sphingosine-1-phosphate and Myocardial-Ischemia

The bioactive lysophospholipids, lysophosphatidic acid (LPA) and sphingosine 1 phosphate (S1P), have potent effects on blood and vascular cells. This review focuses their potential contributions to the development of atherosclerosis, acute complications such as acute myocardial infarction, and chronic ischemic cardiac damage.. Exciting recent developments have provided insight into the molecular underpinnings of LPA and S1P receptor signaling. New lines of evidence suggest roles for these pathways in the development of atherosclerosis. In experimental animal models, the production, signaling, and metabolism of LPA may be influenced by environmental factors in the diet that synergize to promote the progression of atherosclerotic vascular disease. This is supported by observations of human polymorphisms in the lysophospholipid-metabolizing enzyme PPAP2B, which are associated with risk of coronary artery disease and myocardial infarction. S1P signaling protects from myocardial damage that follows acute and chronic ischemia, both by direct effects on cardiomyocytes and through stem cell recruitment to ischemic tissue.. This review will suggest novel strategies to prevent the complications of coronary artery disease by targeting LPA production and signaling. Additionally, ways in which S1P signaling pathways may be harnessed to attenuate ischemia-induced cardiac dysfunction will be explored.

Topics: Animals; Atherosclerosis; Coronary Artery Disease; Humans; Lysophospholipids; Myocardial Ischemia; Signal Transduction; Sphingosine

Increasing evidence suggests that High-density lipoproteins (HDL) are a direct cardioprotective agent in the setting of acute myocardial ischemia/reperfusion injury, and that this cardioprotection occurs independently of their atheroprotective effect. Studies on the involved mechanisms have revealed that the biologically active HDL-compound sphingosine-1-phosphate (S1P) is responsible for the beneficial effect of HDL on the myocardium. There appears to be an intricate interplay between known preconditioning agents and components of the S1P synthesis machinery in the heart, which makes S1P signalling an attractive downstream convergence point of preconditioning and cardioprotection at the level of its G protein-coupled receptors. While local S1P production has been known to protect the heart against ischemia/reperfusion injury and to mediate preconditioning, systemic S1P supply via HDL adds a novel aspect to the regulation of cardioprotection. Thus the S1P-content of HDL may serve both as a potential cardiovascular risk marker and a novel therapeutic target. Strategies for short-term "acute" HDL elevation as well as S1P analogues may prove beneficial not only in the high-risk patient but also in any patient at risk of myocardial ischemia.

Topics: Acute Disease; Cardiovascular Diseases; Creatine Kinase; Humans; Ischemic Preconditioning, Myocardial; Lipoproteins, HDL; Lysophospholipids; Myocardial Ischemia; Myocardial Reperfusion; Myocardium; Phosphotransferases (Alcohol Group Acceptor); Risk Factors; Signal Transduction; Sphingosine

The sphingolipid metabolite sphingosine 1‑phosphate (S1P) has emerged as a potential cardioprotective molecule against ischemic heart disease. Moreover, S1P triggers mobilization and homing of bone marrow-derived stem/progenitor cells into the damaged heart. However, it remains elusive whether S1P promotes mesenchymal stem cells (MSCs)-mediated cardioprotection against ischemic heart diseases.. Adipose tissue-derived MSCs (AT-MSCs) were obtained from GFP transgenic mice or C57BL/6J. Myocardial infarction (MI) was induced in C57BL/6J mice by ligation of the left anterior descending coronary artery (LAD). Subsequently, S1P-treated AT-MSCs or vehicle-treated AT-MSCs were intravenously administered for 24 h after induction of MI or sham procedure.. Pre-conditioning with S1P significantly enhanced the migratory and anti-apoptotic efficacies of AT-MSCs. In MI-induced mice, intravenous administration of S1P-treated AT-MSCs significantly augmented their homing and engraftment in ischemic area. Besides, AT-MSCs with S1P pre-treatment exhibited enhanced potencies to inhibit cardiomyocyte apoptosis and fibrosis, and stimulate angiogenesis and preserve cardiac function. Mechanistic studies revealed that S1P promoted AT-MSCs migration through activation of ERK1/2-MMP-9, and protected AT-MSCs against apoptosis via Akt activation. Further, S1P activated the ERK1/2 and Akt via S1P receptor 2 (S1PR2), but not through S1PR1. S1PR2 knockdown by siRNA, however, significantly attenuated S1P-mediated AT-MSCs migration and anti-apoptosis.. The findings of the present study revealed the protective efficacies of S1P pretreatment on the survival/retention and cardioprotection of engrafted MSCs. Pre-conditioning of donor MSCs with S1P is an effective strategy to promote the therapeutic potential of MSCs for ischemic heart diseases.

