Central nervous system-directed effects of FTY720 (fingolimod)

The sphingosine 1-phosphate analogue, FTY720, modulates the lipidomic signature of the mouse hippocampus

The small-molecule drug, FTY720 (fingolimod), is a synthetic sphingosine 1-phosphate (S1P) analogue currently used to treat relapsing-remitting multiple sclerosis in both adults and children. FTY720 can cross the blood-brain barrier (BBB) and, over time, accumulate in lipid-rich areas of the central nervous system (CNS) by incorporating into phospholipid membranes. FTY720 has been shown to enhance cell membrane fluidity, which can modulate the functions of glial cells and neuronal populations involved in regulating behaviour. Moreover, direct modulation of S1P receptor-mediated lipid signalling by FTY720 can impact homeostatic CNS physiology, including neurotransmitter release probability, the biophysical properties of synaptic membranes, ion channel and transmembrane receptor kinetics, and synaptic plasticity mechanisms. The aim of this study was to investigate how chronic FTY720 treatment alters the lipid composition of CNS tissue in adolescent mice at a key stage of brain maturation. We focused on the hippocampus, a brain region known to be important for learning, memory, and the processing of sensory and emotional stimuli. Using mass spectrometry-based lipidomics, we discovered that FTY720 increases the fatty acid chain length of hydroxy-phosphatidylcholine (PCOH) lipids in the mouse hippocampus. It also decreases PCOH monounsaturated fatty acids (MUFAs) and increases PCOH polyunsaturated fatty acids (PUFAs). A total of 99 lipid species were up-regulated in the mouse hippocampus following 3 weeks of oral FTY720 exposure, whereas only 3 lipid species were down-regulated. FTY720 also modulated anxiety-like behaviours in young mice but did not affect spatial learning or memory formation. Our study presents a comprehensive overview of the lipid classes and lipid species that are altered in the hippocampus following chronic FTY720 exposure and provides novel insight into cellular and molecular mechanisms that may underlie the therapeutic or adverse effects of FTY720 in the central nervous system.

Innovative drug delivery strategies to the CNS for the treatment of multiple sclerosis

Disorders of the central nervous system (CNS), such as multiple sclerosis (MS) represent a great emotional, financial and social burden. Despite intense efforts, great unmet medical needs remain in that field. MS is an autoimmune, chronic inflammatory demyelinating disease with no curative treatment up to date. The current therapies mostly act in the periphery and seek to modulate aberrant immune responses as well as slow down the progression of the disease. Some of these therapies are associated with adverse effects related partly to their administration route and show some limitations due to their rapid clearance and inability to reach the CNS. The scientific community have recently focused their research on developing MS therapies targeting different processes within the CNS. However, delivery of therapeutics to the CNS is mainly limited by the presence of the blood-brain barrier (BBB). Therefore, there is a pressing need to develop new drug delivery strategies that ensure CNS availability to capitalize on identified therapeutic targets. Several approaches have been developed to overcome or bypass the BBB and increase delivery of therapeutics to the CNS. Among these strategies, the use of alternative routes of administration, such as the nose-to-brain (N2B) pathway, offers a promising non-invasive option in the scope of MS, as it would allow a direct transport of the drugs from the nasal cavity to the brain. Moreover, the combination of bioactive molecules within nanocarriers bring forth new opportunities for MS therapies, allowing and/or increasing their transport to the CNS. Here we will review and discuss these alternative administration routes as well as the nanocarrier approaches useful to deliver drugs for MS.

Ameliorative effects of Fingolimod (FTY720) on microglial activation and psychosis-related behavior in short term cuprizone exposed mice

Schizophrenia is a psychiatric disorder that affects around 1% of the population in widespread populations, with severe cases leading to long-term hospitalization and necessitation of lifelong treatment. Recent studies on schizophrenia have highlighted the involvement of inflammatory and immunoregulatory mechanisms with the onset of symptoms, and the usage of anti-inflammatory treatments are being tested against periods of rapid psychosis. In the central nervous system, microglia are the innate immune population which are activated in response to a wide range of physical and psychological stress factors and produce proinflammatory mediators such as cytokines. Microglial activation and neuroinflammation has been associated to numerous psychiatric disorders including schizophrenia, especially during psychotic episodes. Thus, novel treatments which dampen microglial activation may be of great relevance in the treatment of psychiatric disorders. Fingolimod (FTY720) is a drug used as an immunosuppressive treatment to multiple sclerosis. Recent clinical trials have focused on FTY720 as a treatment for the behavioral symptoms in schizophrenia. However, the mechanisms of Fingolimod in treating the symptoms of schizophrenia are not clear. In this study we use a recently developed neuroinflammatory psychosis model in mice: cuprizone short-term exposure, to investigate the effects of FTY720 administration. FTY720 administration was able to completely alleviate methamphetamine hypersensitivity caused by cuprizone exposure. Moreover, administration of FTY720 improved multiple measures of neuroinflammation (microglial activation, cytokine production, and leucocyte infiltration). In conclusion, our results highlight the future use of FTY720 as a direct anti-inflammatory treatment against microglial activation and psychosis.

Sphingosine-1-phosphate receptor modulation improves neurogenesis and functional recovery after stroke

Cerebral ischemia activates neural progenitors that participate in brain remodeling following acute injury. Sphingosine-1-phosphate receptor (S1PR) signaling governs cell proliferation and mobilization, yet its potential impact on neural progenitors and stroke recovery remains poorly understood. The goal of this study was to investigate the impact of S1PR modulation on post-stroke neurogenesis and functional recovery, using a S1PR modulator BAF312. Mice were subjected to 60 min middle cerebral artery occlusion (MCAO) and received BAF312 starting from day 3 after MCAO until the end of experiment. BAF312 facilitated motor function recovery in MCAO mice until day 14 after surgery. Flow cytometry analysis revealed that BAF312 treatment led to an increase of type A cells in subventricular zone (SVZ), but not other progenitor cell subsets in MCAO mice. We found an increase of BrdU incorporation in SVZ DCX⁺ cells from MCAO mice receiving BAF312 and augmented proliferation of DCX⁺ cells in cultured neurospheres isolated from SVZ tissues. Notably, a S1PR1 antagonist W146 abolished BAF312-induced increase of SVZ type A cells from MCAO mice and proliferation of DCX⁺ cells in cultured neurospheres. Additionally, the benefit of BAF312 to improve neurogenesis and stroke recovery remains in Rag2^-/- mice lacking of T and B cells. Our results demonstrate that S1PR modulation improves neurogenesis and functional recovery following brain ischemia.

Fingolimod effects on the brain are mediated through biochemical modulation of bioenergetics, autophagy, and neuroinflammatory networks

Fingolimod (FTY720) is an oral drug approved by the Food and Drug Administration (FDA) for management of multiple sclerosis (MS) symptoms, which has also shown beneficial effects against Alzheimer's (AD) and Parkinson's (PD) diseases pathologies. Although an extensive effort has been made to identify mechanisms underpinning its therapeutic effects, much remains unknown. Here, we investigated Fingolimod induced proteome changes in the cerebellum (CB) and frontal cortex (FC) regions of the brain which are known to be severely affected in MS, using a tandem mass tag (TMT) isobaric labeling-based quantitative mass-spectrometric approach to investigate the mechanism of action of Fingolimod. This study identified 6749 and 6319 proteins in CB and FC, respectively, and returned 2609 and 3086 differentially expressed proteins in mouse CB and FC, respectively, between Fingolimod treated and control groups. Subsequent bioinformatics analyses indicated a metabolic reprogramming in both brain regions of the Fingolimod treated group, where oxidative phosphorylation was upregulated while glycolysis and pentose phosphate pathway were downregulated. In addition, modulation of neuroinflammation in the Fingolimod treated group was indicated by upregulation of retrograde endocannabinoid signaling and autophagy pathways, and downregulation of neuroinflammation related pathways including neutrophil degranulation and the IL-12 mediated signaling pathway. Our findings suggest that Fingolimod may exert its protective effects on the brain by inducing metabolic reprogramming and neuroinflammation pathway modulation.

