Dr Andrew Reid

Background and objective: COVID-19 is complicated by acute lung injury, and death in some individuals. It is caused by SARS-CoV-2 that requires the ACE2 receptor and serine proteases to enter AEC. We determined what factors are associated with ACE2 expression particularly in patients with asthma and COPD. Methods: We obtained lower AEC from 145 people from two independent cohorts, aged 2¿89 years, Newcastle (n = 115) and Perth (n = 30), Australia. The Newcastle cohort was enriched with people with asthma (n = 37) and COPD (n = 38). Gene expression for ACE2 and other genes potentially associated with SARS-CoV-2 cell entry was assessed by qPCR, and protein expression was confirmed with immunohistochemistry on endobronchial biopsies and cultured AEC. Results: Increased gene expression of ACE2 was associated with older age (P = 0.03) and male sex (P = 0.03), but not with pack-years smoked. When we compared gene expression between adults with asthma, COPD and healthy controls, mean ACE2 expression was lower in asthma patients (P = 0.01). Gene expression of furin, a protease that facilitates viral endocytosis, was also lower in patients with asthma (P = 0.02), while ADAM-17, a disintegrin that cleaves ACE2 from the surface, was increased (P = 0.02). ACE2 protein expression was also reduced in endobronchial biopsies from asthma patients. Conclusion: Increased ACE2 expression occurs in older people and males. Asthma patients have reduced expression. Altered ACE2 expression in the lower airway may be an important factor in virus tropism and may in part explain susceptibility factors and why asthma patients are not over-represented in those with COVID-19 complications.

Background and objective: Severe asthma is responsible for a disproportionate burden of illness and healthcare costs spent on asthma. This study analyses sputum transcriptomics to investigate the mechanisms and novel treatment targets of severe asthma. Methods: Induced sputum samples were collected in a cross-sectional study from participants with severe asthma (n = 12, defined as per GINA criteria), non-severe uncontrolled (n = 21) and controlled asthma (n = 21) and healthy controls (n = 15). Sputum RNA was extracted and transcriptomic profiles were generated (Illumina HumanRef-8 V2) and analysed (GeneSpring). Sputum protein lysates were analysed for p38 activation in a validation study (n = 24 asthma, n = 8 healthy) by western blotting. Results: There were 2166 genes differentially expressed between the four groups. In severe asthma, the expression of 1875, 1308 and 563 genes was altered compared to healthy controls, controlled and uncontrolled asthma, respectively. Of the 1875 genes significantly different to healthy controls, 123 were >2-fold change from which four networks were identified. Thirty genes (>2-fold change) were significantly different in severe asthma compared to both controlled asthma and healthy controls. There was enrichment of genes in the p38 signalling pathway that were associated with severe asthma. Phosphorylation of p38 was increased in a subset of severe asthma samples, correlating with neutrophilic airway inflammation. Conclusion: Severe asthma is associated with substantial differences in sputum gene expression that underlie unique cellular mechanisms. The p38 signalling pathway may be important in the pathogenesis of severe asthma, and future investigations into p38 inhibition are warranted as a ¿non-Th2¿ therapeutic option.

In asthma, goblet cell numbers are increased within the airway epithelium, perpetuating the production of mucus that is more difficult to clear and results in airway mucus plugging. Notch1, Notch2, or Notch3, or a combination of these has been shown to influence the differentiation of airway epithelial cells. How the expression of specific Notch isoforms differs in fully differentiated adult asthmatic epithelium and whether Notch influences mucin production after differentiation is currently unknown. We aimed to quantify different Notch isoforms in the airway epithelium of individuals with severe asthma and to examine the impact of Notch signaling on mucin MUC5AC. Human lung sections and primary bronchial epithelial cells from individuals with and without asthma were used in this study. Primary bronchial epithelial cells were differentiated at the air-liquid interface for 28 days. Notch isoform expression was analyzed by Taqman quantitative PCR. Immunohistochemistry was used to localize and quantify Notch isoforms in human airway sections. Notch signaling was inhibited in vitro using dibenzazepine or Notch3-specific siRNA, followed by analysis of MUC5AC. NOTCH3 was highly expressed in asthmatic airway epithelium compared with nonasthmatic epithelium. Dibenzazepine significantly reduced MUC5AC production in air-liquid interface cultures of primary bronchial epithelial cells concomitantly with suppression of NOTCH3 intracellular domain protein. Specific knockdown using NOTCH3 siRNA recapitulated the dibenzazepine-induced reduction in MUC5AC. We demonstrate that NOTCH3 is a regulator of MUC5AC production. Increased NOTCH3 signaling in the asthmatic airway epithelium may therefore be an underlying driver of excess MUC5AC production.

