Therapeutic Effect of Histone Deacetylase Inhibitor, Sodium Butyrate, on Allergic Rhinitis In Vivo

The role of histone deacetylases in inflammatory respiratory diseases: an update

INTRODUCTION

Histone deacetylases (HDACs) catalyze the removal of acetyl groups from lysine residues of histones and other proteins, generally leading to a closed chromosomal configuration and transcriptional repression. Different HDACs have distinct substrate specificities and functions in different biological processes. Accumulating evidence indicates that HDACs play a key role in the pathogenesis of multiple respiratory diseases.

AREAS COVERED

After an extensive search of the PubMed database, Web of Science and ClinicalTrials.gov, covering the period from 1992 to 2024, this review summarizes recent advances in understanding the role of HDACs in inflammatory respiratory diseases, including allergic rhinitis (AR), chronic rhinosinusitis (CRS), asthma and chronic obstructive pulmonary disease (COPD). We also examine recent progress on the efficacy and potential use of histone deacetylase inhibitors (HDACi) for the treatment of these diseases.

EXPERT OPINION

Available data indicate that HDACs play an important role in the development of common inflammatory respiratory diseases, and HDACi have shown promise as treatments for these diseases. However, the exact roles and underlying mechanisms of specific HDACs in disease pathogenesis require further study. Additional work is necessary to develop novel potent HDACi with high isoform selectivity.

Sodium Butyrate Ameliorates Atopic Dermatitis-Induced Inflammation by Inhibiting HDAC3-Mediated STAT1 and NF-κB Pathway

A topic dermatitis (AD) is a common chronic and recurrent skin disorder. The protective effects of sodium butyrate (NaB), a metabolite of short-chain fatty acid breakdown by the gut microbiota, have been widely reported in numerous inflammatory diseases. However, the effect of NaB treatment alone on AD has not been reported. In the current study, AD was induced in BALB/c mice with 2,4-dinitrochlorobenzene (DNCB) for 28 days with NaB (200 mg/kg) treatment by gavage. NaB attenuated AD-induced skin bleeding, scarring, dryness, abrasions and erosions. In addition, NaB inhibited inflammatory cells infiltration and attenuated the expression of inflammatory cytokines and chemokines. Mechanistically, NaB reduced histone deacetylase 3 (HDAC3) expression and NF-κB p65 nuclear translocation by increasing the lysine acetylation levels of STAT1 and NF-κB p65 in AD. Taken together, our study suggests that NaB inhibits inflammatory mediators and ameliorates AD by inhibiting HDAC3 expression, thereby upregulating STAT1 and NF-κB p65 lysine acetylation levels and reducing NF-κB p65 nuclear translocation. Therefore, this study provides a new theoretical basis for NaB in the treatment of AD.

Sodium butyrate alleviates experimental autoimmune prostatitis by inhibiting oxidative stress and NLRP3 inflammasome activation via the Nrf2/HO-1 pathway

BACKGROUND

Chronic prostatitis and chronic pelvic pain syndrome (CP/CPPS) leads to severe discomfort in males and loss of sperm quality. Current therapeutic options have failed to achieve satisfactory results. Sodium butyrate (NaB) plays a beneficial role in reducing inflammation, increasing antioxidant capacities, and improving organ dysfunction; additionally NaB has good safety prospects and great potential for clinical application. The purpose of the current research was to study the effect of NaB on CP/CPPS and the underlying mechanisms using a mouse model of experimental autoimmune prostatitis (EAP) mice.

METHODS

The EAP mouse model was successfully established by subcutaneously injecting a mixture of prostate antigen and complete Freund's adjuvant. Then, EAP mice received daily intraperitoneal injections of NaB (100, 200, or 400 mg/kg/day) for 16 days, from Days 26 to 42. We then explored anti-inflammatory potential mechanisms of NaB by studying the effects of Nrf2 inhibitor ML385 and HO-1 inhibitor zinc protoporphyrin on prostate inflammation and pelvic pain using this model. On Day 42, hematoxylin-eosin staining and dihydroethidium staining were used to evaluate the histological changes and oxidative stress levels of prostate tissues. Chronic pelvic pain was assessed by applying Von Frey filaments to the lower abdomen. The levels of inflammation-related cytokines, such as interleukin (IL)-1β, IL-6, and tumor necrosis factor were detected by enzyme-linked immunosorbent assay. The regulation of Nrf2/HO-1 signaling pathway and the expression of NLRP3 inflammasome-related protein in EAP mice were detected by western blot analysis assay.

RESULTS

Compared with the EAP group, chronic pain development, histological manifestations, and cytokine levels showed that NaB reduced the severity of EAP. NaB treatment could inhibit NLRP3 inflammasome activation. Mechanism studies showed that NaB intervention could alleviate oxidative stress in EAP mice through Nrf2/HO-1 signal pathway. Nrf2/HO-1 pathway inhibitors can inhibit NaB -mediated oxidative stress. The inhibitory effect of NaB on the activation of NLRP3 inflammasome and anti-inflammatory effect can also be blocked by Nrf2/HO-1 pathway.

CONCLUSIONS

NaB treatment can alleviates prostatic inflammation and pelvic pain associated with EAP by inhibiting oxidative stress and NLRP3 inflammasome activation via the Nrf2/HO-1 pathway. NaB has the potential as an effective agent in the treatment of EAP.

Deacetylation of Histones and Non-histone Proteins in Inflammatory Diseases and Cancer Therapeutic Potential of Histone Deacetylase Inhibitors

Epigenetic changes play an important role in the pathophysiology of autoimmune diseases such as allergic asthma, multiple sclerosis, lung diseases, diabetes, cystic fibrosis, atherosclerosis, rheumatoid arthritis, and COVID-19. There are three main classes of epigenetic alterations: post-translational modifications of histone proteins, control by non-coding RNA and DNA methylation. Since histone modifications can directly affect chromatin structure and accessibility, they can regulate gene expression levels. Abnormal expression and activity of histone deacetylases (HDACs) have been reported in immune mediated diseases. Increased acetylated levels of lysine residues have been suggested to be related to the overexpression of inflammatory genes. This review focuses on the effect of HDAC modifications on histone and non-histone proteins in autoimmune diseases. Furthermore, we discuss the potential therapeutic effect of HDAC inhibitors (HDACi) used in these diseases.

