Hepatic Iron Status Research Articles

Pancreatic iron in pediatric transfusion-dependent beta-thalassemia patients: A longitudinal MRI study.

In pediatric transfusion-dependent thalassemia (TDT) patients, we evaluated the prevalence, pattern, and clinical associations of pancreatic siderosis and the changes in pancreatic iron levels and their association with baseline and changes in total body iron balance. We considered 86 pediatric TDT patients consecutively enrolled in the Extension-Myocardial Iron Overload in Thalassemia Network. Iron overload (IO) was quantified by R2* magnetic resonance imaging (MRI). Sixty-three (73%) patients had pancreatic IO (R2*>38Hz). Global pancreas R2* values were significantly correlated with mean serum ferritin levels, MRI liver iron concentration (LIC) values, and global heart R2* values. Global pancreas R2* values were significantly higher in patients with altered versus normal glucose metabolism. Thirty-one patients also performed the follow-up MRI at 18±3months. Higher pancreatic R2* values were detected at the follow-up, but the difference versus the baseline MRI was not significant. The 20% of patients with baseline pancreatic IO showed no pancreatic IO at the follow-up. The 46% of patients without baseline pancreatic IO developed pancreatic siderosis. The changes in global pancreas R2* between the two MRIs were not correlated with baseline serum ferritin levels, baseline, final, and changes in MRI LIC values, or baseline pancreatic iron levels. In children with TDT, pancreatic siderosis is a frequent finding associated with hepatic siderosis and represents a risk factor for myocardial siderosis and alterations of glucose metabolism. Iron removal from the pancreas is exceptionally challenging and independent from hepatic iron status.

Glycemic changes in relation to hepatic iron status in patients with non-transfusion dependent (NTD-SCD) and transfusion dependent sickle cell disease (TD- SCD).

Glycemic changes in relation to hepatic iron status in patients with non-transfusion dependent (NTD-SCD) and transfusion dependent sickle cell disease (TD- SCD).

Heme Oxygenase-1 Regulates Ferrous Iron and Foxo1 in Control of Hepatic Gluconeogenesis.

The liver is a key player for maintaining glucose homeostasis. Excessive hepatic glucose production is considered to be a key for the onset of type 2 diabetes. The primary function of heme oxygenase-1 (HO1) is to catalyze the degradation of heme into biliverdin, ferrous iron, and carbon monoxide. Previous studies have demonstrated that the degradation of heme by HO1 in the liver results in mitochondrial dysfunction and drives insulin resistance. In this study, by overexpressing HO1 in hepatocytes and mice, we showed that HO1 promotes gluconeogenesis in a Foxo1-dependent manner. Importantly, HO1 overexpression increased the generation of ferrous iron in the liver, which further activates nuclear factor-κB and phosphorylates Foxo1 at Ser273 to enhance gluconeogenesis. We further assessed the role of HO1 in insulin-resistant liver-specific knockout of IRS1 and IRS2 genes (L-DKO) mice, which exhibit upregulation of HO1 in the liver and hepatic ferrous iron overload. HO1 knockdown by shRNA or treatment of iron chelator rescued the aberrant gluconeogenesis in L-DKO mice. In addition, we found that systemic iron overload promotes gluconeogenesis by activating the hepatic protein kinase A→Foxo1 axis. Thus, our results demonstrate the role of HO1 in regulating hepatic iron status and Foxo1 to control gluconeogenesis and blood glucose.

Effect of Korean pine nut oil on hepatic iron, copper, and zinc status and expression of genes and proteins related to iron absorption in diet-induced obese mice

Effect of Korean pine nut oil on hepatic iron, copper, and zinc status and expression of genes and proteins related to iron absorption in diet-induced obese mice

