Upregulation of transferrin receptor 2 and ferroportin 1 mRNA in the liver of patients with chronic hepatitis C

MicroRNA profile and iron-related gene expression in hepatitis C-related hepatocellular carcinoma: a preliminary study

INTRODUCTION

Hepatocellular carcinoma (HCC) is very difficult to diagnose, especially in its early stages. Non-invasive diagnostic and prognostic factors for this cancer are urgently needed. The purpose of our study was to investigate whether the microRNAs (miRNAs) regulating genes involved in iron homeostasis, whose disruption is a hallmark of HCC, offer potential as diagnostic or prognostic factors of HCV-related hepatocellular carcinoma.

MATERIAL AND METHODS

Serum and tumor samples, and adjacent liver specimens, were obtained from 65 HCC patients. Additionally, serum samples were obtained from 65 healthy controls. In total, 28 circulating and eight tissue microRNA expression profiles were estimated by TaqMan qPCR.

RESULTS

The expression profiles of all tested miRNAs were altered in the hepatocellular carcinoma patients. Iron level was negatively related to serum miR-96 level in healthy controls. Although the expression of iron metabolism proteins correlated with the level of serum miRNA in the controls, this was not observed in cancer patients. In the group of cancer patients, Let-7a, miR-29b, and miR-133a were positively related to ferroportin, transferrin and ferritin levels, while miR-31, miR-221 and miR-532 were negatively related to ferroportin, transferrin receptor 1 and ferritin levels. According to ROC curve analyses, 15 miRNAs are able to discriminate with 100% sensitivity and specificity between hepatocellular carcinoma patients and healthy subjects, which is more efficient than α-fetoprotein.

CONCLUSIONS

Circulating miRNAs that regulate the expression of iron metabolism proteins should be evaluated as promising candidates for HCV-related HCC diagnostic agents.

Role of transferrin receptor in hepatitis C viral infection

Hepatitis C virus (HCV) is the main pathogen causing chronic hepatitis and primary liver cancer. Various viral proteins and host cell molecules are involved in the HCV cell entry, but the mechanism of infection has not been completely elucidated. The transferrin receptor can act as a receptor for many viruses during cell entry. The transferrin receptor is not only closely related to HCV-induced iron metabolism disorders but also mediates the fusion of HCV with the host cell membrane as a specific receptor for CD81-dependent viral adhesion.

Molecular pathogenesis and clinical consequences of iron overload in liver cirrhosis

BACKGROUND

The liver, as the main iron storage compartment and the place of hepcidin synthesis, is the central organ involved in maintaining iron homeostasis in the body. Excessive accumulation of iron is an important risk factor in liver disease progression to cirrhosis and hepatocellular carcinoma. Here, we review the literature on the molecular pathogenesis of iron overload and its clinical consequences in chronic liver diseases.

DATA SOURCES

PubMed was searched for English-language articles on molecular genesis of primary and secondary iron overload, as well as on their association with liver disease progression. We have also included literature on adjuvant therapeutic interventions aiming to alleviate detrimental effects of excessive body iron load in liver cirrhosis.

RESULTS

Excess of free, unbound iron induces oxidative stress, increases cell sensitivity to other detrimental factors, and can directly affect cellular signaling pathways, resulting in accelerated liver disease progression. Diagnosis of liver cirrhosis is, in turn, often associated with the identification of a pathological accumulation of iron, even in the absence of genetic background of hereditary hemochromatosis. Iron depletion and adjuvant therapy with antioxidants are shown to cause significant improvement of liver functions in patients with iron overload. Phlebotomy can have beneficial effects on liver histology in patients with excessive iron accumulation combined with compensated liver cirrhosis of different etiology.

CONCLUSION

Excessive accumulation of body iron in liver cirrhosis is an important predictor of liver failure and available data suggest that it can be considered as target for adjuvant therapy in this condition.

Iron homeostasis and its regulators over the course of chronic hepatitis C

ABSTRACT: 

Chronic infection with HCV has been diagnosed in approximately 170 million people worldwide. It is an important cause of chronic, progressive liver fibrosis. Late consequences of chronic HCV infection, including liver cirrhosis and hepatocellular carcinoma, have become the major indications for liver transplantation in developed countries. Particular attention is being paid to iron accumulation in chronic hepatitis C and its relation to the current antiviral therapy's efficacy and safety, risk of exacerbation of oxidative stress, development of metabolic disorders and hepatocarcinogenesis. HCV infection disrupts the synthesis of hepcidin, which regulates extracellular iron content. This article discusses the impact of iron on HCV multiplication and the involvement of impaired iron homeostasis in chronic hepatitis C in terms of the pathogenesis of insulin resistance, fatty liver and hepatocarcinogenesis.

