Inhibition of cytokine-induced nitric oxide synthase expression by gene transfer of adenoviral I kappa B alpha

BACKGROUND: Nitric oxide is overexpressed in nearly every organ during sepsis and it has profound biologic effects. Previously, we showed that maximal inducible nitric oxide synthase (iNOS) expression is up-regulated by a combination of cytokines and that this effect is mediated by the transcription factor NF-kappa B. Therefore the purpose of this study was to establish whether gene transfer of the inhibitory molecule I kappa B would result in the abrogation of cytokine-induced iNOS expression.

METHODS: Cultured hepatocytes were infected with an adenoviral vector containing the I kappa B alpha gene (Ad5I kappa B) and after an 18-hour recovery period were stimulated with the cytokine mixture of tumor necrosis factor-alpha (500 U/mL) plus interleukin 1 beta (200 U/mL) plus interferon gamma (100 U/mL).

RESULTS: As expected, cytokine mixture induced significant hepatocyte nitrite (NO2-) and iNOS messenger RNA production. Cells infected with the I kappa B alpha gene showed a dose-dependent decrease in NO2- and iNOS messenger RNA levels. Western blot analysis showed a marked decrease in iNOS protein levels in the presence of Ad5I kappa B alpha. Gel shift assays of nuclear extracts demonstrated that Ad5I kappa B alpha decreased the cytokine-induced DNA binding activity for NF kappa B.

CONCLUSIONS: NF kappa B is an important regulator of cytokine-induced NO expression. These results identify a novel therapeutic approach where gene transfer of the inhibitory molecule I kappa B alpha can be used to down-regulate cytokine-induced iNOS expression as well as other NF kappa B-dependent genes that are up-regulated during the inflammatory response.