FTY720, an immunomodulatory sphingolipid mimetic: translation of a novel mechanism into clinical benefit in multiple sclerosis

Mysterious sphingolipids: metabolic interrelationships at the center of pathophysiology

Metabolic pathways are complex and intertwined. Deficiencies in one or more enzymes in a given pathway are directly linked with genetic diseases, most of them having devastating manifestations. The metabolic pathways undertaken by sphingolipids are diverse and elaborate with ceramide species serving as the hubs of sphingolipid intermediary metabolism and function. Sphingolipids are bioactive lipids that serve a multitude of cellular functions. Being pleiotropic in function, deficiency or overproduction of certain sphingolipids is associated with many genetic and chronic diseases. In this up-to-date review article, we strive to gather recent scientific evidence about sphingolipid metabolism, its enzymes, and regulation. We shed light on the importance of sphingolipid metabolism in a variety of genetic diseases and in nervous and immune system ailments. This is a comprehensive review of the state of the field of sphingolipid biochemistry.

Imidazole-based sphingosine-1-phosphate transporter Spns2 inhibitors

Sphingosine-1-phosphate (S1P) is a chemotactic lipid that influences immune cell positioning. S1P concentration gradients are necessary for proper egress of lymphocytes from the thymus and secondary lymphoid tissues. This trafficking is interdicted by S1P receptor modulators, and it is expected that S1P transporter (Spns2) inhibitors, by reshaping S1P concentration gradients, will do the same. We previously reported SLF1081851 as a prototype Spns2 inhibitor, which provided a scaffold to investigate the importance of the oxadiazole core and the terminal amine. In this report, we disclose a structure-activity relationship study by incorporating imidazole as both a linker and surrogate for a positive charge in SLF1081851. In vitro inhibition of Spns2-dependent S1P transport in HeLa cells identified 7b as an inhibitor with an IC50 of 1.4 ± 0.3 µM. The SAR studies reported herein indicate that imidazolium can be a substitute for the terminal amine in SLF1081851 and that Spns2 inhibition is highly dependent on the lipid alkyl tail length.

Fingolimod-Associated Macular Edema in the Treatment of Multiple Sclerosis

Multiple sclerosis is a neurological disorder categorized by inflammatory processes with a high prevalence worldwide. It affects both motor and sensory pathways and is also associated with the visual pathway. Fingolimod is a commonly used drug for relapsing-remitting multiple sclerosis. It is a sphingosine 1-phosphate modulator acting on its receptors for immune cell accumulation, neuronal function, embryological development, vascular permeability, smooth muscle cell function, and endothelial barrier maintenance. This review aims to understand the processes, mechanisms, risks, and management of fingolimod-associated macular edema. Due to the anti-inflammatory properties of fingolimod, it decreases various cytokines, including interleukin (IL)-1B and IL-6, spike wave, and spike amplitude, in electrophysiological activities and decreases insoluble receptors for advanced glycation end product ligand. A daily dosage of 0.5 mg of fingolimod has an increased association with macular edema. The serious adverse events of fingolimod are lymphopenia, cardiovascular events, ocular events, and carcinoma. Fingolimod decreases brain volume and increases vascular permeability, resulting in increased macular volume and damage to the blood-retinal barrier, which causes an increased risk for macular edema. Cystoid macular edema is more common in older individuals suffering from comorbidities affecting the retina, such as diabetes, or those undergoing ophthalmological surgeries. This review also highlights the importance of regular ophthalmology examinations on patients consuming fingolimod both in the initial stages and chronic use. The treatment options for macular edema include nonsteroidal anti-inflammatory drugs, acetazolamide, triamcinolone, ketorolac, corticosteroids, and intravitreal procedures.

Simultaneous targeting of mitochondrial Kv1.3 and lysosomal acid sphingomyelinase amplifies killing of pancreatic ductal adenocarcinoma cells in vitro and in vivo

Pancreas ductal adenocarcinoma (PDAC) remains a malignant tumor with very poor prognosis and low 5-year overall survival. Here, we aimed to simultaneously target mitochondria and lysosomes as a new treatment paradigm of malignant pancreas cancer in vitro and in vivo. We demonstrate that the clinically used sphingosine analog FTY-720 together with PAPTP, an inhibitor of mitochondrial Kv1.3, induce death of pancreas cancer cells in vitro and in vivo. The combination of both drugs results in a marked inhibition of the acid sphingomyelinase and accumulation of cellular sphingomyelin in vitro and in vivo in orthotopic and flank pancreas cancers. Mechanistically, PAPTP and FTY-720 cause a disruption of both mitochondria and lysosomes, an alteration of mitochondrial bioenergetics and accumulation of cytoplasmic Ca²⁺, events that collectively mediate cell death. Our findings point to an unexpected cross-talk between lysosomes and mitochondria mediated by sphingolipid metabolism. We show that the combination of PAPTP and FTY-720 induces massive death of pancreas cancer cells, thereby leading to a substantially delayed and reduced PDAC growth in vivo. KEY MESSAGES: FTY-720 inhibits acid sphingomyelinase in pancreas cancer cells (PDAC). FTY-720 induces sphingomyelin accumulation and lysosomal dysfunction. The mitochondrial Kv1.3 inhibitor PAPTP disrupts mitochondrial functions. PAPTP and FTY-720 synergistically kill PDAC in vitro. The combination of FTY-720 and PAPTP greatly delays PDAC growth in vivo.

Dual anti-angiogenic and anti-metastatic activity of myriocin synergistically enhances the anti-tumor activity of cisplatin

PURPOSE

Tumor microenvironment consists of various kind of cells, forming complex interactions and signal transductions for tumor growth. Due to this complexity, targeting multiple kinases could yield improved clinical outcomes. In this study, we aimed to investigate the potential of myriocin, from Mycelia sterilia, as a novel dual-kinase inhibitor and suggest myriocin as a candidate for combined chemotherapy.

METHODS

We initially evaluated the anti-tumor and anti-metastatic effect of myriocin in mouse allograft tumor models. We examined the effects of myriocin on angiogenesis and tumor vasculature using in vitro, in vivo, and ex vivo models, and also tested the anti-migration effect of myriocin in in vitro models. Next, we explored the effects of myriocin alone and in combination with cisplatin on tumor growth and vascular normalization in mouse models.

RESULTS

We found that myriocin inhibited tumor growth and lung metastasis in mouse allograft tumor models. Myriocin induced normalization of the tumor vasculature in the mouse models. We also found that myriocin suppressed angiogenesis through the VEGFR2/PI3K/AKT pathway in endothelial cells (ECs), as well as cancer cell migration by blocking the IκBα/NF-κB(p65)/MMP-9 pathway. Finally, we found that myriocin enhanced the drug delivery efficacy of cisplatin by increasing the integrity of tumor vasculature in the mouse models, which synergistically increased the anti-tumor activity of cisplatin.

