18β-glycyrrhetinic acid suppresses experimental autoimmune encephalomyelitis through inhibition of microglia activation and promotion of remyelination

Natural compounds as potential therapeutic candidates for multiple sclerosis: Emerging preclinical evidence

BACKGROUND

Multiple sclerosis is a chronic neurodegenerative disease, with main characteristics of pathological inflammation, neural damage and axonal demyelination. Current mainstream treatments demonstrate more or less side effects, which limit their extensive use.

PURPOSE

Increasing studies indicate that natural compounds benefit multiple sclerosis without remarkable side effects. Given the needs to explore the potential effects of natural compounds of plant origin on multiple sclerosis and their mechanisms, we review publications involving the role of natural compounds in animal models of multiple sclerosis, excluding controlled trials.

STUDY DESIGN AND METHODS

Articles were conducted on PubMed and Web of Science databases using the keywords ``multiple sclerosis'' and ``natural compounds'' published from January 1, 2008, to September 1, 2023.

RESULTS

This review summarized the effects of natural ingredients (flavonoids, terpenoids, polyphenols, alkaloids, glycosides, and others) from three aspects: immune regulation, oxidative stress suppression, and myelin protection and regeneration in multiple sclerosis.

CONCLUSION

Overall, we concluded 80 studies to show the preclinical evidence that natural compounds may attenuate multiple sclerosis progression via suppressing immune attacks and/or promoting myelin protection or endogenous repair processes. It would pave the roads for the future development of effective therapeutic regiments of multiple sclerosis.

Neuroprotective Effects of Sinomenine on Experimental Autoimmune Encephalomyelitis via Anti-Inflammatory and Nrf2-Dependent Anti-Oxidative Stress Activity

Multiple sclerosis (MS) is an autoimmune inflammatory disease of the central nervous system (CNS). Sinomenine (SIN), a bioactive alkaloid extracted from the Chinese medicinal plant Sinomenium acutum, has powerful anti-inflammatory and immunosuppressive therapeutic benefits. In our previous research, we found that SIN increased resistance to oxidative stress via the nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway in PC12 neuronal cells. However, whether SIN can improve the symptoms and pathological features of experimental autoimmune encephalomyelitis (EAE), a murine model of MS, via the Nrf2 signaling pathway remains unclear. EAE was immunized followed by SIN treatment. Then we evaluated the effects of SIN in EAE. Subsequently, primary microglia were cultured to explore the effect of SIN on microglia activation. Further, the levels of Nrf2 and its downstream molecules were detected to assess the molecular mechanisms of SIN. We demonstrated that SIN effectively ameliorated the severity of EAE, accompanied by a reduction in the demyelination, axonal damage and inhibition of inflammatory cell infiltration. Mechanistically, SIN decreased the inflammatory cytokines expression, and suppressed microglia and astrocytes activation in EAE mice. Furthermore, SIN suppressed lipopolysaccharide (LPS)-induced microglial activation and the production of pro-inflammatory factors in vitro. Moreover, SIN inhibited oxidative stress via the activation of the Nrf2 signaling pathway. Our work proves that SIN exerts its neuroprotective effects by the Nrf2-dependent anti-oxidative stress and diminishing neuroinflammation, suggesting that the "antioxiflammation" effect of SIN is expected to be an ideal treatment strategy for MS/EAE.

Signaling pathways in macrophages: molecular mechanisms and therapeutic targets

Macrophages play diverse roles in development, homeostasis, and immunity. Accordingly, the dysfunction of macrophages is involved in the occurrence and progression of various diseases, such as coronavirus disease 2019 and atherosclerosis. The protective or pathogenic effect that macrophages exert in different conditions largely depends on their functional plasticity, which is regulated via signal transduction such as Janus kinase-signal transducer and activator of transcription, Wnt and Notch pathways, stimulated by environmental cues. Over the past few decades, the molecular mechanisms of signaling pathways in macrophages have been gradually elucidated, providing more alternative therapeutic targets for diseases treatment. Here, we provide an overview of the basic physiology of macrophages and expound the regulatory pathways within them. We also address the crucial role macrophages play in the pathogenesis of diseases, including autoimmune, neurodegenerative, metabolic, infectious diseases, and cancer, with a focus on advances in macrophage-targeted strategies exploring modulation of components and regulators of signaling pathways. Last, we discuss the challenges and possible solutions of macrophage-targeted therapy in clinical applications. We hope that this comprehensive review will provide directions for further research on therapeutic strategies targeting macrophage signaling pathways, which are promising to improve the efficacy of disease treatment.

Pharmacological Features of 18β-Glycyrrhetinic Acid: A Pentacyclic Triterpenoid of Therapeutic Potential

Glycyrrhiza glabra L. (belonging to the family Leguminosae), commonly known as Licorice, is a popular medicinal plant that has been used in traditional medicine worldwide for its ethnopharmacological efficacy in treating several ailments. Natural herbal substances with strong biological activity have recently received much attention. The main metabolite of glycyrrhizic acid is 18β-glycyrrhetinic acid (18βGA), a pentacyclic triterpene. A major active plant component derived from licorice root, 18βGA has sparked a lot of attention due to its pharmacological properties. The current review thoroughly examines the literature on 18βGA, a major active plant component obtained from Glycyrrhiza glabra L. The current work provides insight into the pharmacological activities of 18βGA and the potential mechanisms of action involved. The plant contains a variety of phytoconstituents such as 18βGA, which has a variety of biological effects including antiasthmatic, hepatoprotective, anticancer, nephroprotective, antidiabetic, antileishmanial, antiviral, antibacterial, antipsoriasis, antiosteoporosis, antiepileptic, antiarrhythmic, and anti-inflammatory, and is also useful in the management of pulmonary arterial hypertension, antipsychotic-induced hyperprolactinemia, and cerebral ischemia. This review examines research on the pharmacological characteristics of 18βGA throughout recent decades to demonstrate its therapeutic potential and any gaps that may exist, presenting possibilities for future drug research and development.

