Fatty acids as gatekeepers of immune cell regulation

Emerging trade-offs - impact of photoprotectants (PsbS, xanthophylls, and vitamin E) on oxylipins as regulators of development and defense

This review summarizes evidence for a mechanistic link between plant photoprotection and the synthesis of oxylipin hormones as regulators of development and defense. Knockout mutants of Arabidopsis, deficient in various key components of the chloroplast photoprotection system, consistently produced greater concentrations of the hormone jasmonic acid or its precursor 12- oxo-phytodienoic acid (OPDA), both members of the oxylipin messenger family. Characterized plants include several mutants deficient in PsbS (an intrinsic chlorophyll-binding protein of photosystem II) or pigments (zeaxanthin and/or lutein) required for photoprotective thermal dissipation of excess excitation energy in the chloroplast and a mutant deficient in reactive oxygen detoxification via the antioxidant vitamin E (tocopherol). Evidence is also presented that certain plant defenses against herbivores or pathogens are elevated for these mutants. This evidence furthermore indicates that wild-type Arabidopsis plants possess less than maximal defenses against herbivores or pathogens, and suggest that plant lines with superior defenses against abiotic stress may have lower biotic defenses. The implications of this apparent trade-off between abiotic and biotic plant defenses for plant ecology as well as for plant breeding/engineering are explored, and the need for research further addressing this important issue is highlighted.

Fatty acid binding proteins FABP9 and FABP10 participate in antibacterial responses in Chinese mitten crab, Eriocheir sinensis

Invertebrates rely solely on the innate immune system for defense against pathogens and other stimuli. Fatty acid binding proteins (FABP), members of the lipid binding proteins superfamily, play a crucial role in fatty acid transport and lipid metabolism and are also involved in gene expression induced by fatty acids. In the vertebrate immune system, FABP is involved in inflammation regulated by fatty acids through its interaction with peroxidase proliferator activate receptors (PPARs). However, the immune functions of FABP in invertebrates are not well characterized. For this reason, we investigated the immune functionality of two fatty acid binding proteins, Es-FABP9 and Es-FABP10, following lipopolysaccharide (LPS) challenge in the Chinese mitten crab (Eriocheir sinensis). An obvious variation in the expression of Es-FABP9 and Es-FABP10 mRNA in E. sinensis was observed in hepatopancreas, gills, and hemocytes post-LPS challenge. Recombinant proteins rEs-FABP9 and rEs-FABP10 exhibited distinct bacterial binding activity and bacterial agglutination activity against Escherichia coli and Staphylococcus aureus. Furthermore, bacterial growth inhibition assays demonstrated that rEs-FABP9 responds positively to the growth inhibition of Vibrio parahaemolyticuss and S. aureus, while rEs-FABP10 responds positively to the growth inhibition of Aeromonas hydrophila and Bacillus subtilis. Coating of agarose beads with recombinant rEs-FABP9 and rEs-FABP10 dramatically enhanced encapsulation of the beads by crab hemocytes in vitro. In conclusion, the data presented here demonstrate the participation of these two lipid metabolism-related proteins in the innate immune system of E. sinensis.

Trans-fatty acids, dangerous bonds for health? A background review paper of their use, consumption, health implications and regulation in France

INTRODUCTION

Trans-fatty acids (TFAs) can be produced either from bio-hydrogenation in the rumen of ruminants or by industrial hydrogenation. While most of TFAs' effects from ruminants are poorly established, there is increasing evidence that high content of industrial TFAs may cause deleterious effects on human health and life span.

MATERIAL AND METHODS

Indeed, several epidemiological and experimental studies strongly suggest that high content of most TFA isomers could represent a higher risk of developing cardiovascular diseases by a mechanism that lowers the "good HDL cholesterol" and raises the "bad LDL cholesterol."

RESULTS

With respect to the general precautionary principle and considering the existence of an international policy consensus regarding the need for public health action, some industrialized countries, such as France, are still not sufficiently involved in preventive strategies that aim to efficiently reduce TFAs content and TFAs consumption and produce alternative healthier fat sources.

CONCLUSION

In this manuscript, we provide an overview about TFAs origins, their use and consumption among French population. We also discuss their potential human health implications as well as the preventive and regulatory measures undertaken in France.

Ts6 and Ts2 from Tityus serrulatus venom induce inflammation by mechanisms dependent on lipid mediators and cytokine production

Inflammatory mediators are thought to be involved in the systemic and local immune response induced by the Tityus serrulatus scorpion envenomation. New functional aspects of lipid mediators have recently been described. Here, we examine the unreported role of lipid mediators in cell recruitment to the peritoneal cavity after an injection with Ts2 or Ts6 toxins isolated from the T. serrulatus scorpion venom. In this report, we demonstrate that following a single intraperitoneal (i.p.) injection of Ts2 or Ts6 (250 μg/kg) in mice, there was an induction of leukocytosis with a predominance of neutrophils observed at 4, 24, 48 and 96 h. Moreover, total protein, leukotriene (LT)B(4), prostaglandin (PG)E(2) and pro-inflammatory cytokine levels were increased. We also observed an increase of regulatory cytokines, including interleukin (IL)-10, after the Ts2 injection. Finally, we observed that Ts2 or Ts6 injection in 5-lipoxygenase (LO) deficient mice and in wild type (WT) 129sv mice pre-treated with LTs and PGs inhibitors (MK-886 and celecoxib, respectively) a reduction the influx of leukocytes occurs in comparison to WT. The recruitment of these cells demonstrated a phenotype characteristic of neutrophils, macrophages, CD4 and CD8 lymphocytes expressing GR1+, F4/80+, CD3+/CD4+ and CD3+/CD8+, respectively. In conclusion, our data demonstrate that Ts2 and Ts6 induce inflammation by mechanisms dependent on lipid mediators and cytokine production. Ts2 may play a regulatory role whereas Ts6 exhibits pro-inflammatory activity exclusively.

