Fatty acids and lymphocyte functions

Dihomo-gamma-linolenic acid inhibits tumour necrosis factor-alpha production by human leucocytes independently of cyclooxygenase activity

Dietary oils (such as borage oil), which are rich in gamma-linolenic acid (GLA), have been shown to be beneficial under inflammatory conditions. Dihomo-GLA (DGLA) is synthesized directly from GLA and forms a substrate for cyclooxygenase (COX) enzymes, resulting in the synthesis of lipid mediators (eicosanoids). In the present study, the immunomodulatory effects of DGLA were investigated and compared with those of other relevant fatty acids. Freshly isolated human peripheral blood mononuclear cells (PBMC) were cultured in fatty acid (100 microm)-enriched medium for 48 hr. Subsequently, cells were stimulated with lipopolysaccharide (LPS) for 20 hr and the cytokine levels were measured, in supernatants, by enzyme-linked immunosorbent assay (ELISA). Phospholipids were analysed by gas chromatography. Fatty acids were readily taken up, metabolized and incorporated into cellular phospholipids. Compared with the other fatty acids tested, DGLA exerted pronounced modulatory effects on cytokine production. Tumour necrosis factor-alpha (TNF-alpha) and interleukin (IL)-10 levels were reduced to 60% of control levels, whereas IL-6 levels were not affected by DGLA. Kinetic studies showed that peak levels of TNF-alpha, occurring early after LPS addition, were inhibited strongly, whereas IL-10 levels were not affected until 15 hr after stimulation. Both the reduction of cytokine levels and the decrease in arachidonic acid levels in these cells, induced by DGLA, were dose dependent, suggesting a shift in eicosanoid-subtype synthesis. However, although some DGLA-derived eicosanoids similarly reduced TNF-alpha levels, the effects of DGLA were probably not mediated by COX products, as the addition of indomethacin did not alter the effects of DGLA. In conclusion, these results suggest that DGLA affects cytokine production by human PBMC independently of COX activation.

Effect of arachidonic acid on proliferation, cytokines production and pleiotropic genes expression in Jurkat cells--a comparison with oleic acid

The effects of arachidonic (AA) and oleic acids (OA) on proliferation, cytokine production and pleiotropic genes expression in Jurkat T cells were investigated. The following parameters were evaluated: cytotoxicity assessed by loss of membrane integrity and DNA fragmentation, cell proliferation as measured by [14C]-thymidine incorporation, production of IL-2, IL-4, IL-10, and INF-gamma, and expression of pleiotropic genes as determined by macroarray technique (83 genes in total). AA was more toxic for Jurkat cells than OA. However, the inhibiting effect of OA on Jurkat cells proliferation was more pronounced than that of AA. The reduction in the production of IL-2 and INF-gamma was more intense by OA (50 microM) than by AA (5 microM). The percentage of genes changed by the fatty acids was: 20.5% (17 genes) for AA (5 microM) and only 2.4% (2 genes) for OA (50 microM). AA markedly affected the expression of genes clustered as: signal transduction pathways, transcription factors and related genes, cell cycle, defense and repair, apoptosis, DNA synthesis, cell adhesion, cytoskeleton and related genes. In particular, AA induced marked changes in cell cycle, signal transduction, and anti-apoptosis genes expression. Therefore, the effect of AA on T-lymphocyte function does involve regulation of expression of important genes, whereas oleic acid did not markedly affect gene expression of Jurkat cells.

