Analysis of hepcidin expression: In situ hybridization and quantitative polymerase chain reaction from paraffin sections

AIM: To establish methods for quantitative polymerase chain reaction (PCR) for hepcidin using RNAs isolated from paraffin-embedded sections and in situ hybridization of hepatocellular carcinoma (HCC).

METHODS: Total RNA from paraffin-embedded sections was isolated from 68 paraffin-embedded samples of HCC. Samples came from 54 male and 14 female patients with a mean age of 66.8 ± 7.8 years. Quantitative PCR was performed. Immunohistochemistry and in situ hybridization for hepcidin were also performed.

RESULTS: Quantitative PCR for hepcidin using RNAs isolated from paraffin-embedded sections of HCC was performed successfully. The expression level of hepcidin mRNA in cancer tissues was significantly higher than that in non-cancer tissues. A method of in situ hybridization for hepcidin was established successfully, and this demonstrated that hepcidin mRNA was expressed in non-cancerous tissue but absent in cancerous tissue.

CONCLUSION: We have established novel methods for quantitative PCR for hepcidin using RNAs isolated from paraffin-embedded sections and in situ hybridization of HCC.

Hepcidin expression in iron overload diseases is variably modulated by circulating factors

Hepcidin is a regulatory hormone that plays a major role in controlling body iron homeostasis. Circulating factors (holotransferrin, cytokines, erythroid regulators) might variably contribute to hepcidin modulation in different pathological conditions. There are few studies analysing the relationship between hepcidin transcript and related protein expression profiles in humans. Our aims were: a. to measure hepcidin expression at either hepatic, serum and urinary level in three paradigmatic iron overload conditions (hemochromatosis, thalassemia and dysmetabolic iron overload syndrome) and in controls; b. to measure mRNA hepcidin expression in two different hepatic cell lines (HepG2 and Huh-7) exposed to patients and controls sera to assess whether circulating factors could influence hepcidin transcription in different pathological conditions. Our findings suggest that hepcidin assays reflect hepatic hepcidin production, but also indicate that correlation is not ideal, likely due to methodological limits and to several post-trascriptional events. In vitro study showed that THAL sera down-regulated, HFE-HH and C-NAFLD sera up-regulated hepcidin synthesis. HAMP mRNA expression in Huh-7 cells exposed to sera form C-Donors, HFE-HH and THAL reproduced, at lower level, the results observed in HepG2, suggesting the important but not critical role of HFE in hepcidin regulation.

Glycogen synthase kinase 3β inhibition sensitizes pancreatic cancer cells to gemcitabine

BACKGROUND

Pancreatic cancer is obstinate and resistant to gemcitabine, a standard chemotherapeutic agent for the disease. We previously showed a therapeutic effect of glycogen synthase kinase-3β (GSK3β) inhibition against gastrointestinal cancer and glioblastoma. Here, we investigated the effect of GSK3β inhibition on pancreatic cancer cell sensitivity to gemcitabine and the underlying molecular mechanism.

METHODS

Expression, phosphorylation, and activity of GSK3β in pancreatic cancer cells (PANC-1) were examined by Western immunoblotting and in vitro kinase assay. The combined effect of gemcitabine and a GSK3β inhibitor (AR-A014418) against PANC-1 cells was examined by isobologram and PANC-1 xenografts in mice. Changes in gene expression in PANC-1 cells following GSK3β inhibition were studied by cDNA microarray and reverse transcription (RT)-PCR.

RESULTS

PANC-1 cells showed increased GSK3β expression, phosphorylation at tyrosine 216 (active form), and activity compared with non-neoplastic HEK293 cells. Administration of AR-A014418 at pharmacological doses attenuated proliferation of PANC-1 cells and xenografts, and significantly sensitized them to gemcitabine. Isobologram analysis determined that the combined effect was synergistic. DNA microarray analysis detected GSK3β inhibition-associated changes in gene expression in gemcitabine-treated PANC-1 cells. Among these changes, RT-PCR and Western blotting showed that expression of tumor protein 53-induced nuclear protein 1, a gene regulating cell death and DNA repair, was increased by gemcitabine treatment and substantially decreased by GSK3β inhibition.

CONCLUSIONS

The results indicate that GSK3β inhibition sensitizes pancreatic cancer cells to gemcitabine with altered expression of genes involved in DNA repair. This study provides insight into the molecular mechanism of gemcitabine resistance and thus a new strategy for pancreatic cancer chemotherapy.

