Arsenic Impaired Cholesterol Efflux In Macrophages And Hepatic Cells By Regulating Expression Of ABCA1 And ABCG1

Objective:Epidemiologic evidence indicates that humans exposed to arsenic have an increased risk of heart disease and atherosclerosis. Cholesterol efflux channels ATP-binding cassette transporter A1 (ABCA1), ATP-binding cassette transporter G1 (ABCG1) and Scavenger receptor-BI (SR-BI) are the key mediators regulating cholesterol homeostasis which plays a critically important role in the initiation of early atherosclerotic lesion development. However, the influencing of arsenic on cholesterol efflux rate and the expression of related genes is still unclear. The aim of the present study is to elucidate the effect of arsenic on cholesterol efflux and the expression of ABCA1, ABCG1 and SR-BI in hepatic cells and macrophage cells, are the three important channels for cholesterol-mediated efflux from macrophage foam cells.Methods:THP-1 human macrophages and mouse primary macrophage cells are cultured in RPMI medium 1640 containing with 4μg/ml 22R-OHC and 10μmol/L 9-cis-RA for 6 hours, and then culture with 0.625、1.25、2.5 or 5μM NaAsO2 for 18 hours. L-02 cells and the primary hepatic cells are cultured in DMEM containing with 2、4、8、12 or 16μM NaAsO2 for 48 hours. THP-1 human macrophages are incubated with 22R-OHC/9-cis-RA for 6 hours, the cells are cultured with 2.5μM NaAsO2 for 18 hours, and then collect the cells at 12、24、36、 42、48 (change new medium)、60、72、84 or 96 hours. L-02 cells are cultured with 12μM NaAsO2 for 18 hours, and then collect the cells at 12、24、36、42、48 (change new medium)、 60、72、84 or 96 hours. Fluorescence quantitative PCR and Western blot to test the expression levels of ABCA1、ABCG1 and SR-BI in macrophage and hepatic cells treated with arsenic. After 3H isotope tracer to determine arsenic processing intracellular cholesterol changes in the rate of cholesterol efflux. Using t-test to analysis the efflux of cholesterol.Results:In THP-1 human macrophages and mouse primary macrophage cells, more the 0.625μM or more NaAsO2 can significant decrease ABCA1 mRNA, and more the 1.25μM or more NaAsO2 can significant decrease ABCG1 mRNA, but SR-BI has no change, the change of protein as the same as mRNA,3H isotope tracer to determine that 1.25μM or more NaAsO2 can significant decrease the efflux of cholesterol. In L-02 cells and the primary hepatic cells, more the 4μM or more NaAsO2 can significant increase ABCA1 and ABCG1 mRNA, but SR-BI has no change, the change of protein as the same as mRNA,3H isotope tracer to determine that 8μM or more NaAsO2 can significant increase the efflux of cholesterol. THP-1 human macrophages are cultured with 2.5μM NaAsO2, the expression of ABCA1 has significant reduced at 36 hours, after 42 hours, the expression of ABCA1 reduced 60%, and then the expression of ABCA1 back to the original at 84 hours. L-02 cells are cultured with 12μM NaAsO2, the expression of ABCA1 has significant increased at 24 hours, after 36 hours, the expression of ABCA1 increase to 2.5 folds, and then the expression of ABCA1 back to the original at 84 hours.Conclusion:Arsenic can increase cholesterol efflux by improve ABCA1 and ABCG1 in hepatic cells, and also reduce cholesterol efflux by inhibit ABCA1 and ABCG1 in macrophage cells.