Growth Differentiation Factor-15up-regulates ATP-binding Cassette Transporter A1through PI3K/PKCζ/SP1Pathway In THP-1Macrophages

Objective: Growth differentiation factor-15(GDF-15), abundantly expressed inmacrophages on atherosclerotic lesions, and has recently been found that it plays aprotective role in atherosclerosis, but the mechanism is still unknown. The aim of thisstudy was to determine whether ATP-binding cassette transporter A1(ABCA1) wasup-regulated by GDF-15via PI3K/PKCζ/SP1pathway in THP-1macrophages.Methods: THP-1macrophages were treated by oxidized low-density lipoprotein.Then examined ABCA1expression after treated with GDF-15at differentconcentrations or incubated with GDF-15(1.5ng/ml) for increasing periods of time (0,6,12,24,48h). High performance liquid chromatography and Oil red O staining wereused to evaluate the cellular lipid accumulation. Cholesterol efflux was determined byliquid scintillator. The level of ABCA1mRNA was determined by RT-PCR. Westernbolt was used to determine the protein levels of ABCA1, PI3K, PKCζ and so on. Ourexperiment also used PI3K, PKCζ and SP1inhibitor or corresponding siRNA toincubate together with GDF-15for24h. The levels of ABCA1, p-PKCζ and p-SP1activity were examined.Results: The results showed that GDF-15dramatically increased cholesterol effluxand decreased cellular cholesterol levels. Another important found was that ABCA1mRNA and protein levels were also increased by GDF-15in a time-and dose-dependent. However, the effects of GDF-15on ABCA1protein expression, cellularcholesterol efflux were abolished by depletion of PI3K, PKCζ and SP1respectively, suggesting the potential key role of PI3K, PKCζ and SP1on ABCA1expression.Conclusions: Taken together, our results suggest that GDF-15has an overallprotective effect on the progress of atherosclerosis, maybe through inducing ABCA1expression via a PI3K/PKCζ/SP1signaling pathway, and then enhancing cholesterolefflux.