Cuprizone treatment induces distinct demyelination, astrocytosis, and microglia cell invasion or proliferation in the mouse cerebellum

Dynamic Proteome Changes in Cuprizone-Induced Demyelination and Remyelination in the Mouse Brain

This study aimed to gain insights into the dynamic proteome changes and underlying molecular mechanisms of de/remyelination in a cuprizone model, a widely used preclinical model of multiple sclerosis (MS). Longitudinal sampling of control or cuprizone-treated mouse brains was executed at 6 time points over 6 weeks. Data analysis included 8489 quantified proteins. Differential proteomic and GO analyses revealed that 5.9% of the quantified proteome was altered, including reported and novel de/remyelination-relevant protein changes and underlying pathways. We found that oligodendrocyte proteins (Fa2h and Ugt8) were significantly changed during demyelination, suggesting that dysregulated sphingolipid metabolism in MS may stem from oligodendrocyte pathology. Importantly, we showed that the cholesterol biosynthesis pathway was the most enriched biological process in a subset of significantly changed proteins, where myelination was highly enriched. We further validated the changes in the cholesterol biosynthesis pathway through targeted GC-MS analysis of intermediate sterols, supporting the critical role of cholesterol biosynthesis in de/remyelination. Unexpectedly, changes of myelin-associated proteins, Mbp and Plp1, were minimal, while Ermn showed significant reduction tracking with demyelination, indicating that some myelin protein changes are more sensitive to demyelination. Together with a list of significantly altered proteins, the results of this study could benefit future remyelination research.

N-butyl-β-carboline-3-carboxylate (β-CCB) systemic administration promotes remyelination in the cuprizone demyelinating model in mice

Demyelination is generated in several nervous system illnesses. Developing strategies for effective clinical treatments requires the discovery of promyelinating drugs. Increased GABAergic signaling through γ-aminobutyric acid type A receptor (GABAAR) activation in oligodendrocytes has been proposed as a promyelinating condition. GABAAR expressed in oligodendroglia is strongly potentiated by n-butyl-β-carboline-3-carboxylate (β-CCB) compared to that in neurons. Here, mice were subjected to 0.3% cuprizone (CPZ) added in the food to induce central nervous system demyelination, a well-known model for multiple sclerosis. Then β-CCB (1 mg/Kg) was systemically administered to analyze the remyelination status in white and gray matter areas. Myelin content was evaluated using Black-Gold II (BGII) staining, immunofluorescence (IF), and magnetic resonance imaging (MRI). Evidence indicates that β-CCB treatment of CPZ-demyelinated animals promoted remyelination in several white matter structures, such as the fimbria, corpus callosum, internal capsule, and cerebellar peduncles. Moreover, using IF, it was observed that CPZ intake induced an increase in NG2+ and a decrease in CC1+ cell populations, alterations that were importantly retrieved by β-CCB treatment. Thus, the promyelinating character of β-CCB was confirmed in a generalized demyelination model, strengthening the idea that it has clinical potential as a therapeutic drug.

Epilepsy and demyelination: Towards a bidirectional relationship

Demyelination stands out as a prominent feature in individuals with specific types of epilepsy. Concurrently, individuals with demyelinating diseases, such as multiple sclerosis (MS) are at a greater risk of developing epilepsy compared to non-MS individuals. These bidirectional connections raise the question of whether both pathological conditions share common pathogenic mechanisms. This review focuses on the reciprocal relationship between epilepsy and demyelination diseases. We commence with an overview of the neurological basis of epilepsy and demyelination diseases, followed by an exploration of how our comprehension of these two disorders has evolved in tandem. Additionally, we discuss the potential pathogenic mechanisms contributing to the interactive relationship between these two diseases. A more nuanced understanding of the interplay between epilepsy and demyelination diseases has the potential to unveiling the molecular intricacies of their pathological relationships, paving the way for innovative directions in future clinical management and treatment strategies for these diseases.

Immunofluorescence assay for demyelination, remyelination, and proliferation in an acute cuprizone mouse model

Here, we present a protocol to assess demyelination in the corpus callosum of an acute cuprizone mouse model, which is routinely used to induce demyelination for studying myelin regeneration in the rodent brain. We describe the tracing of neural stem cells via intraperitoneal injection of tamoxifen into adult Gli1CreERT2;Ai9 mice and the induction of demyelination with cuprizone diet. We also detail EdU administration, cryosectioning of the mouse brain, EdU labeling, and immunofluorescence staining to examine proliferation and myelination. For complete details on the use and execution of this protocol, please refer to Radecki et al. (2020).1.

The Effects of Cuprizone on Murine Subventricular Zone-Derived Neural Stem Cells and Progenitor Cells Grown as Neurospheres

Despite the extensive use of the cuprizone (CPZ) demyelination animal model, there is little evidence regarding the effects of CPZ on a cellular level. Initial studies have suggested that oligodendrocytes (OL) are the main cell targets for CPZ toxicity. However, recent data have revealed additional effects on neural stem cells and progenitor cells (NSC/NPC), which constitute a reservoir for OL regeneration during brain remyelination. We cultured NSC/NPC as neurospheres to investigate CPZ effects on cell mechanisms which are thought to be involved in demyelination and remyelination processes in vivo. Proliferating NSC/NPC cultures exposed to CPZ showed overproduction of intracellular reactive oxygen species and increased progenitor migration at the expense of a significant inhibition of cell proliferation. Although NSC/NPC survival was not affected by CPZ in proliferative conditions, we found that CPZ-treated cultures undergoing cell differentiation were more prone to cell death than controls. The commitment and cell differentiation towards neural lineages did not seem to be affected by CPZ, as shown by the conserved proportions of OL, astrocytes, and neurons. Nevertheless, when CPZ treatment was performed after cell differentiation, we detected a significant reduction in the number and the morphological complexity of OL, astrogliosis, and neuronal damage. We conclude that, in addition to damaging mature OL, CPZ also reduces NSC/NPC proliferation and activates progenitor migration. These results shed light on CPZ direct effects on NSC proliferation and the progression of in vitro differentiation.

Therapeutic effect of combination vitamin D3 and siponimod on remyelination and modulate microglia activation in cuprizone mouse model of multiple sclerosis

Stimulation of remyelination is critical for the treatment of multiple sclerosis (MS) to alleviate symptoms and protect the myelin sheath from further damage. The current study aimed to investigate the possible therapeutic effects of combining vitamin D3 (Vit D3) and siponimod (Sipo) on enhancing remyelination and modulating microglia phenotypes in the cuprizone (CPZ) demyelination mouse model. The study was divided into two stages; demyelination (first 5 weeks) and remyelination (last 4 weeks). In the first 5 weeks, 85 mice were randomly divided into two groups, control (n = 20, standard rodent chow) and CPZ (n = 65, 0.3% CPZ mixed with chow for 6 weeks, followed by 3 weeks of standard rodent chow). At week 5, the CPZ group was re-divided into four groups (n = 14) for remyelination stages; untreated CPZ (0.2 ml of CMC orally), CPZ+Vit D3 (800 IU/kg Vit D3 orally), CPZ+Sipo (1.5 mg/kg Sipo orally), and CPZ+Vit D3 (800 IU/kg Vit D3) + Sipo (1.5 mg/kg Sipo orally). Various behavioral tasks were performed to evaluate motor performance. Luxol Fast Blue (LFB) staining, the expression level of myelin basic protein (MBP), and M1/M2 microglia phenotype genes were assessed in the corpus callosum (CC). The results showed that the combination of Vit D3 and Sipo improved behavioral deficits, significantly promoted remyelination, and modulated expression levels of microglia phenotype genes in the CC at early and late remyelination stages. These results demonstrate for the first time that a combination of Vit D3 and Sipo can improve the remyelination process in the cuprizone (CPZ) mouse model by attenuating the M1 microglia phenotype. This may help to improve the treatment of MS patients.

