Project Summary/Abstract Cardiovascular disease is the most common cause of death in the USA, mainly due to rupture of atherosclerotic plaques causing myocardial infarction (MI) and stroke. Excess activation of the mineralocorticoid receptor (MR) is associated with vascular inflammation, atherosclerotic plaque rupture, and increased risk of MI and stroke. As MR activation is associated with obesity, heart failure, and hypertension, all very common health conditions, the majority of Americans may be at increased risk for MI and stroke due to inappropriate MR activation. Prior research in our lab and others indicates that MR in the vasculature promotes vascular inflammation and atherosclerosis, while its inhibition results in smaller plaques and fewer adverse cardiovascular events in randomized clinical trials. In response to traditional cardiovascular risk factors such as hypertension, obesity, and, we have recently found, hyperlipidemia, the MR specifically within endothelial cells (EC-MR) mediates vascular dysfunction, which is widely known to be an early step in the formation of atherosclerotic plaques. We have also found that EC-MR promotes leukocyte adhesion and trans-endothelial migration, suggesting a mechanism for how the MR promotes vascular inflammation. We therefore hypothesize that hyperlipidemia induces EC-MR to maladaptively activate intracellular pathways that promote endothelial permeability, thereby facilitating leukocyte trans-endothelial migration and vascular inflammation and contributing to development of atherosclerotic plaques with a phenotype that is prone to rupture. To investigate this hypothesis, we have developed a novel mouse model with the MR specifically deleted from endothelial cells, which we inject with a viral vector containing constitutively active PCSK9 to induce hyperlipidemia and atherosclerosis. In aim 1 of this proposal, we will investigate the role of EC-MR in plaque formation and morphology, vascular inflammation, and leukocyte trans-endothelial migration in vivo using this mouse model. In aim 2, we will treat isolated endothelial cells in culture with oxidized phospholipids to model atherogenic conditions and investigate intracellular signaling, cell-cell junction stability, and leukocyte trans- endothelial migration in vitro. Successful completion of our aims will result in substantial advances in our understanding of atherosclerosis and inflammation and could lead to novel therapies specifically targeting EC- MR to reduce atherosclerotic plaque burden and plaque rupture, drastically reducing the morbidity and mortality from cardiovascular disease. This proposal also includes a detailed training plan including coursework, collaborations, presentations at national meetings, and integration of clinical training to prepare the PI for a successful career as a physician-scientist.