18β-Glycyrrhetinic Acid Ameliorates Neuroinflammation Linked Depressive Behavior Instigated by Chronic Unpredictable Mild Stress via Triggering BDNF/TrkB Signaling Pathway in Rats

Evidence shows that inflammatory responses may encompass the onset of severe depressive illness. Traditionally used licorice contains 18β-glycyrrhetinic acid (18βGA), which has been demonstrated to reduce inflammation and oxidative stress. This study investigates the antidepressant effects of 18βGA and the underlying mechanism in rats exposed to chronic unpredictable mild stress (CUMS). Wistar rats were exposed to CUMS for 36 consecutive days to establish depression. 18βGA (10, 20, and 50 mg/kg) or fluoxetine was given once daily (from day 30 to day 36). Thereafter, behavior parameters (sucrose preference test, forced-swimming test, open-field test, body weight), pro-inflammatory cytokines, neurotransmitters, adrenocorticotropic hormone (ACTH), corticosterone (CORT), and liver biomarkers were studied. Immunohistochemistry and western blot analyses were conducted to investigate the protein's expression. 18βGA (20 and 50 mg/kg) treatment increased sucrose intake, locomotion in the open-field test, decreased immobility time in the forced swim test, and improved body weight in CUMS-exposed rats. The therapy of 18βGA dramatically declined cytokines, ACTH and CORT and improved 5HT and norepinephrine in CUMS rats. Furthermore, BDNF and TrkB proteins were down-regulated in CUMS group, which was increased to varying degrees by 18βGA at doses of 20 and 50 mg/kg. Therefore, 18βGA ameliorates depressive-like behavior persuaded by chronic unpredictable mild stress, decreases neuroinflammation, liver biomarkers, stress hormones, and improves body weight, brain neurotransmitter concentration via activating on BDNF/TrkB signaling pathway in both PFC and hippocampus in rats.

Analysis of the network pharmacology and the structure-activity relationship of glycyrrhizic acid and glycyrrhetinic acid

Licorice, a herbal product derived from the root of Glycyrrhiza species, has been used as a sweetening agent and traditional herbal medicine for hundreds of years. Glycyrrhizic acid (GL) and glycyrrhetinic acid (GA) are the most important active ingredients in licorice. Both GL and GA have pharmacological effects against tumors, inflammation, viral infection, liver diseases, neurological diseases, and metabolic diseases. However, they also exhibit differences. KEGG analysis indicated that licorice is involved in neuroactive ligand‒receptor interactions, while 18β-GA is mostly involved in arrhythmogenic right ventricular cardiomyopathy. In this article, we comprehensively review the therapeutic potential of GL and GA by focusing on their pharmacological effects and working mechanisms. We systemically examine the structure-activity relationship of GL, GA and their isomers. Based on the various pharmacological activities of GL, GA and their isomers, we propose further development of structural derivatives of GA after chemical structure modification, with less cytotoxicity but higher targeting specificity. More research is needed on the clinical applications of licorice and its active ingredients.

Exogenous Antioxidants in Remyelination and Skeletal Muscle Recovery

Inflammatory, oxidative, and autoimmune responses cause severe damage to the nervous system inducing loss of myelin layers or demyelination. Even though demyelination is not considered a direct cause of skeletal muscle disease there is extensive damage in skeletal muscles following demyelination and impaired innervation. In vitro and in vivo evidence using exogenous antioxidants in models of demyelination is showing improvements in myelin formation alongside skeletal muscle recovery. For instance, exogenous antioxidants such as EGCG stimulate nerve structure maintenance, activation of glial cells, and reduction of oxidative stress. Consequently, this evidence is also showing structural and functional recovery of impaired skeletal muscles due to demyelination. Exogenous antioxidants mostly target inflammatory pathways and stimulate remyelinating mechanisms that seem to induce skeletal muscle regeneration. Therefore, the aim of this review is to describe recent evidence related to the molecular mechanisms in nerve and skeletal muscle regeneration induced by exogenous antioxidants. This will be relevant to identifying further targets to improve treatments of neuromuscular demyelinating diseases.

Natural Products as Novel Neuroprotective Agents; Computational Predictions of the Molecular Targets, ADME Properties, and Safety Profile

Neurodegenerative diseases (NDs) are one of the most challenging public health issues. Despite tremendous advances in our understanding of NDs, little progress has been made in establishing effective treatments. Natural products may have enormous potential in preventing and treating NDs by targeting microglia; yet, there have been several clinical concerns about their usage, primarily due to a lack of scientific evidence for their efficacy, molecular targets, physicochemical properties, and safety. To solve this problem, the secondary bioactive metabolites derived from neuroprotective medicinal plants were identified and selected for computational predictions for anti-inflammatory activity, possible molecular targets, physicochemical properties, and safety evaluation using PASS online, Molinspiration, SwissADME, and ProTox-II, respectively. Most of the phytochemicals were active as anti-inflammatory agents as predicted using the PASS online webserver. Moreover, the molecular target predictions for some phytochemicals were similar to the reported experimental targets. Moreover, the phytochemicals that did not violate important physicochemical properties, including blood-brain barrier penetration, GI absorption, molecular weight, and lipophilicity, were selected for further safety evaluation. After screening 54 neuroprotective phytochemicals, our findings suggest that Aromatic-turmerone, Apocynin, and Matrine are the most promising compounds that could be considered when designing novel neuroprotective agents to treat neurodegenerative diseases via modulating microglial polarization.

Protective effect of 18β-glycyrrhetinic acid against H2O2-induced injury in Schwann cells based on network pharmacology and experimental validation

