The hippocampus in multiple sclerosis

Pegylated chitosan nanoparticles of fluoxetine enhance cognitive performance and hippocampal brain derived neurotrophic factor levels in a rat model of local demyelination

Cognitive impairment is a common feature in neurodegenerative diseases such as multiple sclerosis (MS). This study aims to explore the potential of enhancing the beneficial effects of fluoxetine (FLX), a neuroprotective agent known for its ability to increase neural plasticity by utilizing nanoparticles. The study specifically focuses on the synthesis and evaluation of PEGylated chitosan nanoparticles of FLX and its effect on demyelination and the subsequent cognitive impairment (CI) in the hippocampus of rats induced by local injection of lysophosphatidylcholine (LPC). Chitosan/polyethylene glycol nanoparticles were synthesized, and their properties were analyzed. Demyelination was induced in rats via hippocampal injections of lysolecithin. Behavioral assessments included open field maze, elevated plus maze, and novel object recognition memory (NORM) tests. Hippocampal levels of insulin-like growth factor (IGF-1) and brain-derived neurotrophic factor (BDNF) were measured using enzyme-linked immunoassay (ELISA). The extent of remyelination was quantified using Luxol fast blue staining. Nanoparticle size measured 240.2 nm with 53 % encapsulation efficacy. Drug release exhibited a slow pattern, with 76 % released within 4 h. Nanoparticle-treated rats displayed reduced anxiety-like behavior, improved memory, increased BDNF levels, and a reduced extent of demyelination, with no change in IGF- levels. In addition, FLX -loaded chitosan nanoparticles had better effect on cognitive improvement, BDNF levels in the hippocampus that FLX. Altering pharmacokinetics and possibly pharmacodynamics. These findings highlight the potential of innovative drug delivery systems, encouraging further research in this direction.

Protocol to establish a demyelinated animal model to study hippocampal neurogenesis and cognitive function in adult rodents

Cognitive dysfunction is a prevalent feature in multiple sclerosis, a chronic inflammatory demyelinating disease, which may be correlated with the impairment of adult hippocampal neurogenesis. Here, we present a detailed protocol for the induction of cuprizone demyelinated mice to assess the cognitive function and explore the precise mechanisms underlying cognitive deficits in demyelinated hippocampus. We describe steps for behavioral tests, 5-Ethynyl-2'-deoxyuridine (EdU) and bromodeoxyuridine (BrdU) administration, retrovirus packaging and stereotactic injection, hippocampal tissue preparation, and immunofluorescence staining. For complete details on the use and execution of this protocol, please refer to Song et al.1.

PCSK9 inhibitor effectively alleviated cognitive dysfunction in a type 2 diabetes mellitus rat model

Background

The incidence of diabetes-associated cognitive dysfunction (DACD) is increasing; however, few clinical intervention measures are available for the prevention and treatment of this disease. Research has shown that proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors, particularly SBC-115076, have a protective effect against various neurodegenerative diseases. However, their role in DACD remains unknown. In this study, we aimed to explore the impact of PCSK9 inhibitors on DACD.

Methods

Male Sprague-Dawley (SD) rats were used to establish an animal model of type 2 diabetes mellitus (T2DM). The rats were randomly divided into three groups: the Control group (Control, healthy rats, n = 8), the Model group (Model, rats with T2DM, n = 8), and the PCSK9 inhibitor-treated group (Treat, T2DM rats treated with PCSK9 inhibitors, n = 8). To assess the spatial learning and memory of the rats in each group, the Morris water maze (MWM) test was conducted. Hematoxylin-eosin staining and Nissl staining procedures were performed to assess the structural characteristics and functional status of the neurons of rats from each group. Transmission electron microscopy was used to examine the morphology and structure of the hippocampal neurons. Determine serum PCSK9 and lipid metabolism indicators in each group of rats. Use qRT-PCR to detect the expression levels of interleukin (IL)-1β, IL-6, and tumor necrosis factor-alpha (TNF-α) in the hippocampal tissues of each group of rats. Western blot was used to detect the expression of PCSK9 and low-density lipoprotein receptor (LDLR) in the hippocampal tissues of rats. In addition, a 4D label-free quantitative proteomics approach was used to analyse protein expression in rat hippocampal tissues. The expression of selected proteins in hippocampal tissues was verified by parallel reaction monitoring (PRM) and immunohistochemistry (IHC).

Results

The results showed that the PCSK9 inhibitor alleviated cognitive dysfunction in T2DM rats. PCSK9 inhibitors can reduce PCSK9, total cholesterol (TC), and low-density lipoprotein (LDL) levels in the serum of T2DM rats. Meanwhile, it was found that PCSK9 inhibitors can reduce the expression of PCSK9, IL-1β, IL-6, and TNF-α in the hippocampal tissues of T2DM rats, while increasing the expression of LDLR. Thirteen potential target proteins for the action of PCSK9 inhibitors on DACD rats were identified. PRM and IHC revealed that PCSK9 inhibitors effectively counteracted the downregulation of transthyretin in DACD rats.

Conclusion

This study uncovered the target proteins and specific mechanisms of PCSK9 inhibitors in DACD, providing an experimental basis for the clinical application of PCSK9 inhibitors for the potential treatment of DACD.

Regional hippocampal atrophy reflects memory impairment in patients with early relapsing remitting multiple sclerosis

BACKGROUND

Research work has shown that hippocampal subfields are atrophic to varying extents in multiple sclerosis (MS) patients. However, studies examining the functional implications of subfield-specific hippocampal damage in early MS are limited. We aim to gain insights into the relationship between hippocampal atrophy and memory function by investigating the correlation between global and regional hippocampal atrophy and memory performance in early MS patients.

METHODS

From the Italian Neuroimaging Network Initiative (INNI) dataset, we selected 3D-T1-weighted brain MRIs of 219 early relapsing remitting (RR)MS and 246 healthy controls (HC) to identify hippocampal atrophic areas. At the time of MRI, patients underwent Selective-Reminding-Test (SRT) and Spatial-Recall-Test (SPART) and were classified as mildly (MMI-MS: n.110) or severely (SMI-MS: n:109) memory impaired, according to recently proposed cognitive phenotypes.

RESULTS

Early RRMS showed lower hippocampal volumes compared to HC (p < 0.001), while these did not differ between MMI-MS and SMI-MS. In MMI-MS, lower hippocampal volumes correlated with worse memory tests (r = 0.23-0.37, p ≤ 0.01). Atrophic voxels were diffuse in the hippocampus but more prevalent in cornu ammonis (CA, 79%) than in tail (21%). In MMI-MS, decreased subfield volumes correlated with decreases in memory, particularly in the right CA1 (SRT-recall: r = 0.38; SPART: r = 0.34, p < 0.01). No correlations were found in the SMI-MS group.

CONCLUSION

Hippocampal atrophy spreads from CA to tail from early disease stages. Subfield hippocampal atrophy is associated with memory impairment in MMI-MS, while this correlation is lost in SMI-MS. This plays in favor of a limited capacity for an adaptive functional reorganization of the hippocampi in MS patients.

Can International Classification of Functioning, Disability and Health (ICF) Be Used for Prediction of Work Capacity and Employment Status in Multiple Sclerosis?

Background: Multiple sclerosis (MS) affects many body functions and activities, including work capacity and ability to work. An evaluation of work-related parameters is important to understand the barriers to maintaining the job. The aim of this study was to evaluate if a Comprehensive International Classification of Functioning, Disability and Health (ICF) core set for MS can be used to predict work capacity and employment status. Methods: The cohort included 151 participants with MS (99 female/52 male, mean age 49 years) referred for a work capacity evaluation. Results: 71 (47.0%) were employed and a major part (131, 86.7%) had a work capacity between 20 and 40% with no difference between those who were employed and those who were unemployed. The analysis revealed that age and the following categories explained 68.8% of the work capacity: b770 Gait pattern functions; b730 Muscle power functions; b134 Sleep functions; d845 Acquiring, keeping and terminating a job; and b620 Urination functions. The following categories in 79.5% predicted ability to work: b164 Higher-level cognitive functions; d510 Washing oneself; d630; Preparing meals; and d870 Economic self-sufficiency. Conclusions: Here, we show that different functions/activities predicted work capacity in comparison with employment status in MS. Therefore, ICF should be implemented when assessing work ability.

Electroneuromyography comparison between pre-elderly adult females with and without MS; the potential role of a mind-body therapy in improving neurophysiological profile of MS during pandemic

INTRODUCTION

Imaginary exercises seem to be useful therapeutic approaches to modulate neuromuscular functions due to two main reasons: first, this training would not greatly increase body temperature, and secondly, it can positively affect brain-muscle pathways-which are both primary factors should be considered in rehabilitation programs for patients with multiple sclerosis (MS).

METHOD

32 pre-elderly adult females with relapsing-remitting MS (n = 16 - age M (SD): 56.75 (5.07)) and without MS (n = 16 - age M (SD): 56.56 (4.35)) voluntarily recruited. First, they were assigned into two groups: MS patients and healthy controls, to investigate baseline between-group comparison. Then, MS patients were randomly divided into two groups of eight each, designated as experimental and control groups. Recording the nerve conduction velocity (NCV) of tibial nerve and integrated electromyographic muscle activation (IEMG) of gastrocnemius muscle was conducted twice, before and after a six-week mind-body exercise therapy to evaluate its effectiveness on improving neuromuscular function.

