N-3 but not N-6 fatty acids reduce the expression of the combined adhesion and scavenger receptor CD36 in human monocytic cells

Hepatic macrophage mediated immune response in liver steatosis driven carcinogenesis

Obesity confers an independent risk for carcinogenesis. Classically viewed as a genetic disease, owing to the discovery of tumor suppressors and oncogenes, genetic events alone are not sufficient to explain the progression and development of cancers. Tumor development is often associated with metabolic and immunological changes. In particular, obesity is found to significantly increase the mortality rate of liver cancer. As its role is not defined, a fundamental question is whether and how metabolic changes drive the development of cancer. In this review, we will dissect the current literature demonstrating that liver lipid dysfunction is a critical component driving the progression of cancer. We will discuss the involvement of inflammation in lipid dysfunction driven liver cancer development with a focus on the involvement of liver macrophages. We will first discuss the association of steatosis with liver cancer. This will be followed with a literature summary demonstrating the importance of inflammation and particularly macrophages in the progression of liver steatosis and highlighting the evidence that macrophages and macrophage produced inflammatory mediators are critical for liver cancer development. We will then discuss the specific inflammatory mediators and their roles in steatosis driven liver cancer development. Finally, we will summarize the molecular pattern (PAMP and DAMP) as well as lipid particle signals that are involved in the activation, infiltration and reprogramming of liver macrophages. We will also discuss some of the therapies that may interfere with lipid metabolism and also affect liver cancer development.

Targeting Foam Cell Formation in Atherosclerosis: Therapeutic Potential of Natural Products

Foam cell formation and further accumulation in the subendothelial space of the vascular wall is a hallmark of atherosclerotic lesions. Targeting foam cell formation in the atherosclerotic lesions can be a promising approach to treat and prevent atherosclerosis. The formation of foam cells is determined by the balanced effects of three major interrelated biologic processes, including lipid uptake, cholesterol esterification, and cholesterol efflux. Natural products are a promising source for new lead structures. Multiple natural products and pharmaceutical agents can inhibit foam cell formation and thus exhibit antiatherosclerotic capacity by suppressing lipid uptake, cholesterol esterification, and/or promoting cholesterol ester hydrolysis and cholesterol efflux. This review summarizes recent findings on these three biologic processes and natural products with demonstrated potential to target such processes. Discussed also are potential future directions for studying the mechanisms of foam cell formation and the development of foam cell-targeted therapeutic strategies.

Lowering the n-6/n-3 PUFAs ratio inhibits the formation of THP-1 macrophage-derived foam cell

Background

The balance between n-6 and n-3 PUFAs is an important determinant in the risk for cardiovascular disease. The study was to investigate the influence of the n-6 and n-3 PUFAs ratio on the formation of THP-1 monocyte-derived foam cells and explore the probable mechanism of anti-atherosclerosis.

Methods

THP-1 monocyte cells were cultured with PMA and ox-LDL to establish a foam-cell model, while treated with different ratios of n-6 to n-3 PUFAs for 48 h. The cholesterol of foam cells was measured by a cholesterol assay kit. The levels of IL-6 and TNFα in supernatant were detected with ELISA methods. The expressions of CD36, ABCA1, ACAT1, PPARγ and LXRα mRNA were detected with real-time PCR.

Results

Compared with the foam cell model group, the low and middle ratio of n-6 to n-3 PUFAs groups decreased the intracellular concentration of cholesterol (P < 0.01), but the high n-6/n-3 PUFAs ratio did not. Fatty acids decreased the level of IL-6 and TNFα in supernatant in a ratio-dependent manner. Fatty acids treatment also decreased the expressions of CD36、ACTA1、PPARγ、LXRα mRNA in a ratio-dependent manner.

Conclusions

Lowering the ratios of n-6 to n-3 PUFAs can decrease the secretion of inflammatory cytokines then reduce the expressions of CD36 and ACAT1 mRNA. As well, it can decrease the expressions of CD36 mRNA through the PPARγ pathway. This leads to less cholesterol ingestion into the cells and decreased synthesis of cholesteryl ester, which inhibits the formation of the foam cells, further preventing the occurrence and development of atherosclerosis.

Omega-3 fatty acids attenuate constitutive and insulin-induced CD36 expression through a suppression of PPARα/γ activity in microvascular endothelial cells

Microvascular dysfunction occurs in insulin resistance and/or hyperinsulinaemia. Enhanced uptake of free fatty acids (FFA) and oxidised low-density lipoproteins (oxLDL) may lead to oxidative stress and microvascular dysfunction interacting with CD36, a PPARα/γ-regulated scavenger receptor and long-chain FFA transporter. We investigated CD36 expression and CD36-mediated oxLDL uptake before and after insulin treatment in human dermal microvascular endothelial cells (HMVECs), ± different types of fatty acids (FA), including palmitic, oleic, linoleic, arachidonic, eicosapentaenoic (EPA), and docosahexaenoic (DHA) acids. Insulin (10−8 and 10−7 M) time-dependently increased DiI-oxLDL uptake and CD36 surface expression (by 30 ± 13%, p<0.05 vs. untreated control after 24 hours incubation), as assessed by ELISA and flow cytometry, an effect that was potentiated by the PI3-kinase inhibitor wortmannin and reverted by the ERK1/2 inhibitor PD98059 and the PPARα/γ antagonist GW9662. A ≥24 hour exposure to 50 μM DHA or EPA, but not other FA, blunted both the constitutive (by 23 ± 3% and 29 ± 2%, respectively, p<0.05 for both) and insulin-induced CD36 expressions (by 45 ± 27 % and 12 ± 3 %, respectively, p<0.05 for both), along with insulin-induced uptake of DiI-oxLDL and the downregulation of phosphorylated endothelial nitric oxide synthase (P-eNOS). At gel shift assays, DHA reverted insulin-induced basal and oxLDL-stimulated transactivation of PPRE and DNA binding of PPARα/γ and NF-κB. In conclusion, omega-3 fatty acids blunt the increased CD36 expression and activity promoted by high concentrations of insulin. Such mechanisms may be the basis for the use of omega-3 fatty acids in diabetic microvasculopathy.

Circulating CD36+ microparticles are not altered by docosahexaenoic or eicosapentaenoic acid supplementation

BACKGROUND AND AIMS

Circulating microparticles (MP) are the source of a plasma derived form of the scavenger receptor CD36, termed soluble (s)CD36, the levels of which correlate with markers of atherosclerosis and risk of cardiovascular disease. Long chain n-3 polyunsaturated fatty acids have cardioprotective effects that we have previously reported to be gender specific. The aim of this study was to determine if dietary docosahexaenoic acid (DHA) and/or eicosapentaenoic acid (EPA) supplementation affect circulating CD36 + MP levels, and if this occurs differentially in healthy men and women.

