The Experts below are selected from a list of 7125 Experts worldwide ranked by ideXlab platform

Sarah Spiegel - One of the best experts on this subject based on the ideXlab platform.

  • examination of the role of Sphingosine Kinase 2 in a murine model of systemic lupus erythematosus
    The FASEB Journal, 2019
    Co-Authors: Jeremy C Allegood, Sarah Spiegel, Sabira Mohammed, Nalanda S Vineetha, Shirley James, Jayasekharan S Aparna, Manendra Babu Lankadasari, Kuzhuvelil B Harikumar
    Abstract:

    Systemic lupus erythematosus is an autoimmune disease characterized by overproduction of type 1 IFN that causes multiple organ dysfunctions. Plasmacytoid dendritic cells (pDCs) that secrete large amounts of IFN have recently been implicated in the initiation of the disease in preclinical mouse models. Sphingosine-1-phosphate, a bioactive sphingolipid metabolite, is produced by 2 highly conserved isoenzymes, Sphingosine Kinase (SphK) 1 and SphK2, and regulates diverse processes important for immune responses and autoimmunity. However, not much is known about the role of SphK2 in autoimmune disorders. In this work, we examined the role of SphK2 in pDC development and activation and in the pristane-induced lupus model in mice that mimics the hallmarks of the human disease. Increases in pDC-specific markers were observed in peripheral blood of SphK2 knockout mice. In agreement, the absence of SphK2 increased the differentiation of FMS-like tyrosine Kinase 3 ligand dendritic cells as well as expression of endosomal TLRs, TLR7 and TLR9, that modulate production of IFN. Surprisingly, however, SphK2 deficiency did not affect the initiation or progression of pristane-induced lupus. Moreover, although absence of SphK2 increased pDC frequency in pristane-induced lupus, there were no major changes in their activation status. Additionally, SphK2 expression was unaltered in lupus patients. Taken together, our results suggest that SphK2 may play a role in dendritic cell development. Yet, because its deletion had no effect on the clinical lupus parameters in this preclinical model, inhibitors of SphK2 might not be useful for treatment of this devastating disease.-Mohammed, S., Vineetha, N. S., James, S., Aparna, J. S., Lankadasari, M. B., Allegood, J. C., Li, Q.-Z., Spiegel, S., Harikumar, K. B. Examination of the role of Sphingosine Kinase 2 in a murine model of systemic lupus erythematosus.

  • biological characterization of 3 2 amino ethyl 5 3 4 butoxyl phenyl propylidene thiazolidine 2 4 dione k145 as a selective Sphingosine Kinase 2 inhibitor and anticancer agent
    PLOS ONE, 2013
    Co-Authors: Kai Liu, Jeremy C Allegood, Nitai C Hait, Sarah Spiegel, Tai L Guo, Hardik I Parikh, Glen E Kellogg, Steven Grant, Shijun Zhang
    Abstract:

    In our effort to develop selective Sphingosine Kinase-2 (SphK2) inhibitors as pharmacological tools, a thiazolidine-2,4-dione analogue, 3-(2-amino-ethyl)-5-[3-(4-butoxyl-phenyl)-propylidene]-thiazolidine-2,4-dione (K145), was synthesized and biologically characterized. Biochemical assay results indicate that K145 is a selective SphK2 inhibitor. Molecular modeling studies also support this notion. In vitro studies using human leukemia U937 cells demonstrated that K145 accumulates in U937 cells, suppresses the S1P level, and inhibits SphK2. K145 also exhibited inhibitory effects on the growth of U937 cells as well as apoptotic effects in U937 cells, and that these effects may be through the inhibition of down-stream ERK and Akt signaling pathways. K145 also significantly inhibited the growth of U937 tumors in nude mice by both intraperitoneal and oral administration, thus demonstrating its in vivo efficacy as a potential lead anticancer agent. The antitumor activity of K145 was also confirmed in a syngeneic mouse model by implanting murine breast cancer JC cells in BALB/c mice. Collectively, these results strongly encourage further optimization of K145 as a novel lead compound for development of more potent and selective SphK2 inhibitors.

  • a novel role for mitochondrial Sphingosine 1 phosphate produced by Sphingosine Kinase 2 in ptp mediated cell survival during cardioprotection
    Basic Research in Cardiology, 2011
    Co-Authors: Ludovic Gomez, Megan M Price, Qun Chen, Sarah Spiegel, Melanie Paillard, Geoffrey Teixeira, Edward J Lesnefsky
    Abstract:

