Cyclooxygenases-1 and -2 differentially modulate leukocyte recruitment into the inflamed brain

Blood-derived factors to brain communication in brain diseases

Brain diseases, mainly including acute brain injuries, neurodegenerative diseases, and mental disorders, have posed a significant threat to human health worldwide. Due to the limited regenerative capability and the existence of the blood-brain barrier, the brain was previously thought to be separated from the rest of the body. Currently, various cross-talks between the central nervous system (CNS) and peripheral organs have been widely described, including the brain-gut axis, the brain-liver axis, the brain-skeletal muscle axis, and the brain-bone axis. Moreover, several lines of evidence indicate that leveraging systemic biology intervention approaches, including but not limited to lifestyle interventions, exercise, diet, blood administration, and peripheral immune responses, have demonstrated a significant influence on the progress and prognosis of brain diseases. The advancement of innovative proteomic and transcriptomic technologies has enriched our understanding of the nuanced interplay between peripheral organs and brain diseases. An array of novel or previously underappreciated blood-derived factors have been identified to play pivotal roles in mediating these communications. In this review, we provide a comprehensive summary of blood-to-brain communication following brain diseases. Special attention is given to the instrumental role of blood-derived signals, positing them as significant contributors to the complex process of brain diseases. The insights presented here aim to bridge the current knowledge gaps and inspire novel therapeutic strategies for brain diseases.

Neonatal Chlamydia muridarum respiratory infection causes neuroinflammation within the brainstem during the early postnatal period

Respiratory infections are one of the most common causes of illness and morbidity in neonates worldwide. In the acute phase infections are known to cause wide-spread peripheral inflammation. However, the inflammatory consequences to the critical neural control centres for respiration have not been explored. Utilising a well characterised model of neonatal respiratory infection, we investigated acute responses within the medulla oblongata which contains key respiratory regions. Neonatal mice were intranasally inoculated within 24 h of birth, with either Chlamydia muridarum or sham-infected, and tissue collected on postnatal day 15, the peak of peripheral inflammation. A key finding of this study is that, while the periphery appeared to show no sex-specific effects of a neonatal respiratory infection, sex had a significant impact on the inflammatory response of the medulla oblongata. There was a distinct sex-specific response in the medulla coincident with peak of peripheral inflammation, with females demonstrating an upregulation of anti-inflammatory cytokines and males showing very few changes. Microglia also demonstrated sex-specificity with the morphology of females and males differing based upon the nuclei. Astrocytes showed limited changes during the acute response to neonatal infection. These data highlight the strong sex-specific impact of a respiratory infection can have on the medulla in the acute inflammatory phase.

Effect of selective cyclooxygenase inhibitors on animal behaviour and monoaminergic systems of the rat brain

The long-term effects of cyclooxygenase 1 and 2 (COX-1/2) inhibitors are usually tested in terms of the periphery of the organism. Therefore, we studied the effects of SC560 (selective COX-1 inhibitor) and celecoxib (selective COX-2 inhibitor) on the activity of brain monoaminergic systems and animal behaviour. Additionally, we tested the effect of these inhibitors during inflammation. We have observed that long-term administration of celecoxib reduces the activity of the noradrenergic system, increases the activity of dopaminergic and serotonergic systems, increases locomotor activity, and enhances the exploratory behaviour of rats. Administration of SC560 also increases the activity of dopaminergic and serotonergic systems but reduces locomotor activity and impairs the exploratory behaviour of rats. The mechanism responsible for decreased activity of the noradrenergic system may be related to the weakening of activity of the positive feedback loop between the paraventricular nucleus and coeruleus locus. We suggest that the effect of used inhibitors on the dopaminergic system is associated with a possible increase in anandamide concentration and its effect on dopamine reuptake in synaptic clefts. It also appears that cyclooxygenase peroxidase activity may play a role in this process. In turn, changes in the activity of the serotonergic system may be related to the activity of indoleamine-2,3-dioxygenase, which decreases because of the decreased concentration of pro-inflammatory compounds. We believe that behavioural changes induced by COX inhibitors are the result of the modified activity of monoaminergic CNS systems in the brainstem, hypothalamus, and medial prefrontal cortex.

Prenatal disruption of blood-brain barrier formation via cyclooxygenase activation leads to lifelong brain inflammation

Gestational maternal immune activation (MIA) in mice induces persistent brain microglial activation and a range of neuropathologies in the adult offspring. Although long-term phenotypes are well documented, how MIA in utero leads to persistent brain inflammation is not well understood. Here, we found that offspring of mothers treated with polyriboinosinic–polyribocytidylic acid [poly(I:C)] to induce MIA at gestational day 13 exhibit blood–brain barrier (BBB) dysfunction throughout life. Live MRI in utero revealed fetal BBB hyperpermeability 2 d after MIA. Decreased pericyte–endothelium coupling in cerebral blood vessels and increased microglial activation were found in fetal and 1- and 6-mo-old offspring brains. The long-lasting disruptions result from abnormal prenatal BBB formation, driven by increased proliferation of cyclooxygenase-2 (COX2; Ptgs2)-expressing microglia in fetal brain parenchyma and perivascular spaces. Targeted deletion of the Ptgs2 gene in fetal myeloid cells or treatment with the inhibitor celecoxib 24 h after immune activation prevented microglial proliferation and disruption of BBB formation and function, showing that prenatal COX2 activation is a causal pathway of MIA effects. Thus, gestational MIA disrupts fetal BBB formation, inducing persistent BBB dysfunction, which promotes microglial overactivation and behavioral alterations across the offspring life span. Taken together, the data suggest that gestational MIA disruption of BBB formation could be an etiological contributor to neuropsychiatric disorders.

Immune targets for therapeutic development in depression: towards precision medicine

Over the past two decades, compelling evidence has emerged indicating that immune mechanisms can contribute to the pathogenesis of major depressive disorder (MDD) and that drugs with primary immune targets can improve depressive symptoms. Patients with MDD are heterogeneous with respect to symptoms, treatment responses and biological correlates. Defining a narrower patient group based on biology could increase the treatment response rates in certain subgroups: a major advance in clinical psychiatry. For example, patients with MDD and elevated pro-inflammatory biomarkers are less likely to respond to conventional antidepressant drugs, but novel immune-based therapeutics could potentially address their unmet clinical needs. This article outlines a framework for developing drugs targeting a novel patient subtype within MDD and reviews the current state of neuroimmune drug development for mood disorders. We discuss evidence for a causal role of immune mechanisms in the pathogenesis of depression, together with targets under investigation in randomized controlled trials, biomarker evidence elucidating the link to neural mechanisms, biological and phenotypic patient selection strategies, and the unmet clinical need among patients with MDD.

Is cyclooxygenase-1 involved in neuroinflammation?

Purpose: Reactive microglia are an important hallmark of neuroinflammation. Reactive microglia release various inflammatory mediators, such as cytokines, chemokines, and prostaglandins, which are produced by enzymes like cyclooxygenases (COX). The inducible COX‐2 subtype has been associated with inflammation, whereas the constitutively expressed COX‐1 subtype is generally considered as a housekeeping enzyme. However, recent evidence suggests that COX‐1 can also be upregulated and may play a prominent role in the brain during neuroinflammation. In this review, we summarize the evidence that supports this involvement of COX‐1. Methods: Five databases were used to retrieve relevant studies that addressed COX‐1 in the context of neuroinflammation. The search resulted in 32 articles, describing in vitro, in vivo, post mortem, and in vivo imaging studies that specifically investigated the COX‐1 isoform under such conditions. Results: Reviewed literature generally indicated that the overexpression of COX‐1 was induced by an inflammatory stimulus, which resulted in an increased production of prostaglandin E2. The pharmacological inhibition of COX‐1 was shown to suppress the induction of inflammatory mediators like prostaglandin E2. Positron emission tomography (PET) imaging studies in animal models confirmed the overexpression of COX‐1 during neuroinflammation. The same imaging method, however, could not detect any upregulation of COX‐1 in patients with Alzheimer's disease. Conclusion: Taken together, studies in cultured cells and living rodents suggest that COX‐1 is involved in neuroinflammation. Most postmortem studies on human brains indicate that the concentration of COX‐1‐expressing microglial cells is increased near sites of inflammation. However, evidence for the involvement of COX‐1 in neuroinflammation in the living human brain is still largely lacking.

