A long-term study of the interaction between iron and alcohol in an animal model of iron overload

Fetal Alcohol Spectrum Disorder and Iron Homeostasis

Prenatal alcohol exposure results in a spectrum of behavioral, cognitive, and morphological abnormalities collectively referred to as fetal alcohol spectrum disorder (FASD). FASD presents with significant phenotypic variability and may be modified by gestational variables such as maternal nutritional status. Iron serves a critical function in the development of and processes within central nervous system (CNS) structures. Gestational iron deficiency alters CNS development and may contribute to neurodevelopmental impairment in FASD. This review explores the relationship between iron deficiency and fetal alcohol spectrum disorder as described in small animal and human studies. Consideration is given to the pathophysiologic mechanisms linking iron homeostasis and prenatal alcohol exposure. Existing data suggest that iron deficiency contributes to the severity of FASD and provide a mechanistic explanation linking these two conditions.

Hepcidin and Iron Metabolism in Experimental Liver Injury

The liver plays a pivotal role in the regulation of iron metabolism through its ability to sense and respond to iron stores by release of the hormone hepcidin. Under physiologic conditions, regulation of hepcidin expression in response to iron status maintains iron homeostasis. In response to tissue injury, hepcidin expression can be modulated by other factors, such as inflammation and oxidative stress. The resulting dysregulation of hepcidin is proposed to account for alterations in iron homeostasis that are sometimes observed in patients with liver disease. This review describes the effects of experimental forms of liver injury on iron metabolism and hepcidin expression. In general, models of acute liver injury demonstrate increases in hepcidin mRNA and hypoferremia, consistent with hepcidin's role as an acute-phase reactant. Conversely, diverse models of chronic liver injury are associated with decreased hepcidin mRNA but with variable effects on iron status. Elucidating the reasons for the disparate impact of different chronic injuries on iron metabolism is an important research priority, as is a deeper understanding of the interplay among various stimuli, both positive and negative, on hepcidin regulation. Future studies should provide a clearer picture of how dysregulation of hepcidin expression and altered iron homeostasis impact the progression of liver diseases and whether they are a cause or consequence of these pathologies.

Effects of long-term ethanol ingestion on hepatic iron metabolism in two mouse strains

The mechanisms responsible for dysregulation of iron metabolism in response to ethanol ingestion are poorly understood. Relatively brief ethanol exposures in rodents are associated with reduced hepatic hepcidin expression without increases in hepatic iron content. This study evaluated the effects of long-term ethanol treatment on hepatic iron metabolism in two mouse strains. Ethanol was administered in the drinking water to C57BL/6 and BALB/c mice for up to 11 months. Hepatic histology and iron concentrations (HIC) were assessed, along with expression of relevant genes and proteins by real-time RT-PCR and western blot, respectively. The livers of ethanol-consuming mice of both strains showed mild steatosis without inflammation or fibrosis. Stainable hepatocyte iron was modestly increased in both strains ingesting ethanol, although hepatic iron concentrations were significantly higher only in C57BL/6 mice. Long-term ethanol did not affect hepcidin mRNA (Hamp1 or Hamp2) in either strain, nor was the expression of several oxidative stress-responsive genes (glutamate cysteine ligase, gamma-glutamyl transpeptidase, heme oxygenase-1 and growth differentiation factor 15) altered in response to ethanol, suggesting that oxidative stress and suppression of hepcidin expression in short-term ethanol feeding models may be transient phenomena that resolve as mice adapt to ethanol exposure. This murine model of chronic ethanol ingestion demonstrates modest increases in hepatic iron without changes in hepcidin expression, markers of oxidative stress or significant histologic liver injury. Further investigations are needed to characterize the mechanisms of dysregulated iron metabolism resulting from chronic ethanol ingestion.

Computational and biological investigation of the soybean lecithin-gallic acid complex for ameliorating alcoholic liver disease in mice with iron overload

Alcoholic liver disease (ALD) is associated with significant morbidity and mortality globally. In this study, the soybean lecithin-gallic acid complex was synthesized, and its physicochemical properties were evaluated, which confirmed the complex formation. Compared with the free state of the drug, gallic acid exhibited significantly different physicochemical properties after it was complexed with soybean lecithin. To clarify the binding mode between two monomers, computational investigation was performed. From the computational data, we deduced the structure of the compound and predicted that it has a high affinity for human phosphatidylcholine transfer protein and exhibits strong pharmacological activities in vivo. The complex not only effectively ameliorated liver fibrosis, lipid peroxidation, and oxidative stress, but also reduced liver iron overload in a mouse ALD model induced by alcohol (p < 0.05). Additionally, it regulated iron metabolism by inhibiting TfR1 expression (p < 0.05) and promoting hepcidin expression (p < 0.05). These results suggest that the soybean lecithin-gallic acid complex ameliorates hepatic damage and iron overload induced by alcohol and exert hepatoprotective effects.

Iron-Induced Liver Injury: A Critical Reappraisal

Iron is implicated in the pathogenesis of a number of human liver diseases. Hereditary hemochromatosis is the classical example of a liver disease caused by iron, but iron is commonly believed to contribute to the progression of other forms of chronic liver disease such as hepatitis C infection and nonalcoholic fatty liver disease. In this review, we present data from cell culture experiments, animal models, and clinical studies that address the hepatotoxicity of iron. These data demonstrate that iron overload is only weakly fibrogenic in animal models and rarely causes serious liver damage in humans, calling into question the concept that iron overload is an important cause of hepatotoxicity. In situations where iron is pathogenic, iron-induced liver damage may be potentiated by coexisting inflammation, with the resulting hepatocyte necrosis an important factor driving the fibrogenic response. Based on the foregoing evidence that iron is less hepatotoxic than is generally assumed, claims that assign a causal role to iron in liver injury in either animal models or human liver disease should be carefully evaluated.

