Deletion of Nrf2 enhances susceptibility to eosinophilic sinonasal inflammation in a murine model of rhinosinusitis

Mitochondrial dynamics modulate the allergic inflammation in a murine model of allergic rhinitis

OBJECTIVE

Allergic rhinitis (AR) is a common allergic disorder, afflicting thousands of human beings. Aberrant mitochondrial dynamics are important pathological elements for various immune cell dysfunctions and allergic diseases. However, the connection between mitochondrial dynamics and AR remains poorly understood. This study aimed to determine whether mitochondrial dynamics influence the inflammatory response in AR.

METHODS

In the present study, we established a murine model of AR by sensitization with ovalbumin (OVA). Then, we investigated the mitochondrial morphology in mice with AR by transmission electron microscopy and confocal fluorescence microscopy, and evaluated the role of Mdivi-1 (an inhibitor of mitochondrial fission) on allergic symptoms, inflammatory responses, allergic-related signals, and reactive oxygen species formation.

RESULTS

There was a notable enhancement in mitochondrial fragmentation in the nasal mucosa of mice following OVA stimulation, whereas Mdivi-1 prevented aberrant mitochondrial morphology. Indeed, Mdivi-1 alleviated the rubbing and sneezing responses in OVA-sensitized mice. Compared with vehicle-treated ones, mice treated with Mdivi-1 exhibited a reduction in interleukin (IL)-4, IL-5, and specific IgE levels in both serum and nasal lavage fluid, and shown an amelioration in inflammatory response of nasal mucosa. Meanwhile, Mdivi-1 treatment was associated with a suppression in JAK2 and STAT6 activation and reactive oxygen species generation, which act as important signaling for allergic response.

CONCLUSION

Our findings reveal mitochondrial dynamics modulate the allergic responses in AR. Mitochondrial dynamics may represent a promising target for the treatment of AR.

The Effects of Wildfire Smoke on Asthma and Allergy

PURPOSE OF REVIEW

To review the recent literature on the effects of wildfire smoke (WFS) exposure on asthma and allergic disease, and on potential mechanisms of disease.

RECENT FINDINGS

Spatiotemporal modeling and increased ground-level monitoring data are allowing a more detailed picture of the health effects of WFS exposure to emerge, especially with regard to asthma. There is also epidemiologic and some experimental evidence to suggest that WFS exposure increases allergic predisposition and upper airway or sinonasal disease, though much of the literature in this area is focused more generally on PM2.5 and is not specific for WFS. Experimental evidence for mechanisms includes disruption of epithelial integrity with downstream effects on inflammatory or immune pathways, but experimental models to date have not consistently reflected human disease in this area. Exposure to WFS has an acute detrimental effect on asthma. Potential mechanisms are suggested by in vitro and animal studies.

Oxidative Stress and Air Pollution: Its Impact on Chronic Respiratory Diseases

Redox regulation participates in the control of various aspects of metabolism. Reactive oxygen and nitrogen species participate in many reactions under physiological conditions. When these species overcome the antioxidant defense system, a distressed status emerges, increasing biomolecular damage and leading to functional alterations. Air pollution is one of the exogenous sources of reactive oxygen and nitrogen species. Ambient airborne particulate matter (PM) is important because of its complex composition, which includes transition metals and organic compounds. Once in contact with the lungs' epithelium, PM components initiate the synthesis of inflammatory mediators, macrophage activation, modulation of gene expression, and the activation of transcription factors, which are all related to the physiopathology of chronic respiratory diseases, including cancer. Even though the pathophysiological pathways that give rise to the development of distress and biological damage are not fully understood, scientific evidence indicates that redox-dependent signaling pathways are involved. This article presents an overview of the redox interaction of air pollution inside the human body and the courses related to chronic respiratory diseases.

