Role of oxidants in activation of matrix metalloproteinases

Abdominal aortic aneurysm (AAA) is an inflammatory disease of the artery wall and its incidence is increasing in the western world. Degenerative changes in the elastic media characterize the pathology of AAA. Matrix metalloproteinases (MMPs) are assumed to play an important role during the development of AAA, most likely due to their ability to destroy matrix components. Multiple lines of evidence suggest that oxidants activate MMPs in vitro. It has been shown that oxidative intermediates inactivate inhibitors of MMPs, are cytotoxic to smooth muscle cells and damage structural proteins of the artery wall including collagen and elastin. However, the specific pathways that activate MMPs in vivo still have to be elucidated. The aim of this research proposal is to investigate the role of oxidants produced by inflammatory cells of the artery wall during the activation of MMPs and the pathogenesis of AAA. Furthermore the effect of activated MMPs on structural proteins of the artery wall like elastin will be investigated. We will explore three pathways - the myeloperoxidase pathway, the hydroxyl radical pathway and the reactive nitrogen pathway - each of which promotes oxidative reactions in vitro. Each pathway leaves distinctive markers during protein oxidation. We will quantify levels of each of these markers in normal and human AAA tissue using isotope dilution gas chromatography-mass spectrometry. In parallel studies we will expose matrix proteins to these oxidant systems in vitro. Demonstrating similar patterns of oxidation products in vivo and in vitro may permit us to define specific reaction pathways involved in oxidation of artery wall proteins. Furthermore we intend to elucidate the molecular mechanisms of MMP activation by the myeloperoxidase pathway, the hydroxyl radical pathway and the reactive nitrogen pathway.