Identification prognostic features related to sphingolipid metabolism and experimental validation of TRIM47 in hepatocellular carcinoma

Background:The specific impact of sphingolipid metabolism on developing hepatocellular Carcinoma(HCC)remains unclear.This study aims to explore the relationship between sphingolipid metabolism and HCC prognosis,immune response,and drug sensitivity.Methods:Data were obtained from The Cancer Genome Atlas(TCGA)-Hepatocellular Carcinoma(LIHC)and Gene Expression Omnibus(GEO,GSE14520 datasets).47 sphingolipid metabolism genes were obtained from the Kyoto Encyclopedia of Genes and Genomes(KEGG)database.After classifying HCC samples using the Non-negative Matrix Factorization(NMF)clustering method,differentially expressed genes were screened.Then,8 risk genes were obtained by univariate analysis,survival random forest reduction and lasso analysis.The expression of 8 risk genes was verified in vitro.Results:8 risk genes were used to construct the Sphingolipid score model.High-Sphingolipid score predicted poor prognosis of HCC patients.Sphingolipid score was associated with immune checkpoints(IL-1B,TLR4,TGFB1,and IL-10),immune cells(Th2,Treg,MDSC,Neutrophil,Fibroblasts and macrophage),and MAPK Cascade.In the High-Sphingolipid score group,a significantly higher proportion of patients with TP53(p53)mutations was significantly higher(56%).Furthermore,patients with a high-Sphingolipid score were predicted to have a higher sensitivity to chemotherapy drugs.In vitro validation showed that compared with normal liver cells LX-2,TRIM47,and S100A9 significantly increased in liver cancer cells Hep G2,MHCC-97H,and Hep3B2.1-7,while SLC1A7,LPCAT1,and CFHR4 significantly decreased.Silencing TRIM47 reduced the proliferation and promoted apoptosis.The levels of ceramide synthesis-related indexes(CERS1,CERS6,CERS5,and SPTLC2)increased,and the ACER3 related to catalytic hydrolysis decreased.Conclusion:We constructed a sphingolipid metabolism-related prognostic signature(Sphingolipid score)based on 8 risk genes.TRIM47 may affect the development of liver cancer by regulating the relevant indicators of ceramide synthesis and catalytic hydrolysis.

Structural Determination of Three Sphingolipids from Two Marine-derived Mangrove Endophytic Fungal Strains

A set of three sphingolipids, N-2′-hydroxyplmitoyl-1-O-β-D-glucopyranosyl-9-methyl-4E, 8E-sphingadiene （A）, N-2′-hydroxyl-3′E-octadecenoyl-1-O-β-D-glucopyranosyl-9-methyl-4E, 8E-sphingediene （B） and N-palmitoyldihydrosphingosine （C）, were isolated from two marine-derived mangrove endophytic fungal strains （strains No. 1924 and 3893） from the South China Sea. Their structures were elucidated by 2D NMR and FABMS methods. It is the first time that these sphingolipids were separated and obtained from marine-derived mangrove endophytic fungus from the South China Sea.

Obesity-associated steatotic liver exhibits aberrant or altered sphingolipid composition and preferentially accumulates ceramide species containing long chain fatty acids

The sphingolipid (SL) signaling pathways are induced by reactive oxygen species and proin-flammatory molecules, which are shown to be upregulated in the obese state. The present work was conducted to determine if an altered SL pathway exists, and contributes to the pathogenesis of hepatic steatosis associated with obesity. Steatotic and non-steatotic livers were procured from Zucker Obese female rats and their lean counterparts in this pre-clinical study, and assessed for enzymes involved in degradation as well as in phos-phorylation of proapoptotic SLs. The expression of enzymes [sphingo-myelinase (SMase), ceramidase, and sphingosine kinase-1 (SK1)] and apoptotic proteins (Bax and Bcl-2) was quantified by ELISA and by Western Blot. Sphingomyelin (SM), ceramide, ceramide-1 phosphate (C1P), sphingosine (SPH), and sphingosine-1-phosphate (S1P) levels were quantified by high-performance liquid chroma-tography (HPLC)-tandem mass spectroscopy (MS). Obese steatotic livers exhibited significantly upregulated ceramidase and down-regulated SK1 and C1P levels (P < 0.05), as well as significantly lower levels of SM and higher levels of ceramide species containing long chain fatty acids, compared to their lean counterparts. These findings demonstrate that obese liver harbours SLs that favour a proapoptotic environment. Moreover, accumulation of ceramides containing long chain fatty acids could be involved in the pathogenesis of hepatic steatosis.

