Cytokine and chemokine alterations in tissue, CSF, and plasma in early presymptomatic phase of experimental allergic encephalomyelitis (EAE), in a rat model of multiple sclerosis

ApTOLL: A new therapeutic aptamer for cytoprotection and (re)myelination after multiple sclerosis

BACKGROUND AND PURPOSE

ApTOLL is an aptamer selected to antagonize toll-like receptor 4 (TLR4), a relevant actor for innate immunity involved in inflammatory responses in multiple sclerosis (MS) and other diseases. The currently available therapeutic arsenal to treat MS is composed of immunomodulators but, to date, there are no (re)myelinating drugs available in clinics. In our present study, we studied the effect of ApTOLL on different animal models of MS.

EXPERIMENTAL APPROACH

The experimental autoimmune encephalomyelitis (EAE) model was used to evaluate the effect of ApTOLL on reducing the inflammatory component. A more direct effect on oligodendroglia was studied with the cuprizone model and purified primary cultures of murine and human oligodendrocyte precursor cells (OPCs) isolated through magnetic-activated cell sorting (MACS) from samples of brain cortex. Also, we tested these effects in an ex vivo model of organotypic cultures demyelinated with lysolecithin (LPC).

KEY RESULTS

ApTOLL treatment positively impacted the clinical symptomatology of mice in the EAE and cuprizone models, which was associated with better preservation plus restoration of myelin and oligodendrocytes in the demyelinated lesions of animals. Restoration was corroborated on purified cultures of rodent and human OPCs.

CONCLUSION AND IMPLICATIONS

Our findings reveal a new therapeutic approach for the treatment of inflammatory and demyelinating diseases such as MS. The molecular nature of the aptamer exerts not only an anti-inflammatory effect but also neuroprotective and remyelinating effects. The excellent safety profile demonstrated by ApTOLL in animals and humans opens the door to future clinical trials in MS patients.

A novel PROTAC molecule dBET1 alleviates pathogenesis of experimental autoimmune encephalomyelitis in mice by degrading BRD4

Neuroinflammation and neurodegeneration are hallmarks of multiple sclerosis (MS). Bromodomain-containing protein 4 (BRD4), a bromodomain and extra-terminal domain (BET) protein family member, is indispensable for the transcription of pro-inflammatory genes. Therefore, inhibiting BRD4 may be a prospective therapeutic approach for modulating the inflammatory response and regulating the course of MS. dBET1, a newly synthesized proteolysis-targeting chimera (PROTAC), exhibits effectively degrades of BRD4. However, the precise effects of dBET1 on MS require further investigation. Therefore, we assessed the effect of dBET1 in experimental autoimmune encephalomyelitis (EAE), a typical MS experimental model. Our findings revealed that BRD4 is mainly expressed in astrocytes and neurons of the spinal cords, and is up-regulated in the spinal cords of EAE mice. The dBET1 attenuated lipopolysaccharide-induced expression of astrocytic pro-inflammatory mediators and inhibited deleterious molecular activity in astrocytes. Correspondingly, dBET1, used in preventive and therapeutic settings, alleviated the behavioral symptoms in EAE mice, as demonstrated by decreased demyelination, alleviated leukocyte infiltration, reduced microglial and astrocyte activation, and diminished inflammatory mediator levels. In addition, dBET1 corrected the imbalance in peripheral T cells and protected blood-brain barrier integrity in EAE mice. The underlying mechanism involved suppressing the phosphoinositide-3-kinase/protein kinase B, mitogen-activated protein kinase /extracellular signal-regulated kinase, and nuclear factor kappa B pathways. In summary, our data strongly suggests that dBET1 is a promising treatment option for MS.

Retinal transcriptome profiling identifies novel candidate genes associated with visual impairment in a mouse model of multiple sclerosis

Visual impairment is occasionally observed in multiple sclerosis (MS) and its animal model, experimental autoimmune encephalomyelitis (EAE). Although uveitis and optic neuritis have been reported in MS and EAE, the precise mechanisms underlying the pathogenesis of these visual impairments remain poorly understood. This study aims to identify differentially expressed genes (DEGs) in the retinas of mice with EAE to identify genes that may be implicated in EAE-induced visual impairment. Fourteen adult mice were injected with myelin oligodendrocyte glycoprotein35-55 to induce the EAE model. Transcriptomes of retinas with EAE were analyzed by RNA-sequencing. Gene expression analysis revealed 347 DEGs in the retinas of mice with EAE: 345 were upregulated, and 2 were downregulated (adjusted p-value < 0.05 and absolute log2 fold change > 1). Gene ontology (GO) analysis showed that the upregulated genes in the retinas of mice with EAE were primarily related to immune responses, responses to external biotic stimuli, defense responses, and leukocyte-mediated immunity in the GO biological process. The expression of six upregulated hub genes (c1qb, ctss, itgam, itgb2, syk, and tyrobp) from the STRING analysis and the two significantly downregulated DEGs (hapln1 and ndst4) were validated by reverse transcription-quantitative polymerase chain reaction. In addition, gene set enrichment analysis showed that the negatively enriched gene sets in EAE-affected retinas were associated with the neuronal system and phototransduction cascade. This study provides novel molecular evidence for visual impairments in EAE and indicates directions for further research to elucidate the mechanisms of these visual impairments in MS.

Emodin attenuates inflammation and demyelination in experimental autoimmune encephalomyelitis

Emodin, a substance extracted from herbs such as rhubarb, has a protective effect on the central nervous system. However, the potential therapeutic effect of emodin in the context of multiple sclerosis remains unknown. In this study, a rat model of experimental autoimmune encephalomyelitis was established by immune induction to simulate multiple sclerosis, and the rats were intraperitoneally injected with emodin (20 mg/kg/d) from the day of immune induction until they were sacrificed. In this model, the nucleotide-binding domain-like receptor family pyrin domain containing 3 (NLRP3) inflammasome and the microglia exacerbated neuroinflammation, playing an important role in the development of multiple sclerosis. In addition, silent information regulator of transcription 1 (SIRT1)/peroxisome proliferator-activated receptor-alpha coactivator (PGC-1α) was found to inhibit activation of the NLRP3 inflammasome, and SIRT1 activation reduced disease severity in experimental autoimmune encephalomyelitis. Furthermore, treatment with emodin decreased body weight loss and neurobehavioral deficits, alleviated inflammatory cell infiltration and demyelination, reduced the expression of inflammatory cytokines, inhibited microglial aggregation and activation, decreased the levels of NLRP3 signaling pathway molecules, and increased the expression of SIRT1 and PGC-1α. These findings suggest that emodin improves the symptoms of experimental autoimmune encephalomyelitis, possibly through regulating the SIRT1/PGC-1α/NLRP3 signaling pathway and inhibiting microglial inflammation. These findings provide experimental evidence for treatment of multiple sclerosis with emodin, enlarging the scope of clinical application for emodin.

Increased expression of CSF1 in patients with eosinophilic asthma

BACKGROUND

The link between colony-stimulating factor 1 (CSF1) and asthma was reported recently. However, the role and mechanism of CSF1 in asthma remain poorly understood. In this study, we aimed to explore the expression and its potential mechanism of CSF1 in asthma.

METHODS

CSF1 expression in the airway samples from asthmatics and healthy controls were examined, then the correlations between CSF1 and eosinophilic indicators were analyzed. Subsequently, bronchial epithelial cells (BEAS-2B) with CSF1 overexpression and knockdown were constructed to investigate the potential molecular mechanism of CSF1. Finally, the effect of CSF1R inhibitor on STAT1 was investigated.

RESULTS

The expression of CSF1 was significantly increased in patients with asthma compared to healthy controls, especially in patients with severe and eosinophilic asthma. Upregulated CSF1 positively correlated with airway-increased eosinophil inflammation. In vitro, cytokines interleukin 13 (IL-13) and IL-33 can stimulate the upregulation of CSF1 expression. CSF1 overexpression enhanced p-CSF1R/CSF1R and p-STAT1/STAT1 expression, while knockdown CSF1 using anti-CSF1 siRNAs decreased p-CSF1R/CSF1R and p-STAT1/STAT1 expression. Furthermore, the inhibitor of CSF1R significantly decreased p-STAT1/STAT1 expression.

CONCLUSIONS

Sputum CSF1 may be involved in asthmatic airway eosinophil inflammation by interacting with CSF1R and further activating the STAT1 signaling. Interfering this potential pathway could serve as an anti-inflammatory therapy for asthma.

Erythrocyte Plasma Membrane Lipid Composition Mirrors That of Neurons and Glial Cells in Murine Experimental In Vitro and In Vivo Inflammation

Lipid membrane turnover and myelin repair play a central role in diseases and lesions of the central nervous system (CNS). The aim of the present study was to analyze lipid composition changes due to inflammatory conditions. We measured the fatty acid (FA) composition in erythrocytes (RBCs) and spinal cord tissue (gas chromatography) derived from mice affected by experimental allergic encephalomyelitis (EAE) in acute and remission phases; cholesterol membrane content (Filipin) and GM1 membrane assembly (CT-B) in EAE mouse RBCs, and in cultured neurons, oligodendroglial cells and macrophages exposed to inflammatory challenges. During the EAE acute phase, the RBC membrane showed a reduction in polyunsaturated FAs (PUFAs) and an increase in saturated FAs (SFAs) and the omega-6/omega-3 ratios, followed by a restoration to control levels in the remission phase in parallel with an increase in monounsaturated fatty acid residues. A decrease in PUFAs was also shown in the spinal cord. CT-B staining decreased and Filipin staining increased in RBCs during acute EAE, as well as in cultured macrophages, neurons and oligodendrocyte precursor cells exposed to inflammatory challenges. This regulation in lipid content suggests an increased cell membrane rigidity during the inflammatory phase of EAE and supports the investigation of peripheral cell membrane lipids as possible biomarkers for CNS lipid membrane concentration and assembly.

