Anti-inflammatory Activity of Azithromycin as Measured by Its NF-kappa B Inhibitory Activity

Growing data suggest that the antibiotic azithromycin mediates anti-inflammatory activity through the inhibition of the transcription factor NF-kappa B. The purpose of this study was to compare azithromycin's anti-inflammatory potency with that of hydrocortisone and dexamethasone as measured in an activated NF-kappa B assay. Dose-response curves and the corresponding inhibitory potencies (IC50) of azithromycin, hydrocortisone, and dexamethasone were evaluated in a fluorescence assay using A549 cells. All three compounds inhibited TNF alpha stimulated. NF-kappa B activity in a dose-dependent manner. IC50 values of azithromycin, hydrocortisone and dexamethasone were 56 mu M, 2.6 nM, and 0.18 nM, respectively. Hydrocortisone was approximately 4 orders of magnitude more potent than azithromycin, while dexamethasone was approximately 14 times as potent as hydrocortisone. In relative terms the anti-inflammatory potency of azithromycin was about 4 orders of magnitude weaker than that of hydrocortisone.