The role of nuclear factor-κB in interleukin-8 expression by human adenoidal fibroblasts

Objectives/Hypothesis: The production of cytokines by adenoids is known to he associated with inflammation of nasopharynx and the pathogenesis of otitis media with effusion. However, the role of adenoids in producing inflammatory cytokines such as interleukin-8 (IL-8) is not yet clear. In the present study, expression of IL-8 in adenoidal fibroblasts was investigated at the level of transcription factors. Further, the effects of clarithromycin, a 14-member ring macrolide, on IL-8 gene expression and nuclear factor-kappaB (NF-kappaB) activation in adenoidal fibroblasts were evaluated. Study Design: In vitro study for the production of inflammatory cytokine from human adenoidal fibroblasts. Methods. Adenoidal fibroblasts were incubated with nontypeable Haemophilus influenzae endotoxin or interleukin-1beta. Then the expression of IL-8 and the influence of NF-kappaB inhibitor and clarithromycin were evaluated. Interleukin-8 protein production was assessed by ELISA, and IL-8 messenger RNA production was measured by Northern blot analysis and reverse transcriptase-polymerase chain reaction. Activation of NF-kappaB and inhibition of its activation were determined by electrophoretic mobility shift assay. Results. The expression of both IL-8 protein and messenger RNA in adenoidal fibroblasts was enhanced by Haemophilus influenzae endotoxin and interleukin-1beta and was positively correlated with increases in NF-kappaB activity. Treatment of cells with the NF-kappaB inhibitor N-tosyl-(L)-phenylalanine chloromethyl ketone, as well as with clarithromycin, reduced expression of IL-8 and NF-kappaB activity in a dose-dependent manner. Conclusions. Results suggest that adenoidal fibroblasts produce IL-8 in response to endotoxin through NF-kappaB activation. The inhibitory effects of clarithromycin on NF-kappaB activation and IL-8 production in adenoidal fibroblasts might explain, in part, the mechanism of this drug in improving otitis media with effusion.