FTY720: from bench to bedside

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.

Involvement of Lipids in the Pathogenesis of Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by the progressive degeneration of upper and lower motor neurons. To study its underlying mechanisms, a variety of models are currently used at the cellular level and in animals with mutations in multiple ALS associated genes, including SOD1, C9ORF72, TDP-43, and FUS. Key mechanisms involved in the disease include excitotoxicity, oxidative stress, mitochondrial dysfunction, neuroinflammatory, and immune reactions. In addition, significant metabolism alterations of various lipids classes, including phospholipids, fatty acids, sphingolipids, and others have been increasingly recognized. Recently, the mechanisms of programmed cell death (apoptosis), which may be responsible for the degeneration of motor neurons observed in the disease, have been intensively studied. In this context, sphingolipids, which are the most important sources of secondary messengers transmitting signals for cell proliferation, differentiation, and apoptosis, are gaining increasing attention in the context of ALS pathogenesis given their role in the development of neuroinflammatory and immune responses. This review describes changes in lipids content and activity of enzymes involved in their metabolism in ALS, both summarizing current evidence from animal models and clinical studies and discussing the potential of new drugs among modulators of lipid metabolism enzymes.

[The role of sphingolipids in pathogenesis of amyotrophic lateral sclerosis]

Amyotrophic lateral sclerosis (ALS) is an incurable neurodegenerative disease characterized by selective degeneration of motor neurons of the spinal cord and motor cortex and brain stem. The key features of the course of this disease are excitotoxicity, oxidative stress, mitochondrial dysfunction, neuro-inflammatory and immune reactions. Recently, the mechanisms of programmed cell death (apoptosis), which may be responsible for the degeneration of motor neurons in this disease, have been intensively studied. In this regard, sphingolipids, which are the most important sources of secondary messengers that transmit cell proliferation, differentiation and apoptosis signals, and are involved in the development of neuroinflammatory and immune responses, are of particular interest in the context of ALS pathogenesis. The review provides information from domestic and foreign authors on the involvement of various sphingolipids (sphingomyelins, ceramides, sphingosine, sphinganin, sphingosine-1-phosphate, galactosylceramides, glucosylceramides, gangliosides) in the development of pro-inflammatory reactions and apoptosis of motor neurons in ALS. The authors discuss the prospects of using new drugs that control the metabolism of sphingolipids for the treatment of ALS.

Cenerimod, a novel selective S1P1 receptor modulator with unique signaling properties

Sphingosine-1-phosphate receptor 1 (S1P₁ ) modulators sequester circulating lymphocytes within lymph nodes, thereby preventing potentially pathogenic autoimmune cells from exiting into the blood stream and reaching inflamed tissues. S1P₁ receptor modulation may thus offer potential to treat various autoimmune diseases. The first nonselective S1P_1-5 receptor modulator FTY720/fingolimod/Gilenya^® has successfully demonstrated clinical efficacy in relapsing forms of multiple sclerosis. However, cardiovascular, hepatic, and respiratory side-effects were reported and there is a need for novel S1P₁ receptor modulators with better safety profiles. Here, we describe the discovery of cenerimod, a novel, potent and selective S1P₁ receptor modulator with unique S1P₁ receptor signaling properties and absence of broncho- and vasoconstrictor effects ex vivo and in vivo. Cenerimod dose-dependently lowered circulating lymphocyte counts in rats and mice after oral administration and effectively attenuated disease parameters in a mouse experimental autoimmune encephalitis (EAE) model. Cenerimod has potential as novel therapy with improved safety profile for autoimmune diseases with high unmet medical need.

PP2A deactivation is a common event in oral cancer and reactivation by FTY720 shows promising therapeutic potential

Protein phosphatase 2A (PP2A) is a tumor suppressor gene, that has been frequently deactivated in many types of cancer. However, its molecular and clinical relevance in oral squamous cell carcinoma (OSCC) remain unclear. Here we show that, PP2A deactivation is a common event in oral cancer cells and hyperphosphorylation in its tyrosine-307 (Y307) residue contributes to PP2A deactivation. PP2A restoration by FTY720 treatment reduced cell growth and decreased GSK-3β phosphorylation without significantly altering other PP2A targets. We further detected PP2A phosphorylation in 262 OSCC tissues. Increased expression of p-PP2A in the tumor tissues was significantly correlated with higher N2/N3-stage (aOR = 2.1, 95%CI: 1.2-3.8). Patients with high p-PP2A expression had lower overall survival rates than those with low expression. Hazard ratio analysis showed that, high p-PP2A expression was significantly associated with mortality density (aOR = 2.2, 95%CI: 1.2-4.0) and lower 10-year overall survival (p = 0.027) in lymph node metastasis. However, no interaction was observed between p-PP2A expression and lymph node metastasis. All our results suggest that PP2A is frequently deactivated in oral cancer and determines poor outcome, restoring its expression by FTY720 can be an alternative therapeutic approach in OSCC.

