sphingosine-1-phosphate and Hypoxia

Hypoxia, or lack of oxygen, can occur in both physiological (high altitude) and pathological conditions (respiratory diseases). In this narrative review, we introduce high altitude pulmonary edema (HAPE), acute respiratory distress syndrome (ARDS), Chronic Obstructive Pulmonary Disease (COPD), and Cystic Fibrosis (CF) as examples of maladaptation to hypoxia, and highlight some of the potential mechanisms influencing the prognosis of the affected patients. Among the specific pathways modulated in response to hypoxia, iron metabolism has been widely explored in recent years. Recent evidence emphasizes hepcidin as highly involved in the compensatory response to hypoxia in healthy subjects. A less investigated field in the adaptation to hypoxia is the sphingolipid (SPL) metabolism, especially through Ceramide and sphingosine 1 phosphate. Both individually and in concert, iron and SPL are active players of the (mal)adaptation to physiological hypoxia, which can result in the pathological HAPE. Our aim is to identify some pathways and/or markers involved in the physiological adaptation to low atmospheric pressures (high altitudes) that could be involved in pathological adaptation to hypoxia as it occurs in pulmonary inflammatory diseases. Hepcidin, Cer, S1P, and their interplay in hypoxia are raising growing interest both as prognostic factors and therapeutical targets.

Topics: Adaptation, Physiological; Altitude Sickness; Ceramides; Cystic Fibrosis; Hepcidins; Humans; Hypertension, Pulmonary; Hypoxia; Iron; Lysophospholipids; Pulmonary Disease, Chronic Obstructive; Respiratory Distress Syndrome; Sphingolipids; Sphingosine

Hypoxia, defined as a poor oxygenation, has been long recognized as a hallmark of solid tumors and a negative prognostic factor for response to therapeutics and survival of patients. Cancer cells have evolved biochemical mechanisms that allow them to react and adapt to hypoxia. At the cellular level, this adaptation is under the control of two related transcription factors, HIF-1 and HIF-2 (hypoxia-inducible factor), that respond rapidly to decreased oxygen levels to activate the expression of a broad range of genes promoting neoangiogenesis, glycolysis, metastasis, increased tumor growth, and resistance to treatments. Recent studies have identified the sphingosine kinase 1/sphingosine 1-phosphate (SphK1/S1P) signaling pathway-which elicits various cellular processes including cell proliferation, cell survival, or angiogenesis-as a new regulator of HIF-1 or HIF-2 activity. In this review, we will focus on how the inhibition/neutralization of the SphK1/S1P signaling could be exploited for cancer therapy.

Topics: Animals; Antineoplastic Agents; Drug Resistance, Neoplasm; Humans; Hypoxia; Lysophospholipids; Neoplasms; Neovascularization, Pathologic; Phosphotransferases (Alcohol Group Acceptor); Signal Transduction; Sphingosine

Sphingosine 1-phosphate (S1P) is a bioactive lipid that is produced by the sphingosine kinase-catalysed phosphorylation of sphingosine. S1P is an important regulator of cell function, mediating many of its effects through a family of five closely related G protein-coupled receptors (GPCR) termed S1P(1-5) which exhibit high affinity for S1P. These receptors function to relay the effects of extracellular S1P via well-defined signal transduction networks linked to the regulation of cell proliferation, survival, migration etc. Diverse agonists (e.g. cytokines) also activate sphingosine kinase and the resulting S1P formed may bind to specific undefined intracellular targets to elicit cellular responses. The purpose of this review is to discuss some of the spatial/temporal aspects of intracellular S1P signalling and to define the function of sphingosine kinases and lipid phosphate phosphatases (which catalyse dephosphorylation of S1P) in terms of their regulation of cell function. Finally, we survey the function of S1P in relation to disease, where the major challenge is to dissect the role of intracellular versus extracellular actions of S1P in terms of association with defined diseased phenotypes.