METHODS AND RESULTS

Participants (43M, 51F) aged 39.6 ± 1.7 years received 4 weeks of daily supplementation with DHA rich (200 mg EPA; 1000 mg DHA), EPA rich (1000 mg EPA; 200 mg DHA), or placebo (sunola) oil in a double-blinded, randomised, placebo controlled trial. Plasma CD36 + MP were enumerated by flow cytometry and differences between genders and treatments were evaluated by Student's or paired t-test and one way ANOVA. Males and females had similar levels of CD36 + MP at baseline (mean = 1018 ± 325 vs 980 ± 318; p = 0.577) and these were not significantly changed after DHA (M, p = 0.571; F, p = 0.444) or EPA (M, p = 0.361; F, p = 0.901) supplementation. Likewise, the overall percent change in these levels were not different between supplemented cohorts compared to placebo when all participants were combined (% change in CD36 + MP: DHA = 5.7 ± 37.5, EPA = -3.4 ± 35.4, placebo = -11.5 ± 32.9; p = 0.158) or stratified by gender (M, DHA = -2.6 ± 30.6, EPA = -15.1 ± 20.1, placebo = -21.4 ± 28.7, p = 0.187; F, DHA = 11.7 ± 41.5, EPA = 6.8 ± 42.9, placebo = -2.8 ± 34.7, p = 0.552).

CONCLUSION

The cardioprotective effects of DHA and EPA do not act through a CD36 + MP mechanism.

Possible Involvement of Palmitate in Pathogenesis of Periodontitis

Type 2 diabetes (T2D) is characterized by decreased insulin sensitivity and higher concentrations of free fatty acids (FFAs) in plasma. Among FFAs, saturated fatty acids (SFAs), such as palmitate, have been suggested to promote inflammatory responses. Although many epidemiological studies have shown a link between periodontitis and T2D, little is known about the clinical significance of SFAs in periodontitis. In this study, we showed that gingival fibroblasts have cell-surface expression of CD36, which is also known as FAT/fatty acid translocase. Moreover, CD36 expression was increased in gingival fibroblasts of high-fat diet-induced T2D model mice, compared with gingival fibroblasts of mice fed a normal diet. DNA microarray analysis revealed that palmitate increased mRNA expression of pro-inflammatory cytokines and chemokines in human gingival fibroblasts (HGF). Consistent with these results, we confirmed that palmitate-induced interleukin (IL)-6, IL-8, and CXCL1 secretion in HGF, using a cytokine array and ELISA. SFAs, but not an unsaturated fatty acid, oleate, induced IL-8 production. Docosahexaenoic acid (DHA), which is one of the omega-3 polyunsaturated fatty acids, significantly suppressed palmitate-induced IL-6 and IL-8 production. Treatment of HGF with a CD36 inhibitor also inhibited palmitate-induced pro-inflammatory responses. Finally, we demonstrated that Porphyromonas gingivalis (P.g.) lipopolysaccharide and heat-killed P.g. augmented palmitate-induced chemokine secretion in HGF. These results suggest a potential link between SFAs in plasma and the pathogenesis of periodontitis.

Combining eicosapentaenoic acid, decosahexaenoic acid and arachidonic acid, using a fully crossed design, affect gene expression and eicosanoid secretion in salmon head kidney cells in vitro

Future feed for farmed fish are based on untraditional feed ingredients, which will change nutrient profiles compared to traditional feed based on marine ingredients. To understand the impact of oils from different sources on fish health, n-6 and n-3 polyunsaturated fatty acids (PUFAs) were added to salmon head kidney cells, in a fully crossed design, to monitor their individual and combined effects on gene expression. Exposing salmon head kidney cells to single fatty acids, arachidonic acid (AA) or decosahexaenoic acid (DHA), resulted in down-regulation of cell signaling pathway genes and specific fatty acid metabolism genes as well as reduced prostaglandin E2 (PGE2) secretion. Eicosapentaenoic acid (EPA) had no impact on gene transcription in this study, but reduced the cell secretion of PGE2. The combined effect of AA + EPA resulted in up-regulation of eicosanoid pathway genes and the pro-inflammatory cytokine, tumor necrosis factor alpha (TNF-α), Bclx (an inducer of apoptosis) and fatty acid translocase (CD36) as well as increased cell secretion of PGE2 into the media. Adding single fatty acids to salmon head kidney cells decreased inflammation markers in this model. The combination AA + EPA acted differently than the rest of the fatty acid combinations by increasing the inflammation markers in these cells. The concentration of fatty acid used in this experiment did not induce any lipid peroxidation responses.

Insight into the mechanism of lipids binding and uptake by CD36 receptor

The membrane protein CD36 is a member of the class B scavenger receptor family. It plays a crucial role in some cardiovascular pathologies and metabolic diseases. Studying the mechanism of action of CD36 receptor is limited due to the absence of its tridimensional crystallized structure. The molecular docking method has allowed us to perform various simulation of the CD36 receptor interaction with their ligands involved in the development of some diseases. In this work, we predicted a tridimensional structure model of CD36 extracellular domain. In addition, we have achieved several tests of rigid and flexible docking by acting on residues proposed in previous experimental researches as essential in fixing of LFCAs. Furthermore, we have acted on regions that appear a key binding site of LFCAs. The physicoc hemical evaluation indicated the reliability of the proposed CD36 structure used for different molecular docking tests. Based on the docking outcome, we were able to propose the different steps of the mechanism allowing the interaction of fatty acids on CD36 receptor and their penetration into the cell cytoplasm. The obtained results and taking in consideration CD36 receptor as a therapeutic target will help us to suggest the mechanism by which an antagonist may inhibit this receptor by acting on its extracellular domain.

Compare the effect of eicosapentaenoic acid and oxidized low-density lipoprotein on the expression of CD36 and peroxisome proliferator-activated receptor gamma

BACKGROUND

There is evidence that CD36 promotes foam cell formation through internalizing oxidized LDL (ox-LDL) into macrophages; therefore, it plays a key role in pathogenesis of atherosclerosis. In addition, CD36 expression seems to be mediated by nuclear receptor peroxisome proliferator-activated receptor gamma (PPAR-γ). The aim of the present study was to evaluate and compare the effect of PPAR-γ ligands, eicosapentaenoic acid (EPA) as an anti-atherogenic factor and ox-LDL as an atherogenic factor on CD36 expression. Mechanism of PPAR- γ action and its ligands in CD36 expression were also investigated.

