Neutrophilia in severe asthma is reduced in Ormdl3 overexpressing mice.

Genome-wide association studies have linked the ORM (yeast)-like protein isoform 3 (ORMDL3) to asthma severity. Although ORMDL3 is a member of a family that negatively regulates serine palmitoyltransferase (SPT) and thus biosynthesis of sphingolipids, it is still unclear whether ORMDL3 and altered sphingolipid synthesis are causally related to non-Th2 severe asthma associated with a predominant neutrophil inflammation and high interleukin-17 (IL-17) levels. Here, we examined the effects of ORMDL3 overexpression in a preclinical mouse model of allergic lung inflammation that is predominantly neutrophilic and recapitulates many of the clinical features of severe human asthma. ORMDL3 overexpression reduced lung and circulating levels of dihydrosphingosine, the product of SPT. However, the most prominent effect on sphingolipid levels was reduction of circulating S1P. The LPS/OVA challenge increased markers of Th17 inflammation with a predominant infiltration of neutrophils into the lung. A significant decrease of neutrophil infiltration was observed in the Ormdl3 transgenic mice challenged with LPS/OVA compared to the wild type and concomitant decrease in IL-17, that plays a key role in the pathogenesis of neutrophilic asthma. LPS decreased survival of murine neutrophils, which was prevented by co-treatment with S1P. Moreover, S1P potentiated LPS-induced chemotaxis of neutrophil, suggesting that S1P can regulate neutrophil survival and recruitment following LPS airway inflammation. Our findings reveal a novel connection between ORMDL3 overexpression, circulating levels of S1P, IL-17 and neutrophil recruitment into the lung, and questions the potential involvement of ORMDL3 in the pathology, leading to development of severe neutrophilic asthma.

Sphingosine Kinase 2 in Stromal Fibroblasts Creates a Hospitable Tumor Microenvironment in Breast Cancer.

Reciprocal interactions between breast cancer cells and the tumor microenvironment (TME) are important for cancer progression and metastasis. We report here that the deletion or inhibition of sphingosine kinase 2 (SphK2), which produces sphingosine-1-phosphate (S1P), markedly suppresses syngeneic breast tumor growth and lung metastasis in mice by creating a hostile microenvironment for tumor growth and invasion. SphK2 deficiency decreased S1P and concomitantly increased ceramides, including C16-ceramide, in stromal fibroblasts. Ceramide accumulation suppressed activation of cancer-associated fibroblasts (CAF) by upregulating stromal p53, which restrained production of tumor-promoting factors to reprogram the TME and to restrict breast cancer establishment. Ablation of p53 in SphK2-deficient fibroblasts reversed these effects, enabled CAF activation and promoted tumor growth and invasion. These data uncovered a novel role of SphK2 in regulating non-cell-autonomous functions of p53 in stromal fibroblasts and their transition to tumor-promoting CAFs, paving the way for the development of a strategy to target the TME and to enhance therapeutic efficacy. SIGNIFICANCE: Sphingosine kinase 2 (SphK2) facilitates the activation of stromal fibroblasts to tumor-promoting cancer-associated fibroblasts by suppressing host p53 activity, revealing SphK2 as a potential target to reprogram the TME.

Sphingosine kinases regulate ER contacts with late endocytic organelles and cholesterol trafficking.

Membrane contact sites (MCS), close membrane apposition between organelles, are platforms for interorganellar transfer of lipids including cholesterol, regulation of lipid homeostasis, and co-ordination of endocytic trafficking. Sphingosine kinases (SphKs), two isoenzymes that phosphorylate sphingosine to the bioactive sphingosine-1-phosphate (S1P), have been implicated in endocytic trafficking. However, the physiological functions of SphKs in regulation of membrane dynamics, lipid trafficking and MCS are not known. Here, we report that deletion of SphKs decreased S1P with concomitant increases in its precursors sphingosine and ceramide, and markedly reduced endoplasmic reticulum (ER) contacts with late endocytic organelles. Expression of enzymatically active SphK1, but not catalytically inactive, rescued the deficit of these MCS. Although free cholesterol accumulated in late endocytic organelles in SphK null cells, surprisingly however, cholesterol transport to the ER was not reduced. Importantly, deletion of SphKs promoted recruitment of the ER-resident cholesterol transfer protein Aster-B (also called GRAMD1B) to the plasma membrane (PM), consistent with higher accessible cholesterol and ceramide at the PM, to facilitate cholesterol transfer from the PM to the ER. In addition, ceramide enhanced in vitro binding of the Aster-B GRAM domain to phosphatidylserine and cholesterol liposomes. Our study revealed a previously unknown role for SphKs and sphingolipid metabolites in governing diverse MCS between the ER network and late endocytic organelles versus the PM to control the movement of cholesterol between distinct cell membranes.

