Conjugated linoleic acids can change phagocytosis of human monocytes/macrophages by reduction in Cox-2 expression

Distinct biological activities of isomers from several families of branched fatty acid esters of hydroxy fatty acids (FAHFAs)

Branched fatty acid esters of hydroxy fatty acids (FAHFAs) are endogenous lipids with antidiabetic and anti-inflammatory effects. Each FAHFA family consists of esters with different acyl chains and multiple isomers with branch points at different carbons. Some FAHFAs, including palmitic acid hydroxy stearic acids (PAHSAs), improve insulin sensitivity and glucose tolerance in mice by enhancing glucose-stimulated insulin secretion (GSIS), insulin-stimulated glucose transport, and insulin action to suppress hepatic glucose production and reducing adipose tissue inflammation. However, little is known about the biological effects of other FAHFAs. Here, we investigated whether PAHSAs, oleic acid hydroxy stearic acid, palmitoleic acid hydroxy stearic acid, and stearic acid hydroxy stearic acid potentiate GSIS in β-cells and human islets, insulin-stimulated glucose uptake in adipocytes, and anti-inflammatory effects in immune cells. We also investigated whether they activate G protein-coupled receptor 40, which mediates the effects of PAHSAs on insulin secretion and sensitivity in vivo. We show that many FAHFAs potentiate GSIS, activate G protein-coupled receptor 40, and attenuate LPS-induced chemokine and cytokine expression and secretion and phagocytosis in immune cells. However, fewer FAHFAs augment insulin-stimulated glucose uptake in adipocytes. S-9-PAHSA, but not R-9-PAHSA, potentiated GSIS and glucose uptake, while both stereoisomers had anti-inflammatory effects. FAHFAs containing unsaturated acyl chains with higher branching from the carboxylate head group are more likely to potentiate GSIS, whereas FAHFAs with lower branching are more likely to be anti-inflammatory. This study provides insight into the specificity of the biological actions of different FAHFAs and could lead to the development of FAHFAs to treat metabolic and immune-mediated diseases.

Dietary conjugated linoleic acid modulates morphology, selective immune parameters, and gene expressions in the intestine of grass carp

Conjugated linoleic acid (CLA) has been shown to exhibit anti-inflammatory properties in the intestine in mammals. However, the effect of CLA on intestinal immune response in fish is still unknown. Therefore, a 65-day growth trial was conducted to investigate the effects of dietary conjugated linoleic acid (CLA) on morphology, selective immune parameters, and gene expressions in the intestine of grass carp. Seven isonitrogenous and isolipidic diets were formulated as follows: 0 (control), 0.5 (CLA0.5), 1 (CLA1), 1.5 (CLA1.5), 2 (CLA2), 2.5 (CLA2.5), and 3 (CLA3) g CLA per 100g of feed. RESULTS: showed that dietary supplementation of 1.5-3% CLA significantly (P < 0.05) increased the fold and enterocyte heights in the PI and MI of grass carp. Complement 3 (C3) and immunoglobulin M (IgM) contents in three intestinal segments were significantly (P < 0.05) higher in fish fed with CLA1.5 to CLA2.5 diets compared to fish fed the control diet. CLA1.5 to CLA2.5 diets significantly (P < 0.05) increased the mRNA expression levels of anti-inflammatory cytokines (IL-10 and TGFβ1) and significantly (P < 0.05) reduced the mRNA expression levels of pro-inflammatory cytokines (IL-1β, IL-8, and TNF-α) in the PI, MI, and DI. This improved expression of anti-inflammatory cytokines and the inhibited expression of pro-inflammatory cytokines in the intestine of grass carp, might be mediated via TLR4/NF-κB-signaling pathway. Our results suggested that CLA1.5 to CLA2 diets improved intestinal morphology, increased the expression of anti-inflammatory cytokines, and inhibited the expression of pro-inflammatory cytokines in the intestine of grass carp. In conclusion, dietary supplementation of 1.5%-2% CLA show the anti-inflammatory therapeutic potential in the intestine of grass carp. The anti-inflammatory therapeutic potential of CLA might be mediated via TLR4/NF-κB-signaling pathway.