Topics: Cell Differentiation; Cell Division; Cell Movement; Hypoxia; Lysophospholipids; Neoplasms; Phosphatidate Phosphatase; Phosphotransferases (Alcohol Group Acceptor); Receptors, G-Protein-Coupled; Receptors, Lysosphingolipid; Signal Transduction; Sphingosine

Blood storage promotes the rapid depletion of red blood cell (RBC) high-energy adenosine triphosphate (ATP) and 2,3-diphosphoglycerate (DPG), which are critical regulators of erythrocyte physiology and function, as well as oxygen kinetics and posttransfusion survival. Sphingosine-1-phosphate (S1P) promotes fluxes through glycolysis. We hypothesized that S1P supplementation to stored RBC units would improve energy metabolism and posttransfusion recovery. We quantified S1P in 1929 samples (n = 643, storage days 10, 23, and 42) from the REDS RBC Omics study. We then supplemented human and murine RBCs from good storer (C57BL6/J) and poor storer strains (FVB) with S1P (1, 5, and 10 μM) before measurements of metabolism and posttransfusion recovery. Similar experiments were repeated for mice with genetic ablation of the S1P biosynthetic pathway (sphingosine kinase 1 [Sphk1] knockout [KO]). Sample analyses included metabolomics at steady state, tracing experiments with 1,2,3-13C3-glucose, proteomics, and analysis of end-of-storage posttransfusion recovery, under normoxic and hypoxic storage conditions. Storage promoted decreases in S1P levels, which were the highest in units donated by female or older donors. Supplementation of S1P to human and murine RBCs boosted the steady-state levels of glycolytic metabolites and glycolytic fluxes, ie the generation of ATP and DPG, at the expense of the pentose phosphate pathway. Lower posttransfusion recovery was observed upon S1P supplementation. All these phenomena were reversed in Sphk1 KO mice or with hypoxic storage. S1P is a positive regulator of energy metabolism and a negative regulator of antioxidant metabolism in stored RBCs, resulting in lower posttransfusion recoveries in murine models.

Topics: Animals; Erythrocyte Transfusion; Erythrocytes; Female; Humans; Hypoxia; Lysophospholipids; Mice; Mice, Knockout; Sphingosine

Studies have demonstrated that activated pancreatic stellate cells (PSCs) play a crucial role in pancreatic fibrogenesis in chronic pancreatitis (CP); however, the precise mechanism for PSCs activation has not been fully elucidated. We analyzed the role of injured pancreatic acinar cells (iPACs) in the activation of PSCs of CP.. Sphingosine kinase 1 (SPHK1)/sphingosine-1-phosphate (S1P) signaling was evaluated in experimental CP induced by cerulein injection or pancreatic duct ligation, as well as in PACs injured by cholecystokinin. The activation of PSCs and pancreatic fibrosis in CP samples was evaluated by immunohistochemical and immunofluorescence analyses. In vitro coculture assay of iPACs and PSCs was created to evaluate the effect of the SPHK1/S1P pathway and S1P receptor 2 (SIPR2) on autophagy and activation of PSCs. The pathogenesis of CP was assessed in SPHK1. The activated SPHK1/S1P pathway in iPACs induces autophagy and activation of PSCs by regulating the S1PR2/5' adenosine monophosphate-activated protein kinase/mammalian target of rapamycin pathway, which promotes fibrogenesis of CP. The hypoxia microenvironment might contribute to the cross talk between PACs and PSCs in pathogenesis of CP.

Topics: Acinar Cells; Adenosine Monophosphate; AMP-Activated Protein Kinases; Animals; Autophagy; Fibrosis; Hypoxia; Mammals; Mice; Pancreatic Stellate Cells; Pancreatitis, Chronic; Sphingosine-1-Phosphate Receptors

