Published online before print August 31, 2006, doi: 10.1161/01.ATV.0000243925.65265.3c
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© 2006 American Heart Association, Inc.
Atherosclerosis and Lipoproteins |
Cholesteryl Ester Transfer Protein Decreases High-Density Lipoprotein and Severely Aggravates Atherosclerosis in APOE*3-Leiden Mice
From The Netherlands Organization for Applied Scientific Research-Quality of Life (M.W., C.C.v.d.H., W.d.H., J.W.J., L.M.H., P.C.N.R.), Department of Biomedical Research, Gaubius Laboratory, CE Leiden, The Netherlands; Departments of General Internal Medicine, Endocrinology, and Metabolic Diseases (M.W., C.C.v.d.H., W.d.H., E.H.O., L.M.H., P.C.N.R.), and Cardiology (J.W.J.), Leiden University Medical Center, RC Leiden, The Netherlands; Laboratory of Vascular Medicine (G.M.D.-T.), Erasmus Medical Center, DR Rotterdam, The Netherlands.
Correspondence to Marit Westerterp, Leiden University Medical Center, Department Endocrinology and Metabolism, C4-R, P.O. Box 9600, 2300 RC Leiden, The Netherlands. E-mail M.Westerterp{at}lumc.nl
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Abstract |
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Objective— The role of cholesteryl ester transfer protein (CETP) in the development of atherosclerosis is still undergoing debate. Therefore, we evaluated the effect of human CETP expression on atherosclerosis in APOE*3-Leiden (E3L) mice with a humanized lipoprotein profile.
Methods and Results— E3L mice were crossbred with human CETP transgenic mice. On a chow diet, CETP expression increased plasma total cholesterol (TC) (+43%; P<0.05). To evaluate the effects of CETP on the development of atherosclerosis, mice were fed a Western-type diet containing 0.25% cholesterol, leading to 4.3-fold elevated TC levels in both E3L and CETP.E3L mice (P<0.01). On both diets, CETP expression shifted the distribution of cholesterol from high-density lipoprotein (HDL) toward very-low-density lipoprotein (VLDL)/low-density lipoprotein (LDL). Moreover, plasma of CETP.E3L mice had reduced capacity (–39%; P<0.05) to induce SR-BI–mediated cholesterol efflux from Fu5AH cells than plasma of E3L mice. After 19 weeks on the Western-type diet, CETP.E3L mice showed a 7.0-fold increased atherosclerotic lesion area in the aortic root compared with E3L mice (P<0.0001).
Conclusions— CETP expression in E3L mice shifts the distribution of cholesterol from HDL to VLDL/LDL, reduces plasma-mediated SR-BI–dependent cholesterol efflux, and represents a clear pro-atherogenic factor in E3L mice. We anticipate that the CETP.E3L mouse will be a valuable model for the preclinical evaluation of HDL-raising interventions on atherosclerosis development.
The effect of CETP on lipoprotein metabolism and atherosclerosis development was investigated in APOE*3-Leiden mice with a humanized lipoprotein profile. CETP expression shifted the distribution of cholesterol from HDL to VLDL/LDL, and severely aggravated atherosclerosis. The CETP·E3L mouse may be a valuable model for the preclinical evaluation of HDL-raising interventions on atherosclerosis development.
Key Words: CETP • cholesterol efflux • hyperlipidemia • reverse cholesterol transport • transgenic mice
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Introduction |
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Cardiovascular disease (CVD) is the leading cause of death in the Western world and its prevalence is increasing in Eastern Europe and developing countries.1 The main cause of CVD is atherosclerosis, characterized by the combination of chronic inflammation and/or hyperlipidemia.1 Both low high-density lipoprotein (HDL) cholesterol plasma levels and high very-low-density lipoprotein (VLDL)/low-density lipoprotein (LDL) cholesterol levels are independent risk factors for atherosclerosis development.2 The ratio of VLDL/LDL to HDL is to a great extent affected by the cholesteryl ester transfer protein (CETP).3
CETP is a transfer factor that mediates the exchange of cholesteryl esters (CE) and triglycerides (TG) between the apoB-containing lipoproteins (ie, chylomicrons, VLDL, and LDL) and HDL in plasma.3 As such, CETP may be anti-atherogenic by facilitating reverse cholesterol transport (RCT) from peripheral tissues to the liver via the VLDL/LDL pathway. Another potential role of CETP in RCT has recently been supported by the observation that CETP mediates HDL-CE uptake by hepatocytes independently of SR-BI and the LDL receptor (LDLr) in vitro.4 However, CETP may be pro-atherogenic by enhancing the levels of VLDL/LDL with concomitant reduction of anti-atherogenic HDL levels.
