The Critical Role of Neutral Cholesterol Ester Hydrolase 1 in Cholesterol Removal From Human Macrophages

Abstract

Rationale: Hydrolysis of intracellular cholesterol ester (CE) is the key step in the reverse cholesterol transport in macrophage foam cells. We have recently shown that neutral cholesterol ester hydrolase (Nceh)1 and hormone-sensitive lipase (Lipe) are key regulators of this process in mouse macrophages. However, it remains unknown which enzyme is critical in human macrophages and atherosclerosis.Objective: We aimed to identify the enzyme responsible for the CE hydrolysis in human macrophages and to determine its expression in human atherosclerosis. Methods and Results:We compared the expression of NCEH1, LIPE, and cholesterol ester hydrolase (CES1) in human monocyte-derived macrophages (HMMs) and examined the effects of inhibition or overexpression of each enzyme in the cholesterol trafficking. The pattern of expression of NCEH1 was similar to that of neutral CE hydrolase activity during the differentiation of HMMs. Overexpression of human NCEH1 increased the hydrolysis of CE, thereby stimulating cholesterol mobilization from THP-1 macrophages. Knockdown of NCEH1 specifically reduced the neutral CE hydrolase activity. Pharmacological inhibition of NCEH1 also increased the cellular CE in HMMs. In contrast, LIPE was barely detectable in HMMs, and its inhibition did not decrease neutral CE hydrolase activity. Neither overexpression nor knockdown of CES1 affected the neutral CE hydrolase activity. NCEH1 was expressed in CD68-positive macrophage foam cells of human atherosclerotic lesions. A therosclerotic cardiovascular diseases are the leading cause of mortality in industrialized countries, despite advances in the management of coronary risk factors. Heart attacks arise from the thrombotic occlusion of coronary arteries following the rupture of plaques. Lipid-rich plaques, which are characterized by a plethora of cholesterol ester (CE)-laden macrophage foam cells, are prone to rupture. 1 Esterification of cholesterol in macrophages is mediated by acyl-coenzyme A cholesterol acyltransferase 1 or sterol Oacyltransferase 1 (SOAT1). 2 Conflicting results have been reported as to the effects of genetic ablation of SOAT1 on atherosclerosis in mice. 3,4 Furthermore, it has not been successful to demonstrate the efficacy of nonselective inhibitors of SOAT to clinically prevent the atherosclerosis in humans. 5,6 On the other hand, the hydrolysis of intracellular CE is the initial step of reverse cholesterol transport. 7 As the hydrolysis of CE preceding reverse cholesterol transport takes place at neutral pH, the enzymes catalyzing it have been collectively called neutral CE hydrolases. Because this step is rate-limiting, particularly in macrophage foam cells, 8,9 it is important to clarify the mechanisms that mediate the hydrolysis of CE in foam cells. Conclusions: NCEH1 is expressed in human atheromatousTo date, 3 enzymes have been proposed to serve as neutral CE hydrolases in macrophages: hormone-sensitive lipase (LIPE) 10 ; cholesteryl ester hydrolase (CEH), 11 which is identical to human liver carboxylesterase 1 ...

Differential lipid metabolism in monocytes and macrophages: influence of cholesterol loading

“…3B ). Recent fi ndings show that NCEH1 is the enzyme primarily involved in the hydrolysis of CE in human macrophages, and the contribution of CES1 is lower ( 45 ). Future experiments should address the differences in the activity of the specifi c CE hydrolases between monocytes and macrophages.…”

Depot-Specific Expression of Lipolytic Genes in Human Adipose Tissues

“…C D E because 76-0079, a LIPE inhibitor, which is used to inhibit LIPE in PNPLA2-deficient adipocyes, also inhibits p-nitrophenyl butyrate (PNPB) hydrolase activity of human CES1 39) . The role of CES1 in lipolysis was further supported by the significantly positive correlation of its expression with cytosolic TG lipase activities in the subcutaneous and mesenteric fat ( Table 4).…”

Absence of Nceh1 augments 25-hydroxycholesterol-induced ER stress and apoptosis in macrophages

“…We have recently reported that disruption of Nceh1 promotes the formation of foam cells and accelerates the development of atherosclerosis in mice lacking either Apoe or LDL receptor ( Ldlr ) ( 9 ). In humans, NCEH1 plays a more critical role in cholesterol removal from monocyte-derived macrophages ( 10 ). Ultimately, however, accumulating evidence has suggested that reverse cholesterol transport is only one of a number of diverse functions of macrophages in atherogenesis ( 11 ).…”