Altered astrocytic function in experimental neuroinflammation and multiple sclerosis

Myelin debris phagocytosis in demyelinating disease

Demyelinating diseases are often caused by a variety of triggers, including immune responses, viral infections, malnutrition, hypoxia, or genetic factors, all of which result in the loss of myelin in the nervous system. The accumulation of myelin debris at the lesion site leads to neuroinflammation and inhibits remyelination; therefore, it is crucial to promptly remove the myelin debris. Initially, Fc and complement receptors on cellular surfaces were the primary clearance receptors responsible for removing myelin debris. However, subsequent studies have unveiled the involvement of additional receptors, including Mac-2, TAM receptors, and the low-density lipoprotein receptor-related protein 1, in facilitating the removal process. In addition to microglia and macrophages, which serve as the primary effector cells in the disease phase, a variety of other cell types such as astrocytes, Schwann cells, and vascular endothelial cells have been demonstrated to engage in the phagocytosis of myelin debris. Furthermore, we have concluded that oligodendrocyte precursor cells, as myelination precursor cells, also exhibit this phagocytic capability. Moreover, our research group has innovatively identified the low-density lipoprotein receptor as a potential phagocytic receptor for myelin debris. In this article, we discuss the functional processes of various phagocytes in demyelinating diseases. We also highlight the alterations in signaling pathways triggered by phagocytosis, and provide a comprehensive overview of the various phagocytic receptors involved. Such insights are invaluable for pinpointing potential therapeutic strategies for the treatment of demyelinating diseases by targeting phagocytosis.

Quantitative proteomics and multi-omics analysis identifies potential biomarkers and the underlying pathological molecular networks in Chinese patients with multiple sclerosis

Multiple sclerosis (MS) is an autoimmune disorder caused by chronic inflammatory reactions in the central nervous system. Currently, little is known about the changes of plasma proteomic profiles in Chinese patients with MS (CpwMS) and its relationship with the altered profiles of multi-omics such as metabolomics and gut microbiome, as well as potential molecular networks that underlie the etiology of MS. To uncover the characteristics of proteomics landscape and potential multi-omics interaction networks in CpwMS, Plasma samples were collected from 22 CpwMS and 22 healthy controls (HCs) and analyzed using a Tandem Mass Tag (TMT)-based quantitative proteomics approach. Our results showed that the plasma proteomics pattern was significantly different in CpwMS compared to HCs. A total of 90 differentially expressed proteins (DEPs), such as LAMP1 and FCG2A, were identified in CpwMS plasma comparing to HCs. Furthermore, we also observed extensive and significant correlations between the altered proteomic profiles and the changes of metabolome, gut microbiome, as well as altered immunoinflammatory responses in MS-affected patients. For instance, the level of LAMP1 and ERN1 were significantly and positively correlated with the concentrations of metabolite L-glutamic acid and pro-inflammatory factor IL-17 (Padj < 0.05). However, they were negatively correlated with the amounts of other metabolites such as L-tyrosine and sphingosine 1-phosphate, as well as the concentrations of IL-8 and MIP-1α. This study outlined the underlying multi-omics integrated mechanisms that might regulate peripheral immunoinflammatory responses and MS progression. These findings are potentially helpful for developing new assisting diagnostic biomarker and therapeutic strategies for MS.

Upregulated expression of ubiquitin ligase TRIM21 promotes PKM2 nuclear translocation and astrocyte activation in experimental autoimmune encephalomyelitis

Reactive astrocytes play critical roles in the occurrence of various neurological diseases such as multiple sclerosis. Activation of astrocytes is often accompanied by a glycolysis-dominant metabolic switch. However, the role and molecular mechanism of metabolic reprogramming in activation of astrocytes have not been clarified. Here, we found that PKM2, a rate-limiting enzyme of glycolysis, displayed nuclear translocation in astrocytes of EAE (experimental autoimmune encephalomyelitis) mice, an animal model of multiple sclerosis. Prevention of PKM2 nuclear import by DASA-58 significantly reduced the activation of mice primary astrocytes, which was observed by decreased proliferation, glycolysis and secretion of inflammatory cytokines. Most importantly, we identified the ubiquitination-mediated regulation of PKM2 nuclear import by ubiquitin ligase TRIM21. TRIM21 interacted with PKM2, promoted its nuclear translocation and stimulated its nuclear activity to phosphorylate STAT3, NF-κB and interact with c-myc. Further single-cell RNA sequencing and immunofluorescence staining demonstrated that TRIM21 expression was upregulated in astrocytes of EAE. TRIM21 overexpressing in mice primary astrocytes enhanced PKM2-dependent glycolysis and proliferation, which could be reversed by DASA-58. Moreover, intracerebroventricular injection of a lentiviral vector to knockdown TRIM21 in astrocytes or intraperitoneal injection of TEPP-46, which inhibit the nuclear translocation of PKM2, effectively decreased disease severity, CNS inflammation and demyelination in EAE. Collectively, our study provides novel insights into the pathological function of nuclear glycolytic enzyme PKM2 and ubiquitination-mediated regulatory mechanism that are involved in astrocyte activation. Targeting this axis may be a potential therapeutic strategy for the treatment of astrocyte-involved neurological disease.