Ten decadal advances in fungal biology leading towards human well-being

Fungi are an understudied resource possessing huge potential for developing products that can greatly improve human well-being. In the current paper, we highlight some important discoveries and developments in applied mycology and interdisciplinary Life Science research. These examples concern recently introduced drugs for the treatment of infections and neurological diseases; application of -OMICS techniques and genetic tools in medical mycology and the regulation of mycotoxin production; as well as some highlights of mushroom cultivaton in Asia. Examples for new diagnostic tools in medical mycology and the exploitation of new candidates for therapeutic drugs, are also given. In addition, two entries illustrating the latest developments in the use of fungi for biodegradation and fungal biomaterial production are provided. Some other areas where there have been and/or will be significant developments are also included. It is our hope that this paper will help realise the importance of fungi as a potential industrial resource and see the next two decades bring forward many new fungal and fungus-derived products.

Exploring lipophilic compounds that induce BDNF secretion in astrocytes beyond the BBB using a new multi-cultured human in vitro BBB model

Brain-derived neurotrophic factor (BDNF) cannot cross the blood-brain barrier (BBB) when administered peripherally, which hinders its therapeutic potential. We utilized an in vitro BBB model-a tri-culture of a human endothelial cell line, a pericyte cell line, and an astrocyte cell line-to study the effect of twenty candidate lipophilic compounds on stimulating BDNF secretion in pericytes and astrocytes. The prostaglandin E2 receptor 4 agonist and sphingosine-1-phosphate receptor 5 agonist facilitated secretion of BDNF in the astrocyte, but did not decrease the transendothelial electrical resistance. These compounds may be promising agents for neurodegenerative and neuroinflammatory diseases.

Novel 5-fluorouracil sensitizers for colorectal cancer therapy: Design and synthesis of S1P receptor 2 (S1PR2) antagonists

Sphingosine-1-phosphate receptor 2 (S1PR2) has been identified as a brand-new GPCR target for designing antagonists to reverse 5-FU resistance. We herein report the structural optimization and structure-activity relationship of JTE-013 derivatives as S1PR2 antagonists. Compound 9d was the most potent S1PR2 antagonist (K_D = 34.8 nM) among developed compounds. Here, compound 9d could significantly inhibit the expression of dihydropyrimidine dehydrogenase (DPD) to reverse 5-FU-resistance in HCT116^DPD and SW620/5-FU cells. Further mechanism studies demonstrated that compound 9d not only inhibited S1PR2 but also affected the transcription of S1PR2. In addition, compound 9d also showed acceptable selectivity to normal cells (NCM460). Importantly, compound 9d with suitable pharmacokinetic properties could significantly reverse 5-FU-resistance in the HCT116^DPD and SW620/5-FU xenograft models without obvious toxicity, in which the inhibition rates of 5-FU were increased from 23.97% to 65.29% and 27.23% to 60.81%, respectively. Further immunohistochemistry and western blotting analysis also demonstrated that compound 9d significantly decreases the expression of DPD in tumor and liver tissues. These results indicated that compound 9d is a promising lead compound to reverse 5-FU-resistance for colorectal cancer therapy.

Sphingosine-1-Phosphate Signaling in Ischemic Stroke: From Bench to Bedside and Beyond

Sphingosine-1-phosphate (S1P) signaling is being increasingly recognized as a strong modulator of immune cell migration and endothelial function. Fingolimod and other S1P modulators in ischemic stroke treatment have shown promise in emerging experimental models and small-scale clinical trials. In this article, we will review the current knowledge of the role of S1P signaling in brain ischemia from the aspects of inflammation and immune interventions, sustaining endothelial functions, regulation of blood-brain barrier integrity, and functional recovery. We will then discuss the current and future therapeutic perspectives of targeting S1P for the treatment of ischemic stroke. Mechanism studies would help to bridge the gap between preclinical studies and clinical practice. Future success of bench-to-bedside translation shall be based on in depth understanding of S1P signaling during stroke and on the ability to have a fine temporal and spatial regulation of the signal pathway.

Signaling through the S1P-S1PR Axis in the Gut, the Immune and the Central Nervous System in Multiple Sclerosis: Implication for Pathogenesis and Treatment

Sphingosine 1-phosphate (S1P) is a signaling molecule with complex biological functions that are exerted through the activation of sphingosine 1-phosphate receptors 1–5 (S1PR1–5). S1PR expression is necessary for cell proliferation, angiogenesis, neurogenesis and, importantly, for the egress of lymphocytes from secondary lymphoid organs. Since the inflammatory process is a key element of immune-mediated diseases, including multiple sclerosis (MS), S1PR modulators are currently used to ameliorate systemic immune responses. The ubiquitous expression of S1PRs by immune, intestinal and neural cells has significant implications for the regulation of the gut–brain axis. The dysfunction of this bidirectional communication system may be a significant factor contributing to MS pathogenesis, since an impaired intestinal barrier could lead to interaction between immune cells and microbiota with a potential to initiate abnormal local and systemic immune responses towards the central nervous system (CNS). It appears that the secondary mechanisms of S1PR modulators affecting the gut immune system, the intestinal barrier and directly the CNS, are coordinated to promote therapeutic effects. The scope of this review is to focus on S1P−S1PR functions in the cells of the CNS, the gut and the immune system with particular emphasis on the immunologic effects of S1PR modulation and its implication in MS.

Neuroprotective Effects of Fingolimod in a Cellular Model of Optic Neuritis

Visual dysfunction resulting from optic neuritis (ON) is one of the most common clinical manifestations of multiple sclerosis (MS), characterized by loss of retinal ganglion cells, thinning of the nerve fiber layer, and inflammation to the optic nerve. Current treatments available for ON or MS are only partially effective, specifically target the inflammatory phase, and have limited effects on long-term disability. Fingolimod (FTY) is an FDA-approved immunomodulatory agent for MS therapy. The objective of the current study was to evaluate the neuroprotective properties of FTY in the cellular model of ON-associated neuronal damage. R28 retinal neuronal cell damage was induced through treatment with tumor necrosis factor-α (TNFα). In our cell viability analysis, FTY treatment showed significantly reduced TNFα-induced neuronal death. Treatment with FTY attenuated the TNFα-induced changes in cell survival and cell stress signaling molecules. Furthermore, immunofluorescence studies performed using various markers indicated that FTY treatment protects the R28 cells against the TNFα-induced neurodegenerative changes by suppressing reactive oxygen species generation and promoting the expression of neuronal markers. In conclusion, our study suggests neuroprotective effects of FTY in an in vitro model of optic neuritis.

Acting centrally or peripherally: A renewed interest in the central nervous system penetration of disease-modifying drugs in multiple sclerosis

With the recent approval of cladribine tablets, siponimod and ozanimod, there has been a renewed interest into the extent to which these current generation disease-modifying therapies (DMTs) are able to cross into the central nervous system (CNS), and how this penetration of the blood-brain barrier (BBB) may influence their ability to treat multiple sclerosis (MS). The integrity of the CNS is maintained by the BBB, blood-cerebrospinal fluid barrier, and the arachnoid barrier, which all play an important role in preserving the immunological environment and homeostasis within the CNS. The integrity of the BBB decreases during the course of MS, with a putative temporal relationship to disease worsening. Furthermore, it is currently considered that progression of the disease is mediated mainly by resident cells of the CNS. The existing literature provides evidence to show that some of the current generation DMTs for MS are able to penetrate the CNS and potentially exert direct effects on CNS-resident cells, in particular the CNS-penetrating prodrugs cladribine and fingolimod, and other sphingosine-1 phosphate receptor modulators; siponimod and ozanimod. Other current generation DMTs appear to be restricted to the periphery due to their high molecular weight or physicochemical properties. As more effective brain penetrant therapies are developed for the treatment of MS, there is a need to understand whether the potential for direct effects within the CNS are of significance, and whether this brings additional benefits over and above treatment effects mediated in the periphery. In turn, this will require an improved understanding of the structure and function of the BBB, the role it plays in MS and subsequent treatments. This narrative review summarizes the data supporting the biological plausibility of a potential benefit from therapeutic molecules entering the CNS, and discusses the potential significance in the current and future treatment of MS.

