Serum ferritin levels are associated with vascular damage in patients with nonalcoholic fatty liver disease

Abstract
Background and aims
Increased ferritin and body iron stores are frequently observed in nonalcoholic fatty liver disease (NAFLD), associated with heightened susceptibility to vascular damage. Conflicting data have been reported on the role of iron in atherosclerosis, with recent data suggesting that excess iron induces vascular damage by increasing levels of the hormone hepcidin, which would determine iron trapping into macrophages, oxidative stress, and promotion of transformation into foam cells. Aim of this study was to investigate the relationship between iron status and cardiovascular damage in NAFLD.

Methods and results
Vascular damage was evaluated by common carotid arteries intima-media thickness (CC-IMT) measurement and plaque detection by ecocolor-doppler ultrasonography in 506 patients with clinical and ultrasonographic diagnosis of NAFLD, hemochromatosis gene (HFE) mutations by restriction analysis in 342 patients. Serum hepcidin-25 was measured by time-of-flight mass spectrometry in 143 patients. At multivariate analysis CC-IMT was associated with systolic blood pressure, glucose, LDL cholesterol, abdominal circumference, age, and ferritin (p = 0.048). Carotid plaques were independently associated with age, ferritin, glucose, and hypertension. Ferritin reflected iron stores and metabolic syndrome components, but not inflammation or liver damage. Hyperferritinemia was associated with increased vascular damage only in patients with HFE genotypes associated with hepcidin upregulation by iron stores (p < 0.0001), and serum hepcidin-25 was independently associated with carotid plaques (p = 0.05).

Conclusion
Ferritin levels, reflecting iron stores, are independent predictors of vascular damage in NAFLD. The mechanism may involve upregulation of hepcidin by increased iron stores in patients not carrying HFE mutations, and iron compartmentalization into macrophages.


Ramettaa, , S. Fargiona, , and A.L. Fracanzania,

a Center for the Study of Metabolic and Liver Diseases, Department of Internal Medicine, Università degli Studi Milano, Internal Medicine 1B, Hospital Fondazione Policlinico MaRE IRCCS, Granelli pavilion, via F Sforza 35, 20122 Milano, Italy

b Department of Clinical Chemistry, Radboud University Nijmegen Medical Centre, Nijmegen, the Netherlands

Serum ferritin as risk factor for sinusoidal obstruction syndrome of the liver in patients undergoing hematopoietic stem cell transplantation

Hepatic sinusoidal obstruction syndrome (SOS) is a serious complication in hematopoietic stem cell transplant (HSCT) recipients. To determine the impact of pretransplantation hyperferritinemia on the risk of SOS after HSC transplantation, we retrospectively studied 427 HSCT recipients (179 autologous and 248 allogeneic). Serum ferritin levels were measured before transplantation. Patients with and without a diagnosis of SOS were compared regarding demographics; underlying disease; transplant characteristics; receipt of imatinib, busulfan, total body irradiation, gemtuzumab, vancomycin, acyclovir, or methotrexate; and baseline serum ferritin. Univariate and multivariate (stepwise logistic regression) analyses were performed. SOS was diagnosed in 88 patients (21%) at a median of 10 days (range, 2-29 days) after transplantation. By multivariate analysis, allogeneic HSC transplantation (odds ratio [OR] = 8.25; 95% confidence interval [95% CI], 3.31-20.57), receipt of imatinib (OR = 2.60; 95% CI, 1.16-5.84), receipt of busulfan (OR = 2.18; 95% CI, 1.25-3.80), and ferritin serum level higher than 1000 ng/dL (OR = 1.78; 95% CI, 1.02-3.08) were risk factors for SOS.

A ferritin serum level higher than 1000 ng/dL in the pretransplantation period is an independent risk factor for SOS. The results suggest the need for prospective studies addressing the use of iron chelation in the pretransplantation period

Maradei SC, Maiolino A, de Azevedo AM, Colares M, Bouzas LF, Nucci M.
Bone Marrow Transplantation Center (CEMO), Instituto Nacional de Câncer (INCA), Rio de Janeiro, Brazil

Ferritins: A family of molecules for iron storage, antioxidation and more

Ferritins are characterized by highly conserved three-dimensional structures similar to spherical shells, designed to accommodate large amounts of iron in a safe, soluble and bioavailable form. They can have different architectures with 12 or 24 equivalent or non-equivalent subunits, all surrounding a large cavity. All ferritins readily interact with Fe(II) to induce its oxidation and deposition in the cavity in a mineral form, in a reaction that is catalyzed by a ferroxidase center. This is an anti-oxidant activity that consumes Fe(II) and peroxides, the reagents that produce toxic free radicals in the Fenton reaction. The mechanism of ferritin iron incorporation has been characterized in detail, while that of iron release and recycling has been less thoroughly studied. Generally ferritin expression is regulated by iron and by oxidative damage, and in vertebrates it has a central role in the control of cellular iron homeostasis. Ferritin is mostly cytosolic but is found also in mammalian mitochondria and nuclei, in plant plastids and is secreted in insects. In vertebrates the cytosolic ferritins are composed of H and L subunit types and their assembly in a tissues specific ratio that permits flexibility to adapt to cell needs. The H-ferritin can translocate to the nuclei in some cell types to protect DNA from iron toxicity, or can be actively secreted, accomplishing various functions. The mitochondrial ferritin is found in mammals, it has a restricted tissue distribution and it seems to protect the mitochondria from iron toxicity and oxidative damage. The various functions attributed to the cytosolic, nuclear, secretory and mitochondrial ferritins are discussed.

