Monocytic-endothelial cell interaction: regulation of prostanoid synthesis in human coculture

Coculture of a monocytic cell line (HL-60) and iliacal endothelial cells as an in vitro model of vascular inflammation was investigated for cooperative regulatory mechanisms of prostanoid synthesis under conditions of selective prestimulation. In coculture of endothelial cells and 12-O-tetradecanoylphorbol 13-acetate (TPA)-prestimulated monocytic HL-60 cells the capacity of prostanoid synthesis from arachidonic acid was strongly increased compared with monocultures. Concomitant with up-regulation of specific adhesion molecules, cyclooxygenase (COX) 2 mRNA was induced in endothelial cells in coculture independent of cell contact. HL-60 cells exhibited no alterations in mRNA expression of cyclooxygenases or thromboxane synthase. Coculture of TPA-prestimulated endothelial cells with unstimulated HL-60 cells led to a selectively increased capacity of thromboxane production. Under this condition HL-60 cells up-regulated COX1 and COX2 mRNA, whereas endothelial mRNA levels did not change. Our data demonstrate that the increase in prostanoid synthesis in coculture essentially depends on rapid induction of COX2 mRNA within 2 h.