Inhibitors of sphingosine-1-phosphate metabolism (sphingosine kinases and sphingosine-1-phosphate lyase)

1-Phosphate receptor agonists: A promising therapeutic avenue for ischemia-reperfusion injury management

Ischemia-reperfusion injury (IRI) - a complex pathological condition occurring when blood supply is abruptly restored to ischemic tissues, leading to further tissue damage - poses a significant clinical challenge. Sphingosine-1-phosphate receptors (S1PRs), a specialized set of G-protein-coupled receptors comprising five subtypes (S1PR1 to S1PR5), are prominently present in various cell membranes, including those of lymphocytes, cardiac myocytes, and endothelial cells. Increasing evidence highlights the potential of targeting S1PRs for IRI therapeutic intervention. Notably, preconditioning and postconditioning strategies involving S1PR agonists like FTY720 have demonstrated efficacy in mitigating IRI. As the synthesis of a diverse array of S1PR agonists continues, with FTY720 being a prime example, the body of experimental evidence advocating for their role in IRI treatment is expanding. Despite this progress, comprehensive reviews delineating the therapeutic landscape of S1PR agonists in IRI remain limited. This review aspires to meticulously elucidate the protective roles and mechanisms of S1PR agonists in preventing and managing IRI affecting various organs, including the heart, kidney, liver, lungs, intestines, and brain, to foster novel pharmacological approaches in clinical settings.

Alterations in urinary ceramides, sphingoid bases, and their phosphates among patients with kidney disease

Background

To avoid an invasive renal biopsy, noninvasive laboratory testing for the differential diagnosis of kidney diseases is a desirable goal. As sphingolipids are demonstrated to be involved in the pathogenesis of various kidney diseases, we investigated the possible usefulness of the simultaneous measurement of urinary sphingolipids for differentiating kidney diseases.

Materials and methods

Residual urine specimens were collected from patients who had been clinically diagnosed with chronic glomerulonephritis (CGN), diabetic mellitus (DM), systemic lupus erythematosus (SLE), and arterial hypertension (AH). The urinary sphingolipids-CERs C16:0, C18:0, C18:1, C20:0, C22:0, and C24:0; sphingosine [Sph]; dihydrosphingosine; sphingosine 1-phosphate [S1P]; and dihydroS1P [dhS1P]-were measured by liquid chromatography-tandem mass spectrometry. Based on the results, machine learning models were constructed to differentiate the various kidney diseases.

Results

The urinary S1P was higher in patients with DM than in other participants (P < 0.05), whereas dhS1P was lower in the CGN and AH groups compared with control participants (P < 0.05). Sph and dhSph were higher in patients with CGN, AH, and SLE than in those with control participants (P < 0.05). The urinary CERs were significantly higher in patients with CGN, AH, and SLE than in those with control participants (P < 0.05). As a results of constructing a machine learning model discriminating kidney diseases, the resulting diagnostic accuracy and precision were improved from 94.03% and 66.96% to 96.10% and 78.26% respectively, when the urinary CERs, Sph, dhSph, S1P, dhS1P, and their ratios were added to the models.

Conclusion

The urinary CERs, sphingoid bases, and their phosphates show alterations among kidney diseases, suggesting their potential involvement in the development of kidney injury.

The emerging roles of sphingosine 1-phosphate and SphK1 in cancer resistance: a promising therapeutic target

Cancer chemoresistance is a problematic dilemma that significantly restrains numerous cancer management protocols. It can promote cancer recurrence, spreading of cancer, and finally, mortality. Accordingly, enhancing the responsiveness of cancer cells towards chemotherapies could be a vital approach to overcoming cancer chemoresistance. Tumour cells express a high level of sphingosine kinase-1 (SphK1), which acts as a protooncogenic factor and is responsible for the synthesis of sphingosine-1 phosphate (S1P). S1P is released through a Human ATP-binding cassette (ABC) transporter to interact with other phosphosphingolipids components in the interstitial fluid in the tumor microenvironment (TME), provoking communication, progression, invasion, and tumor metastasis. Also, S1P is associated with several impacts, including anti-apoptotic behavior, metastasis, mesenchymal transition (EMT), angiogenesis, and chemotherapy resistance. Recent reports addressed high levels of S1P in several carcinomas, including ovarian, prostate, colorectal, breast, and HCC. Therefore, targeting the S1P/SphK signaling pathway is an emerging therapeutic approach to efficiently attenuate chemoresistance. In this review, we comprehensively discussed S1P functions, metabolism, transport, and signaling. Also, through a bioinformatic framework, we pointed out the alterations of SphK1 gene expression within different cancers with their impact on patient survival, and we demonstrated the protein-protein network of SphK1, elaborating its sparse roles. Furthermore, we made emphasis on different machineries of cancer resistance and the tight link with S1P. We evaluated all publicly available SphK1 inhibitors and their inhibition activity using molecular docking and how SphK1 inhibitors reduce the production of S1P and might reduce chemoresistance, an approach that might be vital in the course of cancer treatment and prognosis.

