Characterization of three human oligodendroglial cell lines as a model to study oligodendrocyte injury: morphology and oligodendrocyte-specific gene expression

Human oligodendrocyte-like cell differentiation is promoted by TSPO-mediated endogenous steroidogenesis

Mature oligodendrocytes (OLs) arise from oligodendrocyte precursor cells that, in case of demyelination, are recruited at the lesion site to remyelinate the axons and therefore restore the transmission of nerve impulses. It has been widely documented that exogenously administered steroid molecules are potent inducers of myelination. However, little is known about how neurosteroids produced de novo by OLs can impact this process. Here, we employed a human OL precursor cell line to investigate the role of de novo neurosteroidogenesis in the regulation of OLs differentiation, paying particular attention to the 18 kDa Translocator Protein (TSPO) which controls the rate-limiting step of the neurosteroidogenic process. Our results showed that, over the time of OL maturation, the availability of cholesterol, which is the neurosteroidogenesis initial substrate, and key members of the neurosteroidogenic machinery, including TSPO, were upregulated. In addition, OLs differentiation was impaired following neurosteroidogenesis inhibition and TSPO silencing. On the contrary, TSPO pharmacological stimulation promoted neurosteroidogenic function and positively impacted differentiation. Collectively, our results suggest that de novo neurosteroidogenesis is actively involved in the autocrine and paracrine regulation of human OL differentiation. Moreover, since TSPO was able to promote OL differentiation through a positive modulation of the neurosteroid biosynthetic process, it could be exploited as a promising target to tackle demyelinating diseases.

A primary culture method for the easy, efficient, and effective acquisition of oligodendrocyte lineage cells from neonatal rodent brains

Oligodendrocytes (OL) are myelin-forming glial cells in the central nervous system. In vitro primary OL culture models offer the benefit of a more readily controlled environment that facilitates the examination of diverse OL stages and their intricate dynamics. Although conventional methods for primary OL culture exist, their performance in terms of simplicity and efficiency can be improved. Here, we introduce a novel method for primary OL culture, namely the E3 (easy, efficient, and effective) method, which greatly improves the simplicity and efficiency of the primary OL culture procedure using neonatal rodent brains. We also provided the optimal media composition for the augmentation of oligodendrocyte progenitor cell (OPC) proliferation and more robust maturation into myelin-forming OLs. Overall, E3 offers an undemanding method for obtaining primary OLs with high yield and quality. Alongside its value as a practical tool, in vitro characteristics of the OL lineage additionally identified during the development of the E3 method have implications for advancing research on OL physiology and pathophysiology.

Glycine disrupts myelin, glutamatergic neurotransmission, and redox homeostasis in a neonatal model for non ketotic hyperglycinemia

Non ketotic hyperglycinemia (NKH) is an inborn error of glycine metabolism caused by mutations in the genes encoding glycine cleavage system proteins. Classic NKH has a neonatal onset, and patients present with severe neurodegeneration. Although glycine accumulation has been implicated in NKH pathophysiology, the exact mechanisms underlying the neurological damage and white matter alterations remain unclear. We investigated the effects of glycine in the brain of neonatal rats and MO3.13 oligodendroglial cells. Glycine decreased myelin basic protein (MBP) and myelin-associated glycoprotein (MAG) in the corpus callosum and striatum of rats on post-natal day (PND) 15. Glycine also reduced neuroglycan 2 (NG2) and N-methyl-d-aspartate receptor subunit 1 (NR1) in the cerebral cortex and striatum on PND15. Moreover, glycine reduced striatal glutamate aspartate transporter 1 (GLAST) content and neuronal nucleus (NeuN), and increased glial fibrillary acidic protein (GFAP) on PND15. Glycine also increased DCFH oxidation and malondialdehyde levels and decreased GSH concentrations in the cerebral cortex and striatum on PND6, but not on PND15. Glycine further reduced viability but did not alter DCFH oxidation and GSH levels in MO3.13 cells after 48- and 72-h incubation. These data indicate that impairment of myelin structure and glutamatergic system and induction of oxidative stress are involved in the neuropathophysiology of NKH.

Using Human Fetal Neural Stem Cells to Elucidate the Role of the JAK-STAT Cell Signaling Pathway in Oligodendrocyte Differentiation In Vitro

Oligodendrocytes (OL) are the myelinating cells of the central nervous system that mediate nerve conduction. Loss of oligodendrocytes results in demyelination, triggering neurological deficits. Developing a better understanding of the cell signaling pathways influencing OL development may aid in the development of therapeutic strategies. The primary focus of this study was to investigate and elucidate the cell signaling pathways implicated in the developmental maturation of oligodendrocytes using human fetal neural stem cells (hFNSCs)-derived primary OL and MO3.13 cell line. Successful differentiation into OL was established by examining morphological changes, increased expression of mature OL markers MBP, MOG and decreased expression of pre-OL markers CSPG4 and O4. Analyzing transcriptional datasets (using RNA sequencing) in pre-OL and mature OL derived from hFNSCs revealed the novel and critical involvement of the JAK-STAT cell signaling pathway in terminal OL maturation. The finding was validated in MO3.13 cell line whose differentiation was accompanied by upregulation of IL-6 and the transcription factor STAT3. Increased phosphorylated STAT3 (pY705) levels were demonstrated by western blotting in hFNSCs-derived primary OL as well as terminal maturation in MO3.13 cells, thus validating the involvement of the JAK-STAT pathway in OL maturation. Pharmacological suppression of STAT3 phosphorylation (confirmed by western blotting) was able to prevent the increase of MBP-positive cells as demonstrated by flow cytometry. These novel findings highlight the involvement of the JAK-STAT pathway in OL maturation and raise the possibility of using this as a therapeutic strategy in demyelinating diseases.

Iron Bioavailability in the Extracellular Environment Is More Relevant Than the Intracellular One in Viability and Gene Expression: A Lesson from Oligodendroglioma Cells

Oligodendroglioma (OG) is a brain tumor that contributes to <1% of brain tumor diagnoses in the pediatric population. Unfortunately, pediatric OG remains without definitive molecular characteristics to aid in diagnosis, and little is known about the tumor microenvironment. Tumor cells' metabolism and proliferation rate are generally higher than those of healthy cells, so their iron demand is also significantly higher. This consideration underlines the great importance of iron for tumor development and progression. In this context, this study aims to evaluate the effect of iron in a cellular in vitro model of human oligodendroglioma brain tumor. Cell morphology, the effect of siderotic medium on cell growth, iron uptake, and the expression of iron-metabolism-related genes were evaluated via optic microscopy, ICP-MS, confocal microscopy, and real-time PCR, respectively. This study underlines the great importance of iron for tumor development and progression and also the possibility of reducing the available iron concentration to determine an antiproliferative effect on OG. Therefore, every attempt can be promising to defeat OG for which there are currently no long-term curative therapies.

Myelin Disruption, Neuroinflammation, and Oxidative Stress Induced by Sulfite in the Striatum of Rats Are Mitigated by the pan-PPAR agonist Bezafibrate

Sulfite predominantly accumulates in the brain of patients with isolated sulfite oxidase (ISOD) and molybdenum cofactor (MoCD) deficiencies. Patients present with severe neurological symptoms and basal ganglia alterations, the pathophysiology of which is not fully established. Therapies are ineffective. To elucidate the pathomechanisms of ISOD and MoCD, we investigated the effects of intrastriatal administration of sulfite on myelin structure, neuroinflammation, and oxidative stress in rat striatum. Sulfite administration decreased Fluoromyelin^TM and myelin basic protein staining, suggesting myelin abnormalities. Sulfite also increased the staining of NG2, a protein marker of oligodendrocyte progenitor cells. In line with this, sulfite also reduced the viability of MO3.13 cells, which express oligodendroglial markers. Furthermore, sulfite altered the expression of interleukin-1β (IL-1β), interleukin-6 (IL-6), interleukin-10 (IL-10), cyclooxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS) and heme oxygenase-1 (HO-1), indicating neuroinflammation and redox homeostasis disturbances. Iba1 staining, another marker of neuroinflammation, was also increased by sulfite. These data suggest that myelin changes and neuroinflammation induced by sulfite contribute to the pathophysiology of ISOD and MoCD. Notably, post-treatment with bezafibrate (BEZ), a pan-PPAR agonist, mitigated alterations in myelin markers and Iba1 staining, and IL-1β, IL-6, iNOS and HO-1 expression in the striatum. MO3.13 cell viability decrease was further prevented. Moreover, pre-treatment with BEZ also attenuated some effects. These findings show the modulation of PPAR as a potential opportunity for therapeutic intervention in these disorders.

In Vitro Effects of Methylprednisolone over Oligodendroglial Cells: Foresight to Future Cell Therapies

The implantation of oligodendrocyte precursor cells may be a useful therapeutic strategy for targeting remyelination. However, it is yet to be established how these cells behave after implantation and whether they retain the capacity to proliferate or differentiate into myelin-forming oligodendrocytes. One essential issue is the creation of administration protocols and determining which factors need to be well established. There is controversy around whether these cells may be implanted simultaneously with corticosteroid treatment, which is widely used in many clinical situations. This study assesses the influence of corticosteroids on the capacity for proliferation and differentiation and the survival of human oligodendroglioma cells. Our findings show that corticosteroids reduce the capacity of these cells to proliferate and to differentiate into oligodendrocytes and decrease cell survival. Thus, their effect does not favour remyelination; this is consistent with the results of studies with rodent cells. In conclusion, protocols for the administration of oligodendrocyte lineage cells with the aim of repopulating oligodendroglial niches or repairing demyelinated axons should not include corticosteroids, given the evidence that the effects of these drugs may undermine the objectives of cell transplantation.

