Docosahexaenoic acid attenuates VCAM-1 expression and NF-κB activation in TNF-α-treated human aortic endothelial cells

Anti-inflammatory effects of fish oil in ovaries of laying hens target prostaglandin pathways

Background

An effective way to control cancer is by prevention. Ovarian cancer is the most lethal gynecological malignancy. Progress in the treatment and prevention of ovarian cancer has been hampered due to the lack of an appropriate animal model and absence of effective chemo-prevention strategies. The domestic hens spontaneously develop ovarian adenocarcinomas that share similar histological appearance and symptoms such as ascites and metastasis with humans. There is a link between chronic inflammation and cancer. Prostaglandin E₂ (PGE₂) is the most pro-inflammatory ecoisanoid and one of the downstream products of two isoforms of cyclooxygenase (COX) enzymes: COX-1 and COX-2. PGE₂ exerts its effects on target cells by coupling to four subtypes of receptors which have been classified as EP1-4. Fish oil is a source of omega-3 fatty acids (OM-3FAs) which may be effective in prevention of ovarian cancer. Our objective was to assess the potential impact of fish oil on expression of COX enzymes, PGE₂ concentration, apoptosis and proliferation in ovaries of laying hens.

Methods

48 white Leghorn hens were fed 50, 100, 175, 375 and 700 mg/kg fish oil for 21 days. The OM3-FAs and omega-6 fatty acids contents of egg yolks were determined by Gas Chromatography. Proliferation, apoptosis, COX-1, COX-2 and prostaglandin receptor subtype 4 (EP4) protein and mRNA expression and PGE₂ concentration in ovaries were measured by PCNA, TUNEL, Western blot, quantitative real-time qPCR and ELISA, respectively.

Results

Consumption of fish oil increased the incorporation of OM-3FAs into yolks and decreased both COX-1 and COX-2 protein and mRNA expression. In correlation with COXs down-regulation, fish oil significantly reduced the concentrations of PGE₂ in ovaries. EP4 protein and mRNA expression in ovaries of hens was not affected by fish oil treatment. A lower dose of fish oil increased the egg laying frequency. 175 and 700 mg/kg fish oil reduced proliferation and 700 mg/kg increased apoptosis in hen ovaries.

Conclusions

Our findings suggest that the lower doses of fish oil reduce inflammatory PG and may be an effective approach in preventing ovarian carcinogenesis. These findings may provide the basis for clinical trials utilizing fish oil as a dietary intervention targeting prostaglandin biosynthesis for the prevention and treatment of ovarian cancer.

Endocannabinoid system as a potential mechanism for n-3 long-chain polyunsaturated fatty acid mediated cardiovascular protection

The presence of an active and functioning endocannabinoid (EC) system within cardiovascular tissues implies that this system has either a physiological or pathophysiological role (or both), and there is a substantial literature to support the notion that, in the main, they are protective in the setting of various CVD states. Moreover, there is an equally extensive literature to demonstrate the cardio- and vasculo-protective effects of n-3 long-chain (LC)-PUFA. It is now becoming evident that there appears to be a close relationship between dietary intervention with n-3 LC-PUFA and changes in tissue levels of EC, raising the question as to whether or not EC may, at least in part, play a role in mediating the cardio-and vasculo-protective effects of n-3 LC-PUFA. This brief review summarises the current understanding of how both EC and n-3 LC-PUFA exert their protective effects in three major cardiovascular disorders (hypertension, atherosclerosis and acute myocardial infarction) and attempts to identify the similarities and differences that may indicate common or integrated mechanisms. From the data available, it is unlikely that in hypertension EC mediate any beneficial effects of n-3 LC-PUFA, since they do not share common mechanisms of blood pressure reduction. However, inhibition of inflammation is an effect shared by EC and n-3 LC-PUFA in the setting of both atherosclerosis and myocardial reperfusion injury, while blockade of L-type Ca2+ channels is one of the possible common mechanisms for their antiarrhythmic effects. Although both EC and n-3 LC-PUFA demonstrate vasculo- and cardio-protection, the literature overwhelmingly shows that n-3 LC-PUFA decrease tissue levels of EC through formation of EC–n-3 LC-PUFA conjugates, which is counter-intuitive to an argument that EC may mediate the effects of n-3 LC-PUFA. However, the discovery that these conjugates have a greater affinity for cannabinoid receptors than the native EC provides a fascinating avenue for further research into novel approaches for the treatment and prevention of atherosclerosis and myocardial injury following ischaemia/reperfusion.

