Iron overload and liver fibrosis

Hereditary hemochromatosis in the post-HFE era

Following the discovery of the HFE gene in 1996 and its linkage to the iron overload disorder hereditary hemochromatosis (HH) there have been profound developments in our understanding of the pathogenesis of the biochemical and clinical manifestations of a number of iron overload disorders. This article provides an update of recent developments and key issues relating to iron homeostasis and inherited disorders of iron overload, with emphasis on HFE-related HH, and is based on the content of the American Association for the Study of Liver Diseases Single-Topic Conference entitled "Hemochromatosis: What has Happened After HFE?" which was held at the Emory Convention Center in Atlanta, September 7-9, 2007.

Effects of dietary baicalin supplementation on iron overload-induced mouse liver oxidative injury

Iron overload is one of the most common metal related toxicity. Under this circumstance, excessive iron deposition in liver will lead to further injury such as hepatocellular necrosis, inflammation, fibrosis, and in some cases even to carcinoma. In this paper, the effect of a nature flavonoid, baicalin, on iron overload-induced mouse liver oxidative injury has been studied. It was found that when iron-dextran-induced iron overload, mice were fed baicalin-containing diet (0.25% and 1%) for 50 days, hepatic iron, liver-to-body weight ratio, and hepatic lipid peroxidation were dose-dependently decreased; while catalase activity, total antioxidant status, and serum iron content were dose dependently increased. The protective effect of baicalin on liver of iron overload mouse may due to both the antioxidant and iron chelation activities of baicalin. These data provide preliminary experimental support for baicalin as medicine for iron overload diseases.

Orally active iron chelators

In patients with transfusion-dependent anemias, iron accumulation is fatal in the absence of chelating therapy. Extended survival, free of most complications of iron overload is observed in patients treated with early, adequate parenteral deferoxamine. Despite its success in prevention and treatment of iron toxicity, the expense and inconvenience of this therapy have stimulated a continued quest for an effective chelating agent that is orally active. Unfortunately, studies emerging over the last five years have confirmed that the most widely administered orally active agent, deferiprone (L1; 1,2-dimethyl-3-hydropyrid-4-one) may be harmfully ineffective in many patients: 18-65% of patients in six studies which obtained hepatic irons after long term deferiprone treatment had body iron exceeding the threshold for cardiac disease and premature death. The impact of deferiprone on cardiac and liver disease must be evaluated further, while the association between deferiprone and accelerated hepatic fibrosis still awaits refutation in large prospective trials. In view of the striking therapeutic successes of deferoxamine over the past 20 years, administration of deferiprone outside the setting of prospective clinical trials may need to be reconsidered. Meanwhile, an orally active iron chelator of demonstrated safety and effectiveness remains an objective for development for transfused patients.

Iron overload impairs pro-inflammatory cytokine responses by Kupffer cells

AIM

The aim of the present study was to determine the effect of chronic iron overload on Kupffer cell cytokine production.

METHODS

Kupffer cells were isolated from rats that were fed either a control or iron-supplemented diet for 12 months. Cytokine mRNA and protein levels were determined by using a ribonuclease protection assay and ELISA, respectively.

RESULTS

Baseline levels of tumor necrosis factor-alpha, transforming growth factor-beta1, interleukin-6 and granulocyte macrophage colony stimulating factor were similar in iron-loaded and control Kupffer cells. Following the addition of lipopolysaccharide to control cells, tumor necrosis factor-alpha, interleukin-1alpha and interleukin-6 mRNA levels increased. Tumor necrosis factor-alpha mRNA and protein levels were reduced by 40 and 60%, respectively, in iron-loaded cells compared with controls following the addition of lipopolysaccharide. Interleukin-6 mRNA levels in iron-loaded Kupffer cells were also reduced. Granulocyte macrophage colony stimulating factor mRNA levels remained unchanged in controls, but were significantly elevated in iron-loaded cells. Tumor growth factor-beta1 mRNA and protein levels were similar in control and iron-loaded cells.

CONCLUSION

Deposition of iron in Kupffer cells in chronic dietary iron overload results in an impaired pro-inflammatory cytokine response to lipopolysaccharide. Our observations may have relevance to the altered immune function observed in chronic iron-overload syndromes.

Dynamic changes of type I, III and IV collagen synthesis and distribution of collagen-producing cells in carbon tetrachloride-induced rat liver fibrosis

AIM: To find out the relationship between the gene transcription of different types of procollagen and the deposition of the relevant collagens in the liver tissue and to confirm the types of collagen producing cells in liver fibrogenesis.

METHODS: Dynamic changes of the expression of α1(I), α1(III) and α1(IV) procollagen mRNA and relevant collagens and the distribution of collagen producing cells during liver fibrogenesis of rat induced by CCl₄ (20 weeks) were investigated with Northern blot analysis, in situ hybridization and immunohistochemical techniques.

RESULTS: The increased expression of α₁(III) procollagen mRNA by Northern blot analysis was the most predominant one among the three mRNAs during fibrogenesis. However, the enhanced expression of α₁(IV) procollagen mRNA occurred very early while the expression of α1(I) mRNA was not enhanced much until the middle stage of the experiment. Desmin (Dm) positive hepatic stellate cells (HSCs) and few myofibroblasts (MFs) in and around the necrotic areas expressed α1(I), α1(III) and α1(IV) procollagen mRNA signals detected by in situ hybridization at the early stage of the experiment. All the three procollagen mRNA signals thereafter mainly localized in fibroblasts (Fbs) and MFs in fibrotic septa during the middle and late stages of fibrosis, which distributed parallel to the corresponding collagens detected by immunohistochemical study. In addition, the endothelial cells of sinusoids and the small blood vessels within the septa also showed α1(IV) procollagen mRNA and type IV collagen expression

CONCLUSION: It is considered that “HSC-MF-Fb” effect cell system is the major cellular source of collagen production in liver fibrosis, in which HSCs are collagen producing precursor cells in the early liver fibrogenesis, thereafter the synthesis of type I, III and IV collagens (Col I, Col III and Col IV) mainly derives from MFs and Fbs, which play a very important role in the progress of liver fibrosis. The endothelial cells along sinusoids, as another source of Col IV production, might participate in the capillization of liver sinusoids.