FTY720: targeting G-protein-coupled receptors for sphingosine 1-phosphate in transplantation and autoimmunity

S1PR1 inhibition induces proapoptotic signaling in T cells and limits humoral responses within lymph nodes

Effective immunity requires a large, diverse naive T cell repertoire circulating among lymphoid organs in search of antigen. Sphingosine 1-phosphate (S1P) and its receptor S1PR1 contribute by both directing T cell migration and supporting T cell survival. Here, we addressed how S1P enables T cell survival and the implications for patients treated with S1PR1 antagonists. We found that S1PR1 limited apoptosis by maintaining the appropriate balance of BCL2 family members via restraint of JNK activity. Interestingly, the same residues of S1PR1 that enable receptor internalization were required to prevent this proapoptotic cascade. Findings in mice were recapitulated in ulcerative colitis patients treated with the S1PR1 antagonist ozanimod, and the loss of naive T cells limited B cell responses. Our findings highlighted an effect of S1PR1 antagonists on the ability to mount immune responses within lymph nodes, beyond their effect on lymph node egress, and suggested both limitations and additional uses of this important class of drugs.

Sphingosine 1-phosphate receptor 1 inhibition induces a pro-apoptotic signaling cascade in T cells

Effective immunity requires a large, diverse naïve T cell repertoire circulating among lymphoid organs in search of antigen. Sphingosine 1-phosphate (S1P) and its receptor S1PR1 contribute by both directing T cell migration and supporting T cell survival. Here, we address how S1P enables T cell survival, and the implications for patients treated with S1PR1 antagonists. Contrary to expectations, we found that S1PR1 limits apoptosis by maintaining the appropriate balance of BCL2 family members via restraint of JNK activity. Interestingly, the same residues of S1PR1 that enable receptor internalization are required to prevent this pro-apoptotic cascade. Findings in mice were recapitulated in ulcerative colitis patients treated with the S1PR1 antagonist ozanimod, and the loss of naïve T cells limited B cell responses. Our findings highlight an unexpected effect of S1PR1 antagonists on the ability to mount immune responses within lymph nodes, beyond their effect on lymph node egress, and suggest both limitations and novel uses of this important class of drugs.

FTY720 administration results in a M2 associated immunoregulatory effect that positively influences the outcome of alveolar bone repair outcome in mice

The alveolar bone repair process may be influenced by multiple local and systemic factors, which include immune system cells and mediators. Macrophages allegedly play important roles in the repair process, and the transition of an initial inflammatory M1 profile into a pro-reparative M2 profile theoretically contributes to a favorable repair outcome. In this context, considering immunoregulatory molecules as potential targets for improving bone repair, this study evaluated the role of the immunoregulatory molecule FTY720, previously described to favor the development of the M2 phenotype, in the process of alveolar bone healing in C57Bl/6 (WT) mice. Experimental groups submitted to tooth extraction and maintained under control conditions or treated with FTY720 were evaluated by microtomographic (μCT), histomorphometric, immunohistochemical and molecular analysis to characterize healing and host response features at 0, 1, 3, 7 and 14 days. Our results demonstrated that the FTY720 group presented higher bone tissue density, higher bone tissue volume, greater tissue volume fraction, greater number and thickness of trabeculae and a higher number of osteoblasts and osteoclasts than the control group. Accordingly, the bone markers BMP2, BMP7, ALPL, SOST and RANK mRNA expressions increased in the FTY720 treated group. Furthermore, the levels of FIZZ, ARG2 and IL-10 mRNA increased in the FTY720 group together with the presence of CD206⁺ cells, suggesting that the boost of bone formation mediated by FTY720 involves an increased polarization and activity of M2 macrophages in healing sites. Thus, our results demonstrate that FTY720 favored the process of alveolar bone repair, probably trough a strengthened M2 response, associated with an increased expression of markers osteogenic differentiation and activity markers. Immunoregulatory strategies based in the modulation of macrophage polarization profile can comprise effective tools to improve the bone repair process.

Molecular Pharmacology and Novel Potential Therapeutic Applications of Fingolimod

Fingolimod is a well-tolerated, highly effective disease-modifying therapy successfully utilized in the management of multiple sclerosis. The active metabolite, fingolimod-phosphate, acts on sphingosine-1-phosphate receptors (S1PRs) to bring about an array of pharmacological effects. While being initially recognized as a novel agent that can profoundly reduce T-cell numbers in circulation and the CNS, thereby suppressing inflammation and MS, there is now rapidly increasing knowledge on its previously unrecognized molecular and potential therapeutic effects in diverse pathological conditions. In addition to exerting inhibitory effects on sphingolipid pathway enzymes, fingolimod also inhibits histone deacetylases, transient receptor potential cation channel subfamily M member 7 (TRMP7), cytosolic phospholipase A2α (cPLA2α), reduces lysophosphatidic acid (LPA) plasma levels, and activates protein phosphatase 2A (PP2A). Furthermore, fingolimod induces apoptosis, autophagy, cell cycle arrest, epigenetic regulations, macrophages M1/M2 shift and enhances BDNF expression. According to recent evidence, fingolimod modulates a range of other molecular pathways deeply rooted in disease initiation or progression. Experimental reports have firmly associated the drug with potentially beneficial therapeutic effects in immunomodulatory diseases, CNS injuries, and diseases including Alzheimer's disease (AD), Parkinson's disease (PD), epilepsy, and even cancer. Attractive pharmacological effects, relative safety, favorable pharmacokinetics, and positive experimental data have collectively led to its testing in clinical trials. Based on the recent reports, fingolimod may soon find its way as an adjunct therapy in various disparate pathological conditions. This review summarizes the up-to-date knowledge about molecular pharmacology and potential therapeutic uses of fingolimod.

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

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

Fingolimod as a Treatment in Neurologic Disorders Beyond Multiple Sclerosis

Fingolimod is an approved treatment for relapsing-remitting multiple sclerosis (MS), and its properties in different pathways have raised interest in therapy research for other neurodegenerative diseases. Fingolimod is an agonist of sphingosine-1-phosphate (S1P) receptors. Its main pharmacologic effect is immunomodulation by lymphocyte homing, thereby reducing the numbers of T and B cells in circulation. Because of the ubiquitous expression of S1P receptors, other effects have also been described. Here, we review preclinical experiments evaluating the effects of treatment with fingolimod in neurodegenerative diseases other than MS, such as Alzheimer's disease or epilepsy. Fingolimod has shown neuroprotective effects in different animal models of neurodegenerative diseases, summarized here, correlating with increased brain-derived neurotrophic factor and improved disease phenotype (cognition and/or motor abilities). As expected, treatment also induced reductions in different neuroinflammatory markers because of not only inhibition of lymphocytes but also direct effects on astrocytes and microglia. Furthermore, fingolimod treatment exhibited additional effects for specific neurodegenerative disorders, such as reduction of amyloid-β production, and antiepileptogenic properties. The neuroprotective effects exerted by fingolimod in these preclinical studies are reviewed and support the translation of fingolimod into clinical trials as treatment in neurodegenerative diseases beyond neuroinflammatory conditions (MS).

