Docosahexaenoic and eicosapentaenoic acids inhibit in vitro human lymphocyte-endothelial cell adhesion

Modulation of endothelial cell responses and vascular function by dietary fatty acids

Healthy and functional endothelial cells play important roles in maintaining vascular homeostasis, whereas endothelial dysfunction initiates and exacerbates vascular disease progression. Interventional studies with dietary fatty acids have shown that these molecules have varying effects on vascular function. It is hypothesized that the actions of dietary fatty acids on vascular function may be mediated in part through endothelial cells. This review summarizes the results of studies that have examined the acute and chronic effects of dietary fatty acids on endothelial function and vascular properties in humans, as well as the potential mechanisms by which n-3 polyunsaturated fatty acids regulate endothelial function. Altogether, this article provides an extensive review of how fatty acids contribute to vascular function through their ability to modulate endothelial cells and discusses relationships between dietary fatty acids and endothelial cells in the context of vascular dysfunction.

Effects of supplemental long-chain omega-3 fatty acids and erythrocyte membrane fatty acid content on circulating inflammatory markers in a randomized controlled trial of healthy adults

The long-chain omega-3 polyunsaturated (n-3 PUFA), eicosapentaenoic (EPA) and docosahexaenoic acid (DHA), may have anti-inflammatory effects. We evaluated the dose-response effect of EPA+DHA supplementation on circulating TNF-α, IL-6, and CRP and explored associations between red blood cell (RBC) membrane PUFA content and TNF-α, IL-6, and CRP. Young adults with low fish intake (n=116) received one of five doses (0, 300, 600, 900, or 1,800 mg/d EPA+DHA) for 5 months. There were no significant effects of supplemental EPA+DHA on IL-6 or CRP; however, there was a marginal treatment effect for TNF-α (p<0.08). At baseline, higher quartiles of RBC DHA were associated with lower TNF-α (p=0.001); higher quartiles of arachidonic acid were associated with higher TNF-α (p=0.005). EPA+DHA supplementation had no dose-response effect on TNF-α, IL-6, or CRP in healthy young adults; however, associations between inflammatory markers and RBC PUFA warrant further investigation.

Endothelium and its alterations in cardiovascular diseases: life style intervention

The endothelium, which forms the inner cellular lining of blood vessels and lymphatics, is a highly metabolically active organ that is involved in many physiopathological processes, including the control of vasomotor tone, barrier function, leukocyte adhesion, and trafficking and inflammation. In this review, we summarized and described the following: (i) endothelial cell function in physiological conditions and (ii) endothelial cell activation and dysfunction in the main cardiovascular diseases (such as atherosclerosis, and hypertension) and to diabetes, cigarette smoking, and aging physiological process. Finally, we presented the currently available evidence that supports the beneficial effects of physical activity and various dietary compounds on endothelial functions.

Effects of n-3 PUFA supplementation on plasma soluble adhesion molecules: a meta-analysis of randomized controlled trials

BACKGROUND

Previous studies indicate that oral supplementation with n-3 PUFA protects against atherosclerotic disease by inhibiting inflammatory processes, which underlie atherosclerosis and are reflected by the plasma concentrations of soluble adhesion molecules. However, consistent results were not obtained among studies.

OBJECTIVE

The objective was to assess the effects of n-3 PUFA supplementation on plasma concentrations of soluble adhesion molecules.

DESIGN

We conducted a meta-analysis of randomized controlled trials identified from PubMed, Embase, the Cochrane Library, and reference lists of relevant articles and reviews.

RESULTS

Eighteen studies were included. n-3 PUFA supplementation reduced plasma concentrations of soluble intercellular adhesion molecule-1 [sICAM-1; weighted mean difference (WMD): -5.17; 95% CI: -10.07, -0.27; P = 0.04] but had no significant effects on soluble vascular cell adhesion molecule-1 (WMD: -5.90; 95% CI: -17.63, 5.84; P = 0.32), soluble P-selectin (WMD: -1.53; 95% CI: -4.33, 1.28; P = 0.29), or soluble E-selectin (WMD: 0.46; 95% CI: -1.54, 2.46; P = 0.65). Subgroup analysis stratified by the subjects' health status showed that n-3 PUFA supplementation reduced sICAM-1 concentrations in healthy subjects (WMD: -8.87; 95% CI: -15.20, -2.53; P = 0.006; heterogeneity test: I² = 0%, P = 0.76) and in subjects with dyslipidemia (WMD: -15.31; 95% CI: -26.82, -3.81; P = 0.009; heterogeneity test: I² = 26%, P = 0.26).

CONCLUSIONS

n-3 PUFA supplementation can reduce plasma concentrations of sICAM-1. The effect is identified in both healthy subjects and subjects with dyslipidemia, which supports the hypothesis that n-3 PUFA can be supplemented as a primary or secondary means for preventing the development as well as the progression of atherosclerosis.

Acquired resistance to Listeria monocytogenes during a secondary infection in a murine model fed dietary lipids

OBJECTIVE

The ω-3 polyunsaturated fatty acids can suppress immune system functions. This property may cause adverse effects by impairing host resistance to infection. The present study focused on estimating the impact of different dietary lipids on the immune system of mice after a secondary infection with Listeria monocytogenes.

METHODS

BALB/c mice were divided into five dietary groups of olive oil, fish oil, sunflower oil, high-oleic sunflower oil, or low fat that was administered for 8 wk. The mice were immunized with 10(3) colony-forming units. Thirty-eight days later, each mouse was challenged with 10(4) colony-forming units. Mice survival and bacterial clearance from livers and spleens were determined. In addition, cytokine, chemokine, and adhesion molecule productions were quantified from the sera.

RESULTS

Survival percentage in mice fed a fish oil diet was 100% and bacterial numbers from spleen were decreased at 72 h. Interleukin-12, intercellular adhesion molecule-1, and vascular cell adhesion molecule-1 productions were decreased. Levels of tumor necrosis factor-α and interferon-γ were increased, whereas macrophage inflammatory protein-1α (MIP-1α) production was unaltered.

