Homocysteine induces oxidative stress by uncoupling of NO synthase activity through reduction of tetrahydrobiopterin
G Topal, A Brunet, E Millanvoye, JL Boucher… - Free Radical Biology …, 2004 - Elsevier
G Topal, A Brunet, E Millanvoye, JL Boucher, F Rendu, MA Devynck, M David-Dufilho
Free Radical Biology and Medicine, 2004•ElsevierHyperhomocysteinemia is a risk factor for cardiovascular diseases that induces endothelial
dysfunction. Here, we examine the participation of endothelial NO synthase (eNOS) in the
homocysteine-induced alterations of NO/O2− balance in endothelial cells from human
umbilical cord vein. When cells were treated for 24 h, homocysteine dose-dependently
inhibited thrombin-activated NO release without altering eNOS phosphorylation and
independently of the endogenous NOS inhibitor, asymmetric dimethylarginine. The …
dysfunction. Here, we examine the participation of endothelial NO synthase (eNOS) in the
homocysteine-induced alterations of NO/O2− balance in endothelial cells from human
umbilical cord vein. When cells were treated for 24 h, homocysteine dose-dependently
inhibited thrombin-activated NO release without altering eNOS phosphorylation and
independently of the endogenous NOS inhibitor, asymmetric dimethylarginine. The …
Hyperhomocysteinemia is a risk factor for cardiovascular diseases that induces endothelial dysfunction. Here, we examine the participation of endothelial NO synthase (eNOS) in the homocysteine-induced alterations of NO/O2− balance in endothelial cells from human umbilical cord vein. When cells were treated for 24 h, homocysteine dose-dependently inhibited thrombin-activated NO release without altering eNOS phosphorylation and independently of the endogenous NOS inhibitor, asymmetric dimethylarginine. The inhibitory effect of homocysteine on NO release was associated with increased production of reactive nitrogen and oxygen species (RNS/ROS) independent of extracellular superoxide anion (O2−) and was suppressed by the NOS inhibitor l-NAME. In unstimulated cells, l-NAME markedly decreased RNS/ROS formation and the ethidium red fluorescence induced by homocysteine. This eNOS-dependent O2− synthesis was associated with reduced intracellular levels of both total biopterins (−45%) and tetrahydrobiopterin (−80%) and increased release of 7,8-dihydrobiopterin and biopterin in the extracellular medium (+40%). In addition, homocysteine suppressed the activating effect of sepiapterin on NO release, but not that of ascorbate. The results show that the oxidative stress and inhibition of NO release induced by homocysteine depend on eNOS uncoupling due to reduction of intracellular tetrahydrobiopterin availability.
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