Inhibition of H3K27me3 demethylases attenuates asthma by reversing the shift in airway smooth muscle phenotype

Role and regulators of N6-methyladenosine (m6A) RNA methylation in inflammatory subtypes of asthma: a comprehensive review

Asthma is a common chronic inflammatory disease of the lungs and airway, yet its inflammatory subtypes and potential pathogenesis have not been completely elucidated and require further study. With advances in epigenetic development, methylation has emerged as a new direction for identifying and decoding the occurrence and subtype manifestations of asthma. N6-methyladenosine (m6A), an RNA methylation modification occurring in the N6-position of adenosine, is a prevalent epigenetic modification observed in eukaryotes. It exerts significant control over mRNA metabolism by regulating alternative splicing, stability, export, and translation. The dynamic process of m6A methylation plays a crucial role in the pathogenesis of asthma and is tightly regulated by three types of regulators: writers, readers, and erasers. This article provides a comprehensive review of the association between m6A regulators and the pathogenesis of inflammatory subtypes of asthma, such as involvement of inflammatory cells and related inflammatory response. Furthermore, the findings presented herein provide new insights and a solid foundation for further research on m6A mRNA methylation as biomarkers for the diagnosis and development of personalized treatment for different subtypes of asthma, particularly neutrophilic asthma and eosinophilic asthma.

Knockdown of JMJD3 ameliorates cigarette smoke extract-triggered bronchial epithelial cell injury via ACSL4-dependent ferroptosis

Chronic obstructive pulmonary disease (COPD), a heterogeneity of chronic respiratory disease pattern, presents considerable prevalence and mortality. We aimed to explore the role and mechanisms of Jumonji domain-containing protein-3 (JMJD3) in COPD. The viability and JMJD3 expression in human bronchial epithelial cell line BEAS-2B were respectively assayed by CCK-8 assay and Western blot following stepwise exposure to increasing concentrations of cigarette smoke extract (CSE). After JMJD3 was silenced and acyl-CoA synthetase long-chain family member 4 (ACSL4) was overexpressed in CSE-treated BEAS-2B cells, cell viability, cytotoxicity, oxidative stress and total iron level were estimated using kits. ELISA estimated inflammatory levels. DCFH-DA probe and BODIPY 581/591 C11 probe were exposed to assess ROS production and lipid peroxidation. Western blot tested the expressions of ferroptosis-associated proteins. Besides, H3K27me3 and ACSL4 expressions were tested by Western blot and immunofluorescence staining. In CSE-induced BEAS-2B cells, JMJD3 expression was increased and deletion of JMJD3 improved cell viability, reduced LDH release, mitigated inflammation, oxidative stress and inhibited ferroptosis. Moreover, JMJD3 interference raised H3K27me3 expression whereas lessened ACSL4 expression in CSE-treated BEAS-2B cells. CSE exposure reduced the abundance of ACSL4 in H3K27me3 antibody. Further ACSL4 elevation reversed the impacts of JMJD3 silencing on the damage of CSE-induced BEAS-2B cells. Collectively, JMJD3 depletion might suppress ferroptosis mediated by ACSL4 to alleviate CSE-triggered inflammation and oxidative stress in BEAS-2B cells.

Histone demethylases in the regulation of immunity and inflammation

Pathogens or danger signals trigger the immune response. Moderate immune response activation removes pathogens and avoids excessive inflammation and tissue damage. Histone demethylases (KDMs) regulate gene expression and play essential roles in numerous physiological processes by removing methyl groups from lysine residues on target proteins. Abnormal expression of KDMs is closely associated with the pathogenesis of various inflammatory diseases such as liver fibrosis, lung injury, and autoimmune diseases. Despite becoming exciting targets for diagnosing and treating these diseases, the role of these enzymes in the regulation of immune and inflammatory response is still unclear. Here, we review the underlying mechanisms through which KDMs regulate immune-related pathways and inflammatory responses. In addition, we also discuss the future applications of KDMs inhibitors in immune and inflammatory diseases.

