Abstract FTY720, also known as fingolimod, is an orally administered sphingosine-1-phosphate (S1P) analogue that is under investigation as a therapy for both relapsing–remitting (RR) and progressive ...forms of multiple sclerosis (MS). The demonstrated beneficial effect of FTY720 on disease activity in RR–MS patients and in the animal model experimental autoimmune encephalomyelitis (EAE) is largely attributed to effects on the systemic immune system. In addition, unlike other current systemic immuno-modulators used in MS, the lipophilic nature of FTY720 allows it to cross the blood-brain barrier (BBB). Since S1P receptors are expressed on all cell types, FTY720 has the potential to exert effects directly on the BBB and on resident cells of the CNS. The latter include cells implicated in regulating immune reactivity within the CNS (astrocytes, microglia), those that are targeted by the disease process (oligodendrocytes, neurons), and those involved in repair (oligodendrocyte progenitor cells). In vitro studies document the dose-dependent effects of FTY720 on neural cell survival, differentiation, and cytoskeletal dynamics. Animal model studies, specifically EAE, indicate an overall neuroprotective effect of FTY720 mediated at least in part by its actions within the CNS. Ongoing studies will need to define the direct and indirect (via immune-modulation) effects of FTY720 on the CNS across the broad clinical spectrum of MS.
Neuroaxonal damage and loss are increasingly recognized as disability determining features in multiple sclerosis (MS) pathology. However, little is known about the long‐term sequelae of inflammatory ...demyelination on neurons and axons.
Spinal cord tissue of 31 MS patients was compared to three amyotrophic lateral sclerosis (ALS) and 10 control subjects. MS lesions were staged according to the density of KiM‐1P positive macrophages and microglia and the presence of myelin basic protein (MBP) positive phagocytes. T cells were quantified in the parenchyma and meninges. Neuroaxonal changes were studied by immunoreactivity (IR) for amyloid precursor protein (APP) and variably phosphorylated neurofilaments (SMI312, SMI31, SMI32).
Little T cell infiltration was still evident in chronic inactive lesions. The loss of SMI32 IR in ventral horn neurons correlated with MS lesion development and disease progression. Similarly, axonal loss in white matter (WM) lesions correlated with disease duration. A selective reduction of axonal phosphorylated neurofilaments (SMI31) was observed in WM lesions. In ALS, the loss of neuronal SMI32 IR was even more pronounced, whereas the relative axonal reduction resembled that found in MS.
Progressive neuroaxonal neurofilament alterations in the context of chronic inflammatory demyelination may reflect changes in neuroaxonal metabolism and result in chronic neuroaxonal dysfunction as a putative substrate of clinical progression.
Tryptophan metabolism by the kynurenine pathway (KP) is important to the pathogenesis of inflammatory, infectious, and degenerative diseases. The 3-hydroxykynurenine (3-HK) branch of the KP is ...activated in macrophages and microglia, leading to the generation of 3-HK, 3-hydroxyanthranilic acid (3-HAA), and quinolinic acid, which are considered neurotoxic owing to their free radical–generating and N -methyl- d -aspartic acid receptor agonist activities. We investigated the role of 3-HAA in inflammatory and antioxidant gene expression and neurotoxicity in primary human fetal central nervous system cultures treated with cytokines (IL-1 with or without interferon-γ) or with Toll-like receptor ligands mimicking the proinflammatory central nervous system environment. Results were analyzed by microarray, Western blot, immunostain, enzyme-linked immunosorbent assay, and neurotoxicity assays. 3-HAA suppressed glial cytokine and chemokine expression and reduced cytokine-induced neuronal death. 3-HK also suppressed cytokine-induced neuronal death. Unexpectedly, 3-HAA was highly effective in inducing in astrocytes the expression of hemeoxygenase-1 (HO-1), an antioxidant enzyme with anti-inflammatory and cytoprotective properties. Optimal induction of HO-1 required 3-HAA and cytokines. In human microglia, 3-HAA weakly induced HO-1 and lipopolysaccharide suppressed microglial HO-1 expression. 3-HAA–mediated HO-1 expression was confirmed in cultured adult human astrocytes and in vivo after 3-HAA injection to mouse brains. Together, our results demonstrate the novel neuroprotective activity of the tryptophan metabolite 3-HAA and have implications for future therapeutic approaches for neuroinflammatory disorders.
Objective
FTY720, a sphingosine‐1‐phosphate (S1P) receptor agonist that crosses the blood–brain barrier, is a potential immuno‐therapy for multiple sclerosis. Our objective was to assess the effect ...of FTY720 on process extension, differentiation, and survival of human oligodendrocyte progenitor cells (OPCs), and link the functional effects with S1P receptor expression and signaling.
