Physical and immunological barrier of human primary nasal epithelial cells from non-allergic and allergic donors

Neuroimmune communication in allergic rhinitis

The prevalence rate of allergic rhinitis (AR) is high worldwide. The inhalation of allergens induces AR, which is an immunoglobulin E-mediated and type 2 inflammation-driven disease. Recently, the role of neuroimmune communication in AR pathogenesis has piqued the interest of the scientific community. Various neuropeptides, such as substance P (SP), vasoactive intestinal peptide (VIP), calcitonin gene-related peptide (CGRP), nerve growth factor (NGF), and neuromedin U (NMU), released via "axon reflexes" or "central sensitization" exert regulatory effects on immune cells to elicit "neurogenic inflammation," which contributes to nasal hyperresponsiveness (NHR) in AR. Additionally, neuropeptides can be produced in immune cells. The frequent colocalization of immune and neuronal cells at certain anatomical regions promotes the establishment of neuroimmune cell units, such as nerve-mast cells, nerve-type 2 innate lymphoid cells (ILC2s), nerve-eosinophils and nerve-basophils units. Receptors expressed both on immune cells and neurons, such as TRPV1, TRPA1, and Mas-related G protein-coupled receptor X2 (MRGPRX2) mediate AR pathogenesis. This review focused on elucidating the mechanisms underlying neuroimmune communication in AR.

Common Pollen Modulate Immune Responses against Viral-Like Challenges in Airway Coculture Model

Recent research indicates that exposure to pollen increases the risk and severity of respiratory infections, while studies also suggest that it may possess a protective function. Our aim was to investigate how exposure to common pollen modifies airway cells' responses to viral- or bacterial-like challenges and vice versa. Cocultured A549 and THP-1 cells were exposed to three doses of four different pollens (Alnus glutinosa, Betula pendula, Phleum pratense, or Ambrosia artemisiifolia) and subsequently to Toll-like receptor (TLR) ligands mimicking bacterial and viral challenges (TLR3, TLR4, TLR7/8). The stimulation experiment was replicated in reverse order. Toxicological and immunological end points were analyzed. When cells were primed with pollen, especially with grass (P. pratense) or weed (A. artemisiifolia), the ability of cells to secrete cytokines in response to bacterial- and viral-like exposure was decreased. In contrast, cells primed with viral ligand TLR7/8 showed greater cytokine responses against pollen than cells exposed to ligands or pollen alone. Our results suggest that pollen exposure potentially weakens immune reactions to bacterial- or viral-like challenges by modulating cytokine production. They also indicate that TLR7/8-mediated viral challenges could elicit exaggerated immune responses against pollen. Both mechanisms could contribute to the acceleration and complication of infections during the pollen season.

Birch pollen-The unpleasant herald of spring

Type I respiratory allergies to birch pollen and pollen from related trees of the order Fagales are increasing in industrialized countries, especially in the temperate zone of the Northern hemisphere, but the reasons for this increase are still debated and seem to be multifaceted. While the most important allergenic molecules of birch pollen have been identified and characterized, the contribution of other pollen components, such as lipids, non-allergenic immunomodulatory proteins, or the pollen microbiome, to the development of allergic reactions are sparsely known. Furthermore, what also needs to be considered is that pollen is exposed to external influences which can alter its allergenicity. These external influences include environmental factors such as gaseous pollutants like ozone or nitrogen oxides or particulate air pollutants, but also meteorological events like changes in temperature, humidity, or precipitation. In this review, we look at the birch pollen from different angles and summarize current knowledge on internal and external influences that have an impact on the allergenicity of birch pollen and its interactions with the epithelial barrier. We focus on epithelial cells since these cells are the first line of defense in respiratory disease and are increasingly considered to be a regulatory tissue for the protection against the development of respiratory allergies.

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.

Allergen-free extracts from birch, ragweed, and hazel pollen activate human and guinea-pig submucous and spinal sensory neurons

BACKGROUND

Non-allergenic, low molecular weight components of pollen grains are suspected to trigger changes in gut functions, sometimes leading to inflammatory conditions. Based on extensive neuroimmune communication in the gut wall, we investigated the effects of aqueous pollen extracts (APE) on enteric and spinal sensory neurons.