Many studies in humans have been performed regarding the association between CETP and lipoprotein levels and the subsequent development of CVD.5–9 For example, CETP deficiency that was observed in a Japanese population increased CVD despite increased HDL levels.8,9 In contrast, high CETP concentrations are associated with a faster atherosclerosis progression in men with proven CVD.6 This finding is corroborated by a correlation study in humans, which showed that the Taq1B polymorphism in CETP is associated with increased plasma CETP, decreased plasma HDL, and an increased progression of CVD.7 However, this might be confined to hypertriglyceridemic subjects as it has been shown in the prospective EPIC-Norfolk study that CETP correlated positively with future CVD risk only in humans with high TG levels (>1.7 mmol/L).5
Because the studies in humans have been associative and the effects of CETP expression on lipid metabolism and atherosclerosis gave conflicting results, the role of CETP has been addressed in mice that are naturally deficient for CETP.10 To evaluate the direct effect of CETP on atherosclerosis development, CETP transgenic mouse models have been generated11 and crossbred on different genetic backgrounds. CETP expression was found to be anti-atherogenic in APOC3 and lecithin:cholesterol acyltransferase (LCAT) transgenic mice.12,13 However, these mouse models may not be the preferred models for atherosclerosis studies because APOC3 and LCAT mice develop only very small atherosclerotic lesions.12,13
In contrast to APOC3 and LCAT mice, CETP was shown to be pro-atherogenic in apoe–/– and ldlr–/– mice.14 Because those mice exhibit both nearly complete blockage of the clearance of VLDL/LDL particles by the liver, it has been hypothesized that the cholesterol-rich particles that are formed as a result of CETP expression accumulate in the vessel wall of these mice.14 However, the suitability of these particular mouse models for evaluating the effect of CETP on atherosclerosis development may be limited as the potential effect of CETP in the facilitation of reverse cholesterol transport (RCT) from peripheral tissues to the liver via the VLDL/LDL pathway is expected to be largely reduced by apoE or LDLr deficiency. Furthermore, expression of CETP in apoe–/– mice resulted in unnaturally elevated TG levels.14 Finally, the CETP.APOB mouse has lipoprotein profiles on a chow diet comparable to normolipidemic humans,15 but does not develop atherosclerosis unless treated with a cholesterol-rich diet containing cholate,16 that, next to facilitating cholesterol absorption, induces chronic inflammation.17
In the present study, we crossbred the human CETP transgenic mouse11 with the APOE*3-Leiden (E3L) mouse.18 The E3L mouse expresses a mutation of the human APOE3 gene resulting in a slightly attenuated clearance of apoB-containing particles via the LDLr pathway.19 As a result, cholesterol and TG levels are only moderately increased on a chow diet.19 On a Western-type diet containing 0.25% cholesterol, these mice exhibit a more humanized lipoprotein cholesterol distribution.20 Its VLDL cholesterol levels are highly susceptible to cholesterol levels in the diet, whereas VLDL–TG levels decline to a normotriglyceridemic human level.20 In the present study, we thus aimed to investigate the effect of CETP on atherosclerosis development in this humanized mouse model.
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Methods |
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Animals and Diet
Human CETP transgenic mice expressing the human CETP gene under control of its natural flanking regions (strain 5203, heterozygous expression of CETP),11 were obtained from Jackson Laboratories (Bar Harbor, Me), and were crossbred with E3L mice,18 of which female mice were used for experiments. CETP.E3L and E3L mice were housed under standard conditions with a 12-hour light cycle (7:00 AM to 7:00 PM) and were fed ad libitum with regular chow. Blood samples were collected by tail vein bleeding 1 week before feeding the mice a Western-type diet (semi-synthetic cholesterol-rich diet, containing 15% [w/w] fat and 0.25% [w/w] cholesterol) (Diet W; Hope Farms, Woerden, The Netherlands) and every 4 weeks thereafter. Hereto, mice were fasted for 4 hours with food withdrawal at 9:00 AM as described previously.21 The experiments were approved by the institutional Ethical Committee on Animal Care and Experimentation.
Lipid and Lipoprotein Analysis
Plasma TC and TG levels were determined using enzymatic kits 236691 and 11488872 (Roche Molecular Biochemicals, Indianapolis, Ind), respectively. For determination of the lipid distribution over plasma lipoproteins by fast performance liquid chromatography, 50 µL of pooled plasma from 11 mice per group was injected onto a Superose 6 HR 10/30 column (Ákta System; Amersham Pharmacia Biotech, Piscataway, NJ) and eluted at a constant flow rate of 50 µL/min phosphate-buffered saline (PBS), 1 mmol/L EDTA (Sigma), pH 7.4. Fractions of 50 µL were collected and assayed for TC and TG using enzymatic assays (Roche Molecular Biochemicals). For the analysis of the apolipoprotein distribution, fractions of 50 µL were diluted 1:1 (v/v) in sample buffer (0.125 mol/L Tris, pH 6.8; 4% [wt/vol]) SDS, 20% [wt/vol] glycerol; 10% [v/v] ß-mercaptoethanol; 0.01% [wt/vol] bromophenol blue). Samples were then applied onto a 4% to 20% Tris Glycine precast polyacrylamide minigel (Gradipore Ltd, French Forest, Australia). Electrophoresis was performed according to manufacturer’s instructions. Protein bands were stained with Coomassie Brilliant Blue R250 (Sigma), and apparent molecular masses were identified.
CETP Activity and Protein Levels
CETP activity in plasma was measured as the transfer of [3H]cholesteryl oleate ([3H]CO) from exogenous LDL to HDL as described elsewhere.22 Hereto, 2.5 µL of plasma of animals on chow and 0.5 µL of plasma of animals on the Western-type diet was added as a CETP source, with and without a preceding precipitation of apoB-containing particles using sodium phosphotungstate in the presence of magnesium chloride.23 CETP activity was calculated as µmol CE transfer per mL plasma per hour. Plasma CETP mass was analyzed as described previously.24 In short, a 2-antibody sandwich immunoassay with a combination of the monoclonal antibodies TP1 and TP2 as coating was used. TP20 labeled with digoxigenin was used as secondary antibody.
Murine apoAI Enzyme-Linked Immunosorbent Assay
Plasma apoAI concentrations were determined using a sandwich enzyme-linked immunosorbent assay (ELISA). Hereto, goat–anti-mouse apoAI polyclonal antibody (ab7614; Abcam plc, Cambridge, UK; dilution 1:1000) was coated overnight onto Costar strips (Costar, Inc, New York, NY) (1 µg/mL) at 4°C and incubated with diluted mouse plasma (dilution 1:40400) for 2 hours at room temperature. Subsequently, rabbit–anti-mouse apoAI antibody (ab20453; Abcam; dilution 1:2000) was added and incubated for 1 hour at RT. Finally, horseradish peroxidase (HRP)-conjugated swine–anti-rabbit IgG antibody (SWARPO; dilution 1:2000) was added and incubated for 1 hour at RT. HRP was detected by incubation with tetramethylbenzidine (Organon Teknika, Boxtel, The Netherlands) for 15 minutes at room temperature. Purified mouse apoAI (A23100m; Biodesign International, Saco, Me) was used as a standard.
