Effects of ethanol on the incorporation of free fatty acids into cerebral membrane phospholipids

Chronic ethanol exposure is known to affect deacylation-reacylation of membrane phospholipids (PL). In our earlier studies we have demonstrated that chronic exposure to ethanol (EtOH) leads to a progressive increase in membrane phospholipase A2 (PLA2) activity. In the current study, we investigated the effects of chronic EtOH exposure on the incorporation of different free fatty acids (FFAs) into membrane PL. The results suggest that the incorporation of fatty acids into four major PL varied from 9.6 fmol/min/mg protein for docosahexaenoic acid (DHA) into phosphatidylinositol (PI) to 795.8 fmol/min/mg protein for linoleic acid (LA) into phosphatidylcholine (PC). These results also suggest a preferential incorporation of DHA into PC; arachidonic acid (AA) into PI; oleic acid into phosphatidylethanolamine (PE) and PC; LA into PC and stearic acid into PE. Chronic EtOH exposure affected the incorporation of unsaturated fatty acid into PI, phosphatidylserine (PS) and PC. However, EtOH did not affect significantly the incorporation of any of the fatty acids (FA) studied into PE. No significant differences were observed with the stearic acid. It is suggested that acyltransferases may play an important role in the membrane adaptation to the injurious effects of EtOH.     

Incorporation of exogenous fatty acids into phospholipids by cultured hamster fibroblasts. Effect of SV40 transformation

In situ incorporation of two saturated (palmitic, 16:0; stearic, 18:0) and three unsaturated fatty acids (oleic, 18:1; linoleic, 18:2; arachidonic, 20:4) into the four major phospholipids, sphingomyelin, PC, PI and PE, was followed. Transformed cells incorporated unsaturated fatty acids more rapidly, whereas no significant differences were found concerning saturated fatty acids. In vitro determination of phospholipid acylation showed that incorporation of coenzyme A-activated forms of two saturated fatty acids (16:0 and 18:0) and one unsaturated fatty acid (18:1) into phospholipids was increased in transformed cells. Comparison of results obtained in situ and in vitro strongly suggests that incorporation of fatty acids into phospholipids in cultured cells is not limited by acyltransferase activities.     

Effects of linoleic acid and mitogenic stimulation on the fatty acid composition of human lymphocytes

Perturbation of the fatty acid composition of human lymphocytes in vitro was investigated by addition of linoleic acid complexed to bovine serum albumin (BSA-LA) and by mitogenic stimulation with phytohaemagglutinin (PHA). BSA-LA resulted in a 45% increase in linoleic acid in phosphatidylethanolamine (PE) and over 100% in phosphatidylcholine (PC) in peripheral blood cells. Supplementation with BSA-LA in PHA-stimulated lymphocytes produced even greater changes: 100% increase in linoleic acid content for PE and over 300% for PC. There was a large decrease in oleic acid: 40% for PE and almost 100% in PC. Significant decreases in arachidonic acid occurred in both phospholipid fractions. PHA alone also altered membrane phospholipid fatty acid composition, with reductions in palmitic, stearic and linoleic acid for PE and increases in oleic acid and arachidonic acid (almost 100%). For PC, there were large decreases in stearic (40%), linoleic (30%) and arachidonic (40%) acids, together with an increase in oleic acid (65%). Cells supplemented with linoleic acid grown in the presence of PHA, compared with those grown in linoleic acid-supplemented medium alone, showed a 40% decrease in palmitic acid and a 55% increase in arachidonic acid in PE. For PC, there were large decreases in stearic acid (40%) and arachidonic acid (57%). Antibody-induced redistribution of surface molecules ('capping') was inhibited by some 14% after incubation with BSA-LA. However, no consistent alterations in PHA-induced cell proliferation were observed. These data suggest that profound alterations of membrane fatty acid composition occur spontaneously during the mitotic cycle, and may be further induced by experimental manipulation, without gross perturbation of cell function.     