CONCLUSION

Immune defense in mice fed a fish oil diet was improved after secondary exposure, acquiring an adequate resistance. This result could be attributable to an increase of a T-helper type 1 response.

Long-chain n-3 polyunsaturated fatty acids: new insights into mechanisms relating to inflammation and coronary heart disease

Evidence from observational studies, prospective cohort studies and randomized clinical intervention studies indicate that moderate doses of long-chain n-3 polyunsaturated fatty acids (LC n-3 PUFA) significantly decrease risk of fatal coronary heart disease (CHD). Higher doses and longer duration of intervention may also protect from non-fatal CHD events. The exact mechanisms through which LC n-3 PUFA has an effect on CHD are not well established but may include a decrease in fasting and postprandial triacylglycerol levels, a decrease in arrhythmias, modulation of platelet aggregation and decreased synthesis of pro-inflammatory agents. The mechanistic relation between LC n-3 PUFA and inflammation has attracted great interest, and in vitro studies have revealed that these fatty acids decrease endothelial activation, affect eicosanoid metabolism (including epoxygenation pathways) and induce inflammatory resolution. However, the effects of LC n-3 PUFA on established biomarkers of inflammation and endothelial activation in vivo are not strong. Consequently we need new and more sensitive and systemic biomarkers to reveal the effects of LC n-3 PUFA on localized inflammatory processes.

Long-chain polyunsaturated fat supplementation in children with low docosahexaenoic acid intakes alters immune phenotypes compared with placebo

OBJECTIVES

The objectives of this study were to assess the effects of long-term supplementation with arachidonic acid (AA; 20:4n-6) and docosahexaenoic acid (DHA; 22:6n-3) on cell phenotypes and cytokine production in children.

PATIENTS AND METHODS

This randomized, double-blind, placebo-controlled trial provided children, (ages 5-7 years; n = 37) who had low intakes of DHA, with a dietary supplement containing AA (20-30 mg daily) and DHA (14-21 mg daily) or a placebo supplement for 7 months. After the supplementation period, a series of stimulants (pokeweed mitogen, phytohemagluttinin, lipopolysaccharide, beta-lactoglobulin, and ibuprofen) was used to stimulate peripheral blood mononuclear cells ex vivo. Antigen expression on T cells (CD25 and CD80), B cells, and macrophages (CD54), as well as cytokine production (interleukin [IL]-4, IL-10, tumor necrosis factor, IL-2, IL-6, and interferon-gamma), were measured using flow cytometry, monoclonal antibodies, and cytometric bead array, respectively.

RESULTS

Mononuclear cells from children provided long-chain polyunsaturated fatty acids (LCPUFAs) had fewer CD8+ cells expressing CD25 and CD80 compared with placebo after exposure to each mitogen. The LCPUFA group also exhibited lower proportions of CD14+ cells after stimulation with beta-lactoglobulin and ibuprofen. The proportion of CD54+ cells was 2-fold higher for the LCPUFA group compared with placebo after exposure to ibuprofen and beta-lactoglobulin (P < 0.05). Each of these immune effects related to the amount of AA and/or DHA in the plasma and erythrocyte phospholipids.

CONCLUSIONS

Alterations in cell phenotypes were evident when children were supplemented with AA and DHA. The results of this study have important implications for immune development and sensitivity to antigens in children.

Influence of very long-chain n-3 fatty acids on plasma markers of inflammation in middle-aged men

This study investigated the effects of a moderate dose of long-chain n-3 polyunsaturated fatty acids (1.8 g eicosapentaenoic acid (EPA) plus 0.3g docosahexaenoic acid (DHA) per day) given for 8 weeks to healthy middle-aged males on cardiovascular risk factors, particularly plasma lipids and inflammatory markers. The study was double-blind and placebo-controlled. The proportion of EPA was significantly increased in plasma phosphatidylcholine (from 1.4% to 5.0% of total fatty acids; P<0.001), cholesteryl esters (from 1.2% to 4.5%; P<0.001) and triacylglycerols (from 0.3% to 1.8%; P<0.001). In contrast, the more modest increases in DHA in these lipid fractions were not significant. There was very little effect of n-3 fatty acids on the risk factors measured, apart from a reduction in plasma soluble intercellular adhesion molecule (sICAM)-1 concentration compared with placebo (P=0.05). The change in plasma sICAM-1 concentration was significantly inversely related to the change in DHA in plasma phosphatidylcholine (r=-0.675; P=0.001), but less so to the change in EPA (r=-0.406; P=0.076). Data from the present study suggest that marine oil providing 1.8 g of EPA plus 0.3g DHA/day is not sufficient to demonstrate marked effects on cardiovascular risk factors (plasma lipids and inflammatory markers) in healthy middle-aged men, although there may be a slight anti-inflammatory effect as indicated by the decrease in sICAM-1. The stronger association between changes in DHA than EPA and sICAM-1 concentrations suggest that DHA may be more anti-inflammatory than EPA. Thus, one reason why only limited effects were seen here may be that the dose of DHA provided was insufficient.

Background diet influences the anti-inflammatory effect of α-linolenic acid in dyslipidaemic subjects

Long-chain n-3 PUFA from fish oils are known to have anti-inflammatory effects. We evaluated the effect of α-linolenic acid (ALA), precursor of n-3 fatty acids, on serum inflammatory markers and soluble cellular adhesion molecules (sCAM) of dyslipidaemic males, relative to their background diet. Participants were assigned to two groups, based upon food intake patterns: (a) twenty-one dyslipidaemic subjects who habitually ate a Mediterranean–Cretan-type diet; (b) nineteen dyslipidaemic subjects who normally ate a Westernised Greek diet. All were supplemented with 8·1 g ALA/d for 12 weeks. We determined serum amyloid A (SAA), C-reactive protein (CRP), macrophage colony-stimulating factor (MCSF), IL-6, soluble vascular cell adhesion molecule-1 (sVCAM-1), soluble intercellular adhesion molecule-1 and soluble E-selectin concentrations at the beginning and the end of the ALA supplementation period. Serum baseline concentrations of inflammatory markers and sCAM were similar across the diet groups. Type of diet had a significant impact on the response of inflammatory markers to ALA supplementation. The Westernised Greek diet group showed a reduction in SAA (P<0·001), CRP (P=0·002), MCSF (P=0·005) and IL-6 (P=0·04) concentrations. The Mediterranean–Cretan-type background diet group showed a significant reduction only in MCSF concentrations (P=0·003). The sVCAM-1 concentrations were significantly reduced in both the Westernised Greek diet group (P=0·001) and the Mediterranean–Cretan-type diet group (P<0·001). The present study demonstrated that ALA supplementation lowered the serum concentrations of inflammatory markers more profoundly when the background diet was rich in saturated fatty acids and poor in MUFA.