hUC-MSCs-derived MFGE8 ameliorates locomotor dysfunction via inhibition of ITGB3/ NF-κB signaling in an NMO mouse model

Neuromyelitis optica (NMO) is a severe autoimmune inflammatory disease of the central nervous system that affects motor function and causes relapsing disability. Human umbilical cord-derived mesenchymal stem cells (hUC-MSCs) have been used extensively in the treatment of various inflammatory diseases, due to their potent regulatory roles that can mitigate inflammation and repair damaged tissues. However, their use in NMO is currently limited, and the mechanism underlying the beneficial effects of hUC-MSCs on motor function in NMO remains unclear. In this study, we investigate the effects of hUC-MSCs on the recovery of motor function in an NMO systemic model. Our findings demonstrate that milk fat globule epidermal growth 8 (MFGE8), a key functional factor secreted by hUC-MSCs, plays a critical role in ameliorating motor impairments. We also elucidate that the MFGE8/Integrin αvβ3/NF-κB signaling pathway is partially responsible for structural and functional recovery, in addition to motor functional enhancements induced by hUC-MSC exposure. Taken together, these findings strongly support the involvement of MFGE8 in mediating hUC-MSCs-induced improvements in motor functional recovery in an NMO mouse model. In addition, this provides new insight on the therapeutic potential of hUC-MSCs and the mechanisms underlying their beneficial effects in NMO.

Assessment of bidirectional relationships between multiple sclerosis and epilepsy: A two-sample Mendelian randomization study

BACKGROUND AND OBJECTIVE

Epidemiological studies indicate that multiple sclerosis (MS) is associated with epilepsy. However, the causality and directionality of this association remain under-elucidated. This study aimed to reveal the causality between MS and epilepsy.

METHODS

A two-sample Mendelian randomization (MR) analysis was performed by using summarized statistics derived from large genome-wide association studies of MS and epilepsy. We used the inverse variance weighted method as the primary approach, and then four other MR methods to bidirectionally evaluate the causality of the association between MS and epilepsy. Additional sensitivity analyses were performed to measure the robustness of the findings.

RESULTS

Genetically predicted MS was positively correlated with developing all epilepsy [odds ratio (OR) = 1.027 (1.003-1.051), P  =  0.028] and generalized epilepsy [OR = 1.050 (1.008-1.094), P = 0.019]. In the reverse MR analysis, all epilepsy [OR = 1.310 (1.112-1.543), P = 0.001], generalized epilepsy [OR = 1.173 (1.010-1.363), P = 0.037], and focal epilepsy [OR = 1.264 (1.069-1.494), P  =  0.006] elevated the risk of developing MS. The result remained robust and congruous across all sensitivity analyses conducted.

CONCLUSIONS

MS is potentially associated with a higher risk of developing epilepsy. Furthermore, epilepsy may be a causal determinant of MS risk. These findings may further the understanding of the interaction of the two conditions.

Bifidobacterium breve Probiotic Compared to Lactobacillus casei Causes a Better Reduction in Demyelination and Oxidative Stress in Cuprizone-Induced Demyelination Model of Rat

Despite the anatomical separation, strong evidence suggested a bidirectional association between gut microbiota and central nervous system. Cross-talk between gut microbiota and brain has an important role in the pathophysiology of neurodegenerative disorders and regenerative processes. However, choosing the appropriate probiotics and combination therapy of probiotics to provide a synergistic effect is very crucial. In the present study, we investigated the effect of Lactobacillus casei (L. casei) and Bifidobacterium breve (B. breve) on alternation performance, oxidant/antioxidant biomarkers, the extent of demyelination, and the expression level of HO-1, Nrf-2, Olig2, MBP, PDGFRα, and BDNF in cuprizone (CPZ)-induced demyelination model of rat corpus callosum. In order to induce this model, rats received oral administration of CPZ 0.6% w/w in corn oil for 28 days. Then, L. casei, B. breve, or their combinations were orally administrated for 28 days. Y maze test was performed to investigate the alternation performance. Oxidant/antioxidant biomarkers were determined by colorimetric methods. Extent of demyelination was investigated using FluoroMyelin staining. The genes' expression levels of antioxidant and myelin lineage cells were assessed by quantitative real time PCR. The results showed the probiotics supplementation significantly improve the alternation performance and antioxidant capacity in demyelinated corpus callosum. Interestingly, B. breve supplementation alleviated demyelination and oxidative stress levels more than the administration of L. casei alone or the combination of two probiotics. These observations suggest that B. breve could provide a supplementary strategy for the treatment of multiple sclerosis by increasing antioxidant capacity and remyelination.