Cre-mediated stress affects sirtuin expression levels, peroxisome biogenesis and metabolism, antioxidant and proinflammatory signaling pathways

Cre-mediated excision of loxP sites is widely used in mice to manipulate gene function in a tissue-specific manner. To analyze phenotypic alterations related to Cre-expression, we have used AMH-Cre-transgenic mice as a model system. Different Cre expression levels were obtained by investigation of C57BL/6J wild type as well as heterozygous and homozygous AMH-Cre-mice. Our results indicate that Cre-expression itself in Sertoli cells already has led to oxidative stress and lipid peroxidation (4-HNE lysine adducts), inducing PPARα/γ, peroxisome proliferation and alterations of peroxisome biogenesis (PEX5, PEX13 and PEX14) as well as metabolic proteins (ABCD1, ABCD3, MFP1, thiolase B, catalase). In addition to the strong catalase increase, a NRF2- and FOXO3-mediated antioxidative response (HMOX1 of the endoplasmic reticulum and mitochondrial SOD2) and a NF-κB activation were noted. TGFβ1 and proinflammatory cytokines like IL1, IL6 and TNFα were upregulated and stress-related signaling pathways were induced. Sertoli cell mRNA-microarray analysis revealed an increase of TNFR2-signaling components. 53BP1 recruitment and expression levels for DNA repair genes as well as for p53 were elevated and the ones for related sirtuin deacetylases affected (SIRT 1, 3-7) in Sertoli cells. Under chronic Cre-mediated DNA damage conditions a strong downregulation of Sirt1 was observed, suggesting that the decrease of this important coordinator between DNA repair and metabolic signaling might induce the repression release of major transcription factors regulating metabolic and cytokine-mediated stress pathways. Indeed, caspase-3 was activated and increased germ cell apoptosis was observed, suggesting paracrine effects. In conclusion, the observed wide stress-induced effects and metabolic alterations suggest that it is essential to use the correct control animals (Cre/Wt) with matched Cre expression levels to differentiate between Cre-mediated and specific gene-knock out-mediated effects.

Lipid body-phagosome interaction in macrophages during infectious diseases: host defense or pathogen survival strategy?

Phagocytosis of invading microorganisms by specialized cells such as macrophages and neutrophils is a key component of the innate immune response. These cells capture and engulf pathogens and subsequently destroy them in intracellular vacuoles—the phagosomes. Pathogen phagocytosis and progression and maturation of pathogen-containing phagosomes, a crucial event to acquire microbicidal features, occurs in parallel with accentuated formation of lipid-rich organelles, termed lipid bodies (LBs), or lipid droplets. Experimental and clinical infections with different pathogens such as bacteria, parasites, and viruses induce LB accumulation in cells from the immune system. Within these cells, LBs synthesize and store inflammatory mediators and are considered structural markers of inflammation. In addition to LB accumulation, interaction of these organelles with pathogen-containing phagosomes has increasingly been recognized in response to infections and may have implications in the outcome or survival of the microorganism within host cells. In this review, we summarize our current knowledge on the LB-phagosome interaction within cells from the immune system, with emphasis on macrophages, and discuss the functional meaning of this event during infectious diseases.

Lipid body function in eicosanoid synthesis: an update

Eicosanoids (prostaglandins, leukotrienes and lipoxins) are signaling lipids derived from arachidonic acid metabolism that have important roles in physiological and pathological processes. Lately, intracellular compartmentalization of eicosanoid-synthetic machinery has emerged as a key component in the regulation of eicosanoid synthesis and functions. Over the past years substantial progresses have been made demonstrating that precursors and enzymes involved in eicosanoid synthesis localize at lipid bodies (also known as lipid droplets) and lipid bodies are distinct sites for eicosanoid generation. Here we will review the current knowledge on the functions of lipid bodies as specialized intracellular sites of compartmentalization of signaling with major roles in eicosanoid formation within cells engaged in inflammatory, infectious and neoplastic process.

A systems biology approach to nutritional immunology - focus on innate immunity

Innate immunity and nutrient metabolism are complex biological systems that must work in concert to sustain and preserve life. The effector cells of the innate immune system rely on essential nutrients to generate energy, produce metabolic precursors for macromolecule biosynthesis and tune their responses to infectious agents. Thus disruptions to nutritional status have a substantial impact on immune competence and can result in increased susceptibility to infection in the case of nutrient deficiency, or chronic inflammation in the case of over-nutrition. The traditional, reductionist methods used in the study of nutritional immunology are incapable of exploring the extremely complex interactions between nutrient metabolism and innate immunity. Here, we review a relatively new analytical approach, systems biology, and highlight how it can be applied to nutritional immunology to provide a comprehensive view of the mechanisms behind nutritional regulation of the innate immune system.

Potential role of single hotdog fold thioesterase in the antiviral response of Fenneropenaeus chinensis

Thioesterase superfamily member 2 (Them2) is a single hotdog fold thioesterase domain-containing protein. Its biological function is not well known. Recently, a hotdog fold thioesterase (FcThem) was cloned for the first time from the Chinese white shrimp. The full length of FcThem is 748bp. It encodes a protein with 142 amino acids with a predicted molecular mass of 14.79kDa and an isoelectric point of 8.76. No signal peptide was predicted. Multiple alignment of FcThem with other Them2 proteins suggested a conserved HGG motif. Phylogenetic analysis showed that FcThem were clustered with vertebrate Them2 protein into one group. The RT-PCR results showed that FcThem was a widely distributed gene and could be detected in the hemocytes, heart, hepatopancreas, gills, stomach, intestines, and ovaries of unchallenged shrimps. In hemocytes, its transcript was upregulated 24h post WSSV challenge. In the gills, the FcThem went up at a 6h WSSV challenge. FcThem expression in the ovaries was also affected by the WSSV and was increased after the 2h WSSV challenge, reaching the highest level at 6h. Our results show that FcThem probably has roles in the innate immunity system of shrimps and investigations will be carried out to explore this finding further.

EicosaCell - an immunofluorescent-based assay to localize newly synthesized eicosanoid lipid mediators at intracellular sites

Eicosanoids (prostaglandins, leukotrienes and lipoxins) are a family of signaling lipids derived from arachidonic acid that have important roles in physiological and pathological processes. Over the past years, it has been established that successful eicosanoid production is not merely determined by arachidonic acid and eicosanoid-forming enzymes availability, but requires sequential interactions between specific biosynthetic proteins acting in cascade and may involve very unique spatial interactions. Direct assessment of specific subcellular locales of eicosanoid synthesis has been elusive, as those lipid mediators are newly formed, not stored and often rapidly released upon cell stimulation. In this chapter, we discuss the EicosaCell protocol for intracellular detection of eicosanoid-synthesizing compartments by means of a strategy to covalently cross-link and immobilize the lipid mediators at their sites of synthesis followed by immunofluorescent-based localization of the targeted eicosanoid.