Cholesterol Efflux
The effect of macrophage CETP on lipid accumulation and cholesterol efflux was investigated using thioglycollate-elicited peritoneal macrophages from E3L and CETP.E3L mice. Macrophages were loaded with acetylated LDL (AcLDL) (50 µg/mL) and [3H]cholesterol (2 µCi/mL) for 48 hours and subsequently half of the cells was lysed to determine the [3H]cholesterol association related to cell protein.25 Cholesterol efflux for a period of 10 hours was assessed in the remainder of those cells, with and without human HDL (50 µg/mL) as a cholesterol acceptor.
The capacity of the plasma from mice fed the Western-type diet to induce ABCA1 dependent cholesterol efflux was determined using J774 murine macrophage-like cells. To induce cholesterol loading, J774 cells were incubated with AcLDL (50 µg/mL) and [3H]cholesterol (2 µCi/mL) for 48 hours. Subsequently, cells were incubated without and with 0.3 mmol/L 8-(4-chlorophenyl thio)adenosine 3':5'-cyclic monophosphate (cAMP analogue; Sigma) for 16 hours to induce ABCA1 expression. Then, J774 macrophages were incubated for 4 hours in the absence or presence of 1% of a plasma pool of 10 mice each. Human apoAI (10 µg/mL) and HDL (50 µg/mL) served as positive controls. The cAMP-dependent cholesterol efflux from J774 cells was considered the ABCA1-mediated efflux.26
The capacity of the plasma from mice fed the Western-type diet to induce SR-BI dependent cholesterol efflux was determined using Fu5AH rat hepatoma cells (generous gift from Dr N. Fournier, Chatenay-Malabry, France). First, cells were loaded with cholesterol (30 µg/mL) in the presence of [3H]cholesterol (2 µCi/mL) for 24 hours. Then, cholesterol laden Fu5AH cells were incubated for 4 hours in the absence or presence of 1% of a plasma pool of 10 mice each. Human apoAI (10 µg/mL) and HDL (50 µg/mL) served as positive controls. Cholesterol efflux was interpreted as the SR-BI–mediated efflux.27
Atherosclerosis Study and Atherosclerotic Lesion Analysis
At 8 weeks of age, CETP.E3L and E3L littermates were fed the Western-type diet. Mice were euthanized after 19 weeks of diet. Hearts were isolated and fixed in phosphate-buffered 4% formaldehyde, dehydrated and embedded in paraffin, and were cross-sectioned (5 µm) throughout the entire aortic root area. Per mouse, 4 sections with 40-µm intervals were used for quantification of atherosclerotic lesion area and characterization of lesion severity. Sections were routinely stained with hematoxylin-phloxine-saffron (HPS). Lesion area was determined using Leica Qwin image analysis software (EIS, Asbury, NJ). Atherosclerotic lesions were also categorized for severity, according to the American Heart System for humans,28 which we have adapted to categorize lesions in mice.29 Three types of categories were discerned: (1) no lesions (type 0); (2) early lesions were fatty streaks containing only foam cells (type 1 to 3); and (3) advanced lesions showing foam cells in the media and presence of fibrosis, cholesterol clefts, mineralization, and/or necrosis (type 4 to 5). The number observed in each category is expressed as a percentage of the total number of lesions present within one group of mice (CETP.E3L or E3L control group).
Statistical Analysis
All data are presented as means±SD. Statistical differences were assessed using the Mann-Whitney U test for all experiments, except for the typing of the atherosclerotic lesions, in which statistical differences were determined using the 
2 test. P<0.05 was regarded as statistically significant.
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Results |
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Effect of CETP Expression on Lipids and Lipoprotein Profiles on a Chow Diet and a Western-Type Diet
The effect of CETP expression on plasma parameters in E3L mice on a chow and a Western type diet are summarized in the Table. On a chow diet, CETP expression resulted in a CETP concentration of 6.2±3.3 µg/mL and activity of 0.25±0.05 µmol CE/mL per hour as measured in whole plasma. This CETP concentration is
3-fold higher than found in normolipidemic humans (ie, 1.8±0.6 µg/mL).30 Precipitation of apoB-containing lipoproteins before determination of CETP concentration and activity did not affect these values (results not shown), indicating that plasma CETP resided specifically on HDL. CETP expression increased plasma TC levels (+43%; P<0.05), and tended to increase plasma TG levels (+23%).
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As compared with the chow diet, the Western-type diet increased TC levels 4.3-fold (P<0.001), whereas TG levels decreased 60% (P<0.01), in both mouse groups (Table). Such a decrease in TG has been found consistently on feeding E3L mouse a Western-type diet,20,31,32 although the mechanism has not been elucidated yet. In CETP.E3L mice, the Western-type diet increased the plasma CETP concentration 11.7-fold (P<0.001) (Table), with a concomitant increase in plasma CETP activity of 4.4-fold (P<0.05). This led to increased TC levels (+43%; P<0.01) and a tendency to increased TG levels (+26%) in CETP.E3L as compared with E3L mice (Table).
Lipoprotein fractionation showed that CETP increased cholesterol in VLDL 2-fold and decreased cholesterol in regularly sized HDL (fractions 17 to 22) by 25% (Figure 1A). Likewise, the plasma apoAI content was reduced by 25% (P<0.05) (Figure 1D). In addition, the lipoprotein particle eluting in fractions 14 to 16 in E3L mice almost disappeared on CETP expression (Figure 1A). This particle was rich in apoE and did not contain apoAI (Figure 1B, 1C), and thus represented large apoE-rich HDL-1, consistent with previous observations.19 Therefore, CETP expression reduced the cholesterol content in total HDL 2-fold.