Cuprizone feed formulation influences the extent of demyelinating disease pathology

Cuprizone is a copper-chelating agent that induces pathology similar to that within some multiple sclerosis (MS) lesions. The reliability and reproducibility of cuprizone for inducing demyelinating disease pathology depends on the animals ingesting consistent doses of cuprizone. Cuprizone-containing pelleted feed is a convenient way of delivering cuprizone, but the efficacy of these pellets at inducing demyelination has been questioned. This study compared the degree of demyelinating disease pathology between mice fed cuprizone delivered in pellets to mice fed a powdered cuprizone formulation at an early 3 week demyelinating timepoint. Within rostral corpus callosum, cuprizone pellets were more effective than cuprizone powder at increasing astrogliosis, microglial activation, DNA damage, and decreasing the density of mature oligodendrocytes. However, cuprizone powder demonstrated greater protein nitration relative to controls. Furthermore, mice fed control powder had significantly fewer mature oligodendrocytes than those fed control pellets. In caudal corpus callosum, cuprizone pellets performed better than cuprizone powder relative to controls at increasing astrogliosis, microglial activation, protein nitration, DNA damage, tissue swelling, and reducing the density of mature oligodendrocytes. Importantly, only cuprizone pellets induced detectable demyelination compared to controls. The two feeds had similar effects on oligodendrocyte precursor cell (OPC) dynamics. Taken together, these data suggest that demyelinating disease pathology is modelled more effectively with cuprizone pellets than powder at 3 weeks. Combined with the added convenience, cuprizone pellets are a suitable choice for inducing early demyelinating disease pathology.

Temporal and spatial evolution of various functional neurons during demyelination induced by cuprizone

Multiple sclerosis (MS) is an inflammatory, demyelinating, and neurodegenerative disease of the central nervous system (CNS). Here we report the temporal and spatial evolution of various functional neurons during demyelination in a cuprizone (CPZ)-induced mouse model. CPZ did not significantly induce the damage of axons and neurons after 2 wk of feeding. However, after 4-6 wk of CPZ feeding, axons and neurons were markedly reduced in the cortex, posterior thalamic nuclear group, and hippocampus. Simultaneously, the expression of TPH⁺ tryptophan neurons and VGLUT1⁺ glutamate neurons was obviously decreased, and the expression of TH⁺ dopaminergic neurons was slightly decreased in the tail part of the substantia nigra striatum, whereas the number of ChAT⁺ cholinergic neurons was not significantly different in the brain. In the second week of feeding, CPZ caused a higher level of glutamate secretion and upregulated the expression of EAAT2 on astrocytes, which should contribute to rapid and sufficient glutamate uptake and removal. This finding reveals that astrocyte-driven glutamate reuptake protected the CNS from excitotoxicity by rapid reuptake of glutamate in 4-6 wk of CPZ feeding. At this stage, although NG2⁺ oligodendroglia progenitor cells (OPCs) were enhanced in the demyelination foci, the myelin sheath was still absent. In conclusion, we comprehensively observed the temporal and spatial evolution of various functional neurons. Our results will assist with understanding how demyelination affects neurons during CPZ-induced demyelination and provide novel information for neuroprotection in myelin regeneration and demyelinating diseases.NEW & NOTEWORTHY Our results further indicate temporal and spatial evolution of various functional neurons during the demyelination in a cuprizone (CPZ)-induced mouse model, which mainly occur 4-6 wk after CPZ feeding. At the same time, the axonal compartment is damaged and, consequently, neuronal death occurs, while glutamate neurons are lost obviously. The astrocyte-mediated glutamate reuptake could protect the neurons from the excitatory effects of glutamate.

Metformin Therapy Attenuates Pro-inflammatory Microglia by Inhibiting NF-κB in Cuprizone Demyelinating Mouse Model of Multiple Sclerosis

Multiple sclerosis (MS) is a chronic disorder characterized by reactive gliosis, inflammation, and demyelination. Microglia plays a crucial role in the pathogenesis of MS and has the dynamic plasticity to polarize between pro-inflammatory (M1) and anti-inflammatory (M2) phenotypes. Metformin, a glucose-lowering drug, attenuates inflammatory responses by activating adenosine monophosphate protein kinase (AMPK) which suppresses nuclear factor kappa B (NF-κB). In this study, we indirectly investigated whether metformin therapy would regulate microglia activity in the cuprizone (CPZ)-induced demyelination mouse model of MS via measuring the markers associated with pro- and anti-inflammatory microglia. Evaluation of myelin by luxol fast blue staining revealed that metformin treatment (CPZ + Met) diminished demyelination, in comparison to CPZ mice. In addition, metformin therapy significantly alleviated reactive microgliosis and astrogliosis in the corpus callosum, as measured by Iba-1 and GFAP staining. Moreover, metformin treatment significantly downregulated the expression of pro-inflammatory associated genes (iNOS, H2-Aa, and TNF-α) in the corpus callosum, whereas expression of anti-inflammatory markers (Arg1, Mrc1, and IL10) was not promoted, compared to CPZ mice. Furthermore, protein levels of iNOS (pro-inflammatory marker) were significantly decreased in the metformin group, while those of Trem2 (anti-inflammatory marker) were increased. In addition, metformin significantly increased AMPK activation in CPZ mice. Finally, metformin administration significantly reduced the activation level of NF-κB in CPZ mice. In summary, our data revealed that metformin attenuated pro-inflammatory microglia markers through suppressing NF-κB activity. The positive effects of metformin on microglia and remyelination suggest that it could be used as a promising candidate to lessen the incidence of inflammatory neurodegenerative diseases such as MS.

CHPG enhances BDNF and myelination in cuprizone-treated mice through astrocytic metabotropic glutamate receptor 5

It is well recognized that astrocytes can produce factors known to affect the myelination process. One such factor, brain-derived neurotrophic factor (BDNF), can enhance the differentiation of oligodendrocyte lineage cells following a demyelinating lesion. Our previous work indicated that enhancing astrocyte-derived BDNF via injection of a general agonist of Group I/II metabotropic glutamate receptors (mGluRs) into the lesion increased myelin proteins in the cuprizone model of demyelination after 4 hr. To determine if this observation has potential therapeutic significance, we now use a more specific mGluR agonist, 2-chloro-5-hydroxyphenylglycine (CHPG), which binds to mGluR5, to examine effects on myelination through the clinically relevant approach of a peripheral injection. In initial studies, intraperitoneal injection of CHPG resulted in an increase in myelin proteins within the lesioned corpus callosum. These effects were blocked when either BDNF or the CHPG receptor, mGluR5, was deleted from glial fibrillary acidic protein (GFAP)+ astrocytes or when the BDNF receptor, tropomyosin receptor kinase B (TrkB), was deleted from proteolipid protein (PLP)+ oligodendrocytes. Moreover, injection of CHPG over 2 weeks not only elevated BDNF and myelin proteins, but also enhanced myelination and reversed behavioral deficits. Interestingly, effects on myelin and myelin proteins were not seen in the control animals, indicating that a lesion is critical in eliciting effects. Taken together, the data suggest that the mGluR agonist CHPG may be a potential therapeutic strategy for treating demyelinating diseases and that it works by enhancing the release of BDNF from astrocytes.

