Cyclooxygenase-1 and -2 differentially modulate lipopolysaccharide-induced blood-brain barrier disruption through matrix metalloproteinase activity

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.

Matrix metalloproteinase 9 (MMP-9) activity, hippocampal extracellular free water, and cognitive deficits are associated with each other in early phase psychosis

Increasing evidence points toward the role of the extracellular matrix, specifically matrix metalloproteinase 9 (MMP-9), in the pathophysiology of psychosis. MMP-9 is a critical regulator of the crosstalk between peripheral and central inflammation, extracellular matrix remodeling, hippocampal development, synaptic pruning, and neuroplasticity. Here, we aim to characterize the relationship between plasma MMP-9 activity, hippocampal microstructure, and cognition in healthy individuals and individuals with early phase psychosis. We collected clinical, blood, and structural and diffusion-weighted magnetic resonance imaging data from 39 individuals with early phase psychosis and 44 age and sex-matched healthy individuals. We measured MMP-9 plasma activity, hippocampal extracellular free water (FW) levels, and hippocampal volumes. We used regression analyses to compare MMP-9 activity, hippocampal FW, and volumes between groups. We then examined associations between MMP-9 activity, FW levels, hippocampal volumes, and cognitive performance assessed with the MATRICS battery. All analyses were controlled for age, sex, body mass index, cigarette smoking, and years of education. Individuals with early phase psychosis demonstrated higher MMP-9 activity (p < 0.0002), higher left (p < 0.05) and right (p < 0.05) hippocampal FW levels, and lower left (p < 0.05) and right (p < 0.05) hippocampal volume than healthy individuals. MMP-9 activity correlated positively with hippocampal FW levels (all participants and individuals with early phase psychosis) and negatively with hippocampal volumes (all participants and healthy individuals). Higher MMP-9 activity and higher hippocampal FW levels were associated with slower processing speed and worse working memory performance in all participants. Our findings show an association between MMP-9 activity and hippocampal microstructural alterations in psychosis and an association between MMP-9 activity and cognitive performance. Further, more extensive longitudinal studies should examine the therapeutic potential of MMP-9 modulators in psychosis.

Deciphering the interplay between LPS/TLR4 pathways, neurotransmitter, and deltamethrin-induced depressive-like behavior: Perspectives from the gut-brain axis

The improper use of deltamethrin (DM) can result in its accumulation in soil, water, food, and even the human body, which is associated with an elevated risk of neurotoxicity and behavioral abnormalities; however, the underlying mechanisms remain insufficiently investigated. Emerging evidence underscores the significance of the gut-brain axis in central nervous system (CNS) dysfunctions. Accordingly, this study investigates the role of the gut-brain axis in DM-induced behavioral anomalies in mice. The results showed that DM exposure induced depressive-like behavior, and the hippocampus, the region that is responsible for the modulation of emotional behavior, showed structural integrity disrupted (neuronal nuclear shrinkage and decreased tight junction protein expression). In addition, DM exposure led to compromised gut barrier integrity (disruptions on crypt surfaces and decreased tight junction protein expression), which might contribute to the gut bacterial-derived lipopolysaccharide (LPS) leakage into the bloodstream and reaching the brain, triggering LPS/toll-like receptor (TLR) 4 -mediated increases in brain pro-inflammatory cytokines. Subsequently, we observed a disturbance in neurotransmitter metabolic pathways following DM exposure, which inhibited the production of 5-hydroxytryptamine (5-HT). Additionally, DM exposure resulted in gut microbiota dysbiosis. Characteristic bacteria, such as Alistipes, Bifidobacterium, Gram-negative bacterium cTPY-13, and Odoribacter exhibited significant correlations with behavior, tight junction proteins, inflammatory response, and neurotransmitters. Further fecal microbiota transplantation (FMT) experiments suggested that DM-induced gut microbiota dysbiosis might contribute to depressive-like behavior. These results provide a new perspective on the toxicity mechanism of DM, indicating that its neurotoxicity may be partially regulated by the microbiota-gut-brain axis.

The contribution of inflammatory astrocytes to BBB impairments in a brain-chip model of Parkinson's disease

Astrocyte dysfunction has previously been linked to multiple neurodegenerative disorders including Parkinson's disease (PD). Among their many roles, astrocytes are mediators of the brain immune response, and astrocyte reactivity is a pathological feature of PD. They are also involved in the formation and maintenance of the blood-brain barrier (BBB), but barrier integrity is compromised in people with PD. This study focuses on an unexplored area of PD pathogenesis by characterizing the interplay between astrocytes, inflammation and BBB integrity, and by combining patient-derived induced pluripotent stem cells with microfluidic technologies to generate a 3D human BBB chip. Here we report that astrocytes derived from female donors harboring the PD-related LRRK2 G2019S mutation are pro-inflammatory and fail to support the formation of a functional capillary in vitro. We show that inhibition of MEK1/2 signaling attenuates the inflammatory profile of mutant astrocytes and rescues BBB formation, providing insights into mechanisms regulating barrier integrity in PD. Lastly, we confirm that vascular changes are also observed in the human postmortem substantia nigra of both males and females with PD.

Neuroinflammation related to the blood-brain barrier and sphingosine-1-phosphate in a pre-clinical model of periodontal diseases and depression in rats

AIM

To explore the potential mechanisms of neuroinflammation (microglia, blood-brain barrier [BBB] permeability, and the sphingosine-1-phosphate [S1P] pathways) resulting from the association between periodontitis and depression in rats.

MATERIALS AND METHODS

This pre-clinical in vivo experimental study used Wistar rats, in which experimental periodontitis (P) was induced by using oral gavages with Porphyromonas gingivalis and Fusobacterium nucleatum. Then, a chronic mild stress (CMS) model was implemented to induce a depressive-like behaviour, resulting in four groups: P with CMS (P+CMS+), P without CMS (P+CMS-), CMS without P (P-CMS+), and control (P-CMS-). After harvesting brain samples, protein/mRNA expression analyses and fluorescence immunohistochemistry were performed in the frontal cortex (FC). Results were analysed by ANOVA.

RESULTS

CMS exposure increased the number of microglia (an indicator of neuroinflammation) in the FC. In the combined model (P+CMS+), there was a decrease in the expression of tight junction proteins (zonula occludens-1 [ZO-1], occludin) and an increase in intercellular and vascular cell adhesion molecules (ICAM-1, VCAM-1) and matrix metalloproteinase 9 (MMP9), suggesting a more severe disruption of the BBB. The enzymes and receptors of S1P were also differentially regulated.