Fingolimod: A Disease-Modifier Drug in a Mouse Model of Amyotrophic Lateral Sclerosis

Fingolimod phosphate (FTY720), the first approved oral therapy for multiple sclerosis, primarily acts as an immunomodulator. Its concomitant effects in the central nervous system, however, indicate a potentially broader spectrum of activity in neurodegenerative diseases. In the present study, we investigated the possible effects of fingolimod in a mouse model of amyotrophic lateral sclerosis (ALS), a neurodegenerative disease characterized by a strong neuroinflammatory component. Fingolimod (0.1 and 1 mg/kg i.p.) was administered to mSOD1G93A mice, a well-characterized mouse model of ALS, starting from the onset of motor symptoms to the end stage of the disease. The drug was able to improve the neurological phenotype (p < 0.05) and to extend the survival (p < 0.01) of ALS mice. The beneficial effect of fingolimod administration was associated with a significant modulation of neuroinflammatory and protective genes (CD11b, Foxp3, iNOS, Il1β, Il10, Arg1, and Bdnf) in motor cortex and spinal cord of animals. Our data show, for the first time, that fingolimod is protective in ALS mice and that its beneficial effects are accompanied by a modulation of microglial activation and innate immunity. Considering that the treatment was started in already symptomatic mice, our data strongly support fingolimod as a potential new therapeutic approach to ALS.

Protein phosphatase 2A: a target for anticancer therapy

Protein phosphatase 2A (PP2A), one of the main serine-threonine phosphatases in mammalian cells, maintains cell homoeostasis by counteracting most of the kinase-driven intracellular signalling pathways. Unrestrained activation of oncogenic kinases together with inhibition of tumour suppressors is often required for development of cancer. PP2A has been shown to be genetically altered or functionally inactivated in many solid cancers and leukaemias, and is therefore a tumour suppressor. For example, the phosphatase activity of PP2A is suppressed in chronic myeloid leukaemia and other malignancies characterised by aberrant activity of oncogenic kinases. Preclinical studies show that pharmacological restoration of PP2A tumour-suppressor activity by PP2A-activating drugs (eg, FTY720) effectively antagonises cancer development and progression. Here, we discuss PP2A as a druggable tumour suppressor in view of the possible introduction of PP2A-activating drugs into anticancer therapeutic protocols.

A novel immunomodulator, FTY-720 reverses existing cardiac hypertrophy and fibrosis from pressure overload by targeting NFAT (nuclear factor of activated T-cells) signaling and periostin

BACKGROUND

Hypertension or aortic stenosis causes pressure overload, which evokes hypertrophic myocardial growth. Sustained cardiac hypertrophy eventually progresses to heart failure. Growing evidence indicates that restraining hypertrophy could be beneficial; here, we discovered that FTY-720, an immunomodulator for treating multiple sclerosis, can reverse existing cardiac hypertrophy/fibrosis.

METHODS AND RESULTS

Male C57/Bl6 mice underwent transverse aortic constriction (TAC) for 1 week followed by FTY-720 treatment for 2 weeks under continuing TAC. Compared with vehicle-treated TAC hearts, FTY-720 significantly reduced ventricular mass, ameliorated fibrosis, and improved cardiac performance. Mechanistic studies led us to discover that FTY-720 appreciably inhibited nuclear factor of activated T-cells (NFAT) activity. Moreover, we found that in primary cardiomyocytes (rat and human) pertussis toxin (Gi-coupled receptor inhibitor) substantially blocked the antihypertrophic effect of FTY-720. This observation was confirmed in a mouse model of pressure overload. Interestingly, gene array analysis of TAC hearts revealed that FTY-720 profoundly decreased gene expression of a group of matricellular proteins, of which periostin was prominent. Analysis of periostin protein expression in TAC-myocardium, as well as in rat and human cardiac fibroblasts, confirmed the array data. Moreover, we found that FTY-720 treatment or knockdown of periostin protein was able to inhibit transforming growth factor-β responsiveness and decrease collagen expression.

CONCLUSIONS

FTY-720 alleviates existing cardiac hypertrophy/fibrosis through mechanisms involving negative regulation of NFAT activity in cardiomyocytes and reduction of periostin expression allowing for a more homeostatic extracellular compartment milieu. Together, FTY-720 or its analogues could be a promising new approach for treating hypertrophic/fibrotic heart disease.

