Conjugated linoleic acids have no effect on TNFα-induced adhesion molecule expression, U937 monocyte adhesion, and chemokine release in human aortic endothelial cells

Association between trans fatty acids and COVID-19: A multivariate Mendelian randomization study

Traditional observational studies have suggested a potential association between trans fatty acids (TFAs), which are considered to be health-damaging fatty acids, and coronavirus disease 2019 (COVID-19). However, whether there is a causal relationship between them is currently unclear. We aimed to investigate the causal link between genetically determined TFAs and COVID-19. We performed univariate and multivariate Mendelian randomization (MR) studies using summary statistics from the European Pedigree TFAs (n = 8013), COVID-19 susceptibility (n = 159 840), COVID-19 hospitalization (n = 44 986), and COVID-19 severity (n = 18 152) genome-wide association studies (GWAS). The inverse variance weighted (IVW) method was used as the primary MR analysis, and several other methods were used as supplements. In univariate MR analysis, higher levels of circulating trans, cis-18:2 TFAs were positively associated with a higher COVID-19 hospitalization rate (p < 0.0033; odds ratio [OR] = 1.637; 95% confidence interval [CI]: 1.116-2.401) and COVID-19 severity (p < 0.0033; OR = 2.575; 95% CI: 1.412-4.698). Furthermore, in multivariate MR analysis, trans, cis-18:2 had an independent and significant causal association with a higher COVID-19 hospitalization rate (p = 0.00044; OR = 1.862; 95% CI = 1.316-2.636) and COVID-19 severity (p = 0.0016; OR = 2.268; 95% CI = 1.361-3.779) after the five TFAs were adjusted for each other. Together, our findings provide evidence that trans, cis-18:2 TFAs have an independent and robust causal effect on COVID-19 hospitalization and severity.

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.

Cryptotanshinone inhibits TNF-α-induced early atherogenic events in vitro

Endothelial dysfunction has been implicated in the pathogenesis of atherosclerosis. Salvia miltiorrhiza (danshen) is a traditional Chinese medicine that has been effectively used to treat cardiovascular disease. Cryptotanshinone (CTS), a major lipophilic compound isolated from S. miltiorrhiza, has been reported to possess cardioprotective effects. However, the anti-atherogenic effects of CTS, particularly on tumor necrosis factor-α (TNF-α)-induced endothelial cell activation, are still unclear. This study aimed to determine the effect of CTS on TNF-α-induced increased endothelial permeability, monocyte adhesion, soluble intercellular adhesion molecule 1 (sICAM-1), soluble vascular cell adhesion molecule 1 (sVCAM-1), monocyte chemoattractant protein 1 (MCP-1) and impaired nitric oxide production in human umbilical vein endothelial cells (HUVECs), all of which are early events occurring in atherogenesis. We showed that CTS significantly suppressed TNF-α-induced increased endothelial permeability, monocyte adhesion, sICAM-1, sVCAM-1 and MCP-1, and restored nitric oxide production. These observations suggest that CTS possesses anti-inflammatory properties and could be a promising treatment for the prevention of cytokine-induced early atherogenesis.

Lancemaside A from Codonopsis lanceolata modulates the inflammatory responses mediated by monocytes and macrophages

In this study, we aimed to examine the cellular and molecular mechanisms of lancemaside A from Codonopsis lanceolata (Campanulaceae) in the inflammatory responses of monocytes (U937 cells) and macrophages (RAW264.7 cells). Lancemaside A significantly suppressed the inflammatory functions of lipopolysaccharide- (LPS-) treated RAW264.7 cells by suppressing the production of nitric oxide (NO), the expression of the NO-producing enzyme inducible NO synthase (iNOS), the upregulation of the costimulatory molecule CD80, and the morphological changes induced by LPS exposure. In addition, lancemaside A diminished the phagocytic activity of RAW264.7 cells and boosted the neutralizing capacity of these cells when treated with the radical generator sodium nitroprusside (SNP). Interestingly, lancemaside A strongly blocked the adhesion activity of RAW264.7 cells to plastic culture plates, inhibited the cell-cell and cell-fibronectin (FN) adhesion of U937 cells that was triggered by treatment with an anti-β1-integrin (CD29) antibody and immobilized FN, respectively. By evaluating the activation of various intracellular signaling pathways and the levels of related nuclear transcription factors, lancemaside A was found to block the activation of inhibitor of κB kinase (IKK) and p65/nuclear factor- (NF-) κB. Taken together, our findings strongly suggest that the anti-inflammatory function of lancemaside A is the result of its strong antioxidative and IKK/NF-κB inhibitory activities.

