Glucocorticoid‐Driven Transcriptomes in Human Airway Epithelial Cells: Insight from Primary Cells and Cell Lines

RATIONALE Glucocorticoids are stress response hormones that act on the glucocorticoid receptor (GR) to execute effects, including repression of inflammatory gene expression. The molecular mechanisms for this process are still elusive, indeed controversial. This is, to a large extent, due the knowledge gap in understanding the functional impacts of the key glucocorticoid‐modulated genes in relevant tissues. Identification of such genes may be problematic because the effects of glucocorticoids on gene expression are context‐dependent and show variable effects between different cell types. This confounds the identification of key gene expression features within the glucocorticoid‐response. The current study addresses this by comparing the glucocorticoid‐driven transcriptomes in 3 variants of human airway epithelial cells, a critical player in airway inflammation and physiological responses to glucocorticoid. These include two airway epithelial cell lines, pulmonary type II A549 and bronchial epithelial BEAS‐2B cells, and primary human bronchial epithelial (HBE) cells. METHODS Gene expression profiling of RNA extracted from A549, BEAS‐2B and HBE cells following budesonide treatment for 6 h was performed using Affymetrix PrimeView microarrays. Genes showing significant induction (fold ≥ 2, P ≤ 0.05) or repression (fold ≤ 0.5, P ≤ 0.05) compared to untreated cells, in any of the cell types were used for further analyses. Representative genes were validated using qPCR. Gene ontology and Ingenuity Pathway Analysis (IPA) were performed using differentially regulated genes in each cell variant. RESULTS Using stringent (fold ≥ 2 or ≤ 0.5, P ≤ 0.05) cutoff criteria, only 17 and 8 of genes induced or repressed, respectively, by glucocorticoid were common to all 3 epithelial cell variants. While a major fraction of the significantly modulated genes was apparently unique to each cell variant, hierarchical clustering revealed greater commonality than was suggested by the stringent cut‐off. Applying less stringent cut‐offs (fold ≥ 1.25 or ≤ 0.8) within the pool of genes identified by stringent cut‐off revealed 93 induced and 82 repressed genes that were in common among all 3 cell variants. Validation of 52 budesonide‐induced genes using qPCR confirmed, for most of the genes, the grouping scheme determined by applying the less stringent cut‐off. Gene ontology (GO) analysis of the genes induced in common showed enrichment of transcriptional control, proliferation/apoptosis and signaling terms. Equally, the GO term growth factor activity was profoundly enriched with budesonide‐repressed genes across all variants. CONCLUSIONS The current comparative transcriptome analysis revealed a surprisingly large variance among 3 variants of airway epithelial cells in response to glucocorticoids. Despite this, the common gene expression features obtained by such analysis represent unbiased listing of potentially key molecular players in glucocorticoid response. While many of these genes, and the associated pathways, are consistent with anti‐inflammatory effects of glucocorticoids, a significant fraction are associated with developmental, proliferative, and metabolic GO terms. The functional impacts for many other genes are still unclear, and, therefore should be given priority for further functional analysis. Filling such gaps is essential for advancing knowledge of glucocorticoid biology. Support or Funding Information Supported by: The Lung Association Alberta & NWT, AstraZeneca, Canadian Institutes of Health Research. This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .

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