Expression of the glucocorticoid receptor alpha and beta isoforms in human nasal mucosa and polyp epithelial cells

Abstract 

The lower sensitivity of the inflamed nasal mucosa to glucocorticoids might be related to an increased expression of the glucocorticoid receptor (GR) beta isoform. We investigated GR α and GR β mRNA expression in epithelial cells from nasal mucosa and nasal polyps. GR α mRNA was at least 1000 times more expressed than GR β mRNA in both tissues. GR β expression (mean±SEM of 10³ cDNA copies/μg of total RNA) was higher in nasal polyps (1.15±0.19; n=27; P<0.01) than in nasal mucosa (0.62±0.10; n=32). Nasal polyps with>3% of inflammatory cells had higher GRβ levels (1.40±0.29; n=16) than both nasal mucosa (P<0.01) and polyps with ≤3% of inflammatory cells (0.80±0.18; n=11; P<0.05). No difference in GRβ expression was found between nasal mucosa and polyps with ≤ 3% of inflammatory cells. GR β expression correlated with the inflammatory cell number, especially with mast cells (r=0.50, P<0.0001). There was no difference in GR α mRNA expression between nasal mucosa and nasal polyps. In summary, GR α is far more expressed than GR β in both tissues. The increased expression of GR β may be related to the presence of inflammatory cells.

Keywords: glucocorticoid receptor isoforms, nasal mucosa, nasal polyp, epithelial cells, inflammatory cells.

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• f1 Correspondence should be addressed to: Dr César Picado, MD, Servei de Pneumologia, Hospital Clı́nic, C/ Villarroel 170, 08036 Barcelona, Catalonia, Spain. Fax: +34 93 4515272; E-mail: cpicado@medicina.ub.es