General anesthetic agents induce neurotoxicity through oligodendrocytes in the developing brain

General anesthetic agents can impact brain function through interactions with neurons and their effects on glial cells.Oligodendrocytes perform essential roles in the central nervous system,including myelin sheath formation,axonal metabolism,and neuroplasticity regulation.They are particularly vulnerable to the effects of general anesthetic agents resulting in impaired proliferation,differentiation,and apoptosis.Neurologists are increasingly interested in the effects of general anesthetic agents on oligodendrocytes.These agents not only act on the surface receptors of oligodendrocytes to elicit neuroinflammation through modulation of signaling pathways,but also disrupt metabolic processes and alter the expression of genes involved in oligodendrocyte development and function.In this review,we summarize the effects of general anesthetic agents on oligodendrocytes.We anticipate that future research will continue to explore these effects and develop strategies to decrease the incidence of adverse reactions associated with the use of general anesthetic agents.

Oligodendrocytes in central nervous system diseases:the effect of cytokine regulation

Cytokines including tumor necrosis factor, interleukins, interferons, and chemokines are abundantly produced in various diseases. As pleiotropic factors, cytokines are involved in nearly every aspect of cellular functions such as migration, survival, proliferation, and differentiation. Oligodendrocytes are the myelin-forming cells in the central nervous system and play critical roles in the conduction of action potentials, supply of metabolic components for axons, and other functions. Emerging evidence suggests that both oligodendrocytes and oligodendrocyte precursor cells are vulnerable to cytokines released under pathological conditions. This review mainly summarizes the effects of cytokines on oligodendrocyte lineage cells in central nervous system diseases. A comprehensive understanding of the effects of cytokines on oligodendrocyte lineage cells contributes to our understanding of central nervous system diseases and offers insights into treatment strategies.

Nogo-A aggravates oxidative damage in oligodendrocytes

Nogo-A is considered one of the most important inhibitors of myelin-associated axonal regeneration in the central nervous system.It is mainly expressed by oligodendrocytes.Although previous studies have found regulatory roles for Nogo-A in neurite outgrowth inhibition,neuronal homeostasis,precursor migration,plasticity,and neurodegeneration,its functions in the process of oxidative injury are largely uncharacterized.In this study,oligodendrocytes were extracted from the cerebral cortex of newborn Sprague-Dawley rats.We used hydrogen peroxide(H2O2)to induce an in vitro oligodendrocyte oxidative damage model and found that endogenously expressed Nogo-A is significantly upregulated in oligodendrocytes.After recombinant virus Ad-ZsGreen-rat Nogo-A infection of oligodendrocytes,Nogo-A expression was increased,and the infected oligodendrocytes were more susceptible to acute oxidative insults and exhibited a markedly elevated rate of cell death.Furthermore,knockdown of Nogo-A expression in oligodendrocytes by Ad-ZsGreen-shRNA-Nogo-A almost completely protected against oxidative stress induced by exogenous H2O2.Intervention with a Nogo-66 antibody,a LINGO1 blocker,or Y27632,an inhibitor in the Nogo-66-NgR/p75/LINGO-1-RhoA-ROCK pathway,did not affect the death of oligodendrocytes.Ad-ZsGreen-shRNA-Nogo-A also increased the levels of phosphorylated extracellular signal-regulated kinase 1/2 and inhibited BCL2 expression in oligodendrocytes.In conclusion,Nogo-A aggravated reactive oxygen species damage in oligodendrocytes,and phosphorylated extracellular signal-regulated kinase 1/2 and BCL2 might be involved in this process.This study was approved by the Ethics Committee of Peking University People’s Hospital,China(approval No.2018PHC081)on December 18,2018.