Effects of hypothyroidism on the distribution and fatty acyl composition of phospholipids in sarcoplasmic reticulum of fast skeletal muscle of the rat

The distribution of phospholipids and fatty acyl composition of individual phospholipids in sarcoplasmic reticulum from fast skeletal muscle of hypothyroid and euthyroid (control) rats have been determined. Hypothyroidism resulted in a 24% decrease in the phosphatidylethanolamine (PE) content and a concomitant increase in the phosphatidylcholine (PC) content of the sarcoplasmic reticulum. The amounts of other phospholipids and cholesterol remained unaffected. Fatty acyl compositions of PE and PC were quantitatively different, but hypothyroidism affected these compositions similarly. Changes included an increase in the proportions of docosahexaenoic (22:6(n - 3)), arachidonic (20:4(n - 6)), icosatrienoic (20:3(n - 6)) and stearic (18:0) acids and a decrease in those of linoleic (18:2(n - 6)), palmitic (16:0) and oleic (18:1(n - 9)) acids. The effects of hypothyroidism on the phospholipid distribution could be reversed by treatment of hypothyroid animals with thyroid hormone for a period of 14 days (10 micrograms T3/100 g body weight per 2 days). The fatty acyl composition of the phospholipids was also restored to the euthyroid values by this treatment. Exceptions were 18:2 and 22:6 in PE, in which case reversal was significant but not complete, and 18:2, 20:4 and 22:6 in PC. The levels of these acids in PC were not reversed to the euthyroid values after the 14-day treatment, but rather the opposite occurred.     

Growth-associated changes in fatty acid compositions of nuclear phospholipids of liver cells

To know the possible relationships between nuclear phospholipids and cell proliferation, we have extensively analyzed phospholipids extracted from the nuclei of rat hepatic cells at various growth states. The content of phospholipid in nuclei as well as its composition was similar among liver cells tested, i.e., the regenerating rat livers (28 h, post-hepatectomy), sham-operated or non-treated control livers, and rat ascites hepatoma, AH7974 cells. In contrast, the fatty acid compositions of phospholipids differed from each other among these cells. At the 2-position of phospholipids in the regenerating liver nuclei at 28 h after partial hepatectomy, 18:1 (oleic acid) increased transiently at the expense of 20:4 (arachidonic acid) and 22:6 (docosahexaenoic acid), compared with those in the sham-operated control nuclei. This change in fatty acid composition was commonly observed throughout all phospholipids analyzed, i.e., phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylinositol (PI) and phosphatidylserine (PS). On the other hand, the change at 1-position was rather limited: in the regenerating liver nuclei (28 h), 18:1 increased only in PC at the expense of 18:0 (stearic acid). The similar and more marked deviation at the 2-position was observed with AH7974 nuclei it contained approximately 2-times more of 18:1 in PC, PE and PI than regenerating liver nuclei (28 h), and the decreased levels of 20:4 and/or 22:6. It should be noted that there were significant differences in the fatty acid compositions of PE and PS between sham-operated and non-treated controls. So, the sham-operated rat is the appropriate control for proliferation.(ABSTRACT TRUNCATED AT 250 WORDS)     

