Effect of iron deficiency and desferrioxamine on DNA synthesis in human cells

Hypoxia and Hypoxia Mimetic Agents As Potential Priming Approaches to Empower Mesenchymal Stem Cells

Mesenchymal stem cells (MSC) exhibit self-renewal capacity and multilineage differentiation potential, making them attractive for research and clinical application. The properties of MSC can vary depending on specific micro-environmental factors. MSC resides in specific niches with low oxygen concentrations, where oxygen functions as a metabolic substrate and a signaling molecule. Conventional physical incubators or chemically hypoxia mimetic agents are applied in cultures to mimic the original low oxygen tension settings where MSC originated. This review aims to focus on the current knowledge of the effects of various physical hypoxic conditions and widely used hypoxia-mimetic agents-PHD inhibitors on mesenchymal stem cells at a cellular and molecular level, including proliferation, stemness, differentiation, viability, apoptosis, senescence, migration, immunomodulation behaviors, as well as epigenetic changes.

Tissue-variation of iron stable isotopes in marine fish coupled with speciation analysis using X-ray absorption fine structure

The Fe stable isotope ratio (δ⁵⁶Fe) in tissues is a potential parameter for examining the Fe metabolism in marine fish. Although the effect of ferritin storage has been proposed as a possible cause of heavy isotope (⁵⁶Fe) enrichment in the liver, no speciation and stable isotope ratio coupling data are available. Here, we report the δ⁵⁶Fe values measured by multicollector ICP-MS and the result of Fe K-edge X-ray absorption near-edge structure (XANES) analysis of multiple tissues obtained from a skipjack tuna (Katsuwonus pelamis) and a chub mackerel (Scomber japonicus). Apparent isotopic fractionation between the liver and the muscle samples (Δ⁵⁶Fe_L-M = δ⁵⁶Fe_liver - δ⁵⁶Fe_muscle) from these species was observed (0.85 ‰ and 0.57 ‰, respectively). The dominant Fe species in the muscle was heme Fe (the sum of methemoglobin, oxyhemoglobin, and deoxyhemoglobin), while ferritin was not detected according to the linear combination fitting of the XANES spectra. In the liver, ferritin contribution was ca. 28 %-54 % of the total Fe content. The apparent difference in δ⁵⁶Fe between heme Fe and ferritin was estimated to range from 1.41 ‰ to 1.52 ‰ based on the tissue-specific δ⁵⁶Fe values and the XANES results. These results indicate that the Fe storage as ferritin does not induce the lowering of δ⁵⁶Fe in the muscle, considering the low contribution of the liver Fe to the total Fe content in the body.

Salmonella Facilitates Iron Acquisition through UMPylation of Ferric Uptake Regulator

Iron limitation is a universal strategy of host immunity during bacterial infection. However, the mechanisms by which pathogens antagonize host nutritional immunity have not been fully elucidated. Here, we identified a requirement for the UMPylator YdiU for this process in Salmonella. The expression of YdiU was dramatically induced by the metal starvation signal. The intracellular iron content was much lower in the ΔydiU strain than in wild-type Salmonella, and the ΔydiU strain exhibited severe growth defect under metal deficiency environments. Genome-wide expression analyses revealed significantly decreased expression of iron uptake genes in ΔydiU strain compared with the wild-type strain. Interestingly, YdiU did not affect the expression level of the major iron uptake regulator Fur but directly UMPylated Fur on its H118 residue in vivo and in vitro. UMPylation destroyed the Fur dimer, promoted Fur aggregation, and eliminated the DNA-binding activity of Fur, thus abolishing the ability of Fur to inhibit iron uptake. Restricting Fur to the deUMPylated state dramatically eliminates Salmonella iron uptake in iron deficiency environments. In parallel, YdiU facilitates Salmonella survival within host cells by regulating the iron uptake pathway.

The emerging therapeutic role of some pharmacological antidotes in management of COVID-19

Background

A novel RNA coronavirus was identified in January 2020 as the cause of a pneumonia epidemic affecting the city of Wuhan; it rapidly spread across China.

Aim of the review

The aim is to discuss the potential efficacy of some pharmacologically known pharmacological antidotes (N-acetylcysteine; hyperbaric oxygen; deferoxamine; low-dose naloxone) for the management of COVID-19-associated symptoms and complications.

Method

An extensive search was accomplished in Medline, Embase, Scopus, Web of Science, and Central databases until the end of April, 2021. Four independent researchers completed the screening, and finally, the associated studies were involved.

Conclusion

The current proof hinders the experts for suggesting the proper pharmacological lines of treatment of COVID-19. Organizations, for example, WHO, should pursue more practical actions and design well-planned clinical trials so that their results may be used in the treatment of future outbreaks.

Analysis of Iron and Iron-Interacting Protein Dynamics During T-Cell Activation

Recent findings have shown that iron is a powerful regulator of immune responses, which is of broad importance because iron deficiency is highly prevalent worldwide. However, the underlying reasons of why iron is needed by lymphocytes remain unclear. Using a combination of mathematical modelling, bioinformatic analysis and experimental work, we studied how iron influences T-cells. We identified iron-interacting proteins in CD4+ and CD8+ T-cell proteomes that were differentially expressed during activation, suggesting that pathways enriched with such proteins, including histone demethylation, may be impaired by iron deficiency. Consistent with this, iron-starved Th17 cells showed elevated expression of the repressive histone mark H3K27me3 and displayed reduced RORγt and IL-17a, highlighting a previously unappreciated role for iron in T-cell differentiation. Quantitatively, we estimated T-cell iron content and calculated that T-cell iron demand rapidly and substantially increases after activation. We modelled that these increased requirements will not be met during clinically defined iron deficiency, indicating that normalizing serum iron may benefit adaptive immunity. Conversely, modelling predicted that excess serum iron would not enhance CD8+ T-cell responses, which we confirmed by immunising inducible hepcidin knock-out mice that have very high serum iron concentrations. Therefore, iron deficiency impairs multiple aspects of T-cell responses, while iron overload likely has milder effects.