H3K27 tri-demethylase JMJD3 inhibits macrophage apoptosis by promoting ADORA2A in lipopolysaccharide-induced acute lung injury

Acute lung injury (ALI) is a common critical disease, which is characterized by an uncontrolled, acute inflammatory response, diffuse lung damage and ultimately directly deteriorates into acute respiratory distress syndrome. The number of pro-inflammatory macrophages is related to the severity of ALI. Up-regulation of lipopolysaccharide (LPS)-activated macrophage apoptosis can reduce the pro-inflammatory reactions. Jumonji domain-containing protein D3 (JMJD3)-mediated histone 3 lysine 27 trimethylation (H3K27me3) demethylation may promote the pro-inflammatory response of macrophages under LPS stimulation. However, the mechanism of JMJD3 affecting macrophage apoptosis is still not clear. To explore this gap in knowledge, the ALI mice model with intratracheal administration of LPS and RAW264.7 cells with LPS stimulation were used as in vivo and in vitro experiments. The expression of JMJD3 and H3K27me3 and their cellular localization were analysed in lung tissue. Apoptosis was evaluated using TUNEL staining and flow cytometry. Expression of H3K27me3, ADORA2A and C/EBPβ were compared among different treatments and chromatin immunoprecipitation was performed to investigate the regulatory relationship. Our study showed that JMJD3 expression was upregulated in LPS-induced ALI mice and RAW264.7 cells. JMJD3-indued H3K27me3 demethylation inhibited caspase-3 cleavage by upregulating ADORA2A to decrease LPS-stimulated macrophage apoptosis and promoted the inflammatory reaction. This H3K27me3 demethylation also increased C/EBPβ expression, which may enhance ADORA2A expression further. Besides, inhibiting ADORA2A can also promote LPS-limited macrophage apoptosis. Moreover, the inhibition of JMJD3 in vivo and in vitro relieved the inhibition of macrophage apoptosis thus leading to the resolution of the inflammation. JMJD3 might inhibit macrophage apoptosis by promoting ADORA2A expression in LPS-induced ALI.

Expression of airway smooth muscle contractile proteins in children with acute interstitial pneumonia

The purpose of the present study was to investigate the expression of α-SMA and SM22α in airway smooth muscle (ASM) of bronchioles from children younger than 14 years who died of acute interstitial pneumonia (AIP). This is based upon the hypothesis that as contractile marker proteins α-SMA and SM22α can serve as an index of the overcontractile phenotype of ASM that is seen in AIP. Lung tissue samples of children were obtained from autopsies and divided into the AIP group (55.9% male and 44.1% female, between 0.4 and 132 months old, n = 34) and the control group (60% male and 40% female, between 2 and 156 months old, n = 10). We recorded the post-mortem interval (PMI), height, clinical symptoms and abdominal fat thickness (AFT) of each case. Haematoxylin-and-eosin-stained sections were used to examine the luminal area and observe the morphological changes in the bronchioles. Immunohistochemistry and Masson's trichrome staining were used to detect the expression of contractile marker proteins and the degree of pulmonary fibrosis respectively. Compared with the control group, the luminal areas of bronchioles in the AIP group were smaller (p < .001). The expression differences in α-SMA and SM22α between the two groups were statistically significant (p = .01 and p = .02 respectively). Also, there was no significant correlation of the contractile marker proteins expression with PMI, height, clinical symptoms and AFT. The collagen deposition difference in lung between the two groups was not statistically significant (p = .224). These findings suggest that enhancement of ASM contractile function appears to be involved in the death mechanism of children with AIP, which affords more insights into the understanding of AIP.

