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      Selectivity and Specificity of Sphingosine-1-Phosphate Receptor Ligands: Caveats and Critical Thinking in Characterizing Receptor-Mediated Effects

      1 , 2

      Frontiers in Pharmacology

      Frontiers Research Foundation

      JTE-013, BML-241, CAY10444, VPC23019, antagonist

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          Abstract

          Receptors for sphingosine-1-phosphate (S1P) have been identified only recently. Their medicinal chemistry is therefore still in its infancy, and few selective agonists or antagonists are available. Furthermore, the selectivity of S1P receptor agonists or antagonists is not well established. JTE-013 and BML-241 (also known as CAY10444), used extensively as specific S1P 2 and S1P 3 receptors antagonists respectively, are cases in point. When analyzing S1P-induced vasoconstriction in mouse basilar artery, we observed that JTE-013 inhibited not only the effect of S1P, but also the effect of U46619, endothelin-1 or high KCl; JTE-013 strongly inhibited responses to S1P in S1P 2 receptor knockout mice. Similarly, BML-241 has been shown to inhibit increases in intracellular Ca 2+ concentration via P 2 receptor or α 1A-adrenoceptor stimulation and α 1A-adrenoceptor-mediated contraction of rat mesenteric artery, while it did not affect S1P 3-mediated decrease of forskolin-induced cyclic AMP accumulation. Another putative S1P 1/3 receptor antagonist, VPC23019, does not inhibit S1P 3-mediated vasoconstriction. With these examples in mind, we discuss caveats about relying on available pharmacological tools to characterize receptor subtypes.

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          Most cited references 63

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          A placebo-controlled trial of oral fingolimod in relapsing multiple sclerosis.

          Oral fingolimod, a sphingosine-1-phosphate-receptor modulator that prevents the egress of lymphocytes from lymph nodes, significantly improved relapse rates and end points measured on magnetic resonance imaging (MRI), as compared with either placebo or intramuscular interferon beta-1a, in phase 2 and 3 studies of multiple sclerosis. In our 24-month, double-blind, randomized study, we enrolled patients who had relapsing-remitting multiple sclerosis, were 18 to 55 years of age, had a score of 0 to 5.5 on the Expanded Disability Status Scale (which ranges from 0 to 10, with higher scores indicating greater disability), and had had one or more relapses in the previous year or two or more in the previous 2 years. Patients received oral fingolimod at a dose of 0.5 mg or 1.25 mg daily or placebo. End points included the annualized relapse rate (the primary end point) and the time to disability progression (a secondary end point). A total of 1033 of the 1272 patients (81.2%) completed the study. The annualized relapse rate was 0.18 with 0.5 mg of fingolimod, 0.16 with 1.25 mg of fingolimod, and 0.40 with placebo (P<0.001 for either dose vs. placebo). Fingolimod at doses of 0.5 mg and 1.25 mg significantly reduced the risk of disability progression over the 24-month period (hazard ratio, 0.70 and 0.68, respectively; P=0.02 vs. placebo, for both comparisons). The cumulative probability of disability progression (confirmed after 3 months) was 17.7% with 0.5 mg of fingolimod, 16.6% with 1.25 mg of fingolimod, and 24.1% with placebo. Both fingolimod doses were superior to placebo with regard to MRI-related measures (number of new or enlarged lesions on T(2)-weighted images, gadolinium-enhancing lesions, and brain-volume loss; P<0.001 for all comparisons at 24 months). Causes of study discontinuation and adverse events related to fingolimod included bradycardia and atrioventricular conduction block at the time of fingolimod initiation, macular edema, elevated liver-enzyme levels, and mild hypertension. As compared with placebo, both doses of oral fingolimod improved the relapse rate, the risk of disability progression, and end points on MRI. These benefits will need to be weighed against possible long-term risks. (ClinicalTrials.gov number, NCT00289978.) Copyright 2010 Massachusetts Medical Society
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            Lymphocyte egress from thymus and peripheral lymphoid organs is dependent on S1P receptor 1.

