oxidised 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphocholine (OxPAPC) is a prototypic biologically active oxidised phospholipid first isolated from LDL minimally modified by oxidation (MM-LDL). OxPAPC is an active principle of MM-LDL that mimics several pro- and anti-inflammatory effects induced by oxidised lipoproteins. Oxidation of PAPC generates a mixture of oxidised phospholipids containing either fragmented or full-length oxygenated sn-2 residues. The best-characterised oxidatively fragmented species contain a five-carbon sn-2 residue bearing omega-aldehyde or omega-carboxyl groups. Oxydation of arachidonic acid residue also produces phospholipids containing esterified isoprostanes. Both fragmented and full-length oxygenated species can regulate immune reactions. Pro-inflammatory effects of OxPAPC include stimulation of endothelial cells to bind monocytes and induction of tissue clotting factor, IL-8, MCP-1, G-CSF and other mediators of atherothrombosis. Anti-inflammatory effects of OxPAPC are mediated by induction of protective enzymes such as heme oxygenase-1 as well as suppression of innate immune responses to bacterial lipopolysaccharide (LPS) due to inhibition of LPS recognition by LPS-binding protein (LBP) and CD14. OxPAPC is active in vivo and was shown to protect mice in several models of acute inflammation induced by bacterial products. In addition, oxidised phospholipids present in OxPAPC are recognised by scavenger receptor CD36 and auto-antibodies present in patients with anti-phospholipid syndrome. Biological activities of OxPAPC are mediated by a variety of signal transduction mechanisms, including elevation of cAMP and Ca2+ levels, activation of MAP kinases, PI-3-kinase and small GTPases Rac-1 and Cdc42. OxPAPC-induced gene expression is mediated by transcription factors such as Egr-1, NFAT, CREB, NRF2, ATF4 but does not involve NFkB-dependent transcription. For biological tests we recommend to use 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphatidylcholine (PAPC, cat.# HC4043) as negative unoxidised controls.
