The aim of this study was to evaluate the inhibitory activity of
adenosine on
tumor necrosis factor-alpha (TNF),
thrombin-, or
phorbol 12-myristate 13-acetate (PMA)-induced
tissue factor (TF) expression on human umbilical vein endothelial cells (HUVECs). This inhibitory effect of
adenosine was found to be counteracted by the non-selective
adenosine receptor (AR) antagonist, 8-(p-sulfophenyl)
theophylline. To clarify the role of ARs (A1, A2a, A2b, and A3) in this regulation, we evaluated the effect of several agonists and antagonists specific for AR-subclass on TF expression. The selective A2aAR agonist, 2-p-(2-carboxyethyl) phenethylamino-5'-N-ethylcarboxamido
adenosine hydrochloride (
CGS 21680), the A3AR agonist, N6-2-(4-aminophenyl) ethyladenosine (
APNEA), and the A1AR antagonist, 1,3-dipropyl-8-(2-amino-4-chlorophenyl)
xanthine (
PACPX) each inhibited TF activity expression induced by TNF,
thrombin, or PMA on HUVECs. In contrast, the selective A1AR agonist, chloro-N6-cyclopentyladenosine (CCPA) and the A2AR antagonist,
3,7-dimethyl-1-propargylxanthine (
DMPX) enhanced each stimulant-induced TF activity expression. All agonist or antagonist alone did not alter the basal TF expression on HUVECs. Our results suggest that stimulation of A2aAR and A3AR down-regulates and that of A1AR up-regulates the endothelial cell TF expression induced by TNF, PMA, or
thrombin. Thus, it appears that
adenosine itself may exert
anticoagulant activity on vascular endothelial cells via its A2a and A3 receptors, particularly during ischemic or atherosclerotic processes which are known to be associated with local increased levels of
adenosine.