Topics: Adipose Tissue; Animals; Apoptosis; Disease Models, Animal; Lysophospholipids; Male; MAP Kinase Signaling System; Matrix Metalloproteinase 9; Mesenchymal Stem Cell Transplantation; Mesenchymal Stem Cells; Mice; Mice, Inbred C57BL; Mice, Transgenic; Myocardial Infarction; Myocardial Ischemia; Proto-Oncogene Proteins c-akt; Signal Transduction; Sphingosine

Sphingosine-1-Phosphate (S1P) is a bioactive sphingolipid with important functions in immunity, inflammation and cardiovascular biology. S1P is associated with prevalence and severity of coronary artery disease and myocardial infarction. However, its relevance in ischemic cardiomyopathy is unknown. We aimed to investigate associations of plasma S1P and other sphingolipids with the extent of heart failure in patients with ischemic heart disease.. 74 patients with ischemic heart disease were investigated in this observational study. Plasma concentrations of S1P, C16 ceramide and sphingomyelin (SM) were measured using liquid chromatography/tandem mass-spectrometry and associated with objective (echocardiography) and subjective (dyspnea) signs of heart failure. Plasma S1P and SM but not C16 ceramide concentrations were negatively associated with left ventricular ejection fraction (LVEF) and dyspnea (ranked by New York Heart Association; LVEF: S1P standardized coefficient beta: -0.25; 95%CI: -273 to -13nM, p=0.03; SM beta: -0.24; 95%CI: -16,310 to -413nM, p=0.04; NYHA: S1P beta: -0.3; 95%CI: -174 to -26nM, p=0.009; SM beta: -0.46; 95%CI: -13,462 to -5013nM, p<0.001). ROC analysis revealed that S1P and SM predicted impaired LVEF with optimal cut-off levels below 843nM and 77μM, respectively.. S1P is associated with the impairment of LVEF and dyspnea. Considering the major effects of S1P on cardiac and vascular functions in experimental models, we put forward the hypothesis that S1P is causally involved in the pathophysiology of heart failure. Interfering pharmacologically with S1P receptors may have an impact on ischemic cardiomyopathy.

Topics: Aged; Dyspnea; Female; Heart Failure, Systolic; Humans; Lysophospholipids; Male; Myocardial Ischemia; Sphingomyelins; Sphingosine; Stroke Volume

Obesity is associated with an increased risk of cardiovascular disease. C1q/TNF-related protein (CTRP)-1 is a poorly characterized adipokine that is up-regulated in association with ischemic heart disease. We investigated the role of CTRP1 in myocardial ischemia injury. CTRP1-knockout mice showed increased myocardial infarct size, cardiomyocyte apoptosis, and proinflammatory gene expression after I/R compared with wild-type (WT) mice. In contrast, systemic delivery of CTRP1 attenuated myocardial damage after I/R in WT mice. Treatment of cardiomyocytes with CTRP1 led to reduction of hypoxia-reoxygenation-induced apoptosis and lipopolysaccharide-stimulated expression of proinflammatory cytokines, which was reversed by inhibition of sphingosine-1-phosphate (S1P) signaling. Treatment of cardiomyocytes with CTRP1 also resulted in the increased production of cAMP, which was blocked by suppression of S1P signaling. The antiapoptotic and anti-inflammatory actions of CTRP1 were cancelled by inhibition of adenylyl cyclase or knockdown of adiponectin receptor 1. Furthermore, blockade of S1P signaling reversed CTRP1-mediated inhibition of myocardial infarct size, apoptosis, and inflammation after I/R in vivo. These data indicate that CTRP1 protects against myocardial ischemic injury by reducing apoptosis and inflammatory response through activation of the S1P/cAMP signaling pathways in cardiomyocytes, suggesting that CTRP1 plays a crucial role in the pathogenesis of ischemic heart disease.

