2-chlorohexadecanal and Arteriosclerosis

A role for myeloperoxidase (MPO) in atherosclerosis has received considerable attention recently. To identify potential chlorinated lipid products in human low density lipoprotein (LDL), studies were designed to demonstrate that MPO-derived reactive chlorinating species (RCS) target the plasmalogen pool of LDL isolated from peripheral human blood in vitro. The vinyl ether bond of LDL plasmalogens was targeted by MPO-derived RCS, resulting in the release of the 16- and 18-carbon-containing alpha-chloro fatty aldehydes, 2-chlorohexadecanal and 2-chlorooctadecanal, respectively, from the plasmalogen glycerol backbone. Targeting of the LDL plasmalogen vinyl ether bond was dependent on the presence of MPO-derived RCS. Electrospray ionization mass spectrometric analysis of MPO-treated LDL demonstrated that a novel population of unsaturated lysophosphatidylcholine molecular species was produced by a phospholipase A2-independent mechanism. Unsaturated lysophosphatidylcholine molecular species elicited cyclic AMP response element binding protein phosphorylation in RAW 264.7 cells. Additionally, MPO-mediated targeting of both monocyte and LDL plasmalogen pools was demonstrated in phorbol myristate acetate-stimulated human monocytes, resulting in the production of both 2-chlorohexadecanal and 2-chlorooctadecanal. In contrast, alpha-chloro fatty aldehydes were not produced in phorbol myristate acetate-stimulated mouse monocytes. Collectively, the present studies demonstrate a novel MPO-specific mechanism that mediates the production of a novel group of unsaturated lysophosphatidylcholine molecular species and chlorinated aldehydes from both LDL and monocyte plasmalogen pools that may have important effects during inflammatory reactions mediated by monocytes, most notably atherosclerosis.

Topics: Aldehydes; Animals; Arteriosclerosis; Blotting, Western; Cell Line; Cells, Cultured; Chlorine; Chromatography, High Pressure Liquid; Cyclic AMP; Cyclic AMP Response Element-Binding Protein; Dose-Response Relationship, Drug; Glycerol; Humans; Hydrogen-Ion Concentration; Lipid Metabolism; Lipoproteins, LDL; Lysophosphatidylcholines; Mice; Mice, Inbred C57BL; Monocytes; Peroxidase; Phospholipases A; Phospholipases A2; Phosphorylation; Plasmalogens; Spectrometry, Mass, Electrospray Ionization; Time Factors

A role for myeloperoxidase (MPO) as a mediator of coronary artery disease and acute coronary syndromes has recently received considerable attention. Although active MPO and hypochlorite-modified proteins and peptides have been detected in human atherosclerotic lesions, detection of novel chlorinated oxidized lipid species with proatherogenic properties in vivo has not yet been reported. In this study we show that MPO-generated reactive chlorinating species promote selective oxidative cleavage of plasmalogens, liberating alpha-chloro fatty aldehydes and unsaturated lysophosphatidylcholine in human atherosclerotic lesions.. Stable isotope dilution gas chromatography-mass spectrometry methods were used to identify and quantitate the alpha-chloro fatty aldehyde, 2-chlorohexadecanal, in atherosclerotic versus normal human aorta. Compared with normal aorta, 2-chlorohexadecanal levels were elevated more than 1400-fold in atherosclerotic tissues. Parallel electrospray ionization mass spectrometry studies confirmed 34- and 20-fold increases in the plasmalogen cooxidation products, unsaturated lysophosphatidylcholine molecular species containing linoleic and arachidonic acid, respectively, within atherosclerotic compared with normal aorta. Unsaturated lysophosphatidylcholine containing docosahexaenoic acid was also detected in atherosclerotic but not in normal aorta. Exposure of primary human coronary artery endothelial cells to plasmalogen-derived lysophosphatidylcholine molecular species produced marked increases in P-selectin surface expression.. The present studies demonstrate that plasmalogens are attacked by MPO-derived reactive chlorinating species within human atheroma. The resultant species formed, alpha-chloro fatty aldehydes and unsaturated lysophospholipids, possess proatherogenic properties, as shown by induction of P-selectin surface expression in primary human coronary artery endothelial cells.

Topics: Aldehydes; Animals; Aorta; Arteriosclerosis; Cells, Cultured; Endothelium, Vascular; Fatty Acids; Fatty Acids, Unsaturated; Humans; Hydrocarbons, Chlorinated; Lysophosphatidylcholines; Mice; P-Selectin; Plasmalogens