High levels of homocysteine downregulate apolipoprotein E expression via nuclear factor kappa B

Figure 5 Homocysteine activates nuclear factor kappa B, but has no effect on activator protein-1 or nuclear factor of activated T cells activity. HEK-293 cells were transiently transfected with (NF-κB)₃-luc construct (A), (AP-1)₇-luc (C), or (NFAT)₃-luc (D) and exposed to homocysteine (50-500 μmol/L). For positive control, the cells were co-transfected with (NF-κB)₃-luc and the vector for the heterodimer p65/50. The activity of the luciferase reporter driven by the corresponding promoter was normalized to the co-transfected β-galactosidase. Treatment with high concentrations of homocysteine (250 and 500 μmol/L) significantly increased (^aP < 0.05) the activity of the promoter containing the three NF-κB binding sites, while no effect of Hcy (P > 0.05) was observed on promoters containing binding sites for AP-1 (C) or NFAT (D). The activity of the (NF-κB)₃-luc construct was greatly enhanced by p65/p50 overexpression, used as positive control (^bP < 0.001). NF-κB: Nuclear factor kappa B; AP-1: Activator protein-1; NFAT: Nuclear factor of activated T cells; Hcy: Homocysteine.