Role of Histone Post-Translational Modifications in Inflammatory Diseases

Inflammation is a defensive reaction for external stimuli to the human body and generally accompanied by immune responses, which is associated with multiple diseases such as atherosclerosis, type 2 diabetes, Alzheimer’s disease, psoriasis, asthma, chronic lung diseases, inflammatory bowel disease, and multiple virus-associated diseases. Epigenetic mechanisms have been demonstrated to play a key role in the regulation of inflammation. Common epigenetic regulations are DNA methylation, histone modifications, and non-coding RNA expression; among these, histone modifications embrace various post-modifications including acetylation, methylation, phosphorylation, ubiquitination, and ADP ribosylation. This review focuses on the significant role of histone modifications in the progression of inflammatory diseases, providing the potential target for clinical therapy of inflammation-associated diseases.

Airway Wall Remodeling in Childhood Asthma-A Personalized Perspective from Cell Type-Specific Biology

Airway wall remodeling is a pathology occurring in chronic inflammatory lung diseases including asthma, chronic obstructive pulmonary disease, and fibrosis. In 2017, the American Thoracic Society released a research statement highlighting the gaps in knowledge and understanding of airway wall remodeling. The four major challenges addressed in this statement were: (i) the lack of consensus to define “airway wall remodeling” in different diseases, (ii) methodologic limitations and inappropriate models, (iii) the lack of anti-remodeling therapies, and (iv) the difficulty to define endpoints and outcomes in relevant studies. This review focuses on the importance of cell-cell interaction, especially the bronchial epithelium, in asthma-associated airway wall remodeling. The pathology of “airway wall remodeling” summarizes all structural changes of the airway wall without differentiating between different pheno- or endo-types of asthma. Indicators of airway wall remodeling have been reported in childhood asthma in the absence of any sign of inflammation; thus, the initiation event remains unknown. Recent studies have implied that the interaction between the epithelium with immune cells and sub-epithelial mesenchymal cells is modified in asthma by a yet unknown epigenetic mechanism during early childhood.

Epigenetic Mechanisms in Allergy Development and Prevention

There has been a substantial increase in the incidence and the prevalence of allergic disorders in the recent decades, which seems to be related to rapid environmental and lifestyle changes, such as higher exposure to factors thought to exert pro-allergic effects but less contact with factors known to be associated with protection against the development of allergies. Pollution is the most remarkable example of the former, while less contact with microorganisms, lower proportion of unprocessed natural products in diet, and others resulting from urbanization and westernization of the lifestyle exemplify the latter. It is strongly believed that the effects of environmental factors on allergy susceptibility and development are mediated by epigenetic mechanisms, i.e. biologically relevant biochemical changes of the chromatin carrying transcriptionally-relevant information but not affecting the nucleotide sequence of the genome. Classical epigenetic mechanisms include DNA methylation and histone modifications, for instance acetylation or methylation. In addition, microRNA controls gene expression at the mRNA level. Such epigenetic mechanisms are involved in crucial regulatory processes in cells playing a pivotal role in allergies. Those include centrally managing cells, such as T lymphocytes, as well as specific structural and effector cells in the affected organs, responsible for the local clinical presentation of allergy, e.g. epithelial or airway smooth muscle cells in asthma. Considering that allergic disorders possess multiple clinical (phenotypes) and mechanistic (endotypes) forms, targeted, stratified treatment strategies based on detailed clinical and molecular diagnostics are required. Since conventional diagnostic or therapeutic approaches do not suffice, this gap could possibly be filled out by epigenetic approaches.

The role of epigenetics in allergy and asthma development

PURPOSE OF REVIEW

Epigenetic mechanisms are known to play a crucial role in the pathogenesis of asthma, allergic rhinitis, atopic dermatitis, food allergy, and other allergic disorders, especially through mediating the effects of the environmental factors, well recognized allergy-risk modifiers. The aim of this work was to provide a concise but comprehensive review of the recent progress in the epigenetics of allergic diseases.

