Brg1 Promotes Airway Mucus Hypersecretion via IL-13 and the JAK1/2-STAT6 Signaling Pathway in Asthma

Backgroud: The chromatin remodeling factor Brg1 (Brahma-related gene 1) is an important nuclear protein that promotes the transcriptional activation or inhibition of target genes by regulating ATP hydrolysis to generate energy which rearranges the position of nucleosomes and the interaction of histone DNA. In this study, we explored the effect of Brg1 on airway mucus hypersecretion in asthma.Methods: Six-to-eight-week-old female wild-type C57BL/6 mice (wild-type, WT) and type II alveolar epithelial cells (AECIIs) specifically knockout Brg1 mice (Brg1fl/fl) were selected as the experimental subjects. The asthma group was established with house dust mite (HDM), and the control group was treated with normal saline (n=10). Wright's staining was used to detect inflammatory cells in bronchoalveolar lavage fluid (BALF). Invasive lung function was used to assess the airway compliance. Hematoxylin and eosin and periodic acid-schiff staining were used to detect mucus secretion. The virus was used to knock down the Brg1 gene in the bronchial epithelial cell line (16HBE) and stimulated with HDM. Immunohistochemistry was used to measure mucin glycoprotein 5AC (MUC5AC) protein expression in the airway epithelium and 16HBE cells. Western blotting was used to detect the expression of the MUC5AC and JAK1/2-STAT6 signaling pathways in mouse lung tissue and 16HBE. Co-immunoprecipitation (Co-IP) and Chromatin Immunoprecipitation (CHIP) were used to detect whether Brg1 could regulate the JAK1/2-STAT6 signaling pathway.Results: Specifically, knocking out the Brg1 gene in AECIIs can reduce airway inflammation, airway compliance, and mucus hypersecretion in asthma. Knockdown of the Brg1 gene can simultaneously reduce Interleukin-13 (IL-13) and the expression of MUC5AC protein in airway epithelial cells and the activation of the JAK1/2-STAT6 signaling pathway. The results of Co-IP and CHIP showed that Brg1 could bind to the JAK1/2 promoter region, regulating the activity of the JAK1/2-STAT6 pathway affects airway mucus secretion in asthma.Conclusion: Brg1 gene knockout in airway epithelial cells can reduce asthmatic airway mucus hypersecretion and the expression of MUC5AC protein in airway epithelial cells partly by inhibiting the activation of the JAK1/2-STAT6 signaling pathway.

Influence of SARS-CoV-2 on airway mucus production: A review and proposed model

Coronavirus disease 2019 (COVID-19) is a worldwide pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that has affected millions of lives. Individuals who survive severe COVID-19 can experience sustained respiratory symptoms that persist for months after initial infection. In other airway diseases, abnormal airway mucus contributes to sustained airway symptoms. However, the impact of SARS-CoV-2 on airway mucus has received limited attention. In the current review, we assess literature describing the impact of SARS-CoV-2 on airway pathophysiology with specific emphasis on mucus production. Accumulating evidence suggests that the 2 major secreted airway mucin glycoproteins, MUC5AC and MUC5B, are abnormal in some patients with COVID-19. Aberrations in MUC5AC or MUC5B in response to SARS-CoV-2 infection are likely due to inflammation, though the responsible mechanisms have yet to be determined. Thus, we also provide a proposed model highlighting mechanisms that can contribute to acute and sustained mucus abnormalities in SARS-CoV-2, with an emphasis on inflammatory cells and mediators, including mast cells and histamine. Last, we bring to light the challenges of studying abnormal mucus production in SARS-CoV-2 infections and discuss the strengths and limitations of model systems commonly used to study COVID-19. The evidence to date suggests that ferrets, nonhuman primates, and cats may have advantages over other models to investigate mucus in COVID-19.

Abnormal Airway Mucus Secretion Induced by Virus Infection

The airway mucus barrier is a primary defensive layer at the airway surface. Mucins are the major structural components of airway mucus that protect the respiratory tract. Respiratory viruses invade human airways and often induce abnormal mucin overproduction and airway mucus secretion, leading to airway obstruction and disease. The mechanism underlying the virus-induced abnormal airway mucus secretion has not been fully studied so far. Understanding the mechanisms by which viruses induce airway mucus hypersecretion may open new avenues to treatment. In this article, we elaborate the clinical and experimental evidence that respiratory viruses cause abnormal airway mucus secretion, review the underlying mechanisms, and also discuss the current research advance as well as potential strategies to treat the abnormal airway mucus secretion caused by SARS-CoV-2.