CONCLUSION

We suggest that myriocin is a novel potent anti-cancer agent that dually targets both VEGFR2 in ECs and IκBα in cancer cells, and exerts more pronounced anti-tumor effects than with either kinase being inhibited alone.

Current status and new developments in sphingosine-1-phosphate receptor antagonism: fingolimod and more

INTRODUCTION

Fingolimod was the first oral disease-modifying treatment approved for relapsing-remitting multiple sclerosis (MS) that serves as a sphingosine-1-phosphate receptor (S1PR) agonist. The efficacy is primarily mediated by S1PR subtype 1 activation, leading to agonist-induced down-modulation of receptor expression and further functional antagonism, blocking the egression of auto-aggressive lymphocytes from the lymph nodes in the peripheral compartment. The role of S1P signaling in the regulation of other pathways in human organisms through different S1PR subtypes has received much attention due to its immune-modulatory function and its significance for the regeneration of the central nervous system (CNS). The more selective second-generation S1PR modulators have improved safety and tolerability profiles.

AREAS COVERED

This review has been carried out based on current data on S1PR modulators, emphasizing the benefits of recent advances in this emergent class of immunomodulatory treatment for MS.

EXPERT OPINION

Ongoing clinical research suggests that S1PR modulators represent an alternative to first-line therapies in selected cases of MS. A better understanding of the relevance of selective S1PR pathways and the ambition to optimize selective modulation has improved the safety and tolerability of S1PR modulators in MS therapy and opened new perspectives for the treatment of other diseases.

FTY720 decreases ceramides levels in the brain and prevents memory impairments in a mouse model of familial Alzheimer's disease expressing APOE4

The protection mediated by the bioactive sphingolipid sphingosine-1-phosphate (S1P) declines during Alzheimer's disease (AD) progression, especially in patients carrying the apolipoprotein E ε4 (APOE4) isoform. The drug FTY720 mimics S1P bioactivity, but its efficacy in treating AD is unclear. Two doses of FTY720 (0.1 mg / kg and 0.5 mg / kg daily) were given by oral gavage for 15 weeks to transgenic mouse models of familial AD carrying human apolipoprotein E (APOE) APOE3 (E3FAD) or APOE4 (E4FAD). After 12 weeks of treatment, animals were subjected to behavioral tests for memory, locomotion, and anxiety. Blood was withdrawn at different time points and brains were collected for sphingolipids analysis by mass spectrometry, gene expression by RT-PCR and Aβ quantification by ELISA. We discovered that low levels of S1P in the plasma is associated with a higher probability of failing the memory test and that FTY720 prevents memory impairments in E4FAD. The beneficial effect of FTY720 was induced by a shift of the sphingolipid metabolism in the brain towards a lower production of toxic metabolites, like ceramide d18:1/16:0 and d18:1/22:0, and reduction of amyloid-β burden and inflammation. In conclusion, we provide further evidence of the druggability of the sphingolipid system in AD.

Lymphocyte Counts and Multiple Sclerosis Therapeutics: Between Mechanisms of Action and Treatment-Limiting Side Effects

Although the detailed pathogenesis of multiple sclerosis (MS) is not completely understood, a broad range of disease-modifying therapies (DMTs) are available. A common side effect of nearly every MS therapeutic agent is lymphopenia, which can be both beneficial and, in some cases, treatment-limiting. A sound knowledge of the underlying mechanism of action of the selected agent is required in order to understand treatment-associated changes in white blood cell counts, as well as monitoring consequences. This review is a comprehensive summary of the currently available DMTs with regard to their effects on lymphocyte count. In the first part, we describe important general information about the role of lymphocytes in the course of MS and the essentials of lymphopenic states. In the second part, we introduce the different DMTs according to their underlying mechanism of action, summarizing recommendations for lymphocyte monitoring and definitions of lymphocyte thresholds for different therapeutic regimens.

Lipid profile of Trichinella papuae muscle-stage larvae

Outbreaks of trichinellosis caused by Trichinella papuae have been reported in South-East Asia. Mebendazole and thiabendazole are the treatments of choice for trichinellosis; however, both drugs result in significant side effects and are less effective for muscle-stage larvae (L1). An alternative therapeutic agent is needed to improve treatment. Information on lipid composition and metabolic pathways may bridge gaps in our knowledge and lead to new antiparasitics. The T. papuae L1 lipidome was analysed using a mass spectrometry-based approach, and 403 lipid components were identified. Eight lipid classes were found and glycerophospholipids were dominant, corresponding to 63% of total lipids, of which the glycerolipid DG (20:1[11Z]/22:4[7Z,10Z,13Z,16Z]/0:0) (iso2) was the most abundant. Overall, 57% of T. papuae lipids were absent in humans; therefore, lipid metabolism may be dissimilar in the two species. Proteins involved T. papuae lipid metabolism were explored using bioinformatics. We found that 4-hydroxybutyrate coenzyme A transferase, uncharacterized protein (A0A0V1MCB5) and ML-domain-containing protein are not present in humans. T. papuae glycerophospholipid metabolic and phosphatidylinositol dephosphorylation processes contain several proteins that are dissimilar to those in humans. These findings provide insights into T. papuae lipid composition and metabolism, which may facilitate the development of novel trichinellosis treatments.

Functional Lipids in Autoimmune Inflammatory Diseases

Lipids are apolar small molecules known not only as components of cell membranes but also, in recent literature, as modulators of different biological functions. Herein, we focused on the bioactive lipids that can influence the immune responses and inflammatory processes regulating vascular hyperreactivity, pain, leukocyte trafficking, and clearance. In the case of excessive pro-inflammatory lipid activity, these lipids also contribute to the transition from acute to chronic inflammation. Based on their biochemical function, these lipids can be divided into different families, including eicosanoids, specialized pro-resolving mediators, lysoglycerophospholipids, sphingolipids, and endocannabinoids. These bioactive lipids are involved in all phases of the inflammatory process and the pathophysiology of different chronic autoimmune diseases such as rheumatoid arthritis, multiple sclerosis, type-1 diabetes, and systemic lupus erythematosus.

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.

Fingolimod Immune Effects Beyond Its Sequestration Ability

Fingolimod is the first orally administered drug approved for the treatment of relapsing-remitting multiple sclerosis (MS). This drug, modulating sphingosine receptors, regulates the trafficking of lymphocytes between primary and secondary lymphoid organs, trapping naïve T cells and central memory T cells in secondary lymphoid organs, without affecting effector memory T cells and therefore without compromising immunosurveillance. Additionally, fingolimod inhibits expression of Th1 and Th17 cytokines and enhances regulatory T-cell differentiation. It also acts on the B arm of immunity through an increased ratio of naïve to memory B cells, higher percentage of plasma cells, and highly increased proportion of transitional B cells as well as additional regulatory subsets. Fingolimod treatment enhances the capacity of regulatory B cells to transmigrate across brain endothelial cells. In fact, patients treated with fingolimod have increased regulatory B-cell frequency in the cerebrospinal fluid. These findings suggest a novel role for fingolimod in MS, by both direct effects and indirect partitioning effects on lymphocytes.

