Involvement Of Neuroinflammation Research Articles

Microglial activation mediates chronic mild stress-induced depressive- and anxiety-like behavior in adult rats

BackgroundDepression is a heterogeneous disorder, with the exact neuronal mechanisms causing the disease yet to be discovered. Recent work suggests it is accompanied by neuro-inflammation, characterized, in particular, by microglial activation. However, microglial activation and its involvement in neuro-inflammation and stress-related depressive disorders are far from understood.MethodsWe utilized multiple detection methods to detect the neuro-inflammation in the hippocampus of rats after exposure to chronic mild stress (CMS). Male Sprague Dawley (SD) rats were subjected to chronic mild stressors for 12 weeks. Microglial activation and hippocampal neuro-inflammation were detected by using a combinatory approach of in vivo [18F] DPA-714 positron emission computed tomography (PET) imaging, ionized calcium-binding adapter molecule 1 and translocator protein (TSPO) immunohistochemistry, and detection of NOD-like receptor protein 3 (NLRP3) inflammasome and some inflammatory mediators. Then, the rats were treated with minocycline during the last 4 weeks to observe its effect on hippocampal neuro-inflammation and depressive-like behavior induced by chronic mild stress.ResultsThe results show that 12 weeks of chronic mild stress induced remarkable depressive- and anxiety-like behavior, simultaneously causing hippocampal microglial activation detected by PET, immunofluorescence staining, and western blotting. Likewise, activation of NLRP3 inflammasome and upregulation of inflammatory mediators, such as interleukin-1β (IL-1β), IL-6, and IL-18, were also observed in the hippocampus after exposure to chronic stress. Interestingly, the anti-inflammatory mediators, such as IL-4 and IL-10, were also increased in the hippocampus following chronic mild stress, which may hint that chronic stress activates different types of microglia, which produce pro-inflammatory cytokines or anti-inflammatory cytokines. Furthermore, chronic minocycline treatment alleviated the depressive-like behavior induced by chronic stress and significantly inhibited microglial activation. Similarly, the activation of NLRP3 inflammasome and the increase of inflammatory mediators were not exhibited or significantly less marked in the minocycline treatment group.ConclusionThese results together indicate that microglial activation mediates the chronic mild stress-induced depressive- and anxiety-like behavior and hippocampal neuro-inflammation.

Application of Europium-Doped Very Small Iron Oxide Nanoparticles to Visualize Neuroinflammation with MRI and Fluorescence Microscopy

Our recent studies demonstrated that electrostatically stabilized very small superparamagnetic iron oxide particles (VSOPs) are promising MRI probes for detecting various pathological aspects of autoimmunity in the central nervous system (CNS). However, investigation of the precise tissue and cellular distribution of VSOP has been technically limited due to the need to use iron detection methods for VSOP visualization. Therefore, we assessed here the utility of europium (Eu)-doped VSOP as an MRI tool for in vivo investigations in the animal model experimental autoimmune encephalomyelitis (EAE), and as a tool to investigate histopathological processes in the CNS using fluorescence microscopy.We demonstrated that Eu-VSOP display the same properties as VSOP in terms of revealing inflammation-mediated changes by binding to brain endothelium in vitro, and in terms of visualizing brain lesions in EAE in vivo. MRI examinations with Eu-VSOP confirm that at peak disease particles accumulated inside the choroid plexus, and in cerebellar and meningeal lesions. Importantly, Eu-VSOP-based MRI showed for the first time in a longitudinal setup that particles were absent from the choroid plexus in mice during remission of EAE, but accumulated again during subsequent relapse. Within the choroid plexus, Eu-VSOP were associated both with monocytes/macrophages present in the plexus stroma, and associated with epithelial cells.Using Eu-VSOP, we demonstrated for the first time the involvement of the choroid plexus in relapses. Thus, Eu-VSOP have the potential to reveal various aspects of choroid plexus involvement in neuroinflammation, including monocyte recruitment from the blood and alterations of the choroid plexus epithelium.

