Sphingosine-1-phosphate Agonist Research Articles

Hirudin, a thrombin inhibitor, attenuates TGF-β-induced fibrosis in renal proximal tubular epithelial cells by inhibition of protease-activated receptor 1 expression via S1P/S1PR2/S1PR3 signaling.

Renal interstitial fibrosis (RIF) is the final common outcome of numerous chronic kidney diseases, contributing to end-stage renal disease. Hirudin, a thrombin inhibitor, has attracted increased attention as a potential treatment approach for renal fibrosis. The present study aimed to investigate the molecular mechanism underlying the effect of hirudin on fibrosis in renal proximal tubular epithelial cells. An in vivo mouse RIF model established using unilateral ureteral obstruction (UUO) and an in vitro of RIF using the renal tubular epithelial cell line HK-2 treated with TGF-β were used. Expressions of sphingosine-1-phosphate (S1P) receptors (S1PR)1-4 and protease-activated receptor 1 (PAR1) were measured by reverse transcription-quantitative PCR and western blotting in mice with UUO and TGF-β induced HK-2 cells. Western blotting was used to detect the expression of N-cadherin, Slug, E-cadherin, Collagen IV, fibronectin, MMP9 and monocyte chemoattractant protein-1. Immunofluorescence staining was conducted to measure α-SMA level expression. The results demonstrated that the expression levels of S1PR1, S1PR2, S1PR3, S1PR4 and PAR1 were upregulated in both TGF-β-induced HK-2 cells and renal tissues from mice with unilateral ureteral ligation. Notably, hirudin inhibited TGF-β-induced PAR1, S1PR2 and S1PR3 upregulation in both HK-2 cells and renal tissues. Additionally, the inhibition of S1PR2 and S1PR3 resulted in PAR1 downregulation. Furthermore, treatment with S1P and PAR1 agonists abolished the effect of hirudin on the expression of EMT, fibrosis-related proteins and monocyte chemoattractant protein 1. In conclusion, hirudin attenuated TGF-β-induced fibrosis in proximal renal tubular epithelial HK-2 cells by inhibiting PAR1 expression via the S1P/S1PR2/S1PR3 signaling pathway. Therefore, hirudin may be considered as a promising therapeutic agent for RIF.

Sphingosine 1 phosphate agonists (SPI); a potential agent to prevent acute lung injury in COVID-19

SARS-CoV-2 is a worldwide pandemic, that has led to the morbidity and mortality of millions of people. This virus rapidly proliferates and destroys lung epithelial cells directly, which is worsened by a subsequent cytokine storm. This cytokine storm diffusely damages the alveolar barriers and leads to fibrin and fluid exudation, hyaline membrane formation, and infiltration of inflammatory cells into the lung causing acute respiratory distress syndrome (ARDS). To date, there exists no medication to treat SARS-CoV-2 infection and novel new therapeutics are still being explored to prevent or limit the damage to the lung. Sphingosine 1-phosphate (S1P) is an effective bioactive lipid mediator and its related signaling pathways are vital for endothelial cell integrity. Stabilizing the pulmonary endothelial barrier and decreasing the inflammatory infiltrate by S1P analogs such as Fingolimod (FTY720-P) would be a new therapeutic approach for the hindrance of pulmonary exudation and subsequent ARDS.

Ursodeoxycholic acid protects cardiomyocytes against cobalt chloride induced hypoxia by regulating transcriptional mediator of cells stress hypoxia inducible factor 1α and p53 protein.

