scholarly journals Biosynthesis of platelet-activating factor (PAF) in human polymorphonuclear leucocytes. The role of lyso-PAF disposal and free arachidonic acid

1990 ◽  
Vol 268 (1) ◽  
pp. 91-98 ◽  
Author(s):  
M D C Garcia ◽  
S Fernandez-Gallardo ◽  
M A Gijon ◽  
C Garcia ◽  
M L Nieto ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Arachidonic Acid ◽  
Phospholipase A2 ◽  
Platelet Activating Factor ◽  
Inhibitory Effect ◽  
Eicosatetraenoic Acid ◽  
Polymorphonuclear Leucocytes ◽  
Maximal Effect ◽  
Dependent Manner ◽  
Dose Dependent

Theophylline and 1-methyl-3-isobutylxanthine (MIX), compounds that block eicosanoid formation and modulate phospholipase A2 activity, inhibited in a dose-dependent manner the formation of both leukotriene B4 (LTB4) and platelet-activating factor (PAF) by human polymorphonuclear leucocytes (PMN) in response to ionophore A23187. Theophylline and MIX lacked any inhibitory effect on acetyl-CoA: lyso-PAF acetyltransferase activity, which is the rate-limiting step for PAF biosynthesis in PMN. The effect of theophylline and MIX on PAF formation could be reversed by incubating the cells in the presence of 1-10 microM exogenous lyso-PAF. Incubation of PMN homogenates in the presence of unsaturated non-esterified fatty acids resulted in dose-dependent inhibition of the acetyltransferase. This effect was linked to the presence of a free carboxyl group, since both arachidonic acid methyl ester and palmitoyl-arachidonoyl phosphatidylcholine lacked inhibitory activity. This inhibitory effect was also dependent on the number of double bonds, since arachidonic acid (C20:4) and eicosapentaenoic acid (C20:5) displayed maximal effect. Kinetic analysis showed that the effect of arachidonic acid was consistent with competitive inhibition, with a Ki value of about 19 microM. Oxidative metabolites of arachidonic acid showed a lesser inhibitory effect with the following order of potency: arachidonic acid greater than 15-HETE (15-hydroxy-6,8,11,14-eicosatetraenoic acid) greater than LTB4 greater than 5-HETE (5-hydroxy-6,8,11,14-eicosatetraenoic acid) greater than lipoxin A4. Examination of enzymes involved in CoA-dependent acylation revealed a low activity of both arachidonoyl-CoA synthetase and arachidonoyl-CoA: lyso-PAF arachidonoyltransferase. These data indicate a strong influence on PAF biosynthesis of the products of the phospholipase A2 reaction, with lyso-PAF disposal being a critical event for PAF formation, and unsaturated fatty acids acting as feed-back inhibitors. The conversion of arachidonic acid via oxidative metabolism into less active inhibitors of acetyl-CoA:lyso-PAF acetyltransferase seems to be an additional mechanism of modulation of this enzyme activity, linked to the function of lipoxygenases. Finally, the enzyme activities involved in arachidonoyl-CoA-dependent acylation of lyso-PAF show a low efficiency in capturing arachidonic acid.

scholarly journals Influence of arachidonic acid on indices of phospholipase A2 activity in the human neutrophil

1993 ◽  
Vol 291 (3) ◽  
pp. 825-831 ◽  
Author(s):  
J D Winkler ◽  
C M Sung ◽  
W C Hubbard ◽  
F H Chilton
Keyword(s):  
Fatty Acids ◽  
Arachidonic Acid ◽  
Protein Kinase ◽  
Phospholipase A2 ◽  
Human Neutrophils ◽  
Maximal Effect ◽  
Dependent Manner ◽  
Pla2 Activity ◽  
Tetraenoic Acid ◽  
Stimulation Of

