Regulation of arachidonic acid release by calcium influx in human endothelial cells.
In response to stimuli, endothelial cells release arachidonic acid, a lipid precursor of various vasoactive substances. We have investigated the relationships between cytosolic Ca2+ movements and arachidonic acid release in human umbilical vein endothelial cells. Histamine, a receptor-dependent agonist, and thapsigargin, a specific inhibitor of sarco-/endoplasmic Ca2+ pumps, time- and dose-dependently increased the release of [1-14C]-arachidonic acid. This release was inhibited by AACOCF3, a selective inhibitor of cytosolic phospholipase A2 (PLA2). In the absence of Ca2+ influx, arachidonic acid release was suppressed in both histamine- and thapsigargin-stimulated cells, despite marked elevations of cytosolic Ca2+ concentration ([Ca2+]i). In the presence of Ca2+ influx, arachidonic acid release was reduced in cells treated with BAPTA, an intracellular Ca2+ buffer, or with SK&F 96365, a receptor-operated Ca2+ channel blocker. Arachidonic acid release was analyzed as a function of the two successive phases of Ca2+ response to stimulation: Ca2+ peak and plateau phase, reflecting Ca2+ mobilization from internal stores and Ca2+ influx, respectively. The amount of arachidonic acid released was directly related to [Ca2+]i values measured at the influx phase with a 80 nM [Ca2+]i threshold, similar to that reported for PLA2 translocation. This suggests that Ca2+ entry from the extracellular space is essential for activating cytosolic PLA2 in human endothelial cells.
Pharmacology, CNRS, UMR 8604, Paris V University, Necker Medical School, Paris, France. millanvoye@necker.fr
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Millanvoye-Van Brussel
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David-Dufilho
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Pham
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Iouzalen
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Aude Devynck
D016718:Arachidonic Acid / Q000378:metabolism*; D001095:Arachidonic Acids / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism / Q000502:physiology*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002478:Cells, Cultured; D003600:Cytosol / Q000378:metabolism; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006632:Histamine / Q000494:pharmacology; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D050356:Lipid Metabolism; D010741:Phospholipases A / Q000037:antagonists & inhibitors; D054467:Phospholipases A2; D019284:Thapsigargin / Q000494:pharmacology
D001095:Arachidonic Acids; D002121:Calcium Channel Blockers; D004791:Enzyme Inhibitors; D007093:Imidazoles; C081565:arachidonyltrifluoromethane; D016718:Arachidonic Acid; D019284:Thapsigargin; D006632:Histamine; D010741:Phospholipases A; D054467:Phospholipases A2; C063159:1-(2-(3-(4-methoxyphenyl)propoxy)-4-methoxyphenylethyl)-1H-imidazole; D002118:Calcium