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Effect of CETP Expression in E3L Macrophages on Cholesterol Uptake and Cholesterol Efflux
To investigate whether macrophage-associated CETP affects the uptake of cholesterol, peritoneal macrophages were isolated from E3L and CETP.E3L mice and incubated with AcLDL and [3H]cholesterol. Macrophages from CETP.E3L mice showed no different cholesterol uptake as compared with those from E3L mice (Figure 2A). Also, CETP expression did not affect cholesterol efflux from macrophages using HDL as a cholesterol acceptor (Figure 2B). Taken together, CETP expression in macrophages did not affect either the uptake or efflux of cholesterol.
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Effect of CETP Expression on the Cholesterol-Accepting Capacity of Plasma
We determined the effect of plasma from E3L and CETP.E3L mice on cellular cholesterol efflux, either from cholesterol-laden cAMP analogue-treated J774 cells (representing ABCA1-mediated efflux)26 or from Fu5AH cells (representing SR-BI-mediated efflux).27
Cholesterol efflux from J774 cells was largely induced in the presence of apoAI, whereas HDL had no effect, which is consistent with ABCA1-mediated efflux (Figure 2C). The ABCA1-dependent cholesterol accepting potencies of plasma of E3L and CETP.E3L mice were similar (12%). Cholesterol efflux from Fu5AH cells was hardly induced on incubation with apoAI, yet largely induced on incubation with HDL, consistent with SR-BI–mediated efflux (Figure 2D). Plasma of CETP.E3L mice was 39% (P<0.05) less efficient in inducing SR-BI–mediated cholesterol efflux as compared with plasma of E3L mice (Figure 3D). Taken together, CETP expression reduced the potency of plasma to mediate SR-BI–dependent cholesterol efflux, without compromising the ABCA1-mediated cholesterol efflux.
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Effect of CETP Expression on Atherosclerosis Development
To investigate the effect of CETP on atherosclerosis development, mice were fed the Western-type diet from 8 weeks of age. In E3L mice, plasma cholesterol levels raised up to 16 mmol/L and in CETP.E3L mice to 23 mmol/L, which remained stable throughout the whole study (supplemental Figure I, available online at http://atvb.ahajournals.org). After 19 weeks of the Western-type diet, the development of atherosclerosis in E3L mice was still in the early phase because a lot of segments were either unaffected (type 0) or contained foam cell-rich lesions (type 1 to 3) (Figure 3A, 3B). In contrast, CETP.E3L mice developed much more advanced lesions that affected the integrity of the media, contained cholesterol clefts, and showed calcification (type 4 to 5) (Figure 3A, 3B). The much more advanced atherosclerosis in CETP.E3L mice was reflected in a 7.0-fold increase in atherosclerotic lesion area (Figure 3C). Collectively, CETP represents a clear pro-atherogenic factor in E3L mice.
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Discussion |
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The role of CETP in atherosclerosis is still undergoing debate.5–9,12–14 In the present study, the effect of CETP expression on atherosclerosis development was evaluated in E3L mice, a mouse model with a more humanized cholesterol distribution over lipoproteins. We found that CETP expression led to a net shift of cholesterol from HDL toward VLDL, resulting in 2-fold increased VLDL cholesterol plasma levels and 2-fold decreased HDL cholesterol levels. This led to a reduced capacity of the plasma to induce SR-BI–mediated cholesterol efflux, yet did not affect ABCA1-mediated cholesterol efflux. Furthermore, CETP expression resulted in much more advanced atherosclerotic lesions and a 7.0-fold increase in atherosclerotic lesion area in E3L mice.
CETP permits bidirectional transfer between apoB-containing lipoproteins and HDL, resulting in net flux of TG from VLDL and LDL to HDL, and net flux of cholesterol from HDL to VLDL and LDL.33 Because apoE3-Leiden has a reduced affinity for the hepatic LDLr as compared with wild-type apoE, E3L mice have increased VLDL cholesterol.19 CETP expression in E3L mice caused an additional increase in VLDL cholesterol, probably by increasing the net cholesterol flux from HDL to VLDL,33 thereby further impeding VLDL clearance. Furthermore, CETP expression in E3L mice reduced HDL levels. Next to a 25% decrease in HDL-2 and HDL-3, as reflected by a decrease in both apoAI and cholesterol in these HDL subpopulations, CETP expression resulted in disappearance of apoAI-deficient and apoE-rich HDL-1, which is present in E3L mice.19 Likewise, CETP expression has been shown to eliminate HDL-1 that accumulates in LCAT transgenic mice.12 Apparently, HDL-1 is a preferential substrate for CETP. This hypothesis is corroborated by the finding that HDL-1 accumulates in CETP-deficient humans.8,9 The CETP-induced reduction in HDL may be explained by: (1) reduced lipidation of HDL apolipoproteins, resulting in enhanced renal clearance of lipid-poor apoAI; (2) enrichment of HDL in TG, resulting in a more efficient hepatic lipase (HL)-mediated HDL catabolism;34 and/or (3) direct uptake of HDL–CE by liver-associated CETP, as has recently been proposed by Gauthier et al.4
On a chow diet, the CETP concentration in CETP.E3L mice was 3-fold higher than in human plasma.30 On the Western-type diet, plasma CETP activity and mass were 4-fold and 12-fold increased, respectively, as compared with the chow diet. This indicates that inactive CETP accumulated on HDL on a Western-type via an as yet unidentified mechanism. The observation that a cholesterol-rich diet leads to CETP accumulation in plasma is consistent with previous observations in apoE-deficient and LDLr-deficient mice.35 Also in humans, a positive correlation between plasma lipid levels and plasma CETP concentration was found.30 In addition, CETP activity was found to correlate with CETP concentration in both normolipidemic humans and hyperlipidemic humans.30 In line with hyperlipidemic versus normolipidemic CETP.E3L mice, also a higher level of inactive CETP was found in hyperlipidemic versus normolipidemic humans.30 Regulation of CETP expression involves an liver X receptor-response element36 that is present in the natural flanking regions of the human CETP transgenic mouse strain that we used for crossbreeding with E3L mice.11 Most likely, the cholesterol diet-induced hypercholesterolemia thus results in increased hepatic cholesterol as well as oxysterols, the natural ligands for the liver X receptor,37 thereby increasing CETP expression, as reflected by increased plasma CETP levels. A similar mechanism may explain the positive correlation between plasma cholesterol and CETP levels in humans.