Interaction between hepatitis C virus and metabolic factors

Hepatitis C virus (HCV) infection disrupts the normal metabolism processes, but is also influenced by several of the host’s metabolic factors. An obvious and significantly detrimental pathophysiological feature of HCV infection is insulin resistance in hepatic and peripheral tissues. Substantial research efforts have been put forth recently to elucidate the molecular mechanism of HCV-induced insulin resistance, and several cytokines, such as tumor necrosis factor-α, have been identified as important contributors to the development of insulin resistance in the distant peripheral tissues of HCV-infected patients and animal models. The demonstrated etiologies of HCV-induced whole-body insulin resistance include oxidative stress, lipid metabolism abnormalities, hepatic steatosis and iron overload. In addition, myriad effects of this condition have been characterized, including glucose intolerance, resistance to antiviral therapy, progression of hepatic fibrosis, development of hepatocellular carcinoma, and general decrease in quality of life. Metabolic-related conditions and disorders, such as visceral obesity and diabetes mellitus, have been shown to synergistically enhance HCV-induced metabolic disturbance, and are associated with worse prognosis. Yet, the molecular interactions between HCV-induced metabolic disturbance and host-associated metabolic factors remain largely unknown. The diet and lifestyle recommendations for chronic hepatitis C are basically the same as those for obesity, diabetes, and metabolic syndrome. Specifically, patients are suggested to restrict their dietary iron intake, abstain from alcohol and tobacco, and increase their intake of green tea and coffee (to attain the beneficial effects of caffeine and polyphenols). While successful clinical management of HCV-infected patients with metabolic disorders has also been achieved with some anti-diabetic (i.e., metformin) and anti-lipid (i.e., statins) medications, it is recommended that sulfonylurea and insulin be avoided.

Branched-chain amino acid supplementation reduces oxidative stress and prolongs survival in rats with advanced liver cirrhosis

Long-term supplementation with branched-chain amino acids (BCAA) is associated with prolonged survival and decreased frequency of development of hepatocellular carcinoma (HCC) in patients with liver cirrhosis. However, the pharmaceutical mechanism underlying this association is still unclear. We investigated whether continuous BCAA supplementation increases survival rate of rats exposed to a fibrogenic agent and influences the iron accumulation, oxidative stress, fibrosis, and gluconeogenesis in the liver. Further, the effects of BCAA on gluconeogenesis in cultured cells were also investigated. A significant improvement in cumulative survival was observed in BCAA-supplemented rats with advanced cirrhosis compared to untreated rats with cirrhosis (P<0.05). The prolonged survival due to BCAA supplementation was associated with reduction of iron contents, reactive oxygen species production and attenuated fibrosis in the liver. In addition, BCAA ameliorated glucose metabolism by forkhead box protein O1 pathway in the liver. BCAA prolongs survival in cirrhotic rats and this was likely the consequences of reduced iron accumulation, oxidative stress and fibrosis and improved glucose metabolism in the liver.

Review article: the iron overload syndromes

BACKGROUND

Iron overload syndromes encompass a wide range of hereditary and acquired conditions. Major developments in the field of genetics and the discovery of hepcidin as a central regulator of iron homeostasis have greatly increased our understanding of the pathophysiology of iron overload syndromes.

AIM

To review advances in iron regulation and iron overload syndrome with special emphasis on hereditary haemochromatosis, the prototype iron overload syndrome.

METHODS

A PubMed search using words such as 'iron overload', 'hemochromatosis', 'HFE', 'Non-HFE', 'secondary iron overload' was undertaken.

RESULTS

Iron overload is associated with significant morbidity and mortality. Sensitive diagnostic tests and effective therapy are widely available and can prevent complications associated with iron accumulation in end- organs. Therapeutic phlebotomy remains the cornerstone of therapy for removal of excess body iron, but novel therapeutic agents including oral iron chelators have been developed for iron overload associated with anaemia.