Isoorientin ameliorates OVA-induced asthma in a murine model of asthma

Allergic asthma which is induced by ovalbumin (OVA) is a chronic airway inflammation disease. Isoorientin (Iso) is a natural C-glucosyl flavone with many biological properties. We aimed to evaluate the effectiveness of Iso on OVA-induced allergic asthma. A total of 30 C57BL/6 mice were randomly divided into five groups: control group, OVA group, Dex (dexamethasone, 10 mg/kg) group, low-dose Iso group (Iso-L, 25 mg/kg), and high-dose Iso group (Iso-H, 50 mg/kg). The serum and bronchoalveolar lavage fluid (BALF) were collected for biochemical parameters, the lung tissue was collected for hematoxylin-eosin (H&E) staining, immunohistochemistry (IHC), and western blot. The levels of IL-4, IL-5, IL-13, malondialdehyde (MDA), NO, and reactive oxygen species (ROS) in Iso-L and Iso-H groups were significantly lower than that in model group (p < 0.05). Simultaneously, the levels of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activity were higher than that in model group (p < 0.05). Iso significantly ameliorated airway hyperresponsiveness. Meanwhile, H&E staining revealed that mice treated with Iso resulted in the ameliorated inflammatory cell infiltration and a reduction in interstitial thickening. The nuclear factor erythroid 2-like 2 (Nrf2) and HO-1 protein expression in Iso-L and Iso-H groups were enhanced over that in model group, while p-NF-κB-p65 and p-IκB-α protein expression was decreased (p < 0.05). Our research indicated that Iso alleviated the OVA-induced allergic asthma, and this effect can be explained by the modulation of Nrf2/HO-1 and NF-κB signaling pathway; thus, the results providing a therapeutic rationale for the treatment of Iso on allergic asthma.

Disruption of Sinonasal Epithelial Nrf2 Enhances Susceptibility to Rhinosinusitis in a Mouse Model

OBJECTIVES/HYPOTHESIS

Oxidative stress has been postulated to play an important role in chronic rhinosinusitis. Nrf2 is a transcription factor that is involved in the regulation of multiple antioxidant genes, and its function has been previously shown to be important in sinonasal inflammation. Although the sinonasal implications of whole body Nrf2-/- has been reported, the function of sinonasal epithelial expression of Nrf2 has not been studied. The primary aim of this study was to generate a mouse model that is genetically deficient in epithelial-specific Nrf2 and to understand its role in regulating sinonasal inflammation.

STUDY DESIGN

Basic science.

METHODS

An epithelial-specific Nrf2 knockout mouse was generated by crossing Krt5-cre(K5) with Nrf2flox/flox . A papain-induced model of rhinosinusitis was performed in the resulting K5 Nrf2-/- mouse. Immunohistochemistry was performed to quantify goblet cell hyperplasia. Mucosal cellular infiltrates were quantified using flow cytometry, and tissue cytokines were measured using an enzyme-linked immunosorbent assay. Lastly, the cellular source of type 2 cytokines was determined using intracellular cytokine staining.

RESULTS

Papain-sensitized mice lacking epithelial-specific Nrf2 demonstrate increased goblet cell hyperplasia, significant tissue eosinophilia, and statistically significant increase in mucosal IL-13 when compared to Nrf2 wild-type mice. Lastly, mucosal T cells were identified as the cellular source of IL-13.

CONCLUSIONS

We demonstrate enhanced severity of eosinophilic sinonasal inflammation from disruption of the epithelial-specific Nrf2 pathway. The responsiveness of Nrf2-directed antioxidant pathways may act as a major determinant of susceptibility to eosinophilic inflammation and may have potential as a therapeutic target for chronic rhinosinusitis.

LEVEL OF EVIDENCE

NA Laryngoscope, 131:713-719, 2021.

Baicalin Ameliorates Inflammatory Response in a Mouse Model of Rhinosinusitis via Regulating the Treg/Th17 Balance

OBJECTIVE

Rhinosinusitis is a global health problem affecting millions of people around the world. Baicalin is a bioactive compound isolated from medicinal plant Scutellaria baicalensis Georgi. The present study aims to investigate potential effects of baicalin on clinicopathological changes in nasal/sinus mucosa in a mouse model.

METHODS

A mouse model of sinonasal inflammation induced by high dose of ovalbumin was applied to evaluate effects of baicalin. Rhinosinusitis symptoms, histopathological features, levels of histamine, immunoglobulin E (IgE), IL-17A, IL-10, and balance of regulatory T cell (Treg)/T-helper 17 (Th17) responses were examined.