Epigenome-wide DNA methylation association study of circulating IgE levels identifies novel targets for asthma

BACKGROUND

Identifying novel epigenetic signatures associated with serum immunoglobulin E (IgE) may improve our understanding of molecular mechanisms underlying asthma and IgE-mediated diseases.

METHODS

We performed an epigenome-wide association study using whole blood from Framingham Heart Study (FHS; n = 3,471, 46% females) participants and validated results using the Childhood Asthma Management Program (CAMP; n = 674, 39% females) and the Genetic Epidemiology of Asthma in Costa Rica Study (CRA; n = 787, 41% females). Using the closest gene to each IgE-associated CpG, we highlighted biologically plausible pathways underlying IgE regulation and analyzed the transcription patterns linked to IgE-associated CpGs (expression quantitative trait methylation loci; eQTMs). Using prior UK Biobank summary data from genome-wide association studies of asthma and allergy, we performed Mendelian randomization (MR) for causal inference testing using the IgE-associated CpGs from FHS with methylation quantitative trait loci (mQTLs) as instrumental variables.

FINDINGS

We identified 490 statistically significant differentially methylated CpGs associated with IgE in FHS, of which 193 (39.3%) replicated in CAMP and CRA (FDR < 0.05). Gene ontology analysis revealed enrichment in pathways related to transcription factor binding, asthma, and other immunological processes. eQTM analysis identified 124 cis-eQTMs for 106 expressed genes (FDR < 0.05). MR in combination with drug-target analysis revealed CTSB and USP20 as putatively causal regulators of IgE levels (Bonferroni adjusted P < 7.94E-04) that can be explored as potential therapeutic targets.

INTERPRETATION

By integrating eQTM and MR analyses in general and clinical asthma populations, our findings provide a deeper understanding of the multidimensional inter-relations of DNA methylation, gene expression, and IgE levels.

FUNDING

US NIH/NHLBI grants: P01HL132825, K99HL159234. N01-HC-25195 and HHSN268201500001I.

The Role of Diet and Nutrition in Allergic Diseases

Allergic diseases are a set of chronic inflammatory disorders of lung, skin, and nose epithelium characterized by aberrant IgE and Th2 cytokine-mediated immune responses to exposed allergens. The prevalence of allergic diseases, including asthma, allergic rhinitis, and atopic dermatitis, has increased dramatically worldwide in the past several decades. Evidence suggests that diet and nutrition play a key role in the development and severity of allergic diseases. Dietary components can differentially regulate allergic inflammation pathways through host and gut microbiota-derived metabolites, therefore influencing allergy outcomes in positive or negative ways. A broad range of nutrients and dietary components (vitamins A, D, and E, minerals Zn, Iron, and Se, dietary fiber, fatty acids, and phytochemicals) are found to be effective in the prevention or treatment of allergic diseases through the suppression of type 2 inflammation. This paper aims to review recent advances in the role of diet and nutrition in the etiology of allergies, nutritional regulation of allergic inflammation, and clinical findings about nutrient supplementation in treating allergic diseases. The current literature suggests the potential efficacy of plant-based diets in reducing allergic symptoms. Further clinical trials are warranted to examine the potential beneficial effects of plant-based diets and anti-allergic nutrients in the prevention and management of allergic diseases.

An antioxidant ameliorates allergic airway inflammation by inhibiting HDAC 1 via HIF-1α/VEGF axis suppression in mice

Histone deacetylase inhibitors (HDACi) are novel class of drugs as they are involved in post translational modification of several proteins involved in signaling pathways related to asthma. HDACi have been reported to elicit protective effects on asthma but the signaling pathways associated with it have not been investigated much. Recently, we have demonstrated that intranasal administrations of Pan-HDAC inhibitors, sodium butyrate and curcumin, which have effectively reduced asthma severity via HDAC1 inhibition in Ovalbumin induced mouse model. Present study aimed to investigate possible pathways by which curcumin and sodium butyrate may minimize asthma pathogenesis via HDAC 1 inhibition. Balb/c mice were exposed (sensitized and challenged) with Ovalbumin to establish allergic asthma model followed by pretreatment of curcumin (5 mg/kg) and sodium butyrate (50 mg/kg) through intranasal route. Effects of curcumin and sodium butyrate on HIF-1α/VEGF signaling through activation of PI3K/Akt axis has been investigated using protein expressions followed by chromatin immunoprecipitation of BCL2 and CCL2 against HDAC1. Molecular docking analysis was also performed to investigate effects of curcumin and butyrate on mucus hypersecretion, goblet cell hyperplasia and airway hyperresponsiveness. Augmented expressions of HDAC-1, HIF-1α, VEGF, p-Akt and p-PI3K were observed in asthmatic group which was suppressed in both the treatments. NRF-2 level was significantly restored by curcumin and butyrate treatments. Protein expressions of p-p38, IL-5 and mRNA expressions of GATA-3 were also reduced in curcumin and butyrate treatment groups. Our findings suggest that curcumin and sodium butyrate may attenuate airway inflammation via down regulation of p-Akt/p-PI3K/HIF-1α/VEGF axis.

International consensus statement on allergy and rhinology: Allergic rhinitis - 2023

BACKGROUND

In the 5 years that have passed since the publication of the 2018 International Consensus Statement on Allergy and Rhinology: Allergic Rhinitis (ICAR-Allergic Rhinitis 2018), the literature has expanded substantially. The ICAR-Allergic Rhinitis 2023 update presents 144 individual topics on allergic rhinitis (AR), expanded by over 40 topics from the 2018 document. Originally presented topics from 2018 have also been reviewed and updated. The executive summary highlights key evidence-based findings and recommendation from the full document.

METHODS

ICAR-Allergic Rhinitis 2023 employed established evidence-based review with recommendation (EBRR) methodology to individually evaluate each topic. Stepwise iterative peer review and consensus was performed for each topic. The final document was then collated and includes the results of this work.