The Potential Role of Inflammation in Modulating Endogenous Hippocampal Neurogenesis After Spinal Cord Injury

Currently there are approximately 291,000 people suffering from a spinal cord injury (SCI) in the United States. SCI is associated with traumatic changes in mobility and neuralgia, as well as many other long-term chronic health complications, including metabolic disorders, diabetes mellitus, non-alcoholic steatohepatitis, osteoporosis, and elevated inflammatory markers. Due to medical advances, patients with SCI survive much longer than previously. This increase in life expectancy exposes them to novel neurological complications such as memory loss, cognitive decline, depression, and Alzheimer's disease. In fact, these usually age-associated disorders are more prevalent in people living with SCI. A common factor of these disorders is the reduction in hippocampal neurogenesis. Inflammation, which is elevated after SCI, plays a major role in modulating hippocampal neurogenesis. While there is no clear consensus on the mechanism of the decline in hippocampal neurogenesis and cognition after SCI, we will examine in this review how SCI-induced inflammation could modulate hippocampal neurogenesis and provoke age-associated neurological disorders. Thereafter, we will discuss possible therapeutic options which may mitigate the influence of SCI associated complications on hippocampal neurogenesis.

Synthesis, Inhibitory Activity, and In Silico Modeling of Selective COX-1 Inhibitors with a Quinazoline Core

Selective cyclooxygenase-1 (COX-1) inhibition has got into the spotlight with the discovery of COX-1 upregulation in various cancers and the cardioprotective role of COX-1 in control of thrombocyte aggregation. Yet, COX-1-selective inhibitors are poorly explored. Thus, three series of quinazoline derivatives were prepared and tested for their potential inhibitory activity toward COX-1 and COX-2. Of the prepared compounds, 11 exhibited interesting COX-1 selectivity, with 8 compounds being totally COX-1-selective. The IC50 value of the best quinazoline inhibitor was 64 nM. The structural features ensuring COX-1 selectivity were elucidated using in silico modeling.

History of Nonsteroidal Anti-inflammatory Drug Use and Functional Outcomes After Spontaneous Intracerebral Hemorrhage

BACKGROUND AND PURPOSE

Preclinical and clinical studies have suggested a potential benefit from COX-2 inhibition on secondary injury activation after spontaneous intracerebral hemorrhage (ICH). The aim of this study was to investigate the effect of pre-admission NSAID use on functional recovery in spontaneous ICH patients.

METHODS

Consecutive adult ICH patients enrolled in the Intracerebral Hemorrhage Outcomes Project (2009-2018) with available 90-day follow-up data were included. Patients were categorized as NSAID (daily COX inhibitor use ≤ 7 days prior to ICH) and non-NSAID users (no daily COX inhibitor use ≤ 7 days prior to ICH). Primary outcome was the ordinal 90-day modified Rankin Scale (mRS) score. Outcomes were compared between cohorts using multivariable regression and propensity score-matched analyses. A secondary analysis excluding aspirin users was performed.

RESULTS

The NSAID and non-NSAID cohorts comprised 228 and 361 patients, respectively. After 1:1 matching, the matched cohorts each comprised 140 patients. The 90-day mRS were comparable between the NSAID and non-NSAID cohorts in both the unmatched (aOR = 0.914 [0.626-1.336], p = 0.644) and matched (aOR = 0.650 [0.392-1.080], p = 0.097) analyses. The likelihood of recurrent ICH at 90 days was also comparable between the NSAID and non-NSAID cohorts in both the unmatched (aOR = 0.845 [0.359-1.992], p = 0.701) and matched analyses (aOR = 0.732 [0.241-2.220], p = 0.581). In the secondary analysis, the non-aspirin NSAID and non-NSAID cohorts comprised 38 and 361 patients, respectively. After 1:1 matching, the matched cohorts each comprised 38 patients. The 90-day mRS were comparable between the non-aspirin NSAID and non-NSAID cohorts in both the unmatched (aOR = 0.615 [0.343-1.101], p = 0.102) and matched (aOR = 0.525 [0.219-1.254], p = 0.147) analyses. The likelihood of recurrent ICH at 90 days was also comparable between the non-aspirin NSAID and non-NSAID cohorts in both the unmatched (aOR = 2.644 [0.258-27.091], p = 0.413) and matched (aOR = 2.586 [0.228-29.309], p = 0.443) analyses. After the exclusion of patients with DNR or withdrawal of care status, NSAID use was associated with lower mRS at 90 days (aOR = 0.379 [0.212-0.679], p = 0.001), lower mRS at hospital discharge (aOR = 0.505 [0.278-0.919], p = 0.025) and lower 90-day mortality rates (aOR = 0.309 [0.108-0.877], p = 0.027).

CONCLUSIONS

History of nonselective COX inhibition may affect functional outcomes in ICH patients. Pre-admission NSAID use did not appear to worsen the severity of presenting ICH or increase the risk of recurrent ICH. Additional clinical studies may be warranted to investigate the effects of pre-admission NSAID use on ICH outcomes.

Neuroinflammation Mechanisms and Phytotherapeutic Intervention: A Systematic Review

Neuroinflammation is indicated in the pathogenesis of several acute and chronic neurological disorders. Acute lesions in the brain parenchyma induce intense and highly complex neuroinflammatory reactions with similar mechanisms among various disease prototypes. Microglial cells in the CNS sense tissue damage and initiate inflammatory responses. The cellular and humoral constituents of the neuroinflammatory reaction to brain injury contribute significantly to secondary brain damage and neurodegeneration. Inflammatory cascades such as proinflammatory cytokines from invading leukocytes and direct cell-mediated cytotoxicity between lymphocytes and neurons are known to cause "collateral damage" in models of acute brain injury. In addition to degeneration and neuronal cell loss, there are secondary inflammatory mechanisms that modulate neuronal activity and affect neuroinflammation which can even be detected at the behavioral level. Hence, several of health conditions result from these pathogenetic conditions which are underlined by progressive neuronal function loss due to chronic inflammation and oxidative stress. In the first part of this Review, we discuss critical neuroinflammatory mediators and their pathways in detail. In the second part, we review the phytochemicals which are considered as potential therapeutic molecules for treating neurodegenerative diseases with an inflammatory component.

Dysregulation of HULC promotes contrast-induced nephropathy (CIN) via regulating signaling pathway of miRNA-512 and prostaglandin E1 (PGE1)

It has been shown that contrast-induced nephropathy (CIN) can be attenuated by the administration of PGE1. As an enzyme responsible for the production of PGE1, PTGS1 was confirmed in this study as a miR-512 target. Meanwhile, HULC has been identified as a competing endogenous RNA of miR-512. Therefore, in this study, we tested the diagnostic value of HULC and miR-512 in subjects with or without CIN. In addition, we evaluated the regulatory relationship among HULC, miR-512, PTGS1 and PGE1 in vitro. We enrolled 320 patients with coronary heart disease and divided them into a CIN group and a non-CIN group. Subsequently, we detected the differential expression of miR-512, HULC and PGE1 in the two groups. We also used a dual luciferase reporter assay to evaluate the regulatory relationship among HULC, miR-512, PTGS1 and PGE1 in THP-1 cells. In patients with CIN, the expression levels of HULC and PGE1 were lower, but the expression level of miR-512 was higher. MiR-512 could directly bind to and negatively regulate the expression of PTGS1 and HULC. The expression of HULC was positively correlated with the expression of PTGS1 and PGE1, while negatively correlated with the expression of miR-512. The findings of this study demonstrated that deregulation of lncRNA-HULC/miR-512/PTGS1/PGE1 might be involved in the pathogenesis of CIN.