CONCLUSIONS

Microglia, BBB permeability, and S1P pathways could be relevant mechanisms explaining the association between periodontitis and depression.

Fluorine-18 Labelled Radioligands for PET Imaging of Cyclooxygenase-2

Molecular imaging probes enable the early and accurate detection of disease-specific biomarkers and facilitate personalized treatment of many chronic diseases, including cancer. Among current clinically used functional imaging modalities, positron emission tomography (PET) plays a significant role in cancer detection and in monitoring the response to therapeutic interventions. Several preclinical and clinical studies have demonstrated the crucial involvement of cyclooxygenase-2 (COX-2) isozyme in cancer development and progression, making COX-2 a promising cancer biomarker. A variety of COX-2-targeting PET radioligands has been developed based on anti-inflammatory drugs and selective COX-2 inhibitors. However, many of those suffer from non-specific binding and insufficient metabolic stability. This article highlights examples of COX-2-targeting PET radioligands labelled with the short-lived positron emitter ¹⁸F, including radiosynthesis and PET imaging studies published in the last decade (2012–2021).

Microglial Activation Damages Dopaminergic Neurons through MMP-2/-9-Mediated Increase of Blood-Brain Barrier Permeability in a Parkinson's Disease Mouse Model

Chronic neuroinflammation has been considered to be involved in the progressive dopaminergic neurodegeneration in Parkinson’s disease (PD). However, the mechanisms remain unknown. Accumulating evidence indicated a key role of the blood–brain barrier (BBB) dysfunction in neurological disorders. This study is designed to elucidate whether chronic neuroinflammation damages dopaminergic neurons through BBB dysfunction by using a rotenone-induced mouse PD model. Results showed that rotenone dose-dependently induced nigral dopaminergic neurodegeneration, which was associated with increased Evans blue content and fibrinogen accumulation as well as reduced expressions of zonula occludens-1 (ZO-1), claudin-5 and occludin, three tight junction proteins for maintaining BBB permeability, in mice, indicating BBB disruption. Rotenone also induced nigral microglial activation. Depletion of microglia or inhibition of microglial activation by PLX3397 or minocycline, respectively, greatly attenuated BBB dysfunction in rotenone-lesioned mice. Mechanistic inquiry revealed that microglia-mediated activation of matrix metalloproteinases-2 and 9 (MMP-2/-9) contributed to rotenone-induced BBB disruption and dopaminergic neurodegeneration. Rotenone-induced activation of MMP-2/-9 was significantly attenuated by microglial depletion and inactivation. Furthermore, inhibition of MMP-2/-9 by a wide-range inhibitor, SB-3CT, abrogated elevation of BBB permeability and simultaneously increased tight junctions expression. Finally, we found that microglial depletion and inactivation as well as inhibition of MMP-2/-9 significantly ameliorated rotenone-elicited nigrostriatal dopaminergic neurodegeneration and motor dysfunction in mice. Altogether, our findings suggested that microglial MMP-2/-9 activation-mediated BBB dysfunction contributed to dopaminergic neurodegeneration in rotenone-induced mouse PD model, providing a novel view for the mechanisms of Parkinsonism.

An Update on Postoperative Cognitive Dysfunction Following Cardiac Surgery

Postoperative cognitive dysfunction is extremely prevalent following cardiac surgery. The increasing patient age and comorbidity profile increases their susceptibility to cognitive impairment. The underlying pathophysiological mechanisms leading to cognitive impairment are not clearly elucidated. Using the contemporary literature (2015-present), this narrative review has three aims. Firstly, to provide an overview of postoperative cognitive impairment. Secondly, to analyse the predominant pathophysiological mechanisms leading to cognitive dysfunction following cardiac surgery such as inflammation, cerebral hypoperfusion, cerebral microemboli, glycaemic control and anaesthesia induced neurotoxicity. Lastly, to assess the current therapeutic strategies of interest to address these pathophysiological mechanisms, including the administration of dexamethasone, the prevention of prolonged cerebral desaturations and the monitoring of cerebral perfusion using near-infrared spectroscopy, surgical management strategies to reduce the neurological effects of microemboli, intraoperative glycaemic control strategies, the effect of volatile vs. intravenous anaesthesia, and the efficacy of dexmedetomidine.

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.

Microglia as therapeutic targets after neurological injury: strategy for cell therapy

INTRODUCTION

Microglia is the resident tissue macrophages of the central nervous system. Prolonged microglial activation often occurs after traumatic brain injury and is associated with deteriorating neurocognitive outcomes. Resolution of microglial activation is associated with limited tissue loss and improved neurocognitive outcomes. Limiting the prolonged pro-inflammatory response and the associated secondary tissue injury provides the rationale and scientific premise for considering microglia as a therapeutic target.

AREAS COVERED

In this review, we discuss markers of microglial activation, such as immunophenotype and microglial response to injury, including cytokine/chemokine release, free radical formation, morphology, phagocytosis, and metabolic shifts. We compare the origin and role in neuroinflammation of microglia and monocytes/macrophages. We review potential therapeutic targets to shift microglial polarization. Finally, we review the effect of cell therapy on microglia.

EXPERT OPINION

Dysregulated microglial activation after neurologic injury, such as traumatic brain injury, can worsen tissue damage and functional outcomes. There are potential targets in microglia to attenuate this activation, such as proteins and molecules that regulate microglia polarization. Cellular therapeutics that limit, but do not eliminate, the inflammatory response have improved outcomes in animal models by reducing pro-inflammatory microglial activation via secondary signaling. These findings have been replicated in early phase clinical trials.

The Role of Intestinal Bacteria and Gut-Brain Axis in Hepatic Encephalopathy

Hepatic encephalopathy (HE) is a neurological disorder that occurs in patients with liver insufficiency. However, its pathogenesis has not been fully elucidated. Pharmacotherapy is the main therapeutic option for HE. It targets the pathogenesis of HE by reducing ammonia levels, improving neurotransmitter signal transduction, and modulating intestinal microbiota. Compared to healthy individuals, the intestinal microbiota of patients with liver disease is significantly different and is associated with the occurrence of HE. Moreover, intestinal microbiota is closely associated with multiple links in the pathogenesis of HE, including the theory of ammonia intoxication, bile acid circulation, GABA-ergic tone hypothesis, and neuroinflammation, which contribute to cognitive and motor disorders in patients. Restoring the homeostasis of intestinal bacteria or providing specific probiotics has significant effects on neurological disorders in HE. Therefore, this review aims at elucidating the potential microbial mechanisms and metabolic effects in the progression of HE through the gut–brain axis and its potential role as a therapeutic target in HE.

