Fingolimod for the treatment of neurological diseases-state of play and future perspectives

Therapeutic Potential of Fingolimod on Psychological Symptoms and Cognitive Function in Neuropsychiatric and Neurological Disorders

Neuropsychiatric and neurological disorders pose a significant global health burden, highlighting the need for innovative therapeutic approaches. Fingolimod (FTY720), a common drug to treat multiple sclerosis, has shown promising efficacy against various neuropsychiatric and neurological disorders. Fingolimod exerts its neuroprotective effects by targeting multiple cellular and molecular processes, such as apoptosis, oxidative stress, neuroinflammation, and autophagy. By modulating Sphingosine-1-Phosphate Receptor activity, a key regulator of immune cell trafficking and neuronal function, it also affects synaptic activity and strengthens memory formation. In the hippocampus, fingolimod decreases glutamate levels and increases GABA levels, suggesting a potential role in modulating synaptic transmission and neuronal excitability. Taken together, fingolimod has emerged as a promising neuroprotective agent for neuropsychiatric and neurological disorders. Its broad spectrum of cellular and molecular effects, including the modulation of apoptosis, oxidative stress, neuroinflammation, autophagy, and synaptic plasticity, provides a comprehensive therapeutic approach for these debilitating conditions. Further research is warranted to fully elucidate the mechanisms of action of fingolimod and optimize its use in the treatment of neuropsychiatric and neurological disorders.

Immuno-MRI for Stroke Diagnosis and Prognosis

Following a stroke, an inflammatory response occurs, characterized by an increased blood-brain barrier permeability, expression of endothelial trafficking molecules, and infiltration of immune cells. Adhesion molecules expressed on activated brain endothelial cells are potential biomarkers of intraparenchymal inflammation. However, in current clinical practice, it is not possible to measure endothelial activation using clinically available imaging. Using targeted micro-sized particles of iron oxide (MPIO), immuno-MRI enables the detection of endothelial adhesion molecules at high resolution and, consequently, facilitates the detection of stroke-induced brain inflammation. In this review, we highlight the most recent studies that used immuno-MRI in models of neurovascular disorders, including transient ischemic attack, ischemic stroke, intracranial hemorrhage, and subarachnoid hemorrhage. We also discuss the potential of immuno-MRI in clinical practice and the necessary next steps for its implementation in patients.

Quercetin regulates dendritic cell activation by targeting STAT4 in the treatment of experimental autoimmune encephalomyelitis

Multiple sclerosis (MS) is a class of autoimmune diseases mainly caused by the immune system attacking the myelin sheath of the axons in the nervous system. Although the pathogenesis of MS is complex, studies have shown that dendritic cells (DCs) play a vital role in the pathogenesis of MS. Quercetin (QU) has a unique advantage in clinical application, especially for treating autoimmune diseases. However, the mechanism of QU in the treatment of experimental autoimmune encephalomyelitis (EAE) remains unclear. In this study, we explore the potential role of QU in EAE. Finally, we find that QU has anti-inflammatory activities and neural protective effects in EAE. The experimental results suggest that the cellular basis for QU's function is to inhibit the activation of DCs while modulating the Th17 cell differentiation in the co-culture system. Further, QU may target STAT4 to inhibit its activation in DCs. This work will be of great significance for the future development and utilization of QU.

Drug repurposing for neurodegenerative diseases

Neurodegenerative diseases (NDDs) are neuronal problems that include the brain and spinal cord and result in loss of sensory and motor dysfunction. Common NDDs include Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), Multiple Sclerosis (MS), and Amyotrophic Lateral Sclerosis (ALS) etc. The occurrence of these diseases increases with age and is one of the challenging problems among elderly people. Though, several scientific research has demonstrated the key pathologies associated with NDDs still the underlying mechanisms and molecular details are not well understood and need to be explored and this poses a lack of effective treatments for NDDs. Several lines of evidence have shown that NDDs have a high prevalence and affect more than a billion individuals globally but still, researchers need to work forward in identifying the best therapeutic target for NDDs. Thus, several researchers are working in the directions to find potential therapeutic targets to alter the disease pathology and treat the diseases. Several steps have been taken to identify the early detection of the disease and drug repurposing for effective treatment of NDDs. Moreover, it is logical that current medications are being evaluated for their efficacy in treating such disorders; therefore, drug repurposing would be an efficient, safe, and cost-effective way in finding out better medication. In the current manuscript we discussed the utilization of drugs that have been repurposed for the treatment of AD, PD, HD, MS, and ALS.

Alzheimer's disease manifests abnormal sphingolipid metabolism

Introduction

Alzheimer's disease (AD) is associated with disturbed metabolism, prompting investigations into specific metabolic pathways that may contribute to its pathogenesis and pathology. Sphingolipids have garnered attention due to their known physiological impact on various diseases.

Methods

We conducted comprehensive profiling of sphingolipids to understand their possible role in AD. Sphingolipid levels were measured in AD brains, Cerad score B brains, and controls, as well as in induced pluripotent stem (iPS) cells (AD, PS, and control), using liquid chromatography mass spectrometry.

Results

AD brains exhibited higher levels of sphingosine (Sph), total ceramide 1-phosphate (Cer1P), and total ceramide (Cer) compared to control and Cerad-B brains. Deoxy-ceramide (Deoxy-Cer) was elevated in Cerad-B and AD brains compared to controls, with increased sphingomyelin (SM) levels exclusively in Cerad-B brains. Analysis of cell lysates revealed elevated dihydroceramide (dhSph), total Cer1P, and total SM in AD and PS cells versus controls. Multivariate analysis highlighted the relevance of Sph, Cer, Cer1P, and SM in AD pathology. Machine learning identified Sph, Cer, and Cer1P as key contributors to AD.

Discussion

Our findings suggest the potential importance of Sph, Cer1P, Cer, and SM in the context of AD pathology. This underscores the significance of sphingolipid metabolism in understanding and potentially targeting mechanisms underlying AD.

Sphingosine-1-phosphate Signalling in Aneurysmal Subarachnoid Haemorrhage: Basic Science to Clinical Translation

Sphingosine-1-phosphate (S1P) is generated intracellularly and, when transported to the extracellular compartment, predominantly signals through S1P receptors. The S1P signalling pathway has been implicated in the pathophysiology of neurological injury following aneurysmal subarachnoid haemorrhage (aSAH). In this review, we bring together all the available data regarding the role of S1P in neurological injury following aSAH. There is agreement in the literature that S1P increases in the cerebrospinal fluid following aSAH and leads to cerebral artery vasospasm. On the other hand, the role of S1P in the parenchyma is less clear cut, with different studies arguing for beneficial and deleterious effects. A parsimonious interpretation of this apparently conflicting data is presented. We discuss the potential of S1P receptor modulators, in clinical use for multiple sclerosis, to be repurposed for aSAH. Finally, we highlight the gaps in our knowledge of S1P signalling in humans, the clinical challenges of targeting the S1P pathway after aSAH and other research priorities.

Fingolimod improves diffuse brain injury by promoting AQP4 polarization and functional recovery of the glymphatic system

BACKGROUND

Diffuse brain injury (DBI) models are characterized by intense global brain inflammation and edema, which characterize the most severe form of TBI. In a previous experiment, we found that fingolimod promoted recovery after controlled cortical impact injury (CCI) by modulating inflammation around brain lesions. However, it remains unclear whether fingolimod can also attenuate DBI because of its different injury mechanisms. Furthermore, whether fingolimod has additional underlying effects on repairing DBI is unknown.

