Demyelination causes synaptic alterations in hippocampi from multiple sclerosis patients

Regional hippocampal vulnerability in early multiple sclerosis: Dynamic pathological spreading from dentate gyrus to CA1

BACKGROUND

Whether hippocampal subfields are differentially vulnerable at the earliest stages of multiple sclerosis (MS) and how this impacts memory performance is a current topic of debate.

METHOD

We prospectively included 56 persons with clinically isolated syndrome (CIS) suggestive of MS in a 1-year longitudinal study, together with 55 matched healthy controls at baseline. Participants were tested for memory performance and scanned with 3 T MRI to assess the volume of 5 distinct hippocampal subfields using automatic segmentation techniques.

RESULTS

At baseline, CA4/dentate gyrus was the only hippocampal subfield with a volume significantly smaller than controls (p < .01). After one year, CA4/dentate gyrus atrophy worsened (-6.4%, p < .0001) and significant CA1 atrophy appeared (both in the stratum-pyramidale and the stratum radiatum-lacunosum-moleculare, -5.6%, p < .001 and -6.2%, p < .01, respectively). CA4/dentate gyrus volume at baseline predicted CA1 volume one year after CIS (R²  = 0.44 to 0.47, p < .001, with age, T2 lesion-load, and global brain atrophy as covariates). The volume of CA4/dentate gyrus at baseline was associated with MS diagnosis during follow-up, independently of T2-lesion load and demographic variables (p < .05). Whereas CA4/dentate gyrus volume was not correlated with memory scores at baseline, CA1 atrophy was an independent correlate of episodic verbal memory performance one year after CIS (ß = 0.87, p < .05).

CONCLUSION

The hippocampal degenerative process spread from dentate gyrus to CA1 at the earliest stage of MS. This dynamic vulnerability is associated with MS diagnosis after CIS and will ultimately impact hippocampal-dependent memory performance.

Myelin injury induces axonal transport impairment but not AD-like pathology in the hippocampus of cuprizone-fed mice

Both multiple sclerosis (MS) and Alzheimer's disease (AD) are progressive neurological disorders with myelin injury and memory impairment. However, whether myelin impairment could cause AD-like neurological pathology remains unclear. To explore neurological pathology following myelin injury, we assessed cognitive function, the expression of myelin proteins, axonal transport-associated proteins, axonal structural proteins, synapse-associated proteins, tau and beta amyloid and the status of neurons, using the cuprizone mouse model of demyelination. We found the mild impairment of learning ability in cuprizone-fed mice and the decreased expression of myelin basic protein (MBP) in the hippocampus. And anti-LINGO-1 improved learning ability and partly restored MBP level. Furthermore, we also found kinesin light chain (KLC), neurofilament light chain (NFL) and neurofilament heavy chain (NF200) were declined in demyelinated hippocampus, which could be partly improved by treatment with anti-LINGO-1. However, we did not observe the increased expression of beta amyloid, hyperphosphorylation of tau and loss of neurons in demyelinated hippocampus. Our results suggest that demyelination might lead to the impairment of neuronal transport, but not cause increased level of hyperphosphorylated tau and beta amyloid. Our research demonstrates remyelination might be an effective pathway to recover the function of neuronal axons and cognition in MS.

The importance of studying sex differences in disease: The example of multiple sclerosis

To date, scientific research has often focused on one sex, with assumptions that study of the other sex would yield similar results. However, many diseases affect males and females differently. The sex of a patient can affect the risk for both disease susceptibility and progression. Such differences can be brought to the laboratory bench to be investigated, potentially bringing new treatments back to the clinic. This method of research, known as a "bedside to bench to bedside" approach, has been applied to studying sex differences in multiple sclerosis (MS). Females have greater susceptibly to MS, while males have worse disease progression. These two characteristics of the disease are influenced by the immune system and the nervous system, respectively. Thus, sex differences in each system must be studied. Personalized medicine has been at the forefront of research recently, and studying sex differences in disease fits with this initiative. This review will discuss the known sex differences in MS and highlight how investigating them can lead to new insights and potential treatments for both men and women. © 2016 Wiley Periodicals, Inc.

Inhibition of GABA A receptor improved spatial memory impairment in the local model of demyelination in rat hippocampus

Cognitive impairment and memory deficit are common features in multiple Sclerosis patients. The mechanism of memory impairment in MS is unknown, but neuroimaging studies suggest that hippocampal demyelination is involved. Here, we investigate the role of GABA A receptor on spatial memory in the local model of hippocampal demyelination. Demyelination was induced in male Wistar rats by bilaterally injection of lysophosphatidylcholine (LPC) 1% into the CA1 region of the hippocampus. The treatment groups were received daily intraventricular injection of bicuculline (0.025, 0.05μg/2μl/animal) or muscimol (0.1, 0.2μg/2μl/animal) 5days after LPC injection. Morris Water Maze was used to evaluate learning and memory in rats. We used Luxol fast blue staining and qPCR to assess demyelination extention and MBP expression level respectively. Immunohistochemistry (IHC) for CD45 and H&E staining were performed to assess inflammatory cells infiltration. Behavioral study revealed that LPC injection in the hippocampus impaired learning and memory function. Animals treated with both doses of bicuculline improved spatial learning and memory function; however, muscimol treatment had no effect. Histological and MBP expression studies confirmed that demylination in LPC group was maximal. Bicuculline treatment significantly reduced demyelination extension and increased the level of MBP expression. H&E and IHC results showed that bicuculline reduced inflammatory cell infiltration in the lesion site. Bicuculline improved learning and memory and decreased demyelination extention in the LPC-induced hippocampal demyelination model. We conclude that disruption of GABAergic homeostasis in hippocampal demyelination context may be involved in memory impairment with the implications for both pathophysiology and therapy.

