acyl-CoA:cholesterol Acyltransferase Inhibitor Research Articles

Discovery of a Potent and Orally Available Acyl-CoA: Cholesterol Acyltransferase Inhibitor as an Anti-atherosclerotic Agent: (4-Phenylcoumarin)acetanilide Derivatives

Acyl-CoA: cholesterol acyltransferase (ACAT) is an intracellular enzyme that catalyzes cholesterol esterification. ACAT inhibitors are expected to be potent therapeutic agents for the treatment of atherosclerosis. A series of potent ACAT inhibitors based on an (4-phenylcoumarin)acetanilide scaffold was identified. Evaluation of the structure-activity relationships of a substituent on this scaffold, with an emphasis on improving the pharmacokinetic profile led to the discovery of 2-[7-chloro-4-(3-chlorophenyl)-6-methyl-2-oxo-2H-chromen-3-yl]-N-[4-chloro-2-(trifluoromethyl)phenyl]acetamide (23), which exhibited potent ACAT inhibitory activity (IC50=12 nM) and good pharmacokinetic profile in mice. Compound 23 also showed regressive effects on atherosclerotic plaques in apolipoprotein (apo)E knock out (KO) mice at a dose of 0.3 mg/kg per os (p.o.).

Cholesterol Esterification During Differentiation by Hexamethylene Bisacetamide of Friend Virus-Induced Erythrokeukemia

AbstractCholesterol is an essential constituent of all mammalian cell membranes, and its availability is therefore a prerequisite for cellular growth and other functions. Several lines of evidence are now indicating an association between alterations of cholesterol homeostasis and cell cycle progression in cancer cells. However, the role of cholesterol in cell differentiation is still largely unknown. To begin to address this issue, in this study we examined changes in cholesterol metabolism and in the mRNA levels of proteins involved in cholesterol import and esterification (multi-drug resistance, MDR-3) and acylCoA:cholesterol acyltransferase (ACAT) and cholesterol export (caveolin-1) in Friend virus-induced erythroleukemia cells (MELC), in the absence or in the presence of the chemical inducer of differentiation, hexamethylene bisacetamide (HMBA). In uninduced MELC, cholesterol synthesis, esterification and MDR-3 and ACAT mRNAs increased as cells progressed from resting to proliferating phase, while caveolin-1 decreased. These results provide evidence that cholesterol esterification “per se” may have a role in cell division. When MELC are treated with HMBA, the reduction of DNA synthesis caused by the inducer is accompanied by an extensive decrease of cholesterol esterification and of ACAT and MDR-3 mRNA levels and by a significant increase in caveolin-1 mRNA. On the other hand, detection of cytoplasmic neutral lipids by staining MELC with oil-ORO, a dye able to evidence CE but not FC, revealed that HMBA-treatment inhibits cholesterol ester accumulation in MELC to approximately the same extent as the ACAT inhibitor, SaH. These results, other than, to add new insights on the possible role of cholesterol metabolism during tumor growth, for the first time indicate a possible involvement of cholesterol esterification pathways in the regulating of differentiation of erythroleukemic cells.

Acyl-coenzyme A: Cholesterol acyltransferase inhibitor Avasimibe affect survival and proliferation of glioma tumor cell lines

Glioblastoma is the most common primary brain tumor in adults and one of its hallmarks is resistance to apoptosis. Acyl-CoA: cholesterol acyltransferase (ACAT) is an intracellular membrane-bound enzyme that uses cholesterol and long chain fatty acyl-CoA as substrates to produce cholesteryl esters. The presence of cholesteryl esters in glioblastoma may be related to vascular and/or cell neoplastic proliferation in the tumor mass, two prerequisites for tumor cell growth. ACAT activity has been detected in glioblastoma cell homogenates. The present study is the first report on the effect of Avasimibe, a specific inhibitor of ACAT, on glioma cell lines (U87, A172, and GL261). Our results showed that Avasimibe inhibited ACAT-1 expression and cholesterol ester synthesis in glioma cell lines. Moreover, Avasimibe inhibited the growth of the cells by inducing cell cycle arrest and induced apoptosis as a result of caspase-8 and caspase-3 activation. Also, Our findings provide proof of principle that targeting ACAT-1 with the inhibitor Avasimibe could be an efficient therapy in the treatment of glioblastoma.