METHODS

The impact acceleration model of DBI was established in adult Sprague-Dawley rats. Fingolimod (0.5 mg/kg) was administered 0.5, 24, and 48 h after injury for 3 consecutive days. Immunohistochemistry, immunofluorescence analysis, cytokine array, and western blotting were used to evaluate inflammatory cells, inflammatory factors, AQP4 polarization, apoptosis in brain cells, and the accumulation of APP after DBI in rats. To evaluate the function of the glymphatic system (GS), a fluorescent tracer was injected into the cistern. The neural function of rats with DBI was evaluated using various tests, including the modified neurological severity score (mNSS), horizontal ladder-crossing test, beam walking test, and tape sensing and removal test. Brain water content was also measured.

RESULTS

Fingolimod administration for 3 consecutive days could reduce the levels of inflammatory cytokines, neutrophil recruitment, microglia, and astrocyte activation in the brain following DBI. Moreover, fingolimod reduced apoptotic protein expression, brain cell apoptosis, brain edema, and APP accumulation. Additionally, fingolimod inhibited the loss of AQP4 polarization, improved lymphatic system function, and reduced damage to nervous system function. Notably, inhibiting the GS weakened the therapeutic effect of fingolimod on the neurological function of rats with DBI and increased the accumulation of APP in the brain.

CONCLUSIONS

In brief, these findings suggest that fingolimod alleviates whole-brain inflammation and GS system damage after DBI and that inhibiting the GS could weaken the positive effect of fingolimod on nerve function in rats with DBI. Thus, inhibiting inflammation and regulating the GS may be critical for the therapeutic effect of fingolimod on DBI.

Density of Sphingosine-1-Phosphate Receptors Is Altered in Cortical Nerve-Terminals of Insulin-Resistant Goto-Kakizaki Rats and Diet-Induced Obese Mice

Sphingosine-1-phosphate (S1P) is a phosphosphingolipid with pleiotropic biological functions. S1P acts as an intracellular second messenger, as well as extracellular ligand to five G-protein coupled receptors (S1PR1-5). In the brain, S1P regulates neuronal proliferation, apoptosis, synaptic activity and neuroglia activation. Moreover, S1P metabolism alterations have been reported in neurodegenerative disorders. We have previously reported that S1PRs are present in nerve terminals, exhibiting distinct sub-synaptic localization and neuromodulation actions. Since type 2 diabetes (T2D) causes synaptic dysfunction, we hypothesized that S1P signaling is modified in nerve terminals. In this study, we determined the density of S1PRs in cortical synaptosomes from insulin-resistant Goto-Kakizaki (GK) rats and Wistar controls, and from mice fed a high-fat diet (HFD) and low-fat-fed controls. Relative to their controls, GK rats showed similar cortical S1P concentration despite higher S1P levels in plasma, yet lower density of S1PR1, S1PR2 and S1PR4 in nerve-terminal-enriched membranes. HFD-fed mice exhibited increased plasma and cortical concentrations of S1P, and decreased density of S1PR1 and S1PR4. These findings point towards altered S1P signaling in synapses of insulin resistance and diet-induced obesity models, suggesting a role of S1P signaling in T2D-associated synaptic dysfunction.

Network pharmacology-and molecular docking-based investigation of Danggui blood-supplementing decoction in ischaemic stroke

Danggui blood-supplementing decoction (DBsD) is an herbal preparation treating several diseases including stroke. The present study sought to investigate the potential mechanism of DBsD in ischaemic stroke (IS) using network pharmacology, molecular docking, and cell experiment. Based on the protein-protein (PPI) network analysis, MAPK1 (0.51, 12), KNG1 (0.57, 28), and TNF (0.64, 39) were found with relatively good performance in degree and closeness centrality. The functional enrichment analysis revealed that DBsD contributed to IS-related biological processes, molecule function, and presynaptic/postsynaptic cellular components. Pathway enrichment indicated that DBsD might protect IS by modulating multi-signalling pathways including the sphingolipid signalling pathway. Molecular docking verified the stigmasterol-KNG1, bifendate-TNF, and formononetin-MAPK1 pairs. Cell experiments confirmed the involvement of KNG1 and sphingolipid signalling pathway in hippocampal neuronal cell apoptosis. This study showed that DBsD can protect neuronal cell injury after IS through multiple components, multiple targets, and multiple pathways.

Glial Sphingosine-Mediated Epigenetic Regulation Stabilizes Synaptic Function in Drosophila Models of Alzheimer's Disease

Destabilization of neural activity caused by failures of homeostatic regulation has been hypothesized to drive the progression of Alzheimer's Disease (AD). However, the underpinning mechanisms that connect synaptic homeostasis and the disease etiology are yet to be fully understood. Here, we demonstrated that neuronal overexpression of amyloid β (Aβ) causes abnormal histone acetylation in peripheral glia and completely blocks presynaptic homeostatic potentiation (PHP) at the neuromuscular junction in Drosophila The synaptic deficits caused by Aβ overexpression in motoneurons are associated with motor function impairment at the adult stage. Moreover, we found that a sphingosine analog drug, Fingolimod, ameliorates synaptic homeostatic plasticity impairment, abnormal glial histone acetylation, and motor behavior defects in the Aβ models. We further demonstrated that perineurial glial sphingosine kinase 2 (Sk2) is not only required for PHP, but also plays a beneficial role in modulating PHP in the Aβ models. Glial overexpression of Sk2 rescues PHP, glial histone acetylation, and motor function deficits that are associated with Aβ in Drosophila Finally, we showed that glial overexpression of Sk2 restores PHP and glial histone acetylation in a genetic loss-of-function mutant of the Spt-Ada-Gcn5 Acetyltransferase complex, strongly suggesting that Sk2 modulates PHP through epigenetic regulation. Both male and female animals were used in the experiments and analyses in this study. Collectively, we provided genetic evidence demonstrating that abnormal glial epigenetic alterations in Aβ models in Drosophila are associated with the impairment of PHP and that the sphingosine signaling pathway displays protective activities in stabilizing synaptic physiology.SIGNIFICANCE STATEMENT Fingolimod, an oral drug to treat multiple sclerosis, is phosphorylated by sphingosine kinases to generate its active form. It is known that Fingolimod enhances the cognitive function in mouse models of Alzheimer's disease (AD), but the role of sphingosine kinases in AD is not clear. We bridge this knowledge gap by demonstrating the relationship between impaired homeostatic plasticity and AD. We show that sphingosine kinase 2 (Sk2) in glial cells is necessary for homeostatic plasticity and that glial Sk2-mediated epigenetic signaling has a protective role in synapse stabilization. Our findings demonstrate the potential of the glial sphingosine signaling as a key player in glia-neuron interactions during homeostatic plasticity, suggesting it could be a promising target for sustaining synaptic function in AD.

The impact of fingolimod on Treg function in brain ischaemia

Fingolimod has generally shown neuroprotective effects in stroke models. Here, we tested the hypothesis that fingolimod modulates T-cell cytokine production towards a regulatory phenotype. Second, we investigated how fingolimod altered the Treg suppressive function and the sensitivity of effector T cells to regulation. Mice that had underwent the permanent electrocoagulation of the left middle cerebral artery received saline or fingolimod (0.5 mg/kg) daily for 10-days post-ischaemia. Fingolimod improved neurobehavioural recovery compared to saline control and increased Treg frequency in the periphery and brain. Tregs from fingolimod-treated animals had a higher expression of CCR8. Fingolimod increased the frequencies of CD4+ IL-10+ , CD4+ IFN-γ+ and CD4+ IL-10+ IFN-γ+ cells in spleen and blood, and CD4+ IL-17+ cells in the spleen, with only minor effects on CD8+ T-cell cytokine production. Treg from post-ischaemic mice had reduced suppressive function compared to Treg from non-ischaemic mice. Fingolimod treatment rescued this function against saline-treated but not fingolimod-treated CD4+ effector T cells. In conclusion, fingolimod seems to improve the suppressive function of Treg post-stroke while also increasing the resistance of CD4+ effector cells to this suppression. Fingolimod's capacity to increase both effector and regulatory functions may explain the lack of consistent improvement in functional recovery in experimental brain ischaemia.

