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。     

鞘氨醇激酶1和1-磷酸鞘氨醇受体2在癫痫大鼠海马组织中表达的变化*

目的:检测鞘氨醇激酶1 (SphK1)和1-磷酸鞘氨醇受体2 (S1PR2) 在癫痫大鼠海马中的表达,探讨SphK1和S1PR2在癫痫中的作用机制。方法:成年雄性SD大鼠108只,随机分为对照(Control)组(n=48)和癫痫(PILO)组(n=60)。癫痫组腹腔注射氯化锂(127 mg/kg),18～20 h后注射匹罗卡品,首剂量为30 mg/kg,发作＜IV级的大鼠重复注射匹罗卡品(10 mg/kg);对照组给予等剂量的生理盐水代替匹罗卡品。根据造模后观察时间和行为学改变,随机分为3个大组,6个亚组:急性期组(E6 h、E1 d、E3 d)、潜伏期组(E7 d)和慢性期组(E30 d、E56 d),每个亚组中对照大鼠和癫痫大鼠各8只。每组取4只大鼠麻醉取海马,另4只取大脑组织。运用Western blot检测SphK1、S1PR2在大鼠海马组织中的表达变化,免疫荧光检测星形胶质细胞活化增生情况及SphK1、S1PR2在星形胶质细胞中的定位表达。结果:与Control组比较,SphK1在造模后急性期(E3 d)、潜伏期(E7 d)和慢性期(E30 d、E56 d)海马中的表达均明显升高(P＜0.05或P＜0.01);S1PR2在急性期(E3 d)、潜伏期(E7 d)和慢性期(E30 d、E56 d)海马组织中的表达均明显下降(P＜0.05或P＜0.01);癫痫大鼠(E7 d)海马星形胶质细胞活化、增生明显(P＜0.05),SphK1和S1PR2在E7d的表达到位为海马星形胶质细胞中。结论:SphK1和S1PR2可能通过调控海马星形胶质细胞活化增生和影响神经元兴奋性参与了癫痫的发病。     

1-磷酸鞘氨醇受体

1-磷酸鞘氨醇(sphingosine-1-phosphate,S1P)对动脉粥样硬化等心血管疾病的发生发展具有重要作用。最近研究发现S1P在不同细胞发挥的生物学效应由其受体(sphingosine-1-phosphate receptor,S1PR)介导,以S1PR及其信号机制为基础的研究及治疗策略成为新的研究热点。本文主要综述S1PR的功能、信号通路及对心血管疾病的影响,为心血管疾病的预防和诊疗提供新的靶点。     

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.     

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-1-磷酸的定量测定——一种新的竞争性结合方法

鞘氨醇-1-磷酸（SPP）是重要的细胞第二信使,影响细胞的生长和死亡.通过培养和收集转染SPP受体-EDG-1的HEK293细胞,与标记及非标记SPP共孵育,利用它们与HEK293细胞的竞争性结合,测定细胞、血清和组织中SPP含量.该法无需特殊仪器,可以测到皮摩尔水平的低含量,批间差异小于15%（6次）.     

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.     

鞘氨醇激酶信号途径对骨重建的调节作用

鞘磷脂是哺乳动物细胞质膜的主要成分之一,在其代谢过程中,鞘氨醇激酶（sphingosine kinase, SPHK）是一个关键性的调节酶.鞘磷脂代谢产物鞘鞍醇经SPHK磷酸化作用产生的鞘氨醇-1-磷酸（S1P）是一种具有生物活性的脂类,参与调节骨骼、神经、免疫、血液系统等多种组织细胞的生物学过程.本文阐述了SPHK/S1P信号途径相关分子,并综述了SPHK/S1P通过调节骨组织细胞的形态结构、增殖、迁移、分化形成及凋亡等功能,进而调节骨重建平衡过程的生物学效应及其机制.     