DDR1 and Its Ligand, Collagen IV, Are Involved in In Vitro Oligodendrocyte Maturation

Discoidin domain receptor 1 (DDR1) is a tyrosine kinase receptor expressed in epithelial cells from different tissues in which collagen binding activates pleiotropic functions. In the brain, DDR1 is mainly expressed in oligodendrocytes (OLs), the function of which is unclear. Whether collagen can activate DDR1 in OLs has not been studied. Here, we assessed the expression of DDR1 during in vitro OL differentiation, including collagen IV incubation, and the capability of collagen IV to induce DDR1 phosphorylation. Experiments were performed using two in vitro models of OL differentiation: OLs derived from adult rat neural stem cells (NSCs) and the HOG16 human oligodendroglial cell line. Immunocytofluorescence, western blotting, and ELISA were performed to analyze these questions. The differentiation of OLs from NSCs was addressed using oligodendrocyte transcription factor 2 (Olig2) and myelin basic protein (MBP). In HOG16 OLs, collagen IV induced DDR1 phosphorylation through slow and sustained kinetics. In NSC-derived OLs, DDR1 was found in a high proportion of differentiating cells (MBP+/Olig2+), but its protein expression was decreased in later stages. The addition of collagen IV did not change the number of DDR1+/MBP+ cells but did accelerate OL branching. Here, we provide the first demonstration that collagen IV mediates the phosphorylation of DDR1 in HOG16 cells and that the in vitro co-expression of DDR1 and MBP is associated with accelerated branching during the differentiation of primary OLs.

miR-23a-3p and miR-181a-5p modulate SNAP-25 expression

SNAP-25 protein is a key protein of the SNARE complex that is involved in synaptic vesicles fusion with plasma membranes and neurotransmitter release, playing a fundamental role in neural plasticity. Recently the concentration of three specific miRNAs-miR-27b-3p, miR-181a-5p and miR-23a-3p -was found to be associated with a specific SNAP-25 polymorphism (rs363050). in silico analysis showed that all the three miRNAs target SNAP-25, but the effect of the interaction between these miRNAs and the 3'UTR of SNAP-25 mRNA is currently unknown. For this reason, we verified in vitro whether miR-27b-3p, miR-181a-5p and miR-23a-3p modulate SNAP-25 gene and protein expression. Initial experiments using miRNAs-co-transfected Vero cells and SNAP-25 3'UTR luciferase reporter plasmids showed that miR-181a-5p (p≤0.01) and miR-23a-3p (p<0.05), but not miR-27b-3p, modulate the luciferase signal, indicating that these two miRNAs bind the SNAP-25 3'UTR. Results obtained using human oligodendroglial cell line (MO3.13) transfected with miR-181a-5p or miR-27b-3p confirmed that miR-181a-5p and miR-23a-3p regulate SNAP-25 gene and protein expression. Interestingly, the two miRNAs modulate in an opposite way SNAP-25, as miR-181a-5p significantly increases (p<0.0005), whereas miR-23a-3p decreases (p<0.0005) its expression. These results for the first time describe the ability of miR-181a-5p and miR-23a-3p to modulate SNAP-25 expression, suggesting their possible use as biomarkers or as therapeutical targets for diseases in which SNAP-25 expression is altered.

Cannabinoids modulate proliferation, differentiation, and migration signaling pathways in oligodendrocytes

Cannabinoid signaling, mainly via CB1 and CB2 receptors, plays an essential role in oligodendrocyte health and functions. However, the specific molecular signals associated with the activation or blockade of CB1 and CB2 receptors in this glial cell have yet to be elucidated. Mass spectrometry-based shotgun proteomics and in silico biology tools were used to determine which signaling pathways and molecular mechanisms are triggered in a human oligodendrocytic cell line (MO3.13) by several pharmacological stimuli: the phytocannabinoid cannabidiol (CBD); CB1 and CB2 agonists ACEA, HU308, and WIN55, 212-2; CB1 and CB2 antagonists AM251 and AM630; and endocannabinoids anandamide (AEA) and 2-arachidonoylglycerol (2-AG). The modulation of cannabinoid signaling in MO3.13 was found to affect pathways linked to cell proliferation, migration, and differentiation of oligodendrocyte progenitor cells. Additionally, we found that carbohydrate and lipid metabolism, as well as mitochondrial function, were modulated by these compounds. Comparing the proteome changes and upstream regulators among treatments, the highest overlap was between the CB1 and CB2 antagonists, followed by overlaps between AEA and 2-AG. Our study opens new windows of opportunities, suggesting that cannabinoid signaling in oligodendrocytes might be relevant in the context of demyelinating and neurodegenerative diseases. Proteomics data are available at ProteomeXchange (PXD031923).

Protein Succinylation and Malonylation as Potential Biomarkers in Schizophrenia

Two protein post-translational modifications, lysine succinylation and malonylation, are implicated in protein regulation, glycolysis, and energy metabolism. The precursors of these modifications, succinyl-CoA and malonyl-CoA, are key players in central metabolic processes. Both modification profiles have been proven to be responsive to metabolic stimuli, such as hypoxia. As mitochondrial dysfunction and metabolic dysregulation are implicated in schizophrenia and other psychiatric illnesses, these modification profiles have the potential to reveal yet another layer of protein regulation and can furthermore represent targets for biomarkers that are indicative of disease as well as its progression and treatment. In this work, data from shotgun mass spectrometry-based quantitative proteomics were compiled and analyzed to probe the succinylome and malonylome of postmortem brain tissue from patients with schizophrenia against controls and the human oligodendrocyte precursor cell line MO3.13 with the dizocilpine chemical model for schizophrenia, three antipsychotics, and co-treatments. Several changes in the succinylome and malonylome were seen in these comparisons, revealing these modifications to be a largely under-studied yet important form of protein regulation with broad potential applications.

Variant rs4149584 (R92Q) of the TNFRSF1A gene in patients with familial multiple sclerosis

INTRODUCTION

Genomic studies have identified numerous genetic variants associated with susceptibility to multiple sclerosis (MS); however, each one explains only a small percentage of the risk of developing the disease. These variants are located in genes involved in specific pathways, which supports the hypothesis that the risk of developing MS may be linked to alterations in these pathways, rather than in specific genes. We analyzed the role of the TNFRSF1A gene, which encodes one of the TNF-α receptors involved in a signaling pathway previously linked to autoimmune disease.

METHODS

We included 138 individuals from 23 families including at least 2 members with MS, and analyzed the presence of exonic variants of TNFRSF1A through whole-exome sequencing. We also conducted a functional study to analyze the pathogenic mechanism of variant rs4149584 (-g.6442643C > G, NM_001065.4:c.362 G > A, R92Q) by plasmid transfection into human oligodendroglioma (HOG) cells, which behave like oligodendrocyte lineage cells; protein labeling was used to locate the protein within cells. We also analyzed the ability of transfected HOG cells to proliferate and differentiate into oligodendrocytes.

RESULTS

Variant rs4149584 was found in 2 patients with MS (3.85%), one patient with another autoimmune disease (7.6%), and in 5 unaffected individuals (7.46%). The 2 patients with MS and variant rs4149584 were homozygous carriers and belonged to the same family, whereas the remaining individuals presented the variant in heterozygosis. The study of HOG cells transfected with the mutation showed that the protein does not reach the cell membrane, but rather accumulates in the cytoplasm, particularly in the endoplasmic reticulum and near the nucleus; this suggests that, in the cells presenting the mutation, TNFRSF1 does not act as a transmembrane protein, which may alter its signaling pathway. The study of cell proliferation and differentiation found that transfected cells continue to be able to differentiate into oligodendrocytes and are probably still capable of producing myelin, although they present a lower rate of proliferation than wild-type cells.

CONCLUSIONS

Variant rs4149584 is associated with risk of developing MS. We analyzed its functional role in oligodendrocyte lineage cells and found an association with MS in homozygous carriers. However, the associated molecular alterations do not influence the differentiation into oligodendrocytes; we were therefore unable to confirm whether this variant alone is pathogenic in MS, at least in heterozygosis.