Apolipoprotein M gene polymorphisms in childhood-onset type 1 diabetes in southern Brazil

Type 1 diabetes mellitus (T1DM), associated with autoimmune destruction of pancreatic β cells, is observed in children and adolescents.

OBJECTIVE

We investigated the potential association of the apolipoprotein M (APOM) polymorphisms rs707921, rs805264, rs805296, rs805297, and rs9404941 in childhood-onset T1DM (n = 144) and compared them to those in healthy (mostly Euro-Brazilian) children (n = 168).

METHODS

This project was approved by the Ethics Committee of the Federal University of Parana (CAAE 24676613.6.0000.0102). Genotyping was performed using PCR-restriction fragment length polymorphisms (rs805296 and rs9404941) and TaqMan probes (rs707921, rs805264, and rs805297).

RESULTS

All polymorphisms were in Hardy-Weinberg equilibrium. In the codominant model, no significant differences (P > 0.05) were observed in genotype and allele frequencies between healthy controls and children with T1DM. The minor allele frequencies (95% CI) for healthy subjects were rs707921 (A, 10.7%; 7-14%), rs805264 (A, 6.5%; 4-9%), rs805296 (C, 3.6%; 2-6%), rs805297 (A, 22.6%; 22-31%), and rs9404941 (C, 2.7%; 1-4%). The frequencies of the rs805297 A allele and rs805296 C allele were similar to those of other Caucasian populations; both the rs707921 and rs805264 A alleles were similar to American and Latin American populations, whereas that of the rs9404941 C allele was lower than that observed in the Caucasian and Asian populations.

CONCLUSIONS

Haplotype analysis suggests that rs805297-C, rs9404941-T, rs805296-T, rs805264-G, and rs707921-C conferred risk (OR: 4.25; 95% CI: 1.81-10.1) to childhood-onset T1DM in the Euro-Brazilian population.

Targeting Sphingosine 1-Phosphate Metabolism as a Therapeutic Avenue for Prostate Cancer

Prostate cancer (PC) is the second most common cancer in men worldwide. More than 65% of men diagnosed with PC are above 65. Patients with localized PC show high long-term survival, however with the disease progression into a metastatic form, it becomes incurable, even after strong radio- and/or chemotherapy. Sphingosine 1-phosphate (S1P) is a bioactive lipid that participates in all the steps of oncogenesis including tumor cell proliferation, survival, migration, invasion, and metastatic spread. The S1P-producing enzymes sphingosine kinases 1 and 2 (SK1 and SK2), and the S1P degrading enzyme S1P lyase (SPL), have been shown to be highly implicated in the onset, development, and therapy resistance of PC during the last 20 years. In this review, the most important studies demonstrating the role of S1P and S1P metabolic partners in PC are discussed. The different in vitro, ex vivo, and in vivo models of PC that were used to demonstrate the implication of S1P metabolism are especially highlighted. Furthermore, the most efficient molecules targeting S1P metabolism that are under preclinical and clinical development for curing PC are summarized. Finally, the possibility of targeting S1P metabolism alone or combined with other therapies in the foreseeable future as an alternative option for PC patients is discussed. Research Strategy: PubMed from INSB was used for article research. First, key words "prostate & sphingosine" were used and 144 articles were found. We also realized other combinations of key words as "prostate cancer bone metastasis" and "prostate cancer treatment". We used the most recent reviews to illustrate prostate cancer topic and sphingolipid metabolism overview topic.

The role of sphingosine 1-phosphate metabolism in brain health and disease

Lipids are essential structural and functional components of the central nervous system (CNS). Sphingolipids are ubiquitous membrane components which were discovered in the brain in the late 19^th century. In mammals, the brain contains the highest concentration of sphingolipids in the body. Sphingosine 1-phosphate (S1P) derived from membrane sphingolipids evokes multiple cellular responses which, depending on its concentration and localization, make S1P a double-edged sword in the brain. In the present review we highlight the role of S1P in brain development and focus on the often contrasting findings regarding its contributions to the initiation, progression and potential recovery of different brain pathologies, including neurodegeneration, multiple sclerosis (MS), brain cancers, and psychiatric illnesses. A detailed understanding of the critical implications of S1P in brain health and disease may open the door for new therapeutic options. Thus, targeting S1P-metabolizing enzymes and/or signaling pathways might help overcome, or at least ameliorate, several brain illnesses.

Antiparkinsonian Agents in Investigational Polymeric Micro- and Nano-Systems

Parkinson's disease (PD) is a devastating neurodegenerative disease characterized by progressive destruction of dopaminergic tissue in the central nervous system (CNS). To date, there is no cure for the disease, with current pharmacological treatments aimed at controlling the symptoms. Therefore, there is an unmet need for new treatments for PD. In addition to new therapeutic options, there exists the need for improved efficiency of the existing ones, as many agents have difficulties in crossing the blood-brain barrier (BBB) to achieve therapeutic levels in the CNS or exhibit inappropriate pharmacokinetic profiles, thereby limiting their clinical benefits. To overcome these limitations, an interesting approach is the use of drug delivery systems, such as polymeric microparticles (MPs) and nanoparticles (NPs) that allow for the controlled release of the active ingredients targeting to the desired site of action, increasing the bioavailability and efficacy of treatments, as well as reducing the number of administrations and adverse effects. Here we review the polymeric micro- and nano-systems under investigation as potential new therapies for PD.

Microglial polarization in TBI: Signaling pathways and influencing pharmaceuticals

Traumatic brain injury (TBI) is a serious disease that threatens life and health of people. It poses a great economic burden on the healthcare system. Thus, seeking effective therapy to cure a patient with TBI is a matter of great urgency. Microglia are macrophages in the central nervous system (CNS) and play an important role in neuroinflammation. When TBI occurs, the human body environment changes dramatically and microglia polarize to one of two different phenotypes: M1 and M2. M1 microglia play a role in promoting the development of inflammation, while M2 microglia play a role in inhibiting inflammation. How to regulate the polarization direction of microglia is of great significance for the treatment of patients with TBI. The polarization of microglia involves many cellular signal transduction pathways, such as the TLR-4/NF-κB, JAK/STAT, HMGB1, MAPK, and PPAR-γ pathways. These provide a theoretical basis for us to seek therapeutic drugs for the patient with TBI. There are several drugs that target these pathways, including fingolimod, minocycline, Tak-242 and erythropoietin (EPO), and CSF-1. In this study, we will review signaling pathways involved in microglial polarization and medications that influence this process.