    Although mitochondria are key determinants of myocardial injury during ischemia–reperfusion (I/R), their interaction with critical cytoprotective signaling systems is not fully understood. Sphingosine-1-phosphate (S1P) produced by Sphingosine Kinase-1 protects the heart from I/R damage. Recently a new role for mitochondrial S1P produced by a second isoform of Sphingosine Kinase, SphK2, was described to regulate complex IV assembly and respiration via interaction with mitochondrial prohibitin-2. Here we investigated the role of SphK2 in cardioprotection by preconditioning. Littermate (WT) and sphk2−/− mice underwent 45 min of in vivo ischemia and 24 h reperfusion. Mice received no intervention (I/R) or preconditioning (PC) via 5 min I/R before the index ischemia. Despite the activation of PC-cytoprotective signaling pathways in both groups, infarct size in sphk2−/− mice was not reduced by PC (42 ± 3% PC vs. 43 ± 4% I/R, p = ns) versus WT (24 ± 3% PC vs. 43 ± 3% I/R, p < 0.05). sphk2−/− mitochondria exhibited decreased oxidative phosphorylation and increased susceptibility to permeability transition (PTP). Unlike WT, PC did not prevent ischemic damage to electron transport or the increased susceptibility to PTP. To evaluate the direct contribution to the resistance of mitochondria to cytoprotection, SphK2, PHB2 or cytochrome oxidase subunit IV was depleted in cardiomyoblasts. PC protection was abolished by each knockdown concomitant with decreased PTP resistance. These results point to a new action of S1P in cardioprotection and suggest that the mitochondrial S1P produced by SphK2 is required for the downstream protective modulation of PTP as an effector of preconditioning protection.

  • involvement of Sphingosine Kinase 2 in p53 independent induction of p21 by the chemotherapeutic drug doxorubicin
    Cancer Research, 2007
    Co-Authors: Heidi Sankala, Nitai C Hait, Sandrine Lépine, Sheldon Milstien, Steven W Paugh, Dai Shida, Lynne W Elmore, Paul Dent, Sarah Spiegel
    Abstract:

    Sphingosine-1-phosphate is a potent lipid mediator formed by phosphorylation of Sphingosine, a metabolite of sphingolipids, catalyzed by two Sphingosine Kinase (SphK) isoenzymes, SphK1 and SphK2. Expression of SphK2, which is enriched in the nucleus of MCF7 human breast cancer cells, increased expression of the cyclin-dependent Kinase inhibitor p21 but had no effect on p53 or its phosphorylation. The anticancer drug doxorubicin is known to increase p21 via p53-dependent and p53-independent mechanisms. Down-regulation of endogenous SphK2 with small interfering RNA targeted to unique mRNA sequences decreased basal and doxorubicin-induced expression of p21 without affecting increased expression of p53. Down-regulation of SphK2 also decreased G2-M arrest and markedly enhanced apoptosis induced by doxorubicin. Moreover, siSphK2 reduced doxorubicin-induced p21 expression in p53-inactivated MCF7 cells. Likewise, in human wild-type p53- and p21-expressing HCT116 colon carcinoma cells, as well as in p53-null counterparts, down-regulation of SphK2 markedly reduced p21 induction by doxorubicin. Knockdown of SphK2 sensitized HCT116 cells to apoptosis induced by doxorubicin with concomitant cleavage of poly(ADP-ribose) polymerase. Collectively, our results show that endogenous SphK2 is important for p53-independent induction of p21 expression by doxorubicin and suggest that SphK2 may influence the balance between cytostasis and apoptosis of human cancer cells. [Cancer Res 2007;67(21):10466–74]

  • involvement of Sphingosine Kinase 2 in p53 independent induction of p21 by the chemotherapeutic drug doxorubicin
    Cancer Research, 2007
    Co-Authors: Heidi Sankala, Nitai C Hait, Sandrine Lépine, Sheldon Milstien, Steven W Paugh, Dai Shida, Lynne W Elmore, Paul Dent, Sarah Spiegel
    Abstract:

    Sphingosine-1-phosphate is a potent lipid mediator formed by phosphorylation of Sphingosine, a metabolite of sphingolipids, catalyzed by two Sphingosine Kinase (SphK) isoenzymes, SphK1 and SphK2. Expression of SphK2, which is enriched in the nucleus of MCF7 human breast cancer cells, increased expression of the cyclin-dependent Kinase inhibitor p21 but had no effect on p53 or its phosphorylation. The anticancer drug doxorubicin is known to increase p21 via p53-dependent and p53-independent mechanisms. Down-regulation of endogenous SphK2 with small interfering RNA targeted to unique mRNA sequences decreased basal and doxorubicin-induced expression of p21 without affecting increased expression of p53. Down-regulation of SphK2 also decreased G(2)-M arrest and markedly enhanced apoptosis induced by doxorubicin. Moreover, siSphK2 reduced doxorubicin-induced p21 expression in p53-inactivated MCF7 cells. Likewise, in human wild-type p53- and p21-expressing HCT116 colon carcinoma cells, as well as in p53-null counterparts, down-regulation of SphK2 markedly reduced p21 induction by doxorubicin. Knockdown of SphK2 sensitized HCT116 cells to apoptosis induced by doxorubicin with concomitant cleavage of poly(ADP-ribose) polymerase. Collectively, our results show that endogenous SphK2 is important for p53-independent induction of p21 expression by doxorubicin and suggest that SphK2 may influence the balance between cytostasis and apoptosis of human cancer cells.