Natural fish oil improves the differentiation and maturation of oligodendrocyte precursor cells to oligodendrocytes in vitro after interaction with the blood–brain barrier

The blood–brain barrier (BBB) tightly controls the microenvironment of the central nervous system (CNS) to allow neurons to function properly. Additionally, emerging studies point to the beneficial effect of natural oils affecting a wide variety of physiological and pathological processes in the human body. In this study, using an in vitro model of the BBB, we tested the influence of natural fish oil mixture (FOM) vs. borage oil (BO), both rich in long-chain polyunsaturated fatty acids (LC-PUFAs) and monounsaturated fatty acids (MUFAs) such as oleic acid (C18:1n9c) or nervonic acid (NA), on human oligodendrocyte precursor cells (hOPCs) during their maturation to oligodendrocytes (OLs) regarding their ability to synthesize myelin peptides and NA. We demonstrated that FOM, opposite to BO, supplemented endothelial cells (ECs) and astrocytes forming the BBB, affecting the function of hOPCs during their maturation. This resulted in improved synthesis of myelin basic protein (MBP), myelin oligodendrocyte glycoprotein (MOG), proteolipid protein (PLP), and NA in mature OLs. This effect is probably the result of BBB cell and hOPC stimulation via free fatty acid receptors (FFARs), which increases insulin growth factor-1 (IGF-1), ciliary neurotrophic factor (CNTF), and brain-derived neurotrophic factor (BDNF) and inhibits fibroblast growth factor 2 (FGF-2) synthesis. The unique formula of fish oil, characterized by much more varied components compared to those of BOs, also improved the enhancement of the tight junction by increasing the expression of claudin-5 and VE-cadherin on ECs. The obtained data justify consideration of naturally derived fish oil intake in human diet as affecting during remyelination.

RNA-Seq Transcriptome Analysis of Differentiated Human Oligodendrocytic MO3.13 Cells Shows Upregulation of Genes Involved in Myogenesis

In this work, we examined the differentiation of oligodendrocytic MO3.13 cells and changes in their gene expression after treatment with phorbol 12-myristate 13-acetate, PMA, or with RNA polymerase I (Pol I) inhibitor, CX-5461. We found that MO3.13 cells changed their morphology when treated with both agents. Interestingly, CX-5461, but not PMA, induced noticeable changes in the integrity of the nucleoli. Then, we analyzed the p53 transcriptional activity in MO3.13 cells and found that it was increased in both cell populations, but particularly in cells treated with PMA. Interestingly, this high p53 transcriptional activity in PMA-treated cells coincided with a lower level of an unmodified (non-phosphorylated) form of this protein. Since morphological changes in MO3.13 cells after PMA and CX-5461 treatment were evident, suggesting that cells were induced to differentiate, we performed RNA-seq analysis of PMA-treated cells, to reveal the direction of alterations in gene expression. The analysis showed that the largest group of upregulated genes consisted of those involved in myogenesis and K-RAS signaling, rather than those associated with oligodendrocyte lineage progression.

Contact-Dependent Granzyme B-Mediated Cytotoxicity of Th17-Polarized Cells Toward Human Oligodendrocytes

Multiple sclerosis (MS) is characterized by the loss of myelin and of myelin-producing oligodendrocytes (OLs) in the central nervous system (CNS). Pro-inflammatory CD4+ Th17 cells are considered pathogenic in MS and are harmful to OLs. We investigated the mechanisms driving human CD4+ T cell-mediated OL cell death. Using fluorescent and brightfield in vitro live imaging, we found that compared to Th2-polarized cells, Th17-polarized cells show greater interactions with primary human OLs and human oligodendrocytic cell line MO3.13, displaying longer duration of contact, lower mean speed, and higher rate of vesicle-like structure formation at the sites of contact. Using single-cell RNA sequencing, we assessed the transcriptomic profile of primary human OLs and Th17-polarized cells in direct contact or separated by an insert. We showed that upon close interaction, OLs upregulate the expression of mRNA coding for chemokines and antioxidant/anti-apoptotic molecules, while Th17-polarized cells upregulate the expression of mRNA coding for chemokines and pro-inflammatory cytokines such as IL-17A, IFN-γ, and granzyme B. We found that secretion of CCL3, CXCL10, IFN-γ, TNFα, and granzyme B is induced upon direct contact in cocultures of human Th17-polarized cells with human OLs. In addition, we validated by flow cytometry and immunofluorescence that granzyme B levels are upregulated in Th17-polarized compared to Th2-polarized cells and are even higher in Th17-polarized cells upon direct contact with OLs or MO3.13 cells compared to Th17-polarized cells separated from OLs by an insert. Moreover, granzyme B is detected in OLs and MO3.13 cells following direct contact with Th17-polarized cells, suggesting the release of granzyme B from Th17-polarized cells into OLs/MO3.13 cells. To confirm granzyme B–mediated cytotoxicity toward OLs, we showed that recombinant human granzyme B can induce OLs and MO3.13 cell death. Furthermore, pretreatment of Th17-polarized cells with a reversible granzyme B blocker (Ac-IEPD-CHO) or a natural granzyme B blocker (serpina3N) improved survival of MO3.13 cells upon coculture with Th17 cells. In conclusion, we showed that human Th17-polarized cells form biologically significant contacts with human OLs and exert direct toxicity by releasing granzyme B.

Accurate identification of circRNA landscape and complexity reveals their pivotal roles in human oligodendroglia differentiation

Background

Circular RNAs (circRNAs), a novel class of poorly conserved non-coding RNAs that regulate gene expression, are highly enriched in the human brain. Despite increasing discoveries of circRNA function in human neurons, the circRNA landscape and function in developing human oligodendroglia, the myelinating cells that govern neuronal conductance, remains unexplored. Meanwhile, improved experimental and computational tools for the accurate identification of circRNAs are needed.

Results

We adopt a published experimental approach for circRNA enrichment and develop CARP (CircRNA identification using A-tailing RNase R approach and Pseudo-reference alignment), a comprehensive 21-module computational framework for accurate circRNA identification and quantification. Using CARP, we identify developmentally programmed human oligodendroglia circRNA landscapes in the HOG oligodendroglioma cell line, distinct from neuronal circRNA landscapes. Numerous circRNAs display oligodendroglia-specific regulation upon differentiation, among which a subclass is regulated independently from their parental mRNAs. We find that circRNA flanking introns often contain cis-regulatory elements for RNA editing and are predicted to bind differentiation-regulated splicing factors. In addition, we discover novel oligodendroglia-specific circRNAs that are predicted to sponge microRNAs, which co-operatively promote oligodendroglia development. Furthermore, we identify circRNA clusters derived from differentiation-regulated alternative circularization events within the same gene, each containing a common circular exon, achieving additive sponging effects that promote human oligodendroglia differentiation.

Conclusions

Our results reveal dynamic regulation of human oligodendroglia circRNA landscapes during early differentiation and suggest critical roles of the circRNA-miRNA-mRNA axis in advancing human oligodendroglia development.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13059-022-02621-1.

1,2-Dichloroethane induces cortex demyelination by depressing myelin basic protein via inhibiting aquaporin 4 in mice

1,2-Dichloroethane (1,2-DCE) is a pervasive environmental pollutant, and overexposure to this hazardous material causes brain edema and demyelination in humans. We found that 1,2-DCE inhibits aquaporin 4 (AQP4) and is a primary pathogenic effector of 1,2-DCE-induced brain edema in animals. However, AQP4 down-regulation's link with cortex demyelination after 1,2-DCE exposure remains unclear. Thus, we exposed wild-type (WT) CD-1 mice and AQP4 knockout (AQP4-KO) mice to 0, 100, 350 and 700 mg/m³ 1,2-DCE by inhalation for 28 days. We applied label-free proteomics and a cell co-culture system to elucidate the role of AQP4 inhibition in 1,2-DCE-induced demyelination. The results showed that 1,2-DCE down-regulated AQP4 in the WT mouse cortexes. Both 1,2-DCE exposure and AQP4 deletion induced neurotoxicity in mice, including increased brain water content, abnormal pathological vacuolations, and neurobehavioral damage. Tests for interaction of multiple regression analysis highlighted different effects of 1,2-DCE exposure level depending on the genotype, indicating the core role of AQP4 in regulation on 1,2-DCE-caused neurotoxicity. We used label-free quantitative proteomics to detect differentially expressed proteins associated with 1,2-DCE exposure and AQP4 inhibition, and identified down-regulation in myelin basic protein (MBP) and tyrosine-protein kinase Fyn (FYN) in a dose-dependent manner in WT mice but not in AQP4-KO mice. 1,2-DCE and AQP4 deletion separately resulted in demyelination, as detected by Luxol fast blue staining, and manifested as disordered nerve fibers and cavitation in the cortexes. Western blot and immunofluorescence confirmed the decreased AQP4 in the astrocytes and the down-regulated MBP in the oligodendrocytes by 1,2-DCE exposure and AQP4 inhibition, respectively. Finally, the co-culture results of SVG p12 and MO3.13 cells showed that 1,2-DCE-induced AQP4 down-regulation in the astrocytes was responsible for demyelination, by decreasing MBP in the oligodendrocytes. In conclusion, 1,2-DCE induced cortex demyelination by depressing MBP via AQP4 inhibition in the mice.

Preimplantation factor modulates oligodendrocytes by H19-induced demethylation of NCOR2

Failed or altered gliogenesis is a major characteristic of diffuse white matter injury in survivors of premature birth. The developmentally regulated long noncoding RNA (lncRNA) H19 inhibits S-adenosylhomocysteine hydrolase (SAHH) and contributes to methylation of diverse cellular components, such as DNA, RNA, proteins, lipids, and neurotransmitters. We showed that the pregnancy-derived synthetic PreImplantation Factor (sPIF) induces expression of the nuclear receptor corepressor 2 (NCOR2) via H19/SAHH-mediated DNA demethylation. In turn, NCOR2 affects oligodendrocyte differentiation markers. Accordingly, after hypoxic-ischemic brain injury in rodents, myelin protection and oligodendrocytes' fate are in part modulated by sPIF and H19. Our results revealed an unexpected mechanism of the H19/SAHH axis underlying myelin preservation during brain recovery and its use in treating neurodegenerative diseases can be envisioned.