Hepatic iron storage is related to body adiposity and hepatic inflammation

BackgroundObesity has been reported to be associated with iron deficiency. However, few studies have investigated iron status in low adiposity. To investigate whether body adiposity was associated with altered hepatic iron status, we compared liver iron levels and markers involved in inflammation and iron absorption in obese, control, and mildly calorie restricted mice.MethodsSeven week old C57BL/6 mice were fed control (10% kcal fat, Control) or high fat (60% kcal fat, HFD) diets, or reduced amount of control diet to achieve 15% calorie restriction (CR) for 16 weeks. Hepatic non-heme iron content and ferritin protein level, and hematocrit and hemoglobin levels were determined to assess iron status. Hepatic expression of Mcp-1 and Tnf-α were measured as hepatic inflammatory markers. Hepatic hepcidin (Hamp) and Bmp6, and duodenal Dmt1, Dcyt1b, hephaestin (Heph) and ferroportin mRNA levels were measured as factors involved in regulation of iron absorption.ResultsHepatic non-heme iron and ferritin protein levels were significantly higher in the CR group compared with the Control group, and significantly lower in the HFD group. These two iron status markers showed significantly negative correlations with the amount of white adipose tissue (r = -0.689 for hepatic non-heme iron and r = -0.740 for ferritin). Hepatic Mcp-1 and Tnf-α mRNA levels were significantly lower in the CR compared with the HFD (74 and 47% lower) and showed significantly negative correlations with hepatic non-heme iron levels (Mcp-1: r = -0.557, P < 0.05; Tnf-α: r = -0.464, P < 0.05). Hepatic Hamp mRNA levels were lower in the HFD and higher in the CR groups compared with the Control group, which could be a response to maintain iron homeostasis. Duodenal Dcyt1b mRNA levels were higher in the CR group compared with the HFD group and duodenal Heph mRNA levels were higher in the CR group than the Control group.ConclusionWe showed that body adiposity was inversely correlated with liver iron status. Low inflammation levels in hepatic milieu and enhanced expression of duodenal oxidoreductases induced by calorie restriction could have contributed to higher iron status.

Lower hepatic iron storage associated with obesity in mice can be restored by decreasing body fat mass through feeding a low-fat diet

High-fat diet (HFD)–induced obesity has been reported to result in low hepatic iron storage. In the current study, we tested the hypothesis that these obesity-related changes in hepatic iron status could be reversed by decreasing adiposity by feeding a low-fat diet. Five-week-old C57BL/6 mice were assigned to 3 groups: the LL group was fed a control diet for 31 weeks, the HH group was fed a HFD for 31 weeks, and the HL group was fed the HFD for 15 weeks and then switched to the control diet for 16 weeks. The fat mass of the HL group decreased by 3.2 g from the 14th to the 30th weeks. Fat mass was significantly different among the groups (11.4, 15.8, and 37.5 g in the LL, HH, and HL groups, respectively; P< .001). The liver iron concentration of the HL group was similar to that of the LL group, which was about 30% higher than that of the HH group (74.2, 72.7, and 55.7 μg/g in the LL, HL, and HH groups, respectively; P< .05). Duodenal cytochrome b messenger RNA (mRNA) levels were higher in the HL group than in the HH group. Although bone morphogenetic protein 6 (Bmp6) mRNA levels showed no significant differences in the liver, duodenal Bmp6 mRNA levels were significantly lower in the HH group compared with the LL and HL groups. Liver Smad1/5 proteins were differentially activated: the HH group had significantly less phosphorylated Smads than did the LL and HL groups. Our data demonstrate that hepatic iron storage levels are closely related to body adiposity, and reducing body fat mass through feeding a lower-fat diet to HFD-induced obese mice restores liver iron storage.

Abstract 2821: Joint relationship between iron and retinoids in patients at high-risk for liver cancer

