Substrate for endothelial prostacyclin production in the presence of platelets exposed to collagen is derived from the platelets rather than the endothelium

Abstract

Interactions between vascular endothelial cells and blood platelets have been investigated using a model microcirculation consisting of microcarrier beads colonized with human umbilical vein endothelial cells (HUVECs) and perfused with washed platelet suspensions. To simulate the effects of endothelial desquamation and exposure of subendothelium, fibrillar collagen in suspension was coinjected with the platelets. In this model, neither the passage of platelets alone nor collagen alone stimulated prostacyclin (PGI2) production by the HUVECs. Platelets activated by coinjection with collagen released thromboxane A2 (TXA2), and this was associated with the simultaneous production of PGI2 by the HUVECs. By means of double-isotope experiments with [3H]arachidonic acid (AA) incorporated into platelets and [14C]-AA into HUVECs, it was shown that all the PGI2 generated was derived from platelet AA and/or endoperoxides. This interpretation was strengthened by the finding that PGI2 production was not prevented by treatment of HUVECs with indomethacin followed by perfusion with collagen-stimulated platelets. AA metabolites in double-isotope label experiments were further characterized by reverse-phase chromatography, and it was shown that both cyclooxygenase and lipoxygenase products of the HUVECs were derived from platelet membrane lipid. Thrombin regularly produced transient PGI2 release, but showed rapid tachyphylaxis. Platelet-derived compounds including ADP, ATP, and platelet-activating factor (PAF) did not produce PGI2 release by HUVECs in this system. Thus, the transfer of AA and metabolites from collagen- stimulated platelets is likely to be the mechanism for PGI2 production in the context of minor degrees of endothelial desquamation.

Ridogrel: An Antiplatelet Agent with Antihypertensive Properties

“…This is evidence that inhibition of TP receptors is necessary for an antiplatelet effect with a TRASI. Another theoretical advantage of TRASIs over COX inhibitors is the redirection of unmetabolized, platelet-derived PGH 2 to the endothelium where it can be converted to prostacyclin (8,28). Doses of aspirin as low as 100 mg daily reduce endothelial prostacyclin synthesis (4), whereas TRASIs should increase such synthesis.…”

Fibroblast growth factor and heparin protect endothelial cells from the effects of interleukin 1

“…Cell cultures were carried out essentially as described pireviously (Minter et al, 1992;Chesterman et al, 1986). Endothelial cells were isolated from human umbilical cords (cells pooled from at least three donor cords) obtained less than 3 h from delivery.…”

Effects of amiloride analogues on the production of prostacyclin by aortic endothelial cells

“…In vitro, the endothelial production of PGI2 is indeed stimulated by factors released from activated platelets e.g. prostaglandin endoperoxides (Marcus et al, 1980;Schafer et al, 1984;Chesterman et al, 1986) and adenine nucleotides, which act via P2Y-purinoceptors (Boeynaems & Galand, 1983;Pearson et al, 1983;Van Coevorden & Boeynaems, 1984;Needham et al, 1987). The biochemical events that mediate the action of adenine nucleotides on aortic endothelial cells have been recently characterized as involving generation of inositol trisphosphate, increase of cytosolic calcium and activation of calcium-dependent protein kinases (Pirotton et al, 1987;Hallam & Pearson, 1986;Demolle et al, 1988).…”