Nuclear receptor coactivator 4-mediated ferritinophagy drives proliferation of dental pulp stem cells in hypoxia

Nuclear receptor coactivator 4 (NCOA4)-mediated ferritinophagy has been implicated in the ferroptosis in cancer cells and hematopoiesis in the bone marrow. However, the role of iron metabolism, especially NCOA4-mediated degradation of ferritin, has not been explored in the proliferation of mesenchymal stem cells. The present study was designed to explore the role of NCOA4-mediated ferritinophagy in hypoxia-treated dental pulp stem cells (DPSCs). Hypoxia treatment increased ROS generation, boosted cytosolic labile iron pool, increased expression of transferrin receptor 1 and NCOA4. Moreover, colocalization of LC3B with NCOA4 and ferritin was observed in hypoxia-treated DPSCs, indicating the development of ferritinophagy. Hypoxia promoted the proliferation of DPSCs, but not ferroptosis, under normal serum supplement and serum deprivation. NCOA4 knock-down reduced ferritin degradation and inhibited proliferation of DPSCs under hypoxia. Furthermore, the activation of hypoxia inducible factor 1α and p38 mitogen-activated protein kinase signaling pathway was involved in the upregulation of NCOA4 in hypoxia. Therefore, our present study suggested that NCOA4-mediated ferritinophagy promoted the level of labile iron pool, leading to enhanced iron availability and elevated cell proliferation of DPSCs. Our present study uncovered a physiological role of ferritinophagy in the proliferation and growth of mesenchymal stem cells under hypoxia.

Hydroxypyridinone-Based Iron Chelators with Broad-Ranging Biological Activities

Iron plays an essential role in all living cells because of its unique chemical properties. It is also the most abundant trace element in mammals. However, when iron is present in excess or inappropriately located, it becomes toxic. Excess iron can become involved in free radical formation, resulting in oxidative stress and cellular damage. Iron chelators are used to treat serious pathological disorders associated with systemic iron overload. Hydroxypyridinones stand out for their outstanding chelation properties, including high selectivity for Fe³⁺ in the biological environment, ease of derivatization, and good biocompatibility. Herein, we overview the potential for multifunctional hydroxypyridinone-based chelators to be used as therapeutic agents against a wide range of diseases associated either with systemic or local elevated iron levels.

Iron Pathways and Iron Chelation Approaches in Viral, Microbial, and Fungal Infections

Iron is an essential element required to support the health of organisms. This element is critical for regulating the activities of cellular enzymes including those involved in cellular metabolism and DNA replication. Mechanisms that underlie the tight control of iron levels are crucial in mediating the interaction between microorganisms and their host and hence, the spread of infection. Microorganisms including viruses, bacteria, and fungi have differing iron acquisition/utilization mechanisms to support their ability to acquire/use iron (e.g., from free iron and heme). These pathways of iron uptake are associated with promoting their growth and virulence and consequently, their pathogenicity. Thus, controlling microorganismal survival by limiting iron availability may prove feasible through the use of agents targeting their iron uptake pathways and/or use of iron chelators as a means to hinder development of infections. This review will serve to assimilate findings regarding iron and the pathogenicity of specific microorganisms, and furthermore, find whether treating infections mediated by such organisms via iron chelation approaches may have potential clinical benefit.

Iron alters Ca2+ homeostasis in doxorubicin-resistant K562 cells

Iron is an essential trace element especially in cell proliferation, and growth for various cellular events. An increasing amount of research has shown that iron metabolism is altered in tumour cells which usually have rapid growth rates. However, the number of studies on iron metabolism, and calcium regulation are limited in drug-resistant tumour cells. Previously, we have shown that modulation of iron metabolism through iron chelation regulated the intracellular calcium, and increased the doxorubicin sensitivity. In the present study, we investigated the effects of iron on mRNA expression profiles of fifteen key genes (IP3 R1/2/3, RYR1/2, SERCA1/2/3, NCX1/2/3, PMCA1/2/3, and PMCA4) related to calcium homeostasis in the parental cell line K562 and its subclone doxorubicin-resistant K562 cells. According to the ΔΔCt method with a two-fold expression difference (P < .05) as a cut-off level, although iron showed differential effects on most of the genes, IP3 R and PMCA genes were especially determined to have changed significantly. These results show that iron metabolism is an important metabolism due to changes in the expression of genes involved in calcium regulation and is a new perspective to overcome cancer/drug resistance.

Subclinical Iron Deficiency in Non-Anemic Individuals: A Retrospective Analysis of Korean Health Examinees

OBJECTIVES

Non-anemic individuals may have undetected subclinical iron deficiency (SID). The aims of this study were to determine the prevalence of SID and identify the associated factors for SID. In addition, the screening performance of red blood cell (RBC) indices for SID in health check-ups was assessed.

METHODS

This study was conducted with 16,485 non-anemic health examinees (3,567 males and 12,918 females) who underwent tests for iron variables (serum iron, total iron-binding capacity, ferritin, and iron saturation) at 16 health-promotion centers in 13 cities in Korea between January 2017 and June 2018. SID was defined as a decreased ferritin level (<24 µg/L in males and <15 µg/L in females) and either a decreased serum iron level (<44 µg/dL in males and <29 µg/dL in females) or a transferrin saturation of <20%.

RESULTS

The prevalence rates of SID were 0.6 and 3.3% in males and females, respectively. In terms of age and sex, SID was most prevalent in males aged ≥70 years (7.8%) and females aged 15-49 years (7.6%). There were significant differences in the hemoglobin (Hb) level, white blood cell count, platelet count, mean corpuscular volume, mean corpuscular Hb (MCH), and RBC distribution width (RDW) between the SID and non-SID groups (p < 0.001). The factors associated with SID in males were older age (odds ratio, OR, 1.069, 95% confidence interval, CI, 1.03-1.109, p = 0.004), lower Hb (OR 0.58, 95% CI 0.345-0.976, p = 0.04), lower MCH (OR 0.433, 95% CI 0.298-0.629, p < 0.001), and higher RDW (OR 1.374, 95% CI 1.001-1.887, p = 0.049), while in females they were lower body mass index (BMI; OR 0.929, 95% CI 0.895-0.963, p < 0.001) and younger age (OR 0.954, 95% CI 0.945-0.963, p < 0.001), as well as lower Hb, lower MCH, and higher RDW. The AUC for the MCH (0.877, 95% CI 0.793-0.960 in males; 0.872, 95% CI 0.853-0.890 in females) indicates that the MCH at cut-offs of 29.2 and 29.3 pg are the best discriminators of SID in males and females, respectively (p < 0.001).

CONCLUSIONS

Reproductive-age females with a lower BMI and elderly males are high-risk groups for SID. MCH is a reliable RBC index for the screening of SID. For the population with defined risk factors, including females with lower BMI and elderly males, screening for SID is needed to prevent the development of anemia.