Toxic Effects of Methamphetamine on Perivascular Health: Co-morbid Effects of Stress and Alcohol Use Disorders

Methamphetamine (Meth) abuse presents a global problem and commonly occurs with stress and/or alcohol use disorders. Regardless, the biological causes and consequences of these comorbidities are unclear. Whereas the mechanisms of Meth, stress, and alcohol abuse have been examined individually and well-characterized, these processes overlap significantly and can impact the neural and peripheral consequences of Meth. This review focuses on the deleterious cardio- and cerebrovascular effects of Meth, stress, alcohol abuse, and their comorbid effects on the brain and periphery. Points of emphasis are on the composition of the blood-brain barrier and their effects on the heart and vasculature. The autonomic nervous system, inflammation, and oxidative stress are specifically highlighted as common mediators of the toxic consequences to vascular and perivascular health. A significant portion of the Meth abusing population also presents with stress and alcohol use disorders, prompting a need to understand the mechanisms underlying their comorbidities. Little is known about their possible convergent effects. Therefore, the purpose of this critical review is to identify shared mechanisms of Meth, chronic stress, and alcohol abuse that contributes to the dysfunction of vascular health and underscores the need for studies that directly address their interactions.

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.

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.

Central and peripheral anti-inflammatory effects of acetylcholinesterase inhibitors

Acetylcholinesterase (AChE) inhibitors modulate acetylcholine hydrolysis and hence play a key role in determining the cholinergic tone and in implementing its impact on the cholinergic blockade of inflammatory processes. Such inhibitors may include rapidly acting small molecule AChE-blocking drugs and poisonous anti-AChE insecticides or war agent inhibitors which penetrate both body and brain. Notably, traumatized patients may be hyper-sensitized to anti-AChEs due to their impaired cholinergic tone, higher levels of circulation pro-inflammatory cytokines and exacerbated peripheral inflammatory responses. Those largely depend on the innate-immune system yet reach the brain via vagus pathways and/or disrupted blood-brain-barrier. Other regulators of the neuro-inflammatory cascade are AChE-targeted microRNAs (miRs) and synthetic chemically protected oligonucleotide blockers thereof, whose size prevents direct brain penetrance. Nevertheless, these larger molecules may exert parallel albeit slower inflammatory regulating effects on brain and body tissues. Additionally, oligonucleotide aptamers interacting with innate immune Toll-Like Receptors (TLRs) may control inflammation through diverse routes and in different rates. Such aptamers may compete with the action of both small molecule inhibitors and AChE-inhibiting miRs in peripheral tissues including muscle and intestine. However, rapid adaptation processes, visualized in neuromuscular junctions enable murine survival under otherwise lethal anti-cholinesterase exposure; and both miR inhibitors and TLR-modulating aptamers may exert body-brain signals protecting experimental mice from acute inflammation. The complex variety of AChE inhibiting molecules identifies diverse body-brain communication pathways which may rapidly induce long-lasting central reactions to peripheral stressful and inflammatory insults in both mice and men. This article is part of the special issue entitled 'Acetylcholinesterase Inhibitors: From Bench to Bedside to Battlefield'.

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.

Neurobiology and Therapeutic Potential of Cyclooxygenase-2 (COX-2) Inhibitors for Inflammation in Neuropsychiatric Disorders

Neuropsychiatric disorders, such as depression, bipolar disorder, schizophrenia, obsessive-compulsive disorder, and neurodevelopmental disorders such as autism spectrum disorder, are associated with significant illness burden. Accumulating evidence supports an association between these disorders and inflammation. Consequently, anti-inflammatory agents, such as the cyclooxygenase-2 inhibitors, represent a novel avenue to prevent and treat neuropsychiatric illness. In this paper, we first review the role of inflammation in psychiatric pathophysiology including inflammatory cytokines' influence on neurotransmitters, the hypothalamic-pituitary-adrenal axis, and microglial mechanisms. We then discuss how cyclooxygenase-2-inhibitors influence these pathways with potential therapeutic benefit, with a focus on celecoxib, due to its superior safety profile. A search was conducted in PubMed, Embase, and PsychINFO databases, in addition to Clinicaltrials.gov and the Stanley Medical Research Institute trial registries. The results were presented as a narrative review. Currently available outcomes for randomized controlled trials up to November 2017 are also discussed. The evidence reviewed here suggests cyclooxygenase-2 inhibitors, and in particular celecoxib, may indeed assist in treating the symptoms of neuropsychiatric disorders; however, further studies are required to assess appropriate illness stage-related indication.

Inflammation, immunity, and amyotrophic lateral sclerosis: II. immune-modulating therapies

With the emerging popularity of immune-modulatory therapies to treat human diseases there is a need to step back from hypotheses aimed at assessing a condition in a single-system context and instead take into account the disease pathology as a whole. In complex diseases, such as amyotrophic lateral sclerosis (ALS), the use of these therapies to treat patients has been largely unsuccessful and likely premature given our lack of understanding of how the immune system influences disease progression and initiation. In addition, we still have an incomplete understanding of the role of these responses in our model systems and how this may translate clinically to human patients. In this review we discuss preclinical evidence and clinical trial results for a selection of recently conducted studies in ALS. We provide evidence-based reasoning for the failure of these trials and offer suggestions to improve the design of future investigations. Muscle Nerve 59:23-33, 2019.

Leaky brain in neurological and psychiatric disorders: Drivers and consequences

BACKGROUND

The blood-brain barrier acts as a highly regulated interface; its dysfunction may exacerbate, and perhaps initiate, neurological and neuropsychiatric disorders.

METHODS

In this narrative review, focussing on redox, inflammatory and mitochondrial pathways and their effects on the blood-brain barrier, a model is proposed detailing mechanisms which might explain how increases in blood-brain barrier permeability occur and can be maintained with increasing inflammatory and oxidative and nitrosative stress being the initial drivers.

RESULTS

Peripheral inflammation, which is causatively implicated in the pathogenesis of major psychiatric disorders, is associated with elevated peripheral pro-inflammatory cytokines, which in turn cause increased blood-brain barrier permeability. Reactive oxygen species, such as superoxide radicals and hydrogen peroxide, and reactive nitrogen species, such as nitric oxide and peroxynitrite, play essential roles in normal brain capillary endothelial cell functioning; however, chronically elevated oxidative and nitrosative stress can lead to mitochondrial dysfunction and damage to the blood-brain barrier. Activated microglia, redox control of which is mediated by nitric oxide synthases and nicotinamide adenine dinucleotide phosphate (NADPH) oxidases, secrete neurotoxic molecules such as reactive oxygen species, nitric oxide, prostaglandin, cyclooxygenase-2, quinolinic acid, several chemokines (including monocyte chemoattractant protein-1 [MCP-1], C-X-C motif chemokine ligand 1 [CXCL-1] and macrophage inflammatory protein 1α [MIP-1α]) and the pro-inflammatory cytokines interleukin-6, tumour necrosis factor-α and interleukin-1β, which can exert a detrimental effect on blood-brain barrier integrity and function. Similarly, reactive astrocytes produce neurotoxic molecules such as prostaglandin E2 and pro-inflammatory cytokines, which can cause a 'leaky brain'.