In hepatocytes, ursodeoxycholic acid (UDCA) activates cell signalling pathways such as p53, intracellular calcium ([Ca2+ ]i ), and sphingosine-1-phosphate (S1P)-receptor via Gαi -coupled-receptor. Recently, UDCA has been shown to protect the heart against hypoxia-reoxygenation injury. However, it is not clear whether UDCA cardioprotection against hypoxia acts through a transcriptional mediator of cells stress, HIF-1α and p53. Therefore, in here, we aimed to investigate whether UDCA could protect cardiomyocytes (CMs) against hypoxia by regulating expression of HIF-1α, p53, [Ca2+ ]i , and S1P-Gαi -coupled-receptor. Cardiomyocytes were isolated from newborn rats (0-2days), and hypoxia was induced by using cobalt chloride (CoCl2 ). Cardiomyocytes were treated with UDCA and cotreated with either FTY720 (S1P-receptor agonist) or pertussis toxin (PTX; Gαi inhibitor). Cells were subjected for proliferation assay, beating frequency, QuantiGene Plex assay, western blot, immunofluorescence, and calcium imaging. Our findings showed that UDCA counteracted the effects of CoCl2 on cell viability, beating frequency, HIF-1α, and p53 protein expression. We found that these cardioprotection effects of UDCA were similar to FTY720, S1P agonist. Furthermore, we observed that UDCA protects CMs against CoCl2 -induced [Ca2+ ]i dynamic alteration. Pharmacological inhibition of the Gαi -sensitive receptor did not abolish the cardioprotection of UDCA against CoCl2 detrimental effects, except for cell viability and [Ca2+ ]i . Pertussis toxin is partially effective in inhibiting UDCA protection against CoCl2 effects on CM cell viability. Interestingly, PTX fully inhibits UDCA cardioprotection on CoCl2 -induced [Ca2+ ]i dynamic changes. We conclude that UDCA cardioprotection against CoCl2 -induced hypoxia is similar to FTY720, and its actions are not fully mediated by the Gαi -coupled protein sensitive pathways. Ursodeoxycholic acid is the most hydrophilic bile acid and is currently used to treat liver diseases. Recently, UDCA is shown to have a cardioprotection effects; however, the mechanism of UDCA cardioprotection is still poorly understood. The current data generated were the first to show that UDCA is able to inhibit the activation of HIF-1α and p53 protein during CoCl2 -induced hypoxia in cardiomyocytes. This study provides an insight of UDCA mechanism in protecting cardiomyocytes against hypoxia.

Targeting sphingosine-1-phosphate signaling for cancer therapy.

Sphingosine-1-phosphate (S1P) is a potent pleotropic bioactive lipid mediator involved in immune cell trafficking, cell survival, cell proliferation, cell migration, angiogenesis and many other cellular processes. S1P either activates S1P receptors (S1PR1-5) through "inside-out signaling" or acts directly on intracellular targets to regulate various cellular processes. In the past two decades, much progress has been made in exploring S1P signaling and its pathogenic roles in diseases as well as in developing modulators of S1P signaling, including S1P agonists, S1P antagonists and sphingosine kinase (SphK) inhibitors. Ceramide and S1P have been defined as reciprocal regulators of cell fate, and S1P signaling has been shown to be crucial for the pathogenesis of various diseases, including autoimmune diseases, inflammation and cancer; therefore, targeting S1P signaling may curtail the process of pathogenesis and serve as a potential therapeutic target for the treatment of these diseases. In this review, we describe recent advances in our understanding of S1P signaling in cancer development (particularly in inflammation- associated cancer) as well as in innate and adaptive immunity, and we also discuss modulators of S1P signaling in cancer treatment.

Interferon targeted therapies in systemic lupus erythematosus.

Type I interferons secreted by plasmacytoid dendritic cells (pDCs) play a crucial role in the pathogenesis of systemic lupus erythematosus by driving the formation of autoantibodies against nuclear debris. Inherited mutations causing activation of the Type I interferon pathway result in a phenotype of systemic autoimmunity which resembles some of the manifestations of lupus. Patients with lupus have increased expression of interferon-stimulated genes in the peripheral blood mononuclear cells which is abrogated following immunosuppressive treatment. Recent therapeutic approaches have involved monoclonal antibodies directly targeting interferon alpha (sifalimumab, rontalizumab) or the use of interferon alpha kinoid to stimulate endogenous production of anti-interferon antibodies in lupus. Other drugs used in lupus such as hydroxychloroquine and bortezomib also reduce circulating levels of type I interferons. Newer therapeutic strategies being investigated in preclinical models of lupus that reduce the production of Type I interferons include dihydroartemisinin, Bruton’s tyrosine kinase antagonists, Bcl-2 antagonists and sphingosine-1 phosphate agonists.

Characterization and Prediction of Cardiovascular Effects of Fingolimod and Siponimod Using a Systems Pharmacology Modeling Approach.