Synthesis and Comprehensive in Vivo Activity Profiling of Olean-12-en-28-ol, 3β-Pentacosanoate in Experimental Autoimmune Encephalomyelitis: A Natural Remyelinating and Anti-Inflammatory Agent

Multiple sclerosis (MS) treatment has received much attention, yet there is still no certain cure. We herein investigate the therapeutic effect of olean-12-en-28-ol, 3β-pentacosanoate (OPCA) on a preclinical model of MS. First, OPCA was synthesized semisynthetically and characterized. Then, the mice with MOG_35-55-induced experimental autoimmune/allergic encephalomyelitis (EAE) were given OPCA along with a reference drug (FTY720). Biochemical, cellular, and molecular analyses were performed in serum and brain tissues to measure anti-inflammatory and neuroprotective responses. OPCA treatment protected EAE-induced changes in mouse brains maintaining blood-brain barrier integrity and preventing inflammation. Moreover, the protein and mRNA levels of MS-related genes such as HLD-DR1, CCL5, TNF-α, IL6, and TGFB1 were significantly reduced in OPCA-treated mouse brains. Notably, the expression of genes, including PLP, MBP, and MAG, involved in the development and structure of myelin was significantly elevated in OPCA-treated EAE. Furthermore, therapeutic OPCA effects included a substantial reduction in pro-inflammatory cytokines in the serum of treated EAE animals. Lastly, following OPCA treatment, the promoter regions for most inflammatory regulators were hypermethylated. These data support that OPCA is a valuable and appealing candidate for human MS treatment since OPCA not only normalizes the pro- and anti-inflammatory immunological bias but also stimulates remyelination in EAE.

Microglia depletion as a therapeutic strategy: friend or foe in multiple sclerosis models?

Multiple sclerosis is a chronic central nervous system demyelinating disease whose onset and progression are driven by a combination of immune dysregulation, genetic predisposition, and environmental factors. The activation of microglia and astrocytes is a key player in multiple sclerosis immunopathology, playing specific roles associated with anatomical location and phase of the disease and controlling demyelination and neurodegeneration. Even though reactive microglia can damage tissue and heighten deleterious effects and neurodegeneration, activated microglia also perform neuroprotective functions such as debris phagocytosis and growth factor secretion. Astrocytes can be activated into pro-inflammatory phenotype A1 through a mechanism mediated by activated neuroinflammatory microglia, which could also mediate neurodegeneration. This A1 phenotype inhibits oligodendrocyte proliferation and differentiation and is toxic to both oligodendrocytes and neurons. However, astroglial activation into phenotype A2 may also take place in response to neurodegeneration and as a protective mechanism. A variety of animal models mimicking specific multiple sclerosis features and the associated pathophysiological processes have helped establish the cascades of events that lead to the initiation, progression, and resolution of the disease. The colony-stimulating factor-1 receptor is expressed by myeloid lineage cells such as peripheral monocytes and macrophages and central nervous system microglia. Importantly, as microglia development and survival critically rely on colony-stimulating factor-1 receptor signaling, colony-stimulating factor-1 receptor inhibition can almost completely eliminate microglia from the brain. In this context, the present review discusses the impact of microglial depletion through colony-stimulating factor-1 receptor inhibition on demyelination, neurodegeneration, astroglial activation, and behavior in different multiple sclerosis models, highlighting the diversity of microglial effects on the progression of demyelinating diseases and the strengths and weaknesses of microglial modulation in therapy design.

Microglia in multiple sclerosis: Protectors turn destroyers

Microglia are implicated in all stages of multiple sclerosis (MS). Microglia alterations are detected by positron emission tomography in people living with MS prior to the formation of structural lesions determined through magnetic resonance imaging. In histological specimens, clusters of microglia form in normal-appearing tissue likely predating the development of lesions. Features of degeneration-associated/pro-inflammatory states of microglia increase with chronicity of MS. However, microglia play many beneficial roles including the removal of neurotoxins and in fostering repair. The protector-gone-rogue microglia in MS is featured herein. We consider mechanisms of microglia neurotoxicity and discuss factors, including aging, osteopontin, and iron metabolism, that cause microglia to lose their protective states and become injurious. We evaluate medications to affect microglia in MS, such as the emerging class of Bruton's tyrosine kinase inhibitors. The framework of microglia-turned-destroyers may instigate new approaches to counter microglia-driven neurodegeneration in MS.

Transcriptomic changes in autophagy-related genes are inversely correlated with inflammation and are associated with multiple sclerosis lesion pathology

Autophagy is a lysosomal degradative pathway essential for maintaining cellular homeostasis and is also implicated in multiple aspects of both innate and adaptive immunity. Neuroinflammation, along with demyelination and axonal loss, is an important component of multiple sclerosis (MS). Induction of autophagy ameliorated disease progression in experimental autoimmune encephalomyelitis (EAE), a mouse model for MS, underlying a possible link between autophagy and MS pathology. However, it is still unclear how autophagy is affected during different stages of MS. Here, we show a decreased expression of the autophagy-related (ATG) genes during the acute phase of EAE development in mice as well as in mixed active/inactive lesions of post-mortem human MS brain tissues. Using spatial transcriptomics, we observed that this decreased ATG gene expression is most prominent in the core of mixed active/inactive lesions. Furthermore, we observed a hyper-activation of the mammalian target of rapamycin complex 1 (mTORC1) in lesions, which could inhibit both the initiation of autophagy and the transcription factors that regulate the expression of the ATG genes. Thus, based on our data, we propose a negative regulation of autophagy in MS, possibly through persistent mTORC1 activation, which depends on the lesion stage. Our results contribute to the understanding of the role of autophagy in different stages of MS pathology and point to the mTORC1 pathway as a potential modulator that likely regulates central nervous system (CNS) homeostasis and neuroinflammation in MS.

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Autophagy is differently regulated in various EAE and MS stages.

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Expression of ATG genes inversely correlates with inflammation in EAE mice.

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ATG gene expression is decreased in mixed active/inactive brain lesions.

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Targeting mTORC1 may be a promising therapeutic target in MS pathology.

Immunomodulatory effects of cyclotides isolated from Viola odorata in an experimental autoimmune encephalomyelitis animal model of multiple sclerosis

BACKGROUND

Multiple sclerosis (MS) is a demyelinating disease of the central nervous system that causes chronic inflammation. Cyclotides are small plant proteins with a wide range of biological activity, making them a target for researchers to investigate. This study was conducted to investigate the possible effects of cyclotide-rich fractions from Viola odorata as an immunomodulatory agent in an experimental autoimmune encephalomyelitis (EAE) model of MS.

METHODS

At room temperature, the plant materials were subjected to maceration in methanol: dichloromethane (1:1; v/v) for 3 days. The extraction was repeated 3 times, and the final concentrated extract was partitioned 3 times by 1/2 volume of double-distilled water. The aqueous phases were separated and freeze-dried. Finally, the crude extract was fractionated by C18 silicagel using vacuum liquid chromatography, with mobile phases of 30%, 50% and 80% of ethanol: water, respectively. The 50%, and 80% fractions were analyzed by HPLC and MALDI-TOF analysis and administrated intraperitoneally to forty-five female C57BL/6 EAE-induced mice, at 5, 25, and 50 mg/kg doses. After 28 days, the animals were evaluated using EAE clinical scoring which was done every 3 days, cytokine levels, and myelination level.

RESULTS

The results confirmed the presence of cyclotides in V. odorata based on their retention time and the composition of mobile phase in HPLC and the molecular weight of the peaks in MALDI-TOF analysis. It was observed that cyclotides, especially in the 80% fraction group at the dose of 50 mg/kg significantly reduced the clinical scores, inflammation, and demyelination in EAE mice compared with the normal saline group (P<0.05), and the results of this group were comparable with fingolimod (P>0.05).

CONCLUSION

It could be concluded that V. odorata is a rich source of cyclotides which they could be extracted by an easily available process and also, they could be used as immunomodulatory agents in MS, with similar effects to fingolimod.

