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PubMed1996

Effect of tumor necrosis factor-alpha on the metabolism of arachidonic acid in human neutrophils.

Although tumor necrosis factor-alpha (TNF-alpha) has been shown to induce marked changes in the physiology/pathophysiology of cells, little is known about the effects of this cytokine on cellular lipid metabolism. In this study we examined the effects of TNF-alpha on the metabolism of eicosatetraenoic acid (arachidonic acid, (20:4(n-6)) in human neutrophils. Pretreatment of neutrophils with TNF-alpha caused a rapid increase in the incorporation of [1-14C]20:4(n-6) substrate into cellular phosphatidylinositol and phosphatidic acid and a slower rise in the incorporation into phosphatidylcholine and phosphatidylethanolamine. Radioactivity was exclusively associated with the sn-2 position of each molecule. The labeling pattern of other phospholipids, neutral lipids, and eicosanoids was unchanged. TNF-alpha had no effect on the distribution of radioactivity in 1-acyl, 1-alkyl, and 1-alk-1-enyl subclasses of phosphatidylcholine, phosphatidylethanolamine, and triglyceride. Chain elongation, beta-oxidation and desaturation of [1-14C]20:4(n-6) were not modulated by the cytokine. TNF-alpha stimulated the release of [3H]20:4(n-6) from prelabeled neutrophils and also induced the production of endogenous unesterified 20:4(n-6). Concomitantly, treatment with the cytokine caused a decrease in the mass of cellular phosphatidylinositol, phosphatidylcholine, and phosphatidylethanolamine and an increase in the levels of corresponding lysophospholipids, but had no significant effect on sphingomyelin, phosphatidic acid, diglyceride, and other lipids. TNF-alpha did not evoke neutrophils prelabeled with [3H]lyso platelet activating factor to produce [3H]phosphatidylethanol, [3H]phosphatidic acid, or [3H]diglyceride in the presence of ethanol, indicating that phospholipases D and C were not activated. Treatment of the leukocytes with the cytokine had no effect on the activity of neutral and acidic sphingomyelinase. These data collectively provide evidence that TNF-alpha specifically induces the turnover of neutrophil phosphatidylinositol, phosphatidylcholine and phosphatidylethanolamine, which are enriched with 20:4(n-6) by the activation of phospholipase A2.

Arachidonic Acid↗
PubMed1996

Activation of the Ras signaling pathway by the CD40 receptor.

The CD40 receptor is an important molecule regulating B lymphocyte proliferation, maturation, Ab class switching, and cell survival. In the present study, we identified signal transduction events triggered by cross-linking the CD40 receptor. Stimulation of Daudi B cells with anti-CD40 resulted in activation of p21ras, an important switch point in the regulation of cell growth and differentiation. Ras activation correlated with a stimulation of Rac1 and MEK-1 as well as tyrosine phosphorylation of phosphatidylinositol 3-kinase. Inhibition of endogenous Ras by transfection of transdominant inhibitory Ras prevented tyrosine phosphorylation or stimulation of phosphatidylinositol 3-kinase, Rac1, or MEK-1 upon CD40 receptor triggering, proving an activation of the Ras pathway by CD40. Ras activation was partially inhibited by either herbimycin A or calphostin pretreatment and completely inhibited by preincubation with a combination of both inhibitors, indicating a synergistic role for protein tyrosine kinases and diglycerides in Ras activation after CD40 stimulation. In support of a role for diglycerides, we detected a 30 +/- 5% decrease of cellular phosphatidylcholine content, correlating with a threefold increase of diacylglycerol synthesis induced by CD40. Supporting a role for protein tyrosine kinase, we measured a five- to eightfold stimulation of p56lyn and p58blk kinase activity. These results suggest the activation of the Ras pathway via an additive function of src kinases and phospholipases that may be important in the mediation of biologic effects after CD40 receptor engagement.

Antibodies, Monoclonal↗
PubMed1977

[Human erythrocyte glycerides].