Sphingolipids in cardiovascular and cerebrovascular systems:Pathological implications and potential therapeutic targets

The sphingolipid metabolites ceramide,sphingosine,and sphingosine-1-phosphate(S1P) and its enzyme sphingosine kinase(SphK) play an important role in the regulation of cell proliferation,survival,inflammation,and cell death.Ceramide and sphingosine usually inhibit proliferation and promote apoptosis,while its metabolite S1P phosphorylated by SphK stimulates growth and suppresses apoptosis.Because these metabolites are interconvertible,it has been proposed that it is not the absolute amounts of these metabolites but rather their relative levels that determine cell fate.The relevance of this "sphingolipid rheostat" and its role in regulating cell fate has been borne out by work in many labs using many different cell types and experimental manipulations.A central finding of these studies is that SphK is a critical regulator of the sphingolipid rheostat,as it not only produces the pro-growth,anti-apoptotic messenger S1P,but also decreases levels of pro-apoptotic ceramide and sphingosine.Activation of bioactive sphingolipid S1P signaling has emerged as a critical protective pathway in response to acute ischemic injury in both cardiac and cerebrovascular disease,and these observations have considerable relevance for future potential therapeutic targets.

Characterization of the sphingolipid profiling of Emiliania huxleyi against virus infection

Lipidomics approach by UPLC-Q-Exactive-MS was used for the identification,quantification,comparison,and characterization of sphingolipids in virus infected marine Emiliania huxleyi BOF92 cells.The results show that 16 significantly changed sphingolipids(including Cer,CerG1,and SPHm)were identified during viral infection.Our data confirmed previously recognized facts that viral infection led to a shift toward virus-specific sphingolipids,which is consistent with the down-regulation of genes involved in the host de novo sphingolipid biosynthesis.Moreover,we revealed the upregulation of virusencoded homologous genes participating in de novo sphingolipids biosynthesis and virus-specific hydroxylated long chain bases(LCBs)as phytoCer,suggesting the competitive inhibition of host sphingolipid synthesis to produce the required building blocks for viral production,replication,and assembly.Additionally,Cer 40꞉1;2,Cer 40꞉2;2 isomer,and CerG139꞉0;2,Cer 39꞉0;2 as novel metabolite markers might indicate the general dysfunctions in E.huxleyi in response to viral infection.Our results show that viral infection led to a profound remodeling of host sphingolipidome,by which viruses depend on the hijacking of host sphingolipid metabolism to support the viral life cycle.

Role of sphingosine kinase localization in sphingolipid signaling

The sphingosine kinases, SK1 and SK2, produce the potent signaling lipid sphingosine-1-phosphate (S1P). These enzymes have garnered increasing interest for their roles in tumorigenesis, inflammation, vascular diseases, and immunity, as well as other functions. The sphingosine kinases are considered signaling enzymes by producing S1P, and their activity is acutely regulated by a variety of agonists. However, these enzymes are also key players in the control of sphingolipid metabolism. A variety of sphingolipids, such as sphingosine and the ceramides, are potent signaling molecules in their own right. The role of sphingosine kinases in regulating sphingolipid metabolism is potentially a critical aspect of their signaling function. A central aspect of signaling lipids is that their hydrophobic nature constrains them to membranes. Most enzymes of sphingolipid metabolism, including the enzymes that degrade S1P, are membrane enzymes. Therefore the localization of the sphingosine kinases and S1P is likely to be important in S1P signaling. Sphingosine kinase localization affects sphingolipid signaling in several ways. Translocation of SK1 to theplasma membrane promotes extracellular secretion of S1P. SK1 and SK2 localization to specific sites appears to direct S1P to intracellular protein effectors. SK localization also determines the access of these enzymes to their substrates. This may be an important mechanism for the regulation of ceramide biosynthesis by diverting dihydrosphingosine, a precursor in the ceramide biosynthetic pathway, from the de novo production of ceramide.