Colony-stimulating factor 1 receptor signaling in the central nervous system and the potential of its pharmacological inhibitors to halt the progression of neurological disorders

Colony Stimulating Factor-1 (CSF-1)/Colony Stimulating Factor-1 Receptor (CSF-1R) signaling axis plays an essential role in the development, maintenance, and proliferation of macrophage lineage cells. Within the central nervous system, CSF-1R signaling primarily maintains microglial homeostasis. Microglia, being the resident macrophage and first responder to any neurological insults, plays critical importance in overall health of the human brain. Aberrant and sustained activation of microglia along with continued proliferation and release of neurotoxic proinflammatory cytokines have been reported in various neurological and neurodegenerative diseases. Therefore, halting the neuroinflammatory pathway via targeting microglial proliferation, which depends on CSF-1R signaling, has emerged as a potential therapeutic target for neurological disorders. However, apart from regulating the microglial function, recently it has been discovered that CSF-1R has much broader role in central nervous system. These findings limit the therapeutic utility of CSF-1R inhibitors but also highlight the need for a complete understanding of CSF-1R function within the central nervous system. Moreover, it has been found that selective inhibitors of CSF-1R may be more efficient in avoiding non-specific targeting and associated side effects. Short-term depletion of microglial population in diseased conditions have also been found to be beneficial; however, the dose and therapeutic window for optimum effects may need to be standardized further.This review summarizes the present understanding of CSF-1R function within the central nervous system. We discuss the CSF-1R signaling in the context of microglia function, crosstalk between microglia and astroglia, and regulation of neuronal cell function. We also discuss a few of the neurological disorders with a focus on the utility of CSF-1R inhibitors as potential therapeutic strategy for halting the progression of neurological diseases.

The preventive effects of colony-stimulating factor 1 receptor (CSF-1R) inhibition on bladder outlet obstruction induced remodeling

INTRODUCTION

Bladder outlet obstruction (BOO) is a common problem that can affect bladder structure and function. Currently, there is no effective drugs available to prevent BOO-induced remodeling. Previous reports have demonstrated that the pathogenesis of BOO is associated with macrophage infiltration and polarization, which is physiologically dependent on colony-stimulating factor 1 receptor (CSF-1R) activation. Here we utilized a highly selective CSF-1R inhibitor, GW2580, to determine its preventive effects on BOO-induced remodeling.

METHODS

A total of 24 Sprague-Dawley rats were randomly divided into sham, BOO + vehicle, and BOO + GW2580 group. GW2580 or vehicle control was administrated by oral gavage at daily doses of 40 mg/kg for 6 weeks. Bladder samples were collected for histopathology, immunohistochemistry, immunofluorescence, western blotting, and flow cytometry analysis.

RESULTS

Our results demonstrated that bladder fibrosis was ameliorated by GW2580 compared with the vehicle group (22.01% ± 5.13% vs. 32.15% ± 7.24%, p < 0.01). Furthermore, treatment with GW2580 induced an inhibition of macrophage infiltration (4.41% ± 1.28% vs. 13.57% ± 3.42%, p < 0.001) and M2 macrophage polarization (10.67% ± 4.15% vs. 28.59% ± 6.38%, p < 0.001). There was also a decrease of profibrotic F4/80⁺  α-smooth muscle actin⁺ (α-SMA⁺ ) macrophage to myofibroblast transition (9.11% ± 2.58% vs. 17.33% ± 4.01%, p < 0.001) and CD163⁺ TGF-β1⁺ cells (7.68% ± 2.10% vs. 14.17% ± 4.09%, p < 0.01) in the GW2580 group when compared with the vehicle group.

CONCLUSIONS

In summary, our findings showed that GW2580 is a worthwhile candidate for a follow-up study to test in the treatment of BOO-induced remodeling.

Neuropathic Pain in Multiple Sclerosis and Its Animal Models: Focus on Mechanisms, Knowledge Gaps and Future Directions

Multiple sclerosis (MS) is a multifaceted, complex and chronic neurological disease that leads to motor, sensory and cognitive deficits. MS symptoms are unpredictable and exceedingly variable. Pain is a frequent symptom of MS and manifests as nociceptive or neuropathic pain, even at early disease stages. Neuropathic pain is one of the most debilitating symptoms that reduces quality of life and interferes with daily activities, particularly because conventional pharmacotherapies do not adequately alleviate neuropathic pain. Despite advances, the mechanisms underlying neuropathic pain in MS remain elusive. The majority of the studies investigating the pathophysiology of MS-associated neuropathic pain have been performed in animal models that replicate some of the clinical and neuropathological features of MS. Experimental autoimmune encephalomyelitis (EAE) is one of the best-characterized and most commonly used animal models of MS. As in the case of individuals with MS, rodents affected by EAE manifest increased sensitivity to pain which can be assessed by well-established assays. Investigations on EAE provided valuable insights into the pathophysiology of neuropathic pain. Nevertheless, additional investigations are warranted to better understand the events that lead to the onset and maintenance of neuropathic pain in order to identify targets that can facilitate the development of more effective therapeutic interventions. The goal of the present review is to provide an overview of several mechanisms implicated in neuropathic pain in EAE by summarizing published reports. We discuss current knowledge gaps and future research directions, especially based on information obtained by use of other animal models of neuropathic pain such as nerve injury.

Treatment With the CSF1R Antagonist GW2580, Sensitizes Microglia to Reactive Oxygen Species

Microglia activation and proliferation are hallmarks of many neurodegenerative disorders and may contribute to disease pathogenesis. Neurons actively regulate microglia survival and function, in part by secreting the microglia mitogen interleukin (IL)-34. Both IL-34 and colony stimulating factor (CSF)-1 bind colony stimulating factor receptor (CSFR)1 expressed on microglia. Systemic treatment with central nervous system (CNS) penetrant, CSFR1 antagonists, results in microglia death in a dose dependent matter, while others, such as GW2580, suppress activation during disease states without altering viability. However, it is not known how treatment with non-penetrant CSF1R antagonists, such as GW2580, affect the normal physiology of microglia. To determine how GW2580 affects microglia function, C57BL/6J mice were orally gavaged with vehicle or GW2580 (80mg/kg/d) for 8 days. Body weights and burrowing behavior were measured throughout the experiment. The effects of GW2580 on circulating leukocyte populations, brain microglia morphology, and the transcriptome of magnetically isolated adult brain microglia were determined. Body weights, burrowing behavior, and circulating leukocytes were not affected by treatment. Analysis of Iba-1 stained brain microglia indicated that GW2580 treatment altered morphology, but not cell number. Analysis of RNA-sequencing data indicated that genes related to reactive oxygen species (ROS) regulation and survival were suppressed by treatment. Treatment of primary microglia cultures with GW2580 resulted in a dose-dependent reduction in viability only when the cells were concurrently treated with LPS, an inducer of ROS. Pre-treatment with the ROS inhibitor, YCG063, blocked treatment induced reductions in viability. Finally, GW2580 sensitized microglia to hydrogen peroxide induced cell death. Together, these data suggest that partial CSF1R antagonism may render microglia more susceptible to reactive oxygen and nitrogen species.

Insights Into the Role of CSF1R in the Central Nervous System and Neurological Disorders

The colony-stimulating factor 1 receptor (CSF1R) is a key tyrosine kinase transmembrane receptor modulating microglial homeostasis, neurogenesis, and neuronal survival in the central nervous system (CNS). CSF1R, which can be proteolytically cleaved into a soluble ectodomain and an intracellular protein fragment, supports the survival of myeloid cells upon activation by two ligands, colony stimulating factor 1 and interleukin 34. CSF1R loss-of-function mutations are the major cause of adult-onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP) and its dysfunction has also been implicated in other neurodegenerative disorders including Alzheimer’s disease (AD). Here, we review the physiological functions of CSF1R in the CNS and its pathological effects in neurological disorders including ALSP, AD, frontotemporal dementia and multiple sclerosis. Understanding the pathophysiology of CSF1R is critical for developing targeted therapies for related neurological diseases.

Triggering Innate Immune Receptors as New Therapies in Alzheimer's Disease and Multiple Sclerosis

Multiple sclerosis and Alzheimer's disease are two complex neurodegenerative diseases involving the immune system. So far, available treatments provide at best mild improvements to patients' conditions. For decades now, a new set of molecules have been used to modulate and regulate the innate immunity in these pathologies. Most studies have been carried out in rodents and some of them have reported tremendous beneficial effects on the disease course. The modulation of innate immune cells is of great interest since it provides new hope for patients. In this review, we will briefly overview the therapeutic potential of some molecules and receptors in multiple sclerosis and Alzheimer's disease and how they could be used to exploit new therapeutic avenues.

Smek1 deficiency exacerbates experimental autoimmune encephalomyelitis by activating proinflammatory microglia and suppressing the IDO1-AhR pathway

BACKGROUND

Experimental autoimmune encephalomyelitis (EAE) is an animal disease model of multiple sclerosis (MS) that involves the immune system and central nervous system (CNS). However, it is unclear how genetic predispositions promote neuroinflammation in MS and EAE. Here, we investigated how partial loss-of-function of suppressor of MEK1 (SMEK1), a regulatory subunit of protein phosphatase 4, facilitates the onset of MS and EAE.

METHODS

C57BL/6 mice were immunized with myelin oligodendrocyte glycoprotein 35-55 (MOG35-55) to establish the EAE model. Clinical signs were recorded and pathogenesis was investigated after immunization. CNS tissues were analyzed by immunostaining, quantitative polymerase chain reaction (qPCR), western blot analysis, and enzyme-linked immunosorbent assay (ELISA). Single-cell analysis was carried out in the cortices and hippocampus. Splenic and lymph node cells were evaluated with flow cytometry, qPCR, and western blot analysis.

