Enhancement Of The Glucocorticoid On The ACAT1 Gene Expression And Analysis Of Endogenous ACAT1 Proteins In Human Cells

Acyl-CoA: cholesterol acyltransferase (ACAT) is an intracellular enzyme presentin various eukaryotic cells and catalyzes the formation of cholesterol esters fromlong-chain fatty acyl coenzyme A and cholesterol. The ACAT1 that presents inmost tissues is believed to be critical for maintaining cholesterol homeostasis andinvolved in the developing atherosclerotic plaque. Dexamethasone (Dex), a kindof glucocorticoids, has been reported to increase incidence of atherosclerosis. Theformer results of Oil O staining indicate that Dex can markedly enhance the roleof OX-LDL in the induction of foam cells formation. The work of Western blotshows that Dex can up-regulate the expressions of ACAT1 proteins in THP-1 andits derived macrophages. Furthermore; luciferase gene reporter activity assayresults confirm that Dex enhances transcriptional activities of human ACAT1 genepromoters in THP-1. During the experiments two types of endogenous ACAT1protein with 50 kDa and 56 kDa sizes are detected in human monocyte(THP-1)-derived macrophages by Western blot analysis. Also Doubleimmunohistochemical and immunofluorescence staining assays proved that thesetwo proteins have the same subcellular locations. Our results from the detailedexperiments may serve evidences to explain the molecular mechanism onexpression regulation of human acyl-coenzyme A: cholesterol acyltransferase-1gene by Dex. These data may provide several fundamental clues to further studyon the role of ACAT in cholesterol homeostasis and atherosclerosis formation.