Molecular mechanisms of lipopolysaccharide induced ICAM-1 expression in A549 cells

Abstract.

Objective and Design: Lung intercellular adhesion molecule-1 (ICAM-1) expression is increased by LPS or hyperoxia on type II cells in vivo. The goals of the present study were to determine the mechanisms of ICAM-1 expression in a lung alveolar epithelial cell line (A549) exposed to lipopolysaccharide (LPS).¶Materials: A549 cells, a transformed human cell line with characteristics of alveolar epithelial cells, were used.¶Treatment: Cells were exposed to LPS, TNF-α, IL-1β, or media alone for up to 12 h.¶Methods: Northern blot analyses were done to determine mRNA expression of ICAM-1 after exposures. Protein binding to NF-κB sequences were determined by gel mobility shift assays and super-shift analysis.¶Results: ICAM-1 mRNA expression was induced in A549 cells with exposure to LPS for 1 to 4 h, and was diminished to baseline at 8 h, and the inductions were independent of TNF-α and IL-1β expression. Nuclear protein extracts from LPS-exposed cells bound to a NF-κB sequence and the timing of increased binding correlated closely with ICAM-1 mRNA induction. Super-shift studies indicated that p65 was involved in the binding to the NF-κB sequence and p50 was not.¶Conclusion: LPS inducibility of ICAM-1 mRNA in A549 cells is independent of TNF- and IL-1 in A549 cells, and the similar time course of mRNA induction and NF-κB activation suggest the induction of ICAM-1 is mediated, in part, by NF-κB.