IL-4, IL-10 and IL-13 modulate A beta(1--42)-induced cytokine and chemokine production in primary murine microglia and a human monocyte cell line

Immunotherapy for depression: Recent insights and future targets

Depression stands as a prominent contributor to global disability, entailing an elevated risk of suicide. Substantial evidence supports the notion that immune dysregulation may play a role in the development of depression and impede responses to antidepressant treatments. Immune dysregulation may cause depression in susceptible individuals through raising inflammatory responses. Differences in immune cell types and the release of pro-inflammatory mediators are observed in the blood and cerebrospinal fluid of patients with major depressive disorder, which is associated with neuroimmune dysfunction. Therefore, the interaction of peripheral and central immune targets in depression needs to be understood. Urgent attention is required for the development of innovative therapeutics directed at modulating immune responses for the treatment of depression. This review delineates the immune mechanisms involved in the pathogenesis of depression, assesses the therapeutic potential of immune system targeting for depression treatment, and deliberates on the merits and constraints of employing immunotherapy in the management of depression.

TREM2 in Alzheimer's disease: Structure, function, therapeutic prospects, and activation challenges

Triggering receptor expressed on myeloid cells 2 (TREM2) is a membrane glycoprotein that plays a crucial role in the regulation of microglial survival, activation, phagocytosis, as well as in the maintenance of brain homeostasis and the inflammatory response to injury or neurodegeneration. This review provides a comprehensive overview of TREM2 structure and functions, highlighting the role of its variants in the development and progression of Alzheimer's disease (AD), a devastating neurodegenerative disease that affects millions of people worldwide. Additionally, the article discusses the potential of TREM2 as a therapeutic target in AD, analyzing the current state of research and future prospects. Given the significant challenges associated with the activation of TREM2, particularly due to its diverse isoforms and the delicate balance required to modulate the immune response without triggering hyperactivation, this review aims to enhance our understanding of TREM2 in AD and inspire further research into this promising yet challenging therapeutic target.

Early treatment with an M1 and sigma-1 receptor agonist prevents cognitive decline in a transgenic rat model displaying Alzheimer-like amyloid pathology

The application of the selective allosteric M1 muscarinic and sigma-1 receptor agonist, AF710B (aka ANAVEX3-71), has shown to attenuate Alzheimer's disease-like hallmarks in McGill-R-Thy1-APP transgenic rats when administered at advanced pathological stages. It remains unknown whether preventive treatment strategies applying this compound may be equally effective. We tested whether daily oral administration of AF710B (10 µg/kg) in 7-month-old, preplaque, McGill-R-Thy1-APP rats for 7 months, followed by a 4-week washout period, could prevent Alzheimer's disease-like pathological hallmarks. Long-term AF710B treatment prevented the cognitive impairment of McGill-R-Thy1-APP rats. The effect was accompanied by a reduction in the number of amyloid plaques in the hippocampus and the levels of Aβ42 and Aβ40 peptides in the cerebral cortex. AF710B treatment also reduced microglia and astrocyte recruitment toward CA1 hippocampal Aβ-burdened neurons compared to vehicle-treated McGill-R-Thy1-APP rats, also altering the inflammatory cytokines profile. Lastly, AF710B treatment rescued the conversion of brain-derived neurotrophic factor precursor to its mature and biologically active form. Overall, these results suggest preventive and disease-modifying properties of the compound.

Investigation of anti-depression effects and potential mechanisms of the ethyl acetate extract of Cynomorium songaricum Rupr. through the integration of in vivo experiments, LC-MS/MS chemical analysis, and a systems biology approach

Background: Cynomorium songaricum Rupr. has long been used as an anti-inflammatory, antidepressant, and anti-aging agent in traditional Chinese medicine in Asia. Its ethyl acetate extract (ECS) has been identified as the main antioxidant component with neuroprotective and estrogen-like effects. However, the potential of ECS in treating depression has not been explored yet. Methods: We identified the primary metabolites in ECS in this study using liquid chromatography-electrospray tandem mass spectrometry (LC-MS/MS). Network analysis was used to find the potential targets and pathways associated with the anti-neuroinflammatory depression action of the ECS. In addition, we established a corticosterone (CORT)-induced depression mouse model to assess ECS's antidepressant effects by monitoring various behavioral changes (e.g., sucrose preference, forced swimming, tail suspension, and open field tests) and biochemical indices of the hippocampus, and validating the network analysis results. Significant pathways underwent verification through western blotting based on network analysis prediction. Results: Our study demonstrates that ECS possesses significant antidepressant activity. The LC-MS/MS analysis of ECS identified 30 main metabolites, including phloridzin, phlorizin, ursolic acid, and naringenin, as well as other flavonoids, terpenoids, and phenolic acids. These metabolites were found to be associated with 64 candidate target proteins related to neuroinflammatory depression from the database, and ten hub proteins were identified through filtration: CXCL8, ICAM1, NOS2, SELP, TNF, IL6, APP, ACHE, MAOA and ADA. Functional enrichment analyses of the candidate targets revealed their primary roles in regulating cytokine production, inflammatory response, cytokine activity, and tumor necrosis factor receptor binding. In vivo, ECS improved hippocampal neuroinflammation in the mouse model. Specifically, ECS reduced the expression of inflammatory factors in the hippocampus, inhibited M1 microglial cell polarization, and alleviated depression through the regulation of the NF-κB-NLRP3 inflammation pathway. Conclusion: Based on experimental and network analysis, this study revealed for the first time that ECS exerted antidepression effect via anti-neuroinflammation. Our research provides valuable information on the use of ECS as an alternative therapeutic approach for depression.

Amelioration of colitis progression by ginseng-derived exosome-like nanoparticles through suppression of inflammatory cytokines

Background

Damage to the healthy intestinal epithelial layer and regulation of the intestinal immune system, closely interrelated, are considered pivotal parts of the curative treatment for inflammatory bowel disease (IBD). Plant-based diets and phytochemicals can support the immune microenvironment in the intestinal epithelial barrier for a balanced immune system by improving the intestinal microecological balance and may have therapeutic potential in colitis. However, there have been only a few reports on the therapeutic potential of plant-derived exosome-like nanoparticles (PENs) and the underlying mechanism in colitis. This study aimed to assess the therapeutic effect of PENs from Panax ginseng, ginseng-derived exosome-like nanoparticles (GENs), in a mouse model of IBD, with a focus on the intestinal immune microenvironment.

Method

To evaluate the anti-inflammatory effect of GENs on acute colitis, we treated GENs in Caco2 and lipopolysaccharide (LPS) -induced RAW 264.7 macrophages and analyzed the gene expression of pro-inflammatory cytokines and anti-inflammatory cytokines such as TNF-α, IL-6, and IL-10 by real-time PCR (RT-PCR). Furthermore, we further examined bacterial DNA from feces and determined the alteration of gut microbiota composition in DSS-induced colitis mice after administration of GENs through 16S rRNA gene sequencing analysis.

Result

GENs with low toxicity showed a long-lasting intestinal retention effect for 48 h, which could lead to effective suppression of pro-inflammatory cytokines such as TNF-α and IL-6 production through inhibition of NF-κB in DSS-induced colitis. As a result, it showed longer colon length and suppressed thickening of the colon wall in the mice treated with GENs. Due to the amelioration of the progression of DSS-induced colitis with GENs treatment, the prolonged survival rate was observed for 17 days compared to 9 days in the PBS-treated group. In the gut microbiota analysis, the ratio of Firmicutes/Bacteroidota was decreased, which means GENs have therapeutic effectiveness against IBD. Ingesting GENs would be expected to slow colitis progression, strengthen the gut microbiota, and maintain gut homeostasis by preventing bacterial dysbiosis.

Conclusion

GENs have a therapeutic effect on colitis through modulation of the intestinal microbiota and immune microenvironment. GENs not only ameliorate the inflammation in the damaged intestine by downregulating pro-inflammatory cytokines but also help balance the microbiota on the intestinal barrier and thereby improve the digestive system.

A systematic review of exercise modalities that reduce pro-inflammatory cytokines in humans and animals' models with mild cognitive impairment or dementia

PURPOSE

To investigate which type, frequency, duration, intensity, and volume of chronic exercise might more strongly reduce pro-inflammatory cytokines and enhance anti-inflammatory cytokines in human and animal models with Mild Cognitive Impairment (MCI) or dementia.

DESIGN

A systematic review.

DATA SOURCE

English-language search of 13 electronic databases: Web of Science, PubMed/Medline, Sport Discus, Scopus, Cochrane, Psych Net, Springer, ScienceDirect, Pascal & Francis, Sage journals, Pedro, Google Scholar, and Sage.

