Intracellular cold trapping of exogenous arachidonic acid and activation of the 5-lipoxygenase pathway of human neutrophils

Inflammation ◽  
1988 ◽  
Vol 12 (1) ◽  
pp. 45-50 ◽  
Author(s):  
Floyd A. Green
Keyword(s):  
Arachidonic Acid ◽  
Human Neutrophils ◽  
Lipoxygenase Pathway ◽  
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.

Molecular mechanism of nucleotide-induced primary granule release in human neutrophils: role for the P2Y2receptor

2004 ◽  
Vol 286 (2) ◽  
pp. C264-C271 ◽  
Author(s):  
John Meshki ◽  
Florin Tuluc ◽  
Ovidiu Bredetean ◽  
Zhongren Ding ◽  
Satya P. Kunapuli
Keyword(s):  
Arachidonic Acid ◽  
P38 Mapk ◽  
Mapk Pathway ◽  
Extracellular Nucleotides ◽  
Human Neutrophils ◽  
Lipoxygenase Pathway ◽  
Arachidonic Acid Metabolites ◽  
Acid Metabolites ◽  
Primary Granule ◽  
Granule Release

Nucleotides are released during vascular injury from activated platelets and broken cells, which could stimulate human neutrophils. In this study, we characterized the P2Y receptors and investigated the functional effects of extracellular nucleotides on human neutrophils. Pharmacological characterization using selective agonists and pertussis toxin revealed that human neutrophils express only functional P2Y2receptors. However, P2Y2receptor agonists ATP or uridine triphosphate (UTP) caused intracellular Ca2+increases in isolated human neutrophils with an EC50of 1 μM but failed to cause release of primary granules from human neutrophils. ATP and UTP were equally potent in causing elastase release from human neutrophils in the presence of exogenous soluble fibrinogen, whereas ADP and UDP were without effect. We investigated whether nucleotides depend on generated arachidonic acid metabolites to cause degranulation. However, phenidone and MK-886, inhibitors of the 5-lipoxygenase pathway, failed to block nucleotide-induced intracellular calcium mobilization and elastase release. ATP and UTP caused activation of p38 MAPK and ERK1/2 in human neutrophils. In addition, the inhibitors of the MAPK pathway, SB-203580 and U-0126, inhibited nucleotide-induced elastase release. We conclude that fibrinogen is required for nucleotide-induced primary granule release from human neutrophils through the P2Y2receptor without a role for arachidonic acid metabolites. Both ERK1/2 and p38 MAPK play an important role in nucleotide-induced primary granule release from human neutrophils.

scholarly journals Neutrophil activation by anti-proteinase 3 antibodies in Wegener's granulomatosis: role of exogenous arachidonic acid and leukotriene B4 generation.

1996 ◽  
Vol 184 (4) ◽  
pp. 1567-1572 ◽  
Author(s):  
F Grimminger ◽  
K Hattar ◽  
C Papavassilis ◽  
B Temmesfeld ◽  
E Csernok ◽  
...  
Keyword(s):  
Arachidonic Acid ◽  
Wegener’S Granulomatosis ◽  
Wegener's Granulomatosis ◽  
Neutrophil Activation ◽  
Tnf Alpha ◽  
Lipid Mediator ◽  
Human Neutrophils ◽  
Proteinase 3 ◽  
Lipoxygenase Pathway

Among the anti-neutrophil cytoplasmic antibodies (ANCA), those targeting proteinase 3 (PR3) have a high specificity for Wegener's granulomatosis (WG). It is known that a preceding priming of neutrophils with cytokines is a prerequisite for membrane surface expression of PR3, which is then accessible to autoantibody binding. Employing a monoclonal antibody directed against human PR3 and ANCA-positive serum from WG patients with specificity for PR3, we now investigated the role of free arachidonic acid (AA) in autoantibody-related human neutrophil activation. Priming of neutrophils with tumor necrosis factor (TNF-alpha) for 15 min or exposure to anti-PR3 antibodies or incubation with free AA (10 microM) as sole events did not provoke superoxide generation, elastase secretion or generation of 5-lipoxygenase products of AA. Similarly, the combination of TNF-alpha-priming and AA incubation was ineffective. When TNF-alpha-primed neutrophils were stimulated by anti-PR3 antibodies, superoxide and elastase secretion was provoked in the absence of lipid mediator generation. However, when free AA was additionally provided, a strong activation of the 5-lipoxygenase pathway was demasked, with the appearance of excessive quantities of leukotriene (LT)B4, LTA4, and 5-hydroxyeicosatetraenoic acid. Moreover, superoxide and elastase secretion were markedly amplified, and studies with 5-lipoxygenase inhibitors and a LTB4-antagonist demonstrated this was due to an LTB4-related autocrine loop of cell activation. In contrast, the increased synthesis of platelet-activating factor in response to TNF-alpha-priming and anti-PR3 stimulation did not contribute to the amplification loop of neutrophil activation under the given conditions. We conclude that anti-PR3 antibodies are potent inductors of the 5-lipoxygenase pathway in primed human neutrophils, and extracellular free AA, as provided at an inflammatory focus, synergizes with the autoantibodies to evoke full-blown lipid mediator generation, granule secretion and respiratory burst. Such events may be enrolled in the pathogenesis of focal necrotizing vascular injury in Wegener's granulomatosis.

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