Hypoxia facilitates an aggressive phenotype and immune evasion in solid tumors including bladder cancer (BC). Sphingosine kinase 1 (SphK1) is aberrantly expressed and correlated with poor prognosis in BC patients. However, its roles in hypoxia-evoked malignancies and immune evasion in BC remain elusive.. The expression of SphK1 in BC tissues was analysed using a bioinformatics database. BC cells were transfected with si-SphK1 or recombinant HIF-1α plasmids under hypoxic conditions. The mRNA level, activity and protein expression of SphK1 were determined. Transwell assay was performed to evaluate cell invasion. After co-culture with natural killer (NK) cells, NK cell cytotoxicity to BC cells was assessed. The involvement of sphingosine-1-phosphate (S1P)/HIF-1α signaling was analysed by ELISA, qRT-PCR and western blot.. UALCAN and GEPIA database confirmed high expression of SphK1 in BC tissues. Moreover, hypoxia increased the expression and activity of SphK1. Loss of SphK1 inhibited hypoxia-induced cell invasion. IL-2 induced NK cell activation by secreting TNF-α and IFN-γ. Hypoxia antagonized NK cell activation-evoked cytotoxicity to BC cells. Intriguingly, SphK1 knockdown reversed hypoxia-induced cell resistance to NK cell killing. Mechanically, SphK1 loss inhibited hypoxia-activated the S1P/HIF-1α signaling. However, S1P addition reversed the inhibitory effects of SphK1 down-regulation on hypoxia-activated S1P/HIF-1α signaling. Notably, reactivating HIF-1α overturned the suppressive roles of SphK1 loss in decreasing hypoxia-induced cell invasion and resistance to NK cell cytotoxicity.. Targeting SphK1 may inhibit hypoxia-evoked invasion and immune evasion via the S1P/HIF-1α signaling, indicating a promising therapeutic target for BC.

Topics: Carcinoma; Cell Death; Humans; Hypoxia; Interleukin-2; Killer Cells, Natural; Oncogenes; Phosphotransferases (Alcohol Group Acceptor); RNA, Messenger; Tumor Necrosis Factor-alpha; Urinary Bladder; Urinary Bladder Neoplasms

We have previously reported that the long-term exposure of Isocarbophos, a kind of organophosphorus compounds, induces vascular dementia (VD) in rats. Studies have also shown that organophosphorus compounds have adverse effects on offsprings. Vitamin B6 is a coenzyme mainly involved in the regulation of metabolism and has been demonstrated to ameliorate VD. Sphingosine-1-phosphate (S1P), a biologically active lipid, plays a vital role in the cardiovascular system. However, whether S1P is involved in the therapeutic effects of Vitamin B6 on posterior cerebral artery injury has yet to be further answered. In the present study, we aimed to explore the potential influence of Vitamin B6 on Isocarbophos-induced posterior cerebral artery injury in offspring rats and the role of the S1P receptor in this process. We found that Vitamin B6 significantly improves the vasoconstriction function of the posterior cerebral artery in rats induced by Isocarbophos by the blood gas analysis and endothelium-dependent relaxation function assay. We further demonstrated that Vitamin B6 alleviates the Isocarbophos-induced elevation of ICAM-1, VCAM-1, IL-1, and IL-6 by using the enzyme-linked immunosorbent assay kits. By performing immunofluorescence and the western blot assay, we revealed that Vitamin B6 prevents the down-regulation of S1P in posterior cerebral artery injury. It is worth noting that Fingolimod, the S1P inhibitor, significantly inhibits the Vitamin B6-induced up-regulation of S1P in posterior cerebral artery injury. Collectively, our data indicate that Vitamin B6 may be a novel drug for the treatment of posterior cerebral artery injury and that S1P may be a drug target for its treatment.

Topics: Acid-Base Equilibrium; Animals; Apoptosis; Caspase 3; Cerebral Arterial Diseases; Cytokines; Disease Models, Animal; Female; Hypoxia; Insecticides; Lysophospholipids; Malathion; Male; Malondialdehyde; Maternal Exposure; Nitric Oxide; Paternal Exposure; Posterior Cerebral Artery; Protective Agents; Rats, Sprague-Dawley; Sphingosine; Sphingosine-1-Phosphate Receptors; Superoxide Dismutase; Up-Regulation; Vasoconstriction; Vitamin B 6