Ceramide and Sphingosine-1-Phosphate in Neurodegenerative Disorders and Their Potential Involvement in Therapy

Neurodegenerative disorders (ND) are progressive diseases of the nervous system, often without resolutive therapy. They are characterized by a progressive impairment and loss of specific brain regions and neuronal populations. Cellular and animal model studies have identified several molecular mechanisms that play an important role in the pathogenesis of ND. Among them are alterations of lipids, in particular sphingolipids, that play a crucial role in neurodegeneration. Overall, during ND, ceramide-dependent pro-apoptotic signalling is promoted, whereas levels of the neuroprotective spingosine-1-phosphate are reduced. Moreover, ND are characterized by alterations of the metabolism of complex sphingolipids. The finding that altered sphingolipid metabolism has a role in ND suggests that its modulation might provide a useful strategy to identify targets for possible therapies. In this review, based on the current literature, we will discuss how bioactive sphingolipids (spingosine-1-phosphate and ceramide) are involved in some ND (Alzheimer’s disease, Parkinson’s disease, amyotrophic lateral sclerosis) and their possible involvement in therapies.

Sphingosine 1-Phoshpate Receptors are Located in Synapses and Control Spontaneous Activity of Mouse Neurons in Culture

Sphingosine-1-phosphate (S1P) is best known for its roles as vascular and immune regulator. Besides, it is also present in the central nervous system (CNS) where it can act as neuromodulator via five S1P receptors (S1PRs), and thus control neurotransmitter release. The distribution of S1PRs in the active zone and postsynaptic density of CNS synapses remains unknown. In the current study, we investigated the localization of S1PR1-5 in synapses of the mouse cortex. Cortical nerve terminals purified in a sucrose gradient were endowed with all five S1PRs. Further subcellular fractionation of cortical nerve terminals revealed S1PR2 and S1PR4 immunoreactivity in the active zone of presynaptic nerve terminals. Interestingly, only S1PR2 and S1PR3 immunoreactivity was found in the postsynaptic density. All receptors were present outside the active zone of nerve terminals. Neurons in the mouse cortex and primary neurons in culture showed immunoreactivity against all five S1PRs, and Ca²⁺ imaging revealed that S1P inhibits spontaneous neuronal activity in a dose-dependent fashion. When testing selective agonists for each of the receptors, we found that only S1PR1, S1PR2 and S1PR4 control spontaneous neuronal activity. We conclude that S1PR2 and S1PR4 are located in the active zone of nerve terminals and inhibit neuronal activity. Future studies need to test whether these receptors modulate stimulation-induced neurotransmitter release.

Fingolimod increases parvalbumin-positive neurons in adult mice

In recent years, it has been shown that central nervous system agents, such as antidepressants and antiepileptic drugs, reopen a critical period in mature animals. Fingolimod, which is used for the treatment of multiple sclerosis, also restores neuroplasticity. In this study, we investigated the effects of parvalbumin (PV)-positive neurons and perineuronal nets (PNN) on fingolimod administration with respect to neuroplasticity. Fingolimod was chronically administered intraperitoneally to mature mice. PV-positive neurons and PNN in the hippocampus, prefrontal cortex, and somatosensory cortex were analyzed. An increase in PV-positive neurons was observed in the hippocampus, prefrontal cortex, and somatosensory cortex of the fingolimod-treated mice. An increase in Wisteria floribunda agglutinin-positive PNN was confirmed in mice treated with fingolimod in the somatosensory cortex only. Fingolimod increased the density of PV-positive neurons in the brains of mature mice. The results indicate that fingolimod may change the critical period in mature animals.

Skeletal Muscle and COVID-19: The Potential Involvement of Bioactive Sphingolipids

SARS-CoV-2 virus infection is the cause of the coronavirus disease 2019 (COVID-19), which is still spreading over the world. The manifestation of this disease can range from mild to severe and can be limited in time (weeks) or persist for months in about 30–50% of patients. COVID-19 is considered a multiple organ dysfunction syndrome and the musculoskeletal system manifestations are beginning to be considered of absolute importance in both COVID-19 patients and in patients recovering from the SARS-CoV-2 infection. Musculoskeletal manifestations of COVID-19 and other coronavirus infections include loss of muscle mass, muscle weakness, fatigue or myalgia, and muscle injury. The molecular mechanisms by which SARS-CoV-2 can cause damage to skeletal muscle (SkM) cells are not yet well understood. Sphingolipids (SLs) represent an important class of eukaryotic lipids with structural functions as well as bioactive molecules able to modulate crucial processes, including inflammation and viral infection. In the last two decades, several reports have highlighted the role of SLs in modulating SkM cell differentiation, regeneration, aging, response to insulin, and contraction. This review summarizes the consequences of SARS-CoV-2 infection on SkM and the potential involvement of SLs in the tissue responses to virus infection. In particular, we highlight the role of sphingosine 1-phosphate signaling in order to aid the prediction of novel targets for preventing and/or treating acute and long-term musculoskeletal manifestations of virus infection in COVID-19.

Vesicle Fusion as a Target Process for the Action of Sphingosine and Its Derived Drugs

The fusion of membranes is a central part of the physiological processes involving the intracellular transport and maturation of vesicles and the final release of their contents, such as neurotransmitters and hormones, by exocytosis. Traditionally, in this process, proteins, such SNAREs have been considered the essential components of the fusion molecular machinery, while lipids have been seen as merely structural elements. Nevertheless, sphingosine, an intracellular signalling lipid, greatly increases the release of neurotransmitters in neuronal and neuroendocrine cells, affecting the exocytotic fusion mode through the direct interaction with SNAREs. Moreover, recent studies suggest that FTY-720 (Fingolimod), a sphingosine structural analogue used in the treatment of multiple sclerosis, simulates sphingosine in the promotion of exocytosis. Furthermore, this drug also induces the intracellular fusion of organelles such as dense vesicles and mitochondria causing cell death in neuroendocrine cells. Therefore, the effect of sphingosine and synthetic derivatives on the heterologous and homologous fusion of organelles can be considered as a new mechanism of action of sphingolipids influencing important physiological processes, which could underlie therapeutic uses of sphingosine derived lipids in the treatment of neurodegenerative disorders and cancers of neuronal origin such neuroblastoma.

A novel fatty acid-binding protein 5 and 7 inhibitor ameliorates oligodendrocyte injury in multiple sclerosis mouse models

BACKGROUND

Multiple sclerosis (MS) is an autoimmune disease characterised by the demyelination of mature oligodendrocytes in the central nervous system. Recently, several studies have indicated the vital roles of fatty acid-binding proteins (FABPs) 5 and 7 in regulating the immune response.

METHODS

We assessed a novel FABP5/FABP7 inhibitor, FABP ligand 6 (MF 6), as a potential therapeutic for MS therapy. In vivo, we established MOG_35-55-administered experimental autoimmune encephalomyelitis (EAE) mice as an MS mouse model, followed by prophylactic and symptomatic treatment with MF 6. The therapeutic effect of MF 6 was determined using behavioural and biochemical analyses. In vitro, MF 6 effects on astrocytes and oligodendrocytes were examined using both astrocyte primary culture and KG-1C cell lines.

FINDINGS

Prophylactic and symptomatic MF 6 therapy reduced myelin loss and clinical EAE symptoms. Furthermore, oxidative stress levels and GFAP-positive and ionised calcium-binding adaptor protein-1-positive cells were reduced in the spinal cord of MF 6-treated mice. In addition, MF 6 attenuated lipopolysaccharide-stimulated interleukin-1β and tumour necrosis factor-α accumulation in primary astrocyte culture. Moreover, MF 6 indicated a powerful protective function for the mitochondria in the oligodendrocytes of EAE mice via FABP5 inhibition.

INTERPRETATIONS

MF 6 is a potent inhibitor of FABP5 and FABP7; targeted inhibition of the two proteins may confer potential therapeutic effects in MS via immune inhibition and oligodendrocyte protection.