A case of congenital dyserythropoietic anemia type 1 in a Japanese adult with a CDAN1 gene mutation and an inappropriately low serum hepcidin-25 level

We describe the first case of genetically diagnosed congenital dyserythropoietic anemia (CDA) type 1 in a Japanese man. The patient had hemolytic anemia since he was a child, and he developed diabetes, hypogonadism, and liver dysfunction in his thirties, presumably from systemic iron overload. When he was 48 years old a diagnosis was finally made by genetic analysis that revealed a homozygous mutation of CDAN1 gene (Pro1129Leu). His serum hepcidin-25 level was inappropriately low. We conclude that physicians should be aware of the possibility of CDA in a patient with anemia and systemic iron overload at any age.

A novel clinical entity, IgG4-related disease (IgG4RD): general concept and details

IgG4-related disease (IgG4RD) is a novel clinical disease entity characterized by elevated serum IgG4 concentration and tumefaction or tissue infiltration by IgG4-positive plasma cells. IgG4RD may be present in a certain proportion of patients with a wide variety of diseases, including Mikulicz’s disease, autoimmune pancreatitis, hypophysitis, Riedel thyroiditis, interstitial pneumonitis, interstitial nephritis, prostatitis, lymphadenopathy, retroperitoneal fibrosis, inflammatory aortic aneurysm, and inflammatory pseudotumor. Although IgG4RD forms a distinct, clinically independent disease category and is attracting strong attention as a new clinical entity, many questions and problems still remain to be elucidated, including its pathogenesis, the establishment of diagnostic criteria, and the role of IgG4. Here we describe the concept of IgG4RD and up-to-date information on this emerging disease entity.

Serum hepcidin-25 levels and anemia in non-dialysis chronic kidney disease patients: a cross-sectional study

BACKGROUND

Hepcidin is a central regulator of iron homeostasis. Increased hepcidin concentrations could cause iron-restricted erythropoiesis in chronic kidney disease (CKD)-associated anemia. This cross-sectional observational study was conducted to evaluate the association between hepcidin and CKD-associated anemia in non-dialysis CKD patients.

METHODS

A total of 505 non-dialysis CKD patients not treated with parenteral iron were recruited, and serum hepcidin-25 levels were measured by liquid chromatography tandem mass spectrometry. Multiple linear regression analysis was used to examine the relationship between hepcidin and glomerular filtration rate (GFR) and the relationship between hemoglobin concentration and predictors including the hepcidin level.

RESULTS

The median hepcidin level among the 505 CKD patients was 15.4 ng/mL (interquartile range, 5.5-33.6 ng/mL). Although hepcidin level significantly increased according to the CKD stage, multivariate analysis did not reveal an association of GFR with the hepcidin level. Hepcidin level was a significant predictor of hemoglobin concentration after the adjustment for confounders, and a significant interaction between hepcidin and ferritin was found. After stratifying at the median ferritin level, 91 ng/mL, we found a negative association between hepcidin level and hemoglobin in the high-ferritin group. A trend toward a negative association between hepcidin level and mean corpuscular volume was observed in the high-ferritin group.

CONCLUSIONS

Serum hepcidin-25 levels were negatively associated with hemoglobin concentrations in non-dialysis CKD patients with sufficient iron stores. We found that ferritin modified the association between hepcidin level and hemoglobin concentration. In addition, our results confirmed that the serum hepcidin level is not associated with GFR.

Ultraviolet B-induced expression of amphiregulin and growth differentiation factor 15 in human lens epithelial cells

PURPOSE

Epidemiological and experimental studies have revealed that exposure to ultraviolet B (UVB) light can induce cataractogenesis. The objective of this study was to determine gene expression changes in human lens epithelial cells in response to UVB exposure and identify factors that can be involved in UVB-induced cataractogenesis.

METHODS

SV40 T-antigen-transformed human lens epithelial cells (SRA01/04) were irradiated at various UVB-energy levels (10-80 mJ/cm²) and checked for viability. An irradiation condition of 30 mJ/cm² was adopted for transcriptome analysis. Total RNAs isolated from UVB-exposed and unexposed cells at 12 h and 24 h after UVB exposure were examined for global gene expression changes using Affymetrix Human Gene 1.0 ST array. mRNA levels of specific genes were examined by RT-PCR and real-time PCR, and protein levels in the conditioned media were assayed by ELISA. To examine mRNA expression in human lens, primary cultured human lens epithelial (HLE) cells were prepared from surgically removed lens epithelium, and used for UVB-irradiation and expression analysis. Effects of certain gene products on SRA01/04 cell metabolism were examined using commercially available recombinant proteins.