Charles D. Smith - One of the best experts on this subject based on the ideXlab platform.

  • the Sphingosine Kinase 2 inhibitor abc294640 displays anti non small cell lung cancer activities in vitro and in vivo
    International Journal of Cancer, 2018
    Co-Authors: Charles D. Smith, Lu Dai, Zhiqiang Qin, Maryam Foroozesh, Lucio Miele
    Abstract:

    Non-small cell lung cancer (NSCLC) accounts for about 85-90% of lung cancer cases, and is the number one killer among cancers in the United States. The majorities of lung cancer patients do not respond well to conventional chemo- and/or radio-therapeutic regimens, and have a dismal 5-year survival rate of ∼15%. The recent introduction of targeted therapy and immunotherapy gives new hopes to NSCLC patients, but even with these agents, not all patients respond, and responses are rarely complete. Thus, there is still an urgent need to identify new therapeutic targets in NSCLC and develop novel anti-cancer agents. Sphingosine Kinase 2 (SphK2) is one of the key enzymes in sphingolipid metabolism. SphK2 expression predicts poor survival in NSCLC patients, and is associated with Gefitinib-resistance. In this study, the anti-NSCLC activities of ABC294640, the only first-in-class orally available inhibitor of SphK2, were explored. The results obtained indicate that ABC294640 treatment causes significant NSCLC cell apoptosis, cell cycle arrest and suppression of tumor growth in vitro and in vivo. Moreover, lipidomics analyses revealed the complete signature of ceramide and dihydro(dh)-ceramide species in the NSCLC cell-lines with or without ABC294640 treatment. These findings indicate that sphingolipid metabolism targeted therapy may be developed as a promising strategy against NSCLC.

  • abc294640 a novel Sphingosine Kinase 2 inhibitor induces oncogenic virus infected cell autophagic death and represses tumor growth
    Molecular Cancer Therapeutics, 2017
    Co-Authors: Charles D. Smith, Lu Dai, Aiping Bai, Paulo C Rodriguez, Zhiqiang Qin
    Abstract:

    Kaposi sarcoma-associated herpes virus (KSHV) is the etiologic agent of several malignancies, including Kaposi sarcoma and primary effusion lymphoma (PEL), which preferentially arise in HIV+ patients and lack effective treatment. Sphingosine Kinase 2 (SphK2) is a key factor within sphingolipid metabolism, responsible for the conversion of proapoptotic ceramides to antiapoptotic Sphingosine-1-phosphate (S1P). We have previously demonstrated that targeting SphK2 using a novel selective inhibitor, ABC294640, leads to the accumulation of intracellular ceramides and induces apoptosis in KSHV-infected primary endothelial cells and PEL tumor cells but not in uninfected cells. In this study, we found that ABC294640 induces autophagic death instead of apoptosis in a KSHV long-term-infected immortalized endothelial cell-line, TIVE-LTC, but not in uninfected TIVE cells, through the upregulation of LC3B protein. Transcriptomic analysis indicates that many genes related to cellular stress responses, cell cycle/proliferation, and cellular metabolic process are altered in TIVE-LTC exposed to ABC294640. One of the candidates, Egr-1, was found to directly regulate LC3B expression and was required for the ABC294640-induced autophagic death. By using a Kaposi sarcoma-like nude mice model with TIVE-LTC, we found that ABC294640 treatment significantly suppressed KSHV-induced tumor growth in vivo, which indicates that targeting sphingolipid metabolism, especially SphK2, may represent a promising therapeutic strategy against KSHV-related malignancies. Mol Cancer Ther; 16(12); 2724-34. ©2017 AACR.

  • suppression of c myc and rrm2 expression in pancreatic cancer cells by the Sphingosine Kinase 2 inhibitor abc294640
    Oncotarget, 2016
    Co-Authors: Clayton S Lewis, Christina Voelkeljohnson, Charles D. Smith
    Abstract:

    // Clayton S. Lewis 1 , Christina Voelkel-Johnson 2 , Charles D. Smith 3 1 Medical University of South Carolina, Department of Drug Discovery and Pharmaceutical Sciences, Charleston, South Carolina, USA 2 Medical University of South Carolina, Department of Microbiology and Immunology, Charleston, South Carolina, USA 3 Apogee Biotechnology Corporation, Hummelstown, Pennsylvania, USA Correspondence to: Charles D. Smith, email: cdsmith@apogee-biotech.com Keywords: Sphingosine Kinase-2, gemcitabine, pancreatic cancer, c-Myc, ribonucleotide reductase Received: October 12, 2015     Accepted: July 06, 2016     Published: August 08, 2016 ABSTRACT Pancreatic cancer remains extremely difficult to treat, with the average lifespan following diagnosis being only 3-6 months, resulting in a death to incidence ratio of 0.94. A major reason for this high mortality rate is resistance to the main chemotherapeutic agent used to treat this disease, gemcitabine. Alterations in nucleoside and gemcitabine metabolism, specifically over-expression of ribonucleotide reductase, have been implicated as a major mechanism of resistance to this drug. Here, we show that inhibition of Sphingosine Kinase-2 by the specific inhibitor ABC294640 is synergistically cytotoxic with gemcitabine toward three human pancreatic cancer cell lines. Treatment with ABC294640 results in decreased expression of both RRM2 and MYC in all three cell lines. Additionally, expression of c-Myc protein and phosphorylation of Rb at S780 both decrease in a dose-dependent manner in response to ABC294640, while acetylation of H3-K9 and p21 levels increase. Pretreatment with the protein phosphatase 1 inhibitor okadaic acid or the ceramide synthase inhibitor fumonisin B1 fails to prevent the effects of ABC294640 on Rb phosphorylation. These data indicate a role for Sphingosine Kinase-2 in E2F and c-Myc mediated transcription through alteration of histone acetylation and p21 expression. These effects of ABC294640 suggest that it may be an effective agent for pancreatic cancer, particularly in combination with gemcitabine.

  • the Sphingosine Kinase 2 inhibitor abc294640 reduces the growth of prostate cancer cells and results in accumulation of dihydroceramides in vitro and in vivo
    Molecular Cancer Therapeutics, 2015
    Co-Authors: Heather Venant, Charles D. Smith, Mehrdad Rahmaniyan, Ellen E Jones, Michael B Lilly, Elizabeth Garrettmayer, Richard R Drake, Jacqueline M Kraveka, Christina Voelkeljohnson
    Abstract:

    Despite recent advances in the development of novel therapies against castration-resistant prostate cancer, the advanced form of the disease remains a major treatment challenge. Aberrant sphingolipid signaling through Sphingosine Kinases and their product, Sphingosine-1-phosphate, can promote proliferation, drug resistance, angiogenesis, and inflammation. The Sphingosine Kinase 2 inhibitor ABC294640 is undergoing clinical testing in cancer patients, and in this study we investigated the effects this first-in-class inhibitor in castration-resistant prostate cancer. In vitro, ABC294640 decreased prostate cancer cell viability as well as the expression of c-Myc and the androgen receptor, while lysosomal acidification increased. ABC294640 also induced a greater than 3-fold increase in dihydroceramides that inversely correlated with inhibition of dihydroceramide desaturase (DEGS) activity. Expression of Sphingosine Kinase 2 was dispensable for the ABC294640-mediated increase in dihydroceramides. In vivo, ABC294640 diminished the growth rate of TRAMP-C2 xenografts in syngeneic hosts and elevated dihydroceramides within tumors as visualized by MALDI imaging mass spectroscopy. The plasma of ABC294640-treated mice contained significantly higher levels of C16- and C24:1-ceramides (but not dihydro-C16-ceramide) compared with vehicle-treated mice. In summary, our results suggest that ABC294640 may reduce the proliferative capacity of castration-resistant prostate cancer cells through inhibition of both Sphingosine Kinase 2 and dihydroceramide desaturase, thereby providing a foundation for future exploration of this small-molecule inhibitor for the treatment of advanced disease.

  • preconditioning stimuli induce autophagy via Sphingosine Kinase 2 in mouse cortical neurons
    Journal of Biological Chemistry, 2014
    Co-Authors: Rui Sheng, Charles D. Smith, Tongtong Zhang, Valeria D Felice, Tao Qin, Zhenghong Qin, Ellen Sapp, Marian Difiglia, Christian Waeber
    Abstract:

    Sphingosine Kinase 2 (SPK2) and autophagy are both involved in brain preconditioning, but whether preconditioning-induced SPK2 up-regulation and autophagy activation are linked mechanistically remains to be elucidated. In this study, we used in vitro and in vivo models to explore the role of SPK2-mediated autophagy in isoflurane and hypoxic preconditioning. In primary mouse cortical neurons, both isoflurane and hypoxic preconditioning induced autophagy. Isoflurane and hypoxic preconditioning protected against subsequent oxygen glucose deprivation or glutamate injury, whereas pretreatment with autophagy inhibitors (3-methyladenine or KU55933) abolished preconditioning-induced tolerance. Pretreatment with SPK2 inhibitors (ABC294640 and SKI-II) or SPK2 knockdown prevented preconditioning-induced autophagy. Isoflurane also induced autophagy in mouse in vivo as shown by Western blots for LC3 and p62, LC3 immunostaining, and electron microscopy. Isoflurane-induced autophagy in mice lacking the SPK1 isoform (SPK1−/−), but not in SPK2−/− mice. Sphingosine 1-phosphate and the Sphingosine 1-phosphate receptor agonist FTY720 did not protect against oxygen glucose deprivation in cultured neurons and did not alter the expression of LC3 and p62, suggesting that SPK2-mediated autophagy and protections are not S1P-dependent. Beclin 1 knockdown abolished preconditioning-induced autophagy, and SPK2 inhibitors abolished isoflurane-induced disruption of the Beclin 1/Bcl-2 association. These results strongly indicate that autophagy is involved in isoflurane preconditioning both in vivo and in vitro and that SPK2 contributes to preconditioning-induced autophagy, possibly by disrupting the Beclin 1/Bcl-2 interaction.