RESULTS

The results showed significant difference in both tibial NCV (P < 0.001) and IEMG (P = 0.001) variables between non-MS group and MS group. Furthermore, there was a significant main effect of intervention (P = 0.05) and time (P < 0.001) on IEMG in the MS group, while there was no significant effect of intervention (P = 0.18) and time (P = 0.23) on NCV (p = 0.89).

CONCLUSION

Neuromuscular dysfunction were apparent in MS patients, and a mind-body therapy of imagery isometric training was found to be useful on improving the neurological deficit in women with MS.

TRIAL REGISTRATION NUMBER

UMIN000046935.

Microwave Radiation Caused Dynamic Metabolic Fluctuations in the Mammalian Hippocampus

To investigate the dynamic changes in hippocampal metabolism after microwave radiation using liquid chromatography in tandem with mass spectrometry/mass spectrometry (LC-MS/MS) and to identify potential biomarkers. Wistar rats were randomly assigned to a sham group and a microwave radiation group. The rats in the microwave radiation group were exposed to 2.856 GHz for 15 min for three times, with 5 min intervals. The rats in the sham group were not exposed. Transmission electron microscope revealed blurring of the synaptic cleft and postsynaptic dense thickening in hippocampal neurons after microwave radiation. Metabolomic analysis revealed 38, 24, and 39 differentially abundant metabolites at 3, 7, and 14 days after radiation, respectively, and the abundance of 9 metabolites, such as argininosuccinic acid, was continuously decreased. After microwave radiation, the abundance of metabolites such as argininosuccinic acid was successively decreased, indicating that these metabolites could be potential biomarkers for hippocampal tissue injury.

Hippocampal subfields and thalamic nuclei associations with clinical outcomes in multiple sclerosis: An ultrahigh field MRI study

BACKGROUND

Previous studies have shown that thalamic and hippocampal neurodegeneration is associated with clinical decline in Multiple Sclerosis (MS). However, contributions of the specific thalamic nuclei and hippocampal subfields require further examination.

OBJECTIVE

Using 7 Tesla (7T) magnetic resonance imaging (MRI), we investigated the cross-sectional associations between functionally grouped thalamic nuclei and hippocampal subfields volumes and T1 relaxation times (T1-RT) and subsequent clinical outcomes in MS.

METHODS

High-resolution T1-weighted and T2-weighted images were acquired at 7T (n=31), preprocessed, and segmented using the Thalamus Optimized Multi Atlas Segmentation (THOMAS, for thalamic nuclei) and the Automatic Segmentation of Hippocampal Subfields (ASHS, for hippocampal subfields) packages. We calculated Pearson correlations between hippocampal subfields and thalamic nuclei volumes and T1-RT and subsequent multi-modal rater-determined and patient-reported clinical outcomes (∼2.5 years after imaging acquisition), correcting for confounders and multiple tests.

RESULTS

Smaller volume bilaterally in the anterior thalamus region correlated with worse performance in gait function, as measured by the Patient Determined Disease Steps (PDDS). Additionally, larger volume in most functional groups of thalamic nuclei correlated with better visual information processing and cognitive function, as measured by the Symbol Digit Modalities Test (SDMT). In bilateral medial and left posterior thalamic regions, there was an inverse association between volumes and T1-RT, potentially indicating higher tissue degeneration in these regions. We also observed marginal associations between the right hippocampal subfields (both volumes and T1-RT) and subsequent clinical outcomes, though they did not survive correction for multiple testing.

CONCLUSION

Ultrahigh field MRI identified markers of structural damage in the thalamic nuclei associated with subsequently worse clinical outcomes in individuals with MS. Longitudinal studies will enable better understanding of the role of microstructural integrity in these brain regions in influencing MS outcomes.

Astrocyte-derived CHI3L1 signaling impairs neurogenesis and cognition in the demyelinated hippocampus

Cognitive dysfunction is a feature in multiple sclerosis (MS), a chronic inflammatory demyelinating disorder. A notable aspect of MS brains is hippocampal demyelination, which is closely associated with cognitive decline. However, the mechanisms underlying this phenomenon remain unclear. Chitinase-3-like (CHI3L1), secreted by activated astrocytes, has been identified as a biomarker for MS progression. Our study investigates CHI3L1's function within the demyelinating hippocampus and demonstrates a correlation between CHI3L1 expression and cognitive impairment in patients with MS. Activated astrocytes release CHI3L1 in reaction to induced demyelination, which adversely affects the proliferation and differentiation of neural stem cells and impairs dendritic growth, complexity, and spine formation in neurons. Our findings indicate that the astrocytic deletion of CHI3L1 can mitigate neurogenic deficits and cognitive dysfunction. We showed that CHI3L1 interacts with CRTH2/receptor for advanced glycation end (RAGE) by attenuating β-catenin signaling. The reactivation of β-catenin signaling can revitalize neurogenesis, which holds promise for therapy of inflammatory demyelination.

Radiologically isolated syndrome in the spectrum of multiple sclerosis

The radiologically isolated syndrome (RIS) currently represents the earliest detectable preclinical phase of multiple sclerosis (MS). Remarkable advancements have been recently made, including the identification of risk factors for disease evolution, revisions to the existing 2009 RIS criteria, and our understanding of the impact of early disease-modifying therapy use in the prevention/delay of symptomatic MS from two randomized clinical trials. Here, we discuss RIS in the context of the spectrum of MS, implications in the clinical management of individuals, and provide insights into future opportunities and challenges given the anticipated inclusion of asymptomatic MS in the formal definition of MS.

Isolated cognitive impairment in people with multiple sclerosis: frequency, MRI patterns and its development over time

OBJECTIVES

To study the frequency of isolated (i.e., single-domain) cognitive impairments, domain specific MRI correlates, and its longitudinal development in people with multiple sclerosis (PwMS).

METHODS

348 PwMS (mean age 48 ± 11 years, 67% female, 244RR/52SP/38PP) underwent neuropsychological testing (extended BRB-N) at baseline and at five-year follow-up. At baseline, structural MRI was acquired. Isolated cognitive impairment was defined as a Z-score of at least 1.5 SD below normative data in one domain only (processing speed, memory, executive functioning/working memory, and attention). Multi-domain cognitive impairment was defined as being affected in ≥ 2 domains, and cognitively preserved otherwise. For PwMS with isolated cognitive impairment, MRI correlates were explored using linear regression. Development of isolated cognitive impairment over time was evaluated based on reliable change index.

RESULTS

At baseline, 108 (31%) PwMS displayed isolated cognitive impairment, 148 (43%) PwMS displayed multi-domain cognitive impairment. Most PwMS with isolated cognitive impairment were impaired on executive functioning/working memory (EF/WM; N = 37), followed by processing speed (IPS; N = 25), memory (N = 23), and attention (N = 23). Isolated IPS impairment was explained by a model of cortical volume and fractional anisotropy (adj. R2 = 0.539, p < 0.001); memory by a model with cortical volume and hippocampal volume (adj. R2 = 0.493, p = 0.002); EF/WM and attention were not associated with any MRI measure. At follow-up, cognitive decline was present in 11/16 (69%) of PwMS with isolated IPS impairment at baseline. This percentage varied between 18 and 31% of PwMS with isolated cognitive impairment in domains other than IPS at baseline.

CONCLUSION

Isolated cognitive impairment is frequently present in PwMS and can serve as a proxy for further decline, particularly when it concerns processing speed. Cortical and deep grey matter atrophy seem to play a pivotal role in isolated cognitive impairment. Timely detection and patient-tailored intervention, predominantly for IPS, may help to postpone further cognitive decline.

Roflumilast: Modulating neuroinflammation and improving motor function and depressive symptoms in multiple sclerosis

BACKGROUND

Multiple sclerosis (MS) is an autoimmune disease causing central nervous system demyelination, often associated with depression. Current treatments for MS do not effectively address both physical disability and depression. Roflumilast, a phosphodiesterase-4 inhibitor with anti-inflammatory properties, has shown promise for autoimmune diseases.

METHODS

We used an experimental autoimmune encephalomyelitis (EAE) rat model to study roflumilast's effects. Motor dysfunction and depression symptoms were assessed, and histopathological analysis evaluated its anti-inflammatory properties. Flow cytometry examined the drug's impact on brain microglia. TNF-α, IL-1β, and IL-6 levels in hippocampal tissue were assessed using ELISA kits.

RESULTS

Roflumilast improved motor dysfunction and depression symptoms in EAE rats. Histopathological analysis revealed reduced inflammation, demyelination, and axonal loss in the spinal cord. Roflumilast suppressed microglial cell activation and conversion to pro-inflammatory M1-type cells. Flow cytometry showed roflumilast inhibited inflammatory marker expression in microglia and their activation in the hippocampus. IL-6 was identified as a roflumilast target for suppressing hippocampal inflammation.

LIMITATIONS

This study used an animal model and did not assess long-term or potential side effects of roflumilast treatment.

CONCLUSIONS

Roflumilast holds promise as a treatment for depression and motor impairment in MS. Its anti-inflammatory properties, reducing inflammation and inhibiting microglial activation, suggest its potential for MS therapy. However, further research is needed to evaluate long-term effects and safety in MS patients.