DNA methylation in demyelinated multiple sclerosis hippocampus

Multiple Sclerosis (MS) is an immune-mediated demyelinating disease of the human central nervous system (CNS). Memory impairments and hippocampal demyelination are common features in MS patients. Our previous data have shown that demyelination alters neuronal gene expression in the hippocampus. DNA methylation is a common epigenetic modifier of gene expression. In this study, we investigated whether DNA methylation is altered in MS hippocampus following demyelination. Our results show that mRNA levels of DNA methyltransferase were increased in demyelinated MS hippocampus, while de-methylation enzymes were decreased. Comparative methylation profiling identify hypo-methylation within upstream sequences of 6 genes and hyper-methylation of 10 genes in demyelinated MS hippocampus. Genes identified in the current study were also validated in an independent microarray dataset generated from MS hippocampus. Independent validation using RT-PCR revealed that DNA methylation inversely correlated with mRNA levels of the candidate genes. Queries across cell-specific databases revealed that a majority of the candidate genes are expressed by astrocytes and neurons in mouse and human CNS. Taken together, our results expands the list of genes previously identified in MS hippocampus and establish DNA methylation as a mechanism of altered gene expression in MS hippocampus.

miR-142-3p Is a Key Regulator of IL-1β-Dependent Synaptopathy in Neuroinflammation

MicroRNAs (miRNA) play an important role in post-transcriptional gene regulation of several physiological and pathological processes. In multiple sclerosis (MS), a chronic inflammatory and degenerative disease of the CNS, and in its mouse model, the experimental autoimmune encephalomyelitis (EAE), miRNA dysregulation has been mainly related to immune system dysfunction and white matter (WM) pathology. However, little is known about their role in gray matter pathology. Here, we explored miRNA involvement in the inflammation-driven alterations of synaptic structure and function, collectively known as synaptopathy, a neuropathological process contributing to excitotoxic neurodegeneration in MS/EAE. Particularly, we observed that miR-142-3p is increased in the CSF of patients with active MS and in EAE brains. We propose miR-142-3p as a molecular mediator of the IL-1β-dependent downregulation of the glial glutamate-aspartate transporter (GLAST), which causes an enhancement of the glutamatergic transmission in the EAE cerebellum. The synaptic abnormalities mediated by IL-1β and the clinical and neuropathological manifestations of EAE disappeared in miR-142 knock-out mice. Furthermore, we observed that in vivo miR-142-3p inhibition, either by a preventive and local treatment or by a therapeutic and systemic strategy, abolished IL-1β- and GLAST-dependent synaptopathy in EAE wild-type mice. Consistently, miR-142-3p was responsible for the glutamatergic synaptic alterations caused by CSF of patients with MS, and CSF levels of miR-142-3p correlated with prospective MS disease progression. Our findings highlight miR-142-3p as key molecular player in IL-1β-mediated synaptic dysfunction, possibly leading to excitotoxic damage in both EAE and MS diseases. Inhibition of miR-142-3p could be neuroprotective in MS.

SIGNIFICANCE STATEMENT

Current studies suggest the role of glutamate excitotoxicity in the development and progression of multiple sclerosis (MS) and of its mouse model experimental autoimmune encephalomyelitis (EAE). The molecular mechanisms linking inflammation and synaptic alterations in MS/EAE are still unknown. Here, we identified miR-142-3p as a determinant molecular actor in inflammation-dependent synaptopathy typical of both MS and EAE. miR-142-3p was upregulated in the CSF of MS patients and in EAE cerebellum. Inhibition of miR-142-3p, locally in EAE brain and in a MS chimeric ex vivo model, recovered glutamatergic synaptic enhancement typical of EAE/MS. We proved that miR-142-3p promoted the IL-1β-dependent glutamate dysfunction by targeting glutamate-aspartate transporter (GLAST), a crucial glial transporter involved in glutamate homeostasis. Finally, we suggest miR-142-3p as a negative prognostic factor in patients with relapsing-remitting multiple sclerosis.

Pattern separation performance is decreased in patients with early multiple sclerosis

BACKGROUND

Hippocampal-dependent memory impairment is frequent and occurs early during the course of multiple sclerosis (MS). While mechanisms responsible for episodic memory dysfunction in patients with MS remain largely unknown, dentate gyrus structure has been suggested as particularly vulnerable at the early stage of the disease. If true, we hypothesized that the pattern separation component of episodic memory (a function known to be critically dependent to dentate gyrus function) would be impaired in patients with early MS (PweMS).

METHODS

Thirty eight participants (19 PweMS and 19 healthy controls matched on age, gender and education level) were tested with a behavioral pattern separation task and also for information processing speed and visuospatial episodic memory.

RESULTS

We report a significant decrease in pattern separation performance in PweMS compared to healthy controls (27.07 vs. 40.01, p = .030 after Holm-Bonferroni correction, d = 1.02) together with a significantly higher pattern completion rate (56.11 vs. 40.95, p = .004 after Holm-Bonferroni correction, d = 1.07) while no difference was found among groups for information processing speed and "global" visuospatial episodic memory regarding learning, long-term recall or recognition.

CONCLUSION

Our results suggest that behavioral pattern separation task can detect subtle memory decline in patients with MS and argue for early dentate gyrus dysfunction during the course of the disease.

Effect of Neuroinflammation on Synaptic Organization and Function in the Developing Brain: Implications for Neurodevelopmental and Neurodegenerative Disorders

The brain is a plastic organ where both the intrinsic CNS milieu and extrinsic cues play important roles in shaping and wiring neural connections. The perinatal period constitutes a critical time in central nervous system development with extensive refinement of neural connections, which are highly sensitive to fetal and neonatal compromise, such as inflammatory challenges. Emerging evidence suggests that inflammatory cells in the brain such as microglia and astrocytes are pivotal in regulating synaptic structure and function. In this article, we will review the role of glia cells in synaptic physiology and pathophysiology, including microglia-mediated elimination of synapses. We propose that activation of the immune system dynamically affects synaptic organization and function in the developing brain. We will discuss the role of neuroinflammation in altered synaptic plasticity following perinatal inflammatory challenges and potential implications for neurodevelopmental and neurodegenerative disorders.

Synaptic pathology in the cerebellar dentate nucleus in chronic multiple sclerosis

In multiple sclerosis, cerebellar symptoms are associated with clinical impairment and an increased likelihood of progressive course. Cortical atrophy and synaptic dysfunction play a prominent role in cerebellar pathology and although the dentate nucleus is a predilection site for lesion development, structural synaptic changes in this region remain largely unexplored. Moreover, the mechanisms leading to synaptic dysfunction have not yet been investigated at an ultrastructural level in multiple sclerosis. Here, we report on synaptic changes of dentate nuclei in post-mortem cerebella of 16 multiple sclerosis patients and eight controls at the histological level as well as an electron microscopy evaluation of afferent synapses of the cerebellar dentate and pontine nuclei of one multiple sclerosis patient and one control. We found a significant reduction of afferent dentate synapses in multiple sclerosis, irrespective of the presence of demyelination, and a close relationship between glial processes and dentate synapses. Ultrastructurally, we show autophagosomes containing degradation products of synaptic vesicles within dendrites, residual bodies within intact-appearing axons and free postsynaptic densities opposed to astrocytic appendages. Our study demonstrates loss of dentate afferent synapses and provides, for the first time, ultrastructural evidence pointing towards neuron-autonomous and neuroglia-mediated mechanisms of synaptic degradation in chronic multiple sclerosis.

