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SummaryInflammatory bowel disease is an important risk factor for colorectal cancer. We show that sphingosine-1-phosphate (S1P) produced by upregulation of sphingosine kinase 1 (SphK1) links chronic intestinal inflammation to colitis-associated cancer (CAC) and both are exacerbated by deletion of Sphk2. S1P is essential for production of the multifunctional NF-κB-regulated cytokine IL-6, persistent activation of the transcription factor STAT3, and consequent upregulation of the S1P receptor, S1PR1. The prodrug FTY720 decreased SphK1 and S1PR1 expression and eliminated the NF-κB/IL-6/STAT3 amplification cascade and development of CAC, even in Sphk2−/− mice, and may be useful in treating colon cancer in individuals with ulcerative colitis. Thus, the SphK1/S1P/S1PR1 axis is at the nexus between NF-κB and STAT3 and connects chronic inflammation and CAC.

Systemic exacerbation of allergic responses, in which mast cells play a critical role, results in life-threatening anaphylactic shock. Sphingosine-1–phosphate (S1P), a ligand for a family of G protein–coupled receptors, is a new addition to the repertoire of bioactive lipids secreted by activated mast cells. Yet little is known of its role in human mast cell functions and in anaphylaxis. We show that S1P2 receptors play a critical role in regulating human mast cell functions, including degranulation and cytokine and chemokine release. Immunoglobulin E–triggered anaphylactic responses, including elevation of circulating histamine and associated pulmonary edema in mice, were significantly attenuated by the S1P2 antagonist JTE-013 and in S1P2-deficient mice, in contrast to anaphylaxis induced by administration of histamine or platelet-activating factor. Hence, S1P and S1P2 on mast cells are determinants of systemic anaphylaxis and associated pulmonary edema and might be beneficial targets for anaphylaxis attenuation and prophylaxis.

Sphingosine-1-phosphate (S1P) is now emerging as a potent lipid mediator produced by mast cells that contributes to inflammatory and allergic responses. In contrast to its weak effect on degranulation of murine mast cells, S1P potently induced degranulation of the human LAD2 mast-cell line and cord blood–derived human mast cells (hMCs). S1P also stimulated production and secretion of cytokines, TNF-α and IL-6, and markedly enhanced secretion of a chemokine, CCL2/MCP-1, important modulators of inflammation. S1P is produced in mast cells by the 2 sphingosine kinases, SphK1 and SphK2. SphK1 but not SphK2 plays a critical role in IgE/Ag-induced degranulation, migration toward antigen, and CCL2 secretion from hMCs, as determined by specifically down-regulating their expression. However, both isoenzymes were required for efficient TNF-α secretion. Taken together, our data suggest that differential formation of S1P by SphK1 and SphK2 has distinct and important actions in hMCs.

Background Sphingosine-1-phosphate (S1P) is a bioactive sphingolipid produced by mast cells (MCs) on cross-linking of their high-affinity receptors for IgE by antigen that can amplify MC responses by binding to its S1P receptors. An acute MC-dependent allergic reaction can lead to systemic shock, but the early events of its development in lung tissues have not been investigated, and S1P functions in the onset of allergic processes remain to be examined. Objective We used a highly specific neutralizing anti-S1P antibody (mAb) and the sphingosine-1-phosphate receptor 2 (S1PR2) antagonist JTE-013 to study the signaling contributions of S1P and S1PR2 to MC- and IgE-dependent airway allergic responses in mice within minutes after antigen challenge. Methods Allergic reaction was triggered by a single intraperitoneal dose of antigen in sensitized mice pretreated intraperitoneally with anti-S1P, isotype control mAb, JTE-013, or vehicle before antigen challenge. Results Kinetics experiments revealed early pulmonary infiltration of mostly T cells around blood vessels of sensitized mice 20 minutes after antigen exposure. Pretreatment with anti-S1P mAb inhibited in vitro MC activation, as well as in vivo development of airway infiltration and MC activation, reducing serum levels of histamine, cytokines, and the chemokines monocyte chemoattractant protein 1/CCL2, macrophage inflammatory protein 1α/CCL3, and RANTES/CCL5. S1PR2 antagonism or deficiency or MC deficiency recapitulated these results. Both in vitro and in vivo experiments demonstrated MC S1PR2 dependency for chemokine release and the necessity for signal transducer and activator of transcription 3 activation. Conclusion Activation of S1PR2 by S1P and downstream signal transducer and activator of transcription 3 signaling in MCs regulate early T-cell recruitment to antigen-challenged lungs through chemokine production.