RESULTS

Expression of most the genes analyzed was essentially unchanged (between 0.5 and 2.0 fold) in UVB-irradiated cells compared to non-irradiated cells at both 12 and 24 h after UVB exposure. Sixty one and 44 genes were upregulated more than twofold by UVB exposure at 12 h and 24 h, respectively. Emphasis was placed on genes encoding extracellular proteins, especially growth factors and cytokines. A total of 18 secreted protein genes were upregulated more than twofold at either or both time points. Amphiregulin (AREG) and growth differentiation factor 15 (GDF15) were chosen because of their higher upregulation and novelty, and their upregulation was confirmed in SRA01/04 cells using RT-PCR and real-time PCR analysis. AREG and GDF15 protein levels in conditioned media significantly increased at all UVB-energy points at 24 h, while they were scarcely detectable at 12 h. AREG and GDF15 mRNA levels were also significantly upregulated in UVB-irradiated primary cultured HLE cells compared with the corresponding control culture. AREG significantly stimulated ³H-thymidine and ³H-leucine uptake in SRA01/04 cells as did a positive control epidermal growth factor (EGF). Recombinant GDF15 did not stimulate ³H-thymidine incorporation at any concentration tested, but significantly stimulated ³H-leucine uptake. RT-PCR analysis demonstrated that primary cultured HLE and SRA01/04 cells expressed not only epidermal growth factor receptor (EGFR) mRNA but also transforming growth factor β receptors (TGFBR1 and TGFBR2) mRNAs.

CONCLUSIONS

These results indicate that AREG and GDF15 produced in response to UVB exposure can affect the growth and protein synthesis of lens epithelial cells, suggesting that they have autocrine and paracrine roles related to pathological changes of lens tissue during long-term UVB exposure.

Measurement of serum hepcidin-25 levels as a potential test for diagnosing hemochromatosis and related disorders

BACKGROUND

Iron overload syndromes include a wide spectrum of genetic and acquired conditions. Recent studies suggest suppressed hepcidin synthesis in the liver to be the molecular basis of hemochromatosis. However, a liver with acquired iron overload synthesizes an adequate amount of hepcidin. Thus, hepcidin could function as a biochemical marker for differential diagnosis of iron overload syndromes.

METHODS

We measured serum iron parameters and hepcidin-25 levels followed by sequencing HFE, HJV, HAMP, TFR2, and SLC40A1 genes in 13 Japanese patients with iron overload syndromes. In addition, we performed direct measurement of serum hepcidin-25 levels using liquid chromatography-tandem mass spectrometry in 3 Japanese patients with aceruloplasminemia and 4 Italians with HFE hemochromatosis.

RESULTS

One patient with HJV hemochromatosis, 2 with TFR2 hemochromatosis, and 3 with ferroportin disease were found among the 13 Japanese patients. The remaining 7 Japanese patients showed no evidence for genetic basis of iron overload syndrome. As far as the serum hepcidin-25 was concerned, seven patients with hemochromatosis and 3 with aceruloplasminemia showed markedly decreased serum hepcidin-25 levels. In contrast, 3 patients with ferroportin disease and 7 with secondary iron overload syndromes showed serum hepcidin levels parallel to their hyperferritinemia. Patients with iron overload syndromes were divided into 2 phenotypes presenting as low and high hepcidinemia. These were then associated with their genotypes.

CONCLUSION

Determining serum hepcidin-25 levels may aid differential diagnosis of iron overload syndromes prior to genetic analysis.

Biological effects of mutant ceruloplasmin on hepcidin-mediated internalization of ferroportin

Ceruloplasmin plays an essential role in cellular iron efflux by oxidizing ferrous iron exported from ferroportin. Ferroportin is posttranslationally regulated through internalization triggered by hepcidin binding. Aceruloplasminemia is an autosomal recessive disorder of iron homeostasis resulting from mutations in the ceruloplasmin gene. The present study investigated the biological effects of glycosylphosphatidylinositol (GPI)-linked ceruloplasmin on the hepcidin-mediated internalization of ferroportin. The prevention of hepcidin-mediated ferroportin internalization was observed in the glioma cells lines expressing endogenous ceruloplasmin as well as in the cells transfected with GPI-linked ceruloplasmin under low levels of hepcidin. A decrease in the extracellular ferrous iron by an iron chelator and incubation with purified ceruloplasmin in the culture medium prevented hepcidin-mediated ferroportin internalization, while the reconstitution of apo-ceruloplasmin was not able to prevent ferroportin internalization. The effect of ceruloplasmin on the ferroportin stability was impaired due to three distinct properties of the mutant ceruloplasmin: namely, a decreased ferroxidase activity, the mislocalization in the endoplasmic reticulum, and the failure of copper incorporation into apo-ceruloplasmin. Patients with aceruloplasminemia exhibited low serum hepcidin levels and a decreased ferroportin protein expression in the liver. The in vivo findings supported the notion that under low levels of hepcidin, mutant ceruloplasmin cannot stabilize ferroportin because of a loss-of-function in the ferroxidase activity, which has been reported to play an important role in the stability of ferroportin. The properties of mutant ceruloplasmin regarding the regulation of ferroportin may therefore provide a therapeutic strategy for aceruloplasminemia patients.