FUNDING

This work was supported by the Strategic Research Program for Brain Sciences from the Japan Agency for Medical Research and Development (JP17dm0107071, JP18dm0107071, JP19dm0107071, and JP20dm0107071).

Microglia and BDNF at the crossroads of stressor related disorders: Towards a unique trophic phenotype

Stressors ranging from psychogenic/social to neurogenic/injury to systemic/microbial can impact microglial inflammatory processes, but less is known regarding their effects on trophic properties of microglia. Recent studies do suggest that microglia can modulate neuronal plasticity, possibly through brain derived neurotrophic factor (BDNF). This is particularly important given the link between BDNF and neuropsychiatric and neurodegenerative pathology. We posit that certain activated states of microglia play a role in maintaining the delicate balance of BDNF release onto neuronal synapses. This focused review will address how different "activators" influence the expression and release of microglial BDNF and address the question of tropomyosin receptor kinase B (TrkB) expression on microglia. We will then assess sex-based differences in microglial function and BDNF expression, and how microglia are involved in the stress response and related disorders such as depression. Drawing on research from a variety of other disorders, we will highlight challenges and opportunities for modulators that can shift microglia to a "trophic" phenotype with a view to potential therapeutics relevant for stressor-related disorders.

Histological, behavioural and flow cytometric datasets relating to acute ischaemic stroke in young, aged and ApoE-/- mice in the presence and absence of immunomodulation with fingolimod

In this work, the sphingosine-1-phosphate receptor modulator fingolimod was assessed as a preclinical candidate for the treatment of acute ischaemic stroke according to the Stroke Therapy Academic Industry Roundtable (STAIR) preclinical recommendations. Young (15-17 weeks), aged (72-73 weeks), and ApoE^-/- mice (20-21 weeks) fed a high fat diet (all C57BL/6 mice) underwent permanent electrocoagulation of the left middle cerebral artery. Mice received either saline or fingolimod (0.5 mg/kg or 1 mg/kg) at 2-, 24-, and 48-hours post-ischaemia via intraperitoneal (i.p.) injection. Another cohort of young mice (8-9 and 17-19 weeks) received short-term (5 days) or long-term (10 days) fingolimod (0.5 mg/kg) treatment in a treatment duration study. For young, aged, and ApoE^-/- mice, motor behavioural tests (cylinder and grid-walking) were performed at days 0, 3, and 7 post-ischaemia to evaluate neurobehavioural recovery. In the treatment duration study, the grid-walking test was performed at days 0, 2, 5 and 10 post-ischaemia. Brain tissue sections were stained with haematoxylin and eosin (H&E), and NeuN to quantify tissue damage. Flow cytometry was used to quantify T cell populations in blood, spleen, and lymph nodes. The data presented in this article improves our understanding of the potential neuroprotective and immunomodulatory effects of fingolimod in a mouse model of brain ischaemia. Such data may be significant in the design of future preclinical and clinical stroke studies for fingolimod.

The effect of fingolimod on regulatory T cells in a mouse model of brain ischaemia

Background

The role of the immune system in stroke is well-recognised. Fingolimod, an immunomodulatory agent licensed for the management of relapsing-remitting multiple sclerosis, has been shown to provide benefit in rodent models of stroke. Its mechanism of action, however, remains unclear. We hypothesised fingolimod increases the number and/or function of regulatory T cells (Treg), a lymphocyte population which promotes stroke recovery. The primary aim of this study was to rigorously investigate the effect of fingolimod on Tregs in a mouse model of brain ischaemia. The effect of fingolimod in mice with common stroke-related comorbidities (ageing and hypercholesteremia) was also investigated.

Methods

Young (15–17 weeks), aged C57BL/6 mice (72–73 weeks), and ApoE^−/− mice fed a high-fat diet (20–21 weeks) underwent permanent electrocoagulation of the left middle cerebral artery. Mice received either saline or fingolimod (0.5 mg/kg or 1 mg/kg) at 2, 24, and 48 h post-ischaemia via intraperitoneal injection. Another cohort of young mice (8–9, 17–19 weeks) received short-term (5 days) or long-term (10 days) fingolimod (0.5 mg/kg) treatment. Flow cytometry was used to quantify Tregs in blood, spleen, and lymph nodes. Immunohistochemistry was used to quantify FoxP3+ cell infiltration into the ischaemic brain.

Results

Fingolimod significantly increased the frequency of Tregs within the CD4+ T cell population in blood and spleen post-ischaemia in all three mouse cohorts compared to untreated ischemic mice. The highest splenic Treg frequency in fingolimod-treated mice was observed in ApoE^−/− mice (9.32 ± 1.73% vs. 7.8 ± 3.01% in young, 6.09 ± 1.64% in aged mice). The highest circulating Treg frequency was also noted in ApoE^−/− mice (8.39 ± 3.26% vs. 5.43 ± 2.74% in young, 4.56 ± 1.60% in aged mice). Fingolimod significantly increased the number of FoxP3+ cells in the infarct core of all mice. The most pronounced effects were seen when mice were treated for 10 days post-ischaemia.

Conclusions

Fingolimod increases Treg frequency in spleen and blood post-ischaemia and enhances the number of FoxP3+ cells in the ischaemic brain. The effect of fingolimod on this regulatory cell population may underlie its neuroprotective activity and could be exploited as part of future stroke therapy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-021-02083-5.

Preclinical and Clinical Evidence for the Involvement of Sphingosine 1-Phosphate Signaling in the Pathophysiology of Vascular Cognitive Impairment

Sphingosine 1-phosphates (S1Ps) are bioactive lipids that mediate a diverse range of effects through the activation of cognate receptors, S1P₁-S1P₅. Scrutiny of S1P-regulated pathways over the past three decades has identified important and occasionally counteracting functions in the brain and cerebrovascular system. For example, while S1P₁ and S1P₃ mediate proinflammatory effects on glial cells and directly promote endothelial cell barrier integrity, S1P₂ is anti-inflammatory but disrupts barrier integrity. Cumulatively, there is significant preclinical evidence implicating critical roles for this pathway in regulating processes that drive cerebrovascular disease and vascular dementia, both being part of the continuum of vascular cognitive impairment (VCI). This is supported by clinical studies that have identified correlations between alterations of S1P and cognitive deficits. We review studies which proposed and evaluated potential mechanisms by which such alterations contribute to pathological S1P signaling that leads to VCI-associated chronic neuroinflammation and neurodegeneration. Notably, S1P receptors have divergent but overlapping expression patterns and demonstrate complex interactions. Therefore, the net effect produced by S1P represents the cumulative contributions of S1P receptors acting additively, synergistically, or antagonistically on the neural, vascular, and immune cells of the brain. Ultimately, an optimized therapeutic strategy that targets S1P signaling will have to consider these complex interactions.