RESULTS

Here, we showed that partial Smek1 deficiency caused more severe symptoms in the EAE model than in controls by activating myeloid cells and that Smek1 was required for maintaining immunosuppressive function by modulating the indoleamine 2,3-dioxygenase (IDO1)-aryl hydrocarbon receptor (AhR) pathway. Single-cell sequencing and an in vitro study showed that Smek1-deficient microglia and macrophages were preactivated at steady state. After MOG35-55 immunization, microglia and macrophages underwent hyperactivation and produced increased IL-1β in Smek1-/+ mice at the peak stage. Moreover, dysfunction of the IDO1-AhR pathway resulted from the reduction of interferon γ (IFN-γ), enhanced antigen presentation ability, and inhibition of anti-inflammatory processes in Smek1-/+ EAE mice.

CONCLUSIONS

The present study suggests a protective role of Smek1 in autoimmune demyelination pathogenesis via immune suppression and inflammation regulation in both the immune system and the central nervous system. Our findings provide an instructive basis for the roles of Smek1 in EAE and broaden the understanding of the genetic factors involved in the pathogenesis of autoimmune demyelination.

Connecting Neuroinflammation and Neurodegeneration in Multiple Sclerosis: Are Oligodendrocyte Precursor Cells a Nexus of Disease?

The pathology in neurodegenerative diseases is often accompanied by inflammation. It is well-known that many cells within the central nervous system (CNS) also contribute to ongoing neuroinflammation, which can promote neurodegeneration. Multiple sclerosis (MS) is both an inflammatory and neurodegenerative disease in which there is a complex interplay between resident CNS cells to mediate myelin and axonal damage, and this communication network can vary depending on the subtype and chronicity of disease. Oligodendrocytes, the myelinating cell of the CNS, and their precursors, oligodendrocyte precursor cells (OPCs), are often thought of as the targets of autoimmune pathology during MS and in several animal models of MS; however, there is emerging evidence that OPCs actively contribute to inflammation that directly and indirectly contributes to neurodegeneration. Here we discuss several contributors to MS disease progression starting with lesion pathology and murine models amenable to studying particular aspects of disease. We then review how OPCs themselves can play an active role in promoting neuroinflammation and neurodegeneration, and how other resident CNS cells including microglia, astrocytes, and neurons can impact OPC function. Further, we outline the very complex and pleiotropic role(s) of several inflammatory cytokines and other secreted factors classically described as solely deleterious during MS and its animal models, but in fact, have many neuroprotective functions and promote a return to homeostasis, in part via modulation of OPC function. Finally, since MS affects patients from the onset of disease throughout their lifespan, we discuss the impact of aging on OPC function and CNS recovery. It is becoming clear that OPCs are not simply a bystander during MS progression and uncovering the active roles they play during different stages of disease will help uncover potential new avenues for therapeutic intervention.

Brain gray matter astroglia-specific connexin 43 ablation attenuates spinal cord inflammatory demyelination

Background

Brain astroglia are activated preceding the onset of experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis (MS). We characterized the effects of brain astroglia on spinal cord inflammation, focusing on astroglial connexin (Cx)43, because we recently reported that Cx43 has a critical role in regulating neuroinflammation.

Methods

Because glutamate aspartate transporter (GLAST)⁺ astroglia are enriched in the brain gray matter, we generated Cx43^fl/fl;GLAST-CreER^T2/+ mice that were brain gray matter astroglia-specific Cx43 conditional knockouts (Cx43 icKO). EAE was induced by immunization with myelin oligodendroglia glycoprotein (MOG) _35–55 peptide 10 days after tamoxifen injection. Cx43^fl/fl mice were used as controls.

Results

Acute and chronic EAE signs were significantly milder in Cx43 icKO mice than in controls whereas splenocyte MOG-specific responses were unaltered. Histologically, Cx43 icKO mice showed significantly less demyelination and fewer CD45⁺ infiltrating immunocytes, including F4/80⁺ macrophages, and Iba1⁺ microglia in the spinal cord than controls. Microarray analysis of the whole cerebellum revealed marked upregulation of anti-inflammatory A2-specific astroglia gene sets in the pre-immunized phase and decreased proinflammatory A1-specific and pan-reactive astroglial gene expression in the onset phase in Cx43 icKO mice compared with controls. Astroglia expressing C3, a representative A1 marker, were significantly decreased in the cerebrum, cerebellum, and spinal cord of Cx43 icKO mice compared with controls in the peak phase. Isolated Cx43 icKO spinal microglia showed more anti-inflammatory and less proinflammatory gene expression than control microglia in the pre-immunized phase. In particular, microglial expression of Ccl2, Ccl5, Ccl7, and Ccl8 in the pre-immunized phase and of Cxcl9 at the peak phase was lower in Cx43 icKO than in controls. Spinal microglia circularity was significantly lower in Cx43 icKO than in controls in the peak phase. Significantly lower interleukin (IL)-6, interferon-γ, and IL-10 levels were present in cerebrospinal fluid from Cx43 icKO mice in the onset phase compared with controls.

Conclusions

The ablation of Cx43 in brain gray matter astroglia attenuates EAE by promoting astroglia toward an anti-inflammatory phenotype and suppressing proinflammatory activation of spinal microglia partly through depressed cerebrospinal fluid proinflammatory cytokine/chemokine levels. Brain astroglial Cx43 might be a novel therapeutic target for MS.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-021-02176-1.

4-Ethylguaiacol modulates neuroinflammation and Th1/Th17 differentiation to ameliorate disease severity in experimental autoimmune encephalomyelitis

BACKGROUND

Multiple sclerosis (MS) is a progressive autoimmune disease characterized by the accumulation of pathogenic inflammatory immune cells in the central nervous system (CNS) that subsequently causes focal inflammation, demyelination, axonal injury, and neuronal damage. Experimental autoimmune encephalomyelitis (EAE) is a well-established murine model that mimics the key features of MS. Presently, the dietary consumption of foods rich in phenols has been reported to offer numerous health benefits, including anti-inflammatory activity. One such compound, 4-ethylguaiacol (4-EG), found in various foods, is known to attenuate inflammatory immune responses. However, whether 4-EG exerts anti-inflammatory effects on modulating the CNS inflammatory immune responses remains unknown. Thus, in this study, we assessed the therapeutic effect of 4-EG in EAE using both chronic and relapsing-remitting animal models and investigated the immunomodulatory effects of 4-EG on neuroinflammation and Th1/Th17 differentiation in EAE.

METHODS

Chronic C57BL/6 EAE and relapsing-remitting SJL/J EAE were induced followed by 4-EG treatment. The effects of 4-EG on disease progression, peripheral Th1/Th17 differentiation, CNS Th1/Th17 infiltration, microglia (MG) activation, and blood-brain barrier (BBB) disruption in EAE were evaluated. In addition, the expression of MMP9, MMP3, HO-1, and Nrf2 was assessed in the CNS of C57BL/6 EAE mice.

RESULTS

Our results showed that 4-EG not only ameliorated disease severity in C57BL/6 chronic EAE but also mitigated disease progression in SJL/J relapsing-remitting EAE. Further investigations of the cellular and molecular mechanisms revealed that 4-EG suppressed MG activation, mitigated BBB disruption, repressed MMP3/MMP9 production, and inhibited Th1 and Th17 infiltration in the CNS of EAE. Furthermore, 4-EG suppressed Th1 and Th17 differentiation in the periphery of EAE and in vitro Th1 and Th17 cultures. Finally, we found 4-EG induced HO-1 expression in the CNS of EAE in vivo as well as in MG, BV2 cells, and macrophages in vitro.

CONCLUSIONS

Our work demonstrates that 4-EG confers protection against autoimmune disease EAE through modulating neuroinflammation and inhibiting Th1 and Th17 differentiation, suggesting 4-EG, a natural compound, could be potentially developed as a therapeutic agent for the treatment of MS/EAE.

Activated microglia drive demyelination via CSF1R signaling

Microgliosis is a prominent pathological feature in many neurological diseases including multiple sclerosis (MS), a progressive auto-immune demyelinating disorder. The precise role of microglia, parenchymal central nervous system (CNS) macrophages, during demyelination, and the relative contributions of peripheral macrophages are incompletely understood. Classical markers used to identify microglia do not reliably discriminate between microglia and peripheral macrophages, confounding analyses. Here, we use a genetic fate mapping strategy to identify microglia as predominant responders and key effectors of demyelination in the cuprizone (CUP) model. Colony-stimulating factor 1 (CSF1), also known as macrophage colony-stimulating factor (M-CSF) - a secreted cytokine that regulates microglia development and survival-is upregulated in demyelinated white matter lesions. Depletion of microglia with the CSF1R inhibitor PLX3397 greatly abrogates the demyelination, loss of oligodendrocytes, and reactive astrocytosis that results from CUP treatment. Electron microscopy (EM) and serial block face imaging show myelin sheaths remain intact in CUP treated mice depleted of microglia. However, these CUP-damaged myelin sheaths are lost and robustly phagocytosed upon-repopulation of microglia. Direct injection of CSF1 into CNS white matter induces focal microgliosis and demyelination indicating active CSF1 signaling can promote demyelination. Finally, mice defective in adopting a toxic astrocyte phenotype that is driven by microglia nevertheless demyelinate normally upon CUP treatment implicating microglia rather than astrocytes as the primary drivers of CUP-mediated demyelination. Together, these studies indicate activated microglia are required for and can drive demyelination directly and implicate CSF1 signaling in these events.