First identification of xanthone sulfonamides as potent acyl-CoA:cholesterol acyltransferase (ACAT) inhibitors

Inhibitors of acyl-CoA:cholesterol acyltransferase (ACAT) would be useful anti-atherogenic agents, since an absence of ACAT affects the absorption and transformation of cholesterol, indirectly resulting in the reduction of cholesteryl ester accumulation in blood vessels. This report discloses xanthone sulfonamides as novel class small molecule inhibitors of ACAT. A series of xanthone sulfonamides were synthesized and evaluated to result in the identification of several potent ACAT inhibitors, among which 2n proved to be more potent than the positive control Sandoz58-35. Moreover, a molecular model for the binding between 2n and the active site of ACAT-2 was provided based computational docking results.

Novel Tetrahydroisoquinoline Derivatives with Inhibitory Activities against Acyl-CoA: Cholesterol Acyltransferase and Lipid Peroxidation

To find a novel acyl-CoA: cholesterol acyltransferase (ACAT) inhibitor with anti-lipid peroxidative activity, a series of tetrahydroisoquinoline derivatives were synthesized and evaluated. A compound with a N-(4-hydroxy-2,3,5-trimethylphenyl)carbamoyl moiety at the 3-position and an octanoyl moiety at the 2-position (7) was demonstrated to show anti-foam cell formation activity stronger than and anti-lipid peroxidative activity comparable to those of Pactimibe, while it was hardly absorbed orally. To increase its bioavailability, the acyl chain at the 2-position was shortened and various polar or basic moieties were introduced at the 7-position of 7. Among the synthesized derivatives, (S)-7-dimethylamino-N-(4-hydroxy-2,3,5-trimethylphenyl)-2-isobutyryl-1,2,3,4-tetrahydroisoquinoline-3-carboxamide hydrochloride (21) showed about 16-fold stronger anti-foam cell formation activity, 3-fold stronger hepatic ACAT inhibitory activity, similar anti-low density lipoprotein (LDL) oxidative activity and 2-fold more potent protective activity against macrophage cell death by oxidative stress in comparison with Pactimibe. Compound 21 was efficiently absorbed after oral administration at 10 mg/kg in rats and dogs and its C(max) values were higher than its IC(50) values for in vitro activities. In conclusion, a tetrahydroisoquinoline structure is a useful scaffold for designing a phenolic anti-oxidative ACAT inhibitor, and compound 21 is expected to effectively prevent atherosclerosis.

Signaling through cholesterol esterification: a new pathway for the cholecystokinin 2 receptor involved in cell growth and invasion

Several studies indicate that cholesterol esterification is deregulated in cancers. The present study aimed to characterize the role of cholesterol esterification in proliferation and invasion of two tumor cells expressing an activated cholecystokinin 2 receptor (CCK2R). A significant increase in cholesterol esterification and activity of Acyl-CoA:cholesterol acyltransferase (ACAT) was measured in tumor cells expressing a constitutively activated oncogenic mutant of the CCK2R (CCK2R-E151A cells) compared with nontumor cells expressing the wild-type CCK2R (CCK2R-WT cells). Inhibition of cholesteryl ester formation and ACAT activity by Sah58-035, an inhibitor of ACAT, decreased by 34% and 73% CCK2R-E151A cell growth and invasion. Sustained activation of CCK2R-WT cells by gastrin increased cholesteryl ester production while addition of cholesteryl oleate to the culture medium of CCK2R-WT cells increased cell proliferation and invasion to a level close to that of CCK2R-E151A cells. In U87 glioma cells, a model of autocrine growth stimulation of the CCK2R, inhibition of cholesterol esterification and ACAT activity by Sah58-035 and two selective antagonists of the CCK2R significantly reduced cell proliferation and invasion. In both models, cholesteryl ester formation was found dependent on protein kinase zeta/ extracellular signal-related kinase 1/2 (PKCzeta/ERK1/2) activation. These results show that signaling through ACAT/cholesterol esterification is a novel pathway for the CCK2R that contributes to tumor cell proliferation and invasion.

