Hereditary iron overload: update on pathophysiology, diagnosis, and treatment

Alcohol Use Unmasking Heterozygous Hereditary Hemochromatosis

Hereditary hemochromatosis (HH) is an autosomal recessive disorder characterized by excess iron absorption in the body following a mutation in the HFE gene. Though prolonged iron deposition has been shown to cause clinical symptoms such as hyperpigmentation, arthralgias, and liver damage, many individuals remain asymptomatic and exhibit no signs of iron overload. Here, we present a case where a 34-year-old with a history of severe alcohol use disorder presented with high iron, ferritin and transferrin saturation levels indicative of iron overload. Further testing for HFE gene mutations revealed simple heterozygote C282Y status, confirming the diagnosis of hereditary hemochromatosis. Simple heterozygotes, however, typically do not present with any symptoms of iron overload. This patient was counseled on lifestyle modifications which included abstaining from alcohol and reducing iron and vitamin C intake. As a result, his iron panel parameters improved. Thus, our case highlights that excessive alcohol consumption can exacerbate hereditary hemochromatosis and risk for overload even among heterozygotes.

Beyond the Usual Suspects: Hereditary Hemochromatosis and Transaminitis in Primary Care

An annual physical examination within a primary care setting, including evaluation of liver enzymes and abnormal serology, is incidental and often asymptomatic. Fatty liver is the most common etiology for transaminitis. Hepatobiliary imaging studies, viral hepatitis serology, evaluation of metabolic liver disease, and alcohol consumption history should be performed for transaminitis evaluation. In patients with prior history of excessive alcohol consumption, transaminitis is often assumed to be alcohol-related. It is prudent to evaluate other infectious and metabolic etiologies, which can change patient management. Iron studies, including ferritin and transferrin saturation, are performed to evaluate hereditary hemochromatosis (HH). We present the case of a 46-year-old patient who visited the clinic for a routine health checkup, during which elevated ferritin levels were detected. Subsequent diagnosis revealed hemochromatosis. The patient underwent phlebotomy, resulting in a reduction of ferritin levels.

Ferroptosis As Ultimate Target of Cancer Therapy

Significance: The significance of ferroptosis in cancer therapeutics has now been unveiled. Specific ferroptosis inducers are expected as a promising strategy for cancer treatment, especially in cancers with epithelial mesenchymal transition and possibly in cancers with activated Hippo signaling pathways, both of which cause resistance to traditional chemotherapy but tend to show ferroptosis susceptibility. Recent Advances: Ferroptosis is a new form of regulated non-apoptotic cell death, which is characterized by iron-dependent lipid peroxidation, leading eventually to plasma membrane rupture. Its core mechanisms have been elucidated, consisting of a driving force as catalytic Fe(II)-dependent Fenton reaction and an incorporation of polyunsaturated fatty acids to membrane phospholipids via peroxisome-dependent and -independent pathways, and suppressing factors as prevention of lipid peroxidation with glutathione peroxidase 4 and direct membrane repair via coenzyme Q10 and ESCRT-III pathways. Critical Issues: Developments of ferroptosis inducers are in progress by nanotechnology-based drugs or by innovative engineering devices. Especially, low-temperature (non-thermal) plasma is a novel technology at the preclinical stage. The exposure can induce ferroptosis selectively in cancer cells rich in catalytic Fe(II). Future Directions: We also summarize and discuss the recently uncovered responsible molecular mechanisms in association with iron metabolism, ferroptosis and cancer therapeutics. Targeting ferroptosis in addition to the current therapeutic modalities would be important to cure advanced-stage cancer.

Misdiagnosis of Rheumatoid Arthritis in a Long-Term Cohort of Early Arthritis Based on the ACR-1987 Classification Criteria

Objective

Correct diagnosis of early rheumatoid arthritis (RA) is essential for optimal treatment choices. No pathognomonic test is available, and diagnosis is based on classification criteria, which can result in misdiagnosis. Here, we examined the differences between actual and misdiagnosed RA cases in a long-term cohort of patients included based on the ACR-1987 classification criteria.

Methods

Patients in the BARFOT (Better Anti-Rheumatic PharmacOTherapy) cohort (n=2543) with at least four follow-up visits during the initial 5 years from enrolment were assessed, and a change in diagnosis was reported by the treating rheumatologist. The groups were analysed with respect to the individual classification criteria, antibodies to citrullinated proteins (ACPA), disease activity (DAS28) and radiographic changes from inclusion up to 2 years.