An ellagic acid isolated from Clerodendrum viscosum leaves ameliorates iron-overload induced hepatotoxicity in Swiss albino mice through inhibition of oxidative stress and the apoptotic pathway

Iron is a vital element required for normal cellular physiology in animal systems, but excess iron accumulation in the biological system accelerates oxidative stress, cellular toxicity, tissue injury and organ fibrosis, which ultimately leads to the generation of chronic liver diseases including cancer. A natural antioxidant, ellagic acid (EA) has been previously reported for its pharmacological properties; however, there is no significant evidence available that could illustrate its protective potential against iron-overload induced hepatotoxicity. In the present work, EA was evaluated for its in vitro free radical scavenging and iron chelation potentials. Further, EA was tested in vivo for its protective activity against iron overload-induced hepatotoxicity in Swiss albino mice by evaluating liver iron content, reactive oxygen species (ROS), liver antioxidant enzymes, serum marker levels, liver damage and fibrosis, histopathological study and finally western blotting analysis. EA treatment significantly decreased liver iron and serum ferritin levels. Elevated ROS levels, decreased antioxidant parameters and elevated serum markers were normalized upon treatment with EA. Cellular morphology, iron -overload and liver fibrosis were found to be effectively ameliorated. Finally, the protective effect of EA against iron overload-induced apoptosis was confirmed by western blotting when its treatment upregulated the expressions of caspase-3 and poly(ADP-ribose) polymerase (PARP) proteins. EA revealed hepatoprotective activity against iron overload-induced toxicity through scavenging free radicals, inhibiting excess ROS production, normalizing liver damage parameters and upregulating caspase-3, PARP expression. Collectively, our findings support the possible use of the natural antioxidant EA as a promising candidate against iron-overloaded diseases.

Iron Supplementation Reverses the Reduction of Hydroxymethylcytosine in Hepatic DNA Associated With Chronic Alcohol Consumption in Rats

Background

Alcohol is known to affect two epigenetic phenomena, DNA methylation and DNA hydroxymethylation, and iron is a cofactor of ten-eleven translocation (TET) enzymes that catalyze the conversion from methylcytosine to hydroxymethylcytosine. In the present study we aimed to determine the effects of alcohol on DNA hydroxymethylation and further effects of iron on alcohol associated epigenetic changes.

Methods

Twenty-four male Sprague-Dawley rats were fed either Lieber-DeCarli alcohol diet (36% calories from ethanol) or Lieber-DeCarli control diet along with or without iron supplementation (0.6% carbonyl iron) for 8 weeks. Hepatic non-heme iron concentrations were measured by colorimetric assays. Protein levels of hepatic ferritin and transferrin receptor were determined by Western blotting. Methylcytosine, hydroxymethylcytosine and unmodified cytosine in DNA were simultaneously measured by liquid chromatography/mass spectrometry method.

Results

Iron supplementation significantly increased hepatic non-heme iron contents (P < 0.05) but alcohol alone did not. However, both alcohol and iron significantly increased hepatic ferritin levels and decreased hepatic transferrin receptor levels (P < 0.05). Alcohol reduced hepatic DNA hydroxymethylation (0.21% ± 0.04% vs. 0.33% ± 0.04%, P = 0.01) compared to control, while iron supplementation to alcohol diet did not change DNA hydroxymethylation. There was no significant difference in methylcytosine levels, while unmodified cytosine levels were significantly increased in alcohol-fed groups compared to control (95.61% ± 0.08% vs. 95.26% ± 0.12%, P = 0.03), suggesting that alcohol further increases the conversion from hydroxymethylcytosine to unmodified cytosine.

Conclusions

Chronic alcohol consumption alters global DNA hydroxymethylation in the liver but iron supplementation reverses the epigenetic effect of alcohol.

Decreased hepatic iron in response to alcohol may contribute to alcohol-induced suppression of hepcidin

Hepatic Fe overload has often been reported in patients with advanced alcoholic liver disease. However, it is not known clearly whether it is the effect of alcohol that is responsible for such overload. To address this lacuna, a time-course study was carried out in mice in order to determine the effect of alcohol on Fe homoeostasis. Male Swiss albino mice were pair-fed Lieber-DeCarli alcohol diet (20 % of total energy provided as alcohol) for 2, 4, 8 or 12 weeks. Expression levels of duodenal and hepatic Fe-related proteins were determined by quantitative PCR and Western blotting, as were Fe levels and parameters of oxidative stress in the liver. Alcohol induced cytochrome P4502E1 and oxidative stress in the liver. Hepatic Fe levels and ferritin protein expression dropped to significantly lower levels after 12 weeks of alcohol feeding, with no significant effects at earlier time points. This was associated, at 12 weeks, with significantly decreased liver hepcidin expression and serum hepcidin levels. Protein expressions of duodenal ferroportin (at 8 and 12 weeks) and divalent metal transporter 1 (at 8 weeks) were increased. Serum Fe levels rose progressively to significantly higher levels at 12 weeks. Histopathological examination of the liver showed mild steatosis, but no stainable Fe in mice fed alcohol for up to 12 weeks. In summary, alcohol ingestion by mice in this study affected several Fe-related parameters, but produced no hepatic Fe accumulation. On the contrary, alcohol-induced decreases in hepatic Fe levels were seen and may contribute to alcohol-induced suppression of hepcidin.