INCLUSION CRITERIA

(i) human and animal studies that included exercise, physical activity, or fitness training as an experimental intervention, (ii) studies that addressed MCI, dementia, or AD, (iii) studies that focused on measuring cytokines and/or other inflammatory and/or neuroinflammatory immune markers, (iii) studies that examined inflammatory indicators in blood, CSF (Cerebrospinal Fluid), and brain tissue.

RESULTS

Of the 1290 human and animal studies found, 38 were included for qualitative analysis, 11 human articles, 27 animal articles, and two articles addressing both human and animal protocols. In the animal model, physical exercise decreased pro-inflammatory markers in 70.8 % of the articles and anti-inflammatory cytokines: IL -4, IL -10, IL-4β, IL -10β, and TGF-β in 26 % of articles. Treadmill running, resistance exercise, and swimming exercise reduce pro-inflammatory cytokines and increase anti-inflammatory cytokines. In the human model, 53.9 % of items reduced pro-inflammatory proteins and 23 % increased anti-inflammatory proteins. Cycling exercise, multimodal, and resistance training effectively decreased pro-inflammatory cytokines.

CONCLUSION

In rodent animal models with AD phenotype, treadmill, swimming, and resistance training remain good interventions that can delay various mechanisms of dementia progression. In the human model, aerobic, multimodal, and resistance training are beneficial in both MCI and AD. Multimodal training of moderate to high intensity multimodal exercise is effective for MCI. Voluntary cycling training, moderate- or high-intensity aerobic exercise is effective in mild AD patients.

The Neuroprotective Effects and Therapeutic Potential of the Chalcone Cardamonin for Alzheimer's Disease

Neurodegenerative diseases (ND) include a wide range of conditions that result from progressive damage to the neurons. Alzheimer's disease (AD) is one of the most common NDs, and neuroinflammation and oxidative stress (OS) are the major factors in the development and progression of the disease. Many naturally occurring phytochemical compounds exhibit antioxidant and anti-inflammatory activities with potential neuroprotective effects. Several plant species, including Alpinia katsumadai and Alpinia conchigera, contain cardamonin (CD). CD (2',4'-dihydroxy-6'methoxychalcone) has many therapeutic properties, including anticancer, anti-inflammatory, antioxidant, antiviral, and antibiotic activities. CD is a potent compound that can reduce OS and modulate the inflammatory processes that play a significant part in developing neurodegenerative diseases. CD has been shown to modulate a variety of signaling molecules involved in the development and progression of ND, including transcription factors (NF-kB and STAT3), cytokines (TNF-α, IL-1, and IL-6), enzymes (COX-2, MMP-9, and ALDH1), and other proteins and genes (Bcl-2, XIAP, and cyclin D1). Additionally, CD effectively modulates miRNA levels and autophagy-related CD-protective mechanisms against neurodegeneration. In summary, this review provides mechanistic insights into CD's ability to modify multiple oxidative stress-antioxidant system pathways, Nrf2, and neuroinflammation. Additionally, it points to the possible therapeutic potential and preventive utilization of CD in neurodegenerative diseases, most specifically AD.

Genome integrity and inflammation in the nervous system

Preservation of genomic integrity is crucial for nervous system development and function. DNA repair deficiency results in several human diseases that are characterized by both neurodegeneration and neuroinflammation. Recent research has highlighted a role for compromised genomic integrity as a key factor driving neuropathology and triggering innate immune signaling to cause inflammation. Here we review the mechanisms by which DNA damage engages innate immune signaling and how this may promote neurological disease. We also consider the contributions of different neural cell types towards DNA damage-driven neuroinflammation. A deeper knowledge of genome maintenance mechanisms that prevent aberrant immune activation in neural cells will guide future therapies to ameliorate neurological disease.

Regulation of the Human IL-10RB Gene Expression by Sp8 and Sp9

BACKGROUND

Interleukin-10 (IL-10) is a classic anti-inflammatory cytokine that exerts its effects via the receptor complexes IL-10RA and IL-10RB. Loss of IL-10RB results in many diseases. Moreover, IL-10RB is closely associated with neuronal survival and synaptic formation. However, the regulation of IL-10RB gene expression remains elusive.

OBJECTIVE

To investigate whether the expression of IL-10RB gene is increased in brain of Alzheimer's disease (AD) and its transcriptional regulation.

METHODS

We examined the gene expression of AD patient brain from public database and detected the protein expression of AD model mouse brain by western blot. We constructed a variety of reporter gene plasmids with different lengths or mutation sites, tested the promoter activity and defined the functional region of the promoter with the luciferase reporter assay. The protein-DNA binding between transcription factors and the promoter was analyzed using chromatin immunoprecipitation (ChIP) and electrophoretic mobility shift assay (EMSA).

RESULTS

We found that the IL-10RB is elevated in the brain of AD patient and AD model mice. The minimal promoter of the IL-10RB gene is located in the -90 to +51 bp region (relative to the transcriptional start site) and is sufficient for high-level expression of the IL-10RB gene. Transcription factors Sp8 and Sp9 bind to the IL-10RB promoter in vitro. The overexpression or knockdown of Sp8 and Sp9 affected the IL-10RB promoter activity and its gene expression.

CONCLUSION

Our study functionally characterized the promoter of the IL-10RB gene and demonstrated that Sp8 and Sp9 regulated its expression.

Interleukin 13 promotes long-term recovery after ischemic stroke by inhibiting the activation of STAT3

BACKGROUND

Microglia/macrophages are activated after cerebral ischemic stroke and can contribute to either brain injury or recovery by polarizing microglia/macrophage into distinctive functional phenotypes with pro- or anti-inflammatory properties. Interleukin-13 (IL-13) is an anti-inflammatory cytokine that regulates microglia/macrophage polarization toward an anti-inflammatory phenotype. However, it is not clear whether IL-13 is beneficial after ischemic stroke long-term and the underlying molecular mechanism(s) remain unknown. Thus, we examined the effect of IL-13 on long-term recovery and microglia/macrophage polarization in mice with transient middle cerebral artery occlusion model (tMCAO).

METHODS

tMCAO was induced in adult male C57BL/6J mice. IL-13 (60 μg/kg) was administered intranasally starting 2 h after stroke and continued for seven consecutive days. Sensorimotor function, spatial learning and memory function, as well as brain infarct volume were assessed up to 35 days after stroke. White matter integrity was evaluated by electrophysiology, immunofluorescence staining, and transmission electron microscopy. Microglia/macrophage activation was assessed using immunofluorescence staining and quantitative real-time polymerase chain reaction. Changes in immune cells in the brain and the periphery, and expression of IL-13 receptors in different brain cells were detected by flow cytometry. Primary neuron/microglia co-cultures and a STAT3 inhibitor were used for mechanistic studies.

RESULTS

Post-treatment with IL-13 improved long-term neurofunctional recovery and decreased brain tissue atrophy after stroke. Intranasal delivery of IL-13 enhanced the structural and functional integrity of white matter after stroke. Furthermore, the neuroprotection afforded by IL-13 administration was not due to a direct effect on neurons, but by indirectly regulating the anti-inflammatory phenotype of microglia/macrophages. IL-13 treatment also had no effect on peripheral immune cells. Mechanistically, IL-13 improved the long-term outcome after ischemic stroke by promoting the polarization of microglia/macrophages toward the anti-inflammatory phenotype at least partially by inhibiting the phosphorylation of STAT3.

CONCLUSIONS

IL-13 promotes white matter repair and improves neurofunctional outcomes after ischemic stroke by modulating microglia/macrophages via inhibition of STAT3 phosphorylation.

Acupuncture Effect Assessment in APP/PS1 Transgenic Mice: On Regulating Learning-Memory Abilities, Gut Microbiota, and Microbial Metabolites

Alzheimer's disease (AD) is a brain illness that affects learning and memory capacities over time. In recent investigations, acupuncture has been shown to be an effective alternative treatment for AD. We investigated the effect of acupuncture on learning and memory abilities using a water maze in APP/PS1 transgenic mice. The amounts of Aβ and tau protein in mice's hippocampal tissue were determined using Western blot. The levels of IL-1β, IL-10, LPS and TNF-α in mice's serum were measured using ELISA. The variations of gut microbiota in mice's feces were determined using the 16SrDNA technique, and the metabolites were examined using a untargeted metabolomics methodology. The results showed that acupuncture treatment improved mice's learning and memory abilities substantially. Acupuncture therapy regulated the Aβ and tau protein concentration as well as the levels of IL-10 and LPS. Acupuncture treatment influenced the mouse microbiota and metabolites and had been linked to six biochemical pathways. This study adds to our understanding of the effect of acupuncture on AD and opens the door to further research into the alterations of intestinal bacteria in the presence of AD.

