Background Intercellular adhesion molecule-1 (ICAM-1) has been shown to mediate the adhesion and migration of eosinophils to the site of allergic inflammation. However, molecular mechanisms regulating the expression of ICAM-1 in eosinophils are still being elucidated. We investigated the effect of tumour necrosis factor-alpha (TNF-α) on ICAM-1 expression of eosinophils.
Methods The surface expression of ICAM-1 on a human eosinophilic leukaemic cell line, EoL-1, was assessed by immunocytochemical staining. The phosphorylation of inhibitor kappa B-alpha (IκB-α) and p38 mitogen-activated protein kinase (MAPK) was detected by Western blot. Nuclear factor kappa-B (NF-κB) pathway-related genes were evaluated by the cDNA expression array system, whereas the activity of NF-κB was measured by electrophoretic mobility shift assay (EMSA).
Results TNF-α was found to induce the cell surface expression of ICAM-1. A specific proteasome inhibitor N-cbz-Leu-Leu-leucinal (MG-132), but not a p38 MAPK inhibitor (SB 203580), was found to suppress the TNF-α-induced expression of ICAM-1 on EoL-1 cells. The gene expressions of ICAM-1, NF-κB and IκBα were up-regulated after the stimulation with TNF-α. Further, TNF-α was shown to induce IκB-α phosphorylation and degradation, thereby indicating the activation of NF-κB. In EMSA, there was a shifted NF-κB band on TNF-α-treated cells with or without SB 203580, but no shifted band was observed on MG-132-treated cells.
ConclusionIn vitro studies of EoL-1 cells, an eosinophilic leukaemic cell line, confirmed that NF-κB plays an important role in the expression of ICAM-1 and recruitment of eosinophils in allergic inflammation.