Raf-independent and MEKK1-dependent activation of NF-κB by hydrogen peroxide in 70Z/3 pre-B lymphocyte tumor cells

✍ Scribed by Michael Lee; Woo Suk Koh

• Publisher: John Wiley and Sons
• Year: 2003
• Tongue: English
• Weight: 385 KB
• Volume: 88
• Category: Article
• ISSN: 0730-2312
• DOI: 10.1002/jcb.10376

✦ Synopsis

We have previously demonstrated that hydrogen peroxide (H(2)O(2)) treatment of murine 70Z/3 pre-B lymphocytes inhibits the immune response to lipopolysaccharide by attenuating signaling through c-Jun N-terminal kinase (JNK) activation. In the present study, we further examined the signaling intermediates responsible for immunosuppression by H(2)O(2), focusing on NF-kappaB, a dimeric transcription factor whose activation is implicated in a number of immune response. Treatment of 70Z/3 pre-B cells with H(2)O(2) caused activation of NF-kappaB in the nuclei by detection of NF-kappaB specific DNA binding, concomitant with phosphorylation of IkappaBalpha. H(2)O(2) stimulation of NF-kappaB occurred within 20 min of treatment, reached maximum level at 60 min, and sustained for 2 h or more. Especially, MEK1 may contribute to H(2)O(2)-induced NF-kappaB activation as shown in the inhibition of NF-kappaB binding activity by the MEK1 inhibitor, PD 98059, and H(2)O(2)-induced MEK1 activation. However, H(2)O(2) exhibited no effect on the activity of Raf-1 kinase, which was an upstream activator of MEK1. Furthermore, B-58l and alpha-hydroxyfarnesylphosphonic acid, two inhibitors of Ras, did not block NF-kappaB activation. In addition, the transient transfection of a dominant negative Ras (RasN17) construct showed a negligible inhibitory effect on the activation of NF-kappaB by H(2)O(2). Instead, treatment of 70Z/3 cells with H(2)O(2) resulted in the activation of MAPK kinase kinase 1 (MEKK1) as well as JNK. Therefore, our data suggest that H(2)O(2) regulates the activity of NF-kappaB by MEK1 activation through MEKK1-dependent but Ras/Raf-independent mechanism.