Nitric oxide and peroxynitrite are reactive, short-lived species that are important mediators of atherosclerosis. One of the downstream pathways of peroxynitrite-mediated vascular injury is related to activation of the nuclear enzyme poly (ADP-ribose) synthetase (PARS). Based on vitro and in vivo preliminary data, the applicants propose that the PARS pathway may play a role in the pathogenesis of the endothelial dysfunction associated with atherosclerosis, and propose studies to directly test this hypothesis. The first aim of the current project is to establish time course of PARS activation and associated vascular dysfunction in atherosclerosis, and to correlate these alterations with reactive nitrogen species formation in the vasculature. Blood vessels will be obtained form mice at various time points after initiation of atherosclerotic changes, induced by two distinct experimental models (collar and Apo/E models). Reactive nitrogen species formation and PARS activation will be investigated using immunohistochemistry, vascular reactivity will be investigated using ex vivo using isometric tension measurements in vascular chambers. The second aim of the project is to perform direct studies into the role of PARS-related endothelial dysfunction, as it relates to the atherosclerosis-associated development of endothelial dysfunction. We will utilize chronic oral treatment with PARS inhibitors of two different classes, followed by evaluation of changes in vascular reactivity and the progress of atherosclerosis. Our studies will provide novel mechanistic information on atherosclerosis-related endothelial dysfunction which will be utilized for the future design and commercial development of novel vasculoprotective agents. PROPOSED COMMERCIAL APPLICATIONS: The annual anticipated revenues for an effective agent for the therapy of atherosclerosis is over 50 billion in the US alone.