Selective dentate gyrus disruption causes memory impairment at the early stage of experimental multiple sclerosis

Memory impairment is an early and disabling manifestation of multiple sclerosis whose anatomical and biological substrates are still poorly understood. We thus investigated whether memory impairment encountered at the early stage of the disease could be explained by a differential vulnerability of particular hippocampal subfields. By using experimental autoimmune encephalomyelitis (EAE), a mouse model of multiple sclerosis, we identified that early memory impairment was associated with selective alteration of the dentate gyrus as pinpointed in vivo with diffusion-tensor-imaging (DTI). Neuromorphometric analyses and electrophysiological recordings confirmed dendritic degeneration, alteration in glutamatergic synaptic transmission and impaired long-term synaptic potentiation selectively in the dentate gyrus, but not in CA1, together with a more severe pattern of microglial activation in this subfield. Systemic injections of the microglial inhibitor minocycline prevented DTI, morphological, electrophysiological and behavioral impairments in EAE-mice. Furthermore, daily infusions of minocycline specifically within the dentate gyrus were sufficient to prevent memory impairment in EAE-mice while infusions of minocycline within CA1 were inefficient. We conclude that early memory impairment in EAE is due to a selective disruption of the dentate gyrus associated with microglia activation. These results open new pathophysiological, imaging, and therapeutic perspectives for memory impairment in multiple sclerosis.

Neurodegeneration in multiple sclerosis and neuromyelitis optica

Multiple sclerosis (MS) and neuromyelitis optica (NMO) are autoimmune demyelinating diseases of the central nervous system (CNS), having distinct immunological and pathological features. They have two pathogenic components, 'inflammation' and 'neurodegeneration', with different degrees of severity and pathogenetic mechanisms. The target antigen of autoimmunity in NMO is the water channel aquaporin-4 (AQP4), and antibodies directed against this antigen result in astrocyte damage. MS is a disease primarily affecting myelin and oligodendrocytes, but thus far, no MS-specific autoantigen has been identified. The distinct inflammatory processes in these diseases may trigger cascades of events leading to disease-specific neurodegeneration. Damage of the CNS tissue appears to be amplified by mechanisms that are in part shared by the two conditions and involve oxidative burst activation in microglia/macrophages, mitochondrial damage and axonal energy failure, Wallerian degeneration and meningeal inflammation. However, they appear to differ regarding the nature of the inflammatory response, the type and extent of cortical injury, and the type of astrocyte reaction and damage. Here, we provide a detailed comparison of the pathology between MS and NMO, which may help to define shared and disease-specific mechanisms of neurodegeneration in these diseases.

Multiple sclerosis animal models: a clinical and histopathological perspective

There is a broad consensus that multiple sclerosis (MS) represents more than an inflammatory disease: it harbors several characteristic aspects of a classical neurodegenerative disorder, that is, damage to axons, synapses and nerve cell bodies. While we are equipped with appropriate therapeutic options to prevent immune-cell driven relapses, effective therapeutic options to prevent the progressing neurodegeneration are still missing. In this review article, we will discuss to what extent pathology of the progressive disease stage can be modeled in MS animal models. While acute and relapsing-remitting forms of experimental autoimmune encephalomyelitis (EAE), which are T cell dependent, are aptly suited to model relapsing-remitting phases of MS, other EAE models, especially the secondary progressive EAE stage in Biozzi ABH mice is better representing the secondary progressive phase of MS, which is refractory to many immune therapies. Besides EAE, the cuprizone model is rapidly gaining popularity to study the formation and progression of demyelinating CNS lesions without T cell involvement. Here, we discuss these two non-popular MS models. It is our aim to point out the pathological hallmarks of MS, and discuss which pathological aspects of the disease can be best studied in the various animal models available.

Cognition and fatigue in patients with relapsing multiple sclerosis treated by subcutaneous interferon β-1a: an observational study SKORE

BACKGROUND

Multiple sclerosis (MS) is a chronic autoimmune disease of the central nervous system, which often causes progressive neurological disability. In addition to motor and sensory dysfunction, cognitive decline and fatigue are frequent manifestations of the disease. Fatigue is probably the most common symptom, with up to 90% of MS individuals reporting fatigue at some point. Cognitive impairment affects about 50% of patients and may be present at all MS stages. The aim of this observational study was to evaluate changes in cognition, fatigue, and disability status in 300 relapsing-remitting MS (RRMS) patients, treated with subcutaneous (sc) interferon (IFN) β-1a over 2 years.

METHODS

The study was designed as an observational, multicentre, prospective, single-arm, phase IV study carried out in 13 MS centres in the Czech Republic. Cognition status was assessed using the Paced Auditory Serial Addition Task (PASAT), fatigue using the Fatigue Descriptive Scale (FDS), and disability using the Expanded Disability Status Scale (EDSS), at baseline, and after 6, 12 and 24 months. The percentage of patients with changed versus stable cognition, fatigue status and disability was calculated at each time point and the changes in these scores were evaluated.

RESULTS

The proportion of patients with cognitive improvement was higher compared with those with a stable or decreased PASAT scores at all time points, and the average cognitive performance improved during the follow-up period. Also the proportion of patients with stable or improved fatigue and EDSS scores was higher compared with those in which FDS or EDSS scores declined, this was found at all time points of the analysed sample. However, the direct effect of IFN β-1a on cognition and fatigue cannot be concluded from this study.

CONCLUSIONS

The results of this observational study have demonstrated a stable or improved cognitive performance, fatigue status, and disability level in the majority of RRMS patients treated with sc IFN β-1a over a two-year follow-up period, in a real life setting, in the Czech Republic.

IL-17 signalling in astrocytes promotes glutamate excitotoxicity: Indications for the link between inflammatory and neurodegenerative events in multiple sclerosis

OBJECTIVE

Th-17 cells have been exclusively referred to inflammatory events in multiple sclerosis (MS), while their importance in the development of glutamate excitotoxicity and the consequent neurodegeneration has been a completely unexplored concept. Accordingly, the objective of our study was to assess IL-17A effect on astrocyte ability to metabolize and release glutamate, considering that astrocytes had the central role in glutamate homeostasis.

