Cholesteryl ester hydroperoxides are biologically active components of minimally oxidized low density lipoprotein.
Oxidation of low density lipoprotein (LDL) occurs in vivo and significantly contributes to the development of atherosclerosis. An important mechanism of LDL oxidation in vivo is its modification with 12/15-lipoxygenase (LO). We have developed a model of minimally oxidized LDL (mmLDL) in which native LDL is modified by cells expressing 12/15LO. This mmLDL activates macrophages inducing membrane ruffling and cell spreading, activation of ERK1/2 and Akt signaling, and secretion of proinflammatory cytokines. In this study, we found that many of the biological activities of mmLDL were associated with cholesteryl ester (CE) hydroperoxides and were diminished by ebselen, a reducing agent. Liquid chromatography coupled with mass spectroscopy demonstrated the presence of many mono- and polyoxygenated CE species in mmLDL but not in native LDL. Nonpolar lipid extracts of mmLDL activated macrophages, although to a lesser degree than intact mmLDL. The macrophage responses were also induced by LDL directly modified with immobilized 12/15LO, and the nonpolar lipids extracted from 12/15LO-modified LDL contained a similar set of oxidized CE. Cholesteryl arachidonate modified with 12/15LO also activated macrophages and contained a similar collection of oxidized CE molecules. Remarkably, many of these oxidized CE were found in the extracts of atherosclerotic lesions isolated from hyperlipidemic apoE(-/-) mice. These results suggest that CE hydroperoxides constitute a class of biologically active components of mmLDL that may be relevant to proinflammatory activation of macrophages in atherosclerotic lesions.
Harkewicz
Richard
R
Department of Pharmacology, Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093, USA.
Hartvigsen
Karsten
K
Almazan
Felicidad
F
Dennis
Edward A
EA
Witztum
Joseph L
JL
Miller
Yury I
YI
D000818:Animals; D001057:Apolipoproteins E / Q000737:chemistry / Q000378:metabolism; D001092:Arachidonate 12-Lipoxygenase / Q000378:metabolism; D001093:Arachidonate 15-Lipoxygenase / Q000378:metabolism; D001095:Arachidonic Acids / Q000737:chemistry; D050197:Atherosclerosis / Q000473:pathology; D001393:Azoles / Q000737:chemistry; D002788:Cholesterol Esters / Q000737:chemistry / Q000378:metabolism*; D054833:Isoindoles; D008077:Lipoproteins, LDL / Q000378:metabolism*; D008264:Macrophages / Q000378:metabolism; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D008954:Models, Biological; D016566:Organoselenium Compounds / Q000737:chemistry; D010100:Oxygen / Q000737:chemistry; D015398:Signal Transduction
C475064:12-15-lipoxygenase; D001057:Apolipoproteins E; D001095:Arachidonic Acids; D001393:Azoles; D002788:Cholesterol Esters; D054833:Isoindoles; D008077:Lipoproteins, LDL; D016566:Organoselenium Compounds; C099252:oxidized low density lipoprotein; C081459:cholesteryl ester hydroperoxide; C042986:ebselen; C029382:cholesteryl arachidonate; D001092:Arachidonate 12-Lipoxygenase; D001093:Arachidonate 15-Lipoxygenase; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D010100:Oxygen