Exploring the Role of Neuroplasticity in Development, Aging, and Neurodegeneration

Neuroplasticity refers to the ability of the brain to reorganize and modify its neural connections in response to environmental stimuli, experience, learning, injury, and disease processes. It encompasses a range of mechanisms, including changes in synaptic strength and connectivity, the formation of new synapses, alterations in the structure and function of neurons, and the generation of new neurons. Neuroplasticity plays a crucial role in developing and maintaining brain function, including learning and memory, as well as in recovery from brain injury and adaptation to environmental changes. In this review, we explore the vast potential of neuroplasticity in various aspects of brain function across the lifespan and in the context of disease. Changes in the aging brain and the significance of neuroplasticity in maintaining cognitive function later in life will also be reviewed. Finally, we will discuss common mechanisms associated with age-related neurodegenerative processes (including protein aggregation and accumulation, mitochondrial dysfunction, oxidative stress, and neuroinflammation) and how these processes can be mitigated, at least partially, by non-invasive and non-pharmacologic lifestyle interventions aimed at promoting and harnessing neuroplasticity.

In Situ Detection of Neuroinflammation using Multi-cellular 3D Neurovascular Unit-on-a-Chip

The human neurovascular system is a complex network of blood vessels and brain cells that is essential to the proper functioning of the brain. In recent years, researchers have become increasingly interested in the role of this system in developing drugs to treat neuroinflammation. This process is believed to contribute to the development of several neurodegenerative diseases, including Alzheimer's and Parkinson's diseases. While much remains to be learned about the precise mechanisms by which the neurovascular system interacts with the brain and how it can be targeted for therapeutic purposes, this area of research holds great promise for the future of neurology and medicine. Currently, creating neurovascular models begins with animal models, followed by testing on humans in clinical trials. However, the high number of medication failures that pass through animal testing indicates that animal models do not always reflect the outcome of human clinical trials. To overcome the challenges of neurovascular systems and the issues with animal models, we have developed a one-of-a-kind in vitro neurovascular unit-on-a-chip to accurately replicate the in vivo human neurovascular microenvironment. This neuroinflammation-on-a-chip platform has the potential to enhance the current methods of drug development and testing to treat neurodegenerative diseases. By replicating the human neurovascular unit in vitro, a more accurate representation of human physiology can be achieved compared to animal models. The ability to detect pro-inflammatory cytokines in situ and monitor physiological changes, such as barrier function, in real-time can provide an invaluable tool for evaluating the efficacy and safety of drugs. Moreover, using nano-sized graphene oxide for in situ detection of inflammatory responses is an innovative approach that can advance the field of neuroinflammation research. Overall, our developed neuroinflammation-on-a-chip system has the potential to provide a more efficient and effective method for developing drugs for treating neurodegenerative diseases and other central nervous system (CNS) diseases.

β-adrenergic signaling triggers enteric glial reactivity and acute enteric gliosis during surgery

BACKGROUND

Enteric glia contribute to the pathophysiology of various intestinal immune-driven diseases, such as postoperative ileus (POI), a motility disorder and common complication after abdominal surgery. Enteric gliosis of the intestinal muscularis externa (ME) has been identified as part of POI development. However, the glia-restricted responses and activation mechanisms are poorly understood. The sympathetic nervous system becomes rapidly activated by abdominal surgery. It modulates intestinal immunity, innervates all intestinal layers, and directly interfaces with enteric glia. We hypothesized that sympathetic innervation controls enteric glia reactivity in response to surgical trauma.

METHODS

Sox10iCreERT2/Rpl22HA/+ mice were subjected to a mouse model of laparotomy or intestinal manipulation to induce POI. Histological, protein, and transcriptomic analyses were performed to analyze glia-specific responses. Interactions between the sympathetic nervous system and enteric glia were studied in mice chemically depleted of TH+ sympathetic neurons and glial-restricted Sox10iCreERT2/JellyOPfl/+/Rpl22HA/+ mice, allowing optogenetic stimulation of β-adrenergic downstream signaling and glial-specific transcriptome analyses. A laparotomy model was used to study the effect of sympathetic signaling on enteric glia in the absence of intestinal manipulation. Mechanistic studies included adrenergic receptor expression profiling in vivo and in vitro and adrenergic agonism treatments of primary enteric glial cell cultures to elucidate the role of sympathetic signaling in acute enteric gliosis and POI.