Identifying intracellular sites of eicosanoid lipid mediator synthesis with EicosaCell assays

Eicosanoids, arachidonic acid-derived signaling lipid mediators, are newly formed and nonstorable molecules that have important roles in physiological and pathological processes. EicosaCell is a microscopic assay that enables the intracellular detection and localization of eicosanoid lipid mediator-synthesizing compartments by means of a strategy to covalently cross-link and immobilize eicosanoids at their sites of synthesis followed by immunofluorescent-based localization of the targeted eicosanoid. EicosaCell is a versatile assay which allows analyses of different types of cell preparations, such as cells isolated from humans or harvested cells from in vivo models of inflammation and adherent or suspension cells stimulated in vitro. EicosaCell assays have been successfully used to identify different intracellular compartments of synthesis of prostaglandins and leukotrienes upon cellular activation. This is of particular interest given that over the past decade intracellular compartmentalization of eicosanoid-synthetic machinery has emerged both as a key component in the regulation of eicosanoid synthesis and in delineating functional intracellular and extracellular actions of eicosanoids. This review covers basics of EicosaCell assay including its selection of reagents, immunodetection design as well as some troubleshooting recommendations.

Chemoselective reductive cross-coupling of 1,5-diene-3-ols with alkynes: a facile entry to stereodefined skipped trienes

A convergent synthesis of highly substituted and stereodefined skipped polyenes is described from the reductive cross-coupling of substituted 1,5-diene-3-ols with alkynes. The control of site selectivity in functionalization of the substituted diene is a central feature of this complex fragment union reaction.

Role of calcium and ROS in cell death induced by polyunsaturated fatty acids in murine thymocytes

We investigated the mechanisms whereby omega-3 and -6 polyunsaturated fatty acids (PUFAs) cause cell death of mouse thymocytes using flow cytometry, focusing on the respective roles of intracellular calcium concentration, [Ca(2+)](i) and reactive oxygen species (ROS). We applied the C-22, 20, and 18 carbon omega-3 (DHA, EPA, ALA) and omega-6 (DTA, ARA, and LNA) fatty acids to isolated thymocytes and monitored cell death using the DNA-binding dye, propidium iodide. When applied at 20 µM concentration, omega-3 fatty acids killed thymocytes over a period of 1 h with a potency of DHA > EPA > ALA. The omega-6 PUFAs were more potent. The C18 omega-6 fatty acid, LNA, was the most potent, followed by DHA and ARA. Cell death was always accompanied by an increase in the levels of [Ca(2+)](i) and ROS. Both increases were in proportion to the potency of the PUFAs in inducing cell death. Removing extracellular calcium did not prevent the elevation in [Ca(2+)](i) nor cell death. However, the intracellular calcium chelator, BAPTA, almost totally reduced both the elevation in [Ca(2+)](i) and cell death, while vitamin E reduced the elevation in ROS and cell death. BAPTA also prevented the elevation in ROS, but vitamin E did not prevent the elevation in [Ca(2+)](i). Thapsigargin, which depletes endoplasmic reticulum calcium, blocked the elevation in [Ca(2+)](i), but CCCP, a mitochondrial calcium uptake inhibitor, did not. These results suggest that the six PUFAs we studied kill thymocytes by causing release of calcium from endoplasmic reticulum, which causes release of ROS from mitochondria which leads to cell death.

Convergent and stereospecific synthesis of complex skipped polyenes and polyunsaturated fatty acids

Skipped polyenes (i.e. 1,4-dienes and higher homologues) are stereodefined components of a vast array of biologically important natural products, including polyunsaturated fatty acids. While widespread in nature, these architectures are generally considered to represent significant barriers to efficient chemical synthesis. While partial reduction of skipped poly-ynes provides a pathway to a subset of such structures, general chemical methods for the preparation of skipped polyenes that contain varied stereochemistries and substitution patterns are lacking. Here, we describe a metal-promoted reductive cross-coupling reaction between vinylcyclopropanes and alkynes (or vinylsilanes) that provides stereoselective access to a diverse array of skipped polyenes through a process that establishes one C–C bond, generates up to three stereodefined alkenes, and can be used to introduce stereogenic centers at the central positions of the skipped polyene motif. We also demonstrate the significance of the present bond construction by preparing substituted and stereodefined polyunsaturated synthetic fatty acids.

Supplementation with fatty acids influences the airway nitric oxide and inflammatory markers in patients with cystic fibrosis

OBJECTIVES

To obtain a balance in the fatty acid (FA) metabolism is important for the inflammatory response and of special importance in cystic fibrosis (CF), which is characterized by impaired FA metabolism, chronic inflammation, and infection in the airways. Nitric oxide (NO) has antimicrobial properties and low nasal (nNO) and exhaled NO (FENO), commonly reported in CF that may affect bacterial status. The present study investigates the effect of different FA blends on nNO and FENO and immunological markers in patients with CF.

PATIENTS AND METHODS

Forty-three patients with CF and "severe" mutations were consecutively enrolled in a randomized double-blind placebo-controlled study with 3 FA blends containing mainly n-3 or n-6 FA or saturated FA acting as placebo. FENO, nNO, serum phospholipid concentrations of FA, and biomarkers of inflammation were measured before and after 3 months of supplementation.

RESULTS

Thirty-five patients in clinically stable condition completed the study. The serum phospholipid FA pattern changed significantly in all 3 groups. An increase of the n-6 FA, arachidonic acid, was associated with a decrease of FENO and nNO. The inflammatory biomarkers, erythrocyte sedimentation rate, and interleukin-8 decreased after supplementation with n-3 FA and erythrocyte sedimentation rate increased after supplementation with n-6 FA.

CONCLUSIONS

This small pilot study indicated that the composition of dietary n-3 and n-6 FA influenced the inflammatory markers in CF. FENO and nNO were influenced by changes in the arachidonic acid concentration, supporting previous studies suggesting that both the lipid abnormality and the colonization with Pseudomonas influenced NO in the airways.

Lipid droplets in inflammation and cancer

Accumulation of lipid droplets (also known as lipid bodies or adiposomes) within leukocytes, epithelial cells, hepatocytes and other non-adipocytic cells is a frequently observed phenotype in infectious, neoplastic and other inflammatory conditions. Lipid droplet biogenesis is a regulated cellular process that culminates in the compartmentalization of lipids and of an array of enzymes, protein kinases and other proteins, suggesting that lipid droplets are inducible organelles with roles in cell signaling, regulation of lipid metabolism, membrane trafficking and control of the synthesis and secretion of inflammatory mediators. Enzymes involved in eicosanoid synthesis are localized at lipid droplets and lipid droplets are sites for eicosanoid generation in cells during inflammation and cancer. In this review, we discuss the current evidence related to the biogenesis and function of lipid droplets in cell metabolism and signaling in inflammation and cancer. Moreover, the potential of lipid droplets as markers of disease and targets for novel anti-inflammatory and antineoplastic therapies will be discussed.