Results

Forty-five patients (1.8%) were misdiagnosed (RA-change group). When compared to those in the RA-change group, the patients who kept their diagnosis (RA-keep) were more often RF positive (64% vs 21%, p<0.001) or ACPA positive (59% vs 8%, p<0.001). They were also more likely to fulfil more than four ACR-1987 criteria (64% vs 33%, p<0.001) and to have radiographic changes at inclusion (RA-keep 27% vs RA-change 12%, p=0.04). The groups had a similar evolution of DAS28 and its components as well as of radiological joint destruction.

Conclusion

Diagnosis of RA according to the ACR-1987 criteria had a high precision in this long-term cohort. A diagnosis of RA should be re-evaluated in patients who do not fulfil more than four ACR-1987 criteria especially in patients negative for RF.

Differential effects of Fe2+ and Fe3+ on osteoblasts and the effects of 1,25(OH)2D3, deferiprone and extracellular calcium on osteoblast viability under iron-overloaded conditions

One of the potential contributing factors for iron overload-induced osteoporosis is the iron toxicity on bone forming cells, osteoblasts. In this study, the comparative effects of Fe³⁺ and Fe²⁺ on osteoblast differentiation and mineralization were studied in UMR-106 osteoblast cells by using ferric ammonium citrate and ferrous ammonium sulfate as Fe³⁺ and Fe²⁺ donors, respectively. Effects of 1,25 dihydroxyvitamin D₃ [1,25(OH)₂D₃] and iron chelator deferiprone on iron uptake ability of osteoblasts were examined, and the potential protective ability of 1,25(OH)₂D₃, deferiprone and extracellular calcium treatment in osteoblast cell survival under iron overload was also elucidated. The differential effects of Fe³⁺ and Fe²⁺ on reactive oxygen species (ROS) production in osteoblasts were also compared. Our results showed that both iron species suppressed alkaline phosphatase gene expression and mineralization with the stronger effects from Fe³⁺ than Fe²⁺. 1,25(OH)₂D₃ significantly increased the intracellular iron but minimally affected osteoblast cell survival under iron overload. Deferiprone markedly decreased intracellular iron in osteoblasts, but it could not recover iron-induced osteoblast cell death. Interestingly, extracellular calcium was able to rescue osteoblasts from iron-induced osteoblast cell death. Additionally, both iron species could induce ROS production and G0/G1 cell cycle arrest in osteoblasts with the stronger effects from Fe³⁺. In conclusions, Fe³⁺ and Fe²⁺ differentially compromised the osteoblast functions and viability, which can be alleviated by an increase in extracellular ionized calcium, but not 1,25(OH)₂D₃ or iron chelator deferiprone. This study has provided the invaluable information for therapeutic design targeting specific iron specie(s) in iron overload-induced osteoporosis. Moreover, an increase in extracellular calcium could be beneficial for this group of patients.

To Eat or to Die: Deciphering Selective Forms of Autophagy

Autophagy is an evolutionarily conserved process whereby damaged and redundant components of the cell are degraded in structures called autophagolysosomes. Currently, three main types of autophagy are recognized: macroautophagy, microautophagy, and chaperone-mediated autophagy (CMA). However, we still know little about some specific types of autophagy that are linked to various intracellular compartments and their roles in the physiology of the whole organism and connections to various diseases. Here, we aim to shed light on the latest insights on and mechanisms of several selective forms of autophagy.

Late-onset Hemochromatosis: Co-inheritance of β-thalassemia and Hereditary Hemochromatosis in a Chinese Family: A Case Report and Epidemiological Analysis of Diverse Populations

Hereditary hemochromatosis and β-thalassemia can both result in the inappropriately low production of the hormone hepcidin, which leads to an increase in intestinal absorption and excessive iron deposition in the parenchymal cells. To the best of our knowledge, there have been no reports on the coexistence of the two disorders in China. We herein report a case in a Chinese who presented with late-onset hepatic cirrhosis with hereditary hemochromatosis and β-thalassemia. We analyzed the pedigree of the two disorders and the iron status in his family members. Our case supports that a heterozygous H63D mutation can interact with β-thalassemia, leading to late-onset hemochromatosis.

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.

Metabolic crosstalk between host and pathogen: sensing, adapting and competing

Our understanding of bacterial pathogenesis is dominated by the cell biology of the host-pathogen interaction. However, the majority of metabolites that are used in prokaryotic and eukaryotic physiology and signalling are chemically similar or identical. Therefore, the metabolic crosstalk between pathogens and host cells may be as important as the interactions between bacterial effector proteins and their host targets. In this Review we focus on host-pathogen interactions at the metabolic level: chemical signalling events that enable pathogens to sense anatomical location and the local physiology of the host; microbial metabolic pathways that are dedicated to circumvent host immune mechanisms; and a few metabolites as central points of competition between the host and bacterial pathogens.