There are difficulties in measuring red cell glycerides mainly because the amount found in erythrocytes is so differne from that of other lipids in blood cells. The red corpuscles contain only very small quantities of glycerides, about 5mg/1, while the amount of cholesterol and phospholipids is 200 to 500 times higher. The methods currently used for estimating glycerides in serum can be used here only after removing these other lipids. The distribution of glycerides in erythrocytes is ver different from that of serum: serum contains mainly triglycerides while there are diglycerides as well as triglycerides in erythrocytes (on average 3,4 micro mol/1 of triglycerides and 1,7 mumol/1 of diglycerides).

Cholesterol↗
PubMedDate not supplied

Phospholipase C treatment of mitochondria.

Heavy beef heart mitochondria depleted of phospholipids by treatment with phospholipase C followed by removal of the by products by lipase treatment or sonication in pentane were analyzed by electron microscopy, chemical analysis and assays of enzymatic activities. The results indicate that diglycerides are present after phospholipase C treatment and are inhibitors of NADH-cytochrome c reductase. After removal of diglycerides with lipase treatment, a phospholipid requirement for NADH-cytochrome c reductase could be demonstrated.

Animals↗
PubMed1997

Analysis of phospholipid molecular species.

A method is described for analysing molecular species of glycerophospholipids. Diglycerides obtained by phospholipase C-catalysed hydrolysis of the phospholipid are separated into the diacyl- alkylacyl- and alkenylacyl- subclasses by HPLC on silicic acid. The molecular species of diacylglycerol are separated by HPLC of underivatised diglycerides on a reverse phase octadecyl-silica column.

Animals↗
PubMed1992

Phosphatidylinositol hydrolysis by phospholipase A2 and C activities in human peripheral blood neutrophils.

We describe here and partially characterize a Ca(2+)-independent phospholipase A2 that acts on phosphatidylinositol in normal human peripheral blood neutrophils. Neutrophils incubated with myo-[3H]inositol to form [3H]phosphatidylinositol and then stimulated with the calcium ionophore A23187 produced [3H]lysophosphatidylinositol. This deacylation was further characterized in cell sonicates by the specific release of [3H]arachidonic acid from exogenous [1-14C]stearoyl-2-[3H]arachidonyl-phosphatidylinositol. This phospholipase A2 is Ca2+ independent, retaining full activity in the presence of 10 mM EDTA, and is optimally active at alkaline pH (pH 9). A phosphatidylinositol-hydrolyzing phospholipase C activity was characterized by the production of [3H]-/[14C]-diglycerides. This phospholipase C activity is dependent on the presence of exogenous Ca2+ and is optimally active at neutral pH (pH 7.5). The lipoxygenase/cyclooxygenase inhibitors eicosatetraenoic acid and nordihydroguaiaretic acid and the calmodulin antagonist trifluoperazine were the only compounds tested that showed significant inhibition of phospholipase A2 activity. However, none of these phosphatidylinositol-hydrolyzing phospholipase A2 inhibitory compounds resulted in the accumulation of any radiolabeled diglyceride, monoglyceride, or phosphatidic acid intermediates. Following subcellular fractionation on sucrose density gradients, it was found that the plasma membrane-enriched fractions contained the highest specific activity for phospholipase A2; however, the cytosolic fraction contained a large part of the total phospholipase A2 activity. Furthermore, when neutrophils were first exposed to several agents, including lipopolysaccharide, phorbol myristate acetate, or N-formyl-methionyl-leucyl- phenylalanine, and then subfractionated, there was a significant translocation of the enzyme activity from the cytosolic fraction to the membrane-enriched fractions. These data suggest that this Ca(2+)-independent, phosphatidylinositol-hydrolyzing phospholipase A2 may play an important role in early cell activation, providing free arachidonic acid for subsequent metabolism into biologically active eicosanoids.

Arachidonic Acid↗
PubMed1989

Multiple and novel specificities of monoclonal antibodies O1, O4, and R-mAb used in the analysis of oligodendrocyte development.

