Abstract

Nuclear factor-κB (NF-κB) is a transcription factor that plays crucial roles in inflammation, immunity, cell proliferation, and apoptosis. Until now, there have been few studies of NF-κB activation in whole animals because of experimental difficulties. Here, we show that mice receiving a simple injection of plasmid vectors can be used to examine NF-κB activation in the liver. Two plasmid vectors, pNF-κB-Luc (firefly luciferase gene) and pRL-SV40 (Renilla reniformis luciferase gene), were injected into the tail vein of mice by the hydrodynamics-based procedure, an established method of gene transfer to mouse liver. Then, the ratio of the firefly and R. reniformis luciferase activities (F/R) was used as an indicator of the NF-κB activity in the liver. Injection of thioacetamide or lipopolysaccharide plus d-galactosamine increased the F/R ratio in the liver, and this was significantly (P < 0.001) inhibited by an intravenous injection of catalase derivatives targeting liver nonparenchymal cells. Imaging the firefly luciferase expression in live mice clearly demonstrated that the catalase derivatives efficiently prevented the NF-κB-mediated expression of the firefly luciferase gene. Plasma transaminases and the survival rate of mice supported the findings obtained by the luminescence-based analyses. Thus, this method, which requires no genetic recombination techniques, is highly sensitive to the activation of NF-κB and allows us to continuously examine the activation in live animals. In conclusion, this novel, simple, and sensitive method can be used not only for analyzing the NF-κB activation in the organ under different inflammatory conditions but also for screening drug candidates for the prevention of liver inflammation.