The aim of the present study was to assess the protective effects of 18β-GA against hydrogen peroxide (H₂O₂)-induced injury. First, the SMILES annotation for 18β-GA was used to search PubChem and for reverse molecular docking in Swiss Target Prediction, the Similarity Ensemble Approach Search Server and the TargetNet database to obtain potential targets. Injury-related molecules were obtained from the GeneCards database and the predicted targets of 18β-GA for injury treatment were selected by Wayne diagram analysis. Subsequently, Kyoto Encyclopedia of Genes and Genomes analysis was performed by WebGestalt. The experimental cells were assorted into control, model, 10 µM SB203580-treated, 5 µM 18β-GA-treated and 10 µM 18β-GA-treated groups. Hoechst 33258 staining was performed and intracellular reactive oxygen species (ROS) levels, cell apoptosis, Bcl-xl, Bcl-2, Bad, Bax, cleaved-caspase 3, cleaved-caspase 7, transient receptor potential ankyrin 1 (TRPA1) and transient receptor potential vanilloid 1 (TRPV1) levels, as well as p38 MAPK phosphorylation were measured. The ‘Inflammatory mediator regulation of TRP channels’ pathway was selected for experimental verification. The results indicated that 10 µM 18β-GA significantly increased cell viability as compared with the H₂O₂-treated model group. As suggested by the difference in intracellular ROS fluorescence intensity, 18β-GA inhibited H₂O₂-induced ROS production in Schwann cells. Hoechst 33258 staining indicated that 18β-GA reversed chromatin condensation and the increase in apoptotic nuclei following H₂O₂ treatment. Furthermore, flow cytometry suggested that 18β-GA substantially inhibited H₂O₂-induced apoptosis. Pre-treatment with 18β-GA obviously reduced Bad, Bax, cleaved-caspase3, cleaved-caspase 7, TRPA1 and TRPV1 levels and p38 MAPK phosphorylation after H₂O₂ treatment and increased Bcl-2 and Bcl-xl levels. In conclusion, 18β-GA inhibited Schwann cell injury and apoptosis induced by H₂O₂ and may be a potential drug to prevent peripheral nerve injury.

Preclinical Evidence for the Pharmacological Actions of Glycyrrhizic Acid: A Comprehensive Review

Glycyrrhiza glabra L. (Family: Fabaceae) is one of the important traditional medicinal plant used extensively in folk medicine. It is known for its ethnopharmacological value in curing a wide variety of ailments. Glycyrrhizin, an active compound of G. glabra, possesses anti-inflammatory activity due to which it is mostly used in traditional herbal medicine for the treatment and management of chronic diseases. The present review is focused extensively on the pharmacology, pharmacokinetics, toxicology, and potential effects of Glycyrrhizic Acid (GA). A thorough literature survey was conducted to identify various studies that reported on the GA on PubMed, Science Direct and Google Scholar.

Role of Plant-Derived Natural Compounds in Experimental Autoimmune Encephalomyelitis: A Review of the Treatment Potential and Development Strategy

Multiple sclerosis (MS) is an autoimmune disease of the central nervous system that is mainly mediated by pathological T-cells. Experimental autoimmune encephalomyelitis (EAE) is a well-known animal model of MS that is used to study the underlying mechanism and offers a theoretical basis for developing a novel therapy for MS. Good therapeutic effects have been observed after the administration of natural compounds and their derivatives as treatments for EAE. However, there has been a severe lag in the research and development of drug mechanisms related to MS. This review examines natural products that have the potential to effectively treat MS. The relevant data were consulted in order to elucidate the regulated mechanisms acting upon EAE by the flavonoids, glycosides, and triterpenoids derived from natural products. In addition, novel technologies such as network pharmacology, molecular docking, and high-throughput screening have been gradually applied in natural product development. The information provided herein can help improve targeting and timeliness for determining the specific mechanisms involved in natural medicine treatment and lay a foundation for further study.

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.

Fasudil enhances the phagocytosis of myelin debris and the expression of neurotrophic factors in cuprizone-induced demyelinating mice

Multiple sclerosis (MS) is mainly associated with the neuroinflammation and demyelination in the central nervous system (CNS), in which the failure of remyelination results in persistent neurological dysfunction. Fasudil, a typical Rho kinase inhibitor, has been exhibited beneficial effects on several models of neurodegenerative disorders. In this study, we showed that Fasudil promoted the uptake of myelin debris by microglia via cell experiments and through a cuprizone (CPZ)-induced demyelinating model. In vitro, microglia with phagocytic debris exhibited enhanced expression of brain-derived neurotrophic factor (BDNF) and glial cell-derived neurotrophic factor (GDNF), and the conditioned medium promoted the maturation of oligodendrocyte precursor cells (OPCs). Meanwhile, Fasudil upregulated TREM2/DAP12 pathway, which positively regulated the phagocytosis of myelin debris by microglia. Similarly, in vivo, Fasudil intervention enhanced the clearance of myelin debris, upregulated the expression of BDNF and GDNF on microglia, and promoted the formation of Oligo2+/PDGFRα+ OPCs and the maturation of MBP + oligodendrocytes in the brain. Our results showed that Fasudil targeted the phagocytic function of microglia, effectively clearing myelin debris produced during pathological process possibly by upregulating TREM2/DAP12 pathway, accompanied by increased expression of BDNF and GDNF. However, the precise mechanism underlying the effects of Fasudil in promoting phagocytic effects and neurotrophic factors remains to be elucidated.

Activation of FXR by ganoderic acid A promotes remyelination in multiple sclerosis via anti-inflammation and regeneration mechanism

Multiple sclerosis (MS), as an inflammatory demyelinating disorder of central nervous system, is the leading cause of non-traumatic neurologic disability in young adults. The pathogenesis of MS remains unknown, however, a dysregulation of glia-neuroimmune signaling plays a key role during progressive disease stage. Most of the existing drugs are aimed at the immune system, but there is no approved drug by promoting remyelination after demyelination so far. There is a great interest in identifying novel agents for treating MS bytargeting to switch the immune imbalance from pro-inflammation and apoptosis to anti-inflammation and regeneration during remyelination phase. Here, we reported that ganoderic acid A (GAA) significantly enhanced the remyelination and rescued motor deficiency in two animal models of MS, including cuprizone-induced demyelination and myelin oligodendrocyte glycoprotein (MOG) 35-55-induced experimental autoimmune encephalomyelitis model. In these two independent MS animal models, GAA modulated neuroimmune to enhance the anti-inflammatory and regeneration markers IL-4 and BDNF, inhibited inflammatory markers IL-1β and IL-6, followed by down-regulation of microglia activation and astrocyte proliferation. Pharmacological and genetic ablation of farnesoid-X-receptor (FXR) abolished GAA-induced remyelination and restoration of motor deficiency in MS mice. Thus, GAA is a novel and potential therapeutic agent that can rescue MS neuroimmune imbalance and remyelination through an FXR receptor-dependent mechanism. Clinical investigation on the therapeutic effect of GAA in improving remyelination of the MS patients to rescue the motor function is warranted.