Inhibition of tumour necrosis factor-alpha and interleukin 6 production by mononuclear cells following dietary fish-oil supplementation in healthy men and response to antioxidant co-supplementation

Increased dietary consumption of the n-3 polyunsaturated fatty acids (PUFA) eicosapentaenoic acid (20 : 5n-3; EPA) and docosahexaenoic acid (22 : 6n-6; DHA) is associated with their incorporation into circulating phospholipid and increased production of lipid peroxide metabolites. The relationship between peripheral blood mononuclear cell (PBMC) function, n-3 PUFA intake and antioxidant co-supplementation is poorly defined. We therefore investigated tumour necrosis factor (TNF)-alpha and interleukin (IL) 6 production by PBMC and phospholipid fatty acid composition in plasma and erythrocytes of healthy male subjects (n 16) receiving supplemental intakes of 0.3, 1.0 and 2.0 g EPA+DHA/d, as consecutive 4-week courses. All subjects were randomised in a double-blind manner to receive a concurrent antioxidant supplement (200 microg Se, 3 mg Mn, 30 mg D-alpha-tocopheryl succinate, 90 mg ascorbic acid, 450 microg vitamin A (beta-carotene and retinol)) or placebo. There was a positive dose-dependent relationship between dietary n-3 PUFA intake and EPA and DHA incorporation into plasma phosphatidylcholine and erythrocyte phosphatidylethanolamine, with a tendency towards a plateau at higher levels of intake. Production of TNF-alpha and IL-6 by PBMC decreased with increasing n-3 PUFA intake but tended towards a 'U-shaped' dose response. Both responses appeared to be augmented by antioxidant co-supplementation at intermediate supplementary n-3 PUFA intakes. Thus, increased dietary n-3 PUFA consumption resulted in defined but contrasting patterns of modulation of phospholipid fatty acid composition and PBMC function, which were further influenced by antioxidant intake.

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.

Effects of dietary n-6 and n-3 fatty acids and vitamin E on the immune response of healthy geriatric dogs

OBJECTIVE

To determine the effect of dietary n-6 to n-3 fatty acid ratios and alpha-tocopheryl acetate concentration on immune functions andT cell subpopulations in healthy dogs.

ANIMALS

Thirty-two 7- to 10-year old female Beagles.

PROCEDURE

For 17 weeks, dogs were fed food that contained low (1.4:1) or high (40:1) ratios of n-6 to n-3 fatty acids in combination with 3 concentrations of all rac-alpha-tocopheryl acetate (low, 17 mg/kg of food; medium, 101 mg/kg; high, 447 mg/kg). Dogs were inoculated twice with a keyhole limpet hemocyanin suspension at 13 and 15 weeks.

RESULTS

After 12 weeks, dogs consuming low concentrations of alpha-tocopheryl acetate had lower percentages of CD8+ T cells, compared with dogs consuming medium or high alpha-tocopheryl acetate concentrations. Also, dogs consuming low alpha-tocopheryl acetate concentrations had higher CD4+ to CD8+ T cell ratios. On day 4 of week 15, the percentage of CD8+ T cells was highest in dogs fed medium concentrations of alpha-tocopheryl acetate, compared with other dogs; however, the CD4+ to CD8+ T cell ratio was higher only in dogs fed low concentrations of alpha-tocopheryl acetate with high concentrations of n-3 fatty acids. Dogs consuming low concentrations of n-3 fatty acids with medium concentrations of alpha-tocopheryl acetate had the largest delayed-type hypersensitivity (DTH) skin test response.

CONCLUSIONS AND CLINICAL RELEVANCE

An optimum amount of dietary alpha-tocopheryl acetate concentration, regardless of the dietary n-6 to n-3 fatty acid ratio, stimulates the CD8+ T cell population. Effects of an optimum amount of dietary alpha-tocopheryl acetate concentration on the DTH response are blunted by dietary n-3 fatty acids.

Relation between the fatty acid composition of peripheral blood mononuclear cells and measures of immune cell function in healthy, free-living subjects aged 25-72 y

BACKGROUND

There is little information about the relation between the fatty acid composition of human immune cells and the function of those cells over the habitual range of fatty acid intakes.

OBJECTIVE

The objective of the study was to determine the relation between the fatty acid composition of human peripheral blood mononuclear cell (PBMC) phospholipids and the functions of human immune cells.

