Lipid ester-bound aldehydes among copper-catalyzed peroxidation products of human plasma lipoproteins.

We have isolated the core aldehydes (aldehydes still bound to parent molecules) of phosphatidylcholine (PC) and cholesteryl esters (CE) from copper-catalyzed peroxida- tion of human plasma low (LDL) and high (HDL) density lipoproteins. The aldehydes were isolated by extraction with acidified chlorofom-methanol containing 2,4-dinitrophenyl- hydrazine. The 2,4-dinitrophenylhydrne (DNPH) deriva- tives formed were resolved by reversed phase high perform- ance liquid chromatography (HPLC) and identified by on-line quadrupole mass spectrometry (LC/MS). The major PC core aldehydes from oxidized LDL and HDL were identified as 1-palmitoyl-( 1-stearoyl) 2-(9-oxononanoyl)-, 1-palmitoyl-( 1- stearoyl) 2-(8-oxooctanoyl)-, and 1-palmitoyl-( 1-stearoyl) 2-(5- oxovaleroy1)-snglycerols after phospholipase C digestion of the DNPH derivatives of the phospholipids. The major alde- hydes from peroxidation of cholesteryl esters were the 9ax- ononanoyl, 8-0xooctanoy1, and 5axovaleroyl esters of choles- terol and 7-ketocholesterol. The core aldehydes were estimated to account for a minimum of 1-2% of the con- sumed linoleate and arachidonate esters. A relatively smaller yield of the PC core aldehydes from LDL compared to HDL was attributed to the presence of greater amounts of phos- pholipases in LDL than in HDL. More comparable yields of PC core aldehydes were obtained in the presence of phenyl- methylsulfonylfluoride, which inhibits phospholipases. We conclude that peroxidation of LDL and HDL results in formation of detectable amounts of cholesteryl and glycero- phospholipid esters containing aldehyde functions. The yield of PC aldehydes varies with the activity of the platelet activat- ing factor (PAF) acetyl hydrolase.--do, H., A. Kulcsis, L. Mar& and J. J. Myher. Lipid ester-bound aldehydes among copper-catalyzed peroxidation products of human plasma lipoproteins. J. Lipid Res. 1995.36 1876-1886.