Modulation of microglial/macrophage activation by macrophage inhibitory factor (TKP) or tuftsin (TKPR) attenuates the disease course of experimental autoimmune encephalomyelitis. BMC Immunol. 2007;8:10. [PMID: 17634104 PMCID: PMC1937009 DOI: 10.1186/1471-2172-8-10]

Transcriptional network analysis of peripheral blood leukocyte subsets in multiple sclerosis identifies a pathogenic role for a cytotoxicity-associated gene network in myeloid cells

Multiple sclerosis (MS) is an autoimmune disease of the central nervous system affecting predominantly adults. It is a complex disease associated with both environmental and genetic risk factors. Although over 230 risk single-nucleotide polymorphisms have been associated with MS, all are common human variants. The mechanisms by which they increase the risk of MS, however, remain elusive. We hypothesized that a complex genetic phenotype such as MS could be driven by coordinated expression of genes controlled by transcriptional regulatory networks. We, therefore, constructed a gene coexpression network from microarray expression analyses of five purified peripheral blood leukocyte subsets of 76 patients with relapsing remitting MS and 104 healthy controls. These analyses identified a major network (or module) of expressed genes associated with MS that play key roles in cell-mediated cytotoxicity which was downregulated in monocytes of patients with MS. Manipulation of the module gene expression was achieved in vitro through small interfering RNA gene knockdown of identified drivers. In a mouse model, network gene knockdown modulated the autoimmune inflammatory MS model disease-experimental autoimmune encephalomyelitis. This research implicates a cytotoxicity-associated gene network in myeloid cells in the pathogenesis of MS.

L-Proline Prevents Endoplasmic Reticulum Stress in Microglial Cells Exposed to L-azetidine-2-carboxylic Acid

L-Azetidine-2-carboxylic acid (AZE) is a non-protein amino acid that shares structural similarities with its proteogenic L-proline amino acid counterpart. For this reason, AZE can be misincorporated in place of L-proline, contributing to AZE toxicity. In previous work, we have shown that AZE induces both polarization and apoptosis in BV2 microglial cells. However, it is still unknown if these detrimental effects involve endoplasmic reticulum (ER) stress and whether L-proline co-administration prevents AZE-induced damage to microglia. Here, we investigated the gene expression of ER stress markers in BV2 microglial cells treated with AZE alone (1000 µM), or co-treated with L-proline (50 µM), for 6 or 24 h. AZE reduced cell viability, nitric oxide (NO) secretion and caused a robust activation of the unfolded protein response (UPR) genes (ATF4, ATF6, ERN1, PERK, XBP1, DDIT3, GADD34). These results were confirmed by immunofluorescence in BV2 and primary microglial cultures. AZE also altered the expression of microglial M1 phenotypic markers (increased IL-6, decreased CD206 and TREM2 expression). These effects were almost completely prevented upon L-proline co-administration. Finally, triple/quadrupole mass spectrometry demonstrated a robust increase in AZE-bound proteins after AZE treatment, which was reduced by 84% upon L-proline co-supplementation. This study identified ER stress as a pathogenic mechanism for AZE-induced microglial activation and death, which is reversed by co-administration of L-proline.

Neuroprotective effect of Vesatolimod in an experimental autoimmune encephalomyelitis mice model

BACKGROUND

Multiple sclerosis is a chronic demyelinating autoimmune disease accompanied by inflammation and loss of axons and neurons. Toll-like receptors play crucial roles in the innate immune system and inflammation. However, few studies have explored the specific effects of toll-like receptor 7 signaling pathway in multiple sclerosis. To explore underlying effects to develop a new therapeutic target, we use Vesatolimod, a safe and well-tolerated agonist of toll-like receptor 7, to assess the possible effects in Experimental autoimmune encephalomyelitis (EAE) animal model.

METHODS

EAE animal model was induced by injection of MOG35-55 and monitored daily for clinical symptoms, and the treatment group was given Vesatolimod at the onset of illness. The therapeutic effects of Vesatolimod on EAE inflammation, demyelination, CD107b cells and T cells infiltration, and microglia activation was evaluated. Autophagy within the spinal cords of EAE mice was also preliminarily assessed.

RESULTS

Treatment with Vesatolimod significantly alleviated clinical symptoms of EAE from day 18 post-immunization and decreased the expression levels of inflammatory cytokines, particularly Eotaxin and IL-12 (P40), in peripheral blood. It also inhibited demyelination in spinal cords. Moreover, VES treatment reduced activation of microglia, infiltration of CD3 + T cells and CD107b + cells, as well as inhibited the autophagy-related proteins expression in the spinal cords of EAE mice.

CONCLUSION

Our results indicate that Vesatolimod exhibits protective effects on EAE mice and is promising for treatment of MS.

Tissue-resident immune cells in the pathogenesis of multiple sclerosis

BACKGROUND

Multiple sclerosis (MS) is a chronic inflammatory autoimmune disease of the central nervous system (CNS) in which genetic and environmental factors contribute to disease progression. Both innate and adaptive immune cells, including T cells, B cells, activated macrophages and microglia, have been identified to be involved in the pathogenesis of MS, leading to the CNS inflammation, neurodegeneration and demyelination. In recent years, there has been considerable progress in understanding the contribution of tissue-resident immune cells in the pathogenesis of MS.

METHODS

We performed a keyword-based search in PubMed database. We combined "multiple sclerosis" with keywords, such as tissue-resident memory T cells, microglia to search for relevant literatures in PubMed.

RESULTS AND CONCLUSION

In this review, we comprehensively describe the characteristics of tissue-resident memory T cells and microglia, summarize their role in the pathogenesis of MS, and discuss their interaction with other immune cells in the CNS.

Implications of microglial heterogeneity in spinal cord injury progression and therapy

Microglia are widely distributed in the central nervous system (CNS), where they aid in the maintenance of neuronal function and perform key auxiliary roles in phagocytosis, neural repair, immunological control, and nutrition delivery. Microglia in the undamaged spinal cord is in a stable state and serve as immune monitors. In the event of spinal cord injury (SCI), severe changes in the microenvironment and glial scar formation lead to axonal regeneration failure. Microglia participates in a series of pathophysiological processes and behave both positive and negative consequences during this period. A deep understanding of the characteristics and functions of microglia can better identify therapeutic targets for SCI. Technological innovations such as single-cell RNA sequencing (Sc-RNAseq) have led to new advances in the study of microglia heterogeneity throughout the lifespan. Here,We review the updated studies searching for heterogeneity of microglia from the developmental and pathological state, survey the activity and function of microglia in SCI and explore the recent therapeutic strategies targeting microglia in the CNS injury.

Exploring the Pro-Phagocytic and Anti-Inflammatory Functions of PACAP and VIP in Microglia: Implications for Multiple Sclerosis

Multiple sclerosis (MS) is a chronic neuroinflammatory and demyelinating disease of the central nervous system (CNS), characterised by the infiltration of peripheral immune cells, multifocal white-matter lesions, and neurodegeneration. In recent years, microglia have emerged as key contributors to MS pathology, acting as scavengers of toxic myelin/cell debris and modulating the inflammatory microenvironment to promote myelin repair. In this review, we explore the role of two neuropeptides, pituitary adenylate cyclase-activating polypeptide (PACAP) and vasoactive intestinal peptide (VIP), as important regulators of microglial functioning during demyelination, myelin phagocytosis, and remyelination, emphasising the potential of these neuropeptides as therapeutic targets for the treatment of MS.