ADAM10 suppresses demyelination and reduces seizure susceptibility in cuprizone-induced demyelination model

The metalloproteinase ADAM10 is the most important amyloid precursor protein (APP) α-secretase, preventing the deposit of neurotoxic amyloid β (Aβ) peptide and generating a soluble APP fragment (sAPP_α) with neurotrophic functions. Recent studies have suggested that ADAM10 also play a role in the pathogenesis of inflammatory CNS diseases, such as multiple sclerosis (MS). Demyelination is the hallmarks of MS but the mechanisms involved remain unclear. Here in this study, we examined the role that ADAM10 might play in the cuprizone-induced demyelination model. Our results demonstrated that ADAM10 expression and sAPP_α production were significantly reduced in the corpus callosum in response to cuprizone treatment. Overexpression of ADAM10 increased sAPP_α production and suppressed demyelination as well as neuroinflammation and oxidative stress in cuprizone-induced demyelination model. Pharmacological inhibition of ADAM10 activity, however, abrogates the protective effect of ADAM10 against demyelination, neuroinflammation and oxidative stress. It has been reported that CNS demyelination may induce seizure activity. Here, we found that overexpression of ADAM10 reduced seizure susceptibility in cuprizone-induced demyelination model, suggesting that ADAM10-derived sAPP_α suppresses demyelination and reduces seizure susceptibility via ameliorating neuroinflammation and oxidative stress in cuprizone-induced demyelination model.

Proteomics of Multiple Sclerosis: Inherent Issues in Defining the Pathoetiology and Identifying (Early) Biomarkers

Multiple Sclerosis (MS) is a demyelinating disease of the human central nervous system having an unconfirmed pathoetiology. Although animal models are used to mimic the pathology and clinical symptoms, no single model successfully replicates the full complexity of MS from its initial clinical identification through disease progression. Most importantly, a lack of preclinical biomarkers is hampering the earliest possible diagnosis and treatment. Notably, the development of rationally targeted therapeutics enabling pre-emptive treatment to halt the disease is also delayed without such biomarkers. Using literature mining and bioinformatic analyses, this review assessed the available proteomic studies of MS patients and animal models to discern (1) whether the models effectively mimic MS; and (2) whether reasonable biomarker candidates have been identified. The implication and necessity of assessing proteoforms and the critical importance of this to identifying rational biomarkers are discussed. Moreover, the challenges of using different proteomic analytical approaches and biological samples are also addressed.

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

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

Oligodendrocyte Lineage Marker Expression in eGFP-GFAP Transgenic Mice

Oligodendrocytes, the myelinating cells of the central nervous system, orchestrate several key cellular functions in the brain and spinal cord, including axon insulation, energy transfer to neurons, and, eventually, modulation of immune responses. There is growing interest for obtaining reliable markers that can specifically label oligodendroglia and their progeny. In many studies, anti-CC1 antibodies, presumably recognizing the protein adenomatous polyposis coli (APC), are used to label mature, myelinating oligodendrocytes. However, it has been discussed whether anti-CC1 antibodies could recognize as well, under pathological conditions, other cell populations, particularly astrocytes. In this study, we used transgenic mice in which astrocytes are labeled by the enhanced green fluorescent protein (eGFP) under the control of the human glial fibrillary acidic protein (GFAP) promoter. By detailed co-localization studies we were able to demonstrate that a significant proportion of eGFP-expressing cells co-express markers of the oligodendrocyte lineage, such as the transcription factor Oligodendrocyte Transcription Factor 2 (OLIG2); the NG2 proteoglycan, also known as chrondroitin sulfate proteoglycan 4 (CSPG4); or APC. The current finding that the GFAP promoter drives transgene expression in cells of the oligodendrocyte lineage should be considered when interpreting results from co-localization studies.

Intranasal anti-caspase-1 therapy preserves myelin and glucose metabolism in a model of progressive multiple sclerosis

Inflammatory demyelination and axonal injury in the central nervous system (CNS) are cardinal features of progressive multiple sclerosis (MS), and linked to activated brain macrophage-like cells (BMCs) including resident microglia and trafficking macrophages. Caspase-1 is a pivotal mediator of inflammation and cell death in the CNS. We investigated the effects of caspase-1 activation and its regulation in models of MS. Brains from progressive MS and non-MS patients, as well as cultured human oligodendrocytes were examined by transcriptomic and morphological methods. Next generation transcriptional sequencing of progressive MS compared to non-MS patients' normal appearing white matter (NAWM) showed induction of caspase-1 as well as other inflammasome-associated genes with concurrent suppression of neuron-specific genes. Oligodendrocytes exposed to TNFα exhibited upregulation of caspase-1 with myelin gene suppression in a cell differentiation state-dependent manner. Brains from cuprizone-exposed mice treated by intranasal delivery of the caspase-1 inhibitor, VX-765 or its vehicle, were investigated in morphological and molecular studies, as well as by fluorodeoxyglucose-positron emission tomography (FDG-PET) imaging. Cuprizone exposure resulted in BMC and caspase-1 activation accompanied by demyelination and axonal injury, which was abrogated by intranasal VX-765 treatment. FDG-PET imaging revealed suppressed glucose metabolism in the thalamus, hippocampus and cortex of cuprizone-exposed mice that was restored with VX-765 treatment. These studies highlight the caspase-1 dependent interactions between inflammation, demyelination, and glucose metabolism in progressive MS and associated models. Intranasal delivery of an anti-caspase-1 therapy represents a promising therapeutic approach for progressive MS and other neuro-inflammatory diseases.

Behavioural and histological changes in cuprizone-fed mice

Feeding cuprizone (CPZ) to mice causes demyelination and reactive gliosis in the central nervous system (CNS), hallmarks of some neurodegenerative diseases like multiple sclerosis. However, relatively little is known regarding the behavioural deficits associated with CPZ-feeding and much of what is known is contradictory. This study investigated whether 37 days oral feeding of 0.2% CPZ to young adult mice evoked sensorimotor behavioural changes. Behavioural tests included measurements of nociceptive withdrawal reflex responses and locomotor tests. Additionally, these were compared to histological analysis of the relevant CNS regions by analysis of neuronal and glial cell components. CPZ-fed mice exhibited more foot slips in walking ladder and beam tests compared to controls. In contrast, no changes in nociceptive thresholds to thermal or mechanical stimuli occurred between groups. Histological analysis showed demyelination throughout the CNS, which was most prominent in white matter tracts in the cerebrum but was also elevated in areas such as the hippocampus, basal ganglia and diencephalon. Profound demyelination and gliosis was seen in the deep cerebellar nuclei and brain stem regions associated with the vestibular system. However, in the spinal cord changes were minimal. No loss of oligodendrocytes, neurons or motoneurons occurred but a significant increase in astrocyte staining ensued throughout the white matter of the spinal cord. The results suggest that CPZ differentially affects oligodendrocytes throughout the CNS and induces subtle motor changes such as ataxia. This is associated with deficits in CNS regions associated with motor and balance functions such as the cerebellum and brain stem.

The Cuprizone Model: Dos and Do Nots

Multiple sclerosis (MS) is a chronic inflammatory demyelinating disease of the central nervous system. Various pre-clinical models with different specific features of the disease are available to study MS pathogenesis and to develop new therapeutic options. During the last decade, the model of toxic demyelination induced by cuprizone has become more and more popular, and it has contributed substantially to our understanding of distinct yet important aspects of the MS pathology. Here, we aim to provide a practical guide on how to use the cuprizone model and which pitfalls should be avoided.