Functional Antagonism of Sphingosine-1-Phosphate Receptor 1 Prevents Harmaline-Induced Ultrastructural Alterations and Caspase-3 Mediated Apoptosis

Background

There is a meaningful necessity for a targeted therapy of essential tremor (ET), as medications have not been developed specifically for ET. For nearly a century, many drugs have been applied in the treatment of tremor but the drug treatment of ET remains still unknown. Some potential therapeutic factors such fingolimod (FTY720) can be effectively used to treat ET in animals. In the present research, the effect of FTY720, the immunomodulatory sphingosine 1-phosphate (S1P) analog, on degeneration of cerebellar and olivary neurons induced by harmaline in male rats was investigated.

Methods

The animals were allotted into control dimethyl sulfoxide (DMSO), saline + harmaline [30 mg/kg, intraperitoneally, (i.p.)], harmaline + FTY720 (1 mg/kg, i.p, 1 h and 24 h before harmaline injection) groups (n = 10). The cerebellum and inferior olive nucleus (ION) were studied for neuronal degeneration using immunohistochemistry (IHC) and ultrastructural study by transmission electron microscopy (TEM) techniques.

Results

Harmaline caused neuronal cell loss, caspase-3 mediated apoptosis, astrocytosis and ultrastructural changes in cerebellar Purkinje cells and inferior olive neurons. FTY720 exhibited neuroprotective effects on cerebellar Purkinje cells and inferior olivary neurons.

Conclusion

These results suggest that FTY720 has potential efficacy for prevention of ET neurodegeneration and astrocytosis induced by harmaline in male rats.

Preclinical discovery and development of fingolimod for the treatment of multiple sclerosis

Introduction: Fingolimod, the first oral disease-modifying treatment (DMT) in multiple sclerosis (MS), is a sphingosine 1-phosphate receptor (S1PR) ligand. Approved in 2010, fingolimod has been extensively studied and has been credited with several mechanisms of actions that contribute to its efficacy in MS, among which is the regulation of lymphocyte circulation between the central nervous system and the periphery. Concerns about toxicity, off-target effects, and real-life performance have been raised over time in post-marketing studies of such that next-generation sphingosine-1 phosphate receptor ligands are now being developed. Areas covered: Herein, the authors expand upon previous systematic reviews obtained via PubMed and through their expert opinion on fingolimod use in clinical practice. Long-term data including long-term efficacy, safety, tolerability, and management especially within growing DMT options and pre-treatment constellation in MS patients are discussed, together with the results of an increased understanding of the chemistry underlying the structure-activity relationship. Expert opinion: Despite the limitations illustrated in this article, fingolimod still constitutes a paradigm shift in MS treatment. However, although immunomodulation via S1PRs on lymphocytes has represented a major breakthrough in the clinical management of MS, modifying the evolution of progressive MS will likely require the development of approaches other than merely targeting S1PRs.

Myeloid sphingosine-1-phosphate receptor 1 is important for CNS autoimmunity and neuroinflammation

The critical role of sphingosine-1-phosphate (S1P) signaling in lymphocyte trafficking is well recognized, however, the contribution of myeloid cell-S1P signaling in neuroimmunity is less well understood. We previously reported that C57BL/6J mice harboring phosphorylation defective S1P receptor 1 (S1P₁) (with mutated serines in the carboxyl terminus, leading to impaired receptor internalization) [S1P₁(S5A)] developed severe, T_H17-dominant experimental autoimmune encephalomyelitis. In this study, we demonstrate that S1P₁-mediated T_H17 polarization is not an intrinsic T cell effect, but dependent on sustained S1P₁ signaling in myeloid cells. First, utilizing the S1P₁(S5A) mice in the EAE model, we observed that S1P₁ activated and enhanced antigen presentation function in myeloid cells. Second, sequential phosphorylation of STAT3 occurred in dendritic cells, monocytes, and macrophages/microglia during neuroinflammation. Third, we show that pro-inflammatory (CD45^hiCD11b⁺Ly6C^hi) monocytes contribute to T_H17 differentiation and neuroinflammation by regulating IL-6 expression. Finally, results from experiments utilizing myeloid cell-specific S1P₁ overexpression (S1pr1^f/stop/f:LysM^Cre) mice demonstrate that myeloid cell S1P₁ directly contributes to severity of neuroinflammation. These findings reveal the critical contribution of myeloid-S1P₁ signaling in CNS autoimmunity.

Click reactions with functional sphingolipids

Sphingolipids and glycosphingolipids can regulate cell recognition and signalling. Ceramide and sphingosine-1-phosphate are major players in the sphingolipid pathways and are involved in the initiation and regulation of signalling, apoptosis, stress responses and infection. Specific chemically synthesised sphingolipid derivatives containing small functionalities like azide or alkyne can mimic the biological properties of natural lipid species, which turns them into useful tools for the investigation of the highly complex sphingolipid metabolism by rapid and selective 'click chemistry' using sensitive tags like fluorophores. Subsequent analysis by various fluorescence microscopy techniques or mass spectrometry allows the identification and quantification of the corresponding sphingolipid metabolites as well as the research of associated enzymes. Here we present an overview of recent advances in the synthesis of ceramide and sphingosine analogues for bioorthogonal click reactions to study biosynthetic pathways and localization of sphingolipids for the development of novel therapeutics against lipid-dependent diseases.

Regulation of lymphocyte trafficking in central nervous system autoimmunity

CD4⁺ T helper (Th) cells play a central role in orchestrating protective immunity but also in autoimmunity. Multiple Sclerosis (MS) is a human autoimmune disease of the central nervous system (CNS) characterized by the infiltration of inflammatory lymphocytes and myeloid cells into the brain and spinal cord, leading to demyelination, axonal damage, and progressive loss of motor functions. The release of T cells in the circulation and their migration in the central nervous system are key and tightly regulated processes which have been targeted to decrease CD4⁺ T cell presence in the CNS and limit disease progression. Here, we review two of these pathways and discuss how their blockade modulate different subsets of CD4⁺ T cells.