CONCLUSION

Chronic inflammatory and oxidative and nitrosative stress is associated with the development of a 'leaky gut'. The following evidence-based approaches, which address the leaky gut and blood-brain barrier dysfunction, are suggested as potential therapeutic interventions for neurological and neuropsychiatric disorders: melatonin, statins, probiotics containing Bifidobacteria and Lactobacilli, N-acetylcysteine, and prebiotics containing fructo-oligosaccharides and galacto-oligosaccharides.

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.

Highly Selective Cyclooxygenase-1 Inhibitors P6 and Mofezolac Counteract Inflammatory State both In Vitro and In Vivo Models of Neuroinflammation

Activated microglia secrete an array of pro-inflammatory factors, such as prostaglandins, whose accumulation contributes to neuronal damages. Prostaglandin endoperoxide synthases or cyclooxygenases (COX-1 and COX-2), which play a critical role in the inflammation, are the pharmacological targets of non-steroidal anti-inflammatory drugs, used to treat pain and inflammation. Since it was reported that COX-1 is the major player in mediating the brain inflammatory response, the aim of this study was to evaluate the effects of highly selective COX-1 inhibitors, such as P6 and mofezolac, in neuroinflammation models. Lipopolysaccharide (LPS)-activated mouse BV-2 microglial cells and LPS intracerebroventricular-injected mice as in vitro and in vivo neuroinflammation models, respectively, were used to probe the antiinflammatory efficacy of P6 and mofezolac. Both P6 and mofezolac reduce COX-1 expression in LPS-activated BV-2 cells. This reduction was accompanied with PGE₂ release reduction and NF-kB activation downregulation. Coextensively, in the in vivo model, both glial fibrillary acidic protein and ionized calcium-binding adapter molecule-1 expression, two markers of inflammation, were reduced by mofezolac to a rank depending on the encephalon area analyzed. The increase of COX-1 expression observed in all the brain sections of LPS-treated mice was selectively downregulated by the in vivo treatment with mofezolac as well as PGE₂ release and Ikβα phosphorylation amount assayed in the brain areas tested. These results indicate the capability of P6 and mofezolac to modulate the NF-kB signaling pathway, emphasizing the neuroprotective effect and therapeutic potential of COX-1 inhibitors in the control of neuroinflammatory diseases.

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.

Jmjd3 mediates blood-spinal cord barrier disruption after spinal cord injury by regulating MMP-3 and MMP-9 expressions

The disruption of the blood-spinal cord barrier (BSCB) by matrix metalloprotease (MMP) activation is a detrimental event that leads to blood cell infiltration, inflammation, and apoptosis, thereby contributing to permanent neurological disability after spinal cord injury (SCI). However, the molecular mechanisms underlying Mmp gene regulation have not been fully elucidated. Here, we demonstrated the critical role of histone H3K27 demethylase Jmjd3 in the regulation of Mmp gene expression and BSCB disruption using in vitro cellular and in vivo animal models. We found that Jmjd3 up-regulation, in cooperation with NF-κB, after SCI is required for Mmp-3 and Mmp-9 gene expressions in injured vascular endothelial cells. In addition, Jmjd3 mRNA depletion inhibited Mmp-3 and Mmp-9 gene expressions and significantly attenuated BSCB permeability and the loss of tight junction proteins. These events further led to improved functional recovery, along with decreased hemorrhage, blood cell infiltration, inflammation, and cell death of neurons and oligodendrocytes after SCI. Thus, our findings suggest that Jmjd3 regulation may serve as a potential therapeutic intervention for preserving BSCB integrity following SCI.

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.

Chemical dampening of Ly6C(hi) monocytes in the periphery produces anti-depressant effects in mice

The involvement of systemic immunity in depression pathogenesis promises a periphery-targeting paradigm in novel anti-depressant discovery. However, relatively little is known about druggable targets in the periphery for mental and behavioral control. Here we report that targeting Ly6C^hi monocytes in blood can serve as a strategy for anti-depressant purpose. A natural compound, ginsenoside Rg1 (Rg1), was firstly validated as a periphery-restricted chemical probe. Rg1 selectively suppressed Ly6C^hi monocytes recruitment to the inflamed mice brain. The proinflammatory potential of Ly6C^hi monocytes to activate astrocytes was abrogated by Rg1, which led to a blunted feedback release of CCL2 to recruit the peripheral monocytes. In vitro study demonstrated that Rg1 pretreatment on activated THP-1 monocytes retarded their ability to trigger CCL2 secretion from co-cultured U251 MG astrocytes. CCL2-triggered p38/MAPK and PI3K/Akt activation were involved in the action of Rg1. Importantly, in mice models, we found that dampening Ly6C^hi monocytes at the periphery ameliorated depression-like behavior induced by neuroinflammation or chronic social defeat stress. Together, our work unravels that blood Ly6C^hi monocytes may serve as the target to enable remote intervention on the depressed brain, and identifies Rg1 as a lead compound for designing drugs targeting peripheral CCL2 signals.

Autophagy Is Required for Neutrophil-Mediated Inflammation

Autophagy, an intracellular degradation and energy recycling mechanism, is emerging as an important regulator of immune responses. However, the role of autophagy in regulating neutrophil functions is not known. We investigated neutrophil biology using myeloid-specific autophagy-deficient mice and found that autophagy deficiency reduced neutrophil degranulation in vitro and in vivo. Mice with autophagy deficiency showed reduced severity of several neutrophil-mediated inflammatory and autoimmune disease models, including PMA-induced ear inflammation, LPS-induced breakdown of blood-brain barrier, and experimental autoimmune encephalomyelitis. NADPH oxidase-mediated reactive oxygen species generation was also reduced in autophagy-deficient neutrophils, and inhibition of NADPH oxidase reduced neutrophil degranulation, suggesting NADPH oxidase to be a player at the intersection of autophagy and degranulation. Overall, this study establishes autophagy as an important regulator of neutrophil functions and neutrophil-mediated inflammation in vivo.