In previous studies in E3L mice, VLDL cholesterol has been found to correlate well with atherosclerotic lesion area, most probably by initiating atherosclerosis on entry of VLDL into the vascular wall.19 Specifically, feeding E3L mice a high-cholesterol diet as compared with a low-cholesterol diet resulted in 2-fold increased VLDL cholesterol levels and a 2-fold increased atherosclerotic lesion area.38 We now observed that a similar 2-fold increase in VLDL cholesterol levels as induced by the introduction of CETP in E3L mice caused even a 7.0-fold increase in atherosclerotic lesion area. This cannot simply be explained by a CETP-mediated increase in VLDL, and suggests that other mechanisms are involved in this process, which may include a local effect of CETP on lipid accumulation in macrophages and/or the observed reduction in HDL.
We found that the expression of CETP in macrophages did not affect AcLDL-induced foam cell formation or cholesterol efflux to human HDL. This is in contrast with findings in a monkey fibroblast cell line (COS-7), which showed that transfection with a CETP construct induces cholesterol efflux.39 This seeming discrepancy may be caused by a difference in CETP expression. However, it is thus unlikely that CETP expression in macrophages contributed to the observed increased atherosclerosis development by affecting the cellular lipid homeostasis.
Alternatively, CETP may affect RCT by reducing plasma levels of HDL, which is crucially involved in RCT. The first step in this process is cholesterol efflux from the macrophage, as mediated by ABCA1 and SR-BI. The shift of plasma cholesterol from HDL to VLDL as induced by CETP expression did not affect ABCA1-mediated cholesterol efflux yet reduced SR-BI-mediated efflux. It has been shown that small lipid-poor HDL has the strongest association with ABCA1-mediated cholesterol efflux, even in the presence of other HDL subpopulations.40 Regarding the HDL cholesterol distribution, CETP.E3L mice mostly express small HDL, probably as a consequence of HDL remodeling by CETP. Apparently, the difference in levels of small HDL particles between plasma from CETP.E3L and E3L mice is not sufficient to affect ABCA1-mediated cholesterol efflux. The observation that CETP expression does not compromise ABCA1-mediated cholesterol efflux to HDL is in agreement with data from a previous study in rabbits treated with a CETP-inhibitor.41
Whereas CETP expression did not affect ABCA1-mediated efflux, it decreased the SR-BI-mediated cholesterol efflux. As different HDL subpopulations contribute equally to SR-BI–mediated cholesterol efflux,40 and total HDL levels were lower in the plasma of CETP.E3L mice (especially HDL-1), this can thus easily explain the reduced SR-BI efflux. Nevertheless, ABCA1 and SR-BI do not constitute all the pathways that mediate cholesterol efflux from macrophages.42 ABCG1 also mediates cholesterol efflux, and has been shown to be highly functional in inducing cholesterol efflux to HDL from CETP-deficient subjects.43 Because ABCG1 and SR-BI both use HDL as cholesterol acceptor,40,43 an additional effect of the CETP-induced lipoprotein shift on ABCG1-mediated efflux cannot be ruled out. Finally, it may be postulated that VLDL contributes to cholesterol efflux, similarly as has been documented for LDL.44 However, even if VLDL contributes to cholesterol efflux, plasma from CETP.E3L mice showed a decreased SR-BI–mediated cholesterol efflux despite higher VLDL levels.
It remains to be elucidated whether CETP-induced reduced HDL will be rate-limiting for integrated RCT in vivo, ie, the transport of cholesterol from macrophages to the liver, leading to fecal secretion. A recent study has demonstrated that CETP inhibition in rabbits does not affect the clearance of HDL cholesterol,45 and we have obtained initial data that CETP expression does not affect HDL–CE turnover in E3L mice (unpublished). However, our observations that CETP expression in E3L mice reduced cholesterol efflux in vitro, and strongly increased atherosclerosis in vivo, suggest that CETP reduced RCT in E3L mice.
Collectively, we have now shown that CETP is a clear pro-atherogenic factor in E3L mice. Because CETP also appeared pro-atherogenic in apoe–/– and ldlr–/– mice,14 CETP thus seems to be consistently pro-atherogenic in the context of reduced hepatic uptake of apoB-containing lipoproteins, at least partly by further increasing the levels of cholesterol-rich VLDL. In contrast, CETP is anti-atherogenic in APOC3 and LCAT transgenic mice.12,13 APOC3 mice accumulate particularly TG-rich VLDL as a result of LPL inhibition, enabling a massive flux of TG from apoB-containing lipoproteins to HDL,46 which may result in an accelerated clearance of TG-rich HDL particles via HL. As a consequence, smaller, cholesterol-poor HDL particles are formed,46 which may have higher anti-atherogenic potential by more efficiently inducing cholesterol efflux. LCAT transgenic mice accumulate apoE-rich HDL-1, that is not efficiently cleared by the liver and therefore are more susceptible to atherosclerosis.12 CETP expression in LCAT mice provides an extra pathway of delivering HDL cholesterol to the liver, resulting in normalization of the HDL particle size12 and presumably increasing its cholesterol-accepting potency.