Metabolism and Disposition of Siponimod, a Novel Selective S1P1/S1P5 Agonist, in Healthy Volunteers and In Vitro Identification of Human Cytochrome P450 Enzymes Involved in Its Oxidative Metabolism

Siponimod, a next-generation selective sphingosine-1-phosphate receptor modulator, is currently being investigated for the treatment of secondary progressive multiple sclerosis. We investigated the absorption, distribution, metabolism, and excretion (ADME) of a single 10-mg oral dose of [¹⁴C]siponimod in four healthy men. Mass balance, blood and plasma radioactivity, and plasma siponimod concentrations were measured. Metabolite profiles were determined in plasma, urine, and feces. Metabolite structures were elucidated using mass spectrometry and comparison with reference compounds. Unchanged siponimod accounted for 57% of the total plasma radioactivity (area under the concentration-time curve), indicating substantial exposure to metabolites. Siponimod showed medium to slow absorption (median T_max: 4 hours) and moderate distribution (Vz/F: 291 l). Siponimod was mainly cleared through biotransformation, predominantly by oxidative metabolism. The mean apparent elimination half-life of siponimod in plasma was 56.6 hours. Siponimod was excreted mostly in feces in the form of oxidative metabolites. The excretion of radioactivity was close to complete after 13 days. Based on the metabolite patterns, a phase II metabolite (M3) formed by glucuronidation of hydroxylated siponimod was the main circulating metabolite in plasma. However, in subsequent mouse ADME and clinical pharmacokinetic studies, a long-lived nonpolar metabolite (M17, cholesterol ester of siponimod) was identified as the most prominent systemic metabolite. We further conducted in vitro experiments to investigate the enzymes responsible for the oxidative metabolism of siponimod. The selective inhibitor and recombinant enzyme results identified cytochrome P450 2C9 (CYP2C9) as the predominant contributor to the human liver microsomal biotransformation of siponimod, with minor contributions from CYP3A4 and other cytochrome P450 enzymes.

Fingolimod hydrochloride for the treatment of relapsing remitting multiple sclerosis

INTRODUCTION

Fingolimod was the first oral and the first in class disease modifying treatment in multiple sclerosis that acts as sphingosine-1-phospathe receptor agonist. Since approval in 2010 there is a growing experience with fingolimod use in clinical practice, but also next-generation sphingosin-1-receptor agonists in ongoing clinical trials. Growing evidence demonstrates additional effects beyond impact on lymphocyte circulation, highlighting further promising targets in multiple sclerosis therapy. Areas covered: Here we present a systematic review using PubMed database searching and expert opinion on fingolimod use in clinical practice. Long-term data of initial clinical trials and post-marketing evaluations including long-term efficacy, safety, tolerability and management especially within growing disease modifying treatment options and pre-treatment constellation in multiple sclerosis patients are critically discussed. Furthermore novel findings in mechanism of actions and prospective on additional use in progressive forms in multiple sclerosis are presented. Expert opinion: There is an extensive long-term experience on fingolimod use in clinical practice demonstrating the favorable benefit-risk of this drug. Using a defined risk management approach experienced MS clinicians should apply fingolimod after critical choice of patients and review of clinical aspects. Further studies are essential to discuss additional benefit in progressive forms in multiple sclerosis.

Effects of sphingosine-1-phosphate receptor 1 phosphorylation in response to FTY720 during neuroinflammation

Fingolimod (FTY720, Gilenya), a sphingosine-1-phosphate receptor (S1PR) modulator, is one of the first-line immunomodulatory therapies for treatment of relapsing-remitting multiple sclerosis (MS). Human S1PR1 variants have been reported to have functional heterogeneity in vitro, suggesting that S1PR1 function may influence FTY720 efficacy. In this study, we examined the influence of S1PR1 phosphorylation on response to FTY720 in neuroinflammation. We found that mice carrying a phosphorylation-defective S1pr1 gene [S1PR1(S5A) mice] were refractory to FTY720 treatment in MOG_35-55-immunized and Th17-mediated experimental autoimmune encephalomyelitis (EAE) models. Long-term treatment with FTY720 induced significant lymphopenia and suppressed Th17 response in the peripheral immune system via downregulating STAT3 phosphorylation in both WT and S1PR1(S5A) mice. However, FTY720 did not effectively prevent neuroinflammation in the S1PR1(S5A) EAE mice as a result of encephalitogenic cells expressing C-C chemokine receptor 6 (CCR6). Combined treatment with FTY720 and anti-CCR6 delayed disease progression in S1PR1(S5A) EAE mice, suggesting that CCR6-mediated cell trafficking can overcome the effects of FTY720. This work may have translational relevance regarding FTY720 efficacy in MS patients and suggests that cell type-specific therapies may enhance therapeutic efficacy in MS.

Inflammatory responses in brain ischemia

Brain infarction causes tissue death by ischemia due to occlusion of the cerebral vessels and recent work has shown that post stroke inflammation contributes significantly to the development of ischemic pathology. Because secondary damage by brain inflammation may have a longer therapeutic time window compared to the rescue of primary damage following arterial occlusion, controlling inflammation would be an obvious therapeutic target. A substantial amount of experimentall progress in this area has been made in recent years. However, it is difficult to elucidate the precise mechanisms of the inflammatory responses following ischemic stroke because inflammation is a complex series of interactions between inflammatory cells and molecules, all of which could be either detrimental or beneficial. We review recent advances in neuroinflammation and the modulation of inflammatory signaling pathways in brain ischemia. Potential targets for treatment of ischemic stroke will also be covered. The roles of the immune system and brain damage versus repair will help to clarify how immune modulation may treat stroke.

Novel effects of FTY720 on perinuclear reorganization of keratin network induced by sphingosylphosphorylcholine: Involvement of protein phosphatase 2A and G-protein-coupled receptor-12

Sphingosylphosphorylcholine (SPC) evokes perinuclear reorganization of keratin 8 (K8) filaments and regulates the viscoelasticity of metastatic cancer cells leading to enhanced migration. Few studies have addressed the compounds modulating the viscoelasticity of metastatic cancer cells. We studied the effects of sphingosine (SPH), sphingosine 1-phosphate (S1P), FTY720 and FTY720-phosphate (FTY720P) on SPC-induced K8 phosphorylation and reorganization using Western blot and confocal microscopy, and also evaluated the elasticity of PANC-1 cells by atomic force microscopy. FTY720, FTY720P, SPH, and S1P concentration-dependently inhibited SPC-evoked phosphorylation and reorganization of K8, and migration of PANC-1 cells. SPC triggered reduction and narrow distribution of elastic constant K and conversely, FTY720 blocked them. A common upstream regulator of JNK and ERK, protein phosphatase 2A (PP2A) expression was reduced by SPC, but was restored by FTY720 and FTY72P. Butyryl forskolin, a PP2A activator, suppressed SPC-induced K8 phosphorylation and okadaic acid, a PP2A inhibitor, induced K8 phosphorylation. Gene silencing of PP2A also led to K8 phosphorylation, reorganization and migration. We also investigated the involvement of GPR12, a high-affinity SPC receptor, in SPC-evoked keratin phosphorylation and reorganization. GPR12 siRNA suppressed the SPC-triggered phosphorylation and reorganization of K8. GPR12 overexpression stimulated keratin phosphorylation and reorganization even without SPC. FTY720 and FTY720P suppressed the GPR12-induced phosphorylation and reorganization of K8. The collective data indicates that FTY720 and FTY720P suppress SPC-induced phosphorylation and reorganization of K8 in PANC-1 cells by restoring the expression of PP2A via GPR12. These findings might be helpful in the development of compounds that modulate the viscoelasticity of metastatic cancer cells and various SPC actions.

