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

Objective and Design: Lung intercellular adhesion molecule-1 (ICAM-1) expre ssion 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 lipopolysaccharid e (LPS). Materials: A549 cells, a transformed human cell line with characte ristics of alveolar epithelial cells, were used. Treatment. Cells were expo sed to LPS, TNF-alpha, IL-1 beta, or media alone for up to 12 h., Methods: Northern blot analyses were done to determine mRNA expression of I CAM-1 after exposures. Protein binding to NF-kappa B sequences were determi ned 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-a and IL-1 beta expression. Nuclear protein extrac ts from LPS-exposed cells bound to a NF-kappa B sequence and the timing of increased binding correlated closely with ICAM-1 mRNA induction. Super-shif t studies indicated that p65 was involved in the binding to the NF-kappa B 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-kappa B activation suggest the induction of ICAM-1 is mediated, in part, by NF-kappa B.