Comparison of adipose‑ and bone marrow‑derived stem cells in protecting against ox‑LDL‑induced inflammation in M1‑macrophage‑derived foam cells

Adipose‑derived stem cells (ADSCs) and bone marrow‑derived stem cells (BMSCs) are considered to be prospective sources of mesenchymal stromal cells (MSCs), that can be used in cell therapy for atherosclerosis. The present study investigated whether ADSCs co‑cultured with M1 foam macrophages via treatment with oxidized low‑density lipoprotein (ox‑LDL) would lead to similar or improved anti‑inflammatory effects compared with BMSCs. ADSCs, peripheral blood monocytes, BMSCs and ox‑LDL were isolated from ten coronary heart disease (CHD) patients. After three passages, the supernatants of the ADSCs and BMSCs were collected and systematically analysed by liquid chromatography‑quadrupole time‑of‑flight‑mass spectrometry (6530; Agilent Technologies, Inc., Santa Clara, CA, USA). Cis‑9, trans‑11 was deemed to be responsible for the potential differences in the metabolic characteristics of ADSCs and BMSCs. These peripheral blood monocytes were characterized using flow cytometry. Following peripheral blood monocytes differentiation into M1 macrophages, the formation of M1 foam macrophages was achieved through treatment with ox‑LDL. Overall, 2x106 ADSCs, BMSCs or BMSCs+cis‑9, trans‑11 were co‑cultured with M1 foam macrophages. Anti‑inflammatory capability, phagocytic activity, anti‑apoptotic capability and cell viability assays were compared among these groups. It was demonstrated that the accumulation of lipid droplets decreased following ADSCs, BMSCs or BMSCs+cis‑9, trans‑11 treatment in M1 macrophages derived from foam cells. Consistently, ADSCs exhibited great advantageous anti‑inflammatory capabilities, phagocytic activity, anti‑apoptotic capability activity and cell viability over BMSCs or BMSCs+cis‑9, trans‑11. Additionally, BMSCs+cis‑9, trans‑11 also demonstrated marked improvement in anti‑inflammatory capability, phagocytic activity, anti‑apoptotic capability activity and cell viability in comparison with BMSCs. The present results indicated that ADSCs would be more appropriate for transplantation to treat atherosclerosis than BMSCs alone or BMSCs+cis‑9, trans‑11. This may be an important mechanism to regulate macrophage immune function.

Impact of Dietary Protein Concentration and Quality on Immune Function of Cats

Protein levels and quality in cat food can vary significantly and might affect immune function in various ways. In the present study, 3 diets with a low protein quality (LQ) and 3 diets with a high protein quality (HQ) were offered to 10 healthy adult cats for 6 weeks each, using a randomized cross-over design. The LQ and HQ diets differed in the collagen content and had low (36.7% and 36.2%), medium (45.0% and 43.3%) and high (56.1% and 54.9%) protein levels. At the end of each feeding period, blood was collected for phenotyping of leukocyte subsets, lymphocyte proliferation assay and cytokine measurements, phagocytosis assay and differential blood count. The results demonstrated no group differences for numbers of CD4⁺CD8^-, CD4⁺CD8⁺, CD4^-CD8⁺, MHCII⁺, CD21⁺, SWC3⁺ and CD14⁺ cells in the blood of the cats. Proliferative activity of lymphocytes when stimulated with pokeweed mitogen, Concanavalin A and Phytohemagglutinin, M form did not differ depending on the dietary protein concentration and quality. Concentrations of tumor necrosis factor alpha and interferon gamma in the supernatant of the proliferation assay were also not affected by the dietary treatment. Blood monocyte phagocytic activity was higher (P = 0.048) and cell numbers of eosinophilic granulocytes in the blood were lower (P = 0.047) when cats were fed the low protein diets. In conclusion, only a few differences in feline immune cell populations and activity depending on dietary protein supply could be detected. However, the observed increase of eosinophilic granulocytes by a higher protein intake indicates an activation of immunological mechanisms and requires further investigation.

Cross-reactive antibodies enhance live attenuated virus infection for increased immunogenicity

Vaccination has achieved remarkable successes in the control of childhood viral diseases. To control emerging infections, however, vaccines will need to be delivered to older individuals who, unlike infants, probably have had prior infection or vaccination with related viruses and thus have cross-reactive antibodies against the vaccines. Whether and how these cross-reactive antibodies impact live attenuated vaccination efficacy is unclear. Using an open-label randomized trial design, we show that subjects with a specific range of cross-reactive antibody titres from a prior inactivated Japanese encephalitis vaccination enhanced yellow fever (YF) immunogenicity upon YF vaccination. Enhancing titres of cross-reactive antibodies prolonged YF vaccine viraemia, provoked greater pro-inflammatory responses, and induced adhesion molecules intrinsic to the activating Fc-receptor signalling pathway, namely immune semaphorins, facilitating immune cell interactions and trafficking. Our findings clinically demonstrate antibody-enhanced infection and suggest that vaccine efficacy could be improved by exploiting cross-reactive antibodies.

