P-selectin induced monocyte synthesis of tissue factor (TF) is enhanced by 12-hydroxyeicosatetraenoic acid (12-hete)

P-selectin, a member of the selectin family of cell-cell adhesion molecules, is an integral membrane glycoprotein of the α-granules and the Weibel-Palade bodies of unstimulated platelets and endothelial cells, respectively. Upon cell stimulation and degranulation, P-selectin is translocated to the external membrane, where it functions as a receptor for the adhesion of granulocytes, monocytes, and a subset of T-lymphocytes. We have demonstrated (Celi et al., Proc. Natl. Acad. Sci. U.S.A. 91:8767-8771, 1994) that P-selectin induces the de novo synthesis of TF, an essential cofactor for the initiation of blood coagulation, by monocytes. However, P-selectin potency is lower than that of endotoxin (lipopolysaccharide, LPS). Since 12-HETE, a product of the lypooxigenase pathway, has been shown to upregulate TF expression by LPS-stimulated mononuclear leukocytes (MN), we evaluated its effects on TF expression by P-selectin stimulated MN. MN were isolated from the peripheral blood of healthy donors and co-cultured with chinese hamster ovary cells transfected with the P-selectin cDNA (CHO-P). Procoagulant activity was then measured by a one stage clotting assay. 12-HETE increased TF expression by monocytes, in the presence of CHO-P, up to 35 fold. The effect was time- and dose-dependent, with maximum activity at 6 hours and 5 μM. Leukotriene C4 and 5-HETE were inactive in this system. 12-HETE had no effect on TF expression by monocytes cultured with untransfected CHO cells. These results indicate that 12-HETE functions as a potent cofactor for P-selectin induced TF synthesis by monocytes. In the area of vascular injury, activated endothelial cells, as well as platelets, recruit monocytes through P-selectin which in turn induces TF synthesis. 12-HETE, contributed by endothelial cells and platelets themselves, increases TF expression, thus potentially playing a role in thrombogenesis and wound healing.