Neuroinflammation in Amyotrophic Lateral Sclerosis and Frontotemporal Dementia and the Interest of Induced Pluripotent Stem Cells to Study Immune Cells Interactions With Neurons

Inflammation is a shared hallmark between amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). For long, studies were conducted on tissues of post-mortem patients and neuroinflammation was thought to be only bystander result of the disease with the immune system reacting to dying neurons. In the last two decades, thanks to improving technologies, the identification of causal genes and the development of new tools and models, the involvement of inflammation has emerged as a potential driver of the diseases and evolved as a new area of intense research. In this review, we present the current knowledge about neuroinflammation in ALS, ALS-FTD, and FTD patients and animal models and we discuss reasons of failures linked to therapeutic trials with immunomodulator drugs. Then we present the induced pluripotent stem cell (iPSC) technology and its interest as a new tool to have a better immunopathological comprehension of both diseases in a human context. The iPSC technology giving the unique opportunity to study cells across differentiation and maturation times, brings the hope to shed light on the different mechanisms linking neurodegeneration and activation of the immune system. Protocols available to differentiate iPSC into different immune cell types are presented. Finally, we discuss the interest in studying monocultures of iPS-derived immune cells, co-cultures with neurons and 3D cultures with different cell types, as more integrated cellular approaches. The hope is that the future work with human iPS-derived cells helps not only to identify disease-specific defects in the different cell types but also to decipher the synergistic effects between neurons and immune cells. These new cellular tools could help to find new therapeutic approaches for all patients with ALS, ALS-FTD, and FTD.

Exposure of Microglia to Interleukin-4 Represses NF-κB-Dependent Transcription of Toll-Like Receptor-Induced Cytokines

Interleukin (IL)-4 is a cytokine that affects both adaptive and innate immune responses. In the central nervous system, microglia express IL-4 receptors and it has been described that IL-4-exposed microglia acquire anti-inflammatory properties. We here demonstrate that IL-4 exposure induces changes in the cell surface protein expression profile of primary rhesus macaque microglia and enhances their potential to induce proliferation of T cells with a regulatory signature. Moreover, we show that Toll like receptor (TLR)-induced cytokine production is broadly impaired in IL-4-exposed microglia at the transcriptional level. IL-4 type 2 receptor-mediated signaling is shown to be crucial for the inhibition of microglial innate immune responses. TLR-induced nuclear translocalization of NF-κB appeared intact, and we found no evidence for epigenetic modulation of target genes. By contrast, nuclear extracts from IL-4-exposed microglia contained significantly less NF-κB capable of binding to its DNA consensus site. Further identification of the molecular mechanisms that underlie the inhibition of TLR-induced responses in IL-4-exposed microglia may aid the design of strategies that aim to modulate innate immune responses in the brain, for example in gliomas.

Neuroprotective Effect of Clobenpropit against Lipopolysaccharide-Induced Cognitive Deficits via Attenuating Neuroinflammation and Enhancing Mitochondrial Functions in Mice

Clobenpropit (CLO), an antagonist on histamine H₃ receptors (HH3R), has been shown to protect NMDA-induced neuronal necrosis in cortical neuronal cell culture from rats. In this work, we explored its potential on lipopolysaccharide (LPS)-induced memory deficits, neuroinflammation, and mitochondrial dysfunction in mice. CLO (1 and 3 mg/kg, p.o.) was treated continually for 30 days, and neurotoxicity was induced by four doses of LPS (250 µg/kg, i.p.). The radial arm maze (RAM) was used to access memory behaviors. After the REM test, brain tissue was collected from each mouse to estimate pro-inflammatory cytokines (TNFα and IL6), anti-inflammatory cytokines (TGF-β1 and IL-10), cyclooxygenase-2 (COX 2), and mitochondrial respiratory chain complex (MRCC- I, II and IV) enzymes. CLO treatment reversed the LPS-induced behavioral deficits by a significant reduction in time taken to consume all five bites (TTB), working memory error (WME), and reference memory error (REM) in the REM test. Regarding neuroinflammation, it attenuated the release of COX, TNF-α, and IL-6, and augmented TGF-β1 and IL-10 levels in the brain. Reversal of LPS-induced brain MRCC (I, II, and IV) levels also resulted with CLO treatment. From these findings, CLO promises neuroprotection against LPS-induced cognitive deficits by ameliorating neuroinflammation and restoring the MRCC enzymes in mice.

Reduced TREM2 activation in microglia of patients with Alzheimer's disease

Loss-of-function variants of triggering receptor expressed on myeloid cells 2 (TREM2) increase the risk of developing Alzheimer's disease (AD). The mechanism through which TREM2 contributes to the disease (TREM2 activation vs inactivation) is largely unknown. Here, we analyzed changes in a gene set downstream of TREM2 to determine whether TREM2 signaling is modified by AD progression. We generated an anti-human TREM2 agonistic antibody and defined TREM2 activation in terms of the downstream expression changes induced by this antibody in microglia developed from human induced pluripotent stem cells (iPSC). Differentially expressed genes (DEGs) following TREM2 activation were compared with the gene set extracted from microglial single nuclear RNA sequencing data of patients with AD, using gene set enrichment analysis. We isolated an anti-TREM2-specific agonistic antibody, Hyb87, from anti-human TREM2 antibodies generated using binding and agonism assays, which helped us identify 300 upregulated and 251 downregulated DEGs. Pathway enrichment analysis suggested that TREM2 activation may be associated with Th2-related pathways. TREM2 activation was lower in AD microglia than in microglia from healthy subjects or patients with mild cognitive impairment. TREM2 activation also showed a significant negative correlation with disease progression. Pathway enrichment analysis of DEGs controlled by TREM2 activity indicated that TREM2 activation in AD may lead to anti-apoptotic signaling, immune response, and cytoskeletal changes in the microglia. We showed that TREM2 activation decreases with AD progression, in support of a protective role of TREM2 activation in AD. In addition, the agonistic anti-TREM2 antibody can be used to identify TREM2 activation state in AD microglia.

Functional Mechanism of Bone Marrow-Derived Mesenchymal Stem Cells in the Treatment of Animal Models with Alzheimer's Disease: Inhibition of Neuroinflammation

The transplantation of bone marrow-derived mesenchymal stem cells (BMMSCs) alleviates neuropathology and improves cognitive deficits in animal models with Alzheimer’s disease. However, the underlying mechanisms remain to be determined. Available data demonstrate transplanted BMMSCs can inhibit neuroinflammation, which may be related to microglial M1/M2 polarization and is regulated by the secretion of autocrine and paracrine cytokines. BMMSCs also mitigate Aβ plaques and Tau tangles in the brain, which may be associated with the recruitment of peripheral blood monocytes and the subsequent comprehensive effects. The therapeutic effects of stem cells involve potential mechanisms such as immunomodulation, apoptosis, and proliferation. BMMSC-mediated functional reconstruction through dynamic remodeling develops a novel balance. Herein, present review recapitulates the molecular basis of BMMSC-assisted biological processes and summarizes the possible mechanisms related to the interaction between BMMSCs and microglia. The transplanted BMMSCs can suppress neuroinflammation that plays a key role in the pathogenesis of Alzheimer’s disease.

The role of meningeal populations of type II innate lymphoid cells in modulating neuroinflammation in neurodegenerative diseases

Recent research into meningeal lymphatics has revealed a never-before appreciated role of type II innate lymphoid cells (ILC2s) in modulating neuroinflammation in the central nervous system (CNS). To date, the role of ILC2-mediated inflammation in the periphery has been well studied. However, the exact distribution of ILC2s in the CNS and therefore their putative role in modulating neuroinflammation in neurodegenerative diseases such as Alzheimer's disease (AD), multiple sclerosis (MS), Parkinson's disease (PD), and major depressive disorder (MDD) remain highly elusive. Here, we review the current evidence of ILC2-mediated modulation of neuroinflammatory cues (i.e., IL-33, IL-25, IL-5, IL-13, IL-10, TNFα, and CXCL16-CXCR6) within the CNS, highlight the distribution of ILC2s in both the periphery and CNS, and discuss some challenges associated with cell type-specific targeting that are important for therapeutics. A comprehensive understanding of the roles of ILC2s in mediating and responding to inflammatory cues may provide valuable insight into potential therapeutic strategies for many dementia-related disorders.