An acyl-CoA-binding protein (FcACBP) and a fatty acid binding protein (FcFABP) respond to microbial infection in Chinese white shrimp, Fenneropenaeus chinensis

Acyl-CoA-binding protein (ACBP) and fatty acid-binding protein (FABP) are involved in lipid metabolism. ACBP plays a key role in multiple cellular tasks including modulation of fatty acid biosynthesis, enzyme regulation, vesicular trafficking, and gene regulation. In our study, a 536 bp cDNA of ACBP (FcACBP) was cloned and identified as a widely distributed gene in the Chinese white shrimp, Fenneropenaeus chinensis. Its expression in intestine was upregulated in response to white spot syndrome virus (WSSV) or Vibrio anguillarum infection. The expression patterns were confirmed by Western blot analysis. FABPs, members of the lipid-binding protein superfamily, play an important role in lipid metabolism and also participate in vertebrate innate immunity. A cDNA of FABP (FcFABP) cloned from the hepatopancreas of the shrimp was 715 bp in size and encoded a 14 kDa protein. FcFABP appeared to be a basic fatty acid binding protein with a predicted isoelectric point of 9.16. It showed sequence similarity to both vertebrate and invertebrate FABPs. Phylogenetic analysis showed that FcFABP, together with LvFABP, were clustered into one group. FcFABP was detected mainly in the hepatopancreas and expression level increased after a challenge with WSSV. FcFABP was down-regulated by V. anguillarum challenge. The protein also had bacterial binding activity. These two lipid metabolism related proteins may play important roles in shrimp innate immunity.

Effect of polyunsaturated fatty acids on the reactive oxygen and nitrogen species production by raw 264.7 macrophages

BACKGROUND

Polyunsaturated fatty acids (PUFAs) can affect various functions of the immune system including inflammatory responses. An oxidative burst of phagocytes accompanied by reactive oxygen species (ROS) and reactive nitrogen species (RNS) formation is one of the phagocyte functions that could be modulated by PUFAs.

AIM OF THE STUDY

To investigate the effects of omega-3 (alpha-linolenic, docosahexaenoic, eicosapentaenoic) and omega-6 (arachidonic, linoleic) PUFAs on lipopolysaccharide (LPS)-stimulated ROS and RNS production by the murine macrophage cell line RAW 264.7.

METHODS

Murine peritoneal macrophages RAW 264.7 were stimulated with LPS (0.1 microg/ml) and treated with 0.1-100 microM omega-3 or omega-6 PUFAs for either 8 (ROS production) or 20 h (RNS production). The cytotoxicity of PUFAs was evaluated by an ATP (adenosine triphosphate) test after both 8 and 20 h of treatment with PUFAs. Changes in ROS production by LPS-treated macrophages subsequently activated with phorbol myristate acetate (PMA) or opsonized zymosan particles (OZP) were determined by luminol-enhanced chemiluminescence, whilst the production of RNS was determined as the concentration of nitrites in cell supernatants (Griess reaction). Changes in inducible nitric oxide synthase (iNOS) expression were evaluated by Western blot analysis. The antioxidant properties of PUFAs were tested by TRAP (total peroxyl radical-trapping antioxidant parameter) assay.

RESULTS

All PUFAs in 100 microM concentration except eicosapentaenoic acid decreased ROS production. The effect was most significant when docosahexaenoic acid was used. Arachidonic acid decreased PMA-activated ROS production even in 1 and 10 microM concentrations. On the other hand, 10 and 100 microM eicosapentaenoic acid potentiated ROS production. As concerns RNS production, all the fatty acids that were tested in a concentration of 100 microM decreased iNOS expression and nitrite accumulation. Fatty acids had no significant effect on the viability and proliferation of RAW 264.7 cells. The TRAP assay confirmed that none of the tested PUFAs exerted any significant antioxidant properties.

CONCLUSION

High concentrations of PUFAs of both omega-3 and omega-6 groups can inhibit ROS and RNS formation by stimulated macrophages. The expression of iNOS can also be inhibited. This effect, together with the absence of antioxidant activity and cytotoxic properties, indicates that PUFAs can participate in the regulation of enzymes responsible for reactive species production.

The activity of lysosomal exoglycosidases in serum of alcohol-dependent men supplemented with borage oil enriched with vitamin E

The aim of this study was to determine the activity of the lysosomal exoglycosidases: alpha-mannosidase (MAN), alpha-fucosidase (FUC), and beta-glucuronidase (GLUCUR) in serum of alcohol-dependent men supplemented and not supplemented with borage oil enriched with vitamin E. Serum was collected from eight social drinkers and 16 alcohol-dependent men after a drinking period. The activity of exoglycosidases and the concentration of protein in serum were determined. The increase in specific activity of MAN and GLUCUR was significant in serum of alcohol-dependent men both not supplemented and supplemented with borage oil enriched with vitamin E, in comparison with the specific activity in serum of social drinkers. In serum of alcohol-dependent men treated with borage oil enriched with vitamin E, specific activity of MAN and GLUCUR fluctuated in comparison with alcohol-dependent men not supplemented. Specific activity of FUC in serum of alcohol-dependent men both not supplemented and supplemented with borage oil enriched with vitamin E showed a tendency to increase, in comparison with social drinkers. Specific activity of FUC had a tendency to decrease in serum of alcohol-dependent men supplemented with borage oil enriched with vitamin E, in comparison with alcohol-dependent men not supplemented. Thus, supplementation of alcohol-dependent men after a long-lasting drinking period with borage oil and vitamin E did not change the rate of catabolism of the oligosaccharide chains of glycoconjugates, as evaluated by serum activity of exoglycosidases.