RECENT FINDINGS

Recent few years have substantially expanded our knowledge on the role of epigenetics in the pathogenesis and clinical picture of allergies. Specifically, it has been shown that epigenetic marks, especially DNA methylation, possess a diagnostic potential for atopic sensitization, asthma, allergic rhinitis, and food allergy. DNA methylation can be a predictor of clinical responses in controlled allergen challenges, including oral food challenges. Furthermore, direct or indirect targeting epigenetic mechanisms, this time especially histone modifications, was able to favorably affect expression of the genes underlying allergies and generally improve airway biology in allergic diseases or their animal models.

SUMMARY

Further studies are needed to explore the diagnostic and therapeutic potential of epigenetic modifications in allergies and to develop respective clinical tools.

Epigenetic-modifying therapies: An emerging avenue for the treatment of inflammatory skin diseases

Epigenetic modifications include DNA methylation, histone modification and the action of microRNAs. These mechanisms coordinate in complex networks to control gene expression, thereby regulating key physiological processes in the skin and immune system. Recently, researchers have turned to the epigenome to understand the pathogenesis of inflammatory skin diseases. In psoriasis and atopic dermatitis, epigenetic modifications contribute to key pathogenic events such as immune activation, T-cell polarization and keratinocyte dysfunction. These discoveries have introduced new possibilities for the treatment of skin diseases; unlike genetics, epigenetic alterations are readily modifiable and potentially reversible. In this viewpoint essay, we summarize the current state of epigenetic research in inflammatory skin diseases and propose that targeting the histone machinery is a promising avenue for the development of new therapies for psoriasis and atopic dermatitis. Expanding on the progress that has already been made in the field of cancer epigenetics, we discuss existing epigenetic-modifying tools that can be applied to the treatment of inflammatory skin diseases and consider future directions for investigation in order to allow for the widespread clinical application of such therapies.

The demethylase inhibitor GSK-J4 limits inflammatory colitis by promoting de novo synthesis of retinoic acid in dendritic cells

Dendritic cells (DCs) promote T-cell mediated tolerance to self-antigens and induce inflammation to innocuous-antigens. This dual potential makes DCs fundamental players in inflammatory disorders. Evidence from inflammatory colitis mouse models and inflammatory bowel diseases (IBD) patients indicated that gut inflammation in IBD is driven mainly by T-helper-1 (Th1) and Th17 cells, suggesting an essential role for DCs in the development of IBD. Here we show that GSK-J4, a selective inhibitor of the histone demethylase JMJD3/UTX, attenuated inflammatory colitis by reducing the inflammatory potential and increasing the tolerogenic features of DCs. Mechanistic analyses revealed that GSK-J4 increased activating epigenetic signals while reducing repressive marks in the promoter of retinaldehyde dehydrogenase isoforms 1 and 3 in DCs, enhancing the production of retinoic acid. This, in turn, has an impact on regulatory T cells (Treg) increasing their lineage stability and gut tropism as well as potentiating their suppressive activity. Our results open new avenues for the treatment of IBD patients.

Developments in the mechanisms of allergy in 2018 through the eyes of Clinical and Experimental Allergy, Part I

In the first of two linked articles, we describe the development in the mechanisms underlying allergy as described by Clinical & Experimental Allergy and other journals in 2018. Experimental models of allergic disease, basic mechanisms and clinical mechanisms are all covered.

Cytokine-induced molecular responses in airway smooth muscle cells inform genome-wide association studies of asthma

BACKGROUND

A challenge in the post-GWAS era is to assign function to disease-associated variants. However, available resources do not include all tissues or environmental exposures that are relevant to all diseases. For example, exaggerated bronchoconstriction of airway smooth muscle cells (ASMCs) defines airway hyperresponsiveness (AHR), a cardinal feature of asthma. However, the contribution of ASMC to genetic and genomic studies has largely been overlooked. Our study aimed to address the gap in data availability from a critical tissue in genomic studies of asthma.

