Background: Thromboxane (TX) A2, prostaglandin endoperoxides and F2-isoprostanes exert their effects through a TX-prostanoid (TP) receptor, also expressed in endothelial cells. We investigated a role of the TP receptor in the endothelial expression of tissue factor (TF), a key trigger to thrombosis.
Methods and results: Human umbilical vein endothelial cells (HUVEC) exposed to the TP receptor agonist U46619 featured a concentration-dependent increase in TF surface exposure and procoagulant activity. HUVEC pre-incubation with the TP receptor antagonist S18886, followed by stimulation with either U46619 or tumor necrosis factor-α (TNF-α), attenuated TF surface exposure and activity compared with stimulated control. Aspirin or indomethacin, while inhibiting cyclooxygenase (COX)-1 and -2 activities, did not mimic this effect. Probing of underlying mechanisms by selective pharmacological and gene silencing experiments showed that S18886 reduced U46619- or TNF-α-induced TF expression inhibiting ROS production, NAD(P)H oxidase and PKC activation. In addition, S18886 also inhibited ERK activation in the presence of both U46619 and TNF-α alone, while inhibition of JNK activation only occurred in the presence of U46619.
Conclusion: The endothelial TP receptor contributes to TF surface exposure and activity induced not only by known TP receptor agonists, but also by TNF-α. Such findings expand the therapeutic potential of TP receptor inhibition.
Keywords: Endothelial cells; Mitogen activated protein kinases; TP receptors; Thromboxane A(2); Tissue factor.
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