Intracellular signaling induced by oxidized phospholipids

The early stages of atherosclerosis are characterized by an increase in monocyte entry into the vessel wall without an increase on neutrophil entry. We have previously identified three phospolipid oxidation products of 1-palmitoyl- 2arachidonyl-sn-glycero-3-phosporylcholine, present in minimally oxidized low density lipoprotein (MM-LDL) and elevated in atherosclerotic lesions. Treatment of endothelial cells (EC) with these bioactive lipids, namely POVPC (1-palmitoyl-2(5)oxovaleroyl-sn-glycero-3-phosporylchlonine), PGPC (1-pamlitoyl-2-glutaroyl-sn- glycero-3-phosphorylchlonine) and PEIPC (1-palmitoyl-2-epoxyisoprostance-sn-glycero-3-phosphorylchlonine) activates endothelial cells to bind monocytes and to produce monocyte chemotactic factors. In addition, one of these phospholipids (POVPC) inhibits the induction of neutrophil binding by lipopolysaccharide and tumor necrosis factor by inhibiting E-selection expression. The induction of monocyte binding, which is due to expression of CS-1 fibronetic on the EC surface, and the inhibition of neutrophil binding were shown to be mediated by cAMP coupled pathway, downregulating NF-kappaB-mediated transcription. IN addition, we have shown that the lipoxygenase pathway plays an important role in the induction of monocyte binding. The induction of monocyte chemotactic factor production appears to be mediated by a separate second messenger pathway involving PPAR activation. The proposed studies will focus on the intracellular signaling pathways induced by these lipids and will examine the mechanism by which E-selectin expression is inhibited. The aim of these studies is to investigate the mechanism by which neutrophils are excluded from vascular wall by the action of oxidized phospolipids. This is an important aspect also in other chronic inflammatory diseases where monocytes are predominant. Furthermore, we want to demonstrate that membrane vesicles shed by activated endothelial cells are an additional source of biologically active oxidized phospholipids, indicating a novel mechanism which may contribute to chronic infalmmation.