Methods
Functional assays and receptor expression studies were conducted on A2B5+ OPCs derived from the human fetal central nervous system. Cells were treated with physiologically relevant concentrations of the active phosphorylated form of FTY720. S1P receptor/signaling modulators were used to elucidate the basis of the FTY720‐induced functional responses.
Results
Short‐term (1 day) FTY720 treatment caused initial process retraction that was reversed by uncoupling S1P3 and 5 from their G protein using suramin, and with a Rho‐kinase inhibitor H1152. Retraction was associated with RhoA‐mediated cytoskeletal signaling and with inhibition of OPC differentiation into more mature phenotypes. Continued FTY720 treatment (2 days) induced process extension and enhanced cell survival associated with increased extracellular signal‐regulated kinases 1 and 2 phosphorylation, mimicked with the S1P1‐specific agonist SEW2871, but not reversed with suramin. Quantitative real‐time polymerase chain reaction showed that FTY720 induced reciprocal and cyclic modulation of S1P1 and S1P5 messenger RNA levels. The observed initial downregulation of S1P5 and subsequently of S1P1 messenger RNA supports functional responses being mediated sequentially by S1P5‐ and later S1P1‐associated signaling.
Interpretation
FTY720 induces time‐dependent modulation of S1P receptors on human OPCs with consequent functional responses that are directly relevant for the remyelination process. Ann Neurol 2007
Characterizing the developmental trajectory of oligodendrocyte progenitor cells (OPC) is of great interest given the importance of these cells in the remyelination process. However, studies of human ...OPC development remain limited by the availability of whole cell samples and material that encompasses a wide age range, including time of peak myelination. In this study, we apply single cell RNA sequencing to viable whole cells across the age span and link transcriptomic signatures of oligodendrocyte‐lineage cells with stage‐specific functional properties. Cells were isolated from surgical tissue samples of second‐trimester fetal, 2‐year‐old pediatric, 13‐year‐old adolescent, and adult donors by mechanical and enzymatic digestion, followed by percoll gradient centrifugation. Gene expression was analyzed using droplet‐based RNA sequencing (10X Chromium). Louvain clustering analysis identified three distinct cellular subpopulations based on 5,613 genes, comprised of an early OPC (e‐OPC) group, a late OPC group (l‐OPC), and a mature OL (MOL) group. Gene ontology terms enriched for e‐OPCs included cell cycle and development, for l‐OPCs included extracellular matrix and cell adhesion, and for MOLs included myelination and cytoskeleton. The e‐OPCs were mostly confined to the premyelinating fetal group, and the l‐OPCs were most highly represented in the pediatric age group, corresponding to the peak age of myelination. Cells expressing a signature characteristic of l‐OPCs were identified in the adult brain in situ using RNAScope. These findings highlight the transcriptomic variability in OL‐lineage cells before, during, and after peak myelination and contribute to identifying novel pathways required to achieve remyelination.
Human scRNA‐seq based OL‐lineage cell data was derived from immediately ex vivo surgically resected specimens covering a wide age range.
Transcriptomic signatures were characterized across distinct stages of OL development, with links to specific biological processes.
Cell-cell interactions in the central nervous system play important roles in neurologic diseases. However, little is known about the specific molecular pathways involved, and methods for their ...systematic identification are limited. Here, we developed a forward genetic screening platform that combines CRISPR-Cas9 perturbations, cell coculture in picoliter droplets, and microfluidic-based fluorescence-activated droplet sorting to identify mechanisms of cell-cell communication. We used SPEAC-seq (systematic perturbation of encapsulated associated cells followed by sequencing), in combination with in vivo genetic perturbations, to identify microglia-produced amphiregulin as a suppressor of disease-promoting astrocyte responses in multiple sclerosis preclinical models and clinical samples. Thus, SPEAC-seq enables the high-throughput systematic identification of cell-cell communication mechanisms.
FTY720 is a sphingosine 1‐phosphate receptor (S1PR) modulator used as a daily therapy to reduce disease activity in the relapsing form of multiple sclerosis (MS). FTY720 readily accesses the CNS. ...Previous studies have shown that phosphorylated FTY720 (FTY720‐p) enhances oligodendrocyte progenitor cell (OPC) survival, differentiation, and remyelination following experimentally induced demyelination in rodents. To elucidate the underlying mechanism, human fetal OPCs alone or in co‐culture with rat dorsal root ganglia neurons (DRGN) were treated daily with FTY720‐p, a condition that desensitizes cellular responses to S1P, the natural ligand of S1PR. In co‐cultures, FTY720‐p and S1P given daily or every three days increased the number of O1/MBP double positive cells and axonal ensheathment. In cultures composed of PDGFRα‐antibody selected cells alone, daily application of FTY720‐p also increased the number of O4/GC double positive cells. At an early time point (day 2), FTY720‐p activated ERK1/2, CREB and p38MAPK in O4‐positive cells, as well as in β‐III Tubulin positive neurons and GFAP positive astrocytes. In later cultures (day 6), FTY720‐p activated p38MAPK in O4 positive cells, p38MAPK and ERK1/2 in neurons, and p38MAPK, ERK1/2 and CREB in astrocytes. A MEK inhibitor (U0126) prevented the differentiation of OPCs into O4‐positive cells, while a p38MAPK inhibitor (PD169316) blocked progression into O4‐positive and into GC‐positive stages of differentiation. Our results demonstrate that FTY720‐p, under conditions that model daily clinical use, can act directly on OPCs to impact differentiation, and also indirectly via neurons and astrocytes by activating ERK1/2 and p38MAPK. GLIA 2014;62:1361–1375
Main Points:
FTY720 enhances human fetal OPC differentiation and axonal ensheathment. Early differentiation requires ERK1/2 and p38MAPK; later stage requires p38MAPK.