Sphingosine-1-phosphate (S1P) is emerging as a hypoxia responsive bio-lipid; systemically raised levels of S1P are proposed to have potential hypoxia pre-conditioning effects. The study aims to evaluate the hypoxia pre-conditioning efficacy of exogenously administered S1P in rats exposed to acute (24-48 hs (h)) and sub-chronic (7 days) hypobaric hypoxia. Sprague-Dawley rats (200 ± 20 g) were preconditioned with 1 μg/kg body weight S1P intravenously for three consecutive days. On the third day, control and S1P preconditioned animals were exposed to hypobaric hypoxia equivalent to 7620 m for 24 h, 48 h and 7 days. Post exposure analysis included body weight quantitation, blood gas/chemistry analysis, vascular permeability assays, evaluation of oxidative stress/inflammation parameters, and estimation of hypoxia responsive molecules. S1P preconditioned rats exposed to acute HH display a significant reduction in body weight loss, as a culmination of improved oxygen carrying capacity, increased 2,3- diphosphoglycerate levels and recuperation from energy deficit. Pathological disturbances such as vascular leakage in the lungs and brain, oxidative stress, pro-inflammatory milieu and raised level of endothelin-1 were also reined. The adaptive and protective advantage conferred by S1P in the acute phase of hypobaric hypoxia exposure, is observed to precipitate into an improved sustenance even after sub-chronic (7d) hypobaric hypoxia exposure as indicated by decreased body weight loss, lower edema index and improvement in general pathology biomarkers. Conclusively, administration of 1 μg/kg body weight S1P, in the aforementioned schedule, confer hypoxia pre-conditioning benefits, sustained up to 7 days of hypobaric hypoxia exposure.

Topics: 2,3-Diphosphoglycerate; Administration, Intravenous; Animals; Biomarkers; Body Weight; Brain; Capillary Permeability; Cytokines; Hypoxia; Inflammation; Lung; Lysophospholipids; Oxidative Stress; Oxygen; Rats; Rats, Sprague-Dawley; Sphingosine; Tissue Distribution

Topics: Erythrocytes; Humans; Hypoxia; Lysophospholipids; Renal Insufficiency, Chronic; Sphingosine

Our previous study showed that Sphingosine-1-phosphate (S1P) could protect cardiomyocytes against hypoxia/reoxygenation (H/R) injury via the JAK-STAT pathway and maintain normal myocardial mitochondria integrity in vivo. However, it is not known yet whether S1P can relieve mitochondrial dysfunction via the mitochondrial apoptotic pathway and its detailed mechanism remains to be investigated. The aim of this study was to demonstrate the mitochondrial protective effects of S1P in a cardiomyocyte H/R injury model. In the present study, we established a H/R model in H9c2 cells. Cell viability was determined by the MTT assay, and apoptosis was evaluated by annexin V-FITC/PI staining. Mitochondrial calcium ion concentration, mitochondrial membrane potential (ΔΨm), opening of the mitochondrial permeability transition pore (mPTP), and release of cytochrome C were detected by laser confocal microscopy. The results showed that S1P inhibited the decrease in cell viability induced by H/R injury and reduced apoptosis. Confocal microscopy showed that S1P prevented loss of ΔΨm, relieved mitochondrial calcium overload, and inhibited opening of the mPTP and release of cytochrome C. The STAT3 inhibitor STATTIC can reverse the antiapoptotic effects of S1P and block the effect of S1P on mitochondria. Taken together, our results indicate that S1P protects cardiomyocytes against H/R injury by relieving mitochondrial dysfunction via the STAT3 pathway.

Topics: Animals; Cell Line; Cell Survival; Hypoxia; Lysophospholipids; Mitochondria, Heart; Myocytes, Cardiac; Oxygen; Protective Agents; Rats; Sphingosine; STAT3 Transcription Factor

Topics: Apoptosis; bcl-2-Associated X Protein; Cytochromes c; Human Umbilical Vein Endothelial Cells; Humans; Hypoxia; Inflammation; Lysophospholipids; Reactive Oxygen Species; Sphingosine