Biotransformation of Oleanane and Ursane Triterpenic Acids

Oleanane and ursane pentacyclic triterpenoids are secondary metabolites of plants found in various climatic zones and regions. This group of compounds is highly attractive due to their diverse biological properties and possible use as intermediates in the synthesis of new pharmacologically promising substances. By now, their antiviral, anti-inflammatory, antimicrobial, antitumor, and other activities have been confirmed. In the last decade, methods of microbial synthesis of these compounds and their further biotransformation using microorganisms are gaining much popularity. The present review provides clear evidence that industrial microbiology can be a promising way to obtain valuable pharmacologically active compounds in environmentally friendly conditions without processing huge amounts of plant biomass and using hazardous and expensive chemicals. This review summarizes data on distribution, microbial synthesis, and biological activities of native oleanane and ursane triterpenoids. Much emphasis is put on the processes of microbial transformation of selected oleanane and ursane pentacyclic triterpenoids and on the bioactivity assessment of the obtained derivatives.

Glycyrrhizic acid promotes neural repair by directly driving functional remyelination

Natural compounds are a rich source of effective candidate drugs for the treatment of neurological disorders. Glycyrrhizic acid (GA), the major water-soluble ingredient isolated from Glycyrrhiza glabra, is reported to show anti-inflammatory and immunomodulatory activities. However, its effect on CNS demyelinating disease is unclear. In this study, we showed that GA ameliorated the clinical disease severity of experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis (MS), especially at the chronic stage of clinical EAE. Histological evaluation demonstrated that, in the prophylactic treatment regimen, GA significantly inhibited inflammatory demyelination in the CNS. During the chronic stage when myelin and axon damage has already occurred, GA induced oligodendrocyte progenitor cell (OPC) differentiation into mature oligodendrocytes, thus effectively accelerating remyelination. Evidence from the cuprizone-induced mouse model of de- and remyelination, ex vivo organotypic slice cultures, and in vitro OPC maturation experiments indicated that the observed efficacy of this compound resulted directly from enhanced remyelination rather than immune suppression. Furthermore, we found that GA promoted oligodendrocyte maturation through modulating GSK-3β signaling pathways. Our data led to the conclusion that GA could be used as a potential therapeutic candidate for the treatment of demyelinating diseases such as MS, which remains refractory to available treatments.

Subcutaneous anti-CD20 antibody treatment delays gray matter atrophy in human myelin oligodendrocyte glycoprotein-induced EAE mice

BACKGROUND

The human myelin oligodendrocyte glycoprotein-induced experimental autoimmune encephalomyelitis (huMOG-EAE) model, generates B-cell driven demyelination in mice, making it a suitable multiple sclerosis model to study B cell depletion.

OBJECTIVES

We investigated the effect of subcutaneous anti-CD20 antibody treatment on huMOG-EAE gray matter (GM) pathology.

METHODS

C57Bl/6, 8-week old mice were immunized with 200 huMOG_1-125 and treated with 50 μg/mouse of anti-CD20 antibody (n = 16) or isotype control (n = 16). Serial brain volumetric 9.4 T MRI scans was performed at baseline, 1 and 5 wkPI. Disease severity was measured by clinical disability score (CDS) and performance on rotarod test.

RESULTS

Anti-CD20 antibody significantly reduced brain volume loss compared with the isotype control across all timepoints longitudinally in the basal ganglia (p = 0.01), isocortex (p = 0.025) and thalamus (p = 0.023). The CDS was reduced significantly with anti-CD20 antibody vs. the isotype control at 3 (p = 0.003) and 4 (p = 0.03) wkPI, while a trend was observed at 5 (p = 0.057) and 6 (p = 0.086) wkPI. Performance on rotarod was also improved significantly at 3 (p = 0.007) and 5 (p = 0.01) wkPI compared with the isotype control. At cellular level, anti-CD20 therapy suppressed the percentage of proliferative nuclear antigen positive microglia in huMOG-EAE isocortex (p = 0.016). Flow cytometry confirmed that anti-CD20 antibody strongly depleted the CD19-expressing B cell fraction in peripheral blood mononuclear cells, reducing it from 39.7% measured in isotype control to 1.59% in anti-CD20 treated mice (p < 0.001).

CONCLUSIONS

Anti-CD20 antibody treatment delayed brain tissue neurodegeneration in GM, and showed clinical benefit on measures of disease severity in huMOG-EAE mice.

The "Treatise on the spleen and stomach" (Pí Wèi Lùn) as the first record of multiple sclerosis in the medical literature - A hypothesis based on the analysis of clinical presentation and herbal medicine

Background

The “Treatise on the spleen and stomach” (Pí Wèi Lùn) is the work of the scholar and physician Li Gao (Jin-Yuan dynasties, 1115–1368 C.E., China). Li Gao described a clinical presentation that today would fall under the diagnosis of Multiple Sclerosis (MS) and proposed the treatment with herbal medicine and nutritional guidelines. The PWL is well known for its application in the treatment of MS and autoimmune conditions. However, this theoretical “MS” has not yet been analyzed through a scientific investigation, and research on its herbal formulations for MS is scant.

Methods

We analyzed the PWL “MS” clinical presentation considering biomedical diagnostic criteria and neurological correlates. To support our review, we searched Pubmed for studies on the PWL main herbal formulas and their herbs/isolates used for the believed “MS” which treated experimental autoimmune encephalomyelitis (EAE)/MS.

Results

We found a very close correlation between the PWL “MS” and the current MS diagnosis. Twenty four studies on the herbs-isolates showed significant amelioration of EAE, neuronal damage, and demyelination.

Discussion

Collectively, Astragali radix, Ginseng radix, Glycyrrhizae radix, and berberine containing Phellodendri cortex reduced the severity of EAE through different signaling pathways and mechanisms of action. These herbs provided a wide range of properties such as anti-inflammatory, anti-oxidant, anti-microglial activation, anti-infiltration of leukocytes, apoptotic/anti-apoptotic balance, and neuronal protection.

Conclusion

Our review proposes that the PWL is the first record of MS in the medical literature. Its formulas and herbs-isolates offer a fertile area for MS research and an invaluable potential for its treatment.