Bile acids and sphingolipids in cholangiocarcinoma

Objective:Cholangiocarcinoma(CCA)is a rare but highly malignant hepatobiliary cancer with a very poor prognosis and limited treatment options.CCA is commonly associated with chronic cholestasis and significantly elevated levels of primary and conjugated bile acids(CBAs),which are correlated with bile duct obstruction.

Sphingolipid metabolism affects the anticancer effect of cisplatin

Cisplatin,a DNA crosslinking agent,is widely used for the treatment of a variety of solid tumors.Numerous studies have demonstrated that sphingolipid metabolism,which acts as a target for cisplatin treatment,is a highly complex network that consists of sphingolipid signaling molecules and related catalytic enzymes.Ceramide(Cer),which is the central molecule of this network,has been established to induce apoptosis.However,another molecule,sphingosine-1-phosphate(S1P),exerts the opposite function,i.e.,serves as a regulator of pro-survival.Other sphingolipid molecules,including dihydroceramide,ceramide-1-phosphate,glucosylceramide(Glu Cer),and sphingosine(Sph),or sphingolipid catalytic enzymes such as Sph kinase(Sph K),Cer synthase(Cer S),and S1 P lyase,have also attracted considerable attention,particularly Cer,Glu Cer,Sph K,Cer S,and S1 P lyase,which have been implicated in cisplatin resistance.This review summarizes specific molecules involved in sphingolipid metabolism and related catalytic enzymes affecting the anticancer effect of cisplatin,particularly in relation to induction of apoptosis and drug resistance.

Emerging roles and therapeutic potentials of sphingolipids in pathophysiology:emphasis on fatty acyl heterogeneity

Sphingolipids not only exert structural roles in cellular membranes,but also act as signaling molecules in various physiological and pathological processes.A myriad of studies have shown that abnormal levels of sphingolipids and their metabolic enzymes are associated with a variety of human diseases.Moreover,blood sphingolipids can also be used as biomarkers for disease diagnosis.This review summarizes the biosynthesis,metabolism,and pathological roles of sphingolipids,with emphasis on the biosynthesis of ceramide,the precursor for the biosynthesis of complex sphingolipids with different fatty acyl chains.The possibility of using sphingolipids for disease prediction,diagnosis,and treatment is also discussed.Targeting endogenous ceramides and complex sphingolipids along with their specific fatty acyl chain to promote future drug development will also be discussed.

α1-COP modulates plasmodesmata function through sphingolipid enzyme regulation

Callose,aβ-1,3-glucan plant cell wall polymer,regulates symplasmic channel size at plasmodesmata(PD)and plays a crucial role in a variety of plant processes.However,elucidating the molecular mechanism of PD callose homeostasis is limited.We screened and identified an Arabidopsis mutant plant with excessive callose deposition at PD and found that the mutated gene wasα1-COP,a member of the coat protein I(COPI)coatomer complex.We report that loss of function ofα1-COP elevates the callose accumulation at PD by affecting subcellular protein localization of callose degradation enzyme Pd BG2.This process is linked to the functions of ERH1,an inositol phosphoryl ceramide synthase,and glucosylceramide synthase through physical interactions with theα1-COP protein.Additionally,the loss of function ofα1-COP alters the subcellular localization of ERH1 and GCS proteins,resulting in a reduction of Glc Cers and Glc HCers molecules,which are key sphingolipid(SL)species for lipid raft formation.Our findings suggest thatα1-COP protein,together with SL modifiers controlling lipid raft compositions,regulates the subcellular localization of GPI-anchored PDBG2 proteins,and hence the callose turnover at PD and symplasmic movement of biomolecules.Our findings provide the first key clue to link the COPI-mediated intracellular trafficking pathway to the callose-mediated intercellular signaling pathway through PD.