HIV-1, methamphetamine and astrocytes at neuroinflammatory Crossroads

As a popular psychostimulant, methamphetamine (METH) use leads to long-lasting, strong euphoric effects. While METH abuse is common in the general population, between 10 and 15% of human immunodeficiency virus-1 (HIV-1) patients report having abused METH. METH exacerbates the severity and onset of HIV-1-associated neurocognitive disorders (HAND) through direct and indirect mechanisms. Repetitive METH use impedes adherence to antiretroviral drug regimens, increasing the likelihood of HIV-1 disease progression toward AIDS. METH exposure also directly affects both innate and adaptive immunity, altering lymphocyte numbers and activity, cytokine signaling, phagocytic function and infiltration through the blood brain barrier. Further, METH triggers the dopamine reward pathway and leads to impaired neuronal activity and direct toxicity. Concurrently, METH and HIV-1 alter the neuroimmune balance and induce neuroinflammation, which modulates a wide range of brain functions including neuronal signaling and activity, glial activation, viral infection, oxidative stress, and excitotoxicity. Pathologically, reactive gliosis is a hallmark of both HIV-1- and METH-associated neuroinflammation. Significant commonality exists in the neurotoxic mechanisms for both METH and HAND; however, the pathways dysregulated in astroglia during METH exposure are less clear. Thus, this review highlights alterations in astrocyte intracellular signaling pathways, gene expression and function during METH and HIV-1 comorbidity, with special emphasis on HAND-associated neuroinflammation. Importantly, this review carefully evaluates interventions targeting astrocytes in HAND and METH as potential novel therapeutic approaches. This comprehensive overview indicates, without a doubt, that during HIV-1 infection and METH abuse, a complex dialog between all neural cells is orchestrated through astrocyte regulated neuroinflammation.

The PANGAEA study design - a prospective, multicenter, non-interventional, long-term study on fingolimod for the treatment of multiple sclerosis in daily practice

BACKGROUND

Fingolimod (Gilenya) is an oral medication for patients with highly active relapsing-remitting Multiple Sclerosis (RRMS). Clinical trials and post-marketing experience on more than 114,000 patients have established a detailed safety profile. Total patient exposure now exceeds 195,000 patient-years as stated in the last financial report (Dec 2014) of the Novartis Pharma AG, Basel, Switzerland. However, less is known about the safety of long-term fingolimod use in daily practice. Here, we describe the study design of PANGAEA (Post-Authorization Non-interventional German sAfety of GilEnyA in RRMS patients), a prospective, multicenter, non-interventional, long-term study to collect safety, efficacy, and pharmacoeconomic data on RRMS patients treated with fingolimod (0.5 mg/daily) under real-world conditions in Germany.

METHODS

PANGAEA is striving to assess a real-world safety and efficacy profile of fingolimod, based on data from 4,000 RRMS patients, obtained during a 60-month observational phase. A pharmacoeconomic sub-study of 800 RRMS patients further collects patient-reported outcome measures of disability, quality of life, compliance, treatment satisfaction, and usage of resources during a 24-month observational phase. Descriptive statistical analyses of the safety set as well as of stratified subgroups such as patients with concomitant diabetes mellitus and pretreated patients (e.g., natalizumab) will be conducted.

DISCUSSION

PANGAEA seeks to confirm the current safety profile of fingolimod obtained in phase I-III clinical trials. The study design presented here will additionally provide guidance on the therapeutic use of fingolimod in clinical practice and possibly assists physicians in making evidence-based decisions.

Fingolimod in a patient with heart failure on the background of pulmonary arterial hypertension and coronary artery disease

BACKGROUND

Fingolimod is the first oral immunomodulatory therapy approved for highly active relapsing remitting multiple sclerosis. Based on the distribution pattern of fingolimod interacting sphingosine-1-phosphat receptors in organism including immune system and cardiovascular system clinical monitoring of patients and evaluation of adverse events are recommended. Despite extensive data on cardiovascular safety, experience with fingolimod in patients with concomitant cardiological disease, especially within the pulmonary circulation, is rare.

CASE PRESENTATION

We report the case of a 46-year-old woman presented with relapsing remitting multiple sclerosis and severe idiopathic pulmonary arterial hypertension. Fingolimod was initiated because of disease activity of multiple sclerosis with two relapses and gadolinium-enhancing lesions in MRI. The patient demonstrated stable disease course of idiopathic pulmonary arterial hypertension when fingolimod was started. Fingolimod therapy did not alter or even worsen the pulmonary or cardiovascular conditions during first dose application as well as follow up of nine months.

CONCLUSION

In this report, we present the first case of fingolimod treatment in a patient with highly active multiple sclerosis and severe idiopathic pulmonary arterial hypertension. We suggest an interdisciplinary approach with detailed cardiopulmonary monitoring for safety in such patients.

Defective sphingosine 1-phosphate receptor 1 (S1P1) phosphorylation exacerbates TH17-mediated autoimmune neuroinflammation

Sphingosine-1-phosphate (S1P) signaling regulates lymphocyte egress from lymphoid organs into systemic circulation. Sphingosine phosphate receptor 1 (S1P₁) agonist, FTY-720 (Gilenya™) arrests immune trafficking and prevents multiple sclerosis (MS) relapses. However, alternative mechanisms of S1P-S1P₁ signaling have been reported. Phosphoproteomic analysis of MS brain lesions revealed S1P₁ phosphorylation on S351, a residue crucial for receptor internalization. Mutant mice harboring a S1pr1 gene encoding phosphorylation-deficient receptors [S1P₁(S5A)] developed severe experimental autoimmune encephalomyelitis (EAE) due to T helper (T_H) 17-mediated autoimmunity in the peripheral immune and nervous system. S1P₁ directly activated Janus-like kinase–signal transducer and activator of transcription 3 (JAK-STAT3) pathway via interleukin 6 (IL-6). Impaired S1P₁ phosphorylation enhances T_H17 polarization and exacerbates autoimmune neuroinflammation. These mechanisms may be pathogenic in MS.