Dysfunction of the oligodendrocytes in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis(ALS)is a fatal neurodegenerative disorder characterized by irreversible deterioration of upper and lower motor neurons(MNs).Previously,studies on the involvement of glial cells in the pathogenic process of ALS have mainly revolved around astrocytes and microglia.And oligodendrocytes(OLs)have only recently been highlighted.Grey matter demyelination within the motor cortex and proliferation of the oligodendrocyte precursor cells(OPCs)was observed in ALS patients.The selective ablation of mutant SOD1(the dysfunctional superoxide dismutase)from the oligodendrocyte progenitors after birth significantly delayed disease onset and prolonged the overall survival in ALS mice model(SOD1G37R).In this study,we review the several mechanisms of oligodendrocyte dysfunction involved in the pathological process of myelin damage and MNs death during ALS.Particularly,we examined the insufficient local energy supply from OLs to axons,impaired differentiation from OPCs into OLs mediated by oxidative stress damage,and inflammatory injury to the OLs.Since increasing evidence depicted that ALS is not a disease limited to MNs damage,exploring the mechanisms by which oligodendrocyte dysfunction is involved in MNs death would contribute to a more comprehensive understanding of ALS and identifying potential drug targets.

The changes of oligodendrocytes induced by anesthesia during brain development

With the advent of modern techniques, drugs, and monitoring, general anesthesia has come to be considered an unlikely cause of harm, particularly for healthy patients. While this is largely true, newly emerging clinical and laboratory studies have sug- gested that exposure to anesthetic agents during early childhood may have long-lasting adverse effects on cognitive function. This concern has been the focus of intense study in the field of anesthesia research. A recent high-profile review by Rappaport et al. （2015） concluded that while many questions remain un- answered, there is strong evidence from laboratory studies that commonly used anesthetics interfere with brain development and that clinical studies suggest a correlation between early childhood exposure to these agents and subsequent effects on learning and cognition. The issue is of sufficient public health importance that a public-private partnership known as Smar- Tots （Strategies for Mitigating Anesthesia-Related Neurotoxicity in Tots） was developed by the FDA to study pediatric anesthetic neurotoxicity. The mechanism of injury underlying this phe- nomenon has yet to be fully elucidated, and there is evidence to suggest that anesthetics may have direct cytotoxic effects on neurons leading to cell death or suppressed neurogenesis （Strat- mann et al., 2010） and that they may interfere with key pro- cesses in neuronal growth and development that underlie brain circuit development （Wagner et al., 2014）.

Co-culture of oligodendrocytes and neurons can be used to assess drugs for axon regeneration in the central nervous system

We present a novel in vitro model in which to investigate the efficacy of experimental drugs for the promotion of axon regeneration in the central nervous system. We co-cultured rat hippocampal neurons and cerebral cortical oligodendrocytes, and tested the co-culture system using a Nogo-66 receptor antagonist peptide（NEP1–40）, which promotes axonal growth. Primary cultured oligodendrocytes suppressed axonal growth in the rat hippocampus, but NEP1–40 stimulated axonal growth in the co-culture system. Our results confirm the validity of the neuron-oligodendrocyte co-culture system as an assay for the evaluation of drugs for axon regeneration in the central nervous system.

Effects of neurotrophin-3 on the differentiation of neural stem cells into neurons and oligodendrocytes

In this study, cells from the cerebral cortex of fetal rats at pregnant 16 days were harvested and cultured with 20 μg/L neurotrophin-3. After 7 days of culture, immunocytochemical staining showed that, 22.4% of cells were positive for nestin, 10.5% were positive for 18-111 tubulin （neuronal marker）, and 60.6% were positive for glial fibrillary acidic protein, but no cells were positive for 04 （oligodendrocytic marker）. At 14 days, there were 5.6% nestin-, 9.6% 13-111 tubulin-, 81.1% glial fibrillary acidic protein-, and 2.2% O4-positive cells. In cells not treated with neurotrophin-3, some were nestin-positive, while the majority showed positive staining for glial fibdllary acidic protein. Our experimental findings indicate that neurotrophin-3 is a crucial factor for inducing neural stem cells differentiation into neurons and oligodendrocytes.

