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Interaction between glucocorticoids and beta2-agonists: alpha and beta glucocorticoid-receptor mRNA expression in
S H Korn1, E F Wouters, G Wesseling
1Department of Pulmonology, Maastricht University, The Netherlands.
Abstract:
Recent studies have suggested that regular use of beta2-agonists has adverse effects on asthma control, due to the cross-talk between cAMP responsive element binding proteins (CREB) and glucocorticoid receptors (GR). The aim of this study was to investigate the interaction between GR and CREB on cytoplasmic protein level with a gel mobility shift assay and to determine the effect of this interaction on mRNA levels by Northern blot analysis. After exposing human bronchial epithelial cells for 1 hr to either 1 microM terbutaline or budesonide, more binding of CREB and GR, respectively, was observed to their responsive elements in DNA. Simultaneous exposure to terbutaline 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 microM budesonide. Simultaneous addition of 1 microM terbutaline prevented this down-regulation. Adding 100 times more budesonide compared to terbutaline again down-regulated both GR forms, although significantly less compared to the down-regulation induced by 1 microM budesonide alone. Addition of terbutaline to cells already exposed to budesonide did not reverse the GR mRNA expression within 44 hr. Similar results were obtained with metallothionein-2 (MT2) mRNA levels. In conclusion, beta2-agonists interfere with the GR function in human bronchial epithelial cells when given simultaneously, with this being overcome by sequential exposure of the cells to first glucocorticoids and later beta2-agonists.
Insights
Beta2-agonists can negatively impact asthma control by interfering with glucocorticoid receptors (GR). Sequential use of glucocorticoids before beta2-agonists preserves GR function in bronchial cells.
Area of Science:
- Pharmacology
- Molecular Biology
- Cell Biology
Background:
- Beta2-agonists' regular use may impair asthma control.
- This impairment is linked to cross-talk between cAMP responsive element binding proteins (CREB) and glucocorticoid receptors (GR).
Purpose of the Study:
- To investigate the interaction between GR and CREB.
- To determine the effect of this interaction on mRNA levels.
Main Methods:
- Gel mobility shift assay to assess protein-DNA binding.
- Northern blot analysis to quantify mRNA levels.
- Exposure of human bronchial epithelial cells to terbutaline and budesonide.
Main Results:
- Simultaneous terbutaline and budesonide increased CREB and GR binding to DNA.
- Budesonide down-regulated GR and metallothionein-2 (MT2) mRNA.
- Terbutaline co-administration prevented GR mRNA down-regulation by budesonide.
- Sequential exposure (glucocorticoids then beta2-agonists) maintained GR function.
Conclusions:
- Beta2-agonists interfere with GR function in human bronchial epithelial cells.
- Simultaneous administration of beta2-agonists and glucocorticoids impacts GR function.
- Sequential administration overcomes the negative effects of beta2-agonists on GR mRNA expression.