Selective modulation of trans-endothelial migration of lymphocyte subsets in multiple sclerosis patients under fingolimod treatment

Multiple sclerosis (MS) is an autoimmune disorder where auto-aggressive T cells target the central nervous system (CNS), causing demyelination. The trans-endothelial migration of leucocytes across the blood-brain barrier (BBB) is one of the earliest CNS events in MS pathogenesis. We examined the effect of the disease state and treatment with fingolimod on the transmigration of peripheral blood mononuclear cells (PBMCs) in an in vitro BBB model. Patients' leucocyte numbers, subsets and phenotypes were assessed by flow cytometry. As expected, fingolimod treatment induced a significant reduction in T cell and B cell numbers compared to untreated MS patients and healthy controls. Interestingly fingolimod led to a marked reduction of CD4+ and a significant increase in CD8⁺ cell numbers. In migrated cells, only CD3⁺ cell numbers were reduced in fingolimod-treated, compared to untreated patients; it had no effect on B cell or monocyte transmigration. T cells were then differentiated into naïve, effector and memory subsets based on their expression of CCR7. This showed that MS patients had increased numbers of effector memory CD4⁺ cells re-expressing CD45RA (TEMRA) and a decrease in central memory (CM) CD8⁺ cells. The former was corrected by fingolimod, while the latter was not. CM CD4⁺ and CD8⁺ cells migrated across BBB more efficiently in fingolimod-treated patients. We found that while fingolimod reduced the proportions of naïve CD19⁺ B cells, it significantly increased the proportions of these cells which migrated. When B cells were further stratified based on CD24, CD27 and CD38 expression, the only effect of fingolimod was an enhancement of CD24^hiCD27⁺ B cell migration, compared to untreated MS patients. The migratory capacities of CD8^hi Natural Killer (NK), CD8^dim NK and NK-T cells were also reduced by fingolimod. While the disease-modifying effects of fingolimod are currently explained by its effect on reducing circulating auto-aggressive lymphocytes, our data suggests that fingolimod may also have a direct though differential effect on the trans-endothelial migration of circulating lymphocyte populations.

Personalized and translational approach for malignant brain tumors in the era of precision medicine: the strategic contribution of an experienced neurosurgery laboratory in a modern neurosurgery and neuro-oncology department

Personalized medicine (PM) aims to optimize patient management, taking into account the individual traits of each patient. The main purpose of PM is to obtain the best response, improving health care and lowering costs. Extending traditional approaches, PM introduces novel patient-specific paradigms from diagnosis to treatment, with greater precision. In neuro-oncology, the concept of PM is well established. Indeed, every neurosurgical intervention for brain tumors has always been highly personalized. In recent years, PM has been introduced in neuro-oncology also to design and prescribe specific therapies for the patient and the patient's tumor. The huge advances in basic and translational research in the fields of genetics, molecular and cellular biology, transcriptomics, proteomics, and metabolomics have led to the introduction of PM into clinical practice. The identification of a patient's individual variation map may allow to design selected therapeutic protocols that ensure successful outcomes and minimize harmful side effects. Thus, clinicians can switch from the "one-size-fits-all" approach to PM, ensuring better patient care and high safety margin. Here, we review emerging trends and the current literature about the development of PM in neuro-oncology, considering the positive impact of innovative advanced researches conducted by a neurosurgical laboratory.

Sphingosine-1-Phosphate: Its Pharmacological Regulation and the Treatment of Multiple Sclerosis: A Review Article

Sphingosine-1-phosphate (S1P), via its G-protein-coupled receptors, is a signaling molecule with important regulatory properties on numerous, widely varied cell types. Five S1P receptors (S1PR1-5) have been identified, each with effects determined by their unique G-protein-driven downstream pathways. The discovery that lymphocyte egress from peripheral lymphoid organs is promoted by S1P via S1PR-1 stimulation led to the development of pharmacological agents which are S1PR antagonists. These agents promote lymphocyte sequestration and reduce lymphocyte-driven inflammatory damage of the central nervous system (CNS) in animal models, encouraging their examination of efficacy in the treatment of multiple sclerosis (MS). Preclinical research has also demonstrated direct protective effects of S1PR antagonists within the CNS, by modulation of S1PRs, particularly S1PR-1 and S1PR-5, and possibly S1PR-2, independent of effects upon lymphocytes. Three of these agents, fingolimod, siponimod and ozanimod have been approved, and ponesimod has been submitted for regulatory approval. In patients with MS, these agents reduce relapse risk, sustained disability progression, magnetic resonance imaging markers of disease activity, and whole brain and/or cortical and deep gray matter atrophy. Future opportunities in the development of more selective and intracellular S1PR-driven downstream pathway modulators may expand the breadth of agents to treat MS.

Ceramide signalling in inherited and multifactorial brain metabolic diseases

In recent years, research on sphingolipids, particularly ceramides, has attracted increased attention, revealing the important roles and many functions of these molecules in several human neurological disorders. The nervous system is enriched with important classes of sphingolipids, e.g., ceramide and its derivatives, which compose the major portion of this group, particularly in the form of myelin. Ceramides have also emerged as important nodes for lipid signalling, both inside the cell and between cells. Until recently, knowledge about ceramides in the nervous system was limited, but currently, multiple links between ceramide signalling and neurological diseases have been reported. Alterations in the regulation of ceramide pathobiology have been shown to influence the risk of developing neurometabolic diseases. Thus, these molecules are critically important in the maintenance and development of the nervous system and are culprits or major contributors to the development of brain disorders, either inherited or multifactorial. In the present review, we highlight the critical role of ceramide signalling in several different neurological disorders as well as the effects of their perturbations and discuss how this emerging class of bioactive sphingolipids has attracted interest in the field of neurological diseases.

Role of sphingolipid metabolism in neurodegeneration

Sphingolipids are a class of lipids highly enriched in the central nervous system (CNS), which shows great diversity and complexity, and has been implicated in CNS development and function. Alterations in sphingolipid metabolism have been described in multiple diseases, including those affecting the central nervous system (CNS). In this review, we discuss the role of sphingolipid metabolism in neurodegeneration, evaluating its direct roles in neuron development and health, and also in the induction of neurotoxic activities in CNS-resident astrocytes and microglia in the context of neurologic diseases such as multiple sclerosis and Alzheimer's disease. Finally, we focus on the metabolism of gangliosides and sphingosine-1-phosphate, its contribution to the pathogenesis of neurologic diseases, and its potential as a candidate target for the therapeutic modulation of neurodegeneration.

Effects of fingolimod treatments on alanine transaminase and aspartate transaminase levels in patients with multiple sclerosis

INTRODUCTION

Multiple Sclerosis (MS) is a chronic neurological disorder with no known cause or cure. Fingolimod (FTY720) is an oral medication recently approved for the treatment of MS as well as other diseases with autoimmune aspects. However, the drug is not without side effects. The severity and prevalence of these side effects are not completely understood. One of the most common causes for the patient cessation of fingolimod is an increase in liver enzymes, indicating possible inflammation or damage to liver cells. Alanine transaminase (ALT) and aspartate transaminase (AST) are the most common liver enzymes used as indicators of hepatic health.

OBJECTIVES

This three-month prospective cohort study selected patients who were diagnosed with relapsing-remitting MS (RRMS) and who were not taking fingolimod oral treatment. ALT and AST levels were determined for these patients at baseline and then after three months of taking FTY720 to determine if these liver enzymes were changed.

METHODS

36 RRMS patients completed this study, which lasted three months. They were started on 0.5 oral FTY720 after approval from a physician and completion of an AST/ALT blood test. Baseline levels were determined and then taken again three months later. Statistical analysis of these values was performed using P<0.05 as a significance threshold.

RESULTS

In this sample of patients, only ALT levels were significantly increased after fingolimod treatment in the general cohort (P=0.00). The general cohort showed an insignificant increase in AST levels. In male and female populations separately, AST was not significantly increased. ALT was only significantly increased in men (P=0.00) and insignificantly increased in women.

CONCLUSION

This study further confirms our concerns about fingolimod's possible effects on the liver. While these numbers do support the claim that the drug does on average increase ALT in patient populations, it is important to note that most of these patients have no real hepatic side effects. In addition, previous studies have cited a return to normal ALT and AST levels after cessation of fingolimod, suggesting its effects are temporary and not severely damaged in the usual patient.