Sphingosine-1-phosphate (S1P) has a role in transpiration in patho-physiological signaling in skeletal muscles. The present study evaluated the pre-conditioning efficacy of S1P in facilitating differentiation of C2C12 myoblasts under a normoxic/hypoxic cell culture environment. Under normoxia, exogenous S1P significantly promoted C2C12 differentiation as evident from morphometric descriptors and differentiation markers of the mature myotubes, but it could facilitate only partial recovery from hypoxia-induced compromised differentiation. Pretreatment of S1P optimized the myokine secretion, intracellular calcium release and energy generation by boosting the aerobic/anaerobic metabolism and mitochondrial mass. In the hypoxia-exposed cells, there was derangement of the S1PR

Topics: Animals; Biomarkers; Calcium; Cell Differentiation; Cell Line; Cell Survival; Energy Metabolism; Homeostasis; Hypoxia; Lysophospholipids; Metabolic Diseases; Mice; Muscle Development; Muscle Fibers, Skeletal; Muscle, Skeletal; Myoblasts; Signal Transduction; Sphingosine

Sphingosine-1-phosphate (S1P) is emerging to have hypoxic preconditioning potential in various preclinical studies. The study aims to evaluate the preclinical preconditioning efficacy of exogenously administered S1P against acute hypobaric hypoxia (HH)-induced pathological disturbances. Male Sprague Dawley rats (200 ± 20 g) were preconditioned with 1, 10, and 100 μg/kg body weight (b.w.) S1P (i.v.) for three consecutive days. On the third day, S1P preconditioned animals, along with hypoxia control animals, were exposed to HH equivalent to 7,620 m (280 mm Hg) for 6 h. Postexposure status of cardiac energy production, circulatory vasoactive mediators, pulmonary and cerebral oxidative damage, and inflammation were assessed. HH exposure led to cardiac energy deficit indicated by low ATP levels and pronounced AMPK activation levels, raised circulatory levels of brain natriuretic peptide and endothelin-1 with respect to total nitrate (NOx), redox imbalance, inflammation, and alterations in NOx levels in the pulmonary and cerebral tissues. These pathological precursors have been routinely reported to be coincident with high-altitude diseases. Preconditioning with S1P, especially 1 µg/kg b.w. dose, was seen to reverse the manifestation of these pathological disturbances. The protective efficacy could be attributed, at least in part, to enhanced activity of cardioprotective protein kinase C and activation of small GTPase Rac1, which led to further induction of hypoxia-adaptive molecular mediators: hypoxia-inducible factor (HIF)-1α and Hsp70. This is a first such report, to the best of our knowledge, elucidating the mechanism of exogenous S1P-mediated HIF-1α/Hsp70 induction. Conclusively, systemic preconditioning with 1 μg/kg b.w. S1P in rats protects against acute HH-induced pathological disturbances. © 2016 IUBMB Life 68(5):365-375, 2016.

Topics: Animals; Cytokines; Drug Evaluation, Preclinical; Endothelin-1; Energy Metabolism; HSP70 Heat-Shock Proteins; Hypoxia; Hypoxia-Inducible Factor 1, alpha Subunit; Lysophospholipids; Male; Myocardium; Natriuretic Peptide, Brain; Nitric Oxide; Oxidation-Reduction; Oxidative Stress; Protein Stability; rac1 GTP-Binding Protein; Rats, Sprague-Dawley; Sphingosine

Our group has recently reported that in the immortal human HepG2 liver cell line, sphingosine 1‑phosphate (S1P) increases transcription of plasminogen activator inhibitor type‑1 (PAI‑1), the major physiological inhibitor of fibrinolysis, within 4 h. The present study aimed to elucidate the molecular mechanisms underlying this effect. PAI‑1 expression was measured by reverse transcription‑quantitative polymerase chain reaction and immunoblotting. It was demonstrated that S1P increased PAI‑1 promoter activity but did not increase the activity of promoters lacking the hypoxia responsive element (HRE) 2. In addition, S1P transiently increased the concentration of hypoxia inducible factor (HIF)‑1α, a transcription factor capable of binding to HRE. When HIF‑1α was knocked down, the induction of transcription of PAI‑1 by S1P was no longer observed. Sphingosine kinase (SPHK) activity is increased by hypoxia. It was demonstrated that increases in the concentration of the HIF‑1α protein induced by hypoxia were prevented by treatment with SPHK inhibitor or S1P receptor antagonists. Thus, modification of the induction of HIF‑1α by S1P, leading to increased transcription of PAI‑1, may be an attractive therapeutic target for thrombosis and consequent inhibition of fibrinolysis associated with hypoxia.

