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International Journal of Molecular... Sep 2022Long-term neurological and mental complications of COVID-19, the so-called post-COVID syndrome or long COVID, affect the quality of life. The most persistent... (Review)
Review
Long-term neurological and mental complications of COVID-19, the so-called post-COVID syndrome or long COVID, affect the quality of life. The most persistent manifestations of long COVID include fatigue, anosmia/hyposmia, insomnia, depression/anxiety, and memory/attention deficits. The physiological basis of neurological and psychiatric disorders is still poorly understood. This review summarizes the current knowledge of neurological sequelae in post-COVID patients and discusses brain demyelination as a possible mechanism of these complications with a focus on neuroimaging findings. Numerous reviews, experimental and theoretical studies consider brain demyelination as one of the mechanisms of the central neural system impairment. Several factors might cause demyelination, such as inflammation, direct effect of the virus on oligodendrocytes, and cerebrovascular disorders, inducing myelin damage. There is a contradiction between the solid fundamental basis underlying demyelination as the mechanism of the neurological injuries and relatively little published clinical evidence related to demyelination in COVID-19 patients. The reason for this probably lies in the fact that most clinical studies used conventional MRI techniques, which can detect only large, clearly visible demyelinating lesions. A very limited number of studies use specific methods for myelin quantification detected changes in the white matter tracts 3 and 10 months after the acute phase of COVID-19. Future research applying quantitative MRI assessment of myelin in combination with neurological and psychological studies will help in understanding the mechanisms of post-COVID complications associated with demyelination.
Topics: Attention Deficit Disorder with Hyperactivity; COVID-19; Demyelinating Diseases; Humans; Quality of Life; Post-Acute COVID-19 Syndrome
PubMed: 36232592
DOI: 10.3390/ijms231911291 -
Aging and Disease May 2024In the central nervous system (CNS), the myelin sheath ensures efficient interconnection between neurons and contributes to the regulation of the proper function of... (Review)
Review
In the central nervous system (CNS), the myelin sheath ensures efficient interconnection between neurons and contributes to the regulation of the proper function of neuronal networks. The maintenance of myelin and the well-organized subtle process of myelin plasticity requires cooperation among myelin-forming cells, glial cells, and neural networks. The process of cooperation is fragile, and the balance is highly susceptible to disruption by microenvironment influences. Reactive microglia play a critical and complicated role in the demyelination and remyelination process. Recent studies have shown that the voltage-gated proton channel Hv1 is selectively expressed in microglia in CNS, which regulates intracellular pH and is involved in the production of reactive oxygen species, underlying multifaceted roles in maintaining microglia function. This paper begins by examining the molecular mechanisms of demyelination and emphasizes the crucial role of the microenvironment in demyelination. It focuses specifically on the role of Hv1 in myelin repair and its therapeutic potential in CNS demyelinating diseases.
Topics: Humans; Microglia; Myelin Sheath; Animals; Demyelinating Diseases; Immunomodulation; Ion Channels; Remyelination; Reactive Oxygen Species
PubMed: 38029392
DOI: 10.14336/AD.2023.1107 -
Journal of Neuroinflammation Aug 2019The association of gut microbiota and diseases of the central nervous system (CNS), including multiple sclerosis (MS), has attracted much attention. Although a previous...
BACKGROUND
The association of gut microbiota and diseases of the central nervous system (CNS), including multiple sclerosis (MS), has attracted much attention. Although a previous analysis of MS gut microbiota revealed a reduction in species producing short-chain fatty acids (SCFAs), the influence of these metabolites on demyelination and remyelination, the critical factors of MS pathogenesis, remains unclear.
METHODS
To investigate the relationship between demyelination and gut microbiota, we administered a mixture of non-absorbing antibiotics or SCFAs to mice with cuprizone-induced demyelination and evaluated demyelination and the accumulation of microglia. To analyze the direct effect of SCFAs on demyelination or remyelination, we induced demyelination in an organotypic cerebellar slice culture using lysolecithin and analyzed the demyelination and maturation of oligodendrocyte precursor cells with or without SCFA treatment.