METHODS

Using Ca²⁺ and fast potentiometric imaging, we recorded the responses of guinea-pig and human submucous and guinea-pig dorsal root ganglion (DRG) neurons to microejection of low (<3 kDa) and high (≥3 kDa) molecular weight APEs of birch, ragweed, and hazel. Histamine was determined pharmacologically and by mass spectrometry (LC-MS/MS).

KEY RESULTS

Birch APE_<3kDa evoked strong [Ca⁺² ]_i signals in the vast majority of guinea-pig DRG neurons, and in guinea-pig and human enteric neurons. The effect of birch APE_≥3kDa was much weaker. Fast neuroimaging in human enteric neurons revealed an instantaneous spike discharge after microejection of birch, ragweed, and hazel APE_<3kDa [median (interquartile range) at 7.0 Hz (6.2/9.8), 5.7 Hz (4.4/7.1), and 8.4 Hz (4.3/12.5), respectively]. The percentage of responding neurons per ganglion were similar [birch 40.0% (33.3/100.0), ragweed 50.8% (34.4/85.6), and hazel 83.3% (57.1/100.0)]. A mixture of histamine receptor (H1-H3) blockers significantly reduced nerve activation evoked by birch and ragweed APEs_<3kDa , but was ineffective on hazel. Histamine concentrations in ragweed, birch and hazel APE's < 3 kDa were 0.764, 0.047, and 0.013 μM, respectively.

CONCLUSIONS

Allergen-free APEs from birch, ragweed, and hazel evoked strong nerve activation. Altered nerve-immune signaling as a result of severe pollen exposure could be a pathophysiological feature of allergic and non-allergic gut inflammation.

Pollen, respiratory viruses, and climate change: Synergistic effects on human health

In recent years, evidence of the synergistic effects of pollen and viruses on respiratory health has begun to accumulate. Pollen exposure is a known risk factor for the incidence and severity of respiratory viral infections. However, recent evidence suggests that pollen exposure may also inhibit or weaken viral infections. A comprehensive summary has not been made and a consensus on the synergistic health effects has not been reached. It is highly possible that climate change will increase the significance of pollen exposure as a cause of respiratory problems and, at the same time, affect the risk of infectious disease outbreaks. It is important to accurately assess how these two factors affect human health separately and concurrently. In this review article, for the first time, the data from previous studies are combined and reviewed and potential research gaps concerning the synergistic effects of pollen and viral exposure are identified.

IL-1β and Allergy: Focusing on Its Role in Allergic Rhinitis

Allergic rhinitis (AR) is a chronic upper airway immune-inflammation response mediated by immunoglobulin E (IgE) to allergens and can seriously affect the quality of life and work efficiency. Previous studies have shown that interleukin-1β (IL-1β) acts as a key cytokine to participate in and promote the occurrence and development of allergic diseases. It has been proposed that IL-1β may be a potential biomarker of AR. However, its definitive role and potential mechanism in AR have not been fully elucidated, and the clinical sample collection and detection methods were inconsistent among different studies, which have limited the use of IL-1β as a clinical diagnosis and treatment marker for AR. This article systematically summarizes the research advances in the roles of IL-1β in allergic diseases, focusing on the changes of IL-1β in AR and the possible interventions. In addition, based on the findings by our team, we provided new insights into the use of IL-1β in AR diagnosis and treatment, in an attempt to further promote the clinical application of IL-1β in AR and other allergic diseases.

Evaluation of climate change adaptation measures for childhood asthma: A systematic review of epidemiological evidence

Global climate change (GCC) is widely accepted as the biggest threat to human health of the 21st century. Children are particularly vulnerable to GCC due to developing organ systems, psychological immaturity, nature of daily activities, and higher level of per-body-unit exposure. There is a rising trend in the disease burden of childhood asthma and allergies in many parts of the world. The associations of CC, air pollution and other environmental exposures with childhood asthma are attracting more research attention, but relatively few studies have focused on CC adaptation measures and childhood asthma. This study aimed to bridge this knowledge gap and conducted the first systematic review on CC adaptation measures and childhood asthma. We searched electronic databases including PubMed, Embase, and Web of Science using a set of MeSH terms and related synonyms, and identified 20 eligible studies included for review. We found that there were a number of adaptation measures proposed for childhood asthma in response to GCC, including vulnerability assessment, improving ventilation and heating, enhancing community education, and developing forecast models and early warning systems. Several randomized controlled trials show that improving ventilation and installing heating in the homes appear to be an effective way to relieve childhood asthma symptoms, especially in winter. However, the effectiveness of most adaptation measures, except for improving ventilation and heating, have not been explored and quantified. Given more extreme weather events (e.g., cold spells and heatwaves) may occur as climate change progresses, this finding may have important implications. Evidently, further research is urgently warranted to evaluate the impacts of CC adaptation measures on childhood asthma. These adaptation measures, if proven to be effective, should be integrated in childhood asthma control and prevention programs as GCC continues.