Abstract Approximately 3.2 million Americans are chronically infected with Hepatitis C, forming the largest group of persons at high risk for HCC, with an annual incidence of 3-4%. Increased oxidative stress is regarded as the major mechanism of progression in chronic liver disease (CLD) and subsequent HCC. Hepatic iron overload facilitates the production of reactive oxygen species (ROS), thereby inducing liver damage and fibrosis. We have previously shown that retinoid and carotenoid depletion occurs early in disease and may represent a major modifiable risk. This study aims to determine, in CLD patients and controls, whether retinoid levels modify the association between serum iron concentrations and: (a) oxidative stress biomarkers in urine (b) tissue changes associated with hepatic stellate cell (HSC) activation, and (c) CLD progression. Patients with HCV undergoing liver biopsy (n = 69) provided fasting blood, fresh tissue, urine and completed a diet history questionnaire (DHQ). Serum and questionnaire data from healthy volunteers (n = 11), normal liver tissue from public repositories and patients without liver disease (n = 11) were also collected. Urinary isoprostanes, serum and tissue retinoid concentrations were obtained by LC-MS-MS. Serum iron, ferritin and transferrin were quantitated. Immunohistochemistry for αSMA was performed on FFPE sections and subsequently quantified via digital image analysis. Associations between urinary isoprostanes, αSMA levels, serum iron, serum and tissue retinoids were assessed using Spearman correlation coefficients and non-parametric tests were utilized to test differences among disease severity groups. There was a significant increasing trend for serum transferrin levels with progressive fibrosis, but not for serum iron and ferritin concentrations. All subjects had transferrin saturation within the normal range. Serum β-carotene and lycopene were inversely associated with serum ferritin concentrations (r = -0.29, P &amp;lt; 0.01; r = -0.29, P &amp;lt; 0.01) however, this relationship was not observed for other serum iron measurements. Serum iron measurements were not associated with hepatic retinoids/carotenoids, αSMA expression or urinary isoprostanes. Tissue retinyl palmitate was inversely and significantly correlated with hepatic αSMA expression (r = -0.3, P &amp;lt; 0.02). Serum iron overload was not evident in this population even though a depletion of serum retinoids/carotenoids is observed. The inverse correlation observed between serum ferritin and retinoids/carotenoids suggests a possible joint effect in CLD patients. Our data provide confirmation that hepatic retinoid loss is accompanied by HSC activation, a key player in fibrosis. Further evaluation of hepatic iron status is warranted to assess the relationships between iron and retinoids in HCV. Citation Format: Yachana Kataria, Ryan Deaton, Erika Enk, Milita Petrauskaite, Scott Cotler, Donald Jensen, Peter Gann. Joint relationship between iron and retinoids in patients at high-risk for liver cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2821. doi:10.1158/1538-7445.AM2015-2821

Correlation of Serum Ferritin with Hepatic Iron Overload among Nontransfusion Dependent Beta Thalassaemia with Haemoglobin E Disease Patients from Eastern India

Introduction: Iron over load estimation was attempted by MRI R2* and serum ferritin, in non -transfusion dependent HbE Beta Thalassaemia patients. Methods: Seventy three patients selected on definite criteria were scanned and tested. Average age of the patients was 20.8 ± 11.14 years, 33 females and 40 male. Average hepatic iron concentration was determined to be 11.09 ± 11.74 mg/g of dry liver tissue and average serum ferritin was 972.44 ± 1121.51 ng/ml. Results: 81% of the patients had hepatic iron concentration more than 2 mg/g of dry liver tissue, whereas only 41% had serum ferritin level >500 ng/ml, irrespective of age. The hepatic iron overload pattern was heterogenous, where age and sex were not well determined variable predictors of such iron overload. Though, higher hepatic iron load was seen more predictably in patients above the age of 10 years and LIC of 5 mg/g of dry tissue correlated with serum ferritin level of approximately 400 ng/ml. Conclusion: It can be concluded that non transfusion dependence does not ensure non iron overload status and such patients should be scanned by using MRI R2* sequence to determine their hepatic iron status and start on excess iron chelation therapy if felt required.

Rimonabant Improves Oxidative/Nitrosative Stress in Mice with Nonalcoholic Fatty Liver Disease.

The present study deals with the effects of rimonabant on oxidative/nitrosative stress in high diet- (HFD-) induced experimental nonalcoholic fatty liver disease (NAFLD). Male mice C57BL/6 were divided into the following groups: control group fed with control diet for 20 weeks (C; n = 6); group fed with HFD for 20 weeks (HF; n = 6); group fed with standard diet and treated with rimonabant after 18 weeks (R; n = 9); group fed with HFD and treated with rimonabant after 18 weeks (HFR; n = 10). Daily dose of rimonabant (10 mg/kg) was administered to HFR and R group by oral gavage for two weeks. Treatment induced a decrease in hepatic malondialdehyde concentration in HFR group compared to HF group (P < 0.01). The concentration of nitrites + nitrates in liver was decreased in HFR group compared to HF group (P < 0.01). Liver content of reduced glutathione was higher in HFR group compared to HF group (P < 0.01). Total liver superoxide dismutase activity in HFR group was decreased in comparison with HF group (P < 0.01). It was found that rimonabant may influence hepatic iron, zinc, copper, and manganese status. Our study indicates potential usefulness of cannabinoid receptor type 1 blockade in the treatment of HFD-induced NAFLD.