CONCLUSIONS

Iron overload disorders are common. Inexpensive screening tests as well as confirmatory diagnostic tests are widely available. Increased awareness of the causes and importance of early diagnosis and knowledge of the appropriate use of genetic testing are encouraged. The availability of novel treatments should increase therapeutic options for patients with iron overload disorders.

Hepatitis C virus induced insulin resistance impairs response to anti viral therapy

Hepatitis C virus (HCV) infection is an important risk factor for insulin resistance (IR). The latter is the pathogenic foundation underlying metabolic syndrome, steatosis and cirrhosis, and possibly hepatocellular carcinoma (HCC). The interplay between genetic and environmental risk factors ultimately leads to the development of IR. Obesity is considered a major risk factor, with dysregulation of levels of secreted adipokines from distended adipose tissue playing a major role in IR. HCV-induced IR may be due to the HCV core protein inducing proteasomal degradation of insulin receptor substrates 1 and 2, blocking intracellular insulin signaling. The latter is mediated by increased levels of both tumour necrosis factor-α (TNF-α) and suppressor of cytokine signaling 3 (SOC-3). IR, through different mechanisms, plays a role in the development of steatosis and its progression to steatohepatitis, cirrhosis and even HCC. In addition, IR has a role in impairing TNF signaling cascade, which in turn blocks STAT-1 translocation and interferon stimulated genes production avoiding the antiviral effect of interferon.

Hepatitis C virus-induced oxidative stress and mitochondrial dysfunction: a focus on recent advances in proteomics

The natural history of chronic hepatitis C virus (HCV) infection presents two major aspects. On one side, the illness is by itself benign, whereas, on the other side, epidemiological evidence clearly identifies chronic HCV infection as the principal cause of cirrhosis, hepatocellular carcinoma, and extrahepatic diseases, such as autoimmune type II mixed cryoglobulinemia and some B cell non-Hodgkin's lymphomas. The mechanisms responsible for the progression of liver disease to severe liver injury are still poorly understood. Nonetheless, considerable biological data and studies from animal models suggest that oxidative stress contributes to steatohepatitis and that the increased generation of reactive oxygen and nitrogen species, together with the decreased antioxidant defense, promotes the development of hepatic and extrahepatic complications of HCV infection. The principal mechanisms causing oxidative stress in HCV-positive subjects have only been partially elucidated and have identified chronic inflammation, iron overload, ER stress, and a direct activity of HCV proteins in increasing mitochondrial ROS production, as key events. This review summarizes current knowledge regarding mechanisms of HCV-induced oxidative stress with its long-term effects in the context of HCV-related diseases, and includes a discussion of recent contributions from proteomics studies.

Iron state in association with retinoid metabolism in non-alcoholic fatty liver disease

AIM

  We have recently reported that hyperdynamic state of retinoid metabolism, which may lead to the shortage of retinoid, is observed in patients with non-alcoholic fatty liver disease (NAFLD). Hepatic iron overload, which causes production of reactive oxygen species (ROS), is also frequently seen in NAFLD patients. The aim of the study is to examine iron state and retinoid metabolic state simultaneously, and to clarify the relationship between two disorders.

METHODS

  Thirty-six persons, comprising 17 patients with simple steatosis (SS), 11 with NASH, and 8 normal controls (N), were examined on hepatic expression of iron metabolism-related genes including hemojuvelin (HJV), hepcidin (HEPC), transferrin receptor 1 and 2 (TfR1, TfR2), ferroportin (FPN), neogenin (NEO) and ferritin heavy chain (FtH) and hepatic iron contents in addition to expression 51 genes which is involved in retinoid metabolism and antioxidative action.

RESULTS

  In patients with NAFLD, expression of HJV, TfR2, FPN, TfR1, FtH, SOD and catalase was increased, compared with that in N. In addition, hepatic iron content, which was increased in NASH, was correlated with expression level of TfR2. Expression of cellular retinoid binding protein (CRBP1), alcohol dehydrogenase 1 (ADH1) and cytochrome P450 26A1(CYP26A1) was significantly correlated with that of HJV, TfR2 and FPN, respectively.

CONCLUSION

  The results of the present study suggest that the reasons responsible for iron accumulation in NASH in the present study may partly be due to enhanced expression of TfRs, especially TfR2, and hyperdynamic state of retinoid metabolism is closely related to iron metabolism in the disease.