DESIGN

One hundred fifty healthy adult subjects provided a fasting blood sample. The phagocytic and oxidative burst activities of monocytes and neutrophils were measured in whole blood. PBMCs were isolated and used to measure lymphocyte proliferation in response to the T cell mitogen concanavalin A and the production of cytokines in response to concanavalin A or bacterial lipopolysaccharide. The fatty acid composition of plasma and PBMC phospholipids was determined.

RESULTS

Wide variations in fatty acid composition of PBMC phospholipids and immune cell functions were identified among the subjects. The proportions of total polyunsaturated fatty acids (PUFAs), of total n-6 and n-3 PUFAs, and of several individual PUFAs in PBMC phospholipids were positively correlated with phagocytosis by neutrophils and monocytes, neutrophil oxidative burst, lymphocyte proliferation, and interferon gamma production. The ratios of saturated fatty acids to PUFAs and of n-6 to n-3 PUFAs were negatively correlated with these same immune functions. The relation of PBMC fatty acid composition to monocyte oxidative burst was the reverse of its relation to monocyte phagocytosis and neutrophil oxidative burst.

CONCLUSION

Variations in the fatty acid composition of PBMC phospholipids account for some of the variability in immune cell functions among healthy adults.

Influence of very low dietary intake of marine oil on some functional aspects of immune cells in healthy elderly people

Ageing is a multifactorial process involving decreased antioxidant defences and immune functions. n-3 Polyunsaturated fatty acids have been associated with human health benefits, especially against inflammatory and autoimmune diseases. However, their immunomodulatory effects were usually observed with high dosages (>2 g/d) known to increase lipid peroxidation. In contrast, very low doses, that may prevent lipid peroxidation, might affect the immune system differently. To study the latter hypothesis further, we investigated whether the supplementation of healthy elderly people with very low doses of marine oil (MO), a docosahexaenoate (DHA)- and eicosapentaenoate (EPA)-rich triacylglycerol, was able to affect lymphocyte proliferation and biochemical markers known to be altered with age. In a randomized, double-blind design, twenty healthy elderly subjects were assigned to a placebo group (600 mg sunflower oil/d) or to a group consuming 600 mg MO/d providing 150 mg DHA + 30 mg (EPA) for 6 weeks. At day 42, the proliferative responses of lymphocytes to several mitogens were significantly (P<0.01) decreased in the MO group compared with control values. This was accompanied by a slight lowering of their cytosolic cyclic nucleotide phosphodiesterase (PDE) activity, a marked and significant (P<0.05) increase of their particulate PDE activity (+56-57 %) and a slight but significant (P<0.05) increase in cyclic nucleotide intracellular levels. At the same time, the glutathione peroxidase activity was markedly and significantly (P<0.01) depressed in the MO group. None of these modifications could be seen in the placebo group. Collectively, these results demonstrate that even very low doses of n-3 fatty acids are sufficient to affect the immune responses of elderly subjects.

Early origins of allergic disease: a review of processes and influences during early immune development

PURPOSE OF REVIEW

With the disturbing increase in allergic disease, there is a pressing need to determine the causes, pathogenesis and safe avenues for disease prevention. Although events in early life appear important, no causal pathways have been identified. This review examines new developments in the area of foetal and early postnatal immune maturation. It secondly addresses early predisposing influences and protective factors that may have a future role in allergy prevention.

RECENT FINDINGS

New developments in the understanding of the ontogeny of allergen-specific immune responses in atopic infants are discussed, including the role of early type 1 and 2 immune responses, and how these are influenced by perinatal antigen presenting cell and T-cell immaturity. The controversial role of early dietary exposures including breastfeeding, food allergens, hydrolyzed formulae and other dietary factors including omega-3 fatty acids are discussed in the context of the most recent literature. Equally contentious, the role of early house dust and pet allergen exposure is discussed in light of new epidemiological studies and disappointing early results of multicentre allergen avoidance studies. Finally, a number of studies in animals and humans suggest that bacterial products can influence early immune development, providing a new potential therapeutic avenue for disease treatment and prevention.