Unlocking the link: how hippocampal glutathione-glutamate coupling predicts cognitive impairment in multiple sclerosis patients

Cognitive impairment is a common symptom of multiple sclerosis and profoundly impacts quality of life. Glutathione (GSH) and glutamate (Glu) are tightly linked in the brain, participating in cognitive function. However, GSH-Glu couplings in cognitive brain regions and their relationship with cognitive impairment in relapsing-remitting multiple sclerosis (RRMS) remains unclear. Forty-one RRMS patients and 43 healthy controls underwent magnetic resonance spectroscopy to measure GSH and Glu levels in the posterior cingulate cortex, medial prefrontal cortex and left hippocampus. Neuropsychological tests were used to evaluate the cognitive function. The Glu/GSH ratio was used to indicate the coupling between GSH and Glu and was tested as a predictor of cognitive performance. The results show that RRMS patients exhibited reduced hippocampal GSH and Glu levels, which were found to be significant predictors of worse verbal and visuospatial memory, respectively. Moreover, GSH levels were dissociated from Glu levels in the left hippocampus of RRMS patients. Hippocampal Glu/GSH ratio is significantly correlated with processing speed and has a greater predictive effect. Here we show the hippocampal Glu/GSH ratio could serve as a new potential marker for characterizing cognitive impairment in RRMS, providing a new direction for clinical detection of cognitive impairment.

Understanding the spectrum of non-motor symptoms in multiple sclerosis: insights from animal models

Multiple sclerosis is a chronic autoimmune disease of the central nervous system and is generally considered to be a non-traumatic, physically debilitating neurological disorder. In addition to experiencing motor disability, patients with multiple sclerosis also experience a variety of non-motor symptoms, including cognitive deficits, anxiety, depression, sensory impairments, and pain. However, the pathogenesis and treatment of such non-motor symptoms in multiple sclerosis are still under research. Preclinical studies for multiple sclerosis benefit from the use of disease-appropriate animal models, including experimental autoimmune encephalomyelitis. Prior to understanding the pathophysiology and developing treatments for non-motor symptoms, it is critical to characterize the animal model in terms of its ability to replicate certain non-motor features of multiple sclerosis. As such, no single animal model can mimic the entire spectrum of symptoms. This review focuses on the non-motor symptoms that have been investigated in animal models of multiple sclerosis as well as possible underlying mechanisms. Further, we highlighted gaps in the literature to explain the non-motor aspects of multiple sclerosis in experimental animal models, which will serve as the basis for future studies.

Exercise Reverses Immune-Related Genes in the Hippocampus of Multiple Sclerosis Patients

BACKGROUND

Multiple sclerosis (MS) is an autoimmune disease characterized by inflammatory demyelinating lesions in the white matter of the central nervous system. Studies have shown that exercise is beneficial for multiple sclerosis (MS). However, the molecular basis is largely unknown.

MATERIALS AND METHODS

We integrated multiple blood and hippocampus transcriptome data from subjects with physical activity or MS. Transcription change associations between physical activity and MS were analyzed with bioinformatic methods including GSEA (Gene Set Enrichment Analysis) and GO (Gene Ontology) analysis.

RESULTS

We find that exercise can specifically reverse immune-related genes in the hippocampus of MS patients, while this effect is not observable in blood. Moreover, many of these reversed genes encode immune-related receptors. Interestingly, higher levels of physical activity have more pronounced effects on the reversal of MS-related transcripts.

CONCLUSIONS

The immune-response related genes or pathways in the hippocampus may be the targets of exercise in alleviating MS conditions, which may offer new therapeutic clues for MS.

Superficial white matter integrity in neuromyelitis optica spectrum disorder and multiple sclerosis

Background

Superficial white matter (SWM) is a particularly vulnerable area of white matter adjacent to cerebral cortex that was shown to be a sensitive marker of disease severity in several neurological and psychiatric disorders, including multiple sclerosis (MS), but has not been studied in neuromyelitis optica spectrum disorder (NMOSD).

Objective

To compare the integrity of SWM between MS patients, NMOSD patients and healthy controls, and explore the correlation of SWM integrity with cognitive performance and overall disability.

Methods

Forty NMOSD patients, 48 MS patients and 52 healthy controls were included in the study. Mean diffusivity (MD) values obtained by diffusion tensor imaging were used as a measure of SWM integrity. Cognitive performance and overall disability were assessed with standardized tests.

Results

Superficial white matter MD was increased in MS patients compared to healthy controls. Higher MD was associated with poorer spatial memory (most prominently in right temporal and right limbic lobe) and poorer information processing speed in MS patients. After adjusting for age, no significant differences of SWM MD were observed between NMOSD patients and healthy controls.

Conclusion

Integrity of SWM is compromised in MS, but not in NMOSD, and can serve as a sensitive marker of disease severity.

Influence of cardiorespiratory fitness and MRI measures of neuroinflammation on hippocampal volume in multiple sclerosis

BACKGROUND

The hippocampus is a clinically relevant region where neurogenesis and neuroplasticity occur throughout the whole lifespan. Neuroinflammation and cardiorespiratory fitness (CRF) may influence hippocampal integrity by modulating the processes promoting neurogenesis and neuroprotection that contribute to the preservation of functions. This study aimed to investigate the effects of neuroinflammation and CRF on hippocampal volume in multiple sclerosis (MS) patients with relapsing-remitting (RR) and progressive (P) clinical phenotypes. The influence of neuroinflammation and CRF on brain, grey matter (GM) and thalamic volumes was also assessed to determine whether the effects were specific for the hippocampus.

METHOD

Brain 3T structural MRI scans and maximum oxygen consumption (VO2max), a proxy of CRF, were acquired from 81 MS patients (27 RR and 54 P) and 45 age-matched and sex-matched healthy controls. T2-hyperintense white matter lesion volume (T2-LV) and choroid plexuses volume (CPV) were quantified as neuroinflammatory measures. Associations of demographic, clinical, neuroinflammatory and CRF measures with normalised brain, GM, hippocampal and thalamic volumes in relapsing-remitting MS (RRMS) and progressive MS patients were assessed using Shapley and best subset selection regression.

RESULTS

For most volumetric measures, the largest portions of variance were explained by T2-LV (variable importance (VI)=9.4-39.4) and CPV (VI=4.5-26.2). VO2max explained the largest portion of variance of normalised hippocampal volume only in RRMS patients (VI=16.9) and was retained as relevant predictor (standardised β=0.374, p=0.023) with T2-LV (standardised β=-0.330, p=0.016).

CONCLUSIONS

A higher CRF may play a specific neuroprotective role on MS patients' hippocampal integrity, but only in the RR phase of the disease.

A mechanistic insight into sources of error of visual working memory in multiple sclerosis

Working memory (WM) is one of the most affected cognitive domains in multiple sclerosis (MS), which is mainly studied by the previously established binary model for information storage (slot model). However, recent observations based on the continuous reproduction paradigms have shown that assuming dynamic allocation of WM resources (resource model) instead of the binary hypothesis will give more accurate predictions in WM assessment. Moreover, continuous reproduction paradigms allow for assessing the distribution of error in recalling information, providing new insights into the organization of the WM system. Hence, by utilizing two continuous reproduction paradigms, memory-guided localization (MGL) and analog recall task with sequential presentation, we investigated WM dysfunction in MS. Our results demonstrated an overall increase in recall error and decreased recall precision in MS. While sequential paradigms were better in distinguishing healthy control from relapsing-remitting MS, MGL were more accurate in discriminating MS subtypes (relapsing-remitting from secondary progressive), providing evidence about the underlying mechanisms of WM deficit in progressive states of the disease. Furthermore, computational modeling of the results from the sequential paradigm determined that imprecision in decoding information and swap error (mistakenly reporting the feature of other presented items) was responsible for WM dysfunction in MS. Overall, this study offered a sensitive measure for assessing WM deficit and provided new insight into the organization of the WM system in MS population.

Altered Expression of Autophagy Biomarkers in Hippocampal Neurons in a Multiple Sclerosis Animal Model

Multiple Sclerosis (MS) is a chronic inflammatory disease that affects the brain and spinal cord. Inflammation, demyelination, synaptic alteration, and neuronal loss are hallmarks detectable in MS. Experimental autoimmune encephalomyelitis (EAE) is an animal model widely used to study pathogenic aspects of MS. Autophagy is a process that maintains cell homeostasis by removing abnormal organelles and damaged proteins and is involved both in protective and detrimental effects that have been seen in a variety of human diseases, such as cancer, neurodegenerative diseases, inflammation, and metabolic disorders. This study is aimed at investigating the autophagy signaling pathway through the analysis of the main autophagic proteins including Beclin-1, microtubule-associated protein light chain (LC3, autophagosome marker), and p62 also called sequestosome1 (SQSTM1, substrate of autophagy-mediated degradation) in the hippocampus of EAE-affected mice. The expression levels of Beclin-1, LC3, and p62 and the Akt/mTOR pathway were examined by Western blot experiments. In EAE mice, compared to control animals, significant reductions of expression levels were detectable for Beclin-1 and LC3 II (indicating the reduction of autophagosomes), and p62 (suggesting that autophagic flux increased). In parallel, molecular analysis detected the deregulation of the Akt/mTOR signaling. Immunofluorescence double-labeling images showed co-localization of NeuN (neuronal nuclear marker) and Beclin-1, LC3, and p62 throughout the CA1 and CA3 hippocampal subfields. Taken together, these data demonstrate that activation of autophagy occurs in the neurons of the hippocampus in this experimental model.

Structural brain changes in patients with post-COVID fatigue: a prospective observational study

BACKGROUND

Post-COVID syndrome is a severe long-term complication of COVID-19. Although fatigue and cognitive complaints are the most prominent symptoms, it is unclear whether they have structural correlates in the brain. We therefore explored the clinical characteristics of post-COVID fatigue, describe associated structural imaging changes, and determine what influences fatigue severity.