Differential Expression of miRNAs and Behavioral Change in the Cuprizone-Induced Demyelination Mouse Model

The demyelinating diseases of the central nervous system involve myelin abnormalities, oligodendrocyte damage, and consequent glia activation. Neurotoxicant cuprizone (CPZ) was used to establish a mouse model of demyelination. However, the effects of CPZ on microRNA (miRNA) expression and behavior have not been clearly reported. We analyzed the behavior of mice administered a diet containing 0.2% CPZ for 6 weeks, followed by 6 weeks of recovery. Rotarod analysis demonstrated that the treated group had poorer motor coordination than control animals. This effect was reversed after 6 weeks of CPZ withdrawal. Open-field tests showed that CPZ-treated mice exhibited significantly increased anxiety and decreased exploratory behavior. CPZ-induced demyelination was observed to be alleviated after 4 weeks of CPZ treatment, according to luxol fast blue (LFB) staining and myelin basic protein (MBP) expression. miRNA expression profiling showed that the expression of 240 miRNAs was significantly changed in CPZ-fed mice compared with controls. Furthermore, miR-155-5p and miR-20a-5p upregulations enhanced NgR induction through Smad 2 and Smad 4 suppression in demyelination. Taken together, our results demonstrate that CPZ-mediated demyelination induces behavioral deficits with apparent alterations in miRNA expression, suggesting that differences in miRNA expression in vivo may be new potential therapeutic targets for remyelination.

Longitudinal evaluation of demyelinated lesions in a multiple sclerosis model using ultrashort echo time magnetization transfer (UTE-MT) imaging

Alterations in myelin integrity are involved in many neurological disorders and demyelinating diseases, such as multiple sclerosis (MS). Although magnetic resonance imaging (MRI) is the gold standard method to diagnose and monitor MS patients, clinically available MRI protocols show limited specificity for myelin detection, notably in cerebral grey matter areas. Ultrashort echo time (UTE) MRI has shown great promise for direct imaging of lipids and myelin sheaths, and thus holds potential to improve lesion detection. In this study, we used a sequence combining magnetization transfer (MT) with UTE ("UTE-MT", TE ​= ​76 ​μs) and with short TE ("STE-MT", TE ​= ​3000 ​μs) to evaluate spatial and temporal changes in brain myelin content in the cuprizone mouse model for MS on a clinical 7 ​T scanner. During demyelination, UTE-MT ratio (UTE-MTR) and STE-MT ratio (STE-MTR) values were significantly decreased in most white matter and grey matter regions. However, only UTE-MTR detected cortical changes. After remyelination in subcortical and cortical areas, UTE-MTR values remained lower than baseline values, indicating that UTE-MT, but not STE-MT, imaging detected long-lasting changes following a demyelinating event. Next, we evaluated the potential correlations between imaging values and underlying histopathological markers. The strongest correlation was observed between UTE-MTR and percent coverage of myelin basic protein (MBP) immunostaining (r² ​= ​0.71). A significant, although lower, correlation was observed between STE-MTR and MBP (r² ​= ​0.48), and no correlation was found between UTE-MTR or STE-MTR and gliosis immunostaining. Interestingly, correlations varied across brain substructures. Altogether, our results demonstrate that UTE-MTR values significantly correlate with myelin content as measured by histopathology, not only in white matter, but also in subcortical and cortical grey matter regions in the cuprizone mouse model for MS. Readily implemented on a clinical 7 ​T system, this approach thus holds great potential for detecting demyelinating/remyelinating events in both white and grey matter areas in humans. When applied to patients with neurological disorders, including MS patient populations, UTE-MT methods may improve the non-invasive longitudinal monitoring of brain lesions, not only during disease progression but also in response to next generation remyelinating therapies.

Imaging and Quantification of Myelin Integrity After Injury With Spectral Confocal Reflectance Microscopy

Developing a high-throughput approach to quantify the extent of myelin integrity in preclinical models of demyelinating diseases will enhance our capacity to identify novel therapies for myelin repair. In light of the technical limitations of electron microscopy and immunohistochemical analyses of myelination, we have utilized a novel imaging technique, spectral confocal reflectance (SCoRe) microscopy. SCoRe takes advantage of the optically reflective properties of compact myelin, allowing the integrity of compact myelin to be quantified over the course of the cuprizone-induced model of central demyelination. We applied SCoRe imaging on fixed frozen brain sections. SCoRe analysis of control mice identified an increase in corpus callosum myelination during the period of cuprizone administration and recovery, suggesting that the normal developmental processes of myelination are ongoing at this time. Importantly, analysis of mice subjected to cuprizone identified a significant reduction in compact myelin in both rostral and caudal corpus callosum compared to age-matched control mice. SCoRe microscopy also allowed the visualization and quantification of the amount of myelin debris in demyelinating lesions. Combining SCoRe imaging with immunohistochemistry, we quantified the amount of myelin debris within IBA-1+ microglia and found that 11% of myelin debris colocalized in microglia irrespective of the callosal regions, with the vast majority of debris outside of microglia. In summary, we have demonstrated that SCoRe microscopy is an effective and powerful tool to perform both quantitative and qualitative analyses of compact myelin integrity in health or after injury in vivo, demonstrating its future application in high-throughput assessments and screening of the therapeutic efficacy of myelin repair therapies in preclinical animal models of demyelinating diseases.

Biological models in multiple sclerosis

Considering the etiology of multiple sclerosis (MS) is still unknown, experimental models resembling specific aspects of this immune-mediated demyelinating human disease have been developed to increase the understanding of processes related to pathogenesis, disease evolution, evaluation of therapeutic interventions, and demyelination and remyelination mechanisms. Based on the nature of the investigation, biological models may include in vitro, in vivo, and ex vivo assessments. Even though these approaches have disclosed valuable information, every disease animal model has limitations and can only replicate specific features of MS. In vitro and ex vivo models generally do not reflect what occurs in the organism, and in vivo animal models are more likely used; nevertheless, they are able to reproduce only certain stages of the disease. In vivo MS disease animal models in mammals include: experimental autoimmune encephalomyelitis, viral encephalomyelitis, and induced demyelination. This review examines and describes the most common biological disease animal models for the study of MS, their specific characteristics and limitations.

Behavioural phenotypes in the cuprizone model of central nervous system demyelination

The feeding of cuprizone (CPZ) to animals has been extensively used to model the processes of demyelination and remyelination, with many papers adopting a narrative linked to demyelinating conditions like multiple sclerosis (MS), the aetiology of which is unknown. However, no current animal model faithfully replicates the myriad of symptoms seen in the clinical condition of MS. CPZ ingestion causes mitochondrial and endoplasmic reticulum stress and subsequent apoptosis of oligodendrocytes leads to central nervous system demyelination and glial cell activation. Although there are a wide variety of behavioural tests available for characterizing the functional deficits in animal models of disease, including that of CPZ-induced deficits, they have focused on a narrow subset of outcomes such as motor performance, cognition, and anxiety. The literature has not been systematically reviewed in relation to these or other symptoms associated with clinical MS. This paper reviews these tests and makes recommendations as to which are the most important in order to better understand the role of this model in examining aspects of demyelinating diseases like MS.