Therapies on the horizon for cholesterol reduction.

Statins are powerful agents for the reduction of low-density lipoprotein cholesterol (LDL-C) and reduction of cardiovascular risk. Newly developed statins with increased potency, such as rosuvastatin (Crestor) and NK-104 (in earlier clinical development), are capable of achieving marked LDL-C reductions. Cholesterol-lowering agents with mechanisms of action distinct from those of the statins are in active development. These include bile transport inhibitors, such as improved bile acid-absorbing resins and specific inhibitors of the ileal Na+/bile acid cotransporter. There are also specific inhibitors of cholesterol absorption, such as ezetimibe, which may provide cholesterol lowering that is additive to that achieved with statin treatment. Another approach is to reduce cardiovascular risk by modifying atherosclerotic processes within the arterial wall, as represented by the acyl CoA:cholesterol acyltransferase (ACAT) inhibitor avasimibe; ACAT inhibitors may reduce atherosclerotic lesions by inhibiting macrophage cholesterol storage.

Novel indoline-based acyl-CoA: cholesterol acyltransferase inhibitor: Effects of introducing a methanesulfonamide group on physicochemical properties and biological activities

A novel series of indoline-based acyl-CoA: cholesterol acyltransferase (ACAT) inhibitors with a methanesulfonamide group at the 5-position were synthesized and their lipophilicity and biological activities were evaluated. Hepatic ACAT inhibitory and anti-foam cell formation activity increased dependent on lipophilicity of derivatives with various alkyl chains at the 1-position. The log D 7.0–biological activity curve of the derivatives with a methanesulfonamide group shifted leftward compared to that of Pactimibe derivatives with a carboxymethyl group, and derivatives with no substituent, suggesting that a methanesulfonamide group plays an important role in the interaction with ACAT protein. Among derivatives, N-(1-ethyl-5-methanesulfonylamino-4,6-dimethylindolin-7-yl)-2,2-dimethylpropanamide ( 1b) had about twofold lower log D 7.0 than Pactimibe, while it showed twofold higher hepatic ACAT inhibition than and the same anti-foam cell formation as Pactimibe, respectively. The C max of 1b (10 mg/kg, po) was higher than that of Pactimibe in rats. The plasma protein binding ratio of 1b was lower than that of Pactimibe: 64.8% and 97.9%, respectively. Compound 1b showed greater inhibitory effects on hepatic cholesterol secretion in mice than Pactimibe. In conclusion, the introduction of a methanesulfonamide group is effective to design less lipophilic, more efficacious and more bioavailable indoline-based ACAT inhibitors than previous indoline-based inhibitors.

Synthesis of a Novel Series of Imidazo[1,2-α]pyridines as Acyl-CoA: Cholesterol Acyltransferase (ACAT) Inhibitors

A novel series of imidazo[1,2-<TEX>$\alpha$</TEX>]pyridines was designed, synthesized, and tested for their ability to inhibit acyl- CoA:cholesterol acyltransferase. Preliminary lead optimization efforts resulted in the identification of ACAT inhibitors represented by analogues 5b, 5c, 6a, 6c, 7b, and 7c. The ACAT inhibitory activity of these compounds was further established by potent inhibition of cholesteryl ester formation in HepG2 cells by a representative analogue 7b.

Role of Cholesterol Pathways in Norovirus Replication

Norwalk virus (NV) is a prototype strain of the noroviruses (family Caliciviridae) that have emerged as major causes of acute gastroenteritis worldwide. I have developed NV replicon systems using reporter proteins such as a neomycin-resistant protein (NV replicon-bearing cells) and a green fluorescent protein (pNV-GFP) and demonstrated that these systems were excellent tools to study virus replication in cell culture. In the present study, I first performed DNA microarray analysis of the replicon-bearing cells to identify cellular factors associated with NV replication. The analysis demonstrated that genes in lipid (cholesterol) or carbohydrate metabolic pathways were significantly (P < 0.001) changed by the gene ontology analysis. Among genes in the cholesterol pathways, I found that mRNA levels of hydroxymethylglutaryl-coenzyme A (HMG-CoA) synthase, squalene epoxidase, and acyl-CoA:cholesterol acyltransferase (ACAT), ACAT2, small heterodimer partner, and low-density lipoprotein receptor (LDLR)-related proteins were significantly changed in the cells. I also found that the inhibition of cholesterol biosynthesis using statins (an HMG-CoA reductase inhibitor) significantly increased the levels of NV proteins and RNA, whereas inhibitors of ACAT significantly reduced the replication of NV in replicon-bearing cells. Up- or downregulation of virus replication with these agents significantly correlated with the mRNA level of LDLR in replicon-bearing cells. Finally, I found that the expression of LDLR promoted NV replication in trans by transfection study with pNV-GFP. I conclude that the cholesterol pathways such as LDLR expression and ACAT activity may be crucial in the replication of noroviruses in cells, which may provide potential therapeutic targets for viral infection.

