The effect of probiotics on immune responses and their therapeutic application: A new treatment option for multiple sclerosis

Multiple sclerosis (MS) is known as a chronic inflammatory disease (CID) that affects the central nervous system and leads to nerve demyelination. However, the exact cause of MS is unknown, but immune system regulation and inhibiting the function of inflammatory pathways may have a beneficial effect on controlling and improving the disease. Studies show that probiotics can alter the gut microbiome, thereby improving and affecting the immune system and inflammatory responses in patients with MS. The results show that probiotics have a good effect on the recovery of patients with MS in humans and animals. The present study investigated the effect of probiotics and possible therapeutic mechanisms of probiotics on immune cells and inflammatory cytokines. This review article showed that probiotics could improve immune cells and inflammatory cytokines in patients with MS and can play an effective role in disease management and control.

Ginsenoside Rg1 promotes remyelination and functional recovery in demyelinating disease by enhancing oligodendrocyte precursor cells-mediated myelin repair

BACKGROUND

Inefficient differentiation of oligodendrocyte precursor cells (OPCs) is one of the significant pathological obstacles of myelin repair and provides an essential therapeutic target against behavioral dysfunction in various neurodegenerative diseases, especially in secondary progressive multiple sclerosis (SPMS). Ginsenoside Rg1 (Rg1) has traditionally been recognized as a protector of neuronal damages, preventing its degeneration.

PURPOSE

We investigated the effects of Rg1 on myelin regeneration-mediated by OPCs and its therapeutic significance in SPMS.

METHODS

A cuprizone (CPZ) model was established and then administered with Rg1 specific for evaluations of functional recovery and remyelination. In vitro, the primary mouse OPCs were isolated and cultured for examining their ability of myelin repair. Furthermore, a chronic experimental autoimmune encephalomyelitis (EAE) model was utilized to assess the therapeutic value on SPMS.

RESULTS

We found that Rg1 promoted functional recovery of the demyelinated mice, including spatial memory, motor function, and anxiety-like behavior. Histologically, Rg1 enhanced myelin-genesis as proven by myelin staining and microstructures of myelin observed by transmission electron microscope. Furthermore, Rg1 significantly increased Olig2+ oligodendrocyte lineage cells in callosum, implying that the pro-remyelination effect of Rg1 was closely correlated to the enhanced differentiation of OPCs. We further demonstrated that Rg1 increased the survival and proliferation of OPCs as well as induced maturation in oligodendrocytes (OLs). Molecular analysis showed that Rg1 transduced the pro-differentiation signaling programmed by the GSK3β/β-Catenin pathway. Notably, relying on its pro-remyelination effects, Rg1 ameliorated severity and histopathology of EAE disease.

CONCLUSION

By paving the way for OPCs differentiation, Rg1 could maintain the integrity of myelin and is a promising candidate for functional recovery in demyelinating diseases.

Gut Microbiota Changes in Experimental Autoimmune Encephalomyelitis and Cuprizone Mice Models

Multiple sclerosis (MS) is a chronic and neurodegenerative disease of the central nervous system (CNS) characterized by the immune mediated attack on axons and the subsequent demyelination. There is growing evidence that the gut microbiota of MS patients is altered; however, the connection between demyelination events and changes in the gut microbiota has not been determined. The objective of the current work was to characterize the microbial dysbiosis in two murine demyelinating models and to study the correlation between them. Concurrently, their suitability as predictors of microbial changes in MS patients was assessed. To this purpose, experimental autoimmune encephalomyelitis (EAE) and cuprizone (CPZ) models were induced in C57BL/6 mice that were monitored for 4 and 9 weeks, respectively. Fecal samples were collected during disease progression. Motor skill performance was evaluated by EAE scale measurement in EAE mice and demyelination by magnetic resonance imaging (MRI) in CPZ ones. EAE and CPZ mice revealed drastic microbial changes according to disease progression, adding a new layer of complexity to the understanding of demyelination and remyelination processes. Besides, the reported microbial changes replicate most of the characteristics that define the potential dysbiosis in MS patients. The controlled environment and stable diet that animals have in research centers offer an exceptional scenario to modify animal's microbiota and provide opportunities to study host microbiota interplay with restrained conditions not achievable in human studies. Nevertheless the slight differences from murine model's and patient's microbiota should be considered in the design of studies aiming to modulate the microbiota.