The influence of oxidative stress induced by iron on telomere length

Oxidative stress can be induced by increased concentrations of iron in the body and consequently can cause shortening of telomeres. Telomeres, called mitotic clocks, are non-coding fragments at the end of chromosomes. During the replication of genetic material they are shortened, playing the role of ageing biomarkers in eukaryotes. In human endothelial cells, oxidative stress causes a decrease in telomerase activity. Shortening of chromosomes in telomeric parts was found in patients with primary hemochromatosis and in patients taking supplements containing iron. Increased level of transferrin saturation is associated with the presence of shorter telomeres in the chromosomes of leukocytes. The relationship between iron status and telomere length is still not fully understood.

Spectroscopic, potentiometric and theoretical studies of novel imino-phenolate chelators for Fe(III)

The present study was targeted to explore the binding properties of two strong chelators for Fe(III) based on tripodal-iminophenolate moiety. Complexation behavior of the tripodal systems cis-cis cyclohexane-1,3,5-tricarboxylic acid tris-({2-[(2-hydroxy-benzylidene)-amino]-ethyl}-amide (CYCOENSAL, L(1)) and cis-cis cyclohexane-1,3,5-tricarboxylic acid tris-({3-[(2-hydroxy-benzylidene)-amino]-propyl}-amide (CYCOPNSAL, L(2)) is described. Three protonation constants obtained are assigned for three hydroxyl groups of aromatic ring were employed for the evaluation of the formation constants of the metal complexes. Both ligands liberate three protons each forming monomeric complexes of type FeLH3, FeLH2, FeLH and FeL (L=L(1) and L(2)). The first species FeLH3 depicted at low pH, where the ligands were coordinated through three imine nitrogen and other species form subsequently from FeLH3 in steps upon deprotonation and coordination of the phenolic oxygen giving encapsulated tris(phenolate) complexes. The probable structures of the metal complexes formed in solution were proposed through molecular modeling calculations. L(2) was observed to be highly selective towards Fe(III) as compared to L(1).

The association of pretransplant ferritin level with waiting list and post-transplant survival. Does ferritin actually predict outcome?

Recent data suggest an association of serum ferritin (SF) with waiting list (WL) and postliver transplant (LT) outcomes. To assess the predictive capacity of SF on pre- and post-LT outcomes, and to identify whether recipient or donor liver siderosis is associated with post-LT survival; a retrospective analysis of 1079 patients assessed for first LT, 2000-2007 was performed. Iron deposition in the liver tissue was assessed using a semi-quantitative grading system. Median age was 54 (18-82) years and 67% were male. Seventeen per cent had hepatocellular carcinoma (HCC). Median Model for End-stage Liver Disease MELD score was 14 (6-40), ferritin was 174 μg/l (4-4597) with 36.5% had a SF ≥ μg/l. Age (OR = 1.028) and MELD score (OR = 1.158) were independently associated with WL mortality (P < 0.001), whilst SF was not (P = NS). Age (OR = 1.018), HCC (OR = 1.542) and cold ischemia time (CIT) ≥ 10 h (OR = 1.418) were independently associated with post-LT survival (P < 0.05). Explant siderosis grade <2 was seen in 376 (71.7%) patients. Patients with explant siderosis grade ≥ 2 had inferior 12-month post-LT survival (P = 0.030). Presence of graft siderosis (15.8% of patients) was not associated with survival. In conclusion, we found a limited role for SF as a prognostic indicator for pre- or post-transplant survival.

Antioxidant, tautomerism and antibacterial studies of Fe(III)-1,2,4-triazole based complexes

New Fe(III) complexes have been synthesized by the reactions of ferric nitrate with Schiff base derived from 3-substituted phenyl-4-amino-5-hydrazino-1,2,4-triazole and indoline-2,3-dione. All these complexes are soluble in DMF and DMSO; low molar conductance values indicate that they are non-electrolytes. Elemental analyses suggest that the complexes have 1:1 stoichiometry of the type [FeLn(H2O)(OH)]·xH2O. Structural and spectroscopic properties have been studied on the basis of elemental analyses, infrared spectra, (1)H and (13)H NMR spectra, electronic spectra, magnetic measurements and FAB mass spectra. FT-IR, (1)H and (13)H NMR studies reveal that the ligand (Ln) exists in the tautomeric enol form in both the states with intramolecular hydrogen bonding. Magnetic moment and reflectance spectral studies reveal that an octahedral geometry has been assigned to all the prepared complexes. FRAP values indicate that all the compounds have a ferric reducing antioxidant power. The compounds 2 and 3 showed relatively high antioxidant activity while compound 1 and 4 shows poor antioxidant power. Also good antimicrobial activities of the complexes against Staphylococcus aureus, Bacillus subtilis, Serratia marcescens, Pseudomonas aeruginosa and Escherichia coli have been found compared to its free ligands.