How Do Pollen Allergens Sensitize?

Plant pollen is one of the main sources of allergens causing allergic diseases such as allergic rhinitis and asthma. Several allergens in plant pollen are panallergens which are also present in other allergen sources. As a result, sensitized individuals may also experience food allergies. The mechanism of sensitization and development of allergic inflammation is a consequence of the interaction of allergens with a large number of molecular factors that often are acting in a complex with other compounds, for example low-molecular-mass ligands, which contribute to the induction a type 2-driven response of immune system. In this review, special attention is paid not only to properties of allergens but also to an important role of their interaction with lipids and other hydrophobic molecules in pollen sensitization. The reactions of epithelial cells lining the nasal and bronchial mucosa and of other immunocompetent cells will also be considered, in particular the mechanisms of the activation of B and T lymphocytes and the formation of allergen-specific antibody responses.

TLR Signals in Epithelial Cells in the Nasal Cavity and Paranasal Sinuses

The respiratory tract is constantly at risk of invasion by microorganisms such as bacteria, viruses, and fungi. In particular, the mucosal epithelium of the nasal cavity and paranasal sinuses is at the very forefront of the battles between the host and the invading pathogens. Recent studies have revealed that the epithelium not only constitutes a physical barrier but also takes an essential role in the activation of the immune system. One of the mechanisms equipped in the epithelium to fight against microorganisms is the Toll-like receptor (TLR) response. TLRs recognize common structural components of microorganisms and activate the innate immune system, resulting in the production of a plethora of cytokines and chemokines in the response against microbes. As the epithelia-derived cytokines are deeply involved in the pathogenesis of inflammatory conditions in the nasal cavity and paranasal sinuses, such as chronic rhinosinusitis (CRS) and allergic rhinitis (AR), the molecules involved in the TLR response may be utilized as therapeutic targets for these diseases. There are several differences in the TLR response between nasal and bronchial epithelial cells, and knowledge of the TLR signals in the upper airway is sparse compared to that in the lower airway. In this review, we provide recent evidence on TLR signaling in the upper airway, focusing on the expression, regulation, and responsiveness of TLRs in human nasal epithelial cells (HNECs). We also discuss how TLRs in the epithelium are involved in the pathogenesis of, and possible therapeutic targeting, for CRS and AR.

Nasal Cytology: A Easy Diagnostic Tool in Precision Medicine for Inflammation in Epithelial Barrier Damage in the Nose. A Perspective Mini Review

Nasal cytology is a diagnostic tool that can be used in precision rhinology medicine. Particularly in non-allergic rhinitis and chronic rhinosinusitis forms it can be useful to evaluate biomarkers of both surgical or biological therapy and especially in the follow-up it must be used to predict the prognostic index of recurrence of nasal polyposis. All inflammatory cytokines are also linked to the presence of cells such as eosinophils and mastcells and nasal cytology is a non-invasive and repeatable method to assess the situation in real life.

Climate Change and Global Issues in Allergy and Immunology

The steady increase in global temperatures, resulting from the combustion of fossil fuels and the accumulation of greenhouse gases (GHG), continues to destabilize all ecosystems worldwide. Although annual emissions must halve by 2030 and reach net-zero by 2050 to limit some of the most catastrophic impacts associated with a warming planet, the world's efforts to curb GHG emissions fall short of the commitments made in the 2015 Paris Agreement (1). To this effect, July 2021 was recently declared the hottest month ever recorded in 142 years (2). The ramifications of these changes on global temperatures are complex and further promote outdoor air pollution, pollen exposure, and extreme weather events. Besides worsening respiratory health, air pollution, promotes atopy and susceptibility to infections. The GHG effects on pollen affect the frequency and severity of asthma and allergic rhinitis. Changes in temperature, air pollution, and extreme weather events exert adverse multisystemic health effects and disproportionally affect disadvantaged and vulnerable populations. This article is an update for allergists and immunologists about the health impacts of climate change, already evident in our daily practices. It is also a call to action and advocacy, including integrating climate change-related mitigation, education, and adaptation measures to protect our patients and avert further injury to our planet.