The present studies were conducted to understand better the regulation of phospholipase A2 (PLA2)-dependent mobilization of lipid mediators by arachidonic acid (C20:4). After stimulation of human neutrophils, g.l.c./m.s. analysis of non-esterified fatty acids indicated that the quantity of C20:4 increased as a function of time after stimulation, from undetectable quantities to > 800 pmol/10(7) cells. In contrast with C20:4, the quantities of other free fatty acids such as oleic and linoleic were high in resting cells and did not change after stimulation. Some 15% of the C20:4 released from cellular lipids remained cell-associated. To examine the effect of C20:4 on its own release, neutrophils were exposed to [2H8]C20:4, to differentiate it by g.l.c./m.s. from naturally occurring C20:4. In A23187-stimulated neutrophils, low concentrations (5-10 microM) of [2H8]C20:4 added just before A23187 increased the quantity of C20:4 produced by the cell, whereas higher concentrations (30-50 microM) decreased the quantity of C20:4 released from phospholipids. As other measures of PLA2 activity, the effects of C20:4 on production of platelet-activity factor (PAF) and leukotriene B4 (LTB4) were assessed. C20:4 treatment just before stimulation of neutrophils blocked PAF and LTB4 production in a concentration-dependent manner (IC50 10-20 microM). The effect of C20:4 was not blocked by the cyclo-oxygenase inhibitor naproxine (10 microM), nor could it be mimicked by 1 microM LTB4, 5-hydroxyeicosa-6,8,11,14-tetraenoic acid (5HETE), 5-hydroperoxyeicosa-6,8,11,14-tetraenoic acid (5HPETE) or 15-hydroxyeicosa-5,8,11,13-tetraenoic acid (15HETE). The 5-lipoxygenase (5LO) inhibitor zileuton induced a concentration-dependent decrease in PAF, with a maximal effect of a 50% decrease at 10-50 microM. The decrease in PAF by the 5LO inhibitor could not be circumvented by addition of 1 microM 5HETE, 5HPETE and LTB4, and may be attributed to the capacity of zileuton to increase the quantity of C20:4 in A23187-treated neutrophils. The inhibitory effect of C20:4 (20-40 microM) on PAF production could be antagonized by the protein kinase C inhibitor staurosporine (30 nM), but not by inhibitors of protein kinase A, tyrosine kinase or calmodulin kinase II. Taken together, these data demonstrate that C20:4 is selectively released from membrane phospholipids of A23187-stimulated neutrophils, and this C20:4 may play an important role in regulating the mobilization of C20:4 by altering PLA2 activity.

scholarly journals Adrenaline Stimulation of Phospholipid Metabolism in Adipocyte Ghosts

1987 ◽  
Vol 40 (4) ◽  
pp. 405
Author(s):  
David Mann ◽  
Audrey M Bersten
Keyword(s):  
Fatty Acids ◽  
Arachidonic Acid ◽  
Linoleic Acid ◽  
Adenylate Cyclase ◽  
Phospholipid Metabolism ◽  
Dependent Manner ◽  
Long Chain Fatty Acids ◽  
Membrane Phospholipids ◽  
Dose Dependent ◽  
Stimulation Of

The incorporation of long-chain fatty acids into phospholipids has been detected in adipocyte ghosts that were incubated with [1_14 C] stearic, [1_14 C] linoleic or [l_14C] arachidonic acid. Adrenaline and adenosine activated this incorporation within 15 s of exposure of the ghosts to the hormones and the response was dose dependent. Maximum incorporation of labelled linoleic acid occurred at 10-5 M adrenaline and 10-7 M adenosine. The a-agonist phenylephrine and the ~-agonist isoproterenol were also shown to stimulate the incorporation of fatty acid in a dose dependent manner. Phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine and phosphatidylinositol were each labelled preferentially with linoleic or arachidonic acid. p-Bromophenacylbromide, quinacrine and centrophenoxine inhibited the adrenaline-stimulated incorporation of fatty acids into ghost membrane phospholipids, and p-bromophenacylbromide also reduced the activation of adenylate cyclase by adrenaline. NaF, an activator of adenylate cyclase, like adrenaline, stimulated the incorporation of linoleic acid into ghost membrane phospholipids.

