Lifestyle and parental allergen sensitization are reflected in the intrauterine environment at gene expression level

Impact of Air Pollution and Allergic Status on Health-Related Quality of Life among University Students in Northern Thailand

BACKGROUND

Global awareness of ambient air pollution has heightened due to its detrimental impact on health, particularly in regions with elevated PM2.5 levels. Chiang Mai has emerged as an area experiencing the highest PM2.5 levels in Thailand.

OBJECTIVES

to examine the prevalence of respiratory allergies and assess the impact of air pollution on the health-related quality of life (QoL) among university students in Chiang Mai.

METHODS

Chiang Mai University (CMU) and Maejo University (MJU) students were recruited. The Global Asthma Network (GAN) questionnaire screened for respiratory allergies (RAs). The disease-specific QoL questionnaire (Rcq-36) was administered twice during low-PM2.5 and high-PM2.5 seasons to evaluate air pollution's impact on health-related QoL. Those showing potential RAs underwent a skin prick test (SPT) to investigate allergic sensitization.

RESULTS

Out of 406 participants, 131 (32%) reported respiratory allergies. Among those undergoing SPT, a high rate (82.54%) had positive results. Across both universities, students reported significantly lower QoL in multiple domains, particularly respiratory, eye, sleep, and emotional well-being, during the high-PM2.5 season. This aligned with their poorer self-reported health on a visual analog scale (VAS; p-value < 0.01). PM2.5 levels significantly impacted social functioning for CMU students (p-value = 0.001) and role limitations for MJU students (p-value < 0.001). Notably, participants without respiratory allergies (non-RAs) were more significantly affected by PM2.5 than RA participants in almost all parameters, despite experiencing fewer baseline symptoms.

CONCLUSIONS

Respiratory allergies, particularly allergic rhinitis, are prevalent among university students in Chiang Mai. This study underscores the substantial negative impact of ambient air pollution on QoL for both allergic and non-allergic students.

A positive feedback loop reinforces the allergic immune response in human peanut allergy

Food allergies are a leading cause of anaphylaxis, and cellular mechanisms involving antigen presentation likely play key roles in their pathogenesis. However, little is known about the response of specific antigen-presenting cell (APC) subsets to food allergens in the setting of food allergies. Here, we show that in peanut-allergic humans, peanut allergen drives the differentiation of CD209+ monocyte-derived dendritic cells (DCs) and CD23+ (FcєRII) myeloid dendritic cells through the action of allergen-specific CD4+ T cells. CD209+ DCs act reciprocally on the same peanut-specific CD4+ T cell population to reinforce Th2 cytokine expression in a positive feedback loop, which may explain the persistence of established food allergy. In support of this novel model, we show clinically that the initiation of oral immunotherapy (OIT) in peanut-allergic patients is associated with a decrease in CD209+ DCs, suggesting that breaking the cycle of positive feedback is associated with therapeutic effect.

The Impact of Milk and Its Components on Epigenetic Programming of Immune Function in Early Life and Beyond: Implications for Allergy and Asthma

Specific and adequate nutrition during pregnancy and early life is an important factor in avoiding non-communicable diseases such as obesity, type 2 diabetes, cardiovascular disease, cancers, and chronic allergic diseases. Although epidemiologic and experimental studies have shown that nutrition is important at all stages of life, it is especially important in prenatal and the first few years of life. During the last decade, there has been a growing interest in the potential role of epigenetic mechanisms in the increasing health problems associated with allergic disease. Epigenetics involves several mechanisms including DNA methylation, histone modifications, and microRNAs which can modify the expression of genes. In this study, we focus on the effects of maternal nutrition during pregnancy, the effects of the bioactive components in human and bovine milk, and the environmental factors that can affect early life (i.e., farming, milk processing, and bacterial exposure), and which contribute to the epigenetic mechanisms underlying the persistent programming of immune functions and allergic diseases. This knowledge will help to improve approaches to nutrition in early life and help prevent allergies in the future.

The use of pharmacogenomics, epigenomics, and transcriptomics to improve childhood asthma management: Where do we stand?

Asthma is a complex multifactorial disease and it is the most common chronic disease in children. There is a high variability in response to asthma treatment, even in patients with good adherence to maintenance treatment, and a correct inhalation technique. Distinct underlying disease mechanisms in childhood asthma might be the reason of this heterogeneity. A deeper knowledge of the underlying molecular mechanisms of asthma has led to the recent development of advanced and mechanism-based treatments such as biologicals. However, biologicals are recommended only for patients with specific asthma phenotypes who remain uncontrolled despite high dosages of conventional asthma treatment. One of the main unmet needs in their application is lack of clinically available biomarkers to individualize pediatric asthma management and guide treatment. Pharmacogenomics, epigenomics, and transcriptomics are three omics fields that are rapidly advancing and can provide tools to identify novel asthma mechanisms and biomarkers to guide treatment. Pharmacogenomics focuses on variants in the DNA, epigenomics studies heritable changes that do not involve changes in the DNA sequence but lead to alteration of gene expression, and transcriptomics investigates gene expression by studying the complete set of mRNA transcripts in a cell or a population of cells. Advances in high-throughput technologies and statistical tools together with well-phenotyped patient inclusion and collaborations between different centers will expand our knowledge of underlying molecular mechanisms involved in disease onset and progress. Furthermore, it could help to select and stratify appropriate therapeutic strategies for subgroups of patients and hopefully bring precision medicine to daily practice.