Dual species sphingosine-1-phosphate lyase inhibitors to combine antifungal and anti-inflammatory activities in cystic fibrosis: a feasibility study

Cystic fibrosis (CF) is an autosomal recessive disorder characterized by respiratory failure due to a vicious cycle of defective Cystic Fibrosis Transmembrane conductance Regulator (CFTR) function, chronic inflammation and recurrent bacterial and fungal infections. Although the recent introduction of CFTR correctors/potentiators has revolutionized the clinical management of CF patients, resurgence of inflammation and persistence of pathogens still posit a major concern and should be targeted contextually. On the background of a network-based selectivity that allows to target the same enzyme in the host and microbes with different outcomes, we focused on sphingosine-1-phosphate (S1P) lyase (SPL) of the sphingolipid metabolism as a potential candidate to uniquely induce anti-inflammatory and antifungal activities in CF. As a feasibility study, herein we show that interfering with S1P metabolism improved the immune response in a murine model of CF with aspergillosis while preventing germination of Aspergillus fumigatus conidia. In addition, in an early drug discovery process, we purified human and A. fumigatus SPL, characterized their biochemical and structural properties, and performed an in silico screening to identify potential dual species SPL inhibitors. We identified two hits behaving as competitive inhibitors of pathogen and host SPL, thus paving the way for hit-to-lead and translational studies for the development of drug candidates capable of restraining fungal growth and increasing antifungal resistance.

Opaganib (ABC294640) Induces Immunogenic Tumor Cell Death and Enhances Checkpoint Antibody Therapy

Antibody-based cancer drugs that target the checkpoint proteins CTLA-4, PD-1 and PD-L1 provide marked improvement in some patients with deadly diseases such as lung cancer and melanoma. However, most patients are either unresponsive or relapse following an initial response, underscoring the need for further improvement in immunotherapy. Certain drugs induce immunogenic cell death (ICD) in tumor cells in which the dying cells promote immunologic responses in the host that may enhance the in vivo activity of checkpoint antibodies. Sphingolipid metabolism is a key pathway in cancer biology, in which ceramides and sphingosine 1-phosphate (S1P) regulate tumor cell death, proliferation and drug resistance, as well as host inflammation and immunity. In particular, sphingosine kinases are key sites for manipulation of the ceramide/S1P balance that regulates tumor cell proliferation and sensitivity to radiation and chemotherapy. We and others have demonstrated that inhibition of sphingosine kinase-2 by the small-molecule investigational drug opaganib (formerly ABC294640) kills tumor cells and increases their sensitivities to other drugs and radiation. Because sphingolipids have been shown to regulate ICD, opaganib may induce ICD and improve the efficacy of checkpoint antibodies for cancer therapy. This was demonstrated by showing that in vitro treatment with opaganib increases the surface expression of the ICD marker calreticulin on a variety of tumor cell types. In vivo confirmation was achieved using the gold standard immunization assay in which B16 melanoma, Lewis lung carcinoma (LLC) or Neuro-2a neuroblastoma cells were treated with opaganib in vitro and then injected subcutaneously into syngeneic mice, followed by implantation of untreated tumor cells 7 days later. In all cases, immunization with opaganib-treated cells strongly suppressed the growth of subsequently injected tumor cells. Interestingly, opaganib treatment induced crossover immunity in that opaganib-treated B16 cells suppressed the growth of both untreated B16 and LLC cells and opaganib-treated LLC cells inhibited the growth of both untreated LLC and B16 cells. Next, the effects of opaganib in combination with a checkpoint antibody on tumor growth in vivo were assessed. Opaganib and anti-PD-1 antibody each slowed the growth of B16 tumors and improved mouse survival, while the combination of opaganib plus anti-PD-1 strongly suppressed tumor growth and improved survival (p < 0.0001). Individually, opaganib and anti-CTLA-4 antibody had modest effects on the growth of LLC tumors and mouse survival, whereas the combination of opaganib with anti-CTLA-4 substantially inhibited tumor growth and increased survival (p < 0.001). Finally, the survival of mice bearing B16 tumors was only marginally improved by opaganib or anti-PD-L1 antibody alone but was nearly doubled by the drugs in combination (p < 0.005). Overall, these studies demonstrate the ability of opaganib to induce ICD in tumor cells, which improves the antitumor activity of checkpoint antibodies.