Protective role of chrysin on 6-hydroxydopamine-induced neurodegeneration a mouse model of Parkinson's disease: Involvement of neuroinflammation and neurotrophins

Chrysin is a natural flavonoid which is found in bee propolis, honey and various plants, and neuroprotective effect of chrysin in mice was previously demonstrated by our group. Neuroinflammation, neurotrophic factors and neuronal recovery factors associated with the neuroprotective effect of this flavonoid require further investigations. Thus, now we investigated the possible involvement of inflammatory cytokines, neurotrophic factors and neuronal recovery in the effect of chrysin in 6-hydroxidopamine (6-OHDA), a well-established model of Parkinson's disease, in striatum of mice. The 6-OHDA microinjection induced behavioral alterations on the rotarod test and apomorphine-induced circling behavior in mice. 6-OHDA administration elevated levels of tumour necrosis factor-α, interferon-gamma, interleukin-1β, interleukin-2, interleukin-6 and nuclear factor-kappa B and decreased the interleukin-10 levels, total reactive antioxidant potential and total antioxidant reactivity in striatum, as well as, modified the calcium-binding protein B (S100B), brain-derived neurotrophic factor, nerve growth factor and glial cell line-derived neurotrophic factor levels. The intrastriatal injection of 6-OHDA also induced an decrease of dopamine, 3,4-dihydroxyphenylacetic acid, homovanylic acid levels and tyrosine hydroxylase content. Oral treatment with chrysin (10 mg/kg, 28 days), culminated with the prevention of these alterations occasioned by 6-OHDA. These results corroborated with the neuroprotective effect of chrysin in the treatment of Parkinson's disease and, indicated the mechanism involved throught the inflammatory cytokines, neurotrophic factors and recovery of dopaminergic neurons in striatum.

Obesity and Metabolic Syndrome Affect the Cholinergic Transmission a nd Cognitive Functions

Worldwide, at least 2.8 million people die each year as a result of being overweight or obese. Obesity leads to metabolic syndrome, a pathological condition characterized by adverse metabolic effects on blood pressure, cholesterol, triglycerides and insulin resistance. Population- based investigations have suggested that obesity and metabolic syndrome may be associated with poorer cognitive performance. A structured search of bibliographic source (PubMed) was undertaken. The following terms "inflammation and obesity and brain", "cholinergic system and obesity", "cholinergic system and metabolic syndrome", "Cognitive impairment and obesity" and "metabolic syndrome and brain" were used as search strings. Over 200 papers, mainly published in the past 10 years were analysed. The major results regarded keyword "metabolic syndrome and brain" followed by, "Cognitive impairment and obesity", "inflammation and obesity and brain", "cholinergic system and obesity" and "cholinergic system and metabolic syndrome". Most papers were pre-clinical but, in general, they were inhomogeneous. Therefore, the results were cited according their contribution to clarify the molecular involvement of obesity and/or metabolic syndrome in cholinergic impairment. This review focuses on the correlation between brain cholinergic system alterations and high-fat diet, describing the involvement of cholinergic system in inflammatory processes related to metabolic syndrome and obesity, which may lead to cognitive decline. Metabolic syndrome has been suggested as a risk factor for cerebrovascular diseases and has been associated with cognitive impairment in different functional brain domains. Preclinical and clinical studies have identified the cholinergic system as a specific target of metabolic syndrome and obesity. The modifications of cholinergic neurotransmission and its involvement in neuro-inflammation may be related to cognitive impairment that affects obese patients.

Neuronal P2X7 Receptors Revisited: Do They Really Exist?

P2X7 receptors (Rs) constitute a subclass of ATP-sensitive ionotropic receptors (P2X1-P2X7). P2X7Rs have many distinguishing features, mostly based on their long intracellular C terminus regulating trafficking to the cell membrane, protein-protein interactions, and post-translational modification. Their C-terminal tail is especially important in enabling the transition from the nonselective ion channel mode to a membrane pore allowing the passage of large molecules. There is an ongoing dispute on the existence of neuronal P2X7Rs with consequences for our knowledge on their involvement in neuroinflammation, aggravating stroke, temporal lobe epilepsy, neuropathic pain, and various neurodegenerative diseases. Whereas early results appeared to support the operation of P2X7Rs at neurons, more recently glial P2X7Rs are increasingly considered as indirect causes of neuronal effects. Specific tools for P2X7Rs are of limited value because of the poor selectivity of agonists, and the inherent failure of antibodies to differentiate between the large number of active and inactive splice variants, or gain-of-function and loss-of-function small nucleotide polymorphisms of the receptor. Unfortunately, the available P2RX7 knock-out mice generated by pharmaceutical companies possess certain splice variants, which evade inactivation. In view of the recently discovered bidirectional dialogue between astrocytes and neurons (and even microglia and neurons), we offer an alternative explanation for previous data, which assumedly support the existence of P2X7Rs at neurons. We think that the unbiased reader will follow our argumentation on astrocytic or microglial P2X7Rs being the primary targets of pathologically high extracellular ATP concentrations, although a neuronal localization of these receptors cannot be fully excluded either.