The contribution of oligodendrocytes and oligodendrocyte progenitor cells to central nervous system repair in multiple sclerosis： perspectives for remyelination therapeutic strategies

Oligodencrocytes（OLs） are the main glial cells of the central nervous system involved in myelination of axons. In multiple sclerosis（MS）, there is an imbalance between demyelination and remyelination processes, the last one performed by oligodendrocyte progenitor cells（OPCs） and OLs, resulting into a permanent demyelination, axonal damage and neuronal loss. In MS lesions, astrocytes and microglias play an important part in permeabilization of blood-brain barrier and initiation of OPCs proliferation. Migration and differentiation of OPCs are influenced by various factors and the process is finalized by insufficient acummulation of OLs into the MS lesion. In relation to all these processes, the author will discuss the potential targets for remyelination strategies.

Electroacupuncture promotes the proliferation of endogenous neural stem cells and oligodendrocytes in the injured spinal cord of adult rats

A contusive model of spinal cord injury at spinal segment T8-9 was established in rats. Huantiao （GB30） and Huatuojiaji （Ex-B05） were punctured with needles, and endogenous neural stem cells were labeled with 5-bromo-2＇-deoxyuridine （BrdU） and NG2. Double immunofluorescence staining showed that electroacupuncture markedly increased the numbers of BrdU＋/NG2＋cells at spinal cord tissue 15 mm away from the injury center in the rostral and caudal directions. The results suggest that electroacupuncture promotes the proliferation of endogenous neural stem cells and oligodendrocytes in rats with spinal cord injury.

Promotive Effects of Yokukansan, a Traditional Japanese Medicine, on Proliferation and Differentiation of Cultured Mouse Cortical Oligodendrocytes

Effects of yokukansan, a traditional Japanese medicine, on proliferation and differentiation of oligodendrocytes were examined using purified mouse cortical oligodendrocyte precursor cells (OPCs). OPCs were cultured for four days, and proliferation was evaluated by counting A2B5 (a specific antibody to OPC)-reactive cells on the second day of cell culture. Differentiation from OPC to oligodendrocyte was evaluated by counting O4 (a specific antibody to detect differentiated cells in various stages)-reactive cells on the fourth day of culture. The effects of yokukansan (final concentration: 100 or 200 μg/ml) on proliferation and differentiation were examined by adding it to the medium for four days. Yokukansan increased not only the number of A2B5-positive cells on the second day but also the number of O4-positive cells on the fourth day compared to those in the corresponding controls. A WST-8 assay was used to identify active components from seven components of Uncaria Hook (UH), one of the constituent galenicals of yokukansan. Geissoschizine methyl ether (GM: 0.1 - 3.0 μM) was identified by this screening assay and increased the number of A2B5-positive cells on the second day and O4-positive cells on the fourth day as yokukansan did. These results suggest that yokukansan promotes the proliferation and differentiation of oligodendrocytes, and also that GM contained in UH is one of active components responsible for this effect of yokukansan.

Inhibition of YIPF2 Improves the Vulnerability of Oligodendrocytes to Human Islet Amyloid Polypeptide

Excessive secretion of human islet amyloid polypeptide(hIAPP)is an important pathological basis of diabetic encephalopathy(DE).In this study,we aimed to investigate the potential implications of hIAPP in DE pathogenesis.Brain magnetic resonance imaging and cognitive scales were applied to evaluate white matter damage and cognitive function.We found that the concentration of serum hIAPP was positively correlated with white matter damage but negatively correlated with cognitive scores in patients with type 2 diabetes mellitus.In vitro assays revealed that oligodendrocytes,compared with neurons,were more prone to acidosis under exogenous hIAPP stimulation.Moreover,western blotting and co-immunoprecipitation indicated that hIAPP interfered with the binding process of monocarboxylate transporter(MCT)1 to its accessory protein CD147 but had no effect on the binding of MCT2 to its accessory protein gp70.Proteomic differential analysis of proteins co-immunoprecipitated with CD147 in oligodendrocytes revealed Yeast Rab GTPase-Interacting protein 2(YIPF2,which modulates the transfer of CD147 to the cell membrane)as a significant target.Furthermore,YIPF2 inhibition significantly improved hIAPP-induced acidosis in oligodendrocytes and alleviated cognitive dysfunction in DE model mice.These findings suggest that increased CD147 translocation by inhibition of YIPF2 optimizes MCT1 and CD147 binding,potentially ameliorating hIAPP-induced acidosis and the consequent DE-related demyelination.