Eicosapentaenoic acid and docosahexaenoic acid modulate mitogen-activated protein kinase activity in endothelium

Omega-3 polyunsaturated fatty acids (PUFA) regulate inflammation and immunoreaction partially via affecting endothelial functions. However, the intracellular signaling mechanisms for inhibiting endothelial activation by omega-3 PUFA remain unclear. We investigated the effects of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) on mitogen-activated protein kinases (MAPK) of endothelium. We analyzed the expression of extracellular signal-related kinases (ERK1/2), Jun amino-terminal kinases (JNK), and p38 mRNA by real-time RT-PCR and the kinases activity by western blotting in tumor necrosis factor-alpha (TNF-alpha)-activated human umbilical vein endothelial cells (HUVEC). We observed that EPA or DHA alone significantly reduced the TNF-alpha-induced activation of p38 and JNK kinases at a concentration of 20 microM, but EPA is a more potent inhibitor than DHA. In contrast, both EPA and DHA significantly counteracted the TNF-alpha-mediated deactivation of ERK1/2 kinases. Meanwhile, both EPA and DHA significantly attenuated the TNF-alpha-induced expression of p38 and ERK1/2 mRNA, and DHA but not EPA also reduced the TNF-alpha-induced JNK mRNA expression. We present data show that both EPA and DHA alone diminish activation of p38 and JNK kinases, while maintaining the activation of ERK1/2 kinases of TNF-alpha-stimulated HUVEC. This may contribute to the inhibiting effects of omega-3 PUFA on endothelial activation by proinflammatory stimuli.

Leukocyte adhesion and the pathophysiology of sickle cell disease

PURPOSE OF REVIEW

This article discusses the importance of leukocyte adhesion in sickle cell disease, and how this could be modulated for clinical benefit.

RECENT FINDINGS

Recurrent inflammation and vasculopathy occur in sickle cell disease. As a result, leukocytes and vascular endothelial cells are activated and increase their expression of adhesion molecules. Adhesion of leukocytes to other blood cells and endothelium contributes to vaso-occlusion in sickle cell disease. High-level expression of adhesion molecules by leukocytes is associated with clinically severe disease. Pancellular membrane lipid abnormalities, including reduced proportions of omega-3 fatty acids, occur in sickle cell disease. These lipid abnormalities are more severe in patients with disease complications and in those with a greater degree of anaemia. Since lipid constitution of cell membranes affects surface expression of adhesion molecules, the above findings could account for earlier observations that omega-3 fatty acids reduce P-selectin expression and reduce the frequency of sickle cell crisis. By inhibition of nuclear factor kappaB, glucocorticoids reduce activation of vascular endothelial cells, their expression of ligands for leukocyte adhesion molecules, and vaso-occlusion. Monoclonal antibodies to vascular endothelial intercellular adhesion molecule-1 inhibited hypoxia-induced vaso-occlusion in transgenic sickle mice.

SUMMARY

Although hydroxyurea and glucocorticoids reduce adhesion molecule expression by leukocytes and vascular endothelial cells, cytotoxicity and systemic side effects dampen enthusiasm for their use in sickle cell disease. Omega-3 fatty acids have shown promising efficacy and safety in pilot studies. A large clinical trial of these naturally occurring substances is required.

New Therapies for Sickle Cell Disease

New and developing therapeutic agents for the treatment of sickle cell disease include hydroxyurea (an unlicensed experimental drug in most countries), omega-3 fatty acids, and the Gardos channel inhibitor ICA-17043. Anti-cellular adhesion therapy has considerable prospects; however, it has yet to be translated into clinical practice. For specific disease manifestations, pulmonary hypertension responds well to oral arginine, l-carnitine, and exchange blood transfusion therapy alone or in combination with other agents. Primary stroke prevention with transfusion therapy is now considered standard care. Oral iron chelators are administered increasingly instead of the more inconvenient parenteral desferrioxamine. Deferiprone is licensed in Europe and India, and deferasirox (ICL670) holds out important promise because it has not been shown to affect blood cell counts.

Dietary (n-3) Polyunsaturated Fatty Acids Do Not Affect the In Vivo Development and Function of Listeria-Specific CD4+ and CD8+ Effector and Memory/Effector T Cells in Mice

We previously reported that in a mouse model, a diet high in (n-3) PUFA diminishes host survival following an infection from Listeria monocytogenes, a gram-positive bacterial pathogen. In this study we investigated the impact of (n-3) PUFA on the adaptive immune response to L. monocytogenes. BALB/c mice were fed experimental diets either devoid of or rich in (n-3) PUFA from fish oil for 4 wk and then infected with 10(6) actA-deficient L. monocytogenes. At 7 and 35 d postchallenge, effector and memory/effector T cells in the spleen were enumerated by flow cytometry. Surprisingly, the number of Listeria-specific CD4(+) and CD8(+) effector and memory/effector T cells in the spleen was not affected by (n-3) PUFA. Also, the effector cells derived from mice fed either diet were equally capable of conferring protective immunity upon adoptive transfer to naive recipients. Despite our previous data, which demonstrated that (n-3) PUFA profoundly impaired host resistance to L. monocytogenes, pathogen-specific T cell responses were not substantially affected by dietary (n-3) PUFA.

