Iron activates NF-kappaB in Kupffer cells.
Iron exacerbates various types of liver injury in which nuclear factor (NF)-kappaB-driven genes are implicated. This study tested a hypothesis that iron directly elicits the signaling required for activation of NF-kappaB and stimulation of tumor necrosis factor (TNF)-alpha gene expression in Kupffer cells. Addition of Fe2+ but not Fe3+ (approximately 5-50 microM) to cultured rat Kupffer cells increased TNF-alpha release and TNF-alpha promoter activity in a NF-kappaB-dependent manner. Cu+ but not Cu2+ stimulated TNF-alpha protein release and promoter activity but with less potency. Fe2+ caused a disappearance of the cytosolic inhibitor kappaBalpha, a concomitant increase in nuclear p65 protein, and increased DNA binding of p50/p50 and p65/p50 without affecting activator protein-1 binding. Addition of Fe2+ to the cells resulted in an increase in electron paramagnetic resonance-detectable.OH peaking at 15 min, preceding activation of NF-kappaB but coinciding with activation of inhibitor kappaB kinase (IKK) but not c-Jun NH2-terminal kinase. In conclusion, Fe2+ serves as a direct agonist to activate IKK, NF-kappaB, and TNF-alpha promoter activity and to induce the release of TNF-alpha protein by cultured Kupffer cells in a redox status-dependent manner. We propose that this finding offers a molecular basis for iron-mediated accentuation of TNF-alpha-dependent liver injury.
Department of Pathology, Keck School of Medicine of the University of Southern California, Los Angeles, California 90033-9141, USA.
Hongyun
H
She
Shigang
S
Xiong
Min
M
Lin
Ebrahim
E
Zandi
Cecilia
C
Giulivi
Hidekazu
H
Tsukamoto
D000818:Animals; D002478:Cells, Cultured; D004578:Electron Spin Resonance Spectroscopy; D004789:Enzyme Activation; D005290:Ferric Compounds / Q000494:pharmacology; D005296:Ferrous Compounds / Q000494:pharmacology; D005609:Free Radicals / Q000378:metabolism; D051550:I-kappa B Kinase; D007501:Iron / Q000494:pharmacology*; D007728:Kupffer Cells / Q000187:drug effects / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism / Q000502:physiology*; D009687:Nuclear Proteins / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000187:drug effects / Q000502:physiology; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D051996:Transcription Factor RelA; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000378:metabolism
D005290:Ferric Compounds; D005296:Ferrous Compounds; D005609:Free Radicals; D016328:NF-kappa B; D009687:Nuclear Proteins; D012333:RNA, Messenger; D051996:Transcription Factor RelA; D014409:Tumor Necrosis Factor-alpha; D007501:Iron; D017346:Protein Serine-Threonine Kinases; D051550:I-kappa B Kinase