RESULTS
The oral administration of antibiotics significantly enhanced cuprizone-induced demyelination. The oral administration of butyrate significantly ameliorated demyelination, even though the accumulation of microglia into demyelinated lesions was not affected. Furthermore, we showed that butyrate treatment significantly suppressed lysolecithin-induced demyelination and enhanced remyelination in an organotypic slice culture in the presence or absence of microglia, suggesting that butyrate may affect oligodendrocytes directly. Butyrate treatment facilitated the differentiation of immature oligodendrocytes.
CONCLUSIONS
We revealed that treatment with butyrate suppressed demyelination and enhanced remyelination in an organotypic slice culture in association with facilitating oligodendrocyte differentiation. Our findings shed light on a novel mechanism of interaction between the metabolites of gut microbiota and the CNS and may provide a strategy to control demyelination and remyelination in MS.
Topics: Animals; Anti-Bacterial Agents; Butyrates; Cell Differentiation; Cuprizone; Demyelinating Diseases; Gastrointestinal Microbiome; Male; Mice; Mice, Inbred C57BL; Myelin Sheath; Oligodendroglia; Organ Culture Techniques; Remyelination
PubMed: 31399117
DOI: 10.1186/s12974-019-1552-y -
AJNR. American Journal of Neuroradiology Sep 2020Radiologically isolated syndrome refers to an entity in which white matter lesions fulfilling the criteria for multiple sclerosis occur in individuals without a history... (Review)
Review
Radiologically isolated syndrome refers to an entity in which white matter lesions fulfilling the criteria for multiple sclerosis occur in individuals without a history of a clinical demyelinating attack or alternative etiology. Since its introduction in 2009, the diagnostic criteria of radiologically isolated syndrome and its clinical relevance have been widely debated by neurologists and radiologists. The aim of the present study was to review the following: 1) historical evolution of radiologically isolated syndrome criteria, 2) clinical and imaging findings in adults and children with radiologically isolated syndrome, 3) imaging features of patients with radiologically isolated syndrome at high risk for conversion to MS, and 4) challenges and controversies for work-up, management, and therapeutic interventions of patients with radiologically isolated syndrome.
Topics: Adult; Child; Demyelinating Diseases; Female; Humans; Magnetic Resonance Imaging; Male; Multiple Sclerosis; Radiologists
PubMed: 32763896
DOI: 10.3174/ajnr.A6649 -
Brain Pathology (Zurich, Switzerland) Sep 2018Damage to myelin is a key feature of multiple sclerosis (MS) pathology. Magnetic resonance imaging (MRI) has revolutionized our ability to detect and monitor MS... (Review)
Review
Damage to myelin is a key feature of multiple sclerosis (MS) pathology. Magnetic resonance imaging (MRI) has revolutionized our ability to detect and monitor MS pathology in vivo. Proton density, T and T can provide qualitative contrast weightings that yield superb in vivo visualization of central nervous system tissue and have proved invaluable as diagnostic and patient management tools in MS. However, standard clinical MR methods are not specific to the types of tissue damage they visualize, and they cannot detect subtle abnormalities in tissue that appears otherwise normal on conventional MRIs. Myelin water imaging is an MR method that provides in vivo measurement of myelin. Histological validation work in both human brain and spinal cord tissue demonstrates a strong correlation between myelin water and staining for myelin, validating myelin water as a marker for myelin. Myelin water varies throughout the brain and spinal cord in healthy controls, and shows good intra- and inter-site reproducibility. MS plaques show variably decreased myelin water fraction, with older lesions demonstrating the greatest myelin loss. Longitudinal study of myelin water can provide insights into the dynamics of demyelination and remyelination in plaques. Normal appearing brain and spinal cord tissues show reduced myelin water, an abnormality which becomes progressively more evident over a timescale of years. Diffusely abnormal white matter, which is evident in 20%-25% of MS patients, also shows reduced myelin water both in vivo and postmortem, and appears to originate from a primary lipid abnormality with relative preservation of myelin proteins. Active research is ongoing in the quest to refine our ability to image myelin and its perturbations in MS and other disorders of the myelin sheath.