Intranasal Administration of Undifferentiated Oligodendrocyte Lineage Cells as a Potential Approach to Deliver Oligodendrocyte Precursor Cells into Brain

Oligodendrocyte precursor cell (OPC) migration is a mechanism involved in remyelination; these cells migrate from niches in the adult CNS. However, age and disease reduce the pool of OPCs; as a result, the remyelination capacity of the CNS decreases over time. Several experimental studies have introduced OPCs to the brain via direct injection or intrathecal administration. In this study, we used the nose-to brain pathway to deliver oligodendrocyte lineage cells (human oligodendroglioma (HOG) cells), which behave similarly to OPCs in vitro. To this end, we administered GFP-labelled HOG cells intranasally to experimental animals, which were subsequently euthanised at 30 or 60 days. Our results show that the intranasal route is a viable route to the CNS and that HOG cells administered intranasally migrate preferentially to niches of OPCs (clusters created during embryonic development and adult life). Our study provides evidence, albeit limited, that HOG cells either form clusters or adhere to clusters of OPCs in the brains of experimental animals.

Cannabidiol Displays Proteomic Similarities to Antipsychotics in Cuprizone-Exposed Human Oligodendrocytic Cell Line MO3.13

Cannabidiol, a compound of Cannabis sativa, has been proposed as an alternative treatment of schizophrenia. Preclinical and clinical data have suggested that cannabidiol shares more similarity with atypical antipsychotics than typical, both of which are customarily used to manage schizophrenia symptoms. While oligodendrocytes are known to be relevant targets of antipsychotics, the biochemical knowledge in this regard is still limited. Here we evaluated the molecular pathways modulated by cannabidiol compared to the antipsychotics clozapine (atypical) and haloperidol (typical), additionally evaluating the effects of benztropine, a muscarinic receptor antagonist that displays a protective effect in oligodendrocytes and myelination. For this purpose, we employed nano-chromatography coupled with mass spectrometry to investigate the proteomic response to these drugs both in healthy oligodendrocytic cells and in a cuprizone-based toxicity model, using the human oligodendrocyte precursor cell line MO3.13. Cannabidiol shares similarities of biochemical pathways with clozapine and benztropine, in agreement with other studies that indicated an atypical antipsychotic profile. All drugs tested affected metabolic and gene expression pathways and cannabidiol, benztropine, and clozapine modulated cell proliferation and apoptosis when administered after cuprizone-induced toxicity. These general pathways are associated with cuprizone-induced cytotoxicity in MO3.13 cells, indicating a possible proteomic approach when acting against the toxic effects of cuprizone. In conclusion, although modeling oligodendrocytic cytotoxicity with cuprizone does not represent the entirety of the pathophysiology of oligodendrocyte impairments, these results provide insight into the mechanisms associated with the effects of cannabidiol and antipsychotics against cuprizone toxicity, offering new directions of study for myelin-related processes and deficits.

5-Hydroxytryptamine Modulates Maturation and Mitochondria Function of Human Oligodendrocyte Progenitor M03-13 Cells

Inside the adult CNS, oligodendrocyte progenitor cells (OPC_S) are able to proliferate, migrate and differentiate into mature oligodendrocytes (OLs) which are responsible for the production of myelin sheet and energy supply for neurons. Moreover, in demyelinating diseases, OPCs are recruited to the lesion areas where they undergo differentiation and myelin synthesis. Serotonin (5-hydroxytryptamine, 5-HT) is involved in OLs’ development and myelination, but so far the molecular mechanisms involved or the effects of 5-HT on mitochondria function have not yet been well documented. Our data show that 5-HT inhibits migration and proliferation committing cells toward differentiation in an immortalized human oligodendrocyte precursor cell line, M03-13. Migration blockage is mediated by reactive oxygen species (ROS) generation since antioxidants, such as Vit C and Cu-Zn superoxide dismutase, prevent the inhibitory effects of 5-HT on cell migration. 5-HT inhibits OPC migration and proliferation and increases OL phenotypic markers myelin basic protein (MBP) and Olig-2 via protein kinase C (PKC) activation since the inhibitor of PKC, bis-indolyl-maleimide (BIM), counteracts 5-HT effects. NOX inhibitors as well, reverse the effects of 5-HT, indicating that 5-HT influences the maturation process of OPCs by NOX-dependent ROS production. Finally, 5-HT increases mitochondria function and antioxidant activity. The identification of the molecular mechanisms underlying the effects of 5-HT on maturation and energy metabolism of OPCs could pave the way for the development of new treatments for autoimmune demyelinating diseases such as Multiple Sclerosis where oligodendrocytes are the primary target of immune attack.

Cuprizone-Induced Neurotoxicity in Human Neural Cell Lines Is Mediated by a Reversible Mitochondrial Dysfunction: Relevance for Demyelination Models

Suitable in vivo and in vitro models are instrumental for the development of new drugs aimed at improving symptoms or progression of multiple sclerosis (MS). The cuprizone (CPZ)-induced murine model has gained momentum in recent decades, aiming to address the demyelination component of the disease. This work aims at assessing the differential cytotoxicity of CPZ in cells of different types and from different species: human oligodendroglial (HOG), human neuroblastoma (SH-SY5Y), human glioblastoma (T-98), and mouse microglial (N-9) cell lines. Moreover, the effect of CPZ was investigated in primary rat brain cells. Cell viability was assayed by oxygen rate consumption and by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide-based (MTT) method. Our results demonstrated that CPZ did not cause death in any of the assayed cell models but affected mitochondrial function and aerobic cell respiration, thus compromising cell metabolism in neural cells and neuron-glia co-cultures. In this sense, we found differential vulnerability between glial cells and neurons as is the case of the CPZ-induced mouse model of MS. In addition, our findings demonstrated that reduced viability was spontaneous reverted in a time-dependent manner by treatment discontinuation. This reversible cell-based model may help to further investigate the role of mitochondria in the disease, and study the molecular intricacies underlying the pathophysiology of the MS and other demyelinating diseases.

Hydrogen Peroxide-Preconditioned Human Adipose-Derived Stem Cells Enhance the Recovery of Oligodendrocyte-Like Cells after Oxidative Stress-Induced Damage

Oxidative stress associated with neuroinflammation is a key process involved in the pathophysiology of neurodegenerative diseases, and therefore, has been proposed as a crucial target for new therapies. Recently, the therapeutic potential of human adipose-derived stem cells (hASCs) has been investigated as a novel strategy for neuroprotection. These cells can be preconditioned by exposing them to mild stress in order to improve their response to oxidative stress. In this study, we evaluate the therapeutic potential of hASCs preconditioned with low doses of H₂O₂ (called HC016 cells) to overcome the deleterious effect of oxidative stress in an in vitro model of oligodendrocyte-like cells (HOGd), through two strategies: i, the culture of oxidized HOGd with HC016 cell-conditioned medium (CM), and ii, the indirect co-culture of oxidized HOGd with HC016 cells, which had or had not been exposed to oxidative stress. The results demonstrated that both strategies had reparative effects, oxidized HC016 cell co-culture being the one associated with the greatest recovery of the damaged HOGd, increasing their viability, reducing their intracellular reactive oxygen species levels and promoting their antioxidant capacity. Taken together, these findings support the view that HC016 cells, given their reparative capacity, might be considered an important breakthrough in cell-based therapies.

In vitro Models of Neurodegenerative Diseases

Neurodegenerative diseases are progressive degenerative conditions characterized by the functional deterioration and ultimate loss of neurons. These incurable and debilitating diseases affect millions of people worldwide, and therefore represent a major global health challenge with severe implications for individuals and society. Recently, several neuroprotective drugs have failed in human clinical trials despite promising pre-clinical data, suggesting that conventional cell cultures and animal models cannot precisely replicate human pathophysiology. To bridge the gap between animal and human studies, three-dimensional cell culture models have been developed from human or animal cells, allowing the effects of new therapies to be predicted more accurately by closely replicating some aspects of the brain environment, mimicking neuronal and glial cell interactions, and incorporating the effects of blood flow. In this review, we discuss the relative merits of different cerebral models, from traditional cell cultures to the latest high-throughput three-dimensional systems. We discuss their advantages and disadvantages as well as their potential to investigate the complex mechanisms of human neurodegenerative diseases. We focus on in vitro models of the most frequent age-related neurodegenerative disorders, such as Parkinson’s disease, Alzheimer’s disease and prion disease, and on multiple sclerosis, a chronic inflammatory neurodegenerative disease affecting young adults.

