Dexamethasone (dex)

PBMCs and BEAS-2B cells were treated with dexamethasone (Sigma-Aldrich, St. Louis, MO, USA) for 45 min, followed by TNFα (10 ng/mL; R&D Systems, Minneapolis, MN, USA) stimulation overnight. The ability of dexamethasone to inhibit TNFα-induced CXCL8 release was determined in cell medium by sandwich ELISA according to the manufacturer’s instructions (R&D Systems). The IC₅₀ of dexamethasone on CXCL8 production (Dex-IC₅₀), calculated using Prism^® 8.0 statistical software (GraphPad, San Diego, CA, USA), was used as a marker for corticosteroid sensitivity.

Nasal epithelial cells were treated with dexamethasone for 45 min, followed by TNFα (10 ng/mL) stimulation overnight. The ability of dexamethasone to inhibit TNFα-induced CXCL8 release was determined in cell medium by sandwich ELISA according to the manufacturer’s instructions (R&D Systems, Minneapolis, MN, USA). IC₅₀ of dexamethasone on CXCL8 production (Dex-IC₅₀), calculated using Prism^® 6.0 statistical software (GraphPad, San Diego, CA, USA), was used as a marker for corticosteroid sensitivity. In addition, BEAS-2B cells were treated overnight with FITC-conjugated dexamethasone (Molecular Probes, Eugene, OR; 10⁻⁶ M). The nuclear fraction was prepared by 10 min incubation with hypotonic buffer (Epigentec, Farmingdale, NY, USA), followed by pulse vortexing. dexamethasone’s ability to translocate into the nucleus was evaluated by FITC-dexamethasone detected in the nuclei using a fluorescent plate reader.