Reviewing the Significance of Blood-Brain Barrier Disruption in Multiple Sclerosis Pathology and Treatment

The disruption of blood–brain barrier (BBB) for multiple sclerosis (MS) pathogenesis has a double effect: early on during the onset of the immune attack and later for the CNS self-sustained ‘inside-out’ demyelination and neurodegeneration processes. This review presents the characteristics of BBB malfunction in MS but mostly highlights current developments regarding the impairment of the neurovascular unit (NVU) and the metabolic and mitochondrial dysfunctions of the BBB’s endothelial cells. The hypoxic hypothesis is largely studied and agreed upon recently in the pathologic processes in MS. Hypoxia in MS might be produced per se by the NVU malfunction or secondary to mitochondria dysfunction. We present three different but related terms that denominate the ongoing neurodegenerative process in progressive forms of MS that are indirectly related to BBB disruption: progression independent of relapses, no evidence of disease activity and smoldering demyelination or silent progression. Dimethyl fumarate (DMF), modulators of S1P receptor, cladribine and laquinimode are DMTs that are able to cross the BBB and exhibit beneficial direct effects in the CNS with very different mechanisms of action, providing hope that a combined therapy might be effective in treating MS. Detailed mechanisms of action of these DMTs are described and also illustrated in dedicated images. With increasing knowledge about the involvement of BBB in MS pathology, BBB might become a therapeutic target in MS not only to make it impenetrable against activated immune cells but also to allow molecules that have a neuroprotective effect in reaching the cell target inside the CNS.

Immunomodulation Eliminates Inflammation in the Hippocampus in Experimental Autoimmune Encephalomyelitis, but Does Not Ameliorate Anxiety-Like Behavior

Multiple sclerosis (MS) is an autoimmune disease targeting the central nervous system, characterized by an unpredictable disease course and a wide range of symptoms. Emotional and cognitive deficits are now recognized as primary disease manifestations and not simply the consequence of living with a chronic condition, raising questions regarding the efficacy of current therapeutics for these specific symptoms. Mechanisms underlying psychiatric sequelae in MS are believed to be similar to those underlying pathogenesis, that is mediated by cytokines and other inflammatory mediators. To gain insight into the pathogenesis of MS depression, we performed behavioral assays in the murine experimental autoimmune encephalomyelitis (EAE) MS model, in the presence or absence of immunomodulation using the drug FTY720, an analogue of the lipid signaling molecule sphingosine-1-phosphate (S1P). Specifically, mice were challenged with the elevated plus maze (EPM) test, a validated experimental paradigm for rodent-specific anxiety-like behavior. FTY720 treatment failed to ameliorate anxiety-like symptoms, irrespective of dosage. On the other hand, it was effective in reducing inflammatory infiltration, microglial reactivity and levels of pro-inflammatory molecules in the hippocampus, confirming the anti-inflammatory capacity of treatment. To explore the absence of FTY720 effect on behavior, we confirmed expression of S1P receptors (S1PR) S1PR1, S1PR3 and S1PR5 in the hippocampus and mapped the dynamics of these receptors in response to drug treatment alone, or in combination with EAE induction. We identified a complex pattern of responses, differing between (1) receptors, (2) dosage and (3) hippocampal sub-field. FTY720 treatment in the absence of EAE resulted in overall downregulation of S1PR1 and S1PR3, while S1PR5 exhibited a dose-dependent upregulation. EAE induction alone resulted in overall downregulation of all three receptors. On the other hand, combined FTY720 and EAE showed generally no effect on S1PR1 and S1PR3 expression except for the fimbrium region, but strong upregulation of S1PR5 over the range of doses examined. These data illustrate a hitherto undescribed complexity of S1PR response to FTY720 in the hippocampus, independent of drug effect on effector immune cells, but simultaneously emphasize the need to explore novel treatment strategies to specifically address mood disorders in MS.

The emerging role of FTY720 as a sphingosine 1-phosphate analog for the treatment of ischemic stroke: The cellular and molecular mechanisms

Finding novel and effective drugs for the treatment of ischemic stroke is warranted because there is not a definitive treatment for this prevalent disease. Due to the relevance between the sphingosine 1-phosphate (S1P) receptor and several neurological diseases including ischemic stroke, it seems that fingolimod (FTY720), as an agonist of S1P receptor, can be a useful therapeutic strategy in these patients. FTY720 is the first oral drug approved by the US food and drug administration for the treatment of multiple sclerosis. Three important mechanisms for neuroprotective effects of FTY720 have been described. First, the functional antagonistic mechanism that is associated with lymphopenia and reduced lymphocytic inflammation. This effect results from the down-regulation and degradation of lymphocytes' S1P receptors, which inhibits lymph node lymphocytes from entering the bloodstream. Second, a functional agonistic activity that is mediated through direct effects via targeting S1P receptors on the membrane of various cells including neurons, microglia, oligodendrocytes, astrocytes, and endothelial cells of blood vessels in the central nervous system (CNS), and the third, receptor-independent mechanisms that are displayed by binding to specific cellular proteins that modulate intracellular signaling pathways or affect epigenetic transcriptions. Therefore, we review these mechanisms in more detail and describe the animal model and in clinical trial studies that support these three mechanisms for the neuroprotective action of FTY720 in ischemic stroke.

A2 B Adenosine Receptors and Sphingosine 1-Phosphate Signaling Cross-Talk in Oligodendrogliogenesis

Oligodendrocyte-formed myelin sheaths allow fast synaptic transmission in the brain. Impairments in the process of myelination, or demyelinating insults, might cause chronic diseases such as multiple sclerosis (MS). Under physiological conditions, remyelination is an ongoing process throughout adult life consisting in the differentiation of oligodendrocyte progenitor cells (OPCs) into mature oligodendrocytes (OLs). During pathological events, this process fails due to unfavorable environment. Adenosine and sphingosine kinase/sphingosine 1-phosphate signaling axes (SphK/S1P) play important roles in remyelination processes. Remarkably, fingolimod (FTY720), a sphingosine analog recently approved for MS treatment, plays important roles in OPC maturation. We recently demonstrated that the selective stimulation of A_{2 B} adenosine receptors (A_{2 B} Rs) inhibit OPC differentiation in vitro and reduce voltage-dependent outward K⁺ currents (I _K ) necessary to OPC maturation, whereas specific SphK1 or SphK2 inhibition exerts the opposite effect. During OPC differentiation A_{2 B} R expression increases, this effect being prevented by SphK1/2 blockade. Furthermore, selective silencing of A_{2 B} R in OPC cultures prompts maturation and, intriguingly, enhances the expression of S1P lyase, the enzyme responsible for irreversible S1P catabolism. Finally, the existence of an interplay between SphK1/S1P pathway and A_{2 B} Rs in OPCs was confirmed since acute stimulation of A_{2 B} Rs activates SphK1 by increasing its phosphorylation. Here the role of A_{2 B} R and SphK/S1P signaling during oligodendrogenesis is reviewed in detail, with the purpose to shed new light on the interaction between A_{2 B} Rs and S1P signaling, as eventual innovative targets for the treatment of demyelinating disorders.

[Disease-modifying treatment of secondary progressive multiple sclerosis]

BACKGROUND

Multiple sclerosis (MS) is a disease continuum from a clinically isolated syndrome through relapsing remitting MS to secondary progressive MS (SPMS). There are numerous therapeutic approaches with proven efficacy on relapse and focal inflammatory disease aspects, whereas treatment of secondary progression and associated neuropathological aspects continues to be a challenge.

OBJECTIVE

Overview of the current options for disease-modifying treatment of SPMS.

MATERIAL AND METHODS

Results of randomized clinical trials are presented and evaluated on a substance-specific basis.

RESULTS

Randomized SPMS trials showed inconsistent results regarding disability progression for beta interferons and negative results for natalizumab. Oral cladribine and ocrelizumab reduced disability progression in relapsing MS but have not been specifically studied in an SPMS population. Positive results for mitoxantrone are only partially applicable to current SPMS patients. For siponimod, a substance that crosses the blood-brain barrier, the EXPAND trial demonstrated a significant reduction in the risk of disability progression in typical SPMS. Subgroup analyses suggest a higher efficacy of siponimod in younger patients with active SPMS.

CONCLUSION

There is limited evidence for the use of previously available disease-modifying treatment in SPMS. Siponimod represents a new therapeutic option for active SPMS, defined by relapses or focal inflammatory MRI activity. To establish the therapeutic indications for siponimod, early detection of relapse-independent progression as well as differentiation of active SPMS from inactive disease are of critical importance.

