Adenosine 3’:5’-Cyclic Monophosphate Induces Regulated Secretion of Tissue-Type Plasminogen Activator and von Willebrand Factor from Cultured Human Endothelial Cells

Abstract

SummaryThe effect of compounds increasing intracellular adenosine 3’:5’-cyclic monophosphate [cAMP]i levels (prostacyclin, isoproterenol, forskolin, cholera toxin), and of the cAMP analogs 8-bromo-cAMP and dibutyryl-cAMP, on the regulated secretion (acute release) of tissue-type plasminogen activator (tPA) and von Willebrand factor (vWF) was studied in cultured human umbilical vein endothelial cells (HUVEC).Prostacyclin, isoproterenol and forskolin, which increased [cAMP]i in HUVEC, and the cell-permeant cAMP analog 8-bromo-cAMP induced dose- and time-dependent secretion of tPA and vWF. The extent of vWF and tPA release correlated with [cAMP]i, and was increased by the phosphodiesterase inhibitor isobutylmethylxanthine.In contrast to thrombin, the cAMP-elevating agents did not increase the intracellular calcium concentration [Ca2+]i in HUVEC. At sub-maximal concentrations, the effects of thrombin and prostacyclin were additive.Our results show that an increase in [cAMP]i resulted in regulated secretion (acute release) of tPA and vWF from HUVEC, without the concomitant increase in [Ca2+]i which is, in HUVEC, essential for thrombin-induced regulated secretion to occur. cAMP-induced secretion represents a novel mechanism for causing regulated secretion of tPA and vWF from endothelial cells.

Tissue-Type Plasminogen Activator Release in Healthy Subjects and Hypertensive Patients

“…37 Muldowney et al 37 reported that the endothelial-derived hyperpolarizing factor 5,6-epoxyeicosatrienoic acid induces the exocytosis of t-PA from storage granules via calcium-and cAMP-dependent pathways, in line with previous experimental findings. 38,39 According to our findings, 5,6-epoxyeicosatrienoic acid-mediated t-PA release was not affected by the ouabain-dependent part of the endothelial-derived hyperpolarizing factor pathway. 37 The major limitation of the present in vivo clinical study concerns the assessment of dynamic endothelial t-PA release in the forearm.…”

cAMP-induced secretion of endothelial von Willebrand factor is regulated by a phosphorylation/dephosphorylation switch in annexin A2

“…4,5 For instance, histamine and thrombin have been shown to mediate secretion of WPBs by increasing the levels of cytosolic free Ca 21 , 6,7 whereas release of WPBs induced by secretagogues such as epinephrine or forskolin involves cAMP-dependent signaling. 8,9 Significant differences exist between Ca 21 -and cAMP-evoked WPB exocytosis and, whereas several cellular factors participating in the Ca 21 -regulated secretion of WPBs have been identified, much less is known about the molecular mechanisms underlying the cAMP-dependent exocytosis of WPBs.…”

Differential regulation of endothelial exocytosis of P-selectin and von Willebrand factor by protease-activated receptors and cAMP

“…24 In addition, agents that elevate intracellular cAMP such as vasopressin receptor agonists, purine nucleotides, epinephrine, and forskolin can also trigger the release of VWF. [25][26][27] The time course of cAMPstimulated VWF release is delayed compared with agonists that increase intracellular Ca 2ϩ . By inference, stimulation of VWF release should also occur in tandem with translocation of P-selectin to the cell surface, because both factors are located in the same secretory granule.…”