Tuftsin ameliorates splenic inflammatory injury by promoting neuropilin-1 in severe acute pancreatitis

Severe acute pancreatitis (SAP)-associated spleen injury causing immune disturbances aggravates organs injuries, which contributes to higher mortality rate. However, there are no effective drugs to cure SAP-induced spleen injury. Here, we found that Tuftsin (TN) is effective for ameliorating SAP-induced pathological damage and inflammation of spleen, mainly via alleviating mitochondrial dysfunction, oxidative stress, ATP depletion and the expression of pro-inflammatory factors. We further found that TN promoted anti-inflammatory macrophage phenotype M2 via up-regulating NRP1 on macrophage in spleen during SAP. Meanwhile, EG00229 (an inhibitor of NRP1 bound to TN) weakened TN's therapeutic effect in SAP-associated spleen injury. And EG00229 also inhibited M2 macrophage, leading to increasing inflammasome formation. Additionally, EG00229 reduced the protective efficiency of TN on mitochondrial dysfunction, and inflammation injury via NRP1 in spleen caused by SAP. Similarly, siRNA-Nrp1 into macrophage also prevented TN's inhibition on apoptosis. These findings reveal that TN alleviates SAP-induced spleen injury by promoting NRP1.

Inhibition of Anti-Inflammatory Macrophage Phenotype Reduces Tumour Growth in Mouse Models of Brain Metastasis

Breast cancer brain metastasis is a significant clinical problem and carries a poor prognosis. Although it is well-established that macrophages are a primary component of the brain metastasis microenvironment, the role of blood-derived macrophages (BDM) and brain-resident microglia in the progression of brain metastases remains uncertain. The aim of this study, therefore, was to determine the role, specifically, of pro- and anti-inflammatory BDM and microglial phenotypes on metastasis progression. Initial in vitro studies demonstrated decreased migration of EO771 metastatic breast cancer cells in the presence of pro-inflammatory, but not anti-inflammatory, stimulated RAW 264.7 macrophages. In vivo, suppression of the anti-inflammatory BDM phenotype, specifically, via myeloid knock out of Krüppel-like Factor 4 (KLF4) significantly reduced EO771 tumour growth in the brains of C57BL/6 mice. Further, pharmacological inhibition of the anti-inflammatory BDM and/or microglial phenotypes, via either Colony Stimulating Factor 1 Receptor (CSF-1R) or STAT6 pathways, significantly decreased tumour burden in two different syngeneic mouse models of breast cancer brain metastasis. These findings suggest that switching BDM and microglia towards a more pro-inflammatory phenotype may be an effective therapeutic strategy in brain metastasis.

Polaryzacja mikrogleju i makrofagów w wybranych chorobach degeneracyjnych i zapalnych układu nerwowego

Makrofagi to komórki efektorowe układu odpornościowego zdolne do polaryzacji, czyli zmiany fenotypu powiązanej ze zmianą aktywności. Można wyróżnić: polaryzację klasyczną (M1), która służy obronie przed patogenami, a makrofagi M1 mają aktywność ogólnie prozapalną, oraz polaryzację alternatywną (M2), która sprzyja wygaszaniu stanu zapalnego i regeneracji tkanki. Makrofagi zasiedlają niemal cały organizm, więc zjawisko ich polaryzacji ma wpływ na wiele procesów zachodzących w różnych tkankach. W układzie nerwowym reprezentacją osiadłych makrofagów jest mikroglej. Jednak w wielu sytuacjach patologicznych w mózgu pojawiają się także makrofagi rekrutowane z monocytów krążących we krwi. Choroby neurodegeneracyjne, urazy i choroby autoimmunologiczne są związane z reakcją układu odpornościowego, która może mieć istotny wpływ na dalszy przebieg choroby i na tempo regeneracji tkanki. Polaryzacja makrofagów ma w związku z tym znaczenie w chorobach centralnego układu nerwowego. Aktywność komórek M1 i M2 może bowiem różnie wpływać na przeżywalność neuronów i oligodendrocytów, na wzrost aksonów, na proces demielinizacji czy na szczelność bariery krew–mózg. Wynika to z różnic między fenotypami w wytwarzaniu reaktywnych form tlenu i tlenku azotu, wydzielaniu cytokin i czynników wzrostu, bezpośrednich oddziaływaniach na sąsiednie komórki i zdolnościach do fagocytozy. W artykule omówiono to zagadnienie w: udarze mózgu, urazie rdzenia kręgowego, chorobie Alzheimera, stwardnieniu zanikowym bocznym i stwardnieniu rozsianym. W wielu spośród tych patologii obserwuje się gradient czasowy lub przestrzenny rozmieszczenia w tkance poszczególnych fenotypów mikrogleju i/lub makrofagów. Wydaje się zatem, że zmiany polaryzacji makrofagów mogą potencjalnie sprzyjać regeneracji tkanki lub hamować rozwój chorób neurodegeneracyjnych.

Crotalphine Attenuates Pain and Neuroinflammation Induced by Experimental Autoimmune Encephalomyelitis in Mice

Multiple sclerosis (MS) is a demyelinating disease of inflammatory and autoimmune origin, which induces sensory and progressive motor impairments, including pain. Cells of the immune system actively participate in the pathogenesis and progression of MS by inducing neuroinflammation, tissue damage, and demyelination. Crotalphine (CRO), a structural analogue to a peptide firstly identified in Crotalus durissus terrificus snake venom, induces analgesia by endogenous opioid release and type 2 cannabinoid receptor (CB2) activation. Since CB2 activation downregulates neuroinflammation and ameliorates symptoms in mice models of MS, it was presently investigated whether CRO has a beneficial effect in the experimental autoimmune encephalomyelitis (EAE). CRO was administered on the 5th day after immunization, in a single dose, or five doses starting at the peak of disease. CRO partially reverted EAE-induced mechanical hyperalgesia and decreased the severity of the clinical signs. In addition, CRO decreases the inflammatory infiltrate and glial cells activation followed by TNF-α and IL-17 downregulation in the spinal cord. Peripherally, CRO recovers the EAE-induced impairment in myelin thickness in the sciatic nerve. Therefore, CRO interferes with central and peripheral neuroinflammation, opening perspectives to MS control.

Microglia in Neuroinflammation and Neurodegeneration: From Understanding to Therapy

Microglia are the resident macrophages of the central nervous system (CNS) acting as the first line of defense in the brain by phagocytosing harmful pathogens and cellular debris. Microglia emerge from early erythromyeloid progenitors of the yolk sac and enter the developing brain before the establishment of a fully mature blood-brain barrier. In physiological conditions, during brain development, microglia contribute to CNS homeostasis by supporting cell proliferation of neural precursors. In post-natal life, such cells contribute to preserving the integrity of neuronal circuits by sculpting synapses. After a CNS injury, microglia change their morphology and down-regulate those genes supporting homeostatic functions. However, it is still unclear whether such changes are accompanied by molecular and functional modifications that might contribute to the pathological process. While comprehensive transcriptome analyses at the single-cell level have identified specific gene perturbations occurring in the "pathological" microglia, still the precise protective/detrimental role of microglia in neurological disorders is far from being fully elucidated. In this review, the results so far obtained regarding the role of microglia in neurodegenerative disorders will be discussed. There is solid and sound evidence suggesting that regulating microglia functions during disease pathology might represent a strategy to develop future therapies aimed at counteracting brain degeneration in multiple sclerosis, Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis.

