Objective To observe the effects of fenofibrate and linoleic acid which was the different activators of PPARα on the expression of PAI-1 and PPARα in HepG2 cells. To investigate the relationship and mechanisms between the promoter and expression of PAI-1 that how the fenofibrate and linoleic acid to act on PAI-1. And to observe if PPARα involved in this procession.
Methods HepG2 cells were exposed to fenofibrate and linoleic acid in varying concentrations, RT-PCR was used to determine the mRNA expression of PAI-1 and PPARα. Several luciferase reporter gene recombinant plasmid containing different length sequences of human PAI-1 gene promoter from −804 to +17bp were constructed and transiently transfected into HepG2 cells. At the same time, co-transfected with PPARα-pSG5 expression plasmid, then different stimulating factors were added to induce the transfected cells. Transcriptional activity of PAI-1 was demonstrated by the measure of luciferase activity.
Results 1. Fenofibrate could remarkably decreased PAI-1 mRNA expression in HepG2 cells (p<0.05 or p<0.01), but linoleic acid could significant increased PAI-1 mRNA level (p<0.05 or p<0.01), and they were all in a concentration-dependent manner. 2. Fenofibrate and linoleic acid could raise the mRNA level of PPARα (p<0.05 or p<0.01), which were also in a concentration-dependent way. 3. The PAI-1 transcriptional activity were significantly suppressed by fenofibrate (p<0.05), but induced by linoleic acid (p<0.01) in HepG2 cells transfected with PAI-pGL3 total length promoter constructs. 4. When co-transfected with PPARα-pSG5, fenofibrate could suppress the level of PAI-1 transcription further more (p<0.05), while increased y linoleic acid (p<0.01). 5. The PAI-1 transcriptional activity were very inconsistent when transfected with the plasmid containing different length sequences of human PAI-1 gene promoter from −804 to +17 bp.
Conclusions Fenofibrate and linoleic acid could increase the mRNA level of PPARα, and they regulate the synthesis of PAI-1 from transcriptional level, which was concerned with the activated of PPARα by Fenofibrate and linoleic acid. The sequences that could regulate the expression of PAI-1 gene induced by fenofibrate might exist in the areas from −804 to −636 and −636 to −449 of PAI-1 promoter and existed in the areas rom −804 to −636 and −449 to −276 induced by linoleic acid. The effects on expression of PAI-1 were very inconsistently, so there might be other mechanisms involved.