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PubMed1989

Sialylation of lacto-N-neotetraosyl ceramide by a solubilized sialyltransferase(s) from chicken skeletal muscle: effect of phosphatidylcholine and sphingomyelin.

The sialytransferase(s) that transfers sialic acid to lacto-N-neotetraosylceramide and other glycosphingolipids with a galactose nonreducing terminus has been successfully solubilized from embryonic chicken skeletal muscle. The enzyme can be stored in 50 mM HEPES (pH 6.8), 1% Triton CF-54, and 20% glycerol at -70 degrees C for as long as six months. Addition of phosphatidylcholine or sphingomyelin (0.167%) readily reactivates the stored inactive enzymes and such activity persists for about two weeks at 0 degrees-4 degrees C with the peak activity occurring at 1 to 2 days. Sphingomyelin from chicken muscle, which contains mainly C16:0 and C18:0, is 2.1-fold more effective than bovine brain sphingomyelin at the same concentration (0.4%).

Animals↗
PubMed1992

Regulation of phospholipase C delta activity by sphingomyelin and sphingosine.

Phospholipase C delta (PLC delta) is strongly inhibited by sphingomyelin (SM). The inhibition occurs in both the presence and the absence of spermine, an activator of PLC delta. Phosphatidylethanolamine (PE), phosphatidylcholine (PC), phosphatidylserine (PS), and phosphatidylinositol (PI) also inhibit PLC delta in the presence of spermine but are much less effective than SM. PE and PC activate and PS and PI inhibit PLC delta in the absence of spermine. Again, the inhibition by PS and PI is much weaker than the inhibition observed with SM. Similar or identical effects are observed in detergent micelle and liposome assays. Comparisons of physiological concentrations of SM with concentrations yielding 50% inhibition of PLC delta in vitro indicate that SM is likely to be a major factor in regulating the activity of PLC delta by inhibition. It is proposed that, in vivo, sphingomyelin acts as an inhibitor of PLC delta, which enables the enzyme to be regulated by activation. In certain circumstances, there is a substantial decline in SM and this may lead to a partial relief of the inhibition. PLC delta is activated by sphingosine in the absence of spermine. However, this activation occurs at unphysiologically high concentrations of sphingosine. The effects of SM and sphingosine on PLC delta in marked contrast to those observed with protein kinase C, which is unaffected by sphingomyelin and inhibited by sphingosine.

Animals↗
PubMed1979

Fatty acid composition and thermal behavior of natural sphingomyelins.

We found significant differences in the fatty acid composition of several bovine brain, egg yolk and sheep erythrocyte sphingomyelins. These differences in fatty acid composition influence the thermal behavior of hydrated sphingomyelin as recorded by differentail scanning calorimetry. Significant differences were also found in the temperature and complexity of the order-disorder phase transitions of bovine brain sphingomyelin obtained from different sources which, in general, correlate with the relative content of the saturated fatty acids (palmitic (C16:0) and stearic acid (C18:0) acids) and the long unsaturated nervonic acid (C24:1).

Animals↗
PubMed1981

Biosynthesis of sphingomyelin from erythro-ceramides and phosphatidylcholine by a microsomal cholinephosphotransferase.

Mouse liver microsomes were shown to be active in the synthesis of sphingomyelin from ceramide and phosphatidylcholine in a reaction independent of CDPcholine. The conversion was not inhibited by calcium chelating reagents, and no evidence for the involvement of phospholipase C activity in the transformation could be adduced. Activity was also demonstrated in monkey liver and heart microsomes. Mouse brain microsomes produced a sphingomyelin analogue, tentatively identified as ceramide phosphorylethanolamine, but not sphingomyelin. Both [14C]ceramide and [G-14]phosphatidylethanolamine were precursors of the brain product, while phosphatidylcholine was inactive. Progress in the partial characterization of the liver enzyme is also described.

Animals↗
PubMed1995

Blood sphingomyelins from two European countries.