Patients with chronic hepatitis C may be more sensitive to iron hepatotoxicity than patients with HFE-hemochromatosis

AIM

In chronic hepatitis C, iron might play an important role as a hepatotoxic co-factor. Therefore, venesection, a standard treatment for hemochromatosis, has been proposed as an alternative for patients who respond poorly to anti-viral therapy. To improve our understanding of iron-induced hepatotoxicity, we compared the responses to venesection between patients with chronic hepatitis C and those with HFE-hemochromatosis.

METHODS

Fourteen Japanese patients with chronic hepatitis C and eight Italian patients with HFE-hemochromatosis underwent repeated venesection with a serum ferritin endpoint of 20 and 50 ng/mL, respectively. Serum iron indices and liver function tests were measured in pre- and post treatment blood samples from each patient. Body iron stores were calculated using the removed blood volume.

RESULTS

In both patients with hepatitis and hemochromatosis, serum ferritin, aminotransferase and hepcidin 25 were reduced after venesection. The serum aminotransferase activity, but not the serum ferritin level, was predictive of effective iron removal treatment. Hepcidin regulation was set at an inappropriately low level in hemochromatosis patients (11.1 ± 9.2 ng/mL), but not so in hepatitis patients (30.7 ± 14.5 ng/mL). Inversely, the estimated body iron stores of hemochromatosis patients were 5,960 ± 2,750 mg, while those of hepatitis patients were 730 ± 560 mg. Judging from the liver enzyme reduction ratio, patients with hepatitis seemed to be more sensitive to iron hepatotoxicity than hemochromatosis patients.

CONCLUSION

Even though the threshold of iron hepatotoxicity and benefit of its removal differ between patients with chronic hepatitis C and those with HFE-hemochromatosis, venesection is a valid choice of treatment to reduce liver disease activity in both diseases.

Iron regulatory hormone hepcidin decreases in chronic heart failure patients with anemia

BACKGROUND

The etiology of anemia is still unclear in patients with chronic heart failure (CHF). Hepcidin is an iron regulatory peptide that is synthesized in the liver to suppress iron absorption and utilization. Hepcidin synthesis is suppressed by anemia, hypoxia and erythropoiesis, and induced by inflammation. Inflammatory cytokines, such as interleukin-6 (IL-6), increase the synthesis of hepcidin, resulting in anemia of inflammation (AI). The serum hepcidin concentration in CHF patients with anemia was measured in order to better understand anemia in CHF.

METHODS AND RESULTS

Serum hepcidin-25, erythropoietin (EPO), ferritin and IL-6 concentrations were measured in 61 CHF patients. Among these patients, 36 patients had anemia. A group of 16 patients without cardiac disease or anemia were recruited as controls. Serum IL-6 and EPO were higher and hepcidin-25 was lower in CHF patients with anemia than in controls. Hepcidin-25 correlated with EPO and ferritin but not with IL-6. Results of multivariable regression analysis showed that independent predictors of serum hepcidin-25 included EPO and ferritin but not IL-6.

CONCLUSIONS

Serum hepcidin-25 concentrations were regulated by iron storage and erythropoiesis but not by IL-6 in CHF patients with anemia. These findings might indicate that AI is a minor cause of anemia in CHF.

Results of the first international round robin for the quantification of urinary and plasma hepcidin assays: need for standardization

The recently discovered iron regulatory peptide hormone hepcidin holds promise as a novel biomarker in iron metabolism disorders. To date, various mass spectrometry and immunochemical methods have been developed for its quantification in plasma and urine. Differences in methodology and analytical performance hinder the comparability of data. As a first step towards method harmonization, several hepcidin assays were compared. Worldwide eight laboratories participated in a urinary and plasma round robin in which hepcidin was analyzed. For both urine and plasma: (i) the absolute hepcidin concentrations differed widely between methods, (ii) the between-sample variation and the analytical variation of the methods are similar. Importantly, the analytical variation as percentage of the total variance is low for all methods, indicating their suitability to distinguish hepcidin levels of different samples. Spearman correlations between methods were generally high. The round robin results inform the scientific and medical community on the status and agreement of the current hepcidin methods. Ongoing initiatives should facilitate standardization by exchanging calibrators and representative samples.