METHODS

We prospectively recruited 50 patients from neurological post-COVID outpatient clinics (age 18-69 years, 39f/8m) and matched non-COVID healthy controls between April 15 and December 31, 2021. Assessments included diffusion and volumetric MR imaging, neuropsychiatric, and cognitive testing. At 7.5 months (median, IQR 6.5-9.2) after the acute SARS-CoV-2 infection, moderate or severe fatigue was identified in 47/50 patients with post-COVID syndrome who were included in the analyses. As a clinical control group, we included 47 matched multiple sclerosis patients with fatigue.

FINDINGS

Our diffusion imaging analyses revealed aberrant fractional anisotropy of the thalamus. Diffusion markers correlated with fatigue severity, such as physical fatigue, fatigue-related impairment in everyday life (Bell score) and daytime sleepiness. Moreover, we observed shape deformations and decreased volumes of the left thalamus, putamen, and pallidum. These overlapped with the more extensive subcortical changes in MS and were associated with impaired short-term memory. While fatigue severity was not related to COVID-19 disease courses (6/47 hospitalised, 2/47 with ICU treatment), post-acute sleep quality and depressiveness emerged as associated factors and were accompanied by increased levels of anxiety and daytime sleepiness.

INTERPRETATION

Characteristic structural imaging changes of the thalamus and basal ganglia underlie the persistent fatigue experienced by patients with post-COVID syndrome. Evidence for pathological changes to these subcortical motor and cognitive hubs provides a key to the understanding of post-COVID fatigue and related neuropsychiatric complications.

FUNDING

Deutsche Forschungsgemeinschaft (DFG) and German Ministry of Education and Research (BMBF).

Word finding, prosody and social cognition in multiple sclerosis

BACKGROUND

Impairments in speech and social cognition have been reported in people with multiple sclerosis (pwMS), although their relationships with neuropsychological outcomes and their clinical utility in MS are unclear.

OBJECTIVES

To evaluate word finding, prosody and social cognition in pwMS relative to healthy controls (HC).

METHODS

We recruited people with relapsing MS (RMS, n = 21), progressive MS (PMS, n = 24) and HC (n = 25) from an outpatient MS clinic. Participants completed a battery of word-finding, social cognitive, neuropsychological and clinical assessments and performed a speech task for prosodic analysis.

RESULTS

Of 45 pwMS, mean (SD) age was 49.4 (9.4) years, and median (range) Expanded Disability Severity Scale score was 3.5 (1.0-6.5). Compared with HC, pwMS were older and had slower information processing speed (measured with the Symbol Digit Modalities Test, SDMT) and higher depression scores. Most speech and social cognitive measures were associated with information processing speed but not with depression. Unlike speech, social cognition consistently correlated with intelligence and memory. Visual naming test mean response time (VNT-MRT) demonstrated worse outcomes in MS versus HC (p = .034, Nagelkerke's R²  = 65.0%), and in PMS versus RMS (p = .009, Nagelkerke's R²  = 50.2%). Rapid automatised object naming demonstrated worse outcomes in MS versus HC (p = .014, Nagelkerke's R²  = 49.1%). These word-finding measures showed larger effect sizes than that of the SDMT (MS vs. HC, p = .010, Nagelkerke's R²  = 40.6%; PMS vs. RMS, p = .023, Nagelkerke's R²  = 43.5%). Prosody and social cognition did not differ between MS and HC.

CONCLUSIONS

Word finding, prosody and social cognition in MS are associated with information processing speed and largely independent of mood. Impairment in visual object meaning perception is potentially a unique MS disease-related deficit that could be further explored and cautiously considered as an adjunct disability metric for MS.

Regional white matter and gray matter damage and cognitive performances in multiple sclerosis according to sex

In this study, we investigated whether regional distribution of white matter (WM) lesions, normal-appearing [NA] WM microstructural abnormalities and gray matter (GM) atrophy may differently contribute to cognitive performance in multiple sclerosis (MS) patients according to sex. Using the same scanner, brain 3.0T MRI was acquired for 287 MS patients (females = 173; mean age = 42.1 [standard deviation, SD = 12.7] years; relapsing-remitting = 196, progressive = 91; median Expanded Disability Status Scale = 2.5 [interquartile range, IQR = 1.5-5.0]; median disease duration = 12.1 [IQR = 6.3-19.0] years; treatment: none = 70, first-line = 130, second-line = 87) and 172 healthy controls (HC) (females = 92; mean age = 39.3 [SD = 14.8] years). MS patients underwent also Rao's neuropsychological battery. Using voxel-wise analyses, we investigated in patients sex-related differences in the association of cognitive performances with WM lesions, NAWM fractional anisotropy (FA) and GM volumes (p < 0.01, family-wise error [FWE]). Sixty-six female (38%) and 48 male (42%) MS patients were cognitively impaired, with no significant between-group difference (p = 0.704). However, verbal memory performance was worse in males (p = 0.001), whereas verbal fluency performance was worse in females (p = 0.004). In both sexes, a higher T2-hyperintense lesion prevalence in cognitively-relevant WM tracts was significantly associated with worse cognitive performance (p ≤ 0.006), with stronger associations in females than males in global cognition (p ≤ 0.004). Compared to sex-matched HC, male and female MS patients had widespread lower NAWM FA and GM volume (p < 0.01). In both sexes, worse cognitive performance was associated with widespread reduced NAWM FA (p < 0.01), with stronger associations in females than males in global cognition and verbal memory (p ≤ 0.009). Worse cognitive performance was significantly associated with clusters of cortical GM atrophy in males (p ≤ 0.007) and mainly with deep GM atrophy in females (p ≤ 0.006). In this study, only limited differences in cognitive performances were found between male and female MS patients. A disconnection syndrome due to focal WM lesions and diffuse NAWM microstructural abnormalities seems to be more relevant in female MS patients to explain cognitive impairment.

Effects of Positive Fighting Experience and Its Subsequent Deprivation on the Expression Profile of Mouse Hippocampal Genes Associated with Neurogenesis

The hippocampus is known as the brain region implicated in visuospatial processes and processes associated with learning and short- and long-term memory. An important functional characteristic of the hippocampus is lifelong neurogenesis. A decrease or increase in adult hippocampal neurogenesis is associated with a wide range of neurological diseases. We have previously shown that in adult male mice with a chronic positive fighting experience in daily agonistic interactions, there is an increase in the proliferation of progenitor neurons and the production of young neurons in the dentate gyrus (in hippocampus), and these neurogenesis parameters remain modified during 2 weeks of deprivation of further fights. The aim of the present work was to identify hippocampal genes associated with neurogenesis and involved in the formation of behavioral features in mice with the chronic experience of wins in aggressive confrontations, as well as during the subsequent 2-week deprivation of agonistic interactions. Hippocampal gene expression profiles were compared among three groups of adult male mice: chronically winning for 20 days in the agonistic interactions, chronically victorious for 20 days followed by the 2-week deprivation of fights, and intact (control) mice. Neurogenesis-associated genes were identified whose transcription levels changed during the social confrontations and in the subsequent period of deprivation of fights. In the experimental males, some of these genes are associated with behavioral traits, including abnormal aggression-related behavior, an abnormal anxiety-related response, and others. Two genes encoding transcription factors (Nr1d1 and Fmr1) were likely to contribute the most to the between-group differences. It can be concluded that the chronic experience of wins in agonistic interactions alters hippocampal levels of transcription of multiple genes in adult male mice. The transcriptome changes get reversed only partially after the 2-week period of deprivation of fights. The identified differentially expressed genes associated with neurogenesis and involved in the control of a behavior/neurological phenotype can be used in further studies to identify targets for therapeutic correction of the neurological disturbances that develop in winners under the conditions of chronic social confrontations.

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.

Cognitive performance in multiple sclerosis: what is the role of the gamma-aminobutyric acid system?

Cognitive impairment occurs in 40-65% of persons with multiple sclerosis and may be related to alterations in glutamatergic and GABAergic neurotransmission. Therefore, the aim of this study was to determine how glutamatergic and GABAergic changes relate to cognitive functioning in multiple sclerosis in vivo. Sixty persons with multiple sclerosis (mean age 45.5 ± 9.6 years, 48 females, 51 relapsing-remitting multiple sclerosis) and 22 age-matched healthy controls (45.6 ± 22.0 years, 17 females) underwent neuropsychological testing and MRI. Persons with multiple sclerosis were classified as cognitively impaired when scoring at least 1.5 standard deviations below normative scores on ≥30% of tests. Glutamate and GABA concentrations were determined in the right hippocampus and bilateral thalamus using magnetic resonance spectroscopy. GABA-receptor density was assessed using quantitative [¹¹C]flumazenil positron emission tomography in a subset of participants. Positron emission tomography outcome measures were the influx rate constant (a measure predominantly reflecting perfusion) and volume of distribution, which is a measure of GABA-receptor density. Twenty persons with multiple sclerosis (33%) fulfilled the criteria for cognitive impairment. No differences were observed in glutamate or GABA concentrations between persons with multiple sclerosis and healthy controls, or between cognitively preserved, impaired and healthy control groups. Twenty-two persons with multiple sclerosis (12 cognitively preserved and 10 impaired) and 10 healthy controls successfully underwent [¹¹C]flumazenil positron emission tomography. Persons with multiple sclerosis showed a lower influx rate constant in the thalamus, indicating lower perfusion. For the volume of distribution, persons with multiple sclerosis showed higher values than controls in deep grey matter, reflecting increased GABA-receptor density. When comparing cognitively impaired and preserved patients to controls, the preserved group showed a significantly higher volume of distribution in cortical and deep grey matter and hippocampus. Positive correlations were observed between both positron emission tomography measures and information processing speed in the multiple sclerosis group only. Whereas concentrations of glutamate and GABA did not differ between multiple sclerosis and control nor between cognitively impaired, preserved and control groups, increased GABA-receptor density was observed in preserved persons with multiple sclerosis that was not seen in cognitively impaired patients. In addition, GABA-receptor density correlated to cognition, in particular with information processing speed. This could indicate that GABA-receptor density is upregulated in the cognitively preserved phase of multiple sclerosis as a means to regulate neurotransmission and potentially preserve cognitive functioning.