Novel immunomodulators based on an oxazolin-2-one-4-carboxamide scaffold

A series of oxazolidin-2-one-4-carboxylic amide compounds (1a-f) were designed and synthesized as the non-phosphate S1P(1) receptor agonists. The single crystal of 1e was prepared and solved to elucidate the structure of 1a-f. EC(50) of 1a-d were about 1.1-3.6 μM in S1P(1) Redistribution® assay, and their cytotoxicity was 8-40-fold lower than FTY720. Though its S1P(1) agonist activities in vitro were about 1000-folds weaker than (S)-FTY720-P, at a dose of 10mg/Kg, the immunosuppressive effects of 1a were comparable to FTY720. So oxazolidin-2-one-4-carboxylic amide derivatives were found as potential immunomodulator, compound 1a could be considered as a lead compound, rational modifications of 1a are anticipated using medicinal chemistry techniques and molecular modeling to obtain analogs with higher affinity and better clinical therapeutic properties.

Autoimmune hepatitis: new paradigms in the pathogenesis, diagnosis, and management

Autoimmune hepatitis (AIH), primary biliary cirrhosis, and primary sclerosing cholangitis are the three major autoimmune diseases affecting the liver, and of these three, AIH is the most typical autoimmune disease being characterized by a T-cell-rich infiltrate, raised circulating γ-globulins, autoantibodies, HLA associations, and links with other autoimmune diseases. It is the only one, of the three diseases, that responds well to immunosuppressive therapy. AIH is caused by dysregulation of immunoregulatory networks and the consequent emergence of autoreactive T cells that orchestrate a progressive destruction of hepatocytes leading untreated to liver failure. T cells play a major role in the immunopathogenesis, and both CD4(+) and CD8(+) T cells are involved together with effector responses mediated by NK cells, γδ T cells, and macrophages. A number of triggering factors have been proposed including viruses, xenobiotics, and drugs, but none have been conclusively shown to be involved in pathogenesis.

Sphingosine 1-phosphate receptor signaling

The sphingosine 1-phosphate (S1P) receptor signaling system is a productive model system. A hydrophobic zwitterionic lysophospholipid ligand with difficult physical properties interacts with five high-affinity G protein-coupled receptors to generate multiple downstream signals. These signals modulate homeostasis and pathology on a steep agonist concentration-response curve. Ligand presence is essential for vascular development and endothelial integrity, while acute increases in ligand concentrations result in cardiac death. Understanding this integrated biochemical system has exemplified the impact of both genetics and chemistry. Developing specific tools with defined biochemical properties for the reversible modulation of signals in real time has been essential to complement insights gained from genetic approaches that may be irreversible and compensated. Despite its knife-edge between life and death, this system, based in part on receptor subtype-selectivity and in part on differential attenuation of deleterious signals, now appears to be on the cusp of meaningful therapy for multiple sclerosis.

Increased survival and reduced renal injury in MRL/lpr mice treated with a novel sphingosine-1-phosphate receptor agonist

Agonists of the type 1 sphingosine-1-phosphate (S1P) receptor inhibit lymphocyte migration, causing their sequestration in lymphoid tissue. The S1P agonist FTY720 prolongs the survival of organ allografts and blocks T-cell mediated autoimmune diseases in experimental models; however, it is a non-selective agonist of four of the five S1P receptors. In this study female MRL/lpr mice, which develop an aggressive form of spontaneous autoimmune kidney disease, were treated with a more selective agonist of the type 1 receptor (KRP-203) or vehicle at 12 or 16 weeks of age. Eighty percent of the mice treated at 12 weeks, before the onset of visible disease, survived to the 24 weeks end point with decreased tubulointerstitial disease and significantly fewer infiltrating CD4(+) and CD8(+) T-cells. Only half of the control vehicle-treated mice survived. All of the mice treated at 16 weeks survived with reduced proteinuria. Mice in both groups had significant reductions in circulating lymphocytes. Mice receiving KRP-203 for 8-12 weeks had significant reductions in T-cells and consequently less adenopathy. Ex vivo treatment of lymphocytes from MRL/lpr mice with KRP-203 enhanced their apoptosis. Our study indicates that KRP-203 attenuates kidney injury in MRL/lpr mice, in part, by reducing T-cell infiltrates.