The Role of Distinct Subsets of Macrophages in the Pathogenesis of MS and the Impact of Different Therapeutic Agents on These Populations

Multiple sclerosis (MS) is a demyelinating inflammatory disorder of the central nervous system (CNS). Besides the vital role of T cells, other immune cells, including B cells, innate immune cells, and macrophages (MФs), also play a critical role in MS pathogenesis. Tissue-resident MФs in the brain’s parenchyma, known as microglia and monocyte-derived MФs, enter into the CNS following alterations in CNS homeostasis that induce inflammatory responses in MS. Although the neuroprotective and anti-inflammatory actions of monocyte-derived MФs and resident MФs are required to maintain CNS tolerance, they can release inflammatory cytokines and reactivate primed T cells during neuroinflammation. In the CNS of MS patients, elevated myeloid cells and activated MФs have been found and associated with demyelination and axonal loss. Thus, according to the role of MФs in neuroinflammation, they have attracted attention as a therapeutic target. Also, due to their different origin, location, and turnover, other strategies may require to target the various myeloid cell populations. Here we review the role of distinct subsets of MФs in the pathogenesis of MS and different therapeutic agents that target these cells.

Qki is an essential regulator of microglial phagocytosis in demyelination

The mechanism underpinning the regulation of microglial phagocytosis in demyelinating diseases is unclear. Here, we showed that the Quaking protein (Qki) in microglia was greatly induced by demyelination in the brains of both mice and humans. Deletion of the Quaking gene (Qk) in microglia severely impaired the clearance of myelin debris. Transcriptomic profiling indicated that depletion of Qki impaired total RNA levels and splicing of the genes involved in phagosome formation and maturation. RNA immunoprecipitation (RIP) confirmed the physical interactions between the Qki protein and the mRNAs of Qki targets that are involved in phagocytosis, indicating that Qki regulates their RNA stability. Both Qki depletion and inhibition of Qki target Cd36 greatly reduced the phagocytic activity of microglia and macrophages. The defective uptake and degradation of myelin debris caused by Qki depletion in microglia resulted in unresolved myelin debris that impaired axon integrity, oligodendrocyte maturation, and subsequent remyelination. Thus, our results demonstrate that Qki is an essential regulator of microglia’s phagocytic activity under demyelinating conditions.

Astroglial and Microglial Purinergic P2X7 Receptor as a Major Contributor to Neuroinflammation during the Course of Multiple Sclerosis

Multiple sclerosis (MS) is an autoimmune inflammatory disease of the central nervous system that leads to the progressive disability of patients. A characteristic feature of the disease is the presence of focal demyelinating lesions accompanied by an inflammatory reaction. Interactions between autoreactive immune cells and glia cells are considered as a central mechanism underlying the pathology of MS. A glia-mediated inflammatory reaction followed by overproduction of free radicals and generation of glutamate-induced excitotoxicity promotes oligodendrocyte injury, contributing to demyelination and subsequent neurodegeneration. Activation of purinergic signaling, in particular P2X7 receptor-mediated signaling, in astrocytes and microglia is an important causative factor in these pathological processes. This review discusses the role of astroglial and microglial cells, and in particular glial P2X7 receptors, in inducing MS-related neuroinflammatory events, highlighting the importance of P2X7R-mediated molecular pathways in MS pathology and identifying these receptors as a potential therapeutic target.

An Antibody-like Polymeric Nanoparticle Removes Intratumoral Galectin-1 to Enhance Antitumor T-Cell Responses in Cancer Immunotherapy

Antibodies have shown potential to deplete immunosuppressive factors in tumor tissues. However, intrinsic drawbacks, including time-consuming processes in preparation, high cost, and short half-life time, greatly restrict their applications. In this work, we report an antibody-like polymeric nanoparticle (APN) that is capable of specifically capturing and removing galectin-1 in tumor tissues, thereby enhancing the antitumor T-cell responses. The APN is composed of an albumin-polymer hybrid nanoparticle (core) and an acid-responsive PEG shell. The core of the APN contains multiple recognition units and Tuftsin peptides to capture target factors and activate macrophage-mediated phagocytosis, respectively. By employing galactose as recognition units, the APN facilitated the phagocytosis of galectin-1 in tumor tissues, thereby improving the antitumor responses of tumor-infiltrating T cells. Since the recognition units in the APN can be further replaced to capture and remove other peptides/proteins, the APN provides a feasible approach for the development of synthetic nanoformulations to regulate biological systems and treat diseases.

Identification of Low Molecular Weight Proteins and Peptides from Schistosoma mekongi Worm, Egg and Infected Mouse Sera

Schistosoma mekongi is found in the lower Mekong river region and causes schistosomiasis. Low sensitivity of diagnosis and development of drug resistance are problems to eliminate this disease. To develop novel therapies and diagnostics for S. mekongi, the basic molecular biology of this pathogen needs to be explored. Bioactive peptides have been reported in several worms and play important roles in biological functions. Limited information is available on the S. mekongi peptidome. Therefore, this study aimed to identify S. mekongi peptides using in silico transcriptome mining and mass spectrometry approaches. Schistosoma peptide components were identified in adult worms, eggs, and infected mouse sera. Thirteen neuropeptide families were identified using in silico predictions from in-house transcriptomic databases of adult S. mekongi worms. Using mass spectrometry approaches, 118 peptides (from 54 precursor proteins) and 194 peptides (from 86 precursor proteins) were identified from adult worms and eggs, respectively. Importantly, eight unique peptides of the S. mekongi ubiquitin thioesterase, trabid, were identified in infected mouse sera 14, 28, and 56 days after infection. This protein may be a potential target for diagnosis of schistosomiasis. The S. mekongi peptide profiles determined in this study could be used for further drug and diagnostic development.

High-Intensity Exercise Training Protects the Brain Against Autoimmune Neuroinflammation: Regulation of Microglial Redox and Pro-inflammatory Functions

Background: Exercise training induces beneficial effects on neurodegenerative diseases, and specifically on multiple sclerosis (MS) and it’s model experimental autoimmune encephalomyelitis (EAE). However, it is unclear whether exercise training exerts direct protective effects on the central nervous system (CNS), nor are the mechanisms of neuroprotection fully understood. In this study, we investigated the direct neuroprotective effects of high-intensity continuous training (HICT) against the development of autoimmune neuroinflammation and the role of resident microglia.

Methods: We used the transfer EAE model to examine the direct effects of training on the CNS. Healthy mice performed HICT by treadmill running, followed by injection of encephalitogenic proteolipid (PLP)-reactive T-cells to induce EAE. EAE severity was assessed clinically and pathologically. Brain microglia from sedentary (SED) and HICT healthy mice, as well as 5-days post EAE induction (before the onset of disease), were analyzed ex vivo for reactive oxygen species (ROS) and nitric oxide (NO) formation, mRNA expression of M1/M2 markers and neurotrophic factors, and secretion of cytokines and chemokines.