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We propose that the Pí Wèi Lùn is the first record of MS in the medical literature.

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All twenty four studies on the PWL’s selected herbs/isolates showed improvement of EAE.

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Different signaling pathways/mechanisms of action provided synergistic properties.

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In the PWL, the gastrointestinal system is key for MS and science supports it.

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The PWL offers a fertile area of research and enormous potential for MS treatment.

Drug delivery to macrophages: A review of targeting drugs and drug carriers to macrophages for inflammatory diseases

Macrophages play a key role in defending against foreign pathogens, healing wounds, and regulating tissue homeostasis. Driving this versatility is their phenotypic plasticity, which enables macrophages to respond to subtle cues in tightly coordinated ways. However, when this coordination is disrupted, macrophages can aid the progression of numerous diseases, including cancer, cardiovascular disease, and autoimmune disease. The central link between these disorders is aberrant macrophage polarization, which misguides their functional programs, secretory products, and regulation of the surrounding tissue microenvironment. As a result of their important and deterministic roles in both health and disease, macrophages have gained considerable attention as targets for drug delivery. Here, we discuss the role of macrophages in the initiation and progression of various inflammatory diseases, summarize the leading drugs used to regulate macrophages, and review drug delivery systems designed to target macrophages. We emphasize strategies that are approved for clinical use or are poised for clinical investigation. Finally, we provide a prospectus of the future of macrophage-targeted drug delivery systems.

Neuroinflammation is a putative target for the prevention and treatment of perioperative neurocognitive disorders

INTRODUCTION

The demographics of aging of the surgical population has increased the risk for perioperative neurocognitive disorders in which trauma-induced neuroinflammation plays a pivotal role.

SOURCES OF DATA

After determining the scope of the review, the authors used PubMed with select phrases encompassing the words in the scope. Both preclinical and clinical reports were considered.

AREAS OF AGREEMENT

Neuroinflammation is a sine qua non for development of perioperative neurocognitive disorders.

AREAS OF CONTROVERSY

What is the best method for ameliorating trauma-induced neuroinflammation while preserving inflammation-based wound healing.

GROWING POINTS

This review considers how to prepare for and manage the vulnerable elderly surgical patient through the entire spectrum, from preoperative assessment to postoperative period.

AREAS TIMELY FOR DEVELOPING RESEARCH

What are the most effective and safest interventions for preventing and/or reversing Perioperative Neurocognitive Disorders.

Dose-dependent neuroprotective effect of oriental phyto-derived glycyrrhizin on experimental neuroterminal norepinephrine depletion in a rat brain model

The dose-dependent neuroprotective role of licorice-derived glycyrrhizin during subacute neuroterminal norepinephrine (NE) depletion was studied in rat brain. Experimental design included thirty 5-week-old male rats randomly divided into five groups. Compared to the saline-injected control group, the group receiving daily intraperitoneal injection of fusaric acid (FA; 5 mg/kg/b.w.) for 30 days showed pharmacological depletion of NE. The neuroprotective effects of three successively increasing oral doses of glycyrrhizin were examined in FA-treated rats. Neurochemical parameters and histo-/immunohistopathological changes in the hippocampus were examined. FA generated global hippocampal stress with altered neurobiochemical parameters, accompanied by immune-confirmed inflammatory tissue damage, and noticeable behavioral changes. Although glycyrrhizin after FA-induced intoxication did not correct the recorded drop in the NE level, it decreased the dopamine levels to control levels. Similarly, glycyrrhizin at a high dose restored the serotonin level to its normal value and blocked the FA-induced increase in the level of its metabolite, 5-hydroxyindoleacetic acid. The FA-induced rise in γ-aminobutyric acid (GABA) and histamine was alleviated after administration of a high dose of glycyrrhizin. This was accompanied by improvements in the bioenergetic status and neuronal regenerative capacity through recovery of ATP and brain-derived neurotrophic factor levels to the pre-intoxicated values. High doses of glycyrrhizin also ameliorated the FA-generated behavioral changes and oxidative damage, manifested by the reduction in the expression of cortical pro-apoptotic caspase 3 in the same group. This study suggests that glycyrrhizin can potentially mend most of the previously evoked neuronal damage induced by FA intoxication in the brain of an experimental rat model.

Natural products as a potential modulator of microglial polarization in neurodegenerative diseases

Neurodegenerative diseases (NDs) are characterized by the progressive loss of structure and function of neurons most common in elderly population, mainly including Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS) and multiple sclerosis (MS). Neuroinflammation caused by microglia as the resident macrophages of the central nervous system (CNS) plays a contributory role in the onset and progression of NDs. Activated microglia, as in macrophages, to be heterogeneous, can polarize into M1 (pro-inflammatory) and M2 (anti-inflammatory) functional phenotypes. The former elaborate pro-inflammatory mediators promoting neuroinflammation and neuronal damage. In contrast, the latter generate anti-inflammatory mediators and neurotrophins that inhibit neuroinflammation and promote neuronal healing. Consistently, the regulation of microglial polarization from M1 to M2 phenotype appears as an outstanding therapeutic and preventive approach for NDs treatment. Although non-steroidal anti-inflammatory drugs (NSAIDs) currently used to alleviate M1 microglia-associated neuroinflammation responsible for the development of NDs, these drugs have different degrees of adverse effects and limited efficacy. As the advantages of novel structure, multi-target, high efficiency and low toxicity, natural products as the modulators of microglial polarization have attracted considerable concerns in the therapeutic areas of NDs. In this review, we mainly summarized the therapeutic potential of natural products and their various molecular mechanisms for NDs treatment through modulating microglial polarization. The aim of the current review is expected to be useful to develop innovative modulators of microglial polarization from natural products for the amelioration and treatment of NDs.

Ethanol extract of Glycyrrhizae Radix modulates the responses of antigen-specific splenocytes in experimental autoimmune encephalomyelitis

BACKGROUND

Multiple sclerosis (MS) is an autoimmune disorder resulting in paralysis, and the responses of reactive T cells against self-antigens are hallmarks. Glycyrrhizae Radix (GR) has been used for detoxification and reducing inflammation. However, very few reports have described the effects of GR on MS.