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.

Abstract P272: Involvement of Neuro-Inflammation in the Pathogenesis of MCT-Induced Pulmonary Hypertension

Background: Pulmonary hypertension (PH) is a devastating disease characterized by increase in pulmonary pressure that eventually leads to right heart failure and death. PH is associated with heightened circulatory cytokines and infiltration of inflammatory cells within the diseased lungs. However, involvement of inflammation within the central nervous system (CNS) in PH pathophysiology has never been investigated. Emerging evidence suggest that activated microglial cells and neuro-inflammation within the CNS play an important role in the pathology of several CNS disorders, including resistant hypertension. Objective: These observations led us to propose the hypothesis that microglial activation and neuro-inflammation in the autonomic brain regions play regulatory role in PH. Minocycline (Mino), an anti-inflammatory antibiotic, which has been reported to inhibit microglial activation in the autonomic brain regions, was used to test this hypothesis. Methods: PH was induced in adult male rats by a single injection of monocrotaline (MCT; 50mg/kg sc). A subset of MCT-injected animals was infused intracerebroventricularly (ICV) with Mino (20mg/ml). After 4 weeks of treatment, animals were sacrificed for the measurement of physiological and pathological parameters. Results: ICV infusion of Mino significantly attenuated right ventricular systolic pressure (RVSP; Con: 30.1±5, MCT: 76.1±14, MCT+Mino: 50.1±11 mmHg) and right ventricular hypertrophy (RVH; Con: 0.26±0.02, MCT: 0.49±0.12, MCT+Mino: 0.38+0.1) induced by MCT. MCT administration resulted in ~2 fold increase in microglial cells, predominantly in the hypothalamic paraventricular nucleus (PVN), an effect significantly attenuated by ICV Mino (Con: 4.0±1.0, MCT: 8.6±1.1, MCT+Mino: 5.0±1.0). MCT injection increased pro-inflammatory cytokines [IL-1β (155%), TNF-α (165%) and IL-6 (113%)] and decreased IL-10 (46%) levels in the PVN. However, ICV Mino treatment restored these cytokines to control levels. Conclusion: Our observations demonstrate that microglial activation in the PVN is involved in PH pathophysiology. They, for the first time, suggest the involvement of neuro-inflammation and autonomic dysregulation in the development and establishment of PH.

Involvement of Neuroinflammation during Brain Development in Social Cognitive Deficits in Autism Spectrum Disorder and Schizophrenia.

Development of social cognition, a unique and high-order function, depends on brain maturation from childhood to adulthood in humans. Autism spectrum disorder (ASD) and schizophrenia have similar social cognitive deficits, although age of onset in each disorder is different. Pathogenesis of these disorders is complex and contains several features, including genetic risk factors, environmental risk factors, and sites of abnormalities in the brain. Although several hypotheses have been postulated, they seem to be insufficient to explain how brain alterations associated with symptoms in these disorders develop at distinct developmental stages. Development of ASD appears to be related to cerebellar dysfunction and subsequent thalamic hyperactivation in early childhood. By contrast, schizophrenia seems to be triggered by thalamic hyperactivation in late adolescence, whereas hippocampal aberration has been possibly initiated in childhood. One of the possible culprits is metal homeostasis disturbances that can induce dysfunction of blood-cerebrospinal fluid barrier. Thalamic hyperactivation is thought to be induced by microglia-mediated neuroinflammation and abnormalities of intracerebral environment. Consequently, it is likely that the thalamic hyperactivation triggers dysregulation of the dorsolateral prefrontal cortex for lower brain regions related to social cognition. In this review, we summarize the brain aberration in ASD and schizophrenia and provide a possible mechanism underlying social cognitive deficits in these disorders based on their distinct ages of onset.