Unsaturated fatty acids and cyclooxygenase inhibitors: effects on pial arterioles

1982 ◽  
Vol 242 (4) ◽  
pp. H629-H632
Author(s):  
W. I. Rosenblum
Keyword(s):  
Fatty Acids ◽  
Unsaturated Fatty Acids ◽  
Eicosatrienoic Acid ◽  
Inhibitory Effect ◽  
Cyclooxygenase Inhibitors ◽  
Dependent Manner ◽  
Double Bonds ◽  
Pial Arterioles ◽  
Dose Dependent

Cerebral surface arterioles of the mouse were constricted in a dose-dependent manner by three different unsaturated fatty acids each with one of its double bonds in the n-6 position: arachidonate, linoleic, and 11,14,17-eicosatrienoic acid (ETA) in doses of 10-200 micrograms/ml. The constriction was transient, and its magnitude was significantly reduced by pretreatment of the mice with intraperitoneal injections of indomethacin (5 mg/kg), aspirin (100 mg/kg), or sodium 2-amino-3-(4 chlorobenzyl)-phenylacetate (AHR-6293, 100 mg/kg). The inhibitory effect of these cyclooxygenase inhibitors suggests that this enzyme is involved in the response to these fatty acids and is in keeping with suggestions in the literature stating that such unsaturated fatty acids may interact with cyclooxygenase even when they cannot form prostaglandin (PG) endoperoxides, The PG endoperoxide formed by arachidonate or the analogous hydroperoxy compounds formed by linoleic or 11,14,17 ETA, may then alter cerebrovascular tone by production of reactive, O2-containing species. Alternate explanations for the data are also proposed.

scholarly journals Stimulation of prostaglandin E2 synthesis by exogenous phospholipase A2 and C in rabbit kidney medulla slices

1984 ◽  
Vol 218 (1) ◽  
pp. 69-74 ◽  
Author(s):  
Y Fujimoto ◽  
N Akamatsu ◽  
A Hattori ◽  
T Fujita
Keyword(s):  
Fatty Acids ◽  
Prostaglandin E2 ◽  
Phospholipase A2 ◽  
Phospholipase C ◽  
Unsaturated Fatty Acids ◽  
Rabbit Kidney ◽  
Dependent Manner ◽  
Kidney Medulla ◽  
Diacylglycerol Lipase ◽  
Dose Dependent

We have investigated the effects of phospholipase A2 and C on the synthesis of prostaglandin E2 in rabbit kidney medulla and the release of fatty acids from the medulla slices. Exogenous phospholipase A2 [from Naja naja (Indian cobra) venom] and phospholipase C (from Clostridium welchii) stimulated prostaglandin E2 production in a dose-dependent manner. At the maximal effective concentrations (0.5 unit of phospholipase A2/ml, 2 units of phospholipase C/ml), phospholipase C increased prostaglandin E2 formation to the level observed with phospholipase A2. Phospholipase A2 enhanced the release only of unsaturated fatty acids, whereas phospholipase C stimulated the release of individual free fatty acids (C 16:0, C 18:0, C 18:1, C 18:2 and C 20:4). Moreover, p-bromophenacyl bromide inhibited phospholipase A2-stimulated prostaglandin E2 production and the release of fatty acids, but it had no influence on prostaglandin E2 formation and the release of fatty acids increased by phospholipase C, indicating that the stimulatory effect of phospholipase C is not mediated through the activation of endogenous phospholipase A2. These results suggest the presence of diacylglycerol lipase and monoacylglycerol lipase in the kidney and the importance of this pathway in prostaglandin synthesis by the kidney.

scholarly journals Hemolytic activity and platelet aggregation inhibitory effect of vipoxin’s basic sPLA2 subunit

2013 ◽  
Vol 6 (3) ◽  
pp. 136-140 ◽  
Author(s):  
Silviya Stoykova ◽  
Yana Goranova ◽  
Ivayla Pantcheva ◽  
Vasil Atanasov ◽  
Dobri Danchev ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Platelet Aggregation ◽  
Hemolytic Activity ◽  
Blood Cells ◽  
Inhibitory Effect ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Erythrocyte Morphology ◽  
Dose Dependent ◽  
Vipera Ammodytes