Arachnoid membrane as a source of sphingosine-1-phosphate that regulates mouse middle cerebral artery tone

Growing evidence indicates that perivascular tissue is critical to modulate vessel function. We hypothesized that the arachnoid membrane surrounding middle cerebral artery (MCA) regulates its function via sphingosine-1-phosphate (S1P)-induced vasoconstriction. The MCA from 3- to 9-month-old male and female wild-type (Oncine France 1 and C57BL/6) mice and sphingosine kinase 2 knockout (SphK2-/-) mice in the C57BL/6 background was mounted in pressure myographs with and without arachnoid membrane. Raman microspectroscopy and imaging were used for in situ detection of S1P. The presence of arachnoid tissue was associated with reduced external and lumen MCA diameters, and with an increase in basal tone regardless of sex and strain background. Strong S1P-positive signals were detected in the arachnoid surrounding the MCA wall in both mice models, as well as in a human post-mortem specimen. Selective S1P receptor 3 antagonist TY 52156 markedly reduced both MCA vasoconstriction induced by exogenous S1P and arachnoid-dependent basal tone increase. Compared to 3-month-old mice, the arachnoid-mediated contractile influence persisted in 9-month-old mice despite a decline in arachnoid S1P deposits. Genetic deletion of SphK2 decreased arachnoid S1P content and vasoconstriction. This is the first experimental evidence that arachnoid membrane regulates the MCA tone mediated by S1P.

Synthesis of PF-543 Derivatives Using Simple Synthetic Methods and Their Biological Effect Analysis for the Development of Anticolorectal Cancer Agents

Background:

Sphingolipids, even in extremely low doses, regulate various physiological functions. Particularly, immune and cancer cells might be controlled by changes in the sphingosine- 1-phosphate (S1P) levels, and S1P has been studied for a long time as a major target for new drug development. Sphingosine kinase (SK) phosphorylates sphingosine to produce S1P. An increase in the S1P levels promotes the growth of cancer cells. SK has 2 isoforms, SK1 and SK2, both of which are involved in the growth of cancer cells.

Objective:

PF-543 has been developed as an SK1 inhibitor and has a non-lipid structure that differs from those of general SK inhibitors. While PF-543 has a potent SK1 inhibitory effect, and has low anticancer activity in some types of cancer cells. Therefore, the development of other PF-543 derivatives is needed.

Methods:

We designed a structurally simplified derivative of PF-543. To primarily demonstrate that the designed structure was biologically active, 8 derivatives were synthesized by a 2-step method using the commercial starting material, and their biological activities were evaluated.

Results:

The SK1-inhibitory effects of the synthesized derivatives were not higher than that of PF- 543. However, the anticancer activity and apoptotic effect of the derivatives were similar to those of PF-543, despite their fabrication from a simple modification of the PF-543 structure. In a docking study, the derivatives were found to bind SK1 in a form similar to PF-543.

Conclusion:

Our analogs, which are similar to PF-543, showed comparable anticancer activity, indicating that the synthesized derivatives are structurally more efficient for anticancer activity than PF-543. Therefore, our study provides important information that may be useful for developing new anticancer substances that target SK1.