Sphingosine 1-phosphate receptor agonism impairs skin dendritic cell migration and homing to secondary lymphoid tissue: association with prolonged allograft survival

The novel immunomodulator FTY720 is a prototypic sphingosine-1-phosphate (S1P) receptor agonist that regulates lymphocyte migration and prolongs allograft survival. Skin dendritic cells (DC) play important roles in cutaneous immunity. We investigated the migration and function of skin DC exposed to FTY720 in vivo, or to its metabolite FTY720 phosphate (P) in vitro. C57BL/10 (H2(b)) recipient (but not donor) FTY720 treatment prolonged median skin C3H (H2(k)) allograft survival significantly, from 12 to 34.5 days. Non-transplanted, FTY720-treated mice revealed a marked increase in skin DC, although total DC in skin-draining lymph nodes (DLN) were unchanged compared with controls. Fewer allogeneic donor DC migrated to DLN of FTY720-treated graft recipients. DC that migrated from the skin of FTY720-treated mice showed reduced MHC class II, CD86 and CCR7 expression, suggesting impaired migratory potential to secondary lymphoid tissue, that correlated with DC retention in skin, and reduced T cell stimulatory activity. Fewer DC migrated from normal skin explants exposed to the FTY720 metabolite, FTY720P than to control medium. DC that did migrate expressed lower levels of MHC class II, CD86 and CCR7, and inferior T cell stimulatory ability. These data demonstrate S1P signaling regulates skin DC trafficking and modulates MHC class II, costimulatory, and homing receptor molecule expression that impairs their ability to elicit allogeneic T cell responses.

FTY720, a new alternative for treating blast crisis chronic myelogenous leukemia and Philadelphia chromosome-positive acute lymphocytic leukemia

Blast crisis chronic myelogenous leukemia (CML-BC) and Philadelphia chromosome-positive (Ph1-positive) acute lymphocytic leukemia (ALL) are 2 fatal BCR/ABL-driven leukemias against which Abl kinase inhibitors fail to induce a long-term response. We recently reported that functional loss of protein phosphatase 2A (PP2A) activity is important for CML blastic transformation. We assessed the therapeutic potential of the PP2A activator FTY720 (2-amino-2-[2-(4-octylphenyl)ethyl]-1,3-propanediol hydrochloride), an immunomodulator in Phase III trials for patients with multiple sclerosis or undergoing organ transplantation, in CML-BC and Ph1 ALL patient cells and in in vitro and in vivo models of these BCR/ABL+ leukemias. Our data indicate that FTY720 induces apoptosis and impairs clonogenicity of imatinib/dasatinib-sensitive and -resistant p210/p190(BCR/ABL) myeloid and lymphoid cell lines and CML-BC(CD34+) and Ph1 ALL(CD34+/CD19+) progenitors but not of normal CD34+ and CD34+/CD19+ bone marrow cells. Furthermore, pharmacologic doses of FTY720 remarkably suppress in vivo p210/p190(BCR/ABL)-driven [including p210/p190(BCR/ABL)(T315I)] leukemogenesis without exerting any toxicity. Altogether, these results highlight the therapeutic relevance of rescuing PP2A tumor suppressor activity in Ph1 leukemias and strongly support the introduction of the PP2A activator FTY720 in the treatment of CML-BC and Ph1 ALL patients.

Drug discovery from natural products

Natural product compounds are the source of numerous therapeutic agents. Recent progress to discover drugs from natural product sources has resulted in compounds that are being developed to treat cancer, resistant bacteria and viruses and immunosuppressive disorders. Many of these compounds were discovered by applying recent advances in understanding the genetics of secondary metabolism in actinomycetes, exploring the marine environment and applying new screening technologies. In many instances, the discovery of a novel natural product serves as a tool to better understand targets and pathways in the disease process. This review describes recent progress in drug discovery from natural sources including several examples of compounds that inhibit novel drug targets.

The sphingosine-1-phosphate receptor agonist FTY720 modulates dendritic cell trafficking in vivo

The pro-drug FTY720 is undergoing phase III clinical trials for prevention of allograft rejection. After phosphorylation, FTY720 targets the G protein-coupled-sphingosine-1-phosphate receptor 1 (S1PR1) on lymphocytes, thereby inhibiting their egress from lymphoid organs and their recirculation to inflammatory sites. Potential effects on dendritic cell (DC) trafficking have not been evaluated. Here, we demonstrate the expression of all five S1PR subtypes (S1PR1-5) by murine DCs. Administration of FTY720 to C57BL/10 mice markedly reduced circulating T and B lymphocytes within 24 h, but not blood-borne DCs, which were enhanced significantly for up to 96 h, while DCs in lymph nodes and spleen were reduced. Numbers of adoptively transferred, fluorochrome-labeled syngeneic or allogeneic DCs in blood were increased significantly in FTY720-treated animals, while donor-derived DCs and allostimulatory activity for host naïve T cells within the spleen were reduced. Administration of the selective S1PR1 agonist SEW2871 significantly enhanced circulating DC numbers. Flow analysis revealed that CD11b, CD31/PECAM-1, CD54/ICAM-1 and CCR7 expression on blood-borne DCs was downregulated following FTY720 administration. Transendothelial migration of FTY720-P-treated immature DCs to the CCR7 ligand CCL19 was reduced. These novel data suggest that modulation of DC trafficking by FTY720 may contribute to its immunosuppressive effects.