Oligodendroglial heterogeneity in health,disease,and recovery:deeper insights into myelin dynamics

Decades of research asserted that the oligodendroglial lineage comprises two cell types:oligodendrocyte precursor cells and oligodendrocytes.However,recent studies employing single-cell RNA sequencing techniques have uncovered novel cell states,prompting a revision of the existing terminology.Going forward,the oligodendroglial lineage should be delineated into five distinct cell states:oligodendrocyte precursor cells,committed oligodendrocyte precursor cells,newly formed oligodendrocytes,myelin-forming oligodendrocytes,and mature oligodendrocytes.This new classification system enables a deeper understanding of the oligodendroglia in both physiological and pathological contexts.Adopting this uniform terminology will facilitate comparison and integration of data across studies.This,including the consolidation of findings from various demyelinating models,is essential to better understand the pathogenesis of demyelinating diseases.Additionally,comparing injury models across species with varying regenerative capacities can provide insights that may lead to new therapeutic strategies to overcome remyelination failure.Thus,by standardizing terminology and synthesizing data from diverse studies across different animal models,we can enhance our understanding of myelin pathology in central nervous system disorders such as multiple sclerosis,Alzheimer's disease,and amyotrophic lateral sclerosis,all of which involve oligodendroglial and myelin dysfunction.

Three-dimensional bioprinting sodium alginate/gelatin scaffold combined with neural stem cells and oligodendrocytes markedly promoting nerve regeneration after spinal cord injury

Accumulating research has indicated that the transplantation of combined stem cells and scaffolds is an effective method for spinal cord injury(SCI).The development of three-dimensional(3D)bioprinting technology can make the 3D scaffolds combined with cells more accurate and effective for SCI treatment.However,unmyelinated newborn nerve fibers have no nerve signaling conduction,hampering recovery of motor function.In this study,we designed and printed a type of sodium alginate/gelatin scaffold loaded with neural stem cells and oligodendrocytes,which were involved in the formation of the myelin sheaths of neural cell axons.In order to observe the effectiveness of this 3D bioprinting scaffold,we transplanted it into the completely transected rat spinal cord,and then immunofluorescence staining,hematoxylin–eosin staining and behavioral assessment were performed.The results showed that this 3D bioprinting scaffold markedly improved the hindlimb motor function and promoted nerve regeneration.These findings suggested that this novel 3D bioprinting scaffold was a good carrier for cells transplantation,thereby enhancing spinal cord repair following injury.

Spatial transcriptomics combined with single-nucleus RNA sequencing reveals glial cell heterogeneity in the human spinal cord

Glial cells play crucial roles in regulating physiological and pathological functions,including sensation,the response to infection and acute injury,and chronic neurodegenerative disorders.Glial cells include astrocytes,microglia,and oligodendrocytes in the central nervous system,and satellite glial cells and Schwann cells in the peripheral nervous system.Despite the greater understanding of glial cell types and functional heterogeneity achieved through single-cell and single-nucleus RNA sequencing in animal models,few studies have investigated the transcriptomic profiles of glial cells in the human spinal cord.Here,we used high-throughput single-nucleus RNA sequencing and spatial transcriptomics to map the cellular and molecular heterogeneity of astrocytes,microglia,and oligodendrocytes in the human spinal cord.To explore the conservation and divergence across species,we compared these findings with those from mice.In the human spinal cord,astrocytes,microglia,and oligodendrocytes were each divided into six distinct transcriptomic subclusters.In the mouse spinal cord,astrocytes,microglia,and oligodendrocytes were divided into five,four,and five distinct transcriptomic subclusters,respectively.The comparative results revealed substantial heterogeneity in all glial cell types between humans and mice.Additionally,we detected sex differences in gene expression in human spinal cord glial cells.Specifically,in all astrocyte subtypes,the levels of NEAT1 and CHI3L1 were higher in males than in females,whereas the levels of CST3 were lower in males than in females.In all microglial subtypes,all differentially expressed genes were located on the sex chromosomes.In addition to sex-specific gene differences,the levels of MT-ND4,MT2A,MT-ATP6,MT-CO3,MT-ND2,MT-ND3,and MT-CO_(2) in all spinal cord oligodendrocyte subtypes were higher in females than in males.Collectively,the present dataset extensively characterizes glial cell heterogeneity and offers a valuable resource for exploring the cellular basis of spinal cordrelated illnesses,including chronic pain,amyotrophic lateral sclerosis,and multiple sclerosis.