Iranian hereditary hemochromatosis patients: baseline characteristics, laboratory data and gene mutations

BACKGROUND

Hereditary hemochromatosis (HH) is the most common autosomal recessive disorder in white people, characterized by highly abnormal uptake of iron from the gastrointestinal tracts. Recently, mutation studies have focused to detect the genes responsible for HH.

MATERIAL/METHODS

In this cross-sectional study, 12 HH patients were recruited, who were referred to Firoozgar Hospital, Tehran, Iran. In addition to the clinical assessments, a complete laboratory evaluation, imaging modalities, histopathologic assessment, atomic absorption spectrophotometry and gene mutation study were performed. The genetic study for HFE gene mutation was examined for all of the patients since 2006, while non-HFE mutation was conducted since December 2010 (only for 1 of them).

RESULTS

Twelve patients were evaluated consisting of 11 men and 1 woman, with the mean age of 39.58±12.68 yr. The average of atomic iron loads was 13.25±4.83-fold higher than normal standards. Four patients had heterozygotic mutation of H63D (33.3%). There was no significant difference in either the iron load of liver (P=0.927) and heart (P=0.164) or serum concentration of ferritin (P=0.907) and TIBC (P=0.937) between the HFE-mutant and without HFE mutation HH cases.

CONCLUSIONS

In contrast to other studies, C282Y mutation was not detected in any of our Iranian HH patients. Heterozygotic mutations of H63D (HFE) and TFR2 (non-HFE) genes were found to be more common in these patients. Similar to previous reports, these mutations were not found to be significantly associated with severity of presentation in HH patients.

Zebrafish erythropoiesis and the utility of fish as models of anemia

Erythrocytes contain oxygen-carrying hemoglobin to all body cells. Impairments in the generation of erythrocytes, a process known as erythropoiesis, or in hemoglobin synthesis alter cell function because of decreased oxygen supply and lead to anemic diseases. Thus, understanding how erythropoiesis is regulated during embryogenesis and adulthood is important to develop novel therapies for anemia. The zebrafish, Danio rerio, provides a powerful model for such study. Their small size and the ability to generate a large number of embryos enable large-scale analysis, and their transparency facilitates the visualization of erythroid cell migration. Importantly, the high conservation of hematopoietic genes among vertebrates and the ability to successfully transplant hematopoietic cells into fish have enabled the establishment of models of human anemic diseases in fish. In this review, we summarize the current progress in our understanding of erythropoiesis on the basis of zebrafish studies and highlight fish models of human anemias. These analyses could enable the discovery of novel drugs as future therapies.

Mammalian iron metabolism

ABSTRACT Iron is an essential transition metal for mammalian cellular and tissue viability. It is critical to supplying oxygen through heme, the mitochondrial respiratory chain, and enzymes such as ribonucleotide reductase. Mammalian organisms have evolved with the means of regulating the metabolism of iron, because if left unregulated, the resulting excess amounts of iron may induce chronic toxicities affecting multiple organ systems. Several homeostatic mechanisms exist to control the amount of intestinal dietary iron uptake, cellular iron uptake, distribution, and export. Within these processes, numerous molecular participants have been identified because of advancements in basic cell biology and efforts in disease-based research of iron storage abnormalities. For example, dietary iron uptake across the intestinal duodenal mucosa is mediated by an intramembrane divalent metal transporter 1 (DMT1), and cellular iron efflux involves ferroportin, the only known iron exporter. In addition to duodenal enterocytes, ferroportin is present in other cell types, and exports iron into plasma. Ferroportin was recently discovered to be regulated by the expression of the circulating hormone hepcidin, a small peptide synthesized in hepatocytes. These recent studies on the role of hepcidin in the regulation of dietary, cellular, and extracellular iron have led to a better understanding of the pathways by which iron balance in humans is influenced, especially its involvement in human genetic diseases of iron overload. Other important molecular pathways include iron binding to transferrin in the bloodstream for cellular delivery through the plasma membrane transferrin receptor (TfR1). In the cytosol, iron regulatory proteins 1 and 2 (IRP1 and IRP2) play a prominent role in sensing the presence of iron in order to posttranscriptionally regulate the expression of TfR1 and ferritin, two important participants in iron metabolism. From a toxicological standpoint, posttranscriptional regulation of these genes aids in the sequestration, control, and hence prevention of cytotoxic effects from free-floating nontransferrin-bound iron. Given the importance of dietary iron in normal physiology, its potential to induce chronic toxicity, and recent discoveries in the regulation of human iron metabolism by hepcidin, this review will address the regulatory mechanisms of normal iron metabolism in mammals with emphasis on dietary exposure. It is the goal of this review that this information may provide in a concise format our current understanding of major pathways and mechanisms involved in mammalian iron metabolism, which is a basis for control of iron toxicity. Such a discussion is intended to facilitate the identification of deficiencies so that future metabolic or toxicological studies may be appropriately focused. A better knowledge of iron metabolism from normal to pathophysiological conditions will ultimately broaden the spectrum of the usefulness of this information in biomedical and toxicological sciences for improving and protecting human health.