Three monoclonal antibodies that react with antigens on the surface of developing oligodendrocytes in a stage-specific manner, O1, O4 (Sommer and Schachner, 1981), and R-mAb (Ranscht et al., 1982), have been studied with respect to their specificities for a number of purified lipids. The observed specificities were consistent regardless of how the antigens were presented to the antibodies. O1 reacted with galactocerebroside, monogalactosyl-diglyceride, and psychosine and, in addition, labeled an unidentified species in rat brain extracts. R-mAb reacted with galactocerebroside, monogalactosyl-diglyceride, sulfatide, seminolipid, and psychosine; the reaction of R-mAb with sulfatide was nearly equal to that with galactocerebroside. O4 reacted with sulfatide, seminolipid, and to some extent with cholesterol. However, oligodendrocyte progenitor cells labeling with O4 that had not yet begun to express the O1 antigen failed to incorporate 35SO4 or [3H]galactose into sulfatide or seminolipid, the syntheses of which first appear in O1-positive cells. Therefore, O4 stains, in addition to sulfatide and seminolipid, and unidentified antigen that appears on the surface of oligodendrocyte progenitors prior to the expression of sulfatide and galactocerebroside. In primary cultures of rat brain, developing O4+ oligodendrocyte progenitors stained slightly earlier with R-mAb than with O1, and thus R-mAb transiently stained a larger population of oligodendrocytes than did O1. None of the three antibodies produced a detectable reaction on Western immunoblot after separation of brain proteins on reducing gels. In conclusion, the results show that O4, R-mAb, and O1 have multiple overlapping specificities, including previously unrecognized cross-reactions.

Animals↗
PubMed2005

Examining the collision-induced decomposition spectra of ammoniated triglycerides as a function of fatty acid chain length and degree of unsaturation. I. The OXO/YOY series.

A series of positionally pure triglycerides (TAGs) of the form OXO and YOY, where O is the oleate moiety and X and Y are large arrays of different fatty acid moieties, was synthesized and analyzed by reversed-phase high-performance liquid chromatography/tandem mass spectrometry. The intensities of the collision-induced decomposition (CID) products of ammoniated TAGs (ammonium ion adducts) were examined as a function of chain length, degree of unsaturation, double-bond position, and cis/trans configuration of X and Y. The major CID products, the diglyceride fragment ions and the MH+ ion, were plotted as functions of chain length for the saturated and mono-unsaturated series of X and Y. Different trends for each of these series were observed. Trends in the abundances of these fragment ions were also characterized as a function of degree of unsaturation in the TAGs. In general, the fractional abundances of the MH+ ions vary linearly with degree of unsaturation. However, the presence of double bonds positioned close to the carbonyl carbon of the fatty acid chain promotes the formation of the diglyceride fragment ion corresponding to loss of that fatty acid. Mechanisms of the formation and decomposition of ammoniated TAGs are proposed that fit the trends observed in the data. Extensions of this work are described, and a vision of a derived library of CID spectra is discussed as a platform for comprehensive analysis of complex TAG mixtures.

Ammonia↗
PubMed1981

The effect of temperature on the growth and lipid composition of the extremely halophilic coccus, Sarcina marina.