RESULTS

ICAR-Allergic Rhinitis 2023 includes 10 major content areas and 144 individual topics related to AR. For a substantial proportion of topics included, an aggregate grade of evidence is presented, which is determined by collating the levels of evidence for each available study identified in the literature. For topics in which a diagnostic or therapeutic intervention is considered, a recommendation summary is presented, which considers the aggregate grade of evidence, benefit, harm, and cost.

CONCLUSION

The ICAR-Allergic Rhinitis 2023 update provides a comprehensive evaluation of AR and the currently available evidence. It is this evidence that contributes to our current knowledge base and recommendations for patient evaluation and treatment.

Vancomycin-induced gut microbiota dysbiosis aggravates allergic rhinitis in mice by altered short-chain fatty acids

OBJECTIVE

This study aims to explore how gut microbiota dysbiosis affects allergic rhinitis (AR) and whether short-chain fatty acids (SCFAs) play a role in this process.

METHODS

A mouse gut microbiota dysbiosis model was established by adding vancomycin to drinking water for 2 weeks before ovalbumin (OVA) sensitization. Then an OVA-alum AR mouse model was established by intraperitoneal OVA injection followed by nasal excitation. Hematoxylin and eosin (H&E) staining was performed to observe pathological changes in nasal and colon tissues of AR mice. Serum levels of total-IgE, OVA-sIgE, IL-4, IL-5, IL-10, and TGF-β1 were measured. The composition and diversity of the mouse gut microbiota were observed by 16S rDNA sequencing. Levels of SCFAs in feces were determined using SCFA-targeted metabolomics. Sodium butyrate (NaB) was added daily to mice on a low-fiber basal diet 2 weeks before the first sensitization, until the end of the study.

RESULTS

After gut microbiota dysbiosis, serum levels of the total IgE, OVA-sIgE, IL-4, and IL-5 in AR mice were significantly increased, compared with the control group. The composition and diversity of gut microbiota were significantly altered after gut microbiota dysbiosis, with the fecal SCFAs significantly reduced as well. The reduced bacterial genera after gut microbiota dysbiosis, such as Ruminococcus and Lactobacillus, were significantly and positively correlated with SCFAs. In contrast, the increased genera in the Van group, such as Escherichia-Shigella and Klebsiella, were significantly negatively correlated with SCFAs in feces. NaB treatment significantly reduced total-IgE, OVA-sIgE, IL-4, and IL-5 levels in serum, and inflammatory infiltration of the nasal and colon mucosa. In addition, serum levels of IL-10 and TGF-β1 increased significantly after NaB treatment. Foxp3 protein in the colon was upregulated considerably after NaB intervention.

CONCLUSION

Vancomycin-induced gut microbiota dysbiosis increased susceptibility and severity of AR, which is significantly related to reduced SCFA-producing bacteria, fecal SCFAs, and specific bacterial taxa. In addition, it was found that NaB alleviated low dietary fiber base-fed symptoms and immune status in AR mice.

The emerging role of histone deacetylase 1 in allergic diseases

Histone deacetylase 1 (HDAC1) is a unique member of the classes I HDACs and helps to regulate acute and chronic adaptation to environmental stimuli such as allergen, stress. Allergic diseases are complex diseases resulting from the effect of multiple genetic and interacting foreign substances. Epigenetics play an important role in both pathological and immunomodulatory conditions of allergic diseases. To be consistent with this role, recent evidence strongly suggests that histone deacetylase 1 (HDAC1) plays a critical role in allergic response. HDAC1 expression is stimulated by allergen and attributes to increase T helper 2 (Th2) cytokine levels, decrease Th1/Th17 cells and anti-inflammatory cytokine Interleukin-10 (IL-10), and TWIK-related potassium channel-1 (Trek-1) expression. This review focuses on the contribution of HDAC1 and the regulatory role in characterizing allergic endotypes with common molecular pathways and understanding allergic multimorbidity relationships, as well as addressing their potential as therapeutic targets for these conditions.

Genetics and Epigenetics in Allergic Rhinitis

The pathogenesis of allergic rhinitis is associated with genetic, environmental, and epigenetic factors. Genotyping of single nucleotide polymorphisms (SNPs) is an advanced technique in the field of molecular genetics that is closely correlated with genome-wide association studies (GWASs) in large population groups with allergic diseases. Many recent studies have paid attention to the role of epigenetics, including alteration of DNA methylation, histone acetylation, and miRNA levels in the pathogenesis of allergic rhinitis. In this review article, genetics and epigenetics of allergic rhinitis, including information regarding functions and significance of previously known and newly-discovered genes, are summarized. Directions for future genetic and epigenetic studies of allergic rhinitis are also proposed.

Intranasal curcumin and sodium butyrate modulates airway inflammation and fibrosis via HDAC inhibition in allergic asthma

Asthma being an inflammatory disease of the airways lead to structural alterations in lungs which often results in the severity of the disease. Curcumin, diferuloylmethane, is well known for its medicinal properties but its anti-inflammatory potential via Histone deacetylase inhibition (HDACi) has not been revealed yet. Therefore, we have explored here, anti-inflammatory and anti-fibrotic potential of intranasal curcumin via HDAC inhibition and compared its potential with Sodium butyrate (SoB), a known histone deacetylase inhibitor of Class I and II series. Anti-inflammatory potential of SoB, has been investigated in cancer but not been studied in asthma before.

MATERIALS AND METHODS

In present study, ovalbumin (OVA) was used to sensitize Balb/c mice and later exposed to (1%) OVA aerosol. Curcumin (5 mg/kg) and Sodium butyrate (50 mg/kg) was administered through intranasal route an hour before OVA aerosol challenge. Efficacies of SoB and Curcumin as HDAC inhibitors were evaluated in terms of different inflammatory parameters like, total inflammatory cell count, reactive oxygen species (ROS), histamine release, nitric oxide and serum IgE levels. Inflammatory cell recruitment was analyzed by H&E staining and structural alterations were revealed by Masson's Trichrome staining of lung sections.

RESULTS

Enhanced Matrix Metalloproteinase-2 and 9 (MMP-2 and MMP-9) activities were observed in bronchoalveolar lavage fluid (BALF) of asthmatic mice by gelatin zymography which was inhibited in both treatment groups. Protein expressions of MMP-9, HDAC 1, H3acK9 and NF-kB p65 were modulated in intranasal curcumin and SoB pretreatment groups.