A Computational Exploration of the Molecular Network Associated to Neuroinflammation in Alzheimer's Disease

Neuroinflammation, as defined by the presence of classically activated microglia, is thought to play a key role in numerous neurodegenerative disorders such as Alzheimer’s disease. While modulating neuroinflammation could prove beneficial against neurodegeneration, identifying its most relevant biological processes and pharmacological targets remains highly challenging. In the present study, we combined text-mining, functional enrichment and protein-level functional interaction analyses to 1) identify the proteins significantly associated to neuroinflammation in Alzheimer’s disease over the scientific literature, 2) distinguish the key proteins most likely to control the neuroinflammatory processes significantly associated to Alzheimer's disease, 3) identify their regulatory microRNAs among those dysregulated in Alzheimer's disease and 4) assess their pharmacological targetability. 94 proteins were found to be significantly associated to neuroinflammation in Alzheimer’s disease over the scientific literature and IL4, IL10 and IL13 signaling as well as TLR-mediated MyD88- and TRAF6-dependent responses were their most significantly enriched biological processes. IL10, TLR4, IL6, AKT1, CRP, IL4, CXCL8, TNF-alpha, ITGAM, CCL2 and NOS3 were identified as the most potent regulators of the functional interaction network formed by these immune processes. These key proteins were indexed to be regulated by 63 microRNAs dysregulated in Alzheimer's disease, 13 long non-coding RNAs and targetable by 55 small molecules and 8 protein-based therapeutics. In conclusion, our study identifies eleven key proteins with the highest ability to control neuroinflammatory processes significantly associated to Alzheimer’s disease, as well as pharmacological compounds with single or pleiotropic actions acting on them. As such, it may facilitate the prioritization of diagnostic and target-engagement biomarkers as well as the development of effective therapeutic strategies against neuroinflammation in Alzheimer’s disease.

Effects of Microglial Activation and Polarization on Brain Injury After Stroke

Stroke is one of the most common causes of death worldwide. The subsequent development of neuroinflammation and brain edema dramatically increases the risks associated with stroke, leading to a substantial increase in mortality. Although considerable progress has been made in improving cerebral perfusion in the acute phase of stroke, effective treatment options for the subacute and chronic phases associated with cerebral infarction are limited. Microglia, the innate immune cells of the central nervous system (CNS), can be activated and polarized to take on different phenotypes in response to stimulations associated with stroke, including pro-inflammatory and anti-inflammatory phenotypes, which affect the prognosis of stroke. Therefore, investigation of the activation and polarizing mechanisms of microglia plays a critical role in treating stroke. The aim of this article was to investigate the significance of microglial phenotype regulation in stroke treatment by summarizing the activation, polarizing mechanisms, and general microglia characteristics.

Salidroside Improves Chronic Stress Induced Depressive Symptoms Through Microglial Activation Suppression

Depression is a severe neurological disorder highly associated with chronic mental stress stimulation, which involves chronic inflammation and microglial activation in the central nervous system (CNS). Salidroside (SLDS) has been reported to exhibit anti-neuroinflammatory and protective properties on neurological diseases. However, the mechanism underlying the effect of SLDS on depressive symptoms has not been well elaborated. In the present study, the effects of SLDS on depressive behaviors and microglia activation in mice CNS were investigated. Behavioral tests, including Forced swimming test (FST), Open field test (OFT) and Morris water maze (MWM) revealed that SLDS treatment attenuated the depressive behaviors in stress mice. SLDS treatment significantly reduced the microglial immunoreactivity for both Iba-1 and CD68, characteristic of deleterious M1 phenotype in hippocampus of stress mice. Additionally, SLDS inhibited microglial activation involving the suppression of ERK1/2, P38 MAPK and p65 NF-κB activation and thus reduced the expression and release of neuroinflammatory cytokines in stress mice as well as in lipopolysaccharide (LPS)-induced primary microglia. Also, SLDS changed microglial morphology, attachment and reduced the phagocytic ability in LPS-induced primary microglia. The results demonstrated that SLDS treatment could improve the depressive symptoms caused by unpredictable chronic stress, indicating a potential therapeutic application of SLDS in depression treatment by interfering microglia-mediated neuroinflammation.

Effect of Combined Electroacupuncture and Selegiline Treatment in Alzheimer's Disease: An Animal Model

The complexity of pathological mechanisms in Alzheimer's disease (AD) poses significant challenges to the development of corresponding drugs. Symptom-specific pharmacological interventions and alternative treatments provide promising treatment possibilities. Therefore, we considered a combination of selegiline (SEL) and electroacupuncture (EA). We used an animal model with AD to investigate the effect of a combination of these treatments on cognitive function. 5XFAD mice received a week of SEL treatment and 2 weeks of EA. Novel object recognition and Y-maze tests were subsequently performed to assess their cognitive functions. To determine the molecular action of the combination treatment, Western blots, Aβ_1-42 enzyme-linked immunosorbent assays (ELISA), and micro-positron-emission tomography were also performed to assess pathological markers and processes. The results were assessed based on the difference between untreated transgenic, SEL-treated, and SEL- and EA-treated groups of mice. Mice in the combined treatment group demonstrated significantly better cognitive functions, and lesser neuroinflammation than the comparative groups. In addition, mice treated with a combination of SEL and EA did not demonstrate a direct modulation of insoluble Aβ but demonstrated greater glucose metabolism. Our findings demonstrated that SEL combined with EA treatment was associated with better cognitive functioning due to inhibition of neuroinflammation and increased glucose metabolism relative to the comparative groups in a mouse model with AD.

Transplantation of Mesenchymal Stem Cells Improves Amyloid-β Pathology by Modifying Microglial Function and Suppressing Oxidative Stress

Mesenchymal stem cells (MSC) are increasingly being studied as a source of cell therapy for neurodegenerative diseases, and several groups have reported their beneficial effects on Alzheimer’s disease (AD). In this study using AD model mice (APdE9), we found that transplantation of MSC via the tail vein improved spatial memory in the Morris water maze test. Using electron paramagnetic resonance imaging to evaluate the in vivo redox state of the brain, we found that MSC transplantation suppressed oxidative stress in AD model mice. To elucidate how MSC treatment ameliorates oxidative stress, we focused on amyloid-β (Aβ) pathology and microglial function. MSC transplantation reduced Aβ deposition in the cortex and hippocampus. Transplantation of MSC also decreased Iba1-positive area in the cortex and reduced activated ameboid shaped microglia. On the other hand, MSC transplantation accelerated accumulation of microglia around Aβ deposits and prompted microglial Aβ uptake and clearance as shown by higher frequency of Aβ-containing microglia. MSC transplantation also increased CD14-positive microglia in vivo, which play a critical role in Aβ uptake. To confirm the effects of MSC on microglia, we co-cultured the mouse microglial cell line MG6 with MSC. Co-culture with MSC enhanced Aβ uptake by MG6 cells accompanied by upregulation of CD14 expression. Additionally, co-culture of MG6 cells with MSC induced microglial phenotype switching from M1 to M2 and suppressed production of proinflammatory cytokines. These data indicate that MSC treatment has the potential to ameliorate oxidative stress through modification of microglial functions, thereby improving Aβ pathology in AD model mice.

TREM2 overexpression rescues cognitive deficits in APP/PS1 transgenic mice by reducing neuroinflammation via the JAK/STAT/SOCS signaling pathway

Overactivated microglia and neuroinflammation are considered to play a crucial role in the progression of Alzheimer's disease (AD). Triggering receptor expressed on myeloid cells-2 (TREM2), a type I transmembrane receptor, expressed uniquely by microglia in the brain, is involved in the neuroinflammatory responses of AD. In this study, to further explore the precise effects of TREM2 on neuroinflammation and the underlying mechanisms in AD, we employed a lentiviral-mediated strategy to overexpress TREM2 in the brain of APPswe/PS1dE9 (APP/PS1) transgenic mice and cultured BV2 cells. Our results showed that TREM2 overexpression rescued cognitive deficits, decreased β-amyloid (Aβ) plaques deposition, reduced synaptic and neuronal loss, as well as ameliorated neuroinflammation. The mechanistic study revealed that these protective effects were likely attributed to inhibition of neuroinflammatory responses through the JAK/STAT/SOCS signaling pathway and subsequent attenuation of pro-inflammatory cytokines. Furthermore, suppression of neuroinflammation might be ascribed to activation of the M2 microglia, as the levels of M2 phenotype markers Arg-1, IL-10 and Ym1 were markedly increased. Similarly, overexpression of TREM2 in BV2 cells also promoted M2 polarization and led to the alleviation of M1 microglial inflammatory responses through JAK/STAT/SOCS signaling pathway, suggesting that TREM2 is an important factor in shifting the microglia from M1 to M2 phenotype. Taken together, our results further provide insights into the role of TREM2 in AD pathogenesis and highlight TREM2 as a potential target against AD.