METHODS

We developed a cell model of AHR to discover variants associated with transcriptional, epigenetic, and cellular responses to two AHR promoting cytokines, IL-13 and IL-17A, and performed a GWAS of bronchial responsiveness (BRI) in humans.

RESULTS

Our study revealed significant response differences between ASMCs from asthma cases and controls, including genes implicated in asthma susceptibility. We defined molecular quantitative trait loci (QTLs) for expression (eQTLs) and methylation (meQTLs), and cellular QTLs for contractility (coQTLs) and performed a GWAS of BRI in human subjects. Variants in asthma GWAS were significantly enriched for ASM QTLs and BRI-associated SNPs, and near genes enriched for ASM function, many with small P values that did not reach stringent thresholds of significance in GWAS.

CONCLUSIONS

Our study identified significant differences between ASMCs from asthma cases and controls, potentially reflecting trained tolerance in these cells, as well as a set of variants, overlooked in previous GWAS, which reflect the AHR component of asthma.

PRMT6 mediates inflammation via activation of the NF-κB/p65 pathway on a cigarette smoke extract-induced murine emphysema model

INTRODUCTION

Smoke-driven lung inflammation is considered to be the major pathophysiology mechanism of Chronic Obstructive Pulmonary Disease (COPD)/emphysema. Protein arginine methyltransferase 6 (PRMT6) is a key epigenetic enzyme, which is related to protecting the tri-methylation of H3K4 (H3K4me3). We hypothesized that PTMT6 protects lung inflammation through the nuclear factor kappa B (NF-κB) pathway.

METHODS

Mice were injected with cigarette smoke extract (CSE) or PBS to establish a mice model, intratracheally instilled with overexpressed PRMT6 or negative control vector. Morphometry of lung slides and lung function were measured. We determined the protein expression of PRMT6 and its related histone targets, the activation of NF-κB pathway, the level of tumor necrosis factor α (TNFα) and interleukin-1β (IL-1β).

RESULTS

After PRMT6 overexpression, the morphometry indexes and lung function were improved. Also, the expression of H3K4me3 was decreased. Overexpressed PRMT6 could suppress CSE-induced NF-κB activation and pro-inflammation genes expression.

CONCLUSIONS

The overexpressed PRMT6 could serve as an inflammation inhibitor, potentially through blocking the NF-κB/p65 pathway in the murine emphysema model.

Recent findings in the genetics and epigenetics of asthma and allergy

In asthma and allergy genetics, a trend towards a few main topics developed over the last 2 years. First, a number of studies have been published recently which focus on overlapping and/or very specific phenotypes: within the allergy spectrum but also reaching beyond, looking for common genetic traits shared between different diseases or disease entities. Secondly, an urgently needed focus has been put on asthma and allergy genetics in populations genetically different from European ancestry. This acknowledges that the majority of new asthma patients today are not white and asthma is a truly worldwide disease. In epigenetics, recent years have seen several large-scale epigenome-wide association studies (EWAS) being published and a further focus was on the interaction between the environment and epigenetic signatures. And finally, the major trends in current asthma and allergy genetics and epigenetics comes from the field of pharmacogenetics, where it is necessary to understand the susceptibility for and mechanisms of current asthma and allergy therapies while at the same time, we need to have scientific answers to the recent availability of novel drugs that hold the promise for a more individualized therapy.

JMJD3 in the regulation of human diseases

In recent years, many studies have shown that histone methylation plays an important role in maintaining the active and silent state of gene expression in human diseases. The Jumonji domain-containing protein D3 (JMJD3), specifically demethylate di- and trimethyl-lysine 27 on histone H3 (H3K27me2/3), has been widely studied in immune diseases, infectious diseases, cancer, developmental diseases, and aging related diseases. We will focus on the recent advances of JMJD3 function in human diseases, and looks ahead to the future of JMJD3 gene research in this review.