Oleic acid induces smooth muscle foam cell formation and enhances atherosclerotic lesion development via CD36

Background: Elevated plasma free fatty acid (FFA) levels have been linked to the development of atherosclerosis. However, how FFA causes atherosclerosis has not been determined. Because fatty acid translocase (FAT/CD36) is responsible for the uptake of FFA, we hypothesized that the atherogenic effects of FFA may be mediated via CD36. Results: We tested this hypothesis using cultured rat aortic smooth muscle cells (SMCs) treated with oleic acid (OA). We found that OA induces lipid accumulation in SMCs in a dose dependent manner. Rat aortic SMCs treated for 48 hours with OA (250 mu mol/L) became foam cells based on morphological (Oil Red O staining) and biochemical (5 times increase in cellular triglyceride) criteria. Moreover, specific inhibition of CD36 by sulfo-N-succinimidyl oleate significantly attenuated OA induced lipid accumulation and foam cell formation. To confirm these results in vivo, we used ApoE-deficient mice fed with normal chow (NC), OA diet, NC plus lipolysis inhibitor acipimox or OA plus acipimox. OA-fed mice showed increased plasma FFA levels and enhanced atherosclerotic lesions in the aortic sinus compared to the NC group (both p < 0.01). This effect was partially reversed by acipimox (lesion area: OA: 3.09 +/- 0.10 x 10(5) mu m(2) vs. OA plus acipimox: 2.60 +/- 0.10 x 10(5) mu m(2), p < 0.05; FFA: OA: 0.91 +/- 0.03 mmol/L vs. OA plus acipimox: 0.78 +/- 0.03 mmol/L, p < 0.05). Conclusions: These findings suggest that OA induces smooth muscle foam cell formation and enhances atherosclerotic lesions in part though CD36. Furthermore, these findings provide a novel model for the investigation of atherosclerosis.