Recombinant ADAMTS 13 Attenuates Brain Injury After Intracerebral Hemorrhage

BACKGROUND AND PURPOSE

Inflammatory responses and blood-brain barrier (BBB) dysfunction play important roles in brain injury after intracerebral hemorrhage (ICH). The metalloprotease ADAMTS 13 (a disintegrin and metalloprotease with thrombospondin type I motif, member 13) was shown to limit inflammatory responses through its proteolytic effects on von Willebrand factor. In the present study, we addressed the role of ADAMTS 13 after experimental ICH.

METHODS

ICH was induced in mice by intracerebral infusion of autologous blood. The peri-hematomal inflammatory responses, levels of matrix metalloproteinase-9 and intercellular adhesion molecule-1, pericyte coverage on brain capillaries, and BBB permeability were quantified at 24 hours. Functional outcomes, cerebral edema, and hemorrhagic lesion volume were quantified at day 3.

RESULTS

Treatment with recombinant ADAMTS 13 (rADAMTS 13) reduced the levels of chemokines and cytokines, myeloperoxidase activity, and microglia activation and neutrophil recruitment after ICH. rADAMTS 13 also decreased interleukin-6 expression in brain endothelial cells stimulated by lipopolysaccharide, whereas recombinant von Willebrand factor reversed this effect. The anti-inflammatory effect of rADAMTS 13 was accompanied by reduced expression of intercellular adhesion molecule-1 and less activation of matrix metalloproteinase, enhanced pericyte coverage of brain microvessels, and attenuated BBB disruption. Furthermore, neutrophil depletion protected against BBB damage, and rADAMTS 13 treatment had no further beneficial effect. Finally, treatment of mice with rADAMTS 13 reduced cerebral edema and hemorrhagic lesion volume and improved neurological functions.

CONCLUSIONS

Our findings reveal the importance of rADAMTS 13 in regulating pathological inflammation and BBB function and suggest that rADAMTS 13 may provide a new therapeutic strategy for ICH.

Systemic inflammation in early neonatal mice induces transient and lasting neurodegenerative effects

Background

The inflammatory mediator lipopolysaccharide (LPS) has been shown to induce acute gliosis in neonatal mice. However, the progressive effects on the murine neurodevelopmental program over the week that follows systemic inflammation are not known. Thus, we investigated the effects of repeated LPS administration in the first postnatal week in mice, a condition mimicking sepsis in late preterm infants, on the developing central nervous system (CNS).

Methods

Systemic inflammation was induced by daily intraperitoneal administration (i.p.) of LPS (6 mg/kg) in newborn mice from postnatal day (PND) 4 to PND6. The effects on neurodevelopment were examined by staining the white matter and neurons with Luxol Fast Blue and Cresyl Violet, respectively. The inflammatory response was assessed by quantifying the expression/activity of matrix metalloproteinases (MMP), toll-like receptor (TLR)-4, high mobility group box (HMGB)-1, and autotaxin (ATX). In addition, B6 CX3CR1^gfp/+ mice combined with cryo-immunofluorescence were used to determine the acute, delayed, and lasting effects on myelination, microglia, and astrocytes.

Results

LPS administration led to acute body and brain weight loss as well as overt structural changes in the brain such as cerebellar hypoplasia, neuronal loss/shrinkage, and delayed myelination. The impaired myelination was associated with alterations in the proliferation and differentiation of NG2 progenitor cells early after LPS administration, rather than with excessive phagocytosis by CNS myeloid cells. In addition to disruptions in brain architecture, a robust inflammatory response to LPS was observed. Quantification of inflammatory biomarkers revealed decreased expression of ATX with concurrent increases in HMGB1, TLR-4, and MMP-9 expression levels. Acute astrogliosis (GFAP⁺ cells) in the brain parenchyma and at the microvasculature interface together with parenchymal microgliosis (CX3CR1⁺ cells) were also observed. These changes preceded the migration/proliferation of CX3CR1⁺ cells around the vessels at later time points and the subsequent loss of GFAP⁺ astrocytes.

Conclusion

Collectively, our study has uncovered a complex innate inflammatory reaction and associated structural changes in the brains of neonatal mice challenged peripherally with LPS. These findings may explain some of the neurobehavioral abnormalities that develop following neonatal sepsis.

p38α (MAPK14) critically regulates the immunological response and the production of specific cytokines and chemokines in astrocytes

In CNS lesions, “reactive astrocytes” form a prominent cellular response. However, the nature of this astrocyte immune activity is not well understood. In order to study astrocytic immune responses to inflammation and injury, we generated mice with conditional deletion of p38α (MAPK14) in GFAP+ astrocytes. We studied the role of p38α signaling in astrocyte immune activation both in vitro and in vivo, and simultaneously examined the effects of astrocyte activation in CNS inflammation. Our results showed that specific subsets of cytokines (TNFα, IL-6) and chemokines (CCL2, CCL4, CXCL1, CXCL2, CXCL10) are critically regulated by p38α signaling in astrocytes. In an in vivo CNS inflammation model of intracerebral injection of LPS, we observed markedly attenuated astrogliosis in conditional GFAPcre p38α^−/− mice. However, GFAPcre p38α^−/− mice showed marked upregulation of CCL2, CCL3, CCL4, CXCL2, CXCL10, TNFα, and IL-1β compared to p38αfl/fl cohorts, suggesting that in vivo responses to LPS after GFAPcre p38α deletion are complex and involve interactions between multiple cell types. This finding was supported by a prominent increase in macrophage/microglia and neutrophil recruitment in GFAPcre p38α^−/− mice compared to p38αfl/fl controls. Together, these studies provide important insights into the critical role of p38α signaling in astrocyte immune activation.

Matrix metalloproteinase-3 promotes early blood-spinal cord barrier disruption and hemorrhage and impairs long-term neurological recovery after spinal cord injury

After spinal cord injury (SCI), blood-spinal cord barrier (BSCB) disruption by matrix metalloproteinases (MMPs) leads to BSCB permeability and blood cell infiltration, contributing to permanent neurological disability. Herein, we report that MMP-3 plays a critical role in BSCB disruption after SCI in mice. MMP-3 was induced in infiltrated neutrophils and blood vessels after SCI, and NF-κB as a transcription factor was involved in MMP-3 expression. BSCB permeability and blood cell infiltration after injury were more reduced in Mmp3 knockout (KO) mice than in wild-type (WT) mice, which was significantly inhibited by Mmp3 siRNA or a general inhibitor of MMPs, N-isobutyl-N-(4-methoxyphenylsulfonyl)glycyl hydroxamic acid. The level of tight junction proteins, such as occludin and zonula occludens-1, which decreased after SCI, was also higher in Mmp3 KO than in WT mice. Exogenously, MMP-3 injection into the normal spinal cord also induced BSCB permeability. Furthermore, MMP-9 activation after injury was mediated by MMP-3 activation. Finally, improved functional recovery was observed in Mmp3 KO mice compared with WT mice after injury. These results demonstrated the role of MMP-3 in BSCB disruption after SCI for the first time and suggest that the regulation of MMP-3 can be considered a therapeutic target to inhibit BSCB disruption and hemorrhage, and thereby enhance functional recovery after acute SCI.