Webster L Santos - One of the best experts on this subject based on the ideXlab platform.

  • probing the substitution pattern of indole based scaffold reveals potent and selective Sphingosine Kinase 2 inhibitors
    European Journal of Medicinal Chemistry, 2021
    Co-Authors: Molly D. Congdon, Yugesh Kharel, Kevin R. Lynch, Anne M Brown, David R Bevan, Russell G Fritzemeier, Vlad Serbulea, Webster L Santos
    Abstract:

    Abstract Elevated levels of Sphingosine 1-phosphate (S1P) and increased expression of Sphingosine Kinase isoforms (SphK1 and SphK2) have been implicated in a variety of disease states including cancer, inflammation, and autoimmunity. Consequently, the S1P signaling axis has become an attractive target for drug discovery. Selective inhibition of either SphK1 or SphK2 has been demonstrated to be effective in modulating S1P levels in animal models. While SphK1 inhibitors have received much attention, the development of potent and selective SphK2 inhibitors are emerging. Previously, our group reported a SphK2 naphthalene-based selective inhibitor, SLC5081308, which displays approximately 7-fold selectivity for hSphK2 over hSphK1 and has a SphK2 Ki value of 1.0 μM. To improve SphK2 potency and selectivity, we designed, synthesized, and evaluated a series of indole-based compounds derived from SLC5081308. After investigating substitution patterns around the indole ring, we discovered that 1,5-disubstitution promoted optimal binding in the SphK2 substrate binding site and subsequent inhibition of enzymatic activity. Our studies led to the identification of SLC5101465 (6r, SphK2 Ki = 90 nM, >110 fold selective for SphK2 over SphK1). Molecular modeling studies revealed key nonpolar interactions with Val308, Phe548, His556, and Cys533 and hydrogen bonds with both Asp211 and Asp308 as responsible for the high SphK2 inhibition and selectivity.

  • discovery of a small side cavity in Sphingosine Kinase 2 that enhances inhibitor potency and selectivity
    Journal of Medicinal Chemistry, 2020
    Co-Authors: Christopher D Sibley, Yugesh Kharel, Kevin R. Lynch, Anne M Brown, Emily A Morris, Tao Huang, David R Bevan, Webster L Santos
    Abstract:

    The Sphingosine-1-phosphate (S1P) signaling pathway is an attractive drug target due to its involvement in immune cell chemotaxis and vascular integrity. The formation of S1P is catalyzed by Sphingosine Kinase 1 or 2 (SphK1 or SphK2) from Sphingosine (Sph) and ATP. Inhibition of SphK1 and SphK2 to attenuate levels of S1P has been reported to be efficacious in animal models of diseases such as cancer, sickle cell disease, and renal fibrosis. While inhibitors of both SphKs have been reported, improvements in potency and selectivity are still needed. Toward that end, we performed structure-activity relationship profiling of 8 (SLM6031434) and discovered a heretofore unrecognized side cavity that increased inhibitor potency toward SphK2. Interrogating this region revealed that relatively small hydrophobic moieties are preferred, with 10 being the most potent SphK2-selective inhibitor (Ki = 89 nM, 73-fold SphK2-selective) with validated in vivo activity.

  • transforming Sphingosine Kinase 1 inhibitors into dual and Sphingosine Kinase 2 selective inhibitors design synthesis and in vivo activity
    Journal of Medicinal Chemistry, 2017
    Co-Authors: Elizabeth S Childress, Yugesh Kharel, Kevin R. Lynch, Anne M Brown, David R Bevan, Webster L Santos
    Abstract:

    Sphingosine 1-phosphate (S1P) is a pleiotropic signaling molecule that interacts with its five G-protein coupled receptors (S1P1–5) to regulate cell growth and survival and has been implicated in a variety of diseases including cancer and sickle cell disease. As the key mediators in the synthesis of S1P, Sphingosine Kinase (SphK) isoforms 1 and 2 have attracted attention as viable targets for pharmaceutical inhibition. In this article, we describe the design, synthesis, and biological evaluation of aminothiazole-based guanidine inhibitors of SphK. Surprisingly, combining features of reported SphK1 inhibitors generated SphK1/2 dual inhibitor 20l (SLC4011540) (hSphK1 Ki = 120 nM, hSphK2 Ki = 90 nM) and SphK2 inhibitor 20dd (SLC4101431) (Ki = 90 nM, 100-fold SphK2 selectivity). These compounds effectively decrease S1P levels in vitro. In vivo administration of 20dd validated that inhibition of SphK2 increases blood S1P levels.

