Chronic nitric oxide deprivation induces an adaptive antioxidant status in human endothelial cells

In a previous work, we showed an increased cell motility due to the accumulation and transcriptional activation of the Hypoxia Inducible Factor-1 alpha (HIF-1 alpha) and a reduced mitochondrial energy production in an in vitro model of endothelial dysfunction (ED) represented by human endothelial cells (ECs) chronically deprived of nitric oxide (NO) by L-NAME treatment. In the present study, in the attempt to unravel the pathway(s) linking NO deficiency to HIF-1 alpha accumulation and activation, we focused our attention on Reactive Oxygen Species (ROS). We found that ROS were partially involved in HIF-1 alpha stabilization, but not in the pro-migratory phenotype. Regarding mitochondrial dysfunction, it did not require neither ROS generation nor HIF-1 alpha activity, and was not due to autophagy. Very interestingly, while acute treatment with L-NAME induced a transient increase in ROS formation, chronic NO deprivation by long term L-NAME exposure drastically reduced cellular ROS content giving rise to an antioxidant environment characterized by an increase in superoxide dismutase-2 (SOD-2) expression and activity, and by nuclear accumulation of the transcription factor NF-E2-related factor-2 (Nrf2). These results might have important implications for our understanding of the consequences of NO deprivation in endothelium behavior and in the onset of cardiovascular diseases. (C) 2013 Elsevier Inc. All rights reserved.