RESULTS

With ~ 4000 differentially expressed genes, the most substantial enteric glia response occurs early after intestinal manipulation. During POI, enteric glia switch into a reactive state and continuously shape their microenvironment by releasing inflammatory and migratory factors. Sympathetic denervation reduced the inflammatory response of enteric glia in the early postoperative phase. Optogenetic and pharmacological stimulation of β-adrenergic downstream signaling triggered enteric glial reactivity. Finally, distinct adrenergic agonists revealed β-1/2 adrenoceptors as the molecular targets of sympathetic-driven enteric glial reactivity.

CONCLUSIONS

Enteric glia act as early responders during post-traumatic intestinal injury and inflammation. Intact sympathetic innervation and active β-adrenergic receptor signaling in enteric glia is a trigger of the immediate glial postoperative inflammatory response. With immune-activating cues originating from the sympathetic nervous system as early as the initial surgical incision, adrenergic signaling in enteric glia presents a promising target for preventing POI development.

Nose to brain delivery of Astragaloside IV by β-Asarone modified chitosan nanoparticles for multiple sclerosis therapy

Multiple sclerosis (MS), an autoimmune disease, has been considered an inflammatory disorder of the central nervous system (CNS) with demyelination and axonal damage. Although there are certain first-line therapies to treat MS, their unsatisfactory efficacy is partly due to the limited CNS access after systemic administration. Besides, there is an urgent need to treat MS by enhancing remyelination or neuroprotection, or dampen the activity of microglia. Astragaloside IV (ASI) bears anti-inflammatory, antioxidant, remyelination and neuroprotective activity. While its poor permeability, relatively high molecular weight and low lipophilicity restrict it to reach the brain. Therefore, β-asarone modified ASI loaded chitosan nanoparticles (ASI-βCS-NP) were prepared to enhance the nose-to-brain delivery and therapeutic effects of ASI on EAE mice. The prepared ASI-βCS-NP showed mean size of about 120 nm, and zeta potential from +19 to +25 mV. DiR-βCS-NP was confirmed with good nose-to-brain targeting ability. After intranasal administration, the ASI-βCS-NP significantly reduced behavioral scores, decreased weight loss, suppressed inflammatory infiltration and astrocyte/microglial activation, reduced demyelination and increased remyelination on a mice EAE model. Our findings indicate that ASI-βCS-NP may be a potent treatment for MS after nose-to-brain drug delivery.

The roles of microglia and astrocytes in myelin phagocytosis in the central nervous system

Myelination is an important process in the central nervous system (CNS). Oligodendrocytes (OLs) extend multiple layers to densely sheath on axons, composing the myelin to achieve efficient electrical signal conduction. The myelination during developmental stage maintains a balanced state. However, numerous CNS diseases including neurodegenerative and cerebrovascular diseases cause demyelination and disrupt the homeostasis, resulting in inflammation and white matter deficits. Effective clearance of myelin debris is needed in the region of demyelination, which is a key step for remyelination and tissue regeneration. Microglia and astrocytes are the major resident phagocytic cells in the brain, which may play different or collaborative roles in myelination. Microglia and astrocytes participate in developmental myelination through engulfing excessive unneeded myelin. They are also involved in the clearance of degenerated myelin debris for accelerating remyelination, or engulfing healthy myelin sheath for inhibiting remyelination. This review focuses on the roles of microglia and astrocytes in phagocytosing myelin in the developmental brain and diseased brain. In addition, the interaction between microglia and astrocytes to mediate myelin engulfment is also summarized.

Synapse Dysfunctions in Multiple Sclerosis

Multiple sclerosis (MS) is a chronic neuroinflammatory disease of the central nervous system (CNS) affecting nearly three million humans worldwide. In MS, cells of an auto-reactive immune system invade the brain and cause neuroinflammation. Neuroinflammation triggers a complex, multi-faceted harmful process not only in the white matter but also in the grey matter of the brain. In the grey matter, neuroinflammation causes synapse dysfunctions. Synapse dysfunctions in MS occur early and independent from white matter demyelination and are likely correlates of cognitive and mental symptoms in MS. Disturbed synapse/glia interactions and elevated neuroinflammatory signals play a central role. Glutamatergic excitotoxic synapse damage emerges as a major mechanism. We review synapse/glia communication under normal conditions and summarize how this communication becomes malfunctional during neuroinflammation in MS. We discuss mechanisms of how disturbed glia/synapse communication can lead to synapse dysfunctions, signaling dysbalance, and neurodegeneration in MS.