Importance of hepatitis C virus-associated insulin resistance: Therapeutic strategies for insulin sensitization

Insulin resistance is one of the pathological features in patients with hepatitis C virus (HCV) infection. Generally, persistence of insulin resistance leads to an increase in the risk of life-threatening complications such as cardiovascular diseases. However, these complications are not major causes of death in patients with HCV-associated insulin resistance. Indeed, insulin resistance plays a crucial role in the development of various complications and events associated with HCV infection. Mounting evidence indicates that HCV-associated insulin resistance may cause (1) hepatic steatosis; (2) resistance to anti-viral treatment; (3) hepatic fibrosis and esophageal varices; (4) hepatocarcinogenesis and proliferation of hepatocellular carcinoma; and (5) extrahepatic manifestations. Thus, HCV-associated insulin resistance is a therapeutic target at any stage of HCV infection. Although the risk of insulin resistance in HCV-infected patients has been documented, therapeutic guidelines for preventing the distinctive complications of HCV-associated insulin resistance have not yet been established. In addition, mechanisms for the development of HCV-associated insulin resistance differ from lifestyle-associated insulin resistance. In order to ameliorate HCV-associated insulin resistance and its complications, the efficacy of the following interventions is discussed: a late evening snack, coffee consumption, dietary iron restriction, phlebotomy, and zinc supplements. Little is known regarding the effect of anti-diabetic agents on HCV infection, however, a possible association between use of exogenous insulin or a sulfonylurea agent and the development of HCC has recently been reported. On the other hand, insulin-sensitizing agents are reported to improve sustained virologic response rates. In this review, we summarize distinctive complications of, and therapeutic strategies for, HCV-associated insulin resistance. Furthermore, we discuss supplementation with branched-chain amino acids as a unique insulin-sensitizing strategy for patients with HCV-associated insulin resistance.

Successful antiviral therapy is associated with a decrease of serum prohepcidin in chronic hepatitis C

AIM: To assess serum concentrations of prohepcidin in chronic hepatitis C individuals and evaluate their associations with disease activity and efficacy of pegylated interferon (PEG-IFN)/ribavirin (RBV) therapy.

METHODS: Prohepcidin was measured in sera of 53 chronic hepatitis C patients. Concentrations of prohepcidin and other iron metabolism markers were analyzed at 9 time points before, during and after the end of antiviral therapy.

RESULTS: In hepatitis C virus (HCV) genotype 1-infected individuals, a gradual decrease of prohepcidin during antiviral therapy was observed in responders (88.8 ± 14.7 ng/mL before therapy vs 60.6 ± 0.3 ng/mL in the 48th wk, P = 0.04). In contrast, no decrease was observed in non-responders. A similar association was observed in HCV genotype 3a individuals, with a statistically significant decline in serum prohepcidin only in the responder group (99.5 ± 5.2 ng/mL at baseline vs 72.7 ± 6.1 ng/mL in the 24th wk, P = 0.01). Moreover, HCV-RNA at week 12 of therapy was positively correlated with baseline (R = 0.63, P < 0.005) and week 12 (R = 0.60, P = 0.01) serum prohepcidin concentrations in HCV genotype 1 infection.

CONCLUSION: Successful PEG-IFN/RBV therapy results in a decline of serum prohepcidin concentration in chronic hepatitis C, which may suggest a direct effect of HCV on iron metabolism at the prohormonal level of hepcidin.

The role of MR imaging in detection of hepatic iron overload in patients with cirrhosis of different origins

Background

There are many pathological conditions with hepatic iron overload. Classical definite diagnostic methods of these disorders are invasive and based on a direct tissue biopsy material. For the last years the role of MR imaging in liver diagnostics has been increasing. MRI shows changes of liver intensity in patients with hepatic iron overload. Changes in MR signal are an indirect consequence of change of relaxation times T2 and T2*, that can be directly measured.

The purpose of the study was to evaluate usefulness of MR imaging in the detection of hepatic iron overload in patients with cirrhosis of different origins.

Methods

MR imaging at 1.5T was prospectively performed in 44 patients with liver cirrhosis who had undergone liver biopsy with histopathological assessment of hepatic iron deposits. In all patients the following sequences were used: SE, Express, GRE in T2 and T1-weighted images. Signal intensity (SI) was measured on images obtained with each T2 weighted sequence by means of regions of interest, placed in the liver and paraspinal muscles. The correlation between iron overload, histopathological score, serum ferritin and SI ratio was analyzed.