The role of the brain in the treatment of multiple sclerosis as a connectomopathy

Multiple sclerosis (MS) is an inflammatory disease of the central nervous system (CNS) causing a variety of symptoms. Although MS is recognized by the demyelinating process, the axonal injury can occur from the start of the disease and lead to neurodegenerative process in the disease. Although MS appears to damage the brain locally, the progressive and neurodegenerative nature of the disease indicate the general and global brain damage. Various studies have indicated this global damage at all areas of white and gray matter. Moreover, the earlier stages of mentioned disease can affect the structural and functional brain connections. Demyelinating lesions, which are local at first glance, lead to a global damage to the functional connections of the brain. Therefore, it seems that the brain network or brain connectome are broadly affected by this disease; therefore, MS can be referred as a connectomopathy. The drugs used in this disease all seek to suppress or regulate the immune system, and the human brain has always been considered as a therapeutic target. However, if the brain is generally involved in the disease, so the treatment should be general. In fact, the treatment process should target the connectomopathy. One of the methods that can be used to achieve the mentioned goal is attending to the role of the brain in its treatment.

Effects of the transcription factor Olig1 on the differentiation and remyelination of oligodendrocyte precursor cells after focal cerebral ischemia in rats

The differentiation and maturation of oligodendrocyte precursor cells (OPCs) is important for remyelination in the central nervous system. Nevertheless, this process is often limited and incomplete in ischemic injury. Oligodendrocyte transcription factor 1 (Olig1) is important for the maturation of OPCs and the repair of demyelinated lesions. However, how Olig1 modulates the development of OPCs or the remyelination associated with ischemic injury remains unclear. The present study aimed to examine alterations in OPCs, and the expression of myelin and Olig1, at different time-points after focal cerebral ischemia using immunohistochemistry and western blot techniques to elucidate the role of Olig1 in the maturation of OPCs and remyelination. The present results showed that the expression of Olig1 significantly decreased at 1 day after middle cerebral artery occlusion (MCAO) and returned to normal levels from day 3 to 28. Additionally, Olig1 was found to translocate into the nucleus following ischemia in the brain. The number of OPCs in the ischemic striatum significantly declined at days 1 and 3 following MCAO, and increased at days 7, 14 and 28 compared with the control. The expression of myelin basic protein, a marker of mature oligodendrocytes and myelin, gradually decreased from day 1 to 7 after ischemia and recovered at day 14 and 28; however, the levels were lower than those in the control group. The present results indicated that the restored normal level of Olig1 following ischemia may play an important role in the maturation of OPCs through its translocation into the nucleus, where it may promote the growth and development of myelin under pathological conditions. However, this endogenous recovery mechanism fails to fully repair the demyelinated lesion. The data of the present study may help clinicians understand the expression pattern of Olig1 and its potential role in endogenous remyelination after ischemia, which may have implications for the treatment of diseases that lead to demyelination.

When an octopus has MS: Application of neurophysiology and immunology of octopuses for multiple sclerosis

Multiple sclerosis (MS) is an immune-mediated disease which can cause different symptoms due to the involvement of different regions of the central nervous system (CNS). Although this disease is characterized by the demyelination process, the most important feature of the disease is its degenerative nature. This nature is clinically manifested as progressive symptoms, especially in patients' walking, which can even lead to complete debilitation. Therefore, finding a treatment to prevent the degenerative processes is one of the most important goals in MS studies. To better understand the process and the effect of drugs, scientists use animal models which mostly consisting of mouse, rat, and monkey. In evolutionary terms, octopuses belong to the invertebrates which have many substantial differences with vertebrates. One of these differences is related to the nervous system of these organisms, which is divided into central and peripheral parts. The difference lies in the fact that the main volume of this system expands in the limbs of these organisms instead of their brain. This offers a kind of freedom of action and processing strength in the octopus limbs. Also, the brain of these organisms follows a non-somatotopic model. Although the complex actions of this organism are stimulated by the brain, in contrast to the human brain, this activity is not related to a specific region of the brain; rather the entire brain area of the octopus is activated during a process. Indeed, the brain mapping or the topological perception of a particular action, such as moving the limbs, reflects itself in how that activity is distributed in the octopus brain neurons. Accordingly, various actions are known with varying degrees of activity of neurons in the brain of octopus. Another important feature of octopuses is their ability to regenerate defective tissues including the central and peripheral nervous system. These characteristics raise the question of what features can an octopus show when it is used as an organism to create experimental autoimmune encephalomyelitis (EAE). Can the immune system damage of the octopus brain cause a regeneration process? Will the autonomy of the organs reduce the severity of the symptoms? This article seeks to provide evidence to prove that use of octopuses as laboratory samples for generation of EAE may open up new approaches for researchers to better approach MS.