Vernal keratoconjunctivitis activity induces decrease of ocular surface CD14, TLR-4 and TLR-9 expression

PURPOSE

CD14 is involved in the modulation of immune reaction via toll-like receptors (TLR) and may influence the development of allergic diseases. The role of CD14 in vernal keratoconjunctivitis (VKC) has not yet been investigated. The aim of this study is to evaluate changes of tear soluble sCD14 and conjunctival CD14, TLR-4 and 9 expression in patients with VKC in the active and quiescent phases.

METHODS

Eighteen patients with VKC during active inflammation (group A, N = 9), in the quiescent phase (group Q, N = 5) and after recovery (group R, N = 4) and 10 healthy subjects were included. Expression of sCD14 in tears and of CD14, TLR-4, and TLR-9 by conjunctival epithelium were evaluated by Western Blot in all groups.

RESULTS

Expression of tear sCD14 and of conjunctival CD14, TLR-4, and TLR-9 was significantly decreased in group A when compared with healthy subjects and with VKC group Q and R. Lower expression of sCD14, CD14, TLR-4, and TLR-9 were significantly correlated with the severity of papillary reaction, while the lower sCD14 was correlated with severity of conjunctival hyperemia.

CONCLUSIONS

Tear sCD14, and conjunctival CD14, TLR4, and TLR-9 decreased during ocular surface inflammatory reaction in patients with VKC. CD14 and TLRs ocular surface evaluation may represent biomarkers of VKC activity and novel therapeutic target.

Der p 1 Disrupts the Epithelial Barrier and Induces IL-6 Production in Patients With House Dust Mite Allergic Rhinitis

Background:Dermatophagoides pteronyssinus 1/2 (Der p 1/Der p 2) are regarded as important allergens of house dust mite (HDM). However, the effect of both products on the epithelial barrier and immune response of patients with and without HDM allergic rhinitis (AR) remains unclear.

Methods: Air–liquid interface (ALI) cultured human nasal epithelial cells (HNECs) derived from control subjects (non-AR) (n = 9) and HDM-AR patients (n = 9) were treated with Der P 1 and Der P 2, followed by testing the transepithelial electrical resistance (TEER), paracellular permeability of fluorescein isothiocyanate (FITC)-dextrans and immunofluorescence of claudin-1 and ZO-1. Interleukin-6 (IL-6) production was evaluated by ELISA.

Results: Der p 1 reduced TEER significantly in a transient and dose-dependent manner in HNEC-ALI cultures from HDM-AR and non-AR patients, whilst the paracellular permeability was not affected. TEER was significantly reduced by Der p 1 at the 10-min time point in HDM-AR patients compared to non-AR patients (p = 0.0259). Compared to no-treatment control, in HNECs derived from HDM-AR patients, Der p 1 significantly cleaved claudin-1 after 30 min exposure (72.7 ± 9.5 % in non-AR group, 39.9 ± 7.1 % in HDM-AR group, p = 0.0286) and induced IL-6 secretion (p = 0.0271).

Conclusions: Our results suggest that patients with HDM-AR are more sensitive to Der p 1 than non-AR patients with increased effects of Der p1 on the mucosal barrier and induction of inflammation, indicating an important role for Der p1 in sensitization and HDM-AR development.

Ragweed plants grown under elevated CO2 levels produce pollen which elicit stronger allergic lung inflammation

BACKGROUND

Common ragweed has been spreading as a neophyte in Europe. Elevated CO₂ levels, a hallmark of global climate change, have been shown to increase ragweed pollen production, but their effects on pollen allergenicity remain to be elucidated.

METHODS

Ragweed was grown in climate-controlled chambers under normal (380 ppm, control) or elevated (700 ppm, based on RCP4.5 scenario) CO₂ levels. Aqueous pollen extracts (RWE) from control- or CO₂ -pollen were administered in vivo in a mouse model for allergic disease (daily for 3-11 days, n = 5) and employed in human in vitro systems of nasal epithelial cells (HNECs), monocyte-derived dendritic cells (DCs), and HNEC-DC co-cultures. Additionally, adjuvant factors and metabolites in control- and CO₂ -RWE were investigated using ELISA and untargeted metabolomics.