Time-Course Changes of Extracellular Matrix Encoding Genes Expression Level in the Spinal Cord Following Contusion Injury-A Data-Driven Approach

The involvement of the extracellular matrix (ECM) in lesion evolution and functional outcome is well recognized in spinal cord injury. Most attention has been dedicated to the “core” area of the lesion and scar formation, while only scattered reports consider ECM modification based on the temporal evolution and the segments adjacent to the lesion. In this study, we investigated the expression profile of 100 genes encoding for ECM proteins at 1, 8 and 45 days post-injury, in the spinal cord segments rostral and caudal to the lesion and in the scar segment, in a rat model. During both the active lesion phases and the lesion stabilization, we observed an asymmetric gene expression induced by the injury, with a higher regulation in the rostral segment of genes involved in ECM remodeling, adhesion and cell migration. Using bioinformatic approaches, the metalloproteases inhibitor Timp1 and the hyaluronan receptor Cd44 emerged as the hub genes at all post-lesion times. Results from the bioinformatic gene expression analysis were then confirmed at protein level by tissue analysis and by cell culture using primary astrocytes. These results indicated that ECM regulation also takes place outside of the lesion area in spinal cord injury.

Early CSF Biomarkers and Late Functional Outcomes in Spinal Cord Injury. A Pilot Study

Although, biomarkers are regarded as an important tool for monitoring injury severity and treatment efficacy, and for predicting clinical evolution in many neurological diseases and disorders including spinal cord injury, there is still a lack of reliable biomarkers for the assessment of clinical course and patient outcome. In this study, a biological dataset of 60 cytokines/chemokines, growth factorsm and intracellular and extracellular matrix proteins, analyzed in CSF within 24 h of injury, was used for correlation analysis with the clinical dataset of the same patients. A heat map was generated of positive and negative correlations between biomarkers and clinical rating scale scores at discharge, and between biomarkers and changes in clinical scores during the observation period. Using very stringent statistical criteria, we found 10 molecules which correlated with clinical scores at discharge, and five molecules, which correlated with changes in clinical scores. The proposed methodology may be useful for generating hypotheses regarding "predictive" and "treatment effectiveness" biomarkers, thereby suggesting potential candidates for disease-modifying therapies using a "bed-to-bench" approach.

Clinically Precedented Protein Kinases: Rationale for Their Use in Neurodegenerative Disease

Kinases are an intensively studied drug target class in current pharmacological research as evidenced by the large number of kinase inhibitors being assessed in clinical trials. Kinase-targeted therapies have potential for treatment of a broad array of indications including central nervous system (CNS) disorders. In addition to the many variables which contribute to identification of a successful therapeutic molecule, drug discovery for CNS-related disorders also requires significant consideration of access to the target organ and specifically crossing the blood-brain barrier (BBB). To date, only a small number of kinase inhibitors have been reported that are specifically designed to be BBB permeable, which nonetheless demonstrates the potential for success. This review considers the potential for kinase inhibitors in the context of unmet medical need for neurodegenerative disease. A subset of kinases that have been the focus of clinical investigations over a 10-year period have been identified and discussed individually. For each kinase target, the data underpinning the validity of each in the context of neurodegenerative disease is critically evaluated. Selected molecules for each kinase are identified with information on modality, binding site and CNS penetrance, if known. Current clinical development in neurodegenerative disease are summarized. Collectively, the review indicates that kinase targets with sufficient rationale warrant careful design approaches with an emphasis on improving brain penetrance and selectivity.

CSF1R signaling is a regulator of pathogenesis in progressive MS

Microglia serve as the innate immune cells of the central nervous system (CNS) by providing continuous surveillance of the CNS microenvironment and initiating defense mechanisms to protect CNS tissue. Upon injury, microglia transition into an activated state altering their transcriptional profile, transforming their morphology, and producing pro-inflammatory cytokines. These activated microglia initially serve a beneficial role, but their continued activation drives neuroinflammation and neurodegeneration. Multiple sclerosis (MS) is a chronic, inflammatory, demyelinating disease of the CNS, and activated microglia and macrophages play a significant role in mediating disease pathophysiology and progression. Colony-stimulating factor-1 receptor (CSF1R) and its ligand CSF1 are elevated in CNS tissue derived from MS patients. We performed a large-scale RNA-sequencing experiment and identified CSF1R as a key node of disease progression in a mouse model of progressive MS. We hypothesized that modulating microglia and infiltrating macrophages through the inhibition of CSF1R will attenuate deleterious CNS inflammation and reduce subsequent demyelination and neurodegeneration. To test this hypothesis, we generated a novel potent and selective small-molecule CSF1R inhibitor (sCSF1R_inh) for preclinical testing. sCSF1R_inh blocked receptor phosphorylation and downstream signaling in both microglia and macrophages and altered cellular functions including proliferation, survival, and cytokine production. In vivo, CSF1R inhibition with sCSF1R_inh attenuated neuroinflammation and reduced microglial proliferation in a murine acute LPS model. Furthermore, the sCSF1R_inh attenuated a disease-associated microglial phenotype and blocked both axonal damage and neurological impairments in an experimental autoimmune encephalomyelitis (EAE) model of MS. While previous studies have focused on microglial depletion following CSF1R inhibition, our data clearly show that signaling downstream of this receptor can be beneficially modulated in the context of CNS injury. Together, these data suggest that CSF1R inhibition can reduce deleterious microglial proliferation and modulate microglial phenotypes during neuroinflammatory pathogenesis, particularly in progressive MS.

Potential for Targeting Myeloid Cells in Controlling CNS Inflammation

Multiple Sclerosis (MS) is characterized by immune cell infiltration to the central nervous system (CNS) as well as loss of myelin. Characterization of the cells in lesions of MS patients revealed an important accumulation of myeloid cells such as macrophages and dendritic cells (DCs). Data from the experimental autoimmune encephalomyelitis (EAE) model of MS supports the importance of peripheral myeloid cells in the disease pathology. However, the majority of MS therapies focus on lymphocytes. As we will discuss in this review, multiple strategies are now in place to target myeloid cells in clinical trials. These strategies have emerged from data in both human and mouse studies. We discuss strategies targeting myeloid cell migration, growth factors and cytokines, biological functions (with a focus on miRNAs), and immunological activities (with a focus on nanoparticles).

Hydroxysafflor Yellow A Exerts Anti-Inflammatory Effects Mediated by SIRT1 in Lipopolysaccharide-Induced Microglia Activation

Abnormal microglia activation causes sever neuroinflammation, contributing to the development of many diseases, yet the mechanism remains incompletely unknown. In current study, we identified that Hydroxysafflor yellow A (HYA), a chalcone glycoside derived from Carthamus tinctorius L effectively attenuates LPS-induced inflammation response in primary microglia via regulating the expression of inflammatory genes and remodeling the polarization of microglia. We also reported the effects of HYA on improving lipopolysaccharide (LPS)-stimulated mitochondrial dysfunction and oxidative stress for the first time. Interestingly, we found that HYA could serves as an effective SIRT1 activator. Deficiency of SIRT1 abrogates the protective effects of HYA against LPS-induced response. Overall, our data suggest HYA, a novel SIRT1 activator, could serve as an effective approach to treat LPS-induced neurodegenerative diseases.

Oleanolic Acid Acetate Alleviates Symptoms of Experimental Autoimmune Encephalomyelitis in Mice by Regulating Toll-Like Receptor 2 Signaling

Toll-like receptor 2 (TLR2) is expressed by several immune cells in the central nervous system and plays an important role in neuroinflammation. TLR2 upregulation has been reported in multiple sclerosis patients and in experimental autoimmune encephalomyelitis (EAE), a mouse model for multiple sclerosis. Therefore, modulating TLR2 signaling can be an effective treatment strategy against MS. Oleanolic acid acetate (OAA) has antiinflammatory and immunomodulatory effects. Hence, this study aimed to examine the effects of OAA on TLR2 signaling and neuroinflammation in EAE. EAE was induced in C57/BL6 mice using synthesized myelin oligodendrocyte glycoprotein (MOG)_35-55 peptide, and OAA was administered daily. Hind limb paralysis and inflammatory cell infiltration were observed in the spinal cords of EAE mice. Moreover, T-cell proliferation was significantly stimulated in splenic cells from EAE mice. The expression of proinflammatory cytokines in the spinal cord was upregulated, and their serum protein levels were increased in EAE mice. Furthermore, upregulation of TLR2 and downstream signaling molecules was observed in the spinal cord. These pathological changes were reversed by OAA treatment. Our results suggest that OAA might have promising therapeutic properties and that the TLR signaling pathway is an effective therapeutic target against multiple sclerosis.

