Project Summary Cardiovascular disease continues to be the major cause of morbidity and mortality in the United States, and is an emerging epidemic world-wide. In particular atherosclerosis is a life-threatening disease strongly associated with risk factors such as hypercholesterolemia, hypertension and diabetes. Importantly, in the face of these potent systemic drivers of cardiovascular risk, certain regions of the arterial vasculature nonetheless remain relatively resistant to the development of atherosclerotic lesions. Several lines of evidence suggest that hemodynamically distinct environments in these arterial geometries exert a protective influence on the vascular endothelium, thus inhibiting early lesion development. However, despite recent progress in our understanding of the transcriptional activators responsible for this “vasoprotection”, this progress has not yet been translated into therapeutic strategies for cardiovascular disease due to the lack of mechanistic understanding of the proximal signaling pathways activated by vasoprotective flow. In this project, previously unrecognized actions of doxorubicin in vascular endothelial cells, recently uncovered in our laboratory, will provide the basis for establishing a novel conceptual and experimental framework seeking to identify novel mechano-activated signaling pathways in the vascular endothelium. To this end, we will perform a loss-of-function screen in human endothelial cells to gain insights into the mechanism of action of doxorubicin-mediated loss of flow-dependent endothelial vasoprotection. Ultimately, the identification of the molecular target(s) of doxorubicin in endothelial cells should contribute to our understanding of how these cells sense, integrate and respond to vasoprotective flow, and could help in the development on new therapeutic interventions against endothelial cell dysfunction.