Intercellular adhesion molecule-1 (ICAM-1) expression is increased in lungs of mice exposed to hyperoxia or lipopolysaccharide (LPS). In oxygen toxicity, upregulation of ICAM-1 occurs predominantly on alveolar epithelial cells, and inhibition of ICAM-1 function by administration of functional antibodies limits lung inflammation. The goal of this study is to determine the mechanisms of ICAM-1 expression in transformed lung epithelial cells (A549) exposed to LPS. ICAM-1 mRNA expression is induced in A549 cells after exposure to LPS for 1h and increases after 2h, but diminishes after 8h. To determine whether TNF-α or IL-1β mediate ICAM-1 induction on A549 cells after exposure to LPS, the concentrations of the cytokines were measured in cell media 1, 2, 4, or 8h after exposure to LPS. The concentrations of TNF-α and IL-1β were below the limits of detection. A549 cells were then incubated with antibody to TNF-α or IL-1β immediately prior to exposure to LPS. There was no inhibition of LPS inducibility of ICAM-1 mRNA. To determine the elements of the murine ICAM-1 gene involved in the regulation of gene expression, we sequenced the 5' flanking sequence of murine ICAM-1 from -2454 to the transcription start site, made serial deletion constructs of the sequence, and ligated these to the luciferase gene.The 5' flanking sequence has a concentration of cis elements between -398 and -280 that have shown protein binding in other studies, and previously we found that LPS induced reporter gene expressions in A549 cells transfected with sequences-355 and -309, but not in cells transfected with -280, suggesting that the sequence between -309 and -280 contains a DNA region important for induction of the ICAM-1 gene by LPS. To determine the specific sequence within this region that is crucial for protein-DNA binding we conducted gel-mobility shift assays in which we used as a probe the sequence from -305 to -281, which contains an AP-1 like site, and observed evidence of protein-DNA binding. Furthermore, mutating the AP-1 like site (TGACTCC to CAGTTCC) abolished protein-DNA binding. However, the same mutation introduced into the -355 and-309 luciferase constructs did not abolish LPS inducibility in transfected cells. In conclusion, LPS inducibility of ICAM-1 is independent of TNF-α and IL-1β in A549 cells, and protein-DNA binding to an AP-1 like site in the murine ICAM-1 promoter does not appear to be important for induction of ICAM-1 by LPS. Further studies to identify the specific protein-DNA interactions important for ICAM-1 expression are crucial to specific molecular interventions in sepsis-states.