A recent investigation highlighted that oxidative modification of low-density lipoprotein (oxLDL) is involved in the pathogenesis of atherosclerotic lesions through the formation of macrophage-derived foam cells. Hibiscus sabdariffa L., a garden plant containing a lot of pigments, was demonstrated to inhibit LDL oxidation and the progression of atherosclerosis in high cholesterol-fed rabbits. In this study, we further evaluated the effect of Hibiscus anthocyanin-rich extracts (HAs) on foam cell formation and the gene expression of scavenger receptor, CD36 and its upstream transcription factor, PPARgamma on oxLDL-treated mouse macrophage J774A.1 cells. Quantitative lipid analysis indicates a dramatic increase in lipid accumulation in oxLDL-treated cells, while treatment of the cells with the HAs (0.05-0.2 mg/ml) largely prevents lipid accumulation. Our results show that HAs is able to decrease oxLDL mediated foam cell formation. The oxLDL-treated J774A.1 cells up-regulates the expression of CD36. After treatment with HAs, the expression of CD36 is found to be decreased both at the mRNA as well as protein level. Treatment of J774A.1 cells with oxLDL is found to significantly increase PPARgamma protein levels in nuclear extracts while treatment with HAs results in significant decreases in nuclear PPARgamma protein levels. Therefore, it suggests that HAs inhibits the macrophage uptake of oxLDL and this may involve CD36 downregulation.