METHODS

By using primary rat astrocyte cultures, astrocyte ability to uptake glutamate was estimated by the alterations of glutamate transporters (GLAST and GLT-1) expression, whereas changes in glutamine synthetase expression were used to estimate the ability to metabolize glutamate. Gene expression was determined by real time polymerase chain reaction (rtPCR). IL-17A effect on astrocyte ability to produce glutamate was investigated directly, by measuring the level of released glutamate using high performance liquid chromatography (HPLC).

RESULTS

Lower concentrations of IL-17A reduced the expressions of both glutamate transporters and glutamine synthetase; however, this effect was lost when IL-17A was applied in a higher dose. IL-17A did not significantly modify glutamate release from astrocyte in basal conditions, but following Ca²⁺ stimulation, as well as Ca²⁺ removal from the culture medium, IL-17A stimulated glutamate release in dose-dependent manner.

CONCLUSION

Together, these results support that IL-17A could promote glutamate excitotoxicity by decreasing astrocyte ability to uptake and convert glutamate to non-toxic glutamine, but also by stimulating Ca²⁺ dependent glutamate release. Such interactions between IL-17A and glutamate excitotoxicity implicate the potential link between inflammation and neurodegeneration during MS pathogenesis, and identify astrocytes as a potential target in achieving neuroprotective effects in MS.

Neuroinflammatory component of gray matter pathology in multiple sclerosis

OBJECTIVE

In multiple sclerosis (MS), using simultaneous magnetic resonance-positron emission tomography (MR-PET) imaging with ¹¹ C-PBR28, we quantified expression of the 18kDa translocator protein (TSPO), a marker of activated microglia/macrophages, in cortex, cortical lesions, deep gray matter (GM), white matter (WM) lesions, and normal-appearing WM (NAWM) to investigate the in vivo pathological and clinical relevance of neuroinflammation.

METHODS

Fifteen secondary-progressive MS (SPMS) patients, 12 relapsing-remitting MS (RRMS) patients, and 14 matched healthy controls underwent ¹¹ C-PBR28 MR-PET. MS subjects underwent 7T T2*-weighted imaging for cortical lesion segmentation, and neurological and cognitive evaluation. ¹¹ C-PBR28 binding was measured using normalized 60- to 90-minute standardized uptake values and volume of distribution ratios.

RESULTS

Relative to controls, MS subjects exhibited abnormally high ¹¹ C-PBR28 binding across the brain, the greatest increases being in cortex and cortical lesions, thalamus, hippocampus, and NAWM. MS WM lesions showed relatively modest TSPO increases. With the exception of cortical lesions, where TSPO expression was similar, ¹¹ C-PBR28 uptake across the brain was greater in SPMS than in RRMS. In MS, increased ¹¹ C-PBR28 binding in cortex, deep GM, and NAWM correlated with neurological disability and impaired cognitive performance; cortical thinning correlated with increased thalamic TSPO levels.

INTERPRETATION

In MS, neuroinflammation is present in the cortex, cortical lesions, deep GM, and NAWM, is closely linked to poor clinical outcome, and is at least partly linked to neurodegeneration. Distinct inflammatory-mediated factors may underlie accumulation of cortical and WM lesions. Quantification of TSPO levels in MS could prove to be a sensitive tool for evaluating in vivo the inflammatory component of GM pathology, particularly in cortical lesions. Ann Neurol 2016;80:776-790.

Hippocampal microstructural damage correlates with memory impairment in clinically isolated syndrome suggestive of multiple sclerosis

OBJECTIVE

We investigated whether diffusion tensor imaging (DTI) could reveal early hippocampal damage and clinically relevant correlates of memory impairment in persons with clinically isolated syndrome (CIS) suggestive of multiple sclerosis (MS).

METHODS

A total of 37 persons with CIS, 32 with MS and 36 controls prospectively included from 2011 to 2014 were tested for cognitive performances and scanned with 3T-magnetic resonance imaging (MRI) to assess volumetric and DTI changes within the hippocampus, whole brain volume and T2-lesion load.

RESULTS

While there was no hippocampal atrophy in the CIS group, hippocampal fractional anisotropy (FA) was significantly decreased compared to controls. Decrease in hippocampal FA together with increased mean diffusivity (MD) was even more prominent in MS patients. In CIS, hippocampal MD was correlated with episodic verbal memory performance ( r = -0.57, p = 0.0002 and odds ratio (OR) = 0.058, 95% confidence interval (CI) = 0.0057-0.59, p = 0.016 adjusted for age, gender, depression and T2-lesion load), but not with cognitive tasks unrelated to hippocampal functions. Hippocampal MD was the only variable discriminating memory-impaired from memory-preserved persons with CIS (area under the curve (AUC) = 0.77, sensitivity = 90.0%, specificity = 70.3%, positive predictive value (PPV) = 52.9%, negative predictive value (NPV) = 95.0%).

CONCLUSION

DTI alterations within the hippocampus might reflect early neurodegenerative processes that are correlated with episodic memory performance, discriminating persons with CIS according to their memory status.

Mechanisms of glutamate toxicity in multiple sclerosis: biomarker and therapeutic opportunities

Research advances support the idea that excessive activation of the glutamatergic pathway plays an important part in the pathophysiology of multiple sclerosis. Beyond the well established direct toxic effects on neurons, additional sites of glutamate-induced cell damage have been described, including effects in oligodendrocytes, astrocytes, endothelial cells, and immune cells. Such toxic effects could provide a link between various pathological aspects of multiple sclerosis, such as axonal damage, oligodendrocyte cell death, demyelination, autoimmunity, and blood-brain barrier dysfunction. Understanding of the mechanisms underlying glutamate toxicity in multiple sclerosis could help in the development of new approaches for diagnosis, treatment, and follow-up in patients with this debilitating disease. While several clinical trials of glutamatergic modulators have had disappointing results, our growing understanding suggests that there is reason to remain optimistic about the therapeutic potential of these drugs.

Activation of Wnt signaling promotes hippocampal neurogenesis in experimental autoimmune encephalomyelitis

Background

Disease progression in multiple sclerosis (MS) and experimental autoimmune encephalomyelitis (EAE), as one of its animal models, is characterized by demyelination and neuronal damage in white and gray matter structures, including the hippocampus. It is thought that dysfunction of the hippocampus, a primary locus of learning and memory consolidation, may contribute to cognitive impairment in MS patients. Previously, we reported an increased generation of hippocampal neuronal progenitors in the acute stage of EAE, whereas the microenvironmental signals triggering this process remained uninvestigated.

