Leukotriene B4 synthesis and metabolism by neutrophils and granule-free cytoplasts.
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.
Haines
K A
KA
Giedd
K N
KN
Weissmann
G
G
D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000097:blood / Q000494:pharmacology; D001792:Blood Platelets / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D003593:Cytoplasm / Q000378:metabolism; D006801:Humans; D008084:Lipoxygenase / Q000097:blood; D009504:Neutrophils / Q000187:drug effects / Q000378:metabolism*; D013189:SRS-A / Q000097:blood*
D001095:Arachidonic Acids; D013189:SRS-A; D016718:Arachidonic Acid; D008084:Lipoxygenase