Type 2 Inflammation Reduces ACE2 Protein in Bronchial and Nasal Epithelial Cells

Abstract

Background: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is associated with several chronic lung-based comorbidities that have been shown to increase severity and mortality, with the notable exception of asthma. Our group has published that bronchial epithelial cells from atopic normal and asthmatic patients and treated with Interleukin-13 (IL-13), a type 2 cytokine, suppressed gene expression of angiotensinconverting enzyme 2 (ACE2), a key receptor for SARS-CoV-2 (Kimura H, et al. 2020). To further complement our studies, we examined ACE2 gene expression from individuals with severe asthma, and also assessed ACE2 protein levels from all groups. Because ACE2 is expressed in nasal epithelium, we also examined the effects of IL-13 on ACE2 expression in nasal epithelial cells. Objective: To determine if ACE2 gene and protein expression in upper and lower airways is modulated by IL-13. Methods: Non-atopic and atopic non-asthmatic normal, nonsevere and severe asthmatic participants were recruited and underwent bronchoscopy and nasal brushings to obtain primary bronchial and nasal epithelial cells. Epithelial cells were cultured at ALI for 2 weeks. Cells were treated with IL-13 (10 ng/ml) for 48 hours for gene expression and at 10, 50 and 100 ng/ml for 72 hours to determine protein expression from cell lysates by ELISA. Results: In bronchial epithelial cells, gene expression of ACE2 decreased following IL-13 treatment compared to untreated control: mean reduction: 0.52 ± 0.12 (p<.001) in atopic normal cells, 0.67 ± 0.14 (p=0.038) in non-severe asthma cells, and 0.66 ± 0.03 (p<.001) in severe asthma cells. There was no significant difference in the reduction in ACE2 gene expression between these three groups following IL-13 treatment. In nasal epithelial cells, the mean reduction in ACE2 gene expression was 0.42 ± 0.08 (p<.001) in atopic normal cells and 0.48 ± 0.01 (p<.001) in non-severe asthma cells) compared to untreated control. IL-13 significantly decreased ACE2 protein levels in bronchial epithelial cells in a dose dependent and similar manner in all groups compared to untreated control (p=0.011 in non-atopic normal, p=0.023 in atopic normal, p=0.016 in non-severe asthma, and p=0.011 in severe asthma, respectively, by Jonckheere-Terpstra test). IL-13 also reduced ACE2 protein expression in atopic normal and non-severe asthma group (p=0.033 and 0.003, respectively) in nasal epithelial cells. Conclusion: IL-13 attenuates ACE2 gene expression and protein production in both nasal and bronchial epithelial cells regardless of asthma and atopic status. These observations suggest that type 2 cytokines may confer protection in SARS-CoV-2 infection.