Inhibition of NF-κB Activation and Its Target Genes by Heparin-Binding Epidermal Growth Factor-Like Growth Factor

Abstract

Many cells upon injury mount extensive, compensatory responses that increase cell survival; however, the intracellular signals that regulate these responses are not completely understood. Heparin-binding epidermal growth factor-like growth factor (HB-EGF) has been implicated as a cytoprotective agent. We have previously demonstrated that pretreatment of human intestinal epithelial cells with HB-EGF significantly decreased cytokine-induced activation of inducible NO synthase mRNA expression and NO production and protected the cells from apoptosis and necrosis. However, the mechanisms by which HB-EGF exerts these effects are not known. Here we show that cytokine exposure (IL-1β and IFN-γ) induced NF-κB activation and IL-8 and NO production in DLD-1 cells. Transient expression of a dominant negative form of IκBα decreased NO production, suggesting that the cytokines stimulated NO production in part through activation of NF-κB. HB-EGF dramatically suppressed NF-κB activity and IL-8 release and decreased NO production in cells pretreated with HB-EGF. HB-EGF blocked NF-κB activation by inhibiting IκB kinase activation and IκB phosphorylation and degradation, thus interfering with NF-κB nuclear translocation, DNA-binding activity, and NF-κB-dependent transcriptional activity. The data demonstrate that HB-EGF decreases inflammatory cytokine and NO production by interfering with the NF-κB signaling pathway. Inhibition of NF-κB may represent one of the mechanisms by which HB-EGF exerts its potent anti-inflammatory and cytoprotective effects.