Trans-10, cis-12 conjugated linoleic acid modulates phagocytic responses of canine peripheral blood polymorphonuclear neutrophilic leukocytes exposed to Clostridium difficile toxin B

Trans-10, cis-12 conjugated linoleic acid (t10c12-CLA) has been reported to enhance phagocyte function. Clostridium difficile toxin B (TcdB) has been known to inhibit Ras-homologous (Rho) guanosine triphosphatases (GTPases) which play essential roles in neutrophil immune functions. Here, we examined whether in vitro treatment with t10c12-CLA modulates the filamentous actin (F-actin) polymerization, phagocytic capacity, and oxidative burst activity (OBA) of canine peripheral blood polymorphonuclear neutrophilic leukocytes (PMNs) exposed to TcdB. Treatment with t10c12-CLA, but not linoleic acid, enhanced PMN F-actin polymerization, phagocytic capacity, and OBA, while TcdB suppressed these functions. t10c12-CLA reversed the suppressive effects of TcdB on these PMN functions. t10c12-CLA stimulated F-actin polymerization regardless of whether phagocytosis was stimulated by microspheres but only elevated OBA when microspheres were added. We asked whether the effects of t10c12-CLA were associated with changes in the activation of the Rho GTPase Cdc42. Treatment with t10c12-CLA augmented Cdc42 activity in both TcdB-treated and TcdB-naive PMNs during phagocytosis. Thus, t10c12-CLA up-regulates PMN phagocytic responses attenuated by TcdB. This effect is associated with an increase in actin polymerization and may involve the activation of Cdc42.

Leukocyte lipid bodies - Biogenesis and functions in inflammation

Lipid body accumulation within leukocytes is a common feature in both clinical and experimental infectious, neoplasic and other inflammatory conditions. Here, we will review the contemporary evidence related to the biogenesis and structure of leukocyte lipid bodies (also known as lipid droplets) as inflammatory organelles. Studies of leukocyte lipid bodies are providing functional, ultrastructural and protein compositional evidences that lipid bodies are not solely storage depots of neutral lipid. Over the past years substantial progresses have been made to demonstrate that lipid body biogenesis is a highly regulated process, that culminate in the compartmentalization of a specific set of proteins and lipids, that place leukocyte lipid bodies as inducible cytoplasmic organelles with roles in cell signaling and activation, regulation of lipid metabolism, membrane trafficking and control of the synthesis and secretion of inflammatory mediators. Pertinent to the roles of lipid bodies in inflammation and cell signaling, enzymes involved in eicosanoid synthesis are localized at lipid bodies and lipid bodies are sites for eicosanoid generation. Collectively, lipid bodies in leukocytes are emerging as critical regulators of different inflammatory diseases, key markers of leukocyte activation and attractive targets for novel anti-inflammatory therapies.

Session 3: Joint Nutrition Society and Irish Nutrition and Dietetic Institute Symposium on ‘Nutrition and autoimmune disease’ PUFA, inflammatory processes and rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease manifested by swollen and painful joints, bone erosion and functional impairment. The joint lesions are characterised by infiltration of T lymphocytes, macrophages and B lymphocytes into the synovium and by synovial inflammation involving eicosanoids, cytokines and matrix metalloproteinases. In relation to inflammatory processes, the main fatty acids of interest are the n-6 PUFA arachidonic acid, which is the precursor of inflammatory eicosanoids such as PGE2 and leukotriene B4, and the n-3 PUFA EPA and DHA, which are found in oily fish and fish oils. Eicosanoids derived from the n-6 PUFA arachidonic acid play a role in RA, and the efficacy of non-steroidal anti-inflammatory drugs in RA indicates the importance of pro-inflammatory cyclooxygenase pathway products of arachidonic acid in the pathophysiology of the disease. EPA and DHA inhibit arachidonic acid metabolism to inflammatory eicosanoids. EPA also gives rise to eicosanoid mediators that are less inflammatory than those produced from arachidonic acid and both EPA and DHA give rise to resolvins that are anti-inflammatory and inflammation resolving. In addition to modifying the lipid mediator profile, n-3 PUFA exert effects on other aspects of immunity relevant to RA such as antigen presentation, T-cell reactivity and inflammatory cytokine production. Fish oil has been shown to slow the development of arthritis in an animal model and to reduce disease severity. Randomised clinical trials have demonstrated a range of clinical benefits in patients with RA that include reducing pain, duration of morning stiffness and use of non-steroidal anti-inflammatory drugs.

Long-chain polyunsaturated fatty acids influence the immune system of infants

Several events occur during the first months of life that allow the immune system to become competent and functional. The aim of this article is to review the rationale and evidence of an influence of (n-3) long-chain PUFA (LCPUFA) on the immune system of infants. The (n-3) LCPUFA exert their immunomodulatory activities at different levels. The (n-3) LCPUFA metabolites induce eicosanoid production, alter gene expression, and modify lipid raft composition, altering T-cell signaling; all contribute to immunological functional changes. However, the roles of these mechanisms and the types of T or other immunological cells involved remain unclear at present. Moreover, the effect of (n-3) LCPUFA on the immune system of infants may vary according to dose, time of exposure, and profile of the immune system (T-helper, Th1/Th2). Most of the interventional studies in infancy have been performed for the prevention of allergy. They all confirmed influence on T-cell function and cytokine profiles, but clinically beneficial effects are more conflicting. Supplementation of the maternal diet in pregnancy or early childhood with (n-3) LCPUFA is potentially a noninvasive intervention strategy to prevent the development of allergy, infection, and possibly other immune-mediated diseases. However, any long-term in vivo effects on (n-3) LCPUFA early in life for immunomodulatory defense in infants and later on immune status and health remain to be assessed.

The relationship between the fatty acid composition of immune cells and their function

The immune system, including its inflammatory components, is fundamental to host defence against pathogenic invaders. It is a complex system involving interactions amongst many different cell types dispersed throughout the body. Central to its actions are phagocytosis of bacteria, processing of antigens derived from intracellular and extracellular pathogens, activation of T cells with clonal expansion (proliferation) and production of cytokines that elicit effector cell functions such as antibody production and killing cell activity. Inappropriate immunologic activity, including inflammation, is a characteristic of many common human disorders. Eicosanoids produced from arachidonic acid have roles in inflammation and regulation of T and B lymphocyte functions. Eicosapentaenoic acid (EPA) also gives rise to eicosanoids and these may have differing properties from those of arachidonic acid-derived eicosanoids. EPA and docosahexaenoic acid (DHA) give rise to newly discovered resolvins which are anti-inflammatory and inflammation resolving. Human immune cells are typically rich in arachidonic acid, but arachidonic acid, EPA and DHA contents can be altered through oral administration of EPA and DHA. This results in a changed pattern of production of eicosanoids and probably also of resolvins, although the latter are not well examined in the human context. Changing the fatty acid composition of immune cells also affects phagocytosis, T cell signaling and antigen presentation capability. These effects appear to mediated at the membrane level suggesting important roles of fatty acids in membrane order, lipid raft structure and function, and membrane trafficking. Thus, the fatty acid composition of human immune cells influences their function and the cell membrane contents of arachidonic acid, EPA and DHA are important. Fatty acids influence immune cell function through a variety of complex mechanisms and these mechanisms are now beginning to be unraveled.