Different kinetics of cholesterol delivery to components of the cholesterol homeostatic machinery: Implications for cholesterol trafficking to the endoplasmic reticulum

Previously, using an oxysterol to induce cholesterol trafficking to the Endoplasmic Reticulum (ER), we reported a dissociation between cholesterol transport to two important cholesterol regulatory components in the ER: the cholesterol esterifying enzyme ACAT (Acyl CoA:Cholesterol Acyltransferase) and the membrane-bound transcription factor SREBP (Sterol Regulatory Element Binding Protein) (X. Du, Y.H. Pham and A.J. Brown, Effects of 25-hydroxycholesterol on cholesterol esterification and SREBP processing are dissociable: implications for cholesterol movement to the regulatory pool in the endoplasmic reticulum, J. Biol Chem. 279 (2004) 47010–47016). Here, we employed low-density lipoprotein (LDL) as a more physiologically-relevant mode of cholesterol delivery, and compared cholesterol transport to ACAT (determined by esterification) and SREBP (assessed by processing) in mutant Chinese Hamster Ovary cells that have cholesterol-trafficking defects (including Niemann–Pick type C). We showed clear differences in kinetics between the two, with impaired cholesterol trafficking to SREBP being resolved more rapidly than to ACAT. This is unlikely to be due to a reduced threshold of cholesterol sensed by the SREBP system relative to ACAT, since both responded to LDL-derived cholesterol within 2 h whereas the divergence observed between the two was prolonged (> 20 h). Furthermore, ACAT inhibition did not expand the ER regulatory pool of cholesterol as judged by unaltered sensitivity of SREBP processing to LDL. Collectively, our data favor the contention that there are different cholesterol pools and/or transport pathways which feed ACAT and SREBP within the ER.

Microsomal Triglyceride Transfer Protein Enhances Cellular Cholesteryl Esterification by Relieving Product Inhibition

Cholesteryl ester synthesis by the acyl-CoA:cholesterol acyltransferase enzymes ACAT1 and ACAT2 is, in part, a cellular homeostatic mechanism to avoid toxicity associated with high free cholesterol levels. In hepatocytes and enterocytes, cholesteryl esters are secreted as part of apoB lipoproteins, the assembly of which is critically dependent on microsomal triglyceride transfer protein (MTP). Conditional genetic ablation of MTP reduces cholesteryl esters and enhances free cholesterol in the liver and intestine without diminishing ACAT1 and ACAT2 mRNA levels. As expected, increases in hepatic free cholesterol are associated with decreases in 3-hydroxy-3-methylglutaryl-CoA reductase and increases in ATP-binding cassette transporter 1 mRNA levels. Chemical inhibition of MTP also decreases esterification of cholesterol in Caco-2 and HepG2 cells. Conversely, coexpression of MTP and apoB in AC29 cells stably transfected with ACAT1 and ACAT2 increases cholesteryl ester synthesis. Liver and enterocyte microsomes from MTP-deficient animals synthesize lesser amounts of cholesteryl esters in vitro, but addition of purified MTP and low density lipoprotein corrects this deficiency. Enrichment of microsomes with cholesteryl esters also inhibits cholesterol ester synthesis. Thus, MTP enhances cellular cholesterol esterification by removing cholesteryl esters from their site of synthesis and depositing them into nascent apoB lipoproteins. Therefore, MTP plays a novel role in regulating cholesteryl ester biosynthesis in cells that produce lipoproteins. We speculate that non-lipoprotein-producing cells may use different mechanisms to alleviate product inhibition and modulate cholesteryl ester biosynthesis.

