Sphingosine Kinase Sphingosine-1-phosphate Research Articles

The Importance of Sphingosine Kinase in Breast Cancer: A Potential for Breast Cancer Management

Breast cancer management includes a combination of surgery, radiation therapy, and chemotherapy. While this management has proven effective, it is not perfect. To expand the umbrella of management to resistant breast cancer tumors, researchers have explored the idea of sphingosine kinase (SphK) and sphingosine-1-phosphate (S1P) as a potential target for treatment. In this article, we review the mechanism of the sphingosine kinase/sphingosine-1-phosphate (SphK/S1P) axis along with its effect on the tumor microenvironment (TME) and compounds that have been studied inhibiting the SphK/S1P axis. We searched for relevant articles in the last five years in Medline and PubMed Central. Inclusion criteria, exclusion criteria, and quality checklists were applied to identify the most relevant articles. We compiled the information that has been summarized in the respective tables and figures provided in this review. The metabolism of sphingolipids was summarized, followed by the SphK/S1P upregulation in breast cancer cells. The variety of effects by upregulation of SphK led to an increase in inflammation, growth, and metastasis in breast cancer tumors. The increase in S1P also impacted the TME, including the cells and surrounding tissue, allowing the breast tumors to thrive. The final point made was a summary of the compounds and drugs that inhibited the SphK/S1P axis. They have proven their effectiveness and show even greater efficacy in combination with docetaxel and doxorubicin in preclinical studies. In conclusion, what is known about the SphK/S1P axis within breast cancer cells is immense but incomplete as we summarize what is known so far. Having a complete picture will allow a faster transition to application in the clinical field but clinical trials have not commenced as of yet.

Functional contribution of sphingosine-1-phosphate to airway pathology in cigarette smoke-exposed mice.

A critical role for sphingosine kinase/sphingosine-1-phosphate (S1P) pathway in the control of airway function has been demonstrated in respiratory diseases. Here, we address S1P contribution in a mouse model of mild chronic obstructive pulmonary disease (COPD). C57BL/6J mice have been exposed to room air or cigarette smoke up to 11months and killed at different time points. Functional and molecular studies have been performed. Cigarette smoke caused emphysematous changes throughout the lung parenchyma coupled to a progressive collagen deposition in both peribronchiolar and peribronchial areas. The high and low airways showed an increased reactivity to cholinergic stimulation and α-smooth muscle actin overexpression. Similarly, an increase in airway reactivity and lung resistances following S1P challenge occurred in smoking mice. A high expression of S1P, Sph-K2 , and S1P receptors (S1P2 and S1P3 ) has been detected in the lung of smoking mice. Sphingosine kinases inhibition reversed the increased cholinergic response in airways of smoking mice. S1P signalling up-regulation follows the disease progression in smoking mice and is involved in the development of airway hyperresponsiveness. Our study defines a therapeutic potential for S1P inhibitors in management of airways hyperresponsiveness associated to emphysema in smokers with both asthma and COPD.

Investigating the Et-1/SphK/S1P Pathway as a Novel Approach for the Prevention of Inflammation-Induced Preterm Birth

Preterm birth (PTB), defined as birth before 37 completed weeks of gestation, occurs in up to 18 percent of births worldwide and accounts for the majority of perinatal morbidity and mortality. While the single most common cause of PTB has been identified as inflammation, safe and effective pharmacotherapy to prevent PTB has yet to be developed. Our group has used an in vivo model of inflammation-driven PTB, biochemical methods, pharmacological approaches, a novel endothelin receptor antagonist that we synthesized and RNA knockdown to help establish the role of endothelin-1 (ET-1) in inflammation-associated PTB. Further, we have used our in vivo model to test whether sphingosine kinase, which acts downstream of ET-1, plays a role in PTB. We have shown that levels of endothelin converting enzyme-1 (ECE-1) and ET-1 are increased when PTB is induced in timed pregnant mice with lipopolysaccharide (LPS) and that blocking ET-1 action, pharmacologically or using ECE-1 RNA silencing, rescues LPS-induced mice from PTB. ET-1 activates the sphingosine kinase/sphingosine-1-phosphate (SphK/S1P) pathway. S1P, in turn, is an important signaling molecule in the proinflammatory response. Interestingly, we have shown that SphK inhibition also prevents LPS-induced PTB in timed pregnant mice. Further, we showed that SphK inhibition suppresses the ECE-1/ET-1 axis, implicating positive feedback regulation of the SphK/S1P/ECE-1/ET-1 axis. The ET-1/SphK/SIP pathway is a potential pharmacotherapeutic target for the prevention of PTB.