Ceramide in apoptosis and oxidative stress in allergic inflammation and asthma.

BACKGROUND: Nothing is known about the mechanisms by which increased ceramide levels in the lung contribute to allergic responses and asthma severity. OBJECTIVE: We sought to investigate the functional role of ceramide in mouse models of allergic airway disease that recapitulate the cardinal clinical features of human allergic asthma. METHODS: Allergic airway disease was induced in mice by repeated intranasal administration of house dust mite or the fungal allergen Alternaria alternata. Processes that can be regulated by ceramide and are important for severity of allergic asthma were correlated with ceramide levels measured by mass spectrometry. RESULTS: Both allergens induced massive pulmonary apoptosis and also significantly increased reactive oxygen species in the lung. Prevention of increases in lung ceramide levels mitigated allergen-induced apoptosis, reactive oxygen species, and neutrophil infiltration. In contrast, dietary supplementation of the antioxidant α-tocopherol decreased reactive oxygen species but had no significant effects on elevation of ceramide level or apoptosis, indicating that the increases in lung ceramide levels in allergen-challenged mice are not mediated by oxidative stress. Moreover, specific ceramide species were altered in bronchoalveolar lavage fluid from patients with severe asthma compared with in bronchoalveolar lavage fluid from individuals without asthma. CONCLUSION: Our data suggest that elevation of ceramide level after allergen challenge contributes to the apoptosis, reactive oxygen species generation, and neutrophilic infiltrate that characterize the severe asthmatic phenotype. Ceramide might be the trigger of formation of Creola bodies found in the sputum of patients with severe asthma and could be a biomarker to optimize diagnosis and to monitor and improve clinical outcomes in this disease.

Targeting defective sphingosine kinase 1 in Niemann-Pick type C disease with an activator mitigates cholesterol accumulation.

Niemann-Pick type C (NPC) disease is a lysosomal storage disorder arising from mutations in the cholesterol-trafficking protein NPC1 (95%) or NPC2 (5%). These mutations result in accumulation of low-density lipoprotein-derived cholesterol in late endosomes/lysosomes, disruption of endocytic trafficking, and stalled autophagic flux. Additionally, NPC disease results in sphingolipid accumulation, yet it is unique among the sphingolipidoses because of the absence of mutations in the enzymes responsible for sphingolipid degradation. In this work, we examined the cause for sphingosine and sphingolipid accumulation in multiple cellular models of NPC disease and observed that the activity of sphingosine kinase 1 (SphK1), one of the two isoenzymes that phosphorylate sphingoid bases, was markedly reduced in both NPC1 mutant and NPC1 knockout cells. Conversely, SphK1 inhibition with the isotype-specific inhibitor SK1-I in WT cells induced accumulation of cholesterol and reduced cholesterol esterification. Of note, a novel SphK1 activator (SK1-A) that we have characterized decreased sphingoid base and complex sphingolipid accumulation and ameliorated autophagic defects in both NPC1 mutant and NPC1 knockout cells. Remarkably, in these cells, SK1-A also reduced cholesterol accumulation and increased cholesterol ester formation. Our results indicate that a SphK1 activator rescues aberrant cholesterol and sphingolipid storage and trafficking in NPC1 mutant cells. These observations highlight a previously unknown link between SphK1 activity, NPC1, and cholesterol trafficking and metabolism.

Role of Sphingosine Kinase 1 and Sphingosine-1-Phosphate Axis in Hepatocellular Carcinoma.