Perilipin-2 mediates ferroptosis in oligodendrocyte progenitor cells and myelin injury after ischemic stroke

Differentiation of oligodendrocyte progenitor cells into mature myelin-forming oligodendrocytes contributes to remyelination.Failure of remyelination due to oligodendrocyte progenitor cell death can result in severe nerve damage.Ferroptosis is an iron-dependent form of regulated cell death caused by membrane rupture induced by lipid peroxidation,and plays an important role in the pathological process of ischemic stroke.However,there are few studies on oligodendrocyte progenitor cell ferroptosis.We analyzed transcriptome sequencing data from GEO databases and identified a role of ferroptosis in oligodendrocyte progenitor cell death and myelin injury after cerebral ischemia.Bioinformatics analysis suggested that perilipin-2(PLIN2)was involved in oligodendrocyte progenitor cell ferroptosis.PLIN2 is a lipid storage protein and a marker of hypoxia-sensitive lipid droplet accumulation.For further investigation,we established a mouse model of cerebral ischemia/reperfusion.We found significant myelin damage after cerebral ischemia,as well as oligodendrocyte progenitor cell death and increased lipid peroxidation levels around the infarct area.The ferroptosis inhibitor,ferrostatin-1,rescued oligodendrocyte progenitor cell death and subsequent myelin injury.We also found increased PLIN2 levels in the peri-infarct area that co-localized with oligodendrocyte progenitor cells.Plin2 knockdown rescued demyelination and improved neurological deficits.Our findings suggest that targeting PLIN2 to regulate oligodendrocyte progenitor cell ferroptosis may be a potential therapeutic strategy for rescuing myelin damage after cerebral ischemia.

High mobility group box 1 in the central nervous system:regeneration hidden beneath inflammation

High-mobility group box 1 was first discovered in the calf thymus as a DNA-binding nuclear protein and has been widely studied in diverse fields,including neurology and neuroscience.High-mobility group box 1 in the extracellular space functions as a pro-inflammatory damage-associated molecular pattern,which has been proven to play an important role in a wide variety of central nervous system disorders such as ischemic stroke,Alzheimer’s disease,frontotemporal dementia,Parkinson’s disease,multiple sclerosis,epilepsy,and traumatic brain injury.Several drugs that inhibit high-mobility group box 1 as a damage-associated molecular pattern,such as glycyrrhizin,ethyl pyruvate,and neutralizing anti-high-mobility group box 1 antibodies,are commonly used to target high-mobility group box 1 activity in central nervous system disorders.Although it is commonly known for its detrimental inflammatory effect,high-mobility group box 1 has also been shown to have beneficial pro-regenerative roles in central nervous system disorders.In this narrative review,we provide a brief summary of the history of high-mobility group box 1 research and its characterization as a damage-associated molecular pattern,its downstream receptors,and intracellular signaling pathways,how high-mobility group box 1 exerts the repair-favoring roles in general and in the central nervous system,and clues on how to differentiate the pro-regenerative from the pro-inflammatory role.Research targeting high-mobility group box 1 in the central nervous system may benefit from differentiating between the two functions rather than overall suppression of high-mobility group box 1.

Macular microvascular and structural changes on optical coherence tomography angiography in atypical optic neuritis