Iron-dependent histone 3 lysine 9 demethylation controls B cell proliferation and humoral immune responses

Trace elements play important roles in human health, but little is known about their functions in humoral immunity. Here, we show an important role for iron in inducing cyclin E and B cell proliferation. We find that iron-deficient individuals exhibit a significantly reduced antibody response to the measles vaccine when compared to iron-normal controls. Mice with iron deficiency also exhibit attenuated T-dependent or T-independent antigen-specific antibody responses. We show that iron is essential for B cell proliferation; both iron deficiency and α-ketoglutarate inhibition could suppress cyclin E1 induction and S phase entry of B cells upon activation. Finally, we demonstrate that three demethylases, KDM2B, KDM3B and KDM4C, are responsible for histone 3 lysine 9 (H3K9) demethylation at the cyclin E1 promoter, cyclin E1 induction and B cell proliferation. Thus, our data reveal a crucial role of H3K9 demethylation in B cell proliferation, and the importance of iron in humoral immunity.

The Roles of NRF2 in Modulating Cellular Iron Homeostasis

SIGNIFICANCE

Iron and oxygen are intimately linked: iron is an essential nutrient utilized as a cofactor in enzymes for oxygen transport, oxidative phosphorylation, and metabolite oxidation. However, excess labile iron facilitates the formation of oxygen-derived free radicals capable of damaging biomolecules. Therefore, biological utilization of iron is a tightly regulated process. The nuclear factor (erythroid-derived 2)-like 2 (NRF2) transcription factor, which can respond to oxidative and electrophilic stress, regulates several genes involved in iron metabolism. Recent Advances: The bulk of NRF2 transcription factor research has focused on its roles in detoxification and cancer prevention. Recent works have identified that several genes involved in heme synthesis, hemoglobin catabolism, iron storage, and iron export are under the control of NRF2. Constitutive NRF2 activation and subsequent deregulation of iron metabolism have been implicated in cancer development: NRF2-mediated upregulation of the iron storage protein ferritin or heme oxygenase 1 can lead to enhanced proliferation and therapy resistance. Of note, NRF2 activation and alterations to iron signaling in cancers may hinder efforts to induce the iron-dependent cell death process known as ferroptosis.

CRITICAL ISSUES

Despite growing recognition of NRF2 as a modulator of iron signaling, exactly how iron metabolism is altered due to NRF2 activation in normal physiology and in pathologic conditions remains imprecise; moreover, the roles of NRF2-mediated iron signaling changes in disease progression are only beginning to be uncovered.

FUTURE DIRECTIONS

Further studies are necessary to connect NRF2 activation with physiological and pathological changes to iron signaling and oxidative stress. Antioxid. Redox Signal. 00, 000-000.

Tailoring Chemotherapy for the African-Centric S47 Variant of TP53

The tumor suppressor TP53 is the most frequently mutated gene in human cancer and serves to restrict tumor initiation and progression. Single-nucleotide polymorphisms (SNP) in TP53 and p53 pathway genes can have a marked impact on p53 tumor suppressor function, and some have been associated with increased cancer risk and impaired response to therapy. Approximately 6% of Africans and 1% of African Americans express a p53 allele with a serine instead of proline at position 47 (Pro47Ser). This SNP impairs p53-mediated apoptosis in response to radiation and genotoxic agents and is associated with increased cancer risk in humans and in a mouse model. In this study, we compared the ability of wild-type (WT) and S47 p53 to suppress tumor development and respond to therapy. Our goal was to find therapeutic compounds that are more, not less, efficacious in S47 tumors. We identified the superior efficacy of two agents, cisplatin and BET inhibitors, on S47 tumors compared with WT. Cisplatin caused dramatic decreases in the progression of S47 tumors by activating the p53/PIN1 axis to drive the mitochondrial cell death program. These findings serve as important proof of principle that chemotherapy can be tailored to p53 genotype.Significance: A rare African-derived radioresistant p53 SNP provides proof of principle that chemotherapy can be tailored to TP53 genotype. Cancer Res; 78(19); 5694-705. ©2018 AACR.

Assessment of peripheral blood lymphocyte subsets in children with iron deficiency anemia

BACKGROUND

Iron plays an important role in body defense and essential for normal immune system development where its deficiency may result in an inadequate immune response. We aimed to assess the lymphocyte subsets in childhood iron deficiency anemia (IDA) with their laboratory correlations.

METHODS

Fifty IDA (< 18 years) and 25 age and sex-matched healthy children were enrolled and a complete history was obtained and clinical examination was performed. Complete blood count, serum iron, total iron binding capacity and serum ferritin, were performed. Flow cytometric determination of peripheral blood CD3+, CD4+, CD8+ T-lymphocytes and CD19+ B-lymphocytes and CD4/CD8 ratio were done.

RESULTS

Patients had significantly lower hemoglobin, Serum iron, ferritin levels and higher lymphocytic count in patients compared with controls (p = 0.001, 0.03, 0.001, 0.001 respectively). CD3 count and percentage were significantly lower in IDA patients compared to controls (p = 0.007 and 0.005 respectively). There was a Significant reduction in the CD4 count, percentage and CD4/CD8 ratio in patients compared with controls (p = 0.001, 0.001 and 0.005 respectively) while there was no significant difference regarding CD8 count and percentage. No significant difference between the two studied groups regarding either CD19 count or percentage (p = 0.28 and 0.18 respectively) were found.

CONCLUSIONS

IDA is associated with impaired cell-mediated immune response specifically T-cell mediated immunity.

A novel hydroxyphenyl hydrazone derivate YCL0426 inhibits cancer cell proliferation through sequestering iron

Cancer cells have an increased requirement for iron than normal cells, and iron chelators are under active consideration for cancer treatment. The metal-sequestering potential and antiproliferative mechanisms of a novel hydroxyphenyl hydrazone derivate YCL0426 were investigated here. Antiproliferative activity of YCL0426 was detected by MTT assay. The iron-sequestering potential was evaluated by ferrozine-Fe(II) sequestering assay and Fe(II) titration assay. Cell-cycle-arresting profile was checked by flow cytometry and the DNA synthesis status was evaluated by BrdU incorporation assay. SW480 cells stably expressing Rad51-EGFP fusion protein were used to evaluate the DNA damaging potential of the compound. The impact of extra Fe(II) supplement on compound activities was also examined. YCL0426 shows significant antiproliferative activity on 15 cancer cell lines with mean IC50 values of 5.25 μmol/l. YCL0426 displayed concentration-dependent Fe(II) sequestering ability in ferrozine-Fe(II) sequestering assay, and induced upregulation of transferrin receptor 1 and divalent metal transporter 1 expression in HepG2 cells, which are genes responsible for Fe(II) uptake. YCL0426 blocked DNA synthesis in BrdU incorporation assay, and arrested cell cycle at S or G1 phase. Besides, YCL0426 induced Rad51 foci formation and histone H2AX phosphorylation with EC50 values of 1.35 and 2.29 μmol/l, respectively, indicating the emergence of DNA damage. All these cellular responses, and even the growth-inhibiting activity of YCL0426, can be readily reversed by Fe(II) repletion, indicating that iron sequestering is responsible, at least in part, for the antiproliferative activity of YCL0426. YCL0426 is a potent iron chelator that exerts significant antiproliferative activities by inducing G1/S arrest and DNA damage.