Brain Derived Exosomes Are a Double-Edged Sword in Alzheimer's Disease

Brain derived exosomes (BDEs) are extracellular nanovesicles that are collectively released by all cell lineages of the central nervous system and contain cargo from their original cells. They are emerging as key mediators of communication and waste management among neurons, glial cells and connective tissue during both physiological and pathological conditions in the brain. We review the rapidly growing frontier of BDEs biology in recent years including the involvement of exosomes in neuronal development, maintenance and communication through their multiple signaling functions. Particularly, we highlight the important role of exosomes in Alzheimer's disease (AD), both as a pathogenic agent and as a disease biomarker. Our understanding of such unique nanovesicles may offer not only answers about the (patho) physiological course in AD and associated neurodegenerative diseases but also ideal methods to develop these vesicles as vehicles for drug delivery or as tools to monitor brain diseases in a non-invasive manner because crossing the blood brain barrier is an inherent capability of exosomes. BDEs have potential as biomarkers and as therapeutic tools for AD and related brain disorders in the near future.

Fingolimod Affects Transcription of Genes Encoding Enzymes of Ceramide Metabolism in Animal Model of Alzheimer's Disease

The imbalance in sphingolipid signaling may be critically linked to the upstream events in the neurodegenerative cascade of Alzheimer’s disease (AD). We analyzed the influence of mutant (V717I) amyloid β precursor protein (AβPP) transgene on sphingolipid metabolism enzymes in mouse hippocampus. At 3 months of age AβPP/Aβ presence upregulated enzymes of ceramide turnover on the salvage pathway: ceramide synthases (CERS2, CERS4, CERS6) and also ceramidase ACER3. At 6 months, only CERS6 was elevated, and no ceramide synthase was increased at 12 months. However, sphingomyelin synthases, which utilize ceramide on the sphingomyelinase pathway, were reduced (SGMS1 at 12 and SGMS2 at 6 months). mRNAs for sphingomyelin synthases SGMS1 and SGMS2 were also significantly downregulated in human AD hippocampus and neocortex when compared with age-matched controls. Our findings suggest early-phase deregulation of sphingolipid homeostasis in favor of ceramide signaling. Fingolimod (FTY720), a modulator of sphingosine-1-phosphate receptors countered the AβPP-dependent upregulation of hippocampal ceramide synthase CERS2 at 3 months. Moreover, at 12 months, FTY720 increased enzymes of ceramide-sphingosine turnover: CERS4, ASAH1, and ACER3. We also observed influence of fingolimod on the expression of the sphingomyelinase pathway enzymes. FTY720 counteracted the AβPP-linked reduction of sphingomyelin synthases SGMS1/2 (at 12 and 6 months, respectively) and led to elevation of sphingomyelinase SMPD2 (at 6 and 12 months). Therefore, our results demonstrate potentially beneficial, age-specific effects of fingolimod on transcription of sphingolipid metabolism enzymes in an animal model of AD.

Repurposed molecules for antiepileptogenesis: Missing an opportunity to prevent epilepsy?

Prevention of epilepsy is a great unmet need. Acute central nervous system (CNS) insults such as traumatic brain injury (TBI), cerebrovascular accidents (CVA), and CNS infections account for 15%-20% of all epilepsy. Following TBI and CVA, there is a latency of days to years before epilepsy develops. This allows treatment to prevent or modify postinjury epilepsy. No such treatment exists. In animal models of acquired epilepsy, a number of medications in clinical use for diverse indications have been shown to have antiepileptogenic or disease-modifying effects, including medications with excellent side effect profiles. These include atorvastatin, ceftriaxone, losartan, isoflurane, N-acetylcysteine, and the antiseizure medications levetiracetam, brivaracetam, topiramate, gabapentin, pregabalin, vigabatrin, and eslicarbazepine acetate. In addition, there are preclinical antiepileptogenic data for anakinra, rapamycin, fingolimod, and erythropoietin, although these medications have potential for more serious side effects. However, except for vigabatrin, there have been almost no translation studies to prevent or modify epilepsy using these potentially "repurposable" medications. We may be missing an opportunity to develop preventive treatment for epilepsy by not evaluating these medications clinically. One reason for the lack of translation studies is that the preclinical data for most of these medications are disparate in terms of types of injury, models within different injury type, dosing, injury-treatment initiation latencies, treatment duration, and epilepsy outcome evaluation mode and duration. This makes it difficult to compare the relative strength of antiepileptogenic evidence across the molecules, and difficult to determine which drug(s) would be the best to evaluate clinically. Furthermore, most preclinical antiepileptogenic studies lack information needed for translation, such as dose-blood level relationship, brain target engagement, and dose-response, and many use treatment parameters that cannot be applied clinically, for example, treatment initiation before or at the time of injury and dosing higher than tolerated human equivalent dosing. Here, we review animal and human antiepileptogenic evidence for these medications. We highlight the gaps in our knowledge for each molecule that need to be filled in order to consider clinical translation, and we suggest a platform of preclinical antiepileptogenesis evaluation of potentially repurposable molecules or their combinations going forward.

Sphingosine-1-Phosphate Receptors Modulators Decrease Signs of Neuroinflammation and Prevent Parkinson's Disease Symptoms in the 1-Methyl-4-Phenyl-1,2,3,6-Tetrahydropyridine Mouse Model

Sphingosine-1-phosphate (S1P) is a potent bioactive lipid mediator that acts as a natural ligand upon binding to five different receptors that are located in astrocytes, oligodendrocytes, microglial and neuronal cells. Recently, global activation of these receptors by FTY720 (fingolimod) has been suggested to provide neuroprotection in animal model of Parkinson’s disease (PD). Among S1P receptors, the subtype 1 (S1P1R) has been linked to features of neuroprotection and, using the selective agonist SEW2871, the present investigation assessed potential benefits (and mechanisms) of this receptor subtype in an established animal model of PD. We demonstrated that oral treatments with SEW2871 are able to provide protection to the same levels as FTY720 against loss of dopaminergic neurons and motor deficits in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) (30 mg/kg, i.p., 5 days) mouse model of PD. At the molecular level, we observed that the beneficial effects of both S1PR agonists were not associated with alterations in ERK and Akt levels, two markers of molecular adaptations in the striatum neurons. However, these compounds have the capacity to prevent signs of neuroinflammation such as the activation of astrocytes and glial cells, as well as MPTP-induced reduction of BDNF levels in key regions of the brain implicated in motor functions. These findings suggest that selective S1P1R modulation has the ability to provide neuroprotection in response to MPTP neurotoxicity. Targeting S1P1R in PD therapy may represent a prominent candidate for treatment of this neurodegenerative conditions.

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.

Sphingolipids as prognostic biomarkers of neurodegeneration, neuroinflammation, and psychiatric diseases and their emerging role in lipidomic investigation methods

Lipids play an important role in neurodegeneration, neuroinflammation, and psychiatric disorders and an imbalance in sphingolipid levels is associated with disease. Although early diagnosis and intervention of these disorders would clearly have favorable long-term outcomes, no diagnostic tests currently exist that can accurately identify people at risk. Reliable prognostic biomarkers that are easily accessible would be beneficial to determine therapy and treatment response in clinical trials. Recent advances in lipidomic investigation methods have greatly progressed the knowledge of sphingolipids in neurodegenerative and psychiatric disorders over the past decades although more longitudinal studies are needed to understand its exact role in these disorders to be used as potential tools in the clinic. In this review, we give an overview of the current knowledge of sphingolipids in neurodegenerative and psychiatric disorders and explore recent advances in investigation methods. Finally, the potential of sphingolipid metabolism products and signaling molecules as potential biomarkers for diagnosis, prognostic, or surrogate markers of treatment response is discussed.