Sphingosine-1-phosphate in acute exercise and training

Sphingosine-1-phosphate (S1P) is a bioactive sphingolipid found in all eukaryotic cells. Although it may function as an intracellular second messenger, most of its effects are induced extracellularly via activation of a family of five specific membrane receptors. Sphingosine-1-phosphate is enriched in plasma, where it is transported by high-density lipoprotein and albumin, as well as in erythrocytes and platelets which store and release large amounts of this sphingolipid. Sphingosine-1-phosphate regulates a host of cellular processes such as growth, proliferation, differentiation, migration, and apoptosis suppression. It was also shown to play an important role in skeletal muscle physiology and pathophysiology. In recent years, S1P metabolism in both muscle and blood was found to be modulated by exercise. In this review, we summarize the current knowledge on the effect of acute exercise and training on S1P metabolism, highlighting the role of this sphingolipid in skeletal muscle adaptation to physical effort.

S1P Lyase siRNA Dampens Malignancy of DLD-1 Colorectal Cancer Cells

Sphingosine-1-phosphate lyase 1 (S1P lyase or SGPL1) is an essential sphingosine-1-phosphate-degrading enzyme. Its manipulation favors onset and progression of colorectal cancer and others in vivo. Thus, SGPL1 is an important modulator of cancer initiation. However, in established cancer, the impact of retrospective SGPL1 modulation is elusive. Herein, we analyzed how SGPL1 siRNA affects malignancy of the human colorectal cancer cells DLD-1 and found that in parallel to the reduction of SGPL1 expression levels, migration, invasion, and differentiation status changed. Diminished SGPL1 expression was accompanied with reduced cell migration and cell invasion in scratch assays and transwell assays, whereas metabolic activity and proliferation was not altered. Decreased migration was attended by increased cell-cell-adhesion through upregulation of E-cadherin and formation of cadherin-actin complexes. Spreading cell islets showed lower vimentin abundance in border cells. Furthermore, SGPL1 siRNA treatment induced expression of epithelial cell differentiation markers, such as intestinal alkaline phosphatase and cytokeratin 20. Hence, interference with SGPL1 expression augmented a partial redifferentiation of colorectal cancer cells toward normal colon epithelial cells. Our investigation showed that SGPL1 siRNA influenced tumorigenic activity of established colorectal cancer cells. We therefore suggest SGPL1 as a target for lowering malignant potential of already existing cancer.

Verification of the Necessity of the Tolyl Group of PF-543 for Sphingosine Kinase 1 Inhibitory Activity

PF-543, the most potent sphingosine kinase (SK) inhibitor, does not demonstrate effective anticancer activity in some cancer cells, unlike other known SK1 inhibitors. PF-543 has a non-lipid structure with a unique toluene backbone; however, the importance of this structure remains unclear. Therefore, the purpose of this study was to investigate changes in SK inhibitory and anticancer activities and to explore the role of the tolyl group structure of PF-543 through various modifications. We transformed the methyl group of PF-543 into hydrogen, fluorine, and hydroxy. PF-543 derivatives in which the methyl group was substituted by hydrogen and fluorine (compound 5) demonstrated SK1 inhibitory and anticancer activities similar to PF-543. Moreover, we performed molecular modeling studies of PF-543 and compound 5. To assess the metabolic stability of PF-543 and compound 5, we determined their degree of degradation using the liver microsomes of four different animal species (human, dog, rat, and mouse). However, both PF-543 and compound 5 showed poor microsomal stability. Therefore, for the medical applications of PF-543, the structural modifications of its other parts may be necessary. Our results provide important information for the design of additional PF-543 analogs.

A Mechanism-Based Sphingosine-1-phosphate Lyase Inhibitor

The synthesis of a series of vinylated analogues of sphingosine-1-phosphate together with their unambiguous configurational assignment by VCD methods is reported. Among them, compound RBM10-8 can irreversibly inhibit human sphingosine-1-phosphate lyase (hS1PL) while behaving also as an enzyme substrate. These findings, together with the postulated mechanism for S1PL activity, reinforce the role of RBM10-8 as a new mechanism-based hS1PL inhibitor.

Sphingosine-1-Phosphate Lyase Inhibition Alters the S1P Gradient and Ameliorates Crohn's-Like Ileitis by Suppressing Thymocyte Maturation

BACKGROUND

Lymphocytes recirculate from tissues to blood following the sphingosine-1-phosphate (S1P) gradient (low in tissues, high in blood), maintained by synthetic and degradative enzymes, among which the S1P lyase (SPL) irreversibly degrades S1P. The role of SPL in the intestine, both during homeostasis and IBD, is poorly understood. We hypothesized that modulation of tissue S1P levels might be advantageous over S1P receptor (S1PR) agonists (eg, fingolimod, ozanimod, etrasimod), as without S1PR engagement there might be less likelihood of potential off-target effects.