Synthesis and biological evaluation of novel (123)I-labeled 4-(4-iodophenyl)butanoyl-L-prolyl-(2S)-pyrrolidines for imaging prolyl oligopeptidase in vivo

Prolyl oligopeptidase (POP) may be associated with neuromodulation and development of neurodegenerative diseases and it was recently shown to participate in the inflammatory cascade along with matrix metalloproteinases. Radiotracers, which can be used for non-invasive imaging, are needed for investigating the role of POP in normal physiology and in pathophysiological conditions in vivo. We synthesized two novel POP-specific (123)I-radiolabeled 4-phenylbutanoyl-L-prolyl-pyrrolidines of which 4-(4-[(123)I]iodophenyl)butanoyl-L-prolyl-2(S)-cyanopyrrolidine ([(123)I]2f, Ki = 4.2 nM) was selected. The selected compound has an electrophilic cyano group that is known to increase the dissociation time of POP inhibitors. [(123)I]2f was synthesized in high radiochemical yield and purity (87 ± 4%, >99%, respectively) and with a specific activity of 456 ± 98 GBq/μmol. [(123)I]2f was evaluated in healthy mice (C57Bl/6JRccHsd) by ex vivo biodistribution studies and SPECT imaging. Pretreatment with the known inhibitor 4-phenylbutanoyl-L-prolyl-(2S)-cyanopyrrolidine (KYP-2047, 2d, Ki = 0.023 nM) showed that binding of [(123)I]2f was POP specific. In addition, [(123)I]2f was evaluated in models of neuroinflammation and acute localized inflammation. A minor increase in binding of [(123)I]2f was observed in the inflamed region in the acute localized inflammation model. Similar increase in binding was not observed in the neuroinflammation model.

Peripheral immunomodulation with ginsenoside Rg1 ameliorates neuroinflammation-induced behavioral deficits in rats

Neuroinflammatory disturbances have been closely associated with depression and many other neuropsychiatric diseases. Although targeting neuroinflammatory mediators with centrally acting drugs has shown certain promise, its translation is faced with several challenges especially drug delivery and safety concerns. Here, we report that neuroinflammation-induced behavioral abnormality could be effectively attenuated with immunomodulatory agents that need not to gain brain penetration. In a rat model with intracerebral lipopolysaccharide (LPS) challenge, we validated that ginsenoside Rg1 (Rg1), a well-established anti-inflammatory agent, was unable to produce a direct action in the brain. Interestingly, peripherally restricted Rg1 could effectively attenuate the weight loss, anorexic- and depressive-like behavior as well as neurochemical disturbances associated with central LPS challenge. Biochemical assay of neuroimmune mediators in the periphery revealed that Rg1 could mitigate the deregulation of the hypothalamic-pituitary-adrenal axis and selectively blunt the increase in circulating interleukin-6 levels. Furthermore, these peripheral regulatory effects were accompanied by dampened microglial activation, mitigated expression of pro-inflammatory mediators and neurotoxic species in the central compartment. Taken together, our work suggested that targeting the peripheral immune system may serve as a novel therapeutic approach to neuroinflammation-induced neuropsychiatric disorders. Moreover, our findings provided the rationale for employing peripherally active agents like Rg1 to combat mental disturbances.

Targeting cyclooxygenase-2 in depression is not a viable therapeutic approach and may even aggravate the pathophysiology underpinning depression

Depression is a complex progressive disorder accompanied by activation of inflammatory and Th-1 driven pathways, oxidative and nitrosative stress (O&NS), lowered antioxidant levels, mitochondrial dysfunctions, neuroprogression and increased bacterial translocation. In depression, activation of immuno-inflammatory pathways is associated with an increased risk for cardio-vascular disorder (CVD). Because of the inflammatory component, the use of cyclooxygenase 2 (COX-2) inhibitors, such as celecoxib, has been advocated to treat depression. Electronic databases, i.e. PUBMED, Scopus and Google Scholar were used as sources for this selective review on the effects of COX-2 inhibitors aggravating the abovementioned pathways. COX-2 inhibitors may induce neuroinflammation, exacerbate Th1 driven responses, increase lipid peroxidation, decrease the levels of key antioxidants, damage mitochondria and aggravate neuroprogression. COX-2 inhibitors may aggravate bacterial translocation and CVD through Th1-driven mechanisms. COX-2 inhibitors may aggravate the pathophysiology of depression. Since Th1 and O&NS pathways are risk factors for CVD, the use of COX-2 inhibitors may further aggravate the increased risk for CVD in depression. Selectively targeting COX-2 may not be a viable therapeutic approach to treat depression. Multi-targeting of the different pathways that play a role in depression is more likely to yield good treatment results.

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.

Persistent neuroinflammatory effects of serial exposure to stress and methamphetamine on the blood-brain barrier

Studies of methamphetamine (Meth)-induced neurotoxicity have traditionally focused on monoaminergic terminal damage while more recent studies have found that stress exacerbates these damaging effects of Meth. Similarities that exist between the mechanisms that cause monoaminergic terminal damage in response to stress and Meth and those capable of producing a disruption of the blood-brain barrier (BBB) suggest that the well-known high co-morbidity of stress and Meth could produce long-lasting structural and functional BBB disruption. The current studies examined the role of neuroinflammation in mediating the effects of exposure to chronic stress and/or Meth on BBB structure and function. Rats were pre-exposed to chronic unpredictable stress (CUS) and/or challenged with Meth. Twenty-four hours after the treatment of Meth in rats pre-exposed to CUS, occludin and claudin-5 immunoreactivity were decreased while truncation of β-dystroglycan, as well as FITC-dextran and water extravasation was increased. All changes other than β-dystroglycan and edema persisted 7 days later, occurred with increases in GFAP and COX-2, and were blocked by ketoprofen after Meth treatment. In addition, persistent increases in FITC-dextran extravasation were prevented by treatment with an EP1 receptor antagonist after Meth exposure. The results indicate that CUS and Meth synergize to produce long-lasting structural and functional BBB disruptions that are mediated by cyclooxygenase and protracted increases in inflammation. These results suggest that stress and Meth can synergize to produce a long-lasting vulnerability of the brain to subsequent environmental insults resulting from the persistent breach of the BBB.