Topics: Adipokines; Animals; Apoptosis; Cyclic AMP; Cytokines; Disease Models, Animal; Heart; Inflammation; Lysophospholipids; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Myocardial Infarction; Myocardial Ischemia; Myocardial Reperfusion Injury; Myocardium; Myocytes, Cardiac; Protective Agents; Signal Transduction; Sphingosine

Increasing evidence points to lipoprotein composition rather than reverse cholesterol transport in the cardioprotective properties of high-density lipoproteins (HDLs). HDL binding to receptors at the surface of cardiomyocytes activates signalling pathways promoting survival, but downstream targets are largely unknown. Here, we investigate the pathways by which the sphingosine-1-phosphate (S1P) constituent of HDL limits cell death induced by cardiac ischaemia-reperfusion (I/R).. Apolipoprotein M (ApoM) transgenic (Apom-Tg) mice, in which plasma S1P is increased by 296%, and wild-type (WT) mice were subjected to in vivo I/R. Infarct size, neutrophil infiltration into the infarcted area, and serum Troponin I were less pronounced in Apom-Tg mice. In vitro experiments suggest that this cardioprotection depends on direct effects of S1P on cardiomyocytes, whereas leucocyte recruitment seems only indirectly affected. Importantly, short-term S1P treatment at the onset of reperfusion was sufficient to reduce I/R injury in isolated perfused hearts. Mechanistic in vitro and ex vivo studies revealed that 5 min of S1P treatment induced phosphorylation of the gap junction protein Connexin43 (Cx43) on Serine368 (S368), which was mediated by S1P2 and S1P3, but not by S1P1, receptors in cardiomyocytes. Finally, S1P-induced reduction of infarct size after ex vivo I/R was lost in hearts of mice with a truncated C-terminus of Cx43 (Cx43(K258/KO)) or in which the S368 is mutated to a non-phosphorylatable alanine (Cx43(S368A/S368A)).. Our study reveals an important molecular pathway by which modulating the apoM/S1P axis has a therapeutic potential in the fight against I/R injury in the heart.

Topics: Animals; Apolipoproteins; Apolipoproteins M; Cardiotonic Agents; Connexin 43; Connexins; Lipoproteins, HDL; Lysophospholipids; Mice, Knockout; Myocardial Ischemia; Myocardial Reperfusion Injury; Myocytes, Cardiac; Phosphorylation; Receptors, Lysosphingolipid; Signal Transduction; Sphingosine

Abnormalities of glucose metabolism in patients with ischaemic heart disease (IHD) are common and are associated with a poor outcome in patients with and without diabetes. Sphingosine-1-phosphate (S1P) is a bioactive lipid which has been shown to increase insulin sensitivity in rodents and to increase myocardial tolerance to ischaemia. In the present review, I explore the relevance of S1P signalling pathway to IHD and abnormalities in glucose tolerance, and its potential as a therapeutic target for patients with abnormal glucose metabolism and IHD.

Topics: Animals; Blood Glucose; Glucose Tolerance Test; Humans; Insulin Resistance; Lysophospholipids; Myocardial Ischemia; Signal Transduction; Sphingosine

