore, in vivo inhibition of COX2 with Nimesulide rescues hypomyelination and behavioral impairment. These findings suggest that neonatal white matter astrocytes can develop "A2" reactivity that contributes to OPC maturation arrest in NWMI through induction of COX2-PGE2 signaling, a pathway that can be targeted for neonatal neuroprotection.

Cyclooxygenase-2 contributes to oxidopamine-mediated neuronal inflammation and injury via the prostaglandin E2 receptor EP2 subtype

Cyclooxygenase-2 (COX-2) triggers pro-inflammatory processes that can aggravate neuronal degeneration and functional impairments in many neurological conditions, mainly via producing prostaglandin E2 (PGE₂) that activates four membrane receptors, EP1-EP4. However, which EP receptor is the culprit of COX-2/PGE₂-mediated neuronal inflammation and degeneration remains largely unclear and presumably depends on the insult types and responding components. Herein, we demonstrated that COX-2 was induced and showed nuclear translocation in two neuronal cell lines – mouse Neuro-2a and human SH-SY5Y – after treatment with neurotoxin 6-hydroxydopamine (6-OHDA), leading to the biosynthesis of PGE₂ and upregulation of pro-inflammatory cytokine interleukin-1β. Inhibiting COX-2 or microsomal prostaglandin E synthase-1 suppressed the 6-OHDA-triggered PGE₂ production in these cells. Treatment with PGE₂ or EP2 selective agonist butaprost, but not EP4 agonist CAY10598, increased cAMP response in both cell lines. PGE₂-initiated cAMP production in these cells was blocked by our recently developed novel selective EP2 antagonists – TG4-155 and TG6-10-1, but not by EP4 selective antagonist GW627368X. The 6-OHDA-promoted cytotoxicity was largely blocked by TG4-155, TG6-10-1 or COX-2 selective inhibitor celecoxib, but not by GW627368X. Our results suggest that PGE₂ receptor EP2 is a key mediator of COX-2 activity-initiated cAMP signaling in Neuro-2a and SH-SY5Y cells following 6-OHDA treatment, and contributes to oxidopamine-mediated neurotoxicity.

PGE2 pulsing of murine bone marrow cells reduces migration of daughter monocytes/macrophages in vitro and in vivo

Monocytes/macrophages differentiating from bone marrow (BM) cells pulsed for 2 hours at 37°C with a stabilized derivative of prostaglandin E₂, 16,16-dimethyl PGE₂ (dmPGE₂), migrated less efficiently toward a chemoattractant than monocytes/macrophages differentiated from BM cells pulsed with vehicle. To confirm that the effect on BM cells was long lasting and to replicate human BM transplantation, chimeric mice were established with donor BM cells pulsed for 2 hours with dmPGE₂ before injection into marrow-ablated congenic recipient mice. After 12 weeks, when high levels (90%) of engraftment were obtained, regenerated BM-derived monocytes/macrophages differentiating in vitro or in vivo migrated inefficiently toward the chemokines colony-stimulating factor-1 (CSF-1) and chemokine (C-C motif) ligand 2 (CCL2) or thioglycollate, respectively. Our results reveal long-lasting changes to progenitor cells of monocytes/macrophages by a 2-hour dmPGE₂ pulse that, in turn, limits the migration of their daughter cells to chemoattractants and inflammatory mediators.

Neuroprotective and Anti-Inflammatory Activities of Allyl Isothiocyanate through Attenuation of JNK/NF-κB/TNF-α Signaling

Allyl isothiocyanate (AITC), present in Wasabia japonica (wasabi), is an aliphatic isothiocyanate derived from the precursor sinigrin, which is a glucosinolate present in vegetables of the Brassica family. Traditionally, it has been used to treat rheumatic arthralgia, blood circulation, and pain. This study focuses on its anti-apoptotic activity through the regulation of lipopolysaccharide (LPS)-induced neuroinflammation. Furthermore, we assessed its neuroprotective efficacy, which it achieves through the upregulation of nerve growth factor (NGF) production. Pretreatment with AITC significantly inhibited inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) expression, decreased tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), prostaglandin E2 (PGE2), and nitric oxide (NO) production in activated microglia, and increased the nerve growth factor (NGF) and neurite outgrowth in neuroblastoma cells. AITC inhibited the nuclear factor (NF-κB-mediated transcription by modulating mitogen activated protein kinase (MAPK) signaling, particularly downregulating c-Jun N-terminal kinase (JNK) phosphorylation, which was followed by a reduction in the TNF-α expression in activated microglia. This promising effect of AITC in controlling JNK/NF-κB/TNF-α cross-linking maintains the Bcl-2 gene family and protects neuroblastoma cells from activated microglia-induced toxicity. These findings provide novel insights into the anti-neuroinflammatory effects of AITC on microglial cells, which may have clinical significance in neurodegeneration.