METHODS

First we examined SPL mRNA transcripts and SPL localization in tissues by quantitative reverse transcription polymerase chain reaction and immunohistochemistry. The in vivo effects of the SPL inhibitors 4-deoxypyridoxine hydrochloride (30 mg/L) and 2-acetyl-4 (tetrahydroxybutyl)imidazole (50 mg/L) were assessed through their oral administration to adult TNF∆ARE mice, which spontaneously develop Crohn's-like chronic ileitis. The effect of SPL inhibition on circulating and tissue lymphocytes, transcriptional regulation of proinflammatory cytokines, and on the histological severity of ileitis was additionally examined. Tissue S1P levels were determined by liquid chromatography-mass spectrometry. Mechanistically, the potential effects of high S1P tissue levels on intestinal leukocyte apoptosis were assessed via terminal deoxynucleotidyl transferase dUTP nick end-labeling assay and annexin 5 staining. Finally, we examined the ability of T cells to home to the intestine, along with the effects of SPL inhibition on cellular subsets within immune compartments via flow and mass cytometry.

RESULTS

S1P lyase was ubiquitously expressed. In the gut, immunohistochemistry predominantly localized it to small intestinal epithelia, although the lamina propria leukocyte fraction had higher mRNA transcripts. Inhibition of SPL markedly increased local intestinal S1P levels, induced peripheral lymphopenia, downregulated proinflammatory cytokines, and attenuated chronic ileitis in mice. SPL inhibition reduced T and myeloid cells in secondary lymphoid tissues and the intestine and decreased naïve T-cell recruitment. The anti-inflammatory activity of SPL inhibition was not mediated by leukocyte apoptosis, nor by interference with the homing of lymphocytes to the intestine, and was independent of its peripheral lymphopenic effect. However, SPL inhibition promoted thymic atrophy and depleted late immature T cells (CD4+CD8+ double positive), with accumulation of mature CD4+CD8- and CD4-CD8+ single-positive cells.

CONCLUSIONS

Inhibition of the S1P lyase alters the S1P gradient and attenuates chronic ileitis via central immunosuppression. SPL inhibition could represent a potential way to tame an overactive immune response during IBD and other T-cell-mediated chronic inflammatory diseases.

Synthesis and Biological Evaluation of BODIPY-PF-543

Sphingosine-1-phosphate (S1P) regulates the proliferation of various cells and promotes the growth of cancer cells. Sphingosine kinase (SK), which transforms sphingosine into S1P, has two isotypes: SK1 and SK2. To date, both isotypes are known to be involved in the proliferation of cancer cells. PF-543, an SK1 inhibitor developed by Pfizer, strongly inhibits SK1. However, despite its strong SK1 inhibitory effect, PF-543 shows low anticancer activity in vitro. Therefore, additional biological evidence on the anticancer activity of SK1 inhibitor is required. The present study aimed to investigate the intracellular localization of PF-543 and identify its association with anticancer activity by introducing a fluoroprobe into PF-543. Boron–dipyrromethene (BODIPY)-introduced PF-543 has a similar SK1 inhibitory effect as PF-543. These results indicate that the introduction of BODIPY does not significantly affect the inhibitory effect of SK1. In confocal microscopy after BODIPY-PF-543 treatment, the compound was mainly located in the cytosol of the cells. This study demonstrated the possibility of introducing fluorescent material into an SK inhibitor and designing a synthesized compound that is permeable to cells while maintaining the SK inhibitory effect.

Targeting sphingosine kinase 1 for the treatment of pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH), characterized by high morbidity and mortality, is a serious hazard to human life. Until now, the long-term survival of the PAH patients is still suboptimal. Recently, sphingosine kinase 1 (SPHK1) has drawn more and more attention due to its essential role in the pulmonary vasoconstriction, remodeling of pulmonary blood vessels and right cardiac lesions in PAH patients, and this enzyme is regarded as a new target for the treatment of PAH. Here, we discussed the multifarious functions of SPHK1 in PAH physiology and pathogenesis. Moreover, the structural features of SPHK1 and binding modes with different inhibitors were summarized. Finally, recent advances in the medicinal chemistry research of SPHK1 inhibitors are presented.