Humanized tau antibodies promote tau uptake by human microglia without any increase of inflammation

Immunotherapies targeting pathological tau have recently emerged as a promising approach for treatment of neurodegenerative disorders. We have previously showed that the mouse antibody DC8E8 discriminates between healthy and pathological tau, reduces tau pathology in murine tauopathy models and inhibits neuronal internalization of AD tau species in vitro.

Here we show, that DC8E8 and antibodies elicited against the first-in-man tau vaccine, AADvac1, which is based on the DC8E8 epitope peptide, both promote uptake of pathological tau by mouse primary microglia. IgG1 and IgG4 isotypes of AX004, the humanized versions of DC8E8, accelerate tau uptake by human primary microglia isolated from post-mortem aged and diseased brains. This promoting activity requires the presence of the Fc-domain of the antibodies.

The IgG1 isotype of AX004 showed greater ability to promote tau uptake compared to the IgG4 isotype, while none of the antibody-tau complexes provoked increased pro-inflammatory activity of microglia. Our data suggest that IgG1 has better suitability for therapeutic development.

Potentiation of IL-4 Signaling by Retinoic Acid in Intestinal Epithelial Cells and Macrophages-Mechanisms and Targets

We previously demonstrated that IL4, IL13, CLCA1, and CCL26 mRNA were significantly upregulated in the lungs of pigs given a low dose of all trans-retinoic acid (ATRA) and infected with Ascaris suum. We also demonstrated that in vitro ATRA induced a state of partial alternative activation in porcine macrophages (Mφs) and amplified certain aspects of M2a activation induced by IL-4. Given these results, we tested the effect of ATRA on IL-4 responses in two porcine intestinal epithelial cell lines, IPEC1 and IPEC-J2 and observed that ATRA increased mRNA for the IL-4 receptor alpha chain. ATRA also increased IL-4 induced phosphorylation of signal transducer and activator of transcription 6 (STAT6) and mRNA expression of the chloride channel, calcium activated, family member 1 (CLCA1), important for mucus formation, and chemokine (C-C motif) ligand 26 (CCL26), a potent eosinophil chemoattractant. We extended these findings to human Mφ THP-1 cells and showed that ATRA synergistically increased IL-4–induced CCL2, CCL13, and CCL26 mRNA and protein levels. Transglutaminase 2 mRNA, protein, and enzyme activity were synergistically induced in THP-1 cells pretreated with ATRA and then treated with IL-4, thus, ATRA increased signaling in response to IL-4 in porcine epithelial cells and porcine and human Mφs. Given the prevalence of allergic and parasitic diseases worldwide and the close similarities in the porcine and human immune responses, these findings have important implications for the nutritional regulation of allergic inflammation at mucosal surfaces.

Associations between brain inflammatory profiles and human neuropathology are altered based on apolipoprotein E ε4 genotype

Alzheimer disease (AD) is a chronic neurodegenerative disease with a multitude of contributing genetic factors, many of which are related to inflammation. The apolipoprotein E (APOE) ε4 allele is the most common genetic risk factor for AD and is related to a pro-inflammatory state. To test the hypothesis that microglia and AD-implicated cytokines were differentially associated with AD pathology based on the presence of APOE ε4, we examined the dorsolateral frontal cortex from deceased participants within a community-based aging cohort (n = 154). Cellular density of Iba1, a marker of microglia, was positively associated with tau pathology only in APOE ε4 positive participants (p = 0.001). The cytokines IL-10, IL-13, IL-4, and IL-1α were negatively associated with tau pathology, independent of Aβ_1–42 levels, only in APOE ε4 negative participants. Overall, the association of mostly anti-inflammatory cytokines with less tau pathology suggests a protective effect in APOE ε4 negative participants. These associations are largely absent in the presence of APOE ε4 where tau pathology was significantly associated with increased microglial cell density. Taken together, these results suggest that APOE ε4 mediates an altered inflammatory response and increased tau pathology independent of Aβ_1–42 pathology.

Adipose-Derived Molecules-Untouched Horizons in Alzheimer's Disease Biology

The global incidence of Alzheimer's disease (AD) is on the rise with the increase in obesity and metabolic disease epidemic. Obesity is co-morbid with the increase in mass of adipose tissue, which secretes numerous molecules that are biologically important. Obesity and its associated conditions are perhaps involved in the causative pathway of AD. Immunologically important cytokines such as IL-1β, IL-10, and IL-18, which are released by adipose tissue, are also found to be associated with AD. Besides, the expression of IL-6, IFNγ, and TNF alpha are also associated with AD. Ang-I and Ang-II are found to mediate the progression of AD. Complement factors B, C4b, and H are differentially expressed in AD. Overall, several adipocyte-derived cytokines are found to be dysregulated in AD, and their role in AD remains to be studied. The induction of autophagy is a very promising strategy in the treatment of AD. A variety of adipose-derived molecules have been shown to modulate autophagy. However, very little literature is available on the role of adipose-derived molecules in inducing autophagy in microglial cells of AD. Understanding the role of adipose-derived molecules in the development of AD, especially in the induction of autophagy, would open up new avenues in devising strategies for the treatment of AD.

Amyloids in Site-Specific Autoimmune Reactions and Inflammatory Responses

Amyloid deposition is a histological hallmark of common human disorders including Alzheimer's disease (AD) and type 2 diabetes. Although some reports highlight that amyloid fibrils might activate the innate immunity system via pattern recognition receptors, here, we provide multiple lines of evidence for the protection by site-specific amyloid protein analogs and fibrils against autoimmune attacks: (1) strategies targeting clearance of the AD-related brain amyloid plaque induce high risk of deadly autoimmune destructions in subjects with cognitive dysfunction; (2) administration of amyloidogenic peptides with either full length or core hexapeptide structure consistently ameliorates signs of experimental autoimmune encephalomyelitis; (3) experimental autoimmune encephalomyelitis is exacerbated following genetic deletion of amyloid precursor proteins; (4) absence of islet amyloid coexists with T-cell-mediated insulitis in autoimmune diabetes and autoimmune polyendocrine syndrome; (5) use of islet amyloid polypeptide agonists rather than antagonists improves diabetes care; and (6) common suppressive signaling pathways by regulatory T cells are activated in both local and systemic amyloidosis. These findings indicate dual modulation activity mediated by amyloid protein monomers, oligomers, and fibrils to maintain immune homeostasis. The protection from autoimmune destruction by amyloid proteins offers a novel therapeutic approach to regenerative medicine for common degenerative diseases.

Efficacy and mechanism of cGAMP to suppress Alzheimer's disease by elevating TREM2

Innate immune responses are considered to play crucial roles in the progression of Alzheimer's disease (AD). Recently, immunotherapy is emerging as an innovative and highly conceivable strategy for AD treatment. The cGAMP-STING-IRF3 signaling pathway plays a pivotal role in mediating innate immune responses. In this study, we provide pioneering investigation to find that the STING stimulator, cGAMP, significantly ameliorates cognitive deficits, improves pathological changes, decreases Aβ plaque load and reduces neuron apoptosis in APP/PS1 transgenetic mice. The stimulation of cGAMP-STING-IRF3 pathway induces expression of triggering receptor expressed on myeloid cells 2 (TREM2), and the overexpression of TREM2 further decreases Aβ deposition and neuron loss while improves AD pathomorphology and cognitive impairment. Additionally, TREM2 regulates microglia polarization from M1 towards M2 phenotype thereby achieves reduction of neuroinflammation in AD. These findings support that the enhancement of TREM2 exerts beneficial effects in ameliorating AD development. Taken together, our results demonstrate that cGAMP is a potential candidate for applications in Alzheimer's disease immunotherapy.

