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February 02, 2009

Glucocorticoids Curb COX-1 in Nasal Polyps

NEW YORK (Reuters Health) Jan 26 - The strong anti-inflammatory effects of topical glucocorticoids on nasal polyps may be in part due to downregulation of the increased epithelial expression of cyclooxygenase-1 (COX-1) seen in the condition, Dutch and Spanish researchers report in the January issue of Allergy.
Dr. F. A. Ebbens of the Academic Medical Center, Amsterdam and colleagues note that the anti-inflammatory action of glucocorticoids in this situation is attributed to their interference with prostanoid synthesis. Both COX-1 and COX-2 are involved in such synthesis.
Based on previous work, the researchers postulated that elevated levels of COX-1, rather than COX-2, were responsible for the relative predominance of pro-inflammatory prostanoids in nasal polyposis.
To investigate further, they examined nasal polyp specimens from 39 patients who had undergone endoscopic sinus surgery. Of this group, 12 had been treated with topical glucocorticoids and the other 27 had not. The researchers also examined normal nasal mucosa from controls.
Compared with normal mucosa, COX-1-positive cells were seen more frequently in nasal polyp tissue that had not been treated with glucocorticoids. "Treatment with glucocorticoids results in a significant decrease in the level of COX-1+ cells in nasal polyp epithelium back to levels similar to normal mucosa," the team reports.
Topical glucocorticoid treatment was not associated with a reduction in COX-2+ cells. In fact, their number may possibly have been upregulated.
"We postulate that the difference in tissue glucocorticoid concentrations between oral and topical glucocorticoids or binding to different subsets of glucocorticoid receptors account for this differential effect," the researchers write.
Allergy 2009;64:96-103.

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