Neonatal Immune State Is Influenced by Maternal Allergic Rhinitis and Associated With Regulatory T cells

Decoding the role of DNA methylation in allergic diseases: from pathogenesis to therapy

Allergic diseases, characterized by a broad spectrum of clinical manifestations and symptoms, encompass a significant category of IgE-mediated atopic disorders, including asthma, allergic rhinitis, atopic dermatitis, and food allergies. These complex conditions arise from the intricate interplay between genetic and environmental factors and are known to contribute to socioeconomic burdens globally. Recent advancements in the study of allergic diseases have illuminated the crucial role of DNA methylation (DNAm) in their pathogenesis. This review explores the factors influencing DNAm in allergic diseases and delves into their mechanisms, offering valuable perspectives for clinicians. Understanding these epigenetic modifications aims to lay the groundwork for improved early prevention strategies. Moreover, our analysis of DNAm mechanisms in these conditions seeks to enhance diagnostic and therapeutic approaches, paving the way for more effective management of allergic diseases in the future.

Contribution of Regulatory T Cell Methylation Modifications to the Pathogenesis of Allergic Airway Diseases

Regulatory T (Treg) cells are a subtype of CD4⁺ T cells that play a significant role in the protection from autoimmunity and the maintenance of immune tolerance via immune regulation. Epigenetic modifications of Treg cells (i.e., cytosine methylation at the promoter region of the transcription factor, Forkhead Box P3) have been found to be closely associated with allergic diseases, including allergic rhinitis, asthma, and food allergies. In this study, we highlighted the recent evidence on the contribution of epigenetic modifications in Treg cells to the pathogenesis of allergic diseases. Moreover, we also discussed directions for future clinical treatment approaches, with a particular emphasis on Treg cell-targeted therapies for allergic disorders.

The Role of CD40 in Allergic Rhinitis and Airway Remodelling

Background

Allergic rhinitis (AR) affects millions of people and is lack of effective treatment. CD40 is an important costimulatory molecule in immunity. However, few studies have focused on the role of CD40 in AR.

Methods

In this study, we built mouse model of chronic AR. The mice were divided into the AR, control, intravenous CD40 siRNA, and nasal CD40 siRNA groups (n = 6 each). We detected OVA-sIgE, IL-4, IL-5, IL-13, IL-10, IFN-γ, and TGF-β levels in serum and supernatant by ELISA, CD40⁺ splenic DCs, and Foxp3⁺ Tregs by flow cytometry and CD40 mRNA by RT²-PCR. We also used PAS and MT stains to assess tissue remodelling.

Results

(1) The OVA-sIgE, IL-4, IL-5, and IL-13 levels in the serum or supernatant of nasal septal membrane of AR mice were significantly higher than control. After treated with CD40 siRNA, those indicators were significantly decreased. The IFN-γ, IL-10, and TGF-β levels in AR mice were significantly lower than that in control and were increased by administration of CD40 siRNA. (2) AR mice had significantly fewer Foxp3⁺ Tregs in the spleen than control mice. After treated with CD40 siRNA, AR mice had significantly more Foxp3⁺ Tregs. (3) AR mice exhibited a significantly higher CD40 mRNA levels than control. Administration of CD40 siRNA significantly reduced the CD40 mRNA level. (4) The AR mice showed significantly greater collagen deposition than the control in MT staining. Applications of CD40 siRNA significantly reduced the collagen deposition in AR mice.

Conclusion

CD40 siRNA therapy shows promise for chronic AR as it significantly attenuated allergic symptoms and Th2-related inflammation and upregulated Foxp3⁺ Tregs. CD40 plays a role in tissue remodelling in AR, which can be inhibited by CD40 siRNA application.