Dynamic Responses of Microglia in Animal Models of Multiple Sclerosis

Microglia play an essential role in maintaining central nervous system (CNS) homeostasis, as well as responding to injury and disease. Most neurological disorders feature microglial activation, a process whereby microglia undergo profound morphological and transcriptional changes aimed at containing CNS damage and promoting repair, but often resulting in overt inflammation that sustains and propagates the neurodegenerative process. This is especially evident in multiple sclerosis (MS), were microglial activation and microglia-driven neuroinflammation are considered key events in the onset, progression, and resolution of the disease. Our understanding of microglial functions in MS has widened exponentially in the last decade by way of new tools and markers to discriminate microglia from other myeloid populations. Consequently, the complex functional and phenotypical diversity of microglia can now be appreciated. This, in combination with a variety of animal models that mimic specific features and processes of MS, has contributed to filling the gap of knowledge in the cascade of events underlying MS pathophysiology. The purpose of this review is to present the most up to date knowledge of the dynamic responses of microglia in the commonly used animal models of MS, specifically the immune-mediated experimental autoimmune encephalomyelitis (EAE) model, and the chemically-induced cuprizone and lysolecithin models. Elucidating the spectrum of microglial functions in these models, from detrimental to protective, is essential to identify emerging targets for therapy and guide drug discovery efforts.

CSF-1R inhibition attenuates ischemia-induced renal injury and fibrosis by reducing Ly6C+ M2-like macrophage infiltration

Acute kidney injury (AKI) to chronic kidney disease (CKD) progression has become a life-threatening disease. However, an effective therapeuticstrategyis still needed. The pathophysiology of AKI-to-CKD progression involves chronic inflammation and renal fibrosis driven by macrophage activation, which is physiologically dependent on colony-stimulating factor-1 receptor (CSF-1R) signaling. In this study, we modulated macrophage infiltration through oral administration of the CSF-1R inhibitor GW2580 in an ischemia-reperfusion (I/R)-induced AKI model to evaluate its therapeutic effects on preventing the progression of AKI to CKD. We found that GW2580 induced a significant reduction in the number of macrophages in I/R-injured kidneys and attenuated I/R-induced renal injury and subsequent interstitial fibrosis. By flow cytometry, we observed that the reduced macrophages were primarily Ly6C⁺ inflammatory macrophages in the GW2580-treated kidneys, while there was no significant difference in the number and percentage of Ly6C^-CX3CR1⁺ macrophages. We further found that these reduced macrophages also demonstrated some characteristics of M2-like macrophages, which have been generally regarded as profibrotic subtypes in chronic inflammation. These results indicate the existence of phenotypic and functional crossover between Ly6C⁺ and M2-like macrophages in I/R kidneys, which induces AKI worsening to CKD. In conclusion, therapeutic GW2580 treatment alleviates acute renal injury and subsequent fibrosis by reducing Ly6C⁺ M2-like macrophage infiltration in ischemia-induced AKI.

In vivo intrathecal IL-1β quantification in rats: Monitoring the molecular signals of neuropathic pain

BACKGROUND

Neuropathic pain, or pain after nerve injury, is a disorder with a significant reliance on the signalling of cytokines such as IL-1β. However, quantifying the cytokine release repeatedly over time in vivo is technically challenging.

AIM

To evaluate if changes in IL-1β are correlated with the presentation of mechanical allodynia over time, by repeatedly quantifying intrathecal IL-1β concentrations following chronic constriction injury of the sciatic nerve in rats. Also, to establish any possible correlation between biochemical spinal marker expression and the in vivo quantification of IL-1β. Finally, to assess the expression of the mature IL-1β in lumbar spinal cord samples.

METHOD

The Chronic Constriction Injury model (CCI) was used to initiate nerve injury in male Sprague Dawley rats and the generation of behavioural mechanical allodynia was quantified. Using an indwelling intrathecal catheter, a stainless steel (SS) wire biosensing device was repeatedly introduced to quantify intrathecal IL-1β concentrations at three timepoints of 0, 7, and 14 days post CCI. Fixed spinal cord samples (L4-L5), collected on day 14, were imaged for the expression of glial fibrillary acidic protein (GFAP, astrocytes) and ionized calcium binding adaptor molecule 1 (IBA1, microglia). Snap frozen spinal cord tissues (L4-L5) were also processed for western blot analysis.

RESULTS

Using the novel SS based biosensing device we established that CCI caused a significant increase in intrathecal IL-1β concentrations from day 0 to day 7 (p = 0.001) and to day 14 (p < 0.0001), while the sham group did not show any significant increase. We also further showed that the degree of mechanical allodynia correlated positively with the increase in the intrathecal concentration of IL-1β in the active CCI animals (p = 0.0007). While there was a significant increase in the ipsilateral GFAP expression in injured animals compared to sham animals (p = 0.03), we did not find any significant correlation between in vivo IL-1β concentration on days 7 and 14 and the area of dorsal horn GFAP or IBA1 positive structures on day 14. The result of western blot analysis of whole lumbar spinal cord revealed that there was no significant change (p = 0.7579) in IL-1β expression on day 14 in the CCI group compared to the sham group.

CONCLUSION

For the first time we have established that the SS based immunosensing platform technology can repeatedly sample the intrathecal space for bioactive peptides, such as IL-1β. Using this novel approach, we have been able to establish the correlation of the intrathecal concentration of IL-1β with the extent of mechanical allodynia, providing a molecular biomarker of the degree of the exaggerated pain state.

Expression of hypothalamic feeding-related peptide genes and neuroendocrine responses in an experimental allergic encephalomyelitis rat model

Experimental allergic encephalomyelitis (EAE) is considered to be a useful animal model of human multiple sclerosis (MS). However, among the various symptoms of MS, the mechanisms contributing to inflammatory anorexia remain unclear. In the present study, we used an EAE rat model to examine changes in expression levels of hypothalamic feeding-related peptide genes and neuroendocrine responses such as the hypothalamo-neurohypophysial system and the hypothalamo-pituitary-adrenal (HPA) axis. The weight gain and cumulative food intake in EAE rats in the early days after immunization was significantly lower than that of the control group. The expression of orexigenic peptide genes Npy and Agrp were significantly increased, whereas the levels of anorectic peptide genes (Pomc and Cart) were significantly decreased in the hypothalamus of EAE rats. There was also a significant increase in the mRNA and plasma oxytocin (OXT) but not of arginine vasopressin (AVP) in the supraoptic and paraventricular nuclei (PVN) of EAE rats at days 12 and 18 after immunization. The expression of corticotropin-releasing hormone (Crh) and Avp was downregulated and upregulated, respectively, in the parvocellular division of the PVN at day 12 after immunization. The expression level of Pomc in the anterior pituitary significantly increased, accompanied by increased plasma corticosterone levels, at days 6, 12, and 18 after immunization. These results suggest that inflammatory anorexia in rat EAE may be caused by activation of the OXT-ergic pathway and HPA axis via changes in the expression of hypothalamic feeding-related peptides, including Avp but not Crh.

Rh-CSF1 attenuates neuroinflammation via the CSF1R/PLCG2/PKCε pathway in a rat model of neonatal HIE

BACKGROUND

Hypoxic-ischemic encephalopathy (HIE) is a life-threatening cerebrovascular disease. Neuroinflammation plays an important role in the pathogenesis of HIE, in which microglia are key cellular mediators in the regulation of neuroinflammatory processes. Colony-stimulating factor 1 (CSF1), a specific endogenous ligand of CSF1 receptor (CSF1R), is crucial in microglial growth, differentiation, and proliferation. Recent studies showed that the activation of CSF1R with CSF1 exerted anti-inflammatory effects in a variety of nervous system diseases. This study aimed to investigate the anti-inflammatory effects of recombinant human CSF1 (rh-CSF1) and the underlying mechanisms in a rat model of HIE.

METHODS

A total of 202 10-day old Sprague Dawley rat pups were used. HI was induced by the right common carotid artery ligation with subsequent exposure of 2.5-h hypoxia. At 1 h and 24 h after HI induction, exogenous rh-CSF1 was administered intranasally. To explore the underlying mechanism, CSF1R inhibitor, BLZ945, and phospholipase C-gamma 2 (PLCG2) inhibitor, U73122, were injected intraperitoneally at 1 h before HI induction, respectively. Brain infarct area, brain water content, neurobehavioral tests, western blot, and immunofluorescence staining were performed.

RESULTS

The expressions of endogenous CSF1, CSF1R, PLCG2, protein kinase C epsilon type (PKCε), and cAMP response element-binding protein (CREB) were gradually increased after HIE. Rh-CSF1 significantly improved the neurological deficits at 48 h and 4 weeks after HI, which was accompanied by a reduction in the brain infarct area, brain edema, brain atrophy, and neuroinflammation. Moreover, activation of CSF1R by rh-CSF1 significantly increased the expressions of p-PLCG2, p-PKCε, and p-CREB, but inhibited the activation of neutrophil infiltration, and downregulated the expressions of IL-1β and TNF-α. Inhibition of CSF1R and PLCG2 abolished these neuroprotective effects of rh-CSF1 after HI.

CONCLUSIONS

Our findings demonstrated that the activation of CSF1R by rh-CSF1 attenuated neuroinflammation and improved neurological deficits after HI. The anti-inflammatory effects of rh-CSF1 partially acted through activating the CSF1R/PLCG2/PKCε/CREB signaling pathway after HI. These results suggest that rh-CSF1 may serve as a potential therapeutic approach to ameliorate injury in HIE patients.

ADAMTS13 ameliorates inflammatory responses in experimental autoimmune encephalomyelitis

BACKGROUND

ADAMTS13 (a disintegrin and metalloprotease with a thrombospondin type 1 motif, member 13) plays a vital role in preventing microvascular thrombosis and inflammation. Reduced ADAMTS13 levels in plasma have been detected in multiple sclerosis (MS) patients. In the present study, we have determined the role of ADAMTS13 in the disease progression of MS using a mouse model of experimental autoimmune encephalomyelitis (EAE).