Results

In the present study, we used the Wnt signaling reporter mouse Axin2^LacZ, to elucidate the molecular mechanisms underlying the activation of the hippocampal neurogenic niche upon autoimmune neuroinflammation. Histological and enzymatic examinations of β-gal during the disease course of EAE, allowed us to survey hippocampal Wnt/β-catenin activity, one of the key signaling pathways of adult neurogenesis. We found that Wnt signaling is transiently upregulated in the acute stage of disease, consistent with a timely induction of canonical Wnt ligands. The enhancement of signaling coincided with hippocampal neuronal damage and local expression of immune cytokines such as TNFα and IFNγ, implicating the role of the inflammatory milieu in activation of the Wnt/β-catenin pathway. Supporting this finding, we show that transient exposure to pro-inflammatory cytokine TNFα triggers Wnt signaling in hippocampal organotypic slice cultures. Importantly, inflammation-mediated activation of the Wnt/β-catenin pathway was associated with enhanced neurogenesis in vitro and in vivo, indicating its potential role in hippocampal tissue regeneration and repair.

Conclusions

This study raises the possibility that enhancement of Wnt signaling may support neurogenic processes to cope with neuronal deficits upon immune-mediated neuroinflammation.

Electronic supplementary material

The online version of this article (doi:10.1186/s13024-016-0117-0) contains supplementary material, which is available to authorized users.

Synaptic pathology: A shared mechanism in neurological disease

Synaptic proteomes have evolved a rich and complex diversity to allow the exquisite control of neuronal communication and information transfer. It is therefore not surprising that many neurological disorders are associated with alterations in synaptic function. As technology has advanced, our ability to study the anatomical and physiological function of synapses in greater detail has revealed a critical role for both central and peripheral synapses in neurodegenerative disease. Synapse loss has a devastating effect on cellular communication, leading to wide ranging effects such as network disruption within central neural systems and muscle wastage in the periphery. These devastating effects link synaptic pathology to a diverse range of neurological disorders, spanning Alzheimer's disease to multiple sclerosis. This review will highlight some of the current literature on synaptic integrity in animal models of disease and human post-mortem studies. Synaptic changes in normal brain ageing will also be discussed and finally the current and prospective treatments for neurodegenerative disorders will be summarised.

Hippocampal Neuroinflammation, Functional Connectivity, and Depressive Symptoms in Multiple Sclerosis

BACKGROUND

Depression, a condition commonly comorbid with multiple sclerosis (MS), is associated more generally with elevated inflammatory markers and hippocampal pathology. We hypothesized that neuroinflammation in the hippocampus is responsible for depression associated with MS. We characterized the relationship between depressive symptoms and hippocampal microglial activation in patients with MS using the 18-kDa translocator protein radioligand [(18)F]PBR111. To evaluate pathophysiologic mechanisms, we explored the relationships between hippocampal neuroinflammation, depressive symptoms, and hippocampal functional connectivities defined by resting-state functional magnetic resonance imaging.

METHODS

The Beck Depression Inventory (BDI) was administered to 11 patients with MS and 22 healthy control subjects before scanning with positron emission tomography and functional magnetic resonance imaging. We tested for higher [(18)F]PBR111 uptake in the hippocampus of patients with MS relative to healthy control subjects and examined the correlations between [(18)F]PBR111 uptake, BDI scores, and hippocampal functional connectivities in the patients with MS.

RESULTS

Patients with MS had an increased hippocampal [(18)F]PBR111 distribution volume ratio relative to healthy control subjects (p = .024), and the hippocampal distribution volume ratio was strongly correlated with the BDI score in patients with MS (r = .86, p = .006). Hippocampal functional connectivities to the subgenual cingulate and prefrontal and parietal regions correlated with BDI scores and [(18)F]PBR111 distribution volume ratio.

CONCLUSIONS

Our results provide evidence that hippocampal microglial activation in MS impairs the brain functional connectivities in regions contributing to maintenance of a normal affective state. Our results suggest a rationale for the responsiveness of depression in some patients with MS to effective control of brain neuroinflammation. Our findings also lend support to further investigation of the role of inflammatory processes in the pathogenesis of depression more generally.

Platelet-Activating Factor Receptors Mediate Excitatory Postsynaptic Hippocampal Injury in Experimental Autoimmune Encephalomyelitis

Gray matter degeneration contributes to progressive disability in multiple sclerosis (MS) and can occur out of proportion to measures of white matter disease. Although white matter pathology, including demyelination and axon injury, can lead to secondary gray matter changes, we hypothesized that neurons can undergo direct excitatory injury within the gray matter independent of these. We tested this using a model of experimental autoimmune encephalomyelitis (EAE) with hippocampal degeneration in C57BL/6 mice, in which immunofluorescent staining showed a 28% loss of PSD95-positive excitatory postsynaptic puncta in hippocampal area CA1 compared with sham-immunized controls, despite preservation of myelin and VGLUT1-positive excitatory axon terminals. Loss of postsynaptic structures was accompanied by appearance of PSD95-positive debris that colocalized with the processes of activated microglia at 25 d after immunization, and clearance of debris was followed by persistently reduced synaptic density at 55 d. In vitro, addition of activated BV2 microglial cells to hippocampal cultures increased neuronal vulnerability to excitotoxic dendritic damage following a burst of synaptic activity in a manner dependent on platelet-activating factor receptor (PAFR) signaling. In vivo treatment with PAFR antagonist BN52021 prevented PSD95-positive synapse loss in hippocampi of mice with EAE but did not affect development of EAE or local microglial activation. These results demonstrate that postsynaptic structures can be a primary target of injury within the gray matter in autoimmune neuroinflammatory disease, and suggest that this may occur via PAFR-mediated modulation of activity-dependent synaptic physiology downstream of microglial activation.

SIGNIFICANCE STATEMENT

Unraveling gray matter degeneration is critical for developing treatments for progressive disability and cognitive impairment in multiple sclerosis (MS). In a mouse model of MS, we show that neurons can undergo injury at their synaptic connections within the gray matter, independent of the white matter pathology, demyelination, and axon injury that have been the focus of most current and emerging treatments. Damage to excitatory synapses in the hippocampus occurs in association with activated microglia, which can promote excitotoxic injury via activation of receptors for platelet-activating factor, a proinflammatory signaling molecule elevated in the brain in MS. Platelet-activating factor receptor blockade protected synapses in the mouse model, identifying a potential target for neuroprotective treatments in MS.