Fumarate Mediates a Chronic Proliferative Signal in Fumarate Hydratase-Inactivated Cancer Cells by Increasing Transcription and Translation of Ferritin Genes

Germ line mutations of the gene encoding the tricarboxylic acid (TCA) cycle enzyme fumarate hydratase (FH) cause a hereditary cancer syndrome known as hereditary leiomyomatosis and renal cell cancer (HLRCC). HLRCC-associated tumors harbor biallelic FH inactivation that results in the accumulation of the TCA cycle metabolite fumarate. Although it is known that fumarate accumulation can alter cellular signaling, if and how fumarate confers a growth advantage remain unclear. Here we show that fumarate accumulation confers a chronic proliferative signal by disrupting cellular iron signaling. Specifically, fumarate covalently modifies cysteine residues on iron regulatory protein 2 (IRP2), rendering it unable to repress ferritin mRNA translation. Simultaneously, fumarate increases ferritin gene transcription by activating the NRF2 (nuclear factor [erythroid-derived 2]-like 2) transcription factor. In turn, increased ferritin protein levels promote the expression of the promitotic transcription factor FOXM1 (Forkhead box protein M1). Consistently, clinical HLRCC tissues showed increased expression levels of both FOXM1 and its proliferation-associated target genes. This finding demonstrates how FH inactivation can endow cells with a growth advantage.

Effect of microbial siderophores on mammalian non-malignant and malignant cell lines

BACKGROUND

Iron is a vital nutrient for all cells, and malignant cells have a higher requirement for the metal due to their rapid multiplication. Bacterial siderophores can be used to reduce free ferric ion concentration from the cellular environment.

METHODS

In the present study, we have evaluated effect of three siderophores - exochelin-MS, mycobactin S and deferoxamine B on the proliferation of mammalian cell lines using MTT assay.

RESULTS

These siderophores caused a significant decrease in the viability of malignant cells, without significantly affecting non-malignant cells.

CONCLUSIONS

Based on these results, we suggest that iron-chelation therapy could be explored as an adjunctive therapeutic option against cancer along with other therapies.

miR-8-3p regulates mitoferrin in the testes of Bactrocera dorsalis to ensure normal spermatogenesis

Genetics-enhanced sterile insect techniques (SIT) are promising novel approaches to control Bactrocera dorsalis, the most destructive horticultural pest in East Asia and the Pacific region. To identify novel genetic agents to alter male fertility of B. dorsalis, previous studies investigated miRNA expression in testes of B. dorsalis. One miRNA, miR-8-3p was predicted to bind the 3'UTR of putative B. dorsalis mitoferrin (bmfrn). The ortholog of bmfrn in D. melanogaster is essential for male fertility. Here we show that bmfrn has all conserved amino acid residues of known mitoferrins and is most abundantly expressed in B. dorsalis testes, making miR-8-3p and mitoferrin candidates for genetics-enhanced SIT. Furthermore, using a dual-luciferase reporter system, we show in HeLa cells that miR-8-3p interacts with the 3'UTR of bmfrn. Dietary treatments of adult male flies with miR-8-3p mimic, antagomiR, or bmfrn dsRNA, altered mitoferrin expression in the testes and resulted in reduced male reproductive capacity due to reduced numbers and viability of spermatozoa. We show for the first time that a mitoferrin is regulated by a miRNA and we demonstrate miR-8-3p as well as bmfrn dsRNA to be promising novel agents that could be used for genetics-enhanced SIT.

Modulation of iron metabolism by iron chelation regulates intracellular calcium and increases sensitivity to doxorubicin

Increased intracellular iron levels can both promote cell proliferation and death, as such; iron has a "two-sided effect" in the delicate balance of human health. Though the role of iron in the development of cancer remains unclear, investigations of iron chelators as anti-tumor agents have revealed promising results. Here, we investigated the influence of iron and desferrioxamine (DFO), the iron chelating agent on intracellular calcium in a human leukemia cell line, K562. Iron uptake is associated with increased reactive oxygen species (ROS) generation. Therefore, we showed that iron also caused dose-dependent ROS generation in K562 cells. The measurement of intracellular calcium was determined using Furo-2 with a fluorescence spectrophotometer. The iron delivery process to the cytoplasmic iron pool was examined by monitoring the fluorescence of cells loaded with calcein-acetoxymethyl. Our data showed that iron increased intracellular calcium, and this response was 8 times higher when cells were incubated with DFO. K562 cells with DFO caused a 3.5 times increase of intracellular calcium in the presence of doxorubicin (DOX). In conclusion, DFO induces intracellular calcium and increases their sensitivity to DOX, a chemotherapeutic agent.

Hepcidin/Ferritin Quotient Helps to Predict Spontaneous Recovery from Iron Loss following Blood Donation

BACKGROUND

Iron supplementation is generally recommended for blood donors even though there are inter-individual differences in iron homeostasis.

METHODS

Ferritin levels of repeat donors were compared with first-time donors, retrospectively. Prospectively, we tested 27 male repeat donors for the following parameters at the day of blood donation as well as 1, 3, 7, 10, and 56 days thereafter: ferritin, hepcidin, transferrin, transferrin receptor, hemoglobin, erythropoietin, reticulocytes, hemoglobin in reticulocyte, twisted gastrulation protein homolog 1, and growth differentiation factor-15.

RESULTS

56 days after blood donation, donors' average ferritin dropped to 55% (range 30-100%) compared to the initial value. Of all tested parameters hepcidin showed the highest and most significant changes beginning 1 day after donation and lasting for the whole period of 56 days. Along with ferritin, there was a high variation in hepcidin levels indicating inter-individual differences in hepcidin response to iron loss. Donors with a hepcidin/ferritin quotient < 0.3 regained 60% of their initial ferritin after 56 days, while those with a quotient ≥ 0.3 reached less than 50%.

