鞘氨醇-1-磷酸与免疫细胞的调节

鞘氨醇-1-磷酸（sphingosine-1 phosphate,S1P）是来源于鞘脂代谢途径的多效性信号分子,其代谢受到多种因素调控。S1P由细胞内的鞘氨醇激酶（sphingosine kinases,SphKs）催化鞘氨醇的磷酸化而合成,可通过转运蛋白释放至细胞外。S1P可通过在胞外结合其特异性G蛋白偶联受体及胞内作用而调节多种重要生物学效应。作为细胞外介质和细胞内信使,S1P在免疫系统中也发挥重要的调节作用。S1P参与免疫细胞的迁移、增殖、分化及死亡细胞清除等过程。本文对S1P的代谢以及其对于免疫细胞的调节作用进行综述。     

鞘磷脂代谢与脑缺血

鞘磷脂特别是鞘脂是髓鞘的主要成分,高度集中在中枢神经系统。在生理和病理生理条件下,具有生物活性的鞘磷脂及其代谢产物以及信号传导过程的重要性正在逐步被人们所认识。鞘脂代谢产物鞘氨醇及其前体物质神经酰胺与细胞生长停滞和凋亡有关,而1-磷酸鞘氨醇与增强细胞增殖、分化和细胞生存以及调节细胞的生理和病理过程有关,具有细胞外第一信使和细胞内第二信使的双重功能。这三者之间的相互转换、鞘脂代谢物的相对水平以及细胞的命运,受到鞘氨醇激酶的活性的强烈影响。鞘氨醇激酶可催化磷酸鞘氨醇产生1-磷酸鞘氨醇。1-磷酸鞘氨醇在中枢神经系统中与G蛋白偶联受体家族结合对中枢神经系统发挥作用。本文对鞘磷脂代谢过程中的鞘氨醇激酶、1-磷酸鞘氨醇及其受体与脑缺血之间的关系进行概述。     

鞘氨醇激酶-磷酸鞘氨醇轴在血管生成相关性疾病中的作用

血管生成是指在原有血管的基础上形成新血管的过程.病理性血管生成是癌症、心血管类疾病和视网膜病变等一系列疾病的标志.1-磷酸鞘氨醇(sphingosine-1-phosphate,S1P)是一种信号脂质,由鞘氨醇激酶(sphingosine kinases,SPHK)合成,通过5种G蛋白偶联受体(sphingosine-...     

脂质活性信号分子鞘氨醇-1-磷酸及其生物学特性

鞘氨醇-1-磷酸(sphingosine-1-phosphate,S1P)是目前颇受关注的脂质信号分子.体内S1P主要由红细胞内鞘氨醇激酶催化鞘氨醇合成,后经由ATP结合盒式转运子释放入血浆.血浆S1P超过半数存在于高密度脂蛋白和血清白蛋白上.S1P可通过直接胞内作用和激活其特异性G蛋白偶联受体产生多种重要生物学效应.S1P1-5型受体在体内各类型组织和细胞表达水平不同,参与包括细胞增殖、存活、迁移等多种生物学过程.     

鞘氨醇-1磷酸盐的生理功能研究进展

鞘氨醇－1磷酸盐（SPP）是神经鞘磷脂代谢产生的一种有生物活性的脂类,在细胞的多种生物学过程中起着重要的作用。包括细胞的增殖、存活、细胞骨架改变、迁移、血管发生、创伤愈合和胚胎发育等。本文综述了SPP在细胞生物功能调节和信号转导中的作用。     

S1P 信号通路：心血管疾病治疗的新靶点

1- 磷酸鞘氨醇是一种有生物活性的脂质代谢产物,具有调节细胞增殖、再生、迁移,细胞内钙离子移动,黏附分子表达以及激活单核细胞黏附内皮细胞等功效,在血管生理性再生及动脉粥样硬化斑块发生发展中发挥重要作用。1- 磷酸鞘氨醇在高密度脂蛋白中含量在所有脂蛋白中最高,其参与调节高密度脂蛋白的抗氧化、抗血栓、抗炎等效应,而这些反应与1- 磷酸鞘氨醇的生物学功能如血管发生、内皮保护、抑制平滑肌细胞迁移、心肌缺血再灌注损伤的保护等密切相关。对1- 磷酸鞘氨醇信号通路在心血管系统中的作用及以该通路为靶点的相关药物研究进展进行综述,为今后研究提供参考。     