Peripheral-to-central immune communication at the area postrema glial-barrier following bleomycin-induced sterile lung injury in adult rats

The pathways for peripheral-to-central immune communication (P → C I-comm) following sterile lung injury (SLI) are unknown. SLI evokes systemic and central inflammation, which alters central respiratory control and viscerosensory transmission in the nucleus tractus solitarii (nTS). These functional changes coincide with increased interleukin-1 beta (IL-1β) in the area postrema, a sensory circumventricular organ that connects P → C I-comm to brainstem circuits that control homeostasis. We hypothesize that IL-1β and its downstream transcriptional target, cyclooxygenase-2 (COX-2), mediate P → C I-comm in the nTS. In a rodent model of SLI induced by intratracheal bleomycin (Bleo), the sigh frequency and duration of post-sigh apnea increased in Bleo- compared to saline- treated rats one week after injury. This SLI-dependent change in respiratory control occurred concurrently with augmented IL-1β and COX-2 immunoreactivity (IR) in the funiculus separans (FS), a barrier between the AP and the brainstem. At this barrier, increases in IL-1β and COX-2 IR were confined to processes that stained for glial fibrillary acidic protein (GFAP) and that projected basolaterally to the nTS. Further, FS radial-glia did not express TNF-α or IL-6 following SLI. To test our hypothesis, we blocked central COX-1/2 activity by intracerebroventricular (ICV) infusion of Indomethacin (Ind). Continuous ICV Ind treatment prevented Bleo-dependent increases in GFAP + and IL-1β + IR, and restored characteristics of sighs that reset the rhythm. These data indicate that changes in sighs following SLI depend partially on activation of a central COX-dependent P → C I-comm via radial-glia of the FS.

Lead (Pb) as a Factor Initiating and Potentiating Inflammation in Human THP-1 Macrophages

The aim of this study was to assess the influence of lead (Pb) at low concentrations (imitating Pb levels in human blood in chronic environmental exposure to this metal) on interleukin 1β (IL-1β) and interleukin 6 (IL-6) concentrations and the activity and expression of COX-1 and COX-2 in THP-1 macrophages. Macrophages were cultured in vitro in the presence of Pb at concentrations of: 1.25 μg/dL; 2.5 μg/dL; 5 μg/dL; 10 μg/dL. The first two concentrations of Pb were selected on the basis of our earlier study, which showed that Pb concentration in whole blood (PbB) of young women living in the northern regions of Poland and in the cord blood of their newborn children was within this range (a dose imitating environmental exposure). Concentrations of 5 μg/dL and 10 μg/dL correspond to the previously permissible PbB concentrations in children or pregnant women, and adults. Our results indicate that even low concentrations of Pb cause an increase in production of inflammatory interleukins (IL-1β and IL-6), increases expression of COX-1 and COX-2, and increases thromboxane B2 and prostaglandin E2 concentration in macrophages. This clearly suggests that the development of inflammation is associated not only with COX-2 but also with COX-1, which, until recently, had only been attributed constitutive expression. It can be concluded that environmental Pb concentrations are able to activate the monocytes/macrophages similarly to the manner observed during inflammation.

In Silico and In Vitro Analysis of the 4,4',4''-((1,3,5-Triazine-2,4,6-triyl)tris(azanediyl))triphenol), an Antioxidant Agent with a Possible Anti-Inflammatory Function

Inflammation is a consequence of an array of biological reactions that occur in response to pain sensation, local injury, and cell damage. A large number of studies have demonstrated that quercetin and other flavonoids show anti-inflammatory effects; thus, in the present work, we evaluated a triazine-phenol derivative (TP derivative) compound as a possible drug candidate with anti-inflammatory activity. This compound was studied as a possible anti-inflammatory drug using synthesis and characterization by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and mass spectrometry (MS). The derivative of melamine was evaluated for its antioxidant activity and exhibited good DPPH and FRAP antioxidant activity. Additionally, we evaluated the putative effect of the molecule on the COX-2 enzyme through molecular dynamic simulation (MDS), and the result suggested that the TP derivative is a potential anti-inflammatory agent that can interact with the COX-2 enzyme because of the high number of protein-ligand interactions observed with MDS. Finally, the study of theoretical physicochemical properties, the observation of low toxicity (hemolysis assay), and the evaluation of oral bioavailability of the TP derivative showed that it is a possible anti-inflammatory drug candidate.

Genetic and Histological Alterations Reveal Key Role of Prostaglandin Synthase and Cyclooxygenase 1 and 2 in Traumatic Brain Injury-Induced Neuroinflammation in the Cerebral Cortex of Rats Exposed to Moderate Fluid Percussion Injury

After the initial insult in traumatic brain injury (TBI), secondary neurodegeneration occurs that is intimately associated with neuroinflammation. Prostaglandin (PG) synthases and cyclooxygenase (COX) 1 and 2 may contribute to inflammation in the brain. Temporal and spatial expression features of PG and COX1 and 2 following trauma may guide the development of antineuroinflammation strategies. Here, we examined PG synthase signaling and COX1 and 2 gene expression levels and COX-1- and 2-positive cell types and their temporal localization in TBI-induced brain in an effort to reveal their participation in the disease’s evolving neuroinflammation. Using brain samples from the cerebral cortex of rats subjected to TBI model of lateral moderate fluid percussion injury (FPI), we sought to characterize the temporal (subacute TBI) and spatial (lateral cortical lesion) brain alterations accompanying the disease progression. Temporal gene expression changes of PG synthase signaling were compared between sham-operated and TBI-treated rats using microarray pathway analysis. Moreover, we examined COX1 and 2 expression patterns and their intracellular distribution in sham-operated and TBI-treated rats by immunohistochemistry. After FPI, COX1 and 2 gene expression levels, and PGE₂ synthase increased while PGD₂ synthase decreased, suggesting that PGE₂ and PGD₂ afforded contraindicative effects of inflammation and anti-inflammation, respectively. Immunohistochemical analyses showed that both COX1 and COX2 increased in a time-dependent manner in the brain, specifically in degenerating neurons of the cortex. Interestingly, the expression of COX cell type was cell-specific, in that COX1 was particularly increased in degenerating neurons while COX2 was expressed in macrophages. In view of the dynamic temporal and spatial expression of PG, COX1 and 2 gene expression and localization in the injured brain regulating PG synthase and COX1 and 2 activity will require a careful disease-specific tailoring of treatments to abrogate the neuroinflammation-plagued secondary cell death due to TBI.

Treatment of bipolar depression with minocycline and/or aspirin: an adaptive, 2×2 double-blind, randomized, placebo-controlled, phase IIA clinical trial

Given evidence of chronic inflammation in bipolar disorder (BD), we tested the efficacy of aspirin and minocycline as augmentation therapy for bipolar depression. Ninety-nine depressed outpatients with BD were enrolled in a 6 week, double-blind, placebo-controlled trial, and randomized to one of four groups: active minocycline (100 mg b.i.d.) + active aspirin (81 mg b.i.d.) (M + A); active minocycline + placebo aspirin (M + P); placebo-minocycline + active aspirin (A + P); and placebo-minocycline + placebo aspirin (P + P). A blinded interim analysis mid-way through the study led to the dropping of the M + P and A + P arms from further enrollment giving numbers per group who were included in the final analysis of: 30 (M + A), 18 (M + P), 19 (A + P), and 28 (P + P). When the study started, there were three primary outcome measures. Based on the results of the interim analysis, the primary outcome variable, response to treatment as defined by >50% decrease in Montgomery-Äsberg Depression Rating Scale (MADRS) score was maintained. The other two (i.e., the change in mean MADRS score from baseline to end of study and the remission rate, with remission being defined as a score of <11 on the MADRS) were reduced to exploratory outcome measures because the interim analysis indicated that the study was adequately powered to test differences in response rate but not the mean change in MADRS scores or remission rates. CRP and IL-6 were assayed to measure inflammation. Urinary thromboxane B2 (11-D-TXB₂) concentrations, which were significantly increased at baseline in the combined BD sample (n = 90) vs. a healthy control group (n = 27), served as an indirect marker of cyclooxygenase (COX) activity. In a two-group analysis, the M + A group showed a greater response rate than the P + P group (p(one-tailed) = 0.034, OR = 2.93, NNT = 4.7). When all four arms were included in the analysis, there was a main effect of aspirin on treatment response that was driven by both the M + A and the A + P groups (p(two-tailed) = 0.019, OR = 3.67, NNT = 4.0). Additionally, there was a significant 3-way interaction between aspirin, minocycline, and IL-6, indicating that response to minocycline was significantly greater in participants in the M + P group with higher IL-6 concentrations. Further, participants in the M + P group who responded to treatment had significantly greater decreases in IL-6 levels between baseline and visit 7 vs. non-responders. Regarding the exploratory outcomes, there was a main effect for aspirin on the remission rate (χ₁² = 4.14, p(2t) = 0.04, OR = 2.52, NNT = 8.0). There was no significant main effect of aspirin or minocycline on the mean change in MADRS score across visits. Aspirin and minocycline may be efficacious adjunctive treatments for bipolar depression. Given their potential import, additional studies to confirm and extend these findings are warranted.