Results: Transfer of encephalitogenic T-cells into HICT mice resulted in milder EAE, compared to sedentary mice, as indicated by reduced clinical severity, attenuated T-cell, and neurotoxic macrophage/microglial infiltration, and reduced loss of myelin and axons. In healthy mice, HICT reduced the number of resident microglia without affecting their profile. Isolated microglia from HICT mice after transfer of encephalitogenic T-cells exhibited reduced ROS formation and released less IL-6 and monocyte chemoattractant protein (MCP) in response to PLP-stimulation.

Conclusions: These findings point to the critical role of training intensity in neuroprotection. HICT protects the CNS against autoimmune neuroinflammation by reducing microglial-derived ROS formation, neurotoxicity, and pro-inflammatory responses involved in the propagation of autoimmune neuroinflammation.

miRNAs in Microglia: Important Players in Multiple Sclerosis Pathology

Microglia are the resident immune cells of the central nervous system and important regulators of brain homeostasis. Central to this role is a dynamic phenotypic plasticity that enables microglia to respond to environmental and pathological stimuli. Importantly, different microglial phenotypes can be both beneficial and detrimental to central nervous system health. Chronically activated inflammatory microglia are a hallmark of neurodegeneration, including the autoimmune disease multiple sclerosis (MS). By contrast, microglial phagocytosis of myelin debris is essential for resolving inflammation and promoting remyelination. As such, microglia are being explored as a potential therapeutic target for MS. MicroRNAs (miRNAs) are short non-coding ribonucleic acids that regulate gene expression and act as master regulators of cellular phenotype and function. Dysregulation of certain miRNAs can aberrantly activate and promote specific polarisation states in microglia to modulate their activity in inflammation and neurodegeneration. In addition, miRNA dysregulation is implicated in MS pathogenesis, with circulating biomarkers and lesion specific miRNAs identified as regulators of inflammation and myelination. However, the role of miRNAs in microglia that specifically contribute to MS progression are still largely unknown. miRNAs are being explored as therapeutic agents, providing an opportunity to modulate microglial function in neurodegenerative diseases such as MS. This review will focus firstly on elucidating the complex role of microglia in MS pathogenesis. Secondly, we explore the essential roles of miRNAs in microglial function. Finally, we focus on miRNAs that are implicated in microglial processes that contribute directly to MS pathology, prioritising targets that could inform novel therapeutic approaches to MS.

Protective roles for myeloid cells in neuroinflammation

Myeloid cells represent the major cellular component of innate immune responses. Myeloid cells include monocytes and macrophages, granulocytes (neutrophils, basophils and eosinophils) and dendritic cells (DC). The role of myeloid cells has been broadly described both in physiological and in pathological conditions. All tissues or organs are equipped with resident myeloid cells, such as parenchymal microglia in the brain, which contribute to maintaining homeostasis. Moreover, in case of infection or tissue damage, other myeloid cells such as monocytes or granulocytes (especially neutrophils) can be recruited from the circulation, at first to promote inflammation and later to participate in repair and regeneration. This review aims to address the regulatory roles of myeloid cells in inflammatory diseases of the central nervous system (CNS), with a particular focus on recent work showing induction of suppressive function via stimulation of innate signalling in multiple sclerosis (MS) and its animal model experimental autoimmune encephalomyelitis (EAE).

Seasonal Variations in Macrophages/Microglia Underlie Changes in the Mouse Model of Multiple Sclerosis Severity

Both immune and neurodegenerative mechanisms underlie multiple sclerosis (MS) and its animal model, experimental autoimmune encephalomyelitis (EAE). MS/EAE are triggered by encephalitogenic immune cells, including Th1 and Th17 cells, whereas T regulatory (Treg) cells are involved in inflammation resolution. Pro-inflammatory macrophages/microglia also play a deleterious role in the disease. Seasonal variations in MS relapses, active lesions, and pro- and anti-inflammatory cytokine levels have been described in MS patients and have been related with both perinatal and adult exposure to sunlight and other environmental factors. However, some data in EAE mice suggest that these variations might be, at least partially, endogenously determined. Thus, our objective was to study the effect of the season of birth and disease induction on the course of EAE, and immune cell infiltration in the central nervous system (CNS) in myelin oligodendrocyte glycoprotein (MOG_35-55)-induced EAE in 8 weeks old, female C57BL/6N mice maintained under constant, controlled conditions. EAE severity as well as pathogenic (Th1, Th17, macrophages/microglia) and protective (Treg) subsets was found to vary according to the season of birth or of EAE induction. Summer-born or summer-immunized animals developed a milder disease, which coincided with variations in numbers of T effector/regulatory subsets, and significantly low numbers of macrophages/microglia. These results suggest that endogenous rhythms in immune responses might cause seasonal variations in EAE severity, and, maybe, in the course of MS, and that they might be related to macrophages/microglia.

Swimming Exercise Ameliorates Symptoms of MOG-Induced Experimental Autoimmune Encephalomyelitis by Inhibiting Inflammation and Demyelination in Rats

Purpose

Multiple sclerosis is an autoimmune disease that affects the central nerve system, resulting in cumulative loss of motor function. Multiple sclerosis is induced through multiple mechanisms and is caused by inflammation and demyelination. This study aims to evaluate the neuroprotective effect of swimming exercise in experimental autoimmune encephalomyelitis (EAE) rats, an animal model of multiple sclerosis.

Methods

EAE was induced by an intradermal injection of 50-μg purified myelin oligodendrocyte glycoprotein 33–55 (MOG_33-55) dissolved in 200-μL saline at the base of the tail. The rats in the swimming exercise group were made to swim for 30 minutes once pert a day for 26 consecutive days, starting 5 days after induction of EAE. To compare the effect of swimming exercise with interferon-β, a drug for multiple sclerosis, interferon-β was injected intraperitoneally into rats of the EAE-induced and interferon-β-treated group during the exercise period.

Results

Injection of MOG_33-55 caused weight loss, decreased clinical disability score, and increased level of pro-inflammatory cytokines and inflammatory mediators in the lumbar spinal cord. Loss of motor function and weakness increased demyelination score. Swimming exercise suppressed demyelination and expression of pro-inflammatory cytokines and inflammatory mediators. These changes promoted recovery of EAE symptoms such as body weight loss, motor dysfunction, and weakness. Swimming exercise caused the same level of improvement as interferon-β treatment.

Conclusions

The results of this experiment suggest the possibility of swimming exercise in urological diseases that are difficult to treat. Swimming exercises can be considered for relief of symptom in incurable multiple sclerosis.

