The Journal of biological chemistry
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Intercellular adhesion molecule 1 (ICAM-1) is a glycoprotein expressed on the surface of both hemopoietic and nonhemopoietic cells that mediates, in part, the emigration of leukocytes out of the vasculature. Expression of ICAM-1 on the surface of human umbilical vein endothelial cells and a human lung carcinoma cell line (A549) was increased by interleukin-1 beta, tumor necrosis factor alpha, and interferon gamma in a concentration-dependent manner. Phosphorothioate antisense oligonucleotides designed to hybridize to 10 target sites on the human ICAM-1 mRNA were tested for inhibition of ICAM-1 expression in both cell lines by an ICAM-1 enzyme-linked immunosorbent assay. ⋯ Neither ISIS 1570 nor ISIS 1939 changed the transcriptional rate of the ICAM-1 gene, demonstrating that both oligonucleotides were working through a post-transcriptional mechanism. 2'-O-Methyl phosphorothioate analogs, which do not support RNase H-mediated cleavage of target mRNA, were used to determine if the active antisense oligonucleotides inhibited ICAM-1 expression by an RNase H-dependent mechanism. The 2'-O-methyl phosphorothioate analog of ISIS 1939 did not significantly reduce interleukin-1 beta-induced ICAM-1 expression, whereas the 2'-O-methyl phosphorothioate analog of ISIS 1570 did inhibit ICAM-1 expression, suggesting that the reduction of ICAM-1 mRNA following treatment with ISIS 1939 was due, in part, to RNase H-mediated hydrolysis. Adherence of HL-60 cells to human umbilical vein cell monolayers was inhibited by ISIS 1570 and ISIS 1939, demonstrating that the reduced levels of ICAM-1 impact on ICAM-1-associated function.