Hepatocellular carcinoma (HCC) is primarily diagnosed in the latter stages of disease progression and is the third leading cause of cancer deaths worldwide. Thus, there is a need to find biomarkers of early HCC as well as the development of more effective treatments for the disease. Sphingosine-1-phosphate (S1P) is a pleiotropic lipid signaling molecule produced by two isoforms of sphingosine kinase (SphK1 and SphK2) that is involved in regulation of many aspects of mammalian physiology and pathophysiology, including inflammation, epithelial and endothelial barrier function, cancer, and metastasis, among many others. Abundant evidence indicates that SphK1 and S1P promote cancer progression and metastasis in multiple types of cancers. However, the role of SphK/S1P in HCC is less well studied. Here, we review the current state of knowledge of SphKs and S1P in HCC, including evidence for the correlation of SphK1 expression and S1P levels with progression of HCC and negative outcomes, and discuss how this information could lead to the design of more effective diagnostic and treatment modalities for HCC.

ORMDL3 and allergic asthma: From physiology to pathology.

There is a strong genetic component to asthma, and numerous genome-wide association studies have identified ORM1 (yeast)-like protein 3 (ORMDL3) as a gene associated with asthma susceptibility. However, how ORMDL3 contributes to asthma pathogenesis and its physiologic functions is not well understood and a matter of great debate. This rostrum describes recent advances and new insights in understanding of the multifaceted functions of ORMDL3 in patients with allergic asthma. We also suggest a potential unifying paradigm and discuss molecular mechanisms for the pathologic functions of ORMDL3 in asthma related to its evolutionarily conserved role in regulation of sphingolipid homeostasis. Finally, we briefly survey the utility of sphingolipid metabolites as potential biomarkers for allergic asthma.

New insights into functions of the sphingosine-1-phosphate transporter SPNS2.

Sphingosine-1-phosphate (S1P) is a potent bioactive signaling molecule that regulates many physiological processes important for development, epithelial and endothelial barrier integrity, and the immune system, as well as for pathologies, such as autoimmune diseases, cancer, and metastasis. Most of the well-known actions of S1P are mediated by five specific G protein-coupled receptors located on the plasma membrane. Because S1P is synthesized intracellularly by two sphingosine kinase isoenzymes, we have proposed the paradigm of inside-out signaling by S1P, suggesting that S1P must be exported out of cells to interact with its receptors. While several transporters of S1P have previously been identified, spinster homologue 2 (SPNS2), a member of the large family of non-ATP-dependent organic ion transporters, has recently attracted much attention as an S1P transporter. Here, we discuss recent advances in understanding the physiological actions of SPNS2 in regulating levels of S1P and the S1P gradient that exists between the high circulating concentrations of S1P and low tissue levels that control lymphocyte trafficking. Special emphasis is on the functions of SPNS2 in inflammatory and autoimmune diseases and its recently discovered unexpected importance in metastasis.

Sphingosine kinase 1 activation by estrogen receptor α36 contributes to tamoxifen resistance in breast cancer.

In breast cancer, 17ß-estradiol (E2) plays critical roles mainly by binding to its canonical receptor, estrogen receptor (ER) α66, and eliciting genomic effects. E2 also triggers rapid, nongenomic responses. E2 activates sphingosine kinase 1 (SphK1), increasing sphingosine-1-phosphate (S1P) that binds to its receptors, leading to important breast cancer signaling. However, the E2 receptor responsible for SphK1 activation has not yet been identified. Here, we demonstrate in triple-negative breast cancer cells, which lack the canonical ERα66 but express the novel splice variant ERα36, that ERα36 is the receptor responsible for E2-induced activation of SphK1 and formation and secretion of S1P and dihydro-S1P, the ligands for S1PRs. Tamoxifen, the first-line endocrine therapy for breast cancer, is an antagonist of ERα66, but an agonist of ERα36, and, like E2, activates SphK1 and markedly increases secretion of S1P. A major problem with tamoxifen therapy is development of acquired resistance. We found that tamoxifen resistance correlated with increased SphK1 and ERα36 expression in tamoxifen-resistant breast cancer cells, in patient-derived xenografts, and in endocrine-resistant breast cancer patients. Our data also indicate that targeting this ERα36 and SphK1 axis may be a therapeutic option to circumvent endocrine resistance and improve patient outcome.

Niemann-Pick type C disease: The atypical sphingolipidosis.

