Superoxide and peroxynitrite inatherosclerosis.

Abstract

The role of reactive oxygen species in the vascular pathology asiated with atherosclerosis was examined by testing the hypothesis that impaired vascular reactivity results from the reaction of nitric oxide (NO) with superoxide (O2), yielding the oxidant peroynitrite (ONOO-). Contractility studies were performed on femoral arteries from rabbits fed a cholesterol-supplemented diet Endothelium-dependent relaxation is impaired in vessels from atherosclerotic patients (1, 2) and hypercholesterolemic animal models (3-6), suggesting the functional modification of endothelium-derived relaxing factor (EDRF) in hyperlipidemia. The dynamic role ofthe endothelium in the regulation of vascular tone was established when it was observed that relaxation of isolated blood vessels by vasoactive agents, such as acetylcholine (ACh) and the calcium ionophore A23187, was dependent on an intact endothelium and a diffusible factor (EDRF) that stimulated cGMP-dependent relaxation of vascular smooth muscle cells (VSMCs; ref. 7).Nitric oxide (-NO) and EDRF share similar chemical and pharmacological properties (8) and are derived from the oxidation of a terminal guanidino group of L-arginine (9, 10).Numerous mechanisms have been suggested for the defect in vascular relaxation in atherosclerosis and hypercholesterolemic animal models. They include an increased diffusional barrier for 'NO due to intimal cell proliferation and lipid deposition (11), L-argifine depletion (3,12,13) Vessel Contraction Studies. New Zealand White rabbits (2.5-3.0 kg) were maintained on rabbit chow containing 1% cholesterol (Ralston Purina) for 6 months prior to study [cholesterol-fed (Chol-fed) group]. Age-and weight-matched controls were fed a standard diet. After exsanguination under ketamine/rompun anesthesia, vessels were isolated and changes in tension were measured in femoral artery ring segments as described (28). After maximal contraction with 70 mM KCl and recovery, phenylephrine was added to achieve 30% of maximal tone. Rings were then exposed to increasing doses of ACh; relaxation is reported as the percentage decrease in preexisting tone. After the generation of cumulative ACh dose-response curves, rings were exposed to 30 ,uM papaverine. In some experiments, rings from control and Chol-fed rabbits were incubated with 3 mM L-arginine for 30 min prior to administration of ACh. In other studies, vessels were treated with native bovine SOD (200 units/ml) before measuring ACh-induced relaxation. All studies were performed in the presence of 5 !uM indomethacin.

Mechanisms of H2O2-induced oxidative stress in endothelial cells

“…This makes CVD the leading cause of death for both men and women of all ethnicities (AHA 2004a). In addition, increases in ROS have been related to the onset of cardiovascular diseases, including hypertension, atherosclerosis, and diabetes mellitus (White et al 1994;Mugge 1998;Kojda et al 1999;Pepine et al 2001;Harrison et al 2003a). Our understanding of the early stages and mechanisms of cardiovascular disease is still developing.…”

Formation of 8‐nitroguanine in DNA treated with peroxynitrite in vitro and its rapid removal from DNA by depurination

“…Increasing evidence now suggests that peroxynitrite is a major agent causing tissue damage induced by inflammation in vivo [9][10][11]. Peroxynitrite oxidizes sulfhydryl groups and induces membrane lipid peroxidation [12][13][14].…”

Metabolic Fate of Peroxynitrite in Aqueous Solution

“…because it is about twice as fast as the maximum velocity of SOD. 1 Consequently, peroxynitrite has been implicated in many pathological conditions including stroke (3), heart disease (4), and atherosclerosis (5,6). The potential cellular targets for peroxynitrite cytotoxicity include the antioxidants ascorbate, ␣-tocopherol, and uric acid (7)(8)(9)(10), protein and non-protein sulfhydryls (11), DNA (12), and membrane phospholipids (13).…”