The effect of ApoE on lipoprotein-induced ABCA1 expression and cholesterol efflux.

<p>For study the effect of ApoB-carrying lipoproteins on ABCA1 expression, mouse macrophages were incubated with 20 µg/ml of wild-type (E⁺/B), ApoE-free (EÎ/B) or ApoE3-enriched (E3/B) lipoproteins, or culture medium alone. <b>Panel A and B:</b> The level of ABCA1 protein was determined by western blot analysis and quantitated relative to β-actin. <b>Panel C:</b> The level of ABCA1 mRNA was determined by quantitative real-time RT-PCR and normalized to GAPDH mRNA. <b>Panel D:</b> For studying the effect of ApoE on lipoprotein-induced cholesterol efflux, mouse macrophages were incubated with [³H]-cholesterol in the presence or absence of 20 µg/ml of E⁺/B, E⁻/B or E3/B lipoproteins. ApoAI-mediated cholesterol efflux was measured as described under Materials and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0021453#s2" target="_blank">Methods</a>. Values represent the mean ± SEM of five independent experiments. Differences among cells treated with E⁺/B, E⁻/B, E3/B lipoproteins or culture medium alone were analyzed by one-way ANOVA followed by Tukey post-hoc tests (B and C) or Student <i>t</i>-test (D). * <i>P</i><0.05 compared to control, ^†<i>P</i><0.05 compared to E⁺/B or E3/B lipoprotein treatment.