Improving Tumor Retention of Effector Cells in Adoptive Cell Transfer Therapies by Magnetic Targeting

Adoptive cell transfer therapy is a promising anti-tumor immunotherapy in which effector immune cells are transferred to patients to treat tumors. However, one of its main limitations is the inefficient trafficking of inoculated effector cells to the tumor site and the small percentage of effector cells that remain activated when reaching the tumor. Multiple strategies have been attempted to improve the entry of effector cells into the tumor environment, often based on tumor types. It would be, however, interesting to develop a more general approach, to improve and facilitate the migration of specific activated effector lymphoid cells to any tumor type. We and others have recently demonstrated the potential for adoptive cell transfer therapy of the combined use of magnetic nanoparticle-loaded lymphoid effector cells together with the application of an external magnetic field to promote the accumulation and retention of lymphoid cells in specific body locations. The aim of this review is to summarize and highlight the recent findings in the field of magnetic accumulation and retention of effector cells in tumors after adoptive transfer, and to discuss the possibility of using this approach for tumor targeting with chimeric antigen receptor (CAR) T-cells.

Fingolimod inhibits multiple stages of the HIV-1 life cycle

Antiretroviral drugs that target various stages of the Human Immunodeficiency Virus (HIV) life cycle have been effective in curbing the AIDS epidemic. However, drug resistance, off-target effects of antiretroviral therapy (ART), and varying efficacy in prevention underscore the need to develop novel and alternative therapeutics. In this study, we investigated whether targeting the signaling molecule Sphingosine-1-phosphate (S1P) would inhibit HIV-1 infection and generation of the latent reservoir in primary CD4 T cells. We show that FTY720 (Fingolimod), an FDA-approved functional antagonist of S1P receptors, blocks cell-free and cell-to-cell transmission of HIV and consequently reduces detectable latent virus. Mechanistically, FTY720 impacts the HIV-1 life cycle at two levels. Firstly, FTY720 reduces the surface density of CD4, thereby inhibiting viral binding and fusion. Secondly, FTY720 decreases the phosphorylation of the innate HIV restriction factor SAMHD1 which is associated with reduced levels of total and integrated HIV, while reducing the expression of Cyclin D3. In conclusion, targeting the S1P pathway with FTY720 could be a novel strategy to inhibit HIV replication and reduce the seeding of the latent reservoir.

Early drop of circulating T cells negatively correlates with the protective immune response to Yellow Fever vaccination

Lymphocyte recirculation within the human body is essential for efficient pathogen detection and immune responses. So far, immune cell migration has been investigated largely using ovine and murine models, with little evidence in humans. Here, we analyzed peripheral blood of healthy individuals following primary vaccination with the Yellow Fever vaccine YF-17D. We found that the number of leukocytes was transiently and sharply reduced in blood as detected on day 7 after vaccine administration. The T cell drop was restricted to cells expressing the lymph node-homing chemokine receptor CCR7. Interestingly, the vaccine-induced drop positively correlated with the expression of CD69 by the T cells before vaccination. This suggests that CCR7⁺ T cells are being trapped within the lymph nodes through CD69-induced suppression of egress. Strikingly, we further found that the T cell drop negatively correlated with CD8 T cell activation and with production of neutralizing antibodies. In conclusion, early and transient T cell depletion in blood negatively correlated with protective immune response events induced by YF-17D vaccination. Our data highlight baseline CD69 expression and early drop in T cells as potential biomarkers of the Yellow Fever vaccine response.

A20 as an immune tolerance factor can determine islet transplant outcomes

Islet transplantation can restore lost glycemic control in type 1 diabetes subjects but is restricted in its clinical application by a limiting supply of islets and the need for heavy immune suppression to prevent rejection. TNFAIP3, encoding the ubiquitin editing enzyme A20, regulates the activation of immune cells by raising NF-κB signaling thresholds. Here, we show that increasing A20 expression in allogeneic islet grafts resulted in permanent survival for ~45% of recipients, and > 80% survival when combined with subtherapeutic rapamycin. Allograft survival was dependent upon Tregs and was antigen specific, and grafts showed reduced expression of inflammatory factors. Transplantation of islets with A20 containing a loss-of-function variant (I325N) resulted in increased RIPK1 ubiquitination and NF-κB signaling, graft hyperinflammation, and acute allograft rejection. Overexpression of A20 in human islets potently reduced expression of inflammatory mediators, with no impact on glucose-stimulated insulin secretion. Therapeutic administration of A20 raises inflammatory signaling thresholds to favor immune tolerance and promotes islet allogeneic survival. Clinically, this would allow for reduced immunosuppression and support the use of alternate islet sources.

Anti-donor MHC Class II Alloantibody Induces Glomerular Injury in Mouse Renal Allografts Subjected to Prolonged Cold Ischemia

BACKGROUND

The mechanisms underlying the effects of prolonged cold-ischemia storage on kidney allografts are poorly understood.

METHODS

To investigate effects of cold ischemia on donor-reactive immune responses and graft pathology, we used a mouse kidney transplantation model that subjected MHC-mismatched BALB/c kidney allografts to cold-ischemia storage for 0.5 or 6 hours before transplant into C57BL/6 mice.

RESULTS

At day 14 post-transplant, recipients of allografts subjected to 6 versus 0.5 hours of cold-ischemia storage had increased levels of anti-MHC class II (but not class I) donor-specific antibodies, increased donor-reactive T cells, and a significantly higher proportion of transplant glomeruli infiltrated with macrophages. By day 60 post-transplant, allografts with a 6 hour cold-ischemia time developed extensive glomerular injury compared with moderate pathology in allografts with 0.5 hour of cold-ischemia time. Pathology was associated with increased serum levels of anti-class 2 but not anti-class 1 donor-specific antibodies. Recipient B cell depletion abrogated early macrophage recruitment, suggesting augmented donor-specific antibodies, rather than T cells, increase glomerular pathology after prolonged cold ischemia. Lymphocyte sequestration with sphingosine-1-phosphate receptor 1 antagonist FTY720 specifically inhibited anti-MHC class II antibody production and abrogated macrophage infiltration into glomeruli. Adoptive transfer of sera containing anti-donor MHC class II antibodies or mAbs against donor MHC class II restored early glomerular macrophage infiltration in FTY720-treated recipients.