Sphingosine 1-phosphate (S1P) receptor agonists are associated with cardiovascular effects in humans. This study aims to develop a systems pharmacology model to identify the site of action (i.e., primary hemodynamic response variable) of S1P receptor agonists, and to predict, in a quantitative manner, the cardiovascular effects of novel S1P receptor agonists in vivo. The cardiovascular effects of once-daily fingolimod (0, 0.1, 0.3, 1, 3, and 10 mg/kg) and siponimod (3 and 15 mg/kg) were continuously recorded in spontaneously hypertensive rats and Wistar-Kyoto rats. The results were analyzed using a recently developed systems cardiovascular pharmacology model, i.e. the CVS model; total peripheral resistance and heart rate were identified as the site of action for fingolimod. Next, the CVS model was interfaced with an S1P agonist pharmacokinetic-pharmacodynamic (PKPD) model. This combined model adequately predicted, in a quantitative manner, the cardiovascular effects of siponimod using in vitro binding assays. In conclusion, the combined CVS and S1P agonist PKPD model adequately describes the hemodynamic effects of S1P receptor agonists in rats and constitutes a basis for the prediction, in a strictly quantitative manner, of the cardiovascular effects of novel S1P receptor agonists.

Enhancement of wound closure by modifying dual release patterns of stromal-derived cell factor-1 and a macrophage recruitment agent from gelatin hydrogels.

The objective of the present study is to evaluate the effects of the release patterns of stromal derived factor (SDF)-1 and sphingosine-1 phosphate agonist (SEW2871), used as MSC and macrophage recruitment agents, on the wound closure of diabetic mouse skin defects. To achieve different release patterns, hydrogels were prepared using two types of gelatin with isoelectric points (IEP) of 5 and 9, into which SDF-1 and SEW2871 were then incorporated in various combinations. When the hydrogels incorporating SDF-1 and SEW2871 were applied into wound defects of diabetic mice, the number of MSCs and macrophages recruited to the defects and the levels of pro- and anti- inflammatory cytokines were found to be dependent on the release profiles of SDF-1 and SEW2871. Of particular interest was the case of a rapid release of SDF-1 combined with a controlled release of SEW2871. This resulted in a higher number of M2 macrophages and gene expression levels of anti-inflammatory cytokines 3 days after implantation and faster wound closure than when pairing the controlled release of SDF-1 with a rapid release of SEW2871. Therefore, the present study demonstrates that different release patterns of SDF-1 and SEW2871 can enhance the in vivo recruitment of MSCs and macrophages, and can promote skin wound closure through the modulation of inflammation. Copyright © 2016 John Wiley & Sons, Ltd.

Recruitment of mesenchymal stem cells and macrophages by dual release of stromal cell-derived factor-1 and a macrophage recruitment agent enhances wound closure.

In this study, the wound closure of mouse skin defects was examined in terms of recruitment of mesenchymal stem cells (MSC) and macrophages. For the cells recruitment, stromal derived factor-1 (SDF-1) of a MSC recruitment agent and sphingosine-1 phosphate agonist (SEW2871) of a macrophages recruitment agent were incorporated into gelatin hydrogels, and then released in a controlled fashion. When applied to a skin wound defect of mice, gelatin hydrogels incorporating mixed 500 ng SDF-1 and 0.4, 0.8, or 1.6 mg SEW2871-micelles recruited a higher number of both MSC and macrophages than those incorporating SDF-1 or phosphate buffered saline. However, the number of M1 phenotype macrophages for the hydrogel incorporating mixed SDF-1 and SEW2871-micelles recruited was remarkably low to a significant extent compared with that for those hydrogel incorporating 0.4, 0.8, or 1.6 mg SEW2871-micelles. On the other hand, the number of M2 macrophages 3 days after the implantation of the hydrogels incorporating SDF-1 and 0.4 mg SEW2871-micelles significantly increased compared with that for other hydrogels. In vivo experiments revealed the hydrogels incorporating SDF-1 and 0.4 mg SEW2871-micelles promoted the wound closure of skin defect to a significant stronger extent than those incorporating SEW2871-micelles, SDF-1, and a mixture of SDF-1 and higher doses of SEW2871-micelles. It is concluded that the in vivo recruitment of MSC and macrophages to the defects may contribute to the tissue regeneration of skin wound.