Advances in the Pathogenesis of Auto-antibody-Induced Cerebellar Synaptopathies

The presence of auto-antibodies that target synaptic machinery proteins was documented recently in immune-mediated cerebellar ataxias. The autoantigens include glutamic acid decarboxylase 65 (GAD65), voltage-gated Ca²⁺ channel (VGCC), metabotropic glutamate receptor type 1 (mGluR1), and glutamate receptor delta (GluRdelta). GAD65 is involved in the synthesis, packaging, and release of GABA, whereas the other three play important roles in the induction of long-term depression (LTD). Thus, the auto-antibodies toward these synaptic molecules likely impair fundamental synaptic machineries involved in unique functions of the cerebellum, potentially leading to the development of cerebellar ataxias (CAs). This concept has been substantiated recently by a series of physiological studies. Anti-GAD65 antibody (Ab) acts on the terminals of inhibitory neurons that suppress GABA release, whereas anti-VGCC, anti-mGluR1, and anti-GluR Abs impair LTD induction. Notably, the mechanisms that link synaptic dysfunction with the manifestations of CAs can be explained by disruption of the "internal models." The latter can be divided into three levels. First, since chained inhibitory neurons shape the output signals through the mechanism of disinhibition/inhibition, impairments of GABA release and LTD distort the conversion process from the "internal model" to the output signals. Second, these antibodies impair the induction of synaptic plasticity, rebound potentiation, and LTD, on Purkinje cells, resulting in loss of restoration and compensation of the distorted "internal models." Finally, the cross-talk between glutamate and microglia/astrocytes could involve a positive feedback loop that accelerates excitotoxicity. This mini-review summarizes the pathophysiological mechanisms and aims to establish the basis of "auto-antibody-induced cerebellar synaptopathies."

Stem Cells Attenuate the Inflammation Crosstalk Between Ischemic Stroke and Multiple Sclerosis: A Review

The immense neuroinflammation induced by multiple sclerosis (MS) promotes a favorable environment for ischemic stroke (IS) development, making IS a deadly complication of MS. The overlapping inflammation in MS and IS is a prelude to the vascular pathology, and an inherent cell death mechanism that exacerbates neurovascular unit (NVU) impairment in the disease progression. Despite this consequence, no therapies focus on reducing IS incidence in patients with MS. To this end, the preclinical and clinical evidence we review here argues for cell-based regenerative medicine that will augment the NVU dysfunction and inflammation to ameliorate IS risk.

Mitofusin 2 confers the suppression of microglial activation by cannabidiol: Insights from in vitro and in vivo models

Currently, there is increasing attention on the regulatory effects of cannabidiol (CBD) on the inflammatory response and the immune system. However, the mechanisms have not yet been completely revealed. Mitofusin 2 (Mfn2) is a mitochondrial fusion protein involved in the inflammatory response. Here, we investigated whether Mfn2 confers the anti-inflammatory effects of CBD. We found that treatment with CBD decreased the levels of tumor necrosis factor α, interleukin 6, inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), and ionized calcium-binding adaptor molecule-1 (Iba1) in lipopolysaccharide (LPS)-challenged microglia. CBD also significantly suppressed the increase in reactive oxygen species (ROS) and the decline of mitochondrial membrane potential in BV-2 cells subjected to LPS. Interestingly, CBD treatment increased the expression of Mfn2, while knockdown of Mfn2 blocked the effect of CBD. By contrast, overexpression of Mfn2 reversed the increase in the levels of iNOS, COX-2, and Iba1 induced by Mfn2 small interfering RNA. In mice challenged with LPS, we found that CBD ameliorated the anxiety responses and cognitive deficits, increased the level of Mfn2, and decreased the expression of Iba1. Since neuro-inflammation and microglial activation are the common events that are observed in the experimental autoimmune encephalomyelitis (EAE) model of multiple sclerosis, we treated EAE mice with CBD. Mice that received CBD showed amelioration of clinical signs, reduced inflammatory response, and increased myelin basic protein level. Most importantly, the adeno-associated virus delivery of short hairpin RNA against Mfn2 reversed the protective effects of CBD. Altogether, these results indicate that Mfn2 is an essential immunomodulator conferring the anti-inflammatory effects of CBD. Our results also shed new light on the mechanisms underlying the protective effects of CBD against inflammatory diseases including multiple sclerosis.