Nerium indicum leaf alleviates iron-induced oxidative stress and hepatic injury in mice

CONTEXT

Nerium indicum Mill. (Apocynaceae) was reported for its efficient in vitro antioxidant and iron-chelating properties.

OBJECTIVE

This study demonstrates the effect of 70% methanol extract of N. indicum leaf (NIME) towards in vitro DNA protection and ameliorating iron-overload-induced liver damage in mice.

MATERIALS AND METHODS

Phytochemical and HPLC analyses were carried out to standardize the extract and the effect of Fe(2+)-mediated pUC18 DNA cessation was studied. Thirty-six Swiss Albino mice were divided into six groups of blank, negative control (iron overload only), and iron-overloaded mice receiving 50, 100, and 200 mg/kg b.w. doses of NIME and desirox (20 mg/kg b.w.). The biochemical markers of hepatic damage, various liver and serum parameters, and reductive release of ferritin iron were studied.

RESULTS AND DISCUSSION

The presence of different phytocomponents was revealed from phytochemical and HPLC analyses. A substantial supercoiled DNA protection, with [P]50 of 70.33 ± 0.32 µg, was observed. NIME (200 mg/kg b.w.) significantly normalized the levels of alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, and bilirubin by 126.27, 125.25, 188.48, and 45.47%, respectively. NIME (200 mg/kg b.w.) was shown to alleviate the reduced levels of superoxide dismutase, catalase, glutathione-S-transferase, and non-enzymatic-reduced glutathione, by 48.95, 35.9, 35.42, and 13.22%, respectively. NIME also lowered raised levels of lipid peroxidation, protein carbonyl, hydroxyproline, and liver iron by 32.28, 64.58, 136.81, and 83.55%, respectively.

CONCLUSION

These findings suggest that the active substances present in NIME may be capable of lessening iron overload-induced toxicity, and possibly be a useful drug for iron-overloaded diseases.

An Antioxidant Extract of the Insectivorous Plant Drosera burmannii Vahl. Alleviates Iron-Induced Oxidative Stress and Hepatic Injury in Mice

Free iron typically leads to the formation of excess free radicals, and additional iron deposition in the liver contributes to the oxidative pathologic processes of liver disease. Many pharmacological properties of the insectivorous plant Drosera burmannii Vahl. have been reported in previous studies; however, there is no evidence of its antioxidant or hepatoprotective potential against iron overload. The antioxidant activity of 70% methanolic extract of D. burmannii (DBME) was evaluated. DBME showed excellent DPPH, hydroxyl, hypochlorous, superoxide, singlet oxygen, nitric oxide, peroxynitrite radical and hydrogen peroxide scavenging activity. A substantial iron chelation (IC₅₀ = 40.90 ± 0.31 μg/ml) and supercoiled DNA protection ([P]₅₀ = 50.41 ± 0.55 μg) were observed. DBME also displayed excellent in vivo hepatoprotective activity in iron-overloaded Swiss albino mice compared to the standard desirox treatment. Administration of DBME significantly normalized serum enzyme levels and restored liver antioxidant enzymes levels. DBME lowered the raised levels of liver damage parameters, also reflected from the morphological analysis of the liver sections. DBME also reduced liver iron content by 115.90% which is also seen by Perls’ staining. A phytochemical analysis of DBME confirms the presence of various phytoconstituents, including phenols, flavonoids, carbohydrates, tannins, alkaloids and ascorbic acid. Alkaloids, phenols and flavonoids were abundantly found in DBME. An HPLC analysis of DBME revealed the presence of purpurin, catechin, tannic acid, reserpine, methyl gallate and rutin. Purpurin, tannic acid, methyl gallate and rutin displayed excellent iron chelation but exhibited cytotoxicity toward normal (WI-38) cells; while DBME found to be non-toxic to the normal cells. These findings suggest that the constituents present in DBME contributed to its iron chelation activity. Additional studies are needed to determine if DBME can be used as a treatment for iron overload diseases.

Abnormal serum iron markers in chronic hepatitis B virus infection may be because of liver injury

OBJECTIVE

In patients with chronic hepatitis B virus (HBV) infection, it is not known whether altered serum iron markers are directly because of the infection or the associated liver injury. We determined the serum iron status of patients with chronic HBV infection, and investigated whether it is HBV infection or HBV-related liver injury that likely causes abnormal serum iron markers in chronic HBV infection.

MATERIALS AND METHODS

For a retrospective study, chronic HBV-infected patients (80 patients with cirrhosis and 76 patients without cirrhosis) and 58 healthy controls were enrolled. Serum alanine transaminase levels were measured to ascertain liver damage. Indicators of iron status included serum iron, ferritin, and transferrin.

RESULTS

Compared with noncirrhotic patients and healthy controls, the serum transferrin of cirrhotic patients was lower and the serum iron and ferritin values were higher (P < 0.001, all). In cirrhotic patients, the serum iron and ferritin levels correlated positively with serum alanine transaminase levels and the transferrin levels were inversely related to both end-stage liver disease scores and iron levels (all P < 0.01).

CONCLUSION

Serum iron markers tended to be aberrant in chronic HBV-infected patients with cirrhosis. The liver injury associated with HBV infection, but not chronic HBV infection directly, is likely the main cause for iron metabolism disorder.