Differential expression of E-type prostanoid receptors 2 and 4 in microglia stimulated with lipopolysaccharide

BACKGROUND

Cyclooxygenase-2 (COX-2) is induced under inflammatory conditions, and prostaglandin E₂ (PGE₂) is one of the products of COX activity. PGE₂ has pleiotropic actions depending on the activation of specific E-type prostanoid EP1-4 receptors. We investigated the involvement of PGE₂ and EP receptors in glial activation in response to an inflammatory challenge induced by LPS.

METHODS

Cultures of mouse microglia or astroglia cells were treated with LPS in the presence or absence of COX-2 inhibitors, and the production of PGE₂ was measured by ELISA. Cells were treated with PGE₂, and the effect on LPS-induced expression of TNF-α messenger RNA (mRNA) and protein was studied in the presence or absence of drug antagonists of the four EP receptors. EP receptor expression and the effects of EP2 and EP4 agonists and antagonists were studied at different time points after LPS.

RESULTS

PGE₂ production after LPS was COX-2-dependent. PGE₂ reduced the glial production of TNF-α after LPS. Microglia expressed higher levels of EP4 and EP2 mRNA than astroglia. Activation of EP4 or EP2 receptors with selective drug agonists attenuated LPS-induced TNF-α in microglia. However, only antagonizing EP4 prevented the PGE₂ effect demonstrating that EP4 was the main target of PGE₂ in naïve microglia. Moreover, the relative expression of EP receptors changed during the course of classical microglial activation since EP4 expression was strongly depressed while EP2 increased 24 h after LPS and was detected in nuclear/peri-nuclear locations. EP2 regulated the expression of iNOS, NADPH oxidase-2, and vascular endothelial growth factor. NADPH oxidase-2 and iNOS activities require the oxidation of NADPH, and the pentose phosphate pathway is a main source of NADPH. LPS increased the mRNA expression of the rate-limiting enzyme of the pentose pathway glucose-6-phosphate dehydrogenase, and EP2 activity was involved in this effect.

CONCLUSIONS

These results show that while selective activation of EP4 or EP2 exerts anti-inflammatory actions, EP4 is the main target of PGE₂ in naïve microglia. The level of EP receptor expression changes from naïve to primed microglia where the COX-2/PGE₂/EP2 axis modulates important adaptive metabolic changes.

Directed transport of neutrophil-derived extracellular vesicles enables platelet-mediated innate immune response

The innate immune response to bacterial infections requires the interaction of neutrophils and platelets. Here, we show that a multistep reciprocal crosstalk exists between these two cell types, ultimately facilitating neutrophil influx into the lung to eliminate infections. Activated platelets adhere to intravascular neutrophils through P-selectin/P-selectin glycoprotein ligand-1 (PSGL-1)-mediated binding, a primary interaction that allows platelets glycoprotein Ibα (GPIbα)-induced generation of neutrophil-derived extracellular vesicles (EV). EV production is directed by exocytosis and allows shuttling of arachidonic acid into platelets. EVs are then specifically internalized into platelets in a Mac1-dependent fashion, and relocated into intracellular compartments enriched in cyclooxygenase1 (Cox1), an enzyme processing arachidonic acid to synthesize thromboxane A₂ (TxA₂). Finally, platelet-derived-TxA₂ elicits a full neutrophil response by inducing the endothelial expression of ICAM-1, intravascular crawling, and extravasation. We conclude that critical substrate–enzyme pairs are compartmentalized in neutrophils and platelets during steady state limiting non-specific inflammation, but bacterial infection triggers regulated EV shuttling resulting in robust inflammation and pathogen clearance.

Interaction between platelets and neutrophils promotes neutrophil activation. Here the authors show that neutrophils initiate the cross-talk with platelets by shuttling arachidonic acid via extracellular vesicles, which platelets convert to thromboxane A₂ that then elicits neutrophil activation.

Changes in brain oxysterols at different stages of Alzheimer's disease: Their involvement in neuroinflammation

Alzheimer's disease (AD) is a gradually debilitating disease that leads to dementia. The molecular mechanisms underlying AD are still not clear, and at present no reliable biomarkers are available for the early diagnosis. In the last several years, together with oxidative stress and neuroinflammation, altered cholesterol metabolism in the brain has become increasingly implicated in AD progression. A significant body of evidence indicates that oxidized cholesterol, in the form of oxysterols, is one of the main triggers of AD. The oxysterols potentially most closely involved in the pathogenesis of AD are 24-hydroxycholesterol and 27-hydroxycholesterol, respectively deriving from cholesterol oxidation by the enzymes CYP46A1 and CYP27A1. However, the possible involvement of oxysterols resulting from cholesterol autooxidation, including 7-ketocholesterol and 7β-hydroxycholesterol, is now emerging. In a systematic analysis of oxysterols in post-mortem human AD brains, classified by the Braak staging system of neurofibrillary pathology, alongside the two oxysterols of enzymatic origin, a variety of oxysterols deriving from cholesterol autoxidation were identified; these included 7-ketocholesterol, 7α-hydroxycholesterol, 4β-hydroxycholesterol, 5α,6α-epoxycholesterol, and 5β,6β-epoxycholesterol. Their levels were quantified and compared across the disease stages. Some inflammatory mediators, and the proteolytic enzyme matrix metalloprotease-9, were also found to be enhanced in the brains, depending on disease progression. This highlights the pathogenic association between the trends of inflammatory molecules and oxysterol levels during the evolution of AD. Conversely, sirtuin 1, an enzyme that regulates several pathways involved in the anti-inflammatory response, was reduced markedly with the progression of AD, supporting the hypothesis that the loss of sirtuin 1 might play a key role in AD. Taken together, these results strongly support the association between changes in oxysterol levels and AD progression.

Fundamental role of pan-inflammation and oxidative-nitrosative pathways in neuropathogenesis of Alzheimer's disease in focal cerebral ischemic rats

Alzheimer's disease (AD) is a chronic progressive neurodegenerative condition of the brain, and it is the most common cause of dementia. Several neurobiological etiologies of AD are described in the literature. These include vascular, infectious, toxic, nutritional, metabolic, and inflammatory. However, these heterogeneous etiologies have a common denominator - viz. Inflammation and oxidative stress. Lipopolysaccharide (LPS) elevates the synthesis of proinflammatory cytokines and chemokines; chronically, together they trigger various pathological responses in the periphery and the CNS including dysfunctional memory consolidation and memory decline. Aging - the main risk factor for AD is inherently associated with inflammation. There are several age-related comorbidities that are also associated with inflammation and oxidative stress. Such co-prevailing aggravating factors, therefore, persist against a background of underlying aging-related pathology. They may converge, and their synergistic propagation may modify the disease course. A critical balance exists between homeostasis/repair and inflammatory factors; chronic, unrelenting inflammatory milieu succeeds in promoting a neuroinflammatory and neurodegenerative outcome. Extensive evidence is available that CNS inflammation is associated with neurodegeneration. LPS, proinflammatory cytokines, several mediators secreted by microglia, and oxidative-nitrosative stress in concert play a pivotal role in triggering neuroinflammatory processes and neurodegeneration. The persistent uncontrolled activity of the above factors can potentiate cognitive decline in tandem enhancing vulnerability to AD. Despite significant progress during the past twenty years, the prevention and treatment of AD have been tantalizingly elusive. Current studies strongly suggest that amelioration/prevention of the deleterious effects of inflammation may prove beneficial in preventing AD onset and retarding cognitive dysfunction in aging and AD. A concerted multi-focal therapeutic effort around the inflammation-oxidative-nitrosative stress paradigm may be crucial in preventing and treating AD. This paper informs on such relevant polypharmacy approach.