The regulatory actions of retinoic acid on M2 polarization of porcine macrophages

We previously demonstrated that the most bioactive vitamin A metabolite, all-trans retinoic acid (ATRA), increased T helper 2-associated responses induced in pigs by infection with the parasitic nematode Ascaris suum We also showed that ATRA potentiated the mRNA expression of several IL-4 induced chemokines (chemokine (CC motif) ligand 11 [(CCL11), CCL17, CCL22 and CCL26] associated with alternative activation (M2a) in porcine macrophages in vitro. Herein, several mechanisms whereby ATRA affects IL-4 signaling are profiled using large-scale real time PCR and RNA-Seq analysis. Twenty-three genes associated with M2a markers in other species were independently upregulated by both IL-4 and ATRA, including the adenosine receptor A2B (ADORA2B), cysteinyl leukotriene receptor 2 (CYSLTR2) and the vitamin D receptor (VDR). ATRA synergistically enhanced IL-4 up-regulation of Hepatitis A virus cellular receptor 2 (HAVCR2) and transglutaminase 2 (TGM2) and further repressed IL-4 down-regulated CD163 and Cytochrome b-245, beta polypeptide (CYBB) mRNA. Macrophages treated with ATRA exhibited a dose-dependent reduction in phagocytosis of opsonized Staphylococcus aureus. In addition, the combination of IL-4 and ATRA up-regulated the anti-inflammatory protein, IL-1R antagonist (IL1RN) and TGM2. These data indicate that ATRA induces a state of partial alternative activation in porcine macrophages, and amplifies certain aspects of M2a activation induced by IL-4. Given the prevalence of allergic and parasitic diseases worldwide and the close similarities in the porcine and human immune responses, these findings have important implications for the nutritional regulation of allergic inflammation at mucosal surfaces.

Heat-Shock Proteins in Neuroinflammation

The heat-shock response, one of the main pro-survival mechanisms of a living organism, has evolved as the biochemical response of cells to cope with heat stress. The most well-characterized aspect of the heat-shock response is the accumulation of a conserved set of proteins termed heat-shock proteins (HSPs). HSPs are key players in protein homeostasis acting as chaperones by aiding the folding and assembly of nascent proteins and protecting against protein aggregation. HSPs have been associated with neurological diseases in the context of their chaperone activity, as they were found to suppress the aggregation of misfolded toxic proteins. In recent times, HSPs have proven to have functions apart from the classical molecular chaperoning in that they play a role in a wider scale of neurological disorders by modulating neuronal survival, inflammation, and disease-specific signaling processes. HSPs are gaining importance based on their ability to fine-tune inflammation and act as immune modulators in various bodily fluids. However, their effect on neuroinflammation processes is not yet fully understood. In this review, we summarize the role of neuroinflammation in acute and chronic pathological conditions affecting the brain. Moreover, we seek to explore the existing literature on HSP-mediated inflammatory function within the central nervous system and compare the function of these proteins when they are localized intracellularly compared to being present in the extracellular milieu.

RVG-modified exosomes derived from mesenchymal stem cells rescue memory deficits by regulating inflammatory responses in a mouse model of Alzheimer's disease

Background

Exosomes are lipid-bilayer enclosed nano-sized vesicles that transfer functional cellular proteins, mRNA and miRNAs. Mesenchymal stem cells (MSCs) derived exosomes have been demonstrated to prevent memory deficits in the animal model of Alzheimer’s disease (AD). However, the intravenously injected exosomes could be abundantly tracked in other organs except for the targeted regions in the brain. Here, we proposed the use of central nervous system-specific rabies viral glycoprotein (RVG) peptide to target intravenously-infused exosomes derived from MSCs (MSC-Exo) to the brain of transgenic APP/PS1 mice. MSC-Exo were conjugated with RVG through a DOPE-NHS linker.

Results

RVG-tagged MSC-Exo exhibited improved targeting to the cortex and hippocampus after being administered intravenously. Compared with the group administered MSC-Exo, in the group administered RVG-conjugated MSC-Exo (MSC-RVG-Exo) plaque deposition and Aβ levels were sharply decreased and activation of astrocytes was obviously reduced. The brain targeted exosomes derived from MSCs was better than unmodified exosomes to improve cognitive function in APP/PS1 mice according to Morris water maze test. Additionally, although MSC-Exo injected intravenously reduced the expression of pro-inflammatory mediators TNF-α, IL-β, and IL-6, but the changes of anti-inflammatory factors IL-10 and IL-13 were not obvious. However, administration of MSC-RVG-Exo significantly reduced the levels of TNF-α, IL-β, and IL-6 while significantly raised the levels of IL-10, IL-4 and IL-13.

Conclusions

Taken together, our results demonstrated a novel method for increasing delivery of exosomes for treatment of AD. By targeting exosomes to the cortex and hippocampus of AD mouse, there was a significant improvement in learning and memory capabilities with reduced plaque deposition and Aβ levels, and normalized levels of inflammatory cytokines.

Electronic supplementary material

The online version of this article (10.1186/s12979-019-0150-2) contains supplementary material, which is available to authorized users.

Interleukin-4 and Interleukin-13 Exacerbate Neurotoxicity of Prothrombin Kringle-2 in Cortex In Vivo via Oxidative Stress

The present study investigated the effects of activated microglia-derived interleukin-4 (IL-4) and IL-13 on neurodegeneration in prothrombin kringle-2 (pKr-2)-treated rat cortex. pKr-2 was unilaterally injected into the Sprague–Dawley rat cerebral cortex and IL-4 and IL-13 neutralizing antibody was used to block the function of IL-4 and IL-13. Immunohistochemical analysis showed a significant loss of NeuN⁺ and Nissl⁺ cells and an increase of OX-42⁺ cells in the cortex at seven days post pKr-2. The levels of IL-4 and IL-13 expression were upregulated in the activated microglia as early as 12 hours post pKr-2 and sustained up to seven days post pKr-2. Neutralization by IL-4 or IL-13 antibodies (NA) significantly increased neuronal survival in pKr-2-treated rat cortex in vivo by suppressing microglial activation and the production of reactive oxygen species, as analyzed by immunohisotochemistry and hydroethidine histochemistry. These results suggest that IL-4 and IL-13 that were endogenously expressed from reactive microglia may play a critical role on neuronal death by regulating oxidative stress during the neurodegenerative diseases, such as Alzheimer’s disease and dementia.

Inflammation as a central mechanism in Alzheimer's disease

Alzheimer's disease (AD) is a progressive neurodegenerative disorder that is characterized by cognitive decline and the presence of two core pathologies, amyloid β plaques and neurofibrillary tangles. Over the last decade, the presence of a sustained immune response in the brain has emerged as a third core pathology in AD. The sustained activation of the brain's resident macrophages (microglia) and other immune cells has been demonstrated to exacerbate both amyloid and tau pathology and may serve as a link in the pathogenesis of the disorder. In the following review, we provide an overview of inflammation in AD and a detailed coverage of a number of microglia-related signaling mechanisms that have been implicated in AD. Additional information on microglia signaling and a number of cytokines in AD are also reviewed. We also review the potential connection of risk factors for AD and how they may be related to inflammatory mechanisms.

Microglia Responses to Pro-inflammatory Stimuli (LPS, IFNγ+TNFα) and Reprogramming by Resolving Cytokines (IL-4, IL-10)

Microglia respond to CNS injuries and diseases with complex reactions, often called "activation." A pro-inflammatory phenotype (also called classical or M1 activation) lies at one extreme of the reactivity spectrum. There were several motivations for this study. First, bacterial endotoxin (lipopolysaccharide, LPS) is the most commonly used pro-inflammatory stimulus for microglia, both in vitro and in vivo; however, pro-inflammatory cytokines (e.g., IFNγ, TNFα) rather than LPS will be encountered with sterile CNS damage and disease. We lack direct comparisons of responses between LPS and such cytokines. Second, while transcriptional profiling is providing substantial data on microglial responses to LPS, these studies mainly use mouse cells and models, and there is increasing evidence that responses of rat microglia can differ. Third, the cytokine milieu is dynamic after acute CNS damage, and an important question in microglial biology is: How malleable are their responses? There are very few studies of effects of resolving cytokines, particularly for rat microglia, and much of the work has focused on pro-inflammatory outcomes. Here, we first exposed primary rat microglia to LPS or to IFNγ+TNFα (I+T) and compared hallmark functional (nitric oxide production, migration) and molecular responses (almost 100 genes), including surface receptors that can be considered part of the sensome. Protein changes for exemplary molecules were also quantified: ARG1, CD206/MRC1, COX-2, iNOS, and PYK2. Despite some similarities, there were notable differences in responses to LPS and I+T. For instance, LPS often evoked higher pro-inflammatory gene expression and also increased several anti-inflammatory genes. Second, we compared the ability of two anti-inflammatory, resolving cytokines (IL-4, IL-10), to counteract responses to LPS and I+T. IL-4 was more effective after I+T than after LPS, and IL-10 was surprisingly ineffective after either stimulus. These results should prove useful in modeling microglial reactivity in vitro; and comparing transcriptional responses to sterile CNS inflammation in vivo.