METHODS

Raw 264.7 macrophage cell line was treated with ox-LDL (100 and 150 μg protein/LDL) and EPA (100 and 200 μM) for 24 and 48 hours in absence or presence of PPAR-γ inhibitor, T0070907. Quantitative real-time PCR and Western-blotting were used for analysis of gene and protein expression, respectively.

RESULTS

Raw 264.7 exposures to ox-LDL and EPA resulted in increased expression of CD36 mRNA and protein; however, mRNA and PPAR-γ protein were not up-regulated significantly. Pre-incubation of cells with T0070907 led to decreased expression of CD36 when treated with ox-LDL and EPA.

CONCLUSION

It was confirmed that both EPA and ox-LDL increased CD36 expression but not PPAR-γ, and also co-treatment with PPAR-γ inhibitor decreased CD36 expression. We concluded that up-regulation of CD36 depends on PPAR-γ activation and is not related to increased expression of PPAR-γ. Induction of CD36 by EPA showed that CD36 suppression is not the means by which ω-3 fatty acids (EPA) provide protection against formation of atherosclerotic plaque.

Polyunsaturated fatty acids and modulation of cholesterol homeostasis in THP-1 macrophage-derived foam cells

Transformation of macrophages to foam cells is determined by the rates of cholesterol uptake and efflux. This study uses a real time RT-PCR technique to investigate the role of conjugated linoleic acid (CLA), α-linolenic acid (ALA) and eicosapentaenoic acid (EPA) in the regulation of the ATP-binding cassette A1 (ABCA1) and liver X receptor α (LXR) genes, which are involved in cholesterol homeostasis. Accordingly, these fatty acids significantly reduced the total, free and esterified cholesterols within the foam cells. While the expression of the ABCA1 and LXRα genes was increased in the presence of the pharmacological LXRα ligand, T0901317, their mRNA expression was not significantly affected by CLA, ALA and EPA. These results suggest that although polyunsaturated fatty acids have an effect on cholesterol homeostasis, they cannot change the expression of the ABCA1 and LXRα genes. Alternatively, several other genes and proteins may be involved.

Fish-oil supplementation induces antiinflammatory gene expression profiles in human blood mononuclear cells

BACKGROUND

Polyunsaturated fatty acids can have beneficial effects on human immune cells, such as peripheral blood mononuclear cells (PBMCs). However, the mechanisms of action of polyunsaturated fatty acids on immune cells are still largely unknown.

OBJECTIVE

The objective was to examine the effects of supplementation with the polyunsaturated fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) on whole-genome PBMC gene expression profiles, in healthy Dutch elderly subjects participating in a double-blind trial, by using whole-genome transcriptomics analysis.

DESIGN

The subjects were randomly allocated to 1 of 3 groups: 1) consumption of 1.8 g EPA+DHA/d (n = 36), 2) consumption of 0.4 g EPA+DHA/d (n = 37), or 3) consumption of 4.0 g high-oleic acid sunflower oil (HOSF)/d (n = 38). All supplements were given in capsules. Before and after 26 wk of intervention, blood samples were collected. Microarray analysis was performed on PBMC RNA from 23 subjects who received 1.8 g EPA+DHA/d and 25 subjects who received HOSF capsules. Quantitative real-time polymerase chain reaction was performed in all 111 subjects.

RESULTS

A high EPA+DHA intake changed the expression of 1040 genes, whereas HOSF intake changed the expression of only 298 genes. EPA+DHA intake resulted in a decreased expression of genes involved in inflammatory- and atherogenic-related pathways, such as nuclear transcription factor kappaB signaling, eicosanoid synthesis, scavenger receptor activity, adipogenesis, and hypoxia signaling.

CONCLUSION

These results are the first to show that intake of EPA+DHA for 26 wk can alter the gene expression profiles of PBMCs to a more antiinflammatory and antiatherogenic status. This trial was registered at clinicaltrials.gov as NCT00124852.

Omega-3 fatty acid effects on biochemical indices following cancer surgery

Epidemiological studies have indicated that a high intake of saturated fat and/or animal fat increases the risk of colon and breast cancer. Laboratory and clinical investigations have shown a reduced risk of colon carcinogenesis after alimentation with omega-3 fatty acids, as found in fish oil. Mechanisms accounting for these anti-tumor effects are reduced levels of PGE(2) and inducible NO synthase as well as an increased lipid peroxidation, or translation inhibition with subsequent cell cycle arrest. Further, omega-3 eicosapentaenoic acid is capable of down-regulating the production and effect of a number of mediators of cachexia, such as IL-1, IL-6, TNF-alpha and proteolysis-inducing factor. In patients with advanced cancer, it is possible to increase energy and protein intake via an enteral or parenteral route, but this seems to have little impact on progressive weight loss. Fish oil administration improved patients' conditions in cancer cachexia and during radio- and chemotherapy. In patients undergoing tumor resection surgery we observed improvement of liver and pancreas biochemical indices when omega-3 fatty acids were administered. This paper is a review of recent developments in the field of nutrition in cancer patients with emphasis on the acute phase response following cancer surgery and the beneficial aspects of fish oil administration.

Linoleic acid increases lectin-like oxidized LDL receptor-1 (LOX-1) expression in human aortic endothelial cells

Results from in vitro studies suggest that selected fatty acids, and especially linoleic acid (LA), can elicit endothelial dysfunction (ED). Because LA is increased in all LDL subfractions in patients with type 2 diabetes, this alteration may contribute to ED associated with diabetes. Lectin-like oxidized LDL receptor-1 (LOX-1) is the major endothelial receptor for oxidized LDL (oxLDL), and uptake of oxLDL through LOX-1 induces ED. To evaluate whether LA may contribute to the upregulation of endothelial LOX-1 in diabetes, we studied the effect of LA on LOX-1 expression in cultured human aortic endothelial cells (HAECs). Treatment of HAECs with LA increased, in a time- and dose-dependent manner, endothelial LOX-1 protein expression. Pretreatment of HAECs with antioxidants and inhibitors of NADPH oxidase, protein kinase C (PKC), and nuclear factor-kappaB (NF-kappaB) inhibited the stimulatory effect of LA on LOX-1 protein expression. Furthermore, in LA-treated HAECs, increased expression of classic PKC isoforms was observed. LA also led to a significant increase in LOX-1 gene expression and enhanced the binding of nuclear proteins extracted from HAECs to the NF-kappaB regulatory element of the LOX-1 gene promoter. Finally, LA enhanced, through LOX-1, oxLDL uptake by endothelial cells. Overall, these results demonstrate that LA enhances endothelial LOX-1 expression through oxidative stress-sensitive and PKC-dependent pathways. This effect seems to be exerted at the transcriptional level and to involve the activation of NF-kappaB. Upregulation of LOX-1 by LA may contribute to ED associated with type 2 diabetes.