Results

In 20 patients with iron overload confirmed by the biopsy, the liver parenchyma demonstrated lower signal intensity than that of paraspinal muscles. This effect was visible only in 8 patients with hepatic iron overload in Express T2-weighted images. Higher signal intensity of liver than that of skeletal muscles on GRE - T2 weighted images was noted in 24 patients with cirrhosis and without elevated hepatic iron concentration. We observed a correlation between low and high iron concentration and liver to muscle SI ratio.

Conclusion

MR imaging is a useful and fast noninvasive diagnostic tool for the detection of liver iron overload in patients with cirrhosis of different origins.

Liver to muscle SI ratio in GRE-T2-weighted sequence facilitates to differentiate patients with low and high degree of hepatic iron overload, which correlates with the origin of liver cirrhosis.

Patterns of hepatic iron distribution in patients with chronically transfused thalassemia and sickle cell disease

Patients with sickle cell disease (SCD) appear to be at lower risk of endocrinopathies and cardiac dysfunction than those with thalassemia major (TM). Circulating redox active iron is lower in these patients, possibly due to increased systemic inflammation and circulating cytokines. Hepcidin synthesis is upregulated during chronic inflammation, reducing intestinal iron absorption and promoting retention of iron in the reticuloendothelial cells. Hence, we hypothesized that livers of patients with SCD would exhibit greater iron deposition in sinusoidal spaces relative to hepatocytes and less in portal tracts when compared to patients with TM. To test this hypothesis, iron scoring analysis was performed on 70 clinically indicated liver biopsy specimens from children and young adults with the two syndromes. Sinusoidal scores were lower in around 1 of 4 patients with TM but the relative iron loading in hepatocytes, and portal tracts was identical in both diseases. Sinusoidal iron burdens saturated at low hepatic iron concentration (HIC) while hepatocyte and portal iron depots increased proportionally to HIC. Liver fibrosis was increased in patients with TM regardless of their chronic hepatitis status. Overall, liver iron distribution was relatively insensitive to differences in disease type and to the presence or absence of hepatitis.

Modulation of Iron-Regulatory Genes in Human Hepatocellular Carcinoma and Its Physiological Consequences

Hepatocellular carcinoma (HCC) commonly develops in patients with underlying chronic liver disease. Additionally, the tumorous lesions of HCC patients are consistently characterized by the lack of iron accumulation even when arising in iron-loaded liver. However, the molecular mechanism leading to this observed phenomenon is currently poorly understood. In this study, all tumorous tissues from 24 HCC patients with chronic HBV infection were stained negative for iron when histologically assessed by Perls’ Prussian blue stain, whereas excess iron deposits were present in 17 of the 24 adjacent non-tumorous liver tissues. To elucidate the concerted regulation of iron homeostasis in these patients, we studied the gene expression profiling of 42 relevant iron-regulatory genes in the tumorous and adjacent non-tumorous liver tissues of these HCC patients along with 10 normal liver controls. Expression for most of the iron-regulatory genes, including hepcidin, transferrin receptor 2 (TfR2), transferrin (Tf), ceruloplasmin (Cp) and iron regulatory protein 1 (IRP1), were significantly down-regulated in the tumorous tissues of these patients compared to the adjacent non-tumorous liver tissues and normal liver controls. On the other hand, expression of hepcidin, TfR2, ferroportin 1 and DMT1 were significantly up-regulated in iron-loaded non-cirrhotic non-tumorous liver tissues as compared with normal liver controls. Hence, the reduction of hepcidin expression within the iron-depleted tumorous lesions likely reflects the physiological consequence of the obligate demand for iron in the rapidly growing neoplastic cells, whereas the up-regulation of hepcidin expression in the iron-loaded adjacent non-tumorous liver tissues is likely a physiological response.