1- 磷酸鞘氨醇受体调节剂的研发现状

1- 磷酸鞘氨醇（S1P）具有多种生物学功能,S1P 受体（S1PR）调节剂可以用于治疗多种免疫性疾病。芬戈莫德是首个上市的 S1PR 调节剂,用于治疗多发性硬化症（MS）,2015 年销售额达到27 亿美元。药渡网数据显示：目前全球有14 个S1PR 调节剂进入临床, 适应证包括MS、银屑病、类风湿性关节炎和炎症性肠病等。国内目前针对S1PR 靶点的药物有1 个新药奥芬米洛已获批临床,另1 个 新药CBP-307 处于临床在审评阶段。简介S1PR 的生物学功能和S1PR 调节剂在国内外的开发情况,为靶向S1PR 的药物开发提供参考。     

1-磷酸鞘氨醇对心肌细胞钾离子通道的作用

目的：研究1-磷酸鞘氨醇（S1P）对豚鼠心室肌细胞延迟整流钾电流（IK）、内向整流钾电流（IK1）的作用。方法：实验用胶原酶酶解法急性分离豚鼠心室肌细胞,利用全细胞膜片钳的方法记录心室肌细胞的延迟整流钾电流（IK）、内向整流钾电流（IK1）。结果：①应用S1P（1．1μmol／L）后IK从（1．24±0．26）nA降至（0．95±0．23）以（P〈0．01,n=6）,而S1P（2．2μmol／L）组IK从（1．43±0．31）nA下降到（1．02±0．28）nA,统计学有显著性差异（P〈0．01,H=6）.而S1P（1．1μmol／L）＋苏拉明（Summin）（200μmol／L）组与对照相比,IK峰值从（1．29±0．26）nA下降（1．26±0．37）nA,统计学无显著性差异（P〉0．05,n=6）．②应用S1P（1．1μmol／L,2．2μmol／L）后与对照组比较,S1P（1．1μmol／L,2．2μmol／L）分别使内向整流钾电流（IK1）峰值从（-8．94±2．01）nA和（-8．81±1．55）nA下降到（18．86±1．59）nA和（-8．55±1．39）nA,统计学无显著性差异（P〉0．05,n=6）.结论：S1P可降低豚鼠心室肌细胞延迟整流钾电流（IK）的幅值,同时S1P对豚鼠心室肌细胞内向整流钾通道（IK1）没有作用。     

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。     

Disruption of sphingolipid metabolism elicits apoptosis-associated reproductive defects in Drosophila

Sphingolipid signaling is thought to regulate apoptosis via mechanisms that are dependent on the concentration of ceramide relative to that of sphingosine-1-phosphate (S1P). This study reports defects in reproductive structures and function that are associated with enhanced apoptosis in Drosophila Sply05091 mutants that lack functional S1P lyase and thereby accumulate sphingolipid long chain base metabolites. Analyses of reproductive structures in these adult mutants unmasked multiple abnormalities, including supernumerary spermathecae, degenerative ovaries, and severely reduced testes. TUNEL assessment revealed increased cell death in mutant egg chambers at most oogenic stages and in affected mutant testes. These reproductive abnormalities and elevated gonadal apoptosis were also observed, to varying degrees, in other mutants affecting sphingolipid metabolism. Importantly, the reproductive defects seen in the Sply05091 mutants were ameliorated both by a second site mutation in the lace gene that restores long chain base levels towards normal and by genetic disruption of the proapoptotic genes reaper, hid and grim. These data thus provide the first evidence in Drosophila that accumulated sphingolipids trigger elevated levels of apoptosis via the modulation of known signaling pathways.     

ATP-independent glucose stimulation of sphingosine kinase in rat pancreatic islets

