AMPKα1 regulates the antioxidant status of vascular endothelial cells

AMPK (AMP-activated protein kinase) is a key regulator of cellular energy because of its capacity to detect changes in the concentration of AMP. Recent evidence, however, indicates the existence of alternative mechanisms of activation of this protein. Mitochondrial ROS (reactive oxygen species), generated as a result of the interaction between nitric oxide and mitochondrial cytochrome c oxidase, activate AMPK alpha 1 in HUVECs (human umbilical-vein endothelial cells) at a low oxygen concentration (i.e. 3%). This activation is independent of changes in AMP. In the present Study we show, using HUVECs in which AMPK alpha 1 has been silenced, that this protein is responsible for the expression of genes involved in antioxidant defence, such as manganese superoxide dismutase, catalase, gamma-glutamylcysteine synthase and thioredoxin. Furthermore, peroxisome proliferator-activated-coactivator-1, cAMP-response-element-binding protein and Foxo3a (forkhead transcription factor 3a) are involved in this signalling pathway. In addition, we show that silencing AMPK alpha 1 in cells results in a reduced mitochondrial and eNOS (endothelial NO synthase) content, reduced cell proliferation, increased accumulation of ROS and apoptosis. Thus AMPK alpha 1 in HUVECs regulates both their mitochondrial content and their antioxidant defences. Pharmacological activation of AMPK alpha 1 in the vascular endothelium may be beneficial in conditions such as metabolic syndrome, Type 2 diabetes and atherosclerosis, not only because of its bioenergetic effects but also because of its ability to counteract oxidative stress.