Topics: Animals; Demyelinating Diseases; Humans; Magnetic Resonance Imaging; Myelin Sheath; Remyelination; Water
PubMed: 30375119
DOI: 10.1111/bpa.12645 -
European Neurology 2018Multiple sclerosis (MS) is a chronic inflammatory demyelination disorder with an immune-mediated pathophysiology that affects the central nervous system (CNS). Like... (Review)
Review
Multiple sclerosis (MS) is a chronic inflammatory demyelination disorder with an immune-mediated pathophysiology that affects the central nervous system (CNS). Like other autoimmune conditions, it has a predilection for female gender. This suggests a gender bias and a possible hormonal association. Inflammation and demyelination are hallmarks of MS. Oligodendrocytes are the myelinating cells of the CNS and these continue to be generated by oligodendrocyte precursor cells (OPCs). The process of remyelination represents a major form of plasticity in the developing adult CNS. Remyelination does occur in MS, but the process is largely inadequate and/or incomplete. Current treatment strategies primarily focus on reducing inflammation or immunosuppression, but there is a need for more extensive research on re-myelination as a possible mechanism of treatment. Previous studies have shown that pregnancy leads to an increase in OPC proliferation, oligodendrocyte generation and the number of myelinated axons in the maternal CNS. Studies have also suggested that this remyelination is possibly mediated by estriol. Sex hormones in particular have been shown to have an immuno-protective effect in TH1-driven autoimmunity diseases. The aim of our article is to review the available research on sex hormone-specific immune modulatory effects, assess its remyelination potential in MS, and suggest a future path for more extensive research on sex hormone as a target for therapeutics in MS.
Topics: Adult; Animals; Demyelinating Diseases; Female; Gonadal Steroid Hormones; Humans; Multiple Sclerosis; Myelin Sheath; Oligodendroglia; Sex Characteristics
PubMed: 30343306
DOI: 10.1159/000494262 -
International Journal of Molecular... Jul 2022The etiology of multiple sclerosis (MS), a demyelinating disease affecting the central nervous system (CNS), remains obscure. Although apoptosis of oligodendrocytes and... (Review)
Review
The etiology of multiple sclerosis (MS), a demyelinating disease affecting the central nervous system (CNS), remains obscure. Although apoptosis of oligodendrocytes and neurons has been observed in MS lesions, the contribution of this cell death process to disease pathogenesis remains controversial. It is usually considered that MS-associated demyelination and axonal degeneration result from neuroinflammation and an autoimmune process targeting myelin proteins. However, experimental data indicate that oligodendrocyte and/or neuronal cell death may indeed precede the development of inflammation and autoimmunity. These findings raise the question as to whether neural cell apoptosis is the key event initiating and/or driving the pathological cascade, leading to clinical functional deficits in MS. Similarly, regarding axonal damage, a key pathological feature of MS lesions, the roles of inflammation-independent and cell autonomous neuronal processes need to be further explored. While oligodendrocyte and neuronal loss in MS may not necessarily be mutually exclusive, particular attention should be given to the role of neuronal apoptosis in the development of axonal loss. If proven, MS could be viewed primarily as a neurodegenerative disease accompanied by a secondary neuroinflammatory and autoimmune process.
Topics: Apoptosis; Demyelinating Diseases; Humans; Inflammation; Multiple Sclerosis; Neurodegenerative Diseases
PubMed: 35886931
DOI: 10.3390/ijms23147584 -
Experimental Neurology Oct 2015Previous research on stroke and traumatic brain injury (TBI) heavily emphasized pathological alterations in neuronal cells within gray matter. However, recent studies... (Review)
Review
Previous research on stroke and traumatic brain injury (TBI) heavily emphasized pathological alterations in neuronal cells within gray matter. However, recent studies have highlighted the equal importance of white matter integrity in long-term recovery from these conditions. Demyelination is a major component of white matter injury and is characterized by loss of the myelin sheath and oligodendrocyte cell death. Demyelination contributes significantly to long-term sensorimotor and cognitive deficits because the adult brain only has limited capacity for oligodendrocyte regeneration and axonal remyelination. In the current review, we will provide an overview of the major causes of demyelination and oligodendrocyte cell death following acute brain injuries, and discuss the crosstalk between myelin, axons, microglia, and astrocytes during the process of demyelination. Recent discoveries of molecules that regulate the processes of remyelination may provide novel therapeutic targets to restore white matter integrity and improve long-term neurological recovery in stroke or TBI patients.
