| Aim The finding of ABC1(ATP Binding Cassette Transporter 1), the most important cholesterol efflux regulatory protein which express mainly in cell membrane and some organells have made the study of cholesterol reverse transportation the hot spot, The main function of ABC1 is to transport cholesterol from cells to HDL, this is very important for decreasing cell cholesterol loading, keeping cholesterol equilibration especially within the vascular wall, regulating lipid metabolism and preventing the development of atherogenesis. It is well known that nuclear receptors play important roles in many physiological and pathological regulatory process within body, and part of them take important action in atherogenesis, cholesterol transportation and lipid metabolism. In this study, we investigate the role of ABC1 in cholesterol reverse transportation and the effects of nuclear receptors PPARγ, LXRα, RXRα on ABC1 expression in THP-1 cell. At the same time we observed the effects of lipoprotein and oxidized lipoprotein on the expression of ABC1mRNA, mechanisms of ABC1mRNA expression regulated by PPARγ, LXRα, RXRα, the discrepancy and it's significance of ABC1 and CD36mRNA expression while PPARγ, LXRα, RXRα activated. The effects of PPARγ, LXRα, RXRα and ABC1 mediated cholesterol efflux on TNFα and IL-6 secretion induced by oxLDL in THP-1 cells were also observed. Furthermore, we investigated the effects of PPARγ, LXRα, RXRα on the expression of CYP7A1, the ratelimit enzyme in cholesterol metabolism, in HepG2 cell line, to get a whole picture of the roles of nuclear receptor PPARγ, LXRα, RXRα in cholesterol transportation and metabolism, and to provide foundation of theory for the regulation of cholesterol transportation and metabolism.Methods 1. Blood sample for the preparation of vLDL, LDL, HDL were taken from fasting healthy person. The different contents (vLDL, LDL, HDL)were obtained by density-gradient ultra centrifugation and the lipoprotein were oxidized by incubated with 15μmol/L H2SO4 for 10-12 hours as the literatures reported before. 2. THP-1 cell line were cultured in RPMI1640 with 10% BSA；3. Model of foam cell were set up by incubate THP-1 cell with 80mg/L oxLDL for 48 hours. 4. Western blot were used to assay ABC1 protein expression in PMA induced THP-1 macrophages treated with Troglitazone, 22(R)-HC, 9-CRA, ligands for the nuclear receptor PPARγ, LXRα,RXRα respectively . 5. Cholesterol levels within foam cells were estimated before and after cholesterol reserve transportation to determine the role of ABC1 in the cholesterol efflux process and the effects of Troglitazone, 22(R)-HC, 9-CRA on the process. 6. ABC1mRNA expression in THP-1 cell in the presence of low and high dose of LDL, HDL, oxLDL, oxHDL were observed by using one step RT-PCR. 7. The expression of PPARγ, LXRα, RXRα, ABC1mRNA in THP-1 cell in the presence of Ttoglitazone, 22(R)-HC and 9-CRA were determined by one step RT-PCR. 8. The discrepancy and it's significance of ABC1 and CD36 mRNA expression while activate nuclear receptor PPARγ, LXRα, RXRα in THP-1 cell were studied by using one step RT-PCR. 9. ELISA was used to detect TNFα, IL-6 secreted by THP-1 cell, which incubated with 40mg/L oxLDL for 24 hours to make out weather Ttoglitazone, 22(R)-HC, 9-CRA and cholesterol efflux mediated by ABC1 had any effect on this process. 10. Expression of CYP7A1mRNA in HepG2 cell treated with Troglitazone, 22(R)-HC, 9-CRA was determined by using one step RT-PCR. 11. In situ hybridization were used to detect the expression of c-myc, an oncogene, in HepG2 cell treated with Ttoglitazone, 22(R)-HC, 9-CRA for 24 hours to make out the correlation between the expression ofCYP7A1mRNA and c-myc in the cell.Results 1. Troglitazone, 22(R)-HC and 9-CRA can increase the expression of ABC1 protein in THP-1 macrophage, and every two of them showed synergetic effect. 2. Troglitazone, 22(R)-HC, 9-CRA can improve cholesterol reverse transportation from foam cell to ApoA-I, cholesterol efflux were abolished by pret...
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