CONCLUSION

This is the first report where intranasal curcumin inhibited asthma severity via affecting HDAC 1 (H3acK9) leading to NF-kB suppression in mouse model of allergic asthma.

Sulforaphane attenuates cisplatin-induced hearing loss by inhibiting histone deacetylase expression

INTRODUCTION

Cruciferous vegetables are a rich source of sulforaphane (SFN), which acts as a natural HDAC inhibitor (HDACi). Our previous study found that HDACi could restore histone acetyltransferase/histone deacetylase (HAT/HDAC) balance in the cochlea and attenuate gentamicin-induced hearing loss in guinea pigs. Here, we investigated the protective effect of SFN on cisplatin-induced hearing loss (CIHL).

METHODS

Thirty rats were randomly divided into 3 equal groups: the control group, cisplatin group, and SFN+cisplatin group. Rats were injected with SFN (30 mg/kg once a day) and cisplatin (7 mg/kg twice a day) for 7 days to investigate the protective role of SFN on CIHL. We observed auditory brainstem response (ABR) threshold shifts and immunostained cochlear basilar membranes of rats. For in vitro experiments, we treated HEI-OC1 cells and rat cochlear organotypic cultures with SFN (5, 10, and 15 μM) and cisplatin (10 μM). Immunofluorescence, cell viability, and protein analysis were performed to further analyze the protective mechanism of SFN on CIHL.

RESULTS

SFN (30 mg/kg once a day) decreased cisplatin (7 mg/kg twice a day)-induced ABR threshold shifts and outer hair cell loss. CCK-8 assay showed that cisplatin (10 μM) reduced the viability of HEI-OC1 cells to 42%, and SFN had a dose-dependent protective effect. In cochlear organotypic cultures, we found that SFN (10 and 15 μM) increased cisplatin (10 μM)-induced myosin 7a⁺ cell count and restored ciliary morphology. SFN (5, 10, and 15 μM) reversed the cisplatin (10 μM)-induced increase in HDAC2, -4, and -5 and SFN (15 μM) reversed the cisplatin (10 μM)-induced decrease in H3-Ack9 [acetyl-histone H3 (Lys9)] protein expression in HEI-OC1 cells. Neither cisplatin nor cisplatin combined with SFN affected the expression of HDAC7, or HDAC9.

CONCLUSION

SFN prevented disruption of the HAT/HDAC balance, protecting against CIHL in rats.

Nasal Epithelial Barrier Integrity and Tight Junctions Disruption in Allergic Rhinitis: Overview and Pathogenic Insights

Allergic rhinitis (AR) is a common disorder affecting up to 40% of the population worldwide and it usually persists throughout life. Nasal epithelial barrier constitutes the first line of defense against invasion of harmful pathogens or aeroallergens. Cell junctions comprising of tight junctions (TJs), adherens junctions, desmosomes and hemidesmosomes form the nasal epithelial barrier. Impairment of TJ molecules plays causative roles in the pathogenesis of AR. In this review, we describe and discuss the components of TJs and their disruption leading to development of AR, as well as regulation of TJs expression by epigenetic changes, neuro-immune interaction, epithelial-derived cytokines (thymic stromal lymphopoietin, IL-25 and IL-33), T helper 2 (Th2) cytokines (IL-4, IL-5, IL-6 and IL-13) and innate lymphoid cells. These growing evidence support the development of novel therapeutic approaches to restore nasal epithelial TJs expression in AR patients.

RGFP966, a selective HDAC3 inhibitor, ameliorates allergic and inflammatory responses in an OVA-induced allergic rhinitis mouse model

RGFP966 is a selective inhibitor of histone deacetylase 3 (HDAC3) playing crucial roles in triggering allergic and inflammatory responses. Whereas, its role in allergic rhinitis (AR) remains uncertain. This study sought to illustrate the role and mechanism of HDAC3 inhibitor RGFP966 on allergic and inflammatory responses in murine AR. RGFP966 administration was applied on murine AR. HE staining, PAS staining, toluidine blue staining, immunohistochemistry staining and real-time PCR methods were used to assess eosinophils, goblet cells, mast cells, HDAC3 positive cells and mRNA levels in nasal tissues of mice. HDAC3 activities in nasal tissues were quantified with HDAC3 Activity Assay Kit. We collected blood and nasal lavage fluid (NLF) of mice for assaying IgE, inflammatory cytokines and inflammatory cells. Results indicated that RGFP966 intervention attenuated sneezing, nose rubbing, IgE, inflammatory cytokines, eosinophils, goblet cells, mast cells, inflammatory cells, HDAC3 levles and activities in RGFP966 treated mice. In conclusion, RGFP966 might reduce HDAC3 expression and HDAC3 activities, and then eosinophils and mast cells recruitment, goblet cells proliferation and inflammatory cytokines levels are decreased, resulting in the alleviation of allergic and inflammatory responses in AR mice.

Reduced occludin and claudin-7 expression is associated with urban locations and exposure to second-hand smoke in allergic rhinitis patients

The breakdown of nasal epithelial barrier occurs in allergic rhinitis (AR) patients. Impairment of cell junction molecules including tight junctions (TJs) and desmosomes plays causative roles in the pathogenesis of AR. In this study, we investigated the transcript expression levels of TJs including occludin (OCLN), claudin-3 and -7 (CLDN3 and CLDN7), desmoglein 3 (DSG3) and thymic stromal lymphopoietin (TSLP) in AR patients (n = 30) and non-allergic controls (n = 30). Nasal epithelial cells of non-allergic controls and AR patients were collected to examine their mRNA expression levels, and to correlate with clinico-demographical and environmental parameters. We demonstrated that the expression of OCLN (p = 0.009), CLDN3 (p = 0.032) or CLDN7 (p = 0.004) transcript was significantly lower in AR patients compared with non-allergic controls. No significant difference was observed in the expression of DSG3 (p = 0.750) or TSLP (p = 0.991) transcript in AR patients compared with non-allergic controls. A significant association between urban locations and lower OCLN expression (p = 0.010), or exposure to second-hand smoke with lower CLDN7 expression (p = 0.042) was found in AR patients. Interestingly, none of the TJs expression was significantly associated with having pets, frequency of changing bedsheet and housekeeping. These results suggest that defective nasal epithelial barrier in AR patients is attributable to reduced expression of OCLN and CLDN7 associated with urban locations and exposure to second-hand smoke, supporting recent findings that air pollution represents one of the causes of AR.