Alpha-tocopherol and BAY 11-7082 reduce vascular cell adhesion molecule in human aortic endothelial cells

BACKGROUND

In endothelial dysfunction, vascular cell adhesion molecule-1 (VCAM-1), E-selectin and intercellular adhesion molecule-1 (ICAM-1) expression (collectively termed cell adhesion molecules; CAMs) increase at sites of atherosclerosis and are stimulated by proinflammatory cytokines such as tumor necrosis factor-α (TNF-α).

METHODS

We evaluated the effect of alpha-tocopherol (AT; 10-150 µM) and BAY 11-7082 (BAY; 0.1 or 1 µM) on CAMs mRNA expression as well as their protein in soluble release form (sCAMs) in human aortic endothelial cells (HAECs) activated by TNF-α (1 or 10 ng/ml). Also, we determined the extent of lymphocyte adhesion to activated HAECs.

RESULTS

BAY reduced VCAM-1, E-selectin and ICAM-1 mRNA expression by 30, 30 and 10%, respectively. Furthermore, protein reduction of sVCAM-1 by 70%, sE-selectin by 51% and sICAM-1 by 25% compared to HAECs stimulated by TNF-α was observed (p < 0.05). AT (50, 75 and 150 µM) decreased VCAM-1 mRNA expression by 30% and sVCAM-1 protein by 33% compared to HAECs stimulated by TNF-α (p < 0.05). TNF-α-activated HAEC adhesion to human Jurkat T lymphocytes was higher compared to nonactivated HAECs (p < 0.05). BAY (2 and 5 µM) reduced this lymphocyte adhesion (p < 0.05).

CONCLUSION

BAY reduces all the CAMs studied as well as cell adhesion, while AT selectively inhibits VCAM-1; both induce endothelial dysfunction improvement.

Role of microRNAs in endothelial inflammation and senescence

The functionality of endothelial cells is fundamental for the homoeostasis of the vascular system. Increasing evidence shows that endothelial inflammation and senescence contribute greatly to multiple vascular diseases including atherosclerosis. However, little is known regarding the complex upstream regulators of gene expression and translation involved in these responses. MicroRNAs (miRNAs) have emerged as a novel class of endogenous, small, non-coding RNAs that negatively regulate over 30% of genes in a cell via degradation or translational inhibition of their target mRNAs. During the past few years, miRNAs have emerged as key regulators for endothelial biology and function. Endothelial inflammation is critically regulated by miRNAs such as miR-126 and miR-10a in vitro and in vivo. Endothelial aging is additionally controlled by miR-217 and miR-34a. In this review, we summarize the role of miRNAs and their target genes in endothelial inflammation and senescence, and discuss their applicability as drug targets.

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.

Metabolism and actions of conjugated linoleic acids on atherosclerosis-related events in vascular endothelial cells and smooth muscle cells

Conjugated linoleic acids (CLAs) are biologically highly active lipid compounds that have attracted great scientific interest due to their ability to cause either inhibition of atherosclerotic plaque development or even regression of pre-established atherosclerotic plaques in mice, hamsters and rabbits. The underlying mechanisms of action, however, are only poorly understood. Since cell culture experiments are appropriate to gain insight into the mechanisms of action of a compound, the present review summarizes data from cell culture studies about the metabolism and the actions of CLAs on atherosclerosis-related events in endothelial cells (ECs) and smooth muscle cells (SMCs), which are important cells contributing to atherosclerotic lesion development. Based on these studies, it can be concluded that CLAs exert several beneficial actions including inhibition of inflammatory and vasoactive mediator release from ECs and SMCs, which may help explain the anti-atherogenic effect of CLAs observed in vivo. The observation that significant levels of CLA metabolites, which have been reported to have significant biological activities, are well detectable in ECs and SMCs indicates that the anti-atherogenic effects observed with CLAs are presumably mediated not only by CLAs themselves but also by their metabolites.