CONCLUSIONS

Post-transplant inflammation augments generation of donor-specific antibodies against MHC class II antigens. Resulting MHC class II-reactive donor-specific antibodies are essential mediators of kidney allograft glomerular injury caused by prolonged cold ischemia.

Fingolimod Improves the Outcome of Experimental Graves' Disease and Associated Orbitopathy by Modulating the Autoimmune Response to the Thyroid-Stimulating Hormone Receptor

Graves' disease (GD) and Graves' orbitopathy are associated with stimulating thyrotropin receptor (TSHR) autoantibodies and autoreactive T cells. Recent in vitro studies suggested that sphingosine-1-phosphate (S1P) signaling is involved in the pathogenesis of orbitopathy. In this study, we explored the immune modulatory potential of S1P receptor antagonist fingolimod in a murine model for GD. Fingolimod was orally administered preventively during disease onset or therapeutically after disease onset. Administration of fingolimod during disease onset completely prevented the formation of TSHR-stimulating autoantibodies. Intervention after disease onset rarely reduced TSHR-stimulating autoantibodies and blocking autoantibodies were induced in some animals. Consequently, autoimmune hyperthyroidism characterized by elevated serum thyroxin levels, hyperplastic thyroid morphology accompanied by T cell infiltration, weight gain, enhanced body temperature, and tachycardia did not manifest preventively and showed milder manifestation in therapeutically treated animals. Importantly, examination of orbital tissue showed significant amelioration of orbitopathy manifestations through reduction of T cell infiltration, adipogenesis, and hyaluronan deposition. Autoimmune hyperthyroidism and orbitopathy were accompanied by changes in peripheral and splenic T cell proportions with high CD3⁺, CD4⁺, and CD8⁺ T cells. Activated T cells CD4⁺CD25⁺ were elevated whereas regulatory T cells CD4⁺Foxp3⁺ cells remained unchanged in spleens. Fingolimod decreased elevated T cell levels and increased CD4⁺CD25⁺Foxp3⁺ regulatory T cell populations. Analysis of total disease outcome revealed that treatment during disease onset protected animals against autoimmune hyperthyroidism and orbitopathy. Of note, therapeutic intervention after disease onset suppressed disease in half of the animals and in the other half disease remained at mild stages. The results of this study support a clinical trial to investigate the immunologic and clinical benefits of early treatment with S1P-based drugs in GD.

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.

Tissue-Resident Lymphocytes in Solid Organ Transplantation: Innocent Passengers or the Key to Organ Transplant Survival?

Short-term outcomes of solid organ transplantation have improved dramatically over the past several decades; however, long-term survival has remained static over the same period, and chronic rejection remains a major cause of graft failure. The importance of donor, or "passenger," lymphocytes to the induction of tolerance to allografts was recognized in the 1990s, but their precise contribution to graft acceptance or rejection has not been elucidated. Recently, specialized populations of tissue-resident lymphocytes in nonlymphoid organs have been described. These lymphocytes include tissue-resident memory T cells, regulatory T cells, γδ T cells, invariant natural killer T cells, and innate lymphoid cells. These cells reside in commonly transplanted solid organs, including the liver, kidneys, heart, and lung; however, their contribution to graft acceptance or rejection has not been examined in detail. Similarly, it is unclear whether tissue-resident cells derived from the pool of recipient-derived lymphocytes play a specific role in transplantation biology. This review summarizes the evidence for the roles of tissue-resident lymphocytes in transplant immunology, focussing on their features, functions, and relevance for solid organ transplantation, with specific reference to liver, kidney, heart, and lung transplantation.

Sphingolipids and their metabolism in physiology and disease

Studies of bioactive lipids in general and sphingolipids in particular have intensified over the past several years, revealing an unprecedented and unanticipated complexity of the lipidome and its many functions, which rivals, if not exceeds, that of the genome or proteome. These results highlight critical roles for bioactive sphingolipids in most, if not all, major cell biological responses, including all major cell signalling pathways, and they link sphingolipid metabolism to key human diseases. Nevertheless, the fairly nascent field of bioactive sphingolipids still faces challenges in its biochemical and molecular underpinnings, including defining the molecular mechanisms of pathway and enzyme regulation, the study of lipid-protein interactions and the development of cellular probes, suitable biomarkers and therapeutic approaches.

Sphingosine 1-phosphate receptor 3 and RhoA signaling mediate inflammatory gene expression in astrocytes

Background

Sphingosine 1-phosphate (S1P) signals through G protein-coupled receptors to elicit a wide range of cellular responses. In CNS injury and disease, the blood-brain barrier is compromised, causing leakage of S1P from blood into the brain. S1P can also be locally generated through the enzyme sphingosine kinase-1 (Sphk1). Our previous studies demonstrated that S1P activates inflammation in murine astrocytes. The S1P₁ receptor subtype has been most associated with CNS disease, particularly multiple sclerosis. S1P₃ is most highly expressed and upregulated on astrocytes, however, thus we explored the involvement of this receptor in inflammatory astrocytic responses.

Methods

Astrocytes isolated from wild-type (WT) or S1P₃ knockout (KO) mice were treated with S1P₃ selective drugs or transfected with short interfering RNA to determine which receptor subtypes mediate S1P-stimulated inflammatory responses. Interleukin-6 (IL-6), and vascular endothelial growth factor A (VEGFa) messenger RNA (mRNA) and cyclooxygenase-2 (COX-2) mRNA and protein were assessed by q-PCR and Western blotting. Activation of RhoA was measured using SRE.L luciferase and RhoA implicated in S1P signaling by knockdown of Gα_12/13 proteins or by inhibiting RhoA activation with C3 exoenzyme. Inflammation was simulated by in vitro scratch injury of cultured astrocytes.

Results

S1P₃ was highly expressed in astrocytes and further upregulated in response to simulated inflammation. Studies using S1P₃ knockdown and S1P₃ KO astrocytes demonstrated that S1P₃ mediates activation of RhoA and induction of COX-2, IL-6, and VEGFa mRNA, with some contribution from S1P₂. S1P induces expression of all of these genes through coupling to the Gα_12/13 proteins which activate RhoA. Studies using S1P₃ selective agonists/antagonists as well as Fingolimod (FTY720) confirmed that stimulation of S1P₃ induces COX-2 expression in astrocytes. Simulated inflammation increased expression of Sphk1 and consequently activated S1P₃, demonstrating an autocrine pathway through which S1P is formed and released from astrocytes to regulate COX-2 expression.