Fingolimod inhibits glutamate release through activation of S1P1 receptors and the G protein βγ subunit-dependent pathway in rat cerebrocortical nerve terminals

Fingolimod, a sphingosine-1-phosphate (S1P) receptor modulator approved for treating multiple sclerosis, is reported to prevent excitotoxic insult. Because excessive glutamate release is a major cause of neuronal damage in various neurological disorders, the effect of fingolimod on glutamate release in rat cerebrocortical nerve terminals (synaptosomes) was investigated in the current study. Fingolimod decreased 4-aminopyridine (4-AP)-stimulated glutamate release and calcium concentration elevation. Fingolimod-mediated inhibition of 4-AP-induced glutamate release was dependent on extracellular calcium, persisted in the presence of the glutamate transporter inhibitor DL-TBOA or intracellular Ca²⁺-releasing inhibitors dantrolene and CGP37157, and was prevented by blocking vesicular transporters or N- and P/Q-type channels. Western blot and immunocytochemical analysis revealed the presence of S1P1 receptor proteins in presynaptic terminals. Fingolimod-mediated inhibition of 4-AP-induced glutamate release was also abolished by the sphingosine kinase inhibitor DMS, selective S1P1 receptor antagonist W146, Gi/o protein inhibitor pertussis toxin, and G protein βγ subunit inhibitor gallein; however, it was unaffected by the adenylyl cyclase inhibitor SQ22536, protein kinase A inhibitor H89, and phospholipase C inhibitor U73122. These data indicate that fingolimod decreases glutamate release from rat cerebrocortical synaptosomes by suppressing N- and P/Q-type Ca²⁺ channel activity; additionally, the activation of presynaptic S1P1 receptors and the G protein βγ subunit participates in achieving the effect.

Sphingosine-1-Phosphate Receptor Modulators and Oligodendroglial Cells: Beyond Immunomodulation

Multiple sclerosis (MS) is an autoimmune inflammatory disease characterized by demyelination, axonal loss, and synaptic impairment in the central nervous system (CNS). The available therapies aim to reduce the severity of the pathology during the early inflammatory stages, but they are not effective in the chronic stage of the disease. In this phase, failure in endogenous remyelination is associated with the impairment of oligodendrocytes progenitor cells (OPCs) to migrate and differentiate into mature myelinating oligodendrocytes. Therefore, stimulating differentiation of OPCs into myelinating oligodendrocytes has become one of the main goals of new therapeutic approaches for MS. Different disease-modifying therapies targeting sphingosine-1-phosphate receptors (S1PRs) have been approved or are being developed to treat MS. Besides their immunomodulatory effects, growing evidence suggests that targeting S1PRs modulates mechanisms beyond immunomodulation, such as remyelination. In this context, this review focuses on the current understanding of S1PR modulators and their direct effect on OPCs and oligodendrocytes.

Beneficial Effects of Fingolimod on Social Interaction, CNS and Peripheral Immune Response in the BTBR Mouse Model of Autism

Autism Spectrum Disorders (ASD) are neurodevelopmental disorders characterized by social communication deficits and repetitive/stereotyped behaviours. We evaluated the effects of a chronic treatment with the immunomodulator drug Fingolimod (FTY720 - a non-selective Sphingosine 1-Phosphate Receptor ligand) in an ASD model, the BTBR T⁺tf/J (BTBR) mouse strain. In adult BTBR males, chronic FTY720 treatment (4 weeks) increased social and vocal response during a male-female interaction and hippocampal expression of BDNF and Neuregulin 1, two trophic factors reduced in BTBR when compared to control C57 mice. FTY720 also re-established the expression of IL-1β and MnSOD in the hippocampus, whereas it did not modify IL-6 mRNA content. In addition to its central effect, FTY720 modulated the activation state of peripheral macrophages in the BTBR model, both in basal conditions and after stimulation with an immune challenge. Furthermore, IL-6 mRNA colonic content of BTBR mice, reduced when compared with C57 mice, was normalized by chronic treatment with FTY720. Our study, while indicating FTY720 as a tool to attenuate relevant alterations of the BTBR neurobehavioural phenotype, emphasizes the importance of gut mucosal immune evaluation as an additional target that deserve to be investigated in preclinical studies of anti-inflammatory therapeutic approaches in ASD.

Fingolimod: Lessons Learned and New Opportunities for Treating Multiple Sclerosis and Other Disorders

Fingolimod (FTY720, Gilenya) was the first US Food and Drug Administration-approved oral therapy for relapsing forms of multiple sclerosis (MS). Research on modified fungal metabolites converged with basic science studies that had identified lysophospholipid (LP) sphingosine 1-phosphate (S1P) receptors, providing mechanistic insights on fingolimod while validating LP receptors as drug targets. Mechanism of action (MOA) studies identified receptor-mediated processes involving the immune system and the central nervous system (CNS). These dual actions represent a more general theme for S1P and likely other LP receptor modulators. Fingolimod's direct CNS activities likely contribute to its efficacy in MS, with particular relevance to treating progressive disease stages and forms that involve neurodegeneration. The evolving understanding of fingolimod's MOA has provided strategies for developing next-generation compounds with superior attributes, suggesting new ways to target S1P as well as other LP receptor modulators for novel therapeutics in the CNS and other organ systems.

Adenosine A2B receptors inhibit K+ currents and cell differentiation in cultured oligodendrocyte precursor cells and modulate sphingosine-1-phosphate signaling pathway

Oligodendrocytes are the only myelinating cells in the brain and differentiate from their progenitors (OPCs) throughout adult life. However, this process fails in demyelinating pathologies. Adenosine is emerging as an important player in OPC differentiation and we recently demonstrated that adenosine A_2A receptors inhibit cell maturation by reducing voltage-dependent K⁺ currents. No data are available to date about the A_2B receptor (A_2BR) subtype. The bioactive lipid mediator sphingosine-1-phosphate (S1P) and its receptors (S1P_1-5) are also crucial modulators of OPC development. An interaction between this pathway and the A_2BR is reported in peripheral cells. We studied the role of A_2BRs in modulating K⁺ currents and cell differentiation in OPC cultures and we investigated a possible interplay with S1P signaling. Our data indicate that the A_2BR agonist BAY60-6583 and its new analogue P453 inhibit K⁺ currents in cultured OPC and the effect was prevented by the A_2BR antagonist MRS1706, by K⁺ channel blockers and was differently modulated by the S1P analogue FTY720-P. An acute (10 min) exposure of OPCs to BAY60-6583 also increased the phosphorylated form of sphingosine kinase 1 (SphK1). A chronic (7 days) treatment with the same agonist decreased OPC differentiation whereas SphK1/2 inhibition exerted the opposite effect. Furthermore, A_2BR was overexpressed during OPC differentiation, an effect prevented by the pan SphK1/2 inhibitor VPC69047. Finally, A_2BR silenced cells showed increased cell maturation, decreased SphK1 expression and enhanced S1P lyase levels. We conclude that A_2BRs inhibit K⁺ currents and cell differentiation and positively modulate S1P synthesis in cultured OPCs.

Sphingolipids in Alzheimer's disease, how can we target them?

Altered levels of sphingolipids and their metabolites in the brain, and the related downstream effects on neuronal homeostasis and the immune system, provide a framework for understanding mechanisms in neurodegenerative disorders and for developing new intervention strategies. In this review we will discuss: the metabolites of sphingolipids that function as second messengers; and functional aberrations of the pathway resulting in Alzheimer's disease (AD) pathophysiology. Focusing on the central product of the sphingolipid pathway ceramide, we describ approaches to pharmacologically decrease ceramide levels in the brain and we argue on how the sphingolipid pathway may represent a new framework for developing novel intervention strategies in AD. We also highlight the possible use of clinical and non-clinical drugs to modulate the sphingolipid pathway and sphingolipid-related biological cascades.

FTY720 (Fingolimod) Ameliorates Brain Injury through Multiple Mechanisms and is a Strong Candidate for Stroke Treatment

FTY720 (Fingolimod) is a known sphingosine-1-phosphate (S1P) receptor agonist that exerts strong anti-inflammatory effects and was approved as the first oral drug for the treatment of multiple sclerosis by the US Food and Drug Administration (FDA) in 2010. FTY720 is mainly associated with unique functional "antagonist" and "agonist" mechanisms. The functional antagonistic mechanism is mediated by the transient down-regulation and degradation of S1P receptors on lymphocytes, which prevents lymphocytes from entering the blood stream from the lymph node. This subsequently results in the development of lymphopenia and reduces lymphocytic inflammation. Functional agonistic mechanisms are executed through S1P receptors expressed on the surface of various cells including neurons, astrocytes, microglia, and blood vessel endothelial cells. These functions might play important roles in regulating anti-apoptotic systems, modulating brain immune and phagocytic activities, preserving the Blood-Brain-Barrier (BBB), and the proliferation of neural precursor cells. Recently, FTY720 have shown receptor-independent effects, including intracellular target bindings and epigenetic modulations. Many researchers have recognized the positive effects of FTY720 and launched basic and clinical experiments to test the use of this agent against stroke. Although the mechanism of FTY720 has not been fully elucidated, its efficacy against cerebral stroke is becoming clear, not only in animal models, but also in ischemic stroke patients through clinical trials. In this article, we review the data obtained from laboratory findings and preliminary clinical trials using FTY720 for stroke treatment.