Background: Sphingosine-1-phosphate (S1P), which is produced by 2 sphingosine kinase (SphK) isoenzymes, SphK1 and SphK2, has been implicated in IgE-mediated mast cell responses. However, studies of allergic inflammation in isotype-specific SphK knockout mice have not clarified their contribution, and the role that S1P plays in vivo in a mast cells and IgE-dependent murine model of allergic asthma has not yet been examined. Objective: We used an isoenzyme-specific SphK1 inhibitor,SK1-I, to investigate the contributions of S1P and SphK1 to mast cell-dependent airway hyperresponsiveness (AHR) and airway inflammation in mice. Methods: Allergic airway inflammation and AHR were examined in a mast cell-dependent murine model of ovalbumin (OVA)-induced asthma. C57BL/6 mice received intranasal delivery of SK1-I before sensitization and challenge with OVA or only before challenge. Results: SK1-I inhibited antigen-dependent activation of human and murine mast cells and suppressed activation of nuclear factor-kB (NF-kB), a master transcription factor that regulates the expression of proinflammatory cytokines. SK1-I treatment of mice sensitized to OVA in the absence of adjuvant, in which mast cell-dependent allergic inflammation develops, significantly reduced OVA-induced AHR to methacholine; decreased numbers of eosinophils and levels of the cytokines IL-4, IL-5, IL-6, IL-13,IFN-g, and TNF-a and the chemokines eotaxin and CCL2 in bronchoalveolar lavage fluid; and decreased pulmonary inflammation, as well as activation of NF-kB in the lungs. Fil: Price, Megan M.. Virginia Commonwealth University. School of Medicine. Department of Biochemistry and Molecular Biology; Estados Unidos Fil: Oskeritzian, Carole A.. Virginia Commonwealth University. School of Medicine. Department of Biochemistry and Molecular Biology; Estados Unidos Fil: Falanga, Yves T.. Virginia Commonwealth University. Department of Microbiology and Immunology; Estados Unidos Fil: Harikumar, Kuzhuvelil B.. Virginia Commonwealth University. School of Medicine. Department of Biochemistry and Molecular Biology; Estados Unidos Fil: Allegood, Jeremy C.. Virginia Commonwealth University. School of Medicine. Department of Biochemistry and Molecular Biology; Estados Unidos Fil: Alvarez, Sergio Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico San Luis. Instituto Multidisciplinario de Investigaciones Biológicas de San Luis; Argentina. Virginia Commonwealth University. School of Medicine. Department of Biochemistry and Molecular Biology; Estados Unidos Fil: Conrad, Daniel. Virginia Commonwealth University. Department of Biology; Estados Unidos Fil: Ryan, John J.. Virginia Commonwealth University. Department of Microbiology and Immunology; Estados Unidos Fil: Milstien, Sheldon. Virginia Commonwealth University. School of Medicine. Department of Biochemistry and Molecular Biology; Estados Unidos Fil: Spiegel, Sarah. Virginia Commonwealth University. School of Medicine. Department of Biochemistry and Molecular Biology; Estados Unidos

Mast cells (MCs) play a critical role in both acute and chronic inflammation and mature in peripheral tissues from bone marrow-derived progenitors that circulate in the blood as immature precursors. MCs developed from cord blood-derived progenitors cultured with stem cell factor (SCF) alone express intragranular tryptase (MCTs), the phenotype predominant in the lung. MC progenitors are likely to encounter the serum-borne bioactive sphingolipid metabolite, sphingosine-1-phosphate (S1P), during migration to target tissues. S1P accelerated the development of cord blood-derived MCs (CB-MCs) and strikingly increased the numbers of MC-expressing chymase. These MCs have functional FceRIs, and similar to skin MCTCs that express both tryptase and chymase, also express CD88 and are activated by anaphylatoxin C5a and the secretagogue compound 48/80. S1P induced release of IL-6, a cytokine known to promote development of functionally mature MCTCs, from cord blood cultures containing adherent macrophages, and from highly purified macrophages, but not from macrophage-depleted CB-MCs. In contrast, S1P stimulated secretion of the chemokine, monocyte chemoattractant protein 1 (MCP-1/CCL2), from these macrophage-depleted and purified CB-MCs. These results suggest crucial roles for S1P in regulating development of human MCs and their functions and reveal a complex interplay between macrophages and MC progenitors in the development of mature human MCs.—Price, M. M., Kapitonov, D., Allegood, J., Milstien, S., Oskeritzian, C. A., Spiegel, S. Sphingosine-1-phosphate induces development of functionally mature chymase-expressing human mast cells from hematopoietic progenitors.

Sphingolipids are not only major lipid components of all eukaryotic cell membranes, but they also comprise an important family of bioactive signaling molecules that regulate a diverse array of biological responses. The sphingolipid metabolite sphingosine-1-phosphate (S1P), is a key regulator of immune responses. Cellular levels of S1P are determined by the balance between its synthesis, involving two sphingosine kinases (SphK1 and SphK2), and its degradation, involving S1P lyase and S1P phosphatases. S1P mainly signals through its cell-surface receptors and may also have intracellular functions. S1P has important functions in mast cells – the major effectors of allergic responses. Antigen triggering of IgE receptors on mast cells activates both SphKs resulting in the production of S1P that is released and regulates and amplifies mast cell functions, including degranulation as well as cytokine and chemokine release.