PUFA-dependent alteration of oxidative parameters of a canine mastocytoma cell line

Allergy Modulation by N-3 Long Chain Polyunsaturated Fatty Acids and Fat Soluble Nutrients of the Mediterranean Diet

The Mediterranean diet, containing valuable nutrients such as n-3 long chain poly-unsaturated fatty acids (LCPUFAs) and other fat-soluble micronutrients, is known for its health promoting and anti-inflammatory effects. Its valuable elements might help in the battle against the rising prevalence of non-communicable diseases (NCD), including the development of allergic diseases and other (chronic) inflammatory diseases. The fat fraction of the Mediterranean diet contains bioactive fatty acids but can also serve as a matrix to dissolve and increase the uptake of fat-soluble vitamins and phytochemicals, such as luteolin, quercetin, resveratrol and lycopene with known immunomodulatory and anti-inflammatory capacities. Especially n-3 LCPUFAs such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) derived from marine oils can target specific receptors or signaling cascades, act as eicosanoid precursors and/or alter membrane fluidity and lipid raft formation, hereby exhibiting anti-inflammatory properties. Beyond n-3 LCPUFAs, fat-soluble vitamins A, D, E, and K1/2 have the potential to affect pro-inflammatory signaling cascades by interacting with receptors or activating/inhibiting signaling proteins or phosphorylation in immune cells (DCs, T-cells, mast cells) involved in allergic sensitization or the elicitation/effector phase of allergic reactions. Moreover, fat-soluble plant-derived phytochemicals can manipulate signaling cascades, mostly by interacting with other receptors or signaling proteins compared to those modified by fat-soluble vitamins, suggesting potential additive or synergistic actions by applying a combination of these nutrients which are all part of the regular Mediterranean diet. Research concerning the effects of phytochemicals such as polyphenols has been hampered due to their poor bio-availability. However, their solubility and uptake are improved by applying them within the dietary fat matrix. Alternatively, they can be prepared for targeted delivery by means of pharmaceutical approaches such as encapsulation within liposomes or even unique nanoparticles. This review illuminates the molecular mechanisms of action and possible immunomodulatory effects of n-3 LCPUFAs and fat-soluble micronutrients from the Mediterranean diet in allergic disease development and allergic inflammation. This will enable us to further appreciate how to make use of the beneficial effects of n-3 LCPUFAs, fat-soluble vitamins and a selection of phytochemicals as active biological components in allergy prevention and/or symptom reduction.

n-3 Long-chain PUFA reduce allergy-related mediator release by human mast cells in vitro via inhibition of reactive oxygen species

Increased n-6 and reduced n-3 long-chain PUFA (LC-PUFA) intake in Western diets may contribute to the increased prevalence of allergic diseases. Key effector cells in allergy are mast cells (MC). The aim of the present study was to investigate the effects of n-6 v. n-3 LC-PUFA on MC phenotype. Human MC lines (LAD2 and HMC-1) were incubated for 24 h with either arachidonic acid (AA, n-6 LC-PUFA) or the n-3 LC-PUFA EPA or DHA. The effects of these three LC-PUFA on degranulation, mediator secretion and reactive oxygen species (ROS) generation were assessed. ROS, mitogen-activated protein kinase (MAPK) or NF-κB inhibitors were used to unravel signalling pathways involved in cytokine secretion. AA, EPA or DHA did not reduce IgE-mediated degranulation by LAD2 cells. However, AA increased PGD₂ and TNF-α secretion by ionomycin/phorbol 12-myristate 13-acetate-stimulated HMC-1, whereas EPA and DHA more prominently inhibited IL-4 and IL-13 secretion. Suppression of IL-4 and IL-13 release by LC-PUFA correlated with reduced ROS generation. IL-4 and IL-13 release by activated HMC-1 was abrogated using ROS inhibitors. Inhibition of MAPK signalling, but not NF-κB, downstream of ROS reduced IL-13 secretion by activated HMC-1. Combined incubation of EPA or DHA with MAPK inhibitors further suppressed IL-13 secretion. In conclusion, the n-6 LC-PUFA AA enhanced pro-inflammatory mediator production by MC, while the n-3 LC-PUFA EPA as well as DHA more effectively suppressed ROS generation and IL-4 and IL-13 release. This suggests that dietary supplementation with EPA and/or DHA may alter the MC phenotype, contributing to a reduced susceptibility to develop and sustain allergic disease.

Unsaturated fatty acids as modulators of macrophage respiratory burst in the immune response against Rhodococcus equi and Pseudomonas aeruginosa

In this paper, using the monocyte/macrophage cell line RAW264.7, we systematically investigate the impact of macrophage enrichment with unsaturated fatty acids on cellular radical synthesis. We found that the intracellular production of reactive nitrogen and oxygen intermediates depends on the activation status of the macrophages. For unstimulated macrophages PUFA enrichment resulted in an increase in cellular radical synthesis. For stimulated macrophages, instead, an impeding action of unsaturated fatty acids on the respiratory burst could be seen. Of particular importance, the impact of unsaturated fatty acids on the macrophage respiratory burst was also observed in RAW264.7 cells cocultivated with viable bacteria of the species Rhodococcus equi or Pseudomonas aeruginosa. PUFA supplementation of macrophages in the presence of R. equi or P. aeruginosa reduced the pathogen-stimulated synthesis of reactive nitrogen and oxygen intermediates. Furthermore, the unsaturated fatty acids were found to impede the expression of the myeloperoxidase gene and to reduce the activity of the enzyme. Hence, our data provide indications of a possible value of PUFA application to people suffering from chronic infections with R. equi and P. aeruginosa as a concomitant treatment to attenuate an excessive respiratory burst.

The impact of membrane lipid composition on macrophage activation in the immune defense against Rhodococcus equi and Pseudomonas aeruginosa

Nutritional fatty acids are known to have an impact on membrane lipid composition of body cells, including cells of the immune system, thus providing a link between dietary fatty acid uptake, inflammation and immunity. In this study we reveal the significance of macrophage membrane lipid composition on gene expression and cytokine synthesis thereby highlighting signal transduction processes, macrophage activation as well as macrophage defense mechanisms. Using RAW264.7 macrophages as a model system, we identified polyunsaturated fatty acids (PUFA) of both the n-3 and the n-6 family to down-regulate the synthesis of: (i) the pro-inflammatory cytokines IL-1β, IL-6 and TNF-α; (ii) the co-stimulatory molecule CD86; as well as (iii) the antimicrobial polypeptide lysozyme. The action of the fatty acids partially depended on the activation status of the macrophages. It is particularly important to note that the anti-inflammatory action of the PUFA could also be seen in case of infection of RAW264.7 with viable microorganisms of the genera R. equi and P. aeruginosa. In summary, our data provide strong evidence that PUFA from both the n-3 and the n-6 family down-regulate inflammation processes in context of chronic infections caused by persistent pathogens.