液相串联质谱法同时定量检测生物样本中鞘脂类化合物

鞘脂类中的主要活性分子鞘氨醇1-磷酸（S1P）,可通过介导细胞增殖、分化和迁移等发挥广泛的生物学功能|同时,S1P可在相关酶的作用下转变为其它形式.本文旨在建立一种简便的鞘脂类的制备方法,并结合液相串联质谱（LC-MS/MS）快速检测生物样本中纳克水平的鞘脂类化合物. 采用甲醇沉淀或经典的脂质提取方法获得鞘脂类化合物,再采用LC-MS/MS在多反应监测模式（MRM）下进行定量分析. 实验结果表明,甲醇沉淀法可简便快捷地获得血浆或脂蛋白中鞘氨醇类化合物; S1P、二氢鞘氨醇（DH-S1P）和鞘氨醇（SPH）的定量限分别为110.5、215.6和44.3 pg;人血浆中S1P、DH-S1P和SPH的含量分别为257.8±49.4 nmol/L、93.5±17.3 nmol/L和44.6± 7.4 nmol/L, 鞘脂类化合物在人血浆脂蛋白上的分布存在显著性差异|在ApoE-/-小鼠血浆中S1P、DH-S1P和SPH的含量分别为590.1±78.2 nmol/L、197.8±60.6 nmol/L和35.4±16.7 nmol/L|每1×106个人脐静脉内皮细胞（EA.hy926）中,S1P和SPH的含量分别为103.7±21.8 pg和16.3±5.3 ng.甲醇沉淀法结合LC-MS/MS可简便快捷地对血浆和脂蛋白中的鞘脂类化合物进行定量检测. 该方法特别适用于大量生物样本中鞘脂类的快速定量分析.     

鞘氨醇1- 磷酸受体4 研究进展

鞘氨醇1-磷酸(Sphingosine-1-phosphate,S1P)是一种具有生物学活性的溶血磷脂信号分子,在体内通过G蛋白偶联受体(G protein coupled receptor,GPCR)家族鞘氨醇1-磷酸受体(S1P receptors)的5个亚型(S1P1-5)介导多种生物学功能。S1P4也称内皮分化基因受体6(Endothelial differentiation gene receptor 6,Edg-6),主要在淋巴组织和造血组织中表达。近年的研究发现,免疫细胞的迁移分化、骨骼肌前体细胞的迁移、乳腺癌细胞的增殖、TGFβ1介导的抑制骨骼肌细胞凋亡均与S1P4相关。本文将综述近几年来关于S1P介导S1P4的生理病理应答及相关的信号转导机制。     

鞘氨醇激酶活性测定方法的建立及其初步应用

目的:建立生物样品中鞘氨醇激酶(SPK)活性和1-磷酸鞘氨醇(S1P)含量的测定方法.方法:用Flag标记的SPK基因表达载体转染ECV304细胞,用Western blot方法检测转染后SPK基因的表达,用酶促反应、同住素掺入和薄层层析的方法检测SPK的活性.提取细胞或组织的S1P,碱性磷酸酶消化去除磷酸根,然后利用SPK的催化活性和同位素标记的方法对S1P进行定量.结果:转染基因后细胞的SPK表达明显升高,活性显著增强,细胞内S1P的含量也明显增多.肝细胞生长因子(HGF)刺激能增强ECV304细胞SPK的活性和细胞内S1P水平.结论:建立了SPK活性和S1P含量的测定方法.     

植物体内的鞘氨醇-1-磷酸(S1P)

鞘氨醇-1-磷酸（S1P）在植物体内也可作为一种信号分子参与ABA介导的保卫细胞信号转导过程,这一途径和异三聚体G蛋白相耦联。文章对此问题的研究进展作了介绍。     

Sphingosine 1-phosphate as a regulator of osteoclast differentiation and osteoclast-osteoblast coupling

Sphingosine 1-phosphate (S1P), produced by sphingosine kinase (SPHK), acts both by intracellular and extracellular modes. We evaluated the role of SPHK1 and S1P in osteoclastogenesis using bone marrow-derived macrophage (BMM) single and BMM/osteoblast coculture systems. In BMM single cultures, the osteoclastogenic factor receptor activator of NF-kappaB ligand (RANKL) upregulated SPHK1 and increased S1P production and secretion. SPHK1 siRNA enhanced and SPHK1 overexpression attenuated osteoclastogenesis via modulation of p38 and ERK activities, and NFATc1 and c-Fos levels. Extracellular S1P had no effect in these cultures. These data suggest that intracellular S1P produced in response to RANKL forms a negative feedback loop in BMM single cultures. In contrast, S1P addition to BMM/osteoblast cocultures greatly increased osteoclastogenesis by increasing RANKL in osteoblasts via cyclooxygenase-2 and PGE(2) regulation. S1P also stimulated osteoblast migration and survival. The RANKL elevation and chemotactic effects were also observed with T cells. These results indicate that secreted S1P attracts and acts on osteoblasts and T cells to augment osteoclastogenesis. Taken together, S1P plays an important role in osteoclastogenesis regulation and in communication between osteoclasts and osteoblasts or T cells.     