Epigenetics and allergy: from basic mechanisms to clinical applications

Allergic diseases are on the rise in the Western world and well-known allergy-protecting and -driving factors such as microbial and dietary exposure, pollution and smoking mediate their influence through alterations of the epigenetic landscape. Here, we review key facts on the involvement of epigenetic modifications in allergic diseases and summarize and critically evaluate the lessons learned from epigenome-wide association studies. We show the potential of epigenetic changes for various clinical applications: as diagnostic tools, to assess tolerance following immunotherapy or possibly predict the success of therapy at an early time point. Furthermore, new technological advances such as epigenome editing and DNAzymes will allow targeted alterations of the epigenome in the future and provide novel therapeutic tools.

The rural-urban enigma of allergy: what can we learn from studies around the world?

Childhood asthma and related allergic conditions have become the most common chronic disorders in the Western world. Many studies from around the world have demonstrated an increasing trend of asthma prevalence over the last few decades (Lancet, 368, 2004, 733). A few recent reports also suggested that childhood asthma prevalence may be showing a plateau or even a decline in few developed countries. Given the rapid changes in the prevalence over a short period of time, environmental factors are the more likely candidates explaining such trend. One of the most consistent epidemiological findings was that subjects living in the rural areas had lower prevalence of allergies when compared to those from urban areas (Clin Exp Allergy 30, 2000, 187; Pediatr Pulmonol 44, 2009, 793). Clear understanding of the mechanisms of how the environmental determinants in the rural environment may affect the early immune system resulting in lower risk of allergies and asthma will facilitate the development of future primary preventive strategies. In this study, we review recent data from around the world and explore the epidemiology and mechanistic studies that may explain the rural-urban difference of allergies.

Impaired function of regulatory T cells in cord blood of children of allergic mothers

Allergy is one of the most common diseases with constantly increasing incidence. The identification of prognostic markers pointing to increased risk of allergy development is of importance. Cord blood represents a suitable source of cells for searching for such prognostic markers. In our previous work, we described the increased reactivity of cord blood cells of newborns of allergic mothers in comparison to newborns of healthy mothers, which raised the question of whether or not this was due to the impaired function of regulatory T cells (T(regs)) in high-risk children. Therefore, the proportion and functional properties of T(regs) in cord blood of children of healthy and allergic mothers were estimated by flow cytometry. The proportion of T(regs) [CD4(+)CD25(high)CD127(low) forkhead box protein 3 (FoxP3(+))] in cord blood of children of allergic mothers tends to be higher while, in contrast, the median of fluorescence intensity of FoxP3 was increased significantly in the healthy group. Intracellular presence of regulatory cytokines interleukin (IL)-10 and transforming growth factor (TGF)-beta was also higher in T(regs) of children of healthy mothers. Although we detected an increased proportion of T(regs) in cord blood of children of allergic mothers, the functional indicators (intracellular presence of regulatory cytokines IL-10 and TGF-beta, median of fluorescence intensity of FoxP3) of those T(regs) were lower in comparison to the healthy group. We can conclude that impaired function of T(regs) in cord blood of children of allergic mothers could be compensated partially by their increased number. Insufficient function of T(regs) could facilitate allergen sensitization in high-risk individuals after subsequent allergen encounter.

Lesson from the farm environment

PURPOSE OF REVIEW

Several population-based studies have replicated the finding that exposure to a farm environment is protective against the development of atopic diseases. From these studies, novel insights into potential allergy-protective mechanisms were retrieved. This review focuses on consistent and novel findings of immune mechanisms involved in the 'farm effect'.

RECENT FINDINGS

The most recent studies suggest that the 'farm effect' mediated by microbial exposure may be attributed to both microbial diversity and species specificity. There is convincing evidence that farm milk components and grass arabinogalactan, commonly found in cowshed, may be important. Furthermore, early exposure to a farming environment, in particular in utero, showed stronger effects than exposure later in life, potentially through modulation of the immature immune system by microbes, also involving epigenetic changes. This protective 'farm effect' remains in later adulthood. Regarding gene-environment interactions, polymorphisms in GRM1 interacted with farming in a genome-wide interaction scan for asthma.

SUMMARY

The novel studies strengthen the role of microbial exposure and farm milk and grass components, especially early in life, in the modulation of the immune system towards a Th1/Treg predominance. This may subsequently lead to a long-lasting lower risk of developing atopic diseases.

DNA methylation levels within the CD14 promoter region are lower in placentas of mothers living on a farm

BACKGROUND

Epigenetic regulation has been suggested to be a link between environmental intrauterine exposures and development of asthma and allergy. The placenta is an essential part of the intrauterine environment. We have previously found the innate immune receptor CD14 to be differentially expressed on the mRNA level in placentas in relation to lifestyle and parental allergen sensitization. We here hypothesized that the promoter region of CD14 may be subject to differential DNA methylation and therefore a link between intrauterine exposure and mRNA expression.