Daphnetin Ameliorates Experimental Autoimmune Encephalomyelitis Through Regulating Heme Oxygenase-1

To assess the potential role of daphnetin, a clinically used anti-inflammatory agent, on the development of the inflammatory and neurodegenerative disease, we investigated its immune regulatory function in a murine model of experimental autoimmune encephalomyelitis (EAE). Significantly, lower levels of pro-inflammatory cytokines including interleukin (IL)-17, interferon-γ, Il6, Il12a, and Il23a were observed in brains of daphnetin-treated EAE mice, compared with those in control littermates. We also confirmed that daphnetin suppressed the production of IL-1β, IL-6, and tumor necrosis factor-α in lipopolysaccharide-stimulated mouse BV2 microglial cells. Mechanistically, heme oxygenase-1 (HO-1), a canonical anti-oxidant and anti-inflammatory factor, was found to be substantially induced by daphnetin treatment in BV2 cells. Also, a significantly higher level of HO-1, accompanied by a decreased level of malondialdehyde, was observed in daphnetin-treated EAE mice. More importantly, the deletion of HO-1 in BV2 microglia largely abrogated daphnetin-mediated inhibition of the inflammatory response. Together, our data demonstrate that daphnetin has an anti-inflammatory and neuroprotective role during the pathogenesis of EAE, which is partially at least, dependent on its regulation of HO-1.

Inflammasome-Mediated Inflammation in Neurodegenerative Diseases

Inflammasomes are protein platforms consisting of multiple proteins. The biological function includes the activation of caspase-1, leading to the maturation of IL-1β and IL-18. These pro-inflammatory cytokines promote fundamental inflammatory processes in numerous infectious diseases. The inflammasome-mediated inflammation has become increasingly important in central nervous system disorders. In neurodegenerative disorders, significant contributors to disease progression include neuroinflammation and inflammatory cascades initiated by the inflammasome protein complex. This review discusses the recent progress of research on inflammasome associated with neurodegenerative disorders.

Microglia pre-activation and neurodegeneration precipitate neuroinflammation without exacerbating tissue injury in experimental autoimmune encephalomyelitis

Human inflammatory or neurodegenerative diseases, such as progressive multiple sclerosis (MS), occur on a background of age-related microglia activation and iron accumulation as well as pre-existing neurodegeneration. Most experimental models for CNS diseases, however, are induced in rodents, which are naturally characterized by a homeostatic microglia phenotype, low cellular iron load and absence of neurodegeneration. Here, we show that naïve LEWzizi rats – Lewis rats with a zitter rat background – show a spontaneous phenotype partly mimicking the changes seen in human aging and particularly in the normal-appearing white and grey matter of patients with progressive MS. Using this model system, we further aimed to investigate (i) whether the acute monophasic MS model experimental autoimmune encephalomyelitis (EAE) transforms into chronic progressive disease and (ii) whether EAE-induced neuroinflammation and tissue damage aggravate on the LEWzizi background. We found that the pre-existing LEWzizi-specific pathology precipitated EAE-related neuroinflammation into forebrain areas, which are devoid of EAE lesions in normal Lewis rats. However, EAE-related tissue damage was neither modified by the LEWzizi-specific pathology nor did EAE-induced neuroinflammation modify the LEWzizi-related pathological process. Our data indicate that the interaction between pre-activated microglia and CD4⁺ autoreactive T cells during the induction and propagation of tissue damage in the CNS is limited.

Lipofuscin-dependent stimulation of microglial cells

PURPOSE

To examine the reaction of microglial cells (MG) when incubated with lipofuscin (LP) in vitro with emphasis on the immunological reaction of the MG toward LP and the suppression of this reaction by immunomodulatory agents. MG are involved in the pathogenesis of degenerative eye disorders such as age-related macular degeneration (AMD). LP is a heterogeneous waste material that accumulates in the retinal pigment epithelium (RPE) cells with advancing age. LP is known to have toxic effects on RPE cells and therefore an elevated LP-derived fundus autofluorescence is a risk factor for AMD development. MG in the subretinal space have been reported in eyes affected by AMD. Moreover, in senescent mice, subretinal MG were found, which display an autofluorescence that may be derived from LP uptake.

METHODS

In this study, we incubated MG (BV-2 cell line and primary cells from murine brain) in vitro with LP isolated from the human RPE. We observed phagocytosis, studied cell morphologies, and analyzed the cell culture supernatants. We also investigated the effect of the immunomodulatory agents hydrocortisone (HC), minocycline, and the tripeptide TKP.

RESULTS

The MG phagocytosed the LP quickly and completely. We detected highly elevated levels of pro-inflammatory cytokines (especially of IL-6, IL-23p19, TNF-α, KC, RANTES, and IL-1α) in the cell culture supernatants. Furthermore, levels of vascular endothelial growth factor (VEGF) were raised in BV-2 cells. Anti-inflammatory agents added to the cell cultures inhibited the inflammatory reaction, in particular hydrocortisone (HC). Minocycline and TKP had less impact on the cytokine release.

CONCLUSION

The interaction of MG and LP could play a role in the development of retinal degeneration by triggering an inflammatory reaction and angiogenesis.

Tuftsin Combines With Remyelinating Therapy and Improves Outcomes in Models of CNS Demyelinating Disease

Though promoting remyelination in multiple sclerosis (MS) has emerged as a promising therapeutic strategy, it does not address inflammatory signals that continue to induce neuronal damage and inhibit effectiveness of repair mechanisms. Our lab has previously characterized the immunomodulatory tetrapeptide, tuftsin, which induces an anti-inflammatory shift in microglia and macrophages. This targeted anti-inflammatory agent improves physical deficits in experimental autoimmune encephalomyelitis (EAE), an animal model of MS. Here, we sought to determine whether tuftsin is also effective in combination with benztropine, an FDA-approved drug that stimulates remyelination, in both EAE and in the cuprizone model of demyelination. We show that combining these two agents to promote anti-inflammatory and remyelinating mechanisms alleviates symptoms in EAE and lessens pathological hallmarks in both MS models. Importantly, tuftsin is required to transform the inflammatory CNS environment normally present in EAE/MS into one of an anti-inflammatory nature, and benztropine is required in the cuprizone model to improve remyelination. Our data further support tuftsin's beneficial immunomodulatory activity in the context of EAE, and show that when studying remyelination in the absence of an autoimmune insult, tuftsin still activated microglia toward an anti-inflammatory fate, but benztropine was necessary for significant repair of the damaged myelin. Overall, tuftsin effectively combined with benztropine to significantly improve MS-like pathologies in both models.

Early P2X7R-dependent activation of microglia during the asymptomatic phase of autoimmune encephalomyelitis

Microglia-mediated neuroinflammation accompanies many central nervous system (CNS) diseases, including multiple sclerosis (MS), and is strongly dependent on the purinergic P2X7 receptor. The nature of the inflammatory response in MS is studied for decades indicating, that proinflammatory microgliosis is involved in advanced stages of MS and is associated with active tissue damage and neurological dysfunctions. Evidence on the role of microgliosis in initial stages of the disease is scarce. Thus, in the present study, we investigated the time course of microglial activation in rat brain subjected to experimental autoimmune encephalomyelitis (EAE) which is the animal model of MS. We show that activation of microglia occurs in brains of immunized rats at a very early stage of EAE, well before the development of neurological symptoms of the disease. Enhanced immunoreactivity of microglia/macrophage-specific protein Iba-1, together with morphological features of microgliosis, was identified beginning at day 4 post immunization. Concomitantly, microglial expression of P2X7R was also examined. Moreover, our results reveal that administration of Brilliant Blue G, an antagonist of P2X7R, delays the onset of the disease and partially inhibits development of neurological symptoms in EAE rats. Blockage of P2X7R significantly reduces activation of microglia as confirmed by decreased Iba-1 immunoreactivity and suppresses neuroinflammation in EAE rat brains, as indicated by decreased protein levels of investigated proinflammatory cytokines: IL-1β, IL-6 and TNF-α. Our results indicate that microglia are involved in inducing neuroinflammation at a very early stage of MS/EAE via a P2X7R-dependent mechanism.