RESULTS

In vivo, CO₂ -RWE induced stronger allergic lung inflammation compared to control-RWE, as indicated by lung inflammatory cell infiltrate and mediators, mucus hypersecretion, and serum total IgE. In vitro, HNECs stimulated with RWE increased indistinctively the production of pro-inflammatory cytokines (IL-8, IL-1β, and IL-6). In contrast, supernatants from CO₂ -RWE-stimulated HNECs, compared to control-RWE-stimulated HNECS, significantly increased TNF and decreased IL-10 production in DCs. Comparable results were obtained by stimulating DCs directly with RWEs. The metabolome analysis revealed differential expression of secondary plant metabolites in control- vs CO₂ -RWE. Mixes of these metabolites elicited similar responses in DCs as compared to respective RWEs.

CONCLUSION

Our results indicate that elevated ambient CO₂ levels elicit a stronger RWE-induced allergic response in vivo and in vitro and that RWE increased allergenicity depends on the interplay of multiple metabolites.

Higher airborne pollen concentrations correlated with increased SARS-CoV-2 infection rates, as evidenced from 31 countries across the globe

Pollen exposure weakens the immunity against certain seasonal respiratory viruses by diminishing the antiviral interferon response. Here we investigate whether the same applies to the pandemic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which is sensitive to antiviral interferons, if infection waves coincide with high airborne pollen concentrations. Our original hypothesis was that more airborne pollen would lead to increases in infection rates. To examine this, we performed a cross-sectional and longitudinal data analysis on SARS-CoV-2 infection, airborne pollen, and meteorological factors. Our dataset is the most comprehensive, largest possible worldwide from 130 stations, across 31 countries and five continents. To explicitly investigate the effects of social contact, we additionally considered population density of each study area, as well as lockdown effects, in all possible combinations: without any lockdown, with mixed lockdown-no lockdown regime, and under complete lockdown. We found that airborne pollen, sometimes in synergy with humidity and temperature, explained, on average, 44% of the infection rate variability. Infection rates increased after higher pollen concentrations most frequently during the four previous days. Without lockdown, an increase of pollen abundance by 100 pollen/m3 resulted in a 4% average increase of infection rates. Lockdown halved infection rates under similar pollen concentrations. As there can be no preventive measures against airborne pollen exposure, we suggest wide dissemination of pollen-virus coexposure dire effect information to encourage high-risk individuals to wear particle filter masks during high springtime pollen concentrations.

Higher airborne pollen concentrations correlated with increased SARS-CoV-2 infection rates, as evidenced from 31 countries across the globe

Pollen exposure weakens the immunity against certain seasonal respiratory viruses by diminishing the antiviral interferon response. Here we investigate whether the same applies to the pandemic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which is sensitive to antiviral interferons, if infection waves coincide with high airborne pollen concentrations. Our original hypothesis was that more airborne pollen would lead to increases in infection rates. To examine this, we performed a cross-sectional and longitudinal data analysis on SARS-CoV-2 infection, airborne pollen, and meteorological factors. Our dataset is the most comprehensive, largest possible worldwide from 130 stations, across 31 countries and five continents. To explicitly investigate the effects of social contact, we additionally considered population density of each study area, as well as lockdown effects, in all possible combinations: without any lockdown, with mixed lockdown-no lockdown regime, and under complete lockdown. We found that airborne pollen, sometimes in synergy with humidity and temperature, explained, on average, 44% of the infection rate variability. Infection rates increased after higher pollen concentrations most frequently during the four previous days. Without lockdown, an increase of pollen abundance by 100 pollen/m³ resulted in a 4% average increase of infection rates. Lockdown halved infection rates under similar pollen concentrations. As there can be no preventive measures against airborne pollen exposure, we suggest wide dissemination of pollen-virus coexposure dire effect information to encourage high-risk individuals to wear particle filter masks during high springtime pollen concentrations.