Effect of hereditary haemochromatosis genotypes and iron overload on other trace elements

PURPOSE

Hereditary haemochromatosis is a common genetic disorder involving dysregulation of iron absorption. There is some evidence to suggest that abnormal iron absorption and metabolism may influence the status of other important trace elements. In this study, the effect of abnormal HFE genotypes and associated iron overload on the status of other trace elements was examined.

METHODS

Dietary data and blood samples were collected from 199 subjects (mean age = 55.4 years; range = 21-81 years). Dietary intakes, serum selenium, copper and zinc concentrations and related antioxidant enzymes (glutathione peroxidase and superoxide dismutase) in subjects with normal HFE genotype (n = 118) were compared to those with abnormal HFE genotype, with both normal iron status (n = 42) and iron overload (n = 39).

RESULTS

For most dietary and biochemical variables measured, there were no significant differences between study groups. Red cell GPx was significantly higher in male subjects with normal genotypes and normal iron status compared to those with abnormal genotypes and normal iron status (P = 0.03) or iron overload (P = 0.001). Red cell GPx was also highest in normal women and significantly lower in the abnormal genotype and normal iron group (P = 0.016), but not in the iron overload group (P = 0.078).

CONCLUSION

Although it may not be possible to exclude a small effect between the genotype groups on RBC GPx, overall, haemochromatosis genotypes or iron overload did not appear to have a significant effect on selenium, copper or zinc status.

Progress in research of molecular markers for hepatic oval cells Li-Ping Sun, Qiao-Xia Tong, Sheng-Hua Jie

Portal hypertension is defined as an increase in blood pressure in the veins of the portal system and extensive formation of portal-systemic communicating branches, which results from a blockage in the portal blood flow or abnormal blood increment. Generally, cirrhotic portal hypertension is common more than non-cirrhotic portal hypertension, but the latter is caused by a group of diseases, such as idiopathic portal hypertension(IPH), pancreatic sinistral portal hypertension (PSPH), cavernous transformation of the portal vein (CTPV), congenital hepatic fibrosis (CHF), Budd-Chiari syndrome (BCS), hepatic sinusoidal obstruction syndrome (SOS), portal vein thrombosis (PVT), myeloproliferative disease (MLD), hepatic amyloidosis, and hemochromatosis (HC). This paper reviews the rare causes of portal hypertension and their diagnosis.

Unusual presentation of hemochromatosis as isolated metacarpophalangeal joint osteoarthritis: a case report

BACKGROUND

Hemochromatosis, North America's most prevalent genetic disorder, tends to present with an insidious onset and subtle, yet characteristic findings. Patients tend to present with both constitutional symptoms and end-organ effects.

METHODS

Clinical criteria such as history, physical examination, imaging criteria with focused radiologic constellations, and laboratory findings were used for diagnosis.

RESULTS

We report the case of a man who lacked classic systemic symptoms, but instead presented with isolated metacarpophalangeal joint disease and characteristic radiologic findings. The diagnosis was confirmed by serum iron studies and subsequent genetic work-up.

CONCLUSIONS

A high index of clinical suspicion is required to diagnose early disease; better prognostic responses are expected with treatment of less severe disease. Hand surgeons should be aware of the characteristic findings for this rare presentation so proper treatment can be initiated early.

