Relationship between TNF-alpha and iron metabolism in differentiating human monocytic THP-1 cells

Computational Modeling of Macrophage Iron Sequestration during Host Defense against Aspergillus

Iron is essential to the virulence of Aspergillus species, and restricting iron availability is a critical mechanism of antimicrobial host defense. Macrophages recruited to the site of infection are at the crux of this process, employing multiple intersecting mechanisms to orchestrate iron sequestration from pathogens. To gain an integrated understanding of how this is achieved in aspergillosis, we generated a transcriptomic time series of the response of human monocyte-derived macrophages to Aspergillus and used this and the available literature to construct a mechanistic computational model of iron handling of macrophages during this infection. We found an overwhelming macrophage response beginning 2 to 4 h after exposure to the fungus, which included upregulated transcription of iron import proteins transferrin receptor-1, divalent metal transporter-1, and ZIP family transporters, and downregulated transcription of the iron exporter ferroportin. The computational model, based on a discrete dynamical systems framework, consisted of 21 3-state nodes, and was validated with additional experimental data that were not used in model generation. The model accurately captures the steady state and the trajectories of most of the quantitatively measured nodes. In the experimental data, we surprisingly found that transferrin receptor-1 upregulation preceded the induction of inflammatory cytokines, a feature that deviated from model predictions. Model simulations suggested that direct induction of transferrin receptor-1 (TfR1) after fungal recognition, independent of the iron regulatory protein-labile iron pool (IRP-LIP) system, explains this finding. We anticipate that this model will contribute to a quantitative understanding of iron regulation as a fundamental host defense mechanism during aspergillosis.

IMPORTANCE Invasive pulmonary aspergillosis is a major cause of death among immunosuppressed individuals despite the best available therapy. Depriving the pathogen of iron is an essential component of host defense in this infection, but the mechanisms by which the host achieves this are complex. To understand how recruited macrophages mediate iron deprivation during the infection, we developed and validated a mechanistic computational model that integrates the available information in the field. The insights provided by this approach can help in designing iron modulation therapies as anti-fungal treatments.

Iron homeostasis pathway DNA methylation trajectories reveal a role for STEAP3 metalloreductase in patient outcomes after aneurysmal subarachnoid hemorrhage

BACKGROUND

Following aneurysmal subarachnoid hemorrhage (aSAH), the brain is susceptible to ferroptosis, a type of iron-dependent cell death. Therapeutic intervention targeting the iron homeostasis pathway shows promise for mitigating ferroptosis and improving recovery in animal models, but little work has been conducted in humans. DNA methylation (DNAm) plays a key role in gene expression and brain function, plasticity, and injury recovery, making it a potentially useful biomarker of outcomes or therapeutic target for intervention. Therefore, in this longitudinal, observational study, we examined the relationships between trajectories of DNAm in candidate genes related to iron homeostasis and acute (cerebral vasospasm and delayed cerebral ischemia) and long-term (Glasgow Outcome Scale [GOS, unfavorable = 1-3] and death) patient outcomes after aSAH.

RESULTS

Longitudinal, genome-wide DNAm data were generated from DNA extracted from post-aSAH cerebrospinal fluid (n = 260 participants). DNAm trajectories of 637 CpG sites in 36 candidate genes related to iron homeostasis were characterized over 13 days post-aSAH using group-based trajectory analysis, an unsupervised clustering method. Significant associations were identified between inferred DNAm trajectory groups at several CpG sites and acute and long-term outcomes. Among our results, cg25713625 in the STEAP3 metalloreductase gene (STEAP3) stood out. Specifically, in comparing the highest cg25713625 DNAm trajectory group with the lowest, we observed significant associations (i.e., based on p-values less than an empirical significance threshold) with unfavorable GOS at 3 and 12 months (OR = 11.7, p = 0.0006 and OR = 15.6, p = 0.0018, respectively) and death at 3 and 12 months (OR = 19.1, p = 0.0093 and OR = 12.8, p = 0.0041, respectively). These results were replicated in an independent sample (n = 100 participants) observing significant associations with GOS at 3 and 12 months (OR = 8.2, p = 0.001 and OR = 6.3, p = 0.0.0047, respectively) and death at 3 months (OR = 2.3, p = 0.008) and a suggestive association (i.e., p-value < 0.05 not meeting an empirical significance threshold) with death at 12 months (OR = 2.0, p = 0.0272). In both samples, an additive effect of the DNAm trajectory group was observed as the percentage of participants with unfavorable long-term outcomes increased substantially with higher DNAm trajectory groups.

CONCLUSION

Our results support a role for DNAm of cg25713625/STEAP3 in recovery following aSAH. Additional research is needed to further explore the role of DNAm of cg25713625/STEAP3 as a biomarker of unfavorable outcomes, or therapeutic target to improve outcomes, to translate these findings clinically.

Ferroptosis: the potential value target in atherosclerosis

In advanced atherosclerosis (AS), defective function-induced cell death leads to the formation of the characteristic necrotic core and vulnerable plaque. The forms and mechanisms of cell death in AS have recently been elucidated. Among them, ferroptosis, an iron-dependent form of necrosis that is characterized by oxidative damage to phospholipids, promotes AS by accelerating endothelial dysfunction in lipid peroxidation. Moreover, disordered intracellular iron causes damage to macrophages, vascular smooth muscle cells (VSMCs), vascular endothelial cells (VECs), and affects many risk factors or pathologic processes of AS such as disturbances in lipid peroxidation, oxidative stress, inflammation, and dyslipidemia. However, the mechanisms through which ferroptosis initiates the development and progression of AS have not been established. This review explains the possible correlations between AS and ferroptosis, and provides a reliable theoretical basis for future studies on its mechanism.

The Iron Curtain: Macrophages at the Interface of Systemic and Microenvironmental Iron Metabolism and Immune Response in Cancer

Macrophages fulfill central functions in systemic iron metabolism and immune response. Infiltration and polarization of macrophages in the tumor microenvironment is associated with differential cancer prognosis. Distinct metabolic iron and immune phenotypes in tumor associated macrophages have been observed in most cancers. While this prompts the hypothesis that macroenvironmental manifestations of dysfunctional iron metabolism have direct associations with microenvironmental tumor immune response, these functional connections are still emerging. We review our current understanding of the role of macrophages in systemic and microenvironmental immune response and iron metabolism and discuss these functions in the context of cancer and immunometabolic precision therapy approaches. Accumulation of tumor associated macrophages with distinct iron pathologies at the invasive tumor front suggests an "Iron Curtain" presenting as an innate functional interface between systemic and microenvironmental iron metabolism and immune response that can be harnessed therapeutically to further our goal of treating and eliminating cancer.

Persistent Microvascular Obstruction After Myocardial Infarction Culminates in the Confluence of Ferric Iron Oxide Crystals, Proinflammatory Burden, and Adverse Remodeling

BACKGROUND

Emerging evidence indicates that persistent microvascular obstruction (PMO) is more predictive of major adverse cardiovascular events than myocardial infarct (MI) size. But it remains unclear how PMO, a phenomenon limited to the acute/subacute period of MI, drives adverse remodeling in chronic MI setting. We hypothesized that PMO resolves into chronic iron crystals within MI territories, which in turn are proinflammatory and favor adverse remodeling post-MI.

