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A more recent version of this article appeared on October 1, 2003
Papers In Press, published online ahead of print July 1, 2003
J. Lipid Res., doi:10.1194/jlr.M300162-JLR200
Submitted on April 17, 2003
Revised on June 24, 2003
Accepted on June 25, 2003
Mobilization of cytoplasmic cholesteryl ester droplets by overexpression of human macrophage cholesterol ester hydrolase
Shobha Ghosh, Richard W. St. Clair, and Lawrence L. Rudel
Internal Medicine, Virginia Commonwealth University, Richmond, VA 23298-0050
Corresponding Author: shobha{at}hsc.vcu.edu
The obligatory first step for the removal of cholesterol from foam cells is the hydrolysis of stored cholesteryl esters (CE) to release free cholesterol (FC). Neutral cholesterol ester hydrolase (CEH) catalyzes this hydrolysis and limiting levels of CEH could play a role in determining the susceptibility to atherosclerosis. We have recently reported the first identification and cloning of a cDNA for human macrophage CEH. In the present study, we have directly assessed the functional properties of the cloned CEH in a cell system where known and reproducible amounts of CE accumulate as a result of constitutive over-expression of acyl CoA:cholesterol acyltransferase1 (ACAT1). We tested the hypothesis that systematically varied levels of over-expression of human macrophage CEH results in a proportional degree of reduction in cellular CE content. CEH expression was confirmed by demonstrating the presence of CEH mRNA and protein with an increase in CEH activity. A significant reduction in intracellular lipid droplets was observed in CEH-expressing cells together with the decrease in cellular CE mass. Consistent with the observed removal of intracellular CE, a two-fold increase in FC efflux was also observed in CEH-expressing cells. These results demonstrate that when human macrophage CEH is expressed in lipid-laden cells, hydrolysis and mobilization of cholesteryl esters (stored as cytoplasmic lipid droplets) occurs. These data establish the possibility that increased CE hydrolysis, mediated by CEH up regulation, could represent an important mechanism for foam cells to reduce their cholesterol burden.

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Copyright © 2003 by the American Society for Biochemistry and Molecular Biology.
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