Activation of RhoA, a low molecular-weight G-protein, plays an important role in protecting the heart against ischemic stress. Studies using non-cardiac cells demonstrate that the expression and subsequent secretion of the matricellular protein CCN1 is induced by GPCR agonists that activate RhoA. In this study we determined whether and how CCN1 is induced by GPCR agonists in cardiomyocytes and examined the role of CCN1 in ischemic cardioprotection in cardiomyocytes and the isolated perfused heart. In neonatal rat ventricular myocytes (NRVMs), sphingosine 1-phosphate (S1P), lysophosphatidic acid (LPA) and endothelin-1 induced robust increases in CCN1 expression while phenylephrine, isoproterenol and carbachol had little or no effect. The ability of agonists to activate the small G-protein RhoA correlated with their ability to induce CCN1. CCN1 induction by S1P was blocked when RhoA function was inhibited with C3 exoenzyme or a pharmacological RhoA inhibitor. Conversely overexpression of RhoA was sufficient to induce CCN1 expression. To delineate the signals downstream of RhoA we tested the role of MRTF-A (MKL1), a co-activator of SRF, in S1P-mediated CCN1 expression. S1P increased the nuclear accumulation of MRTF-A and this was inhibited by the functional inactivation of RhoA. In addition, pharmacological inhibitors of MRTF-A or knockdown of MRTF-A significantly diminished S1P-mediated CCN1 expression, indicating a requirement for RhoA/MRTF-A signaling. We also present data indicating that CCN1 is secreted following agonist treatment and RhoA activation, and binds to cells where it can serve an autocrine function. To determine the functional significance of CCN1 expression and signaling, simulated ischemia/reperfusion (sI/R)-induced apoptosis was assessed in NRVMs. The ability of S1P to protect against sI/R was significantly reduced by the inhibition of RhoA, ROCK or MRTF-A or by CCN1 knockdown. We also demonstrate that ischemia/reperfusion induces CCN1 expression in the isolated perfused heart and that this functions as a cardioprotective mechanism, evidenced by the significant increase in infarct development in response to I/R in the cardiac specific CCN1 KO relative to control mice. Our findings implicate CCN1 as a mediator of cardioprotection induced by GPCR agonists that activate RhoA/MRTF-A signaling.

Topics: Animals; Animals, Newborn; Cardiotonic Agents; Cell Membrane; Cell Nucleus; Cysteine-Rich Protein 61; Heart Ventricles; In Vitro Techniques; Lysophospholipids; Mice, Knockout; Models, Biological; Myocardial Ischemia; Myocytes, Cardiac; Protein Binding; Rats; Rats, Sprague-Dawley; Receptors, G-Protein-Coupled; Reperfusion Injury; rhoA GTP-Binding Protein; RNA, Small Interfering; Sphingosine; Transcription Factors

Ophiopogon japonicus is a traditional Chinese medicine used to treat cardiovascular disease. Recent studies have confirmed the anti-ischemic properties of a water-soluble β-D-fructan (MDG-1) from O. japonicus. The sphingosine 1-phosphate (S1P) signaling pathway is involved in its cytoprotective effects. Herein, we explore the role of the S1P signaling pathway in the anti-ischemic effect of MDG-1 and assess one possible mechanism by which it induces S1P release and sphingosine 1-phosphate receptor 1 (S1P(1)) expression in human microvascular endothelial cells (HMEC-1) and cardiomyocytes. Our evidence demonstrates that MDG-1 promotes sphingosine kinase (SPHK) activity in HMEC-1 cells. An analytical method for measuring the mass of S1P using ESI/MS/MS was developed and we found that MDG-1 increases intracellular S1P levels. Meanwhile, MDG-1 is protective during hypoxia and ischemia through mechanisms that require S1P(1) receptor activation, which was confirmed both in oxygen glucose deprivation (OGD) and coronary artery ligation models by using transfection of cloned human S1P(1) receptor and RNA interference. These data indicate that the increase of intracellular S1P generation, particularly by activation of the SPHK enzyme, coupled with the autocrine and paracrine stimulation of cell surface S1P receptors, is a potential mechanism in the anti-ischemic and cell protective effect of MDG-1.