URMC-099 facilitates amyloid-β clearance in a murine model of Alzheimer's disease

Background

The mixed lineage kinase type 3 inhibitor URMC-099 facilitates amyloid-beta (Aβ) clearance and degradation in cultured murine microglia. One putative mechanism is an effect of URMC-099 on Aβ uptake and degradation. As URMC-099 promotes endolysosomal protein trafficking and reduces Aβ microglial pro-inflammatory activities, we assessed whether these responses affect Aβ pathobiogenesis. To this end, URMC-099’s therapeutic potential, in Aβ precursor protein/presenilin-1 (APP/PS1) double-transgenic mice, was investigated in this model of Alzheimer’s disease (AD).

Methods

Four-month-old APP/PS1 mice were administered intraperitoneal URMC-099 injections at 10 mg/kg daily for 3 weeks. Brain tissues were examined by biochemical, molecular and immunohistochemical tests.

Results

URMC-099 inhibited mitogen-activated protein kinase 3/4-mediated activation and attenuated β-amyloidosis. Microglial nitric oxide synthase-2 and arginase-1 were co-localized with lysosomal-associated membrane protein 1 (Lamp1) and Aβ. Importatly, URMC-099 restored synaptic integrity and hippocampal neurogenesis in APP/PS1 mice.

Conclusions

URMC-099 facilitates Aβ clearance in the brain of APP/PS1 mice. The multifaceted immune modulatory and neuroprotective roles of URMC-099 make it an attractive candidate for ameliorating the course of AD. This is buttressed by removal of pathologic Aβ species and restoration of the brain’s microenvironment during disease.

Inhibition of cyclin-dependent kinase 5 affects early neuroinflammatory signalling in murine model of amyloid beta toxicity

BACKGROUND

Cyclin-dependent kinase 5 (Cdk5) belongs to the family of proline-directed serine/threonine kinases and plays a critical role in neuronal differentiation, migration, synaptogenesis, plasticity, neurotransmission and apoptosis. The deregulation of Cdk5 activity was observed in post mortem analysis of brain tissue of Alzheimer's disease (AD) patients, suggesting the involvement of Cdk5 in the pathomechanism of this neurodegenerative disease. However, our recent study demonstrated the important function of Cdk5 in regulating inflammatory reaction.

METHODS

Since the role of Cdk5 in regulation of inflammatory signalling in AD is unknown, we investigated the involvement of Cdk5 in neuroinflammation induced by single intracerebroventricular (icv) injection of amyloid beta protein (Aβ) oligomers in mouse. The brain tissue was analysed up to 35 days post injection. Roscovitine (intraperitoneal administration) was used as a potent Cdk5 inhibitor. The experiments were also performed on human neuroblastoma SH-SY5Y as well as mouse BV2 cell lines treated with exogenous oligomeric Aβ.

RESULTS

Our results demonstrated that single injection of Aβ oligomers induces long-lasting activation of microglia and astrocytes in the hippocampus. We observed also profound, early inflammatory response in the mice hippocampus, leading to the significant elevation of pro-inflammatory cytokines expression (e.g. TNF-α, IL-1β, IL-6). Moreover, Aβ oligomers elevated the formation of truncated protein p25 in mouse hippocampus and induced overactivation of Cdk5 in neuronal cells. Importantly, administration of roscovitine reduced the inflammatory processes evoked by Aβ in the hippocampus, leading to the significant decrease of cytokines level.

CONCLUSIONS

These studies clearly show the involvement of Cdk5 in modulation of brain inflammatory response induced by Aβ and may indicate this kinase as a novel target for pharmacological intervention in AD.

Palmitate Induces an Anti-Inflammatory Response in Immortalized Microglial BV-2 and IMG Cell Lines that Decreases TNFα Levels in mHypoE-46 Hypothalamic Neurons in Co-Culture

BACKGROUND AND OBJECTIVES

Elevated levels of saturated fatty acids (SFA) induce a state of neuroinflammation in the hypothalamus. It has been suggested that microglia sense palmitate, a prevalent circulating SFA, and act as mediators of this inflammatory process by communicating with neurons, particularly those involved in appetite regulation. In this study, we examined the inflammatory response to palmitate in immortalized microglial cell lines, BV-2 and IMG, and the subsequent effects on inflammatory gene expression in a model of NPY/AgRP neurons, mHypoE-46.

METHODS

The BV-2 cells were treated with 50 µM palmitate for 4 and 24 h, and the transcriptional regulation of markers for inflammation and cellular stress was assessed using an RT2 Profiler PCR Array. Select genes were verified with qRT-PCR. The BV-2 and IMG cells were then co-cultured using 1.0-µm cell culture inserts with an immortalized hypothalamic cell line, mHypoE-46, to investigate potential intercellular communication between microglia and neurons.

RESULTS

We found that palmitate increased the mRNA levels of specific inflammatory genes, and a general anti-inflammatory profile was revealed in the microglia cells. The mRNA changes in TNFα at 4 and 24 h in BV-2 cells were abrogated with the toll-like receptor 4 (TLR4) inhibitor, TAK-242, indicating the involvement of TLR4. Co-culture of mHypoE-46 neurons with microglia pre-treated with palmitate resulted in repression of TNFα expression in the hypothalamic neurons. As palmitate significantly increased IL-13 expression in microglia, the effect of this cytokine was tested in mHypoE-46 neurons. The addition of IL-13 to neuronal cultures normalized the palmitate-mediated increase in IL-6 and AgRP expression, suggesting that microglia may protect surrounding neurons, at least in part, through the release of IL-13.

CONCLUSIONS

These results suggest a potential anti-inflammatory role of microglia towards the palmitate-induced neuroinflammation, and potentially energy homeostasis, in hypothalamic neurons.

Obesity and neurological disorders: Dietary perspective of a global menace

Obesity is considered a major public health concern throughout the world among children, adolescents, as well as adults and several therapeutic, preventive and dietary interventions are available. In addition to life style changes and medical interventions, significant milestones have been achieved in the past decades in the development of several functional foods and dietary regimens to reduce this menace. Being a multifactorial phenomenon and related to increased fat mass that adversely affects health, obesity has been associated with the development of several other co-morbidities. A great body of research and strong scientific evidence identifies obesity as an important risk factor for onset and progression of several neurological disorders. Obesity induced dyslipidaemia, metabolic dysfunction, and inflammation are attributable to the development of a variety of effects on central nervous system (CNS). Evidence suggests that neurological diseases such as Parkinson's disease and Alzheimer's disease could be initiated by various metabolic changes, related to CNS damage, caused by obesity. These metabolic changes could alter the synaptic plasticity of the neurons and lead to neural death, affecting the normal physiology of CNS. Dietary intervention in combination with exercise can affect the molecular events involved in energy metabolism and synaptic plasticity and are considered effective non-invasive strategy to counteract cognitive and neurological disorders. The present review gives an overview of the obesity and related neurological disorders and the possible dietary interventions.

The isozyme selective phosphodiesterase-4 inhibitor, ABI-4, attenuates the effects of lipopolysaccharide in human cells and rodent models of peripheral and CNS inflammation

Inhibitors of phosphodiesterase-4 (PDE4) have been approved for the treatment of inflammatory disorders, but are associated with dose-limiting nausea and vomiting. These side effects are hypothesized to be mediated by inhibition of the PDE4D isozyme. Here we demonstrate the anti-inflammatory effects of the novel brain penetrant PDE4D-sparing PDE4 inhibitor, ABI-4. ABI-4 was a potent (EC₅₀∼14nM) inhibitor of lipopolysaccharide (LPS) induced TNF-α release from mouse microglia and human PBMCs. ABI-4 (0.32mg/kg) blocked LPS-induced release of pro-inflammatory cytokines (TNF-α, IL-1β, IL-6) in blood and brain of mice. In a rat model of endotoxin induced uveitis, ABI-4 (0.03-0.3mg/kg) demonstrated steroid-like efficacy in preventing leucocyte infiltration of the aqueous humor when administered 4h after LPS. LPS (0.32mg/kg×5days) caused a 30% upregulation of translocator protein (TSPO) binding which was prevented by co-administration of ABI-4 (0.32mg/kg). In a paradigm to assess motivation, LPS (0.32mg/kg) reduced the number of rewards received, whereas the effect was significantly blunted in mice dosed with ABI-4 (P<0.05) or in PDE4B-/- mice. PDE4B was also shown to modulate brain and plasma levels of TNF-α and IL-1β in aged mice. Aged mice dosed chronically with ABI-4 (0.32mg/kg) as well as aged PDE4B-/- mice, had significantly lower levels of TNF-α and IL-1β in brain and plasma relative to vehicle treated or PDE4+/+ mice. Together these data demonstrate that the PDE4D sparing, PDE4 inhibitor, ABI-4 retains potency and efficacy in exerting anti-inflammatory effects. This mechanism warrants further investigation in human disorders involving neuroinflammation.

