Figure 1. The effect of ApoE on lipoprotein-induced ABCA1 expression and cholesterol efflux.

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. Panel A and B: The level of ABCA1 protein was determined by western blot analysis and quantitated relative to β-actin. Panel C: The level of ABCA1 mRNA was determined by quantitative real-time RT-PCR and normalized to GAPDH mRNA. Panel D: 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 Methods. 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 t-test (D). * P<0.05 compared to control, ^† P<0.05 compared to E⁺/B or E3/B lipoprotein treatment.