Co-Ultramicronized Palmitoylethanolamide/Luteolin Facilitates the Development of Differentiating and Undifferentiated Rat Oligodendrocyte Progenitor Cells

Oligodendrocytes, the myelin-producing cells of the central nervous system (CNS), have limited capability to bring about repair in chronic CNS neuroinflammatory demyelinating disorders such as multiple sclerosis (MS). MS lesions are characterized by a compromised pool of undifferentiated oligodendrocyte progenitor cells (OPCs) unable to mature into myelin-producing oligodendrocytes. An attractive strategy may be to replace lost OLs and/or promote their maturation. N-palmitoylethanolamine (PEA) is an endogenous fatty acid amide signaling molecule with anti-inflammatory and neuroprotective actions. Recent studies show a co-ultramicronized composite of PEA and the flavonoid luteolin (co-ultraPEALut) to be more efficacious than PEA in improving outcome in CNS injury models. Here, we examined the effects of co-ultraPEALut on development of OPCs from newborn rat cortex cultured under conditions favoring either differentiation (Sato medium) or proliferation (fibroblast growth factor-2 and platelet-derived growth factor (PDGF)-AA-supplemented serum-free medium ("SFM")). OPCs in SFM displayed high expression of PDGF receptor alpha gene and the proliferation marker Ki-67. In Sato medium, in contrast, OPCs showed rapid decreases in PDGF receptor alpha and Ki-67 expression with a concomitant rise in myelin basic protein (MBP) expression. In these conditions, co-ultraPEALut (10 μM) enhanced OPC morphological complexity and expression of MBP and the transcription factor TCF7l2. Surprisingly, co-ultraPEALut also up-regulated MBP mRNA expression in OPCs in SFM. MBP expression in all cases was sensitive to inhibition of mammalian target of rapamycin. Within the context of strategies to promote endogenous remyelination in MS which focus on enhancing long-term survival of OPCs and stimulating their differentiation into remyelinating oligodendrocytes, co-ultraPEALut may represent a novel pharmacological approach.

Oligodendrocyte precursor cells as a therapeutic target for demyelinating diseases

The mechanisms regulating differentiation of multipotent oligodendrocyte progenitor cells (OPCs) into mature oligodendrocytes (OLs) are critical to our understanding of myelination and remyelination. Following acute demyelination in the central nervous system, adult OPCs migrate to the injury site, differentiate into OLs and generate new myelin sheaths. A common feature of regenerative processes is the fact that remyelination efficiency declines with aging and, accounts for the observation that chronic demyelinating diseases like multiple sclerosis (MS) are characterized by an ineffective remyelination. Without doubt, impairment of OPC differentiation is an essential determinant of the aging effects in remyelination. However, spontaneous remyelination is limited in demyelinating diseases such as MS, owing in part to the failure of adult OPCs to differentiate into myelinating OLs. The inability to restore myelin after injury compromises axon integrity and renders them vulnerable to degeneration. Although the genes that regulate the proliferation and differentiation of OPCs during development have been intensively studied, relatively little is known about the molecular signals that regulate the function of adult OPCs after demyelination. Elucidating the mechanisms regulating OPC differentiation are key to identifying pharmacological targets for remyelination-enhancing therapy. This review will discuss OPC biology, myelination, and possible pharmacological targets for promoting the differentiation of OPCs as a strategy to enhance remyelination, including the potential for nanoscale delivery.

Repair strategies for multiple sclerosis: challenges, achievements and perspectives

PURPOSE OF REVIEW

Despite major progress in multiple sclerosis (MS) treatment, to date, accumulation of irreversible clinical disability is not sufficiently prevented with immunotherapies. In this context, repair strategies aimed at reducing axonal damage are becoming a very active field of preclinical and clinical research.