Therapeutic potential of targeting SK1 in human cancers

Sphingosine kinase 1 (SK1) is a lipid enzyme with oncogenic properties that converts the proapoptotic lipids ceramide and sphingosine into the antiapoptotic lipid sphingosine-1-phosphate and activates the signal transduction pathways that lead to cell proliferation, migration, the activation of the inflammatory response, and the impairment of apoptosis. There is compelling evidence that SK1 activation contributes to cancer progression leading to increased oncogenic transformation, tumor growth, resistance to therapies, tumor neovascularization, and metastatic spread. High levels of SK1 expression or activity have been associated with a poor prognosis in several human cancers. Recent studies using cancer cell and mouse models demonstrate a significant potential for SK1-targeting therapies to synergize with the effects of chemotherapy and radiotherapy; however, until recently the absence of clinically applicable SK1 inhibitors has limited the translation of these findings into patients. With the recent discovery of SK1 inhibiting properties of a clinically approved drug FTY720 (Fingolimod), SK1 has gained significant attention from both clinicians and the pharmaceutical industry and it is hoped that trials of newly developed SK1 inhibitors may follow soon. This review provides an overview of the SK1 signaling, its relevance to cancer progression, and the potential clinical significance of targeting SK1 for improved local or systemic control of human cancers.

Sphingolipids in cardiovascular and cerebrovascular systems: Pathological implications and potential therapeutic targets

The sphingolipid metabolites ceramide, sphingosine, and sphingosine-1-phosphate (S1P) and its enzyme sphingosine kinase (SphK) play an important role in the regulation of cell proliferation, survival, inflammation, and cell death. Ceramide and sphingosine usually inhibit proliferation and promote apoptosis, while its metabolite S1P phosphorylated by SphK stimulates growth and suppresses apoptosis. Because these metabolites are interconvertible, it has been proposed that it is not the absolute amounts of these metabolites but rather their relative levels that determine cell fate. The relevance of this “sphingolipid rheostat” and its role in regulating cell fate has been borne out by work in many labs using many different cell types and experimental manipulations. A central finding of these studies is that SphK is a critical regulator of the sphingolipid rheostat, as it not only produces the pro-growth, anti-apoptotic messenger S1P, but also decreases levels of pro-apoptotic ceramide and sphingosine. Activation of bioactive sphingolipid S1P signaling has emerged as a critical protective pathway in response to acute ischemic injury in both cardiac and cerebrovascular disease, and these observations have considerable relevance for future potential therapeutic targets.

The selective sphingosine 1-phosphate receptor modulator BAF312 redirects lymphocyte distribution and has species-specific effects on heart rate

BACKGROUND AND PURPOSE

BAF312 is a next-generation sphingosine 1-phosphate (S1P) receptor modulator, selective for S1P₁ and S1P₅ receptors. S1P₁ receptors are essential for lymphocyte egress from lymph nodes and a drug target in immune-mediated diseases. Here, we have characterized the immunomodulatory potential of BAF312 and the S1P receptor-mediated effects on heart rate using preclinical and human data.

EXPERIMENTAL APPROACH

BAF312 was tested in a rat experimental autoimmune encephalomyelitis (EAE) model. Electrophysiological recordings of G-protein-coupled inwardly rectifying potassium (GIRK) channels were carried out in human atrial myocytes. A Phase I multiple-dose trial studied the pharmacokinetics, pharmacodynamics and safety of BAF312 in 48 healthy subjects.

KEY RESULTS

BAF312 effectively suppressed EAE in rats by internalizing S1P₁ receptors, rendering them insensitive to the egress signal from lymph nodes. In healthy volunteers, BAF312 caused preferential decreases in CD4⁺ T cells, T_naïve, T_{central memory} and B cells within 4–6 h. Cell counts returned to normal ranges within a week after stopping treatment, in line with the elimination half-life of BAF312. Despite sparing S1P₃ receptors (associated with bradycardia in mice), BAF312 induced rapid, transient (day 1 only) bradycardia in humans. BAF312-mediated activation of GIRK channels in human atrial myocytes can fully explain the bradycardia.

CONCLUSION AND IMPLICATIONS

This study illustrates species-specific differences in S1P receptor specificity for first-dose cardiac effects. Based on its profound but rapidly reversible inhibition of lymphocyte trafficking, BAF312 may have potential as a treatment for immune-mediated diseases.

Sphingosine 1-phosphate (S1P) receptors 1 and 2 coordinately induce mesenchymal cell migration through S1P activation of complementary kinase pathways

Normal bone turnover requires tight coupling of bone resorption and bone formation to preserve bone quantity and structure. With aging and during several pathological conditions, this coupling breaks down, leading to either net bone loss or excess bone formation. To preserve or restore normal bone metabolism, it is crucial to determine the mechanisms by which osteoclasts and osteoblast precursors interact and contribute to coupling. We showed that osteoclasts produce the chemokine sphingosine 1-phosphate (S1P), which stimulates osteoblast migration. Thus, osteoclast-derived S1P may recruit osteoblasts to sites of bone resorption as an initial step in replacing lost bone. In this study we investigated the mechanisms by which S1P stimulates mesenchymal (skeletal) cell chemotaxis. S1P treatment of mesenchymal (skeletal) cells activated RhoA GTPase, but this small G protein did not contribute to migration. Rather, two S1P receptors, S1PR1 and S1PR2, coordinately promoted migration through activation of the JAK/STAT3 and FAK/PI3K/AKT signaling pathways, respectively. These data demonstrate that the chemokine S1P couples bone formation to bone resorption through activation of kinase signaling pathways.

FTY720 preserved islet β-cell mass by inhibiting apoptosis and increasing survival of β-cells in db/db mice

BACKGROUND

FTY720, an analogue of sphingosine-1-phosphate, has shown potential in the treatment of several autoimmune diseases, such as multiple sclerosis, type 1 diabetes and systemic lupus erythematosus. It prevents development or cure of autoimmune diabetes in animal models. Recently, we reported that FTY720 also prevents development of diabetes in db/db mice by β-cell regeneration in vivo. This study investigated the effect of FTY720 on apoptosis in β-cells in db/db mice treated with FTY720 16 weeks.

METHODS

Six week old female db/db mice were divided into control and FTY720 groups. FTY720 (10 mg/kg) was orally administrated daily. Body weights and fasting glucose levels were measured once a week after overnight fasting. After 16 weeks of treatment, oral glucose and insulin tolerance tests were performed, serum insulin levels and insulin contents in pancreas were determined, and then all mice were subjected to physiological and histological analyses.

RESULTS

FTY720-treated mice showed normal fasting glucose levels, improved glucose tolerance with normal insulin sensitivity and restored β-cell function to produce and secret insulin. Pancreas histology revealed that FTY720 prevented islet damage and preserved β-cell mass by inhibiting apoptosis and increasing β-cell survival in pancreatic islets.