Exendin-4 protected against cognitive dysfunction in hyperglycemic mice receiving an intrahippocampal lipopolysaccharide injection

Background

Chronic hyperglycemia-associated inflammation plays critical roles in disease initiation and the progression of diabetic complications, including Alzheimer’s disease (AD). However, the association of chronic hyperglycemia with acute inflammation of the central nervous system in the progression of AD still needs to be elucidated. In addition, recent evidence suggests that Glucagon-like peptide-1 receptor (GLP-1R) protects against neuronal damage in the brain. Therefore, the neuroprotective effects of the GLP-1R agonist exendin-4 (EX-4) against hyperglycemia/lipopolysaccharides (LPS) damage were also evaluated in this study.

Methodology/Principal Findings

Ten days after streptozotocin (STZ) or vehicle (sodium citrate) treatment in mice, EX-4 treatment (10 µg/kg/day) was applied to the mice before intrahippocampal CA1 injection of LPS or vehicle (saline) and continued for 28 days. This study examined the molecular alterations in these mice after LPS and EX4 application, respectively. The mouse cognitive function was evaluated during the last 6 days of EX-4 treatment. The results showed that the activation of NF-κB-related inflammatory responses induced cognitive dysfunction in both the hyperglycemic mice and the mice that received acute intrahippocampal LPS injection. Furthermore, acute intrahippocampal LPS injection exacerbated the impairment of spatial learning and memory through a strong decrease in monoaminergic neurons and increases in astrocytes activation and apoptosis in the hyperglycemic mice. However, EX-4 treatment protected against the cognitive dysfunction resulting from hyperglycemia or/and intrahippocampal LPS injection.

Conclusions/Significance

These findings reveal that both hyperglycemia and intrahippocampal LPS injection induced cognitive dysfunction via activation of NF-κB-related inflammatory responses. However, acute intrahippocampal LPS injection exacerbated the progression of cognitive dysfunction in the hyperglycemic mice via a large increase in astrocytes activation-related responses. Furthermore, EX-4 might be considered as a potential adjuvant entity to protect against neurodegenerative diseases.

The CCL2 synthesis inhibitor bindarit targets cells of the neurovascular unit, and suppresses experimental autoimmune encephalomyelitis

BACKGROUND

Production of the chemokine CCL2 by cells of the neurovascular unit (NVU) drives critical aspects of neuroinflammation. Suppression of CCL2 therefore holds promise in treating neuroinflammatory disease. Accordingly, we sought to determine if the compound bindarit, which inhibits CCL2 synthesis, could repress the three NVU sources of CCL2 most commonly reported in neuroinflammation--astrocytes, microglia and brain microvascular endothelial cells (BMEC)--as well as modify the clinical course of neuroinflammatory disease.

METHODS

The effect of bindarit on CCL2 expression by cultured murine astrocytes, microglia and BMEC was examined by quantitative reverse transcription polymerase chain reaction (qRT-PCR). Bindarit action on mouse brain and spinal cord in vivo was similarly investigated by qRT-PCR following LPS injection in mice. And to further gauge the potential remedial effects of bindarit on neuroinflammatory disease, its impact on the clinical course of experimental autoimmune encephalomyelitis (EAE) in mice was also explored.

RESULTS

Bindarit repressed CCL2 expression by all three cultured cells, and antagonized upregulated expression of CCL2 in both brain and spinal cord in vivo following LPS administration. Bindarit also significantly modified the course and severity of clinical EAE, diminished the incidence and onset of disease, and evidenced signs of disease reversal.

CONCLUSION

Bindarit was effective in suppressing CCL2 expression by cultured NVU cells as well as brain and spinal cord tissue in vivo. It further modulated the course of clinical EAE in both preventative and therapeutic ways. Collectively, these results suggest that bindarit might prove an effective treatment for neuroinflammatory disease.

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.

Ablation of cyclooxygenase-2 in forebrain neurons is neuroprotective and dampens brain inflammation after status epilepticus

Cyclooxygenase-2 (COX-2), a source of inflammatory mediators and a multifunctional neuronal modulator, is rapidly induced in select populations of cortical neurons after status epilepticus. The consequences of rapid activity-triggered induction of COX-2 in neurons have been the subject of much study and speculation. To address this issue directly, we created a mouse in which COX-2 is conditionally ablated in selected forebrain neurons. Results following pilocarpine-induced status epilepticus indicate that neuronal COX-2 promotes early neuroprotection and then delayed neurodegeneration of CA1 pyramidal neurons, promotes neurodegeneration of nearby somatostatin interneurons in the CA1 stratum oriens and dentate hilus (which themselves do not express COX-2), intensifies a broad inflammatory reaction involving numerous cytokines and other inflammatory mediators in the hippocampus, and is essential for development of a leaky blood-brain barrier after seizures. These findings point to a profound role of seizure-induced neuronal COX-2 expression in neuropathologies that accompany epileptogenesis.

Dexamethasone inhibits ICAM-1 and MMP-9 expression and reduces brain edema in intracerebral hemorrhagic rats

BACKGROUND

The molecular mechanism of hemorrhagic stroke is unclear, and the identification of therapeutic agents for attenuating post-stroke brain damage remains an unresolved challenge. Dexamethasone (DEX) is used clinically to treat spinal cord injury and brain tumor patients by reducing edema formation, but has produced conflicting results in stroke management.

METHODS

In this study, intracerebral hemorrhage (ICH) was induced in rats by intracranial stereotactic injection of collagenase into the caudate nucleus. DEX was given immediately and 3 days after ICH. The expression of intercellular adhesion molecule-1 (ICAM-1), matrix metalloproteinase-9 (MMP-9), nuclear factor (NF)-κB, and IκB were analyzed by Western blotting, and perihematomal edema formation was evaluated by magnetic resonance imaging.

RESULTS

The results showed that ICH caused an increase of ICAM-1 and MMP-9 expression from 4 h to 7 days, which was inhibited following the administration of DEX. The perihematomal edema volume in ICH rats was high, with two peak periods at 12 h and 3 days, which was also reduced in DEX-treated groups. Furthermore, the administration of DEX not only maintained IκB in cytoplasm, but also decreased NF-κB elevation in the nucleus at 3 and 5 days in ICH rats.

