Aging-related changes in oxidative stress response of human endothelial cells.

Oxidative stress is strongly associated with aging and age-related diseases and plays a crucial role in endothelial dysfunction development. To better understand the molecular mechanisms of aging and stress response in humans, we examined changes to young and older human endothelial cells over time (72, 96 and 120 h), before and after H2O2-induced stress. We measured the expression of the deacetylase Sirtuin 1 (Sirt1) and its transcriptional target Forkhead box O3a (Foxo3a); TBARS, a well-known marker of overall oxidative stress, and catalase activity as index of antioxidation. Moreover, we quantified levels of cellular senescence by senescence-associated β galactosidase (SA-βgal) assay. Under oxidative stress induction older cells showed a progressive decrease of Sirt1 and Foxo3a expression, persistently high TBARS levels with high, but ineffective Cat activity to counteract such levels. In addition cellular senescence drastically increased in older cells compared with Young cells both in presence and in the absence of oxidative stress. By following the cell behavior during the time course, we can hypothesize that while in young cells an oxidative stress induction stimulated an adequate response through activation of molecular factor crucial to counteract oxidative stress, the older cells are not able to adequately adapt themselves to external stress stimuli. During their life, endothelial cells impair the ability to defend themselves from oxidative stress stimuli. This dysfunction involves the pathway of Sirt1 a critical regulator of oxidative stress response and cellular lifespan, underlining its crucial role in endothelial homeostasis control during aging and age-associated diseases.