Hepatic and Hippocampus Iron Status is not Altered in Response to Increased Serum Ceruloplasmin and Serum “Free” Copper in Wistar Rat Model for Non-Wilsonian Brain Copper Toxicosis

Copper and iron dyshomeostasis has been implicated directly or indirectly in the pathogenesis of neurodegenerative diseases. Previously, we have shown the first in vivo evidence of significant increase in the hippocampus copper and zinc content with spatial memory impairments, astrocytes swelling (Alzheimer type-II cells) coupled with increase in the number of astrocytes, copper deposition in the choroid plexus, and degenerated neurons in copper-intoxicated Wistar rats. In continuation with our previous study, the aim of this study was to further investigate the effects of intraperitoneally injected copper lactate (0.15 mg Cu/100 g body weight) daily for 90 days on serum "free" copper levels, iron levels in the liver, and hippocampus by atomic absorption spectrophotometry and histopathological study of the liver and brain tissues of Wistar rats using Perls' Prussian blue (PPB) stain. A massive significant increase in serum "free" copper (79.48% increase) along with strong correlation (r = 0.978) was found between serum copper and serum "free" copper in copper-intoxicated rats. No significant difference was detected in hepatic and hippocampus iron levels between control and copper-intoxicated rats. PPB stain demonstrated very few scattered grade 1 haemosiderin deposits within sinusoidal cells predominantly Kupffer cells; however, brain sections were negatively stained with PPB stain. In conclusion, the current study demonstrates that chronic copper toxicity causes increase in serum "free" copper, which may serve as predisposing factor for the development of neurodegeneration and memory deficits, and grade 1 haemosiderin deposition in Kupffer cells without altering hepatic and hippocampus iron levels in male Wistar rats.

T2* MRI in Regularly Transfused Children with Thalassemia Intermedia: Serum Ferritin Does Not Reflect Liver Iron Stores

Nontransfused patients with thalassemia intermedia (TI) accumulate iron due to increased gastrointestinal absorption of iron. Recent studies using T2* MRI revealed that serum ferritin does not reflect the severity of iron overload in nontransfused TI patients. We evaluated the iron overload status in TI children on monthly transfusion. Based on serum ferritin levels, 11 such patients (mean age 13.18 ± 4.09 years), were classified into two groups, group 1 (six patients) and group 2 (five patients) with serum ferritin levels below and above 1000 ng/mL, respectively. T2* MRI assessments were done for evaluation of hepatic and cardiac iron status. Group 1 and group 2 had mean serum ferritin levels of 817.300 ± 244.690 ng/mL and 1983.80 ± 662.862 ng/mL, respectively (P = .003). T2* MRI showed comparable moderate to severe hepatic iron overload status in both. None of the patients had myocardial iron deposition. We conclude that serum ferritin does not reflect the hepatic iron overload status in our patients with TI on regular transfusion.

Diet-induced obesity leads to decreased hepatic iron storage in mice

An increased risk of iron deficiency has been reported in obese individuals. We investigated hepatic iron status and serum levels of both adipokines and inflammatory markers in obese mice to test the hypothesis that high-fat-diet (HFD)-induced obesity leads to reduced iron storage associated with inflammation. Four-week-old C57BL mice were fed a HFD containing 60% energy from fat for 16 weeks and were compared with mice on a control diet with 10% energy from fat. The HFD group had significantly higher levels of leptin (43.7 ng/mL in control, n = 16 vs 104.3 ng/mL in HFD, n = 17; P < .001) and significantly lower amounts of high-molecular-weight adiponectin (4.80 μg/mL in control, n = 16 vs 3.67 μg/mL in HFD, n = 18; P = .002) compared with the control group. Higher serum amyloid A levels in the HFD group (60.4 μg/mL in control, n = 17 vs 117.9 μg/mL in HFD, n = 18; P < .001) suggest inflammation in the HFD-induced obese animals. The HFD group had lower hepatic nonheme iron (3.12 μg/mg protein in control, n = 17 vs 0.869 μg/mg protein in HFD, n = 16; P < .001). Expression of hepcidin messenger RNA (mRNA) was only 54% of the control levels in HFD mice (P = .016). However, the ratio of hepcidin mRNA expression to nonheme iron was 2.5-fold higher in the HFD compared with the control animals. Hepcidin is a homeostatic regulator of iron metabolism that restricts intestinal iron absorption and is also known as a mediator of inflammation. Increased serum amyloid A levels and a higher ratio of hepatic hepcidin mRNA expression to nonheme iron suggest that lower hepatic iron status in obese animals might be associated with inflammation.