Clozapine administration enhanced functional recovery after cuprizone demyelination

The atypical antipsychotic agent, clozapine, is used to treat a variety of neurological disorders including schizophrenia and Parkinson's disease and readily crosses the blood brain barrier to interact with a wide range of neuroreceptors including those for dopamine and serotonin. Recent work has shown that clozapine can reduce neuroinflammation in experimental autoimmune encephalomyelitis, a neuroinflammatory model of multiple sclerosis (MS) and mediates its effects in the central nervous system. To further characterise the protection provided by clozapine, the cuprizone model of demyelination was used to assess the effect of clozapine treatment on the cellular events surrounding demyelination and remyelination. Using this model of non-immune demyelination, we found that clozapine administration was unable to prevent demyelination, but when administered post demyelination, was able to enhance the rate of functional recovery. The more rapid improvement of clozapine-treated mice correlated with a decreased level of astrocyte and microglial activation but only modestly enhanced remyelination. Together, these studies highlight the potential of clozapine to support enhanced functional recovery after demyelination, such as that occurring during MS.

Pathological changes in mice with long term cuprizone administration

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system (CNS). In MS, a long disease duration is known to be a strong risk factor for converting the clinical course of the disease from relapse remitting MS to secondary progressing MS. There is a hypothesis that long sustained demyelination may exhaust neurons, however, pathological changes induced in neurons following demyelination remain unknown. Cuprizone administration can induce and sustain demyelination in the mouse CNS. We examined pathological changes in mice following long sustained demyelination caused by up to 34-week cuprizone administration. Twelve-week cuprizone administration induced severe demyelination in the cerebral cortex, corpus callosum and deep cerebellar nuclei. Demyelination persisted up to 34 weeks, as shown by myelin basic protein immunohistochemistry. In contrast, cuprizone administration developed demyelination in the striatum by week 34. In these demyelinated regions, no neuronal loss was observed. However, in the striatum and deep cerebellar nuclei, cuprizone-induced demyelination changed the intracellular distribution of parvalbumin (PV). Furthermore, in the striatum, there was an increase in PV in the demyelinated axons and most PV immunoreactivity did not co-localize with SMI32 immunoreactivity in mice with 34-week cuprizone administration. Further, mice with 34-week cuprizone administration showed motor coordination dysfunction in the balance beam test. However, 12-week withdrawal from the cuprizone diet induced remyelination in the regions and motor coordination dysfunction recovered. These results indicate that 34-week cuprizone administration induces and sustains demyelination and results in reversible motor coordination dysfunction. The change of intracellular PV distribution suggests that PV may protect demyelinated axons by Ca²⁺ buffering. This model may be useful to investigate pathological and behavioral changes following demyelination in the CNS.

Effect of the CSF1R inhibitor PLX3397 on remyelination of corpus callosum in a cuprizone-induced demyelination mouse model

Multiple sclerosis (MS) is a chronic inflammatory disease affecting the central nervous system (CNS). Despite introducing multiple immunomodulatory approaches for MS, there are still major concerns about possible ways for improving remyelination in this disease. Microglia exert essential roles in regulation of myelination processes, and interaction between colony-stimulating factor 1 (CSF1) with its receptor CSF1R is considered as a key regulator of microglial differentiation and survival. The aim of this study was to investigate possible roles for a CSF1R inhibitor PLX3397 in recovery of central myelination processes. Chronic demyelination was induced in mice by addition of 0.2% cuprizone to the chow for 12 weeks. Next, animals were undergoing a diet containing 290 mg/kg PLX3397 to induce microglial ablation. The PLX3397 treatment caused a significant decrease in the rate of expression for the CSF1/CSF1R axis, and a reduction in the protein expressions for the microglial marker Iba-1 and for the oligodendrocyte marker Olig-2. Findings from Luxol fast blue (LFB) staining and transmission electron microscopy (TEM) showed an increase in the rate of myelination for the mice receiving PLX3397. The rate of destruction in the nerve fibers and the extent of the gaps formed between layers of myelin sheaths was also reduced after the treatment with PLX3397. In addition, animals experienced an improvement in recovery of motor deficit after receiving PLX3397 (for all P < 0.05). It could be concluded that PLX3397 could retain myelination in the MS model possibly through regulation of the myelin environment.

Five Decades of Cuprizone, an Updated Model to Replicate Demyelinating Diseases

INTRODUCTION

Demyelinating diseases of the central nervous system (CNS) comprise a group of neurological disorders characterized by progressive (and eventually irreversible) loss of oligodendrocytes and myelin sheaths in the white matter tracts. Some of myelin disorders include: Multiple sclerosis, Guillain-Barré syndrome, peripheral nerve polyneuropathy and others. To date, the etiology of these disorders is not well known and no effective treatments are currently available against them. Therefore, further research is needed to gain a better understand and treat these patients. To accomplish this goal, it is necessary to have appropriate animal models that closely resemble the pathophysiology and clinical signs of these diseases. Herein, we describe the model of toxic demyelination induced by cuprizone (CPZ), a copper chelator that reduces the cytochrome and monoamine oxidase activity into the brain, produces mitochondrial stress and triggers the local immune response. These biochemical and cellular responses ultimately result in selective loss of oligodendrocytes and microglia accumulation, which conveys to extensive areas of demyelination and gliosis in corpus callosum, superior cerebellar peduncles and cerebral cortex. Remarkably, some aspects of the histological pattern induced by CPZ are similar to those found in multiple sclerosis. CPZ exposure provokes behavioral changes, impairs motor skills and affects mood as that observed in several demyelinating diseases. Upon CPZ removal, the pathological and histological changes gradually revert. Therefore, some authors have postulated that the CPZ model allows to partially mimic the disease relapses observed in some demyelinating diseases.

CONCLUSION

for five decades, the model of CPZ-induced demyelination is a good experimental approach to study demyelinating diseases that has maintained its validity, and is a suitable pharmacological model for reproducing some key features of demyelinating diseases, including multiple sclerosis.

Changes in neurosteroidogenesis during demyelination and remyelination in cuprizone-treated mice

Changes of neurosteroids may be involved in the pathophysiology of multiple sclerosis (MS). The present study investigated whether changes of neurosteroidogenesis also occurred in the grey and white matter regions of the brain in mice subjected to cuprizone-induced demyelination. Accordingly, we compared the expression of neurosteroidogenic proteins, including steroidogenic acute regulatory protein (StAR), voltage-dependent anion channel (VDAC) and 18 kDa translocator protein (TSPO), as well as neurosteroidogenic enzymes, including the side chain cleavage enzyme (P450scc), 3β-hydroxysteroid dehydrogenase/isomerase and 5α-reductase (5α-R), during the demyelination and remyelination periods. Using immunohistochemistry and a quantitative polymerase chain reaction, we demonstrated a decreased expression of StAR, P450scc and 5α-R with respect to an increase astrocytic and microglial reaction and elevated levels of tumor necrosis factor (TNF)α during the cuprizone demyelination period in the hippocampus, cortex and corpus callosum. These parameters, as well as the glial reaction, were normalised after 2 weeks of spontaneous remyelination in regions containing grey matter. Conversely, persistent elevated levels of TNFα and low levels of StAR and P450scc were observed during remyelination in corpus callosum white matter. We conclude that neurosteroidogenesis/myelination status and glial reactivity are inversely related in the hippocampus and neocortex. Establishing a cause and effect relationship for the measured variables remains a future challenge for understanding the pathophysiology of MS.

