Binding and metabolism of platelet-activating factor by human neutrophils.

O’Flaherty, Joseph T.; Surles, Jefferson R.; Redman, J F; Jacobson, David P.; Piantadosi, Claude A.; Wykle, Robert L.

doi:10.1172/jci112588

Cited by 166 publications

(66 citation statements)

References 41 publications

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“…[3H]PAF and l-O-[3H]hexadecyl-2-1yso-GPC (56 Ci/mmol), PAF, l-O-alkyl-2-1yso-GPC, 1,2-diacyl-GPC, L652731, delipidated BSA, silicone oil, TLC plates, pronase and modified Hanks' buffer were obtained as in [3,6,7]. PAF and analogs were taken up in buffer containing 2.5 mg/ml BSA; 50/~1 of this was added to 950 ~1 cell suspension.…”

Section: Reagents and Buffersmentioning

confidence: 99%

“…PMN were isolated from normal human donors [3]; HL-60 cells were purchased (American Type Culture Collection, Rockville, MD). We conducted [3H]PAF binding at 4°C using centrifugation through silicone oil to separate cells from medium [6].…”

Section: Bindingmentioning

confidence: 99%

“…This unique 1-O-alkyl-2-acetyl-GPC uses plasma membrane receptors to activate diverse cell types. These same target cells deacetylate PAF, acylate the 1-O-alkyl-2-1yso-GPC intermediate, and store the final product, 1-O-alkyl-2-acyl-GPC, in Golgi/granules [2,3]. Furthermore, Lachachi et al [4] reported that a PAF antagonist almost com- pletely blocked rabbit platelet metabolism of PAF.…”

Section: Introductionmentioning

confidence: 99%

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Receptor‐independent metabolism of platelet‐activating factor by myelogenous cells

et al. 1989

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Human neutrophils incorporate and metabolize platelet-activating factor (PAF). We dissociated these events from PAF binding to its receptors. Cells were pretreated with either pronase, a PAF antagonist (L652731), or excess PAF. This reduced PAF receptor numbers by 70 to almost 100% but had no comparable effect upon the neutrophil's ability to metabolize PAF. Furthermore, HL-60 cells efficiently metabolized, but did not specifically bind, PAF. Thus, PAF receptor availability did not correlate with PAF metabolic capacity and we conclude that myelogenous tissues can process this bioactive ligand by a receptor-independent pathway.Platelet-activating factor; Receptor; Phospholipid metabolism; (Polymorphonuclear leukocyte, HL-60 promyelocyte)

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Section: Reagents and Buffersmentioning

confidence: 99%

Section: Bindingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Receptor‐independent metabolism of platelet‐activating factor by myelogenous cells

et al. 1989

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“…5, upper panel), we concluded that compound C is 5,20-dihydroxy-E,Z,Z,Z-6,8,1 lJ4-eicosatetraenoic acid. This metabolite had already been identified in human PMN [9] after incubation with 5-HETE.…”

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confidence: 72%

The ω‐hydroxylation of arachidonic acid by human polymorphonuclear leukocytes

Hatzelmann

Ullrich

1988

European Journal of Biochemistry

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Incubations of [1-'4C]arachidonic acid with unstimulated human polymorphonuclear leukocytes resulted in the formation of four new metabolites in a previously described reverse-phase HPLC system. Three of these metabolites were largely suppressed in a CO/02 (80/20, by vol.) atmosphere indicating a cytochrome-P450-dependent monooxygenase reaction. In agreement with this assumption is their NADPH/02-dependent formation in the microsomal fraction. One metabolite was identified by gas chiomatography/mass spectrometry analysis as o-hydroxy-arachidonic acid and the two others were secondary products identified as w-carboxy-arachidonic acid and 5,2O-dihydroxy-E,Z,Z,Z-6,8,11 ,14-eicosatetraenoic acid. Since the affinity for arachidonate of the w-monooxygenase was quite low and the presence of LTB4 suppressed the w-hydroxylation of arachidonate, we conclude that the known LTB4 w-monooxygenase is responsible for the formation of w-hydroxy-arachidonate. It is unlikely, however, that significant concentrations of these metabolites are formed by activated polymorphonuclear leukocytes in vivo. The fourth metabolite remains tightly associated with the leukocytes but has not been further characterized.The release of arachidonic acid from phospholipids catalyzed by the action of phospholipase A2 is a frequent event subsequent to increases in intracellular cytosolic calcium levels. Depending on the various cell types in which this is observed, the further metabolism of arachidonic acid leads to highly active autacoids derived from either the cyclooxygenase or lipoxygenase pathways. In human polymorphonuclear leukocytes (PMN), two lipoxygenases are present and convert arachidonate to 15-hydroperoxyeicosatetraenoic acid (1 5-HPETE) or 15-hydroxyeicosatetraenoic acid (1 5-HETE) and to a major part to leukotriene B4 (LTB4), a highly chemotactic agent, which is formed from the primary 5-lipoxygenase product 5-HPETE via LTA4 [l]. The activity of 5-lipoxygenase was reported to depend strongly on elevated Ca2+ levels [2,3], but we recently showed that glutathione depletion also has an activating effect, probably by increasing organic peroxide concentrations [4]. Without Ca2+ or peroxides, the addition of arachidonic acid to PMN results in only minor amounts of 5-lipoxygenase-derived metabolites as detected in HPLC chromatograms by monitoring their triene absorption at 280 nm and diene absorption at 237 nm, respectively.In the course of these experiments, we also employed [l-14C]arachidonate and monitored the metabolites by means of a radioactivity detector. The corresponding chromatograms showed four additional metabolites. They all escaped ultraviolet detection because of a lack of an absorbance at the respective wavelength. Since this was an indication against lipoxygenase metabolites, we investigated other routes of Correspondence to V. Ullrich,