Blood mononuclear cells and platelets have abnormal fatty acid composition in homozygous sickle cell disease

Leukocyte adhesion to vascular endothelium contributes to vaso-occlusion and widespread organ damage in sickle cell disease (SCD). Previously, we found high expression of the adhesion molecules alphaMbeta2 integrin and L-selectin in HbSS individuals with severe disease. Since membrane n-6 and n-3 polyunsaturated fatty acids modulate cell adhesion, inflammation, aggregation and vascular tone, we investigated the fatty acid composition of mononuclear cells (MNC) and platelets of HbSS patients in steady state (n=28) and racially matched, healthy HbAA controls with similar age and sex distribution living in the same environment (n=13). MNC phospholipids of the patients had lower levels of docosahexaenoic acid (DHA, p<0.01) and increased arachidonic acid (AA, p<0.005) relative to HbAA controls. Similarly, platelets from HbSS patients had less eicosapentaenoic acid (EPA, p<0.05) and more AA (p<0.05) in choline phosphoglycerides (CPG), with reduced DHA (p<0.05) in ethanolamine phosphoglycerides. Platelet CPG had lower DHA levels in SCD patients with complications compared to those without (p<0.05). Reduced cell content of EPA and DHA relative to AA favours the production of aggregatory and proinflammatory eicosanoids that activate leukocytes and platelets. This facilitates inflammation, leukocyte adhesion, platelet aggregation and vaso-occlusion in SCD.

Reduction in homocysteine by n-3 polyunsaturated fatty acids after 1 year in a randomised double-blind study following an acute myocardial infarction: no effect on endothelial adhesion properties

We hypothesized that n-3 polyunsaturated fatty acids (n-3 PUFAs) as compared to corn oil administered for 1 year following an acute myocardial infarction (MI) may reduce plasma total homocysteine (p-tHcy), ultrasensitive C-reactive protein (microCRP), and the adhesive properties of the endothelium, expressed as soluble E-selectin (sE-selectin) and soluble intercellular adhesion molecule-1 (sICAM-1). In a prospective, randomised, double-blind study, 300 acute MI patients were allocated to highly concentrated n-3 PUFAs (n = 150) or corn oil (n = 150). After 1 year on treatment there was an intergroup difference in p-tHcy in favour of the n-3 group (n = 118), p = 0.022. However, sE-selectin, sICAM-1 and microCRP were unaffected by the treatment. In conclusion, reduction of p-tHcy by long-term n-3 PUFAs treatment was not associated with demonstrable effects on markers of endothelial adhesion properties.

Consumption of (n-3) fatty acids is related to plasma biomarkers of inflammation and endothelial activation in women

We evaluated the hypothesis that intake of (n-3) fatty acids is inversely associated with biomarkers of inflammation and endothelial activation. We conducted a cross-sectional study of 727 women from the Nurses' Health Study I cohort, aged 43-69 y, apparently healthy at time of a blood draw in 1990. Dietary intake was assessed by a validated FFQ in 1986 and 1990. C-reactive protein (CRP) levels were 29% lower among those in the highest quintile of total (n-3) fatty acids, compared with the lowest quintile; interleukin-6 (IL-6) levels were 23% lower, E-selectin levels 10% lower, soluble intracellular adhesion molecule (sICAM-1) levels 7% lower, and soluble vascular adhesion molecule (sVCAM-1) levels 8% lower. The intake of alpha-linolenic acid was inversely related to plasma concentrations of CRP (beta = -0.55, P = 0.02), Il-6 (beta = -0.36, P = 0.01), and E-selectin (beta = -0.24, P = 0.008) after controlling for age, BMI, physical activity, smoking status, alcohol consumption, and intake of linoleic acid (n-6) and saturated fat. Long-chain (n-3) fatty acids (eicosapentaenoic and docosahexaenoic) were inversely related to sICAM-1 (beta = -0.11, P = 0.03) and sVCAM-1 (beta = -0.17, P = 0.003). Total (n-3) fatty acids had an inverse relation with CRP (beta = -0.44, P = 0.007), IL-6 (beta = -0.26, P = 0.009), E-selectin (beta = -0.17, P = 0.004), sICAM-1 (beta = -0.07, P = 0.02), and sVCAM-1 (beta = -0.10, P = 0.004). These associations were not modified by intake of vitamin E, dietary fiber, trans fatty acids, or by the use of postmenopausal hormone therapy. In conclusion, this study suggests that dietary (n-3) fatty acids are associated with levels of these biomarkers reflecting lower levels of inflammation and endothelial activation, which might explain in part the effect of these fatty acids in preventing cardiovascular disease.

Impact of polyunsaturated fatty acids on cytoskeletal linkage of L-selectin

Polyunsaturated fatty acid [omega-3 polyunsaturated fatty acids (omega-3PUFAs)] incorporation into cell membranes has been shown to have potent anti-inflammatory activity, though the mechanisms involved are only partially characterized. Here, we show that PUFA enrichment of T cell membranes decreased the overall expression of L-selectin as well as a highly conserved epitope on L-selectin that may serve as a marker for optimal protein function. Additionally, PUFA enrichment inhibited L-selectin cytoskeletal association, which is thought to be important for optimal functional activity. In support of this, PUFA enrichment of gammadelta T cell membranes reduced L-selectin-dependent rolling interactions under conditions mimicking physiological flow. Taken together, these data suggest that the anti-inflammatory activity of omega-3 polyunsaturated fatty acids may be due, in part, to a novel effect on L-selectin, namely PUFA reduction or prevention of cytoskeletal association of L-selectin.