Conjugated linoleic acid and atherosclerosis: no effect on molecular markers of cholesterol homeostasis in THP-1 macrophages

Macrophage cholesterol homeostasis is a key process involved in the initiation and progression of atherosclerosis. Peroxisome proliferator-activated receptors (PPARs) regulate the transcription of the genes involved in cholesterol homeostasis and thus represent an important therapeutic target in terms of reducing atherosclerosis. Conjugated linoleic acid (CLA) is a potent anti-atherogenic dietary fatty acid in animal models of atherosclerosis and is capable of activating PPARs in vitro and in vivo. Therefore, this study examined whether the anti-atherogenic effects of CLA in vivo could be ascribed to altered cholesterol homeostasis in macrophages and macrophage derived foam cells. Of several genes that regulate cholesterol homeostasis investigated, CLA had most effect on the class B scavenger receptor CD36. The cis-9,trans-11 CLA (c9,t11-CLA) and trans-10,cis-12 CLA (t10,c12-CLA) isomers augmented CD36 mRNA expression (P<0.001). Confocal laser microscopy characterised the three-dimensional expression patterns of CD36 in THP-1 macrophages. Linoleic acid, CLA and the PPARgamma ligand rosiglitazone increased discrete cell surface CD36 localisation, with a heterogeneous punctate pattern of expression. In agreement with the observed increases in CD36 mRNA and cell surface expression, intracellular cholesterol concentrations were greater in macrophages exposed to linoleic acid and CLA. Further analysis of cholesterol metabolism showed that CLA had no effect on THP-1 derived foam cell cholesterol efflux to apo AI. Thus, altered cholesterol homeostasis in the macrophage may not explain the anti-atherogenic effects of CLA observed in vivo.

Fatty acids and the immune system: from basic science to clinical applications

Over the last 25 years, the effects of fatty acids on the immune system have been characterized using in vitro, animal and human studies. Advances in fatty acid biochemistry and molecular techniques have recently suggested new mechanisms by which fatty acids could potentially modify immune responses, including modification of the organization of cellular lipids and interaction with nuclear receptors. Possibilities for the clinical applications of n-3 PUFA are now developing. The present review focuses on the hypothesis that the anti-inflammatory properties of n-3 PUFA in the arterial wall may contribute to the protective effects of n-3 PUFA in CVD, as suggested by epidemiological and secondary prevention studies. Studies are just beginning to show that dietary n-3 PUFA can be incorporated into plaque lipid in human subjects, where they may influence the morphology and stability of the atherosclerotic lesion.

Fatty acids modulate the effect of darglitazone on macrophage CD36 expression

BACKGROUND

Scavenger receptor-mediated uptake of cholesterol by macrophages in the arterial wall is believed to be proatherogenic. Thiazolidinediones are peroxisome proliferator-activated receptor gamma (PPARgamma)-agonists, which are used in the treatment of type II diabetes. They reduce atherogenesis in LDL receptor deficient and ApoE knockout mice, but up-regulate CD36, which may contribute to foam cell formation. The dyslipidaemia in type II diabetes is characterized by high levels of nonesterified fatty acids. Therefore we tested the effect of fatty acids and how fatty acids and the thiazolidinedione darglitazone interact in their effect on CD36 expression in human monocytes and macrophages.

MATERIALS AND METHODS

Flow cytometry and reverse transcription-polymerase chain reaction were used to study CD36 expression. Cellular lipids were analyzed with high performance liquid chromatography.

RESULTS

Darglitazone increased CD36 mRNA and protein expression in human macrophage cells. In the presence of 5% human serum, darglitazone increased the accumulation of triglycerides, but did not affect cholesterol ester levels. In the presence of albumin-bound oleic or linoleic acid, darglitazone did not increase CD36 mRNA, cell-surface CD36 protein or triglyceride content. Fatty acids per se increased CD36 mRNA and protein.

DISCUSSION

The increase in CD36 in macrophages suggests a role for fatty acids in the regulation of foam cell formation. The results also suggest that the potentially proatherogenic CD36 up-regulating effect of thiazolidinediones in macrophages might not be present when the cells have access to physiological levels of albumin-bound fatty acids.

Cholesterol attenuates linoleic acid-induced endothelial cell activation

Vascular endothelial cell activation and dysfunction are critical early events in atherosclerosis. Even though very low or high levels of cholesterol can compromise cellular functions, cholesterol is a critical membrane component and may protect the vascular endothelium from oxidative stress and polyunsaturated fatty acid-mediated inflammatory responses. We have previously shown that the parent omega-6 fatty acid linoleic acid can markedly activate vascular endothelial cells. We now propose that membrane cholesterol can modify and inhibit linoleic acid-mediated endothelial cell dysfunction. To test this hypothesis, pulmonary artery endothelial cells were incubated with cholesterol (0 to 100 micromol/L) for 24 hours and then treated with 90 micromol/L of linoleic acid (18:2n-6) for 6 to 24 hours. In control cells, treatment with linoleic acid reduced intracellular glutathione levels and induced the DNA binding activity of nuclear factor-kappaB (NF-kappaB) leading to the upregulation of interleukin-6 (IL-6). In addition, the expression of endothelial nitric oxide synthase (eNOS) was altered, with linoleic acid increasing eNOS activity. In contrast, enrichment with cholesterol enhanced glutathione levels and reduced the linoleic acid-induced activation of NF-kappaBand the production of IL-6. Prior exposure to 50 micromol/L cholesterol also prevented the fatty acid-induced increase in eNOS activation. Cholesterol loading activated peroxisome proliferator-activated receptor-gamma (PPAR-gamma), a nuclear receptor that can decrease inflammatory responses. Furthermore, the PPAR-gamma agonist thiazolidinedione markedly downregulated the NF-kappaB activation mediated by linoleic acid. Our data suggest that signaling pathways linked to endothelial cell activation by prooxidant and proinflammatory insults may be influenced by cellular cholesterol levels.