Conclusions

S1P₃, through its ability to activate RhoA and its upregulation in astrocytes, plays a unique role in inducing inflammatory responses and should be considered as a potentially important therapeutic target for CNS disease progression.

Urinary collagen degradation products as early markers of progressive renal fibrosis

Background

Renal fibrogenesis is associated with increased ECM remodeling and release of collagen fragments in urine in progressive renal disease. We investigated the diagnostic value of urinary collagen degradation products in a proteinuria-driven fibrosis rat model with and without anti-fibrotic S1P-receptor modulator FTY720 treatment.

Methods

Proteinuria was induced in male Wistar rats by Adriamycin (ADR) injection (n = 16). Healthy rats served as controls (n = 12). Six weeks post-injection, all underwent renal biopsy, and FTY720-treatment started in ADR-rats (n = 8) and controls (n = 6). Others remained untreated. Rats were sacrificed after 12 weeks. Collagen type I (C1M) and III (C3M) degradation fragments were measured in blood and urine using ELISA. Kidneys were stained for various inflammatory and fibrotic markers.

Results

Six weeks post-injection proteinuria increased (versus controls, P < 0.001) and although no accumulation of interstitial renal collagen type III (iColl3) was observed at this time, urinary C3M (uC3M) and C1M (uC1M) were significantly increased (both P < 0.001). At 12 weeks, uC3M (P < 0.001) and uC1M (P < 0.01) further increased in ADR-rats versus controls, just as fibronectin, PDGF-β receptor, hyaluronan (all P < 0.01), iColl3, PAS, myofibroblasts, macrophages and T-cells (all P < 0.05). FTY720-treatment reduced accumulation of immune cells, α-SMA+ myofibroblasts and PAS-score, but not iColl3 and uC3M. Correlation analyses indicated that uC3M and uC1M reflected and predicted tubulointerstitial fibrogenesis.

Conclusions

These data displayed urinary collagen breakdown products as sensitive early markers of interstitial fibrosis, preceding histological fibrotic changes, which might replace the invasive renal biopsy procedure to assess fibrosis. Anti-fibrotic FTY720 intervention reduced some fibrotic markers without affecting collagen type III metabolism.

Exit Strategies: S1P Signaling and T Cell Migration

Whereas the role of sphingosine 1-phosphate receptor 1 (S1PR1) in T cell egress and the regulation of S1P gradients between lymphoid organs and circulatory fluids in homeostasis are increasingly well understood, much remains to be learned about S1P signaling and distribution during an immune response. Recent data suggest that the role of S1PR1 in directing cells from tissues into circulatory fluids is reprised again and again, particularly in guiding activated T cells from non-lymphoid tissues into lymphatics. Conversely, S1P receptor 2 (S1PR2), which antagonizes migration towards chemokines, confines cells within tissues. Here we review the current understanding of the roles of S1P signaling in activated T cell migration. In this context, we outline open questions, particularly regarding the shape of S1P gradients in different tissues in homeostasis and inflammation, and discuss recent strategies to measure S1P.

Differential Effects of Long Term FTY720 Treatment on Endothelial versus Smooth Muscle Cell Signaling to S1P in Rat Mesenteric Arteries

The sphingosine-1-phosphate (S1P) analog FTY720 exerts pleiotropic effects on the cardiovascular system and causes down-regulation of S1P receptors. Myogenic constriction is an important mechanism regulating resistance vessel function and is known to be modulated by S1P. Here we investigated myogenic constriction and vascular function of mesenteric arteries of rats chronically treated with FTY720. Wistar rats received FTY720 1mg/kg/daily for six weeks. At termination, blood pressure was recorded and small mesenteric arteries collected for vascular studies in a perfusion set up. Myogenic constriction to increased intraluminal pressure was low, but a sub-threshold dose of S1P profoundly augmented myogenic constriction in arteries of both controls and animals chronically treated with FTY720. Interestingly, endothelial denudation blocked the response to S1P in arteries of FTY720-treated animals, but not in control rats. In acute experiments, presence of FTY720 significantly augmented the contractile response to S1P, an effect that was partially abolished after the inhibition of cyclooxygenase (COX-)-derived prostaglandins. FTY720 down regulated S1P1 but not S1P2 in renal resistance arteries and in cultured human endothelial cells. This study therefore demonstrates the endothelium is able to compensate for the complete loss of responsiveness of the smooth muscle layer to S1P after long term FTY720 treatment through a mechanism that most likely involves enhanced production of contractile prostaglandins by the endothelium.

From Natural Product to the First Oral Treatment for Multiple Sclerosis: The Discovery of FTY720 (Gilenya™)?

Multiple sclerosis is a devastating chronic autoimmune disease affecting women and men of all ages. Inflammation of the central nervous system causes demyelination and ultimately neuropsychological dysfunction. Myriocin, a natural product with strong immunosuppressant activity was interrogated leading to a new class of immunomodulator with a unique mode of action. In this review, we will summarize these findings, the mechanism hypothesis and discuss the data's ultimately leading to the approval of Gilenya™ as the first oral treatment for multiple sclerosis.

Effect of FTY720 (fingolimod) on graft survival in renal transplant recipients: a systematic review protocol

INTRODUCTION

Studies have shown that FTY720 has inconsistent effects in kidney transplant recipients. Several review articles on FTY720 have been published, but most have focused on the mechanism of action of FTY720. Therefore, this review aims to evaluate and determine the beneficial and harmful effects of FTY720 therapy in kidney transplant recipients.

METHODS AND ANALYSIS

We electronically searched the following databases: PubMed, Scopus, the Web of Sciences, EMBASE, Cochrane databases and the Cochrane Central Registry of Controlled Trials. Any clinical, randomised controlled trials relating to FTY720 for treating kidney transplant recipients were included without publication status or language restriction. Study selection, data extraction and assessment of study quality were performed independently by two researchers. Data were synthesised by either the fixed effects or the random effects model according to a heterogeneity test. If the extracted data were suitable for meta-analysis, STATA software was used to combine the relative risks for dichotomous outcomes, and the mean differences for continuous outcomes with 95% CIs were measured. Death, loss of function and incidence of acute kidney rejection were assessed as the primary outcomes. Renal graft function, malignancy, delayed graft function and infection were evaluated as secondary outcomes.

ETHICS/DISSEMINATION

This review does not require formal ethics approval because the data are not individualised. The resulting review article will be submitted for publication in a peer-reviewed journal.

TRIAL REGISTRATION NUMBER

CRD42015024648.