SUMMARY

Complex multifactorial genetic and environmental interactions make research in this area difficult and apparent associations with allergic disease may not be causal in nature. Many current targets for prevention, such as early allergen exposure and infant feeding practices, are proving to be ineffective and may not be directly implicated in rising rates of disease.

Dietary factors in the pathogenesis of asthma and chronic obstructive pulmonary disease

This review focuses on the role of dietary factors in the pathogenesis of asthma and chronic obstructive pulmonary disease. Reduced pulmonary function and indicators of airway obstruction have been shown to be strong indicators of mortality; therefore, a link with diet in the pathogenesis of these diseases would have important public health implications. The results of the studies identified in the review suggest that people who have a diet rich in fruit and vegetables have a lower risk of poor respiratory health, and that this may be due to the antioxidant nutrients these foods contain. On the basis of the evidence, it seems justified to promote a healthy diet, high in fruits, vegetables, and whole grain foods and low in alcohol and fatty foods, as set out in existing guidelines for prevention of cardiovascular disease and cancer, to protect respiratory health in both children and adults.

Synthesis of cetyl myristoleate and evaluation of its therapeutic efficacy in a murine model of collagen-induced arthritis

Cetyl myristoleate (CM) was reported by Diehl and May [J Pharm Sci 83 (1994) 296] to block inflammation and prevent adjuvant-induced arthritis in rats. To verify this earlier work, we have synthesized pure CM and tested its anti-arthritic properties in a collagen-induced arthritis model in DBA/1LacJ mice. Multiple intraperitoneal injections of CM in 450 and 900 mg kg(-1) doses resulted in a significantly lower incidence of disease and caused a modest but significant diminution in clinical signs in those mice that developed arthritis. CM administered in daily oral doses of 20 mg kg(-1) also reduced the incidence of arthritis and caused a small reduction in the clinical signs in mice that developed arthritis. Although the protective effect of CM in collagen-induced arthritis observed in the present study was less dramatic than that reported earlier, our results confirm the anti-arthritic properties of pure CM.

Polyunsaturated fatty acids and inflammatory diseases

Inflammation is overall a protective response, whose main goal is to liberate the human being of cellular lesions caused by micro-organisms, toxins, allergens, etc., as well as its consequences, and of death cells and necrotic tissues. Chronic inflammation, which is detrimental to tissues, is the basic pathogenic mechanism of hypersensitivity reactions against xenobiotics. Other frequent pathologies, for instance atherosclerosis, chronic hepatitis, inflammatory bowel disease (IBD), liver cirrhosis, lung fibrosis, psoriasis, and rheumatoid arthritis are also chronic inflammatory diseases. Chemical mediators of inflammation are derived from blood plasma or different cell-type activity. Biogenic amines, eicosanoids and cytokines are within the most important mediators of inflammatory processes. The different activities of eicosanoids derived from arachidonic acid (20:4 n-6) versus those derived from eicosapentaenoic acid (20:5 n-3) are one of the most important mechanisms to explain why n-3, or omega-3, polyunsaturated fatty acids (PUFA) exhibit anti-inflammatory properties in many inflammatory diseases. Dietary supplements ranging 1-8 g per day of n-3 PUFA have been reportedly beneficial in the treatment of IBD, eczema, psoriasis and rheumatoid arthritis. In addition, recent experimental studies in rats with experimental ulcerative colitis, induced by intrarectal injection of trinitrobenzene sulphonic acid, have documented that treatment with n-3 long-chain PUFA reduces mucosal damage as assessed by biochemical and histological markers of inflammation. Moreover, the defence antioxidant system in this model is enhanced in treated animals, provided that the n-3 PUFA supply is adequately preserved from oxidation.