Abstract 137: Conditional Knockout of Sphingosine-1-Phosphate Receptor 1 in Renal Collecting Ducts Promotes Sodium Retention in Mice

Sphingosine-1-phosphate (S1P) is a bioactive sphingolipid metabolite formed by phosphorylation of sphingosine. We have recently shown that renal medullary infusion of S1P agonist increases sodium excretion possibly through inhibition of epithelial sodium channel (ENaC) activity via S1P receptor 1 (S1P1), which is prominently localized in the collecting ducts. The present study was to test the hypothesis that the S1P1 in collecting duct plays a pivotal role in the regulation of renal sodium handling. We generated conditional knocked-out (CKO) mice with collecting duct-specific ablation of S1P1 using loxP-Cre system. Functionally, urinary sodium excretion in S1P1 CKO mice was significantly decreased by about 60% compared with that in control mice after acute IV sodium loading (0.84±0.16 vs. 2.22±0.62 μmole/min/g kwt). Moreover, the pressure natriuresis was severely impaired in S1P1 CKO mice compared with that in the control mice (4.32±1.04 vs. 8.73±0.19 μmole/min/g kwt). Furthermore, chronic high salt-induced sodium retention was remarkably enhanced in S1P1 CKO mice comparing to the control animals (5.27±0.39 vs. 2.38±1.04 mmole/24h/100g bw). Our results suggested that S1P1 in collecting duct plays an important role in the regulation of renal sodium excretion and that deficiency of S1P1 in collecting duct impairs renal sodium handling and promotes sodium retention. Modulation of S1P1 function in the renal medulla could be a therapeutic approach for salt-sensitive hypertension.

A sphingosine-1 phosphate agonist (FTY720) limits trauma/hemorrhagic shock-induced multiple organ dysfunction syndrome.

Trauma/hemorrhagic shock (T/HS) is one of the major consequences of battlefield injury as well as civilian trauma. FTY720 (sphingosine-1-phosphate agonist) has the capability to decrease the activity of the innate and adaptive immune systems and, at the same time, maintain endothelial cell barrier function and vascular homeostasis during stress. For this reason, we hypothesize that FTY720, as part of resuscitation therapy, would limit T/HS-induced multiple organ dysfunction syndrome in a rodent T/HS model. Rats subjected to trauma/sham shock (T/SS) or T/HS (30 mm Hg × 90 min) were administered FTY720 (1 mg/kg) post-T/HS during volume resuscitation. Lung injury (permeability to Evans blue dye), polymorphonuclear leukocyte (PMN) priming (respiratory burst activity), and red blood cell (RBC) rigidity were measured. In addition, lymph duct-cannulated rats were used to quantify the effect of FTY720 on gut injury (permeability and morphology) and the biologic activity of T/HS versus T/SS lymph on PMN-RBC and RBC deformability. Trauma/hemorrhagic shock-induced increased lung permeability, PMN priming, and RBC rigidity were all abrogated by FTY720. The systemic protective effect of FTY720 was only partially at the gut level, because FTY720 did not prevent T/HS-induced gut injury (morphology or permeability); however, it did abrogate T/HS lymph-induced increased respiratory burst and RBC rigidity. FTY720 limited T/HS-induced multiple organ dysfunction syndrome (lung injury, red cell injury, and neutrophil priming) as well as T/HS lymph bioactivity, although it did not limit gut injury.

Translational pharmacokinetic modeling of fingolimod (FTY720) as a paradigm compound subject to sphingosine kinase-mediated phosphorylation.

A complicating factor in the translational pharmacology of sphingosine 1-phosphate agonists is that they exert their pharmacological effect through their respective phosphate metabolites, which are formed by the enzyme sphingosine kinase (S1PHK). In this investigation, we present a semimechanistic pharmacokinetic model for the interconversion of S1PHK substrates and their respective phosphates in rats and humans with the aim of investigating whether characterization of the rate of phosphorylation in blood platelets constitutes a basis for interspecies scaling using fingolimod as a model compound. Data on the time course of fingolimod and fingolimod-phosphate (fingolimod-P) blood concentrations after intravenous and oral administration of fingolimod and/or fingolimod-P in rats and after oral administration of fingolimod in doses of 0.5, 1.25, and 5 mg once daily in healthy volunteers were analyzed in conjunction with data on the ex vivo interconversion and blood-plasma distribution in rat and human blood, respectively. Integrating the data from the ex vivo and in vivo studies enabled simulation of fingolimod and fingolimod-P concentrations in plasma rather than blood, which are more relevant for characterizing drug effects. Large interspecies differences in the rate of phosphorylation between rats and humans were quantified. In human, phosphorylation of fingolimod in the platelets was four times slower compared with rat, whereas the dephosphorylation rates were comparable in both species. This partly explained the 10-12-fold overprediction of fingolimod-P exposure in human when applying a dose-by-factor approach on the developed rat model. Additionally, differences in presystemic phosphorylation should also be taken into account.