Niemann-Pick type C (NPC) disease is a lysosomal storage disorder resulting from mutations in either the NPC1 (95%) or NPC2 (5%) genes. NPC typically presents in childhood with visceral lipid accumulation and complex progressive neurodegeneration characterized by cerebellar ataxia, dysphagia, and dementia, resulting in a shortened lifespan. While cholesterol is widely acknowledged as the principal storage lipid in NPC, multiple species of sphingolipids accumulate as well. This accumulation of sphingolipids led to the initial assumption that NPC disease was caused by a deficiency in a sphingolipid catabolism enzyme, similar to sphingomyelinase deficiencies with which it shares a family name. It took about half a century to determine that NPC was in fact caused by a cholesterol trafficking defect, and still as we approach a century after the initial identification of the disease, the mechanisms by which sphingolipids accumulate remain poorly understood. Here we focus on the defects of sphingolipid catabolism in the endolysosomal compartment and how they contribute to the biology and pathology observed in NPC disease. This review highlights the need for further work on understanding and possibly developing treatments to correct the accumulation of sphingolipids in addition to cholesterol in this currently untreatable disease.

ABCC1-Exported Sphingosine-1-phosphate, Produced by Sphingosine Kinase 1, Shortens Survival of Mice and Patients with Breast Cancer.

Sphingosine-1-phosphate (S1P), a bioactive sphingolipid mediator, has been implicated in regulation of many processes important for breast cancer progression. Previously, we observed that S1P is exported out of human breast cancer cells by ATP-binding cassette (ABC) transporter ABCC1, but not by ABCB1, both known multidrug resistance proteins that efflux chemotherapeutic agents. However, the pathologic consequences of these events to breast cancer progression and metastasis have not been elucidated. Here, it is demonstrated that high expression of ABCC1, but not ABCB1, is associated with poor prognosis in breast cancer patients. Overexpression of ABCC1, but not ABCB1, in human MCF7 and murine 4T1 breast cancer cells enhanced S1P secretion, proliferation, and migration of breast cancer cells. Implantation of breast cancer cells overexpressing ABCC1, but not ABCB1, into the mammary fat pad markedly enhanced tumor growth, angiogenesis, and lymphangiogenesis with a concomitant increase in lymph node and lung metastases as well as shorter survival of mice. Interestingly, S1P exported via ABCC1 from breast cancer cells upregulated transcription of sphingosine kinase 1 (SPHK1), thus promoting more S1P formation. Finally, patients with breast cancers that express both activated SPHK1 and ABCC1 have significantly shorter disease-free survival. These findings suggest that export of S1P via ABCC1 functions in a malicious feed-forward manner to amplify the S1P axis involved in breast cancer progression and metastasis, which has important implications for prognosis of breast cancer patients and for potential therapeutic targets.Implication: Multidrug resistant transporter ABCC1 and activation of SPHK1 in breast cancer worsen patient's survival by export of S1P to the tumor microenvironment to enhance key processes involved in cancer progression. Mol Cancer Res; 16(6); 1059-70. ©2018 AACR.

Targeting the SphK1/S1P/S1PR1 Axis That Links Obesity, Chronic Inflammation, and Breast Cancer Metastasis.

Although obesity with associated inflammation is now recognized as a risk factor for breast cancer and distant metastases, the functional basis for these connections remain poorly understood. Here, we show that in breast cancer patients and in animal breast cancer models, obesity is a sufficient cause for increased expression of the bioactive sphingolipid mediator sphingosine-1-phosphate (S1P), which mediates cancer pathogenesis. A high-fat diet was sufficient to upregulate expression of sphingosine kinase 1 (SphK1), the enzyme that produces S1P, along with its receptor S1PR1 in syngeneic and spontaneous breast tumors. Targeting the SphK1/S1P/S1PR1 axis with FTY720/fingolimod attenuated key proinflammatory cytokines, macrophage infiltration, and tumor progression induced by obesity. S1P produced in the lung premetastatic niche by tumor-induced SphK1 increased macrophage recruitment into the lung and induced IL6 and signaling pathways important for lung metastatic colonization. Conversely, FTY720 suppressed IL6, macrophage infiltration, and S1P-mediated signaling pathways in the lung induced by a high-fat diet, and it dramatically reduced formation of metastatic foci. In tumor-bearing mice, FTY720 similarly reduced obesity-related inflammation, S1P signaling, and pulmonary metastasis, thereby prolonging survival. Taken together, our results establish a critical role for circulating S1P produced by tumors and the SphK1/S1P/S1PR1 axis in obesity-related inflammation, formation of lung metastatic niches, and breast cancer metastasis, with potential implications for prevention and treatment.Significance: These findings offer a preclinical proof of concept that signaling by a sphingolipid may be an effective target to prevent obesity-related breast cancer metastasis. Cancer Res; 78(7); 1713-25. ©2018 AACR.