Deficiency in EP4 Receptor-Associated Protein Ameliorates Abnormal Anxiety-Like Behavior and Brain Inflammation in a Mouse Model of Alzheimer Disease

Microglia are thought to play key roles in the progression of Alzheimer disease (AD). Overactivated microglia produce proinflammatory cytokines, such as tumor necrosis factor-α, which appear to contribute to disease progression. Previously, we reported that prostaglandin E₂ type 4 receptor-associated protein (EPRAP) promotes microglial activation. We crossed human amyloid precursor protein transgenic mice from strain J20^+/- onto an EPRAP-deficient background to determine the role of EPRAP in AD. Behavioral tests were performed in 5-month-old male J20^+/-EPRAP^+/+ and J20^+/-EPRAP^-/- mice. EPRAP deficiency reversed the reduced anxiety of J20^+/- mice but did not affect hyperactivity. No differences in spatial memory were observed between J20^+/-EPRAP^+/+ and J20^+/-EPRAP^-/- mice. In comparison with J20^+/-EPRAP^+/+, J20^+/-EPRAP^-/- mice exhibited less microglial accumulation and reductions in the Cd68 and tumor necrosis factor-α mRNAs in the prefrontal cortex and hippocampus. No significant differences were found between the two types of mice in the amount of amyloid-β 40 or 42 in the cortex and hippocampus. J20^+/-EPRAP^-/- mice reversed the reduced anxiety-like behavior and had reduced microglial activation compared with J20^+/-EPRAP^+/+ mice. Further research is required to identify the role of EPRAP in AD, but our results indicate that EPRAP may be related to behavioral and psychological symptoms of dementia and inflammation in patients with AD.

Prostaglandin E2 Produced by Alginate-Encapsulated Mesenchymal Stromal Cells Modulates the Astrocyte Inflammatory Response

Astroglia are well known for their role in propagating secondary injury following brain trauma. Modulation of this injury cascade, including inflammation, is essential to repair and recovery. Mesenchymal stromal cells (MSCs) have been demonstrated as trophic mediators in several models of secondary CNS injury, however, there has been varied success with the use of direct implantation due to a failure to persist at the injury site. To achieve sustained therapeutic benefit, we have encapsulated MSCs in alginate microspheres and evaluated the ability of these encapsulated MSCs to attenuate neuro-inflammation. In this study, astroglial cultures were administered lipopolysaccharide (LPS) to induce inflammation and immediately co-cultured with encapsulated or monolayer human MSCs. Cultures were assayed for the pro-inflammatory cytokine tumor necrosis factor alpha (TNF-α) produced by astroglia, MSC-produced prostaglandin E2, and expression of neurotrophin-associated genes. We found that encapsulated MSCs significantly reduced TNF-α produced by LPS-stimulated astrocytes, more effectively than monolayer MSCs, and this enhanced benefit commences earlier than that of monolayer MSCs. Furthermore, in support of previous findings, encapsulated MSCs constitutively produced high levels of PGE2, while monolayer MSCs required the presence of inflammatory stimuli to induce PGE2 production. The early, constitutive presence of PGE2 significantly reduced astrocyte-produced TNF-α, while delayed administration had no effect. Finally, MSC-produced PGE2 was not only capable of modulating inflammation, but appears to have an additional role in stimulating astrocyte neurotrophin production. Overall, these results support the enhanced benefit of encapsulated MSC treatment, both in modulating the inflammatory response and providing neuroprotection.

Statins Reduce Lipopolysaccharide-Induced Cytokine and Inflammatory Mediator Release in an In Vitro Model of Microglial-Like Cells

The anti-inflammatory effects of statins (HMG-CoA reductase inhibitors) within the cardiovascular system are well-established; however, their neuroinflammatory potential is unclear. It is currently unknown whether statins' neurological effects are lipid-dependent or due to pleiotropic mechanisms. Therefore, the assumption that all statin compounds will have the same effect within the central nervous system is potentially inappropriate, with no studies to date having compared all statins in a single model. Thus, the aim of this study was to compare the effects of the six statins (atorvastatin, fluvastatin, pitavastatin, pravastatin, rosuvastatin, and simvastatin) within a single in vitro model of neuroinflammation. To achieve this, PMA-differentiated THP-1 cells were used as surrogate microglial cells, and LPS was used to induce inflammatory conditions. Here, we show that pretreatment with all statins was able to significantly reduce LPS-induced interleukin (IL)-1β and tumour necrosis factor (TNF)-α release, as well as decrease LPS-induced prostaglandin E2 (PGE2). Similarly, global reactive oxygen species (ROS) and nitric oxide (NO) production were decreased following pretreatment with all statins. Based on these findings, it is suggested that more complex cellular models should be considered to further compare individual statin compounds, including translation into in vivo models of acute and/or chronic neuroinflammation.