Zinc deficiency leads to reduced interleukin-2 production by active gene silencing due to enhanced CREMα expression in T cells

BACKGROUND & AIMS

The micronutrient zinc is essential for proper immune function. Consequently, zinc deficiency leads to impaired immune function, as seen in decreased secretion of interleukin (IL)-2 by T cells. Although this association has been known since the late 1980s, the underlying molecular mechanisms are still unknown. Zinc deficiency and reduced IL-2 levels are especially found in the elderly, which in turn are prone to chronic diseases. Here, we describe a new molecular link between zinc deficiency and reduced IL-2 expression in T cells.

METHODS

The effects of zinc deficiency were first investigated in vitro in the human T cell lines Jurkat and Hut-78 and complemented by in vivo data from zinc-supplemented pigs. A short- and long-term model for zinc deficiency was established. Zinc levels were detected by flow cytometry and expression profiles were investigated on the mRNA and protein level.

RESULTS

The expression of the transcription factor cAMP-responsive-element modulator α (CREMα) is increased during zinc deficiency in vitro, due to increased protein phosphatase 2A (PP2A) activity, resulting in decreased IL-2 production. Additionally, zinc supplementation in vivo reduced CREMα levels causing increased IL-2 expression. On epigenetic levels increased CREMα binding to the IL-2 promoter is mediated by histone deacetylase 1 (HDAC1). The HDAC1 activity is inhibited by zinc. Moreover, deacetylation of the activating histone mark H3K9 was increased under zinc deficiency, resulting in reduced IL-2 expression.

CONCLUSIONS

With the transcription factor CREMα a molecular link was uncovered, connecting zinc deficiency with reduced IL-2 production due to enhanced PP2A and HDAC1 activity.

The Ups and Downs of Metabolism during the Lifespan of a T Cell

Understanding the various mechanisms that govern the development, activation, differentiation, and functions of T cells is crucial as it could provide opportunities for therapeutic interventions to disrupt immune pathogenesis. Immunometabolism is one such area that has garnered significant interest in the recent past as it has become apparent that cellular metabolism is highly dynamic and has a tremendous impact on the ability of T cells to grow, activate, and differentiate. In each phase of the lifespan of a T-cell, cellular metabolism has to be tailored to match the specific functional requirements of that phase. Resting T cells rely on energy-efficient oxidative metabolism but rapidly shift to a highly glycolytic metabolism upon activation in order to meet the bioenergetically demanding process of growth and proliferation. However, upon antigen clearance, T cells return to a more quiescent oxidative metabolism to support T cell memory generation. In addition, each helper T cell subset engages distinct metabolic pathways to support their functional needs. In this review, we provide an overview of the metabolic changes that occur during the lifespan of a T cell and discuss several important studies that provide insights into the regulation of the metabolic landscape of T cells and how they impact T cell development and function.

Zonula occludens and nasal epithelial barrier integrity in allergic rhinitis

Allergic rhinitis (AR) is a common disease affecting 400 million of the population worldwide. Nasal epithelial cells form a barrier against the invasion of environmental pathogens. These nasal epithelial cells are connected together by tight junction (TJ) proteins including zonula occludens-1 (ZO-1), ZO-2 and ZO-3. Impairment of ZO proteins are observed in AR patients whereby dysfunction of ZOs allows allergens to pass the nasal passage into the subepithelium causing AR development. In this review, we discuss ZO proteins and their impairment leading to AR, regulation of their expression by Th1 cytokines (i.e., IL-2, TNF-α and IFN-γ), Th2 cytokines (i.e., IL-4 and IL-13) and histone deacetylases (i.e., HDAC1 and HDAC2). These findings are pivotal for future development of targeted therapies by restoring ZO protein expression and improving nasal epithelial barrier integrity in AR patients.

Outside-in hypothesis revisited: The role of microbial, epithelial, and immune interactions

OBJECTIVE

Our understanding of the origin of allergic diseases has increased in recent years, highlighting the importance of microbial dysbiosis and epithelial barrier dysfunction in affected tissues. Exploring the microbial-epithelial-immune crosstalk underlying the mechanisms of allergic diseases will allow the development of novel prevention and treatment strategies for allergic diseases.

DATA SOURCES

This review summarizes the recent advances in microbial, epithelial, and immune interactions in atopic dermatitis, allergic rhinitis, chronic rhinosinusitis, and asthma.

STUDY SELECTIONS

We performed a literature search, identifying relevant recent primary articles and review articles.

RESULTS

Dynamic crosstalk between the environmental factors and microbial, epithelial, and immune cells in the development of atopic dermatitis, allergic rhinitis, chronic rhinosinusitis, and asthma underlies the pathogenesis of these diseases. There is substantial evidence in the literature suggesting that environmental factors directly affect barrier function of the epithelium. In addition, T-helper 2 (T_H2) cells, type 2 innate lymphoid cells, and their cytokine interleukin 13 (IL-13) damage skin and lung barriers. The effects of environmental factors may at least in part be mediated by epigenetic mechanisms. Histone deacetylase activation by type 2 immune response has a major effect on leaky barriers and blocking of histone deacetylase activity corrects the defective barrier in human air-liquid interface cultures and mouse models of allergic asthma with rhinitis. We also present and discuss a novel device to detect and monitor skin barrier dysfunction, which provides an opportunity to rapidly and robustly assess disease severity.

CONCLUSION

A complex interplay between environmental factors, epithelium, and the immune system is involved in the development of systemic allergic diseases.