CONCLUSION

As hepcidin appears to integrate erythropoietic and iron-loading signals, clinical measurement of hepcidin (together with the hepcidin-ferritin ratio) may become a useful indicator of erythropoiesis and iron kinetics.

Iron Deficiency Impairs Intra-Hepatic Lymphocyte Mediated Immune Response

Hepatic expression of iron homeostasis genes and serum iron parameters predict the success of immunosuppression withdrawal following clinical liver transplantation, a phenomenon known as spontaneous operational tolerance. In experimental animal models, spontaneous liver allograft tolerance is established through a process that requires intra-hepatic lymphocyte activation and deletion. Our aim was to determine if changes in systemic iron status regulate intra-hepatic lymphocyte responses. We used a murine model of lymphocyte-mediated acute liver inflammation induced by Concanavalin A (ConA) injection employing mice fed with an iron-deficient (IrDef) or an iron-balanced diet (IrRepl). While the mild iron deficiency induced by the IrDef diet did not significantly modify the steady state immune cell repertoire and systemic cytokine levels, it significantly dampened inflammatory liver damage after ConA challenge. These findings were associated with a marked decrease in T cell and NKT cell activation following ConA injection in IrDef mice. The decreased liver injury observed in IrDef mice was independent from changes in the gut microflora, and was replicated employing an iron specific chelator that did not modify intra-hepatic hepcidin secretion. Furthermore, low-dose iron chelation markedly impaired the activation of isolated T cells in vitro. All together, these results suggest that small changes in iron homeostasis can have a major effect in the regulation of intra-hepatic lymphocyte mediated responses.

Chaperone protein involved in transmembrane transport of iron

DMT1 (divalent metal transporter 1) is the main iron importer found in animals, and ferrous iron is taken up by cells via DMT1. Once ferrous iron reaches the cytosol, it is subjected to subcellular distribution and delivered to various sites where iron is required for a variety of biochemical reactions in the cell. Until now, the mechanism connecting the transporter and cytosolic distribution had not been clarified. In the present study, we have identified PCBP2 [poly(rC)-binding protein 2] as a DMT1-binding protein. The N-terminal cytoplasmic region of DMT1 is the binding domain for PCBP2. An interaction between DMT1 and PCBP1, which is known to be a paralogue of PCBP2, could not be demonstrated in vivo or in vitro. Iron uptake and subsequent ferritin expression were suppressed by either DMT1 or PCBP2 knockdown. Iron-associated DMT1 could interact with PCBP2 in vitro, whereas iron-chelated DMT1 could not. These results indicate that ferrous iron imported by DMT1 is transferred directly to PCBP2. Moreover, we demonstrated that PCBP2 could bind to ferroportin, which exports ferrous iron out of the cell. These findings suggest that PCBP2 can transfer ferrous iron from DMT1 to the appropriate intracellular sites or ferroportin and could function as an iron chaperone.

ZIP2 protein, a zinc transporter, is associated with keratinocyte differentiation

Zinc is essential for the proper functioning of various enzymes and transcription factors, and its homeostasis is rigorously controlled by zinc transporters (SLC39/ZIP, importers; SLC30/ZnT, exporters). Skin disease is commonly caused by a zinc deficiency. Dietary and inherited zinc deficiencies are known to cause alopecia and the development of vesicular or pustular dermatitis. A previous study demonstrated that zinc played crucial roles in the survival of keratinocytes and their unique functions. High levels of zinc have been detected in the epidermis. Epidermal layers are considered to use a mechanism that preferentially takes in zinc, which is involved with the unique functions of keratinocytes. However, few studies have investigated the ZIP (Zrt- and Irt-like protein) proteins specifically expressed in keratinocytes and their functions. We explored the ZIP proteins specifically expressed in the epidermis and analyzed their functions. Gene expression analysis showed that the expression of ZIP2 was consistently higher in the epidermis than in the dermis. Immunohistochemistry analysis confirmed the expression of ZIP2 in differentiating keratinocytes. The expression of ZIP2 was found to be up-regulated by the differentiation induction of cultured keratinocytes. Intracellular zinc levels were decreased in keratinocytes when ZIP2 was knocked down by siRNA, and this subsequently inhibited the differentiation of keratinocytes. Moreover, we demonstrated that ZIP2 knockdown inhibited the normal formation of a three-dimensional cultured epidermis. Taken together, the results of this study suggest that ZIP2, a zinc transporter expressed specifically in the epidermis, and zinc taken up by ZIP2 are necessary for the differentiation of keratinocytes.

Potential clinical applications of chelating drugs in diseases targeting transferrin-bound iron and other metals

INTRODUCTION

Iron is essential for normal, neoplasmic and microbial cells. Transferrin (Tf) is responsible for iron transport and its interactions with chelators are of physiological and toxicological importance and could lead to new therapeutic applications.

AREAS COVERED

Differential interactions of Tf with chelators such as deferiprone (L1) could be used to modify toxicity and disease pathways in relation to iron and other metal metabolism. Iron mobilization by L1 could achieve normal body iron stores in thalassemia patients. Iron mobilization from the reticuloendothelial system by L1 and exchange with Tf could be used to increase the production of hemoglobin in the anemia of chronic disease. Iron accumulation is pathogenic in neurodegenerative, acute kidney and other diseases and could be removed by L1 with therapeutic implications. Deprivation of iron from neoplasmic and microbial cells by chelators could increase the prospect of improved treatments in cancer and infectious diseases. Other applications include metal detoxification and inhibition of oxidative stress-related conditions.

EXPERT OPINION

Specific mechanisms apply in the interactions of chelators with Tf, which could be used in the design of targeted therapeutic strategies in many conditions. In each case specific chelator protocols have to be designed for achieving optimum therapeutic activity.

High prevalence of subclinical iron deficiency in whole blood donors not deferred for low hemoglobin

BACKGROUND

Blood donors that meet the hemoglobin (Hb) criteria for donation may have undetected subclinical iron deficiency. The aim of this study was to assess the prevalence of subclinical iron deficiency in whole blood donors with Hb levels above cutoff levels for donation by measuring zinc protoporphyrin (ZPP) levels. In addition, prevalence rates based on other iron variables were assessed for comparison.

STUDY DESIGN AND METHODS

The study population comprised 5280 Dutch whole blood donors, who passed the Hb criteria for donation. During donor screening, Hb levels were measured in capillary samples (finger prick), and venous blood samples were taken for measurements of ZPP and other iron variables. These variables included ferritin, transferrin saturation, soluble transferrin receptor (sTfR), hepcidin, red blood cell mean corpuscular volume (MCV), and mean cell Hb (MCH).

