title: Epinephrine induces von Willebrand factor release from cultured endothelial cells: involvement of cyclic AMP-dependent signalling in exocytosis.
abstract: von Willebrand factor (vWf) is released from endothelial cell storage granules after stimulation with thrombin, histamine and several other agents that induce an increase in cytosolic free calcium ([Ca2+]i). In vivo, epinephrine and the vasopressin analog DDAVP increase vWf plasma levels, although they are thought not to induce vWf release from endothelial cells in vitro. Since these agents act via a cAMP-dependent pathway in responsive cells, we examined the role of cAMP in vWf secretion from cultured human umbilical vein endothelial cells. vWf release increased by 50% in response to forskolin, which activates adenylate cyclase. The response to forskolin was much stronger when cAMP degradation was blocked with IBMX, an inhibitor of phosphodiesterases (+200%), whereas IBMX alone had no effect. vWf release could also be induced by the cAMP analogs dibutyryl-cAMP (+40%) and 8-bromo-cAMP (+25%); although their effect was weak, they clearly potentiated the response to thrombin. Epinephrine (together with IBMX) caused a small, dose-dependent increase in vWf release, maximal at 10(-6) M (+50%), and also potentiated the response to thrombin. This effect is mediated by adenylate cyclase-coupled beta-adrenergic receptors, since it is inhibited by propranolol and mimicked by isoproterenol. In contrast to thrombin, neither forskolin nor epinephrine caused an increase in [Ca2+]i as measured by fura-2 fluorescence. In addition, the effects of forskolin and thrombin were additive, suggesting that they act through distinct signaling pathways. We found a close correlation between cellular cAMP content and vWf release after stimulation with epinephrine and forskolin. These results demonstrate that cAMP-dependent signaling events are involved in the control of exocytosis from endothelial cells (an effect not mediated by an increase in [Ca2+]i) and provide an explanation for epinephrine-induced vWf release.
authors.affiliation: Department of Medicine, Centre Médical Universitaire, Geneva, Switzerland. vischer@cmu.unige.ch
authors.forename: U M
authors.initials: UM
authors.lastname: Vischer
authors.forename: C B
authors.initials: CB
authors.lastname: Wollheim
mesh_terms: D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism*; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D004837:Epinephrine / Q000494:pharmacology*; D005089:Exocytosis / Q000187:drug effects*; D006801:Humans; D015398:Signal Transduction / Q000187:drug effects*; D014662:Vasoconstrictor Agents / Q000494:pharmacology*; D014841:von Willebrand Factor / Q000378:metabolism*
chemical_list: D014662:Vasoconstrictor Agents; D014841:von Willebrand Factor; D000242:Cyclic AMP; D004837:Epinephrine