Atheroprotective effects of conjugated linoleic acid

Atherosclerosis, the underlying cause of heart attack and strokes, is a progressive dyslipidaemic and inflammatory disease where monocyte-derived macrophage cells play a pivotal role. Although most of the mechanisms that contribute to the progression of atherosclerosis have been identified, there is limited information on those governing regression. Conjugated linoleic acid (CLA) is a generic term denoting a group of naturally occurring isomers of linoleic acid (18:2, n6) that differ in the position or geometry (i.e. cis or trans) of their double bonds. The most predominant isomers in ruminant fats are cis-9, trans-11 CLA (c9,t11-CLA), which accounts for more than 80% of CLA isomers in dairy products and trans-10, cis-12 CLA (t10,c12-CLA). Dietary administration of a blend of the two most abundant isomers of CLA has been shown to inhibit the progression and induce the regression of pre-established atherosclerosis. Studies investigating the mechanisms involved in CLA-induced atheroprotective effects are continually emerging. The purpose of this review is to discuss comprehensively the effects of CLA on monocyte/macrophage function in atherosclerosis and to identify possible mechanisms through which CLA mediates its atheroprotective effects.

The Immunomodulatory Activity of Jacaric Acid, a Conjugated Linolenic Acid Isomer, on Murine Peritoneal Macrophages

This study aims at demonstrating the immunomodulatory property of jacaric acid, a conjugated linolenic acid (CLNA) isomer that is present in jacaranda seed oil, on murine peritoneal macrophages. Our results showed that jacaric acid exhibited no significant cytotoxicity on the thioglycollate-elicited murine peritoneal macrophages as revealed by the neutral red uptake assay, but markedly increased their cytostatic activity on the T-cell lymphoma MBL-2 cells as measured by the fluorometric CyQuant® NF Cell Proliferation Assay Kit. Flow cytometric analysis indicated that jacaric acid could enhance the endocytic activity of macrophages and elevated their intracellular production of superoxide anion. Moreover, jacaric acid-treated macrophages showed an increase in the production of nitric oxide which was accompanied by an increase in the expression level of inducible nitric oxide synthase protein. In addition, the secretion of several pro-inflammatory cytokines, including interferon-γ, interleukin-1β and tumor necrosis factor-α, was up-regulated. Collectively, our results indicated that the naturally-occurring CLNA isomer, jacaric acid, could exhibit immunomodulating activity on the murine peritoneal macrophages in vitro, suggesting that this CLNA isomer may act as an immunopotentiator which can be exploited for the treatment of some immunological disorders with minimal toxicity and fewer side effects.

PPARγ and the Innate Immune System Mediate the Resolution of Inflammation

The resolution of inflammation is an active and dynamic process, mediated in large part by the innate immune system. Resolution represents not only an increase in anti-inflammatory actions, but also a paradigm shift in immune cell function to restore homeostasis. PPARγ, a ligand activated transcription factor, has long been studied for its anti-inflammatory actions, but an emerging body of literature is investigating the role of PPARγ and its ligands (including thiazolidinediones, prostaglandins, and oleanolic acids) in all phases of resolution. PPARγ can shift production from pro- to anti-inflammatory mediators by neutrophils, platelets, and macrophages. PPARγ and its ligands further modulate platelet and neutrophil function, decreasing trafficking, promoting neutrophil apoptosis, and preventing platelet-leukocyte interactions. PPARγ alters macrophage trafficking, increases efferocytosis and phagocytosis, and promotes alternative M2 macrophage activation. There are also roles for this receptor in the adaptive immune response, particularly regarding B cells. These effects contribute towards the attenuation of multiple disease states, including COPD, colitis, Alzheimer's disease, and obesity in animal models. Finally, novel specialized proresolving mediators-eicosanoids with critical roles in resolution-may act through PPARγ modulation to promote resolution, providing another exciting area of therapeutic potential for this receptor.