Treadmill aerobic training improve beam-walking test, up-regulate expression of main proteins of myelin and myelination in the hippocampus of cuprizone-fed mice

Multiple sclerosis (MS) is a potentially disabling disease of the brain and spinal cord (central nervous system). The aim of this study was to investigate the effect of 6 weeks of aerobic training on the main proteins of myelin including myelin basic protein (MBP), myelin oligodendrocyte (MOG), myelin associated glycoprotein (MAG), and myelin proteolipid protein (PLP) at hippocampus of C57BL/6 mouse model of cuprizone-induced MS. Twenty-eight female C57BL/6 mice (23 ± 3 g) were randomly divided into four groups (n = 7 per group): control, exercise (Exe), cuprizone (CPZ), and cuprizone with exercise (CPZ + Exe). Exercise groups performed treadmill aerobic exercise training 5 days a week, 15-22 m/min, and 15-60 min, during 6 weeks. Cuprizone were fed to mice at CPZ and CPZ + Exe groups for 6 weeks. Animals were sacrificed after 6 weeks. Biochemical and molecular biology analyses were performed. Mice at CPZ group had decreased myelination of nerve cells in the hippocampus. In addition, the use of CPZ in the hippocampus caused a decrease in the MBP, MOG gene expression, as well as a decrease in the MAG and PLP gene and protein expression compared to the healthy control group. However, performing aerobic exercise with CPZ consumption increased MBP gene expression and increased MAG and PLP protein expression, as well as increased myelination of nerve cells in the hippocampus compared to the CPZ group (p < 0.05). It seems that regular aerobic exercise in the MS model controls the destruction of myelin in the nerve cells of hippocampus by upregulating MBP, MAG and PLP, which can have positive effects on cognitive and motor performance.

Transcriptome Profiling in the Hippocampi of Mice with Experimental Autoimmune Encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis (MS), approximates the key histopathological, clinical, and immunological features of MS. Hippocampal dysfunction in MS and EAE causes varying degrees of cognitive and emotional impairments and synaptic abnormalities. However, the molecular alterations underlying hippocampal dysfunctions in MS and EAE are still under investigation. The purpose of this study was to identify differentially expressed genes (DEGs) in the hippocampus of mice with EAE in order to ascertain potential genes associated with hippocampal dysfunction. Gene expression in the hippocampus was analyzed by RNA-sequencing and validated by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Gene expression analysis revealed 1202 DEGs; 1023 were upregulated and 179 were downregulated in the hippocampus of mice with EAE (p-value < 0.05 and fold change >1.5). Gene ontology (GO) analysis showed that the upregulated genes in the hippocampi of mice with EAE were associated with immune system processes, defense responses, immune responses, and regulation of immune responses, whereas the downregulated genes were related to learning or memory, behavior, and nervous system processes in the GO biological process. The expressions of hub genes from the search tool for the retrieval of interacting genes/proteins (STRING) analysis were validated by RT-qPCR. Additionally, gene set enrichment analysis showed that the upregulated genes in the hippocampus were associated with inflammatory responses: interferon-γ responses, allograft rejection, interferon-α responses, IL6_JAK_STAT3 signaling, inflammatory responses, complement, IL2_STAT5 signaling, TNF-α signaling via NF-κB, and apoptosis, whereas the downregulated genes were related to synaptic plasticity, dendritic development, and development of dendritic spine. This study characterized the transcriptome pattern in the hippocampi of mice with EAE and signaling pathways underpinning hippocampal dysfunction. However, further investigation is needed to determine the applicability of these findings from this rodent model to patients with MS. Collectively, these results indicate directions for further research to understand the mechanisms behind hippocampal dysfunction in EAE.

Seizures and multiple sclerosis‑more than an epidemiological association (Review)

In order to increase the quality of life of patients with epilepsy, it is essential to develop tools that facilitate early disease diagnosis and encourage the use of individualized therapies. The association between seizures and other neurological pathologies is well known but incompletely explained, with multiple sclerosis (MS)-seizures correlation being a relevant example. In this context, the present review aimed to highlight the most important facts related to the association between the heterogeneous group of epileptic pathology and MS, in order to provide initial directions for establishing a diagnostic and therapeutic protocol. The first part reviewed the most relevant epidemiological and clinical data on seizures; MS association. Subsequently, it highlighted the most common and actually accepted pathophysiological mechanisms that try to explain the association between the two pathologies. Finally, the importance of paraclinical investigations and the optimal choice of antiseizure-based therapies with respect to seizures associated with MS are presented, also revealing several directions that should be explored in the near future.

Chronic experimental autoimmune encephalomyelitis is an excellent model to study neuroaxonal degeneration in multiple sclerosis

Animal models of multiple sclerosis (MS), specifically experimental autoimmune encephalomyelitis (EAE), have been used extensively to develop anti-inflammatory treatments. However, the similarity between MS and one particular EAE model does not end at inflammation. MS and chronic EAE induced in C57BL/6 mice using myelin oligodendrocyte glycoprotein (MOG) peptide 35-55 share many neuropathologies. Beyond both having white matter lesions in spinal cord, both also have widespread neuropathology in the cerebral cortex, hippocampus, thalamus, striatum, cerebellum, and retina/optic nerve. In this review, we compare neuropathologies in each of these structures in MS with chronic EAE in C57BL/6 mice, and find evidence that this EAE model is well suited to study neuroaxonal degeneration in MS.

Functional connectivity dynamics reflect disability and multi-domain clinical impairment in patients with relapsing-remitting multiple sclerosis

BACKGROUND & AIM

Multiple sclerosis (MS) is an autoimmune disease of the central nervous system associated with deficits in cognitive and motor functioning. While structural brain changes such as demyelination are an early hallmark of the disease, a characteristic profile of functional brain alterations in early MS is lacking. Functional neuroimaging studies at various disease stages have revealed complex and heterogeneous patterns of aberrant functional connectivity (FC) in MS, with previous studies largely being limited to a static account of FC. Thus, it remains unclear how time-resolved FC relates to variance in clinical disability status in early MS. We here aimed to characterize brain network organization in early MS patients with time-resolved FC analysis and to explore the relationship between disability status, multi-domain clinical outcomes and altered network dynamics.

METHODS

Resting-state functional MRI (rs-fMRI) data were acquired from 101 MS patients and 101 age- and sex-matched healthy controls (HC). Based on the Expanded Disability Status Score (EDSS), patients were split into two sub-groups: patients without clinical disability (EDSS ≤ 1, n = 36) and patients with mild to moderate levels of disability (EDSS ≥ 2, n = 39). Five dynamic FC states were extracted from whole-brain rs-fMRI data. Group differences in static and dynamic FC strength, across-state overall connectivity, dwell time, transition frequency, modularity, and global connectivity were assessed. Patients' impairment was quantified as custom clinical outcome z-scores (higher: worse) for the domains depressive symptoms, fatigue, motor, vision, cognition, total brain atrophy, and lesion load. Correlation analyses between functional measures and clinical outcomes were performed with Spearman partial correlation analyses controlling for age.

RESULTS

Patients with mild to moderate levels of disability exhibited a more widespread spatiotemporal pattern of altered FC and spent more time in a high-connectivity, low-occurrence state compared to patients without disability and HCs. Worse symptoms in all clinical outcome domains were positively associated with EDSS scores. Furthermore, depressive symptom severity was positively related to functional dynamics as measured by state-specific global connectivity and default mode network connectivity with attention networks, while fatigue and motor impairment were related to reduced frontoparietal network connectivity with the basal ganglia.

CONCLUSIONS

Despite comparably low impairment levels in early MS, we identified distinct connectivity alterations between patients with mild to moderate disability and those without disability, and these changes were sensitive to clinical outcomes in multiple domains. Furthermore, time-resolved analysis uncovered alterations in network dynamics and clinical correlations that remained undetected with conventional static analyses, showing that accounting for temporal dynamics helps disentangle the relationship between functional alterations, disability status, and symptoms in early MS.

Modeling neurodegenerative disorders in zebrafish

Neurodegeneration is a major cause of Alzheimer's, Parkinson's, Huntington's, multiple and amyotrophic lateral sclerosis, pontocerebellar hypoplasia, dementia and other related brain disorders. Their complex pathogenesis commonly includes genetic and neurochemical deficits, misfolded protein toxicity, demyelination, apoptosis and mitochondrial dysfunctions. Albeit differing in specific underlying mechanisms, neurodegenerative disorders typically display evolutionarily conserved mechanisms across taxa. Here, we review the role of zebrafish models in recapitulating major human and rodent neurodegenerative conditions, demonstrating this species as a highly relevant experimental model for research on neurodegenerative diseases, and discussing how these fish models can further clarify the underlying genetic, neurochemical, neuroanatomical and behavioral pathogenic mechanisms.