FTY720 also acts indirectly by activating ERK1/2, CREB and p38MAPK in neurons and astrocytes.
The Coronavirus disease-19 (COVID-19) pandemic continues to expand across the world. This pandemic has had a significant impact on patients with chronic diseases. Among patients with demyelinating ...diseases of the central nervous system (CNS), such as Multiple Sclerosis (MS) or Neuromyelitis Optica Spectrum Disorder (NMOSD), concerns remain about the potential impact of COVID-19 on these patients given their treatment with immunosuppressive or immunomodulatory therapies. In this study, we review the existing literature investigating the impact of disease-modifying therapies(DMT) on COVID-19 risks in this group of patients.
For this systematic review, we searched PubMed from January 1, 2020, to December 3, 2020. The following keywords were used: “COVID-19” AND “Multiple Sclerosis” OR “Neuromyelitis Optica.” Articles evaluating COVID-19 in patients with demyelinating diseases of CNS were included. This study evaluates the different aspects of the DMTs in these patients during the COVID-19 era.
A total of 262 articles were found. After eliminating duplicates and unrelated research papers, a total of 84 articles met the final inclusion criteria in our study. Overall, the experiences of 2493 MS patients and 37 NMOSD patients with COVID-19 were included in this review. Among them, 46(1.8%) MS patients died(the global death-to-case ratio of Covid-19 was reported about 2.1%). Among DMTs, Rituximab had the highest mortality rate (4%). Despite controversies, especially concerning anti-CD20 monoclonal antibody therapies, a relation between DMT-use and COVID-19 disease- course was not found in many studies. This observation reinforces the recommendation of not stopping current DMTs. Other variables such as age, higher expanded disability status scale (EDSS) scores, cardiac comorbidities, and obesity were independent risk factors for severe COVID-19.
Despite the risks of infection, most patients were willing to continue their DMT during the pandemic because of more significant concern about the risk of relapse or worsening MS symptoms. After the infection, an immune response's attenuation was seen in the patients on Fingolimod and anti-CD20 monoclonal antibodies. This may be a critical finding in future vaccinations.
Multiple sclerosis (MS) is the most frequent inflammatory and demyelinating disease of the Central Nervous System (CNS). Significant progress has been made during recent years in preventing relapses ...by using systemic immunomodulatory or immunosuppressive therapies. However, the limited effectiveness of such therapies for controlling the progressive disease course indicates there is a continuous disease progression independent of relapse activity which may start very early during the disease course. Dissecting the underlying mechanisms and developing therapies for preventing or stopping this disease progression represent, currently, the biggest challenges in the field of MS. Here, we summarize publications of 2022 which provide insight into susceptibility to MS, the basis of disease progression and features of relatively recently recognized distinct forms of inflammatory/demyelinating disorders of the CNS, such as myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD).
This article reviews the influence of age on the development and course of central nervous system (CNS) inflammatory diseases and relates these to genetic and epidemiologic factors and to the ...age-related properties of both the immune and nervous systems and their interactions.
There is increased recognition of the onset of multiple sclerosis, the prototype CNS inflammatory/demyelinating disease, outside the expected peak age in young adults. Study of childhood-onset MS cases with comparison to those with uniphasic acquired inflammatory demyelinating syndromes, has helped to better define the clinical spectrum of both types of disorders and provides opportunities to define mechanisms linking recognized genetic and environmental risk factors and disease. Studies of late-onset cases implicate the enhanced role of innate immune mechanisms and immune responses compartmentalized within the CNS in driving a more progressive disease course. The influence of age on incidence and course of multiple sclerosis is compared with the wider spectrum of CNS inflammatory disorders with identified pathogenic mechanisms.
Intrinsic properties of the immune and nervous systems, coupled with the impacts on these systems by environmental factors and by the consequences of CNS tissue injury, underlie the age-related differences in incidence and course of inflammatory/demyelinating disorders of the CNS.
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