Dunaliella salina exhibits an antileukemic immunity in a mouse model of WEHI-3 leukemia cells

Dunaliella salina has been shown to have antioxidant property and induce apoptotic cell death of human cancer cells in vitro. However, there is no information available on D. salina showing an antileukemia effect or immunomodulatory activity in vivo. This study applied D. salina to syngeneic leukemia-implanted mice (BALB/c and WEHI-3) to investigate its immunological and antileukemia properties. Oral administration of D. salina (184.5, 369, and 922.5 mg/kg) inhibited spleen metastasis and prolonged the survival in BALB/c mice that had received an intravenous injection of WEHI-3 cells. The results revealed that D. salina had reduced spleen enlargement in murine leukemia. It had also increased the population and proliferation of T-cells (CD3) and B-cells (CD19) following Con A/LPS treatment on flow cytometry and MTT assay, respectively. Furthermore, D. salina increased the phagocytosis of macrophages and enhanced the cytotoxicity of natural killer cells on flow cytometry and LDH assay. Moreover, D. salina enhanced the levels of interferon-γ and interleukin 2 (IL-2) but reduced the levels of IL-4 and IL-10 in leukemic mice. In conclusion, these results demonstrated that the application of D. salina had beneficial effects on WEHI-3 leukemic mice by prolonging survival via modulating the immune responses.

Conjugated linoleic acid regulates phosphorylation of PPARγ by modulation of ERK 1/2 and p38 signaling in human macrophages/fatty acid-laden macrophages

Stimulation of macrophages by a variety fatty acids causes activation of MAP kinases (MAPKs). The consequences arising from down-regulation of MAPKs may be a limitation in the activity of PPARγ, which is modulated by a modification catalyzed by these kinases. Phosphorylation of MAP kinases-ERK1/2 and p38 as well as PPARγ was determined by real-time polymerase chain reaction and Western blotting in human macrophages cultured with conjugated linoleic acids (CLAs). We demonstrated that CLA isomers alter MAP kinase phosphorylation and PPARγ activation. Phosphorylation of ERK1/2 was diminished in cells cultivated with cis-9,trans-11 CLA, whereas phosphorylation of p38 was reduced by trans-10,cis-12 CLA. PPARγ was phosphorylated mainly by ERK1/2, and consequently, PPARγ phosphorylation was suppressed mainly by cis-9,trans-11 isomer. In human adipocytes, cis-9,trans-11 C 18:2 raised the activation of PPAR and several of its downstream target genes. We suggest that a similar process may also occur in human macrophages.

Conjugated linoleic acid isomers may diminish human macrophages adhesion to endothelial surface

Dysfunction of endothelial cells and activation of monocytes in the vascular wall are important pathogenetic factors of atherosclerosis. Conjugated linoleic acids (CLAs) can modulate the function of immune system in humans: reduce the concentration of atherogenic lipoproteins, and the intensity of inflammatory processes in the plasma. In this paper, we focus on macrophage's surface integrins (β1 integrin CD49d/CD29-(VLA4); Mac-1 as well as endothelial human vein endothelial cell (HUVEC) surface adhesins: vascular cell adhesion molecule-1 (VCAM-1) and intracellular cell adhesion molecule-1 (ICAM-1)) expression in relation to CLA isomer used during cell culture. Both CLA isomers decreased expression of VLA-4 and Mac-1 on macrophages compared with control cells (cultured with bovine serum albumine (BSA) or oxidized form of low-density lipoproteins). cis-9, trans-11 CLA isomer reduced ICAM-1 and VCAM-1 expression on the endothelium surface. Strong tendency to reduce of adhesion of macrophages to HUVEC in the cells cultured with CLA isomers was observed. The potential role of cis-9, trans-11 CLA in the reduction of adhesion of macrophages to the HUVEC--one of the important steps in the inflammatory process, can be considerate. These mechanisms may contribute to the potent anti-atherosclerotic effects of CLA in vivo.

Expression of mutant alpha-synuclein modulates microglial phenotype in vitro

Background

Increased reactive microglia are a histological characteristic of Parkinson's disease (PD) brains, positively correlating with levels of deposited α-synuclein protein. This suggests that microglial-mediated inflammatory events may contribute to disease pathophysiology. Mutations in the gene coding for α-synuclein lead to a familial form of PD. Based upon our prior findings that α-synuclein expression regulates microglial phenotype we hypothesized that expression of mutant forms of the protein may contribute to the reactive microgliosis characteristic of PD brains.