Changes in aspects such as the collagenous fiber density and foam cell size of atherosclerotic lesions composed of foam cells, smooth muscle cells and fibrous components in rabbits caused by all-cis-5, 8, 11, 14, 17-icosapentaenoic acid

Atherosclerotic plaques composed of foamed macrophages, smooth muscle cells and fibrous components in the twice-injured carotid artery from 1% cholesterol diet (HCD)-fed rabbits were prepared and the effects of all-cis-5, 8, 11, 14, 17-icosapentaenoic acid (EPA) on the histopathological properties of atherosclerotic lesions were examined. During the test period, there was no significant difference between the control and the EPA-treated groups in serum lipid levels. In the control group, atherosclerotic lesions were composed of foamed macrophages, smooth muscle cells and fibrous components. Some of the lesions had a large core of foamed macrophages covered with a thin cap of smooth muscle cells and fibrous components, and were morphologically similar to human vulnerable plaques. The classification of plaques, composing atherosclerotic lesions based on collagenous fiber density and foam cell size indicated that over 70% of plaques in the control group were poor in collagenous fiber, while about 20% of plaques contained only large foam cells. In contrast to the control group, over 70% of plaques in the EPA-treated group were rich in collagenous fiber and only 3% consisted of large foam cells. These results suggest that EPA changes certain aspects of pre-existing atherosclerotic lesions.

Docosahexaenoic acid suppresses the activity of peroxisome proliferator-activated receptors in a colon tumor cell line

Fatty acids are generally considered as agonists for peroxisome proliferator-activated receptors (PPARs). Fatty acids have been shown to bind to and transactivate PPARs; it is not known whether fatty acids act as generalized agonists for PPARs in different cell types, and thus, stimulate the expression of PPAR-regulated target genes. Here, we investigated the potency of unsaturated fatty acids on transactivation of PPRE, DNA-binding activity of PPARs, and the expression of a PPAR-regulated gene product, CD36. Docosahexaenoic acid (DHA) suppressed the basal and PPAR agonist-induced transactivation of PPRE, and DNA binding of PPARs in colon tumor cells (HCT116). The suppression of PPAR transactivation by DHA leads to reduced expression of CD36 in HCT116 cells and human monocytic cells (THP-1) as determined by promoter reporter gene assay and flow cytometric analysis. Our results demonstrate that DHA and other unsaturated fatty acids act as antagonists instead of agonists for transactivation of PPRE and PPAR-regulated gene expression in the cell lines tested. These results suggest that PPAR-mediated gene expression and cellular responses can be dynamically modulated by different types of dietary fatty acids consumed.

Unsaturated fatty acids and their oxidation products stimulate CD36 gene expression in human macrophages

Fatty acids (FA) have been implicated in the control of expression of several atherosclerosis-related genes. Similarly, the CD36 receptor has recently been shown to play an important role in atherosclerosis and other pathologies. The aim of the present study was to evaluate the direct effect of FA and their oxidation products (aldehydes), on the expression of CD36 in both THP-1 macrophages and human monocyte-derived macrophages (HMDM). The FA tested included the saturated FA (SFA) lauric, myristic, palmitic and stearic acid; the monounsaturated FA oleic acid; and the unsaturated FA (UFA) linoleic, arachidonic acid (AA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Aldehydes used were malondialdehyde (MDA), hexanal, 2,4-decadienal (DDE) and 4-hydroxynonenal (HNE). CD36 expression was measured by RT-PCR, Western blot and immunofluorescence. Incubation of THP-1 macrophages for 24 h with non-cytotoxic concentrations of UFA significantly increased CD36 mRNA expression. By contrast, exposure of THP-1 macrophages to SFA did not affect the levels of CD36 mRNA. Among all UFAs tested, EPA and DHA were the strongest inducers of CD36 mRNA levels, followed by oleic and linoleic acid. Incubation of HMDM with either oleic or linoleic acid significantly increased steady-state CD36 mRNA in a dose-dependent manner. Consistent with the increase of CD36 mRNA expression, incubation of THP-1 macrophages with oleic and linoleic acid for 24 h markedly increased CD36 protein expression. Treatment of THP-1 macrophages with MDA or hexanal for 24 h significantly increased CD36 mRNA expression in a dose dependent manner. In contrast, DDE and HNE significantly decreased this parameter. The data provide evidence for a direct regulatory effect of UFA on CD36 gene expression and support a role for aldehydes in the regulation of CD36 expression by FA.

Regulatory potential of n-3 fatty acids in immunological and inflammatory processes

Over the last few years immunonutrition has gained increasing importance. Among other compounds lipids, especially n-3 polyunsaturated fatty acids, were shown to influence the immune response. The anti-inflammatory effects they exert can be induced by free fatty acids, triglyceride fatty acids, after incorporation into the membrane phopspholipid bilayer or following metabolism to eicosanoids. n-3 Fatty acids influence inflammatory cell activation processes from signal transduction to protein expression even involving effects at the genomic level. n-3 Fatty acid-mediated mechanisms decreased cytokine-induced adhesion molecule expression, thereby reducing inflammatory leucocyte-endothelium interactions and modified lipid mediator synthesis, thus influencing the transendothelial migration of leucocytes and leucocyte trafficking in general. Even the metabolic repertoire of specific immunocompetent cells such as cytokine release or proliferation is modified by n-3 fatty acids. Beyond this they regulate lipid homeostasis shifting the metabolic pathways towards energy supply thus optimizing the function of immune cells. Due to the regulatory impact on different processes of inflammatory and immune cell activation n-3 fatty acids provide positive effects on various states of immune deficiencies and diseases with a hyperinflammatory character, among which selected examples are presented.

