Role of iron in NF-kappa B activation and cytokine gene expression by rat hepatic macrophages.
A redox-sensitive nuclear factor, NF-kappa B, induces transcription of tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) in macrophages. The present study has investigated the role of iron in NF-kappa B activation and TNF-alpha and IL-6 expression by rat hepatic macrophages (HM). As an in vivo model, cholestatic liver injury was induced in rats by ligation of the common bile duct (BDL). During the first 2 wk after BDL, there was an increase in the hepatic level of thiobarbituric acid-reactive substances (TBARS) that was accompanied by the appearance of protein-malondialdehyde adducts in the periportal region. This increase was reduced after 3 wk. TNF-alpha and IL-6 mRNA levels in HM from the BDL rats were increased at 1 and 2 wk and attenuated at 3 wk. Gel mobility shift assay of HM nuclear extracts demonstrated the similar temporal pattern of enhanced NF-kappa B binding activity. Treatment of the BDL animals with 1,2-dimethyl-3-hydroxypyrid-4-one (L-1), a lipophilic iron chelator, suppressed the increases in hepatic TBARS by 64%, plasma alanine aminotransferase by 45%, and HM TNF-alpha and IL-6 mRNA by > 84%. Concomitantly, the HM NF-kappa B binding activity was reduced close to the level observed in sham-operated rats. Treatment of cultured HM with L-1 also blocked lipopolysaccharide-stimulated NF-kappa B activation and TNF-alpha and IL-6 expression at mRNA and protein levels. These results demonstrate that the iron chelator effectively blocks NF-kappa B activation and coordinate TNF-alpha and IL-6 gene upregulation by HM in cholestatic liver injury or under in vitro lipopolysaccharide stimulation. These findings support a pivotal role for iron in activation of NF-kappa B and cytokine gene expression by HM in vitro and in vivo.
Lin
M
M
Division of Gastrointestinal and Liver Diseases, University of Southern California School of Medicine, Los Angeles 90033-4581, USA.
Rippe
R A
RA
Niemelä
O
O
Brittenham
G
G
Tsukamoto
H
H
D000818:Animals; D002779:Cholestasis / Q000503:physiopathology*; D003135:Common Bile Duct; D016207:Cytokines / Q000096:biosynthesis*; D000077543:Deferiprone; D015850:Interleukin-6 / Q000096:biosynthesis; D007501:Iron / Q000378:metabolism*; D007502:Iron Chelating Agents / Q000494:pharmacology; D007728:Kupffer Cells / Q000187:drug effects / Q000502:physiology*; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D008315:Malondialdehyde / Q000032:analysis; D016328:NF-kappa B / Q000378:metabolism*; D011728:Pyridones / Q000494:pharmacology*; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D017208:Rats, Wistar; D017392:Thiobarbituric Acid Reactive Substances / Q000378:metabolism; D013997:Time Factors; D014158:Transcription, Genetic; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis
D016207:Cytokines; D015850:Interleukin-6; D007502:Iron Chelating Agents; D016328:NF-kappa B; D011728:Pyridones; D012333:RNA, Messenger; D017392:Thiobarbituric Acid Reactive Substances; D014409:Tumor Necrosis Factor-alpha; D000077543:Deferiprone; D008315:Malondialdehyde; D007501:Iron