Postmortem evidence of cerebral inflammation in schizophrenia: a systematic review.

Schizophrenia is a psychiatric disorder which has a lifetime prevalence of ~1%. Multiple candidate mechanisms have been proposed in the pathogenesis of schizophrenia. One such mechanism is the involvement of neuroinflammation. Clinical studies, including neuroimaging, peripheral biomarkers and randomized control trials, have suggested the presence of neuroinflammation in schizophrenia. Many studies have also measured markers of neuroinflammation in postmortem brain samples from schizophrenia patients. The objective of this study was to conduct a systematic search of the literature on neuroinflammation in postmortem brains of schizophrenia patients indexed in MEDLINE, Embase and PsycINFO. Databases were searched up until 20th March 2016 for articles published on postmortem brains in schizophrenia evaluating microglia, astrocytes, glia, cytokines, the arachidonic cascade, substance P and other markers of neuroinflammation. Two independent reviewers extracted the data. Out of 5385 articles yielded by the search, 119 articles were identified that measured neuroinflammatory markers in schizophrenic postmortem brains. Glial fibrillary acidic protein expression was elevated, lower or unchanged in 6, 6 and 21 studies, respectively, and similar results were obtained for glial cell densities. On the other hand, microglial markers were increased, lower or unchanged in schizophrenia in 11, 3 and 8 studies, respectively. Results were variable across all other markers, but SERPINA3 and IFITM were consistently increased in 4 and 5 studies, respectively. Despite the variability, some studies evaluating neuroinflammation in postmortem brains in schizophrenia suggest an increase in microglial activity and other markers such as SERPINA3 and IFITM. Variability across studies is partially explained by multiple factors including brain region evaluated, source of the brain, diagnosis, age at time of death, age of onset and the presence of suicide victims in the cohort.

Alpha-synuclein oligomers acutely induce memory deficits and brain inflammation

Lewy body dementia (LBD) is an alpha-synucleopathy which is considered as the second most common form of dementia characterized by cognitive dysfunctions, which occur also in patients with Parkinson's disease (PD). Neuropathological hallmarks of LBD and PD are represented by neuronal inclusions composed of alpha-synuclein (α-syn) which is considered as a pathogenetic factor. Emerging evidence suggests that extracellular α-syn oligomers (α-synO) might be central pathological species. Our main objectives were ascertain: 1. the effect of extracellular α-synO on synaptic plasticity and memory; 2. glial cell activation which regulate synaptic plasticity and memory formation; 3. the involvement of the toll-like receptor 4 (TLR4). To test α-synO effect on memory, they were ICV injected in C57 mice (1μM/7.5μL) subsequently tested in the novel object recognition test (NORT). Long term potentiation (LTP) was also measured. The involvement of neuroinflammation was investigated through 1. NORT measuring the ability of an anti-inflammatory drug to prevent α-synO-mediated memory deficit; 2. TLR4 knock-out mice and 3. immunohistochemistry for glial cell activation following α-synO injection. α-synO significantly impaired memory and LTP. In addition we found that a single injection of α-synO induced neuroinflammation. α-synO-mediated neuroinflammation contributed to the memory impairment, since it was prevented by the treatment with an anti-inflammatory drug. We also found that the TLR4 pathway was not involved in mediating the cognitive impairment since α-synO affected memory also in mice lacking the TLR4. Our data provide a new acute mouse model to test the efficacy of new therapeutic approaches directed toward α-synO and to study their mechanism of action at multiple levels.

Peripheral inflammation increases seizure susceptibility via the induction of neuroinflammation and oxidative stress in the hippocampus.