Novel Treatment Strategies Targeting Myelin and Oligodendrocyte Dysfunction in Schizophrenia

Oligodendrocytes are the glial cells responsible for the formation of the myelin sheath around axons. During neurodevelopment, oligodendrocytes undergo maturation and differentiation, and later remyelination in adulthood. Abnormalities in these processes have been associated with behavioral and cognitive dysfunctions and the development of various mental illnesses like schizophrenia. Several studies have implicated oligodendrocyte dysfunction and myelin abnormalities in the disorder, together with altered expression of myelin-related genes such as Olig2, CNP, and NRG1. However, the molecular mechanisms subjacent of these alterations remain elusive. Schizophrenia is a severe, chronic psychiatric disorder affecting more than 23 million individuals worldwide and its symptoms usually appear at the beginning of adulthood. Currently, the major therapeutic strategy for schizophrenia relies on the use of antipsychotics. Despite their widespread use, the effects of antipsychotics on glial cells, especially oligodendrocytes, remain unclear. Thus, in this review we highlight the current knowledge regarding oligodendrocyte dysfunction in schizophrenia, compiling data from (epi)genetic studies and up-to-date models to investigate the role of oligodendrocytes in the disorder. In addition, we examined potential targets currently investigated for the improvement of schizophrenia symptoms. Research in this area has been investigating potential beneficial compounds, including the D-amino acids D-aspartate and D-serine, that act as NMDA receptor agonists, modulating the glutamatergic signaling; the antioxidant N-acetylcysteine, a precursor in the synthesis of glutathione, protecting against the redox imbalance; as well as lithium, an inhibitor of glycogen synthase kinase 3β (GSK3β) signaling, contributing to oligodendrocyte survival and functioning. In conclusion, there is strong evidence linking oligodendrocyte dysfunction to the development of schizophrenia. Hence, a better understanding of oligodendrocyte differentiation, as well as the effects of antipsychotic medication in these cells, could have potential implications for understanding the development of schizophrenia and finding new targets for drug development.

Viral infections and multiple sclerosis

The etiology and pathogenesis of MS is likely to involve multiple factors interacting with each other, and the role of infectious and viral agents is still under debate, however a consistent amount of studies suggests that some viruses are associated with the disease. The strongest documentation has come from the detection of viral nucleic acid or antigen or of an anti-viral antibody response in MS patients. A further step for the study of the mechanism viruses might be involved in can be made using in vitro and in vivo models. While in vitro models, based on glial and neural cell lines from various sources are widely used, in vivo animal models present challenges. Indeed neurotropic animal viruses are currently used to study demyelination in well-established models, but animal models of demyelination by human virus infection have only recently been developed, using animal gammaherpesviruses closely related to Epstein Barr virus (EBV), or using marmosets expressing the specific viral receptor for Human Herpesvirus 6 (HHV-6). The present review will illustrate the main potential mechanisms of MS pathogenesis possibly associated with viral infections and viruses currently used to study demyelination in animal models. Then the viruses most strongly linked with MS will be discussed, in the perspective that more than one virus might have a role, with varying degrees of interaction, contributing to MS heterogeneity.

Multiple Sclerosis CD49d+CD154+ As Myelin-Specific Lymphocytes Induced During Remyelination

Multiple sclerosis (MS) is a demyelinating autoimmune disease of the central nervous system (CNS) mediated by autoreactive lymphocytes. The role of autoreactive lymphocytes in the CNS demyelination is well described, whereas very little is known about their role in remyelination during MS remission. In this study, we identified a new subpopulation of myelin-specific CD49d⁺CD154⁺ lymphocytes presented in the peripheral blood of MS patients during remission, that proliferated in vitro in response to myelin peptides. These lymphocytes possessed the unique ability to migrate towards maturing oligodendrocyte precursor cells (OPCs) and synthetize proinflammatory chemokines/cytokines. The co-culture of maturing OPCs with myelin-specific CD49d⁺CD154⁺ lymphocytes was characterized by the increase in proinflammatory chemokine/cytokine secretion that was not only a result of their cumulative effect of what OPCs and CD49d⁺CD154⁺ lymphocytes produced alone. Moreover, maturing OPCs exposed to exogenous myelin peptides managed to induce CD40-CD154-dependent CD49d⁺CD154⁺ lymphocyte proliferation. We confirmed, in vivo, the presence of CD49d⁺CD154⁺ cells close to maturating OPCs and remyelinating plaque during disease remission in the MS mouse model (C57Bl/6 mice immunized with MOG_35-55) by immunohistochemistry. Three weeks after an acute phase of experimental autoimmune encephalomyelitis, CD49d⁺/CD154⁺ cells were found to be co-localized with O4⁺ cells (oligodendrocyte progenitors) in the areas of remyelination identified by myelin basic protein (MBP) labelling. These data suggested that myelin-specific CD49d⁺CD154⁺ lymphocytes present in the brain can interfere with remyelination mediated by oligodendrocytes probably as a result of establishing proinflammatory environment.

MS CD49d+CD154+ Lymphocytes Reprogram Oligodendrocytes into Immune Reactive Cells Affecting CNS Regeneration

The critical aspect in multiple sclerosis (MS) progression involves insufficient regeneration of CNS resulting from deficient myelin synthesis by newly generated oligodendrocytes (OLs). Although many studies have focused on the role of autoreactive lymphocytes in the inflammatory-induced axonal loss, the problem of insufficient remyelination and disease progression is still unsolved. To determine the effect of myelin-specific lymphocytes on OL function in MS patients and in a mouse model of MS, we cultured myelin induced MS CD49d⁺CD154⁺ circulating lymphocytes as well as Experimental Autoimmune Encephalomyelitis (EAE) mouse brain-derived T and memory B cells with maturing oligodendrocyte precursor cells (OPCs). We found that myelin-specific CD49d⁺CD154⁺ lymphocytes affected OPC maturation toward formation of immune reactive OLs. Newly generated OLs were characterized by imbalanced myelin basic protein (MBP) and proteolipid protein (PLP) production as well as proinflammatory chemokine/cytokine synthesis. The analysis of cellular pathways responsible for OL reprogramming revealed that CD49d⁺CD154⁺ lymphocytes affected miRNA synthesis by dysregulation of polymerase II activity. miR-665 and ELL3 turned out to be the main targets of MS myelin-specific lymphocytes. Neutralization of high intracellular miR-665 concentration restored miRNA and MBP/PLP synthesis. Together, these data point to new targets for therapeutic intervention promoting CNS remyelination.

Reappraisal of Human HOG and MO3.13 Cell Lines as a Model to Study Oligodendrocyte Functioning

Myelination of neuronal axons is essential for proper brain functioning and requires mature myelinating oligodendrocytes (myOLs). The human OL cell lines HOG and MO3.13 have been widely used as in vitro models to study OL (dys) functioning. Here we applied a number of protocols aimed at differentiating HOG and MO3.13 cells into myOLs. However, none of the differentiation protocols led to increased expression of terminal OL differentiation or myelin-sheath formation markers. Surprisingly, the applied protocols did cause changes in the expression of markers for early OLs, neurons, astrocytes and Schwann cells. Furthermore, we noticed that mRNA expression levels in HOG and MO3.13 cells may be affected by the density of the cultured cells. Finally, HOG and MO3.13 co-cultured with human neuronal SH-SY5Y cells did not show myelin formation under several pro-OL-differentiation and pro-myelinating conditions. Together, our results illustrate the difficulty of inducing maturation of HOG and MO3.13 cells into myOLs, implying that these oligodendrocytic cell lines may not represent an appropriate model to study the (dys)functioning of human (my)OLs and OL-linked disease mechanisms.

Myelin Disturbances Produced by Sub-Toxic Concentration of Heavy Metals: The Role of Oligodendrocyte Dysfunction

Evidence has been accumulated demonstrating that heavy metals may accumulate in various organs, leading to tissue damage and toxic effects in mammals. In particular, the Central Nervous System (CNS) seems to be particularly vulnerable to cumulative concentrations of heavy metals, though the pathophysiological mechanisms is still to be clarified. In particular, the potential role of oligodendrocyte dysfunction and myelin production after exposure to subtoxic concentration I confirmed. It is ok of heavy metals is to be better assessed. Here we investigated on the effect of sub-toxic concentration of several essential (Cu^{2 +}, Cr^{3 +}, Ni^{2 +}, Co²⁺) and non-essential (Pb^{2 +}, Cd²⁺, Al³⁺) heavy metals on human oligodendrocyte MO3.13 and human neuronal SHSY5Y cell lines (grown individually or in co-culture). MO3.13 cells are an immortal human–human hybrid cell line with the phenotypic characteristics of primary oligodendrocytes but following the differentiation assume the morphological and biochemical features of mature oligodendrocytes. For this reason, we decided to use differentiated MO3.13 cell line. In particular, exposure of both cell lines to heavy metals produced a reduced cell viability of co-cultured cell lines compared to cells grown separately. This effect was more pronounced in neurons that were more sensitive to metals than oligodendrocytes when the cells were grown in co-culture. On the other hand, a significant reduction of lipid component in cells occurred after their exposure to heavy metals, an effect accompanied by substantial reduction of the main protein that makes up myelin (MBP) in co-cultured cells. Finally, the effect of heavy metals in oligodendrocytes were associated to imbalanced intracellular calcium ion concentration as measured through the fluorescent Rhod-2 probe, thus confirming that heavy metals, even used at subtoxic concentrations, lead to dysfunctional oligodendrocytes. In conclusion, our data show, for the first time, that sub-toxic concentrations of several heavy metals lead to dysfunctional oligodendrocytes, an effect highlighted when these cells are co-cultured with neurons. The pathophysiological mechanism(s) underlying this effect is to be better clarified. However, imbalanced intracellular calcium ion regulation, altered lipid formation and, finally, imbalanced myelin formation seem to play a major role in early stages of heavy metal-related oligodendrocyte dysfunction.

