Intermittent Hypoxia-Reoxygenation and Consecutive Hypoxia Decreased Expression of the SARS-CoV-2 Receptor Gene ACE2, the Interferon-Stimulated Genes CTSL and TNFSF10, the Hypoxia Inducible Factor Gene HIF2A and the Stem Cell Marker Gene TP63 in COPD-Diseased Human Small Airway Epithelial Cells

Rationale: The global pandemic of COVID-19 has urged studies on the expression of coronaviral receptor genes and innate immunity genes in human airway epithelial cells. As ischemia/hypoxia-reperfusion and hypoxemia are associated with lung transplantation and chronic obstructive pulmonary disease (COPD), it is of interest to investigate the effects of intermittent hypoxia-reoxygenation (H/R) and consecutive hypoxia on the expression of viral receptor genes and innate immunity genes. Methods: The normal (N-SAECs) and COPD-diseased (D-SAECs) human small airway epithelial cells were respectively cultured under normoxia (21% O2) for consecutively 3 days, and cultured under 24/24-hour cycles of H/R (i.e., 1% O2 and 21% O2 alternately) for totally 6 days, as well as cultured under 1% O2 for consecutively 3 days followed by 21% O2 for consecutively another 3 days. Total mRNAs were then extracted from N-SAECs and D-SAECs followed by microarray and qPCR analyses. Results: Among the various viral receptor genes analyzed in our study under normoxia, only ACE2 showed a significantly altered mRNA expression level between D-SAECs and N-SAECs. In concordance with significantly increased ACE2 expression in D-SAECs, the expression levels of the interferon-stimulated genes TNFSF10 and OAS1 as well as the innate immunity gene TCN1 were also significantly increased in D-SAECs compared to N-SAECs. On the other hand, intermittent H/R significantly decreased ACE2 expression in D-SAECs but not N-SAECs, whereas significantly decreased the mRNA levels of another coronaviral receptor gene ANPEP and the influenza viral receptor gene ST3GAL4 in both N-SAECs and D-SAECs. Interestingly, intermittent H/R also significantly decreased the mRNA levels of the interferon-stimulated genes TNFSF10, CTSL and HIF1A as well as the innate immunity genes S100P and IRAK3 in D-SAECs only, whereas decreased expression of the interferon-stimulated gene MDK in N-SAECs only, and decreased expression of the interferon-regulatory hypoxia inducible factor gene HIF2A and the stem cell marker gene TP63 in both N-SAECs and D-SAECs. Interestingly, consecutive hypoxia also significantly decreased expression of ACE2 as well as another coronaviral receptor gene DPP4 in D-SAECs only, and also significantly decreased expression of TNFSF10, CTSL, HIF2A, and TP63 in D-SAECs but not N-SAECs. Conclusions: Our study shows for the first time that both intermittent H/R and consecutive hypoxia concordantly decrease expression of ACE2, CTSL, TNFSF10, HIF2A and TP63, and suggests that inhibition of the interferon-regulatory factors HIF2A or TP63 may provide potential preventive or therapeutic applications for COVID-19 treatments.