BackgroundNeuroinflammation with activation of microglia and production of proinflammatory cytokines in the brain plays an active role in epileptic disorders. Brain oxidative stress has also been implicated in the pathogenesis of epilepsy. Damage in the hippocampus is associated with temporal lobe epilepsy, a common form of epilepsy in human. Peripheral inflammation may exacerbate neuroinflammation and brain oxidative stress. This study examined the impact of peripheral inflammation on seizure susceptibility and the involvement of neuroinflammation and oxidative stress in the hippocampus.ResultsIn male, adult Sprague-Dawley rats, peripheral inflammation was induced by the infusion of Escherichia coli lipopolysaccharide (LPS, 2.5 mg/kg/day) into the peritoneal cavity for 7 days via an osmotic minipump. Pharmacological agents were delivered via intracerebroventricular (i.c.v.) infusion with an osmotic minipump. The level of cytokine in plasma or hippocampus was analyzed by ELISA. Redox-related protein expression in hippocampus was evaluated by Western blot. Seizure susceptibility was tested by intraperitoneal (i.p.) injection of kainic acid (KA, 10 mg/kg). We found that i.p. infusion of LPS for 7 days induced peripheral inflammation characterized by the increases in plasma levels of interleukin-1β (IL-1β), interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α). This is associated with a significant increase in number of the activated microglia (Iba-1+ cells), enhanced production of proinflammatory cytokines (including IL-1β, IL-6 and TNF-α), and tissue oxidative stress (upregulations of the NADPH oxidase subunits) in the hippocampus. These cellular and molecular responses to peripheral inflammation were notably blunted by i.c.v. infusion of a cycloxygenase-2 inhibitor, NS398 (5 μg/μl/h). The i.c.v. infusion of tempol (2.5 μg/μl/h), a reactive oxygen species scavenger, protected the hippocampus from oxidative damage with no apparent effect on microglia activation or cytokine production after peripheral inflammation. In the KA-induced seizure model, i.c.v. infusion of both NS398 and tempol ameliorated the increase in seizure susceptibility in animals succumbed to the LPS-induced peripheral inflammation.ConclusionsTogether these results indicated that LPS-induced peripheral inflammation evoked neuroinflammation and the subsequent oxidative stress in the hippocampus, resulting in the increase in KA-induced seizure susceptibility. Moreover, protection from neuroinflammation and oxidative stress in the hippocampus exerted beneficial effect on seizure susceptibility following peripheral inflammation.

P.1.b.011 Flexibility and spatial learning deficits after experimental traumatic brain injury in mice: a consequence of white matter lesion?

Purpose of the study: Traumatic brain injury (TBI) results in white matter injury (WMI), evidenced by demyelination. WMI may originate from neuroinflammation and is associated with late emotional and cognitive disorders in patients. Experimental research focuses on brain lesions and neurological deficits occurring days after injury, occulting long-term consequences of TBI. The present study aims to evaluate the time-course of neuroinflammation, WMI and behavioral disorders related to anxiety, compulsiveness, depression, behavioral flexibility and spatial memory after TBI. Methods used: Three groups of male Swiss mice were studied: non-operated, sham-operated and traumatic brain injured mice. TBI was induced by a controlled cortical impact. Neuroinflammation was determined by microglia activation using CD11b immunostaining. The expression of myelin basic protein (MBP), a marker of myelination, was measured in the corpus callosum using Western blot (for all biomarkers evaluations n = 5−6/group). At 15 days, 1, 2 and 3 months, sensorimotor performances were determined with pole test and spontaneous locomotion with actimeter. Spatial learning and memory, and behavioral flexibility were assessed using Barnes maze: two weeks after TBI, mice were trained to find a target hole 3 trials/day during 4 days, followed by a probe test (i.e. in absence of target box) on the last day. At 1, 2 and 3 months, mice were trained to find a new target hole location as previously described. Compulsiveand anxiety-like behaviors using the marble-burying, the open field and the elevated plus maze tests and immobility/escape behavior in the forced swim test, more relevant to depression, were assessed 3 months postTBI (for all behavioral measurements: n = 9−12/group). Data were analyzed with one-way ANOVA. Results: Number of CD11b+ cells was increased from 24 h (P< 0.001) up to 7 days post-TBI (P< 0.001), showing neuroinflammation. MBP expression was decreased at 7 days and 3 months (P< 0.01) in ipsiand contralateral corpus callosum demonstrating acute and long-term bilateral WMI. Spontaneous locomotor activity, motor coordination performances, anxiety-like and despair-like behavioral measurements were undisturbed by TBI. Although, spatial learning performances were not disturbed at 2 weeks post-TBI, deficit was apparent when moving the target hole location 1, 2 and 3 months after TBI. While all mice discriminated the target zone correctly during the probe tests, latencies to find the new target hole, distances travelled and number of errors, were all significantly higher in injured mice during the first training day (P< 0.05), suggesting that TBI induces an early deficit in learning processes, behavioral adaptability and flexibility disorder. Conclusions: These data clearly demonstrate that TBI induces acute microglial activation that precedes acute and long term demyelination, suggesting the involvement of neuroinflammation in WMI. Moreover, the latter is associated with a reduction of flexibility and a spatial learning deficit, in the absence of sensorimotor and emotional states impairments, suggesting that changes in the escape behavior to the target hole, were related to behavioral flexibility rather than defense behavior. Behavioral evaluation is still ongoing until 12 months after TBI. This model will provide an overview of various late behavioral disorders and demyelination that could help to validate pharmacological strategies.