RESULTS

With a ZPP cutoff level of at least 100 μmol/mol heme, subclinical iron deficiency was present in 6.9% of male donors and in 9.8% of female donors. Based on other iron variables, iron deficiency was also observed. Prevalence rates ranged from 4.8% (based on transferrin saturation) to 27.4% (based on hepcidin concentration) in men and from 5.6% (based on sTfR concentration) to 24.7% (based on hepcidin concentration) in women.

CONCLUSION

Results from this study showed that subclinical iron deficiency is prevalent among blood donors that meet the Hb criteria for blood donation, based on ZPP levels and on other iron variables. This finding needs attention because these donors are at increased risk of developing iron deficiency affecting Hb formation and other cellular processes.

Transferrin polymorphism and opportunistic infections in HIV-infected women in Rwanda

OBJECTIVE

We investigated the prevalence of opportunistic infections in HIV-infected women according to transferrin (TF) phenotype.

METHODS

We conducted a cross-sectional study among 200 HIV-positive women in the Butare University Teaching Hospital in Rwanda. TF phenotypes were determined using starch gel electrophoresis.

RESULTS

Phenotype frequencies of TF CD, CB and CC were 14.5, 3 and 82.5%, respectively. The homozygous TF DD phenotype was not found. Subjects with TF CD phenotype had a significantly higher prevalence of opportunistic infections than subjects with TF CC phenotype, 76 and 52%, respectively (p = 0.026). In logistic regression, there was a significant correlation between TF phenotypes and opportunistic infections (p = 0.012). Subjects with TF CD phenotype had significantly lower values for TF (p = 0.006) than TF CC subjects. Hematological parameters (RBC, RBC indices, hemoglobin, hematocrit, WBC, neutrophils, lymphocytes, platelets and erythrocyte sedimentation rate), iron, ferritin, TF saturation, C-reactive protein and CD4 count did not differ according to TF phenotype.

CONCLUSION

Subjects with TF CC phenotype have a lower prevalence of opportunistic infections. Iron status may play a role in this association.

The role of iron in the proliferation of Drosophila l(2) mbn cells

Iron is essential for life and is needed for cell proliferation and cell cycle progression. Iron deprivation results first in cell cycle arrest and then in apoptosis. The Drosophila tumorous larval hemocyte cell line l(2) mbn was used to study the sensitivity and cellular response to iron deprivation through the chelator desferrioxamine (DFO). At a concentration of 10 μM DFO or more the proliferation was inhibited reversibly, while the amount of dead cells did not increase. FACS analysis showed that the cell cycle was arrested in G1/S-phase and the transcript level of cycE was decreased to less than 50% of control cells. These results show that iron chelation in this insect tumorous cell line causes a specific and coordinated cell cycle arrest.

Modulation of intracellular iron levels by oxidative stress implicates a novel role for iron in signal transduction

Reactive oxygen species (ROS) display cytotoxicity that can be exacerbated by iron. Paradoxically, HeLa cells treated with the ROS-generators menadione and 2,3-dimethoxy-1,4-naphthoquinone display increased free labile iron. HeLa cells exposed to ROS undergo apoptosis but iron chelation limits the extent of cell death suggesting the rise in intracellular iron plays a signaling role in this pathway. This idea is supported by the fact that iron chelation also alters the pattern of ROS-induced phosphorylation of stress-activated protein kinases SAPK/JNK and p38 MAPK. Thus, ROS-induced increases in cellular free iron contribute to signaling events triggered during oxidative stress response.

Chelation of intracellular iron with the antifungal agent ciclopirox olamine induces cell death in leukemia and myeloma cells

Off-patent drugs with previously unrecognized anticancer activity could be rapidly repurposed for this new indication. To identify such compounds, we conducted 2 independent cell-based chemical screens and identified the antimicrobial ciclopirox olamine (CPX) in both screens. CPX decreased cell growth and viability of malignant leukemia, myeloma, and solid tumor cell lines as well as primary AML patient samples at low-micromolar concentrations that appear pharmacologically achievable. Furthermore, oral CPX decreased tumor weight and volume in 3 mouse models of leukemia by up to 65% compared with control without evidence of weight loss or gross organ toxicity. In addition, oral CPX prevented the engraftment of primary AML cells in nonobese diabetic/severe combined immunodeficiency mouse models, thereby establishing its ability to target leukemia stem cells. Mechanistically, CPX bound intracellular iron, and this intracellular iron chelation was functionally important for its cytotoxicity. By electron paramagnetic resonance, CPX inhibited the iron-dependent enzyme ribonucleotide reductase at concentrations associated with cell death. Thus, in summary, CPX has previously unrecognized anticancer activity at concentrations that are pharmacologically achievable. Therefore, CPX could be rapidly repurposed for the treatment of malignancies, including leukemia and myeloma.

Complete hematopoietic recovery after continuous iron chelation therapy in a patient with severe aplastic anemia with secondary hemochromatosis

A 16-yr-old male patient with hemochromatosis due to multiple packed red blood cell transfusions was referred to our emergency center for the treatment of severe aplastic anemia and dyspnea. He was diagnosed with aplastic anemia at 11-yr of age. He had received continuous transfusions because an HLA-matched marrow donor was unavailable. Following a continuous, approximately 5-yr transfusion, he was noted to develop hemochromatosis. He had a dilated cardiomyopathy and required diuretics and digitalis, multiple endocrine and liver dysfunction, generalized bleeding, and skin pigmentation. A total volume of red blood cell transfusion before deferoxamine therapy was about 96,000 mL. He received a regular iron chelation therapy (continuous intravenous infusion of deferoxamine, 50 mg/kg/day for 5 days q 3-4 weeks) for approximately seven years after the onset of multiple organ failures. His cytopenia and organ dysfunctions began to be gradually recovered since about 2002, following a 4-yr deferoxamine treatment. He showed completely normal ranges of peripheral blood cell counts, heart size, and liver function two years ago. He has not received any transfusions for the last four years. This finding suggests that a continuous deferoxamine infusion may play a role in the immune regulation in addition to iron chelation effect.