CHOP-mediated hepcidin suppression modulates hepatic iron load

The liver is the central regulator of iron metabolism and accordingly, chronic liver diseases often lead to systemic iron overload due to diminished expression of the iron-regulatory hormone hepcidin. To study the largely unknown regulation of iron metabolism in the context of hepatic disease, we used two established models of chronic liver injury, ie repeated carbon tetrachloride (CCl(4)) or thioacetamide (TAA) injections. To determine the impact of CCAAT/enhancer-binding protein (C/EBP)-homologous protein (CHOP) on hepcidin production, the effect of a single TAA injection was determined in wild-type and CHOP knockout mice. Furthermore, CHOP and hepcidin expression was assessed in control subjects and patients with alcoholic liver disease. Both chronic injury models developed a distinct iron overload in macrophages. TAA-, but not CCl(4) - injected mice displayed additional iron accumulation in hepatocytes, resulting in a significant hepatic and systemic iron overload which was due to suppressed hepcidin levels. C/EBPα signalling, a known hepcidin inducer, was markedly inhibited in TAA mice, due to lower C/EBPα levels and overexpression of CHOP, a C/EBPα inhibitor. A single TAA injection resulted in a long-lasting (> 6 days) suppression of hepcidin levels and CHOP knockouts (compared to wild-types) displayed significantly attenuated hepcidin down-regulation in response to acute TAA administration. CHOP mRNA levels increased 5-fold in alcoholic liver disease patients versus controls (p < 0.005) and negatively correlated with hepcidin expression. Our results establish CHOP as an important regulator of hepatic hepcidin expression in chronic liver disease. The differences in iron metabolism between the two widely used fibrosis models likely reflect the differential regulation of hepcidin expression in human liver disease.

Accelerated CCl4-induced liver fibrosis in Hjv-/- mice, associated with an oxidative burst and precocious profibrogenic gene expression

Hereditary hemochromatosis is commonly associated with liver fibrosis. Likewise, hepatic iron overload secondary to chronic liver diseases aggravates liver injury. To uncover underlying molecular mechanisms, hemochromatotic hemojuvelin knockout (Hjv-/-) mice and wild type (wt) controls were intoxicated with CCl(4). Hjv-/- mice developed earlier (by 2-4 weeks) and more acute liver damage, reflected in dramatic levels of serum transaminases and ferritin and the development of severe coagulative necrosis and fibrosis. These responses were associated with an oxidative burst and early upregulation of mRNAs encoding α1-(I)-collagen, the profibrogenic cytokines TGF-β1, endothelin-1 and PDGF and, notably, the iron-regulatory hormone hepcidin. Hence, CCl4-induced liver fibrogenesis was exacerbated and progressed precociously in Hjv-/- animals. Even though livers of naïve Hjv-/- mice were devoid of apparent pathology, they exhibited oxidative stress and immunoreactivity towards α-SMA antibodies, a marker of hepatic stellate cells activation. Furthermore, they expressed significantly higher (2-3 fold vs. wt, p<0.05) levels of α1-(I)-collagen, TGF-β1, endothelin-1 and PDGF mRNAs, indicative of early fibrogenesis. Our data suggest that hepatic iron overload in parenchymal cells promotes oxidative stress and triggers premature profibrogenic gene expression, contributing to accelerated onset and precipitous progression of liver fibrogenesis.

Hepcidin modulation in human diseases: From research to clinic

By modulating hepcidin production, an organism controls intestinal iron absorption, iron uptake and mobilization from stores to meet body iron need. In recent years there has been important advancement in our knowledge of hepcidin regulation that also has implications for understanding the physiopathology of some human disorders. Since the discovery of hepcidin and the demonstration of its pivotal role in iron homeostasis, there has been a substantial interest in developing a reliable assay of the hormone in biological fluids. Measurement of hepcidin in biological fluids can improve our understanding of iron diseases and be a useful tool for diagnosis and clinical management of these disorders. We reviewed the literature and our own research on hepcidin to give an updated status of the situation in this rapidly evolving field.

Hepcidin is down-regulated in alcoholic liver injury: implications for the pathogenesis of alcoholic liver disease

BACKGROUND

Alcoholic liver disease is known to be associated with abnormal iron homeostasis, and iron metabolism itself is regulated by the liver-derived peptide hepcidin. Both CCAAT enhancer binding protein alpha (C/EBPalpha) and interleukin 6 (IL-6) have been shown to regulate hepcidin gene transcription.

AIM

To investigate mechanisms underlying alcohol-induced disturbances in iron homeostasis by measuring the expression of hepcidin and C/EBPalpha mRNA using in vivo and in vitro models of alcoholic liver injury.

METHODS

Male rats were pair-fed an alcoholic liquid diet for 12 weeks. RT-PCR was performed on liver tissue using specific primers for hepcidin and C/EBPalpha. The effect of alcohol on hepcidin and C/EBPalpha gene expression was also determined in isolated hepatocytes, HuH-7 cells and HepG2 cells treated with 50 mM ethanol, 200 microM acetaldehyde, and/or 20 ng/ml IL-6.

RESULTS

Hepcidin and C/EBPalpha mRNA expression were significantly decreased in alcohol-fed rats compared with pair-fed controls (6-fold p < 0.001 and 2.2-fold p < 0.0002 reduction, respectively) and hepatic lipid peroxidation was increased by 32.5% (p < 0.05) in alcohol-fed rats compared with controls. Hepcidin gene expression was not altered significantly in cells cultured in the presence of 50 mM ethanol. Following 24 hour stimulation by IL-6, there was a 4-fold increase in hepcidin expression in hepatocytes and a 9-fold increase in HuH-7 cells. Ethanol (50 mM) attenuated the IL-6-induced increase in hepcidin expression in HuH-7 cells (9-fold to a 4-fold increase) but not in hepatocytes. Acetaldehyde had no effect on hepcidin gene expression in cells in culture.

