The goal of Project 1 is to understand oxidized lipoprotein (oxLDL) induced injury to cells relevant to arterial disease. This proposal is focused on apoptotic mechanisms of cell death, which are induced by specific oxLDL constituents. Studies of arterial lesions in humans and animals have revealed high amounts of apoptotic markers associated with macrophages and smooth muscle cells (SMC). We propose to study 7-ketocholesterol (7kchol) based on its prevalence in oxLDL and arterial lesions, and its ability to induce apoptosis in cultured cells. We recently showed that deficiencies in expression or activation of the transcription factor, Statl, impaired optimal apoptosis in response to 7-kchol. In Aim 1, we propose to define the role played by Statl in vascular cell apoptosis. We will elucidate the role of Statl in the intracellular signaling sequence of 7-kchol-induced apoptosis in monocyte/macrophages. We will follow the influence of Statl on apoptotic events, including mitochondria-dependent processes and other molecular events upsteam of caspase activation. We also will determine if Statl influences apoptosis in vivo, and whether changes in Statl alter lesion development. Our studies in Aim 2 focus on the selenoenzyme phospholipid hydroperoxide glutathione peroxidase (PHGPx). PHGPx reduces complex lipid hydroperoxides, including toxic lipid hydroperoxides borne by oxLDL. We propose to test the hypotheses that PHGPx (i) inhibits SMC injury from lipid hydroperoxides formed in excess during oxidant stress; (ii) inhibits 7kchol apoptosis by inhibiting cardiolipin hydroperoxide accumulation in mitochondria; (iii) retards apoptosis of SMC in vascular lesions; and (iv) retards atherosclerosis lesion progression. Working with Dr. Driscoll (Project 2), we developed two transgenic mouse models that overexpress PHGPx under the control of either SMC-specific and endothelial-specific promoters. These mice will be bred to the apoE-/- mouse. We will quantify atherosclerosis lesion development as well as apoptotic and oxidative markers in the lesions. Successful completion of these studies will elucidate the role of 7-kchol in cell death, and potentially, the role of specific mechanisms of cell death in atherosclerotic lesion development.