Nasal epithelial cells maintain eosinophil survival by secreting granulocyte/macrophage colony-stimulating factor (GM-CSF). Corticosteroids antagonize eosinophil viability induced by GM-CSF. We investigated the effect of topical corticosteroids and nedocromil sodium on the release of GM-CSF from nasal polyp epithelial cells.

Epithelial cells were obtained from 19 patients undergoing nasal polypectomy and cultured. After reaching confluence, cultured cells were stimulated with 10% foetal calf serum in the absence and presence of four topical corticosteroids and nedocromil sodium for 48 h. GM-CSF was measured by enzyme linked immunosorbent assay (ELISA).

Fluticasone propionate was the most potent inhibitor of GM-CSF release (IC₂₅=46 p M) closely followed by budesonide (IC₂₅=4 n M), beclomethasone dipropionate (IC₂₅=40 n M) and triamcinolone acetonide (IC₂₅= 75 nM ). Nedocromil sodium had no effect on GM-CSF release.

We conclude that the effect of topical steroids on reducing eosinophil infiltration in nasal polyps may be due in part to downregulation, among other cytokines, of epithelial GM-CSF production which prolongs eosinophil viability. Quantitatively, fluticasone propionate inhibited GM-CSF production more potently than budesonide, beclomethasone dipropionate and triamcinolone acetonide.