Roxithromycin inhibits cytokine production by and neutrophil attachment to human bronchial epithelial cells in vitro

Abstract

We evaluated the effect of roxithromycin on cytokine production and neutrophil attachment to human airway epithelial cells. Roxithromycin suppressed production of interleukin 8 (IL-8), IL-6, and granulocyte-macrophage colony-stimulating factor. It inhibited neutrophil adhesion to epithelial cells. Roxithromycin modulates local recruitment and activation of inflammatory cells, which may have relevance to its efficacy in airway diseases.

FIG. 1

Effect of roxithromycin on IL-8, IL-6, and GM-CSF release by human primary bronchial epithelial cells. (a) Roxithromycin was added to primary bronchial epithelial cells simultaneously with (left panel) and without (right panel) IL-1 α (10 ng/ml). The supernatants were harvested after 24 h for IL-8 measurement. (b) Effect of roxithromycin on IL-6 and GM-CSF release by IL-1 α (10 ng/ml)-stimulated primary human bronchial epithelial cells. Simultaneous treatment with roxithromycin significantly inhibited IL-6 and GM-CSF release after 24 h. For all panels, an asterisk represents a P of <0.01 compared to controls (ANOVA; n = 5). Error bars, standard deviations.

FIG. 2

Northern blot analysis showing effect of roxithromycin (RXM) on IL-8 mRNA expression by IL-1 α (10 ng/ml)-stimulated Bet-1A cells in culture. Roxithromycin was added to the cells with IL-1 α, and total cellular RNA was extracted after 12 h. (a) Roxithromycin showed a concentration-dependent inhibition on the steady-state levels of IL-8 mRNA. (b) Measurement of densitometric signals of IL-8 corrected by β-actin transcripts showed a significant inhibition by roxithromycin. ∗, P < 0.01 compared to controls (ANOVA; n = 4). Error bars, standard deviations.

FIG. 3

Effect of roxithromycin on neutrophil adhesion onto IFN-γ (100 ng/ml)-treated Bet-1A in vitro. Different concentrations of roxithromycin were added to Bet-1A epithelial cells simultaneously with IFN-γ (100 ng/ml) for 18 h. The purified neutrophils were then added with and without 30 min of pretreatment with FMLP (10⁻⁷ M). Roxithromycin showed a concentration-dependent inhibitory effect on neutrophil-epithelium adhesion at a concentration of no less than 1 μg/ml in FMLP-treated neutrophils (MPO assay) (a) and at a concentration of 25 μg/ml in naive neutrophils (b). For both panels, an asterisk represents a P of <0.05 compared to controls (ANOVA; n = 4). Error bars, standard deviations; OD, optical density.

FIG. 4

Effect of roxithromycin (RXM) on ICAM-1 expression on Bet-1A cells. Confluent Bet-1A cells were treated with IFN-γ and roxithromycin. After 18 h, the expression of ICAM-1 molecules was evaluated by cell ELISA. Roxithromycin inhibited the magnitude of ICAM-1 expression in a concentration-dependent fashion. ∗, P < 0.05 (ANOVA; n = 4); OD, optical density.