CONCLUSIONS

In conclusion, these data show that DEX successfully reduced post-stroke brain edema by decreasing MMP-9 and ICAM-1 levels, partially through the IκB/NF-κB signaling pathway. The timing of DEX administration in relation to the onset of brain injury may be critical.

MAPK phosphatase-1 contributes to trichostatin A inhibition of cyclooxygenase-2 expression in human umbilical vascular endothelial cells exposed to lipopolysaccharide

BACKGROUND

Histone deacetylase (HDAC) inhibitors have emerged as a new class of antitumor agents because they were demonstrated to induce cell cycle arrest, promote cell apoptosis, and inhibit metastasis. Recently, HDAC inhibitors were also shown to exhibit pronounced anti-inflammatory properties. However, the underlying mechanism contributing to the suppression of inflammatory responses by HDAC inhibitors remains to be fully defined. In the present study, we explored the actions of trichostatin A (TSA), a potent HDAC inhibitor, on lipopolysaccharide (LPS)-induced cyclooxygenase (COX)-2 expression in human umbilical vascular endothelial cells (HUVECs).

METHODS

HUVECs were exposed to LPS in the absence or presence of TSA. COX-2 expression and signaling molecules (JNK, p38MAPK and c-jun) activated by LPS were assessed.

RESULTS

The LPS-induced cox-2 messenger RNA and protein were markedly suppressed by TSA. TSA inhibited JNK and p38MAPK phosphorylation in cells exposed to LPS. Treatment of cells with a JNK signaling inhibitor (JNK inhibitor II) or a p38MAPK inhibitor (p38MAPK inhibitor III) markedly inhibited LPS-induced COX-2 expression. TSA suppression of JNK and p38MAPK phosphorylation and subsequent COX-2 expression were restored by selective inhibition of MKP-1 using MKP-1 siRNA. In addition, TSA caused an increase in MKP-1 phosphatase activity in HUVECs. In conclusion, TSA may cause MKP-1 activation to dephosphorylate JNK and p38MAPK, leading to the downregulation of COX-2 in HUVECs stimulated by LPS, a proinflammatory stimulus.

GENERAL SIGNIFICANCE

MKP-1 contributes to TSA's protective actions in HUVECs exposed to LPS. The present study also supports the therapeutic value of TSA in treating inflammatory vascular diseases.

In vivo expression of cyclooxygenase-1 in activated microglia and macrophages during neuroinflammation visualized by PET with 11C-ketoprofen methyl ester

Cyclooxygenase (COX)-1 and -2 are prostanoid-synthesizing enzymes that play important roles in the regulation of neuroinflammation and in the development of neurodegenerative disorders. However, the specific functions of these isoforms are still unclear. We recently developed (11)C-labeled ketoprofen methyl ester as a PET probe that targets the COXs for imaging neuroinflammation, though its responsible isoform is yet to be determined. In the present study, we performed ex vivo and in vivo imaging studies with (11)C-ketoprofen methyl ester and determined the contributions of the COX isoforms during the neuroinflammatory process.

METHODS

To identify the COX isoform responsible for (11)C-ketoprofen methyl ester in the brain, we examined the ex vivo autoradiography of (11)C-ketoprofen methyl ester using COX-deficient mice. Time-dependent changes in accumulation of (11)C-ketoprofen methyl ester during the neuroinflammatory process were evaluated by PET in rats with hemispheric neuroinflammation induced by intrastriatal injection of lipopolysaccharide or quinolinic acid. In both rat models, cell-type specificity of COX isoform expression during neuroinflammation was identified immunohistochemically.

RESULTS

Ex vivo autoradiographic analysis of COX-deficient mice revealed a significant reduction of (11)C-ketoprofen methyl ester accumulation only in COX-1-deficient mice, not COX-2-deficient mice. PET of rats after intrastriatal injection of lipopolysaccharide showed a significant increase in accumulation of (11)C-ketoprofen methyl ester in the inflamed area. This increase was evident at the early phase of 6 h, peaked at day 1, and then returned to basal levels by day 7. In addition, immunohistochemical analysis revealed that the population of activated microglia and macrophages was elevated at the early phase with COX-1 expression but not COX-2. A significant increase in (11)C-ketoprofen methyl ester accumulation was also observed at day 1 after intrastriatal injection of quinolinic acid, with increased COX-1-expressing activated microglia and macrophages.

CONCLUSION

We have identified (11)C-ketoprofen methyl ester as a COX-1-selective PET probe, and using this, we have also demonstrated a time-dependent expression of COX-1 in activated microglia and macrophages during the neuroinflammatory process in the living brain. Thus, COX-1 may play a crucial role in the pathology of neuroinflammation and might be a critical target for the diagnosis and therapy of neurodegenerative disorders.

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.

Intracranial pressure following resuscitation with albumin or saline in a cat model of meningitis

OBJECTIVE

To compare the intracranial pressure after resuscitation to normovolemia by using 20% albumin or normal saline in a cat model of meningitis.

DESIGN

Prospective, randomized animal study.

SETTING

University hospital laboratory.

SUBJECTS

Twenty adult, male cats.

INTERVENTIONS

Meningitis was induced by intrathecal injection of Escherichia coli-derived lipopolysaccharide (0.8 × 10 units/kg). Four hours after the lipopolysaccharide injection, the animals were randomized to intravenous treatment with 0.4 mL/kg/hr of 20% albumin or 7.5 mL/kg/hr of 0.9% sodium chloride for 6 hrs (n = 7 per group). A control group receiving lipopolysaccharide but no fluid was also studied (n = 6).

MEASUREMENTS AND MAIN RESULTS

Effects on intracranial pressure, mean arterial pressure, plasma volume (I-albumin technique), plasma oncotic pressure, and brain metabolism via cerebral interstitial lactate/pyruvate ratio and glycerol and glucose levels (microdialysis technique) were evaluated. Plasma volume decreased by approximately 20% and intracranial pressure increased from 10 to approximately 20 mm Hg at 4 hrs after the lipopolysaccharide injection. Six hours later, plasma volume had returned to baseline in both fluid groups while there was a further reduction in the control group. Intracranial pressure was higher in the saline group than in the albumin and control groups and was 25.8 ± 2.8 mm Hg, 18.3 ± 0.6 mm Hg, and 20.4 ± 1.7 mm Hg, respectively. Plasma oncotic pressure was higher in the albumin group than in the saline and control groups. Mean arterial pressure and microdialysis data were within normal range and did not differ among the groups.

CONCLUSIONS

The results showed that the choice of resuscitation fluid may influence intracranial pressure in meningitis. The lower intracranial pressure in the colloid group may be explained by a higher plasma oncotic pressure and less fluid distribution to the brain interstitium.