Many vascular disease states such as diabetes and hypertension are strongly associated with increased levels of reactive oxygen species (ROS) in the vascular wall, a cellular state known as oxidative stress that is often associated with a decrease in vascular .NO bioavailability. All cellular compartments posses several antioxidant enzymes responsible of controlling intracellular ROS levels. In the last decade, it has become clear that ROS, and particularly hydrogen peroxide (H2O2), may play physiological and not only pathological roles and they have been identified as key physiological-signaling mediators controlling a broad array of cellular responses. However, the precise molecular mechanisms through which H2O2 alter specific enzymatic activities in vivo remain less well understood. Protein thiols can undergo reversible modifications in the presence of H2O2 representing attractive targets for redox-signaling pathways. Previous studies of my lab demonstrated that AMP-activated protein kinase (AMPK), a kinase critically involved in regulation of cellular metabolism, is activated by H2O2 through activation of a Ca2+/calmodulin kinase kinase - ? (CaMKK?) but the mechanism of CaMKK? activation in response to H2O2,remains to be elucidated. We are now looking at the chemical basis of the redox control in vascular biology, in particular, in redox-activated AMPK pathway. We expect to identify the mechanism of redox-AMPK activation and contribute to our understanding of the principles of redox signaling in the cardiovascular system.