Changes in serum iron concentration and hepatic enzyme activities in cattle infected with Theileria annulata and Babesia bigemina

Analyses for alanine aminotransferase, aspartate aminotransferase (AST), alkaline phosphatase (ALP) activities, and iron concentration were carried out in infected and uninfected cattle in order to determine the degree of hepatic damage and blood iron status caused by Theileria annulata and Babesia bigemina. Blood samples from 30 infected and 20 uninfected cattle with T. annulata and also from 40 infected and 20 uninfected cattle with B. bigemina were taken. The biochemical analyses revealed increased serum AST and ALP activities in infected cattle with T. annulata and B. bigemina compared with uninfected cattle (P < 0.05). Significant decreases in iron concentration were observed in cattle infected with T. annulata and B. bigemina when compared with uninfected cattle (P < 0.05) although the level of serum iron concentration in infected cattle was within the normal reference values for cattle. It was concluded that iron deficiency anemia is not an important factor in T. annulata- and even in B. bigemina-infected cattle with severe intravascular hemolysis. The increased activities of serum enzymes indicated the hepatic injuries associated with infection with T. annulata and B. bigemina.

Hepatic Iron Overload or Cirrhosis May Occur in Acquired Copper Deficiency and is Likely Mediated by Hypoceruloplasminemia

The metabolic fates of copper and iron are closely linked through ceruloplasmin and hephaestin. Ceruloplasmin is the principal copper carrying protein and decreases in acquired copper deficiency. Congenital absence of ceruloplasmin (aceruloplasminemia) results in tissue iron overload. Animal studies suggest hypoceruloplasminemia and impaired hephaestin function result in tissue iron accumulation. There are no data on hepatic function, pathology, and iron status in patients with acquired copper deficiency. This report studies these issues in 4 patients with acquired copper deficiency. This is a retrospective review of hepatic status (imaging, liver function tests, liver biopsy) in 4 patients with neurologic and hematologic manifestations of acquired copper deficiency who also had imaging and/or pathologic evidence of hepatic dysfunction. Two patients (cases 1 and 2) showed imaging evidence of cirrhosis and pathologic evidence of cirrhosis or advanced fibrosis. Two patients (cases 3 and 4) had pathologic evidence of hepatic iron overload. All patients had some evidence of abnormality on liver function tests. Acquired copper deficiency causes a secondary ceruloplasmin deficiency which can result in hepatic iron overload and/or cirrhosis.

Benefits and Risks of Iron Supplementation in Anemic Neonatal Pigs

Iron deficiency is a common health problem. The most severe consequence of this disorder is iron deficiency anemia (IDA), which is considered the most common nutritional deficiency worldwide. Newborn piglets are an ideal model to explore the multifaceted etiology of IDA in mammals, as IDA is the most prevalent deficiency disorder throughout the early postnatal period in this species and frequently develops into a critical illness. Here, we report the very low expression of duodenal iron transporters in pigs during the first days of life. We postulate that this low expression level is why the iron demands of the piglet body are not met by iron absorption during this period. Interestingly, we found that a low level of duodenal divalent metal transporter 1 and ferroportin, two iron transporters located on the apical and basolateral membrane of duodenal absorptive enterocytes, respectively, correlates with abnormally high expression of hepcidin, despite the poor hepatic and overall iron status of these animals. Parenteral iron supplementation by a unique intramuscular administration of large amounts of iron dextran is current practice for the treatment of IDA in piglets. However, the potential toxicity of such supplemental iron implies the necessity for caution when applying this treatment. Here we demonstrate that a modified strategy for iron supplementation of newborn piglets with iron dextran improves the piglets' hematological status, attenuates the induction of hepcidin expression, and minimizes the toxicity of the administered iron.