Memo Has a Novel Role in S1P Signaling and Crucial for Vascular Development

Memo is a conserved protein that was identified as an essential mediator of tumor cell motility induced by receptor tyrosine kinase activation. Here we show that Memo null mouse embryonic fibroblasts (MEFs) are impaired in PDGF-induced migration and this is due to a defect in sphingosine-1-phosphate (S1P) signaling. S1P is a bioactive phospholipid produced in response to multiple stimuli, which regulates many cellular processes. S1P is secreted to the extracellular milieu where it exerts its function by binding a family of G-protein coupled receptors (S1PRs), causing their activation in an autocrine or paracrine manner. The process, termed cell-autonomous S1PR signaling, plays a role in survival and migration. Indeed, PDGF uses cell-autonomous S1PR signaling to promote cell migration; we show here that this S1P pathway requires Memo. Using vascular endothelial cells (HUVECs) with Memo knock-down we show that their survival in conditions of serum-starvation is impaired. Furthermore, Memo loss in HUVECs causes a reduction of junctional VE-cadherin and an increase in sprout formation. Each of these phenotypes is rescued by S1P or S1P agonist addition, showing that Memo also plays an important role in cell-autonomous S1PR signaling in endothelial cells. We also produced conventional and endothelial cell-specific conditional Memo knock-out mouse strains and show that Memo is essential for embryonic development. Starting at E13.5 embryos of both strains display bleeding and other vascular problems, some of the phenotypes that have been described in mouse strains lacking S1PRs. The essential role of Memo in embryonic vascular development may be due in part to alterations in S1P signaling. Taken together our results show that Memo has a novel role in the S1P pathway and that Memo is needed to promote cell-autonomous S1PR activation.

A3.28 Screening of sphingolipids in SLE – before and after treatment

Background and ObjectivesSystemic lupus erythematosus (SLE) is an autoimmune disease with a heterogeneous presentation of symptoms from joints, skin, kidneys, central nervous system, lungs, and the cardiovascular system. There is...

Involvement of proteinase activated receptor-2in the vascular response to sphingosine 1-phosphate

S1P (sphingosine 1-phosphate) represents one of the key latest additions to the list of vasoactive substances that modulate vascular tone. PAR-2 (proteinase activated receptor-2) has been shown to be involved in cardiovascular function. In the present study, we investigated the involvement of PAR-2 in S1P-induced effect on vascular tone. The present study has been performed by using isolated mouse aortas. Both S1P and PAR-2 agonists induced endothelium-dependent vasorelaxation. L-NAME (N(G)-nitro-L-arginine methyl ester) and wortmannin abrogated the S1P-induced vasorelaxatioin, while significantly inhibiting the PAR-2-mediated effect. Either ENMD1068, a PAR-2 antagonist, or gabexate, a serine protease inhibitor, significantly inhibited S1P-induced vasorelaxation. Aortic tissues harvested from mice overexpressing PAR-2 displayed a significant increase in vascular response to S1P as opposed to PAR-2-null mice. Immunoprecipitation and immunofluorescence studies demonstrated that S1P(1) interacted with PAR-2 and co-localized with PAR-2 on the vascular endothelial surface. Furthermore, S1P administration to vascular tissues triggered PAR-2 mobilization from the plasma membrane to the perinuclear area; S1P-induced translocation of PAR-2 was abrogated when aortic rings were pre-treated with ENMD1068 or when caveolae dysfunction occurred. Similarly, experiments performed in cultured endothelial cells (human umbilical vein endothelial cells) showed a co-localization of S1P(1) and PAR2, as well as the ability of S1P to induce PAR-2 trafficking. Our results suggest that S1P induces endothelium-dependent vasorelaxation mainly through S1P(1) and involves PAR-2 transactivation.