Sphingosine 1-phosphate signaling in astrocytes: Implications for progressive multiple sclerosis

Multiple sclerosis is an autoimmune disorder characterized by recurrent attacks against the central nervous system. After many years, certain patients enter a progressive disease phase, characterized by steady clinical deterioration. However, in 10-15% of patients, the disease is progressive from the beginning, and thus diagnosed as Primary Progressive Multiple Sclerosis. Unlike relapsing-remitting forms, progressive MS lacks effective therapy. Astrocytes are a major component of glial cells and are now thought to play a role in disease progression. Sphingosine 1-phophate is a molecule with extensive receptor expression on both immune and glial cells and is also a target of fingolimod, a drug used in relapsing remitting patients that sequesters lymphocytes within lymph nodes. However, because sphingosine 1-phosphate receptors are also expressed in astrocytes, and also because modification of this pathway has shown interesting benefits in animal models of Multiple Sclerosis, this astrocyte pathway has become an interesting target for developing potential new therapeutic approaches for Multiple Sclerosis.

Targeting tubulointerstitial remodeling in proteinuric nephropathy in rats

Proteinuria is an important cause of tubulointerstitial damage. Anti-proteinuric interventions are not always successful, and residual proteinuria often leads to renal failure. This indicates the need for additional treatment modalities by targeting the harmful downstream consequences of proteinuria. We previously showed that proteinuria triggers renal lymphangiogenesis before the onset of interstitial inflammation and fibrosis. However, the interrelationship of these interstitial events in proteinuria is not yet clear. To this end, we specifically blocked lymphangiogenesis (anti-VEGFR3 antibody), monocyte/macrophage influx (clodronate liposomes) or lymphocyte and myofibroblast influx (S1P agonist FTY720) separately in a rat model to investigate the role and the possible interaction of each of these phenomena in tubulointerstitial remodeling in proteinuric nephropathy. Proteinuria was induced in 3-month old male Wistar rats by adriamycin injection. After 6 weeks, when proteinuria has developed, rats were treated for another 6 weeks by anti-VEGFR3 antibody, clodronate liposomes or FTY720 up to week 12. In proteinuric rats, lymphangiogenesis, influx of macrophages, T cells and myofibroblasts, and collagen III deposition and interstitial fibrosis significantly increased at week 12 vs week 6. Anti-VEGFR3 antibody prevented lymphangiogenesis in proteinuric rats, however, without significant effects on inflammatory and fibrotic markers or proteinuria. Clodronate liposomes inhibited macrophage influx and partly reduced myofibroblast expression; however, neither significantly prevented the development of lymphangiogenesis, nor fibrotic markers and proteinuria. FTY720 prevented myofibroblast accumulation, T-cell influx and interstitial fibrosis, and partially reduced macrophage number and proteinuria; however, it did not significantly influence lymphangiogenesis and collagen III deposition. This study showed that proteinuria-induced interstitial fibrosis cannot be halted by blocking lymphangiogenesis or the influx of macrophages. On the other hand, FTY720 treatment did prevent T-cell influx, myofibroblast accumulation and interstitial fibrosis, but not renal lymphangiogenesis and proteinuria. We conclude that tubulointerstitial fibrosis and inflammation are separate from lymphangiogenesis, at least under proteinuric conditions.

Summary: Targeting lymphangiogenesis, inflammation or fibrosis separately in a rat model of proteinuric nephropathy showed that treating any of these changes alone is not effective in treating the disease.

Effector lymphocyte-induced lymph node-like vasculature enables naive T-cell entry into tumours and enhanced anti-tumour immunity

The presence of lymph node (LN)-like vasculature in tumors, characterized by expression of peripheral node addressin and chemokine CCL21, is correlated with T-cell infiltration and positive prognosis in breast cancer and melanoma patients. However, mechanisms controlling the development of LN-like vasculature and how it might contribute to a beneficial outcome for cancer patients are unknown. Here we demonstrate that LN-like vasculature is present in murine models of melanoma and lung carcinoma. It enables infiltration by naïve T-cells that significantly delay tumor outgrowth after intratumoral activation. Development of this vasculature is controlled by a mechanism involving effector CD8 T-cells and NK cells that secrete LTα₃ and IFNγ. LN-like vasculature is also associated with organized aggregates of B-lymphocytes and gp38⁺ fibroblasts that resemble tertiary lymphoid organs that develop in models of chronic inflammation. These results establish LN-like vasculature as both a consequence of and key contributor to anti-tumor immunity.

Synthesis and evaluation of fluorinated fingolimod (FTY720) analogues for sphingosine-1-phosphate receptor molecular imaging by positron emission tomography

Sphingosine-1-phosphate (S1P) is a lysophospholipid that evokes a variety of biological responses via stimulation of a set of cognate G-protein coupled receptors (GPCRs): S1P1-S1P5. S1P and its receptors (S1PRs) play important roles in the immune, cardiovascular, and central nervous systems and have also been implicated in carcinogenesis. Recently, the S1P analogue Fingolimod (FTY720) has been approved for the treatment of patients with relapsing multiple sclerosis. This work presents the synthesis of various fluorinated structural analogues of FTY720, their in vitro and in vivo biological testing, and their development and application as [(18)F]radiotracers for the study of S1PR biodistribution and imaging in mice using small-animal positron emission tomography (PET).

Loss of lysophosphatidic acid receptor LPA1 alters oligodendrocyte differentiation and myelination in the mouse cerebral cortex

Lysophosphatidic acid (LPA) is an intercellular signaling lipid that regulates multiple cellular functions, acting through specific G-protein coupled receptors (LPA(1-6)). Our previous studies using viable Malaga variant maLPA1-null mice demonstrated the requirement of the LPA1 receptor for normal proliferation, differentiation, and survival of the neuronal precursors. In the cerebral cortex LPA1 is expressed extensively in differentiating oligodendrocytes, in parallel with myelination. Although exogenous LPA-induced effects have been investigated in myelinating cells, the in vivo contribution of LPA1 to normal myelination remains to be demonstrated. This study identified a relevant in vivo role for LPA1 as a regulator of cortical myelination. Immunochemical analysis in adult maLPA1-null mice demonstrated a reduction in the steady-state levels of the myelin proteins MBP, PLP/DM20, and CNPase in the cerebral cortex. The myelin defects were confirmed using magnetic resonance spectroscopy and electron microscopy. Stereological analysis limited the defects to adult differentiating oligodendrocytes, without variation in the NG2+ precursor cells. Finally, a possible mechanism involving oligodendrocyte survival was demonstrated by the impaired intracellular transport of the PLP/DM20 myelin protein which was accompanied by cellular loss, suggesting stress-induced apoptosis. These findings describe a previously uncharacterized in vivo functional role for LPA1 in the regulation of oligodendrocyte differentiation and myelination in the CNS, underlining the importance of the maLPA1-null mouse as a model for the study of demyelinating diseases.

