Endothelial cells (EC) line vessels in every organ system and regulate the flow of nutrient substances, diverse biologically active molecules, and blood cells themselves. The regulation of EC survival and death is critical to vascular development and homeostasis. Perturbations of this balance contribute to various vascular diseases. EC apoptosis is induced by diverse extrinsic and intrinsic signals, such as serum starvation, radiation, oxidative stress from hypoxia, lipopolysaccaride, and cytokines. Endothelial cells are one of major physiological targets of proinflammatory and potentially proapoptotic mediators, such as TNF, IL-1 and LPS. The overall goal of the project is to elucidate the regulation of EC apoptosis and its signaling pathway focusing on PI3 kinase and NF-kB. We have identified RhoA/RhoA kinase pathway as a survival signaling in EC. The results will be published in the Journal of Biological Chemistry soon. In addition, we have also established human microvascluar endothelial cell lines (HMEC) overexpressing a deletion mutant of p85 or Akt, both of them function as the dominant-negative mutants. By using these cell lines, we found that NF-kB activation induced by IL-1 and LPS, but not TNF, is mediated by PI3-kinase/Akt pathway.