Exogenous arachidonic acid inhibits A23187 stimulated macrophage leukotriene B4 synthesisin vitro

1988 ◽  
Vol 23 (1-2) ◽  
pp. 84-85 ◽  
Author(s):  
G. R. Elliott ◽  
J. Lauwen ◽  
J. L. Bonta
Keyword(s):  
Arachidonic Acid ◽  
Leukotriene B4 ◽  
Exogenous Arachidonic Acid

scholarly journals Na+/H+ exchange modulates the production of leukotriene B4 by human neutrophils

1989 ◽  
Vol 257 (3) ◽  
pp. 751-758 ◽  
Author(s):  
M Osaki ◽  
H Sumimoto ◽  
K Takeshige ◽  
E J Cragoe ◽  
Y Hori ◽  
...  
Keyword(s):  
Arachidonic Acid ◽  
Leukotriene B4 ◽  
Human Neutrophils ◽  
Ionophore A23187 ◽  
Cytoplasmic Ph ◽  
Chemotactic Peptide ◽  
Trans Isomers ◽  
Lipoxygenase Pathway ◽  
Exogenous Arachidonic Acid ◽  
Specific Inhibitors

Human neutrophils produce various compounds of the 5-lipoxygenase pathway, including (5S)-hydroxyeicosatetraenoic acid, leukotriene B4, its 6-trans isomers and omega-oxidation metabolites of LTB4, when the cells are stimulated with the Ca2+ ionophore A23187. The elevation in the extracellular pH (pHo) facilitated the cytoplasmic alkalinization induced by the ionophore as determined fluorometrically using 2',7'-bis(carboxyethyl)carboxyfluorescein and enhanced the production of all the 5-lipoxygenase metabolites. The production decreased when the alkalinization was blocked by the decrease in the pHo, the removal of the extracellular Na+ or the addition of specific inhibitors of the Na+/H+ exchange, such as 5-(NN-hexamethylene)amiloride, 5-(N-methyl-N-isobutyl)amiloride and 5-(N-ethyl-N-isopropyl)amiloride. The alkalinization of the cytoplasm with methylamine completely restored the production suppressed by the removal of Na+ from the medium. These findings suggest that the change in the cytoplasmic pH (pHi) mediated by the Na+/H+ exchange regulates the production of the lipoxygenase metabolites. The site of the metabolism controlled by the pHi change seemed to be the 5-lipoxygenase, because the production of all the metabolites decreased in parallel and the release of [3H]arachidonic acid from the neutrophils in response to the ionophore was not affected by the pHi change. Furthermore, the production of the 5-lipoxygenase metabolites stimulated by A23187 with or without exogenous arachidonic acid showed a similar pHo-dependence and the production induced by N-formylmethionyl-leucylphenylalanine (chemotactic peptide) with exogenous arachidonic acid also decreased when the cytoplasmic alkalinization was inhibited.

scholarly journals Leukotriene B4 synthesis and metabolism by neutrophils and granule-free cytoplasts

1986 ◽  
Vol 233 (2) ◽  
pp. 583-588 ◽  
Author(s):  
K A Haines ◽  
K N Giedd ◽  
G Weissmann
Keyword(s):  
Arachidonic Acid ◽  
Plasma Membrane ◽  
Leukotriene B4 ◽  
Ionophore A23187 ◽  
Tetraenoic Acid ◽  
Exogenous Arachidonic Acid ◽  
Neutrophil Degranulation ◽  
Arachidonate Metabolites

Leukotriene B4 [LTB4, (5S,12R)-hydroxyeicosa-6,14-cis-8,10-trans-tetraenoic acid], a potent mediator of inflammation, is released from neutrophils by agonists that provoke degranulation of the cell. To examine whether degranulation is a necessary requirement for synthesis and metabolism of LTB4 (or of other arachidonate metabolites), we prepared neutrophil-derived cytoplasts (neutroplasts), organelle-depleted vesicles of cytoplasm surrounded by the plasma membrane. In the presence of extracellular Ca2+ with or without exogenous arachidonic acid (150 microM), neutroplasts were exposed to the Ca2+ ionophore A23187 (10 microM) and the resultant lipoxygenation products of arachidonate were determined. Neutrophils metabolize arachidonic acid to 5-HETE greater than 15-HETE greater than LTB4 greater than all-trans-LTB4 isomers. Neutroplast products of arachidonate lipoxygenation were 15-HETE greater than 5-HETE greater than LTB4 greater than all-trans-LTB4 isomers. Neutroplasts, like neutrophils, were capable of converting LTB4 into its 20-hydroxy and 20-carboxy metabolites. Finally, neutroplasts could utilize intrinsic arachidonate, since the neutroplasts synthesized LTB4 (30 pmol/mg of protein) in the absence of added arachidonic acid. The data demonstrate that neutrophil degranulation is not required for synthesis or metabolism of LTB4 by neutrophils.

scholarly journals Role of arachidonic acid metabolism in transcriptional induction of tumor necrosis factor gene expression by phorbol ester.

