| Oxidized 1-palmitoyl-2-arachidonyl-sn-glycero-3-phosphorylcholine (Ox-PAPC) and its component phospholipids, which accumulate in atherosclerotic lesions, activate endothelial cells (EC) to bind monocytes and to induce a complex inflammatory response. Previously, we reported induction of genes regulating chemotaxis and sterol metabolism by Ox-PAPC in human EC. Activation of sterol regulatory element binding protein (SREBP), which regulates sterol metabolism, regulated the sustained induction of interleukin-8 (IL-8) transcription by Ox-PAPC. In this dissertation, we have examined the mechanism regulating the rapid induction of IL-8 transcription and the activation of SREBP by Ox-PAPC, as well as the effect of high-density lipoprotein (HDL) on Ox-PAPC signaling in EC.; In chapters 2 and 3, the rapid induction of IL-8 transcription by Ox-PAPC was shown to be mediated through activation of the c-Src kinase/Janus activated kinase (JAK)2/signal transducer and activator of transcription (STAT)3 pathway. These studies also identified a STAT3 binding site, gamma-interferon activation sequence (GAS), in the IL-8 promoter, which regulated IL-8 promoter activation by Ox-PAPC. Furthermore, endothelial STAT3 activation regulated atherogenesis in vivo, as demonstrated by immunohistochemical staining for activated STAT3 in human atherosclerotic lesions, and EC-specific STAT3 knockout mice, which had reduced atherogenesis on the atherogenic diet.; In chapter 4, treatment of EC with Ox-PAPC was shown to activate endothelial nitric oxide synthase (eNOS). Ox-PAPC treatment also uncoupled eNOS to generate reactive oxygen species (ROS), and ROS, rather than nitric oxide (NO ·) itself, regulated the activation of SREBP by Ox-PAPC.; In chapter 5, HDL was shown to have a protective role in regulating Ox-PAPC signaling in human EC. HDL inhibited the induction of inflammatory genes by OxPAPC, but preserved the induction of anti-inflammatory genes, such as heme oxygenase-1. HDL selectively inhibited Ox-PAPC-induced activation of c-Src, STAT3, and SREBP, which regulate the inflammatory effects of Ox-PAPC, and HDL reversed the uncoupling of eNOS by Ox-PAPC, thereby increasing the bioavailability of NO·, an anti-inflammatory molecule.; Taken together, these studies provide additional insight into how oxidized phospholipids activate EC and how HDL can selectively modulate the inflammatory effects of oxidized phospholipids. |