CONCLUSION

The down-regulation of hepcidin and C/EBPalpha gene expression shown in vivo implies disturbed iron sensing contributing to the hepatosiderosis seen in alcoholic liver disease, possibly by mechanisms involving the IL-6 signaling cascade.

Dietary supplementation of baicalin and quercetin attenuates iron overload induced mouse liver injury

The introduction of new iron chelating drugs may ultimately improve iron-chelation therapy for patients with iron overload diseases such as thalassaemia and other disorders. In this paper, the in vivo effects of baicalin and quercetin on iron overload induced liver injury were studied on mice. It was found that when iron-dextran induced iron overload mice were fed baicalin or quercetin containing diet (1% w/w) for 45 days, both flavonoids significantly inhibited iron overload induced lipid peroxidation and protein oxidation of liver, decreased hepatic iron and hepatic collagen content, increased the serum non-heme iron level but not serum ferritin level. Flavonoids supplementation also increased the excretion of iron through feces. In vitro study demonstrated that both flavonoids could release iron from ferritin. These results indicate that besides acting as antioxidants, both flavonoids can also release iron from liver and finally excrete it through feces. The present study provides further support for flavonoids to be medicines for iron overload diseases.

Effect of hepatic iron concentration reduction on hepatic fibrosis and damage in rats with cholestatic liver disease

AIM: To assess the effect of iron reduction after phlebotomy in rats with “normal” hepatic iron concentration (HIC) on the progression of hepatic fibrosis, as a result of bile duct ligation (BDL).

METHODS: Rats underwent phlebotomy before or after sham operation or BDL. Animals undergone only BDL or sham operation served as controls. Two weeks after surgery, indices of hepatic damage and fibrosis were evaluated.

RESULTS: Phlebotomy lowered HIC. Phlebotomy after BDL was associated with body weight increase, lower hepatic weight, less portal hypertension, less periportal necrosis, less portal inflammation, lower hepatic activity index score and higher albumin levels. On the other hand, phlebotomy before BDL was associated with body weight decrease and hepatic activity index score increase. Phlebotomy after sham operation was not associated with any hepatic or systemic adverse effects.

CONCLUSION: Reduction of HIC after induction of liver damage may have beneficial effects in BDL rats. However, iron deficiency could induce impairment of liver function and may make the liver more susceptible to insults like BDL.

Effect of alcohol on viral hepatitis and other forms of liver dysfunction

Alcohol is a known hepatotoxic agent, which may exacerbate liver injury caused by other agents. The wide prevalence of alcohol use and abuse in society makes it an important cofactor in many other liver diseases. Examples of liver diseases that are significantly influenced by ingestion of alcohol include chronic viral hepatitis, disorders of iron overload, and obesity-related liver disease.

Iron overload enhances the development of experimental liver cirrhosis in mice

The role of iron in initiating liver fibrosis in iron overload diseases is not clearly established. Partly, this is due to the lack of suitable animal models that can produce the full liver pathology seen in genetic hemochromatosis. Recent advances in this field have demonstrated that iron may be interacting with other potential liver-damaging agents. The aim of this study was to investigate if feeding with carbonyl iron (CI) facilitates the development of carbon tetrachloride (CCl4)-induced liver fibrosis in the mouse. Mice were given a diet containing 3% CI and treated with CCl4 intraperitoneally twice weekly and 5% alcohol added to the drinking water for 12 weeks. Hepatic iron content increased 15- and 22-fold in animals receiving CI and CI + CCl4. At histological examination, iron-laden hepatocytes were found in CI treated animals, whereas these were absent in animals not exposed to CI. Mice receiving iron-enriched diet alone showed a mild fibrosis. Conversely, a marked collagen deposition was observed in CCl4 and CI + CCl4 groups. In particular, in this latter group, there was evidence of liver cirrhosis. Biochemical evaluation of collagen content substantiated histologic analysis. These results demonstrate that the addition of iron facilitates the development of cirrhosis in animals exposed to subtoxic doses of CCl4. This model may be useful in exploring the pathogenesis of liver cirrhosis. Moreover, its use in genetically altered mouse strains might provide new insight on the role of iron in fibrosis.

Effect of free iron on collagen synthesis, cell proliferation and MMP-2 expression in rat hepatic stellate cells

Various studies on hepatic fibrosis occurring in iron overload suggest that excess of tissue iron may be involved in the stimulation of collagen synthesis. Anyway, up to date, direct evidence on the role of iron in hepatic fibrosis is lacking. Moreover, it is not clear whether iron acts as direct initiator of fibrogenesis or as mediator of hepatocellular necrosis. In the present study, we investigated the effect of nontoxic doses of iron on collagen metabolism and proliferation, key features of liver fibrosis, by means of cultures of hepatic stellate cells, the liver cells responsible for collagen production. Iron treatment increased collagen synthesis without affecting noncollagen proteins. The maximum effect was observed at 5 microM iron (+132%). At this dose, no cell damage or proliferation was detected. Conversely, higher doses of iron (10 and 25 microM) induced cell proliferation and a lower increase in collagen synthesis, suggesting the prevalence of proliferative effect on the synthetic one. These effects occurred without the intervention of serum factors and were not mediated by lipid peroxidation. Our results strongly support the hypothesis that iron "per sé" may act as a profibrogenic agent. Finally, we provide evidence that iron plays a role also in matrix degradation, by stimulating some metalloprotease activities. Iron treatment increased metalloprotease-2 activity in hepatic stellate cells, while no changes were observed for interstitial collagenase activity suggesting that, in these conditions, a pathological accumulation of hepatic extracellular matrix may occur.