PURPOSE

The immunomodulatory effects of GR extract on autoimmune responses were evaluated through in vitro, ex vivo, and in vivo assays using primary mouse splenocytes (SPLC), mouse microglia BV2 cell line, and a mouse model of experimental autoimmune encephalomyelitis (EAE).

STUDY DESIGN

Ethanol extract of GR was used in vitro with primary SPLC in the condition of anti-CD3/CD28 stimulation and interferon (IFN)-γ-producing CD4+ (TH1)/CD8+ (TC1) polarization as well as IFN-γ-stimulated BV2 cells. For EAE induction, female C57BL/6 mice were immunized with 200 μg of myelin oligodendrocyte glycoprotein (MOG)35-55 without pertussis toxin. EAE SPLC (ex vivo) and EAE mice (in vivo) were treated with GR extract to evaluate the changes in antigen-specific responses. SPLC media containing antigen-specific responses were used to stimulate BV2 cells.

RESULTS

GR extract effectively modulated the responses of reactive splenic T cells through the reduction in IFN-γ+ T cell populations, the expressions of cell adhesion molecules (CAMs), and secretions of cytokines containing IFN-γ and a chemokine IFN-γ-induced protein 10 (IP-10) in vitro. In addition, GR extract significantly decreased nitric oxide production and secretion of tumor necrosis factor (TNF)-α and IP-10 in IFN-γ-stimulated BV2 cells. The antigen-specific TH1 and TC1 populations were decreased following administration of 100 mg/kg of GR extract, whereas CD8+IL-17A+ (TC17) population was increased on day 36 after EAE induction. Moreover, IFN-γ, which showed the highest secretion among examined cytokines, and IP-10 decreased on day 36. SPLC media derived from 100 mg/kg GR extract-administered EAE mice revealed the ameliorative effects on BV2 cell stimulation.

CONCLUSION

This is the first report on the immunomodulatory effects of GR extract on antigen-specific SPLC responses in EAE. These results could be helpful for the discovery of drug candidates for MS by focusing on IFN-γ-related autoimmune responses.

Leonurine suppresses neuroinflammation through promoting oligodendrocyte maturation

Focal inflammation and remyelination failure are major hallmarks of multiple sclerosis and its animal model, experimental autoimmune encephalomyelitis (EAE). In this study, we found that leonurine, a bioactive alkaloid, alleviated EAE disease severity along with reduced central nervous system inflammation and myelin damage. During the pathogenesis of EAE, leonurine dramatically suppressed the recruitment of encephalitogenic T cells into the central nervous system, whereas did not impair periphery immune responses and microglia activation. Mechanistically, leonurine protected mice against demyelination along with enhanced remyelination through promoting the maturation of oligodendrocytes in both EAE and cuprizone-induced demyelination mouse models. Moreover, we identified that the expression of demethylase jumonji domain-containing protein D3 was significantly enhanced upon treatment of leonurine, which suppressed the trimethylation of histone H3 lysine-27 and enhanced oligodendrocyte maturation accordingly. Collectively, our study identified the therapeutic effect of leonurine on EAE model, which potentially represents a promising therapeutic strategy for multiple sclerosis, even other demyelination disorders.

TRPM2 Exacerbates Central Nervous System Inflammation in Experimental Autoimmune Encephalomyelitis by Increasing Production of CXCL2 Chemokines

Multiple sclerosis (MS) is a chronic inflammatory disorder of the CNS characterized by demyelination and axonal injury. Current therapies that mainly target lymphocytes do not fully meet clinical need due to the risk of severe side effects and lack of efficacy against progressive MS. Evidence suggests that MS is associated with CNS inflammation, although the underlying molecular mechanism is poorly understood. Transient receptor potential melastatin 2 (TRPM2), a Ca2+-permeable nonselective cation channel, is expressed at high levels in the brain and by immune cells, including monocyte lineage cells. Here, we show that TRPM2 plays a pathological role in experimental autoimmune encephalomyelitis (EAE), an animal model of MS. Knockout (KO) or pharmacological inhibition of TRPM2 inhibited progression of EAE and TRPM2-KO mice showed lower activation of Iba1-immunopositive monocyte lineage cells and neutrophil infiltration of the CNS than WT mice. Moreover, CXCL2 production in TRPM2-KO mice was significantly reduced at day 14, although the severity of EAE was the same as that in WT mice at that time point. In addition, we used BM chimeric mice to show that TRPM2 expressed by CNS-infiltrating macrophages contributes to progression of EAE. Because CXCL2 induces migration of neutrophils, these results indicate that reduced expression of CXCL2 in the CNS suppresses neutrophil infiltration and slows progression of EAE in TRPM2-KO mice. Together, the results suggest that TRPM2 plays an important role in progression of EAE pathology and shed light on its putative role as a therapeutic target for MS.SIGNIFICANCE STATEMENT Current therapies for multiple sclerosis (MS), which mainly target lymphocytes, carry the risk of severe side effects and lack efficacy against the progressive form of the disease. Here, we found that the transient receptor potential melastatin 2 (TRPM2) channel, which is abundantly expressed in CNS-infiltrating macrophages, plays a crucial role in development of experimental autoimmune encephalomyelitis (EAE), an animal model of MS. EAE progression was suppressed by Knockout (KO) or pharmacological inhibition of TRPM2; this was attributed to a reduction in CXCL2 chemokine production by CNS-infiltrating macrophages in TRPM2-KO mice, resulting in suppression of neutrophil infiltration into the CNS. These results reveal an important role of TRPM2 in the pathogenesis of EAE and shed light on its potential as a therapeutic target.

The beneficial effects of 18β-glycyrrhetinic acid on the experimental autoimmune encephalomyelitis (EAE) in C57BL/6 mouse model

AIM

The aim of this study was to investigate the beneficial effects of 18β-glycyrrhetinic acid (GA) on the experimental allergic encephalomyelitis (EAE) in C57BL/6 mice. GA is a natural substance found in the root of licorice and is used in traditional Chinese medicine. It has many pharmacological activities such as antioxidant, anti-inflammatory, and anti-cancer effects.