A potent and selective S1P(1) antagonist with efficacy in experimental autoimmune encephalomyelitis

Lymphocyte trafficking is critically regulated by the Sphingosine 1-phosphate receptor-1 (S1P(1)), a G protein-coupled receptor that has been highlighted as a promising therapeutic target in autoimmunity. Fingolimod (FTY720, Gilenya) is a S1P(1) receptor agonist that has recently been approved for the treatment of multiple sclerosis (MS). Here, we report the discovery of NIBR-0213, a potent and selective S1P(1) antagonist that induces long-lasting reduction of peripheral blood lymphocyte counts after oral dosing. NIBR-0213 showed comparable therapeutic efficacy to fingolimod in experimental autoimmune encephalomyelitis (EAE), a model of human MS. These data provide convincing evidence that S1P(1) antagonists are effective in EAE. In addition, the profile of NIBR-0213 makes it an attractive candidate to further study the consequences of S1P(1) receptor antagonism and to differentiate the effects from those of S1P(1) agonists.

Lung niches for the generation and maintenance of tissue-resident memory T cells

The extent to which tissue-specific viral infections generate memory T cells specifically adapted to and maintained within the target infection site is unknown. Here, we show that respiratory virus-specific memory T cells in mice and humans are generated and maintained in compartmentalized niches in lungs, distinct from populations in lymphoid tissue or circulation. Using a polyclonal mouse model of influenza infection combined with an in vivo antibody labeling approach and confocal imaging, we identify a spatially distinct niche in the lung where influenza-specific T-cell responses are expanded and maintained long term as tissue-resident memory (T(RM)) CD4 and CD8 T cells. Lung T(RM) are further distinguished from circulating memory subsets in lung and spleen based on CD69 expression and persistence independent of lymphoid stores. In humans, influenza-specific T cells are enriched within the lung T(RM) subset, whereas memory CD8 T cells specific for the systemic virus cytomegalovirus are distributed in both lung and spleen, suggesting that the site of infection affects T(RM) generation. Our findings reveal a precise spatial organization to virus-specific T-cell memory, determined by the site of the initial infection, with important implications for the development of targeted strategies to boost immunity at appropriate tissue sites.

Role of sphingolipids in oestrogen signalling in breast cancer cells: an update

The signaling pathways activated by the steroid hormone oestrogen include a variety of cytoplasmic second messengers linked to a multitude of tissue-specific effects. In the last decade, sphingolipids and their membrane receptors were added to the list of oestrogen-activated mediators. Oestrogen triggers the sphingolipid signalling cascade in various tissues including breast cancer. Extensive research has shown that sphingolipids are the key regulatory molecules in growth factor networks. Sphingolipids can control the rate of cell proliferation and the differentiation outcome during malignant transformation. In this study, we summarise novel experimental evidences linking sphingolipids to oestrogen-activated effects, highlight the role of sphingolipids in cancer cells and discuss new avenues for future research at the intersection between oestrogen and sphingolipid signalling.

Targeting S1P1 receptor protects against murine immunological hepatic injury through myeloid-derived suppressor cells

Although FTY720 may alter migration and homing of lymphocytes via sphingosine-1-phosphate (S1P) receptors, our recent studies indicated that FTY720 directly controls the differentiation of Th1 cells to regulatory T cells (Tregs) by targeting S1P1. However, the pharmacological function of FTY720 in immunological hepatic injury remains unknown. In this study, the role and regulatory signaling pathway of S1P receptor were investigated using a pharmacological approach in immune-mediated hepatic injury (IMH). In the context of IMH, FTY720 significantly ameliorated mortality and hepatic pathology. In FTY720-treated mice, recruited CD11b(+)Gr1(+) myeloid-derived suppressor cells (MDSCs) mediate protection against IMH and are functional suppressive immune modulators that result in fewer IFN-γ-producing Th1 cells and more Foxp3(+) Tregs. In agreement, FTY720-treated MDSCs promote the reciprocal differentiation between Th1 cells and Tregs in vitro and in vivo. Mechanistically, FTY720 treatment induced inducible NO synthase expression and NO production in MDSCs. Pharmacologic inhibition of inducible NO synthase completely eliminates MDSC suppressive function and eradicates their inducible effects on T cell differentiation. Finally, the mTOR inhibitor, rapamycin, photocopies the effects of FTY720 on MDSCs, implicating mTOR as a downstream effector of S1P1 signaling. This study identifies MDSCs as an essential component that provides protection against IMH following FTY720 or rapamycin treatment, validating the S1P1-mTOR signaling axis as a potential therapeutic target in hepatic injury.

Diffusion tensor imaging detects treatment effects of FTY720 in experimental autoimmune encephalomyelitis mice

Fingolimod (FTY720) is an orally available sphingosine-1-phosphate (S1P) receptor modulator reducing relapse frequency in patients with relapsing-remitting multiple sclerosis (RRMS). In addition to immunosuppression, neuronal protection by FTY720 has also been suggested, but remains controversial. Axial and radial diffusivities derived from in vivo diffusion tensor imaging (DTI) were employed as noninvasive biomarkers of axonal injury and demyelination to assess axonal protection by FTY720 in experimental autoimmune encephalomyelitis (EAE) mice. EAE was induced through active immunization of C57BL/6 mice using myelin oligodendrocyte glycoprotein peptide 35-55 (MOG(35-55)). We evaluated both the prophylactic and therapeutic treatment effect of FTY720 at doses of 3 and 10 mg/kg on EAE mice by daily clinical scoring and end-point in vivo DTI. Prophylactic administration of FTY720 suppressed the disease onset and prevented axon and myelin damage when compared with EAE mice without treatment. Therapeutic treatment by FTY720 did not prevent EAE onset, but reduced disease severity, improving axial and radial diffusivity towards the control values without statistical significance. Consistent with previous findings, in vivo DTI-derived axial and radial diffusivity correlated with clinical scores in EAE mice. The results support the use of in vivo DTI as an effective outcome measure for preclinical drug development.

