Steroid resistance in nasal polyposis: role of glucocorticoid receptor and TGF-beta1

Abstract

Background: Glucocorticoids (GCs) are considered drugs of choice for treating nasal polyps (NPs). However, a subset of patients shows a limited clinical response even to high doses of GCs. Altered expression of glucocorticoid receptors (GRs), namely GR-alpha; and GR-beta;, is a potential mechanism underlying GC insensitivity. GCs modulate the expression of several cytokines, including transforming growth factor-beta (TGF-beta), which may contribute to cellular proliferation in NPs. The study investigates some biomolecular features of GC-resistant NPs, and examines possible differences from normal mucosa (NM). Methodology: Radioligand binding assay (binding) was used to determine GR-alpha; binding capacity; Western blotting was used to evaluate GR-alpha;, GR-beta;, and TGF-beta; expression and GR-alpha; subcellular distribution. NPs were sampled in 32 patients during ethmoidectomy; NM was taken from 15 healthy patients during rhinoplasty. Results: GR-alpha; was present in NPs and NM, with lower affinity for the ligand in NPs. GR-alpha; was prevalent in the cytosol of NPs that were GR-alpha-negative to the binding assay. GR-beta was expressed in NPs and absent in the majority of NM. TGF-beta1 expression was higher in NPs than in NM. Conclusions: GR-beta and TGF-beta1 might be involved in NP pathogenesis, but their role in modulating GC sensitivity is still unclear.