METHODS

Ninety-four placentas from the ALADDIN (Assessment of Lifestyle and Allergic Disease During Infancy) study were investigated. We used methylation-sensitive high-resolution melting (MS-HRM) analysis to semi-quantitatively analyze the DNA methylation of the promoter region of CD14 in 36 placentas known to have different CD14 mRNA expression. EpiTYPER was used to validate the MS-HRM data and to analyze an additional 58 placentas selected on mothers living on a farm or not.

RESULTS

MS-HRM analysis on 36 placenta samples revealed a relation between methylation of the CD14 promoter region with the level of CD14 mRNA expression. The MS-HRM and EpiTYPER data correlated highly significantly. EpiTYPER analysis of the additional 58 placentas demonstrated that DNA methylation in the CD14 promoter was significantly lower in placentas of mothers living on a farm compared with mothers not living on a farm.

CONCLUSION

Our data suggest that epigenetic regulation of CD14 in placenta might be involved in the protective effect of 'living on a farm', with regard to allergy development.

Traffic-related air pollution and development of allergic sensitization in children during the first 8 years of life

BACKGROUND

The role of exposure to air pollution in the development of allergic sensitization remains unclear.

OBJECTIVE

We sought to assess the development of sensitization until school age related to longitudinal exposure to air pollution from road traffic.

METHODS

More than 2500 children in the birth cohort BAMSE (Children, Allergy, Milieu, Stockholm, Epidemiological Survey) from Stockholm, Sweden, were followed with repeated questionnaires and blood sampling until 8 years of age. Outdoor concentrations of nitrogen oxides, as a marker of exhaust particles, and particles with an aerodynamic diameter of less than 10 μm (PM(10)), mainly representing road dust, were assigned to residential, day care, and school addresses by using dispersion models. Time-weighted average exposures were linked to levels of IgE against common inhalant and food allergens at 4 and 8 years of age.

RESULTS

Air pollution exposure during the first year of life was associated with an increased risk of pollen sensitization at 4 years of age (odds ratio, 1.83; 95% confidence interval, 1.02-3.28) for a 5th to 95th difference in exposure to nitrogen oxides. At 8 years, there was no general increase in the risk of sensitization; however, the risk of food sensitization was increased, particularly among children free of sensitization at 4 years of age (odds ratio, 2.30; 95% confidence interval, 1.10-4.82). Results were similar by using PM(10). No associations between air pollution exposure after the first year of life and sensitization were seen.

CONCLUSION

Traffic-related air pollution exposure does not seem to increase the overall risk of sensitization to common inhalant and food allergens up to school age, but sensitization to certain allergens might be related to exposure during infancy.

Placental macrophage (Hofbauer cell) polarization is independent of maternal allergen-sensitization and presence of chorioamnionitis

BACKGROUND

Macrophages can polarize in which M1/classically activated and M2/alternatively activated macrophages are considered to be the extremes. M1 macrophages are involved in inflammatory reactions, while M2 macrophages are suggested to be involved in homeostasis, parasite killing, tumor promotion, tissue remodeling and in allergic reactions. We hypothesized that polarization of placental macrophages (Hofbauer cells) is influenced by the allergen-sensitization status of the mother and/or the presence of chorioamnionitis, a placental inflammation. This Hofbauer cell polarization might be associated to the intrauterine environment and influence the risk of allergy development for the child. Therefore we aimed to determine the polarization status of Hofbauer cells in health and disease.

METHODS

We determined the expression of CD68, CX3CR1, IL-7R, DC-SIGN/CD209 and CD163 in placentas of sensitized versus non-sensitized mothers (n = 17), and placentas with or without histological chorioamnionitis (n = 10) by means of immunohistochemical analysis and quantitative real-time PCR (qPCR).

RESULTS

Protein expression of the M1 markers (CX3CR1, IL-7R and CCR7) could not be detected in any of the analyzed samples while the M2 markers (DC-SIGN, CD163 and mannose receptor/CD206) were readily detected. Significant differences between non-sensitized versus sensitized mothers and uncomplicated versus chorioamnionitis complicated pregnancies were not detected at protein or at mRNA expression level.

CONCLUSIONS

These results suggest that Hofbauer cells have an M2 phenotype, and that their polarization is not affected by maternal allergen-sensitization or by presence of chorioamnionitis.

IgE in the human placenta: why there?

Immunoglobulin E (IgE) antibodies are key effector molecules in the allergic inflammatory response and are also involved in the protection against extracellular parasites. Allergic symptoms often develop early in life, and the intrauterine environment has been proposed to play an important role in affecting the risk of later allergy development. The placenta constitutes a selective barrier between the maternal and foetal circulation. Recently, we reported that maternal IgE antibodies are present on foetal macrophages in the villous tissue of the human placenta irrespective of maternal allergy status. This review discusses the presence of IgE antibodies in the human placenta and its possible roles in normal and pathologic pregnancy. It also deals with the relationship between placental IgE and development of allergy during childhood. A better understanding of the role of IgE in placenta could give us clues on how to prevent allergy development in the future generations.