Postoperative cognitive dysfunction: Involvement of neuroinflammation and neuronal functioning

Postoperative cognitive dysfunction (POCD) has been hypothesized to be mediated by surgery-induced inflammatory processes, which may influence neuronal functioning either directly or through modulation of intraneuronal pathways, such as the brain derived neurotrophic factor (BDNF) mediated pathway. To study the time course of post-surgical (neuro)inflammation, changes in the BDNF-pathway and POCD, we subjected 3months old male Wistar rats to abdominal surgery and implanted a jugular vein catheter for timed blood sampling. Cognition, affective behavior and markers for (neuro)inflammation, BDNF and neurogenesis were assessed at 1, 2 and 3weeks following surgery. Rats displayed changes in exploratory activity shortly after surgery, associated with postoperatively elevated IL-6 plasma levels. Spatial learning and memory were temporarily impaired in the first 2weeks following surgery, whereas non-spatial cognitive functions seemed unaffected. Analysis of brain tissue revealed increased neuroinflammation (IL-1B and microgliosis) 7days following surgery, decreased BDNF levels on postoperative day 14 and 21, and decreased neurogenesis until at least 21days following surgery. These findings indicate that in young adult rats only spatial learning and memory is affected by surgery, suggesting hippocampal dependent cognition is especially vulnerable to surgery-induced impairment. The observed differences in time course following surgery and relation to plasma IL-6 suggest cognitive dysfunction and mood changes comprise distinct features of postoperative behavioral impairment. The postoperative changes in neuroinflammation, BDNF and neurogenesis may represent aspects of the underlying mechanism for POCD. Future research should be aimed to elucidate how these players interact.

The Role of Microglia and Matrix Metalloproteinases Involvement in Neuroinflammation and Gliomas

Matrix metalloproteinases (MMPs) are involved in the pathogenesis of neuroinflammatory diseases (such as multiple sclerosis) as well as in the expansion of malignant gliomas because they facilitate penetration of anatomical barriers (such as the glia limitans) and migration within the neuropil. This review elucidates pathomechanisms and summarizes the current knowledge of the involvement of MMPs in neuroinflammation and glioma, invasion highlighting microglia as major sources of MMPs. The induction of expression, suppression, and multiple pathways of function of MMPs in these scenarios will also be discussed. Understanding the induction and action of MMPs might provide valuable information and reveal attractive targets for future therapeutic strategies.

Clozapine Protects Dopaminergic Neurons from Inflammation-Induced Damage by Inhibiting Microglial Overactivation