Obesity-associated oxidative stress: strategies finalized to improve redox state

Obesity represents a major risk factor for a plethora of severe diseases, including diabetes, cardiovascular disease, non-alcoholic fatty liver disease, and cancer. It is often accompanied by an increased risk of mortality and, in the case of non-fatal health problems, the quality of life is impaired because of associated conditions, including sleep apnea, respiratory problems, osteoarthritis, and infertility. Recent evidence suggests that oxidative stress may be the mechanistic link between obesity and related complications. In obese patients, antioxidant defenses are lower than normal weight counterparts and their levels inversely correlate with central adiposity; obesity is also characterized by enhanced levels of reactive oxygen or nitrogen species. Inadequacy of antioxidant defenses probably relies on different factors: obese individuals may have a lower intake of antioxidant- and phytochemical-rich foods, such as fruits, vegetables, and legumes; otherwise, consumption of antioxidant nutrients is normal, but obese individuals may have an increased utilization of these molecules, likewise to that reported in diabetic patients and smokers. Also inadequate physical activity may account for a decreased antioxidant state. In this review, we describe current concepts in the meaning of obesity as a state of chronic oxidative stress and the potential interventions to improve redox balance.

Docosahexaenoic acid and eicosapentaenoic acid reduce C-reactive protein expression and STAT3 activation in IL-6-treated HepG2 cells

C-reactive protein (CRP), an acute phase protein in humans, is predominantly produced by hepatocytes in response to interleukin-6 (IL-6). Several epidemiological studies have reported that dietary intake of n-3 polyunsaturated fatty acids (n-3 PUFAs) is inversely associated with serum CRP concentration. However, the molecular mechanism by which n-3 PUFAs reduce the serum CRP level in HepG2 cells remains unclear. The aims of this study were to examine the effect of the n-3 PUFAs, docosahexaenoic acid (DHA), and eicosapentaenoic acid (EPA), on the modulation of IL-6-induced CRP expression and to explore its possible mechanisms. We demonstrated that DHA and EPA inhibited IL-6-induced CRP protein and mRNA expression, as well as reduced CRP promoter activity in HepG2 cells. Knockdown of Signal Transducer and Activator of Transcription 3 (STAT3) and CCAAT box/Enhancer-Binding Protein β (C/EBPβ) by small interfering RNAs (siRNAs) significantly decreased IL-6-induced CRP promoter activity. Gel electrophoresis mobility shift assays (EMSA) showed that pretreatment with DHA and EPA decreased IL-6-induced STAT3 DNA binding activity but not C/EBPβ. By western blot analysis, DHA and EPA inhibited IL-6-induced STAT3 phosphorylation but not ERK1/2 or C/EBPβ. The suppression of the phosphorylation of STAT3 by DHA and EPA was further verified by immunofluorescence staining. Taken together, our results demonstrate that DHA and EPA are able to reduce IL-6-induced CRP expression in HepG2 cells via an inhibition of STAT3 activation. This mechanism, which explains the inhibitory effect of n-3 PUFAs on the CRP expression, provides new insights into the beneficial anti-inflammatory effect of n-3 PUFAs.

