Intermittent hypoxia-reoxygenation-induced miRNAs inhibit expression of IRF and interferon genes but activate NF-κB and expression of pulmonary fibrosis markers in human small airway epithelial cells

Abstract

Aim

Intermittent hypoxia-reoxygenation (H/R) has been demonstrated to be associated with aviation and various respiratory diseases, and hence it is of interest to unravel the regulatory mechanisms underlying the H/R-induced innate immune and inflammatory responses in both healthy and COPD-diseased human small airway epithelial cells (SAECs).

Main methods

The normal healthy and COPD-diseased SAECs (i.e., N-SAECs and D-SAECs) were purchased from PromoCell biotechnology company and respectively cultured under normoxia (21 % O₂) or 12/12-h cycles of H/R (i.e., 1 % O₂ and 21 % O₂ alternately) for 6 days in total for 2D cultures and 21 days in total for the air-liquid interface 3D cultures, followed by qPCR analyses, miRNA fluorescence in situ hybridization, luciferase reporter assays, and immunofluorescence staining.

Key findings

Human SAECs cultured under 12/12-h cycles of H/R showed dramatically increased expression of HIF1A and the H/R-inducible miRNAs miR-129-1-3p, miR-1290 and miR-193b-5p, with miR-129-1-3p and miR-193b-5p targeting and inhibiting IRF5 and IRF7 mRNAs, hence downregulating both the type I and II interferon genes in SAECs cultured under H/R. In addition, miR-129-1-3p, miR-1290 and miR-193b-5p all targeted and inhibited SOCS3 mRNA, hence upregulating transactivation of NF-κB and in turn inducing expression of the inflammatory chemokine genes and pulmonary fibrosis-associated marker genes.

Significance

We show for the first time that intermittent H/R upregulates the NF-κB-induced proinflammatory and fibrosis marker genes whereas downregulates the IRF5/7-induced type I/II interferon expression in human SAECs through distinct HIF1A-inducible miRNAs miR-129-1-3p, miR-193b-5p and miR-1290, which may serve as promising therapeutic targets for airway inflammation and pulmonary fibrosis.