High-Energy Diets, Fatty Acids and Endothelial Cell Function: Implications for Atherosclerosis

Diets high in fat and/or calories can lead to hypertriglyceridemia and postprandial lipemia and thus are considered a risk factor for the development of atherosclerosis. Plasma chylomicron levels are elevated in humans after consuming a high-fat meal, and hepatic synthesis of VLDL is increased when caloric intake is in excess of body needs. High lipoprotein lipase activity and subsequent hydrolysis of triglyceride-rich lipoproteins may be an important source of elevated concentrations of fatty acid anions in the proximity to the endothelium and hence a major risk factor for atherosclerosis. We have shown that selected fatty acids, as well as lipoprotein lipase-derived remnants of lipoproteins isolated from hypertriglyceridemic subjects, can activate vascular endothelial cells and disrupt endothelial integrity. Our studies suggest that omega-6 fatty acids, and especially linoleic acid, cause endothelial cell dysfunction most markedly as well as can potentiate TNF-mediated endothelial cell injury. We propose that high-energy diets, and especially diets rich in linoleic acid, are atherogenic by contributing to an imbalance in cellular oxidative stress/antioxidant status of the endothelium, which can lead to activation of oxidative stress-responsive transcription factors, inflammatory cytokine production and the expression of adhesion molecules. Our data also suggest that nutrients, which have antioxidant and/or membrane stabilizing properties, can protect endothelial cells. These findings contribute to the understanding of the interactive role of high fat/calorie diets and subsequent hypertriglyceridemia with inflammatory components and nutrients that exhibit antiatherogenic properties in the development of atherosclerosis. Moreover, results from our research further support the concept that high-fat/calorie diets and associated postprandial hypertriglyceridemia are significant risk factors for atherosclerosis.

The role of methyl-linoleic acid epoxide and diol metabolites in the amplified toxicity of linoleic acid and polychlorinated biphenyls to vascular endothelial cells

Selected dietary lipids may increase the atherogenic effects of environmental chemicals, such as polychlorinated biphenyls (PCBs), by cross-amplifying mechanisms leading to dysfunction of the vascular endothelium. We have shown previously that the omega-6 parent fatty acid, linoleic acid, or 3,3',4,4'-tetrachlorobiphenyl (PCB 77), an aryl hydrocarbon (Ah) receptor agonist, independently can cause disruption of endothelial barrier function. Furthermore, cellular enrichment with linoleic acid can amplify PCB-induced endothelial cell dysfunction. We hypothesize that the amplified toxicity of linoleic acid and PCBs to endothelial cells could be mediated in part by cytotoxic epoxide metabolites of linoleic acid called leukotoxins (LTX) or their diol derivatives (LTXD). Exposure to LTXD resulted in a dose-dependent increase in albumin transfer across endothelial cell monolayers, whereas this disruption of endothelial barrier function was observed only at a high concentration of LTX. Pretreatment with the cytosolic epoxide hydrolase inhibitor 1-cyclohexyl-3-dodecyl urea partially protected against the observed LTX-induced endothelial dysfunction. Endothelial cell activation mediated by LTX and/or LTXD also enhanced nuclear translocation of the transcription factor NF-kappa B and gene expression of the inflammatory cytokine IL-6. Inhibiting cytosolic epoxide hydrolase decreased the LTX-mediated induction of both NF-kappa B and the IL-6 gene, whereas the antioxidant vitamin E did not block LTX-induced endothelial cell activation. Most importantly, inhibition of cytosolic epoxide hydrolase blocked both linoleic acid-induced cytotoxicity, as well as the additive toxicity of linoleic acid plus PCB 77 to endothelial cells. Interestingly, cellular uptake and accumulation of linoleic acid was markedly enhanced in the presence of PCB 77. These data suggest that cytotoxic epoxide metabolites of linoleic acid play a critical role in linoleic acid-induced endothelial cell dysfunction. Furthermore, the severe toxicity of PCBs in the presence of linoleic acid may be due in part to the generation of epoxide and diol metabolites. These findings have implications in understanding interactive mechanisms of how dietary fats can modulate dysfunction of the vascular endothelium mediated by certain environmental contaminants.

An olive oil-rich diet reduces scavenger receptor mRNA in murine macrophages

During atherogenesis, a pathological accumulation of lipids occurs within aortic intimal macrophages through uptake of oxidised LDL via scavenger receptors. Here we investigated whether some of the anti-atherosclerotic effects ascribed to an olive oil rich-diet are mediated through effects on macrophage scavenger receptors (MSR). Male C57 Bl6 mice aged 6 weeks were fed for 12 weeks on a low-fat diet (containing 25 g corn oil/kg) or on high-fat diets containing 200 g coconut oil, olive oil or safflower oil/kg. Thioglycollate-elicited peritoneal macrophages were analysed for fatty acid composition by GC and the levels of mRNA coding for three MSR (MSRA type I, MSRA type II and CD36) were measured by reverse-transcription polymerase chain reaction. Feeding mice diets enriched with different fats resulted in significant differences in the fatty acid profile of macrophages, which reflected the fatty acid compositions of the diets. These differences were accompanied by a lower level of mRNA for MSRA type I, MSRA type II and CD36 in macrophages from mice fed an olive-oil-enriched diet compared with the mice fed on the low-fat diet. These data suggest that part of the protective effect of olive oil against atherosclerosis might be via reducing macrophage uptake of oxidised LDL. Whether this effect is due to the downregulation of gene transcription directly by unsaturated fatty acids or is the result of the effect of monounsaturated fatty acids or other components of olive oil on LDL composition and oxidation remains to be ascertained.

Dietary fish oil reduces intercellular adhesion molecule 1 and scavenger receptor expression on murine macrophages

During atherogenesis, a pathological accumulation of lipids occurs within aortic intimal macrophages through uptake of oxidised low-density lipoprotein (LDL) via scavenger receptors. Here we investigate whether some of the anti-atherosclerotic effects ascribed to dietary fish oil are mediated through effects on macrophage intercellular adhesion molecule 1 (ICAM-1) and scavenger receptor expression. Mice were fed on a low fat diet (containing 25 g/kg corn oil) or on high fat diets containing 200 g/kg coconut oil, safflower oil or fish oil. Thioglycollate-elicited peritoneal macrophages were analysed for fatty acid composition by gas chromatography. Macrophage scavenger receptor A (MSR-A) type I+type II and ICAM-1 expression were measured by flow cytometry and the levels of mRNA coding for MSR-A type I, MSR-A type II and ICAM-1 were measured by reverse-transcription polymerase chain reaction. Feeding mice diets enriched with different fats resulted in significant changes in the fatty acid profile of macrophages, which reflected the fatty acid compositions of the diets. Macrophages from the fish oil fed mice had the lowest expression of ICAM-1 and MSR-A at the level of both mRNA and cell surface expression. The reduced expression of ICAM-1 and MSR-A on macrophages from mice fed on a fish oil-rich diet supports our hypothesis that part of the protective effect of fish oil against atherosclerosis might be due to an altered macrophage phenotype and function ameliorating macrophage-induced plaque formation.

