Hcy dose-dependently down-regulates HO-1 gene expression in HepG2 cells. HepG2 cells were treated with the indicated concentrations of Hcy for 24 h. (A) Total RNA was extracted and subjected to qRT-PCR for the assessment of HO-1 mRNA level. The bar graph shows mRNA levels of HO-1 after normalization to GAPDH. Data are presented as means ± SEM from 3 three independent experiments. *P < 0.05 vs. control. (B) HepG2 cells were transfected with the HO-1-pGL3 plasmid and then exposed to Hcy for 24 h. The data are expressed as fold change of the luciferase activities normalized toβ-gal activity compared to control. *P < 0.05 vs. control; n = 4. (C) Protein levels of HO-1 were analyzed using Western blotting. Representative results of three independent experiments are shown. β-actin was used as an internal control to ensure equal loading in all lanes of the gel.