Epigenetics and the Environment in Airway Disease: Asthma and Allergic Rhinitis

Asthma and rhinitis are complex, heterogeneous diseases characterized by chronic inflammation of the upper and lower airways. While genome-wide association studies (GWAS) have identified a number of susceptible loci and candidate genes associated with the pathogenesis of asthma and allergic rhinitis (AR), the risk-associated alleles account for only a very small percent of the genetic risk. In allergic airway and other complex diseases, it is thought that epigenetic modifications, including DNA methylation, histone modifications, and non-coding microRNAs, caused by complex interactions between the underlying genome and the environment may account for some of this "missing heritability" and may explain the high degree of plasticity in immune responses. In this chapter, we will focus on the current knowledge of classical epigenetic modifications, DNA methylation and histone modifications, and their potential role in asthma and AR. In particular, we will review epigenetic variations associated with maternal airway disease, demographics, environment, and non-specific associations. The role of specific genetic haplotypes in environmentally induced epigenetic changes are also discussed. A major limitation of many of the current studies of asthma epigenetics is that they evaluate epigenetic modifications in both allergic and non-allergic asthma, making it difficult to distinguish those epigenetic modifications that mediate allergic asthma from those that mediate non-allergic asthma. Additionally, most DNA methylation studies in asthma use peripheral or cord blood due to poor accessibility of airway cells or tissue. Unlike DNA sequences, epigenetic alterations are quite cell- and tissue-specific, and epigenetic changes found in airway tissue or cells may be discordant from that of circulating blood. These two confounding factors should be considered when reviewing epigenetic studies in allergic airway disease.

Epigenetic changes: An emerging potential pharmacological target in allergic rhinitis

The importance of epigenetics has increased due to identification of its role in the pathophysiology of a number of diseases including allergic rhinitis. Amongst the different epigenetic changes in allergic retinitis, deacetylation of histone proteins by histone deacetylase (HDACs), hypermethylation of DNA by DNA methyltransferases (DNMT) and alteration in post-transcriptional process by the changes in the levels of miRNA are widely studied. Studies conducted related to allergic rhinitis have shown the elevation in the levels of HDAC1, 3 and 11 in the nasal epithelia and HDAC inhibitors have shown effectiveness in decreasing the symptoms of rhinitis. Their beneficial effects are attributed to restoration of the expression of TWIK-related potassium channel-1, correction of cytokine profile along with normalization of Th1/Th2 imbalance. Another epigenetic change due to increase in DNMT activity may induce DNA hypermethylation in CpG sites in the airway epithelial cells and CD4⁺ T-cells. The reduction in DNA methylation decreases allergic symptoms and normalizes the over-reactive immune system. Mechanistically, allergens may promote the hypermethylation in the promoter region of IFN-γ gene in CD4⁺ T cells via activation of ERK pathway to decrease the expression of IFN-γ. In allergic rhinitis patients, there is also a downregulation of certain miRNAs including miR-135a, miR-146a, miR-181a, miR-155 and upregulation of miRNA19a. This review discusses the studies describing the epigenetic changes taking place in the host cells in response to allergen along with possible mechanisms.

Complementary Participation of Genetics and Epigenetics in Development of NSAID-exacerbated Respiratory Disease

Nonsteroidal anti-inflammatory drug (NSAID)-exacerbated respiratory disease (NERD) has attracted a great deal of attention because of its association with severe asthma. However, it remains widely underdiagnosed in asthmatics as well as the general population. Upon pharmacological inhibition of cyclooxygenase 1 by NSAIDs, production of anti-inflammatory prostaglandin E2 and lipoxins ceases, while release of proinflammatory cysteinyl leukotrienes increases. To determine the underlying mechanisms, many studies have attempted to elucidate the genetic variants, such as single nucleotide polymorphisms, responsible for alterations of prostaglandins and leukotrienes, but the results of these genetic studies could not explain the whole genetic pathogenesis of NERD. Accordingly, the field of epigenetics has been introduced as an additional contributor to genomic alteration underlying the development of NERD. Recently, changes in CpG methylation, as one of the epigenetic components, have been identified in target tissues of NERD. This review discusses in silico analyses of both genetic and epigenetic components to gain a better understanding of their complementary roles in the development of NERD. Although the molecular mechanisms underlying NERD pathogenesis remain poorly understood, genetic and epigenetic variations play significant roles. Our results enhance the understanding of the genetic and epigenetic mechanisms involved in the development of NERD and suggest new approaches toward better diagnosis and management.