METHODS AND RESULTS

Canines (n=40) were studied with cardiac magnetic resonance imaging to characterize the spatiotemporal relationships among PMO, iron deposition, infarct resorption, and left ventricular remodeling between day 7 (acute) and week 8 (chronic) post-MI. Histology was used to assess iron deposition and to examine relationships between iron content with macrophage infiltration, proinflammatory cytokine synthesis, and matrix metalloproteinase activation. Atomic resolution transmission electron microscopy was used to determine iron crystallinity, and energy-dispersive X-ray spectroscopy was used to identify the chemical composition of the iron composite. PMO with or without reperfusion hemorrhage led to chronic iron deposition, and the extent of this deposition was strongly related to PMO volume (r>0.8). Iron deposits were found within macrophages as aggregates of nanocrystals (≈2.5 nm diameter) in the ferric state. Extent of iron deposits was strongly correlated with proinflammatory burden, collagen-degrading enzyme activity, infarct resorption, and adverse structural remodeling (r>0.5).

CONCLUSIONS

Crystallized iron deposition from PMO is directly related to proinflammatory burden, infarct resorption, and adverse left ventricular remodeling in the chronic phase of MI in canines. Therapeutic strategies to combat adverse remodeling could potentially benefit from taking into account the chronic iron-driven inflammatory process.

HFE mutations and iron in hemodialysis patients

In chronic hemodialysis patients, a disruption in iron metabolism ranging from absolute to functional deficiency, with compartmentalization of this metal into macrophages, is often observed. Chronic inflammation indeed often causes an upregulation of the iron hormone hepcidin, thereby reducing iron absorption and availability to the erythron. We systematically reviewed the literature on the role of genetic risk factors on iron metabolism in hemodialysis. In this setting, mutations in the HFE gene of hereditary hemochromatosis may confer an adaptive benefit by decreasing hepcidin release, thus improving iron availability to erythropoiesis, anemia control, and the response to erythropoiesis stimulating agents and iron itself, and reducing the side effects of these therapies. The HFE protein together with Transferrin receptor-2 may also have a direct role on erythroid differentiation and iron uptake in erythroid cells. In addition, other genetic determinants of iron status, such as variants in Matriptase-2 (TMPRSS6), have been shown to influence iron metabolism in chronic hemodialysis patients, most likely acting through hepcidin regulation. Although data must be confirmed in larger prospective studies, this favorable shift in iron metabolism balance possibly results in reduced mortality, in particular because of cardiovascular and infective diseases. Further genetic studies may offer a valuable tool to test these hypotheses and guide personalized clinical management and the research of new therapies.

Serum Ferritin Relates to Carotid Intima-Media Thickness in Offspring of Fathers With Higher Serum Ferritin Levels

OBJECTIVE

Body iron status has been linked to atherosclerosis in adults. The purposes of our study were to determine (1) the association between circulating ferritin levels and carotid intima-media thickness (cIMT) in a cohort of apparently healthy children and (2) the association between cIMT and parental ferritin levels.

APPROACH AND RESULTS

Circulating ferritin levels (microparticle enzyme immunoassay), metabolic parameters, and cIMT (ultrasonography) were analyzed cross-sectionally in a cohort of 692 healthy white children with a mean age of 8 ± 2 years (52% girls and 48% boys). In consecutive 123 children from the cross-sectional sample, the same serum assessments were also performed at baseline in their parents, and the cIMT was repeated after 3 years of follow-up in the children at a mean age of 11 ± 2 years (53% girls and 47% boys). Weak but significant positive associations were evident between children's circulating ferritin levels and cIMT (r=0.123; P=0.001) and with the change in cIMT 3 years later a tendency was also observed (r=0.185; P=0.048). In multiple regression analyses, circulating ferritin levels contributed independently to cIMT variance (β=0.090; P=0.026; R(2)=10%) and cIMT change variance (β=0.216; P=0.019; R(2)= 3.4%) after controlling for body mass index, high-sensitivity C-reactive protein, age, sex, and low-density lipoprotein-cholesterol levels. This association was, however, remarkably significant (β=0.509; P=0.001; R(2)= 20.4%) in children whose fathers had ferritin levels above the median value (122.5 ng/mL).The latter association remained significant after correction for multiple testing. Maternal's ferritin levels showed no interaction in this association.

CONCLUSIONS

These results suggest a paternal-specific effect on cIMT partially reflected by father's ferritin levels.

Lipocalin-2 ensures host defense against Salmonella Typhimurium by controlling macrophage iron homeostasis and immune response

Lipocalin-2 (Lcn2) is an innate immune peptide with pleiotropic effects. Lcn2 binds iron-laden bacterial siderophores, chemo-attracts neutrophils and has immunomodulatory and apoptosis-regulating effects. In this study, we show that upon infection with Salmonella enterica serovar Typhimurium, Lcn2 promotes iron export from Salmonella-infected macrophages, which reduces cellular iron content and enhances the generation of pro-inflammatory cytokines. Lcn2 represses IL-10 production while augmenting Nos2, TNF-α, and IL-6 expression. Lcn2(-/-) macrophages have elevated IL-10 levels as a consequence of increased iron content. The crucial role of Lcn-2/IL-10 interactions was further demonstrated by the greater ability of Lcn2(-/-) IL-10(-/-) macrophages and mice to control intracellular Salmonella proliferation in comparison to Lcn2(-/-) counterparts. Overexpression of the iron exporter ferroportin-1 in Lcn2(-/-) macrophages represses IL-10 and restores TNF-α and IL-6 production to the levels found in wild-type macrophages, so that killing and clearance of intracellular Salmonella is promoted. Our observations suggest that Lcn2 promotes host resistance to Salmonella Typhimurium infection by binding bacterial siderophores and suppressing IL-10 production, and that both functions are linked to its ability to shuttle iron from macrophages.

Aortic Iron Overload With Oxidative Stress and Inflammation in Human and Murine Abdominal Aortic Aneurysm

Objective—

Although iron is an essential element for maintaining physiological function, excess iron leads to tissue damage caused by oxidative stress and inflammation. Oxidative stress and inflammation play critical roles for the development of abdominal aortic aneurysm (AAA). However, it has not been investigated whether iron plays a role in AAA formation through oxidative stress and inflammation. We, therefore, examined whether iron is involved in the pathophysiology of AAA formation using human AAA walls and murine AAA models.

Approach and Results—

Human aortic walls were collected from 53 patients who underwent cardiovascular surgery (non-AAA=34; AAA=19). Murine AAA was induced by infusion of angiotensin II to apolipoprotein E knockout mice. Iron was accumulated in human and murine AAA walls compared with non-AAA walls. Immunohistochemistry showed that both 8-hydroxy-2′-deoxyguanosine and CD68-positive areas were increased in AAA walls compared with non-AAA walls. The extent of iron accumulated area positively correlated with that of 8-hydroxy-2′-deoxyguanosine expression area and macrophage infiltration area in human and murine AAA walls. We next investigated the effects of dietary iron restriction on AAA formation in mice. Iron restriction reduced the incidence of AAA formation with attenuation of oxidative stress and inflammation. Aortic expression of transferrin receptor 1, intracellular iron transport protein, was increased in human and murine AAA walls, and transferrin receptor 1–positive area was similar to areas where iron accumulated and F4/80 were positive.

Conclusions—

Iron is involved in the pathophysiology of AAA formation with oxidative stress and inflammation. Dietary iron restriction could be a new therapeutic strategy for AAA progression.

Transcriptome analysis of the white body of the squid Euprymna tasmanica with emphasis on immune and hematopoietic gene discovery

In the mutualistic relationship between the squid Euprymna tasmanica and the bioluminescent bacterium Vibrio fischeri, several host factors, including immune-related proteins, are known to interact and respond specifically and exclusively to the presence of the symbiont. In squid and octopus, the white body is considered to be an immune organ mainly due to the fact that blood cells, or hemocytes, are known to be present in high numbers and in different developmental stages. Hence, the white body has been described as the site of hematopoiesis in cephalopods. However, to our knowledge, there are no studies showing any molecular evidence of such functions. In this study, we performed a transcriptomic analysis of white body tissue of the Southern dumpling squid, E. tasmanica. Our primary goal was to gain insights into the functions of this tissue and to test for the presence of gene transcripts associated with hematopoietic and immune processes. Several hematopoiesis genes including CPSF1, GATA 2, TFIID, and FGFR2 were found to be expressed in the white body. In addition, transcripts associated with immune-related signal transduction pathways, such as the toll-like receptor/NF-κβ, and MAPK pathways were also found, as well as other immune genes previously identified in E. tasmanica's sister species, E. scolopes. This study is the first to analyze an immune organ within cephalopods, and to provide gene expression data supporting the white body as a hematopoietic tissue.