Topics: Animals; Cell Survival; Cytoprotection; Endothelial Cells; Gene Expression Regulation; Heart; Humans; Intracellular Space; Lysophospholipids; Male; Myocardial Ischemia; Phosphotransferases (Alcohol Group Acceptor); Polysaccharides; Rats; Rats, Sprague-Dawley; Receptors, Lysosphingolipid; RNA Interference; Signal Transduction; Solubility; Sphingosine; Water

The lysosphingolipid sphingosine 1-phosphate (S1P) is carried in the blood in association with lipoproteins, predominantly high density lipoproteins (HDL). Emerging evidence suggests that many of the effects of HDL on cardiovascular function may be attributable to its S1P cargo.. Here we have evaluated how levels of S1P and related sphingolipids in an HDL-containing fraction of human serum correlate with occurrence of ischemic heart disease (IHD). To accomplish this we used liquid chromatography-mass spectrometry to measure S1P levels in the HDL-containing fraction of serum (depleted of LDL and VLDL) from 204 subjects in the Copenhagen City Heart Study (CCHS). The study group consisted of individuals having high serum HDL cholesterol (HDL-C) (females:≥ 73.5 mg/dL; males:≥ 61.9 mg/dL) and verified IHD; subjects with high HDL-C and no IHD; individuals with low HDL-C (females:≤ 38.7 mg/dL; males:≤ 34.1 mg/dL) and IHD, and subjects with low HDL-C and no IHD.. The results show a highly significant inverse relationship between the level of S1P in the HDL-containing fraction of serum and the occurrence of IHD. Furthermore, an inverse relationship with IHD was also observed for two other sphingolipids, dihydro-S1P and C24:1-ceramide, in the HDL-containing fraction of serum. Additionally, we demonstrated that the amount of S1P on HDL correlates with the magnitude of HDL-induced endothelial cell barrier signaling.. These findings indicate that compositional differences of sphingolipids in the HDL-containing fraction of human serum are related to the occurrence of IHD, and may contribute to the putative protective role of HDL in IHD.

Topics: Cell Movement; Ceramides; Chemical Fractionation; Chromatography, Liquid; Denmark; Electric Impedance; Endothelial Cells; Endothelium, Vascular; Female; Humans; Lipoproteins, HDL; Lysophospholipids; Male; Mass Spectrometry; Middle Aged; Myocardial Ischemia; ROC Curve; Sphingolipids; Sphingosine

We investigated whether plasma long-chain sphingoid base (LCSB) concentrations are altered by transient cardiac ischemia during percutaneous coronary intervention (PCI) in humans and examined the signaling through the sphingosine-1-phosphate (S1P) cascade as a mechanism underlying the S1P cardioprotective effect in cardiac myocytes. Venous samples were collected from either the coronary sinus (n = 7) or femoral vein (n = 24) of 31 patients at 1 and 5 min and 12 h, following induction of transient myocardial ischemia during elective PCI. Coronary sinus levels of LCSB were increased by 1,072% at 1 min and 941% at 5 min (n = 7), while peripheral blood levels of LCSB were increased by 579% at 1 min, 617% at 5 min, and 436% at 12 h (n = 24). In cultured cardiac myocytes, S1P, sphingosine (SPH), and FTY720, a sphingolipid drug candidate, showed protective effects against CoCl induced hypoxia/ischemic cell injury by reducing lactate dehydrogenase activity. Twenty-five nanomolars of FTY720 significantly increased phospho-Pak1 and phospho-Akt levels by 56 and 65.6% in cells treated with this drug for 15 min. Further experiments demonstrated that FTY720 triggered nitric oxide release from cardiac myocytes is through pertussis toxin-sensitive phosphatidylinositol 3-kinase/Akt/endothelial nitric oxide synthase signaling. In ex vivo hearts, ischemic preconditioning was cardioprotective in wild-type control mice (Pak1(f/f)), but this protection appeared to be ineffective in cardiomyocyte-specific Pak1 knockout (Pak1(cko)) hearts. The present study provides the first direct evidence of the behavior of plasma sphingolipids following transient cardiac ischemia with dramatic and early increases in LCSB in humans. We also demonstrated that S1P, SPH, and FTY720 have protective effects against hypoxic/ischemic cell injury, likely a Pak1/Akt1 signaling cascade and nitric oxide release. Further study on a mouse model of cardiac specific deletion of Pak1 demonstrates a crucial role of Pak1 in cardiac protection against ischemia/reperfusion injury.