Transforming growth factor-β-sphingosine kinase 1/S1P signaling upregulates microRNA-21 to promote fibrosis in renal tubular epithelial cells.

Renal fibrosis is a progressive pathological change characterized by tubular cell apoptosis, tubulointerstitial fibroblast proliferation, and excessive deposition of extracellular matrix (ECM). miR-21 has been implicated in transforming growth factor-β (TGF-β)-stimulated tissue fibrosis. Recent studies showed that sphingosine kinase/sphingosine-1-phosphate (SphK/S1P) are also critical for TGF-β-stimulated tissue fibrosis; however, it is not clear whether SphK/S1P interacts with miR-21 or not. In this study, we hypothesized that SphK/S1P signaling is linked to upregulation of miR-21 by TGF-β. To verify this hypothesis, we first determined that miR-21 was highly expressed in renal tubular epithelial cells (TECs) stimulated with TGF-β by using qRT-PCR and Northern blotting. Simultaneously, inhibition of miR-21, mediated by the corresponding antimir, markedly decreased the expression and deposition of type I collagen, fibronectin (Fn), cysteine-rich protein 61 (CCN1), α-smooth muscle actin, and fibroblast-specific protein1 in TGF-β-treated TECs. ELISA and qRT-PCR were used to measure the S1P and SphK1 levels in TECs. S1P production was induced by TGF-β through activation of SphK1. Furthermore, it was observed that TGF-β-stimulated upregulation of miR-21 was abolished by SphK1 siRNA and was restored by the addition of exogenous S1P. Blocking S1PR2 also inhibited upregulation of miR-21. Additionally, miR-21 overexpression attenuated the repression of TGF-β-stimulated ECM deposition and epithelial-mesenchymal transition by SphK1 and S1PR2 siRNA. In summary, our study demonstrates a link between SphK1/S1P and TGF-β-induced miR-21 in renal TECs and may represent a novel therapeutic target in renal fibrosis.

Lysophosphatidic acid stimulates cell migration of satellite cells. A role for the sphingosine kinase/sphingosine 1-phosphate axis.

Regulation of the motility of skeletal muscle precursor cells, such as satellite cells, is critically important for their proper recruitment at the site of tissue damage, and ultimately for its correct repair. Here we show that lysophosphatidic acid (LPA), which is well-recognized as a powerful bioactive agent, strongly stimulates cell migration of activated murine satellite cells. The biological effect exerted by LPA was found to be induced via activation of LPA1 and LPA3 , being abolished by cell treatment with the antagonist Ki16425, and severely impaired by siRNA-mediated down-regulation of the two receptor isoforms. In contrast, silencing of LPA2 potentiated the stimulation of cell motility by LPA, suggesting that it is negatively coupled to cell migration. Pharmacological inhibition of both sphingosine kinase (SK) isoforms using VPC96047, or the selective blocking of SK1 using VPC96091, abolished cell responsiveness to LPA; in agreement, gene silencing of SK1 or SK2 significantly reduced the biological effect of LPA. Moreover, the LPA-dependent stimulation of cell chemotaxis was found to be impaired by down-regulation of the sphingosine 1-phosphate (S1P) receptors S1P1 or S1P4 by specific siRNAs. In summary, the results obtained support the notion that the sphingosine kinase/sphingosine 1-phosphate (SK/S1P) axis is critically involved in the mechanism by which LPA elicits its pro-migratory action. This study provides compelling new information on the regulatory mechanisms of satellite cell motility, and reinforces the view that the SK/S1P signaling pathway plays a crucial role in the control of skeletal muscle precursor cell biology.