ABSTRACT In the present study we evaluated the effect of secreted phospholipase A2 (sPLA2) (the toxic subunit of the heterodimeric neurotoxin vipoxin, isolated from the Bulgarian long-nosed viper Vipera ammodytes meridionalis) on hemolysis, erythrocyte morphology and platelet aggregation. Hemolytic activity of sPLA2 was examined in the presence of saturated (palmitic) and unsaturated (oleic) fatty acids and it was found that oleic acid increased the hemolytic activity of sPLA2 in a concentration-dependent manner, compared to the effect of palmitic acid and controls. The addition of heparin to red blood cells (RBC) suspension containing sPLA2 or mixture of sPLA2 and the corresponding fatty acid led to an inhibition of hemolytic activity. The effect of sPLA2 on RBC morphology resulted in formation of echinocytes (spherocyte subtype), suggesting that RBC could be the possible targets attacked by sPLA2. Vipoxin sPLA2 inhibited (in a dose-dependent manner) platelet aggregation when arachidonic acid and collagen were used as inducers, while in the case of ADP its inhibitory effect was inappreciable.

scholarly journals Effects of bivalent cations on prostaglandin biosynthesis and phospholipase A2 activation in rabbit kidney medulla slices

1979 ◽  
Vol 182 (3) ◽  
pp. 821-825 ◽  
Author(s):  
A Erman ◽  
A Raz
Keyword(s):  
Arachidonic Acid ◽  
Linoleic Acid ◽  
Prostaglandin E2 ◽  
Phospholipase A2 ◽  
Inhibitory Effect ◽  
Rabbit Kidney ◽  
Dependent Manner ◽  
Kidney Medulla ◽  
Bivalent Cations ◽  
Tissue Lipids

The bivalent cations Ca2+, Mg2+, Co2+, Mn2+, Sr2+ and Ba2+ were compared for their stimulatory or inhibitory effect on prostaglandin formation in rabbit kidney medulla slices. Ca2+, Mn2+ and Sr2+ ions stimulated prostaglandin generation up to 3–5-fold in a time- and dose-dependent manner (Ca2+ greater than Mn2+ congruent to Sr2+). The stimulation by Mn2+ (but not by Sr2+) was also observed in incubations of medulla slices in the presence of Ca2+. Mg2+ and Co2+ ions were without significant effects on either basal or Ca2+-stimulated prostaglandin synthesis. The stimulatory effects of Ca2+, Mn2+ and Sr2+ on medullary generation of prostaglandin E2 were found to correlate with their stimulatory effects on the release of arachidonic acid and linoleic acid from tissue lipids. The release of other fatty acids was unaffected, except for a small increase in oleic acid release. As both arachidonic acid and linoleic acid are predominantly found in the 2-position of the glycerol moiety of phospholipids, the stimulation by these cations of prostaglandin E2 formation appears to be mediated via stimulation of phospholipase A2 activity.

scholarly journals The suppression of 5-lipoxygenation of arachidonic acid in human polymorphonuclear leucocytes by the 15-lipoxygenase product (15S)-hydroxy-(5Z,8Z,11Z,13E)-eicosatetraenoic acid: structure-activity relationship and mechanism of action

1996 ◽  
Vol 314 (3) ◽  
pp. 911-916 ◽  
Author(s):  
Karen PETRICH ◽  
Peter LUDWIG ◽  
Hartmut KÜHN ◽  
Tankred SCHEWE
Keyword(s):  
Fatty Acids ◽  
Arachidonic Acid ◽  
Leukotriene B4 ◽  
Eicosatetraenoic Acid ◽  
Ionophore A23187 ◽  
Polymorphonuclear Leucocytes ◽  
Lipoxygenase Inhibitor ◽  
Acid Structure ◽  
Selection Of

(15S)-Hydroxy-(5Z,8Z,11Z,13E)-eicosatetraenoic acid (15-HETE) suppresses in ionophore-A23187-stimulated human polymorphonuclear leucocytes (PMN) the conversion of exogenous arachidonic acid into leukotriene B4 (LTB4) and (5S)-hydroxy-(6E,8Z,11Z,14Z)-eicosatetraenoic acid (5-HETE). However, contrary to earlier suggestions, 15-HETE is not a genuine 5-lipoxygenase inhibitor under these conditions, but rather suppresses the 5-lipoxygenation of arachidonic acid by switching-over of substrate utilization, as judged from a sizeable formation of labelled (5S,15S)-dihydroxy-(6E,8Z,11Z,13E)-eicosatetraenoic acid (5,15-diHETE) from 15-[1-14C]HETE. Identical results were obtained with human recombinant 5-lipoxygenase. In PMN the formation of 5,15-diHETE is strongly stimulated by either hydroperoxypolyenoic fatty acids or arachidonic acid, suggesting a crucial role of the hydroperoxide tone of the cell. A comparison of a selection of hydroxypolyenoic fatty acids with respect to their capability of suppressing 5-lipoxygenation of arachidonic acid revealed that 15-monohydroxyeicosanoids throughout exhibit the highest inhibitory potencies, whereas the other HETEs, 5,15-diHETE as well as octadecanoids, are modest or poor inhibitors. The R and S enantiomers of 15-HETE do not differ from each other, excluding a receptor-like binding of the 15-hydroxy group.