Head group precursors modify phospholipid synthesis in Schistosoma mansoni

The two predominant phospholipids in schistosomula of Schistosoma mansoni are phosphatidylcholine (PC) and phosphatidylethanolamine (PE) which are found in a molar ratio of 0.52 (PE/PC). The incorporation of four fatty acids (arachidonic, myristic, oleic, and palmitic) and glycerol into phospholipids of schistosomula was measured. In two different media (one containing ethanolamine, the other without), all four fatty acids were predominantly incorporated into PC with a PE/PC ratio of approximately 0.1 in a 90-min label. After a 24-h chase, PC remained the predominant labeled phospholipid but the fatty acid-labeled PE/PC ratio increased slightly, the specific activity of labeled neutral lipids decreased, and the specific activity of labeled PE increased. Glycerol was incorporated with a ratio of 0.55 in the presence of ethanolamine but only 0.19 in its absence. Schistosomula also incorporate fatty acids into phosphatidylmonomethylethanolamine (PMME) and phosphatidyldimethylethanolamine (PDME) at rates intermediate to that into PE and PC in the presence of the respective head group precursor; this incorporation was inhibited by choline. Relative to PC, oleic acid is incorporated into PE, PMME, and PDME at rates higher than for palmitic acid. These results suggest that schistosomula possess acyltransferase(s) with head group specificity and that acyl chains are transferred from neutral lipids to phospholipids over time.     

The role of the collagen tripeptide fragment GER in the adhesion activation and modification of fatty acid composition in membrane phospholipids of CHO-K1 cells

It has been found that multiply repeated tripeptide fragment GER (Gly-Glu-Arg) from different collagen types stimulates nonspecific adhesion of CHO-K1 cells. Activation of cell adhesion is accompanied by modifications in fatty acid composition of cell membrane phospholipids. Cell incubation with the synthetic peptide increases the unsaturation indexes of phosphatidylcholin (PC), phosphatidylethanolamine (PEA) and phosphatidylinositol (PI). Arachidonic (C20:4omega6) acid is mainly contributed to the increased unsaturation index of PI. In the case of PC and PEA not only arachidonic acid but also other unsaturated fatty acids: docosatetraenoic (C22:4omega6), docosapentaenoic (C22:5omega3) and docosahexaenoic (C22:6omega3) acids are implicated in the index increasing. Besides, the elevation of relative content of molecules with polyenoic fatty acids in the group of PI molecules is accompanied by decrease in monoenoic fatty acids caused mainly by decrease in the oleic (C18:1) acid level. The role of the investigated peptide: 1) in the activation of cell adhesion as a regulator of active or non active state of integrin receptors: 2) in the alterations of fatty acid composition in main classes of phospholipids as modulator of fluidity level in annular lipid zones around these adhesive molecules is discussed.     

Preferential incorporation of eicosanoid precursor fatty acids into human umbilical vein endothelial cell phospholipids

We have examined the preferential incorporation of specific fatty acids into phospholipid classes of cultured human umbilical vein endothelial cells. Pulse-labeling of human umbilical vein endothelial cell phospholipids with radiolabeled fatty acids and inhibition of radiolabeled fatty acid incorporation by competition with excess, unlabeled fatty acids in pair-wise combinations revealed two distinct classes of esterification systems into human umbilical vein endothelial cell phospholipids. The eicosanoid precursor fatty acids, including arachidonate, 8,11,14-eicosatrienoate (ETA) and 5,8,11,14,17-eicosapentaenoate (EPA), exhibited high affinity incorporation into total phospholipids, whereas other fatty acids, including docosahexaenoate and monohydroxy eicosatetraenoates, showed low affinity incorporation. The relative degree of incorporation of eicosanoid precursor fatty acids into phospholipid classes was phosphatidylcholine (PC) greater than phosphatidylethanolamine (PE) greater than phosphatidylinositol (PI) greater than phosphatidylserine (PS). The specific activity of [14C]arachidonic acid-labeled PI was two times higher than that of any other radiolabeled phospholipids. When competitive incorporation of eicosanoid precursor fatty acids into phospholipid classes was studied, they were found to be acylated into different phospholipid classes at different rates. Although eicosanoid precursor fatty acids were not preferentially incorporated into PC, arachidonic acid was preferentially incorporated into the other phospholipids and exhibited particular selectivity in comparison with the other eicosanoid precursor fatty acids for incorporation into PI. These results demonstrate that human umbilical vein endothelial cells possess selective incorporation mechanisms for specific fatty acids into various phospholipids via the deacylation-reacylation pathway.     

