1-Palmitoyl-2-(5,6-epoxyisoprostanoyl E )-sn-glycero-3-phosphatidylcholine (PEIPC) is emerging as a major regulator of vascular cell function. In endothelial cells it has been demonstrated to increase inflammation, procoagulant responses, to regulate junction permeability and to increase oxidative stress. In macrophages it has been demonstrated to regulate dendritic cell differentiation. The goal of the proposed studies is to synthesize sufficient quantities of the most active diastereomer in order to gain insight into the mechanism of action of PEIPC. In previous studies we synthesized one isomer of PEIPC consistent with the NMR of the natural PEIPC.
In Aim 1 we will now synthesize the diasteromer and identify the most active of the two isomers in regulating endothelial cell responses. We have observed that PEIPC can covalently bind to at least 20 endothelial cell proteins.
In Aim 2 we will identify the PEIPC functionality (likely the enone or the epoxide) that interacts with proteins. We will begin by examining the interaction with functional groups of amino acids, then examine the interaction of the most active functional group of PEIPC with peptides. Using two model proteins that bind PEIPC, VEGFR2 and H-ras, we will determine the amino acid sequence involved in binding of PEIPC or its free fatty acid. Using electrospray ionization-tandem mass spectrometry, unique fragmentation spectra produced by these specific lipid-protein interactions will be identified for use in discovering additional endothelial cell protein targets of PEIPC. Armed with this knowledge of the mechanism of the covalent binding of PEIPC to model proteins, we will synthesize analogues of PEIPC and test their effects on PEIPC action. We have previously determined that activation of VEGFR2 is required for the OxPAPC and PEIPC mediated activation of ERK and SREBP. We have also determined that inactivation of H-Ras is necessary for the activation of beta one integrins that lead to monocyte binding. Effects of antagonists on these responses will be determined. Overall these studies will define the chemistry of the PEIPC interaction with selected proteins that control endothelial cell function and will test the hypothesis that covalent binding of PEIPC activates pathways that control the endothelial cell inflammatory response.
Oxidized phospholipids, which accumulate in atherosclerotic lesions and other chronic inflammatory sites, have been shown to be important regulators of endothelial cell inflammatory and pro-coagulant responses that contribute to atherosclerosis. These studies will gain insight into how a particular oxidized phospholipid, PEIPC, causes this activation and will develop analogues to inhibit activation. These studies thus may provide a new drug target for atherosclerosis and other chronic inflammatory diseases.
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