Early Successful Eye Movement Desensitization and Reprocessing (EMDR) Therapy for Verbal Memory Impairment in an Adjustment Disorder: A Case Report in a Newly-Diagnosed Multiple Sclerosis Patient

Multiple sclerosis (MS) is a chronic inflammatory disease of the immune system affecting the central nervous system. Several phenotypes are possible, and cases usually present with a relapsing-remitting (RR) course with disease onset at a young age. MS diagnosis can represent a traumatic event for the patient, possibly evolving into adjustment disorder (AD). AD is defined by the presence of emotional or behavioral symptoms in response to identifiable stress occurring within the prior three months and similarly to post-traumatic stress disorder (PTSD) can significantly affect quality of life. Usually, neuropsychological disorders are not associated with AD. Several treatments are available for AD, and among them, eye movement desensitization and reprocessing (EMDR) is one of the most effective in relieving depression and anxiety. However, little is known about AD and PTSD in the MS population and no data are available on the effectiveness of EMDR for cognitive impairment associated with AD. We describe a 25-year-old patient with RR MS developing an AD with a verbal memory deficit after being diagnosed. Both the psychological and cognitive deficits were diagnosed using an extensive neuropsychological battery. Considering the high impact of the verbal memory deficit, on the patient’s quality of life, an EMDR intervention was planned. After a six-month EMDR intervention performed by two trained neuropsychologists, the patient was retested. There was an improvement in verbal memory tests and depression anxiety scales and the Dissociative Experiences Scale. It is recognized that emotional changes and psychiatric disorders, frequently affect MS patients at diagnosis. It is imperative to recognize this and promptly set a neuropsychological treatment. Moreover, we suggest checking cognition along with depression and anxiety. Finally, to our knowledge, this is the first report of AD with an isolated neuropsychological deficit (verbal memory) developed after the MS diagnosis and treated beneficially with e EMDR. More studies are needed to confirm the efficacy of EMDR in treating cognitive impairment associated with AD in MS patients.

Beyond the neuron: Role of non-neuronal cells in stress disorders

Stress disorders are leading causes of disease burden in the U.S. and worldwide, yet available therapies are fully effective in less than half of all individuals with these disorders. Although to date, much of the focus has been on neuron-intrinsic mechanisms, emerging evidence suggests that chronic stress can affect a wide range of cell types in the brain and periphery, which are linked to maladaptive behavioral outcomes. Here, we synthesize emerging literature and discuss mechanisms of how non-neuronal cells in limbic regions of brain interface at synapses, the neurovascular unit, and other sites of intercellular communication to mediate the deleterious, or adaptive (i.e., pro-resilient), effects of chronic stress in rodent models and in human stress-related disorders. We believe that such an approach may one day allow us to adopt a holistic "whole body" approach to stress disorder research, which could lead to more precise diagnostic tests and personalized treatment strategies. Stress is a major risk factor for many psychiatric disorders. Cathomas et al. review new insight into how non-neuronal cells mediate the deleterious effects, as well as the adaptive, protective effects, of stress in rodent models and human stress-related disorders.

Examining the relationship between working memory consolidation and long-term consolidation

An emerging area of research is focused on the relationship between working memory and long-term memory and the likely overlap between these processes. Of particular interest is how some information first maintained in working memory is retained for longer periods and eventually preserved in long-term memory. The process of stabilizing transient memory representations for lasting retention is referred to as consolidation in both the working memory and long-term memory literature, although these have historically been viewed as independent constructs. The present review aims to investigate the relationship between working memory consolidation and long-term memory consolidation, which both have rich, but distinct, histories. This review provides an overview of the proposed models and neural mechanisms of both types of consolidation, as well as clinical findings related to consolidation and potential approaches for the manipulation of consolidation. Finally, two hypotheses are proposed to explain the relationship between working memory consolidation and long-term memory consolidation.

Multimodal magnetic resonance imaging quantification of gray matter alterations in relapsing-remitting multiple sclerosis and neuromyelitis optica spectrum disorder

Herein, we combined neurite orientation dispersion and density imaging (NODDI) and synthetic magnetic resonance imaging (SyMRI) to evaluate the spatial distribution and extent of gray matter (GM) microstructural alterations in patients with relapsing-remitting multiple sclerosis (RRMS) and neuromyelitis optica spectrum disorder (NMOSD). The NODDI (neurite density index [NDI], orientation dispersion index [ODI], and isotropic volume fraction [ISOVF]) and SyMRI (myelin volume fraction [MVF]) measures were compared between age- and sex-matched groups of 30 patients with RRMS (6 males and 24 females; mean age, 51.43 ± 8.02 years), 18 patients with anti-aquaporin-4 antibody-positive NMOSD (2 males and 16 females; mean age, 52.67 ± 16.07 years), and 19 healthy controls (6 males and 13 females; mean age, 51.47 ± 9.25 years) using GM-based spatial statistical analysis. Patients with RRMS showed reduced NDI and MVF and increased ODI and ISOVF, predominantly in the limbic and paralimbic regions, when compared with healthy controls, while only increases in ODI and ISOVF were observed when compared with NMOSD. Compared to NDI and MVF, the changes in ODI and ISOVF were observed more widely, including in the cerebellar cortex. These abnormalities were associated with disease progression and disability. In contrast, patients with NMOSD only showed reduced NDI mainly in the cerebellar, limbic, and paralimbic cortices when compared with healthy controls and patients with RRMS. Taken together, our study supports the notion that GM pathologies in RRMS are distinct from those of NMOSD. However, owing to the limitations of the study, the results should be cautiously interpreted.

Structural Plasticity of the Hippocampus in Neurodegenerative Diseases

Neuroplasticity is the capacity of neural networks in the brain to alter through development and rearrangement. It can be classified as structural and functional plasticity. The hippocampus is more susceptible to neuroplasticity as compared to other brain regions. Structural modifications in the hippocampus underpin several neurodegenerative diseases that exhibit cognitive and emotional dysregulation. This article reviews the findings of several preclinical and clinical studies about the role of structural plasticity in the hippocampus in neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, Huntington's disease, and multiple sclerosis. In this study, literature was surveyed using Google Scholar, PubMed, Web of Science, and Scopus, to review the mechanisms that underlie the alterations in the structural plasticity of the hippocampus in neurodegenerative diseases. This review summarizes the role of structural plasticity in the hippocampus for the etiopathogenesis of neurodegenerative diseases and identifies the current focus and gaps in knowledge about hippocampal dysfunctions. Ultimately, this information will be useful to propel future mechanistic and therapeutic research in neurodegenerative diseases.

Divergent time-varying connectivity of thalamic sub-regions characterizes clinical phenotypes and cognitive status in multiple sclerosis

We aimed to investigate abnormal time-varying functional connectivity (FC) for thalamic sub-regions in multiple sclerosis (MS) and their clinical, cognitive and MRI correlates. Eighty-nine MS patients (49 relapsing-remitting [RR] MS; 40 progressive [P] MS) and 53 matched healthy controls underwent neurological, neuropsychological and resting state fMRI assessment. Time-varying connectivity (TVC) was quantified using sliding-window seed-voxel correlation analysis. Standard deviation of FC across windows was taken as measure of TVC, while mean connectivity across windows expressed static FC. MS patients showed reduced TVC vs controls between most of thalamic sub-regions and fronto-temporo-occipital regions. At the same time, they showed increased static FC between all thalamic sub-regions and structurally connected cortico-subcortical regions. TVC reduction was mainly driven by RRMS; while PMS exhibited a variable pattern of TVC abnormalities, characterized by reduced TVC between frontal/motor thalamic seeds and default-mode network areas and increased TVC vs controls/RRMS between posterior thalamic sub-regions and occipito-temporo-insular cortices, associated with severity of clinical disability. Compared with controls, both cognitively preserved and impaired patients showed reduced TVC between anterior thalamic sub-regions and frontal cortex. Cognitively impaired patients also showed increased TVC of the right postcentral thalamic sub-region with the cingulate cortex and postcentral gyrus vs both controls and cognitively preserved patients. Divergent patterns of TVC thalamic abnormalities were found between RRMS and PMS patients. TVC reduction in RRMS may represent the attempt of thalamic network to keep with stable connections. Conversely, increased TVC of posterior thalamic sub-regions characterized PMS and cognitively impaired MS, possibly reflecting maladaptive mechanisms.

Cognitive trajectories in multiple sclerosis: a long-term follow-up study

BACKGROUND

Cognitive impairment occurs in multiple sclerosis (MS) and undergoes a progressive worsening over disease course. However, clinicians still struggle to predict the course of cognitive function. To evaluate baseline clinical and imaging predictors of cognitive abilities worsening over time, we performed a latent trajectory analysis for cognitive performances in MS patients, up to 15 years from disease onset.

METHODS

We collected age, sex, education, dominant and non-dominant 9-hole peg test (9HP) and timed 25-foot walk (T25-FW) as well as MRI measures (grey matter volume and lesion load) within 6 months from disease diagnosis for relapsing-remitting MS (RR-MS) patients. At diagnosis and over the follow-up, we also assessed cognitive status through the symbol digit modalities test (SDMT). Cognitive impairment was defined by applying age-, gender- and education-adjusted normative values. Group-based trajectory analysis was performed to determine trajectories, and the predictive value of clinical and imaging variables at baseline was assessed through multinomial logistic regression.

RESULTS

We included 148 RR-MS (98 females and 50 males). Over 11 ± 4 year follow-up, 51.4% remained cognitively stable whereas 48.6% cognitively worsened. Cognitively worsening patients had a higher T25FW time (p = 0.004) and a reduced hippocampal volume at baseline (p = 0.04).