Reactive Astrocytes Derived From Human Induced Pluripotent Stem Cells Suppress Oligodendrocyte Precursor Cell Differentiation

Astrocytes are instrumental in maintaining central nervous system (CNS) homeostasis and responding to injury. A major limitation of studying neurodegenerative diseases like multiple sclerosis (MS) is lack of human pathological specimens obtained during the acute stages, thereby relegating research to post-mortem specimens obtained years after the initiation of pathology. Rodent reactive astrocytes have been shown to be cytotoxic to neurons and oligodendrocytes but may differ from human cells, especially in diseases with genetic susceptibility. Herein, we purified human CD49f+ astrocytes from induced pluripotent stem cells derived from individual patient and control peripheral leukocytes. We compared TNF and IL1α stimulated human reactive astrocytes from seven persons with MS and six non-MS controls and show their transcriptomes are remarkably similar to those described in rodents. The functional effect of astrocyte conditioned media (ACM) was examined in a human oligodendrocyte precursor cell (OPC) line differentiation assay. ACM was not cytotoxic to the OPCs but robustly inhibited the myelin basic protein (MBP) reporter. No differences were seen between MS and control stimulated astrocytes at either the transcript level or in ACM mediated OPC suppression assays. We next used RNAseq to interrogate differentially expressed genes in the OPC lines that had suppressed differentiation from the human ACM. Remarkably, not only was OPC differentiation and myelin gene expression suppressed, but we observed induction of several immune pathways in OPCs exposed to the ACM. These data support the notion that reactive astrocytes can inhibit OPC differentiation thereby limiting their remyelination capacity, and that OPCs take on an immune profile in the context of inflammatory cues.

Astrocytes and Inflammatory T Helper Cells: A Dangerous Liaison in Multiple Sclerosis

Multiple Sclerosis (MS) is a neurodegenerative autoimmune disorder of the central nervous system (CNS) characterized by the recruitment of self-reactive T lymphocytes, mainly inflammatory T helper (Th) cell subsets. Once recruited within the CNS, inflammatory Th cells produce several inflammatory cytokines and chemokines that activate resident glial cells, thus contributing to the breakdown of blood-brain barrier (BBB), demyelination and axonal loss. Astrocytes are recognized as key players of MS immunopathology, which respond to Th cell-defining cytokines by acquiring a reactive phenotype that amplify neuroinflammation into the CNS and contribute to MS progression. In this review, we summarize current knowledge of the astrocytic changes and behaviour in both MS and experimental autoimmune encephalomyelitis (EAE), and the contribution of pathogenic Th1, Th17 and Th1-like Th17 cell subsets, and CD8⁺ T cells to the morphological and functional modifications occurring in astrocytes and their pathological outcomes.

Reactive Astrocytes Contribute to Alzheimer’s Disease-Related Neurotoxicity and Synaptotoxicity in a Neuron-Astrocyte Co-culture Assay

Pathological hallmarks of Alzheimer’s disease (AD) include deposition and accumulation of amyloid- β (Aβ), neurofibrillary tangle formation, and neuronal loss. Pathogenesis of presymptomatic disease stages remains elusive, although studies suggest that the early structural and functional alterations likely occur at neuronal dendritic spines. Presymptomatic alterations may also affect different CNS cell types. However, specific contributions of these cell types as cause or consequence of pathology are difficult to study in vivo. There is a shortage of relatively simple, well-defined, and validated in vitro models that allow a straightforward interpretation of results and recapitulate aspects of pathophysiology. For instance, dissecting the AD-related processes (e.g., neurotoxicity vs. synaptotoxicity) may be difficult with the common cell-based systems such as neuronal cell lines or primary neurons. To investigate and characterize the impact of reactive astrocytes on neuronal morphology in the context of AD-related cues, we modified an in vitro co-culture assay of primary mouse neurons and primary mouse astrocytes based on the so-called Banker “sandwich” co-culture assay. Here, we provide a simple and modular assay with fully differentiated primary mouse neurons to study the paracrine interactions between the neurons and the astrocytes in the co-culture setting. Readouts were obtained from both cell types in our assay. Astrocyte feeder cells were pre-exposed to neuroinflammatory conditions by means of Aβ42, Aβ40, or lipopolysaccharide (LPS). Non-cell autonomous toxic effects of reactive astrocytes on neurons were assessed using the Sholl analysis to evaluate the dendritic complexity, whereas synaptic puncta served as a readout of synaptotoxicity. Here, we show that astrocytes actively contribute to the phenotype of the primary neurons in an AD-specific context, emphasizing the role of different cell types in AD pathology. The cytokine expression pattern was significantly altered in the treated astrocytes. Of note, the impact of reactive astrocytes on neurons was highly dependent on the defined cell ratios. Our co-culture system is modular, of low cost, and allows us to probe aspects of neurodegeneration and neuroinflammation between the two major CNS cell types, neurons, and astrocytes, under well-defined experimental conditions. Our easy-to-follow protocol, including work-flow figures, may also provide a methodological outline to study the interactions of astrocytes and neurons in the context of other diseases in the future.

