Cyclophilin A Inhibits Cholesterol Accumulation Via The Caveolin-1 Bonding-dependent Pathway In Vascular Smooth Muscle Cells

Backgroud:Epidemiological studies have shown the intracellular decrease of cholesterol or amount reduction of foam cells could reverse angiosclerosis. Cycolphilin A and caveolin-1 as the key proteins participate in cholesterol efflux in foam cells. But the function of these proteins in vascular smooth cells (VSMCs) are still not clear.Objective: To observe the protein expression and function of cyclophilin A and caveolin-1 in lipid-loaded VSMCs induced by oxidized low density lipoprotein and to investigate their effect on cellular cholesterol accumulation.Methods: VSMCs were treated with 75mg/L Ox-LDL for different time (0,24,48, 72h).Western-blot and immunofiuoerscence were used to detect protein expression of cyclophilin A and caveolin-1. Oil Red O dye experiment was used to show the lipid droplets in lipid-loaded VSMCs. High Performance Liquid Chromatography (HPLC) analysis was peformed to determine the content of cellular total cholesterol and cholesterol ester. Cyclosporin A was used to inhibit the activity of cyclophilin A. Co-immunoprecipitation (IP) was used to identify the combination between cyclophilin A and caveolin-1.Results: Westem-blot analysis showed that the protein experssion of both cyclophilin A and caveolin-1 were significantly decreased in a time-dependent manner. Immunofluorescence showed the same trend of cyclophilin A and caveolin-1. Oil Red O dye showed that there were a lot of lipid droplets accumulaetd in VSMCs with Ox-LDL treatment after 48hours. HPLC analysis showed that the contents of intracellular total cholesterol and cholesterol ester were increased greatly.What is more, HPLC showed that the content of extracellular total cholesterol was decreased when the VSMCs were treated with cyclosporin A. Cyclophilin A can combine with caveolin-1 and the combination reduced after VSMCs being treated with cyclosporin A. However the protein expression of caveolin-1 and cyclophilin A was not changed significantly.Conclusion: Cyclophilin A was combined with the caveolin-1 to participate in the transportation of cholesterol in VSMCs. Cyclosporin A can inhibite the combination between cyclophilin A and caveolin-1, and increased the content of cellular total cholesterol in VSMCs.