Arosio P, Ingrassia R, Cavadini P.
Dipartimento Materno Infantile e Tecnologie Biomediche, Università di Brescia, and A.O. Spedali Civili, Brescia, Italy

Ferritin: Dietary and stored iron as predictors of breast cancer risk

Increases in risk of breast cancer in successive generations of migrants to the United States from China and rapid temporal changes in incidence rates in China following social and economic changes clearly implicate environmental factors in the etiology of this disease. Case-control and cohort studies have provided evidence that at least some of these factors may be dietary. Iron, an essential element necessary for cell function, has also been demonstrated to have potential carcinogenic and co-carcinogenic activities.

Dietary and stored iron as predictors of breast cancer risk: A nested case-control study in Shanghai.

Iron overload, which was previously uncommon, has become more common in the United States than iron deficiency and may be increasing in China concurrently with dramatic increases in meat consumption. A case-control study nested in a cohort of women in Shanghai, China, was conducted to evaluate possible associations between risk of proliferative and nonproliferative fibrocystic changes as well as breast cancer and dietary iron intake and plasma ferritin levels.

Plasma ferritin levels and reported dietary iron intake were compared in 346 women with fibrocystic changes, 248 breast cancer cases and 1,040 controls. Increasing ferritin levels were significantly associated with increasing risk of nonproliferative fibrocystic changes (OR: 2.51, 95% CI: 1.16-5.45, p trend = 0.04). Similar, but weaker, trends were observed for proliferative changes and for breast cancer. Risk of breast cancer relative to the risk of fibrocystic changes was associated with dietary iron intake in women with nonproliferative fibrocystic changes (OR: 2.63, 95% CI: 1.04-6.68, p = 0.02).

In conclusion, this study finds significant associations between iron (stored and dietary) and fibrocystic disease and breast cancer

Department of Public Health and Preventive Medicine, Oregon Health and Sciences University, Portland, OR

Methods for reducing nonspecific interaction in antibody–antigen assay via atomic force microscopy

We developed a method to measure the rupture forces between antibody and antigen by atomic force microscopy (AFM). Previous studies have reported that in the measurement of antibody–antigen interaction using AFM, the specific intermolecular forces are often obscured by nonspecific adhesive binding forces between antibody immobilized cantilever and substrate surfaces on which antigen or nonantigen are fixed. Here, we examined whether detergent and nonreactive protein, which have been widely used to reduce nonspecific background signals in ordinary immunoassay and immunoblotting, could reduce the nonspecific forces in the AFM measurement. The results showed that, in the presence of both nonreactive protein and detergent, the rupture forces between anti-ferritin antibodies immobilized on a tip of cantilever and ferritin (antigen) on the substrate could be successfully measured, distinguishing from nonspecific adhesive forces. In addition, we found that approach/retraction velocity of the AFM cantilever was also important in the reduction of nonspecific adhesion. These insights will contribute to the detection of specific molecules at nanometer scale region and the investigation of intermolecular interaction by the use of AFM.

ARTICLE

Epigallocatechin activates haem oxygenase-1 expression via protein kinase Cδ and Nrf2

The Nrf2/anti-oxidant response element (ARE) pathway plays an important role in regulating cellular anti-oxidants, including haem oxygenase-1 (HO-1). Various kinases have been implicated in the pathways leading to Nrf2 activation. Here, we investigated the effect of epigallocatechin (EGC) on ARE-mediated gene expression in human monocytic cells. EGC time and dose dependently increased HO-1 mRNA and protein expression but had minimal effect on expression of other ARE-regulated genes, including NAD(P)H:quinone oxidoreductase 1, glutathione cysteine ligase and ferritin. siRNA knock down of Nrf2 significantly inhibited EGC-induced HO-1 expression. Furthermore, inhibition of PKC by Ro-31-8220 dose dependently decreased EGC-induced HO-1 mRNA expression, whereas MAP kinase and phosphatidylinositol-3-kinase pathway inhibitors had no significant effect. EGC stimulated phosphorylation of PKCαβ and δ in THP-1 cells. PKCδ inhibition significantly decreased EGC-induced HO-1 mRNA expression, whereas PKCα- and β-specific inhibitors had no significant effect. These results demonstrate for the first time that EGC-induced HO-1 expression occurs via PKCδ and Nrf2.

ARTICLE

Iron-independent phosphorylation of iron regulatory protein 2 regulates ferritin during the cell cycle.

Iron regulatory protein 2 (IRP2) is a key iron sensor that post-transcriptionally regulates mammalian iron homeostasis by binding to iron-responsive elements (IREs) in mRNAs that encode proteins involved in iron metabolism (e.g. ferritin and transferrin receptor 1). During iron deficiency, IRP2 binds IREs to regulate mRNA translation or stability whereas during iron sufficiency IRP2 is degraded by the proteasome. Here, we identify an iron-independent IRP2 phosphorylation site that is regulated by the cell cycle. IRP2 S157 is phosphorylated by Cdk1/cyclin B1 during G2/M and is dephosphorylated during mitotic exit by the phosphatase Cdc14A. S157 phosphorylation during G2/M reduces IRP2 RNA-binding activity and increases ferritin synthesis, while S157 dephosphorylation during mitotic exit restores IRP2 RNA-binding activity and represses ferritin synthesis. These data show that reversible phosphorylation of IRP2 during G2/M has a role in modulating the iron-independent expression of ferritin and other IRE-containing mRNAs during the cell cycle.