The objective of this study was to evaluate the influence of ingested L-arginine, L-citrulline, and antioxidants (vitamins C and E) on the progression of atherosclerosis in rabbits fed a highcholesterol diet. The fatty diet caused a marked impairment of endothelium-dependent vasorelaxation in isolated thoracic aorta and blood flow in rabbit ear artery in vivo, the development of atheromatous lesions and increased superoxide anion production in thoracic aorta, and increased oxidation-sensitive gene expression [Elk-1 and phosphorylated cAMP response element-binding protein]. Rabbits were treated orally for 12 weeks with L-arginine, L-citrulline, and͞or antioxidants. L-arginine plus L-citrulline, either alone or in combination with antioxidants, caused a marked improvement in endothelium-dependent vasorelaxation and blood flow, dramatic regression in atheromatous lesions, and decrease in superoxide production and oxidation-sensitive gene expression. These therapeutic effects were associated with concomitant increases in aortic endothelial NO synthase expression and plasma NO 2 ؊ ؉ NO 3 ؊ and cGMP levels. These observations indicate that ingestion of certain NO-boosting substances, including L-arginine, L-citrulline, and antioxidants, can abrogate the state of oxidative stress and reverse the progression of atherosclerosis. This approach may have clinical utility in the treatment of atherosclerosis in humans.antioxidant ͉ nitric oxide ͉ amino acids ͉ endothelial nitric oxide synthase A therosclerosis is an inflammatory disease (1) characterized by vascular endothelial cell dysfunction and diminished production of NO (2-5). Endothelial NO synthase (eNOS) gene transfer can reduce atherogenesis in hypercholesterolemic animals (6). NO is a widespread signaling molecule in the cardiovascular system, which functions in multiple ways to protect against the initiation and progression of atherosclerosis (7-9). For example, NO aids in preventing the adhesion and aggregation of blood cells and platelets along the endothelial cell lining in blood vessels (7,8) and is a potent inhibitor of vascular smooth muscle cell proliferation (10). NO is a potent antioxidant that can elicit antiinflammatory effects by scavenging certain reactive oxygen species (11-13), and it can prevent the oxidation of low-density lipoprotein cholesterol and thereby retard the progression of atherosclerosis (5, 14). Moreover, NO deficiency is generally associated with up-regulation of oxidation-sensitive genes, whereas increased NO production leads to decreased expression of oxidation-sensitive genes (7,15). NO is synthesized by NOS, which utilizes L-arginine as substrate and produces L-citrulline as the second reaction product. L-arginine can be synthesized from L-citrulline in endothelial and other cell types, thereby providing a recycling pathway for the conversion of L-citrulline to NO via L-arginine (16)(17)(18)(19).The oral administration of L-arginine to animals (7, 12, 20-26) and humans (5,8,(27)(28)(29) has been demonstrated to slow the progressi...

Atherosclerosis, an inflammatory disease, is closely associated with hyperglycemia, major sign of diabetes mellitus. Caveolae are vesicular invaginations of the plasma membrane that mediate the intracellular transport of lipids such as cholesterol. We evaluated the relationship between the expression of caveolin-1 and the number of caveolae in macrophages under conditions of high glucose concentration. Increased superoxide production, induction of inducible nitric oxide synthase (iNOS), and decreased caveolin-1 were observed in a concentration-dependent manner in THP-1 derived macrophages with high glucose concentrations. Mannitol, used as an osmotic control, showed no effects. Furthermore, co-localization of the NADPH oxidase component, p47(phox), and caveolin was confirmed by confocal microscopy. An atomic force microscopy (AFM) study showed that high glucose concentrations reduced the number and size of the caveolae. The percentage of cells with fragmented DNA was increased in cells grown in hyperglycemic media. Taken together, high glucose concentrations suppress the levels of caveolin-1 expression and reduce the number of caveolae. This might be due to the actions of superoxide via the activation of NADPH oxidase by translocation of its component and uncoupling of induced iNOS in macrophages. Furthermore, the apoptosis of macrophages might occur with high glucose concentrations, leading to the spreading of lipids from macrophages into intracellular spaces in the vessel wall.

The effects of in vivo gene transfer of endothelial nitric oxide synthase (eNOS) and inducible NOS (iNOS) genes on severe atherosclerosis were investigated in rabbits. The recombinant adenoviruses, Ad.eNOS and Ad.iNOS, which respectively express eNOS and iNOS, were constructed. Atherosclerosis was induced by a balloon injury followed by a high cholesterol diet for 12 weeks. The rabbits were divided into six groups: Gp cont (no treatment); Gp null (adenovirus sham-infected); Gp eNOS (Ad.eNOS); Gp iNOS (Ad.iNOS); Gp e+i (Ad.eNOS plus Ad.iNOS); and Gp heNOS (a high dose of Ad.eNOS). Examinations were carried out 7 days after gene transfer. Plasma lipid levels were not significantly changed, but transfection with Ad.eNOS (Gp eNOS and Gp heNOS) decreased the tissue cholesterol concentration and regressed atherosclerotic lesions. Vessels treated with Ad.iNOS (Gp iNOS and Gp e+i) showed iNOS staining in the atheroma, and slight staining at other parts of the vessels; those treated with Ad.eNOS showed eNOS staining in the endothelium and subintima, and slight staining at other parts. Ad.eNOS transfection, but not Ad.iNOS or Ad.eNOS+Ad.iNOS transfection, improved the impaired aortic endothelium-dependent relaxation (EDR) and basal NO-dependent response, increased tissue cyclic GMP (cGMP), and decreased the release of O2- from vessels. eNOS treatment showed a decreasing tendency in regions with peroxynitrite staining, MMP1 staining, and suspected apoptosis. In conclusion, in vivo gene transfer of eNOS, but not iNOS or eNOS plus iNOS, regressed atherosclerosis. The relations among NO, O2-, and peroxynitrite may be critical, and lipid resorption from the lesions may be responsible for the regression.

Apocynin restores the impairment of endothelial and non-endothelial function in diabetic angiopathy in OLETF without changing plasma glucose and lipid levels. NO and O(2) (-) may play a role in this process by decreasing TNF-alpha levels.

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