Fatty acids and immune function: new insights into mechanisms

Fatty acids are known to play diverse roles in immune cells. They are important as a source of energy, as structural components of cell membranes, as signaling molecules and as precursors for the synthesis of eicosanoids and similar mediators. Recent research has suggested that the localization and organisation of fatty acids into distinct cellular pools has a direct influence on the behaviour of a number of proteins involved in immune cell activation, including those associated with T cell responses, antigen presentation and fatty acid-derived inflammatory mediator production. This article reviews these studies and places them in the context of existing literature in the field. These studies indicate the existence of several novel mechanisms by which altered fatty acid availability can modulate immune responses and impact upon clinical outcomes.

Peroxisome proliferator-activated receptor-gamma2 Pro12Ala polymorphism, cod liver oil and risk of type 1 diabetes

OBJECTIVE

We have previously described an association between use of cod liver oil (a dietary n-3 fatty acid supplement) and reduced risk of type 1 diabetes. n-3 fatty acids are ligands for the peroxisome proliferator-activated receptor-gamma (PPARG), which has recently been implicated in the control of inflammation and possibly autoimmunity. We aimed to estimate the association between the common Pro12Ala polymorphism of PPARG2 and risk of type 1 diabetes, and to test whether there is gene-environment interaction with use of cod liver oil in the first year of life or gene-gene interaction with the established insulin gene (INS) and human leukocyte antigen DQ (HLA-DQ) genetic susceptibility loci.

METHODS

We designed a population-based case-control study of childhood-onset type 1 diabetes in Norway with information on use of cod liver oil in the first year of life from questionnaires and PPARG2 genotype data for 483 cases and 1520 control subjects. We used logistic regression for analysis.

RESULTS

The odds ratio for the PPARG2 Ala/Ala or Pro/Ala vs. Pro/Pro genotype and type 1 diabetes was 0.89 (95% CI: 0.69-1.13, p = 0.33). There was no significant interaction with cod liver oil in the first year of life [P (interaction) = 0.35] or with the INS polymorphism [P(interaction) = 0.42].

CONCLUSIONS

Although the association between PPARG2 and type 1 diabetes was not significant, the observed odds ratio was almost identical to that observed in two previous studies and can contribute to meta-analysis indicating a weak but significant association. Our hypothesized interaction between cod liver oil and PPARG2 in reducing type 1 diabetes risk was not supported.

Rationale for adjuvant fatty acid therapy to prevent radiotherapy failure and tumor recurrence during early laryngeal squamous cell carcinoma

Information from a preceding lipid study contributed to the pathobiological assessment of laryngeal squamous cell carcinoma (LSCC). Lipid-driven signaling pathways are responsible for laryngeal carcinogenesis and immunodeficiency. The construction of fatty acid (FA) profiles for LSCC allowed the identification of FA role players. The integration of lipid and clinicomolecular information encountered in the literature, in turn, allowed the identification of biological prognostic markers to distinguish between early (less aggressive) and advanced (more aggressive) LSCCs. High arachidonic acid (AA) and cyclooxygenase (COX-2) activities are criteria for less aggressive growth, whilst low AA and COX-2 activities occur during more aggressive growth. Excessive tobacco use and environmental smoke or human papillomavirus (HPV) infection and alcohol abuse can, respectively, elicit cumulative oxidative stress and an oxidative burst or interfere with signaling pathways during essential fatty acid (EFA) metabolism, all factors and events which may cause LSCC. Research revealed that enhanced COX-2 activity and Bcl-2 expression prevent apoptosis and, hence, LSCCs become resistant to radiotherapy. It was also observed that recurrent laryngeal cancers become more aggressive after radiotherapy failure. It is predicted that manipulation of AA activity and consequently a cascade of downstream factors that include COX-2 and Bcl-2 expression responsible for LSCC may have therapeutic potential to improve radiotherapy outcome during early LSCC. Adjuvant FA therapy to improve early LSCC management by counteracting radiotherapy failure and unwanted complications for further management is proposed. FA therapeutic strategies before and during radiotherapeutic courses need to be evaluated.

Engineering oilseeds to produce nutritional fatty acids

There is a growing body of evidence suggesting that regular consumption of foods rich in omega-3 long chain polyunsaturated fatty acids has multiple positive health benefits. The fats and oils from marine fish contain high contents of these beneficial fatty acids but increased consumer demand has also increased strain on the ability of the world's fisheries to meet demand from wild capture. Many consumers are choosing fish oil supplements or are eating foods that have been complemented with fish oils instead of consuming fish directly. However, removing undesirable odors, flavors and contaminants is expensive. In contrast, oils derived from land plants such as soybean are inexpensive and contaminant free. Recent strides in plant molecular biology now allow the engineering of oilseeds for the production of novel fats and oils, including those synthesized by complex, multigene biosynthetic pathways such as the omega-3 long chain polyunsaturated fatty acids. Given the potential benefits to the environment with regards to overfishing and the health prospects of increased consumption of these healthy fatty acids, producing these fatty acids in oilseeds is a desirable and worthy goal. In this review, we will describe the recent advances in this field along with some of the technical hurdles encountered thus far.

Butter feeding enhances TNF-alpha production from macrophages and lymphocyte adherence in murine small intestinal microvessels

BACKGROUND AND AIM

Dietary fat is known to modulate immune functions. Intake of an animal fat-rich diet has been linked to increased risk of inflammation; however, little is known about how animal fat ingestion directly affects intestinal immune function. The objective of this study was to assess the effect of butter feeding on lymphocyte migration in intestinal mucosa and the changes in adhesion molecules and cytokines involved in this effect.

METHODS

T-lymphocytes isolated from the spleen were fluorescence-labeled and injected into recipient mice. Butter was administered into the duodenum, and villus microvessels of the small intestinal mucosa were observed under an intravital microscope. mRNA expression of adhesion molecules and cytokines in the intestinal mucosa were determined by quantitative PCR. The effect of butter feeding on tumor necrosis factor (TNF)-alpha mRNA expression of intestinal macrophages was also determined.