Sarcina marina (NCMB 778) grew over the temperature range 20-45 degrees C but no growth was recorded at 15 degrees C or 50 degrees C. At the optimum growth temperature of 34 degrees C the doubling time was 14.5 h. The major polar lipid components, tentatively identified as the diether analogues of phosphatidyl glycerophosphate (PGP), phosphatidyl glycerol (PG), diglycosyl diglyceride (DGD) and triglycosyl diglyceride (TGD), and the major neutral lipid components, tentatively identified as squalene, dihydrosqualene, tetrahydrosqualene, vitamin MK8, geranyl geraniol and di-O-phytanyl glycerol, are identical to those found in other extremely halophilic rods and cocci. The total lipid content varied with growth conditions from 0.6-3.2% of the dry cell weight, polar lipids accounted for between 94.3 and 83.6% of the total lipid, the remainder being neutral lipid. In response to both the transition from exponential to stationary phase and a reduction of 14 degrees C in growth temperature, batch cultures showed: (i) an increase in total lipid content; (ii) a decrease in PG and (iii) an increase in PGP. Specific responses to the temperature decrease were (i) increased total lipid content; (ii) no decrease in neutral lipids in stationary phase; (iii) marked reduction in PG and (iv) raised DGD. (i) and (ii) could be mechanisms for increasing membrane fluidity. In common with all other extreme halophiles investigated the alkyl side chains of S. marina polar lipids were identified as the phytanyl (3R, 7R, 11R, 15-tetramethylhexadecyl) group. Its structure did not appear to vary with temperature so that the normal mechanisms for modifying the structure of lipid alkyl side chains to modulate membrane fluidity in response to temperature changes probably does not occur in this group of microorganisms.

Glycolipids↗
PubMed1990

Protein phosphorylation associated with the stimulation of neutrophils. Modulation of superoxide production by protein kinase C and calcium.

Neutrophils and other phagocytic cells of the immune system possess a superoxide-generating oxidase system which is essential for the efficient killing of microbes. The system is activated by a wide variety of stimuli, some of which operate through pathways involving protein kinase C (PKC), while others appear not to. The PKC-dependent pathway is probably the major signal transduction route for most of the stimuli. Alterations in cellular Ca2+ and diglyceride levels can have a pronounced stimulatory effect on this pathway by their ability to synergistically activate PKC. This review discusses PKC, the different interactions of this kinase with the plasmalemma that are important in superoxide production, the synergy between Ca2+ and diglyceride, and the nature of the phosphoproteins involved. Evidence supporting the existence of the PKC-independent pathway is also reviewed.

Animals↗
PubMed1987

Glycerol incorporation into brain lipids in rat pups born to ethanol-intoxicated dams.

The incorporation of labeled glycerol into glycerolipid of rat brain was influenced by the age of the animal (2-month-old vs. newborn); indeed, 12 min after the administration, diglyceride was the most heavily labeled glycerolipid in the newborn brain, whereas the labeling of glycerophospholipid was highest in the adult. Various amounts of ethanol (0% to 36% of total energy intake) were administered to pregnant female rats, and the brains of their pups were examined for the ability to incorporate labeled glycerol into glycerolipid. The radioactivity incorporated into lipid diminished with increasing the amounts of alcohol consumed. The labeling pattern of lipid classes was also influenced; indeed, the radioactivity of diglyceride decreased markedly, whereas that of triglyceride and glycerophospholipid was affected to a lower degree. The distribution of radioactivity among different phospholipids also varied with age; on a percent basis, phosphatidylcholine was labeled less and phosphatidylinositol was labeled more in the newborn than in the adult. Ethanol influenced the pattern of glycerophospholipid labeling, increasing the radioactivity of phosphatidylserine and decreasing that of phosphatidylinositol.

Age Factors↗
PubMed1977

[Examination and composition of some legume seeds (author's transl)].

The chemical composition of some legume seeds is reviewed. It was found that soy (Glycine soja), field beans (Vicia faba), Vicia sativa and Lens culingris (red seeds) have the highest protein content. There were only minor differences in amino acid composition except for glutamic acid. The lysine content of legume seeds was high. Lysine is the most limiting essential amino acid in cereal proteins, therefore cereal products can be improved nutritionally by addition of legume seed flour. Examination of polar lipids by thin layer chromatography revealed that lecithin, phosphatidyl ethanolamine and phosphatidyl inositol were the major components. However, Lupinus angustifolius contained two unknown polar lipid classes.--In contrary to previous literature the ripe legume seeds contained only a very small amount of galactosyl diglycerides; however legume seeds contain higher amounts of the compounds. The conection between biosynthesis of linolenic acid and the presence of galactosyl diglycerides in higher plants is discussed.

Amino Acids↗
PubMed1981

Studies on topological distribution of arachidonic acid replacement in platelet phospholipids and on enzymes involved in the phospholipid effect accompanying platelet activation.