Sleep disorders in Parkinson's disease: clinical features, iron metabolism and related mechanism

OBJECTIVE

To investigate clinical features, iron metabolism and neuroinflammation in Parkinson's disease (PD) patients with sleep disorders (SD).

METHODS

211 PD patients were evaluated by Pittsburgh Sleep Quality Index (PSQI) and a body of scales for motor symptoms and non-motor symptoms. 94 blood and 38 cerebral spinal fluid (CSF) samples were collected and iron and its metabolism-relating proteins, neuroinflammatory factors were detected and analyzed.

RESULTS

136 cases (64.5%) of PD patients were accompanied by SD. Factor with the highest score in PSQI was daytime dysfunction. Depression, restless leg syndrome, autonomic symptoms and fatigue contributed 68.6% of the variance of PSQI score. Transferrin level in serum and tumor necrosis factor-α level in CSF decreased, and the levels of iron, transferrin, lactoferrin and prostaglandin E2 in CSF increased in PD patients with SD compared with those without SD. In CSF, prostaglandin E2 level was positively correlated with the levels of transferrin and lactoferrin, and tumor necrosis factor-α level was negatively correlated with the levels of iron, transferrin and lactoferrin in CSF.

CONCLUSIONS

Depression, restless leg syndrome, autonomic disorders and fatigue are the important contributors for the poor sleep in PD patients. Abnormal iron metabolism may cause excessive iron deposition in brain and be related to SD in PD patients through dual potential mechanisms, including neuroinflammation by activating microglia and neurotoxicity by targeting neurons. Hence, inhibition of iron deposition-related neuroinflammation and neurotoxicity may cast a new light for drug development for SD in PD patients.

Identification of CD300a as a new hypoxia-inducible gene and a regulator of CCL20 and VEGF production by human monocytes and macrophages

Peripheral blood monocytes are recruited to inflammatory and tumor lesions where they undergo terminal differentiation into macrophages. Monocytes/macrophages integrate stimulatory and inhibitory signals present in the pathologic microenvironment through a defined repertoire of cell surface receptors, and deregulated expression of these molecules may result in amplification of inflammation or establishment of immune escape mechanisms. Characterization of the expression and function of these receptors is required for a better understanding of the regulation of monocyte/macrophage activity at pathologic sites. Hypoxia is a common feature of many pathological situations and an important regulator of monocyte/macrophage pro-inflammatory responses. In this study, we identify the leukocyte membrane antigen, CD300a, a member of the CD300 superfamily of immunoregulatory receptors, as a new hypoxia-inducible gene in primary human monocytes and monocyte-derived macrophages. CD300a mRNA up-regulation by hypoxia was rapid and reversible, paralleled by increased surface protein expression, and mediated by hypoxia-inducible factor-1α. CD300a induction was also triggered by the hypoxia-mimetic agent, desferrioxamine. CD300a exhibited both activating and inhibitory potential, differentially regulating CCL20 and vascular endothelial growth factor pro-inflammatory cytokine production by monocytes/macrophages upon triggering by an agonist Ab. These results suggest that CD300a induction by the hypoxic environment represents a mechanism of regulation of monocyte/macrophage pro-inflammatory responses at pathologic sites.

Hepcidin and HFE protein: Iron metabolism as a target for the anemia of chronic kidney disease

The anemia of chronic kidney disease and hemodialysis is characterized by chronic inflammation and release of cytokines, resulting in the upregulation of the iron hormone hepcidin, also increased by iron therapy and reduced glomerular filtration, with consequent reduction in iron absorption, recycling, and availability to the erythron. This response proves advantageous in the short-term to restrain iron availability to pathogens, but ultimately leads to severe anemia, and impairs the response to erythropoietin (Epo) and iron. Homozygosity for the common C282Y and H63D HFE polymorphisms influence iron metabolism by hampering hepcidin release by hepatocytes in response to increased iron stores, thereby resulting in inadequate inhibition of the activity of Ferroportin-1, inappropriately high iron absorption and recycling, and iron overload. However, in hemodialysis patients, carriage of HFE mutations may confer an adaptive benefit by decreasing hepcidin release in response to iron infusion and inflammation, thereby improving iron availability to erythropoiesis, anemia control, the response to Epo, and possibly survival. Therefore, anti-hepcidin therapies may improve anemia management in hemodialysis. However, HFE mutations directly favor hemoglobinization independently of hepcidin, and reduce macrophages activation in response to inflammation, whereas hepcidin might also play a beneficial anti-inflammatory and anti-microbic action during sepsis, so that direct inhibition of HFE-mediated regulation of iron metabolism may represent a valuable alternative therapeutic target. Genetic studies may offer a valuable tool to test these hypotheses and guide the research of new therapies.

Relationship between gene polymorphisms of two cytokine genes (TNF-α and IL-6) and occurring of lung cancers in the ethnic group Han of China

Tumor necrosis factor (TNF) is a cytokine involved in inflammation and TNF-α might be synthesized ectopically in malignant tumors. Interleukin-6 (IL-6) is an interleukin that acts as both a pro-inflammatory and anti-inflammatory cytokine. The present study is to investigate the relationship between genetic polymorphisms of the TNF-α and IL-6 genes and susceptibility to lung cancers in the ethnic group Han of North China. The genotypes in the -238G locus of TNF-α gene and the -572C locus of the IL-6 gene were determined by PCR-RFLP method in 138 patients with lung cancers and 138 healthy individuals. Software PHASE 1.0 was used to analyze the experimental data. The non-conditional logistic regression model was used to analyze the statistical association of genotypes and susceptibility in two groups adjusted by multiple factors. We found that the TNF-α and IL-6 polymorphisms may be a critical risk for the genetic susceptibility to lung cancers in the ethnic group Han of North China. SNP polymorphisms at the -238G locus of TNF-α gene and the -572C locus of the IL-6 gene were detected by the RFLP-PCR method. We found that high rates of single-base G-to-A alteration at the -238G locus of both alleles and high rates of single-base C-to-G alteration at the -572C locus of both alleles correlated with occurring of lung cancers. It is possible that the SNP markers at the -238G locus of TNF-α gene and the -572C locus of the IL-6 gene serve as biological markers of lung cancers upon further study in the future.

HIV-1 Resistant CDK2-Knockdown Macrophage-Like Cells Generated from 293T Cell-Derived Human Induced Pluripotent Stem Cells

A major challenge in studies of human diseases involving macrophages is low yield and heterogeneity of the primary cells and limited ability of these cells for transfections and genetic manipulations. To address this issue, we developed a simple and efficient three steps method for somatic 293T cells reprogramming into monocytes and macrophage-like cells. First, 293T cells were reprogrammed into induced pluripotent stem cells (iPSCs) through a transfection-mediated expression of two factors, Oct-4 and Sox2, resulting in a high yield of iPSC. Second, the obtained iPSC were differentiated into monocytes using IL-3 and M-CSF treatment. And third, monocytes were differentiated into macrophage-like cells in the presence of M-CSF. As an example, we developed HIV-1-resistant macrophage-like cells from 293T cells with knockdown of CDK2, a factor critical for HIV-1 transcription. Our study provides a proof-of-principle approach that can be used to study the role of host cell factors in HIV-1 infection of human macrophages.