Sphingosine kinase (SPHK) catalyzes sphingosine 1-phosphate production, promoting cell survival and reducing apoptosis in isolated rat pancreatic islets. Glucose, the primary islet β-cell growth factor and insulin secretagogue, increased islet SPHK activity by 3- to 5-fold following acute (1 h) or prolonged (7 days) stimulation. Prolonged stimulation of islets with glucose induced SPHK1a and SPHK2 mRNA levels; there were no changes in SPHK protein expression. To isolate the metabolic effects of glucose on SPHK activation, islets were stimulated with glucose analogs or metabolites. 2-deoxy-D-glucose (2-DG), an analog phosphorylated by glucokinase but not an effective energy source, activated SPHK similarly to glucose. In contrast, 3-o-methylglucose (3-oMeG), which is transported but neither phosphorylated nor metabolized, did not increase islet SPHK activity. Glyceraldehyde and α-ketoisocaproic acid (KIC), metabolites that stimulate glycolysis and the citric acid cycle, respectively, did not activate islet SPHK. Moreover, inorganic phosphate blocked glucose-induced SPHK activation. A role for SPHK activity in β-cell growth was confirmed when small interfering (si)SPHK2 RNA transfection reduced rat insulinoma INS-1e cell SPHK levels and activity and cell growth. Glucose induced an early and sustained increase in islet SPHK activity that was dependent on glucose phosphorylation, but independent of ATP generation or new protein biosynthesis. Glucose-supported β-cell growth appears to be in part mediated by SPHK activity.     

The role of sphingosine-1-phosphate in skeletal muscle: Physiology,mechanisms, and clinical perspectives

Sphingolipids were discovered more than a century ago and were simply considered as a class of cell membrane lipids for a long time. However, after the discovery of several intracellular functions and their role in the control of many physiological and pathophysiological conditions, these molecules have gained much attention. For instance, the sphingosine-1-phosphate (S1P) is a circulating bioactive sphingolipid capable of triggering strong intracellular reactions through the family of S1P receptors (S1PRs) spread in several cell types and tissues. Recently, the role of S1P in the control of skeletal muscle metabolism, atrophy, regeneration, and metabolic disorders has been widely investigated. In this review, we summarized the knowledge of S1P and its effects in skeletal muscle metabolism, highlighting the role of S1P/S1PRs axis in skeletal muscle regeneration, fatigue, ceramide accumulation, and insulin resistance. Finally, we discussed the physical exercise role in S1P/S1PRs signaling in skeletal muscle cells, and how this nonpharmacological strategy may be prospective for future investigations due to its ability to increase S1P levels.     

A benzo[b]thiophene-based selective type 4 S1P receptor agonist

S1P receptors (S1PR1-5) are a group of GPCRs activated by a high affinity binding with S1P that have important roles in the regulation of the immune system. A potent S1PR agonist FTY720 is an immunomodulator used to treat multiple sclerosis and several ‘second generation’ drugs are under clinical development. Subtype-selective agonists have been reported for each S1PR isotype, some of which are used as pharmacological tools for functional studies. Here we report the discovery and initial characterization of compound 5c, a benzo[b]thiophene amino carboxylate which exhibits potent and selective agonist activity for S1PR4. Compound 5c has an EC₅₀ = 200 nM as an agonist in GTPγ³⁵S binding assay for S1PR4 and exhibits no activity against S1PR1,2,3,5. We confirmed its potent activity and decent S1PR subtype selectivity using biochemical and cellular assays.     

S1P mediates human amniotic cells proliferation induced by a 50-Hz magnetic field exposure via ERK1/2 signaling pathway

Extremely low frequency electromagnetic field (ELF-EMF) is a kind of physical stimulus in public and occupational environment. Numerous studies have indicated that exposure of cells to ELF-EMF could promote cell proliferation. But the detailed mechanisms implicated in these proliferative processes remain unclear. In the present experiment, the possible roles of sphingosine-1-phosphate (S1P) in 50-Hz magnetic field (MF)-induced cell proliferation were investigated. Results showed that exposure of human amniotic (FL) cells to a 50-Hz MF with an intensity of 0.4 mT significantly enhanced ceramide metabolism, increased S1P production, activated extracellular signal regulated kinase 1/2 (ERK1/2), and promoted cell proliferation. All of these effects induced by MF exposure could be inhibited by SKI II, an inhibitor of sphingosine kinase (SphK). In addition, both the cell proliferative response and the ERK1/2 activation induced by MF exposure were blocked completely by U0126, a specific inhibitor of MEK (ERK kinases 1 and 2). Taken together, the findings in present study suggested that S1P mediated 50-Hz MF-induced cell proliferation via triggering ERK1/2 signal pathway.     