Advancements in anemias related to chronic conditions

Anemia of chronic disease (ACD), the most frequent anemia among hospitalized patients, occurs in chronic inflammatory disorders, such as chronic infections, cancer and autoimmune diseases. Different causes contribute to ACD including diversion of iron traffic, diminished erythropoiesis, blunted response to erythropoietin, erythrophagocytosis, hematologic malignancies and solid tumors. A particular case of ACD is represented by anemia of chronic kidney disease (CKD). ACD is characterized by hyposideremia and altered iron transport. Cytokines are implicated in the ACD by reducing erythropoiesis and increasing iron sequestration in the reticuloendothelial system. The regulation of iron absorption across the epithelium of the proximal small intestine is essential for maintaining body iron concentrations within a physiologically defined range. Hepcidin controls cellular iron efflux by binding to the iron export protein ferroportin, causing ferroportin to be phosphorylated and degraded in lysosomes. Finally, hepcidin inhibits iron release from the reticulo-endothelial system. Increased expression of hepcidin leads to decreased iron absorption and iron deficient anemia. Hepcidin, therefore, is a negative regulator of iron transport in plasma. Causes of anemia in patients with CKD are multifactorial, but the most well-known cause is inadequate erythropoietin production. In these patients, anemia increases the risk of either cardiovascular disease or renal failure.

Polystyrene microsphere-ferritin conjugates: a robust phantom for correlation of relaxivity and size distribution

In vivo iron load must be monitored to prevent complications from iron overload diseases such as hemochromatosis or transfusion-dependent anemias. While liver biopsy is the gold standard for determining in vivo iron load, MRI offers a noninvasive approach. MR phantoms have been reported that estimate iron concentration in the liver and mimic relaxation characteristics of in vivo deposits of hemosiderin. None of these phantoms take into account the size distribution of hemosiderin, which varies from patient to patient based on iron load. We synthesized stable and reproducible microsphere-ferritin conjugates (ferribeads) of different sizes that are easily characterized for several parameters that are necessary for modeling such as iron content and bead fraction. T(1) s and T(2) s were measured on a 1.41-T low-resolution NMR spectrometer and followed a size-dependent trend. Ferribeads imaged at 4.7 and 14.1 T showed that signal intensities are dependent on the distribution of ferritin around the bead rather than the iron concentration alone. These particles can be used to study the effects of particle size, ferritin distribution, and bead fraction on proton relaxation and may be of use in mimicking hemosiderin in a phantom for estimating iron concentration.

Iron sufficient to cause hepatic fibrosis and ascites does not cause cardiac arrhythmias in the gerbil

Chronic iron overload associated with hereditary hemochromatosis or repeated red cell transfusions is known to cause cardiac failure. Cardiac arrhythmias have been incidentally noted in patients with iron overload, but they are often dismissed as being related to comorbid conditions. Studies with anesthetized iron-loaded gerbils using short recordings suggest a role for iron in the development of arrhythmias. Our goal was to characterize iron-induced arrhythmias in the chronically instrumented, untethered, telemetered gerbil. Electrocardiograms were recorded for 10 s every 30 min for approximately 6 months in iron-loaded (n=23) and control (n=8) gerbils. All gerbils in both groups showed evidence of frequent sinus arrhythmia. There was no difference in heart rate, electrocardiographic parameters, or number of arrhythmias per minute between groups. Gerbils rarely showed significant arrhythmias. Body weight and heart weight were not significantly different between groups, whereas liver weight increased with increasing iron dose in the treated group. Cardiac and hepatic iron concentrations were significantly increased in iron-loaded gerbils. Eight of 14 gerbils loaded to 6.2 g/kg body weight developed ascites. We conclude that an iron load sufficient to cause clinical liver disease does not cause cardiac arrhythmias in the gerbil model of iron overload.

Twenty questions in genetic medicine--an assessment of World Wide Web databases for genetics information at the point of care

PURPOSE

The aim of this article was to determine the accuracy and efficiency of World Wide Web ("Web") resources to help nongeneticists answer four clinical questions about each of five common genetic conditions.

METHODS

Correct answers were established by literature review. Two open-access genetics resources and seven general subscription resources were reviewed. Scoring criteria were established to define complete, partial, vague, inconsistent, not found, and wrong answers. The main outcome measures were number of answers found, accuracy, and completeness of answers. Efficiency (time per answer found) was a secondary measure.

RESULTS

Overall, the databases contained complete answers 33.3% of the time but contained no information as frequently (33.9%). The best database had complete answers 70% of the time, whereas the worst contained no complete answers. Five of the seven subscription databases had a total of eight wrong answers. The other two subscription databases and the two open-access genetics databases had no wrong answers. Search time ranged from 3.2 to 18.3 minutes per complete answer.

CONCLUSIONS

Nongeneticist providers do not have a Web resource that is accessible, accurate, and efficient to answer genetic questions that might arise in practice.