Hfe deficiency impairs pulmonary neutrophil recruitment in response to inflammation

Regulation of iron homeostasis and the inflammatory response are tightly linked to protect the host from infection. Here we investigate how imbalanced systemic iron homeostasis in a murine disease model of hereditary hemochromatosis (Hfe^−/− mice) affects the inflammatory responses of the lung. We induced acute pulmonary inflammation in Hfe^−/− and wild-type mice by intratracheal instillation of 20 µg of lipopolysaccharide (LPS) and analyzed local and systemic inflammatory responses and iron-related parameters. We show that in Hfe^−/− mice neutrophil recruitment to the bronchoalveolar space is attenuated compared to wild-type mice although circulating neutrophil numbers in the bloodstream were elevated to similar levels in Hfe^−/− and wild-type mice. The underlying molecular mechanisms are likely multifactorial and include elevated systemic iron levels, alveolar macrophage iron deficiency and/or hitherto unexplored functions of Hfe in resident pulmonary cell types. As a consequence, pulmonary cytokine expression is out of balance and neutrophils fail to be recruited efficiently to the bronchoalveolar compartment, a process required to protect the host from infections. In conclusion, our findings suggest a novel role for Hfe and/or imbalanced iron homeostasis in the regulation of the inflammatory response in the lung and hereditary hemochromatosis.

The evaluation of carotid intima-media thickness in children with beta-thalassaemia major

BACKGROUND

Cardiovascular complications and vascular changes are common in patients with beta-thalassaemia major. The aim of this study is to investigate the common carotid artery intima-media thickness in children.

METHODS

The study population was consisted of 33 thalassaemic children (22 boys and 11 girls, with a median age of 8 years) and 30 healthy children for control (12 girls and 18 boys, with a median age of 8 years) who were matched for age and gender. Common carotid artery intima-media thickness of the children was measured.

RESULTS

The patients' age at diagnosis ranged from 0.25 to 2 years, with a median of 0.6 months. Their disease duration ranged from 4 to 13.75 years, with a median of 6.5 years. The patients' median common carotid artery intima-media thickness was significantly higher than controls - that is, 0.87 versus 0.74, with a p-value less than 0.005. The mean common carotid artery intima-media thickness value was positively correlated with disease duration (r = 0.535), with a p-value less than 0.01 and ferritin level (r = 0.501), with a p-value less than 0.01.

CONCLUSION

Owing to the nature of the disease, patients with beta-thalassaemia major should be considered to have an increased risk of early vascular alteration and atherosclerosis. For this reason, common carotid artery intima-media thickness measurement can be recommended as a non-invasive and early diagnostic method.

Iron in fatty liver and in the metabolic syndrome: a promising therapeutic target

The dysmetabolic iron overload syndrome (DIOS) is now a frequent finding in the general population, as is detected in about one third of patients with nonalcoholic fatty liver disease (NAFLD) and the metabolic syndrome. The pathogenesis is related to altered regulation of iron transport associated with steatosis, insulin resistance, and subclinical inflammation, often in the presence of predisposing genetic factors. Evidence is accumulating that excessive body iron plays a causal role in insulin resistance through still undefined mechanisms that probably involve a reduced ability to burn carbohydrates and altered function of adipose tissue. Furthermore, DIOS may facilitate the evolution to type 2 diabetes by altering beta-cell function, the progression of cardiovascular disease by contributing to the recruitment and activation of macrophages within arterial lesions, and the natural history of liver disease by inducing oxidative stress in hepatocytes, activation of hepatic stellate cells, and malignant transformation by promotion of cell growth and DNA damage. Based on these premises, the association among DIOS, metabolic syndrome, and NAFLD is being investigated as a new risk factor to predict the development of overt cardiovascular and hepatic diseases, and possibly hepatocellular carcinoma, but most importantly, represents also a treatable condition. Indeed, iron depletion, most frequently achieved by phlebotomy, has been shown to decrease metabolic alterations and liver enzymes in controlled studies in NAFLD. Additional studies are warranted to evaluate the potential of iron reductive therapy on hard clinical outcomes in patients with DIOS.

Serum Hepcidin and Macrophage Iron Correlate With MCP-1 Release and Vascular Damage in Patients With Metabolic Syndrome Alterations

Objective—

Increased body iron stores and hepcidin have been hypothesized to promote atherosclerosis by inducing macrophage iron accumulation and release of cytokines, but direct demonstration in human cells is lacking. The aim of this study was to evaluate the effect of iron on cytokine release in monocytes ex vivo and the correlation with vascular damage and to evaluate the relationship among serum levels of hepcidin, cytokines, and vascular damage in patients with metabolic syndrome alterations.

Methods and Results—

Manipulation of iron status with ferric ammonium citrate and hepcidin-25 induced monocyte chemoattractant protein (MCP)-1 and interleukin-6 in human differentiating monocytes of patients with hyperferritinemia associated with the metabolic syndrome (n=11), but not in subjects with hemochromatosis or HFE mutations impairing iron accumulation (n=15), and the degree of induction correlated with the presence of carotid plaques, detected by echocolor–Doppler. In monocytes of healthy subjects (n=7), iron and hepcidin increased the mRNA levels and release of MCP-1, but not of interleukin-6. In 130 patients with metabolic alterations, MCP-1 levels, as detected by ELISA, were correlated with hepcidin-25 measured by time-of-flight mass spectrometry ( P =0.005) and were an independent predictor of the presence of carotid plaques ( P =0.05).

Conclusion—

Hepcidin and macrophage iron correlate with MCP-1 release and vascular damage in high-risk individuals with metabolic alterations.

Transcriptional up-regulation of a novel ferritin homolog in abalone Haliotis discus hannai Ino by dietary iron

A novel cDNA encoding ferritin (HdhNFT) was cloned from the hepatopancreas of abalone, Haliotis discus hannai Ino. The deduced protein contains 171 amino acid residues with a predicted molecular mass (MW) about 19.8 kDa and theoretical isoelectric point (pI) of 4.792. Amino acid alignment revealed that HdhNFT shared high similarity with other known ferritins. The HdhNFT contained a highly conserved motif for the ferroxidase center, which consists of seven residues of a typical vertebrate heavy-chain ferritin with a typical stem-loop structure. HdhNFT mRNA contains a 27 bp iron-responsive element (IRE) in the 5'-untranslated region. This IRE exhibited 82.14% similarity with abalone H. discus discus and 78.57% similarity with Pacific oyster Crassostrea gigas IREs. By real-time PCR assays, the mRNA transcripts of HdhNFT were found to be higher expressed in kidney, hepatopancreas, gill, mantle and muscle than in haemocytes and gonad. Moreover, mRNA expression levels of HdhNFT in the hepatopancreas and haemocytes were measured by real-time PCR in abalone fed with graded levels of dietary iron (29.2, 65.7, 1267.2 and 6264.7 mg/kg). Results showed that the expression of the HdhNFT mRNA increased with dietary iron contents. Furthermore, the maximum value of the HdhNFT mRNA was found in the treatment with 6264.7 mg/kg of dietary iron. These data indicated that dietary iron can up-regulate HdhNFT at transcriptional level in abalone.