CONCLUSIONS

We concluded that early intervention with FTY720 in db/db mice can prevent development of diabetes through preserving β-cell mass by inhibiting apoptosis and increasing survival of islet β-cells.

Quantitative metabolomic and lipidomic profiling reveals aberrant amino acid metabolism in type 2 diabetes

Type 2 diabetes (T2DM) is a multi-factorial disease with a complex pathogenic mechanism; however a complete understanding of precise biochemical alterations accompanying the onset and progression of T2DM is lacking. Using a combination of untargeted and targeted metabolomic profiling approach we were able to delineate significantly altered metabolites in the diabetic (T2DM) group. Our results indicate significant perturbations in amino acid metabolism, TCA cycle and glycerol-phospholipid metabolism possibly impacting the overall glucose homeostasis in T2DM. A systems approach offers promise towards identification of clinically relevant markers of T2DM and novel molecular targets to foster drug discovery for effective therapeutic development for diabetes.

Discovery of a novel class of zwitterionic, potent, selective and orally active S1P₁ direct agonists

Amido-1,3,4-thiadiazoles have been identified as a novel structural class of potent and selective sphingosine-1-phosphate receptor subtype 1 agonists. Starting from a micromolar HTS hit with the help of an in-house homology model, robust structural-activity relationships were developed to yield compounds with good selectivity and excellent in vivo efficacy in rat models.

Modulation of cellular S1P levels with a novel, potent and specific inhibitor of sphingosine kinase-1

SphK (sphingosine kinase) is the major source of the bioactive lipid and GPCR (G-protein-coupled receptor) agonist S1P (sphingosine 1-phosphate). S1P promotes cell growth, survival and migration, and is a key regulator of lymphocyte trafficking. Inhibition of S1P signalling has been proposed as a strategy for treatment of inflammatory diseases and cancer. In the present paper we describe the discovery and characterization of PF-543, a novel cell-permeant inhibitor of SphK1. PF-543 inhibits SphK1 with a Ki of 3.6 nM, is sphingosine-competitive and is more than 100-fold selective for SphK1 over the SphK2 isoform. In 1483 head and neck carcinoma cells, which are characterized by high levels of SphK1 expression and an unusually high rate of S1P production, PF-543 decreased the level of endogenous S1P 10-fold with a proportional increase in the level of sphingosine. In contrast with past reports that show that the growth of many cancer cell lines is SphK1-dependent, specific inhibition of SphK1 had no effect on the proliferation and survival of 1483 cells, despite a dramatic change in the cellular S1P/sphingosine ratio. PF-543 was effective as a potent inhibitor of S1P formation in whole blood, indicating that the SphK1 isoform of sphingosine kinase is the major source of S1P in human blood. PF-543 is the most potent inhibitor of SphK1 described to date and it will be useful for dissecting specific roles of SphK1-driven S1P signalling.

FTY720, sphingosine 1-phosphate receptor modulator, selectively radioprotects hippocampal neural stem cells

Cranial irradiation is an effective treatment modality for both primary and metastatic brain tumors, yet it induces cognitive decline in a substantial number of patients. At present, there are no established methods for neuroprotection. Recent investigations have revealed a link between radiation-induced cognitive dysfunction and the loss of neural precursor cells in the hippocampus. Hence, identifying pharmacological agents, capable of protecting this cell population, is of interest. FTY720 (fingolimod), an FDA-approved oral drug for the treatment of multiple sclerosis, has been shown to promote the survival and differentiation of neural progenitors, as well as remyelination and repair after brain injury. In this study, we show that FTY720, used at nanomolar concentrations, is capable of increasing the viability and neurogenicity of irradiated neural stem cells from the hippocampus. In contrast, it does not provide radioprotection in a human breast cancer cell line and two glioma cell lines. These results suggest a potential therapeutic role for FTY720 as a neuroprotector during cranial irradiation. Further preclinical studies are warranted to evaluate this possibility.

Pharmacological relevance and potential of sphingosine 1-phosphate in the vascular system

Sphingosine-1-phosphate (S1P) was identified as a crucial molecule for regulating immune responses, inflammatory processes as well as influencing the cardiovascular system. S1P mediates differentiation, proliferation and migration during vascular development and homoeostasis. S1P is a naturally occurring lipid metabolite and is present in human blood in nanomolar concentrations. S1P is not only involved in physiological but also in pathophysiological processes. Therefore, this complex signalling system is potentially interesting for pharmacological intervention. Modulation of the system might influence inflammatory, angiogenic or vasoregulatory processes. S1P activates G-protein coupled receptors, namely S1P(1-5) , whereas only S1P(1-3) is present in vascular cells. S1P can also act as an intracellular signalling molecule. This review highlights the pharmacological potential of S1P signalling in the vascular system by giving an overview of S1P-mediated processes in endothelial cells (ECs) and vascular smooth muscle cells (VSMCs). After a short summary of S1P metabolism and signalling pathways, the role of S1P in EC and VSMC proliferation and migration, the cause of relaxation and constriction of arterial blood vessels, the protective functions on endothelial apoptosis, as well as the regulatory function in leukocyte adhesion and inflammatory responses are summarized. This is followed by a detailed description of currently known pharmacological agonists and antagonists as new tools for mediating S1P signalling in the vasculature. The variety of effects influenced by S1P provides plenty of therapeutic targets currently under investigation for potential pharmacological intervention.

Fingolimod: a review of its use in the management of relapsing-remitting multiple sclerosis

Oral fingolimod (Gilenya™), a sphingosine 1-phosphate (S1P) receptor agonist, is the first oral agent and the first in a novel class of disease-modifying therapies (DMTs) to be approved for use in the US for the treatment of relapsing forms of multiple sclerosis (MS). In the EU, fingolimod is approved for use as a single-agent DMT in selected patients with highly-active, relapsing-remitting (RR) MS. This article reviews the pharmacological properties and clinical use of the drug in patients with RRMS. Fingolimod is rapidly converted in vivo to the active moiety S-fingolimod-phosphate, which binds with high affinity to S1P receptors, thereby sequestering lymphocytes in the lymph nodes and preventing their egress into the peripheral circulation. As a consequence, there is a reduction in the infiltration of autoaggressive lymphocytes into the CNS. Fingolimod-phosphate also acts as a functional antagonist, as its binding to S1P receptors results in their internalization and degradation, thereby downregulating S1P receptors on the lymphocyte cell surface. Since fingolimod crosses the blood : brain barrier, it also potentially acts at S1P receptors on neural cells in the CNS to mitigate neuropathological processes associated with MS. In large multinational trials in adult patients with RRMS, oral fingolimod 0.5 mg/day was more effective than oral placebo (FREEDOMS) and recommended dosages of intramuscular interferon-β (IFNβ)-1a (TRANSFORMS) in reducing the annualized relapse rate and was also generally more effective at slowing progression of neurological disability and at reducing the burden and activity of disease. Fingolimod was generally well tolerated in these trials of up to 2 years' duration, with most adverse events being manageable and of mild to moderate severity; there were two deaths from opportunistic infections, albeit these occurred with fingolimod 1.25 mg/day (higher than the recommended dosage). Limited long-term data indicated that no new safety concerns had arisen after 5 years of fingolimod treatment. However, further clinical experience is required to fully determine the long-term safety profile of fingolimod, particularly with regard to any potentially serious or life-threatening adverse events. In the absence of robust pharmacoeconomic studies and of head-to-head trials comparing fingolimod with other formulations of IFNβ and glatiramer acetate, the relative position of fingolimod with respect to other DMTs remains to be fully determined. In the meantime, given its convenient once-daily oral treatment regimen and better efficacy than intramuscular IFNβ-1a, fingolimod is a valuable emerging option for the treatment of adult patients with relapsing forms of MS.

