-Isoprostanes in Human Atherosclerotic Lesions

F 2 -Isoprostanes are prostaglandin (PG) isomers formed in situ in cell membranes by peroxidation of arachidonic acid. 8-epi PGF 2 a and IPF 2 a -I are F 2 -isoprostanes produced in humans which circulate in plasma and are excreted in urine. Measurement of F 2 -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 2 a ranged from 1.310–3.450 pmol/ m mol phospholipid in atherectomy specimens compared with 0.045–0.115 pmol/ m mol phospholipid ( P , 0.001) in vascular tissue devoid of atherosclerosis. Corresponding values of IPF 2 a -I were 5.6–13.8 vs. 0.16–0.44 pmol/ m mol phospholipid ( P , 0.001). Levels of the two isoprostanes in vascular tissue were highly correlated ( r 5 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 2 a . These cells were also reactive with anti-CD68, an epitope specific for human monocyte/macrophages. 8-epi PGF 2 a immunoreactivity was also detected in cells positive for anti– a -smooth muscle actin antibody, which specifically recognizes vascular smooth muscle cells. Our results indicate that 8-epi PGF 2 a and IPF 2 a -I, two distinct F 2 -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. ( J. Clin. Invest. 1997. 100:2028–2034.)