α and β catalytic subunits of cAMP‐dependent protein kinase regulate formoterol‐induced inflammatory gene expression changes in human bronchial epithelial cells

Abstract

It has been proposed that genomic mechanisms contribute to adverse effects often experienced by asthmatic subjects who take regular, inhaled β2 -adrenoceptor agonists as a monotherapy. Moreover, data from preclinical models of asthma suggest that these gene expression changes are mediated by β-arrestin-2 rather than PKA. Herein, we tested this hypothesis by comparing the genomic effects of formoterol, a β2 -adrenoceptor agonist, with forskolin in human primary bronchial epithelial cells (HBEC). Gene expression changes were determined by RNA-sequencing. Gene silencing and genome editing were employed to explore the roles of β-arrestin-2 and PKA. The formoterol-regulated transcriptome in HBEC treated concurrently with TNFα was defined by 1480 unique gene expression changes. TNFα-induced transcripts modulated by formoterol were annotated with enriched gene ontology terms related to inflammation and proliferation, notably "GO:0070374~positive regulation of ERK1 and ERK2 cascade," which is an apparentβ-arrestin-2 target. However, expression of the formoterol- and forskolin-regulated transcriptomes were highly rank-order correlated and the effects of formoterol on TNFα-induced inflammatory genes were abolished by an inhibitor of PKA. Furthermore, formoterol-induced gene expression changes in BEAS-2B bronchial epithelial cell clones deficient in β-arrestin-2 were comparable with those expressed by their parental counterparts. Contrariwise, gene expression was partially inhibited in clones lacking the α-catalytic subunit (Cα) of PKA and abolished following the additional knockdown of the β-catalytic subunit (Cβ) paralogue. The effects of formoterol on inflammatory gene expression in airway epithelia are mediated by PKA and involve the cooperation of PKA-Cα and PKA-Cβ.