RECENT FINDINGS

Improved understanding of the cellular and molecular mechanisms of myelin repair, together with the emergence of new therapeutic candidates are paving the way for novel therapeutic strategies in MS. In parallel, there is a very active development of imaging methods to assess lesions ongoing remyelination that are crucially needed to evaluate therapeutic efficacy.

SUMMARY

The current development of a very dynamic and multidisciplinary research on remyelination should accelerate the development of myelin repair strategies in MS, to prevent disability progression.

Oligodendrocyte Progenitor Cell Cultures: A Model to Screen Neurotrophic Compounds for Myelin Repair

The protocol presented in this chapter covers the application of rat cortical oligodendrocyte progenitor cells cultured under conditions of differentiation for the evaluation of agents with potential trophic activity, that is, which are capable of promoting maturation under such conditions. As an example we have chosen a co-ultramicronized N-palmitoylethanolamine/luteolin composite, a formulation described in the literature as possessing anti-inflammatory, neuroprotective, and neuroregenerative actions.

Remyelinating Pharmacotherapies in Multiple Sclerosis

We have witnessed major successes in the development of effective immunomodulatory therapies capable of reducing adaptive immune-mediated myelin damage in MS over the last 30 years. However, until it is possible to prevent MS or initiate treatment before it has already caused lesions there is a need to repair myelin damage to prevent further axonal loss. The past decade has brought remarkable advances in our understanding of oligodendrocyte biology and the related search for remyelinating therapies in humans. In this review, we first outline the basic biology of central nervous system myelin and remyelination, including a discussion of the major identified pathways and targets that might help yield CNS remyelinating drugs. In conjunction, we provide an overview of techniques that have helped identify compounds capable of promoting oligodendrocyte precursor cell differentiation and myelination. This includes the methods for both initial in vitro screening and subsequent in vivo confirmation of the target. We then review methods proposed to quantify human remyelination in vivo, including visual evoked potentials and putative imaging modalities. As the remyelination era approaches, with the announcement of the first positive trial in remyelination, we are now tasked with answering new questions regarding patient-specific factors (e.g., age) that may influence the extent and optimal therapeutic window for remyelination.

SCT: Spinal Cord Toolbox, an open-source software for processing spinal cord MRI data

For the past 25 years, the field of neuroimaging has witnessed the development of several software packages for processing multi-parametric magnetic resonance imaging (mpMRI) to study the brain. These software packages are now routinely used by researchers and clinicians, and have contributed to important breakthroughs for the understanding of brain anatomy and function. However, no software package exists to process mpMRI data of the spinal cord. Despite the numerous clinical needs for such advanced mpMRI protocols (multiple sclerosis, spinal cord injury, cervical spondylotic myelopathy, etc.), researchers have been developing specific tools that, while necessary, do not provide an integrative framework that is compatible with most usages and that is capable of reaching the community at large. This hinders cross-validation and the possibility to perform multi-center studies. In this study we introduce the Spinal Cord Toolbox (SCT), a comprehensive software dedicated to the processing of spinal cord MRI data. SCT builds on previously-validated methods and includes state-of-the-art MRI templates and atlases of the spinal cord, algorithms to segment and register new data to the templates, and motion correction methods for diffusion and functional time series. SCT is tailored towards standardization and automation of the processing pipeline, versatility, modularity, and it follows guidelines of software development and distribution. Preliminary applications of SCT cover a variety of studies, from cross-sectional area measures in large databases of patients, to the precise quantification of mpMRI metrics in specific spinal pathways. We anticipate that SCT will bring together the spinal cord neuroimaging community by establishing standard templates and analysis procedures.

Increase of Alternatively Activated Antigen Presenting Cells in Active Experimental Autoimmune Encephalomyelitis