Immune response of postpartum dairy cows fed flaxseed

Thirty Holstein cows were allotted at calving to 10 groups of three cows blocked for similar calving dates to determine the effects of dietary fatty acids on functional properties of immunocompetent cells in early lactation and at breeding. Cows were assigned at calving to one of three isonitrogenous, isoenergetic, and isolipidic supplements based on either calcium salts of palm oil, Megalac, micronized soybeans, or whole flaxseed. On the day of AI and 20 d later, cows were injected with ovalbumin to measure the antibody response. Blood samples were taken at different times after calving (d 5, 21, 42, and 105) and after AI (d 0, 10, 20, and 40) for quantification of serum progesterone, fatty acids, and prostaglandin E2 concentrations. Isolated peripheral blood mononuclear cells were cultured to evaluate the proliferative response to concanavalin A and in vitro productions of interferon-gamma and prostaglandin E2. In general, feeding flaxseed increased serum omega-3 fatty acids concentration compared with feeding Megalac or soybeans, which decreased the omega-6 to omega-3 fatty acids ratio. There was a significant diet x day interaction for the proliferative response of mononuclear cells after calving and AI, indicating that cell responses from cows fed flaxseed were transiently reduced compared with those fed Megalac and soybeans. Moreover, during the breeding period, serum progesterone concentration was significantly greater in cows fed flaxseed compared with those fed Megalac, whereas serum concentration of prostaglandin E2 was significantly lower in cows fed flaxseed than in those fed Megalac or soybeans. Dietary treatments had no effect on the antibody response to ovalbumin and on in vitro productions of interferon-gamma and prostaglandin E2. However, interferon-gamma and prostaglandin E2 were impaired in the first 3 wk after parturition regardless of dietary treatment. These results suggest that changes in fatty acids, progesterone, and prostaglandins E2 concentrations in serum due to dietary treatment and physiological status influenced systemic immunity as shown by reduced proliferative response. However, other mechanisms must be considered and are discussed to explain dietary effect on lymphocyte proliferative response to mitogenic stimulation and other immune functions.

EPA and DHA attenuate ox-LDL-induced expression of adhesion molecules in human coronary artery endothelial cells via protein kinase B pathway

Uptake of oxidized low-density lipoprotein (ox-LDL) by endothelial cells is a critical step for the initiation and development of atherosclerosis. Adhesion molecules are inflammatory makers, which are upregulated by ox-LDL and play a pivotal role in atherogenesis. A number of studies suggest that fish and its constituents can reduce inflammation and decrease atherosclerosis. We hypothesized that fish oil constituents namely docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) may reduce expression of adhesion molecules induced by ox-LDL. Cultured human coronary artery endothelial cells (HCAECs) were incubated with ox-LDL for 24 h. Parallel groups of cells were pretreated with DHA or EPA (10 or 50 microM) overnight before incubation with ox-LDL. Ox-LDL markedly increased the expression of P-selectin and intracellular adhesion molecule-1 (ICAM-1) (both protein and mRNA) in HCAECs, and enhanced the adhesion of monocytes to the cultured HCAECs. Both EPA and DHA decreased ox-LDL-induced upregulation of expression of P-selectin and ICAM-1, and the enhanced adhesion of monocytes to HCAECs. To determine the role of protein kinase B (PKB) as an intracellular-signaling pathway, HCAECs were treated with the PKB upstream inhibitor wortmannin (100 nM) or transfected with plasmids encoding dominant-negative mutants of PKB (PKB-DN) before treatment with DHA. Ox-LDL alone downregulated the activity of PKB; DHA attenuated this effect of ox-LDL, and both wortmannin and PKB-DN blocked the effect of DHA. The present study in human coronary endothelial cells suggests that both EPA and DHA attenuate ox-LDL-induced expression of adhesion molecules, and the adhesion of monocytes to HCAECs by modulation of PKB activation. These effects may be important mechanisms of anti-atherosclerotic effects of fish and fish oils.

Dietary docosahexaenoic acid is more optimal than eicosapentaenoic acid affecting the level of cellular defence responses of the juvenile grouper Epinephelus malabaricus

The combined effects of dietary docosahexaenoic (DHA) and eicosapentaenoic (EPA) acids on phagocytic, respiratory burst, and leucocyte proliferative activities of the juvenile grouper, Epinephelus malabaricus, were investigated. The test fish were fed for 12wk on test diets containing 1g 100g(-1) diet of DHA and EPA in combinations (DHA/EPA: 3/1, 2/1, 1/1, 0.7/1, 0.3/1). In addition to promoting fish growth, high dietary DHA/EPA ratio significantly enhanced phagocytic and respiratory burst activities of grouper head-kidney leucocytes compared with low ratio. Significant correlations were found between leucocyte phagocytic or respiratory burst activities and concentrations of 20:3(n-3), DHA and EPA in fish liver and muscle tissues. Leucocyte proliferation was significantly higher (P< 0.05) when the diets were high in DHA/EPA ratio than low in DHA/EPA ratio, when stimulated by Con A and PHA-P, but not by LPS. Tissue DHA concentrations and leucocyte proliferation were significantly and positively correlated. Fortification of dietary DHA, thus increased T-cell proliferation and phagocytic function of grouper leucocytes. DHA is the only member in the (n-3) highly unsaturated fatty acid family that stimulated phagocytic functions of leucocytes and T-cell proliferation, and is more optimal than EPA affecting the cellular defence responses of the E. malabaricus juveniles.

Exercise, cachexia, and cancer therapy: a molecular rationale

Evidence from recent publications indicates that repeated exercise may enhance the quality of life of cancer patients. The lack of reported negative effects and the consistency of the observed benefits lead one to conclude that physical exercise may provide a low-risk therapy that can improve patients' capacity to perform activities of daily living and improve their quality of life. Repeated physical activity may attenuate the adverse effects of cancer therapy, prevent or reverse cachexia, and reduce risk for a second cancer through suppression of inflammatory responses or enhancement of insulin sensitivity, rates of protein synthesis, and anti-oxidant and phase II enzyme activities. These results most likely come about through the ability of physical exercise to attenuate a chronic inflammatory signaling process and to transiently activate the mitogen-activated protein kinase, c-Jun NH2-terminal kinase, c-Jun NH2-terminal kinase-mitogen-activated protein kinase, and nuclear factor-kappa B pathways and through its ability to enhance insulin sensitivity. Expanded molecular-based research into these areas may provide new insights into the biological mechanisms associated with cancer rehabilitation and endogenous risk.

