Abstract 1614: Neutral Cholesterol Ester Hydrolase is Essential for Cholesterol Removal in Human Macrophages and Atherosclerosis
Background: The hydrolysis of intracellular cholesterol ester (CE) is the key step in the reverse cholesterol transport (RCT) in macrophage foam cells, a hallmark of atherosclerosis. Neutral cholesterol ester hydrolase (NCEH) accounts for a large part of the neutral cholestol ester hydrolase (nCEH) activity in murine macrophages, but its contribution to human macrophages and atherosclerosis is unknown.
Methods and Results: We examined the expression of NCEH in human monocyte-derived macrophages (HMMs) and the effects of inhibition or overexpression of NCEH in the cholesterol trafficking. Substantial evidence supported that the nCEH activity in HMMs is mediated by NCEH.
Expression of NCEH protein and nCEH activity proportionally increased in a time-dependent manner during differentiation of cultured human monocytes into macrophages.
The pattern of subcellular distribution of NCEH in HMMs was similar to that of nCEH activity.
Overexpression of human NCEH resulted in 3.3-fold increase of nCEH activity. And the accumulation of CE in THP-1 macrophages loaded by acLDL was reduced by 55% as compared with control.
RNA silencing of NCEH reduced the amounts of NCEH protein in HMMs as compared with control by 44%.
In parallel, it decreased nCEH activity in HMMs as compared with control by 50%. In contrast, the involvement of hormone-sensitive lipase (HSL) in HMMs would be marginal because HSL was barely detectable in HMMs, and 76 – 0079, an HSL inhibitor, did not reduce the nCEH activity in HMMs. Cholesteryl ester hydrolase (CEH) is also unlikely to contribute to the activity, because its knockdown did not affect the nCEH activity in HMMs. Finally, we investigated the expression of NCEH in human aortas. We stained sections of aortas from 20 autopsy cases whose clinical characteristics are various. Atheromatous plaques were rich in cells positive for CD68 as well as NCEH-positive cells. NCEH was predominantly expressed in CD68-positive macrophages but not in smooth muscle cells. A majority of the CD68-positve cells were also positive for NCEH.
Conclusions: NCEH mediates the hydrolysis of CE in human macrophage foam cells, thereby contributing to the initial part of RCT in human atherosclerosis.