New fluorogenic probes for neutral and alkaline ceramidases

New fluorogenic ceramidase substrates derived from the N-acyl modification of our previously reported probes (RBM14) are reported. While none of the new probes were superior to the known RBM14C12 as acid ceramidase substrates, the corresponding nervonic acid amide (RBM14C24:1) is an efficient and selective substrate for the recombinant human neutral ceramidase, both in cell lysates and in intact cells. A second generation of substrates, incorporating the natural 2-(N-acylamino)-1,3-diol-4-ene framework (compounds RBM15) is also reported. Among them, the corresponding fatty acyl amides with an unsaturated N-acyl chain can be used as substrates to determine alkaline ceramidase (ACER)1 and ACER2 activities. In particular, compound RBM15C18:1 has emerged as the best fluorogenic probe reported so far to measure ACER1 and ACER2 activities in a 96-well plate format.

Sphingolipid biosynthesis in man and microbes

A new review covering up to 2018 Sphingolipids are essential molecules that, despite their long history, are still stimulating interest today. The reasons for this are that, as well as playing structural roles within cell membranes, they have also been shown to perform a myriad of cell signalling functions vital to the correct function of eukaryotic and prokaryotic organisms. Indeed, sphingolipid disregulation that alters the tightly-controlled balance of these key lipids has been closely linked to a number of diseases such as diabetes, asthma and various neuropathologies. Sphingolipid biogenesis, metabolism and regulation is mediated by a large number of enzymes, proteins and second messengers. There appears to be a core pathway common to all sphingolipid-producing organisms but recent studies have begun to dissect out important, species-specific differences. Many of these have only recently been discovered and in most cases the molecular and biochemical details are only beginning to emerge. Where there is a direct link from classic biochemistry to clinical symptoms, a number a drug companies have undertaken a medicinal chemistry campaign to try to deliver a therapeutic intervention to alleviate a number of diseases. Where appropriate, we highlight targets where natural products have been exploited as useful tools. Taking all these aspects into account this review covers the structural, mechanistic and regulatory features of sphingolipid biosynthetic and metabolic enzymes.

Orm/ORMDL proteins: Gate guardians and master regulators

Sphingolipids comprise a diverse family of lipids that perform multiple functions in both structure of cellular membranes and intra- and inter-cellular signaling. The diversity of this family is generated by an array of enzymes that produce individual classes and molecular species of family members and enzymes which catabolize those lipids for recycling pathways. However, all of these lipids begin their lives with a single step, the condensation of an amino acid, almost always serine, and a fatty acyl-CoA, almost always the 16-carbon, saturated fatty acid, palmitate. The enzyme complex that accomplishes this condensation is serine palmitoyltransferase (SPT), a membrane-bound component of the endoplasmic reticulum. This places SPT in the unique position of regulating the production of the entire sphingolipid pool. Understanding how SPT activity is regulated is currently a central focus in the field of sphingolipid biology. In this review we examine the regulation of SPT activity by a set of small, membrane-bound proteins of the endoplasmic reticulum, the Orms (in yeast) and ORMDLs (in vertebrates). We discuss what is known about how these proteins act as homeostatic regulators by monitoring cellular levels of sphingolipid, but also how the Orms/ORMDLs regulate SPT in response to other stimuli. Finally, we discuss the intriguing connection between one of the mammalian ORMDL isoforms, ORMDL3, and the pervasive pulmonary disease, asthma, in humans.

Targeting Sphingosine Kinases for the Treatment of Cancer

Sphingosine kinases (SK1 and SK2) are key, druggable targets within the sphingolipid metabolism pathway that promote tumor growth and pathologic inflammation. A variety of isozyme-selective and dual inhibitors of SK1 and SK2 have been described in the literature, and at least one compound has reached clinical testing in cancer patients. In this chapter, we will review the rationale for targeting SKs and summarize the preclinical and emerging clinical data for ABC294640 as the first-in-class selective inhibitor of SK2.