P.5.a.007 Sphingosine-1-phosphate: from regulation of gene expression to cytoprotection in an experimental model of neurodegenerative disorders

Leukocyte recruitment to sites of inflammation is critical for the development of acute allergic responses. Rapid P-selectin up-regulation by endothelial cells is a key promoter of leukocyte infiltration in response to mediators such as histamine. However, the mechanisms underpinning this process are still incompletely understood. We examined the role of the sphingosine kinase/sphingosine-1-phosphate (SK/S1P) pathway and showed that in human umbilical vein endothelial cells, histamine rapidly activates SK in an extracellular signal-regulated kinase (ERK) 1/2-dependent manner, concurrent with the induction of P-selectin expression. Histamine activated both SK-1 and SK-2 isoforms; inhibition of SK-1, but not SK-2, attenuated histamine-induced P-selectin up-regulation and neutrophil rolling in vitro. S1P receptor antagonists failed to prevent histamine-induced P-selectin expression, and exogenous S1P did not increase P-selectin expression, suggesting that S1P cell surface receptors are not involved in this process. Finally, the role of both SK-1 and SK-2 in histamine-induced leukocyte rolling in vivo was assessed using pharmacological and genetic methods. Consistent with the in vitro findings, mice pretreated with either sphingosine kinase inhibitor or fingolimod (FTY720) significantly attenuated histamine-induced leukocyte rolling in the cremaster muscle. Similarly, Sphk1−/− but not Sphk2−/− mice exhibited reduced histamine-induced leukocyte rolling. These findings demonstrate a key role for SK-1 in histamine-induced rapid P-selectin up-regulation and associated leukocyte rolling, and suggest that endothelial SK-1 is an important contributor to allergic inflammation.

Sphingosine kinase/sphingosine 1-phosphate (S1P)/S1P receptor axis is involved in liver fibrosis-associated angiogenesis

Sphingosine kinase (SphK)/sphingosine 1-phosphate (S1P)/S1P receptor (S1PR) axis is involved in multiple biological processes, including liver fibrosis. Angiogenesis is an important pathophysiological process closely associated with liver fibrosis; however, the functional role of SphK/S1P/S1PR in this process remains incompletely defined. Bile duct ligation or carbon tetrachloride was used to induce liver fibrosis in mice. Human fibrotic samples were obtained from livers of patients undergoing liver transplantation. S1P levels in the liver were examined by HPLC. Expression of angiogenic markers, including angiopoietin 1, CD31, vascular cell adhesion molecule-1, and von Willebrand factor, was characterized by immunofluorescence, real-time RT-PCR, and Western blot in the fibrotic liver and primary mouse hepatic stellate cells (HSCs). SphK inhibitor (SKI) or S1PR antagonists were administered intraperitoneally in mice. S1P levels in the liver were closely correlated with mRNA expression of angiogenic markers. Ang1 is expressed in activated HSCs of the fibrotic liver and in primary HSCs. In HSCs, by using specific antagonists or siRNAs, we demonstrated S1P stimulation induced Ang1 expression via S1PR1 and S1PR3. In vivo, S1P reduction by SKI inhibited angiogenesis in fibrotic mice. Furthermore, S1PR1/3 antagonist significantly blocked upregulation of angiogenic markers in the injured liver, and attenuated the extent of liver fibrosis, while S1PR2 antagonist had no effect on angiogenesis, supporting the key role of S1PR1 and S1PR3 in angiogenesis underlying liver fibrosis process. SphK1/S1P/S1PR1/3 axis plays a crucial role in the angiogenic process required for fibrosis development, which may represent an effective therapeutic strategy for liver fibrosis.

Sphingosine kinase and sphingosine 1-phosphate in the heart: A decade of progress

Activation of sphingosine kinase/sphingosine 1-phosphate (SK/S1P)‐mediated signaling has emerged as a critical cardioprotective pathway in response to acute ischemia/reperfusion injury. S1P is released in both ischemic pre- and post-conditioning. Application of exogenous S1P to cultured cardiac myocytes subjected to hypoxia or treatment of isolated hearts either before ischemia or at the onset of reperfusion exerts prosurvival effects. Synthetic congeners of S1P such as FTY720 mimic these responses. Gene targeted mice null for the SK1 isoform whose hearts are subjected to ischemia/reperfusion injury exhibit increased infarct size and respond poorly either to ischemic pre- or postconditioning. Measurements of cardiac SK activity and S1P parallel these observations. Experiments in SK2 knockout mice have revealed that this isoform is necessary for survival in the heart. High density lipoprotein (HDL) is a major carrier of S1P, and studies of hearts in which selected S1P receptors have been inhibited implicate the S1P cargo of HDL in cardioprotection. Inhibition of S1P lyase, an endogenous enzyme that degrades S1P, also leads to cardioprotection. These observations have considerable relevance for future therapeutic approaches to acute and chronic myocardial injury. This article is part of a Special Issue entitled Advances in Lysophospholipid Research.