Hereditary haemochromatosis: detection and management

Hereditary haemochromatosis is common, affecting one in 200 Australians of Anglo-Celtic descent; it results in iron overload affecting many organs, including the liver, heart, endocrine and musculoskeletal system. Diagnosis requires a high index of suspicion, as presenting symptoms and signs may be non-specific. Once suspected, hereditary haemochromatosis can be readily diagnosed by measurement of serum transferrin saturation and ferritin level, followed by genetic assessment. Homozygosity for the C282Y mutation in the HFE gene accounts for most cases in people of Anglo-Celtic descent in Australia; a genetic test for this mutation is widely available. Liver biopsy is advocated only in selected individuals at risk of cirrhosis or with an unclear diagnosis. Therapeutic phlebotomy remains the treatment and, if instituted early, will prevent many of the organ-specific complications.

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.

Use of rat models to mimic alterations in iron homeostasis during human alcohol abuse and cirrhosis

With alcoholism, there are marked disturbances in iron homeostasis that are linked to alterations in serum transferrin and ferritin concentrations. This study identifies rat models of alcohol abuse that closely mimic these disturbances. Male rats were placed in one of the following three protocols: (1) pair-feeding of liquid diets for 1-8 weeks; (2) agar-block feeding for 8 weeks; or (3) generation of cirrhosis with CCl(4). Serum samples were analyzed for ferritin, transferrin, and iron levels, and the transferrin iron saturation and ferritin/transferrin ratios were calculated. Liver iron concentrations were also determined. Serum transferrin levels were elevated in animals fed alcohol for 8 weeks in pair-feeding and agar-block feeding protocols, but reduced in rats with cirrhosis. Serum ferritin concentration was reduced in rats fed ethanol in the liquid diet, but increased in rats consuming ethanol in agar blocks, in rats pair-fed the liquid control diet, and in rats with cirrhosis. This finding was mirrored by liver nonheme iron concentrations in all experimental groups, but not in the corresponding control groups. Serum iron levels were significantly elevated only in rats fed the liquid control diet. There was a progressive decrease in transferrin iron saturation and ferritin/transferrin ratios for animals fed ethanol in the liquid diet, but not when ethanol was ingested from agar blocks. The development of cirrhosis resulted in elevated liver iron concentrations and doubled ferritin/transferrin ratios. It is concluded that these models may be used to study disturbances in iron homeostasis that occur during alcohol abuse and the (subsequent) development of liver disease.

Characterization of hepatic iron overload following dietary administration of dicyclopentadienyl iron (Ferrocene) to mice: cellular, biochemical, and molecular aspects

A unique organic form of iron (dicyclopentadienyl iron; ferrocene) has been used to further elucidate specific hepatic histopathologic, biochemical, and molecular parameters associated with dietary iron overload. Male C57BL/6Ibg mice fed a diet containing 0.04-0.2% w/w ferrocene for 115 days displayed severe hepatic siderosis of hepatocytes accompanied by a 15-fold induction of nonheme iron content compared to control mice receiving a diet with normal amounts of iron. The ferrocene treatment led to significant increases in hepatocellular necrosis as measured by plasma alanine aminotransferase activity. Histological assessment of hepatic fibrosis revealed mild increases in collagen deposition localized with accumulations of hemosiderin primarily in centrilobular hepatocytes. Hepatic fibrosis was confirmed by measurement of hepatic hydroxyproline content that was increased 4-fold in ferrocene-fed animals compared to control animals not ingesting ferrocene. Hepatic siderosis was accompanied by significant increases in hepatic malondialdehyde content suggesting the ferrocene-induced iron burden initiated lipid peroxidation in vivo. Expression of the heavy-chain isoform of ferritin mRNA and protein measured in liver after ferrocene feeding was increased approximately 8- and 2-fold, respectively, compared to the appropriate controls. These results, using an organic form of iron fed to genetically well-characterized inbred mice, provide new additional insight into the specific molecular and biochemical events that occur in association with histopathologic changes initiated by iron-induced liver injury. These data support the hypothesis that peroxidation of cellular membrane lipids is an important mechanism involved in the toxicity of excess hepatic iron and possibly the initiation of liver fibrogenesis. The results presented here also provide novel in vivo evidence documenting the cellular modulation of ferritin in response to the toxic effects of hepatic iron overloading and iron-mediated oxidative stress.

Interrelationships of alcohol and iron in liver disease with particular reference to the iron-binding proteins, ferritin and transferrin

It is known that the regular consumption of alcohol is responsible for the disruption of normal iron metabolism in humans, resulting in the excess deposition of iron in the liver in approximately one-third of alcoholic subjects. The mechanisms involved are largely unknown; however, it is likely that the two major proteins of iron metabolism, ferritin and transferrin are intimately involved in the process. Tissue damage in alcoholic liver disease and the inherited iron-overload disease, haemochromatosis, are caused by excess alcohol and iron, respectively. The mechanisms of this damage are believed to be similar in both disease conditions and involve free radical-mediated toxicity. A high proportion of haemochromatosis sufferers consume excessive amounts of alcohol and synergistic hepatotoxic events may occur leading to the earlier development of liver cirrhosis. This review describes briefly the role of ferritin and transferrin in normal iron metabolism and in iron overload disease and explores the possible involvement of these proteins in the pathophysiology of excess iron deposition in alcoholic subjects.