Sphingolipid inhibitor response gene GhMYB86 controls fiber elongation by regulating microtubule arrangement

Although the cell membrane and cytoskeleton play essential roles in cellular morphogenesis,the interaction between the membrane and cytoskeleton is poorly understood.Cotton fibers are extremely elongated single cells,which makes them an ideal model for studying cell development.Here,we used the sphingolipid biosynthesis inhibitor,fumonisin B1(FB1),and found that it effectively suppressed the myeloblastosis(MYB)transcription factor GhMYB86,thereby negatively affecting fiber elongation.A direct target of GhMYB86 is GhTUB7,which encodes the tubulin protein,the major component of the microtubule cytoskeleton.Interestingly,both the overexpression of GhMYB86 and GhTUB7 caused an ectopic microtubule arrangement at the fiber tips,and then leading to shortened fibers.Moreover,we found that GhMBE2 interacted with GhMYB86 and that FB1 and reactive oxygen species induced its transport into the nucleus,thereby enhancing the promotion of GhTUB7 by GhMYB86.Overall,we established a GhMBE2-GhMYB86-GhTUB7 regulation module for fiber elongation and revealed that membrane sphingolipids affect fiber elongation by altering microtubule arrangement.

Emerging Roles of Sphingolipid Signaling in Plant Response to Biotic and Abiotic Stresses

Plant sphingolipids are not only structural components of the plasma membrane and other endomembrane systems but also act as signaling molecules during biotic and abiotic stresses.However,the roles of sphingolipids in plant signal transduction in response to environmental cues are yet to be investigated in detail. In this review,we discuss the signaling roles of sphingolipid metabolites with a focus on plant sphingolipids.We also mention some microbial sphingolipids that initiate signals during their interaction with plants, because of the limited literatures on their plant analogs.The equilibrium of nonphosphorylated and phosphorylated sphingolipid species determine the destiny of plant cells,whereas molecular connections among the enzymes responsible for this equilibrium in a coordinated signaling network are poorly understood.A mechanistic link between the phytohormone-sphingolipid interplay has also not yet been fully understood and many key participants involved in this complex interaction operating under stress conditions await to be identified.Future research is needed to fill these gaps and to better understand the signal pathways of plant sphingolipids and their interplay with other signals in response to environmental stresses.

Changes of sphingolipids profiles after ischemia-reperfusion injury in the rat liver

Background Hepatic ischemia-reperfusion （I/R） injury occurs in many clinical procedures. The molecular mechanisms responsible for hepatic I/R injury however remain unknown. Sphingolipids, in particular ceramide, play a role in stress and death receptor-induced hepatocellular death, contributing to the progression of several liver diseases including liver I/R injury. In order to further define the role of sphingolipids in hepatic I/R, systemic analysis of sphingolipids after reperfusion is necessary. Methods We investigated the lipidomic changes of sphingolipids in a rat model of warm hepatic I/R injury, by delayed extraction matrix-assisted laser desorption ionization time-of-flight mass spectrometry （DE MALDI-TOF-MS）. Results The total amounts of ceramide and sphingomyelin and the intensity of most kinds of sphingolipids, mainly sphingomyelin, significantly increased at 1 hour after reperfusion （P 〈0.05） and reached peaks at 6 hours after reperfusion （P 〈0.01） compared to controls. Six new forms of ceramide and sphingomyelins appeared 6 hours after reperfusion, they were （m/z） 537.8, 555.7, 567.7, 583.8, 683.5 and 731.4 respectively. A ceramide-monohexoside （m/z） 804.4 （CMH（d18：1C22：1＋Na）＋） also increased after reperfusion and correlated with extent of liver injury after reperfursion. Conclusions Three main forms of sphingolipids, ceramide, sphingomyelin and ceramide-monohexoside, are related to hepatic I/R injury and provide a new perspective in understanding the mechanisms responsible for hepatic I/R injury.

Bile acids and sphingolipids in non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is one of the fastest-growing diseases, and its global prevalence is estimated to increase >50% by 2030. NAFLD is comorbid with metabolic syndrome, obesity, type 2 diabetes, and insulin resistance. Despite extensive research efforts, there are no pharmacologic or biological therapeutics for the treatment of NAFLD. Bile acids and sphingolipids are well-characterized signaling molecules. Over the last few decades, researchers have uncovered potential mechanisms by which bile acids and sphingolipids regulate hepatic lipid metabolism. Dysregulation of bile acid and sphingolipid metabolism has been linked to steatosis, inflammation, and fibrosis in patients with NAFLD. This clinical observation has been recapitulated in animal models, which are well-accepted by experts in the hepatology field. Recent transcriptomic and lipidomic studies also show that sphingolipids are important players in the pathogenesis of NAFLD. Moreover, the identification of bile acids as activators of sphingolipid-mediated signaling pathways established a novel theory for bile acid and sphingolipid biology. In this review, we summarize the recent advances in the understanding of bile acid and sphingolipid-mediated signaling pathways as potential contributors to NAFLD. A better understanding of the pathologic effects mediated by bile acids and sphingolipids will facilitate the development of new diagnostic and therapeutic strategies for NAFLD.