1α,25-Dihydroxyvitamin D(3) inhibits vascular cellular adhesion molecule-1 expression and interleukin-8 production in human coronary arterial endothelial cells

Kawasaki disease is an acute febrile vasculitis of childhood that is associated with elevated production of inflammatory cytokines, causing damage to the coronary arteries. The production of proinflammatory cytokines and expression of adhesion molecules in human coronary arterial endothelial cells (HCAECs) is regulated by nuclear transcription factor-κB (NF-κB) activation. We have previously reported that the active form of vitamin D, 1α,25-dihydroxyvitamin D(3) (1α,25-(OH)(2)D(3)), inhibits tumor necrosis factor-α (TNF-α)-induced NF-κB activation. In this study, we examined the anti-inflammatory effects of 1α,25-(OH)(2)D(3) on TNF-α-induced adhesion molecule expression (vascular cellular adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1)) and cytokine production (interleukin-6 (IL-6) and IL-8) in HCAECs. Pretreatment with 1α,25-(OH)(2)D(3) significantly inhibited TNF-α-induced VCAM-1 expression and IL-8 production in HCAECs. Our results suggest that adjunctive 1α,25-(OH)(2)D(3) therapy may modulate the inflammatory response during Kawasaki disease vasculitis.

The effect of dietary walnuts compared to fatty fish on eicosanoids, cytokines, soluble endothelial adhesion molecules and lymphocyte subsets: a randomized, controlled crossover trial

We tested the hypothesis that walnut consumption can exert effects on markers of inflammation and endothelial activation similar to those produced by fish consumption. In a crossover dietary intervention trial, 25 normal to mildly hyperlipidemic men and women were randomly assigned to one of three isoenergetic diets: a walnut diet incorporating 42.5 g of walnuts per 10.1 mJ 6 times per week (1.8% of energy n-3 fat); a fish diet providing 113 g of fatty fish per 10.1 mJ 2 times per week (0.8% of energy n-3 fat), or a control diet (no nuts or fish, 0.4% of energy n-3 fat) for 4 weeks on each diet. Both the walnut and fish diets inhibited circulating concentrations of prostaglandin E metabolite (PGEM) and 11-dehydro thromboxane B2, but demonstrated no effect on blood interleukin-1β (IL-1β), interleukin-6 (IL-6), tumor necrosis factor-α¯ (TNF-α¯), and C-reactive protein (CRP) or the number of circulating lymphocyte subsets. On the walnut diet the proportion of plasma phospholipid α¯-linolenic acid (ALA) increased 140% and arachidonic acid (AA) decreased 7% compared to both the control and fish diets. The proportion of plasma phospholipid eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) increased about 200% and 900% respectively on the fish diet relative to either the control or walnut diet. The walnut diet inhibited E-selectin by 12.7% relative to the fish diet, and the fish diet inhibited secretory intercellular adhesion molecule-1 (s-ICAM-1) by 4.5% relative to the control diet. Both walnuts and fish in commonly consumed amounts may have modest albeit distinct effects on circulating adhesion molecules.

IRF-1 and miRNA126 modulate VCAM-1 expression in response to a high-fat meal

RATIONALE

A high-fat diet accompanied by hypertriglyceridemia increases an individual's risk for development of atherosclerosis. An early event in this process is monocyte recruitment through binding to vascular cell adhesion molecule 1 (VCAM-1) upregulated on inflamed arterial endothelium. Diets high in polyunsaturated fatty acids (PUFAs) may provide athero-protection by ameliorating this effect.

OBJECTIVE

We investigated the acute regulation of VCAM-1 expression in human aortic endothelial cells (HAEC) in response to triglyceride-rich lipoproteins (TGRL) isolated from subjects after consumption of a high-fat meal.

METHODS AND RESULTS

Postprandial TGRL isolated from 38 subjects were categorized as proatherogenic or antiatherogenic according to their capacity to alter the inflammatory response of HAEC. Proatherogenic TGRL increased expression of VCAM-1, intercellular adhesion molecule 1 (ICAM-1), and E-selectin by ≈20% compared with stimulation with tumor necrosis factor-α alone, whereas antiatherogenic TGRL decreased VCAM-1 expression by ≈20% while still upregulating ICAM-1. The relative atherogenicity of TGRL positively correlated with particle density of TG, apolipoprotein (Apo)CIII, ApoE, and cholesterol. Ω3-PUFA mimicked the effect of antiatherogenic TGRL by downregulating VCAM-1 expression. TGRL exerted this differential regulation of VCAM-1 by reciprocally modulating expression and activity of the transcription factor interferon regulatory factor 1 (IRF-1) and expression of microRNA 126 (miR-126). Overexpression or silencing of IRF-1 or miR-126 expression recapitulated the proatherogenic or antiatherogenic regulation of VCAM-1.

