Bronchial thermoplasty upregulates the expression of the glucocorticoid receptor in tissue sections

Abstract

<b>Background:</b> Bronchial thermoplasty (BT) is applied to patients with severe uncontrolled asthma. BT reduced airway wall remodeling and increased quality of life and many patients could reduce the steroiduse. BT modified the expression of heat shock proteins which keep the glucocorticoid receptor (GR) in its ligand binding formation. <b>Aims:</b> To examine the expression of the GR in tissue sections of the bronchus before and after BT. <b>Methods:</b> Endobronchial biopsies (n=450) were collected from 30 patients with severe uncontrolled asthma before BT and after one month each of three sequential BT applications. The GR expression was determined in bronchial tissue sections by immunohistochemistry. <b>Results:</b> In all tissues, the GR was expressed in both epithelial cells (EC) and in subepithelial mesenchymal cells (SMC). In EC, the GR expression was higher than in SMC. Compared to before BT, the GR expression was significantly up-regulated after BT in EC (p=0.018) and in SMC (p=0.033). Furthermore, after BT the GR signal was significantly increased in the nucleus compared to tissue section obtained before BT (p=0.036). <b>Conclusion:</b> BT lastingly increased the expression of the GR in EC and SMC. And it was shifted the GR into the nucleus. Epithelial cells require steroids for their recovery from stress and for their differentiation, thus the lasting increased GR expression and its accumulation in the nucleus might help them to repair tissue damage during asthma attacks. In SMC steroids supress proliferation and inflammation.The increased GR expression in SMC might therefore help to reduce airway remodelling. The presented data may explain the reduced requirement of steroids for asthma therapy after BT.