Low-level laser therapy modulates demyelination in mice

There are no effective therapies for remyelination. Low-level laser therapy (LLLT) has been found advantageous in neurogenesis promotion, cell death prevention, and modulation of inflammation in central and peripheral nervous system models. The purpose of this study was to analyse LLLT effects on cuprizone-induced demyelination. Mice were randomly distributed into three groups: Control Laser (CTL), Cuprizone (CPZ), and Cuprizone Laser (CPZL). Mice from CPZ and CPZL groups were exposed to a 0.2% cuprizone oral diet for four complete weeks. Six sessions of transcranial laser irradiation were applied on three consecutive days, during the third and fourth weeks, with parameters of 36 J/cm², 50 mW, 0.028 cm² spot area, continuous wave, 1 J, 20 s, 1.78 W/cm² in a single point equidistant between the eyes and ears of CTL and CPZL mice. Motor coordination was assessed by the rotarod test. Twenty-four hours after the last laser session, all animals were euthanized, and brains were extracted. Serum was obtained for lactate dehydrogenase toxicity testing. Histomorphological analyses consisted of Luxol Fast Blue staining and immunohistochemistry. The results showed that laser-treated animals presented motor performance improvement, attenuation of demyelination, increased number of oligodendrocyte precursor cells, modulated microglial and astrocytes activation, and a milder toxicity by cuprizone. Although further studies are required, it is suggested that LLLT represents a feasible therapy for demyelinating diseases.

Kolaviron Protects the Prefrontal Cortex and Hippocampus against Histomorphological and Neurobehavioural Changes in Cuprizone Model of Multiple Sclerosis

Background

This study explored the efficacy of kolaviron-a biflavonoid complex isolated from the seeds of Garcinia kola-in protecting against cuprizone (CPZ)-induced demyelination in both the prefrontal cortex and the hippocampus of Wistar rats.

Methodology

Thirty rats were treated to receive 0.5 mL phosphate-buffered saline (group A, control), 0.5 mL corn oil (group B), 0.2% CPZ (group C), for 6 weeks, 0.2% CPZ for 3 weeks and then 200 mg/kg of Kv for 3 weeks (group D), or 200 mg/kg of Kv for 3 weeks followed by 0.2% CPZ for 3 weeks (group E). Rats were assessed for exploratory functions and anxiety-like behaviour before being euthanised and perfused transcardially with 4% paraformaldehyde. Prefrontal and hippocampal thin sections were stained in hematoxylin and eosin and cresyl fast violet stains.

Results

CPZ-induced demyelination resulted in behavioural impairment as seen by reduced exploratory activities, rearing behaviour, stretch attend posture, center square entry, and anxiogenic characteristics. Degenerative changes including pyknosis, karyorrhexis, neuronal hypertrophy, and reduced Nissl integrity were also seen. Animals treated with Kv showed significant improvement in behavioural outcomes and a comparatively normal cytoarchitectural profile.

Conclusion

Kv provides protective roles against CPZ-induced neurotoxicity through prevention of ribosomal protein degradation.

Redox metals homeostasis in multiple sclerosis and amyotrophic lateral sclerosis: a review

The effect of redox metals such as iron and copper on multiple sclerosis and amyotrophic lateral sclerosis has been intensively studied. However, the origin of these disorders remains uncertain. This review article critically describes the physiology of redox metals that produce oxidative stress, which in turn leads to cascades of immunomodulatory alteration of neurons in multiple sclerosis and amyotrophic lateral sclerosis. Iron and copper overload has been well established in motor neurons of these diseases’ lesions. On the other hand, the role of other metals like cadmium participating indirectly in the redox cascade of neurobiological mechanism is less studied. In the second part of this review, we focus on this less conspicuous correlation between cadmium as an inactive-redox metal and multiple sclerosis and amyotrophic lateral sclerosis, providing novel treatment modalities and approaches as future prospects.

Quantitative analysis of lipid debris accumulation caused by cuprizone induced myelin degradation in different CNS areas

Degradation of myelin sheath is thought to be the cause of neurodegenerative diseases, such as multiple sclerosis (MS), but definitive agreement on the mechanism of how myelin is lost is currently lacking. Autoimmune initiation of MS has been recently questioned by proposing that the immune response is a consequence of oligodendrocyte degeneration. To study the process of myelin breakdown, we induced demyelination with cuprizone and applied coherent anti-Stokes Raman scattering (CARS) microscopy, a non-destructive label-free method to image lipid structures in living tissue. We confirmed earlier results showing a brain region dependent myelin destructive effect of cuprizone. In addition, high resolution in situ CARS imaging revealed myelin debris forming lipid droplets alongwith myelinated axon fibers. Quantification of lipid debris with custom-made software for segmentation and three dimensional reconstruction revealed brain region dependent accumulation of lipid drops inversely correlated with the thickness of myelin sheaths. Finally, we confirmed that in situ CARS imaging is applicable to living human brain tissue in brain slices derived from a patient. Thus, CARS microscopy is potent tool for quantitative monitoring of myelin degradation in unprecedented spatiotemporal resolution during oligodendrocyte damage. We think that the accumulation of lipid drops around degrading myelin might be instrumental in triggering subsequent inflammatory processes.

The flavonoid Baicalein attenuates cuprizone-induced demyelination via suppression of neuroinflammation

Multiple sclerosis (MS) is a chronic demyelinating disease of the central nervous system characterized by recurrent and progressive demyelination/remyelination cycles, neuroinflammation, oligodendrocyte loss, and axonal pathology. Baicalein isolated from the roots of Scutellaria baicalensis has been shown to exert anti-inflammatory and antioxidant effects. The cuprizone model is an established mouse model of MS and causes demyelination and motor dysfunction and induces neuroinflammation, such as glial activation and pro-inflammatory cytokine production. To determine whether Baicalein attenuates cuprizone-induced demyelination, we administrated Baicalein to cuprizone-exposed mice. Baicalein attenuated weight loss (P<0.05) and motor dysfunction (P<0.05) in the cuprizone model mice. Baicalein treatment effectively suppressed the demyelination (P<0.01) and gene expressions of CNP (P<0.05) and MBP (P<0.05). Baicalein treatment also inhibited the cuprizone-induced increase in Iba1-positive microglia (P<0.001), GFAP-positive astrocytes (P<0.001), and the gene expressions of CD11b (P<0.01), GFAP (P<0.05), TNFα (P<0.05), IL-1β (P<0.05), and iNOS (p<0.01). We found that Baicalein treatment attenuated cuprizone-induced demyelination, glial activation, pro-inflammatory cytokine expression, and motor dysfunction. Our results suggest that Baicalein may be a useful therapeutic agent in demyelinating diseases to suppress neuroinflammation.