Sphingosine 1-Phosphate Mediates Hyperalgesia via a Neutrophil-Dependent Mechanism

Novel classes of pain-relieving molecules are needed to fill the void between non-steroidal anti-inflammatory agents and narcotics. We have recently shown that intraplantar administration of sphingosine 1-phosphate (S1P) in rats causes peripheral sensitization and hyperalgesia through the S1P1 receptor subtype (S1PR1): the mechanism(s) involved are largely unknown and were thus explored in the present study. Intraplantar injection of carrageenan in rats led to a time-dependent development of thermal hyperalgesia that was associated with pronounced edema and infiltration of neutrophils in paw tissues. Inhibition of 1) S1P formation with SK-I, a sphingosine kinase inhibitor, 2) S1P bioavailability with the S1P blocking antibody Sphingomab, LT1002 (but not its negative control, LT1017) or 3) S1P actions through S1PR1 with the selective S1PR1 antagonist, W146 (but not its inactive enantiomer, W140) blocked thermal hyperalgesia and infiltration of neutrophils. Taken together, these findings identify S1P as an important contributor to inflammatory pain acting through S1PR1 to elicit hyperalgesia in a neutrophil-dependant manner. In addition and in further support, we demonstrate that the development of thermal hyperalgesia following intraplantar injection of S1P or SEW2871 (an S1PR1 agonist) was also associated with neutrophilic infiltration in paw tissues as these events were attenuated by fucoidan, an inhibitor of neutrophilic infiltration. Importantly, FTY720, an FDA-approved S1P receptor modulator known to block S1P-S1PR1 signaling, attenuated carrageenan-induced thermal hyperalgesia and associated neutrophil infiltration. Targeting the S1P/S1PR1 axis opens a therapeutic strategy for the development of novel non-narcotic anti-hyperalgesic agents.

Effects of sphingosine-1-phosphate on pacemaker activity of interstitial cells of Cajal from mouse small intestine.

Interstitial cells of Cajal (ICC) are the pacemaker cells that generate the rhythmic oscillation responsible for the production of slow waves in gastrointestinal smooth muscle. Spingolipids are known to present in digestive system and are responsible for multiple important physiological and pathological processes. In this study, we are interested in the action of sphingosine 1-phosphate (S1P) on ICC. S1P depolarized the membrane and increased tonic inward pacemaker currents. FTY720 phosphate (FTY720P, an S1P(1,3,4,5) agonist) and SEW 2871 (an S1P(1) agonist) had no effects on pacemaker activity. Suramin (an S1P(3) antagonist) did not block the S1P-induced action on pacemaker currents. However, JTE-013 (an S1P(2) antagonist) blocked the S1P-induced action. RT-PCR revealed the presence of the S1P(2) in ICC. Calphostin C (a protein kinase C inhibitor), NS-398 (a cyclooxygenase-2 inhibitor), PD 98059 (a p42/44 inhibitor), or SB 203580 (a p38 inhibitor) had no effects on S1P-induced action. However, c-jun NH(2)-terminal kinase (JNK) inhibitor II suppressed S1P-induced action. External Ca(2+)-free solution or thapsigargin (a Ca(2+)-ATPase inhibitor of endoplasmic reticulum) suppressed action of S1P on ICC. In recording of intracellular Ca(2+) ([Ca(2+)](i)) concentration using fluo-4/AM S1P increased intensity of spontaneous [Ca(2+)](i) oscillations in ICC. These results suggest that S1P can modulate pacemaker activity of ICC through S1P(2) via regulation of external and internal Ca(2+) and mitogenactivated protein kinase activation.

Abstract 2342: Sphingosine Kinase & Sphingosine 1-phosphate Modulation On Microglia And Brain Derived Endothelial Cells

Sphingolipid metabolites, have emerged as a new class of potent bioactive molecules, implicated in a variety of cellular processes. In particular, sphingosine-1-phosphate (S1P) the product of sphingosine phosphorylation, through transactivation of five cognate G protein-coupled receptors namely endothelial cell differentiation gene receptors (EDGs/S1P1-5), promotes proliferation, differentiation, enhances cell survival and inhibits apoptosis in different cellular systems. Modulation of sphingolipids and their receptors has been shown in some stroke models to be neuroprotective and anti-inflammatory. We undertook this study to elucidate the role of S1P receptor subtypes and sphinosine kinase (SPHK) in models of brain derived endothelial cells and microglia. We studied mono and co-cultures where endotoxin (LPS) activated microglia stimulate endothelial cell death. After documenting SPHK1/ 2 expression in microglia by immunofluorescence, we found that an agonist of SPHK ((2-(p-Hydrozyanilino)-4(p-chlorophenyl) tiazole, SKI) preserved microvascular endothelial cells, and markedly prevented microglia-induced endothelial cell injury. Furthermore, SKI inhibited iNOS and NO generation in microglia by both endotoxin as well as a second TLR4 agonist (Kdo2-Lipid (ADi[3-deoxy-D-manno-octulosonyl]-lipid A) (*P<0.01). S1P (1) agonists SEW-1 and FTY720 and endogenous ligand S1P had no significant effect in on microglia-mediated cell injury or NO induction by LPS. However, preincubation with the S1P (3) antagonist ( CAY10444 ) dose dependently prevented NO accumulation, while JTE-013 (S1P2 antagonist) & VPC23019 (S1P1 antagonist) were effective in preventing NO release. Our findings indicate that sphingosine phosphorylation promotes immune responses in microglia and its blockade, especially SPHK1 and to lesser extent S1P (3) attenuated these responses. This inhibition also led to decreased cell death due to immune cell activation. Our data suggests that targeting aspects of the sphingolipid pathway may be a new strategy to inhibit microglia activation and preserving endothelial cell integrity in relevant cerebrovascular pathologies such as stroke, trauma, or sepsis