HDAC inhibitor sodium butyrate prevents allergic rhinitis and alters lncRNA and mRNA expression profiles in the nasal mucosa of mice

Our previous study demonstrated that intranasal administration of histone deacetylase inhibitor sodium butyrate (NaB) exhibits therapeutic effects on a mouse model of allergic rhinitis (AR). However, whether NaB is effective on AR when administered orally and prophylactically, as well as its potential effects on gene expression, remained unknown. The present study aimed to investigate the preventive effect of NaB on AR when added to the diet of newly weaned mice and to evaluate the changes in long non-coding (lnc)RNA and mRNA expression profiles in the nasal mucosa. Mice were randomly divided into three groups as follows: i) Control (C) group, (no treatment); ii) AR group [treated with ovalbumin (OVA)]; and iii) NaB + AR group (treated with OVA and NaB). The NaB + AR group was administered NaB in their feed (30 g/kg chow), whereas the other two groups were fed normal feed between 3 and 6 weeks of age. At 7 weeks of age, OVA administration was initiated to induce AR in the AR and NaB + AR groups. Following model establishment, behavioral assessments, western blotting and gene expression analysis were performed. NaB exhibited a preventive effect in the murine AR model, diminished the increases in histone deacetylase 1 (HDAC1) and HDAC8 expression and increased OVA-induced acetylation of histone H3 at lysine 9. In addition, NaB increased the AR-associated low expression of interleukin 2 (IL-2), interferon γ and IL-17 and decreased the expression of IL-4, IL-5 and transforming growth factor β1. Gene Ontology and pathway analyses revealed the top 10 pathways among the groups. Octamer-binding transcription factor 1, ecotropic viral integration site 1 and paired box 4 were predicted to be target genes of lncRNA (NONMMUT057309). Thus, NaB may exhibit a preventive effect on AR. Additionally, the lncRNA and mRNA expression profiles in the nasal mucosa of mice with AR differed significantly following NaB treatment. These results may provide insights into the pathogenesis of AR and suggest new treatment targets.

Dietary Prevention of Atopic March in Pediatric Subjects With Cow's Milk Allergy

Cow's milk allergy (CMA) is one of the most prevalent food allergies and the most expensive allergic diseases in the pediatric age. There is no cure for CMA, and actual disease management is based on strict avoidance of cow milk protein-containing foods, access to rescue medication, and use of substitutive formulas. Early-life CMA could be one of the first steps of the "allergic march" (AM), leading to the occurrence of other atopic manifestations later in the life, including asthma and oculorhinitis, with subsequent further increase of costs for health care systems and families of affected children. In the last years, diet is emerged as a relevant strategy to prevent allergic diseases through, at least in part, epigenetic modulation of immune system. We provide an overview of studies that investigate the potential role of different dietary strategies in preventing the AM in pediatric patients with CMA.

Epigenetic studies and pediatric research

The 2020 Annual Review Issue, "Preventing Disease in the 21st Century" was selected by the Editors-in-Chief of Pediatric Research to include a variety of disease entities that confront health-care practitioners entrusted to the care of infants and children. In keeping with this mandate, this article reviews the subject of epigenetics, which impacts pediatric research from bench to bedside. Epigenetic mechanisms exert their effects through the interaction of environment, various susceptibility genes, and immunologic development and include: (1) DNA methylation; (2) posttranslational modifications of histone proteins through acetylation and methylation, and (3) RNA-mediated gene silencing by microRNA (miRNA) regulation. The effects of epigenetics during fetal life and early periods of development are first reviewed together with clinical applications of cardiovascular and metabolic disorders in later life. The relationships of epigenetics to the allergic and autoimmune diseases and cancer are next reviewed. A specific focus of the article is directed to the recent recognition that many of these disorders are driven by aberrant immune responses in which immunoregulatory events are often poorly functioning and where through interventive epigenetic measures prevention may be possible by alterations in programming of DNA during fetal and early periods as well as in later life.

Exacerbation of Chikungunya Virus Rheumatic Immunopathology by a High Fiber Diet and Butyrate

Chikungunya virus (CHIKV) is a mosquito transmitted alphavirus associated with a robust systemic infection and an acute inflammatory rheumatic disease. A high fiber diet has been widely promoted for its ability to ameliorate inflammatory diseases. Fiber is fermented in the gut into short chain fatty acids such as acetate, propionate, and butyrate, which enter the circulation providing systemic anti-inflammatory activities. Herein we show that mice fed a high fiber diet show a clear exacerbation of CHIKV arthropathy, with increased edema and neutrophil infiltrates. RNA-Seq analyses illustrated that a high fiber diet, in this setting, promoted a range of pro-neutrophil responses including Th17/IL-17. Gene Set Enrichment Analyses demonstrated significant similarities with mouse models of inflammatory psoriasis and significant depression of macrophage resolution phase signatures in the CHIKV arthritic lesions from mice fed a high fiber diet. Supplementation of the drinking water with butyrate also increased edema after CHIKV infection. However, the mechanisms involved were different, with modulation of AP-1 and NF-κB responses identified, potentially implicating deoptimization of endothelial barrier repair. Thus, neither fiber nor short chain fatty acids provided benefits in this acute infectious disease setting, which is characterized by widespread viral cytopathic effects and a need for tissue repair.

FcεRI-HDAC3-MCP1 Signaling Axis Promotes Passive Anaphylaxis Mediated by Cellular Interactions

Anaphylaxis is an acute and life-threatening systemic reaction. Food, drug, aero-allergen and insect sting are known to induce anaphylaxis. Mast cells and basophils are known to mediate Immunoglobulin E (IgE)-dependent anaphylaxis, while macrophages, neutrophils and basophils mediate non IgE-dependent anaphylaxis. Histone deacetylases (HDACs) play various roles in biological processes by deacetylating histones and non-histones proteins. HDAC inhibitors can increase the acetylation of target proteins and affect various inflammatory diseases such as cancers and allergic diseases. HDAC3, a class I HDAC, is known to act as epigenetic and transcriptional regulators. It has been shown that HDAC3 can interact with the high-affinity Immunoglobulin E receptor (FcεRI), to mediate passive anaphylaxis and cellular interactions during passive anaphylaxis. Effects of HDAC3 on anaphylaxis, cellular interactions involving mast cells and macrophages during anaphylaxis, and any tumorigenic potential of cancer cells enhanced by mast cells will be discussed in this review. Roles of microRNAs that form negative feedback loops with hallmarks of anaphylaxis such as HDAC3 in anaphylaxis and cellular interactions will also be discussed. The roles of MCP1 regulated by HDAC3 in cellular interactions during anaphylaxis are discussed. Roles of exosomes in cellular interactions mediated by HDAC3 during anaphylaxis are also discussed. Thus, review might provide clues for development of drugs targeting passive anaphylaxis.