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“…However, neither of these agents, either alone or in combination, significantly affected the response of neutrophils to H 2 O 2 (data not shown). Because they possess high levels of the NADPH-dependent enzyme LTB 4 20-hydroxylase, neutrophils also convert 5-HETE to 5,20-diHETE (35), and this was the major product under the conditions of our assays, amounting to ϳ70 pmol/ml (Fig. 4).…”

Section: Oxidant Stress Enhances the Synthesis Of 5-oxo-ete-asmentioning

confidence: 89%

Oxidative Stress Stimulates the Synthesis of the Eosinophil Chemoattractant 5-Oxo-6,8,11,14-eicosatetraenoic Acid by Inflammatory Cells

Erlemann

Rokach

Powell

2004

Journal of Biological Chemistry

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5-Oxo-ETE (5-oxo-6,8,11,14-eicosatetraenoic acid) is a highly potent granulocyte chemoattractant that acts through a selective G-protein coupled receptor. It is formed by oxidation of the 5-lipoxygenase product 5-HETE (5S-hydroxy-6,8,11,14-eicosatetraenoic acid) by 5-hydroxyeicosanoid dehydrogenase (5-HEDH). Although leukocytes and platelets display high microsomal 5-HEDH activity, unstimulated intact cells do not convert 5-HETE to appreciable amounts of 5-oxo-ETE. To attempt to resolve this dilemma we explored the possibility that 5-oxo-ETE synthesis could be enhanced by oxidative stress. We found that hydrogen peroxide and t-butyl hydroperoxide strongly stimulate 5-oxo-ETE formation by U937 monocytic cells. This was dependent on the GSH redox cycle, as it was blocked by depletion of GSH or inhibition of glutathione reductase and mimicked by oxidation of GSH to GSSG by diamide. Glucose inhibited the response to H 2 O 2 through its metabolism by the pentose phosphate pathway, as its effect was reversed by the glucose-6-phosphate dehydrogenase inhibitor dehydroepiandrosterone. 5-Oxo-ETE synthesis was also strongly stimulated by hydroperoxides in blood monocytes, lymphocytes, and platelets, but not neutrophils. Unlike monocytic cells, lymphocytes and platelets were resistant to the inhibitory effects of glucose. 5-Oxo-ETE synthesis following incubation of peripheral blood mononuclear cells with arachidonic acid and calcium ionophore was also strongly enhanced by t-butyl hydroperoxide. Oxidative stress could act by depleting NADPH, resulting in the formation NADP ؉ , the cofactor for 5-HEDH. This is opposed by the pentose phosphate pathway, which converts NADP ؉ back to NADPH. Oxidative stress could be an important mechanism for stimulating 5-oxo-ETE production in inflammation, promoting further infiltration of granulocytes into inflammatory sites.

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Binding and metabolism of platelet-activating factor by human neutrophils.

Abstract: Human polymorphonuclear neutrophils rapidly incorporated radiolabeled platelet-activating factor, 1-O-Ihexadecyl-9, 10-3H21-2-acetyl-sn-glycero-3-phosphocholine (I3HIPAF), and then metabolized it into its sn-2-fatty acyl derivative.

Cited by 166 publications

References 41 publications

Receptor‐independent metabolism of platelet‐activating factor by myelogenous cells

Receptor‐independent metabolism of platelet‐activating factor by myelogenous cells

The ω‐hydroxylation of arachidonic acid by human polymorphonuclear leukocytes

Oxidative Stress Stimulates the Synthesis of the Eosinophil Chemoattractant 5-Oxo-6,8,11,14-eicosatetraenoic Acid by Inflammatory Cells

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