CONCLUSIONS

In response to a high-fat meal, TGRL bias the inflammatory response of endothelium via transcriptional and posttranscriptional editing of VCAM-1. Subjects with an anti-inflammatory response to a meal produced TGRL that was enriched in nonesterified fatty acids, decreased IRF-1 expression, increased miR-126 activity, and diminished monocyte arrest.

Fish oil and vascular endothelial protection: bench to bedside

Fish oil is recommended for the management of hypertriglyceridemia and to prevent secondary cardiovascular disorders. Fish oil is a major source of ω-3-polyunsaturated fatty acids (PUFAs) such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Clinical studies suggest that fish oil not only prevents the incidence of detrimental cardiovascular events, but also lowers the cardiovascular mortality rate. In addition to a classic lipid-lowering action, ω-3-PUFAs in fish oil could regulate blood pressure and enhance vascular integrity and compliance. Additionally, ω-3-PUFAs have the ability to protect vascular endothelial cells by decreasing oxidative stress, halting atherosclerotic events, and preventing vascular inflammatory and adhesion cascades. Intriguingly, recent studies have demonstrated that ω-3-PUFAs improve the function of vascular endothelium by enhancing the generation and bioavailability of endothelium-derived relaxing factor (nitric oxide) through upregulation and activation of endothelial nitric oxide synthase (eNOS). This certainly opens up a new area of research identifying potential mechanisms influencing fish oil-mediated functional regulatory action on vascular endothelium. We address in this review the potential of fish oil to prevent vascular endothelial dysfunction and associated cardiovascular disorders. Moreover, the mechanisms pertaining to fish oil-mediated eNOS activation and nitric oxide generation in improving endothelial function are delineated. We finally suggest the importance of further studies to determine the dose adjustment of fish oil with an optimal ratio of EPA and DHA for achieving consistent cardiovascular protection.

β2-Glycoprotein I inhibits endothelial cell migration through the nuclear factor κB signalling pathway and endothelial nitric oxide synthase activation

β2-GPI (β2-glycoprotein I) is a plasma glycoprotein ascribed with an anti-angiogenic function; however, the biological role and molecular basis of its action in cell migration remain unknown. The aim of the present study was to assess the contribution of β2-GPI to HAEC (human aortic endothelial cell) migration and the details of its underlying mechanism. Using wound healing and Boyden chamber assays, we found that β2-GPI inhibited endothelial cell migration, which was restored by its neutralizing antibody. NF-κB (nuclear factor κB) inhibitors and lentiviral siRNA (small interfering RNA) silencing of NF-κB significantly attenuated the inhibitory effect of β2-GPI on cell migration. Moreover, β2-GPI was found to induce IκBα (inhibitor of NF-κB) phosphorylation and translocation of p65 and p50. We further demonstrated that mRNA and protein levels of eNOS [endothelial NO (nitric oxide) synthase] and NO production were all increased by β2-GPI and these effects were remarkably inhibited by NF-κB inhibitors and siRNAs of p65 and p50. Furthermore, β2-GPI-mediated inhibition of cell migration was reversed by eNOS inhibitors and eNOS siRNAs. The findings of the present study provide novel insight into the ability of β2-GPI to inhibit endothelial cell migration predominantly through the NF-κB/eNOS/NO signalling pathway, which indicates a potential direction for clinical therapy in vascular diseases.

Effects of fatty acids on endothelial cells: inflammation and monocyte adhesion

BACKGROUND

Diet is known to have an important impact on cardiovascular health. n-3 Fatty acids (FAs), found in high quantity in fish oil, have demonstrated beneficial effects in patients with coronary artery disease. The role of n-6 FAs remains more controversial. The objective of this study was to examine the effect of arachidonic acid (AA), an n-6 FA, and eicosapentanoic acid (EPA), an n-3 FA, on the interaction between monocytes and endothelial cells (ECs).