S100B Protein as a Therapeutic Target in Multiple Sclerosis: The S100B Inhibitor Arundic Acid Protects from Chronic Experimental Autoimmune Encephalomyelitis

S100B is an astrocytic protein behaving at high concentration as a damage-associated molecular pattern molecule. A direct correlation between the increased amount of S100B and inflammatory processes has been demonstrated, and in particular, the inhibitor of S100B activity pentamidine has been shown to ameliorate clinical scores and neuropathologic-biomolecular parameters in the relapsing-remitting experimental autoimmune encephalomyelitis mouse model of multiple sclerosis. This study investigates the effect of arundic acid (AA), a known inhibitor of astrocytic S100B synthesis, in the chronic experimental autoimmune encephalomyelitis, which is another mouse model of multiple sclerosis usually studied. By the daily evaluation of clinical scores and neuropathologic-molecular analysis performed in the spinal cord, we observed that the AA-treated group showed lower severity compared to the vehicle-treated mice, particularly in the early phase of disease onset. We also observed a significant reduction of astrocytosis, demyelination, immune infiltrates, proinflammatory cytokines expression and enzymatic oxidative reactivity in the AA-treated group. Overall, our results reinforce the involvement of S100B in the development of animal models of multiple sclerosis and propose AA targeting the S100B protein as a focused potential drug to be considered for multiple sclerosis treatment.

Clemastine Ameliorates Perioperative Neurocognitive Disorder in Aged Mice Caused by Anesthesia and Surgery

Perioperative neurocognitive disorder (PND) leads to progressive deterioration of cognitive function, especially in aged patients. Demyelination is closely associated with cognitive dysfunction. However, the relationship between PND and demyelination remains unclear. Here we showed that demyelination was related to the pathogenesis of PND. Clemastine, an antihistamine with potency in remyelination, was predicted to have a potential therapeutic effect on PND by next-generation sequencing and bioinformatics in our previous study. In the present study, it was given at 10 mg/kg per day for 2 weeks to evaluate the effects on PND in aged mice. We found that clemastine ameliorated PND and reduced the expression levels of inflammatory factors such as tumor necrosis factor alpha (TNF-α) and interleukin-1 beta (IL-1β). Further investigation suggested clemastine increased the expression of oligodendrocyte transcription factor 2 (OLIG2) and myelin basic protein (MBP) to enhance remyelination by inhibiting the overactivation of the WNT/β-catenin pathway. At the same time, the expression of post-synaptic density protein 95 (PSD95, or DLG4), brain-derived neurotrophic factor (BDNF), synaptosomal-associated protein 25 (SNAP25) and neuronal nuclei (NEUN) were also improved. Our results suggested that clemastine might be a therapy for PND caused by anesthetic and surgical factors in aged patients.

Discovery of Novel Biomarkers for Diagnosing and Predicting the Progression of Multiple Sclerosis Using TMT-Based Quantitative Proteomics

Objective

Here, we aimed to identify protein biomarkers that could rapidly and accurately diagnose multiple sclerosis (MS) using a highly sensitive proteomic immunoassay.

Methods

Tandem mass tag (TMT) quantitative proteomic analysis was performed to determine the differentially expressed proteins (DEPs) in cerebrospinal fluid (CSF) samples collected from 10 patients with MS and 10 non-inflammatory neurological controls (NINCs). The DEPs were analyzed using bioinformatics tools, and the candidate proteins were validated using the ELISA method in another cohort comprising 160 samples (paired CSF and plasma of 40 patients with MS, CSF of 40 NINCs, and plasma of 40 healthy individuals). Receiver operating characteristic (ROC) curves were used to determine the diagnostic potential of this method.

Results

Compared to NINCs, we identified 83 CSF-specific DEPs out of a total of 343 proteins in MS patients. Gene ontology (GO) enrichment analysis revealed that these DEPs are mainly involved in platelet degranulation, negative regulation of proteolysis, and post-translational protein modification. Pathway enrichment analysis revealed that the complement and coagulation cascades, Ras signaling pathway, and PI3K-Akt signaling pathway are the main components. Insulin-like growth factor-binding protein 7 (IGFBP7), insulin-like growth factor 2 (IGF2), and somatostatin (SST) were identified as the potential proteins with high scores, degree, and centrality in the protein-protein interaction (PPI) network. We validated the expression of these three proteins using ELISA. Compared to NINCs, the level of CSF IGFBP7 was significantly upregulated, and the level of CSF SST was significantly downregulated in the MS group.