Alcohol-induced pancreatic oxidative stress: protection by phospholipid repletion

Oxidative stress is considered to be a forerunner of pancreatitis. Since we had found polyenylphosphatidylcholine, a mixture of polyunsaturated phosphatidylcholines extracted from soybeans, to protect against hepatic oxidative stress, we now tested its effects on the pancreas. Sprague-Dawley rats were pair-fed for two months nutritionally adequate liquid diet containing ethanol (36% of energy) or isocaloric carbohydrate, with either polyenylphosphatidylcholine (3 g/1000 kcal) or safflower oil, with or without 5 g/1000 kcal carbonyl iron. Parameters of oxidative stress (F2-isoprostanes, 4-hydroxynonenal, reduced glutathione), ubiquinol-10, ubiquinol-9 and vitamin E, as well as phosphatidylcholine species, were assessed by GC/MS and/or HPLC. Alcohol feeding increased pancreatic 4-hydroxynonenal three-fold, F2-isoprostanes and ubiquinol-9 by more than 70%, whereas it decreased total phospholipids, several phosphatidylcholine species, ubiquinol-10 and glutathione, especially in iron fed rats. Polyenylphosphatidylcholine prevented the rise in 4-hydroxynonenal and F2-isoprostanes, the decrease in dilinoleoylphosphatidylcholine and oleoyllinoleoylphosphatidylcholine and opposed the alcohol-induced decrease of glutathione; alpha-tocopherol remained unchanged. Iron had no significant effect except for decreasing ubiquinol-10 in the pancreas and increasing aminotransferases in the plasma. Thus, the alcohol-induced oxidative stress in the pancreas was shown to be prevented by polyenylphosphatidylcholine which may act, in part, by correcting the depletion of several phosphatidylcholine species.

Relative and combined effects of ethanol and protein deficiency on zinc, iron, copper, and manganese contents in different organs and urinary and fecal excretion

The relative contribution of protein deficiency to the altered metabolism of certain trace elements in chronic alcoholics is not well defined, so this study was performed to analyse the relative and combined effects of ethanol and protein deficiency on liver, bone, muscle, and blood cell content of copper, zinc, iron, and manganese, and also on serum levels and urinary and fecal excretion of these elements in four groups of eight animals each that were pair-fed during 8 weeks with a nutritionally adequate diet, a 36% (as energy) ethanol-containing isocaloric diet, a 2% protein isocaloric diet, and a 36% ethanol 2% protein isocaloric diet, respectively, following the Lieber-DeCarli model. Five additional rats were fed ad lib the control diet. Protein malnutrition, but not ethanol, leads to liver zinc depletion. Both ethanol and protein malnutrition cause muscle zinc depletion and increase urinary zinc and manganese excretion, whereas ethanol also increases urinary iron excretion and liver manganese content. No differences were observed regarding copper metabolism.

Dose-related effects of dietary iron supplementation in producing hepatic iron overload in rats

The influence of varying the level of supplemental dietary iron on the development of hepatic iron overload was examined in rats. Two days after giving birth, Porton rats were fed a diet supplemented with 0, 0.5, 1 or 2% carbonyl iron, to institute dietary iron supplementation to the young via breast milk. After weaning, the offspring continued to receive the assigned diet until 32 weeks of age. Liver biopsies were taken from some rats at 8, 16 and 24 weeks of age and from all rats at 32 weeks of age, for assessment of iron overload. For both male and female rats, hepatic iron content was increased in a dose-related manner by feeding supplemented diet. Hepatic iron content of male rats tended to reach a plateau after 8, 16 weeks of supplementation, while that of female rats continued to rise throughout the experimental period, such that the hepatic iron content of female rats was 2.8-fold that of similarly treated males at 32 weeks of age. Iron supplementation was associated with only moderate retardation of growth. By choosing an appropriate level of iron supplementation, good (grade III-IV) hepatic iron loading can be achieved with minimal adverse effects on the animals' overall health.

Studies on genotoxic effects of iron overload and alcohol in an animal model of hepatocarcinogenesis

BACKGROUND/AIMS

In order to examine whether iron and alcohol act synergistically during tumor initiation in vivo, we investigated the effects of dietary iron overload and a liquid ethanol-containing diet on the initiation phase of the Solt & Farber model of chemical hepatocarcinogenesis.

METHODS

Following dietary supplementation with carbonyl iron for 8 weeks and ethanol pair-feeding according to Lieber deCarli for 5 weeks, animals were subjected to partial hepatectomy in order to induce regenerative cell proliferation and thereby "fix" putative DNA lesions. Levels of malondialdehyde, reduced and oxidized ubiquinone-9, alpha-tocopherol and 8-oxo-2'-deoxyguanosine were analyzed in liver tissue removed at the time of partial hepatectomy, and blood was collected for determination of alanine amino-transferase activities. Following a 2-week recovery period, promotion was achieved with 0.02% dietary 2-acetylaminofluorene and carbon tetrachloride. Two weeks after the completion of promotion, animals were sacrificed and the number of preneoplastic, glutathione S-transferase 7,7-positive lesions counted. Animals initiated with diethylnitrosamine served as a positive control group.

RESULTS

Serum aminotransferase activities were significantly increased, and hepatic contents of ubiquinol-9 (reduced ubiquinone-9) were significantly decreased in animals exposed to the combination of iron and ethanol in comparison to the other groups. Livers from iron-treated animals had decreased levels of alpha-tocopherol and increased contents of malondialdehyde, whereas treatment with ethanol did not further enhance these alterations. Levels of 8-oxo-2'-deoxyguanosine were not significantly different in animals treated with iron, ethanol or iron + ethanol as compared with controls. The number of preneoplastic foci at the time of sacrifice was not increased in livers exposed to iron and/or ethanol as compared with those from control animals. As expected, the number of foci was significantly increased in positive controls which were initiated with diethylnitrosamine.