The Metabolic Requirements of Th2 Cell Differentiation

Upon activation, naïve CD4⁺ T cells differentiate into a number of specialized T helper (Th) cell subsets. Th2 cells are central players in immunity to helminths and are implicated in mediating the inflammatory pathology associated with allergies. The differentiation of Th2 cells is dependent on transcription factors such as GATA3 and STAT6, which prime Th2 cells for the secretion of interleukin- (IL-) 4, IL-5, and IL-13. Several lines of work now suggest that differentiating Th2 cells in the lymph node are potent IL-4 cytokine producers, but do not become competent IL-5- and IL-13-producing cells until after receiving cues from non-lymphoid tissue. It is evident that Th2 cells that enter tissues undergo considerable changes in chromatin architecture and gene expression, and that over this time, the metabolic requirements of these cells change considerably. Herein, we discuss the metabolic requirements of Th2 cells during their early and late differentiation, focusing on the impact of glucose and lipid metabolism, mTOR activation, the nuclear receptor PPAR-γ and several metabolites.

Reduced genetic potential for butyrate fermentation in the gut microbiome of infants who develop allergic sensitization

BACKGROUND

Allergic disease is the most frequent chronic health issue in children and has been linked to early-life gut microbiome dysbiosis. Many lines of evidence suggest that microbially derived short-chain fatty acids, and particularly butyrate, can promote immune tolerance.

OBJECTIVE

We sought to determine whether bacterial butyrate production in the gut during early infancy is protective against the development of atopic disease in children.

METHODS

We used shotgun metagenomic analysis to determine whether dysbiosis in butyrate fermentation could be identified in human infants, before their developing allergic disease.

RESULTS

We found that the microbiome of infants who went on to develop allergic sensitization later in childhood lacked genes encoding key enzymes for carbohydrate breakdown and butyrate production.

CONCLUSIONS

Our findings support the importance of microbial carbohydrate metabolism during early infancy in protecting against the development of allergies.

Blocking histone deacetylase activity as a novel target for epithelial barrier defects in patients with allergic rhinitis

BACKGROUND

A defective epithelial barrier is found in patients with allergic rhinitis (AR) and asthma; however, the underlying mechanisms remain poorly understood. Histone deacetylase (HDAC) activity has been identified as a crucial driver of allergic inflammation and tight junction dysfunction.

OBJECTIVE

We investigated whether HDAC activity has been altered in patients with AR and in a mouse model of house dust mite (HDM)-induced allergic asthma and whether it contributed to epithelial barrier dysfunction.

METHODS

Primary nasal epithelial cells of control subjects and patients with AR were cultured at the air-liquid interface to study transepithelial electrical resistance and paracellular flux of fluorescein isothiocyanate-dextran (4 kDa) together with mRNA expression and immunofluorescence staining of tight junctions. Air-liquid interface cultures were stimulated with different concentrations of JNJ-26481585, a broad-spectrum HDAC inhibitor. In vivo the effect of JNJ-26481585 on mucosal permeability and tight junction function was evaluated in a mouse model of HDM-induced allergic airway inflammation.

RESULTS

General HDAC activity was greater in nasal epithelial cells of patients with AR and correlated inversely with epithelial integrity. Treatment of nasal epithelial cells with JNJ-26481585 restored epithelial integrity by promoting tight junction expression and protein reorganization. HDM-sensitized mice were treated with JNJ-26481585 to demonstrate the in vivo role of HDACs. Treated mice did not have allergic airway inflammation and had no bronchial hyperreactivity. Moreover, JNJ-26481585 treatment restored nasal mucosal function by promoting tight junction expression.

CONCLUSION

Our findings identify increased HDAC activity as a potential tissue-injury mechanism responsible for dysregulated epithelial cell repair, leading to defective epithelial barriers in AR. Blocking HDAC activity is a promising novel target for therapeutic intervention in patients with airway diseases.

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.

P-FN12, an H4R-Based Epitope Vaccine Screened by Phage Display, Regulates the Th1/Th2 Balance in Rat Allergic Rhinitis

Allergic rhinitis (AR) involves antigen-specific immune-inflammation of the nasal mucosa. Classical therapy for AR targets the histamine pathway, e.g., histamine receptor blockers. Histamine H4 receptor (H4R) was suggested as a novel therapeutic target due to its wide expression on almost all immune-related cells. A 12-mer random peptide library was used to select the specific epitope of the H4R. The phage clone showing the highest degree of activation was verified and translated to the corresponding peptide. The peptide FNKWMDCLSVTH, designated as P-FN12, was bound by H4R monoclonal antibody (mcAb) with high affinity. Moreover, the P-FN12 + CTB@Lipo-formulated vaccine, used as nasal drops, decreased allergic symptoms such as sneezing and nasal rubbing in a rat model. The level of ovalbumin (OVA)-specific immunoglobulin E (IgE) decreased significantly after vaccine administration. It also elicited increased levels of interferon (IFN)-γ and interleukin-2 (IL-2) but a decreased level of IL-4, and it elevated the T helper type 1 (Th1):T helper type 2 (Th2) cell ratio in peripheral blood mononuclear cell cultures. Our results indicated that the reduction of allergic inflammation by P-FN12-based vaccine was related to a decrease in production of OVA-specific IgE, Th2 immunity, and tissue eosinophilia. P-FN12 + CTB@Lipo is a promising vaccine that could suppress Th2 response and enhance the induction of Th1 cells in an AR model.