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

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

Axonal activity-dependent myelination in development: Insights for myelin repair

Recent advances in transgenic tools have allowed us to peek into the earliest stages of vertebrate development to study axon-glial communication in the control of peri-natal myelination. The emerging role of neuronal activity in regulating oligodendrocyte progenitor cell behavior during developmental myelination has opened up an exciting possibility-a role for neuronal activity in the early stages of remyelination. Recent work from our laboratory and others has also shown that contrary to previously established dogma in the field, complete remyelination up to pre-demyelination levels can be achieved in mouse models of MS by oligodendrogenic neural precursor cells that derive from the adult subventricular zone. These cells are electrically active and can be depolarized, suggesting that neuronal activity may have a modulatory role in their development and remyelination potential. In this review, we summarize recent advances in our understanding of the development of axon-glia communication and apply those same concepts to remyelination, with an emphasis on the particular roles of different sources of oligodendrocyte progenitor cells.

Changes of synapses in experimental autoimmune encephalomyelitis by using Fasudil

The ROCK signaling pathway is involved in numerous fundamental cellular functions such as cell migration, apoptosis, inflammatory responses, and neurite outgrowth. Previous studies demonstrate that Fasudil exhibited therapeutic potential of experimental autoimmune encephalomyelitis (EAE) possibly through immune-modulation and anti-inflammation. In this study, we observed the effect of Fasudil on synaptic protection of EAE mice. Fasudil ameliorated the clinical severity of EAE and inhibited Rho kinase (ROCK), especially ROCK II, in brain and spinal cord of EAE mice. Protein extracts from spinal cord of Fasudil-treated EAE mice promoted the formation of neurite outgrowth when co-cultured with primary neurons, indicating that peripheral administration of Fasudil can enter the central nervous system (CNS) and exhibited its biological effect on the formation of neurite outgrowth. Synapse-related molecule synaptophysin was enhanced, and CRMP-2, AMPA receptor, and GSK-3β were declined in spinal cord of Fasudil-treated mice. Neurotrophic factor BDNF and GDNF as well as immunomodulatory cytokine IL-10 in spinal cord were elevated in Fasudil-treated mice, while inflammatory cytokine IL-17, IL-1β, IL-6, and TNF-α were obviously inhibited, accompanied by the decrease of inflammatory M1 iNOS and the increase of anti-inflammatory M2 Arg-1, providing a microenvironment that contributes to synaptic protection. Our results indicate that Fasudil treatment protected against synaptic damage and promoted synaptic formation, which may be related with increased neurotrophic factors as well as decreased inflammatory microenvironment in the CNS of EAE mice.

Axonal degeneration in multiple sclerosis: defining therapeutic targets by identifying the causes of pathology

Current therapeutics in multiple sclerosis (MS) target the putative inflammation and immune attack on CNS myelin. Despite their effectiveness in blunting the relapse rate in MS patients, such therapeutics do not prevent MS disease progression. Importantly, specific clinical dilemma arises through inability to predict MS progression and thereby therapeutically target axonal injury during MS, limiting permanent disability. The current review identifies immune and neurobiological principles that govern the sequelae of axonal degeneration during MS disease progression. Defining the specific disease arbiters, inflammatory and autoimmune, oligodendrocyte dystrophy and degenerative myelin, we discuss a basis for a molecular mechanism in axons that may be targeted therapeutically, in spatial and temporal manner to limit axonal degeneration and thereby halt progression of MS.

Synaptopathy connects inflammation and neurodegeneration in multiple sclerosis

Multiple sclerosis (MS) has long been regarded as a chronic inflammatory disease of the white matter that leads to demyelination and eventually to neurodegeneration. In the past decade, several aspects of MS pathogenesis have been challenged, and degenerative changes of the grey matter, which are independent of demyelination, have become a topic of interest. CNS inflammation in MS and experimental autoimmune encephalomyelitis (EAE; a disease model used to study MS in rodents) causes a marked imbalance between GABAergic and glutamatergic transmission, and a loss of synapses, all of which leads to a diffuse 'synaptopathy'. Altered synaptic transmission can occur early in MS and EAE, independently of demyelination and axonal loss, and subsequently causes excitotoxic damage. Inflammation-driven synaptic abnormalities are emerging as a prominent pathogenic mechanism in MS-importantly, they are potentially reversible and, therefore, represent attractive therapeutic targets. In this Review, we focus on the connection between inflammation and synaptopathy in MS and EAE, which sheds light not only on the pathophysiology of MS but also on that of primary neurodegenerative disorders in which inflammatory processes contribute to disease progression.

LINGO-1 antibody ameliorates myelin impairment and spatial memory deficits in experimental autoimmune encephalomyelitis mice

More than 50% of multiple sclerosis patients develop cognitive impairment. However, the underlying mechanisms are still unclear, and there is no effective treatment. LINGO-1 (LRR and Ig domain containing NOGO receptor interacting protein 1) has been identified as an inhibitor of oligodendrocyte differentiation and myelination. Using the experimental autoimmune encephalomyelitis (EAE) mouse model, we assessed cognitive function at early and late stages of EAE, determined brain expression of myelin basic protein (MBP) and investigated whether the LINGO-1 antibody could restore deficits in learning and memory and ameliorate any loss of MBP. We found that deficits in learning and memory occurred in late EAE and identified decreased expression of MBP in the parahippocampal cortex (PHC) and fimbria-fornix. Moreover, the LINGO-1 antibody significantly improved learning and memory in EAE and partially restored MBP in PHC. Furthermore, the LINGO-1 antibody activated the AKT/mTOR signaling pathway regulating myelin growth. Our results suggest that demyelination in the PHC and fimbria-fornix might contribute to cognitive deficits and the LINGO-1 antibody could ameliorate these deficits by promoting myelin growth in the PHC. Our research demonstrates that LINGO-1 antagonism may be an effective approach to the treatment of the cognitive impairment of multiple sclerosis patients.

