Receptor expression sheds light on nasal polyposis

By Sally Robertson, B.Sc.Nov 6 2012

The increased expression of a leukotriene receptor and a glucocorticoid receptor (GR) may contribute to the development of nasal polyposis, report researchers.

Furthermore, the addition of a cysteinyl leukotriene 1 (CysLT1) receptor agonist may confer an additional benefit on nasal polyposis that is resistant to steroid treatment alone.

Recent studies have demonstrated an important role for GRs in steroid resistance in nasal polyps, explain Chae-Seo Rhee (Seoul National University College of Medicine, Korea) and colleagues. In addition, it has been suggested that cysteinyl leukotrienes (CysLTs) are involved in the development of nasal polyps, the biological action of which is partly mediated by the CysLT1 receptor.

As reported in the European Archives of Otorhinolaryngology, the team analyzed nasal biopsies from 32 individuals with chronic rhinosinusitis and nasal polyposis who were resistant to corticosteroid therapy and compared them with samples of middle turbinate tissue from seven healthy controls.

The researchers found that the number of CysLT1 receptor-positive cells was significantly higher in those with nasal polyps than among those with normal tissue, at 281 cells/mm² versus 157 cells/mm²_. The percentage of cells expressing CysLT1 receptor was also significantly increased in the nasal polyps versus normal turbinate groups, at 21.3% versus 10.6%.

There was no significant difference in GR-α expression between the two sample groups, but GR-β expressing cells were significantly more abundant in nasal polyps than in normal tissues, at 36 cells/mm² vs 19 cells/mm². And GR-β positive cells were significantly increased in nasal polyp compared with control samples, at 2.5% versus 1.1%.

Interestingly, while no relationship was found between CysLT-1 receptor and GR-α expression in the nasal polyp samples, CysLT-1 receptor significantly correlated with GR-β expression in nasal polyps in both cell count and the proportion.

"The predominance of CysLT1 receptor in GR-β over-expressed polyps provides a hint for a positive effect of LTRA [leukotriene receptor agonists] as an adjuvant therapy on steroid-unresponsive nasal polyps," say the researchers. "The combination of LTRA and corticosteroids could produce clinical efficacy for treatment of nasal polyposis."

However, "more controlled studies of LTRA add-on therapy in nasal polyps are necessary for reliable data," they conclude.

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