title: Defects in leukocyte-mediated initiation of lipid peroxidation in plasma as studied in myeloperoxidase-deficient subjects: systematic identification of multiple endogenous diffusible substrates for myeloperoxidase in plasma.
abstract: More than a decade ago it was demonstrated that neutrophil activation in plasma results in the time-dependent formation of lipid hydroperoxides through an unknown, ascorbate-sensitive pathway. It is now shown that the mechanism involves myeloperoxidase (MPO)-dependent use of multiple low-molecular-weight substrates in plasma, generating diffusible oxidant species. Addition of activated human neutrophils (from healthy subjects) to plasma (50%, vol/vol) resulted in the peroxidation of endogenous plasma lipids by catalase-, heme poison-, and ascorbate-sensitive pathways, as assessed by high-performance liquid chromatography (HPLC) with on-line electrospray ionization tandem mass spectrometric analysis of free and lipid-bound 9-HETE and 9-HODE. In marked contrast, neutrophils isolated from multiple subjects with MPO deficiency failed to initiate peroxidation of plasma lipids, but they did so after supplementation with isolated human MPO. MPO-dependent use of a low-molecular-weight substrate(s) in plasma for initiating lipid peroxidation was illustrated by demonstrating that the filtrate of plasma (10-kd MWt cutoff) could supply components required for low-density lipoprotein lipid peroxidation in the presence of MPO and H(2)O(2). Subsequent HPLC fractionation of plasma filtrate (10-kd MWt cutoff) by sequential column chromatography identified nitrite, tyrosine, and thiocyanate as major endogenous substrates and 17 beta-estradiol as a novel minor endogenous substrate in plasma for MPO in promoting peroxidation of plasma lipids. These results strongly suggest that the MPO-H(2)O(2) system of human leukocytes serves as a physiological mechanism for initiating lipid peroxidation in vivo.
authors.affiliation: Department of Cell Biology, Cleveland Clinic Foundation, OH 44195, USA.
authors.forename: Renliang
authors.initials: R
authors.lastname: Zhang
authors.forename: Zhongzhou
authors.initials: Z
authors.lastname: Shen
authors.forename: William M
authors.initials: WM
authors.lastname: Nauseef
authors.forename: Stanley L
authors.initials: SL
authors.lastname: Hazen
mesh_terms: D016022:Case-Control Studies; D002851:Chromatography, High Pressure Liquid; D004058:Diffusion; D004958:Estradiol / Q000032:analysis / Q000494:pharmacology; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D007962:Leukocytes / Q000201:enzymology / Q000378:metabolism*; D050356:Lipid Metabolism; D015227:Lipid Peroxidation / Q000187:drug effects*; D009504:Neutrophils / Q000201:enzymology / Q000378:metabolism; D009573:Nitrites / Q000032:analysis / Q000494:pharmacology; D009195:Peroxidase / Q000097:blood / Q000172:deficiency*; D010949:Plasma / Q000737:chemistry / Q000166:cytology / Q000378:metabolism; D013379:Substrate Specificity; D013861:Thiocyanates / Q000032:analysis / Q000494:pharmacology; D014443:Tyrosine / Q000032:analysis / Q000494:pharmacology
chemical_list: D009573:Nitrites; D013861:Thiocyanates; D014443:Tyrosine; D004958:Estradiol; D009195:Peroxidase; C031760:thiocyanate