n-3 Fatty acids inhibit transcription of human IL-13: implications for development of T helper type 2 immune responses

Role of dietary lipids in food allergy

The prevalence of food allergy is raising in industrialized countries, but the mechanisms behind this increased incidence are not fully understood. Environmental factors are believed to play a role in allergic diseases, including lifestyle influences, such as diet. There is a close relationship between allergens and lipids, with many allergenic proteins having the ability to bind lipids. Dietary lipids exert pro-inflammatory or anti-inflammatory functions on cells of the innate immunity and influence antigen presentation to cells of the adaptive immunity. In addition to modifying the immunostimulating properties of proteins, lipids also alter their digestibility and intestinal absorption, changing allergen bioavailability. This study provides an overview of the role of dietary lipids in food allergy, taking into account epidemiological information, as well as results of mechanistic investigations using in vivo, ex vivo and in vitro models. The emerging link among high-fat diets, obesity, and allergy is also discussed.

IL-2 modulates Th2 cell responses to glucocorticosteroid: A cause of persistent type 2 inflammation?

Background

Glucocorticosteroids (GCs) are the main treatment for asthma as they reduce type 2 cytokine expression and induce apoptosis. Asthma severity is associated with type 2 inflammation, circulating Th2 cells and higher GC requirements.

Objective

The aim of this study was to assess whether ex vivo production of interleukin 2 (IL‐2), a T‐cell survival factor, associated with clinical features of asthma severity, the proportion of blood Th2 cells and Th2 cell responses to GC.

Methods

Peripheral blood from asthma patients (n = 18) was obtained and the proportion of Th2 cells determined by flow cytometry. Peripheral blood cells were activated with mitogen (24 hours) and supernatant levels of IL‐2 and IL‐13 measured by enzyme‐linked immunosorbent assay. In vitro differentiated Th2 cells were treated with dexamethasone (DEX) and IL‐2 and assessed for apoptosis by flow cytometry (annexin V). Level of messenger RNA (mRNA) for antiapoptotic (BCL‐2) and proapoptotic (BIM) genes, IL‐13, GC receptor (GR) and FKBP5 were determined by quantitative real‐time polymerase chain reaction. GR binding was assessed by chromatin immunoprecipitation.

Results

IL‐2 produced by activated peripheral blood cells correlated negatively with lung function and positively with a daily dose of inhaled GC. When patients were stratified based on IL‐2 level, high IL‐2 producers made more IL‐13 and had a higher proportion of circulating Th2 cells. In vitro, increasing the level of IL‐2 in the culture media was associated with resistance to DEX‐induced apoptosis, with more BCL‐2/less BIM mRNA. Th2 cells cultured in high IL‐2 had more IL‐13, less GR mRNA, showed reduced binding of the GR to FKBP5, a known GC‐induced gene, and required higher concentrations of DEX for cytokine suppression.

Conclusions and Clinical Relevance

IL‐2 downregulates Th2 cell responses to GC, supporting both their survival and pro‐inflammatory capacity. These results suggest that a patient's potential to produce IL‐2 may be a determinant in asthma severity.

Effect of omega-3 fatty acids supplementation during pregnancy on lung function in preschoolers: a clinical trial

RATIONALE

Prenatal omega-3 fatty acids improve alveolarization, diminish inflammation, and improve pulmonary growth, but it is unclear whether these outcomes translate into improved postnatal lung function.

OBJECTIVE

We assessed the effect of prenatal supplementation with docosahexaenoic acid (DHA) on offspring lung function through 60 months of age.

METHODS

We included a cohort of 772 Mexican preschoolers whose mothers participated in a clinical trial (NCT00646360) of supplementation with DHA or a placebo from week 18-22 of gestation through delivery.

MEASUREMENTS

The children were followed after birth and anthropometric measurements and forced oscillation tests were performed at 36, 48, and 60 months of age. The effect of DHA was tested using a longitudinal mixed effect models.

RESULTS

Overall, mean (Standard Deviation) of the measurements of respiratory system resistance and respiratory system reactance at 6, 8, and 10 Hz during follow up period were 11.3 (2.4), 11.1 (2.4), 10.3 (2.2) and -5.2 (1.6), -4.8 (1.7), -4.6 (1.6), respectively. There were no significant differences in pulmonary function by treatment group. DHA did not affect the average lung function or the trajectories through 60 months.

CONCLUSIONS

Prenatal DHA supplementation did not influence pulmonary function in this cohort of Mexican preschoolers.