MicroRNA-150 targets PU.1 and regulates macrophage differentiation and function in experimental autoimmune encephalomyelitis

PU.1 is a transcription factor which is expressed in myeloid cells. Herein, we investigated the expression of PU.1 and its potentially targeting miRNAs in the central nervous system (CNS) of mice with experimental autoimmune encephalitis (EAE) and in cultured primary macrophages. PU.1 levels where highly induced in EAE spinal cords and in activated macrophages; this was associated with a significant reduction in miR-150-5p levels at chronic phase of disease and in activated cells. Luciferase assays confirmed the PU.1-miR-150-5p interaction. Overexpression of miR-150-5p in macrophages decreased the expression of proinflammatory cytokines and shifted the polarization of macrophages away from the M1-like phenotype.

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.

Adenosine A2A Receptor Signaling in the Immunopathogenesis of Experimental Autoimmune Encephalomyelitis

Our increasing appreciation of adenosine as an endogenous signaling molecule that terminates inflammation has generated excitement regarding the potential to target adenosine receptors (ARs) in the treatment of multiple sclerosis (MS), a disease of chronic neuroinflammation. Of the four G protein-coupled ARs, A2ARs are the principal mediator of adenosine’s anti-inflammatory effects and accordingly, there is a growing body of evidence surrounding the role of A2ARs in experimental autoimmune encephalomyelitis (EAE), the dominant animal model of MS. Such evidence points to a complex, often paradoxical role for A2ARs in the immunopathogenesis of EAE, where they have the ability to both exacerbate and alleviate disease severity. This review seeks to interpret these paradoxical findings and evaluate the therapeutic promise of A2ARs. In essence, the complexities of A2AR signaling arise from two properties. Firstly, A2AR signaling downregulates the inflammatory potential of TH lymphocytes whilst simultaneously facilitating the recruitment of these cells into the CNS. Secondly, A2AR expression by myeloid cells – infiltrating macrophages and CNS-resident microglia – has the capacity to promote both tissue injury and repair in chronic neuroinflammation. Consequently, the therapeutic potential of targeting A2ARs is greatly undermined by the risk of collateral tissue damage in the periphery and/or CNS.

Macrophage migration inhibitory factor (MIF) modulates trophic signaling through interaction with serine protease HTRA1

Macrophage migration inhibitory factor (MIF), a small conserved protein, is abundant in the immune- and central nervous system (CNS). MIF has several receptors and binding partners that can modulate its action on a cellular level. It is upregulated in neurodegenerative diseases and cancer although its function is far from clear. Here, we report the finding of a new binding partner to MIF, the serine protease HTRA1. This enzyme cleaves several growth factors, extracellular matrix molecules and is implicated in some of the same diseases as MIF. We show that the function of the binding between MIF and HTRA1 is to inhibit the proteolytic activity of HTRA1, modulating the availability of molecules that can change cell growth and differentiation. MIF is therefore the first endogenous inhibitor ever found for HTRA1. It was found that both molecules were present in astrocytes and that the functional binding has the ability to modulate astrocytic activities important in development and disease of the CNS.

Splitting the "Unsplittable": Dissecting Resident and Infiltrating Macrophages in Experimental Autoimmune Encephalomyelitis

Macrophages predominate the inflammatory landscape within multiple sclerosis (MS) lesions, not only regarding cellularity but also with respect to the diverse functions this cell fraction provides during disease progression and remission. Researchers have been well aware of the fact that the macrophage pool during central nervous system (CNS) autoimmunity consists of a mixture of myeloid cells. Yet, separating these populations to define their unique contribution to disease pathology has long been challenging due to their similar marker expression. Sophisticated lineage tracing approaches as well as comprehensive transcriptome analysis have elevated our insight into macrophage biology to a new level enabling scientists to dissect the roles of resident (microglia and non-parenchymal macrophages) and infiltrating macrophages with unprecedented precision. To do so in an accurate way, researchers have to know their toolbox, which has been filled with diverse, discriminating approaches from decades of studying neuroinflammation in animal models. Every method has its own strengths and weaknesses, which will be addressed in this review. The focus will be on tools to manipulate and/or identify different macrophage subgroups within the injured murine CNS.

Microglia activation induced by serum of SLE patients

To investigate the potential involvement of microglia in the neuropathology of systemic lupus erythematosus (SLE), we examined whether SLE patient sera could activate BV2 microglia in vitro. Exposure to SLE patient sera resulted in morphological changes in the microglia, an increase in MHC II and CD86 protein expression, and an obvious release of nitric oxide and proinflammatory cytokines. However, the SLE sera did not induce a specific change in the production of immunoregulatory cytokines. Inactivating complements or neutralizing proinflammatory cytokines in the SLE sera did not suppress microglial activation. Our results highlight the potential role of microglia in neuroinflammation in SLE patients.

Modulating inflammation and neuroprotection in multiple sclerosis

Multiple sclerosis (MS) is a neurological disorder of the central nervous system with a presentation and disease course that is largely unpredictable. MS can cause loss of balance, impaired vision or speech, weakness and paralysis, fatigue, depression, and cognitive impairment. Immunomodulation is a major target given the appearance of focal demyelinating lesions in myelin-rich white matter, yet progression and an increasing appreciation for gray matter involvement, even during the earliest phases of the disease, highlights the need to afford neuroprotection and limit neurodegenerative processes that correlate with disability. This review summarizes key aspects of MS pathophysiology and histopathology with a focus on neuroimmune interactions in MS, which may facilitate neurodegeneration through both direct and indirect mechanisms. There is a focus on processes thought to influence disease progression and the role of oxidative stress and mitochondrial dysfunction in MS. The goals and efficacy of current disease-modifying therapies and those in the pipeline are discussed, highlighting recent advances in our understanding of pathways mediating disease progression to identify and translate both immunomodulatory and neuroprotective therapeutics from the bench to the clinic.

3H-1,2-dithiole-3-thione as a novel therapeutic agent for the treatment of experimental autoimmune encephalomyelitis

3H-1,2-dithiole-3-thione (D3T), the simplest member of the sulfur-containing dithiolethiones, is found in cruciferous vegetables, and has been previously reported to be a potent inducer of antioxidant genes and glutathione biosynthesis by activation of the transcription factor Nrf2. D3T is a cancer chemopreventive agent and possesses anti-inflammatory properties. Although D3T has been shown to protect against neoplasia, the effect of D3T in the autoimmune inflammatory disease multiple sclerosis/experimental autoimmune encephalomyelitis (EAE) is unknown. The present study is the first report of the therapeutic effect of D3T in EAE. Our results show D3T, administered post immunization, not only delays disease onset but also dramatically reduces disease severity in EAE. Strikingly, D3T, administered post disease onset of EAE, effectively prevents disease progression and exacerbation. Mechanistic studies revealed that D3T suppresses dendritic cell activation and cytokine production, inhibits pathogenic Th1 and Th17 differentiation, represses microglia activation and inflammatory cytokine expression, and promotes microglia phase II enzyme induction. In summary, these results indicate that D3T affects both innate and adaptive immune cells, and the protective effect of D3T in EAE might be attributed to its effects on modulating dendritic cell and microglia activation and pathogenic Th1/Th17 cell differentiation.