Fundamental role of pan-inflammation and oxidative-nitrosative pathways in neuropathogenesis of Alzheimer's disease

Alzheimer's disease (AD) is a chronic progressive neurodegenerative condition of the brain, and it is the most common cause of dementia. Several neurobiological etiologies of AD are described in the literature. These include vascular, infectious, toxic, nutritional, metabolic, and inflammatory. However, these heterogeneous etiologies have a common denominator - viz. Inflammation and oxidative stress. Lipopolysaccharide (LPS) elevates the synthesis of proinflammatory cytokines and chemokines; chronically, together they trigger various pathological responses in the periphery and the CNS including dysfunctional memory consolidation and memory decline. Aging - the main risk factor for AD is inherently associated with inflammation. There are several age-related comorbidities that are also associated with inflammation and oxidative stress. Such co-prevailing aggravating factors, therefore, persist against a background of underlying aging-related pathology. They may converge, and their synergistic propagation may modify the disease course. A critical balance exists between homeostasis/repair and inflammatory factors; chronic, unrelenting inflammatory milieu succeeds in promoting a neuroinflammatory and neurodegenerative outcome. Extensive evidence is available that CNS inflammation is associated with neurodegeneration. LPS, proinflammatory cytokines, several mediators secreted by microglia, and oxidative-nitrosative stress in concert play a pivotal role in triggering neuroinflammatory processes and neurodegeneration. The persistent uncontrolled activity of the above factors can potentiate cognitive decline in tandem enhancing vulnerability to AD. Despite significant progress during the past twenty years, the prevention and treatment of AD have been tantalizingly elusive. Current studies strongly suggest that amelioration/prevention of the deleterious effects of inflammation may prove beneficial in preventing AD onset and retarding cognitive dysfunction in aging and AD. A concerted multi-focal therapeutic effort around the inflammation-oxidative-nitrosative stress paradigm may be crucial in preventing and treating AD. This paper informs on such relevant polypharmacy approach.

COX-1 and COX-2 polymorphisms in susceptibility to cerebral palsy in very preterm infants

Cerebral palsy (CP) is a nonprogressive motor disorder caused by white matter damage in the developing brain. Recent epidemiological and clinical data suggest intrauterine infection/inflammation as the most common cause of preterm delivery and neonatal complications, including CP. Cyclooxygenases are key enzymes in the conversion of arachidonic acid to prostaglandins. The COX family consists of two isoforms, COX-1 and COX-2. In the brain, COX-2 is constitutively expressed at high levels on pyramidal neurons, while COX-1 is predominantly expressed by microglia and can be upregulated in pathological conditions, such as infection, ischemia and traumatic brain injury. Single nucleotide polymorphisms in the COX-1 and COX-2 gene could have profound effects on COX-1 and COX-2 expression and, directly or indirectly, influence the pathogenesis, development and severity of CP. In this study we investigated the association between single nucleotide polymorphisms of the COX-1 and COX-2 gene and susceptibility to cerebral palsy in very preterm infants. The results of our study showed the association between COX-1 high expression genotype (-842 AA) and COX-1 high expression allele -842A and risk of CP in infants with cystic periventricular leucomalacia (cPVL). Our results support an important role of COX-1 enzyme on microglial activation during neuroinflammation resulting in huge neuroinflammatory response and the proinflammatory mediator overproduction, with the serious white matter damage and CP development as a consequence.

Are Non-steroidal Anti-Inflammatory Drugs Clinically Suitable for the Treatment of Symptoms in Depression-Associated Inflammation?

The aetiology and pathophysiology of depression have long been associated with inflammation, at least in a proportion of patients. Altered cytokine activity in the periphery and in the brain has brought support to a concept of depression-associated inflammation. However, these immunological changes - and inflammation in particular - in depression have only been recently targeted for treatment. Non-steroidal anti-inflammatory drugs (NSAIDs) have been proposed to be of clinical use in the treatment of depression either as monotherapy or as adjuncts in combination with antidepressants. Specifically, selective cyclooxygenase (COX)-2 and non-selective COX inhibitor NSAIDs as adjuncts or monotherapy have been trialled clinically. A limited body of clinical research has been conducted with mixed results so far. Although meta-analyses appear to support the use of NSAIDs in acute depression, the overall effect is mainly biased by the effects of celecoxib for which the best evidence exists to date. Efficacy data of non-selective COX inhibitor NSAIDs on depressive symptoms is limited and out of six studies, only a retrospective analysis shows positive results for non-selective COX inhibitor. Clinical data on aspirin, an irreversible inhibitor of both COX-1 and COX-2, are mainly experimental and hypothetical at this stage, but may be promising in depressed patients with concomitant inflammatory conditions. The main problematic factor is that current evidence rests on trials in acute depression. Because of the dynamic nature of depression, it is important exploring if NSAIDs and other anti-inflammatory treatments may have a preventive role in early stages of depression and for relapse prevention. The possible impact of anti-inflammatory treatments on immune changes in different phases of depression warrants caution for a wide and preventive use of anti-inflammatory agents in depression-associated inflammation.

Cyclooxygenase I and II inhibitors distinctly enhance hippocampal- and cortex-dependent cognitive functions in mice

Cyclooxygenase (COX) enzymes are expressed in the brain; however, their role in hippocampus-dependent and cortex-dependent cognitive functions remains to be fully elucidated. The aim of the present study was to comparatively investigate the effects of piroxicam, a selective COX-I inhibitor, and celecoxib, a selective COX‑II inhibitor, on cognitive functions in an AlCl3‑induced neurotoxicity mouse model to understand the specific role of each COX enzyme in the hippocampus and cortex. The AlCl3 (250 mg/kg) was administered to the mice in drinking water and the drugs were administered in feed for 30 days. Assessments of memory, including a Morris water maze, social behavior and nesting behavior were performed in control and treated mice. The RNA expression of the COX enzymes were analyzed using reverse transcription‑quantitative polymerase chain reaction analysis. An ex‑vivo 2,2‑Diphenyl‑1‑picrylhydrazyl assay was performed in the hippocampus and cortex. Following 30 days of treatment with thedrugs, the mice in the celecoxib‑ and piroxicam‑treated groups exhibited enhanced learning (6.84 ± 0.76 and 9.20 ± 1.08, respectively), compared with the AlCl3‑induced neurotoxicity group (21.14 ± 0.76) on the fifth day of the Morris water maze test. Celecoxib treatment improved social affiliation in the AlCl3‑induced neurotoxicity group, the results of which were superior to piroxicam. Piroxicam led to better improvement in nesting score in the AlCl3‑induced neurotoxicity group. Both drugs decreased the expression levels of COX‑I and COX‑II in the hippocampus and cortex, and rescued oxidative stress levels. These findings suggested that each drug distinctly affected cognitive functions, highlighting the distinctive roles of COX-I and COX-II in learning and memory.