Serum ferritin concentrations and body iron stores in a multicenter, multiethnic primary-care population

How often elevated serum ferritin in primary-care patients reflects increased iron stores (normally 0.8 g in men, 0.4 g in women) is not known. The Hereditary Hemochromatosis and Iron Overload Screening (HEIRS) study screened 101,168 primary-care participants (44% Caucasians, 27% African-Americans, 14% Asians/Pacific Islanders, 13% Hispanics, 2% others). Follow-up clinical evaluation was performed in 302 of 333 HFE C282Y homozygotes regardless of iron measures and 1,375 of 1,920 nonhomozygotes with serum ferritin >300 microg/L (men), >200 microg/L (women) and transferrin saturation >50% (men), >45% (women). Quantitative phlebotomy was conducted in 122 of 175 C282Y homozygotes and 122 of 1,102 nonhomozygotes with non-transfusional serum ferritin elevation at evaluation. The estimated prevalence in the Caucasian population of C282Y homozygotes with serum ferritin >900 microg/L at evaluation was 20 per 10,000 men and 4 per 10,000 women; this constellation was predictive of iron stores >4 g in men and >2 g in women. The estimated prevalence per 10,000 of non-C282Y homozygotes with serum ferritin >900 microg/L at evaluation was 7 among Caucasians, 13 among Hispanics, 20 among African Americans, and 38 among Asians and Pacific Islanders, and this constellation was predictive of iron stores >2 g but <4 g. In conclusion, serum ferritin >900 microg/L after initial elevations of both serum ferritin and transferrin saturation is predictive of mildly increased iron stores in multiple ethnic populations regardless of HFE genotype. Serum ferritin >900 microg/L in male C282Y homozygotes is predictive of moderately increased iron stores.

Body iron metabolism and pathophysiology of iron overload

Iron is an essential metal for the body, while excess iron accumulation causes organ dysfunction through the production of reactive oxygen species. There is a sophisticated balance of body iron metabolism of storage and transport, which is regulated by several factors including the newly identified peptide hepcidin. As there is no passive excretory mechanism of iron, iron is easily accumulated when exogenous iron is loaded by hereditary factors, repeated transfusions, and other diseased conditions. The free irons, non-transferrin-bound iron, and labile plasma iron in the circulation, and the labile iron pool within the cells, are responsible for iron toxicity. The characteristic features of advanced iron overload are failure of vital organs such as liver and heart in addition to endocrine dysfunctions. For the estimation of body iron, there are direct and indirect methods available. Serum ferritin is the most convenient and widely available modality, even though its specificity is sometimes problematic. Recently, new physical detection methods using magnetic resonance imaging and superconducting quantum interference devices have become available to estimate iron concentration in liver and myocardium. The widely used application of iron chelators with high compliance will resolve the problems of organ dysfunction by excess iron and improve patient outcomes.

Mechanisms of iron loading and toxicity

Normal iron homeostasis is a finely balanced system that reflects iron absorption, loss and utilization. The body has no mechanism for the active excretion of iron, so body iron levels are controlled at the point of absorption in the small intestine. Disturbances in this equilibrium, such as those leading to enhanced absorption, can have significant clinical consequences. Continued excessive iron uptake is followed by iron deposition in various tissues, ultimately leading to tissue damage, and possibly end-organ failure. In this review, current concepts in normal iron homeostasis, and iron loading are explained. The clinical consequences as well as the differences between primary and secondary iron loading are also reviewed, and some future research priorities are discussed.

Synthesis of 5-dialkyl(aryl)aminomethyl-8-hydroxyquinoline dansylates as selective fluorescent sensors for Fe3+

A series of 5-dialkyl(aryl)aminomethyl-8-hydroxyquinoline dansylates were synthesized and their fluoroionophoric properties toward representative alkali ions, alkaline earth ions and transition metal ions were investigated. Among the selected ions, Fe3+ caused considerable quenching of the fluorescence, while Cr3+ caused quenching to some extent. The absence of any significant fluorescence quenching effects of the other ions examined, especially Fe2+, renders these compounds highly useful Fe3+-selective fluorescent sensors.

Zinc protoporphyrin, a useful parameter to address hyperferritinemia

Zinc protoporphyrin (ZPP) is produced instead of heme as soon as iron support to erythropoiesis becomes insufficient. In iron deficiency the intra-erythrocytic ZPP concentration is increased. The aim of this study was to investigate whether ZPP is influenced by increased iron levels in hereditary hemochromatosis (HE) and is useful in the clarification of hyperferritinemia. Twenty HE patients and 160 patients with hyperferritinemic caused by anemia of chronic disorders, liver diseases, transfusional iron overload and hematologic or solid malignancies were enrolled. ZPP was measured using the Aviv front-face hematofluorometer (normal <or= 40 micromol/mol heme). In HE, ZPP was significantly lower (median, 20 micromol/mol heme; p = 0.0005) compared to our historical control group. At diagnosis, 15 (75%) HE patients had ZPP values <or=25 micromol/mol heme. After phlebotomy, ZPP remained unchanged (median, 23 micromol/mol heme), although the initially high ferritin concentration decreased to normal. ZPP values in the other hyperferritinemic groups were significantly higher compared to HE and control groups. In contrast to HE, ZPP values <or=25 micromol/mol heme were only observed in 11% of cases with non-transfusional hyperferritinemia. The diagnostic accuracy of a ZPP <or=25 micromol/mol heme to detect HE in non-transfused hyperferritinemic patients was 87%, with a sensitivity of 75% and a specificity of 89%. Showing significantly lower values in HE, ZPP seems to be a useful parameter in distinguishing HE from other hyperferritinemic disorders as those conditions are generally accompanied by an increased ZPP.