Dietary modification of inflammation with lipids

The n-3 polyunsaturated fatty acids (PUFA) eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are found in high proportions in oily fish and fish oils. The n-3 PUFA are structurally and functionally distinct from the n-6 PUFA. Typically, human inflammatory cells contain high proportions of the n-6 PUFA arachidonic acid and low proportions of n-3 PUFA. The significance of this difference is that arachidonic acid is the precursor of 2-series prostaglandins and 4-series leukotrienes, which are highly-active mediators of inflammation. Feeding fish oil results in partial replacement of arachidonic acid in inflammatory cell membranes by EPA. This change leads to decreased production of arachidonic acid-derived mediators. This response alone is a potentially beneficial anti-inflammatory effect of n-3 PUFA. However, n-3 PUFA have a number of other effects which might occur downstream of altered eicosanoid production or might be independent of this activity. For example, animal and human studies have shown that dietary fish oil results in suppressed production of pro-inflammatory cytokines and can decrease adhesion molecule expression. These effects occur at the level of altered gene expression. This action might come about through antagonism of the effects of arachidonic acid-derived mediators or through more direct actions on the intracellular signalling pathways which lead to activation of transcription factors such as nuclear factor kappa B (NFB). Recent studies have shown that n-3 PUFA can down regulate the activity of the nuclear transcription factor NFB. Fish oil feeding has been shown to ameliorate the symptoms in some animal models of chronic inflammatory disease and to protect against the effects of endotoxin and similar inflammatory challenges. Clinical studies have reported that oral fish oil supplementation has beneficial effects in rheumatoid arthritis and among some patients with asthma, supporting the idea that the n-3 PUFA in fish oil are anti-inflammatory. There are indications that inclusion of n-3 PUFA in enteral and parenteral formulas might be beneficial to patients in intensive care or post-surgery.

Ranking the toxicity of fatty acids on Jurkat and Raji cells by flow cytometric analysis

The fatty acids have an important role in the control of leukocyte metabolism and function. Higher concentrations of certain fatty acids, particularly polyunsaturated fatty acids (PUFAs) and volatile fatty acids, can cause cell death via apoptosis or, when concentrations are greater, necrosis. In this study, we determined the highest concentrations of various fatty acids that are non-toxic to two human leukemic cell lines, Jurkat (T-lymphocyte) and Raji (B-lymphocyte). Toxicity was evaluated by either loss of membrane integrity and/or DNA fragmentation using flow cytometric analysis. There were no remarkable differences for the toxicity of the fatty acids between B and T cell lines. The cytotoxicity of the fatty acids was related to the carbon chain length and number of double bonds: docosahexaenoic acid=eicosapentaenoic acid=arachidonic acid=gamma-linolenic acid=stearic acid=palmitic acid > linoleic acid=palmitoleic acid > vacenic acid=lauric acid > oleic acid > elaidic acid > capric acid > butyric acid > caprylic acid=caproic acid=propionic acid. The proportion of cells undergoing apoptosis or necrosis, induced by the fatty acids tested, remains to be investigated.

Influence of dietary supplementation with long-chain n-3 or n-6 polyunsaturated fatty acids on blood inflammatory cell populations and functions and on plasma soluble adhesion molecules in healthy adults

Greatly increasing the amounts of flaxseed oil [rich in alpha-linolenic acid (ALNA)] or fish oil (FO); [rich in eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)] in the diet can decrease inflammatory cell functions and so might impair host defense. The objective of this study was to determine the effect of dietary supplementation with moderate levels of ALNA, gamma-linolenic acid (GLA), arachidonic acid (ARA), DHA, or FO on inflammatory cell numbers and functions and on circulating levels of soluble adhesion molecules. Healthy subjects aged 55 to 75 yr consumed nine capsules per day for 12 wk. The capsules contained placebo oil (an 80:20 mix of palm and sunflowerseed oils) or blends of placebo oil with oils rich in ALNA, GLA, ARA, or DHA or FO. Subjects in these groups consumed 2 g ALNA; approximately 700 mg GLA, ARA, or DHA; or 1 g EPA plus DHA (720 mg EPA + 280 mg DHA) daily from the capsules. Total fat intake from the capsules was 4 g per day. None of the treatments affected inflammatory cell numbers in the bloodstream; neutrophil and monocyte phagocytosis or respiratory burst in response to E. coli; production of tumor necrosis factor-alpha, interleukin-1beta, and interleukin-6 in response to bacterial lipopolysaccharide; or plasma concentrations of soluble intercellular adhesion molecule-1. In contrast, the ALNA and FO treatments decreased the plasma concentrations of soluble vascular cell adhesion molecule-1 (16 and 28% decrease, respectively) and soluble E-selectin (23 and 17% decrease, respectively). It is concluded that, in contrast to previous reports using higher amounts of these fatty acids, a moderate increase in consumption of long-chain n-6 or n-3 polyunsaturated fatty acids does not significantly affect inflammatory cell numbers or neutrophil and monocyte responses in humans and so would not be expected to cause immune impairment. Furthermore, we conclude that moderate levels of ALNA and FO, which could be incorporated into the diet, can decrease some markers of endothelial activation and that this mechanism of action may contribute to the reported health benefits of n-3 fatty acids.

Endothelial cell prostacyclin synthesis induced by lymphocytes is independent of the membrane fatty acid composition of both cell types and of E-selectin, VCAM-1 or ICAM-1-mediated adhesion

Prostacyclin (PGI2), the main prostanoid in most vascular tissues regulates haemostasis and vascular tone, as well as the proliferation of smooth muscle cells. We have previously reported that lymphocyte contact with endothelium enhances endothelial cell PGI2 output. Here, we demonstrate the specificity of lymphocytes for switching on this response. Co-incubation of human umbilical vein endothelial cells (HUVEC) in serum-free medium with allogeneic peripheral blood lymphocytes (PBL), at a PBL:HUVEC ratio of 9:1, enhanced the basal (HUVEC alone) PGI2 output by 2.5-fold under static conditions, and was not altered in conditions mimicking shear stress. It occurred without previous activation of either cell type and was dependent upon specific interactions with PBL. Indeed, the PGI2 output induced by the co-incubation with resting neutrophils, non-activated platelets or latex beads was significantly lower than that induced by PBL. Blocking endothelial cell adhesion molecules (ECAM) E-selectin, vascular cell adhesion molecule-1 (VCAM-1) or intracellular adhesion molecule-1(ICAM-1) did not modify the PBL-induced PGI2 output, although 51Cr-labelled PBL adhesion was significantly decreased with anti-ICAM-1 antibody. Changes in the fatty acid composition of membrane phospholipids induced by incubation with eicosapentaenoic (EPA) or docosahexaenoic acids (DHA) resulted in diminished basal PGI2 output and adhesion of 51Cr-labelled PBL, whereas the PBL-stimulated PGI2 output was not modified. This specific cell-cell interaction represents a new stimulus for PGI2 synthesis that does not primarily involve the ECAM pathway, is independent of cell membrane fatty acid composition and shear stress. This switch-on for PGI2 synthesis, which is induced by lymphocytes, might serve as a protection against atherogenesis.