High expression of sphingosine kinase 1 and S1P receptors in chemotherapy-resistant prostate cancer PC3 cells and their camptothecin-induced up-regulation

Although most of pharmacological therapies for cancer utilize the apoptotic machinery of the cells, the available anti-cancer drugs are limited due to the ability of prostate cancer cells to escape from the anti-cancer drug-induced apoptosis. A human prostate cancer cell line PC3 is resistant to camptothecin (CPT). To elucidate the mechanism of this resistance, we have examined the involvement of sphingosine kinase (SPHK) and sphingosine 1-phosphate (S1P) receptor in CPT-resistant PC3 and -sensitive LNCaP cells. PC3 cells exhibited higher activity accompanied with higher expression levels of protein and mRNA of SPHK1, and also elevated expression of S1P receptors, S1P(1) and S1P(3), as compared with those of LNCaP cells. The knockdown of SPHK1 by small interfering RNA and inhibition of S1P receptor signaling by pertussis toxin in PC3 cells induced significant inhibition of cell growth, suggesting implication of SPHK1 and S1P receptors in cell proliferation in PC3 cells. Furthermore, the treatment of PC3 cells with CPT was found to induce up-regulation of the SPHK1/S1P signaling by induction of both SPHK1 enzyme and S1P(1)/S1P(3) receptors. These findings strongly suggest that high expression and up-regulation of SPHK1 and S1P receptors protect PC3 cells from the apoptosis induced by CPT.     

Identification of PECAM-1 association with sphingosine kinase 1 and its regulation by agonist-induced phosphorylation

Sphingosine 1-phosphate (S1P) is a bioactive lipid mediator generated from sphingosine by sphingosine kinase (SPHK). S1P acts both extracellularly and intracellularly as a signaling molecule, although its intracellular targets are still undefined. Intracellular level of S1P is under strict regulatory control of SPHK regulation, S1P degradation, and S1P dephosphorylation. Therefore, clarifying the mechanisms regulating SPHK activity may help us understand when and where S1P is generated. In this study, we performed yeast two-hybrid screening to search for SPHK1a-binding molecules that may be involved in the regulation of the kinase localization or activity. Platelet endothelial cell adhesion molecule-1 (PECAM-1) was identified as a protein potentially associating with SPHK1a. Their association was confirmed by co-immunoprecipitation analysis using HEK293 cells overexpressing PECAM-1 and SPHK1a. Moreover, the kinase activity appeared to be reduced in stable PECAM-1-expressing cells. PECAM-1 is expressed on the cell surface of vascular cells, and several stimuli are known to induce phosphorylation of its tyrosine residues. We found that such phosphorylation attenuated its association with SPHK1a. This association/dissociation of SPHK with PECAM-1, regulated by the phosphorylated state of the membrane protein, may be involved in the control of localized kinase activity in certain cell types.     

A polysaccharides MDG-1 augments survival in the ischemic heart by inducing S1P release and S1P1 expression

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.     

Sphingosine kinase type 1 promotes estrogen-dependent tumorigenesis of breast cancer MCF-7 cells

The sphingolipid metabolite, sphingosine-1-phosphate (S1P), formed by phosphorylation of sphingosine, has been implicated in cell growth, suppression of apoptosis, and angiogenesis. In this study, we have examined the contribution of intracellular S1P to tumorigenesis of breast adenocarcinoma MCF-7 cells. Enforced expression of sphingosine kinase type 1 (SPHK1) increased S1P levels and blocked MCF-7 cell death induced by anti-cancer drugs, sphingosine, and TNF-alpha. SPHK1 also conferred a growth advantage, as determined by proliferation and growth in soft agar, which was estrogen dependent. While both ERK and Akt have been implicated in MCF-7 cell growth, SPHK1 stimulated ERK1/2 but had no effect on Akt. Surprisingly, parental growth of MCF-7 cells was only weakly stimulated by S1P or dihydro-S1P, ligands for the S1P receptors which usually mediate growth effects. When injected into mammary fat pads of ovariectomized nude mice implanted with estrogen pellets, MCF-7/SPHK1 cells formed more and larger tumors than vector transfectants with higher microvessel density in their periphery. Collectively, our results suggest that SPHK1 may play an important role in breast cancer progression by regulating tumor cell growth and survival.     