Naturally Occurring Nervonic Acid Ester Improves Myelin Synthesis by Human Oligodendrocytes

The dysfunction of oligodendrocytes (OLs) is regarded as one of the major causes of inefficient remyelination in multiple sclerosis, resulting gradually in disease progression. Oligodendrocytes are derived from oligodendrocyte progenitor cells (OPCs), which populate the adult central nervous system, but their physiological capability to myelin synthesis is limited. The low intake of essential lipids for sphingomyelin synthesis in the human diet may account for increased demyelination and the reduced efficiency of the remyelination process. In our study on lipid profiling in an experimental autoimmune encephalomyelitis brain, we revealed that during acute inflammation, nervonic acid synthesis is silenced, which is the effect of shifting the lipid metabolism pathway of common substrates into proinflammatory arachidonic acid production. In the experiments on the human model of maturating oligodendrocyte precursor cells (hOPCs) in vitro, we demonstrated that fish oil mixture (FOM) affected the function of hOPCs, resulting in the improved synthesis of myelin basic protein, myelin oligodendrocyte glycoprotein, and proteolipid protein, as well as sphingomyelin. Additionally, FOM reduces proinflammatory cytokines and chemokines, and enhances fibroblast growth factor 2 (FGF2) and vascular endothelial growth factor (VEGF) synthesis by hOPCs was also demonstrated. Based on these observations, we propose that the intake of FOM rich in the nervonic acid ester may improve OL function, affecting OPC maturation and limiting inflammation.

Expression of DDR1 in the CNS and in myelinating oligodendrocytes

Discoidin domain receptor 1 (DDR1) is a tyrosine kinase receptor that is activated by fibrillar collagens. Here, we review the expression and role of DDR1 in the central nervous system (CNS). In a murine model, DDR1 is expressed in oligodendrocytes in the developing brain and during remyelination. In human adult brain tissue, DDR1 is detected in a similar pattern as other classical myelin proteins such as myelin basic protein (MBP). Up to 50 transcripts of DDR1 have been detected in human tissues, of which 5 isoforms have been identified. In the human brain, all 5 isoforms are detectable, but DDR1b is the most highly expressed, and DDR1c is coexpressed with myelin genes. DDR1 sequence variants have been associated with psychiatric disorders, and upregulation of this gene occurs in gliomas. Moreover, mutations in DDR1 have been found in tumors of Schwann cells, which are the myelinating cells of the peripheral nervous system. All these data suggest that DDR1 plays a role in myelination and is relevant to neuropsychiatric diseases.

Biochemical Pathways Triggered by Antipsychotics in Human [corrected] Oligodendrocytes: Potential of Discovering New Treatment Targets

Schizophrenia is a psychiatric disorder that affects more than 21 million people worldwide. It is an incurable disorder and the primary means of managing symptoms is through administration of pharmacological treatments, which consist heavily of antipsychotics. First-generation antipsychotics have the properties of D₂ receptor antagonists. Second-generation antipsychotics are antagonists of both D₂ and 5HT₂ receptors. Recently, there has been increasing interest in the effects of antipsychotics beyond their neuronal targets and oligodendrocytes are one of the main candidates. Thus, our aim was to evaluate the molecular effects of typical and atypical drugs across the proteome of the human oligodendrocyte cell line, MO3.13. For this, we performed a mass spectrometry-based, bottom-up shotgun proteomic analysis to identify differences triggered by typical (chlorpromazine and haloperidol) and atypical (quetiapine and risperidone) antipsychotics. Proteins which showed changes in their expression levels were analyzed in silico using Ingenuity^® Pathway Analysis, which implicated dysregulation of canonical pathways for each treatment. Our results shed light on the biochemical pathways involved in the mechanisms of action of these drugs, which may guide the identification of novel biomarkers and the development of new and improved treatments.

KIR2DL4-HLAG interaction at human NK cell-oligodendrocyte interfaces regulates IFN-γ-mediated effects

Interactions between germline-encoded natural killer (NK) cell receptors and their respective ligands on tumorigenic or virus-infected cells determine NK cell cytotoxic activity and/or cytokine secretion. NK cell cytokine responses can be augmented in and can potentially contribute to multiple sclerosis (MS), an inflammatory disease of the central nervous system focused upon the oligodendrocytes (OLs). To investigate mechanisms by which NK cells may contribute to MS pathogenesis, we developed an in vitro human model of OL-NK cell interaction. We found that activated, but not resting human NK cells form conjugates with, and mediate cytotoxicity against, human oligodendrocytes. NK cells, when in conjugate with OLs, rapidly synthesize and polarize IFN-γ toward the OLs. IFN-γ  is capable of reducing myelin oligodendrocyte and myelin associated glycoproteins (MOG and MAG) content. This activity is independent of MHC class-I mediated inhibition via KIR2DL1, but dependent upon the interaction between NK cell-expressed KIR2DL4 and its oligodendrocyte-expressed ligand, HLA-G. NK cells from patients with MS express higher levels of IFN-γ following conjugation to OLs, more actively promote in vitro reduction of MOG and MAG and have higher frequencies of the KIR2DL4 positive population. These data collectively suggest a mechanism by which NK cells can promote pathogenic effects upon OLs.

Semaphorin4A and H-ferritin utilize Tim-1 on human oligodendrocytes: A novel neuro-immune axis

Deficiency of trophic factors relating to the survival of oligodendrocytes, combined with direct interactions with the immune system, are favored paradigms that are increasingly implicated in demyelinating diseases of the central nervous system. We and others have previously shown that Sema4A and H-ferritin interact through the T-cell immunoglobulin and mucin domain (Tim-2) receptor in mice. H-ferritin has been identified as the iron delivery protein for oligodendrocytes, whereas Sema4A causes a direct cytotoxic effect. However, the expression of Tim-2 has not been detected in humans. Here, we demonstrate that, similar to rodents, human oligodendrocytes undergo apoptosis when exposed to Sema4A and take up H-ferritin for meeting iron requirements and that these functions are mediated via the Tim-1 receptor. Moreover, we also demonstrate the ability of H-ferritin to block Sema4A-mediated cytotoxicity. Furthermore, we show in a series of pilot studies that Sema4A is detectable in the CSF of multiple sclerosis patients and HIV-seropositive persons and can induce oligodendrocyte cell death. Together, these results identify a novel iron uptake mechanism for human oligodendrocytes and a connection between oligodendrocytes and the immune system.

Combination therapy of lovastatin and AMP-activated protein kinase activator improves mitochondrial and peroxisomal functions and clinical disease in experimental autoimmune encephalomyelitis model

Recent studies report that loss and dysfunction of mitochondria and peroxisomes contribute to the myelin and axonal damage in multiple sclerosis (MS). In this study, we investigated the efficacy of a combination of lovastatin and AMP-activated protein kinase (AMPK) activator (AICAR) on the loss and dysfunction of mitochondria and peroxisomes and myelin and axonal damage in spinal cords, relative to the clinical disease symptoms, using a mouse model of experimental autoimmune encephalomyelitis (EAE, a model for MS). We observed that lovastatin and AICAR treatments individually provided partial protection of mitochondria/peroxisomes and myelin/axons, and therefore partial attenuation of clinical disease in EAE mice. However, treatment of EAE mice with the lovastatin and AICAR combination provided greater protection of mitochondria/peroxisomes and myelin/axons, and greater improvement in clinical disease compared with individual drug treatments. In spinal cords of EAE mice, lovastatin-mediated inhibition of RhoA and AICAR-mediated activation of AMPK cooperatively enhanced the expression of the transcription factors and regulators (e.g. PPARα/β, SIRT-1, NRF-1, and TFAM) required for biogenesis and the functions of mitochondria (e.g. OXPHOS, MnSOD) and peroxisomes (e.g. PMP70 and catalase). In summary, these studies document that oral medication with a combination of lovastatin and AICAR, which are individually known to have immunomodulatory effects, provides potent protection and repair of inflammation-induced loss and dysfunction of mitochondria and peroxisomes as well as myelin and axonal abnormalities in EAE. As statins are known to provide protection in progressive MS (Phase II study), these studies support that supplementation statin treatment with an AMPK activator may provide greater efficacy against MS.

Ion Mobility-Enhanced Data-Independent Acquisitions Enable a Deep Proteomic Landscape of Oligodendrocytes

Oligodendrocytes are a type of neuroglia that provide trophic support and insulation to axons in the central nervous system. The genesis and maturation of oligodendrocytes are essential processes for myelination and the course of CNS development. Using ion mobility-enhanced, data-independent acquisitions and 2D-nanoUPLC fractionation operating at nanoscale flow rates, we established a comprehensive data set of proteins expressed by the human oligodendroglia cell line MO3.13. The final dataset incorporating all fractions comprised 223 531 identified peptides assigned to 10 390 protein hits, an improvement of 4.5 times on identified proteins described previously by our group using the same cell line. Identified proteins play pivotal roles in many biological processes such as cell growth and development and energy metabolism, providing a rich resource for future studies on oligodendrocyte development, myelination, axonal support, and the regulation of such process. Our results can help further studies that use MO3.13 cells as a tool of investigation, not only in relation to oligodendrocyte maturation, but also to diseases that have oligodendrocytes as key players. All MS data have been deposited in the ProteomeXchange with identifier PXD004696.