Fatty acids and signalling in endothelial cells

The endothelium is critical for the maintenance of a proper vessel function. Disturbances of endothelial function, called endothelial dysfunction, have serious implications, and lead to the development of atherosclerosis. It is well established that the risk for atherosclerosis development is influenced by nutritional factors such as the intake of certain fatty acids. Due to the fundamental role of the endothelium for atherosclerosis development, it is, therefore, likely that fatty acids directly influence the function of endothelial cells. The present review aims to explain the divergent effects of different types of fatty acids on cardiovascular disease risk by summarizing in vitro-data on the effects of fatty acids on (1) important signalling pathways involved in the modulation of endothelial cell function, and (2) endothelial cell functional properties, namely vasoactive mediator release and mononuclear cell recruitment, both of which are typically dysregulated during endothelial dysfunction.

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.

Isomer specificity of conjugated linoleic acid (CLA): 9E,11E-CLA

Conjugated linoleic acids (CLA) were identified in 1980's, since then it has been intensively studied due to its various beneficial health effects such as anti-inflammatory, anti-atherogenic, anti-carcinogenic and anti-diabetic/obesity effects. Isomer specificity of a number of CLA isomers, especially predominant isomer 9Z,11E- and 10E,12Z-CLA, is now recognized. However, the less prevalent CLA isomers have not been well characterized. Recently, studies have reported the distinctively different effects of 9E,11E-CLA in colon cancer cells, endothelial cells, and macrophage cells compared to the rest of CLA isomers. In this review, various effects of CLAs, especially anti-inflammatory and anti-atherogenic effects, will be discussed with focusing on the isomer-specific effects and potential mechanism of action of CLA. At last, recent studies about 9E,11E-CLA in in vitro and animal models will be discussed.

Influence of n-3 polyunsaturated fatty acids on soluble cellular adhesion molecules as biomarkers of cardiovascular risk in young healthy subjects

BACKGROUND AND AIM

Serum levels of soluble cellular adhesion molecules (CAMs) and blood lipid parameters have been used as markers of inflammatory processes associated with cardiovascular disease (CVD) events. The present study evaluated the effects of the intake of n-3 polyunsaturated fatty acids (PUFAs) in fish and fish oil within energy-restricted diets, on soluble intercellular adhesion molecule-1 (sICAM-1) and soluble vascular adhesion molecule-1 (sVCAM-1).

METHODS AND RESULTS

Two hundred and seventy-five healthy European subjects aged between 20 and 40 years, were randomized to one of four hypocaloric dietary groups: control (sunflower oil capsules, no seafood), lean fish (3 x 150 g portions of cod/week), fatty fish (3 x 150 g portions of salmon/week), fish oil ((docosahexaenoic acid (DHA)+eicosapentaenoic acid (EPA) capsules, no seafood)). Diets rich in lean fish significantly decreased ICAM-1 levels, around 5% from baseline to endpoint (p<0.05), and had no effect on VCAM-1 levels. No significant differences were observed in sICAM-1 levels after the intervention with fatty fish or fish oils. On the other hand, these two seafood based diets were responsible for a significant increase of VCAM-1 levels [fatty fish; 16.1% and fish oil; 21.9%] respectively (p<0.05).

CONCLUSIONS

CAMs as inflammatory biomarkers in young and healthy subjects are not conclusive for the evaluation of CVD risk. Hypocaloric fish diets had a different effect on CAMs, being lean fish responsible for the highest decrease in ICAM-1. On the other hand, VCAM-1 results allow speculation that a low dose of n-3 PUFA may be anti-inflammatory contrarily to a high dose which can have a pro-inflammatory effect. CAMs mechanism is complex and affected by multiple factors such as lifestyle, gender, and n-3 dose and source.

Acetaldehyde stimulates monocyte adhesion in a P-selectin- and TNFalpha-dependent manner

OBJECTIVE

The aim of this study was to determine the effects of acetaldehyde on various steps of the monocyte recruitment cascade.

METHODS

Human umbilical venous endothelial cells (HUVEC), primary blood monocytes (PBM) and THP-1 monocytes, were treated with acetaldehyde (0.1-0 microM) for 6h. Monocyte adherence experiments were performed using 2',7'-bis(2-carboxyethyl)-5,6-carboxyfluorescein-acetoxymethylester labeled PBM or (3)H-thymidine labeled THP-1 cells. HUVEC TNFalpha mRNA and protein levels were determined by quantitative real-time PCR and immunoassay, respectively, and HUVEC P-selectin and monocyte CCR2 expression were determined by FACS analysis.