The objectives of this study were to isolate and analyse human blood sphingomyelins from two European populations which have significant differences in both the composition of dietary fat source and the rate of mortality from coronary heart disease. Blood samples have been taken from healthy adult volunteers from a Greek (Thessaloniki) and a French (Paris) region. The sphingomyelin fraction from red blood cells and plasma, separately, have been isolated by thin-layer chromatography and analysed by mass spectrometry after soft chemical ionisation with gas ammonia. The conditions used gave spectra with three discrete areas which correspond to ions coming from sphingoid bases, fatty acids and ceramides. Eight sphingoid bases have been detected in both red blood cells and plasma. Sphingosine was the major contributor. The rest of the sphingoid bases have 16 to 19 carbon atoms and 0 to 2 double bonds. Fourteen fatty acids, the same for red blood cells and plasma, have been detected with 16 to 26 carbon atoms and 0 to 2 double bonds. Palmitic acid was the most abundant fatty acid. Thirty eight ceramides have been detected in red blood cells and forty in plasma. Thirty six ceramides were common in red blood cells and plasma. Statistically significant differences (P < 0.01) have been detected between the two populations for some sphingoid bases, fatty acids and ceramides. Differences have also been found between the two populations in the degree of saturation of these sphingomyelin parts. These differences are attributed to (a) high monounsaturated fat, olive oil, consumption by Greeks and (b) other environmental and genetic factors. It is suggested that the detected differences between the two populations contribute to the different coronary heart disease rates observed among Greeks and French.

Adult↗
PubMed1996

Identification of a new sphingolipid 3-O-acyl-D-erythro-sphingomyelin in newborn pig and infant plasma.

A new sphingolipid was found in newborn pig plasma at a level of 2.5 +/- 0.4% of total lipids. The compound decreased to less than half that amount by day one of age and virtually disappeared by the fourth week. On thin-layer chromatography (TLC) the new lipid migrated close to phosphatidylethanolamine. The compound was isolated by TLC from the plasma of newborn piglets and identified as a 3-O-acyl-D-erythro-sphingomyelin by chemical and chromatographic techniques, 1H- and 13C-nuclear magnetic resonance and fast-atom bombardment mass spectrometry. Mild alkaline hydrolysis at room temperature gave mainly C16 and C18 fatty acids and sphingomyelin. Subsequent reaction with Ba(OH)2 released long-chain saturated and monounsaturated fatty acids from C14 to C24, and sphingosine which was identified as the erythro configuration by gas chromatography. Less than 1% of the sphingosine was of the C20 isomer. No hydroxy fatty acids were found. The acylated sphingomyelin was only found in plasma lipids of newborn piglets and not in their red blood cell membranes or platelets of newborn piglets, or in sow plasma. This compound was tentatively identified by chromatography in trace amounts in the serum of cord blood of newborn infants, but not in the plasma lipids of adults.

Acylation↗
PubMed1984

Enhanced N-acylation of palmitic acid in sphingomyelin of antibody-stimulated L cells.

Metabolism of sphingomyelin was stimulated in a fibroblast-like transformed cell line, L-929, when the cells were incubated with antibodies of a specific rabbit antiserum. The cells responded with an increased incorporation of [3H] palmitic acid into sphingomyelin. The stimulated uptake of palmitic acid into sphingomyelin can not be explained by simple mass increases in cellular phospholipids but probably represents a selective N-acyl group turnover. Palmitic acid composed only 7.5 percent of the acyl substituents, as assessed by gas-liquid chromatographic analysis, but [3H] palmitic acid was incorporated at a two-fold higher level into the acyl position than into the long chain base precursor (sphingosine). Since it is known that palmitic acid is the predominant fatty acid forming sphingosine, this represents a considerable selection for N-acyl group turnover. Another saturated fatty acid, stearic acid, which was over twice as abundant constituently was incorporated at a much lower rate when the cells were stimulated. Thus palmitic acid was observed to be selectively turning over in a manner suggestive of acylation-reacylation cycles observed with other classes of phospholipids.