In vitro-targeted gene identification in patients with hepatitis C using a genome-wide microarray technology

Iron in association with reactive oxygen species (ROS) is highly toxic, aggravating oxidative stress reactions. Increased iron not only plays an important role in the progression of hereditary hemochromatosis (HH) but also in common liver diseases such as chronic hepatitis C. The underlying mechanisms of hepatitis C virus (HCV)-mediated iron accumulation, however, are poorly understood. We introduce an in vitro-targeted approach to identify ROS/iron-regulated genes in patients with HCV using a genome-wide DNA microarray. The sensitivity of the 32,231 complementary DNA clone-carrying microarray was approximately 20% as estimated by detecting target genes of the genome-wide transcription factor hypoxia inducible factor 1alpha. Upon in vitro challenge to iron and oxidative stress, 265 iron-related and 1326 ROS-related genes could be identified in HepG2 cells; 233 significantly regulated genes were found in patients with mild (HCV) or severe (HH) iron deposition. Notably, 17 of the in vitro-selected genes corresponded to the genes identified in patients with HCV or HH. Among them, natriuretic peptide precursor B (NPPB) was the only iron-regulated gene identified in vitro that was differentially regulated between HCV and HH. Reverse-transcription polymerase chain reaction confirmed most of the microarray-identified genes in an even larger group of patients (n = 12). In patients with HCV, these included genes that are associated with RNA processing (MED9/NFAT, NSUN2), proliferation, differentiation, hypoxia, or iron metabolism (ISG20, MIG6, HIG2, CA9, NDRG1), whereas none of the nine known iron-related genes showed significant differences between HCV and HH.

CONCLUSION

Although high-density microarray technology is less suitable for routine liver diagnosis, its use in combination with prior in vitro selection is a powerful approach to identify candidate genes relevant for liver disease.

Suppressive effects of retinoids on iron-induced oxidative stress in the liver

BACKGROUND & AIMS

We previously reported that impaired retinoid signaling in the liver causes steatohepatitis and hepatocellular carcinoma. Recently, oxidative stress induced by hepatic iron overload has emerged as an important factor for the progression of liver disease in patients with chronic hepatitis C, alcoholic liver disease, and nonalcoholic steatohepatitis. In this study, the relationship between retinoid signaling and iron metabolism in the liver was investigated.

METHODS

The effect of retinoids on the iron metabolism was examined in HuH7 cells treated with all-trans retinoic acid and acyclic retinoid NIK-333. In in vivo experiments, we used the mice expressing the dominant negative form of retinoic acid receptor alpha gene under the control of albumin enhancer/promoter (RAR-E Tg) and iron-overloaded wild mice fed with retinoid-deficient and retinoid-excess diets.

RESULTS

Hepatic iron accumulation and increased expression of hemojuvelin were observed in RAR-E Tg mouse liver. Retinoid treatment significantly suppressed expression of hemojuvelin and mildly suppressed expression of transferrin receptor type 2 and hepcidin, accompanied by decreased hepatic iron content and iron-induced oxidative stress in vitro and in vivo. Overexpression of hemojuvelin in HuH7 hepatoma cells led to a significant increase in cellular iron content.

CONCLUSIONS

Our results suggest that retinoids are involved in hepatic iron metabolism through transcriptional regulation of hemojuvelin. This study demonstrated a novel functional role of retinoids in preventing iron-induced oxidative stress in the liver.

Viral infection and iron metabolism

Fundamental cellular operations, including DNA synthesis and the generation of ATP, require iron. Viruses hijack cells in order to replicate, and efficient replication needs an iron-replete host. Some viruses selectively infect iron-acquiring cells by binding to transferrin receptor 1 during cell entry. Other viruses alter the expression of proteins involved in iron homeostasis, such as HFE and hepcidin. In HIV-1 and hepatitis C virus infections, iron overload is associated with poor prognosis and could be partly caused by the viruses themselves. Understanding how iron metabolism and viral infection interact might suggest new methods to control disease.

Comparison of hepatic oxidative DNA damage in patients with chronic hepatitis B and C