In this short review recent results obtained on platelet phospholipid metabolism are summarized. The first part reports a topological study of arachidonic acid (AA) replacement in platelet phospholipids. It is shown that incubation of platelets with radioactive free arachidonic acid leads to a labelling of the phospholipids present inside the platelet, whereas the exchange of intact phosphatidylcholine (PC) molecules with the plasma lipoproteins occurs on the platelet outer surface. This should allow a selective labelling of the small external pool of AA in order to follow its behaviour during platelet activation. In the second part, some enzymes involved in the metabolism of phosphatidylinositol (PI) have been further characterized. The first one is a diglyceride-lipase, which is located in the plasma membrane and releases the two fatty acids esterifying the diglycerides formed from PI by the action of the platelet phospholipase C. Such an enzyme is probably responsible for the release of AA from PI occurring upon platelet activation. On the other hand, cytosolic phospholipid exchange proteins able to catalyse the transfer of PI between membranes have been identified. The possible role of the enzymes involved in the acceleration of PI turnover occurring during platelet activation is discussed.

Arachidonic Acid↗
PubMed1981

Enzymatic degradation of polar lipids in deep-frozen parsley.

Under the frozen storage at usual storage temperatures of leafy tissues not pretreated by heat, enzymatic lipid degradation reactions take place, which lead already after a few weeks to a considerable or complete loss of the native polar lipids. These degradation processes being accompanied by a deterioration of the flavour have been studied in greater detail in parsley leaves. Among the reaction products we found large amounts of 6-acylmonogalactosyl diglycerides (formed from monogalactosyl diglycerides by enzymatic transacylation) and phosphatidic acid (formed from phospholipids through phospholipase-D action). The generally assumed reaction sequence: formation of free fatty acids by acyl hydrolases followed by hydroperoxidation through lipoxygenase and degradation of the hydroperoxidation through lipoxygenase and degradation of the hydroperoxides into off-flavour compounds may hence take place, if at all, only to a limited extent. Considerable phospholipase D as well as minor acyl transferase activities are detected at --24 degrees C, whereas at --32 degrees C the lipid loss is very low. Deterioration processes can be avoided by blanching, a treatment not leading to any substantial quality loss.

Food Handling↗
PubMed1996

Separation and quantitation of mono-, di-, and triglycerides and free oleic acid using thin-layer chromatography with flame-ionization detection.

alpha-Monoolein was prepared from glycidol and oleic acid by the regioselective opening of glycidol in the presence of an anionic resin. During the reaction, the lipochemical synthesis medium becomes enriched in monoolein, the effective emulsifying agent. This mixture can be analyzed by thin-layer chromatography coupled with flame-ionization detection (FID). The products and reagents do not need to be derivatized. Diglyceride and triglyceride by-products affecting the selectivity of the reaction also could be detected using this technique. Cholesterol was used as an internal standard. The factors influencing the separation, including the hydrogen flow rate, scan speed, and the composition of the developing solvent, were investigated. The degree of separation is highly sensitive to the hexane/diethyl ether ratio of the developing solvent. Good separation of triglyceride, oleic acid, the two diglycerides, cholesterol, alpha-monoolein, and glycidol was obtained with the mixture hexane/diethyl ether/formic acid (65:35:0.04, by vol). Detector response, detection limits, and rod-to-rod variations also were examined. A range of rod loads giving a straightforward relationship between FID response and amount of compound loaded (relative to oleic acid and alpha-monoolein) was defined. The accuracy of the quantification was illustrated by analysis of a mixture of oleic acid and alpha-monoolein standards of known composition.

Chromatography, Thin Layer↗
PubMed1976

Effect of dietary di-2-ethylhexyl phthalate on lipid biosynthesis in selected tissues from the rat, in vitro.