BACKGROUND Atypical optic neuritis,consisting of neuromyelitis optica spectrum disorders(NMOSD)or myelin oligodendrocyte glycoprotein antibody disease(MOGAD),has a very similar presentation but different prognostic implications and longterm management strategies.Vascular and metabolic factors are being thought to play a role in such autoimmune neuro-inflammatory disorders,apart from the obvious immune mediated damage.With the advent of optical coherence tomography angiography(OCTA),it is easy to pick up on these subclinical macular microvascular and structural changes.AIM To study the macular microvascular and structural changes on OCTA in atypical optic neuritis.METHODS This observational cross-sectional study involved 8 NMOSD and 17 MOGAD patients,diagnosed serologically,as well as 10 healthy controls.Macular vascular density(MVD)and ganglion cell+inner plexiform layer thickness(GCIPL)were studied using OCTA.RESULTS There was a significant reduction in MVD in NMOSD and MOGAD affected as well as unaffected eyes when compared with healthy controls.NMOSD and MOGAD affected eyes had significant GCIPL thinning compared with healthy controls.NMOSD unaffected eyes did not show significant GCIPL thinning compared to healthy controls in contrast to MOGAD unaffected eyes.On comparing NMOSD with MOGAD,there was no significant difference in terms of MVD or GCIPL in the affected or unaffected eyes.CONCLUSION Although significant microvascular and structural changes are present on OCTA between atypical optic neuritis and normal patients,they could not help in differentiating between NMOSD and MOGAD cases.

Experimental study on the apoptosis of the astrocytes and the oligodendrocytes induced by Ca^(2+) reperfusion

Objective: To investigate the apoptosis rules of the astrocytes and oligodendrocytes induced by Ca 2+ reperfusion. Methods: The apoptosis of purified cultured astrocytes and oligodendrocytes induced by Ca 2+ reperfusion and the relationship between the development of the cell apoptosis and post-reperfusion time was observed. Results: Both the astrocytes and oligodendrocytes were obviously in a time-dependent fashion, and the apoptosis ratios of the oligodendrocytes ( 39.73%± 4.16%) were higher than the astrocytes ( 19.64%± 4.67%) 24 hours after Ca 2+ reperfusion. The TUNEL positive cells were 13.6± 1.82 and 21.4± 1.95 at every visual field of astrocytes and oligodendrocytes respectively 24 hours after Ca 2+ reperfusion. Conclusions: The astrocytes and oligodendrocytes are similar with the development rules on apoptosis and have different susceptiveness to the situation.

Vulnerability of premyelinating oligodendrocytes to white-matter damage in neonatal brain injury

Premature birth is a significant economic and public health burden, and its incidence is rising. Periventricular leukomalacia （PVL） is the predominant form of brain injury in premature infants and the leading cause of cerebral palsy. PVL is characterized by selective white-matter damage with prominent oligodendroglial injury. The maturation-dependent vulnerability of developing and premyelinating oligodendrocytes to excitotoxic, oxidative, and inflammatory forms of injury is a major factor in the pathogenesis of PVL. Recent studies using mouse models of PVL reveal that synapses between axons and developing oligodendrocytes are quickly and profoundly damaged in immature white matter. Axon-glia synapses are highly vulnerable to white-matter injury in the developing brain, and the loss of synapses between axons and premyelinating oligodendrocytes occurs before any cellular loss in the immature white matter. Microglial activation and astrogliosis play important roles in triggering white-matter injury. Impairment of white-matter development and function in the neonatal period contributes critically to functional and behavioral deficits. Preservation of the integrity of the white matter is likely key in the treatment of PVL and subsequent neurological consequences and disabilities.

Developmental Origins of Human Cortical Oligodendrocytes and Astrocytes

Human cortical radial glial cells are primary neural stem cells that give rise to cortical glutaminergic projection pyramidal neurons, glial cells (oligodendrocytes and astrocytes) and olfactory bulb GABAergic interneurons. One of prominent features of the human cortex is enriched with glial cells, but there are major gaps in understanding how these glial cells are generated. Herein, by integrating analysis of published human cortical single-cell RNA-Seq datasets with our immunohistochemistical analyses, we show that around gestational week 18, EGFR-expressing human cortical truncated radial glial cells (tRGs) give rise to basal multipotent intermediate progenitors (bMIPCs) that express EGFR, ASCL1, OLIG2 and OLIG1. These bMIPCs undergo several rounds of mitosis and generate cortical oligodendrocytes, astrocytes and olfactory bulb interneurons. We also characterized molecular features of the cortical tRG. Integration of our findings suggests a general picture of the lineage progression of cortical radial glial cells, a fundamental process of the developing human cerebral cortex.