Stem Cell Arrival in Sites of Hematopoiesis Triggers Supportive Endothelial Niche Formation

Abstract 218Hematopoietic stem and progenitor cells (HSPCs) self-renew and give rise to all blood cell types throughout adulthood. In mammals, definitive HSPCs first arise from the hemogenic endothelium of the dorsal aorta, are released into circulation, and then seed the fetal liver as an intermediate tissue before colonizing the adult bone marrow. We have used the zebrafish and mouse as complementary model systems to follow HSPC migration throughout embryonic development. The first HSPCs in the zebrafish embryo emerge from the dorsal aorta and migrate to the caudal hematopoietic tissue (CHT), a vascular plexus in the ventral tail of the embryo. To directly track HSPCs in the live zebrafish embryo, we created a novel transgenic line using the known mouse Runx1 +23 kb intronic enhancer that delineates stem cells, as described by de Bruijn and colleagues (Nottingham et al. Blood 2007). A double transgenic zebrafish embryo for HSPCs (Runx1+23:eGFP) and endothelial cells (flk1:dsRed) allowed us to perform live imaging of stem cells during migration. Upon arrival in the CHT, HSPCs adhere to the endothelial wall of the vessel, cross through the wall by extravasation, and trigger niche formation—endothelial cells actually remodel around the HSPC to create a niche. Once in this niche, the HSPC: 1) remains quiescent; 2) divides symmetrically to give rise to a second progenitor; or 3) divides asymmetrically to give rise to a myeloid progenitor that migrates out of the endothelial niche. To determine if this mechanism of endothelial niche formation in the embryo was conserved in mammals, we dissected fetal livers from E11.5 mouse embryos, the stage that marks the beginning of fetal liver seeding by dorsal aorta HSPCs. Staining these fetal livers with anti-ckit and PECAM antibodies, we could perform live imaging on cultured explants. Strikingly, we observed PECAM+ endothelial cells adhere to and form a rosette around a single ckit+ HSPC—similar to the de novo niche formation we observed in the zebrafish. To better understand the mechanism of how HSPCs navigate their migration from dorsal aorta to fetal liver/CHT, a chemical genetic screen was performed to detect changes in expression of hematopoietic progenitors in the CHT. Surprisingly, we found that sphingosine-1-phosphate (S1P), a signal known to regulate adult progenitor and lymphocyte trafficking, changed the migration pattern of HSPCs after embryo treatment. Knockdown of the s1pr1 receptor, which is required for S1P-dependent HSPC trafficking, resulted in reduction of HSPC markers in the CHT. S1PR1 receptor function was tested using small molecules. A highly specific S1PR1 antagonist (W146), or depletion of endogenous S1P using a sphingosine kinase inhibitor (SKI-2), reduced HSPC markers in the CHT. Endogenous S1P depletion was dose-dependently rescued by addition of exogenous S1P or S1PR1-specific agonist (AUY954). S1PR1 receptor antagonist (W146) effects were also rescued by addition of exogenous S1P. To assess if the effects of the S1P pathway were autonomous to the HSPC, a dominant-negative S1PR1 driven in HSPCs by the Runx1 +23 kb enhancer was injected into fish and followed by time-lapse live imaging. The expressing cells had difficulty engrafting in the CHT. We tested possible synergism between S1P and CXCR4 pathways in the embryo by using combination chemical genetics. Embryos were treated in a dose matrix of two different chemicals, one against CXCR4 and the other against the S1P pathway. Specific dose ratios could synergistically increase hematopoiesis in the CHT to a maximum engraftment, demonstrating an interaction between CXCR4 and S1P signaling. Doses of CXCR4 and S1P signaling could also be found that decreased engraftment, suggesting that the concentration of the two ligands and receptors is critical. We used these same dose ratios to treat whole bone marrow from adult mouse. The combination that gave maximum CHT engraftment also increased cell surface receptor levels of both CXCR4 and S1PR1. Together, our data demonstrate a novel and conserved role for S1P during migration of HSPCs between successive niches during development. Disclosures:Tamplin:Children’s Hospital Boston: Patents & Royalties. Zon:Fate Therapeutics: ; Stemgent: Consultancy.