Bone Marrow-Derived Mesenchymal Stem Cells Differentiate to Hepatic Myofibroblasts by Transforming Growth Factor-β1 via Sphingosine Kinase/Sphingosine 1-Phosphate (S1P)/S1P Receptor Axis

Sphingosine kinase (SphK) is involved in numerous biological processes, including cell growth, proliferation, and differentiation. However, whether SphK participates in the differentiation of bone marrow-derived mesenchymal stem cells (BMSCs) to myofibroblasts has been unknown. In a carbon tetrachloride-treated mouse model, SphK1 was expressed in BMSCs in damaged liver. Furthermore, mRNA expression of both SphK1 and transforming growth factor β1 (TGF-β1) was significantly increased after liver injury, with a positive correlation between them. The SphK inhibitor SKI significantly blocked BMSC differentiation to myofibroblasts during liver injury (the proportion of BMSC-derived myofibroblasts decreased markedly, compared with no SKI treatment) and attenuated the extent of liver fibrosis. Using primary mouse BMSCs, we demonstrated that TGF-β1 induced BMSC differentiation to myofibroblasts, accompanied by the up-regulation of SphK1 and modulation of sphingosine 1-phosphate (S1P) receptor (S1PR) expression. Notably, pharmacological or siRNA-mediated inhibition of SphK1 abrogated the prodifferentiating effect of TGF-β1. Moreover, using either S1PR subtype-specific antagonists or specific siRNAs, we found that the prodifferentiating effect of TGF-β1 was mediated by S1PR(1) and S1PR(3). These data suggest that SphK1 activation by TGF-β1 leads to differentiation of BMSCs to myofibroblasts mediated by S1PR(1) and S1PR(3) up-regulation, thus providing new information on the mechanisms by which TGF-β1 gives rise to fibrosis and opening new perspectives for pharmacological treatment of liver fibrosis.

Rapid Histamine-Induced Neutrophil Recruitment Is Sphingosine Kinase-1 Dependent

Leukocyte recruitment to sites of inflammation is critical for the development of acute allergic responses. Rapid P-selectin up-regulation by endothelial cells is a key promoter of leukocyte infiltration in response to mediators such as histamine. However, the mechanisms underpinning this process are still incompletely understood. We examined the role of the sphingosine kinase/sphingosine-1-phosphate (SK/S1P) pathway and showed that in human umbilical vein endothelial cells, histamine rapidly activates SK in an extracellular signal-regulated kinase (ERK) 1/2-dependent manner, concurrent with the induction of P-selectin expression. Histamine activated both SK-1 and SK-2 isoforms; inhibition of SK-1, but not SK-2, attenuated histamine-induced P-selectin up-regulation and neutrophil rolling in vitro. S1P receptor antagonists failed to prevent histamine-induced P-selectin expression, and exogenous S1P did not increase P-selectin expression, suggesting that S1P cell surface receptors are not involved in this process. Finally, the role of both SK-1 and SK-2 in histamine-induced leukocyte rolling in vivo was assessed using pharmacological and genetic methods. Consistent with the in vitro findings, mice pretreated with either sphingosine kinase inhibitor or fingolimod (FTY720) significantly attenuated histamine-induced leukocyte rolling in the cremaster muscle. Similarly, Sphk1(-/-) but not Sphk2(-/-) mice exhibited reduced histamine-induced leukocyte rolling. These findings demonstrate a key role for SK-1 in histamine-induced rapid P-selectin up-regulation and associated leukocyte rolling, and suggest that endothelial SK-1 is an important contributor to allergic inflammation.

RETRACTED: Berberine ameliorates renal injury in diabetic C57BL/6 mice: Involvement of suppression of SphK–S1P signaling pathway

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editor-in-Chief. This article shows significant data duplication and overlap with Liu, Weihua, et al., Effects of berberine on matrix accumulation and NF-kappa B signal pathway in alloxan-induced diabetic mice with renal injury. European Journal of Pharmacology. 2010 Jul 25;638(1-3):150-5 (https://doi.org/10.1016/j.ejphar.2010.04.033) without adequate referencing. Although there is a slight difference in the methodology section regarding alloxan-induced diabetes models in the two articles, there is a clear overlap between Table 2 of Lan, Tian, et al., (2010); and Tables 1 and 2 of Liu, Weihua, et al. (2010). The two manuscripts were submitted from the same laboratory in the same year.