Suppressed oligodendrocyte steroidogenesis in multiple sclerosis: Implications for regulation of neuroinflammation

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system (CNS). Neurosteroids are reported to exert anti-inflammatory effects in several neurological disorders. We investigated the expression and actions of the neurosteroid, dehydroepiandrosterone (DHEA), and its more stable 3β-sulphated ester, DHEA-S, in MS and associated experimental models. CNS tissues from patients with MS and animals with experimental autoimmune encephalomyelitis (EAE) displayed reduced DHEA concentrations, accompanied by diminished expression of the DHEA-synthesizing enzyme CYP17A1 in oligodendrocytes (ODCs), in association with increased expression of inflammatory genes including interferon (IFN)-γ and interleukin (IL)-1β. CYP17A1 was expressed variably in different human neural cell types but IFN-γ exposure selectively reduced CYP17A1 detection in ODCs. DHEA-S treatment reduced IL-1β and -6 release from activated human myeloid cells with minimal effect on lymphocyte viability. Animals with EAE receiving DHEA-S treatment showed reduced Il1b and Ifng transcript levels in spinal cord compared to vehicle-treated animals with EAE. DHEA-S treatment also preserved myelin basic protein immunoreactivity and reduced axonal loss in animals with EAE, relative to vehicle-treated EAE animals. Neurobehavioral deficits were reduced in DHEA-S-treated EAE animals compared with vehicle-treated animals with EAE. Thus, CYP17A1 expression in ODCs and its product DHEA were downregulated in the CNS during inflammatory demyelination while DHEA-S provision suppressed neuroinflammation, demyelination, and axonal injury that was evident as improved neurobehavioral performance. These findings indicate that DHEA production is an immunoregulatory pathway within the CNS and its restoration represents a novel treatment approach for neuroinflammatory diseases.

Sphingosine Toxicity in EAE and MS: Evidence for Ceramide Generation via Serine-Palmitoyltransferase Activation

Multiple sclerosis (MS) is a demyelinating disorder characterized by massive neurodegeneration and profound axonal loss. Since myelin is enriched with sphingolipids and some of them display toxicity, biological function of sphingolipids in demyelination has been investigated in MS brain tissues. An elevation of sphingosine with a decrease in monoglycosylceramide and psychosine (myelin markers) was observed in MS white matter and plaque compared to normal brain tissue. This indicated that sphingosine toxicity might mediate oligodendrocyte degeneration. To explain the source of sphingosine accumulation, total sphingolipid profile was investigated in Lewis rats after inducing experimental autoimmune encephalomyelitis (EAE) and also in human oligodendrocytes in culture. An intermittent increase in ceramide followed by sphingosine accumulation in EAE spinal cord along with a stimulation of serine-palmitoyltransferase (SPT) activity was observed. Apoptosis was identified in the lumbar spinal cord, the most prominent demyelinating area, in the EAE rats. TNFα and IFNγ stimulation of oligodendrocytes in culture also led to an accumulation of ceramide with an elevation of sphingosine. Ceramide elevation was drastically blocked by myriocin, an inhibitor of SPT, and also by FTY720. Myriocin treatment also protected oligodendrocytes from cytokine mediated apoptosis or programmed cell death. Hence, we propose that sphingosine toxicity may contribute to demyelination in both EAE and MS, and the intermittent ceramide accumulation in EAE may, at least partly, be mediated via SPT activation, which is a novel observation that has not been previously reported.

Absence of antibodies against KIR4.1 in multiple sclerosis: A three-technique approach and systematic review

Introduction

Antibodies targeting the inward-rectifying potassium channel KIR4.1 have been associated with multiple sclerosis (MS) but studies using diverse techniques have failed to replicate this association. The detection of these antibodies is challenging; KIR4.1 glycosylation patterns and the use of diverse technical approaches may account for the disparity of results. We aimed to replicate the association using three different approaches to overcome the technical limitations of a single technique. We also performed a systematic review to examine the association of anti-KIR4.1 antibodies with MS.

Methods

Serum samples from patients with MS (n = 108) and controls (n = 77) were tested for the presence of anti-KIR4.1 antibodies using three methods: 1) by ELISA with the low-glycosylated fraction of recombinant KIR4.1 purified from transfected HEK293 cells according to original protocols; 2) by immunocytochemistry using KIR4.1-transfected HEK293 cells; and 3) by immunocytochemistry using the KIR4.1.-transfected MO3.13 oligodendrocyte cell line. We developed a systematic review and meta-analysis of the association of anti-KIR4.1 antibodies with MS according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines.

Results

We did not detect anti-KIR4.1 antibodies in the MS patients or in controls using ELISA. Neither did we detect any significant reactivity against the antigen on the cell surface using the KIR4.1-transfected HEK293 cells or the KIR4.1-transfected MO3.13 cells. We included 13 prospective controlled studies in the systematic review. Only three studies showed a positive association between anti-KIR4.1 and MS. Clinical and statistical heterogeneity between studies precluded meta-analysis of their results.

Conclusion

We found no association between anti-KIR4.1 antibody positivity and MS. Although this lack of replication may be due to technical limitations, evidence from our study and others is mounting against the role of KIR4.1 as a relevant MS autoantigen.

NCAM1 is the Target of miRNA-572: Validation in the Human Oligodendroglial Cell Line

The neural cell adhesion molecule 1 (NCAM1) is a fundamental protein in cell-cell interaction and in cellular developmental processes, and its dysregulation is involved in a number of diseases including multiple sclerosis. Studies in rats suggest that the modulation of NCAM1 expression is regulated by miRNA-572, but no data are available confirming such interaction in the human system. We analyzed whether this is the case using a human oligodendroglial cell line (MO3.13). MO3.13 cells were transfected with miRNA-572 mimic and inhibitor separately; NCAM1 mRNA and protein expression levels were analyzed at different time points after transfection. Results indicated that NCAM1 expression is increased after transfection with miRNA-572 inhibitor, whereas it is decreased after transfection with the mimic (p < 0.005). The interaction between NCAM1 and miRNA-572 was subsequently confirmed in a Vero cell line that does not express NCAM1, by luciferase assay after transfection with NCAM1. These results confirm that miRNA-572 regulates NCAM1 and for the first time demonstrate that this interaction regulates NCAM1 expression in human cells. Data herein also support the hypothesis that miRNA-572 is involved in diseases associated with NCAM1 deregulation, suggesting its possible use as a biomarker in these diseases.

Glia-neuron interactions in neurological diseases: Testing non-cell autonomy in a dish

For the past century, research on neurological disorders has largely focused on the most prominently affected cell types - the neurons. However, with increasing knowledge of the diverse physiological functions of glial cells, their impact on these diseases has become more evident. Thus, many conditions appear to have more complex origins than initially thought. Since neurological pathologies are often sporadic with unknown etiology, animal models are difficult to create and might only reflect a small portion of patients in which a mutation in a gene has been identified. Therefore, reliable in vitro systems to studying these disorders are urgently needed. They might be a pre-requisite for improving our understanding of the disease mechanisms as well as for the development of potential new therapies. In this review, we will briefly summarize the function of different glial cell types in the healthy central nervous system (CNS) and outline their implication in the development or progression of neurological conditions. We will then describe different types of culture systems to model non-cell autonomous interactions in vitro and evaluate advantages and disadvantages. This article is part of a Special Issue entitled SI: Exploiting human neurons.

MK-801-Treated Oligodendrocytes as a Cellular Model to Study Schizophrenia

Glutamate is the most important excitatory neurotransmitter in the brain. The N-methyl-D-aspartate (NMDA) subtype of glutamate receptor is found both in neurons and glial cells such as oligodendrocytes, which have been shown to be dysfunctional in schizophrenia. For this reasons, the oligodendrocyte MO3.13 cell line has been used to study glutamatergic dysfunction as a model of schizophrenia using the NMDA receptor antagonists such as MK-801 to block receptor function. Here, we describe a comprehensive protocol for culturing and carrying out proteomic analyses of MK-801-treated MO3.13 cells as a means of identifying potential new biomarkers and targets for drug discovery in schizophrenia research.

In vitro and ex vivo models of multiple sclerosis

Multiple sclerosis (MS) is an autoimmune disorder of the central nervous system (CNS). Current therapies suppress a misdirected myelin-destructive immune response. To combat the progressive, neurodestructive phase of MS, the therapeutic research focus is currently on compounds that might boost the endogenous potential of the brain to remyelinate axons, thereby achieving lesion repair. Here, we describe the testing of fingolimod on cultures of oligodendrocytes (OLs) and organotypic brain slices. We detail the protocols, pros, and cons of these in vitro and ex vivo approaches, along with the potential benefit of exploiting skin-punch biopsies from patients with MS, before concluding with a summary of future developments.