Diet‐induced obesity leads to decreased hepatic iron storage associated with inflammation

Increased risk for iron deficiency has been reported in obese subjects. We investigated the effects of high fat diet‐induced obesity on hepatic iron status and serum adipokine and inflammatory marker levels. Four‐ week old C57BL mice were fed diets containing 10 (ND) or 60 (HFD)% energy from fat for 16 wks. Consumption of HFD resulted in higher weight gain (16.3 vs. 30.4g). Serum leptin, total adiponectin, high molecular weight (HMW) adiponectin, and serum amyloid A (SAA) and hepatic non‐heme iron, ferritin, and hepcidin mRNA levels were measured. HFD group had higher leptin (42.6 vs. 104.3 ng/mL), and lower HMW adiponectin (4.80 vs. 3.67 ug/mL) levels. Higher level of SAA in HFD group (57.8 vs. 117.9 ug/mL) suggests inflammation in HFD‐induced obese animals. HFD group had lower hepatic non‐heme iron (3.12 vs 0.869 ug/mg protein) and ferritin levels. HFD group had lower hepcidin expression at 54% level of ND group, however, ratio of hepcidin expression to non‐heme iron was higher (2.5 fold higher in HFD than ND). Hepcidin is a homeostatic regulator of iron metabolism by restricting intestinal iron absorption, but, also known as a mediator of inflammation. Leptin and SAA showed positive correlation with weight gain while HMW adiponectin showed negative correlation. Increased SAA levels and higher hepcidin ratio to iron suggests that lower hepatic iron status in obese animals might be associated with inflammation. Supported by Korea Research Foundation Grant (C00305) and by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (2009‐0063409).

Hepatic iron status and response to therapy in chronic viral hepatitis B and C: A preliminary report

Aim : To investigate if hepatic iron content influences the response to therapy in patients with chronic hepatitis C or B. Background : It seems that the presence of elevated body iron stores and, in particular, elevated hepatic iron levels, is one of the strongest predictors of resistance to interferon treatment for chronic hepatitis C or B. Patients and methods : Two hundred and one patients with chronic hepatitis C or B who were referred to Tehran Hepatitis Center were enrolled in this study. Histological quantification of hepatic iron was carried out by scoring iron separately within hepatocytes, sinusoidal cells, and portal triads. To estimate a cut off point for iron deposit as a predictor of response to treatment, Odd´s ratio with 95% confidence interval was calculated for each level of iron deposit. Results : Iron scores were divided into two levels of high and low at several cut-off points, but the most significant differences were found when score 2 was considered as the cut-off point. Odd's ratios were not significant in any of the hepatic zones. The lowest P-values were related to zone II sinusoidal cells and the total of sinusoidal cells and portal iron score (P= 0.08) in which the Odd's ratios were 6 (95% CI, 0.77 to 46.6) and 3.9 (95% CI, 0.88 to 17.4) respectively. Conclusion : In our society, liver iron content cannot be considered as an important risk factor of resistance to treatment in chronic hepatitis patients because of the very small prevalence. So, hepatic iron measurement and scoring do not seem cost-effective and valuable for all patients with chronic hepatitis in our population.

Transferrin Receptor 2 as a Signaling Receptor

Transferrin receptor 2 (TfR2) is a transferrin-binding protein predominantly found in liver and intestine. Its abundance is generally opposite that of TfR1, a more ubiquitously present protein that is responsible for the uptake of iron into cells. Mutations in the gene encoding TfR2 (or knockout in mice) produce hemochromatosis and iron loading in the liver, suggesting a role for TfR2 in organismal iron homeostasis. Calzolari et al . used various methods to show that TfR2 was present in lipid raft domains in cultured HepG2 or K562 cells and that TfR2 coimmunoprecipitated with caveolin-1 and colocalized with the tetraspanin CD81. Although the protein was most abundant in the plasma membrane, where lipid raft association was increased in the presence of holotransferrin, the majority of intracellular TfR2 was in a compartment distinct from that in which TfR1 was found. Using sucrose gradient centrifugation, the authors separated exosomes from plasma membrane from lipid raft domains and found that TfR1 and TfR2 were present in exosome preparations, along with CD81. Surprisingly, TfR1 and TfR2 appeared to be present on separate populations of exosomes, in that isolated TfR2-positive exosomes did not cross-react with antibodies that recognized TfR1. When K562 cells were serum starved and then exposed to either human transferrin (binds to both TfR1 and TfR2) or bovine transferrin (binds only to TfR2) or to an antibody that cross-links TfR2, the cells exhibited a transient increase in extracellular signal-regulated kinase (ERK) phosphorylation, suggesting activation of the mitogen-activated protein kinase (MAPK) pathway. Cholesterol depletion inhibited the phosphorylation of ERK stimulated by the antibody against TfR2, suggesting that raft association was important for TfR2 to activate the MAPK pathway. This signaling connection supports the hypothesis that TfR2 serves as a sensor of hepatic iron status to regulate the activity of hepcidin, which is a hormone released by the liver that inhibits intestinal iron absorption and iron release by macrophages. A. Calzolari, C. Raggi, S. Deaglio, N. M. Sposi, M. Stafsnes, K. Fecchi, I. Parolini, F. Malavasi, C. Peschle, M. Sargiacomo, U. Testa, TfR2 localizes in lipid raft domains and is released in exosomes to activate signal transduction along the MAPK pathway. J. Cell Sci. 119 , 4486-4498 (2006). [Abstract] [Full Text]

