Anti-inflammatory activity of azithromycin as measured by its NF-kappaB, inhibitory activity.

Growing data suggest that the antibiotic azithromycin mediates anti-inflammatory activity through the inhibition of the transcription factor NF-kappaB. 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-kappaB assay. Dose-response curves and the corresponding inhibitory potencies (IC(50)) of azithromycin, hydrocortisone, and dexamethasone were evaluated in a fluorescence assay using A549 cells. All three compounds inhibited TNFalpha stimulated NF-kappaB activity in a dose-dependent manner. IC(50) values of azithromycin, hydrocortisone and dexamethasone were 56 microM, 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.