TP53 is required for BECN1- and ATG5-dependent cell death induced by sphingosine kinase 1 inhibition.

The bioactive sphingolipid metabolite sphingosine-1-phosphate (S1P) and the enzyme that produces it, SPHK1 (sphingosine kinase 1), regulate many processes important for the etiology of cancer. It has been suggested that SPHK1 levels are regulated by the tumor suppressor protein TP53, a key regulator of cell cycle arrest, apoptosis, and macroautophagy/autophagy. However, little is still known of the relationship between TP53 and SPHK1 activity in the regulation of these processes. To explore this link, we examined the effects of inhibiting SPHK1 in wild-type and TP53 null cancer cell lines. SK1-I, an analog of sphingosine and isozyme-specific SPHK1 inhibitor, suppressed cancer cell growth and clonogenic survival in a TP53-dependent manner. It also more strongly enhanced intrinsic apoptosis in wild-type TP53 cells than in isogenic TP53 null cells. Intriguingly, SK1-I induced phosphorylation of TP53 on Ser15, which increases its transcriptional activity. Consequently, levels of TP53 downstream targets such as pro-apoptotic members of the BCL2 family, including BAX, BAK1, and BID were increased in wild-type but not in TP53 null cells. Inhibition of SPHK1 also increased the formation of autophagic and multivesicular bodies, and increased processing of LC3 and its localization within acidic compartments in a TP53-dependent manner. SK1-I also induced massive accumulation of vacuoles, enhanced autophagy, and increased cell death in an SPHK1-dependent manner that also required TP53 expression. Importantly, downregulation of the key regulators of autophagic flux, BECN1 and ATG5, dramatically decreased the cytotoxicity of SK1-I only in cells with TP53 expression. Hence, our results reveal that TP53 plays an important role in vacuole-associated cell death induced by SPHK1 inhibition in cancer cells.

FTY720/fingolimod increases NPC1 and NPC2 expression and reduces cholesterol and sphingolipid accumulation in Niemann-Pick type C mutant fibroblasts.

Niemann-Pick type C (NPC) disease is a fatal neurodegenerative disorder caused by mutations in NPC1 or NPC2 with decreased functions leading to lysosomal accumulation of cholesterol and sphingolipids. FTY720/fingolimod, used for treatment of multiple sclerosis, is phosphorylated by nuclear sphingosine kinase 2, and its active phosphorylated form (FTY720-P) is an inhibitor of class I histone deacetylases. In this study, administration of clinically relevant doses of FTY720 to mice increased expression of NPC1 and -2 in brain and liver and decreased cholesterol in an SphK2-dependent manner. FTY720 greatly increased expression of NPC1 and -2 in human NPC1 mutant fibroblasts that correlated with formation of FTY720-P and significantly reduced the accumulation of cholesterol and glycosphingolipids. In agreement with this finding, FTY720 pretreatment of human NPC1 mutant fibroblasts restored transport of the cholera toxin B subunit, which binds ganglioside GM1, to the Golgi apparatus. Together, these findings suggest that FTY720 administration can ameliorate cholesterol and sphingolipid storage and trafficking defects in NPC1 mutant fibroblasts. Because neurodegeneration is the main clinical feature of NPC disease, and FTY720 accumulates in the CNS and has several advantages over available histone deacetylase inhibitors now in clinical trials, our work provides a potential opportunity for treatment of this incurable disease.-Newton, J., Hait, N. C., Maceyka, M., Colaco, A., Maczis, M., Wassif, C. A., Cougnoux, A., Porter, F. D., Milstien, S., Platt, N., Platt, F. M., Spiegel, S. FTY720/fingolimod increases NPC1 and NPC2 expression and reduces cholesterol and sphingolipid accumulation in Niemann-Pick type C mutant fibroblasts.

Sphingosine and Sphingosine Kinase 1 Involvement in Endocytic Membrane Trafficking.