Multiple sclerosis drug FTY-720 toxicity is mediated by the heterotypic fusion of organelles in neuroendocrine cells

FTY-720 (Fingolimod) was one of the first compounds authorized for the treatment of multiple sclerosis. Among its other activities, this sphingosine analogue enhances exocytosis in neuroendocrine chromaffin cells, altering the quantal release of catecholamines. Surprisingly, the size of chromaffin granules is reduced within few minutes of treatment, a process that is paralleled by the homotypic fusion of granules and their heterotypic fusion with mitochondria, as witnessed by dynamic confocal and TIRF microscopy. Electron microscopy studies support these observations, revealing the fusion of several vesicles with individual mitochondria to form large, round mixed organelles. This cross-fusion is SNARE-dependent, being partially prevented by the expression of an inactive form of SNAP-25. Fused mitochondria exhibit an altered redox potential, which dramatically enhances cell death. Therefore, the cross-fusion of intracellular organelles appears to be a new mechanism to be borne in mind when considering the effect of FTY-720 on the survival of neuroendocrine cells.

Protein phosphatase 2A as a therapeutic target in inflammation and neurodegeneration

Protein phosphatase 2A (PP2A) is a highly complex heterotrimeric enzyme that catalyzes the selective removal of phosphate groups from protein serine and threonine residues. Emerging evidence suggests that it functions as a tumor suppressor by constraining phosphorylation-dependent signalling pathways that regulate cellular transformation and metastasis. Therefore, PP2A-activating drugs (PADs) are being actively sought and investigated as potential novel anti-cancer treatments. Here we explore the concept that PP2A also constrains inflammatory responses through its inhibitory effects on various signalling pathways, suggesting that PADs may be effective in the treatment of inflammation-mediated pathologies.

Fingolimod reduces neuropathic pain behaviors in a mouse model of multiple sclerosis by a sphingosine-1 phosphate receptor 1-dependent inhibition of central sensitization in the dorsal horn

Multiple sclerosis (MS) is an autoimmune-inflammatory neurodegenerative disease that is often accompanied by a debilitating neuropathic pain. Disease-modifying agents slow down the progression of multiple sclerosis and prevent relapses, yet it remains unclear if they yield analgesia. We explored the analgesic potential of fingolimod (FTY720), an agonist and/or functional antagonist at the sphingosine-1-phosphate receptor 1 (S1PR1), because it reduces hyperalgesia in models of peripheral inflammatory and neuropathic pain. We used a myelin oligodendrocyte glycoprotein 35 to 55 (MOG35-55) mouse model of experimental autoimmune encephalomyelitis, modified to avoid frank paralysis, and thus, allow for assessment of withdrawal behaviors to somatosensory stimuli. Daily intraperitoneal fingolimod reduced behavioral signs of central neuropathic pain (mechanical and cold hypersensitivity) in a dose-dependent and reversible manner. Both autoimmune encephalomyelitis and fingolimod changed hyperalgesia before modifying motor function, suggesting that pain-related effects and clinical neurological deficits were modulated independently. Fingolimod also reduced cellular markers of central sensitization of neurons in the dorsal horn of the spinal cord: glutamate-evoked Ca signaling and stimulus-evoked phospho-extracellular signal-related kinase ERK (pERK) expression, as well as upregulation of astrocytes (GFAP) and macrophage/microglia (Iba1) immunoreactivity. The antihyperalgesic effects of fingolimod were prevented or reversed by the S1PR1 antagonist W146 (1 mg/kg daily, i.p.) and could be mimicked by either repeated or single injection of the S1PR1-selective agonist SEW2871. Fingolimod did not change spinal membrane S1PR1 content, arguing against a functional antagonist mechanism. We conclude that fingolimod behaves as an S1PR1 agonist to reduce pain in multiple sclerosis by reversing central sensitization of spinal nociceptive neurons.

Combination Therapy With Fingolimod and Neural Stem Cells Promotes Functional Myelination in vivo Through a Non-immunomodulatory Mechanism

Myelination, which occurs predominantly postnatally and continues throughout life, is important for proper neurologic function of the mammalian central nervous system (CNS). We have previously demonstrated that the combination therapy of fingolimod (FTY720) and transplanted neural stem cells (NSCs) had a significantly enhanced therapeutic effect on the chronic stage of experimental autoimmune encephalomyelitis, an animal model of CNS autoimmunity, compared to using either one of them alone. However, reduced disease severity may be secondary to the immunomodulatory effects of FTY720 and NSCs, while whether this therapy directly affects myelinogenesis remains unknown. To investigate this important question, we used three myelination models under minimal or non-inflammatory microenvironments. Our results showed that FTY720 drives NSCs to differentiate into oligodendrocytes and promotes myelination in an ex vivo brain slice culture model, and in the developing CNS of healthy postnatal mice in vivo. Elevated levels of neurotrophic factors, e.g., brain-derived neurotrophic factor and glial cell line-derived neurotrophic factor, were observed in the CNS of the treated infant mice. Further, FTY720 and NSCs efficiently prolonged the survival and improved sensorimotor function of shiverer mice. Together, these data demonstrate a direct effect of FTY720, beyond its known immunomodulatory capacity, in NSC differentiation and myelin development as a novel mechanism underlying its therapeutic effect in demyelinating diseases.

Fingolimod Suppresses the Proinflammatory Status of Interferon-γ-Activated Cultured Rat Astrocytes

Astroglia, the primary homeostatic cells of the central nervous system, play an important role in neuroinflammation. They act as facultative immunocompetent antigen-presenting cells (APCs), expressing major histocompatibility complex (MHC) class II antigens upon activation with interferon (IFN)-γ and possibly other proinflammatory cytokines that are upregulated in disease states, including multiple sclerosis (MS). We characterized the anti-inflammatory effects of fingolimod (FTY720), an established drug for MS, and its phosphorylated metabolite (FTY720-P) in IFN-γ-activated cultured rat astrocytes. The expression of MHC class II compartments, β₂ adrenergic receptor (ADR-β₂), and nuclear factor kappa-light-chain enhancer of activated B cells subunit p65 (NF-κB p65) was quantified in immunofluorescence images acquired by laser scanning confocal microscopy. In addition, MHC class II-enriched endocytotic vesicles were labeled by fluorescent dextran and their mobility analyzed in astrocytes subjected to different treatments. FTY720 and FTY720-P treatment significantly reduced the number of IFN-γ-induced MHC class II compartments and substantially increased ADR-β₂ expression, which is otherwise small or absent in astrocytes in MS. These effects could be partially attributed to the observed decrease in NF-κB p65 expression, because the NF-κB signaling cascade is activated in inflammatory processes. We also found attenuated trafficking and secretion from dextran-labeled endo-/lysosomes that may hinder efficient delivery of MHC class II molecules to the plasma membrane. Our data suggest that FTY720 and FTY720-P at submicromolar concentrations mediate anti-inflammatory effects on astrocytes by suppressing their action as APCs, which may further downregulate the inflammatory process in the brain, constituting the therapeutic effect of fingolimod in MS.