Methods

To quantify the effects of wild type and mutant α-synuclein over-expression on microglial phenotype a murine microglial cell line, BV2, was transiently transfected to express human wild type (WT), and mutant α-synuclein (A30P and A53T) proteins. Transfected cells were used to assess changes in microglia phenotype via Western blot analysis, ELISA, phagocytosis, and neurotoxicity assays.

Results

As expected, over-expression of α-synuclein induced a reactive phenotype in the transfected cells. Expression of α-synuclein increased protein levels of cycloxygenase-2 (Cox-2). Transfected cells demonstrated increased secretion of the proinflammatory cytokines, tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6), as well as increased nitric oxide production. Transfected cells also had impaired phagocytic ability correlating with decreased protein levels of lysosomal-associated membrane protein 1 (LAMP-1). In spite of the increased cytokine secretion profile, the transfected cells did not exhibit increased neurotoxic ability above control non-transfected BV2 cells in neuron-microglia co-cultures.

Conclusions

These data demonstrated that over-expression of α-synuclein drives microglial cells into a form of reactive phenotype characterized by elevated levels of arachidonic acid metabolizing enzymes, cytokine secretion, and reactive nitrogen species secretion all superimposed upon impaired phagocytic potential.

Conjugated linoleic acid decreases prostaglandin synthesis in bovine luteal cells in vitro

Feeding conjugated linoleic acids (CLA) improves reproductive performance in dairy cows; however, the molecular mechanisms by which CLA improves reproduction are not understood. The effect of the CLA isomers, trans-10, cis-12 CLA and cis-9, trans-11 CLA on synthesis of progesterone, PGE(2) , and PGF(2α) , in bovine luteal cells was determined in this study. Luteal cells from three cows were cultured in medium containing 0 or 0.1 µM of trans-10, cis-12 CLA and cis-9, trans-11 CLA in varying ratios in the presence and absence of 1 µM of forskolin. Prostaglandin and progesterone concentrations were not altered by CLA isomer and ratio. Luteal cells cultured in the presence of CLA had lower PGF(2α) concentrations (62.6 ± 13.4 pg/ml vs. 55.7 ± 12.2 pg/ml; P = 0.005) and, in the absence of forskolin, lower PGE(2) concentrations (65.3 ± 15.1 pg/ml vs. 32.4 ± 14.1 pg/ml; P = 0.002) in culture media, while progesterone concentrations were not altered (P = 0.63). Relative steady-state mRNA amounts of COX-2 (1.7-fold decrease; P = 0.002), PGE synthase (1.5-fold decrease; P = 0.03) and 3β-hydroxysteroid dehydrogenase (1.6-fold decrease; P = 0.0003) were lower in CLA-treated cultures, but CLA did not significantly alter mRNA amounts of PGE(2) 9-keto-reductase, StAR, and cytochrome P450 side chain cleavage enzyme. In conclusion, a potential mechanism exists by which trans-10, cis-12 CLA and cis-9, trans-11 CLA may improve reproductive performance in dairy cows, by suppressing PGF(2α) synthesis in luteal cells via attenuation of COX-2 gene expression.

Conjugated linoleic acid and inflammatory cell signalling

Conjugated linoleic acids (CLA) are a family of polyunsaturated fatty acids (PUFA), some isomers occurring naturally in beef and dairy products and others being formed as a result of bihydrogenation of vegetable oils to form margarine. Synthetic and natural sources of CLA may have beneficial effects in a range of inflammatory conditions including colitis, atherosclerosis, metabolic syndrome and rheumatoid arthritis. Most of the biological effects have been attributed to the cis9, trans11- (c9, t11-) and the trans10, cis12- (t10, c12-) isomers. Evidence suggests that c9, t11-CLA is responsible for the anti-inflammatory effect attributed to CLA while t10, t12-CLA appears to be responsible for anti-adipogenic effects. This review will focus on the effects of CLA on the inflammatory components associated with insulin resistance, atherosclerosis and Th1 mediated inflammatory disease, at a cellular, systemic and clinical level. Whist CLA may ameliorate certain aspects of the inflammatory response, particularly within cellular and animal models, the relevance of this has yet to be clarified within the context of human health.