Conditional Deletion of the L-Type Calcium Channel Cav1.2 in NG2-Positive Cells Impairs Remyelination in Mice

Exploring the molecular mechanisms that drive the maturation of oligodendrocyte progenitor cells (OPCs) during the remyelination process is essential to developing new therapeutic tools to intervene in demyelinating diseases such as multiple sclerosis. To determine whether L-type voltage-gated calcium channels (L-VGCCs) are required for OPC development during remyelination, we generated an inducible conditional knock-out mouse in which the L-VGCC isoform Cav1.2 was deleted in NG2-positive OPCs (Cav1.2^KO). Using the cuprizone (CPZ) model of demyelination and mice of either sex, we establish that Cav1.2 deletion in OPCs leads to less efficient remyelination of the adult brain. Specifically, Cav1.2^KO OPCs mature slower and produce less myelin than control oligodendrocytes during the recovery period after CPZ intoxication. This reduced remyelination was accompanied by an important decline in the number of myelinating oligodendrocytes and in the rate of OPC proliferation. Furthermore, during the remyelination phase of the CPZ model, the corpus callosum of Cav1.2^KO animals presented a significant decrease in the percentage of myelinated axons and a substantial increase in the mean g-ratio of myelinated axons compared with controls. In addition, in a mouse line in which the Cav1.2^KO OPCs were identified by a Cre reporter, we establish that Cav1.2^KO OPCs display a reduced maturational rate through the entire remyelination process. These results suggest that Ca²⁺ influx mediated by L-VGCCs in oligodendroglial cells is necessary for normal remyelination and is an essential Ca²⁺ channel for OPC maturation during the remyelination of the adult brain.SIGNIFICANCE STATEMENT Ion channels implicated in oligodendrocyte differentiation and maturation may induce positive signals for myelin recovery. Voltage-gated Ca²⁺ channels (VGCCs) are important for normal myelination by acting at several critical steps during oligodendrocyte progenitor cell (OPC) development. To determine whether voltage Ca²⁺ entry is involved in oligodendrocyte differentiation and remyelination, we used a conditional knockout mouse for VGCCs in OPCs. Our results indicate that VGCCs can modulate oligodendrocyte maturation in the demyelinated brain and suggest that voltage-gated Ca²⁺ influx in OPCs is critical for remyelination. These findings could lead to novel approaches for obtaining a better understanding of the factors that control OPC maturation in order to stimulate this pool of progenitors to replace myelin in demyelinating diseases.

Early regional cuprizone-induced demyelination in a rat model revealed with MRI

The cuprizone model of demyelination is well established in the mouse as a tool for the study of the mechanisms of both demyelination and remyelination. It is often desirable, however, to have a larger model, such as the rat, especially for imaging-based studies, yet initial work has failed to show demyelination in cuprizone-fed rats. Several recent studies have demonstrated demyelination in the rat, but only in the corpus callosum. In this study, we acquired high-resolution, three-dimensional images of the whole brain every 2 weeks, using a T₁ -weighted magnetization-prepared rapid acquisition gradient echo imaging sequence, optimized for myelin contrast, in order to assess myelination across the entire rat brain over a period of 8 weeks on a 1% cuprizone diet. We observed a consistent pattern of demyelination, beginning in the cerebellum by 4 weeks and involving more rostral regions of the brain by 8 weeks on the cuprizone diet, with validation using Luxol fast blue histology. This imaging technique permits the effects of cuprizone-induced demyelination to be followed longitudinally in a single animal, over the entire brain. In turn, this may facilitate the establishment of the cuprizone model of demyelination in the rat.

Combination of cuprizone and experimental autoimmune encephalomyelitis to study inflammatory brain lesion formation and progression

Brain-intrinsic degenerative cascades are a proposed factor driving inflammatory lesion formation in multiple sclerosis (MS) patients. We recently described a model combining noninflammatory cytodegeneration (via cuprizone) with the classic active experimental autoimmune encephalomyelitis (Cup/EAE model), which exhibits inflammatory forebrain lesions. Here, we describe the histopathological characteristics and progression of these Cup/EAE lesions. We show that inflammatory lesions develop at various topographical sites in the forebrain, including white matter tracts and cortical and subcortical grey matter areas. The lesions are characterized by focal demyelination, discontinuation of the perivascular glia limitans, focal axonal damage, and neutrophil granulocyte extravasation. Transgenic mice with enhanced green fluorescent protein-expressing microglia and red fluorescent protein-expressing monocytes reveal that both myeloid cell populations contribute to forebrain inflammatory infiltrates. EAE-triggered inflammatory cerebellar lesions were augmented in mice pre-intoxicated with cuprizone. Gene expression studies suggest roles of the chemokines Cxcl10, Ccl2, and Ccl3 in inflammatory lesion formation. Finally, follow-up experiments in Cup/EAE mice with chronic disease revealed that forebrain, but not spinal cord, lesions undergo spontaneous reorganization and repair. This study underpins the significance of brain-intrinsic degenerative cascades for immune cell recruitment and, in consequence, MS lesion formation.

The novel synthetic microneurotrophin BNN27 protects mature oligodendrocytes against cuprizone-induced death, through the NGF receptor TrkA

BNN27, a member of a chemical library of C17-spiroepoxy derivatives of the neurosteroid DHEA, has been shown to regulate neuronal survival through its selective interaction with NGF receptors (TrkA and p75NTR ), but its role on glial populations has not been studied. Here, we present evidence that BNN27 provides trophic action (rescue from apoptosis), in a TrkA-dependent manner, to mature oligodendrocytes when they are challenged with the cuprizone toxin in culture. BNN27 treatment also increases oligodendrocyte maturation and diminishes microglia activation in vitro. The effect of BNN27 in the cuprizone mouse model of demyelination in vivo has also been investigated. In this model, that does not directly involve the adaptive immune system, BNN27 can protect from demyelination without affecting the remyelinating process. BNN27 preserves mature oligodendrocyte during demyelination, while reducing microgliosis and astrogliosis. Our findings suggest that BNN27 may serve as a lead molecule to develop neurotrophin-like blood-brain barrier (BBB)-permeable protective agents of oligodendrocyte populations and myelin, with potential applications in the treatment of demyelinating disorders.

Reduced cuprizone-induced cerebellar demyelination in mice with astrocyte-targeted production of IL-6 is associated with chronically activated, but less responsive microglia

BACKGROUND

Cerebellar pathology is a frequent feature of multiple sclerosis (MS), a demyelinating and neuroinflammatory disease of the central nervous system (CNS). Interleukin (IL)-6 is a multifunctional cytokine with a potential role in MS. Here we studied cuprizone-induced cerebellar pathology in transgenic mice with astrocyte-targeted production of IL-6 (GFAP-IL6), specifically focusing on demyelination, oligodendrocyte depletion and microglial cell response.

RESULTS

Over the course of cuprizone treatment, when compared with WT mice, GFAP-IL6Tg showed a reduced demyelination in the deep lateral cerebellar nuclei (LCN). The oligodendrocyte numbers in the LCN were comparable between WT and GFAP-IL6Tg mice after 4-6weeks of cuprizone treatment, however after the chronic cuprizone treatment (12weeks) we detected higher numbers of oligodendrocytes in GFAP-IL6Tg mice. Contrary to strong cuprizone-induced microglial activation in the LCN of WT mice, GFAP-IL6Tg mice had minimal cuprizone-induced microglial changes, despite an already existing reactive microgliosis in control GFAP-IL6Tg not present in control WT mice.

CONCLUSIONS

Our results show that chronic transgenic production of IL-6 reduced cuprizone-induced cerebellar demyelination and induced a specific activation state of the resident microglia population (Iba1⁺, CD11b⁺, MHCII⁺, CD68^-), likely rendering them less responsive to subsequent injury signals.

Cuprizone-Containing Pellets Are Less Potent to Induce Consistent Demyelination in the Corpus Callosum of C57BL/6 Mice

The chopper chelator cuprizone serves as a valuable chemical tool to induce consistent and reproducible demyelination in the central nervous system. However, the daily preparation of fresh cuprizone powder mixed in finely ground rodent chow might well be a particular health problem. Alternative methods, such as the fabrication of cuprizone-containing pellets, are available. The effectiveness of this method is, however, not known. In the present study, we compared whether intoxication of C57BL/6 mice with 0.25% cuprizone mixed into ground rodent chow does induce demyelination to a similar extent compared to a cuprizone-pellet intoxication protocol. We found that feeding of 0.25% cuprizone in ground chow provides a strong, well-defined, and reproducible demyelination along with increased accumulation of microglia and axonal damage in the corpus callosum, whereas all analyzed parameters were significantly less distinct in mice fed with cuprizone-containing pellets at an equivalent concentration of cuprizone at week 5. Even a higher concentration of cuprizone in pellet formulation was less potent compared to do so. This study illustrates that the established protocol of cuprizone intoxication (i.e., mixed in ground rodent chow) is the gold standard method to achieve consistent and reproducible demyelination. Why cuprizone loses its effectiveness in pellet formulation needs to be addressed in subsequent studies.

