Iron primes hepatic macrophages for NF-kappaB activation in alcoholic liver injury.
NF-kappaB activation induced by lipopolysaccharide (LPS) in cultured hepatic macrophages (HM) may be abrogated by pretreatment of cells with a lipophilic iron chelator, 1,2-dimethyl-3-hydroxypyrid-4-one (L1, deferiprone), suggesting a role for iron in this molecular event [M. Lin, M., R. A. Rippe, O. Niemelä, G. Brittenham, and H. Tsukamoto, Am. J. Physiol. 272 (Gastrointest. Liver Physiol. 35): G1355-G1364, 1997]. To ascertain the relevance in vivo of this hypothesis, HM from an experimental model of alcoholic liver injury were examined for the relationship between nuclear factor (NF)-kappaB activation and iron storage. HM showed a significant increase in nonheme iron concentration (+70%), accompanied by enhanced generation of electron paramagnetic resonance-detected radicals (+200%), NF-kappaB activation (+100%), and tumor necrosis factor-alpha (+150%) and macrophage inflammatory protein-1 (+280%) mRNA induction. Treatment of the cells ex vivo with L1 normalized all these parameters. HM content of ferritin protein, ferritin L chain mRNA, and hemeoxygenase-1 mRNA and splenic content of nonheme iron were increased, suggesting enhanced heme turnover as a cause of the increased iron storage and NF-kappaB activation. To test this possibility, increased iron content in HM was reproduced in vitro by phagocytosis of heat-treated red blood cells. Treatment caused a 40% increase in nonheme iron concentration and accentuated LPS-induced NF-kappaB activation twofold. Both effects could be abolished by pretreatment of cells with zinc protoporphyrin, a hemeoxygenase inhibitor. To extend this observation, animals were splenectomized before 9-wk alcohol feeding. Splenectomy resulted in further increments in HM nonheme iron storage (+60%) and NF-kappaB activation (+90%) and mononuclear cell infiltration (+450%), particularly around the iron-loaded HM in alcohol-fed animals. These results support the pivotal role of heme-derived iron in priming HM for NF-kappaB activation and expression of proinflammatory genes in alcoholic liver injury.
Tsukamoto
H
H
Department of Medicine and Pathology, University of Southern California School of Medicine, Los Angeles 90033, California. htsukamoto@hsc.usc.edu
Lin
M
M
Ohata
M
M
Giulivi
C
C
French
S W
SW
Brittenham
G
G
D000818:Animals; D001052:Apoferritins; D002135:Calcium-Binding Proteins / Q000494:pharmacology; D002492:Central Nervous System Depressants / Q000494:pharmacology; D054407:Chemokine CCL4; D004195:Disease Models, Animal; D004912:Erythrocytes; D000431:Ethanol / Q000494:pharmacology; D005293:Ferritins / Q000235:genetics; D015870:Gene Expression / Q000502:physiology; D006419:Heme Oxygenase (Decyclizing) / Q000235:genetics; D006519:Hepatitis, Alcoholic / Q000188:drug therapy / Q000276:immunology / Q000378:metabolism*; D007501:Iron / Q000378:metabolism*; D007728:Kupffer Cells / Q000187:drug effects / Q000201:enzymology* / Q000276:immunology; D039841:Leukocyte L1 Antigen Complex; D008070:Lipopolysaccharides / Q000494:pharmacology; D008099:Liver / Q000166:cytology / Q000187:drug effects* / Q000276:immunology; D019402:Macrophage Inflammatory Proteins / Q000235:genetics; D008297:Male; D008562:Membrane Glycoproteins / Q000494:pharmacology; D016328:NF-kappa B / Q000276:immunology / Q000378:metabolism*; D019006:Neural Cell Adhesion Molecules / Q000494:pharmacology; D010587:Phagocytosis / Q000276:immunology; D010847:Picolines / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar; D013156:Splenectomy; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics; D051154:Wnt2 Protein
D002135:Calcium-Binding Proteins; D002492:Central Nervous System Depressants; D054407:Chemokine CCL4; D039841:Leukocyte L1 Antigen Complex; D008070:Lipopolysaccharides; D019402:Macrophage Inflammatory Proteins; D008562:Membrane Glycoproteins; D016328:NF-kappa B; D019006:Neural Cell Adhesion Molecules; D010847:Picolines; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D051154:Wnt2 Protein; D000431:Ethanol; C039425:2-tert-butyl-6-methyl-3-hydroxypyridine; D005293:Ferritins; D001052:Apoferritins; D007501:Iron; D006419:Heme Oxygenase (Decyclizing)