The new acyl‐CoA cholesterol acyltransferase inhibitor SMP‐797 does not interact with statins via OATP1B1 in human cryopreserved hepatocytes and oocytes expressing systems

It is possible that SMP-797 will be administered frequently in combination with statins to hyperlipidemic patients. OATP1B1 is thought to be the major transporter that mediates the hepatic uptake of statins. This study investigated whether SMP-797 interacts with statins via OATP1B1 by two approaches. Firstly, the effects of SMP-797 on OATP1B1-mediated uptake of estrone-3-sulfate (ES) by human hepatocytes and by oocytes expressing OATP1B1 were examined. Since OATP1B1-mediated uptake of ES is known to be biphasic (high- and low-affinity sites), concentrations of [(3)H]ES were set lower than the respective K(m) values. Two representative statins were used to assure that statins share OATP1B1 with [(3)H]ES in this in vitro system. Rosuvastatin inhibited OATP1B1-mediated uptake of [(3)H]ES through both sites and pravastatin inhibited a high-affinity site. The inhibition by the positive control (cyclosporin A) was significant. Thus, it is considered that this system was applicable to examine drug-drug interaction with statins on OATP1B1-mediated uptake. In this condition, no apparent inhibition to each site by SMP-797 was observed up to a concentration 3,000-fold higher than the clinical level. Secondly, the uptake of [(14)C]SMP-797 by oocytes expressing OATP1B1 was examined and the activity was negligible. In conclusion, these data suggest that SMP-797 has little potential to interact with statins on OATP1B1.

Discovery and Combinatorial Synthesis of Fungal Metabolites Beauveriolides, Novel Antiatherosclerotic Agents

For discovery of a new type of antiatherosclerotic agents, a cell-based assay of lipid droplet accumulation using primary mouse peritoneal macrophages was conducted as a model of macrophage-derived foam cell accumulation, which occurs in the early stage of atherosclerogenesis. During the screening of microbial metabolites for inhibitors of lipid droplet accumulation, 13-membered cyclodepsipeptides, known beauveriolide I and new beauveriolide III, were isolated from the culture broth of fungal Beauveria sp. FO-6979, a soil isolate, by solvent extraction, ODS column chromatography, silica gel column chromatography, and preparative HPLC. The structure including the absolute stereochemistry of beauveriolide III was elucidated as cyclo-[(3 S,4 S)-3-hydroxy-4-methyloctanoyl- l-phenylalanyl- l-alanyl- d-alloisoleucyl] by spectral analyses, amino acid analyses, and synthetic methods. Furthermore, the absolute stereochemistry was confirmed by the total synthesis of beauveriolides. Study on the mechanism of action revealed that beauveriolides inhibited macrophage acyl-CoA:cholesterol acyltransferase (ACAT) activity to block the synthesis of cholesteryl ester (CE), leading to a reduction of lipid droplets in macrophages. There are two ACAT isozymes in mammals, ACAT1 and ACAT2. ACAT1 is ubiquitously expressed in most tissues and cells including macrophages, while ACAT2 is expressed predominantly in the liver (hepatocytes) and the intestine (enterocytes). Interestingly, beauveriolides inhibited both ACAT1 and ACAT2 to a similar extent in an enzyme assay that utilized microsomes but inhibited ACAT1 selectively in intact cell-based assays. Beauveriolides proved orally active in both low-density lipoprotein receptor and apolipoprotein E knockout mice, reducing the atheroma lesion of heart and aorta without any side effects such as diarrhea or cytotoxicity to adrenal tissues as observed for many synthetic ACAT inhibitors. To obtain more potent inhibitors, a focused library of beauveriolide analogues was prepared by combinatorial chemistry in which solid-phase assembly of linear depsipeptides was carried out using a 2-chlorotrityl linker, followed by solution-phase cyclization, yielding 104 beauveriolide analogues. Among them, diphenyl derivatives were found to show 10 times more potent inhibition of CE synthesis in macrophages than beauveriolide III. Furthermore, most analogues showed selective ACAT1 inhibition or inhibition of both ACAT1 and ACAT2, but interestingly certain analogues gave selective ACAT2 inhibition. These data indicated that subtle structural differences of the inhibitors could discriminate the active sites of the ACAT1 and ACAT2 isozymes. Efforts of further analogue synthesis would make it possible to obtain highly selective ACAT1/ACAT2 inhibitors.