The E3L mouse model has been proven very suitable for testing hypolipidemic drugs that affect VLDL/LDL metabolism.19,47 Atorvastatin,47 rosuvastatin,48 and gemfibrozil49 reduced the levels of the VLDL/LDL in E3L mice comparable to humans. As the introduction of CETP results in the potential to modulate HDL cholesterol levels in addition to VLDL cholesterol levels, we anticipate that the CETP.E3L mouse will be suitable for the preclinical evaluation of HDL-increasing therapies (including CETP inhibitors), which constitute a novel target in the treatment of cardiovascular disease.
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Acknowledgments |
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We thank L.C. van der Zee-van Vark for excellent technical assistance.
Sources of Funding
This work was performed in the framework of the Leiden Center for Cardiovascular Research LUMC-TNO, and supported by the Leiden University Medical Center (Gisela Thier Fellowship to P.C.N.R.), the Netherlands Organization for Scientific Research (NWO grant 908-02-097 and NWO VIDI grant 917.36.351 to P.C.N.R.; NWO grant 903-39-291 to L.M.H.), the Netherlands Heart Foundation (NHS grant 2003B136 to P.C.N.R.), and the Center for Medical Systems Biology (project 115 to L.M.H.). J.W.J. is an established clinical investigator of the Netherlands Heart Foundation (2001D032).
Disclosures
None.
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Footnotes |
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M.W. and C.C.d.v.H. contributed equally to this work.
Original received June 1, 2006; final version accepted August 16, 2006.
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References |
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1. Hansson GK. Mechanisms of disease—inflammation, atherosclerosis, and coronary artery disease. N Engl J Med. 2005; 352: 1685–1695.
2. Glass CK, Witztum JL. Atherosclerosis: the road ahead. Cell. 2001; 104: 503–516.[CrossRef][Medline] [Order article via Infotrieve]
3. Ha YC, Calvert GD, Mcintosh GH, Barter PJ. A physiologic role for the esterified cholesterol transfer protein—in vivo studies in rabbits and pigs. Metabolism-Clin Exp. 1981; 30: 380–383.
4. Gauthier A, Lau P, Zha XH, Milne R, McPherson R. Cholesteryl ester transfer protein directly mediates selective uptake of high density lipoprotein cholesteryl esters by the liver. Arterioscler Thromb Vasc Biol. 2005; 25: 2177–2184.
5. Boekholdt SM, Kuivenhoven JA, Wareham NJ, Peters RJG, Jukema JW, Luben R et al. Plasma levels of cholesteryl ester transfer protein and the risk of future coronary artery disease in apparently healthy men and women—The prospective EPIC (European Prospective Investigation into Cancer and Nutrition)—Norfolk population study. Circulation. 2004; 110: 1418–1423.
6. Klerkx AHEM, de Grooth GJ, Zwinderman AH, Jukema JW, Kuivenhoven JA, Kastelein JJP. Cholesteryl ester transfer protein concentration is associated with progression of atherosclerosis and response to pravastatin in men with coronary artery disease (REGRESS). Eur J Clin Invest. 2004; 34: 21–28.[CrossRef][Medline] [Order article via Infotrieve]
7. Kuivenhoven JA, Jukema JW, Zwinderman AH, de Knijff P, McPherson R, Bruschke AV, Lie KI, Kastelein JJ. The role of a common variant of the cholesteryl ester transfer protein gene in the progression of coronary atherosclerosis. The Regression Growth Evaluation Statin Study Group. N Engl J Med. 1998; 338: 86–93.
8. Nagano M, Yamashita S, Hirano K, Takano M, Maruyama T, Ishihara M, Sagehashi Y, Kujiraoka T, Tanaka K, Hattori H, Sakai N, Nakajima N, Egashira T, Matsuzawa Y. Molecular mechanisms of cholesteryl ester transfer protein deficiency in Japanese. J Atheroscler Thromb. 2004; 11: 110–121.[Medline] [Order article via Infotrieve]
9. Zhong SB, Sharp DS, Grove JS, Bruce C, Yano K, Curb JD, Tall AR. Increased coronary heart disease in Japanese-Am men with mutation in the cholesteryl ester transfer protein gene despite increased HDL levels. J Clin Invest. 1996; 97: 2917–2923.[Medline] [Order article via Infotrieve]
10. Jiao S, Cole TG, Kitchens RT, Pfleger B, Schonfeld G. Genetic heterogeneity of lipoproteins in inbred strains of mice: analysis by gel-permeation chromatography. Metabolism. 1990; 39: 155–160.[CrossRef][Medline] [Order article via Infotrieve]
11. Jiang XC, Agellon LB, Walsh A, Breslow JL, Tall A. Dietary-cholesterol increases transcription of the human cholesteryl ester transfer protein gene in transgenic mice—dependence on natural flanking sequences. J Clin Invest. 1992; 90: 1290–1295.[Medline] [Order article via Infotrieve]
12. Foger B, Chase M, Amar MJ, Vaisman BL, Shamburek RD, Paigen B, Fruchart-Najib J, Paiz JA, Koch CA, Hoyt RF, Brewer HB Jr, Santamarina-Fojo S. Cholesteryl ester transfer protein corrects dysfunctional high density lipoproteins and reduces aortic atherosclerosis in lecithin cholesterol acyltransferase transgenic mice. J Biol Chem. 1999; 274: 36912–36920.
13. Hayek T, Masuccimagoulas L, Jiang X, Walsh A, Rubin E, Breslow JL, Tall AR. Decreased early atherosclerotic lesions in hypertriglyceridemic mice expressing cholesteryl ester transfer protein transgene. J Clin Invest. 1995; 96: 2071–2074.[Medline] [Order article via Infotrieve]
14. Plump AS, Masucci-Magoulas L, Bruce C, Bisgaier CL, Breslow JL, Tall AR. Increased atherosclerosis in apoE and LDL receptor gene knock-out mice as a result of human cholesteryl ester transfer protein transgene expression. Arterioscler Thromb Vasc Biol. 1999; 19: 1105–1110.
