Superoxide-related signaling cascade mediates nuclear factor-kappaB activation in acute inflammation

The nuclear factor-kB (NF-kB) is a transcription factor that plays a pivotal role in the induction of genes involved in physiological processes, as well as in the response to inflammation. In this study, we used a selective nonpeptidyl superoxide dismutase mimetic, M40403, to investigate the role of superoxide anion in NF-kB activation during acute inflammation in mice. Injection of carrageenan into the pleural cavity of mice induced an acute inflammatory response characterized by fluid accumulation in the pleural cavity that contained a large number of neutrophils, as well as an increased production of tumor necrosis factor-alpha and interleukin-1beta. All parameters of inflammation were attenuated by M40403 (10 mg/kg i.p., 30 min prior to carrageenan administration). These inflammatory events were associated with the activation of NF-kB in the lung. In particular, the appearance of inhibitory protein IkB-alpha (IkB-alpha) in homogenates of lung tissues was investigated by immunoblot analysis at 4 h after carrageenan administration. IkB-alpha levels were substantially reduced in the lung tissue from carrageenan-treated mice in comparison with sham-treated mice. Furthermore, to detect NF-kB/DNA binding activity, whole extracts from lung tissue of each mouse were analyzed by electrophoretic mobility-shift assay. The DNA binding activity significantly increased in whole extracts obtained from lung tissues of vehicle-treated mice 4 h after carrageenan administration. Treatment of mice with M40403 caused a significant inhibition of carrageenan-induced IkB-alpha degradation and NF-kB/DNA binding activity. These data confirm that M40403 exerts a potent antiinflammatory activity and clearly demonstrate that the reduction of the inflammatory process is associated with modification of the activation of signal transduction pathways.