Increased glucocorticoid receptor beta in airway cells of glucocorticoid-insensitive asthma

Glucocorticoid (GC)-insensitive asthma is a challenging clinical problem that can be associated with life-threatening disease progression. The molecular basis of GC insensitivity is unknown. Alternative splicing of the GC receptor (GCR) pre-mRNA generates a second GCR, termed GCRbeta, which does not bind GC but antagonizes the transactivating activity of the classic GCR. Thus increased expression of GCRbeta could account for glucocorticoid insensitivity. Bronchoalveolar lavage (BAL) cells and peripheral blood mononuclear cells (PBMC) were examined for GCRbeta immunoreactivity using a GCRbeta-specific antibody by immunohistochemical staining. Cell localization of GCRbeta expression was performed using a double immunostaining technique. Patients with GC-insensitive asthma expressed a significantly higher number of GCRbeta-immunoreactive cells in their BAL and peripheral blood than GC-sensitive asthmatics or normal control subjects. Furthermore, GCRbeta expression in GC-insensitive asthma was particularly high in airway T cells, which are thought to play a major role in the pathogenesis of asthma. We also examined the expression of GCRbeta in specimens from the airways of patients with chronic bronchitis. In chronic bronchitis, few cells were GCRbeta-positive and their numbers did not differ significantly from normal control subjects. We conclude that GC-insensitive asthma is associated with increased expression of GCRbeta in airway T cells.