INHIBITION OF INTERFERON-GAMMA-INDUCED INTERCELLULAR-ADHESION MOLECULE-1 EXPRESSION ON HUMAN KERATINOCYTES BY PHOSPHOROTHIOATE ANTISENSE OLIGODEOXYNUCLEOTIDES IS THE CONSEQUENCE OF ANTISENSE-SPECIFIC AND ANTISENSE-NON-SPECIFIC EFFECTS

Expression of intercellular adhesion molecule-1 (ICAM-1) by keratinocy tes is an important event in the pathogenesis of T-cell-mediated infla mmatory skin diseases. To determine if ICAM-1 expression could be sele ctively modulated, two antisense phosphorothioate oligonucleotides (S- ODN) targeting the translation initiation and 3' untranslated regions of ICAM-1 mRNA were added as lipid complexes to cultures of keratinocy tes. Interferon-gamma was added after 24 h to induce ICAM-1 expression , which was quantitated by flow cytometry after 48 h. The S-ODN target ing the translation initiation site did not inhibit ICAM-1 expression at 0.2-20.0 mu M. In contrast, 0.2-1.0 mu M of the S-ODN targeting a s ite in the 3' untranslated region abrogated ICAM-1 expression in up to 75% of the keratinocytes; this inhibition was reversible when complem entary sense S-ODN was added. Phosphodiester ODN (PD-ODN) targeting th e same sites did not inhibit ICAM-1 expression on keratinocytes, most likely as a consequence of rapid degradation. Inhibition of ICAM-1 by the antisense S-ODN was selective; expression of beta 2-microglobulin, alpha 3-integrin, and beta 1-integrin remained largely unaffected and interferon-gamma-induced HLA-DR expression was inhibited to a much le sser extent than ICAM-1. Antisense-non-specific inhibition was also no ted in that two scrambled S-ODN with an identical nucleotide (14 of 20 cytosines) composition inhibited ICAM-1 expression in up to 44% of th e keratinocytes, whereas a degenerate S-ODN did not. The data demonstr ate the complex effects exerted by antisense S-ODN in that ICAM-1 expr ession was inhibited via antisense-non-specific mechanisms probably du e to the intrinsic properties of the S-ODN as well as via the anticipa ted sequence-specific mechanisms.