Testosterone induces leucocyte migration by NADPH oxidase-driven ROS- and COX2-dependent mechanisms

The mechanisms whereby testosterone increases cardiovascular risk are not clarified. However, oxidative stress and inflammation seem to be determinants. Herein, we sought to determine whether exogenous testosterone, at physiological levels, induces leucocyte migration, a central feature in immune and inflammatory responses and the mediating mechanisms. We hypothesized that testosterone induces leucocyte migration via NADPH oxidase (NADPHox)-driven reactive oxygen species (ROS) and cyclooxygenase (COX)-dependent mechanisms. Sixteen-week-old Wistar rats received an intraperitoneal injection (5 ml) of either testosterone (10(-7) mol/l) or saline. Rats were pre-treated with 5 ml of sodium salicylate (SS, non-selective COX inhibitor, 1.25 × 10(-3) mol/l, 1 h prior to testosterone or saline), flutamide (androgen receptor antagonist, 10(-5) mol/l), apocynin (NADPHox inhibitor, 3 × 10(-4) mol/l), N-[2-Cyclohexyloxy-4-nitrophenyl]methanesulfonamide (NS398, COX2 inhibitor, 10(-4) mol/l) or saline, 4 h before testosterone or saline administration. Leucocyte migration was assessed 24 h after testosterone administration by intravital microscopy of the mesenteric bed. Serum levels of testosterone were measured by radioimmunoassay. NADPHox activity was assessed in membrane fractions of the mesenteric bed by dihydroethidium (DHE) fluorescence and in isolated vascular smooth muscle cells (VSMC) by HPLC. NADPHox subunits and VCAM (vascular cell adhesion molecule) expression were determined by immunoblotting. Testosterone administration did not change serum levels of endogenous testosterone, but increased venular leucocyte migration to the adventia, NADPHox activity and expression (P < 0.05). These effects were blocked by flutamide. SS inhibited testosterone-induced leucocyte migration (P<0.05). Apocynin and NS398 abolished testosterone-induced leucocyte migration and NADPHox activity (P<0.05). Testosterone induces leucocyte migration via NADPHox- and COX2-dependent mechanisms and may contribute to inflammatory processes and oxidative stress in the vasculature potentially increasing cardiovascular risk.

A critical review of the efficacy of non-steroidal anti-inflammatory drugs in depression

Non-steroidal anti-inflammatory drugs (NSAIDs) require further investigation given mixed results regarding efficacy. We critically and systematically reviewed the literature to determine whether selective COX-2 and non-selective COX inhibitor NSAIDs as adjuncts or monotherapy affect depressive symptoms. Electronic databases including Embase, PsycINFO, Ovid Medline, ScienceDirect, Google Scholar and the Cochrane Central Register of Controlled Trials database were searched up to September 2013. We utilised randomised controlled trials (RCTs), cohort studies and an open label study examining the efficacy of NSAIDs as adjuncts or monotherapy on depressive symptoms in subjects without major comorbidities. There were a total of 6 studies exploring the efficacy of selective COX-2 inhibitor NSAIDs on depressive symptoms with a total of 2706 subjects from 6 RCTs. 4 of the RCTs showed a significant effect of NSAIDs; 2 demonstrated no effect. There were a total of 5 studies exploring the efficacy of non-selective COX inhibitor NSAIDs on depressive symptoms with a total of 7978 subjects. There was 1 RCT, 3 cohort studies and 1 open label pilot study. The RCT failed to show a significant result. 1 of the retrospective cohort studies showed a positive result, with the other 2 showing no effect. The pilot study showed a positive result for NSAIDs. These studies demonstrated significant methodological heterogeneity (i.e. age range, sex, presence of antidepressant use, method of depression measure, severity of depressive symptoms, duration and study design (RCT vs. cohort)). The efficacy of NSAIDs on depressive symptoms appears negligible, however firm conclusions are difficult given the inconsistent findings and substantial methodological heterogeneity. Further high quality research is needed to explore NSAID efficacy in clinical and biological subtypes of depression, as monotherapy and adjunct with various antidepressants, and across various ages.

Polyunsaturated fatty acids and their metabolites in brain function and disease

The brain is highly enriched with fatty acids. These include the polyunsaturated fatty acids (PUFAs) arachidonic acid and docosahexaenoic acid, which are largely esterified to the phospholipid cell membrane. Once PUFAs are released from the membrane, they can participate in signal transduction, either directly or after enzymatic conversion to a variety of bioactive derivatives ('mediators'). PUFAs and their mediators regulate several processes within the brain, such as neurotransmission, cell survival and neuroinflammation, and thereby mood and cognition. PUFA levels and the signalling pathways that they regulate are altered in various neurological disorders, including Alzheimer's disease and major depression. Diet and drugs targeting PUFAs may lead to novel therapeutic approaches for the prevention and treatment of brain disorders.

COX-1-derived thromboxane A2 plays an essential role in early B-cell development via regulation of JAK/STAT5 signaling in mouse

Cyclooxygenases (COXs) and their prostanoid products play important roles in a diverse range of physiological processes, including in the immune system. Here, we provide evidence that COX-1 is an essential regulator in early stages of B-cell development. COX-1-deficient mice displayed systematic reduction in total B cells, which was attributed to the arrest of early B-cell development from pro-B to pre-B stage. We further demonstrated that this defect was mediated through downregulation of the Janus kinase/signal transducer and activator of transcription 5 (JAK/STAT5) signaling and its target genes, including Pax5, in COX-1(-/-) mice. Mechanistic studies revealed that COX-1-derived thromboxane A2 (TxA2) could regulate JAK3/STAT5 signaling through the cyclic adenosine monophosphate-protein kinase A pathway, via binding with its receptor thromboxane A2 receptor (TP). Administration of the TP agonist could rescue the defective B-cell development and JAK/STAT5 signaling activity in COX-1-deficient mice. Moreover, administration of low-dose aspirin caused a significant reduction in total B cells in peripheral blood of healthy human volunteers, coincidentally with reduced TxA2 production and downregulation of JAK/STAT5 signaling. Taken together, our results demonstrate that COX-1-derived TxA2 plays a critical role in the stage transition of early B-cell development through regulation of JAK/STAT5 signaling and indicate a potential immune-suppressive effect of low-dose aspirin in humans.

Plexin-A1 is required for Toll-like receptor-mediated microglial activation in the development of lipopolysaccharide-induced encephalopathy

Recent investigations have suggested that semaphorins, which are known repulsive axon guidance molecules, may play a crucial role in maintaining brain homeostasis by regulating microglial activity. Sema3A, secreted in higher amounts from injured neurons, is considered to suppress excessive inflammatory responses by inducing microglial apoptosis through its binding to Plexin-A1 receptors on activated microglia. To clarify the in vivo role of Plexin-A1-mediated signaling in lipopolysaccharide (LPS)-induced injury in mouse brain, we examined the neuroinflammatory changes initiated by LPS administration to the cerebral ventricles of wild-type (WT) and Plexin-A1-deficient (−/−) mice. WT mice administered LPS exhibited a significantly higher expression of COX-2, iNOS, IL-1β and TNF-α in the hippocampus, and a significantly greater ventricular enlargement and intracerebral infiltration of leukocytes, as compared with the saline-treated group. By contrast, Plexin-A1−/− mice administered LPS did not exhibit a significantly increased expression of COX-2, iNOS, IL-1β or TNF-α in the hippocampus as compared with the saline-treated group. Plexin-A1−/− mice administered LPS did not show significant increases in ventricle size or infiltration of leukocytes into the brain, as compared with the saline-treated group. In WT, but not in the Plexin-A1−/− primary microglia treated with LPS, Sema3A induced significantly more nitric oxide production than in the immunoglobulin G control. These results revealed the crucial role of the Sema3A-Plexin-A1 interaction in the Toll-like receptor 4-mediated signaling of the LPS-induced activation of microglia. Thus, results of the present study revealed the essential role of Plexin-A1 in the development of LPS-induced neuroinflammation in mice, suggesting the possible application of microglial control of the semaphorin-plexin signaling system to the treatment of LPS-induced encephalopathy and other psychiatric diseases associated with neuroinflammation.

