Fig. 1.

Ectopically transfected ERα and ERβ differentially regulate ApoE expression. HT-22 cells were transfected with GFP-C3 (vector alone), ERα-GFP-C3, ERβ-GFP-C3 plasmids, or without plasmid DNA (mock transfection) for 24 h and subsequently treated with 10 ng/ml (37 nM) E₂ or vehicle alone for another 24 h. (A) Summary of results derived from real-time RT-PCR. ApoE mRNA levels were first normalized to that of a housekeeping gene β-actin and further calculated by the 2^−ΔΔCt method and plotted as fold change vs. vehicle-treated cells. ERα induced a >3-fold increase in ApoE mRNA, whereas ERβ induced a >4-fold decrease in ApoE mRNA. Data are mean ± SEM; n = 3. ∗, P < 0.05; ∗∗, P < 0.01 vs. control. (B) Differential effects of ERα and ERβ on ApoE protein expression. ApoE immunoblot analysis of protein extracts derived from cells under the same conditions as those in A. (Upper) Results of Western blot analyses indicated that in HT-22 cells transfected with ERα E₂ induced a 57% increase in ApoE expression, whereas in cells transfected with ERβ, E₂ induced a 28% decrease in ApoE expression. ∗∗, P < 0.05, vs. control. (Lower) Western blot profile of ApoE (34 kDa) and β-actin.