Dietary modulation of endothelial function: implications for cardiovascular disease

The vascular endothelium is the primary site of dysfunction in many diseases, particularly cardiovascular disease. A variety of risk factors, including smoking, hypercholesterolemia, hyperhomocysteinemia, hypertension, and diabetes mellitus, adversely affect endothelial function. Emerging evidence suggests an important role of dietary factors in modulating endothelial function. In particular, n-3 fatty acids, antioxidant vitamins (especially vitamins E and C), folic acid, and L-arginine appear to have beneficial effects on vascular endothelial function, either by decreasing endothelial activation or by improving endothelium-dependent vasodilation in patients at high risk of cardiovascular disease as well as in healthy subjects. These effects may serve as one potential mechanism through which these nutrients reduce the risk of cardiovascular disease, as observed in epidemiologic studies and several clinical trials. This article reviews clinical and experimental evidence regarding the role of these nutrients in modulating endothelial function and their potential to prevent cardiovascular disease.

n-3 polyunsaturated fatty acid supplementation, monocyte adhesion molecule expression and pro-inflammatory mediators in Type 2 diabetes mellitus

AIMS

To examine the effect of n-3 polyunsaturated fatty acid supplements on the monocyte surface expression of adhesion molecules involved in proatherogenic monocyte-endothelial interactions, and on pro-inflammatory mediators in Type 2 diabetes mellitus.

METHODS

Twenty-nine subjects with Type 2 diabetes and 21 controls without diabetes were studied. Monocyte expression of leucocyte function-associated antigens 1 and 3, intercellular adhesion molecule-1, and the major histocompatibility complex class II molecule HLA-DR were measured using a laser flow cytometric method. Supplementation with 2.08 g n-3 fatty acids for 21 days was undertaken and measurements repeated. Plasma soluble adhesion molecule concentrations, plasminogen activator inhibitor-1 activity and antigen and pro-inflammatory mediators (cysteinyl leukotriene and monocyte leukotriene B4) were also measured.

RESULTS

Groups did not differ in monocyte expression of adhesion molecules or HLA-DR, or in leukotriene production although plasma soluble adhesion molecule concentrations were higher in the diabetes groups (P<0.05). n-3 fatty acid supplementation influenced neither the expression of these molecules nor plasma soluble adhesion molecule concentrations or leukotriene production.

CONCLUSIONS

This study does not support increased monocyte adhesion molecule expression or abnormal monocyte production of pro-inflammatory mediators as mechanisms for increased atherogenic risk in Type 2 diabetes. Cardioprotective actions of n-3 fatty acids may not be mediated through these mechanisms.

Development of an ex vivo model of pig kidney perfused with human lymphocytes. Analysis of xenogeneic cellular reactions

BACKGROUND

Because of the explosive nature and the extremely rapid process of hyperacute rejection (HAR), significant infiltration of the xenograft by immunocompetent cells is not observed, and the role and the mechanism of action of cell-mediated rejection in discordant xenografts are therefore still under discussion.

METHOD

We developed an experimental approach using pig kidneys perfused with human peripheral blood lymphocytes (PBL) in which the immunologic barrier of hyperacute rejection was excluded and which mimics the in vivo situation.

RESULTS

PBL retention in the kidney was evaluated at 20-minute intervals for 3 hours. Retention increased from 30% to 80% with the time of perfusion and was specific because significantly fewer syngeneic lymphocytes were retained. Phenotype analysis of recovered PBL showed a significant decrease in natural killer (NK) cells. Immunohistochemical studies revealed the presence of NK cells and T lymphocytes in the glomerular and interstitial tubular structures of the kidney. Functional studies showed a progressive cessation of diuresis and augmentation of renal vascular resistance when the kidney was perfused with PBL. Electron microscopy examinations of kidney sections perfused with PBL showed swollen endothelial zones, suggesting alterations to and damage of the endothelium.

CONCLUSIONS

This system provides a valuable model for the study of early discordant xenogeneic cellular rejection and demonstrates the predominance of xenograft infiltration by NK cells.

Extracellular release of free fatty acids by rat T lymphocytes is stimulus-dependent and is affected by dietary lipid manipulation

[(3)H]-Arachidonic acid-labelled rat T lymphocytes released radioactivity extracellularly when stimulated by the calcium ionophore A23187 or by monoclonal antibodies to some cell surface structures (CD2, CD5, CD11a, CD18, CD54, T-cell receptor) but not to others (CD49d, CD62L); release was greater with the calcium ionophore. Almost all of the radioactivity released from anti-CD2-stimulated lymphocytes was recovered in the free fatty acid fraction, whereas only about 50 per cent of that released after A23187 stimulation was recovered in this fraction. A23187 stimulation resulted in release of arachidonic acid from a variety of phospholipids (phosphatidylinositol, phosphatidylcholine and perhaps phosphatidylethanolamine), while the monoclonal antibody stimulation released arachidonic acid from phosphatidylinositol and perhaps phosphatidylcholine. Unstimulated lymphocytes released a range of fatty acids extracellularly, with palmitic acid accounting for 35-40 per cent and arachidonic acid for 5 per cent of released fatty acid. Stimulation of lymphocytes with either anti-CD2 or A23187 increased total fatty acid release 1.5- to 1.8-fold. In both cases palmitic acid remained the most predominant fatty acid released but the contribution of arachidonic acid increased. The type of lipid fed to the rats significantly influenced the amount and type of fatty acid released. Fish oil feeding significantly reduced extracellular fatty acid release by stimulated lymphocytes.