  • Transforming Sphingosine Kinase 1 Inhibitors into Dual and Sphingosine Kinase 2 Selective Inhibitors: Design, Synthesis, and in Vivo Activity
    2017
    Co-Authors: Elizabeth S. Childress, Yugesh Kharel, Kevin R. Lynch, Anne M Brown, David R Bevan, Webster L Santos
    Abstract:

    Sphingosine 1-phosphate (S1P) is a pleiotropic signaling molecule that interacts with its five G-protein coupled receptors (S1P1–5) to regulate cell growth and survival and has been implicated in a variety of diseases including cancer and sickle cell disease. As the key mediators in the synthesis of S1P, Sphingosine Kinase (SphK) isoforms 1 and 2 have attracted attention as viable targets for pharmaceutical inhibition. In this article, we describe the design, synthesis, and biological evaluation of aminothiazole-based guanidine inhibitors of SphK. Surprisingly, combining features of reported SphK1 inhibitors generated SphK1/2 dual inhibitor 20l (SLC4011540) (hSphK1 Ki = 120 nM, hSphK2 Ki = 90 nM) and SphK2 inhibitor 20dd (SLC4101431) (Ki = 90 nM, 100-fold SphK2 selectivity). These compounds effectively decrease S1P levels in vitro. In vivo administration of 20dd validated that inhibition of SphK2 increases blood S1P levels

  • Structure-Activity Relationship Studies and Molecular Modeling of Naphthalene-Based Sphingosine Kinase 2 Inhibitors
    ACS Medicinal Chemistry Letters, 2016
    Co-Authors: Molly D. Congdon, Stephanie N Lewis, Yugesh Kharel, Kevin R. Lynch, Anne M Brown, Webster L Santos
    Abstract:

    The two isoforms of Sphingosine Kinase (SphK1 and SphK2) are the only enzymes that phosphorylate Sphingosine to Sphingosine-1-phosphate (S1P), which is a pleiotropic lipid mediator involved in a broad range of cellular processes including migration, proliferation, and inflammation. SphKs are targets for various diseases such as cancer, fibrosis, and Alzheimer's and sickle cell disease. Herein, we disclose the structure-activity profile of naphthalene-containing SphK inhibitors and molecular modeling studies that reveal a key molecular switch that controls SphK selectivity.

Jeffrey M Gidday - One of the best experts on this subject based on the ideXlab platform.

  • junctional protein regulation by Sphingosine Kinase 2 contributes to blood brain barrier protection in hypoxic preconditioning induced cerebral ischemic tolerance
    Journal of Cerebral Blood Flow and Metabolism, 2012
    Co-Authors: Bradley K Wacker, Angela B Freie, Jennifer L Perfater, Jeffrey M Gidday
    Abstract:

    Protection of the blood–brain barrier (BBB) is correlated with improved outcome in stroke. Sphingosine Kinase (SphK)-directed production of Sphingosine-1-phosphate, which we previously documented as being vital to preconditioning-induced stroke protection, mediates peripheral vascular integrity via junctional protein regulation. We used a hypoxic preconditioning (HPC) model in adult wild-type and SphK2-null mice to examine the isoform-specific role of SphK2 signaling for ischemic tolerance to transient middle cerebral artery occlusion and attendant BBB protection. Reductions in infarct volume and BBB permeability in HPC-treated mice were completely lost in SphK2-null mice. Hypoxic preconditioning-induced attenuation of postischemic BBB disruption in wild types, evidenced by reduced extravascular immunoglobulin G intensity, suggests direct protection of BBB integrity. Measurement of BBB junctional protein status in response to HPC revealed SphK2-dependent increases in triton-insoluble claudin-5 and VE-cadherin, which may serve to strengthen the BBB before stroke. Postischemic loss of VE-cadherin, occludin, and zona occludens-1 in SphK2-null mice with prior HPC suggests that SphK2-dependent protection of these adherens and tight junction proteins is compulsory for HPC to establish a vasculoprotective phenotype. Further elucidation of the mediators of this endogenous, HPC-activated lipid signaling pathway, and their role in protecting the ischemic BBB, may provide new therapeutic targets for cerebrovascular protection in stroke patients.

  • hypoxic preconditioning induced cerebral ischemic tolerance role of microvascular Sphingosine Kinase 2
    Stroke, 2009
    Co-Authors: Bradley K Wacker, T S Park, Jeffrey M Gidday
    Abstract:

    Background and Purpose— The importance of bioactive lipid signaling under physiological and pathophysiological conditions is progressively becoming recognized. The disparate distribution of Sphingosine Kinase (SphK) isoform activity in normal and ischemic brain, particularly the large excess of SphK2 in cerebral microvascular endothelial cells, suggests potentially unique cell- and region-specific signaling by its product Sphingosine-1-phosphate. The present study sought to test the isoform-specific role of SphK as a trigger of hypoxic preconditioning (HPC)-induced ischemic tolerance. Methods— Temporal changes in microvascular SphK activity and expression were measured after HPC. The SphK inhibitor dimethylSphingosine or Sphingosine analog FTY720 was administered to adult male Swiss-Webster ND4 mice before HPC. Two days later, mice underwent a 60-minute transient middle cerebral artery occlusion and at 24 hours of reperfusion, infarct volume, neurological deficit, and hemispheric edema were measured. Results— HPC rapidly increased microvascular SphK2 protein expression (1.7±0.2-fold) and activity (2.5±0.6-fold), peaking at 2 hours, whereas SphK1 was unchanged. SphK inhibition during HPC abrogated reductions in infarct volume, neurological deficit, and ipsilateral edema in HPC-treated mice. FTY720 given 48 hours before stroke also promoted ischemic tolerance; when combined with HPC, even greater (and dimethylSphingosine-reversible) protection was noted. Conclusions— These findings indicate hypoxia-sensitive increases in SphK2 activity may serve as a proximal trigger that ultimately leads to Sphingosine-1-phosphate-mediated alterations in gene expression that promote the ischemia-tolerant phenotype. Thus, components of this bioactive lipid signaling pathway may be suitable therapeutic targets for protecting the neurovascular unit in stroke.

Nitai C Hait - One of the best experts on this subject based on the ideXlab platform.

  • conjugated bile acid activated s1p receptor 2 is a key regulator of Sphingosine Kinase 2 and hepatic gene expression
    Hepatology, 2015
    Co-Authors: Masayuki Nagahashi, Kazuaki Takabe, Runping Liu, Nitai C Hait, Kesong Peng, Xiang Wang, Yun Wang, Xuan Wang
    Abstract:

    UNLABELLED Bile acids are important hormones during the feed/fast cycle, allowing the liver to coordinately regulate nutrient metabolism. How they accomplish this has not been fully elucidated. Conjugated bile acids activate both the ERK1/2 and AKT signaling pathways via Sphingosine 1-phosphate receptor 2 (S1PR2) in rodent hepatocytes and in vivo. Here, we report that feeding mice a high-fat diet, infusion of taurocholate into the chronic bile fistula rat, or overexpression of the gene encoding S1PR2 in mouse hepatocytes significantly upregulated hepatic Sphingosine Kinase 2 (SphK2) but not SphK1. Key genes encoding nuclear receptors/enzymes involved in nutrient metabolism were significantly downregulated in livers of S1PR2(-/-) and SphK2(-/-) mice. In contrast, overexpression of the gene encoding S1PR2 in primary mouse hepatocytes differentially increased SphK2, but not SphK1, and mRNA levels of key genes involved in nutrient metabolism. Nuclear levels of Sphingosine-1-phosphate, an endogenous inhibitor of histone deacetylases 1 and 2, as well as the acetylation of histones H3K9, H4K5, and H2BK12 were significantly decreased in hepatocytes prepared from S1PR2(-/-) and SphK2(-/-) mice. CONCLUSION Both S1PR2(-/-) and SphK2(-/-) mice rapidly developed fatty livers on a high-fat diet, suggesting the importance of conjugated bile acids, S1PR2, and SphK2 in regulating hepatic lipid metabolism.

  • biological characterization of 3 2 amino ethyl 5 3 4 butoxyl phenyl propylidene thiazolidine 2 4 dione k145 as a selective Sphingosine Kinase 2 inhibitor and anticancer agent
    PLOS ONE, 2013
    Co-Authors: Kai Liu, Jeremy C Allegood, Nitai C Hait, Sarah Spiegel, Tai L Guo, Hardik I Parikh, Glen E Kellogg, Steven Grant, Shijun Zhang
    Abstract:

    In our effort to develop selective Sphingosine Kinase-2 (SphK2) inhibitors as pharmacological tools, a thiazolidine-2,4-dione analogue, 3-(2-amino-ethyl)-5-[3-(4-butoxyl-phenyl)-propylidene]-thiazolidine-2,4-dione (K145), was synthesized and biologically characterized. Biochemical assay results indicate that K145 is a selective SphK2 inhibitor. Molecular modeling studies also support this notion. In vitro studies using human leukemia U937 cells demonstrated that K145 accumulates in U937 cells, suppresses the S1P level, and inhibits SphK2. K145 also exhibited inhibitory effects on the growth of U937 cells as well as apoptotic effects in U937 cells, and that these effects may be through the inhibition of down-stream ERK and Akt signaling pathways. K145 also significantly inhibited the growth of U937 tumors in nude mice by both intraperitoneal and oral administration, thus demonstrating its in vivo efficacy as a potential lead anticancer agent. The antitumor activity of K145 was also confirmed in a syngeneic mouse model by implanting murine breast cancer JC cells in BALB/c mice. Collectively, these results strongly encourage further optimization of K145 as a novel lead compound for development of more potent and selective SphK2 inhibitors.