CONCLUSIONS

Iron potentiated the cytotoxic effects of ethanol, resulting in increased serum aminotransferase activities and decreased hepatic contents of ubiquinol. However, the combination of iron and ethanol did not exert genotoxic effects detectable as enhanced hepatic levels of 8-oxo-2'-deoxyguanosine, or increased formation of preneoplastic, glutathione S-transferase 7,7-positive lesions in the Solt & Farber model of chemical hepatocarcinogenesis.

Effect of ursodeoxycholic acid on liver iron stores and distribution in rats with normal or iron-supplemented diet

Iron excess is a potential liver-damaging factor, and bile salts can increase iron digestive absorption and iron biliary excretion. The aim of this study was to investigate in rats the effect of ursodeoxycholic acid, a bile salt used in the treatment of chronic liver disease, on the hepatic iron stores in normal and iron-overload conditions. UDCA was administered by gavage to Sprague-Dawley rats. Iron hyperabsorption and overload were obtained by 5% carbonyl iron addition in diet. Hepatic iron stores and distribution were evaluated by liver iron concentration measurement and histologic assessment, respectively. Whatever the iron content of the diet, liver iron concentration was not modified by UDCA administration compared with the control groups. Iron distribution was not modified by UDCA in rats with normal diet. The total iron score was only transiently lowered by UDCA in iron supplemented rats compared with the control group at 1 month. In conclusion, chronic UDCA administration does not modify liver iron stores and distribution in rats with both normal or increased digestive iron absorption. These data suggest that UDCA is unlikely to increase hepatic iron stores in treated patients and that the benefit of UDCA treatment is probably not related to a decreasing effect of liver iron content.

Alcohol mediates increases in hepatic and serum nonheme iron stores in a rat model for alcohol-induced liver injury

The notion that prolonged ethanol consumption promotes hepatocellular damage through interactions with iron was evaluated in rats fed ethanol with or without supplemental dietary carbonyl iron. The individual and combined pro-oxidant potential of these agents was evaluated in terms of their ability to perturb iron homeostasis and initiate hepatocellular injury. Sprague-Dawely rats received a high fat liquid diet for 8 weeks supplemented with: 35% ethanol-derived calories (Alcohol group), 0.02 to 0.04% (w/v) carbonyl iron (Iron group), ethanol plus carbonyl iron (Alcohol + Iron group), or a diet containing carbohydrate-derived isocaloric calories (Control group). Hepatic and serum nonheme iron stores were significantly elevated (p < 0.05) in all treatment groups, compared with the Controls. Catalytically active low-molecular weight iron was detected in rats consuming alcohol and was markedly elevated (p < 0.05) in rats ingesting iron alone or iron in combination with alcohol. Elevations in serum ALT indicated significant hepatocellular injury in rats ingesting only alcohol, but was most prominent in the rats consuming ethanol in combination with iron (p < 0.05). Significant hepatic fatty infiltration, increased hydroxyproline content, and perturbations in reduced glutathione were also observed in the Alcohol and Iron treatment groups. Histochemical assessment of hepatic iron sequestration revealed that alcohol feeding resulted in deposition of ferric iron in the centrilobular area of the liver lobule. This unique alcohol-mediated iron deposition was histologically graded above Control group and was observed in both hepatocytes and Kupffer cells. Data presented herein suggest that alcohol alone or in combination with iron results in rather specific lobular patterns of hepatic iron deposition relevant to iron overload observed in human alcoholics. Furthermore, data suggest that alcohol- and iron-initiated prefibrotic events occur before extensive hepatocellular necrosis.

Hepatotoxicity induced by iron overload and alcohol. Studies on the role of chelatable iron, cytochrome P450 2E1 and lipid peroxidation

BACKGROUND/AIMS

Clinical experience and studies with experimental animal models indicate a synergistic hepatotoxic effect of dietary iron overload and chronic alcohol ingestion. In order to elucidate the mechanism underlying this synergism, we examined the hepatic levels of ethanol-inducible cytochrome P450 2E1, glutathione and malondialdehyde, and the effect of iron chelation with desferrioxamine, in livers from rats treated with iron and/or ethanol.

METHODS

Animals received diets with or without 2.5-3% carbonyl iron for 6-9 weeks, followed by an ethanol-containing diet or a liquid control diet for 5-9 weeks. Desferrioxamine was administered subcutaneously with mini-osmotic pumps. Alanine aminotransferase activity in serum and hepatic contents of glutathione and malondialdehyde were determined. The hepatic level of cytochrome P450 2E1 was determined with Western Blotting using a specific polyclonal antibody.

RESULTS

The combination of iron and alcohol led to a marked increase in serum alanine aminotransferase activity as compared with all other treatment groups, and iron chelation with desferrioxamine reversed these increases. Treatment with alcohol alone led to slightly increased aminotransferases compared with controls. The level of cytochrome P450 2E1 was significantly elevated in microsomes isolated from ethanol-treated rats, but neither additional iron supplementation nor desferrioxamine influenced this level significantly. Glutathione contents were increased in the livers of animals treated with iron and/or ethanol. Malondialdehyde values were increased in iron-treated animals, whereas neither ethanol nor desferrioxamine altered malondialdehyde levels significantly.

CONCLUSIONS

The toxic effects exerted by the combination of iron overload and chronic ethanol feeding on rat liver are dependent on a pool of chelatable iron. The hepatic level of cytochrome P450 2E1 is markedly induced by ethanol but not further altered by iron overload. Neither increased lipid peroxidation nor depletion of hepatic glutathione levels can explain the synergistic hepatotoxic effects of iron and ethanol in this model.