8-Hydroxydeoxyguanosine (8-OHdG) is a promutagenic DNA lesion produced by hydroxyl radicals and is recognized as a useful marker in estimating DNA damage induced by oxidative stress. The aim of this study was to clarify the clinical significance of hepatic 8-OHdG levels in patients with chronic viral hepatitis. Hepatic 8-OHdG accumulation was investigated in patients with chronic hepatitis C (CH-C) (n = 77) and chronic hepatitis B (CH-B) (n = 34) by immunohistochemical staining of liver biopsy samples. 8-OHdG positive hepatocytes were significantly higher in patients with CH-C compared to CH-B (median 55.0 vs 18.8 cells/10(5) mum(2), P < 0.0001). The number of positive hepatocytes significantly increased with the elevation of serum aminotransferase levels, especially in CH-C patients (8-OHdG vs alanine aminotransferase (ALT)/aspartate aminotrasferase (AST) were r = 0.738/0.720 in CH-C and 0.506/0.515 in CH-B). 8-OHdG reactivity was strongly correlated with body and hepatic iron storage markers in CH-C (vs serum ferritin, r = 0.615; vs hepatic total iron score, r = 0.520; vs hepatic hepcidin mRNA levels, r = 0.571), although it was related to serum HBV-DNA titers (r = 0.540) and age of patients (r = -0.559) in CH-B. These results indicate that hepatic oxidative DNA damage is common in chronic viral hepatitis, in particular chronic HCV-infected patients, suggesting a possible link between chronic hepatic inflammation and hepatocarcinogenesis. The strong positive correlation between hepatic DNA damage and iron overload suggests that iron content is one of the most likely mediators of hepatic oxidative stress and iron reduction may be beneficial to reduce the incidence of hepatic cancer in CH-C patients.

Hepatic iron accumulation is associated with disease progression and resistance to interferon/ribavirin combination therapy in chronic hepatitis C

BACKGROUND AND AIMS

Liver iron accumulation in patients with chronic hepatitis C (CHC) has received increasing attention in recent years. The aim of this study was to determine the prevalence and severity of liver iron deposition in CHC, to assess its relationship with clinical, biochemical and histological characteristics, and to study its influence on the response to interferon (IFN) plus ribavirin combination therapy.

METHODS

We studied liver biopsy specimens from 103 hepatitis C virus (HCV) and 34 hepatitis B virus (HBV) infected patients and total iron score (TIS) was measured. Seventy patients infected with HCV genotype 1b were treated with IFN/ribavirin for 24 weeks.

RESULTS

CHC patients had a significantly higher TIS than chronic hepatitis B (CHB) patients (7.03 +/- 5.34 vs 4.41 +/- 4.49, P = 0.0056). TIS was significantly correlated with alcohol intake (P = 0.0213, r = 0.290), transaminase level (P = 0.0126, r = 0.247), platelet count (P = 0.0002, r = -0.369), histological grading (P = 0.0121, r = 0.248) and staging (P = 0.0003, r = 0.356) in CHC patients. Pretreatment TIS was significantly higher in non-sustained virological responders (SVR) than in SVR to IFN/ribavirin treatment (TIS = 7.69 +/- 5.76 vs 4.39 +/- 3.27, P = 0.0310). Multiple regression analysis showed that TIS was the only independent variable associated with resistance to IFN/ribavirin (P = 0.0277).

CONCLUSIONS

Liver iron deposition was common in CHC compared to CHB and was associated with liver disease progression. Increased hepatic iron stores in CHC were related to resistance to IFN/ribavirin treatment.

Iron overload and cofactors with special reference to alcohol, hepatitis C virus infection and steatosis/insulin resistance

There are several cofactors which affect body iron metabolism and accelerate iron overload. Alcohol and hepatic viral infections are the most typical examples for clarifying the role of cofactors in iron overload. In these conditions, iron is deposited in hepatocytes and Kupffer cells and reactive oxygen species (ROS) produced through Fenton reaction have key role to facilitate cellular uptake of transferrin-bound iron. Furthermore, hepcidin, antimicrobial peptide produced mainly in the liver is also responsible for intestinal iron absorption and reticuloendothelial iron release. In patients with ceruloplasmin deficiency, anemia and secondary iron overload in liver and neurodegeneration are reported. Furthermore, there is accumulating evidence that fatty acid accumulation without alcohol and obesity itself modifies iron overload states. Ineffective erythropoiesis is also an important factor to accelerate iron overload, which is associated with diseases such as thalassemia and myelodysplastic syndrome. When this condition persists, the dietary iron absorption is increased due to the increment of bone marrow erythropoiesis and tissue iron overload will thereafter occurs. In porphyria cutanea tarda, iron is secondarily accumulated in the liver.