CONCLUSION

Physical disability as well as hippocampal atrophy might depict patients at risk of cognitive worsening over the disease course. Therefore, using such predictors, clinicians may select patients to carefully evaluate for cognitive impairment as to eventually introduce cognitive rehabilitation treatments.

Effect of BDNF Val66Met polymorphism on hippocampal subfields in multiple sclerosis patients

Brain-derived neurotrophic factor (BDNF) Val66Met polymorphism was shown to strongly affect BDNF function, but its role in modulating gray matter damage in multiple sclerosis (MS) patients is still not clear. Given BDNF relevance on the hippocampus, we aimed to explore BDNF Val66Met polymorphism effect on hippocampal subfield volumes and its role in cognitive functioning in MS patients. Using a 3T scanner, we obtained dual-echo and 3DT1-weighted sequences from 50 MS patients and 15 healthy controls (HC) consecutively enrolled. MS patients also underwent genotype analysis of BDNF, neurological and neuropsychological evaluation. Hippocampal subfields were segmented by using Freesurfer. The BDNF Val66Met polymorphism was found in 22 MS patients (44%). Compared to HC, MS patients had lower volume in: bilateral hippocampus-amygdala transition area (HATA); cornus ammonis (CA)1, granule cell layer of dentate gyrus (GCL-DG), CA4 and CA3 of the left hippocampal head; molecular layer (ML) of the left hippocampal body; presubiculum of right hippocampal body and right fimbria. Compared to BDNF Val66Val, Val66Met MS patients had higher volume in bilateral hippocampal tail; CA1, ML, CA3, CA4, and GCL-DG of left hippocampal head; CA1, ML, and CA3 of the left hippocampal body; left HATA and presubiculum of the right hippocampal head. In MS patients, higher lesion burden was associated with lower volume of presubiculum of right hippocampal body; lower volume of left hippocampal tail was associated with worse visuospatial memory performance; lower volume of left hippocampal head with worse performance in semantic fluency. Our findings suggest the BNDF Val66Met polymorphism may have a protective role in MS patients against both hippocampal atrophy and cognitive impairment. BDNF genotype might be a potential biomarker for predicting cognitive prognosis, and an interesting target to study for neuroprotective strategies.

Longitudinal changes of deep gray matter shape in multiple sclerosis

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Specific shape changes over time occur at the bilateral ventrolateral pallidal and the left posterolateral striatal surface in relapse-onset multiple sclerosis.

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These shape changes over time were not associated with disease progression.

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The average shape of deep gray matter structures was associated with the patients’ average disease severity as well as white matter lesion-load.

Objective

This study aimed to investigate longitudinal deep gray matter (DGM) shape changes and their relationship with measures of clinical disability and white matter lesion-load in a large multiple sclerosis (MS) cohort.

Materials and Methods

A total of 230 MS patients (179 relapsing-remitting, 51 secondary progressive; baseline age 44.5 ± 11.3 years; baseline disease duration 12.99 ± 9.18) underwent annual clinical and MRI examinations over a maximum of 6 years (mean 4.32 ± 2.07 years). The DGM structures were segmented on the T1-weighted images using the “Multiple Automatically Generated Templates” brain algorithm. White matter lesion-load was measured on T2-weighted MRI. Clinical examination included the expanded disability status scale, 9-hole peg test, timed 25-foot walk test, symbol digit modalities test and paced auditory serial addition test. Vertex‐wise longitudinal analysis of DGM shapes was performed using linear mixed effect models and evaluated the association between average/temporal changes of DGM shapes with average/temporal changes of clinical measurements, respectively.

Results

A significant shrinkage over time of the bilateral ventrolateral pallidal and the left posterolateral striatal surface was observed, whereas no significant shape changes over time were observed at the bilateral thalamic and right striatal surfaces. Higher average lesion-load was associated with an average inwards displacement of the global thalamic surface with relative sparing on the posterior side (slight left-side predominance), the antero-dorso-lateral striatal surfaces bilaterally (symmetric on both sides) and the antero-lateral pallidal surface (left-side predominance). There was also an association between shrinkage of large lateral DGM surfaces with higher clinical motor and cognitive disease severity. However, there was no correlation between any DGM shape changes over time and measurements of clinical progression or lesion-load changes over time.

Conclusions

This study showed specific shape change of DGM structures occurring over time in relapse-onset MS. Although these shape changes over time were not associated with disease progression, we demonstrated a link between DGM shape and the patients’ average disease severity as well as white matter lesion-load.

CSF neurofilament light chain predicts 10-year clinical and radiologic worsening in multiple sclerosis

Background

Neurofilament light chain (NfL) is an attractive biomarker of disease activity and progression in MS, but there is a lack in long-term prognostic data.

Objective

To test the long-term clinical and radiological prognostic value of cerebrospinal fluid (CSF)-NfL among newly diagnosed patients with MS.

Methods

Newly diagnosed MS patients where followed prospectively with baseline CSF-NfL and repeated MRI and clinical assessments for up to 10 years. Associations between baseline CSF-NfL and longitudinal MRI and clinical assessments were found by Generalized Estimating Equations analysis.

Results

Forty-two participants were included. CSF-NfL at baseline was significantly associated with the rate of atrophy in globus pallidus (p = 0.009) and hippocampus (p = 0.001) as evaluated by MRI. Baseline volumes of thalamus (β −0.33; 95% CI −0.57 to −0.10, p = 0.006), T1 (β 0.28; 95% CI 0.11 to 0.44, p = 0.001) and T2 (β 0.16; 95% CI 0.04 to 0.27, p = 0.008) lesions and baseline levels of CSF-NfL (β 0.9; 95% CI 0.3 to 1.5, p = 0.002) significantly predicted EDSS worsening over 10 years. Baseline CSF-NfL gave a comparable prediction to the best MRI volumetric predictors.

Conclusion

CSF-NfL predicted the clinical and radiological course of newly diagnosed patients with MS over a 10-year period, underlining its prognostic role.

Complement C3 mediates early hippocampal neurodegeneration and memory impairment in experimental multiple sclerosis

Memory impairment is one of the disabling manifestations of multiple sclerosis (MS) possibly present from the early stages of the disease and for which there is no specific treatment. Hippocampal synaptic dysfunction and dendritic loss, associated with microglial activation, can underlie memory deficits, yet the molecular mechanisms driving such hippocampal neurodegeneration need to be elucidated. In early-stage experimental autoimmune encephalomyelitis (EAE) female mice, we assessed the expression level of molecules involved in microglia-neuron interactions within the dentate gyrus and found overexpression of genes of the complement pathway. Compared to sham immunized mice, the central element of the complement cascade, C3, showed the strongest and 10-fold upregulation, while there was no increase of downstream factors such as the terminal component C5. The combination of in situ hybridization with immunofluorescence showed that C3 transcripts were essentially produced by activated microglia. Pharmacological inhibition of C3 activity, by daily administration of rosmarinic acid, was sufficient to prevent early dendritic loss, microglia-mediated phagocytosis of synapses in the dentate gyrus, and memory impairment in EAE mice, while morphological markers of microglial activation were still observed. In line, when EAE was induced in C3 deficient mice (C3KO), dendrites and spines of the dentate gyrus as well as memory abilities were preserved. Altogether, these data highlight the central role of microglial C3 in early hippocampal neurodegeneration and memory impairment in EAE and, therefore, pave the way toward new neuroprotective strategies in MS to prevent cognitive deficit using complement inhibitors.

Carbohydrate and lipid metabolism in multiple sclerosis: Clinical implications for etiology, pathogenesis, diagnosis, prognosis, and therapy

Multiple sclerosis (MS) is a complicated autoimmune disease characterized by inflammatory and demyelinating events in the central nervous system. The exact etiology and pathogenesis of MS have not been elucidated. However, a set of metabolic changes and their effects on immune cells and neural functions have been explained. This review highlights the contribution of carbohydrates and lipids metabolism to the etiology and pathogenesis of MS. Then, we have proposed a hypothetical relationship between such metabolic changes and the immune system in patients with MS. Finally, the potential clinical implications of these metabolic changes in diagnosis, prognosis, and discovering therapeutic targets have been discussed. It is concluded that research on the pathophysiological alterations of carbohydrate and lipid metabolism may be a potential strategy for paving the way toward MS treatment.

Exercise protects from hippocampal inflammation and neurodegeneration in experimental autoimmune encephalomyelitis

Exercise is increasingly recommended as a supportive therapy for people with Multiple Sclerosis (pwMS). While clinical research has still not disclosed the real benefits of exercise on MS disease, animal studies suggest a substantial beneficial effect on motor disability and pathological hallmarks such as central and peripheral dysregulated immune response. The hippocampus, a core area for memory formation and learning, is a brain region involved in MS pathophysiology. Human and rodent studies suggest that the hippocampus is highly sensitive to the effects of exercise, the impact of which on MS hippocampal damage is still elusive. Here we addressed the effects of chronic voluntary exercise on hippocampal function and damage in experimental autoimmune encephalomyelitis (EAE), animal model of MS. Mice were housed in standard or wheel-equipped cages starting from the day of immunization and throughout the disease course. Although running activity was reduced during the symptomatic phase, exercise significantly ameliorated motor disability. Exercise improved cognition that was assessed through the novel object recognition test and the nest building in presymptomatic and acute stages of the disease, respectively. In the acute phase exercise was shown to prevent EAE-induced synaptic plasticity abnormalities in the CA1 area, by promoting the survival of parvalbumin-positive (PV+) interneurons and by attenuating inflammation. Indeed, exercise significantly reduced microgliosis in the CA1 area, the expression of tumour necrosis factor (TNF) in microglia and, to a lesser extent, the hippocampal level of interleukin 1 beta (IL-1β), previously shown to contribute to aberrant synaptic plasticity in the EAE hippocampus. Notably, exercise exerted a precocious and long-lasting mitigating effect on microgliosis that preceded its neuroprotective action, likely underlying the improved cognitive function observed in both presymptomatic and acute phase EAE mice. Overall, these data provide evidence that regular exercise improves cognitive function and synaptic and neuronal pathology that typically affect EAE/MS brains.

