The relationship of hydroxyeicosatetraenoic acids and F-2-isoprostanes to plaque instability in human carotid atherosclerosis

Evidence for increased oxidant stress has been reported in human atheroscle rosis. However, no information is available about the importance of in situ oxidant stress in relation to plaque stability. This information is releva nt because the morbidity and mortality of atherosclerosis are essentially t he consequences of acute ischemic syndromes due to unstable plaques. We stu died 30 carotid atherosclerotic plaques retrieved by endarterectomy from 18 asymptomatic (stable plaques) and 12 symptomatic patients (unstable plaque s). Four normal arteries served as controls. After lipid extraction and est er hydrolysis, quantitation of different indices of oxidant stress were ana lyzed, including hydroxyeicosatetraenoic acids (HETEs), epoxyeicosatetraeno ic acids (EETs), ketoeicosatetraenoic acids (oxo-ETEs), and F-2-isoprostane s using online reverse-phase high-performance liquid chromatography tandem mass spectrometry (LC/MS/MS). All measurements were carried out in a strict ly double-blind procedure. We found elevated levels of the different compou nds in atherosclerotic plaques. Levels of HETEs were 24 times higher than E ETs, oxo-ETEs, or F-2-isoprostanes. Levels of HETEs, but not those of EETs, oxo-ETEs or F-2-isoprostanes, were significantly elevated in plaques retri eved from symptomatic patients compared with those retrieved from asymptoma tic patients (1,738 +/- 274 vs. 1,002 +/- 107 pmol/mu mol lipid phosphorous , respectively; P < 0.01). One monooxygenated arachidonate species, 9-HETE, which cannot be derived from known enzymatic reactions, was the most abund ant and significant compound observed in plaques, suggesting that nonenzyma tic lipid peroxidation predominates in advanced atherosclerosis and may pro mote plaque instability.