MATERIALS AND METHODS

A total of 40 C57BL/6 mice were divided equally into four groups: (1) Control, (2) EAE, (3) GA and (4) GA + EAE. 14 days after induction of EAE with MOG35-55 and pertussis toxin, mice were treated with GA at doses of 100 mg/kg/day for 7 days intraperitoneally.

RESULTS

To our results, oxidative stress and lipid peroxidations (elevated TBARS levels, decreased GPx, SOD, CAT, and GSH levels) were significantly (p < .01) increased, causing EAE in brain tissue. Also, histopathological damage (Caspase-3 and IL-17 activity, p ≤ .01) and cytokine levels (TNF-α and IL-1β, p < .01) were induced with EAE in mice brain tissue. On the other hand, GA treatment significantly (p < .01) reversed oxidative histological and immunological alterations caused by EAE.

CONCLUSIONS

In conclusion, the GA treatment can protect the brain tissue against EAE in mice with its antioxidant and anti-inflammatory properties.

TGFβ1 transduction enhances immunomodulatory capacity of neural stem cells in experimental autoimmune encephalomyelitis

Bone marrow-derived neural stem cells (BM-NSCs) have therapeutic effect on EAE, an animal model of multiple sclerosis. However, the beneficial effect is suboptimal due to the limited immunomodulatory capacity of these cells. In this study, we engineered BM-NSCs with inducible TGFβ1, a potent immunosuppressive cytokine, to enhance their anti-inflammatory capacity. We found that i.v. injected TGFβ1-BM-NSCs more effectively suppressed clinical severity, inflammation and demyelination of the central nervous system of EAE mice. Transduction of TGFβ1 resulted in a higher percentage of Tregs and lower percentage of Th1 and Th17 cells in the periphery, with increased production of IL-10, and reduced production of IFN-γ, IL-17 and GM-CSF. Moreover, myelin-specific splenic proliferation was also inhibited more profoundly by TGFβ1-BM-NSCs. We also found that TGFβ1-BM-NSCs have the capacity to switch microglia from M1 to M2 phenotype. On the other hand, transduction of TGFβ1 did not affect proliferative ability and differentiating potential of BM-NSCs in vitro and in vivo. Together, these findings demonstrate that transduction of TGFβ1 significantly enhanced the immunomodulatory capacity of BM-NSCs for EAE treatment, through inducing Tregs and an M2 phenotype of macrophages/microglia, while retaining their capacity for neural cell differentiation. Thus, our study provides an easily accessible, inducible and effective therapy for CNS inflammatory demyelination.

Inhibitors of connexin and pannexin channels as potential therapeutics

While gap junctions support the exchange of a number of molecules between neighboring cells, connexin hemichannels provide communication between the cytosol and the extracellular environment of an individual cell. The latter equally holds true for channels composed of pannexin proteins, which display an architecture reminiscent of connexin hemichannels. In physiological conditions, gap junctions are usually open, while connexin hemichannels and, to a lesser extent, pannexin channels are typically closed, yet they can be activated by a number of pathological triggers. Several agents are available to inhibit channels built up by connexin and pannexin proteins, including alcoholic substances, glycyrrhetinic acid, anesthetics and fatty acids. These compounds not always strictly distinguish between gap junctions, connexin hemichannels and pannexin channels, and may have effects on other targets as well. An exception lies with mimetic peptides, which reproduce specific amino acid sequences in connexin or pannexin primary protein structure. In this paper, a state-of-the-art overview is provided on inhibitors of cellular channels consisting of connexins and pannexins with specific focus on their mode-of-action and therapeutic potential.

Central Administration of 5Z-7-Oxozeaenol Protects Experimental Autoimmune Encephalomyelitis Mice by Inhibiting Microglia Activation

Transforming growth factor β-activated kinase 1 (TAK1), a vital upstream integrator of multiple pro-inflammatory signaling pathways, mediates the production of pro-inflammatory cytokines, chemokines, and adhesion molecules. Investigations targeting TAK1 provide new therapeutic options for chronic inflammatory disorders, autoimmune diseases, and cancer. However, the role and mechanism of the TAK1 inhibitor 5Z-7-oxozeaenol in treating autoimmune demyelinating diseases remain unclear. This work aimed to identify whether 5Z-7-oxozeaenol exerts neuroprotective effects on experimental autoimmune encephalomyelitis (EAE) in mice. Here, we demonstrate that 5Z-7-oxozeaenol efficiently alleviates the symptoms of EAE by decreasing the levels of pro-inflammatory cytokines in splenocytes and central nervous system, diminishing the number of activated microglia and inhibiting the p38MAPK, JNK, and ERK signaling pathways. Furthermore, we demonstrate that administration during the symptomatic time window is required for 5Z-7-oxozeaenol efficacy. These results suggest that TAK1 inhibition may provide a potent approach toward treating autoimmune demyelinating diseases.

How impaired efficacy happened between Gancao and Yuanhua: Compounds, targets and pathways

As recorded in Traditional Chinese Medicine (TCM) theory, Gancao (Glycyrrhizae Radix et Rhizoma) could weaken the pharmacological effect or increase the toxicity of Yuanhua (Genkwa Flos). However, the theory has been suspected due to lack of evidence. Here, we investigate whether Gancao could weaken Yuanhua’s diuretic effect, if so, which chemicals and which targets may be involved. Results showed that Yuanhua exerted diuretic effect through down-regulating renal AQP 2, without electrolyte disturbances such as K⁺ loss which has been observed as side-effect of most diuretics. Gancao had no diuretic effect, but could impair Yuanhua’s diuretic effect through up-regulating renal AQP 2. Glycyrrhetinic acid (GRA) in Gancao could up-regulate AQP 2 and counteract the AQP 2 regulation effect of Yuanhuacine (YHC) and Ginkwanin (GKW) in Yuanhua. Network pharmacology method suggested that YHC, GKW and GRA could bind to MEK1/FGFR1 protein and influence ERK-MAPK pathway, which was verified by Western blotting. This study supports TCM theory and reminds that more attention should be paid to the safety and efficacy problems induced by improper combination between herbs. Moreover, we suggested that promising diuretics with less side effects can be developed from Chinese Medicines such as Yuanhua.