Role of collagen tripeptide fragment GER on activation of adhesion and modification of fatty acid composition in membrane phospholipids of CHO-K1 cells

It has been found that the multiply repeated tripeptide fragment GER (Gly-Glu-Arg) from different collagen types stimulates the nonspecific adhesion of CHO-K1 cells. Activation of cell adhesion is accompanied by modifications to the fatty acid composition in the phospholipids of the cell membrane. Cell incubation with the synthetic GER peptide increases the unsaturation index of phosphatidylcholin (PC), phosphatidylethanolamine (PEA), and phosphatidylinositol (PI). Arachidonic (C20:4ω6) acid is mainly contributed to the increased index of PI. Not only arachidonic acid but other unsaturated fatty acids, such as docosatetraenoic (C22:4ω6), docosapentaenoic (C22:5ω3), and docosahexaenoic (C22:6ω3), are responsible for the increased index of PC and PEA. In addition, the elevation of the relative content of polyenoic fatty acids in PI is concomitant with a reduced amount of monoenoic fatty acids, mainly due to decline in the oleic (C18:1) acid level. The role of GER peptide in (1) the activation of cell adhesion as a regulator of active or inactive states of integrin receptors; (2) modification of fatty acid composition in major classes of phospholipids as a modulator of the fluidity in annular lipid zones surrounding to the adhesive molecules is discussed.     

Effect of the conditions of analysis and obtaining of the sample on the level of free fatty acids in the brain of the rat

Free fatty acids (FFA) have been determined in the rat brain by gas-liquid chromatography after isolation by thin-layer chromatography on silica gel. The brains were removed under three experimental conditions, 1) after freezing in situ with liquid nitrogen, 2) after immersion of the animal in liquid nitrogen, 3) after decapitation, the brain being frozen 3 minutes later. The total FFA level was found to be equal respectively to 20.1, 33.1 and 168 micrograms/g. In any case, the main fatty acids were palmitic, stearic and oleic acid but there were marked increases in arachidonic and docosahexaenoic acids following decapitation. A cause of error in the FFA determination originated in the use of commercial silica gel which contained significant amounts of fatty acids.     

Metabolism of n-3 polyunsaturated fatty acids and modification of phospholipids in cultured rabbit aortic smooth muscle cells

The metabolism of the linolenic acid family (n-3) of fatty acids, e.g., linolenic, eicosapentaenoic, and docosahexaenoic acids, in cultured smooth muscle cells from rabbit aorta was compared to the metabolism of linoleic and arachidonic acids. There was a time-dependent uptake of these fatty acids into cells for 16 hr (arachidonic greater than docosahexaenoic, linoleic, eicosapentaenoic greater than linolenic), and the acids were incorporated mainly into phospholipids and triglycerides. Eicosapentaenoic and arachidonic acids were incorporated more into phosphatidylethanolamine and phosphatidylinositol plus phosphatidylserine and less into phosphatidylcholine than linolenic and linoleic acids. Docosahexaenoic acid was incorporated into phosphatidylethanolamine more than linolenic and linoleic acids and into phosphatidylinositol plus phosphatidylserine less than eicosapentaenoic and arachidonic acids. Added linolenic acid accumulated mainly in phosphatidylcholine and did not decrease the arachidonic acid content of any phospholipid subfraction. Elongation-desaturation metabolites of linoleic acid did not accumulate. Cells treated with eicosapentaenoic acid accumulated both eicosapentaenoic and docosapentaenoic acids mainly in phosphatidylethanolamine and the arachidonic acid content was decreased. Added docosahexaenoic acid accumulated mainly in phosphatidylethanolamine and decreased the content of both arachidonic and oleic acids. The following conclusions are drawn from these results. The three n-3 fatty acids are utilized differently in phospholipids. The arachidonic acid content of phospholipids is reduced by eicosapentaenoic and docosahexaenoic acids, but not by linolenic acid. Smooth muscle cells have little or no desaturase activity, but have significant elongation activity for polyunsaturated fatty acids.     