Effect of Dietary Fiber and Metabolites on Mast Cell Activation and Mast Cell-Associated Diseases

Many mast cell-associated diseases, including allergies and asthma, have seen a strong increase in prevalence during the past decades, especially in Western(ized) countries. It has been suggested that a Western diet may contribute to the prevalence and manifestation of allergies and asthma through reduced intake of dietary fiber and the subsequent production of their metabolites. Indeed, dietary fiber and its metabolites have been shown to positively influence the development of immune disorders via changes in microbiota composition and the regulation of B- and T-cell activation. However, the effects of these dietary components on the activation of mast cells, key effector cells of the inflammatory response in allergies and asthma, remain poorly characterized. Due to their location in the gut and vascularized tissues, mast cells are exposed to high concentrations of dietary fiber and/or its metabolites. Here, we provide a focused overview of current findings regarding the direct effects of dietary fiber and its various metabolites on the regulation of mast cell activity and the pathophysiology of mast cell-associated diseases.

Regulation of type 2 innate lymphoid cell-dependent airway hyperreactivity by butyrate

BACKGROUND

Allergic asthma is characterized by airway hyperreactivity (AHR) and inflammation driven by aberrant T_H2 responses. Type 2 innate lymphoid cells (ILC2s) are a critical source of the T_H2 cytokines IL-5 and IL-13, which promote acute asthma exacerbation. Short-chain fatty acids (SCFAs) have been shown to attenuate T cell-mediated allergic airway inflammation. However, their role in regulation of ILC2-driven AHR and lung inflammation remains unknown.

OBJECTIVE

We investigated the immunomodulatory role of SCFAs in regulation of ILC2-induced AHR and airway inflammation and delineated the mechanism involved.

METHODS

We assessed the role of SCFAs in regulating survival, proliferation, and cytokine production in lung sorted ILC2s. The SCFA butyrate was administered through drinking water or intranasally in BALB/c mice to evaluate its role in the ILC2-driven inflammatory response in IL-33 and Alternaria alternata models of allergic inflammation. We further confirmed our findings in human ILC2s.

RESULTS

We show that butyrate, but not acetate or propionate, inhibited IL-13 and IL-5 production by murine ILC2s. Systemic and local administration of butyrate significantly ameliorated ILC2-driven AHR and airway inflammation. We further demonstrate that butyrate inhibited ILC2 proliferation and GATA3 expression but did not induce cell apoptosis, likely through histone deacetylase (HDAC) inhibition, because trichostatin A, a pan-HDAC inhibitor, exerted similar effects on ILC2s. Importantly, cotreatment with trichostatin A and butyrate did not result in an additive effect. Finally, we show that butyrate reduces cytokine production in human ILC2s.

CONCLUSION

Our findings identify butyrate as a critical regulator of ILC2 proliferation and function through its HDAC inhibitory activity and can serve as a potential therapeutic target for asthma.

In Silico and in Vitro Interactions between Short Chain Fatty Acids and Human Histone Deacetylases

Short chain fatty acids (SCFAs) are postulated to modulate the immune development of neonates via epigenetic regulations such as histone deacetylase (HDAC) inhibition. In the context of atopic diseases, the inhibition of HDAC maintains T-cell homeostasis and induces naïve T-cell differentiation into adaptive Treg, which regulates the production of anti-inflammatory cytokines and suppression of Th2 immune responses. We investigated the structure-inhibition relationships of SCFAs with class I HDAC3 and class IIa HDAC7 using in silico docking simulation and the in vitro human recombinant HDAC inhibition assay. In silico docking simulation demonstrated that the lower binding energy of SCFAs toward HDACs was associated with the longer aliphatic chain length of SCFAs. Conversely, branching of SCFAs increased their binding energies toward both HDAC3 and HDAC7. The in vitro HDAC inhibition assay revealed that SCFAs more potently inhibit HDAC3 than HDAC7, with butyric acid being the most potent HDAC3 inhibitor among SCFAs (IC₅₀ = 0.318 mM). In conclusion, our findings inform novel structural relationships between SCFAs and HDAC3 versus HDAC7. Future investigation of human disposition of SCFAs is important to establish their effects on innate versus adaptive immunity.

Dose- and time- effect responses of DNA methylation and histone H3K9 acetylation changes induced by traffic-related air pollution

As an important risk factor of respiratory disorders, traffic-related air pollution (TRAP) has caused extensive concerns. Epigenetic change has been considered a link between TRAP and respiratory diseases. However, the exact effects of TRAP on epigenetic changes are still unclear. Here we investigated the dose- and time- effect responses of TRAP on DNA methylations and H3K9 acetylation (H3K9ac) in both blood and lung tissues of rats. The findings showed that every 1 μg/m³ increase of TRAP components were associated with changes in %5 mC (95% CI) in LINE-1, iNOS, p16^CDKN2A, and APC ranging from −0.088% (−0.150, −0.026) to 0.102 (0.049, 0.154), as well as 0.276 (0.053, 0.498) to 0.475 (0.103, 0.848) ng/mg increase of H3K9ac. In addition, every 1 more day exposure at high level of TRAP (in tunnel) also significantly changed the levels of DNA methylation (ranging from −0.842% to 0.248%) and H3K9ac (16.033 and 15.718 ng/mg pro in PBMC and lung tissue, respectively) changes. Season and/or sex could interact with air pollutants in affecting DNA methylation and H3K9ac. The findings showed that TRAP exposure is dose- and time- dependently associated with the changes of DNA methylation and H3K9ac.

Recent developments in epigenetics of pediatric asthma

PURPOSE OF REVIEW

The goal of this review was to systematically analyze recent studies updating our knowledge on the role of epigenetic mechanisms in childhood asthma.

RECENT FINDINGS

A systematic literature search was conducted that identified 23 fresh articles published within the last 5 years reporting the results of human studies on the relationships between epigenetic modifications and childhood asthma or its/related phenotypes. In almost all these studies, meaningful associations between levels of epigenetic marks (DNA methylation and/or histone modifications) and pediatric asthma or its/related phenotypes have been observed. In addition, many studies identified by our screening analyzed those associations in the context of environmental factors, such as pollution, tobacco smoke, farming, or diet, showing in a huge majority a modifying effect of those exposures.

SUMMARY

The results of our systematic literature search provide a strong support for the role of epigenetic mechanisms in (mediating the effects of environmental exposure on) pediatric asthma. This knowledge may possibly be translated into diagnostic and/or therapeutic approaches.