Reactive Oxygen Species Derived from NOX3 and NOX5 Drive Differentiation of Human Oligodendrocytes

Reactive oxygen species (ROS) are signaling molecules that mediate stress response, apoptosis, DNA damage, gene expression and differentiation. We report here that differentiation of oligodendrocytes (OLs), the myelin forming cells in the CNS, is driven by ROS. To dissect the OL differentiation pathway, we used the cell line MO3-13, which display the molecular and cellular features of OL precursors. These cells exposed 1-4 days to low levels of H2O2 or to the protein kinase C (PKC) activator, phorbol-12-Myristate-13-Acetate (PMA) increased the expression of specific OL differentiation markers: the specific nuclear factor Olig-2, and Myelin Basic Protein (MBP), which was processed and accumulated selectively in membranes. The induction of differentiation genes was associated with the activation of ERK1-2 and phosphorylation of the nuclear cAMP responsive element binding protein 1 (CREB). PKC mediates ROS-induced differentiation because PKC depletion or bis-indolyl-maleimide (BIM), a PKC inhibitor, reversed the induction of differentiation markers by H2O2. H2O2 and PMA increased the expression of membrane-bound NADPH oxidases, NOX3 and NOX5. Selective depletion of these proteins inhibited differentiation induced by PMA. Furthermore, NOX5 silencing down regulated NOX3 mRNA levels, suggesting that ROS produced by NOX5 up-regulate NOX3 expression. These data unravel an elaborate network of ROS-generating enzymes (NOX5 to NOX3) activated by PKC and necessary for differentiation of OLs. Furthermore, NOX3 and NOX5, as inducers of OL differentiation, represent novel targets for therapies of demyelinating diseases, including multiple sclerosis, associated with impairment of OL differentiation.

Characterization of three human cell line models for high-throughput neuronal cytotoxicity screening

More than 75 000 man-made chemicals contaminate the environment; many of these have not been tested for toxicities. These chemicals demand quantitative high-throughput screening assays to assess them for causative roles in neurotoxicities, including Parkinson's disease and other neurodegenerative disorders. To facilitate high throughput screening for cytotoxicity to neurons, three human neuronal cellular models were compared: SH-SY5Y neuroblastoma cells, LUHMES conditionally-immortalized dopaminergic neurons, and Neural Stem Cells (NSC) derived from human fetal brain. These three cell lines were evaluated for rapidity and degree of differentiation, and sensitivity to 32 known or candidate neurotoxicants. First, expression of neural differentiation genes was assayed during a 7-day differentiation period. Of the three cell lines, LUHMES showed the highest gene expression of neuronal markers after differentiation. Both in the undifferentiated state and after 7 days of neuronal differentiation, LUHMES cells exhibited greater cytotoxic sensitivity to most of 32 suspected or known neurotoxicants than SH-SY5Y or NSCs. LUHMES cells were also unique in being more susceptible to several compounds in the differentiating state than in the undifferentiated state; including known neurotoxicants colchicine, methyl-mercury (II), and vincristine. Gene expression results suggest that differentiating LUHMES cells may be susceptible to apoptosis because they express low levels of anti-apoptotic genes BCL2 and BIRC5/survivin, whereas SH-SY5Y cells may be resistant to apoptosis because they express high levels of BCL2, BIRC5/survivin, and BIRC3 genes. Thus, LUHMES cells exhibited favorable characteristics for neuro-cytotoxicity screening: rapid differentiation into neurons that exhibit high level expression neuronal marker genes, and marked sensitivity of LUHMES cells to known neurotoxicants. Copyright © 2016 John Wiley & Sons, Ltd.

Animal modeling an oligodendrogliopathy--multiple system atrophy

Multiple system atrophy (MSA) is a rare, yet rapidly-progressive neurodegenerative disease that presents clinically with autonomic failure in combination with parkinsonism or cerebellar ataxia. The definitive neuropathology differentiating MSA from Lewy body diseases is the presence of α-synuclein aggregates in oligodendrocytes (called glial cytoplasmic inclusion or GCI) rather than the fibrillar aggregates in neurons (called Lewy bodies). This makes the pathological pathway(s) in MSA unique in that oligodendrocytes are involved rather than predominantly neurons, as is most other neurodegenerative disorders. MSA is therefore regarded as an oligodendrogliopathy. The etiology of MSA is unknown. No definitive risk factors have been identified, although α-synuclein and other genes have been variably linked to MSA risk. Utilization of postmortem brain tissues has greatly advanced our understanding of GCI pathology and the subsequent neurodegeneration. However, extrapolating the early pathogenesis of MSA from such resource has been difficult and limiting. In recent years, cell and animal models developed for MSA have been instrumental in delineating unique MSA pathological pathways, as well as aiding in clinical phenotyping. The purpose of this review is to bring together and discuss various animal models that have been developed for MSA and how they have advanced our understanding of MSA pathogenesis, particularly the dynamics of α-synuclein aggregation. This review will also discuss how animal models have been used to explore potential therapeutic avenues for MSA, and future directions of MSA modeling.

Inhibition of herpes virus infection in oligodendrocyte cultured cells by valproic acid

Valproic acid (VPA) is a small fatty acid used for treatment of different neurologic diseases such as epilepsy, migraines or bipolar disorders. VPA modulates different processes of cell metabolism that can lead to alterations in susceptibility of several cell types to the infection of Human Immunodeficiency Virus (HIV), Epstein-Barr virus (EBV), as well as to exert an inhibitory effect on the replication of different enveloped viruses in cultured cells. Taken these data into account and the fact that HSV-1 has been involved in some neuropathies, we have characterized the effect of VPA on this herpesvirus infection of the differentiation/maturation-inducible human oligodendrocyte cell line HOG, which resulted more susceptible to VPA inhibition of virus growth after cell differentiation. In these cells, the role of VPA in virus entry was tackled. Incubation with VPA induced a slight but reproducible inhibition in the virus particles uptake mainly observed when the drug was added in the adsorption or early upon infection. In addition, transcription and expression of viral proteins were significantly downregulated in the presence of VPA. Remarkably, when the infective viral production was assessed, VPA dramatically blocked the detection of infectious HSV-1 particles. Herein, our results indicate that VPA treatment of HOG cells significantly reduces the effect of HSV-1 infection, virus entry and productivity without affecting cellular viability.

DOPAL is transmissible to and oligomerizes alpha-synuclein in human glial cells

INTRODUCTION

Glial cytoplasmic inclusions (GCIs) containing alpha-synuclein (AS) are a neuropathologic hallmark of multiple system atrophy (MSA). Oligomerized AS is thought to be the pathogenic form of the protein. Glial cells normally express little AS, but they can take up AS from the extracellular fluid. 3,4-Dihydroxyphenylacetaldehyde (DOPAL), an obligate intermediate in the intra-neuronal metabolism of dopamine (DA), potently oligomerizes AS. In this study we tested whether DOPAL is taken up by human glial cells and augments intracellular oligomerization of AS.

METHODS

DOPAL (exogenous or endogenous from co-incubation with PC12 cells) and AS (native or A53T mutant form) were added to the incubation medium of glial cells (glioblastoma or MO3.13 oligodendrocytes). Glial cellular contents of DOPAL and its intracellular metabolite 3,4-dihydroxyphenylacetic acid (DOPAC) were measured at up to 180 min of incubation. Glial cellular AS oligomers were quantified by Western blotting.

RESULTS

Neither glioblastoma nor MO3.13 cells contained endogenous catecholamines or AS. Co-incubation of the cells with DA-producing PC12 cells produced time-related increases in DOPAL and DOPAC contents. Similarly, glial cellular DOPAL and DOPAC contents increased rapidly after addition of DOPAL to the medium. After addition of native or A53T-AS, intracellular AS also increased. Incubation of glial cells with both DOPAL and AS enhanced the intracellular oligomerization of native and A53T-AS.

CONCLUSIONS

DOPAL is transmissible to glial cells and enhances intracellular oligomerization of AS. An interaction of DOPAL with AS might help explain the formation of CGIs in MSA.

In vitro and mouse studies supporting therapeutic utility of triiodothyroacetic acid in MCT8 deficiency

Monocarboxylate transporter 8 (MCT8) transports thyroid hormone (TH) across the plasma membrane. Mutations in MCT8 result in the Allan-Herndon-Dudley syndrome, comprising severe psychomotor retardation and elevated serum T3 levels. Because the neurological symptoms are most likely caused by a lack of TH transport into the central nervous system, the administration of a TH analog that does not require MCT8 for cellular uptake may represent a therapeutic strategy. Here, we investigated the therapeutic potential of the biologically active T3 metabolite Triac (TA3) by studying TA3 transport, metabolism, and action both in vitro and in vivo. Incubation of SH-SY5Y neuroblastoma cells and MO3.13 oligodendrocytes with labeled substrates showed a time-dependent uptake of T3 and TA3. In intact SH-SY5Y cells, both T3 and TA3 were degraded by endogenous type 3 deiodinase, and they influenced gene expression to a similar extent. Fibroblasts from MCT8 patients showed an impaired T3 uptake compared with controls, whereas TA3 uptake was similar in patient and control fibroblasts. In transfected cells, TA3 did not show significant transport by MCT8. Most importantly, treatment of athyroid Pax8-knockout mice and Mct8/Oatp1c1-double knockout mice between postnatal days 1 and 12 with TA3 restored T3-dependent neural differentiation in the cerebral and cerebellar cortex, indicating that TA3 can replace T3 in promoting brain development. In conclusion, we demonstrated uptake of TA3 in neuronal cells and in fibroblasts of MCT8 patients and similar gene responses to T3 and TA3. This indicates that TA3 bypasses MCT8 and may be used to improve the neural status of MCT8 patients.