Oncostatin M and leukemia inhibitory factor increase hepcidin expression in hepatoma cell lines

Overproduction of hepcidin by interleukin-6 (IL-6) is considered to be the main factor responsible for the development of anemia in inflammatory conditions. Since oncostatin M (OSM), a member of the IL-6 family, plays an important role in immune and inflammatory responses, we assessed the effect of OSM on hepcidin expression, as well as that of leukemia inhibitory factor (LIF), another member of the IL-6 family. We found that hepcidin expression was markedly induced by OSM and LIF in a time- and dose-dependent manner in hepatoma cell lines, and this expression was induced independent of IL-6/IL-6 receptor signaling. Luciferase assay revealed that OSM and LIF stimulated a -1.3-kb hepcidin promoter. This effect was markedly reduced when the signal transducer and activator of transcription (STAT) site of the promoter was mutated, and was almost completely abolished in the presence of AG-490, a Janus kinase (JAK) inhibitor. Hence, the JAK/STAT pathway plays a major role in OSM- and LIF-induced activation of the hepcidin promoter. In conclusion, we demonstrated that OSM and LIF can induce hepcidin expression mainly through the JAK/STAT pathways. Further studies are warranted to evaluate the clinical significance of OSM and LIF in the development of anemia in various inflammatory diseases.

Clinical significance of serum hepcidin levels on early infectious complications in allogeneic hematopoietic stem cell transplantation

The association of iron overload with complications of allogeneic hematopoietic stem cell transplantation (HSCT) has been suggested in previous studies. Because hepcidin plays a central role in the regulation of iron homeostasis, we analyzed the association between pretransplant serum hepcidin-25 levels and early infectious complications after allogeneic HSCT. We studied 55 consecutive adult patients with a median age of 47 years (range: 20-64 years) who underwent allogeneic HSCT for hematologic malignancies at our institution. Thirty-two patients had myelogenous malignancies; the remaining 23 had lymphogenous malignancies. The median pretransplant serum hepcidin level of patients in the study was 21.6 ng/mL (range: 1.4-371 ng/mL), which was comparable to that of healthy volunteers (median: 19.1 ng/mL [range: 2.3-37 ng/mL]; n = 17). When cumulative incidences of documented bacterial and cytomegalovirus (CMV) infections at day 100 were compared according to pretransplant hepcidin-25 levels, the incidence of bacterial, but not CMV, infection, was significantly higher in the high-hepcidin group (> or = 50 ng/mL; n = 17) than in the low-hepcidin group (<50 ng/mL; n = 38) (65% [95% confidence interval, 38%-82%] versus 11% [3%-23%]; P < .001). This finding was confirmed by multivariate Cox analysis adjusted for confounders, including pretransplant ferritin and C-reactive protein (CRP) levels. No fungal infection was documented in either group. These results suggest that the pretransplant serum hepcidin-25 level may be a useful marker for predicting the risk of early bacterial complications after allogeneic HSCT. Larger prospective studies are, however, warranted to confirm our findings.

Increased serum hepcidin-25 level and increased tumor expression of hepcidin mRNA are associated with metastasis of renal cell carcinoma

Background

Hepcidin has an important role in iron metabolism. We investigated whether hepcidin was involved in renal cell carcinoma (RCC).

Methods

We measured serum hepcidin-25 levels in 32 patients by liquid chromatograpy (LC)-mass spectrometry (MS)/MS, and assessed hepcidin mRNA expression in paired tumor and non-tumor tissue samples from the surgical specimens of 53 consecutive patients with RCC by real-time reverse transcription polymerase chain reaction.

Results

The serum hepcidin-25 level was higher in patients with metastatic RCC than nonmetastatic RCC (P < 0.0001), and was positively correlated with the serum interleukin-6 and C-reactive protein levels (P < 0.001). Expression of hepcidin mRNA was lower in tumor tissues than in non-tumor tissues (P < 0.0001). The serum hepcidin-25 level was not correlated with the expression of hepcidin mRNA in the corresponding tumor tissue specimens from 32 patients. Hepcidin mRNA expression in tumor tissue was correlated with metastatic potential, but not with histological differentiation or tumor stage. Kaplan-Meier analysis showed that over expression of hepcidin mRNA was related to shorter overall survival in RCC patients. Univariate analysis (Cox proportional hazards model) showed that the hepcidin mRNA level was an independent prognostic factor for overall survival.

Conclusion

Our findings suggest that a high serum hepcidin-25 level may indicate the progression of RCC, and that upregulation of hepcidin mRNA expression in tumor tissue may be related to increased metastatic potential.