SPHK1 promotes metastasis of thyroid carcinoma through activation of the S1P/S1PR3/Notch signaling pathway

Thyroid carcinoma is characterized by an aggressive behavior, lack of effective targeted therapies and a high rate of relapse. Sphingosine kinase 1 (SPHK1) has been reported to be a critical regulatory factor in the progression of thyroid carcinoma, but the correlation between SPHK1 and clinical prognosis of patients with thyroid carcinoma has remained to be fully elucidated. The present study aimed to systematically assess the roles of SPHK1 in thyroid carcinoma metastasis and further investigate the possible underlying mechanisms. First, the expression of SPHK1 was detected in tissue samples from 53 thyroid carcinoma patients and in thyroid carcinoma cell lines by reverse transcription-quantitative polymerase chain reaction analysis. Furthermore, the level of phospho-(p)-SPHK1 was immunohistochemically detected in human thyroid carcinoma tissue samples. The activity of SPHK1 was measured with a commercial SPHK1 Activity Assay kit. A sphingosine-1-phosphate (S1P) competitive ELISA kit was used to determine the extracellular S1P levels. The metastatic potential was assessed by a Transwell assay. In addition, the association between SPHK1 and clinicopathological features of the patients was analyzed. The results indicated that the expression of SPHK1 in thyroid carcinoma samples was significantly higher than in paired adjacent normal thyroid tissues. High levels of SPHK1 were positively correlated with poor overall survival and progression-free survival. Downregulation of SPHK1 by lentiviral vector expressing SPHK1 small interfering (si)RNA evidently repressed Notch signaling and reduced the migration and invasion of thyroid carcinoma cells in vitro and in a NOD/SCID mouse model. Furthermore, inhibition of SPHK1 by siRNA or treatment with SPHK1 inhibitor 5C sensitized thyroid carcinoma to cisplatin and doxorubicin. In addition, it was demonstrated that silencing of SPHK1 effectively inhibits processes associated with thyroid carcinoma metastasis through the Notch signaling pathway, and SPHK1 may therefore represent a potential therapeutic target in thyroid carcinoma. In conclusion, the present study indicated that high levels of p-SPHK1 were positively correlated with high levels of S1P which in turn promoted thyroid carcinoma metastasis via the S1P/S1P receptor 3/Notch signaling pathway, suggesting possible prognostic markers and therapeutic targets.

The first fluorogenic sensor for sphingosine-1-phosphate lyase activity in intact cells

New fluorogenic sensors with suitable kinetic parameters and sensitivity have been developed for the determination of sphingosine-1-phosphate lyase activity in cell lysates. The probe RBM148 can be efficiently loaded into cationic liposomes and used to determine S1PL activity in intact cells.

Sphingosine 1-phosphate (S1P) signalling: Role in bone biology and potential therapeutic target for bone repair

The lipid mediator sphingosine 1-phosphate (S1P) affects cellular functions in most systems. Interest in its therapeutic potential has increased following the discovery of its G protein-coupled receptors and the recent availability of agents that can be safely administered in humans. Although the role of S1P in bone biology has been the focus of much less research than its role in the nervous, cardiovascular and immune systems, it is becoming clear that this lipid influences many of the functions, pathways and cell types that play a key role in bone maintenance and repair. Indeed, S1P is implicated in many osteogenesis-related processes including stem cell recruitment and subsequent differentiation, differentiation and survival of osteoblasts, and coupling of the latter cell type with osteoclasts. In addition, S1P's role in promoting angiogenesis is well-established. The pleiotropic effects of S1P on bone and blood vessels have significant potential therapeutic implications, as current therapeutic approaches for critical bone defects show significant limitations. Because of the complex effects of S1P on bone, the pharmacology of S1P-like agents and their physico-chemical properties, it is likely that therapeutic delivery of S1P agents will offer significant advantages compared to larger molecular weight factors. Hence, it is important to explore novel methods of utilizing S1P agents therapeutically, and improve our understanding of how S1P and its receptors modulate bone physiology and repair.