Acylation↗
PubMed1993

An efficient route to N-palmitoyl-D-erythro-sphingomyelin and its 13C-labeled derivatives.

We describe here a practical and efficient route to a homogeneous N-palmitoyl-D-erythro-sphingomyelin and its 13C-labeled derivatives. (2S,3R,4E)-2-Azido-3-(tert-butyldimethylsilyloxy)-4-octad ecene-1-ol 1 was converted to the sphingosine equivalent 2 by treatment with triphenylphosphine and water. Amine 2 was then coupled with palmitic acid, affording the ceramide derivative 3a. In the following two reactions the phosphorylcholine functional group was generated by using 2-chloro-2-oxo-1,3,2-dioxaphospholane and trimethylamine, respectively. The final deprotection of the secondary hydroxyl group in 5a produced the desired N-palmitoyl-D-erythro-sphingomyelin 6a. The overall yield of this five-step synthesis is 43%. The melting point, 213-215 degrees C, the specific rotation, [alpha]20D = +6.8 (c = 1.3, CH2Cl2/MeOH 1:1) and 1H- and 13C-NMR data indicate that the synthetic sphingomyelin is enantiomerically pure. The 13C-labeled derivatives 6b, 6c and 6d were synthesized by employing the same scheme.

Carbon Isotopes↗
PubMed1990

Sphingomyelin is synthesized in the cis Golgi.

We have employed in vitro a truncated ceramide analogue with 8 carbon atoms in the sphingosine and the fatty acyl residue, each, to investigate the activity of various membrane fractions to synthesize truncated sphingomyelin. This shortened ceramide readily diffuses through membranes and therefore can easily find access to the lumina of intact organelles. Sphingomyelin synthase activity resides in the Golgi apparatus, and after sucrose density gradient centrifugation of Golgi-enriched fractions sphingomyelin synthesis follows a cis Golgi marker enzyme.

Animals↗
PubMed1990

Sphingomyelin synthesis in Fasciola hepatica.

Whole worms and/or homogenates of F. hepatica incorporate label from cytidine-5-diphospho[methyl-14C]choline,[1-14C]palmitoylCoA,[U- 14C]serine,[2-14C]methionine, [U-14C]glycine, [U-14C]threonine and [U-14C]aspartate into the various intermediates of sphingomyelin synthesis (ketosphinganine, sphinganine, sphingosine, ceramide and sphingomyelin). This suggests that sphingomyelin synthesis in F. hepatica occurs by a pathway similar to that found in mammals. However, there is some evidence that in F. hepatica 3-ketosphinganine may be N-acylated prior to reduction and dehydrogenation.

Amino Acids↗
PubMed1993

Sphingomyelin synthesis in Ascaridia galli.

Adult Ascaridia galli incorporate label from [U-14C] serine into various intermediates of sphingomyelin synthesis (ketosphinganine, sphinganine, sphingosine, ceramide and sphingomyelin). From the results it is concluded that A. galli possesses the five enzymes involved in sphingomyelin synthesis, namely: serine palmitoyltransferase, 3-ketosphinganine reductase, flavoprotein sphinganine reductase, sphingosine acyltransferase and ceramide choline phosphotransferase.

Animals↗
PubMed1991

Sphingomyelin and derivatives as cellular signals.

This comprehensive review was necessitated by recent observations suggesting that sphingomyelin and derivatives may serve second messenger functions. It has attempted to remain true to the theme of cellular signalling. Hence, it has focussed on the lipids involved primarily with respect to their metabolism and properties in mammalian systems. The enzymology involved has been emphasized. An attempt was made to define directions in which signals may be flowing. However, the evidence presented to date is insufficient to conclusively designate the mechanisms of stimulated lipid metabolism. Hence, the proposed pathways must be viewed as preliminary. Further, the biologic functions of these lipids is for the most part uncertain. Thus, it is difficult to presently integrate this sphingomyelin pathway into the greater realm of cell biology. Nevertheless, the present evidence appears to suggest that a sphingomyelin pathway is likely to possess important bioregulatory functions. Hopefully, interest in this novel pathway will grow and allow a more complete understanding of the roles of these sphingolipids in physiology and pathology.

