Potentiation of Ca2+ signaling in endothelial cells by 11,12-epoxyeicosatrienoic acid.
Incubation of endothelium with an increased epoxyeicosatrienoic acid (EET) concentration specifically augments the endothelium-dependent relaxation ascribed to endothelium-derived hyperpolarizing factor in porcine coronary arteries (Weintraub et al., Circ Res 1997;81:258-267). Experiments were designed to test whether such sustained increased levels of EETs in the environment of endothelial cells alters Ca2+ signaling. Changes in cytosolic Ca2+ were monitored in cultured porcine aortic endothelial cells (PAECs) and in the human endothelial EA.hy926 cell line after incubation (or not) with 5 microM 11,12-epoxyeicosatrienoic acid (EET). Although the mobilization of intracellular Ca2+ induced by 2 microM thapsigargin was not affected significantly, EET treatment augmented the capacitative Ca2+ entry evoked by the Ca(2+)-ATPase) inhibitor in both cell types. Similar observations were obtained by using histamine as a stimulant in EA.hy926 cells. As assessed in PAECs, 2 micrograms/ml triacsin C, a known inhibitor of the incorporation of EETs into phospholipids, did not significantly affect the potentiating action of EETs on Ca2+ signaling in response to thapsigargin. However, in solvent-control cells, triacsin C significantly reduced both the mobilization of Ca2+ from intracellular stores and the capacitative Ca2+ entry provoked by thapsigargin. Thus the EET-potentiating effect overcomes the inhibitory action of triacsin C on Ca2+ signaling in endothelial cells. Taken together, these results demonstrate that sustained increases in EETs may amplify Ca2+ signaling. However, contrary to the EET-induced augmentation of endothelium-dependent relaxation in the porcine coronary artery, resistance of this novel action of EETs to triacsin C suggests that the mechanism involved does not depend on incorporation into phospholipids.
Mombouli
J V
JV
Department of Medical Biochemistry, Karl Franzens University of Graz, Austria.
Holzmann
S
S
Kostner
G M
GM
Graier
W F
WF
D015126:8,11,14-Eicosatrienoic Acid / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D001011:Aorta / Q000166:cytology / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D013552:Swine; D014226:Triazenes / Q000494:pharmacology
D004791:Enzyme Inhibitors; D014226:Triazenes; C046783:11,12-epoxy-5,8,14-eicosatrienoic acid; C034613:triacsin C; D015126:8,11,14-Eicosatrienoic Acid; D002118:Calcium