scholarly journals Effect of diarachidonin on prostaglandin E2 synthesis in rabbit kidney medulla slices

1985 ◽  
Vol 232 (3) ◽  
pp. 625-628 ◽  
Author(s):  
Y Fujimoto ◽  
H Uno ◽  
C Kagen ◽  
T Ueno ◽  
T Fujita
Keyword(s):  
Arachidonic Acid ◽  
Phosphatidic Acid ◽  
Prostaglandin E2 ◽  
Phospholipase A2 ◽  
Rabbit Kidney ◽  
Dependent Manner ◽  
Kidney Medulla ◽  
Sequential Action ◽  
Acid Release ◽  
Dose Dependent

The effect of diarachidonin on the synthesis of prostaglandin E2 in rabbit kidney medulla slices was examined. The addition of diarachidonin stimulated prostaglandin E2 production in a dose-dependent manner. At three concentrations (10, 50 and 100 microM), increases in prostaglandin E2 formation induced by exogenous diarachidonin were 2-fold greater than those induced by exogenous arachidonic acid. Diacylglycerol or phosphatidic acid from egg lecithin had little or no effect on prostaglandin E2 production. Moreover, EGTA failed to inhibit diarachidonin-stimulated prostaglandin E2 formation, indicating that the stimulatory effect of diarachidonin is not mediated through the activation of endogenous phospholipase A2 (including phosphatidic acid-specific phospholipase A2). These results are discussed in the light of our former hypothesis that arachidonic acid release from kidney medulla phospholipids might occur through the sequential action of a phospholipase C coupled to diacylglycerol and monoacylglycerol lipases [Fujimoto, Akamatsu, Hattori & Fujita (1984) Biochem. J. 218, 69-74].

scholarly journals Biosynthesis of platelet-activating factor in glandular gastric mucosa. Evidence for the involvement of the ‘de novo’ pathway and modulation by fatty acids

1988 ◽  
Vol 254 (3) ◽  
pp. 707-714 ◽  
Author(s):  
S Fernandez-Gallardo ◽  
M A Gijon ◽  
M C Garcia ◽  
E Cano ◽  
M Sanchez Crespo
Keyword(s):  
Fatty Acids ◽  
Arachidonic Acid ◽  
Gastric Mucosa ◽  
De Novo ◽  
Potent Inhibitor ◽  
Specific Activity ◽  
Platelet Activating Factor ◽  
Exocrine Glands ◽  
Acetyl Coa ◽  
Dose Dependent