RESULTS

Baicalin significantly relieved rhinosinusitis symptoms in mice, reduced histopathological changes, and suppressed serum levels of histamine and IgE in a dose-dependent manner. In lymphocytes of mice, baicalin modulated balance of Treg/Th17 proportions by attenuating Th17 cells and enhancing Treg cells, respectively. The serum IL-17A was decreased and IL-10 was increased in mice treated by baicalin. In addition, baicalin promoted levels of Smad protein 3 (p-Smad3) and forkhead box P3 (FOXP3) to promote Treg cells while suppressed levels of p-Stat3 and retineic-acid-receptor-related orphan nuclear receptor γt (RORγt) to inhibit Th17 cells.

CONCLUSIONS

These data demonstrate that baicalin effectively ameliorates sinonasal inflammation in a mouse model by recovering the immunological balance of Treg/Th17 responses. Our finding highlights the potential value of baicalin for the treatment of rhinosinusitis.

Deletion of Arno Reduces Eosinophilic Inflammation and Interleukin-5 Expression in a Murine Model of Rhinitis

BACKGROUND

ARF nucleotide-binding site opener (ARNO) is a guanine nucleotide-exchange factor for ADP-ribosylation factor proteins. ARF nucleotide-binding site opener also binds MyD88, and small-molecule inhibition of ARNO reduces inflammation in animal models of inflammatory arthritis and acute inflammation. However, whether genetic deletion of Arno in mice reduces pathologic inflammation has not yet been reported. Furthermore, its role in the nasal cavity has yet to be investigated.

OBJECTIVE

To generate Arno knockout mice and to determine whether genetic loss of ARNO reduces eosinophilic inflammation in the ovalbumin (OVA) murine model of rhinitis.

METHODS

Arno knockout mice were generated and wild type and knockout littermates were subjected to the OVA-induced mouse model of rhinosinutitis. Eosinophilic inflammation was assessed through immunofluorescent quantification of EMBP⁺ eosinophils in the septal mucosa and cytokine expression was assessed by quantitative polymerase chain reaction.

RESULTS

Arno knockout mice are viable and fertile without any noted deficits. Arno wild type and knockout mice subjected to the OVA-induced model of rhinitis demonstrated an average of 314.5 and 153.8 EMBP⁺ cells per mm² septal tissue, respectively (P < .05). Goblet cells per mm of basal lamina were assessed via Alcian blue and there was no statistically significant difference between Arno wild type and knockout mice. Ovalbumin-induced expression of interleukin-5 (IL-5) was significantly reduced in Arno knockout mice (P < .05). There was no statistically significant reduction in IL-4, IL-13, or eotaxin-1 expression.

CONCLUSIONS

These data demonstrate that deletion of Arno reduces eosinophilic inflammation and IL-5 expression in an OVA-induced model of rhinitis.

Vegetable dietary pattern may protect mild and persistent allergic rhinitis phenotype depending on genetic risk in school children

BACKGROUND

The effect of diet on allergic rhinitis (AR), its severity in children, and whether it modifies AR depending on genetic susceptibility are unknown. We investigated the association between dietary patterns and AR in school children and the influence of diet on AR according to a genetic risk score (GRS).

METHODS

Totally, 435 7-year-old school children were recruited from the Panel Study on Korean Children. We used dietary patterns (vegetable, sugar, and meat) and dietary inflammatory index (DII) as dietary parameters. AR and its severity were defined by questionnaires about treatment in the previous 12 months and the Allergic Rhinitis and its Impact on Asthma (ARIA) guideline, respectively. A GRS was calculated using 6 single nucleotide polymorphisms for allergic diseases.

RESULTS

A vegetable diet containing a lot of anti-inflammatory nutrients and higher vitamin D level in blood were negatively correlated, while DII was positively correlated with triglyceride level and triglyceride/HDL cholesterol. Vegetable diet (aOR, 95% CI = 0.73, 0.58-0.94) and DII (1.13, 1.01-1.28) were associated with AR risk. In particular, a high-vegetable diet resulted in a lower risk of mild and persistent AR (aOR, 95% CI = 0.24, 0.10-0.56) while a high DII represented a higher risk (2.33, 1.06-5.10). The protective effect of vegetable diet on AR appeared only among children with a lower GRS (adjusted P = .018).

CONCLUSIONS

A vegetable dietary pattern characterized by high intake of anti-inflammatory nutrients and higher vitamin D level in blood might be associated with a lower risk of mild and persistent AR. This beneficial effect is modified by a genetic factor.