Topics: Autocrine Communication; Gene Expression Regulation, Neoplastic; Hep G2 Cells; Humans; Hypoxia; Hypoxia-Inducible Factor 1, alpha Subunit; Lysophospholipids; Paracrine Communication; Plasminogen Activator Inhibitor 1; Promoter Regions, Genetic; Receptor, ErbB-2; Sphingosine; Transcriptional Activation

Sphingosine-1-phosphate (S1P) is a bioactive signalling lipid highly enriched in mature erythrocytes, with unknown functions pertaining to erythrocyte physiology. Here by employing nonbiased high-throughput metabolomic profiling, we show that erythrocyte S1P levels rapidly increase in 21 healthy lowland volunteers at 5,260 m altitude on day 1 and continue increasing to 16 days with concurrently elevated erythrocyte sphingonisne kinase 1 (Sphk1) activity and haemoglobin (Hb) oxygen (O2) release capacity. Mouse genetic studies show that elevated erythrocyte Sphk1-induced S1P protects against tissue hypoxia by inducing O2 release. Mechanistically, we show that intracellular S1P promotes deoxygenated Hb anchoring to the membrane, enhances the release of membrane-bound glycolytic enzymes to the cytosol, induces glycolysis and thus the production of 2,3-bisphosphoglycerate (2,3-BPG), an erythrocyte-specific glycolytic intermediate, which facilitates O2 release. Altogether, we reveal S1P as an intracellular hypoxia-responsive biolipid promoting erythrocyte glycolysis, O2 delivery and thus new therapeutic opportunities to counteract tissue hypoxia.

Topics: 2,3-Diphosphoglycerate; Adaptation, Physiological; Adult; Altitude Sickness; Animals; Erythrocytes; Female; Glyceraldehyde-3-Phosphate Dehydrogenase (Phosphorylating); Glycolysis; Humans; Hypoxia; Lysophospholipids; Male; Mice, Inbred C57BL; Mice, Mutant Strains; Oxygen; Phosphotransferases (Alcohol Group Acceptor); Sphingosine

Clear cell renal cell carcinoma (ccRCC) is characterized by intratumoral hypoxia and chemoresistance. The hypoxia-inducible factors HIF1α and HIF2α play a crucial role in ccRCC initiation and progression. We previously identified the sphingosine kinase 1/sphingosine 1-phosphate (SphK1/S1P) pathway as a new modulator of HIF1α and HIF2α under hypoxia in various cancer cell models. Here, we report that FTY720, an inhibitor of the S1P signaling pathway, inhibits both HIF1α and HIF2α accumulation in several human cancer cell lines. In a ccRCC heterotopic xenograft model, we show that FTY720 transiently decreases HIF1α and HIF2α intratumoral level and modifies tumor vessel architecture within 5 days of treatment, suggesting a vascular normalization. In mice bearing subcutaneous ccRCC tumor, FTY720 and a gemcitabine-based chemotherapy alone display a limited effect, whereas, in combination, there is a significant effect on tumor size without toxicity. Noteworthy, administration of FTY720 for 5 days before chemotherapy is not associated with a more effective tumor control, suggesting a mode of action mainly independent of the vascular remodeling. In conclusion, these findings demonstrate that FTY720 could successfully sensitize ccRCC to chemotherapy and establish this molecule as a potent therapeutic agent for ccRCC treatment, independently of drug scheduling. Mol Cancer Ther; 15(10); 2465-74. ©2016 AACR.

