Formation of non-cyclooxygenase-derived prostanoids (F2-isoprostanes) in plasma and low density lipoprotein exposed to oxidative stress in vitro.
F2-isoprostanes are prostaglandin F2-like compounds that are known to be formed in vivo by free radical oxidation of arachidonyl-containing lipids, and their plasma levels have been suggested as indicators of in vivo oxidative stress. As oxidation of LDL, a likely causal factor in atherosclerosis, involves lipid peroxidation, we investigated whether F2-isoprostanes are formed in plasma and LDL exposed to oxidative stress, and how F2-isoprostane formation is related to endogenous antioxidant status. In plasma exposed to aqueous peroxyl radicals, lipid hydroperoxides and esterified F2-isoprostanes were formed simultaneously after endogenous ascorbate and ubiquinol-10 had been exhausted, despite the continued presence of urate, alpha-tocopherol, beta-carotene, and lycopene. In isolated LDL exposed to aqueous peroxyl radicals or Cu2+, consumption of endogenous ubiquinol-10 and alpha-tocopherol was followed by rapid formation and subsequent breakdown of lipid hydroperoxides and esterified F2-isoprostanes, and a continuous increase in LDL's electronegativity, indicative of atherogenic modification. In Cu(2+)-exposed LDL, the decrease in esterified F2-isoprostane levels was paralleled by the appearance of free F2-isoprostanes, suggesting that hydrolysis by an LDL-associated activity had occurred. Our data suggest that F2-isoprostanes are useful markers of LDL oxidation in vivo. As F2-isoprostanes are potent vasoconstrictors and can modulate platelet aggregation, their formation in LDL demonstrated here may also have important implications for the etiology of cardiovascular disease.
Lynch
S M
SM
Department of Nutrition, Harvard School of Public Health, Boston, Massachusetts 02115.
Morrow
J D
JD
Roberts
L J
LJ
Frei
B
B
D000578:Amidines / Q000494:pharmacology; D000975:Antioxidants / Q000378:metabolism; D003300:Copper / Q000494:pharmacology; D015237:Dinoprost / Q000096:biosynthesis; D006801:Humans; D066298:In Vitro Techniques; D015227:Lipid Peroxidation; D008077:Lipoproteins, LDL / Q000378:metabolism*; D008297:Male; D010084:Oxidation-Reduction; D011453:Prostaglandins / Q000096:biosynthesis* / Q000097:blood
D000578:Amidines; D000975:Antioxidants; D008077:Lipoproteins, LDL; D011453:Prostaglandins; C046728:2,2'-azobis(2-amidinopropane); D003300:Copper; D015237:Dinoprost