Sphingosine kinase regulation and cardioprotection

Activation of sphingosine kinase/sphingosine-1-phosphate (SK/S1P)-mediated signalling has been recognized as critical for cardioprotection in response to acute ischaemia/reperfusion injury. Incubation of S1P with cultured cardiac myocytes subjected to hypoxia or treatment of isolated hearts either before ischaemia or at the onset of reperfusion (pharmacologic pre- or postconditioning) results in reduced myocyte injury. Synthetic agonists active at S1P receptors mimic these responses. Gene-targeted mice null for the SK1 isoform whose hearts are subjected to ischaemia/reperfusion injury exhibit increased infarct size and respond poorly either to ischaemic pre- or postconditioning. Measurements of cardiac SK activity and S1P parallel these observations. Ischaemic postconditioning combined with sphingosine and S1P rescues the heart from prolonged ischaemia. These observations may have considerable relevance for future therapeutic approaches to acute and chronic myocardial injury.

Acid Ceramidase but Not Acid Sphingomyelinase Is Required for Tumor Necrosis Factor-α-induced PGE2 Production

Sphingolipids are well established effectors of signal transduction downstream of the tumor necrosis factor (TNF) receptor. In a previous study, we showed that the sphingosine kinase/sphingosine 1-phosphate (S1P) pathway couples TNF receptor to induction of the cyclooxygenase 2 gene and prostaglandin synthesis (Pettus, B. J., Bielawski, J., Porcelli, A. M., Reames, D. L., Johnson, K. R., Morrow, J., Chalfant, C. E., Obeid, L. M., and Hannun, Y. A. (2003) FASEB J. 17, 1411-1421). In this study, the requirement for acid sphingomyelinase and sphingomyelin metabolites in the TNFalpha/prostaglandin E(2) (PGE(2)) pathway was investigated. The amphiphilic compound desipramine, a frequently employed inhibitor of acid sphingomyelinase (ASMase), blocked PGE(2) production. However, the action of desipramine was independent of its action on ASMase, since neither genetic loss of ASMase (Niemann-Pick fibroblasts) nor knockdown of ASMase using RNA interference affected TNFalpha-induced PGE(2) synthesis. Further investigations revealed that desipramine down-regulated acid ceramidase (AC), but not sphingosine kinase, at the protein level. This resulted in a time-dependent drop in sphingosine and S1P levels. Moreover, exogenous administration of either sphingosine or S1P rescued PGE(2) biosynthesis after desipramine treatment. Interestingly, knockdown of endogenous AC by RNA interference attenuated cyclooxygenase 2 induction by TNFalpha and subsequent PGE(2) biosynthesis. Taken together, these results define a novel role for AC in the TNFalpha/PGE(2) pathway. In addition, the results of this study warrant careful reconsideration of desipramine as a specific inhibitor for ASMase.

Products by the sphingosine kinase/sphingosine 1‐phosphate (S1P) lyase pathway but not S1P stimulate mitogenesis

Sphingosine 1-phosphate (S1P) functions as a ligand for the S1P/EDG family receptors. For years, intracellular signaling roles for S1P have also been suggested, especially in cell proliferation. Now, we have generated several mouse F9 embryonic carcinoma cell lines varying in expression of the S1P-degrading enzyme, S1P lyase (SPL) and/or sphingosine kinase (SPHK1). All these cell lines accumulated S1P compared to the wild-type F9 cells, but the amounts varied. We investigated the ability of these cells to proliferate under low serum conditions, as measured by a thymidine uptake assay. Although F9 cells over-expressing SPHK1 did exhibit enhanced DNA synthesis, other S1P-accumulating cells (SPL-null cells and SPL-null cells over-expressing SPHK1) did not. The overproduction of both SPL and SPHK1 resulted in the most striking mitogenic effect. Moreover, nM concentrations of sphingosine (or dihydrosphingosine) stimulated DNA synthesis in an SPL-dependent manner. These results indicate that products by the SPL pathway, not S1P itself, function in mitogenesis.