Involvement of calcium in the thimerosal-stimulated formation of leukotriene by fMLP in human polymorphonuclear leukocytes.
Only small amounts of leukotrienes could be detected by reverse-phase HPLC analysis after stimulation of human polymorphonuclear leukocytes (PMN) by the receptor agonist N-formyl-methionyl-leucyl-phenylalanine (fMLP). Preincubation of the cells with the organomercury compound thimerosal prior to fMLP-addition, however, resulted in the formation of significant amounts of 5-lipoxygenase derived metabolites. This effect was dose-dependent with respect both to fMLP and thimerosal. Thimerosal alone did neither lead to the formation of HPLC-detectable leukotrienes nor to the release of arachidonic acid in [1-14C]arachidonic acid prelabelled cells. The formation of leukotrienes by fMLP/thimerosal required extracellular Ca2+. Measurements of intracellular Ca2(+)-levels revealed that (i) thimerosal alone is able to release Ca2+ from internal stores and (ii) thimerosal causes a persistent accumulation of Ca2+ within the cells after stimulation by fMLP. We conclude that by the synergistic action of fMLP and thimerosal the Ca2(+)-levels exceed the threshold for phospholipase A2 activation resulting in the liberation of arachidonic acid and subsequently in the formation of 5-lipoxygenase products. Our results suggest that thimerosal may provide a model for leukotriene formation under pathophysiological conditions when SH-group oxidation leads to increased intracellular Ca2(+)-levels.
Hatzelmann
A
A
Faculty of Biology, University of Konstanz, Federal Republic of Germany.
Haurand
M
M
Ullrich
V
V
D001094:Arachidonate 5-Lipoxygenase / Q000378:metabolism; D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D004357:Drug Synergism; D004533:Egtazic Acid / Q000494:pharmacology; D005035:Ethylmercury Compounds / Q000494:pharmacology*; D006801:Humans; D007975:Leukotriene B4 / Q000096:biosynthesis*; D016859:Lipoxygenase Inhibitors; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology*; D009504:Neutrophils / Q000187:drug effects / Q000378:metabolism*; D010741:Phospholipases A / Q000037:antagonists & inhibitors; D054467:Phospholipases A2; D013849:Thimerosal / Q000494:pharmacology*
D001095:Arachidonic Acids; D005035:Ethylmercury Compounds; D016859:Lipoxygenase Inhibitors; D007975:Leukotriene B4; D013849:Thimerosal; D016718:Arachidonic Acid; D004533:Egtazic Acid; D009240:N-Formylmethionine Leucyl-Phenylalanine; D001094:Arachidonate 5-Lipoxygenase; D010741:Phospholipases A; D054467:Phospholipases A2; D002118:Calcium