METHODS

Female C57BL/6 mice were immunized with MOG_35-55 peptide and then treated with ADAMTS13 or vehicle in preventive and therapeutic settings. Mice were analyzed for clinical deficit, white matter demyelination and inflammatory cell infiltration. To explore the underlying mechanism, VWF expression and blood-spinal cord barriers (BSCB) were determined.

RESULTS

Plasma ADAMTS13 activity was suppressed in EAE mice. ADAMTS13-treated EAE mice exhibited an ameliorated disease course, reduced demyelination, and decreased T lymphocyte, neutrophil and monocyte infiltration into the spinal cord. Consistently, ADAMTS13 treatment reduced VWF levels and inhibited BSCB breakdown in the spinal cords of EAE mice. However, leukocytes in the blood and spleen of EAE mice remained unaffected by ADAMTS13 administration.

CONCLUSION

Our results demonstrate that ADAMTS13 treatment ameliorates inflammatory responses, demyelination and disease course in EAE mice. Therefore, our study suggests that ADAMTS13 may represent a potential therapeutic strategy for MS patients.

Clozapine reduces infiltration into the CNS by targeting migration in experimental autoimmune encephalomyelitis

Background

Atypical antipsychotic agents, such as clozapine, are used to treat schizophrenia and other psychiatric disorders by a mechanism that is believed to involve modulating the immune system. Multiple sclerosis is an immune-mediated neurological disease, and recently, clozapine was shown to reduce disease severity in an animal model of MS, experimental autoimmune encephalomyelitis (EAE). However, the mode of action by which clozapine reduces disease in this model is poorly understood.

Methods

Because the mode of action by which clozapine reduces neuroinflammation is poorly understood, we used the EAE model to elucidate the in vivo and in vitro effects of clozapine.

Results

In this study, we report that clozapine treatment reduced the infiltration of peripheral immune cells into the central nervous system (CNS) and that this correlated with reduced expression of the chemokines CCL2 and CCL5 transcripts in the brain and spinal cord. We assessed to what extent immune cell populations were affected by clozapine treatment and we found that clozapine targets the expression of chemokines by macrophages and primary microglia. Furthermore, in addition to decreasing CNS infiltration by reducing chemokine expression, we found that clozapine directly inhibits chemokine-induced migration of immune cells. This direct target on the immune cells was not mediated by a change in receptor expression on the immune cell surface but by decreasing downstream signaling via these receptors leading to a reduced migration.

Conclusions

Taken together, our study indicates that clozapine protects against EAE by two different mechanisms; first, by reducing the chemoattractant proteins in the CNS; and second, by direct targeting the migration potential of peripheral immune cells.

Differential effects of glucose deprivation on the survival of fetal versus adult neural stem cells-derived oligodendrocyte precursor cells

Impaired myelination is a key feature in neonatal hypoxia/ischemia (HI), the most common perinatal/neonatal cause of death and permanent disabilities, which is triggered by the establishment of an inflammatory and hypoxic environment during the most critical period of myelin development. This process is dependent on oligodendrocyte precursor cells (OPCs) and their capability to differentiate into mature oligodendrocytes. In this study, we investigated the vulnerability of fetal and adult OPCs derived from neural stem cells (NSCs) to inflammatory and HI insults. The resulting OPCs/astrocytes cultures were exposed to cytokines to mimic inflammation, or to oxygen-glucose deprivation (OGD) to mimic an HI condition. The differentiation of both fetal and adult OPCs is completely abolished following exposure to inflammatory cytokines, while only fetal-derived OPCs degenerate when exposed to OGD. We then investigated possible mechanisms involved in OGD-mediated toxicity: (a) T3-mediated maturation induction; (b) glutamate excitotoxicity; (c) glucose metabolism. We found that while no substantial differences were observed in T3 intracellular content regulation and glutamate-mediated toxicity, glucose deprivation lead to selective OPC cell death and impaired differentiation in fetal cultures only. These results indicate that the biological response of OPCs to inflammation and demyelination is different in fetal and adult cells, and that the glucose metabolism perturbation in fetal central nervous system (CNS) may significantly contribute to neonatal pathologies. An understanding of the underlying molecular mechanism will contribute greatly to differentiating myelination enhancing and neuroprotective therapies for neonatal and adult CNS white matter lesions.

Ginsenoside Rg1 Exerts Anti-inflammatory Effects via G Protein-Coupled Estrogen Receptor in Lipopolysaccharide-Induced Microglia Activation

Neuroinflammation plays a pivotal role in the pathogenesis of Parkinson's disease. Ginsenoside Rg1, the most active ingredient of ginseng, has been reported to exert neuroprotective effects via estrogen and glucocorticoid receptors. The present study evaluated the involvement of the G protein-coupled estrogen receptor (GPER) in the anti-inflammatory effects of ginsenoside Rg1 against lipopolysaccharide (LPS)-induced microglia activation in the BV2 microglial cell line and ventral mesencephalic primary microglial culture. The pharmacological blockade and lentivirus-mediated small interfering RNA (siRNA) knockdown of GPER were used to study the underlying mechanism. Rg1 attenuated LPS-induced upregulation of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), inducible nitric oxide synthase (iNOS), and cyclooxygenase-2 (COX-2) mRNA and protein levels. The GPER antagonist G15 blocked the inhibitory effects of Rg1 and the GPER-specific agonist G1 on LPS-induced microglia activation. Rg1 mimicked the effects of G1 by inhibiting the LPS-induced activation of nuclear transcription factor-kappa B (NF-κB) and mitogen activated protein kinase signaling pathways, which was also blocked by G15. Moreover, lentivirus-mediated siRNA knockdown of GPER inhibited the anti-inflammatory effects of Rg1. Taken together, our results indicate that GPER is involved in the anti-inflammatory effects of Rg1 against LPS-induced microglia activation. These findings provide a new biological target of Rg1 for the treatment of neuroinflammatory disorders.

Potential biomarkers for neuroinflammation and neurodegeneration at short and long term after neonatal hypoxic-ischemic insult in rat

BACKGROUND

Hypoxic-ischemic (HI) encephalopathy causes life-long morbidity and premature mortality in term neonates. Therapies in addition to whole-body cooling are under development to treat the neonate at risk for HI encephalopathy, but are not a quickly measured serum inflammatory or neuronal biomarkers to rapidly and accurately identify brain injury in order to follow the efficacy of therapies.

METHODS

In order to identify potential biomarkers for early inflammatory and neurodegenerative events after neonatal hypoxia-ischemia, both male and female Wistar rat pups at postnatal day 7 (P7) were used and had their right carotid artery permanently doubly occluded and exposed to 8% oxygen for 90 min. Sensory and cognitive parameters were assessed by open field, rotarod, CatWalk, and Morris water maze (MWM) test. Plasma and CSF biomarkers were investigated on the acute (24 h and 72 h) and chronic phase (4 weeks). Brains were assessed for gene expression analysis by quantitative RT-PCR Array.

RESULTS

We found a delay of neurological reflex maturation in HI rats. We observed anxiolytic-like baseline behavior in males more than females following HI injury. HI rats held on the rotarod for a shorter time comparing to sham. HI injury impaired spatial learning ability on MWM test. The CatWalk assessment demonstrated a long-term deficit in gait parameters related to the hind paw. Proinflammatory biomarkers such as IL-6 in plasma and CCL2 and TNF-α in CSF showed an upregulation at 24 h after HI while other cytokines, such as IL-17A and CCL5, were upregulated after 72 h in CSF. At 24 h post-injury, we observed an increase of Edn1, Hif1-α, and Mmp9 mRNA levels in the ipsilateral vs the contralateral hemisphere of HI rats. An upregulation of genes involved with clotting and hematopoietic processes was observed 72 h post-injury.

CONCLUSIONS

Our work showed that, in the immature brain, the HI injury induced an early increased production of several proinflammatory mediators detectable in plasma and CSF, followed by tissue damage in the hypoxic hemisphere and short-term as well as long-lasting neurobehavioral deficits.

Rheumatoid arthritis and depression: an inflammatory perspective

The coexistence of immune-mediated inflammatory diseases with depression has long been recognised. Data that illustrate the intimate associations between peripheral and brain immune responses raise the possibility of shared pathophysiological mechanisms. These associations include the negative effects of proinflammatory cytokines on monoaminergic neurotransmission, neurotrophic factors, and measures of synaptic plasticity. The evidence supporting this association is accumulating and includes findings from clinical trials of immunomodulatory therapy, indicating that these interventions can provide benefits to mental health independent of improvements in physical disease scores. In this Review, we assess this evidence in relation to rheumatoid arthritis and depression, with a focus on innate immune and molecular responses to inflammation, and discuss the challenges of assessing causation in this population, acknowledging the difficulty of assessing the confounding and contributory effects of pain and fatigue. We also discuss how future clinical and preclinical research might improve diagnosis of depression in people with rheumatoid arthritis and shed light on mechanisms that could be substrates for therapeutic interventions.

