Identification of Hydrogen Peroxide as the Relevant Messenger in the Activation Pathway of Transcription Factor NF-κB

The inducible higher eukaryotic transcription factor NF-κB is activated by a large variety of distinct simuli [1–3]. In unstimulated cells, this factor resides in a latent form in the cytoplasm [4]. Latency is achieved by association of the DNA-binding NF-κB dimer with an inhibitory subunit, called IκB [5]. IΚB suppresses DNA-binding and nuclear transport of NF-κB. Upon stimulation of cells, IκB is phosphorylated and proteolytically degraded [6–9]. Both reactions are required for activation [10]. The released NF-κB is then translocated to the nucleus where it initiates transcription of target genes. Among the numerous proteins which are induced by a concerted action of NF-kB with other transcription factors are cytokines, chemokines, cell adhesion molecules, hematopoetic growth factors and receptors, histocompatibility antigens and acute phase proteins [1–3]. While NF-κB may be indispensable as inducer of many immediate-early inflammatory and immune reactions, the transcription factor is likely to play a fatal role in certain diseases and syndromes that involve an abberrant expression of inflammatory cytokines [22–24].