Bridge between neuroimmunity and traumatic brain injury

The pathophysiology of degenerative, infectious, inflammatory and traumatic diseases of the central nervous system includes a significant immune component. As to the latter, damage to the cerebral vasculature and neural cell bodies, caused by traumatic brain injury (TBI) activates innate immunity with concomitant infiltration of immunocytes into the damaged nervous system. This leads to proinflammatory cytokine and prostaglandin production and lost synaptic integrity and more generalized neurotoxicity. Engagement of adaptive immune responses follows including the production of antibodies and lymphocyte proliferation. These affect the tempo of disease along with tissue repair and as such provide a number of potential targets for pharmacological treatments for TBI. However, despite a large body of research, no such treatment intervention is currently available. In this review we will discuss the immune response initiated following brain injuries, drawing on knowledge gained from a broad array of experimental and clinical studies. Our discussion seeks to address potential therapeutic targets and propose ways in which the immune system can be controlled to promote neuroprotection.

Cyclooxygenase-2 deficiency in macrophages leads to defective p110γ PI3K signaling and impairs cell adhesion and migration

Cyclooxygenase (Cox)-2 dependent PGs modulate several functions in many pathophysiological processes, including migration of immune cells. In this study, we addressed the role of Cox-2 in macrophage migration by using in vivo and in vitro models. Upon thioglycolate challenge, CD11b(+) F4/80(+) macrophages showed a diminished ability to migrate to the peritoneal cavity in cox-2(-/-) mice. In vivo migration of cox-2(-/-) macrophages from the peritoneal cavity to lymph nodes, as well as cell adhesion to the mesothelium, was reduced in response to LPS. In vitro migration of cox-2(-/-) macrophages toward MCP-1, RANTES, MIP-1α, or MIP-1β, as well as cell adhesion to ICAM-1 or fibronectin, was impaired. Defects in cell migration were not due to changes in chemokine receptor expression. Remarkably, cox-2(-/-) macrophages showed a deficiency in focal adhesion formation, with reduced phosphorylation of paxillin (Tyr(188)). Interestingly, expression of the p110γ catalytic subunit of PI3K was severely reduced in the absence of Cox-2, leading to defective Akt phosphorylation, as well as cdc42 and Rac-1 activation. Our results indicate that the paxillin/p110γ-PI3K/Cdc42/Rac1 axis is defective in cox-2(-/-) macrophages, which results in impaired cell adhesion and migration.

Celecoxib attenuates systemic lipopolysaccharide-induced brain inflammation and white matter injury in the neonatal rats

Lipopolysaccharide (LPS)-induced white matter injury in the neonatal rat brain is associated with inflammatory processes. Cyclooxygenase-2 (COX-2) can be induced by inflammatory stimuli, such as cytokines and pro-inflammatory molecules, suggesting that COX-2 may be considered as the target for anti-inflammation. The objective of the present study was to examine whether celecoxib, a selective COX-2 inhibitor, can reduce systemic LPS-induced brain inflammation and brain damage. Intraperitoneal (i.p.) injection of LPS (2mg/kg) was performed in postnatal day 5 (P5) of Sprague-Dawley rat pups and celecoxib (20mg/kg) or vehicle was administered i.p. 5 min after LPS injection. The body weight and wire-hanging maneuver test was performed 24h after the LPS exposure, and brain injury was examined after these tests. Systemic LPS exposure resulted in an impairment of behavioral performance and acute brain injury, as indicated by apoptotic death of oligodendrocytes (OLs) and loss of OL immunoreactivity in the neonatal rat brain. Treatments with celecoxib significantly reduced systemic LPS-induced neurobehavioral disturbance and brain damage. Celecoxib administration significantly attenuated systemic LPS-induced increments in the number of activated microglia and astrocytes, concentrations of IL-1β and TNFα, and protein levels of phosphorylated-p38 MAPK in the neonatal rat brain. The protection of celecoxib was also associated with a reduction of systemic LPS-induced COX-2+ cells which were double labeled with GFAP+ (astrocyte) cells. The overall results suggest that celecoxib was capable of attenuating the brain injury and neurobehavioral disturbance induced by systemic LPS exposure, and the protective effects are associated with its anti-inflammatory properties.

Cyclooxygenase-1 inhibition reduces amyloid pathology and improves memory deficits in a mouse model of Alzheimer's disease

Several epidemiological and preclinical studies suggest that non-steroidal anti-inflammatory drugs (NSAIDs), which inhibit cyclooxygenase (COX), reduce the risk of Alzheimer's disease (AD) and can lower β-amyloid (Aβ) production and inhibit neuroinflammation. However, follow-up clinical trials, mostly using selective cyclooxygenase (COX)-2 inhibitors, failed to show any beneficial effect in AD patients with mild to severe cognitive deficits. Recent data indicated that COX-1, classically viewed as the homeostatic isoform, is localized in microglia and is actively involved in brain injury induced by pro-inflammatory stimuli including Aβ, lipopolysaccharide, and interleukins. We hypothesized that neuroinflammation is critical for disease progression and selective COX-1 inhibition, rather than COX-2 inhibition, can reduce neuroinflammation and AD pathology. Here, we show that treatment of 20-month-old triple transgenic AD (3 × Tg-AD) mice with the COX-1 selective inhibitor SC-560 improved spatial learning and memory, and reduced amyloid deposits and tau hyperphosphorylation. SC-560 also reduced glial activation and brain expression of inflammatory markers in 3 × Tg-AD mice, and switched the activated microglia phenotype promoting their phagocytic ability. The present findings are the first to demonstrate that selective COX-1 inhibition reduces neuroinflammation, neuropathology, and improves cognitive function in 3 × Tg-AD mice. Thus, selective COX-1 inhibition should be further investigated as a potential therapeutic approach for AD.

Lentiviral infection of rhesus macaques causes long-term injury to cortical and hippocampal projections of prostaglandin-expressing cholinergic basal forebrain neurons

The simian immunodeficiency virus (SIV) macaque model resembles human immunodeficiency virus-acquired immunodeficiency syndrome (AIDS) and associated brain dysfunction. Altered expression of synaptic markers and transmitters in neuro-AIDS has been reported, but limited data exist for the cholinergic system and lipid mediators such as prostaglandins. Here, we analyzed cholinergic basal forebrain neurons with their telencephalic projections and the rate-limiting enzymes for prostaglandin synthesis, cyclooxygenase isotypes 1 and 2 (COX1 and COX2) in the brains of SIV-infected macaques with or without encephalitis and antiretroviral therapy and uninfected controls.Cyclooxygenase isotype 1, but not COX2, was coexpressed with markers of cholinergic phenotype, that is, choline acetyltransferase and vesicular acetylcholine transporter (VAChT), in basal forebrain neurons of monkey, as well as human, brain. Cyclooxygenase isotype 1 was decreased in basal forebrain neurons in macaques with AIDS versus uninfected and asymptomatic SIV-infected macaques. The VAChT-positive fiber density was reduced in frontal, parietal, and hippocampal-entorhinal cortex. Although brain SIV burden and associated COX1- and COX2-positive mononuclear and endothelial inflammatory reactions were mostly reversed in AIDS-diseased macaques that received 6-chloro-2',3'-dideoxyguanosine treatment, decreased VAChT-positive terminal density and reduced cholinergic COX1 expression were not. Thus, COX1 expression is a feature of primate cholinergic basal forebrain neurons; it may be functionally important and a critical biomarker of cholinergic dysregulation accompanying lentiviral encephalopathy. These results further imply that insufficiently prompt initiation of antiretroviral therapy in lentiviral infection may lead to neurostructurally unremarkable but neurochemically prominent irreversible brain damage.

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.

Minocycline and aspirin in the treatment of bipolar depression: a protocol for a proof-of-concept, randomised, double-blind, placebo-controlled, 2x2 clinical trial

INTRODUCTION

New medication classes are needed to improve treatment effectiveness in the depressed phase of bipolar disorder (BD). Extant evidence suggests that BD is characterised by neural changes such as dendritic remodelling and glial and neuronal cell loss. These changes have been hypothesised to result from chronic inflammation. The principal aims of the proposed research is to evaluate the antidepressant efficacy in bipolar depression of minocycline, a drug with neuroprotective and immune-modulating properties, and of aspirin, at doses expected to selectively inhibit cyclooxygenase 1 (COX-1).