Omega-3 fatty acids alter soluble markers of endothelial function in coronary heart disease patients

Several studies have indicated that omega-3 poly-unsaturated fatty acids in fish oil have protective effects on cardiovascular disease by reducing vascular endothelial inflammation in atherosclerosis. In a recent study, supplementation of patients with fish oil following coronary angioplasty elevated levels of lipid peroxides and two adhesion molecules in plasma suggesting a proinflammatory action of fish oil. However, decreases in several plasma markers of endothelial hemostatic activity indicated a healthier and better vasculature associated with fish oil supplementation.

Effects of eicosapentaenoic acid and docosahexaenoic acid on plasma membrane fluidity of aortic endothelial cells

We investigated the relative effects of n-3 eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3) on the plasma membrane fluidity of endothelial cells (EC) cultured from the thoracic aorta by determining fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene (DPH) and its cationic derivative trimethylamino-DPH (TMA-DPH). Fluidity assessed by TMA-DPH demonstrated no significant differences in plasma membranes of vehicle (dimethyl sulfoxide; DMSO)-, EPA-, and DHA-treated EC. Plasma membrane fluidity assessed by DPH polarization, however, was significantly higher in the order of DHA > EPA > DMSO. Total cholesterol content decreased significantly by 28.4 and 15.9% in the plasma membranes of DHA- and EPA-treated cells, respectively. Total phospholipid content remained unaltered in the plasma membranes of the three groups of cells; however, the molar ratio of total cholesterol to phospholipid decreased significantly only in the membranes of DHA-treated EC. The unsaturation index in the plasma membranes of EPA- and DHA-treated cells increased by 35.7 and 64.3%, respectively, compared with that in the plasma membranes of control cells. The activities of catalase and glutathione peroxidase in the whole-cell homogenates, and levels of lipid peroxides in either the whole-cell homogenates or in plasma membrane fractions were not altered in EPA- or DHA-treated EC. These results indicate that the influence of DHA is greater than that of EPA in increasing plasma membrane fluidity of vascular EC. We speculate that the greater effect of DHA compared to EPA is due to its greater ability to decrease membrane cholesterol content or the cholesterol/phospholipid molar ratio, or both, and also to its greater ability in elevating the unsaturation index in the plasma membranes of EC.

Dietary fish oil diminishes lymphocyte adhesion to macrophage and endothelial cell monolayers

To further investigate the immunomodulatory effects of dietary lipids, rats were fed on a low-fat diet or on high-fat diets that contained hydrogenated coconut, olive, safflower, evening primrose or fish oil as the principal fat source. The fish oil diet decreased the level of expression of CD2, CD11a, CD18 and CD44 on the surface of freshly prepared lymphocytes and of CD2, CD11a, CD18, CD54 (intercellular adhesion molecule-1; ICAM-1) and CD62L (L-selectin) on the surface of concanavalin A (Con A)-stimulated lymphocytes. The olive oil diet also resulted in decreased expression of some adhesion molecules. The fish or olive oil diets, and to a lesser extent the safflower or evening primrose oil diets, decreased the adhesion of both freshly prepared and Con A-stimulated lymphocytes to macrophage monolayers. The fish oil diet, and to a lesser extent the olive or evening primrose oil diets, reduced the ability of Con A-stimulated lymphocytes to adhere to untreated endothelial cells. Furthermore, the fish oil diet resulted in a 50% reduction in Con A-stimulated lymphocyte adhesion to tumour necrosis factor-alpha (TNF-alpha)-stimulated endothelial cells. This study demonstrates that dietary lipids affect the expression of functionally important adhesion molecules on the surface of lymphocytes. Furthermore, this study suggests that such diet-induced effects on adhesion molecule expression might alter the ability of lymphocytes to bind to macrophages and to endothelial cells. Of the diets studied fish oil causes the most significant effects. The results of this study suggest that a reduction in cellular infiltration may partly explain the protective effect of a fish-oil-rich diet against the development of inflammatory and cardiovascular diseases.

Lipids and the immune response

The effects of fatty acids on immune responses have been studied since the early 1970s, but much controversy still remains. The present review examines recent studies in both animals and in humans, and highlights some new and exciting ideas concerning the mechanism by which fatty acids may affect immune responses in both normal and pathological situations, an area which is likely to progress rapidly over the next few years.

Clinical use of lipids to control inflammatory disease

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

Inhibitory effects of oleic and docosahexaenoic acids on lung metastasis by colon-carcinoma-26 cells are associated with reduced matrix metalloproteinase-2 and -9 activities

In order to determine the effects of single unsaturated fatty acids (UFAs) or combinations on establishment of lung metastatic colonies, UFAs were administered orally to CDF1 mice bearing s.c. implants of the highly metastatic colon carcinoma 26. Oleic acid (OA), docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) demonstrated significant inhibition. In the case of DHA, this inhibitory potential was markedly reduced by co-administration of linoleic acid (LA) or EPA. Furthermore, while tumor cells treated with DHA showed a very low potential for lung colony formation when injected i.v., this again being partially reversed by co-administration of EPA. UFAs were found to be well absorbed into tumor tissues after oral administration, causing marked changes in relative levels, the arachidonic acid (AA) content, in particular, being markedly decreased by treatment with DHA or EPA, but not with DHA plus EPA or with DHA plus LA. Investigation of the gelatinolytic activity of the 57-kDa and 92-kDa isoforms of type-IV collagenase (MMP-2 and MMP-9, respectively) showed a clear reduction in the former by treatment with OA, while DHA, but not DHA plus LA or EPA, caused a decrease in the 92-kDa isoform, which was well correlated with AA content in tumor tissues (r = 0.900, p < 0.001). These results suggest that inhibition of metastasis due to treatment with OA and DHA might be due to depressed type-IV collagenase activity.