Increase of neurofilament-H protein in sensory neurons in antiretroviral neuropathy: Evidence for a neuroprotective response mediated by the RNA-binding protein HuD

Nucleoside reverse transcriptase inhibitors (NRTIs) are key components of HIV/AIDS treatment to reduce viral load. However, antiretroviral toxic neuropathy has become a common peripheral neuropathy among HIV/AIDS patients leading to discontinuation of antiretroviral therapy, for which the underlying pathogenesis is uncertain. This study examines the role of neurofilament (NF) proteins in the spinal dorsal horn, DRG and sciatic nerve after NRTI neurotoxicity in mice treated with zalcitabine (2',3'-dideoxycitidine; ddC). ddC administration up-regulated NF-M and pNF-H proteins with no effect on NF-L. The increase of pNF-H levels was counteracted by the silencing of HuD, an RNA binding protein involved in neuronal development and differentiation. Sciatic nerve sections of ddC exposed mice showed an increased axonal caliber, concomitantly to a pNF-H up-regulation. Both events were prevented by HuD silencing. pNF-H and HuD colocalize in DRG and spinal dorsal horn axons. However, the capability of HuD to bind NF mRNA was not demonstrated, indicating the presence of an indirect mechanism of control of NF expression by HuD. RNA immunoprecipitation experiments showed the capability of HuD to bind the BDNF mRNA and the administration of an anti-BDNF antibody prevented pNF-H increase. These data indicate the presence of a HuD - BDNF - NF-H pathway activated as a regenerative response to the axonal damage induced by ddC treatment to counteract the antiretroviral neurotoxicity. Since analgesics clinically used to treat neuropathic pain are ineffective on antiretroviral neuropathy, a neuroregenerative strategy might represent a new therapeutic opportunity to counteract neurotoxicity and avoid discontinuation or abandon of NRTI therapy.

Compromised axon initial segment integrity in EAE is preceded by microglial reactivity and contact

Axonal pathology is a key contributor to long-term disability in multiple sclerosis (MS), an inflammatory demyelinating disease of the central nervous system (CNS), but the mechanisms that underlie axonal pathology in MS remain elusive. Evidence suggests that axonal pathology is a direct consequence of demyelination, as we and others have shown that the node of Ranvier disassembles following loss of myelin. In contrast to the node of Ranvier, we now show that the axon initial segment (AIS), the axonal domain responsible for action potential initiation, remains intact following cuprizone-induced cortical demyelination. Instead, we find that the AIS is disrupted in the neocortex of mice that develop experimental autoimmune encephalomyelitis (EAE) independent of local demyelination. EAE-induced mice demonstrate profound compromise of AIS integrity with a progressive disruption that corresponds to EAE clinical disease severity and duration, in addition to cortical microglial reactivity. Furthermore, treatment with the drug didox results in attenuation of AIS pathology concomitantly with microglial reversion to a less reactive state. Together, our findings suggest that inflammation, but not demyelination, disrupts AIS integrity and that therapeutic intervention may protect and reverse this pathology. GLIA 2016;64:1190-1209.

Double Roles of Macrophages in Human Neuroimmune Diseases and Their Animal Models

Macrophages are important immune cells of the innate immune system that are involved in organ-specific homeostasis and contribute to both pathology and resolution of diseases including infections, cancer, obesity, atherosclerosis, and autoimmune disorders. Multiple lines of evidence point to macrophages as a remarkably heterogeneous cell type. Different phenotypes of macrophages exert either proinflammatory or anti-inflammatory roles depending on the cytokines and other mediators that they are exposed to in the local microenvironment. Proinflammatory macrophages secrete detrimental molecules to induce disease development, while anti-inflammatory macrophages produce beneficial mediators to promote disease recovery. The conversion of the phenotypes of macrophages can regulate the initiation, development, and recovery of autoimmune diseases. Human neuroimmune diseases majorly include multiple sclerosis (MS), neuromyelitis optica (NMO), myasthenia gravis (MG), and Guillain-Barré syndrome (GBS) and macrophages contribute to the pathogenesis of these neuroimmune diseases. In this review, we summarize the double roles of macrophage in neuroimmune diseases and their animal models to further explore the mechanisms of macrophages involved in the pathogenesis of these disorders, which may provide a potential therapeutic approach for these disorders in the future.

Tuftsin-driven experimental autoimmune encephalomyelitis recovery requires neuropilin-1

Experimental autoimmune encephalomyelitis (EAE) is an animal model of demyelinating autoimmune disease, such as multiple sclerosis (MS), which is characterized by central nervous system white matter lesions, microglial activation, and peripheral T-cell infiltration secondary to blood-brain barrier disruption. We have previously shown that treatment with tuftsin, a tetrapeptide generated from IgG proteolysis, dramatically improves disease symptoms in EAE. Here, we report that microglial expression of Neuropilin-1 (Nrp1) is required for tuftsin-driven amelioration of EAE symptoms. Nrp1 ablation in microglia blocks microglial signaling and polarization to the anti-inflammatory M2 phenotype, and ablation in either the microglia or immunosuppressive regulatory T cells (Tregs) reduces extended functional contacts between them and Treg activation, implicating a role for microglia in the activation process, and more generally, how immune surveillance is conducted in the CNS. Taken together, our findings delineate the mechanistic action of tuftsin as a candidate therapeutic against immune-mediated demyelinating lesions.

Programmed Death Ligand-1 on Microglia Regulates Th1 Differentiation via Nitric Oxide in Experimental Autoimmune Encephalomyelitis

Microglia are considered to be potential antigen-presenting cells and have the ability to present antigen under pathological conditions. Nevertheless, whether and how microglia are involved in immune regulation are largely unknown. Here, we investigated the suppressive activity of microglia during experimental autoimmune encephalomyelitis (EAE) induced by myelin oligodendrocyte glycoprotein, with the goal of understanding their role in regulating the T cell reaction. Using flow cytometric analysis, we found that microglia were characterized by increased cell number and up-regulated programmed death ligand-1 (PD-L1) at the peak phase of EAE. Meanwhile, both the CD4(+) T cells and microglia that infiltrated the central nervous system expressed higher levels of PD1, the receptor for PD-L1, accompanied by a decline of Th1 cells. In an ex vivo co-culture system, microglia from EAE mice inhibited the proliferation of antigen-specific CD4(+) T cells and the differentiation of Th1 cells, and this was significantly inhibited by PD-L1 blockade. Further, microglia suppressed Th1 cells via nitric oxide (NO), the production of which was dependent on PD-L1. Thus, these data suggest a scenario in which microglia are involved in the regulation of EAE by suppressing Th1-cell differentiation via the PD-L1-NO pathway.