Identification of functional nuclear export sequences in human sphingosine kinase 1

Sphingosine kinase (SPHK) is an enzyme that phosphorylates sphingosine to form sphingosine 1-phosphate (S1P). Human SPHK1 (hSPHK1) was localized predominantly in the cytoplasm when transiently expressed in Cos7 cells. In this study, we have found two functional nuclear export signal (NES) sequences in the middle region of hSPHK1. Deletion and mutagenesis studies revealed that the cytoplasmic localization of SPHK1 depends on its nuclear export, directed by the NES. Furthermore, upon treatment with leptomycin B, a specific inhibitor of the nuclear export receptor CRM1, a marked nuclear accumulation of hSPHK1 was observed, indicating that hSPHK1 shuttles between the cytoplasm and the nucleus. Our results provide the first evidence of the active nuclear export of SPHK1 and suggest it is mediated by a CRM1-dependent pathway.     

Sphingosine-1-phosphate signaling and biological activities in the cardiovascular system

The plasma lysophospholipid mediator sphingosine-1-phosphate (S1P) is produced exclusively by sphingosine kinase (SPHK) 1 and SPHK2 in vivo, and plays diverse biological and pathophysiological roles by acting largely through three members of the G protein-coupled S1P receptors, S1P(1), S1P(2) and S1P(3). S1P(1) expressed on endothelial cells mediates embryonic vascular maturation and maintains vascular integrity by contributing to eNOS activation, inhibiting vascular permeability and inducing endothelial cell chemotaxis via Gi-coupled mechanisms. By contrast, S1P(2), is expressed in high levels on vascular smooth muscle cells (VSMCs) and certain types of tumor cells, inhibiting Rac and cell migration via a G(12/13)-and Rho-dependent mechanism. In rat neointimal VSMCs, S1P(1) is upregulated to mediate local production of platelet-derived growth factor, which is a key player in vascular remodeling. S1P(3) expressed on endothelial cells also mediates chemotaxis toward S1P and vasorelaxation via NO production in certain vascular bed, playing protective roles for vascular integrity. S1P(3) expressed on VSMCs and cardiac sinoatrial node cells mediates vasopressor and negative chronotropic effect, respectively. In addition, S1P(3), together with S1P(2) and SPHK1, is suggested to play a protective role against acute myocardial ischemia. However, our recent work indicates that overexpressed SPHK1 is involved in cardiomyocyte degeneration and fibrosis in vivo, in part through S1P activation of the S1P(3) signaling. We also demonstrated that exogenously administered S1P accelerates neovascularization and blood flow recovery in ischemic limbs, suggesting its usefulness for angiogenic therapy. These results provide evidence for S1P receptor subtype-specific pharmacological intervention as a novel therapeutic approach to cardiovascular diseases and cancer.     

SPHK1 (sphingosine kinase 1) induces epithelial-mesenchymal transition by promoting the autophagy-linked lysosomal degradation of CDH1/E-cadherin in hepatoma cells

SPHK1 (sphingosine kinase 1), a regulator of sphingolipid metabolites, plays a causal role in the development of hepatocellular carcinoma (HCC) through augmenting HCC invasion and metastasis. However, the mechanism by which SPHK1 signaling promotes invasion and metastasis in HCC remains to be clarified. Here, we reported that SPHK1 induced the epithelial-mesenchymal transition (EMT) by accelerating CDH1/E-cadherin lysosomal degradation and facilitating the invasion and metastasis of HepG2 cells. Initially, we found that SPHK1 promoted cell migration and invasion and induced the EMT process through decreasing the expression of CDH1, which is an epithelial marker. Furthermore, SPHK1 accelerated the lysosomal degradation of CDH1 to induce EMT, which depended on TRAF2 (TNF receptor associated factor 2)-mediated macroautophagy/autophagy activation. In addition, the inhibition of autophagy recovered CDH1 expression and reduced cell migration and invasion through delaying the degradation of CDH1 in SPHK1-overexpressing cells. Moreover, the overexpression of SPHK1 produced intracellular sphingosine-1-phosphate (S1P). In response to S1P stimulation, TRAF2 bound to BECN1/Beclin 1 and catalyzed the lysine 63-linked ubiquitination of BECN1 for triggering autophagy. The deletion of the RING domain of TRAF2 inhibited autophagy and the interaction of BECN1 and TRAF2. Our findings define a novel mechanism responsible for the regulation of the EMT via SPHK1-TRAF2-BECN1-CDH1 signal cascades in HCC cells. Our work indicates that the blockage of SPHK1 activity to attenuate autophagy may be a promising strategy for the prevention and treatment of HCC.