Investigation of Cuprizone Inactivation by Temperature

Animal models, such as cuprizone (bis-cyclohexanone oxaldihydrazone) feeding, are helpful to study experimental demyelination and remyelination in the context of diseases like multiple sclerosis. Cuprizone is a copper chelator, which when supplemented to the normal food of C57BL/6J mice in a concentration of 0.2% leads to oligodendroglial loss, subsequent microglia and astrocyte activation, resulting in demyelination. Termination of the cuprizone diet results in remyelination, promoted by newly formed mature oligodendrocytes. The exact mode of cuprizone's action is not well understood, and information about its inactivation and cleavage are still not available. The knowledge of these processes could lead to a better understanding of cuprizone's mode of action, as well as a safer handling of this toxin. We therefore performed experiments with the aim to inactivate cuprizone by thermal heating, since it was suggested in the past that cuprizone is heat sensitive. C57BL/6J mice were fed for 4 weeks with 0.2% cuprizone, either thermally pretreated (60, 80, 105, 121 °C) or not heated. In addition, primary rat oligodendrocytes, as a known selective toxic target of cuprizone, were incubated with 350 μM cuprizone solutions, which were either thermally pretreated or not. Our results demonstrate that none of the tested thermal pretreatment conditions could abrogate or restrict the toxic and demyelinating effects of cuprizone, neither in vitro nor in vivo. In conclusion, the current study rebuts the hypothesis of cuprizone as a heat-sensitive compound, as well as the assumption that heat exposure is a reason for an insufficient demyelination of cuprizone-containing pellets.

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.

Whole-brain ex-vivo quantitative MRI of the cuprizone mouse model

Myelin is a critical component of the nervous system and a major contributor to contrast in Magnetic Resonance (MR) images. However, the precise contribution of myelination to multiple MR modalities is still under debate. The cuprizone mouse is a well-established model of demyelination that has been used in several MR studies, but these have often imaged only a single slice and analysed a small region of interest in the corpus callosum. We imaged and analyzed the whole brain of the cuprizone mouse ex-vivo using high-resolution quantitative MR methods (multi-component relaxometry, Diffusion Tensor Imaging (DTI) and morphometry) and found changes in multiple regions, including the corpus callosum, cerebellum, thalamus and hippocampus. The presence of inflammation, confirmed with histology, presents difficulties in isolating the sensitivity and specificity of these MR methods to demyelination using this model.

Activation of the astrocytic Nrf2/ARE system ameliorates the formation of demyelinating lesions in a multiple sclerosis animal model

Oxidative stress critically contributes to the pathogenesis of a variety of neurodegenerative diseases such as multiple sclerosis. Astrocytes are the main regulators of oxidative homeostasis in the brain and dysregulation of these cells likely contributes to the accumulation of oxidative damage. The nuclear factor erythroid 2-related factor 2 (Nrf2) is the main transcriptional regulator of the anti-oxidant stress defense. In this study, we elucidate the effects of astrocytic Nrf2-activation on brain-intrinsic inflammation and lesion development. Cells deficient for the Nrf2 repressor kelch-like ECH-associated protein 1 (Keap1) are characterized by hyperactivation of Nrf2-signaling. Therefore, wild type mice and mice with a GFAP-specific Keap1-deletion were fed with 0.25% cuprizone for 1 or 3 weeks. Cuprizone intoxication induced pronounced oligodendrocyte loss, demyelination and reactive gliosis in wild type animals. In contrast, astrocyte-specific Nrf2-activation was sufficient to prevent oligodendrocyte loss and demyelination, to ameliorate brain intrinsic inflammation and to counteract axonal damage. Our results highlight the potential of the Nrf2/ARE system for the treatment of neuroinflammation in general and of multiple sclerosis in particular. © GLIA 2016;64:2219-2230.

Involvement of Neuroinflammation during Brain Development in Social Cognitive Deficits in Autism Spectrum Disorder and Schizophrenia

Development of social cognition, a unique and high-order function, depends on brain maturation from childhood to adulthood in humans. Autism spectrum disorder (ASD) and schizophrenia have similar social cognitive deficits, although age of onset in each disorder is different. Pathogenesis of these disorders is complex and contains several features, including genetic risk factors, environmental risk factors, and sites of abnormalities in the brain. Although several hypotheses have been postulated, they seem to be insufficient to explain how brain alterations associated with symptoms in these disorders develop at distinct developmental stages. Development of ASD appears to be related to cerebellar dysfunction and subsequent thalamic hyperactivation in early childhood. By contrast, schizophrenia seems to be triggered by thalamic hyperactivation in late adolescence, whereas hippocampal aberration has been possibly initiated in childhood. One of the possible culprits is metal homeostasis disturbances that can induce dysfunction of blood-cerebrospinal fluid barrier. Thalamic hyperactivation is thought to be induced by microglia-mediated neuroinflammation and abnormalities of intracerebral environment. Consequently, it is likely that the thalamic hyperactivation triggers dysregulation of the dorsolateral prefrontal cortex for lower brain regions related to social cognition. In this review, we summarize the brain aberration in ASD and schizophrenia and provide a possible mechanism underlying social cognitive deficits in these disorders based on their distinct ages of onset.

Resveratrol Promotes Remyelination in Cuprizone Model of Multiple Sclerosis: Biochemical and Histological Study

Multiple sclerosis (MS) is a demyelinating neurodegenerative disease, representing a major cause of neurological disability in young adults. Resveratrol is a stilbenoid polyphenol, known to pass blood brain barrier and exhibit antioxidant, anti-inflammatory, and neuroprotective effects in several brain injuries. Cuprizone model of MS is particularly beneficial in studying demyelination/remyelination. Our study examined the potential neuroprotective and pro-remyelination effects of resveratrol in cuprizone-intoxicated C57Bl/6 mice. Mice were fed with chow containing 0.7 % cuprizone for 7 days, followed by 3 weeks on 0.2 % cuprizone diet. Resveratrol (250 mg/kg/day, p.o.) was given for 3 weeks starting from the second week. At the end of the experiment, animals were tested on rotarod to evaluate changes in balance and motor coordination. Mice were then sacrificed to measure the brain content of glutathione, lipid peroxidation products, adenosine triphosphate, and phospho-inhibitory subunit of nuclear factor κB-α. The activities of cytochrome oxidase and superoxide dismutase were also assessed. The gene expression of myelin basic protein, 2',3'-cyclic nucleotide 3' phosphodiesterase, oligodendrocyte transcription factor-1 (Olig1), NF-κB p65 subunit, and tumor necrosis factor-α was also estimated. Luxol fast blue/periodic acid-Schiff stained brain sections were blindly scored to assess the myelin status. Resveratrol effectively enhanced motor coordination and balance, reversed cuprizone-induced demyelination, improved mitochondrial function, alleviated oxidative stress, and inhibited NF-κB signaling. Interestingly, resveratrol increased Olig1 expression that is positively correlated to active remyelination. The present study may be the first to indicate a pro-remyelinative effect for resveratrol which might represent a potential additive benefit in treating MS.