Hepcidin expression in the liver: relatively low level in patients with chronic hepatitis C

Patients with chronic hepatitis C frequently have serum and hepatic iron overload, but the mechanism is unknown. Recently identified hepcidin, exclusively synthesized in the liver, is thought to be a key regulator for iron homeostasis and is induced by infection and inflammation. This study was conducted to determine the hepatic hepcidin expression levels in patients with various liver diseases. We investigated hepcidin mRNA levels of liver samples by real-time detection-polymerase chain reaction; 56 were hepatitis C virus (HCV) positive, 34 were hepatitis B virus (HBV) positive, and 42 were negative for HCV and HBV (3 cases of auto-immune hepatitis, 7 alcoholic liver disease, 13 primary biliary cirrhosis, 9 nonalcoholic fatty liver disease, and 10 normal liver). We analyzed the relation of hepcidin to clinical, hematological, histological, and etiological findings. Hepcidin expression levels were strongly correlated with serum ferritin (P < 0.0001) and the degree of iron deposit in liver tissues (P < 0.0001). Hepcidin was also correlated with hematological parameters (vs. hemoglobin, P = 0.0073; vs. serum iron, P = 0.0012; vs. transferrin saturation, P < 0.0001) and transaminase levels (P = 0.0013). The hepcidin-to-ferritin ratio was significantly lower in HCV(+) patients than in HBV(+) patients (P = 0.0129) or control subjects (P = 0.0080). In conclusion, hepcidin expression levels in chronic liver diseases were strongly correlated with either the serum ferritin concentration or degree of iron deposits in the liver. When adjusted by either serum ferritin values or hepatic iron scores, hepcidin indices were significantly lower in HCV(+) patients than in HBV(+) patients, suggesting that hepcidin may play a pivotal role in the pathogenesis of iron overload in patients with chronic hepatitis C.

TfR2 localizes in lipid raft domains and is released in exosomes to activate signal transduction along the MAPK pathway

Transferrin receptor 2 (TfR2) possesses a YQRV motif similar to the YTRF motif of transferrin receptor 1 (TfR1) responsible for the internalization and secretion through the endosomal pathway. Raft biochemical dissection showed that TfR2 is a component of the low-density Triton-insoluble (LDTI) plasma membrane domain, able to co-immunoprecipitate with caveolin-1 and CD81, two structural raft proteins. In addition, subcellular fractionation experiments showed that TfR1, which spontaneously undergoes endocytosis and recycling, largely distributed to intracellular organelles, whereas TfR2 was mainly associated with the plasma membrane. Given the TfR2 localization in lipid rafts, we tested its capability to activate cell signalling. Interaction with an anti-TfR2 antibody or with human or bovine holotransferrin showed that it activated ERK1/ERK2 and p38 MAP kinases. Integrity of lipid rafts was required for MAPK activation. Co-localization of TfR2 with CD81, a raft tetraspanin exported through exosomes, prompted us to investigate exosomes released by HepG2 and K562 cells into culture medium. TfR2, CD81 and to a lesser extent caveolin-1, were found to be part of the exosomal budding vesicles. In conclusion, the present study indicates that TfR2 localizes in LDTI microdomains, where it promotes cell signalling, and is exported out of the cells through the exosome pathway, where it acts as an intercellular messenger.

Role of transferrin receptor 2 in hepatic accumulation of iron in patients with chronic hepatitis C

BACKGROUND AND AIM

Iron deposition in the liver is a common finding in patients with chronic hepatitis C (CH-C). The mechanism of this hepatic accumulation of iron is not completely understood. This study assessed if the protein expression of transferrin receptor 2 (TfR2) is upregulated in the liver of patients with CH-C and if TfR2 protein mediates iron accumulation during hepatitis C virus (HCV) infection.

METHOD

Liver specimens from patients with CH-C that underwent interferon (IFN) therapy (n=23) and from patients with CH-B (n=18) were evaluated. Hepatic expression of TfR2 protein was analyzed by immunohistochemistry. Total hepatic iron score (THIS) was evaluated by Prussian blue staining.

RESULTS

TfR2 protein was expressed in the cell membrane and cytosol of hepatocytes. Cytosol TfR2 protein was found to co-localize with Tf. THIS (P=0.0198) and hepatic TfR2 (P=0.0047) expression were significantly higher in CH-C than in CH-B. The change in THIS values (rho=0.580, P=0.0079) and the grade of histological activity (rho=0.444, P=0.0373) were significantly correlated with changes in TfR2 expression after IFN therapy.

CONCLUSIONS

The protein expression of TfR2 is significantly associated with iron deposition in the liver in patients with CH-C. HCV infection may affect the hepatic expression of TfR2, leading to iron accumulation in the liver.