LDL Cholesteryl Oleate

Cholesteryl esters (CE) are synthesized by 2 enzymes, lecithin:cholesterol acyltransferase (LCAT) and acylCoA:cholesterol acyltransferase (ACAT). LCAT functions in the plasma and forms CE in HDL by transferring polyunsaturated fatty acid from phosphatidylcholine to cholesterol. ACAT, which functions intracellularly, uses fatty acid from acylCoA and forms CE enriched in monounsaturated fatty acid. Two isoforms of ACAT are expressed.1 ACAT1 is present in many tissues and produces the CE that are stored intracellularly, whereas ACAT2 is expressed in the intestine and liver and produces the CE that are secreted in chylomicrons and VLDL.2 See page 1396 In this issue of Arteriosclerosis, Thrombosis, and Vascular Biology , Bell et al report that ACAT2 gene deletion prevents hypercholesterolemia and atherosclerosis induced by diets containing 10% saturated or monounsaturated fat in a murine model of high LDL apoB100 only, LDL receptor-deleted (LDLr−/−) mice.3 These mice also had larger LDL particle size and hypertriglyceridemia. They attribute the protection of ACAT2 deficiency to a decrease in LDL particles enriched in CE derived from oleate (monounsaturated). When the diet contains large amounts of monounsaturated fats, ACAT2 activity appears to favor production of VLDL particles containing an excessive amount of cholesteryl oleate,4 and these monounsaturated CE remain associated with the lipoprotein particle when it undergoes conversion to LDL. These findings remind us that CE synthesized in the liver can be a source of CE for LDL, a fact that tends to be overlooked because of the current emphasis on the role of the reverse cholesterol transport pathway and cholesteryl ester transport protein (CETP) in supplying CE to VLDL and ultimately LDL. The Figure illustrates how LCAT, CETP, and ACAT2 function to supply monounsaturated and polyunsaturated CE that can accumulate in LDL. A schematic summary of the pathways that provide cholesteryl esters (CE) for incorporation …

3‐Heptylamino‐5‐Phenylpyridazine Derivatives as Analogues of Acyl‐CoA: Cholesterol Acyltransferase Inhibitors Containing the N‐Heptyl‐N′‐Arylureidic Moiety

A series of novel Acyl-CoA: cholesterol acyltransferase (ACAT) inhibitors 8a-f was synthesized; the substances were characterized by the presence of a 2,5-dimethylpyrazin-3-yl moiety at one end and a 3-heptylamino-5-phenylpyridazine system at the other one, linked through linear alkyl spacers of different length. The new derivatives were designed based on the hypothesis that the 3-amino-5-phenylpyridazine moiety could mimic the aryl substituted urea, which was present in a number of ACAT inhibitors previously described. The choice of the 2,5-dimethylpyrazin-3-yl substituent was supported by a preliminary investigation, which indicated that this moiety is the most powerful in conferring ACAT inhibitory properties to the new series. The pharmacological results proved the idea to be sound. Finally, compounds 9a-c, lacking the phenylpyridazine moiety were prepared and tested to further strengthen our hypothesis.

新規ACAT阻害剤SMP-797の薬物輸送トランスポーターOATP1B1を介したin vitro相互作用に関する検討

新規ACAT阻害剤SMP-797の薬物輸送トランスポーターOATP1B1を介したin vitro相互作用に関する検討

Direct Effect of F12511, A Systemic Inhibitor of Acyl-CoA Cholesterol Acyltransferase on Bovine Aortic Endothelial Cells