The importance of CD11c⁺ antigen-presenting cells (APCs) in the pathogenesis of experimental autoimmune encephalomyelitis (EAE) is well accepted and the gate keeper function of perivascular CD11c⁺ APCs has been demonstrated. CD11c can be expressed by APCs from external sources or by central nervous system (CNS) resident APCs such as microglia. Yet, changes in the gene expression pattern of CNS CD11c⁺ APCs during disease are still unclear and differentially expressed genes might play a decisive role in EAE progression. Due to their low numbers in the diseased brain and due to the absence of considerable numbers in the healthy CNS, analysis of CNS CD11c⁺ cells is technically difficult. To ask whether the CD11c⁺ APC population contributes to remission of EAE disease, we used Illumina deep mRNA sequencing (RNA-Seq) and quantitative real time polymerase chain reaction (qRT-PCR) analyses to identify the transcriptome of CD11c⁺ APCs during disease course. We identified a battery of genes that were significantly regulated during the exacerbation of the disease compared to remission and relapse. Three of these genes, Arginase-1, Chi3l3 and Ms4a8a, showed a higher expression at the exacerbation than at later time points during the disease, both in SJL/J and in C57BL/6 mice, and could be attributed to alternatively activated APCs. Expression of Arginase-1, Chi3l3 and Ms4a8a genes was linked to the disease phase of EAE rather than to disease score. Expression of these genes suggested that APCs resembling alternatively activated macrophages are involved during the first wave of neuroinflammation and can be directly associated with the disease progress.

Dendritic cells as therapeutic targets in neuroinflammation

Multiple sclerosis (MS) is the most common chronic inflammatory demyelinating disorder of the central nervous system characterized by infiltration of immune cells and progressive damage to myelin sheaths and neurons. There is still no cure for the disease, but drug regimens can reduce the frequency of relapses and slightly delay progression. Myeloid cells or antigen-presenting cells (APCs) such as dendritic cells (DC), macrophages, and resident microglia, are key players in both mediating immune responses and inducing immune tolerance. Mounting evidence indicates a contribution of these myeloid cells to the pathogenesis of multiple sclerosis and to the effects of treatment, the understanding of which might provide strategies for more potent novel therapeutic interventions. Here, we review recent insights into the role of APCs, with specific focus on DCs in the modulation of neuroinflammation in MS.

Co-ultramicronized Palmitoylethanolamide/Luteolin Promotes the Maturation of Oligodendrocyte Precursor Cells

Oligodendrocytes have limited ability to repair the damage to themselves or to other nerve cells, as seen in demyelinating diseases like multiple sclerosis. An important strategy may be to replace the lost oligodendrocytes and/or promote the maturation of undifferentiated oligodendrocyte precursor cells (OPCs). Recent studies show that a composite of co-ultramicronized N-palmitoylethanolamine (PEA) and luteolin (co-ultramicronized PEA/luteolin, 10:1 by mass) is efficacious in improving outcome in experimental models of spinal cord and traumatic brain injuries. Here, we examined the ability of co-ultramicronized PEA/luteolin to promote progression of OPCs into a more differentiated phenotype. OPCs derived from newborn rat cortex were placed in culture and treated the following day with 10 μM co-ultramicronized PEA/luteolin. Cells were collected 1, 4 and 8 days later and analyzed for expression of myelin basic protein (MBP). qPCR and Western blot analyses revealed a time-dependent increase in expression of both mRNA for MBP and MBP content, along with an increased expression of genes involved in lipid biogenesis. Ultramicronized PEA or luteolin, either singly or in simple combination, were ineffective. Further, co-ultramicronized PEA/luteolin promoted morphological development of OPCs and total protein content without affecting proliferation. Co-ultramicronized PEA/luteolin may represent a novel pharmacological strategy to promote OPC maturation.

Positron-emission tomography molecular imaging of glia and myelin in drug discovery for multiple sclerosis

INTRODUCTION

Therapies acting on glial cells are being explored for new drug development for multiple sclerosis. Molecular imaging using positron-emission tomography (PET) could address relevant questions in early phase clinical trials.

AREAS COVERED

In this article, the authors critically review human PET methods that can be applied in specialised centres for imaging activated microglia and astrocytes and myelin.

EXPERT OPINION

Strengths of PET lie in the molecular selectivity, sensitivity and potential for absolute quantitation. Even now, translocator protein PET radioligands could be used in exploratory studies for interventions targeting brain microglial activation. The clinical and neuropathological meaningfulness of signal from PET radioligands reporting on astrocyte activation through cellular expression of either monoamine oxidase B or the I2-imidazoline receptor or metabolism of [(11)C]acetate can now explored. [(11)C] N-methyl-4,4'-diaminostilbene, a PET marker for myelin, could soon enter first human trials. However, use of any of these PET glial markers demands a well-focused hypothesis and a commitment to validation in the context of use. Enhanced access to these radioligands, standardisation of analyses and lowering the costs of using them are needed if their full promise is to be realised.