RESULTS

Acetaldehyde dose-dependently increased the number of CCR2 positive THP-1 monocytes, with a maximal increase of approximately 50% observed in the presence of 10 microM acetaldehyde. There was a significant increase in both the number of P-selectin positive cells and P-selectin receptor density when HUVEC were incubated with acetaldehyde. HUVEC TNFalpha mRNA expression and secretion were enhanced by acetaldehyde. Moreover, acetaldehyde increased THP-1 and PBM adhesion to HUVEC. Inhibition of P-selectin or TNFalpha, using antibodies or siRNA-directed gene knockdown, attenuated acetaldehyde-induced monocyte adhesion. In conclusion, acetaldehyde increased the number of CCR2 positive monocytes and stimulated endothelial cell P-selectin and TNFalpha expression. Moreover, acetaldehyde increased monocyte adhesion to endothelial cells, an effect that was both P-selectin- and TNFalpha-dependent.

CONCLUSION

These effects of acetaldehyde may contribute, in part, to the increase in coronary heart disease that is associated with binge patterns of alcohol consumption.

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.

Conjugated linoleic acid modulation of risk factors associated with atherosclerosis

Conjugated linoleic acid (CLA) has been the subject of extensive investigation regarding its possible benefits on a variety of human diseases. In some animal studies, CLA has been shown to have a beneficial effect on sclerotic lesions associated with atherosclerosis, be a possible anti-carcinogen, increase feed efficiency, and act as a lean body mass supplement. However, the results have been inconsistent, and the effects of CLA on atherogenesis appear to be dose-, isomer-, tissue-, and species-specific. Similarly, CLA trials in humans have resulted in conflicting findings. Both the human and animal study results may be attributed to contrasting doses of CLA, isomers, the coexistence of other dietary fatty acids, length of study, and inter-and/or intra-species diversities. Recent research advances have suggested the importance of CLA isomers in modulating gene expression involved in oxidative damage, fatty acid metabolism, immune/inflammatory responses, and ultimately atherosclerosis. Although the possible mechanisms of action of CLA have been suggested, they have yet to be determined.

Conjugated linoleic acid modulation of risk factors associated with atherosclerosis

Conjugated linoleic acid (CLA) has been the subject of extensive investigation regarding its possible benefits on a variety of human diseases. In some animal studies, CLA has been shown to have a beneficial effect on sclerotic lesions associated with atherosclerosis, be a possible anti-carcinogen, increase feed efficiency, and act as a lean body mass supplement. However, the results have been inconsistent, and the effects of CLA on atherogenesis appear to be dose-, isomer-, tissue-, and species-specific. Similarly, CLA trials in humans have resulted in conflicting findings. Both the human and animal study results may be attributed to contrasting doses of CLA, isomers, the coexistence of other dietary fatty acids, length of study, and inter-and/or intra-species diversities. Recent research advances have suggested the importance of CLA isomers in modulating gene expression involved in oxidative damage, fatty acid metabolism, immune/inflammatory responses, and ultimately atherosclerosis. Although the possible mechanisms of action of CLA have been suggested, they have yet to be determined.

Activation of peroxisome proliferator-activated receptor gamma (PPARgamma) suppresses Rho GTPases in human brain microvascular endothelial cells and inhibits adhesion and transendothelial migration of HIV-1 infected monocytes

Under inflammatory conditions (including HIV-1 encephalitis and multiple sclerosis), activated brain endothelium enhances the adhesion and transmigration of monocytes across the blood-brain barrier (BBB). Synthetic ligands that activate the peroxisome proliferator-activated receptors (PPARs) have anti-inflammatory properties, and PPAR stimulation prevents the interaction of leukocytes with cytokine stimulated-endothelium. However, the mechanism underlying these effects of PPAR ligands and their ability to intervene with leukocyte adhesion and migration across brain endothelial cells has yet to be explored. For the first time, using primary human brain endothelial cells (BMVEC), we demonstrated that monocyte adhesion and transendothelial migration across inflamed endothelium were markedly reduced by PPARgamma activation. In contrast to non-brain-derived endothelial cells, PPARalpha activation in the BMVEC had no significant effect on monocyte-endothelial interaction. Previously, our work indicated a critical role of Rho GTPases (like RhoA) in BMVEC to control migration of HIV-1 infected monocytes across BBB. In this study, we show that in the BMVEC PPARgamma stimulation prevented activation of two GTPases, Rac1 and RhoA, which correlated with decreased monocyte adhesion to and migration across brain endothelium. Relevant to HIV-1 neuropathogenesis, enhanced adhesion and migration of HIV-1 infected monocytes across the BBB were significantly reduced when BMVEC were treated with PPARgamma agonist. These findings indicate that Rac1 and RhoA inhibition by PPARgamma agonists could be a new approach for treatment of neuroinflammation by preventing monocyte migration across the BBB.

