title: Quantitative determination of phosphatidylcholine hydroperoxides during copper oxidation of LDL and HDL by liquid chromatography/mass spectrometry.
abstract: 1-Palmitoyl-2-linoleoylphosphatidylcholine monohydroperoxide (PC 16:0/18:2-OOH) and 1-stearoyl-2-linoleoylphosphatidylcholine monohydroperoxide (PC 18:0/18:2-OOH) were measured by liquid chromatography/mass spectrometry (LC/MS) using nonendogenous 1-palmitoyl-2-heptadecenoylphosphatidylcholine monohydroperoxide as an internal standard. The calibration curves for synthetic PC 16:0/18:2-OOH and PC 18:0/18:2-OOH, which were obtained by direct injection of the internal standard into the LC/MS system, were linear throughout the calibration range (0.8-12.8 pmol). Within-day and between-day coefficients of variation were less than 10%, and the recoveries were between 86% and 105%. The limit of detection (LOD) and the limit of quantification (LOQ) were determined using synthetic standards. The LOD (signal-to-noise ratio 3:1) was 0.01 pmol, and the LOQ (signal-to-noise ratio 6:1) was 0.08 pmol for both PC 16:0/18:2-OOH and PC 18:0/18:2-OOH. With use of this method, the concentrations of PC 16:0/18:2-OOH and PC 18:0/18:2-OOH in the lipoprotein fractions during copper-mediated oxidation were determined. We prepared oxLDL and oxHDL by incubating native LDL and native HDL from human plasma (n =  10) with CuSO(4) for up to 4 h. The time course of the PC 16:0/18:2-OOH and PC 18:0/18:2-OOH levels during oxidation consisted of three phases. For oxidized LDL, both compounds exhibited a slow lag phase and a subsequent rapidly increasing propagation phase, followed by a gradually decreasing degradation phase. In contrast, for oxidized HDL, both compounds initially exhibited a prompt propagation phase with a subsequent plateau phase, followed by a rapid degradation phase. The analytical LC/MS method for phosphatidylcholine hydroperoxides might be useful for the analysis of biological samples.
authors.affiliation: Faculty of Health Sciences, Hokkaido University, Kita-12, Nishi-5, Sapporo 060-0812, Japan.
authors.forename: Shu-Ping
authors.initials: SP
authors.lastname: Hui
authors.forename: Yudai
authors.initials: Y
authors.lastname: Taguchi
authors.forename: Seiji
authors.initials: S
authors.lastname: Takeda
authors.forename: Futaba
authors.initials: F
authors.lastname: Ohkawa
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Sakurai
authors.forename: Shinobu
authors.initials: S
authors.lastname: Yamaki
authors.forename: Shigeki
authors.initials: S
authors.lastname: Jin
authors.forename: Hirotoshi
authors.initials: H
authors.lastname: Fuda
authors.forename: Takao
authors.initials: T
authors.lastname: Kurosawa
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Chiba
mesh_terms: D000328:Adult; D002138:Calibration; D002853:Chromatography, Liquid; D003300:Copper / Q000737:chemistry*; D005260:Female; D006801:Humans; D057230:Limit of Detection; D008075:Lipoproteins, HDL / Q000737:chemistry*; D008077:Lipoproteins, LDL / Q000737:chemistry*; D008297:Male; D013058:Mass Spectrometry; D010084:Oxidation-Reduction; D010713:Phosphatidylcholines / Q000032:analysis*; D012015:Reference Standards; D015203:Reproducibility of Results
chemical_list: D008075:Lipoproteins, HDL; D008077:Lipoproteins, LDL; D010713:Phosphatidylcholines; C057590:phosphatidylcholine hydroperoxide; D003300:Copper