The biosynthesis of platelet-activating factor (PAF), a phospholipid autocoid with potent ulcerogenic properties that is produced in secretory exocrine glands by physiological secretagogues, was assessed in microsomal preparations of glandular gastric mucosa. For this purpose, 1-O-alkyl-2-lyso-sn-glycero-3-phosphocholine (lyso-PAF):acetyl-CoA acetyltransferase (EC 2.3.1.67); the enzymes of the ‘de novo’ pathway: 1-O-alkyl-2-lyso-sn-glycero-3-phosphate (alkyl-lyso-GP):acetyl-CoA acetyltransferase and 1-O-alkyl-2-acetyl-sn-glycerol (alkylacetyl-G):CDP-choline cholinephosphotransferase (EC 2.7.8.16); and some enzymes involved in the catabolism of PAF and lyso-PAF were assayed. Only the enzymes of the ‘de novo’ pathway and small amounts of PAF acetylhydrolase, phospholipase A2 and a lysophospholipase D acting on either lipids could be detected in the gastric preparations, whereas lyso-PAF:acetyl-CoA acetyltransferase activity was undetectable. The specific activity of alkyl-lyso-GP:acetyl-CoA acetyltransferase in the gastric mucosa was about one-tenth of that found in spleen microsomes and its apparent Km for acetyl-CoA was 454 microM compared with 277 microM in spleen microsomes. Glandular mucosa homogenates contained preformed PAF at a concentration of 2.7 +/- 0.7 ng equivalents of PAF (hexadecyl)/mg of protein. When gastric microsomes were incubated with micromolar concentrations of fatty acids (arachidonic, palmitic and oleic) prior to the assay of dithiothreitol (DTT)-insensitive cholinephosphotransferase, a dose-dependent reduction in the formation of PAF was observed, arachidonic acid being the most potent inhibitor, followed by linoleic acid (only tested on spleen microsomes) and oleic acid. By contrast, 1,2-diolein and phosphatidylcholine (dipalmitoyl) showed no or little effect. These results indicate that glandular gastric mucosa can produce PAF through the ‘de novo’ pathway, and that fatty acids, especially unsaturated, can reduce that synthesis by modulating the expression of DTT-insensitive cholinephosphotransferase.

scholarly journals Activation of phospholipase A2 in human neutrophils by polyunsaturated fatty acids and its role in stimulation of superoxide production

1998 ◽  
Vol 336 (3) ◽  
pp. 611-617 ◽  
Author(s):  
Brenton S. ROBINSON ◽  
Charles S. T. HII ◽  
Antonio FERRANTE
Keyword(s):  
Fatty Acids ◽  
Polyunsaturated Fatty Acids ◽  
Phospholipase A2 ◽  
Saturated Fatty Acids ◽  
Superoxide Production ◽  
Eicosatetraenoic Acid ◽  
Human Neutrophils ◽  
Dependent Manner ◽  
Biological Responses ◽  
Cytosolic Pla2

Although polyunsaturated fatty acids (PUFA) have been shown to stimulate neutrophil responses such as the oxygen-dependent respiratory burst (superoxide production), the mechanisms involved still remain undefined. Here we investigate the effect of PUFA on the phospholipase A2 (PLA2)-signal transduction process in human neutrophils. Exogenous eicosatetraenoic acid [arachidonic acid; C20:4(n-6)] or docosahexaenoic acid [C22:6(n-3)] promoted the release of [3H]C20:4(n-6) from prelabelled neutrophils in a time- and dose-dependent manner, which is indicative of PLA2 activation. The release of [3H]C20:4(n-6) from the cells by C20:4(n-6) and C22:6(n-3) was suppressed by PLA2 inhibitors. Other PUFA {eicosapentaenoic [C20:5(n-3)], octadecatrienoic [γ-linolenic; C18:3(n-6)] and octadecadienoic [linoleic; C18:2(n-6)] acids} also had the ability to release [3H]C20:4(n-6); however, certain C20:4(n-6) derivatives [15-hydroperoxyeicosatetraenoic acid, 15-hydroxyeicosatetraenoic acid and C20:4(n-6) methyl ester] and saturated fatty acids [octadecanoic (stearic; C18:0) and eicosanoic (arachidic; C20:0) acids] had no significant effect. Treatment of the neutrophils with exogenous C22:6(n-3) caused the mass of endogenous unesterified C20:4(n-6) to increase. Incubation of the leucocytes with C20:4(n-6) or C22:6(n-3) evoked activation of the 85 kDa cytosolic PLA2 (cPLA2) and the 14 kDa secretory PLA2 (sPLA2), but not the cytosolic Ca2+-independent PLA2. In contrast, C20:0 did not activate any of the PLA2 isoforms. Activation of cPLA2 by PUFA was found to precede that of sPLA2. C22:6(n-3), C20:4(n-6) and other PUFA induced punctate localization of cPLA2 in the cells, which was not observed with saturated fatty acids. Pretreatment of the leucocytes with PLA2 inhibitors markedly decreased superoxide production induced by C20:4(n-6). These results show that PUFA activate PLA2 in neutrophils, which might have a mandatory role in biological responses.

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