The next-generation sphingosine-1 receptor modulator BAF312 (siponimod) improves cortical network functionality in focal autoimmune encephalomyelitis

Autoimmune diseases of the central nervous system (CNS) like multiple sclerosis (MS) are characterized by inflammation and demyelinated lesions in white and grey matter regions. While inflammation is present at all stages of MS, it is more pronounced in the relapsing forms of the disease, whereas progressive MS (PMS) shows significant neuroaxonal damage and grey and white matter atrophy. Hence, disease-modifying treatments beneficial in patients with relapsing MS have limited success in PMS. BAF312 (siponimod) is a novel sphingosine-1-phosphate receptor modulator shown to delay progression in PMS. Besides reducing inflammation by sequestering lymphocytes in lymphoid tissues, BAF312 crosses the blood-brain barrier and binds its receptors on neurons, astrocytes and oligodendrocytes. To evaluate potential direct neuroprotective effects, BAF312 was systemically or locally administered in the CNS of experimental autoimmune encephalomyelitis mice with distinct grey- and white-matter lesions (focal experimental autoimmune encephalomyelitis using an osmotic mini-pump). Ex-vivo flow cytometry revealed that systemic but not local BAF312 administration lowered immune cell infiltration in animals with both grey and white matter lesions. Ex-vivo voltage-sensitive dye imaging of acute brain slices revealed an altered spatio-temporal pattern of activation in the lesioned cortex compared to controls in response to electrical stimulation of incoming white-matter fiber tracts. Here, BAF312 administration showed partial restore of cortical neuronal circuit function. The data suggest that BAF312 exerts a neuroprotective effect after crossing the blood-brain barrier independently of peripheral effects on immune cells. Experiments were carried out in accordance with German and EU animal protection law and approved by local authorities (Landesamt für Natur, Umwelt und Verbraucherschutz Nordrhein-Westfalen; 87-51.04.2010.A331) on December 28, 2010.

Local delivery of FTY720 and NSCs on electrospun PLGA scaffolds improves functional recovery after spinal cord injury

Spinal cord injury (SCI) is a common issue in the clinic that causes severe motor and sensory dysfunction below the lesion level. FTY720, also known as fingolimod, has recently been reported to exert a positive effect on the recovery from a spinal cord injury. Through local delivery to the lesion site, FTY720 effectively integrates with biomaterials, and the systemic adverse effects are alleviated. However, the effects of the proper mass ratio of FTY720 in biomaterials on neural stem cell (NSC) proliferation and differentiation, as well as functional recovery after SCI, have not been thoroughly investigated. In our study, we fabricated electrospun poly (lactide-co-glycolide) (PLGA)/FTY720 scaffolds at different mass ratios (0.1%, 1%, and 10%) and characterized these scaffolds. The effects of electrospun PLGA/FTY720 scaffolds on NSC proliferation and differentiation were measured. Then, a rat model of spinal transection was established to investigate the effects of PLGA/FTY720 scaffolds loaded with NSCs. Notably, 1% PLGA/FTY720 scaffolds exerted the best effects on the proliferation and differentiation of NSCs and 10% PLGA/FTY720 was cytotoxic to NSCs. Based on the Basso, Beattie, and Bresnahan (BBB) score, HE staining and immunofluorescence staining, the PLGA/FTY720 scaffold loaded with NSCs effectively promoted the recovery of spinal cord function. Thus, FTY720 properly integrated with electrospun PLGA scaffolds, and electrospun PLGA/FTY720 scaffolds loaded with NSCs may have potential applications for SCI as a nerve implant.

Spinal cord injury (SCI) is a common issue in the clinic that causes severe motor and sensory dysfunction below the lesion level.

Could α-Synuclein Modulation of Insulin and Dopamine Identify a Novel Link Between Parkinson's Disease and Diabetes as Well as Potential Therapies?

Characterizing the normal function(s) of the protein α-Synuclein (aSyn) has the potential to illuminate links between Parkinson’s disease (PD) and diabetes and also point the way toward new therapies for these disorders. Here we provide a perspective for consideration based on our discovery that aSyn normally acts to inhibit insulin secretion from pancreatic β-cells by interacting with the Kir6.2 subunit of the ATP-sensitive potassium channel (K-ATP). It is also known that K-ATP channels act to inhibit brain dopamine secretion, and we have also shown that aSyn is a normal inhibitor of dopamine synthesis. The finding, that aSyn modulates Kir6.2 and other proteins involved in dopamine and insulin secretion, suggests that aSyn interacting proteins may be negatively impacted when aSyn aggregates inside cells, whether in brain or pancreas. Furthermore, identifying therapies for PD that can counteract dysfunction found in diabetes, would be highly beneficial. One such compound may be the multiple sclerosis drug, FTY720, which like aSyn can stimulate the activity of the catalytic subunit of protein phosphatase 2A (PP2Ac) as well as insulin secretion. In aging aSyn transgenic mice given long term oral FTY720, the mice had reduced aSyn pathology and increased levels of the protective molecule, brain derived neurotrophic factor (BDNF) (Vidal-Martinez et al., 2016). In collaboration with medicinal chemists, we made two non-immunosuppressive FTY720s that also enhance PP2Ac activity, and BDNF expression (Vargas-Medrano et al., 2014; Enoru et al., 2016; Segura-Ulate et al., 2017a). FTY720 and our novel FTY720-based-derivatives, may thus have therapeutic potential for both diabetes and PD.

The role of sphingosine-1-phosphate in skeletal muscle: Physiology, mechanisms, and clinical perspectives

Sphingolipids were discovered more than a century ago and were simply considered as a class of cell membrane lipids for a long time. However, after the discovery of several intracellular functions and their role in the control of many physiological and pathophysiological conditions, these molecules have gained much attention. For instance, the sphingosine-1-phosphate (S1P) is a circulating bioactive sphingolipid capable of triggering strong intracellular reactions through the family of S1P receptors (S1PRs) spread in several cell types and tissues. Recently, the role of S1P in the control of skeletal muscle metabolism, atrophy, regeneration, and metabolic disorders has been widely investigated. In this review, we summarized the knowledge of S1P and its effects in skeletal muscle metabolism, highlighting the role of S1P/S1PRs axis in skeletal muscle regeneration, fatigue, ceramide accumulation, and insulin resistance. Finally, we discussed the physical exercise role in S1P/S1PRs signaling in skeletal muscle cells, and how this nonpharmacological strategy may be prospective for future investigations due to its ability to increase S1P levels.

Inflammation, immunity, and amyotrophic lateral sclerosis: II. immune-modulating therapies

With the emerging popularity of immune-modulatory therapies to treat human diseases there is a need to step back from hypotheses aimed at assessing a condition in a single-system context and instead take into account the disease pathology as a whole. In complex diseases, such as amyotrophic lateral sclerosis (ALS), the use of these therapies to treat patients has been largely unsuccessful and likely premature given our lack of understanding of how the immune system influences disease progression and initiation. In addition, we still have an incomplete understanding of the role of these responses in our model systems and how this may translate clinically to human patients. In this review we discuss preclinical evidence and clinical trial results for a selection of recently conducted studies in ALS. We provide evidence-based reasoning for the failure of these trials and offer suggestions to improve the design of future investigations. Muscle Nerve 59:23-33, 2019.

Sphingosine-1-Phosphate (S1P) Signaling in Neural Progenitors

Sphingosine-1-phosphate (S1P) and its receptors are important in nervous system development. Reliable in vitro human model systems are needed to further define specific roles for S1P signaling in neural development. We have described S1P-regulated signaling, survival, and differentiation in a human embryonic stem cell-derived neuroepithelial progenitor cell line (hNP1) that expresses functional S1P receptors. These cells can be further differentiated to a neuronal cell type and therefore represent a good model system to study the role of S1P signaling in human neural development. The following sections describe in detail the culture and differentiation of hNP1 cells and two assays to measure S1P signaling in these cells.

Fingolimod promotes blood-nerve barrier properties in vitro

OBJECTIVE

The main effect of fingolimod is thought to be functional antagonism of lymphocytic S1P1 receptors and the prevention of lymphocyte egress from lymphoid tissues, thereby reducing lymphocyte infiltration into the nervous system. However, a growing number of reports suggest that fingolimod also has a direct effect on several cell types in the nervous system. Although we previously reported that fingolimod enhances blood-brain barrier (BBB) functions, there have been no investigations regarding the blood-nerve barrier (BNB). In this study, we examine how fingolimod affects the BNB.

METHODS

An immortalized human peripheral nerve microvascular endothelial cell line (HPnMEC) was used to evaluate BNB barrier properties. We examined tight junction proteins and barrier functions of HPnMECs in conditioned medium with or without fingolimod-phosphate and blood sera from patients with typical chronic inflammatory demyelinating polyneuropathy (CIDP).