The balance between cholesterol and sphingolipids within the plasma membrane has long been implicated in endocytic membrane trafficking. However, in contrast to cholesterol functions, little is still known about the roles of sphingolipids and their metabolites. Perturbing the cholesterol/sphingomyelin balance was shown to induce narrow tubular plasma membrane invaginations enriched with sphingosine kinase 1 (SphK1), the enzyme that converts the bioactive sphingolipid metabolite sphingosine to sphingosine-1-phosphate, and suggested a role for sphingosine phosphorylation in endocytic membrane trafficking. Here we show that sphingosine and sphingosine-like SphK1 inhibitors induced rapid and massive formation of vesicles in diverse cell types that accumulated as dilated late endosomes. However, much smaller vesicles were formed in SphK1-deficient cells. Moreover, inhibition or deletion of SphK1 prolonged the lifetime of sphingosine-induced vesicles. Perturbing the plasma membrane cholesterol/sphingomyelin balance abrogated vesicle formation. This massive endosomal influx was accompanied by dramatic recruitment of the intracellular SphK1 and Bin/Amphiphysin/Rvs domain-containing proteins endophilin-A2 and endophilin-B1 to enlarged endosomes and formation of highly dynamic filamentous networks containing endophilin-B1 and SphK1. Together, our results highlight the importance of sphingosine and its conversion to sphingosine-1-phosphate by SphK1 in endocytic membrane trafficking.

ORMDL proteins regulate ceramide levels during sterile inflammation.

The bioactive sphingolipid metabolite, ceramide, regulates physiological processes important for inflammation and elevated levels of ceramide have been implicated in IL-1-mediated events. Although much has been learned about ceramide generation by activation of sphingomyelinases in response to IL-1, the contribution of the de novo pathway is not completely understood. Because yeast ORM1 and ORM2 proteins negatively regulate ceramide levels through inhibition of serine palmitoyltransferase, the first committed step in ceramide biosynthesis, we examined the functions of individual mammalian ORM orthologs, ORM (yeast)-like (ORMDL)1-3, in regulation of ceramide levels. In HepG2 liver cells, downregulation of ORMDL3 markedly increased the ceramide precursors, dihydrosphingosine and dihydroceramide, primarily from de novo biosynthesis based on [U-(13)C]palmitate incorporation into base-labeled and dual-labeled dihydroceramides, whereas downregulation of each isoform increased dihydroceramides [(13)C]labeled in only the amide-linked fatty acid. IL-1 and the IL-6 family cytokine, oncostatin M, increased dihydroceramide and ceramide levels in HepG2 cells and concomitantly decreased ORMDL proteins. Moreover, during irritant-induced sterile inflammation in mice leading to induction of the acute-phase response, which is dependent on IL-1, expression of ORMDL proteins in the liver was strongly downregulated and accompanied by increased ceramide levels in the liver and accumulation in the blood. Together, our results suggest that ORMDLs may be involved in regulation of ceramides during IL-1-mediated sterile inflammation.

Sphingosine-1-phosphate phosphatase 2 promotes disruption of mucosal integrity, and contributes to ulcerative colitis in mice and humans.

The bioactive sphingolipid sphingosine-1-phosphate (S1P) and the kinase that produces it have been implicated in inflammatory bowel diseases in mice and humans; however, little is known about the role of the 2 S1P-specific phosphohydrolase isoforms, SGPP1 and SGPP2, which catalyze dephosphorylation of S1P to sphingosine. To elucidate their functions, we generated specific knockout mice. Deletion of Sgpp2, which is mainly expressed in the gastrointestinal tract, significantly reduced dextran sodium sulfate (DSS)-induced colitis severity, whereas deletion of ubiquitously expressed Sgpp1 slightly worsened colitis. Moreover, Sgpp1 deletion enhanced expression of multifunctional proinflammatory cytokines, IL-6, TNF-α, and IL-1ß, activation of the transcription factor signal transducer and activator of transcription 3, and immune cell infiltration into the colon. Conversely, Sgpp2-null mice failed to mount a DSS-induced systemic inflammatory response. Of interest, Sgpp2 deficiency suppressed DSS-induced intestinal epithelial cell apoptosis and improved mucosal barrier integrity. Furthermore, down-regulation of Sgpp2 attenuated LPS-induced paracellular permeability in cultured cells and enhanced expression of the adherens junction protein E-cadherin. Finally, in patients with ulcerative colitis, SGPP2 expression was elevated in colitis tissues relative to that in uninvolved tissues. These results indicate that induction of SGPP2 expression contributes to the pathogenesis of colitis by promoting disruption of the mucosal barrier function. SGPP2 may represent a novel therapeutic target in inflammatory bowel disease.-Huang, W.-C., Liang, J., Nagahashi, M., Avni, D., Yamada, A., Maceyka, M., Wolen, A. R., Kordula, T., Milstien, S., Takabe, K., Oravecz, T., Spiegel, S. Sphingosine-1-phosphate phosphatase 2 promotes disruption of mucosal integrity, and contributes to ulcerative colitis in mice and humans.