Iron status is an important cause of anemia in HIV-infected Tanzanian women but is not related to accelerated HIV disease progression

In HIV-infected populations from developing countries, it is unclear what proportion of anemia is attributable to iron deficiency (ID) and whether high body iron stores worsen HIV disease progression. We therefore evaluated these research questions in 584 HIV-infected Tanzanian women. Hemoglobin (Hb), serum ferritin (SF), serum transferrin receptor (sTfR), and C-reactive protein (CRP) concentrations were evaluated between 13 and 43 wk after women gave birth. ID was defined as SF or sTfR outside normal ranges, and ID anemia (IDA) as ID plus low Hb. In multivariate Cox regression models, the association between SF and HIV disease progression was assessed. Participants received iron + folate supplements during pregnancy. Hb (r = -0.159; P = 0.0001), SF (r = 0.355; P < 0.0001), and sTfR/log SF index (r = -0.119; P = 0.004) were related to CRP, whereas sTfR (r = 0.029; P = 0.48) was not. Prevalence estimates were 39.7% for ID and 23.6% for IDA. ID was associated with 48.9% of anemia cases. Categories of SF were not significantly associated with HIV-related mortality or progression to stage 4. Nevertheless, SF > 150.0 microg/L was related to a nonsignificantly elevated risk of progression to stage 4 (rate ratio = 1.78; 95% CI = 0.68-4.64; P = 0.24) compared with SF < 12.0 microg/L. In HIV-infected, parous women from sub-Saharan Africa, ID is of moderately high prevalence and is an important underlying cause of anemia. High storage iron does not appear to be related to HIV disease progression in this population, but more research on the role of iron during HIV disease is needed.

Iron supplementation protects against lead-induced apoptosis through MAPK pathway in weanling rat cortex

Recent studies indicate that iron (Fe) is involved in neurotoxicity caused by inorganic lead (Pb). We studied the role of Fe in the effects Pb-induced cerebral apoptosis during rat development and to explore its possible regulatory mechanism. In the present study, weanling male Sprague-Dawley rats were randomly divided into four groups. Three groups of rats received 400 microg/mL Pb acetate solution in drinking water, among which two of the groups were concurrently given 20mg/kg and 40mg/kg FeSO(4) solution, respectively, as the low and high Fe group, for 6 weeks. The Fe doses were administered orally by gavage every other day according to animal body weight. For the control group, Na acetate with an acetate concentration equivalent to the high dose of Pb acetate was prepared in the same manner. At the end of the study, exposure to Pb in drinking water significantly promoted internucleosomal DNA fragmentation, enhanced the percentage of TUNEL-positive cells and increased the caspase-3 activities in cortex as compared to the controls. At the same time, it did cause a significant decrease in cortex Fe concentrations. Concomitant supplement with different dose Fe appeared to restore brain Fe level to the normal level. Although the low dose of Fe restored brain Pb level to the normal level and the high dose of Fe did not, both of them reduced the formation of DNA fragments, showed few TUNEL-positive cells with yellow nuclei and inhibited Pb-induced procaspase-3 degradation. Western blot showed that exposure to Pb caused a significant elevation in the phosphorylation of ERK1/2, JNK1/2, and Elk-1. Low Fe supplemental treatment suppressed the phosphorylation of ERK1/2 and JNK1/2 but not Elk-1. Interestingly, high Fe treatment slightly suppressed the phosphorylation of JNK1/2, but significantly elevated the phosphorylation of ERK1/2 and Elk-1. Collectively, the current study suggests that supplementation of Fe during Pb treatment prevents against cytotoxicity and apoptosis induced by Pb insults, in which MAPK pathways play an important role in Pb-induced cerebral apoptosis by activating the MEK-ERK pathway that suppresses JNK signaling.

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.

The struggle for iron: gastrointestinal microbes modulate the host immune response during infection

The gastrointestinal track is one source of potential bacterial entry into the host, and the local immune system at the mucosal border is paramount in establishing host immune tolerance and the immune response to invading organisms. Macrophages use iron for production of hydroxy-radical and superoxide reactions, which are necessary for microbial killing. Presumably, as a survival strategy, bacteria, which also require iron for survival, have adapted the ability to sequester iron from the host, thereby limiting the availability to macrophages. As current modes of antimicrobial therapy are evolving, examination of nontraditional therapies is emerging. One such potential therapy involves altering the bacterial micronutrient iron concentration. Necrotizing enterocolitis is a clinical condition where such a strategy makes intuitive sense. This review will describe the immune response to gastrointestinal infection, the mechanisms that the gastrointestinal system uses to absorb intraluminal iron, and the critical role iron plays in the infectious process.

N-picolyl derivatives of Kemp's triamine as potential antitumor agents: a preliminary investigation

Preorganized tripodal ligands such as the N-picolyl derivatives of cis,cis-1,3,5-triamino-cis,cis-1,3,5-trimethylcyclohexane (Kemp's triamine) were prepared as analogues to N,N',N''-tris(2-pyridylmethyl)-cis,cis-1,3,5-triaminocyclohexane (tachpyr) in hopes of enhancing the rate of formation and stability of the metal complexes. A tricyclic bisaminal was formed via the reduction of the Schiff base, while the tri(picolyl) derivative was synthesized via reductive amination of pyridine carboxaldehyde. Their cytotoxicities to the HeLa cell line were evaluated and directly compared to tachpyr and N,N',N''-tris(2-pyridylmethyl)tris(2-aminoethyl)amine (trenpyr). Results indicate that N,N',N''-tris(2-pyridylmethyl)-cis,cis-1,3,5-triamino-cis,cis-1,3,5-trimethylcyclohexane (Kemp's pyr) exhibits cytotoxic activity against the HeLa cancer cell line comparable to tachpyr (IC50 approximately 8.0 microM). Both Kemp's pyr and tachpyr show higher cytotoxic activity over the aliphatic analogue of trenpyr (IC50 approximately 14 microM), suggesting that the major contributor to the activity is the ligand's ability to form a stable and tight complex and that the equatorial/axial equilibrium impacting the complex formation for the cyclohexane-based ligands is not significant.