Conclusion

Our results suggest that SST and IGFBP7 might be associated with the pathogenesis of MS and would be helpful in diagnosing MS. Since IGFBP7 was used to classify relapsing remitting MS (RRMS) and secondary progressive MS (SPMS) patients, therefore, it may act as a potential key marker and therapeutic target in MS.

The Histamine and Multiple Sclerosis Alliance: Pleiotropic Actions and Functional Validation

Multiple sclerosis (MS) is a disease with a resilient inflammatory component caused by accumulation into the CNS of inflammatory infiltrates and macrophage/microglia contributing to severe demyelination and neurodegeneration. While the causes are still in part unclear, key pathogenic mechanisms are the direct loss of myelin-producing cells and/or their impairment caused by the immune system. Proposed etiology includes genetic and environmental factors triggered by viral infections. Although several diagnostic methods and new treatments are under development, there is no curative but only palliative care against the relapsing-remitting or progressive forms of MS. In recent times, there has been a boost of awareness on the role of histamine signaling in physiological and pathological functions of the nervous system. Particularly in MS, evidence is raising that histamine might be directly implicated in the disease by acting at different cellular and molecular levels. For instance, constitutively active histamine regulates the differentiation of oligodendrocyte precursors, thus playing a central role in the remyelination process; histamine reduces the ability of myelin-autoreactive T cells to adhere to inflamed brain vessels, a crucial step in the development of MS; histamine levels are found increased in the cerebrospinal fluid of MS patients. The aim of the present work is to present further proofs about the alliance of histamine with MS and to introduce the most recent and innovative histamine paradigms for therapy. We will report on how a long-standing molecule with previously recognized immunomodulatory and neuroprotective functions, histamine, might still provide a renewed and far-reaching role in MS.

AZD8055 ameliorates experimental autoimmune encephalomyelitis via the mTOR/ROS/NLRP3 pathway

AIMS

Experimental autoimmune encephalomyelitis (EAE), a mouse model of multiple sclerosis (MS), is characterized by immune-mediated demyelination and neurodegeneration. NOD-like receptor protein 3 (NLRP3) inflammasome activation aggravates spinal cord inflammation in EAE. Autophagy is associated with alleviation of systemic inflammation, including that encountered in EAE. However, the effects of autophagy on NLRP3 in EAE are still unclear. Here, we evaluated the effects of the autophagy activator AZD8055 on EAE.

METHODS

EAE model mice were established, histological examination was performed to assess the degree of inflammatory cell infiltration and demyelination. And the levels of autophagy and NLRP3-mediated pyroptosis in spinal cords were assessed. Western blotting and immunofluorescence analyses were performed to evaluate protein expression and localization.

RESULTS

AZD8055 significantly enhanced autophagy in the spinal cords of EAE model mice, coupled with decreased abnormal clinical behavior scores and increased body weights. The degree of inflammatory cell infiltration and demyelination was mild in AZD8055-treated EAE model mice.Meanwhile, the pathway of ROS/NLRP3 was downregulated, and LC3 and NLRP3 were colocalized.

CONCLUSIONS

AZD8055 ameliorated EAE through anti-inflammatory and anti-pyroptosis effects via the mammalian target of mTOR/ROS/NLRP3 pathway. These findings provide insights into the interactions between autophagy and pyroptosis and may facilitate the development of novel treatments for MS.

Neuroglia in Psychiatric Disorders

In the twentieth century, neuropsychiatric disorders have been perceived solely from a neurone-centric point of view, which considers neurones as the key cellular elements of pathological processes. This dogma has been challenged thanks to the better comprehension of the brain functioning, which, even if far from being complete, has revealed the complexity of interactions that exist between neurones and neuroglia. Glial cells represent a highly heterogeneous population of cells of neural (astroglia and oligodendroglia) and non-neural (microglia) origin populating the central nervous system. The variety of glia reflects the innumerable functions that glial cells perform to support functions of the nervous system. Aberrant execution of glial functions contributes to the development of neuropsychiatric pathologies. Arguably, all types of glial cells are implicated in the neuropathology; however, astrocytes have received particular attention in recent years because of their pleiotropic functions that make them decisive in maintaining cerebral homeostasis. This chapter describes the multiple roles of astrocytes in the healthy central nervous system and discusses the diversity of astroglial responses in neuropsychiatric disorders suggesting that targeting astrocytes may represent an effective therapeutic strategy.