  • Sphingosine 1 phosphate produced by Sphingosine Kinase 2 in mitochondria interacts with prohibitin 2 to regulate complex iv assembly and respiration
    The FASEB Journal, 2011
    Co-Authors: Graham M Strub, Jeremy C Allegood, M Paillard, Jie Liang, Ludovic Gomez, Nitai C Hait, Michael Maceyka, Megan M Price, Qun Chen, David Simpson
    Abstract:

    The potent lipid mediator Sphingosine-1-phosphate (S1P) regulates diverse physiological processes by binding to 5 specific GPCRs, although it also has intracellular targets. Here, we demonstrate that S1P, produced in the mitochondria mainly by Sphingosine Kinase 2 (SphK2), binds with high affinity and specificity to prohibitin 2 (PHB2), a highly conserved protein that regulates mitochondrial assembly and function. In contrast, S1P did not bind to the closely related protein PHB1, which forms large, multimeric complexes with PHB2. In mitochondria from SphK2-null mice, a new aberrant band of cytochrome-c oxidase was detected by blue native PAGE, and interaction between subunit IV of cytochrome-c oxidase and PHB2 was greatly reduced. Moreover, depletion of SphK2 or PHB2 led to a dysfunction in mitochondrial respiration through cytochrome-c oxidase. Our data point to a new action of S1P in mitochondria and suggest that interaction of S1P with homomeric PHB2 is important for cytochrome-c oxidase assembly and mitochondrial respiration.—Strub, G. M., Paillard, M., Liang, J., Gomez, L., Allegood, J. C., Hait, N. C., Maceyka, M., Price, M. M., Chen, Q., Simpson, D. C., Kordula, T., Milstien, S., Lesnefsky, E. J., Spiegel, S. Sphingosine-1-phosphate produced by Sphingosine Kinase 2 in mitochondria interacts with prohibitin 2 to regulate complex IV assembly and respiration.

  • regulation of histone acetylation in the nucleus by Sphingosine 1 phosphate
    Science, 2009
    Co-Authors: Nitai C Hait, Jeremy C Allegood, Graham M Strub, Michael Maceyka, Kuzhuvelil B Harikumar, Sandeep Kumar Singh, Cheng Luo, Ronen Marmorstein, Tomasz Kordula, Sheldon Milstien
    Abstract:

    The pleiotropic lipid mediator Sphingosine-1-phosphate (S1P) can act intracellularly independently of its cell surface receptors through unknown mechanisms. Sphingosine Kinase 2 (SphK2), one of the isoenzymes that generates S1P, was associated with histone H3 and produced S1P that regulated histone acetylation. S1P specifically bound to the histone deacetylases HDAC1 and HDAC2 and inhibited their enzymatic activity, preventing the removal of acetyl groups from lysine residues within histone tails. SphK2 associated with HDAC1 and HDAC2 in repressor complexes and was selectively enriched at the promoters of the genes encoding the cyclin-dependent Kinase inhibitor p21 or the transcriptional regulator c-fos, where it enhanced local histone H3 acetylation and transcription. Thus, HDACs are direct intracellular targets of S1P and link nuclear S1P to epigenetic regulation of gene expression.

  • involvement of Sphingosine Kinase 2 in p53 independent induction of p21 by the chemotherapeutic drug doxorubicin
    Cancer Research, 2007
    Co-Authors: Heidi Sankala, Nitai C Hait, Sandrine Lépine, Sheldon Milstien, Steven W Paugh, Dai Shida, Lynne W Elmore, Paul Dent, Sarah Spiegel
    Abstract:

    Sphingosine-1-phosphate is a potent lipid mediator formed by phosphorylation of Sphingosine, a metabolite of sphingolipids, catalyzed by two Sphingosine Kinase (SphK) isoenzymes, SphK1 and SphK2. Expression of SphK2, which is enriched in the nucleus of MCF7 human breast cancer cells, increased expression of the cyclin-dependent Kinase inhibitor p21 but had no effect on p53 or its phosphorylation. The anticancer drug doxorubicin is known to increase p21 via p53-dependent and p53-independent mechanisms. Down-regulation of endogenous SphK2 with small interfering RNA targeted to unique mRNA sequences decreased basal and doxorubicin-induced expression of p21 without affecting increased expression of p53. Down-regulation of SphK2 also decreased G2-M arrest and markedly enhanced apoptosis induced by doxorubicin. Moreover, siSphK2 reduced doxorubicin-induced p21 expression in p53-inactivated MCF7 cells. Likewise, in human wild-type p53- and p21-expressing HCT116 colon carcinoma cells, as well as in p53-null counterparts, down-regulation of SphK2 markedly reduced p21 induction by doxorubicin. Knockdown of SphK2 sensitized HCT116 cells to apoptosis induced by doxorubicin with concomitant cleavage of poly(ADP-ribose) polymerase. Collectively, our results show that endogenous SphK2 is important for p53-independent induction of p21 expression by doxorubicin and suggest that SphK2 may influence the balance between cytostasis and apoptosis of human cancer cells. [Cancer Res 2007;67(21):10466–74]