Induction of apoE secretion by apoA-I in macrophage foam cells (MFCs). Panel A, apoE was analyzed by Western blot in the media and cellular lysate from lipid loaded macrophages incubated in the presence of 10 μg/ml apoA-I (apoA-I) or without (Control) for 24h. Panel B, bands were quantified (ImageJ v1.42q software) and the bars represent the intensity of apoE bands normalized to intensity of actin band. Panel C, increasing concentrations of apoA-I were added in the culture media of MFC and apoE concentration was quantified after 3h of incubation. ApoE concentration was determined by ELISA and values were normalized to total cell protein concentration. A linear relationship between apoA-I and apoE concentration was observed (R2 = 0.959). The dots and error bars represent the mean ± SD calculated from triplicates. The results are representative for at least 3 independent experiments.