Scavenger receptor regulation and atherosclerosis

Atherosclerosis and its complications, such as coronary heart disease, heart infarction and stroke, are the leading causes of death in the developed world. High blood pressure, diabetes, smoking and a diet high in cholesterol and lipids clearly increase the likelihood of premature atherosclerosis, albeit other factors, such as the individual genetic makeup, may play an additional role. During atherosclerosis, uncontrolled cholesterol and lipid accumulation in macrophages and smooth muscle cells leads to foam cell formation and to the progression of the atherosclerotic plaque. This review will focus on foam cell formation within the atherosclerotic lesion, the involvement of the scavenger receptor genes in this process, and the possibility to interfere with scavenger receptor function to reduce the progression of atherosclerosis. To date, the regulatory mechanisms for the expression of scavenger receptor genes and their role in atherosclerosis are not well characterized. Knowledge on this subject could lead to a better understanding of the process, prevention and therapy of this disease.

Eicosapentanoic acid reduces plasma levels of remnant lipoproteins and prevents in vivo peroxidation of LDL in dialysis patients

Causative factors of uremia-associated atherosclerosis are complex. However, it is likely that atherogenic lipoproteins accumulated in plasma are involved. Remnant lipoproteins are atherogenic and are frequently observed in uremic plasma. LDL from uremic patients has been shown to be susceptible to in vitro peroxidation, suggesting that oxidized LDL (ox-LDL) could be excessively generated in those patients. No effective treatments to prevent accumulation of both atherogenic lipoproteins in dialysis patients have been published. Eicosapentanoic acid (EPA) may change synthesis and/or catabolism of remnant lipoproteins and increase stability of LDL to peroxidation by altering the fatty acid composition of lipoproteins. A prospective comparative study was conducted to assess the efficacy of EPA on metabolism of remnant lipoproteins and ox-LDL in dialysis patients using two new methods: an immunoaffinity gel separation for quantifying plasma remnant lipoproteins and an enzyme-linked immunosorbent assay for measuring plasma ox-LDL levels, a marker for in vivo LDL peroxidation. Twenty-two hemodialysis and 16 continuous ambulatory peritoneal dialysis patients with relatively high plasma levels of remnant lipoproteins and ox-LDL were randomized to either EPA or placebo. Highly purified EPA, in an ethyl-ester form (ethyl all-cis-5,8,11,14,17-icosapentanoate) with a purity greater than 91%, was administered at a dose of 1800 mg daily. Overall, 3 mo of treatment with EPA significantly reduced the levels of both remnant lipoproteins (52% reduction) and ox-LDL (38% reduction). Additionally, gel filtration chromatography of lipoproteins showed that EPA treatment concomitantly normalized other potential abnormalities in lipoproteins. Treatment compliance was good and no critical adverse effects were observed. In conclusion, EPA administration proved to be effective and safe treatment to decrease plasma remnant lipoproteins and prevent in vivo peroxidation of LDL in dialysis patients.

Depression and bipolar disorder: relationships to impaired fatty acid and phospholipid metabolism and to diabetes, cardiovascular disease, immunological abnormalities, cancer, ageing and osteoporosis. Possible candidate genes

Depression and bipolar disorder are two of the commonest illnesses in the developed world. While some patients can be treated effectively with available drugs, many do not respond, especially in the depression related to bipolar disorder. Depression is associated with diabetes, cardiovascular disease, immunological abnormalities, multiple sclerosis, cancer, osteoporosis and ageing: in each case depressed individuals have a worse outcome than non-depressed individuals. In all of these conditions there is now evidence of impaired phospholipid metabolism and impaired fatty acid-related signal transduction processes. Impaired fatty acid and phospholipid metabolism may be a primary cause of depression in many patients and may explain the interactions with other diseases. Several novel gene candidates for involvement in depression and bipolar disorder are proposed.

The role of linoleic acid in endothelial cell gene expression. Relationship to atherosclerosis

There is evidence that linoleic acid plays a critical role in gene expression and vascular function as it relates to the pathogenesis of atherosclerosis. The lipid environment, particularly linoleic acid and its derivatives, of the vascular endothelium may profoundly influence the inflammatory response mediated by cytokines. Modulations in the level of activity of a select set of endothelial transcription factors appear to provide a mechanism for linking lipid/cytokine-mediated vessel wall dysfunction, including endothelial cell activation, altered proteoglycan metabolism, and endothelial barrier dysfunction, with the onset of atherosclerotic lesion formation. The activity of endothelial transcription factors is in part regulated by the balance of cellular oxidative stress and antioxidant status. Our data suggest that linoleic acid can activate the vascular endothelium and may thus be an atherogenic fatty acid. Furthermore, nutrients/chemicals with antioxidant properties can protect endothelial cells against lipid-mediated cell injury, suggesting that oxidative stress is a critical component in linoleic acid-mediated gene expression. Our discoveries that linoleic acid can influence significantly the cytokine-mediated inflammatory response may open new fields in dietary intervention of atherosclerosis.

Dietary omega-3, omega-6, and omega-9 unsaturated fatty acids and growth factor and cytokine gene expression in unstimulated and stimulated monocytes. A randomized volunteer study

Dietary omega-3 fatty acids retard coronary atherosclerosis. Previously, we demonstrated that dietary omega-3 fatty acids reduce platelet-derived growth factor (PDGF)-A and PDGF-B mRNA levels in unstimulated, human mononuclear cells (MNCs). In a randomized, investigator-blinded intervention trial, we have now compared the effect of ingestion of 7 g/d omega-3, omega-6, or omega-9 fatty acids for 4 weeks versus no dietary intervention on PDGF-A, PDGF-B, heparin-bound epidermal growth factor (HB-EGF), monocyte chemoattractant protein-1 (MCP-1), and interleukin-10 gene expression in unstimulated MNCs and in monocytes that were adherence-activated ex vivo in a total of 28 volunteers. In unstimulated MNCs, mRNA steady-state levels of PDGF-A, PDGF-B, and MCP-1 were reduced by 25+/-10%, 31+/-13%, and 40+/-14%, respectively, after omega-3 fatty acid ingestion, as assessed by quantitative polymerase chain reaction (all P<0.05). In monocytes that were adherence-activated ex vivo for 4 and 20 hours, mRNA steady-state levels of PDGF-A, PDGF-B, and MCP-1 were reduced by 25+/-13%, 20+/-15%, and 30+/-8%, respectively (all P<0.05). Interleukin-10 and HB-EGF mRNA steady-state levels were not influenced by omega-3 fatty acid ingestion. Expression of all respective mRNAs in control volunteers or in those ingesting omega-6 or omega-9 fatty acids were not altered. We conclude that human gene expression for PDGF-A, PDGF-B, and MCP-1, factors thought relevant to atherosclerosis, is constitutive, is constant, and can be reduced only by dietary omega-3 fatty acids in unstimulated and adherence-activated monocytes.