RESULTS

Incubation with fingolimod-phosphate increased levels of claudin-5 mRNA and protein as well as TEER values in HPnMECs. Conversely, typical CIDP sera decreased claudin-5 mRNA/protein levels and TEER values in HPnMECs; however, pretreatment with fingolimod-phosphate inhibited the effects of the typical CIDP sera.

CONCLUSIONS

Fingolimod-phosphate directly modifies the BNB and enhances barrier properties. This mechanism may be a viable therapeutic target for CIDP, and fingolimod may be useful in patients with typical CIDP who have severe barrier disruption.

Fingolimod effect on gray matter, thalamus, and white matter in patients with multiple sclerosis

Objective

To study the effect of fingolimod on deep gray matter (dGM), thalamus, cortical GM (cGM), white matter (WM), and ventricular volume (VV) in patients with relapsing-remitting multiple sclerosis (RRMS).

Methods

Data were pooled from 2 phase III studies. A total of 2,064 of 2,355 (88%) contributed to the analysis: fingolimod 0.5 mg n = 783, fingolimod 1.25 mg n = 799, or placebo n = 773. Percentage change from baseline in dGM and thalamic volumes was evaluated with FMRIB’s Integrated Registration & Segmentation Tool; WM, cGM, and VV were evaluated with structural image evaluation using normalization of atrophy cross-sectional version (SIENAX) at months 12 and 24.

Results

At baseline, compound brain volume (brain volume in the z block [BVz] = cGM + dGM + WM) correlated with SIENAX-normalized brain volume (r = 0.938, p < 0.001); percentage change from baseline in BVz over 2 years correlated with structural image evaluation using normalization of atrophy percentage brain volume change (r = 0.713, p < 0.001). For placebo, volume reductions were most pronounced in cGM, and relative changes from baseline were strongest in dGM. Over 24 months, there were significant reductions with fingolimod vs placebo for dGM (0.5 mg −14.5%, p = 0.017; 1.25 mg −26.6%, p < 0.01) and thalamus (0.5 mg −26.1%, p = 0.006; 1.25 mg −49.7%, p < 0.001). Reduction of cGM volume loss was not significant. Significantly less WM loss and VV enlargement were seen with fingolimod vs placebo (all p < 0.001). A high T2 lesion volume at baseline predicted on-study cGM, dGM, and thalamic volume loss (p < 0.0001) but not WM loss. Patients taking placebo with high dGM (hazard ratio [HR] 0.54, p = 0.0323) or thalamic (HR 0.58, p = 0.0663) volume at baseline were less likely to show future disability worsening.

Conclusions

Fingolimod significantly reduced dGM volume loss (including thalamus) vs placebo in patients with RRMS. Reducing dGM and thalamic volume loss might improve long-term outcome.

TNFα disrupts blood brain barrier integrity to maintain prolonged depressive-like behavior in mice

Recovery from major depressive disorder is difficult, particularly in patients who are refractory to antidepressant treatments. To examine factors that regulate recovery, we developed a prolonged learned helplessness depression model in mice. After the induction of learned helplessness, mice were separated into groups that recovered or did not recover within 4 weeks. Comparisons were made between groups in hippocampal proteins, inflammatory cytokines, and blood brain barrier (BBB) permeability. Compared with mice that recovered and control mice, non-recovered mice displaying prolonged learned helplessness had greater hippocampal activation of glycogen synthase kinase-3 (GSK3), higher levels of tumor necrosis factor-α (TNFα), interleukin-17A, and interleukin-23, increased permeability of the blood brain barrier (BBB), and lower levels of the BBB tight junction proteins occludin, ZO1, and claudin-5. Treatment with the GSK3 inhibitor TDZD-8 reduced inflammatory cytokine levels, increased tight junction protein levels, and reversed impaired recovery from learned helplessness, demonstrating that prolonged learned helplessness is reversible and is maintained by abnormally active GSK3. In non-recovered mice with prolonged learned helpless, stimulation of sphingosine 1-phosphate receptors by Fingolimod or administration of the TNFα inhibitor etanercept repaired the BBB and reversed impaired recovery from prolonged learned helplessness. Thus, disrupted BBB integrity mediated in part by TNFα contributes to blocking recovery from prolonged learned helplessness depression-like behavior. Overall, this report describes a new model of prolonged depression-like behavior and demonstrates that stress-induced GSK3 activation contributes to disruption of BBB integrity mediated by inflammation, particularly TNFα, which contributes to impaired recovery from prolonged learned helplessness.

Fingolimod reduces the clinical expression of active demyelinating lesions in MS

BACKGROUND

Fingolimod is a modulator of Central and peripheral sphingosine pathways, which is currently approved for treatment of Multiple Sclerosis (MS). In animal models it reduces inflammation, but it is also able to potentiate glutamatergic transmission and synaptic plasticity. We aimed to explore whether Fingolimod is able to modify the clinical expression of new demyelinating lesions with respect to IFNβ-1a in relapsing remitting MS (RRMS) patients suboptimal responders to IFNβ-1a.

METHODS

103 patients with RRMS switching for inefficacy from IFNβ-1a to Fingolimod and treated for at least 12 months were included. Annualised Relapse Rate (ARR), EDSS and the number of new brain and spinal gadolinium enhancing (Gd +) and T2 lesions were retrospectively assessed in the whole group during each treatment period. The likelihood of co-occurrence of new Gd + lesions and clinical relapses during IFNβ-1a and Fingolimod treatment was analysed.

RESULTS

The mean duration of treatment with IFNβ-1a and Fingolimod was 3.14 (SD 1.6) and 3.22 years (SD 1.1) respectively. Significant reduction of ARR (p < .001), total number of Gd + and T2 lesions (p < .001) was found switching from IFNβ-1a to Fingolimod. Gd + lesions occurring during treatment with Fingolimod were more likely to be asymptomatic compared with IFNβ-1a (88% vs 30.9%, p = < .025).

CONCLUSION

Fingolimod reduces clinical and radiological inflammation in MS. Additionally, it limits the clinical expression of new Gd + lesions, possibly reducing local inflammatory processes and improving brain network plasticity in patients with suboptimal response to IFNβ-1a.

Potential neuroprotective effect of Fingolimod in multiple sclerosis and its association with clinical variables

INTRODUCTION

Multiple sclerosis (MS) is a chronic inflammatory, demyelinating disease of the central nervous system affecting both white matter and grey matter in the earliest phases of its course. The crucial role of neurodegeneration in disability progression in MS, regardless of white matter damage, has been confirmed by several imaging and neuropathological studies. Fingolimod is an effective immunomodulator of the sphingosine 1-phosphate receptor, approved in relapsing remitting MS and able to cross the blood-brain barrier and to slow disability progression and brain volume loss. However, it remains unclear whether this neuroprotective action is due to a peripheral anti-inflammatory effect and/or to a direct effect on neuronal cells.

AREAS COVERED

In this review, the authors summarize the published preclinical and clinical studies on the effect of Fingolimod in limiting the focal and diffuse grey matter damage in MS.

EXPERT OPINION

Fingolimod might have a significant neuroprotective effect on relapsing remitting MS based on its modulatory effect on oligodendroglial cells and astrocytes, and on its direct effect on cortical neurons. Future clinical studies including measures of grey matter damage are required to confirm in vivo such neuroprotective effect.

Emerging PET Radiotracers and Targets for Imaging of Neuroinflammation in Neurodegenerative Diseases: Outlook Beyond TSPO

The dynamic and multicellular processes of neuroinflammation are mediated by the nonneuronal cells of the central nervous system, which include astrocytes and the brain's resident macrophages, microglia. Although initiation of an inflammatory response may be beneficial in response to injury of the nervous system, chronic or maladaptive neuroinflammation can have harmful outcomes in many neurological diseases. An acute neuroinflammatory response is protective when activated neuroglia facilitate tissue repair by releasing anti-inflammatory cytokines and neurotrophic factors. On the other hand, chronic neuroglial activation is a major pathological mechanism in neurodegenerative diseases, likely contributing to neuronal dysfunction, injury, and disease progression. Therefore, the development of specific and sensitive probes for positron emission tomography (PET) studies of neuroinflammation is attracting immense scientific and clinical interest. An early phase of this research emphasized PET studies of the prototypical imaging biomarker of glial activation, translocator protein-18 kDa (TSPO), which presents difficulties for quantitation and lacks absolute cellular specificity. Many alternate molecular targets present themselves for PET imaging of neuroinflammation in vivo, including enzymes, intracellular signaling molecules as well as ionotropic, G-protein coupled, and immunoglobulin receptors. We now review the lead structures in radiotracer development for PET studies of neuroinflammation targets for neurodegenerative diseases extending beyond TSPO, including glycogen synthase kinase 3, monoamine oxidase-B, reactive oxygen species, imidazoline-2 binding sites, cyclooxygenase, the phospholipase A2/arachidonic acid pathway, sphingosine-1-phosphate receptor-1, cannabinoid-2 receptor, the chemokine receptor CX3CR1, purinergic receptors: P2X7 and P2Y12, the receptor for advanced glycation end products, Mer tyrosine kinase, and triggering receptor expressed on myeloid cells-1. We provide a brief overview of the cellular expression and function of these targets, noting their selectivity for astrocytes and/or microglia, and highlight the classes of PET radiotracers that have been investigated in early-stage preclinical or clinical research studies of neuroinflammation.