Quercetin inhibited murine leukemia WEHI-3 cells in vivo and promoted immune response

Enhanced flavonoid consumption is closely related with a reduced cancer incidence as shown in epidemiological studies. Quercetin (3,5,7,3',4'-pentahydroxylflavone) is one of the active components of flavonoids which exist in natural plants, particularly in onions and fruits. It was reported that quercetin induced apoptosis in human cancer cell lines, including human leukemia HL-60 cells, but there is no available information as to its effects on leukemia cells in vivo. The purpose of the present studies was to focus on the in vivo effects of quercetin on leukemia WEHI-3 cells. The effects of quercetin on WEHI-3 cells injected into BALB/c mice were examined. Quercetin decreased the percentage of Mac-3 and CD11b markers, suggesting that the differentiation of the precursors of macrophages and T cells was inhibited. There was no effect on CD3 levels but increased CD19 levels. Quercetin decreased the weight of the spleen and liver compared with the olive oil treated animals. Quercetin stimulated macrophage phagocytosis of cells isolated from peritoneum. Quercetin also promoted natural killer cell activity. Based on pathological examination, an effect of quercetin was observed in the spleen of mice previously injected with WEHI-3 cells. Apparently, quercetin affects WEHI-3 cells in vivo.

Influence of conjugated linoleic acids on functional properties of vascular cells

Conjugated linoleic acids (CLA) are biologically highly active lipid compounds that inhibit the development of atherosclerotic plaques in experimental animals. The underlying mechanisms of action, however, are only poorly understood. Since cell-culture experiments are appropriate to provide a detailed view into the mechanisms of action of a compound, the present review summarises results fromin vitrostudies dealing with the effects of CLA isomers and CLA mixtures on functional properties of cells of the vascular wall, such as endothelial cells, smooth muscle cells and monocyte-derived macrophages, which are amongst the major cells contributing to atherosclerotic lesion development. Based on these studies, it can be concluded that CLA exert several beneficial actions in cells of the vascular wall through the activation of nuclear PPAR. These actions of CLA, which may, at least partially, explain the inhibition of atherogenesis by dietary CLA, include modulation of vasoactive mediator release from endothelial cells, inhibition of inflammatory and fibrotic processes in activated smooth muscle cells, abrogation of inflammatory responses in activated macrophages, and reduction of cholesterol accumulation in macrophage-derived foam cells.

Bioactive food components, inflammatory targets, and cancer prevention

Various dietary components may modify chronic inflammatory processes at the stage of cytokine production, amplification of nuclear factor-kappaB-mediated inflammatory gene expression, and the release of anti-inflammatory cytokine, transforming growth factor-beta. This review provides a synopsis of the strengths and weaknesses of the evidence that specific bioactive food components influence inflammation-related targets linked to cancer. A target repeatedly surfacing as a site of action for several dietary components is transforming growth factor beta. Whereas the use of dietary intervention strategies offers intriguing possibilities for maintaining normal cell function by modifying a process that is essential for cancer development and progression, more information is needed to characterize the minimum quantity of the bioactive food components required to bring about a change in inflammation-mediated cancer, the ideal time for intervention, and the importance of genetics in determining the response. Unquestionably, the societal benefits of using foods and their components to prevent chronic inflammation and associated complications, including cancer, are enormous.

Conjugated linoleic acid isomers reduce cholesterol accumulation in acetylated LDL-induced mouse RAW264.7 macrophage-derived foam cells

Synthetic activators of peroxisome proliferator-activated receptors (PPAR)-alpha and -gamma are capable of reducing macrophage foam cell cholesterol accumulation through the activation of genes involved in cholesterol homeostasis. Since conjugated linoleic acids (CLA) were also demonstrated to activate PPARalpha and PPARgamma in vivo and in vitro, we tested the hypothesis that CLA are also capable of reducing macrophage foam cell cholesterol accumulation. Thus, mouse RAW264.7 macrophage-derived foam cells were treated with CLA isomers, c9t11-CLA and t10c12-CLA, and linoleic acid (LA), as reference fatty acid, and analyzed for the concentrations of free and esterified cholesterol, cholesterol efflux and expression of genes involved in cholesterol homeostasis (CD36, ABCA1, LXRalpha, NPC-1, and NPC-2). Treatment with c9t11-CLA and t10c12-CLA, but not LA, lowered cholesterol accumulation, stimulated acceptor-dependent cholesterol efflux, and increased relative mRNA concentrations of CD36, ABCA1, LXRalpha, NPC-1, and NPC-2 (P < 0.05). In conclusion, the present study showed that CLA isomers reduce cholesterol accumulation in RAW264.7 macrophage-derived foam cells presumably by enhancing lipid acceptor-dependent cholesterol efflux.