Serum Interleukin-10 Levels Correlate with Cerebrospinal Fluid Amyloid Beta Deposition in Alzheimer Disease Patients

BACKGROUND AND OBJECTIVE

In Alzheimer disease (AD) inflammation becomes evident throughout the course of the disease. However, the association between inflammation, cognitive impairment, and cerebrospinal biomarkers (Aβ42, t-tau, p-tau181, and Aβ42/p-tau181 ratio) is poorly understood.

METHODS

A large panel of inflammatory cytokines (interleukin [IL]-1β, IL-1ra, IL-2, IL-4, IL-6, IL-10, IL-17, interferon-γ, tumor necrosis factor-α, and vascular endothelial growth factor) was analyzed using a multiplex immunoassay in 27 patients with a diagnosis of AD dementia and in 18 control subjects. In a subgroup with available cerebrospinal fluid (CSF) samples, cytokines in serum were correlated with the levels of neurodegenerative CSF biomarkers (Aβ42, t-tau, p-tau181, and Aβ42/p-tau181 ratio).

RESULTS

Compared to control subjects, AD patients showed a significant upregulation of IL-10, IL-1β, and IL-17 serum levels. Several cytokines appeared intercorrelated, and IL-10 in particular presented a significant inverse correlation with CFS levels of Aβ42 and the Aβ42/p-tau ratio.

CONCLUSION

Our findings indicate that serum levels of IL-10 may represent a possible peripheral expression of amyloid beta deposition in AD patients.

Minocycline reduces inflammatory parameters in the brain structures and serum and reverses memory impairment caused by the administration of amyloid β (1-42) in mice

Alzheimer's disease (AD) is a neurodegenerative disorder and the most common type of age-related dementia. Cognitive decline, beta-amyloid (Aβ) accumulation, neurofibrillary tangles, and neuroinflammation are the main pathophysiological characteristics of AD. Minocycline is a tetracycline derivative with anti-inflammatory properties that has a neuroprotective effect. The aim of this study was to evaluate the effect of minocycline on memory, neurotrophins and neuroinflammation in an animal model of AD induced by the administration of Aβ (1-42) oligomer. Male BALB/c mice were treated with minocycline (50mg/kg) via the oral route for a total of 17days, 24h after intracerebroventricular administration of Aβ (1-42) oligomer. At the end of this period, was performed the radial maze test, and 24h after the last minocycline administration, serum was collected and the cortex and hippocampus were dissected for biochemical analysis. The administration of minocycline reversed the memory impairment caused by Aβ (1-42). In the hippocampus, minocycline reversed the increases in the levels of interleukin (IL-1β), Tumor Necrosis Factor- alpha (TNF-α) and, IL-10 caused by Aβ (1-42). In the cortex, AD-like model increase the levels of IL-1β, TNF-α and, IL-4. Minocycline treatment reversed this. In the serum, Aβ (1-42) increased the levels of IL-1β and IL-4, and minocycline was able to reverse this action, but not to reverse the decrease of IL-10 levels. Minocycline also reversed the increase in the levels of Brain-derived neurotrophic factor (BDNF) in the hippocampus caused by Aβ (1-42), and reduced Nerve Growth Factor (NGF) increases in the total cortex. Therefore, our results indicate that minocycline causes improvements in the spatial memory, and cytokine levels were correlated with this effect in the brain it. Besides this, minocycline reduced BDNF and NGF levels, highlighting the promising effects of minocycline in treating AD-like dementia.

The impact of obesity on neurodegenerative diseases

Neurodegenerative diseases are a growing health concern. The increasing incidences of these disorders have a great impact on the patients' quality of life. Although the mechanisms of neurodegenerative diseases are still far from being clarified, several studies look for new discoveries about their pathophysiology and prevention. Furthermore, evidence has shown a strong correlation between obesity and the development of Alzheimer's disease (AD) and Parkinson's disease (PD). Metabolic changes caused by overweight are related to damage to the central nervous system (CNS), which can lead to neural death, either by apoptosis or cell necrosis, as well as alter the synaptic plasticity of the neuron. This review aims to show the association between neurodegenerative diseases, focusing on AD and PD, and metabolic alterations.

Role of inflammatory molecules in the Alzheimer's disease progression and diagnosis

Alzheimer's disease (AD) is a complex disorder and the most common form of neurodegenerative dementia. Several genetic, environmental, and physiological factors, including inflammations and metabolic influences, are involved in the progression of AD. Inflammations are composed of complicated networks of many chemokines and cytokines with diverse cells. Inflammatory molecules are needed for the protection against pathogens, and maintaining their balances is important for normal physiological function. Recent studies demonstrated that inflammation may be involved in neurodegenerative dementia. Cellular immune components, such as microglia or astrocytes, mediate the release of inflammatory molecules, including tumor necrosis factor, growth factors, adhesion molecules, or chemokines. Over- and underexpression of pro- and anti-inflammatory molecules, respectively, may result in neuroinflammation and thus disease initiation and progression. In addition, levels of several inflammatory factors were reported to be altered in the brain or bodily fluids of patients with AD, reflecting their neuropathological changes. Therefore, simultaneous detection of several inflammatory molecules in the early or pre-symptomatic stage may improve the early diagnosis of AD. Further studies are needed to determine, how induction or inhibition of inflammatory factors could be used for AD therapies. This review summarizes the role or possible role of immune cells and inflammatory molecules in disease progression or prevention.

5-Fluorouracil chemotherapy upregulates cytokines and alters hippocampal dendritic complexity in aged mice

5-Fluorouracil (5-Fu) is commonly used chemotherapy drug, but it can lead to the impairment of cognitive function. The pathogenesis of this injury is unknown but may involve modifications to dendritic structure and/or alterations in dendritic spine density and morphology. Dendritic spines are sites of excitatory synaptic transmission and changes in spine structure and dendrite morphology are thought to represent a morphological correlate of altered brain functions associated with hippocampal dependent learning and memory. A total of 28 one-year-old C57BL6/J male mice were used in this study; 14 mice received 5-Fu treatment and 14 were given saline injections. One month post treatment, 14 cytokines were measured at the same time Golgi samples were taken. 8 analytes were significantly elevated in mice treated with 5-Fu. 5-Fu significantly compromised the dendritic architecture and reduced spine density throughout the hippocampal tri-synaptic network. The present data provide the evidence that 5-Fu has deleterious effects on mature neurons associated with hippocampal learning and memory.

Effects of bacterial cell wall components (PAMPs) on the expression of monocyte chemoattractant protein-1 (MCP-1), macrophage inflammatory protein-1α (MIP-1α) and the chemokine receptor CCR2 by purified human blood monocytes

Regulation of chemokine production and the expression of chemokine receptors play an important role during inflammation and infectious diseases. The present study was designed to study the effects of five different bacterial cell wall components (PAMPs) on the production of MCP-1 and MIP-1α and the expression of CCR2 by highly purified human blood monocytes. All five PAMPs induced high expression of mRNA and protein synthesis of both chemokines. Generally, MCP-1 mRNA and protein levels were higher than MIP-1α levels. Expression of MCP-1 and MIP-1α differed both at the mRNA and at the protein levels, MIP-1α always showing a more rapid initial increase, attaining lower protein levels than MCP-1. Antibodies against CD14 significantly inhibited the inducing effects of all the PAMPs used. Antibody against TLR2 inhibited the chemokine production induced by LTA and AraLAM by more than 36% ( P < 0.05) while chemokine production induced by Escherichia coli-LPS, purified E. coli-LPS and Neisseria meningitidis-LPS was inhibited by more than 60% by antibody against TLR4 ( P < 0.05). The inducing effects of all five PAMPs could be inhibited by rIL-4, rIL-10 and rIL-13. rIL-4 was the most effective. Generally, IC50 of these anti-inflammatory cytokines were lower for the MIP-1α than for the MCP-1 production. The cell surface expression of CCR2 was significantly down-regulated by all five PAMPs in addition to a decrease in cytosolic free calcium and binding of rMCP-1. We conclude that MCP-1 and MIP-1α as well as the MCP-1 receptor CCR2 will be substantially regulated upon monocyte contact with various cell wall components (PAMPs) from Gram-negative and Gram-positive bacteria as well as from mycobacteria.