Topics: Animals; Axons; Brain Injuries; Cell Death; Cognition Disorders; Cytokines; Demyelinating Diseases; Humans; Ischemia; Nerve Regeneration; Oligodendroglia
PubMed: 25819104
DOI: 10.1016/j.expneurol.2015.03.017 -
International Journal of Molecular... Jan 2024Multiple sclerosis (MS) is an autoimmune and inflammatory disorder affecting the central nervous system whose cause is still largely unknown. Oligodendrocyte... (Review)
Review
Multiple sclerosis (MS) is an autoimmune and inflammatory disorder affecting the central nervous system whose cause is still largely unknown. Oligodendrocyte degeneration results in demyelination of axons, which can eventually be repaired by a mechanism called remyelination. Prevention of demyelination and the pharmacological support of remyelination are two promising strategies to ameliorate disease progression in MS patients. The cuprizone model is commonly employed to investigate oligodendrocyte degeneration mechanisms or to explore remyelination pathways. During the last decades, several different protocols have been applied, and all have their pros and cons. This article intends to offer guidance for conducting pre-clinical trials using the cuprizone model in mice, focusing on discovering new treatment approaches to prevent oligodendrocyte degeneration or enhance remyelination.
Topics: Humans; Mice; Animals; Cuprizone; Myelin Sheath; Demyelinating Diseases; Remyelination; Oligodendroglia; Multiple Sclerosis; Mice, Inbred C57BL; Disease Models, Animal
PubMed: 38338724
DOI: 10.3390/ijms25031445 -
Brain : a Journal of Neurology Dec 2022The anterior optic pathway is one of the preferential sites of involvement in CNS inflammatory demyelinating diseases, such as multiple sclerosis and neuromyelitis...
The anterior optic pathway is one of the preferential sites of involvement in CNS inflammatory demyelinating diseases, such as multiple sclerosis and neuromyelitis optica, with optic neuritis being a common presenting symptom. What is more, optic nerve involvement in these diseases is often subclinical, with optical coherence tomography demonstrating progressive neuroretinal thinning in the absence of optic neuritis. The pathological substrate for these findings is poorly understood and requires investigation. We had access to post-mortem tissue samples of optic nerves, chiasms and tracts from 29 multiple sclerosis (mean age 59.5, range 25-84 years; 73 samples), six neuromyelitis optica spectrum disorders (mean age 56, range 18-84 years; 22 samples), six acute disseminated encephalomyelitis (mean age 25, range 10-39 years; 12 samples) cases and five non-neurological controls (mean age 55.2, range 44-64 years; 16 samples). Formalin-fixed paraffin-embedded samples were immunolabelled for myelin, inflammation (microglial/macrophage, T- and B-cells, complement), acute axonal injury and astrocytes. We assessed the extent and distribution of these markers along the anterior optic pathway for each case in all compartments (i.e. parenchymal, perivascular and meningeal), where relevant. Demyelinated plaques were classified as active based on established criteria. In multiple sclerosis, demyelination was present in 82.8% of cases, of which 75% showed activity. Microglia/macrophage and lymphocyte inflammation were frequently found both in the parenchymal and meningeal compartments in non-demyelinated regions. Acute axonal injury affected 41.4% of cases and correlated with extent of inflammatory activity in each compartment, even in cases that died at advanced age with over 20 years of disease duration. An antero-posterior gradient of anterior optic pathway involvement was observed with optic nerves being most severely affected by inflammation and acute axonal injury compared with the optic tract, where a higher proportion of remyelinated plaques were seen. In neuromyelitis optica spectrum disorder, cases with a history of optic neuritis had extensive demyelination and lost aquaporin-4 reactivity. In contrast, those without prior optic neuritis did not have demyelination but rather diffuse microglial/macrophage, T- and B-lymphocyte inflammation in both parenchymal and meningeal compartments, and acute axonal injury was present in 75% of cases. Acute demyelinating encephalomyelitis featured intense inflammation, and perivenular demyelination in 33% of cases. Our findings suggest that chronic inflammation is frequent and leads to neurodegeneration in multiple sclerosis and neuromyelitis optica, regardless of disease stage. The chronic inflammation and subsequent neurodegeneration occurring along the optic pathway broadens the plaque-centred view of these diseases and partly explains the progressive neuroretinal changes observed in optic coherence tomography studies.
Topics: Humans; Adult; Middle Aged; Aged; Aged, 80 and over; Adolescent; Young Adult; Child; Neuromyelitis Optica; Optic Nerve; Optic Neuritis; Multiple Sclerosis; Inflammation
PubMed: 35134111
DOI: 10.1093/brain/awac030