Topics: Adult; Aged; Angioplasty, Balloon, Coronary; Animals; Arrhythmias, Cardiac; Biotransformation; Blotting, Western; Cardiotonic Agents; Cell Hypoxia; Cell Survival; Coronary Occlusion; Female; Fingolimod Hydrochloride; Humans; In Vitro Techniques; L-Lactate Dehydrogenase; Lysophospholipids; Male; Middle Aged; Myocardial Ischemia; Myocytes, Cardiac; Nitric Oxide; Nitric Oxide Synthase Type III; Oncogene Protein v-akt; p21-Activated Kinases; Pertussis Toxin; Propylene Glycols; Rats; Sphingolipids; Sphingosine

HDL, through sphingosine-1-phosphate (S1P), exerts direct cardioprotective effects on ischemic myocardium. It remains unclear whether other HDL-associated sphingophospholipids have similar effects. We therefore examined if HDL-associated sphingosylphosphorylcholine (SPC) reduces infarct size in a mouse model of transient myocardial ischemia/reperfusion. Intravenously administered SPC dose-dependently reduced infarct size after 30 minutes of myocardial ischemia and 24 hours reperfusion compared to controls. Infarct size was also reduced by postischemic, therapeutical administration of SPC. Immunohistochemistry revealed reduced polymorphonuclear neutrophil recruitment to the infarcted area after SPC treatment, and apoptosis was attenuated as measured by TUNEL. In vitro, SPC inhibited leukocyte adhesion to TNFα-activated endothelial cells and protected rat neonatal cardiomyocytes from apoptosis. S1P₃ was identified as the lysophospholipid receptor mediating the cardioprotection by SPC, since its effect was completely absent in S1P₃-deficient mice. We conclude that HDL-associated SPC directly protects against myocardial reperfusion injury in vivo via the S1P₃ receptor.

Topics: Animals; Cardiotonic Agents; Dose-Response Relationship, Drug; Heart; Humans; Lipoproteins, HDL; Lysophospholipids; Mice; Mice, Inbred C57BL; Myocardial Ischemia; Myocardial Reperfusion Injury; Myocardium; Myocytes, Cardiac; Phosphorylcholine; Rats; Sphingosine

Sphingosine 1-phosphate (S1P) is released at sites of tissue injury and effects cellular responses through activation of G protein-coupled receptors. The role of S1P in regulating cardiomyocyte survival following in vivo myocardial ischemia-reperfusion (I/R) injury was examined by using mice in which specific S1P receptor subtypes were deleted. Mice lacking either S1P(2) or S1P(3) receptors and subjected to 1-h coronary occlusion followed by 2 h of reperfusion developed infarcts equivalent to those of wild-type (WT) mice. However, in S1P(2,3) receptor double-knockout mice, infarct size following I/R was increased by >50%. I/R leads to activation of ERK, JNK, and p38 MAP kinases; however, these responses were not diminished in S1P(2,3) receptor knockout compared with WT mice. In contrast, activation of Akt in response to I/R was markedly attenuated in S1P(2,3) receptor knockout mouse hearts. Neither S1P(2) nor S1P(3) receptor deletion alone impaired I/R-induced Akt activation, which suggests redundant signaling through these receptors and is consistent with the finding that deletion of either receptor alone did not increase I/R injury. The involvement of cardiomyocytes in S1P(2) and S1P(3) receptor mediated activation of Akt was tested by using cells from WT and S1P receptor knockout hearts. Akt was activated by S1P, and this was modestly diminished in cardiomyocytes from S1P(2) or S1P(3) receptor knockout mice and completely abolished in the S1P(2,3) receptor double-knockout myocytes. Our data demonstrate that activation of S1P(2) and S1P(3) receptors plays a significant role in protecting cardiomyocytes from I/R damage in vivo and implicate the release of S1P and receptor-mediated Akt activation in this process.