The effects of berberine on a murine model of multiple sclerosis and the SPHK1/S1P signaling pathway

Berberine (BBR) has shown neuroprotective properties. The present study aims to investigate the effects of BBR on experimental autoimmune encephalomyelitis (EAE), a murine model of multiple sclerosis (MS), and SphK1/S1P signaling, which plays a key role in MS. EAE was induced in mice, followed by treatment with BBR at 50, 100, or 300 mg/kg/d. Neurophysiological function was evaluated daily; inflammation, cell infiltration, and the severity of demyelination were also examined. The SphK1, SphK2, and S1P levels in the animals and primary astrocyte culture were measured. We found that treatment with BBR reduced the loss of neurophysiological function and the degree of demyelination. Moreover, BBR was associated with a decrease in SphK1 and S1P levels both in the animals and in culture. These results indicated that BBR suppresses demyelination and loss of neurophysiological function by inhibiting the SphK1/S1P signaling pathway. The use of BBR as a treatment of MS warrant further exploration.

A Useful Allene for the Stereoselective Synthesis of Protected Quaternary 2-Amino-2-vinyl-1,3-diols

Treatment of readily available allene 1 with Cy₂BH followed by addition of an aldehyde led to quaternary protected 2-amino-2-vinyl-1,3-diols in high yield and excellent stereochemical purity. The choice of benzoyl as N-protecting group is critical since the observed N- to O-Bz transfer during the process prevents later undesired isomerizations in the adducts and keeps all heteroatoms protected.

Scintillation Proximity Assay to Detect the Changes in Cellular Dihydrosphingosine 1-Phosphate Levels

Compounds that modulate the activity of sphingosine 1-phosphate (S1P)-metabolizing enzymes are expected to be potential therapeutic agents for various diseases. Investigation of their potencies requires not only cell-free but also cell-based assays in which intracellular accumulation/depletion of S1P could be monitored. However, conventional methods have limitations to their simplicity, mainly due to the necessity of a separation process that separates S1P from its related substances. Here, we describe a method utilizing a scintillation proximity assay (SPA) for semi-quantifying intracellular [(3)H]-labeled dihydroS1P ([(3)H]dhS1P), which is also a substrate for S1P-metabolizing enzymes. We found that uncoated yttrium silicate SPA beads could selectively bind to and detect [(3)H]dhS1P rather than [(3)H]dihydrosphingosine (the non-phosphorylated form of [(3)H]dhS1P). Based on this, we developed a novel cell-based assay system which does not require any organic solvent extraction or chromatographic separation, and confirmed its practicality by using siRNA targeting S1P lyase (S1PL) and known S1PL inhibitors as models. Our results demonstrated that this assay is useful for rapid and easy evaluation of S1PL inhibitors, and could be potentially applicable for all compounds that modulate the activity of S1P-metabolizing enzymes.

Therapeutic Strategies and Pharmacological Tools Influencing S1P Signaling and Metabolism

During the last two decades the study of the sphingolipid anabolic, catabolic, and signaling pathways has attracted enormous interest. Especially the introduction of fingolimod into market as first p.o. therapeutic for the treatment of multiple sclerosis has boosted this effect. Although the complex regulation of sphingosine-1-phosphate (S1P) and other catabolic and anabolic sphingosine-related compounds is not fully understood, the influence on different (patho)physiological states from inflammation to cytotoxicity as well as the availability of versatile pharmacological tools that represent new approaches to study these states are described. Here, we have summarized various aspects concerning the many faces of sphingolipid function modulation by different pharmacological tools up to clinical candidates. Due to the immense heterogeneity of physiological or pharmacological actions and complex cross regulations, it is difficult to predict their role in upcoming therapeutic approaches. Currently, inflammatory, immunological, and/or antitumor aspects are discussed.

Sphingosine 1-phosphate signaling impacts lymphocyte migration, inflammation and infection

Sphingosine 1-phosphate (S1P) is a sphingosine containing lipid intermediate obtained from ceramide. S1P is known to be an important signaling molecule and plays multiple roles in the context of immunity. This lysophospholipid binds and activates G-protein-coupled receptors (GPCRs) known as S1P receptors 1-5 (S1P1-5). Once activated, these GPCRs mediate signaling that can lead to alterations in cell proliferation, survival or migration, and can also have other effects such as promoting angiogenesis. In this review, we will present evidence demonstrating a role for S1P in lymphocyte migration, inflammation and infection, as well as in cancer. The therapeutic potential of targeting S1P receptors, kinases and lyase will also be discussed.