Isolation and Functional Characterisation of the Genes Encoding Δ~8-Sphingolipid Desaturase from Brassica rapa

8-Sphingolipid desaturase is the key enzyme that catalyses desaturation at the C8 position of the long-chain base of sphingolipids in higher plants. There have been no previous studies on the genes encoding AS-sphingolipid desaturases in Brassica rapa. In this study, four genes encoding AS-sphingolipid desaturases from B. rapa were isolated and characterised. Phylogenetic analyses indicated that these genes could be divided into two groups： BrD8A, BrD8C and BrD8D in group I, and BrD8B in group II. The two groups of genes diverged before the separation of Arabidopsis and Brassica. Though the four genes shared a high sequence similarity, and their coding desaturases all located in endoplasmic reticulum, they exhibited distinct expression patterns. Heterologous expression in Saccharomyces cerevisiae revealed that BrD8A/B/C/D were functionally diverse AS-sphingolipid desaturases that catalyse different ratios of the two products 8（Z）- and 8（E）-C18-phytosphingenine. The aluminium tolerance of transgenic yeasts expressing BrD8A/B/C/D was enhanced compared with that of control cells. Expression of BrD8A in Arabidopsis changed the ratio of 8（Z）：8（E）-C 18-phytosphingenine in transgenic plants. The information reported here provides new insights into the biochemical functional diversity and evolutionary relationship of AS-sphingolipid desaturase in plants and lays a foundation for further investigation of the mechanism of 8（Z）- and 8（E）-C18- phytosphingenine biosynthesis.

Sphingolipid metabolism, transport, and functions in plants:Recent progress and future perspectives

Sphingolipids,which comprise membrane systems together with other lipids,are ubiquitous in cellular organisms.They show a high degree of diversity across plant species and vary in their structures,properties,and functions.Benefiting from the development of lipidomic techniques,over 300 plant sphingolipids have been identified.Generally divided into free long-chain bases(LCBs),ceramides,glycosylceramides(GlcCers)and glycosyl inositol phosphoceramides(GIPCs),plant sphingolipids exhibit organized aggregation within lipid membranes to form raft domains with sterols.Accumulating evidence has revealed that sphingolipids obey certain trafficking and distribution rules and confer unique properties to membranes.Functional studies using sphingolipid biosynthetic mutants demonstrate that sphingolipids participate in plant developmental regulation,stimulus sensing,and stress responses.Here,we present an updated metabolism/degradation map and summarize the structures of plant sphingolipids,review recent progress in understanding the functions of sphingolipids in plant development and stress responses,and review sphingolipid distribution and trafficking in plant cells.We also highlight some important challenges and issues that we may face during the process of studying sphingolipids.

Sphingolipid profiles and their relationship with inflammatory factors in asthmatic patients of different sexes

Background:Asthma is a heterogeneous disease with distinct prevalence and manifestation between sexes.This study was to identify sex-specific features of asthma via metabolomic analysis of sphingolipids.Methods:Forty-two asthma patients(27 women and 15 men)admitted to the Peking University Third Hospital from January 2015 to December 2015 were enrolled.Peripheral venous blood was collected for metabolomic analysis by targeted liquid chromatography-mass spectrometry.Sex hormones(estradiol,progesterone,testosterone,and androstenedione)and multiple inflammatory factors(periostin,leptin,IgE,IL-4,IL-5,IL-10,IL-13,IL-17A,and IFN-γ)were also assessed.The eosinophil percentage in induced sputum was also detected.All these data were applied to comparative analysis between sexes.Results:Testosterone was negatively related to periostin(ρ=-0.420,P=0.009)and IL-5(ρ=-0.540,P=0.012),while estradiol was positively related to the blood eosinophil percentage(ρ=0.384,P=0.025).Among the eighteen species of sphingolipids detected in the 42 patients,five ceramide(Cer)species(Cer16:0,Cer:20:0,Cer22:0,Cer24:0,and Cer26:0)and one sphingomyelin(SM)species(SM38:0)were significantly higher in male than in female patients.Further investigation found that the correlation between Cer20:0 and IL-5 was positive in males(ρ=0.943,P=0.005)but negative in females(ρ=-0.561,P=0.030).Conclusions:Testosterone was negatively correlated with eosinophil inflammatory factors,but estradiol was positively correlated.Male asthma patients had higher ceramide and sphingomyelin levels than female patients.Different sexes had opposite correlations with ceramide and IL-5,respectively,suggesting that therapeutic strategies targeting ceramide should be different between sexes.