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.

Biosynthesis of long chain base in sphingolipids in animals, plants and fungi

Long chain base (LCB) is a unique building block found in sphingolipids. The initial step of LCB biosynthesis stems from serine:palmitoyl-CoA transferase enzyme, producing 3-ketodihydrosphingosine with multiple regulatory proteins including small subunit SPT a/b and orosomucoid-like protein1-3. 3-Ketodihydrosphingosine reductase and sphingolipid Δ4-desaturase, both of them poorly characterized mammalian enzymes, play key roles for neurological homeostasis based on their pathogenic mutation in humans. Ceramide synthase in mammals has six isoforms with distinct phenotype in each knockout mouse. In plants and fungi, sphingolipids also contain phytosphingosine due to sphingolipid C4-hydroxylase. In contrast to previous notion that dietary intake might be its major route in animals, emerging evidences suggested that phytosphingosine biosynthesis does occur in some tissues such as the skin by mammalian C4-hydroxylase activity of the DEGS2 gene. This short review summarizes LCB biosynthesis with their associating metabolic pathways in animals, plants and fungi.

Sphingolipid is a group of lipids that contains a unique building block known as long chain base (LCB). LCB is susceptible to various biosynthetic reactions such as unsaturation, hydroxylation and methylation. A failure of these enzymatic reactions leads to the pathogenesis in humans with an elevation of LCB-derived specific biomarkers. Herein, we summarized emerging evidences in mammalian LCB biosynthesis in sphingolipids. Some unique metabolic pathways in plants and fungi were also discussed.

Neuroinflammation and Microvascular Dysfunction After Experimental Subarachnoid Hemorrhage: Emerging Components of Early Brain Injury Related to Outcome

Aneurysmal subarachnoid hemorrhage has a high mortality rate and, for those who survive this devastating injury, can lead to lifelong impairment. Clinical trials have demonstrated that cerebral vasospasm of larger extraparenchymal vessels is not the sole contributor to neurological outcome. Recently, the focus of intense investigation has turned to mechanisms of early brain injury that may play a larger role in outcome, including neuroinflammation and microvascular dysfunction. Extravasated blood after aneurysm rupture results in a robust inflammatory response characterized by activation of microglia, upregulation of cellular adhesion molecules, recruitment of peripheral immune cells, as well as impaired neurovascular coupling, disruption of the blood-brain barrier, and imbalances in endogenous vasodilators and vasoconstrictors. Each of these phenomena is either directly or indirectly associated with neuronal death and brain injury. Here, we review recent studies investigating these various mechanisms in experimental models of subarachnoid hemorrhage with special emphasis on neuroinflammation and its effect on microvascular dysfunction. We discuss the various therapeutic targets that have risen from these mechanistic studies and suggest the utility of a multi-targeted approach to preventing delayed injury and improving outcome after subarachnoid hemorrhage.

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.

ASP1126, a Novel Sphingosine-1-Phosphate-Selective Agonist With a Favorable Safety Profile, Prolongs Allograft Survival in Rats and Nonhuman Primates in Combination With Tacrolimus With a Broad Safety Margin for Bradycardia

Sphingosine-1-phosphate (S1P) is a biologically active sphingolipid that acts through the members of a family of 5 G protein-coupled receptors (S1P₁ to S1P₅). Among these, S1P₁ is a major regulator of lymphocyte trafficking. Fingolimod, whose active metabolite, fingolimod phosphate, acts as a nonselective S1P-receptor agonist, exerts its immunomodulatory effect, at least in part, by regulating lymphocyte trafficking via downregulation of S1P₁ expression on lymphocytes. Here, we describe the pharmacologic profile of a novel S1P₁ agonist, ASP1126. ASP1126 preferentially activated S1P₁ compared to S1P₃ in rat and human guanosine-5'-(γ-thio)-triphosphate (GTPγS) assays. Oral single administration of ASP1126 decreased the number of peripheral lymphocytes and repeated dosing showed a cumulative effect on lymphopenia in both rats and monkeys. ASP1126 prolonged allograft survival in a rat heterotopic heart transplantation model in combination with a subtherapeutic dose of tacrolimus that was independent of drug-drug interactions. In addition, in nonhuman primate (NHP) renal transplantation, pretreatment with ASP1126 reduced not only the number of naive T cells and central memory T cells but also effector memory T cells in the peripheral blood, all of which could contribute to acute graft rejection and prolonged allograft survival in combination with tacrolimus. Further, we confirmed that ASP1126 has a broad ranging safety margin with respect to its effect on lung weight in rats and bradycardia in NHPs, which were the adverse events found in clinical studies of fingolimod. ASP1126 with improved safety profile has the potential to be an adjunct therapy in combination with tacrolimus in clinical transplantation.

Perspectives for Ezrin and Radixin in Astrocytes: Kinases, Functions and Pathology

Astrocytes are increasingly perceived as active partners in physiological brain function and behaviour. The structural correlations of the glia–synaptic interaction are the peripheral astrocyte processes (PAPs), where ezrin and radixin, the two astrocytic members of the ezrin-radixin-moesin (ERM) family of proteins are preferentially localised. While the molecular mechanisms of ERM (in)activation appear universal, at least in mammalian cells, and have been studied in great detail, the actual ezrin and radixin kinases, phosphatases and binding partners appear cell type specific and may be multiplexed within a cell. In astrocytes, ezrin is involved in process motility, which can be stimulated by the neurotransmitter glutamate, through activation of the glial metabotropic glutamate receptors (mGluRs) 3 or 5. However, it has remained open how this mGluR stimulus is transduced to ezrin activation. Knowing upstream signals of ezrin activation, ezrin kinase(s), and membrane-bound binding partners of ezrin in astrocytes might open new approaches to the glial role in brain function. Ezrin has also been implicated in invasive behaviour of astrocytomas, and glial activation. Here, we review data pertaining to potential molecular interaction partners of ezrin in astrocytes, with a focus on PKC and GRK2, and in gliomas and other diseases, to stimulate further research on their potential roles in glia-synaptic physiology and pathology.

Loss of the sphingolipid desaturase DEGS1 causes hypomyelinating leukodystrophy

Sphingolipid imbalance is the culprit in a variety of neurological diseases, some affecting the myelin sheath. We have used whole-exome sequencing in patients with undetermined leukoencephalopathies to uncover the endoplasmic reticulum lipid desaturase DEGS1 as the causative gene in 19 patients from 13 unrelated families. Shared features among the cases include severe motor arrest, early nystagmus, dystonia, spasticity, and profound failure to thrive. MRI showed hypomyelination, thinning of the corpus callosum, and progressive thalamic and cerebellar atrophy, suggesting a critical role of DEGS1 in myelin development and maintenance. This enzyme converts dihydroceramide (DhCer) into ceramide (Cer) in the final step of the de novo biosynthesis pathway. We detected a marked increase of the substrate DhCer and DhCer/Cer ratios in patients' fibroblasts and muscle. Further, we used a knockdown approach for disease modeling in Danio rerio, followed by a preclinical test with the first-line treatment for multiple sclerosis, fingolimod (FTY720, Gilenya). The enzymatic inhibition of Cer synthase by fingolimod, 1 step prior to DEGS1 in the pathway, reduced the critical DhCer/Cer imbalance and the severe locomotor disability, increasing the number of myelinating oligodendrocytes in a zebrafish model. These proof-of-concept results pave the way to clinical translation.