Hippocampal-DMN disconnectivity in MS is related to WM lesions and depression

The hippocampus is part of the default-mode network (DMN) and is functionally hit early in multiple sclerosis (MS). Hippocampal and DMN dysfunctions have been associated with depression, both in patients with MS and in major depressive disorders. We hypothesized that white matter lesions may contribute, through a disconnection mechanism, to hippocampal dysfunction. To test this, we assessed the relationship between hippocampal resting-state (RS) functional connectivity (FC) abnormalities with brain T2 lesion volumes and the presence and severity of depression. Structural and RS fMRI images were acquired from 69 patients with cognitively intact MS and 42 matched healthy controls (HC). Depression was quantified using the Montgomery-Asberg Depression Rating Scale. Seed-voxel hippocampal RS FC was assessed. SPM8 was used for between-group comparisons and correlation analysis between RS FC abnormalities with clinical and structural MRI variables. Compared to HC, patients with MS showed a significant atrophy of the whole brain and left hippocampus (P < 0.001), and a distributed pattern of decreased RS FC between the hippocampi and several cortical-subcortical regions, which were mostly located within the DMN. Reduced hippocampal RS FC with regions of the DMN was strongly correlated with higher T2 lesion volume, longer disease duration, and the severity of depression and disability. In patients with cognitively preserved MS, brain focal WM lesions are related to the functional integration of the hippocampus to other brain regions of the DMN, suggesting a disconnection syndrome. Such a disruption of hippocampal RS FC is likely to contribute to the occurrence of depression and to clinical disability.

In vivo evidence of hippocampal dentate gyrus expansion in multiple sclerosis

Using MR-based radial mapping, we assessed morphological alterations of the hippocampal dentate gyrus (DG) in patients with relapse-onset multiple sclerosis (MS). We analyzed different stages of the disease and the association of DG alterations with hippocampal-related cognitive functions. Using high-resolution morphological imaging, hippocampal radial mapping analysis was performed in 28 relapsing-remitting (RR), 34 secondary progressive, and 26 benign MS patients and 28 healthy controls (HC). Between-groups differences of DG radial distance (from surface points to the central core of the hippocampus) and correlations with clinical, neuropsychological, and radiological measures were evaluated using surface-based mesh modeling. Compared with HC, all MS clinical phenotypes revealed a larger radial distance of the DG, which was more marked on the left side. Radial distance enlargement was more pronounced in RRMS patients compared with the other disease clinical phenotypes and was inversely correlated to disease duration. Radial distance enlargement was correlated with higher T2 lesion volume and a better cognitive performance in RRMS and with a poor cognitive performance in secondary progressive and benign MS patients. Surface expansion of the DG might represent an inflammation-induced neurogenic (reactive) process of the subgranular zone of the hippocampus primarily aimed at rescuing the functional competence of hippocampal circuitry.

Amyloid precursor protein at node of Ranvier modulates nodal formation

Amyloid precursor protein (APP), commonly associated with Alzheimer disease, is upregulated and distributes evenly along the injured axons, and therefore, also known as a marker of demyelinating axonal injury and axonal degeneration. However, the physiological distribution and function of APP along myelinated axons was unknown. We report that APP aggregates at nodes of Ranvier (NOR) in the myelinated central nervous system (CNS) axons but not in the peripheral nervous system (PNS). At CNS NORs, APP expression co-localizes with tenascin-R and is flanked by juxtaparanodal potassium channel expression demonstrating that APP localized to NOR. In APP-knockout (KO) mice, nodal length is significantly increased, while sodium channels are still clustered at NORs. Moreover, APP KO and APP-overexpressing transgenic (APP TG) mice exhibited a decreased and an increased thickness of myelin in spinal cords, respectively, although the changes are limited in comparison to their littermate WT mice. The thickness of myelin in APP KO sciatic nerve also increased in comparison to that in WT mice. Our observations indicate that APP acts as a novel component at CNS NORs, modulating nodal formation and has minor effects in promoting myelination.

The hippocampus in aging and disease: From plasticity to vulnerability

The hippocampus has a pivotal role in learning and in the formation and consolidation of memory and is critically involved in the regulation of emotion, fear, anxiety, and stress. Studies of the hippocampus have been central to the study of memory in humans and in recent years, the regional specialization and organization of hippocampal functions have been elucidated in experimental models and in human neurological and psychiatric diseases. The hippocampus has long been considered a classic model for the study of neuroplasticity as many examples of synaptic plasticity such as long-term potentiation and -depression have been identified and demonstrated in hippocampal circuits. Neuroplasticity is the ability to adapt and reorganize the structure or function to internal or external stimuli and occurs at the cellular, population, network or behavioral level and is reflected in the cytological and network architecture as well as in intrinsic properties of hippocampal neurons and circuits. The high degree of hippocampal neuroplasticity might, however, be also negatively reflected in the pronounced vulnerability of the hippocampus to deleterious conditions such as ischemia, epilepsy, chronic stress, neurodegeneration and aging targeting hippocampal structure and function and leading to cognitive deficits. Considering this framework of plasticity and vulnerability, we here review basic principles of hippocampal anatomy and neuroplasticity on various levels as well as recent findings regarding the functional organization of the hippocampus in light of the regional vulnerability in Alzheimer's disease, ischemia, epilepsy, neuroinflammation and aging.

Chronic intermittent ethanol induced axon and myelin degeneration is attenuated by calpain inhibition

Chronic alcohol consumption causes multifaceted damage to the central nervous system (CNS), underlying mechanisms of which are gradually being unraveled. In our previous studies, activation of calpain, a calcium-activated neutral protease has been found to cause detrimental alterations in spinal motor neurons following ethanol (EtOH) exposure in vitro. However, it is not known whether calpain plays a pivotal role in chronic EtOH exposure-induced structural damage to CNS in vivo. To test the possible involvement of calpain in EtOH-associated neurodegenerative mechanisms the present investigation was conducted in a well-established mouse model of alcohol dependence - chronic intermittent EtOH (CIE) exposure and withdrawal. Our studies indicated significant loss of axonal proteins (neurofilament light and heavy, 50-60%), myelin proteins (myelin basic protein, 20-40% proteolipid protein, 25%) and enzyme (2', 3'-cyclic-nucleotide 3'-phosphodiesterase, 21-55%) following CIE in multiple regions of brain including hippocampus, corpus callosum, cerebellum, and importantly in spinal cord. These CIE-induced deleterious effects escalated after withdrawal in each CNS region tested. Increased expression and activity of calpain along with enhanced ratio of active calpain to calpastatin (sole endogenous inhibitor) was observed after withdrawal compared to EtOH exposure. Pharmacological inhibition of calpain with calpeptin (25 μg/kg) prior to each EtOH vapor inhalation significantly attenuated damage to axons and myelin as demonstrated by immuno-profiles of axonal and myelin proteins, and Luxol Fast Blue staining. Calpain inhibition significantly protected the ultrastructural integrity of axons and myelin compared to control as confirmed by electron microscopy. Together, these findings confirm CIE exposure and withdrawal induced structural alterations in axons and myelin, predominantly after withdrawal and corroborate calpain inhibition as a potential protective strategy against EtOH associated CNS degeneration.

