Nuclear factor-kappa B-dependent induction of interleukin-8 gene expression by tumor necrosis factor alpha: Evidence for an antioxidant sensitive activating pathway distinct from nuclear translocation

Tumor necrosis factor alpha (TNF alpha) is a pluripotent activator of infla mmation by inducing a proinflammatory cytokine cascade. This phenomenon is mediated, in part, through inducible expression of the CXC chemokine, inter leukin-8 (IL-8), In this study, we investigate the role of TNF alpha-induci ble reactive oxygen species (ROS) in IL-8 expression by "monocyte-like" U93 7 histiocytic lymphoma cells. TNF alpha is a rapid activator of IL-8 gene e xpression by U937, producing a 50-fold induction of mRNA within 1 hour of t reatment. In gene transfection assays, the effect of TNF alpha requires the presence of an inducible nuclear factor-kappa B (NF-kappa B) (Rel A) bindi ng site in the IL-8 promoter. TNF alpha treatment induces a rapid transloca tion of the 65 kD transcriptional activator NF-kappa B subunit, Rel A, whos e binding in the nucleus occurs before changes in intracellular ROS, Pretre atment (or up to 15 minutes posttreatment) relative to TNF alpha with the a ntioxidant dimethyl sulfoxide (DMSO) (2% [vol/vol]) blocks 80% of NF-kappa B-dependent transcription, Surprisingly, however, DMSO has no effect on ind ucible Rel A binding. Similar selective effects on NF-kappa B transcription are seen with the unrelated antioxidants, N-acetylcysteine (NAC) and vitam in C, These data indicate that TNF alpha induces a delayed ROS-dependent si gnalling pathway that is required for NF-kappa B transcriptional activation and is separable from that required for its nuclear translocation, Further definition of this pathway will yield new insights into inflammation initi ated by TNF alpha signalling. (C) 1999 by The American Society of Hematolog y.