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

Abstract

Purpose: : Azithromycin has been reported to possess anti-inflammatory and immunosuppressive activities. This study used an activated NF-ΚB assay to assess azithromycin’s anti-inflammatory potency, and compared that to a commonly used anti-inflammatory agent, hydrocortisone.

Methods: : A reporter gene assay employing A549 cells was used to examine the effects of azithromycin and hydrocortisone on TNF- stimulated NF-ΚB activity. By constructing the dose-response curves, the corresponding inhibitory potencies (IC₅₀s) of azithromycin and hydrocortisone were estimated. Dexamethasone was also tested in the assay to compare its NF-ΚB inhibitory activity as related to the glucocorticoid activity.

Results: : All three compounds dose-dependently inhibited TNF- stimulated NF-ΚB activity. IC₅₀ values of azithromycin, hydrocortisone and dexamethasone were 56 µM, 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. The latter approximates the reported glucocorticoid activity ratio between dexamethasone and hydrocortisone.

Conclusions: : In addition to its antibiotic activity, azithromycin also possesses a weak anti-inflammatory activity relative to the glucocorticoids. Since azithromycin can achieve much higher tissue concentration and has a long tissue half-life at clinical doses, this antibiotic might have utility for certain inflammatory ocular surface diseases.

Keywords: inflammation • antibiotics/antifungals/antiparasitics • corticosteroids