Objectives Increased levels of homocysteine (Hcy) in the blood are considered to be a risk factor for atherosclerosis. Endothelial damage induced by Hcy can lead to deterioration of coronary, cerebral, and peripheral vascular beds, contributing to cardiovascular morbidity and mortality. However, the mechanisms underlying Hcy-induced damage have not been fully elucidated. This study aimed to investigate the effect of Hcy on low-density lipoprotein (LDL) oxidation and inducible nitric oxide synthase (iNOS) expression, both of which are thought to play a role in the pathogenesis of atherosclerotic plaque formation and regulation of inflammation.Methods L-929 fibroblast-like cells and RAW 264.7 macrophages were treated with varying concentrations of Hcy (50, 100 and 200 mu g/mL for L-929 cells, 10, 25, 100, 200 mu g/mL for RAW 264.7 cells) to assess LDL oxidation and iNOS expression using immunocytochemical and immunofluorescence methods. Images obtained from cell culture experiments were quantitatively analyzed using color and brightness histograms, followed by statistical evaluation.Results Hcy significantly and dose-dependently increased LDL oxidation and intracellular oxidized LDL (ox-LDL) accumulation in both cell groups. Hcy also significantly increased iNOS expression in both cell groups in a dose-dependent manner.Conclusions These findings suggest that Hcy may play a role in the pathogenesis of atherosclerosis and inflammatory processes. The increased levels of ox-LDL and the elevated iNOS expression, particularly in macrophages, may contribute to the exacerbation of atherosclerosis and related diseases.