Complement C1q-C3-associated synaptic changes in multiple sclerosis hippocampus

OBJECTIVE

Multiple sclerosis (MS) is a demyelinating disease of the central nervous system, leading to memory impairment in up to 65% of patients. Memory dysfunction in MS has been associated with loss of synapses in the hippocampus, but its molecular basis is unknown. Accumulating evidence suggests that components of the complement system, C1q and C3, can mediate elimination of synapses.

METHODS

To investigate the involvement of complement in synaptic changes in MS, gene and protein expression and localization of C1q and C3 were analyzed in relation to neuropathological changes in myelinated and demyelinated hippocampi from postmortem MS brains. Findings were compared to hippocampi of Alzheimer disease (AD) and non-neurological controls.

RESULTS

C1q expression and C3 activation were increased in myelinated and demyelinated MS hippocampi, mainly in the CA3/2 and CA1 subfields, which also showed a marked decrease in synaptic density and increased neuronal staining for the mitochondrial heat shock protein 70 (mtHSP70) stress marker. Neurons were the major source of C1q mRNA. C1q protein and activated C3 localized at synapses within human leukocyte antigen-positive cell processes and lysosomes, suggesting engulfment of complement-tagged synapses by microglia. A significant association (p < 0.0001) between the density of C1q and synaptophysin-positive synapses or mtHSP70 was seen in myelinated MS hippocampi, further pointing toward a link between the complement pathway and synaptic changes. In contrast to AD, MS hippocampi were consistently negative for the terminal complement activation complex C5b9.

INTERPRETATION

These data support a role for the C1q-C3 complement axis in synaptic alterations in the MS hippocampus.

The role of immune cells, glia and neurons in white and gray matter pathology in multiple sclerosis

Multiple sclerosis is one of the most common causes of chronic neurological disability beginning in early to middle adult life. Multiple sclerosis is idiopathic in nature, yet increasing correlative evidence supports a strong association between one's genetic predisposition, the environment and the immune system. Symptoms of multiple sclerosis have primarily been shown to result from a disruption in the integrity of myelinated tracts within the white matter of the central nervous system. However, recent research has also highlighted the hitherto underappreciated involvement of gray matter in multiple sclerosis disease pathophysiology, which may be especially relevant when considering the accumulation of irreversible damage and progressive disability. This review aims at providing a comprehensive overview of the interplay between inflammation, glial/neuronal damage and regeneration throughout the course of multiple sclerosis via the analysis of both white and gray matter lesional pathology. Further, we describe the common pathological mechanisms underlying both relapsing and progressive forms of multiple sclerosis, and analyze how current (as well as future) treatments may interact and/or interfere with its pathology. Understanding the putative mechanisms that drive disease pathogenesis will be key in helping to develop effective therapeutic strategies to prevent, mitigate, and treat the diverse morbidities associated with multiple sclerosis.

Hippocampal function is compromised in an animal model of multiple sclerosis

Multiple sclerosis (MS) is a progressive inflammatory autoimmune disease that is characterized by demyelination and axonal damage in the nervous system. One obvious consequence is a cumulative loss of muscle control. However, cognitive dysfunction affects roughly half of MS sufferers, sometimes already early in the disease course. Although long-term (remote) memory is typically unaffected, the ability to form new declarative memories becomes compromised. A major structure for the encoding of new declarative memories is the hippocampus. Encoding is believed to be mediated by synaptic plasticity in the form of long-term potentiation (LTP) and long-term depression (LTD) of synaptic strength. Here, in an animal model of MS we explored whether disease symptoms are accompanied by a loss of functional neuronal integrity, synaptic plasticity, or hippocampus-dependent learning ability. In mice that developed MOG35-55-induced experimental autoimmune encephalomyelitis (EAE), passive properties of CA1 pyramidal neurons were unaffected, although the ability to fire action potentials became reduced in the late phase of EAE. LTP remained normal in the early phase of MOG35-55-induced EAE. However, in the late phase, LTP was impaired and LTP-related spatial memory was impaired. In contrast, LTD and hippocampus-dependent object recognition memory were unaffected. These data suggest that in an animal model of MS hippocampal function becomes compromised as the disease progresses.

Glatiramer acetate guards against rapid memory decline during relapsing-remitting experimental autoimmune encephalomyelitis

Cognitive decline presents a therapeutic challenge for patients with multiple sclerosis (MS), a disease characterized by recurrent autoimmune demyelination and by progressive CNS degeneration. Glatiramer acetate (GA, also known as Copolymer 1, Cop-1, or Copaxone), commonly used to treat MS, reduces the frequency of relapses; it has both anti-inflammatory and neuroprotective properties. However, clinical trials have not definitively shown that GA improves cognitive impairment during MS. Using an in vivo animal model of autoimmune demyelination, i.e., relapsing-remitting experimental autoimmune encephalomyelitis (EAE), we tested short-term memory in EAE mice (EAE), in EAE mice treated with GA for 10 days starting at the time of immunization (EAE + GA), and in age-matched healthy, naïve mice (Naïve). Short-term memory was assessed using the cross-maze test at 10, 20, and 30 days post-immunization (d.p.i.); data were analyzed at each time point and over time. At 10 d.p.i., EAE and EAE + GA mice had better memory function than Naïve mice. However, at the later time points, EAE mice had a steep negative slope of memory function (indicating decline), whereas EAE + GA mice had a flatter, less-negative slope of memory function. Notably, the memory function of EAE mice significantly decreased over time compared with that of Naïve mice, indicating that EAE had a negative impact on cognitive ability. In contrast, there was no statistically significant difference between the slopes of memory function in mice with EAE treated with GA versus Naïve mice, which revealed effective, albeit partial, protection by GA treatment against progressive memory decline during EAE disease. Of particular interest, although EAE mice had memory decline over 30 d.p.i., their clinical disease scores improved during that time. Thus, our results suggest that EAE mice had a significant progressive memory decline and that GA, administered at the time of immunization, partially guards against rapid memory decline.