Conjugated linoleic acid isomers inhibit platelet-derived growth factor-induced NF-kappaB transactivation and collagen formation in human vascular smooth muscle cells

BACKGROUND

Atherosclerosis is characterized by extensive thickening of the arterial intima partially resulting from deposition of collagen by vascular smooth muscle cells (SMCs). Polyunsaturated fatty acids stimulate collagen formation through NF-kappaB activation.

AIM OF THE STUDY

The present study aimed to explore the effect of conjugated linoleic acids (CLAs) which are known to inhibit NF-kappaB activation on collagen formation by SMCs.

METHODS

Vascular SMCs were cultured with 50 micromol/l of CLA isomers (c9t11-CLA, t10c12-CLA) or linoleic acid (LA) and analysed for collagen formation and NF-kappaB p50 transactivation.

RESULTS

Treatment with CLA isomers but not LA significantly reduced PDGF-stimulated [(3)H] proline incorporation into cell layer protein of SMCs without altering cell proliferation. Simultaneous treatment with the PPARgamma inhibitor T0070907 abrogated this effect. Treatment of SMCs with c9t11-CLA and t10c12-CLA significantly reduced PDGF-induced NF-kappaB p50 activation.

CONCLUSIONS

CLA isomers inhibit PDGF-stimulated collagen production by vascular SMCs, which is considered to be a hallmark of atherosclerosis, in a PPARgamma-dependent manner. Whether inhibition of the NF-kappaB-pathway is of significance for the reduction of collagen formation by CLA isomers needs further investigation.

Regulation of adhesion molecule expression in human endothelial and smooth muscle cells by omega-3 fatty acids and conjugated linoleic acids: involvement of the transcription factor NF-kappaB?

We previously showed conjugated linoleic acids (CLA) inhibited TNF-alpha-induced monocyte (THP-1) adhesion to human umbilical vein endothelial cells (HUVEC) in vitro which involved an increase in platelet activating factor (PAF). Here we show adhesion molecule (ADM) regulation by fatty acids and the differing role of nuclear factor kappa B (NF-kappaB) activation in HUVEC and vascular smooth muscle cells (vSMC). CLA and omega-3 long-chain polyunsaturated fatty acids (PUFA) (FA) reduced TNF-alpha-induced expression of ADMs (intercellular adhesion molecule-1 (ICAM-1); vascular cell adhesion molecule-1 (VCAM-1) but not E-selectin) on HUVEC and vSMC to different extents depending on FA type and concentration, cell type and method of analysis. IkappaBalpha phosphorylation in HUVEC and vSMC and transient transfection with NF-kappaB-luciferase reporter plasmid (HUVEC only) indicated differential NF-kappaB involvement during FA modulation (cis-9, trans-11; trans-10, cis-12 and a 50:50 mix of both CLA isomers; eicosapentaenoic acid (EPA); docosahexaenoic acid (DHA)). TNF-alpha-induced ADM expression in both cell types by 2-10-fold. In HUVEC, CLA t10, c12 and CLA mix (50:50 mixture of CLA c9, t11 and t10, c12) and EPA and DHA reduced ICAM-1 expression (15-35%) at 12.5, 25 and/or 50 microM. VCAM-1 expression was reduced by 25 microM t10, c12 isomer and mix; omega-3 PUFA and other concentrations of CLA and TNF-alpha-induced E-selectin expression were unaffected. TNFalpha-induced inhibitor kappa B (IkappaB) phosphorylation was biphasic peaking at 5 min in both cell types and 60 and 120 min in HUVEC and SMC, respectively. IkappaBalpha phosphorylation and NF-kappaB activity was reduced (29% and 30%, respectively) by 25 microM CLA mix. n-3 PUFA did not reduce IkappaBalpha phosphorylation or NF-kappaB activity but reduced ADM expression. We show that n-3 PUFA and CLA reduce expression of ADM on HUVEC and vSMC. This reflected reduced adherence of monocytes to HUVEC previously reported by our group. Reduction of ICAM-1 and VCAM-1 protein expression by n-3 PUFA was less dependent on the NF-kappaB pathway than reduction by CLA which reflected the parallel attenuation of NF-kappaB activity. This indicated involvement of other transcription factors (i.e. AP-1) in the FA regulation of ADM expression and has, to our knowledge, not been previously reported.

