Summary
Tissue factor (TF) plays a pivotal role in thrombus formation and atherogenesis in
acute coronary syndrome. Tissue factor pathway inhibitor (TFPI) is a specific physiological
inhibitor of TF/ FVIIa complex that regulates TF-induced coagulation. Adiponectin
(Adp) is an adipocyte-specific adipocytokine with anti-atherogenic and anti-diabetic
properties. Adp inhibits inflammatory cytokine and adhesion molecules expression,
and it can prevent endothelial dysfunction. In this study, we investigated the effects
of Adp on tumor necrosis factor-α (TNF-α)-induced expression of TF and TFPI in human
umbilical vein endothelial cells (HU-VECs), and the signaling transduction pathways
involved. It was found that Adp significantly inhibited both TF protein expression
and activity in TNF-α-stimulated HUVECs. In the meanwhile, it increased TFPI protein
expression and activity for about two folds. Adp also inhibited TF mRNA expression
induced by TNF-α, but had no effect on TFPI mRNA expression. The inhibitory effect
of Adp onTNF-α-inducedTF expression was prevented by pretreatment with Rp-cAMPs, a
PKA inhibitor. Adp increased intracellular cAMP content and PKA activity levels in
a dose-dependent manner. Phosphorylation of IκB-α was decreased by Adp, but phosphorylation
of p44/42MAPK, SAPK/ JNK, and p38MAPK were not affected. These results suggested that
Adp inhibits TF expression through inhibition of a PKA dependent nuclear factor- κB
(NF-κB) signaling pathway. It was also found that adiponectin promoted Akt and AMP-activated
protein kinase phosphorylation. The inhibitory effect of Adp on TNF-α-induced TF synthesis
was abrogated in part by pretreatment with the PI3kinase inhibitor LY 294002, suggesting
that Akt activation might inhibit TF expression induced by TNF-α. The inhibitory effect
of Adp is almost completely abrogated by inhibition of both the cAMP/PKA pathway and
PI3K/Akt pathway. In conclusion, our data indicated that inhibition of NF-κB through
stabilization of IκB-α and activation of Akt phosphorylation may mediate the inhibitory
effect of Adp on TF expression; but the enhancement effect of Adp on the TFPI production
might occur via translational rather than transcriptional regulation.
Keywords
Adiponectin - endothelial cells - tissue factor - tissue factor pathway inhibitor
- Akt - PKA