The Toxicological Mechanisms of Environmental Soot (Black Carbon) and Carbon Black: Focus on Oxidative Stress and Inflammatory Pathways

The environmental soot and carbon blacks (CBs) cause many diseases in humans, but their underlying mechanisms of toxicity are still poorly understood. Both are formed after the incomplete combustion of hydrocarbons but differ in their constituents and percent carbon contents. For the first time, “Sir Percival Pott” described soot as a carcinogen, which was subsequently confirmed by many others. The existing data suggest three main types of diseases due to soot and CB exposures: cancer, respiratory diseases, and cardiovascular dysfunctions. Experimental models revealed the involvement of oxidative stress, DNA methylation, formation of DNA adducts, and Aryl hydrocarbon receptor activation as the key mechanisms of soot- and CB-induced cancers. Metals including Si, Fe, Mn, Ti, and Co in soot also contribute in the reactive oxygen species (ROS)-mediated DNA damage. Mechanistically, ROS-induced DNA damage is further enhanced by eosinophils and neutrophils via halide (Cl⁻ and Br⁻) dependent DNA adducts formation. The activation of pulmonary dendritic cells, T helper type 2 cells, and mast cells is crucial mediators in the pathology of soot- or CB-induced respiratory disease. Polyunsaturated fatty acids (PUFAs) were also found to modulate T cells functions in respiratory diseases. Particularly, telomerase reverse transcriptase was found to play the critical role in soot- and CB-induced cardiovascular dysfunctions. In this review, we propose integrated mechanisms of soot- and CB-induced toxicity emphasizing the role of inflammatory mediators and oxidative stress. We also suggest use of antioxidants and PUFAs as protective strategies against soot- and CB-induced disorders.

The impact of diet on asthma and allergic diseases

The incidence of allergic diseases is increasing, both in developed and developing countries, concomitantly with the rise in living standards and the adoption of a 'western lifestyle'. For two decades, the hygiene hypothesis - which proposes that the lack of early childhood exposure to infectious agents increases susceptibility to allergic diseases in later life - provided the conceptual framework for unravelling the mechanisms that could account for the increased incidence of allergic diseases. In this Review, we discuss recent evidence that highlights the role of diet as a key factor influencing immune homeostasis and the development of allergic diseases through a complex interplay between nutrients, their metabolites and immune cell populations. Although further investigations are still required to understand these complex relationships, recent data have established a possible connection between metabolic homeostasis and allergic diseases.

Fenretinide prevents inflammation and airway hyperresponsiveness in a mouse model of allergic asthma

Arachidonic acid (AA) and docosahexaenoic acid (DHA) play important roles in inflammation and disease progression, where AA is viewed as proinflammatory and DHA as antiinflammatory. We observe in our model of allergic asthma that the AA/DHA ratio is significantly skewed in a proinflammatory direction. Fenretinide, a vitamin A derivative, has been shown to correct fatty acid imbalances in other diseases. Therefore, we explored if fenretinide can have a protective effect in allergic asthma. To accomplish this, we measured the levels of AA and DHA in the lungs of nonallergic, ovalbumin-induced allergic, and fenretinide-treated allergic mice. We also investigated the effect of allergic asthma and fenretinide treatment on markers of oxidative stress, levels of metabolites, IgE production, airway hyperresponsiveness, and histological changes. Our data demonstrate that treatment of allergen-sensitized mice with fenretinide before allergen challenge prevents ovalbumin-induced changes in the AA/DHA ratio. The levels of several metabolites, such as serotonin, and markers of cellular stress, which are increased after ovalbumin challenge, are also controlled by fenretinide treatment. We observed the protective effect of fenretinide against ovalbumin-induced airway hyperresponsiveness and inflammation in the lungs, illustrated by a complete block in the infiltration of inflammatory cells to the airways and dramatically diminished goblet cell proliferation, even though IgE remained high. Our results demonstrate that fenretinide is an effective agent targeting inflammation, oxidation, and lung pathology observed in allergic asthma.

ITCH deficiency protects from diet-induced obesity

Classically activated macrophages (M1) secrete proinflammatory cytokine and are predominant in obese adipose tissue. M2 macrophages, prevalent in lean adipose tissue, are induced by IL-13 and IL-4, mainly secreted by Th2 lymphocytes, and produce the anti-inflammatory cytokine IL-10. ITCH is a ubiquitously expressed E3 ubiquitin ligase involved in T-cell differentiation and in a wide range of inflammatory pathways. ITCH downregulation in lymphocytes causes aberrant Th2 differentiation. To investigate the role of Th2/M2 polarization in obesity-related inflammation and insulin resistance, we compared wild-type and Itch(-/-) mice in a context of diet-induced obesity (high-fat diet [HFD]). When subjected to HFD, Itch(-/-) mice did not show an increase in body weight or insulin resistance; calorimetric analysis suggested an accelerated metabolism. The molecular analysis of metabolically active tissue revealed increased levels of M2 markers and genes involved in fatty acid oxidation. Histological examination of livers from Itch(-/-) mice suggested that ITCH deficiency protects mice from obesity-related nonalcoholic fatty liver disease. We also found a negative correlation between ITCH and M2 marker expression in human adipose tissues. Taken together, our data indicate that ITCH E3 ubiquitin ligase deficiency protects from the metabolic disorder caused by obesity.