Second generation S1P pathway modulators: research strategies and clinical developments

Multiple Sclerosis (MS) is a chronic autoimmune disorder affecting the central nervous system (CNS) through demyelination and neurodegeneration. Until recently, major therapeutic treatments have relied on agents requiring injection delivery. In September 2010, fingolimod/FTY720 (Gilenya, Novartis) was approved as the first oral treatment for relapsing forms of MS. Fingolimod causes down-modulation of S1P1 receptors on lymphocytes which prevents the invasion of autoaggressive T cells into the CNS. In astrocytes, down-modulation of S1P1 by the drug reduces astrogliosis, a hallmark of MS, thereby allowing restoration of productive astrocyte communication with other neural cells and the blood brain barrier. Animal data further suggest that the drug directly supports the recovery of nerve conduction and remyelination. In human MS, such mechanisms may explain the significant decrease in the number of inflammatory markers on brain magnetic resonance imaging in recent clinical trials, and the reduction of brain atrophy by the drug. Fingolimod binds to 4 of the 5 known S1P receptor subtypes, and significant efforts were made over the past 5 years to develop next generation S1P receptor modulators and determine the minimal receptor selectivity needed for maximal therapeutic efficacy in MS patients. Other approaches considered were competitive antagonists of the S1P1 receptor, inhibitors of the S1P lyase to prevent S1P degradation, and anti-S1P antibodies. Below we discuss the current status of the field, and the functional properties of the most advanced compounds. This article is part of a Special Issue entitled New Frontiers in Sphingolipid Biology.

Deliberate fingolimod overdose presenting with delayed hypotension and bradycardia responsive to atropine

INTRODUCTION

Fingolimod is an immunomodulating agent used in multiple sclerosis (MS). It is a sphingosine-1-phosphate (S1P) receptor agonist prescribed for relapsing forms of MS to delay onset of physical disability. As fingolimod is known to cause first-dose bradycardia, telemetry is recommended for the first 6 h post-dose. We present the first reported case of deliberate fingolimod overdose requiring atropine administration for bradycardia and hemodynamic instability.

CASE REPORT

A 33-year-old woman ingested 14 mg of fingolimod and 2 g of phenoxymethylpenicillin. After presenting to the emergency department 19 h later, she was initially hemodynamically stable (heart rate (HR) 60, blood pressure (BP) 113/89 mmHg). Two hours later, she then developed bradycardia (HR 48) and hypotension (87/57 mmHg). Despite intravenous fluids, stabilisation was only achieved after administration of atropine (300 μg). She was then admitted to the intensive care unit (ICU) for further monitoring where another episode of bradycardia and hypotension required atropine. She was monitored in the ICU for 48 h and then discharged on day 5 with no further episodes.

DISCUSSION

Fingolimod is known to cause bradycardia in the first 6 h post first therapeutic dose. Following intentional overdose, onset of bradycardia occurred at 21 h post-ingestion and was associated with hypotension. Atropine was successful in treating bradycardia and associated hypotension.

Therapeutic use of a selective S1P1 receptor modulator ponesimod in autoimmune diabetes

In the present study, we investigated the therapeutic potential of a selective S1P₁ receptor modulator, ponesimod, to protect and reverse autoimmune diabetes in non-obese diabetic (NOD) mice. Ponesimod was administered orally to NOD mice starting at 6, 10, 13 and 16 weeks of age up to 35 weeks of age or to NOD mice showing recent onset diabetes. Peripheral blood and spleen B and T cell counts were significantly reduced after ponesimod administration. In pancreatic lymph nodes, B lymphocytes were increased and expressed a transitional 1-like phenotype. Chronic oral ponesimod treatment efficiently prevented autoimmune diabetes in 6, 10 and 16 week-old pre-diabetic NOD mice. Treatment withdrawal led to synchronized disease relapse. Ponesimod did not inhibit the differentiation of autoreactive T cells as assessed by adoptive transfer of lymphocytes from treated disease-free NOD mice. In addition, it did not affect the migration, proliferation and activation of transgenic BDC2.5 cells into the target tissue. However, ponesimod inhibited spreading of the T cell responses to islet-specific glucose-6-phosphatase catalytic subunit-related protein (IGRP). Treatment of diabetic NOD mice with ponesimod induced disease remission. However, here again, upon treatment cessation, the disease rapidly recurred. This recurrence was effectively prevented by combination treatment with a CD3 antibody leading to the restoration of self-tolerance. In conclusion, treatment with a selective S1P₁ modulator in combination with CD3 antibody represents a promising therapeutic approach for the treatment of autoimmune diabetes.

Delivery of S1P receptor-targeted drugs via biodegradable polymer scaffolds enhances bone regeneration in a critical size cranial defect

Biodegradable polymer scaffolds can be used to deliver soluble factors to enhance osseous remodeling in bone defects. To this end, we designed a poly(lactic-co-glycolic acid) (PLAGA) microsphere scaffold to sustain the release of FTY720, a selective agonist for sphingosine 1-phosphate (S1P) receptors. The microsphere scaffolds were created from fast degrading 50:50 PLAGA and/or from slow-degrading 85:15 PLAGA. Temporal and spatial regulation of bone remodeling depended on the use of appropriate scaffolds for drug delivery. The release profiles from the scaffolds were used to design an optimal delivery system to treat critical size cranial defects in a rodent model. The ability of local FTY720 delivery to maximize bone regeneration was evaluated with micro-computed tomography (microCT) and histology. Following 4 weeks of defect healing, FTY720 delivery from 85:15 PLAGA scaffolds resulted in a significant increase in bone volumes in the defect region compared to the controls. A 85:15 microsphere scaffolds maintain their structural integrity over a longer period of time, and cause an initial burst release of FTY720 due to surface localization of the drug. This encourages cellular in-growth and an increase in new bone formation.

Lipid receptor S1P₁ activation scheme concluded from microsecond all-atom molecular dynamics simulations

Sphingosine 1-phosphate (S1P) is a lysophospholipid mediator which activates G protein–coupled sphingosine 1-phosphate receptors and thus evokes a variety of cell and tissue responses including lymphocyte trafficking, endothelial development, integrity, and maturation. We performed five all-atom 700 ns molecular dynamics simulations of the sphingosine 1-phosphate receptor 1 (S1P₁) based on recently released crystal structure of that receptor with an antagonist. We found that the initial movements of amino acid residues occurred in the area of highly conserved W269^6.48 in TM6 which is close to the ligand binding location. Those residues located in the central part of the receptor and adjacent to kinks of TM helices comprise of a transmission switch. Side chains movements of those residues were coupled to the movements of water molecules inside the receptor which helped in the gradual opening of intracellular part of the receptor. The most stable parts of the protein were helices TM1 and TM2, while the largest movement was observed for TM7, possibly due to the short intracellular part starting with a helix kink at P^7.50, which might be the first helix to move at the intracellular side. We show for the first time the detailed view of the concerted action of the transmission switch and Trp (W^6.48) rotamer toggle switch leading to redirection of water molecules flow in the central part of the receptor. That event is a prerequisite for subsequent changes in intracellular part of the receptor involving water influx and opening of the receptor structure.

