Mitsuhiro Yokoyama

Orally Administered Eicosapentaenoic Acid Induces Rapid Regression of Atherosclerosis Via Modulating the Phenotype of Dendritic Cells in LDL Receptor-Deficient Mice

Objective— Eicosapentaenoic acid (EPA) has been shown to have beneficial effects on cardiovascular diseases, although the precise mechanism is unknown. We investigated the effect of EPA on the regression of atherosclerosis. Methods and Results— LDL-receptor–deficient mice were fed a high-cholesterol diet for 8 weeks to build up aortic sinus atherosclerotic lesions and then were fed a normal diet with or without 5% EPA for 4 weeks. Atherosclerotic lesions were histologically assessed, and immunologic assays were performed. EPA treatment significantly regressed atherosclerosis (−22.7%, P<0.05) and decreased the content of macrophages, CD4+ T cells, and dendritic cells (DCs) in atherosclerotic lesions, though only changing the chow never induced the regression. Flow cytometric analysis revealed that EPA increased immature DCs (CD11c+ CD80− CD86−), increased the indoleamine 2,3-dioxygenase (IDO) in DCs, and decreased the number of CD4+ T cells. In the presence of the IDO inhibitor, the beneficial effects of EPA on regression were inhibited, suggesting that the effect of EPA was mainly mediated through IDO. Conclusion— In addition to lowering plasma cholesterol, EPA regressed atherosclerosis probably due to modulation of DC phenotype and reduction in T cell numbers. The present findings might partly explain the beneficial effects of EPA in clinics and support clinical evidence.

The Inhibition of Endothelium-Dependent Vasorelaxation by Oxidized Low Density Lipoprotein and Lysophosphatidylcholine

The vascular endothelium produces endothelium-derived relaxing factor(s) which regulate(s) vascular tone. In atherosclerotic arteries, endothelium-dependent relaxation is markedly reduced; this impairment is thought to play an important role in the pathogenesis of coronary spasm. The purpose of this study was to evaluate the effects of native and modified low density lipoprotein (LDL) on endothelium-dependent relaxation and to clarify the mechanism underlying the inhibitory effects of oxidized LDL. LDL(density, 1.020–1.060) was isolated by ultracentrifugation from freshly-harvested normal human plasma. Phospholipase A2-treated LDL and copper-oxidized LDL were prepared by the method of Quinn et al. For recording isometric force, rabbit aortic strips equilibrated with oxygenated Kreb’s buffer were precontracted with phenylephrine. We measured phosphoinositide hydrolysis by a 3H inositol labelling method and cytosolic Ca2+ level by using fura-2 fluorescence spectroscopy in cultured bovine aortic endothelial cells. Preincubation of the strips with native LDL(0.5–2 mg protein/ml) had no effect on acetylcholine(Ach)- induced endothelium-dependent relaxation. Oxidized LDL(0.1–0.5 mg protein/ml) and phospholipase A2-treated LDL (0.01–0.1 mg protein/ml) inhibited this relaxation. Native and modified LDL did not inhibit nitroglycerin-induced relaxation. Lysophosphatidylcholine(LPC) extracted from modified LDL by thin layer chromatography inhibited Ach-induced relaxation.