Mitochondrial lipids in Bufo arenarum full-grown oocytes

Both the content and composition of polar and neutral lipids from the mitochondrial fraction of ovarian full-grown Bufo arenarum oocytes were analysed in the present study. Triacylglycerols (TAG) represent 33% of the total lipids, followed by phosphatidylcholine (PC), free fatty acids (FFA) and phosphatidylethanolamine (PE). Diphosphatidylglycerol (DPG) or cardiolipin, a specific component of the inner mitochondrial membrane, represents about 4% of the total lipid content. Palmitic (16:0) and arachidonic (20:4n6) acids are the most abundant fatty acids in PC and PE, respectively. DPG is enriched in fatty acids with carbon chain lengths of 18, the principal component being linoleic acid. In phosphatidylinositol (PI), 20:4n6 and stearic acid (18:0) represent about 72 mol% of the total acyl group level. The main fatty acids in TAG are linoleic (18:2), oleic (18:1), and palmitic acids. The fatty acid composition of FFA and diacylglycerols (DAG) is similar, 16:0 being the most abundant acyl group. PE is the most unsaturated lipid and sphingomyelin (SM) has the lowest unsaturation index.     

Arachidonic acid-containing phosphatidylcholine inhibits lymphocyte proliferation and decreases interleukin-2 and interferon-gamma production from concanavalin A-stimulated rat lymphocytes

The proliferation of concanavalin A (Con A)-stimulated rat lymphocytes was markedly inhibited by phosphatidylcholine containing arachidonic and stearic acids (PC(A-S)), but not by phosphatidylcholine containing oleic and stearic acids or phosphatidylinositol containing arachidonic and stearic acids. The concentration of PC(A-S) which inhibited Con A-stimulated proliferation by 50% was 31 microM and near total inhibition was observed at 154 microM . Phosphatidylserine containing only oleic acid enhanced proliferation by 37% at a concentration of 31 microM , but phosphatidylethanolamine and phosphatidylcholine containing only oleic acid did not affect proliferation at this concentration. It is concluded that both the head group and the fatty acid composition contribute to the influence of phospholipids on lymphocyte proliferation. The effects of PC(A-S) on T-lymphocyte responses were investigated further. In parallel with the inhibition of proliferation PC(A-S) caused a concentration-dependent decrease in the production of the Th1-type cytokines interleukin (IL)-2 and interferon (IFN)-gamma; inhibition of cytokine production was >85% at the highest concentration of PC(A-S) used (154 microM ). Production of the Th2-type cytokines IL-4 and IL-10 was not affected. The possible role of prostaglandins in mediating the effects of PC(A-S) was examined by adding indomethacin into the medium and the participation of lipid peroxidation was examined by adding vitamin E and vitamin C. Indomethacin and vitamin E did not affect the inhibition caused by PC(A-S) but vitamin C caused a partial reversal. It is concluded that inhibition of T-lymphocyte proliferation by phospholipids involves both the head group and the fatty acyl chains, that this inhibition is not mediated by prostaglandins but may involve some form of oxidant stress and that some phospholipids (e.g., PC(A-S)) can markedly influence cytokine profiles.     

Fatty acid composition and incorporation of arachidonic acid into phospholipids of hemocytes from the tobacco hornworm Manduca sexta

The fatty acid compositions were determined for total lipids, triacylglycerols, phospholipids and four phospholipid fractions, including phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylserine/phosphatidylinositol (PS/PI) and cardiolipin (CA) obtained from hemocytes and cell-free serum from second day, fifth instar larvae of the tobacco hornworm Manduca sexta and the standard Manduca rearing medium. The hemocyte fatty acid profiles were considerably different from the profiles of the medium the insects were reared on and from the profiles of the cell-free serum. Hemocyte neutral lipids had lower proportions of polyunsaturated fatty acids than phospholipids. The fatty acid profiles of PC, PE, PS/PI and CA differ from each other and from the total lipid profiles, indicating selective fatty acid incorporation into hemocyte phospholipid species. Studies with radioactive arachidonic acid similarly indicated selective incorporation of polyunsaturated fatty acids into hemocyte lipids. Under our in vitro conditions, >40% of the total radioactivity was incorporated into hemocyte lipids. About 93% of the incorporated radioactivity was found in phospholipids. Within phospholipids. most of the radioactivity was associated with PC (46%), and less with PE (28%) and PS/PI (21%). Very little radioactivity was recovered in CA (0.9%).     