RESULTS

Intraluminal butter administration significantly increased lymphocyte adherence to intestinal microvessels accompanied by increases in expression levels of adhesion molecules ICAM-1, MAdCAM-1 and VCAM-1. This accumulation was significantly attenuated by anti-MAdCAM-1 and anti-ICAM-1 antibodies. Butter administration significantly increased TNF-alpha in the lamina proprial macrophages but not interleukin-6. Anti-TNF-alpha treatment attenuated the enhanced expression of adhesion molecules induced by butter administration.

CONCLUSION

T-lymphocyte adherence to microvessels of the small intestinal mucosa was significantly enhanced after butter ingestion. This enhancement is due to increase in expression levels of adhesion molecules of the intestinal mucosa, which is mediated by TNF-alpha from macrophages in the intestinal lamina propria.

Immunomodulation by omega-3 fatty acids

The immune system, including its inflammatory components, is fundamental to host defense against pathogenic invaders. It is a complex system involving interactions amongst many different cell types dispersed throughout the body. Central to its actions are phagocytosis, processing of antigens derived from intracellular and extracellular pathogens, activation of T cells with proliferation and production of cytokines that elicit effector cell functions such as antibody production and killing cell activity. Inappropriate immunologic activity, including inflammation, is a characteristic of many common human disorders. Eicosanoids produced from arachidonic acid have roles in inflammation and regulation of T and B lymphocyte functions. Eicosapentaenoic acid (EPA) also gives rise to eicosanoids and docosahexaenoic acid (DHA) to docosanoids; these may have differing properties to arachidonic acid-derived eicosanoids. EPA and DHA give rise to newly discovered resolvins. Human immune cells are typically rich in arachidonic acid, but arachidonic acid, EPA and DHA contents can be altered through oral administration of those fatty acids. This results in a change pattern of production of eicosanoids and probably also of docosanoids and resolvins, although the latter are not well examined in the human context. Changing the fatty acid composition of immune cells also affects phagocytosis, T-cell signaling and antigen presentation capability. These effects appear to mediated at the membrane level suggesting important roles of fatty acids in membrane order, lipid raft structure and function and membrane trafficking.

Immune modulation by parenteral lipid emulsions

Total parenteral nutrition is the final option for nutritional support of patients with severe intestinal failure. Lipid emulsions constitute the main source of fuel calories and fatty acids (FAs) in parenteral nutrition formulations. However, adverse effects on patient outcomes have been attributed to the use of lipids, mostly in relation to impaired immune defenses and altered inflammatory responses. Over the years, this issue has remained in the limelight, also because technical advances have provided no safeguard against the most daunting problems, ie, infectious complications. Nevertheless, numerous investigations have failed to produce a clear picture of the immunologic characteristics of the most commonly used soybean oil-derived lipid emulsions, although their high content of n-6 polyunsaturated FAs (PUFAs) has been considered a drawback because of their proinflammatory potential. This concern initiated the development of emulsions in which part of the n-6 FA component is replaced by less bioactive FAs, such as coconut oil (rich in medium-chain saturated FAs) or olive oil (rich in the n-9 monounsaturated FA oleic acid). Another approach has been to use fish oil (rich in n-3 PUFA), the FAs of which have biological activities different from those of n-6 PUFAs. Recent studies on the modulation of host defenses and inflammation by fish-oil emulsions have yielded consistent data, which indicate that these emulsions may provide a tool to beneficially alter the course of immune-mediated conditions. Although most of these lipids have not yet become available on the US market, this review synthesizes available information on immunologic characteristics of the different lipids that currently can be applied via parenteral nutrition support.

The membrane and lipids as integral participants in signal transduction: lipid signal transduction for the non-lipid biochemist

Reviews of signal transduction have often focused on the cascades of protein kinases and protein phosphatases and their cytoplasmic substrates that become activated in response to extracellular signals. Lipids, lipid kinases, and lipid phosphatases have not received the same amount of attention as proteins in studies of signal transduction. However, lipids serve a variety of roles in signal transduction. They act as ligands that activate signal transduction pathways as well as mediators of signaling pathways, and lipids are the substrates of lipid kinases and lipid phosphatases. Cell membranes are the source of the lipids involved in signal transduction, but membranes also constitute lipid barriers that must be traversed by signal transduction pathways. The purpose of this review is to explore the magnitude and diversity of the roles of the cell membrane and lipids in signal transduction and to highlight the interrelatedness of families of lipid mediators in signal transduction.

Polyunsaturated fatty acids, membrane organization, T cells, and antigen presentation

Dietary supplementation with polyunsaturated fatty acids (PUFAs), especially those of the n-3 class, has immunosuppressive effects on both innate and adaptive immunity through various mechanisms. In this review, we focus on the PUFA modulation of membrane architecture and its consequent effects on both T cell responses and antigen presentation. We first use data from in vitro and in vivo experiments to make the case that the immunosuppressive effects of PUFAs begin with membrane incorporation and modulation of lipid-protein lateral organization. This in turn inhibits downstream signaling mediated by T cell receptors and suppresses T cell activation and proliferation. Next, we review evidence for PUFA-mediated alteration of major histocompatibility complex class I and II surface expression and antigen presentation. We propose that PUFAs influence the expression of major histocompatibility complex by altering its conformation, orientation, lateral organization, and trafficking, with consequences for recognition by effector T cells. Finally, we present data from model membrane studies to explain the physical principles that make PUFA acyl chains unique in modifying membrane lateral organization and protein function. An important concept to emerge from these studies is that PUFA acyl chains and cholesterol molecules are sterically incompatible. By applying this concept to the T cell activation and signaling model, mechanisms emerge by which PUFAs can modulate membrane lipid-protein lateral organization. Our data-based models show that membrane modification of both effectors and targets is an important, often overlooked, mechanism of immunomodulation by PUFAs.