Increased expression of colony-stimulating factor-1 in mouse spinal cord with experimental autoimmune encephalomyelitis correlates with microglial activation and neuronal loss

Microglia contribute to pathophysiology at all stages of multiple sclerosis. Colony-stimulating factor-1 (CSF1) is crucial for microglial proliferation and activation. In this study we measured the CSF1 levels and studied its cellular expression in the mouse spinal cords with experimental autoimmune encephalomyelitis (EAE) to explore the potential contribution of CSF1 in neuronal death. ELISA data showed that CSF1 levels were significantly higher in the spinal cords with acute and chronic EAE than those of normal and adjuvant-injected mice. Immunohistochemical studies demonstrated that CSF1 was expressed in astrocytes and neurons in normal mouse spinal cord. In acute EAE, CSF1 expression was significantly increased, especially in astrocytes in peripheral white matter and large motoneurons. High density of activated microglia was observed in the gray matter where motoneurons expressed high-level CSF1 in acute EAE. Significant large motoneuron loss was seen in chronic EAE and the remaining motoneurons with high-level CSF1 were enwrapped by microglia. Viral vector mediated over-expression of CSF1 in spinal neurons induced profound proliferation and activation of microglia at the injection site and microglia enwrapped CSF1-transduced neurons and their neurites. Significant loss of large CSF1-transduced neurons was seen at 2 and 3 weeks post-viral injection. Demyelination in the CSF1-transduced areas was also significant. These results implicate that CSF1 upregulation in CNS may play an important role in the proliferation and activation of microglia in EAE, contributing to neuroinflammation and neurodegeneration. © 2018 Wiley Periodicals, Inc.

Pharmacological blockade of CXCR3 by (±)-NBI-74330 reduces neuropathic pain and enhances opioid effectiveness - Evidence from in vivo and in vitro studies

It has been suggested that CXCR3 is important for nociception. Our experiments were conducted to evaluate involvement of CXCR3 and its ligands (CXCL4, CXCL9, CXCL10, CXCL11/CCL21) in neuropathic pain. Our studies give new evidence that intrathecal administration of each CXCR3 ligand induces pain-like behaviour in naive mice that occurs shortly after injection due to its location of neurons, which is confirmed by immunofluorescent staining. Moreover, intrathecal administrations of CXCL9, CXCL10, CCL21 neutralizing antibodies diminished pain-related behaviour. RT-PCR/Western blot analysis unprecedentedly showed spinal elevated levels of CXCR3 after chronic constriction injury of the sciatic nerve in rats in parallel with different time-course changes of its endogenous ligands. Initially, on day 2 we observed spinal increased levels of CXCL10 and CXCL11 indicating that these chemokines have important roles in triggering neuropathy. Then, on day 7, we observed increased levels of CXCL4, CXCL9, CXCL10. Interestingly, changes in CXCL9 level persisted until day 28, suggesting that these chemokines are responsible for long-term, persistent neuropathy. Additionally, in DRG the CXCL4, CXCL9 were elevated. The results obtained from primary glial cultures, suggests that all CXCR3 ligands can be produced in microglia, but also, except for CXCL4, in astrocytes. We provide the first evidence that in neuropathy chronic intrathecal administration of CXCR3 antagonist, (±)-NBI-74330, attenuates hypersensitivity with concomitant occurrence of microglial and some of CXCR3 ligands activation observed in the spinal cord and/or DRG level. This paper underlies the significance of CXCR3 in neuropathic pain and shows therapeutic potential of its blockade for enhancement of morphine analgesia as the major novelty of this work.

CCDC134 ameliorated experimental autoimmune encephalomyelitis by suppressing Th1 and Th17 cells

CCDC134 (coiled-coil domain containing 134), a cytokine-like molecule, was previously reported to exert antitumor effects by augmenting CD8⁺ T-cell mediated immunity. However, the dynamic changes in CCDC134 expression patterns in the spinal cord that may be involved in the progression of experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis, remains unclear. In this study, we found that CCDC134 expression was markedly increased in the spinal cord during the progression of EAE. Furthermore, we demonstrated that CCDC134 significantly reduced the severity and slowed the progression of EAE, which correlated with reduced spinal cord inflammation and demyelination. The underlying mechanism of CCDC134-induced effects involved inhibition of T helper (Th)-1 and Th17 cell differentiation and secretion of its key effector molecules IFN-γ and IL-17A via regulation of JAK/STAT signaling. These findings indicate that CCDC134 exerts potent anti-inflammatory effects through the selective modulation of pathogenic Th1 and Th17 cells by targeting critical signaling pathways. The study provides insights into the role of CCDC134 as a unique therapeutic agent for the treatment of autoimmune diseases.

Csf1R inhibition attenuates experimental autoimmune encephalomyelitis and promotes recovery

Multiple sclerosis (MS) is a chronic autoimmune disease of the central nervous system (CNS) characterized by progressive neuronal demyelination and degeneration. Much of this damage can be attributed to microglia, the resident innate immune cells of the CNS, as well as monocyte-derived macrophages, which breach the blood-brain barrier in this inflammatory state. Upon activation, both microglia and macrophages release a variety of factors that greatly contribute to disease progression, and thus therapeutic approaches in MS focus on diminishing their activity. We use the CSF1R inhibitor PLX5622, administered in mouse chow, to ablate microglia and macrophages during the course of experimental autoimmune encephalomyelitis (EAE), an animal model of MS. Here, we show that ablation of these cells significantly improves animal mobility and weight gain in EAE. Further, we show that this treatment addresses the pathological hallmarks of MS, as it reduces demyelination and immune activation. White matter lesion areas in microglia/macrophage-depleted animals show substantial preservation of mature, myelinating oligodendrocytes in comparison to control animals. Taken together, these findings suggest that ablation of microglia/macrophages during the symptomatic phase of EAE reduces CNS inflammation and may also promote a more permissive environment for remyelination and recovery. This microglia and macrophage-targeted therapy could be a promising avenue for treatment of MS.

Functional morphology of the blood-brain barrier in health and disease

The adult quiescent blood-brain barrier (BBB), a structure organised by endothelial cells through interactions with pericytes, astrocytes, neurons and microglia in the neurovascular unit, is highly regulated but fragile at the same time. In the past decade, there has been considerable progress in understanding not only the molecular pathways involved in BBB development, but also BBB breakdown in neurological diseases. Specifically, the Wnt/β-catenin, retinoic acid and sonic hedgehog pathways moved into the focus of BBB research. Moreover, angiopoietin/Tie2 signalling that is linked to angiogenic processes has gained attention in the BBB field. Blood vessels play an essential role in initiation and progression of many diseases, including inflammation outside the central nervous system (CNS). Therefore, the potential influence of CNS blood vessels in neurological diseases associated with BBB alterations or neuroinflammation has become a major focus of current research to understand their contribution to pathogenesis. Moreover, the BBB remains a major obstacle to pharmaceutical intervention in the CNS. The complications may either be expressed by inadequate therapeutic delivery like in brain tumours, or by poor delivery of the drug across the BBB and ineffective bioavailability. In this review, we initially describe the cellular and molecular components that contribute to the steady state of the healthy BBB. We then discuss BBB alterations in ischaemic stroke, primary and metastatic brain tumour, chronic inflammation and Alzheimer's disease. Throughout the review, we highlight common mechanisms of BBB abnormalities among these diseases, in particular the contribution of neuroinflammation to BBB dysfunction and disease progression, and emphasise unique aspects of BBB alteration in certain diseases such as brain tumours. Moreover, this review highlights novel strategies to monitor BBB function by non-invasive imaging techniques focussing on ischaemic stroke, as well as novel ways to modulate BBB permeability and function to promote treatment of brain tumours, inflammation and Alzheimer's disease. In conclusion, a deep understanding of signals that maintain the healthy BBB and promote fluctuations in BBB permeability in disease states will be key to elucidate disease mechanisms and to identify potential targets for diagnostics and therapeutic modulation of the BBB.

A new focal model resembling features of cortical pathology of the progressive forms of multiple sclerosis: Influence of innate immunity

Multiple sclerosis (MS) is an inflammatory and demyelinating disease of unknown aetiology that causes neurological disabilities in young adults. MS displays different clinical patterns, including recurrent episodes with remission periods ("relapsing-remitting MS" (RRMS)), which can progress over several years to a secondary progressive form (SPMS). However, 10% of patients display persistent progression at the onset of disease ("primary progressive MS" (PPMS)). Currently, no specific therapeutic agents are available for the progressive forms, mainly because the underlying pathogenic mechanisms are not clear and because no animal models have been specifically developed for these forms. The development of MS animal models is required to clarify the pathological mechanisms and to test novel therapeutic agents. In the present work, we overexpressed interleukin 1 beta (IL-1β) in the cortex to develop an animal model reflecting the main pathological hallmarks of MS. The treated animals presented with neuroinflammation, demyelination, glial activation, and neurodegeneration along with cognitive symptoms and MRI images consistent with MS pathology. We also demonstrated the presence of meningeal inflammation close to cortical lesions, with characteristics similar to those described in MS patients. Systemic pro-inflammatory stimulation caused a flare-up of the cortical lesions and behavioural symptoms, including impairment of working memory and the appearance of anxiety-like symptoms. Our work demonstrated induced cortical lesions, reflecting the main histopathological hallmarks and cognitive impairments characterizing the cortical pathology described in MS patients with progressive forms of the disease.