Cyclooxygenase-2 Signalling Pathway in the Cortex is Involved in the Pathophysiological Mechanisms in the Rat Model of Depression

This study was designed to investigate the effect of the cortical cyclooxygenase-2 (COX2) pathway on depressive behaviour in rats. Meloxicam, COX2 overexpressed lentivirus and COX2 RNAi lentivirus were administered to Sprague-Dawley rats subjected to chronic unpredictable mild stress (CUMS). Behaviour tests, biochemistry and immunohistochemistry methods, enzyme-linked immunosorbent assays, western blotting and reverse transcription polymerase chain reactions were used to evaluate the changes in rat behaviour and the cortical COX2 pathway. CUMS rats showed depressive–like behaviours. The superoxide dismutase activity and cyclic adenosine monophosphate (cAMP) contents were significantly decreased, the contents of malondialdehyde, prostaglandin E2 (PGE2) and inflammatory cytokines were significantly increased. The expressions of protein kinase A (PKA) and cAMP response element-binding protein (CREB) were decreased, and the levels of brain-derived neurotrophic factor (BDNF) and COX2 were significantly increased. Meloxicam and COX2 RNAi lentivirus significantly alleviated the abnormalities induced by CUMS, while COX2 overexpressed lentivirus aggravated these abnormalities. Our results indicated that the cortical COX2 pathway was activated in CUMS rats. Inhibition of COX2 activity/expression can obviously improve depressive behaviours in CUMS rats. Upregulating COX2 expression can increase the susceptibility of rats to CUMS. An imbalance in the cortical COX2-PGE2-cAMP/PKA-CREB-BDNF signalling pathway participates in the pathogenic mechanism of depression.

The effects of omega-3 fatty acids and vitamin E co-supplementation on clinical and metabolic status in patients with Parkinson's disease: A randomized, double-blind, placebo-controlled trial

The current research was performed to evaluate the effects of omega-3 fatty acids and vitamin E co-supplementation on clinical signs and metabolic status in people with Parkinson's disease (PD). This randomized double-blind placebo-controlled clinical trial was conducted in 60 patients with PD. Participants were randomly assigned into two groups to receive either 1000 mg omega-3 fatty acids from flaxseed oil plus 400 IU vitamin E supplements (n = 30) or placebo (n = 30) for 12 weeks. Unified Parkinson's disease rating stage (UPDRS) were recorded at baseline and the after 3-month intervention. After 12 weeks' intervention, compared with the placebo, omega-3 fatty acids and vitamin E co-supplementation led to a significant improve in UPDRS (-3.3 ± 10.0 vs. +4.4 ± 14.9, P = 0.02). Furthermore, co-supplementation decreased high-sensitivity C-reactive protein (hs-CRP) (-0.3 ± 0.6 vs. +0.3 ± 0.3 μg/mL, P < 0.001), and increased total antioxidant capacity (TAC) (+65.2 ± 68.7 vs. +16 ± 52.4 μmol/L, P = 0.003) and glutathione (GSH) concentrations (+41.4 ± 80.6 vs. -19.6 ± 55.9 μmol/L, P = 0.001) compared with the placebo. Additionally, co-supplementation meaningfully decreased insulin (-2.1 ± 4.9 vs. +1.4 ± 6.2 μIU/mL, P = 0.01), homeostasis model of assessment-estimated insulin resistance (-0.7 ± 1.8 vs.+0.3 ± 1.6, P = 0.02) and Beta cell function (-5.9 ± 13.9 vs. +5.7 ± 25.5, P = 0.03), and increased quantitative insulin sensitivity check index (+0.009 ± 0.02 vs. -0.006 ± 0.03, P = 0.03) compared with the placebo. Overall, our study demonstrated that omega-3 fatty acids and vitamin E co-supplementation in people with PD had favorable effects on UPDRS, hs-CRP, TAC, GSH and markers of insulin metabolism.