Neural Stem Cell-Based Regenerative Approaches for the Treatment of Multiple Sclerosis

Multiple sclerosis (MS) is a chronic, autoimmune, inflammatory, and demyelinating disorder of the central nervous system (CNS), which ultimately leads to axonal loss and permanent neurological disability. Current treatments for MS are largely comprised of medications that are either immunomodulatory or immunosuppressive and are aimed at reducing the frequency and intensity of relapses. Neural stem cells (NSCs) in the adult brain can differentiate into oligodendrocytes in a context-specific manner and are shown to be involved in the remyelination in these patients. NSCs may exert their beneficial effects not only through oligodendrocyte replacement but also by providing trophic support and immunomodulation, a phenomenon now known as "therapeutic plasticity." In this review, we first provided an update on the current knowledge regarding MS pathogenesis and the role of immune cells, microglia, and oligodendrocytes in MS disease progression. Next, we reviewed the current progress on research aimed toward stimulating endogenous NSC proliferation and differentiation to oligodendrocytes in vivo and in animal models of demyelination. In addition, we explored the neuroprotective and immunomodulatory effects of transplanted exogenous NSCs on T cell activation, microglial activation, and endogenous remyelination and their effects on the pathological process and prognosis in animal models of MS. Finally, we examined various protocols to generate genetically engineered NSCs as a potential therapy for MS. Overall, this review highlights the studies involving the immunomodulatory, neurotrophic, and regenerative effects of NSCs and novel methods aiming at stimulating the potential of NSCs for the treatment of MS.

Matrine promotes NT3 expression in CNS cells in experimental autoimmune encephalomyelitis

Neurotrophin 3 (NT3) is a potent neurotrophic factor for promoting remyelination and recovery of neuronal function; upregulation of its expression in the central nervous system (CNS) is thus of major therapeutic importance for neurological deficits. Matrine (MAT), a quinolizidine alkaloid derived from the herb Radix Sophorae Flavescent, has been recently reported to effectively ameliorate clinical signs in experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis (MS), by secreting antiinflammatory cytokines. In the present study, our goal was to investigate whether MAT could affect NT3 expression of glial cells in the CNS, the major cell populations in the CNS foci of MS/EAE. We found that MAT markedly upregulated NT3 expression in the CNS not only by microglia/macrophages and astrocytes, but also by oligodendrocyte precursor cells, indicative of both paracrine and autocrine effects on myelinating cells. While MAT treatment reduced the numbers of iNOS⁺ M1, but increased Arg1⁺ M2 microglia/macrophage phenotypes, NT3 expression was upregulated in both phenotypes. These results indicate that MAT therapy for EAE acts, at least in part, by stimulating local production of NT3 by glial cells in the CNS, which protects neural cells from CNS inflammation-induced tissue damage.

Glycyrrhetinic acid and its derivatives in infectious diseases

Introduction. Licorice or liquorice (Glycyrrhiza glabra, Leguminosae) is a perennial plant naturally occurring or cultivated in Europe and Asia. It was appreciated by many ancient cultures, and was employed within Arabic medicine and (beginning in the Middle Ages) in Europe folk medicine as a remedy for many diseases. Currently, the sweet flavoured root of this plant – Radix Glycyrrhizae (Liquirtiae), is widely taken for the treating of various upper respiratory tract diseases, as well as for gastric ulcer disease. It is also utilized as a sweetening and flavouring agent in the food, tobacco and pharmacy industries. The main active ingredient of liquorice is the triterpenoid saponin, glycyrrhizin, which is a mixture of calcium, magnesium and potassium salts of glycyrrhizic acid (GA). Glycyrrhizic acid is composed of an aglycone, that is 18β-glycyrrhetinic acid (GE), and a D-glucuronic acid dimer. The aim of this review is to discuss some aspects of the activity of glycyrrhetinic acid and its derivatives in infectious diseases.

State of knowledge. The pentacyclic system of glycyrrhetinic acid consists of condensed six-membered rings with a hydroxyl group at C-3, a carboxyl moiety at C-30 and a ketone functional group at C-11. Considering the presence of the above mentioned functional groups, many structural transformations have been proposed, including those by way of esterification, alkylation and reduction reactions. The introduction of various chemical residues into its structure, as well as the modification of the glycyrrhetinic acid in its pentacyclic triterpene skeleton, has led to the generation of compounds with many valuable antimicrobial, anti-parasitic, antiviral properties and modified lipophilic parameters.

Summary. In summary, glycyrrhetinic acid derivatives appear to have promise as active pharmaceutical ingredients that contain a wide range of biological and pharmacological properties.

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.

Quetiapine Inhibits Microglial Activation by Neutralizing Abnormal STIM1-Mediated Intercellular Calcium Homeostasis and Promotes Myelin Repair in a Cuprizone-Induced Mouse Model of Demyelination

Microglial activation has been considered as a crucial process in the pathogenesis of neuroinflammation and psychiatric disorders. Several antipsychotic drugs (APDs) have been shown to display inhibitory effects on microglial activation in vitro, possibly through the suppression of elevated intracellular calcium (Ca(2+)) concentration. However, the exact underlying mechanisms still remain elusive. In this study, we aimed to investigate the inhibitory effects of quetiapine (Que), an atypical APD, on microglial activation. We utilized a chronic cuprizone (CPZ)-induced demyelination mouse model to determine the direct effect of Que on microglial activation. Our results showed that treatment with Que significantly reduced recruitment and activation of microglia/macrophage in the lesion of corpus callosum and promoted remyelination after CPZ withdrawal. Our in vitro studies also confirmed the direct effect of Que on lipopolysaccharide (LPS)-induced activation of microglial N9 cells, whereby Que significantly inhibited the release of nitric oxide (NO) and tumor necrosis factor α (TNF-α). Moreover, we demonstrated that pretreatment with Que, neutralized the up-regulation of STIM1 induced by LPS and declined both LPS and thapsigargin (Tg)-induced store-operated Ca(2+) entry (SOCE). Finally, we found that pretreatment with Que significantly reduced the translocation of nuclear factor kappa B (NF-κB) p65 subunit from cytoplasm to nuclei in LPS-activated primary microglial cells. Overall, our data suggested that Que may inhibit microglial activation by neutralization of the LPS-induced abnormal STIM1-mediated intercellular calcium homeostasis.