DESIGN

We used a cellular model of ECs (EA.hy.926) and monocytes (human leukemic myelomonocytic U937). Confluent ECs were treated with AA or EPA, in the presence of tumor necrosis factor-alpha (TNF-α) or vehicle alone for either 4 or 24h. Adhesion of monocytes to the endothelial monolayer was performed. For gene expression, reverse transcription, followed by real-time quantitative polymerase chain reaction, was performed.

RESULTS

There was a significant increase in adhesion of monocytes to the endothelial monolayer in the presence of n-6 FAs, both in the presence and in the absence of TNF-α at 4 and 24h. The adhesion of monocytes to the endothelial monolayer was decreased with n-3 FAs at 24h. Intercellular adhesion molecule 1, vascular cell adhesion molecule 1, E-Selectin, Interleukin 6, and TNF-α were significantly increased in ECs treated with n-6 FAs.

CONCLUSIONS

We conclude that AA increases inflammation and enhances the ability of ECs to bind monocytes in vitro. EPA leads to a decrease in the ability of EA.hy.926 to bind monocytes, although the effect appears more modest. Taken together, these data indicate that the n-6 FA AA could potentiate inflammation and early events of atherosclerosis.

Docosahexaenoic acid inhibits UVB-induced activation of NF-κB and expression of COX-2 and NOX-4 in HR-1 hairless mouse skin by blocking MSK1 signaling

Exposure to ultraviolet-B (UVB) radiation induces inflammation and photocarcinogenesis in mammalian skin. Docosahexaenoic acid (DHA), a representative ω-3 polyunsaturated fatty acid, has been reported to possess anti-inflammatory and chemopreventive properties. In the present study, we investigated the molecular mechanisms underlying the inhibitory effects of DHA on UVB-induced inflammation in mouse skin. Our study revealed that topical application of DHA prior to UVB irradiation attenuated the expression of cyclooxygenase-2 (COX-2) and NAD(P)H:oxidase-4 (NOX-4) in hairless mouse skin. DHA pretreatment also attenuated UVB-induced DNA binding of nuclear factor-kappaB (NF-κB) through the inhibition of phosphorylation of IκB kinase-α/β, phosphorylation and degradation of IκBα and nuclear translocation of p50 and p65. In addition, UVB-induced phosphorylation of p65 at the serine 276 residue was significantly inhibited by topical application of DHA. Irradiation with UVB induced phosphorylation of mitogen and stress-activated kinase-1 (MSK1), extracellular signal-regulated kinase (ERK) and p38 mitogen-activated protein (MAP) kinase, and all these events were attenuated by pretreatment with DHA. Blocking ERK and p38 MAP kinase signaling by U0126 and SB203580, respectively, diminished MSK1 phosphorylation in UVB-irradiated mouse skin. Pretreatment with H-89, a pharmacological inhibitor of MSK1, abrogated UVB-induced activation of NF-κB and the expression of COX-2 and NOX-4 in mouse skin. In conclusion, topically applied DHA inhibits the UVB-induced activation of NF-κB and the expression of COX-2 and NOX-4 by blocking the phosphorylation of MSK1, a kinase downstream of ERK and p38 MAP kinase, in hairless mouse skin.

Vasoprotection by dietary supplements and exercise: role of TNFα signaling

Vascular dysfunction contributes to the pathogenesis of various cardiovascular diseases. Dietary supplements, including fish oil, dietary fibers, and various natural products, and exercise training exert vasoprotective effects. However, the mechanisms underlying the vasoprotective benefits of dietary supplements and physical activity demand extensive investigation. Accumulating evidence suggests that inflammatory cytokine tumor necrosis factor-alpha (TNFα) plays a pivotal role in the dysregulation of macrovascular and microvascular function. TNFα induces vascular inflammation, monocyte adhesion to endothelial cells, vascular oxidative stress, apoptosis, and atherogenic response and participates in the regulation of thrombosis and coagulation through multiple signaling pathways involving NFκB, Sp1, activator protein 1, JNK, p38, STAT3, and so forth. Dietary supplements and exercise training decrease TNFα production and ameliorate TNFα-mediated pathological changes in vasculature. Thus, the inhibitory effects of dietary supplements and physical exercise on TNFα production and TNFα signaling may contribute to their vasoprotective properties.