Complement-associated loss of CA2 inhibitory synapses in the demyelinated hippocampus impairs memory

The complement system is implicated in synapse loss in the MS hippocampus, but the functional consequences of synapse loss remain poorly understood. Here, in post-mortem MS hippocampi with demyelination we find that deposits of the complement component C1q are enriched in the CA2 subfield, are linked to loss of inhibitory synapses and are significantly higher in MS patients with cognitive impairments compared to those with preserved cognitive functions. Using the cuprizone mouse model of demyelination, we corroborated that C1q deposits are highest within the demyelinated dorsal hippocampal CA2 pyramidal layer and co-localized with inhibitory synapses engulfed by microglia/macrophages. In agreement with the loss of inhibitory perisomatic synapses, we found that Schaffer collateral feedforward inhibition but not excitation was impaired in CA2 pyramidal neurons and accompanied by intrinsic changes and a reduced spike output. Finally, consistent with excitability deficits, we show that cuprizone-treated mice exhibit impaired encoding of social memories. Together, our findings identify CA2 as a critical circuit in demyelinated intrahippocampal lesions and memory dysfunctions in MS.

Correlations between hippocampal functional connectivity, structural changes, and clinical data in patients with relapsing-remitting multiple sclerosis: a case-control study using multimodal magnetic resonance imaging

Multiple sclerosis is associated with structural and functional brain alterations leading to cognitive impairments across multiple domains including attention, memory, and the speed of information processing. The hippocampus, which is a brain important structure involved in memory, undergoes microstructural changes in the early stage of multiple sclerosis. In this study, we analyzed hippocampal function and structure in patients with relapsing-remitting multiple sclerosis and explored correlations between the functional connectivity of the hippocampus to the whole brain, changes in local brain function and microstructure, and cognitive function at rest. We retrospectively analyzed data from 20 relapsing-remitting multiple sclerosis patients admitted to the Department of Neurology at the China-Japan Union Hospital of Jilin University, China, from April 2015 to November 2019. Sixteen healthy volunteers were recruited as the healthy control group. All participants were evaluated using a scale of extended disability status and the Montreal cognitive assessment within 1 week before and after head diffusion tensor imaging and functional magnetic resonance imaging. Compared with the healthy control group, the patients with relapsing-remitting multiple sclerosis had lower Montreal cognitive assessment scores and regions of simultaneously enhanced and attenuated whole-brain functional connectivity and local functional connectivity in the bilateral hippocampus. Hippocampal diffusion tensor imaging data showed that, compared with the healthy control group, patients with relapsing-remitting multiple sclerosis had lower hippocampal fractional anisotropy values and higher mean diffusivity values, suggesting abnormal hippocampal structure. The left hippocampus whole-brain functional connectivity was negatively correlated with the Montreal cognitive assessment score (r = −0.698, P = 0.025), and whole-brain functional connectivity of the right hippocampus was negatively correlated with extended disability status scale score (r = −0.649, P = 0.042). The mean diffusivity value of the left hippocampus was negatively correlated with the Montreal cognitive assessment score (r = −0.729, P = 0.017) and positively correlated with the extended disability status scale score (r = 0.653, P = 0.041). The right hippocampal mean diffusivity value was positively correlated with the extended disability status scale score (r = 0.684, P = 0.029). These data suggest that the functional connectivity and presence of structural abnormalities in the hippocampus in patients with relapse-remission multiple sclerosis are correlated with the degree of cognitive function and extent of disability. This study was approved by the Ethics Committee of China-Japan Union Hospital of Jilin University, China (approval No. 201702202) on February 22, 2017.

Sex-specific signatures of intrinsic hippocampal networks and regional integrity underlying cognitive status in multiple sclerosis

The hippocampus is an anatomically compartmentalized structure embedded in highly wired networks that are essential for cognitive functions. The hippocampal vulnerability has been postulated in acute and chronic neuroinflammation in multiple sclerosis, while the patterns of occurring inflammation, neurodegeneration or compensation have not yet been described. Besides focal damage to hippocampal tissue, network disruption is an important contributor to cognitive decline in multiple sclerosis patients. We postulate sex-specific trajectories in hippocampal network reorganization and regional integrity and address their relationship to markers of neuroinflammation, cognitive/memory performance and clinical severity. In a large cohort of multiple sclerosis patients (n = 476; 337 females, age 35 ± 10 years, disease duration 16 ± 14 months) and healthy subjects (n = 110, 54 females; age 34 ± 15 years), we utilized MRI at baseline and at 2-year follow-up to quantify regional hippocampal volumetry and reconstruct single-subject hippocampal networks. Through graph analytical tools we assessed the clustered topology of the hippocampal networks. Mixed-effects analyses served to model sex-based differences in hippocampal network and subfield integrity between multiple sclerosis patients and healthy subjects at both time points and longitudinally. Afterwards, hippocampal network and subfield integrity were related to clinical and radiological variables in dependency of sex attribution. We found a more clustered network architecture in both female and male patients compared to their healthy counterparts. At both time points, female patients displayed a more clustered network topology in comparison to male patients. Over time, multiple sclerosis patients developed an even more clustered network architecture, though with a greater magnitude in females. We detected reduced regional volumes in most of the addressed hippocampal subfields in both female and male patients compared to healthy subjects. Compared to male patients, females displayed lower volumes of para- and presubiculum but higher volumes of the molecular layer. Longitudinally, volumetric alterations were more pronounced in female patients, which showed a more extensive regional tissue loss. Despite a comparable cognitive/memory performance between female and male patients over the follow-up period, we identified a strong interrelation between hippocampal network properties and cognitive/memory performance only in female patients. Our findings evidence a more clustered hippocampal network topology in female patients with a more extensive subfield volume loss over time. A stronger relation between cognitive/memory performance and the network topology in female patients suggests greater entrainment of the brain’s reserve. These results may serve to adapt sex-targeted neuropsychological interventions.

Effects of walking exercise training on learning and memory and hippocampal neuroimaging outcomes in MS: A targeted, pilot randomized controlled trial

PURPOSE

The current pilot study involved a single-blind, randomized controlled trial (RCT) on the effects of treadmill walking exercise training compared with an active control condition on learning and memory (L/M) and hippocampal neuroimaging outcomes in 11 fully-ambulatory persons with multiple sclerosis (MS) who demonstrated impairments in new learning.

METHODS

The study protocol is registered at clinicaltrials.gov: NCT03319771 (February 2018). Eleven fully-ambulatory persons with MS-related impairments in new learning were randomly assigned into either 12-weeks of supervised, treadmill walking exercise training or 12-weeks of low-intensity resistive exercise (active control condition). Participants underwent neuropsychological tests of L/M and hippocampal neuroimaging before and after the 12-week study period; outcomes were administered by treatment-blinded assessors.

RESULTS

There were moderate-to-large intervention effects on measures of verbal L/M (η_p² = 0.11, d = 0.63, 95% CI: -0.61, 1.83), whereby those in the intervention condition demonstrated improvement in California Verbal Learning Test-II (CVLT-II) scores compared with the control condition. There were smaller effects on a composite L/M measure (η_p² = 0.02, d = 0.28, 95% CI: -0.93, 1.46). There were large intervention effects on normalized hippocampal volume (η_p² = 0.36, d = 1.13, 95% CI: 0.09, 2.82), whereby hippocampal volume was preserved in the intervention condition, compared with hippocampal atrophy in the control condition. By comparison, there were no intervention effects on hippocampal resting-state functional connectivity.

CONCLUSIONS

Collectively, this study provides initial proof-of-concept data for further examining treadmill walking exercise training as a possible behavioral approach for managing L/M impairment and preserving hippocampal volume as common and debilitating manifestations of MS.

Valproic acid suppresses cuprizone-induced hippocampal demyelination and anxiety-like behavior by promoting cholesterol biosynthesis

Myelin consists of several layers of tightly compacted membranes that form an insulating sheath around axons. These membranes are highly enriched in cholesterol, which is essential for the myelination process. Proper myelination is crucial for various neurophysiological functions while demyelination may cause CNS disease, such as multiple sclerosis (MS). Recent studies demonstrated that demyelination occurs not only in the white matter but also in the grey matter, such as the hippocampus, which may cause cognitive deficits and mental disorders. Valproic acid (VPA) is an anticonvulsant agent prescribed for the treatment of epilepsy and seizure. Recently, VPA was reported to alter cholesterol metabolism in neural cells, suggesting that it may play an important role in myelin biogenesis. Here in this study, we found significant demyelination in the hippocampus of the mouse cuprizone model, which is accompanied by reduced cholesterol biosynthesis and increased anxiety-like behavior. VPA treatment, however, suppressed cuprizone-induced hippocampal demyelination and anxiety-like behavior by promoting cholesterol biosynthesis. These data identify an important role of VPA in the hippocampal demyelination process and the hippocampal demyelination-related behavior deficit via regulation of cholesterol biosynthesis, which provides new insights into the mechanisms of VPA as a protective agent against CNS demyelination.