Animals↗
PubMed1985

Sphingomyelin synthesis in Hymenolepis diminuta (Cestoda).

Adult Hymenolepis diminuta incorporated label from L[U-14C]serine, [1-14C]palmitic acid, [1-14C]palmitoyl-CoA and cytidine-5'-diphospho[methyl-14C]choline into the various intermediates of sphingomyelin synthesis (ketosphingosine, dihydrosphingosine, sphingosine, ceramide and sphingomyelin). From the results it was concluded that H. diminuta possessed the five enzymes involved in sphingomyelin synthesis, namely serine palmitoyl-transferase, 3-oxosphinganine reductase, flavoprotein dihydrosphingosine reductase, sphingosine acyltransferase and ceramide choline-phosphotransferase.

Acyltransferases↗
PubMed2003

Sphingomyelin in the suppression of colon tumors: prevention versus intervention.

Intestinal cells are regularly exposed to sphingolipid metabolites, i.e., ceramide and sphingoid bases, after hydrolysis of complex sphingolipids from the diet. These metabolites are known regulators of cell growth, differentiation, and death. Non-pharmacological amounts in the diet have been shown to inhibit early stages of chemically induced colon cancer in mice. To distinguish between chemopreventive and chemotherapeutic effects of sphingomyelin supplements, mice were fed sphingomyelin before and after tumor initiation. Both applications drastically reduced tumor formation, without a significant difference among the groups, indicating that sphingolipids are as effective in the chemoprevention of tumors as in early intervention. The normalization of cell proliferation and rate of apoptosis, but not the induction of differentiation, seem to be key players in the suppression of tumor formation by dietary sphingomyelin. This may have implications for the development of a cancer prevention or treatment strategy with sphingolipids as an alternative to conventional drugs.

1,2-Dimethylhydrazine↗
PubMed2004

Overexpression of phosphatidylinositol transfer protein beta in NIH3T3 cells has a stimulatory effect on sphingomyelin synthesis and apoptosis.

Phosphatidylinositol transfer proteins (PI-TPs) consist of two isoforms (PI-TPalpha and PI-TPbeta), which differ in phospholipid transfer properties and intracellular localization. Both PI-TP isoforms are substrates for protein kinase C and contain a minor phosphorylation site (Ser166 in PI-TPalpha; Ser165 in PI-TPbeta). Only PI-TPbeta contains a major phosphorylation site at Ser262, which must be phosphorylated for PI-TPbeta to be associated with the Golgi. The PI-TP isoforms are completely conserved between mammals. Although their function is still not clear, their importance follows from knock-out studies, showing that mice lacking PI-TPalpha die soon after birth and that embryonic stems cells lacking PI-TPbeta cannot be generated [Mol. Biol. Cell 13 (2002) 739]. We determined the levels of the PI-TP isoforms in various mouse tissues by immunoblotting. PI-TPalpha is present in all tissues investigated, with highest levels in brain (167 ng/100 microg total protein). The levels of PI-TPbeta are 50-100 times lower than those of PI-TPalpha, with relatively high levels found in liver and brain (1.2 and 1.8 ng/100 microg of total protein, respectively). In contrast to NIH3T3 cells overexpressing PI-TPalpha, cells overexpressing PI-TPbeta (SPIbeta cells) were able to maintain steady-state levels of sphingomyelin in plasma membrane under conditions where this lipid is degraded by exogenous sphingomyelinase. This process of rapid sphingomyelin replenishment is dependent on PI-TPbeta being associated with the Golgi as cells overexpressing a mutant PI-TPbeta in which the major phosphorylation site is replaced (PI-TPbeta(S262A) behave as wild-type NIH3T3 cells. Since the SPIbeta cells display a decreased growth rate (35 h as compared to 21 h for wtNIH3T3 cells), we have investigated the sensitivity of these cells towards UV-induced apoptosis. We have found that the SPIbeta cells, but not the cells overexpressing PI-TPbeta(S262A), are very sensitive. We are currently investigating whether a relationship exists between PI-TPbeta being involved in maintaining plasma membrane sphingomyelin levels and the enhanced sensitivity towards apoptosis.