Sphingolipid metabolism and drug resistance in ovarian cancer

Despite progress in understanding molecular aberrations that contribute to the development and progression of ovarian cancer,virtually all patients succumb to drug resistant disease at relapse.Emerging data implicate bioactive sphingolipids and regulation of sphingolipid metabolism as components of response to chemotherapy or development of resistance.Increases in cytosolic ceramide induce apoptosis in response to therapy with multiple classes of chemotherapeutic agents.Aberrations in sphingolipid metabolism that accelerate the catabolism of ceramide or that prevent the production and accumulation of ceramide contribute to resistance to standard of care platinum-and taxane-based agents.The aim of this review is to highlight current literature and research investigating the influence of the sphingolipids and enzymes that comprise the sphingosine-1-phosphate pathway on the progression of ovarian cancer.The focus of the review is on the utility of sphingolipid-centric therapeutics as a mechanism to circumvent drug resistance in this tumor type.

Phosphorylation of the LCB1 subunit of Arabidopsis serine palmitoyltransferase stimulates its activity and modulates sphingolipid biosynthesis

Sphingolipids are the structural components of membrane lipid bilayers and act as signaling molecules in many cellular processes.Serine palmitoyltransferase(SPT)is the first committed and rate-limiting enzyme in the de novo sphingolipids biosynthetic pathway.The core SPT enzyme is a heterodimer consisting of LONG-CHAIN BASE1(LCB1)and LCB2 subunits.SPT activity is inhibited by orosomucoid proteins and stimulated by small subunits of SPT(ssSPTs).However,whether LCB1 is modified and how such modification might regulate SPT activity have to date been unclear.Here,we show that activation of MITOGEN-ACTIVATED PROTEIN KINASE 3(MPK3)and MPK6 by upstream MKK9 and treatment with Flg22(a pathogen-associated molecular pattern)increases SPT activity and induces the accumulation of sphingosine long-chain base t18:0 in Arabidopsis thaliana,with activated MPK3and MPK6 phosphorylating AtLCB1.Phosphorylation of AtLCB1 strengthened its binding with AtLCB2b,promoted its binding with ssSPTs,and stimulated the formation of higher order oligomeric and active SPT complexes.Our findings therefore suggest a novel regulatory mechanism for SPT activity.

Sphingolipids Profiling of Plasma in Patients with Diabetes Mellitus Associated with Atherosclerosis by a Novel Normal-Phase UPLC-QToF MS Method

A novel normal-phase UPLC-QToF MS method was developed for sphingolipids analysis,which was then applied to separate and identify seven classes of sphingolipids in plasma.The time-consuming of this novel method was much shorter than previous 2D LC–MS method,while the sensitivity,repeatability and resolution for sphingolipids analysis were better or comparable.Besides,the differences of lipids in human plasma among diabetes mellitus patients,diabetes mellitus associated with atherosclerosis patients and control subjects were also compared.Finally,12 sphingolipids species were identified as the amounts of which in diabetes mellitus associated with atherosclerosis patients were significantly higher than them in diabetes mellitus patients(VIP>1.0,p value<0.05,fold change>1.5).As the isomers of GalCs and GluCs were successfully separated,it was found that five GluCs,rather than GalCs,were included in these 12 potential biomarkers.These results suggest the need to separate GalCs from GluCs,and also indicated that there may be some extra activation pathways of diabetes mellitus associated with atherosclerosis,different from the atherosclerosis pathway and the diabetes mellitus pathway,causing cardiovascular disease.