Troglitazone but not conjugated linoleic acid reduces gene expression and activity of matrix-metalloproteinases-2 and -9 in PMA-differentiated THP-1 macrophages

Gene expression and activity of matrix-metalloproteinases (MMP)-2 and -9 in macrophages are reduced through peroxisome proliferator-activated receptor gamma (PPARgamma)-dependent inhibition of NF-kappaB. Since conjugated linoleic acids (CLAs) are PPARgamma ligands and known to inhibit NF-kappaB via PPARgamma, we studied whether CLA isomers are capable of reducing gene expression and gelatinolytic activity of MMP-2 and -9 in PMA-differentiated THP-1 macrophages, which has not yet been investigated. Incubation of PMA-differentiated THP-1 cells with either c9t11-CLA, t10c12-CLA or linoleic acid (LA), as a reference fatty acid, resulted in a significant incorporation of the respective fatty acids into total cell lipids relative to control cells (P<.05). Treatment of PMA-differentiated THP-1 cells with 10 and 20 micromol/L troglitazone but not with 10 or 100 micromol/L c9t11-CLA, t10c12-CLA or LA reduced relative mRNA concentrations and activity of MMP-2 and MMP-9 compared to control cells (P<.05). DNA-binding activity of NF-kappaB and PPARgamma and mRNA expression of the NF-kappaB target gene cPLA2 were not influenced by treatment with CLA. In contrast, treatment of PMA-differentiated THP-1 cells with troglitazone significantly increased transactivation of PPARgamma and decreased DNA-binding activity of NF-kappaB and relative mRNA concentration of cPLA2 relative to control cells (P<.05). In conclusion, the present study revealed that CLA isomers, in contrast to troglitazone, did not reduce gene expression and activity of MMP-2 and -9 in PMA-differentiated THP-1 macrophages, which is probably explained by the observation that CLA isomers neither activated PPARgamma nor reduced DNA-binding activity of NF-kappaB. This suggests that CLA isomers are ineffective in MMP-associated extracellular matrix degradation which is thought to contribute to the progression and rupture of advanced atherosclerotic plaques.

Cilostazol inhibits monocytic cell adhesion to vascular endothelium via upregulation of cAMP

AIM

Cilostazol is clinically used as an inhibitor of platelet aggregation. Although several reports have demonstrated its anti-inflammatory effect, its effect on monocytes and their adhesive interaction to vascular endothelium remains unclear. We thus examined the potential role of cilostazol towards monocyte endothelial interaction under physiological flow conditions.

METHODS

THP-1 cells, a monocytic cell line, were pretreated with cilostazol (5 microM) for 48 hours. The cells were then perfused over TNF-alpha (5 microg/mL for 4 hours)-stimulated monolayers of human umbilical vein endothelial cells (HUVECs) at shear stress of 1.0 dyen/cm(2).

RESULTS

TNF-alpha-activated HUVECs supported significantly more monocyte adhesion to HUVECs (7.32+/-1.25/HPF) compared to inactivated HUVECs (0.74+/-0.15/HPF), and the amount of adhesion to TNF-alpha-activated HUVECs was markedly reduced (3.63+/-0.55/HPF) when THP-1 cells were incubated in the presence of cilostazol at 5 microM. Interestingly, surface expressions of integrins were not dramatically changed after cilostazol treatment. Intracellular concentration of cAMP was significantly increased after cilostazol treatment, and treatment with Forskolin and Dibutyryl-cAMP, potent inducers of cAMP, dramatically increased THP-1 adhesion to HUVECs.

CONCLUSION

These data suggest that cilostazol has a potential anti-inflammatory effect on monocyte-endothelial interactions via the upregulation of intracellular cAMP.

Comparative effects of fatty acids on endothelial inflammatory gene expression

BACKGROUND

Endothelial dysfunction may be related to adverse effects of some dietary fatty acids (FAs). Although in vitro studies have failed to show consistent findings, this may reflect the diverse experimental protocols employed and the limited range of FAs and end points studied.

