Interaction between glucocorticoids and beta(2)-agonists: alpha and beta glucocorticoid-receptor mRNA expression in human bronchial epithelial cells

Recent studies have suggested that regular use of beta(2)-agonists has adve rse effects on asthma control, due to the cross-talk between cAMP responsiv e element binding proteins (CREB) and glucocorticoid receptors (GR). The ai m of this study was to investigate the interaction between GR and CREB on c ytoplasmic protein level with a gel mobility shift assay and to determine t he effect of this interaction on mRNA levels by Northern blot analysis. Aft er exposing human bronchial epithelial cells for 1 hr to either 1 mu M terb utaline or budesonide, more binding of CREB and GR, respectively, was obser ved to their responsive elements in DNA. Simultaneous exposure to terbutali ne and budesonide also increased the binding of CREB and GR to DNA. After 4 hr, both alpha and beta GR mRNAs were down-regulated by 1 mu M budesonide. Simultaneous addition of 1 mu M terbutaline prevented this down-regulation . Adding 100 times more budesonide compared to terbutaline again down-regul ated both GR forms, although significantly less compared to the down-regula tion induced by 1 mu M budesonide alone. Addition of terbutaline to cells a lready exposed to budesonide did not reverse the GR mRNA expression within 44 hr. Similar results were obtained with metallothionein-2 (MT2) mRNA leve ls. In conclusion, beta(2)-agonists interfere with the GR function in human bronchial epithelial cells when given simultaneously, with this being over come by sequential exposure of the cells to first glucocorticoids and later beta(2)-agonists. BIOCHEM PHARMACOL 56;12:1561-1569, 1998. (C) 1998 Elsevi er Science Inc.