Desferal inhibits breast tumor growth and does not interfere with the tumoricidal activity of doxorubicin

Desferal is a clinically approved iron chelator used to treat iron overload. Doxorubicin is an anthracycline cancer chemotherapy drug used in the treatment of breast cancer. It can undergo redox cycling in the presence of iron to produce reactive oxygen species. The oxidant-generating activity of doxorubicin is thought to be responsible for the cardiotoxic side effects of the drug, but it is unclear whether it is also required for its anti-tumor activity. To test whether an iron-chelating antioxidant would interfere with the tumor-killing activity of doxorubicin, nude mice were transplanted with xenografts of human breast cancer MDA-MB 231 cells and then treated with doxorubicin and/or desferal. Not only did desferal not interfere with the anti-tumor activity of doxorubicin, it inhibited tumor growth on its own. In vitro studies confirmed that desferal inhibits breast tumor growth. However, it did not induce apoptosis, nor did it induce cell cycle arrest. Instead, desferal caused cytostasis, apparently through iron depletion. The cytostatic activity of desferal was partially ameliorated by pretreatment with iron-saturated transferrin, and transferrin receptor expression on breast cancer cells nearly doubled after exposure to desferal. In contrast to its effect on tumor cells, desferal did not inhibit growth of normal breast epithelial cells. The data indicate that the anti-tumor activity of doxorubicin is not dependent on iron-mediated ROS production. Furthermore, desferal may have utility as an adjunctive chemotherapy due to its ability to inhibit breast tumor growth and cardiotoxic side effects without compromising the tumor-killing activity of an anthracycline chemotherapy drug.

Multimutated herpes simplex virus g207 is a potent inhibitor of angiogenesis

The mode of the antitumoral activity of multimutated oncolytic herpes simplex virus type 1 G207 has not been fully elucidated yet. Because the antitumoral activity of many drugs involves the inhibition of tumor blood vessel formation, we determined if G207 had an influence on angiogenesis. Monolayers of human umbilical vein endothelial cells and human dermal microvascular endothelial cells, but not human dermal fibroblasts, bronchial epithelial cells, and retinal glial cells, were highly sensitive to the replicative and cytotoxic effects of G207. Moreover, G207 infection caused the destruction of endothelial cell tubes in vitro. In the in vivo Matrigel plug assay in mice, G207 suppressed the formation of perfused vessels. Intratumoral treatment of established human rhabdomyosarcoma xenografts with G207 led to the destruction of tumor vessels and tumor regression. Ultrastructural investigations revealed the presence of viral particles in both tumor and endothelial cells of G207-treated xenografts, but not in adjacent normal tissues. These findings show that G207 may suppress tumor growth, in part, due to inhibition of angiogenesis.

The effect of iron overload on in vitro HIV-1 infection

BACKGROUND

It has been shown that Fe is required by HIV-infected cells for production of viral particles. Excess iron in the cell is detrimental to the host but beneficial to the pathogen.

OBJECTIVES

Here, we investigated the effect of excess Fe (overload) and chelation of the metal on in vitro HIV infection by assessing host cell responses (viability/death, stress protein expression and cytokine production) as well as virus replication (core protein content and enzyme activity).

RESULTS AND CONCLUSION

Excess iron decreased viability (21%, P<0.01) of HIV-infected cells, increased p24 levels by 8.6% (P=0.32) and elevated reverse transcriptase (RT) activity (81.7%, P<0.01). The stimulation of viral replication was decreased when Fe was first complexed to desferrioxamine (DFO). DFO alone (in the absence of excess Fe), lowered cell viability (35%, P=0.039) and in the presence of virus lowered both p24 levels (66%, P=0.054) and RT activity (43%, P<0.01) and unexpectedly increased cell viability (25%, P=0.01047). Interleukin-2 (IL-2) production of infected cells was completely inhibited by DFO and excess iron while stress protein (Hsp70) levels were lowered in the presence of HIV in combination with excess iron (37%, P<0.01) or DFO (47.2%, P<0.01) when compared to untreated cells. According to flow cytometric data, HIV infection caused a two-fold increase in the numbers of necrotic (P=0.006) and decreased apoptotic cells (28.5%, P=0.15) cells. These findings indicate that Fe overload associated with HIV infection is detrimental to host cell responses against viral infection and that chelation can prevent and/or reverse this effect.

Effects of iron deprivation or chelation on DNA damage in experimental colitis

BACKGROUND AND AIMS

In inflammatory bowel diseases iron contributes to the formation of DNA adducts through the production of hydroxyl radicals. The aim of our study was to evaluate the effects of dietary or pharmacological iron deprivation in an experimental model of colitis in the rat and its potential protective effect against DNA damage.

METHODS

Colitis was induced in rats by intracolonic instillation of dinitrobenzene sulphonic acid. Rats were assigned to an iron-deprived diet or to desferrioxamine preceding the induction of colitis. The severity of colitis was assessed by the presence of bloody diarrhea, colonic macroscopic damage score, body-weight variations and the amount of DNA colonic adducts. Hepatic and colonic iron concentrations were measured.

RESULTS

Treated rats experienced less diarrhea and did not lose weight in comparison to untreated animals. The macroscopic damage score was significantly reduced in the iron-deprived diet for the 5-week group (P=0.03). Liver and colonic iron levels were significantly more reduced in the iron-deprived groups than in the standard diet group (P<0.03 and P<0.01 after a 3- and 5-week iron-deprived diet, respectively). DNA adduct formation was significantly reduced in the groups deprived of iron for 5 weeks (P<0.001) or treated with desferrioxamine (P<0.01).

CONCLUSIONS

The degree of colitis caused by DNBS is macroscopically improved by dietary iron deprivation and to a lesser extent by pharmacological chelation; genomic damage is reduced by dietary iron deprivation or chelation, and this may have clinical implications on cancer prevention.

Increased GADD153 gene expression during iron chelation-induced apoptosis in Jurkat T-lymphocytes

Depriving cells of iron likely stresses them and can result in cell death. To examine the potential relationship between this form of stress and cell death, Jurkat T-lymphocytes were made iron-deficient by exposing them to the iron chelator, deferoxamine (DFO). Such treatment produced evidence of apoptosis, including cell shrinkage, membrane blebbing, chromatin condensation and fragmentation, and also formation of apoptotic bodies. Additionally, proteolytic cleavage of poly(ADP-ribose)polymerase was detected, suggesting involvement of caspases in initiating apoptosis. Indeed, a selective caspase-3 inhibitor prevented the effects of DFO. During the early induction period of apoptosis, GRP78 and HSP70 mRNA expression was not affected. In contrast, there was mainly increased mRNA expression of Growth Arrest and DNA Damage-inducible gene 153 (GADD153), which seemed to be at the level of transcription rather than mRNA stability. Furthermore, fortifying cells with antioxidants did not prevent the increased GADD153 mRNA expression, and no evidence of single-strand breaks in DNA was found, suggesting that neither reactive oxygen species nor DNA damage was involved in triggering GADD153 gene activation. DFO also caused GADD153 protein to be expressed. Because GADD153 is recognized as a pro-apoptotic gene, these findings generate the notion that GADD153 might help mediate apoptosis in iron-deficient cells.