Interstitial Fluid Sphingosine-1-Phosphate in Murine Mammary Gland and Cancer and Human Breast Tissue and Cancer Determined by Novel Methods.

The tumor microenvironment is a determining factor for cancer biology and progression. Sphingosine-1-phosphate (S1P), produced by sphingosine kinases (SphKs), is a bioactive lipid mediator that regulates processes important for cancer progression. Despite its critical roles, the levels of S1P in interstitial fluid (IF), an important component of the tumor microenvironment, have never previously been measured due to a lack of efficient methods for collecting and quantifying IF. The purpose of this study is to clarify the levels of S1P in the IF from murine mammary glands and its tumors utilizing our novel methods. We developed an improved centrifugation method to collect IF. Sphingolipids in IF, blood, and tissue samples were measured by mass spectrometry. In mice with a deletion of SphK1, but not SphK2, levels of S1P in IF from the mammary glands were greatly attenuated. Levels of S1P in IF from mammary tumors were reduced when tumor growth was suppressed by oral administration of FTY720/fingolimod. Importantly, sphingosine, dihydro-sphingosine, and S1P levels, but not dihydro-S1P, were significantly higher in human breast tumor tissue IF than in the normal breast tissue IF. To our knowledge, this is the first reported S1P IF measurement in murine normal mammary glands and mammary tumors, as well as in human patients with breast cancer. S1P tumor IF measurement illuminates new aspects of the role of S1P in the tumor microenvironment.

Sphingosine-1-phosphate and estrogen signaling in breast cancer.

Breast cancer remains the most common malignant disease in women. The estrogen receptor-α (ERα) and its ligand 17ß-estradiol (E2) play important roles in breast cancer. E2 elicits cellular effects by binding to ERα in the cytosol followed by receptor dimerization and translocation to the nucleus where it regulates gene expression by binding to ERE response elements. However, it has become apparent that E2 also exerts rapid non-genomic effects through membrane-associated receptors. There is emerging evidence that this induces formation of the bioactive sphingolipid metabolite sphingosine-1-phosphate (S1P). S1P in turn has been implicated in many processes important in breast cancer progression. One of the enzymes that produce S1P, sphingosine kinase 1 (SphK1), is upregulated in breast cancer and its expression has been correlated with poor prognosis. This review is focused on the role of the SphK/S1P axis in estrogen signaling and breast cancer progression and will discuss new therapeutic approaches targeting this axis for breast cancer treatment.

Spinster 2, a sphingosine-1-phosphate transporter, plays a critical role in inflammatory and autoimmune diseases.

Sphingosine 1-phosphate (S1P) is a pleiotropic bioactive sphingolipid metabolite that regulates numerous processes important for immune responses. S1P is made within cells and must be transported out of cells to exert its effects through activation of 5 specific cell surface GPCRs in an autocrine or paracrine fashion. Spinster 2 (Spns2) transports S1P out of cells, and its deletion in mice reduces circulating levels of S1P, alters immune cell trafficking, and induces lymphopenia. Here we examined the effects of Spns2 deletion on adaptive immune responses and in autoimmune disease models. Airway inflammation and hypersensitivity as well as delayed-type contact hypersensitivity were attenuated in Spns2(-/-) mice. Similarly, Spns2 deletion reduced dextran sodium sulfate- and oxazolone-induced colitis. Intriguingly, Spns2(-/-) mice were protected from the development of experimental autoimmune encephalopathy, a model of the autoimmune disease multiple sclerosis. Deletion of Spns2 also strongly alleviated disease development in collagen-induced arthritis. These results point to a broad role for Spns2-mediated S1P transport in the initiation and development of adaptive immune related disorders.