Compare the effect of eicosapentaenoic acid and oxidized low-density lipoprotein on the expression of CD36 and peroxisome proliferator-activated receptor gamma

There is evidence that CD36 promotes foam cell formation through internalizing oxidized LDL (ox-LDL) into macrophages; therefore, it plays a key role in pathogenesis of atherosclerosis. In addition, CD36 expression seems to be mediated by nuclear receptor peroxisome proliferator-activated receptor gamma (PPAR-γ). The aim of the present study was to evaluate and compare the effect of PPAR-γ ligands, eicosapentaenoic acid (EPA) as an anti-atherogenic factor and ox-LDL as an atherogenic factor on CD36 expression. Mechanism of PPAR- γ action and its ligands in CD36 expression were also investigated. Raw 264.7 macrophage cell line was treated with ox-LDL (100 and 150 μg protein/LDL) and EPA (100 and 200 μM) for 24 and 48 hours in absence or presence of PPAR-γ inhibitor, T0070907. Quantitative real-time PCR and Western-blotting were used for analysis of gene and protein expression, respectively. Raw 264.7 exposures to ox-LDL and EPA resulted in increased expression of CD36 mRNA and protein; however, mRNA and PPAR-γ protein were not up-regulated significantly. Pre-incubation of cells with T0070907 led to decreased expression of CD36 when treated with ox-LDL and EPA. It was confirmed that both EPA and ox-LDL increased CD36 expression but not PPAR-γ, and also co-treatment with PPAR-γ inhibitor decreased CD36 expression. We concluded that up-regulation of CD36 depends on PPAR-γ activation and is not related to increased expression of PPAR-γ. Induction of CD36 by EPA showed that CD36 suppression is not the means by which ω-3 fatty acids (EPA) provide protection against formation of atherosclerotic plaque.