Tumour promotion versus tumour suppression in chronic hepatic iron overload

Abstract

Although iron-catalysed oxidative damage is presumed to be a major mechanism of injury leading to cirrhosis and hepatocellular carcinoma in hemochromatosis, these events have been difficult to recapitulate in an animal model. In this study, we evaluated regulators of hepatocarcinogenesis in a rodent model of chronic iron overload. Sprague-Dawley rats were iron loaded with iron dextran over 6 months. Livers were harvested and analysed for markers of oxidative stress, as well as the following proteins: p53, murine double minute 2, the Shc proteins p66, p52, p46; β-catenin, CHOP, C/EBPα and Yes-associated protein. In this model, iron loading is associated with hepatocyte proliferation, and indices of oxidative damage are mildly increased in tandem with augmented antioxidant defenses. Alterations potentially favouring carcinogenesis included a modest but significant decrease in p53 levels and increases in p52, p46 and β-catenin levels compared with control livers. Countering these factors, the iron-loaded livers demonstrated a significant decrease in CHOP, which has recently been implicated in the development of hepatocellular carcinoma, as well as a reciprocal increase in C/EBPα and decrease in Yes-associated protein. Our results suggest that chronic iron overload elicits both tumour suppressive as well as tumour-promoting mechanisms in rodent liver.

Strain‐ and time‐dependent alterations in hepatic iron metabolism in a murine model of nonalcoholic steatohepatitis

“…Liver tissue was homogenized in RIPA buffer (50mM Tris, 150mM NaCl, 0.25% sodium deoxycholate, 1% triton‐X, 1mM EDTA, 1mM Na 3 VO 4 ), and the protein concentration of each sample was determined by the Bradford protein assay (BioRad, Hercules, California). Immunoblotting was performed as previously described . Primary antibodies were obtained from the following sources: Sigma, St Louis, Missouri (ferritin; F5012); Santa Cruz Biotechnology, Santa Cruz, California (divalent metal transporter‐1 [DMT‐1]; SC30120); and Alpha Diagnostics International, Inc, San Antonio, Texas (ferroportin [Fpn]; MTP11‐S).…”

“…Immunoblotting was performed as previously described. 27 Primary antibodies were obtained from the following sources: Sigma, St Louis, Missouri (ferritin; F5012); Santa Cruz Biotechnology, Santa Cruz, California (divalent metal transporter-1 [DMT-1]; SC30120); and Alpha Diagnostics International, Inc, San Antonio, Texas (ferroportin [Fpn]; MTP11-S).…”

Sexual dimorphism in the hepatic protein response to a moderate trans fat diet in senescence-accelerated mice

“…The intensity of staining was quantified with Image lab, and the band density of the protein of interest was normalized to the intensity of the Ponceau stain. We and others have shown that protein abundance on nitrocellulose membranes is better quantified with Ponceau staining compared to routine protein loading controls such as beta-actin [ 14 , 15 ]. Results were further normalized to the adult male control diet group, which was given a value of 1.…”

Iron-Induced Liver Injury: A Critical Reappraisal

“…Contrary to the commonly held view of iron as hepatotoxic, there are numerous examples of iron inducing protective responses in the liver, including the upregulation of ferritin, heme oxygenase-1, gamma glutamylcysteine synthetase, cysteine, thioredoxin1, NAD(P)H:quinone oxidoreductase, and tumor suppressor proteins [54,80,87,88].…”