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


METHODS
A549 cells, a transformed human cell line with characteristics of alveolar epithelial cells, were used.


METHODS
Cells were exposed to LPS, TNF-alpha, IL-1beta, 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-kappaB 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-alpha and IL-1beta expression. Nuclear protein extracts from LPS-exposed cells bound to a NF-kappaB 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-kappaB sequence and p50 was not.


CONCLUSIONS
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-kappaB activation suggest the induction of ICAM-1 is mediated, in part, by NF-kappaB.
Fakler
C R
CR
Department of Pediatrics, Baylor College of Medicine, Houston, TX 77030, USA. cfakler@neo.bcm.tmc.edu
Wu
B
B
McMicken
H W
HW
Geske
R S
RS
Welty
S E
SE
D001665:Binding Sites; D015152:Blotting, Northern; D002461:Cell Line, Transformed; D004847:Epithelial Cells / Q000378:metabolism; D015870:Gene Expression / Q000187:drug effects*; D006801:Humans; D018799:Intercellular Adhesion Molecule-1 / Q000235:genetics*; D007375:Interleukin-1 / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000494:pharmacology*; D016328:NF-kappa B / Q000378:metabolism; D011650:Pulmonary Alveoli / Q000378:metabolism*; D012333:RNA, Messenger / Q000096:biosynthesis; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D007375:Interleukin-1; D008070:Lipopolysaccharides; D016328:NF-kappa B; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D018799:Intercellular Adhesion Molecule-1