Tumor necrosis factor-alpha promoter variants and iron phenotypes in 785 hemochromatosis and iron overload screening (HEIRS) study participants

We sought to determine if TNF promoter variants could explain iron phenotype heterogeneity in adults with previous HFE genotyping. HEIRS Study participants genotyped for C282Y and H63D were designated as high transferrin saturation (TS) and/or serum ferritin (SF) (high TS/SF), low TS/SF, or controls. We grouped 191 C282Y homozygotes as high TS/SF, low TS/SF, or controls, and 594 other participants by race/ethnicity as high TS/SF or controls. Using denaturing high-performance liquid chromatography (DHPLC), we screened the TNF promoter region in each participant. We performed multiple regression analyses in C282Y homozygotes using age, sex, HEIRS Study Field Center, and positivity for TNF -308G-->A and -238G-->A to determine if these attributes predicted ln TS or ln SF. DHPLC analyses were successful in 99.3% of 791 participants and detected 9 different variants; TNF -308G-->A and -238G-->A were the most prevalent. Most subjects positive for variants were heterozygous. The phenotype frequencies of each variant did not differ significantly (p<0.05) across subgroups of C282Y homozygotes, or across white, black, Hispanic, and Asian non-C282Y homozygotes subgrouped as high TS/SF phenotypes and controls. TNF -308G-->A positivity was a significant predictor of initial screening ln TS but not ln SF; TNF -238G-->A predicted neither ln TS nor ln SF. We conclude that TNF promoter variants have little, if any, effect on initial screening SF values in adults with or without C282Y homozygosity. We cannot exclude a possible association of homozygosity for TNF promoter variants on TS and SF values.

Comparison of vascular complications between conventional treatment and bone marrow transplantation for children with beta-thalassemia disease

Patients with ss-thalassemia may be predisposed to premature atherosclerosis due to vascular dysfunction. This is observed in adults. Whether atherosclerosis changes in ss-thalassemia disease (BTD) occur early in childhood is not clear. To prevent cardiovascular complications, this needs evaluation. Moreover, it remains uncertain whether curative treatment with bone marrow transplantation (BMT) would improve this vascular alteration. For this study, 37 ss-thalassemia children age 10.1 +/- 2.7 years were classified into group 1 (25 children with BTD treated conventionally) and group 2 (12 children with BTD who underwent BMT). A control group of 29 age-matched healthy children were studied simultaneously. The carotid stiffness index and intima-media thickness (IMT) were measured. Group1 had a greater arterial stiffness index than the control subjects (4.57 +/- 1.78 vs. 2.87 +/- 1.07; p < 0.001). The carotid IMT was significantly greater in both BTD groups than in the control group (group 1: 0.45 +/- 0.03 vs. 0.34 +/- 0.04 mm; p < 0.001; group 2: 0.43 +/- 0.03 vs. 0.34 +/- 0.04 mm; p < 0.001). Carotid IMT and arterial stiffness are increased in conventionally treated children with ss-thalassemia, suggesting an early atherosclerotic change in these children, whereas children with BTD who underwent BMT had an increased carotid IMT but normal arterial stiffness.

Differential ferritin expression is associated with iron deficiency in coeliac disease

BACKGROUND

Sixty percent of people with coeliac disease (CD) are iron deficient. Many, however, remain iron replete despite the disease.

AIMS

(i) To characterize the changes in duodenal iron transport proteins in CD with and without iron deficiency. (ii) To examine if iron-activated gut lymphocytes can inhibit iron export in an enterocyte cell model.

METHODS

Endoscopic duodenal biopsies were collected from patients with normal duodenum with and without iron deficiency anaemia and untreated CD sufferers with iron deficiency (n=10 each group). mRNA expression of iron transport proteins was determined by quantitative real time PCR. Protein localization and expression was determined from histology sections in patients with normal duodenum (n=20), and patients with untreated CD with and without iron deficiency (n=20). In addition, CaCo2 cells were cocultured with iron-activated lymphocytes 55Fe was used to determine the effect on CaCo2 cell iron transport.

RESULTS

The expression of divalent metal transporter 1 and ferroportin was increased in CD with or without iron deficiency. Ferritin expression was increased in CD but only in those with associated iron deficiency. TNF-alpha produced by activated lymphocytes inhibited iron export from CaCo2 cells.

CONCLUSION

Increased enterocyte ferritin expression may promote iron deficiency in CD and this effect seems to be dependent upon TNF-alpha expression in gut lymphocytes.

HFE mutations modulate the effect of iron on serum hepcidin-25 in chronic hemodialysis patients

BACKGROUND AND OBJECTIVES

Increased serum hepcidin has been reported in patients receiving chronic hemodialysis, and hypothesized to contribute to the alterations of iron metabolism of end-stage renal disease. However, no quantitative assessment is available to date; the clinical determinants are still under definition; and the role of genetic factors, namely HFE mutations, has not yet been evaluated. The aim of this study was to quantitatively assess serum hepcidin-25 in hemodialysis patients versus controls, and analyze the relationship between hepcidin, iron indices, HFE genotype, and erythropoietic parameters.

DESIGN, SETTING, PARTICIPANTS & MEASUREMENTS

Sixty-five hemodialysis patients and 57 healthy controls were considered. Hepcidin-25 was evaluated by surface-enhanced laser desorption/ionization time-of-flight mass spectrometry, HFE genotype by restriction analysis.

RESULTS

Serum hepcidin-25 was higher in hemodialysis patients compared with controls. In patients, hepcidin-25 correlated positively with ferritin and C reactive protein, and negatively with serum iron after adjustment for confounders. Hepcidin/ferritin ratio was lower in patients with (n = 25) than in those without (n = 40) HFE mutations. At multivariate analysis, hepcidin-25 was independently associated with ferritin and HFE status. In a subgroup of 22 "stable" patients, i.e., with Hb levels on target, normal CRP levels, and absence of complications for at least 1 yr, hepcidin-25 was negatively correlated with Hb levels independently of confounders.

CONCLUSIONS

Serum hepcidin-25 is increased in hemodialysis patients, regulated by iron stores and inflammation, and relatively reduced in subjects carrying frequent HFE mutations. Hepcidin-25 may contribute to the pathogenesis of anemia by decreasing iron availability.

Iron overload following red blood cell transfusion and its impact on disease severity

Transfusion of red blood cells can be a life-saving therapy both for patients with chronic anemias and for those who are critically ill with acute blood loss. However, transfusion has been associated with significant morbidity. Chronic transfusion results in accumulation of excess iron that surpasses the binding capacity of the major iron transport protein, transferrin. The resulting non-transferrin bound iron (NTBI) can catalyze the production of highly reactive oxygen species (ROS) leading to significant and wide spread injury to the liver, heart, and endocrine organs as well as increases in infection. Acute transfusion of red blood cells in critically ill patients likewise has significant effects including increased mortality, prolonged hospital stays, and elevated risk of nosocomial infection. These effects appear to be more profound with increasing age of stored blood. The progressive release of free iron associated with storage time suggests that morbidity following acute transfusion, like that seen in chronic transfusion, may be due in part to elevated levels of NTBI. It is clear that transfusion is necessary in many instances; however, its risks and benefits must be carefully balanced before proceeding to avoid unnecessary iron toxicity.

Tumor necrosis factor SNP haplotypes are associated with iron deficiency anemia in West African children

Plasma levels of tumor necrosis factor-alpha (TNF-alpha) are significantly raised in malaria infection and TNF-alpha is thought to inhibit intestinal iron absorption and macrophage iron release. This study investigated putative functional single nucleotide polymorphisms (SNPs) and haplotypes across the major histocompatibility complex (MHC) class III region, including TNF and its immediate neighbors nuclear factor of kappa light polypeptide gene enhancer in B cells (lkappaBL), inhibitor-like 1 and lymphotoxin alpha (LTA), in relation to nutritional iron status and anemia, in a cohort of 780 children across a malaria season. The prevalence of iron deficiency anemia (IDA) increased over the malaria season (P < .001). The TNF(-308) AA genotype was associated with an increased risk of iron deficiency (adjusted OR 8.1; P = .001) and IDA (adjusted OR 5.1; P = .01) at the end of the malaria season. No genotypes were associated with IDA before the malaria season. Thus, TNF appears to be a risk factor for iron deficiency and IDA in children in a malaria-endemic environment and this is likely to be due to a TNF-alpha-induced block in iron absorption.