Characterization of plasma membrane lipids and luteinizing hormone receptors of ovine corpora lutea during luteolysis and early pregnancy

Lipid composition of plasma membranes from luteal cells was examined to determine whether changes in this organelle occur during regression and maintenance of the corpus luteum in nonpregnant (NP) and pregnant (P) ewes, respectively. Forty ewes were assigned to be killed on Day 13 or 15 of the estrous cycle (D13-NP and D15-NP) or pregnancy (D13-P and D15-P). Purification of luteal plasma membranes on discontinuous sucrose gradients yielded two fractions, designated F1 and F2, that exhibited the greatest enrichment of 5'-nucleotidase activity (five- and fourfold, respectively) over that of the homogenate. These fractions also yielded the lowest contamination by endoplasmic reticulum as represented by nicotinamide adenine dinucleotide phosphate (NADPH) cytochrome C reductase activity and mitochondrial membranes as indicated by succinate dehydrogenase activity. Predominant phospholipids identified in membranes obtained from all groups were phosphatidylcholine (PC, 48.9 +/- 0.6% of total phospholipid), phosphatidylethanolamine (PE, 33.3 +/- 0.4%), sphingomyelin (SPH, 9.7 +/- 0.3%), phosphatidylserine (PS, 3.5 +/- 0.2%), and phosphatidylinositol (PI, 4.0 +/- 0.5%). No changes in microgram phospholipid/mg membrane protein were observed for any luteal phospholipid on D13 and 15 of the estrous cycle or pregnancy. No significant changes in the relative percentages of major fatty acids present in PC (palmitic [16:0], oleic [18:1]), PE (stearic [18:0], 18:1 and arachidonic [20:4]), or PS (18:0, 18:1, docosatetraenoic [22:4]), nor in the ratios of unsaturated (U) to saturated (S) fatty acids in these phospholipids were observed. Significant differences in unsaturated fatty acids of chain length greater than 20 carbons present in minor quantities in PC, PE, and PS were detected between NP and P ewes as well as between days within reproductive stage. The profile of major fatty acids present in PI revealed decreases in 18:0 and 20:4 in D15-NP and increases in 22:4 and docosapentaenoic acid (22:5) in luteal membranes of both D13- and D15-NP ewes relative to the levels of these fatty acids in PI of corresponding groups of pregnant ewes. There was a general trend for 20:4 levels of PC and PI in membranes of D15-NP ewes to be inversely related to those of D15-P ewes. Collectively, these changes were reflected by an increased U:S fatty acid ratio in luteal membrane PI during the estrous cycle. Specific binding of [125I] iodo-human chorionic gonadotropin to luteal plasma membranes from NP and P ewes on D13 and 15 (6/group) revealed similar affinities and concentrations of unoccupied luteinizing hormone (LH) receptors.(ABSTRACT TRUNCATED AT 400 WORDS)     

The influence of ionic detergents on the phospholipid fatty acid compositions of Porphyridium purpureum