1989 ◽  
Vol 9 (1) ◽  
pp. 252-258 ◽  
Author(s):  
J Horiguchi ◽  
D Spriggs ◽  
K Imamura ◽  
R Stone ◽  
R Luebbers ◽  
...  
Keyword(s):  
Gene Expression ◽  
Arachidonic Acid ◽  
Tumor Necrosis Factor ◽  
Tumor Necrosis ◽  
Leukotriene B4 ◽  
Mrna Levels ◽  
Arachidonic Acid Release ◽  
Acid Release ◽  
Tnf Gene ◽  
Necrosis Factor

The treatment of human HL-60 promyelocytic leukemia cells with 12-O-tetradecanoylphorbol-13-acetate (TPA) is associated with induction of tumor necrosis factor (TNF) transcript. The study reported here has examined TPA-induced signaling mechanisms responsible for the regulation of TNF gene expression in these cells. Run-on assays demonstrated that TPA increases TNF mRNA levels by transcriptional activation of this gene. The induction of TNF transcripts by TPA was inhibited by the isoquinolinesulfonamide derivative H7 but not by HA1004, suggesting that this effect of TPA is mediated by activation of protein kinase C. TPA treatment also resulted in increased arachidonic acid release. Moreover, inhibitors of phospholipase A2 blocked both the increase in arachidonic acid release and the induction of TNF transcripts. These findings suggest that TPA induces TNF gene expression through the formation of arachidonic acid metabolites. Although indomethacin had no detectable effect on this induction of TNF transcripts, ketoconazole, an inhibitor of 5-lipoxygenase, blocked TPA-induced increases in TNF mRNA levels. Moreover, TNF mRNA levels were increased by the 5-lipoxygenase metabolite leukotriene B4. In contrast, the cyclooxygenase metabolite prostaglandin E2 inhibited the induction of TNF transcripts by TPA. Taken together, these results suggest that TPA induces TNF gene expression through the arachidonic acid cascade and that the level of TNF transcripts is regulated by metabolites of the pathway, leukotriene B4 and prostaglandin E2.

scholarly journals Lipopolysaccharides prime whole human blood and isolated neutrophils for the increased synthesis of 5-lipoxygenase products by enhancing arachidonic acid availability: involvement of the CD14 antigen.

1993 ◽  
Vol 178 (4) ◽  
pp. 1347-1355 ◽  
Author(s):  
M E Surette ◽  
R Palmantier ◽  
J Gosselin ◽  
P Borgeat
Keyword(s):  
Arachidonic Acid ◽  
Mononuclear Cells ◽  
Leukotriene B4 ◽  
Eicosatetraenoic Acid ◽  
Tnf Alpha ◽  
Peripheral Blood Mononuclear ◽  
Necrosis Factor Alpha ◽  
Factor Alpha ◽  
Priming Activity

Stimulation of heparinized blood with 1 microM formyl-methionyl-leucyl-phenylalanine (FMLP) resulted in the formation of < 30 pmol/ml plasma of 5-lipoxygenase (5-LO) products. The preincubation of blood with 1 microgram/ml of lipopolysaccharide (LPS) (Escherichia coli 0111-B4) for 30 min before stimulation with FMLP resulted in the accumulation of 250-300 pmol of 5-LO products per ml plasma. The major products detected were leukotriene B4 and (5S)-hydroxy-6,8,11,14-eicosatetraenoic acid which were produced in equivalent amounts. The priming activity was detectable with as little as 1-10 ng LPS per ml blood and was optimal using 1-10 micrograms LPS/ml blood. The priming for 5-LO product synthesis was optimal after 20-30 min of preincubation with LPS and declined at preincubation times > 30 min. The priming effect of LPS was also observed using the complement fragment C5a or interleukin 8 as agonists. Polymorphonuclear leukocytes (PMN) and peripheral blood mononuclear cells accounted for 80 and 20% of the synthesis of 5-LO products, respectively. The ability of LPS to prime isolated PMN was dependent on the presence of plasma and was inhibited by the anti-CD14 antibody IOM2, indicating a CD14-dependent priming mechanism. The priming of whole blood with tumor necrosis factor alpha (TNF-alpha) and LPS was additive and the presence of mononuclear cells did not enhance the ability of LPS to prime PMN, indicating that the priming activity of LPS is independent of LPS-induced TNF-alpha synthesis. The mechanism by which LPS enhance 5-LO product synthesis in PMN was investigated. Treatment of PMN with LPS strongly enhanced the release of arachidonic acid after stimulation with FMLP. The release of arachidonic acid was optimal 2-3 min after stimulation with FMLP, attaining levels 5-15-fold greater than those observed in unprimed cells stimulated with FMLP. These results demonstrate that LPS dramatically increases the ability of blood to generate 5-LO products, and support the putative role of leukotrienes in pathological states involving LPS.

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