Multiple polymorphic loci determine basal hepatic and splenic iron status in mice

Polymorphisms of genes linked to iron metabolism may account for individual variability in hemochromatosis and iron status connected with liver and cardiovascular diseases, cancers, toxicity, and infection. Mouse strains exhibit marked differences in levels of non-heme iron, with C57BL/6J and SWR showing low and high levels, respectively. The genetic basis for this variability was examined using quantitative trait loci (QTL) analysis together with expression profiling and chromosomal positions of known iron-related genes. Non-heme iron levels in liver and spleen of C57BL/6J x SWR F2 mice were poorly correlated, indicating independent regulation. Highly significant (P < .01) polymorphic loci were found on chromosomes 2 and 16 for liver and on chromosomes 8 and 9 for spleen. With sex as a covariate, additional significant or suggestive (P < 0.1) QTL were detected on chromosomes 7, 8, 11, and 19 for liver and on chromosome 2 for spleen. A gene array showed no clear association between most loci and differential iron-related gene expression. The gene for transferrin and a transferrin-like gene map close to the QTL on chromosome 9. Transferrin saturation was significantly lower in C57BL/6J mice than in SWR mice, but there was no significant difference in the serum level of transferrin, hepatic expression, or functional change in cDNA sequence. beta2-Microglobulin, which, unlike other loci, was associated with C57BL/6J alleles, is a candidate for the chromosome 2 QTL for higher iron. In conclusion, the findings show the location of polymorphic genes that determine basal iron status in wild-type mice. Human equivalents may be pertinent in predisposition to hepatic and other disorders.

Successful interferon therapy reverses enhanced hepatic iron accumulation and lipid peroxidation in chronic hepatitis C.

Hepatic iron deposition has been reported in chronic hepatitis C (CH-C), and iron-induced lipid peroxidation may be involved in the pathogenesis of CH-C. The aims of the present study were: 1) to determine whether patients with CH-C have evidence of enhanced hepatic lipid peroxidation and to evaluate its relation to iron status, compared with that in patients with chronic hepatitis B (CH-B); and 2) to assess the effect of interferon (IFN) therapy on hepatic iron and lipid peroxidation. In the liver biopsies of 40 patients with CH-C and 26 patients with CH-B, immunohistochemical detection of 4-hydroxy-2-nonenal (HNE)-protein adducts for evaluation of lipid peroxidation was performed, and hepatic iron status was biochemically and histologically assessed. In 16 CH-C patients with normal serum transaminases and undetectable serum HCV-RNA >6 months after the end of IFN treatment (responders) and in 11 nonresponders, hepatic HNE-protein adducts and siderosis were evaluated in pre- and posttreatment liver biopsies. Hepatocytic HNE-protein adducts and iron deposits were more abundant in the patients with CH-C than in those with CH-B. No correlation was found between the levels of hepatocytic HNE-protein adducts and hepatic iron status in either of the two groups. In the responders to IFN treatment for CH-C, hepatocytic HNE-protein adducts disappeared or attenuated with improvement of hepatic siderosis after the treatment, whereas IFN treatment did not improve hepatocytic expression of HNE-protein adducts and hepatic siderosis in the nonresponders. Patients with CH-C have evidence of enhanced hepatic iron accumulation and lipid peroxidation compared to those with CH-B. In CH-C, hepatic siderosis and lipid peroxidation are improved with successful IFN treatment. These results suggest that hepatic lipid peroxidation and iron may potentially play contributory roles in the pathogenesis of CH-C.