S1P1 Receptor Modulation with Cyclical Recovery from Lymphopenia Ameliorates Mouse Model of Multiple Sclerosis

Multiple sclerosis (MS) therapies modulate T-cell autoimmunity in the central nervous system (CNS) but may exacerbate latent infections. Fingolimod, a nonselective sphingosine-1-phosphate (S1P) receptor agonist that induces sustained lymphopenia and accumulates in the CNS, represents a new treatment modality for MS. We hypothesized that sustained lymphopenia would not be required for efficacy and that a selective, CNS-penetrant, peripherally short-acting, S1P(1) agonist would show full efficacy in a mouse MS model. Using daily treatment with 10 mg/kg 2-(4-(5-(3,4-diethoxyphenyl)-1,2,4-oxadiazol-3-yl)-2,3-dihydro-1H-inden-1-yl amino)ethanol (CYM-5442) at the onset of clinical signs in myelin oligodendrocyte glycoprotein MOG(35-55)- induced experimental allergic encephalomyelitis (EAE), we assessed clinical scores, CNS cellular infiltration, demyelination, and gliosis for 12 days with CYM-5442, vehicle, or fingolimod. CYM-5442 levels in CNS and plasma were determined at experiment termination, and blood lymphopenia was measured 3 and 24 h after the last injection. Plasma levels of cytokines were assayed at the end of the protocol. Changes in S1P(1)-enhanced green fluorescent protein expression on neurons and astrocytes during active EAE and upon CYM-5442 treatment were quantified with flow cytometry and Western blotting by using native-locus enhanced green fluorescent protein-tagged S1P(1) mice. S1P(1) agonism alone reduced pathological features as did fingolimod (maximally lymphopenic throughout), despite full reversal of lymphopenia within each dosing interval. CYM-5442 levels in CNS but not in plasma were sustained. Neuronal and astrocytic S1P(1) expression in EAE was suppressed by CYM-5442 treatment, relative to vehicle, and levels of key cytokines, such as interleukin 17A, were also significantly reduced in drug-treated mice. S1P(1)-selective agonists that induce reversible lymphopenia while persisting in the CNS may be effective MS treatments.

Discovery of a Brain-Penetrant S1P3-Sparing Direct Agonist of the S1P1 and S1P5 Receptors Efficacious at Low Oral Dose

2-Amino-2-(4-octylphenethyl)propane-1,3-diol 1 (fingolimod, FTY720) has been recently marketed in the United States for the treatment of patients with remitting relapsing multiple sclerosis (RRMS). Its efficacy has been primarily linked to the agonism on T cells of S1P(1), one of the five sphingosine 1-phosphate (S1P) G-protein-coupled receptors, while its cardiovascular side effects have been associated with activity at S1P(3). Emerging data suggest that the ability of this molecule to cross the blood-brain barrier and to interact with both S1P(1) and S1P(5) in the central nervous system (CNS) may contribute to its efficacy in treating patients with RRMS. We have recently disclosed the structure of an advanced, first generation S1P(3)-sparing S1P(1) agonist, a zwitterion with limited CNS exposure. In this Article, we highlight our strategy toward the identification of CNS-penetrant S1P(3)-sparing S1P(1) and S1P(5) agonists resulting in the discovery of 5-(3-{2-[2-hydroxy-1-(hydroxymethyl)ethyl]-5-methyl-1,2,3,4-tetrahydro-6-isoquinolinyl}-1,2,4-oxadiazol-5-yl)-2-[(1-methylethyl)oxy]benzonitrile 15. Its exceptional in vivo potency and good pharmacokinetic properties translate into a very low predicted therapeutic dose in human (<1 mg p.o. once daily).