Oxidized LDL increases and interferon-gamma decreases expression of CD36 in human monocyte-derived macrophages

CD36 is a glycoprotein with an Mr of 88 kDa that is expressed on platelets, monocytes/macrophages, capillary endothelial cells, and adipocytes. We previously demonstrated that CD36 is involved in the uptake of oxidized low density lipoprotein (OxLDL) by using CD36-deficient macrophages (J Clin Invest. 1995;96:1859). However, the regulation of CD36 expression in human monocyte-derived macrophages has not been fully elucidated. The current study attempted to clarify the effect of OxLDL and cytokines, both of which are present in atherosclerotic lesions and may play an important role in atherogenesis, on the expression of CD36. A cell enzyme-linked immunosorbent assay and flow cytometry were used to detect CD36 protein. A ribonuclease protection assay was used to measure CD36 mRNA in human monocyte-derived macrophages. The expression of CD36 was increased during the differentiation of monocytes to macrophages. Incubation of macrophages with 25 microg/mL OxLDL for 24 hours increased the level of CD36 protein by 56% and that of CD36 mRNA by 58%. Lysophosphatidylcholine did not affect the expression of CD36. The effects of OxLDL were demonstrated in macrophages that had already differentiated to the point where CD36 expression was almost maximal. Interferon-gamma (IFN-gamma) reduced the expression of CD36 in a dose-dependent manner. A concentration of 1000 U/mL IFN-gamma significantly reduced the expression of CD36 protein by 57% and that of CD36 mRNA by 30%. In conclusion, CD36 may be important in the formation of foam cells by induction through its ligand (OxLDL). Moreover, some local factors, such as IFN-gamma, may suppress CD36 expression on macrophages in human atherosclerotic lesions.

Clinical use of lipids to control inflammatory disease

Selective dietary supplementation with lipids has long been used to influence the course of chronic inflammatory diseases. This review describes new aspects of the molecular mechanism of lipids to modulate leukocyte activity and highlights some recent clinical studies on therapeutic lipid administration. New promising advances in parenteral application of lipids as well as the impact on acute inflammatory disorders are discussed.

Native and modified low density lipoproteins increase the functional expression of the macrophage class B scavenger receptor, CD36

The uptake of oxidized low density lipoprotein (OxLDL) by macrophages is a key event implicated in the initiation and development of atherosclerotic lesions. Two macrophage surface receptors, CD36 (a class B scavenger receptor) and the macrophage scavenger receptor (a class A scavenger receptor), have been identified as the major receptors that bind and internalize OxLDL. Expression of CD36 in monocyte/macrophages in tissue culture is dependent both on the differentiation state as well as exposure to soluble mediators (cytokines and growth factors). The regulatory mechanisms of this receptor in vivo are undetermined as is the role of lipoproteins themselves in modulating CD36 expression. We studied the effect of lipoproteins, native LDL and modified LDL (acetylated LDL (AcLDL) and OxLDL) on the expression of CD36 in J774 cells, a murine macrophage cell line. Exposure to lipoproteins resulted in a marked induction of CD36 mRNA expression (4-8-fold). Time course studies showed that maximum induction was observed 2 h after treatment with AcLDL and at 4 h with LDL and OxLDL. Increased expression of CD36 mRNA persisted for 24 h with each treatment group. Induction of CD36 mRNA expression was paralleled by an increase in CD36 protein as determined by Western blot with the greatest induction by OxLDL (4-fold). In the presence of actinomycin D, treatment of macrophages with LDL, AcLDL, or OxLDL did not affect CD36 mRNA stability, implying that CD36 mRNA was transcriptionally regulated by lipoproteins. To determine the mechanism(s) by which lipoproteins increased expression of CD36 we evaluated the effects of lipoprotein components on CD36 mRNA expression. ApoB 100 increased CD36 mRNA expression significantly, whereas phospholipid/cholesterol liposomes had less effect. Incubation of macrophages with bovine serum albumin or HDL reduced expression of CD36 mRNA in a dose-dependent manner. Finally, to evaluate the in vivo relevance of the induction of CD36 mRNA expression by lipoproteins, peritoneal macrophages were isolated from mice following intraperitoneal injection of lipoproteins. Macrophage expression of CD36 mRNA was significantly increased by LDL, AcLDL, or OxLDL in relation to mice infused with phosphate-buffered saline, with OxLDL causing the greatest induction (8-fold). This is the first demonstration that exposure to free and esterified lipids augments functional expression of the class B scavenger receptor, CD36. These data imply that lipoproteins can further contribute to foam cell development in atherosclerosis by up-regulating a major OxLDL receptor.

Lovastatin reduces expression of the combined adhesion and scavenger receptor CD36 in human monocytic cells

The thrombospondin and collagen receptor CD36 was recently found to function, also, as a dominating scavenger receptor for oxidized low-density lipoproteins (oxLDL). Thus, CD36 might be a key factor in monocyte adhesion and foam cell formation. We, therefore, studied CD36 expression in monocytic cells under conditions of cholesterol depletion and overload. Human monocytic U937 cells were cultured under control conditions and in the presence of lovastatin, native, and oxLDL. The expression of lipoprotein receptors was measured by quantitative reverse transcriptase polymerase chain reaction (RT-PCR) and fluorescence-activated cell sorting (FACS). In sharp contrast to the feedback-controlled ApoB100 specific receptor for native low-density lipoprotein (LDL-R), CD36 expression was significantly reduced by lovastatin in a dose-dependent manner, both at the RNA and protein level, resulting in decreased cellular oxLDL binding. The addition of mevalonate completely reversed lovastatin effects, whereas excess LDL was only partially effective. Similarly to native LDL, oxLDL reduced LDL-R transcription, but did not affect CD36 transcription. CD36 protein surface expression fell, however, due to internalization of CD36 loaded with oxLDL. In summary, monocytic expression of CD36, in contrast to the native LDL-R, is reduced by cholesterol synthesis inhibition and not by feedback inhibition from substrate overexposure. CD36 suppression is a new pharmacological action of lovastatin that may contribute to its clinical benefit by attenuating monocyte adhesion and foam cell formation, key steps in atherosclerosis.