Differences in iron requirements by concanavalin A-treated and anti-CD3-treated murine splenic lymphocytes

Fe availability is critical for optimal lymphocyte proliferation; however, the minimum required levels are unknown. Such information is valuable when assessingin vitroimmune responses in Fe-deficient subjects, because serum (Fe) added to the culture medium may replete lymphocytes. To address this issue, splenic lymphocytes obtained from seventeen 3-month-old C57BL/6 mice were incubated without and with 1 mg/l concanavalin A or 50 μg/l anti-CD3 antibody in media that contained between 0·113 and 9·74 μmol Fe/l. Fe was provided by either fetal calf serum (FCS, 0–100 ml/l), newborn calf serum (NBCS, 0–100 ml/l), or NBCS (10 ml/l) plus ferric ammonium citrate. As expected, the rate of DNA synthesis increased with Fe levels (P<0·01). Maximum DNA synthesis was obtained with 2·26 μmol Fe/l (50 ml FCS/l) for concanavalin A and 0·895 μmol/l (20 ml FCS/l) for anti-CD3-treated cells. In serum-free media (0·113 μmol Fe/l), the proliferative responses to concanavalin A were below the background, while they rose 5·5-fold in anti-CD3-treated cells (P<0·05). In apotransferrin-supplemented media (0·13 μmol Fe/l), the proliferative responses to concanavalin A and anti-CD3 antibody were 18·6 and 71 %, respectively, of that obtained with 4·66 μmol Fe/l (100 ml FCS/l). Interleukin 2 secretion also followed the same trend as lymphocyte proliferation. Since differences between both mitogens persisted after FCS was substituted with NBCS, we can rule out an effect on ribonucleotide reductase activity, or by other serum growth factors. We speculate an Fe effect at an early step of T-cell activation. Data suggest that the minimum Fe concentration required for lymphocyte proliferation varies with the mitogen.

Tumor necrosis factor-alpha -308G>A allelic variant modulates iron accumulation in patients with hereditary hemochromatosis

BACKGROUND

In vitro and animal studies suggest that tumor necrosis factor alpha (TNF-alpha) modulates intestinal iron transport. We hypothesized that the effect of TNF-alpha might be particularly relevant if iron absorption is not effectively controlled by the HFE gene.

METHODS

In patients with homozygous C282Y hemochromatosis, we investigated the influence of TNF-alpha -308G>A allelic variant on total body iron overload, determined in all patients by measuring iron removed during depletion therapy, and hepatic iron index and need for phlebotomy to prevent iron reaccumulation, measured in patient subgroups.

RESULTS

Of 86 patients with hereditary hemochromatosis, 16 (19%) were heterozygous carriers and 1 (1%) was a homozygous carrier of the TNF-alpha promoter -308A allele. Mean (SD) total body iron overload was increased 2-fold in TNF-alpha -308A allele carriers [10.9 (7.6) g] compared with homozygous carriers of the G allele [5.6 (5.0) g, P<0.001]. Hepatic iron index differed markedly between TNF-alpha -308A allele carriers [5.6 (3.5) micromol/g/year] and homozygous G allele carriers [3.1 (2.2) micromol/g/year, P=0.040, n=30]. After iron depletion, the need for phlebotomy to prevent iron reaccumulation (maintenance therapy) was substantially higher in TNF-alpha -308A allele carriers than in homozygous G allele carriers (P=0.014, n=73). We used multiple regression analyses to exclude possible confounding effects of sex, age, family screening, body-mass index, and meat or alcohol intake.

CONCLUSION

TNF-alpha -308G>A allelic variant modulates iron accumulation in patients with hereditary (homozygous C282Y) hemochromatosis, but the effect of the TNF-alpha -308A allele on clinical manifestations of hemochromatosis was less accentuated than expected from the increased iron load associated with this allele.

Ferritin subunits in CSF are decreased in restless legs syndrome

Restless legs syndrome (RLS) is a neurological disorder that may be related to iron misregulation at the level of the central nervous system. Evidence that iron is involved in RLS comes from magnetic resonance imaging data, autopsy studies, analyses of cerebrospinal fluid (CSF), and correlations of symptoms with serum ferritin. To further examine the possibility that brain iron status is insufficient in RLS, we determined ferritin levels in the CSF. Specifically, we differentiated between the H- and L-subunits of ferritin, because these peptides are expressed from different chromosomes and have different functions. We measured H- and L-ferritin subunit levels in control and RLS human CSF using immunoblot analysis and found that both H- and L-ferritin are significantly decreased in early but not late-onset RLS. Additionally, we quantified total protein in each CSF sample to establish that the decrease in ferritin subunits in RLS did not reflect a decrease in total protein in CSF. Furthermore, we used equal amounts of total CSF protein in the immunoblot analyses, in contrast to previously published studies that provided only volumetric data, to determine which approach was more accurate for quantifying the amount of ferritin relative to other proteins in CSF. Our results establish a protein standard in RLS, provide a comparative analysis of protein-controlled versus volumetric immunoblot techniques, and argue for a profound loss of iron storage capacity in the brain in RLS, specifically in the early onset RLS phenotype. These data suggest that CSF ferritin levels may provide a biomarker for assisting in the diagnosis of RLS.

Iron chelator induces THP-1 cell differentiation potentially by modulating intracellular glutathione levels

Iron chelators have been implicated to modulate certain inflammatory mediators and regulate inflammatory processes. Here we report that iron chelator deferoxamine (DFO) induces differentiation of monocytic THP-1 cells into functional macrophages. DFO rapidly phosphorylated both extracellular signal-regulated kinase (ERK) and p38 kinase. Blockade of ERK signaling by the MEK1/2 inhibitor PD098059 abolished DFO-induced class A scavenger receptor (SR-A) expression and phagocytic activity, indicating that ERK cascades mediate the induction of THP-1 differentiation. In contrast, in cells treated with the p38 inhibitor SB203580 or transfected with the dominant-negative variant of p38 kinase, DFO-mediated ERK activation became more prominent, and the induction of SR-A expression and phagocytic activity were significantly increased. Interestingly, differentiation by DFO was associated with decrease in cellular glutathione (GSH) level. Both MAPK inhibitors did not influence the GSH level; however, treatment with ferric citrate (Fe3+) or N-acetyl-cysteine, a major precursor of GSH, markedly recovered GSH level to a normal extent, along with the significant decrease of differentiation. Collectively, these results indicate that oxidative stress by DFO and the resulting activation of ERK cascade play dominant roles in the process of THP-1 differentiation, while p38 acts as a negative signal transmitter.

Effects of Anaplasma phagocytophilum on host cell ferritin mRNA and protein levels

Ferritin is a major intracellular iron storage protein and also functions as a cytoprotectant by sequestering iron to minimize the formation of reactive oxygen species. Anaplasma phagocytophilum, the causative agent of human granulocytic anaplasmosis, is an obligate intracellular bacterium that colonizes neutrophils. We have previously reported that human promyelocytic HL-60 cells infected with A. phagocytophilum demonstrate increased transcription of ferritin heavy chain and also that the bacterium stimulates neutrophil NADPH oxidase assembly and degranulation during the initial hours of infection (J. A. Carlyon, W. T. Chan, J. Galan, D. Roos, and E. Fikrig, J. Immunol. 169:7009-7018, 2002, and J. A. Carlyon, D. Abdel-Latif, M. Pypaert, P. Lacy, and E. Fikrig, Infect. Immun. 72:4772-4783, 2004). In this study, we assessed ferritin mRNA and protein levels during A. phagocytophilum infection in vitro using HL-60 cells and neutrophils and in vivo using neutrophils from infected mice. The addition of A. phagocytophilum, as well as Escherichia coli and serum-opsonized zymosan, to neutrophils results in a pronounced increase in ferritin light-chain transcription and a concomitant rise in ferritin protein levels. Neutrophils from A. phagocytophilum-infected mice demonstrate elevated ferritin heavy-chain mRNA expression, a phenomenon consistent with infections by intracellular pathogens. Notably, ferritin protein levels of infected HL-60 cells were markedly diminished in a dose- and time-dependent manner. These studies provide insight into the effects A. phagocytophilum has on the ferritin levels of its host cell.