15. Grass DS, Saini U, Felkner RH, Wallace RE, Lago WJP, Young SG, Swanson ME. Transgenic mice expressing both human apolipoprotein-B and human CETP have a lipoprotein cholesterol distribution similar to that of normolipidemic humans. J Lipid Res. 1995; 36: 1082–1091.[Abstract]
16. Zuckerman SH, Evans GF, Schelm JA, Eacho PI, Sandusky G. Estrogen-mediated increases in LDL cholesterol and foam cell-containing lesions in human ApoB100xCETP transgenic mice. Arterioscler Thromb Vasc Biol. 1999; 19: 1476–1483.
17. Getz GS, Reardon CA. Diet and murine atherosclerosis. Arterioscler Thromb Vasc Biol. 2006; 26: 242–249.
18. Vandenmaagdenberg AMJM, Hofker MH, Krimpenfort PJA, Debruijn I, Vanvlijmen B, Vanderboom H, Havekes LM, Frants RR. Transgenic mice carrying the apolipoprotein-E3-Leiden gene exhibit hyperlipoproteinemia. J Biol Chem. 1993; 268: 10540–10545.
19. Vanvlijmen BJM, Vandenmaagdenberg AMJM, Gijbels MJJ, Vanderboom H, Hogenesch H, Frants RR, Hofker MH, Havekes LM. Diet-induced hyperlipoproteinemia and atherosclerosis in apolipoprotein E3 Leiden transgenic mice. J Clin Invest. 1994; 93: 1403–1410.[Medline] [Order article via Infotrieve]
20. Vanvlijmen BJM, vanDijk KW, vantHof HB, vanGorp PJJ, vanderZee A, Vanderboom H, Breuer ML, Hofker MH, Havekes LM. In the absence of endogenous mouse apolipoprotein E, apolipoprotein E*2(Arg-158->Cys) transgenic mice develop more severe hyperlipoproteinemia than apolipoprotein E*3-Leiden transgenic mice. J Biol Chem. 1996; 271: 30595–30602.
21. Berbee JFP, van der Hoogt CC, Sundararaman D, Havekes LM, Rensen PCN. Severe hypertriglyceridemia in human APOC1 transgenic mice is caused by apoC-I-induced inhibition of LPL. J Lipid Res. 2005; 46: 297–306.
22. Speijer H, Groener JEM, Vanramshorst E, Vantol A. Different locations of cholesteryl ester transfer protein and phospholipid transfer protein activities in plasma. Atherosclerosis. 1991; 90: 159–168.[CrossRef][Medline] [Order article via Infotrieve]
23. Burstein M, Morfin R. [Precipitation of alpha lipoproteins in serum by sodium phosphotungstate in the presence of magnesium chloride]. Life Sci. 1969; 8: 345–348.[CrossRef][Medline] [Order article via Infotrieve]
24. Niemeijer-Kanters SDJM, Dallinga-Thie GM, Ruijter-Heijstek FC, Algra A, Erkelens DW, Banga JD, Jansen H. Effect of intensive lipid-lowering strategy on low-density lipoprotein particle size in patients with type 2 diabetes mellitus. Atherosclerosis. 2001; 156: 209–216.[CrossRef][Medline] [Order article via Infotrieve]
25. Lowry OH, Rosebrough NJ, Farr AL, Randall RJ. Protein measurement with the folin phenol reagent. J Biol Chem. 1951; 193: 265–275.
26. Fournier N, Atger V, Paul JL, Sturm M, Duverger N, Rothblat GH, Moatti N. Human ApoA-IV overexpression in transgenic mice induces cAMP-stimulated cholesterol efflux from J774 macrophages to whole serum. Arterioscler Thromb Vasc Biol. 2000; 20: 1283–1292.
27. Ji Y, Jian B, Wang N, Sun Y, Moya MDLL, Phillips MC, Rothblat GH, Swaney JB, Tall AR. Scavenger receptor BI promotes high density lipoprotein-mediated cellular cholesterol efflux. J Biol Chem. 1997; 272: 20982–20985.
28. Stary HC, Chandler AB, Dinsmore RE, Fuster V, Glagov S, Insull W, Rosenfeld ME, Schwartz CJ, Wagner WD, Wissler RW. A definition of advanced types of atherosclerotic lesions and a histological classification of atherosclerosis—a report from the committee on vascular-lesions of the Council on Arteriosclerosis, American Heart Association. Circulation. 1995; 92: 1355–1374.
29. Gijbels MJJ, van der Cammen M, van der Laan LJW, Emeis JJ, Havekes LM, Hofker MH, Kraal G. Progression and regression of atherosclerosis in APOE3-Leiden transgenic mice: an immunohistochemical study. Atherosclerosis. 1999; 143: 15–25.[CrossRef][Medline] [Order article via Infotrieve]
30. McPherson R, Mann CJ, Tall AR, Hogue M, Martin L, Milne RW, Marcel YL. Plasma concentrations of cholesteryl ester transfer protein in hyperlipoproteinemia. Relation to cholesteryl ester transfer protein activity and other lipoprotein variables. Arterioscler Thromb. 1991; 11: 797–804.
31. Groot PHE, Vanvlijmen BJM, Benson GM, Hofker MH, Schiffelers R, Vidgeonhart M, Havekes LM. Quantitative assessment of aortic atherosclerosis in APOE*3 Leiden transgenic mice and its relationship to serum cholesterol exposure. Arterioscler Thromb Vasc Biol. 1996; 16: 926–933.
32. vanVlijmen BJ, vanDijk KW, vantHof BH, vanGorp PJ, vanderZee A, Vanderboom H, Breuer ML, Hofker MH, Havekes LM. APOE*2(158) transgenic mice develop a more severe hyperlipoproteinemic phenotype than APOE*3-Leiden transgenic mice. Circulation. 1996; 94: 3032.