The activation of G-protein-coupled receptors (GPCRs) depends on small differences in agonist and antagonist structures resulting in specific forces they impose on the helical bundle of the receptor. Having the crystal structures of GPCRs in different stages of activation it is possible to investigate the successive conformational changes leading to full activation. The long molecular dynamics simulations can fill the gap spanning between those structures and provide an overview of the activation processes. The water molecules are recognized to be crucial in the activation process which link shifting of ligand in the binding site, the actions of molecular switches and finally the movements of fragments of TM helices. Here, we present five 700 ns MD simulations of lipid S1P₁ receptor, either in Apo form, or bound to antagonist ML056 or natural agonist S1P. The Apo and antagonist-bound receptor structures exhibited similar behavior, with their TM bundles nearly intact, while in the case of the agonist-bound receptor we observed movements of intracellular ends of some of TM helices.

FTY720 ameliorates murine sclerodermatous chronic graft-versus-host disease by promoting expansion of splenic regulatory cells and inhibiting immune cell infiltration into skin

OBJECTIVE

Sphingosine 1-phosphate (S1P) exerts a variety of activities in immune, inflammatory, and vascular systems. S1P plays an important role in systemic sclerosis (SSc) pathogenesis. Regulation of S1P in fibrotic diseases as well as in SSc was recently reported. FTY720, an oral S1P receptor modulator, has been shown to be a useful agent for the prevention of transplant rejection and autoimmune diseases. Murine sclerodermatous chronic graft-versus-host disease (GVHD) is a model for human sclerodermatous chronic GVHD and SSc. We undertook this study to investigate the effects of FTY720 in murine sclerodermatous chronic GVHD.

METHODS

FTY720 was orally administered to allogeneic recipient mice from day 0 to day 20 (short-term, early-treatment group), from day 0 to day 42 (full-term, early-treatment group), or from day 22 to day 42 (delayed-treatment group) after bone marrow transplantation.

RESULTS

Delayed administration of FTY720 attenuated, and early administration of FTY720 inhibited, the severity and fibrosis in murine sclerodermatous chronic GVHD. With early treatment, FTY720 induced expansion of splenic myeloid-derived suppressor cells, Treg cells, and Breg cells. Vascular damage in chronic GVHD was inhibited by FTY720 through down-regulating serum levels of S1P and soluble E-selectin. FTY720 inhibited infiltration of immune cells into skin. Moreover, FTY720 diminished the expression of messenger RNA for monocyte chemotactic protein 1, macrophage inflammatory protein 1α, RANTES, tumor necrosis factor α, interferon-γ, interleukin-6 (IL-6), IL-10, IL-17A, and transforming growth factor β1 in the skin.

CONCLUSION

FTY720 suppressed the immune response by promoting the expansion of regulatory cells and reducing vascular damage and infiltration of immune cells into the skin. Taken together, these results have important implications for the potential use of FTY720 in the treatment of sclerodermatous chronic GVHD and SSc in humans.

Sphingosine 1-phosphate (S1P) induces S1P2 receptor-dependent tonic contraction in murine iliac lymph vessels

OBJECTIVE

We studied the effects of S1P on the diameter and spontaneous contraction of murine iliac collecting lymph vessels.

METHODS

The isolated lymph vessel was cannulated with two glass micropipettes and then pressurized to 4 cmH(2) O at the intraluminal pressure. The changes in lymph vessel diameter were measured using a custom-made diameter-detection device. Immunohistochemical studies were also performed to confirm S1P receptors on the lymph vessels.

RESULTS

S1P (10(-7) M) had no significant effect on the frequency or amplitude of the lymph vessels' spontaneous contractions. In contrast, S1P (10(-8) -10(-6) M) produced a concentration-related reduction in lymph vessel diameter (tonic contraction). Pretreatment with 10(-4) M l-NAME or 10(-5) M aspirin had no significant effect on the S1P-induced tonic contraction of the lymph vessels. To evaluate the intracellular signal transduction pathway responsible for the S1P-induced tonic contractions and their Ca(2+) -dependence, we investigated the effects of JTE013, VPC23019, U-73122, xestospongin C, and nifedipine on the S1P-induced tonic contractions. All of these inhibitors except VPC23019 and nifedipine significantly reduced the S1P-induced tonic contractions. S1P (5x10(-7) M) also induced significant tonic contractions in the lymph vessels that had been superfused with high K(+) Krebs-bicarbonate solution or Ca(2+) -free high K(+) Krebs solution containing 1 mM EGTA. S1P2 receptors were immunohistochemically detected in the lymph vessels.

CONCLUSION

These findings suggest that neither endogenous NO nor prostaglandins are involved in the S1P-induced tonic contraction of lymph vessels, which is mainly caused by Ca(2+) release from intracellular Ca(2+) stores through the activation of S1P2 and 1,4,5 IP(3) receptors.

Sphingosine lysolipids in the CNS: endogenous cannabinoid antagonists or a parallel pain modulatory system?

A significant number of patients experience chronic pain and the intractable side effects of currently prescribed pain medications. Recent evidence indicates important pain-modulatory roles for two classes of G-protein-coupled receptors that are activated by endogenous lipid ligands, the endocannabinoid (eCB) and sphingosine-1-phosphate (S1P) receptors, which are widely expressed in both the immune and nervous systems. In the central nervous system (CNS), CB1 cannabinoid and S1P1 receptors are most abundantly expressed and exhibit overlapping anatomical distributions and similar signaling mechanisms. The eCB system has emerged as a potential target for treatment of chronic pain, but comparatively little is known about the roles of S1P in pain regulation. Both eCB and S1P systems modulate pain perception via the central and peripheral nervous systems. In most paradigms studied, the eCB system mainly inhibits pain perception. In contrast, S1P acting peripherally at S1P1 and S1P3 receptors can enhance sensitivity to various pain stimuli or elicit spontaneous pain. However, S1P acting at S1P1 receptors and possibly other targets in the CNS can attenuate sensitivity to various pain stimuli. Interestingly, other endogenous sphingolipid derivatives might play a role in central pain sensitization. Moreover, these sphingolipids can also act as CB1 cannabinoid receptor antagonists, but the physiological relevance of this interaction is unknown. Overall, both eCB and sphingolipid systems offer promising targets for the treatment of chronic pain. This review compares and contrasts the eCB and S1P systems with a focus on their roles in pain modulation, and considers possible points of interaction between these systems.

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.