Topics: Animals; Cells, Cultured; Disease Models, Animal; Enzyme Activation; Lysophospholipids; MAP Kinase Signaling System; Mice; Mice, Transgenic; Myocardial Infarction; Myocardial Ischemia; Myocardial Reperfusion Injury; Myocytes, Cardiac; Proto-Oncogene Proteins c-akt; Receptors, Lysosphingolipid; Signal Transduction; Sphingosine; Sphingosine-1-Phosphate Receptors

Activation of sphingosine kinase (SphK), which has two known isoforms, is responsible for the synthesis of sphingosine 1-phosphate (S1P), a cell survival factor. We tested the following hypotheses: 1] cardiac myocytes null for the SphK1 gene are more vulnerable to the stress of hypoxia+glucose deprivation; 2] the monoganglioside GM-1, which activates SphK via protein kinase C epsilon, is ineffective in SphK1-null myocytes; 3] S1P generated by SphK activation requires cellular export to be cardioprotective.. We cultured adult mouse cardiac myocytes from wildtype and SphK1-null mice (deletion of exons 3-6) and measured cell viability by trypan blue exclusion.. In wildtype adult mouse cardiomyocytes subjected to 4 h of hypoxic stress+glucose deprivation, cell viability was significantly higher than in SphK1-null cardiomyocytes. SphK1-null cells also displayed more mitochondrial cytochrome C release. Cell death induced by hypoxia+glucose deprivation was substantially prevented by pretreatment with exogenous S1P in both wildtype and SphK1-null myocytes, but S1P was effective at a lower concentration in wildtype cells. Hence, the absence of the Sphk1 gene did not affect receptor coupling or downstream signal transduction. Pretreatment for 1 h with 1 microM of the monoganglioside GM-1 increased survival in wildtype cells, but not in SphK1-null myocytes. Thus, activation of SphK1 by GM-1 leads to cell survival. In wildtype cells, enhanced survival produced by GM-1 was abrogated by pretreatment either with 300 nM of the S1P(1) receptor-selective antagonist VPC23019 or with 100 ng/ml of pertussis toxin for 16 h before exposure to hypoxia+glucose deprivation.. As the effect of GM-1 is blocked both at the receptor and the G-protein (Gi) levels, we conclude that S1P generated by GM-1 treatment must be exported from the cell and acts in a paracrine or autocrine manner to couple with its cognate receptor.

Topics: Animals; Apoptosis; Biomarkers; Blotting, Western; Cell Hypoxia; Cell Survival; Cells, Cultured; Cytochromes c; Enzyme Activation; Enzyme Inhibitors; Ginsenosides; Glucose; Hypoglycemic Agents; Lysophospholipids; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Mitochondria, Heart; Myocardial Ischemia; Myocytes, Cardiac; Pertussis Toxin; Phosphotransferases (Alcohol Group Acceptor); Sphingosine

Nitric oxide plays a crucial role in myocardial ischemia reperfusion injury as well as in myocardial adaptation to ischemic stress. To understand the dichotomy of nitric oxide behavior in the ischemic myocardium, isolated rat hearts were subjected to ischemia/reperfusion protocol. The tissue contents of sphingomyelin (SM), ceramide and sphingosine were determined by high performance thin layer chromatography (HPTLC). The myocardial plasma proteins were immunoprecipitated with caveolin-1 specific antibody. Ischemia/reperfusion resulted in the breakdown of SM with corresponding accumulation of ceramide and sphingosine. Immunoprecipitation with eNOS-specific antibody revealed the association of eNOS with caveolin-1 fraction of the heart. Ischemia/reperfusion caused a depression of contractile function and an increased apoptotic cell death and myocardial infarct size, which were reversed by pre-perfusing the hearts with desipramine, an sphingomyelinase inhibitor that also prevented ceramide accumulation and eNOS association with caveolin-1. The similar results were obtained when the hearts were adapted to ischemic stress by subjecting them to repeated reversible ischemia and reperfusion. The results indicate that ischemia/reperfusion causes an increase in eNOS, which is unavailable to the ischemic heart because of its binding with caveolin-1. Ceramide plays a crucial role in this process, because prevention of ceramide formation either by myocardial adaptation to ischemia or with desipramine results in the inhibition of eNOS association with caveolin-1 thereby reducing myocardial ischemic reperfusion injury.