TNF, IFN-γ, and endotoxin increase expression of DMT1 in bronchial epithelial cells

Regulation of the metal transport protein divalent metal transporter-1 (DMT1) may contribute to the uptake and detoxification of iron by cells resident in the respiratory tract. Inflammation has been associated with an increased availability of this metal resulting in an oxidative stress. Because proinflammatory cytokines and LPS have been demonstrated to affect an elevated expression of DMT1 in a macrophage cell line, we tested the hypothesis that tumor necrosis factor (TNF)-α, interferon (IFN)-γ, and LPS increase DMT1 expression in airway epithelial cells. We used RT-PCR to detect mRNA for both −IRE DMT1 and +IRE DMT1 in BEAS-2B cells. Treatment with TNF-α, IFN-γ, or LPS increased both forms. Western blot analysis also demonstrated an increase in the expression of both isoforms of DMT1 after these treatments. Twenty-four hours after exposure of an animal model to TNF-α, IFN-γ, or LPS, a significant increase in pulmonary expression of −IRE DMT1 was seen by immunohistochemistry; the level of +IRE DMT1 was too low in the lung to be visualized using this methodology. Finally, iron transport into BEAS-2B cells was increased after inclusion of TNF-α, IFN-γ, or LPS in the media. We conclude that proinflammatory cytokines and LPS increase mRNA and protein expression of DMT1 in airway cells in vitro and in vivo. Furthermore, both −IRE and +IRE isoforms are elevated after exposures. Increased expression of this protein appears to be included in a coordinated response of the cell and tissue where the function might be to diminish availability of metal.

Tumour necrosis factor alpha regulates iron transport and transporter expression in human intestinal epithelial cells

TNFalpha has dramatic effects on iron metabolism contributing to the generation of hypoferraemia in the anaemia of chronic disease. Interestingly, TNFalpha is also synthesised and released within the intestinal mucosa, suggesting that this pro-inflammatory cytokine may play a role in regulating dietary iron absorption. To investigate this possibility, we stimulated intestinal Caco-2 cells with TNFalpha (10 ng/ml). In TNFalpha-treated cells, apical iron uptake was significantly decreased and this was accompanied by a reduction in divalent metal transporter protein and mRNA expression. Our data suggest that TNFalpha could regulate dietary iron absorption and that the apical transport machinery is the target for these actions.

Mycobacterium's arrest of phagosome maturation in macrophages requires Rab5 activity and accessibility to iron

Many mycobacteria are intramacrophage pathogens that reside within nonacidified phagosomes that fuse with early endosomes but do not mature to phagolysosomes. The mechanism by which mycobacteria block this maturation process remains elusive. To gain insight into whether fusion with early endosomes is required for mycobacteria-mediated inhibition of phagosome maturation, we investigated how perturbing the GTPase cycles of Rab5 and Rab7, GTPases that regulate early and late endosome fusion, respectively, would affect phagosome maturation. Retroviral transduction of the constitutively activated forms of both GTPases into primary murine macrophages had no effect on Mycobacterium avium retention in an early endosomal compartment. Interestingly, expression of dominant negative Rab5, Rab5(S34N), but not dominant negative Rab7, resulted in a significant increase in colocalization of M. avium with markers of late endosomes/lysosomes and increased mycobacterial killing. This colocalization was specific to mycobacteria since Rab5(S34N) expressing cells showed diminished trafficking of endocytic tracers to lysosomes. We further demonstrated that maturation of M. avium phagosomes was halted in Rab5(S34N) expressing macrophages supplemented with exogenous iron. These findings suggest that fusion with early endosomes is required for mycobacterial retention in early phagosomal compartments and that an inadequate supply of iron is one factor in mycobacteria's inability to prevent the normal maturation process in Rab5(S34N)-expressing macrophages.

Hemochromatosis protein (HFE) and tumor necrosis factor receptor 2 (TNFR2) influence tissue iron levels: elements of a common gut pathway?

Quantitative genetic analysis of hepatic and splenic iron levels in recombinant inbred mice yielded a quantitative trait locus that was found to coincide with the genomic locale encompassing the tumor necrosis factor receptor 2 gene (Tnfr2). When fed an iron-enriched diet, mice nullizygous with respect to Tnfr2, but not the Tnfr1 gene, showed a significant increase in splenic non-heme iron levels. This result contrasted with mice deficient in the hemochromatosis protein, HFE, which demonstrated a significant increase in normally high hepatic iron levels, but no change in splenic iron, when fed an iron-enriched chow. Both Tnfr2 knockout and HFE knockout mice fed an iron-enriched diet failed to demonstrate intestinal epithelial cell iron following the application of the Perls' stain, as compared to both Tnfr1 knockout and normal control mice. Moreover, intestinal intraepithelial lymphocytes (IELs) isolated from HFE knockout mice did not show an increase in TNF expression following challenge with the iron-enriched diet, in contrast to normal controls. These results suggest that HFE and TNFR2 are both involved in regulating iron deposition in tissues and that the regulation occurs at the level of the intestine through IEL-orchestrated production of TNF following the binding to TNFR2. These data suggest that HFE and TNFR2 may contribute to a common pathway of the iron stores regulator insuring the controlled efflux of gut iron.

Seeking candidate mutations that affect iron homeostasis

Hereditary hemochromatosis is characterized by marked variation of expression of the defect: very few homozygotes with the C282Y/C282Y HFE genotype have full-blown clinical disease, a larger number show biochemical stigmata of iron overload, and some seem normal biochemically. The following candidate genes have been examined in detail to determine whether polymorphisms in them may be responsible for this variation: transferrin, transferrin receptor 1, transferrin receptor 2, ferritin-L, ferritin-H, IRP1, IRP2, HFE, beta(2) microglobulin, mobilferrin/calreticulin, ceruloplasmin, ferroportin, NRAMP1, NRAMP2 (DMT1), haptoglobin, heme oxygenase-1, heme oxygenase-2, hepcidin, USF2, ZIRTL, duodenal cytochrome b ferric reductase (DCYTB), TNFalpha, keratin 8, and keratin 18. The coding sequence, exon-intron junctions, and promoters of each of these genes was sequenced in DNA from 20 subjects: 5 HFE C282Y/C282Y with clinical disease, 5 HFE C282Y/C282Y with normal/low ferritin levels and no disease, 5 wt/wt with high ferritin and transferrin saturation, and 5 wt/wt normal controls. When coding or promoter polymorphisms were encountered, DNA from large numbers of ethnically defined subjects was examined for these polymorphisms and a relationship between their existence and abnormalities of iron homeostasis was sought. Only in the case of one transferrin mutation did we find a strong relationship between the polymorphism and iron deficiency anemia. The putative genes that affect the expression of HFE mutations remain elusive.

Free radical production and labile iron pool decrease triggered by subtoxic concentration of aclarubicin in human leukemia cell lines

Aclarubicin (ACLA), which belongs to the antracycline class of antineoplasic agents, has been demonstrated as a differentiating agent for a broad range of human solid tumors and leukemia. By using dihydroethidium as a fluorescent probe, we show the ability of subtoxic (i.e. differentiating) concentration of ACLA to generate reactive oxygen species in both K562 and HL-60 leukemia cell lines. Besides, we have used a calcein-based spectrofluorimetric assay to determine the influence of ACLA treatment on the cellular labile iron pool (LIP). In both cell lines, the LIP level was markedly decreased in the presence of ACLA. Nevertheless, whereas ACLA-induced differentiation was obviously ROS-dependent, the LIP decrease was rather ROS-independent.