AIMS

To investigate the effect of dietary FA type (saturated, monounsaturated, n-6 and n-3 polyunsaturated fatty acids), concentration, incubation time and cell stimulation state, on a broad spectrum of endothelial inflammatory gene expression.

METHODS

Using human umbilical vein endothelial cells, with and without stimulation (+/-10 ng/ml TNFalpha), the effects of arachidonic (AA), docosahexaenoic (DHA), eicosapentaenoic (EPA), linoleic (LA), oleic (OA) and palmitic acids (PA) (10, 25 and 100 microM), on the expression of genes encoding a number of inflammatory proteins and transcription factors were assessed by quantitative real time RT-PCR.

RESULTS

Individual FAs differentially affect endothelial inflammatory gene expression in a gene-specific manner. EPA, LA and OA significantly up-regulated MCP-1 gene expression compared to AA (p = 0.001, 0.013, 0.008, respectively) and DHA (p < 0.0005, = 0.004, 0.002, respectively). Furthermore, cell stimulation state and FA incubation time significantly influenced reported FA effects on gene expression.

CONCLUSION

The comparative effects of saturated, monounsaturated, n-6 and n-3 polyunsaturated FAs on endothelial gene expression depend on the specific FA investigated, its length of incubation, cell stimulation state and the gene investigated. These findings may explain existing disparity in the literature.

The diversity of health effects of individual trans fatty acid isomers

There are multiple adverse effects of trans fatty acids (TFA) that are produced by partial hydrogenation (i.e., manufactured TFA), on CVD, blood lipids, inflammation, oxidative stress, endothelial health, body weight, insulin sensitivity, and cancer. It is not yet clear how specific TFA isomers vary in their biological activity and mechanisms of action. There is evidence of health benefits on some of the endpoints that have been studied for some animal TFA isomers, such as conjugated linoleic acid; however, these are not a major TFA source in the diet. Future research will bring clarity to our understanding of the biological effects of the individual TFA isomers. At this point, it is not possible to plan diets that emphasize individual TFA from animal sources at levels that would be expected to have significant health effects. Due to the multiple adverse effects of manufactured TFA, numerous agencies and governing bodies recommend limiting TFA in the diet and reducing TFA in the food supply. These initiatives and regulations, along with potential TFA alternatives, are presented herein.

Effect of conjugated linoleic acid on bone formation and rheumatoid arthritis

Conjugated linoleic acid (CLA) has shown a variety of biologically beneficial effects. Dietary CLA inhibits eddosteal bone resorption, increases endocortical bone formation, and modulates the action and expression of cyclooxygenase (COX) enzyme, thereby decreasing prostaglandin-dependent bone resorption. CLA also enhances calcium absorption and may improve bone formation in animals, although results are not consistent. Since CLA can also affect inflammatory cytokines, it is hypothesized that CLA may be a good tool for prevention or reduction of rheumatoid arthritis symptoms. The possible mechanisms by which CLA prevents rheumatoid arthritis as well as other inflammatory diseases is discussed.

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

Prostaglandin E2 produced endogenously (by cyclooxygenases) can regulate macrophage phagocytosis. Cyclooxygenase activity reduction (mainly through inhibition of inducible Cox-2) can induce PGE2 synthesis depression and can activate the phagocytosis process. There are no reports in the literature explaining whether conjugated linoleic acid dienes (trans-10, cis-12 CLA and cis-9, trans-11 CLA) modify the phagocytic activity of human macrophages. For the purpose of this study, monocytes were isolated from venous blood, incubated for 7 days with 30 microM CLAs, and then (in some experiments) LPS (1 microg/mL) was added to the medium. Subsequently, monocyte/macrophage phagocytosis, NF-kappaB transcription factor activity, Cox-2 and PPARgamma mRNA expression (and the amounts of Cox-2 and PPARgamma proteins) and PGE2 synthesis were determined. Both CLA isomers increased macrophage phagocytosis through inhibition of Cox-2 expression (might by inactivation the NF-kappaB pathway). The inhibition of mRNA Cox-2 expression contributed (particularly with respect to trans-10, cis-12 CLA) to a decrease in protein Cox-2 synthesis and to reduction of prostaglandin E2 content in the cell. The inhibition of PGE2 synthesis (by CLA treatment) enhanced the phagocytosis process in macrophages.