The phospholipid fatty acid composition of Porphyridium purpureum on a solid medium was studied in the presence of sodium dodecyl sulphate (SDS) and cetyl trimethylammonium bromide (CTAB). The most common fatty acids in phosphatidyl choline (PC) and phosphatidyl ethanolamine (PE) were palmitic (16:0), stearic (18: 0), linoleic (18:2ω 6), arachidonic (20:4ω 6) and eicosapentaenoic (20:5ω 3) acids, 20:4ω 6 being very abundant. In phosphatidyl glycerol (PG) the most common acids were 16:0, trans-hexadecenoic acid (tr 16:1ω 13), oleic acid (18:1) and 20:4ω 6. Both detergents increased the saturation grade of PC and PE by decreasing the relative amount of the polyunsaturated acids, especially 20:4ω 6. A corresponding increase in the amounts of saturated acids was observed in PC and PE. The changes in PG fatty acid composition were not very significant: a slight increase was observed in the amounts of 16:0 and tr 16:1ω 13 , with a corresponding decrease in the amounts of 20:4ω 6 and 20:5ω 3. Both detergents decreased the PC/PE and the (PC + PE)/PG ratios very markedly, most probably as a result of increases in the amounts of PE and PG. In the presence of CTAB the cells seemed to contain much more phospholipids than in the presence of SDS, perhaps as a result of the mucilage-precipitating effect of CTAB. The significance of the findings is discussed.     

Low-salt diet alters the phospholipid composition of rat colonocytes

The effect of low-salt diet on phospholipid composition and remodeling was examined in rat colon which represents a mineralocorticoid target tissue. To elucidate this question, male Wistar rats were fed a low-salt diet and drank distilled water (LS, low-salt group) or saline instead of water (HS, high-salt group) for 12 days before the phospholipid concentration and fatty acid composition of isolated colonocytes were examined. The dietary regimens significantly influenced the plasma concentration of aldosterone which was high in LS group and almost zero in HS group. Plasma concentration of corticosterone was unchanged. When expressed in terms of cellular protein content, a significantly higher concentration of phospholipids was found in LS group, with the exception of sphingomyelin (SM) and phosphatidylserine (PS). Phosphatidylcholine (PC) and phosphatidylethanolamine (PE) accounted for more than 70% of total phospholipids in both groups. A comparison of phospholipid distribution in LS and HS groups demonstrated a higher percentage of PE and a small, but significant, decrease of PC and SM in LS group. The percentage of phosphatidylinositol (PI), PS and cardiolipin (CL) were not affected by mineralocorticoid treatment. With respect to the major phospholipids (PE, PC), a higher level of n-6 polyunsaturated fatty acids (PUFA) and lower levels of monounsaturated fatty acids were detected in PC of LS group. The increase of PUFA predominantly reflected an increase in arachidonic acid by 53%. In comparison to the HS group, oleic acid content was decreased in PC and PE isolated from colonocytes of the LS group. Our data indicate that alterations in phospholipid concentration and metabolism can be detected in rats with secondary hyperaldosteronism. The changes in phospholipid concentration and their fatty acid composition during fully developed effect of low dietary Na+ intake may reflect a physiologically important phenomenon with long-term consequences for membrane structure and function.     

Modification of the fatty acid composition of individual phospholipids and neutral lipids after infection of the simian erythrocyte by Plasmodium knowlesi

Using capillary gas-liquid chromatography, we have analyzed the alteration in the total fatty acid, phospholipid and neutral lipid compositions of the monkey erythrocyte, after infection by the malarial parasite Plasmodium knowlesi. Data based on fatty acid quantitation show that the phospholipid composition is altered, with particularly large increases in phosphatidylcholine (PC) and phosphatidylethanolamine (PE), the most abundant phospholipids in normal and P. knowlesi-schizont-infected cells. Unesterified fatty acids were found to be less abundant in infected cells. The total fatty acid content of the cell is increased 6-fold during infection, and total fatty acid composition is also changed: the infected cells are richer in palmitate (+23%), oleate (+29%) and linoleate (+89%), but contained less stearate (-27%) and arachidonate (-40%). The determination of the fatty acid composition of individual phospholipids, neutral lipids and unesterified fatty acids showed that choline-containing phospholipids (PC and sphingomyelin) were not as altered in their fatty acid pattern as anionic phospholipids (PE, phosphatidylserine (PS) and phosphatidylinositol (PI) and lysophosphatidylcholine (lysoPC). Specific alterations in the fatty acid compositions of individual phospholipids were detected, whereas the rise in linoleic acid was the only change during infection that was recovered in each phospholipid (except PC), neutral lipid and unesterified fatty acids. The fatty acid composition of the neutral lipids and unesterified fatty acids was particularly modified: the only rise in arachidonic acid level was observed in these lipid classes after infection. The total plasmalogen level of the erythrocyte is decreased in infected cells (-60%), but their level is increased in PI.     