High-throughput screening assay for sphingosine kinase inhibitors in whole blood using RapidFire® mass spectrometry

To facilitate discovery of compounds modulating sphingosine-1-phosphate (S1P) signaling, the authors used high-throughput mass spectrometry technology to measure S1P formation in human whole blood. Since blood contains endogenous sphingosine (SPH) and S1P, mass spectrometry was chosen to detect the conversion of an exogenously added 17-carbon-long variant of sphingosine, C17SPH, into C17S1P. The authors developed procedures to achieve homogeneous mixing of whole blood in 384-well plates and for a method requiring minimal manipulations to extract S1P from blood in 96- and 384-well plates prior to analyses using the RapidFire(®) mass spectrometry system.

A view on sphingolipids and disease

Sphingolipid and glycosphingolipid levels and expression of sphingolipid metabolizing enzymes are altered in a variety of diseases or in response to drug treatment. Inherited defects of enzymes and other proteins required for the lysosomal degradation of these lipids lead to human sphingolipidoses. Also genetic defects that affect sphingolipid biosynthesis are known. Although the molecular details are often far from clear, (glyco)sphingolipids have been implicated to play a role in atherosclerosis, insulin resistance, cancer, and infections by pathogens. More general aspects of selected diseases are discussed.

Anti-inflammatory effects of FTY720 do not prevent neuronal cell loss in a rat model of optic neuritis

In multiple sclerosis, long-term disability is caused by axonal and neuronal damage. Established therapies target primarily the inflammatory component of the disease, but fail to prevent neurodegeneration. Fingolimod (codenamed FTY720) is an oral sphingosine 1-phosphate (S1P) receptor modulator with promising results in phase II trials in multiple sclerosis patients and is under further development as a novel treatment for multiple sclerosis. To evaluate whether FTY720 has neuroprotective properties, we tested this drug in a rat model of myelin oligodendrocyte glycoprotein-induced optic neuritis. FTY720 exerted significant anti-inflammatory effects during optic neuritis and reduced inflammation, demyelination, and axonal damage; however, FTY720 treatment did not prevent apoptosis of retinal ganglion cells (RGCs), the neurons that form the axons of the optic nerve. Consistent with this lack of effect on RGC survival, FTY720 treatment did not improve visual function, nor did it prevent apoptosis of RGCs in vitro. We observed a persistent activation of apoptotic signaling pathways in RGCs under FTY720 treatment, a possible underlying mechanism for the lack of neuroprotection in the presence of strong anti-inflammatory effects, Furthermore, FTY720 shifted the remaining inflammation in the optic nerve toward neurotoxicity by modest up-regulation of potential neurotoxic cytokines. We conclude that FTY720-induced anti-inflammation and axon protection did not of itself protect neurons from apoptotic cell death.

Benzofuran Derivatives as Potent, Orally Active S1P1 Receptor Agonists: A Preclinical Lead Molecule for MS

We have discovered novel benzofuran-based S1P1 agonists with excellent in vitro potency and selectivity. 1-((4-(5-Benzylbenzofuran-2-yl)-3-fluorophenyl)methyl) azetidine-3-carboxylic acid (18) is a potent S1P1 agonist with >1000× selectivity over S1P3. It demonstrated a good in vitro ADME profile and excellent oral bioavailability across species. Dosed orally at 0.3 mg/kg, 18 significantly reduced blood lymphocyte counts 24 h postdose and demonstrated efficacy in a mouse EAE model of relapsing MS.

Mechanism of action of oral fingolimod (FTY720) in multiple sclerosis

Fingolimod (FTY720) is a first-in-class orally bioavailable compound that has shown efficacy in advanced clinical trials for the treatment of multiple sclerosis (MS). In vivo, fingolimod is phosphorylated to form fingolimod-phosphate, which resembles naturally occurring sphingosine 1-phosphate (S1P), an extracellular lipid mediator whose major effects are mediated by cognate G protein-coupled receptors. There are at least 5 S1P receptor subtypes, known as S1P subtypes 1-5 (S1P1-5), 4 of which bind fingolimod-phosphate. These receptors are expressed on a wide range of cells that are involved in many biological processes relevant to MS. S1P1 plays a key role in the immune system, regulating lymphocyte egress from lymphoid tissues into the circulation. Fingolimod-phosphate initially activates lymphocyte S1P1 via high-affinity receptor binding yet subsequently induces S1P1 down-regulation that prevents lymphocyte egress from lymphoid tissues, thereby reducing autoaggressive lymphocyte infiltration into the central nervous system (CNS). S1P receptors are also expressed by many CNS cell types and have been shown to influence cell proliferation, morphology, and migration. Fingolimod crosses the blood-brain barrier and may therefore have direct CNS effects, distinguishing it from immunologically targeted MS therapies. Prophylactic administration of fingolimod to animals with experimental autoimmune encephalitis (EAE), a model of MS, completely prevents development of EAE features, whereas therapeutic administration significantly reduces clinical severity of EAE. Therapeutic efficacy observed in animal studies has been substantiated in phase 2 and 3 trials involving patients with relapsing or relapsing-remitting MS.

Control of metabolism and signaling of simple bioactive sphingolipids: Implications in disease

Simple bioactive sphingolipids include ceramide, sphingosine and their phosphorylated forms sphingosine 1-phosphate and ceramide 1-phosphate. These molecules are crucial regulators of cell functions. In particular, they play important roles in the regulation of angiogenesis, apoptosis, cell proliferation, differentiation, migration, and inflammation. Decoding the mechanisms by which these cellular functions are regulated requires detailed understanding of the signaling pathways that are implicated in these processes. Most importantly, the development of inhibitors of the enzymes involved in their metabolism may be crucial for establishing new therapeutic strategies for treatment of disease.