Regulation of LDL receptor expression by the effect of curcumin on sterol regulatory element pathway.

To investigate the molecular mechanisms of the effect of curcumin on up-regulation of LDL receptor expression, a sterol regulatory report system was established in Xenopus laevis oocytes by microinjection of a plasmid pLXRN-4SRE-fPA, in which green fluorescence protein (GFP) gene was constructed downstream from the sterol regulatory element-1 (SRE-1), in the nucleus of the oocytes. The oocytes were treated with different kinds of natural medicines: curcumin, tea polyphenols, tanshinone, ligustrazine, ginkgolide, astragalosides. The expression of GFP was induced only by curcumin. In addition, it was also proved that the curcumin can increase the expression of functional LDL receptors in human liver hepatoma cell line HepG2. In conclusion, curcumin may up-regulate the expression of LDL receptor by its effect on SRE pathway.