Involvement of released sphingosine 1-phosphate/sphingosine 1-phosphate receptor axis in skeletal muscle atrophy

Skeletal muscle (SkM) atrophy is caused by several and heterogeneous conditions, such as cancer, neuromuscular disorders and aging. In most types of SkM atrophy overall rates of protein synthesis are suppressed, protein degradation is consistently elevated and atrogenes, such as the ubiquitin ligase Atrogin-1/MAFbx, are up-regulated. The molecular regulators of SkM waste are multiple and only in part known.Sphingolipids represent a class of bioactive molecules capable of modulating the destiny of many cell types, including SkM cells. In particular, we and others have shown that sphingosine 1phosphate (S1P), formed by sphingosine kinase (SphK), is able to act as trophic and morphogenic factor in myoblasts.Here, we report the first evidence that the atrophic phenotype observed in both muscle obtained from mice bearing the C26 adenocarcinoma and C2C12 myotubes treated with dexamethasone was characterized by reduced levels of active phospho-SphK1. The importance of SphK1 activity is also confirmed by the specific pharmacological inhibition of SphK1 able to increase Atrogin-1/MAFbx expression and reduce myotube size and myonuclei number. Furthermore, we found that SkM atrophy was accomplished by significant increase of S1P transporter Spns2 and in changes in the pattern of S1P receptor (S1PRs) subtype expression paralleled by increased Atrogin-1/MAFbx expression, suggesting a role for the released S1P and of specific S1PR-mediated signaling pathways in the control of the ubiquitin ligase. Altogether, these findings provide the first evidence that SphK1/released S1P/S1PR axis acts as a molecular regulator of SkM atrophy, thereby representing a new possible target for therapy in many patho-physiological conditions.     

Sphingosine-1-phosphate metabolism: A structural perspective

Abstract

Sphingolipids represent an important class of bioactive signaling lipids which have key roles in numerous cellular processes. Over the last few decades, the levels of bioactive sphingolipids and/or their metabolizing enzymes have been realized to be important factors involved in disease development and progression, most notably in cancer. Targeting sphingolipid-metabolizing enzymes in disease states has been the focus of many studies and has resulted in a number of pharmacological inhibitors, with some making it into the clinic as therapeutics. In order to better understand the regulation of sphingolipid-metabolizing enzymes as well as to develop much more potent and specific inhibitors, the field of sphingolipids has recently taken a turn toward structural biology. The last decade has seen the structural determination of a number of sphingolipid enzymes and effector proteins. In these terms, one of the most complete arms of the sphingolipid pathway is the sphingosine-1-phosphate (S1P) arm. The structures of proteins involved in the function and regulation of S1P are being used to investigate further the regulation of said proteins as well as in the design and development of inhibitors as potential therapeutics.     

The Selective Agonist for Sphingosine-1-Phosphate Receptors Siponimod Increases the Expression Level of NR4A Genes in Microglia Cell Line

Fingolimod (FTY720) and siponimod (BAF312) are selective agonists for sphingosine-1-phosphate (S1P) receptors approved for the treatment of relapsing–remitting (RR) and secondary progressive (SP) multiple sclerosis (MS), respectively. BAF312 exerts pro-myelination and neuro-protective functions on CNS resident cells, although the underlying molecular mechanism is not yet fully understood. NR4A2 is an anti-inflammatory gene, belonging to the NR4A family, whose expression is reduced in blood from treatment-naïve patients with RRMS, but is restored in patients treated with FTY720 for more than two years. We performed an in vitro study to investigate the potential involvement of the NR4A genes in the protective and restorative effects of BAF312. We showed that BAF312 enhances the expression of NR4A1 and NR4A2 in the N9 microglial cell line, but has no effect in the peripheral blood mononuclear cells and oligodendrocytes. This study suggests a novel molecular mechanism of action for the selective agonists for S1P receptors within the CNS.