Increasing evidence suggests a possible involvement of neuroinflammation in some psychiatric disorders, and also pharmacological reports indicate that anti-inflammatory effects are associated with therapeutic actions of psychoactive drugs, such as anti-depressants and antipsychotics. The purpose of this study was to explore whether clozapine, a widely used antipsychotic drugs, displays anti-inflammatory and neuroprotective effects. Using primary cortical and mesencephalic neuron-glia cultures, we found that clozapine was protective against inflammation-related neurodegeneration induced by lipopolysaccharide (LPS). Pretreatment of cortical or mesencephalic neuron-glia cultures with clozapine (0.1 or 1 μM) for 24 h attenuated LPS-induced neurotoxicity. Clozapine also protected neurons against 1-methyl-4-phenylpyridinium(+) (MPP(+))-induced neurotoxicity, but only in cultures containing microglia, indicating an indispensable role of microglia in clozapine-afforded neuroprotection. Further observation revealed attenuated LPS-induced microglial activation in primary neuron-glia cultures and in HAPI microglial cell line with clozapine pretreatment. Clozapine ameliorated the production of microglia-derived superoxide and intracellular reactive oxygen species (ROS), as well as the production of nitric oxide and TNF-α following LPS. In addition, the protective effect of clozapine was not observed in neuron-glia cultures from mice lacking functional NADPH oxidase (PHOX), a key enzyme for superoxide production in immune cells. Further mechanistic studies demonstrated that clozapine pretreatment inhibited LPS-induced translocation of cytosolic subunit p47(phox) to the membrane in microglia, which was most likely through inhibiting the phosphoinositide 3-kinase (PI3K) pathway. Taken together, this study demonstrates that clozapine exerts neuroprotective effect via the attenuation of microglia activation through inhibition of PHOX-generated ROS production and suggests potential use of antipsychotic drugs for neuroprotection.

The involvement of neuroinflammation and kynurenine pathway in Parkinson's disease.

Parkinson's disease (PD) is a common neurodegenerative disorder characterised by loss of dopaminergic neurons and localized neuroinflammation occurring in the midbrain several years before the actual onset of symptoms. Activated microglia themselves release a large number of inflammatory mediators thus perpetuating neuroinflammation and neurotoxicity. The Kynurenine pathway (KP), the main catabolic pathway for tryptophan, is one of the major regulators of the immune response and may also be implicated in the inflammatory response in parkinsonism. The KP generates several neuroactive compounds and therefore has either a neurotoxic or neuroprotective effect. Several of these molecules produced by microglia can activate the N-methyl-D-aspartate (NMDA) receptor-signalling pathway, leading to an excitotoxic response. Previous studies have shown that NMDA antagonists can ease symptoms and exert a neuroprotective effect in PD both in vivo and in vitro. There are to date several lines of evidence linking some of the KP intermediates and the neuropathogenesis of PD. Moreover, it is likely that pharmacological modulation of the KP will represent a new therapeutic strategy for PD.

Protective effects of indomethacin-loaded nanocapsules against oxygen-glucose deprivation in organotypic hippocampal slice cultures: Involvement of neuroinflammation

Targeted treatment of diseases of the central nervous system remains problematic due to the complex pathogenesis of these disorders and the difficulty in drug delivery. Here we investigate the neuroprotective effect of indomethacin-loaded nanocapsules (IndOH-NC) in an in vitro model of ischemia. For this purpose we used organotypic hippocampal cultures exposed to oxygen-glucose deprivation (OGD). When the cultures were exposed to 60 min of OGD, 54.5 ± 14.7% of the total area of the hippocampal slices was labeled with propidium iodide. On the other hand, when the cultures were treated with 50 or 100 μM of IndOH-NC the cell death was significantly reduced to 31 ± 7% ( P < 0.05) and 20 ± 4% ( P < 0.001), respectively. The treatment with IndOH-NC markedly inhibited the levels of the pro-inflammatory cytokines IL-1β, IL-6 and TNF-α levels even 48 h after OGD. Immunoblotting revealed that treatment with 100 μM of IndOH-NC was able to significantly reduce to the levels of control cultures the levels of ERK1/2 and JNK phosphorylation, as well as iNOS activation. Additionally, IndOH-NC prevented glial activation induced by OGD, as evidenced by a decrease of GFAP immunocontent and Isolectin B 4 reactivity. Our results clearly demonstrate that IndOH-NC might represent a promising pharmaceutical neuroprotective formulation for cerebral ischemia, most probably by inhibiting the inflammatory cascades.