F12511(S)-2',3',5'-trimethyl-4'-hydroxy-alpha-dodecylthio-alpha-phenylacetanilide (F12511) is a new Acyl-CoA cholesterol acyltransferase (ACAT) inhibitor that not only reduces the plasma cholesterol levels but also has anti-atherosclerotic actions in animals models. The study's aim was to analyze if F12511 may directly modify the ability of tumor necrosis factor--alpha (TNF-alpha)-incubated bovine aortic endothelial cells (BAEC) to express endothelial nitric oxide synthase (eNOS) protein and inflammatory-related proteins such as platelet endothelial cell adhesion molecule (PECAM) and CD40 ligand (CD40L). The addition of increasing concentrations of F12511 (10 to 10 mol/L) failed to modify the level of eNOS protein expressed in control BAEC. TNF-alpha (10 ng/mL) reduced the expression of eNOS protein. In TNF-alpha--incubated BAEC, F12511 protected eNOS expression in a concentration-dependent manner. TNF-alpha stimulated the expression of both CD40L and PECAM in cultured BAEC. F12511 (10 mol/L) failed to modify the expression of CD40L and PECAM in control and TNF-alpha-incubated BAEC. Reverse transcriptase polymerase chain reaction showed a marked expression of the ACAT-2 isoform and absent of expression of the ACAT-1 isoform in BAEC. The presence of ACAT-2 isoform in BAEC was further confirmed by Western blot. F12511 failed to modify the expression of the proinflammatory associated proteins PECAM and CD40L in the endothelium but protected eNOS expression in the endothelial cells exposed to inflammatory conditions.

Novel Agents to Manage Dyslipidemias and Impact Atherosclerosis

Strong epidemiological evidence linked elevated levels of low-density lipoprotein cholesterol (LDL-C) to risk of atherosclerotic heart disease. As a consequence, LDL-C lowering has been the main goal of therapy to reduce cardiovascular risk for the past few decades and hydroxymethylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors (statins) have become some of the most commonly prescribed drugs. In spite of the proven efficacy of these drugs, statins reduce cardiovascular events by only 30-40%. Epidemiological analyses clearly indicate that a significant portion of risk is linked to other particles such as low high-density lipoprotein cholesterol (HDL-C), high triglycerides and others. Furthermore, several quantitative coronary angiography studies showing regression of atherosclerosis and reduction in subsequent events utilized a combination of drugs effective on LDL-C as well as other lipoproteins. Hence, several new drugs are being investigated that affect more than the traditional LDL-C pathways. In this article, we review lipoprotein-modifying agents that have either been recently released, or are still in various phases of development. They include agents that reduce LDL-C levels by mechanisms other than HMG-CoA inhibition (such as cholesterol absorption inhibitors, Acyl-CoA cholesterol acyl transferase inhibitors, sterol-regulating binding protein cleavage activating protein ligands, microsomal triglyceride transfer protein inhibitors, LDL-C receptor activators and farnesoid X receptor antagonists) and agents that raise HDL-C cholesterol or improve cholesterol efflux (such as cholesterol ester transfer protein inhibitors, retinoid X receptor selective agonists, specific peroxisome proliferator-activated receptor (PPAR) agonists and estrogen like compounds).

Intravascular ultrasound assessment of novel antiatherosclerotic therapies: Rationale and design of the Acyl-CoA:Cholesterol Acyltransferase Intravascular Atherosclerosis Treatment Evaluation (ACTIVATE) Study

Inhibiting the enzyme acyl-CoA:cholesterol acyltransferase (ACAT) has beneficial effects on foam cell formation and therefore has the potential to favorably influence the progression of coronary atherosclerosis. The aim of this study is to determine whether ACAT inhibition, when added to usual medical care, reduces atheroma progression in subjects with coronary artery disease. Five hundred thirty-four subjects with established coronary artery disease on angiography were randomized to receive the experimental ACAT inhibitor, pactimibe, 100 mg daily or matching placebo for 18 months. The primary efficacy parameter will be the nominal change in percent atheroma volume determined by analysis of pullback intravascular ultrasound (IVUS) images of matched coronary artery segments acquired at baseline and 18-month follow-up. In addition, the effect of pactimibe on plasma lipids and inflammatory markers and the incidence of clinical cardiovascular events will also be assessed. Serial IVUS has emerged as a sensitive imaging modality to assess the impact that novel antiatherosclerotic strategies have on the arterial wall. In this study, IVUS will be used to assess whether ACAT inhibition modifies progression of atherosclerotic plaque.