Docosahexaenoic acid inhibits the adhesion of flowing neutrophils to cytokine stimulated human umbilical vein endothelial cells

The (n-3) PUFA, DHA, is widely thought to posses the ability to modulate the inflammatory response. However, its modes of interaction with inflammatory cells are poorly understood. In particular, there are limited data on the interactions of DHA with vascular endothelium, the cells that regulate the traffic of leukocytes from the blood into inflamed tissue. Using human umbilical vein endothelial cells (EC) cultured in a flow-based adhesion assay and activated with TNFα, we tested whether supplementing human umbilical vein EC with physiologically achievable concentrations of DHA would inhibit the recruitment of flowing neutrophils. DHA caused a dose-dependent reduction in neutrophil recruitment to the EC surface, although cells that became adherent were activated and could migrate across the human umbilical vein EC monolayer normally. Using EPA as an alternative supplement had no effect on the levels of neutrophil adhesion in this assay. Analysis of adhesion receptor expression by qPCR demonstrated that DHA did not alter the transcriptional activity of human umbilical vein EC. However, DHA did significantly reduce E-selectin expression at the human umbilical vein EC surface without altering the total cellular pool of this adhesion receptor. Thus, we have identified a novel mechanism by which DHA alters the trafficking of leukocytes during inflammation and demonstrate that this involves disruption of intracellular transport mechanisms used to present adhesion molecules on the surface of cytokine-stimulated EC.

Hydrogen sulfide attenuated tumor necrosis factor-α-induced inflammatory signaling and dysfunction in vascular endothelial cells

BACKGROUND

Hydrogen sulfide (H(2)S), the third physiologically relevant gaseous molecule, is recognized increasingly as an anti-inflammatory mediator in various inflammatory conditions. Herein, we explored the effects and mechanisms of sodium hydrosulfide (NaHS, a H(2)S donor) on tumor necrosis factor (TNF)-α-induced human umbilical vein endothelial cells (HUVEC) dysfunction.

METHODOLOGY AND PRINCIPAL FINDINGS

Application of NaHS concentration-dependently suppressed TNF-α-induced mRNA and proteins expressions of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1), mRNA expression of P-selectin and E-selectin as well as U937 monocytes adhesion to HUVEC. Western blot analysis revealed that the expression of the cytoprotective enzyme, heme oxygenase-1 (HO-1), was induced and coincident with the anti-inflammatory action of NaHS. Furthermore, TNF-α-induced NF-κB activation assessed by IκBα degradation and p65 phosphorylation and nuclear translocation and ROS production were diminished in cells subjected to treatment with NaHS.

SIGNIFICANCE

H(2)S can exert an anti-inflammatory effect in endothelial cells through a mechanism that involves the up-regulation of HO-1.

Caveolae: a regulatory platform for nutritional modulation of inflammatory diseases

Dietary intervention strategies have proven to be an effective means of decreasing several risk factors associated with the development of atherosclerosis. Endothelial cell dysfunction influences vascular inflammation and is involved in promoting the earliest stages of lesion formation. Caveolae are lipid raft microdomains abundant within the plasma membrane of endothelial cells and are responsible for modulating receptor-mediated signal transduction, thus influencing endothelial activation. Caveolae have been implicated in the regulation of enzymes associated with several key signaling pathways capable of determining intracellular redox status. Diet and plasma-derived nutrients may modulate an inflammatory outcome by interacting with and altering caveolae-associated cellular signaling. For example, omega-3 fatty acids and several polyphenolics have been shown to improve endothelial cell function by decreasing the formation of ROS and increasing NO bioavailability, events associated with altered caveolae composition. Thus, nutritional modulation of caveolae-mediated signaling events may provide an opportunity to ameliorate inflammatory signaling pathways capable of promoting the formation of vascular diseases, including atherosclerosis.