33. Tall AR. Plasma cholesteryl ester transfer protein. J Lipid Res. 1993; 34: 1255–1274.[Medline] [Order article via Infotrieve]
34. ApplebaumBowden D, Kobayashi J, Kashyap VS, Brown DR, Berard A, Meyn S, Parrott C, Maeda N, Shamburek R, Brewer HB, SantamarinaFojo S. Hepatic lipase gene therapy in hepatic lipase-deficient mice—adenovirus-mediated replacement of a lipolytic enzyme to the vascular endothelium. J Clin Invest. 1996; 97: 799–805.[Medline] [Order article via Infotrieve]
35. Masuccimagoulas L, Plump A, Jiang XC, Walsh A, Breslow JL, Tall AR. Profound induction of hepatic cholesteryl ester transfer protein transgene expression in apolipoprotein E and low density lipoprotein receptor gene knockout mice—a novel mechanism signals changes in plasma cholesterol levels. J Clin Invest. 1996; 97: 154–161.[Medline] [Order article via Infotrieve]
36. Luo Y, Tall AR. Sterol upregulation of human CETP expression in vitro and in transgenic mice by an LXR element. J Clin Invest. 2000; 105: 513–520.[Medline] [Order article via Infotrieve]
37. Janowski BA, Willy PJ, Devi TR, Falck JR, Mangelsdorf DJ. An oxysterol signalling pathway mediated by the nuclear receptor LXR alpha. Nature. 1996; 383: 728–731.[CrossRef][Medline] [Order article via Infotrieve]
38. Kleemann R, Princen HMG, Emeis JJ, Jukema JW, Fontijn RD, Horrevoets AJG, Kooistra T, Havekes LM. Rosuvastatin reduces atherosclerosis development beyond and independent of its plasma cholesterol-lowering effect in APOE*3-Leiden transgenic mice - Evidence for antiinflammatory effects of rosuvastatin. Circulation. 2003; 108: 1368–1374.
39. Zhang ZY, Yamashita S, Hirano K, Nakagawa-Toyama Y, Matsuyama A, Nishida M, Sakai N, Fukusawa M, Arai H, Mijagawa J, Matsuzawa Y. Expression of cholesteryl ester transfer protein in human atherosclerotic lesions and its implication in reverse cholesterol transport. Atherosclerosis. 2001; 159: 67–75.[CrossRef][Medline] [Order article via Infotrieve]
40. Asztalos BF, Llera-Moya M, Dallal GE, Horvath KV, Schaefer EJ, Rothblat GH. Differential effects of HDL subpopulations on cellular ABCA1- and SR-BI-mediated cholesterol efflux. J Lipid Res. 2005; 46: 2246–2253.
41. Kobayashi J, Okamoto H, Otabe M, Bujo H, Saito Y. Effect of HDL, from Japanese white rabbit administered a new cholesteryl ester transfer protein inhibitor JTT-705, on cholesteryl ester accumulation induced by acetylated low density lipoprotein in J774 macrophage. Atherosclerosis. 2002; 162: 131–135.[CrossRef][Medline] [Order article via Infotrieve]
42. Duong M, Collins HL, Jin WJ, Zanotti I, Favari E, Rothblat GH. Relative contributions of ABCA1 and SR-BI to cholesterol efflux to serum from fibroblasts and macrophages. Arterioscler Thromb Vasc Biol. 2006; 26: 541–547.
43. Matsuura F, Wang N, Chen WG, Jiang XC, Tall AR. HDL from CETP-deficient subjects shows enhanced ability to promote cholesterol efflux from macrophages in an apoE- and ABCG1-dependent pathway. J Clin Invest. 2006; 116: 1435–1442.[CrossRef][Medline] [Order article via Infotrieve]
44. Wang N, Lan DB, Chen WG, Matsuura F, Tall AR. ATP-binding cassette transporters G1 and G4 mediate cellular cholesterol efflux to high-density lipoproteins. Proc Natl Acad Sci U S A. 2004; 101: 9774–9779.
45. Kee P, Caiazza D, Rye KA, Barrett PHR, Morehouse LA, Barter PJ. Effect of inhibiting cholesteryl ester transfer protein on the kinetics of high-density lipoprotein cholesteryl ester transport in plasma - In vivo studies in rabbits. Arterioscler Thromb Vasc Biol. 2006; 26: 884–890.
46. Hayek T, Azrolan N, Verdery RB, Walsh A, Chajekshaul T, Agellon LB, Tall AR, Bresolw JL. Hypertriglyceridemia and cholesteryl ester transfer protein interact to dramatically alter high-density-lipoprotein levels, particle sizes, and metabolism—studies in transgenic mice. J Clin Invest. 1993; 92: 1143–1152.[Medline] [Order article via Infotrieve]
47. Delsing DJ, Jukema JW, van de Wiel MA, Emeis JJ, van der LA, Havekes LM, Princen HM. Differential effects of amlodipine and atorvastatin treatment and their combination on atherosclerosis in ApoE*3-Leiden transgenic mice. J Cardiovasc Pharmacol. 2003; 42: 63–70.[CrossRef][Medline] [Order article via Infotrieve]
48. Delsing DJM, Post SM, Groenendijk M, Solaas K, Van der Boom H, van Duyvenvoorde W, De Wit ECM, Bloks VW, Kuipers F, Havekes LM, Princen HM. Rosuvastatin reduces plasma lipids by inhibiting VLDL production and enhancing hepatobiliary lipid excretion in ApoE*3-Leiden mice. J Cardiovasc Pharmacol. 2005; 45: 53–60.[CrossRef][Medline] [Order article via Infotrieve]
49. van Vlijmen BJM, Pearce NJ, Bergo M, Staels B, Yates JW, Gribble AD, Bond BC, Hofker MH, Havekes LM, Groot PHE. Apolipoprotein E*3 Leiden transgenic mice as a test model for hypolipidaemic drugs. Arzneimittel-Forschung-Drug Res. 1998; 48: 396–402.
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