Topics: Animals; Antineoplastic Agents; Apoptosis; Basic Helix-Loop-Helix Transcription Factors; Carcinoma, Renal Cell; Cell Line, Tumor; Cell Proliferation; Disease Models, Animal; Drug Resistance, Neoplasm; Female; Fingolimod Hydrochloride; Gene Expression; Humans; Hypoxia; Hypoxia-Inducible Factor 1, alpha Subunit; Lysophospholipids; Mice; Neovascularization, Pathologic; Oxygen Consumption; Phosphotransferases (Alcohol Group Acceptor); Receptors, Lysosphingolipid; Signal Transduction; Sphingosine; Vascular Endothelial Growth Factor A; Vascular Remodeling; Xenograft Model Antitumor Assays

Recent preclinical and clinical studies have unfolded the potential of pharmacological modulation of activities of sphingosine-1-phosphate (S1P) receptors and S1P metabolizing enzymes for the development of therapeutic interventions against a variety of pathologies. An understanding of differential and temporal effects of hypoxia exposure on the key components of S1P signalling would certainly aid in designing improved drug development strategies in this direction. In view of this, the aim of the present study was to assess the effect of progressive hypobaric hypoxia exposure on expression of S1P receptors (S1PR1-5) and specific activities of S1P synthesizing enzymes--neutral sphingomyelinase (nSMase) and sphingosine kinase (Sphk) in pulmonary and cerebral tissues of rats exposed to simulated altitude of 21,000 feet in an animal decompression chamber. Along with this, development of cerebral and pulmonary edema and markers of inflammation were studied at 12, 24, and 48 h to validate our study model of hypobaric hypoxia-induced stress. The protein expression of S1PR1-5 and activities of Sphk and nSMase enzymes were observed to be dramatically affected by simulated hypobaric hypoxia exposure, concurrent with deterioration of pathology, with 12 h of exposure appearing to be the most critical of the various time points studied.

Topics: Animals; Brain; Capillary Permeability; Cytokines; Hypoxia; Lung; Lysophospholipids; Phosphotransferases (Alcohol Group Acceptor); Rats; Rats, Sprague-Dawley; Receptors, Lysosphingolipid; Signal Transduction; Sphingomyelin Phosphodiesterase; Sphingosine; Sphingosine-1-Phosphate Receptors

Topics: Antibodies; Humans; Hypoxia; Lysophospholipids; Neoplasms; Neovascularization, Pathologic; Sphingosine; Tumor Microenvironment

Sphingosine-1-phosphate (S1P), a biologically active pleiotropic lipid, is involved in several physiological processes especially in the area of vascular biology and immunology encompassing cell survival, angiogenesis, vascular tone, immune response etc. by interacting with specific cell surface receptors. Hypoxia, a condition common to innumerable pathologies, is known to lethally affect cell survival by throwing off balance global gene expression, redox homeostasis, bioenergetics etc. Several molecular events of cellular adaptations to hypoxia have been closely linked to stabilization of hypoxia inducible factor-1α (HIF-1α). Signalling functions of S1P in physiological events central to hypoxia-induced pathologies led us to investigate efficacy of exogenous S1P in preconditioning murine splenocytes to sustain during cellular stress associated with sub-optimal oxygen. The present study recapitulated the pro-survival benefits of exogenous S1P under normobaric hypoxia. Results indicate a direct effect of S1P supplementation on boosting cellular adaptive responses via HIF-1α stabilization and, activation of pro-survival mediators ERK and Akt. Overwhelming anti-oxidative and anti-inflammatory benefits of S1P preconditioning could also be captured in the present study, as indicated by improved redox homeostasis, reduced oxidative damage, balanced anti/pro-inflammatory cytokine profiles and temporal regulation of nitric oxide secretion and intra-cellular calcium release. Hypoxia induced cell death and the associated stress in cellular milieu in terms of oxidative damage and inflammation could be alleviated with exogenous S1P preconditioning.