Ferritin, iron homeostasis, and oxidative damage

Ferritin is one of the major proteins of iron metabolism. It is almost ubiquitous and tightly regulated by the metal. Biochemical and structural properties of the ferritins are largely conserved from bacteria to man, although the role in the regulation of iron trafficking varies in the different organisms. Recent studies have clarified some of the major aspects of the reaction between iron and ferritin, which results in the formation of the iron core and production of hydrogen peroxide. The characterization of cellular models in which ferritin expression is modulated has shown that the ferroxidase catalytic site on the H-chain has a central role in regulating iron availability. In turn, this has secondary effects on a number of cellular activities, which include proliferation and resistance to oxidative damage. Moreover, the response to apoptotic stimuli is affected by H-ferritin expression. Altered ferritin L-chain expression has been found in at least two types of genetic disorders, although its role in the determination of the pathology has not been fully clarified. The recent discovery of a new ferritin specific for the mitochondria, which is functionally similar to the H-ferritin, opens new perspectives in the study of the relationships between iron, oxidative damage and free radicals.

Regulation and modulation of abnormal immune responses in endometriosis

There is ample evidence demonstrating that endometriosis is accompanied by inflammatory reactions in the peritoneum, resulting in abnormal levels of a variety of cytokines and chemokines in the peritoneal fluid. Among the immunological parameters that have been shown to be altered in the peritoneal cavity of women with endometriosis, an increase in the number of activated nonadherent macrophages that show reduced surface expression of scavenger receptors has been observed. The cause-and-effect relationship between aberrant peritoneal macrophage activity and endometriosis is still unknown. We have demonstrated that steroid hormone receptor agonists and antagonists [e.g., retinoids, antiglucocorticoids, ligands to peroxisome proliferator activated receptors (PPARs)] can regulate macrophage functions in ways that could either suppress or stimulate the growth of ectopic endometrial lesions. Our studies include a number of relevant findings: (1) RU486, acting as an antioxidant, can suppress activation of NFkappaB, a nuclear transcription factor that affects the expression of several inflammatory genes such as those for MCP-1, GM-CSF, CSF-1, and various adhesion molecules; (2) IL-6 secretion from a variety of cell types including endometrial cells is inhibited by retinoic acid; and (3) retinoids and PPARgamma ligands can upregulate the expression of scavenger receptors in cells of the monocyte/macrophage lineage. These observations, combined with the possibility that macrophage activity may play a fundamental role in endometriosis, suggest that pharmacologic manipulation of macrophage function may provide a novel mechanism for treating this disease.

Effect of iron deficiency on placental cytokine expression and fetal growth in the pregnant rat

Iron deficiency anemia is the most common nutritional disorder in the world. Anemia is especially serious during pregnancy, with deleterious consequences for both the mother and her developing fetus. We have developed a model to investigate the mechanisms whereby fetal growth and development are affected by maternal anemia. Weanling rats were fed a control or iron-deficient diet before and throughout pregnancy and were killed at Day 21. Dams on the deficient diet had lower hematocrits, serum iron concentrations, and liver iron levels. Similar results were recorded in the fetus, except that the degree of deficiency was markedly less, indicating compensation by the placenta. No effect was observed on maternal weight or the number and viability of fetuses. The fetuses from iron-deficient dams, however, were smaller than controls, with higher placental:fetal ratios and relatively smaller livers. Iron deficiency increased levels of tumor necrosis factor alpha (TNFalpha) only in the trophoblast giant cells of the placenta. In contrast, levels of type 1 TNFalpha receptor increased significantly in giant cells, labyrinth, cytotrophoblast, and fetal vessels. Leptin levels increased significantly in labyrinth and marginally (P = 0.054) in trophoblast giant cells. No change was observed in leptin receptor levels in any region of the placentas from iron-deficient dams. The data show that iron deficiency not only has direct effects on iron levels and metabolism but also on other regulators of growth and development, such as placental cytokines, and that these changes may, in part at least, explain the deleterious consequences of maternal iron deficiency during pregnancy.

Tumor necrosis factor alpha promoter polymorphisms and insulin resistance in nonalcoholic fatty liver disease

BACKGROUND & AIMS

Nonalcoholic fatty liver disease, which can range from fatty liver alone to nonalcoholic steatohepatitis and cirrhosis, is related to insulin resistance. Tumor necrosis factor alpha (TNF-alpha) may induce insulin resistance, and polymorphisms of its promoter have been associated with an increased release of this cytokine. We analyzed (1) the prevalence of insulin resistance, (2) the prevalence of the 238 and 308 TNF-alpha polymorphisms, and (3) the relationship among TNF-alpha polymorphisms, insulin resistance, and the occurrence of steatohepatitis in 99 patients with nonalcoholic fatty liver diagnosed by ultrasonography and confirmed by histologic analysis in the 53 who underwent biopsy.

METHODS

Insulin resistance was evaluated by the homeostatic metabolic assessment insulin resistance indices and TNF-alpha polymorphisms by polymerase chain reaction and restriction fragment length polymorphism analysis.

RESULTS

Insulin resistance was detected in almost all of the patients and was more severe in those with steatohepatitis. The prevalence of the 238, but not of the 308, TNF-alpha polymorphism was higher in subjects with nonalcoholic fatty liver than in controls (31% vs. 15%; P < 0.0001), and patients positive for TNF-alpha polymorphisms had higher insulin resistance indices, a higher prevalence of impaired glucose tolerance, and a lower number of associated risk factors for steatosis.

CONCLUSIONS

TNF-alpha polymorphisms could represent a susceptibility genotype for insulin resistance, nonalcoholic fatty liver, and steatohepatitis.

Tumor necrosis factor alpha promoter polymorphisms influence the phenotypic expression of hereditary hemochromatosis

Severe iron overload usually develops in patients with hereditary hemochromatosis (HHC), but variability in the phenotypic expression of the disease has been reported. This study assessed whether tumor necrosis factor alpha (TNF-alpha) plays a role in phenotypic expression of HHC. Sixty-four patients with HHC and 172 healthy volunteers (controls) were studied. Release of TNF-alpha from stimulated peripheral blood monocytes was measured by enzyme-linked immunosorbent assay, and 308 and 238 TNF-alpha polymorphisms were detected with polymerase chain reaction and restriction fragment-length polymorphism analysis. The relation between TNF-alpha polymorphisms and clinical expression of HHC was evaluated. Patients with HHC released less TNF-alpha than controls, but the difference was significant only in homozygotes for the C282Y mutation. The prevalence of the 308 TNF-alpha polymorphism was similar in patients and controls, whereas the prevalence of the 238 polymorphic allele was significantly lower in patients (3% versus 16%; P =.002). A lower prevalence of cirrhosis was observed in patients with TNF-alpha polymorphism than in those without it (4 of 15 [27%] versus 28 of 49 [57%]), but the difference was not significant (P =.07). In nonhomozygotes for the C282Y mutation, severe liver siderosis was less prevalent in patients with the 308 polymorphism than in those without it (P =.05). Alanine aminotransferase (ALT) values were significantly lower in patients with TNF-alpha polymorphism (P =.006), even when patients with other hepatotoxic factors were excluded. Multivariate analysis showed that TNF-alpha polymorphism was independently associated with ALT values (P =.0008 and P =.045, respectively, in homozygotes and nonhomozygotes for the C282Y mutation) and siderosis in nonhomozygotes (P =.047). Thus, TNF-alpha appears to play a role in HHC by modulating the severity of liver damage. (Blood. 2001;97:3707-3712)