Characterization of Innate Immune Responses to House Dust Mite Allergens: Pitfalls and Limitations

Whereas house dust mite (HDM) allergy results from a dysregulated Th2-biased adaptive immune response, activation of innate immune signaling pathways is a critical prerequisite for the initiation of HDM sensitizations. Such innate sensing is mainly controlled by the airway epithelium and the skin. The resulting release of epithelial-derived proinflammatory cytokines and innate alarmins such as GM-CSF, IL-25, IL-33 and TSLP mediates the activation of ILC2 cells and cDCs to promote Th2-biased inflammation. Significant progress in the elucidation of HDM innate immune activation has been made in the past decade and highlighted key roles of the LPS/TLR4 axis, chitin-dependent pathways together with HDM protease allergens. However, the precise mechanisms by which HDM allergens are sensed by the innate immune system remain largely unknown. Such investigations are made difficult for several reasons. Among these are (1) the natural association of HDM allergens with immunostimulators from the mite exoskeleton as well as from environmental microorganisms/pollutants or endosymbiotic bacteria; (2) the purification of individual HDM allergens from extracts in sufficient amounts and devoid of any microbial and protein impurities; (3) the production of correctly folded recombinant HDM allergens which could display the same biological activity than their natural counterparts; (4) the accessibility to human epithelial samples with cellular heterogeneities and inter-donor variations; (5) the translation of experimental data from mouse models to humans is almost missing. The goal of the present mini-review is to emphasize some important limitations and pitfalls in the elucidation of innate immunostimulatory properties of HDM allergens.

mRNA vaccine: a potential therapeutic strategy

mRNA vaccines have tremendous potential to fight against cancer and viral diseases due to superiorities in safety, efficacy and industrial production. In recent decades, we have witnessed the development of different kinds of mRNAs by sequence optimization to overcome the disadvantage of excessive mRNA immunogenicity, instability and inefficiency. Based on the immunological study, mRNA vaccines are coupled with immunologic adjuvant and various delivery strategies. Except for sequence optimization, the assistance of mRNA-delivering strategies is another method to stabilize mRNAs and improve their efficacy. The understanding of increasing the antigen reactiveness gains insight into mRNA-induced innate immunity and adaptive immunity without antibody-dependent enhancement activity. Therefore, to address the problem, scientists further exploited carrier-based mRNA vaccines (lipid-based delivery, polymer-based delivery, peptide-based delivery, virus-like replicon particle and cationic nanoemulsion), naked mRNA vaccines and dendritic cells-based mRNA vaccines. The article will discuss the molecular biology of mRNA vaccines and underlying anti-virus and anti-tumor mechanisms, with an introduction of their immunological phenomena, delivery strategies, their importance on Corona Virus Disease 2019 (COVID-19) and related clinical trials against cancer and viral diseases. Finally, we will discuss the challenge of mRNA vaccines against bacterial and parasitic diseases.

TRPV4-Mediated Epithelial Junction Disruption in Allergic Rhinitis Triggered by House Dust Mites

BACKGROUND

Epithelial barrier disruption is a crucial feature of allergic rhinitis (AR). Previous reports have indicated the role of transient receptor potential vanilloid (TRPV) 4 in regulating the intercellular junctions in various cells. However, the role of TRPV4 and its regulation by T helper 2 cell cytokines in the epithelial cells of patients with AR remains unclear.

OBJECTIVE

We aimed to elucidate the expression of TRPV4 in nasal epithelial cells and its cytokine-induced regulation, and to reveal its role in house dust mite-induced junction disruption in AR.

METHODS

The expression of TRPV4 in nasal epithelial cells was measured using real-time polymerase chain reaction, western blot, and immunohistochemical assays, and the expression levels were compared between the patients with AR and healthy controls. Altered expression of TRPV4 was induced in cultured nasal epithelial cells by stimulation of interleukin (IL) 4, IL-13, and tumor necrosis factor alpha. In addition, expression of E-cadherin and zonula occludens 1 was induced in Der p 1-stimulated epithelial cells by treatment with either a TRPV4 agonist (GSK1016790A) or a TRPV4 antagonist (RN1734).

RESULTS

TRPV4 expression was increased in epithelial cells harvested from the affected turbinates compared to those from the normal turbinates. The stimulation of cultured epithelial cells with IL-4 and IL-13 resulted in TRPV4 upregulation. Additionally, E-cadherin and zonula occludens 1 expression levels decreased in the cultured epithelial cells treated with GSK1016790A after stimulation with Der p 1, whereas Der p 1 stimulation alone showed no effect on junctional protein expression.

CONCLUSIONS

Increased TRPV4 expression occurred in epithelial cells harvested from patients with AR and epithelial cells stimulated by Th2 cytokines. Decreased junctional protein expression in epithelial cells after the stimulation by house dust mite allergen with TRPV4 agonist indicates a possible role of TRPV4 in the pathogenesis of allergen-induced epithelial barrier disruption in AR.