We investigated here the effect Of L-arginine on asymmetric dimethylarginine (ADMA) or homocysteine-accelerated endothelial aging. Endothelial cells were cultured in medium containing 70 mu mol/L arginine until fourteenth passage. ADMA, DL-homocysteine, and L-arginine were replaced every 48 h starting at the fourth passage. ADMA or homocysteine inhibited significantly the population doublings (PD) and accelerated the process of aging. Co-incubation With L-arginine enhanced PD, inhibited senescence associated beta-galactosidase activity, and increased telomerase activity. This effect was associated with an increase in NO synthesis and NO synthase protein expression. Furthermore, L-arginine-induced NO formation was accompanied by a reduction in oxidative stress and an increase in protein expression and enzyme activity of heme oxygenase (HO)-1. The NO synthase inhibitor L-NAME completely abolished the effect of L-arginine on ADMA or homocysteine-accelerated aging. These findings demonstrate that L-arginine prevents the onset of endothelial aging in ADMA or homocysteine-treated cells by increasing NO formation and consequently the induction of HO-1. This might provide a new strategy to delay ADMA or homocysteine-accelerated aging. (c) 2006 Elsevier Inc. All rights reserved.