Promotion of Remyelination by Sulfasalazine in a Transgenic Zebrafish Model of Demyelination

Most of the axons in the vertebrate nervous system are surrounded by a lipid-rich membrane called myelin, which promotes rapid conduction of nerve impulses and protects the axon from being damaged. Multiple sclerosis (MS) is a chronic demyelinating disease of the CNS characterized by infiltration of immune cells and progressive damage to myelin and axons. One potential way to treat MS is to enhance the endogenous remyelination process, but at present there are no available treatments to promote remyelination in patients with demyelinating diseases. Sulfasalazine is an anti-inflammatory and immune-modulating drug that is used in rheumatology and inflammatory bowel disease. Its anti-inflammatory and immunomodulatory properties prompted us to test the ability of sulfasalazine to promote remyelination. In this study, we found that sulfasalazine promotes remyelination in the CNS of a transgenic zebrafish model of NTR/MTZ-induced demyelination. We also found that sulfasalazine treatment reduced the number of macrophages/microglia in the CNS of demyelinated zebrafish larvae, suggesting that the acceleration of remyelination is mediated by the immunomodulatory function of sulfasalazine. Our data suggest that temporal modulation of the immune response by sulfasalazine can be used to overcome MS by enhancing myelin repair and remyelination in the CNS.

Do not judge a cell by its cover--diversity of CNS resident, adjoining and infiltrating myeloid cells in inflammation

Specialized populations of tissue-resident myeloid cells inhabit every organ of the body. While many of these populations appear similar morphologically and phenotypically, they exhibit great functional diversity. The central nervous system (CNS), as an immune privileged organ, possesses a unique tissue-resident macrophage population, the microglia, as well as numerous myeloid cell subsets at its boarders and barriers in CNS-adjoining tissues, namely the meninges, the perivascular space, and the choroid plexus. Recent research has added much to our knowledge about microglia, whereas the populations of CNS-surrounding phagocytes are just starting to be appreciated. As guardians of CNS homeostasis, these myeloid cells perform immune surveillance and immune modulatory tasks in health and disease. As such, microglia and CNS-surrounding antigen-presenting cells have been shown to be crucially involved not only in the initiation and progression but also resolution of multiple sclerosis (MS). MS and its rodent model, experimental autoimmune encephalomyelitis, are autoimmune inflammatory demyelinating CNS pathologies. While some crucial aspects of the disease pathogenesis have been solved, much of the complex involvement and interplay of the innate immune compartment remains yet to be clarified. Here, we will discuss the current understanding of the scope of phenotypes and functions of myeloid cells involved in CNS neuroinflammation.

Differential roles of resident microglia and infiltrating monocytes in murine CNS autoimmunity

Macrophages can be of dual origin. Most tissue-resident macrophage compartments are generated before birth and subsequently maintain themselves independently from each other locally in healthy tissue. Under inflammatory conditions, these cells can however be complemented by macrophages derived from acute monocyte infiltrates. Due to the lack of suitable experimental systems, differential functional contributions of central nervous system (CNS)-resident microglia and monocyte-derived macrophages (MoMF) to CNS inflammation, such as experimental autoimmune encephalomyelitis (EAE), the mouse model of multiple sclerosis (MS), remain poorly understood. Here, we will review recent progress in this field that suggest distinct roles of microglia and MoMF in disease induction and progression, capitalizing on novel transgenic mouse models. The latter finding could have major implications for the rationale development of therapeutic approaches to the management of brain inflammation and MS therapy.

Early treatment of minocycline alleviates white matter and cognitive impairments after chronic cerebral hypoperfusion

Subcortical ischemic vascular dementia (SIVD) caused by chronic cerebral hypoperfusion develops with progressive white matter and cognitive impairments, yet no effective therapy is available. We investigated the temporal effects of minocycline on an experimental SIVD exerted by right unilateral common carotid arteries occlusion (rUCCAO). Minocycline treated at the early stage (day 0–3), but not the late stage after rUCCAO (day 4–32) alleviated the white matter and cognitive impairments, and promoted remyelination. The actions of minocycline may not involve the inhibition of microglia activation, based on the effects after the application of a microglial activation inhibitor, macrophage migration inhibitory factor, and co-treatment with lipopolysaccharides. Furthermore, minocycline treatment at the early stage promoted the proliferation of oligodendrocyte progenitor cells (OPCs) in subventricular zone, increased OPC number and alleviated apoptosis of mature oligodendrocytes in white matter. In vitro, minocycline promoted OPC proliferation and increased the percentage of OPCs in S and G2/M phases. We provided direct evidence that early treatment is critical for minocycline to alleviate white matter and cognitive impairments after chronic cerebral hypoperfusion, which may be due to its robust effects on OPC proliferation and mature oligodendrocyte loss. So, early therapeutic time window may be crucial for its application in SIVD.

Nicotine modulates neurogenesis in the central canal during experimental autoimmune encephalomyelitis

Nicotine has been shown to attenuate experimental autoimmune encephalomyelitis (EAE) through inhibiting inflammation in microglial populations during the disease course. In this study, we investigated whether nicotine modified the regenerative process in EAE by examining nestin-expressing neural stem cells (NSCs) in the spinal cord, which is the primary area of demyelination and inflammation in EAE. Our results show that the endogenous neurogenic responses in the spinal cord after EAE are limited and delayed: while nestin expression is increased, the proliferation of ependymal cells is inhibited compared to healthy animals. Nicotine application significantly reduced nestin expression and partially allowed for the proliferation of ependymal cells. We found that reduction of ependymal cell proliferation correlated with inflammation in the same area, which was relieved by the administration of nicotine. Further, increased numbers of oligodendrocytes (OLs) were observed after nicotine treatment. These findings give a new insight into the mechanism of how nicotine functions to attenuate EAE.

Modified laparoscopic splenectomy and azygoportal disconnection combined with cell salvage is feasible and might reduce the need for blood transfusion

AIM: To investigate perioperative outcomes in patients undergoing modified laparoscopic splenectomy and azygoportal disconnection (MLSD) with intraoperative autologous cell salvage.

METHODS: We retrospectively evaluated outcomes in 79 patients admitted to the Clinical Medical College of Yangzhou University with cirrhosis, portal hypertensive bleeding and secondary hypersplenism who underwent MLSD without (n = 46) or with intraoperative cell salvage and autologous blood transfusion, including splenic blood and operative hemorrhage (n = 33), between February 2012 and January 2014. Their intraoperative and postoperative variables were compared. These variables mainly included: operation time; estimated intraoperative blood loss; volume of allogeneic blood transfused; visual analog scale for pain on the first postoperative day; time to first oral intake; initial passage of flatus and off-bed activity; perioperative hemoglobin (Hb) concentration; and red blood cell concentration.

RESULTS: There were no significant differences between the groups in terms of duration of surgery, estimated intraoperative blood loss and overall perioperative complication rate. In those receiving salvaged autologous blood, Hb concentration increased by an average of 11.2 ± 4.8 g/L (P < 0.05) from preoperative levels by the first postoperative day, but it had fallen by 9.8 ± 6.45 g/L (P < 0.05) in the group in which cell salvage was not used. Preoperative Hb was similar in the two groups (P > 0.05), but Hb on the first postoperative day was significantly higher in the autologous blood transfusion group (118.5 ± 15.8 g/L vs 102.7 ± 15.6 g/L, P < 0.05). The autologous blood transfusion group experienced significantly fewer postoperative days of temperature > 38.0 °C (P < 0.05).

CONCLUSION: Intraoperative cell salvage during MLSD is feasible and safe and may become the gold standard for liver cirrhosis with portal hypertensive bleeding and hypersplenism.