Patients with frequent exacerbations represent a chronic obstructive pulmonary disease (COPD) subgroup requiring better treatment options. The aim of this study was to determine the innate immune mechanisms that underlie susceptibility to frequent exacerbations in COPD. We measured sputum expression of immune mediators and bacterial loads in samples from patients with COPD at stable state and during virusassociated exacerbations. In vitro immune responses to rhinovirus infection in differentiated primary bronchial epithelial cells (BECs) sampled from patients with COPD were additionally evaluated. Patients were stratified as frequent exacerbators (=2 exacerbations in the preceding year) or infrequent exacerbators (<2 exacerbations in the preceding year) with comparisons made between these groups. Frequent exacerbators had reduced sputum cell mRNA expression of the antiviral immune mediators type I and III interferons and reduced interferon-stimulated gene (ISG) expression when clinically stable and during virus-associated exacerbation. A role for epithelial cellintrinsic innate immune dysregulation was identified: induction of interferons and ISGs during in vitro rhinovirus (RV) infection was also impaired in differentiated BECs from frequent exacerbators. Frequent exacerbators additionally had increased sputum bacterial loads at 2 wk following virus-associated exacerbation onset. These data implicate deficient airway innate immunity involving epithelial cells in the increased propensity to exacerbations observed in some patients with COPD. Therapeutic approaches to boost innate antimicrobial immunity in the lung could be a viable strategy for prevention and treatment of frequent exacerbations.

Dysregulated induction of goblet cell differentiation results in excessive production and retention of mucus and is a common feature of several chronic airways diseases. To date, therapeutic strategies to reduce mucus accumulation have focused primarily on altering the properties of the mucus itself, or have aimed to limit the production of mucus-stimulating cytokines. Here we review the current knowledge of key molecular pathways that are dysregulated during persistent goblet cell differentiation and highlights both pre-existing and novel therapeutic strategies to combat this pathology.

The epithelium of asthmatics is characterized by reduced expression of E-cadherin and increased expression of the basal cell markers ck-5 and p63 that is indicative of a relatively undifferentiated repairing epithelium. This phenotype correlates with increased proliferation, compromised wound healing and an enhanced capacity to undergo epithelial-mesenchymal transition (EMT). The transcription factor ß-catenin plays a vital role in epithelial cell differentiation and regeneration, depending on the co-factor recruited. Transcriptional programs driven by the ß-catenin/CBP axis are critical for maintaining an undifferentiated and proliferative state, whereas the ß-catenin/p300 axis is associated with cell differentiation. We hypothesized that disrupting the ß-catenin/CBP signaling axis would promote epithelial differentiation and inhibit EMT. We treated monolayer cultures of human airway epithelial cells with TGFß1 in the presence or absence of the selective small molecule ICG-001 to inhibit ß-catenin/CBP signaling. We used western blots to assess expression of an EMT signature, CBP, p300, ß-catenin, fibronectin and ITGß1 and scratch wound assays to assess epithelial cell migration. Snai-1 and -2 expressions were determined using q-PCR. Exposure to TGFß1 induced EMT, characterized by reduced E-cadherin expression with increased expression of a-smooth muscle actin and EDA-fibronectin. Either co-treatment or therapeutic administration of ICG-001 completely inhibited TGFß1-induced EMT. ICG-001 also reduced the expression of ck-5 and -19 independent of TGFß1. Exposure to ICG-001 significantly inhibited epithelial cell proliferation and migration, coincident with a down regulation of ITGß1 and fibronectin expression. These data support our hypothesis that modulating the ß-catenin/CBP signaling axis plays a key role in epithelial plasticity and function.