Summary
Previous studies have shown the regulatory effect of nitric oxide (NO) on endotoxin-induced
tissue factor (TF) in endothelial cells. Asymmetric dimethylarginine (ADMA), a major
endogenous NO synthase (NOS) inhibitor, could inhibit NO production in vivo and in vitro. ADMA and its major hydrolase dimethylarginine dimethylaminohydrolase (DDAH) have
recently been thought of as a novel regulatory system of endogenous NO production.
The aim of the present study was to determine whether the DDAH/ADMA pathway is involved
in the effect of lipopolysaccharide (LPS) on TF expression in endothelial cells. Human
umbilical vein endothelial cells (HUVECs) were treated with LPS (1 µ g/ml) to induce
TF expression. Exogenous ADMA significantly enhanced the increase in both TF mRNA
level and activity induced by LPS, whereas L-arginine, the NOS substrate, markedly
attenuated the LPS-induced TF increment. LPS markedly increased the level of ADMA
in cultured medium and decreased DDAH activity in endothelial cells, and overexpression
of DDAH2 could significantly suppress LPS-induced TF increment in endothelial cells.
LPS could increase intracellular reactive oxygen species (ROS) production and activate
nuclear factor-κ B, which were enhanced by exogenous ADMA and attenuated by either
L-arginine or overexpression of DDAH2. Therefore, our present results for the first
time suggest that the DDAH/ADMA pathway can regulate LPS-inducedTF expression via
ROS-nuclear factor- κ B-dependent pathway in endothelial cells.
Keywords
Asymmetric dimethylarginine - dimethylarginine dimethylaminohydrolase - endothelial
cells - lipopolysaccharide - nuclear factor-κ B - tissue factor