Leukocyte lipid bodies regulation and function: contribution to allergy and host defense

Lipid bodies are lipid-rich organelles found in the cytoplasm of a variety of cells, including leukocytes. Lipid body morphology, its ability to interact with other organelles and its functions are dictated by its lipid arrangement, as well as its protein composition. Both may vary according to the cell type and with the specific lipid body biogenic stimulatory pathways. Nascent lipid bodies, which are formed in vivo in the course of a variety of immunopathological conditions, are sites of enzyme localization, eicosanoid production, as well as, sites for cytokine storage in inflammatory leukocytes, suggesting that lipid bodies function as inducible intracellular platforms for spatial segregation and organization of signaling leading to inflammatory mediator secretion during inflammation. The emerging role of lipid bodies as inflammatory organelles raises lipid body status to critical regulators of different inflammatory diseases, key markers of leukocyte activation and attractive targets for novel anti-inflammatory therapies.

Statins inhibit NK cell cytotoxicity by membrane raft depletion rather than inhibition of isoprenylation

To investigate the potential determinants of the pleiotropic effects of statins, we measured NK cell cytotoxicity in samples from normal subjects and patients, including patients receiving statin therapy. In a multivariate analysis, NK cell cytotoxicity was related to total plasma cholesterol concentration rather than statin use. In vitro, we investigated the role of lipid modification, specifically the effects on membrane rafts and raft-dependent signal transduction. We demonstrate that statins reduce NK cell cytotoxicity and that membrane cholesterol depletion by cyclodextrins has a similar effect. In contrast, isoprenyl transferase inhibitors had little or no effect on NK cell function. We hypothesise that the pleiotropic effects of statins reflect changes in membrane cholesterol and, specifically, the density of membrane rafts. Moreover, there is likely to be a relationship between membrane cholesterol, membrane rafts and cell function that may be involved in the pathogenesis of cardiovascular and metabolic diseases.

n-3 polyunsaturated fatty acids, inflammation, and inflammatory diseases

Inflammation is part of the normal host response to infection and injury. However, excessive or inappropriate inflammation contributes to a range of acute and chronic human diseases and is characterized by the production of inflammatory cytokines, arachidonic acid-derived eicosanoids (prostaglandins, thromboxanes, leukotrienes, and other oxidized derivatives), other inflammatory agents (e.g., reactive oxygen species), and adhesion molecules. At sufficiently high intakes, long-chain n-3 polyunsaturated fatty acids (PUFAs), as found in oily fish and fish oils, decrease the production of inflammatory eicosanoids, cytokines, and reactive oxygen species and the expression of adhesion molecules. Long-chain n-3 PUFAs act both directly (e.g., by replacing arachidonic acid as an eicosanoid substrate and inhibiting arachidonic acid metabolism) and indirectly (e.g., by altering the expression of inflammatory genes through effects on transcription factor activation). Long-chain n-3 PUFAs also give rise to a family of antiinflammatory mediators termed resolvins. Thus, n-3 PUFAs are potentially potent antiinflammatory agents. As such, they may be of therapeutic use in a variety of acute and chronic inflammatory settings. Evidence of their clinical efficacy is reasonably strong in some settings (e.g., in rheumatoid arthritis) but is weak in others (e.g., in inflammatory bowel diseases and asthma). More, better designed, and larger trials are required to assess the therapeutic potential of long-chain n-3 PUFAs in inflammatory diseases. The precursor n-3 PUFA alpha-linolenic acid does not appear to exert antiinflammatory effects at achievable intakes.

Fish oil alters T-lymphocyte proliferation and macrophage responses in Walker 256 tumor-bearing rats

OBJECTIVE

We investigated the effect of the dietary ratio of omega-6 to omega-3 polyunsaturated fatty acids (PUFAs) from postweaning until adulthood on T-lymphocyte proliferation, T-lymphocyte subpopulations (helper and cytotoxic), and production of cytotoxic mediators by macrophages in tumor-bearing rodents.

METHODS

Weanling male Wistar rats received a normal low-fat (40 g/kg of diet) chow diet or a high-fat (300 g /kg) diet that included fish or sunflower oil or blends of fish and sunflower oils to yield omega-6:omega-3 PUFA ratios of approximately 6:1, 30:1, and 60:1 ad libitum. After 8 wk, 50% of rats in each group were inoculated with 1 mL of 2 x 10(7) Walker 256 cells. Fourteen days after tumor inoculation, animals were killed and lymphocytes and macrophages were obtained for study.

RESULTS

The diets richest in omega-6 PUFA resulted in higher proliferation of thymus, spleen, and gut-associated lymphocytes compared with the chow diet irrespective of tumor burden. In contrast, the fish oil diet resulted in lower proliferation of thymus and spleen lymphocytes compared with the chow diet. Diets rich in omega-6 PUFA decreased the proportion of CD8+ lymphocytes. In non-tumor-bearing and tumor-bearing rats, hydrogen peroxide production by macrophages was highest in rats that consumed diets high in omega-3 PUFAs. Superoxide and nitric oxide production were little affected by the dietary ratio of omega-6 to omega-3 PUFAs.

CONCLUSION

Dietary omega-6 and omega-3 PUFA contents alter immune function in non-tumor-bearing and tumor-bearing rats. The omega-3 PUFAs decreased T-cell proliferation but increased hydrogen peroxide production compared with omega-6 PUFAs. Decreased tumor growth and cachexia and increased survival previously reported for fish oil in Walker 256 tumor-bearing rats may be related to improved macrophage function rather than to improved T-cell function.

Parenteral lipids modulate leukocyte phenotypes in whole blood, depending on their fatty acid composition

To characterize the immunological effects of various lipids that are applied as part of total parenteral nutrition (TPN) formulations, we analyzed phenotypical changes in leukocytes following lipid exposure. Importantly, the study was performed with whole blood in order to prevent the functional changes that are induced by isolation procedures. Briefly, blood samples from 10 healthy volunteers were incubated with lipids containing pure long-chain triglycerides (L), mixed long- and medium-chain triglycerides (LM), synthetic structured lipids (SL), or emulsions based on olive oil (OO), or fish oil (FO). After immune fluorescent staining, leukocyte phenotype characteristics were analyzed by flowcytometry. Exposure to LM increased in a dose-dependent manner the expression of membrane surface markers for adhesion (CD11b) and degranulation (CD66b), while decreasing CD62L, on neutrophils and monocytes. These findings demonstrate that LM activates leukocytes in peripheral whole blood. On the other hand, decreased expression of activation markers was observed with L and FO. Lipids effects on the phenotype of T lymphocytes and Natural Killer cells were not seen during incubation for up to 4 h. These results indicate that (i) the composition of TPN formulations with regard to lipid structure has implications for the function of exposed immune competent cells and (ii) medium-chain triglycerides, which have been regarded as functionally inert deliverers of fuel calories, have distinct biological effects.