Topics: Animals; Caveolae; Caveolin 1; Ceramides; Ischemic Preconditioning, Myocardial; Lysophospholipids; Male; Membrane Microdomains; Myocardial Ischemia; Myocardial Reperfusion; Nitric Oxide; Nitric Oxide Synthase Type III; Rats; Signal Transduction; Sphingosine

All treatments of acute myocardial infarction are aimed at rapid revascularization of the occluded vessel; however, no clinical strategies are currently available to protect the heart from ischemia/reperfusion injury after restitution of blood flow. We hypothesized that some of the cholesterol transport-independent biological properties of high-density lipoprotein (HDL) implied in atheroprotection may also be beneficial in settings of acute myocardial reperfusion injury.. In an in vivo mouse model of myocardial ischemia/reperfusion, we observed that HDL and its sphingolipid component, sphingosine-1-phosphate (S1P), dramatically attenuated infarction size by approximately 20% and 40%, respectively. The underlying mechanism was an inhibition of inflammatory neutrophil recruitment and cardiomyocyte apoptosis in the infarcted area. In vitro, HDL and S1P potently suppressed leukocyte adhesion to activated endothelium under flow and protected rat neonatal cardiomyocytes against apoptosis. In vivo, HDL- and S1P-mediated cardioprotection was dependent on nitric oxide (NO) and the S1P3 lysophospholipid receptor, because it was abolished by pharmacological NO synthase inhibition and was completely absent in S1P3-deficient mice.. Our data demonstrate that HDL and its constituent, S1P, acutely protect the heart against ischemia/reperfusion injury in vivo via an S1P3-mediated and NO-dependent pathway. A rapid therapeutic elevation of S1P-containing HDL plasma levels may be beneficial in patients at high risk of acute myocardial ischemia.

Topics: Animals; Apoptosis; Cardiotonic Agents; Cell Adhesion; Cells, Cultured; Chemotaxis, Leukocyte; Endothelial Cells; Female; Humans; Lipoproteins, HDL; Lipoproteins, LDL; Lysophospholipids; Macrophages; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Myocardial Ischemia; Myocardial Reperfusion Injury; Myocytes, Cardiac; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Synthase; Receptors, Lysosphingolipid; Sphingosine; Sphingosine-1-Phosphate Receptors; Tumor Necrosis Factor-alpha

Sphingosine-1-phosphate (S1P) protects neonatal rat cardiac myocytes from hypoxic damage through unknown signaling pathways. We tested the hypothesis that S1P-induced cardioprotection requires activation by the epsilon-isoform of protein kinase C (PKC epsilon) by subjecting hearts isolated from PKC epsilon knockout mice and wild-type mice to 20 min of global ischemia and 30 min of reperfusion. Pretreatment with a 2-min infusion of 10 nM S1P improved recovery of left ventricular developed pressure (LVDP) in both wild-type and PKC epsilon knockout hearts and reduced the rise in LV end-diastolic pressure (LVEDP) and creatine kinase (CK) release. Pretreatment for 2 min with 10 nM of the ganglioside GM-1 also improved recovery of LVDP and suppressed CK release in wild-type hearts but not in PKC epsilon knockout hearts. Importantly, GM-1 but not S1P, increased the proportion of PKC epsilon localized to particulate fractions. Our results suggest that GM-1, which enhances endogenous S1P production, reduces cardiac injury through PKC epsilon-dependent intracellular pathways. In contrast, extracellular S1P induces equivalent cardioprotection through PKC epsilon-independent signaling pathways.

Topics: Alkaloids; Animals; Animals, Newborn; Benzophenanthridines; Blotting, Western; Cells, Cultured; Creatine Kinase; Enzyme Inhibitors; G(M1) Ganglioside; Isoenzymes; Lysophospholipids; Mice; Mice, Knockout; Myocardial Ischemia; Myocardial Reperfusion Injury; Myocardium; Phenanthridines; Protein Kinase C; Signal Transduction; Sphingosine; Ventricular Function, Left