METHODS AND ANALYSIS

120 outpatients between 18 and 55 years of age, who meet DSM-IV-TR criteria for BD (type I or II) and for a current major depressive episode will be recruited to take part in a randomised, double-blind, placebo-controlled, parallel-group, proof-of-concept clinical trial following a 2×2 design. As adjuncts to existing treatment, subjects will be randomised to receive one of the four treatment combinations: placebo-minocycline plus placebo-aspirin, active-minocycline plus placebo-aspirin, placebo-minocycline plus active-aspirin or active-minocycline plus active-aspirin. The dose of minocycline and aspirin is 100 mg twice daily and 81 mg twice daily, respectively. Antidepressant response will be evaluated by assessing changes in the Montgomery-Asberg Depression Rating Scale scores between baseline and the end of the 6-week trial. As secondary outcome measures, the anti-inflammatory effects of minocycline and aspirin will be tested by measuring pre-treatment and post-treatment levels of C reactive protein and inflammatory cytokines.

ETHICS AND DISSEMINATION

Minocycline has been widely used as an antibiotic in doses up to 400 mg/day. Low-dose aspirin has been safely used on a worldwide scale for its role as an antithrombotic and thrombolytic. The study progress will be overseen by a Data, Safety and Monitoring Board, which will meet once every 6 months. Results of the study will be published in peer-reviewed publications.

TRIAL REGISTRATION NUMBER

Clinical Trials.gov: NCT01429272.

Inhibition of NADPH oxidase promotes alternative and anti-inflammatory microglial activation during neuroinflammation

Like macrophages, microglia are functionally polarized into different phenotypic activation states, referred as classical and alternative. The balance of the two phenotypes may be critical to ensure proper brain homeostasis, and may be altered in brain pathological states, such as Alzheimer's disease. We investigated the role of NADPH oxidase in microglial activation state using p47(phox) and gp91(phox) -deficient mice as well as apocynin, a NADPH oxidase inhibitor during neuroinflammation induced by an intracerebroventricular injection of LPS or Aβ₁₋₄₂. We showed that NADPH oxidase plays a critical role in the modulation of microglial phenotype and subsequent inflammatory response. We demonstrated that inhibition of NADPH oxidase or gene deletion of its functional p47(phox) subunit switched microglial activation from a classical to an alternative state in response to an inflammatory challenge. Moreover, we showed a shift in redox state towards an oxidized milieu and that subpopulations of microglia retain their detrimental phenotype in Alzheimer's disease brains. Microglia can change their activation phenotype depending on NADPH oxidase-dependent redox state of microenvironment. Inhibition of NADPH oxidase represents a promising neuroprotective approach to reduce oxidative stress and modulate microglial phenotype towards an alternative state.

Cyclooxygenase-1 is involved in the inhibition of hippocampal neurogenesis after lipopolysaccharide-induced neuroinflammation

Growing evidence indicates that neuroinflammation can alter adult neurogenesis by mechanisms as yet unclear. We have previously demonstrated that the neuroinflammatory response and neuronal damage after lipopolysaccharide (LPS) injection is reduced in cyclooxygenase-1 deficient (COX-1(-/-)) mice. In this study, we investigated the role of COX-1 on hippocampal neurogenesis during LPS-induced neuroinflammation, using COX-1(-/-) and wild type (WT) mice. We found that LPS-induced neuroinflammation resulted in the decrease of proliferation, survival and differentiation of hippocampal progenitor cells in WT but not in COX-1(-/-) mice. Thus, we demonstrate for the first time that COX-1 is involved in the inhibition of BrdU progenitor cells in proliferation and hippocampal neurogenesis after LPS. These results suggest that COX-1 may represent a viable therapeutic target to reduce neuroinflammation and promote neurogenesis in neurodegenerative diseases with a strong inflammatory component.

COX1 and COX2 expression in non-neuronal cellular compartments of the rhesus macaque brain during lentiviral infection

Recent evidence suggests that cyclooxygenases COX1 and COX2 differentially affect brain immunity. Limited data exist about their expressional changes in neurodegenerative diseases such as neuro-AIDS. Here, we analyzed the regulation of non-neuronal COX1/2 expression in rhesus macaque brain during infection with SIV(δ670) and antiretroviral treatment. COX1 was constitutively expressed in microglia and endothelial cells and was not changed in early SIV infection. Late stage of disease was characterized by increased COX1 expression in globally activated microglia, macrophage nodules, infiltrates, and multinucleated giant cells. Endothelial COX1 expression was unaltered. In contrast, COX2 was not expressed in non-neuronal cells in the brain of uninfected and asymptomatically SIV-infected monkeys but was induced in nodule- and syncytium-forming macrophages and in endothelial cells in areas with infiltrates and SIV in monkeys with AIDS. Antiretroviral treatment of AIDS-diseased monkeys with 6-chloro-2',3'-dideoxyguanosine markedly reduced SIV burden, appearance of COX1-positive macrophage nodules, giant cells, and infiltrates, and COX2 induction in the brain. However, the number of COX1-positive diffuse microglia was still increased in antiretrovirally treated animals as compared to uninfected or asymptomatic SIV-infected monkeys. Our data imply that both COX isoforms are differentially regulated and may distinctly modulate local immune responses in the brain during lentiviral disease.

Targeting cyclooxygenases-1 and -2 in neuroinflammation: Therapeutic implications

Neuroinflammation has been implicated in the pathogenesis or the progression of a variety of acute and chronic neurological and neurodegenerative disorders, including Alzheimer's disease. Prostaglandin H synthases or cyclooxygenases (COX -1 and COX-2) play a central role in the inflammatory cascade by converting arachidonic acid into bioactive prostanoids. In this review, we highlighted recent experimental data that challenge the classical view that the inducible isoform COX-2 is the most appropriate target to treat neuroinflammation. First, we discuss data showing that COX-2 activity is linked to anti-inflammatory and neuroprotective actions and is involved in the generation of novel lipid mediators with pro-resolution properties. Then, we review recent data demonstrating that COX-1, classically viewed as the homeostatic isoform, is actively involved in brain injury induced by pro-inflammatory stimuli including Aβ, lipopolysaccharide, IL-1β, and TNF-α. Overall, we suggest revisiting the traditional views on the roles of each COX during neuroinflammation and we propose COX-1 inhibition as a viable therapeutic approach to treat CNS diseases with a marked inflammatory component.

Neuronal overexpression of cyclooxygenase-2 does not alter the neuroinflammatory response during brain innate immune activation

Neuroinflammation is a critical component in the progression of several neurological and neurodegenerative diseases and cyclooxygenases (COX)-1 and -2 are key regulators of innate immune responses. We recently demonstrated that COX-1 deletion attenuates, whereas COX-2 deletion enhances, the neuroinflammatory response, blood-brain barrier permeability and leukocyte recruitment during lipopolysaccharide (LPS)-induced innate immune activation. Here, we used transgenic mice, which overexpressed human COX-2 via neuron-specific Thy-1 promoter (TgCOX-2), causing elevated prostaglandins (PGs) levels. We tested whether neuronal COX-2 overexpression affects the glial response to a single intracerebroventricular injection of LPS, which produces a robust neuroinflammatory reaction. Relative to non-transgenic controls (NTg), 7 month-old TgCOX-2 did not show any basal neuroinflammation, as assessed by gene expression of markers of inflammation and oxidative stress, neuronal damage, as assessed by Fluoro-JadeB staining, or systemic inflammation, as assessed by plasma levels of IL-1beta and corticosterone. Twenty-four hours after LPS injection, all mice showed increased microglial activation, as indicated by Iba1 immunostaining, neuronal damage, mRNA expression of cytokines (TNF-alpha, IL-6), reactive oxygen expressing enzymes (iNOS and NADPH oxidase subunits), endogenous COX-2, cPLA(2) and mPGES-1, and hippocampal and cortical IL-1beta levels. However, the increases were similar in TgCOX-2 and NTg. In NTg, LPS increased brain PGE(2) to the levels observed in TgCOX-2. These results suggest that PGs derived from neuronal COX-2 do not play a role in the neuroinflammatory response to acute activation of brain innate immunity. This is likely due to the direct effect of LPS on glial rather than neuronal cells.