Topics: Animals; Anti-Inflammatory Agents; Antioxidants; Cell Survival; Cells, Cultured; Cytokines; Hypoxia; Hypoxia-Inducible Factor 1, alpha Subunit; Lysophospholipids; MAP Kinase Signaling System; Mice; Mice, Inbred BALB C; Oxidative Stress; Proto-Oncogene Proteins c-akt; Sphingosine; Spleen

The physiological challenges posed by hypobaric hypoxia warrant exploration of pharmacological entities to improve acclimatization to hypoxia. The present study investigates the preclinical efficacy of sphingosine-1-phosphate (S1P) to improve acclimatization to simulated hypobaric hypoxia.. Efficacy of intravenously administered S1P in improving haematological and metabolic acclimatization was evaluated in rats exposed to simulated acute hypobaric hypoxia (7620 m for 6 hours) following S1P pre-treatment for three days.. Altitude exposure of the control rats caused systemic hypoxia, hypocapnia (plausible sign of hyperventilation) and respiratory alkalosis due to suboptimal renal compensation indicated by an overt alkaline pH of the mixed venous blood. This was associated with pronounced energy deficit in the hepatic tissue along with systemic oxidative stress and inflammation. S1P pre-treatment improved blood oxygen-carrying-capacity by increasing haemoglobin, haematocrit, and RBC count, probably as an outcome of hypoxia inducible factor-1α mediated erythropoiesis and renal S1P receptor 1 mediated haemoconcentation. The improved partial pressure of oxygen in the blood could further restore aerobic respiration and increase ATP content in the hepatic tissue of S1P treated animals. S1P could also protect the animals from hypoxia mediated oxidative stress and inflammation.. The study findings highlight S1P's merits as a preconditioning agent for improving acclimatization to acute hypobaric hypoxia exposure. The results may have long term clinical application for improving physiological acclimatization of subjects venturing into high altitude for occupational or recreational purposes.

Topics: Acclimatization; Animals; Biomarkers; Electrolytes; Energy Metabolism; Gene Expression Regulation; Hypoxia; Hypoxia-Inducible Factor 1, alpha Subunit; Inflammation; Inflammation Mediators; Kidney; Lactates; Lysophospholipids; Oxidative Stress; Oxygen; Rats, Sprague-Dawley; Receptors, Lysosphingolipid; Sphingosine

Metabolism of sphingolipids into downstream lipid mediators followed by signaling modulates tumor microenvironment and the cancer cells to influence tumor progression. As such, sphingolipid signaling represents a novel way to modulate tumor biology. Neuroblastoma (NB), the most common extracranial solid tumor of childhood, is highly angiogenic and often displays poor prognosis. However, the role of sphingolipid mediators is not known in NB. We found that NB expresses high levels of sphingosine kinase-2, which is essential for the formation of sphingosine-1-phosphate (S1P). S1P induced VEGF expression in SK-N-AS NB cells. The effect occurred at the transcriptional level. Hypoxia in combination with S1P had a synergistic effect on VEGF expression. Strong correlation was detected between S1P receptor-2 (S1P(2)) and VEGF mRNAs in 11 different cell lines and 17 NB tissues. Blockade of S1P(2) with the selective antagonist JTE-013 significantly inhibited S1P-induced VEGF expression. Overexpression and knockdown of S1P(2) in SK-N-AS cells increased or inhibited S1P-induced VEGF secretion, respectively. Interestingly, JTE-013 significantly inhibited tumor growth, VEGF mRNA expression, and induced apoptosis in the NB tumor xenografts. Taken together, our data suggest that enhanced formation of sphingolipid mediator S1P in NB profoundly influences tumor microenvironment by inducing VEGF expression via S1P(2). Modulation of sphingolipid signaling by inhibiting S1P(2) may constitute a novel strategy to control NB.

Topics: Angiogenesis Inducing Agents; Animals; Brain Neoplasms; Cell Line, Tumor; Enzyme-Linked Immunosorbent Assay; Gene Expression Regulation, Neoplastic; Humans; Hypoxia; In Situ Nick-End Labeling; Lysophospholipids; Male; Mice; Mice, Nude; Neuroblastoma; Phosphotransferases (Alcohol Group Acceptor); Platelet Endothelial Cell Adhesion Molecule-1; Sphingolipids; Sphingosine; Vascular Endothelial Growth Factor A