Arachidonic acid-containing phosphatidylcholine inhibits lymphocyte proliferation and decreases interleukin-2 and interferon-γ production from concanavalin A-stimulated rat lymphocytes

The proliferation of concanavalin A (Con A)-stimulated rat lymphocytes was markedly inhibited by phosphatidylcholine containing arachidonic and stearic acids (PC(A-S)), but not by phosphatidylcholine containing oleic and stearic acids or phosphatidylinositol containing arachidonic and stearic acids. The concentration of PC(A-S) which inhibited Con A-stimulated proliferation by 50% was 31 μM and near total inhibition was observed at 154 μM. Phosphatidylserine containing only oleic acid enhanced proliferation by 37% at a concentration of 31 μM, but phosphatidylethanolamine and phosphatidylcholine containing only oleic acid did not affect proliferation at this concentration. It is concluded that both the head group and the fatty acid composition contribute to the influence of phospholipids on lymphocyte proliferation. The effects of PC(A-S) on T-lymphocyte responses were investigated further. In parallel with the inhibition of proliferation PC(A-S) caused a concentration-dependent decrease in the production of the Th1-type cytokines interleukin (IL)-2 and interferon (IFN)-γ; inhibition of cytokine production was >85% at the highest concentration of PC(A-S) used (154 μM). Production of the Th2-type cytokines IL-4 and IL-10 was not affected. The possible role of prostaglandins in mediating the effects of PC(A-S) was examined by adding indomethacin into the medium and the participation of lipid peroxidation was examined by adding vitamin E and vitamin C. Indomethacin and vitamin E did not affect the inhibition caused by PC(A-S) but vitamin C caused a partial reversal. It is concluded that inhibition of T-lymphocyte proliferation by phospholipids involves both the head group and the fatty acyl chains, that this inhibition is not mediated by prostaglandins but may involve some form of oxidant stress and that some phospholipids (e.g., PC(A-S)) can markedly influence cytokine profiles.     

Polyunsaturated fatty acids stimulate phosphatidylcholine synthesis in PC12 cells

The synthesis of phospholipids in mammalian cells is regulated by the availability of three critical precursor pools: those of choline, cytidine triphosphate and diacylglycerol. Diacylglycerols containing polyunsaturated fatty acids (PUFAs) apparently are preferentially utilized for phosphatide synthesis. PUFAs are known to play an important role in the development and function of mammalian brains. We therefore studied the effects of unsaturated, monounsaturated and polyunsaturated fatty acids on the overall rates of phospholipid biosynthesis in PC12 rat pheochromocytoma cells. Docosahexaenoic acid (DHA, 22:6n-3), eicosapentaenoic acid (EPA, 20:5n-3) and arachidonic acid (AA, 20:4n-6) all significantly stimulated the incorporation of (14)C-choline into total cellular phospholipids. In contrast, monounsaturated oleic acid (OA) and the saturated palmitic (PA) and stearic (SA) acids did not have this effect. The action of DHA was concentration-dependent between 5 and 50 microM; it became statistically significant by 3 h after DHA treatment and then increased over the ensuing 3 h. DHA was preferentially incorporated into phosphatidylethanolamine (PE) and phosphatidylserine (PS), while AA predominated in phosphatidylcholine (PC).