            Adaptive immunity depends on T-cell exit from the thymus and T and B cells travelling between secondary lymphoid organs to survey for antigens. After activation in lymphoid organs, T cells must again return to circulation to reach sites of infection; however, the mechanisms regulating lymphoid organ exit are unknown. An immunosuppressant drug, FTY720, inhibits lymphocyte emigration from lymphoid organs, and phosphorylated FTY720 binds and activates four of the five known sphingosine-1-phosphate (S1P) receptors. However, the role of S1P receptors in normal immune cell trafficking is unclear. Here we show that in mice whose haematopoietic cells lack a single S1P receptor (S1P1; also known as Edg1) there are no T cells in the periphery because mature T cells are unable to exit the thymus. Although B cells are present in peripheral lymphoid organs, they are severely deficient in blood and lymph. Adoptive cell transfer experiments establish an intrinsic requirement for S1P1 in T and B cells for lymphoid organ egress. Furthermore, S1P1-dependent chemotactic responsiveness is strongly upregulated in T-cell development before exit from the thymus, whereas S1P1 is downregulated during peripheral lymphocyte activation, and this is associated with retention in lymphoid organs. We find that FTY720 treatment downregulates S1P1, creating a temporary pharmacological S1P1-null state in lymphocytes, providing an explanation for the mechanism of FTY720-induced lymphocyte sequestration. These findings establish that S1P1 is essential for lymphocyte recirculation and that it regulates egress from both thymus and peripheral lymphoid organs.
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              Estradiol induces export of sphingosine 1-phosphate from breast cancer cells via ABCC1 and ABCG2.

              Sphingosine 1-phosphate (S1P), a potent sphingolipid mediator produced by sphingosine kinase isoenzymes (SphK1 and SphK2), regulates diverse cellular processes important for breast cancer progression acting in an autocrine and/or paracrine manner. Here we show that SphK1, but not SphK2, increased S1P export from MCF-7 cells. Whereas for both estradiol (E(2)) and epidermal growth factor-activated SphK1 and production of S1P, only E(2) stimulated rapid release of S1P and dihydro-S1P from MCF-7 cells. E(2)-induced S1P and dihydro-S1P export required estrogen receptor-alpha, not GPR30, and was suppressed either by pharmacological inhibitors or gene silencing of ABCC1 (multidrug resistant protein 1) or ABCG2 (breast cancer resistance protein). Inhibiting these transporters also blocked E(2)-induced activation of ERK1/2, indicating that E(2) activates ERK via downstream signaling of S1P. Taken together, our findings suggest that E(2)-induced export of S1P mediated by ABCC1 and ABCG2 transporters and consequent activation of S1P receptors may contribute to nongenomic signaling of E(2) important for breast cancer pathophysiology.
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                Author and article information

                Journal
                Front Pharmacol
                Front. Pharmacol.
                Frontiers in Pharmacology
                Frontiers Research Foundation
                1663-9812
                22 February 2011
                2011
                : 2
                Affiliations
                1simpleDepartment of Clinical and Molecular Biomedicine, Catania University Catania, Italy
                2simpleStroke and Neurovascular Laboratory Regulation, Department of Radiology, Massachusetts General Hospital Charlestown, MA, USA
                Author notes

                Edited by: Martin C. Michel, Academic Medical Center, Netherlands

                Reviewed by: Dagmar Meyer Zu Heringdorf, Goethe University, Germany; Maikel Jongsma, Netherlands Cancer Institute, Netherlands

                *Correspondence: Christian Waeber, Massachusetts General Hospital, CNY149 Room 6403, 149 13th Street, Charlestown, MA 02129, USA. e-mail: waeber@ 123456helix.mgh.harvard.edu

                This article was submitted to Frontiers in Experimental Pharmacology and Drugs Discovery, a specialty of Frontiers in Pharmacology.

                Article
                10.3389/fphar.2011.00009
                3110020
                21687504
                Copyright © 2011 Salomone and Waeber.

                This is an open-access article subject to an exclusive license agreement between the authors and Frontiers Media SA, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are credited.

                Page count
                Figures: 0, Tables: 2, Equations: 0, References: 63, Pages: 8, Words: 6067
                Categories
                Pharmacology
                Perspective Article

                Pharmacology & Pharmaceutical medicine

                vpc23019, bml-241, cay10444, antagonist, jte-013

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