Functional antagonism of sphingosine-1-phosphate receptor 1 prevents cuprizone-induced demyelination

Recent evidence suggests that the oral drug Fingolimod (FTY720) for relapsing-remitting multiple sclerosis (MS) may act directly on the central nervous system (CNS) and modulate disease pathogenesis and progression in experimental models of MS. However, the specific subtype of sphingosine-1-phosphate (S1P) receptors that mediates the effect of FTY720 on the CNS cells has not been fully elucidated. Here, we report that S1P receptor 1 (S1PR1) is elevated in reactive astrocytes in an autoimmunity independent mouse model of MS and that selective S1PR1 modulation is sufficient to ameliorate the loss of oligodendrocytes and demyelination. The non-selective S1PR modulator, FTY720, or a short-lived S1PR1-specific modulator, CYM5442, was administered daily to mice while on cuprizone diet. Both FTY720- and CYM5422-treated mice displayed a significant reduction in oligodendrocyte apoptosis and astrocyte and microglial activation in comparison to vehicle-treated groups, which was associated with decreased production of proinflammatory mediators and down-regulation of astrocytic S1PR1 protein. Interestingly, S1PR1 modulation during the early phase of cuprizone intoxication was required to suppress oligodendrocyte death and consequent demyelination as drug treatment from 10 days after the initiation of cuprizone feeding was no longer effective. CYM5442 treatment during the brief cuprizone exposure significantly prevented Il-1β, Il-6, Cxcl10, and Cxcl3 induction, resulting in suppression of subsequent reactive gliosis and demyelination. Our study identifies functional antagonism of S1PR1 as a major mechanism for the protective effect of FTY720 in the cuprizone model and suggests pathogenic contributions of astrocyte S1PR1 signaling in primary demyelination and its potential as a therapeutic target for CNS inflammation.

Experimental Autoimmune Encephalomyelitis Is Successfully Controlled by Epicutaneous Administration of MOG Plus Vitamin D Analog

Multiple sclerosis (MS) is an inflammatory and demyelinating disorder of the central nervous system (CNS). Experimental autoimmune encephalomyelitis (EAE) has been widely employed to evaluate new strategies to control MS, including procedures to induce immunological tolerance. Considering that skin exposure to protein antigens can induce tolerance and that vitamin D analogs conserve immunomodulatory potential and are less toxic, we investigated the efficacy of epicutaneous application of a myelin oligodendrocyte glycoprotein peptide (MOG_35–55) associated with paricalcitol (PARI) on EAE development. Three and 11 days after EAE induction, C57BL/6 mice were treated with an occlusive patch containing MOG plus PARI. Clinical parameters were daily assessed, whereas immunological and histological evaluations were performed during the acute EAE phase. MOG and MOG + PARI significantly controlled disease development reducing weight loss and clinical score. Moreover, MOG and MOG + PARI reduced the inflammatory process and preserved the myelin sheath in the CNS. High percentages of Foxp3⁺ regulatory T cells (Tregs) and lower MHCII fluorescence intensity in dendritic cells in draining lymph nodes were concomitantly observed. MOG + PARI association was, however, more efficient being able to reduce disease incidence and clinical scores more significantly than MOG or PARI alone. This experimental group also displayed a higher ratio between mRNA expression for Foxp3 and RORc and a higher percentage of Foxp3⁺ cells in the CNS. Modulation of activation markers observed in microglial cells eluted from EAE treated mice were confirmed by in vitro studies with the BV-2 microglial cell line. The results show that MOG + PARI association applied by an epicutaneous route controlled EAE development. Protective involved mechanisms include mainly a higher proportion of Tregs and also a direct immunomodulatory effect of PARI on microglial cells.

Effects of FTY720 on brain neurogenic niches in vitro and after kainic acid-induced injury

Background

FTY720 (fingolimod, Gilenya™) is an oral, blood-brain barrier (BBB)-passing drug approved as immunomodulatory treatment for relapsing-remitting form of the multiple sclerosis (MS). In addition, FTY720 exerts several effects in the central nervous system (CNS), ranging from neuroprotection to reduction of neuroinflammation. However, the neurogenic and oligodendrogenic potential of FTY720 has been poorly investigated. In this study, we assessed the effect of FTY720 on the production of new neurons and oligodendrocytes from neural stem/precursor cells both in vitro and in vivo.

Methods

Neural stem cells (NSCs) derived from the young rat subventricular zone (SVZ) were exposed to FTY720 (10, 100 nM), and their differentiation into neurons and oligodendrocytes was measured using immunofluorescence for anti-β-III tubulin or CNPase (2′,3′-cyclic nucleotide 3′-phosphodiesterase) as markers of mature neurons or oligodendrocytes, respectively. In addition, intracerebroventricular (icv) administration of kainic acid (KA; 0.5 μg/2 μl) in Sprague-Dawley rats was used as an in vivo model of neuronal death and inflammation. FTY720 was applied icv (1 μg/2 μl), together with KA, plus intraperitoneally (ip; 1 mg/kg) 24 h before, and daily, until sacrifice 8 days after KA injection. To visualize cell proliferation in the hippocampus and in white matter regions, rats were administered 5-bromo-2-deoxyuridine (BrdU) 100 mg/kg, ip injected every 2 days. Immunohistochemical analyses were performed on rat brain slices to measure the production of new neuronal precursors (doublecortin/DCX⁺ cells) and new oligodendrocytes precursors (proteoglycan/NG2⁺ cells).

Results

In this study, we observed that FTY720 increased postnatal NSCs differentiation into both neurons and oligodendrocytes in vitro. In turn, in adult animals, FTY720 enhanced the percentage of BrdU⁺ cells coexpressing DCX marker, both in basal (FTY720 alone) and in neurodegenerative (FTY720 + KA) conditions. However, FTY720 had only a partial effect on proliferation and differentiation of oligodendrocyte progenitor cell (OPC) population in vivo.

Conclusions

FTY720 promotes neurogenesis and oligodendrogenesis in vitro under basal conditions. In addition, it increases the generation of neuroblasts and oligodendrocytes after excitotoxic brain injury. This suggests that FTY720 has the potential to activate the neurogenic niche and thus favour tissue repair after lesion.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-017-0922-6) contains supplementary material, which is available to authorized users.

Spasticity in multiple sclerosis: Contribution of inflammation, autoimmune mediated neuronal damage and therapeutic interventions

In contrast to other diseases that go along with spasticity (e.g. spinal cord injury), spasticity in chronic autoimmune diseases involving the CNS is complicated by the ongoing damage of neuronal networks that leads to permanent changes in the clinical picture of spasticity. Multiple sclerosis (MS) is the most frequent autoimmune disease of the central nervous system (CNS) and spasticity is one of the most disabling symptoms. It occurs in more than 80% MS patients at some point of the disease and is associated with impaired ambulation, pain and the development of contractures. Besides causing cumulative structural damage, neuroinflammation occurring in MS leads to dynamic changes in motor circuit function and muscle tone that are caused by cytokines, prostaglandins, reactive oxygen species and stress hormones that affect neuronal circuits and thereby spasticity. The situation is complicated further by the fact that therapeutics used for the immunotherapy of MS may worsen spasticity and drugs used for the symptomatic treatment of spasticity have been shown to have the potential to alter immune cell function and CNS autoimmunity itself. This review summarizes the current knowledge on the immunologic pathways that are involved in the development, maintenance, dynamic changes and pharmacological modulation of spasticity in MS.