A peroxisome proliferator response elements regulatory system in xenopus oocytes and its application

Background Peroxisome proliferator-activated receptor-gamma ( PPARγ) is a kind of ligand-activated transcription factors binding to peroxisome proliferator response element (PPRE), a specific recognition site. It is thought to play a critical role in glucose and lipid metabolism and in inflammation control. The aim of this study was to establish a new cellular model for the quick screening of lipid-lowering drugs, which may be effective as PPAR-γ ligands on the PPRE-mediated pathway regulatory system. Methods Two plasmids were constructed: pXOE-PPARγ, in which the human PPARγ gene was in the downstream of TF III A gene promoter, and pLXRN-PPRE-d2EGFP, in which the enhanced green fluorescent protein (EGFP) gene was subcloned into PPRE. The xenopus oocytes were injected with these two plamids, and consequently treated with prostaglandin El, pioglitazone, and different kinds of lipid-lowering drugs. After 3 days, the oocytes were observed under a fluorescence microscope. To confirm the drug action, we injected pXOE-PPARγ plasmid into the oocytes, which then treated with prostaglandin Eland Hawthorn flavonoids. The mass of expressed lipoprotein lipase (LPL) in the cells was determined by enzyme labeling linked immunosorbent assay (EUSA). Results The expression of EGFP was only induced by prostagalandin El, pioglitazone, Hawthorn flavonoids. A concentration-response relationship was seen between expressed EGFP and Hawthorn flavonoids. The levels of LPL in both Hawthorn flavonoids groups and PPARγ ligand prostagalandin El group injected with pXOE-PPARγ plamid increased significantly (P <0. 001) compared with controls, and a concentration-response relationship was observed between LPL mass and Hawthorn flavonoids. Conclusions It is possible to establish a PPRE regulatory EGFP reporter system in xenopus oocytes to monitor the activity of PPARγ ligand. Hawthorn flavonoids can increase the expression of gene downsteam of PPRE by effect on the PPRE pathway regulatory system.