Animals↗
PubMed2005

Differential lipid packing abilities and dynamics in giant unilamellar vesicles composed of short-chain saturated glycerol-phospholipids, sphingomyelin and cholesterol.

The ability of membrane components to arrange themselves heterogeneously within the bilayer induces the formation of microdomains. Much work has been devoted to mimicking domain-assembly in artificial bilayers and characterizing their physico-chemical properties. Ternary lipid mixtures composed of unsaturated phospholipids, sphingomyelin and cholesterol give rise to large, round domains. Here, we replaced the unsaturated phospholipid in the ternary mixture with sphingomyelin and cholesterol by saturated glycero-phospholipids of different chain length and characterized the critical role of cholesterol in sorting these lipids by confocal imaging and fluorescence correlation spectroscopy (FCS). More cholesterol is needed to obtain phase segregation in ternary mixtures, in which the unsaturated phospholipid is replaced by a saturated one. Finally, lipid dynamics in distinct phases is very low and astonishingly similar, thereby suggesting the poor ability of cholesterol in sorting short-chain saturated glycero-phospholipids and sphingomyelin.

Cholesterol↗
PubMed2007

Reverse cholesterol transport is regulated by varying fatty acyl chain saturation and sphingomyelin content in reconstituted high-density lipoproteins.

Because phospholipid composition of high-density lipoprotein (HDL) plays a vital role in its reverse cholesterol transport (RCT) function, we studied RCT in vitro (uptake and efflux) with reconstituted HDLs (rHDLs) containing phosphatidylcholine (PC) with fatty acids of increasing saturation levels (stearic, oleic, linoleic, linolenic) and without or with sphingomyelin (SM). Uptake significantly increased from basal value when the PC component included up to 50 mol % of oleic or linolenic acid, but did not change with linoleic acid. Increasing oleic and linoleic acids to 100 mol % significantly decreased uptake, but increasing linolenic acid to the same value did not affect it. Sphingomyelin in rHDL significantly decreased uptake, but only with PC-containing unsaturated fatty acids, and not with saturated fatty acid. Efflux was not affected in a dose-dependent manner when oleic or linoleic acid content was increased, but was significantly increased with levels of linolenic acid up to 25 mol % in PC, and was dramatically lowered with higher levels. Sphingomyelin in rHDL (PC/SM, 20:80, mol/mol) significantly increased efflux only with oleic or linoleic acid-containing rHDLs, compared with efflux without SM. In conclusion, enrichment of PC component up to 25 mol % as linolenic acid has a beneficial effect on RCT, whereas a higher percentage of it or other unsaturated fatty acids seems to be detrimental. In addition, high SM content decreases uptake with rHDL-containing unsaturated fatty acids, whereas it increases efflux for rHDL-containing oleic or linoleic acid. These results show for the first time the importance of SM in RCT in a well-defined in vitro system.

Animals↗
PubMed2000

Structural determination of sphingomyelin by tandem mass spectrometry with electrospray ionization.

Alkaline metal adduct ions of sphingomyelin were formed by electrospray ionization in positive ion mode. Under low energy collisionally activated dissociation (CAD), the product ion spectra yield abundant fragment ions representative of both long chain base and fatty acid which permit unequivocal determination of the structure. Tandem spectra obtained by constant neutral loss scanning permit identification of sphingomyelin class and specific long chain base subclass in the mixture. The fragmentation pathways under CAD were proposed, and were further confirmed by source CAD tandem mass spectrometry. The total analysis of sphingomyelin mixtures from bovine brain, bovine erythrocytes, and chicken egg yolk is also presented.

Lithium↗