Neuroinflammation, Oxidative Stress and the Pathogenesis of Alzheimers Disease

Alzheimer's disease (AD) is the most common neurodegenerative disorder that affects the elderly. The increase of life-expectancy is transforming AD into a major health-care problem. AD is characterized by a progressive impairment of memory and other cognitive skills leading to dementia. The major pathogenic factor associated to AD seems to be amyloid-beta peptide (Aβ) oligomers that tend to accumulate extracellularly as amyloid deposits and are associated with reactive microglia and astrocytes as well as with degeneration of neuronal processes. The involvement of microglia and astrocytes in the onset and progress of neurodegenerative process in AD is becoming increasingly recognized, albeit it is commonly accepted that neuroinflammation and oxidative stress can have both detrimental and beneficial influences on the neural tissue. However, little is known about the interplay of microglia, astrocytes and neurons in response to Aβ, especially in the early phases of AD. This review discusses current knowledge about the involvement of neuroinflammation in AD pathogenesis, focusing on phenotypic and functional responses of microglia, astrocytes and neurons in this process. The abnormal production by glia cells of pro-inflammatory cytokines, chemokines and the complement system, as well as reactive oxygen and nitrogen species, can disrupt nerve terminals activity causing dysfunction and loss of synapses, which correlates with memory decline; these are phenomena preceding the neuronal death associated with late stages of AD. Thus, therapeutic strategies directed at controlling the activation of microglia and astrocytes and the excessive production of pro-inflammatory and pro-oxidant factors may be valuable to control neurodegeneration in dementia.

Non-Steroidal Anti-Inflammatory Drugs as Anti-Amyloidogenic Compounds

Amyloidosis is a clinical disorder caused by deposition of proteins that abnormally self-assemble into insoluble fibrils and impair organ function. More than 20 unrelated precursor proteins lose their native structure and misfold, leading to the formation of amyloid fibrils. The latter share cross-beta core structure in vivo and in vitro and gain abnormal functions. Local amyloid deposition occurs in the central nervous system in Alzheimer's disease (AD) and cerebral amyloid angiopathy. AD is the most common form of neurodegenerative disorder, with dementia in the elderly as well as dementia with Lewy bodies (DLB). Extracellular deposition of amyloid beta-peptide (Abeta) has been implicated as a critical step in the pathogenesis of AD. Involvement of neuroinflammation and microglial activation has been emphasized in the AD brain. Recent epidemiological studies have shown that long-term therapeutic use of non-steroidal anti-inflammatory drugs (NSAIDs) reduces the risk of developing AD and delayed the onset of AD. We review epidemiological studies of anti-AD effects of NSAIDs, experimental studies of anti-amyloidogenic as well as anti-inflammatory effects of NSAIDs, and recent clinical trials for AD with NSAIDs. We refer to the anti-fibrillogenic and fibril-destabilizing activities of NSAIDs for other proteins that can aggregate and form amyloid-like fibrils, including alpha-synuclein in DLB. The anti-amyloidogenic properties of some NSAIDs provide new insights for future therapeutic and preventative opportunities for AD and other amyloidoses, and protein-misfolding disorders.

Non-steroidal anti-inflammatory drugs have potent anti-fibrillogenic and fibril-destabilizing effects for α-synuclein fibrils in vitro

The aggregation of α-synuclein (αS) in the brain has been implicated as a critical step in the development of Lewy body diseases (LBD) [Parkinson's disease (PD)/dementia with Lewy bodies (DLB)] and multiple system atrophy (MSA). The involvement of neuroinflammation and microglial activation has been emphasized in the pathogenesis of PD. Recent epidemiological studies have revealed that therapeutic use of non-steroidal anti-inflammatory drugs (NSAIDs) reduces the risk of developing PD. Here, we examined the effects of NSAIDs, such as ibuprofen, aspirin, acetaminophen, meclofenamic acid sodium salt, sulindac sulfide, ketoprofen, flurbiprofen, diclofenac sodium salt, naproxen, and indomethacin, on the formation and destabilization of αS fibrils (fαS) at pH 7.5 and 37 °C in vitro, using fluorescence spectroscopy with thioflavin S and electron microscopy. All examined NSAIDs, except for naproxen and indomethacin, inhibited the formation of fαS in a dose-dependent manner. Moreover, these molecules dose-dependently destabilized preformed fαS. The overall activity was in the order: ibuprofen ≈ aspirin ≈ acetaminophen ≈ meclofenamic acid sodium salt ≈ sulindac sulfide > ketoprofen ≈ flurbiprofen ≈ diclofenac sodium salt > naproxen ≈ indomethacin. These findings indicate that NSAIDs could be key molecules for the development of therapeutic or preventive agents for LBD and MSA.