Localization of distinct F2-isoprostanes in human atherosclerotic lesions

Abstract

F2-Isoprostanes are prostaglandin (PG) isomers formed in situ in cell membranes by peroxidation of arachidonic acid. 8-epi PGF(2α) and IPF(2α)-I are F2-isoprostanes produced in humans which circulate in plasma and are excreted in urine. Measurement of F2-isoprostanes may offer a sensitive, specific, and noninvasive method for measuring oxidant stress in clinical settings where reactive oxygen species are putatively involved. We determined whether isoprostanes were present in human atherosclerotic lesions, where lipid peroxidation is thought to occur in vivo. 8-epi PGF(2α) ranged from 1.310-3.450 pmol/μmol phospholipid in atherectomy specimens compared with 0.045-0.115 pmol/μmol phospholipid (P < 0.001) in vascular tissue devoid of atherosclerosis. Corresponding values of IPF(2α)-I were 5.6-13.8 vs. 0.16- 0.44 pmol/μmol phospholipid (P < 0.001). Levels of the two isoprostanes in vascular tissue were highly correlated (r = 0.80, P < 0.0001). Immunohistochemical studies confirmed that foam cells adjacent to the lipid necrotic core of the plaque were markedly positive for 8-epi PGF(2α). These cells were also reactive with anti-CD68, an epitope specific for human monocyte/macrophages. 8-epi PGF(2α) immunoreactivity was also detected in cells positive for anti-α-smooth muscle actin antibody, which specifically recognizes vascular smooth muscle cells. Our results indicate that 8-epi PGF(2α) and IPF(2α)-I, two distinct F2-isoprostanes and markers of oxidative stress in vivo, are present in human atherosclerotic plaque. Quantitation of these chemically stable products of lipid peroxidation in target tissues, as well as in biological fluids, may aid in the rational development of antioxidant drugs in humans.