The alpha(1S) subunit of the L-type calcium channel is not a predisposition gene for thyrotoxic periodic paralysis

OBJECTIVE

Thyrotoxic periodic paralysis (TTP) has been associated with genetic variations in the gene encoding the alpha 1 subunit of the L-type calcium channel (CACNA1S). Mutations in CACNA1S are known to account for the majority of cases of familial hypokalaemic periodic paralysis (HOKPP). In this study we have examined 48 genetic polymorphisms in the CACNA1S gene and genotyped a tagging set of representative polymorphisms to determine the role of this gene in TPP.

DESIGN AND PATIENTS

A genetic association study was carried out with 98 TPP patients and 162 male thyrotoxic controls. Among 47 polymorphisms evaluated for linkage disequilibrium (LD) and the spectrum of haplotypes in the Chinese population, 31 were selected as tagging single-nucleotide polymorphisms (SNPs) for genotyping the whole sample. A new genotyping protocol was used to analyse an insertion/deletion (I/D) polymorphism.

RESULTS

We studied the LD among 47 polymorphisms in the CACNA1S gene, which comprised a set of high-density markers with an average of one SNP every 2 kb. Subsequently, 31 tagSNPs were genotyped for all the samples. The gene is composed of three LD blocks. With this block structure, we were confident that variations of the gene were comprehensively covered by the tagSNPs. No significant association was found between the polymorphisms and TPP.

CONCLUSION

We established the LD structure of this calcium channel subunit gene (CACNA1S) for the first time. However, its genetic variations are not associated with TPP in Chinese patients.

Molecular mechanism of ferricsiderophore passage through the outer membrane receptor proteins of Escherichia coli

Iron is an essential nutrient for all microorganisms with a few exceptions. Microorganisms use a variety of systems to acquire iron from the surrounding environment. One such system includes production of an organic molecule known as a siderophore by many bacteria and fungi. Siderophores have the capacity to specifically chelate ferric ions. The ferricsiderophore complex is then transported into the cell via a specific receptor protein located in the outer membrane. This is an energy dependent process and is the subject of investigation in many research laboratories. The crystal structures of three outer membrane ferricsiderophore receptor proteins FepA, FhuA and FecA from Escherichia coli and two FpvA and FptA from Pseudomonas aeruginosa have recently been solved. Four of them, FhuA, FecA, FpvA and FptA have been solved in ligand-bound forms, which gave insight into the residues involved in ligand binding. The structures are similar and show the presence of similar domains; for example, all of them consist of a 22 strand-beta-barrel formed by approximately 600 C-terminal residues while approximately 150 N-terminal residues fold inside the barrel to form a plug domain. The plug domain obstructs the passage through the barrel; therefore our research focuses on the mechanism through which the ferricsiderophore complex is transported across the receptor into the periplasm. There are two possibilities, one in which the plug domain is expelled into the periplasm making way for the ferricsiderophore complex and the second in which the plug domain undergoes structural rearrangement to form a channel through which the complex slides into the periplasm. Multiple alignment studies involving protein sequences of a large number of outer membrane receptor proteins that transport ferricsiderophores have identified several conserved residues. All of the conserved residues are located within the plug and barrel domain below the ligand binding site. We have substituted a number of these residues in FepA and FhuA with either alanine or glutamine resulting in substantial changes in the chemical properties of the residues. This was done to study the effect of the substitutions on the transport of ferricsiderophores. Another strategy used was to create a disulfide bond between the residues located on two adjacent beta-strands of the plug domain or between the residues of the plug domain and the beta-barrel in FhuA by substituting appropriate residues with cysteine. We have looked for the variants where the transport is affected without altering the binding. The data suggest a distinct role of these residues in the mechanism of transport. Our data also indicate that these transporters share a common mechanism of transport and that the plug remains within the barrel and possibly undergoes rearrangement to form a channel to transport the ferricsiderophore from the binding site to the periplasm.