Formation of biologically active autacoids is regulated by calcium influx in endothelial cells.

Abstract

The blocker of receptor-mediated calcium entry SK&F 96365 was used to evaluate the contribution of calcium influx to the formation of biologically active endothelial prostanoids and endothelium-derived relaxing factor (EDRF). SK&F 96365 inhibited histamine-stimulated calcium entry into human umbilical vein endothelial cells but not its discharge from intracellular stores as determined spectrofluorometrically by changes of intracellular calcium concentration in fura-2-loaded cells. Concordantly, SK&F 96365 inhibited histamine-induced endothelial synthesis of 6-keto-prostaglandin F la and thromboxane B, in a dose-dependent manner. To assess the functional significance of endothelial formation of prostacyclin and EDRF to platelets, the cAMP-and cGMPdependent phosphorylation of two platelet proteins, raplB and a 50-kD vasodilator-stimulated phosphoprotein (VASP), was analyzed in coincubation experiments of endothelial cells with platelets. Autacoids released by histamine-stimulated E ndothelium-derived autacoids are crucial for the maintenance of local vascular homeostasis and endothelium-platelet interactions. Endothelial cells (ECs) respond to hormonal, chemical, and physical stimuli with the generation and release of prostacyclin and endothelium-derived relaxing factor (EDRF; nitric oxide or nitric oxide-releasing compounds), both of which are known to dilate vessels and inhibit platelet function in a paracrine manner. 15 Concomitantly, ECs also release the potent vasoconstrictor and stimulator of platelet aggregation thromboxane A 2 (TXA 2 ).6 ' 7The increase of cytosolic calcium concentration ([Ca 2+ ],), a key step in the stimulus-response coupling of ECs, leads to the activation of calcium-dependent enzymes such as phospholipase A 2 and nitric oxide synthase. 89 A variety of blood-borne mediators interact with endothelial surface receptors and raise [Ca 2+ ], by both inducing second messenger-mediated discharge of calcium from internal stores and promoting influx from the extracellular milieu.1 Calcium entry into nonexcitable cells occurs voltage independently via receptorcoupled channels of the plasma membrane that are not well characterized. 10Formation and release of EDRF and prostanoids by the vascular endothelium are coupled to an increase in Received May 31, 1994; accepted Jury 25, 1994. From the Institut fur Prophylaxe und Epidemiologie der Kreislaufkrankheiten, University of Munich, FRG.Correspondence to H.-J. Kruse, Institut fur Prophylaxe und Epidemiologie der Kreislaufkrankheiten, UniversitSt Munchen, Pettenkoferstr 9, 80336 Munchen, Germany.O 1994 American Heart Association, Inc.endothelial cells caused the phosphorylation of rap IB and VASP in platelets, which was only partly inhibited by either indomethacin or A r°-monomethyl-L-arginine but was almost completely suppressed by SK&F 96365. The concomitant endothelial release of thromboxane A 2 had no effect on protein kinase C-and calcium-dependent phosphorylation of platelet proteins. The results demonstrate that blockade of recepto...

Acute exercise enhances vasorelaxation by modulating endothelial calcium signaling in rat aortas

“…Existing evidence not only supports that eNOS is a Ca 2ϩ -dependent enzyme (15,19) and that ACh-induced vasorelaxation is coupled to EC [Ca 2ϩ ] i elevation (2,12,18), but also indicates that NO is capable of inducing intracellular calcium rise in cultured EC (1,25). In this study, we observed that L-NNA, a NOS inhibitor, abolished the exercise effects on ACh-induced vasorelaxation and the EC [Ca 2ϩ ] i response.…”

Chronic Exercise Improves Endothelial Calcium Signaling and Vasodilatation in Hypercholesterolemic Rabbit Femoral Artery

“…Existing evidence not only supports the notion that eNOS is a Ca 2ϩ -dependent enzyme 19 and that ACh-induced vasorelaxation is coupled to EC [Ca 2ϩ ] i elevation 16,17,23 but also indicates that NO is capable of inducing EC [Ca 2ϩ ] i elevation in culture. 33,34 Our previous study 23 also suggests that a high concentration of ACh-stimulated NO after exercise is capable of evoking EC [Ca 2ϩ ] i elevation.…”

“…16 -18 Besides, endothelial NO synthase (eNOS) is known to be a calcium-dependent enzyme. 19 It is likely that agonist-evoked endothelial intracellular calcium (EC [Ca 2ϩ ] i ) signaling is involved in the exercise-induced vascular adaptation. Our previous study 20 has demonstrated that chronic exercise increases the ACh-evoked EC [Ca 2ϩ ] i elevation response in normal rats.…”

Ca2+-independent PLA2 controls endothelial store-operated Ca2+ entry and vascular tone in intact aorta

“…It has been demonstrated that the sustained store-operated Ca 2ϩ entry occurring during agonist stimulation of endothelial cells contributes to Ca 2ϩ -dependent NO synthesis and subsequent vessel relaxation (10,21,23,24,40,41). To investigate whether the iPLA 2 -dependent Ca 2ϩ entry occurring during ATP stimulation significantly contributes to the relaxing effect of this hormone, the effect of iPLA 2 inhibition was tested on ATP-induced endothelium-dependent relaxation (4,15,17,25).…”

“…This sustained Ca 2ϩ entry through store-operated channels significantly contributes to the increase in cytosolic Ca 2ϩ concentration necessary for the release of vasoactive compounds such as nitric oxide (NO) or prostacyclin by endothelial cells (10,21,23,24,40,41). Indeed, it has been shown that the lack of endothelial store-operated Ca 2ϩ influx impairs agonist-induced endothelium-dependent relaxation (13).…”