miR-200b downregulates CFTR during hypoxia in human lung epithelial cells

Sylwia Bartoszewska, Wojciech Kamysz, Bogdan Jakiela, Marek Sanak, Jarosław Króliczewski, Zsuzsa Bebok, Rafal Bartoszewski, James F. Collawn

Hypoxic conditions induce the expression of hypoxia-inducible factors (HIFs) that allow cells to adapt to the changing conditions and alter the expression of a number of genes including the cystic fibrosis transmembrane conductance regulator (CFTR). CFTR is a low abundance mRNA in airway epithelial cells even during normoxic conditions, but during hypoxia its mRNA expression decreases even further. In the current studies, we examined the kinetics of hypoxia-induced changes in CFTR mRNA and protein levels in two human airway epithelial cell lines, Calu-3 and 16HBE14o-, and in normal primary bronchial epithelial cells. Our goal was to examine the posttranscriptional modifications that affected CFTR expression during hypoxia. We utilized in silico predictive protocols to establish potential miRNAs that could potentially regulate CFTR message stability and identified miR-200b as a candidate molecule. Analysis of each of the epithelial cell types during prolonged hypoxia revealed that CFTR expression decreased after 12 h during a time when miR-200b was continuously upregulated. Furthermore, manipulation of the miRNA levels during normoxia and hypoxia using miR-200b mimics and antagomirs decreased and increased CFTR mRNA levels, respectively, and thus established that miR-200b downregulates CFTR message levels during hypoxic conditions. The data suggest that miR-200b may be a suitable target for modulating CFTR levels in vivo.