Carbamylated Low-Density Lipoprotein Induces Monocyte Adhesion to Endothelial Cells Through Intercellular Adhesion Molecule-1 and Vascular Cell Adhesion Molecule-1

Objective— Carbamylated low-density lipoprotein (LDL), the most abundant modified LDL isoform in human blood, has been recently implicated in causing the atherosclerosis-prone injuries to endothelial cells in vitro and atherosclerosis in humans. This study was aimed at testing the hypothesis that carbamylated LDL acts via inducing monocyte adhesion to endothelial cells and determining the adhesion molecules responsible for the recruitment of monocytes.

Methods and Results— Exposure of human coronary artery endothelial cells with carbamylated LDL but not native LDL caused U937 monocyte adhesion and the induction of intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 adhesion molecules as measured by cell enzyme-linked immunosorbent assay. Silencing of intercellular adhesion molecule-1 by siRNA or its inhibition using neutralizing antibody resulted in decreased monocyte adhesion to the endothelial cells. Similar silencing or neutralizing of vascular cell adhesion molecule-1 alone did not have an effect but was shown to contribute to intercellular adhesion molecule-1 when tested simultaneously.

Conclusions— Taken together, these data provide evidence that intercellular adhesion molecule-1 in cooperation with vascular cell adhesion molecule-1 are essential for monocyte adhesion by carbamylated low-density lipoprotein-activated human vascular endothelial cells in vitro.

Conjugated linoleic acid: a functional nutrient in the different pathophysiological components of the metabolic syndrome?

PURPOSE OF REVIEW

Much attention has focused on the therapeutic potential of conjugated linoleic acid with the most abundant isomers being cis-9,trans-11 conjugated linoleic acid and trans-10,cis-12 conjugated linoleic acid. Initial animal studies associated conjugated linoleic acid with beneficial health properties, such as reducing the risk of cancer, diabetes, atherosclerosis, inflammation and obesity. This review has appraised the evidence in relation to the effect of conjugated linoleic acid on components of the metabolic syndrome (clinically or experimentally), in particular, obesity, insulin resistance, atherosclerosis and inflammation.

RECENT FINDINGS

More recent human conjugated linoleic acid supplementation studies have often shown conflicting and less convincing health benefits. The marked variation between studies may reflect the isomer-specific effect of the individual conjugated linoleic acid isomers, which can often have opposing effects. Detrimental effects have been observed in some studies, in particular after supplementation with the trans-10,cis-12 conjugated linoleic acid isomer.

SUMMARY

Further studies and long-term clinical trials will be required to determine the efficacy and safety of conjugated linoleic acid isomers before conjugated linoleic acid could be considered as a functional nutrient in humans.

Cytokine-induced monocyte adhesion to endothelial cells involves platelet-activating factor: suppression by conjugated linoleic acid

Monocyte-endothelium interaction is key to many acute and chronic inflammatory diseases. We have investigated the factors regulating monocyte attachment to cytokine-activated human umbilical vein endothelial cells (HUVEC) and the modulatory effect of the polyunsaturated fatty acid (PUFA), conjugated linoleic acid (CLA) in this process. Both TNF-alpha and IL-1beta induced HUVEC platelet-activating factor (PAF) production and PAF was required for subsequent firm THP-1 monocyte adhesion since it was inhibited by both PAF receptor antagonists (BN-52021 or CV-6209) and a PAF synthesis inhibitor (sanguinarine). CLA inhibited the binding of both THP-1 and isolated human peripheral blood monocytes to HUVEC by up to 40% with the CLA t10,c12 isomer suppressing adhesion dose-dependently. Investigation into the mechanism involved demonstrated that with IL-1beta, VCAM-1 and ICAM-1 levels and pro-inflammatory cytokine expression were largely unaffected by CLA. Through the use of PAF receptor antagonists and PAF synthesis inhibitors, CLA was shown to inhibit cytokine-induced binding by suppressing PAF production. Direct assay of PAF levels confirmed this result. We conclude that endothelial-generated PAF plays a central role in cytokine-induced monocyte adherence to endothelium and that the anti-inflammatory action of PUFAs such as CLA in suppressing monocyte-endothelial interaction is mediated through attenuation of pro-inflammatory phospholipids such as PAF.