Di-2-ethylhexyl phthalate (DEHP), a plasticizer commonly used in the production of polyvinyl chloride plastics, has become an environmental pollutant. At the present time, the biological significance of phthalates in the environment is unknown. In the present studies, we observed that addition of DEHP to a stock diet of rats resulted in marked effects on incorporation of 14C-acetate into lipid by liver and kidney slices; other organs, such as heart, testes, and aorta, were unaffected. Incorporation of 14C-acetate into total lipid of liver (dpm/mg wet wt) from rats fed 0.5% or 1.0% DEHP for 10 or 18 days, respectively, was decreased to ca. 50% of control values. The decreased incorporation into liver lipid is not attributable to any one lipid fraction, inasmuch as incorporation into the phospholipid, sterol + diglyceride, free fatty acid, triglyceride, and sterol ester + hydrocarbon fractions was decreased 30-70% with respect to controls. In addition, the percent distribution of 14C-acetate among the individual phospholipids was ca. 25% lower in phosphatidyl choline of the DEHP-fed rats. In rats fed 0.5% DEHP, incorporation of 14C-acetate into total lipid of kidney was similar to control values, but incorporation into the triglyceride and sterol ester + hydrocarbon fraction was decreased 30-40%, whereas incorporation into the sterol + diglyceride fraction was increased 38%. Livers from DEHP-fed rats were ca. 20% larger than livers from control rats and, at the 0.5% level of DEHP feeding, testes wts were elevated; no significant changes were noted in wts of spleen, heart, aorta, kidney, or body wt gains in rats fed DEHP. These studies emphasize a subtle toxicity of phthalate esters not previously reported and emphasize the need for further biochemical studies to evaluate the effect of phthalates on biological systems.

Animals↗
PubMed1982

Uptake and metabolism of free fatty acids by the Morris 7777 hepatoma and host rat liver.

The relative capacity of Morris 7777 hepatomas and livers of tumor-bearing rats to take up and subsequently metabolize intravenously injected radiolabeled free fatty acids was investigated. The objective was to determine differences in lipid metabolism which may affect the lipid composition previously observed in this tumor. Both tissues demonstrated comparable selectivity in the uptake of palmitate, linoleate and arachidonate from blood, although the hepatoma took up one-tenth as much free fatty acid per g wet wt as liver. A much greater percentage of fatty acid taken up by the hepatoma was converted to aqueous soluble radioactivity, perhaps the result of oxidation. In the hepatoma, palmitate was incorporated into phospholipid molecular species in a pattern similar to that observed for diglyceride, which suggested that phospholipid synthesis occurred predominantly de novo. On the other hand, in liver, a large percentage of palmitate was incorporated into polyunsaturated phospholipid molecular species that were not present in the diglyceride pool, which suggested significant incorporation by the acylation of monoacyl phosphoglycerides. These studies indicate that the specificity for the uptake of fatty acids was not different in the two tissues; however, the subsequent metabolic processes are markedly different.

Animals↗
PubMed1999

Methyl Jasmonate Reduces Water Stress in Strawberry.

The effect of methyl jasmonate (MJ) on changes of oxygen-scavenging enzyme activities and membrane lipid composition was studied in strawberry leaves under water stress. Under water stress, MJ treatment reduced the increase of peroxidase (EC 1.11.1.7; POD) activity, maintained higher catalase (EC 1.11.1.6; CAT) and superoxide dismutase (EC 1.15.1.1; SOD) activities, and ascorbic acid content. In addition, MJ treatment reduced transpiration and membrane-lipid peroxidation as expressed by malondialdehyde (MDA) content, lessened the reduction of membrane lipids, glycolipids [monogalactosyl diglyceride (MGDG), digalactosyl diglyceride (DGDG)], and phospholipids [phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylglycerol (PG), and phosphatidylinositol (PI)]. In water-deficit conditions, MJ treatment also alleviated the decline in the degree of fatty acid unsaturation and the ratio of linolenic (18:3) to linoleic acid (18:2). These results indicate that MJ treatment appears to alter the metabolism of strawberry plants rendering the tissue better able to withstand water stress.

Journal Article↗